Abstract:
An eco-friendly process for coating a plastic product includes several steps: (a) adding a conducting material to a thermoplastic material, (b) mixing the conducting material and the thermoplastic material homogeneously, and then molding into a product (c) spraying charged paint uniformly on the product (d) baking the painted product in ambient temperature atmosphere. Under this arrangement, plastic product made of different material could be produced without pre-treatment.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a process for coating a plastic product, and more particularly to an eco-friendly process in which a coating process combines with a thermal-cycling and an infrared baking technology for coating plastic products under certain temperature condition about 120-160° C. 
         [0003]    2. Description of Related Art 
         [0004]    In the past, when a factory wants to improve a coating quality of the plastic products, a lot of processes for coating are necessary. 
         [0005]    A conventional process for coating a plastic product is as following: first, cleaning the surface of the plastic product; second, coating the surface of the plastic product with chemical adhesive; third, coating the surface of the plastic product with the paint mixed with the solvent (e.g. formaldehyde, methyl benzene . . . etc.); fourth, re-coating to increase the coating thickness; fifth, coating the surface of the plastic product with protective paint for reinforcing the hardness of product surface. However, it may cause lots of environmental pollution (e.g. water pollution, air pollution, soil pollution . . . etc.) and waste lots of resources (e.g. water, electric power . . . etc.) during these processes. 
         [0006]    The disadvantage of the conventional process for coating a plastic product is as following: 
         [0007]    1. The wasted paint and solvent cannot be reused during these processes, and it may be harmful to human body or cause kinds of the environmental pollution. 
         [0008]    2. The baking process costs a lot of time after coating for reinforcing the adhesion between paint and surface, and it will consume large energy resources. 
         [0009]    3. It is difficult to separate the paint from the plastic surface during the recycling, and the product is hard to recycle. 
         [0010]    Furthermore, a conventional process for coating a plastic product has to suffer a procedure for baking the plastic product to harden the product. The baking temperature is about 120-220° C. However, the plastic product may be deformed and the strength of the product may be reduced because the baking temperature is too high. 
         [0011]    The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional method. 
       SUMMARY OF THE INVENTION 
       [0012]    The main objective of the present invention is to provide an eco-friendly process for coating a plastic product. 
         [0013]    To achieve the objective, an eco-friendly process for coating a plastic product in accordance with the present invention comprises the following steps: (a) selecting a thermoplastic material which might be PA mixing with fiberglass or PBT mixing with fiberglass, and then adding a conductive material into the thermoplastic material to make the melting point of the thermoplastic material above 140° C.; (b) mixing the conductive material and the thermoplastic material together and pour into a mold for forming a plastic product by injection molding or compression molding; (c) spraying a kind of charged paint on the plastic product by an electrostatic gun, wherein the temperature condition of paint should be below 160° C.; (d) taking the plastic product into an oven, wherein the plastic product is baked under one certain temperature condition about 120-160° C. for 10 to 15 minutes. 
         [0014]    Furthermore, the conductive material might be carbon nanotubes, graphite, carbon fibers, or black dyes with carbon element . . . etc. The electrostatic gun makes the paint charged and the charged paint is firmly attached on the plastic product. The resistivity of the paint in the present invention is around 10-1000000000000 ohm. The plastic product is baked through one thermal-cycling procedure or one infrared baking procedure for reinforcing the surface hardness. The failed product is taken into the heat-treatment after the broken-treatment and is baked under 190-260° C. to separate the paint from the thermoplastic material so that the separated thermoplastic material is recycled. The dust-collecting equipment can collect the non-coated paint in the chamber during spraying and the non-coated paint is collected for reusing. 
         [0015]    Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a flow chart of an eco-friendly process for coating a plastic product in accordance with the present invention; and 
           [0017]      FIG. 2  is a flow chart for showing the recycling process in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring to the drawings and initially to  FIGS. 1-2 , an eco-friendly process for coating a plastic product in accordance with the present invention comprises a thermoplastic material  10 . The thermoplastic material  10  might be ABS, AS, PS, PP, PE, PA, PC, POM, PPE, PC mixing with ABS, PPO, TPU, PVC, PET, PBT, PBT mixing with fiberglass, PA mixing with fiberglass, ABS mixing with fiberglass, or PC mixing with fiberglass . . . etc. A conductive material  12  is added into the thermoplastic material  10 . The conductive material  12  might be carbon nanotubes, graphite, carbon fibers, or black dyes with carbon element . . . etc. The conductive material  12  and the thermoplastic material  10  are mixing together and poured into a mold  14 . Thereafter, a plastic product  16  is formed by injection molding or by compression molding. After the plastic product  16  is solidified, an electrostatic gun  18  sprays one kind of charged paint  181  (not shown) over the plastic product  16 . The electrostatic gun  18  makes the paint  181  charged and the temperature condition of the paint  181  should be below 160° C. Finally, the plastic product  16  is taken into an oven  20  (tunnel type). The plastic product  16  is baked by a thermal-cycling procedure or an infrared baking procedure. The plastic product  16  is baked under a certain temperature condition about 120-160° C. for 10 to 15 minutes (the parameters of temperature and duration are based on the patterns of the plastic product  16 ). After these processes mentioned above, a finished product  22  comes to the world. 
         [0019]    One advantage of the present invention should be mentioned here. A conventional thickness of paint on the product is only 30 μm. However, the thickness of paint  181  on the plastic product  16  according to the present invention can reach 60-120 μm. Therefore, the paint  181  is firmly attached on the plastic product  16  and makes the finished product  22  more graceful and attractive. 
         [0020]    The eco-friendly process for coating a plastic product comprises the following steps:
   (a) select one thermoplastic material  10  which might be PA mixing with fiberglass or PBT mixing with fiberglass, and then add one conductive material  12  into the thermoplastic material  10  to make the melting point of the thermoplastic material  10  above 140° C.   (b) mix the conductive material  12  and the thermoplastic material  10  together and pour into one mold  14  for forming one plastic product  16  by injection molding or compression molding.   (c) spray paint  181  on the plastic product  16  by one electrostatic gun  18 , wherein the electrostatic gun  18  makes the paint  181  charged and the temperature condition of the paint  181  should be below 160° C. Therefore, the paint  181  is charged through the electrostatic gun  18  and the charged paint  181  is firmly attached on the plastic product  16 .   (d) take the plastic product  16  into one oven  20  (tunnel type) and bake the plastic product  16  through one thermal-cycling procedure or one infrared baking procedure for reinforcing the surface hardness, wherein the plastic product  16  is baked under one certain temperature condition about 120-160° C. for 10 to 15 minutes. After baking, one finished product  22  is produced.   
 
         [0025]    In the present invention, the thermoplastic material  10  is PA mixing with fiberglass or PBT mixing with fiberglass because these two materials have the better performance. The electrostatic gun  18  directly sprays the paint  181  (the resistivity of the paint  181  in the present invention is around 10-1000000000000 ohm) over the plastic product  16  without any pre-treatments. Instead of any pre-treatment, the conductive material  12  is added into the thermoplastic material  10  for making the charged paint  181  sprayed over the plastic product  16  homogeneously. Thereafter, the plastic product  16  is taken into the oven  20  (tunnel type) and is baked through the thermal-cycling procedure and the infrared baking procedure. The melting point of the thermoplastic material  10  is above 140° C. Thus, the plastic product  16  is partially melting on its surface when the plastic product  16  is baking in the oven  20 . Thereafter, the paint  181  is easily attached on the partial melting surface of the plastic product  16  so that the finished product  22  is produced efficiently. If the finished product  22  is failed to produce, the failed product can be recycled. The failed product is taken into the heat-treatment after the broken-treatment. The failed product is baked under 190-260° C. (based on the characteristic of the thermoplastic material  10 ). The paint  181  is easily separated from the thermoplastic material  10  during the heat-treatment because the pre-treatment is not necessary in the present invention. Consequently, the separated thermoplastic material  10  is recycled (as shown in  FIG. 2 ). 
         [0026]    Furthermore, the present invention comprises a dust-collecting equipment  23 . When the paint  181  is spread during spraying, the dust-collecting equipment  23  can collect the non-coated paint  181  in the chamber and the non-coated paint  181  is collected for reusing. The recycled thermoplastic material  10  can be manufactured with various colors by the various colors of paint  181 . However, the conventional recycling process only deal with the product without suffering any coating process, and the recycled material is manufactured for original color or black color.