JPH08309901A - Composite material consisting of foam and skin material and molding obtained therefrom - Google Patents

Abstract

PURPOSE: To prevent that polypropylene resin foam is collapsed to become thin and non-uniform in thickness and unevenness is generated on the surface of a skin material when aggregate is integrally molded into a composite object by bonding the skin material to one surface of the polypropylene resin foam of which the closed cell ratio and gell ratio are respectively specific values or more. CONSTITUTION: A composite material consists of polypropylene resin foam wherein a closed cell ratio is 70% or more and a gell ratio is 40% or more and the skin material bonded to one surface of the foam. When the closed cell ratio of the foam is below 70% and the gell ratio thereof is below 40%, when a thermoplastic resin for aggregate is integrally molded, the foam is collapsed by heat and pressure to become thin and non-uniform in thickness. The polypropylene resin foam by a predetermined crosslinking method is produced by melting and kneading a compd. obtained by adding a foaming agent and a crosslinking agent to a polypropylene resin to prepare a foamable polypropylene resin compsn. and forming a sheet from this compsn. to crosslink the same and foaming the foaming agent by heating to form foam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material comprising a polypropylene resin foam and a skin material, and a molded product obtained from the composite material. Such a molded product is used, for example, as a vehicle interior component such as an automobile ceiling material or a door trim.

[0002]

2. Description of the Related Art Generally, a molded article of this type is manufactured by a stamping molding method. That is, a thermoplastic resin for aggregate is supplied in the form of a large number of balls or sheets on the pressing surface of the lower die of the molding die, and on top of that, from the upper skin material and the lower polypropylene resin foam, The composite material is supplied in a heated state, and in that state, a thermoplastic resin in a molten state, which becomes an aggregate under appropriate heating and pressurizing conditions, is integrally molded on the lower surface of the foam to obtain a molded product having a required shape. can get.

Conventionally, the following has been proposed as a polypropylene resin foam used for obtaining such a molded product.

(1) Polypropylene resin foam having a gel fraction of 35% or more and an average cell diameter of 200 μm or less in a surface layer portion from at least one surface to a depth of 1 mm (Japanese Patent Laid-Open No. 102034/1990). reference).

(2) 10 to 55% by weight of a block copolymer comprising styrene polymers at both ends and an ethylene-butylene copolymer or an ethylene-propylene copolymer at the center, and a polypropylene resin 40 to 85% by weight. , A resin mixture composition containing 5 to 40% by weight of a polyethylene resin, an elastic recovery rate of 10% or less, and moldability L / D (L; depth of molding die, D: diameter of molding die) of 0. A continuous sheet-like crosslinked foamed product having a size of 3 to 1.0 (see JP-A-2-255739).

(3) Apparent density is 0.20 to 0.025 g /
cm ^3, a gel fraction of 0.5 to 75%, and the surface roughness of the absolute value of a skin material laminated polyolefin-based resin foam formed by heating and compressing so as to 15μm or less (JP-A-1
-222229 publication).

[0007]

However, when an attempt is made to obtain a molded product of the required shape as described above by the stamping molding method using the polypropylene resin foam having the above-mentioned constitution, in any case When the melt of the thermoplastic resin of is integrally molded on the foam side of the composite material composed of the foam and the skin material, the foam is crushed by the heat and pressure of the molten thermoplastic resin to make the thickness uneven, and However, there has been a problem that the thickness of the foamed material is partially changed to easily cause unevenness on the surface of the skin material.

In view of the above points, an object of the present invention is to crush the foam when the melt of the thermoplastic resin for the aggregate is integrally molded on the foam side of the composite material in the stamping mold, so that the foam is crushed thinly. Provide a polypropylene resin foam / skin material composite material that is free from the risk of fleshing and unevenness on the surface of the skin material, and a molded product obtained from the composite material used for interior parts of vehicles such as automobiles. To provide.

[0009]

The composite material according to the invention comprises:
The polypropylene resin foam has a closed cell ratio of 70% or more and a gel fraction of 40% or more, and a skin material attached to one surface of the foam.

The polypropylene resin foam preferably has a closed cell ratio of 80% to 99%.

According to the present invention, there is provided a molded product in which the composite material having the above-mentioned constitution is molded into a required shape and the thermoplastic resin aggregate is integrally molded on the other surface of the foam.

The propylene-based resin composition used as a raw material for producing the polypropylene-based resin foam is a polypropylene-based resin, a thermal decomposition type foaming agent, a cross-linking aid, and a peroxide which is optionally used in combination with the aid. An antioxidant, a pigment, and other additives which are added as necessary.

The polypropylene resin is not particularly limited as long as it is based on polypropylene (for example, containing 50% by weight or more of a propylene component), and is a propylene homopolymer; propylene and other olefins, for example. Copolymers of ethylene, vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, etc .; terpolymers of propylene and other olefins such as ethylene, butene; polypropylene resins and other olefin resins Can be a block, a random block, a random copolymer, or the like. These polymers may be used alone or in combination of two or more. When the polypropylene resin alone lacks flexibility, 5 to 50 parts by weight, preferably 30 to 50 parts by weight of low density polyethylene, linear low density polyethylene, high density polyethylene or ethylene-vinyl acetate copolymer is used depending on the required quality. -40 parts by weight may be blended.

The thermal decomposition type foaming agent can be used without particular limitation as long as it has a thermal decomposition temperature higher than the melting temperature of the polypropylene resin composition. For example, azodicarbonamide or the like. Alternatively, hydradodicarbonamide, barium azodicarboxylic acid salt, dinitrosopentaethylenetetramine, nitrosoguanidine, p, p′-oxybisbenzenesulfonyl semicarbazide, etc., which have a thermal decomposition temperature higher than that, are exemplified. These thermal decomposition type foaming agents may be used alone or in combination of two or more kinds. Further, in order to accelerate the decomposition of the foaming agent, a known decomposition aid such as zinc oxide or zinc stearate may be added as appropriate.

The content of the thermal decomposition type foaming agent is preferably 0.01 to 30 parts by weight, more preferably 0.05 to 15 parts by weight, based on 100 parts by weight of the polypropylene resin.

Examples of the crosslinking aid include bifunctional monomers such as divinylbenzene, diallylbenzene, divinylnaphthalene, polyethylene dimethacrylate, 1,9-nonanediol dimethacrylate, diallyl phthalate, trimethylolpropane trimethacrylate and triallyl isocyanate. Trifunctional monomers such as nurate and triallyl trimellitate are used. These crosslinking aids may be used alone or in combination of two or more.

The amount of the crosslinking aid added is preferably 0.01 to 30 parts by weight, more preferably 0.05 to 15 parts by weight, based on 100 parts by weight of the polypropylene resin.

Examples of the organic peroxide which is optionally used in combination with the crosslinking aid for chemical crosslinking include methyl ethyl ketone peroxide, t-butyl peroxide, dicumyl peroxide and the like.

The content of the peroxide is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the polypropylene resin.

In addition to the polypropylene-based resin composition, an antioxidant, a heat stabilizer, a metal damage inhibitor, an inorganic filler, an ultraviolet absorber, a pigment, a petroleum resin, etc. may be added as required. it can.

The polypropylene resin foam may be obtained by a so-called pre-crosslinking method, but is not limited thereto.

In the method for producing a polypropylene resin foam by the pre-crosslinking method, a blowing agent, a crosslinking aid, etc. are added to the polypropylene resin, and if necessary, an inorganic filler, a coupling agent and various additives are added. The obtained composition is melt-kneaded to form a foamable polypropylene resin composition, a sheet is formed from this composition, the obtained sheet is crosslinked, and then heated to decompose the foaming agent to foam. , A foam. The above-mentioned sheet is formed as follows. Using a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Henschel mixer, a Banbury mixer, a kneader mixer, and a mixing roll, the mixture is melt-kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent,
The kneaded material obtained is formed into a sheet.

As a heating means for foaming, hot air, infrared ray or electric heater, steam heating, ultrasonic heating or a combination thereof is used.

As a crosslinking method, an electron beam crosslinking method or a chemical crosslinking method can be applied. In the electron beam cross-linking method, α rays, β rays, γ
Ionizing radiation such as rays, X-rays, and ultraviolet rays is used. The irradiation dose is usually 1 to 50.0 Mrad. The above-exemplified organic peroxides are used in the chemical crosslinking method.

The expansion ratio of the foam thus obtained is usually 10 to 20, and the thickness is usually 1.0 to 4.0 m.
m.

The closed cell ratio of the foam used in the present invention is 70.
% Or more, preferably 80% to 99%. If the closed cell ratio is less than 70%, the foam is crushed by the heat and pressure during the integral molding of the thermoplastic resin for aggregates, and the thickness of the foam becomes uneven.

The gel fraction of the foam used in the present invention is 40%.
It is above, and preferably 50 to 75%. When the gel fraction is less than 40%, the foam is crushed by the heat and pressure during the integral molding of the thermoplastic resin for aggregates, and the thickness is unevenly thinned.

As the skin material to be bonded to one surface of the polypropylene resin foam, a polyvinyl chloride sheet, a thermoplastic elastomer sheet, an ABS resin-containing polyvinyl chloride sheet, synthetic leather, natural fiber or synthetic fiber is used. A cloth-like material or the like is used. The thickness of the skin material is usually 0.3 to 1 mm.

The thermoplastic resin forming the aggregate integrally molded on the other surface of the polypropylene resin foam is not particularly limited, but it is preferable to use a polyolefin resin. This is advantageous in that it is lighter in weight than the conventionally used plant fiber-based hardboard or ABS injection product. Examples of the polyolefin-based resin include a polypropylene-based resin in which another olefin-based resin is blocked, a random block, or a random copolymer. Further, a copolymer of propylene and ethylene, vinyl acetate, acrylic ester or the like can also be used.

Further, the thermoplastic resin for aggregate is talc,
Inorganic substances such as silicic acid and calcium carbonate may be blended within a range that does not impair the properties of the resin for aggregate, and an olefin system such as ABS resin, polystyrene resin, petroleum resin, etc. within a range that does not impair the moldability. Other resins may be added.

Next, the molding method of the composite material according to the present invention will be described. In order to reduce the bubble breakage of the foam and the like, the hot stamping molding method, which requires less pressure than the injection molding, is preferable.

FIG. 1 attached shows an example of molding a composite material by the pot stamping molding method.

First, as shown in FIG. 1 (a), an appropriate amount of dumpling-shaped thermoplastic resin for aggregates (6) is supplied to the pressing surface of the lower mold (5) which is a pair of upper and lower molds, A composite material (3) in which a skin material (2) is attached to a sheet-shaped polypropylene resin foam (1) is supplied so that the foam (1) faces the lower mold (5).

Then, as shown in FIG. 1B, the upper die
The composite (3) and the aggregate (7) were integrated with the foam (1) of the composite (3) by press-molding the (4) and the lower mold (5) together under a predetermined temperature condition. Molded product (8) is molded. The thickness of the aggregate is usually 1 to 5 mm.

Thereafter, as shown in FIG. 1 (c), the molding die is opened and the molded product (8) is taken out from the die.

[0036]

According to the present invention, since the closed cell ratio of the foam integrally molded with the thermoplastic resin for the aggregate is set to 70% or more and the gel fraction is set to 40% or more, the aggregate is composite. When molded integrally with a material, the foam of the composite material is not crushed by the heat and pressure of the thermoplastic resin for aggregates, preventing unevenness on the surface of the molded product, and high quality vehicle interior A molded product can be obtained.

[0037]

【Example】

Example 1 80% by weight of ethylene-propylene random copolymer (propylene content: 96% by weight, melt index: 2)
And linear polyethylene (melt index: 6) 20
6 parts by weight of azodicarbonamide as a foaming agent, 2.4 parts by weight of trimethylpropanetrimethacrylate as a cross-linking agent, and 1,9 parts by weight of 100% by weight of a resin blend.
-Nonanediol dimethacrylate (0.6 parts by weight) and BHT (0.5 parts by weight) as a stabilizer were blended, and the resulting blend was melt-kneaded with a twin-screw extruder (120φ) to form a kneaded product of azodicarbonamide. It was extruded by the T-die method at a temperature below the decomposition temperature to form a sheet having a thickness of 1.5 mm.

Then, the sheet was irradiated with an electron beam of 6.0 Mrad so that the average gel fraction was about 60% to crosslink the sheet.

Then, the obtained crosslinked sheet was heat-foamed in a hot air vertical foaming furnace at 280 ° C. so that the closed cell ratio was about 85%.

In this way, a crosslinked foamed sheet having a smooth surface with a thickness of 3 mm was obtained.

Next, corona treatment was applied to one side of the foamed sheet, and a soft polyvinyl chloride sheet having a thickness of 0.6 mm was adhered as a skin material to the treated surface using a urethane adhesive to bond the foamed sheet and the skin material. A composite material composed of and was produced.

Next, a polypropylene resin as a thermoplastic resin for aggregate was melted at a temperature of about 200 ° C.,
It is placed on the pressing surface of the lower die for stamping mold, the composite material is placed above the resin so that the foam sheet is on the lower side, and pressure is applied with a pressure of 70 kg / cm ² ,
The above resin was heat-sealed integrally with the composite material to prepare an interior molded article for a vehicle.

Example 2 A molded article was produced by the same procedure as in Example 1 except that the amount of the foaming agent was changed to 15 parts by weight.

Examples 3 to 4 The ratio of polypropylene resin to linear polyethylene was 6
The same operations as in Examples 1 and 2 were carried out except that 0% by weight to 40% by weight were changed, and respective molded products were produced. Examples 5 to 6 The same operations as in Examples 1 to 2 were performed except that the foaming conditions were changed so that the closed cell ratio was around 90%, and molded products were produced.

Examples 7 to 8 Molded articles were produced by the same operations as in Examples 3 to 4 except that the foaming conditions were changed so that the closed cell ratio was around 90%.

Comparative Example 1 A molded product was produced by the same procedure as in Example 1 except that the extruded sheet was irradiated with an electron beam so that the average gel fraction was about 39%.

Comparative Example 2 A molded product was produced by the same procedure as in Comparative Example 1 except that the amount of the foaming agent was changed to 15 parts by weight.

Comparative Examples 3 to 4 The ratio of polypropylene resin to linear polyethylene was 6
The same operations as in Comparative Examples 1 and 2 were carried out except that 0% by weight to 40% by weight were changed, and respective molded products were produced.

Comparative Examples 5 to 6 The same operations as in Examples 1 to 2 were carried out except that the foaming conditions were changed so that the closed cell ratio was around 65%, and molded products were produced.

Comparative Examples 7 to 8 The same operations as in Examples 3 to 4 were carried out except that the foaming conditions were changed so that the closed cell ratio was about 65%, to produce molded products.

Performance test a) Density of foam The density of the foam was measured by the following method.

The foam was cut into a size of 10 cm × 10 cm, and the thickness of the obtained sample was measured according to JIS-K-6767.
Measure with a dial gauge according to, and calculate the volume (V) from this measured value.

Next, the weight (W) of this sample is weighed.

The density of the foam is given by the formula:

Foam density (g / cm ³ ) = W / V

B) Closed Cell Rate of Foam The closed cell rate of the foam is determined by ASTM-D-2856.
It was carried out according to. Specifically, first, the foam is 4 cm x
Accurately cut into a size of 3 cm, the thickness of the obtained sample is measured with a dial gauge according to JIS-K-6767, and the volume is calculated from this measured value.

Next, using this value, a predetermined operation is carried out with an air comparison type hydrometer (MODEL930 model manufactured by BECKMAN) to obtain a measured numerical value (A), and the weight (B) of the sample is measured. The volume (C) of the sample after measurement with an air-comparison hydrometer is read in cc units with a graduated cylinder. The specific gravity of the polypropylene resin is (D). The closed cell rate is given by the following equation.

[0058]

C) Gel Fraction The gel fraction of the foam was measured by the following method.

First, about 0.2 g of a foam sample is precisely weighed, and the weight is designated as E (g).

Then, this sample was immersed in 50 ml of xylene at a temperature of 120 ° C. for 24 hours, filtered through a 200-mesh wire net, the insoluble matter on the wire net was vacuum dried, and the weight of the insoluble matter was measured. Precisely weigh and use the weight F
(G).

The gel fraction is calculated by the following formula.

Gel fraction (%) = F / E × 100

D) Reduction rate of foam thickness The reduction rate of foam thickness was measured by the following method.

The thickness (G) of the foam is measured in the state of FIG. 1 (a) before molding. Figure 1 shows the resulting molded product after molding.
It cut | disconnects by the cross section which follows the AA 'line in (c), and measures the thickness (H) of the foam in this cut surface with the magnifier with a scale.

The reduction rate of the foam thickness is given by the following equation.

Reduction rate of foam thickness (%) = (GH) /
G x 100

The evaluation criteria for the degree of decrease in foam thickness are as follows.

X: Reduction rate of foam thickness of 50% or more, Δ: 40% to 50%, ◯: 30% to 40%

E) Asperity on the surface of the skin material The asperity on the surface of the skin material was visually observed. The evaluation criteria for unevenness on the surface of the skin material are as follows.

XX: severe unevenness X: unevenness ◯: no unevenness

The results of the performance test are summarized in Table 1.

[0073]

[Table 1] As is clear from the above table, it is recognized that the molded products of the examples show good results in all items.

[0074]

As is apparent from the above description, according to the present invention, when the melt of the thermoplastic resin for the aggregate is integrally molded on the foam side of the composite in the stamping mold, the heat for the aggregate is reduced. It is possible to prevent the foam of the composite material from being crushed by the heat and pressure of the plastic resin, prevent the surface of the molded product from becoming uneven, and obtain a high quality vehicle interior molded product.

[0075]

【Example】

[Brief description of drawings]

1 (a), (b) and (c) are vertical cross-sectional views showing a molding example of a vehicle interior molded product by a pot stamping molding method.

[Explanation of symbols]

 1: Foam 2: Skin material 3: Composite material 4: Upper mold 5: Lower mold 6: Thermoplastic resin for aggregate 7: Aggregate 8: Molded product

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Claims (4)

[Claims] 1. The closed cell ratio is 70% or more and the gel fraction is 4
A composite material comprising 0% or more polypropylene-based resin foam and a skin material attached to one surface of the foam. 2. The composite material according to claim 1, wherein the polypropylene resin foam has a closed cell ratio of 80% to 99%. 3. A molded product obtained by molding the composite material according to claim 1 into a required shape and integrally molding a thermoplastic resin aggregate on the other surface of the foam. 4. A molded product obtained by molding the composite material according to claim 2 into a required shape and integrally molding an aggregate made of a thermoplastic resin on the other surface of the foam.