JP2001138377A - Method for foam molding thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for foam molding a thermoplastic resin by which fine, uniform and delicate air bubbles can be formed and a foam with a clean surface and a high foaming magnification can be formed, in a foam molding process of the thermoplastic resin by an extrusion molding machine or an injection molding machine. SOLUTION: A mixture of a thermally expanding microcapsule, a routine foaming agent and a thermoplastic resin is foam molded using a screw extrusion molding machine or a screw injection molding machine with a mixing mechanism. Thus, the thermally expanding microcapsule foams in the screw, resulting in a rise in the internal pressure of the screw and the subsequent retention of the pressure of the entire system. Consequently, gas originating from the routine foaming agent is retained in the screw instead of suddenly expanding to escape, so that a satisfactory foaming condition is obtained. Further, the mixture is sufficiently kneaded by the mixing mechanism of the screw to form each fine and uniform air bubble as a cell without a rough surface, in addition to the foaming by the foaming agent. These results contribute to a high foaming magnification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for foaming a thermoplastic resin, and relates to a method for forming a foamed article of a thermoplastic resin by using an extruder or an injection molding machine while maintaining uniform and dense cells. Is increased so that foam molding can be performed.

[0002]

2. Description of the Related Art Foam molding using a thermoplastic resin is used for molding various synthetic resin products. By foaming, it is possible to reduce the weight of a synthetic resin product, improve heat insulation, and impart cushioning properties. Rolls in the field of OA equipment, packing and damping materials for industrial materials, furniture, building materials, shock absorbing materials, various protective materials, and the like.

[0003] As a general method of foam molding with such a thermoplastic resin, for example, a chemical foaming agent such as azodicarbonamide is mixed with a thermoplastic resin raw material, and heat is applied when the thermoplastic resin raw material is melted. There are a method of generating a gas by thermally decomposing a chemical foaming agent and a method of injecting a gaseous gas such as water vapor, nitrogen, or carbon dioxide as a physical foaming agent into a molten thermoplastic resin.

[0004]

In the foam molding using such a thermoplastic resin, foam molding is carried out using a pyrolysis gas or a gas to be injected separately in a state where the thermoplastic resin raw material is melted and the viscosity is extremely reduced. The bubble state changes greatly due to slight pressure fluctuations of the pyrolysis gas or injected gas, making it difficult to obtain a uniform and dense molded product. It is difficult to obtain a molded product in a state, and particularly difficult to obtain a molded product having a large expansion ratio.

[0005] In the case of extrusion molding or injection molding using a thermoplastic resin, when the foamed resin passes through a die,
Extrusion or injection of thermoplastic resin, such as the gas expanding further due to the rapid pressure drop, which causes fine irregularities on the surface of the molded product, which tends to cause shark skin-like phenomena and makes it impossible to obtain a clean surface. There is a problem that it is generally difficult to obtain a foam by molding.

Therefore, instead of a chemical foaming agent or a physical foaming agent,
A method has been proposed in which a thermally expandable microcapsule is added to a thermoplastic resin raw material to obtain a foamed molded article (Japanese Patent Laid-Open No. 10-15).
2575) is very effective in the case of a low expansion ratio, but there is a limit to a high expansion ratio.

On the other hand, there is a demand for the development of a foamed molded article having a novel function by utilizing properties such as productivity and physical properties of a thermoplastic resin.

The present invention has been made in view of the above-mentioned problems of the prior art, and can form a fine, uniform and dense foamed state of a thermoplastic resin in a foaming molding by an extrusion molding machine or an injection molding machine, and has a clean surface. Further, it is an object of the present invention to provide a method for foaming and molding a thermoplastic resin capable of molding a foam having a large expansion ratio.

[0009]

In order to solve the above-mentioned problems of the prior art, in the method of foaming a thermoplastic resin according to the first aspect of the present invention, the foaming mechanism of the prior art is such that the gas is injected into the extruder. Or melt it in the molten resin under pressure in an injection molding machine, pass it through the dice while maintaining its state in the screw, expand the gas after exiting the dice and expand it by foaming, '' In order to obtain a good foam by increasing the pressure and maintaining the pressure of the whole system, it is necessary to knead the resin sufficiently to form a uniform and dense cell. Is based on
The specific configuration is, when foaming a thermoplastic resin using an extrusion molding machine or an injection molding machine, using a thermally expandable microcapsule and a foaming agent in combination with a thermoplastic resin raw material,
It is characterized in that foam molding is carried out with a screw provided with a mixing mechanism.

According to the thermoplastic resin foam molding method, a heat-expandable microcapsule and a usual foaming agent are added to the thermoplastic resin and foamed by a screw extruder or an injection molder equipped with a mixing mechanism. When this heat-expandable microcapsule foams in the screw, the pressure in the screw rises, the overall system pressure is maintained, and the gas due to the normal foaming agent expands rapidly and escapes Held in the screw without
A good foaming state can be obtained, and by sufficiently kneading with a screw mixing mechanism, each cell is a fine and uniform cell, the surface is not roughened, and a large foaming ratio can be achieved in combination with foaming by a foaming agent.

Further, the present inventors have conducted intensive studies on kneading of a thermoplastic resin, a foaming agent, and a heat-expandable microcapsule with a screw. In the case of a general non-foamed solid resin, the effective length of the screw (with respect to the screw diameter D) is considered. The ratio L / D of about 25 is used. In the case of foam molding, the effective length L / D is used.
In the case of 25, the kneading shortage usually occurs and the effective length L / D
Is required to be about 30 to 35.

However, when the effective length L / D of the screw is increased to about 30 to 35 using a thermoplastic resin, a foaming agent and a heat-expandable microcapsule as raw materials, a large shearing force is applied by kneading by the screw, and the temperature rises. As a result, the heat-expandable microcapsules are destroyed or the gas of the foaming agent escapes, so that a uniform and dense cell foam cannot be formed.

Therefore, in the method of foaming and molding a thermoplastic resin according to the second aspect of the present invention, the screw itself is provided with a mixing mechanism, and by setting the effective length L / D of the screw appropriately, a uniform and dense cell is formed. The specific configuration is the effective length of the screw provided with the mixing mechanism (the screw length with respect to the screw diameter D) in addition to the configuration according to claim 1. (L ratio) L / D is set to 22 or more and less than 30 to perform foam molding.

According to this method of foaming thermoplastic resin, the effective length L of the screw provided with the mixing mechanism is
/ D is 22 or more and less than 30 so that foaming can be performed by sufficiently kneading without destroying the heat-expandable microcapsules or escaping the gas of the foaming agent. , Each bubble is fine and uniform,
There is no surface roughness, and a large expansion ratio can be achieved in combination with foaming by the foaming agent.

Here, as the thermoplastic resin in the present invention, for example, a general thermoplastic resin such as PVC (polyvinyl chloride), PVA (polyvinyl alcohol),
PS (polystyrene), PP (polypropylene), PP
O (polypropylene oxide), PE (polyethylene)
PBT (polybutylene terephthalate), nylon, PC (polycarbonate), PET (polyethylene terephthalate) as engineering plastics
And thermoplastic elastomers such as ethylene-based, vinyl chloride-based, olefin-based, urethane-based, and ester-based resins can be used. These resins may be used in combination. In addition, if necessary, a necessary auxiliary agent such as a lubricant, a plasticizer, an antioxidant, and a pigment may be added to these thermoplastic resins.

A heat-expandable microcapsule is a synthetic resin capsule in which a liquid or a gas that expands when heated is encapsulated. The liquid or gas contained therein expands the softened microcapsules that become the outer shell by expanding, but depending on the temperature conditions at the time of molding, a material that completes molding without melting or bursting is used.

Therefore, the melting temperature of the shell of the heat-expandable microcapsules is higher than the melting temperature of the thermoplastic resin raw material by 20 ° C. to 80 ° C., preferably 30 to 60 ° C., more preferably 40 ° C. or higher. Is done. If the melting temperature is lower than 20 ° C, the shell of the microcapsule is melted and broken during kneading with a thermoplastic resin raw material with a screw or the like, and the gas inside leaks out. The shell does not soften and the gas cannot be expanded to a foamed state. By securing the above temperature difference between the melting temperature of the shell of the heat-expandable microcapsule and the melting temperature of the thermoplastic resin raw material, the microcapsules in the resin form a dense cell while maintaining a perfect sphere. Become.

The particle size of the microcapsules used in the present invention is about 5 to 50 μm before expansion and about 10 to 250 μm after expansion.

As a material for the microcapsules, for example, a copolymer containing acrylonitrile as one of the monomer components is used. As other monomer components which may be copolymerized with acrylonitrile, for example, acrylic acid, methacrylic acid, acrylic Examples thereof include, but are not limited to, acid esters, methacrylic esters, styrene, vinyl acetate, and vinylidene chloride.

The liquid or gas contained in the microcapsules is a gas or a gas which expands at a temperature lower than the softening point of the microcapsules. For example, propane, propylene, butene, normal butane, isobutane, isopentane, neopentane, normal pentane , Hexane, peptane, petroleum ether, halides of methane such as methyl chloride, methylene chloride, CCl ₃ F, CCl ₂ F
_In addition to low-boiling liquids such as chlorofluorocarbons such as ₂ and tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane, compounds such as AIBN that is thermally decomposed by heating and becomes gaseous are used.

As the foaming agent, a foaming agent used for foam molding of a usual thermoplastic resin is used. Either a chemical foaming agent or a physical foaming agent can be used. For example, a chemical foaming agent such as azodicarbonamide is used. A method of injecting an agent or a gaseous gas at normal temperature, for example, N ₂ , CO ₂ , pentane, butane, etc. as it is, or liquefying and injecting it into an extruder, or injecting a gaseous liquid at normal temperature, for example, freon, etc. Used for gasification.

The screw provided with the mixing mechanism
It is not a full flight screw but a screw with a mixing mechanism having a kneading effect, and examples thereof include various screws such as a dalmage screw, a pin screw, a multi-pin screw, a unimelt screw, an HM screw, and a DIS screw. .

The effective length L / D of a screw refers to the ratio of the screw length L to the screw diameter D. Here, a screw having an effective length L / D of 22 or more and less than 30 is used. The kneading required when foaming is performed by an extrusion molding machine or an injection molding machine using a heat-expandable microcapsule and a foaming agent in combination with a plastic resin raw material. If the effective length L / D is less than 22, kneading is insufficient. On the other hand, if the effective length L / D is 30 or more, uniform and dense cells cannot be obtained due to the effects of shearing force and temperature rise due to kneading. This effective length L / D is preferably 24 or more and 28 or more.
As described below, more sufficient kneading is performed, and the shearing force and temperature rise due to the kneading can be suppressed as much as possible, so that more uniform and dense cells can be obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below.

In the method for foaming and molding a thermoplastic resin according to the present invention, a non-full-flight mixing mechanism of an extruder or an injection molding machine using a thermoplastic resin, thermally expandable microcapsules and a usual foaming agent as raw materials. It is kneaded by a screw provided, and is press-fitted into a die or a mold to foam-mold.

When a foam is obtained by an extrusion molding machine or an injection molding machine using a conventional thermoplastic resin, a chemical foaming agent such as a pyrolytic foaming agent represented by azodicarbonamide is used as a foaming agent. Alternatively, physical foaming agents such as CO2, N2, and chlorofluorocarbon are generally used. However, in the case of using only a normal foaming agent, the gas expands further due to a rapid pressure drop, so that the foaming moldability is poor. However, there has been a problem that the internal cells are not turbulent and uniform, and the appearance is rough.

Therefore, in order to solve these problems, according to the present invention, when extrusion molding or injection molding is performed using a thermoplastic resin, heat-expandable microcapsules are added in addition to the thermoplastic resin and a general foaming agent. As a result, the synthetic resin outer shell of the heat-expandable microcapsules is softened when the thermoplastic raw resin is heated and melted, and the liquid or gas contained inside is heated to a gas. The pressure increases due to the microcapsules expanded (foamed) in the screw of an extruder or the like, and the pressure increases due to the expansion and expansion of the outer shell made of synthetic resin. The gas is prevented from further expanding due to the pressure drop, and the overall system pressure is maintained to obtain a good foam having dense cells.

In addition to such a thermoplastic resin and a usual foaming agent, the molding conditions of the foaming molding by an extrusion molding machine or an injection molding machine using heat-expandable microcapsules were studied. When the kneading with the foaming agent and the heat-expandable microcapsules is insufficient, the internal cells may be disturbed and may not be uniform, and it may be necessary to prevent insufficient kneading.

For this reason, if the effective length L / D is increased in order to enhance the kneading effect of the screw of the extruder or the injection molding machine, the effect of the shearing force due to the kneading and the rise of the temperature due to the kneading can be achieved despite sufficient kneading. It was also found that a dense and uniform foaming state was not obtained due to the influence.

Therefore, as a molding condition that the thermoplastic resin is sufficiently kneaded with the foaming agent and the heat-expandable microcapsules, and that the influence of the shearing force and the temperature rise due to the kneading can be suppressed, it is not a full flight type. Experiments have shown that it is effective to use a screw provided with a mixing mechanism and to set the effective length L / D of the screw to 22 or more and less than 30.

A screw equipped with a mixing mechanism that exerts a mixing effect by providing pins and projections and the like with a full flight screw that has nothing to the screw, reduces the effective length L / D and at the same time realizes sufficient kneading. When the effective length L / D is less than 22, kneading becomes insufficient, and when the effective length L / D is 30 or more, the effects of shearing force and temperature rise due to kneading cannot be suppressed.

The effective length L / D of the screw provided with the mixing mechanism is preferably in the range of 24 to 28, and is more dense and uniform by sufficient kneading without being affected by shearing force or temperature rise. It is possible to obtain a foam having a suitable internal cell.

The mixing mechanism provided on the screw includes, for example, a dalmage screw, a pin screw, a multi-pin screw, a unimelt screw, an HM
Mixing portions of various screws such as a screw and a DIS screw can be used.

In addition to these molding conditions, the shell of the heat-expandable microcapsules must have a temperature characteristic of softening but not melting under the molding temperature conditions of the thermoplastic resin raw material. The material and temperature characteristics are appropriately selected from the thermal expansion microcapsules already listed according to the type of thermoplastic resin, and the low-boiling liquid, etc., contained inside expands into a gas at the melting temperature of the thermoplastic resin raw material. It is used by selecting from those already raised.

In extrusion molding and injection molding, since the raw material supplied from the hopper is kneaded by an extruder or an injection molding machine with a screw having a mixing mechanism, the shearing of the heat-expandable microcapsules is also performed by kneading. Forces and the like are applied, and furthermore, a pushing force and a radiating force are applied when the material is extruded into a die or a mold.Therefore, it is necessary that the microcapsules are not broken even when these forces are applied. The temperature characteristics of the shell of the expandable microcapsule are determined, and the size and the like are selected.

As a specific temperature characteristic, the melting temperature of the shell of the heat-expandable microcapsule is determined by the relationship between the melting temperature of the shell of the microcapsule and the melting temperature of the thermoplastic resin material. 20 ° C or higher and 80 ° C or higher
The temperature is preferably 30 ° C. or higher and 60 ° C. or lower, more preferably 40 ° C. or higher and 60 ° C. or lower.

According to the foam molded or extruded by sufficiently kneading with the screw having the mixing mechanism, the thermally expandable microcapsules are expanded and contained in the thermoplastic resin. , It is possible to mold a foam in a state in which gas by the foaming agent is present,
Each bubble is stable because the one wrapped in microcapsules and the one with normal gas are uniformly dispersed.
In the case of extrusion molding, even when the pressure is released after being extruded from the die, the pressure of the entire system is maintained and the gas does not escape directly to the outside of the foam, and a foam having a good surface appearance is obtained. be able to.

Therefore, in the foam molded article formed by such extrusion molding or injection molding, the number and the size of the heat-expandable microcapsules after expansion and the size and size of the bubbles depending on the particle diameter, and the expanded foam. The density (expansion ratio) of the molded article is determined by the sum of the amount and the size of the bubbles by the foaming agent later, and the foaming agent is compared with the case where only the thermally expandable microcapsules are mixed with the thermoplastic resin raw material. A high foaming state in which the density of the molded body is reduced by the amount of mixing can be achieved.

Furthermore, unlike the case of using only the foaming agent, the state of the foamed cells and the appearance of the molded product are uniform and excellent as in the case of using only the microcapsules.

The number of unexpanded thermally expandable microcapsules (mixing amount) to be mixed with the thermoplastic resin raw material and the particle size of the thermally expandable microcapsules after expansion due to the heating amount during molding are estimated based on the microcapsule fraction. Since the foaming state can be controlled only by increasing the amount of the heat-expandable microcapsules, the density of the molded article and the foaming state can be easily controlled, and the desired density can be achieved relatively easily. it can.

As described above, the density (expansion ratio) of the foamed molded article
For example, the mixing amount of the heat-expandable microcapsules is set to 0.5 to 20 with respect to 100 parts by weight of the thermoplastic resin raw material.
Parts by weight, preferably 2 to 10 parts by weight, the mixing amount of a blowing agent such as a chemical blowing agent is 0.1 to 10 parts by weight, preferably 1 to 10 parts by weight.
By setting it to 5 parts by weight, the density of the foamed molded article is 0.80 to
0.35, and can be in a highly foamed state.

If the mixing amount of the foaming agent is large, the cost is effective, but there may be a problem in terms of cell uniformity and appearance of the molded product. Therefore, the mixing amount of the microcapsules and the foaming agent is appropriately determined depending on the purpose of use of the molded article.

Thus, when lightweight and heat insulating properties are required as in building materials, the particle size of the heat-expandable microcapsules should be relatively large, and the mixing amount including the foaming agent should be increased. It can respond by doing.

When a uniform and dense foaming state is required as in the case of a roll for OA equipment, the heat-expandable microcapsules to be mixed with the thermoplastic resin are made into very small spherical particles, and the foaming agent is used. The particle size after expansion is, for example, 5 to 30 μm.
A uniform and dense foamed article can be obtained with a thickness of about 100 μm.

Further, even in the case where it is necessary to foam such that water does not penetrate, such as a sponge for a shoe sole, etc., closed cells are formed by the heat-expandable microcapsules and the foaming agent. It can be dealt with by controlling the size and amount of bubbles according to the required cushioning property without water penetration.

[0046]

EXAMPLES Examples of the present invention and comparative examples will be described below, but the present invention is not limited to these examples.

As an example, when a general molded article using a thermoplastic polyolefin-based elastomer (TPO) as a thermoplastic resin is foam-formed using an extruder (Example 1), a thermoplastic polyester-based polyurethane elastomer is used. When a roll for OA equipment using (TPU) is foam-formed using an extruder (Example 2), a thermoplastic polyester-based polyurethane elastomer (TPU)
When the roll for OA equipment was foam-formed using an extruder with a screw having a large effective length using (Example 3),
As a comparative example, in comparison with Example 2, the screw without a mixing mechanism (Comparative Example 1), and without using a heat-expandable microcapsule (Comparative Example 2), the effective length was increased with a screw without a mixing mechanism. In the case (Comparative Example 3), foam molding was performed by an extrusion molding machine, and these are summarized in Table 1.

(Example 1) 2 parts by weight of azodicarbonamide as a chemical foaming agent and 5 parts by weight of an inorganic filler are based on 100 parts by weight of a thermoplastic polyolefin-based elastomer (TPO: Santoprene 203-50 manufactured by AES Japan). Parts, and 2 parts of the heat-expandable microcapsules, were extruded by an extruder having a screw equipped with a mixing mechanism, and subjected to foam molding.

The extrusion conditions in this case are as follows: the effective length L / D of the screw is 25; the mixing mechanism is a four-flight Dalmage tip; the compression ratio CR is 2.5; the gap between the screw crest and the cylinder wall is 0.05 to 0.150 mm,
As the temperature condition, the inlet temperature of the screw cylinder is set to 20.
0 ° C. and the head inlet temperature were adjusted to 210 ° C.

Here, the compression ratio CR is represented by CR = V2 / V1, where V1 is the volume of one pitch relative to the screw tip depth h1, and V2 is the volume of one pitch relative to the screw root depth h2.

At this time, the melting temperature of the thermoplastic polyolefin-based elastomer was 180 ° C., and the heat-expandable microcapsules having a melting temperature of about 220 ° C. were selected.

The foam molded article thus obtained was excellent in the kneading state, the internal cells were dense and uniform, and the appearance was good.

Example 2 Thermoplastic polyester-based polyurethane elastomer (TPU: Dainichi Seika Rezamin P)
-1078) A mixing mechanism was provided for a resin composition obtained by adding 2 parts by weight of azodicarbonamide as a chemical foaming agent, 5 parts by weight of an inorganic filler, and 2 parts of thermally expandable microcapsules to 100 parts by weight. Extrusion foam molding was performed with an extruder having a screw.

In this case, the extrusion molding conditions are as follows: the effective length L / D of the screw is 28, the mixing mechanism is 4 flights at the tip and 2 flights at the center, and the compression ratio is C.
R was 2.3, the gap between the screw peak and the cylinder wall was 0.05 to 0.150 mm, and the temperature conditions were adjusted to 160 ° C. for the inlet of the screw cylinder and 160 ° C. for the head.

At this time, the melting temperature of the thermoplastic polyester-based polyurethane elastomer was 150 ° C., and the heat-expandable microcapsules were selected to have a melting temperature of about 190 ° C.

The foam molded article obtained as the roll for OA equipment thus obtained was excellent in the kneaded state, the internal cells were dense and uniform, and the appearance was good.

(Example 3) Thermoplastic polyester-based polyurethane elastomer (TPU: Dainichi Seika Resamine P)
-1078) A mixing mechanism was provided for a resin composition obtained by adding 2 parts by weight of azodicarbonamide as a chemical foaming agent, 5 parts by weight of an inorganic filler, and 2 parts of thermally expandable microcapsules to 100 parts by weight. Extrusion foam molding was performed with an extruder having a screw.

In this case, the extrusion molding conditions were as follows: the effective length L / D of the screw was 33, the mixing mechanism was 4 flights at the tip and 2 flights at the center, and the compression ratio C
R was 2.3, the gap between the screw peak and the cylinder wall was 0.05 to 0.150 mm, and the temperature conditions were adjusted to 160 ° C. for the inlet of the screw cylinder and 160 ° C. for the head.

At this time, the melting temperature of the thermoplastic polyester-based polyurethane elastomer was 150 ° C., and the heat-expandable microcapsules were selected to have a melting temperature of about 190 ° C.

The foam molded article obtained as a roll for OA equipment thus obtained was excellent in the kneaded state, but had some roughening in the cell state, was somewhat uneven, and had some streaks in appearance.

Comparative Example 1 The same resin composition as in Example 2 (thermoplastic polyester-based polyurethane elastomer 1
A resin composition in which 2 parts by weight of azodicarbonamide as a chemical foaming agent, 5 parts by weight of an inorganic filler, and 2 parts by weight of heat-expandable microcapsules are added to 00 parts by weight.
Was extruded and foamed by an extruder having a general screw.

Extrusion molding conditions in this case were the same as in Example 2 except that a screw without a mixing mechanism was used (effective length L / D of screw: 28, compression ratio CR: 2.3, screw peak) The gap between the cylinder wall is 0.0
The temperature was adjusted to 160 ° C. and the head inlet temperature to 160 ° C.).

The foam molded article as the roll for OA equipment thus obtained had a dense cell, but insufficient kneading, and had an unevenly foamed portion inside.

Comparative Example 2 A resin composition obtained by removing the heat-expandable microcapsules from the resin composition of Example 2 (2 parts of azodicarbonamide was used as a chemical foaming agent for 100 parts by weight of a thermoplastic polyester-based polyurethane elastomer). Extrusion molding conditions (the effective length L / D of the screw was 28, and the mixing mechanism was the tip darmage 4 flight and the center) except that the resin composition containing 5 parts by weight of an inorganic filler was used. The damage 2 flight, the compression ratio CR is 2.3, the gap between the screw crest and the cylinder wall is 0.05 to 0.150 mm, and the temperature conditions of the screw cylinder inlet temperature are 160 ° C and the head inlet temperature are 160 ° C. C.) and extrusion foaming was performed to obtain a roll for OA equipment.

The foam molded article as the roll for OA equipment thus obtained did not have a dense foam cell and had a portion where foaming was uneven.

Comparative Example 3 The same resin composition as in Example 2 (thermoplastic polyester-based polyurethane elastomer 1
A resin composition in which 2 parts by weight of azodicarbonamide as a chemical foaming agent, 5 parts by weight of an inorganic filler, and 2 parts by weight of heat-expandable microcapsules are added to 00 parts by weight.
Was extruded and foamed by an extruder having a general screw. Extrusion molding conditions in this case are the same as in Example 2 except that a screw without a mixing mechanism was used and the effective length L / D was 33 (the effective length L / D of the screw was 33, The compression ratio CR is 2.3, and the gap between the screw top and the cylinder wall is 0.05 to 0.150.
mm, and as the temperature conditions, the inlet temperature of the screw cylinder was adjusted to 160 ° C., and the inlet temperature of the head was adjusted to 160 ° C.).

The foam molded article as the roll for OA equipment thus obtained did not have a dense foam cell and had a portion where foaming was uneven.

[0068]

[Table 1]

As described above, the heat-expandable microcapsules and the usual foaming agent are added to the thermoplastic resin, and the mixture is foamed by a screw extruder or an injection molding machine equipped with a mixing mechanism. Is sufficiently kneaded, the cells are fine and uniform in each cell, the surface is not rough, and a foam having a large expansion ratio can be obtained by the heat-expandable microcapsules in addition to the foaming with a normal foaming agent.

In this case, by appropriately setting the effective length L / D of the screw provided with the mixing mechanism to 22 or more and less than 30, a uniform and dense cell foam can be obtained.

On the other hand, in the case of a screw without a mixing mechanism, the cells become non-uniform (Comparative Example 1). Even if the effective length of the screw is increased, the cells cannot be made uniform (Comparative Example 3). If the heat-expandable microcapsules are not used in combination even with a screw having a mixing mechanism, a dense foam cell cannot be obtained, and a nonuniform foam portion is obtained (Comparative Example 2).

[0072]

According to the foam molding method for a thermoplastic resin according to the first aspect of the present invention, as specifically described above with reference to one embodiment, a heat-expandable microcapsule and a normal foaming agent are used. Was added to the thermoplastic resin, and the foam was molded by a screw extruder or an injection molding machine equipped with a mixing mechanism, so when the thermally expandable microcapsules foamed in the screw, the pressure in the screw increased, The pressure of the entire system is maintained, the gas by the normal blowing agent is rapidly expanded and held in the screw without escaping, and a good foaming state can be achieved,
By sufficiently kneading with the screw mixing mechanism,
The cells are fine and uniform in each cell, the surface is not rough, and the expansion ratio can be increased by using the heat-expandable microcapsules together with the foaming agent.

According to the thermoplastic resin foam molding method of the second aspect of the present invention, the effective length L / D of the screw provided with the mixing mechanism is set to 22 or more and less than 30 to carry out foam molding. It can be sufficiently kneaded without breaking the heat-expandable microcapsules or escaping the gas of the foaming agent, making it possible to obtain a better foaming state, and each bubble is fine and uniform, and the surface is rough. In addition, the foaming ratio can be increased in combination with the foaming by the foaming agent.

Thus, the uniform and dense air bubbles required for paper feeding of the roll of OA equipment can be provided, the lightweight and heat insulating properties of the building material can be obtained, and the cushioning properties of sponges for shoe soles can be obtained. It can easily be made to have the property of not allowing water to permeate.

Continued on the front page F-term (reference) 4F074 AA17 AA24 AA25 AA32 AA35 AA42 AA66 AA70 AA71 AA76 AA78 BA13 BA32 BA33 BA36 BA37 BA38 BA39 BA40 BA44 BA45 BA84 BA91 CA22 CA26 4F206 AA03 AA24 AA45 AB02 A07 AB16 ACO08 A JF01 JF04 JL02 JM01 JN03 JQ11 4F207 AA03 AA24 AA45 AB02 AB11 AB16 AC08 AE07 AG08 AG20 AH04 AH13 AH46 KA01 KA11 KF04 KK12 KL01 KL23

Claims (2)

[Claims] 1. When foaming a thermoplastic resin using an extrusion molding machine or an injection molding machine, a thermoplastic resin raw material is used in combination with a heat-expandable microcapsule and a foaming agent, and foaming is performed with a screw having a mixing mechanism. A foam molding method for a thermoplastic resin, characterized by being molded. 2. The foaming molding wherein the effective length (ratio of the screw length L to the screw diameter D) L / D of the screw provided with the mixing mechanism is 22 or more and less than 30. A foam molding method for the thermoplastic resin according to the above.