JP7193285B2 - Crosslinked polyolefin resin foam and molding - Google Patents

Description

The present invention relates to crosslinked polyolefin resin foams and molded articles.

BACKGROUND ART Crosslinked polyolefin resin foams have excellent heat resistance and heat insulating properties, and thus have been used in a wide range of fields as heat insulating materials, cushioning materials, and the like. In particular, in automobile applications, it is used as a heat insulating material and interior material for ceilings, doors, instrument panels, cooler covers and the like.
Crosslinked polyolefin resin foams are often produced by a method of heating and foaming a composition containing a polyolefin resin and a foaming agent. be. For example, in an automobile in which a molded article of crosslinked polyolefin resin foam is incorporated as an automobile interior material, an odor is generated, and the user often feels uncomfortable.
As techniques for reducing the odor of crosslinked polyolefin resin foams, for example, a method using a deodorant such as activated carbon (Patent Document 1), a method using carbon black or the like as an odor suppressant (Patent Document 2), and the like are known. there is

JP-A-11-60774 JP-A-11-263863

However, for example, in automobiles equipped with automotive interior materials made of crosslinked polyolefin resin foam moldings, especially in hot summer months, there is a problem that odors cannot be sufficiently reduced even by using conventional techniques. There is
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a crosslinked polyolefin resin foam that can reduce the generation of odor, and a molded article obtained by molding the crosslinked polyolefin resin foam.

（式中、Ｒは、水素原子、基－ＮＨ－ＮＨ_２、又はモノ、ジ、トリもしくはテトラカルボン酸からカルボキシル基を除いた残基を表し、ｎは１～４の整数を表す。）
［２］独立気泡率が７０％以上である、上記［１］に記載の架橋ポリオレフィン樹脂発泡体。
［３］見掛け密度が２０～１００ｋｇ／ｍ^３である、上記［１］又は［２］に記載の架橋ポリオレフィン樹脂発泡体。
［４］厚さが０．０５～１５ｍｍである、上記［１］～［３］のいずれか１つに記載の架橋ポリオレフィン樹脂発泡体。
［５］架橋度が１５～６５質量％である、上記［１］～［４］のいずれか１つに記載の架橋ポリオレフィン樹脂発泡体。
［６］上記［１］～［５］のいずれか１つに記載の架橋ポリオレフィン樹脂発泡体を成形してなる成形体。
［７］架橋ポリオレフィン樹脂発泡体に表皮材が積層された、上記［６］に記載の成形体。
［８］自動車内装材である、上記［６］又は［７］に記載の成形体。 The inventors of the present invention have made intensive studies to achieve the above object, and found that the odor of the foam can be eliminated by incorporating a deodorant containing porous particles and a predetermined hydrazide into the foamable composition. The inventors have found that the occurrence can be reduced, and completed the present invention.
That is, the present invention relates to the following [1] to [7].
[1] A crosslinked polyolefin resin foam obtained by foaming a foamable composition containing a polyolefin resin and a deodorant, wherein the foamable composition contains the deodorant with respect to 100 parts by mass of the polyolefin resin. A crosslinked polyolefin resin foam containing 0.2 to 6.5 parts by mass, wherein the deodorant contains porous particles and hydrazides represented by the following general formula (1).

(Wherein, R represents a hydrogen atom, a group —NH—NH ₂ , or a residue obtained by removing a carboxyl group from a mono-, di-, tri- or tetracarboxylic acid, and n represents an integer of 1 to 4.)
[2] The crosslinked polyolefin resin foam according to [1] above, which has a closed cell content of 70% or more.
[3] The crosslinked polyolefin resin foam according to [1] or [2] above, which has an apparent density of 20 to 100 kg/m ³ .
[4] The crosslinked polyolefin resin foam according to any one of [1] to [3] above, which has a thickness of 0.05 to 15 mm.
[5] The crosslinked polyolefin resin foam according to any one of [1] to [4] above, which has a degree of crosslinking of 15 to 65% by mass.
[6] A molded article obtained by molding the crosslinked polyolefin resin foam according to any one of [1] to [5] above.
[7] The molded article according to [6] above, wherein a skin material is laminated on a crosslinked polyolefin resin foam.
[8] The molded article according to the above [6] or [7], which is an automotive interior material.

ADVANTAGE OF THE INVENTION According to this invention, the crosslinked polyolefin resin foam which can reduce generation|occurrence|production of an odor, and the molded object which shape|molds the crosslinked polyolefin resin foam can be provided.

（式中、Ｒは、水素原子、基－ＮＨ－ＮＨ_２、又はモノ、ジ、トリもしくはテトラカルボン酸からカルボキシル基を除いた残基を表し、ｎは１～４の整数を表す。） [Crosslinked polyolefin resin foam]
The crosslinked polyolefin resin foam of the present invention is obtained by foaming a foamable composition containing a polyolefin resin and a deodorant. The foamable composition contains 0.2 to 6.5 parts by mass of a deodorant with respect to 100 parts by mass of the polyolefin resin, and the deodorant is porous particles and hydrazides represented by the following general formula (1). including.

(Wherein, R represents a hydrogen atom, a group —NH—NH ₂ , or a residue obtained by removing a carboxyl group from a mono-, di-, tri- or tetracarboxylic acid, and n represents an integer of 1 to 4.)

(polyolefin resin)
Polyolefin resins contained in the foamable composition include, for example, polyethylene resins, polypropylene resins, ethylene vinyl acetate resins, polyolefin thermoplastic elastomers, and the like. The polyolefin resin preferably contains a polypropylene-based resin, and more preferably contains both a polypropylene-based resin and a polyethylene-based resin, from the viewpoint of improving the heat resistance and moldability of the resulting crosslinked polyolefin resin foam. preferable.

Examples of polypropylene-based resins include homopolypropylene, ethylene-propylene random copolymers containing propylene as a main component, and ethylene-propylene block copolymers containing propylene as a main component. They may be used or two or more may be used in combination. Among them, it is preferable to use an ethylene-propylene random copolymer containing propylene as a main component.
The melt flow rate (hereinafter referred to as "MFR") of the polypropylene-based resin is preferably 70 g/10 minutes or less, more preferably 50 g/10 minutes or less, and still more preferably 25 g/10 minutes or less. Also, the lower limit of MFR is usually 0.1 g/10 minutes.
The above MFR is a value measured under conditions of a temperature of 230° C. and a load of 21.2 N in accordance with JIS K 7210.

Examples of polyethylene resins include, but are not limited to, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymers containing ethylene as a main component. These may be used singly or in combination of two or more. Among the above polyethylene-based resins, linear low-density polyethylene is preferred. The density of the linear low-density polyethylene is preferably 0.900-0.925 g/cm ³ , more preferably 0.902-0.922 g/cm ³ .
The MFR of the polyethylene resin is preferably 0.5 to 70 g/10 minutes, more preferably 1.5 to 50 g/10 minutes.
The above MFR is a value measured under conditions of a temperature of 190° C. and a load of 21.2 N in accordance with JIS K 7210.

When the polyolefin resin contains a polypropylene-based resin, it preferably contains 50% by mass or more, more preferably 55% by mass or more of the polypropylene-based resin in the polyolefin resin from the viewpoint of improving heat resistance.
When the polyolefin resin contains a polyethylene-based resin and a polypropylene-based resin, it is preferable that the amount of the polypropylene-based resin is larger. It is 50% by mass or more, more preferably 55% by mass or more. With such a compounding amount, the heat resistance and flexibility of the crosslinked polyolefin resin foam are improved.
In addition, the foamable composition may contain resins other than polyolefin resin, but the content of polyolefin resin is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably, based on the total resin. is 90% by mass or more.
In addition, when the polyolefin resin contains a polypropylene-based resin, it is necessary to foam the foamable composition at a high temperature. Therefore, when the polyolefin resin contains a polypropylene-based resin, an aldehyde compound having 6 to 11 carbon atoms, which is an odor-causing substance, is likely to be generated. However, in the crosslinked polyolefin resin foam of the present invention, odor generation is reduced by adjusting the deodorant, other additives, and various production methods.

(Deodorants)
The foamable composition contains 0.2 to 6.5 parts by mass of a deodorant with respect to 100 parts by mass of the polyolefin resin, and the deodorant contains porous particles and hydrazides represented by the general formula (1). include. As a result, the foamable composition is appropriately foamed, the apparent density of the foam can be lowered, and the generation of odor from the foam can be effectively reduced.
If the content of the deodorant is less than 0.2 parts by mass per 100 parts by mass of the polyolefin resin, the degree of reduction in odor generation from the crosslinked polyolefin resin foam becomes small. On the other hand, when the content of the deodorant is more than 6.5 parts by mass per 100 parts by mass of the polyolefin resin, the apparent density of the crosslinked polyolefin resin foam increases and the flexibility of the crosslinked polyolefin resin foam increases. sexuality worsens. On the other hand, if the content of the deodorant is too large, the degree of reduction in the generation of odor from the crosslinked polyolefin resin foam becomes smaller. From this point of view, the content of the deodorant is preferably 0.3 to 6.0 parts by mass, more preferably 0.4 to 5.5 parts by mass, relative to 100 parts by mass of the polyolefin resin. Yes, more preferably 0.5 to 5.0 parts by mass.

A deodorant is usually powdery. The average particle size of the deodorant is preferably 0.1 to 100 μm, more preferably 0.5 to 20 μm, and still more preferably 2 to 2 μm, as a volume-based median diameter measured with a laser diffraction particle size distribution meter. 10 μm.

<Porous particles>
The porous particles contained in the deodorant are not particularly limited as long as they are porous. From the viewpoint of dispersing the hydrazides represented by the general formula (1) on the surfaces of the porous particles, the porous particles are preferably porous particles capable of supporting the hydrazides. From this point of view, the porous particles are preferably inorganic porous particles, more preferably silica-based porous particles. Silica-based porous particles include, for example, silica such as silica gel, zeolite, montrollilonite, hydrotalcite, and the like. Porous particles other than silica-based porous particles include, for example, aluminum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, water Zirconium oxide, zirconium phosphate, titanium phosphate, aluminum phosphate and the like can be mentioned. These may be used individually by 1 type, and may be used in mixture of 2 or more types. Among these, silica such as silica gel, zeolite, and the like are preferable, and silica is more preferable. When the deodorant does not contain porous particles, the hydrazides represented by the general formula (1) suppress the foaming by the foaming agent and increase the bulk density of the crosslinked polyolefin resin foam. However, when the deodorant contains porous particles, suppression of foaming by the hydrazides represented by the general formula (1) can be suppressed, and the bulk density of the crosslinked polyolefin resin foam can be lowered. Moreover, this can effectively suppress the generation of odors from the crosslinked polyolefin resin foam. It is presumed that this is because hydrazides are less likely to inhibit foaming when the porous particles support hydrazides.

<Hydrazides>
The hydrazides represented by the general formula (1) include, for example, a monohydrazide compound having one hydrazide group in the molecule, a dihydrazide compound having two hydrazide groups in the molecule, and three hydrazide groups in the molecule. and a tetrahydrazide compound having four hydrazide groups in the molecule. When R is a residue obtained by removing a carboxyl group from a mono-, di-, tri- or tetracarboxylic acid, the carbon number is preferably 1 to 30, more preferably 1 to 20, still more preferably 1 to 15.

（式中、Ｒ^１は水素原子、炭素数１～１２のアルキル基又は置換基を有することもあるアリール基を示す。）で表されるモノヒドラジド化合物を挙げることができる。 Monohydrazide compounds include, for example, monohydrazide compounds represented by the following general formula (2).

(wherein R ¹ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group which may have a substituent).

In the general formula (1) above, the alkyl group represented by R ¹ includes, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group and n-heptyl group. , n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group and the like. The aryl group represented by R ¹ includes, for example, a phenyl group, a biphenyl group, a naphthyl group, etc. Among these, a phenyl group is preferred. Examples of substituents of the aryl group include, for example, hydroxyl group, halogen atoms such as fluorine, chlorine and bromine, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, iso A linear or branched alkyl group having 1 to 4 carbon atoms such as -butyl group.

Examples of the monohydrazide compound represented by the general formula (2) include lauric hydrazide, salicylic hydrazide, formhydrazide, acetohydrazide, propionic hydrazide, p-hydroxybenzoic hydrazide, naphthoic hydrazide, and 3-hydroxy-2-naphthoic acid. and acid hydrazides.

（式中、Ｒ^２は基－ＣＯ－又は基－ＣＯ－Ｒ^３－ＣＯ－を示す。Ｒ^３は置換基を有することもある炭素数１～１２のアルキレン基又は置換基を有することもあるアリーレン基を示す。） Dihydrazide compounds include, for example, dihydrazide compounds represented by the following general formula (3).

(In the formula, R ² represents a group —CO— or a group —CO—R ³ —CO—. R ³ may have a C 1-12 alkylene group or a substituent represents an arylene group.)

In the above general formula ( ³ ), the alkylene group represented by R3 includes, for example, methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, nonamethylene straight-chain alkylene groups having 1 to 12 carbon atoms such as a decamethylene group, an undecamethylene group, and the like. Preferred alkylene groups are linear alkylene groups having 2 to 6 carbon atoms, and more preferred are ethylene, tetramethylene and hexamethylene groups. Substituents for the alkylene group include, for example, a hydroxyl group and the like. The arylene group represented by R3 includes ^, for example, a phenylene group, a biphenylene group, a naphthylene group, an anthrylene group, a phenanthrylene group, etc. Among these, a phenylene group, a naphthylene group, etc. are preferable. Examples of substituents for the arylene group include those similar to the substituents for the aryl group described above.

Examples of the dihydrazide compound of the general formula (3) include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecane-diacid dihydrazide, and maleic acid dihydrazide. , fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, dimer acid dihydrazide, dibasic acid dihydrazide such as 2,6-naphthoic acid dihydrazide.

Trihydrazide compounds include, for example, citric acid trihydrazide, trinitroacetic acid trihydrazide, nitriloacetic acid trihydrazide, cyclohexanetricarboxylic acid trihydrazide and the like.

Tetrahydrazide compounds include, for example, ethylenediaminetetraacetic acid tetrahydrazide and naphthoic acid tetrahydrazide.

These hydrazides may be used singly or in combination of two or more. Among these, dihydrazide compounds are more preferred, and among the dihydrazide compounds, carbohydrazide, succinic acid dihydrazide, adipic acid dihydrazide, isophthalic acid dihydrazide and the like are more preferred.

From the viewpoint of more effectively suppressing the generation of odor from the crosslinked polyolefin resin foam, the hydrazides are preferably carried on the porous particles. For example, hydrazides can be supported on porous particles by an impregnation method.

The content of the hydrazides represented by the above general formula (1) in the deodorant is preferably 10 to 90 parts by mass, more preferably 100 parts by mass in total of the silica-based substance and the hydrazides. It is 10 to 50 parts by mass, more preferably 10 to 30 parts by mass.

The deodorant may contain compounds other than the porous particles and the hydrazides represented by the general formula (1) as long as the effects of the present invention are not impaired. In this case, the total content of the porous particles and the hydrazides represented by the general formula (1) in the deodorant is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably. is 90% by mass or more.

<Antioxidant>
The foamable composition used for the crosslinked polyolefin resin foam of the present invention preferably contains an antioxidant. By containing an antioxidant, it is possible to suppress oxidative deterioration of the polyolefin resin and to reduce the generation of odor from the crosslinked polyolefin resin foam. The content of the antioxidant is preferably 0.5 to 5.0 parts by mass, more preferably 1.0 to 4.0 parts by mass, based on 100 parts by mass of the polyolefin resin.
By adding 0.5 parts by mass or more of the antioxidant to 100 parts by mass of the polyolefin resin, the oxidative deterioration of the polyolefin resin is further suppressed, and the odor generation of the crosslinked polyolefin resin foam can be further reduced. . Moreover, by setting the antioxidant to 5.0 parts by mass or less with respect to 100 parts by mass of the polyolefin resin, it is possible to suppress excessive antioxidant from becoming an odorant.

Although the type of antioxidant is not particularly limited, examples thereof include phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, and amine antioxidants. Among these, phenol-based antioxidants are preferred from the viewpoint of reducing the generation of odors from the crosslinked polyolefin resin foam.
Phenolic antioxidants include 2,6-di-tert-butyl-p-cresol, n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2-tert- Butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate ] methane and the like. Among these, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane is preferred.
One type of antioxidant may be used alone, or two or more types may be used in combination.

<Crosslinking aid>
The foamable composition preferably contains a cross-linking aid. The content of the cross-linking aid in the foamable composition is preferably 2.0 to 5.0 parts by mass, more preferably 2.5 to 4.7 parts by mass with respect to 100 parts by mass of the polyolefin resin. more preferred.
By using 2.0 parts by mass or more of the cross-linking aid with respect to 100 parts by mass of the polyolefin resin, it is possible to reduce the odor of the foam. This is presumably because the polyolefin resin is crosslinked to some extent, thereby suppressing deterioration due to heat and the like, and as a result, suppressing the production of odor-causing substances. By setting the cross-linking aid to 5.0 parts by mass or less with respect to 100 parts by mass of the polyolefin resin, it becomes easy to prevent defective foaming.
In addition, by setting the amount of the cross-linking aid in the foamable composition to such a range and setting the amount of the antioxidant to the above range, the generation of odor-causing substances in the foam can be suppressed, and the effect is improved. Odor generation from the foam can be effectively reduced.
As will be described later, the odor-causing substance of the foam is considered to be an aldehyde compound having 6 to 11 carbon atoms.

Examples of cross-linking aids include trifunctional (meth)acrylate compounds, polyfunctional (meth)acrylate compounds such as bifunctional (meth)acrylate compounds, compounds having three functional groups in one molecule, and the like. mentioned. Other cross-linking aids include compounds having two functional groups in one molecule such as divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethylvinylbenzene, lauryl methacrylate, stearyl methacrylate, and the like. be done.
Examples of trifunctional (meth)acrylate compounds include trimethylolpropane trimethacrylate and trimethylolpropane triacrylate.
Bifunctional (meth)acrylate compounds include 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, neopentyl glycol dimethacrylate and the like.
Compounds having three functional groups in one molecule include triallyl trimellitate, triallyl 1,2,4-benzenetricarboxylic acid, and triallyl isocyanurate.
A cross-linking coagent can be used individually or in combination of 2 or more.
Among these, polyfunctional (meth)acrylate-based compounds are preferred, bifunctional (meth)acrylate-based compounds are more preferred, and 1,9-nonanediol dimethacrylate is even more preferred, from the viewpoint of reducing the generation of odor from the foam. .

<Blowing agent>
Methods for foaming foamable compositions include chemical foaming methods and physical foaming methods. The chemical foaming method is a method of forming bubbles by gas generated by thermal decomposition of a compound added to the foaming composition, and the physical foaming method impregnates the foaming composition with a low boiling point liquid (foaming agent). After that, the foaming agent is volatilized to form cells. The foaming method is not particularly limited, but a chemical foaming method is preferred.
As the foaming agent, a thermally decomposable foaming agent is preferably used. For example, an organic or inorganic chemical foaming agent having a decomposition temperature of about 140 to 270° C. can be used.
Examples of organic foaming agents include azodicarbonamide, azodicarboxylic acid metal salts (barium azodicarboxylate, etc.), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, Hydrazodicarbonamide, 4,4'-oxybis(benzenesulfonyl hydrazide), hydrazine derivatives such as toluenesulfonyl hydrazide, semicarbazide compounds such as toluenesulfonyl semicarbazide, and the like.

Examples of inorganic foaming agents include ammonium acid, sodium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosoda citric acid.
Among these, azo compounds and nitroso compounds are preferred from the viewpoint of obtaining fine air bubbles and from the viewpoints of economy and safety, and azodicarbonamide, azobisisobutyronitrile, and N,N'-dinitrosopentamethylene. Tetramine is more preferred, and azodicarbonamide is particularly preferred.
A foaming agent can be used individually or in combination of 2 or more types.
The amount of the foaming agent added to the foamable composition is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the polyolefin resin, from the viewpoint of easily adjusting the apparent density of the foam to the above range. , 3 to 12 parts by mass is more preferable.

<Other additives>
Additives commonly used for foams such as heat stabilizers, colorants, flame retardants, antistatic agents, fillers, rust inhibitors, decomposition temperature regulators, etc. may be blended.

<Independent porosity>
The closed porosity of the crosslinked polyolefin resin foam of the present invention is preferably 70% or more. When the closed porosity is 70% or more, the odor generation of the foam can be further reduced.
The closed porosity of the foam is more preferably 80% or more, still more preferably 85% or more, from the viewpoint of further reducing odor generation.
The closed cell rate can be measured by the method described in Examples below.

<Apparent density>
The apparent density of the crosslinked polyolefin resin foam of the present invention is not particularly limited, but is preferably 20 to 100 kg/m ³ , more preferably 25 to 80 kg/m ³ , still more preferably 40 to 70 kg/m ³ . is. When the apparent density is 20 kg/m ³ or more, the mechanical strength of the foam can be improved, and when the apparent density is 100 kg/m ³ or less, the flexibility of the foam can be easily secured. The apparent density of the crosslinked polyolefin resin foam is measured by the method described in Examples below.
The apparent density can be measured by the method described in Examples below.

<Thickness>
The thickness of the crosslinked polyolefin resin foam is not particularly limited, but is preferably 0.05 to 15 mm, more preferably 1 to 10 mm. The thickness of the crosslinked polyolefin resin foam is measured by the method described in Examples below.
The thickness can be measured by the method described in Examples below.

<Degree of cross-linking>
The degree of cross-linking of the cross-linked polyolefin resin foam of the present invention is preferably 15 to 65% by mass. When the degree of cross-linking is 15 to 65% by mass, the mechanical strength, flexibility and moldability of the foam can be improved in a well-balanced manner. From the viewpoint that the mechanical strength, flexibility and moldability of the foam can be improved in a well-balanced manner, the degree of cross-linking of the cross-linked polyolefin resin foam of the present invention is more preferably 20 to 55% by mass, and even more preferably. is 30 to 50% by mass.
The degree of cross-linking can be measured by the method described in Examples below.

<Content of aldehyde compound>
In the crosslinked polyolefin resin foam of the present invention, the total concentration of aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is preferably 0.07 ppm by volume or less. As a result of extensive research, the inventors of the present invention have found that aldehyde compounds having 6 to 11 carbon atoms are causative substances of the odor of crosslinked polyolefin resin foams. The aldehyde compound-containing nitrogen gas is a 10 L sampling bag containing two crosslinked olefin resin foams with dimensions of 100 mm × 100 mm × 3.0 mm. It is a gas obtained by heating at the heating temperature for 2 hours. More specifically, it is an aldehyde compound-containing nitrogen gas obtained by the method of Examples described later. Specifically, the concentration of the aldehyde compound having 6 to 11 carbon atoms is the sum of n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde and n-undecylaldehyde. concentration.

When the total concentration of the aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is 0.07 volume ppm or less, the generation of odor from the crosslinked polyolefin resin foam can be further reduced. The total concentration of the aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is more preferably 0.06 volume ppm or less, further preferably 0.05 volume ppm or less. By setting the total concentration of the aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas within this range, it is possible to further reduce the generation of odors from the crosslinked polyolefin resin foam.

[Method for producing crosslinked polyolefin resin foam]
The production method for producing the crosslinked polyolefin resin foam of the present invention may include, for example, steps 1 to 3 below.
(Step 1) Step of processing a foamable composition containing a polyolefin resin into a sheet to produce a foamable sheet (Step 2) Irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet Step (Step 3) A step of foaming the crosslinked foamable sheet to produce a crosslinked polyolefin resin foam

(Step 1)
Step 1 is a step of processing a foamable composition containing a polyolefin resin into a sheet to produce a foamable sheet. A foamable composition can be kneaded using a kneader such as a Banbury mixer or a pressure kneader, and then continuously extruded using an extruder, a calendar, conveyor belt casting, or the like to produce a polyolefin resin foamable sheet. can. The foamable composition includes a polyolefin resin and a deodorant.

(Step 2)
Step 2 is a step of irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet.
The irradiation dose when irradiating the ionizing radiation is preferably 1.2 to 2.5 Mrad, more preferably 1.3 to 2.3 Mrad, from the viewpoint of reducing the odor generation of the crosslinked polyolefin resin foam. and more preferably 1.4 to 2.1 Mrad.
From the viewpoint of further reducing the generation of odor from the crosslinked polyolefin resin foam, it is preferable to adjust the amount of the cross-linking aid in the foamable composition within the above range and to set the ionizing radiation irradiation conditions within the above range.
Ionizing radiation may be applied to one surface or both surfaces of the foam sheet. It is preferable to do this on both sides.
Examples of ionizing radiation include electron beams, α-rays, β-rays, γ-rays, and X-rays. Among these, an electron beam is preferable from the viewpoint of productivity and uniform irradiation.

(Step 3)
Step 3 is a step of foaming the crosslinked foamable sheet to produce a sheet-like crosslinked polyolefin resin foam. Examples of the method for foaming the crosslinkable sheet include a batch method such as an oven, and a continuous foaming method in which the crosslinkable and foamable sheet is continuously passed through a heating furnace.
The temperature at which the crosslinkable foamable sheet is foamed is preferably 160 to 280°C. By setting the temperature to 160°C or higher, foaming can be facilitated, and by setting the temperature to 280°C or lower, generation of odor from the crosslinked polyolefin resin foam can be reduced. The temperature at which the crosslinkable foamable sheet is foamed is more preferably 180 to 270°C, more preferably 200 to 260°C.
The method for adjusting the temperature to the above temperature is not particularly limited, but hot air may be used, or infrared rays may be used.
Moreover, the crosslinkable foamable sheet may be stretched in one or both of the MD direction and the CD direction after foaming or while being foamed.

[Molded body]
The molded article of the present invention is obtained by molding the crosslinked polyolefin resin foam of the present invention. The molded article of the present invention is obtained by molding the crosslinked polyolefin resin foam of the present invention by a known method. When producing a molded article, other materials such as a base material and a skin material can be laminated on the crosslinked polyolefin resin foam and laminated. The molded article of the present invention is preferably obtained by laminating a skin material on a crosslinked polyolefin resin foam.

Examples of surface materials include polyvinyl chloride sheets, sheets made of mixed resin of polyvinyl chloride and ABS resin, thermoplastic elastomer sheets, woven fabrics, knitted fabrics, non-woven fabrics, artificial leather and synthetic leather using natural fibers and artificial fibers. Examples include leather, metal, and the like. Also, a molded article having a design such as a leather or wood grain pattern on the surface thereof may be formed by using a silicone stamper or the like with unevenness transferred from genuine leather, stone, wood, or the like.
By bonding the skin material to the crosslinked polyolefin resin foam and molding, it is possible to obtain a molded body in which the skin material is laminated on the crosslinked polyolefin resin foam.
Examples of methods for laminating the skin material include extrusion lamination, adhesive lamination in which adhesive is applied and then lamination, thermal lamination (heat fusion bonding), hot melt method, high-frequency welder method, and electroless bonding for metals, etc. Plating, electroplating, vapor deposition, and the like can be used, but any method may be used to bond the two together.

The base material serves as the skeleton of the molded article, and is usually made of a thermoplastic resin. As the thermoplastic resin for the base material, the above-mentioned polyolefin resin, copolymer of ethylene and α-olefin, vinyl acetate, acrylic ester, etc., ABS resin, polystyrene resin, and the like can be applied.

Examples of the method for molding the molded article of the present invention include stamping molding, vacuum molding, compression molding, injection molding and the like. Among these, the stamping molding method and the vacuum molding method are preferred. As the vacuum forming method, both the male-pulling vacuum forming method and the female-pulling vacuum forming method can be employed, but the male-pulling vacuum forming method is more preferable.
A molded article obtained by molding the crosslinked polyolefin resin foam of the present invention can be used as a heat insulating material, a cushioning material, and the like. Molded articles obtained by molding the crosslinked polyolefin resin foam of the present invention are less likely to emit odors even in the hot summer months. can be suitably used as

The present invention will be described in more detail with reference to examples, but the present invention is not limited by these examples.

(Example 1)
60 parts by mass of polypropylene resin, 40 parts by mass of linear low-density polyethylene, 2.5 parts by mass of phenolic antioxidant, 3 parts by mass of cross-linking aid, 0.5 parts by mass of deodorant, 8 parts by mass of foaming agent was melt-kneaded at a temperature of 180° C. by a single-screw extruder to form a foamable sheet. Both surfaces of the foamable sheet were irradiated with 2.0 Mrad of ionizing radiation (electron beam) at an acceleration voltage of 1000 keV to obtain a crosslinked foamable sheet. After that, the crosslinked foamable sheet was supplied to a vertical hot air foaming furnace having an internal temperature of 250° C., and heated and foamed while being stretched to obtain the desired crosslinked polyolefin resin foam.
The crosslinked polyolefin resin foam was evaluated for thickness, apparent density, degree of crosslinking, closed cell ratio, concentration of aldehyde having 6 to 11 carbon atoms, and odor as follows. Table 1 shows the results.
The details of each raw material used in the examples are as follows.
・Polypropylene resin: ethylene-propylene random copolymer, manufactured by Sumitomo Chemical Co., Ltd., trade name "AD571", density 0.90 g/cm ³ , MFR 0.5 g/10 minutes (230°C)
・Linear low-density polyethylene: manufactured by Prime Polymer Co., Ltd., trade name “Ultrazex 1020L”, density 0.909 g/cm ³ , MFR 2 g/10 min (190° C.)
· Blowing agent: Azodicarbonamide, manufactured by Eiwa Kasei Kogyo Co., Ltd., trade name "Vinihole AC-K3-TA", decomposition temperature: 208 ° C.
Crosslinking aid: 1,9-nonanediol dimethacrylate, manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester 1,9ND”, viscosity 8 mPa s/25°C
・ Phenolic antioxidant: BASF Japan Ltd., trade name “Irganox 1010”
・Deodorant 1: A deodorant containing silica (content: about 80% by mass) and adipic hydrazide (content: about 20% by mass), manufactured by Sinanen Zeomic Co., Ltd., trade name "Dashlight 7MH"
・Deodorant 2: Adipic acid hydrazide (deodorant containing no porous particles), manufactured by Otsuka Chemical Co., Ltd., trade name “Chemcatch H-6000HS”, melting point: 180 ° C.

(Examples 2-4, Comparative Examples 1-3)
Foams of Examples 2 to 4 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the composition of the foamable composition was changed as shown in Table 1.

(foam thickness)
The thickness of the foams of Examples and Comparative Examples was measured according to JIS K6767.

(Apparent density of foam)
The apparent densities of the foams of Examples and Comparative Examples were measured according to JIS K7222.

(Degree of cross-linking)
A test piece of about 100 mg was taken from the foam, and the mass A (mg) of the test piece was accurately weighed. Next, after immersing this test piece in 30 cm ³ of xylene at 120° C. and leaving it for 24 hours, it is filtered through a 200-mesh wire mesh to collect the insoluble matter on the wire mesh, dried in vacuum, and weighed the insoluble matter. B (mg) was accurately weighed. From the obtained values, the degree of cross-linking (% by mass) was calculated according to the following formula.
Crosslinking degree (mass%) = 100 x (B/A)

(Closed cell rate)
A test piece having a square shape with a side of 5 cm and a constant thickness was cut out from the foamed resin sheet. The thickness of the test piece was measured, the apparent volume V1 of the test piece was calculated, and the weight W1 of the test piece was measured. Next, the apparent volume V2 occupied by the bubbles was calculated based on the following formula. The density of the resin constituting the test piece was 1 g/cm ³ .
Apparent volume occupied by bubbles V2 = V1 - W1
Subsequently, the test piece was submerged in distilled water at 23° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa was applied to the test piece for 3 minutes. After releasing the pressure in water, remove the test piece from the water, remove the moisture adhering to the surface of the test piece, measure the weight W2 of the test piece, open cell rate F1 based on the following formula, and closed cell rate F2 was calculated.
Open cell rate F1 (%) = 100 × (W2 - W1) / V2
Closed cell rate F2 (%) = 100-F1

(Analysis of aldehyde compounds)
In order to sample the gas emitted from the foam, two pieces of foam cut to 100×100 mm were placed in a 10 L sampling bag (manufactured by GL Sciences Co., Ltd., trade name “Skypier Bag AAK-10”). Then, the opening of the sampling bag was closed using a heat sealer and filled with 5 L of nitrogen gas. This sampling bag was placed in a constant temperature bath at a temperature of 80° C. for 2 hours. An aldehyde compound-containing nitrogen gas was thus obtained. Then, using a sampling pump (manufactured by GL Sciences Co., Ltd., trade name "SP208-000DualII"), the aldehyde compound-containing nitrogen gas in the sampling bag was collected into a collection tube (manufactured by GL Sciences Co., Ltd., trade name "Tenax TA 150 mg. ”) was collected. The sampling conditions were as follows.
Gas filling amount: _N2 , 5L
Heating temperature: 80°C
Collection time: 1 hour Collection amount: 1 to 2 L
Collection flow rate: 400 mL/min

After sampling the aldehyde compound-containing nitrogen gas, it was thermally desorbed using a thermal desorption apparatus (manufactured by GL Sciences, trade name "HandyTD TD265"). Then, it is introduced into a sniffing system (manufactured by GL Sciences Co., Ltd., trade name "OPV277") using a gas chromatograph (manufactured by GL Sciences Co., Ltd., trade name "GC-4000Plus (A type)") to analyze aldehyde compounds. did The conditions for thermal desorption and gas chromatography were as follows.
<Thermal desorption conditions>
System pressure: 190kPa
Prepurge time: 0min
Thermal desorption temperature: 270°C
Thermal desorption time: 5 min
Heating rate: 45°C/sec
<Gas chromatograph conditions>
Column: InertCap Pure-WAX (manufactured by GL Sciences Inc.), inner diameter 0.25 mm, length 60 m, film thickness 0.25 μm
Temperature conditions: 40°C (6min hold)-10°C/min-240°C (14min hold)
Carrier gas: He, 160 kPa
Injection method: Split 10:1
Inlet temperature: 270°C
Detector: FID
Detector temperature: 280°C
_H2 flow rate: 35 mL/min
Make-up flow rate: N ₂ 30 mL/min
Air flow rate: 250mL/min

A calibration curve for calculating the concentration of aldehyde compounds in the aldehyde compound-containing nitrogen gas from the measurement results of the gas chromatograph was prepared as follows.
Approximately 100 mg of each of aldehyde compounds having 6 to 11 carbon atoms (n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde and n-undecylaldehyde) was collected using an electronic balance, Poured into a 20 mL volumetric flask. Then, it was diluted with methanol to prepare an aldehyde mixed standard solution (concentration: 5000 μg/L). 0.2 μL of this aldehyde mixed standard solution was collected with a syringe. Then, an aldehyde mixed standard solution collected in a collection tube (manufactured by GL Sciences, trade name “Tenax TA 150 mg”) or a sampling bag (manufactured by GL Sciences, trade name “Skypier Back AAK-10”) was added. . In the case of a collection tube, it was set in a calibration curve creation tool of a sniffing system (manufactured by GL Sciences, trade name "OPV277") and dry-purged (50 mL/min, 2 min). In the case of a sampling bag, 1 L of nitrogen was filled after the addition and heated at a temperature of 80° C. for 2 hours using a constant temperature bath to collect all the gas in the sampling bag in a collection tube. Each collection tube was thermally desorbed using a thermal desorption device (manufactured by GL Sciences Co., Ltd., trade name "HandyTD TD265") and introduced into a gas chromatograph. Then, a calibration curve was created using the measurement results of the gas chromatograph.

(Odor evaluation)
An odor evaluation test was performed on each foam obtained in Examples and Comparative Examples. The conditions of the odor evaluation test were as follows.
Sampling days: Immediately after foam production Sampling size: 100 cm ²
Odor bottle: 100 cm ² glass container Test temperature: 80°C x 2 hours → cool to 60°C Sniffing temperature: 60°C
Number of people tested: 5 How to sniff the odor: Open the lid of the odor bottle and tilt the odor bottle at an angle of 45° with respect to the horizontal plane. Then, with the nostril placed in the center of the mouth of the odor bottle and the nostril separated from the mouth of the odor bottle by 1 cm, the subject smelled the gas emitted from the odor bottle for 5 to 10 seconds.

Odor evaluation was performed as follows. Aqueous n-butanol solutions having the following n-butanol concentrations were used as odor intensity standard solutions. 150 mL of each of these solutions was weighed into a 1 L glass bottle and used as a reference odor. Then, the odor of the foam was evaluated based on the odor intensity of these standard odors.
Strength grade 1: n-butanol concentration 0 ml / L
Strength grade 1.5: n-butanol concentration 1.4 ml/L
Strength grade 2: n-butanol concentration 2.0 ml / L
Strength grade 2.5: n-butanol concentration 3.6 ml / L
Strength grade 3: n-butanol concentration 6.0 ml / L
Strength grade 3.5: n-butanol concentration 9.0 ml / L
Strength grade 4: n-butanol concentration 18.0 ml / L
Strength grade 4.5: n-butanol concentration 22.7 ml/L
Strength grade 5: n-butanol concentration 30.0 ml / L
Strength grade 5.5: n-butanol concentration 57.0 ml / L
Strength grade 6: n-butanol only

Table 1 shows the thickness, apparent density, closed cell ratio, cross-linking degree, aldehyde compound analysis results, and odor evaluation results of the foams of Examples 1 to 4 and Comparative Examples 1 to 3.

From the results of the above examples, 0.2 to 6.5 parts by mass of a deodorant containing porous particles, a hydrazide represented by the general formula (1), and an aldehyde compound is added to 100 parts by mass of the polyolefin resin. The foams of Examples 1 to 4 obtained by foaming the foamable composition containing the above gave good results in odor evaluation. On the other hand, the foam of Comparative Example 1 obtained by foaming the foamable composition containing more than 6.5 mass of the deodorant with respect to 100 mass parts of the polyolefin resin obtained good results in odor evaluation. I couldn't do it. Also, the crosslinked polyolefin resin foams of Comparative Examples 2 and 3 obtained by foaming a foamable composition containing no porous particles could not obtain good results in odor evaluation.
From the results of the concentration of aldehyde compounds having 6 to 11 carbon atoms and the results of the odor evaluation, the cause of the odor of the crosslinked polyolefin resin foam is the aldehyde compound having 6 to 11 carbon atoms emitted from the crosslinked polyolefin resin foam. I understand.

Claims (8)

A crosslinked polyolefin resin foam obtained by foaming a foamable composition containing a polyolefin resin and a deodorant,
The foamable composition contains 0.2 to 6.5 parts by mass of the deodorant with respect to 100 parts by mass of the polyolefin resin,
The deodorant contains porous particles and hydrazides represented by the following general formula (1) ,
The polyolefin resin contains a polypropylene-based resin,
A crosslinked polyolefin resin foam, wherein the porous particles are silica .

(Wherein, R represents a hydrogen atom, a group —NH—NH ₂ , or a residue obtained by removing a carboxyl group from a mono-, di-, tri- or tetracarboxylic acid, and n represents an integer of 1 to 4.) The crosslinked polyolefin resin foam according to claim 1, which has a closed cell rate of 70% or more. 3. The crosslinked polyolefin resin foam according to claim 1, which has an apparent density of 20 to 100 kg/m ³ . The crosslinked polyolefin resin foam according to any one of claims 1 to 3, having a thickness of 0.05 to 15 mm. The crosslinked polyolefin resin foam according to any one of claims 1 to 4, having a degree of crosslinking of 15 to 65% by mass. A molded article obtained by molding the crosslinked polyolefin resin foam according to any one of claims 1 to 5. 7. The molded article according to claim 6, wherein the skin material is laminated on the crosslinked polyolefin resin foam. The molded article according to claim 6 or 7, which is an automobile interior material.