JP4386269B2 - Curable resin composition and sheet - Google Patents

Description

  The present invention relates to a curable resin composition and a sheet thereof, and more specifically, a resin composition that becomes a cured product having flexibility to follow the shape when applied to an article shape, and a curable resin containing thermally conductive particles The present invention relates to a composition and a sheet thereof.

  In recent years, silicone gel has been widely used as a special packaging material for shoe soles, sports equipment, rotating equipment, insulators for office automation equipment, precision measuring equipment and high value-added products. Such a silicone gel has good follow-up to the shape of the article and is excellent in mechanical properties such as heat resistance, cold resistance, weather resistance, electrical properties and buffering properties, but is expensive at the same time. Since low molecular weight siloxane remains, there are concerns about environmental hormones, and there is a demand for inexpensive materials that do not have such concerns in the market.

  In addition to silicone gels, several materials aiming at the above properties have been proposed (for example, Patent Documents 1 to 3). Patent Document 1 describes a low-hardness polyurethane gel for the purpose of a similar shock absorber or vibration isolator. However, in Patent Document 1, a plasticizer, a high boiling point solvent or the like may be added as a thinning agent, and environmental hormone substances such as dioctyl phthalate and dioctyl adipate are used in all examples. The reduction in hardness can be analogized with the plasticizing effect of the plasticizer. Patent Document 2 discloses a shock-absorbing gel material composed of a styrene / vinyl isoprene / styrene copolymer, liquid polybutene, and the like and a crosslinking agent, and all of the examples have a Shore A hardness of 40 or more. Sufficient flexibility is not obtained.

  Patent Document 3 describes a method for producing microgel composition particles having a crosslinked polymer nucleus on a large number of polymer arms attached to the nucleus. The manufacturing process includes reacting a living prepolymer component with a monomer component, the monomer component including a monoolefin monomer. However, Patent Document 3 only describes a method for adjusting a microgel in Examples, and does not describe specific characteristics of the microgel.

  On the other hand, even in a pressure-sensitive adhesive such as an adhesive tape, a material having excellent conformability to the article shape as described above is expected to have extremely important characteristics depending on the usage form. As related technologies, Patent Documents 4 and 5 disclose, in solvent monomers and solute polymers therein, ethylenically unsaturated monomers having a radiation sensitive hydrogen abstraction group or ethylenic having a radiation sensitive hydrogen abstraction group. An acrylic syrup is disclosed in which there are partial units derived from unsaturated monomers and can be cured into a viscoelastic polymeric material by UV irradiation. However, these inventions are crosslinked for the purpose of obtaining well-balanced peelability and shear adhesion, and there is no description of shape followability to the article as described above. In addition, the ethylenically unsaturated monomers having the radiation-sensitive hydrogen abstraction group and the radiation-sensitive α-cleavable group used in these inventions are very special and are not generally available. It cannot be easily manufactured by those skilled in the art.

  On the other hand, it is widely used that a curable resin composition filled with a heat conductive filler is formed into a sheet shape and used as a heat conductive sheet for heat dissipation of electronic devices or the like (for example, Patent Document 6). 7). In Patent Document 6, a composition comprising a mixture of a polysiloxane having a C═C bond in a molecule and an organopolysiloxane having an SH group in the molecule is mixed with a thermally conductive filler, and molded and crosslinked. Although a thermally conductive insulating sheet is disclosed, it is an object of the invention to fill a large amount of a high thermal conductivity filler such as alumina and thereby improve heat dissipation characteristics. The shape following property to the article as described above is not described. Moreover, there is a concern about the problem of environmental hormones by using polysiloxane.

The resin composition that is a cured product having good conformity to the shape of the article such as silicon gel is useful as a vibration-proofing material, a cushioning material, a special packaging material, and a pressure-sensitive adhesive, and particularly a thermally conductive filler. Although it is useful as a heat conductive sheet used as a binder, as described above, sufficiently satisfactory characteristics are clearly shown in the prior art except those made of polysiloxane and those using a plasticizer. Not. In addition, those made of polysiloxane and those using a plasticizer are concerned about the elution of low molecular components contained in them.
JP 2002-121254 A JP-A-9-12934 JP-T-2002-514667 Japanese National Patent Publication No. 10-503548 Japanese National Patent Publication No. 10-503802 JP 58-214209 A JP-A-11-292998

  The present invention solves the above-mentioned problems of the prior art, and is excellent in conformity to special shapes such as curved surfaces without adding a low molecular weight softening material such as a plasticizer, other than polysiloxane. It is providing the resin composition which can obtain hardened | cured material, and providing the sheet | seat which consists of hardened | cured material of this resin composition containing the heat conductive particle. The “resin composition” as used in the present invention includes a blend of a plurality of monomer components and additives that become a resin composition when cured by a reaction such as polymerization or crosslinking.

As a result of intensive studies to solve the above problems, the present inventors have added a low molecular weight substance such as a plasticizer when a resin composition obtained by adding a specific polythiol to a specific acrylic compound is cured. Therefore, the present invention has been found to be extremely excellent in conformity to a special shape such as a curved surface of an article because it has a very soft gel-like cured product and low hardness.

That is, in the present invention, when the total of the photopolymerization initiator and the resin composition is 100% by mass, (a) the average molecular weight represented by the following formula (2), formula (3) or formula (4) is 50 to 15000 mercapto groups containing 0.01 to 5% by mass of a polythiol which is a mercaptan compound having two or more, and the main component is one or a mixture of two or more selected from the following (b) to (c) It is a resin composition for heat dissipation members .
(B) An acrylate or methacrylate having an alkyl group having 2 to 12 carbon atoms (c) An acrylic monomer represented by the formula (1)





In the formula (1), R1 represents hydrogen or a methyl group. R2 represents an alkylene group such as an ethylene group, a propylene group, or a butylene group, R3 represents hydrogen, an alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted phenyl group, and n represents an integer of 1-12.
In formulas (2) to (4), Z is an organic residue having m functional groups, m is an integer of 2-6, and p and q are 0 or an integer of 1-3.
Moreover, this invention is a sheet | seat which consists of the said resin composition characterized by containing a heat conductive particle, and the resin composition.
Their to, be one obtained by curing these resin compositions, the hardness was measured after after pressurization for 60 seconds using a type E durometer and compliant JIS K6253 is cured is less than 40. Furthermore, it is a sheet | seat which consists of hardened | cured material of the said resin composition containing heat conductive particle.

  Since the resin composition of the present invention can be cured to obtain a gel-like product having extremely low hardness without adding a low-molecular weight softening material such as low-molecular siloxane or plasticizer, the cured product is obtained from the article. Excellent follow-up to special shapes such as curved surfaces. And the sheet | seat shape | molded and hardened by making this resin composition contain a heat conductive particle is excellent in a softness | flexibility (low hardness), and excellent in the peelability and heat conductivity when it affixes on a metal plate. ing.

The acrylate or methacrylate having (b) an alkyl group having 2 to 12 carbon atoms in the resin composition of the present invention is an acrylic acid alkyl ester or methacrylic acid alkyl ester having 2 to 12 carbon atoms. Examples of the component (b) include ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, isooctyl acrylate, decyl acrylate, decyl methacrylate, dodecyl methacrylate, and the like.
The acrylic monomer represented by formula (1) of (c) in the resin composition of the present invention is represented by formula (1).
Here, R ₁ represents hydrogen or a methyl group. R ₂ represents an alkylene group such as an ethylene group, a propylene group, or a butylene group, R ₃ represents hydrogen, an alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted phenyl group, and n represents an integer of 1 to 12 To express.

  Examples of the component (c) include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-methoxyethyl acrylate, ethoxyethyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, and nonylphenoxyethyl acrylate. 2-ethylhexyl carbitol acrylate, diethylene glycol monoacrylate, triethylene glycol monoacrylate, ethylene glycol unit repeat number 12 or less polyethylene glycol monoacrylate, methoxydiethylene glycol monoacrylate, methoxytriethylene glycol monoacrylate, ethylene glycol unit repeat number 12 or less methoxy polyethylene glycol Monoacrylate, ethoxydiethylene glycol monoacrylate, ethoxytriethylene glycol monoacrylate, ethoxypolyethylene glycol monoacrylate with ethylene glycol unit repeat number of 12 or less, phenoxydiethylene glycol monoacrylate, phenoxytriethylene glycol monoacrylate, ethylene glycol unit repeat number of 12 or less Phenoxypolyethylene glycol monoacrylate, dipropylene glycol monoacrylate, tripropylene glycol monoacrylate, polypropylene glycol monoacrylate, methoxydipropylene glycol monoacrylate, methoxytripropylene glycol monoacrylate having a propylene glycol unit repeating number of 12 or less Relate, methoxypolypropylene glycol monoacrylate, ethoxydipropylene glycol monoacrylate, ethoxytripropylene glycol monoacrylate, ethoxypolypropylene glycol monoacrylate having 12 or fewer propylene glycol units, phenoxydipropylene glycol Monoacrylate, Phenoxytripropylene glycol monoacrylate, Phenoxypolypropylene glycol monoacrylate having 12 or less propylene glycol units, Dibutylene glycol monoacrylate, Tributylene glycol monoacrylate, Polybutylene glycol mono having 12 or less repeats of butylene glycol units A Chrylate, diethylene glycol monomethacrylate, triethylene glycol monomethacrylate, polyethylene glycol monomethacrylate with ethylene glycol unit repeat number of 12 or less, dipropylene glycol monomethacrylate, tripropylene glycol monomethacrylate, polypropylene glycol monoester with propylene glycol unit repeat number of 12 or less Examples thereof include, but are not limited to, methacrylate, dibutylene glycol monomethacrylate, tributylene glycol monomethacrylate, polybutylene glycol monomethacrylate having a butylene glycol unit repeating number of 12 or less, and the like.

The polythiol (a) in the resin composition of the present invention represents a mercaptan compound having two or more mercapto groups, and the average molecular weight represented by the formula (2), the formula (3) or the formula (4) is 50 to 15000. It is a substance.

In the formulas (2) to (4), Z is an organic residue having m functional groups, m is an integer of 2-6, and p and q are integers of 0 or 1-3. Further, the organic residue Z in the formula (2), the formula (3) and the formula (4) is changed to the formula (5), the formula (6), the formula (7), the formula (8), the formula (9), or the formula (10). ) Is preferred.
In the formulas (5) to (8), v, w, x, y, and z are integers of 1-6.

  When the resin composition of the present invention comprises one or more mixtures selected from (b) and (c) as a main component and the total amount of the resin composition is 100% by mass, the component (a) The content of is 0.01 to 5 mass%, more preferably 0.1 to 2 mass%. When the content of the component (a) is less than 0.01% by mass, the cured product is not excellent in followability to a special shape such as a curved surface, and when it exceeds 5% by mass, the effect of chain transfer is large and the curability is poor. Become.

  In addition to the components (a), (b) and (c), the resin composition of the present invention is a known polymerizable compound, known polyfunctional vinyl compound, Copolymerizable crosslinking components such as polyfunctional acrylates and polyfunctional allyl compounds can be included. Moreover, a well-known additive can be added as needed in the range which does not have influence at the time of hardening of the resin composition of this invention. Examples of additives include various additives for controlling viscosity and viscosity, other modifiers, anti-aging agents, heat stabilizers, colorants, and the like.

  The resin composition of the present invention can be cured by a general method. For example, it can be cured by a method such as thermal polymerization using a thermal polymerization initiator, photopolymerization using a photopolymerization initiator, or polymerization using a thermal polymerization initiator and a curing accelerator.

  The thermal polymerization initiator is not particularly limited, but an azo compound or an organic peroxide can be preferably used. Examples of useful azo compounds include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutylnitrile), and the like. It is done. Useful organic peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, acetylacetone peroxide, 1,1, -di (tertiary butyl peroxy) cyclohexane, 2,2-di (tertiary butyl peroxy) butane, n -Butyl 4,4-di (tertiary butyl peroxy) valerate, 2,2-di (4,4-di (tertiary butyl peroxy) cyclohexyl) propane, p-menthane hydroperoxide, diisopropylbenzene hydro Peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, tertiary butyl hydroperoxide, di (2-tertiary butyl peroxyisopropyl) benzene, dicumyl peroxide, 2 , 5- Methyl-2,5-di (tertiary butyl peroxy) hexane, tertiary butyl cumyl peroxide, ditertiary butyl peroxide, ditertiary hexyl peroxide, 2,5-dimethyl-2,5-di (tertiary butyl) Peroxy) hexyne-3, diisobutyryl peroxide, di (3,5,5-trimethylhexanoyl) peroxide, di-n-octanoyl peroxide, dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide , Di (4-methylbenzoyl) peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di (4-tertiarybutylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) per Xylodicarbonate, cumyl peroxyneodecanoate, tertiary butyl peroxyneodecanoate, tertiary butyl peroxypivalate, 2,5-dimethyl-2,5-di (2-ethylhexanoyl peroxy) Hexane, tertiary butyl peroxy-2-ethylhexanoate, tertiary butyl peroxyisobutyrate, tertiary butyl peroxymaleic acid, tertiary butyl peroxy-3,5,5-trimethylhexanoate, Di-tertiary butyl peroxy hexahydroterephthalate, tertiary butyl peroxy isopropyl monocarbonate, tertiary butyl peroxy-2-ethylhexyl monocarbonate, 2,5-dimethyl-2,5-di (benzoyl peroxy) ) Hexane, tertiary butyl peroxyacetate, tertiary butyl peroxybenzoate and the like.

  On the other hand, as the photopolymerization initiator, benzophenone, p-methoxybenzophenone, 4,4-bisdimethylaminobenzophenone, xanthone, thioxanthone, chlorothioxanthone, m-chloroacetone, propiophenone, anthraquinone, benzoin methyl ether , Benzoin ethyl ether, benzoisopropyl ether, benzoin butyl ether, benzyl, 2,2-dimethoxy-1,2-diphenylethane-1-one, acetophenone, 2,2-diethoxyacetophenone, 2-hydroxy-2,2-dimethyl Although acetophenone etc. are mentioned, it is not limited to these.

  As the curing accelerator, any known curing accelerator that reacts with the thermal polymerization initiator and generates radicals can be used. Typical curing accelerators include, for example, tertiary amines, thiourea derivatives, transition metal salts and the like. Examples of the tertiary amine include triethylamine, tripropylamine, tributylamine, and N, N-dimethyl-p-toluidine. Examples of the thiourea derivative include 2-mercaptobenzimidazole, methylthiourea, sibutylthiourea, tetramethylthiourea, and ethylenethiourea. Examples of the transition metal salt include cobalt naphthenate, copper naphthenate, and vanadyl acetylacetonate. Among these, N, N-dimethyl-p-toluidine, ethylenethiourea, cobalt naphthenate, and vanadyl acetylacetonate are preferable because of their good curability.

  The resin composition of the present invention is mixed into a thin container by mixing thermally conductive particles, or formed into a sheet shape by a general method such as applying a certain thickness on a release paper, etc. It can be used as a heat conductive sheet. Examples of the thermally conductive particles include metal oxides such as aluminum oxide and titanium dioxide, nitrides such as aluminum nitride, boron nitride, and silicon nitride, silicon carbide, and aluminum hydroxide, but are not limited thereto. It can be used alone or in combination of several kinds. In general, a heat conductive sheet is often required to have flame retardancy, and aluminum hydroxide is preferable in that it can improve both the characteristics of heat conductivity and flame retardancy. The particle size of such heat conductive particles is preferably about 1 to 100 μm in order to obtain a dispersion liquid. The blending amount of the heat conductive particles may be adjusted according to the heat conductivity required depending on the application to be used, but is generally about 20 to 300 parts by mass with respect to 100 parts by mass of the resin composition.

  As described above, the resin composition of the present invention is cured by thermal polymerization using a thermal polymerization initiator or photopolymerization using a photopolymerization initiator to obtain a gel-like cured product. This cured product is gel-like. It is very important that the hardness is very low. As a measure of the hardness of the cured product, the hardness measured 60 seconds after pressing using a type E durometer in accordance with JIS K6253 is preferably less than 40, more preferably less than 30. When the hardness is 40 or more, there are cases where excellent followability to special shapes such as the curved surface of the article as described above cannot be obtained.

  The present invention will be specifically described with reference to examples.

(Evaluation methods)
(1) Hardness measurement Using the samples of each Example and Comparative Example, the hardness was measured 60 seconds after pressing using a type E durometer in accordance with JIS K6253.
(2) 180 degree peeling adhesive strength
According to JIS-Z-0237, the 180 ° peel adhesive strength of the sheets prepared in Examples 8 and 9 and Comparative Example 3 was measured.

(3) Thermal conductivity The sheets prepared in Examples 8 and 9 and Comparative Example 3 were sandwiched between a TO-3 type copper heater case (TO-3 shape: 6 cm ² ) and a copper plate, and the thickness After screwing to 10% compression, apply power 15W to the heater case until the temperature difference between the heater case and the copper plate becomes constant, measure the temperature difference, and calculate the thermal resistance from the following formula (11). did.
Based on the value of the obtained thermal resistance, the thermal conductivity was calculated from the following formula (12). In addition, the thickness of the material here is the thickness at the time of thermal resistance measurement (thickness measured by screwing so that the sheet thickness is compressed by 10% and measuring the thermal resistance). The heat transfer area is 0.0006 m ² of the TO-3 type heat transfer area.

Example 1
After mixing 100 parts by mass of phenoxyethyl acrylate (light acrylate PO-A Kyoeisha Chemical Co., Ltd.) and 1.0 part by mass of triethylene glycol dimercaptan (DMDO Maruzen Chemical Co., Ltd.), di-tertiary butyl 0.8 parts by mass of peroxyhexahydroterephthalate (Kaya ester HTP-65W Kayaku Akzo Co., Ltd.) was dissolved to prepare a resin composition. The resin composition was filled in an aluminum cup having a diameter of 60 mm and a height of 15 mm, and a curing reaction was carried out in a constant temperature bath at 100 ° C. for 24 hours. As a result of measuring the type E durometer hardness by the above method, a hardened product having a hardness of zero and extremely flexible was obtained.

(Examples 2-6, Comparative Examples 1 and 2)
A blend was blended according to the blending table in Table 1 to obtain a resin composition. A polyester rubber frame (width 50 mm, length 50 mm, thickness 2 mm) is placed on the polyester film whose surface has been subjected to a release treatment, and a polyester film having a release treatment applied to the surface. A cured sheet was obtained by irradiating with 3000 mJ / cm ^{2 of} 365 nm ultraviolet rays. The obtained sheets were overlapped and the hardness was measured by the above method. The results are shown in Table 1. In the sheets of Examples 2 to 6, a very soft sheet was obtained with any formulation. On the other hand, when polythiol was not used as in Comparative Example 1, Type E durometer hardness was too high, and when Monothiol was used as in Comparative Example 2, it became a viscous liquid and hardness measurement could not be performed.

(Abbreviations in Table 1)
AP-400: Polypropylene glycol monoacrylate (manufactured by NOF Corporation)
EHA: 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd.)
IOAA: Isooctyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
APG-200: Tripropylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
DMDO: Triethylene glycol dimercaptan (Maruzen Chemical Co., Ltd.)
TMTP: Trimethylolpropane tristhiopropionate (manufactured by Sakai Chemical Co., Ltd.)
PETP: Pentaerythritol tetrakisthiopropionate (manufactured by Sakai Chemical Co., Ltd.)
DDT: Dodecanethiol (manufactured by Kanto Chemical Co., Inc.)
BDK: 2,2-dimethoxy-1,2-diphenylethane-1-one (Ciba Specialty Chemicals Co., Ltd.)

(Example 7)
100 parts by mass of phenoxyethyl acrylate, 1.0 part by mass of triethylene glycol dimercaptan, and 180 parts by mass of aluminum hydroxide (Hidelite H32, manufactured by Showa Denko KK) as heat conductive particles were mixed. A resin composition containing 0 part by mass, 0.5 part by mass of N, N-dimethyl-p-toluidine, and 1.0 part by mass of cobalt octenoate was prepared, and the resin composition was applied to an aluminum cup having a diameter of 60 mm and a height of 15 mm. The product was filled and cured at room temperature for 24 hours, and then heated at 100 ° C. for 2 hours. The obtained cured product was a flexible cured product of type E durometer hardness 0.

(Examples 8 and 9, Comparative Example 3)
According to the formulation of Table 2, the formulation was blended to obtain a resin composition containing thermally conductive particles. A cured sheet was prepared in the same manner as in Example 2, and its type E durometer hardness was measured. These sheets were evaluated for 180-degree peeling adhesive strength and thermal conductivity by the following method, and the results are summarized in Table 2.

(Abbreviations in Table 2)
AP-400: Polypropylene glycol monoacrylate (manufactured by NOF Corporation)
EHA: 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd.)
HEA: 2-hydroxyethyl acrylate (manufactured by Kyoeisha Co., Ltd.)
APG-200: Tripropylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
DMDO: Triethylene glycol dimercaptan (Maruzen Chemical Co., Ltd.)
BDK: 2,2-dimethoxy-1,2-diphenylethane-1-one (Ciba Specialty Chemicals Co., Ltd.)
H32: Aluminum hydroxide (made by Showa Denko KK)
A-11: Aluminum oxide (made by Nippon Light Metal Co., Ltd.)

  In Examples 8 and 9, a sheet excellent in any of the properties of sheet hardness, adhesive strength, and thermal conductivity is obtained. On the other hand, in Comparative Example 3, the thermal conductivity is sufficient, but the hardness of the sheet is high and the adhesive strength is also inferior.

  The gel-like cured product obtained from the resin composition of the present invention does not contain low-molecular substances such as low-molecular siloxanes and plasticizers, and is excellent in conformity to special shapes of articles. Possibility of use as cushioning materials, special packaging materials, and pressure sensitive adhesives. In addition, the resin composition containing a thermally conductive filler and molded and cured into a sheet form has excellent adhesion to articles and excellent 180 degree peelability from metal. Therefore, it is useful as a heat conductive sheet or the like used by being attached to an electronic component that generates heat.

Claims (4)

When the total of the photopolymerization initiator and the resin composition is 100% by mass, (a) a mercapto having an average molecular weight of 50-15000 represented by the following formula (2), formula (3) or formula (4) For heat-dissipating members containing 0.01 to 5% by mass of polythiol, which is a mercaptan compound having two or more groups, and comprising one or more mixtures selected from the following (b) to (c) as main components acrylic monomers represented by the resin composition (b) an acrylate or methacrylate having an alkyl group of 2-12 carbon atoms (c) formula (1)




In the formula (1), R1 represents hydrogen or a methyl group. R2 represents an alkylene group such as an ethylene group, a propylene group, or a butylene group, R3 represents hydrogen, an alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted phenyl group, and n represents an integer of 1 to 12.
In formulas (2) to (4), Z is an organic residue having m functional groups, m is an integer of 2-6, and p and q are 0 or an integer of 1-3. The resin composition for a heat radiating member according to claim 1 , comprising thermally conductive particles. A cured product obtained by curing the resin composition of claim 1 or 2 and having a hardness of less than 40 measured 60 seconds after pressing using a type E durometer in accordance with JIS K6253. A sheet comprising a cured product of the resin composition of claim 2 .