JP2014031463A - Method for producing silica particle-containing acrylic resin and silica particle-containing acrylic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silica particle-containing acrylic resin which has transparency, surface hardness, heat resistance and rigidity and is excellent in practicality.SOLUTION: Provided is a method for producing a silica particle-containing acrylic resin, which polymerizes (C) a (meth)acrylic acid ester in an aqueous medium containing (A) an acrylic resin, (B) silica particles, (C) the (meth)acrylic acid ester, (D) a chain transfer agent, and (E) a radical polymerization initiator. The ratio (a) of the acrylic resin (A) and the ratio (b) of the silica particles (B) based on 100 wt.% of the total of the acrylic resin (A), the silica particles (B), the (meth)acrylic acid ester (C), the chain transfer agent (D) and the radical polymerization initiator (E) satisfy a predetermined relationship, and viscosity (η) of the aqueous medium containing the acrylic resin (A), the silica particles (B), the (meth)acrylic acid ester (C), the chain transfer agent (D), and the radical polymerization initiator (E) satisfies a predetermined relationship.

Description

The present invention relates to a method for producing a silica particle-containing acrylic resin, a silica particle-containing acrylic resin obtained by the production method, and a molded article obtained by molding the silica particle-containing acrylic resin.

An acrylic resin such as methacrylic resin is useful as a plastic material having excellent transparency. However, the acrylic resin is not necessarily good in rigidity, hardness, and heat resistance, and improvement is desired. Therefore, a silica particle-containing acrylic resin containing silica particles has been reported as a plastic material that is excellent in rigidity, hardness, and heat resistance in addition to transparency.

In Patent Document 1, silica particles are surface-modified using a resin monomer having a hydrogen-bonding functional group and an unsaturated double bond group, and then the surface-modified silica particles are treated with methyl methacrylate, a polymerization initiator. In addition, it is disclosed that a nanocomposite resin composition is obtained by polymerizing a resin monomer of surface-modified silica particles and methyl methacrylate in a mixed solution containing a solvent and a solvent. However, the obtained nanocomposite resin composition is not satisfactory in material properties.

Patent Document 2 discloses that a polymer nanocomposite is obtained by mixing a silica particle dispersion in which surface-modified silica particles are dispersed and an acrylic resin monomer, and then polymerizing the monomer. However, the resulting polymer nanocomposites can aggregate and become difficult to handle.

Patent Document 3 discloses that a silica particle-containing methacrylic resin is obtained by emulsion polymerization in water in the presence of methyl methacrylate, a surfactant, a polymerization initiator, a chain transfer agent, and silica particles. . However, the resulting silica particle-containing methacrylic resin has room for improving transparency.

Patent Document 4 discloses a composite of silica particles surface-modified with a titanate surface treatment agent and an acrylic resin. However, titanate-based surface treatment agents are very expensive and problematic from the viewpoint of cost.

JP 2004-51681 A JP 2006-299126 A JP 2007-119701 A JP 2008-174613 A

An object of the present invention is to provide a method for producing a silica particle-containing acrylic resin having transparency, surface hardness, heat resistance and rigidity and excellent in practicality. An object of the present invention is to provide a silica particle-containing acrylic resin having transparency, surface hardness, heat resistance and rigidity and excellent in practicality. Furthermore, the objective of this invention is providing the molded object formed by shape | molding a silica particle containing acrylic resin.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention relates to the following inventions.
<1> In an aqueous medium containing (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator, (C ) A method for producing a silica particle-containing acrylic resin for polymerizing (meth) acrylic acid ester,
(A) acrylic resin per 100% by weight in total of (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator The ratio (a) of the resin and the ratio (b) of the (B) silica particles satisfy the following (1), and (A) acrylic resin, (B) silica particles, (C) (meth) The viscosity (η) at 30 ° C. measured in accordance with JIS Z8803 of an aqueous medium containing an acrylic ester, (D) chain transfer agent, and (E) radical polymerization initiator satisfies the following (2). A method for producing a silica particle-containing acrylic resin, characterized in that:
(1) {(b-5) / 70} <a <{(580−b × 9) / 40}
(2) η ≧ (0.046 × b + 0.08)
<2> (B) The production method according to <1>, wherein the silica particles are surface-modified with an organosilicon compound having no radically polymerizable unsaturated double bond.
<3> (B) per 100% by weight in total of (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator The production method according to <1> or <2>, wherein the ratio of silica particles is 5 to 60% by weight.
<4> (B) The production method according to any one of <1> to <3>, wherein the primary particle diameter of the silica particles is 1 to 50 nm.
<5> (A) The acrylic resin is obtained by polymerizing one or more (meth) acrylic acid esters having one radical double polymerizable unsaturated double bond <1> to <4> The manufacturing method in any one of.
<6> (A) Acrylic resin is a homopolymer of methyl (meth) acrylate, or radical polymerization other than 50-99.9% by weight of methyl methacrylate and 0.1-50% by weight of methyl methacrylate. The production method according to any one of <1> to <5>, which is a copolymer with one or more (meth) acrylic acid esters having one possible unsaturated double bond.
<7> The production method according to <6>, wherein the (meth) acrylic acid ester having one radical polymerizable unsaturated double bond other than methyl methacrylate is methyl acrylate.
<8> The production method according to any one of <1> to <7>, wherein the aqueous medium is water.
<9> The production method according to any one of <1> to <8>, wherein the aqueous medium contains a suspension stabilizer.
<10> The production method according to <9>, wherein the suspension stabilizer is a water-soluble polymer or a salt thereof.
<11> The production method according to <10>, wherein the water-soluble polymer is a metal salt of poly (meth) acrylic acid.
<12> Silica particle-containing acrylic resin obtained by the production method according to any one of <1> to <11>.
<13> A molded product obtained by molding the silica particle-containing acrylic resin according to <12>.

According to the present invention, it is possible to produce a silica particle-containing acrylic resin having transparency, surface hardness, heat resistance and rigidity and excellent in practicality.

The production method of the present invention may be described as (A) an acrylic resin (hereinafter sometimes referred to as “component (A)”), (B) silica particles (hereinafter referred to as “component (B)”). ), (C) (meth) acrylic acid ester (hereinafter sometimes referred to as “component (C)”), (D) chain transfer agent (hereinafter sometimes referred to as “component (D)”) (E) Silica particle-containing acrylic resin that polymerizes (C) (meth) acrylic acid ester in an aqueous medium containing a radical polymerization initiator (hereinafter sometimes referred to as “component (E)”) It is a manufacturing method.

<(A) Acrylic resin>
The (A) acrylic resin used in the present invention is not particularly limited. For example, a homopolymer of (meth) acrylic monomers such as (meth) acrylic acid ester and (meth) acrylonitrile, or two or more kinds of copolymers Examples thereof include copolymers and copolymers of acrylic monomers and other monomers. In the present specification, the term “(meth) acryl” means “acryl” or “methacryl”.

As the acrylic resin, it is preferable to use a methacrylic resin from the viewpoint of having excellent hardness, weather resistance, transparency and the like. A methacrylic resin is a polymer obtained by polymerizing a monomer mainly composed of a methacrylic acid ester (alkyl methacrylate). For example, a methacrylic acid ester homopolymer (polyalkyl methacrylate) or a methacrylic acid ester Examples thereof include a polymer, a copolymer of 50% by weight or more of a methacrylic ester and a monomer other than 50% by weight of a methacrylic ester. In the case of a copolymer of a methacrylic acid ester and a monomer other than the methacrylic acid ester, the methacrylic acid ester is preferably 70% by weight or more and the other monomer is 30% by weight or less based on the total amount of monomers. More preferably, the methacrylic acid ester is 90% by weight or more and the other monomer is 10% by weight or less.

  The methacrylic acid ester is represented by the following formula (I).

R ^{1 in} formula (I) is a chain alkyl, a cyclic alkyl or an aromatic ring.

Specific examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, heptyl methacrylate, methacrylic acid 2 -Ethylhexyl, n-octyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, decyl methacrylate, undecyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, lauryl methacrylate, benzyl methacrylate, phenyl methacrylate, methacryl Examples include cyclohexyl acid, methoxyethyl methacrylate, ethoxyethyl methacrylate, 2-naphthyl methacrylate, phenoxymethyl methacrylate, and the like. Among these, alkyl methacrylate having 1 to 8 carbon atoms in the alkyl group portion is preferable, and methyl methacrylate is more preferable.

As monomers other than methacrylic acid ester, acrylic acid ester (alkyl acrylate) monomer, aromatic vinyl monomer, unsaturated nitrile monomer, ethylenically unsaturated ether monomer, vinyl halide series Monomers, aliphatic conjugated diene monomers, and the like can be mentioned, and among them, acrylic acid esters are preferably used.
In addition, monomers other than methacrylic acid ester may be used independently and may use 2 or more types together.

  The acrylate monomer is represented by the following formula (II).

R ^{2 in} formula (II) is a chain alkyl, a cyclic alkyl or an aromatic ring.

Specific examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, heptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and acrylic. Acid n-nonyl, isononyl acrylate, decyl acrylate, undecyl acrylate, n-amyl acrylate, isoamyl acrylate, lauryl acrylate, benzyl methacrylate, phenyl acrylate, cyclohexyl methacrylate, methoxyethyl acrylate, acrylic acid Examples include ethoxyethyl, 2-naphthyl acrylate, phenoxymethyl acrylate, and the like. Among these, alkyl acrylates having 1 to 8 carbon atoms in the alkyl group portion are preferable, and methyl acrylate is more preferable.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p- Examples include methoxystyrene, p-acetoxystyrene, α-vinylnaphthalene, and 2-vinylfluorene. Among these, styrene is more preferable.

Examples of the unsaturated nitrile monomer include acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, vinylidene cyanide, and the like.

Examples of the ethylenically unsaturated ether monomer include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, ethyl allyl ether, and the like.

Examples of the vinyl halide monomer include vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene, and the like.

Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-neopentyl-1,3-butadiene. 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1, Examples include 3-butadiene, substituted linear conjugated pentadienes, linear and side chain conjugated hexadienes, and the like.

Among acrylic resins, homopolymers of methyl methacrylate (polymethyl methacrylate), or (meth) acrylic other than 50 to 99.9% by weight of methyl methacrylate and 0.1 to 50% by weight of methyl methacrylate A copolymer with an acid ester is particularly preferred. A copolymer of 50 to 99.9% by weight of methyl methacrylate and 0.1 to 50% by weight of (meth) acrylic acid ester other than methyl methacrylate is methyl methacrylate and the (meth) acrylic acid. Methyl methacrylate is contained in a proportion of 50 to 99.9% by weight, and (meth) acrylic acid ester other than methyl methacrylate is contained in a proportion of 0.1 to 50% by weight with respect to the total amount with the ester. It is a copolymer obtained by polymerizing the monomer mixture. The proportion of methyl methacrylate in this monomer mixture is preferably 70 to 99.9% by weight, more preferably 90 to 99.9% by weight.

The acrylic resin can be obtained by subjecting the above monomer to a polymerization method such as an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, or a liquid injection polymerization method (cast polymerization method). Polymerization is performed using light irradiation or a polymerization initiator, and an azo initiator (for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), etc.) ), Peroxide initiators (lauroyl peroxide, benzoyl peroxide, etc.), and polymerization initiators such as redox initiators in which organic peroxides and amines are combined are preferably used. The polymerization initiator is usually used in a proportion of 0.01 to 1 part by mass, preferably 0.01 to 0.5 part by mass with respect to 100 parts by mass of the monomer constituting the acrylic resin. Further, a chain transfer agent for controlling the molecular weight (a linear or branched alkyl mercaptan compound such as methyl mercaptan, n-butyl mercaptan, t-butyl mercaptan, etc.), a crosslinking agent or the like may be added.

The acrylic resin preferably has a viscosity average molecular weight of 50,000 to 300,000, more preferably 70,000 to 2,000,000.

<(B) Silica particles>
The (B) silica particles used in the present invention preferably have a primary particle diameter of 1 to 50 nm, more preferably 5 from the transparency of a molded product obtained by molding a silica particle-containing acrylic resin. It is -40nm, More preferably, it is 10-30nm.

  From the viewpoint of the dispersibility of the silica particles in the silica particle-containing acrylic resin and the moldability of the silica particle-containing acrylic resin, the silica particles are preferably those that have been surface-modified with an organosilicon compound, The organosilicon compound is preferably an organosilicon compound having no radically polymerizable unsaturated double bond. In the present specification, surface modification means hydrophobizing the surface of silica particles. The surface of the surface-modified silica particles becomes more hydrophobic than the surface before the surface modification.

Examples of the method of modifying the surface of the silica particles include a method of modifying the surface of the silica particles with a surface treatment agent such as a silylating agent or a silane coupling agent. When using a surface treating agent, a reaction catalyst can be used as needed.

Examples of the surface treatment agent include trimethylsilyl chloride, triethylsilyl chloride, hexamethyldisilazane, tert-butyldimethylsilyl chloride, tri-i-propylsilyl chloride, 1,3-dichloro-1,1,3,3-tetra -Tri-i-propyldisiloxane, chloromethyltrimethylsilane, triethylsilane, tert-butyldimethylsilane, hexamethylmethyltrimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, phenyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, hexamethyldi And the like can be given Rokisan. Among these, trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, and hexamethyldisiloxane are more preferable.

The amount of the organosilicon compound having no radically polymerizable unsaturated double bond introduced to the surface of the silica particles is about 100% by weight in total of the silica particles and the organosilicon compound introduced to the surface of the silica particles. It is preferably 1 to 10% by weight, more preferably 1 to 7% by weight, and further preferably 1 to 5% by weight. If the introduction amount of the organosilicon compound is too small, the effect of improving the dispersibility of the silica particles in the silica particle-containing acrylic resin may be small. If the introduction amount is too large, the silica particle-containing acrylic resin may be molded. The surface hardness and heat resistance of the resulting molded product may be reduced. The amount of the organosilicon compound introduced into the surface of the silica particles can be measured, for example, by the method described in the examples.

The silica particles are preferably contained in a proportion of 5 to 60% by weight, more preferably 7 to 50% by weight per 100% by weight of the silica particle-containing acrylic resin. More preferably, it is contained in a proportion of 40% by weight. It is preferable that the content ratio of the silica particles is within the predetermined range because physical properties such as heat resistance and rigidity are improved and melt molding is possible while maintaining the transparency of the acrylic resin. There may be only one kind of silica particles, or two or more kinds of the primary particle diameter and the introduction amount of the organosilicon compound not having an unsaturated double bond capable of radical polymerization may be different.

<(C) (Meth) acrylic acid ester>
Examples of (C) (meth) acrylic acid esters include those similar to the methacrylic acid esters and acrylic acid esters exemplified as the monomer of the above (A) acrylic resin. (C) (meth) acrylic acid ester may be only 1 type, and 2 or more types may be sufficient as it.

<(D) Chain transfer agent>
As the chain transfer agent, any one used in general radical polymerization is used, and examples thereof include mercaptan compounds such as butyl mercaptan, n-octyl mercaptan, dodecyl mercaptan, and 2-ethylhexyl thioglycolate. Only one type of chain transfer agent may be used, or two or more types may be used.

<(E) Radical polymerization initiator>
Examples of the radical polymerization initiator include 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2,4,4-trimethylpentene), 2,2′-azobis (2- Methylpropane), 2-cyano-2-propyrazoformamide, 2,2′-azobis (2-hydroxy-methylpropionate), 2,2′-azobis (2-methyl-butyronitrile), 2,2′- Azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), 2,2′-azobis (2,4-dimethyl-4methoxyvaleronitrile), 2,2′-azobis [ 2- (2-imidazolin-2-yl) propane], azo compounds such as dimethyl 2,2′-azobis (2-methylpropionate); dicumyl peroxide, t-butylcumyl Diacyl peroxide-based or dialkyl peroxide-based initiators such as peroxide, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide; t-butylperoxy-3,3,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisobutyrate, t-butyl peroxyacetate, di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxyazelate, t-butylperoxy Such as 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, t-butylperoxypivalate Peroxyester initiator; t-butyl pero Parkinate initiators such as sialyl carbonate, t-butyl peroxyisopropyl carbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate; 1,1-di-t-butylperoxycyclohexane, 1,1- Peroxyketal initiators such as di-t-butyl peroxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butyl peroxy-3,3,5-trimethylcyclohexane; It is done. Only one kind of radical initiator may be used, or two or more kinds thereof may be used.

<Suspension stabilizer>
The aqueous medium may contain a suspension stabilizer. Examples of the suspension stabilizer include organic suspension stabilizers such as polyalkyl acrylate-acrylic acid, polysodium methacrylate, polyacrylic acid polyolefin-maleic acid, polyvinyl pyrrolidone, polyvinyl alcohol and cellulose, and tricalcium phosphate. Inorganic suspension stabilizers. Among these, polysodium methacrylate and polyvinyl alcohol are preferable. Only one suspension stabilizer may be used, or two or more suspension stabilizers may be used.

<Aqueous medium>
Examples of the aqueous medium include water, a mixed medium of water and a water-soluble solvent, and the like. Of these, water is preferred. The content ratio of the water-soluble medium in the mixed medium is preferably 40 to 90% by weight, more preferably 50 to 80% by weight.

  Examples of the water-soluble solvent include methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol (sec-butyl alcohol), 2-methyl-1-propanol (isobutyl alcohol), Alcohols such as 2-methyl-2-propanol (tert-butyl alcohol), 2-ethoxyethanol, 2-butoxyethanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 1-ethoxy-2 -Alkoxy alcohols such as propanol, ketols such as diacetone alcohol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, aromatic hydrocarbons such as toluene, xylene, ethyl acetate, butyl acetate, etc. Na Ester, etc. can be mentioned, which may be used alone or in combination.

The aqueous medium is substantially neutral when it contains (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator. Preferably, the pH is 6 to 8, more preferably 6 to 7, and even more preferably 7. The aqueous medium may contain a pH adjusting agent in order to adjust the pH.

<Manufacturing method>
Silica particle-containing acrylic resin is an aqueous medium containing (A) acrylic resin, (B) silica particles, (C) (meth) acrylic ester, (D) chain transfer agent, and (E) radical polymerization initiator. It is produced by polymerizing (C) (meth) acrylic acid ester.

  In an aqueous medium containing (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator, (C) (meta To polymerize the acrylate ester, for example, first, (C) (meth) acrylate ester, (A) acrylic resin, (B) silica particles, (D) chain transfer agent, (E) radical polymerization A solution in which the initiator is dissolved or dispersed and an aqueous medium in which the suspension stabilizer is dissolved are prepared. Next, while stirring the solution, an aqueous medium is added to the solution, or while stirring the aqueous medium, the solution is added to the aqueous medium, and (A) an acrylic resin, (B) silica particles An aqueous medium containing (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator is prepared. And the prepared aqueous medium should just be heated to the temperature more than the thermal decomposition temperature of a radical polymerization initiator, stirring.

  (C) The silica particles (B) dispersed in the (meth) acrylic acid ester may be powdery or colloidal silica in which the silica particles are dispersed in a medium. Examples of the medium in which the silica particles are dispersed include water and organic solvents. Examples of the organic solvent include the above-described water-soluble solvents such as ethyl acetate, and (meth) acrylic acid esters such as methyl methacrylate.

In the production method of the present invention, the aqueous medium contains (A) acrylic resin, (B) silica particles, (C) (meth) acrylic ester, (D) chain transfer agent, and (E) radical polymerization initiator. When this is done, the ratio (a) of the acrylic resin (a) and the ratio (b) of the silica particles (b) per 100% by weight in total satisfy the following (1). When (a) is smaller than the left side {(b-5) / 70} or larger than the right side, the resulting silica particle-containing acrylic resin is agglomerated and difficult to handle, and its practicality is low.
(1) {(b-5) / 70} <a <{(580−b × 9) / 40}

The aqueous medium when the aqueous medium contains (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator The viscosity (η) of the above satisfies the following (2). When the viscosity (η) of the aqueous medium is low, the dispersion stability of the silica particles in the aqueous medium is low, and the resulting silica particle-containing acrylic resin is agglomerated and difficult to handle, resulting in low practicality.
(2) η ≧ (0.046 × b + 0.08)
Η in the formula (2) is a viscosity at 30 ° C. measured in accordance with JIS Z8803.

In the polymerization, it is preferable to remove oxygen in advance. For example, oxygen in water is preferably removed beforehand by bubbling an inert gas such as nitrogen. Furthermore, it is preferable to polymerize in an inert gas atmosphere.

The heating temperature is usually in the range of 50 ° C. to 90 ° C., and the time required for the polymerization is usually in the range of 1 to 10 hours.

After polymerization, the temperature may be raised to about 90 ° C. to 120 ° C. for the purpose of completing the polymerization of unpolymerized (C) (meth) acrylic acid ester.

Thus, (C) (meth) acrylic acid ester is polymerized to become an acrylic resin, and (B) the desired silica particle-containing acrylic resin containing silica particles can be obtained.

From the polymerized mixture after polymerization, the desired silica particle-containing acrylic resin can be obtained as a solid content by an ordinary solid-liquid separation method such as a centrifugal separation method or a drying method.

  Thus, a silica particle-containing acrylic resin having transparency, surface hardness, heat resistance and rigidity and excellent in practicality can be obtained.

<Silica particle-containing acrylic resin>
The silica particle-containing acrylic resin contains an acrylic resin and silica particles. The acrylic resin is preferably contained in a proportion of 40 to 95% by weight, more preferably 50 to 93% by weight, and still more preferably 60 to 90% by weight, based on the total amount of the acrylic resin and the silica particles. Is preferably 5 to 60% by weight, more preferably 7 to 50% by weight, and still more preferably 10 to 40% by weight.

Various additives generally used may be added to the silica particle-containing acrylic resin as long as the effects of the present invention are not impaired. Examples of the additive include a stabilizer, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, a foaming agent, a lubricant, a release agent, an antistatic agent, a flame retardant, a release agent, a polymerization inhibitor, and a difficulty. Examples include a fuel aid and a reinforcing agent.

These additives only need to be present in the resin composition of the present invention and may be contained in any of the components. When polymerizing the (C) (meth) acrylic acid ester in an aqueous medium, It may be added to the aqueous medium, or may be added during melt kneading described later, or may be added after melt kneading.

The silica particle-containing acrylic resin is preferably transparent when visually observed. Further, when the resin is molded into a plate-like molded body having a thickness of 3 mm, all measured in accordance with JIS K7361-1. The light transmittance is preferably 87% or more, more preferably 89% or more.

When the silica particle-containing acrylic resin is molded into a plate-like molded product having a thickness of 3 mm, the haze measured in accordance with JIS K7136 is preferably 2.5% or less, more preferably 2.0%. It is as follows.

When the silica particle-containing acrylic resin is molded into a plate-shaped molded product having a thickness of 3 mm, the melt flow rate measured in accordance with JIS K7210 is preferably 0.1 to 20 g / 10 min, more preferably Is 0.2 to 10 g / 10 min.

The silica particle-containing acrylic resin obtained by polymerizing (C) (meth) acrylic acid ester in an aqueous medium may be further melt-kneaded. When (C) (meth) acrylic acid ester is polymerized in an aqueous medium, a bead-shaped silica particle-containing acrylic resin may be obtained. When a molded product is obtained by molding a silica particle-containing acrylic resin, it is easier to handle in the molding process when the resin is in the form of pellets than in the form of beads. Therefore, it is preferable that the bead-like silica particle-containing acrylic resin is melt-kneaded and the extruded melt is cooled and then cut with a strand cutter to form a pellet.

The temperature at which the melt kneading is performed is preferably 150 to 350 ° C, more preferably 170 to 320 ° C, and further preferably 180 to 300 ° C. When the temperature is lower than 150 ° C., the resin may not melt. On the other hand, when the temperature at the time of melt kneading exceeds 350 ° C., the resin may be thermally decomposed. In order to obtain a resin composition in which each component is more uniformly mixed, the melt kneading is preferably performed at a temperature of 170 to 320 ° C., more preferably 180 to 300 ° C., preferably 50 to 3000 sec ⁻¹ , and more. Preferably, it is performed at a shear rate of 60 to 1000 sec ⁻¹ .

Shear rate when performing melt-kneading is preferably 10～5000Sec ^-1, more preferably 50～3000Sec ^-1, further preferably 60~1000sec ^-1. When the shear rate is less than 10 sec ⁻¹ , the kneading may not be sufficiently performed. On the other hand, when the shear rate during melt kneading exceeds 5000 sec ⁻¹ , the resin may be decomposed.

As an apparatus used for melt kneading, a normal mixer or kneader can be used. Specific examples include a single-screw kneader, a twin-screw kneader, another-screw extruder, a Henschel mixer, a Banbury mixer, a kneader, and a roll mill. Further, when the shear rate is increased within the above range, a high shear processing device or the like may be used. As a high shear processing apparatus, for example, “NHSS2-28” manufactured by Niigata Machine Techno Co., Ltd. is commercially available. Melt-kneading may be performed in an inert gas atmosphere such as nitrogen gas, argon gas, helium gas, if necessary.

  The silica particle-containing acrylic resin of the present invention is used in various applications that require transparency, surface hardness, heat resistance, and rigidity, such as lens materials in the field of electronic and electrical equipment, optical equipment, and carport roofs in the field of building materials. It can be effectively used for various applications such as materials and surface layers. In particular, the silica particle-containing acrylic resin is suitable as a surface layer material of various articles as glass substitutes, for example, an automotive glazing material, a laminated film, and the like.

<Molded body>
The silica particle-containing acrylic resin is processed into a desired shape and processed into a molded body excellent in both transparency and heat resistance. Such a molded body is useful, for example, as an automobile part, an electric / electronic part, an OA equipment part, or the like. For molding, the resin composition melt-kneaded by the above-described production method may be molded using the melt-kneader as it is. Further, after the obtained resin composition is made into a pellet or the like, it may be melt-molded in a molding machine using a molding machine such as an injection molding machine or a hydraulic press.

The molding temperature is usually about 150 to 350 ° C, preferably about 170 to 320 ° C, more preferably about 180 to 300 ° C.

  The molded body obtained by molding the silica particle-containing acrylic resin of the present invention can be subjected to surface polishing treatment, antistatic treatment, hard coat treatment, and other post-treatments, and those treatments as necessary. By performing the above, it can be used effectively for the above-mentioned applications and other applications. In the case of the production method of the present invention, the colloidal silica-containing acrylic resin composition of the present invention having the above-described excellent characteristics can be produced efficiently and smoothly by a simple operation.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples.

  (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, (E) radical polymerization initiator used in the following examples and comparative examples, It is as follows.

(A) Acrylic resin: Sumipex (registered trademark) MH (manufactured by Sumitomo Chemical Co., Ltd., methacrylic resin mainly composed of methyl methacrylate) was used.
(B) Silica particles: EAc-ST (manufactured by Nissan Chemical Industries, Ltd., silica particles having a primary particle diameter of 20 nm are dispersed in ethyl acetate, and the concentration of the silica particles is 30% by weight. Silica sol) was used.
The amount of the organosilicon compound introduced into the surface of the silica particles was evaluated by the following method. Ethyl acetate was removed from EAc-ST to obtain silica particles, and the obtained silica particles were used at 25 ° C. under a nitrogen atmosphere (flow rate 200 ml / min) using TG / DTA6300 (manufactured by Seiko Instruments Inc.). Weight loss was measured when the temperature was raised to 500 ° C. at 10 ° C./min. The amount of weight reduction was 1.7% by weight with respect to 100% by weight of silica particles before the temperature was raised. From this weight reduction amount, it was evaluated that the introduction amount of the organosilicon compound to the surface of the silica particles was 1.7% by weight.
(C) (Meth) acrylic acid ester: methyl methacrylate and methyl acrylate were used.
(D) Chain transfer agent: n-octyl mercaptan was used.
(E) Radical polymerization initiator: Lauryl peroxide was used.

  The viscosity and pH of the aqueous medium containing the components (A) to (E) prepared in the following Examples and Comparative Examples, and the practicality of the silica particle-containing acrylic resin were evaluated by the following methods.

(viscosity)
About the aqueous medium containing a component (A)-a component (E), the viscosity ((eta)) in 30 degreeC was measured based on JISZ8803 using the E-type viscosity meter. It shows that the viscosity of an aqueous medium is so high that this value is high. The results are shown in Table 1.

(PH)
About the aqueous medium containing a component (A)-a component (E), pH was measured visually using the pH test paper. The results are shown in Table 1.

(Practicality)
The silica particle-containing acrylic resin obtained by suspension polymerization was evaluated for practicality according to the following criteria. The results are shown in Table 1.
○: When the silica particle-containing acrylic resin is in the form of beads.
×: Silica particle-containing acrylic resin is not in the form of beads but is agglomerated.

Example 1
First, from methyl methacrylate to Sumipex (registered trademark) MH, EAc-ST so that the ratio (a) of Sumipex (registered trademark) MH is 1% by weight and the ratio (b) of silica particles is 40% by weight. Silica particles obtained by distilling off ethyl acetate, methyl acrylate, n-octyl mercaptan and lauryl peroxide were added to prepare a solution. At this time, n-octyl mercaptan and lauryl peroxide were 0.20% by weight and 0.15% by weight with respect to the total amount of methyl methacrylate and methyl acrylate, respectively, so that methyl acrylate was 2% by weight. So that it was added to methyl methacrylate. Next, 100.0 parts by weight of the prepared solution was added to 285.5 parts by weight of an aqueous medium prepared by adding 0.5 parts by weight of sodium polyacrylate as a suspension stabilizer to 285 parts by weight of ion-exchanged water. The medium was added with stirring. Thereafter, the aqueous medium to which the solution was added was heated at 80 ° C. for 3 hours with stirring to perform suspension polymerization. After suspension polymerization, the slurry-like reaction liquid was dehydrated and washed with a dehydrator, and then dried to obtain a bead-like silica particle-containing acrylic resin. The obtained bead-like silica particle-containing acrylic resin is melt-kneaded under the conditions of a temperature of 260 ° C. and a rotation speed of 200 rpm using a twin-screw kneader (TEX-30, manufactured by Nippon Steel Works, Ltd.). After the melt extruded into a shape was cooled, it was cut with a strand cutter to obtain a pellet-shaped silica particle-containing acrylic resin.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Example 2)
A bead-like silica particle-containing acrylic resin was obtained in the same manner as in Example 1 except that the proportion (b) of silica particles was changed to 20% by weight and sodium polyacrylate was changed to 0.17 parts by weight. . About the obtained bead-shaped silica particle-containing acrylic resin, pellet-shaped silica particle-containing acrylic resin was obtained using the same method as in Example 1.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Example 3)
A bead-like silica particle-containing acrylic resin was obtained in the same manner as in Example 1 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 3% by weight. About the obtained bead-shaped silica particle-containing acrylic resin, pellet-shaped silica particle-containing acrylic resin was obtained using the same method as in Example 1.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

Example 4
A bead-like silica particle-containing acrylic resin was obtained in the same manner as in Example 2 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 1% by weight. About the obtained bead-shaped silica particle-containing acrylic resin, pellet-shaped silica particle-containing acrylic resin was obtained using the same method as in Example 1.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Example 5)
A bead-like silica particle-containing acrylic resin was obtained in the same manner as in Example 2 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 5% by weight. About the obtained bead-shaped silica particle-containing acrylic resin, pellet-shaped silica particle-containing acrylic resin was obtained using the same method as in Example 1.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Comparative Example 1)
Example 1 was subjected to suspension polymerization using the same method except that the amount of sodium polyacrylate was changed to 0.17 parts by weight. The obtained silica particle-containing acrylic resin was not bead-shaped but agglomerated.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Comparative Example 2)
Suspension polymerization was performed in the same manner as in Example 1 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 0.5% by weight. The obtained silica particle-containing acrylic resin was not bead-shaped but agglomerated.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Comparative Example 3)
Suspension polymerization was performed in the same manner as in Example 2 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 0% by weight. The obtained silica particle-containing acrylic resin was not bead-shaped but agglomerated.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Comparative Example 4)
Suspension polymerization was performed in the same manner as in Example 1 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 10% by weight. The obtained silica particle-containing acrylic resin was not bead-shaped but agglomerated.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Comparative Example 5)
Suspension polymerization was performed in the same manner as in Example 1 except that the ratio (a) of Sumipex (registered trademark) MH was changed to 5.5% by weight. The obtained silica particle-containing acrylic resin was not bead-shaped but agglomerated.
Table 1 shows the ratio (a) of Sumipex (registered trademark) MH and the ratio (b) of silica particles. Table 1 shows the result of calculating the left-hand side term and the right-hand side term of (1) described above and the result of calculating the right-hand side term of (2) described above based on the value of (b).

(Evaluation)
The pellet-shaped silica particle-containing acrylic resin obtained in Examples 1 and 2 was set to 60 ° C. at a cylinder temperature of 260 ° C. using an injection molding machine (“IS130FII” manufactured by Toshiba Machine Co., Ltd.). The mold was injection molded to obtain a plate-like molded body of 50 mm × 50 mm × 3.4 mm. The following evaluation was performed about the obtained plate-shaped molded object.

(Total light transmittance)
About each obtained plate-shaped molded object, total light transmittance was measured based on JISK7361-1 using HR-100 (made by Murakami Color Research Laboratory Co., Ltd.). The larger this value, the greater the light transmission, that is, the higher the transparency. The results are shown in Table 2.

(Haze)
About each obtained plate-shaped molded object, haze was measured based on JISK7136 using said HR-100. It shows that transparency is so high that this figure is small. The results are shown in Table 2.

(surface hardness)
About each obtained plate-shaped molded object, pencil hardness was measured based on JISK5600. The larger the value, the better the surface hardness and the less the surface is scratched. The results are shown in Table 2.

(Heat-resistant)
About each obtained plate-shaped molded object, it cut | disconnected to the magnitude | size of 20 mm x 20 mm x 3.4 mm, and produced the test piece. The Vicat softening temperature of the obtained test piece was measured under the conditions of a load of 50 N and a heating rate of 50 ° C./hour in accordance with JIS K7206 B50 method. The higher the temperature, the higher the heat resistance. The results are shown in Table 2.

(rigidity)
About each obtained plate-shaped molded object, the test piece was produced with the magnitude | size of 60 mm x 20 mm. The flexural modulus of the obtained test piece was measured according to JIS K7171. The higher this value, the higher the rigidity. The results are shown in Table 2.

Claims (13)

In an aqueous medium containing (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator, (C) (meta ) A method for producing an acrylic resin containing silica particles for polymerizing an acrylic ester,
(A) acrylic resin per 100% by weight in total of (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, and (E) radical polymerization initiator The ratio (a) of the resin and the ratio (b) of the (B) silica particles satisfy the following (1), and (A) acrylic resin, (B) silica particles, (C) (meth) The viscosity (η) at 30 ° C. measured in accordance with JIS Z8803 of an aqueous medium containing an acrylic ester, (D) chain transfer agent, and (E) radical polymerization initiator satisfies the following (2). A method for producing a silica particle-containing acrylic resin, characterized in that:
(1) {(b-5) / 70} <a <{(580−b × 9) / 40}
(2) η ≧ (0.046 × b + 0.08)   (B) The production method according to claim 1, wherein the silica particles are surface-modified with an organosilicon compound having no radically polymerizable unsaturated double bond.   (A) acrylic resin, (B) silica particles, (C) (meth) acrylic acid ester, (D) chain transfer agent, (E) radical polymerization initiator of (B) silica particles per 100% by weight in total The production method according to claim 1 or 2, wherein the ratio is 5 to 60% by weight.   (B) The production method according to claim 1, wherein the primary particle diameter of the silica particles is 1 to 50 nm.   The acrylic resin (A) is obtained by polymerizing one kind or two or more kinds of (meth) acrylic acid ester having one unsaturated double bond capable of radical polymerization. The manufacturing method as described in.   (A) Acrylic resin is a homopolymer of methyl (meth) acrylate, or a radically polymerizable non-polymerizable polymer other than 50-99.9 mass% methyl methacrylate and 0.1-50 mass% methyl methacrylate. The production method according to any one of claims 1 to 5, which is a copolymer with one or more (meth) acrylic acid esters having one saturated double bond.   The production method according to claim 6, wherein the (meth) acrylic acid ester having one unsaturated double bond capable of radical polymerization other than methyl methacrylate is methyl acrylate.   The production method according to claim 1, wherein the aqueous medium is water.   The production method according to claim 1, wherein the aqueous medium contains a suspension stabilizer.   The production method according to claim 9, wherein the suspension stabilizer is a water-soluble polymer or a salt thereof.   The production method according to claim 10, wherein the water-soluble polymer is a metal salt of poly (meth) acrylic acid.   The silica particle containing acrylic resin obtained by the manufacturing method in any one of Claims 1-11.   A molded product obtained by molding the silica particle-containing acrylic resin according to claim 12.