JP2005239766A - Trilaminar-structured acrylic polymer particle, preparation method therefor and plastisol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic polymer particle which is excellent in dispersibility in a plasticizer and is suitable for obtaining a plastisol which is excellent in shelf stability of sol viscosity, shows no bleeding of the plasticizer and yields a molded product excellent in adhesion to a metal. <P>SOLUTION: The trilaminar-structured acrylic polymer particle consists of (A1) 30-80 mass% core polymer layer obtained by polymerizing (a1) a (meth)acrylate monomer, (A2) 16-66 mass% intermediate polymer layer obtained by polymerizing (a2) a (meth)acrylate monomer mixture containing a (meth)acrylate monomer having a hydroxyl group and (A3) 4-9 mass% outer shell polymer layer obtained by polymerizing (a3) a (meth)acrylate monomer mixture containing a monomer having an organic acid group. The organic acid group contained in the outer shell polymer layer (A3) is neutralized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a three-layer acrylic polymer particle comprising a core polymer layer, an intermediate polymer layer and an outer shell polymer layer, and suitable for plastisol use and the like, and a method for producing the same.

  A plastisol is a liquid or paste-like mixture in which resin polymer particles are dispersed in a liquid plasticizer, and other fillers are usually dispersed, and this mixture is heated to an appropriate temperature. A molding material in which resin polymer particles are solidified with a plasticizer to give a film or a molded product.

  As such a plastisol, one obtained by dispersing polyvinyl chloride resin particles in a plasticizer has been known for a long time, and has been used for forming a protective coating film for automobiles, for example. When the plastisol containing the polyvinyl chloride resin particles is stored at room temperature, the polyvinyl chloride resin particles are dispersed without being plasticized by the plasticizer over a long period of time, and the viscosity at room temperature over time It has an excellent property that the increase is small.

  However, polyvinyl chloride resin has problems such as generation of harmful hydrogen chloride gas during combustion and difficulty in recycling and use. From the viewpoint of protecting the global environment, polyvinyl chloride resin is also used. There is a strong demand for plastisols made of other resins instead of resins.

  Various plastisols using acrylic polymer particles have been studied as plastisols made of another resin instead of the polyvinyl chloride resin. For example, Patent Document 1 describes a plastisol composition containing particles having a single-layer structure obtained by polymerizing a specific acrylate monomer by a one-step method, such as a paint for preventing wear and corrosion of steel substrates, and the like. The use of is proposed.

  Further, Patent Document 2 is based on a methacrylic acid copolymer, and the copolymer is composed of a core material (core component) that is compatible with a plasticizer and a shell material (shell component) that is incompatible with a plasticizer. A plastisol, which is a structured emulsion polymer, is disclosed, and it is described that a molded body can be produced by coating on a metal or non-metal substrate and heating to gel. Patent document 3 reports the use of acrylic polymer particles having the same core / shell structure and plastisol.

  Further, Patent Documents 4 to 5 propose acrylic polymer particles in which monomer units are changed in multiple steps or continuously from the center of the acrylic polymer particles toward the outermost part.

However, in spite of these efforts, various sol properties such as acrylic polymer particles have good dispersibility in plasticizers, excellent storage stability of sol viscosity, and no plasticizer bleeding so far. A plastisol that gives a molded article having excellent mechanical properties has not been obtained. In particular, a molded article obtained by heat-sealing plastisol itself has not been obtained with sufficient adhesion to metal.
JP-A-5-255563 JP-A-53-144950 WO00 / 01748 JP-A-8-295850 Japanese Patent Laid-Open No. 9-77950

  Accordingly, an object of the present invention is to provide a plastisol that provides a molded article having excellent storage stability of sol viscosity, no plasticizer bleeding, and excellent adhesion to metal, and a plasticizer suitable for obtaining the same. It is an object of the present invention to provide acrylic polymer particles having excellent dispersibility and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by acrylic polymer particles having a specific three-layer structure, and the present invention is completed based on this finding. It came to.

Thus, according to the present invention, the following inventions 1 to 7 are provided. In this specification, “(meth) acrylic acid” means “methacrylic acid” and / or “acrylic acid”.
1. A (meth) acrylic acid ester monomer mixture comprising a core polymer layer (A1) obtained by polymerizing the (meth) acrylic acid ester monomer (a1) and a (meth) acrylic acid ester monomer having a hydroxyl group. An outer polymer layer formed by polymerizing an intermediate polymer layer (A2) obtained by polymerizing (a2) and a (meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group (A3), the core polymer layer (A1) is 30 to 80% by mass, the intermediate polymer layer (A2) is 16 to 66% by mass, and the outer polymer layer (A3) is 4%. Three-layer structure acrylic polymer particles, wherein the organic acid group contained in the outer shell polymer layer (A3) is neutralized by ˜9% by mass.
2. The three-layer structure acrylic polymer particle according to 1, wherein the (meth) acrylic acid ester monomer mixture (a3) further contains a monomer having an epoxy group.
3. The three-layer structure acrylic polymer particles according to the above 1 or 2, wherein the pH is 6.0 to 7.5 when re-dispersed in water at pH 7.0 at a concentration of 30% by mass.
4). In the presence of the core polymer layer (A1), a step of polymerizing the (meth) acrylic acid ester monomer (a1) to form a core polymer layer (A1) of 30 to 80 parts by mass, A (meth) acrylic acid ester monomer mixture (a2) containing a (meth) acrylic acid ester monomer having a hydroxyl group is polymerized to form an intermediate polymer layer (A2) of 16 to 66 parts by mass, (Meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group in the presence of the step of producing 91 to 96 parts by mass of a two-layer structure polymer and the two-layer structure polymer. ) To form 4 to 9 parts by mass of the outer shell polymer layer (A3) to produce 100 parts by weight of the three-layer structure polymer, and the outer shell polymer layer (A3). And a step of neutralizing the organic acid group contained therein. Method for producing a drill polymer particles.
5). The three-layer structure acrylic polymer particles according to any one of the above 1 to 3, which are used for plastisol.
6). 6. A plastisol comprising the three-layer acrylic polymer particles as described in 5 above and a plasticizer.
7). 7. The plastisol according to 6, wherein the plasticizer is mainly composed of a phthalic acid dialkyl ester compound.

  The three-layer structure acrylic polymer particles of the present invention are excellent in dispersibility in a plasticizer. The plastisol using the three-layer structure acrylic polymer particles of the present invention is excellent in the storage stability of the sol viscosity, the gelation property at the time of molding, and the melt / film forming property. In addition, after the molding of plastisol, the plasticizer does not bleed, the adhesion to metal is excellent, and the mechanical properties are excellent.

  The three-layer structure acrylic polymer particle of the present invention has three core layers (A1), an intermediate polymer layer (A2), and an outer shell polymer layer (A3) laminated in this order from the inside to the outside of the particle. It has a layer structure.

  The core polymer layer (A1) is formed by polymerizing the (meth) acrylic acid ester monomer (a1). The (meth) acrylate monomer (a1) may be a kind of (meth) acrylate monomer or a mixture of two or more (meth) acrylate monomers. Also good.

  The intermediate polymer layer (A2) is formed by polymerizing a (meth) acrylic acid ester monomer mixture (a2) containing a (meth) acrylic acid ester monomer having a hydroxyl group.

  The outer shell polymer layer (A3) is formed by polymerizing a (meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group.

  Thus, the three-layer structure acrylic polymer particles of the present invention have a three-layer structure consisting of the core polymer layer (A1), the intermediate polymer layer (A2), and the outer shell polymer layer (A3). The reason why such a specific three-layer structure is adopted will be described below.

  Generally, if the compatibility between the polymer particles in the plastisol and the plasticizer is high, the plasticizer enters the polymer particles and gels during storage of the plastisol, so that the storage stability is lacking. On the other hand, if the compatibility between the polymer particles in the plastisol and the plasticizer is small, the storage stability is good. However, the gelation property, the melt / film-forming property during the heat molding (hereinafter referred to as “molding properties”). May be abbreviated as “.” And the mechanical properties of the obtained molded product are inferior, and the plasticizer tends to bleed out from the molded product.

  As described above, the storage stability of plastisol, the molding characteristics and the mechanical characteristics of the molded article are contradictory characteristics. However, as a means for providing both of them, a core having high compatibility with a plasticizer. It has been proposed to form a core / shell particle having a shell having a low compatibility with the plasticizer. Specifically, a composition in which a monomer unit having an organic acid group is contained in a shell layer of core / shell particles mainly composed of (meth) acrylic acid ester has been proposed. In this case, since the monomer having an organic acid group has low compatibility with the plasticizer, the outer layer containing the monomer functions as a shell that prevents plastisol from gelling.

  However, when a large amount of monomer having an organic acid group that is not compatible with the plasticizer (2 to 3% by mass or more of the whole particle) is used, the plastisol molding properties and the mechanical properties of the molded product are reduced. It will be inferior.

  Therefore, it is necessary to reduce the amount of the monomer having an organic acid group as much as possible. As a method for this, the thickness of the shell containing the monomer having the organic acid group is made as thin as possible to have the organic acid group. It is conceivable that the monomer is localized only in the vicinity of the interface between the particle and the outside.

  In addition, as described above, when the monomer having an organic acid group is localized only in the vicinity of the interface between the particle and the outside, the content of the monomer having an organic acid group in the entire particle is small. Therefore, the plastisol has good molding properties and the like, but there is a problem that the storage stability of plastisol may be somewhat deteriorated in summer when the storage temperature is high.

  In the present invention, the monomer having an organic acid group is localized only in the vicinity of the interface between the particle and the outside world in order to balance the storage stability and molding characteristics of the plastisol and the mechanical properties of the molded product. In addition, in order to improve the storage stability in summer, in the three-layer structure acrylic polymer particles, the outer polymer layer (A3) having a small compatibility with the plasticizer is formed as thin as possible, While maintaining the storage stability of plastisol, the molding characteristics and the mechanical properties of the molded product are improved. Further, an intermediate polymer layer (A2) is formed as a layer located between the core polymer layer (A1) and the outer shell polymer layer (A3), and the intermediate polymer layer (A2) has a hydroxyl group (meta ) Acrylic acid ester monomer unit was contained. The intermediate polymer layer (A2) has an intermediate phase compared with the core polymer layer (A1) having a high compatibility with the plasticizer and the outer shell polymer layer (A3) having a low compatibility with the plasticizer. It has solubility. By providing this intermediate polymer layer (A2), the three-layer acrylic polymer particles of the present invention improve the storage stability of plastisol without deteriorating the molding properties and the mechanical properties of the molded product. In addition, the storage stability in summer could be improved.

  In addition, when using adhesiveness to metal as an application development of plastisol, in order to improve the adhesiveness, many monomers having polar groups such as organic acid groups are included on the outer surface of the particles. It is preferable. Therefore, in the present invention, by localizing the monomer having an organic acid group in the vicinity of the interface between the particle and the outside, the organic acid group can be present at a high concentration on the outer surface of the particle. It is also possible to improve the adhesion.

  In the three-layer structure acrylic polymer particles of the present invention, the core polymer layer (A1) is 30 to 80% by mass, the intermediate polymer layer (A2) is 16 to 66% by mass, and the outer polymer layer (A3) is It is formed at a rate of 4 to 9% by mass. By setting the ratio of the outer shell polymer layer (A3) to the above range, the amount of the monomer having an organic acid group in the outer shell polymer layer (A3) is set to 2 to 3% by mass or less of the entire particle. Can be suppressed. Thereby, it is possible to improve the molding characteristics and the mechanical characteristics of the molded article while maintaining the storage stability of the plastisol. Further, by setting the ratio of the intermediate polymer layer (A2) within the above range, the storage stability of plastisol can be improved even in summer when the storage temperature is high.

1. Core polymer layer (A1)
The core polymer layer (A1) is a layer formed by polymerizing the (meth) acrylic acid ester monomer (a1). The (meth) acrylic acid ester monomer (a1) may be one kind of (meth) acrylic acid ester monomer or a mixture of two or more kinds of (meth) acrylic acid ester monomers. May be.

  As a preferable composition of the (meth) acrylic acid ester monomer (a1) forming the core polymer layer (A1), a (meth) acrylic acid ester monomer having 6 to 21 carbon atoms (35 to 100% by mass) ), Methyl methacrylate (0 to 65% by mass), aromatic monovinyl monomer (0 to 50% by mass), and other monomers (0 to 20% by mass).

  Examples of the (meth) acrylic acid ester monomer having 6 to 21 carbon atoms include ethyl methacrylate, (meth) butyl acrylate, (meth) acrylic acid-i-butyl, (meth) acrylic acid-sec-butyl, (Meth) acrylic acid-t-butyl, (meth) acrylic acid hexyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid decyl, (meth) acrylic acid lauryl, (meth) acrylic acid cyclohexyl, (meta ) Benzyl acrylate, phenyl (meth) acrylate, and the like. Among these, Preferably, it is (meth) acrylic acid butyl, (meth) acrylic-acid-i-butyl, (meth) acrylic-acid-t-butyl, Especially preferably, it is methacrylic acid-i-butyl.

  The reason why the (meth) acrylic acid ester monomer having 6 to 21 carbon atoms is that the number of carbon atoms is 6 or more can prevent the plastisol molded body from increasing in hardness, and the plasticizer can easily bleed. Can be prevented. Moreover, it can prevent that the tensile strength of a plastisol molded object becomes notably small by making carbon number 21 or less. A preferable range of the carbon number is 7 to 19, and a more preferable range is 8 to 15.

  Specific examples of the aromatic monovinyl monomer include styrene, α-methylstyrene, vinyltoluene and the like. Of these monomers, styrene is preferred.

  Other monomers are not particularly limited as long as they are copolymerizable with other component monomers, and one kind may be used alone, or two or more kinds may be used in combination. . Specific examples of such other monomers include ethylenically unsaturated nitrile monomers, vinyl carboxylates, vinyl ether monomers, vinyl ketone monomers, α-olefin monomers, diene monomers, and the like. Can be mentioned.

  Specific examples of the ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-ethyl (meth) acrylonitrile and the like.

  Specific examples of the vinyl carboxylate monomer include vinyl acetate, vinyl propionate, and vinyl caproate.

  Specific examples of the vinyl ether monomer include allyl glycidyl ether and methyl vinyl ether.

  Specific examples of the vinyl ketone monomer include methyl vinyl ketone.

  Specific examples of the α-olefin monomer include ethylene, propylene, butene, pentene and the like.

  Specific examples of the diene monomer include conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and cyclopentadiene. Monomers; Non-conjugated diene monomers such as 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene and the like can be mentioned.

2. Intermediate polymer layer (A2)
The intermediate polymer layer (A2) is a layer formed by polymerizing a (meth) acrylic acid ester monomer mixture (a2) containing a (meth) acrylic acid ester monomer having a hydroxyl group.

  As a preferable composition of the (meth) acrylic acid ester monomer mixture (a2) forming the intermediate polymer layer (A2), the (meth) acrylic acid ester monomer having 6 to 21 carbon atoms (29 to 70 mass) %), Methyl methacrylate (25 to 70% by mass), (meth) acrylic acid ester monomer having a hydroxyl group (1 to 15% by mass), and other monomers (0 to 20% by mass).

  As the (meth) acrylic acid ester monomer having a hydroxyl group, preferably, hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 4-hydroxybutyl, particularly preferably 2-hydroxyethyl (meth) acrylate.

  Moreover, as a (meth) acrylic acid ester monomer having 6 to 21 carbon atoms and other monomers, the same monomers as those in the core polymer layer (A1) can be used.

3. Outer polymer layer (A3)
The outer polymer layer (A3) is a layer obtained by polymerizing a (meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group. Due to the organic acid group contained in the outer shell polymer layer (A3), the compatibility between the outer shell polymer layer (A3) and the plasticizer is lowered, and the storage stability of the plastisol is improved. Further, when the organic acid group in the outer shell polymer layer (A3) is neutralized and ion-crosslinked, the compatibility with the plasticizer is further lowered and the storage stability is improved. In order to improve storage stability and adhesion to metal, the organic acid group in the outer shell polymer layer (A3) is neutralized with a monovalent or divalent cation. It is desirable.

  Thus, by neutralizing the organic acid group in the outer shell polymer layer (A3), the compatibility with the plasticizer is further reduced, and accordingly, the molding characteristics of the plastisol and the mechanical properties of the molded product are reduced. There is a risk that the characteristics and the like may deteriorate. However, in the three-layer structure acrylic polymer particles of the present invention, organic acid groups that cause a decrease in compatibility with the plasticizer are localized in the outermost layer, so that the amount of organic acid groups is minimized. Further, the disadvantage that the plastisol molding characteristics and the mechanical properties of the molded article are reduced is eliminated.

  As a preferable composition of the (meth) acrylic acid ester monomer mixture (a3) forming the outer shell polymer layer (A3), a (meth) acrylic acid ester monomer having 6 to 21 carbon atoms (15 to 55). Mass%), a methyl methacrylate monomer (30 to 70 mass%), a monomer having an organic acid (12.5 to 35 mass%), a (meth) acrylic acid ester monomer having a hydroxyl group (0 to 0 mass%). 30 mass%), monomers having an epoxy group (0 to 30 mass%), and other monomers (0 to 20 mass%).

  As the monomer having an organic acid group, α, β-ethylenically unsaturated carboxylic acid is preferable, and (meth) acrylic acid is particularly preferable.

  The α, β-ethylenically unsaturated carboxylic acid that can be used in the present invention is not particularly limited, and specific examples thereof include α, β-ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid. Carboxylic acid; α, β-ethylenically unsaturated polyvalent carboxylic acid such as itaconic acid, maleic acid and fumaric acid; α, β-ethylenically unsaturated polyvalent carboxylic acid such as itaconic acid monomethyl, maleic acid monobutyl and monoethyl fumarate Acid partial ester; and the like. Further, an acid anhydride that can be derived into an α, β-ethylenically unsaturated carboxylic acid by hydrolysis or the like, such as maleic anhydride, can also be used. Of the α, β-ethylenically unsaturated carboxylic acids and derivatives thereof, acrylic acid and methacrylic acid are preferred. These are industrially inexpensive and can be easily obtained, have good copolymerizability with other monomer components, and are preferable in terms of productivity.

  In the present invention, the α, β-ethylenically unsaturated carboxylic acid unit may be introduced into the outer shell polymer layer (A3) by copolymerization of α, β-ethylenically unsaturated carboxylic acid. The α, β-ethylenically unsaturated carboxylic acid ester unit or the α, β-ethylenically unsaturated carboxylic acid anhydride unit may be hydrolyzed by a known polymer reaction or the like.

  The monomer having an epoxy group is preferably an epoxy group-containing (meth) acrylic acid ester, and particularly preferably glycidyl (meth) acrylate.

  As the (meth) acrylic acid ester monomer having 6 to 21 carbon atoms and other monomers, those similar to those in the core polymer layer (A1) can be used. Moreover, as a (meth) acrylic acid ester monomer which has a hydroxyl group, the thing similar to the thing in an intermediate polymer layer (A2) can be used.

4). Neutralization treatment In the three-layer structure acrylic polymer particles of the present invention, the organic acid contained in the outer shell polymer layer (A3) is neutralized. By neutralizing the organic acid group, the compatibility of the outer polymer layer (A3) containing the organic acid group with respect to the plasticizer is further lowered, and the storage stability of plastisol is improved. When the outer shell polymer layer (A3) is neutralized, the plastisol can exhibit the desired storage stability even if the amount of the organic acid contained in the outer shell polymer layer (A3) is small. Therefore, since the amount of organic acid in the outer shell polymer layer (A3) can be relatively reduced, the influence of the organic acid on the physical properties of the plastisol is reduced.

  The neutralizing agent for neutralizing the organic acid group contained in the outer shell polymer layer (A3) is not particularly limited as long as it is a base, and examples thereof include alkali hydroxides such as sodium hydroxide and potassium hydroxide; ammonia; Examples thereof include amines such as methylamine, ethylamine, and triethylamine; carbonates such as ammonium carbonate, sodium carbonate, and potassium carbonate; bicarbonates such as ammonium bicarbonate, sodium bicarbonate, and potassium bicarbonate. Of these, sodium hydroxide and potassium hydroxide are preferable.

5). Production Method In the three-layer structure acrylic polymer particles of the present invention, first, the core polymer layer (A1) is formed, and then the intermediate polymer layer (A2) is formed so as to cover the core polymer layer (A1). Finally, the outer polymer layer (A3) is formed so as to cover the intermediate polymer layer (A2).

  Typically, first, the monomer constituting the core polymer layer (A1) is polymerized, then the monomer constituting the intermediate polymer layer (A2) is polymerized, and finally the outer shell. Polymerization of the monomer constituting the polymer layer (A3) is performed. In this case, when the polymerization conversion rate of the monomer constituting the core polymer layer (A1) reaches 90% by mass or more, the polymerization of the monomer constituting the intermediate polymer layer (A2) is started. Further, it is more preferable to start the polymerization when the polymerization conversion rate becomes 95% by mass or more. Further, when the polymerization conversion rate of the monomer constituting the intermediate polymer layer (A2) reaches 90% by mass or more, the polymerization of the monomer constituting the outer polymer layer (A3) is started. Further, it is more preferable to start the polymerization when the polymerization conversion rate becomes 95% by mass or more.

  Moreover, you may use what was synthesize | combined separately as a core polymer layer (A1).

  Note that seed particles may be used in the polymerization of the monomers constituting the core polymer layer (A1).

  Furthermore, the polymerization conversion rate of the monomer constituting the outer shell polymer layer (A3) is preferably 90% by mass or more, and more preferably 95% by mass or more.

  In producing the three-layer structure acrylic polymer particles of the present invention, the polymerization method is not particularly limited, and any method such as an emulsion polymerization method, a suspension polymerization method, or a fine suspension polymerization method can be employed. Moreover, there is no restriction | limiting also in the kind and quantity of a polymerization initiator, an emulsifier, a dispersing agent, a crosslinking agent, a chelating agent, etc. which are used for superposition | polymerization. Of course, it can also be synthesized by so-called soap-free polymerization without using an emulsifier. Furthermore, there are no particular restrictions on the monomer concentration, polymerization temperature, pressure / atmosphere during polymerization, stirring method, and the like.

  The three-layer structure acrylic polymer particles of the present invention are preferably produced by the following production method. That is, in the method for producing the three-layer structure acrylic polymer particles of the present invention, the (meth) acrylic acid ester monomer (a1) is polymerized to form 30 to 80 parts by mass of the core polymer layer (A1). In the presence of the core polymer layer (A1), the (meth) acrylate monomer mixture (a2) is polymerized to form an intermediate polymer layer (A2) of 16 to 66 parts by mass. In the step of producing 91 to 96 parts by mass of the two-layer structure polymer, and in the presence of the two-layer structure polymer, the (meth) acrylic acid ester monomer mixture (a3) is polymerized, and 4 to 4 A step of forming 9 parts by mass of the outer shell polymer layer (A3) to produce 100 parts by weight of the three-layer structure polymer, and neutralizing organic acid groups contained in the outer shell polymer layer (A3) Process.

  The three-layer structure acrylic polymer particles obtained in this way can be used as a polymer particle dispersion, or the dispersion medium can be removed by any method such as spray drying and used as polymer particles. You can also When the acrylic polymer particles taken out are redispersed in water at pH 7.0 at a concentration of 30% by mass, the pH of the dispersion is preferably in the range of 6.0 to 7.5. When the pH of the dispersion is in the range of 6.0 to 7.5, the storage stability of the plastisol sol viscosity is good, and the sol dispersibility is also good.

  The three-layer structure acrylic polymer particles of the present invention usually have a single average particle size of 0.5 to 2.5 μm.

6). Plastisol The three-layer structure acrylic polymer particles of the present invention are suitably used for plastisols.
The plastisol of the present invention comprises the three-layer acrylic polymer particles of the present invention and a plasticizer.

  The type of plasticizer is not particularly limited, but includes phthalate ester plasticizers; alkylphenol sulfate ester plasticizers; phosphate ester plasticizers; adipate ester plasticizers; sebacate ester plasticizers; diethylene glycol dibenzoate, dibenzoate Examples include glycol derivative plasticizers such as dipropylene glycol benzoate; glycerin derivative plasticizers such as glycerol triacetate and glycerol tributyrate; epoxy derivative plasticizers such as epoxidized soybean oil; and the like.

  Specific examples of the phthalate ester plasticizer include dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, and the like; Mention may be made of alkylbenzyl phthalate plasticizers such as octylbenzyl, butylbenzyl phthalate and myristylbenzyl phthalate; alkylaryl phthalate plasticizers; dibenzyl phthalate plasticizers; diaryl phthalate plasticizers.

Specific examples of the phosphate ester plasticizer include triaryl phosphate plasticizers such as tricresyl phosphate; trialkyl phosphate plasticizers such as trioctyl phosphate; alkylaryl phosphate plasticizers.
These may be selected according to the required characteristics of the target plastisol.

Of these plasticizers, phthalic acid ester plasticizers are preferred from the viewpoints of being industrially inexpensive and readily available, workability, low toxicity, and the like, and more preferred are phthalic acid dialkyl esters. Of these, diisononyl phthalate is most preferred from the viewpoint of environmental impact.
These plasticizers may be used alone or in combination of two or more.

  The content of the plasticizer is preferably in the range of 50 to 180 parts by mass with respect to 100 parts by mass of the three-layer structure acrylic polymer particles. By setting the content of the plasticizer to 180 parts by mass or less, it is possible to prevent the plasticizer from bleeding out from the molded body. Moreover, by setting it as 50 mass parts or more, it can be set as the sol viscosity with which an application | coating process etc. are easy. From the viewpoint of the film forming property of plastisol, the strength and flexibility of the molded product, the more preferable content of the plasticizer is in the range of 70 to 150 parts by mass with respect to 100 parts by mass of the three-layer structure acrylic polymer particles.

  The plastisol of the present invention can be obtained by mixing the three-layer structure acrylic polymer particles of the present invention and a plasticizer.

  The mixing method is not particularly limited, and as the mixer, a vacuum defoaming planetary mixer, a disper, or the like can be used.

  Various additives can be blended in the plastisol of the present invention depending on the application. Specific examples of these additives include fillers such as calcium carbonate, aluminum hydroxide, baryta, clay, colloidal silica, mica powder, quartz sand, diatomaceous earth, kaolin, talc, bentonite, glass powder, aluminum oxide; titanium oxide , Carbon black and other pigments; diluents such as mineral terpenes and mineral spirits; antifoaming agents; antifungal agents; deodorants; antibacterial agents; surfactants; lubricants; benzophenone UV absorbers, benzotriazole UV absorbers or UV absorbers such as salicylate ester UV absorbers; fragrances; foaming agents; leveling agents; adhesives;

  The plastisol of the present invention is applied by a known method such as dipping, spraying, brush coating or doctor coating on a substrate such as a resin film or metal at a thickness of 5 μm to 5 mm, and gelled at 120 ° C. to 200 ° C. to be molded. You can get a body. Moreover, the molded object of various structures can also be obtained by gelatinizing in a suitable type | mold.

  Hereinafter, the present invention will be described in more detail with reference to examples. Parts and percentages in the examples are based on mass unless otherwise specified.

  In addition, the evaluation method of each characteristic of a three-layer structure acrylic polymer particle, an acrylic sol, and an acrylic sol molded body is as follows.

(1) Primary particle average particle diameter It measured using the laser diffraction scattering method particle size distribution measuring device LS-230 (made by Beckman Coulter).

(2) Viscosity of plastisol and storage stability of sol viscosity The viscosity of plastisol was measured using a Brookfield (BM) rotational viscometer [manufactured by Tokimec Co., Ltd.] under conditions of rotor No. 25 at 25 ° C. and relative humidity 60%. 4 was measured at a rotational speed of 60 (min ⁻¹ ).
The storage stability of the sol viscosity was evaluated as follows. That is, after preparing the plastisol, the viscosity was measured under the above conditions, and immediately thereafter, the plastisol was placed in a constant temperature bath at 40 ° C., taken out after 7 days, and left in an atmosphere of 25 ° C. and relative humidity 60% for 1 hour. The viscosity was expressed by an index obtained by dividing the viscosity by the viscosity immediately after the preparation of plastisol. The smaller this value, the better the storage stability of the sol viscosity.

(3) Bleed resistance of plasticizer After applying plastisol with a solid content of 50% obtained by mixing equal amounts of acrylic polymer particles and plasticizer on a glass plate to a thickness of 0.3 mm, hot air circulation A sheet was prepared by heating to 140 ° C. for 20 minutes in a furnace. The sheet was allowed to stand for 30 days in an atmosphere at a temperature of 25 ° C. and a relative humidity of 60%, and then visually observed and evaluated according to the following criteria.
○: No bleeding is observed.
Δ: Slight bleed is observed.
X: Bleed is observed.

(4) Sol dispersibility Ishikawa-type crusher No. 18 is charged with 200 g of the three-layer structure acrylic polymer particles of the present invention and 200 g of diisononyl phthalate at the same time, sol is formed, and the time required for sol is measured. Judgment was made according to the following criteria.
○: Sol is formed within 60 seconds.
Δ: Solized in more than 60 seconds and less than 120 seconds.
X: It takes 120 seconds or more for solification or does not sol.

(5) Adhesiveness to metal Resin / Plasticizer (Diisononyl phthalate (DINP)) A mixture of 100 parts / 80 parts was prepared, and an acrylic resin composition was formed on a steel sheet having a length of 150 mm, a width of 25 mm, and a thickness of 1.0 mm. Was applied to a thickness of 300 μm using a doctor blade, placed in an oven at a temperature of 140 ° C. for 30 minutes and then taken out, and the obtained sheet was used at a temperature of 23 ° C. at a temperature of 23 ° C. by a method according to JIS K 6854. Was measured at a peeling rate of 200 mm / min and evaluated according to the following criteria.
×: Less than 1.0 kN / m ○: 1.0 kN / m or more, less than 2.0 kN / m ◎: 2.0 kN / m or more

Example 1
The acrylic resin was manufactured by the following method.
In a stainless steel container, 50 parts by mass of a monomer mixture composed of 54% methyl methacrylate and 46% i-butyl methacrylate as a methacrylate monomer, 1.0 part by mass of sodium dodecylbenzenesulfonate as an emulsifier, and as a dispersant After adding 1.5 parts by mass of a higher alcohol having 18 carbon atoms and 0.3 parts by mass of benzoyl peroxide and 150 parts by mass of deionized water as a polymerization initiator, stirring and mixing at room temperature for 30 minutes, The mixture was homogenized under high shear to obtain a fine suspension having an oil phase particle size of 0.1 to 4 μm. After that, it was transferred to a stainless steel polymerization vessel with two-stage blades, and then polymerized with stirring at a polymerization temperature of 65 ° C. for 5 hours, and a polymerization rate of 95% or more was confirmed by the solid content concentration of the sampled reaction solution. As a result, a core polymer layer (A1) was obtained.

  Subsequently, 43 parts by mass of a monomer mixture consisting of 60% methyl methacrylate, 5% 2-hydroxyethyl methacrylate, and 35% i-butyl methacrylate was continuously added to the polymer container over 120 minutes. Even after completion of the monomer mixture addition, the temperature was maintained at 80 ° C. for 90 minutes to obtain an intermediate polymer layer (A2).

  After confirming that the polymerization conversion rate of the monomer mixture constituting the intermediate polymer layer (A2) was 95% or more, methyl methacrylate 43%, methacrylic acid 27%, methacrylic acid-i-butyl 30 7 parts by mass of the monomer mixture consisting of 15% is continuously added to the polymer container over 120 minutes, and polymerization is performed when the polymerization conversion rate of the monomer mixture constituting the outer shell polymer layer (A3) is 95% or more. Was terminated.

  A 3% aqueous potassium hydroxide solution was added to the obtained latex (polymer dispersion) and mixed at 23 ° C. for 10 minutes to adjust the pH of the latex to 7.0. The obtained latex was spray-dried in a nitrogen gas stream at 150 ° C. to obtain three-layer structure acrylic polymer particles. The primary average particle diameter of the obtained polymer particles was 2.2 μm. When the polymer particles were redispersed at a concentration of 30% in water having a pH of 7.0, the pH was 7.0.

  100 parts of the resulting three-layer structure acrylic polymer particles and 100 parts of diisononyl phthalate were put together in a vacuum defoaming planetary mixer, mixed for 10 minutes, and defoamed at the same time to prepare a plastisol. At this time, the sol-formation at the beginning of mixing was completed in 30 seconds. The viscosity of this plastisol was 8.1 Pa · s (25 ° C.). The storage stability of the sol viscosity was 1.8. In addition, no diisononyl phthalate bleed was observed after molding. Moreover, the adhesiveness to a metal was 1.0-2.0 kN / m.

Example 2
The composition of the monomer constituting the outer shell polymer layer (A3) is shown in Table 1, with 43% methyl methacrylate, 17% methacrylic acid, 30% methacrylic acid-i-butyl, and 10% glycidyl methacrylate. The three-layer structure acrylic polymer particles and plastisol were prepared in the same manner as in Example 1 except that the changes were made, and various evaluations were performed. The results are shown in Table 1.

Example 3
The composition of the monomer constituting the core polymer layer (A1) was changed to 54% methyl methacrylate, 36% i-butyl methacrylate, and 10% styrene as shown in Table 1, Three-layer structure acrylic polymer particles and plastisol were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

Comparative Example 1
Except that the composition of the monomer constituting the intermediate polymer layer (A2) was changed to 65% methyl methacrylate and 35% methacrylate-i-butyl as shown in Table 1, it was the same as in Example 1. Three-layer acrylic polymer particles and plastisol were prepared and subjected to various evaluations. The results are shown in Table 1.

Comparative Example 2
Same as Example 1 except that the composition of the monomer constituting the outer polymer layer (A3) was changed as shown in Table 1 to 59% methyl methacrylate and 41% i-butyl methacrylate. Three-layer structure acrylic polymer particles and plastisol were prepared and subjected to various evaluations. The results are shown in Table 1.

Comparative Example 3
The amount of the core polymer in Example 1 was reduced from 50 parts by weight to 30 parts by weight, and the amount of the outer shell polymer was increased from 7 parts by weight to 27 parts by weight. Acrylic polymer particles and plastisol were prepared. Since the bleed-out of the plasticizer was severe, a sheet for measuring adhesion to metal could not be produced. The results are shown in Table 1.

Comparative Example 4
The monomer composing the intermediate polymer layer of Example 1 and the monomer composing the outer polymer layer are mixed, and the monomer mixture is continuously added in the presence of the core polymer particles to perform polymerization. The outer shell polymer layer (in this case, there is no intermediate polymer layer, and the outer shell polymer layer becomes the second layer) was prepared in the same manner as in Example 1 to obtain a two-layer structure. Acrylic polymer particles and plastisol were prepared and subjected to various evaluations. The results are shown in Table 1.

From the results in Table 1, the following can be understood.
When 2-hydroxyethyl methacrylate was not used for the intermediate polymer layer (A2), the storage stability of the sol viscosity and the sol dispersibility were inferior (Comparative Example 1). When methacrylic acid is not used for the outer shell polymer layer (A3), the viscosity of the plastisol is large and the storage stability of the sol viscosity is inferior. Dispersibility and adhesion to metal were poor (Comparative Example 2). When the mass ratio of the core polymer layer (A1) / intermediate polymer (A2) / shell polymer layer (A3) is changed to 30/43/27, the viscosity of the plastisol is large and the plasticizer bleeds out. And sol dispersibility was inferior (Comparative Example 3). The intermediate polymer layer (A2) in Example 1 was not formed, but the monomer constituting it and the monomer constituting the outer shell polymer layer were mixed to obtain an outer shell polymer layer. In the case of acrylic polymer particles having a structure, the concentration of the monomer containing an organic acid group in the outer shell polymer layer was lowered, so that the adhesion to metal was inferior (Comparative Example 4).

On the other hand, the plastisol (Examples 1 to 3) using the three-layer structure acrylic polymer particles of the present invention has good plastisol viscosity, sol viscosity storage stability, and sol dispersibility, The plastisol molded product thus obtained did not bleed the plasticizer and had excellent adhesion to metal.

Claims (7)

A core polymer layer (A1) obtained by polymerizing the (meth) acrylic acid ester monomer (a1);
An intermediate polymer layer (A2) formed by polymerizing a (meth) acrylic acid ester monomer mixture (a2) containing a (meth) acrylic acid ester monomer having a hydroxyl group;
An outer polymer layer (A3) formed by polymerizing a (meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group,
The core polymer layer (A1) is 30 to 80% by mass, the intermediate polymer layer (A2) is 16 to 66% by mass, and the outer polymer layer (A3) is 4 to 9% by mass,
Three-layer structure acrylic polymer particles, wherein organic acid groups contained in the outer shell polymer layer (A3) are neutralized. The three-layer structure acrylic polymer particle according to claim 1, wherein the (meth) acrylic acid ester monomer mixture (a3) further contains a monomer having an epoxy group. The three-layer structure acrylic polymer particles according to claim 1 or 2, having a pH of 6.0 to 7.5 when redispersed at a concentration of 30% by mass in water of pH 7.0. A step of polymerizing the (meth) acrylic acid ester monomer (a1) to form 30 to 80 parts by mass of the core polymer layer (A1);
In the presence of the core polymer layer (A1), a (meth) acrylic acid ester monomer mixture (a2) containing a (meth) acrylic acid ester monomer having a hydroxyl group is polymerized to obtain 16 to 66 parts by mass. Forming an intermediate polymer layer (A2) and producing 91 to 96 parts by mass of a two-layer structure polymer;
In the presence of the two-layer structure polymer, a (meth) acrylic acid ester monomer mixture (a3) containing a monomer having an organic acid group is polymerized to obtain 4 to 9 parts by mass of an outer shell polymer layer Forming (A3) and producing 100 parts by mass of a three-layer polymer;
And a step of neutralizing an organic acid group contained in the outer shell polymer layer (A3). The three-layer structure acrylic polymer particle according to any one of claims 1 to 3, which is used for plastisol. A plastisol comprising the three-layer structure acrylic polymer particles according to claim 5 and a plasticizer. The plastisol according to claim 6, wherein the plasticizer is mainly composed of a dialkyl phthalate-based compound.