Patent Publication Number: US-2022219368-A1

Title: Extrusion molding die and extrusion molding machine

Description:
FIELD OF THE INVENTION 
     The present invention relates to an extrusion molding die and an extrusion molding machine. 
     BACKGROUND OF THE INVENTION 
     When a molding material is molded into a sheet shape using an extrusion molding machine, a flat die (hereinafter referred to as a “die”) is provided at a discharge port of the extrusion molding machine. The die generally includes a pair of die bodies having: a pair of lip ports arranged so as to face each other to form a slit port; and a pair of introduction portions arranged so as to face each other to form an introduction port. The molding material extruded through the extrusion molding machine is introduced into the interior of the die through the introduction port and passes through the slit port to be molded into a sheet shape. 
     As a type of die body, a coat hanger die having a manifold portion is widely used. As used herein, the term “coat hanger die” is a concept that includes T-dies. Also known is a coat hanger die having a mechanism to control a width of a slit portion in a short direction (e.g., Patent Literature 1). 
     A fishtail die is also used as a die body (Non-Patent Literature 1). Although the fishtail die is not as widely used as the coat hanger die, it is used for molding resin materials having low thermal stability. However, there is no fishtail die having a mechanism to control the width of the slit port in the short direction at present. 
     In addition, these die bodies are used in a pair of two die bodies of the same type. 
     CITATION LIST 
     Patent Literatures 
     
         
         [Patent Literature 1] Japanese Patent No. 5204147B 
       
    
     Non-Patent Literature 
     
         
         [Non-Patent Literature] Tadashi ITOH, “Flow in Flat Die, Part 1: Fishtail Dies”, Polymer Chemistry, Vol. 20, No. 216, pp. 193-200, 1963 
       
    
     SUMMARY OF THE INVENTION 
     The present invention relates to an extrusion molding die comprising a pair of die bodies, the die bodies having: a pair of lip portions arranged so as to face each other to form a slit port; and a pair of introduction portions arranged so as to face each other to form an introduction port; 
     wherein one of the die bodies is a coat hanger die having at least one thickness adjustment mechanism, and the other of the die bodies is a fishtail die. 
     The present invention also relates to an extrusion molding machine comprising the extrusion molding die as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic enlarged cross-sectional view of an extrusion molding die according to an embodiment of the present invention; 
         FIG. 2  is a schematic perspective view of a coat hanger die used for an extrusion molding die according to an embodiment of the present invention; 
         FIG. 3  is a schematic top view of the coat hanger die in  FIG. 2 ; 
         FIG. 4  is a schematic perspective view of a fishtail die used for an extrusion molding die according to an embodiment of the present invention; 
         FIG. 5  is a schematic top view of the fishtail die in  FIG. 4 ; 
         FIG. 6  is a schematic top view of a coat hanger die provided with a deckle portion; 
         FIG. 7  is a schematic perspective view of a fishtail die used in Comparative Example 3; and 
         FIG. 8  is graphs each showing results of a molding velocity at each position in each width direction in Examples and Comparative Examples. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In recent years, various molding materials have often been molded in the form of a sheet. However, depending on the type of the molding material, the molding material may be difficult to be molded into the sheet shape even if the coat hanger die or the fishtail die is used as the die body, or a thickness of a sheet-shaped molded body may become non-uniform. For example, when a molding material containing ceramic particles is used, the coat hanger die results in a significantly decreased molding velocity on the edge side as compared with the center in the longitudinal direction of the slit port, so that it may not be possible to mold the molding material into the sheet shape. Further, although the fishtail die can mold the molding material into the sheet shape, it is difficult to obtain a sheet-shaped molded body having uniform thickness, because the width of the slit port in the short direction cannot be controlled. The disadvantages of the fishtail die would be solved by developing a fishtail die having a mechanism to control the width of the slit port in the short hand direction. However, the development of such a fishtail die is expensive, which would not be practical. 
     The present invention has been made to solve the above problems. An object of the present invention is to provide an extrusion molding die and an extrusion molding machine, which can mold a molding material into a sheet shape having a uniform thickness regardless of a type of molding material. 
     As a result of intensive studies for extrusion molding dies, the present inventors have found that the above problems can be solved by using a combination of a coat hanger die having a thickness adjustment mechanism with a fishtail die as a pair of die bodies, and have completed the present invention. 
     According to the present invention, it is possible to provide an extrusion molding die and an extrusion molding machine, which can mold a molding material into a sheet shape having a uniform thickness regardless of a type of molding material. 
     Hereinafter, embodiments according to the present invention will be specifically described. It is to understand that the present invention is not limited to the following embodiments, and various modifications and improvements, which will be within the scope of the present invention, may be made based on ordinary knowledge of a person skilled in the art, without departing from the spirit of the present invention. 
     An extrusion molding die according to an embodiment of the present invention (which may, hereinafter, be abbreviated as a “die”) includes a pair of die bodies, the die bodies having: a pair of lip portions arranged so as to face each other to form a slit port; and a pair of introduction portions arranged so as to face each other to form an introduction port. 
     One of the pair of die bodies is a coat hanger die having a thickness adjustment mechanism, and the other of the die bodies is a fishtail die. By using such a combination of different die bodies, it is possible to acquire a function to be formed into a sheet shape by the fishtail die while utilizing the thickness adjustment function of the coat hanger die. Therefore, the molding material can be molded into a sheet shape having a uniform thickness regardless of the type of molding material. 
     The details of the extrusion molding die will be described below with the drawings. 
       FIG. 1  is a schematic enlarged cross-sectional view of an extrusion molding die according to an embodiment of the present invention. 
     As shown in  FIG. 1 , a die  100  is formed by combining a pair of die bodies  10   a ,  10   b . The pair of die bodies  10   a ,  10   b  are generally joined together using bolts (not shown) or the like. 
     The die bodies  10   a ,  10   b  are provided with lip portions  11   a,    11   b,  respectively, and the pair of lip portions  11   a ,  11   b  face each other to form a slit port  20  when the die bodies  10   a ,  10   b  are combined. 
     Further, the die bodies  10   a ,  10   b  are also provided with introduction portions  12   a ,  12   b , respectively, and the pair of introduction portions  12   a ,  12   b  face each other to form an introduction port  30  when the die bodies  10   a ,  10   b  are combined. 
     The die body  10   a  is a coat hanger die having at least one thickness adjustment mechanism. 
     A shape or the like of the coat hunger die is not particularly limited as long as the coat hanger die has the thickness adjustment mechanism. 
     The thickness adjustment mechanism is not particularly limited, and it may employ any mechanism known in the art. For example, it is preferable that a plurality of thickness adjustment mechanisms are arranged side by side on the lip portion  11   a  in a longitudinal direction (direction Y) of the slit port  20 , and are configured to be able to increase or decrease the width of the slit port  20  in the short direction (direction Z) by deforming at least a part of the lip portion  11   a . More specifically, a plurality of adjustment bolts  40  are arranged on the lip portion  11   a  in lines in the longitudinal direction (direction Y) of the slit port  20 , and the tightening of the adjustment bolts  40  can be controlled to deform at least a part of the lip portion  11   a . By using the thickness adjustment mechanism having such a structure, the molding material can be molded into a sheet having a uniform thickness. 
     Here,  FIG. 2  shows a schematic perspective view of a typical coat hanger die used in the extrusion molding die according to an embodiment of the present invention. In  FIG. 2 , the flow path side of the molding material is an upper surface, and the thickness adjusting mechanism is omitted. Further,  FIG. 3  shows a schematic top view of the coat hanger die in  FIG. 2 . 
     As shown in  FIGS. 2 and 3 , the coat hanger die  50  as the die body  10   a  includes: a lip portion  11   a ; an introduction portion  12   a ; a manifold portion  13  formed between the introduction portion  12   a  and the lip portion  11   a ; and a land portion  14  formed between the manifold portion  13  and the lip portion  11   a.    
     The coat hanger die  50  preferably has an opening angle a of the manifold portion  13  with respect to the introduction portion  12   a  of from 120 to 180°. By controlling the opening angle a at such an angle, the combination of the coat hanger die  50  with the fishtail die can stably decrease a velocity distribution of the molding material in the slit port  20  in the longitudinal direction (direction Y). Therefore, the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     The opening angle a of the manifold portion  13  refers to an angle in a direction in which the manifold portion  13  expands with respect to the flow path direction (direction X) of the introduction portion  12   a.    
     In the coat hanger die  50 , the land portion  14  preferably includes a horizontal plane  14   a , and inclined surfaces  14   b ,  14   c . By controlling the land portion  14  to such a shape, the velocity distribution of the molding material in the slit port  20  in the longitudinal direction (direction Y) can be stably decreased when the coat hanger die  50  is used in combination with the fishtail die. Therefore, the molding material can be stably molded into the sheet shape corresponding to the slit port  20 . 
     The die body  10   b  is a fishtail die. 
     The fishtail die is not limited, and various fishtail die having various shapes may be used. 
     Here,  FIG. 4  shows a schematic view of a typical fishtail die used for the extrusion molding die according to the present invention. Also,  FIG. 5  is a schematic top view of the fishtail die in  FIG. 4 . 
     As shown in  FIGS. 4 and 5 , the fishtail die  60  as the die body  10   b  has a lip portion  11   b , an introduction portion  12   b , and an enlarged portion  15  formed between the introduction portion  12   b  and the lip portion  11   b.    
     The introduction portion  12   b  of the fishtail die  60  preferably includes a portion having substantially the same shape as that of the introduction portion  12   a  of the coat hanger die  50 . Such a shape can allow the molding material to be stably fed to the interior of the die  100 . 
     As used herein, “a portion having substantially the same shape as the introduction portion  12   a  of the coat hanger die  50 ” means that the portion has substantially the same shape as a flow path shape (for example, a flow path width and a flow path depth) of the introduction portion  12   a  of the coat hanger die  50 . Further, the expression “substantially the same shape” means that a difference between the shape and a reference shape is within ±5%. 
     The fishtail die  60  preferably has an opening angle β of the enlarged portion  15  with respect to the introduction portion  12   b  of from 30 to 120°. By controlling the opening angle β at such an angle, the combination of the fishtail die  60  with the coat hanger die  50  can stably decrease the velocity distribution of the molding material of the slit port  20  in the longitudinal direction (direction Y). Therefore, the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     The opening angle β of the fishtail die  60  refers to an angle in a direction in which both ends of the expanded portion  15  expand with respect to the flow path direction (direction X) of the introduction portion  12   b.    
     In the fishtail die  60 , it is preferable that the enlarged portion  15  has a ridge line  15   a  extending from the introduction portion  12   b  to the lip portion  11   b , and includes two inclined surfaces  15   b ,  15   c  separated by the ridge line  15   a . By controlling the enlarged portion  15  in such a shape, the combination of the fishtail die  60  with the coat hanger die  50  can stably decrease the velocity distribution of the molding material in the slit port  20  in the longitudinal direction (direction Y). Therefore, the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     It is preferable that the two inclined surfaces  15   b ,  15   c  have substantially the same area. Such a structure can allow the molding material to flow uniformly to both ends of the slit port  20  in the longitudinal direction (direction Y). Therefore, the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     As used herein, the phrase “substantially the same area” means that a difference between the areas is within ±5%. 
     An inclination angle of the ridge line  15   a  is preferably from 1 to 75°. Such a structure can allow the molding material to be stably expanded in the longitudinal direction (direction Y) in the enlarged portion  15 , so that the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     As used herein, the “inclination angle of the ridge line  15   a  ” means an angle of the ridge line  15   a  inclined in the direction Y when a position of the ridge line  15   a  in contact with the bottom of the introduction portion  12   b  is used as a reference of a horizontal plane. 
     The combination of the coat hanger die  50  with the fishtail die  60  may generate positions where the molding material is difficult to flow at both ends of the manifold portion  13  of the coat hanger die  50 . Therefore, as shown in  FIG. 6 , the die  100  further includes a deckle portion  70  capable of regulating the flow path of the coat hanger die  50  so as to have an opening angle γ which is substantially the same as the enlarged portion  15  of the fishtail die  60 . The provision of the deckle portion  70  can reduce the positions where the molding material is difficult to flow at both ends of the manifold portion  13  of the coat hanger die  50  when the coat hanger die  50  is combined with the fishtail die  60 , so that it is easy to stably mold the molding material into a sheet shape corresponding to the slit port  20 . 
     As used herein, the opening angle γ formed by the deckle portion  70  means an angle of the flow path side end faces of the pair of deckle portions  70  with respect to the flow path direction (direction X) of the introduction portion  12   a.    
     The deckle portion  70  may be made of any material such as resins, although not particularly limited thereto. 
     The die  100  preferably has a ratio (L 2 /L 1 ) of a length L 2  from the introduction port  30  to the slit port  20  to a width L 1  of the slit port  20  in the longitudinal direction (direction Y), of from 0.2 to 2.0. By controlling the ratio within such a range, the molding material can be stably molded into a sheet shape corresponding to the slit port  20 . 
     The die  100  can be used for extrusion molding of various types of molding materials. In particular, even if the molding material has a lower viscosity, the die  100  can extrude it into a sheet. Therefore, the die  100  is preferably used for extrusion molding of a molding material containing ceramic particles, and more preferably used for extrusion molding of a molding material containing ceramic particles as a main component (ceramic molding material). 
     As used herein, the “main component” means that a percentage of the component relative to the total component is 50% by mass or more, and more preferably 60% by mass or more, and further preferably 70% by mass or more. 
     The viscosity (shear viscosity) of the molding material is preferably 1.0×10 2  Pa·s or more at a shear rate of 10 s −1 . It is difficult to mold the molding material having such a viscosity into a sheet when two coat hanger dies  50  are used in combination as a pair of die bodies  10   a ,  10   b . Further, it is difficult to obtain a sheet-shaped molded body having a uniform thickness when two fishtail dies  60  are used in combination as a pair of die bodies  10   a ,  10   b . Therefore, when the molding material having such a viscosity is used, it is particularly useful to use the die  100 . 
     The viscosity of the molding material can be measured according to JIS K 7199: 1999. 
     Examples of the ceramic particles include, but not particularly limited to, particles formed of alumina, cordierite, silicon carbide, a silicon-silicon carbide composite material, mullite, aluminum titanate, or the like. 
     The molding material may optionally contain a dispersion medium, an organic binder, an inorganic binder, a pore former, a surfactant, and the like, in addition to the ceramic particles. These components are not particularly limited, and those known in the art may be used. 
     The die  100  can be installed and used in an extrusion molding machine. 
     The extrusion molding machine is not particularly limited as long as it has a structure capable of providing the die  100 . 
     A typical extrusion molding machine includes an extrusion portion and a molding portion connected to the extrusion portion. The extrusion portion is not particularly limited as long as it has a function of extruding the molding material, and may optionally have a function of kneading the molding material. 
     The die  100  is arranged at one end of the molding portion, and the other end is connected to an extrusion port of the extrusion portion. 
     Since the extrusion molding machine having the above structure is provided with the die  100 , it can be molded into a sheet having a uniform thickness regardless of the type of molding material. 
     EXAMPLES 
     Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. 
     (Preparation of Molding Material) 
     As a molding material, a ceramic molding material was used, which was obtained by mixing and kneading 100 parts by mass of alumina powder (ceramic particles), 10 parts by mass of methyl cellulose (organic binder) and 30 parts by mass of water (dispersion medium). A part of the molding material was colored into blue color using a colorant to evaluate the molding velocity. 
     The molding material had a viscosity of 1.5×10 5  Pa·s at a shear rate of 0.1 s −1 , a viscosity of 2.0×10 4  Pa·s at a shear rate of 1 s −1 , and a viscosity of 3.0×10 3  Pa·s at a shear rate of 10 s −1 . 
     The viscosity of the molding material was measured in accordance with JIS K 7199: 1999. A commercially available capillary rheometer was used for the measurement. The capillary tube had a diameter of from 1 to 2 mm and a length of from 25 to 50 mm. 
     Example 1 
     A die that combined a coat hanger die having a thickness adjustment mechanism with a fishtail die as a pair of die bodies was used to extrude the molding material as described above. 
     The coat hanger die used had the shape as shown in  FIGS. 2 and 3  (a flow path width of the introduction portion of 19 mm, a flow path depth of the introduction portion of 9.5 mm, an opening angle α of the manifold portion of 180°). The fishtail die used had the shape as shown in  FIGS. 4 and 5  (a flow path width of the introduction portion of 19 mm, a flow path depth of the introduction portion of 9.5 mm, an opening angle β of the enlarged portion of 80°, and an inclination angle of the ridge line of 10°). The width L 1  of the slit port in the longitudinal direction (direction Y) was 200 mm, the length L 2  from the introduction port to the slit port was 200 mm, and the width of the slit port in the short direction (direction Z) was 1.5 mm. 
     The extrusion molding was carried out by filling the above molding material into a cylinder with the die placed at one end and inserting a piston from the other end of the cylinder. In this case, the molding material was filled into the cylinder in such a way that layers of the colored molding material and layers of an uncolored molding material were alternately arranged every 5 mm. An insertion rate of the piston was 0.8 mm/s before feeding the molding material to the die and was 2.4 mm/s after feeding the molding material to the die. 
     For the extruded, sheet-shaped molded material, molding velocities of the sheet-shaped molded material in the width direction (at five positions) were measured using a velocity meter (FC-2000 from Keyence Corporation). 
     Comparative Example 1 
     Using a die that combined two coat hanger dies having no thickness adjustment mechanism as a pair of die bodies, extrusion molding was carried out in the same method as that of Example 1. Then, the molding velocities of the sheet-shaped molded material in the width direction (five positions) were measured in the same method as that of Example 1. 
     The two coat hanger dies have the same structure as the coat hanger die used in Example 1, with the exception that they do not have the thickness adjustment mechanism. The width L 1  of the slit port in the longitudinal direction (direction Y) was 200 mm, the length L 2  from the introduction port to the slit port was 200 mm, and the width of the slit port in the short direction (direction Z) was 1.5 mm. 
     Comparative Example 2 
     Using a die that combined a coat hanger die having a thickness adjustment mechanism with a coat hanger die having no thickness adjustment mechanism as a pair of die bodies, extrusion molding was carried out in the same method as that of Example 1. Then, the molding velocities of the sheet-shaped molded material in the width direction (five positions) were measured in the same method as that of Example 1. 
     The coat hanger die having the thickness adjustment mechanism used had the same structure as that of Example 1. The coat hanger die having no thickness adjustment mechanism used had the same structure as that of Comparative Example 1. The width L 1  of the slit port in the longitudinal direction (direction Y) was 200 mm, the length L 2  from the introduction port to the slit port was 200 mm, and the width of the slit port in the short direction (direction Z) was 1.5 mm. 
     Comparative Example 3 
     Using a die that combined two fishtail dies as a pair of die bodies, extrusion molding was carried out in the same method as that of Example 1. Then, the molding velocities of the sheet-shaped molded material in the width direction (five positions) were measured in the same method as that of Example 1. 
     The fishtail die used had the shape as shown in  FIG. 7  (a width of the introduction port of 31 mm, a depth of the introduction port of 15.5 mm, an opening angle β of the enlarged portion of 60°, an inclination angle of the ridge line of 10°). The width L 1  of the slit port in the longitudinal direction (direction Y) was 200 mm, the length L 2  from the introduction port to the slit port was 200 mm, and the width of the slit port in the short direction (direction Z) was 1.5 mm. 
     Comparative Example 4 
     Using a die that combined a coat hanger die having no thickness adjustment mechanism with a fishtail die as a pair of die bodies, extrusion molding was carried out in the same method as that of Example 1. Then, the molding velocities of the sheet-shaped molded material in the width direction (five positions) were measured in the same method as that of Example 1. 
     The coat hanger die having no thickness adjustment mechanism used had the same structure as that of Comparative Example 1. The width L 1  of the slit port in the longitudinal direction (direction Y) was 200 mm, the length L 2  from the introduction port to the slit port was 200 mm, and the width of the slit port in the short direction (direction Z) was 1.5 mm. 
     The results of the molding velocities at the respective positions (five positions) in the width direction in Examples and Comparative Examples as described above are shown in  FIG. 8 . 
     As shown in  FIG. 8 , in Example  1 , a difference between the molding velocities at the five positions was up to 1 mm/s which was very small, and the molding material could be molded into a sheet having a uniform thickness. 
     In contrast, in Comparative Example 1, a difference between the molding velocities at five positions was up to 13 mm/s which was larger, and the molding material could not be molded into the sheet shape near the end portions in the width direction. 
     In Comparative Example 2, a difference between the molding velocities at the five positions was up to 11 mm/s which was larger, and the molding material could not be molded into the sheet shape near the end portions in the width direction. 
     In Comparative Example 3, a difference between the molding velocities at five positions was up to 2.5 mm/s which was smaller, but the thickness of the sheet-shaped molded material was non-uniform. 
     In Comparative Example 4, a difference between the molding velocities at the five positions was up to 4.0 mm/s which was smaller, but the thickness of the sheet-shaped molded body was non-uniform. 
     As can be seen from the above results, the present invention can provide an extrusion molding die and an extrusion machine that can be molded into a sheet shape having a uniform thickness regardless of the type of molding material. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10   a ,  10   b  die body 
           11   a,    11   b  lip portion 
           12   a ,  12   b  introduction portion 
           13  manifold portion 
           14  land portion 
           14   a  horizontal plane 
           14   b ,  14   c  inclined surface 
           15  expanded portion 
           15   a  ridge line 
           15   b ,  15   c  inclined surface 
           20  slit port 
           30  introduction port 
           40  adjustment bolt 
           50  coat hanger die 
           60  fishtail die 
           70  deckle portion 
           100  die