WO2020067382A1

WO2020067382A1 - Crosslinked polyolefin resin foam

Info

Publication number: WO2020067382A1
Application number: PCT/JP2019/038041
Authority: WO
Inventors: 拓明宇野; 杉江　幸弘; 洋輝三上
Original assignee: 積水化学工業株式会社
Priority date: 2018-09-28
Filing date: 2019-09-26
Publication date: 2020-04-02
Also published as: CN112752791B; CN112752791A; JP2020055913A; JP7160615B2

Abstract

Provided is a crosslinked polyolefin resin foam that prevents fogging even without the incorporation of a special additive. The crosslinked polyolefin resin foam is a crosslinked polyolefin resin foam provided by crosslinking and foaming a polyolefin resin composition, wherein the intensity peak at 10 to 15 minutes for the extracted ion chromatogram value in thermal desorption gas chromatography-mass spectrometry is not more than 200,000. Preferably, at least 50 mass% of the resins contained in the polyolefin resin composition is a polypropylene resin, and a blowing agent contained in the polyolefin resin composition is azodicarbonamide.

Description

Crosslinked polyolefin resin foam

The present invention relates to a crosslinked polyolefin resin foam in which fogging is suppressed.

自動車 Secondary processing of crosslinked polyolefin resin foam is widely used for automotive interior materials such as ceiling materials, doors, and instrument panels. In the production of a crosslinked polyolefin-based resin foam, a thermally decomposable blowing agent such as azodicarbonamide is generally used as a blowing agent. The thermal decomposition type foaming agent causes a small amount of decomposition residue to remain in the resin after foaming. However, since a part of the decomposition residue has sublimability, it may cause fogging. Fogging is a phenomenon in which a minute amount of sublimate generated from a resin material or a resin foam used as an interior material adheres to an inner surface of a windshield or the like, causing fogging.

Conventionally, in order to prevent fogging caused by azodicarbonamide, a foaming agent composition containing at least one selected from the group consisting of a basic magnesium compound and a basic calcium compound together with azodicarbonamide has been studied. (For example, see Patent Document 1). However, in the polyolefin resin foam formed by the foaming agent composition of Patent Document 1, huge bubbles are generated, and the appearance of the foam tends to deteriorate. Therefore, for example, Patent Document 2 considers blending a basic magnesium having an average particle size of 0.1 to 15 μm into a polyolefin-based resin composition together with azodicarbonamide (see, for example, Patent Document 2). ).

Japanese Patent No. 3532791 WO 2016/158701 pamphlet

Even if a specific basic compound as described in Patent Literatures 1 and 2 is not blended, a crosslinked polyolefin-based resin foam in which fogging is suppressed has been demanded. No foam was provided.

The inventors of the present invention have further studied a crosslinked polyolefin-based resin foam in which fogging is suppressed even when a specific special additive is not blended. As a result, they found that a crosslinked polyolefin-based resin foam having a specific intensity peak measured by a heat desorption gas chromatograph mass spectrometry method of a certain value or less was a foam in which fogging was suppressed, and completed the present invention. It led to.
The present invention provides the following crosslinked polyolefin resin foam.
[1] A crosslinked polyolefin-based resin foam obtained by crosslinking and foaming a polyolefin-based resin composition, wherein the intensity peak of the extracted ion chromatogram by heat desorption gas chromatography / mass spectrometry for 10 to 15 minutes is 200,000. The following crosslinked polyolefin resin foam.
[2] The crosslinked polyolefin-based resin foam according to [1], wherein the density is 0.02 to 0.2 g / cm ³ .
[3] The crosslinked polyolefin-based 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 resin 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-based resin foam according to any one of [1] to [5], wherein the foam is a sheet, and the strength peak / sheet thickness (mm) is 65,000 or less.

The present invention can provide a crosslinked polyolefin resin foam in which fogging is suppressed.

Hereinafter, the present invention will be described in more detail using embodiments.
The crosslinked polyolefin-based resin foam of the present invention (hereinafter sometimes simply referred to as “foam”) is a polyolefin-based resin composition containing a polyolefin-based resin (hereinafter sometimes simply referred to as “resin composition”). Are crosslinked and foamed. Hereinafter, each component contained in the resin composition will be described in detail.

The polyolefin-based resin composition contains a polyolefin-based resin such as a polypropylene-based resin and a polyethylene-based resin.

Specific examples of the polypropylene-based resin include homopropylene, which is 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 include a block copolymer, a random copolymer, and a random block copolymer, and a random copolymer (ie, random polypropylene) is preferred.
Specific examples of α-olefins other than propylene include those having 4 to 4 carbon atoms such as ethylene having 2 carbon atoms, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene. About 10 α-olefins. Among these, ethylene is preferred from the viewpoint of moldability and heat resistance. In the copolymer, these α-olefins are used alone or in combination of two or more.
In addition, the polypropylene-based resin may be used alone or in combination of two or more.

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

Specific examples of the polyethylene resin are a low density polyethylene resin, a medium density polyethylene resin, a high density polyethylene resin, and a linear low density polyethylene resin. Among these, a linear low-density polyethylene resin (LLDPE) is preferred.
Linear low density polyethylene resin, density of 0.910 g / cm ³ or more 0.950 g / cm ³ less than the polyethylene, preferably a density of 0.910 g / cm ³ or more 0.930 g / cm ³ or less of Things. Since the foam contains a low-density linear low-density polyethylene-based resin, the processability when processing the resin composition into a foam, the moldability when molding the foam into a molded body, and the like are good. Easy to be. The density of the linear low-density polyethylene resin is measured according to JIS K7112.
The linear low-density polyethylene usually contains ethylene as a main component (at least 50% by mass, preferably at least 70% by mass, more preferably at least 90% by mass of all monomers), and is composed of ethylene and a small amount of α-olefin. It is a polymer. Here, specific examples of the α-olefin are those having 3 to 12 carbon atoms, preferably 4 to 10 carbon atoms, and specifically, 1-butene, 1-pentene, 1-hexene, 4-methyl- 1-pentene, 1-heptene, 1-octene and the like. In the copolymer, these α-olefins are used alone or in combination of two or more.
Moreover, the polyethylene resin may be used alone or in combination of two or more.

The composition may contain the polypropylene resin, the polyethylene resin, or a mixture thereof, but may also contain a polyolefin resin component other than the polypropylene resin and the polyethylene resin.
Specific examples of such resin components include ethylene-propylene-rubber (EPR), ethylene-propylene-diene rubber (EPDM), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- (meth) alkyl Acrylate copolymers, modified copolymers of these copolymerized with maleic anhydride, polyolefin-based thermoplastic elastomers 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 as long as the object of the present invention is not impaired.
The polyolefin resin is usually contained in an amount of 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 above-mentioned polypropylene-based resin in an amount of preferably 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.
When the main component of the resin contained in the resin composition is a polypropylene resin, the mechanical strength, heat resistance, and the like of a foam obtained by crosslinking and foaming the resin composition can be improved. When a polypropylene-based resin is used as a main component, high-temperature heating is required at the time of foaming the resin composition, and impurities are generated from the foaming agent, and the impurities cause fogging. In the present invention, by appropriately adjusting the production conditions and the like, the intensity peak of the extracted ion chromatogram, which will be described later, is set to 10 to 15 minutes to 200,000 or less, so that the polypropylene resin is used as the main component. However, fogging can be suppressed.

The resin composition preferably contains the polyethylene resin in addition to the polypropylene resin as a polyolefin resin. In this case, the preferred 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 resin contained in the resin composition.
When the resin composition contains a polyethylene resin in addition to the polypropylene resin, the processability and the moldability are improved while the mechanical strength, heat resistance and the like are improved.

方法 As a method for foaming the resin composition, there is a chemical foaming method. The chemical foaming method is a method in which bubbles are formed by a gas generated by a foaming agent added to a resin composition. As the foaming agent, a thermal decomposition type foaming agent is used. 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 ° C. is used.

Specific examples of the organic thermal decomposition type foaming agent include azo compounds such as azodicarbonamide, metal salts of azodicarboxylic acid (such as barium azodicarboxylate), azobisisobutyronitrile, and N, N'-dinitrosopentamethylenetetramine. And the like, hydrazodicarbonamide, hydrazine derivatives such as 4,4'-oxybis (benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonyl semicarbazide.
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, anhydrous sodium citrate and the like.
Among these, from the viewpoint of obtaining fine bubbles, and from the viewpoint of economy and safety, organic thermal decomposition type foaming agents are preferable, azo compounds and nitroso compounds are more preferable, and azodicarbonamide and azobisisobutyronitrile are preferable. And the like, and azodicarbonamide is particularly preferred.
These foaming agents may be used alone or in combination of two or more.
The blending amount of the organic thermal decomposition type foaming agent 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 amount of the organic thermal decomposition type foaming agent is within this range, the foamability of the expandable polyolefin resin sheet is improved, and a crosslinked polyolefin resin foam sheet having a desired expansion ratio is obtained.

The resin composition may contain additives other than the olefin resin and the foaming agent. Preferred additives contained in the resin composition include a crosslinking aid and an antioxidant. These may be contained both, or only one may be contained.

As a crosslinking assistant, a polyfunctional monomer can be used. Specific examples of the polyfunctional monomer include trifunctional (meth) acrylate compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate, triallyl ester triallyl ester, 1,2,4-benzenetricarboxylic acid triallyl ester, Compounds having three functional groups in one molecule, such as triallyl isocyanurate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, neopentyl glycol dimethacrylate Bifunctional (meth) acrylate compounds such as methacrylate, compounds having two functional groups in one molecule such as divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethylvinylbenzene, lauryl methacrylate, It is stearyl methacrylate, and the like. The crosslinking assistants can be used alone or in combination of two or more. Among these, a trifunctional (meth) acrylate compound is more preferable.
By adding a crosslinking aid to the resin composition, the resin composition can be crosslinked with a small ionizing radiation dose. For this reason, cutting and deterioration of each resin molecule due to irradiation with ionizing radiation can be prevented.
The preferred content of the crosslinking aid is 0.2 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and still more preferably 100 to 100 parts by mass of the resin in the resin composition. The content is 1 to 5 parts by mass. When the content of the crosslinking aid is 0.2 parts by mass or more, it becomes easy to adjust the degree of crosslinking to a desired degree when foaming the resin composition. When the amount is 10 parts by mass or less, control of the degree of crosslinking imparted to the resin composition becomes easy.

Specific examples of the antioxidant include a phenolic antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, and an amine-based antioxidant. Among these, a phenolic antioxidant and a sulfuric antioxidant are preferred, and a combined use of a phenolic antioxidant and a sulfuric antioxidant is more preferred.
Specific examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol, n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 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 in combination of two or more.
Specific examples of the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, and pentaerythrityl tetrakis (3-lauryl thiopropionate). These sulfur-based antioxidants may be used alone or in combination of two or more.
The preferred content of the antioxidant is 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the resin in the resin composition.

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

The intensity peak of the extracted ion chromatogram of the foam of the present invention in the extracted ion chromatogram by thermal desorption gas chromatography / mass spectrometry (GC / MS) method of 10 to 15 minutes is 200,000 or less. The preferred intensity peak is 190,000 or less, the more preferred intensity peak is 180,000 or less, and the still more preferred intensity peak is 170,000 or less. If the intensity peak is larger than 200,000, the foam tends to fog.
The method for reducing the intensity peak to 200,000 or less is not particularly limited. 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 reduced by performing a predetermined heat treatment on the foam as described later.

The density (apparent density) of the foam of the present invention is not particularly limited. The preferable density is 0.02 to 0.20 g / cm ³ , and the more preferable density is 0.03 to 0.15 g / cm ³ in order to improve the flexibility and strength of the foam in a well-balanced manner. . In addition, when the density of the foam decreases as described above, that is, when the expansion ratio increases, the amount of the foaming agent used increases, and fogging tends to occur in the foam. However, in the present invention, the intensity peak is reduced as described above. The fogging of the foam can be suppressed by lowering.

The degree of cross-linking of the foam of the present invention is not particularly limited, but the preferable degree of cross-linking is 30 to 60%, and the more preferable degree of cross-linking is 30 to improve the mechanical strength, flexibility, and moldability in a well-balanced manner. It is 32 to 55%. The method for measuring the degree of crosslinking of the foam is as described in Examples described later.

One embodiment of the foam of the present invention is a sheet, the thickness of which is not particularly limited, but is preferably 0.5 to 10 mm, more preferably the thickness, so that it can be appropriately molded into an interior material for automobiles. Is 1 to 8 mm, and the more preferable thickness is 2 to 4 mm.

(4) A preferred value of the strength peak / sheet thickness (mm) of the foam sheet is 65,000 or less, and the more preferred value is 60,000 or less, and further preferably 50,000 or less. When the value is sufficiently small, fogging of the foam is suppressed.

The method for producing a foam according to one embodiment of the present invention preferably includes the following steps (1) to (3).
Step (1): A resin, a pyrolytic foaming agent and other additives to be blended if necessary are supplied to an extruder, and are melted and kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent. Step (2) of extruding the composition from an extruder to obtain a resin composition having a predetermined shape such as a sheet shape: Step of irradiating the resin composition having the predetermined shape with ionizing radiation to cross-link (3): Cross-linking Heating the foamed resin composition to a temperature equal to or higher than the decomposition temperature of the pyrolytic foaming agent to obtain a foam.

Specific examples of the extruder used in the production method include a single-screw extruder and a twin-screw extruder. The temperature of the resin composition inside the extruder is preferably from 130 to 195 ° C, more preferably from 160 to 195 ° C.
Specific examples of the ionizing radiation used in the step (2) include α-rays, β-rays, γ-rays, and electron beams, but electron beams are preferable. The irradiation amount of the ionizing radiation is not particularly limited as long as a desired degree of crosslinking can be obtained, but is preferably 0.1 to 10 Mrad, more preferably 0.2 to 5 Mrad. Since the irradiation amount of the ionizing radiation is affected by the olefin resin, the foaming agent and other additives, the irradiation amount is usually adjusted while measuring the degree of crosslinking.
In the step (3), the temperature at which the resin composition is heated and foamed is usually from 200 to 290 ° C, preferably from 220 to 280 ° C. The time for heating and foaming the resin composition is usually 1 to 30 minutes, preferably 1 to 10 minutes.
Further, in the step (3), the foam may be stretched in the MD direction or the CD direction or both after and after the foaming.

The crosslinked polyolefin-based resin foam obtained by crosslinking and foaming the resin composition is preferably heat-treated after foaming. The heating temperature of the heat treatment is preferably 50 to 120 ° C., more preferably 60 to 110 ° C., and further preferably 70 to 100 ° C. The heating time of 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 as described above, an intensity peak of 10 to 15 minutes of an extracted ion chromatogram value of a thermal desorption gas chromatograph mass spectrometry (GC / MS) method described later can be reduced.
The manufacturing method described above is an embodiment of the method for manufacturing a foam of the present invention, and the foam of the present invention may be manufactured by another manufacturing method.

The foam of the present invention may be used as a single foam, but is preferably laminated 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 stamping molding. Of these, vacuum forming is preferred. The vacuum forming includes male pull vacuum forming and female pull vacuum forming. Preferred vacuum forming is female pull vacuum forming. Specific examples of the dissimilar material include a sheet such as a resin sheet, a thermoplastic elastomer sheet, and a fabric.
The molded article can be used for various purposes, but is preferably used as an automobile interior material such as an automobile ceiling material, a door, or an instrument panel.

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

The method for evaluating the foam is as follows.
(1) Degree of Crosslinking Approximately 100 mg of a test piece was collected from the foam, and the mass A (mg) of the test piece was precisely weighed. Next, the test piece was immersed in 30 ml of xylene at 120 ° C. and allowed to stand for 24 hours, and then filtered through a 200-mesh wire net to collect the insoluble matter on the wire mesh, dried under vacuum, and dried. (Mg) was precisely weighed. From the obtained values, the degree of crosslinking (% by mass) was calculated by the following equation.
Degree of crosslinking (% by mass) = 100 × (B / A)
(2) Density The density (apparent density) of the foam was measured in accordance with JIS K7222.
(3) Thickness of foam The thickness of the foam was measured with a dial gauge.
(4) Evaluation of fogging The evaluation of fogging was performed by using a facility based on ISO6452, after curing the foam at 100 ° C. for 20 hours, and measuring the haze. The haze was measured using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Those having a haze of 15% or less were regarded as acceptable.
(5) Heat desorption GC / MS
A sample piece cut out from the foam into a piece of 10 cm × 10 cm was heated at 100 ° C. for 30 minutes to volatilize volatiles, and the obtained volatiles were subjected to heat desorption GC / MS analysis under the following conditions. The intensity peak was measured for 10-15 minutes. In addition, the thickness of the sample piece was the same as the thickness of the foam.
Heat desorption device: TD-20 manufactured by Shimadzu Corporation
Sample amount: Approximately 5 mg Precision heating: 100 ° C, 30 minutes (25 ml / min)
Secondary desorption: 300 ° C, 5 minutes GC / MS equipment: GCMS-TQ manufactured by Shimadzu Corporation
Column: Sigma-Aldrich Japan SLB-5MS (fine polarity) 0.25 mm × 30 m × 0.25 μm
GC temperature rise: 40 ° C (4 minutes) → 10 ° C / minute → 300 ° C (10 minutes)
He flow rate: 1.25 ml / min, split ratio 1:30
Ionization voltage: 70 eV
MS measurement range: 35-600 amu
MS temperature: ion source 200 ° C, interface 230 ° C

Examples 1-5, Comparative Examples 1-2
In each of Examples and Comparative Examples, the components shown in Table 1 were put into a single screw extruder in the number of parts shown in Table 1, and the resin composition was melt-kneaded at 190 ° C. and extruded. A sheet-shaped resin composition was obtained. The sheet-shaped resin composition was cross-linked by irradiating an electron beam at an acceleration voltage of 800 kV with an irradiation amount of 1 Mrad on both surfaces of the sheet-shaped resin composition. Thereafter, the crosslinked resin composition was heated at 250 ° C. for 5 minutes in a hot air oven, foamed by the heating, and further heated at 80 ° C. in a hot air oven for the times shown in Table 1 for Examples 2 to 5. A foamed sheet (foam) having the thickness shown in Table 1 was obtained. Table 1 shows the evaluation results of the foams of Examples and Comparative Examples.

The resins and additives in Table 1 are as follows.
-Random PP: ethylene-propylene random copolymer (EG7F, manufactured by Nippon Polypropylene Co., Ltd., MFR = 1.3 g / 10 min, ethylene content = 3% by mass)
LLDPE: linear low-density polyethylene (5220G, manufactured by Dow Chemical Japan, density = 0.915 g / cm ³ )
・ Cross-linking aid: trimethylolpropane trimethacrylate (TMPTMA)

フォ Fogging of the foams of Examples 1 to 5 where the intensity peak was 200,000 or less was suppressed. On the other hand, for the foams of Comparative Examples 1 and 2 whose intensity peak was larger than 200,000, fogging could not be sufficiently suppressed.

Claims

A crosslinked polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin composition, wherein the intensity peak of the extracted ion chromatogram by heat desorption gas chromatography / mass spectrometry for 10 to 15 minutes is 200,000 or less. Crosslinked polyolefin resin foam.
2. The crosslinked polyolefin resin foam according to claim 1, having a density of 0.02 to 0.2 g / cm 3 .
架橋 The crosslinked polyolefin-based resin foam according to claim 1 or 2, which is a sheet having a thickness of 2 to 4 mm.
The crosslinked polyolefin resin foam according to any one of claims 1 to 3, wherein 50% by mass or more of the resin contained in the polyolefin resin composition is a polypropylene resin.
The crosslinked polyolefin resin foam according to any one of claims 1 to 4, wherein the polyolefin resin composition contains azodicarbonamide.
The crosslinked polyolefin resin foam according to any one of claims 1 to 5, wherein the crosslinked polyolefin resin foam is a sheet, and the strength peak / sheet thickness (mm) is 65,000 or less.