JPH0431445A - Production of crosslinked olefin resin foam - Google Patents

Abstract

PURPOSE:To obtain a surface-modified crosslinked olefin resin foam improved in adhesiveness by mixing an expandable resin composition comprising an olefin resin and a thermally decomposable blowing agent with a specified amount of maleic acid (anhydride) or maleimide and crosslinking and expanding the mixture. CONSTITUTION:An expandable resin composition comprising 100 pts.wt. olefin resin, 0.05-2.5 pts.wt. at least one monomer selected from among maleic acid, maleic anhydride and maleimide, a thermally decomposable blowing agent and optionally an organic peroxide is molded into a sheet. This sheet is crosslinked and expanded by heating in the presence of an organic peroxide, or it is crosslinked by irradiation with electron beams or a radiation and expanded by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a crosslinked olefinic resin foam with improved adhesion.

[Prior art] Olefin resin crosslinked foams have appropriate hardness and flexibility, have excellent heat insulation properties, and are also suitable for heat processing such as vacuum forming and press forming, so they are used in a variety of applications. has been done.

However, olefin-based resin crosslinked foams have poor adhesion to different materials because olefin-based resins have high hydrophobicity.

The same type of first nofine resin crosslinked foams, or the crosslinked foams and an olefin resin sheet or film can be easily bonded together by a heat-melt adhesion method. However, the olefin resin crosslinked foam has extremely poor adhesion to different materials such as polyvinyl chloride (PVC) and polyurethane. In particular, when this cross-linked foam is used for vehicle interior materials, etc., it is often laminated with PVC leather, but it requires a great deal of effort in selecting adhesives and methods to improve adhesion. is the current situation.

Conventionally, in order to improve the adhesion of crosslinked olefin resin foams, corona discharge treatment, flame treatment, or surface oxidation treatment with an aqueous solution of chemicals such as potassium permanganate has been applied to add carbonyl groups to resin molecules on the surface of the foam. A method of introducing polar groups such as
Published on March 28th, pp. 205-220).

However, such methods require special treatment equipment, the results vary due to slight changes in the atmosphere or treatment conditions, it is difficult to obtain a constant degree of modification, and it is difficult to control the degree of modification. And more.

The surface may become uneven or have holes, which may impair the appearance of the foam.

As described above, with conventional methods for improving the adhesion of crosslinked polyolefin resin foams, quality control during processing is difficult, and unexpected defects often occur during subsequent adhesion processing and thermal processing steps.

[Problems to be Solved by the Invention] The purpose of the present invention is not to improve adhesion through post-treatment, but to
It is an object of the present invention to provide a method for producing a crosslinked olefin resin foam whose surface is easily and rationally modified in a normal production process for olefin resin crosslinked foams and whose adhesiveness is improved.

Another object of the present invention is to provide a method for producing an olefin resin crosslinked foam that has a large modification effect for improving adhesion, is stable, and does not cause abnormalities on the surface of the foam.

As a result of intensive research to overcome the problems of the prior art, the present inventors have found that a specific amount of maleic acid, maleic anhydride, etc. Alternatively, the inventors discovered that by blending maleimide and cross-linking and foaming the same, one surface was modified and a cross-linked foam with improved adhesiveness could be obtained, and based on this knowledge, the present invention was completed.

[Means to solve the problem]

Thus, according to the present invention, olefinic resin (^)1
00 parts by weight, at least one selected from maleic acid, maleic anhydride and maleimide CB10
．． A foamable resin composition containing 05 to 2.5 parts by weight, a thermally decomposable blowing agent (C), and optionally an organic peroxide (Dl) is formed into a sheet shape, and then a modified peroxide (Dl) is formed into a sheet. D
), or crosslinked by irradiation with electron beams or radiation, and then heated and foamed. A manufacturing method is provided.

The present invention will be explained in detail below.

(Foamable resin composition) The foamable resin composition used in the present invention contains an olefin resin and a pyrolyzable blowing agent varied depending on the desired expansion ratio, and when crosslinked with an organic peroxide, At least one selected from maleic acid, maleic anhydride, and maleimide, containing a crosslinking agent and, if necessary, a foaming aid, a crosslinking aid, a flame retardant, an anti-fouling agent, a filler, a coloring agent, etc. One type of monomer is blended at a ratio of 0.05 to 2.5 parts by weight per 100 parts by weight of the olefin resin.

Olefin, A Examples of the olefin resin used in the present invention include:
Low density polyethylene, medium to high density polyethylene, linear polyethylene, ethylene copolymers such as ethylene-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, ethylene acrylate copolymer, polypropylene, butene-polypropylene copolymer Polypropylene copolymers such as ethylene-propylene copolymers, mixtures thereof, and the like can be mentioned.

When it is desired to further improve the compatibility with maleic acid, ma]twinic acid anhydride, and maleimide, it is desirable to use an ethylene-vinyl acetate copolymer or an ethylene-acrylate copolymer.

The pyrolytic foaming agent used in the present invention includes various foaming agents that decompose with heat and generate gas, such as azodicarbonamide, dinitrosopentamethylenetetramine, and oxybisbenzenesulfonyl hydrazide. Agents can be mentioned.

The proportion of the pyrolytic foaming agent used varies depending on the desired magnification, but for boat fishing, it is 2 to 25 parts by weight per 100 parts by weight of the olefin resin.

1 plate'D Examples of the organic peroxide used in the present invention include n-
Butyl-4,4-di(t-butylperoxy)valerate, dicumyl peroxide, α.

α'-bis(t-butylperoxydiisopropyl)benzene, t-butylperoxycumene, 1.1'-di(
Examples include t-butylperoxy)3,3.5-trimethylcyclohexane and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

When using an organic peroxide, the proportion is usually preferably 0.4 to 2.0 parts by weight per 100 parts by weight of the olefin resin.

The foamable composition of the present invention contains, for example, a foaming aid such as a fatty acid metal salt or zinc white, a crosslinking aid such as divinylbenzene or trimethylolpropane trimethacrylate, a flame retardant, a filler, Antioxidants, colorants, etc. can be optionally added.

(Production method for crosslinking and foaming) The foamable resin composition is kneaded using a sheet molding stone at a temperature above the melting temperature of the olefin resin and below the temperature at which the pyrolytic foaming agent and crosslinking agent decompose. is formed into.

Next, the sheet is irradiated with electron beams or radiation to give the resin crosslinking that provides the viscoelasticity necessary for foaming, and then the pyrolyzable foaming agent is thermally decomposed to generate gas in the resin and cause foaming. , to obtain a cross-linked foam sheet.

Alternatively, in the case of crosslinking with an organic peroxide, the foamable resin composition sheet is preheated and crosslinked before foaming to give the resin the viscoelasticity necessary for foaming, and then heated and foamed, or the foam is foamed at the same time as crosslinking. A cross-linked foam sheet is obtained.

In this case, maleic acid, maleic anhydride, and maleimide all have vinyl groups with strong radical reactivity, so they react with the radicals generated above the olefin resin during the crosslinking step of the olefin resin, and graft onto the olefin resin. do.

Since the radicals used for crosslinking are used for grafting these monomers (B), they are reduced.
Depending on the olefin resin used, the crosslinking efficiency may decrease, but the addition ratio of monomer (B) is 0.05.
~2.5 parts by weight is irradiation energy! (Mr.
By increasing the amount of d) or organic peroxide added, the degree of crosslinking can be sufficiently adjusted.

The reason for limiting the blending ratio of the monomer (B) selected from maleic acid, maleic anhydride, and maleimide to 0.05 to 2.5 parts by weight is that the modification effect is insufficient if it is less than 0.05 parts by weight. On the other hand, if the amount exceeds 2.5 parts by weight, a large amount of the monomer (B) that has not been grafted onto the olefin resin will remain, and the compatibility with the olefin resin will be poor, causing it to bleed onto the surface over time. In particular, the monomer (B) bleeds to the surface before crosslinking, increasing the surface concentration, and during crosslinking, the ungrafted monomer residue on the surface increases, creating a monomer molecular layer on the foam surface, and the adhesiveness is rather reduced. This is because there are problems such as that the crosslinking efficiency may be decreased, and furthermore, that the crosslinking efficiency is greatly affected. The preferred blending ratio is 0.2-1, 5 parts by weight.

It is presumed that the 71-twin acid, maleic anhydride, and maleimide grafted on the foam surface layer conform with the acid groups, acid anhydride groups, and imide groups facing outward, and the tension on the foam surface due to wrinkling (sagging index) ) increases, improving compatibility with adhesives.

Furthermore, in the case of epoxy-based adhesives, urethane-based adhesives, and the like, unreacted terminal groups react with acid groups, acid anhydride groups, and imide groups located on the surface of the foam, so that the adhesion becomes stronger. however,
In order to stabilize the amount of maleic acid, maleic anhydride, and maleimide on the surface, it is desirable to carry out the crosslinking operation within 10 hours after molding the foamable resin composition sheet. This is to graft and fix the monomer before the amount of monomer bleed onto the surface increases.

In addition, in order to make the modification more effective, the crosslinked foam obtained above may be further subjected to corona treatment or the like.

〔Example〕

The present invention will be explained in more detail below by giving Examples and Comparative Examples. Note that parts represent parts by weight.

[Examples 1 to 5, Comparative Examples 1 to 2] Low density polyethylene (MI = 3.0, density = 0.923
), 15 parts of azodicarbonamide as a pyrolytic foaming agent, 1 part of zinc white as a foaming aid, and the parts of maleic acid, maleic anhydride, or maleimide as a monomer shown in Table 1 were added, and the mixture was heated using a Henschel mixer. mixed with.

This mixture was put into an extruder with a diameter of 65 mm (L/D=26), melted and kneaded, and extruded from a T-die to a thickness of 2 mm.
A foamable resin composition sheet with a width of 450 mm was molded.

Each sheet obtained was irradiated with an electron beam using a high voltage (800 keV) electron beam irradiation machine at a dose (Mrad) shown in Table 1.
Grafting and crosslinking were performed. Thereafter, the mixture was introduced into an oven heated to 230° C. to decompose the azodicarbonamide, thereby obtaining a crosslinked foam sheet with a thickness of about 4.5 mm, a width of about 800 mm, and a foaming ratio of about 30 times.

The wetting index (dyne/cm) of the foamed sheet was evaluated using a wetting reagent, and the results are shown in Table 1.

For comparison, maleic acid, maleic anhydride, and maleimide were not added (Comparative Example 1), maleic anhydride was added to 3.
A crosslinked foam sheet was obtained in the same manner as in Example except that 5 parts of the foam was added (Comparative Example 2). The evaluations are also shown in Table 1.

To confirm that the modifier monomer has been grafted, immerse a small piece of the crosslinked foam sheet in xylene at 125°C (
5 hours) to extract the soluble portion of the polyethylene resin, cast this extract on a hot plate set at 135°C, scatter the xylene solvent, and create a transparent film of the resin. After washing and drying, characteristic absorption was measured using an infrared spectrophotometer. The characteristic absorption used is maleic acid 170
0 to 1725 cm-', maleic anhydride 1780 cm-'
', this is an absorption caused by the carbonyl of maleimide 1700-1750 cm-'.

Peeling test> In addition, a 300 μm thick soft PVC sheet was coated with an epoxy adhesive manufactured by Bostik Japan Co., Ltd. at a rate of 25 g/I, heated to about 100°C, and tested in Examples 1 to 5 and Comparative Example. One to two crosslinked foam sheets were glued together. After being left at room temperature for 24 hours, a peel test was performed to evaluate adhesiveness.

Regarding the foam sheets of Examples 1 to 5, the surface on the foam side was destroyed by peeling, and the adhesiveness was sufficient. However, for the foam sheet of Comparative Example 1, there was interfacial peeling between the foam sheet and the adhesive layer, and for the foam sheet of Comparative Example 2, there was partial material failure on the foam side surface. In addition, there was a state of partial interfacial peeling between the adhesive layer and the adhesive layer.

The results of the peel test are also shown in Table 1.

[Effects of the Invention]' According to the present invention, maleic acid,
By simply adding the necessary amounts of maleic anhydride and maleimide, the surface of the foam can be easily modified in a normal olefin crosslinking foam production line and its adhesion can be improved. No processing equipment required.

Furthermore, according to the present invention, the modification degree is not modified by coating or other operations on the surface of the foam, but is bonded to the olefin resin through a graft reaction to form an integrated product, so the degree of modification changes or deteriorates over time. You can trust the quality without any hassle.

Claims (1)

[Claims] (1) 100 parts by weight of olefin resin (A), 0.05 to 2.5 parts by weight of at least one monomer selected from maleic acid, maleic anhydride, and maleimide (B), pyrolyzable blowing agent (C) ), and optionally an organic peroxide (D), is formed into a sheet shape, and then heated to crosslink and foam in the presence of the organic peroxide (D). Alternatively, a method for producing an olefin resin crosslinked foam with improved adhesiveness, comprising crosslinking by irradiating with an electron beam or radiation and then foaming by heating.