JP3086213B2 - Method for producing multilayer foam molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a multilayer foam molded article. More specifically, the present invention relates to a method for manufacturing a lightweight and highly rigid multilayer foam molded article that can be used for interior materials for automobiles and the like.

[0002]

2. Description of the Related Art Automobile interior materials such as door trims, rear package trims, seat back garnishes, instrument panels, etc. are usually provided with a skin material such as leather or fabric applied to a base material via a pad material such as a foam sheet. The combined one is used.

[0003] As a method of manufacturing such interior materials for automobiles, a mold stamping molding method using a resin material such as a polypropylene resin as a base material is known. That is,
In the manufacturing method, for example, the skin material of the layered sheet is placed between the upper and lower molds of the injection mold, and then the resin material for the base material in a molten state is injected into the cavities of the upper and lower molds. It is a method of forming and integrating the skin material and the base material.
This method has advantages such as fewer steps and no effect on the environment due to the solvent of the adhesive.

[0004] However, the molded product obtained by the conventional mold stamping molding method has a large weight of the substrate, so that the entire molded product is heavy, which has been an obstacle to reducing the weight of the automobile and improving the fuel efficiency. Accordingly, a method has been attempted in which a foaming agent is mixed with a resin material constituting the base material, injection compression molding and foam molding are combined, and the resin material is foamed to reduce rigidity while maintaining rigidity. Kaihei 6-63972
JP-A-8-267626 and the like.

However, in these methods, it is necessary to interpose a skin layer forming sheet or the like between the base material and the skin material in order to make the foaming of the base material uniform (Japanese Patent Laid-Open No. 6-63).
972). Also, in recent years, there has been an increasing demand for molded articles using a fabric as a skin, but in these methods, particularly when a fabric is used as a skin, the fabric may be damaged during injection compression. .

In view of the above, a mold stamping molding method capable of producing a lightweight and high-rigidity multilayer foam molded product by a simpler method, particularly when a fabric is used as a skin, gives a molded product with less damage to the fabric and good appearance. Development of a molding method was desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily producing a lightweight, high-rigidity, and excellent appearance multi-layer foam molded article which can be used for interior materials for automobiles and the like. And

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of such a situation, and as a result, the above-mentioned problems can be solved by adopting specific injection compression conditions including a multi-stage compression step. The inventors have found that the present invention has been achieved.

That is, the present invention is a method for producing a multilayer foam molded article comprising a foamed base material layer made of a polypropylene resin material and a skin layer made of a skin material using upper and lower dies for mold stamping. (A) placing a skin material between the upper and lower molds; and (b) forming the upper and lower molds from the upper and lower molds with the upper and lower molds opened.
Polypropylene resin material and foaming agent in cavity
Injecting and filling a resin composition for forming a base material comprising:
(B-1) and the upper and lower molds are clamped at a speed of 10 to 40 m.
pre-stage compression for mold clamping with speed control at m / sec,
Mold clamping by controlling the pressure of the mold with mold clamping pressure of 150 to 350t
The cavity by multi-stage compression including post-stage compression
An injection compression step comprising a compression step (b-2) of compressing the inside; and (c) a foaming step of opening the upper and lower molds and foaming the resin composition for forming a base material to form a foamed base material layer. And (d) a cooling and solidifying step of cooling and solidifying the foamed base material layer.

[0010] The present invention also provides the compression step (b-2).
Wherein the transition from the first-stage compression to the second-stage compression is performed when the opening amount of the upper and lower dies is in the range of 0.5 to 1 mm.

[0011]

Embodiments of the present invention will be described below. In the production method of the present invention, after a skin material is set between the upper and lower molds of a mold stamping molding machine, an injection compression is performed in which a resin composition for forming a base material including a polypropylene resin material and a foaming agent is injection-filled and mold-clamped. After molding,
This is a method including a step of opening the upper and lower molds and foaming.

(1) Substrate-forming resin composition The substrate-forming resin composition used in the present invention is obtained by mixing a foaming agent with a polypropylene resin material.

The polypropylene resin material is mainly composed of a polypropylene resin. Examples of the polypropylene resin include a propylene homopolymer and a propylene block copolymer.

The propylene block copolymer is an ordinary block copolymer, for example, a crystalline propylene polymer block (a), an ethylene polymer block (b),
Propylene comprising a rubber block (c) composed of one or more rubbers selected from the group consisting of ethylene-propylene copolymer rubber, styrene-butadiene rubber and styrene-butadiene block copolymer・
Examples include an ethylene block copolymer or a propylene block copolymer composed of the crystalline propylene polymer block (a) and the rubber block (c).

The propylene / ethylene block copolymer is obtained by polymerizing olefins in one polymerization reaction system in the presence of a stereoregular catalyst, preferably a catalyst comprising a transition metal component with a carrier and an organoaluminum compound. Is a so-called non-polymer blend type copolymer obtained by the method described in JP-A-52-98.
No. 045 and Japanese Patent Publication No. 57-26613.

The above-mentioned propylene / ethylene block copolymer and propylene block copolymer are not necessarily limited to one kind of polymer obtained by polymerizing in one polymerization reaction system, but may be two kinds of polymerized separately. A mixture of the above propylene / ethylene block copolymer and propylene block copolymer may be used.

The polypropylene resin used in the present invention may be a resin mixture obtained by blending the propylene homopolymer or propylene block copolymer with an olefin resin other than these propylene resins.

Examples of such olefin resins include ethylene homopolymers, α-olefin homopolymers having 4 to 10 carbon atoms, and copolymers between α-olefins having 2 to 10 carbon atoms.

As the α-olefin constituting the α-olefin homopolymer having 4 to 10 carbon atoms, specifically, butene-1, pentene-1, 4-methylpentene-
1, hexene-1, heptene-1, octene-1, nonene-1, decene-1 and the like.

Examples of the copolymer between α-olefins having 2 to 10 carbon atoms include ethylene-propylene copolymer rubber (EPR) and ethylene-butene-1.
Copolymer rubber (EBR), ethylene / octene copolymer rubber (EOR), and the like.

The mixing ratio of the olefin resin in the resin mixture is preferably from 0 to 50 based on the total amount of the resin mixture.
%, More preferably 0 to 30% by weight. Particularly preferred as the polypropylene resin of the present invention is a resin mixture containing 70 to 90% by weight of crystalline polypropylene and 10 to 30% by weight of an ethylene / octene copolymer rubber.

The polypropylene resin of the present invention has a melt flow rate (ASTM-D1238, L) of usually 1
0-100 g / 10 min, preferably 40-90 g / 10
Within minutes. In the present invention, particularly when forming bosses and ribs, it is desirable that the melt flow rate of the polypropylene resin is in the above range.

The polypropylene resin material of the present invention has an overall MFR of 30 to 120 g / 10 min, preferably 5 to 120 g / 10 min.
It is preferable to be within the range of 0 to 110 g / 10 minutes. If the MFR is larger than the above range, the impact resistance of the product ultimately decreases. Further, when the MFR is smaller than the above range, the fluidity is reduced, the resin pressure is increased, and the skin is easily damaged. In this case, the MFR is J
It is a value measured according to IS-K6758.

The polypropylene resin material of the present invention is mainly composed of the above-described polypropylene resin. The polypropylene resin may be used alone, or may be a material in which a filler is added. Specific examples of the filler used in the present invention include glass fiber, talc, calcium carbonate, and barium sulfate. In the present invention, glass fiber or talc is particularly suitable from the viewpoint of improving foaming properties and rigidity.

The compounding ratio of the filler to the whole polypropylene resin material of the present invention is preferably 0 to 30% by weight, more preferably 0 to 20% by weight. By blending the filler at such a ratio, the rigidity, heat resistance and dimensional stability of the obtained multilayer foam molded article can be improved.

Further, the polypropylene resin material of the present invention may be further blended with various commonly used additives and the like as long as the effects of the present invention are not significantly impaired. Additives include nucleating agents, phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, neutralizing agents, light stabilizers, ultraviolet absorbers, and lubricants used as ordinary compounding agents for polyolefin resins. , Antistatic agent, metal deactivator,
Antibacterial and fungicides, fluorescent whitening agents and the like can be mentioned.

Specific examples of the foaming agent blended in the polypropylene resin material of the present invention include azodicarbonamide (ADCA), N, N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis ( Benzenesulfonylhydrazide), diphenylsulfone-3,
Organic foaming agents such as 3′-disulfonylhydrazide, p-toluenesulfonyl semicarbazide, and trihydrazinotriazine; and inorganic foaming agents such as sodium hydrocarbon, ammonium hydrogencarbonate, and ammonium carbonate. Among them, as the organic foaming agent, azodicarbonamide (ADCA), N, N'-dinitrosopentamethylenetetramine, and trihydrazinotriazine are preferable.
As the inorganic blowing agent, sodium hydrogen carbonate is preferable.

The foaming agent is preferably 0.2 to 2% by weight, more preferably 0.1 to 2% by weight, based on the total amount of the resin composition for forming a substrate.
It is used in a ratio of 4 to 1.4% by weight. By using the foaming agent at such a ratio, the foaming ratio of the foamed base material layer made of the polypropylene resin material can be set to a desired ratio of about 1.1 to 2.0 times.

The resin composition for forming a base material used in the present invention comprises the above-mentioned polypropylene resin, a filler to be added as required, other additives and the above-mentioned foaming agent, and a Henschel mixer, a super mixer, a V-blender. ,
It can be prepared by uniformly mixing by a known method using a tumbler mixer, a ribbon blender, a Banbury mixer, a kneader blender or the like.

(2) Skin Material The skin material used in the present invention is mainly composed of a skin such as a nonwoven fabric, a cloth or a fabric, and may be composed of a single skin layer. May be a laminate in which layers made of the above materials are laminated.

As the skin, leather such as polyvinyl chloride resin (PVC), thermoplastic elastomer (TPE), and polyurethane (PU) is used in addition to the above-described nonwoven fabric, cloth, and fabric. The layer other than the skin that can constitute the skin material is a skin protection layer (a cloth protection layer when the skin is a fabric), and is provided so as to be located between the skin and the base material layer.

Examples of the skin protective layer include foam sheets such as polypropylene foam and polyurethane foam. When a laminate having a skin protective layer is used as the skin material, such a foam sheet or the like is attached to the skin to obtain the laminate.

In the present invention, the effect of the present invention is particularly remarkably exhibited when a material composed of a single layer of skin or a laminate of the cloth skin layer and the fabric protective layer is used as the skin material. You. That is, by manufacturing a multilayer foam molded product composed of a fabric and a substrate by the method of the present invention, a molded product having a good appearance can be obtained without damaging the fabric. Although the fabric is not particularly limited, a woven fabric (moquette, soft wave), a knitted fabric (tricot, double Russell, jersey), a nonwoven fabric, and the like can be used.

(3) Manufacturing Step The method for manufacturing a multilayer foam molded article of the present invention is a method in which injection compression molding and foam molding are combined using upper and lower molds for mold stamping molding. ,
(B) an injection compression step, (c) a foaming step, and (d) a cooling and solidifying step. An example of the manufacturing method of the present invention is shown in FIGS.

(A) Skin material installation step: In this step (a), the skin material is installed between the upper and lower dies for mold stamping. That is, as shown in FIG. 1, the skin material 3 is set between the upper mold 1 and the lower mold 2.

In the present invention, since the upper mold 1 comes into contact with the skin material later, the mold temperature of the upper mold 1 is set to 10 to 50 ° C., preferably to prevent the skin material 3 from being damaged. 1
The temperature is preferably set to 0 to 30 ° C.

When a laminate of the skin and another layer such as a skin protective layer is used as the skin material, the skin material is provided so that the other layer is formed in contact with the foamed base material layer. The skin material may be a flat sheet-like unformed state,
Further, a member molded in a predetermined shape in advance may be installed.

(B) Injection filling step: In this step (b), the resin composition for forming a base material is injected and filled into a cavity formed by the upper and lower molds while the upper and lower molds are opened. I do.

That is, first, the resin composition for forming a base material prepared by the above-described method is heated in a cylinder of an extruder provided in a mold stamping molding machine to a temperature not lower than the decomposition temperature of a foaming agent and 180 to 240 ° C. , Preferably 18
Melts at a temperature of 0-220 ° C. Even if the resin composition is melted at a temperature higher than the decomposition temperature of the foaming agent, the resin composition hardly starts foaming because the resin composition is pressurized in the cylinder.

Next, as shown in FIG. 2, a molten resin 6 is injected and filled from a gate 4 provided in the lower mold into a cavity 5 which is a space formed by the opened upper and lower molds 1 and 2. I do. The injection conditions at this time can be appropriately selected from those used in known injection molding methods, but the mold temperature is 20 to 60 ° C. and the injection pressure is 50 to 50.
About 0 kgf / cm ² is preferable.

The opening amount of the upper and lower molds at the start of injection filling (distance between upper and lower molds: initial clearance. FIG. 2)
Medium A) is 3 to 10 mm, more preferably 8 to 10 mm
It is desirable that If the mold opening amount is less than the lower limit of the above range, the resin pressure at the time of injection becomes too high, and the skin may be damaged. On the other hand, when it is larger than the upper limit of the above range, foaming of the resin starts after the injection, and the final foaming ratio is reduced.

In this step (b), while performing such injection filling, as shown in FIG.
Is closed, the mold is clamped, and the inside of the cavity 5 is compressed. More specifically, the step (b) is more specifically described in an injection filling step of injecting a resin composition for forming a base material into a cavity formed from the upper and lower molds while the upper and lower molds are opened ( b-1), while performing such injection filling, FIG.
As shown in (2), a compression step (b-2) of closing the upper and lower molds 1 and 2 and closing the molds to compress the inside of the cavity is included.

In the injection compression step, the resin composition 6 is formed into a desired shape to form a base material layer, and at the same time, the skin material 3 and the base material layer installed in the step (a) are integrated. . In addition, foaming of the resin composition is suppressed by the compression.

The compression speed (mold closing speed) at this time is 10
-40 mm / sec, preferably 20-40 mm / sec. By increasing the compression speed in this way, damage to the epidermis can be reduced. The internal pressure during compression, that is, the compressive stress (clamping force) is preferably 350 t or less, and more preferably 150 to 350 t. By limiting the compressive force in this way, damage to the epidermis can be reduced.

Here, the compression step (b-2) includes a pre-stage compression in which the upper and lower dies are clamped by controlling the speed at a mold clamping speed of 10 to 40 mm / sec, and a pressing pressure of 150 mm for the upper and lower dies. ~
This is performed by multi-stage compression including the latter stage compression in which the pressure is controlled at 350 t and the mold is clamped. Here, first-stage compression is performed by speed control, and then, after mold clamping progresses and is compressed to a predetermined mold opening amount, switching to second-stage compression by pressure control is performed. The transition from the first-stage compression to the second-stage compression is preferably performed when the opening amount of the upper and lower dies is in the range of 0.5 to 1 mm. When the mold opening amount is smaller than 0.5 mm,
The resin pressure in the mold easily rises and skin damage is easily caused. On the other hand, when the mold opening amount is larger than 1 mm, the pressure tends to be difficult to control because the resin pressure is low.

As described above, in the first stage of the compression process, compression is performed by setting a constant mold clamping speed, and then, in the second stage, compression is performed by setting a constant pressure and controlling the pressure. If the entire compression process is performed at a constant mold clamping speed, the resin will be over-pressurized as the mold clamping progresses, and may damage the skin inside the mold during injection filling. On the other hand, in the method including the multi-stage compression step of the present invention, after the mold clamping has progressed by a predetermined amount, by switching to compression by pressure control, the mold clamping pressure is controlled according to the pressure of the resin itself, Damage to the epidermis can be prevented.

If the mold closing speed in the first stage compression is higher than the above range, the skin is easily damaged, and if it is lower than the above range, the compression step time becomes longer and the solidification of the resin proceeds, so that in the subsequent foaming step, The foaming ratio decreases. On the other hand, if the clamping pressure in the second-stage compression is higher than the above range, the skin is easily damaged.

The above-mentioned first-stage compression and second-stage compression are performed by:
Each stage may be further divided into multiple stages, and the mold clamping speed may be varied stepwise, or the mold clamping pressure may be varied stepwise, or these may be appropriately combined to form a multistage compression process of three or more stages.

The compression can be started after the injection and filling of the resin composition for forming a base material is completed. In the present invention, while the injection and filling from the gate into the cavity is performed, the upper and lower molds are simultaneously closed. It is preferable to compress and terminate the compression when the filling of the resin composition for forming a base material is completed. More preferably, the compression is started when the resin composition for forming a base material is injected and filled up to 85 to 97% of the total injected filling amount. By starting compression before the resin composition for forming a base material is completely injected and filled, molding can be performed while maintaining fluidity and spreadability of the resin composition, and moldability is improved.

If compression starts when the injection filling amount of the resin composition for forming a base material is less than 85% of the total injection filling amount, the mold clamping ends before the end of the injection filling, and the injection pressure becomes too high. It is not preferable because it may damage the epidermis. On the other hand, when the compression is started after the injection filling amount of the base material forming resin composition exceeds 97% of the total injection filling amount, the flowability of the resin in the mold cannot be maintained, and the moldability is deteriorated. Absent.

The distance between the upper and lower molds after compression (mold clearance, B in FIG. 3) is preferably 2 to 3.5 mm, more preferably 2 to 3 mm. In addition, the mold closing time is set to 0.1.
About 5 to 3.5 seconds is preferable.

(C) Foaming Step: In this step (c), the upper and lower molds are opened at a predetermined speed by a predetermined amount, and the base material layer portion made of the resin composition for forming a base material is foamed to form a foamed base material layer. Form.

That is, in the injection compression step (b), after clamping and compression to integrate the base layer made of the resin composition and the skin layer, in this step, as shown in FIG. The molds 1 and 2 are opened to a predetermined distance. This allows
The pressure in the cavity is released, and foaming of the resin composition for forming a base material is started by the decomposed foaming agent.
Is formed. In this case, the amount of enlargement of the upper and lower molds (the distance between the upper and lower molds after opening the mold, C in FIG. 4) is preferably about 1 to 2 mm. The mold opening speed is preferably about 0.6 to 40 mm / min.

(D) Cooling and solidifying step: In this step (d), the foamed base material layer formed by foaming the resin composition for forming a base material in the step (c) is cooled and solidified.

Finally, the upper and lower molds are opened to take out the multilayer foam molded article having the skin layer and the foam base material layer from the mold.

(4) Multi-layer foam molded article The multi-layer foam molded article manufactured through the above steps is
It is composed of a foamed base material layer made of a polypropylene resin material and a skin layer made of a skin material. The polypropylene resin material constituting the foamed base material layer may contain a residual foaming agent.

Further, the multilayer foam molded article of the present invention may be provided with another layer in addition to the skin layer and the foam base material layer. For example, a known skin layer forming sheet may be laminated between the skin layer and the foam base layer in order to quickly cool the foam base layer. The skin layer forming sheet has a thickness of 0.05 to 1.0 m of the olefinic thermoplastic elastomer alone or a blend with polypropylene.
m sheets are preferably used. In addition, non-woven fabrics and woven fabrics can be used.

When a skin layer forming sheet is provided between the skin layer and the foam base material layer, the skin layer forming sheet is attached to the skin material before the skin material is placed on the upper and lower molds. deep. The method of sticking is not particularly limited. When the skin layer forming sheet is a sheet of the above-mentioned polypropylene or thermoplastic elastomer, a method of laminating these molten sheets on a skin material by heat fusion and integrating them by fusion is advantageous. When the skin material is adhered to a PVC or PU foam, it is preferable to attach the skin material with an adhesive.
When a nonwoven fabric and a woven fabric are used for the skin layer forming sheet, they can be integrated by bonding to a foam sheet with a general adhesive.

The multilayer foam molded article obtained by the production method of the present invention has a foaming base layer having an expansion ratio of 1.1 to 2.0.
The cell size is about 0.05 to 0.3 mm and uniform. Therefore, it is lightweight and excellent in rigidity as compared with the foam molded product manufactured by the conventional mold stamping molding method.

Furthermore, even when the fabric is used as the skin material, the fabric is not damaged at the time of molding, so that it is possible to obtain a molded article having a good appearance and attached to the fabric.

Accordingly, the multilayer foam molded article of the present invention
It is particularly useful as an automotive interior material such as door trim, rear package trim, seat back garnish, instrument panel, trunk side trim, and the like.

[0062]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In these examples, molding was performed based on the steps shown in FIGS. 1 to 4 above, and the injection molding machine used was a mold stamping molding machine (manufactured by Kobe Steel Co., Ltd., 500t vertical injection compression composite). The molding machine was a door trim-shaped injection compression molding mold having a mold clearance (B in FIG. 3) of 2.5 mm.

[0063]

Example 1 In this example, a knitted fabric (jersey made by Kawashima Textile) was used as a skin material. Further, as a resin composition for forming a base material, 100 parts by weight of a propylene block copolymer [ethylene / octene copolymer rubber (EOR) content: 20% by weight, MFR: 80 g / 10 minutes], and a pyrolytic foaming agent (Mitsubishi Chemical Co., Ltd., trade name "Fine Blow S20N") 3 parts by weight and a resin composition obtained by mixing with a tumbler mixer.

First, the skin material was set between the upper mold surface and the lower mold surface of the mold for injection compression molding so that the surface of the skin material product faced upward. The set temperature of the upper mold (1 in FIG. 1) is 30 ° C., and the set temperature of the lower mold (2 in FIG. 1) is 50 ° C.
And Next, the upper and lower dies were clamped until the opening amount (initial clearance, A in FIG. 2) became 10 mm.

Next, the resin composition for forming a base material was put into an extruder provided in the mold stamping molding machine and melted. In addition, the temperature of the cylinder and the die of the extruder was set to 190 ° C. when the resin composition was charged into the extruder.

Next, the molten resin composition was injected and filled into the cavity formed by the upper and lower molds from the gate of the lower mold. The injection speed at this time was set to 90% of the maximum set value.

Next, when the injection filling amount of the resin composition reached 90% of the maximum filling amount (total injection filling amount), mold clamping was started. The mold clamping is performed at a speed of 20 mm / sec until the mold opening amount becomes 0.5 mm.
After reaching m, the mold was clamped by pressure control with the pressure set to 300 t.

After the completion of the injection filling of the molten resin, the valve gate of the mold was closed. Next, after performing mold clamping under pressure control for 1.5 seconds, the mold was opened by a predetermined amount to obtain a multilayer foam molded product. The mold opening speed at this time is 40 mm / min,
The mold enlargement amount (C in FIG. 4) was 1.5 mm.

The thickness of the skin layer of the obtained multilayer foam molded article was 0.5 mm, and the thickness of the foam base material layer was 3.5 mm. The expansion ratio in the foamed base material layer is 1.5 times,
The size of the foam cells ranged from 0.05 to 0.3 mm. In addition, the touch feeling of the skin layer is good, and the product rigidity is 7.
The weight was 8 kg / cm and the weight was 1450 g. As for the method of measuring the product rigidity, first, a test piece having a width of 50 mm was cut out, the distance between the spans was 100 mm, and the test speed was 50 m.
A bending test was performed at m / min, and the elastic gradient was used as the product rigidity.

[0070]

Example 2 Except for using a knitted material laminated with a protective layer (made of Achilles, urethane foam having a thickness of 5 mm) as a skin material, injection compression molding was performed in the same manner as in Example 1 to obtain a multilayer foam. A molded product was obtained.

When the skin material is set between the upper die surface and the lower die surface of the injection compression molding die, the protective layer is placed on the back side of the product (that is, between the skin layer and the foam base material layer). ) Was set with the surface on which the protective layer was laminated facing the lower mold.

The thickness of the skin layer of the obtained multilayer foam molded article was 0.5 mm, and the thickness of the foam base material layer was 3.5 mm. The expansion ratio in the foamed base material layer was 1.5 times, and the size of the foamed cells was in the range of 0.05 to 0.3 mm. In addition, the touch feeling of the skin layer is good, and the product rigidity is 7.8 kg.
/ Cm, and the weight was 1500 g.

[0073]

Comparative Example 1 Propylene block copolymer [ethylene
Octene copolymer rubber (EOR) content: 20% by weight, M
FR: 80 g / 10 min] and 10% by weight of talc,
The mixture was mixed with a tumbler mixer to obtain a resin composition for forming a substrate. No blowing agent was added.

Using the obtained resin composition for forming a base material,
A molded article was formed in the same manner as in Example 1 except that the foaming step was not performed. That is, after the injection compression step, the step of opening the upper and lower molds by a predetermined amount to perform foaming was not performed. Instead, the molds were opened after cooling and solidification, and the molded product was taken out.

The thickness of the skin layer of the obtained molded article is 0.5 m
m, and the thickness of the base material layer was 2.8 mm. Also,
The product rigidity was 7.9 kg / cm and the weight was 1700 g. Although the product rigidity was almost the same as that of the example, the weight was increased, and the weight could not be reduced.

[0076]

According to the production method of the present invention, by adopting molding conditions including a specific multi-stage compression step, the base material layer having uniform foam cells without damaging the skin material. Can be formed. Therefore, it is possible to obtain a molded article that is lightweight, highly rigid, and excellent in appearance and suitable for interior materials for automobiles.

[Brief description of the drawings]

FIG. 1 shows a step of installing a skin material in the production method of the present invention.
It is a figure showing the state where the skin material was installed between the upper and lower dies.

FIG. 2 is a view showing a state before a molten resin is injected and compressed in an injection compression step of the production method of the present invention.

FIG. 3 is a view showing a state where upper and lower dies are clamped and compressed in an injection compression step of the manufacturing method of the present invention.

FIG. 4 is a view showing a state in which foaming is started by opening upper and lower molds in a foaming step of the production method of the present invention.

[Explanation of symbols]

 1. Upper mold 2. Lower mold 3. Skin material 4. Gate 5. Cavity 6. Molten resin 7. Foamed base material layer A. Mold opening (initial clearance) Mold clearance C. Mold expansion amount

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FIB29L 9:00 31:58 (72) Inventor Naganori Masuchi 1 Tohocho, Yokkaichi-shi, Mie Japan Polychem Co., Ltd. Material Development Center (56) References JP-A-6-344362 (JP, A) JP-A-6-91774 (JP, A) JP-A-9-52246 (JP, A) JP-A-8-323789 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 43/18-43/20 B29C 43/32-43/42 B29C 43/50-43/58 B29C 45/14-45/16 B29C 45 / 70

Claims (2)

(57) [Claims] 1. A method for producing a multilayer foam molded article comprising a foam base material layer made of a polypropylene resin material and a skin layer made of a skin material using upper and lower molds for mold stamping molding, comprising: A) placing a skin material between the upper and lower molds; and (b) forming the upper and lower molds from the upper and lower molds with the upper and lower molds opened.
Polypropylene resin material and foaming agent in cavity
Injecting and filling a resin composition for forming a base material comprising:
(B-1) and the upper and lower molds are clamped at a speed of 10 to 40 m.
pre-stage compression for mold clamping with speed control at m / sec,
Mold clamping by controlling the pressure of the mold with mold clamping pressure of 150 to 350t
The cavity by multi-stage compression including post-stage compression
An injection compression step comprising a compression step (b-2) of compressing the inside; and (c) a foaming step of opening the upper and lower molds and foaming the resin composition for forming a base material to form a foamed base material layer. (D) a cooling and solidifying step of cooling and solidifying the foamed base material layer, wherein the method comprises the steps of: 2. In the compression step (b-2), the transition from pre-compression to post-compression is performed when the opening of the upper and lower dies is in the range of 0.5 to 1 mm. The method for producing a multilayer foam molded article according to claim 1.