JP2012025798A - Method of producing polyolefin resin foam - Google Patents

Abstract

A method for producing a polyolefin resin foam capable of obtaining a polyolefin resin foam having high thickness accuracy is provided.
A process for producing a polyolefin resin foam according to the present invention involves a reaction of a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin, and a gel fraction of 10 to 60 parts by weight. The reactant is foamed using a physical foaming agent that is a gas having a boiling point of 120 ° C. or lower, or a physical foaming agent that is a gas at 25 ° C. And a step of obtaining a polyolefin resin foam having a density of 25 to 500 kg / m ³ .
[Selection figure] None

Description

  The present invention relates to a method for producing a polyolefin resin foam, and more particularly, to a method for producing a polyolefin resin foam capable of obtaining a polyolefin resin foam having high thickness accuracy.

  Polyolefin resin foams obtained by foaming polyolefin resins such as polyethylene and polypropylene are used in various fields such as architecture, civil engineering, electricity, electronics, and vehicles. The said foam is used in order to raise the air-conditioning effect, for example as a heat insulating material for buildings, and a heat insulating material for vehicle interiors.

  Conventionally, in order to obtain the above foam, a foaming agent is added in advance to a resin composition containing a polyolefin resin, and a resin composition containing the polyolefin resin and the foaming agent is foam-molded by melt extrusion or contains a polyolefin resin. A method of foam-molding a resin composition by melt extrusion while adding a foaming agent is generally used. Also known is a method of obtaining a foam by crosslinking and foaming a polyolefin resin using a resin composition containing a polyolefin resin, an organic peroxide, and a foaming agent.

  Moreover, as an example of the manufacturing method of the said foam, the following patent document 1 contains the resin composition containing the chain olefin resin comprised by the polymer alloy of polyethylene resin and polypropylene resin, and cyclic olefin resin. A method for producing a foam that is foam-molded by melt extrusion or the like is disclosed.

JP 2009-138029 A

  In the conventional foam production method, the thickness accuracy of the obtained foam may not be sufficiently high. Moreover, even with the foam production method described in Patent Document 1, the thickness accuracy of the foam obtained may not be sufficiently high. Furthermore, in the conventional manufacturing method, when carbon dioxide, nitrogen, or argon is used as the foaming agent, it is difficult to form a good foam structure.

  As the foaming agent, azodicarbonamide, which is a chemical foaming agent, is often used. However, when azodicarbonamide is used, ammonia is generated at the time of foaming, and there is a problem that a residue derived from azodicarbonamide is easily generated.

  The objective of this invention is providing the manufacturing method of the polyolefin resin foam which can obtain the polyolefin resin foam with a high thickness precision.

According to a wide aspect of the present invention, the reaction of a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin is allowed to proceed to obtain a reactant having a gel fraction of 10 to 60% by weight. Then, as the foaming agent, a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that is a liquid having a boiling point of 120 ° C. or lower is used to foam the reaction product, and the density is 25 to 500 kg / m ^3. And a process for obtaining a polyolefin resin foam is provided.

  In a specific aspect of the method for producing a polyolefin resin foam according to the present invention, the material is irradiated with an electron beam, and the reaction of the material proceeds so that the gel fraction becomes 10 to 60% by weight.

  In another specific aspect of the method for producing a polyolefin resin foam according to the present invention, carbon dioxide, nitrogen or argon which is a physical foaming agent is used as the foaming agent.

  In another specific aspect of the method for producing a polyolefin resin foam according to the present invention, the foaming agent is added to the reactant after the step of obtaining the reactant.

  In still another specific aspect of the method for producing a polyolefin resin foam according to the present invention, a composition containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin is molded, and the material that is a molded body is formed. The obtaining step is further provided.

In the method for producing a polyolefin resin foam according to the present invention, the reaction of a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin is allowed to proceed, and the gel fraction is 10 to 60% by weight. After obtaining the product, the reaction product is prepared so that the density becomes 25 to 500 kg / m ³ using a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that is a liquid having a boiling point of 120 ° C. or less. Since foaming is performed, a polyolefin resin foam having high thickness accuracy can be obtained.

  Details of the present invention will be described below.

In the method for producing a polyolefin resin foam according to the present invention, the reaction of a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin is allowed to proceed, and the gel fraction is 10 to 60% by weight. The reaction product is foamed using a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that has a boiling point of 120 ° C. or less as a foaming agent, and the density is 25 to 25%. Obtaining a polyolefin resin foam of 500 kg / m ³ .

  By manufacturing a polyolefin resin foam through each above-mentioned process, the thickness precision of the obtained polyolefin resin foam can be improved. Therefore, according to the present invention, a polyolefin resin foam having a desired shape can be easily obtained. Furthermore, by obtaining the reaction product in advance, a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that has a boiling point of 120 ° C. or less can be used as the foaming agent. Argon can also be used.

  Moreover, the method for producing a polyolefin resin foam according to the present invention further includes a step of molding a composition containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin to obtain the material as a molded body. It is preferable. The step of obtaining the reaction product is preferably performed using the material that is the molded body.

  Hereinafter, each process which manufactures the said polyolefin resin foam is demonstrated concretely.

  First, when obtaining the said polyolefin resin foam, Preferably, the composition containing 100 weight part of chain | strand-shaped polyolefin and 1-40 weight part of cyclic polyolefins as mentioned above is shape | molded, and the material which is a molded object is obtained. . However, the step of obtaining the above-mentioned reaction product may be performed by obtaining the molded body without using the step of obtaining the molded body. Moreover, you may perform the process of obtaining the said reaction material, for example using the said paste-form material, without using a molded object. The molded body is preferably a sheet. The molded body is preferably a molded body obtained by press molding.

  Next, the reaction of the material is advanced using the material, preferably the material that is a molded body, to obtain a reaction product having a gel fraction of 10 to 60% by weight. That is, the reaction of the above materials is allowed to proceed so that the gel fraction is 10 to 60% by weight to obtain a reaction product.

  The main feature of the present invention is that a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin is used to obtain the reaction product, and the gel fraction is 10 to 10 in advance before foaming. The reaction of the above materials is allowed to proceed to 60% by weight to obtain a reaction product. By producing such a reactant and foaming the reactant, the thickness accuracy of the resulting polyolefin resin foam can be increased.

  In order to set the gel fraction of the reaction product to 10 to 60% by weight, for example, the material is irradiated with an electron beam. The material is preferably irradiated with an electron beam and the reaction of the material is allowed to proceed so that the gel fraction is 10 to 60% by weight. Examples of the electron beam include α rays, β rays, and γ rays. The irradiation amount of the electron beam is appropriately adjusted so that the gel fraction is 10 to 60% by weight. The irradiation amount of the electron beam is about 0.2 Mrad to 10 Mrad.

  From the viewpoint of obtaining a polyolefin resin foam that is more excellent in heat resistance and thickness accuracy, it is preferable to proceed the crosslinking reaction of the above materials so that the gel fraction is 10 to 60% by weight to obtain a crosslinked reaction product. The chain polyolefin and the cyclic polyolefin are preferably cross-linked by electron beam irradiation. When a composition containing a polyolefin resin is foamed without crosslinking using isobutane, pentane, carbon dioxide, or the like as a foaming agent, the polyolefin resin is not crosslinked, so that the heat resistance is low, and the foam There is a tendency that the thickness accuracy of the sheet becomes low. On the other hand, by introducing a crosslinked structure by irradiation with an electron beam, the heat resistance of the resulting polyolefin resin foam can be increased, and the thickness accuracy can be further enhanced.

  As a method for crosslinking the chain polyolefin and the cyclic polyolefin, a method other than the method using the electron beam irradiation may be used. As a method of crosslinking the chain polyolefin and the cyclic polyolefin, a crosslinking agent such as an organic peroxide is added to the material and the crosslinking agent is thermally decomposed to crosslink. And a method of crosslinking by ionizing radiation irradiation, a method of using silane crosslinking, and the like.

  The gel fraction of the obtained reaction product is measured as follows.

  50 mg (initial weight) of the reaction product is immersed in xylene at 120 ° C. for 24 hours. Thereafter, the reaction product is taken out, and the xylene elution is removed by filtration with a 200-mesh wire mesh. Next, the residue (xylene insoluble matter) is dried at 80 ° C. for 8 hours. The weight of the residue after drying is measured, and the gel fraction is determined by the following formula (1).

  Gel fraction (% by weight) = (weight of residue after drying / initial weight of reaction product) × 100 Formula (1)

  From the viewpoint of obtaining a polyolefin resin foam that is more excellent in thickness accuracy, the gel fraction is preferably 15% by weight or more, and preferably 50% by weight or less.

  The foaming agent may be added to the material in advance, or the foaming agent may be added to the reactant after the step of obtaining the reactant. That is, after obtaining the reaction product, a foaming agent may be added to the reaction product to foam the reaction product. Among these, from the viewpoint of further improving the foaming efficiency and foaming uniformity, it is preferable to add the foaming agent to the reactant after the step of obtaining the reactant. From the viewpoint of further improving the foaming efficiency and foaming uniformity, it is more preferable that the reactant is impregnated with the upper foaming agent after the step of obtaining the reactant.

  Heating is preferably performed when the reaction product is foamed. From the viewpoint of further improving the foaming efficiency and foaming uniformity, the heating temperature is preferably 120 to 240 ° C. When the foaming agent uses a physical foaming agent having a boiling point of 120 ° C. or lower, the heating temperature is preferably higher by 10 ° C. than the boiling point of the physical foaming agent, It is preferable to exceed.

Next, the obtained reaction product is foamed using a foaming agent. In the present invention, as the foaming agent, a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that is a liquid having a boiling point of 120 ° C. or less is used. In the present invention, the reaction product is foamed to obtain a polyolefin resin foam having a density of 25 to 500 kg / m ³ . That is, the reaction product is foamed to obtain a polyolefin resin foam so that the density is 25 to 500 kg / m ³ . By foaming so that the density is within the above range using the specific physical foaming agent, a polyolefin resin foam excellent in thickness accuracy can be obtained. Conventionally, when the physical foaming agent is used, it has been difficult to obtain a polyolefin resin foam excellent in thickness accuracy. On the other hand, in the present invention, a polyolefin resin foam excellent in thickness accuracy can be obtained even when a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that has a boiling point of 120 ° C. or lower is used. Can do.

  Hereinafter, the details of other components used in obtaining the chain polyolefin and cyclic polyolefin, the foaming agent, and the polyolefin resin foam contained in the material will be described.

(Chain polyolefin)
Examples of the chain polyolefin include ethylene homopolymer, ethylene / α-olefin copolymer, ethylene / (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid ester copolymer. Polymer, copolymer of ethylene and vinyl acetate, homopolymer of propylene, copolymer of propylene and α-olefin, random copolymer or block copolymer of propylene and ethylene, homopolymer of butene And homopolymers or copolymers of conjugated dienes such as butadiene and isoprene. Further, polymethylpentene may be used as the chain polyolefin. Only 1 type may be used for these linear polyolefins, and 2 or more types may be used together. In the present specification, (meth) acryl means acryl and methacryl.

  The chain polyolefin is preferably a polypropylene resin using propylene or a polyethylene resin using ethylene. The chain polyolefin may be an ethylene homopolymer, a propylene homopolymer, a copolymer of ethylene and an α-olefin copolymerizable with ethylene, or an α-polymerizable with propylene and propylene. A copolymer with olefin is preferred.

  Examples of the polypropylene resin include homopolypropylene or a copolymer of propylene and another monomer. When the polypropylene resin is a copolymer of propylene and another monomer, propylene is used as a main component in the polypropylene resin, for example, a total of 100 monomers for obtaining a propylene / α-olefin copolymer. Propylene is used in an amount of 50% by weight or more.

  Examples of the copolymer of propylene and other monomers include a propylene / α-olefin copolymer. The form of copolymerization of a copolymer of propylene and another monomer is not particularly limited. The copolymer of propylene and another monomer may be any of a block copolymer, a random copolymer, a random block copolymer, and the like.

  Examples of the α-olefin in the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene. It is done.

  Examples of the polyethylene resin include homopolyethylene or a copolymer of ethylene and another monomer. When the polyethylene resin is a copolymer of ethylene and another monomer, ethylene is used as a main component in the polyethylene resin, for example, a total of 100 weights of monomers for obtaining an ethylene / α-olefin copolymer. % Of ethylene is used in an amount of 50% by weight or more.

  Examples of the copolymer of ethylene and other monomers include an ethylene / α-olefin copolymer. The form of copolymerization of a copolymer of ethylene and another monomer is not particularly limited. The copolymer of ethylene and another monomer may be any of a block copolymer, a random copolymer, a random block copolymer, and the like.

(Cyclic polyolefin)
Examples of the cyclic polyolefin include a copolymer of a norbornene monomer and an olefin monomer, a homopolymer or copolymer of a norbornene monomer, and derivatives thereof. As for the said cyclic polyolefin, only 1 type may be used and 2 or more types may be used together. In order to reduce the amount of carbon-carbon unsaturated double bonds and increase the weather resistance, the cyclic polyolefin may be saturated by hydrogenation.

  The cyclic polyolefin is preferably a copolymer of a norbornene monomer and an olefin monomer other than the norbornene monomer. Examples of olefin monomers other than the norbornene monomers include acyclic olefin monomers and cyclic olefin monomers. Of these, acyclic olefin monomers are preferably used.

  The norbornene-based monomer is not particularly limited as long as it is a monomer having a norbornene ring. Examples of the norbornene-based monomer include bicyclic compounds such as norbornene and norbornadiene, tricyclic compounds such as dicyclopentadiene and dihydroxypentadiene, tetracyclic compounds such as tetracyclododecene, pentacyclic compounds such as cyclopentadiene trimer, tetra 7-rings such as cyclopentadiene, alkyl substitutions such as methyl, ethyl, propyl and butyl, alkenyl substitutions such as vinyl, alkylidene substitutions such as ethylidene, phenyls, tolyl and naphthyl Aryl substituents, and ester groups, ether groups, cyano groups, halogen groups, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carboxylic acid groups, amino groups, hydroxyl-free groups, silyl groups, epoxy groups, and (meth) acryloyl, etc. Polar groups containing elements other than carbon and hydrogen Substitution products having like. As for the said norbornene-type monomer, only 1 type may be used and 2 or more types may be used together.

  Specific examples of the norbornene-based monomer include, for example, norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and 5-methoxycarbonyl. 2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5 Methyl-2-norbornene, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5 8-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-ethylidene-1 4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydro Naphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano- 1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a Octahydronaphthalene, 1,4-dimethano-1,4,4a, 4b, 5,8,8a, 9a-octahydrofluorene, 5,8-methano-1,2,3,4,4a, 5,8 , 8a-octahydro-2,3-cyclopentadienonaphthalene, 4,9: 5,8- Methano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6 , 9, 9a, 10, 10a, 11, 11a-dodecahydro-1H-cyclopentaanthracene, 5,6-dihydrodicyclopentadiene, and the like.

  Examples of the olefinic monomer include ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1 -Octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and the like. Since the copolymerizability is high, an α-olefin monomer having 2 to 10 carbon atoms is preferable, and ethylene is more preferable.

  It does not specifically limit as said acyclic olefin type monomer, For example, linear olefin type monomers, such as ethylene or an alpha olefin, are mentioned. Examples of the cyclic olefin monomer include cyclopentene and cyclooctene.

  The cyclic polyolefin is preferably a copolymer obtained by copolymerizing the norbornene monomer and an olefin monomer other than the norbornene monomer.

  In the said material, content of the said cyclic polyolefin is 1-40 weight part with respect to 100 weight part of said linear polyolefin. The content of the cyclic polyolefin is preferably 5 parts by weight or more, preferably 35 parts by weight or less, more preferably 30 parts by weight or less with respect to 100 parts by weight of the chain polyolefin. When the content of the cyclic polyolefin is not less than the above lower limit and not more than the above upper limit, a polyolefin resin foam more excellent in thickness accuracy can be obtained.

(Crosslinking agent, crosslinking aid and other components)
In order to efficiently introduce a crosslinked structure into the polyolefin resin molded body, the material preferably contains a crosslinking agent, and a material containing a crosslinking agent is preferably used as the material. By using the crosslinking agent, the polyolefin resin can be crosslinked to obtain a crosslinked polyolefin resin foam in which the polyolefin resin is crosslinked. By introducing the crosslinked structure, the heat resistance and thickness accuracy of the polyolefin resin foam are further enhanced.

  The said crosslinking agent is not specifically limited. A conventionally well-known crosslinking agent can be used as said crosslinking agent. The crosslinking agent is preferably an organic peroxide. Examples of the organic peroxide include dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, and 2,5-dimethyl-2,5-di (t-butyloxy) hexane. . However, you may use crosslinking agents other than these. As for the said crosslinking agent, only 1 type may be used and 2 or more types may be used together.

  The content of the crosslinking agent is preferably 0.01 to 5 parts by weight with respect to a total of 100 parts by weight of the chain polyolefin and the cyclic polyolefin. The content of the crosslinking agent is more preferably 0.1 parts by weight or more and more preferably 2 parts by weight or less with respect to 100 parts by weight of the total of the chain polyolefin and the cyclic polyolefin.

  The material may contain a crosslinking aid. For example, when polypropylene or polymethylpentene is used as the cyclic polyolefin, a crosslinking aid having an acryloyl group or a methacryloyl group such as trimethylolpropane triacrylate (TMPT) is added to the material as a crosslinking aid. It may be mixed and used.

  Additives such as antioxidants, metal damage inhibitors, flame retardants, fillers, antistatic agents, stabilizers and pigments may be added to the above materials. As for these additives, only 1 type may be used and 2 or more types may be used together.

(Foaming agent)
In the present invention, a physical foaming agent that is a gas at 25 ° C. or a physical foaming agent that is a liquid having a boiling point of 120 ° C. or less is used as the foaming agent. As the foaming agent, a physical foaming agent that is a gas at 25 ° C. is preferably used. The physical foaming agent is sometimes called a volatile foaming agent.

  The physical foam which is a gas at 25 ° C. is preferably an inert gas. Although it does not specifically limit as said physical type foaming agent which is gas at the said 25 degreeC, A carbon dioxide, nitrogen, argon, etc. are mentioned. Since the environmental load is small and hardly remains in the obtained polyolefin resin molded article, it is preferable to use isobutane, carbon dioxide, nitrogen or argon as a physical foaming agent as the foaming agent, and carbon dioxide as a physical foaming agent. More preferably, nitrogen or argon is used, and carbon dioxide or nitrogen which is a physical foaming agent is more preferably used. In the present invention, a polyolefin resin foam excellent in thickness accuracy can be obtained even when carbon dioxide, nitrogen, or argon, which is a physical foaming agent, is used as a foaming agent instead of a chemical foaming agent.

  The physical foaming agent which is a liquid having a boiling point of 120 ° C. or lower is liquid at 25 ° C. Although it does not specifically limit as said physical type foaming agent which is a liquid whose said boiling point is 120 degrees C or less, Water, hexane, pentane, isopentane, etc. are mentioned.

  Hereinafter, the present invention will be specifically described by giving examples and comparative examples. The present invention is not limited to the following examples.

  In order to obtain a polyolefin resin foam, the following commercial products were prepared.

LE520H (Chain polyolefin, manufactured by Nippon Polyethylene Co., Ltd., MI 3.6, density 0.923 g / cm ³ )
Topas 6013 (cyclic polyolefin, manufactured by Polyplastics Co., Ltd., MVR (260 ° C., 2.26 kg) 14, density 1.02 g / cm ³ , norbornene monomer content 80% by weight)
Arton 5013 (cyclic polyolefin, manufactured by JSR)

Example 1
90 parts by weight of LE520H (chain polyolefin) and 10 parts by weight of Topas 6013 (cyclic polyolefin) were mixed at 240 ° C. for 5 minutes by plastograph, and press molded at 240 ° C. for 5 minutes to obtain a sheet having a thickness of 1 mm.

  The obtained sheet was irradiated with an electron beam at a dose of 2.54 Mrad at 800 kv, and the reaction of the sheet was advanced to obtain a reaction product. The obtained reaction product was cut into a size of 3 cm × 3 cm.

  The obtained reaction product was set in an autoclave, 17 MPa of carbon dioxide was introduced, and allowed to stand at 23 ° C. for 24 hours, so that the reaction product was impregnated with carbon dioxide.

  Thereafter, the pressure was released, and the reaction product impregnated with carbon dioxide was left at 23 ° C. for 1 hour. Next, the reaction product impregnated with carbon dioxide was immersed in an oil bath at 200 ° C. and foamed to obtain a polyolefin resin foam.

(Examples 2 to 7 and Comparative Example 1)
A polyolefin resin foam was obtained in the same manner as in Example 1 except that the type and blending amount of the polyolefin resin and the irradiation amount of the electron beam were changed as shown in Table 1 below.

(Comparative Example 2)
80 parts by weight of LE520H (chain polyolefin) and 20 parts by weight of Topas 6013 (cyclic polyolefin) were mixed by plastograph at 240 ° C. for 5 minutes, and press molded at 240 ° C. for 5 minutes to obtain a sheet having a thickness of 1 mm. . The obtained sheet was cut into a size of 3 cm × 3 cm.

  Without irradiating the obtained sheet with an electron beam, the sheet was set in an autoclave, 17 MPa of carbon dioxide was introduced, left at 23 ° C. for 24 hours, and the reaction product was impregnated with carbon dioxide.

  Thereafter, the pressure was released, and the sheet impregnated with carbon dioxide was left at 23 ° C. for 1 hour. Next, the sheet impregnated with carbon dioxide was immersed in an oil bath at 200 ° C. and foamed to obtain a polyolefin resin foam.

(Evaluation)
(1) Gel fraction The gel fraction was calculated | required by making the reaction material used in Examples 1-7 and Comparative Example 1 and the sheet | seat used in Comparative Example 2 into a measurement sample.

  The measurement sample was cut to a weight of 50 mg, and the initial weight of the cut measurement sample was measured. Next, the cut measurement sample was immersed in xylene at 120 ° C. for 24 hours. Then, the measurement sample was taken out, and the xylene elution was removed by filtration with a 200 mesh wire net. Next, the residue (xylene insoluble matter) was dried at 80 ° C. for 8 hours. The weight of the residue after drying was measured, and the gel fraction was determined by the following formula (1A).

  Gel fraction (% by weight) = (weight of residue after drying / initial weight of measurement sample) × 100 (1A)

(2) Density Using a specific gravity meter, the specific gravity between the obtained polyolefin resin foam and ion-exchanged water was calculated. The density of the polyolefin resin foam was calculated by converting the obtained specific gravity into a density.

(3) Appearance (surface condition)
The appearance (surface state) of the obtained polyolefin resin foam was visually observed. The appearance (surface state) was determined according to the following criteria.

[Criteria for appearance (surface condition)]
○: Uniform foaming with no variation in appearance (surface state) △: Slight variation in appearance (surface state), partially non-uniform foaming, but use of polyolefin resin foam No problem ×: There are variations in appearance (surface state), there are many non-uniform foamed parts, and there are problems in using polyolefin resin foam

(4) Thickness accuracy The thickness of the central part of the 3 cm x 3 cm polyolefin resin foam and the thickness of the four corners in total are measured with a micrometer, and the maximum and minimum thicknesses are measured. And the average value of the thicknesses at the five locations, the value calculated by the following formula (1) was taken as the thickness accuracy. If the thickness accuracy is 0.2 or less, it can be determined that the thickness accuracy is good. The thickness accuracy was determined according to the following criteria.

  (Maximum thickness-minimum thickness) / average thickness value (1)

[Thickness accuracy criteria]
○: Thickness accuracy is 0.2 or less ×: Thickness accuracy exceeds 0.2 The results are shown in Table 1 below.

Claims (5)

A step of causing a reaction of a material containing 100 parts by weight of a chain polyolefin and 1 to 40 parts by weight of a cyclic polyolefin to obtain a reaction product having a gel fraction of 10 to 60% by weight;
Using a physical type foaming agent that is a gas at 25 ° C. or a physical type foaming agent that has a boiling point of 120 ° C. or less as the foaming agent, the reaction product is foamed, and the density is 25 to 500 kg / m ³ . A method for producing a polyolefin resin foam, comprising a step of obtaining a polyolefin resin foam.   The production of the polyolefin resin foam according to claim 1, wherein, in the step of obtaining the reactant, the material is irradiated with an electron beam to cause the reaction of the material to proceed so that the gel fraction becomes 10 to 60% by weight. Method.   The method for producing a polyolefin resin foam according to claim 1 or 2, wherein carbon dioxide, nitrogen or argon which is a physical foaming agent is used as the foaming agent.   The method for producing a polyolefin resin foam according to any one of claims 1 to 3, wherein the foaming agent is added to the reactant after the step of obtaining the reactant.   The polyolefin of any one of Claims 1-4 further equipped with the process of shape | molding the composition containing 100 weight part of chain | strand-shaped polyolefin and 1-40 weight part of cyclic polyolefin, and obtaining the said material which is a molded object. Manufacturing method of resin foam.