Laminated product
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a laminated product for use as motorcar seats, carpets, blankets, sofas, chairs seats and the like to create antistatic effect. 
     2. Prior Art 
     Interior materials for vehicles, particularly for motorcars have been variously improved these days to let persons in motorcars feel comfortable as though they were in house. To prevent static electricity from generating is extremely important because persons are shocked by discharge when they get in and out of the motorcars, they feel their cloths uncomfortably adhesive to their skin in the motorcars, and various kinds of motorcar control means which are supposed to become electronic in the future are forced to malfunction. 
     In order to make skin sheets (made of cloth in many cases) antistatic, (1) conductive fibers were woven into the sheets and (2) antistatic agent whose main component is a surface-active agent was sprayed onto the surface of the sheets. 
     SUMMARY OF THE INVENTION 
     When the above measure (1) is employed, however, the comfortable feeing of the cloth-made skin materials is lost and their cost becomes comparatively high. When the measure (2) is used, problems or technical problems are left unsolved relating to the durability of the antistatic agent and the continuation of antistatic effect. 
     The present invention is therefore intended to eliminate the above-mentioned drawbacks in such a way that polyurethane foam which has antistatic effect is laminated on the back sides of skin materials to make these skin materials antistatic. 
     Accordingly, an object of the present invention is to provide a laminated product for use as motorcar seats and the like to make them antistatic without losing the comfortable feeling of their skin materials and making their cost high. 
     Another object of the present invention is to provide a laminated product excellent in its durability and continuation of antistatic effect. 
     These and other objects as well as merits of the present invention will become apparent from the following detailed description with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 through 3 are graphs showing changes of the surface potential decay characteristic of laminated products. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A laminated product according to the present invention comprises laminating polyurethane foam the back side of a skin material, said polyurethane foam having a surface apparent resistivity smaller than 1×10 13  ohms/sq. (condition: 23° C., 8%RH ) provide antistatic effect. 
     The reason why the surface of the skin material can be made antistatic only by adding antistatic capacity not to the skin material but to polyurethane foam which is laminated on the back side of the skin material cannot be cleared with certainty because various factors complicatedly combine with one another to create total effect. 
     In a case where the skin material in the present invention is a cloth woven by those threads which are twisted by fibers, it may be supposed that &#34;charge-escaping passage&#34; through which charge on the surface of the fibers moves to urethane foam is formed because the charged fibers or the bottoms of those fibers which are contacted with the charged fibers are contacted with the electrostatically conductive urethane foam. As apparent from the examples which will be described later, however, the antistatic effect can be attained even when a sheet of vinyl chloride (0.5 mm thick) or unwoven cloth is used as the skin material. It is not certain therefore how the &#34;charge-escaping passage&#34; is formed, but it can be imagined that the &#34;charge-escaping passage&#34; or something is formed. 
     As the skin material employed by the present invention, it is preferable to use cloths such as fabric (moquette fabric, plain weave fabric), knitted cloth (tricot, double russel) and unwoven cloth. However, the skin material employed by the present invention is not limited to them but it may be a sheet of resin (or sheet of vinyl chloride, 0.5 mm thick, for example). 
     When cloths are used as the skin material, their raw material may be natural fibers such as fur and cotton, synthetic fibers such as nylon and polyester, and blendings of these fibers, and these fibers used as the raw material are not limited in their shape. There is no limit, too, in the specifications (thickness, apparent density and the like) of finished cloths and sheets. 
     Polyurethane foam employed by the present invention and having the antistatic effect is prepared by adding a surface-active agent of the anion, cation, or nonionic system to the raw material at the time when polyurethane is foamed, so as to disperse the surface-active agent in the resin or to cause a part of the surface-active agent to react with the resin, or by coating the skeleton surface of the foam directly with an antistatic agent or conductive matter according to the immersion manner or the like. 
     As the antistatic agent employed by the present invention, there can be cited plasticizers, alkali metal salts such as sodium thiocyanate, alkaline-earth metal salts, hydrophilic matters, humectants and combinations of these matters. Needless to say, the above-mentioned surface-active agents can also be used as the antistatic agent and the above-cited matters have the antistatic effect. 
     As the conductive matters employed by the present invention, there can be cited carbon black, metal, metal powder, conductive macromocules and the like. 
     Their surface apparent resistivity is smaller than 1×10 13  ohms/sq. (condition: 23° C., 8%RH). When it becomes larger than 1×10 13  ohms/sq. the antistatic capacity of urethane foam itself is not sufficient and it is not expected that the urethane foam can provide sufficient antistatic effect even if it is laminated. The lower limit of the surface apparent resistivity cannot be defined but it is difficult from the practical viewpoint to make the urethane foam have a value smaller than 1×10 5  ohms/sq. It is therefore preferable from the viewpoint of manufacturing cost that the surface apparent resistivity is larger than 1×10 5  ohm/sq. The surface apparent resistivity is preferably in a range of 1×10 12  -1×10 5  ohms/sq. 
     The surface apparent resistivity of conventional urethane foam to which no antistatic measure is applied is larger than 1×10 15  ohms/sq. (condition: 23° C., 8%RH). 
     The surface apparent resistivity in the present invention was measured by connecting insulation resistance measuring sample foils (TR42) to the digital electrometer (TK-8652) made by Advantest Corporation. 
     The thickness of antistatic urethane foam which is laminated on the back side of the skin material may be larger than 1 mm, but it is preferable from the viewpoint of physical strength and capacity continuation that the urethane foam which is usually used as the welding material from the viewpoint of feeling is 8-10 mm thick. The urethane foam has no limit in its density and physical property, but it may have flame retarding and flame laminating abilities. 
     It is not particularly limited how the skin material and the antistatic urethane foam are laminated. They may be bonded each other by a common bonding agent, for example. The bonding agent is preferably of the polyurethane system and it may have antistatic capacity. They may be bonded each other according to the flame laminating manner which is now popular from the viewpoint of feeling and cost, because it is preferable from the viewpoint of performance that the antistatic foam is contacted directly with the cloth. They may be bonded each other according to the flame laminating or kilting manner. 
     One, two or more layers of conductive matter may be bonded to the open side of polyurethane foam or the polyurethane foam itself may be piled in two or more layers in the present invention. 
     Some examples of the laminated product according to the present invention will be described but it should be understood that the present invention is not limited to these examples. The word &#34;part&#34; which will be set forth below means weight part unless it is specified. 
     EXAMPLE 1: 
     Urethane foam (A), 2 m (width)×1 m (height)=2 m (length), was prepared from the following urethane foam raw materials, using the well-known polyurethane slub stock foam manufacturing apparatus. The surface apparent resistivity of this urethane foam was 5×10 11  ohms/sq. (23° C., 8%RH). 
     
         ______________________________________                                    
Urethane foam raw materials                                               
Name                         Parts                                        
______________________________________                                    
Polyol of the glycerine base polyether system (Mw 3000)                   
                             100.0                                        
(Trade name: Voranol made by Dow Chemical                                 
Corporation)                                                              
Water                        3.4                                          
Surfactant of the dimethyl polysiloxane system (Trade                     
                             1.0                                          
name: &#34;L-520&#34; made by Japan Unica Corporation)                            
Triethylenediamine (including 67% of dipropylene glycol)                  
                             0.3                                          
(Trade name: &#34;Dabuco 33LV&#34; made by Mitsui Air                             
Product Corporation)                                                      
Stannus octate (Trade name: &#34;Stanoct&#34; made by                             
                             0.4                                          
Yoshihuji Pharmaceutical Corporation)                                     
Alkyldimethylethylammoniumethylsulfate (including 20%                     
                             10.0                                         
of dipropylene glycol)                                                    
 ##STR1##                                                                 
(R represents alkyl radical having carbons 6-8) (Trade                    
name: &#34;LAROSTAT 377 DPG&#34; made by Jordan                                   
Chemical Corporation, U.S.A)                                              
Nethylortho (and para) toluene sulfon amide                               
                             10.0                                         
 ##STR2##                                                                 
(Trade name: Topcizer No. 3 made by Fuji Amide                            
Chemical Corporation)                                                     
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     The urethane foam (A) was sliced, each 10 mm thick, to form an antistatic foam a (A). This antistatic foam a (A) was bonded to wool moquette cloth (C) which was used for motorcar seats by means of a bonding agent of the polyurethane system. A laminated product according to the present invention was thus obtained. This was called our sample 1 and the electrostatic property of our this sample 1 was valued as follows. 
     The electrostatic property of laminated products was valued according to the Federal Test Method Standard 101C Method 4046 (1985). The measuring device used as STATIC DECAY METER (Model 406C) made by ETS Corporation, U.S.A. based on the above standard. Samples to be measured were conditioned over 24 hours under the measuring condition. Concrete results were obtained by applying a potential of 5000 V to the surfaces of objects to be measured and measuring the times during which the potential decays to 500 V. When this decay time is shorter than 1/2sec, preferable electrostatic property is exhibited (see an American Standard NFPA 99 1984). 
     The time during which the surface potential decays from 5000 V to 500 V is shown in Table 1 and the decay characteristic is shown in FIG. 1. 
     COMPARISON EXAMPLE 1: 
     A conventional urethane foam (B) was obtained same as in the case of the example 1 but without adding any antistatic agent. The surface apparent resistivity of this conventional urethane foam (B) was 3×10 15  ohms/sq. (23° C., 8%RH). The conventional urethane foam (B) was sliced same as in the case of the example 1 and bonded to the cloth (C). A comparison sample 1 was thus obtained. 
     The comparison sample 1 was valued, same as in the case of the example 1, about its electrostatic property. Results thus obtained are shown in Table 1 and FIG. 1. 
     A reference sample 1 was prepared only by the antistatic foam a (A) of the example 1, a reference sample 2 was prepared only by the conventional urethane foam (B) used in the comparison example 1, and a reference sample 3 was prepared only by the wool moquette cloth (C), and their electrostatic properties were valued same as in the case of the example 1.  Results thus obtained are shown in Table 1. 
     EXAMPLE 2: 
     An antistatic foam b (E) was prepared by immersing the common urethane foam (B) which was used in the comparison example 1 with carbon black. The surface apparent resistivity of this antistatic foam b (E) was 7×10 5  ohms/sq. (23° C., 8%RH). 
     The antistatic foam b (E) was sliced, each 10 mm thick, and bonded to a polyester moquette cloth (D) which is used for motorcar seats by a bonding agent of the polyurethane system. A laminated product according to the present invention was thus obtained and used as our sample 2. 
     This sample was valued, same as in the case of the example 1, about its electrostatic property. Results thus obtained are shown in Table 1 and FIG. 2. 
     COMPARISON EXAMPLE 2: 
     A laminated product was prepared same as in the case of the example 2 but without immersing it with carbon black. This laminated product was used as a comparison example 2. The electrostatic property of this comparison sample 2 was valued same as in the case of the example 1 and results thus obtained are shown in Table 1 and FIG. 2. 
     EXAMPLE 3: 
     Laminated products were prepared same as in the case of the example 1 but changing the cloth (C) as follows and these laminated products were used as our samples 3-6. 
     Sample 3: raised tricot 
     Raw material: polyester 
     Surface apparent resistivity: 7.54×10 14  ohms/sq. 
     Sample 4: plain weave 
     Raw material: polyester 
     Surface apparent resistivity: 7.54×10 15  ohms/sq. 
     Sample 5: unwoven cloth 
     Raw material: polyester. Characteristic value: 36 g/m 2   
     Surface apparent resistivity: 9.42×10 15  ohms/sq. 
     Sample 6: sheet of vinyl chloride 
     Raw material: polyvinyl chloride 
     Surface apparent resistivity: 1.56×10 14  ohms/sq. 
     The samples 3-6 were valued, same as in the case of the example 1, about their electrostatic properties, and results thus obtained are shown in Table 1 and FIG. 3. 
     EXAMPLE 4: 
     Our sample 7 was prepared same as in the case of the example 1 but being flame-laminated without using the bonding agent of the polyurethane system. The electrostatic property of our this sample 7 was valued same as in the case of the example 1, and a result thus obtained is shown in Table 1. 
     
                       TABLE 1                                                     
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                              5000 V-500 V                                
                              Decay time                                  
       Sample No.                                                         
                Sample Component                                          
                              (Sec)                                       
______________________________________                                    
Example 1                                                                 
         Our Sample 1                                                     
                    Antistatic foam a                                     
                                  0.34                                    
and                 (A) was bonded to                                     
Comparison          cloth (C)                                             
Example 1                                                                 
         Comparison Conventional  Not decay to                            
         Sample 1   urethane foam (B)                                     
                                  500 V                                   
                    was bonded to                                         
                    cloth (C)                                             
         Reference  Antistatic foam a                                     
         Sample 1   (A) only      0.14                                    
         Reference  Conventional  Not decay to                            
         Sample 2   urethane foam (B)                                     
                                  500 V                                   
                    only                                                  
         Reference  Cloth (C) only                                        
                                  Not decay                               
         Sample 3                 to 500 V                                
Example 2                                                                 
         Our Sample 2                                                     
                    Antistatic foam                                       
                                  0.07                                    
and                 b (E) was bonded                                      
Comparison          to cloth (D)                                          
Example 2                                                                 
         Comparison Conventional  Not decay to                            
         Sample 2   urethane foam (B)                                     
                                  500 V                                   
                    was bonded to                                         
                    cloth (D)                                             
Example 3                                                                 
         Our Sample 3                                                     
                    Antistatic foam a                                     
                                  0.32                                    
                    (A) was bonded to                                     
                    raised tricot cloth                                   
         Our Sample 4                                                     
                    Antistatic foam a                                     
                                  0.31                                    
                    (A) was bonded to                                     
                    plain woven cloth                                     
         Our Sample 5                                                     
                    Antistatic foam a                                     
                                  0.31                                    
                    (A) was bonded to                                     
                    unwoven cloth                                         
         Our Sample 6                                                     
                    Antistatic foam a                                     
                                  0.13                                    
                    (A) was bonded to                                     
                    vinyl chloride sheet                                  
Example 4                                                                 
         Our Sample 7                                                     
                    Antistatic foam a                                     
                                  0.28                                    
                    (A) was flame-                                        
                    laminated                                             
                    to cloth (C)                                          
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 Condition: 23° C. (Temperature), 8% RH (Humidity)