JP2004291621A - Method for producing thermoplastic resin container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel and improved method for producing a thermoplastic resin container having high heat resistance at high efficiency, besides having no problem in a production method by extrusion molding as the first step. <P>SOLUTION: In a method for producing a thermoplastic resin container comprising a pre-molded article formation process of forming a pre-molded article of a thermoplastic resin and a thermoforming process of forming under heating the pre-molded article to give a thermoplastic resin cup container, the process of thermoforming comprises subjecting the pre-molded article to a blow molding, followed by stretching and heating to set, then shrinking back the resultant to the shape of a molded plug member and finally cooling the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a cup-shaped thermoplastic resin container which can be conveniently used as a container for food and drink.

  As is well known, as a container for food and drink, a cup-shaped thermoplastic resin container having a flange, a cylindrical side wall hanging down from an inner edge of the flange, and a bottom wall closing a lower end of the side wall has been widely put to practical use. Such containers are generally extruded from a thermoplastic resin sheet, then heated and softened to simultaneously pneumatically and / or vacuum form multiple areas of the sheet into the required cup shape, and then into the cup shape. It is manufactured by cutting a molded part at a portion surrounding the molded part and separating the molded part from a sheet.

  However, in the manufacturing method as described above, the remaining portion (so-called skeleton portion) of the sheet obtained by separating the cup-shaped portion occupies a substantial portion of the sheet, usually 40 to 60%, and such a remaining portion is wastefully discarded. Therefore, the material yield is significantly reduced. The remainder of the sheet is also intended to be melted and reused, but reuse reduces the quality of the material, and in order to avoid excessive degradation of material quality, reuse is not the whole of the sheet but the entire remainder of the sheet. I have to limit it to only a part. When the sheet layer is a multilayer sheet containing an additional layer such as a gas barrier layer together with the main layer, it is practically impossible to reuse the rest of the sheet. Further, the thickness of the container strongly depends on the thickness of the sheet, and it is difficult to appropriately select the thickness distribution of the container. Further, for the convenience of the manufacturing process, it is desired that the sheet can be wound in a roll shape, so that the thickness of the sheet is limited to, for example, 1.2 mm or less, and thus the thickness of the bottom wall of the container, Therefore, the strength tends to be too low.

  In Patent Document 1 below, a thermoplastic resin preformed body (a so-called preform) having a thermoformed main part and a flange part is molded by injection molding, and then the thermoformed main part of the preformed body is subjected to plug assist vacuum and A manufacturing method of forming a cup-shaped thermoplastic resin container by pressure forming is disclosed.

Further, in Patent Document 2 below, a thermoplastic resin preformed body having a thermoformed main part and a flange part is formed by injection molding, and then the thermoformed main part of the preformed body is subjected to matched mold vacuum forming to form a cup. A method for manufacturing a shaped thermoplastic resin container is disclosed. At the time of matched mold vacuum forming, one of the mold members is heated to a temperature higher than the crystallization start temperature, so that the thermoplastic resin container formed into a cup shape is thermally fixed.
JP-A-5-69478 Japanese Patent Publication No. 7-67737

  In the manufacturing methods disclosed in Patent Documents 1 and 2, there is no problem as described above in the manufacturing method in which a sheet is first extruded. However, these production methods are still not sufficiently satisfactory, and have the following problems to be solved. In the manufacturing method disclosed in Patent Document 1, the thermoplastic resin is not thermally fixed, and thus the manufactured thermoplastic resin container has poor heat resistance. According to the manufacturing method disclosed in Patent Document 2, the heat resistance is improved because the thermoplastic resin is thermally fixed, but the thermoforming of the thermoforming main portion is heated to a temperature higher than the crystallization start temperature. In addition, the time required for heat setting and the time required for cooling the thermoformed container are compared because one mold member is closely fitted to the other mold member at a temperature lower than the crystallization start temperature. Target length and low production efficiency.

  Further, in any of the manufacturing method disclosed in Patent Document 1 and the manufacturing method disclosed in Patent Document 2, a flange of a thermoplastic resin container to be finally molded is subjected to heat treatment. In many cases, the heat resistance of the flange is insufficient.

  Further, when the flange is crystallized in order to impart heat resistance to the flange, it may be difficult to provide a sealing material on the upper surface of the flange by heat sealing. That is, if the flange is crystallized to improve heat resistance, melting or softening does not occur unless the flange is heated to an extremely high temperature (for example, about 200 ° C.).

  The present invention has been made in view of the above facts, and its main technical problem is that, in addition to the above-mentioned problems in the manufacturing method of first extruding a sheet, a thermoplastic resin having sufficient heat resistance is provided. An object of the present invention is to provide a new and improved manufacturing method capable of manufacturing a resin container with high efficiency.

  Another technical object of the present invention is to provide a new and improved manufacturing method capable of manufacturing a thermoplastic resin container in which a flange is also provided with sufficient heat resistance, in addition to the achievement of the main technical problems described above. It is to be.

  Still another technical problem of the present invention is that the lower surface side of the flange is selectively crystallized to improve heat resistance, and an amorphous or low-crystal heat sealable portion remains on the upper surface side of the flange. The object is to provide a thermoplastic resin container.

  As a result of intensive studies, the present inventors have found that in the thermoforming step, the preformed body is blow-molded, stretched, heated and heat-fixed, then shrink-backed into the molded shape of the plug member, and cooled. As a result, it has been found that the main technical problem can be achieved.

That is, according to the present invention, as a production method for achieving the above-mentioned main technical problem, a pre-molded article molding step of molding a thermoplastic resin pre-molded article, and a cup-shaped thermoplastic resin formed by thermoforming the pre-molded article In a method for producing a thermoplastic resin container including a thermoforming step of molding a container,
The thermoforming step includes blow molding and stretching the preformed body, heating and heat setting, and then shrinking back into a molded shape of a plug member, shaping, and cooling. A manufacturing method is provided.

In the thermoforming step, the following means can be adopted.
(1) In the thermoforming step, the preformed body is heated to a temperature equal to or higher than a glass transition temperature and lower than a crystallization start temperature.
(2) The thermoforming step includes stretching in an axial direction by a stretching rod before the blow molding.
(3) The pre-molded body is heat-set by being formed into a molded shape of a female mold member heated to a temperature equal to or higher than a crystallization start temperature and equal to or lower than a melting point by the blow molding.
(4) In the thermoforming step, the preformed body is subjected to free blow molding, and then heated in a heating oven to be heat-set.
(5) In the thermoforming step, when the stretching is performed in the axial direction by the stretching rod, the plug member is inserted into the blow-molded and stretched preformed body, and oven heating is performed in this state. And then heat shrink and then shrink back to the shape of the plug member to shape it.
(6) The temperature of the plug member is lower than the crystallization start temperature or higher than the crystallization start temperature.
(7) The tip diameter of the elongated rod is 0.3 times or more and less than 1.0 times the bottom diameter of the final molded body.
(8) Pressing a bottom shaping die against the final formed body shaped into the shape of the plug member to further shape.
(9) The temperature of the bottom shaping mold is not lower than the crystallization start temperature and lower than the melting point.
(10) Cooling is performed by spraying a cooling blow on the final molded body shaped into the molded shape of the plug member.
(11) The shrink bank is performed by vacuum and / or pressure forming.
(12) Injection molding the preformed body in the preformed body forming step.
(13) The pre-formed body is compression-molded in the pre-formed body forming step.
(14) The pre-formed body is composed of a thermoformed main portion and a flange portion, and the flange portion is heated to a temperature equal to or higher than the glass transition temperature and lower than the melting point to be stretched under pressure to crystallize. Include a chemical treatment step.
(15) The preformed body is composed of a thermoformed main part and a flange part, and includes a flange part crystallization treatment step of heating the flange part to a temperature higher than the crystallization start temperature and lower than the melting point to cause crystallization. thing.
(16) The flange portion crystallization step is performed after the pre-formed body forming step and before the thermoforming step.
(17) A trimming step of trimming the flange into a required shape after the thermoforming step.
(18) The pre-formed body has a multilayer structure.

Further, according to the present invention, the production of a thermoplastic resin container including a thermoforming step of forming a cup-shaped thermoplastic resin container by thermoforming a thermoplastic resin preform comprising a thermoformed main portion and a flange portion. In the method,
The thermoforming step includes a step of blow-molding and stretching the thermoformed main part of the preformed body, heating and heat-setting, then shrinking back to the molded shape of the plug member, shaping, and cooling. While
Prior to or during the thermoforming step, the lower surface of the flange portion is selectively crystallized so that at least an amorphous or low crystalline heat seal portion remains on the upper surface side of the flange portion. A manufacturing method is provided wherein a selective crystallization process of the flange portion is performed.

In the manufacturing method of the present invention in which such a flange portion selective crystallization process is performed, the following means can be employed.
(19) A convex portion serving as a heat seal portion is provided on the upper surface of the flange portion. In the step of selectively crystallizing the flange portion, the flange portion is stretched under pressure while regulating the flow of the convex portion. By doing so, the lower surface of the flange portion is selectively oriented and crystallized.
(20) In the case where the flange portion selective crystallization treatment step is performed by pressure stretching as described above, this step must be performed prior to the thermoforming step.
(21) In the flange portion crystallization step, the lower surface side of the flange portion is maintained at a temperature equal to or higher than the crystallization start temperature and lower than the melting point while at least a part of the upper surface side of the flange portion is maintained at a temperature lower than the start of crystallization. Selectively heating to thermally crystallize the lower surface of the flange portion selectively.

  In the method for producing a thermoplastic resin container of the present invention, in addition to having no problem in the production method of first extruding a sheet, it is possible to produce a thermoplastic resin container having sufficient heat resistance with high efficiency. it can. In addition, if necessary, a thermoplastic resin container having a flange with sufficient heat resistance can be manufactured.

  Further, in the manufacturing method of the present invention in which the flange portion selective crystallization process is performed, the lower surface of the flange portion is selectively crystallized to provide heat resistance, and the upper surface of the flange portion is easily heat-sealed. Since a non-crystallized or low-crystallized portion is formed, a sealing material such as an aluminum foil can be easily heat-sealed. That is, since the non-crystallized or low-crystallized portion on the upper surface of the flange portion is softened or tackified by heating at a low temperature of about 70 ° C., heat sealing of the sealing material can be easily performed at a low temperature.

  Hereinafter, preferred embodiments of a method for manufacturing a thermoplastic resin container configured according to the present invention will be described in more detail with reference to the accompanying drawings.

  In a preferred embodiment of the manufacturing method according to the present invention, first, an appropriate thermoplastic resin is compression-molded or injection-molded to form a pre-molded body 2 having a form as shown in FIG. The compression molding or injection molding mode itself may be in a known form. The illustrated preformed body 2 comprises a substantially disc-shaped thermoformed main portion 4 and an annular flange portion 6 located around the main portion. The flange portion 6 is relatively thick, for example, has a thickness of about 1.8 mm.

  Examples of the thermoplastic resin that can be suitably used for compression molding or injection molding of the pre-molded body 2 include, but are not limited to, a polyester resin, a polyolefin resin, a polystyrene resin, and a polyamide resin. Resins and polycarbonate resins.

  In the production method of the present invention, various polyester-based resins can be suitably used, and in particular, a polyester resin which can obtain excellent transparency and impact resistance by stretching and effectively acts on heat fixing is desirable. Polyesters whose main components are polyethylene terephthalate, polypropylene terephthalate, and polylactic acid having a glass transition temperature of room temperature or higher and crystallinity can be particularly preferably used. In particular, polyethylene terephthalate in which ethylene terephthalate units account for 80 mol% or more, particularly 90 mol% or more, is preferable from the viewpoint of economy, moldability, and molded article properties. When such a polyethylene terephthalate is used, the copolymerization component is preferably isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-butanediol, 1,4-cyclohexanedimethanol, or the like. As the thermoplastic polyester resin, polyethylene terephthalate is most preferable, but is not limited thereto. Polyethylene / butylene terephthalate, polyethylene terephthalate / 2,6-naphthalate, polyethylene terephthalate / isophthalate, and polybutylene terephthalate, Polybutylene terephthalate / isophthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate / adipate, polyethylene-2,6-naphthalate / isophthalate, polybutylene terephthalate / adipate, or a blend of two or more thereof Can be used. Polyester has an intrinsic viscosity [IV] of 0.5 as measured using a phenol / tetrachloroethane mixed solvent as a solvent in view of moldability of a preform, moldability in container molding, mechanical properties of a container, and heat resistance. As described above, those having a range of 0.6 to 1.5 are particularly preferable. The polyester may be blended with at least one of an ethylene polymer, a thermoplastic elastomer, a polyarylate, and a polycarbonate as a modifying resin component. The modified resin component is generally used in an amount of up to 60 parts by weight, particularly preferably in an amount of 3 to 20 parts by weight, per 100 parts by weight of the polyester.

  Examples of the polyolefin resin include low-medium-high-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, propylene-ethylene copolymer, ethylene-vinyl acetate copolymer, ethylenically unsaturated carboxylic acid and its anhydride. Olefin resin graft-modified with a product.

  Examples of the polycarbonate resin include a carbonate resin derived from a bicyclic dihydric phenol and phosgene, and a bisphenol such as 2,2′-bis (4-hydroxyphenyl) propane (bisphenol A) Preferred are polycarbonates derived from 2,2'-bis (4-hydroxyphenyl) butane (bisphenol B), 1,2-bis (4-hydroxyphenyl) ethane, and the like.

  The thermoplastic resin used in the production method of the present invention includes a compounding agent known per se, for example, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, a filler, a lubricant, and an inorganic or organic compound. A coloring agent and the like can be blended.

  Continuing with reference to FIG. 2, the preform 2 taken out of a compression molding device or an injection molding device (not shown) is heated to the required thermoforming temperature, after which the whole is designated by the numeral 8. It is supplied to a thermoforming device. In particular, when the preformed body 2 is obtained in a substantially amorphous state, such as a polyester resin, the heating temperature of the preformed body 2 is not lower than the glass transition temperature (Tg) and lower than the crystallization start temperature (Tic). Preferably it is. When the heating temperature is lower than the glass transition temperature (Tg), an excessive force is required for thermoforming. On the other hand, when the temperature exceeds the crystallization start temperature (Tic), spherulites tend to be formed and the transparency tends to be impaired. The glass transition temperature (Tg) and the crystallization onset temperature (Tic) used in the specification were determined by using a differential scanning calorimeter (DSC) by arbitrarily sampling about 10 mg from a molded object to be measured. The temperature is held at 300 ° C. for 3 minutes in a nitrogen gas atmosphere, then rapidly cooled to room temperature, and the temperature is increased at a heating rate of 20 ° C. per minute.

  The illustrated thermoforming device 8 includes a female mold member 10, a pressing / clamping member 12, a plug member 14, and an extension rod 16. The female molding member 10 is formed with a molding cavity 18 extending downward from its upper surface. The upper portion of the inner peripheral surface of the molding cavity 18 is cylindrical, and the middle and lower portions of the inner peripheral surface are inverted truncated conical cylinders whose inner diameter is gradually reduced downward, and the bottom surface is a substantially horizontal circular shape. It is. The female mold member 10 is also provided with a communication hole 20 penetrating the bottom wall. The pressing / clamping member 12 is annular, and the inside diameter of the opening provided at the center thereof is made substantially the same as the inside diameter of the upper end of the molding cavity 18 in which the female molding member 10 is formed. . The plug member 14 has a cylindrical upper portion and an inverted truncated conical lower portion whose outer diameter is gradually reduced downward. The plug member 14 has a through hole 22 extending therethrough in the axial direction. The extension rod 16 has an elongated cylindrical shape, and is inserted through the through hole 22 of the plug member 14. The through hole defined in the cylindrical extension rod 16 functions as a communication hole 24.

  As shown in FIG. 2, the preform 2 heated to the required thermoforming temperature is placed on the upper surface of the female mold member 10 and the thermoforming main part 4 is positioned corresponding to the molding cavity 18. . Thereafter, as shown in FIG. 3, the pressing / clamping member 12 is lowered, and the flange portion of the pre-molded body 2 is moved between the upper surface of the female mold member 10 and the lower surface of the pressing / clamping member 12. 6 is pressed and tightened. When performing the flange crystallization process for imparting heat resistance to the flange 6, the flange 6 is locally heated to a temperature lower than the crystallization start temperature (Tic) to less than the melting point (Tm) for crystallization. . Further, according to the experience of the present inventors, when the flange 6 heated to a temperature equal to or higher than the glass transition point is pressed with a considerable pressure, for example, a pressure of about 4.5 to 13 MPa, the flange 6 is stretched. As a result, the thickness of the flange portion 6 is reduced to, for example, about 1/3 to 1/2, and is oriented and crystallized due to the flow of the resin. Furthermore, by bringing the flange portion 6 into contact with the upper surface of the female mold member 10 heated to a temperature lower than the crystallization start temperature (Tic) to the melting point (Tm), relaxation of molding strain caused by the flow orientation of the resin and heat resistance are improved. Crystallization is performed. Then, the heat resistance and the strength of the flange portion 6 are improved by the crystallization and the relaxation of the molding strain. In order to promote the flow of the resin in the flange portion 6, the upper surface and the lower surface of the flange portion 6, the lower surface of the pressurizing / clamping member 12, or the female molding die member 10 before the pressing and tightening of the flange portion 6. It is preferable to apply an appropriate lubricant such as silicone oil to any of the upper surfaces. In the illustrated embodiment, when the pressing and tightening member 12 is lowered and the flange portion 6 is pressed and tightened, the flange portion 6 is crystallized. 6 and the crystallization process of the flange portion 6 is performed.

  In the above-described flange portion crystallization process, the female molding member 10 having a predetermined temperature is used, and the flange portion 6 of the pre-molded body 2 placed on the upper end of the female molding member 10 is pressed and tightened. This is performed by tightening with the member 12, but it is also possible to use a separate support member without using such a female mold member 10. In this case, the flange portion 6 of the pre-formed body 2 supported on the support member heated to the predetermined temperature is tightened by the above-mentioned pressing / tightening member 12 to perform the flange portion crystallization process. Then, the preformed body may be introduced onto the female mold member 10.

  Subsequent to the crystallization process of the flange portion 6 on the female mold member 10, thermoforming of the thermoforming main portion 4 of the preform 2 is performed. In the embodiment shown, this thermoforming is performed in three stages: drawing by the draw rod 16, blow molding and shrinkback. In the first stage of the thermoforming step, as shown in FIG. 4, the stretching rod 16 is lowered to the position shown, whereby the thermoforming main part 4 of the preform 2 is stretched in the axial direction. Next, in the second stage, as shown in FIG. 5, the communication hole 24 of the stretching rod 16 is connected to a compressed air source (not shown), and the stretched thermoformed main part 4 is connected to the communication hole 24. It is blow-molded by the action of compressed air ejected from the mold, and is formed into the shape of the female mold member 10, that is, the shape corresponding to the inner surface of the molding cavity 18. At the time of such blow molding, the female mold member 10 is heated by a suitable heating means (not shown) such as an electric resistance heater, and the inner surface of the molding cavity 18 is heated to a temperature equal to or higher than the crystallization start temperature of the thermoplastic resin. In addition, the temperature is set to be lower than the melting point, for example, about 180 ° C. Accordingly, the blow molded thermoformed main part 4 is heated and thermally fixed by being brought into contact with the inner surface of the molding cavity 18 of the female mold member 10. The heat setting temperature is higher than the crystallization start temperature (Tic) of the thermoplastic resin, but is preferably lower than the melting point (Tm), particularly preferably −10 ° C. or lower. When the heat setting temperature is equal to or higher than the melting point (Tm), the thermoforming main part 4 tends to be welded to the female mold member 10. If the temperature is lower than the crystallization start temperature (Tic), crystallization and relaxation of molding strain become insufficient, and heat resistance and strength cannot be obtained. In the third stage of the thermoforming process, the plug member 14 is lowered to the position shown in FIG. Then, the communication hole 24 of the extension rod 16 is communicated with a vacuum source (not shown), and the communication hole 20 of the female mold member 10 is communicated with a compressed air source (not shown). Thus, the thermoformed main part 4 is shrunk back into the shape of the plug member 14, that is, the outer shape of the plug member 14 by the compressed air pressurization and the vacuum suction, and is shaped into the final shape, that is, the container 26. Then, it is cooled by being brought into contact with the plug member 14. At this time, the temperature of the surface of the plug member 14 may be an appropriate temperature in the range from around room temperature to the crystallization start temperature or lower.

  After the container 26 has been sufficiently cooled, the container 26 is removed from the thermoforming device 8. As shown in FIG. 7, the removed container 26 has an annular flange 28, a side wall 30 hanging down from the inner peripheral edge of the flange 28, and a bottom wall 32 closing the lower end of the side wall 30. In the illustrated embodiment, as shown by a two-dot chain line in FIG. 7, the flange 28 that has been stretched under pressure is further trimmed to a required outer diameter. The trimming of the flange 28 can be performed in a known manner.

  8 to 11 show another embodiment of the manufacturing method constituted according to the present invention. This embodiment is an example of so-called free blow in which blow molding is performed without using the female mold member 10, and in this example, a thermoforming device indicated by reference numeral 108 as a whole is used. The thermoforming device 108 includes a receiving member 110, a pressing / clamping member 112, and a plug member 114. The receiving member 110 and the pressing / clamping member 112 are both annular, and the inner diameter of the opening disposed at the center of the receiving member 110 and the inner diameter of the opening disposed at the center of the pressing / clamping member 112 are: Substantially the same. The plug member 114 has a cylindrical upper portion and an inverted truncated conical lower portion whose outer shape is gradually reduced downward. The plug member 114 has a communication hole 124 extending therethrough in the axial direction.

  When performing the thermoforming step, as shown in FIG. 8, the preformed body 2 which is injection-molded or compression-molded and heated to a required thermoforming temperature (the preformed body 2 is referred to FIG. 1 to FIG. 7). (Previously the same as the pre-formed body 2 described above) is placed on the receiving member 110. Thereafter, as shown in FIG. 9, the pressing / clamping member 112 is lowered, and the flange portion 6 of the pre-formed body 2 is moved between the upper surface of the receiving member 110 and the lower surface of the pressing / clamping member 112. Pressed and tightened. Thus, as in the case of the embodiment described with reference to FIGS. 1 to 7, the flange portion 6 is extended, and the thickness of the flange portion 6 is reduced to, for example, about 1/3 to 1/2. Is oriented and crystallized due to the flow of the resin. In addition, by bringing the flange portion 6 into contact with the upper surface of the female mold member 10 heated to a temperature lower than the crystallization start temperature (Tic) to the melting point (Tm), relaxation of molding strain caused by the flow orientation of the resin and heat resistance are improved. The applied crystallization is performed. Then, the heat resistance and the strength of the flange portion 6 are improved by the crystallization and the relaxation of the molding strain.

  Next, the communication hole 124 of the plug member 114 is communicated with a compressed air source (not shown), and compressed air is ejected from the communication hole 124 toward the thermoforming main part 4 of the preformed body 2, whereby The thermoforming main part 4 is blown free.

  Thereafter, as shown in FIG. 11, the plug member 114 is lowered to a predetermined position, and the thermoforming main part 4 formed by free blow molding has appropriate heating means 118a, 118b and 118c such as electric resistance heating means. Is introduced into a heating oven (only the heating means 118a, 118b and 118c are shown in a simplified manner), and is higher than the crystallization start temperature (Tic) of the thermoplastic resin but lower than the melting point (Tm), particularly the melting point (Tm). Tm) It is heated to a preferable temperature of -10C or lower. Simultaneously or subsequently, the communication hole 124 of the plug member 114 is communicated with a vacuum source (not shown), and the free-blown thermoformed main part 4 is formed into the shape of the plug member 114, that is, the plug member 114. Is shrunk back to the outer shape. Thus, the thermoformed body 4 is shaped into its final shape or container 26 (FIG. 7) and is also cooled by being brought into contact with the plug member 114. At this time, the temperature of the surface of the plug member 14 may be an appropriate temperature in the range from around room temperature to the crystallization start temperature or lower. Further, in this case, the plug member 14 is heated to a temperature equal to or higher than the crystallization start temperature (Tic) of the thermoplastic resin and lower than the melting point (Tm), and particularly equal to or lower than the melting point (Tm) -10 ° C. by an electric resistance heating means or the like. May be. By using the plug member 14 thus heated, the time required for the heat fixing treatment by the heating oven can be shortened.

  Further, as described with reference to FIG. 7, after the container 26 is sufficiently cooled, the container 26 is taken out from the thermoforming device 8, and the pressurized and stretched flange 28 is trimmed to a required outer diameter. I'm sullen. In the case where the heated plug member 14 is used, cooling is performed in a state where heating by the electric resistance heating means is turned off.

  Further, in the present invention, as still another embodiment, a thermoplastic resin container can be manufactured by the process shown in FIG.

  In FIG. 12, for example, a pre-molded body 2 whose flange portion has been crystallized by a predetermined crystallization process is a female mold member held at an appropriate temperature between room temperature and a thermal crystallization start temperature (Tic). (A cooling mold) 10, an annular holder 12a, and a stretching rod (stretch rod) 16 are introduced into a thermoforming apparatus (step a), and the flange portion 6 of the pre-molded body 2 is formed into a female molding member. (Cooling mold) It is sandwiched between the upper end of the cooling die 10 and the lowered annular holder 12a (step b). In this state, the stretching rod 16 is lowered to stretch the thermoformed main part 4 of the preformed body 2 in the axial direction (step c). At this time, the tip diameter of the stretched rod is desirably 0.3 times or more and less than 1 time the inner diameter of the intermediate molded body 50 (the inner diameter of the flange). In the initial stage of the stretching process, the pushing of the stretching rod proceeds while being supported by the frictional force between the tip of the stretching rod and the material resin. Therefore, resin stretching does not occur in a portion in contact with the tip of the stretching rod, and uniaxial stretching in other portions becomes dominant. Thereafter, when the uniaxially stretched portion is sufficiently oriented and crystallized and work-hardened, biaxial stretching of the contacted portion is started. Therefore, when the tip diameter of the stretching rod is in the range of 0.3 times or more and less than 1 time, uniaxial stretching ends and biaxial stretching starts at a relatively early stage of stretching, so even at the bottom of the intermediate molded body 50. Sufficient biaxial stretching can be performed. As a result, in the subsequent heat fixing step (f), whitening does not occur in the portion, and transparency and impact resistance are obtained as well as heat resistance. On the other hand, when the tip diameter of the stretching rod is less than 0.3 times, the biaxial stretching is not started or insufficient even at the stretching end stage, and as a result, sufficient biaxial stretching is performed on the bottom of the intermediate molded body 50. In the subsequent heat setting step (f), the portion becomes white, and transparency and impact resistance cannot be obtained. Furthermore, blow molding is performed by blowing compressed air from the through hole 16a of the extension rod 16 to obtain an intermediate molded body 50 having a shape corresponding to the inner surface of the molding cavity 18 of the female molding member 10 (step d). The molded body 50 is removed from the female mold member 10 (step e). The steps a to d are the steps shown in FIGS. 3 to 5 described above, except that the female mold member 10 maintained at an appropriate temperature lower than the thermal crystallization start temperature (Tic) is used. For example, the thermoforming main part 4 of the preform 2 is maintained at a temperature equal to or higher than the glass transition point and lower than the crystallization start temperature, and the stretching in the axial direction by the stretching rod 16 and the blow molding are performed.

  In FIG. 12, the above-mentioned intermediate molded body 50 is further arranged in a heating oven provided with electric resistance heating means 118a, 118b and 118c, and the plug member 14 is inserted into the intermediate molded body 50 (step f). . In this state, the intermediate molded body 50 is heated by a heating oven to a temperature equal to or higher than the crystallization start temperature (Tic) and lower than the melting point (Tm) to perform heat fixing and at the same time through the through-hole 24 of the plug member 14. , The intermediate molded body 50 is shrink-backed to the outer shape of the plug member 14, and the container 26 shaped to the final shape is obtained (step g). At the time of heat fixing, the plug member 14 is heated to a temperature equal to or higher than the crystallization start temperature (Tic) and lower than the melting point (Tm) by a suitable electric resistance heating means (not shown) at the same time as the heating by the heating oven. It is desirable that the heat setting time be shortened.

  In this case, the temperature of the plug member 14 may be adjusted to a temperature equal to or higher than the glass transition point temperature of the thermoplastic resin and lower than the crystallization start temperature by hot water temperature adjusting means or the like. By using the plug member 14 whose temperature has been adjusted in this way, the heat fixing time cannot be shortened as described above, but since the final container 26 can be cooled, the subsequent cooling blow step (h) becomes unnecessary. (The actual plug temperature is preferably about 110 ° C.)

  If the bottom portion of the container 26 obtained in the step (g) is not sufficiently shaped, the bottom portion of the container is pressed down by the bottom shaping die 42 to assist the shaping as in the step (g ′). Is also good. In this case, the temperature of the shaping mold is desirably equal to or higher than the crystallization start temperature. When the temperature of the shaping mold is equal to or higher than the crystallization start temperature, it is possible to remove the molding distortion caused by pressing the bottom portion, so that the shapeability can be improved without impairing the heat resistance of the container. On the other hand, when the temperature is lower than the crystallization start temperature, the heat resistance of the bottom part is inferior to other parts such as the side wall part.

  The container 26 obtained in the above step g is introduced into a cooling mold 40 having a predetermined through hole with the plug member 14 still inserted, and is subjected to a cooling blow by blowing cooling air ( Step h) After the cooling, the plug member 14 is pulled out, whereby the final container 26 can be obtained.

(Selective crystallization of flange)
In the present invention, a cup-shaped container having a flange excellent in heat sealability can be manufactured by selectively crystallizing the lower side of the flange portion 6 of the above-mentioned pre-processed molded body 2.

  Such a selective crystallization treatment of the flange portion 6 can be broadly performed by two means of selective orientation crystallization and selective heating crystallization.

  In the selective orientation crystallization, for example, as shown in FIG. 13, a protrusion 60 serving as a heat seal portion is formed on the upper surface 6 a of the flange portion 6 of the pre-formed body 2, and a pair of annular pressure / tightening is performed. The pressing can be performed by sandwiching the flange portion 6 between the tools 13a and 13b. In this case, in FIG. 13A, the protrusion 60 is formed at the outer end of the upper surface 6a, and in FIG. 13B, the protrusion 60 is formed slightly inside the outer end of the upper surface 6a. In any case, a concave portion 62 corresponding to the protrusion 60 is formed in the upper pressing / clamping tool 13a.

  That is, as described above, using the annular holders 13a and 13b described above, a pressure (pressure of about 4.5 to 13 MPa) at which oriented crystallization is performed and a temperature higher than the glass transition temperature. However, in this case, in the protrusion 60 formed on the upper surface 6a, the flow is caused by the concave portion 62 of the upper pressing / clamping tool 13a. Is suppressed. As a result, in particular, although the flange portion 6 undergoes oriented crystallization due to the flow of the resin, the protrusion 60 formed on the upper surface 6a suppresses the flow of the resin in the flange surface direction. It does not occur and becomes non-crystalline or low-crystalline.

  The flange portion 6 is heated to a temperature equal to or higher than the glass transition point temperature, but must not be heated to a temperature higher than the crystallization start temperature. This is because if heated to a temperature higher than the crystallization start temperature, thermal crystallization of the protrusion 60 occurs.

  The heating of the flange portion 6 is performed from both surfaces of the flange portion 6 by, for example, electric resistance heating means provided on the annular pressurizing / clamping tools 13a and 13b. Therefore, a heating means may be provided only on the lower annular pressurizing / clamping tool 13b, and only the lower surface 6b side of the flange portion 6 may be heated to the glass transition temperature or higher. In this case, if the protrusion 60 of the upper surface 6a is not heated to a temperature higher than the crystallization start temperature, the lower surface 6b side of the flange portion 6 may be heated to a temperature higher than the crystallization start temperature (but lower than the melting point).

  The flange portion 6 on which the selective crystallization process has been performed as described above may not be partially oriented and crystallized on the upper surface 6a side depending on the heating conditions. The protrusions 60 formed on at least the upper surface 6a are not oriented and crystallized and are non-crystalline or low-crystalline, so that the protrusions 60 are formed at a relatively low temperature (for example, about 70 ° C.). (At temperature), it can be softened or tackified, and exhibits good heat sealability.

  In the above method, the width w of the projection 60 should be large enough to secure a sufficient heat sealing area, and is usually set to about 0.5 to 3.0 mm. If the height h is too small, it becomes difficult to sufficiently suppress the flow of the resin, or a sufficient amount of the resin cannot be secured. It doesn't make much sense to raise it. Therefore, this height is generally set to about 0.1 to 1.0 mm. Further, the protrusion 60 is usually formed in a continuous annular shape over the entire circumference of the flange portion 6. However, as long as the heat seal is performed over the entire circumference of the flange portion 6 by the melt flow at the time of heat sealing, in some cases, the protrusion 60 may be formed. Alternatively, the shape may be an intermittent annular shape.

  On the other hand, in the selective heating crystallization, the flange portion 6 of the preform 2 is not subjected to pressure stretching, and the upper surface 6a side of the flange portion 6 is not thermally crystallized by selective heating. For thermal crystallization. Such selective heating includes a contact type and a radiant type.

  FIG. 14 shows a contact-type selective heating method. In this method, the flange 6 of the preform 2 is sandwiched between an annular mold 70 for cooling and an annular mold 72 for heating. Selective heating is performed in the state. That is, the cooling water passage 70a is provided in the annular mold 70 which is in contact with the upper surface 6a of the flange portion 6, and the upper surface 6a of the flange portion 6 is cooled by flowing cooling water through the cooling water passage 70a. It has become. On the other hand, a band heater 72a is attached to the outer surface of the annular mold 72 that contacts the lower surface 6b of the flange portion 6, so that the lower surface 6b of the flange portion 6a can be heated.

  That is, in the method of FIG. 14, the lower heating annular mold 72 is used to lower the lower surface 6 b of the flange portion 6 from the crystallization start temperature (Tic) to the melting point (Tm), particularly the melting point (Tm) −10 ° C. or lower. By heating to the temperature and cooling by the upper cooling annular mold 70, the temperature of the upper surface 6a of the flange portion 6a is prevented from becoming higher than the crystallization start temperature (Tic).

  FIG. 15 shows a selective heating method using a radiant heat method. In this method, the lower side of the preform 2 is supported by the annular support 74 so that the lower surface 6b of the flange portion 6 is exposed. In this state, a cooling annular mold 70 similar to that used in FIG. 14 is disposed in contact with the upper surface of the flange portion 6. A heater 76 (for example, an infrared heater) that can heat the lower surface 6b of the flange portion 6 with radiant heat is disposed at an appropriate interval outside the flange portion 6.

  That is, in the method of FIG. 15, the lower surface 6b of the flange portion 6 is heated to a temperature equal to or higher than the crystallization start temperature (Tic) to lower than the melting point (Tm), particularly, equal to or lower than the melting point (Tm) -10 ° C. by radiant heating by the heater 76. Further, the temperature of the upper surface 6a of the flange portion 6 is prevented from being higher than the crystallization start temperature (Tic) due to the cooling by the upper cooling annular mold 70.

  As described above, according to the selective heating shown in FIGS. 14 and 15, as shown in FIG. 16, an amorphous or low-crystalline portion 80 is formed in a layer on the upper surface 6 a of the flange portion 6, and this portion 80 is formed. The remaining part is thermally crystallized. Accordingly, the flange portion 6 exhibits excellent heat resistance due to thermal crystallization and, at the same time, exhibits excellent heat sealing properties due to the presence of the amorphous or low-crystalline portion 80.

  Also, in the method of FIGS. 14 and 15, as shown in FIG. 17, the projection 82 can be formed in an annular shape on the upper surface 6a of the flange portion 6. With the formation of the projections 82, the pressure of the sealing material at the time of heat sealing can be increased, and heat sealing can be performed more effectively.

  When the projections 82 as shown in FIG. 17 are formed and selective heating is performed, for example, the lower surface of the cooling mold 70 (the upper surface of the flange portion 6) used in FIGS. A concave portion (not shown) corresponding to the projection 82 is formed on the contact surface with the projection 6a, and substantially the entire upper surface 6a of the flange portion 6 including the projection 82 contacts the cooling mold 16. It is preferable to keep it. That is, in this case, as shown in FIG. 17A, the amorphous or low-crystalline portion 80 including the protrusion 82 is formed in a layer on the upper surface 6a to secure a sufficient heat sealing area. be able to. If such a concave portion is not formed on the lower surface of the cooling mold 16, only the upper surface of the projection 82 is cooled. For example, as shown in FIG. Amorphous to low crystalline portions 80 are obtained.

  Therefore, as shown in FIG. 17B, when only the portion of the protrusion 82 is made to be the amorphous or low-crystalline portion 80, the size of the protrusion 82 is the same as that of the protrusion 60 shown in FIG. It is preferable that the size is approximately the same as the above. On the other hand, as shown in FIG. 17A, when the amorphous or low-crystalline portion 80 is formed on the entire upper surface 6a including the protrusion 82, the protrusion 82 is smaller than the protrusion 60 in FIG. The protrusion 82 may be formed intermittently.

  In the selective crystallization process of the flange portion 6 described above, for example, the selective orientation crystallization shown in FIG. 13 is performed prior to the thermoforming step of the preform 2 and the selective heating crystallization shown in FIG. 14 and FIG. The formation may be performed prior to the thermoforming step of the preformed body 2 or may be performed simultaneously with the heat setting by heating the oven during the thermoforming step.

  When the selective crystallization process of the flange portion 6 is performed, it is necessary to take care that the upper surface 6a of the flange portion 6 is not heated to a temperature higher than the thermal crystallization temperature in, for example, a thermoforming process. For example, it is preferable to avoid blow molding by heating a mold, and it is desirable to perform blow molding using a cooling mold as shown in FIG. 12 or blow molding by free blow. When the shrinkback is performed by heating and holding the plug member 14, it is desirable to perform the shrinkback while cooling the upper surface 6a of the flange portion 6 with the cooling mold 70 described above.

  As described above, the preferred embodiments of the manufacturing method configured according to the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and does not depart from the scope of the present invention. It should be understood that various changes and modifications are possible. For example, in the above-described embodiment, the pre-molded body 2 formed from a single thermoplastic resin is injection-molded, and then the pre-molded body 2 is thermoformed. It is also possible to manufacture a container by injection-molding a pre-molded article having a multilayer structure composed of an additional thermoplastic resin wrapped in a thermoplastic resin, and thermoforming the pre-molded article. Examples of the additional thermoplastic resin include a resin having excellent gas barrier properties, a recycled resin, an oxygen-absorbing resin, and a moisture-resistant resin.

FIG. 3 is a cross-sectional view showing a pre-formed body that has been injection-molded. Sectional drawing which shows the state which supplied the pre-molded body to the thermoforming apparatus in the suitable embodiment of the manufacturing method of the thermoplastic resin container comprised according to this invention. FIG. 3 is a cross-sectional view showing a mode in which a flange portion of a preformed body is stretched under pressure in the thermoforming apparatus of FIG. 2. FIG. 3 is a cross-sectional view showing a mode in which a thermoforming main part of a preformed body is stretched by a stretching rod in the thermoforming apparatus of FIG. 2. FIG. 3 is a cross-sectional view showing a method of blow molding the main part of the preformed body in the thermoforming apparatus of FIG. 2. FIG. 3 is a cross-sectional view showing a mode of shrinking back a thermoformed main part of a preformed body in the thermoforming apparatus of FIG. 2. Sectional drawing which shows the container completed by trimming the flange. Sectional drawing which shows the state which supplied the preforming body to the thermoforming apparatus in other embodiment of the manufacturing method of the thermoplastic resin container comprised according to this invention. FIG. 9 is a cross-sectional view showing a manner in which the flange portion of the pre-formed body is stretched under pressure in the thermoforming device of FIG. 8. FIG. 9 is a cross-sectional view showing a mode in which the thermoforming main part of the preform is free blown in the thermoforming apparatus of FIG. 8. FIG. 9 is a cross-sectional view showing a mode of shrinking back the thermoformed main part of the preformed body in the thermoforming apparatus of FIG. 8. FIG. 9 is a process chart showing a process of still another embodiment of the method for producing a thermoplastic resin container of the present invention. The figure which shows the example of the selective orientation crystallization method for performing the selective crystallization process of a flange part. The figure which shows an example (contact type selective heating) of the selective thermal crystallization method for performing the selective crystallization process of a flange part. The figure which shows an example (radiative heat type selective heating) of the selective thermal crystallization method for performing the selective crystallization process of a flange part. The figure which shows an example of the state of the flange part obtained by the selective crystallization process of a flange part. The figure which shows the other example of the state of the flange part obtained by the selective crystallization process of a flange part.

Explanation of reference numerals

2: Pre-molded body 4: Thermoforming main part 6: Flange part 6a: Upper surface of flange part 6b: Lower surface of flange part 8: Thermoforming device 10: Female molding member 12: Pressing / tightening member 14: Plug member 16: Stretched rod 26: Container 50: Intermediate molded body 60: Protrusion provided on the upper surface of flange 70: Cooling mold 72: Heating mold 80: Amorphous to low crystal part 108: Thermoforming device 110: receiving member 112: pressing / tightening member 114: plug member

Claims (23)

In a method of manufacturing a thermoplastic resin container including a pre-molded body molding step of molding a thermoplastic resin pre-molded body, and a thermoforming step of thermoforming the pre-molded body to form a cup-shaped thermoplastic resin container,
The thermoforming step includes blow molding and stretching the preformed body, heating and heat setting, and then shrinking back into a molded shape of a plug member, shaping, and cooling. Manufacturing method.   The method according to claim 1, wherein in the thermoforming step, the preformed body is heated to a temperature equal to or higher than a glass transition temperature and lower than a crystallization start temperature.   The method according to claim 1 or 2, wherein the thermoforming step includes stretching in an axial direction by a stretching rod before the blow molding.   The heat-fixing method according to any one of claims 1 to 3, wherein the pre-formed body is heat-set by being formed into a shape of a female mold member heated to a temperature higher than a crystallization start temperature and lower than a melting point by the blow molding. Production method.   The method according to claim 1, wherein in the thermoforming step, the preformed body is subjected to free blow molding, and then heated in a heating oven and heat-set.   In the thermoforming step, the plug member is inserted into the blow-molded and stretched pre-formed body, heated in an oven in this state, heat-fixed, and then shrink-backed into the shape of the plug member to shape it. The production method according to claim 3.   The method according to claim 1, wherein a temperature of the plug member is lower than a crystallization start temperature or higher than a crystallization start temperature.   The production method according to claim 3, wherein a tip diameter of the stretched rod is 0.3 times or more and less than 1.0 times a bottom diameter of the final molded body.   The manufacturing method according to any one of claims 1 to 7, wherein a bottom shaping die is pressed against the final formed body shaped into the shape of the plug member, and further shaping is performed.   The production method according to claim 9, wherein the temperature of the bottom shaping mold is equal to or higher than the crystallization start temperature and lower than the melting point.   The manufacturing method according to any one of claims 1 to 7, wherein cooling is performed by spraying a cooling blow on the final molded body formed into the shape of the plug member.   The manufacturing method according to any one of claims 1 to 11, wherein the shrink bank is performed by vacuum and / or pressure forming.   The manufacturing method according to any one of claims 1 to 12, wherein the preformed body is injection-molded in the preformed body forming step.   The production method according to any one of claims 1 to 12, wherein the preformed body is compression-molded in the preformed body forming step.   The preformed body is composed of a thermoformed main part and a flange part, and a flange part crystallization treatment step in which the flange part is heated to a temperature equal to or higher than the glass transition point and lower than the melting point to be stretched under pressure and crystallized. The method according to any one of claims 1 to 14, comprising:   The pre-formed body is composed of a thermoformed main part and a flange part, and includes a flange part crystallization treatment step of heating the flange part to a temperature higher than a crystallization start temperature and lower than a melting point to cause crystallization. 15. The production method according to any one of 1 to 14.   17. The manufacturing method according to claim 15, wherein the flange portion crystallization step is performed after the preformed body forming step and before the thermoforming step.   The method according to any one of claims 15 to 17, further comprising a trimming step of trimming the flange portion into a required shape after the thermoforming step.   The method according to any one of claims 1 to 18, wherein the preform has a multilayer structure. In a method for producing a thermoplastic resin container including a thermoforming step of forming a cup-shaped thermoplastic resin container by thermoforming a thermoplastic resin preform comprising a thermoformed main portion and a flange portion,
The thermoforming step includes a step of blow-molding and stretching the thermoformed main part of the preformed body, heating and heat-setting, then shrinking back to the molded shape of the plug member, shaping, and cooling. While
Prior to or during the thermoforming step, the lower surface of the flange portion is selectively crystallized so that at least an amorphous or low crystalline heat seal portion remains on the upper surface side of the flange portion. A manufacturing method, wherein a selective crystallization process of a flange portion is performed.   A convex portion serving as a heat seal portion is provided on the upper surface of the flange portion, and in the flange portion selective crystallization process, by performing pressure stretching of the flange portion while controlling the flow of the convex portion. The method according to claim 20, wherein the lower surface of the flange portion is selectively oriented and crystallized.   22. The method according to claim 21, wherein the flange portion selective crystallization process is performed prior to the thermoforming process.   In the flange portion selective crystallization step, the lower surface side of the flange portion is kept at a temperature higher than the crystallization start temperature and lower than the melting point while maintaining at least a part of the upper surface side of the flange portion below the crystallization start temperature. The manufacturing method according to claim 17, wherein the lower surface of the flange portion is selectively thermally crystallized by selectively heating.

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