Process for producing multilayer molded article

Abstract: A multilayer molded article having a thermoplastic resin body and a skin material covering the resin body is produced by supplying a skin material between a pair of molds (1, 7), holding the skin material between a skin material-holding frame (3)which is moved in a direction perpendicular to a mold-closing direction and a skin material-supporting frame (9) which is moved in the mold-closing direction, supplying a mass of a thermoplastic resin melt, and closing the molds (1, 7) to form a multilayer molded article, in which at least one moving member (11) which moves forward or rearward in the mold closing direction is provided around a mold face and is recessed in the mold closing direction after the supply of the resin melt, at least one ejector (5) which is provided on the skin material-holding frame (3) is ejected to fold an edge of the skin material towards a center of the mold, and the moving member (11) is forwarded till the mold face so as to fold back the edge of the skin material over the back of the resin body.

Description: The present invention relates to a process for producing a multilayer molded article comprising a body of a thermoplastic resin and a skin material. In particular, the present invention relates to a process for producing a multilayer molded article in which edges of the skin material are folded back over a back of the molded article of the thermoplastic resin. The molded article produced by the process of the present invention can be used as, for example, an automobile part which is installed with folding back the edges of the skin material over the back of the article. Hitherto, the above described kind of the molded article is produced by trimming the skin material and then folding the edges of the skin material with hands. However, such folding process is troublesome and it is difficult to sharply fold some skin materials. Japanese Patent Kokai Publication No. 137714/1986 and corresponding U.S. Patent Application Serial No. 07/458,401 disclose a process for producing a multilayer molded article having a skin material which covers the resin body till its edges by means of a molding machine having a frame for fixing the skin material which is movably attached to one of male and female molds with expansion means in which the male mold has a sliding plane around the whole periphery of the male mold, and the frame for fixing the skin material and the female mold form a mechanism for cutting the skin material and a skin material-holding part therebetween. However the disclosed process does not fold back the edges of the skin material over the back of the resin body. JP-A-61-41517 relates to the manufacture of a molded item with skin. In the process a skin is arranged in the mold and a dragging member having an opening smaller than the circumference of the opening of a molding recess is arranged with a sheet on the side of a movable mold. Then the movable mold is moved to be registered and when a melted polypropylene resin is injection molded, the skin is stretched by the injection pressure to be forced against the molding surface of the molding recess. As a result, the skin is integrated with a base with the skin fed onto the undersurface of the base at a cavity edge. Then the movable mold is moved to be opened, a center pillar interior material with the skin fed onto the undersurface of the base is removed and unrequired part of the skin is cut off at a turned section of the skin on the undersurface of the base using a trimming cutter. An object of the present invention is to provide a process for producing a multilayer molded article having a skin material edges of which are folded back over a back of a resin body of the molded article. According to the present invention, there is provided a process for producing a multilayer molded article comprising a thermoplastic resin body and a skin material covering the resin body, which process comprises steps of supplying a skin material between a pair of molds (1 and 7), holding said skin material between a skin material-holding frame (3) which is moved in a direction perpendicular to a mold-closing direction and a skin material-supporting frame (9) which is moved in the mold-closing direction, supplying a mass of a thermoplastic resin melt, and closing the molds to form a multilayer molded article, wherein at least one moving member (11) which moves forward or rearward in the mold closing direction is provided around a mold face (8) and is recessed in the mold closing direction after the supply of said resin melt; at least one ejector (5) which is provided on the skin material-holding frame (3) is ejected to fold an edge (19) of the skin material towards a center of the mold; and the moving member (11) is forwarded till the mold face (8) so as to fold back the edge of the skin material over the back of the resin body. BRIEF DESCRIPTION OF THE INVENTION Figs. 1 to 6 schematically show cross sections of a molding apparatus in various steps of one embodiment of the molding process of the present invention, Figs. 7 and 8 schematically show cross section of a molding apparatus used in another embodiment of the molding process of the present invention, and Fig. 9 schematically shows a cross section of a molding apparatus used in a further embodiment of the molding process of the present invention. DETAILED DESCRIPTION OF THE DRAWINGS Specific examples of the skin material are woven or nonwoven fabric, nets made of fibers or thermoplastic resins, paper, metal foils, and a sheet or a film of a thermoplastic resin or a thermoplastic elastomer. The skin material may be decorated with uneven patterns such as grain patterns, printing, dying and the like. In addition, the skin material may be made of foamed materials of thermoplastic resins, thermosetting resins and rubbers. Also, a laminate comprising at least two layers each made of the same material or different materials which are bonded to each other with an adhesive can be used as the skin material. As the thermoplastic resin to be molded by the process of the present invention, any of conventionally used in compression molding, injection molding and extrusion molding can be used. The thermoplastic resins to be used according to the present invention include expandable or non-expandable resins such as thermoplastic resins (e.g. polypropylene, polyethylene, polystyrene, acrylonitrilestyrene-butadiene block copolymers, polyamide, etc.) and thermoplastic elastomers (e.g. ethylene-propylene block copolymers, styrene-butadiene block copolymers, etc.). The resin may contain at least one additive such as fillers (e.g. inorganic fillers and glass fibers), pigments, lubricants, antistatic agents and the like. Now, the process of the present invention will be explained by making reference to the accompanying drawings. Figs. 1-6 schematically shows cross sections of an molding apparatus in several steps of the process of the present invention. As shown in Fig. 1, on a peripheral surface of a mold face 2 of an upper mold 1, there is provided a skin material-holding frame 3 which is moved in a direction perpendicular to a mold-closing direction by expansion members 4. On an outer peripheral surface of a mold face 8 of a lower mold 7, there is provided a skin material-supporting frame 9 which is moved by expansion members 10 in the mold-closing direction. A skin material 15 is provided between the upper and lower molds 1, 7, and the molds are closed to hold the skin material 15 between the skin material-holding frame 3 and the skin material-supporting frame 9. Then, a mass of a thermoplastic resin melt is supplied through a resin supply conduit 13 as shown in Fig. 2. Since a tension is applied on the skin material, edges of the skin material slightly slide inwardly as shown in Fig. 3. Thereafter, the mold is cooled to complete the molding. Next, moving members 11, which are positioned around the mold face 8, are recessed in the mold closing direction using expansion members 12, and ejectors 5 are ejected with expansion members 6 into spaces which are formed by the recession of the moving members 11, whereby the edges 19 of the skin material 15 are folded towards a center of the mold as shown in Fig. 4. Then, as shown in Fig. 5, the moving members 11 are forwarded till they reach the molding face so that the edges of the skin material are folded back onto over back of the resin body. Thereafter, as shown in Fig. 6, the molds are opened, the skin material-holding frame are withdrawn outwardly and the multilayer molded article is removed from the mold. As the expansion members 4, 6, 10 and 12, air cylinders, hydraulic cylinders and the like may be used. In another embodiment shown in Fig. 7, cutting blades 16 and expansion members 17 can be provided on the skin material-holding frame 3. As shown in Fig. 8, after the resin melt is supplied, the molds are closed, the skin material is held between the skin material-holding frame 3 and the skin material-supporting frame 9, and the cutting blades are forwarded to cut marginal parts of the edges of the skin material. In this method, it is not necessary to adjust the size or length of the skin material, and the edges have sufficient lengths for folding them with the ejectors. As the expansion members 17, air cylinders, hydraulic cylinders and the like may be used. In a further embodiment shown in Fig. 9, heaters 18 for heating the edges of the skin material for a short time may be provided at tip ends of the moving member 11. With the heaters, parts of the back of the molded resin are molten. Thereafter, the moving members are lowered, the edges of the skin materials are folded towards the center of the mold and the the moving members are lifted to adhere the edges of the skin material to the molten parts of the molded resin. As shown in Fig. 3, at parts of the skin material-holding frame corresponding to folded parts of the skin-material edges, heaters 20 can be provided to locally heat the skin material for a short time so that the edges of the skin material can be sharply folded back over the back of the resin body. PREFERRED EMBODIMENTS OF THE INVENTION The present invention will be explained by following Examples. Example 1 Using the apparatus and method shown in Figs. 7 and 8, a multilayer molded article was molded. As a thermoplastic resin, Sumitomo Noblen (trademark) AX 568 (Sumitomo Chemical Co., Ltd.) having a melt flow index of 65 was used. As a skin material, a laminate of a polyvinyl chloride sheet having a thickness of 0.7 mm a surface of which was embossed and a foamed polypropylene sheet (15 times expansion) having a thickness of 3.0 mm (manufactured by Toray) was used. Between an upper mold heated at 40°C and a lower mold heated at 30°C, the skin material was provided and held between the skin material-holding frame and the skin material-supporting frame. Then, the thermoplastic resin melt heated at 200°C was supplied through the resin supply conduit, the mold was closed under molding pressure of 50 kg/cm 2 , and the edges of the skin material were cut by projecting the cutting blades which were provided on the skin material-holding frame. Thereafter, the moving members 11 were recessed from the mold face, and the ejectors 5 were ejected to fold the edges of the skin material 15 towards the center of the mold. The moving members 11 were lifted up to fold the edges of the skin material over the back of the molded resin body. In the multilayer molded article, the edges of the skin material were precisely folded back over the back of the resin body. Example 2 Using the apparatus and method shown in Fig. 9, a multilayer molded article was molded. The heaters 18 were provided at the tip ends of the moving members 11 at constant intervals. As a thermoplastic resin, Sumitomo Noblen (trademark) BP 5077 (Sumitomo Chemical Co., Ltd.) containing 15 % by weight of talk and having a melt flow index of 40 was used. As a skin material, a polyvinyl chloride sheet having a thickness of 0.7 mm a surface of which was embossed and which was lined with an expandable fabric was used. Between an upper mold heated at 40°C and a lower mold heated at 30°C, the skin material was provided and held between the skin material-holding frame and the skin material-supporting frame. Then, the thermoplastic resin melt heated at 200°C was supplied through the resin supply conduit, the mold was closed under molding pressure of 50 kg/cm 2 , and the edges of the skin material were cut by projecting the cutting blades which were provided on the skin material-holding frame. Simultaneously, parts of the back of the molded resin were molten with the heaters 18. Thereafter, the moving members 11 were recessed from the molding face, and the ejectors 5 were ejected to fold the edges of the skin material 15 towards the center of the mold. The moving members 11 were lifted up to fold the edges of the skin material over the back of the molded resin body so that the edges were bonded to the molten parts of the resin body at the constant intervals. In the multilayer molded article, the edges of the skin material were precisely folded back and bonded to the back of the resin body.

Claims: A process for producing a multilayer molded article comprising a thermoplastic resin body and a skin material covering the resin body, which process comprises steps of supplying a skin material between a pair of molds(1 and 7),holding said skin material between a skin material-holding frame (3) which is moved in a direction perpendicular to a mold-closing direction and a skin material-supporting frame (9) which is moved in the mold-closing direction, supplying a mass of a thermoplastic resin melt, and closing the molds to form a multilayer molded article, characterized in that at least one moving member (11) which moves forward or rearward in the mold closing direction is provided around a mold face (8) and is recessed in the mold closing direction after the supply of said resin melt; at least one ejector (5) which is provided on the skin material-holding frame (3) is ejected to fold an edge (19) of the skin material towards a center of the mold; and the moving member (11) is forwarded till the mold face (8) so as to fold back the edge of the skin material over the back of the resin body. The process according to claim 1, wherein at least one cutting blade is provided on the skin material-holding frame (3) ,and a marginal part of the edge (21) of the skin material is cut with the cutting blade and then the moving member (11) is recessed from the mold face (8). The process according to claim 1 or 2, which further comprises melting a part of the back of the resin body with a heater (18) provided at a tip end of the moving member (11), recessing the moving member (11) from the mold face (8), ejecting the ejector (5)to fold the edge (19) of the skin material towards the center of the mold and forwarding the moving member (11) till the mold face (8) so as to fold the edge of the skin material over the back of the resin body and bond the edge of the skin material to the molten part of the resin body. The process according to any of claims 1 to 3, which further comprises partly heating the skin material with a heater (20) provided at a part of the skin material-holding frame corresponding to the folded part of the skin material and folding the edge (19) of the skin material towards the center of the mold. A mold for producing a multilayer molded article comprising a pair of molds (1 and 7), a skin material-holding frame (3) which is moved in a direction perpendicular to a mold-closing direction on a peripheral surface of a mold face (2) of said mold (1), and a skin material-supporting frame (9) which is moved in the mold-closing direction on an outer peripheral surface of a mold face (8) of said mold (7), characterized in that the mold comprises at least one moving member (11) which is positioned around said mold face (8) and is recessed and forwarded in the mold-closing direction, and at least one ejector (5) provided in said skin material-holding frame (3). The mold according to claim 5, which further comprises a cutting blade (16) provided on said skin material-holding frame (3). The mold according to claim 5 or 6, which further comprises a heater (18) provided at a tip end of said moving member (11). The mold according to claim 5, 6 or 7, which further comprises a heater (20) at a part of said skin material-holding frame (3) corresponding to a part of said skin material to be folded.

Inventors: HARA TAKAHISA, MATSUMOTO MASAHITO, MATUBARA SHIGEYOSHI, USUI NOBUHIRO, HARA, TAKAHISA, MATSUMOTO, MASAHITO, MATUBARA, SHIGEYOSHI, USUI, NOBUHIRO
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1992
Main classification: B29C43
IPC codes: B29C45, B29C33, B29K105, B29C70, B29C63, B29C43, B29L9