JP2007223141A - Manufacturing process of foamed molding and foamed molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly form a foamed molding having a selectively formed foam layer. <P>SOLUTION: Before the preheating process the preform 10 is in advance impregnated with gas bubbles, then in the preheating process the part to be heated 12 excluding at least a part of the preform 10 is heated and softened, thereafter in the molding process the part to be heated 12 of the preform 10 is molded, and in these preheating and molding processes, by the heat acting on the part 12 to be heated of the preform 10, the gas bubbles, of the above gas bubbles, impregnated into the part to be heated 12 of the preform 10 are selectively expanded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a foamed molded product having a foamed layer and a foamed molded product.

In general, this type of foamed molded body is softened by a preheating step in which a preformed body made of a resin material is heated and softened until it becomes moldable, for example, as shown in Patent Documents 1 to 4 below. The molding is performed in this order through a molding process in which a preform is molded to form a foam molded body.
And conventionally, after mixing the foaming agent into the molten resin, the resin is molded to form a preform, and then the preform is sequentially subjected to the preheating step and the molding step described above, and the process The foaming agent is foamed to generate bubbles, and the bubbles are further grown to form a foam molded article having a foam layer. In addition, the surface of the foaming molding which has this foaming layer becomes uneven | corrugated shape.
By the way, in recent years, there is a demand for a configuration in which a foamed layer is not partially formed in a foam molded article. For example, if a foamed layer is formed in the mouth of the molded body and the surface of the mouth becomes uneven, when a cap is screwed or fitted into the mouth, a good sealing property is provided between them. If the content is a beverage, or if the customer drinks the content with a mouth on the mouth, the uneven shape makes the lips feel uncomfortable. There is a problem that there is a risk of feeling.
Japanese Patent No. 3090398 Japanese Patent Laid-Open No. 10-329203 Japanese Patent Laid-Open No. 11-156923 JP-A 61-53021

  However, in the manufacturing method of the conventional foamed molded product, after the foaming agent is mixed into the molten resin, this resin is molded to form a preformed body. Therefore, due to the heat at the time of mixing and molding, At the stage of the preform, the foaming agent is already foamed in the entire area of the preform to generate bubbles, and further, the bubbles may grow. There is a problem that it is difficult to realize the configuration.

  The present invention has been made in view of such circumstances, and provides a method for producing a foam molded body and a foam molded body capable of reliably forming a foam molded body in which an unfoamed portion is selectively formed. The purpose is to do.

  In order to solve the above-described problems and achieve such an object, the method for producing a foamed molded article of the present invention is a preheating process in which a preformed article made of a resin material is heated and softened until it becomes moldable. A foamed molded body manufacturing method comprising a step and a molding step of forming a foamed molded body by forming a softened molded body, wherein the preformed body is impregnated with bubbles in advance before the preheating step. Thereafter, in the preheating step, the heated portion excluding at least a part of the preform is heated and softened, and then the heated portion of the preform is molded in the molding step, and these preheating steps are performed. In the molding step, the air that is impregnated in the heated portion of the preform is selectively expanded by heat acting on the heated portion of the preform.

In the present invention, since the solid preform is impregnated with the bubbles in advance before the preheating step, it is possible to suppress the growth of bubbles inside the preform at the stage of the preform. It can prevent that the surface of a preforming body becomes uneven | corrugated shape over the whole region. Therefore, only the bubbles contained in the heated portion among the bubbles contained in the preform are obtained by applying heat to the heated portion of the preform in a preheating step and a molding step. It is possible to selectively inflate, and it is possible to prevent a foamed layer from being formed in a portion corresponding to the at least part of the foamed molded body, thereby preventing the surface from being uneven.
As described above, the foamed layer is formed only in the heated portion, and the foamed molded body in which the foamed layer is not formed can be reliably formed in the other portions.
Furthermore, it becomes possible to form a foamed layer only from a resin material without mixing a foaming agent, a filler, etc. into the resin material, and it is possible to form a foamed molded article excellent in recyclability.
In addition, since the preheating step and the molding step can be applied with the current method and apparatus as they are, it is possible to reduce the obstruction factor when the manufacturing method of the present invention is performed.
Moreover, it becomes possible to make the said foaming layer act also as a heat insulation layer, and the heat retention of the contents can be improved.
Furthermore, since the portion where the foamed layer is formed on the outer surface of the foam molded body has an uneven shape, it becomes possible to make the tactile sensation felt by the user's hand gripping this portion, The consumer's willingness to purchase can be aroused by touching the foamed molded product.
In addition, since the foam layer has a network structure having a large number of bubbles, it is possible to reduce the weight while maintaining the mechanical strength such as the rigidity and buckling strength of the foam molded body.

Here, the molding step may be blow molding.
In this case, when the preform is impregnated with bubbles and the resin material is stretched, a large number of fine bubbles with a diameter of several microns are newly generated in addition to the bubbles that grow by the heating. Thus, the formed foam layer can be provided with good light shielding properties (visible light, ultraviolet light, etc.). Accordingly, it is not necessary to use, for example, a resin material containing a pigment or to wrap a shrink label around the body of the foam molded body in order to provide the foam molded body with light shielding properties. This makes it possible to form a recyclable foamed molded product and reduce the manufacturing cost of the molded product.

  The preform may be a bottomed cylindrical body having a mouth, and the heated portion may be a portion of the preform that excludes the mouth.

In this case, a foamed layer is formed in a portion of the foamed molded product excluding the mouth portion, and no foamed layer is formed in the mouth portion. Therefore, the surface of the mouth portion can be made substantially smooth. Therefore, for example, when a cap is screwed or fitted into the mouth portion, it is possible to provide a good sealing property between them, and when the content is a beverage, the consumer attaches a mouth. When drinking the contents, it is possible to prevent the lips from feeling uncomfortable.
In order to form a foamed molded body in which only the mouth portion is thermally crystallized (whitened), before the preform is impregnated with bubbles, only the mouth portion of the preform is heated to be thermally crystallized, and then By impregnating the preform with air bubbles as described above, a foamed layer is formed in a portion of the foamed molded product excluding the mouth, and a foamed layer is not formed in the thermally crystallized mouth. A molded body can be formed.

  Moreover, it is formed by the manufacturing method of the foaming molding in any one of Claim 1 to 3, The foaming layer is selectively formed in the part corresponding to the said to-be-heated part in this foaming molding, And

  According to the method for producing a foamed molded product and the foamed molded product according to the present invention, the formation of the foamed layer can be partially selected, and the foamed molded product in which the unfoamed portion is selectively formed according to the purpose is reliably formed. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. The method for manufacturing a foamed molded body according to the present embodiment includes a preheating step in which the preformed body 10 made of a resin material is heated to soften it until it can be blow-molded, and the softened preformed body 10 is blow-molded. And forming a foamed molded body. The foamed layer is formed only in a certain part and the foamed layer is not formed in the other part.

  A preformed body 10 shown in FIG. 1A is a bottomed cylindrical body having a mouth 11. A male screw portion 11 a is formed on the outer peripheral surface of the mouth portion 11, and protrudes outward in the radial direction below the male screw portion 11 a in the central axis O direction of the pre-formed body 10 on the outer peripheral surface of the mouth portion 11. The support ring 11b is formed. The upper end surface of the mouth portion 11 in the direction of the central axis O is an open end surface 11c.

  The preform 10 is formed of one or more resin materials such as polyester, polyolefin, and biodegradable resin (for example, aliphatic polyester (mainly polylactic acid)). Further, a portion of the preformed body 10 located below the mouth portion 11 in the direction of the central axis O is a molding portion (a heated portion) 12 to be preheated and blow-molded later. The interior of the molded part 12 is a space communicating with the opening end face 11c.

  Then, as shown in FIG. 1 (b), the preform 10 is placed in a pressure resistant container 20 to seal the container 20, and then the inside of the container 20 is heated. A gas G such as nitrogen or carbon dioxide is injected until the internal pressure reaches a predetermined value (for example, about 5 MPa to about 15 MPa). Thereby, the preform 10 is impregnated with bubbles over the entire area.

At this time, by heating the pressure vessel 20 to a temperature higher than the glass transition temperature of the resin material forming the preform 10 (glass transition temperature + 10 ° C. or less), the preform 10 is shaped as described above. It is made to be in a state where bubbles are easily impregnated while being held.
In the present embodiment, for the purpose of obtaining a good foamed state, in the case of the preform 10 made of polyethylene terephthalate resin, the amount of dissolved bubbles is 4.8 ml / g or more and 12.2 ml / It is set in the range of g or less.
Next, the pressure-resistant container 20 is decompressed to normal pressure and cooled, and then the preform 10 is taken out from the pressure-resistant container 20. Prior to decompression, it is desirable to cool to a temperature at which the impregnated bubbles can be prevented from expanding during decompression.

  Then, in the preformed body 10 taken out from the pressure resistant container 20 and impregnated with bubbles, the molded portion 12 excluding the mouth portion 11 is heated and softened until it becomes ready for blow molding (preheating). Process). For example, when the preform 10 is formed of polyethylene terephthalate, the preform 10 is heated until the temperature of the outer surface of the preform 10 is about 70 ° C to about 115 ° C. In this preliminary heating step, it is preferable to reliably prevent heat from being conducted to the mouth portion 11 by shielding the mouth portion 11 with a heat insulating member.

Next, the preheated preform 10 is disposed in the cavity 30a of the biaxially stretched mold 30 as shown in FIG. At this time, the mouth portion 11 of the preform 10 is held by the mouth die 31 in the cavity 30a, and the molding portion 12 of the preform 10 excluding the mouth 11 is disposed in the blow die 32.
The shape of the inner peripheral surface of the blow mold 32 corresponds to the shape of the outer peripheral surface of the portion of the foamed molded product that is located below the mouth portion 11 in the direction of the central axis O.

And air A is blown toward the inside of the preformed body 10 from the opening end surface 11c of the mouth part 11, and only the molding part 12 excluding the mouth part 11 in the preformed body 10 is biaxially stretch blow molded (molding process). .
The heating temperature and the air A blow pressure in these preheating step and molding step can be made substantially equal to those in the case of forming the current blow molded body.

  In this embodiment, the heat acting on the molded part 12 in the preheating step and the molding step, that is, the heating in the preheating step, the transition from the preheating step to the blow molding, and the residual heat at the time of blow molding. By placing the molding part 12 in a state of a predetermined temperature or higher for a predetermined time, the bubbles impregnated in the part 12 are selectively expanded. As a result, in the foamed molded body, a foamed layer is formed over the entire area of the portion corresponding to the molded portion 12 of the preformed body 10, that is, the portion located below the mouth portion 11 in the central axis O direction.

  Furthermore, when the resin material is stretched during the blow molding, a large number of fine bubbles are newly generated in addition to the bubbles growing by the heating, and the surface on which the foam layer is formed in the foam molded product is cloudy. Turn into.

  The foam layer is not limited to the case where bubbles are present over the entire thickness direction of the foamed molded article, but when bubbles are present only on the outer surface side, the bubbles are present only on the inner surface side. Or in the case where bubbles are present on both the outer surface side and the inner surface side except for the central portion in the thickness direction.

The foamed state (bubble diameter, dispersed state, etc.) in the above foamed layer is adjusted, for example, by the gas impregnation conditions, the heating and preheating temperature and time in the preheating step and the molding step, and the heating position and state. Can be set as appropriate.
As an example, by heating the molded part 12 only from the outer surface, it is possible to form a foamed molded article having large bubbles on the outer surface side.
Furthermore, the foamed state can be changed by making the preformed body 10 into a laminated structure and changing the material of the resin material of each layer.

  As described above, according to the method for manufacturing a foamed molded body according to the present embodiment, the solid preformed body 10 is impregnated with bubbles in advance before the preheating step. It is possible to suppress the growth of the bubbles inside, and it is possible to prevent the surface of the preformed body 10 from being uneven over the entire area.

Therefore, only the bubbles contained in the molding part 12 among the bubbles contained in the preform 10 are selected by applying limited heat to the molding part 12 of the preform 10 in the preheating step and the molding step. Therefore, it is possible to prevent the surface from becoming uneven by forming a foam layer in the mouth portion 11.
As described above, the foamed layer is formed only on the portion excluding the mouth portion 11, and a foamed molded body without the foamed layer can be reliably formed on the mouth portion 11.

Furthermore, it is possible to form a foamed layer only from the resin material without mixing a foaming agent, a filler, or the like into the resin material, and it is possible to obtain a foamed molded article excellent in recycling suitability.
In addition, since the preheating step and the molding step can be applied with the current method and apparatus as they are, it is possible to reduce an obstruction factor when the manufacturing method of the present embodiment is performed.

  Further, when the preform 10 impregnated with bubbles is blow-molded and the resin material is stretched, a large number of fine bubbles having a diameter of several μ are newly generated in addition to the bubbles growing by the heating. Therefore, the formed foam layer can be provided with good light shielding properties (visible light, ultraviolet light, etc.). Accordingly, it is not necessary to use, for example, a resin material containing a pigment or to wrap a shrink label around the body of the foam molded body in order to provide the foam molded body with light shielding properties. This makes it possible to form a recyclable foamed molded product and reduce the manufacturing cost of the molded product.

Moreover, it becomes possible to make the said foaming layer act also as a heat insulation layer, and the heat retention of the contents can be improved.
Furthermore, since the portion where the foamed layer is formed on the outer surface of the foam molded body has an uneven shape, it becomes possible to make the tactile sensation felt by the user's hand gripping this portion, The consumer's willingness to purchase can be aroused by touching the foamed molded product.
In addition, since the foam layer has a network structure having a large number of bubbles, it is possible to reduce the weight while maintaining the mechanical strength such as the rigidity and buckling strength of the foam molded body.

  Further, when the preform 10 is impregnated with bubbles, the preform 10 is placed in the pressure-resistant container 20 in a heated state, and gas is injected into the container 20 until the internal pressure reaches a predetermined value. Even if the preform 10 is solid, it can be satisfactorily impregnated with bubbles.

Further, in the present embodiment, the preformed body 10 is a bottomed cylindrical body having a mouth portion 11, and in the preheating step, by heating the molded portion 12 excluding the mouth portion 11 of the preformed body 10, Among the bubbles, the bubbles impregnated in the molded portion 12 of the preform 10 are selectively expanded, so that a foam layer is formed only in a portion corresponding to the molded portion 12 in the foam molded body, Does not form a foam layer, and the surface of the mouth portion 11 can be made substantially smooth.
Therefore, for example, when a cap is screwed or fitted into the mouth portion 11, it becomes possible to provide a good sealing property between them, and when the content is a beverage, It is possible to prevent the user from feeling uncomfortable when touching the contents.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the said embodiment, although the bottomed cylindrical body which has the opening part 11 was shown as the preforming body 10, this form is not specifically limited. Moreover, this preform can be formed by, for example, injection molding, extrusion molding, thermoforming, extrusion blow molding or the like, and the production method thereof is not particularly limited.

  Further, before impregnating the preform 10 with air bubbles, only the mouth portion 11 is heated and thermally crystallized (whitened), the strength of the mouth portion 11 is increased, and then the same as in the above embodiment. After the preform 10 is impregnated with bubbles, a preheating step and a molding step may be performed. In this case, it is possible to form a foamed molded body in which the foamed layer is formed only on the portion excluding the mouth part 11 in the foamed molded body, and the foamed layer is not formed on the thermally crystallized mouth part 11.

  Moreover, in the said embodiment, although the foaming layer was formed only in the part except the mouth part 11 in the foaming molding, instead of this, for example, in the foaming molding, the center of the trunk part from the mouth part 11 The foam layer may be formed only on a portion excluding the portion applied to the upper portion in the axis O direction, or the foam layer may be formed only on the body portion excluding the mouth portion 11 and the bottom portion. The portion where the foam layer is formed and the portion where the foam layer is not formed may be any part of the foam molded article.

Furthermore, the form and use of the foamed molded product are not particularly limited. For example, there are plastic containers filled with various foods such as liquids and semi-fluids, plastic containers such as cups, and chemicals such as detergents. It can be applied to a resin container to be filled.
In addition, when the preform is formed into a sheet shape or a plate shape, the preform that has been preheated can be formed into a foam molded body by thermoforming or the like.

  A foamed layer is formed only in a certain part, and a foamed molded product in which the foamed layer is not formed in the other part can be surely formed.

It is process drawing of the manufacturing method of the foaming molding shown as one Embodiment which concerns on this invention.

Explanation of symbols

10 Pre-formed body 11 Mouth 12 Molded part (heated part)
20 Pressure vessel G Gas

Claims (4)

Manufacture of a foam molded body having a preheating step of heating a preform made of a resin material until it becomes moldable, and a molding step of forming the foamed molded body by molding the softened preform A method,
Prior to the preheating step, the preform is impregnated with bubbles,
Thereafter, in the preheating step, after heating and softening the heated portion excluding at least a portion of the preform, the heated portion of the preform is molded in the molding step,
In these preheating step and molding step, the bubbles acting on the heated portion of the preform are selectively expanded by heat acting on the heated portion of the preform. A method for producing a foamed molded product. In the manufacturing method of the foaming molding of Claim 1,
The method for producing a foam molded article, wherein the molding step is blow molding. In the manufacturing method of the foaming molding of Claim 1 or 2,
The preformed body is a bottomed cylindrical body having a mouth portion, and the heated portion is a portion excluding the mouth portion in the preformed body. It is formed by the manufacturing method of the foaming molding in any one of Claim 1 to 3, The foaming layer is selectively formed in the part corresponding to the said to-be-heated part in this foaming molding, Foam molded body.

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