An epoxy toughening curing agent, its preparation method, and an epoxy resin composition

Abstract

The present invention belongs to the technical field of polymer materials, and provides an epoxy toughening curing agent and a preparation method thereof, and an epoxy resin composition. The raw materials for preparing the epoxy toughening curing agent include a hydroxyl-containing acrylate copolymer, a diisocyanate, and a blocking agent; the polymerization monomers of the hydroxyl-containing acrylate copolymer include (meth) acrylic acid, (meth) acrylate, and hydroxyl-containing (meth) acrylate. The present invention uses the epoxy toughening curing agent in the epoxy resin composition through the design and mutual compounding of the raw materials, and can undergo a curing reaction with the epoxy resin, and at the same time has thermal deblocking properties, and can release active isocyanate groups in thermal curing to react with active hydrogen groups in the resin system to form a multiple cross-linked structure, so that the cured product of the epoxy resin composition has significantly improved toughness, and maintains high strength and high elastic modulus, and obtains excellent comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to an epoxy toughening curing agent, a preparation method thereof, and an epoxy resin composition. Background Art

[0002] Epoxy resin is a thermosetting polymer. When it cures, no low-molecular substances are precipitated. The cured product has a low molding shrinkage rate, good dimensional stability, good resistance to acid, alkali, and solvent corrosion, and at the same time has excellent electrical insulation, heat resistance, and weather resistance. It has been widely used in many fields such as aerospace, construction, machinery, electronic telecommunications, and vehicle engineering. However, epoxy resin also has some inherent disadvantages. For example, its crosslinking density is relatively high, the cured product is brittle, lacks toughness, has a low impact strength, and is prone to cracking. These disadvantages make it difficult for the epoxy resin cured product to meet the requirements of the increasingly developing engineering technology, and limit the further application of epoxy resin in some high-tech fields.

[0003] In order to solve the brittleness problem of epoxy resin cured products, toughening and modifying them is a common idea in the industry. For example, CN109651767A discloses an epoxy resin composition toughened with epoxy liquid rubber, the raw material composition by weight is: 100 parts of epoxy resin, 1-20 parts of epoxy liquid rubber, 1-40 parts of curing agent, 1-20 parts of accelerator; the epoxy liquid rubber is a mixture of one or more of epoxy liquid natural rubber, epoxy liquid polyisoprene rubber, epoxy liquid nitrile rubber, epoxy polyacrylate liquid rubber; the composition has a significant toughening effect after curing. CN105176003A discloses an epoxy resin composite, which comprises 39-84% of epoxy resin and 8.4-23.4% of nano core-shell rubber particles by weight, and further comprises a silane coupling agent, which is added to the composite in the form of coating on the surface of the nano core-shell rubber particles, and the content of the silane coupling agent is 1-10% of the weight of the nano core-shell rubber particles; the nano core-shell rubber particles are butadiene-styrene-methyl methacrylate ternary graft copolymers, which can improve the strength and flexibility of the epoxy resin. CN114671996A discloses a polyurethane epoxy toughening agent and an epoxy resin composition, wherein the polyurethane epoxy toughening agent is prepared by macromolecular diol, micromolecular diol, bisphenol A polyoxyethylene ether, epoxy resin, diisocyanate and end-capping agent, has a segment structure similar to conventional epoxy resin, has good compatibility with epoxy resin, contains epoxy group and acrylate group in the molecule, and can be chemically bonded with epoxy resin matrix through amine curing agent, so that epoxy resin cured product has higher strength and toughness. CN1536021A discloses a toughened epoxy resin composition, comprising epoxy resin and composite powder with a mass ratio of 100:(0.5-95), wherein the composite powder comprises inorganic particles and rubber particles, and is prepared by uniformly mixing raw materials comprising irradiated or non-irradiated rubber latex and inorganic particle slurry and drying, and using the composite powder to modify epoxy resin can reduce the loss of resin rigidity while improving toughness of epoxy resin.

[0004] Currently known epoxy toughening agents mainly include rubber materials, inorganic particles, polyurethane, etc., but they all have certain defects. For example, while rubber materials improve toughness, they will lead to a loss of yield strength and elastic modulus; inorganic particles have poor dispersibility and their toughening effect is not obvious enough; polyurethane and other materials have a large load when used for epoxy toughening, and will lead to a decrease in the elastic modulus and strength of epoxy cured products. Therefore, how to make epoxy resin cured products have high toughness, high strength and high elastic modulus is a problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide an epoxy toughening curing agent and a preparation method thereof, and an epoxy resin composition. Through the design and compounding of raw materials, the epoxy toughening curing agent is used in the epoxy resin composition, can undergo a curing reaction with the epoxy resin, and has thermal deblocking properties. It can release active isocyanate groups during thermal curing to react with active hydrogen groups in the resin system to form a multiple cross-linked structure, so that the cured product of the epoxy resin composition has significantly improved toughness, maintains high strength and high elastic modulus, and obtains excellent comprehensive performance.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an epoxy toughening curing agent, wherein raw materials for preparing the epoxy toughening curing agent include a hydroxyl-containing acrylate copolymer, a diisocyanate and a blocking agent; the polymerization monomers of the hydroxyl-containing acrylate copolymer include a combination of (meth)acrylic acid, (meth)acrylate and hydroxyl-containing (meth)acrylate; the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is denoted as n1, the molar amount of NCO groups in the diisocyanate is denoted as n2, and the molar amount of the blocking agent is denoted as n3, n1:n2=1:(1.2-2), 1≤(n1+n3) / n2≤1.1.

[0008] In the preparation raw materials of the present invention, the hydroxyl-containing acrylate copolymer contains hydroxyl and carboxyl groups, wherein the hydroxyl group reacts with diisocyanate to obtain a prepolymer containing NCO groups, and the prepolymer reacts with a blocking agent to block the NCO groups to obtain an epoxy toughening curing agent having carboxyl groups. The epoxy toughening curing agent is used in an epoxy resin composition. On the one hand, it can utilize the carboxyl groups therein to undergo a curing reaction with epoxy resin, and on the other hand, it has thermal deblocking properties, releasing active NCO groups during thermal curing to undergo cross-linking reactions with active hydrogen groups (such as hydroxyl groups, amino groups, etc.) in the resin system, forming a multiple cross-linked network structure in the resin system, so that the cured product of the epoxy resin composition has significantly improved toughness and higher elongation, as well as high strength and high elastic modulus, thereby obtaining excellent comprehensive mechanical properties.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0010] In the present invention, the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is denoted as n1, the molar amount of NCO groups in the diisocyanate is denoted as n2, and the molar amount of the blocking agent is denoted as n3. Then, n1:n2 = 1:(1.2 - 2). For example, n1:n2 can be 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5, 1:1.55, 1:1.6, 1:1.65, 1:1.7, 1:1.75, 1:1.8, 1:1.85, 1:1.9, 1:1.95, etc. Preferably, it is 1:(1.5 - 2).

[0011] 1 ≤ (n1 + n3) / n2 ≤ 1.1. For example, (n1 + n3) / n2 can be 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, or 1.09, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range. Preferably, 1 < (n1 + n3) / n2 ≤ 1.06.

[0012] In the present invention, the term “(meth)acrylic acid” means acrylic acid and / or methacrylic acid. The term “(meth)acrylate” means acrylate and / or methacrylate. The term “hydroxyl-containing (meth)acrylate” means hydroxyl-containing acrylate and / or hydroxyl-containing methacrylate. When similar expressions are involved hereinafter, they have similar meanings.

[0013] Preferably, the (meth)acrylate includes any one or a combination of at least two of (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-propyl ester, (meth)acrylic acid isopropyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid isobutyl ester, and (meth)acrylic acid isobornyl ester. Further preferably, it is any one or a combination of at least two of methyl methacrylate, methyl acrylate, n-butyl methacrylate, n-butyl acrylate, isobornyl methacrylate, and isobornyl acrylate.

[0014] Preferably, the hydroxyl-containing (meth)acrylate includes any one or a combination of at least two of (meth)acrylic acid hydroxyethyl ester, (meth)acrylic acid hydroxypropyl ester, and (meth)acrylic acid hydroxybutyl ester. Further preferably, it is (meth)acrylic acid hydroxyethyl ester.

[0015] Preferably, the polymerization monomers of the hydroxyl-containing acrylate copolymer include the following components by mass parts:

[0016] 60 - 80 parts of methyl methacrylate,

[0017] 2 - 10 parts of (meth)acrylic acid,

[0018] 5-15 parts of n-butyl (meth)acrylate,

[0019] 8-15 parts of 2-hydroxyethyl (meth)acrylate,

[0020] 1-10 parts of isobornyl (meth)acrylate.

[0021] Among them, the mass parts of methyl methacrylate are 60-80 parts, for example, it can be 62 parts, 65 parts, 68 parts, 70 parts, 72 parts, 75 parts or 78 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0022] Preferably, the hydroxyl-containing acrylate copolymer uses methyl methacrylate as the main monomer, and the mass percentage content of methyl methacrylate in the comonomer is ≥55%, for example, it can be 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78% or 80%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0023] The mass parts of (meth)acrylic acid are 2-10 parts, for example, it can be 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 9 parts or 9.5 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0024] Preferably, the mass percentage content of (meth)acrylic acid in the comonomer is ≥2%, for example, it can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 9% or 9.5%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range, and further preferably 3-8%.

[0025] The (meth)acrylic acid is acrylic acid and / or methyl acrylic acid, preferably methyl acrylic acid.

[0026] The mass parts of n-butyl (meth)acrylate are 5-15 parts, for example, it can be 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts or 14 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0027] Preferably, the mass percentage content of n-butyl (meth)acrylate in the comonomer is ≥4%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0028] The n-butyl (meth)acrylate is n-butyl acrylate and / or n-butyl methacrylate, preferably n-butyl acrylate.

[0029] The parts by mass of 2-hydroxyethyl (meth)acrylate are 8-15 parts, for example, it can be 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts or 14.5 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0030] Preferably, the mass percentage content of 2-hydroxyethyl (meth)acrylate in the comonomer is ≥7%, for example, it can be 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5% or 15%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0031] The 2-hydroxyethyl (meth)acrylate is 2-hydroxyethyl acrylate and / or 2-hydroxyethyl methacrylate, preferably 2-hydroxyethyl methacrylate.

[0032] The parts by mass of isobornyl (meth)acrylate are 1-10 parts, for example, it can be 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 9 parts or 9.5 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range, and further preferably 4-8 parts.

[0033] Preferably, the mass percentage content of isobornyl (meth)acrylate in the comonomer is ≥0.5%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range, and further preferably 3-8%.

[0034] The isobornyl (meth)acrylate is isobornyl acrylate and / or isobornyl methacrylate, preferably isobornyl methacrylate.

[0035] Preferably, the number-average molecular weight of the hydroxyacrylate copolymer is 2,000-20,000, for example, it can be 2,200, 2,500, 2,800, 3,000, 3,200, 3,500, 3,800, 4,000, 4,200, 4,500, 4,800, 5,000, 5,200, 5,500, 5,800, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000 or 19,000, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0036] Preferably, the hydroxyl value of the hydroxyacrylate copolymer is 40-100 mg KOH / g, for example, it can be 45 mg KOH / g, 50 mg KOH / g, 55 mg KOH / g, 60 mg KOH / g, 65 mg KOH / g, 70 mg KOH / g, 75 mg KOH / g, 80 mg KOH / g, 85 mg KOH / g, 90 mg KOH / g or 95 mg KOH / g, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range. More preferably, it is 48-78 mg KOH / g.

[0037] In the present invention, the hydroxyacrylate copolymer is prepared by a free radical polymerization reaction known in the art. Exemplarily, its preparation method includes: the polymerization monomers are subjected to a polymerization reaction in the presence of an initiator and a solvent to obtain the hydroxyacrylate copolymer.

[0038] Preferably, the initiator includes an azo initiator and / or an organic peroxide, and more preferably any one or a combination of at least two of azodiisobutyronitrile, benzoyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide.

[0039] Preferably, based on the mass of the polymerization monomers being 100%, the mass of the initiator is 0.1-1%, for example, it can be 0.2%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9% or 0.95%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0040] Preferably, the solvent includes any one or a combination of at least two of ester solvents, aromatic hydrocarbon solvents, and ketone solvents, and ethyl acetate and / or butyl acetate are further preferred.

[0041] Preferably, the mass ratio of the solvent to the polymerization monomer is (0.1 - 1):1, and can be, for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, or 0.9:1, etc., and (0.2 - 0.6):1 is further preferred.

[0042] Preferably, an inhibitor is further added to the polymerization reaction.

[0043] Preferably, the inhibitor includes any one or a combination of at least two of hydroquinone, 2,6 - di - tert - butyl - p - cresol, hydroquinone, benzoquinone, and 2,2,6,6 - tetramethylpiperidine nitroxide radical.

[0044] Preferably, based on the mass of the polymerization monomer being 100%, the mass of the inhibitor ≤ 0.5%, and can be, for example, 0, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, or 0.45%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range, and 0 - 0.12% is further preferred.

[0045] Preferably, the temperature of the polymerization reaction is 80 - 120 °C, and can be, for example, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, or 115 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0046] Preferably, the time of the polymerization reaction is 1 - 12 h, and can be, for example, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 4.8 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, or 11.5 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0047] Preferably, the diisocyanate includes any one or a combination of at least two of aliphatic diisocyanates, cycloaliphatic diisocyanates, and aromatic diisocyanates.

[0048] Preferably, the diisocyanate includes any one or a combination of at least two of isophthalic diisocyanate (XDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), tetramethyl-m-xylene diisocyanate (TMXDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI).

[0049] Preferably, the blocking agent includes any one or a combination of at least two of 3,5-dimethylpyrazole, 3-methylpyrazole, pyrazole, methyl ethyl ketoxime, and caprolactam.

[0050] In a second aspect, the present invention provides a method for preparing an epoxy toughening curing agent as described in the first aspect, and the preparation method includes:

[0051] Performing a first reaction on the hydroxyl-containing acrylate copolymer and the diisocyanate to obtain a prepolymer;

[0052] Performing a second reaction on the prepolymer and the blocking agent to obtain the epoxy toughening curing agent.

[0053] Preferably, the first reaction is carried out in the presence of a catalyst.

[0054] Preferably, the catalyst includes any one or a combination of at least two of organic bismuth catalysts, organic tin catalysts, and amine catalysts.

[0055] Preferably, the first reaction is carried out in the presence of a solvent.

[0056] Preferably, the solvent includes any one or a combination of at least two of ester solvents, aromatic solvents, and ketone solvents, and further preferably any one or a combination of at least two of ethyl acetate, butyl acetate, acetone, and methyl ethyl ketone.

[0057] Preferably, the temperature of the first reaction is 50 - 130 °C, for example, it can be 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, or 125 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0058] Preferably, the time of the first reaction is 1 - 6 h, for example, it can be 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h, 5 h, 5.2 h, 5.5 h or 5.8 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0059] Preferably, the temperature of the second reaction is 30 - 120 °C, for example, it can be 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C or 115 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0060] Preferably, the time of the second reaction is 0.5 - 6 h, for example, it can be 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h, 5 h, 5.2 h, 5.5 h or 5.8 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0061] Preferably, after the second reaction, it further includes the step of removing the solvent.

[0062] Preferably, the method of removal includes vacuum distillation.

[0063] On the other hand, the present invention provides an application of the epoxy toughening curing agent as described in the first aspect, and the epoxy toughening curing agent is applied to epoxy electronic glue, wind turbine blade toughening material or carbon fiber composite reinforcing material.

[0064] In the third aspect, the present invention provides an epoxy resin composition, and the epoxy resin composition includes epoxy resin and the epoxy toughening curing agent as described in the first aspect.

[0065] Preferably, the epoxy resin composition further includes a curing agent.

[0066] Preferably, the epoxy resin composition includes the following components by mass parts:

[0067] Epoxy resin 100 parts,

[0068] The curing agent is 5 - 150 parts,

[0069] and the epoxy toughening curing agent is 5 - 25 parts.

[0070] Preferably, the epoxy resin includes any one or a combination of at least two of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenolic epoxy resin, and biphenyl epoxy resin.

[0071] Preferably, based on 100 parts by mass of the epoxy resin, the mass parts of the curing agent are 5 - 150 parts, for example, it can be 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts or 140 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the scope.

[0072] Preferably, the curing agent includes any one or a combination of at least two of amine curing agents, anhydride curing agents, and phenolic curing agents, and amine curing agents are further preferred.

[0073] Preferably, based on 100 parts by mass of the epoxy resin, the mass parts of the epoxy toughening curing agent are 5 - 25 parts, for example, it can be 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts or 24 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the scope.

[0074] Preferably, the epoxy resin composition further includes a curing accelerator.

[0075] Preferably, the curing accelerator includes any one or a combination of at least two of imidazole compounds, tertiary amines, and tertiary phosphines.

[0076] Preferably, the curing method of the epoxy resin composition includes: subjecting the epoxy resin composition to a curing reaction under heat treatment conditions to obtain an epoxy resin cured product.

[0077] Preferably, the temperature of the curing reaction is 130 - 180 °C, for example, it can be 135 °C, 140 °C, 145 °C, 150 °C, 155 °C, 160 °C, 165 °C, 170 °C or 175 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the scope.

[0078] Preferably, the curing reaction time is 10-60 min, for example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0079] In a fourth aspect, the present invention provides a use of the epoxy resin composition as described in the third aspect in epoxy electronic adhesive, wind blades or prepregs.

[0080] In a fifth aspect, the present invention provides a reinforced composite material, comprising a reinforcing material and the epoxy resin composition as described in the third aspect attached to the reinforcing material.

[0081] Optionally, the reinforcement material includes carbon fiber reinforcement material, such as carbon fiber cloth.

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] (1) The raw materials for preparing the epoxy toughening curing agent provided by the present invention include a hydroxyl-containing acrylate copolymer, a diisocyanate and a blocking agent. Through the design and compounding of the raw materials, the epoxy toughening curing agent can be used in an epoxy resin composition. On the one hand, it can undergo a curing reaction with the epoxy resin. On the other hand, it has thermal deblocking properties and can release active NCO groups during thermal curing to react with active hydrogen groups in the resin system to form a multiple cross-linking structure, so that the cured product of the epoxy resin composition has significantly improved toughness and maintains high strength and high elastic modulus.

[0084] (2) The present invention designs and optimizes the epoxy toughening curing agent so that the elastic modulus of the cured epoxy resin composition using the epoxy toughening curing agent is ≥687 MPa and the elongation at break is ≥28%. The epoxy toughening curing agent has high toughness, high strength and high modulus and has excellent comprehensive mechanical properties. DETAILED DESCRIPTION

[0085] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0086] As used herein, the terms "comprises," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0087] "Optionally", "alternatively" or "either" means that the matters or events described thereafter may or may not occur, and such description includes the situations where the events occur and the situations where the events do not occur.

[0088] In the present invention, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features, which are used to distinguish and describe the features, without any order or importance. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0089] In the following specific embodiments of the present invention, the materials for which the preparation methods are not provided are all commercially available chemicals.

[0090] In the following, a plurality of embodiments will be taken as examples to elaborate on the epoxy toughening curing agent and its preparation method described in the present invention, but the epoxy toughening curing agent and its preparation method described in the present invention are not limited to these embodiments.

[0091] Example 1

[0092] An epoxy toughening curing agent, the preparation raw materials of which include a hydroxyl group-containing acrylate copolymer, a diisocyanate (HDI) and a blocking agent (3,5-dimethylpyrazole). The molar amount of the hydroxyl group in the hydroxyl group-containing acrylate copolymer is n1, the molar amount of the NCO group in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3, n1:n2 = 1:1.5, (n1 + n3) / n2 = 1.02; the polymerization monomers of the hydroxyl group-containing acrylate copolymer include the following components in parts by mass:

[0093] 60 parts of methyl methacrylate

[0094] 4 parts of methacrylic acid

[0095] 5 parts of n-butyl acrylate

[0096] 8 parts of 2-hydroxyethyl methacrylate

[0097] 6 parts of isobornyl methacrylate.

[0098] The preparation method of the epoxy toughening curing agent is as follows:

[0099] (1) Preparation of the hydroxyl group-containing acrylate copolymer

[0100] The polymerization monomer and ethyl acetate (industrial grade) were mixed evenly at a mass ratio of 7:3. An initiator (azobisisobutyronitrile, AIBN) was added. Based on the total mass of the polymerization monomer being 100%, the mass of AIBN was 0.5%. Then, a polymerization inhibitor (2,6-di-tert-butyl-p-cresol, BHT, and the mass of BHT was 0.3% of the total mass of the polymerization monomer) was added. The system was heated to 60 °C and reacted for 10 h to obtain a solution containing a hydroxy acrylate copolymer. The number-average molecular weight of the hydroxy acrylate copolymer was 17,542, and the hydroxyl value was 64 mg KOH / g.

[0101] (2) Preparation of an epoxy toughening curing agent

[0102] Diisocyanate HDI was added to the solution of the hydroxy acrylate copolymer obtained in step (1), and the reaction was carried out at 70 °C for 4 h to obtain a prepolymer containing NCO groups; then 3,5-dimethylpyrazole was added, and the reaction was carried out at 70 °C for 4 h to consume the NCO groups. Then, the solvent was removed by vacuum distillation to obtain the epoxy toughening curing agent.

[0103] Example 2

[0104] An epoxy toughening curing agent, the preparation raw materials of which include a hydroxy acrylate copolymer, a diisocyanate (HDI), and a blocking agent (methyl ethyl ketoxime). The molar amount of hydroxyl groups in the hydroxy acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3. n1:n2 = 1:1.5, (n1 + n3) / n2 = 1.02; the polymerization monomers of the hydroxy acrylate copolymer include the following components by mass:

[0105] 62 parts of methyl methacrylate

[0106] 5 parts of methacrylic acid

[0107] 8 parts of n-butyl acrylate

[0108] 10 parts of 2-hydroxyethyl methacrylate

[0109] 6 parts of isobornyl methacrylate.

[0110] The preparation method of the epoxy toughening curing agent is as follows:

[0111] (1) Preparation of a hydroxy acrylate copolymer

[0112] Mix the polymerization monomer and ethyl acetate (industrial grade) evenly at a mass ratio of 7:3, add an initiator (AIBN). Based on the total mass of the polymerization monomer being 100%, the mass of AIBN is 0.5%. Then add a polymerization inhibitor (BHT, whose mass is 0.3% of the total mass of the polymerization monomer). Heat the system to 65 °C and react for 8 h to obtain a solution containing a hydroxy acrylate copolymer. The number-average molecular weight of the hydroxy acrylate copolymer is 18928, and the hydroxyl value is 68 mg KOH / g.

[0113] (2) Prepare an epoxy toughening curing agent

[0114] Add diisocyanate HDI to the solution of the hydroxy acrylate copolymer obtained in step (1), react at 75 °C for 3.5 h to obtain a prepolymer containing NCO groups; then add methyl ethyl ketoxime and react at 70 °C for 4 h to consume the NCO groups, and then remove the solvent by vacuum distillation to obtain the epoxy toughening curing agent.

[0115] Example 3

[0116] An epoxy toughening curing agent, the preparation raw materials of which include a hydroxy acrylate copolymer, a diisocyanate (HDI) and a blocking agent (pyrazole). The molar amount of hydroxyl groups in the hydroxy acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3, n1:n2 = 1:1.6, (n1 + n3) / n2 = 1.03; the polymerization monomers of the hydroxy acrylate copolymer include the following components by mass parts:

[0117] 65 parts of methyl methacrylate

[0118] 8 parts of methacrylic acid

[0119] 12 parts of n-butyl acrylate

[0120] 12 parts of 2-hydroxyethyl methacrylate

[0121] 8 parts of isobornyl methacrylate.

[0122] The preparation method of the epoxy toughening curing agent is as follows:

[0123] (1) Prepare a hydroxy acrylate copolymer

[0124] Mix the polymerization monomer and ethyl acetate (industrial grade) evenly at a mass ratio of 7:3, add the initiator AIBN. Based on the total mass of the polymerization monomer being 100%, the mass of AIBN is 0.5% of the total mass of the polymerization monomer. Then add the inhibitor (BHT, whose mass is 0.2% of the total mass of the polymerization monomer). Heat the system to 60 °C and react for 10 h to obtain a solution containing a hydroxyacrylate copolymer. The number-average molecular weight of the hydroxyacrylate copolymer is 17207, and the hydroxyl value is 62 mg KOH / g.

[0125] (2) Prepare an epoxy toughening curing agent

[0126] Add the diisocyanate HDI to the solution of the hydroxyacrylate copolymer obtained in step (1), react at 75 °C for 3 h to obtain a prepolymer containing NCO groups; then add pyrazole and react at 70 °C for 2 h to consume the NCO groups, and then remove the solvent by vacuum distillation to obtain the epoxy toughening curing agent.

[0127] Example 4

[0128] An epoxy toughening curing agent, the preparation raw materials of which include a hydroxyacrylate copolymer, a diisocyanate (IPDI) and a blocking agent (3,5-dimethylpyrazole). The molar amount of hydroxyl groups in the hydroxyacrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3. n1:n2 = 1:1.3, (n1 + n3) / n2 = 1.02; the polymerization monomers of the hydroxyacrylate copolymer include the following components in parts by mass:

[0129] 80 parts of methyl methacrylate

[0130] 4 parts of methacrylic acid

[0131] 6 parts of n-butyl acrylate

[0132] 8 parts of 2-hydroxyethyl methacrylate

[0133] 6 parts of isobornyl methacrylate.

[0134] The preparation method of the epoxy toughening curing agent is as follows:

[0135] (1) Prepare a hydroxyacrylate copolymer

[0136] The polymerizable monomers and ethyl acetate (industrial grade) were mixed evenly at a mass ratio of 7:3. Then, initiator AIBN was added. Based on the total mass of the polymerizable monomers being 100%, the mass of AIBN was 0.5% of the total mass of the polymerizable monomers. Next, a polymerization inhibitor (BHT, with a mass of 0.2% of the total mass of the polymerizable monomers) was added. The system was heated to 60 °C and reacted for 10 h to obtain a solution containing a hydroxyacrylate copolymer. The number-average molecular weight of the hydroxyacrylate copolymer was 16,211, and the hydroxyl value was 51 mg KOH / g.

[0137] (2) Preparation of an epoxy toughening curing agent

[0138] Diisocyanate IPDI was added to the solution of the hydroxyacrylate copolymer obtained in step (1), and the reaction was carried out at 70 °C for 3 h to obtain a prepolymer containing NCO groups. Then, 3,5-dimethylpyrazole was added, and the reaction was carried out at 70 °C for 2 h to consume the NCO groups. Subsequently, the solvent was removed by vacuum distillation to obtain the epoxy toughening curing agent.

[0139] Example 5

[0140] An epoxy toughening curing agent, the preparation raw materials of which include a hydroxyacrylate copolymer, a diisocyanate (IPDI), and a blocking agent (methyl ethyl ketoxime). The molar amount of hydroxyl groups in the hydroxyacrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3. n1:n2 = 1:1.3, (n1 + n3) / n2 = 1.02. The polymerizable monomers of the hydroxyacrylate copolymer include the following components in parts by mass:

[0141] 75 parts of methyl methacrylate

[0142] 5 parts of methacrylic acid

[0143] 5 parts of n-butyl acrylate

[0144] 10 parts of 2-hydroxyethyl methacrylate

[0145] 6 parts of isobornyl methacrylate.

[0146] The preparation method of the epoxy toughening curing agent is as follows:

[0147] (1) Preparation of a hydroxyacrylate copolymer

[0148] The polymerizable monomers and ethyl acetate (industrial grade) were mixed evenly at a mass ratio of 7:3. Then, initiator AIBN was added. Based on the total mass of the polymerizable monomers being 100%, the mass of AIBN was 0.5% of the total mass of the polymerizable monomers. Next, a polymerization inhibitor (BHT, with a mass of 0.2% of the total mass of the polymerizable monomers) was added. The system was heated to 60 °C and reacted for 10 h to obtain a solution containing a hydroxyacrylate copolymer. The number-average molecular weight of the hydroxyacrylate copolymer was 13,856, and the hydroxyl value was 62 mg KOH / g.

[0149] (2) Preparation of an epoxy toughening curing agent

[0150] Diisocyanate IPDI was added to the solution of the hydroxyacrylate copolymer obtained in step (1), and the reaction was carried out at 75 °C for 3 h to obtain a prepolymer containing NCO groups. Then, methyl ethyl ketoxime was added, and the reaction was carried out at 70 °C for 2 h to consume the NCO groups. Subsequently, the solvent was removed by vacuum distillation to obtain the epoxy toughening curing agent.

[0151] Example 6

[0152] An epoxy toughening curing agent, whose preparation raw materials include a hydroxyacrylate copolymer, diisocyanate (IPDI), and a blocking agent (pyrazole). The molar amount of hydroxyl groups in the hydroxyacrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, and the molar amount of the blocking agent is denoted as n3. n1:n2 = 1:1.5, (n1 + n3) / n2 = 1.03. The polymerizable monomers of the hydroxyacrylate copolymer include the following components in parts by mass:

[0153] 70 parts of methyl methacrylate

[0154] 5 parts of methacrylic acid

[0155] 7 parts of n-butyl acrylate

[0156] 9 parts of 2-hydroxyethyl methacrylate

[0157] 6 parts of isobornyl methacrylate.

[0158] The preparation method of the epoxy toughening curing agent is as follows:

[0159] (1) Preparation of a hydroxyacrylate copolymer

[0160] The polymerization monomer and ethyl acetate (industrial grade) were mixed evenly at a mass ratio of 7:3. Initiator AIBN was added. Based on the total mass of the polymerization monomer being 100%, the mass of AIBN was 0.5% of the total mass of the polymerization monomer. Then, a polymerization inhibitor (BHT, with its mass being 0.2% of the total mass of the polymerization monomer) was added. The system was heated to 60 °C and reacted for 10 h to obtain a solution containing a hydroxyacrylate copolymer. The number-average molecular weight of the hydroxyacrylate copolymer was 15,892, and the hydroxyl value was 55 mg KOH / g.

[0161] (2)Preparation of epoxy toughening curing agent

[0162] Diisocyanate IPDI was added to the solution of the hydroxyacrylate copolymer obtained in step (1), and the reaction was carried out at 75 °C for 3 h to obtain a prepolymer containing NCO groups; then pyrazole was added, and the reaction was carried out at 70 °C for 2 h to consume the NCO groups. Then, the solvent was removed by vacuum distillation to obtain the epoxy toughening curing agent.

[0163] Comparative Example 1

[0164] An epoxy toughening curing agent, the difference in its preparation raw materials from those of Example 1 was only that the blocking agent was replaced with an equimolar amount of 2-hydroxyethyl methacrylate, and other components, dosages, and preparation methods were the same as those of Example 1.

[0165] Comparative Example 2

[0166] An epoxy toughening curing agent, the difference in its preparation raw materials from those of Example 1 was only that the polymerization monomer of the hydroxyacrylate copolymer did not contain methacrylic acid, and other components, dosages, and preparation methods were the same as those of Example 1.

[0167] Comparative Example 3

[0168] An epoxy toughening curing agent, which was a commercially available polyurethane prepolymer FS-2211 (Guangzhou Haoyi New Materials).

[0169] The following will detail the epoxy resin composition of the present invention with multiple application examples, but the epoxy resin composition of the present invention is not limited to these application examples.

[0170] Application Examples 1-6, Comparative Application Examples 1-3

[0171] An epoxy resin composition, comprising the following components in parts by mass:

[0172] 100 parts of epoxy resin

[0173] 120 parts of curing agent

[0174] 10 parts of epoxy toughening curing agent;

[0175] Among them, the epoxy resin is a mixture of bisphenol A epoxy resin (epoxy resin E44, Linyuan) and bisphenol F epoxy resin (NPEF-170, Nan Ya) in a mass ratio of 4:6, the curing agent is an amine curing agent (Ecure-05, Shanghai Feimi Materials), and the epoxy toughening curing agent is the epoxy toughening curing agent provided in Examples 1-6 and Comparative Examples 1-3 respectively.

[0176] Comparative Application Example 4

[0177] An epoxy resin composition is different from Application Example 1 only in that no epoxy toughening curing agent is added, and other components and amounts are the same as those in Application Example 1.

[0178] The epoxy resin composition was tested for performance as follows:

[0179] Prepare standard specimens and make them into dog-bone (dumbbell) specimens to ensure the accuracy and repeatability of the test results. Apply the epoxy resin composition to be tested on the dog-bone mold, place it in an oven at 150°C for 30 min, and demold it after curing to ensure the integrity of the specimen. The cured product is tested for elongation according to the method in standard GB / T 1040.2-2022 "Determination of tensile properties of plastics", and the flexural modulus is tested according to the method in standard GB / T 9341-2008. The test results are shown in Table 1:

[0180] Table 1

[0181]

[0182] Combined with the test data in Table 1, it can be seen that the present invention, through the design of the epoxy toughening curing agent, can be used in the epoxy resin composition to form a multiple cross-linked network, provide excellent toughening and strengthening effects, so that the elastic modulus of the cured epoxy resin composition is 687-742 MPa, and the elongation at break is ≥28%, which can reach 28-38%; compared with the comparative application example 4 without toughening modification, the epoxy resin composition provided by the application examples 1-6 of the present invention has significantly improved toughness after curing, and maintains high strength and high elastic modulus, and obtains excellent comprehensive mechanical properties.

[0183] The epoxy toughening curing agent in Comparative Application Example 1 does not have thermal desealing properties and cannot form a multiple cross-linking structure in the epoxy resin system, resulting in a significant decrease in both the elongation at break and the elastic modulus; the epoxy toughening curing agent in Comparative Application Example 2 does not contain a carboxyl group and cannot cause sufficient cross-linking reaction of the epoxy resin, which can improve the elongation at break to a certain extent, but the elastic modulus is greatly reduced; Comparative Application Example 3 uses a conventional toughening agent, which can improve the elongation of the cured product, but the elastic modulus of the material is greatly reduced.

[0184] The applicant declares that the present invention illustrates the epoxy toughening curing agent, its preparation method and the epoxy resin composition through the above-mentioned embodiments. However, the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. An epoxy toughening curing agent, characterized in that, The raw materials for preparing the epoxy toughening curing agent include a hydroxyl-containing acrylate copolymer, a diisocyanate, and a blocking agent; The polymerization monomers of the hydroxyl-containing acrylate copolymer include a combination of (meth)acrylic acid, (meth)acrylate, and hydroxyl-containing (meth)acrylate; The molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is denoted as n1, the molar amount of NCO groups in the diisocyanate is denoted as n2, and the molar amount of the blocking agent is denoted as n3, where n1:n2 = 1:(1.2 - 2), and 1 ≤ (n1 + n3) / n2 ≤ 1.1; The polymerization monomers of the hydroxyl-containing acrylate copolymer include the following components by mass: 60 - 80 parts of methyl methacrylate, 2 - 10 parts of (meth)acrylic acid, 5 - 15 parts of n-butyl (meth)acrylate, 8 - 15 parts of 2-hydroxyethyl (meth)acrylate, 1 - 10 parts of isobornyl (meth)acrylate; The preparation method of the epoxy toughening curing agent includes: Performing a first reaction on the hydroxyl-containing acrylate copolymer and the diisocyanate to obtain a prepolymer; Performing a second reaction on the prepolymer and the blocking agent to obtain the epoxy toughening curing agent.

2. The epoxy toughening curing agent according to claim 1, wherein The number-average molecular weight of the hydroxyl-containing acrylate copolymer is 2000 - 20000.

3. The epoxy toughening curing agent according to claim 1, characterized in that, The diisocyanate includes any one or a combination of at least two of isophthalic diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, tetramethyl-m-xylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, the blocking agent includes any one or a combination of at least two of 3,5-dimethylpyrazole, 3-methylpyrazole, pyrazole, methyl ethyl ketone oxime, and caprolactam.

4. A method for preparing an epoxy toughening curing agent according to any one of claims 1-3, characterized in that, The preparation method includes: Performing a first reaction on the hydroxyl-containing acrylate copolymer and the diisocyanate to obtain a prepolymer; Performing a second reaction on the prepolymer and the blocking agent to obtain the epoxy toughening curing agent.

5. The preparation method according to claim 4, characterized in that The temperature of the first reaction is 50 - 130°C, and the time is 1 - 6 h; And / or, the temperature of the second reaction is 30 - 120°C, and the time is 0.5 - 6 h.

6. An epoxy resin composition, characterized in that, The epoxy resin composition includes an epoxy resin and the epoxy toughening curing agent according to any one of claims 1 - 3.

7. The epoxy resin composition according to claim 6, wherein The epoxy resin composition includes the following components by mass: 100 parts of epoxy resin, 5 - 150 parts of curing agent, 5 - 25 parts of the epoxy toughening curing agent; The curing agent includes any one or a combination of at least two of amine curing agents, anhydride curing agents, and phenolic curing agents.

8. Use of the epoxy resin composition according to claim 6 or 7 in epoxy electronic adhesives, wind turbine blades, or prepregs.

9. A reinforced composite material, characterized in that, The reinforced composite material includes a reinforcing material and the epoxy resin composition according to claim 6 or 7 attached to the reinforcing material.

10. The reinforced composite material according to claim 9, wherein The reinforcing material includes a carbon fiber reinforcing material.

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