JP3272021B2 - Method for producing polypropylene-based crosslinked foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cross-linked polypropylene foam which is obtained by cross-linking a sheet of a polypropylene resin composition containing a foaming agent and a cross-linking aid by irradiation with radiation and then heating and foaming. About. The polypropylene-based crosslinked foam thus obtained is used, for example, in the field of vehicles, especially doors and door uppers manufactured by vacuum molding,
Used for vehicle interior molded products such as instrument panels.

[0002]

2. Description of the Related Art The above-mentioned crosslinked polypropylene foams are widely used in molded articles for vehicle interiors as described above because of their excellent moldability and heat resistance. However, they have poor adhesion to skin materials and aggregates. It has been proposed to blend a petroleum resin into a polypropylene resin composition because of its poor quality (Japanese Patent Application Laid-Open No.
3-145344, JP-A-1-163225 and JP-A-63-92730.

It is known that a polyfunctional monomer is added as a crosslinking aid for accelerating crosslinking in the production of a crosslinked polypropylene foam by radiation crosslinking with an electron beam or the like. It is also known that, depending on the type of the polyfunctional monomer, the high-temperature physical properties of the foam are remarkably reduced, and conversely, the performance is improved.

[0004]

SUMMARY OF THE INVENTION A composite material is formed by bonding a cross-linked polypropylene foam to an outer layer made of polyvinyl chloride containing ABS resin via an adhesive, and the peel strength is measured. In the range of 120 ° C., the foam broke down and showed good adhesiveness.
At a high temperature of 0 ° C., a so-called interfacial peeling phenomenon occurs in which the foam does not break and peels off at the interface with the adhesive. For this reason, when the composite material is integrally molded with the aggregate by the vacuum molding method, the molding temperature range is narrowed, and there is a problem that the moldability is inferior.

[0005] In view of the above points, an object of the present invention is to provide a 13
A method for producing a polypropylene-based crosslinked foam capable of improving the peel strength between a foam and a skin so as not to cause an interfacial peeling phenomenon at a high temperature of 0 ° C. or more, thereby improving moldability during vacuum molding. The point is to provide.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve the above-mentioned problems, and a specific compound is used as a crosslinking aid, and the above-mentioned object is achieved by blending a required amount of a petroleum resin into a resin composition. It has been completed with the knowledge that is achieved.

That is, in the method for producing a crosslinked polypropylene foam according to the present invention, a polypropylene resin composition containing a foaming agent and a crosslinking aid is molded into a required shape, the molded product is crosslinked by irradiation, and then heated. Upon foaming, as a crosslinking aid,

Embedded image (Wherein, R ^1, R ² and R ³ denotes a substituent having olefinic double bonds) with an aromatic trifunctional monomer represented by the resin composition, the poly in the resin composition
Relative to 100 parts by weight of propylene-based resin, a petroleum resin 0.
One or more parts are blended.

The polypropylene resin in the present invention is not particularly limited as long as it is based on polypropylene. Homopolymer of propylene, propylene and other olefins, vinyl acetate, acrylic acid,
It may be a copolymer with an acrylic acid ester or the like, or a block copolymer, a random block, or a random copolymer of another olefin resin with a polypropylene resin. If polypropylene alone lacks flexibility, low-density polyethylene, linear low-density polyethylene,
5 high density polyethylene, ethylene vinyl acetate copolymer
-50 parts by weight, preferably 30-40 parts by weight.

[0009] The cross-linking treatment of the molded product is performed by electron beam, α-ray, β-beam,
This is performed using ionizing radiation such as gamma rays, gamma rays, X-rays, and ultraviolet rays. The irradiation dose is usually between 1 and 20 Mrad.

Aromatic Trifunctional Monomer as Crosslinking Aid
In the above, the substituent R having an olefinic double bond¹,
R^TwoAnd R^ThreeExamples of vinyl, allyl, isop
Alkenyl groups such as lophenyl: allyloxycarbonyl
(-COOCH_TwoCH = CH _Two), Such as alkenyloxy
A cicarbonyl group. Substituent R on benzene ring
¹, R^TwoAnd R^ThreeIs not limited. Especially suitable
The crosslinking aid is triallyl trimellitate.

As the blowing agent, azodicarbonamide,
An organic decomposition type foaming agent such as dinitrosopentamethylenetetramine, allophanamide, p, p'-oxybisbenzenesulfonylhydrazide, and an inorganic decomposition type foaming agent such as sodium bicarbonate can be appropriately used. Of these, azodicarbonamide or those based thereon are preferred. In order to accelerate the decomposition of the foaming agent, a known decomposition aid such as zinc oxide or zinc stearate may be appropriately added. The amount of foaming agent added is polypropylene resin 1
It is usually 5 to 15 parts by weight based on 00 parts by weight.

As a heating means for foaming, hot air, a heater or a combination thereof is used.

The petroleum resin used in the present invention is a polymerizable substance obtained by naphtha cracking, that is, an olefinic or aromatic petroleum resin obtained by polymerizing olefins, diolefins, alkenyl aromatics, etc., as well as natural petroleum resins. Or a synthetic rosin resin, terpene resin, cumarone resin, or the like. The petroleum resin may or may not contain a polar group, but is preferably a petroleum resin containing no polar group. These petroleum resins may or may not be hydrogenated, but hydrogenated petroleum resins are more preferred. Particularly preferred as a petroleum resin is "Alcon P-100" manufactured by Arakawa Chemical which is a hydrogenated aromatic petroleum resin.
(Softening point = 100 ° C., density = 0.966), “Alcon P-125” (softening point = 125 ° C., density = 0.966)
Etc. can be used. The amount of petroleum resin is polypropylene
0.100 parts by weight based resin . 1 part or more, preferably 3
~ 5 parts are blended. When the amount is less than 0.1 part by weight, when the skin is peeled from the composite material of the foam and the skin, an interface peeling phenomenon occurs at a high temperature, and the molding temperature cannot be set widely in vacuum molding.

The polypropylene resin composition containing a foaming agent, a crosslinking aid and a petroleum resin may contain an antioxidant, a heat stabilizer, a metal harm inhibitor, an inorganic filler, an ultraviolet absorber, a pigment, etc., if necessary. Can be added.

The method for producing a polypropylene resin foam according to the present invention comprises the steps of: adding a foaming agent, a crosslinking assistant and a petroleum resin to a polypropylene resin;
A coupling agent and various additives are added, and the resulting compound is melt-kneaded to form an expandable polypropylene resin composition. The composition is molded into a required shape, and the resulting molded article is irradiated with ionizing radiation. And then foaming by heating to decompose the foaming agent to form a foam. The molding is performed as follows. Using a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, or a roll, the compound is melt-kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, and the obtained kneading is performed. The object is usually formed into a sheet.

[0016]

Next, embodiments of the present invention will be described.

Example 1 Ethylene-propylene random copolymer (melt index = 2.0, melting point = 143 ° C., ethylene content = 5.
70% by weight of polyethylene (density = 0.92)
0, melt index = 2.0, melting point = 120 ° C.) 3
0 parts by weight, 10 parts by weight of azodicarbonamide as a foaming agent, 2 parts by weight of triallyl trimellitate as a crosslinking aid, and hydrogenated aromatic petroleum resin as a petroleum resin ("Alcon P-100" manufactured by Arakawa Chemical) 3 parts by weight and 1.0 part of a phenolic antioxidant were added, and the resulting mixture was melt-kneaded with a twin-screw extruder (120φ), and the kneaded product was extruded at a temperature lower than the decomposition temperature of azodicarbonamide. , Thickness 1.
A 0 mm sheet was formed. Then, after irradiating the sheet with an electron beam of 3.0 Mrad, the sheet was heated and foamed at 270 ° C. in a hot-air type foaming furnace, with a magnification of 25 times and a thickness of 2.0 mm.
Was obtained.

Further, the foam is subjected to a corona treatment,
A skin made of a polyvinyl chloride sheet (0.6 mm) containing an ABS resin was adhered to the treated surface using a urethane-based adhesive to prepare a composite material consisting of a foam and a skin.

Comparative Examples 1 to 3 A composite material comprising a foam and a skin was prepared in the same manner as in Example 1 except that no petroleum resin was blended.

Adhesion Test Each of the composite materials obtained in Examples and Comparative Examples was subjected to a skin peel strength measurement test by the following method. That is,
The skin was peeled off from the foam at the end of the test piece (25 mm × 150 mm) of the composite material, and the foam and the skin were pulled at a speed of 200 mm / min using a measuring instrument “Tensilon” manufactured by Toyo Seiki. In the case of high-temperature test conditions, the measurement was performed after the test piece was left in the test box for 5 minutes.

Table 1 shows the test results.

[0022]

[Table 1] As is clear from the above table, it is recognized that the composite materials of Examples have remarkably superior skin peeling strength at high temperatures as compared with those of Comparative Examples.

[0023]

According to the present invention, since a specific compound is used as a crosslinking aid and a required amount of petroleum resin is blended in the resin composition, the peel strength between the foam and the skin is improved, and
No interfacial peeling phenomenon occurs even at a high temperature of not less than ℃. as a result,
A wide range of vacuum molding temperature conditions can be obtained, and a foam having good moldability can be supplied.

Claims (1)

(57) [Claims] 1. A polypropylene-based resin composition containing a foaming agent and a crosslinking aid is molded into a desired shape, and the molded product is crosslinked by irradiation with radiation, followed by heating and foaming. (Wherein, R ¹ , R ² and R ³ each represent a substituent having an olefinic double bond), and an aromatic trifunctional monomer represented by the following formula: Polypropylene resin
Relative to 100 parts by weight, characterized by blending a petroleum resin 0.1 parts production method of the polypropylene-based crosslinked foam.