JPH11228722A - Manufacture of polyolefin-based resin foamed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyolefin-based resin foamed body which necessitates only a small investment for equipment, produces a crosslinked foamed body showing excellent homogeneity and shape followability, makes an easy adjustment of a foaming ratio and further enables recovery of used famed bodies for melting and reforming. SOLUTION: A polyolefin-based resin (A) is modified by melting and blending 100 pts.wt. of the resin (A) with 0.05-5 pts.wt. of a dioxime compound at temperatures in the range from 170 deg.C to a decomposition temperature of the polyolefin based resin. The obtained modified resin composition (B) is blended with an unmodified polyolefin-based resin (C), the weight ratio of (B):(C) being 20-80:80-20 (wherein (B)+(C)=100). The obtained blended compound is kneaded with a thermally decomposable chemical foaming agent and then the obtained expandable resin composition is heated and foamed by decomposition of the foaming agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyolefin resin foam having excellent recyclability.

[0002]

2. Description of the Related Art Polyolefin foams are widely used as industrial materials because they have an excellent balance between mechanical and thermal properties and can be heated and shaped later. Of these, for example, interior materials such as car doors and ceilings,
Foams mainly composed of polypropylene-based resins have become mainstream because of their good heat resistance.

[0003] Conventionally, 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, a foaming agent is added to a polypropylene-based resin composition, the composition is formed into a sheet, and the composition is cross-linked until a gel fraction of about 30 to 50% is exhibited. A production method of decomposing and foaming is employed.

The sheet-like polyolefin resin composition may be crosslinked by irradiation with radiation or an electron beam, irradiation with ultraviolet rays, a method using a thermal decomposition type chemical crosslinking agent such as an organic peroxide, or polyolefin. There is a method of introducing an alkoxysilyl group and subjecting it to a condensation reaction.

[0005] Further, by improving the melt strength by these crosslinking, the obtained foam can be heated and shaped in a later step to be processed into an arbitrary shape.

[0006]

SUMMARY OF THE INVENTION Among these methods,
The crosslinking method using an electron beam has excellent productivity and is widely practiced industrially. For example, Japanese Patent Publication No. 6-45717 discloses that
A specific ethylene copolymer, a specific ethylene-α-olefin copolymer and a specific vinyl monomer are added to a polypropylene-based resin, and a foaming agent is added to the melt-blended sheet-like molded product, and the electron beam is continuously applied. To a gel fraction of 20
A method for producing a crosslinked foam in which the obtained continuous crosslinked sheet is foamed after setting the content to ６０60% is disclosed.

However, this method requires a large capital investment for an electron beam irradiator, and since the crosslinking occurs only in the amorphous portion of the polymer, the subsequent foaming becomes non-uniform, resulting in a pinhole. There is a dislike that defective products having such factors are generated. Further, the shape of the molded product is limited to a sheet shape, and it is difficult to form a bar shape, a thick board, an irregular shape, and the like.

On the other hand, Japanese Patent Publication No. 58-57452 discloses a cross-linking / foaming method in which a composition obtained by adding a specific polyfunctional monomer and a pyrolytic foaming agent to a polypropylene resin and melt-mixing the whole is heated and cross-linked and foamed. A method for producing a foam is described.

Japanese Patent Application Laid-Open No. 48-100470 discloses a crosslinked foam which is formed by kneading a resin obtained by grafting or copolymerizing a silicon-containing compound with a thermal decomposition type foaming agent, crosslinking by a dehydration condensation reaction, and foaming by heating. Is disclosed. These methods require less capital investment and are excellent in the homogeneity of the obtained crosslinked foam as compared with the crosslinking method using an electron beam or radiation. Further, these methods can cope with irregular shapes to some extent. However, since the crosslinking time is long and it is difficult to keep the degree of crosslinking constant, there is a problem that it is difficult to stably maintain productivity and quality.

In recent years, as a measure against environmental resource problems,
For example, automotive parts are required to be recyclable, and technical efforts have already been made on polypropylene parts such as bumpers and interior skin materials. However, since the polyolefin resin foam such as the polypropylene resin is usually crosslinked as described above, even if collected after use, it cannot be melted again and is not suitable for recycling.

In view of the above, an object of the present invention is to reduce the capital investment, to obtain a crosslinked foam having excellent homogeneity and shape adaptability, to easily adjust the expansion ratio, and to further use the crosslinked foam. It is an object of the present invention to provide a method for producing a polyolefin-based resin foam which can collect a later-formed foam, melt and re-mold the foam.

[0012]

The method for producing a polyolefin resin foam according to the present invention comprises the steps of:
(A) 100 parts by weight and 0.05 to 5 parts by weight of a dioxime compound are melt-mixed in a temperature range from 170 ° C. to the decomposition temperature of polyolefin resin (A) to modify the resin, and the modified resin composition obtained Product (B) with unmodified polyolefin resin (C),
Weight ratio (B) :( C) = 20-80: 80-20 (however
(B) + (C) = 100), kneading a thermally decomposable chemical foaming agent into the obtained blend, and heating the resulting foamable resin composition to foam by decomposing the foaming agent. It is a method characterized by the following.

In the method of the present invention, the polyolefin which is the main component of the unmodified polyolefin resin (A) and the polyolefin resin (C) is a homopolymer of an olefinic monomer, or a main component olefinic monomer and another monomer. Is not particularly limited, for example, low density polyethylene, high density polyethylene, polyethylene such as linear low density polyethylene, homo-type polypropylene, random type polypropylene, polypropylene such as block type polypropylene Ethylene as a main component, such as polybutene, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, eletin-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene-acrylate copolymer. Examples of copolymers and the like , Or it may be two or more combinations thereof.

The polyolefin resin refers to a resin composition in which the proportion of the polyolefin is 70 to 100% by weight. The resin other than the polyolefin constituting the polyolefin resin is not limited, and examples thereof include polystyrene and styrene elastomer. If the proportion of polyolefin in the polyolefin resin is less than 70% by weight, not only the characteristics of polyolefin such as light weight, chemical resistance, flexibility and elasticity cannot be exhibited, but also it is difficult to secure the melt viscosity required for foaming. This is not preferable because it may result in

The unmodified polyolefin-based resin (A) and polyolefin-based resin (C) in the method of the present invention may be the same resin or different resins, but may be one or a combination of two or more of polyethylene and polypropylene. preferable.

In particular, the polyolefin resin (A) contains 23
A polypropylene resin having a melt flow rate at 0 ° C. of less than 4 g / 10 minutes is preferred. A resin having a melt flow rate of 4 or more is insufficiently modified, may not have a sufficient melt tension, and tends to cause a reduction in magnification during foaming.

The melt flow rate referred to herein is AS
This is a numerical value that is obtained by extruding a thermoplastic resin from an orifice at a constant temperature and pressure using an extrusion type plastometer specified in TMD 1238 and converting the extruded amount into grams per 10 minutes.

In order to obtain a modified resin composition, a polyolefin resin and a dioxime compound are melt-mixed under predetermined conditions. Specifically, the above-mentioned two 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 not higher than the decomposition temperature of the polyolefin resin (generally about 300 ° C.), preferably 200 ° C. to 250 ° C. Melt mixing temperature is 170 ℃
If it is less than, the reforming is insufficient, and the expansion ratio of the finally obtained foam may not be sufficiently high. If it exceeds about 300 ° C, the polyolefin-based resin is easily decomposed.

The dioxime compound used in the method of the present invention refers to a compound represented by the following general formula in which an oxime group (formula I) or a hydrogen atom thereof is substituted with another atomic group (mainly a hydrocarbon group). A compound having two (chemical formula II) in a molecule, for example, p-quinonedioxime (chemical formula
III), p, p-dibenzoylquinone dioxime (chemical formula IV). The dioxime compounds can be used in combination of two or more.

[0020]

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[0021]

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[0022]

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[0023]

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The amount of the dioxime compound to be added is 0.05 to 5 parts by weight, preferably 0.2 to 3 parts by weight, per 100 parts by weight of the polyolefin resin (A). If the amount is less than 0.05 parts by weight, the melt viscosity required for foaming cannot be imparted. If the amount exceeds 5 parts by weight, the degree of crosslinking is too high and the extrudability is poor (for example, high load In addition, 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 proportion of unreacted dioxime remaining in the product increases, irritating the human body, and lowering the efficiency of product formation with respect to raw materials.

The kneading apparatus used for the above-mentioned melt kneading may be a screw kneader or any other melt 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 latter stage of the extruder is effective for preventing volatiles from remaining in the resin composition.

When a screw extruder is used, the polyolefin-based resin (A) is usually introduced into the extruder from a hopper.
It is also preferable to use a weight control type feeder or the like.

The dioxime compound may be introduced into the extruder simultaneously from the hopper simultaneously with the polyolefin resin (A).
(A) into the extruder at the same position, or from the injection hole provided in the extruder from the position where the polyolefin resin melts, using a side feeder or the like, using the side feeder, etc. Is also good.

Next, the modified resin composition obtained in the above step
(B) is an unmodified polyolefin resin (C)
(B): (C) = 20 to 80: 80 to 20 (however, (B) +
(C) = 100).

In this step, the ratio of the modified resin composition (B) is at least 20%, preferably at least 30%. When 20% or more of the modified resin composition (B) is present, it is possible to maintain the melt tension required for foaming, and to exhibit good foaming properties. As the polyolefin resin (C), a resin most suitable for required physical properties is selected according to the purpose. For example, if it is desired to improve the flowability of the foam, a resin having a low viscosity is used as the resin (C) to be blended. If a soft foam is desired, a resin having a low density is used as the polyolefin resin (C). Thus, by blending the polyolefin-based resin (C) with the modified resin composition (B), it is possible to give the raw material and the foam a wide range of performances. If the proportion of the modified resin composition (B) is less than 20% of the whole, the melt tension required for foaming cannot be maintained, so that the foaming ratio is reduced and a good foam cannot be obtained.

The proportion of the modified resin composition (B) is at most 80%, preferably at most 70%. If the proportion of the modified resin composition (B) is too large, the moldability at the time of extrusion becomes poor, and the surface properties of the molded article may be impaired.

Further, a thermally decomposable chemical blowing agent is kneaded with the blend obtained in the above step to obtain a foamable resin composition.

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.

When kneading a thermally decomposable chemical foaming agent into the above-mentioned blend, it is important to knead the foaming agent in an extruder in advance at a temperature at which the foaming agent does not primarily foam. For example, when no foaming aid is added to azodicarbonamide, its decomposition temperature is around 185 ° C., so the temperature condition when the foaming agent is mixed into the blend should be 185 ° C. or less. Temperature is 185
If the temperature exceeds ℃, initial foaming occurs in the kneading machine, and non-uniform air bubbles are mixed into the raw material. As a result, reduction of the expansion ratio, generation of non-uniform coarse cells in the foam, deterioration of the quality of the foam, etc. Problems may arise.

The thermal decomposition type chemical foaming agent is a modified resin composition
(B) It is used in an appropriate amount in the range of 1 to 50 parts by weight, preferably 2 to 35 parts by weight, based on 100 parts by weight, depending on the desired expansion ratio.

Thus, the polyolefin resin
Modified resin composition obtained from (A) and a dioxime compound
(B) is blended with an unmodified polyolefin resin (C), and the resulting blend is kneaded with a thermal decomposition type chemical blowing agent to obtain a foamable resin composition. Melt kneading device and another kneading device for mixing a blowing agent (the structure may be the same as that of the melting kneading device for reforming)
Are mixed at a temperature below the maximum temperature at which the blowing agent does not substantially decompose. The mode of the melt kneading is as follows.

(A) A modified resin composition (B) obtained by melt-mixing a polyolefin-based resin (A) and a dioxime compound in a batch-type or continuous-type melt-kneading apparatus for reforming.
The resin composition (B) is taken out of the melt-kneading apparatus, solidified, granulated, etc., and then transferred to a batch-type or continuous-type kneading apparatus for mixing a foaming agent. Resin (C) Next, a foaming agent is charged, and the three are melt-kneaded to obtain a foamable resin composition.

(B) In a batch type melt-kneading apparatus for reforming, the polyolefin resin and the dioxime compound
The mixture is melt-mixed at a temperature of not less than ℃ and reformed, and the resulting modified resin composition is cooled to a temperature of, for example, 185 ° C. in the same kneading apparatus, and then the unmodified polyolefin resin is added thereto.
(C) Next, a foaming agent is additionally introduced, and the three are melt-kneaded to obtain a foamable resin composition.

(C) A polyolefin resin and a dioxime compound are melt-mixed at a temperature of 190 ° C. or more in a reforming screw extruder (continuous melt kneading apparatus), and the resulting modified resin composition is 185 After lowering the temperature to below ℃, the unmodified polyolefin-based resin (C) is further fed through a supply port provided in the middle of the screw extruder, and then a foaming agent is added, and the three components are melt-kneaded to form a foamable resin. Obtain the composition.

(D) In another mode of the continuous operation, two screw extruders and the like are connected, and the polyolefin resin and the dioxime compound are melt-mixed in the first unit, and the resulting modified resin composition is obtained. After lowering the temperature in the same manner as above, the same resin composition was transferred to a second unit, and an unmodified polyolefin-based resin (C) was then charged with a foaming agent, and the three were melt-kneaded,
A foamable resin composition is obtained.

The foamable resin composition obtained by kneading the blend with a pyrolytic chemical foaming agent may be shaped as required. As a shaping method, in addition to extrusion molding, a method generally performed in plastic molding such as press molding, blow molding, calendaring molding, injection molding, or the like can be applied.

In particular, the foamable resin composition obtained according to the above methods (a) and (b) is taken out from a batch-type kneading apparatus for mixing a foaming agent, and is put into a screw extruder to continuously form a sheet. Method of shaping into a shape, or the above (a)
According to the methods (c) and (d), a method of directly shaping the foamable resin composition discharged from the screw extruder is preferable from the viewpoint of productivity.

The foamable resin composition thus obtained or the shaped product thereof is heated under appropriate temperature conditions,
It can be foamed to a desired expansion ratio under a constant pressure. The heating is usually performed in a temperature range from the decomposition temperature of the thermal decomposition type chemical foaming agent to the decomposition temperature + 100 ° C.
As a foaming apparatus for performing this, a vertical or horizontal foaming furnace, a hot air thermostat, or a hot bath such as an oil bath, a metal bath, or a salt bath, which is operated in an air atmosphere, is generally used.

The foam raw material produced by such a method has good flowability while ensuring foaming properties, enables molding of irregularly shaped products, and furthermore, melts and pelletizes after product molding. Then you can use it again.

Although it is not clear why such characteristics are exhibited, the present resin is in a finely crosslinked state, and the crosslinked resin is finely dispersed in the unmodified resin, so that the unmodified resin wraps the crosslinked resin. It is considered that the flowability can be ensured while maintaining the melt tension necessary for foaming, because of the simple structure.

The expansion ratio (specific volume of the foam) of the foam produced by the method of the present invention is preferably 10 times (cc / cc).
g) or more, more preferably 12 times (cc / g) or more. When the expansion ratio is less than 10 times, heat insulation, cushioning,
In some cases, a foam excellent in sound insulation, flexibility, buoyancy and the like cannot be obtained.

[0046]

The foam raw material produced by the method of the present invention is a finely cross-linked molded article, so that the cross-linked portion can maintain the melt tension required for foaming. On the other hand, since a large amount of components that do not contribute to crosslinking are present, the melt fluidity can be maintained as much as possible for kneading and shaping. Therefore, in addition to being capable of being formed into a heterogeneous shape, it also has a recyclability of melting and reusing it after molding.

[0047]

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 reforming comprises:
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 reforming 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 (200 m in width).
mx 1 mm in thickness).

In the apparatus having the above-mentioned structure, first, the polyolefin resin (A) and the dioxime compound part are charged into the reforming screw extruder (1) from the rear end hopper, and the temperature is set to 220 ° C. and 150 rpm in all sections. Were melt-mixed to obtain a modified resin composition (B). 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
Melt flow rate at 30 ° C .; 0.7 g / 10 min), and the supply amount was 5 kg / h.

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

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

Next, an unmodified polyolefin-based resin (C) is charged into the extruder (2) for kneading and blending the resin from the rear end of the extruder (2) through a connecting portion from the extruder (1) for reforming. The modified resin composition (B) was supplied, and these were sufficiently kneaded and dispersed. The weight ratio of the modified resin composition (B) to the unmodified polyolefin resin (C) was 5: 5. Thereafter, a foaming agent was supplied from the side feeder (3) of the extruder (2), dispersed therein, and a sheet-like molded product was obtained from the T-die (4) at the tip of the extruder.

The unmodified polyolefin resin (C) is a homopolymer of polypropylene (“EA7” manufactured by Mitsubishi Chemical Corporation, 2
Melt flow rate at 30 ° C .; 1.2 g / 10 min),
The blowing agent is azodicarbonamide (ADCA), the extruder conditions are 185 ° C. × 30 rpm, and the extrusion rate is 5 kg /
h, 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 thus 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 expansion ratio of the foam obtained (measured value of the specific volume of the foam sample) was 30 cc / g.

The reflowability was evaluated as follows. The same specifications as the reforming screw extruder (1) above,
The cylinder barrel temperature was set to 220 ° C. using an extruder fitted with a strand die of mm. With this extruder, 20% by weight of the obtained crushed foam and 80% by weight of the original polyolefin resin (A) were kneaded and extruded, and the appearance of the extruded product was checked. The reflowability evaluation results show good moldability,
There was no foreign matter.

Example 2 The weight ratio of the modified resin composition (B) to the unmodified polyolefin resin (C) was changed to 3: 7,
Addition amount of quinone dioxime to polyolefin resin (A)
The same operation as in Example 1 was performed except that the amount was changed to 2.5 parts by weight with respect to 100 parts by weight.

The expansion ratio of the obtained foam was 30 cc / g.
Met. The reflowability evaluation result was good, and there was no problem in recyclability.

Example 3 As the polyolefin-based resin (A) and the unmodified polyolefin-based resin (C), both polyethylene (“Affinity” manufactured by Dow Chemical Company) was used.
PL1880 ”, melt flow rate at 190 ° C .;
1.0 g / 10 min), and the weight ratio of the modified resin composition (B) to the unmodified polyolefin resin (C) is 5: 5,
Addition amount of quinone dioxime to polyolefin resin (A)
The same operation as in Example 1 was performed except that the amount was changed to 0.1 part by weight and the number of revolutions of the screw extruder (1) was changed to 50 rpm.

The expansion ratio of the obtained foam was 30 cc / g.
Met. The reflowability evaluation result was good, and there was no problem in recyclability.

Example 4 As the polyolefin resin (A) and the unmodified polyolefin resin (C), both were homopolymers of polypropylene (“FY” manufactured by Mitsubishi Chemical Corporation).
4 ", melt flow rate at 230 ° C; 5 g / 10
), The weight ratio of the modified resin composition (B) to the unmodified polyolefin-based resin (C) is 5: 5, and the amount of quinonedioxime added is 100 parts by weight of the polyolefin-based resin (A). The same operation as in Example 1 was performed except that the amount was changed to 4 parts by weight.

The expansion ratio of the obtained foam was 23 cc / g.
Met. The reflowability evaluation result was good, and there was no problem in recyclability.

Table 1 shows the structures and evaluation results of Examples 1 to 4.
Are shown together.

[0069]

[Table 1]

Comparative Example 1 Reforming Screw Extruder (1)
, The same operation as in Example 1 was performed except that the resin reforming temperature was changed to 160 ° C.

The expansion ratio of the obtained foam was 8 cc / g. There was no problem in recyclability.

Comparative Example 2 The weight ratio of the modified resin composition (B) to the unmodified polyolefin resin (C) was changed to 1: 9.
Addition amount of quinone dioxime to polyolefin resin (A)
The same operation as in Example 1 was performed except that the amount was changed to 7.5 parts by weight with respect to 100 parts by weight.

The expansion ratio of the obtained foam was 9 cc / g. As for the reflowability, melt fracture occurred in the strand, and the recyclability was somewhat poor.

Comparative Example 3 As the polyolefin resin (A) and the unmodified polyolefin resin (C), both polyethylene (Affinity EG81 manufactured by Asahi Dow) was used.
50 ”, melt flow rate at 190 ° C .;
10 minutes), the weight ratio of the modified resin composition (B) to the unmodified polyolefin resin (C) is 1: 9, and the amount of quinonedioxime added is 100 parts by weight of the polyolefin resin (A). The same operation as in Example 1 was carried out except that the amount was 0.04 parts by weight and the number of revolutions of the reforming screw extruder (1) was 50 rpm.

The expansion ratio of the obtained foam was 6 cc / g. There was no problem in recyclability.

Comparative Example 4 A polypropylene random copolymer (“EG8” manufactured by Mitsubishi Chemical Corporation, 230 ° C.) was used as a polyolefin resin (A) using a screw extruder (2) for kneading a foaming agent and resin blending. (Melt flow rate; 0.5 g / 10 min) 1 part by weight of quinone dioxime and 15 parts by weight of ADCA are added to 100 parts by weight,
A sheet having a width of 200 mm and a thickness of 1 mm was formed. next,
600 with an electron beam irradiator (Nissin High Voltage)
Both sides of the sheet were irradiated with an electron beam at 10 Mrad by kev.
A molded sheet made of the obtained foamable resin composition was treated with 200
The cut piece was left in a 230 ° C. hot air drier for 5 minutes to foam.

The expansion ratio of the obtained foam was 28 cc / g.
Met. Regarding the reflowability evaluation (recyclability), the back pressure of the extruder was too high and extrusion was not possible.

Table 2 shows the structures and evaluation results of Comparative Examples 1 to 4.
Are shown together.

[0079]

[Table 2]

[0080]

According to the first aspect of the present invention, a small amount of polymer is crosslinked to maintain a melt fluidity that allows kneading and shaping with a foaming agent later, and at the same time, a foaming degree that allows foaming. A modified resin composition having a melt strength can be obtained,
By adding an unmodified resin to the modified resin composition, a polyolefin-based resin foam having excellent homogeneity, and having excellent recyclability, capable of recovering the used foam, melting and molding it again. Can be manufactured with little capital investment.

Further, according to the second aspect of the present invention, a foam having a high magnification can be stably obtained, and a foam excellent in heat resistance and strength can be obtained.

[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.

[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 resin is modified by melting and mixing 100 parts by weight of a polyolefin resin (A) and 0.05 to 5 parts by weight of a dioxime compound in a temperature range from 170 ° C. to a decomposition temperature of the polyolefin resin (A). The unmodified polyolefin resin (C) is added to the obtained modified resin composition (B) by the weight ratio (B) :( C).
= 20-80: 80-20 (however, (B) + (C) = 10
Polyolefin resin foaming characterized in that the resulting blended product is kneaded with a pyrolytic chemical foaming agent, and the foamable resin composition is heated and foamed by decomposition of the foaming agent. How to make the body. 2. The polyolefin resin (A) has a temperature of 230 ° C.
The method for producing a polyolefin-based resin foam according to claim 1, wherein the resin is a polypropylene resin having a melt flow rate of less than 4 g / 10 minutes.