JP2009167327A - Graft copolymer, resin composition containing it, and molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graft copolymer suppressing increase with the lapse of time in viscosity of a resin composition for lowering an elastic modulus of an obtained molded product, and the molded product of the graft copolymer. <P>SOLUTION: The graft copolymer is obtained when a monomer mixture (B) containing (meth)acrylic acid ester monomers is polymerized in the presence of a (meth)acrylic acid ester polymer (A) with a glass transition temperature of 0&deg;C or less found using a Fox equation. In the polymer obtained by polymerizing the monomer mixture (B), a glass transition temperature found using the Fox equation is higher than 0&deg;C. The monomer mixture (B) contains 1.0 mol% or more of cross-linkable monomers when the content of the monomer mixture (B) is 100 mol%. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a graft copolymer, a resin composition containing the graft copolymer, and a molded body. In particular, the present invention relates to a resin composition used for an electronic material such as a semiconductor, for example, a resin composition for a semiconductor sealing material, a graft copolymer useful for blending in a resin composition for an adhesive, The present invention relates to a resin composition containing a graft copolymer and a molded article.

Resin molded bodies are manufactured according to various uses such as electric / electronic parts, automobile parts, and building materials. In these resin moldings, one or several kinds of resins and additives are used in order to develop the performance required according to the purpose.
For example, in electrical / electronic parts such as transistors and ICs, resin sealing using an epoxy resin composition has become mainstream. Resin sealing with this epoxy resin composition is excellent in mass productivity and inexpensive production is possible, but since the linear expansion coefficient of the resin is larger than that of semiconductor elements, stress relaxation after sealing is a major issue. .

Epoxy resins are also widely used in insulation layers for electrical insulation laminates and printed wiring boards. With recent advances in printed wiring board mounting technology and changes in the usage environment, there is a need for lower elastic modulus. It is high.
In order to reduce the elastic modulus of the epoxy resin composition, a method of blending butadiene rubber particles as a modifier has been proposed (Patent Document 1). However, when such a rubber component is blended with a liquid epoxy resin, the resin composition thickens with time, so that the storage stability is not sufficient.

In order to improve the storage stability of the resin composition, methods have been proposed in which a crosslinkable monomer is copolymerized with the graft component of the graft copolymer to be blended (Patent Documents 2 and 3). However, the resin compositions proposed by these methods are not sufficient when higher storage stability is required.
Japanese Unexamined Patent Publication No. 2000-7890 JP-A-5-65391 JP-A-5-214310

  The present invention has been made to solve the problems of the prior art as described above, and when blended with a resin, it suppresses the thickening of the resin composition over time, and the resulting molded product has a low elastic modulus. It is an object to provide a graft copolymer to be converted, a resin composition containing the graft copolymer, and a molded product thereof.

  As a result of intensive studies, the inventors of the present invention have suppressed the increase in viscosity of the resin composition obtained over time by copolymerizing a specific amount or more of the crosslinkable monomer in the graft layer of the graft copolymer. It was found that the obtained molded article has a low elastic modulus.

  That is, the graft copolymer of the present invention comprises a (meth) acrylic acid ester monomer in the presence of a (meth) acrylic acid ester polymer (A) having a glass transition temperature determined by the Fox formula of 0 ° C. or lower. In the graft copolymer obtained by polymerizing the monomer mixture (B) containing a polymer, the glass transition temperature of the polymer obtained by polymerizing the monomer mixture (B) is 0 ° C. The monomer mixture (B) contains 1.0 mol% or more of a crosslinkable monomer (provided that (B) is 100 mol%).

The resin composition of the present invention contains the aforementioned graft copolymer and resin, and is preferably used for a semiconductor sealing material or an adhesive.
The molded product of the present invention is obtained by molding the above resin composition.

By using the graft copolymer of the present invention, it is possible to suppress the thickening of the resin composition over time and to lower the elastic modulus of the obtained molded product.
The resin composition of the present invention can suppress a thickening over time, and can obtain a molded article having a low elastic modulus.
Since the molded article of the present invention has a low elastic modulus and improved impact resistance, it is useful for a semiconductor encapsulant.

  Hereinafter, preferred embodiments of the present invention will be described. However, it should be understood that the present invention is not limited to these embodiments, and various modifications can be made within the spirit and scope of the present invention.

The graft copolymer of the present invention contains a (meth) acrylic acid ester monomer in the presence of a (meth) acrylic acid ester polymer (A) having a glass transition temperature of 0 ° C. or less determined by the Fox formula. In the graft copolymer obtained by polymerizing the monomer mixture (B), the glass transition temperature obtained by the Fox equation of the polymer obtained by polymerizing the monomer mixture (B) exceeds 0 ° C. The monomer mixture (B) contains 1.0 mol% or more of a crosslinkable monomer (provided that (B) is 100 mol%).
In the present invention, (meth) acryl means acryl or methacryl.

The polymer (A) of the present invention is obtained by polymerizing a monomer mixture (a) containing a (meth) acrylic acid ester monomer (a1), and has a glass transition temperature (Tg) determined by the Fox formula. Is 0 ° C. or lower.
By polymerizing the monomer mixture (a) whose main component is the (meth) acrylic acid ester monomer (a1) having a homopolymer Tg of 0 ° C. or less, the Tg determined by the Fox formula is 0 ° C. The following polymer (A) is obtained.

Examples of the (meth) acrylic acid ester monomer (a1) in which the Tg of the homopolymer is 0 ° C. or lower include ethyl acrylate (Tg of the homopolymer: −24 ° C.), n-propyl acrylate (same as above). : -37 ° C), n-butyl acrylate (same as -54 ° C), i-butyl acrylate (same as -49 ° C), and 2-ethylhexyl acrylate (same as -50 ° C).
These monomers may be used individually by 1 type, and may use 2 or more types together.

Here, as the numerical value of the Tg of the homopolymer, the numerical value described in POLYMER HANDBOOK THIRD EDITION (WILEY INTERSCIENCE) was used.
Tg of a polymer (A) can be calculated | required by Fox formula using the numerical value of said Tg. In the case where the monomer mixture (a) contains a crosslinkable monomer and / or a graft crossing agent, Tg is obtained for the monomer excluding the crosslinkable monomer and the graft crossing agent. To do.

The monomer mixture (a) is a range in which the Tg determined by the Fox formula of the polymer (A) is 0 ° C. or lower, and if necessary, other than the (meth) acrylate monomer (a1), You may contain another monomer (a2).
Examples of the other monomer (a2) include aromatic vinyl monomers such as styrene, α-methylstyrene, and vinyl toluene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; methacrylic acid-modified silicone; Examples include fluorine-containing vinyl monomers.

It is preferable that the content rate of the other monomer (a2) in a monomer mixture (a) (100 mass%) is the range of 0-20 mass%.
When the content of the other monomer (a2) in the monomer mixture (a) (100% by mass) is 20% by mass or less, the resulting resin composition has a low elastic modulus.

Moreover, the monomer mixture (a) may contain a crosslinkable monomer (a3) and / or a graft crossing agent (a4) as necessary.
Examples of the crosslinkable monomer (a3) include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, divinylbenzene, polyfunctional A methacryl group modified silicone is mentioned. Examples of the graft crossing agent (a4) include allyl methacrylate, triallyl cyanurate, and triallyl isocyanurate. Allyl methacrylate can also be used as a crosslinkable monomer.
These crosslinkable monomers (a3) and / or graft crossing agents (a4) may be used alone or in combination of two or more. By using these crosslinkable monomers (a3) and / or graft crossing agents (a4), a polymer (A) having a crosslinked structure can be obtained.

The content of the crosslinkable monomer (a3) and / or the graft crossing agent (a4) is preferably in the range of 0 to 15 mol% when the entire monomer mixture (a) is 100 mol%. The range of 0.01 to 10 mol% is more preferable.
If the content of the crosslinkable monomer (a3) and / or the graft crossing agent (a4) in the monomer mixture (a) (100 mol%) is 15 mol% or less, the resulting resin composition has low elasticity. Become a rate.

  The polymer (A) may have a single layer or a multilayer structure of two or more layers. Further, it may be a (meth) acrylic ester-based composite rubber containing two or more components and having two or more Tg.

In the monomer mixture (B) of the present invention, the polymer obtained by polymerization has a Tg determined by the Fox formula of more than 0 ° C., and the crosslinkable monomer (b2) is 1.0 mol% or more (provided that (B) is 100 mol%).
By using the (meth) acrylic acid ester monomer (b1) whose homopolymer Tg exceeds 0 ° C. as a main component, the monomer mixture (B) is obtained by polymerizing it. Tg determined by the Fox equation exceeds 0 ° C.

Examples of the (meth) acrylic acid ester monomer (b1) whose Tg of the homopolymer exceeds 0 ° C. include, for example, methyl methacrylate (Tg of the homopolymer: 105 ° C.), ethyl methacrylate (same: 65 ° C.) Methacrylic acid alkyl esters such as n-butyl methacrylate (same as 20 ° C.) and i-butyl methacrylate (same as 60 ° C.); and alkyl acrylates such as methyl acrylate (same as 10 ° C.).
These monomers may be used individually by 1 type, and may use 2 or more types together.

Here, as the numerical value of the Tg of the homopolymer, the numerical value described in POLYMER HANDBOOK THIRD EDITION (WILEY INTERSCIENCE) was used.
The Tg of the polymer obtained by polymerizing the monomer mixture (B) can be determined by the Fox equation using the above Tg value. The Tg of the polymer obtained by polymerizing the monomer mixture (B) is determined for the monomer obtained by removing the crosslinkable monomer from the monomer mixture (B).

The monomer mixture (B) is a polymer obtained by polymerizing the monomer mixture (B), and if necessary, (meth) acrylic acid in the range where Tg determined by the Fox formula exceeds 0 ° C. Other monomers (b3) other than the ester monomer (b1) may be contained.
Other monomers (b3) include, for example, aromatic vinyl monomers such as styrene, α-methylstyrene and vinyltoluene; acrylic acid alkyl esters such as ethyl acrylate and n-butyl acrylate; acrylonitrile, methacrylate Vinyl cyanide monomers such as nitrile; vinyl monomers having a glycidyl group such as glycidyl (meth) acrylate and allyl glycidyl ether; vinyl monomers having a hydroxy group such as 2-hydroxyethyl methacrylate It is done.

It is preferable that the content rate of the other monomer (b3) in a monomer mixture (B) (100 mass%) is the range of 0-20 mass%.
When the content of the other monomer (b3) in the monomer mixture (B) (100% by mass) is 20% by mass or less, the handleability as a powder of the graft copolymer becomes good. .

Examples of the crosslinkable monomer (b2) include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, divinylbenzene, polyfunctional Examples thereof include methacrylic group-modified silicone and allyl methacrylate.
These crosslinkable monomers (b2) may be used individually by 1 type, and may use 2 or more types together.

The content rate of a crosslinkable monomer (b2) is 1.0 mol% or more when the whole monomer mixture (B) is 100 mol%.
Further, the content of the crosslinkable monomer (b2) is preferably 10.0 mol% or less, and is 5.0 mol% or less when the entire monomer mixture (B) is 100 mol%. It is more preferable.

If the content of the crosslinkable monomer (b2) in the monomer mixture (B) (100 mol%) is 1.0 mol% or more, the resin composition when the graft copolymer is blended with the resin The increase in viscosity over time can be suppressed.
If the content of the crosslinkable monomer (b2) in the monomer mixture (B) (100 mol%) is 10.0 mol% or less, the graft copolymer does not become brittle, and fine powder is generated in the drying process. Is suppressed.

  When the graft copolymer of the present invention is 100% by mass of the entire graft copolymer (the total of the graft parts obtained by polymerizing the polymer (A) and the monomer mixture (B)), It is preferable that it is 5-50 mass% of graft parts obtained by superposing | polymerizing a polymer (A) 50-95 mass% and a monomer mixture (B).

If the content of the polymer (A) in the entire graft copolymer (100% by mass) is 50% by mass or more, the resulting resin composition has a low elastic modulus, and if it is 95% by mass or less, It is possible to suppress the increase in viscosity over time when the graft copolymer is blended with the resin.
If the content of the graft part obtained by polymerizing the monomer mixture (B) in the entire graft copolymer (100% by mass) is 5% by mass or more, the graft copolymer was blended with the resin. The thickening with time can be suppressed, and if it is 50% by mass or less, the resulting resin composition has a low elastic modulus.

The graft copolymer of the present invention is obtained by polymerizing the monomer mixture (B) in the presence of the polymer (A). Polymerizing the monomer mixture (B) in the presence of the polymer (A) is intended to graft the monomer mixture (B) to the polymer (A), but the monomer The mixture (B) does not graft onto the polymer (A), and a free polymer polymerized alone is also produced as a by-product, and is obtained as a mixture of the graft copolymer and the free polymer.
In the present invention, the by-product free polymer is also referred to as a graft copolymer. Moreover, about the polymer obtained by superposing | polymerizing a monomer mixture (B), it is called a graft part also including a free polymer.

As a method for producing the polymer (A), aqueous polymerization is suitable, and emulsion polymerization is preferred.
Aqueous polymerization is characterized in that the polymer is obtained in the form of particles, and when the graft copolymer is blended with the resin, for example, good dispersibility that cannot be achieved by bulk polymerization is obtained.

  When the polymer (A) is produced by emulsion polymerization, in addition to the emulsion polymerization using a normal polymerization initiator and a surfactant, substantially no normal surfactant is used, and ammonium persulfate, 2,2′- Soap-free emulsion polymerization combining so-called soap-free polymerization and emulsion polymerization using an initiator having a hydrophilic group such as azobis [N- (2-carboxyethyl) -2-methyl-propionamidine] can be used. If necessary, forced emulsion polymerization may be used.

  Examples of the polymerization initiator used for producing the polymer (A) include 2,2′-azobisisobutyronitrile, 4,4′-azobis (4-cyanovaleric acid), and 2,2′-azobis. Azo compounds such as [N- (2-carboxyethyl) -2-methyl-propionamidine]; persulfates such as ammonium persulfate; diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, cumane hydroperoxide, t -Organic peroxides such as butyl hydroperoxide; Redox initiators containing the persulfate as a component; Redox initiators containing the organic peroxide as a component.

  Examples of the emulsifier used in the production of the polymer (A) include alkali metal salts and ammonium salts of higher fatty acids such as disproportionated rosin acid, oleic acid and stearic acid; alkali metal salts of sulfonic acids such as dodecylbenzenesulfonic acid. And ammonium salts; nonionic emulsifiers.

  For the production of the polymer (A), a chain transfer agent such as t-dodecyl mercaptan, n-octyl mercaptan, or α-methylstyrene may be used.

  Moreover, in order to control the particle diameter of a polymer (A), the method of enlarging the latex of the obtained polymer (A) with an acid or a salt etc. can also be used.

The graft copolymer of the present invention can be obtained by adding the monomer mixture (B) in the presence of the latex of the polymer (A) and performing graft polymerization.
Graft polymerization can be carried out by emulsion polymerization using a normal polymerization initiator and a surfactant.

As a radical polymerization initiator used for graft polymerization, the same polymerization initiator as used for production of the polymer (A) can be used.
As an emulsifier used for graft polymerization, the same emulsifier as used for the production of the polymer (A) can be used.
Moreover, the same chain transfer agent as the chain transfer agent used for manufacture of a polymer (A) can be used for graft polymerization.

The latex of the graft copolymer obtained by emulsion polymerization can be recovered as a powder of the graft copolymer by a treatment such as spray drying or freeze drying. In this, since the dispersibility of the graft copolymer in resin becomes favorable, the spray-drying method is preferable.
In addition, a coagulation method using an acid or a salt can be used as long as it does not depart from the object of the present invention.
In addition, antioxidant and an additive can be mix | blended with the latex of a graft copolymer as needed.

In the spray drying method, latex of a graft copolymer is sprayed in the form of fine droplets and dried by applying hot air to the latex.
As a device for generating droplets, any of a rotating disk type, a pressure nozzle type, a two-fluid nozzle type, a pressurized two-fluid nozzle type, etc. can be used.
Further, the dryer capacity can be used from a small scale used in a laboratory to a large scale used industrially.

The temperature of hot air introduced into the apparatus (hot air inlet temperature), that is, the maximum temperature of hot air that can come into contact with the graft copolymer is preferably 200 ° C. or less, particularly preferably 120 to 180 ° C.
In addition, when spray drying, the latex of the graft polymer may be a single latex or a mixture of a plurality of latexes. Furthermore, in order to improve powder characteristics such as blocking and bulk specific gravity during spray drying, an optional component such as silica can be added to perform spray drying.

The average particle size of the graft copolymer powder obtained by spray drying is preferably in the range of 10 to 200 μm, and more preferably in the range of 20 to 180 μm.
If the average particle size of the powder is 10 μm or more, aggregation in the resin is difficult to occur, so that the expression of physical properties is improved, and if it is 200 μm or less, the dispersibility in the resin is good.

The proportion of moisture contained in the graft copolymer powder is preferably 1.5% or less, and more preferably 1% or less.
If the ratio of the water content of the graft copolymer powder is 1.5% or less, there is little risk of cracks occurring when the resin composition is molded.

When the graft copolymer of the present invention is blended with another resin (hereinafter, also referred to as a target resin) as a modifier, the effect is remarkably exhibited. Various curable resins or thermoplastic resins are applied as the target resin, and it is particularly effective to use a curable resin composition, and in particular, an epoxy resin composition, for example, an epoxy resin for a semiconductor sealing material A composition is preferred.
The blending amount of the graft copolymer relative to the target resin can be appropriately set according to the blending purpose.

  Examples of the curable resin include a thermosetting resin and a photocurable resin. For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a melamine resin, and a urea resin can be used. Moreover, if there is no malfunction, they can be mixed and used.

  As the epoxy resin, known resins can be used, and the molecular structure, molecular weight, etc. are not particularly limited as long as they have at least two epoxy bonds in the molecule. For example, various epoxy resins such as dicyclopentadiene type, cresol novolak type, phenol novolak type, bisphenol type, biphenyl type and the like may be used alone or in combination of two or more.

Examples of epoxy resin curing agents include phenolic curing agents such as phenol novolac resins and cresol novolac resins; amine curing agents; acid anhydride curing agents. These may be used alone or in combination of two or more.
Although there is no restriction | limiting in particular about the usage-amount of the hardening | curing agent of an epoxy resin, It is necessary to add the stoichiometric amount of an epoxy group.

Known phenol resins can be used, and examples thereof include resol type or novolak type phenol resins derived from various phenols and formaldehyde or C2 or higher aldehyde. These phenol resins may be modified with drying oil, xylene resin, melamine resin or the like.
In the case of a novolak type phenol resin, usually a curing agent such as a polyamine such as hexamine, an epoxy resin, an isocyanate compound, a polyformaldehyde compound, or a resol type phenol resin is further used in combination.

As the unsaturated polyester resin, known ones can be used, for example, isophthalic acid, orthophthalic acid, phthalic anhydride, succinic acid, adipic acid, sebacic acid, endmethylenetetrahydrophthalic anhydride and other saturated dibasic acids, ethylene Polyhydric alcohols such as glycol, dipropylene glycol, 1,3-butanediol, hydrogenated bisphenol A, neopentyl glycol, isopentyl glycol, 1,6-hexanediol, maleic acid, maleic anhydride, fumaric acid, itacone What is obtained by making it react with unsaturated dibasic acids, such as an acid, at 180-250 degreeC is mentioned.
Moreover, vinyl monomers, such as styrene, t-butyl styrene, divinyl benzene, diallyl phthalate, vinyl toluene, acrylic ester, can also be copolymerized.

  Known additives can be used in combination with the curable resin composition as necessary. For example, curing accelerators; mold release agents such as silicone oil, natural wax, and synthetic wax; powders such as crystalline silica, fused silica, calcium silicate, and alumina; fibers such as glass fibers and carbon fibers; antimony trioxide, etc. Flame retardants; halogen trapping agents such as hydrotalcite and rare earth oxides; colorants such as carbon black and bengara; silane coupling agents.

  As a method for preparing the curable resin composition, a known technique can be used. For example, the resin composition is mixed in a solution state or melt-mixed using a mixing roll or kneader, cooled, pulverized or tableted, and then subjected to transfer molding, sheet compound molding, bulk molding, etc. Can be done. Furthermore, it can also be used as a resin composition for adhesives.

Examples of the thermoplastic resin include hard, semi-rigid and soft chlorine-containing resins such as vinyl chloride resin (PVC), chlorinated polyethylene resin, chlorinated vinyl chloride resin and vinylidene chloride resin; polypropylene (PP), polyethylene ( Olefin resins such as PE); polystyrene (PS), high impact polystyrene (HIPS), (meth) acrylate-styrene copolymer (MS), styrene-acrylonitrile copolymer (SAN), styrene-maleic anhydride copolymer Styrene resin (St resin) such as coalescence (SMA), acrylonitrile-butadiene-styrene resin (ABS), acrylate-styrene-acrylonitrile resin (ASA), acrylonitrile-ethylene propylene rubber-styrene resin (AES); polymethyl methacrylate (PMMA Acrylic resins such as Ac resins; Polycarbonate resins (PC resins); Polyamide resins (PA resins); Polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) (PEs resins) ); Polylactic acid resin, thermoplastic polyvinyl alcohol resin, other biodegradable plant raw materials, environmentally friendly resins derived from petroleum raw materials (biodegradable resins); (modified) polyphenylene ether resins (PPE resins), polyoxy Engineering such as methylene resin (POM resin), polysulfone resin (PSO resin), polyarylate resin (PAr resin), polyphenylene resin (PPS resin), thermoplastic polyurethane resin (PU resin) Plastics: Styrene elastomers, olefins Thermoplastic elastomers (TPE) such as steamers, vinyl chloride elastomers, urethane elastomers, polyester elastomers, polyamide elastomers, fluorine elastomers, 1,2-polybutadiene, trans 1,4-polyisoprene; PC / ABS, etc. PC-based resin / St-based resin alloy, PVC-based resin such as PVC / ABS / St-based resin alloy, PA-based resin such as PA / ABS / St-based resin alloy, PA-based resin / TPE alloy, PA such as PA / PP Resin / polyolefin resin alloy, PBT resin / TPE, PC resin such as PC / PBT / PEs resin alloy, polyolefin resin / TPE, alloy between olefin resins such as PP / PE, PPE / HIPS, PPE resin alloys such as PPE / PBT and PPE / PA, PV It is a polymer alloy such as PVC resin such as C / PMMA / Ac resin alloy.
These may be used alone or in combination of two or more.

  Known additives can be used in combination with the thermoplastic resin composition as necessary. For example, phenolic, phosphite-based, sulfur-based, amine-based stabilizers; ultraviolet absorbers; hydrolysis resistance modifiers; flame retardants; fillers such as titanium oxide and talc; Plasticizers can be used.

  A known technique can be used as a method for preparing the thermoplastic resin composition. For example, a method in which powder and granular materials are mixed with a Henschel mixer, tumbler, etc., and this is melt-mixed with an extruder, kneader, mixer, etc., a method in which other components are sequentially mixed with previously melted components, Various methods such as a method of directly molding the mixture with an injection molding machine can be used. In addition to injection molding, calendar molding, blow molding, extrusion molding, thermoforming, foam molding, melt spinning, and the like can be used.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
In the examples, “part” means part by mass, “%” means mass%, and “mol%” means mol% relative to the monomer mixture.
Moreover, the average particle diameter of polymer latex and the average particle diameter of polymer powder were measured by the method shown below.

(1) Average particle diameter of polymer latex The polymer latex was diluted with deionized water, and a 50% volume average particle diameter was measured using a laser diffraction scattering type particle size distribution analyzer (LA-910, manufactured by Horiba, Ltd.). Was measured.

(2) Average particle diameter of polymer powder The polymer powder is dispersed in deionized water, and a 50% volume average is obtained using a laser diffraction scattering type particle size distribution analyzer (LA-910, manufactured by Horiba, Ltd.). The particle size was measured.

<Example 1>
Production of Graft Copolymer (1) Into a separable flask equipped with a thermometer, a nitrogen introduction tube, a cooling tube and a stirrer, the following monomer mixture (1) and deionized water were added, While stirring at 250 rpm, the internal temperature of the separable flask was raised to 80 ° C.
Monomer mixture (1):
N-Butyl acrylate 4.961 parts Allyl methacrylate 0.039 parts (0.78 mol% based on monomer mixture (1))
92.6 parts of deionized water Next, the following initiator aqueous solution was added and held for 60 minutes to perform first-stage soap-free polymerization.
Initiator aqueous solution:
Ammonium persulfate 0.1 part Deionized water 5.2 parts

Subsequently, the following monomer mixture (2) and aqueous emulsifier solution (1) were mixed and added dropwise over 180 minutes. After the completion of dropping, the mixture was held for 60 minutes, and the second emulsion polymerization was performed to obtain a polymer (A1).
Monomer mixture (2):
N-butyl acrylate 76.41 parts allyl methacrylate 0.59 parts (0.78 mol% based on monomer mixture (2))
Emulsifier aqueous solution (1):
Ammonium di-2-ethylhexyl sulfosuccinate 0.8 parts Deionized water 39.0 parts

Next, the following monomer mixture (B) and aqueous emulsifier solution (2) were mixed and added dropwise over 100 minutes. After completion of the dropwise addition, the polymerization was terminated by maintaining for 60 minutes to obtain a latex of the graft copolymer (1).
Monomer mixture (B):
Methyl methacrylate 16.94 parts n-butyl acrylate 0.38 parts Allyl methacrylate 0.68 parts (3.0 mol% with respect to monomer mixture (B))
Emulsifier aqueous solution (2):
Di-2-ethylhexyl ammonium sulfosuccinate 0.2 part Deionized water 10.4 parts

The obtained latex of the graft copolymer (1) is dried with a spray dryer (pressure nozzle type sprayed into fine droplets, hot air inlet temperature 180 ° C.), and the graft copolymer (1) powder is obtained. It was collected.
The average particle size of the latex of the graft copolymer (1) was 600 nm. The average particle size of the powder of the graft copolymer (1) was 38 μm.

<Example 2>
Production of Graft Copolymer (2) A graft copolymer (2) was produced in the same manner as in Example 1, except that the composition of the monomer mixture (B) was changed as follows.
Monomer mixture (B):
Methyl methacrylate 16.77 parts n-butyl acrylate 0.38 parts Allyl methacrylate 0.85 parts (3.8 mol% with respect to monomer mixture (B))

  The average particle size of the latex of the graft copolymer (2) was 600 nm. The average particle size of the powder of the graft copolymer (2) was 39 μm.

<Example 3>
Production of Graft Copolymer (3) A graft copolymer (3) was produced in the same manner as in Example 1 except that the composition of the monomer mixture (B) was changed as follows.
Monomer mixture (B):
Methyl methacrylate 16.61 parts n-butyl acrylate 0.38 parts Allyl methacrylate 1.01 parts (4.5 mol% with respect to monomer mixture (B))

  The average particle size of the latex of the graft copolymer (3) was 590 nm. The average particle size of the powder of the graft copolymer (3) was 42 μm.

<Example 4>
Production of graft copolymer (4) A graft copolymer (4) was produced in the same manner as in Example 1 except that the composition of the monomer mixture (B) was changed as follows.
Monomer mixture (B):
Methyl methacrylate 15.98 parts N-butyl acrylate 0.38 parts Allyl methacrylate 1.64 parts (7.4 mol% with respect to monomer mixture (B))

  The average particle size of the latex of the graft copolymer (4) was 610 nm. The average particle size of the powder of the graft copolymer (4) was 40 μm.

<Example 5>
Production of Graft Copolymer (5) A graft copolymer (5) was produced in the same manner as in Example 1 except that the composition of the monomer mixture (B) was changed as follows.
Monomer mixture (B):
Methyl methacrylate 15.20 parts n-butyl acrylate 0.38 parts Allyl methacrylate 2.42 parts (11.0 mol% based on monomer mixture (B))

  The average particle size of the latex of the graft copolymer (5) was 620 nm. The average particle size of the powder of the graft copolymer (5) was 39 μm.

<Example 6>
Production of Graft Copolymer (6) Into a separable flask equipped with a thermometer, a nitrogen introduction tube, a cooling tube and a stirrer, the following monomer mixture (1) and deionized water were added, While stirring at 250 rpm, the internal temperature of the separable flask was raised to 80 ° C.
Monomer mixture (1):
N-Butyl acrylate 4.961 parts Allyl methacrylate 0.039 parts (0.78 mol% based on monomer mixture (1))
Deionized water 88.0 parts Next, the following initiator aqueous solution was added and held for 60 minutes to perform first-stage soap-free polymerization.
Initiator aqueous solution:
Ammonium persulfate 0.1 part Deionized water 5.2 parts

Subsequently, the following monomer mixture (2) and aqueous emulsifier solution (1) were mixed and added dropwise over 160 minutes. After the completion of dropping, the mixture was held for 60 minutes, and the second emulsion polymerization was performed to obtain a polymer (A2).
Monomer mixture (2):
N-butyl acrylate 60.53 parts allyl methacrylate 0.47 parts (0.78 mol% based on monomer mixture (2))
Emulsifier aqueous solution (1):
Di-2-ethylhexyl ammonium sulfosuccinate 0.7 parts Deionized water 28.6 parts

Next, the following monomer mixture (B) and aqueous emulsifier solution (2) were mixed and added dropwise over 120 minutes. After completion of the dropwise addition, the polymerization was terminated by holding for 60 minutes to obtain a latex of graft copolymer (6).
Monomer mixture (B):
Methyl methacrylate 31.44 parts n-butyl acrylate 0.66 parts Allyl methacrylate 1.90 parts (4.5 mol% with respect to monomer mixture (B))
Emulsifier aqueous solution (2):
Di-2-ethylhexyl ammonium sulfosuccinate 0.3 part Deionized water 20.8 parts

Subsequent operations were performed in the same manner as in Example 1, and the powder of the graft copolymer (6) was recovered.
The average particle size of the latex of the graft copolymer (6) was 590 nm. The average particle size of the powder of the graft copolymer (6) was 40 μm.

<Example 7>
Production of Graft Copolymer (7) Into a separable flask equipped with a thermometer, a nitrogen introduction tube, a cooling tube and a stirrer, the following monomer mixture (1) and deionized water were added, While stirring at 250 rpm, the internal temperature of the separable flask was raised to 80 ° C.
Monomer mixture (1):
N-Butyl acrylate 4.961 parts Allyl methacrylate 0.039 parts (0.78 mol% based on monomer mixture (1))
Deionized water 88.0 parts Next, the following initiator aqueous solution was added and held for 60 minutes to perform first-stage soap-free polymerization.
Initiator aqueous solution:
Ammonium persulfate 0.1 part Deionized water 5.2 parts

Next, the following monomer mixture (2) and aqueous emulsifier solution (1) were mixed and added dropwise over 200 minutes. After the completion of the dropping, the mixture was held for 60 minutes, and the second emulsion polymerization was performed to obtain a polymer (A3).
Monomer mixture (2):
N-Butyl acrylate 84.35 parts Allyl methacrylate 0.65 parts (0.78 mol% based on monomer mixture (2))
Emulsifier aqueous solution (1):
Ammonium di-2-ethylhexyl sulfosuccinate 0.8 parts Deionized water 41.7 parts

Next, the following monomer mixture (B) and aqueous emulsifier solution (2) were mixed and added dropwise over 100 minutes. After completion of the dropwise addition, the polymerization was terminated by holding for 60 minutes to obtain a latex of graft copolymer (7).
Monomer mixture (B):
Methyl methacrylate 9.24 parts n-butyl acrylate 0.2 parts Allyl methacrylate 0.56 parts (4.5 mol% with respect to monomer mixture (B))
Emulsifier aqueous solution (2):
Di-2-ethylhexyl ammonium sulfosuccinate 0.2 parts Deionized water 7.8 parts

Subsequent operations were performed in the same manner as in Example 1, and the powder of the graft copolymer (6) was recovered.
The average particle size of the latex of the graft copolymer (7) was 620 nm. The average particle size of the powder of the graft copolymer (7) was 43 μm.

<Comparative Example 1>
Production of graft copolymer (8) A graft copolymer (8) was produced in the same manner as in Example 6 except that the composition of the monomer mixture (B) was changed as follows.
Monomer mixture (B):
Methyl methacrylate 33.01 parts N-butyl acrylate 0.66 parts Allyl methacrylate 0.33 parts (0.78 mol% based on monomer mixture (B))

  The average particle size of the latex of the graft copolymer (8) was 600 nm. The average particle size of the powder of the graft copolymer (8) was 39 μm.

  Of the obtained graft copolymers (1) to (8), the content [%] of the polymer (A) in the graft copolymer, and the crosslinkable monomer in the monomer mixture (B). The content [mol%] is shown in Table 1.

<Examples 8 to 15, Comparative Examples 2 and 3>
A bisphenol A type epoxy resin (Epicoat 828, manufactured by Japan Epoxy Resin Co., Ltd.) and a graft copolymer were blended in the composition described in Table 2, and kneaded with three rolls to obtain a resin composition.
The following evaluation was performed about the obtained resin composition.

(Initial viscosity)
The viscosity of the resin composition was measured with a B-type viscometer. This viscosity is the initial viscosity of the resin composition.

(Viscosity after 100 hours)
The resin composition was placed in a container and allowed to stand in a constant temperature water bath at 40 ° C. or 80 ° C. for 100 hours, and then the viscosity was measured with a B-type viscometer. This viscosity is defined as the viscosity after 100 hours of the resin composition.

(Storage stability)
Using the numerical values of “initial viscosity” and “viscosity after 100 hours” measured in the above evaluation, the storage stability of the resin composition at 40 ° C. or 80 ° C. was evaluated.
“Viscosity after 100 hours” / “initial viscosity” was used as an index of storage stability and evaluated according to the following criteria. The results are shown in Table 2.
○: “viscosity after 100 hours” / “initial viscosity” ≦ 1.10.
Δ: 1.10 <“viscosity after 100 hours” / “initial viscosity” ≦ 1.15
×: 1.15 <“viscosity after 100 hours” / “initial viscosity”

<Examples 16 to 23, Comparative Examples 4 and 5>
Bisphenol A type epoxy resin (Epicoat 828, manufactured by Japan Epoxy Resin Co., Ltd.), curing agent (Adeka Hardener EH-3326 (tetrahydromethylphthalic anhydride), manufactured by Asahi Denka Co., Ltd.), and graft copolymer 3 and blended with three rolls to obtain a resin composition.
Next, a curing accelerator (N-benzyl-2-methylimidazole) is added and mixed with stirring. The obtained resin composition is filled in a mold and heated at 80 ° C. for 2 hours and further at 120 ° C. for 6 hours. And cured to obtain a sheet-like molded body.
The molded body was evaluated as follows.

(Izod impact strength)
After cutting the molded body, Izod impact strength was measured according to ASTM D256. The thickness of the test piece is 1/4 inch.
Table 3 shows the measurement results.

(Flexural modulus)
The molded body was cut into a length of 60 mm × width 10 mm × thickness 3 mm to obtain a test piece, and the flexural modulus was measured according to JIS K7171. The measurement was performed at 23 ° C.
Table 3 shows the measurement results.

As is apparent from Table 2, the resin compositions of Examples 8 to 15 blended with the graft copolymer of the present invention are excellent in storage stability at 40 ° C. and 80 ° C., and there is little increase in viscosity after 100 hours. It was.
On the other hand, the content of the crosslinkable monomer in the monomer mixture (B) is low, and the resin composition of Comparative Example 3 blended with the graft copolymer deviating from the scope of the present invention is 40 ° C. and The storage stability at 80 ° C. was poor, and the thickening after 100 hours was large.

As is apparent from Table 3, it was confirmed that the molded bodies of Examples 16 to 23 blended and cured with the graft copolymer of the present invention were excellent in impact resistance and had a low elastic modulus. .
In contrast, the molded article of Comparative Example 4 in which the graft copolymer of the present invention was not blended had low impact resistance and high elastic modulus.

  By using the graft copolymer of the present invention, it is possible to suppress the thickening of the resin composition over time and to lower the elastic modulus of the obtained molded product. A molded product obtained by molding a resin composition containing the graft copolymer of the present invention is excellent in impact resistance and has a low elastic modulus, and thus is useful as a semiconductor encapsulant.

Claims (5)

In the presence of the (meth) acrylate polymer (A) having a glass transition temperature of 0 ° C. or less determined by the Fox formula, a monomer mixture (B) containing a (meth) acrylate monomer is used. In the graft copolymer obtained by polymerization,
The polymer obtained by polymerizing the monomer mixture (B) has a glass transition temperature determined by the Fox formula exceeding 0 ° C,
A graft copolymer, wherein the monomer mixture (B) contains 1.0 mol% or more of a crosslinkable monomer (provided that (B) is 100 mol%).   A resin composition comprising the graft copolymer according to claim 1 and a resin.   The resin composition for semiconductor sealing materials containing the graft copolymer of Claim 1, and resin.   A resin composition for an adhesive comprising the graft copolymer according to claim 1 and a resin.   The molded object obtained by shape | molding the resin composition of Claim 2 or 3.