JP6834142B2 - Flame-retardant polyolefin resin cross-linked foam - Google Patents

Description

The present invention relates to a flame-retardant polyolefin-based resin crosslinked foam having flame retardancy and excellent moldability.

In recent years, due to environmental problems, regulations on halogen-based flame retardants such as brominated flame retardants have become stricter in each country. However, many of the non-halogen flame retardants that have been studied so far are not expected to have a flame retardant effect, or even if they have a flame retardant effect, the amount added is large and the physical properties are significantly deteriorated ( See Patent Document 1).

On the other hand, polyolefin-based resin crosslinked foams are widely used in many building materials due to their excellent heat insulating properties and moldability. For example, it is used for heat insulation of water pipes or their joints, copper pipes used for heat exchange of air conditioners, heat insulation of their joints, and heat insulation of pipes from centralized water heaters such as heat pump water heaters. ing. Of these, in copper pipes used for heat exchange in air conditioners and the like, the refrigerant has been changed to flammable in order to improve heat exchange efficiency, and the demand for flame retardant building materials is increasing.

JP-A-2007-231216

In view of the background of the prior art, the present invention provides a flame-retardant polyolefin-based resin crosslinked foam having flame retardancy and excellent moldability.

The present invention employs the following means in order to solve such a problem. That is, the flame-retardant polyolefin resin crosslinked foam of the present invention is as follows.
(1) Contains a flame retardant, FMVSS No. A flame-retardant polyolefin resin crosslinked foam in which 302 (JIS D1201) is 100 mm / min or less and satisfies the following relationship.

Tensile strength (kPa) (temperature condition 23 ° C) / apparent density (kg / m ³ ) ≥ 10
(2) The flame-retardant polyolefin-based resin crosslinked foam according to (1), wherein the basic skeleton of the flame retardant used does not contain a halogen element.
(3) The flame-retardant polyolefin-based resin crosslinked foam according to (1) or (2), which contains 1 part by mass to 40 parts by mass of the flame retardant.
(4) The flame-retardant polyolefin-based resin crosslinked foam according to any one of (1) to (3), wherein the flame retardant is a condensed phosphonic acid ester.

According to the present invention, it is possible to provide a flame-retardant polyolefin-based resin crosslinked foam suitable for a heat insulating material for home appliances because it has flame retardancy and is excellent in moldability.

The present invention has been diligently studied on the above problems.
By having flame retardancy and excellent moldability, it is possible to provide a flame retardant polyolefin resin crosslinked foam suitable for a heat insulating material for home appliances.
The details of the invention will be described below.

The polyolefin-based resin used in the present invention is not particularly limited, but is, for example, a polyethylene-based resin represented by low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, or the like (definition of density here). Ultra-low density: ^{less than 0.910 g / cm 3} , low density: 0.910 g / cm ³ or more and 0.940 g / cm ³ or less, high density: 0.940 ^{g / cm greater than 3} and 0.965 g / cm Cm ³ or less), polyethylene-based copolymers, or polypropylene-based resins typified by homopolypropylene, ethylene-propylene random copolymers, polyethylene-propylene block copolymers, etc., and these. It may be any mixture of. Examples of the ethylene-based copolymer include ethylene and an α-olefin having four or more carbon atoms (for example, ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc. Examples thereof include ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, etc. obtained by polymerizing 1-heptene, 1-octene, etc.). The polyolefin-based resin is more preferably low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-α-olefin copolymer, or ethylene-vinyl acetate copolymer. More preferably, it is low density polyethylene, linear low density polyethylene, or ultra low density polyethylene. These polyolefin-based resins may be either one kind or a mixture of two or more kinds. Most preferably, it is a mixture of low density polyethylene and linear low density polyethylene.

The melt flow rate (MFR) of the polyethylene resin used for the flame-retardant polyolefin resin crosslinked 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). It is preferably in the range of 1.0 to 30 g / 10 min. When this MFR is less than 1.0 g / 10 min, the surface of the sheet becomes rough when it is formed into a sheet in the step of producing the flame-retardant polyolefin resin crosslinked foam, and the obtained foam becomes apparently May cause problems. If the MFR exceeds 30 g / 10 min, the heat resistance of the flame-retardant polyolefin resin crosslinked foam may be insufficient. The melt flow rate (MFR) of the polyethylene resin is more preferably 2.0 to 15 g / 10 min.

The melt flow rate (MFR) of the polypropylene resin used for the flame-retardant polyolefin resin crosslinked foam is not particularly limited, but is measured under normal conditions of a temperature of 230 ° C. and a load of 2.16 kgf in accordance with JIS K7210 (1999). It is preferably in the range of 0.5 to 15 g / 10 min. When this MFR is less than 0.5 g / 10 min, the surface of the sheet becomes rough when the sheet is formed in the step of producing the flame-retardant polyolefin resin crosslinked foam, and the obtained foam is visually May cause problems. If the MFR exceeds 15 g / 10 min, the heat resistance of the flame-retardant polyolefin resin crosslinked foam may be insufficient. The melt flow rate (MFR) of the polypropylene-based resin is more preferably 1.0 to 10 g / 10 min.

Further, a thermoplastic resin other than the polyolefin resin may be added to the foam as long as the characteristics of the flame-retardant polyolefin resin crosslinked foam of the present invention are not significantly impaired. The thermoplastic resins other than the polyolefin-based resin mentioned here are, in the case of halogen-free resins, polystyrene, acrylic resins such as polymethylmethacrylate and styrene-acrylic acid copolymers, and styrene-butadiene copolymers. , Ethylene-vinyl acetate copolymer, polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, petroleum resin, cellulose, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose and other cellulose derivatives, low Aromatic polyester resins such as molecular weight polyethylene, high molecular weight polyethylene, polypropylene such as polypropylene, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, and polyarite, polyamide resin, polyacetal resin, polycarbonate resin, polyester sulfone resin, polyphenylene sulfide resin, polyether. Examples thereof include a ketone resin, a vinyl polymerizable monomer, and a copolymer having a nitrogen-containing vinyl monomer. Further, elastomers such as isoprene rubber, styrene-butadiene rubber, butyl rubber, dimethyl silicone rubber, and ethylene propylene rubber are also included. Examples of the halogen-containing resin include polyvinyl chloride, polyvinylidene chloride, polyvinylidene trichloride, polyvinylidene chloride resin, fluorocarbon resin, perfluorocarbon resin, and solvent-soluble perfluorocarbon resin. The thermoplastic resin other than these polyolefin resins may be one kind or may contain a plurality of kinds. The type and amount are selected according to the desired physical properties.

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

The gel fraction of the flame-retardant polyolefin resin crosslinked foam of the present invention is not particularly limited, but 10 to 40% is preferably used. More preferably, it is 15 to 35%. If the gel fraction is less than 10%, the surface tends to be rough when foaming, and if it exceeds 40%, it may be difficult to process when foaming and the yield may be poor, which is not preferable.

The thermally decomposable foaming agent used in producing the flame-retardant polyolefin resin crosslinked foam of the present invention has a decomposition temperature higher than the melting temperature of the resin composition containing the polyolefin resin which is the raw material of the foam. It is not particularly limited as long as it has. Preferably, azodicarboxylic amide is mentioned, and further, hydrazosicarboxylic amide, azodicarboxylic acid barium salt, dinitrosopentaethylenetetramine, nitrosoguanidine, p, p'which have a decomposition temperature equal to or higher than that of azodicarboxylic amide. -Oxybisbenzenesulfonyl semicarbazide, trihydrazine symmetric triazine, bisbenzenesulfonylhydrazide, barium azodicarbaxylate, azobisisobutyronitrile, toluenesulfonylhydrazide and the like can be used. These pyrolyzable foaming agents may be used alone or in combination of two or more. The blending amount of the pyrolysis type foaming agent is 100 parts by mass of the total amount of the resin components (hereinafter, 100 parts by mass of the total amount of the resin components is the total amount of 100 parts of all resins such as polyolefin resin and other thermoplastic resins. It means parts by mass. In this case, the amount of resin in pellets obtained by master batching (pelletizing with resin) of additives and the like is also included in the resin component), which is generally about 2 to 40 parts by mass. It is set according to the desired foaming ratio.

The apparent density of the flame-retardant polyolefin resin crosslinked foam of the present invention is preferably 15 to 200 kg / m ^3. More preferably, it is 20 to 67 kg / m ³ . If it is less than 15 kg / m ³ , the surface of the foam is easily scratched, and if it is more than 200 kg / m ³ , it is difficult to follow the mold of the foam.

The apparent density can be controlled by the amount of the above-mentioned pyrolyzable foaming agent added. It is important to arbitrarily select the amount to be added depending on the type of pyrolytic foaming agent, the amount of gas, the polyolefin resin used, other thermoplastic resins, and the like.

When producing the flame-retardant polyolefin resin crosslinked foam of the present invention, a crosslinking aid is added to the resin composition containing the polyolefin resin which is the raw material of the foam as long as the characteristics of the foam are not impaired. It can contain a polyfunctional monomer as. Examples of the polyfunctional monomer include divinylbenzene, diallylbenzene, divinylnaphthalene, divinylbiphenyl, divinylcarbazole, divinylpyridine, nuclear-substituted compounds and related homologues thereof, ethylene glycol di (meth) acrylate, butylene glycol di (meth). Acrylic, 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 (Meta) acrylic acid compounds such as di (meth) acrylate, vinyl esters of aliphatic and aromatic divalent carboxylic acids such as divinyl phthalate, diallyl phthalate, diallyl malate, and bisacryloyloxyethyl terephthalate, allyl esters, and acryloyloxy. Divinyl ethers of aliphatic and aromatic dihydric alcohols such as alkyl esters, methacryloyloxyalkyl esters, diethylene glycol divinyl ethers, triethylene glycol divinyl ethers, tetraethylene glycol divinyl ethers, polyethylene glycol divinyl ethers, hydroquinone divinyl ethers, and bisphenol A diallyl ethers. It is possible to use monomers such as maleimide compounds such as allyl ether, N-phenylmaleimide, N, N'-m-phenylene bismaleimide, and compounds having two triple bonds such as dipropagil phthalate and dipropagil maleate. .. In addition, trimethylolpropane tri (meth) acrylate and 1,6-hexanediol di (meth) acrylate, trimethylol propanetri (meth) acrylate and 1,6-hexanediol di (meth) acrylate and 1,9-nonanediol Di (meth) acrylate, trimethylolpropan tri (meth) acrylate and divinylbenzene, trimethylol propane tri (meth) acrylate and triaryl cyanurate and 1,6-hexanediol di (meth) acrylate, triaryl cyanurate and 1 , 6-Hexanediol di (meth) acrylate, triallyl isocyanurate and 1,6-hexanediol di (meth) acrylate 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 above-mentioned cross-linking aid may be used alone or in combination of two or more. The blending amount of the cross-linking 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 a desired gel fraction. Will be done.

Further, a cross-linking aid and an organic peroxide can be combined for cross-linking. As the organic peroxide, for example, methyl ethyl ketone peroxide, t-butyl peroxide, dicumyl peroxide and the like are used. The blending amount of the organic peroxide is 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the total amount of the resin components, depending on the desired gel fraction. Set.

The flame retardant used in the present invention is not particularly specified, but includes bromine-based flame retardants such as pentabromodiphenyl ether, octabromodiphenyl ether, decabromodiphenyl ether, tetrabromobisphenol A, hexabromosiloctodecan, and hexabromobenzene, and triphenyl phosphate. In addition to phosphoric acid esters, phosphorus-based organic flame retardants such as condensed phosphoric acid ester, phosphonic acid ester, and condensed phosphonic acid ester, phosphorus-based inorganic flame retardants such as red phosphorus, and metal hydroxides such as aluminum hydroxide and magnesium hydroxide. Examples include flame retardants. Of these, one type or a mixture of two or more types may be used.
The flame retardant used in the present invention preferably does not contain a halogen element in its basic skeleton. This is also suitable for the regulations of each country due to recent environmental problems. Among these exemplified flame retardants, a phosphorus-based organic flame retardant is preferable, and a condensed phosphonic acid ester is most preferable.

The amount of the flame retardant added in the present invention is preferably 1 part by mass to 40 parts by mass with respect to 100 parts by mass of the flame-retardant polyolefin resin crosslinked foam. More preferably, it is 3 to 30 parts by mass. When 40 parts by mass or more is added, the flexibility as a foam is reduced.

In addition, as long as the characteristics of the present invention are not impaired, various additives such as a foaming agent decomposition accelerator, a bubble nucleating agent, an antioxidant, a heat stabilizer, a colorant, an antistatic agent, and an inorganic filler are used. The polyolefin-based resin composition which is a raw material of the flame-retardant polyolefin-based resin crosslinked foam of the present invention can be included.
In the present invention, a polyolefin-based resin composition obtained by blending the above components is molded into a predetermined shape, and then crosslinked and foamed to produce a flame-retardant polyolefin-based resin crosslinked foam.

Specifically, for example, the following manufacturing method can be mentioned. A predetermined amount of the polyolefin-based resin composition is uniformly melted at a temperature lower than the decomposition temperature of the pyrolysis foaming agent by using a kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, or a mixing roll. Knead and mold this into a sheet.

Next, the obtained sheet is irradiated with an ionizing radiation at a predetermined dose to crosslink the olefin resin, and the crosslinked sheet is heated to a temperature equal to or higher than the decomposition temperature of the pyrolytic foaming agent to foam. Instead of the cross-linking by ionizing radiation irradiation, cross-linking with peroxide or silane cross-linking 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 the desired gel fraction. The foamable sheet in which the resin is crosslinked is, for example, by hot air, infrared rays, a metal bath, an oil bath, a salt bath or the like, at a temperature equal to or higher than the decomposition temperature of the thermal decomposition type foaming agent and above the melting point of the resin, for example, 190 to 290 ° C. The resin is foamed by the decomposition gas of the foaming agent, thereby obtaining a flame-retardant polyolefin-based resin crosslinked foam.

The flame-retardant polyolefin resin crosslinked foam of the present invention needs to have flame retardancy. As this evaluation method, the F-MVSS specified in JIS D1201 (1998 version) is used for evaluation. The flame-retardant polyolefin resin crosslinked foam of the present invention needs to have a combustion rate of less than 100 mm / min, preferably 80 mm / min, and most preferably self-extinguishing.

Normally, when a flame retardant is added, the tensile strength decreases, but if the flame-retardant polyolefin resin crosslinked foam of the present invention has the same apparent density, the tensile strength is higher than that before the addition of the flame retardant. It is improving. The density and tensile strength referred to here are based on the method specified in JIS K6767 (1999 edition).

In the present invention, it is necessary that the relationship between the apparent density of the foam and the tensile strength satisfies the relationship of tensile strength (kPa) (temperature condition 23 ° C.) / apparent density (kg / m ^{3) ≥ 10.} Preferably, the tensile strength (kPa) (temperature condition 23 ° C.) / apparent density (kg / m ³ ) ≥ 12.

Further, the molding drawing ratio of the flame-retardant polyolefin resin crosslinked foam of the present invention is preferably 0.5 or more. The molding draw ratio referred to here is when the foam is heated on a vertical cylindrical female mold having a diameter D and a depth H and straight molding is performed using a vacuum forming machine when the surface temperature reaches 170 ° C. It is the value of H / D at the limit where the foam is developed and stretched in a cylindrical shape without being torn. 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. If it is less than 0.5, it may be torn during molding, which is not preferable. This is preferably 0.6 or more, more preferably 0.65 or more.

Further, a laminated body can be obtained by using the flame-retardant polyolefin-based resin crosslinked foam obtained by the methods described so far.

When the flame-retardant polyolefin resin crosslinked foam of the present invention is used to form a laminate, the layers to be laminated include a cloth-like material using natural or artificial fibers, a sheet made of a polyvinyl chloride resin, and a thermoplastic olefin. Sheets made of (TPO), thermoplastic elastomer sheets, skin materials such as leather, non-woven fabrics using thermoplastic resin fibers, polyolefin-based resin non-crosslinked foam sheets, for example, open cell foams using polyurethane, polyester films and poly Films typified by acrylic films, cardboard plastics, foamed paper, metal layers typified by copper, silver, nickel, etc. are selected from at least one type, and a plurality of them are laminated. Alternatively, it may be laminated on both the front surface and the back surface of the flame-retardant polyolefin resin crosslinked foam, or may be laminated on only one side.

The method of laminating the flame-retardant polyolefin resin crosslinked foam of the present invention and the above-mentioned layer to form a laminate is, for example, an extrusion laminating method in which a thermoplastic resin is melted on the foam, or an adhesive on the foam. Adhesive laminating method (also called fusion) in which flame-retardant polyolefin resin cross-linked foam is also heated and bonded together with the skin material, etc., hot melt method, high-frequency welder method, Examples of metals include a non-electrolytic plating method, an electrolytic plating method, a vapor deposition method, and the like, but they are not specified in these methods and may be adhered by any method.
The resin foam of the present invention is a cylindrical body capable of coating according to the shape of the pipe in order to efficiently keep heat, cool, and prevent dew condensation of a fluid object such as a gas or liquid flowing in the pipe. It is possible. The method of forming such a foam into a cylinder is not particularly limited, but for example, the foam produced by the above method is cut into a width corresponding to the diameter of the cylinder, and the foam is formed by a known heat source such as hot air or an infrared heater. A method of passing a conical base while heating, or cutting a resin foam to a width corresponding to the diameter of a cylinder and passing the conical base while heating the foam with a known heat source such as hot air or an infrared heater. After forming a cylinder, a polyolefin-based resin layer formed into an unstretched film cut to an appropriate width is bonded with a known liquid, gel-like, or solid adhesive such as solvent-based or water-based, or a known adhesive tape. The method of doing this is illustrated.
Types of pipes that cover the resin foam of the present invention include refrigerant pipes used for residential heating and cooling equipment, water pipes used for water supply and hot water supply, and connecting pipes for hot water storage type water heaters. Examples of the pipe material include vinyl chloride pipe, cross-linked polyethylene pipe, polyvinyl chloride pipe, vinyl chloride lining pipe, copper pipe, and stainless steel pipe. The resin foam has a remarkably low residual ammonia concentration and is effective in preventing the copper tube from corroding.
In addition, parts where the shape of the pipe is different from the cylindrical body, such as curved parts of the pipe, joint parts, flow rate control parts such as valves, etc., should be molded into a predetermined shape with the same shape as the part so that it can be covered. Is desirable. The method for forming such a foam into a molded body having a predetermined shape is not particularly limited, but for example, after heating the foam with a known heat source such as a circulating hot air oven or an infrared heater, a metal or wood having fine pores can be used. An example is a method in which the foam is placed on a predetermined mold, air is evacuated from the micropores, and the foam and the predetermined mold are brought into close contact with each other.

Physical characteristics were evaluated by the following methods.

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

(Resin density measurement method)
According to JIS K6922-1, 2 (1997) "Plastic-polyethylene (PE) molding and extrusion materials". Specifically, it is measured with an extruded melt indexer. The sample extruded with a standard melt indexer at 190 ° C. is cut into appropriate lengths so as not to contain air bubbles, and left on a cold metal plate. Then, it is placed in 200 mL of boiling water for 30 minutes to perform annealing treatment, and then the density is measured 24 hours later. Here, a melt indexer model F-B01 manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.

(Measurement method of melt flow rate)
According to JIS K7210 (1999) "Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastic-thermoplastic plastic". Based on Annex B (Reference) "Standards and Designations of Thermoplastic Plastic Materials and Their Test Conditions" of the above standards, polypropylene-based resin has a load of 230 ° C, load of 2.16 kgf (21.7 N), and polyethylene-based resin has a temperature of 190 ° C. The load was 2.16 kgf (21.7 N). Melt indexer model F-B01 manufactured by Toyo Seiki Seisakusho Co., Ltd. is used, a manual cutting method is adopted, and it is defined by the mass of the resin that comes out from the die in 10 minutes.

(Measurement method of gel fraction)
The flame-retardant polyolefin resin cross-linked foam is first cut into strips in the longitudinal direction at 0.5 mm intervals with a single blade, and then cut at 0.5 mm intervals in the width direction using scissors, and weighed precisely about 50 mg. After immersing in 200 ml of tetralin at 130 ° C. for 3 hours, naturally filter with a 200 mesh stainless steel wire mesh, wash with acetone and apply dry air for 15 seconds, and then remove the insoluble matter on the wire mesh at 120 ° C. for 1 hour. Dry in a hot air oven. Then, it was cooled in a desiccator containing silica gel for 10 minutes, the mass of this insoluble matter was precisely 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)} x 100
Then, the average value of 3 points obtained by removing the upper and lower limit values from the values obtained by the measurement of 5 samples was taken as the gel fraction.

(Measurement method of apparent density)
It was measured based on JIS K6767 (1999) "Foam Plastic-Polyethylene-Test Method".
For example, the sample size (for example, 10 cm square) is punched to be ^{15 cm 3 or more, and the thickness and mass are measured.} The volume was calculated from the area of the sample (100 cm ^{2 in} the 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) x sample area (m ² )}
Then, the average value of 3 points obtained by removing the upper and lower limit values from the values obtained by the measurement of 5 samples was taken as the apparent density.

(Flame retardancy evaluation method for foam)
FMVSS No. specified in JIS D1201 (1998). It was evaluated by the numerical value of the horizontal combustion speed measured according to 302. If the flame does not propagate to the marked line, it is assumed to have self-extinguishing properties.

(Method for measuring tensile strength and tensile elongation of foam)
Tensile strength and tensile elongation were measured under the temperature conditions shown in Table 1 in accordance with JIS K6767 (1999).

(Compressive permanent strain)
The compression set was measured according to JIS K6767 (1999).

(Heating surface test)
The surface of the sheet of the obtained crosslinked polyolefin resin foam was heated to 170 ° C., cooled to room temperature, and then the surface condition was visually observed.
⊚: The surface was smooth and glossy.
◯: Although slightly inferior to ◎, the surface condition was good. ×: Roughness was observed on the surface.

(Moldability (flattening))
The resin foam was cut to a width of 110 mm, and a cylindrical body having an inner diameter of 18 mm was obtained through a conical base while heating the resin foam with hot air at 300 ° C.

The value obtained by the minor axis / major axis × 100 of the cylinder is defined as the flatness, and the case of less than 85% is defined as (×), the case of 85 to 90% is defined as (Δ), and the value of greater than 90% is defined as (○). ..

(Workability of molded products, repeatability)
When applying a heat insulating material molded into a cylindrical body to a copper tube with a nominal diameter of 15 A (outer diameter 15.88 mm) and a wall thickness of 1.02 mm, if the heat insulating material cannot be passed through at all and cannot be used (x), If there is a slight resistance but it can be used by pushing it in (△), if there is no resistance at all, it is (○). In addition, it was attached and detached 5 times, and the level at which blurring, chipping, etc. occurred was marked with (x), and the level without change was marked with (○).

(Molding draw ratio)
What is the molding draw ratio? When the foam is heated on a vertical cylindrical female mold with a diameter D and a depth H and straight-molded using a vacuum forming machine when the surface temperature reaches 170 ° C, the foam is formed. It is the value of H / D at the limit of expansion and extension in a cylindrical shape 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.

(Reference example 1)
Low density polyethylene: Japan Polyethylene Novatec LD LE520H, MFR = 4g / 10 minutes, density = 923kg / m ³
(Reference example 2)
Foaming agent: Azodicarbonamide: Eiwa Kasei Kogyo Vinihole AC # LQ
(Reference example 3)
Flame Retardant A: Aromatic Phosphonate Ester: Made by Maruhishi Yuka Kogyo, Product Name: Nonnen 73
Flame Retardant B: Ethylene Bispentabromodiphenyl: Made by Albemarle, Product Name: SAYTEX 8010) 2.5 parts by mass (Reference Example 4)
Flame retardant aid C: Antimony trioxide: Nihon Seiko PATOX-K
( Comparative Example 6 )
Low density polyethylene as an olefin resin (Novatec LD LE520H made by Nippon Polyethylene, MFR = 4 g / 10 minutes, density = 923 kg / m ³ ): 100 parts by mass, flame retardant A: aromatic phosphonic acid ester (manufactured by Maruhishi Yuka Kogyo) , Product name: Nonnen 73) 5 parts by mass and azodicarboxylic amide (Vinihole AC # LQ manufactured by Eiwa Kasei Kogyo Co., Ltd.): 10 parts by mass, antioxidant (IRGANOX 1010 manufactured by BASF): 0.5 parts by mass The mixture was mixed with a mixer and melt-extruded at 150 ° C. using a single-screw extruder to prepare a polyethylene-based resin sheet having a thickness of 1.5 mm using a T-die. This sheet was irradiated with an electron beam having an acceleration voltage of 800 kV and 15 kGy from both sides to obtain a crosslinked sheet, which was then floated on a salt bath at 220 ° C. and heated from above with an infrared heater to foam. The foam was cooled with water at 50 ° C., the surface of the foam was washed with water and dried to obtain a long roll of foam ^{having a thickness of 3.0 mm and an apparent density of 33 kg / m 3.} The evaluation results of this foam are shown in Table 1.
Further, the resin foam obtained above was cut into a width corresponding to the diameter (18 mm) of the cylinder, and the resin foam was heated with hot air at 300 ° C. and passed through a conical mouthpiece to obtain a cylindrical heat insulating material. ..

(Examples 2 to 3)
In Examples 2 and 3, low-density polyolefin resins, foaming agents, and flame retardants were added in the mass parts shown in Table 1, and foams were prepared in the same manner as in Comparative Example 6 for the others. The evaluation results of these foams are shown in Table 1.

(Example 4)
For the low-density polyolefin resin, foaming agent, and flame retardant, add the mass parts shown in Table 1, prepare a sheet with a thickness of 1.7 mm using a T-die, and use the same method as in Comparative Example 6 for other foams. It was created. The evaluation results of these foams are shown in Table 1.
Further, the resin foam obtained above was cut into a width corresponding to the diameter (18 mm) of the cylinder, and the resin foam was heated with hot air at 300 ° C. and passed through a conical mouthpiece to obtain a cylindrical heat insulating material. ..

(Comparative Example 1)
Low-density polyethylene as an olefin resin (Novatec LD LE520H made by Nippon Polyethylene, MFR = 4 g / 10 minutes, density = 923 kg / m ³ ): 100 parts by mass and azodicarbonamide as a foaming agent (Vinihole AC # LQ manufactured by Eiwa Kasei Kogyo) : 10 parts by mass, antioxidant (IRGANOX 1010 manufactured by BASF): 0.5 parts by mass is mixed with a Henshell mixer, melt-extruded at 150 ° C. using a single-screw extruder, and thickness: using a T-die. A 1.5 mm polyethylene resin sheet was prepared. This sheet was irradiated with an electron beam having an acceleration voltage of 800 kV and 15 kGy from both sides to obtain a crosslinked sheet, which was then floated on a salt bath at 220 ° C. and heated from above with an infrared heater to foam. The foam was cooled with water at 50 ° C., the surface of the foam was washed with water and dried to obtain a long roll of foam having a thickness of 3.0 mm and an apparent density of 32 kg / m3. The evaluation of this foam is shown in Table 1.
Further, the resin foam obtained above was cut into a width corresponding to the diameter (18 mm) of the cylinder, and the resin foam was heated with hot air at 300 ° C. and passed through a conical mouthpiece to obtain a cylindrical heat insulating material. ..

(Comparative Example 2)
Low density polyethylene as an olefin resin (Novatec LD LE520H made by Nippon Polyethylene, MFR = 4 g / 10 minutes, density = 923 kg / m ³ ): 100 parts by mass, flame retardant B: ethylene bispentabromodiphenyl (manufactured by Albemar, product name: SAYTEX 8010) 2.5 parts by mass, flame retardant: Antimon trioxide (PATOX-K manufactured by Nippon Seiko Co., Ltd.) 1.0 parts by mass, and azodicarboxylic amide as a foaming agent (Vinihole AC # LQ manufactured by Eiwa Kasei Kogyo): 10 parts by mass, antioxidant (IRGANOX 1010 manufactured by BASF): 0.5 parts by mass was mixed with a Henshell mixer, melt-extruded at 150 ° C. using a single shaft extruder, and thickness: 1 using a T-die. A polyethylene resin sheet of .5 mm was prepared. This sheet was irradiated with an electron beam having an acceleration voltage of 800 kV and 15 kGy from both sides to obtain a crosslinked sheet, which was then floated on a salt bath at 220 ° C. and heated from above with an infrared heater to foam. The foam was cooled with water at 50 ° C., the surface of the foam was washed with water and dried to obtain a long roll of foam ^{having a thickness of 3.0 mm and an apparent density of 33 kg / m 3.} The evaluation of this foam is shown in Table 1.
Further, the resin foam obtained above was cut into a width corresponding to the diameter (18 mm) of the cylinder, and the resin foam was heated with hot air at 300 ° C. and passed through a conical mouthpiece to obtain a cylindrical heat insulating material. ..

(Comparative Examples 3 and 4)
In Comparative Examples 3 and 4, the conditions such as the polyolefin resin, the foaming agent, the antioxidant, and the ionizing radiation were the same as those in Comparative Example 2, except that the flame retardant and the flame retardant aid were added in parts by mass as shown in Table 1. , A foam was prepared in the same manner as in Comparative Example 6. As a result, it is shown in Table 1.
Further, the resin foam obtained above was cut into a width corresponding to the diameter (18 mm) of the cylinder, and the resin foam was heated with hot air at 300 ° C. and passed through a conical mouthpiece to obtain a cylindrical heat insulating material. ..

Claims (3)

Contains a flame retardant, FMVSS No. 302 (JIS D1201) is 100 mm / min or less, the flame retardant is contained in an amount of 14 to 30 parts by mass with respect to 100 parts by mass of the polyolefin resin crosslinked foam, and the flame retardant is a condensed phosphonic acid ester. A flame-retardant polyolefin resin crosslinked foam that satisfies the following relationship.
Tensile strength (kPa) (temperature condition 23 ° C) / apparent density (kg / m ³ ) ≧ 12 The flame-retardant polyolefin-based resin crosslinked foam according to claim 1, which has an apparent density of 20 to 67 kg / m ^3. The flame-retardant polyolefin resin crosslinked foam according to claim 1, which has an apparent density of 26 to 38 kg / m ^3.