JPH0138807B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel vinyl chloride resin foam composition. The basic method of making sponges or foams of chlorine-containing resins, such as vinyl chloride, from plastisols using emulsion-polymerized resins is well known. Many such methods involve the use of chemical blowing agents, such as those of the azodicarbonamide type, to foam plastisols that have already been heated and melted. Conventionally, it has been difficult to increase the expansion ratio while controlling the density and cell size of resin foams molded from plastisol. When foaming materials are heated to gel and foam, cells often coalesce or break, resulting in cavities, large irregularities, layer cracks, loss of elasticity, and an irregular cell structure. In order to avoid such disadvantages, attempts have been made to incorporate various foaming aids. For example, a foaming aid that changes the decomposition temperature of a chemical foaming agent to effectively foam it is called a blower, and includes metal salts of organic acids such as salicylic acid, stearic acid, and phthalic acid, particularly zinc salts, and zinc oxide. However, a satisfactory high foaming ratio has not yet been achieved. As a result of intensive research aimed at improving this problem, the present inventors discovered a polyvinyl chloride foam composition that maintains thermal stability, has a fine and uniform cell structure, and has a high expansion ratio, leading to the present invention. That is, the present invention provides a vinyl chloride resin foaming composition containing zinc oxide having an average particle size of 0.27 microns or less in a plastisol containing an emulsion-polymerized vinyl chloride resin, a plasticizer, and a blowing agent. The zinc oxide used in the present invention with an average particle diameter of 0.27 microns or less is much finer than that commercially available, and is obtained by a special manufacturing method such as a rapid oxidation method. By adding the zinc oxide, a product with an unprecedentedly high expansion ratio can be obtained. In the present invention, the emulsion polymerized vinyl chloride resin includes polyvinyl chloride homopolymer, vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-maleate ester copolymer or vinyl chloride-fumarate ester copolymer etc. can be mentioned. Plasticizers that can be added to the present invention include phthalate esters such as diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, aliphatic dibasic acid esters such as dioctyl adipate and dioctyl sebacate, and diphenyl phosphate. Phosphate esters such as 2-ethylhexyl, fatty acid esters such as ethyl stearate and butyl oleate, polyhydric alcohol esters such as glycerin toacetate and pentaerythritol stearate, epoxy plasticizers, polyester plasticizers,
Examples include chlorine plasticizers. In addition to the above-mentioned auxiliaries, additives used in actual foaming include metallic heat stabilizers such as Ca, Mg, Ba, Al, Sr, Sn, Na, and K, fillers, flame retardants, mold release agents,
Coloring agents, antioxidants, crosslinking agents, ultraviolet absorbers, epoxy compounds, etc. can be optionally added. Example 1 A composition with the following formulation was spread on a glass plate to a thickness of 0.3 mm and left in a gear oven at 170°C for 1 minute to prepare a cure sheet.
The foam was placed in a gear oven kept at 220°C and the foaming state was measured every hour. The expansion ratio was calculated by measuring the thickness of the sheet. The results are shown in Table 1. <Composition> PVC (Geon 121) 100 parts DOP 80 Azodicarbonamide 3 Barium stearate 0.5 Zinc oxide from Table 1 3

[Table] *No. 1 is Comparative Example Example 2 The foaming state of the composition with the following formulation was measured in the same manner as in Example 1, and the influence of the types of zinc oxide and foaming agent was investigated. <Composition> PVC (Geon 121) 100 parts DOP 80 Foaming agent 3 Zinc oxide 3

[Table] From the above results, it was found that a high expansion ratio could be obtained when azodicarbonamide was used as a foaming agent and zinc oxide of 0.27 microns or less was blended. Example 3 In order to examine the effects of different vinyl chloride resins, sheets were prepared by kneading the following compositions at a roll temperature of 150° C. for 5 minutes. This was placed in a gear oven maintained at 220° C. and the expansion ratio was measured every hour. The results are shown in Table 3. <Composition> PVC 100 parts DOP 80 Azodicarbonamide 3 Zinc oxide 3

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Claims (1)

[Claims] 1. A highly foamable vinyl chloride resin composition comprising an emulsion polymerized vinyl chloride resin, a plasticizer, and a plastisol containing azodicarbonamide as a blowing agent, containing zinc oxide with an average particle size of 0.27 microns or less. .