JP3950325B2 - Molding of laminated composites by powder slush molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated composite in which a surface layer of a polyolefin-based thermoplastic elastomer has a structure capable of utilizing the elasticity of a buffer layer of a polyurethane foam. The present invention specifically relates to a laminated composite having an elastic skin layer useful as an automobile interior material. Another invention relates to a molding process that allows industrial production of such laminated composites.
[0002]
[Prior art]
Conventionally, a laminated composite used for an automobile interior material (for example, an instrument panel and a console box) is formed by laminating a buffer layer of a polyurethane foam on a polyvinyl chloride skin layer and a core material on the buffer layer. It has a structure in which (a material that maintains the form and strength of the laminated composite) is laminated, and when it is disposed of as a whole during disposal, harmful components such as dioxins derived from polyvinyl chloride are generated. Then there was a problem.
[0003]
For this purpose, a polyolefin-based thermoplastic elastomer for skin layers that replaces polyvinyl chloride has been proposed, which includes a polyolefin-based resin containing a carboxyl group or its anhydride group and an ethylene-alpha-olefin copolymer rubber. A mixture with a partially crosslinked product (see JP-A-59-1561), a mixture of a plurality of polyolefin resins (see JP-A-59-1561), an oil-extended polyolefin copolymer rubber and a polyolefin resin A mixture of a polyolefin resin and an alpha-olefin copolymer rubber (see Japanese Patent Application Laid-Open No. 2-57310), and a polyolefin resin and an ethylene-a-olefin copolymer. Mixture with rubber (see JP-A-5-5050, JP-A-6-170871, etc.) And the like. However, even if the polyolefin-based thermoplastic elastomer according to those proposals is used as a skin layer, a material that is firmly interposed between the polyurethane foam buffer layer and the like is unknown.
[0004]
Accordingly, the present inventors have conducted a search and examination of materials having strong adhesiveness between the polyolefin-based thermoplastic elastomer of the skin layer and the polyurethane foam buffer layer, and the ethylene- It has been found that the acrylic acid copolymer layer has strong adhesion to both the surface layer of the polyolefin-based thermoplastic elastomer and the buffer layer of the polyurethane foam, and a patent application has already been filed (Patent Publication 2000-). 190428).
[0005]
[Problems to be solved by the invention]
However, as a result of further studies by the inventor, when an adhesive layer of an ethylene-acrylic acid copolymer is molded by a conventional powder molding method (particularly, a powder slush molding method), a thin layer of 100 μm or less is formed. Has been found to be difficult. Since the rigidity of the ethylene-acrylic acid copolymer is larger than that of the polyolefin-based thermoplastic elastomer, if the adhesive layer of the ethylene-acrylic acid copolymer exceeds 100 μm, the polyurethane foam layer (buffer layer) It has been found that the elasticity is substantially blocked by the adhesive layer and the surface layer of the polyolefin-based thermoplastic elastomer becomes hard, resulting in inferior buffering performance used for automobile interior materials and the like.
[0006]
In addition, the function of the adhesive layer is to interpose between the skin layer and the buffer layer and firmly bond them, and as long as the function can be expressed, it is economical that the layer is as thin as possible. From the viewpoint of sex. Therefore, the present inventor has found the present invention by examining the structure of a laminated composite in which the properties such as elasticity of the buffer layer are effectively expressed in the skin layer of the polyolefin-based thermoplastic elastomer by the inventor in detail. It was.
[0007]
An object of the present invention is to provide a molding method effective for industrial implementation of a laminated composite capable of expressing the elasticity of a polyurethane foam buffer layer on the surface layer of a polyolefin-based thermoplastic elastomer. It is another object of the present invention to provide a molding method effective for industrial implementation of a laminated composite that can effectively utilize a skin layer of a polyolefin-based thermoplastic elastomer as a skin of an automobile interior material.
[0008]
[Means for Solving the Problems]
The method for forming a laminated composite by the powder duster slush molding method of the present invention according to claim 1 comprises:
A thermal melt layer of a skin layer welded to a slush mold is formed from a polyolefin-based heat-curable elastomer or a molding material containing the same, and an ethylene-acrylic acid copolymer powder to which a charge is imparted is formed so that the elasticity of the buffer layer The first step of spraying with a thickness of 10 to 100 μm that can be transmitted to the skin layer and laminating as an adhesive layer, and the laminated composite obtained in the first step is attached to a urethane-injected foaming mold, and laminated composite And a second step of laminating a polyurethane foam buffer layer on the body adhesive layer .
[0009]
According to a second aspect of the present invention, there is provided a method of forming a laminated composite by a powder slush molding method, comprising the steps of forming a thermal melt layer of a skin layer welded to a slush mold from a polyolefin-based heat-resistant elastomer or a molding material containing the same. First, an ethylene-acrylic acid copolymer powder to which a negative ion charge has been imparted is sprayed with a thickness of 10 to 100 μm so that the elasticity of the buffer layer can be transmitted to the skin layer. a step, a first laminated composite obtained in the step and the core member is attached to the urethane injection foaming mold, then, the prepolymer of the polyurethane is injected between the adhesive layer and the core material of the layered composite And a second step of forming a laminated composite composed of a skin layer / adhesive layer / polyurethane foam buffer layer / core material by crosslinking and foaming.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described. In FIG. 1 and FIG. 2 used for the description, the same reference numerals denote the same or equivalent ones.
[0011]
[ Molding method of laminated composite according to the present invention]:
The present invention is a method for forming a laminated composite comprising a skin layer (polyolefin-based thermoplastic elastomer layer) / adhesive layer (ethylene-acrylic acid copolymer layer) / buffer layer (polyurethane foam layer), adhesive layer, ethylene was granted the charge of negative ions - hot melt raw materials acrylic acid copolymer powder skin layer (typically, thermal melt formed in the molding die in powder molding) The powder having a negative ion charge is melted by a hot melt to form a laminated composite of the skin layer and the adhesive layer. The thickness is such that the elasticity of the buffer layer can be transmitted to the skin layer. The charge of the ethylene-acrylic acid copolymer powder is generally a negative charge. For example, negative ions are clustered by applying a voltage of -50 to -125 kV in the ethylene-acrylic acid copolymer powder. Charge through region.
[0012]
Then, if the charged ethylene-acrylic acid copolymer powder is in contact with, thermally melted, and bonded and laminated to the raw material melt of the skin layer (for example, 180 to 300 □), the elasticity of the buffer layer is improved. A laminated composite in which the skin layer / adhesive layer / buffer layer is firmly integrated through the thin adhesive layer can be obtained. It is done.
The adhesive layer has a thickness before a phenomenon (so-called electrostatic equilibrium phenomenon) in which a powder particle layer having a certain thickness or more is not formed due to repulsion between charged particles in electrostatic coating. If the average particle diameter of the ethylene-acrylic acid copolymer powder is, for example, 10 to 150 μm, the target adhesive layer can be easily formed.
[0013]
For the application and spraying of an electric charge to the ethylene-acrylic acid copolymer powder, a powder electrostatic coating method can be used. However, in the electrostatic powder coating method, a charge is applied to the powder to be sprayed and sprayed onto the conductive object to be coated, and the powder and the object to be coated are fixed by electrical coupling of opposite charges. Is the method. However, in the present invention, a non-conductive or low-conductive elastomer is made into a hot melt and sprayed on it without performing the process of imparting conductivity to the elastomer.
[0014]
< Skin layer of laminated composite >:
The skin layer is a layer in which a raw material made of a polyolefin-based thermoplastic elastomer (hereinafter sometimes abbreviated as an elastomer) or a molding material containing the same is molded by a powder slush molding method. In the elastomer, the thermoplastic resin component (hard layer, hard segment) is polyolefin (typically polyethylene, polypropylene and a copolymer thereof), and the rubber component (soft layer, soft segment) is Typically, it consists of ethylene / propylene / diene copolymer (EPDM), ethylene / propylene rubber (EPR), and the like. There are no particular restrictions on the restraint mode between the thermoplastic resin component and the rubber component. A molding material containing an elastomer is a molding material prepared using an elastomer as a main raw material for a powder molding method (particularly, a powder slush molding method). In the molding material, various additives suitable for powder molding (for example, a colorant, a heat stabilizer, an ultraviolet absorber, a lubricant or an antistatic agent) are blended in appropriate amounts as auxiliary materials.
[0015]
< Adhesive layer of laminated composite >
For example, if the ethylene-acrylic acid copolymer has an acrylic acid content of 4 to 10% by weight, an adhesive layer suitable for the present invention can be formed, and a content of 10% by weight or more is possible. It is also possible. The ethylene-acrylic acid copolymer can be used by blending additives such as an antioxidant, a heat stabilizer, a filler, and an ultraviolet absorber, if necessary. The adhesive layer is controlled to a thickness capable of transmitting the elasticity of the buffer layer to the skin layer by controlling the charge amount (negative ions) of the ethylene-acrylic acid copolymer powder and the amount of spraying. The adhesive layer is desirably thick to some extent from the viewpoint of firmly adhering to the skin layer and the buffer layer to form a laminated composite to form an integral structure. For example, if the adhesive layer has a thickness of 10 to 100 μm, it can satisfy both conditions.
[0016]
The “thickness capable of transmitting the elasticity of the buffer layer to the skin layer” in the present invention means a thickness that can clearly recognize that the elasticity of the skin layer includes the elasticity of the buffer layer. The state in which the elasticity of the skin layer in the laminated composite of the adhesive layer, the adhesive layer, and the buffer layer is only about 0 to 30% less than the elasticity of the laminated skin layer in which the skin layer is directly stacked on the buffer layer It is. Elasticity is measured by placing a weight of the same shape on the skin layer and sinking. When the reduction in the elasticity of the skin layer exceeds about 30%, the elasticity of the automobile interior material as the skin tends to be insufficient.
[0017]
The hot melt layer as the raw material for the skin layer to which the ethylene-acrylic acid copolymer powder is sprayed is an elastomer hot melt layer formed in a powder slush mold. The thermoplastic resin that is in a molten state by heating is called a hot melt, a molten resin, a hot melt, a melt, a liquid resin, a liquid resin, or the like, all of which are synonymous. . In this specification, the term “hot melt” is used.
[0018]
< Buffer layer of laminated composite >:
A polyurethane foam (cross-linked foam) is laminated on the adhesive layer as a buffer layer, and the laminate of the skin layer and the adhesive layer is attached to a urethane-injected foam mold, and a foam raw material (for example, polyol and isocyanate) -A mixture of foams), foamed and cured into a polyurethane foam layer adhered to the adhesive layer.
[0019]
< Laminated composite >:
The laminated composite has a structure in which a core material (material that maintains the shape and strength of the laminated composite) is laminated on a polyurethane foam layer (buffer material layer), and an elastomer (skin layer) / ethylene-acrylic acid It is possible to make an automobile interior material comprising a copolymer (adhesive layer) / polyurethane foam layer (buffer material layer) / core material. When the laminated composite is an automobile interior material, an injection molded body such as ABS resin and polypropylene is generally used as a core material. However, the laminated composite may not require a core material for its use.
[0020]
[ Forming method of laminated composite ]:
Molding of laminated composites can be carried out using various powder molding methods, but the powder-slash molding method is used from the viewpoint that complex shaped skin layers can be molded with high efficiency and high accuracy. Is suitable.
[0021]
< Powder slush molding method >:
The powder-slush molding method is generally a method comprising a heating process of a slush mold, a powdering process, a reheating process of the slush mold, a cooling process of the slush mold, and a process of removing the molded product from the slush mold. It is. The powdering step is a step of forming a welded resin layer by melting and adhering resin powder to a heated mold surface of a slush mold. FIG. 1 is an explanatory diagram showing a powdering process, in which FIG. 1A is an explanatory diagram at the start of powdering, and FIG. 1C is an explanatory diagram at the end of powdering. . The general operation of powdering is as follows. At the start of powdering, the powder of the slush mold 1 having the molding die surface heated to the melting temperature of the resin powder or higher in the heating process of the slush mold is loaded with the resin powder 2. -It is joined and fixed to the box 3 to form an assembly 4 (see FIG. 1A). Next, when the assembly 4 rotates up and down and the powder box 3 is positioned above, the resin powder 2 falls from the powder box 3 to the molding die surface 5 due to its own weight and melts and adheres. Further, when the assembly 4 rotates and the upper and lower positions return to the original state (see FIG. 1A), the excess resin powder 2 is collected in the powder box 3 and is placed on the molding die surface 5. The deposited hot melt layer 6 is formed and the powdering is completed. The hot melt layer 6 welded to the molding die surface 5 is cooled and solidified into a molded product in the subsequent steps.
[0022]
< Lamination of skin layer and adhesive layer in the first step >:
Molding of the laminated composite, powder of FIG. 1 (A) - box 3 Elastomer - by loading a powder, come to Ri by the general operation of powdering in FIG. 1 (C), the molding die surface A hot melt layer of elastomer welded to 5 is formed.
Next, the assembly 4 is separated into the slush mold 1 and the powder box 3, and negative ions are applied to the hot melt layer 6 welded to the mold surface 5 by a spray gun of a powder electrostatic coating device. The obtained ethylene-acrylic acid copolymer powder is sprayed to the thickness as described in the first aspect of the present invention and thermally melted by the heat storage of the hot melt layer 6, and then cooled and solidified to form the skin layer and the adhesive layer. And laminated composite.
The “slush mold” is synonymous with a mold or a slash mold, and when it is made of electroforming (many are electroformed), it may be referred to as an electroforming mold or a casting mold. . “Molding mold surface” is synonymous with molding surface, molding surface, or mold surface, and when it is made of electroforming, it is a mold, a mold surface, an electroforming mold, a shell surface, a shell mold, or electroforming. Sometimes referred to as a shell surface. “Powder box” is synonymous with a bucket, a reservoir or a reserve tank.
[0023]
< Lamination of adhesive layer and buffer layer in the second step >:
The laminated composite of the skin layer and the adhesive layer is placed in a uretan-injected foaming mold, and a polyurethane prepolymer is injected to perform foam molding, and a buffer layer is laminated on the adhesive layer. FIG. 2 is an explanatory diagram of foam molding. FIG. 2 shows an adhesive layer in which a laminated composite 20 of a skin layer and an adhesive layer and a core material (for example, an injection-molded article of a thermoplastic resin) 21 are loaded in a urethane injection foaming mold (not shown). 2 is an explanatory view showing a state in which a polyurethane prepolymer 23 is injected between the core material 21 and the core material 21 from the direction of the arrow. When the prepolymer 23 is crosslinked and foamed and then taken out from the urethane injection foaming mold, a laminated composite of skin layer / adhesive layer / buffer layer / core material is obtained. Urentane injection foaming and foaming can be performed by known techniques.
[0024]
In the present invention, it is in accordance with the object of the present invention, and any modification or partial change and addition is optional as long as the effects of the present invention are not particularly impaired. It is.
[0025]
【The invention's effect】
According to the present invention, it is possible to obtain a laminated composite in which the elasticity of the buffer layer of the polyurethane foam can be expressed on the skin layer of the polyolefin-based thermoplastic elastomer. In addition, since the formation of the adhesive layer is controlled by the amount of powder sprayed and the amount of charged charge, it becomes easy to form a thin adhesive layer to obtain a laminated structure having a strong monolithic structure. Can be formed.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a powdering process.
FIG. 2 is an explanatory view of polyurethane foam molding.
[Explanation of symbols]
1 Slush Mold 2 Resin Powder 3 Powder Box 4 Assembly 5 Mold Surface 6 Hot Melt Layer 20 Laminated Composite 21 Core Material 22 Adhesive Layer 23 Prepolymer

Claims (3)

A thermal melt layer of a skin layer welded to a slush mold is formed from a polyolefin-based heat-curable elastomer or a molding material containing the same, and an ethylene-acrylic acid copolymer powder to which a charge is imparted is formed so that the elasticity of the buffer layer The first step of spraying with a thickness of 10 to 100 μm that can be transmitted to the skin layer and laminating as an adhesive layer, and the laminated composite obtained in the first step is attached to a urethane-injected foaming mold, and laminated composite And a second step of laminating a buffer layer of polyurethane foam on the adhesive layer of the body . A heat-melt layer of a skin layer welded to a slush mold from a polyolefin-based thermosetting elastomer or a molding material containing the same is formed, and an ethylene-acrylic acid copolymer powder to which a negative ion charge is imparted is formed as a buffer layer. The first step of laminating as an adhesive layer by spraying with a thickness of 10 to 100 μm that allows the elasticity of the skin to be transmitted to the skin layer, and the urethane composite foam mold obtained by the first step and the laminated composite and the core material Then, a polyurethane prepolymer is injected between the adhesive layer and the core material of the laminated composite to crosslink and foam, and from the skin layer / adhesive layer / polyurethane foam buffer layer / core material A method for forming a laminated composite by a powder slush molding method, comprising a second step of forming a laminated composite for an automobile interior material . The molding method of the laminated composite of Claim 1 or the laminated composite of Claim 2 provided with one or more of the characteristics of following (1)-(4).
(1) The ethylene-acrylic acid copolymer powder provided with the negative ion charge is contact-heat-melted / bonded and laminated on a heat melt of a skin layer at 180 to 300 ° C.
(2) The adhesive layer is formed from an ethylene-acrylic acid copolymer having an acrylic acid content of 4 to 10% by weight.
(3) The adhesive layer is formed by spraying an ethylene-acrylic acid copolymer powder having an average particle size of 10 to 150 μm.
(4) The core material is made of an injection molded body.

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