阅读说明：本技术 交联聚烯烃系树脂发泡体 (Crosslinked polyolefin resin foam ) 是由 宇野拓明 杉江幸弘 三上洋辉 于 2019-09-26 设计创作，主要内容包括：提供即使不混配特别的添加剂,也抑制雾化的交联聚烯烃系树脂发泡体。交联聚烯烃系树脂发泡体是将聚烯烃系树脂组合物交联并发泡而成的交联聚烯烃系树脂发泡体,通过热脱附气相色谱质谱法测得的提取离子色谱值在10～15分钟的强度峰为200,000以下。优选聚烯烃系树脂组合物中含有的树脂中,50质量％以上为聚丙烯系树脂,聚烯烃系树脂组合物中含有的发泡剂为偶氮二甲酰胺。(Provided is a crosslinked polyolefin resin foam wherein fogging is suppressed without adding any special additive. The crosslinked polyolefin resin foam is obtained by crosslinking and foaming a polyolefin resin composition, and has an intensity peak at 10 to 15 minutes of an extracted ion chromatogram value measured by thermal desorption gas chromatography-mass spectrometry of 200,000 or less. Preferably, 50% by mass or more of the resins contained in the polyolefin resin composition are polypropylene resins, and the foaming agent contained in the polyolefin resin composition is azodicarbonamide.)

1. A crosslinked polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin composition, wherein the crosslinked polyolefin resin foam has an intensity peak of 200,000 or less at an extracted ion chromatographic value of 10 to 15 minutes as measured by thermal desorption gas chromatography-mass spectrometry.

2. The crosslinked polyolefin resin foam according to claim 1, wherein the density of the foam is 0.02 to 0.2g/cm³。

3. The crosslinked polyolefin resin foam according to claim 1 or 2, which is a sheet having a thickness of 2 to 4 mm.

4. The crosslinked polyolefin resin foam according to any one of claims 1 to 3, wherein 50% by mass or more of the resins contained in the polyolefin resin composition are polypropylene resins.

5. The crosslinked polyolefin resin foam according to any one of claims 1 to 4, wherein the polyolefin resin composition contains azodicarbonamide.

6. The crosslinked polyolefin resin foam according to any one of claims 1 to 5, which is a sheet, and the peak strength/sheet thickness is 65,000 or less, and the unit of thickness is mm.

Technical Field

The present invention relates to a crosslinked polyolefin resin foam which suppresses fogging.

Background

In automobile interior materials such as a roof material, a door, and an instrument panel, a crosslinked polyolefin resin foam subjected to secondary processing is widely used. In the production of crosslinked polyolefin resin foams, a thermally decomposable foaming agent such as azodicarbonamide is generally used as the foaming agent. The thermal decomposition type foaming agent causes a trace amount of decomposition residue to remain in the resin after foaming, but a part of the decomposition residue has sublimability and thus may cause fogging. Fogging is a phenomenon in which a minute amount of sublimates generated from a resin material or a resin foam used as an interior material adheres to the inner surface of a windshield or the like, thereby causing clouding.

Conventionally, in order to prevent fogging caused by azodicarbonamide, a foaming agent composition in which at least 1 selected from the group consisting of basic magnesium compounds and basic calcium compounds is blended with azodicarbonamide has been studied (for example, see patent document 1). However, in the polyolefin resin foam formed from the foaming agent composition of patent document 1, large bubbles are generated, and the appearance of the foam is likely to deteriorate. Thus, for example, patent document 2 has studied to blend basic magnesium having an average particle diameter of 0.1 to 15 μm with azodicarbonamide in a polyolefin resin composition (for example, see patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3532791

Patent document 2: international publication No. 2016/158701 pamphlet

Disclosure of Invention

Problems to be solved by the invention

Although there is a demand for crosslinked polyolefin resin foams in which fogging is suppressed even without compounding a specific basic compound as described in patent documents 1 and 2, such crosslinked polyolefin resin foams have not been provided.

Means for solving the problems

The present inventors have further studied a crosslinked polyolefin resin foam in which fogging is suppressed even without adding a specific additive. As a result, they have found that a crosslinked polyolefin resin foam having a specific intensity peak of a certain value or less as measured by thermal desorption gas chromatography-mass spectrometry is a foam for suppressing fogging, and have completed the present invention.

The present invention provides the following crosslinked polyolefin resin foam.

[1] A crosslinked polyolefin resin foam which is obtained by crosslinking and foaming a polyolefin resin composition and which has an intensity peak of 200,000 or less at 10 to 15 minutes as measured by thermal desorption gas chromatography-mass spectrometry.

[2]According to [1]The crosslinked polyolefin resin foam has a density of 0.02 to 0.2g/cm³。

[3] The crosslinked polyolefin resin foam according to [1] or [2], which is a sheet having a thickness of 2 to 4 mm.

[4] The crosslinked polyolefin resin foam according to any one of [1] to [3], wherein 50% by mass or more of the resins contained in the polyolefin resin composition is a polypropylene resin.

[5] The crosslinked polyolefin resin foam according to any one of [1] to [4], wherein the polyolefin resin composition contains azodicarbonamide.

[6] The crosslinked polyolefin resin foam according to any one of [1] to [5], which is a sheet, and has a strength peak/thickness (mm) of 65,000 or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a crosslinked polyolefin resin foam which is inhibited from fogging.

Detailed Description

The present invention will be described in detail below with reference to embodiments.

The crosslinked polyolefin resin foam of the present invention (hereinafter, may be simply referred to as "foam") is obtained by crosslinking and foaming a polyolefin resin composition containing a polyolefin resin (hereinafter, may be simply referred to as "resin composition"). Hereinafter, each component contained in the resin composition will be described in detail.

The polyolefin resin composition contains a polyolefin resin such as a polypropylene resin or a polyethylene resin.

Specific examples of the polypropylene-based resin include homopolypropylene as a homopolymer of propylene and a copolymer of propylene and an α -olefin other than propylene. Specific examples of the copolymer of propylene and an α -olefin other than propylene are a block copolymer, a random copolymer, and a random block copolymer, but a random copolymer (i.e., random polypropylene) is preferable.

Specific examples of the α -olefin other than propylene include α -olefins having about 4 to 10 carbon atoms such as ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene having 2 carbon atoms. Among them, ethylene is preferable from the viewpoint of moldability and heat resistance. In addition, in the copolymer, these alpha-olefins can be used alone or in combination of 2 or more.

The polypropylene resin may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The random polypropylene is preferably obtained by copolymerizing 50 mass% or more and less than 100 mass% of propylene with 50 mass% or less of an α -olefin other than propylene. Here, the amount of propylene is more preferably 80 to 99.9% by mass, the amount of α -olefin other than propylene is 0.1 to 20% by mass, still more preferably 90 to 99.5% by mass, the amount of α -olefin other than propylene is 0.5 to 10% by mass, particularly preferably 95 to 99% by mass, and the amount of α -olefin other than propylene is 1 to 5% by mass, based on the total monomer components constituting the copolymer.

Specific examples of the polyethylene resin include a low-density polyethylene resin, a medium-density polyethylene resin, a high-density polyethylene resin, and a linear low-density polyethylene resin. Among them, linear low-density polyethylene resins (LLDPE) are preferable.

The linear low-density polyethylene resin has a density of 0.910g/cm³Above and less than 0.950g/cm³Preferably a polyethylene having a density of 0.910g/cm³Above and 0.930g/cm³The following are providedPolyethylene. By containing a linear low-density polyethylene resin having a low density in the foam, the foam is likely to have good processability when the resin composition is processed into a foam, moldability when the foam is molded into a molded article, and the like. The density of the linear low-density polyethylene resin was measured according to JIS K7112.

The linear low-density polyethylene is generally a copolymer of ethylene and a small amount of α -olefin, the copolymer having ethylene as a main component (50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more of the total monomers). Specific examples of the α -olefin include α -olefins having 3 to 12 carbon atoms, preferably 4 to 10 carbon atoms, specifically 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene. In addition, in the copolymer, these alpha-olefins can be used alone or in combination of 2 or more.

Further, the polyethylene resin may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The composition may contain the polypropylene-based resin, the polyethylene-based resin, or a mixture thereof, and may contain a polyolefin-based resin component other than the polypropylene-based resin and the polyethylene-based resin.

Specific examples of such a resin component include ethylene-propylene-rubber (EPR), ethylene-propylene-diene rubber (EPDM), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- (meth) alkyl acrylate copolymer, modified copolymer obtained by copolymerizing maleic anhydride with these, polyolefin-based thermoplastic elastomer, and the like.

The resin contained in the resin composition may be composed of a polyolefin resin alone, but may contain a resin component other than the polyolefin resin within a range not impairing the object of the present invention.

The polyolefin resin is contained in an amount of usually 70% by mass or more, preferably 80 to 100% by mass, more preferably 90 to 100% by mass, based on the total amount of the resin contained in the resin composition.

The resin contained in the resin composition preferably contains the polypropylene-based resin in an amount of 50% by mass or more, more preferably 55 to 90% by mass, based on the total amount of the resin contained in the resin composition.

If the resin contained in the resin composition is a polypropylene-based resin as a main component, the foam obtained by crosslinking and foaming the resin composition can have good mechanical strength, heat resistance, and the like. Further, if the polypropylene resin is used as a main component, high-temperature heating is required during foaming of the resin composition, and impurities are generated from the foaming agent, which causes fogging. In the present invention, the strength peak of the extracted ion chromatogram, which will be described later, in 10 to 15 minutes is 200,000 or less by appropriately adjusting the production conditions and the like, whereby fogging can be suppressed even when a polypropylene-based resin is used as a main component.

The resin composition preferably contains the polyethylene resin as a polyolefin resin in addition to the polypropylene resin. In this case, the preferable content of the polyethylene resin is 1 to 50% by mass, and more preferably 10 to 45% by mass, based on the total amount of the resins contained in the resin composition.

The resin composition, when containing a polyethylene resin in addition to a polypropylene resin, has improved mechanical strength, heat resistance, etc., and also has good processability and moldability.

As a method of foaming the resin composition, there is a chemical foaming method. The chemical foaming method is a method of forming bubbles by gas generated from a foaming agent added to a resin composition. As the foaming agent, a thermal decomposition type foaming agent is used, and for example, an organic thermal decomposition type foaming agent or an inorganic thermal decomposition type foaming agent having a decomposition temperature of about 160 to 270 ℃ is used.

Specific examples of the organic thermal decomposition type foaming agent include azodicarbonamide, metal salts of azodicarboxylic acid (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.

Specific examples of the inorganic thermal decomposition type foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, monosodium citrate anhydride, and the like.

Among them, from the viewpoint of obtaining fine bubbles and from the viewpoint of economy and safety, an organic thermal decomposition type foaming agent is preferable, an azo compound or a nitroso compound is more preferable, an azo compound such as azodicarbonamide or azobisisobutyronitrile is further more preferable, and azodicarbonamide is particularly preferable.

These blowing agents may be used alone, or 2 or more kinds may be used in combination.

The amount of the organic thermal decomposition type foaming agent to be mixed in the resin composition is preferably 2 to 20 parts by mass, more preferably 3 to 12 parts by mass, per 100 parts by mass of the resin in the resin composition. When the mixing amount of the organic thermal decomposition type foaming agent is within this range, the foamability of the foamable polyolefin resin sheet is improved, and a crosslinked polyolefin resin foamed sheet having a desired expansion ratio is obtained.

The resin composition may contain an additive in addition to the olefin resin and the blowing agent. Preferable additives contained in the resin composition include a crosslinking assistant and an antioxidant. They may be contained in both or only one of them.

As the crosslinking assistant, a polyfunctional monomer may be used. Specific examples of the polyfunctional monomer include 3-functional (meth) acrylate compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate, triallyl trimellitate, triallyl 1,2, 4-benzenetricarboxylate, triallyl isocyanurate, 1, 6-hexanediol dimethacrylate, 1, 9-nonanediol dimethacrylate, 1, 10-decanediol dimethacrylate, 2-functional (meth) acrylate compounds such as neopentyl glycol dimethacrylate, 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. The crosslinking assistant may be used alone or in combination of 2 or more. Among them, a 3-functional (meth) acrylate compound is more preferable.

By adding the crosslinking aid to the resin composition, the resin composition can be crosslinked with a small ionizing radiation dose. Therefore, the resin molecules can be prevented from being cut or deteriorated due to the irradiation of the ionizing radiation.

The crosslinking assistant is preferably contained in an amount of 0.2 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and still more preferably 1 to 5 parts by mass, based on 100 parts by mass of the resin in the resin composition. When the content of the crosslinking assistant is 0.2 parts by mass or more, the degree of crosslinking can be easily adjusted to a desired degree when the resin composition is foamed. In addition, if the weight of 10 parts by weight or less, to impart resin composition crosslinking degree control becomes easy.

Specific examples of the antioxidant include phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, amine-based antioxidants and the like. Among them, preferred are phenol-based antioxidants and sulfur-based antioxidants, and more preferred is a combination of a phenol-based antioxidant and a sulfur-based antioxidant.

Specific examples of the phenolic antioxidant 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. These phenolic antioxidants may be used alone, or 2 or more of them may be used in combination.

Specific examples of the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, and pentaerythrityl tetrakis (3-laurylthiopropionate). These sulfur-based antioxidants may be used alone, or 2 or more of them may be used in combination.

The antioxidant is preferably contained in an amount of 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, based on 100 parts by mass of the resin in the resin composition.

The resin composition may contain, if necessary, additives other than the above additives, such as a decomposition temperature regulator such as zinc oxide or zinc stearate, a flame retardant, a metal damage preventing agent, an antistatic agent, a stabilizer, a filler, and a pigment.

The foam of the present invention has an intensity peak at 10 to 15 minutes of an extracted ion chromatography value measured by a thermal desorption gas chromatography-mass spectrometry (GC/MS) method of 200,000 or less. The intensity peak is preferably 190,000 or less, more preferably 180,000 or less, and still more preferably 170,000 or less. If the above-mentioned intensity peak is larger than 200,000, the foam is liable to undergo fogging.

The method for adjusting the intensity peak to 200,000 or less is not particularly limited, and for example, the intensity peak can be reduced by reducing the thickness of the foam. When the foam is thick, the strength peak can be lowered by subjecting the foam to a predetermined heat treatment as described later.

The density (apparent density) of the foam of the present invention is not particularly limited. In order to achieve a good balance between flexibility and strength of the foam, the density is preferably 0.02 to 0.20g/cm³More preferably, the density is 0.03 to 0.15g/cm³. Further, if the density of the foam is decreased as described above, that is, if the expansion ratio is increased, the amount of the foaming agent used is increased, and the foam is likely to be atomized.

The degree of crosslinking of the foam of the present invention is not particularly limited, but in order to balance the mechanical strength, flexibility and moldability well, the degree of crosslinking is preferably 30 to 60%, and more preferably 32 to 55%. The method of measuring the degree of crosslinking of the foam is as described in the examples below.

One embodiment of the foam of the present invention is a sheet, and the thickness thereof is not particularly limited, but the thickness is preferably 0.5 to 10mm, more preferably 1 to 8mm, and still more preferably 2 to 4mm in order to be suitably molded into an interior material for an automobile.

The value of the peak strength/thickness (mm) of the foam sheet is preferably 65,000 or less, more preferably 60,000 or less, and still more preferably 50,000 or less. If the value is sufficiently small, the foam atomization is suppressed.

The method for producing a foam according to an embodiment of the present invention preferably includes the following steps (1) to (3).

Step (1): a step of supplying the resin, the thermal decomposition type foaming agent and other additives compounded as required to an extruder, melting and kneading the mixture at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent, and then extruding the resin composition from the extruder to obtain a resin composition having a predetermined shape such as a sheet shape

Step (2): a step of irradiating the resin composition of the predetermined shape with ionizing radiation to crosslink the resin composition

Step (3): heating the crosslinked resin composition to a temperature not lower than the decomposition temperature of the thermal decomposition type foaming agent to foam the composition, thereby obtaining a foam

Specific examples of the extruder used in the above-mentioned production method include a single-screw extruder and a twin-screw extruder. In addition, the temperature of the resin composition in the extruder is preferably 130 to 195 ℃, and more preferably 160 to 195 ℃.

Specific examples of the ionizing radiation used in step (2) include α rays, β rays, γ rays, and electron rays, but electron rays are preferred. The dose of ionizing radiation is preferably 0.1 to 10Mrad, more preferably 0.2 to 5Mrad, as long as the desired degree of crosslinking can be obtained. The dose of ionizing radiation is generally adjusted while measuring the degree of crosslinking because it has the influence of the olefinic resin, the blowing agent, other additives, and the like.

In the step (3), the temperature for heating and foaming the resin composition is usually 200 to 290 ℃, preferably 220 to 280 ℃. The time for heating and foaming the resin composition is usually 1 to 30 minutes, preferably 1 to 10 minutes.

In addition, in the step (3), the foam may be stretched in either or both of the MD direction and the CD direction after foaming or while foaming.

The crosslinked polyolefin resin foam obtained by crosslinking and foaming the resin composition is preferably subjected to heat treatment after foaming. The heating temperature of the heat treatment is preferably 50 to 120 ℃, more preferably 60 to 110 ℃, and further preferably 70 to 100 ℃. The heating time for the heat treatment is preferably 1 to 350 hours, more preferably 20 to 300 hours, and further preferably 50 to 250 hours. When the heat treatment temperature and the heat treatment time are set to the above values, the intensity peak at 10 to 15 minutes of the extracted ion chromatogram measured by a thermal desorption gas chromatography mass spectrometry (GC/MS) method, which will be described later, can be made small.

The above-described production method is one embodiment of the production method of the foam of the present invention, and the foam of the present invention can be produced by other production methods.

The foam of the present invention may be used alone, but is preferably polymerized with a different material and molded by a known method to form a laminate. Specific examples of the molding method include vacuum molding, compression molding, and press molding. Among them, vacuum forming is preferable. Vacuum forming includes vacuum forming using a male mold and vacuum forming using a female mold, but vacuum forming using a female mold is preferred. Specific examples of the different types of materials include sheet-like materials such as resin sheets, thermoplastic elastomer sheets, and fabrics.

The molded article can be used for various applications, but is preferably used as a roof material of an automobile, and an interior material for an automobile such as a door and an instrument panel.

Examples

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

Evaluation methods of the foams are as follows.

(1) Degree of crosslinking

A test piece of about 100mg was sampled from the foam, and the mass A (mg) of the test piece was precisely measured. Next, the test piece was immersed in 30ml of xylene at 120 ℃ and left for 24 hours, and then filtered through a 200-mesh wire gauze to collect insoluble matter on the wire gauze, followed by vacuum drying, and the mass B (mg) of the insoluble matter was precisely measured. From the obtained value, the degree of crosslinking (% by mass) was calculated by the following formula.

Degree of crosslinking (mass%) < 100 × (B/a)

(2) Density of

The density (apparent density) of the foam was measured in accordance with JIS K7222.

(3) Thickness of the foam

The thickness of the foam was measured by a direct thickness meter.

(4) Evaluation of fogging

The fogging evaluation was carried out by curing the foam at 100 ℃ for 20 hours using a device in accordance with ISO6452 and measuring the haze. The haze was measured using NDH-300A manufactured by Nippon Denshoku industries Ltd. The haze was set to be 15% or less.

(5) Thermal desorption GC/MS

A sample piece cut out of 10cm × 10cm from the foam was heated at 100 ℃ for 30 minutes to volatilize the volatile matter, and the obtained volatile matter was subjected to thermal desorption GC/MS analysis under the following conditions, and the intensity peak of the extracted ion chromatogram was measured at 10 to 15 minutes. The thickness of the sample piece was the same as that of the foam.

A thermal desorption device: TD-20 made by Shimadzu corporation

Sample amount: about 5mg precision weighing

Heating: 30 minutes at 100 ℃ (25 ml/min)

Secondary desorption: 300 ℃ for 5 minutes

GC/MS apparatus: GCMS-TQ manufactured by Shimadzu corporation

Column: シグマアルドリッチジャパン SLB-5MS (micropolar) 0.25mm X30 m X0.25 μm

And (3) GC temperature rise: 40 ℃ (4 min) → 10 ℃/min → 300 ℃ (10 min)

He flow rate: 1.25 ml/min, split ratio 1: 30

Ionization voltage: 70eV

MS measurement range: 35 to 600amu

MS temperature: ion source 200 deg.C, interface 230 deg.C

Examples 1 to 5 and comparative examples 1 to 2

In each of examples and comparative examples, the components shown in table 1 were fed into a single-screw extruder in the parts shown in table 1, and the resin composition was melt-kneaded at 190 ℃ and extruded to obtain a sheet-like resin composition having a thickness shown in table 1. The sheet-like resin composition was crosslinked by irradiating both surfaces thereof with electron beams at an accelerating voltage of 800kV and at an irradiation dose of 1 Mrad. Then, the crosslinked resin composition was heated at 250 ℃ for 5 minutes by a hot-air furnace and foamed by the heating, and in examples 2 to 5, the resin composition was further heated at 80 ℃ for the time shown in table 1 by a hot-air furnace to prepare foamed sheets (foams) having the thicknesses shown in table 1. The evaluation results of the foams of the examples and comparative examples are shown in table 1.

[ Table 1]

TABLE 1

The resins and additives in table 1 are as follows.

Random PP: ethylene-propylene random copolymer (EG 7F, manufactured by Japan ポリプロ Co., Ltd., MFR 1.3g/10 min, ethylene content 3 mass%)

LLDPE: linear low-density polyethylene (5220G, manufactured by ダウケミカル Japan, density: 0.915G/cm)³)

Crosslinking coagents: trimethylolpropane trimethacrylate (TMPTMA)

The foam of examples 1 to 5 had an intensity peak of 200,000 or less, and fogging thereof was suppressed. On the other hand, the foams of comparative examples 1 to 2 having the above-mentioned intensity peak of more than 200,000 were not sufficiently suppressed in fogging.