Epoxy toughening curing agent, preparation method thereof and epoxy resin composition

Abstract

The 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 epoxy toughening curing agent is prepared from the following raw materials: a hydroxyl-containing acrylate copolymer, diisocyanate and a sealing agent; polymeric monomers of the hydroxyl-containing acrylate copolymer comprise (methyl) acrylic acid, (methyl) acrylate and hydroxyl-containing (methyl) acrylate. Through design and mutual compounding of the raw materials, the epoxy toughening curing agent is used in an epoxy resin composition, can be subjected to a curing reaction with epoxy resin, has thermal deblocking property, and can release active isocyanate groups in thermal curing to react with reactive hydrogen groups in a resin system to form a multi-crosslinking structure, so that the curing effect of the epoxy toughening curing agent is improved, and the service life of the epoxy toughening curing agent is prolonged. The cured product of the epoxy resin composition has significantly improved toughness, maintains high strength and high elastic modulus, and obtains excellent comprehensive performance.

Description

Technical Field

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

[0002] Epoxy resin is a thermosetting polymer. When it cures, no low molecular weight substances are precipitated. The cured product has low shrinkage, good dimensional stability, good resistance to acid, alkali and solvent corrosion, and excellent electrical insulation, heat resistance and weather resistance. It has been widely used in aerospace, construction, machinery, electronic telecommunications, vehicle engineering and other fields. However, epoxy resin also has some inherent disadvantages, such as high cross-linking density, high brittleness of the cured product, insufficient toughness, low impact strength and easy cracking. These disadvantages make it difficult for epoxy resin cured products to meet the requirements of the increasingly developed engineering technology, limiting 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 recorded as n1, the molar amount of NCO groups in the diisocyanate is recorded as n2, and the molar amount of the blocking agent is recorded 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 1:(1.5-2).

[0011] 1≤(n1+n3) / n2≤1.1, for example, (n1+n3) / n2 may be 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08 or 1.09, 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, and 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 mentioned below, they have similar meanings.

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

[0014] Preferably, the hydroxyl-containing (meth)acrylate includes any one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate, or a combination of at least two thereof, and hydroxyethyl (meth)acrylate is more preferred.

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

[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 hydroxyethyl (meth)acrylate,

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

[0021] Among them, the mass parts of the 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 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.

[0022] Preferably, the hydroxyl-containing acrylate copolymer uses methyl methacrylate as the main monomer, and the mass percentage of methyl methacrylate in the copolymer is ≥55%, for example, it can be 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78% or 80%, 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.

[0023] The mass parts of the (meth)acrylic acid are 2-10 parts, for example, 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 specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively enumerates the specific points included in the range.

[0024] Preferably, the mass percentage 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 specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively enumerates the specific points included in the range, and 3-8% is further preferred.

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

[0026] The mass parts of the n-butyl (meth)acrylate are 5-15 parts, for example, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts or 14 parts, 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.

[0027] Preferably, the mass percentage 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 specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

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

[0029] The mass parts of the hydroxyethyl (meth)acrylate are 8-15 parts, for example, 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 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 said range.

[0030] Preferably, the mass percentage of 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 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.

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

[0032] The mass proportion of the isobornyl (meth)acrylate is 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 specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range, and 4-8 parts are further preferred.

[0033] Preferably, the mass percentage 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 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, and 3-8% is further preferred.

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

[0035] Preferably, the number average molecular weight of the hydroxyl-containing acrylate copolymer is 2000-20000, for example, it can be 2200, 2500, 2800, 3000, 3200, 3500, 3800, 4000, 4200, 4500, 4800, 5000, 5200, 5500, 5800, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000 or 19000, 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.

[0036] Preferably, the hydroxyl value of the hydroxyl-containing acrylate 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 mgKOH / g, 80 mg KOH / g, 85 mg KOH / g, 90 mg KOH / g or 95 mg KOH / g, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively enumerates the specific points included in the range, and 48-78 mg KOH / g is further preferred.

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

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

[0039] Preferably, based on the mass of the polymerized monomer as 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 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.

[0040] Preferably, the solvent includes any one of an ester solvent, an aromatic hydrocarbon solvent, and a ketone solvent, or a combination of at least two thereof, and more preferably ethyl acetate and / or butyl acetate.

[0041] Preferably, the mass ratio of the solvent to the polymerizable monomer is (0.1-1):1, for example, it can be 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, and more preferably (0.2-0.6):1.

[0042] Preferably, a polymerization inhibitor is also added into the polymerization reaction.

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

[0044] Preferably, based on the mass of the polymerized monomer as 100%, the mass of the inhibitor is ≤0.5%, for example, it can be 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 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, and 0-0.12% is further preferred.

[0045] Preferably, the polymerization reaction temperature is 80-120°C, for example, it can be 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or 115°C, 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.

[0046] Preferably, the polymerization reaction time is 1-12 h, for example, it can be 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 specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively enumerates the specific point values ​​included in the range.

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

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

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

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

[0051] The hydroxyl-containing acrylate copolymer is first reacted with diisocyanate to obtain a prepolymer;

[0052] The prepolymer and the blocking agent are subjected to a second reaction 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 of an organic bismuth catalyst, an organic tin catalyst, and an amine catalyst, or a combination of at least two of them.

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

[0056] Preferably, the solvent includes any one of an ester solvent, an aromatic hydrocarbon solvent, and a ketone solvent, or a combination of at least two thereof, and more preferably any one of ethyl acetate, butyl acetate, acetone, and butanone, or a combination of at least two thereof.

[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 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.

[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 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.

[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 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.

[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 specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively enumerates the specific point values ​​included in the range.

[0061] Preferably, the second reaction further comprises a step of removing the solvent after completion.

[0062] Preferably, the removal method comprises distillation under reduced pressure.

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

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

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

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

[0067] Epoxy resin 100 parts,

[0068] Curing agent 5-150 parts,

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

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

[0071] Preferably, based on 100 parts by mass of the epoxy resin, the mass of the curing agent is 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 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.

[0072] Preferably, the curing agent includes any one of an amine curing agent, an acid anhydride curing agent, and a phenol curing agent, or a combination of at least two of them, and an amine curing agent is more preferred.

[0073] Preferably, based on 100 parts by mass of the epoxy resin, the mass of the epoxy toughening curing agent is 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 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.

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

[0075] Preferably, the curing accelerator includes any one of an imidazole compound, a tertiary amine, and a tertiary phosphine, or a combination of at least two of them.

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

[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 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.

[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 used 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", "optionally" or "either" means that the subsequently described matter or event can or cannot occur, and that the description includes cases where the event occurs and cases where it does not.

[0088] In the present invention, the features defined as "first" or "second" may include one or more of the features explicitly or implicitly, and are used to distinguish and describe the features, without distinction of order or importance. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

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

[0090] The epoxy toughening curing agent and the preparation method thereof of the present invention are described in detail below by taking a plurality of embodiments as examples, but the epoxy toughening curing agent and the preparation method thereof of 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-containing acrylate copolymer, a diisocyanate (HDI) and a blocking agent (3,5-dimethylpyrazole), the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.5, (n1+n3) / n2=1.02; the polymerized monomers of the hydroxyl-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 Hydroxyethyl Methacrylate

[0097] Isobornyl methacrylate 6 parts.

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

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

[0100] The polymerization monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, an initiator (azobisisobutyronitrile, AIBN) was added, and the mass of AIBN was 0.5% based on the total mass of the polymerization monomer as 100%, and then an inhibitor (2,6-di-tert-butyl-p-cresol, BHT, 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 of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 17542, and the hydroxyl value was 64 mg KOH / g.

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

[0102] Add diisocyanate HDI to the solution of the hydroxyl acrylate copolymer obtained in step (1), react at 70° C. for 4 h to obtain a prepolymer containing NCO groups; then add 3,5-dimethylpyrazole, react at 70° C. for 4 h to consume the NCO groups, and then remove the solvent by reduced pressure 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 hydroxyl-containing acrylate copolymer, a diisocyanate (HDI) and a blocking agent (methyl ethyl ketone oxime), the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.5, (n1+n3) / n2=1.02; the polymerized monomers of the hydroxyl-containing acrylate copolymer include the following components in parts by mass:

[0105] Methyl methacrylate 62 parts

[0106] Methacrylic acid 5 parts

[0107] 8 parts of n-butyl acrylate

[0108] 10 parts of Hydroxyethyl Methacrylate

[0109] Isobornyl methacrylate 6 parts.

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

[0111] (1) Preparation of hydroxyl-containing acrylate copolymer

[0112] The polymerization monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, an initiator (AIBN) was added, and the mass of AIBN was 0.5% based on the total mass of the polymerization monomer as 100%, and then an inhibitor (BHT, the mass of which was 0.3% of the total mass of the polymerization monomer) was added, and the system was heated to 65°C and reacted for 8 hours to obtain a solution of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 18928, and the hydroxyl value was 68 mg KOH / g.

[0113] (2) Preparation of epoxy toughening curing agent

[0114] Add diisocyanate HDI to the solution of the hydroxyl acrylate copolymer obtained in step (1), react at 75°C for 3.5 hours to obtain a prepolymer containing NCO groups; then add methyl ethyl ketone oxime, react at 70°C for 4 hours to consume the NCO groups, and then remove the solvent by reduced pressure 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 hydroxyl-containing acrylate copolymer, a diisocyanate (HDI) and a blocking agent (pyrazole), the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.6, (n1+n3) / n2=1.03; the polymerized monomers of the hydroxyl-containing acrylate copolymer include the following components in parts by mass:

[0117] 65 parts of methyl methacrylate

[0118] Methacrylic acid 8 parts

[0119] 12 parts of n-butyl acrylate

[0120] 12 parts of Hydroxyethyl Methacrylate

[0121] Isobornyl methacrylate 8 parts.

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

[0123] (1) Preparation of hydroxyl-containing acrylate copolymer

[0124] The polymerizable monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, and an initiator AIBN was added. The mass of AIBN was 0.5% of the total mass of the polymerizable monomer, based on the total mass of the polymerizable monomer being 100%. Then, a polymerization inhibitor (BHT, whose mass was 0.2% of the total mass of the polymerizable monomer) was added, and the system was heated to 60° C. and reacted for 10 h to obtain a solution of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 17207, and the hydroxyl value was 62 mg KOH / g.

[0125] (2) Preparation of epoxy toughening curing agent

[0126] Add diisocyanate HDI to the solution of the hydroxyl acrylate 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, then remove the solvent by reduced pressure 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 hydroxyl-containing acrylate copolymer, a diisocyanate (IPDI) and a blocking agent (3,5-dimethylpyrazole), the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.3, (n1+n3) / n2=1.02; the polymerized monomers of the hydroxyl-containing acrylate 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 Hydroxyethyl Methacrylate

[0133] Isobornyl methacrylate 6 parts.

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

[0135] (1) Preparation of hydroxyl-containing acrylate copolymer

[0136] The polymerizable monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, and an initiator AIBN was added. The mass of AIBN was 0.5% of the total mass of the polymerizable monomer, based on the total mass of the polymerizable monomer being 100%. Then, a polymerization inhibitor (BHT, whose mass was 0.2% of the total mass of the polymerizable monomer) was added, and the system was heated to 60° C. and reacted for 10 h to obtain a solution of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 16211, and the hydroxyl value was 51 mg KOH / g.

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

[0138] Add IPDI diisocyanate to the solution of the hydroxyl acrylate copolymer obtained in step (1), react at 70° C. for 3 h to obtain a prepolymer containing NCO groups; then add 3,5-dimethylpyrazole, react at 70° C. for 2 h to consume the NCO groups, and then remove the solvent by reduced pressure 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 hydroxyl-containing acrylate copolymer, a diisocyanate (IPDI) and a blocking agent (methyl ethyl ketone oxime), the molar amount of hydroxyl groups in the hydroxyl-containing acrylate copolymer is n1, the molar amount of NCO groups in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.3, (n1+n3) / n2=1.02; the polymerized monomers of the hydroxyl-containing acrylate copolymer include the following components in parts by mass:

[0141] Methyl methacrylate 75 parts

[0142] Methacrylic acid 5 parts

[0143] 5 parts of n-butyl acrylate

[0144] 10 parts of Hydroxyethyl Methacrylate

[0145] Isobornyl methacrylate 6 parts.

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

[0147] (1) Preparation of hydroxyl-containing acrylate copolymer

[0148] The polymerizable monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, and an initiator AIBN was added. The mass of AIBN was 0.5% of the total mass of the polymerizable monomer, based on the total mass of the polymerizable monomer being 100%. Then, a polymerization inhibitor (BHT, whose mass was 0.2% of the total mass of the polymerizable monomer) was added, and the system was heated to 60° C. and reacted for 10 h to obtain a solution of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 13856, and the hydroxyl value was 62 mg KOH / g.

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

[0150] Add IPDI diisocyanate to the solution of the hydroxyl acrylate copolymer obtained in step (1), react at 75°C for 3 h to obtain a prepolymer containing NCO groups; then add methyl ethyl ketone oxime, react at 70°C for 2 h to consume the NCO groups, and then remove the solvent by reduced pressure distillation to obtain the epoxy toughening curing agent.

[0151] Example 6

[0152] An epoxy toughening curing agent, wherein the raw materials for preparing the epoxy toughening curing agent include a hydroxyl-containing acrylate copolymer, a diisocyanate (IPDI) and a blocking agent (pyrazole), wherein the molar amount of the hydroxyl group in the hydroxyl-containing acrylate copolymer is n1, the molar amount of the NCO group in the diisocyanate is n2, the molar amount of the blocking agent is n3, n1:n2=1:1.5, (n1+n3) / n2=1.03; the polymerized monomers of the hydroxyl-containing acrylate copolymer include the following components in parts by mass:

[0153] Methyl methacrylate 70 parts

[0154] Methacrylic acid 5 parts

[0155] 7 parts of n-butyl acrylate

[0156] 9 parts of Hydroxyethyl Methacrylate

[0157] Isobornyl methacrylate 6 parts.

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

[0159] (1) Preparation of hydroxyl-containing acrylate copolymer

[0160] The polymerizable monomer and ethyl acetate (industrial grade) were uniformly mixed in a mass ratio of 7:3, and an initiator AIBN was added. The mass of AIBN was 0.5% of the total mass of the polymerizable monomer, based on the total mass of the polymerizable monomer being 100%. Then, a polymerization inhibitor (BHT, whose mass was 0.2% of the total mass of the polymerizable monomer) was added, and the system was heated to 60° C. and reacted for 10 h to obtain a solution of a hydroxyl-containing acrylate copolymer, wherein the number average molecular weight of the hydroxyl-containing acrylate copolymer was 15892, and the hydroxyl value was 55 mg KOH / g.

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

[0162] Add IPDI diisocyanate to the solution of the hydroxyl acrylate 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 reduced pressure distillation to obtain the epoxy toughening curing agent.

[0163] Comparative Example 1

[0164] An epoxy toughening curing agent, the raw materials for its preparation are different from those in Example 1 only in that the sealing agent is replaced by an equal molar amount of hydroxyethyl methacrylate, and the other components, amounts and preparation methods are the same as those in Example 1.

[0165] Comparative Example 2

[0166] An epoxy toughening curing agent, the raw materials for its preparation are different from those in Example 1 only in that the polymerization monomer of the hydroxyl-containing acrylate copolymer does not contain methacrylic acid, and other components, amounts and preparation methods are the same as those in Example 1.

[0167] Comparative Example 3

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

[0169] The epoxy resin composition of the present invention will be described in detail below by taking a plurality of application examples as examples, but the epoxy resin composition of the present invention is not limited to these application examples.

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

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

[0172] Epoxy resin 100 parts

[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 and its preparation method and epoxy resin composition of the present invention through the above-mentioned embodiments, but 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 of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and 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 hydroxyl-containing acrylate copolymer, diisocyanate and sealing agent; The polymerizable 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 recorded as n1, the molar amount of NCO groups in the diisocyanate is recorded as n2, and the molar amount of the blocking agent is recorded as n3, n1:n2=1:(1.2-2), 1≤(n1+n3) / n2≤1.

1.

2. The epoxy toughening curing agent according to claim 1, characterized in that: The (meth)acrylate includes any one of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and isobornyl (meth)acrylate, or a combination of at least two thereof; And / or, the hydroxyl-containing (meth)acrylate includes any one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate, or a combination of at least two thereof.

3. The epoxy toughening curing agent according to claim 1, characterized in that: The polymerized monomers of the hydroxyl-containing acrylate copolymer include the following components in parts 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 hydroxyethyl (meth)acrylate, 1-10 parts of isobornyl (meth)acrylate; And / or, the number average molecular weight of the hydroxyl-containing acrylate copolymer is 2,000-20,000.

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

5. A method for preparing the epoxy toughening curing agent according to any one of claims 1 to 4, characterized in that: The preparation method comprises: The hydroxyl-containing acrylate copolymer is first reacted with diisocyanate to obtain a prepolymer; The prepolymer and the blocking agent are subjected to a second reaction to obtain the epoxy toughening curing agent.

6. The preparation method according to claim 5, 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.

7. An epoxy resin composition, characterized in that The epoxy resin composition comprises an epoxy resin and the epoxy toughening curing agent according to any one of claims 1 to 4.

8. The epoxy resin composition according to claim 7, characterized in that The epoxy resin composition comprises the following components in parts by mass: Epoxy resin 100 parts, Curing agent 5-150 parts, The epoxy toughening curing agent is 5-25 parts.

9. Use of the epoxy resin composition according to claim 7 or 8 in epoxy electronic adhesive, wind blades or prepregs.

10. A reinforced composite material, characterized in that: The reinforced composite material comprises a reinforcing material and the epoxy resin composition according to claim 7 or 8 attached to the reinforcing material; Optionally, the reinforcement material includes carbon fiber reinforcement material.

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