JP7157568B2 - epoxy resin composition - Google Patents

Description

The present invention relates to epoxy resin compositions.

BACKGROUND ART Conventionally, epoxy resin compositions have been widely used as adhesives for structural members of automobiles, for example. For example, Patent Documents 1 and 2 describe adhesives for automotive structural members comprising a resin composition containing an epoxy resin and a butyral resin.

Japanese Patent Application Laid-Open No. 2-4887 JP-A-3-212474

However, the adhesives described in Patent Literature 1 and Patent Literature 2 do not have sufficient adhesiveness. In particular, a cured product of a resin composition containing an epoxy resin is oxidatively decomposed by heat and oxygen at high temperatures, and thus has a problem of reduced strength and durability.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an epoxy resin composition having excellent strength and durability even at high temperatures.

In order to achieve the above object, the epoxy resin composition of the present invention is
at least one epoxy resin;
a blocked urethane resin containing a polyol, a polyisocyanate, and a hindered phenol compound having a tertiary butyl group;
is characterized by including

An epoxy resin composition having excellent strength and durability even at high temperatures can be provided.

An embodiment according to the present invention will be described below with reference to the drawings. However, the constituent elements described in the following embodiments are examples, and are not intended to limit the technical scope of the present invention only to them.

The present invention is an epoxy resin composition (hereinafter referred to as a resin composition according to the present embodiment) containing at least one type of epoxy resin and block urethane resin as a main component.

Each component will be described in detail below.

≪Epoxy Resin≫
The epoxy resin, which is one of the main components in the resin composition according to the present embodiment, includes, for example, bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, Bifunctional glycidyl ether epoxy resins such as epoxy compounds having a bisphenyl group such as a biphenyl type, polyalkylene glycol type, alkylene glycol type epoxy compounds, epoxy compounds having a naphthalene ring, and epoxy compounds having a fluorene group; Polyfunctional glycidyl ether type epoxy resins such as phenol novolak type, ortho cresol novolak type, trishydroxyphenylmethane type, and tetraphenylolethane type; synthetic fatty acid glycidyl ester type epoxy resins such as dimer acid; ,N',N'-tetraglycidyldiaminodiphenylmethane (TGDDM), tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, N,N-diglycidylaniline. Resin; epoxy compounds having a tricyclodecane ring, and the like.

The epoxy resin in the resin composition according to the present embodiment preferably contains a bisphenol A type epoxy resin and a carboxyl group-containing nitrile-butadiene rubber-modified epoxy resin. These epoxy resins are described in detail below.

<Bisphenol A type epoxy resin>
The bisphenol A type epoxy resin, which is one of the main components in the resin composition according to this embodiment, will be described.

The epoxy resin contained in the resin composition according to this embodiment is a bisphenol A type epoxy resin having a bisphenol skeleton. By containing a bisphenol A type epoxy resin, a resin composition having sufficient strength as an adhesive can be obtained.

The bisphenol A type epoxy resin according to this embodiment preferably has an epoxy equivalent of 150 or more and 260 or less. Moreover, the amount of the bisphenol A type epoxy resin in the resin composition according to the present embodiment is preferably 20 to 80% by mass. By setting it as the said range, the resin composition which is more excellent in impact resistance is obtained.

<Carboxyl Group-Containing Nitrile-Butadiene Rubber-Modified Epoxy Resin>
The carboxyl group-containing nitrile-butadiene rubber-modified epoxy resin, which is one of the main components in the resin composition according to the present embodiment, will be described.

The resin composition according to the present embodiment contains an epoxy resin having a rubber skeleton, and specifically contains a carboxyl group-containing NBR (nitrile-butadiene rubber)-modified epoxy resin. By containing the NBR-modified epoxy resin, a resin composition having excellent heat resistance, impact resistance, and flexibility can be obtained.

The NBR-modified epoxy resin according to the present embodiment preferably has an epoxy equivalent of 200 or more and 500 or less. Moreover, the amount of the NBR-modified epoxy resin in the resin composition according to the present embodiment is preferably 5 to 70% by mass. By setting it as the said range, the resin composition which is more excellent in impact resistance and flexibility is obtained.

The epoxy resin used in producing the NBR-modified epoxy resin is not particularly limited, and conventionally known epoxy resins can be used. Moreover, an epoxy resin may be used individually by 1 type, and may be used in combination of 2 or more types.

In the present invention, the epoxy equivalent and addition amount of the NBR-modified epoxy resin are the epoxy equivalent and addition amount of the NBR-modified epoxy resin containing excess epoxy resin used during production.

≪Block urethane resin≫
The resin composition according to the present embodiment contains a blocked urethane resin in which a urethane prepolymer obtained by reacting a polyhydroxy compound and a polyisocyanate compound is blocked with a hindered phenol compound having a tertiary butyl group. Since the hindered phenol compound having a tertiary butyl group has an antioxidant function, the inclusion of a block urethane resin having this function suppresses the oxidative decomposition of the cured product by heat and oxygen even at high temperatures. . In addition, by containing a hindered phenol compound having a tertiary butyl group, the compatibility with other resin components to be blended is improved, and the toughness of the cured product is improved.

<Polyhydroxy compound>
The polyhydroxy compound is not particularly limited in terms of its molecular weight, skeleton, etc., as long as it is a compound having two or more hydroxyl groups. Mixed polyols of these and the like are included.

Specific examples of polyhydric alcohols include ethylene glycol (EG), diethylene glycol, propylene glycol (PG), dipropylene glycol, (1,3- or 1,4-) butanediol, pentanediol, neo low-molecular-weight polyols such as pentyl glycol, hexanediol, cyclohexanedimethanol, glycerin, trimethylolpropane (TMP), 1,2,5-hexanetriol and pentaerythritol; sugars such as sorbitol;

As polyether polyols and polyester polyols, those derived from the above polyhydric alcohols may be used, or those derived from aromatic diols and amines shown below may be used.

Specific examples of aromatic diols include resorcinol (m-dihydroxybenzene), xylylene glycol, 1,4-benzenedimethanol, styrene glycol, and 4,4'-dihydroxyethylphenol; bisphenol A structure (4,4'-dihydroxyphenylpropane), bisphenol F structure (4,4'-dihydroxyphenylmethane), brominated bisphenol A structure, hydrogenated bisphenol A structure, bisphenol S structure, bisphenol AF structure those having a skeleton; and the like.

Further, specific examples of amines include ethylenediamine and hexamethylenediamine, and specific examples of alkanolamines include ethanolamine and propanolamine.

Examples of polyether polyols include at least one compound selected from the compounds exemplified as the above polyhydric alcohols, the above aromatic diols, and the above amines, ethylene oxide, propylene oxide, butylene oxide (tetramethylene oxide), tetrahydrofuran. and polyols obtained by adding at least one selected from alkylene oxides, styrene oxides, and the like.

Specific examples of such polyether polyols include polyethylene glycol, polypropylene glycol (PPG), polypropylene triol, ethylene oxide/propylene oxide copolymer, polytetramethylene glycol (PTMG), polytetraethylene glycol, sorbitol polyol, and the like. is mentioned.

Similarly, examples of polyester polyols include condensates of polyhydric alcohols, aromatic diols, amines, and polybasic carboxylic acids; lactone polyols; polycarbonate polyols; . Specific examples of the lactone-based polyol include those obtained by ring-opening polymerization of lactones such as ε-caprolactone, α-methyl-ε-caprolactone, ε-methyl-ε-caprolactone, and the like with an appropriate polymerization initiator. Examples include those having hydroxyl groups at both ends.

Specific examples of other polyols include acrylic polyols; polybutadiene polyols; and polymer polyols having a carbon-carbon bond in the main chain skeleton such as hydrogenated polybutadiene polyols.

These polyhydroxy compounds may be used singly or in combination of two or more.

<Polyisocyanate compound>
The polyisocyanate compound is not particularly limited as long as it is a compound having two or more isocyanate groups, and examples thereof include aliphatic polyisocyanates, aromatic polyisocyanates, and alicyclic polyisocyanates.

Specific examples of polyisocyanate compounds include aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanate (NBDI); TDI (e.g., 2,4- tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI)), MDI (e.g. 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4 ′-diphenylmethane diisocyanate (2,4′-MDI)), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1 Aromatic polyisocyanates such as ,5-naphthalene diisocyanate (NDI), triphenylmethane triisocyanate; transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate Alicyclic polyisocyanates such as (H12MDI) and the like can be mentioned. One type of these polyisocyanate compounds may be used alone, or two or more types may be used in combination.

<Hindered phenol compound having tertiary butyl group>
A urethane prepolymer containing free isocyanate groups at the terminals is obtained by the reaction of the polyhydroxy compound and the polyisocyanate. By reacting this urethane prepolymer with a hindered phenol compound having a tertiary butyl group described below, a blocked urethane resin blocked by hindered phenol can be obtained.

Conventionally, as a blocking agent for urethane prepolymers, there have been block urethane resins that use amine-based monomers as blocking agents, but amine-based monomers promote self-polymerization of epoxy groups, resulting in poor storage stability. had a point. In this embodiment, a hindered phenol having a tertiary butyl group is used as a blocking agent. Since the hindered phenol having a tertiary butyl group has an antioxidant function, by containing a block urethane resin having this, an epoxy resin composition having excellent strength and durability even at high temperatures can be obtained.

Hindered phenols having a tertiary butyl group include, for example, 2-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-methylphenol (dibutylhydroxytoluene), 2,6-di-tert -Butyl-4-ethylphenol, 2,2'-methylenebis(4ethyl-6-tert-butylphenol), 2,2'-methylenebis(4methyl-6-tert-butylphenol), 4,4'-butylidenebis(3 -methyl-6-tert-butylphenol), 4,4′-thiobis(3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, triethylene glycol-bis-[3-(3 -t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4- Bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl-tetrakis[3-(3,5-di-t -butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5- di-t-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t- Butyl-4-hydroxy-benzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3 , 5-di-t-butyl-4-hydroxybenzylphosphonate ethyl) calcium, tris-(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, N,N'-bis[3-( 3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, tris(2,4-di-t-butylphenyl)phosphite, 2-(3,5-di-t-butyl-2- hydroxyphenyl)benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)- 5-chlorobenzotria sol, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, bis 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate (1,2,2,6,6-pentamethyl-4-piperidyl), 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and the like. These hindered phenol compounds may be used singly or in combination of two or more.

The amount of the hindered phenol compound to be added is preferably 5 to 30 mass % with respect to the total of the polyhydroxy compound and the polyisocyanate compound.

<Catalyst>
Catalysts which are suitable for the reaction to synthesize block urethane resins are commercially available, for example metal- or transition metal compounds based on aluminum, tin, zinc, titanium, manganese, bismuth or zirconium, such as dibutyltin dilaurate, zinc octoate, titanium tetrabutylate, zirconium octoate, and the like.

Moreover, the amount of the block urethane resin in the resin composition according to the present embodiment is preferably 3 to 50% by mass. By setting the content within the above range, a resin composition having excellent strength and durability even at high temperatures can be obtained.

≪Other ingredients≫
The resin composition according to the present embodiment contains other components such as a curing agent and a curing accelerator listed below as components other than the main components described above. Each component is described in detail below.

<Curing agent>
As the curing agent according to the present embodiment, one that is commonly used as a curing agent for epoxy resins can be used as it is.

Specific examples of curing agents include dicyandiamide, 4,4′-diaminodiphenyl sulfone, imidazole derivatives such as 2-n-heptadecyl imidazole, isophthalic acid dihydrazide, N,N-dialkyl urea derivatives, N,N-di Alkylthiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, isophoronediamine, m-phenylenediamine, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compounds, trisdimethylaminomethylphenol and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types.

Among the above curing agents, dicyandiamide can be preferably used. Dicyandiamide is a latent curing agent that can be stably stored at room temperature and has the function of rapidly curing by being melted and activated by heating. Therefore, by using dicyandiamide, a resin composition having excellent strength and durability even at high temperatures can be obtained.

The content of the curing agent in the resin composition according to this embodiment is not particularly limited, and an optimum amount for each curing agent can be preferably used.

<Curing accelerator>
The curing accelerator according to this embodiment has the effect of accelerating the curing reaction of dicyandiamide, which is suitably used as a curing agent. The curing accelerator used in the composition of the present embodiment is not particularly limited as long as it has the effect of accelerating the curing reaction of dicyandiamide, and conventionally known curing accelerators can be used. Specific examples of curing accelerators include aliphatic dimethylurea and aromatic dimethylurea. One type of these curing accelerators may be used alone, or two or more types may be used in combination.

<Furthermore, other ingredients>
The resin composition according to the present embodiment may further contain inorganic fillers, organic or polymeric fillers, flame retardants, antistatic agents, conductivity-imparting agents, lubricants, slidability-imparting agents, surfactants, etc., depending on the application. It may contain agents, colorants, and the like. These may contain one type alone, or may contain two or more types in combination. Specific examples of other components include calcium carbonate, talc, wallastonite, fumed silica, aluminum hydroxide, calcium oxide, bentonite, kaolin, and carbon black.

<<Method for producing epoxy resin composition>>
The method for producing the resin composition according to the present embodiment is not particularly limited, and it can be produced by a conventionally known method. For example, it can be obtained by homogeneously kneading a bisphenol A type epoxy resin, an NBR-modified epoxy resin, a block urethane resin, and, if necessary, other components at room temperature.

≪Example≫
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.

(Synthesis of block urethane resin of Example 1)
1000 parts by weight of glycerin-based polyether polyol (hydroxyl equivalent of 1000) was charged, and 221 parts by weight of isophorone diisocyanate was charged after top-purging with nitrogen. The mixture was heated to 80° C., 0.01 part by weight of dibutyltin dilaurate was charged as a catalyst, and reacted at a temperature of 80 to 90° C. for 3 hours.

Next, 220 parts by weight of dibutylhydroxytoluene was charged and reacted at a temperature of 80 to 90° C. for 3 hours. It was confirmed by an infrared spectrophotometer (IR) that the absorption of NCO had disappeared, and block urethane resin (BUR-1) of Example 1 was obtained.

(Synthesis of block urethane resin of Example 2)
1000 parts by weight of polytetramethylene glycol (hydroxyl equivalent: 1000) was charged as a polyether polyol, and 221 parts by weight of isophorone diisocyanate was charged after top-substitution with nitrogen. The mixture was heated to 80° C., 0.01 part by weight of dibutyltin dilaurate was charged as a catalyst, and reacted at a temperature of 80 to 90° C. for 3 hours.

Next, 164 parts by weight of 2-tert-butyl-p-cresol was charged and reacted at a temperature of 80 to 90° C. for 3 hours. It was confirmed by an infrared spectrophotometer (IR) that the absorption of NCO had disappeared, and block urethane resin (BUR-2) of Example 2 was obtained.

(Synthesis of block urethane resin of Comparative Example 1)
1000 parts by weight of glycerin-based polyether polyol (hydroxyl equivalent weight: 1000) was charged, and 221 parts by weight of isophorone diisocyanate was charged by top-purging with nitrogen. The mixture was heated to 80° C., 0.01 part by weight of dibutyltin dilaurate was charged as a catalyst, and reacted at a temperature of 80 to 90° C. for 3 hours.

Next, 94 parts by weight of phenol was charged and reacted at a temperature of 80 to 90° C. for 3 hours. It was confirmed by an infrared spectrophotometer (IR) that the absorption of NCO had disappeared, and block urethane resin (BURX-1) of Comparative Example 1 was obtained.

(Synthesis of block urethane resin of Comparative Example 2)
1000 parts by weight of glycerin-based polyether polyol (hydroxyl equivalent weight: 1000) was charged, and 221 parts by weight of isophorone diisocyanate was charged by top-purging with nitrogen. The mixture was heated to 80° C., 0.01 part by weight of dibutyltin dilaurate was charged as a catalyst, and reacted at a temperature of 80 to 90° C. for 3 hours.

Next, 181 parts by weight of dicyclohexylamine was added and reacted at a temperature of 80 to 90° C. for 3 hours. It was confirmed by an infrared spectrophotometer (IR) that the absorption of NCO had disappeared, and block urethane resin (BURX-2) of Comparative Example 2 was obtained.

(Production of epoxy resin composition in each example and each comparative example)
Using predetermined amounts of bisphenol A type epoxy resin, NBR-modified epoxy resin, block urethane resin, dicyandiamide, 1-phenyl-3,3-dimethylurea and fumed silica, these were uniformly kneaded to obtain each example and An epoxy resin composition of each comparative example was obtained. In Comparative Examples 3 and 4, the amount of block urethane resin (BUR-1) added was 2% by mass and 60% by mass, respectively, based on the epoxy resin composition. Table 1 shows the amount (parts by weight) of each component added.

(evaluation)
The composition obtained in each example and each comparative example is applied to the surface of a mild steel plate and cured at a predetermined temperature (180 ° C. or 210 ° C.) for a predetermined time (30 minutes), and a tensile shear strength test and It was subjected to a T-peel strength test. The test was performed under the following conditions.

Tensile shear strength test: Compliant with JIS K-6850 Test speed 5mm/min
Coating film thickness 0.2mm
Coating area 12.5 x 25mm
T-type peel strength test: Complies with JIS K-6854 Test speed 100mm/min
Coating film thickness 0.2mm
Coating area 25×100mm
Table 1 shows other conditions.

Table 1 shows the results for each evaluation.

In each example, tensile shear strength and T-peel strength were good at both curing temperatures of 180°C and 210°C. On the other hand, in Comparative Examples 1 and 2, which did not contain a blocked urethane resin containing a hindered phenol compound having a tertiary butyl group, the strength was lower than that of Examples at a high curing temperature of 210°C. Therefore, it was found that the epoxy resin compositions in Examples had excellent strength even at high temperatures.
In addition, Comparative Example 3 in which the content of the block urethane resin is lower than the lower limit of 3 to 50% by mass with respect to the epoxy resin composition and Comparative Example 4 in which the content is higher than the upper limit are the same as in the examples in all the strength tests conducted. It had a lower strength.

Furthermore, the initial viscosity of the epoxy resin composition of each example and each comparative example was measured. Next, the epoxy resin composition was stored in a constant temperature bath at 40°C for two weeks. The viscosity of the stored epoxy resin composition was measured to calculate the viscosity increase rate.

Table 1 shows the results of each evaluation.

All of the epoxy resin compositions of Examples are excellent in storage stability. Comparative Examples 1, 3 and 4 have storage stability equivalent to that of the present invention, but Comparative Example 2 is inferior in storage stability.

Claims (6)

at least one epoxy resin;
a blocked urethane resin containing a polyol, a polyisocyanate, and a hindered phenol compound having a tertiary butyl group at the ortho position;
including
The hindered phenol compounds include 2-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-methylphenol (dibutylhydroxytoluene), 2,6-di-tert-butyl-4-ethyl Phenol, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert -butylphenol), 4,4′-thiobis(3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, triethylene glycol-bis-[3-(3-t-butyl-5 -methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio )-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxy phenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t-butyl-4-hydroxy- Benzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,5-di-t -butyl-4-hydroxybenzylphosphonate ethyl) calcium, tris-(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, N,N'-bis[3-(3,5-di- t-butyl-4-hydroxyphenyl)propionyl]hydrazine, tris(2,4-di-t-butylphenyl)phosphite, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t- amyl-2-hydroxyphenyl)benzotriazole, 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl- 4-piperidyl) and 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate containing one or more hindered phenol compounds selected from epoxy resins Composition.
However, the content of the block urethane resin is 3 to 50% by mass with respect to the epoxy resin composition. The epoxy resin includes a bisphenol A type epoxy resin,
The epoxy resin composition according to claim 1. The epoxy resin contains a carboxyl group-containing nitrile-butadiene rubber-modified epoxy resin,
The epoxy resin composition according to claim 1 or 2. 4. The epoxy resin composition according to any one of claims 1 to 3, wherein the epoxy resin composition further comprises dicyandiamide. 5. The epoxy resin composition according to claim 4, further comprising a urea-based catalyst as a curing accelerator for said dicyandiamide. The epoxy resin composition further comprises one or more compounds selected from calcium carbonate, talc, wallastonite, fumed silica, aluminum hydroxide, calcium oxide, bentonite, kaolin, and carbon black.
The epoxy resin composition according to any one of claims 1 to 5.