JPH0717022B2 - Method for producing synthetic resin foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a synthetic resin foam, which is a plate-shaped foam that is lightweight and has high heat insulation performance and high strength and is continuously extruded. The present invention relates to a manufacturing method in which a product is cut into a certain length.

These synthetic resin foams can be effectively used mainly in the fields of heat insulating materials, flooring materials and cushioning materials mainly for construction purposes by taking advantage of their characteristics of light weight, high heat insulating performance and high strength.

2. Description of the Related Art Conventionally, a synthetic resin foam is produced by mixing and melting a synthetic resin with a foaming agent and other additives in an extruder, cooling the mixture, and then releasing the pressure from a high pressure region to a low pressure region in a die part to form a plate-like foam by a molding device. I was shaping my body.

At the time of molding, the foam must be molded into a certain cross-sectional shape (for example, a thickness of about 20 to 150 mm x a width of about 1000 mm).

Problems to be Solved by the Invention However, in order to obtain a foam having a constant cross-sectional shape at the time of molding, for example, in the case of obtaining a foam having a large cross-sectional shape, the foam is placed in a molding die. The flow is stagnant, that is, the force is applied in the opposite direction but in the direction of extrusion, and in the case of obtaining a foam with a small cross-sectional shape, the longitudinal force pulling out the foam is applied, so the strength is A well-balanced foam was obtained.

The strength described here is the compressive strength as its evaluation item, and the strength balance is 3 in the product thickness direction, width direction and extrusion direction.
Balance the direction.

This imbalance in strength causes various inconveniences. For example, when the width and the strength in the extrusion direction are weak, the dimensional stability, heat resistance, and bending strength of the product decrease.

Further, when the strength in the thickness direction is weak, the practical performance such as repeated compression strength and local compression strength is deteriorated.

Conventionally, this strength balance is almost determined at the time of molding immediately after the die, and in order to adjust this balance, the die shape,
Although the temperature and the composition were adjusted and molded, an effective adjusting method could not be obtained.

MEANS FOR SOLVING PROBLEMS In the present invention, attention is paid to the fact that sufficient foaming power remains in a foam immediately after molding in order to overcome the problems of the prior art. To facilitate free foaming by passing through a furnace in a high temperature atmosphere, and by stretch molding with a roll installed at the exit of the furnace to remove the strain on the foam that was added during molding immediately after the die, Further, they have found that a foam having a good strength balance can be obtained by adding stretching in the extrusion direction, thus completing the present invention.

For the method of reheating the foam immediately after extrusion, see Japanese Examined Patent Publication No. 61-2497.
6, disclosed in JP-A-63-37916 and JP-A-63-159034, all of which are a method for reducing the foam density and a means for uniforming the density distribution, immediately after extrusion or After cooling only the surface layer part, the foam is reheated to a temperature not lower than the heat distortion temperature by using hot air, water vapor, or far infrared rays alone or in combination to achieve the above-mentioned low density and uniform density distribution. On the other hand, the present invention, as a means of changing the anisotropy of the cell structure that governs the imbalance of the foam strength, reheats the foam after extrusion and then stretch-molds in the extrusion direction to add the foam strength balance. Is intended to be adjusted arbitrarily, which is different from the prior art.

That is, the present invention is a method for producing a synthetic resin foam by mixing and melting a synthetic resin with a foaming agent and other additives in an extruder, and then releasing the pressure from a high pressure region to a low pressure region after cooling.
Immediately after releasing the pressure, it is molded by a molding die and a first roll, then passed through a furnace whose inside is kept at a high temperature atmosphere, and remolded by a second roll provided at its outlet, which is characterized by being remolded. In the manufacturing method.

A manufacturing method according to the present invention will be described with reference to the drawings.

The process up to the die is conventional, conventional extrusion. Synthetic resin and additives are supplied from a hopper, and a foaming agent is mixed in the middle, mixed and melted by a screw under high temperature and high pressure, and sent into an extruder. After that, the resin is cooled to a foamable resin viscosity range and sent to a die. The die (1) is used to release the pressure from the high pressure region to the low pressure region, and a plate-shaped foam having a desired cross-sectional shape is molded by the molding die (2) and the first roll (3). According to the present invention, it is then reheated by passing through a furnace (5) equipped with a hot air generator (6) whose temperature can be set in the range of 100 to 160 ° C. and adjusting the speed of the second roll (4). Stretching force is applied to the foam to obtain a foam while controlling the strength balance.

The temperature in the furnace is equal to or higher than the softening point of the foam, and the temperature range satisfying the condition that the foam surface melts and the cell does not break, preferably 105 to 160 ° C, and more preferably 12
0 to 140 ℃.

The residence time of the furnace is determined by the linear velocity of the foam to be extruded and the length of the furnace, the required residence time is determined by the target strength adjustment range and heating temperature, but at least 30 seconds or more, preferably 45 to 100 seconds is is necessary.

The speed ratio of the first and second rolls varies depending on the strength balance to be obtained and the temperature conditions in the furnace. For example, if the ratio of the second roll speed / the first roll speed is too large, the foam in the furnace will be If the ratio of the second roll speed / the first roll speed is too small, the foam may meander in the furnace due to free foaming during reheating.

Therefore, the adjustable range of the roll speed ratio is preferably the second roll speed / the first roll speed = 1.1 to
1.6, and more preferably 1.2 to 1.4.

The styrenic resin used in the method of the present invention includes not only a homopolymer of a styrenic monomer but also a copolymer.

Styrene monomers include styrene, methyl styrene,
Ethyl styrene and the like are also included. Further, the copolymer contains a copolymer containing 50 mol% or more of a styrene-based monomer. Examples of the partner monomer for copolymerization include methacrylic acid esters such as methyl methacrylate, acrylic acid esters, acrylic acid, methacrylic acid, acrylonitrile, and maleic anhydride. When the heat distortion temperature changes due to these copolymer compositions, it is possible to adjust the temperature in the furnace to develop a target strength balance.

The blowing agent used in the method of the present invention is an aliphatic hydrocarbon or a halogenated aliphatic hydrocarbon having a boiling point lower than the heat distortion temperature of the styrene resin.

Examples of aliphatic hydrocarbons are saturated aliphatic hydrocarbons such as propane, butane, pentane, hexane, and unsaturated aliphatic hydrocarbons such as propylene, butene.

Examples of halogenated aliphatic hydrocarbons are methyl chloride, methylene chloride, dichlorodifluoromethane,
Examples include tetrafluoroethane and dichlorotetrafluoroethane.

These may be used alone or in admixture of two or more. In the method of the present invention, the cell diameter is adjusted by the amount of nucleating agent in extrusion.

As a nucleating agent, organic type (for example, barium stearate,
Magnesium stearate or the like) and an inorganic powder (for example, talc) are used alone or in a mixed system thereof.

According to the production method of the present invention, it is possible to perform flexible production in which the foam strength balance can be controlled according to the required performance for each application, and by optimizing the strength balance, it is possible to reduce the weight while maintaining the performance. It has the effect of cost reduction.

Next, the method for producing the synthetic resin foam of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Using polystyrene as a resin, 100 parts of polystyrene and 1.0 part of talc were mixed and supplied to an extruder. As a foaming agent, 6.0 parts of methyl chloride and 3.0 parts of propane were pressed into an extruder, mixed and melted, and then extruded from a slit die. Using the apparatus shown in the drawing, a foam having a thickness of 110 mm, a width of 1014 mm and a density of 28 kg / m ³ was obtained under the conditions of a furnace temperature of 135 ° C., a residence time of 52 sec, and a take-up speed ratio of 1.2 between the first roll and the second roll.

When the physical properties of this foam are measured, the physical properties shown in Table 1 are obtained, and it can be seen that the balance is improved and the bending strength and thermal conductivity are improved compared to the values given in Comparative Example 1.

Comparative Example 1 Extruded from a slit die in the same manner as in Example 1 and molded according to the conventional technique without passing through a furnace and a second roll to obtain a foam having a thickness of 120 mm, a width of 1020 mm and a density of 28 kg / m ³ .

Example 2 Using polystyrene as a resin, 0.25 parts of talc and 0.3 part of barium stearate were mixed with 100 parts of polystyrene and the mixture was supplied to an extruder. As a foaming agent, 5.5 parts of methyl chloride and 2.0 parts of propane were pressed into an extruder, mixed and melted, and then extruded from a slit die. Then, with the equipment shown in the drawing, the temperature inside the furnace was 130 ° C, the residence time was 153 seconds, and the roll speed ratio was 1.00.
~ 1.16 thickness about 80mm, width 160mm, density 29 ~ 30kg / m ³
A foam of

When the compressive strengths of these foams are measured in three directions, the physical properties shown in Table 2 are obtained, and the strength balance can be controlled by the speed difference between the first roll and the second roll.

Example 3 Using polystyrene as a resin, 100 parts of polystyrene and 1.0 part of talc were mixed and supplied to an extruder. As a foaming agent, 6.0 parts of methyl chloride and 3.0 parts of propane were pressed into an extruder, mixed and melted, and then extruded from a slit die. Then, using the apparatus shown in the drawing, a foam having a thickness of about 115 mm and a width of about 1000 mm was obtained under the conditions of a furnace temperature of 130 ° C., a residence time of 55 sec, and a roll speed ratio of 1.2.

When the physical properties of this foam are measured, the physical properties shown in Table 3 are obtained, and it can be seen that the strength balance is improved and the bending strength and the thermal conductivity are improved despite the weight reduction due to the secondary foaming.

[Brief description of drawings]

The drawing is a schematic representation of an apparatus for carrying out the invention. 1 is a die, 2 is a molding die, 3 is a first roll, 4 is a second roll, 5 is a furnace, and 6 is a hot air generator.

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Claims (5)

[Claims] 1. A method for producing a synthetic resin foam by mixing and melting a synthetic resin together with a foaming agent and other additives in an extruder, cooling the mixture, and then releasing the pressure from a high pressure region to a low pressure region. Molded by a mold and a first roll, and once the surface layer is allowed to cool, it is passed through a furnace whose inside is kept in a high temperature atmosphere, and stretch-molded by a second roll provided at its outlet, which is a synthetic resin foaming. Body manufacturing method. 2. The take-up speed of the first roll and the second roll installed across the heating furnace is controlled so that the second roll is the first roll.
The method for producing a synthetic resin foam according to claim 1, wherein the foam is stretched 1.1 times or more in the extrusion direction. 3. The foam is subjected to secondary foaming by passing through a furnace kept in a high temperature atmosphere to reduce the foam density, and the strength properties which are degraded by the secondary foaming can be obtained by stretch molding with a second roll. The method for producing a synthetic resin foam according to claim 2, wherein the synthetic resin foam is recovered. 4. The method for producing a synthetic resin foam according to any one of claims 1 to 3, wherein the synthetic resin foam is a polystyrene resin extruded foam. 5. The method for producing a synthetic resin foam according to any one of claims 1 to 4, wherein the inside of the furnace is kept in a high temperature atmosphere by heated air.