JP5102524B2 - Plastic bottle manufacturing method - Google Patents

Description

  The present invention relates to a method for blow-molding a prototype of a plastic bottle such as a PET bottle.

  Conventionally, many PET bottles that are packed with drinking water and sold for sale have the same design, but it has become mainstream to sell many types of PET bottles on the shelves at convenience stores. As a result, the design of PET bottles has a major impact on sales. For this reason, PET bottles of various designs that have a good appearance and can increase the willingness to purchase have been demanded.

  The design of such plastic bottles such as PET bottles for beverages is evaluated by producing sample model molds such as mock-up models. However, although the model type is meaningful as a design sample, it is possible to evaluate the filling performance of drinking water, ease of drinking water, bottle performance such as strength, and handling properties as plastic bottles for beverages. In addition, it is not possible to evaluate the specific design properties of plastic containers. For this reason, it is necessary to make several tens to several hundreds of plastic bottles based on a model model of the sample, and test the prototype for the above evaluation.

  Here, plastic bottles such as PET bottles are generally manufactured by blow molding using a mold for blow molding (see, for example, Patent Document 1).

  However, it takes a lot of cost and time to manufacture a mold, and there is a problem that it is not cost-effective to manufacture a mold for producing tens to hundreds of prototypes. In addition, it is necessary to repeat trial production and testing many times at the trial production stage. Producing a mold every time not only requires enormous costs, but also trial production and testing in the time required to produce the mold. There is also a problem that it takes a long time. In addition, when performing blow molding by hand when making a prototype, since the mold is heavy, it is difficult to handle by hand, and the mold easily conducts heat. During repeated molding, the heat of the parison heated and softened is transferred to the mold surface, and the mold surface temperature rises. In this respect, the mold is handled manually. It has a problem with sex.

  On the other hand, although it is a type | mold used for injection molding etc., the technique which produces a resin type | mold based on a model type | mold, and shape | molds with this resin type | mold is also proposed (refer patent document 2). This model fixes the model mold to the mold, injects the liquid first mold forming resin into the mold on one side of the model mold, and after the first mold forming resin is solidified, the model A liquid second mold forming resin is injected into the mold on the other side of the mold, and after the second mold forming resin is solidified, the first mold forming resin and the second mold forming resin are solidified. By separating the resin and removing the model mold, it is possible to produce a resin mold with the part from which the model mold has been removed serving as a molding surface.

However, since the molding die is manufactured by injecting a liquid mold forming resin into the mold and solidifying it in this Patent Document 2, it takes time to manufacture the molding die. In addition, there is a problem that it takes a long time to make a prototype and a test in the time required to produce the mold.
JP 2003-334854 A Japanese Patent Laid-Open No. 11-156862

  The present invention has been made in view of the above points. A blow mold can be produced in a short time and at a low cost, and a prototype plastic bottle can be produced quickly and at the same time, the cost of trial production can be reduced. It is possible to provide a plastic bottle manufacturing method that can easily manufacture a plastic bottle for trial production with good workability by using a blow mold that is light in weight and low in thermal conductivity. It is the purpose.

  The plastic bottle manufacturing method according to claim 1 of the present invention cuts the foamable resin block 2 on the basis of the external dimension data of the model 1 of the plastic bottle, and the external shape of the model 1 and the male / female. The blow molding die 4 is produced by processing the reverse molding surface 3 into the foamable resin block 2, and the softened parison 5 of the thermoplastic resin is inserted into the blow molding die 4 and air is supplied to the parison 5. A prototype plastic bottle 6 is manufactured by molding on the molding surface 3 of the blow mold 4 by blowing.

The invention of claim 2 is characterized in that, in claim 1, the blow mold 4 made of the foamable resin block 2 has an apparent density of 0.2 to 1.1 g / cm ^3. It is.

The invention of claim 3 is characterized in that, in claim 1 or 2, the blow mold 4 made of a foamable resin block has a thermal conductivity of 0.01 to ¹ Wm ⁻¹ K ^−1. To do.

The invention of claim 1, the blanking low mold 4, a plurality of side molding split mold portion 8 formed side molding concave 7 for molding the sides of the plastic bottle 6 as a molding surface 3, as a molding surface 3 A bottom molding die 10 having a bottom molding surface 9 for molding the bottom of the plastic bottle 6, and the side molding concave portion 7 of each side molding split mold 8 is formed on the bottom side of the plastic bottle 6. At the end position, the fitting recess 11 is cut and recessed, and the fitting convex portion 12 is protruded from the outer peripheral portion of the bottom molding die portion 10 so that the fitting recess 11 of the side molding split die portion 8 is provided. In the state where the fitting convex portion 12 of the bottom molding die portion 10 is fitted to the bottom molding die portion 10 and the bottom molding die portion 10 is attached between the side molding die portions 8, each side molding die portion 8 is molded. Then, the side surface forming concave portion 7 of the side surface forming mold portion 8 and the bottom portion forming portion of the bottom portion forming die portion 10 are formed. It is characterized in that to perform the blow molding by inserting a parison 5 into a cavity surrounded by the surface 9.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the plastic bottle 6 is a PET bottle.

According to the present invention, the blow mold 4 is manufactured by cutting the foamable resin block 2 based on the external dimension data of the model mold 1, and can be manufactured by cutting metal or resin. The blow mold 4 can be produced in a short time without requiring the time required for injection and solidification, so that the prototype plastic bottle 6 can be quickly produced. is there. Further, the blow mold 4 manufactured by cutting the foamable resin block 2 can be manufactured at a lower cost than the mold, and the cost for making the plastic bottle 6 can be reduced. . Blow mold 4 which is produced by further cutting the block 2 of the foamable resin, together with handling potentially Ri taken a light is good, also has low thermal conductivity excellent in heat insulating property, when blow molding It is possible to prevent the surface from becoming hot due to the heat conduction and to improve the handleability and to easily manufacture the prototype plastic bottle 6.

Moreover, when producing the blow mold 4 lightweight and making it easy to handle, the blow mold 4 preferably has an apparent density of 0.2 to 1.1 g / cm ³ .

Furthermore, when making the blow mold 4 highly heat-insulating and making it easy to handle, the blow mold 4 preferably has a thermal conductivity of 0.01 to ¹ Wm ⁻¹ K ⁻¹ .

  Further, the blow molding die 4 is used as the molding surface 3 to form a plurality of side molding mold parts 8 formed with side molding concave surfaces 7 for molding the side surfaces of the plastic bottle 6, and the bottom of the plastic bottle 6 is molded as the molding surface 3. When the bottom molding surface 10 is formed with the bottom molding die 10, the side molding concave portion 7 of each side molding split mold 8 is fitted to the bottom side of the plastic bottle 6 at the end position. The recess 11 is cut and provided, and a fitting convex portion 12 is provided on the outer periphery of the bottom molding die 10 so that the bottom molding die portion is provided in the fitting recess 11 of the side molding split mold portion 8. 10 by fitting the fitting projections 12 of 10 and attaching the bottom forming mold part 10 between the side forming mold parts 8 to each other, Between the side mold part 8 by fitting the fitting convex part 12 to the fitting recess 11 The bottom molding die 10 can be fixed and held, and a jig or the like for fixing the bottom molding die 10 to the side molding split mold 8 can be eliminated. is there.

  Hereinafter, the best mode for carrying out the present invention will be described.

  Although it does not specifically limit as the block 2 of a foamable resin, What was formed with the molded product of foaming polyurethane or a polystyrene foam can be used. The foamed polyurethane or polystyrene may contain hollow microspheres such as hollow microsphere resin made of polyvinylidene chloride or phenol resin, hollow microsphere made of inorganic material such as glass.

The density and thermal conductivity of the expandable resin block 2 can be adjusted by adjusting the expansion ratio and the content of hollow microspheres. In the present invention, the apparent density of the expandable resin block 2 is It is preferable to set it in the range of 0.2 to 1.1 g / cm ³ . When the apparent density of the foamable resin block 2 is 1.1 g / cm ³ or less, a lightweight blow molding die 4 can be produced, and the handleability at the time of blow molding is improved. If it is higher than 1.1 g / cm ³ , the effect of reducing the weight of the blow mold 4 cannot be obtained sufficiently. When the apparent density of the foamable resin block 2 is lower than 0.2 g / cm ³ , the strength of the blow mold 4 to be produced is lowered and a problem occurs in durability. Is preferably higher than 0.2 g / cm ³ .

Moreover, it is preferable to set the thermal conductivity of the foamable resin block 2 in the range of 0.01 to ¹ Wm ⁻¹ K ⁻¹ . When the thermal conductivity of the foamable resin block 2 is ¹ Wm ⁻¹ K ⁻¹ or less, the blow molding die 4 with high heat insulation can be produced, and the surface of the blow molding die 4 becomes high temperature during blow molding. It is possible to improve the handleability by preventing this, and when the thermal conductivity of the foamable resin block 2 is higher than ¹ Wm ⁻¹ K ⁻¹ , the effect of producing the blow molding die 4 having a high heat insulating property Can't get enough. In order to make the thermal conductivity of the foamable resin block 2 lower than 0.01 Wm ⁻¹ K ^−1, it is necessary to form the foamable resin block 2 with a low apparent density. Therefore, the thermal conductivity of the foamable resin block 2 is preferably 0.01 Wm ⁻¹ K ⁻¹ or more.

  Next, a method for producing the blow mold 4 using the foamable resin block 2 will be described. First, a model mold 1 such as a mockup is produced based on the design of the plastic bottle 6. The production of the model mold 1 can be performed by paper lamination mockup modeling in which thin paper is sequentially cut and produced to produce a mockup. Of course, the method is not limited to this method, and the model mold 1 can also be manufactured by cutting an acrylic resin or the like. An example of model type 1 is shown in FIG.

  After producing the model mold 1 based on the design of the plastic bottle 6 in this way, the rectangular plate while controlling the NC cutting machine and the MC cutting machine by the CAD / CAM method based on the external dimension data of the model mold 1 1 side of the shaped foamable resin block 2 is cut, and the opposite shaped female shape and male shaped molding surface 3 corresponding to the male shape and female shape of the model mold 1 are processed into the foamable resin block 2. Thus, the blow mold 4 can be produced. Since the foamable resin block 2 is made of a foamed resin, it is much easier to cut than when metal is cut like a mold, and the blow mold 4 is produced in a short time. Is something that can be done. Further, in the cutting process, a molding die can be produced in a shorter time than when a liquid resin is poured into a mold and solidified. Therefore, it is possible to produce the blow mold 4 in response to the production of the prototype plastic bottle 6 quickly. Further, the blow mold 4 made of the foamable resin block 2 is very inexpensive as compared with the mold, and the trial production of the plastic bottle 6 can be performed at a low cost.

  Here, the blow mold 4 includes a plurality of side mold parts 8 for molding the side surfaces of the plastic bottle 6 and a bottom mold part 10 for molding the bottom of the plastic bottle 6 as shown in FIG. Since the side mold part 8 for molds is normally formed as a pair of split molds, the blow mold 4 is composed of three mold parts. The bottom surface 6a of the plastic bottle 6 is curved to the inside of the plastic bottle 6 as shown in FIG. 6, and in the case where the blow mold 4 is formed only by the pair of side surface mold parts 8, the mold after blow molding Since it becomes difficult to open, a bottom molding die 10 for molding the bottom of the plastic bottle 6 is required in addition to the two side molding molds 8.

  As shown in FIG. 3, the side surface forming mold part 8 is formed by cutting the side surface forming concave surface 7 for forming the side surface of the plastic bottle 6 as the forming surface 3. The upper end portion is a mouth-and-neck molding portion 7 a that molds the mouth-and-neck portion 6 b of the plastic bottle 6. As shown in FIG. 4, the bottom molding die 10 is formed by cutting the bottom molding surface 9 for molding the bottom surface 6 a of the plastic bottle 6 as the molding surface 3.

  Further, the side molding part 8 is connected to the end of the side molding concave surface 7 at a position corresponding to the bottom of the plastic bottle 6, and is a fitting recess that is further dug down and cut from the side molding concave surface 7. 11 is formed. On the other hand, a fitting projection 12 that can be fitted into the fitting recess 11 is formed on the outer periphery of the bottom molding die 10 so as to protrude.

  When the plastic bottle 6 is blow-molded using the prototype blow-molding die 4 of FIG. 2 produced as described above, the bottom portions are respectively provided in the fitting recesses 11 of the pair of side-molding split mold portions 8. In a state where the fitting convex portion 12 of the molding die portion 10 is fitted, the pair of side molding split die portions 8 are clamped. By assembling the pair of side molding mold parts 8 and the bottom molding part 10 in this way and clamping, the side molding concave surfaces of the pair of side molding mold parts 8 are shown in FIG. 7 and a cavity 15 surrounded by the bottom molding surface 9 of the bottom molding die 10 is formed. And the cylindrical parison 5 preformed so that the lower end is closed is inserted into the blow mold 4 from the opening at the upper end formed by the neck-and-neck forming part 7a, and about 2 to 3 MPa from the opening at the upper end of the parison 5 Blow in the air. At this time, the screw part 5a is preformed on the outer periphery of the opening at the upper end of the parison 5, and the part below the screw part 5a is heated to about 100 ° C. and is in a softened state. . Therefore, by blowing air into the parison 5, the portion below the screw portion 5a of the parison 5 is expanded in the cavity 15 of the blow molding die 4, and the side molding concave surface 7 and the bottom of the side molding split mold portion 8 are inflated. A plastic bottle 6 as shown in FIG. 6 is blow molded by molding the side surface shape with the side molding concave surface 7 and by molding the bottom shape with the bottom molding surface 9 by closely contacting the bottom molding surface 9 of the molding die 10. Is something that can be done.

  After performing blow molding in this way, when the plastic bottle 6 is removed from the blow mold 4, first, the pair of side surface forming split mold portions 8 are opened so as to be separated. At this stage, the bottom molding die 10 remains on the bottom surface of the plastic bottle 6, and after the side surface forming split mold portion 8 is opened and the fitting recess 11 and the fitting projection 12 are disengaged, The bottom molding die 10 can be released downward from the bottom surface 6 a of the plastic bottle 6. The bottom surface 6a of the plastic bottle 6 is formed into a convex shape, but by separating the pair of side surface forming mold parts 8 and the bottom part forming mold part 10 from the plastic bottle 6 in different directions as described above, The plastic bottle 6 can be removed from the mold without the hindrance of the convex shape of the bottom surface 6a.

  Here, the blow mold 4 is divided into the side mold part 8 and the bottom mold so that the convex shape of the bottom surface 6a of the plastic bottle 6 can be removed without hindrance. It is formed by dividing into a part 10, but when the side-molding mold part 8 and the bottom-molding mold part 10 are assembled and blow-molded, the side-molding mold part 8 is fitted. The bottom molding die 10 can be fixed to the side molding split mold 8 by fitting the fitting projection 12 of the bottom molding die 10 to the recess 11. Therefore, it is not necessary to use a jig or the like for fixing the bottom molding die 10 to the side molding die 8, and the mold structure of the blow molding die 4 can be simplified.

When the plastic bottle 6 is prototyped using the blow mold 4 as described above, when blow molding is performed manually using a simple blow molding device, the blow mold 4 has an apparent density of 1 as described above. It is made of a foamable resin block 2 of 1 g / cm ³ or less, and the blow mold 4 is formed to be lightweight. Therefore, manual work performed by lifting the blow molding die 4 is facilitated, and workability of blow molding by manual work is improved.

The blow mold 4 is made of the foamable resin block 2 having a thermal conductivity of ¹ Wm ⁻¹ K ⁻¹ or less as described above, and the blow mold 4 is formed with high heat insulation. Therefore, even if the parison 5 heated to about 100 ° C. is repeatedly blow-molded by the blow mold 4, the heat of the parison 5 is reduced from being conducted to the surface of the blow mold 4, and the blow mold 4 The surface of the mold can be prevented from becoming hot, and the manual work performed by touching the surface of the blow mold 4 is facilitated, and the workability of manual blow molding is improved. It will be.

  Here, as the above-mentioned parison 5 used for blow molding, any thermoplastic resin can be used, but PET that is generally used for beverages by blow molding using the parison 5 of polyethylene terephthalate. Prototype bottles can be manufactured.

It is sectional drawing which shows an example of embodiment of this invention. It is a disassembled perspective view which shows an example of a blow molding die same as the above. It is a perspective view which shows an example of the split mold part for side molding same as the above. It is a perspective view which shows an example of the bottom mold part same as the above. It is a perspective view which shows an example of a model type same as the above. It is sectional drawing which shows a plastic bottle same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Model type | mold 2 Foamable resin block 3 Molding surface 4 Blow molding die 5 Parison 6 Plastic bottle 7 Side molding concave surface 8 Side molding split mold part 9 Bottom molding surface 10 Bottom molding mold part 11 Fitting recess 12 Fitting Convex

Claims (4)

Based on the data of the model type of external dimension of plastic bottles, by cutting a block of foamed resin, by modeling of the contour and the male and female to process the reverse of the molding surface to the block of the foamed resin, molding A plurality of side surface forming mold parts that form side surface forming concave surfaces for forming the side surfaces of the plastic bottle as surfaces, and a bottom part forming die portion that forms a bottom forming surface for forming the bottom part of the plastic bottles as forming surfaces. A blow molding die is manufactured, and a fitting recess is cut and formed in the side surface forming concave surface of each side surface molding die portion at the end portion on the bottom side of the plastic bottle and the outer peripheral portion of the bottom molding die portion A projection is provided on the side, and a bottom molding die is fitted between each side molding split mold by fitting the fitting convex of the bottom molding die into the fitting recess of the side molding split mold. Each side molding split mold with the part attached Was clamping, the parison is inserted parison of a thermoplastic resin which softens the cavity surrounded by the bottom forming surface for side molding concave and the bottom mold part of these side mold part of the blow mold A method for producing a plastic bottle, characterized by producing a prototype plastic bottle molded on a molding surface of a blow mold by blowing air. The method for producing a plastic bottle according to claim 1, wherein the blow mold made of the foamable resin block has an apparent density of 0.2 to 1.1 g / cm ³ . 3. The method for producing a plastic bottle according to claim 1, wherein the blow molding die made of the foamable resin block has a thermal conductivity of 0.01 to ¹ Wm ⁻¹ K ⁻¹ . The method for producing a plastic bottle according to any one of claims 1 to 3 , wherein the plastic bottle is a PET bottle.

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