Patent Publication Number: US-2006016051-A1

Title: Method for manufacturing waterproof zipper and the device manufactured from the same

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This is a divisional application Ser. No. 10/734.912, filed Dec. 9, 2003 now a pending application is divided by products in its entirety herein. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to waterproof zippers, and particularly to a method for manufacturing a waterproof zipper and the device made from the same.  
     BACKGROUND OF THE INVENTION  
      In the prior art of manufacturing slide fastener, it is found that the slide fastener can be immersed in repellant liquid so that mist will not be absorbed by stringer tapes easily. However, the result cannot be maintained for a longer time. When it is flushed by large amount of water, the stringer tapes always exposes in the steam, the waterproof effect will be reduced.  
      In Taiwan Patent Publication No. 094285, published on Dec. 16, 1987, “an impermeable water proof slide fastener”, applied by Japanese YKK CO., a flexible plastic membrane with the stringer tapes is heated and sealed for resisting water seepage. However, this prior art still needs improvement. It needs a C type slider to slide along the gripper elements to protect them from moisture. The bond needs to be detached from the stringer tapes due to long time abrasion. The adhesive of the bond between stringer tapes and membrane would have been diminished.  
      In Taiwan Patent Publication No. 126351, published on Jan. 6, 1990. “water proof zipper” applied by Japanese YKK Co. disclosed a prior art, where in manufacturing slide fasteners, water-absorptive swollen material Lanceal-F must be incorporated into nylon gripper elements. Then the nylon gripper elements with Lanceal-F is seamed on the stringer tapes. This prior art needs more labors and costs than other ways of manufacturing.  
      In another Taiwan Patent Publication No. 503715, published on Sep. 21, 2002. “liquid impermeable slide fastener” also applied by Jap. YKK Co. In this prior art, a special kind of slider instead of the popular coupling slider is used, but this special slider can not be matched with other sliders and thus can not be widely used.  
      Moreover, in U.S. Pat; No. 6,105,214 patent, “water proof slide fastener and process for preparing the same” assigned to Stuart Press on Aug. 22, 2000. The characteristics of the invention are a water resistant slide fastener, including a pair of stringer tapes each having first and second opposed surfaces and each having a series of gripper elements positioned along edges of said first surface; and a water resistant layer on said second surfaces, wherein said water resistant layer has an adhesion to said stringer tapes of at least about 6 lb/in. Thus, a combined multi-layer film adheres to the surface of stringer tapes. As they oriented outward to bear the abrasion or impact directly, they will be damaged. The water proof effect is reduced.  
      In U.S. Pat. No. 6,427,294 “water proof slide fastener and manufacturing method thereof assigned to YKK Co on Aug. 6, 2002, disclosed a multi-layer film laminated to the stringer tapes. Providing a waterproof slide fastener in which a synthetic resin film is fused to a fastener tape in order to prevent a perforation phenomenon that the synthetic resin film does not exist locally. A laminated synthetic resin film composed of low melting point resin layer having melting point of, for example, 100-140° C. and high melting point resin layer having melting point of, for example, 150-230° C. is fused to a surface or both surfaces of a pair of the fastener tapes with the low melting point resin layer being in contact with and opposing the fastener tape by heating with pressure. Fastener elements are mounted onto a side edge of the fastener tape and the laminated synthetic resin film is formed so as to protrude outward from the side edge of the fastener tape and a center point of coupling of the fastener elements. Because the high melting point resin layer disposed on the surface of the fastener tape is not melted, no perforation phenomenon occurs. Further, because the laminated synthetic resin film protrudes from the side edge, waterproof function is secured.  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.  
     SUMMARY OF THE INVENTION  
      Accordingly, the primary object of the present invention is to provide a method for manufacturing a waterproof zipper comprising steps of: (a) feeding a nylon zipper to a feeding device; (b) passing the nylon zipper to a gluing device and coating PU gel on backsides of the fastener strips of the nylon zipper; (c) adhering a PU film with PU gel on backsides of the fastener strips by using rollers to press the PU film so as to be formed as a waterproof layer; wherein the PU film is adhered on a release paper; (d) heating the PU film and PU gel to be formed as a waterproof layer; (e) cutting the waterproof layer along a center of the waterproof layer so as to be formed with two waterproof layers which are located at the two fastener strips; and thus a waterproof zipper being formed and (f) guiding the waterproof zipper out.  
      Another object of the present invention is to provide a nylon waterproof zipper comprising two symmetric fastener strips; each fastener strip has a front surface and a back surface; an inner side of the front surface of each fastener strip having a cord thread protruded from the surface; two chains being mounted along the cord threads, respectively; the cord threads being fixed to the fastener strips, respectively; the two chains being engaged by a coupling slider; a back surface of each fastener strip being combined with a thin waterproof layer; characterized in that: a back surface of each fastener strip is permeated with PU gel; and then a PU film is adhered to the back surface by thermal plastic stage so as to be formed as a waterproof layer which includes an inner layer of the PU gel permeating into the fastener strips and an outer layer at an outer side of the fastener strips. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a front view of the waterproof zipper of the present invention.  
       FIG. 2A  is backside perspective view of the waterproof zipper of the present invention.  
       FIG. 2B  is a backside perspective view of the waterproof zipper of the present invention, wherein the zipper is patterned.  
       FIG. 2C  is a backside elevation perspective view of the waterproof zipper with patterns.  
       FIG. 3  is a block diagram of the first stage of the first embodiment of the present invention.  
       FIG. 4  is a manufacturing flow diagram of the first stage of the first embodiment of the present invention.  
       FIG. 4A  is a cross sectional view showing the nylon zipper of the present invention.  
       FIG. 4B  is a cross sectional view showing the nylon zipper added with PU gel.  
       FIG. 4C  is a cross sectional view showing that the PU gel is permeated into the fibers of the fastener strips of the present invention.  
       FIG. 5  is a manufacturing block diagram of the second stage of the first embodiment of the present invention.  
       FIG. 6  is a manufacturing flow diagram of the second stage of the first embodiment of the present invention.  
       FIG. 6A  is a cross sectional view showing the nylon zipper of the present invention.  
       FIG. 6B  is a cross sectional view about the nylon zipper with PU film in the present invention, where the PU film is combined with PU gel.  
       FIG. 6C  is a cross sectional view about the nylon zipper of the present invention, where the nylon zipper is combined with a waterproof layer by thermal plastics, and the PU film is combined with PU gel.  
       FIG. 7  is a block diagram for the manufacturing stage in the second embodiment of the present invention.  
       FIG. 8  is a flow diagram about the manufacturing stage of the second embodiment of the present invention.  
       FIG. 9  is a block diagram about the manufacturing stage of the third embodiment of the present invention.  
       FIG. 10  is a flow diagram about the manufacturing stage of the third embodiment of the present invention.  
       FIG. 11  is a block diagram about the manufacturing stage of the fourth embodiment of the present invention.  
       FIG. 12  is a cross sectional view about the nylon zipper of the present invention after screen printing.  
       FIG. 13  is a cross sectional view about the nylon zipper of the present invention after press-printing.  
       FIG. 14  shows the appearances of the samples of the present invention and the prior art are boiled in water.  
       FIG. 15  shows the appearances of the samples of the present invention and the prior art are sunk in organic solvent.  
       FIG. 16  shows the waterproof zipper of the present invention has two printed patterns.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In order that those skilled in the art can further understand the present invention, a description will be described in the following in details. However, these descriptions and the appended drawings are only used to cause those skilled in the art to understand the objects, features, and characteristics of the present invention, but not to be used to confine the scope and spirit of the present invention defined in the appended claims.  
      Referring to  FIG. 1 , the nylon waterproof zipper  10  of the present invention includes two symmetric fastener strips  11 ,  12 . Each fastener strip has a front surface and a back surface. An inner side of the front surface of each fastener strip  11 ,  12  has a cord thread  13 ,  14  protruded from the surface thereof. The chains  15 ,  16  are mounted along the cord threads  13 ,  14 , respectively. The cord threads  13 ,  14  are fixed to the fastener strips  11 ,  12 , respectively. Two chains  15 ,  16  are meshed with a coupling slider.  
      Referring to  FIG. 2A , the back surfaces of the fastener strips  11 ,  12  are illustrated. It is illustrated that the cord threads  13 ,  14  and chains  15 ,  16  are hidden in the fastener strips  11 ,  12 . Each back surface is combined with a thin waterproof layer  17 ,  18 . After engaging the chains  15 ,  16  closely, the waterproof layers  17 ,  18  have the effect of waterproof so that water will not drain into the fastener strips  11 ,  12 .  
     First Embodiment  
      In this embodiment, the performance is described in two stages.  FIG. 3  shows the first stage and  FIG. 5  shows the second stage. At first, referring to  FIG. 3 , the first stage includes the steps of feeding material  21 , gluing  22 , pressing  23 , drying  24 , and outputting  25 .  
      As shown in  FIG. 4 , in the feeding stage  21 , the nylon zipper  10  passes through a feeding device (formed by an upper and a lower rollers  32 ,  33 ) and is taken out from the feeding tank  31  so that the nylon zipper  10  is extended properly to be in flat state. The cross section view thereof is shown in  FIG. 4A .  
      Next, a gluing step  22  is performed. In this step, the fastener strips  11 ,  12  are gluing so that the back sides of the fastener strips  11 ,  12  are coated with a layer of high adhesive gel. The main component of the glue is di-thermal liquid bridging polyester urine resin (i.e., PU gel) mixed with bridging agent. The gluing device is made of a gel storage tank  34  with a gluing roller  35  therein. A pressing roller  36  with a rotation direction opposite to the gluing roller  35  is installed at one side of the nylon zipper  10  opposite to the gluing roller  35 . When the gluing roller  35  is adhered with PU gel  37  in the gel storage tank  34 , the pressing roller  36  presses the fastener strips  11 ,  12  so that the PU gel  37  is transferred to the back sides of the fastener strips  11 ,  12  and is combined to the polyester fibers. The cross sectional view of the gluing nylon zipper  10  is illustrated in  FIG. 4B . The PU gel includes PU adhesive and solvent. If material of the fastener strips are changed the gel can be replaced by other adhesives.  
      Next, a pressing step  23  is performed. When the fastener strips  11 ,  12  passes through the pressing rollers  38 ,  39 , the PU gel is pressed into the polyester fibers of the fastener strips  11 ,  12 . The capillary is helpful to the addition of the gel by pressing without increasing the thickness of the fastener strips  11 ,  12 . Meanwhile, a good combining force is generated. At this time, the cross sectional view of the nylon zipper  10 ′ is illustrated in  FIG. 4C . Besides, the pressing rollers  38 ,  39  have further function of extending and smoothing the fastener strips  11 ,  12  with the guide rollers  41 ,  42  for drying.  
      In drying step  24 , the fastener strips  11 ,  12  are heated in the heating box  40  so that solvent of the PU gel  37  vaporizes. The temperature of the drying box is about 120-180° C. The heating time is determined by temperature, for example, about 12 seconds in 150° C.  
      Finally, the guiding step  25  is performed. In the guide device formed by the rollers  41 ,  42 , when the active roller  41  rotates, the fastener strips  11 ,  12  will be driven so as to output the nylon zipper  10  coated with PU gel. Besides, the two rollers move speedily with a pull force for adjusting fastener strips  11 ,  12 .  
      In above stages, the first stage can be repeated 1 to 3 times for increasing the coating and adhering effect between the PU gel  37  and the fastener strips  11 ,  12 . This is related to the combining effect of the second manufacturing stage and PU gel  37 .  
      With reference to  FIG. 5 , the block diagram of the second stage of the present invention is illustrated. Moreover,  FIG. 6  shows the flow diagram of the second stage. From  FIG. 5 , it is shown that the stage includes the steps of feeding  26 , adhering  27 , heating and extruding  28 , cutting  29  and guiding  30 .  
      In above feeding step  26 , the nylon zipper  10  coated with PU gel  37  are driven by two rollers  44 ,  45  and then are taken out from the feeding tank  43 . The nylon zipper  10  is extended properly. The cross sectional view of the structure of the nylon zipper  10  is illustrated in  FIG. 6A .  
      Next, the adhering step  27  is executed. A compound film formed by a release paper  50  and PU film  51  is wound along a winding roller  46 . The width of the film is equal to that of the nylon zipper  10  coated with PU gel  37 . When the compound film and nylon zipper are pressed by the rollers  47 ,  48 , the PU film  51  is tightly adhered to the PU gel  37  at the backside of the fastener strips, as shown in  FIG. 6B . Furthermore, the release paper  50  of the film is separated from the PU film  51  behind the roller  47 , then separated release paper  50  guided out by another roller  49 . Generally, the thickness of the PU film  51  is about 2-5 mm, which can be increased based on the manufacturing conditions. The PU film  51  is a single layer film. It is especially suited for batch production with a variety of types of different colors. Besides, the pigment can be added in the manufacturing of the film for getting the desired colors. If no pigment is added, agents for preventing change of color or yellowing can be added for getting a transparent PU film. Moreover, anti-freeze agent, anti-acid agent, anti-alkali agent, anti-hardening agent, etc. can be added. Moreover, since the coarseness of the surface of the release paper is not uniform, when it is separated from the PU film  51 , the inner surface of the PU film  51  may be coarse or smooth. If it is a coarse surface, the waterproof layer has a dim surface. If it is smooth, the waterproof layer is bright. In other words, a bright surface is transparent, and the dim surface is semi-transparent.  
      Then, the heating step  28  is executed. Mainly, the nylon zipper  10 ″ adhering on the PU film  51  is transferred to a heating box  52  to be heated in a temperature of 120-200° C. through 12-17 seconds so that the PU film  51  is combined with the PU gel  37  by thermal plastics (referring to  FIG. 6C ). Since the PU film  51  and PU gel  37  are main components, after overheating, they are provided as plasticizer on the compatiblility of the zipper and then they are combined. Furthermore, a rear end of the heating box  52  may be installed with an extruding device formed by an upper press roller  54  and a lower press roller  53 . The rollers presses the zipper  10  so that the backsides of the fastener strips  11 ,  12  are formed with waterproof layers  17 ,  18 . Since the adhesion of the waterproof layers and the fastener strips  11 ,  12  are concrete, the two are firmly secured.  
      Next, the cutting stage  29  is performed. A thin knife  55  between the two fastener strips  11 ,  12  cut the moving PU film  51  through the median line thereof so that the original single sheet waterproof layer is cut into a left waterproof layer  17  and a right waterproof layer  18  (referring to  FIG. 2A ). The cutting depth can be determined by the thickness of the PU film  51 . Since the waterproof layer cut by the cutting knife  55 , so general sliders can be adapted to the well-formed zipper after it is finished. There is no need to design a special kind of slider for the zipper products of the present invention.  
      Finally, a guide device formed by a set of upper and lower rollers  56  and  57  are used in the guide step  30 . The roller  56  is a driving wheel and the roller  57  is a driven roller. The driving wheel  56  rotates to drive the fastener strips  11 ,  12  so as to output the nylon zipper  10  with waterproof layers  17  and  18  at the backside thereof. Besides, the two rollers  56 ,  57  have the function-of adjusting the pull force and speed of the fastener strips. Furthermore, when a distal end of the heating box  52  is installed with two press rollers  53 ,  54 , the rollers  56 ,  57  can be used to replace the two press rollers  53 ,  54  for pressing the PU film  51 , PU gel  37  and the fastener strips  11 ,  12  so as to have an optimum effect.  
      Above mentioned is one preferred embodiment of the present invention for describing the present invention in detail, however, some modified embodiments within the spirit of the present invention can be used without confine the scope of the present invention. For example, in the first stage, the feeding step  21  and the gluing step  2  with a preheat step (not shown). Thereby, the unglued zipper  10 ′ is preheated in temperature between 70-120° C. Thereby, the unglued nylon zipper  10 ′ is more suitable to be adhered to the PU gel  37 . In other words, heated unglued nylon zipper  10  has a preferred adhesion coating effect to the PU gel  37 .  
      Moreover, in the second step  22 , other adhesive combinable to the PU film  51 , such as base material polymer (polyester polyol or acrylic acid polyol) or micro inorganic stuff agent) which is formed by bridging and hardening). Thereby, it is not confined to above said PU gel  37 .  
      Further, in second stage, the heating box  52  can be changed as many sets of heating and pressing rollers necessary. Besides, a plurality of press rollers or a plurality of heating sections can be used in the present invention so that the PU film  51 , PU gel  37  and fastener strips  11 ,  12  have an optimum combining effect.  
     Second Embodiment  
      In this embodiment, the first and second manufacturing stages are integrated as a continuous production line, as shown in  FIGS. 7 and 8 . The steps are feeding step  21 , gluing step  22 , pressing step  23 , drying step  24 , adhesion step  27 , heating step  28 , cutting step  29 , guide step  30 . In this embodiment, the guide device  25  in the first step and the feeding step  26  in the second stage can be reduced.  
     Third Embodiment  
      To simplify the manufacturing lines in  FIGS. 7 and 8 , the block diagram in  FIG. 9  can be performed. The stages includes the step of feeding step  21 , gluing step  22 , adhesion step  27 , heating step  28 , cutting step  29  and guide step  30 , as shown in  FIG. 10 . In this embodiment, not only the manufacturing stage is simplified, but also a batch of small amount in manufacturing can be performed easily. From above description, it is known that the embodiments in  FIGS. 9 and 10  are basic and simple manufacturing method in the present invention.  
     Fourth Embodiment  
      In above mentioned three manufacturing method, a printing step  221  or a press step  222  is added between the gluing step  22  and the adhesion step  23  (referring to  FIG. 11 ). In the printing step  221 , the inner surface of the PU film  51  (not outer surface) is printed with beautiful pattern  512  (referring to  FIG. 12 ) by screen printing. If it is presented by a perspective view, as shown in  FIG. 2B , and practical view is illustrated in  FIG. 16 . In the press step  222 , the convex or concave textures are printed on the inner surface (not outer surface) of the PU film  51  to form textures  513  (referring to  FIG. 13 ). A perspective view is illustrated in  FIG. 2C . In this embodiment, after the PU film  51  is combined with the PU gel  37 , the patterns  512  or the texture  513  will not disappear out due to friction or scraping. Since the waterproof layer is transparent, the pattern or texture is clear and it can be identified easily. Moreover, the transparent texture  513  can be presented as protrusion texture.  
      In above  FIGS. 12, 13 , it is found that for example, the waterproof layer  18  includes an inner layer  18   a  in the fastener strips  12  made of polyester fibers and an outer layer  18   b  at the outer side of the fastener strips  12 . The thickness of the inner layer  18   a  is over ⅓ of the fastener strips, preferably, over ½.  
      The difference of the present invention with the manufacturing stage disclosed in U.S. Pat. No. 6,105,214 is that in the prior art, the glued waterproof film is transferred to the backside of the fastener strip of the zipper after the waterproof film is coated with gel, or after a low hardness film is transferred to the fastener strip, it is coated on the backside of the fastener strip. Then, the PU film is adhered to the backside of the fastener strip. Then by heating, the PU gel and PU film are combined as a waterproof layer by thermal plastic stage. Therefore, in the present invention, the physical properties, such as adhesion, heat-tolerance, etc. of the single layer waterproof layer are improved so that the waterproof layer can be generated with pattern or texture. This is not disclosed by the prior art.  
      Effect of the present invention will be described herein. In the present invention, the PU gel is permeated into the fibers of the fastener strip so that the fastener strip is adhesive and has the function of waterproof. That is to say, when the outer PU film is destroyed by external force, the inner PU gel has the effect of waterproof. The PU gel and PU film are combined as a single film by thermal plastic stage and thus the manufacturing stage is simple and cost-efficient. The present invention can be suitable for different climate factors even boiled in water, which is also designed for preventing from yellowing and deformation. The solvent of the inner PU gel can vaporize completely so as not to harm the body. The inner texture or pattern of the waterproof layer can prevent from scraping and have the function of counterfeit-proof.  
     COMPARISON OF THE PRESENT INVENTION WITH PRIOR ART  
      In the following, the present invention is compared with a waterproof zipper adhered by thermal melting gel.  
      As shown in  FIG. 14 , the waterproof zipper of the present invention (black) and the prior art waterproof zipper (white) are used as examples. In a temperature of 100° C. and boiling in water through 30 minutes, the waterproof layer of the waterproof zipper of the present invention is retained in a good condition and the waterproof layer of the prior art waterproof zipper scraped.  
      Referring to  FIG. 15 , when the two waterproof zippers are sunk in organic solvent (ether) through 5 minutes. The waterproof layer of the waterproof zipper of the present invention is retained as the original condition, but the waterproof layer of the prior art has been scraped.  
      Both in physical and chemical tests, the waterproof zipper of the present invention matches the requirement of international standard.  
      Determination of Amines in Dyestuff  
      As per Adidas-Salomon A-01 requirement with reference to German test procedure for detection of carcinogenic amine in dyed materials published in German official compilation of test and inspection procedures, extracted by citrate buffered solution pH 6 at 70° C. and detected by combination of gas chromatographic-mass spectrometric (GC-MS) and this layer chromatographic (TLC) analysis. Based on German Texture method (B82.02-2 January 1998) and polyester method (B82.02-4 January 1998) Following amino material is tested:  
      4-Aminodiphenyl  
      Benzidin  
      4-Chlor-O-Toluidin  
      2-Naphthylamin  
      O-Aminoazotoluol  
      2-Amino-4-Nitrotoluol  
      P-Chloroanilin2,4′-Diaminoanisol(4-Methoxy-M-Phenylenediamin)  
      4,4′-Diaminodiphenylmethan  
      3,3′-Dichlorobenzidin  
      3,3′-Dimethoxybenzidin  
      3,3′-Dimethylbenzidin  
      3,3′-Dimethyl-4,4′Diaminodiphenylmethan  
      P-Kresidin(2-Methoxy-5-Methylanilin)  
      4,4′-Methylen-Bis-(2-Chloranilin)  
      4,4′-Oxydianilin  
      4,4′-Thiodianilin  
      O-Toluidin  
      2,4-Toluylendiamin  
      2,4,5-Trimethylanilin  
      O-Anisidine  
      2,4-Xylidine  
      2,6-Xylidine  
      4-Aminoazobenzene  
      The test result is below 5 ppm, it can assure that the minimum and maximum capacity is 30 ppm. The result is matched to the test standard.  
      (2) Detection by German standard test method: the heavy metal in the chromatography of the waterproof layer is lower than standard value.  
                                           Tested item   Test method   Result   Limit                                                Sb   DIN38405D 32   &lt;1     10 ppm       Cd   DIN38406D 19   &lt;0.01    0.1 ppm       Pb   DIN38406D 6   &lt;0.1     1 ppm       Hg   DIN38406D 12   &lt;0.01   0.02 ppm       Cr   DIN38406D 10   &lt;0.1     2 ppm                  
 
      Remarks: &lt;=Less than  
      ppm=Parts per million  
      (3) Referring to German Industrial Standard (DIN53314:1996), the content of the six bond chromium by the ultraviolet ray analysis:  
                                       Test component   Result in ppm   Limit ppm (Max)                  Cr   ND (&lt;0.1)   3                  
 
      Remarks: ppm=Parts per million  
      &lt;=Less than  
      ND=Not detected  
      (4) Referring to Japan 112 by spectrophotometer analysis to detect the content of Formaldehyde.  
                                       Test component   Result in ppm   Limit ppm                                            Formaldehyde   &lt;1   75 ppm                  
 
      Remarks: ppm=Parts per million  
      &lt;=Less than  
      (5) By Analysis by gas chromatography  
                                       Test sample   Result (ppm As Sn)   Limit (ppm As Sn)                  Mono-butyl tin (MBT)   0.19 ppm   1 ppm                  
 
      Remarks: ND=Not detected  
      Detection limit=0.05 ppm As Sn  
      ppm=Parts per million  
      (6) Analysis by gas chromatography  
                                       Test sample   Result (ppm As Sn)   Limit (ppm As Sn)                                            Di-butyl tin (DBT)   0.40   1 ppm                  
 
      Remarks: ND=Not detected  
      Detection limit=0.05 ppm As Sn  
      ppm=Parts per million  
      (7) Analysis by gas chromatography  
                                       Test sample   Result (ppm As Sn)   Limit (ppm As Sn)                  Tri-butyl tin (TBT)   ND   ND                  
 
      Remarks: ND=Not detected  
      Detection limit=0.05 ppm As Sn  
      ppm=Parts per million  
      (8) (PH) Vaule detection  
                                       Test sample   pH value   Limit                                            PH   5.67   4.0-7.5                  
 
      Result  
      All the test is in safety range:  
                                                   Item:   Result:                          Dry containing nitrogen   qualified           Components of heavy metal   qualified           Content chromium   qualified           Content of Formaldehyde   qualified           Mono-butyl tin (MBT)   qualified           Contents of Di-butyl tin (DBT)   qualified           Contents of Tri-butyl tin (TBT)   qualified           PH value   qualified                      
 
      Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.