JPH08197664A - Crosslinked polyolefinic resin foam and preparation thereof and laminate using the foam - Google Patents

Abstract

PURPOSE: To improve elongation at high temperatures, to prevent an interfacial peeling phenomenon, and to obtain good moldability in both vacuum molding and stamping molding. CONSTITUTION: An expandable resin laminate sheet, after being crosslinked, is expanded, in which an expandable resin layer A comprising polyolefin containing polypropylene and polyethylene, multifunctional monomer having a (meth)acrylate group, and a heat decomposition type foaming agent is laminated at least on one side of an expandable resin layer B comprising polyolefin containing polypropylene and polyethylene, multifunctional monomer having a allyl group or a vinyl group and a heat decomposition type foaming agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked polyolefin resin foam, a method for producing the same, and a laminated body, and more specifically, a crosslinked polyolefin excellent in high-temperature elongation, peeling resistance from a skin material, and moldability. TECHNICAL FIELD The present invention relates to a resin foam, a method for producing the same, and a laminate using the foam.

[0002]

2. Description of the Related Art Crosslinked polyolefin resin foams are used in a wide variety of fields as heat insulating materials, cushioning materials and the like. Particularly, in automotive applications, it is used as an interior material such as a ceiling material, a door inner surface material, an instrument panel, a console box, a rear wheel house cover, a luggage house cover, a trunk room cover, and a cooler cover.

The crosslinked polyolefin resin foam is generally used as a composite material by laminating a surface material such as a soft vinyl chloride sheet on the surface thereof. The crosslinked polyolefin resin foam and the skin material are usually laminated using an adhesive such as a urethane adhesive, and then,
It is formed into a desired shape by a forming method such as vacuum forming such as female type grain reversal or stamping forming. The composite molded article thus obtained is set on an aggregate such as a polypropylene resin sheet which has been melted by heating with an infrared heater or the like and pressed. Therefore, the crosslinked polyolefin-based resin foam is required to have excellent heat resistance and high-temperature moldability as well as excellent adhesion (peeling resistance) to the skin material.

By the way, in recent years, the shape of door / instrument panels has become deeper, and air is generated between the skin material and the foam, especially in the armrest and the wood grain portion where the expansion rate (expansion rate) of the foam is large. There is a further need for countermeasures against the so-called blistering phenomenon. In particular, in the matched die method in which a male mold and a female mold are combined and vacuum-molded, the foam receives a strong shearing force between mold clearances, and as a result of being squeezed, the same blistering phenomenon easily occurs, and in the conventional technology, It is difficult to deal with it sufficiently.

In recent years, the molding cycle has been shortened, the shapes of molded products have become complicated, and the number of deep-drawn molded products has increased. Therefore, during hot stamping molding, a greater shearing force than before has been applied to the material, and more. It was often heated to a high temperature. To deal with the blistering phenomenon,
It is conceivable to increase the peel strength at high temperature (100 ° C. or higher) as well as to increase the elongation at high temperature and decrease the elastic modulus at high temperature.

In stamping molding as well, recently, it is the mainstream that stamping molding is carried out after preliminary molding by vacuum molding using a mold having shallow irregularities, and elongation at high temperature is required. For example, a conventional foam sheet with skin material is vacuum-molded in advance into a desired shape in a concave shape, and the aggregate made of molten thermoplastic resin is supplied to this, and hot stamping molding is performed by embossing in a convex shape. In this case, if the expansion of the foam sheet is small, the aggregate resin may partially enter the foam sheet, or the foam sheet may be partially torn by the invading aggregate resin. Cannot be obtained.

Conventionally, for example, a crosslinked polypropylene resin foam has a polypropylene resin, a pyrolyzable foaming agent, and
A polyfunctional monomer such as diethylene glycol dimethacrylate or trimethylolpropane trimethacrylate as a cross-linking aid is blended, molded into a sheet, cross-linked by irradiation with an electron beam, and then heated above the decomposition temperature of the thermal decomposition type foaming agent. And foamed (for example, Japanese Patent Publication No. 5
8-57452).

[0008]

However, a foam obtained by using a polyfunctional monomer having a (meth) acryl group as a cross-linking aid does not have sufficient elongation at high temperature, and the elongation increases as the molding temperature rises. Decreases rapidly. Therefore, the conventional crosslinked polypropylene-based resin foam is liable to cause breakage due to insufficient elongation during vacuum forming or the like.

Recently, it has been proposed to use a mixture of 1,2,4-benzenetricarboxylic acid triallyl ester (ie, triallyl trimellitate) and 1,9-nonanediol dimethacrylate as a crosslinking aid. (Japanese Patent Laid-Open No. 5-93083). When a polyfunctional monomer having an allyl group such as triallyl trimellitate is used as a cross-linking aid, the expansion degree of the foam at high temperature is increased,
Although it is possible to impart a low elastic modulus, when it is exposed to a high temperature of 140 ° C. or higher after being bonded to a skin material, it may peel off at the interface between the skin material and the foam.

The object of the present invention is to provide excellent elongation at high temperature,
To provide a crosslinked polyolefin resin foam having excellent moldability in both vacuum molding and stamping molding, a method for producing the same, and a laminate using the foam, in which there is no occurrence of an interfacial peeling phenomenon with a skin material. It is in.

[0011]

The crosslinked polyolefin resin foam of the present invention according to claim 1 is a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having an allyl group or a vinyl group, and A polyolefin-based resin containing a polypropylene-based resin and a polyethylene-based resin on at least one surface of a foamable resin layer B containing a pyrolytic foaming agent, (meth)
A foamable resin laminated sheet obtained by laminating a foamable resin layer A containing a polyfunctional monomer having an acrylic group and a thermal decomposition type foaming agent is crosslinked and then foamed.

The crosslinked polyolefin resin foam of the present invention according to claim 2 contains at least 4 polypropylene resins.
It is characterized by using a polyolefin resin containing 0% by weight.

The method for producing a crosslinked polyolefin resin foam according to the present invention is a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having an allyl group or a vinyl group, and a thermal decomposition type. At least one surface of the foamable resin layer B containing a foaming agent, a polyolefin resin containing a polypropylene resin and a polyethylene resin, a (meth) acrylic group-containing polyfunctional monomer, and a thermal decomposition type foaming agent. The foamable resin laminated sheet obtained by laminating the foamable resin layer A thus obtained is crosslinked and then foamed.

The method for producing a foam according to claim 4 is the same as the method for producing a polyolefin resin foam according to claim 3, wherein the polypropylene resin is at least 40% by weight.
It is characterized by using a contained polyolefin resin.

The laminate according to claim 5 is the laminate according to claim 1 or 2.
The polyolefin-based resin foam described in (1) above is obtained by laminating a skin material on the surface of the foam obtained by foaming the expandable resin layer A.

The present invention will be described in detail below. Polyolefin Resin In the present invention, a polyolefin resin containing a polypropylene resin and a polyethylene resin is used in order to impart a high degree of elongation at high temperature and heat resistance. This polyolefin-based resin preferably contains at least 40% by weight of polypropylene-based resin, and the mixing ratio of the polypropylene-based resin and the polyethylene-based resin is 50-80% by weight of the polypropylene-based resin and 2% of the polyethylene-based resin.
It is more preferably 0 to 50% by weight. When the content is within the above range, it is possible to obtain a crosslinked foam having excellent physical properties at high temperature, moldability, and appearance.

The polypropylene resin composition may be a homopolymer of propylene, a block copolymer or random copolymer of 50% by weight or more of propylene and ethylene, or a terpolymer of propylene and ethylene, butene or the like. Or a mixture thereof, and a copolymer of any of the above with ethylene or an ethylene-α-olefin.

The polypropylene resin has a melt index (MI: measured according to ASTM D-1238) of
Usually, it is 0.3 to 10, preferably 0.4 to 5, and more preferably 0.4 to 2. MI of polypropylene resin
Is less than 0.3, there is a problem in appearance when formed into a sheet, and when it exceeds 10, heat resistance becomes insufficient, and thus both are not preferable. In order to impart heat resistance and high temperature elongation,
Those having MI in the range of 0.4 to 2 are particularly preferable.

As the polyethylene resin, low density polyethylene, medium density polyethylene, high density polyethylene,
Either linear low-density polyethylene or ultra-low-density polyethylene may be used, but the melt index is 1.0 to
It is 20, and linear low density polyethylene is preferable in order to impart elongation especially at high temperature.

The MI of polyethylene resin is usually 1 to
50, preferably 3 to 30, more preferably 4 to 25. If the MI of the polyethylene resin is less than 1, there is a problem in appearance when formed into a sheet, and if it exceeds 50, there is a problem in heat resistance. Linear low density polyethylene (LLD) to impart high temperature elongation
PE) is particularly preferred.

Polyfunctional Monomer In the present invention, a foamable resin layer (B layer) in which a polyfunctional monomer having an allyl group or a vinyl group is mixed is arranged in the central layer, and a polyfunctional monomer having a (meth) acrylic group is provided on at least one surface thereof. A foamable resin laminated sheet in which layers (A layer and C layer) of a foamable resin composition containing a functional monomer are arranged is produced.

The foamable resin laminated sheet having such a structure can be easily produced by, for example, a coextrusion method using a plurality of extruders and the like. Alternatively, a laminated sheet may be prepared by preparing a sheet of each foamable resin composition containing a polyfunctional monomer having a different functional group, stacking them, and hot pressing them. The method for producing the laminate is not particularly limited, but the coextrusion method is preferable because it can be continuously molded.

Examples of the polyfunctional monomer having a (meth) acrylic group include 1,9-nonanediol di (meth) acrylate, 1,10 decanediol di (meth) acrylate and trimethylolpropane tri (meth) acrylate. And these are either
Combinations of more than one species can be used.

Examples of the polyfunctional monomer having an allyl group include diallyl phthalate, diallyl fumarate, diallyl maleate, triallyl trimellitate, and the like. These may be used alone or in admixture of two or more. Can be used.

Examples of the polyfunctional monomer having a vinyl group include divinylbenzene, divinylnaphthalene and vinyltoluene, which may be used alone or in combination of two or more.

The polyfunctional monomer having an allyl group, the polyfunctional monomer having a vinyl group, and the polyfunctional monomer having a (meth) acryl group are the polyolefin resin 1
0.1 to 30 parts by weight, preferably 0.5 to 20 parts by weight, and more preferably 1 to 100 parts by weight, respectively.
It is used in a ratio of 10 to 10 parts by weight. If this ratio is too low, it becomes difficult to obtain a uniform foam due to insufficient cross-linking and the heat resistance becomes low. If this ratio is too large, the degree of crosslinking will be too high, and the flexibility will be impaired, and at the same time, elongation at high temperature will be reduced, resulting in problems in moldability.

Thermally Decomposable Foaming Agent The thermally decomposable foaming agent is not particularly limited as long as it has a decomposition temperature higher than the melting temperature of the polyolefin resin. As specific examples, azodicarbonamide, hydrazodicarbonamide having a decomposition point equivalent to or higher than that of azodicarbonamide, azodicarboxylic acid amide, azodicarboxylic acid barium salt, dinitrosopentaethylenetetramine, nitrosoguanidine, p,
P'-oxybisbenzenesulfonyl semicarbazide and the like can be used alone or in combination. Other,
Trihydrazine symmetric triazine, bisbenzenesulfonyl hydrazide, barium azodicarboxylate, azobisisobutyronitrile, toluenesulfonyl hydrazide and the like can be used. Among these, azodicarbonamide is particularly preferable.

The thermal decomposition type foaming agent is used in an amount of usually 1 to 50 parts by weight, preferably 1 to 30 parts by weight, more preferably 2 to 25 parts by weight, based on 100 parts by weight of the polyolefin resin. Within the above range, the blending amount can be appropriately selected according to the desired expansion ratio.

Method for producing crosslinked polyolefin resin foam
Method Polyolefin resin, a polyfunctional monomer, a thermal decomposition type foaming agent, and, if necessary, an antioxidant, a heat stabilizer,
A foamable resin composition is prepared by mixing additives such as a pigment, a colorant, an antistatic agent, a flame retardant, a plasticizer, and a filler. In this case, a foaming resin A containing a polyfunctional monomer having a (meth) acrylic group as a polyfunctional monomer and a foaming resin B containing a polyfunctional monomer having an allyl group or a vinyl group as a polyfunctional monomer are prepared. .

Specifically, each component is melt-kneaded at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent by using a kneading device such as a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader mixer and a roll. To obtain a foamable resin composition, which is molded into a sheet. The co-extrusion method is preferably used to form the foamable resin composition into a sheet. That is, a foamable resin layer (B layer) in which a polyfunctional monomer having an allyl group or a vinyl group is mixed is arranged in the central layer, and a polyfunctional monomer having a (meth) acrylic group is mixed in at least one surface thereof. By laminating the layers (A layer and C layer) and performing coextrusion molding, it is possible to obtain a laminated sheet including a foamable resin layer. As another method, the expandable resin composition to be the A layer and the C layer and the B layer may be separately extrusion-molded, and then laminated and hot pressed to produce a laminated sheet.

The foamable laminate thus obtained is usually crosslinked by irradiating both sides with ionizing radiation such as an electron beam, and thereafter, at a temperature not lower than the decomposition temperature of the thermal decomposition type foaming agent. Heat to foam. Instead of irradiation crosslinking, crosslinking may be performed using a chemical crosslinking agent such as peroxide. Further, ionizing radiation and a chemical crosslinking agent may be used in combination for crosslinking.
When a chemical crosslinking agent is used, it is added at the stage of preparing the foamable resin composition.

A combination of ionizing radiation and a chemical crosslinking agent,
The degree of cross-linking of each layer can be made different by combining different radiation doses or by varying irradiation angles. The total gel fraction is usually 20 to 75% by weight, preferably 30 to 65% by weight. By setting the crosslinking degree within this range, it is possible to obtain a foam excellent in heat resistance and elongation at high temperature while ensuring the stability of foaming. The gel fraction is a value obtained by the following formula.

In the present invention, A layer / B layer or A layer / B layer /
A foamable laminated sheet having a laminated structure of C layer is produced. A high degree of elongation can be obtained by forming the central layer (B layer) as a foamable resin layer containing a polyfunctional monomer having an allyl group or a vinyl group. The crosslinked structure by the polyfunctional monomer having an allyl group or a vinyl group is considered to be a bundle type crosslink like IPN, not a crosslink crosslink. This is supported by the fact that the gel fraction obtained by the solvent extraction method decreases significantly with time. It is considered that by adopting the bundle-type cross-linking structure, the movement of the molecular chain with respect to stress is improved and a high degree of elongation can be obtained.

When the surface layers (A layer and C layer) are made of a foamable resin layer containing a polyfunctional monomer having a (meth) acrylic group, interfacial peeling of the skin material can be prevented. The interfacial peeling phenomenon is considered to be due to a decrease in molecular weight due to uncrosslinking / crosslinking deterioration near the surface of the foam, but a polyfunctional monomer having a (meth) acrylic group is highly reactive and causes such a decrease in molecular weight. Since it is not present, it is considered that it exhibits good adhesion to the skin material.

The thickness ratio (A: B) between the A layer and the B layer is usually preferably in the range of 1: 2 to 1:20. When the thickness of the B layer is smaller than the above range, the contribution effect of the B layer becomes too small, and it becomes difficult to obtain sufficient high temperature elongation. It is desirable that the A layer and the C layer have the same thickness ratio (1: 1) in order to obtain a uniform crosslinked foam, but if desired, the thickness ratio (A: C) of both layers is 10: 5 to 5:10. , Preferably 1
It may be changed within the range of 0: 8 to 8:10.

The cross-linked polyolefin resin foam thus obtained can be used by being compounded with various skin materials by a conventional method. As the skin material, if it is a cloth-based skin material, a synthetic fiber such as polyester, polyamide, or acrylic, or a natural fiber such as cellulosic material may be mentioned. If it is a resin-based skin material, it may be vinyl chloride-based or thermoplastic. Elastomer type etc. can be used arbitrarily. As a method for laminating the crosslinked foam and the skin material, an adhesive method, a thermal laminating method, an extrusion laminating method, or the like can be arbitrarily used.

[0037]

In the crosslinked polyolefin resin foam of the present invention according to claims 1 and 2, the central layer (B layer) is gently crosslinked or bundle-type crosslinked with a polyfunctional monomer having an allyl group or a vinyl group. Therefore, the movement of the molecular chain with respect to the stress is improved, and the degree of elongation is high. In addition, since the polyfunctional monomer having a (meth) acrylic group used on at least one surface of the layer B has high reactivity, it does not cause a decrease in the molecular weight of the polyolefin resin due to uncrosslinking or crosslink deterioration, and has excellent lamination strength between layers. Becomes

In the method for producing a foam according to claims 3 and 4, a foamable resin layer (B layer) containing a multifunctional monomer having an allyl group or a vinyl group is arranged in the central layer, and both surfaces thereof are arranged. Since a foamable resin laminated sheet obtained by arranging a foamable resin layer (A layer and C layer) containing a polyfunctional monomer having a (meth) acrylic group in the layer is cross-linked and then heat-foamed, the B layer is The gentle cross-linking or bundle-type cross-linking by the polyfunctional monomer having an allyl group or a vinyl group improves the movement of the molecular chain with respect to stress and can give the foam a high degree of elongation.

Since the polyfunctional monomer having a (meth) acrylic group used for both surface layers has high reactivity, it does not cause a decrease in the molecular weight of the polyolefin resin due to uncrosslinking or crosslinking deterioration, thereby preventing interfacial peeling between layers. You can

The laminate according to claim 5 has a large degree of elongation by heating, has excellent adhesiveness to the skin material laminated on the foam, and does not cause interfacial peeling.

[0041]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. (Examples 1 and 2) Polypropylene resin (MI = 1.
0, 60 parts by weight of a propylene-ethylene random copolymer having an ethylene content of 3.6% by weight, and 40 parts by weight of a polyethylene resin (MI = 8.0, linear low density polyethylene having a density of 0.920 g / cm ³ ). And a part were mixed to prepare a polyolefin resin. Foamable resin layer (A
Layer and C layer), azodicarbonamide as a thermal decomposition type foaming agent, trimethylolpropane trimethacrylate and 1,9-nonanediol dimethacrylate as a crosslinking aid, and 100 parts by weight of the above polyolefin resin A resin formulation was prepared by blending the inhibitor (BHT) in the amounts shown in Table 1.

On the other hand, a foamable resin layer (B layer) serving as a central layer
As a resin for use, 100 parts by weight of the above-mentioned polyolefin resin was mixed with azodicarbonamide as a thermal decomposition type foaming agent, triallyl trimellitate as a crosslinking aid, and an antioxidant (BHT) in the amounts shown in Table 1. To prepare a resin formulation.

These resin blends were simultaneously extruded using three extruders at temperatures below the decomposition temperature of the foaming agent, and the thickness ratio of each layer was A (surface layer) / B (center layer) / C (surface layer). = 1 /
8/1, the sheet was molded into a sheet-like shape so that the thickness of the entire sheet was 1.5 mm to prepare a foamable sheet. Combine this foam sheet with electron beam (800 KV) from both sides to 1.
The polyolefin resin was cross-linked by irradiation with 5 Mrad, and then introduced into a hot air type foaming furnace at 280 ° C. to be heat-foamed to obtain a cross-linked polyolefin resin foam. The crosslinked polyolefin resin foam had a thickness of 3 mm, an expansion ratio represented by the following formula of 25 times, and a gel fraction of 40% after extraction in xylene at 120 ° C. for 24 hours.

(Examples 3 to 6) 70 parts by weight of the same polypropylene resin as that used in Example 1 and Example 1
A polyolefin resin was prepared by mixing with 30 parts by weight of the polyethylene resin used in.

A foamable resin layer (A layer and C layer) serving as a surface layer.
Trimethylolpropane trimethacrylate as a cross-linking aid in the resin for layer) and divinylbenzene as the cross-linking aid in the resin for the foamable resin layer (B layer) to be the central layer in the amounts shown in Tables 1 and 2 and others. In the same manner as in Example 1, crosslinked polyolefin resin foams having the physical properties shown in Tables 1 and 2 were obtained.

(Comparative Examples 1 to 7) Using the resin formulations shown in Table 3, a single layer sheet was extrusion-molded with an extruder, crosslinked and foamed in the same manner as in Example 1, and shown in Table 3. The crosslinked polyolefin resin foam shown was obtained.

Performance Evaluation The vacuum moldability and peel strength of the crosslinked polyolefin resin foams obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were examined by the following methods. The results are shown in Tables 1 to 3.

(1) Vacuum Formability Using the crosslinked polyolefin resin foams (10 samples) of Examples and Comparative Examples, the foam surface was heated to 180 ° C. and the molding draw ratio (depth / (Diameter 100 mm)
The vacuum moldability was evaluated by the ratio (number of passes / number of moldings) of the number of cases in which the case was vacuum-formed with a cylindrical concave type of 0.8 and could be formed into a cup shape without breaking the foamed product. .

(2) Peel Strength A urethane vinyl adhesive was used on one side of the cross-linked polyolefin resin foams of Examples and Comparative Examples, and a skin material made of a soft vinyl chloride resin sheet (thickness 0.4 mm) was attached to each other. A foamed sheet with a skin material was created. This is 25m wide
After being cut into strips of m, and left for 5 minutes at 150 ° C. using a tensile tester (Tensilon manufactured by Orientec),
The foamed sheet and the skin material were peeled off at a pulling speed of 200 mm / min, and the peel strength was measured. The above results are shown in Tables 1 to 3.
Shown in

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

(* 1) Polyolefin resin: Mixture of 60 parts by weight of propylene-ethylene random copolymer and 40 parts by weight of linear low-density polyethylene (* 2) Polyolefin resin: propylene-ethylene random copolymer 70 A mixture of parts by weight and 30 parts by weight of linear low density polyethylene.

[0054]

Industrial Applicability According to the invention, a crosslinked polyolefin resin foam excellent in extensibility at high temperature and free from interfacial peeling phenomenon with a skin material and having excellent moldability in both vacuum molding and stamping molding, and the same are disclosed. It is possible to provide a manufacturing method and a laminate using the foam.

Claims (5)

[Claims] 1. A foamable resin layer B formed by blending a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having an allyl group or a vinyl group, and a thermal decomposition type foaming agent. A foamable resin obtained by laminating a foamable resin layer A containing a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having a (meth) acrylic group, and a thermal decomposition type foaming agent. A crosslinked polyolefin resin foam, wherein the laminated sheet is foamed after crosslinking. 2. A polypropylene resin of at least 40
The crosslinked polyolefin resin foam according to claim 1, wherein the polyolefin resin is contained in a weight percentage. 3. A foamable resin layer B formed by blending a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having an allyl group or a vinyl group, and a thermal decomposition type foaming agent on at least one surface of the foamable resin layer B. A foamable resin obtained by laminating a foamable resin layer A containing a polyolefin resin containing a polypropylene resin and a polyethylene resin, a polyfunctional monomer having a (meth) acrylic group, and a thermal decomposition type foaming agent. A method for producing a crosslinked polyolefin resin foam, which comprises foaming after laminating a laminated sheet. 4. A polypropylene resin of at least 40
The method for producing a polyolefin resin foam according to claim 3, wherein the polyolefin resin is contained in an amount of wt%. 5. The polyolefin resin foam according to claim 1 or 2, which is obtained by laminating a skin material on the surface of the foam obtained by foaming the expandable resin layer A. Characteristic laminate.