JPS6289743A - Production of styrene resin foam - Google Patents

Abstract

PURPOSE:A styrene resin is mixed with sodium bicarbonate and monosodium citrate anhydride and foam-molded by extrusion or injection to give foamed products having uniformly fine cells and smooth surfaces. CONSTITUTION:In extrusion or injection foam-moldings, sodium bicarbonate and monosodium citrate anhydride are used as foaming agents. The weight ratio of sodium bicarbonate to monosodium citrate anhydride is 20/80-80/20, preferably 40/60-60/40.

Description

Detailed Description of the Invention The present invention produces a foam having a uniform fine cell structure in extrusion foam molding of styrene resin, and produces a foam with a smooth surface and internal foaming in injection foam molding. It is about the method.

Conventionally, mainly in extrusion foaming of styrene resin,
Propane, butane, pentane, hexane, as blowing agents
Non-reactive gases or volatile blowing agents such as Freon-113 have been used.

However, when using these blowing agents, the cell diameters are uneven and coarse regardless of the magnification of the foam, resulting in poor surface smoothness, so various improvements have been made.

For example, the following are bubble control agents (nucleating agents):
It has been added as.

■ Inorganic fillers such as talc [F] Inorganic carbonates or bicarbonates and organic weak acids such as sodium bicarbonate and citric acid (Japanese Patent Publication No. 40-1071
7) ■ Carbonate and citric acid monoalkali salt
731) ■ Acidic salts of polyhydric carboxylic acids (Special Publication No. 19712-1973)
However, in each of these methods of ■■0■, although it is recognized that the bubbles are made finer by adding them, the cell diameter is still large in both the low-magnification foam and the high-magnification foam (and the appearance is bad, In vacuum forming, the bubbles were large, so there were limits to its applications.

Therefore, as a result of various studies on the formation of fine cells in extruded foam beyond the various methods described above, we found that sodium bicarbonate and monosodium citrate anhydrous (C6H) were used as blowing agents.
7NaO□), compared to the foam molded product obtained by using a volatile blowing agent as the blowing agent in the conventional method and adding a cell regulator as listed in ■ to ■ above. It was found that the bubble size was one rank smaller. Even more unexpectedly, when sodium bicarbonate and monosodium citrate anhydride were used as blowing agents in injection foam molding of styrenic resins, azodicarbonamide and P,P'-oxybis(benzenesulfonyl hydrazide) An unexpected effect appeared: flow marks and swirls caused by foaming gas on the surface of molded products, which could not be solved using conventional pyrolytic foaming agents, were eliminated.

This smooth finish on the surface of the injection molded product had the great effect of reducing the number of times the surface was coated.

The purpose of the present invention is to uniformly refine the cells in extrusion foam molding of styrene resin to obtain a foam sheet with a smooth surface.In injection foam molding, only the inside of the molded product is foamed, and the surface is -The problem lies in not producing marks or swirls.

A feature of the practice of the process of the invention is the use of sodium bicarbonate and anhydrous monosodium citrate as blowing agents.

That is, in conventional extrusion foaming, a gas or a volatile foaming agent has been used as a foaming agent, and the above-mentioned ones have been added as a foam control agent.

Therefore, the process of the present invention differs from conventional processes in that the present invention does not use any gas or volatile blowing agent.

Naturally, the combination of sulfur bicarbonate and monosodium citrate anhydride used in the present invention generates gas when heated, but the gas generation occurs gradually and continuously. As a result of gas measurement, it was found that the process proceeds in two stages and that the amount of gas generated per unit weight is large.If a foaming agent with such gas generation state is used as a blowing agent, the resulting foam will have fine cells. It was found that it has a structure.

Figure 1 shows the gas evolution during temperature rise with a 50:50 combination of sodium bicarbonate and monosodium citrate anhydride (C6H7NaO /min.

In other words, Figure 1 shows that gas is mainly generated at 150 to 170"C.
and 190 to 220°C, and the gentle slope of the curve indicates that the decomposition rate is low.

In this way, especially in the case of extrusion foaming, a blowing agent that decomposes, generates gas, and supplies continuously and continuously generates fine bubbles at the processing temperature of the thermoplastic resin. This decomposition property is utilized not only as a regulating agent (nucleating agent) but also as an expanding agent.

The weight ratio of sodium bicarbonate and monosodium citrate anhydride used in the present invention is 20 to 80:80 to 20, preferably 40 to 6.
0:60-40.

The amount used is 100 parts by weight of styrene resin (hereinafter referred to as parts)
On the other hand, it is preferably 0.4 to 20 parts for extrusion foaming, and 0.2 to 5 parts for injection foam molding.

The blowing agent can be added to the styrenic resin by adding sodium bicarbonate and monosodium citrate anhydride separately (or adding them as a mixture). It is also possible to add a blend with a resin modifier such as methacrylic, a processing aid such as talc, waxes, stearates, etc.

The styrenic resin of the present invention refers to CP type polystyrene, HI type polystyrene, and acrylonitrile-butadiene-styrene copolymer (ABs) resin.

Example 1 050 mm, width 500 mm at the tip of an extruder with L/D = 22
Extrusion foaming was carried out using an apparatus equipped with a straight manifold T die of ffff. Polystyrene resin (
Dialex HT- manufactured by Mitsubishi Monsando Kasei Co., Ltd.
516) 0.8 parts of a mixture of sodium bicarbonate and monosodium citrate anhydrous in a ratio of 50:50 to 100 parts
1 part added and fed to the extruder, cylinder temperature 170~2
Extrusion foaming was carried out by setting the 05° C1 screw rotation speed to 23 rpm and the opening degree of the lip of the T-die to Q, 5 yttyt.

The resulting foamed sheet has a thickness of 1.0 mm, a foaming ratio of 2.4 times, a uniform bubble size of 50 to 80 x 50 microns, and a beautiful foamed sheet with a glossy and smooth surface. It was a sheet.

Next, use this foam sheet and vacuum form it to a height of 90 f.
A copper with a diameter of 60 to 80 M was obtained, but the bubbles were fine and undisturbed.

Example 2 The ratio of sodium bicarbonate and monosodium citrate anhydride to 100 parts of polystyrene resin (Dialex HT-190 manufactured by Mitsubishi Monsando Chemical Co., Ltd.) was 50:
Extrusion foaming was carried out under the same conditions as in Example 1, except that 2 parts of the mixture of No. 50 and the lip opening of Example 1 were changed to 0.3 wings.

The obtained foam sheet had a thickness of 1.0 and a foaming ratio of 4.0.
The bubble size was 50-80 x 50 microns with a smooth surface.

Comparative Example 1 Using the extruder and T-die of Example 1, expandable styrene beads containing volatile blowing agents such as butane and pentane (Styropol JK-50 manufactured by Yuka Badissier Co., Ltd.) were produced.
0), 1.2 times more talc was added, and the temperature of Example 2 was lowered to 1.
Extrusion foaming was carried out under the same conditions as in Example 2, except that the temperature was changed to 20 to 170°C and the conditions were set to the conditions that produced the most minute bubbles. The obtained foam had a thickness of 1'z and a foaming ratio of 4.0 times, which was slightly larger than that of Example 2 when the cell diameter was measured.
00 x 300 microns, but the appearance and surface smoothness were quite poor.

The results such as bubble diameter are shown in Table 1.

Table 1 A: indicates the surface smoothness of a 50:50 mixture of anhydrous sodium bicarbonate and monosodium citrate.○ indicates good surface smoothness, and Δ indicates unevenness.

Example 3 Polystyrene resin (manufactured by Mitsubishi Monsando Kasei Co., Ltd.)
Dialex HF-77) 0.3 part of a mixture of 100 fflHC1 sodium bicarbonate and monosodium citrate anhydride in a ratio of 50:50 was added and injection foam molding was performed.

The injection molding conditions were as follows: Machine: 2.5 oz (with needle nozzle) Cylinder temperature: 200-220'Cq Injection pressure: 704゜q Back pressure: 104□ Mold: 6 x 70 x 140 mm Mold temperature: 30-40'C Cooling time: 90 seconds The molded product had an expansion ratio of 1.04 times, and there were no flow marks on the surface (it was a molded plate with only fine bubbles inside and a smooth surface).

Example 4 BS resin (Denka ABS GR-1 manufactured by Denki Kagaku Kogyo Co., Ltd.)
000) 100 parts of a mixture of sodium bicarbonate and monosodium citrate anhydrous in a ratio of 50:50 to 0.3
5 parts, methacrylic resin (Mitsubishi Rayon Co., Ltd. Metablane)
P-53p) 1 part of the mixture was used for injection molding.

The same molding machine and molding conditions as in Example 2 were used.

The obtained molded product had an expansion ratio of 1.03 times and a smooth surface.

Patent applicant: Eiwa Kasei Kogyo Co., Ltd. Figure 1 Temperature (°C) Procedural amendment (formality) %formula% 1.Display of the incident Patent application No. 135745, 1986 2. Name of the invention Method for producing styrenic tree-based foam 3. Person who makes corrections 4. Date of amendment order (shipment date) October 8, 1986 , −・−l　7,゛・.

6 Contents of the amendment (1) A section for a brief explanation of the drawings will be added from page 10, line 18 onward.

[Brief explanation of drawings]

Figure 1 shows the gas measured by adding 10 Mt of liquid paraffin to 1 gram of the blowing agent of the present invention, a combination of sodium bicarbonate and monosodium citrate anhydrous in a ratio of 50:50, at a temperature increase rate of 2 degrees. It is a diagram of occurrence. (2) Amend the drawing as shown in the attached sheet. Drawing Plan 1 Temperature (°C)

Claims (1)

[Claims] A method for producing a styrenic resin foam, which comprises using sodium bicarbonate and monosodium citrate anhydride as blowing agents in extrusion foam molding or injection foam molding of a styrenic resin.