BACKGROUND OF INVENTION Liquid-crystal (L-C) polymers are known to form esophases having one- and two-dimensional order as disclosed by Flory, P. J., Advances in Polymer Science, Liquid Crystal Polymers I; Springer-Verlag: New York (1984) Volume 59; Schwarz, J. Mackro ol, Che . Rapid Co mun. (1986) 2 _. 21. Further, mesophases are well known to impart strength, toughness and thermal stability to plastics and fibers as described by Kwolek et al in Macromolecules (1977) 1-0, 1390; and by Dobb et al,

Advances in Polymer Science. Li-quid Crystal Polymers II/III (1986) 255(4) . 179.

While L-C polymers have been widely studied, their potential utility as coatings binders seems to have been overlooked. Japanese patents claiming that p-hydroxybenzoic acid (PHBA) , a monomer commonly used in L-C polymers, enhances the properties of polyester powder coatings are among the very few reports that may describe L-C polymers in coatings; Japanese Kokai 75/40,629 (1975) to Maruya a et al; Japanese Kokai 76/56,839 (1976) to

Nakamura et al; Japanese Kokai 76/44,130 (1976) to Nogami et al; and Japanese Kokai 77/73,929 (1977) to Nogami et al.

Hardness and impact resistance are two desirable characteristics of coatings. However, because hardness is associated with higher Tgs (glass transition temperatures) , and good impact resistance with lower Tgs, there is usually a trade-off between hardness and impact resistance. Further, non-baked polymeric vehicles with low viscosities which provide binder coating films with improved hardness and shorter drying times through combinations of polymers with mesogenic groups are not disclosed in the prior art and are to be desired.

An object of this invention is to provide new and unique mesogenic _^ compositions and a method for making such compositions.

An object of this invention is the provision of modified polymers comprising low Tg polymers covalently bonded with mesogenic groups for use in formulated coatings to provide improved films.

Another object of this invention is to provide a polymeric vehicle which includes a modified polymer which is an epoxy resin covalently bonded to mesogenic groups. Yet another object of this invention is to provide coatings of improved hardness and impact resistance.

Other important objects are to provide high solids/low viscosity, non-baking formulated coatings comprising polymeric vehicles for providing films wherein the coating formulation is fast drying and provides hard and impact resistant films.

Still further objects and advantages of the invention will be found by reference to the following description.

BRIEF DESCRIPTION OF THE FIGURE FIG. 1 outlines the synthesis of modified alkyds.

SUMMARY OF THE INVENTION

In accord with this invention a polymeric vehicle is prepared, the polymeric vehicle comprising a modified

polymer containing covalently bonded mesogenic groups. This modified polymer may be used as the sole component of a polymeric vehicle for a coating, to which may be added solvents and known additives such as pigments, thereby providing a formulated coating. Optionally the polymeric vehicle comprises a modified polymer in a mixture with other polymers, modified or unmodified, and . with cross-linking resins. Solvents and additives may be added to such a mixture of polymers and resins to make a formulated coating. An aspect of the invention is provision of a coating binder which is the polymer portion which includes the modified polymer, of a coating film which has high hardness, flexibility, and impact resistance. After the formulated coating is applied to a base or substrate, solvents (if present) evaporate leaving a solvent-free film. Evaporation may be accelerated by heating, as by baking. In some forms of the invention, no further chemical reaction is necessary to impart useful properties to the resulting solvent-free film. In other forms of the invention, optimum properties are attained only after chemical reactions occur within the film, forming covalent bonds and increasing the molecular weight of the modified polymer and usually converting it into a three-dimensional cross-linked polymeric network. In some cases these chemical reactions occur between the modified polymer and a cross-linking resin if present in the formulated coating. In other cases, the modified polymer may chemically react with substances to which the film is exposed after solvent evaporation, for example, with oxygen in the air. The chemical reactions that form a cross-linked network may be accelerated by heating (baking) . It is the provision of this improved film with improved hardness, flexibility and impact resistance, and the coating binder therefor, to which this invention is particularly directed. Since the coating binder primarily provides the desired film characteristics, the properties

of the coating binder are particularly described primarily by tests which measure hardness and impact resistance.

This invention also provides for using a polymeric vehicle comprising a modified polymer which after film formation provides a low Tg coating binder which has hardness and impact resistance. We have found that the presence of mesogenic groups covalently bonded to otherwise amorphous polymers provides coating binders that are substantially harder than comparable coating binders not having mesogenic groups and have found that this is obtained without substantially raising Tg of the coating binder. The presence of covalently bound mesogenic groups also imparts other desirable properties to the formulated coating. Thus, according to the invention, it is possible to prepare very hard coating binders and films while retaining the impact resistance, flexibility and adhesion associated with a low Tg. Coating binders with Tgs in a range from -50 degrees C. to +10 ' C. are often very elasti and impact resistant, but they are generally too soft to be useful in most coatings applications. On the other hand, non-crosslinked coatings with Tgs above 60 degrees C. are usually hard, but they are generally brittle and have very poor impact resistance. It is, therefore, beneficial to impart hardness to coating binders without sacrificing impact resistance. Moreover, the presence of covalently bound mesogenic groups imparts other desirable properties to the formulated coating. Fo example, this invention can alleviate a common problem of formulated coatings: that substantial amounts of solvent are required to reduce viscosity to a level low enough fo application of polymers whose Tgs and molecular weights are high enough to provide good properties. The use of large amounts of solvent results in increased costs and often in unacceptable levels of atmospheric pollution. Especially large amounts of solvent are often required fo conventional coatings vehicles whose Tgs and molecular weight are high enough to impart desirable properties

without cross-linking. Presence of mesogenic groups can both improve their properties and reduce the amount of solvent required.

The groups that provide the coating binder of the invention are called "mesogenic groups". The mesogenic groups of this invention are chemical structures that contain a rigid sequence of at least two aromatic rings connected in the para position by a covalent bond or by rigid or semi-rigid chemical linkages. Optionally, one of the rigid aromatic rings may be a naphthalenic rings linked at the 1,5- or 2,6- positions. Modified polymers containing mesogenic groups are called "mesomorphouε." The coating binders of this invention contain between 5 percent and 50 percent by weight of mesogenic groups to provide the desired characteristics. When a polymer is referred to as "liquid crystalline" herein it is meant to cover such polymers which exhibit mesophases. The presence of mesophases are often associated with the presence of mesogenic groups. An important aspect of this invention are the mesogenic compounds

0

HO " ^{0H which is} 4 ^, -hydroxypheny 4-hydroxybenzoate (1)

HO -<0>- ,® - ^« -w <Q> - ^« < ² > and

the synthesis thereof and the reaction products of 1, 2 and 3 and mixtures thereof with epoxy polymers such as the diglycidyl ether of Bisphenol A which has the formula

wherein n > O, preferrably > 0.12, but not greater than about 20 wherein 17 is an average value.

Yet another important aspect of this invention is the mesogenic epoxy compound having the general formula

-ζ ^~ w (5)

wherein n .> 0 but not greater than about 20 wherein n is

0

- C - O -, - CO - or combinations thereof and the synthesis thereof. This epoxy compound is the diglycidyl ether of 4'-hydroxyphenyl 4-hydroxybenzoate (1), formula 2, formula 3 or mixtures thereof. As the term is used herein, this diglycidyl ether (5) of (1) , (2) or (3) is an "epoxy polymer" when n > 0.

Epoxies can react with multifunctional epoxy cross-linkers such as di or polya ines through the epoxide groups to give cured films. Epoxies with -OH function¬ ality can also be cured with a inoplast resins such as hexakis (methoxymethyl) mela ine resin (HMMM) through the OH groups.

As used in this application, "polymer" means a polymeric or oligomeric component of a coating vehicle such as an epoxy polymer, acrylic polymer or a polyester polymer; alkyd polymers are considered to be a sub-class of polyester polymers. "Cross-linker resin" means a di-

or polyfunctional substance containing functional groups that are capable of forming covalent bonds with epoxy hydroxyl, carboxyl and -SH groups that are optionally present on the polymer; a inoplaεt and polyisocyanate resins are members of this class; melamine resins are a sub-class of aminoplast resins; di or polya ines, carboxylic acids and mercaptans are epoxy resin cross-linkers. "Modified polymer" means a polymer having covalently bound mesogenic groups as described herein and for purposes of this application includes formula (5) wherein n = 0. "Polymeric vehicle" means all polymeric and resinous components in the formulated coating, i.e. before film formation, including but not limited to modified polymers. "Coating binder" means the polymeric part of the film of the coating after solvent has evaporated and, in cases where cross-linking occurs, after cross-linking. "Formulated coating" means the polymeric vehicle and solvents, pigments, catalysts and additives which may optionally be added to impart desirable application characteristics to the formulated coating and desirable properties such as opacity and color to the film. "Film" is formed by application of the formulated coating to a base or substrate, evaporation of solvent, if present, and cross-linking, if desired. "Air-dried formulated coating" means a formulated coating that produces a satisfactory film without heating or baking. "Baked formulated coating" means a formulated coating that provides optimum film properties upon heating or baking above ambient temperatures. Acrylic polymer means a polymer or copolymers of

-y

H ₂ C = C

wherein y = CH ₃ or H

- -& OR, C ₆ H ₅ - or tolyl

R = straight chain or branched carbons,

CH-, 0

-CH ₂ C IH-OH, -CH ₂ CH ₂ OC»CH ₂ CH ₂ COOH and H n = 2 to 7.

In the case of hydroxy-substituted alkyl acrylates the monomers may include members selected from the group consisting of the following esters of acrylic or ethacrylic acid and aliphatic glycols: 2-hydroxy ethyl acrylate; 3-chloro-2-hydroxypropyl acrylate; 2-hydroxy-l-methylethyl acrylate; 2-hydroxypropyl acrylate; 3-hydroxypropyl acrylate; 2,3-dihydroxypropyl acrylate; 2-hydroxybutyl acrylate; 4-hydroxybutyl acrylate; diethylene-glycol acrylate; 5-hydroxypentyl acrylate; 6-hydroxyhexyl acrylate; triethyleneglycol acrylate; 7-hydroxyheptyl acrylate;

2-hydroxy-l-methylethyl methacrylate; 2-hydroxy-propyl methacrylate; 3-hydroxypropyl methacrylate; 2,3-dihydroxypropyl methacrylate; 2-hydroxybutyl methacrylate; 4-hydroxybutyl methacrylate; 3,4-dihydroxybutyl methacrylate; 5-hydroxypentyl methacrylate; 6-hydroxyhexyl methacrylate; 1,3-dimethyl-3-hydroxybutyl methacrylate; 5,6-dihydroxyhexyl methacrylate; and 7-hydroxyheptyl methacrylate.

"Polyester polymers" means the polymerized reaction product of polyacids and polyols; polyacids include diacids such as isophthalic, terephthalic, and furoaric acids and HOOC(CH ₂ ) _n COOH where n = 2 to 14 and "dimer acids", anhydrides of diacids such as maleic, phthalic, hexahydrophthalic, and succinic, and anhydrides

of polyacids such as trimellitic acid anhydride. The polyols include linear diols such as HO (CH ₂ ) _πι OH where m = 2 to 16, branched aliphatic diols such as neopentyl glycol, 1,3-butylene glycol, propylene glycol and 1,3-dihydroxy-2,2,4-trimethylpentane, cycloaliphatic diols such as hydroquinone, 1,4-dihydroxymethyl- cyclohexane and "hydrogenated Bisphenol A", diol ethers such a diethylene glycol, triethylene glycol and dipropylene glycol, and polyols such as glycerol, pentaerythritol, trimethylol propane, trimethylol ethane, dipentaerythritol, sorbitol and εtyrene-allyl alcohol copolymer.

Esterification catalysts that are used in the process for preparing polyesters are organo tin catalysts such as butyl εtannoic acid (sold under the name Fascat 4100 by M&T Chemicalε, Inc.), barium oxide, barium hydroxide, barium naphthenate, calcium oxide, calcium hydroxide, calcium naphthenate, lead oxide, lithium hydroxide, lithium naphthenate, lithium recinoleate, sodium hydroxide, sodium naphthenate, zinc oxide, and lead tallate.

In this invention "alkyd polymers" are considered to be a sub-clasε of "polyeεter polymers." Alkyds are condensation polymers of the polyacids and polyols as described above that also contain monobasic acids. The monobasic acids may include εaturated or unεaturated fatty acids having between 9 and 26 carbon atoms and monobasic aromatic acids.

Fatty, or other carboxylic, acids that are used to prepare alkyd resinε include HOOC(CH ₂ ) _n CH ₃ where n = 7 to 22, oleic acid, linolelic acid, linolenic acid, erucic acid, soybean oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, sunflower oil fatty acids, coconut oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, benzoic acid, toluic acid and t-butylbenzoic acid. Fatty acids may be

incorporated into the alkyd polymer as such or as a component of triglycerides.

In this application epoxy polymer means a polymer having more than one repeating monomeric unit, the polymer having terminal or pendant epoxy groups

CH ₂ - CH - ,

epoxy polymers including a diglycidyl ether of Bisphenol A DGEBPA (see formula 4) the diglycidyl ether of 1, 4 butanediol (DGE-1,-4BD) which is available commercially from Ciba-Geigy, under the name of Araldite RD-2, and the diglycidyl ether of 4'-hydroxyphenyl 4-hydroxybenzoate (see formula 5) .

Although it is especially important that covalently bonded mesogenic groups, according to the invention, impart substantially improved hardness to coating binders without sacrificing impact resistance, the mesogenic groups often improve coatings in at least two other ways. In some caseε inclusion of modified polymers according to the invention effectively lowers the viscosity of formulated coatings at a given solids content relative to the viscosity of comparable unmodified polymers in comparable solvents at the same solids level. The reason is that mesogenic groups tend to cause modified polymers to form stable dispersions rather than solutions in many common solvents. Thus, lesε solvent is required, reducing cost and air pollution. Furthermore, in the case of air dried formulated coatings, the mesogenic groups greatly reduce the time necessary for the polymeric vehicle to harden into a film, referred to as "dry-to-touch" time.

We have found that mesogenic groups covalently bound to polymers can improve polymeric vehicles which provide non-epoxy coating binders having a Tg as low as -50 ^β C. or as high as +60 ^β C. while providing improved hardness, adhesion, impact resistance and flexibility. We have found mesogenic groups covalently bound in an epoxy

SUBSTITUTE SHEET

polymer can improve polymeric vehicles which provide coating binders with a Tg as high as +180*C while providing improved hardness, adhesion, impact resistance and flexibility. The epoxy polymers of the invention can be used as cured casting resins for any product which can be cast such as in electrical equipment applications, pipes and sport equipment. In such application the epoxy polymers may be cured using polyfunctional amines and commonly known accelerators. Reinforcing fibers such as metal, asbestos, carbon fibers, glass fibers, cotton, polyamide, polyester, polyacrylonitrile or polycarbonate fibers all may be used to reinforce the molded product. Fillers such as chalk, talcum, quartz power and ground shale, kaoline, lime spar, dolomite, mica, heavy spar, kieselguhr and aluminas also may be used. Other standard auxiliaries and additives which may be used with the epoxy polymer of the invention include, for example, organic and inorganic pigments, dyes, lubricants and release agents, thixotropizing agent, UV-absorbers, and shrinkage-reducing additives.

DETAILED DESCRIPTION OF THE INVENTION In accord with this invention, mesogenic groups in various forms are used to modify polymers for polymeric vehicles thereby providing films, some of which are transparent, with desired characteristics. The polymeric vehicle comprises a modified polymer in the range of from about 100 to about 35 weight percent based upon the weight of the polymeric vehicle, and unmodified polymers and/or cross-linking resins in the range of from about 0 to about 65 weight percent based upon the polymeric vehicle. The modified polymer may be the diglycidyl ether of compounds having formulas (_D, (2, (3) or mixtures thereof, e.g. compound (5) alone or the modified polymer may be another type of

SUBSTITUTESHEET

an epoxy polymer or an acrylic polymer or a polyester polymer to which mesogenic groups are covalently bound such that the coating binder contains from about 5 to about 50 weight percent mesogenic groups, based upon the weight of the modified polymer. The mesogenic groups are selected from the group consisting of

or covalently bonded σαibinatiαns

I. of such general formula

or covalently bonded coπibinationε

II. of such general formula

ently bonded combinations

III. general formula

or covalently bonded

IV. C-crnbinations εelected iεting II and

V. Cαrribinations of III and

wherein

0 O 0 O O

II •I II II II

X = - 0 - C -, - C - 0 -, -CH = N -, - s -, - S -, - C -,

•I

O CH,

II

- 0 -, - 0 - C - 0 -, - O-CHp -, - C = N -

0 0 0

II II ti

0 - C .H - 0 - C C - o

/

C = C \ C = C H \ C - 0 - H / \ H

U = X m = an integer from 2 to 8; n = 1 or 2; p = an integer frcn 1 to 4; and q = an integer from 1 to 3.

An important aspect of the invention is where the mesogenic groupε have the general formula

- ° -(O)- ^W -(§)- ° - wherein W iε εelected from the group conεiεting of

The mesogenic groups may be reacted with the polymer as seen in the examples.

When one of the reactive constituentε of the meεogenic groupε are not reacted with the polymer, they are terminated by -H,-CN,-COOR,-OOCR and -OR wherein R is H, alkyl (which is straight chained or branched) having 1 to 12 carbon atoms or aryl εuch aε having from 6 to 12 carbon atomε.

The polymeric vehicle which includes a modified epoxy polymer provideε a coating binder having a Tg not greater than about 180*C aε meaεured by Differential Scanning Colorimetry (DSC) (or not greater than 60*C if the polymeric vehicle includeε a modified acrylic or polyester polymer) ; and, at a thickness of about 1 mil, the coating binder haε a pencil hardness of at least about "H" and a reverse impact resiεtance of at leaεt about 30 inch-poundε. Films which include coating binder generally will range from about 0.05 mil to about 50 mil in thickness, but hardness and impact reεistance may vary with the thickneεε of the film; hence hardness and impact resiεtance are deεcribed at a thickneεε of about 1 mil.

An important aεpect of the invention iε when the modified polymer iε croεε-1inked. It may be croεε-1inked with a cross-linking resin selected from the group consiεting of a di or polyamine, aminoplaεt reεins, pol isocyanate reεinε, and mixtures thereof; melamine reεins are a sub-clasε of aminoplaεt resins; optionally, the isocyanate groups of the polyisocyanate resin may be blocked with active hydrogen compounds such as alcohols, phenols, oximes and lactams. In an important embodiment an aminoplast or polyisocyanate resin crosε-links a modified polymer which is a a polyol or contains pendant or terminal -COOH or -SH groups.

In one important embodiment mesogens having the general formula:

- o -(g)- w - >- o - wherein W iε εelected from the group conεiεting of O

•I

- C - O -,

- CO ^■ ©- ; - 0 - and

0 0 n •• - C - 0 -<0\ 0 - C - are made and then uεed to make a modified polymer through a reaction of any one of εuch meεogenε or a mixture thereof with an epoxy resin, particularly DC-EEPA (4 ) . Thereafter the modified polymer is crosε-linked with an a ine reεin εuch aε hexakiε (methyloxy-methyl) melamine (HMMM) .

In another embodiment a mesogenic polyol has the general formula:

R' = 0(CH ₂ ) _n O,

{O[(CH ₂ ) ₅ C00] _p R"">2' or 0[R' ^, OOCR'''COOJpR'O;

R'' and R' ^/, = a aliphatic or cycloaliphatic radical having 12 carbon ato ε or less; R'" = aromatic radical having 10 carbon atoms or less, cycloaliphatic radical having 12 carbon atoms or less, or an aliphatic radical having 36 carbon atoms or less; n = 5 to 16; m = 2 to 200; and p = 1 to 20. An important aspect of this invention is the synthesis of the mesogenε having the general formula

wherein W iε εelected from the group conεiεting of

O

II

- C - O -, o o

- CO -(O/- C - O - , and O O

- c - o - 0 - 0 - C - by the reaction of hydroquinone with parahydroxybenzoic acid in an aromatic εolvent εuch aε benzene or an alkyl benzene aε follows:

p-TSA

2 HO/~VOH + i HO/ .COOH -*22!U 22.

175-200 ^W C 30 min.

f—— II II —.

HO -^ - co - yo T/)- OH

An important aspect of this invention is the use of these mesogens (6) to provide a modified polymer which is a reaction of the mesogen with an epoxide polymer such as DGΞBPA which modified polymer may or may not be croεε-1inked. The uncroεs-1inked modified polymer may provide a film or the modified polymer may be cross-linked to provide a film. Cross-linking may be achieved with an aminoplaεt such as HMMM resin. The modified polymer, cross-linked or uncross-1inked provides a polymeric vehicle which when applied to a substrate provides a binder having a Tg not greater than about 180"C, a pencil hardness of at least about H, and a reverse impact resistance of at least about 30 inch lbs. at a binder thickness of about 1 mil. Another important aspect of the invention arises in cases where the mesogenic groups are bonded to acrylic or polyester polymers by graft polymerization to prepare modified polymers. In this aspect, non-mesogenic acrylic

SUBSTITUTE SHEET

and polyester polymers containing reactive groups such as -COOH and -OH are synthesized. The reactive groups serve as sites for grafting.

Especially preferred are grafting sites consiεting of -COOH groups. Acrylic polymers containing such groups can be prepared by including -COOH functional monomers such as (meth) crylic acid among the monomerε uεed to prepare the acrylic monomer. Polyeεter reεinε with -COOH groupε can be synthesized by using an excesε of polyacid monomers over polyol monomers. Alternatively, -OH functional acrylic and polyester polymers can be provided with -COOH functional groups by reacting them with spacers such as diacids such as adipic, isophthalic or terephthalic acids or with cyclic anhydrides such as phthalic, succinic or aleic anhydrides. It is advantageous in some circumstances to convert -OH groups to -COOH groups becauεe εo e reactantε graft more readily to -COOH groups. p-Hydroxybenzoic acid, PHBA, is a commonly used component of the mesogenic group in modified polymers. It may be grafted to acrylic or polyester polymers having -OH or -COOH groups; the latter are preferred. A typical grafting process is shown in Figure 1. In this case the mesogenic groups are grafted onto the polymer to form the modified polymer are oligomeric PHBA having the general formula:

where n - 2 to 8 and preferably the number average degree of polymerization of graft segments is between about 2.0 to about 6.0. See Tables 29 a-h for mesogenic examples. See Tables 29 a-c (Mono-functional Derivates) , 29 d-g (Di-Functional Derivates) , 29 h (Miscellaneous

Derivatives) for a description of specific mesogenic

SUBSTITUTESHEET

groupε of the invention. In Table 29 one or both open bonds of the difunctional mesogenic groups may be bonded to the modified polymer. If only one is bonded to the polymer, the other functional end may be bonded to -H or " ^R ι» where R^- is a C to C ₁₂ alkyl group.

The modified polymer may comprise the entire polymeric vehicle, it may be blended with other polymers and/or with cross-linking resins, or it may be cross-linked by substances to which the film is exposed after application. In cases where the modified polymer is not cross-1inked, it should have a number average molecular weight (H _n ) above about 10,000 for modified acrylic polymers and about 7,000 for modified polyester polymers. Preferred rangeε are about 15,000 to 10 ⁶ for acrylicε and about 10,000 to 10 ⁵ for polyesters. When the modified polymers undergo chemical reactions after application they may have lower M _n . Preferred ranges of M _n are from about 1,000 to 50,000 for cross-linkable modified acrylic copolymers and about 500 to 20,000 for cross-linkable modified polyester copolymers. Cross- linking is effective for baked and non-baked films.

If the film is to be baked, the modified polymer and croεε-1inking resin, such as a inoplastε and blocked iεocyanateε, may be combined as components of the coating formulation. Reaction of the modified polymer and such cross-linking resins is normally very slow until the coating is applied and baked. When highly reactive cross-linking resins such a polyisocyanate resins are used, it is usually desirable to mix the components within a few hours of the time of application. Such coatings require little or no baking. Cross-linking may also be effected by exposure of the film to reactants, such as oxygen, after application; in such cases baking is optional. The following examples set forth methods of imparting the desired characteristics to polymeric binders and to films. In these examples the properties of

SUBSTITUTESHEET

coatingε containing modified polymers are compared to those containing similar non-modified polymers in order to demonstrate the improvements of the invention: 1) a lowered solution viscosity, 2) a hard, adherent, flexible film having excellent impact resistance and 3) greatly reduced dry-to-touch time in the case of air-dried coatings.

EXAMPLE 1 o

N

A. Preparation of HO- (θ/-C-0-(0)-OH ( 1) (4'-hydroxyphenyl

O O

4-hydroxybenzoate) , and

A 500-mL three-neck round bottom flask was equipped with mechanical εtirrer, Dean-Stark trap, condenser, thermometer and N ₂ inlet. Hydroquinone (143.0 g, 1.30 mol), p-hydroxybenzoic acid (89.7 g, 0.65 mol), p-toluene sulfonic acid (0.32 g) and Aromatic 150 (a mixed alkyl benzene solvent commercially available from Exxon Chemical Company) (16 g) were charged into the flask. The mixture was heated (under N ₂ ) to 200'C; H ₂ 0 began azeotroping and collecting in the Dean-Stark trap at 175'C. The temperature was held at 200'C until the theoretical water of reaction was collected (about 30 in) . The hot product was poured into a steel can and allowed to cool. The solidified product was ground into a powder and dissolved in 500-600 L of hot MeOH. The solution was filtered while hot to remove insoluble by-products 2 and/or 3.

A large volume of water (about 3000 mL) waε added to the MeOH solution to precipitate the product (1) ; (2) and/or (3) being previously separated by hot filtration. The product (1) was filtered and disεolved in MeOH and the precipitation process waε repeated twice. The product was dried for 2 h at 100*C and then overnight under vacuum at room temperature. Yield of (1) was 60 g (40% yield) . p 241-243'C (lit. 245'C ⁶ ). H NMR (Me ₂ SO-dg) 10.45 (ε, 1H) , 9.40 (ε, 1H) , 7.95 (d, 2H, j=8.4), 6.85 ( , 6H) . Anal calcd for C ₁₃ H ₁₀ O ₄ : C, 67.82; H, 4.38; O, 27.78. Found: C, 67.66; H,4.43; O, 27.35.

The by-product waε waεhed with hot MeOH, dried and yielded 48 g of (2 and/or 3), mp (DSC) 327-330'C. I.R. (KBr) ; 3250 cm ^"1 (OH), 1650 cm ^"1 (C=0) , 1600 cm ^"1 (phenyl) . Anal, calcd for C ₂₀ H ₁₄ O ₆ : C,

68.56; H, 4.03; 0, 27.40. Found: C, 68.55: H, 4.01; O, 26.78.

B. Preparation of Resins And Coatings By Reacting A Diepoxy Resin With The Mesogens of Example 1A. The diepoxies uεed were DER 343 (Dow) a diglycidyl ether of Biεphenol-A (DGEBPA) (Formula 3) where n= 0.1 (determined by titration of epoxide groupε). DER 343 contains a proprietary catalyεt which εelectively catalyzes the phenol-epoxide reaction. Resinε baεed on Araldite RD-2 (Ciba-Geigy, the diglycidyl ether of 1,4-butanediol (DGE-1,4-BD) , eq. wt. = 128) were also investigated. Triphenylphosphine waε uεed aε a ring opening catalyεt for reactions with RD-2. The meεogen (1) prepared is described in Example 1, Part A. Controls were prepared by substituting Bisphenol-A

(4,4'-isopropylidenediphenol or "Bis A") for (1) (on an equal molar basiε) in the formulations.

The formulations of the polymers prepared is shown in Table 1.

Table 1. Polymerε Prepared - mol ratioε of diphenol/epoxy are given.

i. Synthesis of Diphenol (4'-hydroxyphenyl 4-hydroxybenzoate or Bis A)/DGEBPA = 1/1 to form a coating.

The 1/1 materials were prepared as a lacquer directly on a Bonderite 1000 steel panels. The Diphenol and DGEBPA were combined in a molar ratio of 1.04:1. The mixture containing 4'-hydroxyphenyl 4-hydroxybenzoate (1) forms a smooth/fine paεte. This was obtained by mixing with a vortex mixer. Excellent wetting of (1) by the epoxy is obtained. In the case of the Bisphenol-A control, a εmall amount of methyliεobutyl ketone (MIBK) iε necessary to dissolve the Bisphenol-A in the epoxy. The mixtures were applied to Bondrite 1000 steel panelε uεing a 2 mil wire wound draw-down bar and placed in a convection oven at 200'C for 1 hr. The cured filmε were 1.5 mil thick and were transparent.

ii. Synthesis of '-hydroxyphenyl

4-hydroxybenzoate (1)/DGEBPA = 3/2

A 50-ml round bottom flask waε e-quipped with thermometer, N ₂ and magnetic stirrer. '-hydroxyphenyl

4-hydroxybenzoate (1) (9.67 g, 0.042 mol), DGEBPA (10.47 g, 0.028 mol) and xylene (2 g) were charged into the flask. The mixture was heated to 175'C for 1.65 h. (1) takes about 10 min at 175*C to completely disεolve.

Extent of reaction was 99% (determined by titration of epoxy group with 0.104 N HBr in acetic acid).

The reaction with Bisphenol-A was carried out in the same manner - total reaction time = 2 hr (99% extent reaction) .

iii. Synthesis of 4'-hydroxyphenyl

4-hydroxybenzoate (1)/DGEBPA 1/2

A 50-mL round-bottom flask was equipped as described above. 4'-hydroxyphenyl 4-hydroxybenzoate (1) (3.57 g, 0.016 mol), DGEBPA (11.59 g, 0.032 mol) and xylene (1.5) were charged into the flask. The mixture was heated to 175 *C for about 5 min. Final epoxy eq. wt. = 520 (theo eq. wt. = 488).

The Biεphenol-A baεed reεin was prepared in the same way - total reaction time = 10 min; epoxy eq. wt. = 503.

iv. Synthesis of 4'-hydroxyphenyl

4-hydroxybenzoate (1)/DGE-1,4-BD = 2/3

A 50-mL round-bottom flask waε equipped aε deεcribed above. 4'-hydroxyphenyl 4-hydroxybenzoate (1) (9.21 g, 0.040 mol)DGE-l,4-BD (15.36 g, 0.060 mol), triphenylphoεphine (0.025 g) and xylene (1.25 g) were charged into the flaεk and the mixture waε heated to 175 ^* C for 45 min. Epoxy eq. wt. of product = 774 (theoret. eq. wt. = 614) .

For the reaction with Biεphenol-A; reaction time - 1 hr at 175'C. Epoxy eq. wt. = 500.

v. Synthesis of 4'-hydroxyphenyl

4-hydroxybenzoate (1)/DGE-1,4-BD = 1/1

4'-hydroxyphenyl 4-hydroxybenzoate (1) (0.924 g,

0.0040 mol), DGE-1,4-BD (1.026 g, 0.0040 mol) and triphenylphosphine (0.002 g) were placed in a 15 L vial.

The mixture waε heated under nitrogen atmoεphere at 175"C for 1 h (95% reaction based on epoxy titration) .

vi. Syntheses of the diglycidyl ether of 4'-hydroxyphenyl -hydroxybenzoate

A three-neck 50 mL flask was equipped with thermometer, magnetic εtirrer, addition funnel and cόndenεer. 4'-hydroxyphenyl 4-hydroxybenzoate (1) (1.40 g, 6.1 x 10 ^"3 mol) epichlorohydrin (5.64 g, 0.061 mol) and dioxane (5.6 g) were added to the flask. Aqueous NaOH

(2.23 g of 24% NaOH solution) waε added to the addition funnel. The mixture waε heated to reflux. The NaOH εolution was dripped into the mixture over 3 h while the mixture was kept at reflux temperature (90-100'C). The mixture waε held at 90 ^* C for 1 additional hour. 10 L of tetrahydrofuran (THF was added to the mixture and the mixture was filtered. The solvent was removed under vacuum. 10 mL of THF was added to the reεinouε product and the εolution waε dried with MgS0 ₄ , filtered and the εolvent removed under vacuum at 80'C for 1 h. 1.7 g (82% yield) of light yellow, clear viεcouε product waε obtained. I.R. 3400 cm ^"1 (OH), 1710 cm ^"1 (C=0) , 1600 cm ^"1 (phenyl) , 915 cm ^"1 (epoxide) . Epoxy equivalent wt. = 230 (determined by titration with 0.104 N HBr in acetic acid) . The resin crystallizes upon standing overnight.

A sample of the epoxy waε mixed with triethylenetetramine (very roughly about 50:50) and cured on a glass εlide at 120*C for 39 min. The cured film haε a Tukon hardneεε of 25 knoops. The sample also cures to a hard film at room temperature.

C. Results and Discussion For Example 1

Table 2 shows the film properties of the 1/1 diphenol/DGEBPA based coatings. The film propertieε of the Biεphenol-A baεed coatings are very poor — the film being very brittle. The mesogen baεed coating haε excellent impact propertieε aε well aε excellent chemical and corroεion reεiεtance The Tg of the-meεogen baεed coating is about 20 ^* C higher than the Bisphenol-A based coating The Bisphenol-A based coating iε soluble in THF

and has a M _n of about 5500. The meεogen baεed coating on the other hand is party insoluble in THF — it breaks up into εmall εwollen fragments.

The insolubility of the mesogen baεed coating suggests that the film iε somewhat crosε-linked. While not intending to be bound by any theory, a poεεible explanation iε baεed on the solubility and mp of 4'-hydroxyphenyl 4-hydroxybenzoate (1). 4'-hydroxyphenyl 4-hydroxybenzoate (1)/DGEBPA mixture iε heterogeneous when applied to the panel. It takeε about 5-10 min. at 200'C for 4'-hydroxyphenyl 4-hydroxybenzoate (1) to dissolve (for the coating to become clear) . During this time some reaction between epoxide groups and aliphatic OH groups on the epoxy backbone may take place causing some branching or croεε-linking to occur before or during reaction of the the epoxy with the phenolic meεogen. The OH's of 4'-hydroxyphenyl 4-hydroxybenzoate (1) may also be lesε reactive toward the ring opening reaction compared to Bisphenol-A. The differenceε in the Tg'ε and film properties between 4'-hydroxyphenyl 4-hydroxybenzoate (1) and Biεphenol-A baεed coatingε thuε may be due to εtructural differenceε of the diphenolε and/or differences in the structure of the polymer backbone caused by branching or croεε-linking.

Table 2. Film propertieε of 1/1 diphenol/DGEBPA filmε.

Diphenol Tg Mn Rev. Impact Tukon Hard.

4'-hy roxyphenyl 4-hydroxybenzoate (1) 104*C * >160 in-lb 13 Knoops

Bis.-A 83' 5460 <5 12

Tests on 4 '-hydroxyphenyl 4-hydroxybenzoate mesogen based coating

Continued .... Test Results

Salt Spray - (300 hr)

Bliεtering ASTM No Effect

Ruεting ASTM No Effect

Humidity - (300 hr)

Bliεtering ASTM No Effect

Ruεting ASTM No Effect

Test Results

Chemical Reεiεtance HCL - 10% - (300 hr) Bliεtering ' ASTM No Effect Color change Score No Effect Gloεε change Score No Effect Softening

(1 day recovery) Score No Effect

NaOH - 10% - (300 hr)

Bliεtering ASTM No Effect

Color change Score Trace

Gloεε change Score Trace

Softening Score Very slight Softening

(1 day recovery) Score Excellent

MEK (methyl-ethyl ketone) Rubs Cycles 45

Table 3 shows the Tg and size exclusion chro atography (SEC) , polydisperεity index

(PDI =_Mw_ wherein Mn is number average molecular weight Mn and Mw = weight average molecular weight) data measured for the 2/1 DGEBPA/diphenol epoxies. Tg's of the reεinε could not be obtained becauεe the resin εolutionε gelled when heated to remove εolvent. The mol. wt. and also the polydiεperεity index (PDI) of the meεogen baεed epoxy is higher than that of the Biεphenol-A baεed epoxy. The differenceε in Tg and mol. wt. and PDI may be due to the structural differences of the diphenols or differences in the network structure (branching) as stated previously.

The difference in mol. wt. and PDI εuggeεts that some branching is occurring during the syntheεis of the mesogen based polymer.

Table 3. TG and SEC data for 2/1 DGEBPA/diphenol based epoxies.*

Diphenol Tα (film*) Mn PDI

(1) 87* 920 5.8

Bis.-A 79 ^* 690 3.4

* cured wi th 10X tr .ethyt-snetetr.siTi.ne, 120*C/30m.n

Table 4 showε the cured film propertieε of amine cured 2/1 DGEBPA diphenol epoxieε. The modified epoxieε were cured with triethylenetetramine at 120 ^* C for 30 min. All fil ε (meεogen and Biεphenol-A baεed) diεplay excellent reverεe impact εtrength when cured with 7-15 wt.% amine. The meεogen baεed films are about 20% harder than the Bisphenol-A based films. All films have excellent acetone rub resiεtance.

Table 4. Cured film properties of 2/1 DGEBPA/diphenol baεed epoxieε.

* cured with triethylenetetramine »t 120*C for 30 min.

1. Reverεe Impact Strength

Reverse impact strength was determined by ASTM method D2794. A 4 lb. steel cylinder with a rounded head (5/8" diameter) is dropped through a vertical guide tube onto the coated steel panel, supported film side down on a steel

support Ring. Impact strength is defined as the maximum height (measured in in-lb) which the weight is dropped whic doeε not crack the coating.

2. Tukon Hardneεε

5 Film hardneεε waε determined using a Wilson model MO Tukon hardness tester— STM method D384. A diamond εhaped εcribe iε mechanically lowered onto the film for a set time (-30 sec). The εcribe reεts on the film with a 25 g load. The length of the indentation made on the film is meaεured 0 via a calibrated grid in the opticε of a viewing microscope. The length of the indentation on the film is converted uεing a standard, recognized table to Knoop hardneεε units.

3. Acetone Resistance 5 Acetone resiεtance of the cured filmε waε determined by rubbing a acetone εaturated Kim-Wipe over the surface of th film. The number of rubs to mar to disεolve the film iε reported. A value of >200 meanε that no effect waε obεerve after 200 + rubs. o The acetone rub resiεtance is a qualitative measure of the degree of crosε-linking of a polymer film. A low numbe of rubε (< 20) indicateε that the film iε not fully cured. A value of >200 indicateε that the film iε fully cured.

5

Table 5 shows the DSC and SEC data of the 3/2 diphenol/DGEBPA based polymers. The Tg of the

4'-hydroxyphenyl 4-_hydroxybenzoate mesogen based polymer is considerably higher (20'C) than that of the polymer _Q based on Bisphenol-A. The 4'-hydroxyphenyl

4-hydroxybenzoate mesogen based polymer is about 40% higher in mol. wt. than the Bisphenol-A based polymer. These differences in Tg and mol. wt. may due to the εtructural differences of the diphenols or differences in 5 the network structure (branching) as stated previously.

The 4'-hydroxyphenyl 4-hydroxybenzoate mesogen takes about 10 min to disεolve when the reaction temperature reacheε

175'C. Some intramolecular reactionε of epoxide and aliphatic OH groups of the DGEBPA resin may occur before (1) is disεolved.

Table 6 εhowε the cured film propertieε of the polymerε. The polymers were cured with HMMM reεin. All filmε (both 4'-hydroxyphenyl 4-hydroxybenzoate (1) and Bisphenol-A based) are .quite brittle aε reflected in the impact propertieε. All filmε have good hardneεε. The 4'-hydroxyphenyl 4-hydroxybenzoate meεogen baεed filmε are 20-25% harder than the correεponding Biεphenol-A based filmε.

Table 5. DSC and SEC data of 3/2 diphenol/DGEBPA reεin.

Table 7 εhowε the phyεical propertieε of the 1/1 4'-hydroxyphenyl 4-hydroxybenzoate meεogen/DGE-l,4-BD polymer. Thiε polymer waε prepared to see if it would be liquid crystalline since it is made from alternating

meεogenic and flexible spacer (DGE-1,4-BD) groups. The reεin εhowε no obεervable texture under a polarizing microεcope; it appearε to be completely amorphouε. From the large PDI it iε apparent that εome branching occurred during εyntheεiε. A significant amount of branching would decrease the ability of the oligomer to form the meεophaεe.

Table 7. Phyεical propertieε of 1/1 (1)/DGE-1,4-BD polymer.

_ Optical

To Mn PDI Texture

20' 2630 9.9 amorphouε

Table 8 εhowε the reεin and film propertieε of the 3/2DGE-l,4-BD/diphenol. The mol. wt. of the 4'-hydroxyphenyl 4-hydroxybenzoate meεogen baεed polymer iε εubstantially higher than the Biεphenol-A based polymer. The reεinε were cured with 25 wt.% Polyamide 840 (Ciba-Geigy) at 120*C for 30 min. Both filmε had excellent reverεe impact εtrength but were very soft.

Table 8. Resin and film propertieε of 3/2 DGE-1,4- BD/diphenol.*

The cured film properties of the meεogen baεed polymerε are εuperior to thoεe of the Biεphenol-A baεed polymerε. Reverεe impact εtrength of the mesogen based 1/1 diphenol/DGEBPA coating is excellent while the

Biεphenol-A based coating has very poor impact strength. Films based upon the diglycidyl ether of 4'-hydroxyphenyl 4-hydroxybenzoate indicated a superior utility. In the hard coatings studied the mesogen based films have εuperior hardnesε (15-25% harder than Biεphenol-A baεed filmε) .

EXAMPLE 2 This example concerns model alkyd reεins made by a synthetic procedure. The example involves grafting oligo eric esters of p-hydroxybenzoic acid (PHBA) or of PHBA/terephthalic acid (TPA) to alkyd resins so that liquid crystalline phases are formed. Here the objective is to demonstrate the uεefulneεε of L-C alkydε. Materials

Linoleic acid (Emersol 315, Emery Ind. Inc., equivalent weight 288) was dried with anhydrous Na ₂ S0 ₄ . Pyridine (Aldrich) was distilled and dried with anhydrous Na ₂ S0 ₄ . All other materials (Aldrich) were used as received.

Synthesis of Grafted Model Alkyds G1-G5 Synthesiε of grafted PHBA-modified alkydε is outlined in Fig. 1.

(A.) Preparation of unmodified alkyd Ul. A low molecular weight model alkyd, Ul, with 55% oil length and 22% OH excess was prepared from 25.00 g (0.0868 mol) of linoleic acid, 10.70 g (0.0722 mol) of phthalic anhydride, and 12.61 g (0.094 mol) of trimethylolpropane using the DCC-p-TSA process described by Kangas, S. and Jones, F.N. , "Model alkyd resinε for higher-solids coatings, I", J.

Coat. Technol.. 59(744), 89 (1987). DCC is dicyclohexyl carbodii ide. Yield was 85%. The OH value was 56 mg-KOH/g determined by the phthalic anhydride/pyridine method. (Bl.) Modification with succinic anhydride.

Alkyd Ul was heated with succinic anhydride (one mol per equiv OH) in pyridine at 80* C for 12 hr. The solution

waε concentrated; the reεidue waε diεεolved in CH ₂ C1 ₂ and waεhed with 10% aq. HC1. The CH ₂ C1 ₂ layer waε concentrated and the reεidue waε vacuum dried at 80 C. Yield of resin was above 90%; acid number waε 64 5 mg-KOH/g.

(B2.) Modification with terephthalic acid fTPA) . A εolution of 10.0 g (0.010 equiv) of alkyd Ul, 8.51 g (0.050 mol) of terephthalic acid (TPA) 2.27 g (0.011 mol) of DCC and 0.11 g of p-tolueneεulfonic acid 0 (p-TSA) in 150 ml of pyridine waε εtirred at 25 C for 12 hr. The mixture waε filtered to remove DCU (dimethylcyclohexylurea) and exceεε TPA. The filtrate waε concentrated, disεolved in CH ₂ C1 ₂ , waεhed with 10% aq. HC1 and concentrated aε above. Traceε of cryεtalline 5 material were removed by diεεolving the reεidue in 1/1 pentane/ethyl acetate, cooling in a freezer, filtering, reconcentrating and vacuum drying at 80 C. Yield waε 9.62 g of reεin; acid number waε 62 mg-KOH/g.

(C.) Grafting to form alkyds G1-G5. The o intermediate step of reacting alkyd Ul with succinic anhydride or with TPA iε deεirable to improve grafting efficiency. Thiε εtep convertε -OH groupε of Ul to -COOH groups; grafting to -COOH groups is more efficient. The εuccinic anhydride modified alkyd waε grafted or

₂₅ covalently bonded with PHBA uεing the DCC-p-TSA/pyridine proceεε. Weight ratioε (PHBA/alkyd) of 0.1, 0.2, 0.3 and 0.5 gave alkydε Gl - G4 reεpectively. For example, the εyntheεiε on alkyd G2 iε deεcribed:

A solution of 10.0 g (0.0114 equiv) of carboxyl-

₃₀ terminated model alkyd (prepared as described in Bl. above), 2.0 g (0.0145 mol) of PHBA, 3.14 g (0.0152 mol) of DCC, and 0.16 g of p-TSA in 120 ml of pyridine was stirred at 25 C for 12 hrs. The product (10.2 g, 85% yield) was isolated esεentially aε deεcribed immediately above in the

_ -3D,. TPA reaction.

TPA modified alkyd prepared as deεcribed in B2 waε covalently bonded by a similar procesε uεing a weight ratio (PHBA/alkyd) of 0.5 to give alkyd G5. Modification with TPA haε the additional advantage of putting half the structure needed for liquid crystal formation into place.

Synthesis of "Random" Model Alkvds R1-R3

A serieε of random model alkydε Rl, R2 and R3 containing 15%, 22% and 27% by weight in the feed were prepared from linoleic acid, phthalic anhydride, tri ethylolpropane, and PHBA in a εingle εtep by the

DCC-p-TSA proceεs. These weight percents correεpond roughly to the weight percentε of PHBA actually incorporated in alkyds G2, G3 and G4, respectively. For example, preparation of R3 is described:

A solution of 5.5 g (0.0190 mol) of linoleic acid, 2.54 g (0.017 mol) of phthalic anhydride, 2.91 g (0.022 mol) of trimethylolpropane, 4 g (0.029 mol) of PHBA, 12.24 g (0.060 mol) of DCC, and 0.612 g of p-TSA in 200 ml of anhydrous pyridine were mixed in a 250 ml flask for 12 hrs. at 25 C. Alkyd R3 waε isolated essentially as described above in the TPA reaction.

Alkyd Structure Characterization ¹ H-NMR εpectra were determined at 34 C uεing a

Varian Aεsociates EM 390 NMR spectrometer with Me ₄ Si as internal standard. IR εpectra were recorded on a Perkin-Elmer 137 εpectrophotometer uεing a 20 weight percent solution in CH ₂ C1 ₂ . Differential scanning calorimetry (DSC) was effected with a du Pont model 990 thermal analyzer at a heating rate of 20 C/min using samples that had been vacuum dried at 80 C to constant weight. Tg was asεigned as the onset of the endothermic inflection. Clearing points (T _cl ) of L-C phaseε were aεεigned aε the maxima of the endothermic peaks.

Equivalent weight per carboxyl group waε determined by titration of pyridine solution with KOH/CH ₃ OH to the phenolphthalein end point.

Number average molecular weight (M _n ) , weight average molecular weight _y ) , and polydiεperεity index (PDI = _y M _jj ) were meaεured by gel permeation chromatography (GPC) in tetrahydrofuran uεing a Waterε model 510 pump, a R401 refractive index detector and a model M730 data module; columnε were Ultraεtyragel 100 A, 500 A, 10 ³ A, and 10 ⁴ A. Monodiεperse polyεtyrene calibration εtandards were used.

Optical textures were examined with a Leitz D-6330 polarizing microscope equipped with a Reichert hot stage. Grafting efficiency (GE%) and average number of

PHBA units per COOH were estimated from equivalent weight difference as described in Chen, D.S. and Jones, F.N. , "Graft-copolvmers of p-hydroxylbenzoic acid. Part I. A general method for grafting meεogenic groupε to oligomerε". J. Polym. Sci.. Polv . Chem. Ed.. Vol. 25, pg. 1109-1125 (1987).

Measurement of Viεcoεity and Tests of Films Properties Solution viscosity was measured in xylene using an ICI cone and plate viscometer at 25'C. Films were prepared by dissolving or dispersing resinε and drierε in xylene and casting films on untreated rolled steel panels by a casting bar to give the dry thickness of 0.5 ml. Dry-to-touch time was measured according to ASTM

D1640. Film propertieε were meaεured after 7 days of drying at ambient temperature. Reverse impact resistance and pencil hardness were measured according to ASTM D2794 and D3363 respectively; resiεtance to acetone was measured by the number of double rubs to remove trace of film with paper tissue after the dropping of acetone on the dry film. Extractability was measured by subjecting

cured filmε to 8 hr. in a Soxhlet extractor uεing tetrahydrofuran.

The equivalent weight per carboxyl, M _n , _y , PDI, and number average PHBA unitε per carboxyl of the control alkyd and the PHBA-grafted alkydε are shown in Table 9. As PHBA content increaseε equivalent weight, M _n , and M _y increaεe in proportion to the mass of PHBA grafted but no more; PDI remains nearly constant. These results indicate that little or no coupling of molecules occurs during grafting. Data for "random" alkyds Rl - R3 are shown in Table 10.

Table 9. Characterization of ungrafted alkyd Ul and PHBA-grafted Gl - G4:

Ul Gl G2 G3 G4

* After grafting with εuccinic anhydride.

** Before grafting with εuccinic anhydride.

*** Clearing temperature.

Table 10.

IR spectra of the PHBA grafted alkyds are characterized by two sharp peaks at 1610 and 1510 cm ^"1 . ¹ H-NMR spectra show complex peaks in the range of 7.0 - 8.0 ppm. These spectral features are characteristic of PHBA grafted polymers. IR of random alkyds Rl - R3 also showed two sharp peaks at 1610 and 1510 cm ^"1 .

Onset Tg (by DSC) of the unmodified alkyd Ul was -29 C; PHBA-grafted alkyds Gl - G5 had onset Tgs at -24, -20, -15, -10, and +17 C, respectively. DSC traces of the alkyd Ul and grafted alkyds Gl - G3 were featurelesε except for the inflection assigned to Tg and the broad exothermic peaks due to thermal cross-linking. DSCs of alkyds G4 and T5 had sharp endothermic peaks at 190* and 225 ° C , reεpectively; these peaks are attributable to the clearing temperature ( _c ^) of the L-C phaεeε. DSC thermogra ε of random alkydε Rl - R3 are εimilar to thoεe of alkydε Ul, Gl, G2, and G3, no endothermic peakε appeared. Tgε of Rl, R2, and R3 were -23, -18, and -12 C, reεpectively.

Optical textureε of the dried filmε were examined under a polarizing microεcope with a hot εtage. Films of alkyds Ul, Gl - G3 and Rl - R3 had no visible L-C phaseε. However, L-C (meεomorphouse) phaεeε were clearly viεible in films of alkyds G4 and G5. The L-C phase in films of alkyd G4 disappeared when the specimen was heated above 190*C and reappeared quickly as it was cooled to around 190*C.

Viscosity and Appearance of Solutions and Dispersions

Alkyds Ul, Gl - G3 and Rl - R3 appeared soluble in commercial xylene at all concentrations. In contrast, alkyds G4 and G5 formed stable, opaque disperεions in xylene at concentrationε of 5 wt% or higher.

The relationship between viscosity and PHBA content of 70/30 (w/w) mixtures of alkydε Gl - G4 and Rl - R3 in xylene waε investigated. Viscoεity increaεes with increasing PHBA content for alkyds Gl - G3, but it drops sharply for alkyd G4. This drop iε preεumably aεεociated with the tendency of alkyd G4 to form non-aqueouε diεperεions. On the other hand, "random" alkyd R3, whose overall composition is similar to that of G4, has the highest viεcoεity in the series. Dry Time and Film Properties

As shown in Table 11. all PHBA-grafted alkydε dried faster than unmodified alkyd Ul, and drying speed increased with PHBA content. Acceleration of drying is by far the greatest for L-C alkyds G4 and G5. The latter dried very rapidly (in 5 minutes) . Aε εhown in Table 12. the drying εpeed of "random" alkydε Rl - R3 alεo increaεed with the PHBA content, but the effect waε much ε aller than obεerved for their grafted counterpartε G2 - G4. Coatingε made from all alkydε had good adheεion.

Films made from alkyds Ul, Gl G3 and Rl - R3 were glosεy and tranεparent, while film from alkydε G4 and G5 were gloεεy and tranεlucent.

Aε εhown in Table 11. seven-day old films of PHBA-grafted alkyds Gl - G5 had better reverεe impact reεiεtance, were harder, and had slightly better acetone reεiεtance than alkyd Ul. All theεe film properties are favored by higher PHBA content. Alkyd G4 had the beεt balance of propertieε, while alkyd G5 waε the hardest.

Table 11.

Dry-to-touch timeε and film propertieε of Ul and grafted alkydε Gl - G5:

film propertieε

* dryerε = 0.05% Co-naphthenate + 0.15% Zn-naphthenate by weight per reεin. D = day, H = hour, M = minute. GL = glosεy, TP = tranεparent, TL = tranεlucent.

Hardneεε and solvent resiεtance of filmε made from "random" alkydε Rl - R3 improved with increaεing PHBA content (Table 12) . On the other hand, impact strength decreased with increasing PHBA content.

Table 12.

Dry-to-touch times and film properties of "random alkydε" Rl - R3:

Rl R2 R3

Dry time* 5 H 4.5 H 3.5 H

Film Propertieε

Hardneεε HB HB H reverεe impact εtrength

(in-lb) crosεhatch adheεion

10

Reεiεtance to acetone

(number of rubε) film appearance

* dryerε = 0.05% Co-naphthenate + 0.15% Zn-naphthenate 15 per reεin.

H = hour, GL = Gloεεy, TP = Tranεparent.

The data of the above example indicateε the improvementε made in an alkyd coating and reεin when meεogenic groupε are covalently bonded to the alkyd.

20

EXAMPLE 3

Thiε example reportε use of mesogenic groupε to modify acrylic polymerε. The experimental approach waε to prepare εeveral series of -COOH functional acrylic

25 copolymers in which molecular weight, Tg, and functionality were varied and then to graft p-hydroxybenzoic acid (PHBA) to the -COOH groups. The PHBA groups were the mesogenic groups which imparted the desired L-C characteristics.

₃₀ Two types of L-C acrylic polymers were synthesized. In type A the PHBA was grafted to -COOH groups attached directly to methyl methacrylate/butylacrylate/methacrylic acid (MMA/BA/MAA) acrylic copolymer backbones. In type B an 8-unit

_,. flexible spacer was placed between the copolymer backbone

and the PHBA. The behavior of these copolymers as film for erε waε inveεtigated.

Materials. Monomers were distilled before use. Pyridine was distilled and then dried by stirring with anhydrous Na ₂ S0 ₄ . All other reagents (Aldrich) were used as received.

Preparation of COOH-Functional Acrylic Polymers

COOH-functional acrylic polymers were prepared as substrates for grafting by radical copolymerization in toluene at 90 ^* - 100'C under monomer starved conditions aε deεcribed by R.A. Gray, J. Coat. Technol.. 57, 83 (1985), uεing azobiεiεobutyronitrile (AIBN) aε initiator. Subεtrateε for Type A copoly erε were co poεed of methyl methacrylate (MMA) , butyl acrylate (BA) , and acrylic acid (AA) or methacrylic acid (MAA) . Subεtrateε for Type B copolymerε were compoεed of MMA, BA, and 2-hydroxyethyl methacrylate (HEMA) ; they were modified to become COOH-functional by treatment with stoichiometrically equivalent amount of succinic anhydride in pyridine at 80'C. The following is an example for the preparation of a COOH-functional acrylic polymer of Type B:

(a) . Polymerization: Toluene (57 g) was placed in a 250-ml, 3-neck flask, heated in an oil bath and stirred mechanically. A solution of 32.68 g (0.255 mol) of BA, 22.03 g (0.22 mol) of MMA, 3.25 g (0.025 mol) of HEMA, and 0.57 g of AIBN was added dropwise during 3 hr with continuous stirring. Temperature was maintained at 95' to 100'C during addition and for 2 hr. thereafter. A solution of 0.2 g of AIBN in 10 g of toluene was added during 10 min, and the temperature was maintained for 1 hr. The solution was concentrated on a rotary evaporator and was vacuum dried at 80*C. The residue

(polymer B6) had 5 mol % OH functionality (calcd) , a Tg of 10'C (calcd) and Mn of 15,400 (meaεured by GPC) . Acrylic copolymers of type A were prepared similarly.

(b) . Modification with succinic anhydride: A solution of 11.45 g (0.005 eq OH) of the above polymer and 0.50 g (0.005 mol) of succinic anhydride in 50 g of pyridine was εtirred and heated at 80'C for 12 hr. The solution was concentrated; the residue was disεolved in CH ₂ C1 ₂ and waεhed with 10% aq. HC1. The CH ₂ C1 ₂ layer waε concentrated and the reεidue waε vacuum dried at 80'C. Yield waε 92%. Acid number was 24.

Grafting with PHBA Both types of COOH-functional acrylic copolymers were grafted with PHBA in pyridine at 100*C for 36 hr by the DCC-p-TSA procesε. Ratioε of mol of PHBA to equiv of -COOH ("equivalent ratioε") were 3.5, 5.5, and 7.0 in order to vary the length of the grafted PHBA εegmentε. The PHBA-grafted productε of Typeε A and B were designated GA and GB respectively. The procedure is exemplified by the grafting of succinic anhydride-modified polymer B6 at equivalent ratio of 7.0:

A solution of 11.80 g (0.005 eq COOH) of polymer B6, 4.84 g (0.035 mol) of PHBA, 7.94 g (0.0385 mol) of dicyclohexycarbodiimide (DCC), and 0.40 g of p-toluenesulfonic acid (p-TSA) in 150 g of pyridine waε stirred at 100*C for 36 hr. The mixture waε filtered to remove urea of DCC (DCU) and PHBA oligomers. The filtrate was concentrated, disεolved in CH ₂ C1 ₂ , waεhed with 10% aq. HCl, and concentrated. Traceε of cryεtalline contaminateε were removed by diεεolving the reεidue in 1:1 pentane-ethyl acetate, cooling in a freezer, filtering, reconcentrating, and vacuum drying at 80 ^* C. Yield was 85%. The combined crystalline by-products weighed 9.40 g after vacuum drying at 80'C to constant weight. Grafting efficiency (GE%) was estimated to be 70% indicating an

average length of PHBA grafts (IPHBA/CODH) of 4.9 PHBA units.

Grafting was effected to give L-C copolymers of Types GA and GB. Theεe types differ in that the mesogenic PHBA-grafts are attached directly to the polymer backbone of Type GA copolymers while Type GB copolymers have eight-atom flexible spacers between the polymer backbone and the mesogenic grafts. Individual copolymers were numbered as shown in Tableε 13 to 19. Grafting efficiency (GE%) waε determined gravimetrically. It ranged from about 85% to about 70%. Aε expected, GE% decreaεed as the COOH equivalent ratio of PHBA/acrylic increased.

Average #PHBA/COOH ratios were calculated from GE%. In order to achieve *PHBA/COOH ratios of 3 + 0.2, 4 + 0.2, and 5 + 0.3 it proved necesεary to feed PHBA monomer in the ratio of 3.5, 5.5 and 7.0 moleε, reεpectively, to the grafting reaction.

Structure Characterization ^-H- R εpectra, IR spectra, differential scanning calorimetry (DSC) , optical textures under polarizing microscope, M _n , M _y , polydisperεity index, and average #PHBA/COOH ratio were determined aε described in Chen and Jones. The term "#PHBA/COOH ratio" refers to the number average degree of polymerization of PHBA graft segments actually incorporated in the graft copolymer.

X-ray spectra were recorded with a Philip wide angle diffracto eter at 25"C. Sampleε for X-ray diffraction studies were dissolved or dispersed in acetone, cast on glass slides, and vacuum dried at 80*C for 12 hr.

Measurement of Viscosity Viscosity was measured using an ICI cone and plate viscometer (shear rate 10 ^* * s" ¹ ) at 25'C.

Samples were dissolved or thoroughly dispersed in methylisobutylketone (MIBK) before measuring.

Obεervation of Solution Appearance Sampleε were diεεolved or diεpersed thoroughly in MIBK and then put in test tubes. Appearance was observed when the teεt tubeε were immerεed in an oil bath and equilibrated, at different temperatureε. Optical textureε of εome L-C polymer diεperεionε were examined under polarizing microεcope. at 25'C.

Tests of Film Properties Samples were disεolved or diεperεed in MIBK and caεt on untreated cold rolled εteel panelε by a casting bar to give the dry film thicknesε of 1.0 ml. Reverεe impact εtrength and pencil hardness were measured according to ASTM D2794 and D3363, respectively. Characterization of Polymer Structures The IR spectra of the PHBA grafted acrylics have sharp peakε at 1610 cm ^"1 and 1510 cm ^"1 aεεignable to the para aromatic C-H εtretching. These two peaks are characteriεtic of oligo-PHBA grafted polymers. They are absent in the ungrafted acrylicε. ^-N R εpectra of the PHBA-grafted acrylicε εhow multiple peakε in the range of 7.0 - 7.3 pp and 8.0 - 8.3 ppm, aεεignable to the aromatic protonε ortho to the OH group and to the COOH group, reεpectively. They are abεent in the ungrafted acrylicε.

Characterization of Microεtructure Polarizing icroεcopy, differential scanning calorimetry (DSC) , and wide angle X-ray diffraction (WAXS) were uεed to further characterize the microεtructureε of the graft copolymerε in the bulk phaεe. Results (Tables 13 and 14) were consiεtent with aεεignment of L-C icrostructure to all polymers except GA21a-c.

Table 13.

Compoεitionε of type A acrylic εubεtrateε and type A PHBA-grafted acrylic copolymerε-

(a) . Type A acrylic εubεtrateε: al . The -MMA-BA- AA- series

(b) . Type GA PHBA-grafted acrylic copolymers: fbl) . series from -MMA-BA-AA-

# #PHBA/COOH PHBA content Tg ∑ _cl _ LC phase*

(wt %) (*C, measured)

20.0 -2 173 smectic 21.0 -4 175 smectic 21.0 -2 174 smectic 20.3 -3 174 smectic 20.0 -2 173 smectic 20.7 -4 174 smectic 20.3 7 173 ε ectic 29.0 9 174 εmectic 33.6 14 181 εmectic 19.8 4 175 εmectic

*—according to optical texture.

(b2) . Series from -MMA-BA-MAA-

§ IPHBA/COOH PHBA content T ₄ _ -Ξm-∑cl ^LC Phase*

(wt %) (*C, meaεured)

25.2 16 147 crystal 30.1 22 186 crystal 34.0 25 210 crystal 20.3 15 165 smectic 23.2 18 175 smectic 27.6 20 184 smectic 14.0 14 162 smectic 17.4 15 173 smectic 21.1 17 178 smectic

*—according to optical texture.

Table 14.

Compoεitionε of type B acrylic εubεtrates and type GB PHBA-grafted acrylic copolymerε—

(a) . Type B acrylic εubεtrateε

# mol fraction Tg Mn

(MMA/BA/HEMA) (*C, calcd.)

#PHBA/COOH PHBA content ϊg ∑ _c LC phase*

(wt %) (*C, measured)

*—according to optical texture.

The shear viscoεitieε (εhear rate 10 ⁴ s ^"1 ) of MIBK solutionε of three ungrafted acrylic copolymerε and of a diεperεion of an L-C graft copolymer derived

from one of them aε a function of concentration were studied. The ungrafted copolymerε (Bl, B2, and B6) differ only in Tg (-10, 0, +10 ^* C, reεpectively) ; all three have M _n of about 15,000 and functionality of 5 mol %. L-C copolymer GB1 waε prepared by grafting Bl with an average #PHBA/COOH ratio of 5.0. Aε expected, solution viscosities of ungrafted copolymers increase moderately aε Tg increaεeε. However, viεcoεity of GB1, an aniεotropic diεperεion throughout most of the concentration range studied, was subεtantially lower than that of the copolymer from which it waε made. The viscosity range 0.1 to 0.2 Pa.s (a viscosity suitable for spray application of coatings) was attained at about 40 to 45 wt. % with the ungrafted polymers and at about 45 to 50 wt. % with L-C copolymer GB1.

The effect of #PHBA/COOH ratio on viscoεity waε studied. B2 iε an ungrafted acrylic copolymer with M _n of about 15,000, Tg of O'C, and functionality of 5 mol %. GB2a and GB2b are L-C graft copolymerε prepared from B2 with actual #PHBA/COOH ratios of 4.8 and 3.2, respectively. Again, viscoεitieε of aniεotropic diεperεionε of the grafted copolymerε were εignificantly lower than solutionε of the copolymers from which they were made. It appears that increaεing #PHBA/COOH ratio εlightly reduceε viεcoεity of the diεperεions. Viscoεity of diεperεionε of a third L-C copolymer in thiε εerieε, GB2c ( PHBA/COOH ratio = 4.1) was intermediate between GB2a and GB2b.

The behavior of L-C copoly er/MIBK mixtures depended on temperature, concentration and #PHBA/COOH ratio. Behavior of two copolymers, GB2b (#PHBA/COOH = 3.2) and GB2a (#PHBA/COOH = 4.8) are from the same acrylic copolymer substrate; they differ only in #PHBA/COOH ratio. Both copolymers formed transparent isotropic "solutions" (A) at low concentrations and/or at elevated temperatures. At lower temperatureε both

copolymers formed biphasic εtateε (B) and anisotropic stateε (C) at high concentrationε. Thiε εort of behavior iε typical of lyotropic L-C polymerε. Increaεing IPHBA/COOH ratio from 3 to 5 decreaεes solubility, shifting the phase diagram by about 10 wt% as shown. ■fPHBA/COOH ratio strongly affected the concentrationε at phaεe boundrieε. Aε #PHBA/COOH ratio increaεeε the phaεe boundarieε εhift to lower concentrationε. Temperature alεo affect the phaεe boundarieε. For example, both the biphaεic εtate and the anisotropic εtate become isotropic (i.e., they "clear") when heated. The clearing temperatures increaεed aε the #PHBA/COOH ratioέ increaεed.

Propertieε of caεt filmε of εelected L-C acrylic copolymerε were compared with thoεe of a εerieε of ungrafted, amorphouε acrylic copolymerε (Al - A10) . Three empirical indicatorε of film propertieε were uεed: croεεhatch adheεion, reverεe impact reεiεtance and pencil hardneεε. Adheεion waε good in every caεe; other reεultε are εhown in Table 15.

Film propertieε of the amorphouε copolymerε were poor. When calculated Tg waε below 25'C, the filmε were very εoft, and when it waε higher they were very brittle. When ϊ? _n waε below 30,000 impact reεiεtance was negligible regardlesε of Tg. Copolymer A10 (M _n = 39,500 and Tg = +10*C) had the beεt propertieε in the εerieε, although filmε are too εoft for practical uεe.

Film propertieε of representative L-C copolymers were substantially better than those of amorphouε counterparts (Table 15) . Reverεe impact resistance of 65 to 80 in-lb is attainable with backbone M _n as low as 15,000, and pencil hardnesε of H to 3H is attainable with Tg as low as -10'C.

Table 15.

Comparisons of film properties between amorphouε and LC acrylic copolymers:

Note: functionality of all the above polymerε iε 5% by mol.

It iε evident from the above reεults that films made from L-C acrylic copolymers can have subεtantially better hardneεε and impact reεistance than those made from comparable amorphouε copolymerε.

Preliminary Guidelineε for LC Copolymer Deεign - Having eεtabliεhed that liquid crystallinity can dramatically improve film properties, a εecond objective waε addreεεed to develop preliminary guidelineε for copolymer design to optimize film properties of non-crosε-1inked acrylic coatings. Variables studied included M _n , Tg, functionality (number of graft segments) , flexible εpacer effects, and fPHBA/COOH ratio (length of graft segments) . Results are shown in Tables 16 through 20.

Effectε of M n of ungrafted and grafted acrylic copolymer backboneε are εhown in Table 16. Tg, _c ^, and adheεion were esεentially independent of M _n regard- lesε of the presence or absence of flexible spacer. However, reverse impact resiεtance and hardneεε increased greatly with M _n . L-C copolymers with backbone M _n of 15,000 and 28,000 had excellent reverse impact resiεtance (> 70 in-lb) and good hardneεε (H - 2H) when Tg, functionality, and #PHBA/COOH ratio were optimal.

Table 16.

Effectε of acrylic backbone Mn on the film propertieε of LC copolymers:

(a) . Copolymers with flexible spacer:

(b) . Copolymers without flexible spacer:

Backbone #PHBA/ T , . T, Rev . Imp . Hardnesε Croεεhatch ^{"n C00H} S Su ed (in-lb) adheεion

Note: The functionality of all the acrylic polymers is 5% by mol .

Tg effectε for graft copolymerε having a functionality of 5 mol % are shown in Table 17. It can be seen that grafting oligo-PHBA has only a εlight effect on Tg of the amorphous backbone of the copolymer, increasing it by about 'to 5'C. Backbone Tg has only a modest effect on clearing temperatures (T _c ^) of the esophaεeε; _c ^ increaεed by 6*C aε backbone Tgε increaεed from -10* to +10*C. However, backbone Tg substantially affected the empirical film properties. Reverεe impact reεiεtance ranged from poor (< 10 in-lb) when backbone Tg was 10'C to excellent (> 80 in-lb) when Tg was -10'C. Hardnesε increaεed with backbone Tg.

Table 17.

Effectε of the acrylic backbone Tg on the film propertieε of the LC acrylics:

functionalitieε are compared. While the reported data were obtained for L-C copolymerε with backbone Mnε of about 5,000, similar trends were observed for higher M _n s. It can be εeen that increaεing functionality increased Tg and T _c ^. Increasing functionality increased hardnesε but had an adverse effect on reverse impact resistance. In general, films with functionality above 7.5 mol % had poor reverse impact resistance.

Table 18.

Effectε of functionality on the film propertieε of the LC acrylic copolymerε:

Noteε: Mn of acrylic backboneε iε 4,800 + 300 and calcd T iε OC.

The effectε of the preεence of flexible εpacer between the acrylic backbone and the oligo-PHBA εegmentε are exemplified in Table 19. The flexible εpacer reduceε the effect of grafting on Tg. Impact reεiεtance improved when flexible spacer was present. However, the effect of flexible εpacer on reverse impact resiεtance appeared less εubεtantial when the backbone Tg waε decreaεed to about -10*C. Films with flexible εpacer were εlightly εofter than thoεe without one.

Table 19.

Effectε of flexible εpacer on the film propertieε of the L acrylic copolymerε:

# To fC) T _c τ J.PHBA/COOH Rev.Imp. Hardneε Backbone After (C) (in-lb)

Grafting (calcd) (meaεured)

Effectε of #PHBA/COOH ratio are exemplified in Table 20. Aε thiε ratio increaεed, Tg (after grafting) increased slightly, T _c ^ of L-C phase increased εignifi- cantly, reverεe impact reεiεtance increaεed greatly, and hardneεε increaεed εlightly.

Table 20.

Effectε of average #PHBA/COOH on the film properties of LC acrylics:

Notes—1. TL = translucent; OP = opaque.

2. Acrylic backbone: M_ = 15130, calcd Tg = 0 C, and functionality = 5% by mol.

Appearance of filmε were alεo greatly influenced by the PHBA/COOH ratio. At functionality of 5 mol %, films were tranεlucent when thiε ratio waε about 3, but they were opaque when it waε 4 or above.

To εummarize the obεervations in this example, it appears that the following guidelines may be uεeful in deεigning L-C acrylic copolymerε for coatingε binderε: (1) Tg of the amorphouε part of the copolymer may be low; the optimum for a given end uεe may be in the range of -20* to 0* C. Amorphouε copolymerε of εuch low Tg are normally far too soft to be usable as coatings. Acrylic lacquers are usually formulated with Tg near or εlightly above the highest service temperature. Apparently the presence of L-C domains can harden low Tg filmε, yet the elaεticity aεεociated with low Tg iε at leaεt partly retained.

(2) The best combination of hardness and elasticity is attained when functionality is low but PHBA/COOH ratio is high.

(3) Flexible εpacer improveε impact resistance when backbone Tg is O'C or higher but has relatively little effect when Tg is -10'C. Introduction of flexible spacer by the method used in this study has the disadvantage of placing relatively unhindered ester groups between the acrylic backbone and the mesogenic group; these ester groupε are relatively vulnerable to hydrolyεiε in water and weather. Other potential routes for introducing flexible εpacers are costly. Thus for practical purposes it may be preferable to use low Tg backbones and dispenεe with flexible εpacer. EXAMPLE 4

In this example it will be demonstrated that the L-C acrylic copolymers of Example 3 can be cross-linked with a melamine resin to provide hard, tough enamels. Amorphous acrylic copolymers composed of MMA, BA, and acrylic acid having calculated Tg of -30', -10", and +10*C and M _n of 4,700 + 200 and functionality of 5 mol percent acrylic acid were syntheεized aε deεcribed in Example 2. Each waε grafted with PHBA, aε deεcribed, to provide L-C graft copolymerε having PHBA-COOH ratioε of 4 + 0.2. Liquid cryεtallinity waε confirmed by polarizing miεcroεcopy.

Each of the above copolymerε waε diεεolved or diεpersed in a methyl iεobutyl ketone solution containing HMMM crosεlinking reεin and p-toluene εulfonic acid (p-TSA) catalyεt. The weight ratio waε 70.6/28.6/0.7 L-C copolymer/HMMM/p-TSA. The mixture waε expoεed to ultraεonic energy to promote mixing. It waε caεt on untreated cold, rolled εteel panelε and baked in a forced air oven for 30 minutes at 150'C to give a cured film.

Knoop hardneεε and reverεe impact reεiεtance of the 6 enamelε were teεted aε deεcribed in Example 2. Reεultε are εhown in Table 21.

Thuε, it iε evident that the preεence of meεogenic groupε improved both hardneεε and impact reεiεtance for enamelε made from copolymerε having Tgε of -30" and -lO'C. When Tg iε +10, the impact reεiεtance of the L-C film iε inferior but the finish is extraordinarily hard. For comparison, the hardnesε of current auto topcoat enamelε iε about about 12 Kn. In other experimentε it waε determined that the optimum M _n for HMMM crosslinked L-C copolymerε for high-εolidε enamelε iε about 5,000. Aε εhown in Example 2, higher molecular weightε are deεirable for uncroεslinked enamels.

EXAMPLE 5 L-C telechelic oligoester diolε are prepared and croεε-linked with a reεin, preferably a melamine reεin, to provide the coatingε of thiε example. After baking, the coatingε retained their L-C character which provided the improved characteriεticε to the coatings. The properties of the coatings were tested on cold-rolled steel panels.

The ratio of L-C telechelic oligoester diols to resin should be in the range of 95:5 to 50:50, and is

preferably about 70:30. The L-C oligoeεter diolε were prepared by reacting 4,4 ^, -terephthaloyldioxydibenzoyl (TOBC) with molar equivalentε of aliphatic diols. Non-liquid crystal diols (2a-g) were prepared for comparison, the L-C and non-L-C diols having the general formula:

•• ^R =" ^~ ^5)— ^{for la} to g , R s ~(CH ₂ ^- for 2a to g n s 10 12

The value of n, sometimes referred to as spacer length, should preferably be in the range of 5 to 12. hen n = 5 or lesε, there iε poor miεcibility in forming enamelε and at higher n valueε mixing becomeε increaεingly difficult.

Coatingε were prepared by mixing the L-C oligoeεter diolε or polyolε after εolubilization with melamine or polyiεocyante reεin in the preεence of an accelerator. The coatings were cast on panels and baked at cross-linking temperatures for teεting. L-C oligoeεter polyolε may be prepared by replacing part of the aliphatic diol with a triol or tetrol. Teεting.

Proton NMR εpectra were recorded at 34*C on a Varian Associateε EM-390 90 MHz NMR εpectrometer, using Me ₄ Si aε internal standard. IR spectra were recorded at 25'C on a Mattson Cygnus FT-IR uεing films cast on NaCl plates with polyεtyrene aε εtandard. A DuPont model

990 thermal analyzer waε uεed for differential εcanning calorimetry (DSC) at heating rateε of 10/min. After the cryεtalline-meεophaεe tranεition temperature (T _m ) waε reached, the temperature waε held for 1 min. before the scan was resumed. Capillary melting points were used to confirm the thermal data. M _n and M _y were determined by gel-permeation chromatography (GPC) with a Waters model 520 pump equipped with a model R401 refractive index detector, a model M730 data analyzer, and Ultraεtragel 100 A, 500 A, 1000 A, and 10000 A columnε. Maεε analyεiε waε performed. A Leitz Labolux microεcope equipped with a polarizing filter waε used for optical micrographs at 500x magnification; diols were observed immediately after heating to T _m , enamels were observed at room temperature.

Seven sampleε of the L-C oligoeεter diolε were prepared and deεignated la to lg, incluεive and, for compariεon, εeven εampleε of non L-C oligoeεter diolε were prepared and deεignated 2a to 2g, incluεive, having correεponding n valueε and made into amorphouε coatingε. Theεe correεponding n valueε are indicated, aε above. In the preparation of the productε, reagent materialε were uεed and the εteel panelε which were coated were commercially available cold-rolled εteel panelε εold under the trademark Bonderite 1000 and having a εize of 3 incheε by 9 incheε by 24 GA. Preparation of la-g.

TOBC waε prepared from terephthaloyl chloride and p-hydroxybenzoic acid (PHBA) aε deεcribed by Bilibin et al at Polymer Science USSR (1984) 2 , 2882. TOBC

(0.005 mol), diol (0.025 mol), and diphenyl oxide (10 L) were placed in a 100 mL εingle-necked round-bottomed flaεk equipped with a magnetic εtirring bar, a diεtillation adapter, and a εeptu . The flaεk waε flushed with argon for 15 min. , and was stirred and heated in an oil bath at 190-200'C under slow argon

flow. The reaction mixture became ho ogeneouε after 5 minuteε and the evolution of HCl waε observed. The reaction was continued until the evolution of HCl was no longer detectable by moistened litmus paper (405 hr.). The hot reaction mixture was poured cautiously into 100 mL of toluene and cooled. The oily residue that separated was dissolved in CH ₂ C1 ₂ , washed 3 times with water, and dried over anhydrous MgS0 ₄ . The εolution was filtered and concentrated using a rotary evaporator. The residue waε precipitated from methanol. Yields were 87-92% baεed on TOBC ¹ H NMR for lc in CDC1 ₃ ; 1.4 (broad), 3.6 (triplet), 4.2 (multiplet) , 6.8 (doublet), 8.1 ppm (multiplet). FT-IR for lc: 3420, 2960, 2938, 1720,1606, 1512 cm ^"1 . L-C diolε la-g had εimilar εpectra.

For compariεon to the L-C oligoester diols of this example, non-L-C oligoester diols were prepared from diolε in which R = (CH ₂ ) ₄ and made into amorphouε coatingε. Preparation of 2a-g.

The diacid chloride precurεor waε prepared by substituting adipoyl chloride for terephthaloyl chloride in Bilibin's procedure. Reaction of this precursor with diols waε carried out aε deεcribed for la-g except that the productε were not poured into toluene. Diols 2a-g were reεinous solids which solidified on standing. Enamel formation.

Oligoeεter diols lb-g and 2a-g, HMMM [hexakis (methyloxy-methyl) melamine resin], methyl isobutyl ketone (MIBK) , aε a εolvent and p-toluenesulfonic acid (p-TSA) as a catalyst were thoroughly mixed in a 70/30/30/0.3 wt. ratio. The εolution was cast on cold rolled steel panels and baked at 150C for 30 minutes. Lesε soluble L-C diols le-g were melted, dispersed in εolvent, mixed with HMMM and immediately cast as films.

Oligoester Diols. The physical properties of la-g obtained by GPC, DSC and polarizing optical microscopy are summarized in Table 22.

Table 22. - Physical Properties of la-g

diol n M _τh ^a Mn M _{y ppi} T _ffi T. texture la 4 550 480 720 1.5 110 204

H NMR and 1R εpectra were consistent with εtructureε la-g and 2a-g assuming that partial chain extension occurred as indicated by GPC. Low M _n valueε and εlightly high H analyεeε εuggeεt that εmall amountε of unreacted HO(CH ₂ ) _n OH were preεent in the productε.

The L-C nature of la-g waε demonεtrated by DSC in which two firεt order tranεitionε were obεerved; the cryεtalline- eεophaεe tranεition temperature (T _m ) , and the eεophaεe-iεotropic tranεition temperature (T^) . The thermal data revealed an odd-even εpacer effect for

T _m . S ectic-nematic tranεitionε were not evident in the DSC.

In contraεt, diols 2a-g were apparently not L-C materials. Only one first order transition waε obεerved _{by DSC}

The meεophaεeε of la-g were obεerved in polarized optical micrographε taken immediately after melting the εample. Textureε were identified by comparing appearance with publiεhed micrographs. See: Noel, Polymeric Liquid Crystalε, Plenum Press, New York,

(1984). A nematic texture iε observed for If, while more highly ordered εmectic textureε are obεerved for lb-e and lg. Cryεtalε were obεerved by microεcopy for diolε 2a-g. Croεs-1inked Enamels. Diols lb-g and 2a-g were crosε-linked with HMMM at 150'C, which fallε within the temperature range at which lb-g are liquid cryεtalline. Enamel formation of la waε nearly impoεεible becauεe of itε poor miεcibility. The propertieε of the crosε-linked enamelε are εummarized in Table 23.

Table 23.

Propertieε of Enamelε Prepared from lb-g and 2a-g. Diol: HMMM:p-TSA 70:30:0.3 by wt., cure cycle 150/30 min.

5B is 100% croεε-hatch adheεion; units are 1/1000 in.; ^c onεet of tranεition, determined by DSC.

Aε εhown in Table 23 , all enamelε had excellent adheεion, solvent resiεtance, and flexibility. The L-C enamelε were far εuperior to control enamelε in both hardneεε (5H-6H vs. H-2H) and impact resiεtance (50 to 80 in-lb vs. 8 to 15 in-lb). The odd spacers lb and Id afforded the best properties. Spacer variations did

not measurably affect enamel properties in the control oligoesterε.

DSC thermogra s of the crosε-linked enamelε revealed onεet of glass transitionε (Tg) ranging from Tg 15* to 35*C for L-C enamelε lb-g and amorphouε enamels 2a-g. An odd-even pattern was not observed in either type.

Polarized optical micrographs revealed L-C regions in the crosε-linked enamelε of lb-g. Enamelε of 2a-g appeared amorphouε. IR εpectra of the baked L-C and amorphouε enamelε had peakε attributable to unreacted OH groupε at 3420 cm ^"1 (OH εtretch) and at 1271 cm" ¹ (OH bend) .

In εummary, the method uεed to make oligoeεter diolε la-g waε adapted from Bilibin's method for making chain L-C high polymers by uεing a five-fold excesε of HO(CH ₂ ) _n OH. Spectral, chromatographic and maεε analytical evidence all indicated that the expected productε were obtained from the adapted proceεε. GPC and analytical data suggested that the structureε with x=l and x=2 predominate; εmaller amountε of εtructureε with x > 2 and of HO(CH ₂ ) _n OH are probably preεent in la-g and 2a-g.

The thermal behavior of la-g obεerved by DSC confirmε the preεence of meεophaεes and iε typical of low molecular weight liguid cryεtals. The odd-even effect is of interest becauεe of itε direct affect on the phyεical propertieε of the L-C diols. The lower T _m for lb and Id is consistent with the higher entropy of activation for crystallization of odd-n spacerε, demonεtrated in εeveral main chain L-C polymerε, Ober et al, Advanceε in Polymer Science. Li-guid Cryεtal Polymerε I. Springer-Verlag (1984), Vol. 59. The apparent abεence of nematic-εmetic tranεitionε in the DSC εuggeεtε the obεerved morphology exiεtε for the entire meεophaεe.

The nematic texture of oligomeric L-C diol If is

the same as reported for the homologouε main chain L-C high polymer, Lenz, Journal Polymer Science. Polymer Sy poεium (1985) 72, 1-8.

Oligomeric diolε lb-d were εoluble in MIBK and were miεcible with the HMMM croεε-linker; filmε were readily caεt. Higher melting diolε le-g were leεε miεcible, but the conεiεtently good film properties indicate that adequate mixing was achieved. Mixing of diol la with HMMM was inadequate to produce uniform films.

Enamels made from odd-n L-C diols lb and Id had better impact resistance than those made from even-n diols. This effect may be attributed to an odd-even effect, although other variables may be involved. The enhanced propertieε of the L-C diol enamelε are not εimply explainable by the monomer raiεing the Tg of the coating. In fact, Tgε of the crosε-linked enamels of lb-g are abnormally low for hard coatings, and are εimilar to the much εofter control enamelε.

EXAMPLE 6

A non-L-C linear oligoeεter diol is prepared by heating a mixture of phthalic acid (PA) , adipic acid (AA) and neopentyl glycol (NPG) . The reaction of the mixture is effected under N ₂ at 230C with removal of H ₂ 0 until the acid number was lesε than 10 mg KOH/g. The sum of the olε of acids should be lesε than the mols of diols and the ratio should be in the range of 1:2 to 1:1.1. A particular example of a mixture of PA, AA and NPG at a mol ratio of 1:1:3 was highly satisfactory.

A mixture of the diol or polyol, PHBA, an acid catalyst and particularly p-TSA and solvent was heated under N ₂ in a 3-neck flask equipped with εtirrer, Dean-Stark trap, condenser and thermometer. The PHBA was in substantially pure form so as not to affect catalytic action. The PHBA/diol or PHBA/polyol weight ratio varied

from 20/80 to 60/40, but the preferred ratio iε about 40/60; 0.2 weight % of p-TSA waε uεed aε an acid catalyεt to provide a predominantly phenolic L-C oligoeεter diol or polyol. About 10 weight % of εolvent waε uεed; the amount waε adjuεted to maintain the temperature in the range of 210'C to 250'C, and preferably in the range of 227 to 233'C. In an actual preparation the temperature waε held at 230 +/- 3C. Diεtillate (cloudy H ₂ 0) waε collected in the Dean-Stark trap during 9 to 11 hr. The reaction masε waε cooled to 115*C, and MIBK waε added to yield a εolution (20/80 PHBA/diol ratio) or suspenεion (other PHBA/diol ratioε) of the crude L-C polyol. A preferred εolvent iε "Aromatic 150" εold by Exxon.

It iε important that the acid catalyεt be uεed and that the temperature be controlled to provide the L-C predominately phenolic oligoeεterε of the invention. Likewise, it is important that the PHBA be used in the weight ratio range specified to give the L-C diols desired. The linear oligoester diol was heated with salycilic acid and with MHBA uεing a εimilar procedure to yield modified polyolε. 60% to 80% of theoretical diεtillation waε obtained. Purification. The crude L-C polyolε made from 20/80 and 30/70

PHBA/diol ratios were concentrated and disεolved in CH ₂ C1 ₂ . The εolution waε waεhed 5 times with H ₂ 0, dried with Na ₂ S0 ₄ , and concentrated on a rotary evaporator. The residues were heated at 120*C to constant weight. The crude L-C polyols made from 40/60 to 60/40 ratios were purified similarly but were not washed with water. They were heated at about 80'C under vacuum on a rotary evaporator to remove small amounts of volatile, crystalline material.

Enamel preparation.

Solutions or mixtures of L-C polyol, HMMM and p-TSA in a 75/25/0.25 weight ratio were cast on cold-rolled panels and baked at 175*C for the specified time. Dry film thicknesεes were 20 to 25 um. Characterization and testing.

1R spectra were recorded using a Perkin-Elmer 137 NaCl-priε εpectrophotometer. A DuPont model 990 thermal analyzer waε uεed for differential scanning calorimetry (DSC) at heating rates of 10/min. After the crystalline-mesophaεe tranεition temperature (T_) waε reached, the temperature waε held for 1 min. before the εcan waε reεumed. Capillary melting pointε were uεed to confirm the thermal data. M _n and M _y were determined by gel-permeation chromatography (GPC) with a Waterε model 520 pump equipped with a model R401 refractive index detector, a model M730 data analyzer, and Ultraεtragel 100 A, 500 A, 1000 A and 10000 A columnε. Masε analyεiε waε performed. A Leitz Labolux microεcope equipped with a polarizing filter waε uεed for optical icrographε at 500x magnification; L-C polyolε were caεt on glaεε εlideε and were dried and obεerved at 25'C, and enamelε were baked at 175*C for 20 minuteε on the glaεε εlideε. Hydroxyl numberε were determined by the pyromellitic dianhydride/i idazole method. See: Demareεt, B.O.; Harper, L. E. Journal of Coating Technology 1983, 55(701), 65-77. Impact reεiεtance and pencil hardneεε were teεted according to ASTM-D 2793 and ASTM-D 3363, respectively. Solvent resiεtance waε teεted by εpotting filmε with methyl ethyl ketone. Potentiometric titration in DMF indicated that a substantial fraction of phenolic groups are preεent in the oligomerε, but it haε not yet been feaεible to reproducibly obtain quantitative reεultε because precipitate formed during titration.

This preparation yields PHBA-modified oligomers, apparently with side reactions. The odor of phenol was

barely detectable in the productε, indicating that little phenol had been formed. p-TSA catalyεt playε a crucial role. When p-TSA waε not uεed in the 30/70 PHBA/diol reaction only 75% of theoretical diεtillate was collected, and the product smelled strongly of phenol. Solvent also playε an important role by helping control temperature and by facilitating removal of water. If deεired, the productε can be purified aε deεcribed to remove εmall amountε of unreacted PHBA and poεεibly of phenol.

Modification of the PA/AA/NPG diol with εalicylic and m-hydroxybenzoic acidε apparently did not proceed aε ε oothly aε the modification with PHBA. No liquid cryεtalε could be detected in the productε by polarizing microεcopy.

Potentiometric titration and infrared εpectra (peak at 3400 cm ^"1 ) indicate that phenolic end groupε predominate in the product oligomers.

Molecular weights determined by GPC are provided in Table 26. Also provided are rough estimateε of the average number of PHBA unitε per number average molecule. Theεe eεtimateε were obtained by multiplying product M _n by the weight fraction of PHBA charged and dividing the reεult by 120, the molar maεε of PHBA inuε water.

Table 26.

Gel Permeation Chromatography of Polyolε _

PHBA/diol ratio _ _ ^M w ^/M n ^{avg PHBA} wt. mol M_n M„w. reεidue/molecul

♦Filtered to remove a εmall fraction of THF-inεoluble material.

The L-C character of PHBA-containing oligomers was demonstrated by polarizing microscopy as indicated in

DSC data in Table 27 indicate that Tg increases with increasing PHBA/diol ratios except for the 60/40 PHBA/diol ratio.

Table 27.

Differential Scanning Calorimetry and Polarizing Microscop of Polyols

PHBA/diol ratio 0/100 20/80 30/70 40/60 50/50 60/40

Tg(C) , -10 7 14 19 27 14

Appearance, 500x clear a few L-C L-C L-C L-C spots

Enamel Coatings Propertieε.

Clear coatingε were formed by croεε-linking the PHBA- odified oligomerε with a εtandard melamine reεin. Baking at 175C waε necessary to obtain optimal properties. The cured filmε were nearly tranεparent and gloεεy except for filmε made from 60/40 PHBA ratio L-C polyol. Adheεion waε excellent.

The outεtanding feature of enamelε made from 40/60 to 50/50 PHBA/diol ratio L-C polyolε iε that they are both very hard and very impact reεiεtant aε εhown in Table 28.

Table 28.

Impact Resistance and Pencil Hardnesε of Baked Enamels

p: pasεeε 80 in-lb reverse impact test; f: fails;

*: appears to pass but cracks after standing several days.

The enamelε described in Table 28 with pencil hardnesε of 3H to 6H had excellent εolvent (methyl ethyl ketone) reεistance.

The εalycilic acid modified oligomerε did not cure at 175*C. The MHBA modified oligomerε cured at 175'C to give hard films, but all failed the 80 in-lb impact resiεtance teεt.

Polarizing micrographε εhowed clear evidence of the presence of birefringent phases in enamel films made from polyols modified by 30 percent or --more of PHBA. L-C regions were not viεible in cured filmε made from the PA/AA/NPG polyol or from the MPHA- odified enamels.

The results of the above experiments indicate that meεogenic groupε εubεtantially enhance a polymer reεin ^, ε coating quality. Grafting oligomeric εegmentε derived from PHBA or TPA/PHBA onto coating resinε yieldε reεinε that contain liquid cryεtalline (L-C) phaεes. These phaseε impart at leaεt three benefitε: "εolution" viεcoεity iε reduced by the formation of non-aqueouε diεperεionε, dry-to-touch timeε are εharply reduced, and films are both hardened and toughened. Imparting L-C characteriεticε to a reεin minimizes the hardneεε/impact reεiεtance tradeoff neceεεary with non-modified coating reεinε.

Although the invention haε been deεcribed with regard to itε preferred embodimentε, it εhould be underεtood that various changes and modifications aε would be obviouε to one having the ordinary skill in thiε art may be made without departing from the scope of the invention which iε set forth in the claims appended hereto.

The various features of this invention which are believed new are set forth in the following claims.

a e a Monofunctional Derivatives

^* -~ ^OK -

Table "29 b Monofunctional Derivatives

Monofunctional Derivatives

Table 29 d Difunctional Derivatives

Difunctional Derivatives

Table 29 G Difunctional Derivatives

Table 29 H Miscellaneous ^* Derivatives

-°-0- ^R -0- ^β -

9 9 wherein R = - 0 - C - CH = CH - C - 0