JP7603499B2 - Expandable suspension-type porous polyvinyl chloride resin powder and polyvinyl chloride plastisol composition - Google Patents

Description

The present invention relates to a foamable suspension-based porous polyvinyl chloride resin powder and a polyvinyl chloride plastisol composition containing such a foamable suspension-based porous polyvinyl chloride resin powder.

In recent years, it has become common to use tile carpets with sides of about 50 cm on the floors of office buildings (see, for example, Patent Document 1).
This tile carpet usually has an upper pile layer in which the carpet pile is embedded, and a backing layer for maintaining strength. The backing material used for this backing layer is often a vinyl chloride resin for paste processing, which has excellent gelling properties, because it can maintain strength even under low-temperature processing conditions. In addition, this backing layer usually contains an inorganic filler such as calcium carbonate to maintain strength.

JP 2018-110716 A

As mentioned above, the backing layer of tile carpets usually contains inorganic fillers, which causes the tile carpet products to be heavy. Therefore, foaming agents have been used to create a foamed resin layer, reducing the specific gravity and weight of the resin layer. However, when foaming agents are used, non-uniform foam cells (voids) are formed in the resin layer, and the appearance and functionality are not necessarily satisfactory.

The object of the present invention is to provide a foamable resin powder that enables fine and uniform foaming to be achieved, thereby enabling a lightweight foamed resin layer with uniform properties to be obtained, and a vinyl chloride-based plastisol composition that contains the same.

The inventors have found that the above problems can be solved by incorporating a thermally decomposable foaming component into the pores of a suspension-type porous polyvinyl chloride resin and using this foamable suspension-type porous polyvinyl chloride resin powder as part of a resin layer-forming material (plastisol composition), and have thus completed the present invention. That is, the weight of the resin layer can be reduced by foaming the thermally decomposable foaming component during heat molding, and further, the extremely fine and uniform foaming caused by gasification of the thermally decomposable foaming component in the pores can form uniform foam cells in the resin layer, thereby obtaining a foamed resin layer with uniform properties.

That is, the present invention is as follows.
[1] An expandable suspension-type porous polyvinyl chloride resin powder, characterized in that the powder contains within its pores a heat-decomposable foaming component having a decomposition temperature of 100 to 220°C.
[2] The expandable suspension-type porous polyvinyl chloride resin powder according to [1], characterized in that the content of the thermally decomposable foaming component in the pores of the suspension-type porous polyvinyl chloride resin powder is an amount that generates 5 to 50 ml/g of thermal decomposition gas when heated at 220°C.
[3] The expandable suspension-type porous polyvinyl chloride resin powder according to [1] or [2], characterized in that the content of the thermally decomposable foaming component in the pores of the suspension-type porous polyvinyl chloride resin powder is 10 volume % or more relative to the pore volume of the suspension-type porous polyvinyl chloride resin powder.
[4] The expandable suspension-type porous polyvinyl chloride resin powder according to any one of [1] to [3], characterized in that the suspension-type porous polyvinyl chloride resin powder has a pore volume of 0.09 to 0.45 ml/g.

[5] A method for producing an expandable suspension-type porous polyvinyl chloride resin powder, comprising mixing a suspension-type porous polyvinyl chloride resin powder with a dispersion of a heat-decomposable foaming component having a decomposition temperature of 100 to 220°C under a heating temperature of 50°C or higher and lower than the decomposition temperature of the heat-decomposable foaming component, to produce the expandable suspension-type porous polyvinyl chloride resin powder according to any one of [1] to [4].
[6] The method for producing the expandable suspension-type porous polyvinyl chloride resin powder according to [5], characterized in that the dispersion medium of the dispersion liquid of the thermally decomposable foaming component having a decomposition temperature of 100 to 220°C is a plasticizer.
[7] A vinyl chloride-based plastisol composition comprising a vinyl chloride-based resin powder for paste processing, the expandable suspension-type porous vinyl chloride-based resin powder according to any one of [1] to [4], and a plasticizer.

[8] A method for producing a vinyl chloride foam layer, comprising coating the vinyl chloride plastisol composition according to [7] and then heating to foam the composition.
[9] The method for producing a vinyl chloride foamed layer according to [8], wherein the vinyl chloride foamed layer is a layer constituting a tile carpet.

By using a vinyl chloride plastisol composition containing the foamable suspension-based porous vinyl chloride resin powder of the present invention, a lightweight foamed resin layer with uniform properties can be obtained.

1 is a cross-sectional photograph of a foam layer produced in Example 1. 1 is a cross-sectional photograph of a foam layer produced in Example 2. 1 is a cross-sectional photograph of a foam layer produced in Example 12. 1 is a cross-sectional photograph of a foam layer produced in Comparative Example 1. 1 is a cross-sectional photograph of a foam layer produced in Comparative Example 2.

[Foamable suspension-based porous polyvinyl chloride resin powder]
The expandable suspension-type porous polyvinyl chloride resin powder of the present invention is characterized in that it contains a thermally decomposable foaming component having a decomposition temperature of 100 to 220° C. in the pores of the suspension-type porous polyvinyl chloride resin powder.

(Suspension-type porous polyvinyl chloride resin powder)
The suspension-based porous vinyl chloride resin in the present invention is a vinyl chloride resin consisting of porous irregular particles obtained mainly by suspension polymerization, and is also called a general-purpose vinyl chloride resin. Such suspension-based porous vinyl chloride resins include homopolymers of vinyl chloride as well as copolymers mainly made of vinyl chloride. Mainly made of vinyl chloride means, for example, that vinyl chloride is 50% by mass or more of the total, preferably 70% by mass or more, and more preferably 90% by mass or more.

Examples of monomers that can be copolymerized with vinyl chloride include olefin compounds such as ethylene and propylene; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; unsaturated monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, and N,N-dimethylaminoethyl methacrylate; unsaturated amides such as acrylamide and methacrylamide; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated dicarboxylic acids such as maleic acid and fumaric acid; esters and anhydrides of these; N-substituted maleimides; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; and vinylidene compounds such as vinylidene chloride.

The suspension-based porous vinyl chloride resin of the present invention can be obtained by polymerizing vinyl chloride alone or a monomer mixture consisting of vinyl chloride and an unsaturated monomer copolymerizable therewith by a conventionally known method. For example, it can be obtained by suspension polymerization. By appropriately setting various reaction conditions such as temperature, type and amount of dispersant, and stirring speed, a resin with the desired particle size, pore volume (porosity), and polymerization degree can be obtained.

Suspension-type porous polyvinyl chloride resins generally have an average particle size (D50) of about 50 to 200 μm, preferably 70 to 180 μm, and more preferably 100 to 150 μm.
The average particle size (D50) is shown as the 50% passing diameter using a JIS Z8801 sieve according to JIS Z8815 (dry sieving test method).

The suspension-type porous vinyl chloride resin has a low specific gravity because it is porous. The pore volume of this suspension-type porous vinyl chloride resin is preferably 0.09 to 0.45 ml/g, more preferably 0.15 to 0.40 ml/g, and even more preferably 0.20 to 0.40 ml/g. By using a suspension-type porous vinyl chloride resin having a pore volume in this range as a part of a vinyl chloride plastisol composition (resin layer forming material) described later, a lightweight, homogeneous, and well-balanced foamed resin layer can be obtained.
The pore volume can be determined by mercury intrusion method (porosimeter).

The average degree of polymerization of the suspension porous vinyl chloride resin is preferably 600 to 1700, more preferably 700 to 1500, and even more preferably 800 to 1300. By using a suspension porous vinyl chloride resin having an average degree of polymerization in this range as part of a vinyl chloride plastisol composition described below, a sol composition having good handleability and a desired viscosity can be obtained, and sufficient strength can be obtained in the formed resin layer.
This average degree of polymerization is calculated by converting the reduced viscosity (K value) measured in accordance with the measurement method of the Vinyl Chloride Resin Test Method (published by the PVC Industry and Environment Association in April 2003) in accordance with JIS K7367-2 using the approximate formula: K value = 20.42 * Ln (degree of polymerization) - 74.93.

(Thermolybdic foaming component)
The pores of the suspension-based porous polyvinyl chloride resin powder contain a thermally decomposable foaming component having a decomposition temperature of 100 to 220° C. This thermally decomposable foaming component gasifies during heat molding of the resin layer, causing fine foaming, making it possible to reduce the weight of the resin layer. In addition, the thermally decomposable foaming component supported in the fine pores gasifies to cause very fine and uniform foaming, so that uniform foam cells are formed in the resin layer, and a foamed resin layer with uniform properties can be obtained.

The thermally decomposable foaming component used in the present invention is not particularly limited as long as it is a component that decomposes and foams at 100 to 220°C, and may be an organic foaming component or an inorganic foaming component. Examples of organic foaming components include dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), p,p'-oxybisbenzenesulfonylhydrazide (OBSH), hydrazodicarbonamide (HDCA), azobisisobutyronitrile (AIBN), etc. Examples of inorganic foaming components include sodium bicarbonate (sodium bicarbonate) and sodium borohydride. These foaming components can be used in appropriate combinations, such as organic components together, inorganic components together, or organic and inorganic components together.

The decomposition temperature of the thermally decomposable foaming component may be any temperature at which the component decomposes at the heat molding temperature of the resin layer, and as described above, in the present invention, the decomposition temperature is 100 to 220° C., but preferably 120 to 210° C. In addition, since the use of a kicker component in combination with the thermally decomposable foaming component can lower the thermal decomposition temperature of the thermally decomposable foaming component and achieve foaming properties at low temperatures, it is preferable to use a kicker component in combination. Examples of the kicker component include metal oxides such as zinc oxide, magnesium oxide, and lead oxide, metal fatty acids such as zinc stearate, barium stearate, and calcium stearate contained in a heat stabilizer, and urea compounds.
By appropriately combining with a kicker component, the decomposition temperature of the thermally decomposable foaming component is preferably adjusted to 120 to 180°C, more preferably 140 to 160°C.

The content of the thermally decomposable foaming component in the pores of the suspension-type porous polyvinyl chloride resin powder (per 1 g of resin) is preferably an amount that generates 5 to 50 ml/g of thermal decomposition gas when the expandable suspension-type porous polyvinyl chloride resin powder is heated to 220° C., more preferably an amount that generates 10 to 50 ml/g of thermal decomposition gas, and even more preferably an amount that generates 20 to 50 ml/g of thermal decomposition gas. By using a content that can generate gas in this range, a light, homogeneous, and more well-balanced foamed resin layer can be obtained.
The amount of pyrolysis gas generated is measured by thoroughly heating the suspension-type porous polyvinyl chloride resin powder at 220° C. and measuring the amount of gas generated using a measuring device such as a gas burette.

In addition, the content of the thermally decomposable foaming component relative to the pore volume of the suspension-based porous polyvinyl chloride resin powder is preferably 10% by volume or more, more preferably 15% by volume or more, even more preferably 20% by volume or more, and particularly preferably 30% by volume or more. The upper limit of the content is not particularly limited, and is preferably less than 100% by volume, and more preferably 95% by volume or less. By having the content in this range, a light, homogeneous, and more well-balanced foamed resin layer can be obtained, as described above.
The content of the thermally decomposable foaming component relative to the pore volume is calculated using the amount of the thermally decomposable foaming component introduced, the amount of the thermally decomposable foaming component present outside the pores, the pore volume of the resin powder, and the density of the thermally decomposable foaming component. Specifically, as shown in the examples.

In addition, a portion of the thermally decomposable foaming component may be present outside the pores, such as on the surface of the resin powder (particles), but from the viewpoint of enabling fine foaming, it is preferable that most of it is present inside the pores. For example, the thermally decomposable foaming component present outside the pores is preferably 50% by mass or less of the thermally decomposable foaming component present inside the pores, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

(Method for producing expandable suspension-type porous polyvinyl chloride resin powder)
The expandable suspension-type porous polyvinyl chloride resin powder can be produced by mixing a suspension-type porous polyvinyl chloride resin powder with a dispersion of a thermally decomposable foaming component having a decomposition temperature of 100 to 220°C under a heating temperature of 50°C or higher and lower than the decomposition temperature of the thermally decomposable foaming component.

Considering that the foamable suspension-based porous vinyl chloride resin powder is used by blending it with a vinyl chloride-based plastisol composition for forming a resin layer, it is preferable to use a plasticizer used in the vinyl chloride-based plastisol composition as the dispersion medium. Details of the vinyl chloride-based plastisol composition and the plasticizer will be described later. In addition, organic solvents other than plasticizers may be used. Examples of organic solvents include toluene, cyclohexane, 2-methylhexane, normal heptane, cycloheptane, normal octane, 2,2,4-trimethylpentane, ethanol, 1-butanol, 2-butanol, t-butyl alcohol, 1-propanol, 2-propanol, 2-pentanol, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,4-dioxane, ethyl acetate, butyl acetate, propyl acetate, isopropyl acetate, methyl propionate, ethyl propionate, isopropyl propionate, methyl butyrate, methyl isobutyrate, ethyl isobutyrate, 2-butanone, 2-pentanone, 3-pentanone, and 4-methyl-2-pentanone.

In this manufacturing method, it is preferable to use a high-concentration dispersion of the thermally decomposable foaming component and heat mix it in order to facilitate penetration and support of the thermally decomposable foaming component into the pores of the suspension-type porous polyvinyl chloride resin powder.

The concentration of the thermally decomposable foaming component (and kicker component) in the thermally decomposable foaming component dispersion is, for example, preferably 40 to 70% by mass, and more preferably 50 to 60% by mass.

The heating temperature during mixing is not particularly limited as long as it is 50°C or higher and lower than the decomposition temperature of the thermally decomposable foaming component, as described above. However, from the viewpoint of allowing the thermally decomposable foaming component to penetrate more smoothly into the pores, it is preferably 60°C or higher, and more preferably 80°C or higher.

The thermally decomposable foaming component (and kicker component) is preferably one having a small particle size, for example, smaller than the average pore size of the suspension-type porous polyvinyl chloride resin powder. In other words, it is preferable to use a commercially available component having a small particle size so that it can easily penetrate into the pores of the foamable suspension-type porous polyvinyl chloride resin powder, or to crush the component before heating and mixing with the foamable suspension-type porous polyvinyl chloride resin powder.

By producing a foamable suspension-type porous polyvinyl chloride resin powder under the appropriate conditions as described above, it is possible to support preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more of the thermally decomposable components added within the pores.

It is also preferable to wash the foamable suspension-based porous polyvinyl chloride resin powder produced as described above with a dispersion medium (plasticizer) or the like to remove the thermally decomposable foaming components adhering to the outer surface of the powder. This ensures that the thermally decomposable foaming components are present only within the pores of the resin powder, allowing for finer and more uniform foaming during the heat molding of the resin layer.

On the other hand, when used by blending with a vinyl chloride plastisol composition for forming a resin layer, it may be used without washing from the viewpoint of production efficiency. Even if used without washing, by producing a foamable suspension-type porous vinyl chloride resin powder under appropriate conditions as described above, most of the thermally decomposable foaming component is supported within the pores, and a homogeneous foam layer that can withstand practical use can be formed.

[Vinyl chloride plastisol composition]
The vinyl chloride plastisol composition of the present invention is characterized by containing the vinyl chloride resin powder for paste processing, the expandable suspension-type porous vinyl chloride resin powder explained above, and a plasticizer.

The vinyl chloride plastisol composition of the present invention can form a resin layer that is lightweight and has uniform properties. That is, by using the foamable suspension-type porous vinyl chloride resin of the present invention, which contains a thermally decomposable foaming component in the pores, in combination with a vinyl chloride resin for paste processing, foaming is possible due to gasification of the thermally decomposable foaming component during heat molding, and the specific gravity can be reduced to achieve weight reduction. In addition, the gasification of the thermally decomposable foaming component present in the pores produces fine and uniform foaming, so a homogeneous resin layer with uniform foam cells can be formed.

The vinyl chloride plastisol composition of the present invention preferably contains 10 to 50 mass %, more preferably 20 to 40 mass %, and even more preferably 25 to 35 mass % of the expandable suspension porous vinyl chloride resin powder. By containing the expandable suspension porous vinyl chloride resin powder in this range, it is possible to suppress an increase in viscosity and obtain a sol that is easy to handle. In addition, when a resin layer is formed, the resin layer can be sufficiently lightened and sufficient strength can be obtained.

(Vinyl chloride resin powder for paste processing)
The porous vinyl chloride resin for paste processing in the present invention is a vinyl chloride resin consisting of non-porous spherical fine particles obtained mainly by emulsion polymerization (including seeded emulsion polymerization) or fine suspension polymerization (including seeded fine suspension polymerization). The vinyl chloride resin powder for paste processing used in the vinyl chloride plastisol composition of the present invention may be a vinyl chloride homopolymer or a copolymer mainly composed of vinyl chloride, similar to the foamable suspension porous vinyl chloride resin powder explained above.

The vinyl chloride resin powder for paste processing of the present invention can be obtained by polymerizing vinyl chloride alone or a monomer mixture consisting of vinyl chloride and an unsaturated monomer copolymerizable therewith by a conventionally known method. For example, it can be obtained by emulsion polymerization (including seeded emulsion polymerization) or fine suspension polymerization (including seeded fine suspension polymerization).

The polyvinyl chloride resin powder for paste processing is generally a fine particle having an average primary particle diameter (D50) of 0.1 to 10 μm. The average particle diameter (D50) is preferably 0.1 to 5.0 μm, and more preferably 0.5 to 3.0 μm.
The average particle diameter (D50) means a particle diameter at 50% on a cumulative volume distribution curve in which the total volume of the particle size distribution determined on a volume basis is taken as 100%, i.e., a volume-based cumulative 50% diameter. The particle size distribution can be determined by a laser diffraction/scattering type particle size distribution measuring device (for example, LA-960 manufactured by Horiba, Ltd.).

The average degree of polymerization of the polyvinyl chloride resin powder for paste processing is preferably 600 to 1700, and more preferably 900 to 1500. This average degree of polymerization is calculated in the same way as for the suspension-type porous polyvinyl chloride resin powder.

(Plasticizer)
In the vinyl chloride plastisol composition of the present invention, any of the plasticizers known in the art for vinyl chloride plastisols can be used.

In the present invention, for example, phthalic acid derivatives such as dibutyl phthalate, di-(2-ethylhexyl) phthalate, di-n-octyl phthalate, diisobutyl phthalate, diheptyl phthalate, diphenyl phthalate, diisodecyl phthalate, diundecyl phthalate, butyl benzyl phthalate, dinonyl phthalate, and dicyclohexyl phthalate; isophthalic acid derivatives such as di-(2-ethylhexyl) isophthalate, diisooctyl isophthalate, and diisononyl phthalate; tetrahydrophthalic acid derivatives such as di-(2-ethylhexyl) tetrahydrophthalate, di-n-octyl tetrahydrophthalate, and diisodecyl tetrahydrophthalate; adipic acid derivatives such as di-n-butyl adipate, di-(2-ethylhexyl) adipate, diisodecyl adipate, and diisononyl adipate; azelaic acid derivatives such as di-n-butyl sebacate and di-(2-ethylhexyl) sebacate; maleic acid derivatives such as di-n-butyl maleate, dimethyl maleate, diethyl maleate and di-(2-ethylhexyl) maleate; di-n-butyl fumarate and di-(2-ethylhexyl) fumarate; fumaric acid derivatives such as fumaric acid ester, tri-(2-ethylhexyl) trimellitate, tri-n-octyl trimellitate, triisodecyl trimellitate, triisooctyl trimellitate, tri-n-hexyl trimellitate, triisononyl trimellitate, etc.; pyromellitic acid derivatives such as tetra-(2-ethylhexyl) pyromellitate, tetra-n-octyl pyromellitate, etc.; triethylene Citric acid derivatives such as ethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, and acetyl tri-(2-ethylhexyl) citrate; itaconic acid derivatives such as monomethyl itaconate, monobutyl itaconate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, and di-(2-ethylhexyl) itaconate; oleic acid derivatives such as butyl oleate, glyceryl monooleate, and diethylene glycol monooleate; ricinoleic acid derivatives such as glyceryl monoricinoleate and diethylene glycol monoricinoleate; stearic acid derivatives such as glycerin monostearate and diethylene glycol distearate; other fatty acid derivatives such as diethylene glycol monolaurate, diethylene glycol dipelargonate, and pentaerythritol fatty acid esters; triethyl Phosphoric acid derivatives such as phosphate, tributyl phosphate, tri-(2-ethylhexyl) phosphate, triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, and tris(chloroethyl) phosphate; glycol derivatives such as diethylene glycol dibenzoate, dipropylene glycol dibenzoate, triethylene glycol dibenzoate, and dibutylmethylene bisthioglycolate; glycerin derivatives such as glycerol monoacetate, glycerol triacetate, and glycerol tributyrate; polyester plasticizers such as adipic acid polyesters, sebacic acid polyesters, and phthalic acid polyesters; or partially hydrogenated terphenyls, adhesive plasticizers; and even polymerizable plasticizers such as diallyl phthalate, acrylic monomers, and oligomers.

Among these, phthalate ester-based plasticizers are preferred. These plasticizers may be used alone or in combination of two or more. The amount of plasticizer to be used may be selected appropriately depending on the application, but is preferably 30 to 150 parts by weight, more preferably 50 to 120 parts by weight, per 100 parts by weight of vinyl chloride resin.

(Other ingredients)
In the vinyl chloride plastisol composition of the present invention, in addition to the vinyl chloride resin powder for paste processing, the expandable suspension-type porous vinyl chloride resin powder, and the plasticizer, various other components may be blended in. Examples of the other components include a heat stabilizer, a filler, a foaming agent, a foaming accelerator, a viscosity regulator, an adhesion imparting agent, a colorant, a diluent, an ultraviolet absorber, an antioxidant, and a reinforcing agent.

The vinyl chloride plastisol composition of the present invention is a sol with a relatively low viscosity, and the optimum viscosity varies depending on the molding method, but from the viewpoints of handling and adhesiveness, it is preferably 2000 to 13000 mPa·s, and more preferably 3000 to 12000 mPa·s. This viscosity is measured by the measurement method shown in the examples.

[Method of producing vinyl chloride plastisol composition]
The vinyl chloride plastisol composition of the present invention can be produced by mixing the vinyl chloride resin powder for paste processing, the expandable suspension porous vinyl chloride resin powder, and the plasticizer, and other components as necessary. The vinyl chloride resin for paste processing, the expandable suspension porous vinyl chloride resin, and the plasticizer can be mixed in any order. That is, the three components can be mixed simultaneously, or two components can be mixed and then the remaining component can be mixed.

[Method of manufacturing vinyl chloride foam layer]
The method for producing a vinyl chloride-based foam layer of the present invention is characterized in that the vinyl chloride-based plastisol composition of the present invention is applied to a substrate or the like, and then heated to foam. In the production method of the present invention, fine bubbles are generated during heating and foaming, so that the foam layer produced becomes a light and homogeneous layer. The heating temperature is not particularly limited as long as it is a temperature at which the vinyl chloride-based plastisol composition of the present invention melts and the thermally decomposable foaming component decomposes, but is, for example, 120 to 250°C, and preferably 150 to 200°C.

Specific examples of the vinyl chloride foam layer include layers that make up tile carpets, such as the backing layer and adhesive layer of tile carpets. Other examples include layers that make up wall materials, floor materials, and leather.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Example 1]
<Production of Expandable Suspension-Type Porous Polyvinyl Chloride Resin Powder>
80 g of di-(2-ethylhexyl)phthalate (DOP, manufactured by J-Plus Co., Ltd.) as a dispersion medium, 20 g of a Ba-Zn-based stabilizer (BZ-100CJ, manufactured by Katsuta Kako Co., Ltd.) as a kicker component, and 80 g of a foaming agent (ADCA, Vinihol AC#3-K2, manufactured by Eiwa Kasei Kogyo Co., Ltd.) as a thermally decomposable foaming component were charged into a mortar, and mixed while grinding the foaming agent with a mortar for 30 minutes to prepare a foaming agent dispersion.

Thereafter, 400 g of suspension-type porous polyvinyl chloride resin powder (ZEST 1700ZI (Shin-Dai-Ichi Vinyl Co., Ltd.), internal pore volume 0.37 ^cm3 /g) was added to a 2 L Henschel mixer (manufactured by Mitsui Miike Machinery Works, Ltd.), and then the entire amount of the blowing agent dispersion prepared above was added while stirring at a rotation speed of 1000 rpm. The jacket was heated to raise the temperature to 90°C and then cooled to room temperature.

In order to remove the foaming agent present on the outside (external surface, etc.) of the internal pores of the foamable suspension-type porous polyvinyl chloride resin powder produced above, 100 g of DOP was added to 100 g of foamable suspension-type porous polyvinyl chloride resin, and filtered through a 500 mesh (opening diameter 25 μm) wire mesh. Furthermore, by subjecting the mixture to a centrifuge at 1000 rpm for 2 minutes, a foamable suspension-type porous polyvinyl chloride resin powder with the foaming agent supported in the internal pores was obtained.

<Production of Vinyl Chloride Plastisol Composition>
Into a 1 L plastic cup, 70 g of vinyl chloride resin for paste processing (ZEST PQ135 (Shin Daiichi Vinyl Co., Ltd.)), 45 g of the foamable suspension-type porous vinyl chloride resin powder produced above (containing 30 g of ZEST 1700ZI), 142 g of DOP (total amount including DOP in the foamable suspension-type porous vinyl chloride resin powder was 150 g), 2 g of Ba-Zn-based stabilizer (BZ-100CJ, Katsuta Kako Co., Ltd.), and 300 g of calcium carbonate (Kansui #70, Nitto Funka Kogyo Co., Ltd.) were added, and the mixture was stirred at 600 rpm for 10 minutes using a mechanically controlled stirrer to produce a vinyl chloride-based plastisol composition.

<Production of vinyl chloride foam layer>
The vinyl chloride plastisol composition was coated onto a stainless steel plate (thickness 0.8 mm) with a doctor blade to a thickness of 1 mm, and immediately heated in a Geer oven at 200° C. for 5 minutes to obtain a foam layer (foam-molded sheet).

[Example 2]
The same procedure as in Example 1 was repeated, except that the amount of foaming agent used when supporting the foaming agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to 140 g.

[Example 3]
The same procedure as in Example 1 was repeated, except that the jacket heating condition for supporting the blowing agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to 60°C.

[Example 4]
The same procedure as in Example 1 was repeated, except that the jacket heating condition for supporting the blowing agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to 30°C.

[Example 5]
The same procedure as in Example 1 was repeated, except that the plasticizer used to support the blowing agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to diisononyl phthalate (DINP).

[Example 6]
The same procedure as in Example 1 was repeated, except that the plasticizer used for supporting the blowing agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to di-(2-ethylhexyl) adipate (DOA).

[Example 7]
The same procedure as in Example 1 was repeated, except that the blowing agent supported in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to p,p'-oxybisbenzenesulfonylhydrazide (OBSH).

[Example 8]
The same procedure as in Example 1 was repeated, except that the suspension-type porous polyvinyl chloride resin powder (ZEST 1700ZI) carrying the blowing agent was changed to ZEST 1000Z (Shin-Dai-Ichi Vinyl Co., Ltd., internal pore volume 0.27 cm ³ /g).

[Example 9]
The same procedure as in Example 1 was repeated, except that the dispersion medium used to support the blowing agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to toluene (an organic solvent).

[Example 10]
The same procedure as in Example 1 was repeated, except that the amount of foaming agent used when supporting the foaming agent in the internal pores of the suspension-type porous polyvinyl chloride resin powder was changed to 10 g.

[Example 11]
The same procedure as in Example 1 was repeated, except that the suspension-type porous polyvinyl chloride resin powder (ZEST 1700ZI) carrying the blowing agent was changed to ZEST 700L (Shin-Dai-Ichi Vinyl Co., Ltd., internal pore volume 0.09 cm ³ /g).

[Example 12]
The same procedure as in Example 2 was repeated, except that no treatment was carried out to remove the foaming agent present outside the internal pores of the suspension-type porous polyvinyl chloride resin powder carrying the foaming agent.

[Comparative Example 1]
The same procedure as in Example 1 was repeated except that no foaming agent was supported in the internal pores of the suspension-type porous polyvinyl chloride resin powder, and when producing the polyvinyl chloride plastisol, 100 g of polyvinyl chloride resin powder for paste, 150 g of DOP, 5.4 g of ADCA, 3.5 g of Ba-Zn stabilizer, and 300 g of calcium carbonate were added and stirred for 10 minutes at 600 rpm using a mechanically controlled stirrer to produce a polyvinyl chloride plastisol composition.

[Comparative Example 2]
In Example 1, a foaming agent was not supported in the internal pores of the suspension-type porous polyvinyl chloride resin powder, and when producing a polyvinyl chloride plastisol, 70 g of a paste-use polyvinyl chloride resin, 30 g of a suspension-type porous polyvinyl chloride resin, 150 g of DOP, 5.4 g of ADCA, 3.5 g of a Ba-Zn-type stabilizer, and 300 g of calcium carbonate were added, and the mixture was stirred at 600 rpm for 10 minutes using a mechanically controlled stirrer to produce a polyvinyl chloride plastisol composition, except that the same procedure as in Example 1 was used.

The following measurements and evaluations were carried out on the expandable suspension-based porous polyvinyl chloride resin powder, polyvinyl chloride-based plastisol composition, and polyvinyl chloride-based foam layer (foam-molded sheet) according to the above-mentioned Examples 1 to 12 and Comparative Examples 1 and 2.

(Pore volume of expandable suspension-type porous polyvinyl chloride resin powder)
The measurement was performed using a mercury intrusion pore distribution measuring device (porosimeter).

(Amount of pyrolysis gas generated from expandable suspension-type porous polyvinyl chloride resin powder)
10 g of foamable suspension-type porous polyvinyl chloride resin powder carrying a foaming agent in its internal pores was placed in a three-neck flask, and then 30 g of liquid paraffin was added, followed by heating to 220° C. in an oil bath. After heating at 220° C. for 20 minutes, the amount of gas generated was measured using a gas burette.

(Blowing agent content relative to pore volume of suspension-type porous polyvinyl chloride resin powder (volume fraction φ))
The volume fraction φ was calculated from the following formula.

Volume fraction φ (%) = (mb-ma)/ρ/v

In the formula, "ma" is the mass (g) of the pyrolyzable foaming component outside the pores recovered by centrifugation, "mb" is the theoretical value (g) of the pyrolyzable foaming component contained in 100 g of blowing agent-supported suspension-type porous polyvinyl chloride resin powder (amount added per 100 g of resin powder), "v" is the pore volume ( ^cm3 /g) per 1 g of suspension-type porous polyvinyl chloride resin powder, and "ρ" is the density (g/ ^cm3 ) of the pyrolyzable foaming component (ρ = 1.50 for both ADCA and OBSH).

(Viscosity of Vinyl Chloride Plastisol Composition)
The plastisol composition was allowed to stand for 1 hour in an atmosphere of 23° C. and 50% RH, and then thoroughly mixed, and the viscosity was measured using a Brookfield viscometer (LVDV-3T, manufactured by Eiko Seiki Co., Ltd.) rotor No. 4 at 60 rpm.

(Expansion ratio of foam layer)
The center of the foam-molded sheet was punched out with a 4 cm square die, and the cross section of the foam-molded sheet was magnified and observed with a CCD camera, and the average value of the distance between two points in the thickness direction was recorded as the thickness L. The thickness of the coating layer (before foaming) was regarded as _L0 , which was obtained by the above-mentioned measurement method for a molded sheet obtained by heating for 5 minutes in an oven with an internal temperature of 140°C, and the expansion ratio was calculated as L/ _L0 .

(Specific gravity of foam layer)
The foamed sheet was punched out with a 4 cm square (16 cm ² ) die, and the mass was measured with a precision balance. The volume was calculated by multiplying the surface area by the thickness calculated in the measurement of the foaming ratio, and the mass was divided by the volume to calculate the specific gravity.

(Tensile strength of foam layer)
The tensile strength was measured by preparing a dumbbell-shaped tensile test piece from the foam-molded sheet and measuring the tensile strength with an autograph (AGS-H manufactured by Shimadzu Corporation). The tensile strength test sample used was a No. 2 type test piece, and the test was performed at a test speed of 200 mm, and the average value of n=5 was calculated.

(Cross-section evaluation of foam layer)
The cross section of the foam layer (foam-molded sheet) was observed at a magnification of 50 times with a CCD camera, and the denseness of the foam layer was evaluated according to the following criteria.

⊚: Extremely dense and uniform foam cells.
◯: Somewhat dense and uniform foam cells are present.
Δ: Somewhat coarse or non-uniform foam cells are present.
×: Coarse foam cells are present.

The above results are shown in Tables 1 to 3. Figures 1 to 5 show cross-sectional photographs of the foam layers of Examples 1, 2, and 12, and Comparative Examples 1 and 2.

As shown in Tables 1-2 and Figures 1-3, by using the vinyl chloride plastisol compositions of Examples 1-12, a foam layer with a high expansion ratio and low specific gravity was produced, and dense, uniform foam cells were formed in the produced foam layer, resulting in a uniform foam layer. The tensile strength was also sufficiently high. Furthermore, the viscosity of the plastisol composition was low, making it easy to handle.

The amount of pyrolysis gas generated by the resin powder of Example 2 was 43.1 ml/g, and the amount of pyrolysis gas generated by the resin powder of Example 12 was 54.3 ml/g. From these results, it can be seen that the amount of pyrolysis foaming component present on the outside (outer surface) of the internal pores of the resin powder in Example 12 was 26.0% of the amount of pyrolysis foaming component supported in the internal pores. Example 12, in which the pyrolysis foaming component is present on the resin powder surface, had inferior foam cell properties compared to Example 2, but was sufficiently practical.

On the other hand, as shown in Table 3 and Figures 4 to 5, when a thermally decomposable foaming component was added to the plastisol composition without using a suspension-based porous polyvinyl chloride resin powder as in Comparative Example 1, or when a foaming component was not included in the suspension-based porous polyvinyl chloride resin powder and a thermally decomposable foaming component was added to the plastisol composition as in Comparative Example 2, coarse and non-uniform foam cells were formed in the produced foam layer.

INDUSTRIAL APPLICABILITY The vinyl chloride plastisol composition of the present invention is industrially useful since it can be used for forming a backing layer of a tile carpet, etc.

Claims (8)

A thermally decomposable foaming component having a decomposition temperature of 100 to 220°C is contained in the pores of a suspension-type porous polyvinyl chloride resin powder having an average particle size (D50) of 50 to 150 μm,
The content of the thermally decomposable foaming component in the pores of the suspension-type porous polyvinyl chloride resin powder is an amount that generates 20 to 50 ml/g of thermal decomposition gas when heated at 220°C.
1. A foamable suspension-type porous polyvinyl chloride resin powder comprising: 2. The expandable suspension-type porous polyvinyl chloride resin powder according to claim 1, characterized in that the content of the thermally decomposable foaming component in the pores of the suspension-type porous polyvinyl chloride resin powder is 10 volume % or more relative to the pore volume of the suspension-type porous polyvinyl chloride resin powder. 3. The expandable suspension-type porous polyvinyl chloride resin powder according to claim 1, characterized in that the pore volume of the suspension-type porous polyvinyl chloride resin powder is 0.09 to 0.45 ml/g. A method for producing an expandable suspension-type porous polyvinyl chloride resin powder, comprising mixing a suspension-type porous polyvinyl chloride resin powder with a dispersion of a heat-decomposable foaming component having a decomposition temperature of 100 to 220°C under a heating temperature of 50°C or higher and lower than the decomposition temperature of the heat-decomposable foaming component, to produce the expandable suspension-type porous polyvinyl chloride resin powder according to any one of claims 1 to 3 . The method for producing the expandable suspension-type porous polyvinyl chloride resin powder according to claim 4, characterized in that the dispersion medium of the dispersion liquid of the thermally decomposable foaming component having a decomposition temperature of 100 to 220°C is a plasticizer. A vinyl chloride-based plastisol composition comprising a vinyl chloride-based resin powder for paste processing, the expandable suspension-type porous vinyl chloride-based resin powder according to any one of claims 1 to 3 , and a plasticizer. 7. A method for producing a vinyl chloride foamed layer, comprising coating the vinyl chloride plastisol composition according to claim 6 and then heating to foam the composition. 8. The method for producing a vinyl chloride foamed layer according to claim 7 , wherein the vinyl chloride foamed layer is a layer constituting a tile carpet.