JP6724509B2 - Permeable polyolefin resin foam - Google Patents

Description

The present invention provides a polyolefin resin foam that can be suitably used as various sealing materials and light shielding sheet materials in the fields of construction, electricity, electronics, vehicles and the like.

A foam using a polyolefin resin is generally excellent in flexibility, cushioning property, and heat insulating property and is therefore used as a laminate having an adhesive layer in various industrial fields. For example, when it is used as a base material for an adhesive tape, it can be easily attached to an uneven wall or the like by utilizing the flexibility of a foam, but an adhesive tape having a transparent film-shaped base material such as cellophane tape. Compared with the above, the other side of the adhesive tape was not visible, and thus positioning and the like were difficult.
Further, in recent years, a foamed body using a polyolefin resin has a display panel, and is widely used as a cushioning material or a sealing material for a device (a mobile phone, a smartphone, etc.) equipped with a touch panel, a product in which the touch panel is incorporated, There is a demand for protection from external factors such as shocks and prevention of malfunctions and malfunctions due to water intrusion. For example, in this application, there is a demand for miniaturization and sophistication of the attachment dimensional accuracy, and there has been a demand for confirmation of the attachment position through the transmission. However, it is difficult to make transparent because the resin forming the foam and the air in the foam have different refractive indices of light because of the large number of foam inside the foam.
As an interior material of a vehicle or the like, a rubber foam made of synthetic rubber or natural rubber such as polyurethane rubber, ethylene-propylene-diene copolymer rubber (EPDM), ethylene-propylene copolymer rubber (EPR) and chloroprene rubber, Thermoplastic resin foams made of polyethylene-based resin, polypropylene-based resin, etc. have been used, but since heat resistance is required, usable parts have been restricted. Further, there is no sealing material having a heat-resistant thin foam that can be used in a portion having extremely narrow clearance.

Patent Document 1 describes a method of heating and pressurizing only a portion of a polyolefin-based resin foam to be made transparent so as to reduce the number of bubbles, but making the entire foam (entire surface) transparent. However, there is a problem that the expansion ratio is extremely reduced due to the reduction of air bubbles, resulting in a decrease in flexibility and heat insulation properties, and a problem that irregularities are formed in the transparent portion.

JP 2007-138150

The present invention provides a polyolefin resin foam that can be suitably used as various sealing materials having excellent permeability, flexibility, cushioning property, and heat insulating property in fields such as construction, electricity, electronics, and vehicles. With the goal.

(1) It has a closed cell structure, the total light transmittance is 15% or more, and the shrinkage rate in the length direction (MD) and the width direction (TD) is -5 to 0% in an environment of 120° C. for 1 hour. A polyolefin having an average cell diameter in the length direction (MD) of 200 μm or more, a thickness of 80 μm to 350 μm, an apparent density of 33 to 165 kg/m ³ , and a 25% compression hardness of 10 to 100 kPa. Resin foam.
(2) The polyolefin resin foam contains 10 to 70% by mass of a thermoplastic elastomer resin, and has two or more endothermic peaks at 110° C. or higher by a differential scanning calorimeter (DSC). Item 2. The polyolefin resin foam according to Item 1.
(3) The polyolefin resin foam according to claim 1 or 2, which has an adhesive layer on a part or the whole surface.

The polyolefin-based resin foam of the present invention can be obtained as a polyolefin-based resin foam having excellent permeability, cushioning properties, and heat insulation properties.
INDUSTRIAL APPLICABILITY The polyolefin-based resin foam of the present invention has excellent permeability, flexibility, cushioning property, and heat insulating property, and therefore is suitably used as a light-shielding sheet material that can be attached to various sealing materials and windows (glass etc.). It is possible to obtain a polyolefin resin foam capable of

Hereinafter, the present invention will be specifically described.

The permeable polyolefin resin foam of the present invention has a closed cell structure and a total light transmittance of 15% or more. The closed cell ratio of the closed cell structure is preferably 90% or more, and more preferably 95% or more. If the closed cell ratio is less than 90%, the bubble film may be broken to lower flexibility and heat insulation properties, and may absorb water, which is unsuitable as a sealing material. The closed cell content of the foam is a value measured by the air pycnometer method described in ASTM-D2856.

The total light transmittance as an index of transparency is preferably 15% or more, more preferably 30% or more. 50% or more is more preferable so that light can be transmitted and the bonding position can be confirmed through the transparent polyolefin resin foam of the present invention. If the total light transmittance is 15% or less, most of the light is not transmitted, and an object (when sandwiched) through the polyolefin resin foam of the present invention cannot be confirmed. The total light transmittance is measured according to the method A described in JIS K7105 (1981).

The permeable polyolefin-based resin foam of the present invention has a shrinkage rate of −5 to 0% in the length direction (MD) and the width direction (TD) under the environment of 120° C. for 1 hour, and the length direction. (MD) has an average bubble diameter of 200 μm or more, a thickness of 80 μm to 350 μm, an apparent density of 33 to 165 kg/m ³ , and a 25% compression hardness of 10 to 100 kPa.

The polyolefin resin foam preferably has a shrinkage rate of -5 to 0% in the length direction (MD) and the width direction (TD) under an environment of 120°C for 1 hour, more preferably -2 to. It is 0%. If the shrinkage ratio in the length direction (MD) and the width direction (TD) is less than -5% under an environment of 120°C for 1 hour, the dimensional change is large and the material may be dislocated from the base material or displaced. If the shrinkage ratio in the length direction (MD) and the width direction (TD) is greater than 0% under the environment of 120° C. for 1 hour, the base material may be deformed. Otherwise, there is a risk of appearance defects such as wrinkles.

The permeable polyolefin resin foam of the present invention preferably has an average cell diameter in the length direction (MD) of 200 μm or more. If the average bubble diameter is less than 200 μm, the number of bubbles per unit area will increase, the refraction amount of light will increase, and the transmittance will decrease. Sex is also reduced.

The permeable polyolefin resin foam of the present invention preferably has a thickness of 80 μm to 350 μm, more preferably 80 μm to 150 μm. When the thickness is more than 350 μm, the heat insulating property and the buffer property are improved, but the transmittance is lowered. If the average bubble diameter is less than 80 μm, the desired heat insulating property and buffering property are deteriorated.

The permeable polyolefin resin foam of the present invention preferably has an apparent density of 33 to 165 kg/m ³ , and more preferably 55 to 145 kg/m ³ . If the apparent density is less than 33 kg/m ³ , the strength of the polyolefin-based resin foam will decrease, and defects such as tears will occur when used as a sealing material. If the apparent density is larger than 165 kg/m ³ , the shape is stable, but there is a problem that flexibility and cushioning property are deteriorated.

The permeable polyolefin resin foam of the present invention preferably has a 25% compression hardness of 10 to 100 kPa, and more preferably has a 25% compression hardness of 20 to 60 kPa because the flexibility and the buffering property are improved. good. If the 25% compression hardness is less than 10 kPa, it will be crushed when compressed and a proper rebound cannot be obtained, and if the 25% compression hardness is more than 100 kPa, it will not be properly crushed and a sealing property will be obtained. Absent.

The permeable polyolefin-based resin foam of the present invention preferably contains the thermoplastic elastomer-based resin in an amount of 10 to 70% by mass in 100% by mass of the polyolefin-based resin. It is more preferable that the elastomer resin is contained in an amount of 30 to 60% by mass. If the thermoplastic elastomer-based resin is less than 10% by mass, excellent flexibility and cushioning property cannot be obtained, and if the thermoplastic elastomer-based resin is greater than 70% by mass, the flexibility is improved and when compressed as a sealing material. There is no appropriate repulsion, and defects such as water leakage occur.

Examples of the thermoplastic elastomer-based resin include polystyrene-based thermoplastic elastomer (SBC, TPS), polyolefin-based thermoplastic elastomer (TPO), vinyl chloride-based thermoplastic elastomer (TPVC), polyurethane-based thermoplastic elastomer (TPU), polyester-based Any conventionally known thermoplastic elastomer (TPEE, TPC), polyamide thermoplastic elastomer (TPAE, TPA), polyolefin block copolymer, polybutadiene thermoplastic elastomer, or the like may be used.

The molecular structure of these thermoplastic elastomers is often composed of a soft segment (a polymer having elasticity) and a hard segment (a polymer having plasticity). If necessary, ethylene monomers and propylene monomers and other copolymerizable monomers may be added. The copolymer of can also be used. These thermoplastic elastomer-based resins may be blended not only in one kind but in two or more kinds. Further, the method for polymerizing these thermoplastic elastomer-based resins is not particularly limited, and any of a high pressure method, a slurry method, a solution method, and a gas phase method may be used. Regarding the polymerization catalyst, a Ziegler catalyst, a metallocene catalyst, or a phenoxyimine complex is also used. The catalyst and the like are not particularly limited. Further, two or more kinds of polymers that form a hard segment and polymers that form a soft segment can be physically mixed to obtain a thermoplastic alloy as a polymer alloy.

As the thermoplastic elastomer-based resin used in the present invention, Mitsui Chemicals "Toughmer" (registered trademark) PN-3560, "Prime TPO" (registered trademark) M142E manufactured by Prime Polymer, "INFUSE" from Dow Chemical Company are commercially available products. (Registered trademark) 9107 and the like.

The permeable polyolefin resin foam of the present invention can be obtained by mixing two or more kinds of resins. In addition to the thermoplastic elastomer-based resin, general polypropylene-based resins (such as homopolypropylene, random polypropylene, block polypropylene, etc. may be mentioned, and if necessary, use a copolymer of a propylene monomer and another copolymerizable monomer. Can also be used) and general polyethylene resins (high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate) Examples thereof include a copolymer (EBA), and if necessary, a copolymer of an ethylene monomer and another copolymerizable monomer can be used).

The permeable polyolefin resin foam of the present invention is characterized by having two or more endothermic peaks at 110° C. or higher by a differential scanning calorimeter (DSC) as an index of heat resistance. Preferably, it has endothermic peaks at 110°C to 130°C and 140°C to 160°C, respectively, and more preferably has two peaks at 120°C or higher. If the endothermic peak is 110° C. or less, it cannot be used in automobile interior materials and the like used at high temperatures because of low heat resistance.

The permeable polyolefin resin foam of the present invention may have an adhesive layer on a part or the entire surface. As the pressure-sensitive adhesive, any conventionally known rubber-based pressure-sensitive adhesive, acrylic pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, or urethane-based pressure-sensitive adhesive may be used.

The method for applying the adhesive to the permeable polyolefin resin foam of the present invention is not particularly limited, and may be a bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater. Alternatively, a knife coater, a reverse coater, a spin coater or release paper may be used. Any conventionally known coating method can be used.

The permeable polyolefin resin foam of the present invention, within the range that does not impair the effects of the present invention, phenolic, phosphorus, amine and sulfur antioxidants, metal damage inhibitors, divinylbenzene, Trimethylolpropane trimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, triallyl isocyanurate, ethyl vinylbenzene, ethylene vinyl dimethacrylate, 1,2 -Crosslinking aids such as benzenedicarboxylic acid diallyl ester, 1,3-benzenedicarboxylic acid diallyl ester, 1,4-benzenedicarboxylic acid diallyl ester and 1,2,4-benzenetricarboxylic acid diallyl ester, filling of mica, talc, etc. Agents, bromine- and phosphorus-based flame retardants, antimony trioxide and other flame retardant aids, antistatic agents, lubricants, pigments, and polyolefin additives such as polytetrafluoroethylene can be added.

The permeable polyolefin resin foam of the present invention is produced by mixing a mixture of polyolefin resin with a foaming agent capable of generating gas. As a chemical agent, a thermal decomposition type chemical foaming agent is added and melt-kneaded, and an atmospheric pressure foaming method is used in which foaming is performed by heating at atmospheric pressure. A thermal decomposition type chemical foaming agent is thermally decomposed in an extruder and foamed while extruding under high pressure. Extrusion foaming method, heat-decomposition of a pyrolytic chemical foaming agent in a press die, press-foaming method of foaming while decompressing, and melt mixing of gas or vaporized solvent in an extruder, and foaming while extruding under high pressure Examples thereof include extrusion foaming method.

The thermal decomposition type chemical foaming agent used here is a chemical foaming agent that decomposes and releases gas when heat is applied, and examples thereof include azodicarbonamide, N,N′-dinitrosopentamethylenetetramine, and P,P. Examples thereof include organic foaming agents such as'-oxybenzenesulfonyl hydrazide, and inorganic foaming agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and calcium azide.

The foaming agents can be used alone or in combination of two or more kinds. In order to obtain a foamed product which is flexible, has high moldability, and has a smooth surface and a high magnification, an atmospheric pressure foaming method using azodicarbonamide as a foaming agent is preferably used.

As the permeable polyolefin resin foam of the present invention, both a crosslinked resin foam (referred to as a crosslinked foam) and a non-crosslinked resin foam (referred to as a non-crosslinked foam) can be used. An appropriate resin foam may be selected according to the above. However, a crosslinked foam is preferable as the polyolefin-based resin foam because the surface of the resin foam has smoothness and is excellent in appearance.

The method for converting the polyolefin resin foam into a crosslinked foam is not particularly limited. As a method for obtaining a crosslinked foam, for example, a silane group, a peroxide, a hydroxyl group, an amide group, a chemical crosslinking method of chemically crosslinking by including in the raw material a crosslinking agent having a chemical structure, Examples include a radiation crosslinking method in which the polyolefin resin is crosslinked by irradiating the polyolefin resin with electron beams, α rays, β rays, γ rays, and ultraviolet rays. In order to make the polyolefin-based resin foam a crosslinked foam from the viewpoint that the cells of the foam are made uniform, while maintaining flexibility and heat resistance, the surface appearance of the foam is smooth and the appearance of the laminated sheet is excellent. Is preferably radiation-crosslinked with an electron beam.

However, when it is difficult to construct a crosslinked structure by electron beam crosslinking, it is possible to obtain a crosslinked foam by electron beam by incorporating a crosslinking aid in the raw material for producing the polyolefin resin foam. You can The crosslinking aid is not particularly limited, but it is preferable to use a polyfunctional monomer. Examples of the polyfunctional monomer include divinylbenzene, trimethylolpropane trimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate and trimellitic acid triallyl ester. , Triallyl isocyanurate, ethyl vinyl benzene and the like can be used. These polyfunctional monomers may be used alone or in combination of two or more.

When the permeable polyolefin resin foam of the present invention is crosslinked, the gel fraction showing the crosslinked state is preferably in the range of 10% to 60%, and more preferably in the range of 30% to 50%. It is preferable. If this gel fraction is less than 10%, the gas of the foaming agent will escape from the surface during foaming, making it difficult to obtain a product with the desired expansion ratio, while if the gel fraction exceeds 60%, excessive crosslinking will occur. When the secondary processing is performed, it may be difficult to obtain a product having a smooth surface and a high expansion ratio, and mechanical strength such as elongation at break may be deteriorated to deteriorate moldability.

The permeable polyolefin-based resin foam of the present invention is a polyolefin-based resin foam having a thickness of at least twice the thickness set for each application of the polyolefin-based resin foam, and using a slicing machine A sliced surface obtained by cutting the film, a method of slicing a sheet having a skin layer on the opposite back surface into two pieces, or a crosslinked closed-cell type foam sheet having a thickness slightly thicker than the thickness set for each application, Examples include a method in which the skin layer on one surface of the foam sheet is sliced and removed, one surface is a sliced surface obtained by cutting the cell membrane, and the skin layer is left on the opposite back surface.

The permeable polyolefin-based resin foam of the present invention is a crosslinked closed-cell foam sheet that is slightly thicker than the thickness set for each application of the polyolefin-based resin foam, and one of the skin surfaces is polished. One side is a sliced surface where the bubble film is destroyed, and the other method is to leave a skin layer on the back surface.
The permeable polyolefin-based resin foam of the present invention has a length direction (MD), a width direction (TD), a length (MD) while heating the polyolefin-based resin foam from which one of the skin surfaces has been removed. ) It is obtained in the form of a long sheet by stretching in both the width direction (TD).
The permeable polyolefin-based resin foam of the present invention can be inexpensively supplied in large quantities by forming a long sheet.

Next, the method for producing the foam of the present invention will be described as an example.

A pyrolytic foaming agent such as azodicarbonamide is further added to the thermoplastic elastomer-based resin, polypropylene-based resin, and polyethylene-based resin, and they are uniformly mixed using a mixing device such as a Henschel mixer or a tumbler. After that, using a melt-kneading device such as an extruder or a pressure kneader, the mixture is melt-kneaded uniformly at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent, molded into a sheet shape by a T-shaped die, and then irradiated with ionizing radiation. Crosslink.

Next, by raising the temperature above the decomposition temperature of the thermal decomposition type foaming agent by a method of floating the obtained sheet-like material on a salt bath that serves as a heat medium, or a method of throwing in an atmosphere such as hot air, by decomposition. By foaming with the generated gas, the polyolefin resin foam obtained by the production method of the present invention can be obtained.

For the polyolefin resin foam, a polyolefin resin foam having a thickness of 1.0 mm or more is prepared, and the polyolefin resin foam is sandwiched by upper and lower nip rolls and fed at a feeding speed of 3.0 m/min to 30.0 m/min. Slicing the vicinity of the central part with a rotary blade to obtain two single-skin polyolefin resin foam sheets with one side having a sliced surface obtained by cutting a cell membrane and the other side having a skin layer left on the opposite side. be able to.

The device for slicing the foam may be any one capable of slicing an industrial soft material or a rubber sheet, and for example, "NP-120RS" manufactured by Nippi Machine Co., Ltd. can be used.

The polyolefin resin foam is a crosslinked closed-cell type foam sheet slightly thicker than the thickness set for each application, and one skin surface is polished and one surface is a polished surface on which the cell membrane is destroyed, the other surface is opposite. It is possible to obtain a single-skin polyolefin resin foam sheet having different front and back surfaces, in which a skin skin layer is left on the back surface. Any generally used foam polishing machine may be used, such as belt sander polishing, router polishing, and CMP (chemical mechanical polishing) in which a chemical action is combined with a mechanical polishing method.

Said one surface is a sliced surface obtained by cutting a cell membrane, and a polyolefin resin foam sheet of one skin having different front and back surfaces with a skin layer left on the opposite back surface is heated at 80 to 200° C. in a heating furnace, and the length direction ( It is possible to obtain a polyolefin resin foam having transparency by stretching 1.2 to 2.5 times in MD).

The heat stretching method can obtain a permeable polyolefin resin foam by any of the length direction (MD), the width direction (TD), the length direction and the width direction simultaneous stretching.

In the case of laminating a pressure-sensitive adhesive on a part or the front surface of the permeable polyolefin-based resin foam, an acrylic pressure-sensitive adhesive or the like applied to release paper is superposed on the permeable polyolefin-based resin foam. By adhering and separating from the release paper, a permeable polyolefin resin foam having tackiness can be obtained.

The evaluation methods used in the following examples and comparative examples are as follows.

(1) Method of measuring closed cell rate The closed cell rate of the foam was measured by the air pycnometer method described in ASTM-D2856, using an air comparison type hydrometer 1000 manufactured by Tokyo Science Co., Ltd.

(2) Transmittance measurement method According to the method A described in JIS K7105 (1981), the measurement was performed using a fully automatic direct reading haze computer HGM-2DP (for C light source) manufactured by Suga Test Instruments Co., Ltd. Light rays were made incident respectively from the front surface and the back surface of the foam and measured, and the average value was defined as the total light transmittance of the measurement object.

(3) Method of measuring average cell diameter The cross section of the produced polyolefin resin foam was observed with a scanning electron microscope (SEM) (S-3000N, manufactured by Hitachi High-Technologies Corporation) at a magnification of 50 times. The bubble diameter (diameter) of the obtained image was measured in an arbitrary range using measurement software. In addition, the bubble diameter was measured so that the longitudinal direction (MD) and the width direction (TD) within a range of 1 mm×1 mm of the photographed image were measured, and the average bubble diameter was calculated.

(4) Thickness measurement method According to ISO 1923 (1981) "foamed plastic and rubber-measurement of linear dimension". Specifically, the thickness of the foam is measured using a dial gauge having a measurement area of about 10 cm ² .

(5) Method of measuring apparent density It is measured based on JIS K6767 (1999) "Expanded plastic-polyethylene-Test method". For example, a sample size (for example, 10 cm square) of 15 cm ³ or more is punched out, and the thickness and mass are measured. The volume was calculated from the area of the sample (100 cm ² in case of 10 cm square) and its thickness, and the apparent density was calculated by the following formula.
Apparent density (kg/m ³ )=Sample weight (kg)/{Sample thickness (m)×Sample area (m ² )}
Then, the average value of the three points obtained by removing the upper and lower limits from the values obtained by measuring the five samples was defined as the apparent density.

(6) Measurement of dimensional change rate The dimensional change rate of the foam is a value measured based on JIS K6767 (1999) "foamed plastic-polyethylene-test method". Specifically, the polyolefin resin foam is accurately cut into a 15 cm square and left in an oven set at 120° C. for 60 minutes. After 60 minutes, remove from the oven and cool at room temperature for about 30-60 minutes. The dimensions of the sample were measured, and the dimensional change rate was calculated as a percentage based on the following formula.
Heating dimensional change rate (%)=[{sample length before putting in oven-sample length after taking out from oven}/sample length before putting in oven]×100.

(7) 25% compression hardness measuring method The 25% compression hardness of a foam is a value measured based on JIS K6767 (1999) "foamed plastic-polyethylene-test method". Specifically, the foam is cut into 50 mm×50 mm, stacked so that the thickness is 20 mm or more and 30 mm or less, and the initial thickness is measured. The sample was placed on a flat plate, compressed to a thickness of 25% of the initial thickness at a speed of 10 mm/min, stopped, and the load after 20 seconds was measured, and the 25% compression hardness (kPa) was calculated by the following formula.
-25% compression hardness (kPa) = load (N)/25 (cm< ² >)/10 after 20 seconds of 25% compression.

(8) Melting point temperature of polyolefin resin:
In the present invention, the melting point of the polyolefin resin is the maximum temperature obtained from the endothermic peak of the DSC curve in which the vertical axis obtained in the differential scanning calorimetric analysis shows the amount of heat (mW) and the horizontal axis shows the temperature. 2 mg of each sample was prepared using a meter (DSC: RDC220 manufactured by Seiko Instruments Inc.-Robot DSC), and measurement was performed under a nitrogen environment. The measurement conditions are as follows: the sample is heated to a temperature of 200° C. and melted, cooled to a temperature of −50° C. at a rate of 10° C./minute, and then heated at a rate of 10° C./minute to obtain a unit mass. The endothermic peak per hit was measured and used as the melting point temperature.

(9) Method for measuring gel fraction The gel fraction is a value calculated by the following method. The polyolefin resin cross-linked foam was first cut into strips in the longitudinal direction at intervals of 0.5 mm with a single blade, and then cut with scissors in the width direction at intervals of 0.5 mm. After being soaked in 200 ml of tetralin of 3 hours, naturally filtered through a 200-mesh stainless steel wire net, washed with acetone and exposed to dry air for 15 seconds, then the insoluble matter on the wire net is placed in a hot air oven at 120°C for 1 hour. To dry. Then, the mixture was cooled in a desiccator containing silica gel for 10 minutes, the mass of the insoluble matter was accurately weighed, and the gel fraction was calculated as a percentage according to the following formula.
Gel fraction (%)={mass of insoluble matter (mg)/mass of weighed polyolefin resin foam (mg)}×100
Then, the average value of 3 points excluding the upper and lower limits from the values obtained by the measurement of 5 samples was taken as the gel fraction.

(10) Method for measuring melt flow rate According to JIS K7210 (1999) "Plastic-thermoplastic melt mass flow rate (MFR) and melt volume flow rate (MVR) test method". Based on Annex B (reference) "Standards and designations of thermoplastic materials and their test conditions" of the above standard, polypropylene resin is 230°C, load is 2.16kgf (21.7N), polyethylene resin is 190°C, The load was 2.16 kgf (21.7 N). Toyo Seiki Seisakusho Co., Ltd. Melt Indexer Model F-B01 is used, the manual cutting method is adopted, and it is defined by the mass of the resin that has come out from the die in 10 minutes.

The resins used in the examples and comparative examples are as follows.
Thermoplastic elastomer-based resin: “Toughmer” (registered trademark) PN-3560(a-1) manufactured by Mitsui Chemicals, density 866 kg/m ³ , MFR (230° C.)=6.0 g/10 minutes, melting point=160° C., crystal Aging temperature=135℃
Thermoplastic elastomer-based resin: "Prime TPO" (registered trademark) M142E (a-2) manufactured by Prime Polymer, density 900 kg/m ³ , MFR (230°C) = 10.0 g/10 minutes, melting point = 153°C, crystallization Temperature = 115°C
Thermoplastic elastomer resin: “INFUSE” (registered trademark) 9507 (a-3) manufactured by Dow Chemical Company, density: 867 kg/m ³ , MFR=5.0 g/10 minutes, melting point=119° C.
Polypropylene resin: "Prime Polypro" (registered trademark) J452HAP manufactured by Prime Polymer, density: 900 kg/m ^3, MFR (230°C) = 3.5 g/10 minutes, melting point = 163°C
Polyethylene-based resin: "Novatech" (registered trademark) LL UJ960 manufactured by Japan Polyethylene, density: 935 kg/m ³ , MFR (190°C) = 5 g/10 minutes, melting point = 126°C.
Polyethylene-based resin: "Novatech" (registered trademark) LD LE520H manufactured by Japan Polyethylene, density = 923 kg/m ^3, MFR (190 °C) = 4 g/10 minutes, melting point = 81 °C.
Foaming agent: Azodicarbonamide "Vinihol AC#R" (registered trademark) manufactured by Eiwa Chemical Industry
Crosslinking aid: 55% divinylbenzene antioxidant manufactured by Wako Pure Chemical Industries: "IRGANOX" (registered trademark) 1010 manufactured by BASF.

[Examples 1 to 7] [Comparative examples 3 to 5]
When the composition obtained by mixing 30 to 60% by weight of the thermoplastic elastomer, 25 to 50% by weight of the polypropylene resin, and 15 to 25% by weight of the polyethylene resin in the ratio shown in Table 1 is taken as 100% by weight, a foaming agent: azodicarboxylic Amido Eiwa Chemical Industry Co., Ltd. "Vinihol AC#R" (registered trademark) 5 to 15% by mass, crosslinking aid: Wako Pure Chemical Industries 55% divinylbenzene 3 parts by mass, antioxidant: BASF company "IRGANOX" ( 0.5 parts by mass of the registered trademark) 1010 and 0.1 parts by mass of carbon black were added to make the color of the foam black, and they were mixed using a Henschel mixer. Next, using a 60Φ extruder, melt extrusion was performed at a temperature of 170 to 185° C., and a polyolefin resin sheet having a thickness of 0.6 mm to 1.2 mm was produced using a T die. The polyolefin resin sheet thus obtained was irradiated with an electron beam having an acceleration voltage of 650 to 950 kV and 30 to 65 kGy from one side to obtain a crosslinked sheet, and the crosslinked sheet was then heated at a temperature of 200 to 220° C. It floated on the bath and was heated by an infrared heater from above to foam. The foam is cooled with water at a temperature of 60° C., the surface of the foam is washed with water and dried to have a thickness of 0.8 to 2.0 mm, an apparent density of 50 to 100 kg/m ³ , and a gel fraction of 25. A long roll of polyolefin resin foam having both skins of about 45% was obtained. The polyolefin resin foam is sliced using "NP-120RS" manufactured by Nippi Machinery Co., Ltd. at a processing speed of 5 m/min so as to cut a cell layer in the thickness direction, and a product thickness of 0.3 mm to A one-skin polyolefin resin foam having 1.5 mm, an apparent density of 50 to 95 kg/m ³ , and a 25% compression hardness of 30 to 100 kPa was obtained.
The obtained one-skin polyolefin resin foam is heated with an infrared heater and stretched 1.5 to 2.0 times in the length direction (MD) to give a transparency of 0.08 mm to 0.45 mm. The obtained polyolefin resin foam was obtained. Table 1 shows the evaluation results of the polyolefin resin foam having this permeability.

[Comparative Examples 1 and 2]
Polyethylene resin (“Novatech” (registered trademark) LD LE520H manufactured by Japan Polyethylene) 100% by weight, foaming agent (azodicarbonamide (“Vinihol AC#R” (registered trademark) manufactured by Eiwa Chemical Industry Co., Ltd.) 10 parts by mass, antioxidant (BASF IRGANOX 1010): 0.5 part by mass, 0.1 part by mass of carbon black was added to make the color of the foam black, and the mixture was mixed with a Henschel mixer. Melt extrusion was performed at 150° C., and a polyethylene resin sheet having a thickness of 1.0 mm was produced using a T die.This sheet was irradiated with an electron beam with an acceleration voltage of 800 kV and 30 kGy to obtain a crosslinked sheet, and then 200° C. It was floated on the salt bath and heated from above with an infrared heater to form a foam.The foam was cooled with water at 60°C, the surface of the foam was washed with water and dried to a thickness of 1.8 mm and an apparent density of 86 kg. A long roll of polyolefin-based resin foam of both skin products of /m ³ was obtained at a processing speed of 5 m/min using the “NP-120RS” manufactured by Nippi Machine Co., Ltd. One-skin polyolefin resin with a product thickness of 0.3 mm to 1.5 mm, an apparent density of 85 to 95 kg/m ³ , and a 25% compression hardness of 80 to 100 kPa by slicing so as to cut the bubble layer in the thickness direction. A foam was obtained.
The obtained one-skin polyolefin resin foam is heated with an infrared heater and stretched 1.8 times in the length direction (MD) to obtain a polyolefin resin foam of 0.1 mm to 0.35 mm. It was The evaluation results of this polyolefin resin foam are shown in Table 1.

Claims (2)

It has a closed cell structure, the total light transmittance is 15% or more, the shrinkage rate in the length direction (MD) and the width direction (TD) is -5 to 0% under the environment of 120°C and 1 hour, and is the average cell diameter direction (MD) is 200μm or more and a thickness of 80Myuemu～350myuemu, apparent density 33~165kg ^/ m 3, 25% compressive hardness is Ru 10~100kPa der polyolefin resin foam, The polyolefin resin foam comprises 10 to 70% by mass of a thermoplastic elastomer resin and has two or more endothermic peaks at 110° C. or higher as measured by a differential scanning calorimeter (DSC). Body . The polyolefin resin foam according to claim 1 , which has an adhesive layer on a part or the whole surface.