JP2016166264A - Polyolefin resin crosslinked foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin crosslinked foam which is excellent in cushioning properties, causes little bleeding of a chemical substance, has no bottom-touching feeling and is lightweight due to a closed-cell structure.SOLUTION: A polyolefin resin crosslinked foam is obtained by using a propylene-based resin (A) that has stereoregularity of an atactic structure, and a peak of a loss coefficient tan δ in a range of -30 to 40°C in a dynamic measurement test described in JIS K6394 "vulcanized rubber and thermoplastic rubber-how to determine dynamic properties-general guideline".SELECTED DRAWING: None

Description

  The present invention relates to a polyolefin resin cross-linked foam.

The rubber foam has an excellent cushioning property and is useful for applications such as a cushion material, a pad material, and a sealant. As is well known, when comparing closed cells and open cells in the foam structure, the former has a structure in which the bubbles are partitioned by a partition in the form of a three-dimensional lattice, whereas the latter has the structure of the closed cell structure. In this structure, the partition between the series of bubbles partitioned by the partition is removed, and the latter is more easily mechanically deformed. However, in the case of open cells, there is a limitation on the thickness and the expansion ratio because there is a case where the original cushioning bottoms out due to the ease of deformation and the original buffer property may not be sufficiently exhibited. On the other hand, there are cases in which sufficient cushioning properties and mold-alignment properties cannot be obtained with closed cells.
In addition, many rubber foams are often vulcanized with sulfur, which can be difficult to use due to metal corrosion caused by sulfur compounds that bleed out of these rubber foams, and health hazards such as phthalic acid derivatives. Including plasticizers of increasing concern, and this may bleed out, limiting the use. As a solution, a semi-independent and semi-open cell foam is provided (see Patent Document 1). However, even in this case, there is a problem that it is difficult to obtain sufficient buffering properties.

JP 2011-052044 A

  In view of the background of the prior art, the present invention provides a polyolefin resin cross-linked foam that is excellent in buffering properties, has few chemical bleeds, has no bottoming feeling due to a closed cell structure, and is lightweight. It is.

The present invention employs the following means in order to solve such problems. That is, the polyolefin resin cross-linked foam of the present invention is as follows.
(1) The stereoregularity has an atactic structure, and the dynamic measurement test described in JIS K6394 “Vulcanized rubber and thermoplastic rubber-Determination of dynamic properties-General guidelines” A polyolefin resin cross-linked foam using a propylene resin (A) having a peak of loss factor tan δ and a maximum value exceeding 1.
(2) The polyolefin resin cross-linked foam according to (1), wherein the propylene resin (A) is amorphous.
(3) Polyolefin resin cross-linking as described in (1) or (2) above, wherein the propylene resin (A) having no melting point peak between 130 and 170 ° C. in differential scanning calorimetry is used. Foam.
(4) From the previous period (1) to (3), wherein the propylene resin (A) is 50 to 100% by mass when the total amount of resin used in the polyolefin resin crosslinked foam is 100% by mass. The polyolefin resin cross-linked foam according to any one of the above.

  According to the present invention, it is possible to provide a polyolefin resin cross-linked foam that is excellent in buffering properties, has little bleed of a chemical substance, has no bottom feeling due to a closed cell structure, and is lightweight.

  The present invention has been intensively studied on the above problems, and intends to provide a polyolefin resin cross-linked foam that is excellent in buffering properties, has little bleed of a chemical substance, has no bottoming feeling due to a closed cell structure, and is lightweight. is there. Details of the invention will be described below.

The stereoregularity of the propylene-based resin (A) used in the present invention has an atactic structure. Among the stereoregularity of the polymer, there are isotactic, syndiotactic, atactic and the like. In the present invention, it is necessary to have an atactic structure. Polypropylene that has become a polymer has a structure in which methyl (—CH ₃ ) groups appear obliquely laterally when the C—C bonds that form the main chain are aligned on the same line and become one. In this case, isotactic is the case where methyl groups are arranged in the same direction, and syndiotactic is alternately appearing obliquely. In atactic, this appears irregularly, which inhibits the crystal structure.

  The propylene-based resin (A) used in the present invention is preferably amorphous because the crystal structure is inhibited by having the atactic structure. The term “amorphous” as used herein is different from crystalline, in that the molecule is in an irregular shape and solidified in an irregular state. Also called glass body. By having an amorphous property, the buffering property and the mold-alignment property are improved. In this case, the along-moulding property needs to be filled along the die to fill a gap when used in a sealant or the like, and this degree is called along-moulding property. If the repulsion against bending is high, deformation along the mold becomes difficult, which may not be preferable.

  The propylene resin (A) used in the present invention preferably has no melting point peak between 130 and 170 ° C. when measured by differential scanning calorimetry (DSC). Usually, a crystalline propylene resin has a sharp melting point peak in the same range and is often an indicator of heat resistance, but the propylene resin (A) in the present invention has an obvious melting point in this range. Preferably no peak is present. If there is no melting point peak between 130 and 170 ° C., the buffering property and the mold alignment are improved, which is preferable.

  Examples of the propylene resin (A) used in the present invention include homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, and ethylene-propylene random block copolymer.

  The propylene-based resin (A) used in the present invention has a loss coefficient tanδ peak of −30 to 30 in a dynamic measurement test described in JIS K6394 “Vulcanized rubber and thermoplastic rubber—How to obtain dynamic properties—General guidelines”. It must be present between 40 ° C. When there is a peak below −30 ° C., the characteristics are not exhibited when used at room temperature, and the same is true when it has a peak at 40 ° C. or higher.

  The peak top (maximum value) of the loss coefficient tan δ of the propylene-based resin (A) used in the present invention needs to exceed 1. This is because the present invention aims to improve the buffering property at room temperature. If it does not exceed 1, the storage shear modulus becomes superior to the loss shear modulus, and the resilience modulus does not change with heat. Is not preferable.

  The ratio of the propylene-based resin (A) in the present invention needs to be 50 to 100% by mass. . If the amount is less than 50% by mass, the buffering properties and mold alignment properties intended by the present invention may not be sufficiently obtained.

Other polyolefin resins used in the present invention are not particularly limited. For example, polyethylene resins represented by low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, etc. definitions are as follows very low density:. 0.910 g / cm less than ^3, a low density: 0.910 g / cm ³ or more 0.940 g / cm ³ or less, high density: 0.940 g / cm ³ greater than 0. 965 g / cm ³ or less), copolymers based on ethylene, or polypropylene resins represented by homopolypropylene, ethylene-propylene random copolymers, ethylene-propylene block copolymers, etc. Any of these mixtures may be used. Examples of the ethylene-based copolymer include ethylene and α-olefins having 4 or more carbon atoms (for example, ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like) may be mentioned, and an ethylene-α-olefin copolymer and an ethylene-vinyl acetate copolymer obtained by polymerization. The polyolefin resin is more preferably a low density polyethylene, a linear low density polyethylene, an ultra low density polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer. More preferred are low density polyethylene, linear low density polyethylene, and ultra low density polyethylene. These polyolefin resins may be either one kind or a mixture of two or more kinds. Most preferred is a mixture of low density polyethylene and linear low density polyethylene.

  In the present invention, the crystalline propylene resin (B) may be used as long as the characteristics of the present invention are not significantly impaired. The stereoregularity of the crystalline propylene resin (B) is preferably an isotactic structure or a syndiotactic structure, unlike the propylene resin (A). This is preferable because the crystallinity is increased and the heat resistance is increased.

  Examples of the crystalline propylene resin (B) include homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, and ethylene-propylene random block copolymer.

  The melt flow rate (MFR) of the propylene resin (A) and crystalline polypropylene resin (B) used for the polyolefin resin crosslinked foam is not particularly limited, but conforms to JIS K7210 (1999), temperature 230 ° C., load Those measured under normal conditions of 2.16 kgf, preferably in the range of 0.5 to 15 g / 10 min. When the MFR is less than 0.5 g / 10 min, the surface of the sheet is roughened when the polyolefin resin crosslinked foam is produced, and the resulting foam causes a problem in appearance. There is a case. Moreover, when MFR exceeds 15 g / 10min, the heat resistance of polyolefin resin cross-linked foam may be insufficient. The melt flow rate (MFR) of the polypropylene resin is more preferably 1.0 to 10 g / 10 min.

  The melt flow rate (MFR) of the polyethylene resin used for the polyolefin resin cross-linked foam is not particularly limited, but is measured under normal conditions of a temperature of 190 ° C. and a load of 2.16 kgf based on JIS K7210 (1999). In the range of 1.0 to 30 g / 10 min. When the MFR is less than 1.0 g / 10 min, the surface of the sheet becomes rough when the polyolefin resin-crosslinked foam is produced, and the resulting foam causes a problem in appearance. There is a case. Moreover, when MFR exceeds 30 g / 10min, the heat resistance of polyolefin resin cross-linked foam may be insufficient. The melt flow rate (MFR) of the polyethylene resin is more preferably 2.0 to 15 g / 10 min.

  In addition, a thermoplastic resin other than the polyolefin resin may be added to the foam as long as the properties of the polyolefin resin crosslinked foam of the present invention are not significantly impaired. The thermoplastic resin other than the polyolefin-based resin here is an acrylic resin such as polystyrene, polymethyl methacrylate or styrene-acrylic acid copolymer, styrene-butadiene copolymer, etc. , Ethylene-vinyl acetate copolymer, polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose and other cellulose derivatives, low Polyolefin such as molecular weight polyethylene, high molecular weight polyethylene, polypropylene, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate Aromatic polyester resins such Poriariteto, polyamide resins, polyacetal resins, polycarbonate resins, polyester sulfone resin, polyphenylene sulfide resin, polyether ketone resin, and a copolymer having a vinyl polymerizable monomer and nitrogen-containing vinyl monomers. Furthermore, elastomers such as isoprene rubber, styrene butadiene rubber, butyl rubber, dimethyl silicone rubber, and ethylene propylene rubber are also included. Examples of the resin containing halogen include polyvinyl chloride, polyvinylidene chloride, polychloroethylene trifluoride, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, and solvent-soluble perfluorocarbon resin. One type of thermoplastic resin other than these polyolefin-based resins may be used, or a plurality of types may be included. The type and amount are selected according to the desired physical properties.

  It is important that the polyolefin resin cross-linked foam of the present invention is mainly composed of a polyolefin resin. Here, the main component means the largest component in mass in the polyolefin resin crosslinked foam. More preferably, the polyolefin resin is 50% by mass or more and 100% by mass or less in 100% by mass of all components of the polyolefin resin cross-linked foam. The thermoplastic resin other than the above-mentioned polyolefin resin, other additives, etc. are 0% by mass or more and 50% by mass or less in 100% by mass of all components of the polyolefin resin crosslinked foam.

  The gel fraction of the polyolefin resin cross-linked foam of the present invention is not particularly limited, but 10 to 60% is preferably used. The gel fraction referred to here is a kind of method for expressing the degree of crosslinking, which is calculated by immersing in a heated solvent for a certain period of time and dividing the remaining insoluble mass by the mass before dissolution. . More preferably, it is 15 to 40%. When the gel fraction is less than 10%, the surface tends to become rough when foaming, and when it exceeds 60%, it is difficult to process when foaming and the yield may be deteriorated.

  The thermal decomposable foaming agent used when producing the polyolefin resin cross-linked foam of the present invention has a decomposition temperature higher than the melting temperature of the resin composition containing the polyolefin resin that is a raw material of the foam. If it is, it will not specifically limit. Preferably, azodicarbonamide is used, and hydrazosicarbonamide having a decomposition temperature equal to or higher than that of azodicarbonamide, azodicarboxylic acid barium salt, dinitrosopentaethylenetetramine, nitrosoguanidine, p, p ′ -Oxybisbenzenesulfonyl semicarbazide, trihydrazine symmetric triazine, bisbenzenesulfonyl hydrazide, barium azodicarbaxylate, azobisisobutyronitrile, toluenesulfonyl hydrazide and the like can be used. These pyrolytic foaming agents may be used alone or in combination of two or more. The compounding amount of the pyrolytic foaming agent is 100 parts by mass of the total amount of the resin components (hereinafter, the total amount of resin components of 100 parts by mass is the total amount of all resins such as polyolefin resins and other thermoplastic resins 100 In this case, it is generally about 2 to 40 parts by weight with respect to the resin in the pellet obtained by masterbatching the additive and the like (the resin component is also included in the resin component). It is set according to the desired expansion ratio.

The apparent density of the polyolefin resin cross-linked foam of the present invention is preferably 0.015 to 0.500 g / cm ³ . More preferably, it is 0.020-0.200 g / cm < ³ >. Most preferably, it is 0.020-0.050 g / cm < ³ >. If it is less than 0.015 g / cm ³ , the surface of the foam is likely to be damaged, and if it exceeds 0.500 g / cm ³ , it is difficult to maintain the intended lightness of the present invention.

  The apparent density can be controlled by the amount of the aforementioned pyrolytic foaming agent added. It is important to select the addition amount arbitrarily according to the kind of pyrolytic foaming agent, the amount of gas, the polyolefin resin to be used, and other thermoplastic resins.

  When the polyolefin resin cross-linked foam of the present invention is produced, a polyfunctional as a crosslinking aid is included in the resin composition containing the polyolefin resin as a raw material of the foam within a range not impairing the properties of the foam. Monomers can be included. Examples of the polyfunctional monomer include divinylbenzene, diallylbenzene, divinylnaphthalene, divinylbiphenyl, divinylcarbazole, divinylpyridine, and their nucleus-substituted compounds and related homologues, ethylene glycol di (meth) acrylate, butylene glycol di (meth). Acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol Aliphatic and aromatic divalent carbo such as (meth) acrylic compounds such as di (meth) acrylate, divinyl phthalate, diallyl phthalate, diallyl malate, bisacryloyloxyethyl terephthalate Fats such as acid vinyl ester, allyl ester, acryloyloxyalkyl ester, methacryloyloxyalkyl ester, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, polyethylene glycol divinyl ether, hydroquinone divinyl ether, bisphenol A diallyl ether Has two triple bonds such as vinyl ethers and allyl ethers of aromatic and aromatic dihydric alcohols, maleimide compounds such as N-phenylmaleimide, N, N′-m-phenylenebismaleimide, dipropargyl phthalate, dipropargyl maleate, etc. Monomers such as compounds can be used. Further, trimethylolpropane tri (meth) acrylate and 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate and 1,9-nonanediol Di (meth) acrylate, trimethylolpropane tri (meth) acrylate and divinylbenzene, trimethylolpropane tri (meth) acrylate and triallyl cyanurate and 1,6-hexanediol di (meth) acrylate, triallyl cyanurate and 1 1,6-hexanediol di (meth) acrylate, triallyl isocyanurate, 1,6-hexanediol di (meth) acrylate, and the like can also be used. For example, divinylbenzene, trimethylolpropane trimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, trimellitic acid triallyl ester, triallyl isocyanurate, ethyl vinylbenzene and the like can be used. . The crosslinking aids may be used alone or in combination of two or more. The compounding amount of the crosslinking aid is 0.1 to 30 parts by mass, more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the total amount of the resin components, and is set according to the desired gel fraction. Is done.

  Moreover, it can also bridge | crosslink combining a crosslinking adjuvant and an organic peroxide. As this organic peroxide, for example, methyl ethyl ketone peroxide, t-butyl peroxide, dicumyl peroxide and the like are used. The compounding quantity of an organic peroxide is 0.01-10 mass parts with respect to 100 mass parts of total amounts of a resin component, More preferably, it is 0.05-5 mass parts, According to a desired gel fraction. Is set.

It is preferable that the polyolefin resin cross-linked foam of the present invention does not contain a sulfur compound or a plasticizer. This is to suppress the bleeding of the chemical substance that is the object of the present invention.
However, various additives such as a foaming agent decomposition accelerator, a cell nucleus modifier, an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, and an inorganic filler, as long as the characteristics of the present invention are not impaired. Can be included in the polyolefin resin composition which is a raw material of the polyolefin resin cross-linked foam of the present invention.

  The polyolefin resin cross-linked foam of the present invention preferably has a closed cell structure. The closed cell structure here refers to a structure in which there is no hole in the resin film between the bubbles and the gas layer is not exchanged between adjacent bubbles. On the other hand, in the open cell structure, holes are opened in the resin film, and the air layer is structured to go back and forth. By having a closed cell structure, there is no feeling of bottoming and it is firmly buffered. The closed cell ratio is preferably at least 90%.

The polyolefin resin cross-linked foam of the present invention preferably has an acceleration of less than 80 G in a floor hardness test described in JIS A6519 “Steel Flooring Base Material for Gymnasium”. Sufficient buffering properties can be obtained by having the configuration of the present invention.
In the present invention, a polyolefin resin composition obtained by blending the above components is molded into a predetermined shape, and then crosslinked and foamed to produce a polyolefin resin crosslinked foam.

  Specifically, the following manufacturing method is mentioned, for example. A predetermined amount of the polyolefin-based resin composition is uniformly melted at a temperature lower than the decomposition temperature of the pyrolytic foaming agent using a kneading apparatus such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, or a mixing roll. This is kneaded and formed into a sheet.

  Next, the resulting sheet is irradiated with a predetermined dose of ionizing radiation to crosslink the olefin resin, and the crosslinked sheet is heated to a temperature equal to or higher than the decomposition temperature of the thermally decomposable foaming agent to be foamed. Instead of crosslinking by ionizing radiation irradiation, peroxide crosslinking or silane crosslinking may be performed.

  Then, the foamable sheet is irradiated with ionizing radiation to crosslink the resin constituting the foamable sheet. As the ionizing radiation, electron beam, X-ray, β-ray, γ-ray and the like are used.

  The irradiation dose is generally about 1 to 300 kGy, and the dose is set according to a desired gel fraction.

  The foamed sheet in which the resin is crosslinked is, for example, hot air, infrared rays, metal bath, oil bath, salt bath, or the like, at a temperature higher than the decomposition temperature of the pyrolytic foaming agent and higher than the melting point of the resin, for example, 190 to 290 ° C. And the resin is foamed by the decomposition gas of the foaming agent, and thus a polyolefin-based resin cross-linked foam is obtained.

  In addition, it is preferable that the polyolefin resin crosslinked foam of this invention is a foam of a single layer structure. A foam having a single layer structure is preferable in that the cost can be suppressed as compared with a foam having a multilayer structure.

  Moreover, a laminated body can be obtained using the polyolefin-type resin crosslinked foam obtained by the method described so far. As a layer to be laminated when the polyolefin resin cross-linked foam of the present invention is used as a laminate, a fabric-like material using natural or artificial fibers, a sheet made of a polyvinyl chloride resin, a thermoplastic olefin (TPO) Sheet, thermoplastic elastomer sheet, leather and other skin materials, non-woven fabric using thermoplastic resin fiber, polyolefin resin non-crosslinked foam sheet, for example, open cell foam using polyurethane, polyester film, polyacryl film, etc. Film, corrugated cardboard, foamed paper, metal layers typified by copper, silver, nickel, etc. It may be laminated on both the front and back surfaces of the polyolefin resin cross-linked foam. It may be stacked only on one side.

  The polyolefin resin cross-linked foam of the present invention and the above-mentioned layer are laminated to form a laminate, for example, an extrusion laminating method in which a thermoplastic resin is melted on the foam, and an adhesive is applied on the foam. Adhesion laminating method after pasting, heat lamination method (also referred to as fusion), hot melt method, high frequency welder method, electroless plating, etc. Examples of the method include an electroplating method, an electrolytic plating method, and a vapor deposition method, but the method is not limited to these, and any method may be used.

  The polyolefin-based resin crosslinked foam obtained in the present invention is suitably used as a buffer material. Here, the cushioning material means a material used for absorbing an impact, and many of them are used for electrical appliances, building materials, automobile parts and the like. It is important not to give a feeling of bottoming as well as a necessary characteristic as a cushioning material. Further, particularly when used in electrical appliances, it is desirable that the chemical properties are excellent, specifically, no unnecessary bleed out occurs.

  However, in addition to the cushioning material, the application is not limited to this when the characteristics such as the sealing material and the packaging / packaging material can be utilized.

The physical properties were evaluated by the following methods.

(Thickness measurement method)
In accordance with ISO 1923 (1981) "Foamed plastics and rubbers-Measurement of linear dimensions". Specifically, the thickness of the foam is measured using a dial gauge having a measurement area of about 10 cm ² .

(Measuring method of melting point by differential scanning calorimetry)
Differential scanning calorimetry was performed by the following method. About 10 mg of polyolefin-based resin was placed in a platinum pan and measured with a differential scanning calorimeter (DSC: RDC220-Robot DSC manufactured by Seiko Denshi Kogyo Co., Ltd.). Measurement conditions were such that the sample was melted once, cooled to −50 ° C. at a rate of 10 ° C./min, and then heated at a rate of 5 ° C./min. The endothermic peak obtained when the temperature was raised again was taken as the melting point.

(Resin density measurement method)
The measurement was performed according to JIS K6922 (2011) “Plastic-polyethylene (PE) molding and extrusion material”.

(Measuring method of melt flow rate)
Conforms to JIS K7210 (1999) “Plastics—Test methods for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics”. Based on Annex B (reference) “Standards and designation of thermoplastic materials and test conditions” of the above standards, polypropylene resin is 230 ° C., load is 2.16 kgf (21.7 N), polyethylene resin is 190 ° C., The test was performed under a load of 2.16 kgf (21.7 N). It is defined by the mass of the resin coming out of the die for 10 minutes using the melt indexer model F-B01 manufactured by Toyo Seiki Seisakusho Co., Ltd.

(Measurement method of gel fraction)
The gel fraction is a value calculated by the following method. A polyolefin resin cross-linked foam is first cut into a strip shape in the longitudinal direction with a single blade at intervals of 0.5 mm, and then cut with a scissors at intervals of 0.5 mm in the width direction, accurately weighed about 50 mg, and 130 ° C. After being soaked in 200 ml of tetralin for 3 hours, it is naturally filtered with a 200 mesh stainless steel wire mesh, washed with acetone, dried air is applied for 15 seconds, and the insoluble content on the wire mesh is placed in a hot air oven at 120 ° C. for 1 hour. And dry. Next, the mixture was cooled in a desiccator containing silica gel for 10 minutes, the mass of this 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) / weight of weighed polyolefin resin foam (mg)} × 100
And the average value of 3 points | pieces remove | excluding the upper and lower limit from the value obtained by the measurement of 5 samples was made into the gel fraction.

(Apparent density measurement method)
Measured based on JIS K6767 (1999) “Foamed plastics-polyethylene test method”.
For example, a sample size (for example, 10 cm square) that is 15 cm ³ or more is punched, and the thickness and mass are measured. The volume was calculated from the area of the sample (100 cm ^{2 in} the case of a 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 )}
And the average value of 3 points | pieces remove | excluding the upper and lower limit from the value obtained by the measurement of 5 samples was made into the apparent density.

(Measurement method of loss factor tan δ)
Measured based on JIS K6394 “Vulcanized rubber and thermoplastic rubber—Determination of dynamic properties—General guidelines”.

  Specifically, the loss coefficient was calculated by the central vibration method using a viscoelasticity measuring device RSA-3 manufactured by TAINSTRUMENTS.

(Rebound characteristics)
The rebound characteristics were judged by a falling ball test. Several samples are placed on the steel plate so that the thickness is 25 mm or more, and an iron ball with a weight of 50 g and a diameter of 10 mm is dropped from a height of 30 cm and bounced back to the original height before dropping. The value expressed as a percentage divided by the height was used.
A: Rebound characteristics of less than 20%.
○: Rebound characteristics in the range of 20% or more and less than 40%.
Δ: Rebound characteristics in the range of 40% to less than 60%.
X: Rebound characteristics of 60% or more.

(Bottom feeling)
Judgment is made from the result of sensuously judging from the feeling when a sample is placed on a single steel plate and pressed with a finger. When the feeling of the steel plate is felt, specifically, when the finger is pushed with a certain stroke, the softness up to that point is lost and the hardness is judged to increase.

  (Double-circle): The feel of a steel plate is not felt.

  ○: Feeling of steel sheet, but at a level where there is no problem in use.

  X: The feel of a steel plate is felt and is bottomed out.

(Formability)
Judging from the molding drawing ratio. Note that the molding drawing ratio means that when a foam is heated on a vertical cylindrical female mold having a diameter D and a depth H and the surface temperature is 200 ° C., when straight molding is performed using a vacuum molding machine, It is the value of H / D at the limit at which the foam can be expanded and elongated without breaking. Here, the diameter D is 50 mm. The female mold used here is made of iron and has a surface roughness Ra of 5 μm or less.

  A: 0.60 or more.

  ○: The range of 0.45 or more and less than 0.60.

  X: Less than 0.45.

(Comprehensive evaluation)
The result judged comprehensively from the above results is shown.

  Rebound characteristics: 20 points for ◎, 10 points for ◯, 2 points for △, and -30 points for ×. For other characteristics, ◎ is assigned 5 points, ○ is 3 points, × is -1 point, and the total is calculated. It was used as an index for comprehensive evaluation based on the values obtained. ◎ The above was considered acceptable.

◎: 20 points or more ○: 5 points or more and less than 10 points △: 0 points or more and less than 5 points ×: Less than 0 points.

(Raw materials used in the examples)
<Propylene resin (A)>
-Sumitomo Chemical Tough Selenium (R) X1102
<Crystalline propylene resin (B)>
・ Novatec ^TM PP EG7F made by Nippon Polypro
・ NIPPON POLYPRO WINTEC ^TM WFW4M
-Nippon Polypro Co., Ltd. Novatec ^TM PP PL500A
-Polypropylene Sun Allomer (R) PC480A manufactured by Sun Allomer.

<Polyolefin resin (others)>
-Tosoh Corporation made two-polon (R) -L F35
・ Tosoh Petrocene (R) 231F
・ Novatec ^TM HD HF560 manufactured by Nippon Polyethylene.

<Thermoplastic resin>
・ DYNARON (R) 1321P made by JSR
・ DYNARON (R) 6200P made by JSR
-NATUREWORKS Ingeo ^TM 4032D.

<Foaming agent>
・ Uniform AZ made by Otsuka Chemical Co., Ltd.
<Crosslinking aid>
・ DVB810 made by Nippon Steel Chemical Co., Ltd.
<Heat stabilizer>
-Irganox 1010 manufactured by BASF Japan.

(Examples 1-10, Comparative Examples 1-14)
Propylene-based resin (A), crystalline propylene-based resin (B), polyolefin-based resin (others), thermoplastic resin, foaming agent, and cross-linking aid are the same as those listed in the table, and as heat stabilizers. 3 parts by mass of Irganox 1010 are mixed with a Henschel mixer, put into a 60φ extruder, melted and kneaded in a temperature-controlled state so that the temperature in the cylinder is 150 ° C., and then a predetermined foam thickness is obtained. Once the sheet is formed, the sheet is wound up.

  Further, this polyolefin resin foamed sheet was irradiated with ionizing radiation so as to have a predetermined gel fraction using an electron beam irradiation machine, and then foamed on a salt salt bath (salt bath temperature 230 ° C.). A foam having the characteristics described in 1) was obtained. Each physical property and evaluation result are also shown in the table.

Claims (3)

In the dynamic measurement test described in JIS K6394 “Vulcanized rubber and thermoplastic rubber—Determination of dynamic properties—General guidelines”, the stereoregularity has an atactic structure. When the total amount of the resin is 100% by mass, the propylene-based resin (A) is 50 to 100% by mass. A polyolefin resin cross-linked foam characterized by the following.   The polyolefin resin cross-linked foam according to claim 1, wherein the propylene resin (A) is amorphous. The polyolefin resin cross-linked foam according to claim 1 or 2, wherein the propylene resin (A) does not have a melting point peak between 130 and 170 ° C in differential scanning calorimetry.