JP3236146B2 - Method of peeling a foam from a laminate containing a crosslinked polypropylene resin foam as a constituent material - 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 peeling a cross-linked foam containing a specific crosslinked polypropylene resin as a constituent material.

[0002]

2. Description of the Related Art A crosslinked polypropylene resin foam is formed by mixing a polypropylene resin composition comprising a polypropylene resin, a crosslinking accelerator and a foaming agent, molding the mixture, cross-linking with ionizing radiation, and then forming the foaming agent. It is manufactured by heating and foaming above the decomposition temperature of
0-11935, JP-A-4-292624, JP-A-5-25309, etc.).

[0003] Such a crosslinked polypropylene resin foam is widely used as a vehicle interior material for automobiles and the like, as a heat insulating material for ceilings, doors, instrument panels, etc., because of its excellent heat resistance, flexibility and heat insulating properties. ing. When used as these vehicle interior materials, polypropylene-based resin cross-linked foams are mainly laminated using resin-based materials such as vinyl chloride resin and thermoplastic elastomer, or natural or artificial cloth-based materials as skin materials. It is used in the form of a body (Japanese Utility Model Publication No. 5-20608, Japanese Utility Model Publication No. 5-20609, Japanese Patent Publication No. 5-28177).

[0004]

By the way, it may be necessary to peel off the foam from the laminate containing the crosslinked polypropylene resin foam as a constituent material as described above. For example, when discarding the above laminate,
In the case of a laminate that is laminated with a vinyl chloride resin material, harmful hydrogen chloride gas is generated if the foam and the vinyl chloride resin are incinerated as they are without being separated. This is the case when only the foam is separated and incinerated.
Further, as another case, when using the laminate as a vehicle interior material, after laminating the laminate and the core material, the end of the laminate is wrapped around the core material. With only the skin material, the foam needs to be peeled from the skin material.

Heretofore, these materials have been merely mechanically applied for peeling, but it has been difficult to peel them at the interface between the skin material and the foam.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to convert a specific polypropylene-based resin crosslinked foam from a laminate containing the same to another constituent material. It is an object of the present invention to provide a method capable of peeling off from the interface of the substrate.

[0007]

Means for Solving the Problems A method for peeling a foamed resin from a laminate containing the crosslinked foamed polypropylene resin as a constituent material according to the present invention comprises the following steps: (a) a polypropylene resin; A crosslinking accelerator comprising a compound represented by [I] or [II], and

[0008]

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Wherein R ¹ is an n-valent alkyl or aryl group, and n is an integer of 1 to 4.

[0010]

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(Wherein, R ² is an m-valent alkyl group or an aryl group, and m is an integer of 1 to 4). (C) Mixing and molding a polypropylene resin composition containing an organic pyrolysis type foaming agent Then, after cross-linking with ionizing radiation in the presence of oxygen, a laminate containing, as a constituent material, a polypropylene-based resin cross-linked foam obtained by heating and foaming at a temperature equal to or higher than the decomposition temperature of the organic pyrolytic foaming agent. While heating to a temperature of 150 ° C. or higher, the foam in the laminate is separated from other constituent materials.

The polypropylene resin (a) used in the present invention is a propylene homopolymer, a block copolymer of propylene and ethylene, a random copolymer of propylene and ethylene, a ternary copolymer of propylene and ethylene, butene or the like. Or a mixture comprising 50% by weight or more of the above, and an ethylene homopolymer or an ethylene-α-olefin copolymer, or a mixture thereof. As the α-olefin of the ethylene-α-olefin copolymer, those having 4 to 8 carbon atoms are preferable. Specifically, for example, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, -Pentene and the like.

The crosslinking accelerator (b) used in the present invention is a compound represented by the above general formula [I] or [II], and a compound represented by the general formula [I] includes: For example, triallylic acid triallyl ester can be mentioned, and as the compound represented by the general formula [II], for example, divinylbenzene, divinylnaphthalene and the like can be mentioned. The crosslinking accelerator (b) is preferably used in a proportion of 0.1 to 30 parts by weight, more preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the polypropylene resin (a).

The organic pyrolytic foaming agent (c) used in the present invention generates a decomposed gas by heating and has a decomposition temperature higher than the melting temperature of the polyolefin resin used in the present invention. If it is a thing, it will not be specifically limited. Preferably, azodicarbonamide, further hydrazodicarbonamide having a decomposition point equal to or higher than azodicarbonamide,
Azodicarboxylic amide, barium azodicarboxylate, dinitrosopentaethylenetetramine, nitrosoguanidine, p, p'-oxybisbenzenesulfonyl semicarbazide, etc. can be used alone or in combination. In addition, trihydrazine symmetric triazine, bisbenzenesulfonyl hydrazide, barium azodicarboxylate, azobisisobutyronitrile, toluenesulfonyl hydrazide and the like are used.

The organic thermal decomposition type foaming agent (c) is used in an appropriate amount according to a desired expansion ratio within a range of 1 to 50 parts by weight based on 100 parts by weight of the polypropylene resin (a). used.

The polypropylene resin composition used in the present invention may contain, if necessary, an antioxidant, an antioxidant,
Stabilizers, pigments and the like can be blended.

The method for producing the crosslinked polypropylene resin foam used in the present invention is as follows. First,
A polypropylene-based resin composition comprising a polypropylene-based resin (a), a crosslinking accelerator (b), an organic pyrolysis-type foaming agent (c), and an additive added as necessary is mixed with a single-screw extruder, Using a general-purpose kneading device such as a screw extruder, a Banbury mixer, a kneader mixer, or a roll, the mixture is melt-mixed at a temperature lower than the decomposition temperature of the foaming agent, and usually formed into a sheet. Next, the obtained foamable resin composition sheet is cross-linked by irradiating with ionizing radiation in the presence of oxygen, and the obtained foamable molded article is heated to a temperature equal to or higher than the decomposition temperature of the organic thermal decomposition-type foaming agent and foamed. Thus, a crosslinked polypropylene resin foam is produced.

In the presence of oxygen, not only the presence of oxygen alone, but also other gases may coexist, for example, in the air.

As ionizing radiation, α-ray, β-ray, γ
Rays, electron beams, etc., and when the irradiation dose is small, the obtained foam has insufficient heat resistance, and when the irradiation dose is large, the foam becomes unnecessarily hard.
ad is preferred. As a standard of the irradiation dose, the gel fraction of the foamable resin composition sheet after irradiation (measured by extracting in xylene at 120 ° C. for 24 hours) is 20 to 7
0% is preferable, and 30 to 60% is more preferable.

The laminate used in the present invention only needs to contain the above-mentioned crosslinked foamed polypropylene resin as a constituent material, and the foam may be present on the surface or inside of the laminate. Good.

Examples of the material used for producing the laminate used in the present invention by laminating with the above-mentioned crosslinked foamed polypropylene resin include resin-based or cloth-based materials. Examples of the resin-based material include vinyl chloride resin and thermoplastic elastomer, and examples of the cloth-based material include synthetic fibers such as polyester, polyamide, and acrylic, and natural fibers such as cellulose.

As a method of laminating the laminate, any method such as a method using an adhesive, a method using a heat laminating method, a method using an extruding laminating method and the like can be used.

In the present invention, as a method of peeling the foam from a laminate containing the above-mentioned specific crosslinked foam of a polypropylene resin as a constituent material, the laminate is heated at 150 ° C.
A method of peeling while heating to the above temperature is used. If the heating temperature is lowered, the foam cannot be peeled off from the interface with other constituent materials. The heating method is not particularly limited, as long as the temperature of the laminate can be heated to 150 ° C. or higher, and examples thereof include a method of heating in an oven.

[0024]

The reason why the crosslinked polypropylene resin foam can be peeled off from the interface with other constituent materials by the method of the present invention is not clear, but is presumed as follows.
When the molded article of the polypropylene resin composition is crosslinked by ionizing radiation irradiation in the presence of oxygen, the specific crosslinking used in the present invention is promoted by ozone gas generated by irradiation of ionizing radiation in the presence of oxygen. It is conceivable that the functional group of the agent is deteriorated, crosslinking inhibition occurs in the surface layer of the molded article, and the molecular weight of the polypropylene resin in the surface layer is reduced. For this reason, when the laminate is exposed to a temperature exceeding the melting point of the polypropylene-based resin, it is considered that this surface layer softens and peels off at the interface with another laminated material.

[0025]

EXAMPLES Examples and comparative examples of the present invention will be described below. (Example 1) (1) Production of cross-linked foam of polypropylene resin Ethylene-propylene random copolymer (content of ethylene component = 3.6% by weight,
55% by weight (melt index = 1.8) and linear low density polyethylene (melt index = 18, density = 0.
920) 100 parts by weight of a mixture consisting of 45% by weight
2.5 parts by weight of triallylic acid triallyl ester as a crosslinking accelerator and azodicarbonamide 10 as a blowing agent
Parts by weight and other additives such as an antioxidant were added, and after mixing, the mixture was supplied to a 120 mmφ extruder at a temperature of 180 ° C.
The mixture was melted and kneaded at an appropriate temperature and extruded to obtain a sheet having a thickness of 1.6 mm. An acceleration voltage of 600 was applied to the obtained sheet in the presence of air.
Cross-linking was performed by irradiation with an electron beam of 2.5 Mrad at kV (the gel fraction was measured by extracting the obtained sheet in xylene at 120 ° C. for 24 hours and found to be about 45%). Put the obtained sheet in an oven, temperature 260 ℃
To obtain a sheet of a crosslinked foamed polypropylene resin having a thickness of 3 mm. The apparent density of the obtained foam was 0.04 g / cm ³ .

(2) Production of Laminate The sheet obtained above was applied as a skin material with a thickness of 0.4 m.
Then, a vinyl chloride resin sheet having a thickness of m was bonded using a urethane-based adhesive to obtain a laminate.

(3) Peeling test of crosslinked polypropylene resin foam The laminate obtained above was cut into a width of 25 mm, and the crosslinked polypropylene resin foam side was attached to a stainless steel plate using an adhesive. Then, a stainless steel plate was used as one grip of a tensile tester, and a sheet made of
It was folded back to 0 degrees and set on the other grip. After standing at 150 ° C. for 15 minutes in this state, the sheet was pulled at a speed of 200 mm / min until the vinyl chloride resin sheet was completely peeled off, and the load at that time was determined. As a result, peeling was performed at the interface between the foam and the skin material, and the load at the time of peeling was 10 gf.
/ 25 mm.

(Comparative Example 1) The peeling of the crosslinked foamed polypropylene resin in step (3) of Example 1 was carried out at 150 ° C.
A peeling test was performed in the same manner as in Example 1 except that the heating was performed at a temperature of 130 ° C. instead of heating at a temperature of. As a result, without peeling at the interface between the foam and the skin material,
The foam was broken inside the foam while remaining adhered to the skin material, and the load at the time of breaking was 50 gf / 25 mm.

Example 2 In step (1) of Example 1, 2.5 parts by weight of divinylbenzene was used in place of 2.5 parts by weight of triallylic acid triallyl ester as a crosslinking accelerator. Except that, a crosslinked polypropylene resin was produced in the same manner as in Example 1 (the gel fraction of the sheet after electron beam irradiation was about 45%, and the apparent density of the crosslinked foamed polypropylene resin was , 0.04
g / cm ³ ), and production of a laminate and a peeling test were performed in the same manner as in Example 1. As a result, in the peel test,
Peel off at the interface between the foam and the skin material, the load at the time of peeling is 10g
f / 25 mm.

(Comparative Example 2) In the peeling of the crosslinked foamed polypropylene resin in step (3) of Example 2, the temperature was set to 150 ° C.
A peeling test was performed in the same manner as in Example 2 except that the heating was performed at a temperature of 130 ° C. instead of heating at a temperature of 130 ° C. As a result, without peeling at the interface between the foam and the skin material,
The foam was broken inside the foam while remaining adhered to the skin material, and the load at the time of breaking was 50 gf / 25 mm.

(Comparative Example 3) In step (1) of Example 1, instead of using 2.5 parts by weight of triallylic acid triallyl ester as a crosslinking accelerator, trimethylolpropane trimethacrylate was added in an amount of 2.5 parts by weight. A crosslinked polypropylene-based resin was produced in the same manner as in Example 1 except that parts by weight were used (the gel fraction of the sheet after electron beam irradiation was about 45%, The apparent density of was 0.04 g / cm ³ ), and the production of a laminate and a peeling test were performed in the same manner as in Example 1. As a result, in the peeling test, the foam did not peel at the interface between the foam and the skin material, but broke inside the foam while the adhesive remained on the skin material, and the load at the time of breaking was 30 gf / 2.
5 mm.

[0032]

The method of peeling the foamed product from the laminate containing the crosslinked foamed polypropylene resin of the present invention as a constituent material is as described above, and the polypropylene resin has the general formula [I] or [II]. A cross-linking accelerator consisting of a compound represented by the formula and an organic pyrolytic foaming agent are blended, cross-linked by ionizing radiation in the presence of oxygen, and then a specific polypropylene-based cross-linked foam obtained by foaming. It is effective as a method for easily peeling the foam from an interface with another constituent material from the laminate containing the constituent material, and is effective when discarding the laminate or when using the laminate. This is an effective method when it is desired to separate only the foam from other constituent materials at the position, for example.

Claims (1)

(57) [Claims] 1. A (a) polypropylene resin, (b) a crosslinking accelerator comprising a compound represented by the following general formula [I] or [II], and (Wherein, R ¹ is an n-valent alkyl group or aryl group, n
Is an integer of 1 to 4) (Wherein R ² is an m-valent alkyl group or aryl group, m
(C) is an integer of 1 to 4) (c) A polypropylene-based resin composition containing an organic pyrolysis-type foaming agent is mixed and molded, and crosslinked by ionizing radiation in the presence of oxygen. While heating a laminate containing a polypropylene-based resin crosslinked foam as a constituent material obtained by heating and foaming to a temperature not lower than the decomposition temperature of the mold foaming agent, the foam in the laminate and the other A method for peeling a foamed material from a laminate containing a crosslinked polypropylene resin foam as a material, wherein the foamed material is separated from the foamed material.