Patent Publication Number: US-2022227036-A1

Title: Method for manufacturing container having covering layer and molding mold

Description:
TECHNICAL FIELD 
     The invention relates to a method for manufacturing a container having a covering layer and to a molding mold. 
     BACKGROUND ART 
     There is a known container made of a synthetic resin, the container being manufactured in such a manner that a preform is formed by using a synthetic resin, such as polyethylene terephthalate, and this preform is molded into a bottle shape by stretch blow molding or the like. The containers made of a synthetic resin are used as beverage containers that contain various beverages, for example. 
     There are known composite containers where the periphery of the container is covered by a covering layer so as to allow such containers to have various functions or characteristics. For example, Patent Literature 1 discloses a composite container and a method for manufacturing the composite container. In the disclosed manufacturing method, first, a preform made of a plastic material is prepared. Then, a plastic member is provided to surround the outer side of this preform, and the preform and the plastic member are brought into close contact with each other to prepare a composite preform. Next, blow molding is performed on the composite preform in a blow mold to cause the preform and the plastic member of the composite preform to inflate as an integral body. The composite container where the plastic member is provided to the periphery of a container body is manufactured in this manner. 
     In the composite container disclosed in Patent Literature 1, to allow the plastic member to be easily peeled and removed from the container body when the container is discarded, perforated openings are formed in the plastic member. These perforated openings facilitate cutting of the plastic member. These openings are formed in such a manner that openings are formed in the plastic member of the composite preform and, thereafter, blow molding is performed on the composite preform. 
     PRIOR ART DOCUMENT 
     Patent Literature 
     
         
         Patent Literature 1: JP 2016-55524 A 
       
    
     SUMMARY OF INVENTION 
     It is an object of the invention to provide a method for manufacturing a container having a covering layer with a slit formed at a portion of the covering layer. 
     One aspect of the invention is directed to a method for manufacturing a container having a covering layer, the method including: acquiring a preform having a preform covering layer formed by using a synthetic resin having thermoplasticity, the preform being a material for forming a container having a covering layer manufactured by blow molding; setting the preform in a blow mold wherein a blade is provided to a portion of a surface of the blow mold with where the container is brought into contact, the blade having a height that corresponds to a thickness of the covering layer; and forming the container having the covering layer by performing blow molding on the preform, the covering layer having a slit formed by the blade. 
     Another aspect of the invention is directed to a molding mold used in blow molding for a container, the molding mold including: a first barrel mold and a second barrel mold configured to form a shape of a body of the container; a bottom mold configured to form a shape of a bottom portion of the container; and a neck insert configured to form a shape of a neck portion of the container, wherein the neck insert has a neck portion contact surface and a neck ring contact surface, the neck portion contact surface being brought into contact with the neck portion, the neck ring contact surface being brought into contact with a neck ring of the container, and the neck insert includes a blade extending from the neck portion contact surface to the neck ring contact surface. 
     According to the invention, it is possible to provide a method for manufacturing a container having a covering layer with a slit formed at a portion of the covering layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a cross-sectional view schematically showing a constitutional example of a container according to one embodiment. 
         FIG. 1B  is a perspective view schematically showing a constitutional example of an area around a neck portion of the container according to the embodiment. 
         FIG. 2  is a cross-sectional view schematically showing a constitutional example of a preform according to the embodiment. 
         FIG. 3  is a view for describing one example of blow molding according to the embodiment. 
         FIG. 4  is a view schematically showing one example of the locus of the movement of a mold used in blow molding according to the embodiment when the mold is closed and opened. 
         FIG. 5A  is a perspective view schematically showing a constitutional example of neck inserts according to the embodiment. 
         FIG. 5B  is a plan view schematically showing a constitutional example of the neck inserts according to the embodiment. 
         FIG. 5C  is a front view schematically showing a constitutional example of a first neck insert according to the embodiment. 
         FIG. 5D  is an enlarged perspective view schematically showing a constitutional example of center portions of the neck inserts according to the embodiment. 
         FIG. 5E  is an enlarged view schematically showing a constitutional example of an area in the vicinity of blades of the neck insert according to the embodiment. 
         FIG. 5F  is an enlarged view schematically showing a constitutional example of an area in the vicinity of the blade of the neck insert according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     One embodiment of the invention will be described with reference to drawings. This embodiment relates to a container made of a synthetic resin. This embodiment particularly relates to a method for manufacturing a container made of a synthetic resin. The container made of a synthetic resin according to this embodiment is a composite container having a multilayered structure. In the composite container, a covering layer has slits at a portion thereof to facilitate peeling of the covering layer when the composite container is discarded. 
     [Container] 
       FIG. 1A  is a longitudinal cross-sectional view schematically showing a configuration example of a container  100  according to this embodiment. In the drawing, the detailed shape for the design or the function of the container  100  is omitted, and only the outline shape of the container  100  is illustrated. In an example shown in  FIG. 1A , the container  100  is a bottomed bottle having a substantially cylindrical shape with a mouth at one end thereof. That is, as shown in  FIG. 1A , the container  100  includes a body  110  and a mouth portion  120  having a smaller diameter than the body  110 , contents being stored in the body  110 , contents being taken into and out from the container  100  through the mouth portion  120 . The end portion of the container  100  on the side opposite to the mouth portion  120  is closed into a bottom portion  130 . The body  110  includes a barrel portion  111 , a shoulder portion  112 , and a neck portion  113 , the barrel portion  111  having a substantially cylindrical shape, the shoulder portion  112  having a substantially truncated cone shape that gradually reduces a diameter from the barrel portion  111  toward the mouth portion, the neck portion  113  having a substantially cylindrical shape that connects the upper end of the shoulder portion  112  and the mouth portion  120 . A screw thread  121  is formed on the mouth portion  120  to allow attachment of a cap not shown in the drawing. A neck ring  122  having an annular shape is provided on a boundary between the mouth portion  120  and the body  110  along the circumferential direction, the neck ring  122  protruding outward in the radial direction. 
     The body  110 , the mouth portion  120 , and the bottom portion  130  of the container  100  are formed of a container body  102  as an integral body. The container  100  includes a covering layer  104  that covers the container body  102  on the body  110  and the bottom portion  130 . As described above, the container  100  is a composite container having the covering layer. In this embodiment, the covering layer  104  covers the container body  102  from the bottom portion  130  to a lower surface  114  of the neck ring  122  through the barrel portion  111 , the shoulder portion  112  and the neck portion  113  of the body  110 . 
     The container body  102  is made of a thermoplastic resin. The container body  102  is formed by using an ethylene terephthalate-based thermoplastic polyester resin, such as polyethylene terephthalate, for example. The thermoplastic polyester resin is not limited to polyethylene terephthalate, and polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, copolymers thereof or the like may also be used. A mixture of these resins, a mixture of these resins and another resin or the like may also be used. Further, polycarbonate, an acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, or the like may also be used. 
     The covering layer  104  is also made of a thermoplastic resin. It is preferable that the covering layer  104  be formed by using a thermoplastic resin that is immiscible with a thermoplastic resin used for forming the container body  102 . By using a thermoplastic resin that is immiscible with a thermoplastic resin used for forming the container body  102 , the covering layer  104  can be easily peeled from the container body  102 . Such a configuration facilitates recycling of the container  100 . In the case where ethylene terephthalate-based thermoplastic polyester is used for forming the container body  102 , it is preferable that a polyolefin-based resin, such as polyethylene or polypropylene, or ethylene-vinyl alcohol copolymer, or a polyamide-based resin, such as poly-meta-xylylene adipamide (MXD6), for example, be used for forming the covering layer  104 . 
     The covering layer  104  may be colored, decorated, or caused to have various functions. For example, a pigment, a colorant, or the like may be added to color the covering layer  104 . The covering layer  104  may have light-shielding property, for example. The container body  102  and the covering layer  104  can be easily separated and hence, recyclability of the colorless transparent container body  102  is maintained regardless of the colored covering layer  104 . 
       FIG. 1B  is a perspective view of the neck ring  122  shown in  FIG. 1A  as viewed from below. As shown in the drawing, in the container  100  according to this embodiment, slits  190  are formed at the upper end portion of the covering layer  104 . The slits  190  are portions where only the covering layer  104  or only the upper layer of the covering layer  104  is cut with no damage or practically no damage to the container body  102 . The slits  190  are portions that form starting points for tearing off the covering layer  104  when the covering layer  104  is separated from the container body  102 . Two slits  190  are formed within a range shown in  FIG. 1B . Each slit  190  is linearly provided from the edge of the lower surface  114  of the neck ring  122  to the neck portion  113 . The slits  190  may also be formed on a side opposite to a portion of the neck portion  113  shown in  FIG. 1B  in the same manner. 
     [Method for Manufacturing Container] 
     A method for manufacturing the container  100  according to this embodiment will be described. In this embodiment, the container  100  is manufactured by a so-called two-stage method. That is, first, a preform having a bottomed cylindrical shape is prepared by injection molding. Next, the preform is softened by heating. This softened preform is set in a mold, and is molded into a predetermined container shape by biaxially stretching blow molding, for example. 
     A configuration example of the preform prepared in this embodiment is schematically shown in  FIG. 2 . A preform  200  prepared in this embodiment has a substantially cylindrical shape with one end open and the other end closed. A mouth portion  220  is formed on the open end of the preform  200 . The closed end of the preform  200  is referred to as a bottom portion  230 . The bottom portion  230  has a hemispherical shape. A cylindrical portion between the mouth portion  220  and the bottom portion  230  is referred to as a barrel portion  210 . 
     The mouth portion  220  of the preform  200  is not stretched in the blow molding, which is performed in a later stage. Accordingly, the mouth portion  220  of the preform  200  becomes the mouth portion  120  of the container  100  without any change. A screw thread  221  is formed on the outer peripheral surface of the mouth portion  220  of the preform  200  to allow attachment of a cap not shown in the drawing. The screw thread  221  becomes the screw thread  121  of the container  100  without any change. A neck ring  222  is also provided to the barrel-portion- 210  side of the mouth portion  220 , the neck ring  222  annularly protruding along the circumferential direction. The neck ring  222  becomes the neck ring  122  of the container  100  without any change. 
     The preform  200  includes a preform body  202  that forms the mouth portion  220 , the barrel portion  210 , and the bottom portion  230 . The preform  200  also includes a preform covering layer  204  that covers the preform body  202  on the barrel portion  210  and the bottom portion  230 . The preform covering layer  204  is provided up to the edge portion of a lower surface  214  of the neck ring  222  from the bottom portion  230 . 
     In the blow molding, which is performed in a later stage, the preform body  202  is stretched to form the container body  102  of the container  100 , and the preform covering layer  204  is stretched to form the covering layer  104  of the container  100 . The preform body  202  and the preform covering layer  204  are integrally stretched. 
     The preform  200  is prepared by a so-called double injection molding (two-color injection molding) method, for example. The method for preparing the preform  200  is not limited to the double injection molding. Compression molding or the like may be used for the preparation of the preform  200 . Further, the preform covering layer  204  may be formed such that a heat shrink material is disposed around the preform body  202  and is heat-shrunk. According to the double injection molding, the preform covering layer  204  can be easily formed such that the preform covering layer  204  covers the entire bottom portion  230  of the preform  200 . That is, it is possible to easily form the covering layer  104  that covers the entire bottom portion  130  of the container  100 . 
     The preform  200  is heated, conveyed to a blow molding apparatus, and set in a blow mold. The container  100  is formed by performing blow molding on the heated preform  200 . The blow molding apparatus successively performs blow molding on the heated preforms  200 , which are successively conveyed, by using a plurality of blow molds. Preforms used as the material for blow molding may be prepared in the same factory. Alternatively, preforms prepared in another factory may be procured as preforms to be used as the material for blow molding. A method for acquiring preforms is not particularly limited. 
     The blow molding will be described with reference to the schematic cross-sectional view shown in  FIG. 3 . In  FIG. 3 , broken lines schematically show the shape of the preform  200  before blow molding is performed. 
     The preform  200  is conveyed in a state of being held by a holder  380 . The holder  380  has a substantially cylindrical shape, and is inserted into the mouth portion  220  of the preform  200 . In the blow mold, the mouth portion  220  is fixed by a fixing member  385  that surrounds the periphery of the mouth portion  220 . Portions of the preform  200  that are closer to the bottom portion  230  than the neck ring  222 , such as the barrel portion  210 , are disposed in a blow mold  310  having a hollow cavity when the blow mold  310  is closed. 
     The blow mold  310  includes, for example, a first barrel mold  311  and a second barrel mold  312 , a bottom mold  313 , and a neck insert  400 . The first barrel mold  311  and the second barrel mold  312  mainly form the shape of the body  110  of the container  100 . The bottom mold  313  mainly forms the shape of the bottom portion  130  of the container  100 . The neck insert  400  forms the shape of the neck portion  113  of the container  100 . The neck insert  400  is an insert mold in the first barrel mold  311  and the second barrel mold  312  for forming the neck portion  113 . The neck insert  400  includes a first neck insert  401  and a second neck insert  402 , the first neck insert  401  being fitted in the first barrel mold  311 , the second neck insert  402  being fitted in the second barrel mold  312 . The configuration of the blow mold  310  described in this embodiment is merely for the sake of example, and the configuration of the blow mold  310  is not limited to the above. 
     The preform  200  disposed in the closed blow mold  310  is stretched by using a stretching rod and pressurized air, for example. The preform  200  is stretched in the axial direction by the stretching rod not shown in the drawing, for example, and is stretched in the axial direction and the circumferential direction by pressurized air that is blown into the preform  200 . As a result, the container  100  that conforms to the inner surface shape of the blow mold  310  is formed. The preform body  202  and the preform covering layer  204  of the preform  200  are integrally stretched. As a result, the container body  102  and the covering layer  104  that covers the container body  102  are formed. Thereafter, the blow mold  310  is opened to take out the formed container  100 . 
     [Molding Mold] 
       FIG. 4  schematically shows the locus of the movement of the blow mold when the blow mold according to this embodiment is closed and opened. As shown in the drawing, the first barrel mold  311 , in which the first neck insert  401  is fitted, and the second barrel mold  312 , in which the second neck insert  402  is fitted, move to trace an arc about a movement center O. 
       FIG. 5A  to  FIG. 5F  schematically show a configuration example of the neck insert  400  according to this embodiment.  FIG. 5A  is a perspective view.  FIG. 5B  is a plan view.  FIG. 5C  is a view of a plane C-C shown in  FIG. 5B , that is,  FIG. 5C  is a front view of the first neck insert  401 .  FIG. 5D  is an enlarged perspective view of a center portion.  FIG. 5E  is an enlarged view of a circle portion E shown in  FIG. 5B .  FIG. 5F  is an enlarged view of a circle portion F shown in  FIG. 5C . 
     The first neck insert  401  and the second neck insert  402  have a symmetrical shape with respect to a parting plane. Each of a body  410  of the first neck insert  401  and a body  410  of the second neck insert  402  has a substantially semicircular disc shape having a semi-circular cutout that forms a hole  420  in which the neck portion  113  of the container  100  is fitted. A principal surface of the body  410  which is disposed close to the mouth portion  120  of the container  100  is referred to as a first surface  411 , and a principal surface of the body  410  which is disposed close to the bottom portion  130  of the container  100  is referred to as a second surface  412 . A recess is formed on the first surface  411  of the body  410  at a position in the vicinity of the cutout forming the hole  420 , and the neck ring  122  of the container  100  is fitted in the recess. The portion of the body  410  having such a recess has a smaller thickness than other portions of the body  410 . A surface configured to be brought into contact with the lower surface  114  of the neck ring  122  is referred to as a neck ring contact surface  432 , and a surface configured to be brought into contact with the neck portion  113  is referred to as a neck portion contact surface  434 . 
     In this embodiment, blades  440  are provided to the neck ring contact surface  432  and the neck portion contact surface  434  of the body  410  so as to form the slits  190 . In this embodiment, two blades  440 , that is a first blade  441  and a second blade  442 , are provided to each of the first neck insert  401  and the second neck insert  402 . The height of the blades  440  is substantially equal to the thickness of the covering layer  104  of the container  100 . In this embodiment, the neck portion  113  is minimally stretched at the time of performing blow molding and hence, the thickness of the covering layer  104  matches the thickness of the preform covering layer  204  at this portion. 
     When the first neck insert  401  and the second neck insert  402  hold the neck portion of the preform  200  at the time of performing blow molding, the preform covering layer  204  is cut by the blades  440 . As a result, after blow molding is performed, the covering layer  104  of the container  100  has the slits  190  at the neck portion  113 . 
     The height of the blades is not limited to a height that matches the thickness of the covering layer  104 . The height of the blades may be slightly lower or higher than the thickness of the covering layer  104  provided that the height of the blades corresponds to the thickness of the covering layer  104 . When the height of the blades is slightly lower than the thickness of the covering layer  104 , the covering layer  104  is not completely separated by the slits  190  with only grooves being formed on the covering layer  104 . Also in this case, the covering layer  104  can be easily broken from the slits  190 . When the height of the blades is slightly higher than the thickness of the covering layer  104 , slight flaws are formed on the container body  102 . However, provided that such flaws cause no problem in practical use, the height of the blades may be slightly higher than the thickness of the covering layer  104 . 
     As described above, when the mold is closed and opened, the first neck insert  401  and the second neck insert  402  move to trace an arc. With such movement of the first neck insert  401  and the second neck insert  402 , the blades  440  provided to each of the first neck insert  401  and the second neck insert  402  also move to trace an arc. In view of the above, the blades  440  of this embodiment are provided as described below. That is, the blades  440  protruding from the neck portion contact surface  434  are provided to perpendicularly pierce into the covering layer  104  on the neck portion  113  at the time of closing and opening the mold. Therefore, as shown in  FIG. 5B , each blade  440  protruding from the neck portion contact surface  434  protrudes along the arc traced by the locus of the movement of the blade tip about the movement center O, that is, protrudes in a tangential direction at a position on the arc where the blade  440  is attached. Each blade  440  protruding from the neck ring contact surface  432  is provided such that a blade tip moves along a movement path that allows the blade tip to draw a line on the lower surface  114  of the neck ring  122  at the time of closing and opening the mold. Therefore, as shown in  FIG. 5B , each blade  440  is provided along the arc traced by the locus of the movement of the blade tip about the movement center O, that is, provided along the tangent line at a position on the arc where the blade  440  is attached. As described above, the blades  440  are disposed along the locus of the movement of the first neck insert  401  and the second neck insert  402 . The blades  440  are disposed as described above and hence, there is no possibility of the covering layer  104  being torn due to the movement of the blades  440  when the mold is closed and opened, and the thin slits  190  are formed in the covering layer  104 . 
     One example of the dimensions of the neck insert  400  is shown in  FIG. 5B ,  FIG. 5E , and  FIG. 5F . The neck insert  400  shown in  FIG. 5B  has the hole  420  into which the neck portion  113  of the container  100  is inserted, and a diameter ϕ 1  of the hole  420  is 26.2 mm, for example. The blades  440  come into contact with a circle shown in  FIG. 5E , and the circle has a diameter ϕ 2  of 24.7 mm, for example. 
     The blade  440  disposed at a position close to the movement center O of the first neck insert  401  and the second neck insert  402  when the mold is closed and opened is taken as the first blade  441 , and the blade  440  disposed at a position away from the movement center O is taken as the second blade  442 . A distance shown in  FIG. 5B  from the movement center O to the center of the neck insert  400 , that is, a radius R 1  of the locus of the center of the neck insert  400  is 120.0 mm, for example. A distance from the movement center O to the first blade  441 , that is, a radius R 2  of the locus of the first blade  441  is 114.4 mm, for example. A distance from the movement center O to the second blade  442 , that is, a radius R 3  of the locus of the second blade  442  is 126.4 mm, for example. A distance L 1  from the distal end of the first blade  441  to the distal end of the second blade  442  is 12 mm, for example. 
     As shown in  FIG. 5E , regarding the heights of the blade tip of the first blade  441  measured from the neck portion contact surface  434 , a height L 11  at a position close to the movement center O is 0.53 mm, for example, and a height L 12  at a position away from the movement center O is 0.97 mm, for example. As for the heights of the blade tip of the second blade  442  from the neck portion contact surface  434 , a height L 21  at a position away from the movement center O is 0.57 mm, for example, and a height L 22  at a position close to the movement center O is 1.08 mm, for example. As shown in  FIG. 5F , a height L 3  of the blade tip of the blade  440  from the neck ring contact surface  432  is 0.5 mm, for example. 
     As shown in  FIG. 5E  and  FIG. 5F , radii of curvature R 11 , R 21 , R 31  at the distal ends of the blades  440  are 0.1 mm, for example, and blade angles θ 1 , θ 2 , θ 3  of the blades  440  are 30°, for example. At portions where the blades  440  are connected to the neck portion contact surface  434  or the neck ring contact surface  432 , radii of curvature R 12 , R 13 , R 22 , R 23 , R 32 , R 33  are 0.2 mm, for example. 
     These dimensions are merely for the sake of example, and may be suitably changed. 
     In the neck insert  400 , for example, Thomson blades may be attached, as replaceable blades  440 , to the body  410  of the neck insert  400  formed by cutting, grinding or the like, for example. The blades  440  may also be formed by cutting, grinding, electric discharge machining or the like at the time of forming the body  410  of the neck insert  400 . When the blades  440  are formed as bodies separate from the body  410 , only the blades  440  can be replaced and hence, ease of maintenance is improved. 
     According to this embodiment, when the preform  200  is held by the neck insert  400  at the time of performing blow molding, the slits are formed in the preform covering layer  204  by the blades  440  provided to the neck insert  400 . As a result, the slits  190  are formed in the covering layer  104  of the container  100  manufactured by blow molding. By forming such slits  190 , recyclability of the container  100  is improved. That is, when the container  100  is discarded after the container  100  is used, the covering layer  104  can be easily torn from the slits  190 , and the covering layer  104  can be easily separated from the container body  102 . As described above, the slits  190  can serve as separation starting points at the time of tearing off the covering layer  104 . The covering layer  104  may contribute to the aesthetic appearance of the container as a decorative layer having a three-dimensional design, may contribute to the function, such as light shielding property, of the container, or may apply various added values to the container  100 . 
     According to this embodiment, the slits  190  are formed at the time of performing blow molding and hence, it is possible to easily form the slits  190  at consistent positions on the container  100 . According to this embodiment, positioning is performed at the time of performing blow molding and hence, it is not necessary to expend labor on performing positioning again only for forming the slits  190 . 
     [Modification] 
     In the above-mentioned embodiment, the two slits  190  are formed side by side on each of the front surface and the back surface. However, the configuration is not limited to the above. The number of slits  190 , positions where the slits  190  are formed or the like may be suitably changed. 
     In the above-mentioned embodiment, continuous slits are shown as the slits  190 . However, the slits are not limited to the above. Each slit may be intermittently formed, thus being provided in a so-called perforated manner. In this case, the blade  440  includes blades that are intermittently provided. 
     The above-mentioned embodiment shows an example where the blades  440  are provided only to a portion of the neck insert  400 , and the slits  190  are formed only at a portion of the neck portion  113  of the container  100 . However, the configuration is not limited to the above. That is, the neck insert  400  is a blade-equipped mold having the blades  440  in the above-mentioned embodiment. However, the blade-equipped mold is not limited to the neck insert  400 . The first barrel mold  311 , the second barrel mold  312 , the bottom mold  313  and the like may also be blade-equipped molds having blades. For example, a configuration may be adopted where blades are intermittently provided to the first barrel mold  311 , the second barrel mold  312 , and the like so as to intermittently form slits also on the barrel portion  111  of the container  100  in a so-called perforated manner. Such slits formed in a perforated manner may serve as separation guides when the covering layer  104  is torn. In a case where the blades are provided to the first barrel mold  311 , the second barrel mold  312  and the like, the covering layer  104  that is brought into contact with the blades is the covering layer  104  that is stretched by blow molding. Therefore, the height of the blades is determined by taking into account the thickness of the stretched covering layer  104 . Also in this case, blades are provided along the locus of the movement of the first barrel mold  311 , the second barrel mold  312  and the like to prevent the blades from tearing off the covering layer  104  when the mold is opened. 
     The above-mentioned embodiment describes an example where the first barrel mold  311  and the first neck insert  401 , the second barrel mold  312  and the second neck insert  402 , and the like move along arc-shaped loci when the mold is closed and opened. However, the configuration is not limited to the above. These molds may move along other loci, such as a linear locus, for example. Also in such a case, a configuration is adopted where the blades  440  are provided with the directions of the blades  440  matching the locus of the mold, the blades  440  move perpendicularly to the covering layer  104 , and the blades  440  are prevented from scratching the covering layer  104  with the movement of the mold. 
     The invention has been described heretofore with reference to the preferred embodiment. However, the invention is not limited to the above-mentioned embodiment, and it is needless to say that various modifications are conceivable without departing from the scope of the invention. 
     The contents of the documents described in this Description and the Description of the Japanese application that is the basis of Paris priority of the present application are all incorporated herein. 
     REFERENCE SIGNS LIST 
     
         
           100  container 
           102  container body 
           104  covering layer 
           110  body 
           111  barrel portion 
           112  shoulder portion 
           113  neck portion 
           114  lower surface of neck ring 
           120  mouth portion 
           121  screw thread 
           122  neck ring 
           130  bottom portion 
           190  slit 
           200  preform 
           202  preform body 
           204  preform covering layer 
           210  barrel portion 
           214  lower surface of neck ring 
           220  mouth portion 
           221  screw thread 
           222  neck ring 
           230  bottom portion 
           310  blow mold 
           311  first barrel mold 
           312  second barrel mold 
           313  bottom mold 
           380  holder 
           385  fixing member 
           400  neck insert 
           401  first neck insert 
           402  second neck insert 
           410  body 
           411  first surface 
           412  second surface 
           420  hole 
           432  neck ring contact surface 
           434  neck portion contact surface 
           440  blade 
           441  first blade 
           442  second blade