JPH07196834A - Production of cross-linked olefin resin foam - Google Patents

Abstract

PURPOSE:To obtain a cross-linked olefin resin foam which has good fabricability and laminatability and high elongation, adhesive strength, and heat resistance by compounding a specific propylene resin, a specific ethylene resin, an allyl ester of an arom. carboxylic acid, and a blowing agent. CONSTITUTION:This foam is obtd. by homogeneously mixing 100 pts.wt. resin component comprising 40-90 pts.wt. propylene resin having a melt index of 0.1-12g/10min and 10-60 pts.wt. linear low-density ethylene resin contg. 0.5-10wt.% copolymerized a-olefin units with 0.1-10 pts.wt. polyallyl ester of an arom. polycarboxylic acid (pref. triallyl 1,2,4-benzenetricarboxylate), 1-50 pts.wt. at least one thermally decomposable org. blowing agent, and other necessary additives at a temp. lower than the decomposition temp. of the blowing agent, molding the resulting mixture, irradiating the resulting molding with an ionizing radiation such as alpha-, beta-, or gamma-ray or an electron beam, and heating the molding to a temp. higher than the decomposition temp. of the blowing agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an olefin resin crosslinked foam. In particular, the present invention relates to a method for producing an olefin resin crosslinked foam suitable as a vehicle interior material.

[0002]

BACKGROUND OF THE INVENTION Olefinic resin crosslinked foams such as polyethylene crosslinked foams have excellent flexibility and heat insulation properties and have been used for various purposes. It is often used as a vehicle interior material such as a ceiling, a door, an instrument panel, etc. by being molded into a sheet or laminated on a skin material such as a polyvinyl chloride sheet, a thermoplastic elastomer sheet, a natural or artificial cloth-like material. Thus, when it is used as a vehicle interior material, it is molded and adhered. Therefore, the vehicle olefin resin crosslinked foam is required to have excellent moldability and adhesiveness. Further, in vacuum molding or compression molding, heat resistance is required because molding is performed at a high temperature of 120 to 200 ° C. Therefore, polyethylene crosslinked foam having poor heat resistance cannot be used.

Therefore, an olefin-based resin cross-linked foam made of polypropylene, which is superior in heat resistance to polyethylene, is used. However, by simply replacing polyethylene with polypropylene, the peroxide used for cross-linking is used. Since the molecular chain is easily broken by a cross-linking agent such as the above and ionizing radiation, the resulting foam is not good. At present, various attempts have been made to produce an olefin resin crosslinked foam obtained by foaming a propylene resin.

For example, in JP-B-46-38716, a crystalline propylene-ethylene random copolymer is used, and in JP-B-63-1977, a propylene-ethylene random copolymer and polyethylene are used. As described using a mixed resin, it is known to use a special propylene resin or a mixed resin of this special propylene resin and polyethylene.
Further, as described in JP-B-58-57452, it is known to use a cross-linking agent such as trimethylolpropane triacrylate in polypropylene.
Further, JP-A-4-80238 discloses a composition comprising a low density ethylene resin obtained by copolymerizing a propylene-ethylene copolymer and octene-1 and a foaming agent.

[0005]

However, the above propylene-based resin crosslinked foam does not have satisfactory performances in heat resistance, moldability and adhesiveness. That is, Japanese Patent Publication No. 46
The olefin resin foam produced by the method using only the crystalline propylene-ethylene random copolymer described in JP-A-38716 has a small elongation, and therefore only a foam having poor moldability can be obtained, and a vinyl chloride resin. There is a problem that adhesion to a sheet or the like is poor and peeling is easily performed. Also, in this method, it is described that a peroxide is used as a cross-linking agent. However, when a peroxide is used as described above, it is difficult or dangerous to control the degree of cross-linking, and the peroxide is Since it is difficult to uniformly disperse the product in the resin, the product is crosslinked unevenly, and as a result, a foam having a uniformly foamed and smooth surface cannot be obtained.

Further, in the method of using a mixed resin of propylene-ethylene random copolymer and polyethylene, which is described in Japanese Patent Publication No. 63-38716, it is conventionally used for a mixed resin of propylene-ethylene copolymer and polyethylene. Cross-linking agents and cross-linking aids, in particular, when reactive polyfunctional monomers are mixed and cross-linked by ionizing radiation, cross-linking agents and cross-linking aids for each resin component (polypropylene and polyethylene) in the resin composition Since the compatibility of the above is different, the cross-linking agent such as the polyfunctional monomer or the cross-linking aid is contained in the resin component exhibiting the best compatibility. As a result, when the resin composition is irradiated with ionizing radiation, the resin containing a large amount of the crosslinking agent or the crosslinking aid has a high degree of crosslinking and the other resins have a low degree of crosslinking. Therefore, the olefin resin crosslinked foamed product obtained by heating and foaming the resin thus produced has a problem that the physical properties thereof are rapidly lowered when heated for processing.

Further, in an olefin resin foam produced by using a cross-linking agent such as trimethylolpropane triacrylate described in JP-B-58-57452, this cross-linking agent is usually used as a cross-linking aid. As can be seen from the above, the crosslinking action is small, and therefore, as described in the above publication, the heat resistance is low and the elongation is 110.
% Or less, and the moldability is poor.
Further, the composition described in JP-A-4-80238, which is composed of polyethylene in which propylene-ethylene random copolymer is copolymerized with octene-1 and a foaming agent, is used as a cross-linking aid such as trimethylolpropane trimethacrylate. However, there is a problem that the heat resistance is inferior although the crosslinking is insufficient and the elongation at a low temperature is large.

Generally, an olefin resin crosslinked foam containing a propylene resin as a main component by a conventionally known method has a small elongation and is inferior in workability (it breaks or swells during processing, has a small adhesive strength, and is easily manufactured). There is a problem that it peels off) or the heat resistance is inferior, and there is no olefin resin foam that satisfies both of them. Therefore, there has been a strong demand for an olefin resin foam which has good heat resistance, good moldability, and good adhesiveness as a vehicle interior material.

Therefore, as a result of research by the inventor of the present invention to obtain a good foam having good heat resistance and good moldability and adhesiveness, a propylene having a specific melt index as a resin component. System resin and a linear low density ethylene resin obtained by copolymerizing a specific amount of an α-olefin component with a resin mixture in a specific ratio, and the resin mixture contains a crosslinking auxiliary agent having a specific chemical structure. It has been found that a good foam can be obtained by irradiating a resin composition in which a thermal decomposition type foaming agent is combined with ionizing radiation and heating to foam, thereby completing the present invention. That is, the object of the present invention is to have good secondary workability and bonding at high temperature, that is,
It is an object of the present invention to provide a method for producing a uniformly foamed olefin resin crosslinked foam having a large elongation, a large adhesive strength, and good heat resistance.

[0010]

The present invention has been made in order to achieve the above object, and (a) 40 to 90 parts by weight of a propylene resin having a melt index of 0.1 to 12 g / 10 minutes. And (b) 10 to 60 parts by weight of a linear low-density ethylene resin containing 0.5 to 10% by weight of α-olefin as a copolymerization component, (c) the propylene resin (a) and a linear chain. 0.1 to 10 parts by weight of an aromatic polyvalent carboxylic acid polyvalent allyl ester, and (d) an organic pyrolyzable foaming agent 1 to 100 parts by weight of the total low-density ethylene resin (b). An olefin resin composition consisting of 50 parts by weight is uniformly kneaded and molded at a temperature not higher than the decomposition temperature of the organic thermal decomposition type foaming agent and molded, and after irradiation with ionizing radiation, the decomposition temperature of the organic thermal decomposition type foaming agent. The above is heated to foam.

The propylene-based resin used in the present invention refers to a propylene homopolymer or a copolymer of propylene and an α-olefin other than propylene. here,
As α-olefins other than propylene, ethylene,
1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like are preferable. If the melt index (hereinafter referred to as MI) of the propylene-based resin is small, the moldability of the resulting foam is lowered, and if it is large, the heat resistance of the obtained foam is lowered, so that MI is 0 in the present invention. .1 to 12 g /
Propylene resin is used for 10 minutes, preferably 0.3 to 10 g / 10 minutes, and more preferably 0.5 to 8 g / 10 minutes.

The linear low-density ethylene resin used in the present invention means a resin obtained by copolymerizing ethylene and α-olefin. Here, as the α-olefin, for example,
Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like are preferable. If the content of the α-olefin in the linear low-density ethylene-based resin is small or large, moldability such as elongation of the obtained foam will be deteriorated.
Therefore, in the present invention, the amount of α-olefin is 0.5 to
A linear low density ethylene resin containing 10 parts by weight, preferably 1.0 to 8% by weight, is used.

As for the mixing ratio of the propylene-based resin and the linear low-density ethylene resin, when the ratio of the propylene-based resin is large, the obtained foam becomes harder than necessary and the moldability is deteriorated. When the ratio is low, the heat resistance is low. Therefore, in the present invention, a mixed resin in which the proportion of the propylene resin in the mixed resin is 40 to 90% by weight, preferably 45 to 85% by weight is used.

The aromatic polyvalent carboxylic acid polyvalent allyl ester used in the present invention is used as a crosslinking aid. As the aromatic polycarboxylic acid polyallyl ester, 1,2-benzenedicarboxylic acid diallyl ester, 1,3-benzenedicarboxylic acid diallyl ester,
1,4-benzenedicarboxylic acid diallyl ester, 1,
2,4-Benzenetricarboxylic acid triallyl ester, and nuclear substitution compounds and related homologues thereof are preferable.
Particularly, 1,2,4-benzenetricarboxylic acid triallyl ester is preferable. These aromatic polycarboxylic acid polyvalent allyl esters may be used alone or in combination of two or more. Furthermore, the above-mentioned aromatic polycarboxylic acid polyvalent allyl ester and a polyfunctional crosslinking aid, for example, divinylbenzene, trimethylolpropane trimethacrylate, 1,9-nonadiol dimethacrylate, 1,10-decanediol dimethacrylate. , Triallyl isocyanurate, ethyl vinyl benzene and the like may be used in combination. At that time, the aromatic polycarboxylic acid polyallyl ester is preferably 30% by weight or more in the total crosslinking aid.

If the amount of this aromatic polyvalent carboxylic acid polyallyl ester used is small or large, the moldability of the resulting foam will be deteriorated. The divalent allyl ester is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the total of the propylene resin and the linear low-density ethylene resin.

The organic thermal decomposition type foaming agent used in the present invention is one which decomposes upon heating to generate gas, and the organic thermal decomposition type foaming agent conventionally used for olefin resin type foams is Can be used. For example, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like can be used. These organic thermal decomposition type foaming agents may be used alone or in combination of two or more kinds.

When the amount of the organic pyrolyzable foaming agent added is small, the foamability of the resulting foam is low, and when the amount is high, the strength of the foamed product is low. The decomposing type blowing agent is used in an amount of 1 to 50 parts by weight, preferably 4 to 25 parts by weight, based on 100 parts by weight of the total of the propylene resin and the linear low-density ethylene resin. In the present invention, additives other than the above may be added as needed. For example, a phenol-based, phosphorus-based, amine-based or sulfur-based antioxidant, a metal damage inhibitor, a flame retardant, a filler, an antistatic agent, a stabilizer, a pigment or the like may be added.

The ionizing radiation used in the present invention is for irradiating the above resin composition to cross-link the propylene resin and the linear low-density ethylene resin.
Rays, γ rays, electron rays and the like can be mentioned. When the dose of this ionizing radiation is small, the heat resistance of the resulting foam is insufficient, and when the dose is large, the foam becomes harder than necessary. This irradiation amount varies depending on the components and amount of the resin composition, especially the type and amount of the crosslinking aid, but is usually 0.5 to 20 Mrad, and more preferably 1 to 15 Mrad.

In the present invention, the respective components are mixed and kneaded and molded at a temperature not higher than the decomposition temperature of the organic thermal decomposition type foaming agent. As the kneading / molding method, a conventional thermoplastic resin molding method can be used. For example, the above components are mixed in predetermined amounts and heated to a temperature not higher than the decomposition temperature of the organic pyrolysis type foaming agent using a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, and a roll. It is melt-kneaded and molded into an appropriate shape, for example, a sheet. Next, when the molded article is irradiated with ionizing radiation, the resin composition uniformly crosslinks the propylene-based resin and the linear low-density ethylene-based resin with the aid of the crosslinking aid. Next, the organic thermal decomposition type foaming agent is heated to a temperature equal to or higher than the decomposition temperature to foam. Then, a uniformly foamed olefin resin foam having good heat resistance and good moldability and adhesiveness is obtained.

[0020]

In the method for producing an olefin resin foam according to the present invention, a special propylene resin having a melt index of 0.1 to 12 g / 10 minutes and a cross-linking aid having substantially the same compatibility, and an α-olefin as a copolymerization component. 0.5 to 10
Since it is used by mixing with a special linear low-density ethylene resin such as containing by weight%, the crosslinking aid is uniformly dispersed in each component, and a uniformly foamed good foam can be obtained. .

The propylene resin is mixed in a specific ratio of 40 to 90 parts by weight and the linear low-density ethylene resin in a specific ratio of 10 to 60 parts by weight. A specific cross-linking aid called polyvalent carboxylic acid polyvalent allyl ester is blended in a specific ratio of 0.1 to 10 parts by weight and an organic thermal decomposition type foaming agent in an amount of 1 to 50 parts by weight and irradiated with ionizing radiation. By heat-foaming, a uniformly expanded olefin resin crosslinked foam having good heat resistance, high elongation and good adhesion can be obtained.

Particularly, in the present invention, when 1,2,4-benzenetricarboxylic acid triallyl ester is used as the aromatic polycarboxylic acid polyallyl ester, a very good foam is obtained.

[0023]

EXAMPLES Next, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In this embodiment, simply "part" means "part by weight".

(Example 1) Ethylene-propylene random copolymer (ethylene content 4.0% by weight, MI: 0.
5 g / 10 min) 60 parts by weight, linear low density ethylene resin (4-methyl-1-pentene content 2.5% by weight, M
I: 8 g / 10 minutes, density 0.920 g / cm ³ ) 40
Parts, 2.0 parts of 1,2,4-benzenetricarboxylic acid triallyl ester as a crosslinking aid, 13 parts of azodicarbonamide as an organic thermal decomposition type foaming agent, and 2,6-di-t-butyl as an antioxidant. -P-Cresol 0.3 part, dilauryl thiodipropionate 0.3 part, and methylbenzotriazole 0.5 part as a metal damage inhibitor were added to a twin-screw extruder (manufactured by Ikegai Tekko KK, type: PCM87). ), Melt-knead at a temperature of 190 ° C, and extrude to a thickness of 1 m.
m sheets were obtained. Acceleration voltage 600 is applied to the obtained sheet.
An electron beam of 6.0 Mrad was irradiated at kV for crosslinking, and this sheet was put in an oven and allowed to freely foam for 5 minutes at a temperature of 250 ° C. to obtain an olefin resin crosslinked foam. The surface of the obtained cross-linked olefin resin foam was subjected to corona discharge treatment, a two-component curable polyester adhesive was used, and a thickness of 0.
65mm vinyl chloride resin sheet and acrylonitrile-
A butadiene-styrene copolymer resin mixed resin sheet was adhered to obtain a laminate.

With respect to the obtained olefin resin crosslinked foamed product, the elongation to break was measured by a tensile tester, and the peel strength of the laminated product was measured. Further, vacuum forming was performed to evaluate the appearance and formability. The appearance is done visually.
The formability was represented by the ratio (H / D) of the depth (H) and the diameter (D). Details of the test method are given in the notes after Table 1. The evaluation results are shown in Table 1.

(Examples 2 to 5 and Comparative Examples 3 to 5) Ethylene-propylene random copolymer (ethylene content 4.0%) as propylene resin, linear low density ethylene resin, and mixing ratio of resin , Type and amount of crosslinking aid,
Example 1 except that the dose of electron beam was set as shown in Table 1.
An olefin-based resin crosslinked foam and a laminate thereof were obtained in the same manner as in. The resulting foam and laminate were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 1 Ethylene-propylene random copolymer (ethylene content 4.0%, MI: 3.5 g)
/ 10 minutes) 70 parts, linear low density ethylene resin (1-
Butene content 1.5% by weight, MI: 12 g / min, density 0.925 g / cm ³ ) 30 parts, divinylbenzene 6.0 parts as a crosslinking aid, cumene hydroperoxide 1 part as a crosslinking agent, organic heat 13 parts of azodicarbonamide as a decomposition type foaming agent and 2,6-di-t- as an antioxidant
16 parts of 0.3 parts of butyl-p-cresol and 0.3 part of dilauryldithiopropinate and 0.5 part of methylbenzotriazole as a metal damage inhibitor were added by a Henschel mixer.
Pelletized at 0 ° C. The pellets thus obtained were placed in a mold having a thickness of 2 mm which can be sealed so that the filling rate was 90% or more, and 150 minutes for 10 minutes with a hot press heated to 180 ° C.
A crosslinked sheet was obtained by heating under pressure to kg / cm ² .

The obtained crosslinked sheet was placed in an oven and freely foamed at a temperature of 250 ° C. for 5 minutes to obtain an olefin resin crosslinked foam. This olefin resin crosslinked foam was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 Ethylene-propylene random copolymer (ethylene content 4.0%, MI: 1.5 g)
/ 10 minutes) 75 parts, linear low density ethylene resin (1-
Butene content 3.0% by weight, MI: 18 g / 10 min, density 0.922 g / cm ³ ) 25 parts, trimethylolpropane trimethacrylate 8.0 parts as a crosslinking aid, cumene hydroperoxide 1 part as a crosslinking agent , 13 parts of azodicarbonamide as an organic thermal decomposition type foaming agent, 0.3 part of 2,6-di-t-butyl-p-cresol as an antioxidant and 0.3 parts of dilauryldithiopropionate.
Parts, methyl benzotriazole as a metal damage inhibitor.
Five parts were pelletized with a Henschel mixer at 160 ° C.

The pellets thus obtained were put in a mold having a thickness of 2 mm which can be closed so that the filling rate was 90% by weight or more.
After heat treatment for 10 minutes with a hot press heated to 80 ° C., it was placed in an oven and freely foamed at a temperature of 250 ° C. for 5 minutes to obtain an olefin resin crosslinked foam. This olefin-based resin crosslinked foam was evaluated in the same manner as in Examples, and the results are shown in Table 1.

[0031]

[Table 1]

(Note 1) The tensile test is JIS-K-6767.
The elongation (%) at break at temperatures of 120 ° C. and 160 ° C. was measured. (Note 2) Peel strength is 25 width produced by cutting the laminate.
mm, 100 mm long test piece was left at 150 ° C. for 5 minutes, and then autograph (Model DCS-5, manufactured by Shimadzu Corporation)
000) when peeled at the same temperature (kg
/ 25 mm width) was measured. (Note 3) H / D is defined by the following method. The surface temperature of the foam is 150 with a far infrared heater.
It is heated to ~ 160 ° C and vacuum-molded using a cylindrical female mold having a diameter of 100 mm.
(Cm) and diameter D (cm) were measured and displayed as the ratio H / D. (Note 4) The appearance was evaluated by visually observing the appearance after the above vacuum forming. When no blurring, blistering, dents, surface roughness, etc. were observed, ◯ was evaluated, and when even one was observed, it was evaluated as x.

As can be seen by comparing Examples 1 to 5 with Comparative Examples 1 to 4, Comparative Examples 1 and 2 crosslinked by using a crosslinking agent and the linear low density ethylene resin were not mixed. In Comparative Example 3 and Comparative Example 4 in which no α-olefin was contained as the linear low-density ethylene resin, heat resistance was poor, peel strength was weak, elongation was small, and H / D was small. That is, it can be seen that the heat resistance, workability, and adhesiveness are inferior, and it is not good as a vehicle interior material.

As can be seen by comparing Examples 1 to 5 with Comparative Example 5, when a propylene resin having a large melt index is used, the elongation is large at 120 ° C.
It can be seen that at a high temperature such as 60 ° C., the heat resistance is suddenly reduced to 150%, the heat resistance is poor, and the peeling strength is small and the peeling adhesion is poor. Further, it is understood that the workability is poor because the H / D is small and the appearance is poor.

[0035]

As described above, in the present invention, a specific propylene-based resin and a specific linear low-density ethylene-based resin are used in a specific ratio, and an aromatic polyvalent carboxylic acid polyvalent is added to this mixed resin. A special cross-linking aid called an allyl ester and an organic thermal decomposition type foaming agent are mixed and cross-linked by ionizing radiation to heat foam, so that it has excellent heat resistance and is uniformly foamed with excellent processability and adhesiveness. An olefin resin crosslinked foam suitable as an interior material is obtained, which is an extremely useful invention.
In the present invention, when 1,2,4-benzenetricarboxylic acid triallyl ester is used as the aromatic polyvalent carboxylic acid polyallyl ester which is a crosslinking aid, a particularly good foam is obtained.

Claims (2)

[Claims] 1. (a) A melt index of 0.1 to 1
40 to 90 parts by weight of a propylene-based resin which is 2 g / 10 minutes, and (b) 0.5 to α-olefin as a copolymerization component.
Linear low density ethylene resin containing 10% by weight 10
To 60 parts by weight, and (c) the total of 100 parts by weight of the propylene-based resin (a) and the linear low-density ethylene-based resin (b), 0.1 parts of an aromatic polycarboxylic acid polyvalent allyl ester is added. 10 to 10 parts by weight, and (d) organic thermal decomposition type foaming agent 1
˜50 parts by weight of an olefinic resin composition is uniformly kneaded at a temperature not higher than the decomposition temperature of the organic thermal decomposition type foaming agent and molded, and irradiated with ionizing radiation, and then the organic thermal decomposition type foaming agent is decomposed. A method for producing an olefin-based resin crosslinked foam, which comprises heating to a temperature or higher to foam. 2. The method for producing an olefin resin crosslinked foam according to claim 1, wherein the aromatic polycarboxylic acid polyallyl ester is 1,2,4-benzenetricarboxylic acid triallyl ester. A method for producing an olefin resin crosslinked foam.