JP3241112B2 - Laminated foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention, which relates to laminated foam, more particularly, excellent heat resistance, and complex fabrication shapes are possible in various skin material adhered to a surface in particular those about the good laminated foam peel strength between.

[0002]

2. Description of the Related Art A polyolefin resin foam can be formed into a sheet and has excellent flexibility and heat insulation. For this reason, in recent years, it has been widely used as an interior material for vehicles such as automobiles, particularly for ceilings, doors, instrument panels, and the like. As described above, when used as an interior material or the like, various products have been produced by forming a crosslinked polyolefin foam sheet by vacuum forming, compression molding, or stamping. However, since the molding temperature at this time is generally as high as 120 ° C. to 200 ° C., the conventional crosslinked polyethylene foam cannot be used because of its poor heat resistance. Therefore, in recent years, a polyolefin-based resin foam mainly containing polypropylene has been used. In general, when a polypropylene-based foam sheet is used as an interior material for an automobile as described above, a skin material such as a vinyl chloride sheet or a thermoplastic elastomer sheet is usually bonded and laminated.

[0003] Various adhesives such as a solvent type and an emulsion type are appropriately used as the adhesive. When the laminated and bonded products are formed into a desired shape, a partial peeling occurs between the polypropylene-based resin foam and the skin material, causing phenomena such as blisters and very appearance. There was a problem. A foam sheet using polypropylene was first proposed in Japanese Patent Publication No. 46-38716. However, at present, the temperature conditions have become more severe and the shape of the molded article has become more complicated. Such problems as blisters have become apparent. Therefore, at present, more excellent elongation and material strength are required at the same time as heat resistance.

Hitherto, as a measure against blisters and the like as described above, attempts have been made mainly to improve the adhesiveness between the skin material and the polyolefin resin foam. The most common of these means is a corona discharge treatment. This is to improve the wettability of the surface of the olefin foam by corona discharge. Similarly, as a method for improving wettability, Japanese Patent Publication No. 2-255740 discloses nitrate and / or nitrate.
Alternatively, a method of treating a foam surface with nitrite has been proposed.

[0005]

However, when the molding temperature is high, especially near the melting point, even if the adhesion is improved by the surface treatment, the resin composition is melted, so that the adhesive peel strength, that is, the material strength is increased. In many cases, a desired product cannot be obtained. For this reason, measures have been taken to increase the degree of cross-linking. However, if sufficient material strength is to be obtained, the expansion of the foam itself will be lost, causing problems such as cutting of the foam itself during molding.

The present invention is excellent in both material strength and adhesiveness (wettability), and is excellent in heat resistance, toughness, and moldability, without the need to increase the degree of cross-linking. It is an object of the present invention to provide a laminated foam in which a skin material is laminated on a crosslinked polyolefin resin foam which does not cause a problem such as blistering.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, have used a specific polypropylene resin having a free-end long-chain branch as a resin component. It has been found that the above object can be achieved by blending a mixture of a linear (usually) polypropylene-based resin and a polyethylene-based resin as required and mixing a crosslinking aid and a pyrolytic foaming agent in a specific ratio. The present invention has been completed based on the findings.

That is, according to the present invention, 0.03 to 8 parts by weight of a polyfunctional monomer as a cross-linking assistant and 100 to 4 parts by weight of a polyolefin resin composition,
0 parts by weight crosslinked foamed polyolefin-based resin sets having containing a
Crosslinked polyolefin resin obtained by crosslinking and foaming the product
A laminated foam in which a skin material is laminated on a foam, wherein the polyolefin-based resin composition has 3 to 100% by weight of a polypropylene-based resin having a free-end long-chain branching portion.
A mixture of 30 to 100% by weight of a linear (normal) polypropylene resin and 70 to 0% by weight of a polyethylene resin is mixed with 9
It is characterized by being blended at 7 to 0% by weight.

[0009] below, the components of the laminated foam of the present invention will be described.

[0010] Polypropylene system containing free-end long-chain branching
Resin The free-end long-chain branch-containing polypropylene resin used in the present invention has long-chain branching, and is not particularly limited as long as it is a polypropylene resin whose end is a free end. Those having physical properties such as the melt extensional viscosity described above are preferable.

That is, in the physical properties of the melt extensional viscosity of a polyolefin measured by a melten rheometer (manufactured by Toyo Seiki Co., Ltd.), the elongation strain rate is 0.01 to 1.0 S ^-1.
When the amount of elongation deformation strain at any two points measurable in the range of A is B, the respective melt extension viscosities η (A),
The maximum value of the ratio of η (B) is expressed by the following (Equation 1) and (Equation 2), and a polypropylene resin containing no gel component is preferable. Here, “containing no gel component” means that when dissolved in xylene at 120 ° C. for 24 hours, there is no insoluble component.

Η (B) / η (A) = 3.0 to 100 (Equation 1) B / A = 10 (Equation 2) (where A and B are the extensional deformation of the sample at the time of measurement) The amount of distortion is shown, and the amount of distortion of A is in the range of 0.1 to 1.0).

[0013] The polypropylene resin having a free-end long-chain branch used in the present invention can be obtained by copolymerization or graft polymerization.
No. 1704 and Japanese Patent Publication No. 2-298536. The methods disclosed in these publications are methods for imparting desired free-end long-chain branching by subjecting polypropylene to electron beam irradiation or peroxide treatment. These publications show that a polypropylene-based resin having free-end long-chain branching is a resin that is most suitable for a coating material, a stretched film, and a blow film, and has been developed for those uses.

The present inventors have paid attention to a polypropylene resin having a free-end long-chain branch that exhibits strength during elongation. By using such a polypropylene resin, vacuum moldability, heat resistance, and skin material can be improved. It has been found that a laminated foam having excellent peel strength and appearance can be obtained. The polypropylene resin having long-chain free-end branching used in the present invention may be any of a polypropylene homopolymer, a copolymer containing propylene as a main component, and a mixture thereof. Examples of the copolymer include a polypropylene-α-olefin copolymer containing a polypropylene portion in an amount of 85% by weight or more. Examples of the α-olefin include ethylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene and the like.

Linear (Normal) Polypropylene The linear polypropylene used in the present invention is not particularly limited, and may be any of a polypropylene homopolymer, a copolymer containing propylene as a main component, and a mixture thereof. Good. Examples of the copolymer include a polypropylene-α-olefin copolymer containing a polypropylene portion in an amount of 85% by weight or more. Examples of the α-olefin include ethylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene and the like. The polypropylene used in the present invention is a melt index (hereinafter abbreviated as “MI”; ASTM D).
1238) is preferably 0.05 to 12. It is more preferably 0.1 to 10, and most preferably 0.2 to 8. If the MI of the polypropylene is less than 0.05, sheeting becomes difficult, and the MI
When it is 12 or more, the heat resistance becomes insufficient.

Polyethylene The polyethylene resin used in the present invention may be either a polyethylene homopolymer, a copolymer containing ethylene as a main component, or a mixture thereof. Examples of the copolymer include a polyethylene-α-olefin copolymer containing a polyethylene portion in an amount of 80% by weight or more. Examples of the α-olefin include propylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene and the like.

The polyethylene used in the present invention has a MI
Is preferably 2 to 40. More preferably, 2
-30, most preferably 2-25. If the MI of the polyethylene is less than 2, a problem occurs in appearance when the sheet is formed, and if the MI exceeds 40, a problem occurs in heat resistance.

In the present invention, the blending ratio of the polyolefin resin composition is such that the linear polypropylene resin 30 to 100% by weight and the polyethylene resin 70 9% by weight of a polyolefin resin mixture.
It is in the range of 7 to 0% by weight. By being in the range of the above compounding ratio, physical properties at high temperature, moldability, excellent cross-linking degree, heat resistance, toughness, excellent moldability,
Not such occur the appearance on the blister problems such as automobile interior materials
It is possible to obtain a laminated onset foam.

Crosslinking Aid The crosslinking aid used in the present invention may be any one which is a polyfunctional monomer and can cause a crosslinking reaction by electron beam / radiation or peroxide. You may mix and use more than it. Typical examples thereof include aromatic or aliphatic compounds containing one or more vinyl groups or allyl groups in one molecule,
And compounds containing one or more acryloyloxy or methacryloyloxy groups.

For example, divinylbenzene, diallylbenzene, divinylnaphthalene, trimethylolpropane trimethacrylate, ethylvinylbenzene, 1,9-nonanediol dimethacrylate, 1-nonane monomethacrylate, 1,6-hexanediol dimethacrylate,
2,2-bis [4- (acryloxydiethoxy) phenyl] propane, 1,2,4-benzenetricarboxylic acid triallyl ester, 1,2-benzenedicarboxylic acid diallyl ester, 1,3-benzenedicarboxylic acid diallyl ester , 1,4-benzenedicarboxylic acid diallyl ester and their closely related homologs.

In the present invention, the crosslinking aid is added in an amount of 0.03 to 8 parts by weight based on 100 parts by weight of the total amount of the polypropylene and polyethylene resin compositions as resin components. If the amount is less than 0.03 part by weight, a homogeneous foam cannot be obtained due to insufficient crosslinking, or the material strength at high temperature becomes insufficient. If the compounding ratio of the crosslinking assistant exceeds 8 parts by weight, the crosslinking density will be too high, causing a problem in moldability. A more preferable mixing ratio of the crosslinking aid is 0.1 to
It is in the range of 4.5 parts by weight.

Pyrolytic foaming agent The pyrolytic foaming agent used in the present invention is not particularly limited as long as it generates a decomposition gas by heating.
Specifically, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine,
Toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like can be mentioned. These may be used alone or as a mixture of two or more.

In the present invention, the mixing ratio of the pyrolytic foaming agent is 1 to 40 with respect to 100 parts by weight of the total amount of the resin component.
Parts by weight. If the blending ratio of the thermal decomposition type foaming agent is less than 1 part by weight, a desired expansion ratio cannot be obtained. On the other hand, if the blending ratio of the thermal decomposition type foaming agent exceeds 40 parts by weight, uniform foams cannot be obtained because the cells burst or some large bubbles are formed. In the present invention, the more preferable mixing ratio of the pyrolytic foaming agent is 2 to 35 parts by weight.

Other Components In the present invention, an antioxidant, a stabilizer, a pigment, a metal damage inhibitor and the like can be added to the polyolefin resin composition according to the purpose. The antioxidant is preferably used in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the total of resin components such as a polypropylene resin and a polyethylene resin. A more preferable mixing ratio is 0.5 to 100 parts by weight of the total of the resin components.
3.5 parts by weight. As the stabilizer, any of phenol-based, phosphorus-based, sulfur-based, and amine-based stabilizers can be used.

In the present invention, the polyolefin-based resin composition is prepared by mixing each component with a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, or a roll.
Melt and kneaded at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent,
Usually, it is formed into a sheet. A sheet of the obtained resin composition is irradiated with ionizing radiation to crosslink, and then the sheet is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent and foamed, whereby a crosslinked polyolefin-based resin foam can be obtained.
As the ionizing radiation, α-rays, β-rays, γ-rays, electron beams and the like can be used, and the irradiation dose is usually 1 to 20 Mrad.
It is. In the present invention, the crosslinked polyolefin-based
A skin material is laminated on the resin foam. As the skin material,
Commonly used vinyl chloride sheet and thermoplastic elastomer
Sheet.

[0026]

In the present invention, a polypropylene resin having long-chain branching at the free end is blended at a constant ratio. A polypropylene resin having free-end long-chain branching has a remarkably high melt extension viscosity at a melting point or higher as compared with a conventionally used polypropylene resin. For this reason,
Since the resin strength at the time of melt elongation is strong, and the resin itself expands uniformly and shows some resistance during foaming,
The foam is characterized in that defects such as thinning are reduced.

Also, it is considered that problems such as cutting at the time of extension are eliminated in a complicated shape or a formed portion of a deep concave portion also in the secondary processing. Furthermore, conventionally, since the material strength of the foam at the interface also various surface material and the outgoing foam without foam was cut during secondary processing is small, there is a problem that destroying the material peeling . According to the present invention, when obtained by bonding the fully foaming agent and table surface material by corona treatment or the like, since a large melt extensional viscosity, does not cause problems such as peeling in the material itself even when subjected to shear. Therefore, it is considered that a problem such as surface peeling does not occur in interior materials for automobiles and the like.

[0028]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 Polypropylene Resin 1 Having Free-Ended Long Chain Branch
0% by weight of ordinary (linear) polypropylene (M
I = 1.5) 60% by weight and polyethylene [LLDPE]
(MI = 8.0) 90% by weight of a polyolefin resin mixture composed of 40% by weight, and 2.0 parts by weight of trimethylolpropane trimethacrylate as a cross-linking aid and 100 parts by weight of this mixture, and foaming As an agent, 15 parts by weight of azodicarbonamide and an appropriate amount of an antioxidant and a metal harm inhibitor were mixed. The obtained mixture was mixed and kneaded with a 6-inch roll at 170 ° C. at a speed of 20 rotations / minute for 5 minutes to form a plate. 180 ° C.
The sheet was formed into a 1 mm sheet at a pressure of 100 kg / cm ² , and the sheet was irradiated with an electron beam at 4.0 Mrad to crosslink. Thereafter, this was put into an oven at 250 ° C. for 5 minutes to obtain a crosslinked foam.

[0029] Adjust the formulations according to the formulation shown in Example 2-6及 beauty Comparative Examples 1-3 Table 1, in the same manner as in Example 1 to prepare a foamable resin composition sheet with this,
After irradiating this with an electron beam, the sheet was heated and foamed to obtain a crosslinked foam.

As the foaming material, azodicarbonamide 1
5 parts by weight were used. In addition, the abbreviation of the crosslinking aid shown in Table 1 shows the following. TMPT = trimethylolpropane trimethacrylate NOD = 1,9-nonanediol dimethacrylate TRIAM = 1,2,4-benzenetricarboxylic acid triallyl ester DVB = divinylbenzene

[0031]

[Table 1]

The method for measuring the physical properties of the raw materials and the method for evaluating the obtained crosslinked foam will be described below. (A) Regarding the ratio of melt extensional viscosity η (B) / η (A);
Using Toyo Seiki Merten Rheometer, 180
C., the strain rate was measured within the range of 0.01 to 1.0 S ^-1 . As a sample for measurement, a rod-shaped sample having a diameter of about 3 mm and a length of 30 cm was used with a small extruder.

(B) Tm (melting point): The polymer sample was heated at a rate of 5 ° C./min using a DSC manufactured by Seiko Electronics Co., Ltd., and the endothermic maximum peak temperature was measured. (C) MI; measured according to ASTM T1238.

(D) Gel fraction: The obtained crosslinked foam was placed in xylene at 120 ° C. (2,6 as an antioxidant).
-Di-tert-butyl-4-methylphenol), and the insoluble matter was gelled for 24 hours, dried, weighed, and expressed in% by weight with respect to the crosslinked foam before dissolution. Rate.

(E) Vacuum formability H / D: The surface of the obtained crosslinked foam was subjected to corona discharge treatment, and a PVC-based skin material (thickness: 0.5 mm) was applied with a polyester-based adhesive.
The laminated foam is heated with a far-infrared heater so that the surface temperature of the foam becomes 150 to 160 ° C., vacuum-formed using a cylindrical female mold, and the depth during the forming. Vacuum formability was evaluated as the ratio of H to diameter D. The larger the value, the better the moldability.

(F) Appearance: The surface of the obtained cross-linked foam is subjected to corona discharge treatment, and a PVC skin material (thickness: 0.5 mm) is laminated and bonded with a polyester-based adhesive. Vacuum forming was performed, and the appearance was visually evaluated and evaluated. (G) Foaming heat resistance: The obtained crosslinked foam sheet itself was placed in a 180 ° C. oven for 3 minutes, and the foam surface was visually observed and evaluated.

(H) Peeling strength with skin material: The surface of the obtained crosslinked foam was subjected to corona discharge treatment, and a PVC skin material (thickness 0.5 mm) was laminated and bonded with a polyester-based adhesive. The foam was heated with a hot air heater at 150 ° C. for 5 minutes, and a peel test was performed. The amount of electron beam irradiation and the expansion ratio of each of the examples and comparative examples are as shown in Table 2. Table 2 shows the evaluation results of the crosslinked foam.

[0038]

[Table 2]

As is clear from Tables 1 and 2, the laminated foams obtained from the crosslinked foams of the examples according to the present invention were :
Compared with those of the comparative examples, they are superior in vacuum formability, heat resistance, peel strength with the skin material, and appearance.

[0040]

According to the present invention, a crosslinked polyolefin resin foam having a good appearance and a toughness can be obtained by using a polypropylene resin having a free-end long-chain branching portion. Laminated onset foam that obtained according to the present invention is not to be disconnected at vacuum forming at high temperature, also because it is excellent in adhesive strength That material strength during peeling of the skin material, swelling of the skin material surface and the like Molding can be performed without the problem described above.

[0041] By using the above cross-linking foaming polyolefin resin composition, the appearance is good, it can be excellent in heat resistance, and obtain a complicated shape fabrication also laminated onset foam. Therefore, in applications such as automotive interior materials, the strength of the various skin materials adhered to the surface and the foam is particularly excellent, and problems such as blisters do not occur.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B32B 27/32 C08J 9/00-9/42 C08L 23/00-23/36

Claims (2)

(57) [Claims] 1. A polyfunctional monomer having a content of from 0.03 to 100 parts by weight based on 100 parts by weight of a polyolefin resin composition.
8 parts by weight, a cross-linked foaming polyolefin resin composition containing 1 to 40 parts by weight of a pyrolytic foaming agent is crosslinked and foamed.
Skin material is laminated on the crosslinked polyolefin resin foam
A laminated foam , wherein the polyolefin-based resin composition is 30 to 100% by weight of a linear polypropylene-based resin with respect to 3 to 100% by weight of a polypropylene-based resin having a free-end long-chain branched portion.
And a mixture of 70 to 0% by weight of polyethylene resin and 97% by weight.
A laminated foam, characterized in that it is a polyolefin-based resin composition blended in an amount of from 0 to 0% by weight . 2. The polypropylene resin having a free-end long-chain branching part has an elongation strain rate of 0.01 to 1 in terms of the melt extensional viscosity of a polyolefin measured by a Melten rheometer (manufactured by Toyo Seiki Co., Ltd.). 0.0S ^-1 at any two points that can be measured within the range of
Melt extension viscosity η (A), η when B
The maximum value of the ratio of (B) is shown below (Equation 1) and (Equation 2)
The laminated foam according to claim 1, wherein the laminated foam does not include a gel component at all . η (B) / η (A) = 3.0-100 (Equation 1) B / A = 10 (Equation 2) (where A and B are measured values) Shows the amount of elongation deformation strain of the sample in the above, and the amount of strain of A is in the range of 0.1 to 1.0.)