Abstract:
A composite of an adhesive film contains a thermoplastic elastomer selected from rubber-based thermoplastic elastomer or rubber series material, polyethylene-based coupling agent or ethylene vinyl acetate (EVA)-based coupling agent, montan wax, and fatty acid esters with pentaerythritol having five to nine carbons. The adhesive film is typically useful to produce footwear by molding a shoe sole in a mold, and thus, not requiring the conventional labor-consuming and hazardous processes, such as cleaning, primer coating, and bonding processes, to separately produce an outsole, a midsole, and an upper, and then binding together to manufacture a shoe.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of U.S. application Ser. No. 13/353,401 filed on Jan. 19, 2012, now issued as U.S. Pat. No. 8,568,548, and claims the priority benefit of Korean Patent Application No. 10-2011-0143127 filed on Dec. 27, 2011, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method of manufacturing footwear using adhesive films, and more particularly, to a method of manufacturing footwear using adhesive films, which does not need additional bonding and cleaning facilities as well as processes of cleaning, UV priming (or UV radiation), aqueous priming, and bonding when footwear including an outsole, a midsole and an upper is manufactured, which is eco-friendly, and which can reduce the number of workers, and to a composite of the adhesive film. 
     BACKGROUND OF THE INVENTION 
     As well known, footwear is used to protect a wearer&#39;s feet and is manufactured and sold in various forms and kinds. In generally, the footwear includes: an upper for covering and protecting the top of the foot and the ankle; and a sole for protecting the sole of the wearer&#39;s foot and increasing a frictional force between the footwear and the ground to thereby improve the wearer&#39;s walking performance and relieve the shock applied to the sole of the wearer&#39;s foot while walking. 
     Moreover, the sole includes: an insole that is the interior bottom of the footwear; a midsole that is made of rubber, foamed resin or sponge with an excellent buffer power to resiliently disperse and support the wearer&#39;s weight; and an outsole that is attached to the bottom surface of the midsole and is made of rubber material to provide a frictional force while the wearer walks. As described above, the upper, the midsole and the outsole are separately manufactured and joined together through the processes of cleaning, priming and bonding. 
     In the meantime, Korean Patent No. 10-0978284 discloses a method of manufacturing footwear including an outsole, a midsole and an upper in detail. Referring to  FIG. 8 , the method of manufacturing footwear disclosed in Korean Patent No. 10-0978284 will be described in detail. 
     As shown in  FIG. 8 , first, a method of manufacturing the outsole includes the steps of: forming the outsole by putting a rubber sheet in a mold and pressing it at high temperature and high pressure; buffing to make the surface of the outsole rough in order to increase an contact area between the outsole and the midsole; cleaning the molded outsole with aqueous alkali cleaner (pH 10 to 12) (or hydro-cleanser, in which is mixed with water) for five to ten minutes using a cleaning machine; coating aqueous or oil primer containing acetone so that adhesive is smoothly applied onto the surface of the outsole; drying the coated outsole; applying the adhesive; and drying. 
     Next, a method of manufacturing the midsole includes the steps of: putting a raw material (generally, EVA) in a press phylon mold or a CMP (Compressed Molded Phylon) mold to mold a pre-foamed midsole; putting the pre-foamed midsole into another phylon mold to complete the shape of the phylon midsole, wherein the midsole molding process generally includes three or two steps of foaming EVA of a biscuit form in such a way as to be about 190 percent larger than the actual size of the midsole, forcedly putting the foamed EVA into a phylon mold, and forcedly press-molding it to become a midsole of the actual size; cleaning the midsole with water of 40° C. to 60° C. for 5 minutes to 10 minutes using a cleaning machine; coating with UV primer and radiating UV rays to modify the coated surface of the midsole so that the midsole and the upper can be bonded firmly; coating the surface of the midsole with aqueous primer and adhesive; and drying the midsole 
     Next, a method of manufacturing the upper includes the steps of: cutting woven fabric or leather to form the upper; cleaning the upper with methyl ethyl ketone (MEK) so that the upper and the midsole can be bonded firmly; coating the upper with aqueous primer; drying the coated upper; applying adhesive to the upper; and drying the upper. 
     After the outsole, the midsole and the upper are manufactured through the above processes, when fixed heat and pressure are applied in a state where the outsole and the midsole are put in a mold in order, the midsole and the outsole are bonded together, so that the sole having the midsole and the outsole is manufactured. 
     After bonding of the midsole and the outsole is completed, when fixed heat and pressure are applied in a state where the sole and the upper are put in a mold in order, the sole and the upper are joined together, so that the footwear is completely finished. 
     However, the conventional method of manufacturing footwear including the above processes has several problems as follows. 
     First, as described above, there are many environmental obstacles, consumption of many raw materials, and a great deal of processes in manufacturing the outsole, the midsole and the upper, and it causes deterioration of productivity and increase of manufacturing costs. 
     For instance, in the case of the buffing process of making the surface of the outsole rough in order to increase a contact area between the midsole and the outsole, it aggravates working environment because dust of rubber, which is a material of the outsole and is harmful to the human body, is generated. Furthermore, in order to remove foreign matters stained on the outsole, a worker has to use aqueous alkali cleaner (or water and hydro cleanser) using a separate cleaning machine, and hence, it has several problems in that additional costs are incurred due to purchase of machines, footwear manufacturing processes are increased, and it requires a lot of manpower. 
     Second, the above problems are incurred also when the midsole is manufactured. 
     Third, when the outsole, the midsole and the upper are manufactured, all of the manufacturing methods require the process of coating UV primer or radiating UV rays and coating primer containing acetone and the process of applying adhesive in order to achieve a firm bonding, however, the processes increase the manufacturing costs due to a lot of manpower and increase of footwear manufacturing processes (namely, the primer coating and adhesive applying processes). 
     Fourth, solvents used for the UV primer coating, UV radiating, and acetone-containing primer coating processes may damage the worker&#39;s eyes, irritate the skin, cause respiratory irritation and nausea, sickness, and sleepiness and affect lungs when the worker inhale the solvents, and cause paralysis and convulsion as long-term symptoms, and hence, the solvents may give the worker a fatal damage. 
     Fifth, according to the conventional footwear manufacturing method, the outsole, the midsole and the upper are separately molded and are bonded together through a great deal of processes, such as cleaning, primer coating, adhesive applying, drying steps, and hence, it causes deterioration of productivity and increase of manufacturing costs due to a lot of raw materials and manpower. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide a method of manufacturing footwear using adhesive films and a composite of the adhesive film, which can simultaneously manufacture a midsole and an outsole in a phylon mold for a midsole without carrying out a cleaning step, a primer coating step, and a bonding step when footwear including the outsole, the midsole and a upper is manufactured. 
     It is another object of the present invention to provide a method of manufacturing footwear using adhesive films and a composite of the adhesive film, which there is no need to use additional bonding machine and cleaning machine when the footwear is manufactured, which is eco-friendly, and which can reduce manpower and remarkably reduce the number of footwear manufacturing processes. 
     It is a further object of the present invention to provide a method of manufacturing footwear using adhesive films and a composite of the adhesive film, which can simultaneously mold the outsole and the midsole using the adhesive film. 
     It is a still further object of the present invention to provide a method of manufacturing footwear using adhesive films and a composite of the adhesive film, which can simultaneously mold the midsole and the outsole and simply bond the upper and the sole with each other. 
     To accomplish the above objects, according to the present invention, there is provided a method of manufacturing footwear using adhesive films including the steps of: inserting a rubber sheet  100  into a mold ( 10 ) generally used for molding outsoles, putting a first adhesive film ( 200 ) on the rubber sheet, and pressurizing them to mold an outsole ( 300 ); inserting the molded outsole ( 300 ) into a phylon mold ( 20 ) used for molding midsoles, putting an adhesive film ( 400 ) on the outsole ( 300 ), putting an EVA foam ( 500   a ) on the first adhesive film ( 400 ), putting a second adhesive film  600  or the first adhesive film  400 , and pressurizing them to form and manufacture a shoe sole ( 700 ); and bonding the shoe sole ( 700 ) and an upper with each other using the second adhesive film ( 600 ) or the first adhesive film ( 400 ) bonded on the surface of the midsole. 
     More preferably, the first adhesive films are adhesive films for bonding the outsole and the midsole with each other, and a composite of the first adhesive films consists of: syndiotactic 1,2-polybutadiene; polyethylene-based coupling agent containing 7 percent of maleic anhydride; montan wax; and fatty acid esters with pentaerythritol having five to nine carbons. 
     Furthermore, the second adhesive film is an adhesive film for bonding an upper and a shoe sole having the outsole and the midsole with each other, and a composite of the second adhesive film consists of: polyester-type thermoplastic polyurethane; ethylene vinyl acetate (EVA)-based compatibilizer containing maleic anhydride; montan wax; and fatty acid esters with pentaerythritol having five to nine carbons. 
     As described above, the present invention can remarkably reduce the footwear manufacturing process and prevent waste of manpower necessary for carrying cleaning and bonding (primer coating) processes because the midsole made of EVA foam and the outsole made of rubber are simultaneously molded in the phylon mold. 
     Moreover, the present invention can enhance productivity of products, reduce manufacturing costs, and minimize the number of manpower because the present invention does not need additional processes of cleaning the midsole and the outsole, coating primer, and applying adhesives when footwear including the outsole, the midsole and the upper is manufactured. 
     Furthermore, the present invention is eco-friendly and can realize clean working environment and protect workers from harmful ingredients or materials because there is no need to carry out the primer coating process and the bonding process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a view showing a method of manufacturing footwear using adhesive films according to a preferred embodiment of the present invention; 
         FIG. 2  is a view showing a method of molding an outsole shown in  FIG. 1 ; 
         FIG. 3  is a view showing the outsole molded by the method of  FIG. 2 ; 
         FIG. 4  is a view showing how to simultaneously mold the outsole and a midsole shown in  FIG. 1 ; 
         FIG. 5  is a view showing a shoe sole on which the outsole and the midsole are simultaneously molded by the method of  FIG. 4 ; 
         FIG. 6  is a graph showing a differential thermal analysis of first adhesive films shown in  FIG. 1 ; 
         FIG. 7  is a graph showing a differential thermal analysis of a second adhesive film shown in  FIG. 2 ; and 
         FIG. 8  is a view showing a method of manufacturing footwear including an outsole, a midsole and an upper according to a prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will be now made in detail to the preferred embodiment of the present invention with reference to the attached drawings. The representative embodiment will be written in the following detailed description to achieve the above-stated objects. Moreover, the description will be substituted for other embodiments, which may be proposed in the present invention. 
     The present invention is to realize a method of manufacturing footwear using adhesive films and a composite of the adhesive film, which can allow an outsole and a midsole to be simultaneously molded and formed through the steps of putting the midsole made of EVA foam and the outsole made of rubber into a mold, inserting an adhesive film between the midsole and the outsole, and applying high temperature and high pressure to the midsole and the outsole, thereby not needing to carry out a cleaning process, a primer coating process, and a bonding process when an outsole and a midsole are manufactured, not needing additional facilities for the cleaning and bonding processes, reducing unnecessary manpower, and improving working environments. 
     For this, a method of simultaneously forming the midsole and the outsole should be disclosed in detail, and composite of the adhesive film used when the midsole and the outsole are simultaneously formed should be described in detail. 
     Hereinafter, referring to the drawings, the preferred embodiment of the present invention will be described in detail. 
       FIGS. 1 to 5  are detailed views showing the method of simultaneously forming and manufacturing footwear, which includes an outsole, a midsole, and an upper, using adhesive films according to a preferred embodiment of the present invention. 
     A method of molding a shoe sole  700  having an outsole  300  and a midsole  500  simultaneously molded includes the steps of: inserting a first adhesive film  200  and a rubber sheet  100  into a mold  10 , which is generally used for molding outsoles, applying high temperature and high pressure to the mold to mold an outsole  300 , inserting the molded outsole  300  with the first adhesive film  200  into a phylon mold  20 , which is generally used for molding midsoles; putting a first adhesive film  400 , an EVA foam  500   a , and a second adhesive film  600  in order; and molding them at high temperature and high pressure. That is, the outsole  300  and the midsole  500  are bonded by the first adhesive films  200  and  400  inside the phylon mold  20 , and the shoe sole  700  formed by bonding of the outsole  300  and the midsole  500  and the upper are bonded by the second adhesive film  600 . In this instance, when the shoe sole  700  and the upper are bonded together, the first adhesive films  200  and  400  in lieu of the second adhesive film  600  may be used. 
     Referring to  FIGS. 1 and 2 , the outsole  300  shown in  FIG. 3  is molded through the steps of inserting unvulcanized rubber into the mold  10  for outsoles, putting the first adhesive film  200  on the unvulcanized rubber, and vulcanizing them at high temperature and high pressure (preferably, at temperature of 150° C. to 160° C. and at pressure ranging from 100 kgf/cm 2  to 160 kgf/cm 2 ) for five to ten minutes. When the outsole  300  is molded as described above, if the first adhesive film  200  is used, there is no need to carry out the processes required to bond the outsole and the midsole, in detail, buffing, cleaning, primer coating, and bonding processes. The composite and properties of the first adhesive film  200  will be described later in detail. 
     Next, as shown in  FIG. 4 , the outsole  300  on which the first adhesive film  200  is molded integrally is inserted into the phylon mold  20 , the first adhesive film  400  is put on the outsole  300 , the EVA foam  500   a  is put on the first adhesive film  400 , and then, the second adhesive film  600  is put on the EVA foam  500   a . In this instance, the EVA foam  500   a  means the EVA foam foamed by a general method, for instance, an EVA of a biscuit form is foamed and molded about 190 percent larger than the actual size of the midsole. Moreover, the phylon mold  20  is a generally used mold, namely, means a mold generally used when midsoles are manufactured. It is preferable that the phylon mold  20  used in the present invention is deeper than the conventional phylon mold. The reason is to insert all of the outsole  300 , the first adhesive film  400 , the EVA foam  500   a , and the second adhesive film  600  into the phylon mold  20  at once. 
     After that, as shown in  FIG. 4 , when the outsole  300 , the first adhesive film  400 , the EVA foam  500   a , and the second adhesive film  600  inserted into the phylon mold  20  are pressurized at temperature of 160° C. and at pressure of 60 kgf/cm 2 , the shoe sole  700  that the outsole  300  and the midsole  500  are molded simultaneously as shown in  FIG. 5  is manufactured. 
     Finally, when the shoe sole (preferably, shoe sole that the outsole and the midsole are simultaneously molded in the phylon mold) manufactured through the above molding method and the upper (not shown) manufactured through a general method are bonded together, the footwear according to the present invention is manufactured. In this instance, the shoe sole  700 , in detail, the midsole  500 , and the upper are bonded by the second adhesive film  600 . 
     In the meantime, as described above, the adhesive films are used in order to simultaneously pressurize and mold the outsole  300  and the midsole  500  inserted into the phylon mold, and in detail, the first adhesive films  200  and  400  are used to bond the outsole  300  and the EVA-foamed midsole  500 , and the second adhesive film  600  is used to bond the midsole  500  and the upper. Hereinafter, composites and properties of the first and second adhesive films  200 ,  400  and  600  will be described in detail. 
     First, as shown in  FIG. 4 , the first adhesive films  200  and  400 , used when the outsole  300  and the midsole  500  are simultaneously bonded and molded in the phylon mold  20 , contain rubber-based thermo plastic elastomer (hereinafter, called “TPE”) or olefin series material or rubber series material as the main ingredient for rubber bonding, preferably, 50 to 98 percent by weight of syndiotactic 1,2-polybutadiene. In this instance, if syndiotactic 1,2-polybutadiene which is less than 50 percent by weight is used, linearity and intensity of the films are decreased, and if syndiotactic 1,2-polybutadiene which is more than 98 percent by weight is used, the adhesive force is deteriorated. 
     Furthermore, the first adhesive films  200  and  400  contain polyethylene-based coupling agent or ethylene vinyl acetate (hereinafter, called “EVA”)-based coupling agent as the main ingredient for EVA foam bonding, preferably, 2 to 50 percent by weight of polyethylene-based coupling agent, which contains 2 to 20 percent of maleic anhydride. In this instance, if the polyethylene-based coupling agent which is less than 2 percent by weight is used, the adhesive force is deteriorated, and if the polyethylene-based coupling agent which is more than 50 percent by weight is used, linearity and intensity of the films are decreased. 
     Moreover, in the present invention, processing materials for 100 parts by weight of the main ingredients are additionally used. In detail, 0.2 parts by weight of montan wax and 2 parts by weight of fatty acid (C=5-9) esters with pentaerythritol having five to nine carbons are used. In this instance, the processing materials are used to make the first adhesive films  200  and  300  smoothly get out of a T-die without being attached to a dies lip when they are extruded in the T-die. 
     The following Table 1 shows a detailed composition ratio of the first adhesive films  200  and  400 . 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Composite of 1 st  adhesive 
                   
                   
               
               
                 film 
                 Composition Ratio 
                 Remark 
               
               
                   
               
             
             
               
                 Syndiotactic 1,2- 
                 95% by weight 
                   
               
               
                 polybutadiene 
                   
                   
               
               
                 Polyethylene-based coupling 
                  5% by weight 
                   
               
               
                 agent (containing 7 percent 
                   
                   
               
               
                 of maleic anhydride) 
                   
                   
               
               
                 Montan wax 
                 0.2 pbw 
                 part by weight 
               
               
                 Esters with Pentaerythritol 
                 2 pbw 
                 part by weight 
               
               
                   
               
             
          
         
       
     
     The following Table 2 shows test data values obtained through comparison and analysis of properties of the first adhesive films  200  and  400  and properties of the ingredient materials. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                 First  
               
               
                   
                   
                   
                   
                 adhesive 
               
               
                   
                   
                 Syndiotactic 
                 Polyethylene- 
                 Film of the 
               
               
                   
                 Specifi- 
                 1,2- 
                 based 
                 Present 
               
               
                 Test Method 
                 cation 
                 polybutadiene 
                 coupling agent 
                 invention 
               
               
                   
               
             
             
               
                 Type 
                 FT-IR 
                 TPE 
                 PE Base 
                   
               
               
                   
                   
                 (Rubber Base) 
                 Containing 
                   
               
               
                   
                   
                   
                 MA 
                   
               
               
                 Melt 
                 DSC 
                 96.11° C. 
                 111.7° C. 
                 116.35° C. 
               
               
                 Temperature 
                   
                   
                   
                   
               
               
                 Flow Beginning 
                 Capillary 
                 105.9° C. 
                 108.9° C. 
                 106.6° C. 
               
               
                 Temperature 
                 Rheo- 
                   
                   
                   
               
               
                   
                 meter 
                   
                   
                   
               
               
                 Specific Gravity 
                   
                   
                   
                 0.943 g/cc 
               
               
                 100% Modulus 
                 UTM 
                   
                   
                 78 kgf/cm 2   
               
               
                 Tensile strength 
                 UTM 
                   
                   
                 175 kgf/cm 2   
               
               
                 Tear Strength 
                 UTM 
                   
                   
                 78 kgf/cm 
               
               
                 Elongation 
                 UTM 
                   
                   
                 500% 
               
               
                   
               
             
          
         
       
     
     In addition,  FIG. 6  shows a differential thermal analysis of the first adhesive films  200  and  400  having the properties shown in Table 2. The graph of  FIG. 6  shows melt temperatures and heat flows of the first adhesive films  200  and  400 , and for this, a DSC (Differential Scanning Calorimetry) is used. 
     Meanwhile, as shown in  FIG. 4 , when the outsole  300  and the midsole  500  are simultaneously molded in the phylon mold  20 , the second adhesive film  600  put on the EVA foam  500   a  contains 50 to 98 percent by weight of polyester-type TPU as the main ingredient for bonding with the upper (for instance, made of textile, synthetic leather, or natural leather) and 2 to 50 percent by weight of EVA-based compatibilizer (containing 2 to 20 percent of maleic anhydride, preferably, 6 percent of maleic anhydride) as the main ingredient for EVA foam bonding. In this instance, if polyester-type TPU which is less than 50 percent by weight is used, the bond strength is deteriorated, and if polyester-type TPU which is more than 98 percent by weight is used, compatibility with an adherend and wetting mechanism are decreased, and hence, the adhesive film  600  is not adhered. Moreover, if EVA-based compatibilizer which is less than 2 percent by weight is used, compatibility with the adherend and wetting mechanism are decreased, and hence, the adhesive film  600  is not adhered. If EVA-based compatibilizer which is more than 50 percent by weight is used, bond strength is deteriorated. 
     In addition, in the present invention, processing materials for 100 parts by weight of the main ingredients are additionally used. In detail, 0.2 parts by weight of montan wax and 2 parts by weight of fatty acid (C=5-9) esters with pentaerythritol having five to nine carbons are used. In this instance, the processing materials are used to make the second adhesive film  600  smoothly get out of a T-die without being attached to a dies lip when they are extruded in the T-die. 
     The following Table 3 shows a detailed composition ratio of the second adhesive film  600 . 
     
       
         
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Composite of 2 nd  adhesive film 
                 Composition Ratio 
                 Remark 
               
               
                   
               
             
             
               
                 Polyester type TPU 
                 77.5% by weight 
                   
               
               
                 EVA-based compatibilizer 
                 22.5% by weight 
                   
               
               
                 (containing 6 percent of maleic 
                   
                   
               
               
                 anhydride) 
                   
                   
               
               
                 Montan wax 
                 0.2 pbw 
                 part by weight 
               
               
                 Esters with Pentaerythritol 
                 2 pbw 
                 part by weight 
               
               
                   
               
             
          
         
       
     
     Additionally, the following Table 4 shows the properties of the second adhesive film  600  in detail. 
     
       
         
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Test Method 
                 Specification 
                 Second adhesive film 
               
               
                   
               
             
             
               
                 Melt Temperature 
                 DSC 
                 102.35° C. 
               
               
                   
                   
                 158.15° C. 
               
               
                 Flow Beginning 
                 Capillary Rheo-meter 
                 155.2° C. 
               
               
                 Temperature 
                   
                   
               
               
                 Specific Gravity 
                   
                 1.141 g/cc 
               
               
                 Thickness 
                 Thickness Gauge 
                 0.11 mm 
               
               
                 300% Modulus 
                 UTM 
                 130 kgf/cm 2   
               
               
                 Tensile strength 
                 UTM 
                 610 kgf/cm 2   
               
               
                 Tear Strength 
                 UTM 
                 107 kgf/cm 
               
               
                   
                 UTM 
                 560% 
               
               
                   
               
             
          
         
       
     
     Moreover,  FIG. 7  shows a differential thermal analysis of the second adhesive film  600  having the properties shown in Table 4. The graph of  FIG. 7  shows melt temperatures and heat flows of the second adhesive film  600 , and for this, a DSC (Differential Scanning Calorimetry) is used. 
     As described above, the adhesive films of the present invention are divided into the second adhesive film  600  for bonding the midsole made of EVA foam and the upper with each other and the first adhesive films  200  and  400  for bonding the outsole and the midsole made of EVA foam, and through the adhesive films, as shown in  FIG. 4 , the outsole  300  and the EVA foam midsole  500   a  are simultaneously molded in the phylon mold  20 , and finally, the shoe sole  700  having the outsole  300  and the midsole  500  simultaneously bonded and molded in one mold (phylon mold) as shown in  FIG. 5  is manufactured. Finally, the upper is simply bonded to the midsole  500  by the second adhesive film  600  adhered on the midsole  500 , so that the footwear according to the present invention is completely manufactured.