MX2007014357A - Crosslinked polyolefin resin foam. - Google Patents

Abstract

Disclosed is a crosslinked polyolefin resin foam having excellent heat resistance, which can be secondarily processed into a complicated shape. Specifically disclosed is a crosslinked polyolefin resin foam obtained from a polyolefin resin composition containing 20-50% by weight of a polypropylene resin (A) having at least one endothermic peak determined by a differential scanning calorimeter of not less than 160 degree degree C, 20-50% by weight of a polypropylene resin (B) having at least one endothermic peak determined by a differential scanning calorimeter of less than 160 degree C, and 20-40% by weight of a polyethylene resin (C). The crosslinked polyolefin resin foam can be obtained by molding the polyolefin resin composition into a desired shape and then foaming/crosslinking the resin.

Description

EFINA RETICU ADA POLYESUM RESIN FOAM Technical Field The present invention relates to a crosslinked polyolefin resin foam, which is excellent in heat resistance and can also be processed secondarily in a complicated manner by vacuum forming or compression forming. BACKGROUND ART Cross-linked polyolefin resin foams are commonly excellent in flexibility, light weight properties and heat insulation properties and have been conventionally used as automotive interior materials such as roofs, doors and instrument panels. These automotive interior materials are usually obtained by secondary processing of a sheet-like crosslinked polyolefin resin foam into a predetermined shape through vacuum formation or compression formation. Also, the crosslinked polyolefin resin foam is usually used as a laminate obtained by laminating sheets made of a polyvinyl chloride resin, sheets made of a thermoplastic elastomer, or skin materials (other materials) such as similar articles to natural fabric or articles similar to artificial cloth or furs to each other.

In vacuum forming, or compression forming such as stamping of crosslinked polyolefin resin foam, it has recently been required that a processing temperature be adjusted to high temperature conditions within a range of 120 to 200 ° C such that improve productivity, and deep draft formation is conducted such that it forms towards a complicated figure. Therefore, the crosslinked polyolefin resin foam is required to be excellent in high temperature forming capacity. As a method to solve the above problems, a method is proposed in which heat resistance is improved by increasing the melting point of a resin (see patent document 1). However, in this proposal, the elongation sometimes becomes insufficient to cause breakage to an extremely projected portion in a formed article, a vertical wall portion where a flow rate of a resin serving as an aggregate increases in case of stamping , and a portion to which high shear force is applied, such as a portion of granulate. Patent Document 1: Japanese Patent 3,308,724. Disclosure of the Invention Problems to be Resolved by the Invention In light of the background of the prior art, an object of the present invention is to provide a cross-linked polyolefin resin foam which is excellent in resistance to heat and high temperature forming capacity, and can also be processed secondarily towards a complicated figure. Means for Solving Problems The present invention employs the following means such that the above objective is achieved. That is, the crosslinked polyolefin foam of the present invention is a crosslinked polyolefin resin foam comprising a polyolefin resin composition containing from 20 to 50% by weight of a polypropylene (A) based resin which shows at less an endothermic peak measured by differential examination calorimeter at a temperature of 160 ° C or higher, 20 to 50% by weight of a polypropylene based resin (B) which shows at least one endothermic peak measured by examination calorimeter differential at a temperature lower than 160 ° C, and 20 to 40% by weight of a polyethylene-based resin (C). According to a preferred aspect of the crosslinked polyolefin resin foam of the present invention, the polypropylene-based resin (A) is preferably at least one type of a resin selected from the group consisting of a co-polymer. ethylene-propylene block polymer, a homo-polypropylene and a random ethylene-propylene co-polymer. According to a preferred aspect of foam crosslinked polyolefin resin of the present invention, a melt flow rate (occasionally abbreviated as MFR) of the polypropylene based resin (A) is within the range of 0.4 to 1.8 g / 10 min and a weight ratio of the resin Based on polypropylene (A) with the polypropylene based resin (B) they are within a range of 1: 0.5 to 1: 1.5. The crosslinked polyolefin resin foam of the present invention can be laminated with other materials such as skin material to form a laminate. The crosslinked polyolefin resin foam of the present invention and the laminate can be formed into an optional figure to form a formed article. The crosslinked polyolefin resin foam of the present invention, the laminate or article formed can preferably be used as an automotive interior material. Effects of the Invention In accordance with the present invention, it is possible to obtain a cross-linked polyolefin resin foam which can be formed into a complicated shape without causing formation defects and is excellent in heat resistance and high temperature forming capacity, and also reconciles heat-forming capacity and heat resistance in good balance, particularly a cross-linked polyolefin resin foam which is preferably used for stamping an automotive interior material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the melt flow rate (MFR) of a polypropylene-based resin (A) used in the present invention and a more preferred ratio with a weight ratio of the polypropylene-based resin ( A) to a resin based on polypropylene (B). Also, Figure 1 is a schematic view showing defects which may arise in each section of the relationship. Specifically, in Figure 1, when the polypropylene-based resin (A) has a low melt flow rate (MFR), decomposition of an insufflation agent of the thermal decomposition type is accelerated by applying a high shear force. in the case of kneading a polyolefin resin composition and the appearance of the resulting cross-linked polyolefin resin foam may deteriorate. Also, when the polypropylene-based resin (A) has a high MFR, elongation at sufficient tension at normal temperature may not be obtained when it is used in a common forming method (e.g., a stamping method or a forming method). vacuum) and sufficient heat resistance may not be obtained when used in a particular manner in a stamping method. When the content of the polypropylene-based resin (B) is small in the ratio by weight of the polypropylene-based resin (A) to the polypropylene-based resin (B), it may cause elongation at insufficient stress at temperature normal Also, when the content of the polypropylene-based resin (B) is large, sufficient heat resistance may not be obtained when used in the stamping method. Figure 1 shows that the MFR of the polypropylene-based resin (A) is particularly preferably within a range of 0.4 to 1.8 g / 10 min and the weight ratio of the polypropylene-based resin (A) to the Polypropylene-based resin (B) is particularly preferably within a range of 1: 0.5 to 1: 1.5. BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied intensively about the above objective, that is, a cross-linked polyolefin resin foam having excellent heat resistance, which can be formed into a complicated figure without causing formation defects, and found that the above objective can be achieved by forming a polyolefin resin composition composed of a polypropylene-based resin (A) having a specific melting point peak, a polypropylene-based resin (B) having a peak of specific melting point and a polyethylene-based resin, followed by cross-linking and further foaming of the formed polyolefin resin composition. Thus, the present invention has been completed. That is, the crosslinked polyolefin resin foam of the present invention is basically composed of a polyolefin resin composition containing 20 to 50% by weight of a polypropylene based resin (A) which shows at least one endothermic peak measured by differential examination calorimeter at a temperature of 160 ° C or higher, 20 to 50 % by weight of a polypropylene-based resin (B) which shows at least one endothermic peak measured by differential examination calorimeter at a temperature of less than 160 ° C, and 20 to 40% by weight of a resin based of polyethylene (C). Examples of the polypropylene-based resin (A) used in the present invention include resins such as a random ethylene-propylene copolymer, an ethylene-propylene block copolymer, a random ethylene-propylene block co-polymer. and a homo-polypropylene, among these, an ethylene-propylene block copolymer having excellent characteristics at low temperature while maintaining heat resistance to be achieved by the present invention is particularly preferably used. The ethylene content of the ethylene-propylene random co-polymer and that of the random ethylene-propylene block co-polymer between these co-polymers is preferably less than 1% by weight in view of an endothermic peak measured by a calorimeter of differential examination. Also, the content of the ethylene-propylene rubber in the ethylene-propylene block copolymer and the random ethylene-propylene block copolymer is not specifically limited, but is preference within a range where the effect of the present invention is not adversely affected, for example, less than 30% by weight. The molecular weight of the polypropylene-based resin (A) in the present invention can be a common molecular weight and is not specifically limited. For example, the polypropylene-based resin (A) to be used preferably has a weight average molecular weight within a range of 100,000 to 1,500,000 and a molecular weight distribution (average molecular weight by weight / number average molecular weight) within a range of 1.5 to 10. The melt flow rate (MFR) of the polypropylene-based resin (A) is measured under conventional conditions of a temperature of 230 ° C and a load of 2.16 kgf in accordance with JIS K7210 (1999), and the MFR of the polypropylene-based resin (A) used in the present invention is preferably within a range of 0.4 to 1.8 g / 10 min. When the MFR is less than 0.4 g / 10 min, the thermal decomposition type blowing agent decomposes by shear stress when formed in a sheet, and thus can cause a problem of appearance. In contrast, when the MFR is greater than 1.8 g / 10 min, the foamed sheet may have insufficient heat resistance. The MFR of the polypropylene-based resin (A) is more preferably 0.5 to 1.7 g / 10 min, and even more preferably 0.6 to 1.6 g / 10 min.

MFR commonly has a strong correlation with a molecular weight and when the molecular weight is large, the MFR value decreases. In contrast, when the molecular weight is small, the MFR value increases. However, the value can not be unconditionally limited because it varies depending on the polymerization ratio and molecular weight distribution. It is important that at least one of the endothermic peaks measured by a differential examination calorimeter of the polypropylene-based resin (A) used in the present invention is shown at 160 ° C or higher. The term "endothermic peak" as used herein refers to a peak which is measured by an endothermic reaction, which arises when a crystal of a crystalline polymer is melted, using a differential examination calorimeter and is commonly treated as a melting point. As the endothermic peak increases, it becomes more difficult to melt and the heat resistance is excellent. To adjust at least one of the endothermic peaks measured by a differential examination calorimeter of the polypropylene-based resin (A) used in the present invention at 160 ° C or higher, the average molecular weight by weight is preferably 100,000 or more. more. In the case of the polypropylene-based resin in which ethylene molecules are introduced into a main chain, such as the random ethylene-propylene co-polymer and the random block co-polymer of ethylene-propylene, the ethylene content is preferably less than 1% by weight. In the crosslinked polyolefin resin foam of the present invention, it is important that the amount of polypropylene-based resin (A) is 20 to 50% by weight. The amount is preferably 25 to 45% by weight, and more preferably 28 to 42% by weight. If the amount of the polypropylene-based resin (A) is less than 20% by weight, the surface can be hardened by flow of resin over stamping due to insufficient resistance to heat upon formation. In contrast, when the amount of polypropylene-based resin (A) is greater than 50% by weight, it can cause an appearance problem because the thermal decomposition blowing agent decomposes when formed into a sheet. It is important that an endothermic peak measured by a differential examination calorimeter of the polypropylene-based resin (B) used in the present invention is shown at less than 160 ° C. The term "endothermic peak" as used herein is as defined with respect to the polypropylene-based resin (A). In the homo-propylene and the ethylene-propylene block co-polymer, the average molecular weight per weight is preferably 100,000 or less. In the ethylene-propylene random co-polymer and the random ethylene-propylene block co-polymer, the ethylene content is preferably 1% by weight or more. Examples of the polypropylene-based resin (B) used in the present invention include propylene homo-polymers such as isotactic homo-polypropylene, syndiotactic homo-polypropylene and atactic homo-polypropylene; α-olefin-propylene co-polymers (the term "α-olefin" used herein refers to ethylene, 1-butene, 1-pentene, 1-hexylene, 1-heptene, 1-octene and 1-nonene) such as ethylene-propylene random co-polymer, ethylene-propylene block copolymer and ethylene-propylene random block copolymer; and propylene block copolymers having a block fraction, such as modified polypropylene resin, and ethylene, isoprene, butadiene and styrene. These resins can be used alone or in combination. As the polypropylene-based resin (B), a random copolymer of ethylene-propylene is particularly preferably used since it is possible to reconcile the forming capacity and heat resistance in good balance. The MFR of the polypropylene-based resin (B) is not specifically limited. The MFR can optionally be decided as long as the desired physical properties and production defects do not arise. The molecular weight of the polypropylene-based resin (B) in the present invention can be a common molecular weight and is not specifically limited. For example, molecular weight Average weight by weight of the polypropylene-based resin to be used is preferably within a range of 1,000 to 1,500,000. In the crosslinked polyolefin resin foam of the present invention, it is important that the amount of the base resin of polypropylene (B) having an endothermic peak measured by differential examination calorimeter of less than 160 ° C is within a range of 20 to 50% by weight, and preferably 30 to 40% by weight. When the amount of the polypropylene based resin (B) is more than 50% by weight, it causes a problem of heat resistance. In contrast, when the amount is less than 20% by weight, the desired training capacity can not be obtained. The polyethylene-based resin (C) used in the present invention can be a homo-polymer (ultra-low density: less than 0.910 g / cm3, low density: 0.910 to 0.925 g / cm3, average density: 0.926 to 0.940 g / cm3, high density: 0.941 to 0.965 g / cm3) of ethylene, a co-polymer containing ethylene as the main component, or a mixture thereof. Examples of the co-polymer containing ethylene as the main component include ethylene-α-olefin co-polymer (a linear low density polyethylene) obtained by polymerizing ethylene with α-olefin having 4 or more carbon atoms (eg, ethylene, 1-butene, 1-pentene, 1-hexylene, 4-methyl-1-pentene, 1-heptene and 1-octene), and ethylene-vinyl acetate co-polymer. In the present invention, a linear low density polyethylene is particularly preferably used as the polyethylene based resin. Linear low density polyethylene is preferably used because an improvement in the forming ability to be achieved by the present invention is expected. The molecular weight of the polyethylene-based resin (C) can be a common molecular weight and is not specifically limited. For example, the polypropylene-based resin to be used preferably has a number average molecular weight within a range of 1,000 to 1,000,000. The melt flow rate (MFR) of the polyethylene-based resin (C) is measured under conventional conditions of a temperature of 190 ° C, load 2.16 kg in accordance with ISK7210 (1999). The melt flow rate (MFR) of the polyethylene-based resin (C) is preferably within a range of 0.5 to 15 g / 10 min. When the MFR is less than 0.5 g / 10 min, the surface can harden when it forms on a sheet to cause an appearance problem. In contrast, when the MFR is more than 15 g / 10 min, the foamed sheet may have insufficient heat resistance. The MFR is more preferably within a range of 1.0 to 10 g / 10 min. MFR commonly has a strong correlation with a molecular weight and when the molecular weight is large, the MFR value decreases. In contrast, when the molecular weight is small, the value of MFR increases. However, the value can not be unconditionally limited because it varies depending on the branched shape and number of molecules, and the molecular weight distribution. In the cross-linked polyolefin resin foam of the present invention, taking into account the balance with deterioration of heat resistance due to the mixing of the polyethylene-based resin (C), the amount of the polyethylene-based resin (C) to be added can be decided according to the objective physical properties. The amount of the polyethylene-based resin is specifically from 20 to 40% by weight, and preferably from 20 to 35% by weight. When the amount of the polyethylene-based resin (C) to be added is less than 20% by weight, a high shear force is applied when the polyolefin resin composition is formed into a sheet and decomposition of the agent Injection of the thermal decomposition type is accelerated, and thus the appearance may be impaired when forming towards the crosslinked polyolefin resin foam. In contrast, when the amount is more than 40% by weight, the heat resistance to be achieved by the present invention can be impaired. In the crosslinked polyolefin resin foam of the present invention, other thermoplastic resins may be added as long as features of the present invention are not drastically impaired.

Examples of the other thermoplastic resins used in the present invention include non-halogen-containing resins, for example, polystyrene, poly (methyl methacrylate), an acrylic resin such as a styrene-acrylic acid copolymer, styrene co-polymer -butadiene, ethylene-vinyl acetate co-polymer, poly (vinyl acetate), poly (vinyl alcohol), poly (vinyl acetate), poly (vinyl pyrrolidone), petroleum resin, cellulose derivative such as cellulose, acetate of cellulose, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxymethyl cellulose or hydroxypropyl cellulose, a saturated alkyl polyester resin, poly (ethylene terephthalate) and poly (butylene terephthalate), an aromatic polyester resin such as polyalitate, resin of polyamide, polyacetal resin, polycarbonate resin, polyester sulfone resin, poly (phenylene sulfide) resin, polyether ketone resin, and copolymer including a polymeric monomer vinyl bin and vinyl monomer containing nitrogen. The other thermoplastic resin also includes elastomers such as isoprene rubber, styrene butadiene rubber, butyl rubber, dimethylsilicone rubber and ethylene propylene rubber. Also, examples of the other thermoplastic resins containing a halogen include poly (vinyl chloride), poly (vinylidene chloride), poly (chloro-trifluoro-ethylene), poly (vinylidene fluoride) resin, fluorocarbon resin, resin perfluorocarbon, and soluble perfluorocarbon resin in solvent. These resins to be contained can be used alone or in combination. According to physical properties to be desired in the crosslinked polyolefin resin foam of the present invention, the type and amount of other thermoplastic resins are selected. The term "gel" used in the present invention refers to a resin obtained by crosslinking and polymerization, that is, a portion which is not completely plasticized at a forming temperature, for example, 180 ° C. When the content of this portion increases, the heat resistance is improved, but the formation capacity deteriorates. Therefore, the proportion of the gel (which is referred to as a gel fraction later in the present invention) is optionally selected depending on the formation method. As the gel fraction of the crosslinked polyolefin resin foam of the present invention, an optional value may be selected depending on the formation method. For example, the gel fraction of the crosslinked polyolefin resin foam formed by a low pressure injection forming method is preferably 45 to 65%, and more preferably 50 to 60%. Also, the gel fraction of the crosslinked polyolefin resin foam formed by a vacuum forming method is preferably 25 to 50%, and more preferably 30 to 45%. The gel fraction of the crosslinked polyolefin resin foam formed by a method of The formation of driving a low pressure injection formation after vacuum pre-formation is preferably 40 to 60%, and more preferably 45 to 55%. The term "gel fraction" used in the present invention refers to a calculated value. Specifically, the gel fraction is determined as follows. That is, about 50 mg of the crosslinked polyolefin resin foam is accurately weighed, immersed in 25 ml of xylene at a temperature of 120 ° C for 24 hours and filtered through a wire mesh network 200 made of stainless steel, and the insoluble component in the form of wire mesh net is vacuum dried. This insoluble component is weighed accurately. The gel fraction refers to the percentage by weight of this insoluble component with the weight of the foam before dissolution and is represented by the following formula. Gel fraction (%) = (Insoluble Component Weight / Foam Weight before dissolving) x 100 In the crosslinked polyolefin resin foam of the present invention, an indicator which expresses the forming capacity is that in which a Stress elongation a (%) at normal temperature measured in accordance with JIS K6767 (1999) satisfies a ratio in the following formula (1) with an apparent density b (kg / m3) and a gel fraction c (%). a > 2 x b - 3 x c + 200 Formula (1) When it does not satisfy the formula (1) above, breaking This can be caused by the application of a high force of cutting force to the corner R when the formation by injection at low pressure is conducted. In the present invention, there is a more preferred relationship with respect to the melt flow rate (MFR) of the polypropylene-based resin (A) to be used and a ratio of the polypropylene-based resin (A) to the resin based on polypropylene (B). A more preferred molten flow rate of the polypropylene-based resin (A) is within a range of 0.4 to 1.8 g / 10 min. When the melt flow rate of the polypropylene-based resin (A) is less than 0.4 g / 10 min, as described above, the thermal decomposition type blowing agent is decomposed by a shear force applied when is formed in a sheet, a problem of appearance arises. In contrast, when the melt flow rate is more than 1.8 g / 10 min, heat resistance can deteriorate and also the stress elongation may be insufficient. The weight ratio of the polypropylene-based resin (A) to the polypropylene-based resin (B) is preferably within a range of 1: 0.5 to 1: 1.5. When the weight ratio of the polypropylene-based resin (B) is less than 0.5, a high shear force is applied to the kneading, and thus the thermal decomposition type blowing agent can be decomposed and the surface state -cial gets worse. In contrast, when the ratio by weight of the polypropylene-based resin (B) is more than 1.5, the resultant cross-linked polyolefin resin foam may have insufficient heat resistance. Defects, which may arise in each section of the relationship, are shown schematically in Figure 1. In the case of producing a foam from the polyolefin resin composition containing a polypropylene-based resin (A), a resin Based on polypropylene (B) and a polyethylene-based resin (C) used in the present invention, an insufflation agent of the thermal decomposition type is preferably used. The thermal decomposition type blowing agent can be an insufflation agent of the thermal decomposition type having a decomposition temperature which is higher than a melting temperature of the polyolefin resin composition. The thermal decomposition type blowing agent is preferably azodicarbonamide and further includes hydrazonecarbonamide, barium salt of azodicarboxylic acid, dinitrosopentathylenenetetramine, nitrosoguanidine, p, p'-oxybisben-cenosulfonylsemicarbazide, symmetrical trihydrazine triazine, bisbenzenesulfonylhydrazide, barium azodicarboxylate, azobis- sobutyronitrile, and toluenesulfonylhydrazide, each having the same or higher decomposition temperature than that of azodicarbonamide. These thermal decomposition type blowing agents can be used alone or in combination. The amount of the thermal decomposition type blowing agent is commonly from about 2 to 40 parts by weight based on 100 parts by weight of the total amount of the resin component and is adjusted depending on the desired foaming ratio. In the case of producing the crosslinked polyolefin resin foam of the present invention, an auxiliary crosslinking agent can also be used. In the present invention, a polyfunctional monomer can be used as the auxiliary crosslinking agent. Examples of usable polyfunctional monomers include monomers, for example, divinylbenzene, diallybenzene, divinylnaphthalene, divinylbiphenyl, divinylcarbazole, divinylpyridine, and nucleically substituted compounds and related analogues thereof; acrylic acid-based compounds or methacrylic acid-based compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, glycol diacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol diacrylate, and dimethacrylate 1, 10-decanodiol; vinyl ester, allyl ester, acryloyloxyalkyl ester and methacryloyloxyalkyl ester of aliphatic dihydric carboxylic acid or aromatic dihydric carboxylic acid, such as divinyl phthalate, diallyl phthalate, diallyl maleate and bisacryloyloxyethyl terphthalate; vinyl ether and allyl ether of aliphatic alcohol dihydric or aromatic dihydric alcohol, such as diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, polyethylene glycol divinyl ether, hydroquinone divinyl ether and bisphenol A diallyl ether; maleimide-based compounds such as N-phenylmaleimide and N, '-m-phenylenebismaleimide; and compounds having two triple bonds such as dipropalgyl phthalate and dipropalgyl maleate. Moreover, in the present invention, it is possible to use, as the other auxiliary cross-linking agent, compounds based on acrylic acid or methacrylic acid-based compounds, such as trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane triacrylate, trimethacrylate, tetramethylolmethane lactide, tetramethylolmethane tetraacrylate, and tetramethylolmethane tetramethacrylate; poly (vinyl ester), poly (allylester), poly (acryloyloxyalkyl ester) and poly (methacryloyloxyalkyl ester) of carboxylic polyhydric aromatic acids or carboxylic polyhydric aliphatic acids, such as triallyl trimellitate ester, triallyl pyromellitate ester and tetraalyl pyromellitate ester; allyl ester of cyanuric acid or isocyanuric acid, such as triallyl cyanurate and triallyl isocyanurate; and polyfunctional monomers such as triallyl phosphate and trisacryloxyethyl phosphate. These auxiliary crosslinking agents can be used alone or in combination. The amount of the auxiliary crosslinking agent is preferably 0.1 to 30 parts by weight, more preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the total amount of the resin component and is adjusted depending on the fraction of gel desired. Also, the polyolefin resin composition can be crosslinked by using the auxiliary crosslinking agent in combination with an organic peroxide. As the organic peroxide, for example, methyl ethyl ketone peroxide, t-butyl peroxide and dicumyl peroxide are used. The amount of the organic peroxide is preferably 0.01 to 10 parts by weight, and more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the total amount of the resin component, and is adjusted depending on the fraction of gel desired. In the present invention, the gel fraction is adjusted taking into account the properties of heat resistance and cushioning. In the present invention, the so-called chemical crosslinking methods and crosslinking method through ionizing radiation can be used in combination in the case of crosslinking the polyolefin resin composition. Provided the characteristic of the present invention is not impaired, the polyolefin resin composition can be mixed with various additives such as blowing agent decomposition accelerators, cell nucleation adjusters, antioxidants, heat stabilizers, dyes, flame retardants, anti-static agents and inorganic fillers. In the present invention, the crosslinked polyolefin resin foam can be produced by forming the polyolefin resin composition mixed with several components described above to a predetermined shape, followed by crosslinking and foaming. The method for producing a cross-linked polyolefin resin foam includes, for example, the following methods. A predetermined amount of the above polyolefin resin composition is kneaded uniformly melted at a temperature lower than a decomposition temperature of the thermal decomposition type blowing agent using a kneader such as a single screw extruder, screw extruder Twins, Banbury mixer, kneading mixer or mixing roller, and then the kneaded mixture is formed into a foil. Then, the resulting sheet-like article is irradiated with ionizing radiation at a predetermined dose, thereby curing a resin, and the cross-linked sheet-like article is foamed by heating at the temperature which is higher than the decomposition temperature of the crosslinking agent. insufflated type of thermal decomposition. As ionizing radiation, for example, beam of electrons, X-rays, ß-rays and rays? are used. The irradiation dose is commonly around 1 to 300 kGy and the dose is adjusted depending on the desired gel fraction. Also crosslinking or crosslinking of silane with a peroxide can be conducted in place of crosslinking with irradiation using ionizing radiation. The article similar to foamable sheet in which a resin is crosslinked is heated to a temperature, which is the decomposition temperature of the blowing agent of thermal decomposition type or higher and the melting point of the resin or higher, for example , 190 to 290 ° C using hot air, infrared rays, a metal bath, an oil bath or a salt bath, and then the resin is foamed by a decomposition gas of an insufflating agent to obtain the resin foam of crosslinked polyolefin of the present invention. The endothermic peak measured by a differential examination calorimeter of the crosslinked polyolefin resin foam is preferably 155 ° C or higher. The reason is as follows. That is, appearance faults such as melt (gate marks) of a foam in a gate portion, where a molten resin is expelled, caused by low pressure injection and melt (craters) of a foam caused, are expected. by application of a high shear force on a vertical wall portion is reduced as compared to the case where the endothermic peak is not within the previous range. Thus, the cross-linked polyolefin resin foam, which includes closed cells and optionally shows a foaming ratio within a range of 2 to 45 depending on the amount of the blowing agent, and also has a beautiful appearance, can be obtained. In a method for evaluating the heat resistance of the crosslinked polyolefin resin foam of the present invention, characteristics of a high temperature elongation can be used as an indicator. The heat resistance preferably satisfies a ratio between an elongation at tension (%) at 150 ° C or less and an elongation at tension (%) at 170 ° C or less of the following formula (2). (Elongation to Stress (%) at 170 ° C or less) / (Elongation to Stress (%) at 150 ° C or less) > 1 Formula (2) When formula (2) is not satisfied, acceleration of deterioration to heat is considered and defects may arise when forming at high temperature. In evaluating the forming ability of the crosslinked polyolefin resin foam of the present invention, a stretch ratio can be used as an indicator. As the stretching ratio, an optional value can be selected depending on the training method. For example, the draw ratio of the crosslinked polyolefin resin foam obtained by a low pressure injection forming method is preferably 0.4 or more, and preferably 0.5 or more. Also, in the case of a method of vacuum formation, the stretching ratio is preferably 0.6 or more, and more preferably 0.7 or more. In the case of a forming method in which low pressure injection forming is conducted after vacuum pre-forming, the draw ratio is preferably 0.5 or more, and more preferably 0.6 or more. It is possible to obtain a laminate, which exhibits more excellent heat resistance upon heating before formation, using the cross-linked polyolefin resin foam obtained by the method described above. The laminate can be produced by laminating the crosslinked polyolefin resin foam with other materials using a conventionally known method. Examples of other materials, which are laminated with the crosslinked polyolefin resin foam of the present invention, include those selected from at least one of known materials such as a cloth-like article made of a natural fiber or a artificial fiber, a sheet-like article made of a polyvinyl chloride resin, a sheet-like article made of thermoplastic olefin (TPO), an article similar to thermoplastic elastomer sheet, a skin material such as animal skin, a non-woven fabric made of a thermoplastic resin fiber, an article similar to non-crosslinked foamed sheet of polyolefin resin (e.g., a continuous cellular foam made of polyurethane), films such as a polyester film and a film from polyacryl, a plastic board, a foamed paper, and a metal layer made of copper, silver or nickel. In the present invention, a plurality of these other materials can be laminated, or the other material is laminated on both surfaces of the crosslinked polyolefin resin foam, or two or more types of these other materials can be combined. Examples of the method for laminating the crosslinked polyolefin resin foam of the present invention with the other above material include an extrusion lamination method of melting a thermoplastic resin, a laminate bond lamination method after applying an adhesive, a method lamination with heat (also referred to as melting) of rolling a skin material and, if necessary, a cross-linked polyolefin resin foam with heating, a hot melt method, and a high frequency welding method, and also include a method of deposition without electrons, an electro-deposition method and a vacuum deposition method in the case of using metal. However, the method is not limited to these methods and can be any method as long as both are linked. A formed article can be obtained by forming the cross-linked or laminated polyolefin resin foam obtained by the method described above in an optional figure. Examples of the training method include a high pressure injection forming method, a formation method by low pressure injection, a male pull vacuum forming method, a female pull vacuum forming method and a compression forming method. In the above forming method, a thermoplastic resin is commonly used as a base material. The term "base material" used in the present invention serves as a skeleton of the formed article and the figure is selected depending on the figure of a desired shaped article, for example, a plate or bar. As the thermoplastic resin for a base material used in the present invention, for example, it is possible to apply a polypropylene resin, a polypropylene resin in which propylene and α-olefin (examples of the α-olefin include ethylene, 1-butene , 1-pentene, 1-hexylene, 1-heptene, and 1-octene) are randomly co-polymerized, random / blocky or blocky, a polyethylene resin, a co-polymer resin of ethylene and α-olefin, a vinyl acetate co-polymer resin and an acrylate ester, a polyolefin resin or an ABS resin obtained by optionally mixing these resins, and a polystyrene resin. When a resin having a considerably high melting point such as a polyamide-based resin or a polybutylene terphthalate-based resin is used as a base material in the cross-linked polyolefin resin foam, the melting temperature of a layer of material base is increases, and thus can cause a problem in which cells of the crosslinked polyolefin resin foam break before forming with pressure. Therefore, it is necessary to appropriately select a resin for a base material taking into account a training method. The term "base material layer" used in the present invention is distinguished from the base material of the crosslinked polyolefin resin foam or the skin material of the laminate in the article formed in that it is laminated upon formation. The present invention makes it possible to obtain automotive interior materials such as roof, door and instrument panel in which the crosslinked polyolefin resin foam, laminate or formed article obtained by the method described above is used. It is expected to obtain the effect of reducing the rejection percentage by exhibiting excellent heat resistance in heating in case of processing by formation, for example, low pressure injection formation. EXAMPLES In the present invention, the respective physical properties were evaluated by the following methods. (Method for Measuring the Melt Flow Rate) The measurement is conducted in accordance with JIS K7210 (1999) "Method of Testing the Melt Flow Rate and Rate of Melt Volume Flow (MVR) of Plastic-Thermoplastic Plastic. "The test is conducted under the conditions of temperature of 230 ° C and a load of 2.16 kgf in the case of a resin based on polypropylene (A), or conducts under the conditions of a temperature of 190 ° C and a load of 2.16 kgf in the case of a resin based on polyethylene on the basis of Annex B (Reference) of the above standards "Standards, Designation and Testing Conditions of Materials Thermoplastic Plastics. "A molten flow rate in the present invention is determined by measuring the weight of an extruded resin through a die for 10 minutes by an annual cut method using an Indicator of Cast Model F-B01 manufactured by Toyo Seiki Seisakujyo Co. , Ltd. (Method for Endothermic Peak Analysis Using Differential Examination Calorimeter) In the present invention, an endothermic peak was analyzed by the following method using a differential examination calorimeter. About 10 mg of a polyolefin resin (a polypropylene-based resin or a polyethylene-based resin in the present invention) or a crosslinked polyolefin resin foam whose cells have been collapsed with a roller was placed in a tray of platinum and an endothermic peak was measured using a differential examination calorimeter (DSC: RDC220-DSC Robot manufactured by Seiko Electronic Co. Ltd.). The endothermic peak was measured after a mixture it was melted once, cooled to a temperature of -50 ° C at a rate of 10 ° C / min and then heated at a rate of 5 ° C / min. (Method for Measurement of Molecular Weight Distribution) As a method for measuring molecular weight distribution in the present invention, a method for gel permeation chromatography (GPC) was employed. To 5 mg of a sample (here, a resin based on polypropylene (A), a resin based on polypropylene (B) and a resin based on polyethylene (C)), 5 mL of ortho-dichlorobenzene (ODCB) ) They were added. After dissolving the sample with heating at a temperature of 140 ° C for 2 hours or more, the solution was filtered through a 0.5 μm filter and the filtrate was used as a test solution. 150C ALC / GPC (manufactured by Waters Co.) was used as a device and Shodex AT-806MS measuring 8 meters, x 250 mm *. (2 columns) was used as a column, and differential refractometry was used as a detector. A mobile phase was ortho-dichlorobenzene described above and the measurement was conducted under the conditions of a rate of 1.0 mL / min and a temperature of 140 ° C or less. As a measured value, an equivalent value of polystyrene was used. (Method for Gel Fraction Measurement) A gel fraction means a calculated value. A cross-linked polyolefin resin foam (about 50 mg) was weighed accurately, immersed in 25 mL of xylene at a temperature of 120 ° C for 24 hours and filtered through a network 200 mesh stainless steel wire mesh, and then the insoluble component of wire mesh network figure was dried under vacuum. The weight of this insoluble component was weighted accurately and a% gel fraction was calculated by the following formula (3). Fraction of gel (%) =. { Weight (mg) of Insoluble Component / Weight (mg) of Heavy Polyolefin Resin Foam} x 100 Formula (3) (Method for Apparent Density Measurement) An apparent density was measured in accordance with JIS K6767 (1999) "Foamed Plastic Polyethylene Test Method". Specifically, the resulting sheet-like crosslinked polyolefin resin foam was punched out to obtain a sample having a size of 15 cm3 or more and the thickness and weight were measured, and then a bulk density was calculated by the following formula (4) . Apparent density (kg / m3) = Sample Weight (kg) /. { Sample thickness (m) x Sample area (m2)} Formula (4) (Method for Measuring Stress Elongation at Normal Temperature) An elongation at tension was measured in accordance with JIS K6767 (1999) "Foamed Plastic Polyethylene Test Method". Specifically, the cross-linked polyolefin resin foam similar to the resulting sheet was drilled to obtain a specimen in the form of a No. 1 weigth. The elongation to the tension of the specimen was measured by the Instron UCT-500 Universal Voltage Tester manufactured by Orientec Co. , Ltd. and was calculated as follows. That is, a difference between a length between marked lines after breaking and a length between original marked lines is divided by a length between original marked lines and the resulting value is expressed as a percentage. (Method for Evaluation of Stress Elongation at Normal Temperature) With respect to this measured value, the following expression of relation (1) is used as an evaluation criterion. a > 2 x b - 3 x c + 200 Formula (1) where a denotes an elongation at tension (%), b denotes an apparent density (kg / m3), and c denotes a gel fraction (%). (Method for Measuring Stress Elongation at High Tempera- ture) An elongation to voltage is measured according to "Method for Measuring Stress Elongation at Normal Temperature". The following heating method was employed. This is, a high-low temperature constant temperature bath TLF2-U2-J-F manufactured by Orientec Co. , Ltd. was adjusted to a desired temperature and a parallel clamp jaw portion (portion to be measured) of the Instron Universal Voltage Tester was heated while surrounding the bath. A sample was mounted, preheated for 6 minutes and then measured. (Method for Evaluation of Heat Resistance) The value measured by the "Method for Measuring Stress Elongation at High Temperature" was evaluated according to the following evaluation criteria. (Stretch Elongation% at 170 ° C) / (Elongation at Voltage% at 150 ° C) = 1 Formula (2) With heat resistance 0: satisfying formula (2) above Without heat resistance X: not satisfying Formula (2) above (Method for Evaluation of Surface Properties) The surface properties were evaluated as follows. That is, the surface hardness was measured using a surface hardness meter SURFCORDER SE-2300 manufactured by Kosaka Laboratory Ltd. and the surface properties were evaluated from the measured value of Ra75 according to the following criteria. Surface properties O: value Ra75 is less than 25 μm Surface properties ?: Ra75 value is 25 μm or more and less than 30 μm Surface properties X: Ra75 value is 30 μm or more (Method for Evaluation of Formation Capacity) Foam The resulting cross-linked polyolefin resin was vacuum-foamed and then the appearance and stretch ratio were evaluated. The appearance was visually observed whether or not blisters and wrinkles occurred. A stretch ratio denotes a H / D value at a boundary where a foam expands and extends into a cylindrical shape without breaking when the foam is heated in a female die having a vertical cylindrical shape having a diameter of D and a depth of H and then formed straight using a vacuum forming machine. In the present, diameter D is 50 mm. The stretch ratio was measured at three points of the foam, each having a surface temperature of 160 ° C, 180 ° C and 200 ° C, and then the value was evaluated according to the following criteria. Training capacity O: At two or more points of a different temperature, a stretch ratio is 0.50 or more and good appearance is obtained. Training capacity ?: At a temperature point, a stretch ratio is 0.50 or more and good appearance is obtained. Training capacity X: At no point in a temperature, a stretch ratio is 0.50 or more, or poor appearance is obtained. (General evaluation) From the evaluation results in "Method for Evaluation of Heat Resistance", "Method for Evaluation of Surface Properties" and "Method for Evaluation of Training Capacity ", the general evaluation was conducted according to the following criteria.

General evaluation O: All samples were rated "0". Overall assessment ?: TWO samples or less were rated "0" and no sample was rated "X". General evaluation X: One or more samples were graded "X" The evaluation results are as follows. 0: Excellent: Good X: Poor Example 1 A mixture obtained by mixing 40% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 40% by weight of a polypropylene based resin (B) (ethylene-propylene random co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), % by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 8 parts of azodicarbonamide as an insufflation agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 ram single screw extruder. with a ventilation. The sheet thus obtained was irradiated with a beam of 100 kGy electrons using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.1 mm, a bulk density of 67 kg / m 3 and a gel fraction of 56% . With respect to the resulting crosslinked polyolefin resin foam, an elongation to tension at normal temperature was measured and found to be 180%. Also, cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 156 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 200% and an elongation to the tension at a temperature of 170 ° C was 220%. Also, the Ra75 value of surface hardness was 20 μm. Example 2 A mixture obtained by mixing 30% by weight of a resin based on polypropylene (A) (homo-polypropylene: MFR = 0.9 g / 10 min, peak temperature DSC: 164 ° C, Mw = 560,000), 40% by weight weight of a polypropylene-based resin (B) (ethylene-propylene random co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 30% by weight of a resin a polyethylene base (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 9 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an agent of auxiliary crosslinking using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder *. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 150 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 1.9 mm, a bulk density of 70 kg / m 3 and a gel fraction of 54% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 190%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 159 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 190% and an elongation to the tension at a temperature of 170 ° C was 210%. Also, the value Ra75 of surface hardness was 19 μm. Example 3 A mixture obtained by mixing 50% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 30% by weight of a polypropylene based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1, 100, 000 ), 20% by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 6 parts of azodicarbonamide as an agent of insufflation and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder *. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 1.6 mm, a bulk density of 85 kg / m 3 and a gel fraction of 54% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 240%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 156 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 210% and an elongation to the tension at a temperature of 170 ° C was 260%. Also, the Ra75 value of surface hardness was 17 μm. Example 4 A mixture obtained by mixing 40% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 162 ° C, Mw = 420,000), 40% by weight of a polypropylene based resin (B) (ethylene-propylene random co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 20% by weight of a polyethylene-based resin (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 7 parts of azodicarbonamide as an insufflating agent and parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, with it reticulating the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.0 mm, a bulk density of 67 kg / m 3 and a gel fraction of 50% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 250%. Also, the cells were collapsed by pressing the resultant cross-linked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 155 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 210% and an elongation to the tension at a temperature of 170 ° C was 260%. Also, the Ra75 value of surface hardness was 17 μm. Example 5 A mixture obtained by mixing 40% by weight of a resin based on polypropylene (A) (homo-polypropylene: MFR = 0.5 g / 10 min, peak temperature DSC: 165 ° C, Mw = 860,000), 40% by weight of a polypropylene-based resin (B) (random ethylene-propylene co-polymer: MFR = 2.2 g / 10 min, peak temperature DSC: 138 ° C, Mw = 0.000), 20% by weight of a resin a polyethylene base (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 6 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm sheet of thickness by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 120 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 1.7 mm, a bulk density of 72 kg / m 3 and a gel fraction of 52% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 220%. Also, the cells were collapsed by pressing the resultant cross-linked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 155 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the voltage at a temperature of 150 ° C was 210% and an elongation to the voltage at a temperature of 170 ° C was 230%. Also, the Ra75 value of surface hardness was 22 μm.

Example 6 A mixture obtained by mixing 50% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 25% by weight of a polypropylene-based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1, 100, 000 ), 25% by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000 **), 10 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with a 100 kGy electron beam using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.0 mm, a bulk density of 53 kg / m3 and a gel fraction of 52% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 190%. Also, the cells were collapsed by pressing the polyolefin resin foam.

Finely cross-linked using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 159 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 200 ° C. An elongation to the tension at a temperature of 150 ° C was 200% and an elongation to the tension at a temperature of 170 ° C was 220%. Also, the Ra75 value of surface hardness was 21 μm. Example 7 A mixture obtained by mixing 40% by weight of a resin based on polypropylene (A) (homo-polypropylene: MFR = 2.2 g / 10 min, peak temperature DSC: 166 ° C, Mw = 350,000), 40% by weight weight of a polypropylene based resin (B) (ethylene-propylene random co-polymer: MFR = 2.2 g / 10 min, peak temperature DSC: 138 ° C, Mw = 830,000), 20% by weight of a resin a polyethylene base (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 12 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an agent of auxiliary crosslinking using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder *. with a ventilation. The sheet thus obtained was irradiated with a 100 kGy electron beam using an electron beam irradiator, thereby crosslinking the resin. The reticulated sheet was submerged in a salt bath heated to a temperature of 240 ° C to obtain a cross-linked polyolefin resin foam having a thickness of 2.2 mm, a bulk density of 49 kg / m3 and a gel fraction of 51%. With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 220%. Also, the cells were collapsed by pressing the resulting cross-linked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 157 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 180 ° C. An elongation to the tension at a temperature of 150 ° C was 210% and an elongation to the tension at a temperature of 170 ° C was 220%. Also, the Ra75 value of surface hardness was 23 μm. Example 8 A mixture obtained by mixing 40% by weight of a resin based on polypropylene (A) (homo-polypropylene: MFR = 0.35 g / 10 min, peak temperature DSC: 165 ° C, Mw = 1,050,000), 40% by weight of a polypropylene-based resin (B) (ethylene-propylene random copolymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 20% by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 8 parts of azodicarbonamide as an blowing agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 m single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 80 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.3 mm, a bulk density of 53 kg / m3 and a gel fraction of 52% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 200%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 156 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 220% and an elongation to the tension at a temperature of 170 ° C was 240%. Also, the Ra75 value of surface hardness was 25 μm. The results of examples 1 to 8 are summarized in the Table 1 Table 1 The cross-linked polyolefin resin foam obtained in Example 1 was subjected to a corona discharge treatment and coated with a two-pack urethane-based adhesive, and then the coated cross-linked polyolefin resin foam was laminated with a sheet of poly (vinyl chloride) (0.55 mm) to obtain a laminate. The laminate was formed by a low pressure injection forming method (a thermoplastic resin: homo-polypropylene, MFR = 20 g / min, resin temperature: 180 ° C) to obtain an article formed having a beautiful appearance. Comparative Example 1 A mixture obtained by mixing 60% by weight of a polypropylene-based resin (A) (ethylene-propylene block copolymer: MFR = 1.3 g / 10 min, DSC peak temperature: 164 ° C, Mw = 470,000), 40% by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 8 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 125 kGy using an electron beam irradiator, thereby crosslinking the resin. The cross-linked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtaining a crosslinked polyolefin resin foam having a thickness of 2.1 mm, a bulk density of 67 kg / m3 and a gel fraction of 56%. With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 160%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 158 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 180% and an elongation to the tension at a temperature of 170 ° C was 210%. Also, the Ra75 value of surface hardness was 19 μm. Comparative Example 2 A mixture obtained by mixing 60% by weight of a resin based on polypropylene (A) (homo-polypropylene: MFR = 2.2 g / 10 min, peak temperature DSC: 166 ° C, Mw = 350,000), % by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 8 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 133 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.1 mm, a bulk density of 63 kg / m 3 and a gel fraction of 58% . With respect to the resultant crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 140%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 161 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 180% and an elongation to the tension at a temperature of 170 ° C was 200%. Also, the Ra75 value of surface hardness was 18 μm. Comparative Example 3 A test to form a mixture obtained by mixing 60% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, DSC peak temperature: 164 ° C, Mw = 470,000), 40% by weight of a polypropylene-based resin (B) (ethylene-propylene block copolymer: MFR = 0.8 g / 10 min, DSC peak temperature: 148 ° C, Mw = 1,100,000), 8 parts of azodicarbonamide as an agent of insufflation and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation was done. However, the blowing agent broke down and the surface condition was not good, and therefore irradiation and foaming were finished. Comparative Example 4 A mixture obtained by mixing 20% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 50% by weight of a polypropylene-based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 30 % by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 10 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with a beam of 110 kGy electrons using an electron beam irradiator, thereby reticulating the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.4 mm, a bulk density of 60 kg / m 3 and a gel fraction of 56% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 190%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 153 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the voltage at a temperature of 150 ° C was 240% and an elongation to the voltage at a temperature of 170 ° C was 220%. Also, the Ra75 value of surface hardness was 20 μm. Comparative Example 5 A mixture obtained by mixing 25% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 25% by weight of a polypropylene based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1, 100, 000), 50% by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 10 parts of azodicarbonamide as an insufflation agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.1 mm, a bulk density of 61 kg / m3 and a gel fraction of 54% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 210%. As well, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 154 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 260% and an elongation to the tension at a temperature of 170 ° C was 240%. He too Ra75 value of surface hardness was 19 μm. Comparative Example 6 A mixture obtained by mixing 60% by weight of a polypropylene-based resin (A) (ethylene-propylene block copolymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 20% by weight of a polypropylene based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 20 % by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 9 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, thereby crosslinking the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.0 mm, a bulk density of 66 kg / m 3 and a gel fraction of 54% . With respect to the resultant crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 150%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 158 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 190% and an elongation to the tension at a temperature of 170 ° C was 200%. Also, the Ra75 value of surface hardness was 20 μm. Comparative Example 7 A mixture obtained by mixing 20% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 60% by weight of a polypropylene-based resin (B) (random ethylene-propylene co-polymer: MFR = 0.8 g / 10 min, peak temperature DSC: 148 ° C, Mw = 1,100,000), 20 % by weight of a resin based on polyethylene (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 9 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, with it reticulating the resin. The crosslinked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtain a crosslinked polyolefin resin foam having a thickness of 2.2 mm, a bulk density of 65 kg / m 3 and a gel fraction of 54% . With respect to the resulting crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 220%. Also, the cells were collapsed by pressing the resultant cross-linked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 151 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or less at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 230% and an elongation to the tension at a temperature of 170 ° C was 200%. Also, the Ra75 value of surface hardness was 17 μm. Comparative Example 8 A test to form a mixture obtained by mixing 40% by weight of a polypropylene-based resin (A) (ethylene-propylene block co-polymer: MFR = 1.3 g / 10 min, peak temperature DSC: 164 ° C, Mw = 470,000), 40% by weight of a polypropylene-based resin (B) (homo-propylene) : MFR = 0.9 g / 10 min, peak temperature DSC: 167 ° C, Mw = 560,000) and 20% by weight of a resin based on polyethylene (C) (linear polyethylene low density: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 12 parts of azodicarbonamide as an insufflating agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed in a 1 mm thick sheet by extruding through a 60 mm single screw extruder. with a ventilation was done. However, the blowing agent broke down and the surface condition was not good, and therefore irradiation and foaming were finished. Comparative Example 9 A mixture obtained by mixing 80% by weight of a resin based on polypropylene (B) (random ethylene-propylene co-polymer: MFR = 2.2 g / 10 min, peak temperature DSC: 138 ° C, Mw = 830,000), 20% by weight of a polyethylene-based resin (C) (linear low density polyethylene: MFR = 12 g / 10 min, density: 0.932 g / cm3, Mw = 60,000), 10 parts of azodicarbonamide as a Blowing agent and 5 parts of divinylbenzene as an auxiliary crosslinking agent using a Henschel mixer were formed into a 1 mm thick sheet by extruding through a 60 m single screw extruder. with a ventilation. The sheet thus obtained was irradiated with an electron beam of 110 kGy using an electron beam irradiator, thereby crosslinking the resin. The cross-linked sheet was immersed in a salt bath heated to a temperature of 240 ° C to obtaining a crosslinked polyolefin resin foam having a thickness of 2.1 mm, a bulk density of 61 kg / m3 and a gel fraction of 52%. With respect to the resultant crosslinked polyolefin resin foam, an elongation at normal temperature tension was measured and found to be 280%. Also, the cells were collapsed by pressing the resultant crosslinked polyolefin resin foam using a mixing roller and an endothermic peak temperature was confirmed by a differential examination calorimeter and found to be 136 ° C. Moreover, a stretch ratio was measured and found to be 0.50 or more at a temperature of 160 ° C, 180 ° C and 200 ° C. An elongation to the tension at a temperature of 150 ° C was 310% and an elongation to the tension at a temperature of 170 ° C was 220%. Also, the Ra75 value of surface hardness was 20 μm. The results of Comparative Examples 1 to 9 are summarized in Table 2.

Table 2 Industrial Application It is expected that the cross-linked polyolefin resin foam obtained in the present invention exerts the effect of decreasing the fraction defects by showing excellent heat resistance against processing heating upon formation, eg, low pressure injection forming heating . The crosslinked polyolefin resin foam of the present invention is excellent in flexibility, light weight properties and heat insulation properties, and is preferably used as a material for automotive interiors such as a roof, a door and a panel of instruments.

Claims (7)

1. REIVI DICATIONS 1. A crosslinked polyolefin resin foam comprising a polyolefin resin composition containing 20 to 50% by weight of a polypropylene based resin (A) which shows at least one endothermic peak measured by examination calorimeter differential at a temperature of 160 ° C or higher, 20 to 50% by weight of a polypropylene-based resin (B) which shows at least one endothermic peak measured by differential examination calorimeter at a temperature of less than 160 ° C, and 20 to 40% by weight of a polyethylene-based resin (C).
2. 2. The crosslinked polyolefin resin foam according to claim 1, wherein the polypropylene-based resin (A) is a block copolymer of ethylene-propylene.
3. 3. The crosslinked polyolefin resin foam according to claim 1, wherein the polypropylene-based resin (A) is a homo-polypropylene.
4. 4. The crosslinked polyolefin resin foam according to claim 1, wherein the polypropylene-based resin (A) is a random ethylene-propylene co-polymer. 5. The crosslinked polyolefin resin foam according to claim 1, wherein a melt flow rate of the polypropylene based resin (A) is 0.4 to 1.8 g / 10 min and a weight ratio of the resin to Polypropylene base (A) to the polypropylene based resin (B) is from 1: 0.5 to 1: 1.
5. 5. 6. A laminate comprising the crosslinked polyolefin resin foam according to claim 1, and other materials, which are laminated together. 7. A shaped article obtained by forming the crosslinked polyolefin resin foam according to claim 1 or the laminate according to claim
6. 6. 8. A material for automotive interiors using any of the crosslinked polyolefin resin foam of according to claim 1, the laminate according to claim 6 and the article formed according to claim
7. 7.