JP2006096834A - Adhesive composition including epoxy resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin-based adhesive composition that has high adhesive strength, excellent heat resistance, weather resistance, good handleability and workability because of low viscosity. <P>SOLUTION: This adhesive composition comprises a copolymer that includes an epoxy group-bearing monomer unit and an epoxy group-free (meth)acrylic ester unit with the weight-average molecular weight of 500 to 5,000 and an epoxy resin. The copolymer is preferably prepared by continuously polymerizing the starting monomers at a temperature of 150 to 350°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an adhesive composition containing an epoxy resin (hereinafter also referred to as an epoxy resin-based adhesive composition).

Epoxy resins having a bisphenol skeleton (hereinafter also referred to as bisphenol-based epoxy resins) are used for high-strength adhesives and rust prevention primers. For the purpose of modifying such epoxy resins, blends of various compounds have been studied. For example, it is known to blend acrylic polymers to impart initial tackiness, reduce ionic impurities, and improve paint adhesion. (Patent Documents 1, 2, and 3).
It is known that a composition containing an acrylic polymer having an epoxy group and an epoxy resin, and a general composition are effective as a self-fixing adhesive (Patent Document 4). It is also known that a composition containing an acrylic polymer having an epoxy group and an epoxy resin is useful for bonding a flexible printed board to a copper foil or a semiconductor chip (Patent Documents 5 and 6).
However, when the acrylic polymer used in the above invention is blended, the dispersibility in the epoxy resin is insufficient, and it may be difficult to improve the adhesion.
In addition, epoxy resins are highly viscous liquids or solids, and compositions with an epoxy resin as the main component have poor handling workability. Therefore, low viscosity by adding a solvent or plasticizer has been studied. Foaming of the adhesive layer due to the molecular plasticizer, reduction in strength and reduction in heat resistance occurred, which was not preferable.
Although low molecular weight compounds having an epoxy group are also known as reactive diluents (Non-patent Document 1), such reactive diluents are effective in reducing viscosity, but heat resistance and weather resistance are reduced. Limited use.

USP 5086088 JP 9-316419 A Japanese Patent No. 2630393 Special Table 2002-53671 JP-A-7-173449 JP 2004-2386 A Published by Tatsuya Imoto, “Manufacturing and Application of Epoxy Resins”, published in 1963, 298 pages, published by Polymer Chemistry

An object of the present invention is to provide an epoxy resin adhesive composition having not only high adhesive strength but also excellent heat resistance and weather resistance, low viscosity and excellent handling workability.

In order to solve the above problems, the adhesive composition of the present invention includes a monomer unit having an epoxy group and a (meth) acrylic acid ester unit having no epoxy group as a constituent unit, and a weight average molecular weight of 500 to 5,000. It contains a copolymer and an epoxy resin.

The composition of the present invention has a high adhesive strength, is excellent in heat resistance and weather resistance, is excellent in handling workability, and is suitable as an adhesive composition.

  The copolymer of the present invention has a weight average molecular weight of 500 to 5000, preferably 1000 to 4000, and particularly preferably 1500 to 3000. If it is less than 500, the adhesive tends to foam, and if it is 5000 or more, the viscosity of the adhesive does not decrease, which is not preferable.

  Examples of the monomer having an epoxy group include glycidyl (meth) acrylate, epoxycyclohexyl (meth) acrylate, epoxycyclohexanemethyl (meth) acrylate, allyl glycidyl ether, and vinyl glycidyl ether. Glycidyl methacrylate, which is easily available and easily improves the adhesive strength, is preferred.

Examples of the (meth) acrylic acid ester having no epoxy group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, Isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, neopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, (meta ) Alkyl (meth) acrylates such as lauryl acrylate, tridecyl (meth) acrylate and stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and tricyclodecynyl (meth) acrylate (Meth) acrylic acid alicyclic alkyl, (meth) acrylic Heteroatom-containing (meth) acrylates such as 2-methoxyethyl, dimethylaminoethyl (meth) acrylate, chloroethyl (meth) acrylate, trifluoroethyl (meth) acrylate and tetrahydrofurfuryl (meth) acrylate Is mentioned. These monomers can be used alone or in combination of two or more.
Since the resulting copolymer has a low Tg and a decrease in viscosity can be expected, the proportion of the acrylic acid ester having 4 to 8 carbon atoms in the total of the monomers is preferably 70% by mass or more.

  The proportion of the monomer having an epoxy group and the (meth) acrylic acid ester having no epoxy group is preferably 5 to 50 parts by mass and 50 to 95 parts by mass, respectively, based on the total amount of 100 parts by mass of both. 10-30 mass parts and 70-90 mass parts are respectively more preferable. When the proportion of the monomer having an epoxy group is less than 5 parts by mass, the effect of decreasing the viscosity is small and the adhesive strength may not be improved. When the proportion of the monomer having an epoxy group exceeds 50 parts by mass, the compatibility between the obtained copolymer and the epoxy resin increases, and the adhesive strength may decrease.

There are no particular restrictions on the other monomers that can be used as the constituent unit of the copolymer, such as (meth) acrylic acid, hydroxyethyl (meth) acrylate, styrene, α-methylstyrene, acrylonitrile, vinyl acetate, and the like. Can be mentioned.
The copolymer of the present invention is incompatible with the epoxy resin in the cured state, and can relieve stress at the time of curing by making microdomains in the phase of the epoxy resin, thereby improving the adhesive strength. it can. Therefore, the (meth) acrylic acid ester containing an aromatic group improves compatibility with the epoxy resin, but it is preferable not to use it because it lowers the adhesive strength.

  The glass transition temperature (hereinafter also referred to as Tg) of the copolymer is preferably −10 ° C. or lower. When it exceeds −10 ° C., the effect of reducing the viscosity of the adhesive may be small.

  The copolymer of the present invention can be obtained by polymerizing a monomer selected according to the purpose by a known method. Any of solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like may be used. When adopting solution polymerization, the organic solvent may be one usually used as a solvent, for example, cyclic ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbon compounds such as benzene, toluene and xylene, ethyl acetate and butyl acetate, etc. Esters, ketones such as acetone, methyl ethyl ketone and cyclohexanone, alcohols such as methanol, ethanol and isopropanol, and the like, and one or more of these can be used.

  As radical polymerization initiators, peroxides such as diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, benzoyl peroxide, lauroyl peroxide and ditertiary butyl peroxide, or azobisisobutyronitrile, azobis An azo compound such as isovaleronitrile and an inorganic peroxide such as ammonium persulfate and potassium persulfate can be used. A chain transfer agent such as an alcohol or a mercaptan-based compound may also be used, but it is preferably not used because it has a strong odor and adversely affects the environment, leading to a decrease in weather resistance.

  A copolymer obtained by polymerizing a monomer at a temperature of 150 to 350 ° C. is preferable because it has almost no impurities and tends to have excellent adhesive strength and weather resistance. The polymerization temperature is more preferably 180 to 320 ° C, further preferably 200 to 300 ° C. Any of batch polymerization, semi-continuous polymerization, continuous polymerization and the like can be adopted, but continuous polymerization using a stirred tank reactor is particularly preferable because of excellent productivity. Such high-temperature continuous polymerization is known (Japanese Patent Publication No. 57-502171, Japanese Patent Publication No. 59-6207, Japanese Patent Publication No. 60-511992).

A well-known thing is employ | adopted for the epoxy resin of this invention. Examples of such epoxy resins include epichlorohydrin-bisphenol A type epoxy resins, epichlorohydrin-bisphenol F type epoxy resins, flame retardant epoxy resins such as tetrabromobisphenol A glycidyl ether, novolac type epoxy resins, hydrogenated bisphenol A type epoxy resins, Bisphenol A propylene oxide adduct glycidyl ether type epoxy resin, p-oxybenzoic acid glycidyl ether ester type epoxy resin, m-aminophenol type epoxy resin, diaminodiphenylmethane type epoxy resin, urethane modified epoxy resin, various alicyclic epoxy resins N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, triglycidyl isocyanurate, polyalkylene glycol diglycidyl ester Examples include glycidyl ethers of polyhydric alcohols such as tellurium and glycerin, epoxidized products of unsaturated polymers such as hydantoin type epoxy resins and petroleum resins, but are not limited to these and are generally used. Any epoxy resin can be used. Of these epoxy resins, those containing at least two epoxy groups in the molecule are particularly preferred because they are highly reactive during curing and the cured product easily forms a three-dimensional network. Among these, bisphenol A type epoxy resin is preferable from the viewpoint of heat resistance.
Among the bisphenol A type epoxy resins, liquid resins having an epoxy equivalent of 170 to 270 (g / eq) are particularly preferable.

  The ratio (mass ratio) between the bisphenol A type epoxy resin (X) and the copolymer (Y) is preferably X / Y = 60 to 95/5 to 40, based on the total of both 100, and 70 to 90 / 10-30 are more preferable. When X is less than 60% by mass, the adhesive strength may be reduced, and when it exceeds 95% by mass, the viscosity is not effectively reduced and the adhesive strength may not be improved.

The adhesive composition of the present invention is preferably one to which a curing agent for epoxy resin is added. Curing agents for epoxy resins include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, diethylaminopropylamine, N-aminoethylpiperazine, isophoronediamine, diaminodicyclohexylmethane, m-xylenediamine, m- Primary amines such as phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, etc., linear diamines represented by (CH3) 2N (CH2) nN (CH3) 2 (where n is an integer from 1 to 10), (CH3) 2 Linear tertiary amine represented by -N (CH2) n-CH3 (wherein n is an integer of 0 to 10), tetramethylguanidine, N {(CH2) nCH3} 3 (wherein n is 1 to 10) An alkyl tertiary monoamine represented by an integer), trisdimethylamino Ruphenol, triethanolamine, piperidine, N, N'-dimethylpiperazine, triethylenediamine, pyridine, picoline, diazabicycloundecene, benzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris Secondary or tertiary amines such as (dimethylaminomethyl) phenol, BASF Ramilon C-260, CIBA Araldit HY-964, and Rohm and Haas Mensendiamine, 1,2-ethylenebis (iso Pentylideneimine), 1,2-hexylenebis (isopentylideneimine), 1,2-propylenebis (isopentylideneimine), p, p'-biphenylenebis (isopentylideneimine), 1,2-ethylenebis (Isopropylideneimine), 1,3-propylenebis (isopropylidene) Pyridenimine), p-phenylenebis (isopentylidenimine) and other ketimines, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride and other acid anhydrides, various polyamide resins, dicyandiamide and derivatives thereof And various imidazoles. The amount of the curing agent used is preferably 5 to 100 parts with respect to 100 parts of the epoxy resin.
Moreover, you may use a photoinitiator instead of a hardening | curing agent. Examples of such photoinitiators include onium salts or cationic organometallics.

  The composition of the present invention may be added with a reactive diluent as necessary. Examples of such diluents include monofunctional low molecular weight glycidyl ethers such as alkyl glycidyl ether, o-cresyl glycidyl ether, alkylphenol glycidyl ether, cyclohexanedimethanol monoglycidyl ether, and bromine-containing glycidyl ether.

  The composition of the present invention may be one to which an adhesion enhancer has been added in order to enhance the adhesion to the substrate. Specific examples thereof include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl)- Examples include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane, γ-triethoxysilyl-N (1,3-dimethylbutylidene) propylamine, and the like.

The composition of the present invention may be added with phenol, bisphenol A, phenol resin or the like in order to adjust the curing rate. In order to adjust workability, silane coupling agents containing epoxy groups, isocyanate groups, vinyl groups, thixotropic agents such as silica, UV absorbers, matting agents, pigments, fillers, etc. are added. There may be.

<Production Example 1>
A 1000 ml capacity pressurized stirred tank reactor equipped with an electric heater was maintained at a temperature of 230 ° C. Next, while maintaining the reactor pressure constant, a raw material mixture comprising 100 parts of the monomer mixture shown in Table 1, 10 parts of MEK, and 1 part of ditertiary butyl peroxide as a polymerization initiator was supplied at a constant feed rate (80 g / Min., Residence time: 12 minutes), the raw material tank was continuously supplied to the reactor, and the reaction liquid corresponding to the supply amount of the raw material mixture was continuously extracted from the outlet. Immediately after the start of the reaction, once the reaction temperature decreased, a temperature increase due to the heat of polymerization was observed, but the reaction temperature was maintained at 245 ° C. by controlling the heater. The time when the temperature was stabilized from the start of the supply of the raw material mixture was taken as the starting point for collecting the reaction liquid, and 2 kg of the raw material mixture liquid was supplied over 25 minutes, and 1.9 kg of the reaction liquid was recovered. Thereafter, the reaction solution was introduced into a thin film evaporator to separate volatile components such as unreacted monomers to obtain a concentrated solution. From the gas chromatographic analysis, no unreacted monomer was present in the concentrate. Tetrahydrofuran was used as a solvent, and the weight average molecular weight in terms of polystyrene (hereinafter referred to as Mw) measured by gel permeation chromatography (hereinafter referred to as GPC) was 1800. The copolymer that is a component of the concentrated solution is referred to as “polymer 1”.

<Manufacture examples 2-5> Except having changed conditions as Table 1, superposition | polymerization and the process were performed similarly to manufacture example 1, and the copolymer was manufactured. The obtained polymers are referred to as polymers 2 to 5, respectively. The results of these analyzes are shown in Table 1.

The meanings of the abbreviations in Table 1 are as follows.
MMA: Methyl methacrylate BA: Butyl acrylate HA: 2-ethylhexyl acrylate GMA: Glycidyl methacrylate M100: Epoxycyclohexylmethyl methacrylate (Daicel Cyclomer M100)

<Examples 1-6>
Polymers 1 to 5 were blended under the conditions shown in Table 2 to prepare a composition. After applying the above composition to a cold-rolled stainless steel plate (SUS304) that has been polished with a sandpaper in advance and then wiped with acetone, the two pieces are bonded together, and a sample for tensile shear test (according to ASTM D1002-53T) It was created. The formulation in Table 2 is a mass ratio. After curing at 23 ° C. for 2 days and at 50 ° C. for 3 days, the tensile shear strength was measured. The results are shown in Table 3.
Moreover, the sheet | seat of hardened | cured material was created so that it might become a film thickness of 1 mm, and it used for the weather resistance test.

<Comparative Examples 1-3> A composition for comparison was prepared by blending under the conditions shown in Table 2, and the same tests as in Examples were conducted.

What was used other than the polymers 1-5 as a compounding component in Table 2 is as follows.
HEROXY 8: Reactive Diluent ARUFON UP1110 manufactured by Japan Epoxy Resin Co., Ltd. Non-functional acrylic polymer (Mw = 2600) manufactured by Toagosei
Epicoat 828: Bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd. (epoxy equivalent 189 g / eq)
EpiCure H30: Ketimine type curing agent manufactured by Japan Epoxy Resin Co., Ltd.

The following tests were conducted using the compositions shown in Table 2.
<Adhesiveness>
Tensileon 200 (manufactured by Toyo Seiki Co., Ltd.) was used to pull the cured tensile test sample after curing, and the strength at break was measured.
<Heat resistance>
The shear tensile test sample was put into a thermostat set at 70 ° C., and a tensile test was conducted after 1 hour.
<Weather resistance>
The cured sheet was placed in a metal weather weathering tester (manufactured by Daipurwines), and the appearance after the 100-hour test was observed.
<Workability>
A blend of a polymer, an epoxy resin and a curing agent described in Table 2 was applied to a 10 cm × 10 cm with a spatula, and the spatula was evaluated.
The results are shown in Table 3.

  The composition of the present invention is not only high in adhesive strength but also excellent in heat resistance and weather resistance, low viscosity, good handling workability, and useful as an adhesive.

Claims (6)

An adhesive composition containing a copolymer having a monomer unit having an epoxy group and a (meth) acrylic acid ester unit having no epoxy group as a constituent unit and having a weight average molecular weight of 500 to 5,000 and an epoxy resin. The copolymer is based on a total of 100 parts by mass of a monomer unit having an epoxy group and a (meth) acrylic acid ester unit having no epoxy group, and 5 to 50 parts by mass of a monomer unit having an epoxy group and It has 50-95 mass parts of (meth) acrylic acid ester units which do not have an epoxy group, The adhesive composition of Claim 1 characterized by the above-mentioned. The adhesive composition according to claim 1, comprising 5 to 40 parts by mass of a copolymer and 60 to 95 parts by mass of an epoxy resin based on 100 parts by mass of the total of the copolymer and the epoxy resin. The adhesive composition according to claim 1, wherein the copolymer has a glass transition temperature of −10 ° C. or lower. The adhesive composition according to claim 1, wherein the copolymer is obtained by continuously polymerizing raw material monomers at a temperature of 150 to 350 ° C. The adhesive composition according to claim 1, wherein the epoxy resin has a bisphenol A skeleton.