JPH0725953A - Core-shell polymer and plastisol prepared therefrom - Google Patents

Abstract

PURPOSE:To provide a core-shell polymer having a combination of such fluidity as to be suitable for work at the atmospheric temperature, high storage stability and good compatibility with plasticizers so as not to leach plasticizers on the surface of a gelled product developed when cooled to the atmospheric temperature after heat treated, thus suitable for obtaining plastisols. CONSTITUTION:The objective core-shell polymer is made up of (A) core layer consisting of a polymer prepared by polymerizing monomers predominant in an aromatic monovinyl monomer and (B) shell layer prepared by polymerizing the second monomers composed of (1) 25-95wt.% of an aromatic monovinyl monomer, (2) 5-40wt.% of at least one kind of monomer selected from alpha,beta- ethylenic unsaturated carboxylic acids and alpha,beta-ethylenic unsaturated carboxylic acid hydroxyalkyl esters and (3) 0-70wt.% of another comonomer. The shell layer accounts for 5-70wt.% of the final polymer, and the weight-average particle diameter of the present polymer is 0.1-50mum. The other objective plastisol can be obtained by dispersing this core-shell polymer in a plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core-shell polymer and a plastisol obtained from it, and more specifically, it has excellent fluidity and storage stability, and can be treated with a tough coating by heating at a suitable temperature. It relates to plastisols which give moldings, and to core-shell polymers suitable for obtaining such plastisols.

[0002]

2. Description of the Related Art Plastisol is a liquid or pasty mixture prepared by dispersing polymer fine particles in a liquid plasticizer and usually further dispersing other fillers and is useful as a molding material. . That is, plastisol is a molding material which, when heat-treated at an appropriate temperature, polymer fine particles are compatibilized with a plasticizer to give a film or a molded product as a gelled product.

Conventionally, as such a plastisol,
A material obtained by dispersing polyvinyl chloride in a plasticizer has been known for a long time, and is particularly advantageously used for forming a protective coating film for automobiles and the like. In such a polyvinyl chloride plastisol, during storage at room temperature, the polyvinyl chloride fine particles are dispersed for a long period of time without being plasticized by the plasticizer, and the viscosity at room temperature also increases with time. It has an excellent property that the polyvinyl chloride fine particles and the plasticizer are compatibilized and solidified only when the plastisol is heated to an appropriate temperature.

However, polyvinyl chloride has problems that it generates harmful hydrogen chloride gas during combustion, and that it is difficult to recycle and use it for resource saving. From the viewpoint of protection, there has been a strong demand for a plastisol, which is another resin instead of polyvinyl chloride plastisol.

Therefore, in plastisols, various polymers composed of vinyl monomers containing no halogen have been investigated as alternatives to the above-mentioned polyvinyl chloride. Coalescence also has various problems depending on the degree of compatibility with the plasticizer. That is, for example, when a polymer is dispersed in a plasticizer, it is immediately compatibilized and solidified at room temperature, so that it is inferior in storage stability. Although it is liquid at room temperature, its viscosity increases with time, Poor fluidity, at room temperature, while maintaining a stable liquid state, after heat treatment, when returned to room temperature, the plasticizer exudes from the surface of the solid produced, there is a problem such as poor compatibility, Furthermore, the coating formed by the heat treatment has a significantly low tensile strength when the compatibility between the polymer and the plasticizer is good, and on the contrary, when the compatibility is poor, the coating does not extend, There is also a problem that it becomes fragile and lacks practicality. Due to these various problems, a plastisol, which is another resin that replaces the polyvinyl chloride plastisol, has not yet been put to practical use.

For example, Japanese Patent Application Laid-Open No. 51-71344 proposes a plastisol in which an alkyl methacrylate or a copolymer of the alkyl methacrylate and another monomer is combined with various plasticizers. However, since the compatibility with the plasticizer of the polymer and the fluidity and storage stability of the plastisol have contradictory properties, among the proposed plastisols, for example, the compatibility with the plasticizer of the polymer is good,
Moreover, plastisol, which gives a gelled product with excellent flexibility by heat treatment, has a large increase in viscosity at room temperature over time, and thus has a problem in storage stability. On the other hand, plastisol, which does not have sufficient compatibility with the plasticizer of the polymer, has good storage stability at room temperature, but it is difficult to put it into practical use because the gelled product obtained by heating it is hard and brittle. Is.

Japanese Patent Laid-Open No. 54-117553 proposes a plastisol in which polymethylmethacrylate coated with a polycarboxylic acid salt or a copolymer thereof is dispersed in a plasticizer. Such plastisols do not replace vinyl chloride plastisols, as they have the same important problems as described above. In addition, JP-A-53-
Japanese Patent No. 144950 discloses a core-shell polymer comprising a core having a good compatibility with a plasticizer and a shell which is incompatible with the plasticizer and has a glass transition temperature of 50 ° C. or higher. ing. However, in such a core / shell polymer, the boundary between the core layer and the shell layer is not clear due to the mutual affinity of the polymers due to the monomer composition used in each layer. Have a problem. That is, first, when the shell layer is thin, the compatibility of the surface of the polymer with the plasticizer is not constant, and the plastisol in which such a polymer is dispersed in the plasticizer has poor storage stability.
Secondly, if the shell layer is made thick to obtain storage stability, the polymer of the shell layer, which is incompatible with the plasticizer and has a high glass transition temperature, has a high polymerization fraction. Films and molded articles obtained from plastisol do not have elongation and are brittle.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have proposed a novel core-shell polymer in order to solve the above problems in plastisols which have been conventionally proposed as an alternative to polyvinyl chloride plastisols. As a result of earnest research from the viewpoint of the development and utilization thereof, it was found that excellent results can be obtained when a core-shell polymer having a predetermined structure is used as a polymer component in plastisol, and the present invention has been completed. It is a thing.

That is, the present invention contains such a core-shell polymer as polymer fine particles, and has excellent fluidity suitable for working at room temperature, an increase in viscosity with time during long-term storage, and excellent storage that does not cause gelation. Stability, good compatibility with a plasticizer such that the plasticizer does not exude on the surface of the gelled product when cooled to room temperature after heat treatment, and also gives a toughened gelled product. You can
Thus, it is an object to provide a practical plastisol which replaces the conventional polyvinyl chloride plastisols, and an object is to provide a core-shell polymer suitable for obtaining such plastisols.

[0010]

The core-shell polymer according to the present invention comprises: (a) a core layer made of a polymer obtained by polymerizing a monomer containing an aromatic monovinyl monomer as a main component; b) (b1) an aromatic monovinyl monomer, (b2) at least one monomer selected from α, β-ethylenically unsaturated carboxylic acid and α, β-ethylenically unsaturated carboxylic acid hydroxyalkyl ester, And (b3) other monomer having copolymerizability with the above-mentioned monomer (wherein, among the above-mentioned monomers, (b1) is 25 to 95% by weight, (b2) is 5 to 40% by weight, (B3) is 0 to 70% by weight), and a shell layer formed by polymerizing a monomer mixture consisting of 5 to 70% by weight, and the weight average particle diameter is 0.1
It is characterized by being in the range of ˜50 μm.

The plastisol according to the present invention is characterized in that the core-shell polymer as described above is dispersed in an appropriate dispersion medium, and particularly preferably, it is dispersed in a plasticizer.

First, the core-shell polymer according to the present invention will be described. The core-shell polymer according to the present invention is
The polymer of the previous stage can be obtained by a continuous multi-step seed emulsion polymerization method or a multi-step suspension polymerization method in which the polymer of the later step is sequentially coated. In the case of a multi-step seed emulsion polymerization method, usually, a seed latex is prepared by emulsion polymerization by adding monomers all at once, and then seed polymerization is performed in the presence of this seed latex to obtain a core latex, and further, By repeating seed polymerization in the presence of this core latex, a latex of a core / shell polymer is obtained. The seed latex can be obtained, for example, by collectively adding monomers according to the required characteristics and emulsion-polymerizing the monomers. As the monomer, styrene, methyl methacrylate, ethyl acrylate, or a mixture thereof is usually often used.

When the core / shell polymer is produced by emulsion polymerization, an anionic surfactant such as sodium dodecylbenzene sulfonate or sodium lauryl sulfate, polyoxyethylene nonyl is used as an emulsifier according to a conventional method during the polymerization. Phenyl ether, using a nonionic surfactant such as sorbitan monolaurate, or a cationic surfactant such as octadecylamine acetate, potassium persulfate as a polymerization initiator, a peroxide such as cumene peroxide, 2,2 '-Azobis (2-amidinopropane)
An azo compound such as hydrochloride can be used.

On the other hand, when the core-shell polymer is produced by suspension polymerization, an organic compound such as polyvinyl alcohol or hydroxyethyl cellulose, or tricalcium phosphate or the like is used as a protective colloid according to a conventional method during polymerization. Inorganic compounds can be used, and benzoyl peroxide, 2,2'- as a polymerization initiator.
A peroxide such as azobisisobutyronitrile or an azo compound can be used.

Hereinafter, for simplification, the first stage seed polymerization for forming the core layer and the second stage seed polymerization in the presence of the latex of the polymer particles constituting the core layer are carried out. The production of the core-shell polymer according to the present invention will be described by taking the two-step polymerization method as an example. The first-stage polymerization is a polymerization in which a monomer containing an aromatic monovinyl monomer as a main component is polymerized to form a core layer made of a glassy polymer having good compatibility with a plasticizer. is there. here,
As will be described later, the monomer for forming the core layer preferably consists of a single aromatic monovinyl monomer, but is a mixture containing an aromatic monovinyl monomer as a main component. May be.

In the present invention, specific examples of the aromatic monovinyl monomer include, for example, styrene, α-methylstyrene, α-chlorostyrene, α-bromostyrene,
Examples thereof include styrene-based monomers such as 3,4-dichlorostyrene, alkyltoluenebenzene such as vinyltoluene and ethylvinylbenzene, and polycyclic aromatic monovinyl compounds such as vinylnaphthalene. These aromatic monovinyl monomers are used alone or in combination of two or more kinds. Particularly, in the present invention, the aromatic monovinyl monomer is preferably a styrene-based monomer, and among them,
Styrene is preferably used.

The monomer for forming the core layer used in the first-stage polymerization may contain a non-aromatic vinyl monomer copolymerizable with the aromatic monovinyl monomer. Examples of such non-aromatic monovinyl monomer include aliphatic conjugated diene compounds having 4 to 6 carbon atoms such as butadiene, isoprene, and chloroprene, such as ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-. Examples thereof include an alkyl (meth) acrylate having an alkyl group having 1 to 10 carbon atoms such as ethylhexyl acrylate, methyl methacrylate and butyl methacrylate, vinyl cyanide such as acrylonitrile and methacrylonitrile, and vinylidene cyanide.

Further, as the non-aromatic vinyl monomer,
For example, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, particularly α, β-ethylenically unsaturated aliphatic carboxylic acids such as hydroxyethyl (meth) acrylate,
Examples thereof include hydroxyalkyl (meth) acrylates having an alkyl group having 1 to 10 carbon atoms such as hydroxypropyl (meth) acrylate and glycidyl (meth) acrylate.

In the present invention, in the first-stage polymerization, the crosslinkable monomer is used in an amount of 5% by weight or less, preferably 2% by weight or less based on the total monomers for forming the core layer. Can be used together. Further, the grafting monomer can be used in combination in an amount of 5% by weight or less, preferably 2% by weight or less based on the total monomers for forming the core layer.
If necessary, both a crosslinkable monomer and a grafting monomer may be used.

Thus, in the first-stage polymerization, the core-shell polymer obtained by copolymerizing the crosslinking layer monomer or the grafted monomer together with the monomer for forming the core layer is When this is used in plastisol, the same effect as adding a cross-linking agent to plastisol can be obtained, as described later.

The use of crosslinkable and grafting monomers in the preparation of core / shell polymers is described, for example, in US Pat. No. 4,096,202,
It is already well known. That is, the crosslinkable monomer refers to a polyfunctional monomer having two or more addition-polymerizable (ethylenic) unsaturated bonds in the molecule and having substantially the same reactivity. Such a crosslinkable monomer partially brings about a three-dimensional network structure, that is, a crosslinked polymer structure, in the polymer forming the core layer.

As such a crosslinkable monomer, for example,
Aromatic divinyl compounds such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane diacrylate Alkane polyol poly (meth) acrylates such as acrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate and the like can be mentioned.

Further, the grafted monomer means 2 in the molecule.
A polyfunctional monomer having one or more addition-polymerizable (ethylenic) unsaturated bonds, but at least one of them having a reactivity different from that of at least one of the rest. Such a grafted monomer leaves an ethylenically unsaturated bond on or near the surface of the core layer after the core layer is formed, and is polymerized on the surface of the core layer after formation of the core layer to form a shell layer. When the shell layer is formed, the ethylenically unsaturated bond left on the surface of the core layer or in the vicinity thereof participates in the polymerization for forming the shell layer, and at least a part of the shell layer chemically reacts with the core layer. Will be combined with.

Examples of such grafting monomers include allyl acrylate, allyl methacrylate, diallyl malate, diallyl fumarate, diallyl itaconate, allyl acid malate (half ester), allyl acid fumarate (half ester), A typical example is an ethylenically unsaturated carboxylic acid allyl ester such as allyl acid itaconate (half ester).

In the present invention, in the first-stage polymerization, the aromatic monovinyl monomer, particularly the styrene-based monomer, which is the main component of the polymer forming the core layer, is used for the core layer. It is preferably 50% by weight or more, and particularly preferably 80% by weight or more of the monomer. From a practical point of view, in the present invention, the core layer is a polymer obtained by substantially polymerizing only styrene, or a monomer mixture consisting of styrene and a crosslinkable monomer is copolymerized. It is preferably a cross-linked polymer obtained by the treatment.

Further, according to the present invention, the polymer forming the core layer is preferably a glassy polymer having a glass transition temperature of 30 ° C. or higher, particularly 40 ° C. or higher.

The second-stage polymerization is a polymerization for forming a shell layer which is poorly compatible with a plasticizer at room temperature. The shell layer is composed of (b1) an aromatic monovinyl monomer, (b1)
2) α, β-ethylenically unsaturated carboxylic acid and α, β-
At least one monomer selected from ethylenically unsaturated carboxylic acid hydroxyalkyl ester, and (b3) another monomer having copolymerizability with the above monomer (here,
Of the monomer (b), (b1) is 25 to 95% by weight, (b2)
Is 5 to 40% by weight, and (b3) is 0 to 70% by weight. )
It can be obtained by polymerizing a monomer mixture consisting of.

In the present invention, the aromatic monovinyl monomer which is the first monomer (b1) in the monomer mixture for forming the shell layer is the main monomer forming the shell layer. The component is used in the range of 25 to 95% by weight, preferably 35 to 90% by weight, most preferably 45 to 85% by weight of the total monomer mixture for forming the shell layer.

Specific examples of the aromatic monovinyl monomer (b1), which is the first monomer in the monomer mixture for forming the shell layer, include, for example, styrene, α-methylstyrene, Examples thereof include styrene-based monomers such as α-chlorostyrene, α-bromostyrene, and 3,4-dichlorostyrene, alkylvinylbenzene such as vinyltoluene and ethylvinylbenzene, and polycyclic aromatic vinyl compounds such as vinylnaphthalene. it can. These aromatic monovinyl monomers are used alone or in combination of two or more kinds. Particularly, in the present invention, as the first aromatic monovinyl monomer (b1), a styrene-based monomer is preferable, and among them, styrene is most preferably used.

In the present invention, the α, β-ethylenically unsaturated carboxylic acid as the second monomer (b2) in the monomer mixture for forming the shell layer is acrylic acid or methacrylic acid. Examples thereof include acids, α-ethyl acrylic acid, β-ethyl acrylic acid, α, β-dimethyl acrylic acid and the like. Among these, methacrylic acid is particularly preferably used. As the α, β-ethylenically unsaturated carboxylic acid, unsaturated dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, methylenemalonic acid, α-methyleneglutaric acid, and half esters thereof. Can also be used.

As the α, β-ethylenically unsaturated carboxylic acid hydroxyalkyl ester, hydroxyethyl acrylate, hydroxypropyl acrylate,
Hydroxyethyl methacrylate and the like are preferably used. Of these, hydroxyethyl methacrylate is particularly preferably used. Particularly, in the present invention, methacrylic acid, 2-hydroxyethyl (meth) acrylate or a mixture thereof is preferably used as the second monomer (b2).

These second monomers (b2) are 5 to 40% by weight, preferably 5 to 35% by weight, and most preferably 5 to 30% by weight of the total monomer mixture used for forming the shell layer. Used in the range of%.

Further, in the present invention, as the other third monomer (b3) having copolymerizability with the first monomer (b1) and the second monomer (b2), Monomers such as (meth) acrylic acid esters, vinyl cyanides, vinylidene cyanides, carboxylic acid vinyl esters, unsaturated carboxylic acid amides, maleimides, and aliphatic conjugated diene compounds can be used.

Among such third monomer (b3),
Examples of the (meth) acrylic acid ester include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and glycidyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, Examples thereof include methacrylic acid esters such as glycidyl methacrylate. Examples of vinyl cyanides or vinylidene cyanides include acrylonitrile and methacrylonitrile. Examples of vinyl carboxylates include vinyl acetate and vinyl propionate. Examples of unsaturated carboxylic acid amides include (meth) acrylamide,
Examples thereof include N-methylol acrylamide and N-butoxymethyl acrylamide. Examples of maleimides include N-phenylmaleimide. Further, examples of the aliphatic conjugated diene compounds include butadiene, isoprene, chloroprene and the like.

Among these third monomers (b3), methyl methacrylate, acrylonitrile and the like are particularly preferably used. Further, in the present invention, the third monomer (b3) is 0 to 70% by weight, preferably 5 to 65% by weight of the total monomer mixture used for forming the shell layer.
Most preferably, it is used in the range of 10 to 60% by weight.

In the present invention, also in the second-stage polymerization, the above-mentioned crosslinkable monomer or grafting is carried out in an amount of 5% by weight or less based on the total monomers for forming the shell layer. A monomer can be used in combination.

In the present invention, the polymer forming the shell layer has a glass transition temperature of 40 ° C. or higher, preferably 50.
A glassy polymer that has a very low or no compatibility with plasticizers at room temperature or higher at room temperature and has a property of being compatible with a plasticizer when heat-treated at an appropriate temperature. Is a polymer having

In the core-shell polymer according to the present invention, the ratio of the core layer and the shell layer is appropriately selected according to the degree of compatibility with each plasticizer. According to the present invention, the core-shell polymer is used. In, the shell layer is
It is preferably in the range of 5 to 70% by weight, particularly preferably in the range of 20 to 50% by weight. Therefore, the core layer is preferably 30 to 30 in the core-shell polymer.
95% by weight, particularly preferably 50 to 80% by weight.

In the gelled product obtained by heat-treating the plastisol containing the core-shell polymer according to the present invention, the core layer having good compatibility with the plasticizer and the shell layer having poor compatibility are phase-separated. Although present, when the shell layer exceeds 70% by weight of the core-shell polymer, the gelled product becomes brittle and may have poor toughness. On the other hand, when the shell layer is less than 5% by weight, the coating of the core layer with the shell layer may be insufficient and the storage stability may decrease.

The core-shell polymer according to the present invention basically comprises two layers, a core layer having high compatibility with a plasticizer and a shell layer poorly or incompatible with the plasticizer at room temperature. Although it has a structure, if necessary, each of the core layer and the shell layer may be formed of a plurality of layers.

The core-shell polymer according to the present invention has a weight average particle size of 0.1 to 5 μm, preferably, when produced by a known seed emulsion polymerization method.
A latex in the range of 0.3 to 2 μm, more preferably 0.5 to 1 μm is produced, and the resulting polymer particles are separated from the reaction system by freeze-thawing or salting out, and then centrifugal dehydration, If dried, it can be obtained as a powder. The weight average particle diameter of the obtained core-shell polymer is 0.
When it is less than 1 μm, the coating of the core layer with the shell layer is insufficient, and the storage stability may be poor when dispersed in a liquid dispersion medium for use as a plastisol. On the other hand, when the weight average particle diameter of the core / shell polymer is larger than 5 μm, it takes a long time for the polymerization, which is not preferable in practice.

On the other hand, when the core-shell polymer according to the present invention is produced by a two-step suspension polymerization method, a suspension having a weight average particle diameter of 5 to 50 μm is usually prepared and then centrifugally dehydrated. If dried, it can be obtained as a powder. When the weight average particle diameter of the core / shell polymer is larger than 50 μm, it may take an unnecessarily long time to obtain a gelated product by heat treatment of the obtained plastisol.

By spray-drying the above-mentioned latex or suspension using a spray dryer, the core-shell polymer can be immediately obtained as a powder. The plastisol according to the present invention can be obtained by dispersing the core-shell polymer as described above in an appropriate liquid dispersion medium, preferably a liquid plasticizer. The plasticizer used in the present invention is compatible with the core layer of the core-shell polymer at room temperature and is not compatible with the shell layer, but is compatible with the shell layer by heating to an appropriate temperature, and then When cooled to room temperature, it forms a gel having strength and toughness, that is, a plastigel.

The plasticizer that can be used in the present invention is not particularly limited, and any plasticizer that has been conventionally used for producing polyvinyl chloride plastisols may be used. , Dibutyl phthalate, dioctyl phthalate, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, ditridecyl phthalate, dilauryl phthalate, octyl decyl phthalate, distearyl phthalate, butyl benzyl phthalate, phthalic acid diesters such as dibenzyl phthalate, dioctyl adipate, etc. Adipic acid diester, sebacic acid diester such as dioctyl sebacate, tributyl phosphate, tris (2-ethylhexyl) phosphate, tricresyl phosphate, cresyl diphenylphosphine Feto, diphenyl octyl phosphate, phosphoric acid organic esters such as triisopropyl phenyl phosphate, epoxy plasticizers such as epoxidized soybean oil, and polyester-based plasticizers.

The amount of the above-mentioned plasticizer in the plastisol according to the present invention affects the fluidity of the plastisol and the physical properties of the gelled product, so it is appropriately selected according to the required physical properties. It is in the range of 50 to 200 parts by weight with respect to 100 parts by weight of the combined body.

According to the present invention, a cross-linking agent may be added to the plastisol in order to impart more tough physical properties to the coating or molded article produced by heating the plastisol. Here, the cross-linking agent means that a functional group capable of reacting with the carboxyl group and / or the hydroxyl group of the shell layer is incorporated into the molecule.
A compound having three or more compounds, such as an epoxy group, an amino group, an isocyanate group, a blocked isocyanate group, a hydroxyl group, N
Examples thereof include a methylol group and an N-alkoxymethyl group. In the present invention, among these, a compound having two or more epoxy groups in the molecule is particularly preferably used as the crosslinking agent.

As the compound having an epoxy group,
For example, glycidyl ether type epoxy resins such as bisphenol A type, bisphenol F type and novolak type, glycidyl ester type epoxy resins such as polycarboxylic acid glycidyl ester, cycloaliphatic epoxy resin, glycidyl amine type epoxy resin, heterocyclic epoxy Resin etc. can be mentioned. Among these, particularly in the present invention, a flexible epoxy resin containing a polyethylene oxide chain or the like in the molecule is preferably used.

Such a cross-linking agent in the present invention is
Usually, it is 0.1 for 100 parts by weight of the core-shell polymer.
To 50 parts by weight, preferably 0.5 to 20 parts by weight.

Further, in addition to the above, the plastisol according to the present invention may be added with an appropriate amount of a diluent, an inorganic filler, an organic filler, a dye, a pigment, a corrosion inhibitor, etc., if necessary. .

The plastisol according to the present invention as described above is
At room temperature, it has excellent workability and storage stability, and when it is heat-treated at 100 to 180 ° C., it becomes compatible and solidified. Since it gives a gelled product having
It can be advantageously used for forming a protective coating film for automobiles.

[0051]

As described above, the core-shell polymer according to the present invention has a core layer mainly composed of a monomer composed of an aromatic monovinyl monomer, preferably a polymer prepared by polymerizing styrene, The shell layer is an aromatic monovinyl monomer,
It is preferably composed of a copolymer obtained by polymerizing a monomer mixture containing styrene as a main component.

The plastisol according to the present invention has such a core-shell polymer as a polymer component and has fluidity,
It has excellent storage stability and compatibility, and since such plastisols give coatings and molded articles as tough gels, they should be used in place of conventional plastisols containing polyvinyl chloride as a polymer component. You can

[0053]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, all "parts" indicate parts by weight. The abbreviations used below are as shown below.

Abbreviations Methyl Methacrylate: MMA Butyl Methacrylate: BMA 2-Hydroxyethyl Methacrylate: HEMA Methacrylic Acid: MAA Styrene: St Acrylonitrile: AN 1,4-Butylene Glycol Diacrylate BGDA 1,6-Hexanediol Diacrylate HDDA Deionized Water: DIW Dioctyl sulfosuccinate sodium salt: SSS Sodium persulfate: SPS Sodium hydrogen carbonate: SHC Diisononyl phthalate: DINP 1,4-diazabicyclo [2,2,2] octane: DABCO

Method for Measuring Physical Properties of Core / Shell Polymer The weight average particle size of the core / shell polymer was measured by a laser particle size analysis system LPA-3000 manufactured by Otsuka Electronics Co., Ltd.

The strength at break and the elongation at break were obtained by press-molding plastisol at a temperature of 140 ° C. and a pressure of 100 kgf / cm ^{2 for} 30 minutes to form a sheet having a thickness of about 1 mm. It measured based on -6301. The storage stability was good when it was kept at 40 ° C. for 10 days and stable and no gelation occurred.

Example 1 (Production of core-shell polymer A) 3 equipped with a reflux condenser
DIW 19 parts, 1% SSS in a liter capacity polymerization container
An aqueous solution (0.3 parts) and a 1% SHC aqueous solution (1.3 parts) were charged, and the temperature was raised to 70 ° C. with stirring under a nitrogen stream. Then
St 0.3 parts was added thereto and dispersed for 10 minutes, and then 7.5 parts of a 2% SPS aqueous solution was added to initiate seed emulsion polymerization. After reacting for 10 minutes to prepare a seed latex, 6 parts of a monomer emulsion for the first stage polymerization consisting of St59.7 parts, 1% SSS aqueous solution 50 parts and 1% SHC aqueous solution 9 parts was added. It was continuously supplied over a period of time, then the internal temperature was raised from 70 ° C. to 90 ° C., and aging was carried out for 1 hour.

Next, the internal temperature was adjusted to 70 ° C. and 2% SPS was applied.
After adding 2 parts of the aqueous solution, St 28 parts, MAA 6 parts, MM
A6 parts, 1% SSS aqueous solution 2 parts, 1% SHC aqueous solution 6 parts and DIW30 parts for monomer polymerization liquid for the second stage of polymerization were continuously supplied over 4 hours, and then the internal temperature was increased. The temperature was raised from 70 ° C. to 90 ° C., and aged for 1 hour. After the reaction was completed, the reaction mixture was cooled to room temperature and filtered through a 300-mesh wire net to obtain a solid content of 44.0% and a weight average particle size of 68.
A 0 nm core-shell polymer latex was obtained. This latex is spray-dried to give a core-shell polymer A
Of powder was obtained.

Examples 2 to 7 and Comparative Example 1 (Preparation of Core / Shell Polymers B to H) Core / Shell Polymers B to B having the compositions shown in Table 1 were prepared in the same manner as in Example 1.
A powder of H was prepared.

[0060]

[Table 1]

Examples 8 to 15 and Comparative Example 2 (Preparation of plastisol and evaluation of its physical properties) As shown in Table 2, core-shell polymers A to H obtained in Examples 1 to 7 and Comparative Example 1 Was mixed with a plasticizer, a cross-linking agent and a catalyst and uniformly dispersed to prepare a plastisol. Table 2 shows the storage stability of the obtained plastisol and the physical properties of the coating film obtained from this plastisol.

[0062]

[Table 2]

Claims (22)

[Claims] 1. A core layer comprising (a) a polymer obtained by polymerizing a monomer containing an aromatic monovinyl monomer as a main component, (b) (b1) an aromatic monovinyl monomer, and (b2) ) At least one monomer selected from α, β-ethylenically unsaturated carboxylic acid and α, β-ethylenically unsaturated carboxylic acid hydroxyalkyl ester, and (b3) having copolymerizability with the above monomer From other monomers (here, (b1) is 25 to 95% by weight, (b2) is 5 to 40% by weight, and (b3) is 0 to 70% by weight among the above monomers). And a shell layer formed by polymerizing a monomer mixture, wherein the shell layer is in the range of 5 to 70% by weight, and the weight average particle diameter is 0.1.
A core-shell polymer characterized by being in the range of ˜50 μm. 2. The core-shell polymer according to claim 1, wherein the monomer for forming the core layer contains a crosslinkable monomer, and the core layer is a crosslinked polymer. 3. A monomer for forming a core layer is 5% by weight.
The core according to claim 2, which contains a crosslinkable monomer in the following range:
Shell polymer. 4. The core-shell polymer according to claim 1, wherein 50% by weight or more of the monomer for forming the core layer is an aromatic monovinyl monomer. 5. The core-shell polymer according to claim 1, wherein 80% by weight or more of the monomer for forming the core layer is an aromatic monovinyl monomer. 6. The core-shell polymer according to claim 1, wherein the aromatic monovinyl monomer in the monomer for forming the core layer is styrene. 7. The core-shell polymer according to claim 1, wherein the core layer comprises a glassy polymer having a glass transition point of 30 ° C. or higher. 8. The core-shell polymer according to claim 1, wherein the core layer consists essentially of a polymer of styrene. 9. The core-shell polymer according to claim 1, wherein the core layer consists essentially of a cross-linked polymer of styrene. 10. A monomer mixture for forming a shell layer, wherein (b1) is 35 to 90% by weight and (b2) is 5 to 3%.
The core-shell polymer according to claim 1, wherein the content of (b3) is 5% by weight and the amount of (b3) is 5 to 65% by weight. 11. The core-shell polymer according to claim 1, wherein the shell layer has a glass transition point of 40 ° C. or higher. 12. A monomer mixture for forming a shell layer, wherein (b1) is at least one selected from styrene, (b2) is methacrylic acid, and (b3) is at least one selected from methyl methacrylate and acrylonitrile. 1. The core-shell polymer described in 1. 13. The core layer consists essentially of a non-crosslinked or crosslinked polymer of styrene, and the shell layer consists essentially of (b1) styrene, (b2) methacrylic acid and (b3) methyl methacrylate and acrylonitrile. The core according to claim 1, which comprises at least one copolymer selected from
Shell polymer. 14. The shell layer-forming monomer mixture is substantially selected from (b1) styrene 45 to 85% by weight, (b2) methacrylic acid 5 to 30% by weight, and (b3) methyl methacrylate and acrylonitrile. At least one kind 1
The core-shell polymer according to claim 1, which comprises 0 to 60% by weight of the copolymer. 15. The core-shell polymer according to claim 1, wherein the shell layer is in the range of 20 to 50% by weight. 16. A plastisol obtained by dispersing the core-shell polymer according to any one of claims 1 to 15 in a liquid dispersion medium. 17. The liquid dispersion medium is a plasticizer.
The described plastisols. 18. The plastisol according to claim 17, wherein the plasticizer is a phthalic acid diester. 19. The plastisol according to claim 16, which further contains a crosslinking agent. 20. The plastisol according to claim 19, wherein the cross-linking agent is a compound having in the molecule at least two functional groups which react with a carboxyl group and / or a hydroxyl group of the core-shell polymer. 21. The plastisol according to claim 19, wherein the crosslinking agent is a compound having two or more epoxy groups in the molecule. 22. The plastisol according to claim 19, wherein the crosslinking agent is contained in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the core-shell polymer.