JPS59227426A - Preparation of expanded thermoplastic resin article - Google Patents

Abstract

PURPOSE:To make it possible to efficiently recover a volatile blowing agent, by a method wherein a volatile blowing agent-containing thermoplastic resin is extruded into a vacuum chamber from a die to be expanded while the expanded resin is introduced into a water tank constituted so as to hermetically close the outlet of the vacuum chamber. CONSTITUTION:A resin 1 is extruded into a vacuum chamber 3 from a die 2 to be expanded. In this case, the pressure of the vacuum chamber 3 is usually set to atmospheric pressure or less, pref., 60-760mm.Hg (absolute pressure). In addition, the recovery rate of a volatile blowing agent can be enhanced by heating the vacuum chamber 3 by a heating apparatus 4. Thus obtained expanded thermoplastic resin article 5 is introduced into a water tank 6 constituted so as to hermetically close the outlet of the vacuum chamber 3 while the cooled expanded thermoplastic resin article 5 is continuously taken up in the atomosphere by a take-up roll 7. Even if this take-up speed is extremely accelerated to the max. 100-150m/min and high speed molding is performed, an excellent expanded article can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin foam, and more specifically, a method for efficiently recovering a volatile blowing agent and continuously producing a thermoplastic resin foam having excellent properties at high speed. The present invention relates to a method for producing a thermoplastic resin foam that can be produced.

Thermoplastic resin foams are generally made of aliphatic hydrocarbons.

It is obtained by extrusion molding a resin melt containing a volatile blowing agent such as a fluorinated chlorinated hydrocarbon or an alcohol using an extruder. In particular, when producing a foam with a high expansion ratio, a large amount of volatile blowing agent is used. These volatile blowing agents contribute to the formation of cells after being extruded from the die, and some of them directly escape from the resin into the atmosphere. In addition, the volatile blowing agent that contributed to the formation of the bubbles also secondarily passes through the bubble membrane and escapes into the atmosphere. These volatile blowing agent gases escaping into the atmosphere not only worsen the working environment, but also pose health and safety problems, so efficient recovery is desired. Furthermore, in the case of foams with high expansion ratios, the cost of the blowing agent that is involved in the production of the foam cannot be ignored.

The present invention solves the above-mentioned conventional drawbacks, and provides a thermoplastic resin foam that can efficiently recover volatile blowing agents and produce thermoplastic resin foams having excellent properties continuously at high speed. The purpose of this invention is to provide a method for manufacturing.

That is, in the present invention, a thermoplastic resin containing a volatile foaming agent is extruded from a die into a vacuum chamber and foamed, and then introduced into a water tank configured to seal the outlet of the vacuum chamber, and then taken out and removed from the vacuum chamber. The present invention provides a method for producing a thermoplastic resin foam characterized by recovering a volatile blowing agent.

The thermoplastic resin used in the production method of the present invention is not particularly limited, and various thermoplastic resins may be used. For example, polyolefins such as polyethylene and polypropylene; copolymers of olefins such as ethylene and propylene with other copolymer components; polystyrene; copolymers of styrene and other copolymer components; polyvinyl chloride; polyamide; polyester; Examples include polyacetal and mixtures thereof.

Next, there are no particular restrictions on volatile foaming agents, but for example,
Examples include aliphatic hydrocarbons such as propane, butane, pentane, and hexane; alcohols such as trichloromonofluoromethane, dichlorotetrafluoroethane, and dichloro, and mixtures thereof.

The blending ratio of the thermoplastic resin and the volatile foaming agent is usually 5 to 200 parts by weight, preferably 50 to 150 parts by weight, per 100 parts by weight of the former.

Furthermore, in the present invention, Merck may be used as necessary.

A cell nucleating agent such as clay or silica can also be added as appropriate. The amount of this bubble nucleating agent added is usually 1 part of the thermoplastic resin.
By using the 0-cell nucleating agent in an amount of 5 parts by weight or less per 00 parts by weight, the bubbles can be made uniform and the cell diameter can be reduced, making it possible to effectively utilize the volatile blowing agent. can.

In addition, various stabilizers (oxidation,
heat, light, etc.), fillers (calcium carbonate.

Merck, clay, carbon black, etc.), rubbers, antistatic agents, plasticizers, colorants, etc. can be added as appropriate.

Next, the manufacturing method of the present invention will be explained based on the drawings.

FIG. 1 is a schematic diagram showing an example of an apparatus used in the manufacturing method of the present invention.

First, various additives are added to a melted thermoplastic resin using a molding machine such as an extrusion molding machine, and then a volatile foaming agent is added. J'iI: The foaming agent is usually 10 to 200 k
It is preferable to press fit into the thermoplastic resin at a pressure of 100 mm.

Next, the above melted volatile blowing agent-containing thermoplastic resin 1
While sufficiently mixing, the resin is cooled to about -45°C to +10°C relative to the melting point or softening point of the resin.

Next, the resin 1 is extruded from the die 2 into the vacuum chamber 3 and foamed. Here, the pressure in the decompression chamber 3 varies depending on the type of thermoplastic resin, volatile foaming agent, etc., and is difficult to determine unambiguously, but is usually set to below atmospheric pressure. Preferably 60 m
m1lji (absolute pressure) to 760 mmB, 9 (absolute pressure). Further, it is preferable that the decompression chamber 3 be heated by a heating device 4 . This heating temperature also varies depending on the type of thermoplastic resin and volatile blowing agent, and is difficult to determine unambiguously, but it ranges from room temperature to a temperature 10 degrees Celsius lower than the melting point or softening point of the resin, usually 50 to 150 degrees Celsius. It is. As the heating device 4, a known device such as a heater can be used. By heating the vacuum chamber 3, the recovery rate of the volatile foaming agent can be further improved.

In addition, as the format of the die 2, either a flat die type or a circular die type can be used.

By using the flat die method, it is possible to produce film- or sheet-shaped thermoplastic resin foams, and by using the circular die method, it is possible to produce cylindrical thermoplastic resin foams. .

The thermoplastic resin foam 5 thus obtained is introduced into a water tank 6 configured to seal the outlet of the vacuum chamber 3.

Here, the water tank 6 is not particularly limited as long as it is a borrowed one that seals the decompression chamber 3, that is, blocks ventilation between the decompression chamber 3 and the outside air. By introducing the thermoplastic resin foam into the water tank 6, the thermoplastic resin foam 5 is cooled.

Next, the thermoplastic resin foam 5 introduced into the water tank 6 and cooled is continuously taken up into the atmosphere by a take-up roll 7 or the like. In addition, the maximum take-up speed of the foam 5 is 100 to 150
It is possible to obtain an excellent foam even when molding is performed at a very high speed of m/min.

Furthermore, in the manufacturing method of the present invention, it is necessary to recover the gaseous volatile foaming agent from the vacuum chamber 3 by turning on a recovery device 8 such as a vacuum pump. There is no particular restriction on the recovery method for the volatile blowing agent, and any of the condensation type, adsorption type, and absorption type can be used.

By repeating the above operation using the volatile foaming agent thus recovered, a thermoplastic resin foam can be manufactured.

As explained above, in the manufacturing method of the present invention, a molten thermoplastic resin containing a volatile blowing agent is extruded from a die into a vacuum chamber and foamed, and then introduced into a water tank configured to seal the outlet of the vacuum chamber. The inside of the decompression chamber is sealed off from the atmosphere. In the present invention, the once-used volatile foaming agent is recovered from such a vacuum chamber and the volatile foaming agent is reused, so that the manufacturing cost of the foam can be reduced.

Moreover, as mentioned above, since the decompression chamber is a closed system, 1
The volatile foaming agent can be efficiently recovered, the recovery time can be shortened, and the foam can be continuously molded at high speed. Therefore, the production method of the present invention is highly economical. It is.

Further, as a volatile blowing agent, a blowing agent that generates flammable gas or harmful gas can also be used. However, even if these blowing agents are used, the working environment in other processes will not be deteriorated.

Further, since one water tank can simultaneously isolate the decompression chamber from the atmosphere and cool the S5-3 foam, no other cooling means is required.

Moreover, since the molten thermoplastic resin containing a volatile blowing agent is extruded from a die into a vacuum chamber and foamed, a foam having excellent properties can be obtained.

Therefore, the manufacturing method of the present invention can be effectively utilized for manufacturing thermoplastic resin foams used as n-bag materials, heat insulating materials, and the like.

Next, examples of the present invention will be shown.

Example 1 A thermoplastic resin foam was manufactured by the following method using the apparatus shown in FIG.

Polypropylene (density 0.91.!iI/crn3. Melt index (MI) 0.6 jl/10 min) melted at 200°C using an extrusion molding machine was used for 100 nail parts, TrikuOo monofluoropmethane 81 Parts by weight and dichlorotetrafluoroethane 9 parts 150
145" while press-fitting at kW/an2 and thoroughly kneading.
C; to make it uniform. Next, this melted volatile foaming agent-containing thermoplastic ↑1:, resin 1 is poured into a vacuum chamber 3 (+-E
At the same time, pressurized air is supplied to the inside of the bubble from the air supply port of the die.
A cylindrical foam 5 with a bubble diameter of 200 mm was obtained. This cylindrical foam 5 was introduced into the water tank 6 from the vacuum chamber 3 via the pinch rolls 9, and then continuously drawn into the atmosphere by the drawing row A/7. The temperature of the vacuum chamber 3 was set to 100''C, and the gaseous rjlj )A foaming agent in the vacuum chamber was recovered by a vacuum pump (recovery device 8).

The residence time of the cylindrical foam 5 in the vacuum chamber in a steady state 50 minutes after the start of operation was 20 seconds, and the recovery rate of the volatile blowing agent measured by gas chromatography was 82% for trichloromonofluoromethane and 82% for dichlorotetrafluoromethane. ethane 60
%Met.

Example 2 In Example 1, except that the conditions of the decompression chamber were 115°C hot water temperature and 630 mnl1jj (absolute pressure),
A foam was obtained in accordance with Example 1.

Steady state volatile blowing agent recoveries were 90% for trichloromonofluoromethane and 68% for dichlorotetrafluoroethane.
%Met.

Example 3 In Example 1, the temperature of the vacuum chamber was 60°C.

A foam was obtained in the same manner as in Example 1, except that the pressure was 630 tnrnN (absolute pressure).

Steady state volatile blowing agent recoveries were 60% for trichloromonofluoromethane and 31% for dichlorotetrafluoroethane.
%Met.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus used in the manufacturing method of the present invention. 1... Thermoplastic resin containing volatile foaming agent. 2...Die, 3...Decompression chamber, 4...Heating device. 5...Thermoplastic resin foam, 6°°°water tank, 7.
...Take-up roll, 8...Recovery device. 9... Pinch roll patent applicant Idemitsu Petrochemical Co., Ltd.

Claims (1)

[Claims] 1. After extruding a thermoplastic resin containing a volatile foaming agent into a vacuum chamber and foaming it, the resin is introduced into a ladle-formed water tank so as to seal the outlet of the vacuum chamber, and then With,
A method for producing a thermoplastic resin foam, comprising recovering a volatile foaming agent from the vacuum chamber. 2. The manufacturing method according to claim 1, wherein the reduced pressure chamber is heated to 50° C. or higher.