JPH11293021A - Method for producing polyolefin resin open cell foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyolefin resin foam excellent in recyclability by appropriately selecting a material by freely selecting the material, and also to have an excellent process stability in the open cells of the polyolefin resin. Provided is a method for producing a foam. SOLUTION: A polyolefin resin and a dioxime compound are melt-mixed to modify the resin, and a thermally decomposable chemical foaming agent is added to the modified resin and kneaded, and the resulting foamable resin composition is shaped. Then, the mixture is heated and foamed, and the obtained foam is further heated in a temperature range of 200 to 250 ° C. for 10 to 180 minutes. Preferably, a random type polypropylene resin and a dioxime compound are melt-mixed to modify the resin, the resulting modified resin is blended with an unmodified homo-type polypropylene resin, and the resulting blend is subjected to a pyrolytic chemical blowing agent. Is added and kneaded, and the resulting foamable resin composition is shaped and heated and foamed, and the resulting foam is further heated at a temperature in the range of 200 to 250 ° C. for 10 to 180 minutes.

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 polyolefin resin open cell foam having excellent recyclability.

[0002]

2. Description of the Related Art Polyolefin resin foams are widely used as industrial materials because they have an excellent balance between mechanical and thermal properties and can be subjected to secondary processing by heating and shaping.

In order to produce a sheet-like foam of a polyolefin resin, it is necessary to crosslink the resin so that the resin has a foamable melt strength. For example, Japanese Patent Publication No. 6-45717 discloses a melt-mixed product obtained by adding a specific ethylene copolymer, a specific ethylene-α-olefin copolymer and a specific vinyl monomer to a polypropylene resin, and further adding a foaming agent. A method for producing a crosslinked foam is disclosed in which a sheet-like molded product is continuously irradiated with an electron beam to adjust the gel fraction to 20 to 60%, and then the obtained continuous crosslinked sheet is foamed. Although the foam obtained by this method exhibits excellent properties by thermoforming or the like, since the cells have a closed cell structure, they are inferior in air permeability, flexibility, and flexibility, and are used for applications such as filters. Can not do. In recent years, as a measure against environmental resource problems, the recyclability of used members has been required, but in fact, the foam crosslinked with an electron beam cannot be re-melted even if collected after use, and is not suitable for recycling. .

On the other hand, Japanese Patent Publication No. Hei 7-35446 discloses that
As a method for obtaining an open-cell olefin resin foam having excellent air permeability, an organic peroxide is used for a polyolefin resin.
While precisely controlling the decomposition rate of the foaming agent and the decomposition rate of the cross-linking agent, the foaming resin composition mainly composed of a thermal decomposition type chemical foaming agent and silicone oil is foamed during the period from the start of foaming to the completion of foaming. A method for crosslinking is described. In this manufacturing method, the control of the interfacial tension of the cells by the silicone oil is added, and an open-cell foam having a fine and uniform cell diameter can be obtained.

However, since this production process is very delicate, there is little freedom in selecting resins and other materials, and at present, foams based mainly on ethylene-vinyl acetate copolymers can be obtained. In addition to this, the foam has poor heat resistance, and has poor mechanical properties (compression properties and creep properties).

[0006]

DISCLOSURE OF THE INVENTION In view of the above-mentioned problems, the present invention provides a polyolefin resin foam having excellent recyclability, which is capable of collecting a used foam and melting and molding the foam again. An object of the present invention is to provide a method for producing a polyolefin-based resin open-cell foam which can be appropriately produced by a free choice of the above and has excellent process stability.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for producing an open-celled polyolefin-based resin foam, which comprises melting and mixing a polyolefin-based resin and a dioxime compound to modify the resin. A foaming agent is added and kneaded, the obtained foamable resin composition is shaped and heated and foamed, and the obtained foam is further heated in a temperature range of 200 to 250 ° C. for 10 to 180 minutes. How to

In a particularly preferred embodiment of the present invention, a random type polypropylene resin and a dioxime compound are melt-mixed to modify the resin, and the resulting modified resin is blended with an unmodified homo-type polypropylene resin. A thermal decomposition type chemical foaming agent is added to the obtained blend and kneaded. The obtained foamable resin composition is shaped and heated and foamed, and the obtained foam is further subjected to a temperature range of 200 to 250 ° C. A method for producing a polypropylene open-cell foam, comprising heating for 10 to 180 minutes.

The polyolefin constituting the main component of the unmodified polyolefin resin in the method of the present invention is a homopolymer of an olefinic monomer or a copolymer of a main component olefinic monomer and another monomer, and is particularly limited. Although not limited, for example, polyethylene, polypropylene, polybutene and the like are used.

Examples of the polyethylene include homo-type polyethylenes such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene, and random or block copolymers containing ethylene as a main component. You. As the ethylene-based copolymer, ethylene-propylene copolymer, ethylene-
Examples thereof include a propylene-diene terpolymer, an ethylene-butene copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, and an ethylene-acrylate copolymer.

Examples of the polypropylene include a homo-type polypropylene and a random or block copolymer containing propylene as a main component. Examples of the propylene-based copolymer include a random copolymer of propylene and an α-olefin, and a block copolymer of propylene and an α-olefin (provided that the α-olefin is ethylene, 1-hexene, -Methyl-1-pentene, 1-octene, 1-butene, 1-pentene and the like are exemplified).

The above-mentioned polyolefins may be used alone or in combination of two or more. In the method of the present invention, in particular, polypropylene is preferably used in terms of heat resistance and thermoformability, and polyethylene is preferably used in terms of flexibility.

In the present invention, the polyolefin resin means that the above polyolefin may be a blend with another resin. In the case of a polypropylene-based resin, examples of other resins include polyethylene, ethylene-vinyl acetate copolymer, olefin-based thermoplastic elastomer, polystyrene, and styrene-based thermoplastic elastomer. The proportion of polyolefin is preferably from 70 to 100% by weight of the whole blend. If this ratio is less than 70% by weight, not only the characteristics (light weight, chemical resistance, flexibility, elasticity, etc.) of the polyolefin cannot be exhibited, but also in the case of a blend with another polyolefin resin, the melt viscosity required for foaming is reduced. It may be difficult to secure them.

The dioxime compound used in the present invention is an oxime group represented by the following chemical formula (I) or
As shown by the chemical formula (II), the compound has two groups in a molecule in which a hydrogen atom of an oxime group is substituted with another atomic group (mainly a hydrocarbon group). Representative examples of such a dioxime compound include a p-quinone dioxime compound represented by the chemical formula (III) and a p, p′- represented by the chemical formula (IV).
And dibenzoylquinone dioxime compounds. These compounds may be used alone or in combination of two or more.

[0015]

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The amount of the dioxime compound is 0.05 to 5 parts by weight, preferably 0.2 to 3 parts by weight, based on 100 parts by weight of the polyolefin resin. If the amount is less than 0.05 part by weight, the melt viscosity required for foaming cannot be imparted. If the amount exceeds 5 parts by weight, the degree of crosslinking becomes too high and the extrudability deteriorates (for example, high load Such,
On the other hand, a foaming agent to be added later cannot be uniformly kneaded in the resin composition, and the gel fraction is unnecessarily increased, thereby impairing recyclability. In addition, the ratio of the dioxime compound remaining as an unreacted substance in the product is increased, which irritates the human body and lowers the efficiency of product formation for the raw material.

The thermal decomposition type chemical blowing agent used in the present invention is not particularly limited as long as it generates a decomposition gas by heating. A typical example of a pyrolytic chemical blowing agent is
Azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, and 4,4-oxybis (benzenesulfonylhydrazide). These may be used alone or in combination of two or more. Among them, azodicarbonamide is particularly preferably used.

The thermal decomposition type chemical foaming agent is the modified resin composition 1
1 to 50 parts by weight, preferably 2 to 50 parts by weight,
It is used in an appropriate amount in the range of 35 parts by weight depending on the desired expansion ratio.

In order to obtain a modified resin composition, a polyolefin resin and a dioxime compound are melt-mixed. Specifically, the above-mentioned substances are charged in required amounts into a kneading device such as a screw extruder or a kneader, and are melt-mixed. The melt mixing temperature is 170 ° C. or higher and the decomposition temperature of the polyolefin resin (usually around 300 ° C.), preferably 200 ° C.
２５０250 ° C. If the melt mixing temperature is lower than 170 ° C., the expansion ratio of the finally obtained foam will not be sufficiently high,
When the temperature exceeds 300 ° C., the polyolefin resin is easily decomposed.

The kneading apparatus used for the melt kneading is not limited to a screw extruder, but may be any kneading apparatus that can be generally used in plastic molding.
Examples thereof include a rotor and a continuous kneader. Among them, a screw extruder capable of continuous operation is preferable, and a single-screw extruder, a twin-screw extruder, a multi-screw extruder having three or more screws, and the like are all suitably used. As a single screw extruder, in addition to a general full flight screw, an extruder having a discontinuous flight screw, a pin barrel, a mixing head, and the like are also used. Further, as the twin screw extruder, a meshing co-rotating extruder, a meshing different direction rotating extruder, a non-meshing different direction rotating extruder and the like can be suitably used. Providing a vacuum vent at the subsequent stage of the extruder is effective for preventing volatiles from remaining in the modified resin composition.

When a screw extruder is used, the polyolefin-based resin is fed into the extruder from a usual hopper, but it is also preferable to use a screw type feeder, a weight control type feeder or the like in order to increase the quantitativeness.

The method for supplying the dioxime compound is not particularly limited. For example, the following method is preferably performed.

I) After dry-blending the polyolefin resin and the dioxime compound, the blend is put into a general hopper at a time.

Ii) The polyolefin resin and the dioxime compound are charged into the extruder using separate feeders. For example, using a separate quantitative feeder, the dioxime compound is charged into the extruder from the same portion as the polyolefin resin. Alternatively, the dioxime compound is introduced from the middle of the extruder using a side feeder.

After the resin modification step, preferably, an unmodified polyolefin resin is added to the obtained modified polyolefin resin.

The addition of the unmodified resin improves the resin flow during extrusion. The ratio of the unmodified resin to be added is preferably 20 to 80% (weight), more preferably 30 to 70%, based on the whole resin. If the ratio of the modified resin is less than 20%, the melt tension required for foaming cannot be maintained, and the magnification may be reduced, so that a good foam may not be obtained. On the other hand, if the ratio of the modified resin exceeds 80%, the effect of improving the resin flowability during extrusion may not be sufficiently exhibited.

The resin composition having high process stability in obtaining an open-cell foam is preferably a resin composition in which a random type polypropylene is used as a modified resin and a homo-type polypropylene is used as an unmodified resin. In the resin composition of this combination, the decrease in the expansion ratio during heating is greatly suppressed, and open cells can be gradually obtained, so that the precise control of the open cell ratio becomes possible and the production stability is dramatically improved. To improve.

In order to obtain a foamable resin composition by melt-mixing a polyolefin resin and a dioxime compound and kneading a thermally decomposable chemical foaming agent into the obtained modified resin composition, the above-described melt-kneading apparatus for modification is used. Using a kneading device for mixing a foaming agent, which is integrated with or separate from the kneading device (the structure may be the same as that of the melt-kneading device for modification), the following operation is performed, for example.

(A) A polyolefin resin and a dioxime compound are melt-mixed in a batch or continuous melt-kneading apparatus for denaturation, and the resulting modified resin composition is taken out of the melt-kneading apparatus, solidified, and granulated. After doing something like
The resin composition is transferred to a batch-type or continuous kneading device for mixing a foaming agent, a foaming agent is charged therein, and both are melt-kneaded to obtain a foamable resin composition.

(B) The polyolefin resin and the dioxime compound are melt-mixed in a batch-type melt-kneading device for denaturation to carry out denaturation, and the resulting modified resin composition is substantially mixed with a blowing agent in the kneading device. After cooling to a temperature at which the foaming agent does not decompose, a foaming agent is added thereto, and the two are melt-kneaded to obtain a foamable resin composition.

(C) The polyolefin resin and the dioxime compound are melt-mixed in a screw extruder (continuous melt kneading apparatus) for modification, and then the melt is cooled to a temperature at which the foaming agent does not substantially decompose. Then, a foaming agent is introduced from a supply port provided in the middle of the screw extruder, and the two are melt-kneaded to obtain a foamable resin composition.

(D) In another mode of the continuous operation, two screw extruders are connected to each other, and the polyolefin resin and the dioxime compound are melt-mixed with the first screw extruder, and the resulting modified resin composition is mixed. After lowering the temperature in the same manner as above, the same resin composition is transferred to a second unit, a foaming agent is charged therein, and the two are melt-kneaded to obtain a foamable resin composition.

The resin composition kneaded with the thermal decomposition type chemical foaming agent may be further shaped. In addition to extrusion, press molding, blow molding, calendering molding,
A method generally performed in plastic molding, such as injection molding, can be applied.

In particular, a method of directly shaping the foamable resin composition discharged from the screw extruder according to the above methods (c) and (d) is preferable from the viewpoint of productivity.

The shaped foamable resin composition comprising the modified resin composition and the foaming agent can be foamed to a desired foaming ratio under a constant pressure by heating under an appropriate temperature condition. The heating is usually performed in a temperature range from the decomposition temperature of the thermal decomposition type chemical foaming agent to (decomposition temperature + 100 ° C). As a foaming apparatus for performing such foaming, a vertical or horizontal foaming furnace, a hot air thermostat or an oil bath, a metal bath, a salt bath, or another heat bath generally operated in an air atmosphere is used. .

The foam raw material produced by such a method has good flowability while ensuring foaming properties, enables molding of an irregular-shaped product, and melts the molded product even after the product is molded. Once pelletized, it can be reused.

Although the reason for exhibiting such characteristics is not clear, the modified resin is in a finely crosslinked state, the crosslinked resin is finely dispersed in the uncrosslinked resin, and the crosslinked resin wraps around the crosslinked resin. With such a structure, it is considered that flowability can be secured while maintaining the melt tension necessary for foaming.

Next, the foam thus produced is further heated to convert closed cells into open cells. The heating method is
It may be the same as the method described in the description of the foaming step,
For example, there are a method of heating with high-temperature air, a method of heating with high-temperature oil, and a method of heating with an infrared heater. The heating conditions vary depending on the resin composition of the foam used,
C. to 250.degree. C. for 10 minutes to 180 minutes. When the foam is heated in this range, the normal polyolefin-based foam breaks bubbles, loses its shape-retaining ability, and causes a significant reduction in magnification. However, in the foam obtained by the method of the present invention, the ratio of open cells can be increased in proportion to the heating time without much reduction in magnification. For this reason,
The open cell ratio can be controlled to a desired value, and the production stability is good. If the temperature range is less than 200 ° C. or the heating time is less than 10 minutes, the closed cell rate of the foam cannot be reduced so much. The temperature range is 250
If the temperature exceeds 180 ° C or the heating time exceeds 180 minutes,
The resin is deteriorated, and the desired expansion ratio cannot be maintained.

Here, the open cell ratio is defined as the total cell of the foam, that is, the sum of the number of closed cells and the number of open cells.
Ratio of open cells (number of open cells / total number of cells) x
The closed cell ratio refers to the ratio of the number of closed cells to the total number of closed cells (the number of closed cells / the total number of cells) × 100 (%). The closed cell refers to a bubble shape in which each cell is independent and isolated from the others, and the open cell refers to a bubble shape in which each cell communicates.

[0040]

According to the method of the present invention, a polyolefin resin and a dioxime compound are melt-mixed to modify the resin, and a thermally decomposable chemical foaming agent is added to the modified resin and kneaded to obtain a foamable resin composition. The foam obtained by shaping and heating and foaming is excellent in shape retention at high temperatures and can withstand prolonged heating. Therefore, by heating under predetermined conditions, only the open cell ratio can be increased without much reduction in magnification, and a polyolefin resin open cell foam can be stably manufactured.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to embodiments.

(Example 1) i) Production of foamable resin composition First, an apparatus used for modifying a resin and kneading and blending a foaming agent in the method of the present invention will be described.

In FIG. 1, the screw extruder (1) for modification is
It is connected to the screw extruder (2) via a connecting pipe provided at the tip thereof and a connecting pipe provided at a middle portion of the screw extruder (2) for foaming agent kneading and resin blending. . Screw extruder for foaming agent kneading and resin blending (2)
And a forming die (4) at the tip. Volatile suction pumps (5) and (6) are connected to the tip of each of these two screw extruders (1) and (2). These extruders are also equipped with thermocouples (7) (8) ) (9) It has (10).

The screw extruder (1) for modification is BT40
This is a co-rotating twin-screw extruder (manufactured by Plastic Engineering Laboratory Co., Ltd.), which is equipped with a self-wiping double-start screw.

The screw extruder (2) for foaming agent kneading and resin blending is a TEX-44 type (manufactured by Nippon Steel Works Co., Ltd.) co-rotating twin-screw extruder, which is equipped with a self-wiping double screw. L / D is 45.5,
D is 47 mm.

The forming die is a sheet-shaped T die (width 200 m).
mx 1 mm in thickness).

In the apparatus having the above structure, first, the polyolefin resin (A) and the dioxime compound are charged into the modifying screw extruder (1) from the rear end hopper, and the whole section is set at a set temperature of 220 ° C. and 150 rpm. Both were melt-mixed to obtain a modified resin composition. At this time, the volatile components generated in the extruder were evacuated by a suction pump (5).

The polyolefin resin (A) is a polypropylene random copolymer (“EG8” manufactured by Mitsubishi Chemical Corporation, 2
The melt flow rate at 30 ° C. is 0.7 g / 10 min, and the density is 0.9 g / cm ³ ).
h.

A quinone dioxime (manufactured by Ouchi Shinko Chemical Co., Ltd.) as a dioxime compound is a polyolefin resin (A) 10
1.5 parts by weight was supplied to 0 parts by weight.

The denaturation temperature of the resin measured with a thermocouple (7) in the denaturing screw extruder (1) was 228 ° C.

Next, an unmodified polyolefin resin (B) is charged into the extruder (2) for foaming agent kneading and resin blending through a rear end popper, and the modified resin is passed through a connecting portion from the extruder (1) for modification. The compositions were supplied and kneaded and dispersed sufficiently. The supply weight ratio of the modified resin composition to the unmodified polyolefin resin (B) was 5: 5. After that, foaming agent is supplied from the side feeder (3) of this extruder (2),
The mixture was dispersed and a sheet-like molded product was obtained from the T-die (4) at the tip of the extruder.

The unmodified polyolefin resin (B) is a homopolymer of polypropylene (“EA7” manufactured by Mitsubishi Chemical Corporation, 2
Melt flow rate at 30 ° C .; 1.2 g / 10 min, density; 0.9 g / cm ³ ), blowing agent is azodicarbonamide (ADCA), and extruder conditions are 185 ° C. × 30 r.
pm, the extrusion rate was 5 kg / h, and the mold temperature was 165 ° C. The resin temperatures measured by thermocouples (8), (9) and (10) were 190 ° C., 185 ° C. and 163 ° C., respectively.

Ii) Preparation of Foam A molded sheet made of the foamable resin composition obtained was treated with 100
The cut piece was left in a 230 ° C. hot air drier for 5 minutes to foam.

Iii) Physical properties of foam The foam obtained was 300 x 300 x 3.4 mm, and the expansion ratio was 30 times.

Iv) Open Cell Formation A large number of the above foam samples were prepared and heated in a hot air circulating oven at 230 ° C., and samples were sequentially taken out of the oven at 10 minute intervals, and the expansion ratio and closed cell ratio were measured. The results are shown in the graph of FIG.

V) Physical Properties of Open Cell Foam The foam sample was heated in a hot air circulating oven at 230 ° C. for 120 minutes. As a result, the expansion ratio was 28 and the open cell ratio was 1.
A 00% open cell foam could be obtained.

The reflowability of this open-cell foam was evaluated. As a result, the moldability was good and the appearance characteristics were also good.

The expansion ratio is the specific volume (cc / g) of a foam sample measured using a buoyancy type density measuring device, and the open cell ratio is determined by an air pycnometer method specified in ASTM-D-2856. It is a value measured according to the above. The evaluation of reflowability was performed as follows. The cylinder barrel temperature was set to 220 ° C. using an extruder having the same specifications as the above-mentioned modified screw extruder (1) and having a 3 mm-diameter strand die attached to the tip. With this extruder, 20% by weight of the obtained crushed foam and 80% by weight of the original propylene random polymer were kneaded and extruded, and the appearance of the extrudate was checked.

(Example 2) In steps i) and ii), a high-density polyethylene ("HE420" manufactured by Nippon Polychem Co., Ltd.) was used as an unmodified resin in order to prepare a closed-cell foam sample. Performed the same operation as in Example 1.

In the open cell forming step iv), a large number of the above foam samples are prepared and heated in a hot air circulating oven at 230 ° C., and the samples are sequentially taken out of the oven at intervals of 5 minutes. It was measured. This result is shown in FIG.
Is shown in the graph.

As a result of heating the above foam sample in a hot air circulating oven at 230 ° C. for 10 minutes, an open cell foam having an expansion ratio of 32 and an open cell ratio of 100% was obtained. There was no problem with reflowability.

(Comparative Example 1) A number of electron beam crosslinked polypropylene foam sheets (expansion ratio: 25, closed cell ratio: 98%, thickness: 3 mm) were prepared as foam samples and placed in a hot-air circulation oven at 230 ° C. , And samples were sequentially taken out of the oven at 3 minute intervals, and the expansion ratio and closed cell ratio were measured. The results are shown in the graph of FIG.

The above foam sample was heated in a hot air circulating oven at 230 ° C. for 10 minutes.
%, But the expansion ratio was greatly reduced to 5 times.

(Comparative Example 2) The same operation as in Example 1 was performed except that the heating conditions in the open cell forming step iv) were changed to a heating temperature of 180 ° C and a heating time of 180 minutes. As a result, the expansion ratio was 30 times, but the closed cell ratio was 80%.
And it was not possible to form open cells.

(Comparative Example 3) The same operation as in Example 1 was performed except that the heating conditions in the open cell forming step iv) were changed to a heating temperature of 270 ° C and a heating time of 10 minutes. As a result, the expansion ratio was significantly reduced to 15 times (closed cell ratio was 0%). In addition, the appearance was poor due to resin deterioration.

(Comparative Example 4) The same operation as in Example 1 was performed except that the heating conditions in the open cell forming step iv) were changed to a heating temperature of 240 ° C and a heating time of 5 minutes. as a result,
The expansion ratio was 30 times, but the closed cell ratio was as high as 80%, and it was not possible to form open cells.

(Comparative Example 5) The same operation as in Example 1 was performed except that the heating conditions in the open cell forming step iv) were changed to a heating temperature of 230 ° C and a heating time of 240 minutes. As a result, the expansion ratio was reduced to 20 (closed cell ratio was 0%).
In addition, the appearance was poor due to resin deterioration.

The open-cell forming process of the above Examples and Comparative Examples
Table 1 summarizes the heating temperature and heating time in iv), and the expansion ratio and closed cell ratio of the obtained foam.

[0069]

[Table 1]

[0070]

According to the method of the present invention, a polyolefin resin and a dioxime compound are melt-mixed to modify the resin,
A foam obtained by adding a thermal decomposition type chemical foaming agent to the modified resin, kneading, shaping the resulting foamable resin composition and then heat foaming is excellent in shape retention at high temperatures. , Can withstand prolonged heating. Therefore, by heating under predetermined conditions, only the open cell ratio can be increased without much reduction in magnification, and a polyolefin resin open cell foam can be stably manufactured.

The open-cell foam thus obtained is excellent in heat resistance, mechanical properties such as compression and creep, and air permeability, and therefore can be applied to filters, culture floor materials, sealing materials and the like.

Further, according to the method of the present invention, a polyolefin resin foam having excellent recyclability, which is capable of recovering the used foam and melting and molding the foam again, is appropriately produced by freely selecting the material. In addition, the process stability is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an apparatus for producing a continuous foamable resin composition used for modifying a resin, kneading a foaming agent, and blending a resin.

FIG. 2 is a graph showing the relationship between the heating time, the expansion ratio and the closed cell ratio in Examples 1 and 2.

FIG. 3 is a graph showing the relationship between the heating time, the expansion ratio, and the closed cell ratio in Comparative Example 1.

[Explanation of symbols]

 1: screw extruder for reforming 2: screw extruder for foaming agent kneading and resin blending 3: foaming agent supply side feeder 4: molding die 5, 6: volatile matter suction pump 7, 8, 9, 10: thermocouple

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Okabe 2-2 Sekisui Kagaku Kogyo Co., Ltd.

Claims (2)

[Claims] 1. A polyolefin-based resin and a dioxime compound are melt-mixed to modify the resin, and a thermally decomposable chemical foaming agent is added to the modified resin and kneaded, and the resulting foamable resin composition is shaped. A method for producing a polyolefin-based resin open-cell foam, further comprising heating and foaming, and further heating the obtained foam in a temperature range of 200 to 250 ° C for 10 to 180 minutes. 2. A random type polypropylene resin and a dioxime compound are melt-mixed to modify the resin, and the resulting modified resin is blended with an unmodified homo-type polypropylene resin. A foaming agent is added and kneaded, the resulting foamable resin composition is shaped, and then heated and foamed, and the obtained foam is further subjected to 200 to 25.
A method for producing an open-cell polypropylene foam, comprising heating at a temperature of 0 ° C for 10 to 180 minutes.