JPS5945331A - Manufacture of foam-molded article - Google Patents

Abstract

PURPOSE:To manufacture a high-quality practical foam-molded article without causing the rusting and corrosion of the mold, by adding a foaming agent composed of a specific compound and sodium bicarbonate to a thermoplastic resin, and injection molding the composition at a temperature above the decomposition initiation temperature of the foaming agent. CONSTITUTION:A foaming agent obtained by mixing 1mol of a monoamine salt of citric acid, itaconic acid or tartaric acid with 1-0.2mol of sodium bicarbonate, is added to a thermoplastic resin (e.g. polyamide), and the composition is injection-molded by a particular injection molding machine for structural foam at a temperature above the decomposition initiation temperature of the foaming agent (about 200 deg.C) to obtain the objective foam-molded article. EFFECT:The venting time of the foam-molded article can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention discloses a method for producing a thermal F+1 plastic resin foam molded product such as a structural foam having a sandwich structure of a skin layer and a foam layer.

Pholamide, hollyester. In the case of foam injection molding of special polymers with high melting points such as modified polyphenylene oxide, ABS, and polystyrene, conventionally, aso yarn, nitroso type, etc. are used as blowing agents. Foaming agents such as hydrazine are used, and among them, azo dicarbon 7 mil' is most commonly used. However, while these foaming agents exhibit excellent foaming performance, they require work to remove foaming agent residue from bosses, ribs, holes, etc. every few shots, and the mold rust due to the residue. It has major drawbacks such as corrosion and corrosion. Furthermore, molded products using these blowing agents have a slow gas diffusion rate within the molded product, and if painted immediately after molding, the gas inside the molded product will cause holes in the paint film. There are disadvantages, such as the difficulty of having to stock molded products for a long time to vent the gas.

To explain this in more detail based on experiments, foaming methods using sodium bicarbonate or its combination with citric acid or tartaric acid have generally been used for a long time.
It is well known.

By the way, looking at the gas generation during temperature rise for foaming with only sodium bicarbonate, the rate of rise was 29 atmospheres, and the liquid paraffin was 100 ac.

Considering o07, it is as shown in Figure 1, and 14
The increase in the amount of gas generated at 0°C to 160°C 1C causes decomposition residue on the surface of the molded product, and there is concern that it will have an adverse effect on the coating π.

To this, at a rising rate of 2°C, in 1 OCC of liquid paraffin, under the same conditions as the sample], OOO\, add citric acid equivalent to π of the blowing agent, and add 0.2857 ml of sodium bicarbonate.
In an experiment using a mixture of V and citric acid 0.7143P, the gas generation situation during temperature rise was as shown in Figure 2.
The above-mentioned situation can be eliminated by neutralization with citric acid, but on the other hand, the decomposition temperature becomes low, and the decomposition is too rapid for high melting point polymers, resulting in rough bubbles, insufficient foaming ratio due to gas escape, and mold failure. Corrosion problems occur.

Thus, the present invention focuses on problems such as tilting, eliminates the drawbacks, eliminates the concern of mold rust and corrosion even when foam molding is performed using a high melting point polymer, and eliminates the risk of mold rust and corrosion. Foam molded products with shortened punching time? How to manufacture? This is what we provide.

That is, the present invention aims to find a blowing agent to replace conventional blowing agents and to perform foam molding at a required temperature. Injection molding using a combination of one amine salt of itaconic acid or tartaric acid and thorium bicarbonate at a humidity above the decomposition temperature of the blowing agent.
It is characterized by

Here, que' introduced to the 17 um of sodium bicarbonate.
#1. The amine salt of itaconic acid or tartaric acid is one selected from the group consisting of tartaric acid, citric acid, or the carboxylic acid of itaconic acid, such as cyclohegycylamine, isopropylamine, butylamine, octylamine, and doasilyamine. Oleylamine.

It is an organic amine salt such as stearylamine,
When used in combination with sodium bicarbonate, the molar ratio of the amine salt and sulfur/lium bicarbonate is preferably 1:1 to 0.2.

The blowing agent created by this combination has a decomposition starting temperature of bicarbonate during foaming. Amine salt prevents mold corrosion, and
Unlike the azo type, carbon dioxide type foams have good gas diffusion within the molded product, requiring a short degassing period, making them ideal blowing agents.

Figure 3 shows the state of gas generation during temperature rise of this blowing agent, as in Figures 1 and 2 above, with a rising rate of 2° Chin, 10 cc of liquid halafine, 10 oOV, and 0.4000 sodium bicarbonate! This is the result of an experiment using a blowing agent of 0.6000 f/, cyclohexylamine citric acid salt, and 0.6000 f/.

Therefore, in the present invention, the decomposition start humidity of the blowing agent and the temperature at which the amount of stagnation and carbon dioxide gas generation start to occur suddenly are about 200° C., as shown in FIG. 3 above.

In particular, in the present invention, the relationship between the amount of carbon dioxide gas generated and its temperature is important in order to obtain a foam molded product with uniform fine cells using carbon dioxide gas, and the molding temperature is an important requirement.

Regarding this point, the present invention is also characterized by injection molding at a temperature higher than the decomposition start temperature described in III.

If molding is carried out at a turbidity below the start of Be decomposition, less carbon dioxide gas is generated and sufficient foaming at the 7% stage cannot be obtained.

Note that the molding temperature in this case is the temperature of a part of the cylinder where the hot n1 plastic resin and the foaming agent are melt-kneaded.

In the present invention, since the decomposition humidity of the blowing agent is as high as 200"C or more as shown in Figure 3 above, polyamide, polyester, modified polyphenylene oxide, and A are used as thermoplastic persimmon fats suitable for this decomposition humidity. Ru.

Further, for injection molding, a normal injection molding machine is used, and although various molding machines may be used as the injection molding machine, a special molding machine for Struknayal foam is mainly used.

The present invention will be described in more detail below with reference to Examples.

Example 1 Modified polyphenylene oxide 1007 with a ratio of 1.1, 0.87 sodium bicarbonate, and xylamine salt 1. Mix in a tumbler at a ratio of
Both the cylinder and the manifold were molded at a temperature of 260° C. using a molding machine manufactured by Matsumoto Co., Ltd. (400 tons). The obtained lζ product had uniform fine bubbles and a foaming ratio of 611.3 times.

In addition, there was no rust formation on the mold, and no abnormality was observed in the coating film even when it was painted 2 hours after molding.

Example 2 Modified polyphenylene oxide 100 π with specific gravity 1.1
Mix 0.8 y of sodium bicarbonate and 0.82 y of tartaric acid cyclohegycylamine salt in a tumbler. Low-pressure SF machine (400 manufactured by Ex-Oe 11-0)
+, n) for both cylinder and manifold.
Molded at a temperature of ℃.

The obtained product has uniform fine cells, and the foaming ratio is 1.3.
It was double that. In addition, there was no rust on the mold, and no abnormalities were observed in the coating film even when it was painted 2 hours after molding.

Example 3 AES resin with a specific gravity of 1.06 was mixed in a tumbler at a ratio of 0.8% thorium carbonate and 79% isopropylamine salt of itaconate, and then heated under low pressure. SF dedicated machine (Ex C! θ11-0 made 400
!・Both cylinder and manifold are 210°.
It was molded at a temperature of C. The obtained product had uniform fine cells, and the expansion ratio was 5 times.

In addition, there was no rust formation on the mold, and no abnormality was observed in the coating film even if it was painted after three molding cycles.

As is clear from the above examples, according to the method of the present invention, it is possible to easily produce a structural foam that is a high-quality product with uniform fine cells and has a sufficient expansion ratio, even in the case of foam molding of a high melting point polymer. Moreover, there is no problem of mold corrosion, and there is no adverse effect on the coating, making it a practical VC.

[Brief explanation of drawings]

FIGS. 1 to 3 are charts showing the state of gas generation during temperature rise, FIGS. 1 and 2 are comparative examples, and FIG. 3 is a diagram showing an embodiment of the invention. Rod once '5T & 11 ('C) 94Z chart temperature (・C)

Claims (1)

[Claims] / When foaming injection molding is performed by adding a blowing agent to a thermoplastic resin, a small amount selected from the group consisting of a monoamine salt of citric acid, a monoamine salt of itaconic acid, or a monoamine salt of tartaric acid is used as the blowing agent. 1. A method for producing a foamed molded article, which uses a combination of foam and sodium bicarbonate, and performs injection molding at a temperature equal to or higher than the decomposition temperature of the foaming agent.