JP2001260209A - Method for producing thermoplastic resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin foam having a predetermined expansion ratio as a foam in which a gas is effectively applied to foam even when a filler is blended in a large amount, and the filler is blended in a large amount. And a method for producing the same. SOLUTION: A resin composition in which a high-pressure gas is impregnated and in which 50 to 1000 parts by weight of a filler is blended with 100 parts by weight of a thermoplastic resin is kneaded by an extruder (12), and a mold is formed. (3) A method for continuously producing a foam by extruding from the leading edge (37) and releasing pressure, when extruding the resin composition from the mold leading edge to release pressure, A method for producing a thermoplastic resin foam in which a thin skin layer is formed on the surface of the foam by cooling the surface of the resin composition passing through the mold tip edge (37) through the mold (3) .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin foam containing a large amount of a filler.

[0002]

2. Description of the Related Art As a conventional method for producing a thermoplastic resin foam, a thermoplastic resin is supplied to an extruder and melted.
The physical foaming method in which an organic gas such as a fluorocarbon gas or a low molecular weight hydrocarbon, or an inorganic gas such as carbon dioxide is supplied, and foaming is performed by releasing pressure at a mold tip, that is, an extrusion foaming method using a gas is generally widely used. Are known. In such a manufacturing method, there is known a means for cooling the surface of the foam at the tip of the mold and forming a skin layer in order to prevent foam breakage on the surface of the foam and improve the expansion ratio.

[0003] For example, Japanese Patent Application Laid-Open No. 5-228980 discloses that a composition containing non-crosslinked crystalline polypropylene as a main component is extruded from a mold by blowing an inert gas as a cooling medium onto a foam to break bubbles. It is described that a foam having a small amount of high foaming can be obtained. In some cases, a temperature control mechanism independent of the mold body may be provided at the tip of the mold. For example, Japanese Patent Application Laid-Open No. 9-216273 discloses that the lip portion of the T die has a relatively high clearance up to the portion with the smallest clearance. Thermoplastic foam sheet with a skin layer by controlling the temperature at the temperature, attaching a cooling plate with a shape that enlarges the clearance at the tip of the die, and cooling the sheet that is foaming at the enlarged clearance with the cooling plate Are described.

[0004]

On the other hand, a filler is sometimes added to a thermoplastic resin in order to impart functionality such as flame retardancy or moisture absorption / release properties, or to reduce material costs. On the other hand, the thermoplastic resin targeted in the above prior art is assumed to be a simple substance or a mixture of a small amount of a compounding agent such as a lubricant and a nucleating agent. When a large amount of filler is mixed into a thermoplastic resin, it has been extremely difficult to obtain a good foam even using the conventional technique.

[0005] This is because the gas is separated from the resin composition at the moment of discharge from the mold, and travels along the minute interface between the resin and the filler at a much higher speed than in the case where the filler is not mixed. It has been found that a phenomenon of so-called gas release, which is released into the atmosphere, occurs, and the gas does not function sufficiently for the growth of bubbles. If this gas escape is extreme, a phenomenon occurs in which the gas separated from the resin inside the mold tip where the resin pressure is low passes through the interface between the resin and the mold and escapes in the discharge direction. It does not contribute to growth.

In an extreme case, for example, a thickness of 1 mm
When an attempt is made to produce a foamed sheet having a thickness of about 1%, most of the gas in the resin composition is released into the atmosphere when the mold is discharged, and almost no air bubbles are formed even in the center in the thickness direction.
In some cases, the foaming ratio was as low as 1.2 times.
Therefore, as in the above-mentioned Japanese Patent Application Laid-Open No. 5-228980, it is expected that the timing of cooling is slow even when showering is performed with a refrigerant in the foam expansion process after extrusion, and gas escape occurs immediately after discharge from the mold. In addition, in the method described in Japanese Patent Application Laid-Open No. 9-216273, even if cooling is performed in the clearance expansion portion where bubbles grow, gas release is expected to occur because the resin pressure in the portion to be cooled is low.

That is, even if a conventional extrusion foaming method using a gas is applied in order to foam a resin composition containing a large amount of filler, gas escape occurs at the moment the resin composition is discharged. In fact, it is difficult to obtain the expansion ratio of

Accordingly, the present invention provides a thermoplastic resin foam having a predetermined foaming ratio as a foam containing a large amount of a filler by effectively using gas even when a large amount of a filler is blended. It is intended to provide a method of manufacturing.

[0009]

In order to achieve the above-mentioned object, the present invention according to the first aspect of the present invention is directed to a method of filling 50 to 1000 parts by weight of 100 parts by weight of a thermoplastic resin impregnated with a high-pressure gas. A method for continuously producing a foam by kneading a resin composition in which a material is blended with an extruder and extruding from a mold leading edge to release pressure, wherein the resin is molded from the mold leading edge. A method for producing a thermoplastic resin foam wherein a thin skin layer is formed on the surface of the foam by cooling the surface of the resin composition passing through the leading edge of the mold when extruding the composition to release the pressure. I will provide a.

According to a second aspect of the present invention, when the pressure is released by extruding the resin composition from the front edge of the mold, the surface of the resin composition at the front end of the mold where sufficient pressure exists. The method for producing a thermoplastic resin foam according to claim 1, wherein the thermoplastic resin foam is cooled. The present invention according to claim 3 provides:
Using a crystalline resin as the thermoplastic resin, the temperature setting of the mold body is set to −15 to + 20 ° C. of the melting point of the thermoplastic resin, and the temperature setting of the mold tip is set to 10 degrees with respect to the temperature setting of the mold body. A method for producing a thermoplastic resin foam according to claim 2, wherein the temperature is set to a temperature lower than or equal to ° C.

The thermoplastic resin used in the present invention is not particularly limited. For example, polyethylene, polypropylene, E
Polyolefin resin such as VA, polyvinyl chloride, polyvinylidene chloride, ABS resin, AS resin, polystyrene,
Examples include methacrylic resin, polyamide, polycarbonate, polyacetal, polyester, acrylic resin, thermoplastic elastomer, and powdered rubber. These may be used alone or in combination. Further, a modified or crosslinked resin may be used as long as the object of the present invention is not impaired.

The filler used in the present invention is not particularly limited, and may be an organic filler or an inorganic filler. Specific examples include silica, mica, talc, stone powder, diatomaceous earth, clay, graphite, carbon black, calcium carbonate, titanium oxide, alumina, aluminum powder, iron powder, molybdenum disulfide, barium sulfate, lithium soap, wood powder, glass , Pulp and the like.
These may be used alone or in combination.

The amount of these fillers is 50 to 1000 parts by weight based on 100 parts by weight of the thermoplastic resin. 50
If the amount is less than 1 part by weight, the effect of the predetermined filler compounding is not exhibited.On the other hand, if the amount exceeds 1000 parts by weight, the viscosity of the composition is remarkably increased, or the molded article is very poor. This is because it becomes brittle and cannot maintain its shape.
In the resin composition of the present invention, in addition to the thermoplastic resin and the filler, a lubricant, a stabilizer, an antiblocking agent, an antifoaming agent, an additive such as a pigment and a dye do not impair the object of the present invention. It may be mixed in the degree. In addition, a plasticizer and a solvent may be similarly blended, but it is desirable not to use them from the viewpoint of environment and safety.

In order to knead the resin composition impregnated with the high-pressure gas with an extruder, as described in detail later,
0 parts by weight of a thermoplastic resin and 50 to 1000 parts by weight of a resin composition blended with a filler, after supplying the extruder upstream,
A high-pressure gas may be supplied in the middle of the extruder, and the resin composition and the high-pressure gas may be impregnated and kneaded.After the resin composition previously impregnated with the high-pressure gas is supplied to the extruder, the resin composition May be kneaded.

The extruder used in this case is an extruder having one screw, two or more screws, or a combination thereof. In the case of two screws, the rotation directions of the screws may be opposite to each other or the same. The shaft type may be a parallel type or a conical type. Further, a tandem system in which extruders are combined in multiple stages may be used. The high-pressure gas in the present invention is an organic or inorganic substance that is in a gaseous state at normal temperature and normal pressure, and is not particularly limited as long as it has good impregnating property at high temperature and high pressure and does not deteriorate the resin. Possible,
Since it is in a gaseous state at normal temperature and normal pressure, it can be easily removed from the resin after use. In addition, a gas that is safe and easy to collect for the environment and the health of workers without the danger of fire, explosion, etc. is desirable. Examples of such a gas include carbon dioxide, nitrogen, argon, neon, helium, and oxygen. And an organic gas such as a fluorocarbon gas and a low-molecular-weight hydrocarbon, and those most impregnated in the resin used are preferably selected.

It is desirable that the gas is in a supercritical state where the impregnation rate is high. The supercritical state refers to a state where the temperature is equal to or higher than the critical temperature and equal to or higher than the critical pressure. For example, if the gas is carbon dioxide, the critical temperature is 30.9 ° C and the critical pressure is 7.4MP
a, In the case of nitrogen, the critical temperature is -146.9 ° C and the critical pressure is 3.4MP
a. The amount of gas impregnated in the thermoplastic resin may be any amount as long as necessary foaming can be performed, and can be appropriately selected depending on the type of resin and the type of gas. It is desirable to impregnate the gas. It is most preferable that the gas impregnation is in a saturated state, but it need not necessarily be achieved.

As a specific means for impregnating the resin composition with a high-pressure gas, for example, as described in Japanese Patent Application Laid-Open No. Hei 9-52595, a high-pressure space in which gas impregnation to supply to an extruder is closed. And an extruder provided with a pressure hopper. Alternatively, after supplying the resin composition to the extruder under normal pressure, the gas and the resin composition may be sealed and kneaded in the extruder, and as a means for realizing this content,
Examples of the method include a method of supplying a gas to a connection portion using a tandem-type extruder, and a method of supplying a gas between resin seals using screws capable of forming two molten resin seals in the extruder.

The mold used in the present invention is not particularly limited. For example, a wide sheet mold includes a T-die and a circular die. When a circular die is used, the sheet is cut open after extrusion to form a sheet. Further, in addition to the sheet mold, a shape having a different tip cross-sectional shape such as a pipe, a column, or a polygon may be used.

Regarding the structure of the mold tip, an existing mold may be used and a coolant may be blown only to the tip of the mold, or an independent temperature control mechanism (refrigerant flow) may be applied to the tip of the existing mold. Path or the like), or a tip plate having a temperature control mechanism, a nozzle, or the like may be additionally provided at the tip of the mold. Most desirably, the mold body and the tip are separated and independent, and a structure in which a temperature-controllable tip part is added.

The cooling system is not particularly limited, and a coolant such as water, air, chlorofluorocarbon or the like may be passed through the coolant channel, or water, air, alcohol, liquefied nitrogen, or liquefied carbon dioxide may be passed through the tip of the mold. The cooling may be performed by directly spraying the additionally installed tip. Regarding the degree of cooling, the number of parts of the filler, the amount of gas impregnation, the properties of the resin, extrusion operation conditions and the like can not be described unconditionally, but if the cooling is too weak, the effect of the present invention is not enough, the resin composition from the Outgassing cannot be prevented.

If the cooling is too strong, the surface condition of the foam is deteriorated. In an extreme case, not only the surface but also the inside of the resin at the tip of the mold is cooled and solidified, and the resin is clogged. Pressure may rise excessively, making the operation of the extruder itself impossible. For this reason, it is necessary to appropriately control the temperature of the tip of the mold in accordance with the number of fillers, the amount of gas impregnation, the characteristics of the resin, and the operating conditions of the extrusion. In order to achieve appropriate temperature control, a tip plate, nozzle, etc. are additionally installed in a shape that minimizes heat conduction with the mold body, and the refrigerant is circulated using a temperature-controllable refrigerant unit. It is desirable that the temperature of the tip can be strictly controlled.

According to the second aspect of the present invention, when the pressure is released by extruding the resin composition from the front edge of the mold, the surface of the resin composition is removed at the front end of the mold where sufficient pressure exists. 2. The method for producing a thermoplastic resin foam according to claim 1, wherein the surface of the resin composition is cooled via a mold. Cooling the surface of the resin composition at the mold tip where there is sufficient pressure, when releasing the pressure applied to the resin composition by extruding the resin composition from the mold tip edge, Of course, the closer to the tip edge at the mold tip, the more the resin pressure is close to the atmospheric pressure and the more easily gas escape occurs in the mold. Therefore, the surface of the resin composition at a position where the pressure is sufficiently present To prevent outgassing.

The tip of the mold where a sufficient pressure is present generally corresponds to a portion from the portion adjacent to the mold body to immediately before the edge of the tip. It is a part that can be cooled when refrigerant is blown to the mold or when an independent temperature control mechanism is provided at the tip of the existing mold,
Also, when a plate or nozzle is mounted on the tip, it means those parts. As a preferred mode, in the mold body, the resin composition is uniformly controlled to a temperature suitable for foaming, and a high resin pressure is maintained. There is a case where the temperature is rapidly lowered, and at the same time, only the temperature of the surface of the resin composition is rapidly lowered. The shorter the cooling time, the more desirable it is because a thinner skin layer can be produced.

Specifically, in the mold body, the flow path clearance is set relatively large, and the clearance is gradually set small in the die tip portion of about 5 to 50 mm (extrusion direction), and cooling is performed at this tip portion. Is preferred. Although the pressure value at the position where the resin pressure at the tip of the mold is sufficient is not clear, it is 3 to 15MP.
a degree.

In the present invention according to claim 3, the crystalline resin is a polyolefin resin such as polyethylene or polypropylene obtained by polymerizing an olefin monomer among the above-mentioned thermoplastic resins, or a polyolefin resin copolymerizable with the olefin monomer.
A copolymer with a monomer having a heavy bond, for example, represented by a polyolefin resin such as EVA, is a thermoplastic resin having a melting point.

The temperature of the mold body is set at -15 to + 20 ° C., which is the melting point of the thermoplastic resin. If the temperature is lower than −15 ° C., the temperature of the resin composition itself becomes too low, and foaming becomes difficult,
Excessive flow resistance in the mold makes operation of the extruder difficult. On the other hand, if the temperature exceeds + 20 ° C., the temperature of the resin composition itself is too high, and the cooling at the tip of the mold becomes insufficient, and the prevention of outgassing due to the formation of a skin layer becomes insufficient. In addition, the flow resistance in the mold may be excessively reduced, the back pressure at the extruder tip may be excessively reduced, and the discharge amount may fluctuate, making it impossible to operate the extruder stably. .

Further, since the gas impregnated in the thermoplastic resin functions as a plasticizer and there is a phenomenon of lowering the viscosity of the resin composition, it is low when the gas impregnation amount is large within the range of -15 to + 20 ° C. When the gas impregnation amount is small, it is preferable to set a high temperature. The temperature of the tip of the mold is set at a temperature lower than the temperature of the mold body by 10 ° C. or more. At a low temperature of less than 10 ° C. with respect to the temperature setting of the mold body, the effect of forming a skin layer by cooling and preventing outgassing is small. For a temperature setting lower than 10 ° C,
As a more preferable range, it depends on the number of parts of the filler, the amount of gas impregnation, the properties of the resin, the extrusion operation conditions, etc., but it cannot be said unconditionally, but if too much cooling is performed, the surface state of the foam is deteriorated. In extreme cases, when not only the surface of the resin but also the inside of the mold at the tip of the mold is cooled and solidified, and the resin is clogged, the mold pressure rises excessively and the operation of the extruder itself becomes impossible. There is. For this reason, it is necessary to appropriately control the temperature of the tip of the mold in accordance with the number of fillers, the amount of gas impregnation, the characteristics of the resin, and the operating conditions of the extrusion.

(Function) The problem when foaming a resin composition in which a filler is mixed in a large amount in a thermoplastic resin is that the gas is separated from the resin composition at the moment of discharge from the mold according to the study of the present inventors. Then, as compared with the case where the filler is not mixed, the so-called outgassing which is released to the atmosphere through the minute interface between the resin and the filler at a remarkably fast speed occurs, and the resin pressure is low. It was found that the gas was separated from the resin inside the tip of the mold, and passed through the interface between the resin and the mold and escaped in the discharge direction. In the present invention, in the mold body, the resin composition is uniformly controlled to a temperature suitable for foaming, and a high resin pressure is maintained. And when releasing to atmospheric pressure at the mold tip edge, reduce the pressure as rapidly as possible,
At the same time, only the temperature of the surface of the resin composition is rapidly reduced.

At this time, it is preferable that the cooling be started from the tip end of the mold where the resin pressure is sufficiently present. As a result, the resin composition discharged from the front end of the mold is released from pressure and foams, and a thin skin layer generated by cooling is present on the surface to prevent gas from leaking from the surface, Is kept at a temperature suitable for foaming without being greatly affected by the instantaneous cooling of only the tip end of the mold, and foaming grows. In addition, by cooling the mold tip, the pressure loss in this area increases, keeping the resin pressure in the mold body before cooling high, and enabling rapid release of pressure at the tip edge. There is also a positive effect. From the above effects, in the present invention, even with a resin composition containing a large amount of a filler, a gas can be made to function effectively for foaming, and a foam having a higher foaming ratio than before can be obtained. On the other hand, even when a normal mold having no independent tip is used, the expansion ratio can be easily improved by cooling only the tip. In addition, the skin layer can be easily applied to the surface of the foam without using a complicated apparatus such as applying the skin layer by using an extruder different from the multilayer mold.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. The equipment and devices used in the examples and comparative examples are as follows. In the examples, the desired substantially flat thermoplastic resin foam was obtained. The outline of the apparatus is shown in FIGS. Extruder: tandem extruder 1st stage (11) ·· φ40 single screw extruder L / D = 22, 5.5kw Second stage (12) ·· φ70 single screw extruder L / D = 10, 5.5kw ( The back pressure at the tip is listed in the table) Die A (3): Slit die with body part (31), width 30mm, outlet thickness 1.4mm. A pressure sensor was installed 15 mm upstream, and the measured pressure was described in the table as "die tip pressure". Incidentally, (32) is a heat medium passage. Tip (33): width 30 mm, outlet thickness 1.0 mm, total length (extrusion direction) 25 mm, temperature control using water. In addition, (34) is a coolant flow path, and (37) is a die tip edge.

Die B (4): Main body (41) A slit die with a width of 30 mm and an outlet thickness of 1.0 mm, which controls the temperature using oil and a pressure sensor 55 mm upstream from the outlet of the main body. Was installed, and the measured pressure was described in the table as "die tip pressure". Incidentally, (42) is a heat medium flow path. Independent tip part ... none. In addition, (47) is a die tip edge.

Raw material: Ethylene vinyl acetate resin copolymer (“Novatech EVA LV660” manufactured by Nippon Polychem Co., Ltd.)
Melting point 71 ° C) (pulverized) 100 parts by weight Wood flour (manufactured by Sanwa Cellulosin, # 100 mesh passed)
Average particle size 28μm) 100 parts by weight Lubricant (Kao wax 220) 5 parts by weight The above raw materials are pre-mixed and put into an extruder (bulk specific gravity: about 0.2 g)
/ cm ³ , solid specific gravity: about 1.16 g / cm ³ ) Gas: carbon dioxide, gas supply amount (parts by weight based on 100 parts by weight of resin) and supply pressure are described in the table. Molding conditions: first stage: screw rotation speed 20 rpm, temperature setting 80-130 ° C, raw materials were fed in a fixed amount by a feeder. Second stage: Screw rotation speed 4.5 to 9 rpm (for controlling the resin filling state), temperature setting 100 to 130 ° C. Extrusion amount: 2 kg / hour Mold temperature setting: described in the table.

The first-stage extruder (11) shown in FIG. 1 obtains a resin composition in which 50 to 1000 parts by weight of a filler is blended with 100 parts by weight of a thermoplastic resin, and partially kneads the resin composition. The raw material was supplied from a feeder (7) to an extruder (11) via a hopper, and was extruded to a second-stage extruder (12). Then, at the most upstream part of the second stage extruder (12) (immediately after the connection with the first stage), the gas cylinder (61) and the pump (62)
Was supplied through the column (pressure is described in the table), and the raw material resin was impregnated. In the case of Examples 1-4 and Comparative Examples 5-8, this gas impregnated resin composition was used in a mold A (3).
And Examples 5-6 and Comparative Examples 1-4 and 9-1
In the case of 0, it is supplied to the mold B (4) and the mold tip edge (37) or (4
By extruding from 7) and releasing the pressure, a substantially flat thermoplastic resin foam was obtained. The mold A (3) of the apparatus shown in FIG. 1 is simply shown, and details thereof are as shown in FIG.

(Method of Evaluating Foam) An extruded foam sample was frozen and broken with liquid nitrogen and observed with a scanning electron microscope (SEM). Set the thickness of the skin layer (one side) to 1
The average value was determined as the skin layer thickness by measuring 0 points. The expansion ratio was determined by measuring the overall density of the sample and calculating the expansion ratio from the previously measured density of the solid body of the resin composition. Examples and comparative examples performed using the above apparatus,
The results are shown in Tables 1 and 2.

(Comparative Examples 1 to 4) In Comparative Examples 1 to 4, the mold B (4) having no independent mold tip was used to completely cool the tip such as blowing air to the discharge port. This is an example of molding without using. Because there was no cooling at the tip, the temperature at the tip of the mold had a maximum deviation of about −4 ° C. from the temperature setting of the mold body. The gas supply amount is twice as large as in Examples 1 and 2 described later,
Compared to Examples 3 to 6, the foams obtained in Comparative Examples 1 to 4 had a low expansion ratio despite the same gas supply amount.

(Examples 1 and 2 and Comparative Examples 5 and 6) In Examples 1 and 2, a mold A (3) having a coolable mold tip was mounted.
This is an example in which air is blown to the discharge port to form the sheet (No refrigerant). It can be seen that the foaming ratio is improved in spite of the gas supply amount being half that of Comparative Examples 1 to 4. However, while the temperature of the mold body is set to + 4 ° C. and the example 14 at + 14 ° C. is capable of foaming with respect to the melting point of the resin of 71 ° C., the comparative example 5 at −16 ° C. operates with excessive back pressure. I had to cancel. In Comparative Example 6 at + 24 ° C., the pressure in the mold was not stable, and gas and resin were ejected from the tip of the mold, and the operation had to be stopped. From the above, by using the present invention that cools the independent mold tip, it is possible to make the impregnated gas function efficiently for foaming by preventing outgassing even if the gas supply amount is small, and improve the foaming ratio. I understand.

(Embodiments 3 and 4 and Comparative Examples 7 and 8) In Embodiments 3 and 4, the mold A having the coolable mold tip was mounted.
(3) is an example in which, in addition to blowing air to the discharge port performed in Examples 1 and 2 and cooling the tip end portion of the mold with water as a coolant, molding is performed. It can be seen that the foaming ratio is greatly improved as compared with Comparative Examples 1 to 4 in which the gas supply amount is the same. Also, while the temperature setting of the mold body was −11 ° C. for Example 3 and the + 9 ° C. Example 4 for the resin melting point of 71 ° C., foaming was possible, whereas the comparative example 7 of −16 ° C. was operated by excessive back pressure. In Comparative Example 8 at + 24 ° C., the pressure in the mold was not stable, gas and resin were ejected from the tip of the mold, and the operation had to be stopped. From the above,
It can be seen that the use of the present invention, in which the independent mold tip is cooled, allows the impregnated gas to efficiently function for foaming by preventing outgassing as compared with the prior art, thereby greatly improving the foaming ratio.

(Examples 5 and 6 and Comparative Examples 9 and 10) In Examples 5 and 6, the discharge ports used in Examples 1 to 4 were manufactured using the mold B (4) having no independent mold tip. This is an example in which air was blown to the mold in the same manner and then molded. It can be seen that the foaming ratio is improved as compared with Comparative Examples 1 to 4 in which the gas supply amount is the same. In addition, in Example 5 where the temperature setting of the mold body was −6 ° C. and in Example 6 where the temperature was + 4 ° C., foaming was possible with respect to the melting point of the resin of 71 ° C., whereas in Comparative Example 9 where the temperature was −16 ° C., the operation was performed due to excessive back pressure. In Comparative Example 10 at + 24 ° C., the pressure in the mold was not stable, and gas and resin were ejected from the tip edge of the mold, so that the operation had to be stopped. From the above, the use of the present invention that simply cools the tip without having an independent mold tip makes it possible to prevent outgassing more than before, and to reduce the impregnated gas efficiency. It can be seen that the foaming function can be improved and the expansion ratio can be improved.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

The method for producing a thermoplastic resin foam of the present invention is constituted as described above, and according to the present invention, even if the above resin composition containing a large amount of filler is used, it can be used as compared with the conventional one. A foam having a skin layer on the surface with a high expansion ratio can be manufactured. Therefore, it is possible to provide a foam having a flexible and good texture in which a larger amount of filler is blended than before. At this time, the skin layer can be easily applied to the surface of the foam without using a complicated apparatus such as applying the skin layer by using a multi-layer mold and another extruder. Further, the efficiency of high pressure gas foaming is improved, and a foam having a foaming ratio equal to or higher than that of a conventional foam can be manufactured with a smaller gas supply amount than before. On the other hand, even when a normal mold having no independent tip is used, the expansion ratio can be easily improved by cooling only the tip.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an apparatus suitable for use in the manufacturing method of the present invention.

FIG. 2 is a schematic view showing an example of a mold (independent tip installation) suitable for use in the manufacturing method of the present invention.

FIG. 3 is a schematic view showing another example of a mold (a type in which a mold body and a tip portion are integrated) suitable for use in the manufacturing method of the present invention.

[Explanation of symbols]

 (12) ・ ・ ・ Extruder (3) ・ ・ ・ Mold A (31) ・ ・ ・ Mould main body (33) ・ ・ ・ Mold tip (37) ・ ・ ・ Mold tip edge (4) ・..Mold B (47) ・ ・ ・ Mold tip edge

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F074 AA17 AA97 BA31 BA32 CA22 CC05Z CC22X DA19 4F207 AA10 AB02 AB11 AG20 KA01 KA14 KK45 KK48

Claims (3)

[Claims] 1. A resin composition comprising 100 parts by weight of a thermoplastic resin and 50 to 1000 parts by weight of a filler, which is impregnated with a high-pressure gas, is kneaded with an extruder, and the leading edge of a mold is kneaded. A method for continuously producing a foam by extruding from the mold and releasing pressure, wherein the resin passes through the mold tip when extruding the resin composition from the mold tip and releasing the pressure. A method for producing a thermoplastic resin foam, comprising forming a thin skin layer on the surface of a foam by cooling the surface of the composition. 2. The method according to claim 1, wherein when releasing the pressure by extruding the resin composition from a die tip edge, the surface of the resin composition is cooled at a die tip where pressure is sufficiently present. Item 4. The method for producing a thermoplastic resin foam according to Item 1. 3. A crystalline resin is used as a thermoplastic resin.
Set the temperature of the mold body to -15 to +20 of the melting point of the thermoplastic resin.
3. The method for producing a thermoplastic resin foam according to claim 2, wherein the temperature is set to 10 ° C. and the temperature of the tip of the mold is set to a temperature lower than the temperature of the mold body by 10 ° C. or more.