JPH0841236A - Production of polystyrene foam sheet - Google Patents

Abstract

PURPOSE:To obtain a polystyrene foam sheet which has good appearance with a high expansion rate without any adverse effect on its sheet properties by effecting foam extrusion molding of a PS resin using a specific foaming agent and a surfactant safely with markedly reduced loading to the environment. CONSTITUTION:(A) A PS resin is subjected to foam extrusion molding, as (B) a needed amount of water or a combination thereof with nitrogen for foaming and (C) a nonionic surfactant such as polyoxyethylene lauryl ether are used. Preferably, the component C has 12-18 HLB and its amount is 0.1-5.0wt.% based on the component A, while the amount of the water in the component B is 0.1-5.0wt.% based on the component A. The extrusion is carried out, for example, at a temperature of 160-170 deg.C in the extruder under a pressure of about 250kg/cm<2>G.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polystyrene foam sheet. More specifically, it relates to a method for producing a polystyrene foam sheet using an environment-friendly foaming agent composed of water or water and nitrogen.

[0002]

2. Description of the Related Art Conventionally, blowing agents such as lower aliphatic hydrocarbons and halogenated hydrocarbons have been used. Since these foaming agents are compatible with the styrene resin, the resin viscosity is reduced. Therefore, the molten resin temperature can be lowered sufficiently. Also, when foaming by extruding into the atmosphere through a mold, the foaming agent dissolved in the styrene resin is vaporized, and at the same time, heat is taken from the styrene resin and the bubble film is solidified, so that a uniform independent Bubbles can be formed.

However, these blowing agents such as lower aliphatic hydrocarbons and halogenated hydrocarbons have problems in handling such as destruction of the ozone layer of the earth and easy ignition. Therefore, as a foaming agent for the production of polystyrene-based resin foam, gas or water having low solubility in polystyrene-based resin such as nitrogen, which does not cause environmental problems and has no safety problem, is used. Many attempts have been reported.

However, when extrusion molding is carried out using nitrogen as a foaming agent, since the nitrogen has a low compatibility with the polystyrene resin, the temperature of the molten resin cannot be lowered sufficiently, and the uniform dispersion and heat of vaporization of the foaming agent. There arises a problem that the essential items for producing a high-multiplied product, that is, the solidification of a bubble film by using it, are insufficient. On the other hand, when water is extrusion-molded using a foaming agent, water is hardly soluble in polystyrene resin as in the case of nitrogen, and therefore the same problem as nitrogen occurs. Further, immediately after molding, the vaporized water is liquefied, which causes a problem that the foamed sheet shrinks or the bubbles become coarse.

Therefore, it has been difficult to produce a sheet having a beautiful appearance with a foaming ratio of about 10 times or more by using nitrogen or water alone as a foaming agent. In addition, Japanese Patent Laid-Open No. 3-1114
Japanese Patent No. 33 reports a method for producing a foaming material using nitrogen and alcohol as a foaming agent. However, it is known that a foaming agent containing alcohol has poor foamability, and it is difficult to increase the foaming ratio. In addition, there are safety problems such as the smell of alcohol remaining in the foam and the risk of ignition.

[0006]

Thus, according to the present invention, extrusion foam molding is performed by using, in a polystyrene resin, an amount of water required for foaming or a foaming agent consisting of water and nitrogen and a nonionic surfactant. A method for manufacturing a polystyrene foam sheet is provided. The polystyrene resin that can be used in the present invention is not particularly limited as long as it can be foam-molded. For example, in addition to styrene homopolymer, styrene and butadiene (for example, HI
Resin), a copolymer of styrene and acrylonitrile, a copolymer of styrene and methyl methacrylate, a terpolymer of acrylonitrile, butadiene and styrene, and the like. It is also possible to use mixtures of these. Further, a mixture with polyethylene, butyl rubber or the like can be used.

The styrene resin may contain a flame retardant, a coloring agent, an antistatic agent, a bubble control agent, etc. within a range that does not impair its physical properties. Examples of the flame retardant include tricresyl phosphate, chlorinated paraffin, antimony oxide, monoammonium phosphate, boric acid and the like, and examples of the colorant include azo type, anthraquinone type, thioindigo type, quinoline type and indanthrene type. Dyes, phthalocyanine-based, quinacridone-based, benzidine-based organic pigments, oxides of various metals, sulfides, inorganic pigments such as sulfates, and the like, and as the antistatic agent, inorganic salts, polyhydric alcohols, metals Examples thereof include compounds and carbon, and examples of the air bubble modifier include talc and the like.

In the present invention, a foaming agent composed of water or water and nitrogen is used. Here, when water is used as a foaming agent, since water has a large heat of vaporization, the vaporization removes heat from the styrene resin, and the bubble film is solidified,
Uniform, independent bubbles can be formed. The amount of water required for foaming in the present invention, relative to the styrene resin,
0.10 to 5.0% by weight, preferably 0.10 to 2.0
% By weight. When it is 0.10% by weight or less, it hardly forms a foam. Also, in the case of 5.0% by weight or more,
Problems such as poor dispersion, non-foaming, and coarse bubbles occur.

Further, when nitrogen is used as a foaming agent, the gaseous nitrogen serves as both a nucleating agent and a foaming agent, so that the bubbles can be made finer. However, a sheet foamed with only nitrogen is brittle and the sheet itself is easily broken. Therefore, when used in combination with water, brittleness becomes weak and flexibility can be improved. When used in combination, 0.10 to 5.0% by weight and 0.10 to 1.50% by weight of water and nitrogen, preferably 0.10 to 2.
0 wt% and 0.10 to 0.65 wt% are added.

Further, in the present invention, it was surprisingly found that by adding a nonionic surfactant, a sheet having a high expansion ratio and a beautiful appearance can be obtained even if the above-mentioned foaming agent is used. This means that nonionic surfactants
Since it has the function of increasing the affinity with water and uniformly adhering water to the styrene resin, it can prevent the water from separating from the styrene resin and stably extrude a sheet with fine bubbles. It is thought that it can be done.

Nonionic surfactants that can be used in the present invention are, for example, alkyl and alkylallyl polyoxyethylene ethers (more specifically, single chain polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, polyoxyethylene secondary alcohol ethers, Oxyethylene alkyl phenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, etc.), alkylallyl formaldehyde condensed polyoxyethylene ether (more specifically, ethylene oxide derivative of alkylphenol formalin condensate, etc.), polyoxyethylene poly Oxypropylene block polymer, ether type such as polyoxyethylene polyoxypropyl alkyl ether, polyoxyethylene ether of glycerin ester (more specifically, Xyloxyethylene glycerin fatty acid ester, polyoxyethylene castor oil and hydrogenated castor oil, etc.), polyoxyethylene sorbitan fatty acid ester, etc., ether ester type such as polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester , Ester type such as sorbitan fatty acid ester, propylene glycol fatty acid ester and sucrose fatty acid ester, and nitrogen-containing type such as fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine and amine oxide. Among the above, the nonionic surfactant is more preferably a single chain polyoxyethylene alkyl ether, and particularly preferably polyoxyethylene lauryl ether or polyoxyethylene tridecyl ether.

Among the above nonionic surfactants, HLB
(Hydrophillie-Lipophile Bal
It is particularly preferable to use a nonionic surfactant having an ance of 12 to 18, particularly 14 to 17. HL
When B is 18 or more and 12 or less, it is not preferable because the water of the foaming agent cannot be separated from the styrene resin and extruded.

The blending ratio of the nonionic surfactant is 0.1 to 5.0% by weight, preferably 0.2 to 2.0% by weight, based on the polystyrene resin. Within this range, although depending on the foaming conditions, a sheet of 2.5 to 20 times can be easily obtained. Here, when the blending ratio is 0.1% by weight or less, water is separated from the styrene resin, the foam cannot be slipped and extruded in the extruder, or water vaporized immediately after molding is liquefied and foamed. The sheet shrinks,
There arises a problem that the bubbles become coarse. Also,
If it is 5.0% by weight or more, poor dispersion may occur, resulting in coarse bubbles.

As the extrusion foam molding machine used in the manufacturing method of the present invention, any known apparatus can be used. For extrusion, the temperature inside the molding machine is 160 to 170 ° C., and the pressure is about 250 Kg.
/ Cm ² G conditions. According to the method of the present invention described above, the thickness is 0.5 to 3.0 mm, and the bubble diameter is 0.08 to 0.3.
mm, density 5.0 × 10 ^{-2 to} 2.6 × 10 ^-1 g / cm ³
The polystyrene foam sheet can be obtained.

[0015]

In the method for producing a polystyrene foam sheet of the present invention, the polystyrene foam resin is extruded and foam-molded using the amount of water required for foaming or a foaming agent consisting of water and nitrogen and a nonionic surfactant. Therefore, an environment-friendly foaming agent can be used without impairing the properties of the sheet.

Further, the nonionic surfactant has an HLB of 12 to 18, and the nonionic surfactant is used in an amount of 0.1 to 5.0% by weight based on the polystyrene resin. The polystyrene foam sheet is extruded and foamed without being separated from the resin.

[0017]

【Example】

Example 1 Polystyrene resin (manufactured by Denki Kagaku Co., Ltd., trade name: HRM)
-3-200, melt index: 0.7) 80 parts by weight, HI resin (Nippon Steel Chemical Co., Ltd., trade name: Estyrene S-61, melt index: 2.5) 20 parts by weight,
1.0 parts by weight of talc and 16 of HLB as a foam control agent
0.2 parts by weight of polyoxyethylene lauryl ether was mixed and the resulting mixture was supplied from a hopper of a tandem extruder (manufactured by Mitsubishi Heavy Industries, Ltd.) having a diameter of φ50-φ65, and 50 g of water (liquid) was supplied. Supplied from the tip of φ50 at a discharge rate of 20 kg / hr (extrusion pressure of 300 kg / cm
³ G), when extruded at a temperature of 165 ° C. in the extruder, the expansion ratio was 4.0 times, the thickness was 1.0 mm, and the cell diameter was 0.1.
A sheet having a smooth appearance of 6 mm was obtained.

Example 2 Polyoxyethylene lauryl ether having an HLB of 16 was used in an amount of 0.4 parts by weight, and a water injection amount of 100 g / h.
Extrusion was carried out under the same conditions as in Example 1 except that r was used.
The obtained sheet had a foaming ratio of about 7.0 times and a thickness of 1.
The sheet had a smooth appearance of 2 mm and a bubble diameter of 0.20 mm.

Example 3 A polyoxyethylene lauryl ether having an HLB of 16 was used in an amount of 0.6 parts by weight, and a water injection amount was 200 g / h.
Extrusion was carried out under the same conditions as in Example 1 except that r was used.
The obtained sheet has a foaming ratio of about 12 times and a thickness of 1.6.
mm, and the bubble diameter was 0.25 mm, and the sheet had a smooth appearance.

Example 4 Extrusion was carried out under the same conditions as in Example 3 except that nitrogen was further injected at 50 g / hr. The obtained sheet was a sheet having a smooth appearance with a foaming ratio of about 16 times, a thickness of 2.5 mm, and a cell diameter of 0.26 mm. Example 5 Extrusion was carried out under the same conditions as in Example 3 except that nitrogen was further injected at 100 g / hr. The obtained sheet had a foaming ratio of about 20 times, a thickness of 3.8 mm, and a cell diameter of 0.28 mm.
The sheet had a smooth appearance.

Example 6 Extrusion was carried out under the same conditions as in Example 1 except that 0.2 part by weight of polyoxyethylene tridecyl ether having an HLB of 12.6 was used. The obtained sheet has an expansion ratio of 3.
The sheet had a smooth appearance with a thickness of about 8 times 0.9 mm and a bubble diameter of 0.18 mm.

Example 7 Extrusion was carried out under the same conditions as in Example 5 except that 0.6 part by weight of polyoxyethylene tridecyl ether having HLB of 12.6 was used. The obtained sheet has an expansion ratio of 14
The sheet had a smooth appearance with a double thickness of 1.8 mm and a bubble diameter of 0.30 mm.

Comparative Example 1 Extrusion was carried out under the same conditions as in Example 1 except that polyoxyethylene lauryl ether was not used. However, since the water separated from the styrene in the cylinder of the extruder, the styrene resin slipped and extrusion could not be performed. Comparative Example 2 Extrusion was performed under the same conditions as in Example 1 except that polyoxyethylene nonylphenyl ether having an HLB of 19 was used. However, since the water separated from the styrene in the cylinder of the extruder, the styrene resin slipped and extrusion could not be performed.

Comparative Example 3 Extrusion was carried out under the same conditions as in Example 1 except that polyoxyethylene octylphenyl ether having an HLB of 9.0 was used. However, since the water separated from the styrene in the cylinder of the extruder, the styrene resin slipped and extrusion could not be performed.

[0025]

Industrial Applicability The method for producing a polystyrene foam sheet of the present invention is an extrusion foam molding using a polystyrene resin with an amount of water required for foaming or a blowing agent consisting of water and nitrogen and a nonionic surfactant. Therefore, it is possible to use an environment-friendly foaming agent without impairing the properties of the sheet.

Further, the nonionic surfactant has an HLB of 12 to 18, and the nonionic surfactant is used in an amount of 0.1 to 5.0% by weight based on the polystyrene resin, whereby water is converted to styrene. The polystyrene foam sheet can be extruded and foamed without separating from the resin.

Claims (2)

[Claims] 1. A method for producing a polystyrene foam sheet, which comprises subjecting a polystyrene-based resin to a foaming agent comprising water or water and nitrogen in an amount necessary for foaming and a nonionic surfactant to perform extrusion foam molding. Law. 2. The nonionic surfactant has an HLB of 12
18. The method according to claim 1, wherein the nonionic surfactant is used in an amount of 0.1 to 5.0% by weight based on the polystyrene resin.