METHOD OF PRODUCING VEHICLE INTERIOR MATERIAL HAVING SANDWICH STRUCTURE

Abstract: To produce a vehicle interior base material being light and excellent in dimension stability, such as a ceiling material or a door trim material for a vehicle. Used is a method of producing a vehicle interior material having a sandwich structure, comprising the steps of (I) stacking a polyurethane foam, vegetable fibers, a thermosetting adhesive, and optionally a skin for surface decoration and/or a film preventing the exudation of the adhesive, (II) charging the laminate into a mold having a temperature of 80 to 150 DEG C, and closing the mold to cure the adhesive, and (III) demolding a molded product after the curing of the adhesive, characterized in that the size of the vegetable fibers is adjusted to be a diameter of at most 1.0 mm and a length of 10 mm to 100 mm.

Description: METHOD OF PRODUCING VEHICLE INTERIOR MATERIAL HAVING SANDWICH STRUCTURE The present invention relates to a method of producing a vehicle interior base material being light and excellent in dimensional stability, such as a ceiling material or a door trim material for a vehicle, and to a larninate having a sandwich structure that can be used as an interior base material for a vehicle. As a technique for producing a vehicle interior base material having a sandwich structure, there is proposed a method of producing a molded product in which isocyanate is immersed in a flexible polyurethane foam or a rigid polyurethane foam; water and a urethanization catalyst are added thereto; and both surfaces are reinforced with glass mats (Japanese Patent Kokoku Publication No. 63-7577 (7577/1988) titled "Method of producing a light and rigid or semi-rigid composite panel"). Further, there is also proposed a method of sandwiching a polyurethane foam, which has open cells and is moldable at an ordinary temperature, between two glass mats provided with an adhesive and mermoforming it (Japanese Patent Kokai Publication No. 04-211416 (211416/1992) titled "Method of producing a rigid polyurethane foam having open cells and being moldable at an ordinary temperature, and use of the same for producing a molded article"). In all of these methods, glass fibers are used as a reinforcing material. These glass fibers, though being extremely excellent in reinforcing effects, are considerably expensive and irritant to operator's skin, and are non-flarnmable when discarded, so that the disposal thereof is a great problem. There is already an example in which a woven fabric made by weaving fibers made of intertwined hemp with a considerably rough mesh of 2 to 3 mm is used as a reinforcing material (Opel: Vectra etc.). However, if a woven fabric is used as a reinforcing material, wrinkles are generated at a draw- formed portion because it is not freely expandable or contractible. Further, since an adhesive is not easily immersed into the inside of intertwined fibers, the curing is insufficient and the surface is likely to have unevenness. As a result of intensive studies made to obtain a molded product that can be recycled easily and are light and inexpensive without using glass fibers as a reinforcing material, we have discovered that vegetable fibers such as wood fibers, bamboo fibers, cut hemp, and cut kenaf can be fully used in place of glass fibers. In addition, we have discovered that it is advantageous in terms of costs and effects if vegetable fibers cut to a suitable length and an adhesive are mixed and spread uniformly on a polyurethane foam. The present invention provides a method of producing a vehicle interior material having a sandwich structure, comprising the steps of: (I) stacking (a) a thermoformable polyurethane foam having open cells and a density of 20 to 100 kg/m 3 , (b) vegetable fibers of 100 g/m 2 to 300 g/m 2 positioned on both main surfaces of the polyurethane foam (a), (c) a thermosetting adhesive forming bonds between the polyurethane foam (a) and the vegetable fibers (b) and bonds between the vegetable fibers (b) each other, and optionally (d) a skin for surface decoration and/or a film preventing the exudation of the adhesive, (II) charging the laminate into a mold having a temperature of 80 to 150 °C, and closing the mold to cure the adhesive, and (III) demolding a molded product after the curing of the adhesive, characterized in that the size of the vegetable fibers is adjusted to be a diameter of at most 1.0 mm and a length of 10 mm to 100 mm. The present invention also provides a laminate comprising: (A) a layer composed of a thermoformable polyurethane foam having open cells and a density of 20 to l00 kg/m 3 ; and (B) layers composed of vegetable fibers of 100 g/m 2 to 300 g/m 3 and a thermosetting adhesive, the (A) layer being sandwiched between the two (B) layers, wherein the vegetable fibers have a diameter of at most 1.0 mm and a length of 10 mm to 100 mm. The laminate is preferably such that the polyurethane foam is a rigid polyurethane foam; the thermosetting adhesive is an adhesive comprising an aromatic polyisocyanate, water, a catalyst, and optionally a polyol; and the vegetable fibers are those obtained by cutting or grinding of hemp, kenaf, sisal fibers, bamboo fibers, wood fibers. The thermoformable polyurethane foam having open cells may have a density of 20 to 100 kg/m 3 , for example, 25 to 40 kg/m 3 , particularly 25 to 35 kg/m 3 . The polyurethane form is preferably a rigid polyurethane foam. The rigid polyurethane foam is one obtained by reacting a polyisocyanate component and a polyol component. The polyol component may comprise a polyol, a catalyst, a foaming agent, and optionally a flame- retarder, a viscosity reducer, and a surfactant. The polyurethane foam may be sheet-like, and may have a thickness of 3 to 8 mm. The vegetable fibers are distributed uniformly on both sides of a polyurethane foam layer at 100 to 300 g/m 2 , for example, at 100 to 200 g/m 2 as a reinforcing material. It is necessary that the size of the vegetable fibers is adjusted to a diameter of at most 1.0 mm (for example, 0.2 to 0.8 mm) and a length of 10 to 100 mm (for example, 15 to 50 mm). If fibers having a diameter exceeding 1.0 mm are used as a reinforcing material, unevenness will appear on the surface of the molded product, thereby considerably deteriorating the appearance. The diameter as used herein refers to the smaller of the longitudinal and lateral dimensions of the fiber cross section. These fibers can be cut to a length of 10 to 100 mm by means of a simple equipment. If the length is smaller than 10 mm, the required reinforcing effects are not obtained, whereas if the fibers are too long, they will be entangled with each other, so that they cannot be dispersed uniformly on the foam. It is necessary that the size is adjusted to be between 10 and 100 mm in order that the fibers can be spread comparatively easily and uniformly on a molded product such as a vehicle ceiling material having a large area, and in order to obtain sufficient reinforcing effects. The vegetable fibers may be those obtained by cutting or grinding of vegetables mainly containing cellulose. The vegetable fibers may be, for example, hemp, kenaf, sisal fibers, bamboo fibers, wood fibers. The wood fibers are obtained from wood. The wood may be, for example, cedar, pine, zelkova, sun tree, biba arborvitae, cherry, poplar, or fir. The thermosetting adhesive forms bonds between the polyurethane foam and the vegetable fibers and bonds between the vegetable fibers each other. In the case where the vegetable fibers are bonded to each other, the adhesive is immersed among the vegetable fibers to form a layer made of the vegetable fibers and the adhesive. The tl ermosetting adhesive may be an adhesive comprising an aromatic polyisocyanate, water, a catalyst, and optionally a polyol. The aromatic polyisocyanate may be, for example, tolylene diisocyanate, diphenylmethane diisocyanate, or polymethylene polyphenyl polyisocyanate (polymeric MDI). and is preferably polymeric MDI. The water may be 10 to 50 parts by weight, for example, 15 to 30 parts by weight, based on 100 parts by weight of the aromatic polyisocyanate. The catalyst may be, for example, an amine such as monoamine, diamine, or triamine (for example, bis(dimemylaminoethyl) ether, N,N^'^'^'-pentametJ yldiethylenetriamine, triemylenediamine, or dimemylethanolamine). The catalyst may be from 0.1 to 1.0 part by weight, for example, from 0.2 to 0.5 part by weight, based on 100 parts by weight of the aromatic polyisocyanate. The polyol to be used may be, for example, a polyhydric alcohol (for example, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sugar), a polyether polyol, or a polyester polyol. Examples of the polyether polyol include a polyether polyol obtained by adding an alkylene oxide (for example, propylene oxide or ethylene oxide) to a polyhydric alcohol, and a polyether polyol obtained by adding an alkylene oxide (for example, propylene oxide or ethylene oxide) to an aliphatic amine (for example, monoethylamine, ethylenediamine, N,N-dime ylemylamine, or ώethylenetriamine). The polyether polyol may have a hydroxyl value of 100 to 1000 mgKOH/g, for example, 300 to 600 mgKOH g. The amount of polyol may be at most 10 parts by weight, for example, from 2 to 5 parts by weight, based on 100 parts by weight of the polyisocyanate. The amount of the thermosetting adhesive may be from 50 to 300 parts by weight, for example, 70 to 150 parts by weight, based on 100 parts of the vegetable fibers. Optionally, a skin for surface decoration and/or a film preventing the exudation of the adhesive may be provided on the layer made of the vegetable fibers and the thermosetting adhesive. The skin for surface decoration may be woven or non-woven fabric of polyolefin, polyester or polyamide, a vinyl leather, or the like. The thickness of the skin for surface decoration may be, for example, from 0.1 to 3 mm. The film preventing the exudation of the adhesive may be an olefin film or a polyamide film. The thickness of the film preventing the exudation of the adhesive may be, for example, from 10 to 40 m. The laminate can be produced, for example, by applying (for example, applying with a spray) a thermosetting adhesive on both surfaces of a polyurethane foam, spreading vegetable fibers on both surfaces, optionally disposing a skin for surface decoration and/or a film preventing the exudation of the adhesive to give a laminate, charging the laminate into a mold heated to a temperature of 80 to 150 °C, for example, 120 to 140 °C. for pressurizing, curing the adhesive, and demolding the molded product from the mold. Alternatively, after the thermosetting adhesive or one component (for example, aromatic polyisocyanate) of the thermosetting adhesive is mixed with the vegetable fibers in advance, the mixture may be applied on both surface of the polyurethane foam. In the laminate, the thickness of the layer made of the polyurethane foam may be from 4 to 8 mm, and the thickness of the layer made of the vegetable fibers and the thermosetting adhesive may be from 0.2 to 2 mm. The laminate of the present invention can be used as an interior base material for an automobile, for example, a ceiling material or a door trim material for an automobile. Hereafter, Examples will be shown, and the present invention will be specifically explained. Examples In the following examples, the evaluation of a molded product was performed as follows. (1) Flexural modulus The flexural modulus was measured according to JIS K6301. A sample having a length of 150 mm and a width of 50 mm was cut out from a molded product, and the flexural modulus was measured with an interfulcrum distance of 100 mm and a test speed of 50 mm/min. (2) Moldability The moldability was judged by the rigidity at the demolding, the damage degree of the skin for surface decoration, and the like. Example 1 Polymeric MDI (SBU Isocyanate 0418, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was applied in an amount of 70 g/m 2 by a spray on both surfaces of a thermoformable rigid polyurethane foam sheet (size: 30 cm x 30 cm x 5.5 mm) having open cells and a weight per unit area of 200 g/m 2 . Next, water containing 1 wt% of a urethanization catalyst (SBU Catalyst H544, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was applied in an amount of 20 g/m 2 by a spray. Then, wood fibers (type: groundwood pulp) having a diameter of 0.7 mm and a length of 10 to 50 mm were spread at a basis weight of about 150 g/m 2 on both surfaces, and a nonwoven fabric (polyester: thickness 0.1 mm) of about 40 g/m 2 was disposed on both surfaces to give a laminate, and the laminate was pressurized for 60 seconds in a mold at 130 °C to fabricate a molded product having a thickness of 5 mm. This molded product, though having a density (apparent density) of 0.15 g/cm 3 and a weight per unit area of 750 g/m 2 to be extremely light, exhibited a flexural modulus of 3,000 kg/cm 2 and had a full capability as a ceiling material. Example 2 Water containing 1 wt% of a urethanization catalyst (SBU Catalyst H544, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was applied in an amount of 20 g/m 2 by a spray on both surfaces of a thermoformable rigid polyurethane foam sheet (size: 30 cm x 30 cm x 5.5 mm) having open cells and a weight per unit area of 200 g/m 2 . To 100 parts by weight of bamboo fibers having a diameter of 0.7 mm and a length of 10 to 50 mm were added 50 parts by weight of polymeric MDI (SBU Isocyanate 0418, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and the mixture was well stirred. The mixture of polymeric MDI and bamboo fibers was spread uniformly at a basis weight of about 200 g/m 2 on both surfaces of the polyurethane foam sheet having the urethanization catalyst- containing water applied thereon. Onto the outside thereof, about 200 g/m 2 of a skin (polyester: thickness 1 mm) for surface decoration was disposed to give a laminate, and the laminate was pressurized for 60 seconds in a mold at 130 °C. to fabricate a molded product having a thickness of 5 mm. This molded product, though having a base material density (apparent density) of 0.14 g/cm 3 and a weight per unit base material area of 700 g/m 2 to be extremely light, exhibited a flexural modulus of 3,000 kg/cm 2 , and the skin for surface decoration had not been damaged at all. Comparative Example 1 Water containing 1 wt% of a urethanization catalyst (SBU Catalyst H544, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was applied in an amount of 20 g/m 2 by a spray on both surfaces of a thermoformable rigid polyurethane foam sheet (size: 30 cm x 30 cm x 5.5 mm) having open cells and a weight per unit area of 200 gm 2 . To 100 parts by weight of wood fibers (groundwood pulp) having a diameter of about 2 mm and a length of 2 to 15 mm were added 50 parts by weight of polymeric MDI (SBU Isocyanate 0418, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and the mixture was well stirred. The mixture of polymeric MDI and wood fibers was spread uniformly at a basis weight of about 200 g/m 2 on both surfaces of the sheet having the urethanization catalyst-containing water applied thereon. Onto the outside thereof, about 200 g/m 2 of a skin (polyester: thickness 1 mm) for surface decoration was disposed to give a laminate, and the laminate was pressurized for 60 seconds in a mold at 130 °C to fabricate a molded product having a thickness of 5 mm. This molded product had a base material density (apparent density) of 0.14 g/cm 3 and a weight per unit base material area of 700 g/m 2 . The rigidity at the demolding time was low, and it was difficult to demold the molded product Moreover, the flexural modulus was only as much as 1,000 kg/cm 2 , so that a molded product usable as a ceiling material could not be obtained. The molded product obtained according to the present invention, in spite of being extremely light, exhibits a high rigidity.

Claims: Claims 1. A method of producing a vehicle interior material having a sandwich structure, comprising the steps of: (I) stacking (a) a thermoformable polyurethane foam having open cells and a density of 20 to 100 kgm 3 , (b) vegetable fibers of 100 g/m 2 to 300 g/m 2 positioned on both main surfaces of the polyurethane foam (a), (c) a thermosetting adhesive forming bonds between the polyurethane foam (a) and the vegetable fibers (b) and bonds between the vegetable fibers (b) each other, and optionally (d) a skin for surface decoration and/or a film preventing the exudation of the adhesive, (ID charging the laminate into a mold having a temperature of 80 to 150 °C, and closing the mold to cure the adhesive, and (UI) demolding a molded product after the curing of the adhesive, characterized in that the size of the vegetable fibers is adjusted to be a diameter of at most 1.0 mm and a length of 10 mm to 100 mm. 2. The method according to claim 1, wherein the polyurethane foam is a rigid polyurethane foam; the thermosetting adhesive is an adhesive comprising an aromatic polyisocyanate, water, a catalyst, and optionally a polyol; and the vegetable fibers are those obtained by cutting or grinding of hemp, kenaf, sisal fibers, bamboo fibers, wood fibers.

Inventors: ITABA HIROSHI, SENTOH JUNICHI, ITABA, HIROSHI, SENTOH, JUNICHI
Applicants: BAYER AG, ITABA HIROSHI, SENTOH JUNICHI, BAYER AKTIENGESELLSCHAFT, ITABA, HIROSHI, SENTOH, JUNICHI
Application year: 2000
Main classification: B32B9
IPC codes: B32B5, B32B27, B32B37, B60R13