"Copolymerization method"

The present invention relates to methods of selectively copolymerizing at least one benzoxazine component and at least one epoxy component.

Properties of polymers are often adapted to meet certain technical requirements by the use of a mixture of monomers in the polymerization process. The polymerization of a mixture of two or more monomers is often referred to as copolymerization and leads, for example, to copolymers containing two different types of monomers.

Copolymers of epoxy and benzoxazine components are known. See e.g. U.S. Patent Nos. 4,607,091 (Schreiber), 5,021 ,484 (Schreiber), and 5,200,452 (Schreiber). These copolymers appear to be potentially useful commercially, as the epoxy resins can reduce the melt viscosity of benzoxazines allowing for the use of higher filler loading while maintaining a processable viscosity. However, epoxy resins oftentimes undesirably increase the temperature at which benzoxazines polymerize.

In said copolymers, certain technical properties can often be established in dependence upon the epoxy/benzoxazine monomer ratio. However, depending on the chemical nature of said monomers, it still remains a difficult task to control the exact structure and properties of the formed copolymer. Further, it is desirable to develop methods for curing said epoxy/benzoxazine compositions at relatively low temperatures in short time periods. Therefore it is an ongoing effort to look for ways to improve the polymerization process by reducing the reaction temperature.

Notwithstanding the state of the technology, it would be desirable to create a method for selectively copolymerizing a benzoxazine component and an epoxy component at relatively low temperatures in short time periods.

SUMMARY OF THE INVENTION

The present invention provides a method for selectively copolymerizing at least one benzoxazine component and at least one epoxy component. The method includes the steps of providing a polymerizable composition comprising at least one benzoxazine component, and at least one epoxy component, providing at least one catalyst and subjecting the polymerizable composition and the at least one catalyst to conditions appropriate to selectively polymerize the polymerizable composition.

More specifically, said at least one catalyst is selected from a) at least one nitrogen containing heterocycle and/or derivatives thereof, and/or b) at least one catalyst according to formula (I),

formula (I) wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1=y'+z', and/or c) at least one metal complex of an organic sulfur containing acid and/or at least one metal complex of a derivative of an organic sulfur containing acid.

The polymerizable compositions used in said method are in particular suitable as coatings, adhesives, sealants and matrices for the preparation of reinforced material such as prepregs and towpregs and/or can be used in injection molding or extrusion.

The invention also provides a cured product obtained by the inventive method, in particular a cured product containing bundles or layers of fibers, and a method of preparing such material.

It is a remarkable advantage of the present invention that by choosing at least one of the inventive catalysts, the at least one epoxy component and the at least one benzoxazine component can be copolymerized selectively.

DETAILED DESCRIPTION OF THE INVENTION

The at least one benzoxazine component can be any curable monomer, oligomer or polymer comprising at least one benzoxazine moiety. Preferably monomers containing up to four benzoxazine moieties are employed as the benzoxazine component in form of single compounds or mixtures of two or more different benzoxazines.

In the following a broad spectrum of different suitable benzoxazines containing one to four benzoxazine moieties are presented.

One possible benzoxazine may be embraced by the following structure (B-I):

(B-I) where o is 1-4, X is selected from a direct bond (when o is 2), alkyl (when o is 1 ), alkylene (when o is 2-4), carbonyl (when o is 2), sulfur (when o is 1 ), thioether (when o is 2), sulfoxide (when o is 2), sulfone (when o is 2) and oxygen (when o is 2), R ¹ is selected from hydrogen, alkyl, alkenyl and aryl, and R ⁴ is selected from hydrogen, halogen, alkyl and alkenyl, or R ⁴ is a divalent residue creating a naphthoxazine residue out of the benzoxazine structure.

More specifically, within structure (B-I) the benzoxazine may be embraced by the following structure (B-Il):

(B-Il) where X is selected from a direct bond, CH ₂ , C(CH ₃ ) ₂ , C=O, O, S, S=O and O=S=O, R ¹ and R ² are the same or different and are selected from hydrogen, alkyl, such as methyl, ethyl, propyls and butyls, alkenyl, such as allyl, and aryl, and R ⁴ are the same or different and defined as above.

Representative benzoxazines within structure (B-Il) include:

(B-III)

(B-IV)

(B-Vl) where R ¹ , R ² and R ⁴ are as defined above.

Alternatively, the at least one benzoxazine may be embraced by the following structure (B-VII):

(B-VII) where p is 2, Y is selected from biphenyl, diphenyl methane, diphenyl isopropane, diphenyl sulfide, diphenyl sulfoxide, diphenyl sulfone, and diphenyl ketone, and R ⁴ is selected from hydrogen, halogen, alkyl and alkenyl, or R ⁴ is a divalent residue creating a naphthoxazine residue out of the benzoxazine structure.

Though not embraced by structures (B-I) or (B-VII) additional benzoxazines are within the following structures:

(B-VIII)

(B-X) where R ¹ , R ² and R ⁴ are as defined above, and R ³ is defined as R ¹ , R ² or R ⁴ .

Specific examples of the above generically described benzoxazines include:

(B-XII)

(B-XIV)

(B-XVII)

(B-XVIII)

The at least one benzoxazine component may include the combination of multifunctional benzoxazines and monofunctional benzoxazines, or may be the combination of one or more multifunctional benzoxazines or one or more monofunctional benzoxazines.

Examples of monofunctional benzoxazines may be embraced by the following structure (B-XIX):

(B-XIX) where R is alkyl, such as methyl, ethyl, propyls and butyls, or aryl with or without substitution on one, some or all of the available substitutable sites, and R ⁴ is selected from hydrogen, halogen, alkyl and alkenyl, or R ⁴ is a divalent residue creating a maphthoxazine residue out of the benzoxazine structure.

For instance, monofunctional benzoxazines may be embraced by general structure (B-XX):

(B-XX) where in this case R ¹ is selected from alkyl, alkenyl, each of which being optionally substituted or interupted by one or more O, N, S, C=O, COO, and NHC=O, and aryl; m is O to 4; and R", R ¹ ", R ^IV , R ^v and R ^vι are independently selected from hydrogen, alkyl, alkenyl, each of which being optionally substituted or interrupted by one or more O, N, S, C=O, COOH, and NHC=O, and aryl.

Specific examples of such a monofunctional benzoxazine are:

(B-XXI) where R is as defined above; or

(B-XXII)

Benzoxazines are presently available commercially from several sources, including Huntsman Advanced Materials; Georgia-Pacific Resins, Inc.; and Shikoku Chemicals Corporation, Chiba, Japan.

If desired, however, instead of using commercially available sources, the at least one benzoxazine may typically be prepared by reacting a phenolic compound, such as a bisphenol A, bisphenol F, bisphenol S or thiodiphenol, with an aldehyde and an alkyl or aryl amine. U.S. Patent No. 5,543,516, hereby expressly incorporated herein by reference, describes a method of forming benzoxazines, where the reaction time can vary from a few minutes to a few hours, depending on reactant concentration, reactivity and temperature. See also Burke et al., J. Org. Chem. , 30(10), 3423 (1965); see generally U.S. Patent Nos. 4,607,091 (Schreiber), 5,021 ,484 (Schreiber), 5,200,452 (Schreiber) and 5,443,91 1 (Schreiber).

The at least one epoxy component can be any curable monomer, oligomer or polymer comprising at least one, preferably at least two epoxy group.

The at least one epoxy component used may include multifunctional epoxy- containing components, such as C ₁ -C _2S alkyl-, poly-phenol glycidyl ethers; polyglycidyl ethers of pyrocatechol, resorcinol, hydroquinone, 4,4'-dihydroxydiphenyl methane (or bisphenol F, such as RE-303-S or RE-404-S available commercially from Nippon Kayuku, Japan), 4,4'-dihydroxy-3,3'- dimethyldiphenyl methane, 4,4'-dihydroxydiphenyl dimethyl methane (or bisphenol A), 4,4'- dihydroxydiphenyl methyl methane, 4,4'-dihydroxydiphenyl cyclohexane, 4,4'-dihydroxy-3,3'- dimethyldiphenyl propane, 4,4'-dihydroxydiphenyl sulfone, and tris(4-hydroxyphenyl) methane; polyglycidyl ethers of transition metal complexes; chlorination and bromination products of the above-mentioned diphenols; polyglycidyl ethers of novolacs; polyglycidyl ethers of diphenols

obtained by esterifying ethers of diphenols obtained by esterifying salts of an aromatic hydrocarboxylic acid with a dihaloalkane or dihalogen dialkyl ether; polyglycidyl ethers of polyphenols obtained by condensing phenols and long-chain halogen paraffins containing at least two halogen atoms; phenol novolac epoxy; cresol novolac epoxy; and combinations thereof.

Among the commercially available epoxy components suitable for use in the present invention are polyglycidyl derivatives of phenolic compounds, such as those available under the tradenames EPON 825, EPON 826, EPON 828, EPON 1001 , EPON 1007 and EPON 1009, cycloaliphatic epoxy-containing compounds such as Araldite CY179 from Huntsman or waterborne dispersions under the tradenames EPI-REZ 3510, EPI-REZ 3515, EPI-REZ 3520, EPI-REZ 3522, EPI-REZ 3540 or EPI-REZ 3546 from Hexion; DER 331 , DER 332, DER 383, DER 354, and DER 542 from Dow Chemical Co.; GY285 from Huntsman, Inc.; and BREN-S from Nippon Kayaku, Japan. Other suitable epoxy-components include polyepoxides prepared from polyols and the like and polyglycidyl derivatives of phenol-formaldehyde novolacs, the latter of which are available commercially under the tradenames DEN 431 , DEN 438, and DEN 439 from Dow Chemical Company and a waterborne dispersion ARALDITE PZ 323 from Huntsman.

Cresol analogs are also available commercially such as ECN 1273, ECN 1280, ECN 1285, and ECN 1299 or waterborne dispersions ARALDITE ECN 1400 from Huntsman, Inc. SU-8 and EPI- REZ 5003 are bisphenol A-type epoxy novolacs available from Hexion. Epoxy or phenoxy functional modifiers to improve adhesion, flexibility and toughness, such as the HELOXY brand epoxy modifiers 67, 71 , 84, and 505. When used, the epoxy or phenoxy functional modifiers may be used in an amount of about 1 :1 to about 5:1 with regard to the heat curable resin.

Of course, combinations of the different epoxy resins (epoxy components) are also desirable for use herein.

Additionally, the polymerizable composition may comprise further polymerizable components preferably selected from lactones, lactams, oxetanes, tetrahydrofuranes, aziridines, oxazolines, acid anhydrides, and/or phenolic resins and/or mixtures thereof.

In certain embodiments of the present invention, the polymerizable composition comprise at least one epoxy component in an amount from about 10 to about 90 percent by weight, preferably from about 20 to about 80 percent by weight and more preferably from about 40 to 60 percent by weight based on the total amount of the polymerizable composition.

In further embodiments of the present invention, the polymerizable composition comprise at least one benzoxazine component in an amount from about 10 to about 90 percent by weight, preferably from about 20 to about 80 percent by weight and more preferably from about 40 to 60 percent by weight based on the total amount of the polymerizable composition.

Preferably, the polymerizable composition comprises at least one epoxy component in an amount from about 30 to about 70 percent by weight and at least one benzoxazine component in an amount from about 30 to about 70 percent by weight based on the total amount of the polymerizable composition.

In a further preferred embodiment of the present invention the polymerizable composition comprises epoxy group(s) and benzoxazine group(s) in a molar ratio (epoxy to benzoxazine groups) from 95:5 to 5:95, preferable from 80:20 to 20:80. Preferably, the molar ratio of epoxy group(s) to benzoxazine group(s) in said composition is 50:50.

The at least one catalyst used in the inventive method may exclusively be selected from at least one nitrogen containing heterocycle and/or derivatives thereof or may exclusively be selected from catalysts according to formula (I),

formula (I) wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1=y'+z',.

Additionally the at least one catalyst of the present invention may exclusively be selected from metal complexes of organic sulfur containing acids and/or derivatives thereof.

Preferably, the catalyst used in the inventive method is a combination of at least one nitrogen containing heterocycle and/or derivatives thereof, and at least one catalyst according to formula (I),

formula (I) wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a

carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1=y'+z'.

The at least one catalyst used in the inventive method may also be a combination of at least one nitrogen containing heterocycle and/or derivatives thereof, and at least one metal complex of an organic sulfur containing acid and/or derivatives thereof.

Additionally, the at least one catalyst used in the inventive method may also be combination of at least one catalyst according to formula (I),

formula (I) wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1 =y'+z', and at least one metal complex of an organic sulfur containing acid and/or derivatives thereof.

In another embodiment of the present invention the catalyst used in the inventive method is a combination of at least one nitrogen containing heterocycle and/or derivatives thereof, and at least one catalyst according to formula (I)

formula (I), wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1=y'+z', and at least one metal complex of an organic sulfur containing acid and/or at least one metal complex of a derivative of an organic sulfur.

The at least one nitrogen containing heterocycle according to the present invention can preferably be saturated, unsaturated, or aromatic. It may also be preferred that the at least one nitrogen

containing heterocycle is a thiazole, an oxazole, an imidazole, a pyridine, a piperidine, or a pyrimidine, a piperazine, a pyrrole, an indole or a benzthiazolyl. It is further on preferred that there is no acidic functional group present at the at least one nitrogen containing heterocycle. Most preferably, the nitrogen containing heterocyclic moiety is a thiazole and/or an imidazole.

In particular it is preferred that the at least one nitrogen containing heterocycle and/or its derivatives according to the present invention are selected from the group of imidazoles and/or imidazole derivatives with formula (II),

R ¹ R ²

,N N

R ' \<^

R ⁴

formula (II) with R ¹ , R ² , R ³ and R ⁴ being independently selected from hydrogen or aliphatic or aromatic hydrocarbons, whereas it is especially preferred that said imidazole is selected from the group of imidazole, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2- phenylimidazole, 1 ,2-dimethyl imidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4- methylimidazole, 1-benzyl-2-phenylimidazole, i-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole or 1- aminoethyl-2-methylimidazole.

As used in the present invention the term "derivative of a nitrogen containing heterocycle" includes catalytically active salts of the nitrogen containing heterocycle, such as salts derived from sulfonic acid, like trifluormethane sulfonic acid.

A further catalyst used in the method of the present invention is selected from at least one compound according to formula (I),

formula (I) wherein n = 1 , 2, 3 or 4, preferably 2 or 3 and E1 as well as E2 are electron withdrawing substituents, R is a hydrogen or linear or branched substituted or non substituted alkyl group with 1 to 20 C-atoms, or an aryl- or hydroxyl-group or an ether bridged alkyl chain, preferably with a carbon number of less than 12 or halogen such as F, Cl and the Metal is selected from the group of all metals which are capable of forming metal:ligand complexes and 2x+1=y+z, and 2x'+1=y'+z'.

Under the substituent E the present invention understands all kind of electron-withdrawing substituents, whereas E ¹ and E ² may be identical or different. According to the present invention the term "electron withdrawing substituent" relates to all substituents having a (-I) and/or (-M) effect. Examples without restricting the scope to those groups are all types of nitrate, sulphate, sulphonic, halogenic, carbonate, carboxylate, formate, aldehyde, keto, acetal, and further groups. In one preferred embodiment of the present invention the substituent E has a (-I) and a (+M) effect. It is also preferred according to the present invention to have at least one electron-withdrawing substituent, which is a monovalent substituent. It is most preferred according to the present invention if E is selected from the group of halogenic elements, in particular if E is F. It is also preferred if E ¹ and E ² are identical.

The preferred metal centers (Metal) are selected from manganese (Mn), iron (Fe), and cobalt (Co). Nevertheless also further metal centers which show metal:ligand complexing properties like those specific metals fall under the scope of this invention. In particular metals in the transition group of the periodic system metals which are capable of forming metal:ligand complexes are preferred for the purpose of the present invention. Examples are metals like Fe, Co, Ni, Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, In, Mn, Cu, Zn, Cd. The most preferred metals in the view of the present invention are selected from manganese (Mn), iron (Fe), and cobalt (Co).

It has also to be mentioned that y and y' or z and z' may also be 0, whereas it is preferred that x<4, x'<4, z>y, z'>y'. In particular it is preferred that y=y'=O and R=H.

Some examples of such catalysts are:

The at least one metal complex of an organic sulfur containing acid and/or the at least one metal complex of a derivative of an organic sulfur containing acid may preferably be represented by formula (III),

M n formula (III) wherein S is at least one organic sulfur containing acid and/or at least one derivative of an organic sulfur containing acid and M is a metal selected from the group of all metals which are capable of forming S-M complexes and n = 1 , 2, 3, 4, 5 or 6. In a preferred embodiment of the present invention n = 1 or n = 2.

It is preferred, that the organic sulfur containing acid and/or the derivative of an organic sulfur containing acid according to the present invention are selected from the group of sulfonic acids according to formula (IV)

O

R ⁵ _S -O H

Ii formula (IV) wherein R ⁵ is selected from optionally substituted aryl and alkyl groups. Preferably R ⁵ is selected from fluorinated alkyl goups, such as CF ₃ , C ₂ F ₅ , C ₃ F ₇ and C ₄ F ₉ .

In particular the organic sulfonic acid of the present invention is selected from the group of sulfonic acids according to formula (V), (Vl), (VII) and (VIII).

formula (V) formula (Vl) formula (VII) formula (VIII).

The preferred metal (M) in formula (III) is selected from alkali metals, such as lithium (Li), sodium (Na), potassium (K), alkali earth metals, such as magnesium (Mg), calcium (Ca), barium (Ba), scandium (Sc), yttrium (Y), lanthanoid metals, such as lanthanum (La), cerium (Ce), europium (Eu), ytterbium (Yb), copper (Cu), zinc (Zn), and boron (B). Particularly preferable are Sc, Y, and lanthanoid as metal (M).

As mentioned before, it is an advantage of the present invention that by choosing at least one of the catalysts of the present invention the at least one epoxy component and the at least one benzoxazine component can be copolymerized selectively.

The term "selective copolymerization" preferably refers to a copolymerization process, where the polymerization kinetics of the at least one benzoxazine and the at least one epoxy component can be controlled at the same time by using at least one catalyst of the present invention. Therefore the chemical nature of the cured product can be controlled by the inventive method and a copolymer selected from the group consisting of hybrid copolymers consisting of two homopolymers, materials

having an interpenetrate network-structure, block copolymers, graft copolymers, and/or statistical copolymers, and/or mixtures thereof can be obtained.

Depending on the chemical nature of the benzoxazine and epoxy component the method of the present invention allows to cure one component in preference to the other component or allows to cure both components at substantially the same time.

In one preferred embodiment of the present invention, the at least one catalyst begins to cure at least one epoxy component first in preference to the first curing benzoxazine component. Particularly preferably, the at least one catalyst begins to cure all epoxy components present in the polymerizable composition first in preference to the first curing benzoxazine component.

In an alternative embodiment of the present invention the at least one catalyst begins to cure the first curing epoxy component and the first curing benzoxazine component at substantially the same time.

In a further embodiment of the present invention, the at least one catalyst begins to cure at least one benzoxazine component first in preference to the first curing epoxy component. Particularly preferably, the at least one catalyst begins to cure all benzoxazine components present in the polymerizable composition first in preference to the first curing epoxy component.

The term "begins to cure first" preferably refers to the polymerization kinetics of the at least one benzoxazine component and the at least one epoxy component in the polymerizable composition. According to the present invention a component is cured first in preference to the other component if after 50% conversion of the faster curing component the slower curing component shows a conversion of less than 30%, preferably less than 20% and more preferably less than 10%, 5% or 2%.

The term "begins to cure at substantially the same time" preferably refers to the polymerization kinetics of the at least one benzoxazine component and the at least one epoxy component in the polymerizable composition. According to the present invention, two components are cured substantially at the same time if after 50% conversion of one component the other component shows a conversion of 40 to 60%, preferably of 45 to 55%.

The conversion of each component can easily be determined by a man skilled in the art using known techniques, such as GC-analysis, NMR- or IR spectroscopy.

In one embodiment of the present invention, the at least one catalyst selected from at least one nitrogen containing heterocycle and/or derivatives thereof begins to cure at least one benzoxazine component first in preference to the first curing epoxy component, such as 3,4-epoxycyclohexyl-1-

carboxylic-acid methyl ester, or begins to cure at least one epoxy component, such as glycidyl phenyl ether first in preference to the first curing benzoxazine component.

In another embodiment of the present invention the at least one catalyst selected from a catalyst according to formula (I), begins to cure the first curing epoxy component, such as 3,4- epoxycyclohexyl-1 -carboxylic-acid methyl ester, and the first curing benzoxazine component at substantially the same time or begins to cure at least one epoxy component, such glycidyl phenyl ether, first in preference to the first curing benzoxazine component.

In a further embodiment of the present invention the at least one catalyst selected from at least one metal complex of an organic sulfur containing acid and/or at least one metal complex of a derivative of an sulfur containing acid, begins to cure at least one epoxy component, such as 3,4- epoxycyclohexyl-1 -carboxylic-acid methyl ester, or glycidyl phenyl ether, first in preference to the first curing benzoxazine component.

By the inventive method of selectively copolymerizing a benzoxazine component and an epoxy component completely different cured materials with completely different material properties can be obtained such as hybrid materials consisting of two homopolymers, materials having an interpenetrate network-structure, block copolymers, graft copolymers, or statistical copolymers.

According to the present invention the at least one catalyst is present in an amount sufficient to cure the polymerizable composition. Preferably the molar ratio between said components (epoxy component and benzoxazine component) and said at least one catalyst is 90:10 to 99.9 to 0.1 , preferably 95:5 to 99.5:0.5.

In general, the polymerizable composition is polymerized at conditions appropriate to selectively polymerize the polymerizable composition. Preferably, the polymerizable composition is polymerized at temperatures from 5O ⁰ C to 300 ⁰ C, preferably from 7O ⁰ C to 25O ⁰ C, more preferably from 100 ⁰ C to 15O ⁰ C and/or pressures between 1 to 10 atm, preferably under atmospheric pressure.

If desired, reactive diluents, for example styrene oxide, butyl glycidyl ether, 2,2,4-trimethylpentyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether or glycidyl esters of synthetic, highly branched, mainly tertiary, aliphatic monocarboxylic acids, oxazoline group containing compounds may be added to the polymerizable composition to reduce its viscosity.

Other additives which the inventive polymerizable composition can include are tougheners, plasticizers, extenders, microspheres, fillers and reinforcing agents, for example coal tar, bitumen, textile fibres, glass fibres, asbestos fibres, boron fibres, carbon fibres, mineral silicates, mica, powdered quartz, hydrated aluminum oxide, bentonite, wollastonite, kaolin, silica, aerogel or metal

powders, for example aluminium powder or iron powder, and also pigments and dyes, such as carbon black, oxide colors and titanium dioxide, fire-retarding agents, thixotropic agents, flow control agents, such as silicones, waxes and stearates, which can, in part, also be used as mold release agents, adhesion promoters, antioxidants and light stabilizers, the particle size and distribution of many of which may be controlled to vary the physical properties and performance of the inventive polymerizable composition.

When used, fillers are used in an amount sufficient to provide the desired rheological properties.

Fillers may be used in an amount up to about 50 percent by weight, such as about 5 to about 32 percent by weight, for instance about 10 to about 25 percent by weight.

The fillers may be inorganic ones, such as silicas. For instance, the silica filler may be a silica nanoparticle.

As noted, the polymerizable compositions used in the inventive method are in particular suitable as coatings, adhesives, sealants and matrices for the preparation of reinforced material such as prepregs and towpregs and/or can be used in injection molding or extrusion or in the formation of prepregs or towpregs formed from a layer or bundle of fibers infused with the polymerizable composition.

The invention also provides a cured product obtained by the inventive method, in particular cured products containing bundles or layers of fibers, and a method of preparing such material.

In this regard, the invention relates to processes for producing a prepreg or a towpreg. One such process includes the steps of (a) providing a layer or bundle of fibers; (b) providing a polymerizable composition used in the inventive method; and (c) joining said polymerizable composition and the layer or bundle of fibers to form a prepreg or a towpreg assembly, respectively, and exposing the resulting prepreg or towpreg assembly to elevated temperature and pressure conditions sufficient to infuse the layer or bundle of fibers with the polymerizable composition to form a prepreg or towpreg, respectively.

Another such process for producing a prepreg or towpreg, includes the steps of (a) providing a layer or bundle of fibers; (b) providing a polymerizable composition used in the inventive method in liquid form; (c) passing the layer or bundle of fibers through said polymerizable composition to infuse the layer or bundle of fibers with said polymerizable composition; and (d) removing excess of said polymerizable composition from the prepreg or towpreg assembly.

Generally, the fiber layer or bundle may be constructed from unidirectional fibers, woven fibers, chopped fibers, non-woven fibers or long, discontinuous fibers.

The fiber chosen may be selected from carbon, glass, aramid, boron, polyalkylene, quartz, polybenzimidazole, polyetheretherketone, polyphenylene sulfide, poly p-phenylene benzobisoaxazole, silicon carbide, phenolformaldehyde, phthalate and napthenoate.

The carbon is selected from polyacrylonitrile, pitch and acrylic, and the glass is selected from S glass, S2 glass, E glass, R glass, A glass, AR glass, C glass, D glass, ECR glass, glass filament, staple glass, T glass and zirconium oxide glass.

The inventive polymerizable composition and the prepregs or towpregs are particularly useful in the manufacture and assembly of composite parts for aerospace and industrial end uses, bonding of composite and metal parts, core and core-fill for sandwich structures and composite surfacing.

Therefore, the polymerizable composition used in the inventive method may be in the form of an adhesive, sealant or coating, in which case one or more of an adhesion promoter, a flame retardant, a filler (such as the inorganic filler noted above, or a different one), a thermoplastic additive, a reactive or non-reactive diluent, and a thixotrope may be included. In addition, the polymerizable compositions in adhesive form may be placed in film form, in which case a support e.g. constructed from nylon, glass, carbon, polyester, polyalkylene, quartz, polybenzimidazole, polyetheretherketone, polyphenylene sulfide, poly p-phenylene benzobisoaxazole, silicon carbide, phenolformaldehyde, phthalate and naphthenoate may be included.

This invention is further illustrated by the following representative examples.

EXAMPLES

General

methyl ester B

Glycidyl phenyl ether Epoxide 3

Example 1. Copolymerization by scandium triflate (Sc(OTf) ₃ ) at 100 ⁰ C

A solution of scandium triflate (65.3 mg) in ethyl acetate (2.0 ml_) was divided into ten portions (200 μl_ each) and each of them was placed in a test tube. The resulting 10 test tubes were placed under vacuum to remove the solvent ethyl acetate overnight. In another vessel, benzoxazine 1 (1.46 g; 6.48 mmol) and epoxide 2 (1.04 g; 6.66 mmol) were mixed to obtain a homogeneous mixture, and this mixture was divided into ten portions (220 μl_ each; 250 mg each) and each of them was placed in one of the 10 test tubes containing scandium catalyst. Argon inlets were attached to these test tubes and then they were heated in an oil bath at 100 ⁰ C. From time to time, these test tubes were taken away from the oil bath one-by-one, and each of the mixture was analyzed by GC to determine conversions of the monomers. The resulting time-conversion relationships are shown in Table 1 and visualized in Figure 1.

Table 1. Copolymerization by Sc(OTf) ₃ at 100 ⁰ C

Example 2. Copolymerization by 2-ethyl-4-methylimidazole (EMI) at 150 ⁰ C Benzoxazine 1 (1.47 g; 6.51 mmol), epoxide 2 (1.048 g; 6.71 mmol), and EMI (14.7 mg; 0.134 mmol) were mixed to obtain a homogeneous mixture. The mixture was divided into ten portions (253 mg each) and each of them was placed in a test tube. Argon inlets were attached to the resulting 10 test tubes an then they were heated in an oil bath at 150 ⁰ C. From time to time, these test tubes were taken away from the oil bath one-by-one, and each of the mixture was analyzed by

GC to determine conversions of the monomers. The resulting time-conversion relationships are shown in Table 2 and visualized in Figure 2.

Table 2. Copolymerization by EMI at 150 ⁰ C

Example 3. Copolymerization by manganese (II) bis(hexafluoroacetoacetonato) (Mn(F-acac) ₂ ) at

15O ⁰ C

Benzoxazine 1 (1.463 g; 6.50 mmol), epoxide 2 (1.041 g; 6.66 mmol), and Mn(F-acac) ₂ (62.4 mg;

0.133 mmol) were mixed to obtain a homogeneous mixture. This mixture was treated according to the procedure used for the example 2 and the time-conversion relationships were investigated similarly. The resulting time-conversion relationships are shown in Table 3 and visualized in Figure

3.

Table 3. Copolymerization by Mn(F-acac) ₂ at 150 ⁰ C

Utilization of Sc(OTf) ₃ resulted in rapid consumption of epoxide 2 followed by fast consumption of benzoxazine 1 This behavior implies that the copolymerization system allows rapid formation of the homopolymer of epoxide 2 in the early stages and gradual formation of the homopolymer of benzoxazine 1 , to give a hybrid material/copolymer comprising two homopolymers. Generally, application of such a system to curing reactions using multifunctional monomers is a convenient approach to materials having an interpenetrate network-structure.

On the other hand, as shown in Figure 2, utilization of EMI resulted in faster consumption of benzoxazine 1 than that of epoxide 2. This behavior is totally different from that for the copolymerization by Sc(OTf) ₃ . The formed material can once again be a hybrid material/copolymer comprising two homopolymers or a graft copolymer, which can be formed by graft polymerization of epoxide 2 from the phenolic side chain of the benzoxazine homopolymer formed in the early stages.

Utilization of Mn(F-acac) ₂ resulted in consumptions of the two monomers in the same rate, suggesting the formation of a statistical copolymer, a totally different material than the material obtained by using Sc(OTf) ₃ ) or EMI as catalysts.

Example 4. Copolymerization by scandium triflate (Sc(OTf) ₃ ) at 100 ⁰ C

A solution of scandium triflate (56.1 mg) in ethyl acetate (0.5 ml_) was divided into ten portions (49 μl_ each) and each of them was placed in a test tube. The resulting 10 test tubes were placed under vacuum to remove the solvent ethyl acetate overnight. In another vessel, benzoxazine 1 (1.36 g; 6.01 mmol) and epoxide 3 (0.901 g; 6.00 mmol) were mixed to obtain a homogeneous mixture, and this mixture was divided into ten portions (200 mg each) and each of them was placed in one of the 10 test tubes containing scandium catalyst. Nitrogen inlets were attached to these test tubes and then they were heated in an oil bath at 100 ⁰ C. From time to time, these test tubes were taken away from the oil bath one-by-one, and each of the mixture was analyzed by GC to determine conversions of the monomers. The resulting time-conversion relationships are shown in Table 4.

Example 5. Copolymerization by 2-ethyl-4-methylimidazole (EMI) at 150 ⁰ C Benzoxazine 1 (1.35 g; 6.00 mmol), epoxide 3 (0.902 g; 6.01 mmol), and EMI (13.2 mg; 0.120 mmol) were mixed to obtain a homogeneous mixture. The mixture was divided into ten portions (200 mg each) and each of them was placed in a test tube. Nitrogen inlets were attached to the resulting 10 test tubes and then they were heated in an oil bath at 150 ⁰ C. From time to time, these test tubes were taken away from the oil bath one-by-one, and each of the mixture was analyzed by GC to determine conversions of the monomers. The resulting time-conversion relationships are shown in Table 5.

Table 5. Copolymerization by EMI at 150 ⁰ C

Example 6. Copolymerization by manganese (II) bis(hexafluoroacetoacetonato) (Mn(F-acac) ₂ ) at

15O ⁰ C

Benzoxazine 1 (1.35 g; 6.00 mmol), epoxide 3 (0.903 g; 0.601 mmol), and Mn(F-acac) ₂ (56.2 mg;

0.120 mmol) were mixed to obtain a homogeneous mixture. This mixture was treated according to the procedure used for the example 5 and the time-conversion relationships were investigated similarly. The resulting time-conversion relationships are shown in Table 6.

Table 6. Copolymerization by Mn(F-acac) ₂ at 150 ⁰ C

Example 7. Copolymerization by manganese (II) bis(hexafluoroacetoacetonato) (Mn(F-acac) ₂ ) at 12O ⁰ C

Benzoxazine 1 (1.35 g; 6.00 mmol), epoxide 3 (0.901 g; 0.600 mmol), and Mn(F-acac) ₂ (55.7 mg; 0.119 mmol) were mixed to obtain a homogeneous mixture. This mixture was treated according to the procedure used for the example 5 except temperature of oil bath (120 ⁰ C). The time- conversion relationships were investigated similarly. The resulting time-conversion relationships are shown in Table 7.

Table 7. Copolymerization by Mn(F-acac) ₂ at 120 ⁰ C

Example 8. Copolymerization by PTS-EMI salt at 150 ⁰ C

Benzoxazine 1 (1.36 g; 6.04 mmol), epoxide 3 (0.900 g; 0.599 mmol), p-toluenesulfonic acid ^« H ₂ O (22.4 mg; 0.118 mmol), and EMI (13.1 mg; 0.119 mmol) were mixed to obtain a homogeneous mixture. This mixture was treated according to the procedure used for the example 5 and the time- conversion relationships were investigated similarly. The resulting time-conversion relationships are shown in Table 8.

Table 8. Copolymerization by PTS-EMI at 150 ⁰ C

In summary, by choosing different catalysts, materials with different chemical structures and/or different properties can be specifically obtained from benzoxazines and epoxides.