JP2017155173A - Polyolefin resin crosslinked foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin crosslinked foam having stable physical properties by using a novel foaming agent that generates gas components in a sufficient volume for foaming, has its decomposition temperature suitable for processing temperature, and smoothly foams.SOLUTION: A polyolefin resin crosslinked foam has a combination of p-toluene sulfonyl semicarbazide and a foaming aid.SELECTED DRAWING: None

Description

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

  Polyolefin resin crosslinked foams are used in many applications because of their stability, heat insulation and buffering properties. For example, it is used as a dew condensation prevention material such as a tape base material, packing, roof, etc., a pipe heat insulating material, an automobile interior base material, etc.

  However, in the foam manufacturing process, there is a movement to regulate azodicarbonamide, which is frequently used in pyrolytic foaming agents, in the EU due to concerns such as health damage. On the other hand, the foaming agent (i) is excellent in gas amount and gas component, and (ii) its decomposition temperature is more suitable for processing temperatures of plastics and rubber than other foaming agents, and has been widely used in this field. Other features include that the blowing agent is large (iii) has a high decomposition rate and (iv) reacts in a chain with an exothermic reaction.

  Although it has been widely used particularly in polyolefin resin cross-linked foams due to the above four characteristics, there is a concern that use may be restricted or restricted due to the movement of the EU.

  Patent Document 1 proposes p 1, p′-oxybisbenzenesulfonyl hydrazide. However, p, p'-oxybisbenzenesulfonyl hydrazide has a low decomposition temperature and is suitably used for rubber foams as disclosed in Patent Document 1, but is not suitable for polyolefin resin crosslinked foams.

  In Patent Document 2, dinitropentadienetetramine is exemplified as one of foaming agents. However, dinitropentadienetetramine is known to be flammable and requires care in handling.

JP 2007-316228 A JP 2009-74014 A

  In view of the background of such prior art, the present invention generates a sufficient amount of gas and gas components necessary for foaming, has a decomposition temperature suitable for processing temperature, and uses a new foaming agent that smoothly foams to stabilize the physical properties. It is intended to provide a crosslinked polyolefin-based resin foam.

  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) A polyolefin-based resin-crosslinked foam characterized by using p-toluenesulfonyl semicarbazide and a foaming aid in combination.

  (2) The polyolefin resin cross-linked foam according to (1), wherein the foaming aid is a compound having a decomposition exothermic peak between 150 ° C. and 200 ° C.

  (3) The polyolefin resin cross-linked foam according to (1) and (2), wherein the foaming aid is urea.

  (4) The polyolefin resin cross-linked foam according to any one of (1) to (3), wherein a decomposition accelerator is used in combination.

  (5) The polyolefin resin crosslinked foam according to any one of (1) to (4), wherein the decomposition accelerator is a metal hydroxide or a metal oxide.

  (6) The polyolefin-based resin crosslinked foam according to any one of (1) to (5) above, wherein p-toluenesulfonyl semicarbazide and a foaming aid are mixed in a ratio of 95: 5 to 70:30. .

  According to the present invention, a polyolefin resin cross-linked foam having stable physical properties by generating a sufficient amount of gas and gas components necessary for foaming, using a new foaming agent that has a decomposition temperature suitable for the processing temperature, and foams smoothly. The body can be provided.

  The present invention has been intensively studied on the above problems, generates a sufficient amount of gas and gas components necessary for foaming, has a stable physical property by using a new foaming agent that has a decomposition temperature suitable for processing temperature and foams smoothly. A polyolefin resin cross-linked foam is to be provided. Details of the invention will be described below.

The polyolefin resin used in the present invention is not particularly limited. For example, a polyethylene resin typified by low density polyethylene, high density polyethylene, linear low density polyethylene, ultra low density polyethylene, etc. as follows ultralow 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, density: greater than 0.940 g / cm ³ 0.965 g / cm ³ or less), copolymers based on ethylene, or polypropylene resins typified 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. As the polyolefin resin, polyethylene resins such as low density polyethylene, linear low density polyethylene, and ultra low density polyethylene, ethylene-α-olefin copolymers, and ethylene-vinyl acetate copolymers are more preferable. 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.

  The polyolefin resin used in the present invention may be polymerized with a publicly known catalyst. For example, Ziegler catalyst represented by titanium tetrachloride / organoaluminum catalyst, Natta catalyst of titanium trichloride / organoaluminum catalyst, titanium chloride-supported titanium catalyst, Kaminsky catalyst also called metallocene catalyst, phenoxyimine complex catalyst, phenoxyimine Complex / Zn catalyst, Ti / chelate type diamide complex, etc. are mentioned.

  The melt flow rate (MFR) of the polypropylene resin used for the polyolefin resin cross-linked foam is not particularly limited, but is measured in accordance with JIS K7210 (1999) under normal conditions of a temperature of 230 ° C. and a load of 2.16 kgf. And what is in the range of 0.5-15 g / 10min is preferable. 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. It is. In the present invention, it is necessary to use p-toluenesulfonyl semicarbazide and a foaming aid in combination. Although the decomposition temperature of p-toluenesulfonyl semicarbazide is higher than that of azodicarbonamide and the like, it is often not suitable for the processing temperature of the resin, but this is solved by using it together with a foaming aid.
Moreover, you may use another thermal decomposition type foaming agent in the range which does not inhibit the characteristic of the polyolefin resin crosslinked foam of this invention remarkably. In that case, although not particularly limited, preferably azodicarbonamide, hydrazosicarbonamide, 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.
Although it does not specifically limit about the foaming adjuvant used by this invention, It is preferable that it is a substance decomposed | disassembled by heating. For example, urea, sodium chlorite, sodium nitrite, ammonium chloride, ammonium nitrate, sodium nitrate, sodium chlorate, sodium persulfate, hydrosulfite, potassium chlorate, potassium persulfate, potassium nitrite, chromic anhydride, dichromium Sodium oxide, chromium nitride, metastannic acid, ammonium thiocyanate, copper sulfate, copper carbonate, lead cyanamide, lead (IV) oxide, nickel sulfate, hydrazine, sodium silicofluoride, potassium silicofluoride, sodium borofluoride, potassium borofluoride, borofluoride Ammonium fluoride, tungsten hexafluoride, lithium hexafluorophosphate, boric acid, sodium borohydride, magnesium nitrate, magnesium hydroxide, magnesium carbonate, manganese (II) sulfate, potassium permanganate, yellow phosphorus, phosphoric acid, zinc Phosphoric acid, hypophosphorous acid, acidic Sodium pyrophosphate, sodium hydroxide, sodium bromate, 2,2'-azobis- (2-aminodipropane) dihydrochloride, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propion Amido], 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), ethylenediaminetetraacetic acid, ethylene cyanohydrin, guanylthiourea, guanyl urea phosphate, guanyl urea sulfate, sodium gluconate, 2 -Chloroethylamine hydrochloride, copper (II) acetate, lead (II) acetate, manganese (II) acetate, thiosemicarbazide, neopentyl glycol, magnesium alcoholate, malonic acid, di-α-cumyl peroxide, 2,5-diamino Toluene sulfate, sodium styrenesulfonate, tetramethylammonium iodide, 1,1,1 ', 1'-tetramethyl-4,4'-(methylenedi-p-phenylene) disemicarbazide, 2,6- Phthalenedicarboxylic acid, 1,4-dihydroxy-2-naphthoic acid, phenylhydrazine, protocatechuic acid, maleic hydrazide, acetaldehyde ammonia, isocyanuric acid, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino- 6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct, 2-amino-4,5-dicyanoimidazole, N, N′-dinitrosopentamethylenetetramine, 2, 5-dimercapto-1,3,4-thiadiazole, spiroglycol, 5,5'-bi-1H-tetrazole, 5-phenyl-1H-tetrazole, picolinic acid, 1-hydroxybenzotriazole monohydrate, pyrazine monocarboxylic Acid, 2,3-pyridinedicarboxylic acid, 5-fluorouracil, tetramethylammonium bromide, lithium trifluoromethanesulfonate, dibutyltin oxide, Such as butyltin oxide is raised, the compound may be mixed alone or in combination.
The foaming aid used in the present invention is preferably a compound having a decomposition exothermic peak between 150 ° C. and 200 ° C. If this decomposition exothermic peak is 150 ° C. or lower, decomposition occurs during heating in the mixing stage of the resin, the foaming agent and the foaming aid using an extruder or the like, which is not preferable. On the other hand, when it exceeds 200 ° C., the heating conditions become severe during foaming, and it is difficult to obtain stable physical properties that are the characteristics of the present invention.
Further, the foaming aid used in the present invention is required to have safety which is one of the purposes of the present application.
In view of the above, the foaming aid is preferably urea, 1-hydroxybenzotriazole monohydrate, 1,4-dihydroxy-2-naphthoic acid and protocatechuic acid, and more preferably urea.
In the present invention, p-toluenesulfonyl semicarbazide and the foaming aid are preferably mixed in a ratio of 95: 5 to 70:30. When it is further away than the ratio of 95: 5, the effect of the foaming auxiliary agent is not exhibited, and the decomposition temperature is not sufficiently lowered. When the ratio is closer than 70:30, the decomposition temperature is excessively lowered, and decomposition occurs during heating in the mixing stage of the resin, the foaming agent, and the foaming aid, which is not preferable. More preferably, it is 90: 10-75: 25.
The polyolefin resin cross-linked foam of the present invention may be used in combination with a decomposition accelerator. The decomposition accelerator as used in the present invention means a catalyst that promotes the decomposition of the thermal decomposition type foaming agent and can start foaming at a low temperature.
Although it does not specifically limit as a decomposition accelerator, A well-known and publicly used metal hydroxide, a metal oxide, etc. are used. For example, zinc hydroxide, zinc oxide, antimony trioxide and the like are known.

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.
As long as the characteristics of the present invention are not impaired, various additives such as a cell nucleus modifier, an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, and an inorganic filler are added to the polyolefin resin cross-linking of the present invention. The polyolefin resin composition that is the raw material of the foam can be included.

The polyolefin resin cross-linked foam of the present invention preferably has a closed cell structure. The closed cell structure as used herein 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%.
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.

  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 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 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.

(Elongation measurement)
Measured based on JIS K6767 (1999) “Foamed plastics-polyethylene test method”.

(Appearance evaluation)
The surface condition of the foam is evaluated in three stages by sensory evaluation.

  A: Appearance is beautiful and no problem.

  ○: There is no problem in use.

  X: Conspicuous unevenness etc.

(Molding evaluation)
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. (Process evaluation)
Productivity in the process, especially ease of foaming, ease of handling, odor, safety, etc. are comprehensively judged and evaluated in three stages.

  A: There is no particular problem.

  ○: Some problems.

  X: There is a problem.

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

  ◎ is 5 points, ○ is 3 points, × is 0 points. The sum of these values was used as an index for comprehensive evaluation. △ or more was accepted.

◎: 15 points ○: 10 points or more and less than 15 points Δ: 5 points or more and less than 10 points ×: Less than 5 points.

(Raw materials and abbreviations used in Examples)
<Resin 1, 2>
(Propylene resin: Polypropylene)
PP1: Prime Polypro (R) J105G manufactured by Prime Polymer Co., Ltd.
PP2: Novatec (R) BC8 manufactured by Nippon Polypro Co., Ltd.
(Ethylene resin: PolyEthylene)
PE1: Nispolon Hard (R) 4010 manufactured by Tosoh Corporation
PE2: Novatec (R) UF640MA manufactured by Nippon Polyethylene
PE3: Umerit (R) 3540N made by Ube Maruzen Polyethylene
<Blowing assistant: Blowing Assistant>
BA1: Urea BA2: 1-hydroxybenzotriazole monohydrate BA3: Diphosphorous acid BA4: Ammonium nitrate <Decomposition accelerator: Decomposition Agent>
DA1: Zinc oxide DA2: Zinc hydroxide <Foaming agent>
p-TSSC: p-Toluenesulfonyl semicarbazide ADCA: Uniform AZ manufactured by Otsuka Chemical Co., Ltd.
<Crosslinking aid>
DVB: Nippon Steel Chemical Co., Ltd. DVB810
<Heat stabilizer: AntiOxidant>
AO1: BASF Japan Co., Ltd. Irganox (R) 1010
Example 1
A composition comprising 80% by mass of Prime Polypro (R) J105G (hereinafter referred to as PP1) manufactured by Prime Polymer as Resin 1 and 20% by mass of Umerit (R) 3540N (hereinafter referred to as PE3) manufactured by Ube Maruzen Polyethylene as Resin 2 When it is 100 parts by mass, 9.5 parts by mass of p-toluenesulfonyl semicarbazide (hereinafter referred to as p-TSSC) as a foaming agent, 0.5 parts by mass of urea (hereinafter referred to as BA1) as a foaming aid, and other raw materials 3 parts by mass of Nippon Steel Chemical's DVB810 (hereinafter referred to as DVB), which is a crosslinking aid, and 1.0 part by mass of BASF Japan's Irganox (R) 1010 (hereinafter referred to as AO1) as a heat stabilizer in a Henschel mixer. Mix and feed into a 60φ extruder, melt and knead with the temperature adjusted so that the temperature in the cylinder is 180 ° C. I wound up having been subjected to the molding once.

  Further, this polyolefin resin foamed sheet was irradiated with ionizing radiation at an irradiation dose of 60 kGy using an electron beam irradiator, and then foamed on a salt bath (salt bath temperature 200 ° C.) to have the characteristics described in the table. Got the body. Each physical property and evaluation result are also shown in the table.

(Examples 2 to 10)
Resin 1, Resin 2, Foaming agent, Foaming aid, Decomposition accelerator, Crosslinking aid, Thermal stabilizer, Sheet thickness, Irradiation dose, Foaming method, Foaming temperature, etc. As a result, a foam having the characteristics described in the table was obtained. Each physical property and evaluation result are also shown in the table.

(Comparative Example 1)
When 100 mass% of Novatec® UF640MA (hereinafter referred to as PE2) manufactured by Nippon Polyethylene Co., Ltd. is used as resin 1 as 100 mass parts, 10 parts by mass of p-TSSC as a foaming agent is used, and 1 heat stabilizer AO1 is used as other raw materials. 0.0 parts by weight are mixed with a Henschel mixer, put into a 60φ extruder, melted and kneaded with the temperature adjusted so that the temperature in the cylinder is 180 ° C, and then molded into a sheet of 1.0 mm Roll up the cake once.

Furthermore, this polyolefin resin foamed sheet was irradiated with ionizing radiation at an irradiation dose of 50 kGy using an electron beam irradiator, and then an attempt was made to foam on a salt bath (salt bath temperature 200 ° C.), but foaming did not occur. When the salt bath temperature was heated to 250 ° C., a foam having the characteristics described in the table was obtained. Each physical property and evaluation result are also shown in the table.
(Comparative Example 2)
When the composition obtained by mixing 80% by mass of Novatec® BC8 (hereinafter referred to as PP2) manufactured by Nippon Polypro Co., Ltd. as Resin 1 and 20% by mass of PE3 as Resin 2 is defined as 100 parts by mass of BA1 as a foaming aid. 5 parts by mass, 3 parts by mass of DVB as a crosslinking aid as a raw material, and 1.0 part by mass of AO1 as a heat stabilizer are mixed in a Henschel mixer and put into a 60φ extruder, and the temperature in the cylinder becomes 180 ° C. In such a temperature-controlled state, after being melted and kneaded, a sheet that has been formed to 1.0 mm is wound up.

Furthermore, this polyolefin resin foamed sheet was irradiated with ionizing radiation at an exposure dose of 60 kGy using an electron beam irradiator, and then an attempt was made to foam on a salt bath (salt bath temperature 200 ° C.), but foaming did not occur. The salt bath temperature was heated to 250 ° C., but no foaming was observed, so the evaluation was completed.
(Comparative Example 3)
When 100% by mass of PE2 as resin 1 is 100 parts by mass, 10 parts by mass of p-TSSC as a foaming agent and 1.0 part by mass of zinc hydroxide (hereinafter referred to as DA2) as a decomposition accelerator as other raw materials Then, 1.0 part by mass of heat stabilizer AO1 is mixed in a Henschel mixer, charged into a 60φ extruder, melted and kneaded in a temperature-controlled state so that the temperature in the cylinder becomes 180 ° C., and then adjusted to 1.0 mm. Once the sheet is formed, the sheet is wound up.
Furthermore, this polyolefin resin foam sheet was irradiated with ionizing radiation at an irradiation dose of 40 kGy using an electron beam irradiator, and then an attempt was made to foam it on a salt bath (salt bath temperature 200 ° C.), but it did not foam. When the salt bath temperature was heated to 240 ° C., a foam having the characteristics described in the table was obtained. Each physical property and evaluation result are also shown in the table. (Comparative Example 4)
100 parts by mass of 80% by mass of PP2 as resin 1 and 20% by mass of PE3 as resin 2 is 10 parts by mass of uniform AZ (hereinafter referred to as ADCA) made by Otsuka Chemical Co., which is a foaming agent. 3 parts by mass of DVB as a crosslinking aid and 1.0 part by mass of AO1 as a heat stabilizer as raw materials were mixed with a Henschel mixer and charged into a 60φ extruder, and the temperature inside the cylinder was adjusted to 180 ° C. In this state, after being melted and kneaded, the sheet formed so as to be 1.0 mm is temporarily wound up.
Further, this polyolefin resin foamed sheet was irradiated with ionizing radiation at an irradiation dose of 60 kGy using an electron beam irradiator, and then foamed on a salt bath (salt bath temperature 200 ° C.) to have the characteristics described in the table. Got the body. All of the external appearance evaluation, molding evaluation, and process evaluation were good evaluations. However, since they were different from the purpose of the present application, the overall evaluation was x.
(Comparative Example 5)
When 100 parts by mass of a composition in which 80% by mass of PP1 as resin 1 and 20% by mass of PE2 as resin 2 is mixed is 100 parts by mass, no foaming agent or foaming assistant is added, and the decomposition accelerator DA2 is 1.0 as other raw materials. Part by weight, 3 parts by weight of crosslinking aid DVB and 1.0 part by weight of heat stabilizer AO1 are mixed in a Henschel mixer and charged into a 60φ extruder, and the temperature inside the cylinder is adjusted to 180 ° C. In this state, after being melted and kneaded, the sheet molded so as to be 1.0 mm is once wound up.

  Furthermore, this polyolefin resin foamed sheet was irradiated with ionizing radiation at an exposure dose of 60 kGy using an electron beam irradiator, and then an attempt was made to foam on a salt bath (salt bath temperature 200 ° C.), but foaming did not occur. The salt bath temperature was heated to 250 ° C., but no foaming was observed, so the evaluation was completed.

Claims (6)

A polyolefin-based resin cross-linked foam comprising a combination of p-toluenesulfonyl semicarbazide and a foaming aid.   The polyolefin resin cross-linked foam according to claim 1, wherein the foaming auxiliary agent is a compound having a decomposition exothermic peak between 150 ° C and 200 ° C.   The polyolefin resin cross-linked foam according to claim 1 or 2, wherein the foaming assistant is urea. The polyolefin resin cross-linked foam according to any one of claims 1 to 3, wherein a decomposition accelerator is used in combination.   The polyolefin-based resin crosslinked foam according to any one of claims 1 to 4, wherein the decomposition accelerator is a metal hydroxide or a metal oxide. 6. The polyolefin-based resin crosslinked foam according to claim 1, wherein p-toluenesulfonyl semicarbazide and a foaming aid are mixed in a ratio of 95: 5 to 70:30.