阅读说明：本技术 聚烯烃树脂发泡体、聚烯烃树脂发泡体的制造方法及成形体 (Polyolefin resin foam, process for producing polyolefin resin foam, and molded article ) 是由 金泽太 宇野拓明 高杉基 杉江幸弘 三上洋辉 于 2019-03-29 设计创作，主要内容包括：本发明是碳原子数6～11的醛化合物的含量为0.1ppm以下的聚烯烃树脂发泡体。根据本发明,可提供能够减少刺激性气体的产生的聚烯烃树脂发泡体。(The polyolefin resin foam has a content of C6-11 aldehyde compound of 0.1ppm or less. According to the present invention, a polyolefin resin foam capable of reducing the generation of an irritant gas can be provided.)

1. A polyolefin resin foam having a content of an aldehyde compound having 6 to 11 carbon atoms of 0.1ppm or less.

2. The polyolefin resin foam according to claim 1, wherein a concentration of n-nonanal in the aldehyde compound-containing nitrogen gas obtained by filling 5L of nitrogen gas into a 10L sample bag containing 2 pieces of the polyolefin resin foam having a size of 100mm x 3.1 ± 0.2mm and heating the sample bag at a heating temperature of 80 ℃ for 2 hours is 0.07 ppm by volume or less.

3. The polyolefin resin foam according to claim 2, wherein the concentration of n-octanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

4. The polyolefin resin foam according to claim 2 or 3, wherein the concentration of n-heptanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

5. The polyolefin resin foam according to any one of claims 2 to 4, wherein the concentration of n-decanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

6. The polyolefin resin foam according to any one of claims 1 to 5, which is obtained by foaming an expandable composition containing a polyolefin resin.

7. The polyolefin resin foam according to claim 6, wherein the foamable composition contains 1.0 to 5.0 parts by mass of an antioxidant per 100 parts by mass of the polyolefin resin.

8. The polyolefin resin foam according to claim 6 or 7, wherein the foamable composition contains 2.0 to 5.0 parts by mass of a crosslinking assistant per 100 parts by mass of the polyolefin resin.

9. The polyolefin resin foam according to any one of claims 6 to 8, wherein the foamable composition contains 0.6 to 10.0 parts by mass of a heavy metal deactivator per 100 parts by mass of the polyolefin resin.

10. The method for producing a polyolefin resin foam according to any one of claims 1 to 9, which comprises the following steps 1 to 3,

A step 1 of processing a foamable composition containing a polyolefin resin into a sheet form to produce a foamable sheet;

A step 2 of irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet;

And a step 3 of foaming the crosslinked foamable sheet to produce a polyolefin resin foam.

11. the process for producing a polyolefin resin foam according to claim 9, wherein in the step 3, the temperature at which the crosslinked foamable sheet is foamed is 140 to 280 ℃.

12. A molded article obtained by molding the polyolefin resin foam according to any one of claims 1 to 9.

13. The molded article of claim 12, wherein a skin material is laminated on the polyolefin resin foam.

14. The shaped body according to claim 12 or 13, which is an automotive interior material.

Technical Field

The present invention relates to a polyolefin resin foam, a method for producing a polyolefin resin foam, and a molded article.

Background

Polyolefin resin foams have been widely used in various fields as heat insulating materials, cushioning materials, and the like because of their excellent heat resistance and heat insulating properties. In particular, in automotive applications, the heat insulating material and the interior material are used as heat insulating materials such as roofs, doors, instrument panels, and cooler covers.

Polyolefin resin foams are mostly produced by a method of foaming a composition containing a polyolefin resin and a foaming agent by heating, but have a problem of generation of irritating gases due to decomposition products of the polyolefin resin. For example, in automobiles in which a molded article obtained by molding a polyolefin resin foam is incorporated as an automobile interior material, irritating gases are often generated, and users feel uncomfortable.

As a technique for suppressing the irritating gas of the polyolefin resin foam, for example, a method using a deodorant such as activated carbon (patent document 1), a method using carbon black or the like as an irritating gas inhibitor (patent document 2), and the like are known.

Disclosure of Invention

Problems to be solved by the invention

However, for example, in an automobile or the like including an automobile interior material formed of a molded article of a polyolefin resin foam, the following problems arise: the prior art does not adequately suppress irritant gases, particularly during hot summer periods.

Accordingly, an object of the present invention is to provide a polyolefin resin foam which can reduce the generation of an irritant gas.

Means for solving the problems

The present inventors have made extensive studies to achieve the above object and found that: the irritant gas generated by the polyolefin resin foam, especially the irritant gas generated during hot summer is caused by the aldehyde compound with 6-11 carbon atoms. Based on these findings, the present inventors have found that: the content of the aldehyde compound having 6 to 11 carbon atoms in the polyolefin resin foam is set to a certain value or less, whereby the generation of irritant gases can be reduced, and the present invention has been completed. That is, the present invention relates to the following [1] to [14 ].

[1] A polyolefin resin foam having a content of an aldehyde compound having 6 to 11 carbon atoms of 0.1ppm or less.

[2] The polyolefin resin foam according to the [1], wherein a concentration of n-nonanal in nitrogen containing an aldehyde compound obtained by filling 5L of nitrogen into a 10L sample bag containing 2 pieces of the polyolefin resin foam having a size of 100mm × 100mm × 3.1 ± 0.2mm and heating the sample bag at a heating temperature of 80 ℃ for 2 hours is 0.07 ppm by volume or less.

[3] The polyolefin resin foam according to [2], wherein the concentration of n-octanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

[4] The polyolefin resin foam according to [2] or [3], wherein a concentration of n-heptanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

[5] The polyolefin resin foam according to any one of [2] to [4], wherein a concentration of n-decanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

[6] The polyolefin resin foam according to any one of the above [1] to [5], which is obtained by foaming an expandable composition containing a polyolefin resin.

[7] The polyolefin resin foam according to [6], wherein the foamable composition contains 1.0 to 5.0 parts by mass of an antioxidant per 100 parts by mass of the polyolefin resin.

[8] The polyolefin resin foam according to [6] or [7], wherein the foamable composition contains 2.0 to 5.0 parts by mass of a crosslinking assistant per 100 parts by mass of the polyolefin resin.

[9] The polyolefin resin foam according to any one of [6] to [8], wherein the foamable composition contains 0.6 to 10.0 parts by mass of a heavy metal deactivator per 100 parts by mass of the polyolefin resin.

[10] The process for producing a polyolefin resin foam according to any one of [1] to [9], which comprises the following steps 1 to 3,

A step (1) wherein a foamable composition containing a polyolefin resin is processed into a sheet form to produce a foamable sheet;

(step 2) irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet;

(step 3) the crosslinked foamable sheet is foamed to produce a polyolefin resin foam.

[11] The process for producing a polyolefin resin foam according to [9], wherein in the step 3, the temperature at which the crosslinked foamable sheet is foamed is 140 to 280 ℃.

[12] A molded article obtained by molding the polyolefin resin foam according to any one of [1] to [9 ].

[13] The molded article according to the above [12], wherein a skin material is laminated on the polyolefin resin foam.

[14] The molded body according to the above [12] or [13], which is an automotive interior material.

Effects of the invention

According to the present invention, a polyolefin resin foam capable of reducing the generation of an irritant gas can be provided.

Detailed Description

[ polyolefin resin foam ]

< content of aldehyde Compound >

The polyolefin resin foam of the present invention has a content of an aldehyde compound having 6 to 11 carbon atoms of 0.1ppm or less. The content of the aldehyde compound is a volume-based amount (vol ppm). The content of the C6-11 aldehyde compound is the total amount of the C6-11 aldehyde compounds.

When the content of the C6-11 aldehyde compound exceeds 0.1ppm, the polyolefin resin foam is likely to generate an irritant gas. The content of the C6-11 aldehyde compound is preferably 0.08ppm or less, more preferably 0.05ppm or less. When the content of the aldehyde compound having 6 to 11 carbon atoms is in such a range, the amount of irritating gases generated by the polyolefin resin foam can be further reduced.

Examples of the aldehyde compound having 6 to 11 carbon atoms include n-hexanal, 2-ethylbutanal, n-heptanal, 2-ethylhexanal, n-octanal, n-nonanal, n-decanal, benzaldehyde, cinnamaldehyde, and n-undecanal.

The method for setting the content of the aldehyde compound having 6 to 11 carbon atoms in the polyolefin resin foam to 0.1ppm or less is not particularly limited, and the following methods are exemplified: the amounts of the antioxidant and the crosslinking aid in the foamable composition for producing the foam, the irradiation conditions of ionizing radiation during the production of the foam, the foaming conditions, and the like are appropriately controlled.

< n-nonanal >

The polyolefin resin foam of the present invention preferably has a n-nonanal concentration of 0.07 ppm by volume or less in nitrogen containing an aldehyde compound. The nitrogen gas containing an aldehyde compound means a gas obtained by filling 5L of nitrogen gas into a 10L sample bag containing 2 polyolefin resin foams having a size of 100mm × 100mm × 3.1 + -0.2 mm and then heating the sample bag at a heating temperature of 80 ℃ for 2 hours. More specifically, the nitrogen gas containing an aldehyde compound was obtained by the method of the example described later. When the n-nonanal concentration in the nitrogen gas containing the aldehyde compound is 0.07 ppm by volume or less, the amount of irritating gas generated by the polyolefin resin foam becomes small. The concentration of n-nonanal in the nitrogen gas containing the aldehyde compound is more preferably 0.05ppm by volume or less, and still more preferably 0.03 ppm by volume or less. By setting the concentration of n-nonanal in the nitrogen gas containing the aldehyde compound in such a range, the generation of irritating gases in the polyolefin resin foam can be further reduced.

< n-octanal >

The polyolefin resin foam of the present invention is preferably a polyolefin resin foam in which the concentration of n-octanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less.

When the concentration of n-octanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less, the generation of irritating gases in the polyolefin resin foam can be further reduced. The concentration of n-octanal in the nitrogen gas containing the aldehyde compound is more preferably 0.02 ppm by volume or less, and still more preferably 0.015 ppm by volume or less. By setting the concentration of n-octanal in the nitrogen gas containing the aldehyde compound in such a range, the generation of irritating gases in the polyolefin resin foam can be further reduced.

< n-heptanal >

In the polyolefin resin foam of the present invention, the concentration of n-heptanal in the nitrogen gas containing the aldehyde compound is preferably 0.03 ppm by volume or less.

When the n-heptanal concentration in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less, the generation of irritating gases in the polyolefin resin foam can be further reduced. The concentration of n-heptanal in the nitrogen gas containing the aldehyde compound is more preferably 0.02 ppm by volume or less, and still more preferably 0.015 ppm by volume or less. By setting the concentration of n-heptanal in the nitrogen gas containing the aldehyde compound in such a range, the generation of irritating gases of the polyolefin resin foam can be further reduced.

< n-decanal >)

In the polyolefin resin foam of the present invention, the concentration of n-decanal in the nitrogen gas containing the aldehyde compound is preferably 0.03 ppm by volume or less.

When the concentration of n-decanal in the nitrogen gas containing the aldehyde compound is 0.03 ppm by volume or less, the generation of irritating gases in the polyolefin resin foam can be further reduced. The concentration of n-decanal in the nitrogen gas containing the aldehyde compound is more preferably 0.02 ppm by volume or less, and still more preferably 0.015 ppm by volume or less. By setting the concentration of n-decanal in the nitrogen gas containing the aldehyde compound in such a range, the generation of irritating gases of the polyolefin resin foam can be further reduced.

A method of setting the respective concentrations of n-nonanal, n-octanal, n-heptanal, and n-decanal in the nitrogen gas containing the aldehyde compound to be within the above-mentioned content ranges is not particularly limited. Such methods include, for example, the following methods: the compounding amounts of additives such as an antioxidant, a heavy metal deactivator, and a crosslinking aid in the foamable composition used for producing the foam, the irradiation conditions of ionizing radiation at the time of crosslinking of the foamable composition, the temperature of the foamable composition at the time of foaming, and the like are appropriately controlled.

< expansion ratio >

The expansion ratio of the polyolefin resin foam of the present invention is not particularly limited, but is preferably 5 to 25cc/g, more preferably 10 to 22cc/g, and still more preferably 12 to 20 cc/g. When the expansion ratio is 5cc/g or more, the flexibility of the foam can be easily ensured, and when the expansion ratio is 25cc/g or less, the mechanical strength of the foam can be improved.

(apparent Density)

The polyolefin resin foam of the present invention has an apparent density of preferably 20 to 300kg/m ³, more preferably 25 to 250kg/m ³, and when the apparent density is 20kg/m ³ or more, the mechanical strength of the foam is good, and when the apparent density is 300kg/m ³ or less, the flexibility of the foam is easily ensured.

< thickness >

The thickness of the polyolefin resin foam is not particularly limited, but is preferably 1.1 to 10mm, more preferably 1.5 to 8mm, and still more preferably 2 to 5 mm.

< antioxidant >

The polyolefin resin foam of the present invention is preferably a foam obtained by foaming a foamable composition containing a polyolefin resin.

The foamable composition preferably contains an antioxidant. By containing the antioxidant, oxidative deterioration of the polyolefin resin can be suppressed. The antioxidant is preferably contained in an amount of 1.0 to 5.0 parts by mass, more preferably 1.5 to 4.5 parts by mass, per 100 parts by mass of the polyolefin resin.

By containing the antioxidant in an amount of 1.0 part by mass or more per 100 parts by mass of the polyolefin resin, the polyolefin resin can be inhibited from oxidative deterioration, and the concentration of the aldehyde compound having 6 to 11 carbon atoms can be reduced. Further, by containing 5.0 parts by mass or less of an antioxidant per 100 parts by mass of the polyolefin resin, the concentration of the aldehyde compound having 6 to 11 carbon atoms can be reduced by suppressing the excessive antioxidant from becoming a irritating gas substance.

Further, when the antioxidant in the foamable composition is in the above range, the release of a linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal, in the polyolefin resin foam can be further reduced.

The type of the antioxidant is not particularly limited, and examples thereof include a phenol-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, and an amine-based antioxidant. Among these antioxidants, a phenol-based antioxidant is preferable from the viewpoint of reducing the concentration of an aldehyde compound having 6 to 11 carbon atoms, particularly from the viewpoint of reducing the emission of a linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal.

Examples of the phenolic antioxidant include 2, 6-di-t-butyl-p-cresol, n-octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, and tetrakis [ methylene-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] methane. Among these, tetrakis [ methylene-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] methane is preferable.

The antioxidant may be used alone or in combination of two or more.

< Cross-linking Co-agent >

The foamable composition preferably contains a crosslinking assistant. The content of the crosslinking aid in the foamable composition is preferably 2.0 to 5.0 parts by mass, and more preferably 2.5 to 4.7 parts by mass, per 100 parts by mass of the polyolefin resin.

By containing the crosslinking assistant in an amount of 2.0 parts by mass or more per 100 parts by mass of the polyolefin resin, the concentration of the aldehyde compound having 6 to 11 carbon atoms in the foam can be reduced. This is because the polyolefin resin is crosslinked to some extent, and deterioration due to heat or the like is suppressed, thereby suppressing the generation of aldehyde compounds. By containing the crosslinking aid in an amount of 5.0 parts by mass or less based on 100 parts by mass of the polyolefin resin, foaming failure can be easily prevented.

Further, when the amount of the crosslinking aid in the foamable composition is in the above range and the amount of the antioxidant is in the above range, the concentration of the aldehyde compound having 6 to 11 carbon atoms can be more effectively reduced, and the amount of the linear aldehyde compound having 7 to 10 carbon atoms, particularly, the amount of n-nonanal released can be reduced.

Examples of the crosslinking assistant include polyfunctional (meth) acrylate compounds such as 3-functional (meth) acrylate compounds and 2-functional (meth) acrylate compounds, and compounds having 3 functional groups in 1 molecule. Examples of the crosslinking assistant other than these include compounds having 2 functional groups in 1 molecule such as divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethylvinylbenzene, lauryl methacrylate, stearyl methacrylate, and the like.

Examples of the 3-functional (meth) acrylate compound include trimethylolpropane trimethacrylate and trimethylolpropane triacrylate.

Examples of the 2-functional (meth) acrylate compound include 1, 6-hexanediol dimethacrylate, 1, 9-nonanediol dimethacrylate, 1, 10-decanediol di (meth) acrylate, and neopentyl glycol dimethacrylate.

Examples of the compound having 3 functional groups in 1 molecule include triallyl trimellitate, triallyl 1,2, 4-benzenetricarboxylate, triallyl isocyanurate, and the like.

The crosslinking assistant may be used alone or in combination of two or more.

Among these, from the viewpoint of reducing the concentration of the aldehyde compound having 6 to 11 carbon atoms, a polyfunctional (meth) acrylate compound is preferable, a 2-functional (meth) acrylate compound is more preferable, and 1, 9-nonanediol dimethacrylate is even more preferable.

< polyolefin resin >

Examples of the polyolefin resin contained in the foamable composition include 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 the molding processability of the resulting polyolefin resin foam.

Examples of the polypropylene resin include homopolypropylene, an ethylene-propylene random copolymer containing propylene as a main component, and an ethylene-propylene block copolymer containing propylene as a main component, and these may be used alone or in combination of two or more. Among them, an ethylene-propylene random copolymer containing propylene as a main component is preferably used.

The melt flow rate (hereinafter referred to as "MFR") of the polypropylene resin is preferably 70g/10 min or less, more preferably 50g/10 min or less, and still more preferably 25g/10 min or less. Further, the lower limit of MFR is usually 0.1g/10 min.

The MFR is a value measured according to JIS K7210 at a temperature of 230 ℃ under a load of 21.2N.

^{3 3}The polyethylene resin is not particularly limited, and examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and an ethylene- α -olefin copolymer containing ethylene as a main component, and these may be used alone or in combination of two or more.

The polyethylene resin preferably has an MFR of 0.5 to 70g/10 min, more preferably 1.5 to 50g/10 min, and still more preferably 2 to 30g/10 min.

The MFR is a value measured under the conditions of a temperature of 190 ℃ and a load of 21.2N in accordance with JIS K7210.

When the polyolefin resin contains a polypropylene-based resin, the polypropylene-based resin is preferably contained in an amount of 50 mass% or more, more preferably 60 mass% or more, of the polyolefin resin, from the viewpoint of improving heat resistance.

When the polyolefin resin contains a polyethylene resin and a polypropylene resin, the amount of the polypropylene resin is preferably large, and the polypropylene resin is preferably 55 mass% or more, more preferably 60 mass% or more, based on the total amount of the polyethylene resin and the polypropylene resin. By setting the blending amount as described above, the polyolefin resin foam becomes excellent in heat resistance and flexibility.

The foamable composition may contain a resin other than the polyolefin resin, and the content of the polyolefin resin in the polyolefin resin foam is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

When the polyolefin resin contains a polypropylene resin, the foamable composition needs to be foamed at a high temperature. Therefore, when the polyolefin resin contains a polypropylene resin, a linear aldehyde compound having 7 to 10 carbon atoms, which is a causative substance of the irritant gas, is easily generated. However, even in such a case, by adjusting the antioxidant, the heavy metal deactivator, and the various production methods, the generation of the linear aldehyde compound having 7 to 10 carbon atoms can be suppressed, and the generation of the irritant gas can be reduced.

< blowing agent >

As a method for foaming the foamable composition, there are a chemical foaming method and a physical foaming method. The chemical foaming method is a method of forming bubbles by utilizing a gas generated by thermal decomposition of a compound added to the foamable composition, and the physical foaming method is a method of impregnating a low boiling point liquid (foaming agent) into the foamable composition and then volatilizing the foaming agent to form cells. The foaming method is not particularly limited, and a chemical foaming method is preferable.

As the foaming agent, a thermal decomposition type foaming agent is preferably used, and for example, an organic or inorganic chemical foaming agent having a decomposition temperature of about 140 to 270 ℃ can be used.

Examples of the organic blowing agent include azodicarbonamide, azodicarbonic acid metal salts (such as barium azodicarboxylate), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N, N '-dinitrosopentamethylenetetramine, hydrazine derivatives such as biurea, 4' -oxybis (benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonylsemicarbazide.

Examples of the inorganic foaming agent include ammonium sulfate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate.

Among these, from the viewpoint of obtaining fine bubbles, and from the viewpoint of economy and safety, azo compounds and nitroso compounds are preferable, azodicarbonamide, azobisisobutyronitrile, and N, N' -dinitrosopentamethylenetetramine are more preferable, and azodicarbonamide is particularly preferable.

The blowing agent may be used alone or in combination of two or more.

The amount of the blowing agent added to the foamable composition is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and still more preferably 3 to 12 parts by mass, per 100 parts by mass of the polyolefin resin, from the viewpoint of facilitating the expansion ratio of the foam to fall within the above range.

< heavy Metal deactivator >

The foamable composition used in the polyolefin resin foam of the present invention preferably contains a heavy metal deactivator. The inclusion of the heavy metal deactivator can suppress oxidative degradation of the polyolefin resin due to heavy metal ions, and can further reduce the release of a linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal, from the polyolefin resin foam. The content of the metal deactivator is preferably 0.6 to 10.0 parts by mass, more preferably 1.0 to 4.0 parts by mass, per 100 parts by mass of the polyolefin resin.

by setting the content of the heavy metal deactivator to 0.6 parts by mass or more per 100 parts by mass of the polyolefin resin, oxidative deterioration of the polyolefin resin due to heavy metal ions can be further suppressed, and the release of a linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal, from the crosslinked polyolefin resin foam can be further reduced. Further, by setting the content of the heavy metal deactivator to 5.0 parts by mass or less with respect to 100 parts by mass of the polyolefin resin, it is possible to suppress the excessive heavy metal deactivator from becoming a irritating gaseous substance.

The type of the heavy metal deactivator is not particularly limited, and examples thereof include oxalic acid derivatives, salicylic acid derivatives, and hydrazide derivatives. Among these, hydrazide derivatives are preferable from the viewpoint of effectively reducing the emission of linear aldehyde compounds having 7 to 10 carbon atoms, particularly n-nonanal, in the polyolefin resin foam.

Examples of the hydrazide derivative include N, N' -bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, and isophthalic acid bis (2-phenoxypropionylhydrazide). Among these, N' -bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionyl ] hydrazine is preferable from the viewpoint of further reducing the amount of a linear aldehyde compound having 7 to 10 carbon atoms, particularly N-nonanal, released from the crosslinked polyolefin resin foam. The heavy metal passivator can be used singly or in combination of two or more.

< other additives >

The foamable composition may contain additives usually used for foams, such as a heat stabilizer, a colorant, a flame retardant, an antistatic agent, a filler, a rust inhibitor, and a decomposition temperature adjuster, if necessary.

[ Process for producing polyolefin resin foam ]

The method for producing the polyolefin resin foam of the present invention is not particularly limited, and preferably includes the following steps 1 to 3.

(step 1) Process for producing an expandable sheet by processing an expandable composition containing a polyolefin resin into a sheet

(step 2) Process for producing a crosslinked foamable sheet by irradiating the foamable sheet with ionizing radiation

(step 3) Process for producing a polyolefin resin foam by foaming a crosslinked foamable sheet (step 1)

Step 1 is a step of processing a foamable composition containing a polyolefin resin into a sheet form to produce a foamable sheet. The foamable composition is kneaded using a kneader such as a Banbury mixer or a pressure kneader, and then continuously extruded by an extruder, a calender, a belt casting or the like, thereby producing a polyolefin resin foamable sheet. The foamable composition preferably contains an antioxidant, a crosslinking assistant, a foaming agent, and the like as described above, and more preferably contains an antioxidant, a heavy metal deactivator, a crosslinking assistant, a foaming agent, and the like.

(step 2)

Step 2 is a step of irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet.

The dose of ionizing radiation is preferably 1.2 to 2.5Mrad, more preferably 1.3 to 2.3Mrad, and even more preferably 1.4 to 2.1Mrad, from the viewpoint of reducing the content of the C6 to 11 aldehyde compound, particularly the emission of a C7 to 10 linear aldehyde compound, particularly n-nonanal.

From the viewpoint of reducing the content of the aldehyde compound having 6 to 11 carbon atoms, particularly from the viewpoint of reducing the emission of the linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal, it is preferable to adjust the amount of the crosslinking assistant in the foamable composition to the above range and to set the irradiation conditions of the ionizing radiation to the above range.

The ionizing radiation may be irradiated to one side or both sides of the foamable sheet, and is preferably irradiated to both sides from the viewpoint of reducing the content of the aldehyde compound having 6 to 11 carbon atoms, particularly from the viewpoint of reducing the emission of a linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal.

Examples of the ionizing radiation include electron beams, α rays, β rays, γ rays, and X rays. Among these, from the viewpoint of productivity and uniform irradiation, an electron beam is preferable.

(step 3)

Step 3 is a step of foaming the crosslinked foamable sheet to produce a sheet-like polyolefin resin foam. Examples of the method of foaming the crosslinked foamable sheet include a batch method such as an oven and a continuous foaming method in which the crosslinked foamable sheet is continuously passed through a heating furnace.

The temperature for foaming the crosslinked foamable sheet is preferably 140 to 280 ℃, more preferably 160 to 280 ℃. The foaming can be easily performed by setting the temperature to 140 ℃ or higher, and the content of the aldehyde compound having 6 to 11 carbon atoms can be reduced by setting the temperature to 280 ℃ or lower, and the generation of the linear aldehyde compound having 7 to 10 carbon atoms, particularly n-nonanal, can be suppressed. The temperature for foaming the crosslinked foamable sheet is more preferably 180 to 270 ℃, still more preferably 200 to 260 ℃, and still more preferably 210 to 240 ℃.

The method for adjusting the temperature is not particularly limited, and hot air or infrared rays may be used.

The crosslinked foamable sheet may be stretched in either or both of the MD direction and the CD direction after foaming or while foaming.

[ formed article ]

The molded article obtained by molding the polyolefin resin foam of the present invention is obtained by molding the polyolefin resin foam of the present invention by a known method. In the production of the molded article, other materials such as a base material and a skin material may be laminated on the polyolefin resin foam and then bonded. The molded article of the present invention is preferably obtained by laminating a skin material on a polyolefin resin foam.

Examples of the skin material include a polyvinyl chloride sheet, a sheet containing a mixed resin of polyvinyl chloride and an ABS resin, a thermoplastic elastomer sheet, a woven fabric, a knitted fabric, a nonwoven fabric, a leather such as artificial leather or synthetic leather using natural fibers or artificial fibers, and a metal. Further, a molded body having a design such as a skin hole or a wood grain pattern on the surface thereof, such as a silicone stamper having irregularities transferred from natural leather, stone, wood, or the like, may be used.

The skin material is laminated to the polyolefin resin foam and molded, whereby a molded article having the skin material laminated to the polyolefin resin foam can be obtained.

Examples of the method for bonding the skin material include extrusion lamination, adhesive lamination after applying an adhesive, heat lamination (heat fusion method), hot melt method, high frequency welding method, electroless plating method for metals and the like, electrolytic plating method, vapor deposition method, and the like, and any method may be used as long as both methods are bonded.

The base material is a skeleton of the molded body, and a thermoplastic resin is generally used. As the thermoplastic resin for the substrate, the above-mentioned polyolefin resin, copolymer of ethylene and α -olefin, vinyl acetate, acrylic ester, etc., ABS resin, polystyrene resin, etc. can be used.

Examples of the molding method of the molded article of the present invention include a press molding method, a vacuum molding method, a compression molding method, an injection molding method, and the like. Among these, press forming and vacuum forming are preferable. As the vacuum forming method, either of a punch vacuum forming method and a die vacuum forming method can be used, and a punch vacuum forming method is more preferable.

The molded article obtained by molding the polyolefin resin foam of the present invention can be used as a heat insulator, a cushion material, or the like. The molded article obtained by molding the polyolefin resin foam of the present invention hardly generates irritating gases even in hot summer, and is suitable for use as an automobile interior material such as a roof material, a door, and an instrument panel, particularly in the automobile field.