Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-06-22
2002-04-30
Cophenheaver, Blain (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423100, C428S500000, C428S509000, C428S515000, C428S517000, C525S066000, C525S067000
Reexamination Certificate
active
06379802
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic skin sheet used for interior parts of automobiles, more particularly to a thermoplastic skin sheet suffering from no cracking and rupture by thermal forming, and to a thermoplastic skin sheet with a matte surface suitable for decorative skin sheets for interior parts of automobiles, and their production method.
Interior parts of automobiles such as instrument panels should not only be integrally formed into complicated shapes but also have good hand such as softness, elasticity, etc., with matte surfaces such as embossed surfaces. For this purpose, a foamed layer is conventionally disposed between a substrate sheet and a surface skin layer for interior parts of automobiles such as instrument panels, and a surface of the skin layer is subjected to embossing or matte coating.
Conventional interior parts have skin sheets made of polyvinyl chloride resins from the aspect of hand, wear resistance, weathering resistance, etc., and inner foam layers mostly constituted by polyurethane foams. Substrate sheets for the conventional interior parts are made of polypropylene, ABS resins, etc., from the aspect of formability, mechanical strength, etc. Because conventional interior pan having such laminate structures are formed by different resins, the interior parts should be separated depending on the types of resins for the purpose of recycling. However, it is not easy to conduct the separation of polyvinyl chloride resin skin layers from the substrate sheets made of ABS resins or polypropylene, which are bonded to each other via polyurethane foam layers. In addition, cross-linked, foamed polyurethane layers cannot be recycled. Further, because environmentally toxic gas is generated by burning the polyvinyl chloride resins, the polyvinyl chloride resins should be burned in large-scale incinerators equipped with toxic gas-removing means. As a result, the interior parts of automobiles are actually pulverized to fine particles, which are then discarded as dust in dumpsites.
In view of recent concern about industrial waste problems and the environment, recycling the interior parts is strongly desired to decrease waste generated from automobiles, and such recycling is partly put into practical use. For the purpose of recycling, each layer is desirably made of the same resin, particularly polyolefin resins. However, because the skin layers of the interior parts made of a polyolefin resins are poor in coatability, the skin layers should be coated with primers or subjected to corona discharge treatment. It is also common from the viewpoint of productivity. to prepare a skin sheet with a surface coating, adhere a polypropylene foam and a substrate sheet to the skin sheet, and subject the resultant laminate to vacuum forming.
Known as primers for skin sheets made of thermoplastic polyolefin resins are chlorinated polypropylene paints, reactive paints containing saturated polyesters and polyisocyanates. Proposals have been made to apply a reactive paint containing a saturated polyester and a polyisocyanate to a surface of a skin sheet coated with a chlorinated polypropylene primer or a surface of a skin sheet subjected to a corona discharge treatment, and apply a paint containing a saturated polyester, acrylic resin, etc., and a optionally polyisocyanate or a polyurethane paint as a topcoat.
Specifically, for instance, Japanese Patent bid-Open No. 60-197741 discloses a method for producing a sheet usable as skin sheets of instrument panels, etc., among the interior parts of automobiles, comprising forming a sheet from a material containing a polyolefin resin such as polypropylene and partially cross-linked ethylenes-&agr;-olefin copolymers, and coating a surface of this sheet with a reactive paint containing a saturated polyester resin, an acrylate resin, and an isocyanate resin.
Japanese Patent Publication No. 7-14655 discloses a method for producing a printed composite skin sheet for use in ceilings, door rims, etc., of automobiles, comprising applying a chlorinated polypropylene primer to one surface of a skin sheet made of thermoplastic elastomers such as polypropylene elastomers, printing the primer-coated surface with an ink composition comprising an acrylic resin, a saturated polyester resin and an ink, and integrally fusing the resultant printed skin sheet made of thermoplastic elastomers to one or both surfaces of a pad composed of a polypropylene foam.
Further, Japanese Patent 2,533,147 discloses a thermoplastic elastomer article formed by coating a thermoplastic elastomer formed product with a primer containing at least one compound selected from a saturated polyester and a chlorinated polyolefin, and coating the resultant primer layer with a topcoat comprising at least one compound selected from a saturated polyester, an acrylate resin, a polyvinyl chloride resin and an isocyanate resin (the topcoat includes at least an acrylate resin if the primer layer consists only of a saturated polyester), the thermoplastic elastomer formed product comprising (I) 100-30 parts by weight of partially cross-linked copolymer rubber composition obtained by kinetically heat-treating a mixture of (a) 90-20 parts by weight of an ethylene-&agr;-olefin copolymer rubber, (b) 10-80 parts by weight of a polyolefin resin, (a)+(b) being 100 parts by weight, and optionally (c) a hydrocarbon rubber material not crosslinkable with peroxide, and (d) 0-200 parts by weight of a mineral oil softening agent, in the presence of a cross-linking agent; and (II) 0-70 parts by weight of a polyolefin resin, (I)+(II) being 100 parts by weight.
However, any of the above conventional skin sheets are disadvantageous in that they suffer from cracking and rupture on the surface when thermally formed into desired shapes. Recently spray coating is widely used to improve the appearance of formed products, but such spray coating aggravates the above phenomenon. Further, the use of chlorinated polyolefin resins such as chlorinated polypropylene as primers in Japanese Patent Laid-Open No. 60-197741 and Japanese Patent Publication No. 7-14655 not only deteriorates the resistance of the skin sheets to hydrocarbon solvents such as petroleum benzene, gasoline, etc., but also causes remarkable thermal discoloration of the skin sheets over a long period of use.
In addition, reactive primers containing saturated polyesters and polyisocyanates disclosed in Japanese Patent Laid-Open No. 60-197741 and Japanese Patent 2,533,147 cause problems that a surface of a thermoplastic skin sheet should be subjected to an oxidation treatment such as a corona discharge treatment, etc., making the entire process too lengthy; and that a mixture of a polyester and a polyisocyanate cannot be stored for a long period of time due to its reactivity, making impossible its reuse later and thus making it inevitable to discard all remaining primer liquids.
As a result of research in view of the above problems, the inventors have found the following facts:
(1) With respect to solvent resistance, the chlorinated polypropylene per se is easily eroded by hydrocarbon solvents.
(2) With respect to thermal discoloration, chlorine gas or hydrochloride gas generated by thermal decomposition of the chlorinated polypropylene causes the thermal discoloration.
(3) The reason why the corona discharge treatment is necessary in using reactive primers containing saturated polyesters and polyisocyanates is that the primers would not adhere to surfaces of thermoplastic sheets made of thermoplastic polyolefin resins or thermoplastic elastomers unless polar groups such as hydroxyl group reactive to isocyanate components in the primers are generated.
(4) The reason why the remaining primer liquids cannot be stored for a long period of time is that isocyanate components in the primers containing saturated polyesters and polyisocyanates react with the remaining hydroxyl groups in the saturated polyesters and moisture in the air with time, whereby the isocyanate components become unreactive to polar groups on t
Honjo Keiichi
Imada Masami
Ito Sukekuni
Kudoh Manabu
Cophenheaver Blain
Honda Giken Kogyo Kabushiki Kaisha
Paulraj Christopher
Sughrue Mion Zinn Macpeak & Seas, PLLC
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