JP2006316098A - Acrylic polymer microparticle for plastisol, and acrylic plastisol composition and molded form using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide acrylic polymer microparticles for plastisol, capable of obtaining molded forms including films that enable environmental pollution to be reduced in undergoing disposal by incineration and are excellent in foamability, compression recovery, alkali resistance, water resistance, etc. <P>SOLUTION: The acrylic polymer microparticles for plastisol contain 10 wt.% or more of molecules each with a weight-average molecular weight of 100,000 or lower determined by GPC. An acrylic plastisol composition is also provided, comprising the above microparticles, a foaming agent that generates a gas under heating, and a plasticizer. The molded forms are such as to be obtained by using the above acrylic plastisol composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acrylic polymer fine particle for plastisol that can be mixed with a plasticizer to obtain a plastisol, an acrylic plastisol composition, and a molded body using the same. More specifically, by not containing a halogen-based polymer such as vinyl chloride, it is possible to suppress environmental contamination, have good foamability, and provide a film having excellent compression recovery and water resistance. The present invention relates to a molded body such as coalesced fine particles, an acrylic plastisol composition, and a film using the same.

  A sol-like material in which fine particles (powder) of a thermoplastic resin are dispersed in a plasticizer is called a plastisol, and is used when a coating film or a molded body is produced. Since plastisol has high fluidity at room temperature, it is easy to apply and cast, and when heated, it gels in a short time to give a coating film or molded product. Various physical properties such as softness and rubber elasticity required for the molded body are controlled by the blending amount such as the amount of plasticizer. Taking advantage of these characteristics, plastisol is widely used in various industrial fields, and typical examples include vinyl chloride plastisol (hereinafter abbreviated as vinyl chloride sol) using vinyl chloride resin and acrylic resin. An acrylic plastisol (hereinafter abbreviated as “acrylic sol”) may be mentioned.

  Of these, vinyl chloride sol has recently been highlighted as an environmental pollution problem derived from chlorine atoms, and its use is regarded as a problem. For example, when incinerating PVC sol products, hydrogen chloride gas is generated, which may damage the incinerator and cause acid rain. On the other hand, acrylic sols are attracting attention as materials that replace vinyl chloride sols because they do not contain chlorine atoms, are easy to incinerate, and have little environmental impact. However, in the case of acrylic sol, it has been pointed out that various performances that could be realized with vinyl chloride sol cannot be satisfactorily realized. For example, in the foaming field such as wallpaper and cushion floors, it has been pointed out that acrylic sol has a low foaming rate, an insufficient compression recovery rate, and foamed cells are coarse and low in quality.

Various improvements have been made to such acrylic sols, and a plastisol with good foamability has been reported by mixing a vinyl chloride polymer and an acrylic polymer (Patent Document 1). However, this plastisol requires a vinyl chloride polymer, which is insufficient as a drastic measure against environmental pollution. Moreover, the foam decoration sheet which comprised the foaming layer using the plastisol containing an acrylic polymer with an average molecular weight of less than 1 million is reported (patent document 2). As a result, the foamability itself is improved, but if it remains as it is, there are problems such as stickiness of the surface and insufficient film strength, and it is essential to use an acrylic resin having a high molecular weight as a top coat. Further, an acrylic sol composition that improves foamability using a powdery acrylic resin and a liquid low molecular weight acrylic polymer has been proposed (Patent Document 3). Although this certainly improves the foamability itself, there are also problems such as stickiness of the surface and bleeding out of the liquid polymer. Furthermore, the plastisol which is excellent in foaming strength by specifying the composition of an acrylic resin is proposed (Patent Document 4). However, in this case, among the polymers having a core / shell structure, the composition of the shell polymer has a very high acid value, which causes a problem that foamability is lowered and alkali resistance and water resistance are poor.
Japanese Patent Publication No. 5-38014 Japanese Patent Laid-Open No. 10-24536 JP 2002-128936 A JP 2002-194027 A

  The present invention does not contain a halogen-based polymer, can reduce environmental pollution at the time of disposal by incineration, has a significant effect on global environmental protection, Acrylic polymer fine particles for plastisol and acrylic plastisol composition that can improve the meltability of acrylic polymer fine particles and obtain molded products such as films with excellent foamability, compression recovery property, alkali resistance, water resistance, etc. The object is to provide a molded article using the same.

  As a result of intensive studies on the above problems, the present inventors have found that the above-mentioned physical properties greatly depend on the molten state of the polymer fine particles in the acrylic sol, and the molten state is closely related to the molecular weight distribution of the fine particles. It has been found that the reason why conventional acrylic sols have poor meltability during heating is due to the fact that they contain a large amount of high molecular weight components. By containing fine particles containing an acrylic copolymer having a specific molecular weight distribution, an acrylic plastisol composition capable of producing a molded article excellent in foaming property, compression recovery property, water resistance, etc. is obtained. As a result, the present invention has been completed based on such knowledge.

  That is, the gist of the present invention is acrylic polymer fine particles for plastisol characterized by containing 10% by mass or more of molecules having a weight average molecular weight of 100,000 or less by GPC measurement.

  The present invention does not contain a halogen-based polymer, can reduce environmental pollution at the time of disposal by incineration, has a significant effect on global environmental protection, By improving the meltability of the acrylic polymer fine particles, it is possible to obtain a molded body such as a film excellent in foaming property, compression recovery property, alkali resistance, water resistance and the like.

  The acrylic polymer fine particle for plastisol of the present invention is not particularly limited as long as it contains 10% by mass or more of molecules having a weight average molecular weight of 100,000 or less by GPC measurement method, but has a multilayer structure. It is preferable that the core part and the shell part have a core / shell structure containing an acrylic polymer in each. The core portion improves the storage stability of the acrylic plastisol composition (acrylic sol composition) used together with the plasticizer, and also causes the plasticizer to bleed out in a film or molded product obtained by thermoforming the acrylic sol composition. In order to suppress, it is constituted by an acrylic copolymer having a composition compatible with the plasticizer, and the shell portion is constituted by an acrylic copolymer having a composition incompatible with the plasticizer. preferable.

  The acrylic polymer contained in the core part and the shell part each contains an alkyl (meth) acrylate unit of C2 or more, a methyl (meth) acrylate unit, and a monomer unit that can be copolymerized if necessary. Is preferred. Specific examples of monomers that can be used to obtain C2 or higher alkyl (meth) acrylate units as the monomer units include ethyl (meth) acrylate, n-butyl (meth) acrylate, and i-butyl. (Meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylates of linear alkyl alcohols such as octyl (meth) acrylate, or cyclohexyl (meth) acrylate And (meth) acrylates of cyclic alkyl alcohols such as

  As a monomer for obtaining a monomer unit contained if necessary in the acrylic polymer contained in the core part and the shell part, as the acid group-containing monomer, methacrylic acid, acrylic acid, itaconic acid, Crotonic acid, maleic acid, fumaric acid, methacrylic acid 2-succinoloyloxyethyl, carboxyl group-containing monomers such as 2-hexahydrophthaloyloxyethyl, sulfonic acid group-containing monomers such as allyl sulfonic acid, 2- (meth) Mention may be made of phosphoric acid group-containing (meth) acrylates such as acryloxyethyl acid phosphate. By containing these acid-containing monomer units, the storage stability of the acrylic sol composition can be improved. Such an acid-containing monomer unit is preferably copolymerized in the shell portion, and in addition, in the acrylic polymer constituting the shell, the copolymerization ratio is preferably 10% by mass or less, and more preferably 5% by mass. The following is more preferable. If the content in the acrylic polymer constituting the shell is 10% by mass or less, a high foaming ratio can be obtained in a molded product produced using the acrylic polymer fine particles, and excellent water resistance, Has alkali resistance.

  In addition to this, monomers having various functional groups for obtaining a copolymerizable monomer if necessary include hydroxyl groups such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Group containing (meth) acrylates, carbonyl group containing (meth) acrylates such as acetoacetoxyethyl (meth) acrylate, amino group containing such as N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate (Meth) acrylates and the like can be mentioned.

  In addition, the acrylic polymer contained in the core part and the shell part may contain a monomer unit that forms a cross-linkage as necessary. Polyfunctional monomers such as polyfunctional (meth) acrylates such as (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, etc. Can be mentioned. However, the degree of crosslinking needs to be within a range where the polymer can be sufficiently melted by the plasticizer and formed into a gelled film, and the content of the monomer unit that generates crosslinking in the acrylic polymer is 0. It is preferable that it is 1 mass% or less.

  Furthermore, examples of the auxiliary monomer that forms a monomer unit that the acrylic polymer may contain as necessary include acrylamide and derivatives thereof. Specifically, diacetone acrylamide, N -Methylol acrylamide, N-methoxymethyl acrylamide, N-ethoxymethyl acrylamide, N-butoxymethyl acrylamide, (meth) acrylonitrile, etc. can be mentioned. Furthermore, special monomers such as styrene and its derivatives, vinyl acetate, urethane-modified acrylates, epoxy-modified acrylates, and silicone-modified acrylates can also be used as the structural unit of the acrylic polymer. However, the monomer that can be used as the monomer for forming the structural unit of the acrylic polymer is not limited to the above examples.

  The C2 or higher alkyl (meth) acrylate unit contained in the acrylic polymer contained in the core part and the shell part of the acrylic polymer fine particles for plastisol of the present invention is the entire acrylic copolymer contained in the core part and the shell part. The content is preferably in the range of 10 to 70% by weight, and more preferably 20 to 50% by weight for the improvement of the compression recovery and the storage stability of the sol composition. The methyl (meth) acrylate unit contained in the acrylic polymer contained in the core part and the shell part is contained in the range of 90 to 30% by weight with respect to the whole acrylic copolymer contained in the core part and the shell part. Further, it is more preferably 80 to 50% by weight from the viewpoints of compression recovery and storage stability of the sol composition. Furthermore, the monomer unit contained in the acrylic polymer, which is copolymerized as necessary, is contained in the range of 0 to 50% by weight with respect to the whole acrylic copolymer contained in the core part and the shell part. The content of 0 to 30% by weight is preferable because it does not significantly affect the storage stability of the sol composition, and the physical properties such as the expansion ratio and the compression recovery property.

  Moreover, it is preferable that the acrylic polymer fine particles contain a monomer having a functional group that generates a cross-linking bond when heated in the core part and / or the shell part. Whether the cross-linking bond is formed in the acrylic polymer fine particles or between the fine particles, the functional group in the fine particles reacts with the compound blended in the acrylic sol composition. It doesn't matter. Furthermore, it is preferable that the crosslink bonds of these acrylic polymers are generated for the first time when the acrylic sol composition is heated and melted to form a molded product. If a cross-linking bond is already formed in the acrylic polymer fine particles before the acrylic sol composition is heated and melted to form a molded product, the meltability of the acrylic polymer fine particles is reduced, and the strength of the molded product is reduced. It is because foamability will fall. On the other hand, if this crosslinked bond is produced for the first time when the molded body is molded by heating and melting, not only high-quality and fine cells are formed, but the strength of the molded body is increased, and further, the formation of the crosslinked bond is increased. At this time, since the molded article slightly shrinks, the surface gloss of the coating film and the molded product is suppressed, and a matte surface can be obtained. For this reason, as a functional group which produces | generates a crosslinking bond by heating, what has the production temperature of a crosslinking bond in the temperature range higher than the foaming temperature of a foaming agent is preferable.

  The temperature for generating the cross-linked bond is preferably in the range of 130 to 250 ° C, more preferably in the range of 180 ° C to 200 ° C. When the heating temperature is 130 ° C. or higher, the acrylic polymer fine particles are sufficiently melted, and a high expansion ratio can be obtained in the molded product.

  Preferable examples of the functional group that generates a cross-linking bond upon heating include methylol cross-linking typified by N-butoxymethylacrylamide, cross-linking by glycidyl group and carboxyl group, cross-linking by glycidyl group and hydrazide group, and by carboxyl group and hydroxyl group Crosslinking, hydroxyl group and isocyanate group, acetoacetoxy group and melamine, etc. can be mentioned. Moreover, the functional group which produces | generates these bridge | crosslinking bonds is an acrylic polymer by copolymerizing the monomer which has these functional groups with said C2 or more alkyl (meth) acrylate and methyl (meth) acrylate. These functional groups may be incorporated into an aggregate latex containing acrylic copolymer fine particles obtained by copolymerization with the above-mentioned C2 or higher alkyl (meth) acrylate and methyl (meth) acrylate. You may introduce | transduce by melt | dissolving the monomer which has. Further, it may be introduced by a method of adding at the time of blending the acrylic sol composition.

  The acrylic polymer contained in the acrylic polymer fine particles of the present invention must contain 10% by mass or more of a component having a weight average molecular weight measured by GPC of 100,000 or less as a total of the core part and the shell part. is there. The content of components having a weight average molecular weight of 100,000 or less as measured by GPC is preferably 20% by mass or more, and more preferably 30% by mass or more. The reason is that the foamability of the plastisol containing the acrylic polymer fine particles of the present invention is remarkably improved because the acrylic polymer contains 10% by mass or more of components having a weight average molecular weight of 100,000 or less as a whole. be able to. On the other hand, the acrylic sol composition containing the acrylic polymer fine particles for plastisol of the present invention that the acrylic polymer contains a component having a weight average molecular weight of 100,000 or less as a total of the core part and the shell part of 90% by mass or less. It is preferable because the storage stability can be improved, more preferably 80% by mass or less.

  Examples of the method for producing the acrylic polymer of the present invention include an emulsion polymerization method, a soap-free polymerization method, a suspension polymerization method, a fine suspension polymerization method, and a dispersion polymerization method. Among these, the emulsion polymerization method or the soap-free polymerization method is preferable because the control at the time of preparing the core / shell structure is easy. The primary particles as acrylic polymer fine particles obtained by polymerization preferably have a particle size in the range of 400 nm to 1200 nm, and more preferably in the range of 600 nm to 1000 nm.

  The acrylic polymer fine particles of the present invention may be of any property or structure as a dry powder. For example, aggregated particles (secondary particles) in which a large number of primary particles obtained by the above polymerization are aggregated may be formed, or a higher order structure may be formed. However, in the case of such an agglomerated structure, it is preferable that the primary particles are not firmly bonded to each other and are loosely aggregated because the primary particles of the acrylic polymer are finely and uniformly dispersed in the plasticizer. .

  The acrylic polymer fine particles of the present invention need not be used alone, and may be a blend of two or more types of polymer fine particles obtained by different methods.

  The acrylic plastisol composition of the present invention is not particularly limited as long as it contains the acrylic polymer fine particles of the present invention, a foaming agent that generates gas upon heating, and a plasticizer. As such a foaming agent, a thermally decomposable foaming agent, a thermal expansion microcapsule in which a low-boiling hydrocarbon or the like is encapsulated in a shell made of a thermoplastic resin, and the like can be used.

  Specific examples of the heat decomposable foaming agent include azo heat decomposable foaming agents such as azodicarbondiamide, azobisisobutyronitrile, azobishexahydrobenzonitrile, azobisformamide, benzenesulfonylhydrazide, p. -Toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfonyl hydrazide) and other hydrazine-based heat decomposable foaming agents, N, N'-dinitrosopentamethylenetetramine, N, N'-dinitroso-N, N'-dimethyl A nitroso heat decomposable foaming agent such as terephthalamide can be mentioned.

Specific examples of the thermal expansion microcapsules include microballoons from Matsumoto Yushi Seiyaku Kogyo Co., Ltd., EXPANSEL from EXPANSEL, and Saran Microsphere from Dow Chemical.

  These foaming agents may be used alone or in combination of two or more. Further, zinc oxide can be used for the purpose of lowering the decomposition temperature of the heat decomposable foaming agent. Furthermore, the foaming agent may contain a foaming aid as necessary. As the foaming aid, additives having actions such as lowering the decomposition temperature of the foaming agent, accelerating the decomposition, and uniformizing the bubbles can be used. Specifically, organic acids such as salicylic acid, phthalic acid and stearic acid can be used. And so on.

  The content of the foaming agent can be 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the acrylic polymer fine particles for plastisol. The content of the foaming aid can be 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight with respect to 100 parts by weight of the acrylic polymer fine particles for plastisol.

  Examples of the plasticizer contained in the acrylic plastisol composition of the present invention include phthalic acid plasticizers such as diisononyl phthalate, di- (2-ethylhexyl) phthalate, diisodecyl phthalate, and butyl benzyl phthalate, and di- (2-ethylhexyl). ) Fatty acid ester plasticizers such as adipate, di-n-decyl adipate, di- (2-ethylhexyl) azelate, dibutyl sebacate, phosphate ester plasticizers such as tributyl phosphate, 2-ethylhexyl diphenyl phosphate, epoxidation Epoxy plasticizers such as soybean oil, other polyester plasticizers, benzoic acid plasticizers, and the like can be used. Any one of these plasticizers may be used alone, or two or more thereof may be used in combination. The content is particularly preferably 30 to 500 parts by weight, preferably 50 to 300 parts by weight, and more preferably 60 to 150 parts by weight with respect to 100 parts by weight of the acrylic polymer fine particles for plastisol. If the amount of plasticizer used is too large, bleeding out of the plasticizer from the final product may occur.

  The acrylic plastisol composition of the present invention may further include calcium carbonate, aluminum hydroxide, pearlite, clay, colloidal silica, mica powder, quartz sand, diatomaceous earth, kaolin, talc, bentonite, glass powder, aluminum oxide, fly as necessary. According to the purpose, fillers such as ash and shirasu balloon can be appropriately selected in terms of type and amount.

  In the acrylic plastisol composition of the present invention, if necessary, pigments such as titanium oxide and carbon black, diluents such as mineral terpenes and mineral spirits, antifoaming agents, antifungal agents, deodorants, antibacterial agents, Surfactants, lubricants, ultraviolet absorbers, fragrances, leveling agents, adhesives and the like can be freely blended.

  The molded article of the present invention is not particularly limited as long as it uses the acrylic plastisol composition of the present invention, but the foaming agent is foamed by heating the acrylic plastisol composition of the present invention. Thereafter, those formed by crosslinking an acrylic polymer are preferred. By foaming the foaming agent and then cross-linking the acrylic polymer, a large number of fine cells are formed, and the foam can be obtained with increased strength, and a molded product with reduced surface gloss can be obtained. it can.

  As such a molded body, it can be applied to a wide range including a field where a conventional vinyl chloride sol has been used. Specifically, tile carpet backing materials, cushion floors, wallpaper, steel plate paints, toys, food samples, shoes, building materials and other adhesives, various sealers, gaskets, automobile inner layer skin materials, synthetic leather, erasers and other foams However, it is not limited to these.

Hereinafter, the acrylic polymer fine particles, acrylic plastisol, and molded product of the present invention will be specifically described.
[Preparation of polymer (A)]
200 g of pure water is put into a 500 ml four-necked flask equipped with a thermometer, nitrogen gas inlet tube, stirring rod, dropping funnel, and cooling tube, and nitrogen gas is thoroughly bubbled for 30 minutes to replace dissolved oxygen in pure water. did. After stopping nitrogen gas ventilation, 2.0 g of methyl methacrylate and 1.0 g of n-butyl acrylate were added, and the temperature was raised to 80 ° C. while stirring at 200 rpm. When the internal temperature reached 80 ° C., 0.1 g of potassium persulfate dissolved in 5.0 g of pure water was added at once, and soap-free polymerization was started. Stirring was continued for 60 minutes at 80 ° C.

  Subsequently, a mixed solution in which a monomer (51 g of methyl methacrylate, 49 g of n-butyl methacrylate, 0.5 g of N-butoxymethylacrylamide) and an emulsifier (1.0 g of sodium dioctylsulfosuccinate) were uniformly dissolved as a first drop was added at 40 g / hr. Then, stirring was continued at 80 ° C. for 1 hour to obtain a polymer latex.

  Next, as a second drop, the monomer (86 g of methyl methacrylate, 14 g of n-butyl methacrylate, 0.5 g of N-butoxymethylacrylamide) and the emulsifier (1.0 g of sodium dioctylsulfosuccinate, 0.05 g of n-octyl mercaptan) are uniformly dissolved. The mixed liquid was dropped at a rate of 40 g / hr, and the stirring was continued at 80 ° C. for 1 hour to obtain a polymer latex.

After cooling the obtained polymer latex to room temperature, an inlet temperature of 170 ° C., an outlet temperature of 75 ° C., and an atomizer speed of 2 using a spray dryer (Okawara Kako Co., Ltd., L8 type).
The polymer (A) was obtained by spray drying at 5000 rpm.
[Preparation of polymer (B)]
The polymer composition was changed to the monomer composition shown in Table 1, and the polymer (B) was prepared in the same manner as in the case of the polymer (A) with the addition amount of the emulsifier to the monomer, the dropping rate of the monomer, and the spray drying conditions.
[Preparation of polymer (C)]
A polymer latex was obtained in the same manner as in the case of the polymer (A) except that the monomer composition shown in Table 1 was changed. 3 g of adipic acid dihydrazide was dissolved in the obtained polymer latex and spray-dried with a spray dryer to obtain a polymer (C).
[Preparation of polymers (D) to (F)]
Other than changing to the monomer composition shown in Table 1 and adding 0.05 g of n-octyl mercaptan, the amount of the emulsifier added to the monomer, the dropping rate of the monomer, the spray drying conditions, etc. are the same as those for the polymer (A). Similarly, polymers (D) to (F) were prepared.

[Measurement method of molecular weight]
It is the polystyrene conversion value by GPC method, and measured on condition of the following.
Sample Preparation Method Acrylic polymer fine particles were dissolved at a concentration of 0.3% by mass using tetrahydrofuran as a solvent. When insoluble matter was generated, it was centrifuged (15,000 rpm for 30 minutes), the supernatant solution was filtered through a PTFE 0.5 micron filter, and only the soluble matter was used for measurement.
Apparatus: Tosoh Co., Ltd., high-speed GPC apparatus HLC-8020
Column: manufactured by Tosoh Corporation, three TSKgelGMHXL connected in series Oven temperature: 38 ° C
Eluent: Tetrahydrofuran Sample concentration: 0.3% by mass
Flow rate: 1 mL / min Injection amount: 0.1 mL
Detector: RI (differential refractometer)
From the obtained GPC chart, the area ratio of the average molecular weight of 100,000 or less was obtained at 100 fraction with respect to the total average molecular weight distribution.
[Preparation of plastisol]
100 parts of polymer fine particles, 100 parts of diisononyl phthalate as a plasticizer, 20 parts of calcium carbonate (manufactured by Bihoku Powder Chemical Co., Ltd., trade name: [BF-200]), azodicarbonamide (Yewa Kasei Co., Ltd.) as a foaming agent Product name: Azo-based foaming agent [Binihol AC # 3C]) 3 parts, and 3 parts of zinc oxide as a foaming aid were added and defoamed with a vacuum mixer (ARV-200, manufactured by Shinky Corporation). (After mixing at atmospheric pressure for 10 seconds, the pressure was reduced to 20 mmHg and mixed for 90 seconds) to obtain a uniform plastisol composition.

[Preparation of foam]
A plastisol obtained by the above-described preparation was formed on a glass plate having a size of 150 mm × 150 mm and a thickness of 1 mm using a knife coater to form a 0.3 mm-thick coating film. Thereafter, it was preheated in an oven at 170 ° C. for 1 minute to obtain an unfoamed gelled product. Furthermore, this gelled product was heated at 200 ° C. for 3 minutes to decompose the foaming agent in the gelled product, thereby obtaining a foam.
[Examples 1-3, Comparative Examples 1-3]
Except for the acrylic polymer, plastisol was prepared by the same method. For the foams of Examples 1 to 3 and Comparative Examples 1 to 3 prepared by the same method, the expansion ratio, cell state, matte property, compression recovery The sex was evaluated as follows. Table 1 shows the results.
[Evaluation of foam]
[Foaming ratio]
The foamability of the plastisol coating film was evaluated according to the following criteria based on the value of (film thickness after foaming treatment) / (film thickness before foaming).

A: More than 4.0 B: 2.0 to 4.0
Δ: 1.5 to 2.0
X: 1.5 or less
[Uniformity of foamed cells]
The gelled product after foaming was cut with a razor until it reached the glass substrate, the cross section in the thickness direction was visually observed, and the cell state of the foam was evaluated according to the following criteria.

  A: Foamed cells are dense and uniform in size, and there are no large cells in which adjacent cells are combined.

  ○: The size of the foamed cells is almost uniform, but there are some sags and some vertically long cells. There is no large cell where adjacent cells merge.

  (Triangle | delta): The magnitude | size of a foaming cell is non-uniform | heterogenous, and it is comprised by the cell with a poor foaming, or the big cell which the cell which adjoined partly couple | bonded.

  X: The size of the foam cell is non-uniform, and a cell with poor foam, a large cell in which partially adjacent cells are combined, a large bulge, or the like is mixed.

[Matte]
Evaluation was made by measuring the value of 60 ° reflectance (%) with a gloss meter VG-1D manufactured by Nippon Denshoku Industries Co., Ltd. The smaller this value is, the better the matte property is, and the evaluation is based on the following criteria.

◎: 10 or less ○: 10-20
Δ: 20-30
X: 30 or more
[Recovery]
The compression recovery rate (%) of the foam was evaluated by a value of {(initial dent amount T ₀ ) − (residual dent amount T ₁ )} / (initial dent amount T ₀ ) × 100. In the formula, the initial dent amount T ₀ indicates the measured value of the dent amount after 10 minutes of load application by applying a load of 222 N for 5 minutes with a hemispherical steel rod with a tip of 20 mm in diameter on the foamed coating film. The dent amount T ₁ indicates the measurement of the dent amount 60 minutes after the load is removed. The higher the compression recovery rate (%), the better the compression recovery, and the evaluation was made according to the following criteria.

◎: 90 (%) or more ○: 80 to 90 (%)
Δ: 60-80 (%)
×: 60 (%) or less

MMA: methyl methacrylate nBMA: normal butyl methacrylate MAA: methacrylic acid GMA: glycidyl methacrylate acrylate WMA BMA: N-butoxymethyl acrylamide ADH: adipic acid dihydrazide Example 1 is N-butoxymethyl acrylamide as a crosslinkable monomer, Example 2 Is an example of copolymerization of glycidyl metaacrylate and methyl methacrylate. In any case, since a cross-linking bond was generated upon heating, the strength of the foam, that is, the compression recovery property was excellent, and the matte property due to cross-linking shrinkage was good. Furthermore, since each of the components having a weight average molecular weight of 100,000 or less contains 40% or more, the expansion ratio was very good.

  In Example 3, glycidyl methacrylate was copolymerized with acrylic polymer fine particles and adipic acid dihydrazide was added as a monomer that generates a cross-linking bond upon heating. Similar to Examples 1 and 2, the crosslinking reaction during heating was excellent in compression recovery and matting, and the foaming ratio was also good.

  Comparative Examples 1 and 3 are examples in which a component having a weight average molecular weight of 100,000 or less does not contain 10% or more, and a component that generates a crosslink during heating is not contained. Since the molecular weight is large, the meltability of the particles during heating becomes insufficient, a good expansion ratio cannot be obtained, and the heat-crosslinkable monomer is not included, so that the compression recovery rate is insufficient.

  Comparative Example 2 is an example in which a component having a weight average molecular weight of 100,000 or less does not contain 10% or more, and the copolymerization ratio of the carboxyl group-containing monomer unit to the shell polymer contains 10 mol% or more. As in Comparative Example 1, a good expansion ratio was not obtained, and the amount of the carboxyl group-containing monomer was large, so that the expanded cell was coarse and large bulge occurred.

  Comparative Example 4 is an example that does not contain 10% or more of a component having a weight average molecular weight of 100,000 or less and contains 40 mol% or more of an alkyl (meth) acrylate unit of C2 or more. As in Comparative Example 1, a good expansion ratio could not be obtained, and a sufficient compression recovery rate could not be obtained.

Claims (3)

Acrylic polymer fine particles for plastisol, comprising 10% by mass or more of molecules having a weight average molecular weight of 100,000 or less by GPC measurement. An acrylic plastisol composition comprising the acrylic polymer fine particles for plastisol according to claim 1, a foaming agent that generates a gas upon heating, and a plasticizer. A molded product comprising the acrylic plastisol composition according to claim 2.