JP7323313B2 - Crosslinked polyolefin resin foam sheet and molding - Google Patents

Description

The present invention relates to a crosslinked polyolefin resin foam sheet and molded article.

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.
By the way, since the polyolefin resin has no polarity, it is necessary to subject the crosslinked polyolefin resin foam to surface treatment such as corona treatment in order to impart adhesiveness. Therefore, when laminating a skin material on one side of the crosslinked polyolefin resin foam and an aggregate on the other side in order to use the crosslinked polyolefin resin foam as an interior material, both sides of the crosslinked polyolefin resin foam are laminated. It was thought that corona treatment was necessary.
In addition, crosslinked polyolefin resin foams are often produced by heating and foaming a composition containing a polyolefin resin and a foaming agent. Sometimes. 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 suppressing the odor of crosslinked polyolefin resin foams, for example, a method using a deodorant such as activated carbon (Patent Document 1) and a method using carbon black or the like as an odor suppressant (Patent Document 2) are known. there is

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

However, for example, in automobiles equipped with automobile interior materials made of crosslinked polyolefin resin foam molded articles, especially during hot summer months, there is a problem that odors cannot be sufficiently reduced even by using conventional techniques. There is
Accordingly, an object of the present invention is to provide a crosslinked polyolefin resin foam sheet capable of reducing the generation of odors, and a molded article obtained by molding the crosslinked polyolefin resin foam sheet.

The inventors of the present invention have made intensive studies to achieve the above object, and found that the odor generated from the crosslinked polyolefin resin foam sheet, especially during the hot summer season, is an aldehyde having 6 to 11 carbon atoms. We found that it was caused by a compound. Furthermore, the present inventors have found that the generation of the aldehyde compound is accelerated when the crosslinked polyolefin resin foam sheet is subjected to surface treatment in order to impart adhesiveness to the crosslinked polyolefin resin foam sheet. Based on such findings, the present inventors have performed surface treatment on only one side of the crosslinked polyolefin resin foam sheet, and have also performed an aldehyde compound having 6 to 11 carbon atoms released from the crosslinked polyolefin resin foam. The inventors have found that the generation of odor can be reduced by reducing the release amount of , and completed the present invention.
That is, the present invention relates to the following [1] to [11].
[1] A crosslinked polyolefin resin foam sheet having a first surface and a second surface opposite to the first surface, wherein the wet tension of the first surface is 34 mN/m or more, The wetting tension of the second surface is less than 34 mN/m, and 5 L of nitrogen is added to a 10 L sampling bag containing two of the crosslinked olefin resin foam sheets having dimensions of 100 mm x 100 mm x 3.0 ± 0.2 mm. After filling the gas, the concentration of the aldehyde compound having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas obtained by heating the sampling bag at a heating temperature of 80 ° C. for 2 hours is 0.2 ppm by volume or less. A crosslinked polyolefin resin foam sheet.
[2] The crosslinked polyolefin resin foam sheet according to [1] above, wherein the concentration of n-nonyl aldehyde in the aldehyde compound-containing nitrogen gas is 0.07 ppm by volume or less.
[3] The crosslinked polyolefin resin foam according to [1] or [2] above, wherein the surface roughness of the first surface is 45 μm or less in terms of arithmetic mean roughness Ra and 360 μm or less in terms of maximum height Rz. sheet.
[4] The crosslinked polyolefin resin foam sheet according to any one of [1] to [3] above, which is formed by foaming a foamable composition containing a polyolefin resin.
[5] The crosslinked polyolefin resin foam sheet according to [4] above, wherein the content of the polypropylene resin in the polyolefin resin is 5 to 85% by mass.
[6] The crosslinked polyolefin resin foam sheet according to [4] above, wherein the foamable composition contains 0.1 to 5.0 parts by mass of an antioxidant with respect to 100 parts by mass of the polyolefin resin.
[7] The crosslinked polyolefin resin foam sheet according to any one of [1] to [6] above, which has an apparent density of 20 to 100 kg/m ³ .
[8] The crosslinked polyolefin resin foam sheet according to any one of [1] to [7] above, which has a closed cell content of 80 to 100%.
[9] A molded article obtained by molding the crosslinked polyolefin resin foam sheet according to any one of [1] to [8] above.
[10] The molded article according to [9] above, wherein a skin material is laminated on the crosslinked polyolefin resin foam sheet.
[11] The molded article according to [9] or [10] above, which is an automotive interior material.

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

[Crosslinked polyolefin resin foam sheet]
The crosslinked polyolefin resin foam sheet of the present invention has a first surface and a second surface opposite to the first surface, the first surface has a wet tension of 34 mN/m or more, and the second surface has a wet tension of 34 mN/m or more. is less than 34 mN/m. Further, in the crosslinked polyolefin resin foam sheet of the present invention, the concentration of the aldehyde compound having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is 0.2 volume ppm or less. The aldehyde compound-containing nitrogen gas is a 10 L sampling bag containing two crosslinked olefin resin foam sheets with dimensions of 100 mm × 100 mm × 3.0 ± 0.2 mm. It is a gas obtained by heating the bag at a heating temperature of 80° C. for 2 hours. More specifically, it is an aldehyde compound-containing nitrogen gas obtained by the method of Examples described later. Odor generation from the crosslinked polyolefin resin foam sheet can thereby be reduced. The crosslinked polyolefin resin foam sheet (hereinafter sometimes simply referred to as foam sheet) of the present invention will be described in detail below.

(wet tension)
The foam sheet of the present invention has a first surface and a second surface opposite to the first surface, the first surface has a wet tension of 34 mN / m or more, and the second surface has a wet tension of 34 mN / m or more. Wetting tension is less than 34 mN/m. By the way, since the wet tension of polyolefin resins such as polyethylene and polypropylene is about 30 mN/m, the wet tension of the surface of the foam sheet without surface treatment is less than 34 mN/m. Therefore, by surface-treating the first surface of the foam sheet, the wet tension of the first surface of the foam sheet can be 34 mN/m or more, and the second surface is surface-treated. Wetting tension of the second surface can be less than 34 mN/m. Wetting tension can be measured according to JIS K6768.
The first surface of the foam sheet has a wet tension of 34 mN/m or more and the second surface of the foam sheet has a wet tension of less than 34 mN/m, that is, the first surface of the foam sheet is surface-treated. By not performing surface treatment on the second surface, oxidation of the foam sheet due to surface treatment can be suppressed. In addition, generation of aldehyde compounds having 6 to 11 carbon atoms, which cause odor, can be suppressed.

The wet tension of the first surface of the foam sheet of the present invention is 34 mN/m or more. If the wet tension of the first surface of the foam sheet is less than 34 mN/m, the first surface may not be completely wetted by adhesives, primers, etc. Adhesion between the body sheets may be insufficient. From such a viewpoint, the wet tension of the first surface of the foam sheet is preferably 36 mN/m or more, more preferably 38 mN/m or more, and still more preferably 40 mN/m or more. The upper limit of the range of wet tension of the first surface of the foam sheet is not particularly limited, but is, for example, 58 mN/m.

The wetting tension of the second side of the foam sheet of the present invention is less than 34 mN/m. If the second surface of the foam sheet has a wet tension of 34 mN/m or more, the second surface is also surface-treated, which may increase the generation of odor from the foam sheet. From this point of view, the wet tension of the second surface of the foam sheet is preferably 33 mN/m or less, more preferably 32 mN/m or less. Although the lower limit of the wet tension range of the second surface of the foam sheet is not particularly limited, it is 30 mN/m because the wet tension of the polyolefin resin is about 30 mN/m as described above.

(surface treatment)
As described above, by surface-treating the first surface of the foam sheet, the wet tension of the first surface can be increased to 34 mN/m or more. The surface treatment applied to the first surface of the foam sheet is not particularly limited as long as the wet tension of the first surface can be 34 mN/m or more. Examples of surface treatment methods for the first surface of the foam sheet include corona treatment, low pressure plasma treatment, atmospheric pressure plasma treatment, and the like. Among these surface treatments, the energy supply source is electric power, it is easy to control, and it is an apparatus and is easy to adopt industrially. Therefore, the surface treatment method for the first surface of the foam sheet is Corona treatment is preferred.

Corona treatment is performed by passing a sample between electrodes using alternating current power, which is usually a few millimeters apart, by causing an electrical discharge between the electrodes. For this reason, samples are limited to films or sheets. Devices are commercially available with a voltage between the electrodes of 15-50 kV and an alternating frequency of ˜45 kHz.

Corona treatment is usually carried out in air. Since the resin molecules of the foam sheet hardly bond with nitrogen in the atmosphere and bond only with oxygen, the oxidation reaction progresses. As a result, functional groups such as peroxide groups, hydroxyl groups, carbonyl groups, carboxyl groups and epoxy groups are generated on the surface of the foam sheet. In addition, molecular cleavage occurs in the resin on the surface, and the resin on the surface is reduced in molecular weight. As a result, the molecular motion on the surface of the foam sheet becomes vigorous, and at the same time, volatile low-molecular-weight compounds are also generated. The formation of the functional group and the formation of the low-molecular-weight compound improve the wettability of the corona-treated surface of the foam sheet.

As noted above, corona treatment oxidizes the foam sheet. Therefore, by performing corona treatment on only one surface of the foam sheet, oxidation of the foam sheet can be suppressed as compared with the case where both surfaces of the foam are subjected to corona treatment. In addition, generation of aldehyde compounds having 6 to 11 carbon atoms, which cause odor, can be suppressed. In the past, it was not known that the corona treatment was the cause of the odor. was treated with corona.

(Content of aldehyde compound)
<Aldehyde compound having 6 to 11 carbon atoms>
In the foam sheet of the present invention, the total concentration of aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is 0.2 volume ppm or less. 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 ± 0.2 mm. is a gas obtained by heating at a heating temperature of 80° C. for 2 hours. More specifically, it is an aldehyde compound-containing nitrogen gas obtained by the method of Examples described later. If the total concentration of aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas exceeds 0.2 ppm by volume, the odor generated from the foam sheet becomes strong. The total concentration of the aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is preferably 0.15 volume ppm or less, more preferably 0.1 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 such a range, it is possible to further reduce the generation of odor from the foam sheet.

If the total concentration of aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas is within the above range, n-nonylaldehyde, n-octylaldehyde, n-heptylaldehyde and n - Each concentration of decyl aldehyde is not particularly limited. However, from the viewpoint of further reducing the odor generation of the foam sheet, the respective concentrations of n-nonylaldehyde, n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde in the aldehyde compound-containing nitrogen gas are as follows. is preferably within the range of

<n-nonyl aldehyde>
The foam sheet of the present invention is preferably a foam sheet in which the concentration of n-nonyl aldehyde in the aldehyde compound-containing nitrogen gas is 0.07 ppm by volume or less.
When the concentration of n-nonyl aldehyde in the aldehyde compound-containing nitrogen gas is 0.07 ppm by volume or less, the generation of odor from the foam sheet can be further reduced. The concentration of n-nonylaldehyde in the aldehyde compound-containing nitrogen gas is more preferably 0.05 ppm by volume or less, and even more preferably 0.03 ppm by volume or less. By setting the concentration of n-nonyl aldehyde in the aldehyde compound-containing nitrogen gas to such a range, it is possible to further reduce the generation of odor from the foam sheet.

<n-octylaldehyde>
The foam sheet of the present invention is preferably a foam sheet in which the concentration of n-octylaldehyde in the aldehyde compound-containing nitrogen gas is 0.03 ppm by volume or less.
When the concentration of n-octylaldehyde in the aldehyde compound-containing nitrogen gas is 0.03 ppm by volume or less, the generation of odor from the foam sheet can be further reduced. The concentration of n-octylaldehyde in the aldehyde compound-containing nitrogen gas is more preferably 0.02 ppm by volume or less, and even more preferably 0.017 ppm by volume or less. By setting the concentration of n-octylaldehyde in the aldehyde compound-containing nitrogen gas within this range, it is possible to further reduce the generation of odors from the foam sheet.

<n-heptylaldehyde>
In the foam sheet of the present invention, the concentration of n-heptylaldehyde in the aldehyde compound-containing nitrogen gas is preferably 0.03 ppm by volume or less.
When the concentration of n-heptylaldehyde in the aldehyde compound-containing nitrogen gas is 0.03 ppm by volume or less, the generation of odor from the foam sheet can be further reduced. The concentration of n-heptylaldehyde in the aldehyde compound-containing nitrogen gas is more preferably 0.02 ppm by volume or less, and even more preferably 0.018 ppm by volume or less. By setting the concentration of n-heptylaldehyde in the aldehyde compound-containing nitrogen gas to such a range, it is possible to further reduce the generation of odor from the foam sheet.

<n-decyl aldehyde>
In the foam sheet of the present invention, the concentration of n-decylaldehyde in the aldehyde compound-containing nitrogen gas is preferably 0.03 ppm by volume or less.
When the concentration of n-decyl aldehyde in the aldehyde compound-containing nitrogen gas is 0.03 ppm by volume or less, the generation of odor from the foam sheet can be further reduced. The concentration of n-decylaldehyde in the aldehyde compound-containing nitrogen gas is more preferably 0.02 ppm by volume or less, and even more preferably 0.017 ppm by volume or less. By setting the concentration of n-decyl aldehyde in the aldehyde compound-containing nitrogen gas to such a range, it is possible to further reduce the generation of odor from the foam sheet.

Among aldehyde compounds having 6 to 11 carbon atoms, the concentration of n-nonyl aldehyde within the above range is most effective for suppressing odor generation. From this point of view, as long as the n-nonylaldehyde in the aldehyde compound-containing nitrogen gas is within the above range, the concentrations of n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde are not within the above range. good. However, from the viewpoint of further suppressing the generation of odor, the n-nonylaldehyde in the aldehyde compound-containing nitrogen gas is within the above range, and the group consisting of n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde The concentration of at least one aldehyde compound selected from is preferably within the above range. Further, from the above viewpoint, the n-nonylaldehyde in the aldehyde compound-containing nitrogen gas is within the above range, and at least two selected from the group consisting of n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde is more preferably within the above range. Furthermore, from the above point of view, the concentration of n-nonylaldehyde, n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde in the aldehyde compound-containing nitrogen gas is more preferably within the above range.

The total concentration of aldehyde compounds having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas, and the concentrations of each of n-nonylaldehyde, n-octylaldehyde, n-heptylaldehyde and n-decylaldehyde is not particularly limited. Such methods include, for example, the blending amount of additives such as antioxidants and cross-linking aids in the foamable composition used for producing the foam sheet, and ionizing radiation during cross-linking of the foamable composition. , the temperature at which the foamable composition is foamed, the surface treatment conditions, and the like.

(Surface roughness)
The surface roughness of the first surface of the foam sheet of the present invention is preferably 45 μm or less in arithmetic mean roughness Ra. When the surface roughness of the first surface is 45 μm or less in arithmetic mean roughness Ra, the appearance of the first surface of the foam sheet is good. From this point of view, the surface roughness of the first surface of the foam sheet is more preferably 20 μm or less, still more preferably 10 μm or less, in terms of arithmetic mean roughness Ra. Although the lower limit of the range of surface roughness is not particularly limited, it is, for example, 1 μm. Further, the arithmetic mean roughness Ra is a value determined in accordance with JIS B0601 (2001), and specifically, it can be determined by the method described in Examples.

Furthermore, the surface roughness of the first surface of the foam sheet of the present invention is preferably 360 μm or less at maximum height Rz. When the surface roughness of the first surface is 360 μm or less at the maximum height Rz, the appearance of the first surface of the foam sheet is good. From such a point of view, the surface roughness of the first surface of the foam sheet is more preferably 280 μm or less, still more preferably 200 μm or less, in maximum height Rz. Although the lower limit of the range of surface roughness is not particularly limited, it is, for example, 10 μm. Further, the maximum height Rz is a value determined in accordance with JIS B0601 (2001), and specifically, it can be determined by the method described in Examples.

When a foam sheet is obtained by slicing the foam, the surface roughness of the sliced surface of the foam sheet has an arithmetic mean roughness Ra of more than 45 μm and a maximum height Rz of more than 360 μm. From this point of view, the surface roughness of the foam sheet is set to 45 μm or less in arithmetic mean roughness Ra and 360 μm or less in maximum height Rz by forming the foam sheet without slicing. be able to. In addition, by appropriately controlling the degree of cross-linking of the foamable composition used for producing the foam sheet, the dose of ionizing radiation during cross-linking, the expansion ratio (apparent density) of the foam sheet, etc., The surface roughness of the body sheet can be within the above range.

(apparent density)
The apparent density of the foam sheet of the present invention is preferably 20-100 kg/m ³ , more preferably 40-80 kg/m ³ . When the apparent density is 20 kg/m ³ or more, the mechanical strength of the foam sheet can be improved, and when the apparent density is 100 kg/m ³ or less, the flexibility of the foam sheet can be easily secured. . The apparent density of the foam sheet is measured by the method described in Examples below.

(thickness)
The thickness of the foam sheet of the present invention is preferably 1-15 mm, more preferably 2-10 mm. The thickness of the foam sheet is measured by the method described in Examples below.

(Closed cell rate)
The foam sheet of the present invention preferably has a closed cell rate of 80 to 100%. When the closed cell ratio is 80% or more, the cells contained inside the foam sheet are generally closed cells, and the cushioning properties are likely to be improved. As a result, the tactile sensation of other materials such as the skin material adhered to the foam sheet is improved. From this point of view, the closed cell ratio is more preferably 87 to 100%. The closed cell content can be obtained according to ASTM D2856 (1998).

More specifically, the closed cell content can be measured in the manner described below.
First, a flat square test piece with a side of 5 cm is cut out from the foam sheet. Then, the thickness of the test piece is measured to calculate the apparent volume V1 of the test piece, and the weight _W1 of the test piece is measured.
Next, the volume _V2 occupied by the bubbles is calculated based on the following formula. The density of the matrix resin constituting the test piece is ρ (g/cm ³ ).
Volume occupied by bubbles V ₂ = V ₁ - W ₁ /ρ
Subsequently, the test piece is submerged in distilled water at 23° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa is applied to the test piece for 3 minutes. Then, after releasing the pressure in water and standing for 1 minute, remove the test piece from the water and remove the moisture adhering to the surface of the test piece to measure the weight W ₂ of the test piece, based on the following formula Calculate the open cell rate F1 and closed cell rate _F2 .
Open cell rate F ₁ (%) = 100 × (W ₂ - W ₁ )/V ₂
Closed cell rate F ₂ (%) = 100 - F ₁

(Effervescent composition)
From the viewpoint of easily obtaining a foam sheet having the above-described aldehyde compound concentration, apparent density, thickness, etc., the foam sheet of the present invention is a foam obtained by foaming a foamable composition containing a polyolefin resin. Sheets are preferred.

<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 foam sheet.

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 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 according to JIS K7210.

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 according to JIS K7210.

When the polyolefin resin contains a polypropylene resin, the polypropylene resin is preferably 5% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass in the polyolefin resin from the viewpoint of improving heat resistance. More preferably, it contains 55% by mass or more. Further, from the viewpoint of improving flexibility, the polypropylene resin in the polyolefin resin is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less. contains.
When the polyolefin resin contains a polyethylene-based resin and a polypropylene-based resin, the amount of the polypropylene-based resin is preferably larger, and the polypropylene-based resin is preferable based on the total amount of the polyethylene-based resin and the polypropylene-based resin 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 foam sheet are improved.
In addition, the foamable composition may contain resins other than polyolefin resin, but the content of polyolefin resin is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably, based on the total resin. is 80% by mass or more, more preferably 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 foam sheet of the present invention, the blending amount of additives such as antioxidants and cross-linking aids in the foamable composition, the irradiation conditions of ionizing radiation during cross-linking of the foamable composition, and the By appropriately controlling the temperature during foaming, surface treatment conditions, etc., the production of aldehyde compounds with 6 to 11 carbon atoms is suppressed, and the generation of odor is reduced.

<Antioxidant>
The foamable composition used for the foam sheet of the present invention preferably contains an antioxidant. By containing an antioxidant, it is possible to suppress oxidation degradation of the polyolefin resin and to further reduce the release of aldehyde compounds having 6 to 11 carbon atoms from the foam sheet. The content of the antioxidant is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 3.0 parts by mass, based on 100 parts by mass of the polyolefin resin.
By adding 0.1 part by mass or more of the antioxidant to 100 parts by mass of the polyolefin resin, the oxidation deterioration of the polyolefin resin is further suppressed, and the release of aldehyde compounds having 6 to 11 carbon atoms from the foam sheet is suppressed. 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, phenolic antioxidants are preferred from the viewpoint of reducing the amount of aldehyde compounds having 6 to 11 carbon atoms released from the foam sheet.
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 used for the foam sheet of the present invention 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 release of linear aldehyde compounds having 6 to 11 carbon atoms, particularly n-nonyl aldehyde, from the foam. can. This is probably because the polyolefin resin is cross-linked to some extent, thereby suppressing deterioration due to heat and the like, and as a result, suppressing the production of aldehyde compounds having 6 to 11 carbon atoms. 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.
Further, by setting the amount of the antioxidant in the above range while setting the amount of the cross-linking aid in the foamable composition to the above range, the aldehyde compound having 6 to 11 carbon atoms is more effectively removed from the foam. can be further reduced.

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, and neopentyl glycol dimethacrylate.
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, from the viewpoint of reducing the release of aldehyde compounds having 6 to 11 carbon atoms from the foam, polyfunctional (meth)acrylate compounds are preferred, and bifunctional (meth)acrylate compounds are more preferred. - nonanediol dimethacrylate is more preferred.

<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. That is, the foamable composition used for the foam sheet of the present invention preferably contains a foaming agent.
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.
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(benzenesulfonylhydrazide), hydrazine derivatives such as toluenesulfonylhydrazide, semicarbazide compounds such as toluenesulfonylsemicarbazide, and the like.

Examples of inorganic foaming agents include ammonium carbonate, 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.

<Heavy metal deactivator>
The foamable composition used for the crosslinked polyolefin resin foam of the present invention may contain a heavy metal deactivator. By containing a heavy metal deactivator, it is possible to suppress oxidative deterioration of the polyolefin resin caused by heavy metal ions, thereby further reducing the release of aldehyde compounds having 6 to 11 carbon atoms from the crosslinked polyolefin resin foam. can. 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, based on 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 with respect to 100 parts by mass of the polyolefin resin, the oxidation deterioration of the polyolefin resin due to heavy metal ions is further suppressed, and the number of carbon atoms from the crosslinked polyolefin resin foam is reduced. The release of aldehyde compounds of 6-11 can be further reduced. Moreover, 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 excessive heavy metal deactivator from becoming an odorant.

Although the type of heavy metal deactivator is not particularly limited, examples thereof include oxalic acid derivatives, salicylic acid derivatives, hydrazide derivatives and the like. Among these, hydrazide derivatives are preferred from the viewpoint of being able to effectively reduce the release of aldehyde compounds having 6 to 11 carbon atoms from the crosslinked polyolefin resin foam.
Hydrazide derivatives include N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine and bis(2-phenoxypropionylhydrazide) isophthalate. Among these, N,N'-bis{3-(3,5-di-tert-butyl -4-Hydroxyphenyl)propionyl}hydrazine is preferred.
Heavy metal deactivators may be used alone or in combination of two or more.

<Other additives>
Additives commonly used for foams such as heat stabilizers, colorants, flame retardants, antistatic agents, fillers, rust inhibitors, and decomposition temperature regulators are added to the foamable composition as necessary. may be blended.

[Method for producing crosslinked polyolefin resin foam sheet]
The method for producing a foam sheet of the present invention includes steps 1 to 4 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 3) Step of foaming the crosslinked foam sheet to produce a crosslinked polyolefin resin foam sheet (Step 4) The crosslinked foam sheet being foamed or the crosslinked polyolefin resin foam sheet obtained in Step 3 Surface treatment process

(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 preferably contains an antioxidant, a heavy metal deactivator, a cross-linking aid, a foaming agent, etc., as described above.

(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 ionizing radiation is preferably 1.2 to 2.5 Mrad, more preferably 1.2 to 2.5 Mrad, from the viewpoint of reducing the release of aldehyde compounds having 6 to 11 carbon atoms from the foam. It is 3 to 2.3 Mrad, more preferably 1.4 to 2.1 Mrad.
From the viewpoint of further reducing the amount of aldehyde compounds having 6 to 11 carbon atoms released from the foam sheet, the amount of the cross-linking aid in the foamable composition is adjusted to the above range, and the ionizing radiation irradiation conditions are set to the above range. A range is preferred.
Ionizing radiation irradiation may be performed on one surface of the foam sheet or may be performed on both surfaces. From the viewpoint of further reducing
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. A temperature of 160° C. or higher facilitates the progress of foaming, and a temperature of 280° C. or lower can suppress the formation of aldehyde compounds having 6 to 11 carbon atoms in the foam sheet. 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.

(Step 4)
Step 4 is a step of surface-treating the crosslinked expandable sheet being foamed or the crosslinked polyolefin resin foam sheet obtained in Step 3. That is, in step 4, the surface treatment may be performed while foaming the crosslinkable foamable sheet, or the surface treatment may be performed after foaming the crosslinkable foamable sheet. A preferred surface treatment in step 4 is corona treatment. The amount of discharge during corona treatment is preferably 20 to 90 W·min/m ² , more preferably 25 to 85 W·min/m ² .

[Molded body]
The molded article of the present invention is obtained by molding the foam sheet of the present invention. The molded article of the present invention is obtained by molding the foam sheet of the present invention by a known method. When manufacturing a molded article, it is possible to manufacture the molded article by laminating another material such as a skin material to the foam sheet. Moreover, when manufacturing a molded article, the foam sheet and the base material can be integrally molded by injection molding. The molded article of the present invention preferably comprises a foam sheet with a skin material laminated on the first surface and a base material laminated on the second surface.

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. Alternatively, a molded body 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 foam sheet and molding, it is possible to obtain a molded body in which the skin material is laminated on the foam sheet.
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. However, the adhesive lamination method is preferable from the viewpoint that the skin material can be easily attached to the molded foam sheet.

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 substrate, the above-mentioned polyolefin resin, copolymer of ethylene and α-olefin, vinyl acetate, acrylic acid ester, etc., ABS resin, polystyrene resin, and the like can be applied. For example, the substrate can be laminated to the foam sheet by injection molding a thermoplastic resin onto the second side of the foam sheet.

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 foam sheet of the present invention can be used as a heat insulating material, a cushioning material, and the like. Molded articles obtained by molding the foam sheet of the present invention are suitable for automobile interior materials such as ceiling materials, door trims, instrument panels, etc., especially in the automobile field, because odors are less likely to occur even in hot summer months. can be used for

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)
A foamable composition obtained by mixing 60 parts by mass of a polypropylene resin, 40 parts by mass of a linear low-density polyethylene, 0.5 parts by mass of a phenolic antioxidant, 3 parts by mass of a cross-linking aid, and 8 parts by mass of a foaming agent. The material 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 is supplied to a vertical hot air foaming furnace having an internal temperature of 250° C. equipped with a corona treatment device, and heated while being stretched and subjected to corona treatment with a discharge amount of 45 W min/m ² . Foaming was performed to obtain the desired foam sheet.
The foam sheet was evaluated for thickness, apparent density, wet tension, aldehyde concentration, odor evaluation, adhesion evaluation, and appearance evaluation 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.)
· Foaming 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”

(Examples 2-3, Comparative Examples 1-3)
Foam sheets of Examples 2 and 3 and Comparative Examples 1 and 3 were obtained in the same manner as in Example 1, except that the composition of the foamable composition and the corona treatment conditions were 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.

(Closed cell rate)
The closed cell ratios of the foams of Examples and Comparative Examples were obtained according to ASTM D2856 (1998). Specifically, it was measured as described in the description of the item of closed cell content above.

(Wetting tension of foam)
The wet tension of the foams of Examples and Comparative Examples was measured according to JIS K6768.

(Surface roughness of foam)
The surface roughness of the foam was determined according to JIS B0601 (2001). Specifically, using a laser microscope "VK-X100" manufactured by Keyence Corporation, the surface of the resin foam sheet was photographed at a magnification of 10 times, and then analyzed using the attached analysis application. A measurement line with a length of 1 mm was set at an arbitrary position on the photographed screen, and the line roughness curve of that portion was measured. Next, the obtained curve was analyzed under the following conditions to calculate the maximum height Rz and the arithmetic mean roughness Ra at the arbitrary position. Furthermore, similar measurements were performed at three arbitrary locations on the foamed resin sheet, and the average value was taken as the maximum height Rz and the arithmetic mean roughness Ra of the foamed resin sheet.
<Analysis conditions>
・Light intensity smoothing: none ・Height smoothing: simple average of ±12 ・Tilt correction: none ・Cutoff by phase compensation reduction filter: λs 25 μm, λc none

(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, thermal desorption was performed using a thermal desorption apparatus (manufactured by GL Sciences, trade name "HandyTD TD265"). Then, a gas chromatograph (manufactured by GL Sciences Co., Ltd., trade name "GC-4000Plus (A type)") is introduced into an odor sniffing system (manufactured by GL Sciences Co., Ltd., trade name "OPV277") 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

Gas chromatographic detection peaks of n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde and n-undecanealdehyde were detected. Incidentally, n-hexylaldehyde is a linear aldehyde compound having 6 carbon atoms, and n-heptylaldehyde is a linear aldehyde compound having 7 carbon atoms. n-octylaldehyde is a straight-chain aldehyde compound with 8 carbon atoms, and n-nonylaldehyde is a straight-chain aldehyde compound with 9 carbon atoms. The n-decyl aldehyde is a linear aldehyde compound with 10 carbon atoms, and the n-undecane aldehyde compound is a linear aldehyde compound with 11 carbon atoms. The total concentration of n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde and n-undecanealdehyde was defined as the concentration of aldehyde compounds having 6 to 11 carbon atoms.

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 n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde and n-undecanealdehyde was sampled using an electronic balance and charged 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 collecting 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 from 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 1.4ml/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

(Adhesion between skin material and first surface of foam)
A skin material (polyvinyl chloride sheet) was adhered to the first surface of the foam sheet using an adhesive (manufactured by Hitachi Chemical Co., Ltd., trade name: Hibon YA1212). And it evaluated as follows.
◯: The first surface of the foam sheet could be completely wetted with the adhesive, and the skin material could be sufficiently adhered to the first surface of the foam.
x: The first surface of the foam sheet could not be sufficiently wetted with the adhesive, and the skin material could not be sufficiently adhered to the first surface of the foam.

(Appearance of skin material bonded to foam)
The skin material attached to the first surface of the foam was visually observed, and whether or not the roughness of the first surface poses a problem for the appearance of the skin material was evaluated according to the following criteria.
◯: Roughness of the first surface of the foam sheet is at a practically acceptable level.
x: The first surface of the foam sheet is rough and is at a level that poses a practical problem.

Table 1 shows the foam thickness, apparent density, closed cell ratio, aldehyde compound analysis results, and odor evaluation results.

From the results of the above examples, the wetting tension of the first surface is set to a predetermined value or more, the wetting tension of the second surface is set to a predetermined value or less, and the concentration of the aldehyde compound having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas The foam sheet of the present invention with a constant value or less gave good results in odor evaluation. In addition, the foam sheet of Comparative Example 3, in which both the first surface and the second surface had low wet tension, gave good results in the odor evaluation, but had poor adhesion to the skin material. Therefore, it is considered that the foam sheet of Comparative Example 3 is not suitable for use as an automobile interior material.

Claims (11)

A crosslinked polyolefin resin foam sheet having a first surface and a second surface opposite to the first surface,
Wetting tension of the first surface is 34 mN/m or more,
Wetting tension of the second surface is less than 34 mN/m,
The wetting tension is measured according to JIS K6768,
After filling a 10 L sampling bag containing two crosslinked olefin resin foam sheets with dimensions of 100 mm × 100 mm × 3.0 ± 0.2 mm with 5 L of nitrogen gas, the sampling bag was heated at a heating temperature of 80 ° C. A crosslinked polyolefin resin foam sheet in which the concentration of an aldehyde compound having 6 to 11 carbon atoms in the aldehyde compound-containing nitrogen gas obtained by heating for 2 hours is 0.2 volume ppm or less. 2. The crosslinked polyolefin resin foam sheet according to claim 1, wherein the concentration of n-nonylaldehyde in the aldehyde compound-containing nitrogen gas is 0.07 volume ppm or less. 3. The crosslinked polyolefin resin foam sheet according to claim 1, wherein the surface roughness of said first surface is 45 [mu]m or less in terms of arithmetic mean roughness Ra and 360 [mu]m or less in terms of maximum height Rz. The crosslinked polyolefin resin foam sheet according to any one of claims 1 to 3, which is obtained by foaming a foamable composition containing a polyolefin resin. 5. The crosslinked polyolefin resin foam sheet according to claim 4, wherein the content of the polypropylene resin in the polyolefin resin is 5 to 85% by mass. 5. The crosslinked polyolefin resin foam sheet according to claim 4, wherein the foamable composition contains 0.1 to 5.0 parts by mass of an antioxidant with respect to 100 parts by mass of the polyolefin resin. The crosslinked polyolefin resin foam sheet according to any one of claims 1 to 6, having an apparent density of 20 to 100 kg/m ³ . The crosslinked polyolefin resin foam sheet according to any one of claims 1 to 7, which has a closed cell rate of 80 to 100%. A molded article obtained by molding the crosslinked polyolefin resin foam sheet according to any one of claims 1 to 8. 10. The molded article according to claim 9, wherein the skin material is laminated on the crosslinked polyolefin resin foam sheet. The molded article according to claim 9 or 10, which is an automobile interior material.