Field of the invention

The present invention relates to a method for emulsion polymerizing hydrophobic monomers at high temperatures.

Background

One of the main requirements for protective coatings is the ability to confer water resistance to painted substrates. Current research is aimed at providing more effective barrier properties by increasing the hydrophobic nature of the polymers produced. That, in turn, requires means for effectively and efficiently polymerizing hydrophobic monomers.

Latex paint coatings typically are applied to substrates and dried to form continuous films for decorative purposes as well as to protect the substrate. Such paint coatings are often applied to architectural interior or exterior surfaces under conditions where the coatings are sufficiently fluid to form a continuous paint film and dry at ambient temperatures. Exterior durability requires a high degree of hydrophobicity to protect the film from water penetration and subsequent coating failure. That, in turn, also requires means for effectively and efficiently polymerizing hydrophobic monomers.

Three main types of polymers commonly used in formulating latex paints are: (i) an all acrylic system, e.g., copolymers of methyl methacrylate, butyl acrylate or 2-ethylhexyl acrylate with small amounts of functional monomers, such as carboxylic acids; (ii) styrene-acrylate system, e.g., typical copolymer of styrene, methyl methacrylate, butyl acrylate and acrylic acid; and (iii) vinyl acetate- based copolymers, usually in combination with a small proportion of the above- mentioned lower alkyl acrylates. However, for hydrophobic monomers like long chain alkyl (meth)acrylates and silane / halothane acrylates, etc., it is very difficult to copolymerize, and more so to homopolymerize, these monomers using known techniques of emulsion polymerization, especially when they make up more than 50% of the polymer composition. Evidence of this difficulty is the fact that it is very difficult using known techniques to polymerize such monomers to make clean latexes with a reasonable monomer conversion, i.e., latexes should be fairly homogenous and stable and, when filtered through a 250-mesh sieve for example, leave little or no residue or coagulation. That, in turn, also points to the need for means to effectively and efficiently polymerize hydrophobic monomers.

Another disadvantage of using very hydrophobic monomers in emulsion polymerization is the very low water solubility of the monomers, which results in slow monomer transport and low reactivity.

Attempts to make homopolymers of very hydrophobic monomers, such as those of vinyl branched esters, have failed because of very low conversions even if the polymerization is conducted for a long time, e.g. in excess of 48 hours. There is also evidence of a curious inhibition, which is not well understood. (Balic, R., deBruyn, H., Gilbert, R. G., Miller, C. M. and Bassett, D. R., "Inhibition and Retardation in Emulsion Polymerization" , Proc. 74 ^th Colloid and Surf. Sci. Symp., Lehigh University, June, p. 19 (2000).

Many attempts to polymerize said monomers resort to costly techniques such as: use of organic solvents or other monomers to act as solvents for the hydrophobic monomer; use of macromolecular organic compounds having a hydrophobic cavity; and use of high levels of surfactants.

For example, U.S. Pat. No. 5,521,266 describes an aqueous polymerization method for forming polymers containing, as polymerized units, at least one monomer having low water solubility, including the steps of:

1) complexing at least one monomer having low water solubility with a macromolecular organic compound having a hydrophobic cavity; and

2) polymerizing in an aqueous system from about 0.1% to about 100%, by weight of the monomer component, based on the total weight of the polymer, of the complexed monomer having low water solubility with from about 0% to about 99.9% by weight, based on the total weight of the polymer, of at least one monomer having high water solubility.

The macromolecular organic compounds with a hydrophobic cavity used in U.S. Pat. No. 5,521,266 include cyclodextrins and cyclodextrin derivatives.

U.S. Pat. No. 5,777,003 relates to redispersible polymer powder compositions, which comprise homo- or copolymers of ethylenically unsaturated monomers and cyclodextrins or cyclodextrin derivatives. Polymer dispersions are spray- dried and the resulting powders are formulated into mortar compositions. The flexural tensile strength and the adhesive strength of the mortars are enhanced in the presence of the cyclodextrin-containing dispersion powder, while the compressive strength is only slightly influenced.

The polymerization of stearyl acrylate, a hydrophobic monomer, using methyl- beta-cyclodextrin as a phase transfer agent and dodecyl benzene sulfonate as a surfactant is described by Leyrer, R. J. and Machtle, W. in Macromol. Chem. Phys., 201, No. 12, 1235-1243 (2000). Stealyl acrylate is one of the hydrophobic monomers used in the examples of both U.S. Pat. Nos. 5,521,266 and 6, 160,049.

Cyclodextrins and chemically modified cyclodextrins are very expensive compared to other components used in emulsion polymerization. In addition, cyclodextrins are water-soluble and their inclusion during the polymerization may impart undesirable properties to the polymer film such as reduced hydrophobicity. In addition, some monomers will be unable to diffuse or penetrate into the interior of the beads resulting in a reduced capacity and the need for larger amounts of cyclodextrins. This, in turn, results in undesirable attributes for the polymer films, brought about by the reduced hydrophobicity, which can be detrimental in coating applications.

U.S. Pat. No. 5,686,518 discloses a polymerization process, referred to as miniemulsion polymerization, for polymerizing monomers and monomer mixtures which are said to be essentially insoluble in water, i.e., which have water solubility ranging from 0 to about 5 weight percent. The monomer or monomer mixture is emulsified to a very small droplet size, smaller than 0.5 microns under high shear, and is subsequently polymerized by conventional means. In order to achieve a miniemulsion, in addition to a surfactant, a polymeric co-surfactant is used at a level of 0.5 wt % to 5 wt % based on monomer. The co-surfactant accomplishes a reduction in monomer droplet size and as a result in latex particle size. Because the co-surfactant prevents monomer transfer from the small monomer droplets to the larger ones (i.e., Ostwald ripening), nucleation of the monomer droplets results in a final latex particle size similar to that of the monomer droplets. U.S. Pat. No. 6,160,049 discloses an emulsion polymerization process that combines macroemulsion and miniemulsion feed streams for preparing an aqueous polymer dispersion from free-radically polymerizable compounds. The process requires feeding in separate streams a monomer with a solubility of at least 0.001 wt % and a monomer with a solubility of less than 0.001 wt %, and requires emulsification of both monomer streams. The emulsification of the monomer streams is done using high pressure homogenizers at pressures of up to 1200 bar. However, this peripheral equipment is not commonly found in conventional emulsion polymerization practice.

The emulsion polymerization of butadiene and the copolymerization of butadiene and styrene at temperatures near 110 °C is described by Marvel et. al. in Journal of Polymer Science, 1947, 2(5), 488-502. The reference did not investigate the applicability of this process to other hydrophobic monomers.

U.S. Patent No. 6,696,533 discloses an emulsion polymerization process for polymerizing styrene, butyl aery late and/or acrylonitrile at a temperature higher than 100 °C in the presence of an initiator and a stable N-oxy radical. The stable N-oxyl radical was believed to be a stable free radical agent which does not irreversibly terminate, but merely temporarily block reactive free radical ends of a growing polymer chain at an elevated temperature. This process results in an average molecular weight which grows in proportion with the polymerization conversion such that a polymer having a relatively narrow polydispersity forms. This reference did not investigate the applicability of this process to other hydrophobic monomers either.

Despite the disclosure of the above references, a process is needed that is capable of polymerizing hydrophobic monomers, especially to produce latexes, especially those that are useful for hydrophobic coatings. A process capable of covering the entire monomer solubility range from hydrophobic to extremely hydrophobic monomers would be desired in order to impart the maximum possible hydrophobicity to coatings.

Summary of the invention

In one aspect, the present invention provides a process for emulsion polymerizing at least one hydrophobic monomer or a monomer composition comprising at least 5 wt% of the at least one hydrophobic monomer, based on the total weight of the monomer composition, wherein,

the emulsion polymerization is conducted at 95-200 °C,

the hydrophobic monomer has a water solubility not greater than 0.1 g/100 g water at 20 °C.

In another aspect, the present invention provides an emulsion polymer obtained from the process of the present invention.

In a third aspect, the present invention provides a use of the emulsion polymer of the present invention in preparing coatings.

Detailed description of the invention

The expression "at least one hydrophobic monomer" used herein means the present invention can be used to form homopolymers and copolymers. The term emulsion polymerization of the present invention comprises emulsion homopolymerization and emulsion copolymerization.

It is possible to choose various emulsion polymerization procedures for the present invention, for example a batch process (discontinuous) or semicontinuous or fully continuous processes, such as feed processes or seed procedures.

The emulsion polymerization of the present invention differs from miniemulsion polymerization of which the droplet size ranges from 50-500 nm at the start of the reaction, and polymerization occurs in small droplets of monomer mixture, in contrast to polymerization in micelles in classical emulsion polymerization. The small or ultra fine droplets of miniemulsion polymerization are normally achieved by pre-emulsion under ultra high shear or ultrasound.

It is widely accepted that specific surface area of monomer droplets is much smaller in classical emulsion polymerization, due to the big droplet size, which results that monomer droplets can hardly capture radicals from water and make small micelles the main place for polymerization. However, droplet size of monomers is small enough, less than 500 nm in miniemulsion polymerization. Thus monomer droplets in miniemulsion polymerization are like micelles in classical emulsion polymerization so as to be able to capture radicals competitively and efficiently, and then make it possible for polymerization. The size of monomer droplets in the emulsion polymerization of the present invention is bigger than the droplet size of the miniemulsion polymerization at the start of the reaction.

Preferably the size of monomer droplets in the emulsion polymerization of the present invention falls between 0.8-10 μπι at the start of the reaction. The monomers are polymerized in micelles to form polymers. And a transportation of monomers from droplets to water and then into micelles exists until the end of polymerization. The procedure is forced by equilibrium swelling of monomers in micelles and affected by solubility in water. Transportation becomes much difficult with hydrophobic and especially extremely hydrophobic monomers by the reason of low saturation concentration in water. Therefore, consumption rate of these monomers falls far behind polymerization process, even when all other monomers have turned into polymers.

As used herein, the hydrophobic monomer has a water solubility not greater than 0.1 g/100 g water at 20 °C. Water solubility of monomers depends on their structures and polarities, also on temperature and for gaseous monomers on pressure. Hydrophobic monomers usually have lower polarity and hydrogen bond index, comparing to hydrophilic monomers having ionizable groups (such as acid, alkali and salt) or groups having higher polarity and hydrogen bond index. Although water solubility is not always a linear function of temperature, high temperature can increase diffusivity for low polar and non-polar monomers. By elevating temperature, it is possible to increase saturation concentration of hydrophobic monomers in water, which makes it possible for emulsion polymerizing hydrophobic monomers. Therefore, ultra high shear or ultrasound is not necessarily required to form ultra fine droplets for preparing monomer pre-emulsion in the present invention.

Preferably, the hydrophobic monomer has a water solubility not greater than 0.02 g/100 g water at 20 °C.

Preferably, the hydrophobic monomer is in liquid or solid form at 20 °C at 1 bar.

Preferably, the hydrophobic monomer is one or more selected from esters of (meth)acrylic acid, (meth)acrylamides, vinyl esters and partly or fully fluorine and/or silicon substituted substances of above mentioned monomers. Preferably, the hydrophobic monomer is one or more selected from alkyl (meth)acrylates, aryl (meth)acrylates, aralkyl (meth)acrylates, alkyl aryl (meth)acrylates, fluothane (meth)acrylates, silane (meth)acrylates, flurosilane (meth)acrylates, alkyl acyloxy vinyl esters, fluothane acyloxy vinyl esters, silane acyloxy vinyl esters and vinyl silanes.

Preferably, the hydrophobic monomer is one or more selected from C6-C2 ₄ alkyl esters of (meth)acrylic acid, C ₆ -C ₂₄ alkyl acyloxy vinyl esters, halothane (meth)acrylates, silane (meth)acrylates and flurosilane (meth)acrylates

Preferably, the hydrophobic monomer is one or more selected from hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethyl hexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tetradecyl (meth)acrylate, 2-methyl-7-ethyl-4-undecyl (meth)acrylate, cetyl (meth)acrylate, oleyl (meth)acrylate, stearyl (meth)acrylate, eicosyl (meth)acrylate , behenyl (meth)acrylate, cetyl-eicosyl (meth)acrylate, benzyl (meth)acrylate, phenylethyl (meth)acrylate, m-tolyl (meth)acrylate, o-tolyl (meth)acrylate, p-tolyl (meth)acrylate, (3- methoxyphenyl)methyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2- naphthyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, 9-anthracenyl (methyl)acrylate, 1-methylcyclohexyl (meth)acrylate, 1-methylcyclopentyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2- adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2- adamantyl (meth)acrylate, 3 -hydroxy- 1-adamantyl (meth)acrylate, 3,5- dimethyladamantyl (meth)acrylate, 3,5-diethyladamantyl (meth)acrylate, 2-(4- ( 1 -methyl- 1 -phenylethyl)phenoxy)ethyl (meth)acrylate, 3a,4,5,6,7,7a- hexahydro-4,7-methano-lH-indenyl acrylate, 4-

(meth)acryloyloxybenzophenone, 2-phenylphenoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, 4,7- methanooctahydro-lh-indene-5-yl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, vinyl neodecanoate, 2,2,2-trifluoroethyl (meth) acrylate, ΙΗ,ΙΗ- pentafluoropropyl, lH,lH,3H-tetrafluoropropyl (meth)acrylate, 2- (perfluorobutyl)ethyl (meth)acrylate, lH,lH,2H,2H-perfluorooctyl

(meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorodecyl)ethyl (meth)acrylate, 1,1,1,3,3,3-hexafluoroisopropyl (meth)acrylate, 1H, 1H,7H- dodecafluoroheptyl (meth)acrylate, 2-(perfluorododecyl)ethyl (meth)acrylate, 1 H, 1 H,3H-hexafluorobutyl (meth)acrylate, 1 H, 1 H,5H-octafluoropentyl (meth)acrylate, lH, lH,9H-hexadecafluorononyl (meth)acrylate, methyl 2- fluoroacrylate, 5,5,6,6,7,7,7-heptafluoro-3-oxaheptyl (meth)acrylate, 2,2,3,3,5,5,5-heptafluoro-4-oxapentyl (meth)acrylate, heptafluoro-2-propyl (meth)acrylate, lH, lH-nonafluoro-4-oxahexyl (meth)acrylate, 3-fluoroalkyl a- fluoroacrylate, 4-fluoroalkyl a-fluoroacrylate, 8-fluoroalkyl a-fluoroacrylate, fluoromethyl (meth)acrylate, triethylvinylsilane, trimethylvinylsilane, triphenoxyvinylsilane, vinyl tris(trimethylsiloxy)silane, 3- chloropropydimethylvinylsilane, ( 1 -fluorovinyl)methyldiphenylsilane, 1 ,2,2- trifluorovinyl-triphenylsilane, (meth)acryloxymethyltris(trimethylsiloxy)silane.

Preferably, the remaining monomer of the monomer composition is one or more selected from (meth)acrylic acid; Ci-C ₅ alkyl esters, hydroxyl esters, poly(alkylene glycol) ether esters, Ci-C ₅ alkyl terminated poly(alkylene glycol) ether esters, glycidyl esters, and alkyl tertiary amine esters of (meth)acrylic acid; (meth)acrylamide, N-alkylol (meth)acrylamide, N-alkyl tertiary amine (meth)acrylamide; salt of alkyl tertiary amine esters of (meth)acrylic acid and N-alkyl tertiary amine (meth)acrylamide; Ci-C ₅ alkyl acyloxy vinyl esters; vinyl siloxane, (meth)acyloxy siloxane.

Preferably, the solvent of the emulsion is an aqueous solvent, preferably water.

Preferably, the emulsion polymerization is conducted at 100 to 150 °C.

Preferably, the emulsion polymerization is conducted at 1 to 10 bar.

Preferably, the emulsion polymerization of the present invention is carried out in the absence of a stable free radical agent, especially the stable N-oxyl radicals mentioned in U.S. Patent No. 6,696,533.

Polymerization is usually effected using at least one initiator. At least one initiator may be a peroxide. Examples of suitable peroxides are alkali metal peroxodisulfates such as, for example, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, organic peroxides, such as diacetyl peroxide, di-tert-butyl peroxide, diamyl peroxide, dioctanoyl peroxide, didecanoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, bis(o-toluoyl) peroxide, succinyl peroxide, tert-butyl peracetate, tert- butyl permaleate, tert-butyl perisobutyrate, tert-butyl perpivalate, tert-butyl peroctanoate, tert-butyl perneodecanoate, tert-butyl perbenzoate, di-tert-butyl peroxide, tert-butyl hydroperoxide, cumyl hydroperoxide, tert-butyl peroxy-2- ethylhexanoate and diisopropyl peroxidicarbamate. Azo compounds, such as, for example, azobisisobutyronitrile, l-[(l-cyano-l-methylethyl)azo]formamide, 2,2'-azobis {2-methyl-N-[2-(l-hydroxybutyl)]propionamide} , 2,2'-azobis[2- methyl-N-(2-hydroxyethyl)-propionamide] , 2,2 ' -azobis {2-methyl-N- [1, 1- bis(hydroxymethyl)-2-hydroxyethyl]propionamide } ,

2,2'-azobis(l-imino-l-pyrrolidino-2-methylpropane)dihydrochl oride, azobis(2- amidopropane) dihydrochloride and 2,2'-azobis(2-methylbutyronitrile) are also suitable.

Redox initiators are likewise suitable, for example comprising peroxides and oxidizable sulfur compound. Systems comprising acetone bisulfite and organic peroxide, such as tert-C ₄ H ₉ -OOH, Na ₂ S ₂ 0 ₅ (sodium disulfite) and organic peroxide, such as tert-C ₄ H ₉ -OOH or HO-CH ₂ S0 ₂ Na, and organic peroxide, such as tert-C ₄ H ₉ -OOH, can be used. Systems such as ascorbic acid/H ₂ 0 ₂ can also be used.

Macro initiators having same or similar initiating groups as the above mentioned compounds can also be used. Macro initiators are, for example, 4,4'- (l ,2-diazenediyl)bis[4-cyano-, polymer with a-hydro-ro-hydroxypoly(oxy- 1 ,2- ethanediyl) pentanoic acid, (VPE0201 , VPE0401 , and VPE0601, all from Wako Pure Chemical Industries, Ltd., CAS No.: 105744-24-9), 4,4'-azobis[4-cyano-, polymer with a-[(3-aminopropyl)dimethylsilyl]-ff>-[[(3- aminopropyl)dimethylsilyl]oxy]poly[oxy(dimethylsilylene)] pentanoic acid (VPS0501 and VPS 1001 , both from Wako Pure Chemical Industries, Ltd., CAS No.: 158947-07-0).

It is possible to use at least one emulsifier which may be anionic, cationic or nonionic.

Customary nonionic emulsifiers are, for example, ethoxylated mono-, di- and trialkylphenols (degree of ethoxylation: 3 to 50, alkyl radical: C ₄ -Ci ₂ ) and ethoxylated fatty alcohols (degree of ethoxylation: 3 to 80; alkyl radical: C ₈ - C ₃₅ ). Examples are Lutensol® from BASF and Triton® from Dow. Emulsification capability is usually affected and limited by cloud point for nonionic emulsifiers. Consequently, nonionic emulsifiers can be selectively comprised in recipe, or used as post-add after polymerization. Nevertheless, those ones with high cloud point are preferable for high temperature polymerization.

Customary anionic emulsifiers are, for example, alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C ₈ to Ci ₂ ), of sulfuric acid monoesters of ethoxylated alkanols (degree of ethoxylation: 4 to 30, alkyl radical: Ci ₂ -Ci ₈ ) and of ethoxylated alkylphenols (degree of ethoxylation: 3 to 50, alkyl radical: C ₄ - Ci ₂ ), of alkanesulfonic acids (alkyl radical: Ci ₂ -Ci ₈ ) and of alkylarylsulfonic acids (alkyl radical: C9-C13).

Suitable cationic emulsifiers are as a rule primary, secondary, tertiary or quaternary ammonium salts having a C ₆ -Ci ₈ -alkyl, C ₆ -Ci ₈ -aralkyl or heterocyclic radical, alkanolammonium salts, pyridinium salts, imidazolinium salts, oxazolinium salts, mo holinium salts, thiazolinium salts and salts of amine oxides, quinolinium salts, isoquinolinium salts, tropylium salts, sulfonium salts and phosphonium salts. Dodecylammonium acetate or the corresponding hydrochloride, the chlorides or acetates of various 2-(N,N,N- trimethylammonium)ethylparafflnic acid esters, N-cetylpyridinium chloride, N- laurylpyridinium sulfate and N-cetyl-N,N,N-trimethylammonium bromide, N- dodecyl-N,N,N-trimethylammonium bromide, N,N-distearyl-N,N- dimethylammonium chloride and the Gemini surfactant N,N- (lauryldimethyl)ethylenediamine dibromide may be mentioned by way of example. Numerous further examples appear in H. Stache, Tensid-Taschenbuch, Carl-Hanser-Verlag, Munich, Vienna, 1981, and in McCutcheon's, Emulsifiers & Detergents, MC Publishing Company, Glen Rock, 1989.

Reactive emulsifiers or polymerizable emulsifiers, can also be used to form stable emulsion in the present invention. These emulsifiers have polymerizable groups like unsaturated ethylene groups and can be incorporated into the final polymer. Examples of these emulsifiers include sodium ethylenesulphonate, 2- acrylamido-2-methyl-l-propanesulfonic acid sodium salt, 3-allyloxy-2- hydroxy- l-propanesulfonic acid sodium salt.

Further additives which are customary in emulsion polymerization may be added to the reaction mixture, for example glycols, polyethylene glycols, protective colloids and buffer/pH regulators.

A duration in the range from 30 minutes to 12 hours, preferably from 2 to 8 hours, may be chosen as the duration for the emulsion polymerization. In an embodiment of the present invention, a post polymerization is effected, for example by addition of initiator which is identical or different from the initiator used in the actual copolymerization.

In an embodiment of the present invention, the emulsion polymerization takes place substantially completely.

In an embodiment of the present invention, the process according to the invention is carried out in the manner of a one-stage process. In the context of the present invention, one-stage process is to be understood as meaning, for example, batch processes and feed processes in which a proportion of the comonomers can be initially taken and proportions of the comonomers are added during the copolymerization (feed), the composition of the feed in relation to the comonomers remaining substantially constant during the copolymerization.

In another embodiment of the present invention, the process according to the invention is carried out in the manner of a step procedure. In the context of the present invention, this is to be understood as meaning continuous or batchwise feed processes in which the composition of the feed changes during the emulsion polymerization.

The emulsion polymerization process of the present invention can achieve high hydrophobic monomer conversion, preferably more than 95%, and up to 100%. Thus the incorporation of hydrophobic monomers in the final polymer can be significantly increased.

Preferably, the emulsion polymer obtained from the process of the present invention is used in preparing water resistant coatings.

Hydrophobic monomers, due to their hydrophobic characteristic, have been known as good candidates to provide excellent properties for acrylic coatings. When the present invention is used in coating industry, such hydrophobic monomers can easily be copolymerized in emulsion polymers, in this way, even water based acrylic polymers can be developed with excellent water resistance, emulsion polymer obtained can be used in many fields, such as advanced composites, adhesives, printing inks, particularly in coatings used for architectural, wood-, automotive and other industrial coatings. While, moisture or rain will not damage the coatings easily, coatings will remain its excellent properties through time.

Examples

Chemicals

Initiators

Ammonium persulfate (APS);

1 -[( 1 -cyano- 1 -methylethyl)azo]formamide (V30);

2,2'-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086);

V30 and VA-086 are both azo initiators commercially available from Wako

Pure Chemical Industries, Ltd.

Emulsifiers

Anionic emulsifier:

Sodium dodecylbenzenesulphonate (SDS),

Onist®A6828,

Emulsogen®EPA 073;

Reactive and anionic emulsifier:

Onist®V20S;

Nonionic emulsifier:

Triton®X 100,

Lutensol®TO10;

Triton® and Lutensol® are commercially available from Dow and BASF. Onist® is commercially available from Shanghai Honesty Fine Chemical Co., Ltd. Emulsogen® is commercially available from Clariant International Ltd.

Monomers

methacrylic acid,

methyl methacrylate,

n-butyl acrylate,

2-ethyl hexyl methacrylate,

lauryl methacrylate,

C12-C14 alkyl esters of methacrylic acid (Visiomer®C13-MA),

C1 ₆ -C1 ₈ alkyl esters of methacrylic acid (Visiomer®C17.4-MA), stearyl methacrylate,

vinyl neo-nonanoate,

1H, lH,2H,2H-Perfluorooctyl aery late

vinyl terminated polydimethylsiloxane (4-8cs).

Visiomer®C13-MA is a mixture of C ₁₂ -C14 alkyl esters of methacrylic acid. Visiomer®C17.4-MA is a mixture of Ci ₆ -Ci ₈ alkyl esters of methacrylic acid. Both are commercially available from Evonik Industries. Vinyl terminated polydimethylsiloxane (4-8cs) is commercially available from Beijing HWRK Chem Co., Ltd.

Neutralizing agent

Ammonia

Water solubility test for monomers

Water solubility for the above monomers was measured at 20 °C with deionized water as solvent. The solubility values were determined by Gas Chromatography and expressed as g/100 g water as below. In the present invention, hydrophobic monomers are those having a water solubility not greater than 0.1 g/100 g, preferably not greater than 0.02 g/100 g water at 20 °C. methacrylic acid: miscible;

methyl methacrylate: 1.59;

n-butyl acrylate: 0.15;

2-ethyl hexyl methacrylate: 0.0014;

lauryl methacrylate: O.001;

Visiomer®C13-MA: O.001;

Visiomer®C17.4-MA: O.001;

stearyl methacrylate: <0.001;

vinyl neo-nonanoate: O.001;

lH, lH,2H,2H-Perfluorooctyl acrylate: <0.001;

vinyl terminated polydimethylsiloxane (4-8cs): <0.001.

General process for emulsion olymerization

A 1 -liter, jacketed pressure reactor was equipped with a paddle stirrer, a thermometer, a nitrogen inlet, a feeding line, a vent valve and pressure meter (including a pressure relief system). Air in the kettle was replaced by nitrogen gas before experiment. As indicated in Table 1, an initiator solution was prepared by dissolving an initiator in deionized water (DW). And an initial amount of DW was pumped to the reactor kettle and heated to 105-165°C. Then, a mixture comprising DW, part of the initiator solution, one or more emulsifiers was charged to the kettle. The mixture was stirred for 15 minutes.

As indicated in Table 2, a monomer emulsion (ME I) prepared by mixing DW, one or more emulsifiers, and several monomers was then pumped into the kettle. The mixture was stirred for 30 minutes to form seeds.

As indicated in Table 3, a second monomer emulsion (ME II) prepared by mixing DW, the rest initiator solution, one or more emulsifiers, and several monomers at a shearing rate of 1,000-10,000 rpm for 5-15 minutes, was charged to the kettle over 2 hours. The reaction mixture was stirred for 15 or 30 minutes.

As indicated in Table 4, a chaser solution was prepared and charged to the kettle. The reaction mixture was stirred for another hour for post- polymerization. Then the mixture was cooled to room temperature and filtered to remove any coagulation formed. The final emulsion was optionally neutralized by ammonia.

Tg, coagulum weight, solid content, monomer conversion, viscosity, particle size, polydispersity indexs (particle size and molecular weight), pH, Mn and Mw of Examples 1-10 were calculated or measured. The results are reported in Table 5.

It can be seen from Table 5 that the monomer conversion is greater than 95%, and even close to 100%, which means hydrophobic monomers can be efficiently polymerized by the emulsion polymerization process of the present invention.

Comparative examples are also given with/without hydrophobic monomers at low temperature about 80 °C, see Ex. 1 1-12. It can be found emulsion polymerizing hydrophobic monomers at 80 °C results into high coagulation and low monomer conversion, which has been proved by repeated experiments.

Performance test for the resulting emulsion polymer The emulsion polymers obtained from examples were tested for its performance as a coating. Films were prepared by spreading the emulsion and evaporating the solvent. Water absorption, weight loss and blocking point of films were tested.

Water absorption and weight loss

Water absorption is the percentage of water absorbed by the films, which represents the ability of water resistance. This value was measured by preparing a 3*3 cm film from the emulsions, keeping the film in water at room temperature for two days. Water absorption was calculated from the weight up- taken of film during the time. And weight loss was measured by calculating the percentage of weight loss of the film after it was dried at 80 °C for 4-6 hours.

Blocking point

To determine the blocking point, 100*20 mm pieces were cut from the film having a thickness of approximately 0.5 mm. The pieces were folded in half and placed between two glass plates. The folded films were loaded with weights of 500 g, so that was a load of exactly 50 g / cm . And the loaded films were heated for 1 h in an oven at 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C individually. Blocking point was the highest temperature at which the inter-contacting surfaces of the pieces were still attached to each other but not glued, so that the surface would not be damaged even when pulled apart.

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6