CURABLE RESIN COMPOSITIONS CONTAINING ALIPHATIC POLYKETONE Tougheners AND COMPOSITES MADE THEREFROM - Patent application

Abstract

The present disclosure provides a curable resin composition comprising a thermosetting resin, an aliphatic polyketone as a toughening agent, and a curing agent. The curable resin composition may be combined with reinforcing fibers and then cured to form a fiber-reinforced composite article having a high glass transition temperature, excellent mechanical properties, and low moisture absorption. The fiber-reinforced composite article may be used in a variety of applications, such as transportation applications, including aerospace, aviation, marine, and land vehicles.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 946,085, filed Dec. 10, 2019, the entire contents of which are expressly incorporated herein by reference.

[0002] The present disclosure generally relates to the use of aliphatic polyketones to modify the properties of curable resin compositions, such as compression after impact and wettability. The disclosure also relates to the use of such curable resin compositions, which may be cured in the presence of reinforcing fibers to form fiber-reinforced composite articles and aerospace structural parts made from the fiber-reinforced composite articles. [Background technology]

[0003] Thermosetting materials such as cured epoxy resins are known for their heat and chemical resistance. They also exhibit good mechanical properties, but often lack toughness and tend to be very brittle. This is especially true when their crosslink density is increased or the monomer functionality is increased beyond 2. Attempts have been made to toughen or robusten epoxy resins and other thermosetting materials (e.g., bismaleimide resins, benzoxazine resins, cyanate ester resins, epoxy vinyl ester resins, and unsaturated polyester resins) by incorporating various toughening agents therein.

[0004] Such toughening agents may be compared to one another according to their structural, morphological, or thermal properties. The structural backbone of the toughening agent may be aromatic, aliphatic, or both aromatic and aliphatic. Aromatic toughening agents, such as polyetheretherketones or polyimides, provide thermoset materials that provide ideal improvements in toughening, i.e., compression after impact, and also exhibit low moisture absorption when subjected to high temperature and humid environments due to the aromatic structure of the toughening agent. Conversely, aliphatic toughening agents, such as nylons (also known as polyamides), provide thermoset materials that exhibit significant improvements in compression after impact, but exhibit higher than desired moisture absorption when subjected to high temperature and humid environments, which may reduce the compressive strength and compressive modulus. Other toughening agents, such as core-shell polymers, can provide thermoset materials that exhibit good damage resistance. However, they tend to adversely affect the processability and glass transition temperature of the thermoset materials. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need for further improvement over the state of the art by using new toughening agents in the curable resin composition that exhibit high glass transition temperature, excellent mechanical properties, and low moisture absorption so that after curing of the resin composition, the cured product does not deteriorate in its thermomechanical properties when subjected to high temperature and humid environment. [Means for solving the problem]

[0006] The present disclosure generally provides a curable resin composition comprising (a) a thermosetting resin, (b) an aliphatic polyketone toughening agent, and (c) a curing agent. The present disclosure also provides a fiber reinforced resin composition comprising a reinforcing fiber and the curable resin composition of the present disclosure. The fiber reinforced resin composition may be cured to form a fiber reinforced composite article that may be utilized in a variety of applications, such as, for example, transportation applications (including aerospace, aviation, marine, and land vehicles, as well as the automotive, rail, and coach industries), building / construction applications, or other commercial applications. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present disclosure generally provides a curable resin composition comprising (a) a thermosetting resin, (b) an aliphatic polyketone as a toughening agent, and (c) a curing agent. The curable resin composition may be used alone, but the composition may also be combined with reinforcing fibers to form a fiber-reinforced resin composition and cured to form a fiber-reinforced composite article. Surprisingly, it has been found that the presence of the aliphatic polyketone toughening agent may enable the composite article to exhibit chemical and mechanical properties particularly suitable for primary and secondary aerospace structural applications, as well as structural materials in other moving bodies, including automobiles, ships, and rail vehicles. In particular, the fiber-reinforced composite article may exhibit good compression after impact (CAI), a glass transition temperature of at least 190°C, and the ability to retain important mechanical properties after hot and humid conditioning.

[0008] The following terms shall have the following meanings: The terms "cure", "cured" or similar terms such as "curing" or "curing" refer to the hardening of a thermosetting resin by chemical crosslinking. The term "curable" means that the composition is capable of being subjected to conditions that cause the composition to become in a hardened or thermoset state or condition.

[0009] The term "comprising" and its derivatives are not intended to exclude the presence of any additional components, steps or procedures, whether or not they are disclosed herein. For the avoidance of any doubt, all compositions claimed herein may include any additional additives or compounds by use of the term "comprising", unless stated to the contrary. In contrast, the term "consisting essentially of", when appearing herein, excludes from the scope of any succeeding citation any other components, steps or procedures, except those that are not essential to operability, and the term "consisting of", when used, excludes any component, step or procedure not specifically described or listed. The term "or" refers to the listed members individually and in any combination, unless otherwise specified.

[0010] The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an epoxy resin" means one epoxy resin or more than one epoxy resin.

[0011] The phrases "in one embodiment," "according to one embodiment," and the like generally mean that the particular feature, structure, or characteristic that follows the phrase is included in at least one aspect of the present disclosure, and may be included in more than one embodiment of the present disclosure. Importantly, such phrases do not necessarily refer to the same embodiment.

[0012] If the specification states that a component or feature "may," "can," "could" or "might" be included or have a characteristic, that particular component or feature need not be included or have the characteristic.

[0013] As used herein, the term "about" may allow for some variability in values ​​or ranges, for example, "about" may be within 10%, within 5%, or within 1% of the stated value or limit of the stated range.

[0014] Values ​​expressed in range format should be interpreted flexibly to include not only the numerical values ​​explicitly recited as the limits of the range, but also all of the individual numerical values ​​or subranges subsumed within that range, as if each numerical value and subrange were explicitly recited. For example, a range such as 1 to 6 should be considered to have specifically disclosed subranges such as 1 to 3, 2 to 4, 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the broadness of the range.

[0015] The terms "preferred" and "preferably" refer to embodiments that may provide certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present disclosure.

[0016] According to a first aspect, the present disclosure provides a curable resin composition that generally includes (a) a thermosetting resin, (b) an aliphatic polyketone, and (c) a curing agent.

[0017] In one embodiment, the thermosetting resin may be an epoxy resin, a bismaleimide resin, a benzoxazine resin, a cyanate ester resin, a phenolic resin, a vinyl ester resin, or a mixture thereof. In one particular embodiment, the thermosetting resin is an epoxy resin.

[0018] Generally, any epoxy-containing compound is suitable for use as an epoxy resin in the present disclosure, such as those disclosed in U.S. Patent No. 5,476,748, which is incorporated herein by reference. According to one embodiment, the epoxy resin is selected from difunctional (thus having two epoxide groups), trifunctional (thus having three epoxide groups), tetrafunctional (thus having four epoxide groups), and mixtures thereof.

[0019] Illustrative non-limiting examples of difunctional epoxy resins are: bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A polyethylene glycol diglycidyl ether, bisphenol A polypropylene glycol diglycidyl ether, 3,4-epoxycyclohexylmethyl carboxylate, hexahydrophthalic acid diglycidyl ester, methyltetrahydrophthalic acid diglycidyl ester, and mixtures thereof.

[0020] Illustrative non-limiting examples of trifunctional epoxy resins are: triglycidyl ether of para-aminophenol, triglycidyl ether of meta-aminophenol, dicyclopentadiene-based epoxy resins, N,N,O-triglycidyl-4-amino-m- or -5-amino-o-cresol type epoxy resins, and 1,1,1-(triglycidyloxyphenyl)methane type epoxy resins.

[0021] Illustrative non-limiting examples of tetrafunctional epoxy resins are: N,N,N',N'-tetraglycidylmethylenedianiline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, tetraglycidyldiaminodiphenylmethane, sorbitol polyglycidyl ether, pentaerythritol tetraglycidyl ether, tetraglycidyl bisaminomethylcyclohexane, and tetraglycidyl glycoluril.

[0022] In one embodiment, the amount of epoxy resin present in the curable resin composition can be from about 10% to about 90% by weight, or from about 15% to about 75% by weight, or from about 20% to about 60% by weight, or from about 25% to about 55% by weight, based on the total weight of the curable resin composition.

[0023] In yet another embodiment, the epoxy resin is at least one trifunctional epoxy resin or tetrafunctional epoxy resin. The curable resin composition may comprise at least one difunctional epoxy resin, a functional epoxy resin or mixtures thereof, and at least one difunctional epoxy resin. In such an embodiment, the difunctional epoxy resin may be present in the curable resin composition in an amount of about 10% to 40% by weight, or about 12% to about 25% by weight, or about 15% to 20% by weight, based on the total weight of the curable resin composition, and the trifunctional epoxy resin and / or tetrafunctional epoxy resin may be present in the curable resin composition in an amount of about 15% to 50% by weight, or about 20% to about 40% by weight, or about 25% to 35% by weight, based on the total weight of the curable resin composition. In a particular embodiment, the curable resin composition may comprise the difunctional resin in the above amounts, the trifunctional epoxy resin in an amount of about 5% to about 30% by weight, and the tetrafunctional epoxy resin in an amount of about 10% to about 35% by weight, based on the total weight of the curable resin composition.

[0024] The curable resin composition also includes an aliphatic polyketone as a toughening agent. Such aliphatic polyketones are linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, and are distinguished by the absence of aromatic groups along the polymer backbone. In some embodiments, the aliphatic polyketone will substantially contain one molecule of carbon monoxide for each molecule of ethylenically unsaturated hydrocarbon.

[0025] It is possible to use many different ethylenically unsaturated hydrocarbons as monomers in the same aliphatic polyketone. According to one embodiment, the ethylenically unsaturated hydrocarbons include compounds that are completely aliphatic, and in some embodiments may have up to about 20 carbon atoms, or in other embodiments up to about 10 carbon atoms. Non-limiting examples of ethylenically unsaturated hydrocarbons include ethylene, propylene, n-butene, n-octene, n-dodecene, and other α-olefins. Thus, for example, the aliphatic polyketone may be a copolymer of carbon monoxide and ethylene, or a terpolymer of carbon monoxide, ethylene, and a second ethylenically unsaturated hydrocarbon of at least 3 carbon atoms, such as propylene. Additional monomers may be used and still fall within the scope of the aliphatic polyketones described herein. That is, the aliphatic polyketone may be made from a combination of 4, 5, or more ethylenically unsaturated hydrocarbon monomers.

[0026] When the aliphatic polyketone is a terpolymer, there are at least about 2 units in the terpolymer that incorporate an ethylene moiety for each unit that incorporates a second or subsequent ethylenically unsaturated hydrocarbon moiety, in some embodiments there may be from about 10 units to about 100 units that incorporate a second ethylenically unsaturated hydrocarbon moiety.

[0027] Thus, the polymer chain of an aliphatic polyketone has the repeating structure -[CH 2 -CH 2 -CO] x -[G-CO] y -, where G is an ethylenically unsaturated hydrocarbon moiety of at least 3 carbon atoms polymerized through ethylenic unsaturation, and the ratio of y:x is about 0.5 or less. When a copolymer of carbon monoxide and ethylene is used, the second ethylenically unsaturated hydrocarbon is not present and the aliphatic polyketone is represented by the above formula where y is 0. When y is other than 0, i.e., a terpolymer is used, [CH 2 -CH 2The [-CO] units and [G-CO] units are randomly distributed throughout the polymer chain, and the ratio of y:x may be from about 0.01 to about 0.1. In some embodiments, the aliphatic polyketone may have a number average molecular weight of from about 1,000 to about 200,000 or from about 20,000 to about 90,000. In other embodiments, the aliphatic polyketone may have a glass transition temperature of about 50 °C, or less than about 40 °C, or less than about 35 °C, or less than about 25 °C.

[0028] The aliphatic polyketone is produced by contacting carbon monoxide and an ethylenically unsaturated hydrocarbon under polymerization conditions in the presence of a catalytic amount of a catalyst formed from a Group VIII metal compound (e.g., palladium, cobalt, and nickel), an anion of a non-halogenated hydrofluoric acid having a pKa of less than about 6, and a bidentate ligand of phosphorus, sulfur, arsenic, or antimony. The range of polymerization is broad, but for illustration, a suitable Group VIII metal compound is palladium acetate, a suitable anion is trifluoroacetate anion or para-toluenesulfonate anion, and suitable bidentate ligands are 1,3-bis(diphenylphosphino)propane or 1,3-bis[di(2-methoxyphenyl)phosphino]propane.

[0029] The polymerization of the aliphatic polyketone can be carried out under conventional polymerization conditions, typically at high temperature and high pressure. The polymerization can be carried out in the gas phase or in the liquid phase in the presence of an inert diluent, such as a lower alcohol like methanol or ethanol. The reaction participants can be contacted by conventional methods such as stirring or shaking, and after the reaction, the aliphatic polyketone product can be recovered, for example, by decantation or filtration. The product may contain metal residues from the catalyst, which can be removed by contact with a selective solvent for the residue. Further details regarding the preparation of aliphatic polyketones are shown, for example, in U.S. Patent Nos. 4,808,699; 4,868,282; 4,761,449; 4,885,328; 4,921,897; 4,935,304; and 5,648,117, each disclosure of which is incorporated herein by reference.

[0030] Thus, in one embodiment, the curable resin composition of the present disclosure may comprise an aliphatic polyketone in an amount of from about 1% to about 30% by weight, or from about 2% to about 25% by weight, or from about 3% to about 20% by weight, or from about 4% to about 17.5% by weight, or from about 5% to about 15% by weight, or even from about 6% to about 12.5% ​​by weight, based on the total weight of the curable resin composition.

[0031] According to another aspect, curing of the curable resin composition may be accomplished by the addition of any chemical material known in the art for curing such adhesives. Such materials are compounds having reactive moieties capable of reacting with the epoxy groups of the epoxy resin, and are referred to herein as "hardeners", although the term "curing agents" is used interchangeably with "hardeners". Curatives also include materials known to those skilled in the art as curatives, activators, catalysts or accelerators. Certain curing agents promote curing by catalytic action, while others participate directly in the resin reaction and become incorporated into the thermoplastic polymer network formed by condensation, chain extension and / or crosslinking of the resin. Depending on the curing agent, heat may or may not be required for significant reaction to occur. Curing agents for epoxy resins include, but are not limited to, aromatic amines, cyclic amines, aliphatic amines, alkylamines, polyetheramines including polyetheramines that may be derived from polypropylene oxide and / or polyethylene oxide, 9,9-bis(4-amino-3-chlorophenyl)fluorene (CAF), acid anhydrides, carboxylic acid amides, polyamides, polyphenols, cresol and phenol novolac resins, imidazoles, guanidines, substituted guanidines, substituted ureas, melamine resins, guanamine derivatives, tertiary amines, Lewis acid complexes such as boron trifluoride and boron trichloride, and polymercaptans. Epoxy modified amine products, Mannich modified products, and Michael modified addition products of any of the above curing agents may also be used. All of the above mentioned curing agents may be used alone or in any combination.

[0032] In one embodiment, the curing agent is a polyfunctional amine. The term "polyfunctional amine" as used herein refers to an amine having at least two primary and / or secondary amino groups in the molecule. For example, the polyfunctional amine may be an aromatic polyfunctional amine having two amino groups bonded to benzene in any one of ortho, meta and para positions, such as phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and 3,5-diaminobenzoic acid, an aliphatic polyfunctional amine such as ethylenediamine and propylenediamine, an alicyclic polyfunctional amine such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 1,3-bispiperidylpropane and 4-aminomethylpiperazine, etc. These polyfunctional amines include: They may be used alone or in mixtures thereof.

[0033] Exemplary aromatic amines are 1,8 diaminonaphthalene, m-phenylenediamine, diethylene glycol toluene diamine, diaminodiphenyl sulfone, diaminodiphenylmethane, diaminodimethyldiphenylmethane, 4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(2-isopropyl-6-methylaniline), 4,4'-methylenebis(2,6-diisopropylaniline), 4,4'-methylenebis(3-chloro-2,6-diphenylamine), 4,4'-methylenebis(2 ... 4,4'-[1,4-phenylenebis(1-methyl-ethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methyl-ethylidene)]bisaniline, 1,3-bis(3-aminophenoxy)benzene, bis-[4-(3-aminophenoxy)phenyl]sulfone, bis-[4-(4-aminophenoxy)phenyl]sulfone, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane. Additionally, aromatic amines may include heterocyclic polyfunctional amine adducts as disclosed in U.S. Pat. Nos. 4,427,802 and 4,599,413, both of which are incorporated herein by reference in their entireties.

[0034] Examples of cyclic amines include, but are not limited to, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpyrazine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, m-xylylenediamine, isophoronediamine, menthene diamine, 1,4-bis(2-amino-2-methylpropyl)piperazine, N,N'-dimethylpiperazine, pyridine, picoline, 1,8-diazabicyclo[5,4,0]-7-undecene, benzylmethylamine, 2-(dimethylaminomethyl)-phenol, 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole.

[0035] Exemplary aliphatic amines include, but are not limited to, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 3-(dimethylamino)propylamine, 3-(diethylamino)-propylamine, 3-(methylamino)propylamine, tris(2-aminoethyl)amine; 3-(2-ethylhexyloxy)propylamine, 3-ethoxypropylamine, 3-methoxypropylamine, 3-(dibutylamino)propylamine, and tetramethyl-ethylenediamine; ethylenediamine; 3,3'-iminobis(propylamine), N-methyl-3,3'-iminobis(propylamine); allylamine, diallylamine, triallylamine, polyoxypropylenediamine, and polyoxypropylenetriamine.

[0036] Exemplary alkylamines include, but are not limited to, methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, t-butylamine, n-octylamine, 2-ethylhexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, di-sec-butylamine, di-t-butylamine, di-n-octylamine, and di-2-ethylhexylamine.

[0037] Exemplary acid anhydrides include cyclohexane-l,2-dicarboxylic anhydride, l-cycloxene-l,2-dicarboxylic anhydride, 2-cycloxene-1,2-dicarboxylic anhydride, 3-cycloxene-1,2-dicarboxylic anhydride, 4-cycloxene-1,2-dicarboxylic anhydride, l-methyl-2-cycloxene-1,2-dicarboxylic anhydride, 1-methyl-4-cycloxene-1,2-dicarboxylic anhydride, 3-methyl-4-cycloxene-1,2-dicarboxylic anhydride, 4-methyl-4-cycloxene-1,2-dicarboxylic anhydride, dodecenylsuccinic anhydride, succinic anhydride, 4-methyl-1-cycloxene-1,2 -dicarboxylic anhydrides, including, but not limited to, phthalic anhydride, hexahydrophthalic anhydride, nadic methyl anhydride, dodecenylsuccinic anhydride, tetrahydrophthalic anhydride, maleic anhydride, pyromellitic anhydride, trimellitic anhydride, benzophenonetetracarboxylic dianhydride, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, dichloromaleic anhydride, chlorendic anhydride, tetrachlorophthalic anhydride, and any derivative or adduct thereof.

[0038] Exemplary imidazoles are imidazole, 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-n-propylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-isopropyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole,

[0043] Examples of imidazoles that may be used include, but are not limited to, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1,2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-dodecyl-2-methylimidazole and 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole.

[0039] Exemplary substituted guanidines are methylguanidine, dimethylguanidine, trimethylguanidine, tetramethylguanidine, methylisobiguanidine, dimethylisobiguanidine, tetramethylisobiguanidine, hexamethylisobiguanidine, heptamethylisobiguanidine and cyanoguanidine (dicyandiamide). Representatives of guanamine derivatives that may be mentioned are alkylated benzoguanamine resins, benzoguanamine resins or methoxymethylethoxymethylbenzoguanamine. Substituted ureas may include p-chlorophenyl-N,N-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron) or 3,4-dichlorophenyl-N,N-dimethylurea (diuron).

[0040] Exemplary tertiary amines are trimethylamine, tripropylamine, triisopropylamine, tributylamine, tri-sec-butylamine, tri-t-butylamine, tri-n-octylamine, N,N-dimethylaniline, N,N-dimethyl-benzylamine, pyridine, methylpiperidine, methylmorpholine, N,N-dimethylaminopyridine, derivatives of morpholine, such as bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(4 Bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(2,6-diethyl-4-morpholino)ethyl)amine, tris(2-(4-morpholino)ethyl)amine, and tris(2-(4-morpholino)propyl)amine, diazabicyclooctane (DABCO), and heterocyclic compounds having an amidine bond, such as 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0041] Amine-epoxy adducts are well known in the art and are described, for example, in U.S. Pat. Nos. 3,756,984, 4,066,625, 4,268,656, 4,360,649, 4,542,202, 4,546,155, 5,134,239, 5,407,978, 5,543,486, 5,548,058, 5,430,112, and 5,464,910, each of which is incorporated herein by reference in its entirety. , 5,439,977, 5,717,011, 5,733,954, 5,789,498, 5,798,399 and 5,801,218. Such amine-epoxy adducts are the product of a reaction between one or more amine compounds and one or more epoxy compounds. Preferably, the adducts are solids that are insoluble in the epoxy resin at room temperature but become soluble upon heating and function as accelerators to increase the cure rate. While any type of amine can be used (heterocyclic amines and / or amines containing at least one secondary nitrogen atom are preferred), imidazole compounds are particularly preferred. Illustrative imidazoles include 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and the like. Other suitable amines include, but are not limited to, piperazines, piperidines, pyrazoles, purines, and triazoles. As the other starting material for the adduct, any type of epoxy compound can be used, including monofunctional and multifunctional epoxy compounds such as those previously described for the epoxy resin component.

[0042] In an embodiment, the curable resin composition of the present disclosure may include a curing agent in an amount of about 5% to about 60% by weight, or about 10% to about 50% by weight, or about 15% to about 45% by weight, or about 20% to about 40% by weight, based on the total weight of the curable resin composition.

[0043] In another embodiment, the curable resin composition may include an additional toughening agent other than the aliphatic polyketone. Examples of such additional toughening agents include, but are not limited to, polyethersulfone (PES), polyetherethersulfone (PEES), polyphenylsulfone, polysulfone, polyimide, polyetherimide, aramid, polyamide, polyester, polyetheretherketone (PEEK), polyurethane, polyurea, polyarylether, polyarylsulfide, polycarbonate, polyphenylene oxide (PPO), modified PPO, and mixtures thereof.

[0044] In some embodiments, the amount of such additional toughening agents present in the curable composition may be from about 0.5% to about 30% by weight, or from about 1% to about 25% by weight, or from about 2% to about 20% by weight, or from about 5% to about 15% by weight, based on the total weight of the curable resin composition.

[0045] In yet another embodiment, the curable resin compositions may also include one or more other additives useful for their intended use. For example, useful optional additives include diluents, stabilizers, surfactants, flow control agents, mold release agents, matting agents, degassing agents, thermoplastic particles (e.g., carboxyl-terminated liquid butadiene acrylonitrile rubber (CTBN), acrylic-terminated liquid butadiene acrylonitrile rubber (ATBN), epoxy-terminated liquid butadiene acrylonitrile rubber (ETBN), elastomeric liquid epoxy resin (LER) adducts, and preformed core-shell rubbers), cure initiators, cure inhibitors, wetting agents, processing aids, fluorescent compounds, UV stabilizers, antioxidants, impact modifiers, corrosion inhibitors, tackifiers, high density particulate fillers (e.g., various naturally occurring clays, e.g., Other naturally occurring or derived materials such as mica, calcium carbonate and aluminum carbonate; various oxides such as ferric oxide, titanium dioxide, calcium oxide and silicon dioxide (e.g., sand); various man-made materials such as precipitated calcium carbonate; and various waste materials such as crushed blast furnace slag), conductive particles (e.g., conductive grades of silver, gold, copper, nickel, aluminum, and carbon and carbon nanotubes) and mixtures thereof.

[0046] When present, the amount of additive included in the curable resin composition may be at least about 0.5 wt%, or at least 2 wt%, or at least 5 wt%, or at least 10 wt%, based on the total weight of the curable resin composition. The amount of additive included in the article may be about 30% by weight or less, or 25% by weight or less, or 20% by weight or less, or 15% by weight or less, based on the total weight of the curable resin composition.

[0047] The curable resin compositions may be prepared, for example, by premixing the individual components and then mixing these premixes, or by mixing all of the components together using conventional equipment such as a stirred vessel, stirring rod, ball mill, sample mixer, static mixer, high shear mixer, ribbon blender, or by hot melting.

[0048] Thus, according to another aspect, the curable resin composition of the present disclosure may be prepared by mixing together about 10% to about 90% by weight of an epoxy resin, about 1% to about 30% by weight of an aliphatic polyketone, and about 5% to about 60% by weight of a curing agent, where the weight percentages are based on the total weight of the curable resin composition.

[0049] Thermoset resins can be formed from the curable resin composition of the present disclosure by mixing the epoxy resin, aliphatic polyketone, and curing agent in the aforementioned ratios and then curing the curable resin composition. In some embodiments, it may be necessary to heat the composition at an elevated temperature, generally to obtain a rapid cure. In a molding process, such as for making fiber-reinforced composite articles, the curable resin composition may be introduced into a mold along with any reinforcing fibers and / or inserts that may be contained within the mold. The cure temperature may be, for example, from about 60°C to about 190°C. If a long (at least 5 minutes, preferably at least 10 minutes) gel time is desired, the cure temperature is preferably 150°C or less. If both a long gel time and a short demold time are desired, a suitable cure temperature may be from about 100°C to about 150°C, preferably 110-150°C, and especially 120-150°C. In some embodiments, it may be preferable to continue the cure until the resulting composite reaches a glass transition temperature that is above the cure temperature. The glass transition temperature at demolding may be at least about 100° C., or at least about 110° C., or at least about 120° C., or even at least about 130° C. Demolding times at cure temperatures of from about 95° C. to about 120° C., especially from about 105° C. to about 120° C., are typically 350 seconds or less, preferably 300 seconds or less, and more preferably 240 seconds or less.

[0050] Thus, according to one embodiment, there is provided a process for producing a fiber reinforced composite article, generally comprising: (i) contacting reinforcing fibers with a curable resin composition in a mold to coat and / or impregnate the reinforcing fibers; and (ii) curing the coated and / or impregnated reinforcing fibers at a temperature of at least about 120°C, or at least about 170°C to about 190°C.

[0051] Thus, to make high performance composite materials and prepregs, reinforcing fibers may be combined with a curable resin composition to form a fiber reinforced resin composition, which may then be cured. The curable resin composition may be combined with the reinforcing fibers according to any of the known prepreg manufacturing techniques. The reinforcing fibers may be fully or partially impregnated with the curable resin composition. In an alternative embodiment, the curable resin composition may be applied to the reinforcing fibers as a separate layer, which is adjacent to and in contact with the reinforcing fibers, but does not substantially impregnate the reinforcing fibers. The prepregs are typically covered on both sides with a protective film and rolled up for storage and shipping, typically at temperatures kept significantly below room temperature to avoid premature curing. Any of the other prepreg manufacturing processes and storage / shipping systems may be used as desired.

[0052] Suitable reinforcing fibers may include, but are not limited to, fibers having high tensile strength, for example, greater than 500 ksi (i.e., 3447 MPa). Fibers useful for this purpose include carbon or graphite fibers, glass fibers, and fibers made of silicon carbide, alumina, boron, quartz, etc. and fibers formed from organic polymers such as polyolefins, poly(benzothiazoles), poly(benzimidazoles), polyarylates, poly(benzoxazoles), aromatic polyamides, polyarylethers, and may include blends having two or more of such fibers. Preferably, the fibers are selected from glass fibers, carbon fibers, and aromatic polyamide fibers. The reinforcing fibers may be used in the form of discontinuous or continuous tows composed of multiple filaments, as continuous unidirectional or multidirectional tapes, or as woven, noncrimped, or nonwoven fabrics. The woven fabric configuration may be selected from plain, satin, or twill patterns. Noncrimped fabrics may have multiple plies and fiber orientations.

[0053] The reinforcing fibers may be sized or not and may be present in a content of about 50% to about 90% by weight, preferably at least 55% by weight, based on the total weight of the fiber reinforced resin composition. For structural applications, it is preferred to use in particular 30% to 70% by volume, more in particular 50% to 7% by volume, of continuous fibers, such as glass or carbon fibers, based on the total volume of the fiber reinforced resin composition.

[0054] To form a fiber reinforced composite article, a plurality of curable, flexible prepreg plies may be laid up in a stacking sequence on a tool to form a prepreg layup. The prepreg plies in the layup may be arranged at a selected orientation, such as 0°, ±45°, 90°, etc., relative to one another. The prepreg layup may be manufactured by techniques that may include, but are not limited to, hand layup, automated tape laying (ATL), advanced fiber placement (AFP), and filament winding.

[0055] Each prepreg is comprised of a sheet or layer of reinforcing fibers impregnated within at least a portion of its volume with a curable resin composition, hi one embodiment, the prepreg has a fiber volume fraction of about 0.50 to 0.60, based on the total volume of the prepreg.

[0056] Prepregs useful in the manufacture of aerospace structures are usually resin-impregnated sheets of unidirectional reinforcing fibers, typically carbon fibers, often referred to as "tapes" or "unidirectional tapes" or "unitapes." The prepregs may be fully impregnated or partially impregnated. The curable resin composition that impregnates the reinforcing fibers may be in a partially cured or uncured state.

[0057] Typically, the prepreg is in a pliable or flexible form ready to be laid up and molded into a three-dimensional structure, then cured into the final fiber-reinforced composite part. This type of prepreg is particularly suitable for the manufacture of load-bearing structural parts, such as aircraft wings, fuselages, bulkheads and control surfaces. Key properties of cured prepreg are high strength and stiffness with reduced weight.

[0058] As mentioned above, curing of the prepreg layup is generally carried out at elevated temperatures up to about 190°C, preferably in the range of about 170°C to about 190°C, and at elevated pressures to suppress the deformation effects of escaping gas or to suppress void formation, suitably at pressures up to 10 bar (1 MPa), preferably in the range of 3 bar (0.3 MPa) to 7 bar (0.7 MPa). Preferably, the curing temperature is achieved by heating at up to 5°C / min, for example 2°C / min to 3°C / min, and maintained for the required period of up to 9 hours, preferably up to 6 hours, for example 2 hours to 4 hours. The use of a catalyst in the curable resin composition may allow even lower curing temperatures. Pressure may be released throughout and the temperature reduced by cooling at up to 5°C / min, for example 3°C / min. Post curing may be carried out at temperatures in the range of about 190°C to about 350°C and at atmospheric pressure, using appropriate heating rates.

[0059] The coating and / or impregnation may be effected by either a wet method or a hot melt method. In the wet method, the curable resin composition is first dissolved in a solvent to reduce the viscosity, after which the coating and / or impregnation of the reinforcing fibers is carried out, and the solvent is evaporated using an oven or the like. In the hot melt method, the coating and / or impregnation may be effected by directly coating and / or impregnating the reinforcing fibers with the curable resin composition, which has been heated to reduce its viscosity, or alternatively, a coating film of the curable resin composition may first be produced on a release paper or the like, the film being placed on one or both sides of the reinforcing fibers, and heat and pressure being applied to achieve the coating and / or impregnation.

[0060] In yet another aspect, a method is provided for producing a fiber reinforced composite article in a reaction injection molding (RIM) system, generally comprising the steps of: a) introducing a fiber preform containing reinforcing fibers into a mold; b) injecting a curable resin composition into the mold; c) impregnating the fiber preform with the curable resin composition; d) heating the impregnated fiber preform at a temperature of at least about 100° C. or at least about 150° C. for a time period to produce an at least partially cured fiber reinforced composite article; and e) optionally subjecting the partially cured fiber reinforced composite article to a post-cure operation at a temperature of from about 100° C. to about 350° C.

[0061] In an alternative aspect, the present disclosure generally provides a method for producing a fiber reinforced composite article in a vacuum resin impregnation molding (VaRTM) system, the process comprising: a) introducing a fiber preform containing reinforcing fibers into a mold; b) injecting a curable resin composition into the mold; c) reducing the pressure in the mold; d) maintaining the mold at about the reduced pressure; e) impregnating the fiber preform with the curable resin composition; f) heating the impregnated fiber preform at a temperature of at least about 100° C. or at least about 150° C. for a time period to produce an at least partially cured fiber reinforced composite article; and optionally subjecting the at least partially cured fiber reinforced composite article to a post-cure operation at a temperature of from about 100° C. to about 350° C.

[0062] The process of the present invention is useful for the manufacture of a wide variety of fiber-reinforced composite articles, including various types of aerospace structures and automotive, rail and marine structures. Examples of aerospace structures include primary and secondary aerospace structural materials (wings, fuselages, bulkheads, flaps, ailerons, cowls, fairings, interior trims, etc.), rocket motor cases, and structural materials for satellites. Examples of automotive structures include vertical and horizontal body panels (fenders, door skins, hoods, roof skins, decklids, tailgates, etc.) and car and truck chassis components.

[0063] While the making and using of various embodiments of the invention have been described in detail above, it should be understood that the invention provides numerous applicable inventive concepts that can be embodied in a wide variety of specific situations. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention. EXAMPLES

[0064] Example 1 An exemplary resin formulation was prepared using the components listed in "Example 1" of Table 1. The formulation was prepared by blending the epoxy resins (Araldite® GY 285, Araldite® MY 0610, Araldite® MY 721, available from Huntsman International LLC or its affiliates) together at room temperature (i.e., about 23°C), then heating the resins to 70°C and adding polyethersulfone commercially available as Virantage® VW-10200 RFP (available from Solvay Specialty Polymers USA, LLC). The mixture was then heated to 120°C and vacuum was applied appropriately for about 30 minutes. The polyethersulfone was dissolved and the volatiles were removed using a solvent, and the mixture was then cooled to 90° C. and the remaining ingredients of Example 1 shown in Table 1 were thoroughly mixed into the resin.

[0065] The exemplary formulation described above was mixed with unidirectional carbon fiber (12K, 185 grams / m 2 Prepregs were prepared using 100% polyester (100% polyester, gsm) to achieve 36 wt % resin in total uncured prepreg. Uncured layups were prepared and the laminates tested according to ASTM methods (described below) for the laminate properties shown in Table 1. The layups were cured in an autoclave at a temperature of about 180° C. for 2 hours using typical manufacturing techniques.

[0066] Several 12-ply laminates having a unidirectional layup and a thickness of about 2.1 mm were formed and subjected to the following tests: ASTM D3039 to measure tensile strength; ASTM D6641 to measure compressive strength; and ASTM D2344 to measure interlaminar shear strength.

[0067] To measure the compressive strength after impact, a 32-ply laminate having a layup according to the construction (+45, 0, -45, +90)n and a thickness of approximately 5.5 mm was impacted at 30 J according to ASTM D7136 and evaluated according to ASTM D7137.

[0068] Environmental conditioning of the composites was performed by immersing the samples in water at 100 °C for 3 days followed by hot and wet mechanical evaluation. Comparative Examples 1 to 3 Comparative Examples 1-3 (Comparative Example 1, Comparative Example 2, and Comparative Example 3) were prepared, cured, and evaluated in the same manner as Example 1 described above. Each prepreg used a different formulation by replacing the aliphatic polyketone toughening agent with a chemically unique toughening agent (i.e., polyamide / nylon, aromatic polyketone, and core-shell rubber). The same carbon fiber and manufacturing methods were used to produce the prepreg laminates. The same ASTM test methods and laminate orientations / thicknesses were used to evaluate tensile, compressive, and interlaminar strengths.

[0069] [Table 1]

[0070] Referring to Table 1, ARADURE® 4,4'-DDS is an epoxy curing agent available from Huntsman International LLC or its affiliates. Ketoprix® EK 63 is a polyketone toughening agent available from Esprix Technologies. Orgasol® 1002 and Orgasol® 3502 are spherical polyamides available from Arkema. Ketaspire® KT 820 SFP is an unreinforced polyetheretherketone (PEEK) available from Solvay. Clearstrength® XT 100 is a methyl methacrylate-butadiene-styrene ("MBS") core-shell additive powder available from Arkema.

[0071] The results in Table 1 show a clear increase in compressive strength, especially compression and interlaminar shear strength, of the exemplary formulations using aliphatic polyketones compared to the comparative examples using nylon, polyetheretherketone, and core-shell rubber toughening agents after hot and humid conditioning. In addition, higher damage resistance as measured by compressive strength after impact was observed. This higher performance does not adversely affect other beneficial properties such as glass transition temperature (Tg), processing, or prepreg tack. One skilled in the art would expect similar benefits for the various embodiments of the curable resin compositions disclosed herein.

Claims

1. 1. A curable resin composition comprising: (a) a thermosetting resin; (b) 1 wt % to 30 wt % of an aliphatic polyketone, based on the total weight of the curable resin composition; (c) a curing agent; and (d) a toughening agent comprising polyethersulfone, polyetherethersulfone, polyphenylsulfone, polysulfone, polyimide, polyetherimide, aramid, polyamide, polyester, polyetheretherketone, polyurethane, polyurea, polyarylether, polyarylsulfide, polycarbonate, polyphenylene oxide, modified polyphenylene oxide, or a mixture thereof.

2. The curable resin composition according to claim 1 , wherein the thermosetting resin is an epoxy resin.

3. 3. The curable resin composition of claim 2, wherein the epoxy resin is selected from difunctional epoxy resins, trifunctional epoxy resins, tetrafunctional epoxy resins, and mixtures thereof.

4. The curable resin composition of claim 2, wherein the aliphatic polyketone is a linear alternating polymer of carbon monoxide and ethylene.

5. 3. The curable resin composition of claim 2, wherein the aliphatic polyketone is a terpolymer of carbon monoxide, ethylene, and one of propylene, n-butene, n-octene, or n-dodecene.

6. A method for preparing a curable resin composition comprising mixing together 10% to 90% by weight of an epoxy resin and 1% to 30% by weight of an aliphatic polyketone, 5% to 60% by weight of a hardener, and 0.5% to 30% by weight of a further toughening agent selected from polyethersulfone, polyetherethersulfone, polyphenylsulfone, polysulfone, polyimide, polyetherimide, aramid, polyamide, polyester, polyetheretherketone, polyurethane, polyurea, polyarylether, polyarylsulfide, polycarbonate, polyphenylene oxide, modified polyphenylene oxide, and mixtures thereof, wherein the weight percentages are based on the total weight of the curable resin composition.

7. A fiber-reinforced resin composition comprising reinforcing fibers and the curable resin composition according to claim 1.

8. 8. The fiber reinforced resin composition according to claim 7, wherein the reinforcing fibers are selected from graphite fibers, glass fibers, fibers formed from silicon carbide, fibers formed from alumina, fibers formed from boron, fibers formed from quartz, fibers formed from organic polymers, and mixtures thereof.

9. 8. The fiber reinforced resin composition of claim 7, wherein the reinforcing fibers are present in an amount of 50% to 90% by weight, based on the total weight of the fiber reinforced resin composition.

10. 13. A method for making a fiber reinforced composite article, comprising the steps of: (i) contacting reinforcing fibers in a mold with the curable resin composition of claim 1 to coat and / or impregnate the reinforcing fibers; and (ii) curing the coated and / or impregnated reinforcing fibers at a temperature of at least 60°C.

11. 11. A method for producing a fiber-reinforced composite article, comprising: contacting reinforcing fibers with the curable resin composition of claim 1 to coat and / or impregnate the reinforcing fibers; and curing the coated and / or impregnated reinforcing fibers.

12. 11. A method for producing a fiber reinforced composite article in a RIM system, comprising: a) introducing a fiber preform containing reinforcing fibers into a mold; b) injecting the curable resin composition of claim 1 into the mold; c) impregnating the fiber preform with the curable resin composition; d) heating the impregnated fiber preform at a temperature of at least 60°C for a time to produce an at least partially cured fiber reinforced composite article; and e) optionally subjecting the partially cured fiber reinforced composite article to a post-curing operation at a temperature of from 100°C to 350°C.

13. 11. A method for producing a fiber reinforced composite article in a VaRTM system, comprising: a) introducing a fiber preform containing reinforcing fibers into a mold; b) injecting the curable resin composition of claim 1 into the mold; c) reducing the pressure in the mold; d) maintaining the mold at about the reduced pressure; e) impregnating the fiber preform with the curable resin composition; f) heating the impregnated fiber preform at a temperature of at least 60°C for a time to produce an at least partially cured fiber reinforced composite article; and optionally subjecting the at least partially cured fiber reinforced composite article to a post-cure operation at a temperature of from 100°C to 350°C.

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