JP2011235606A - Method for manufacturing of foaming polyethylene terephthalate sheet molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control cost concerning molding and to inhibit degradation of quality of a molding.SOLUTION: A method for manufacturing of a foaming polyethylene terephthalate sheet molding includes: step S2 which performs heating to a condition in which a foaming polyethylene terephthalate sheet of high crystallinity is softened to be molded; and step S3 in which the foaming polyethylene terephthalate sheet of high crystallinity which has been heated to a condition to be softened to be molded is molded with a mold heated at a thermal deformation temperature and which performs molding of an inhibition section P2 which inhibits a force added to the molding section around a molding section P1 becoming a molding.

Description

  The present invention relates to a method for producing a foamed polyethylene terephthalate sheet molded article.

Conventionally, a method of forming a crystalline foamed polyethylene terephthalate sheet by heat is known.
In this molding method, a sheet made of a crystalline foamed polyethylene terephthalate sheet is heated until it is softened in a preheating process, and then the softened sheet is conveyed to the molding process for molding.
However, when the sheet is heated to a temperature necessary for forming the sheet in the preheating step, the sheet is softened and contraction and distortion occur. When a sheet having contraction and distortion is formed with a heated mold, further distortion occurs in the sheet. Further, when the mold is removed from the sheet after the sheet is formed, there is a problem that the shape of the molded product is greatly different from the designed one due to the shrinkage or distortion of the sheet that occurs during preheating or molding. Occurrence of such a problem greatly reduces the yield and adversely affects the production efficiency of the molded product.

In order to solve such problems, the molded sheet is cooled using a mold maintained at a temperature lower than the temperature necessary for forming the sheet, and the rigidity around the molded product is increased and the sheet is contracted and distorted. A method of strengthening has been proposed (see, for example, Patent Document 1).
Specifically, as shown in FIG. 6, a sheet 101 made of crystalline foamed polyethylene terephthalate is conveyed to an oven 102, and is a temperature necessary for forming the sheet 101 and less than a temperature that promotes crystallization of the sheet 101. Preheat with.
Next, using the mold 103 heated to a temperature that promotes crystallization of the sheet 101, the sheet 101 is formed into a desired shape and crystallized.
Finally, the sheet 101 is cooled using the mold 104 maintained at a temperature lower than the temperature necessary for forming the sheet 101.

Japanese Patent No. 2551854

  However, the molding method described in Patent Document 1 requires a cooling mold that is separate from the mold used at the time of molding, which increases the cost of the mold. In addition, since the sheet is formed twice by the mold during molding and the mold during cooling, if there is a misalignment during the conveyance of the sheet, a misalignment occurs in the finished molded product. End up.

  The present invention has been made in order to solve the above-described problems, and provides a method for producing a foamed polyethylene terephthalate sheet molded product capable of suppressing the deterioration of the quality of the molded product while suppressing the cost for molding. For the purpose.

In order to solve the above problems, in the method for producing a foamed polyethylene terephthalate sheet molded article according to the present invention,
Heating until the high crystallinity foamed polyethylene terephthalate sheet is softened into a moldable state;
A foamed polyethylene terephthalate sheet having a high crystallinity heated until it is softened into a moldable state is molded with a mold heated to a heat distortion temperature, and the molded product part is formed around the molded product part that becomes a molded product. Forming a restraining portion that suppresses the force applied to the
It is characterized by having.

Moreover, in the method for producing a foamed polyethylene terephthalate sheet molded article according to the present invention,
The molding of the restraining part is characterized by forming a concavo-convex shape or a planar shape around a molded product part that becomes a molded product.

Moreover, in the method for producing a foamed polyethylene terephthalate sheet molded article according to the present invention,
When the foamed polyethylene terephthalate sheet having a high crystallinity is molded by the molding die, the suppressing portion is molded so as to surround the periphery of the molded product portion.

Moreover, in the method for producing a foamed polyethylene terephthalate sheet molded article according to the present invention,
The suppression part is formed while cooling the heated polyethylene terephthalate sheet having a high crystallinity.

According to the present invention, when the foamed polyethylene terephthalate sheet having a high degree of crystallinity is molded by the molding die, the suppression part is molded around the molded part, so that the foamed polyethylene having a high degree of crystallinity generated at the time of heating or molding. It is possible to suppress the force due to the shrinkage and distortion of the terephthalate sheet from being transmitted to the molded product part by the suppressing unit.
Thereby, since the shaping | molding die which cools a molded article part after shaping | molding becomes unnecessary, the cost concerning shaping | molding can be suppressed. Moreover, since shrinkage | contraction and distortion of a highly crystalline foamed polyethylene terephthalate sheet | seat can be suppressed, the fall of the quality of a molded article can be suppressed.

The figure which showed the outline | summary of the shaping | molding apparatus. The top view drawn simplified in order to show the position and magnitude | size of each part of the shaping | molding apparatus of FIG. The block diagram explaining each structure connected to a control part. The flowchart which shows the manufacturing method of the molded article using a sheet | seat. The figure which shows the other form of a shaping | molding apparatus in FIG. The figure which showed the outline | summary of the conventional shaping | molding apparatus.

  An embodiment of a method for producing a foamed polyethylene terephthalate sheet molded article according to the present invention will be described. Below, a foamed polyethylene terephthalate sheet is demonstrated first, the shaping | molding apparatus for shape | molding next is demonstrated, and the manufacturing method of the foamed polyethylene terephthalate sheet molded product using a shaping | molding apparatus is demonstrated after that.

<Polyethylene terephthalate sheet>
A foamed polyethylene terephthalate sheet (hereinafter referred to as a sheet) is a sheet having high crystallinity and thermoplasticity.
As the sheet, for example, a polyethylene terephthalate extruded sheet is impregnated with carbon dioxide under high pressure and then heated and foamed, and a fine foamed sheet having an internal cell diameter of 50 μm or less (for example, Furukawa Electric) MCPET (registered trademark) manufactured by Kogyo Co., Ltd.). The sheet has a skin layer and a foam layer. Here, the skin layer refers to a surface layer without bubbles.
Specifically, a sheet having a thickness of 1 mm, an expansion ratio of 3 to 4 times, an average cell diameter of 10 μm, and a crystallinity of 30% or more, preferably 37 to 40% (so-called high crystallinity) is used. It is done. If this sheet is just manufactured, the inert gas contained in the sheet expands due to the heat of the preheating process and the molding process, so that secondary foaming occurs in the sheet, and after heating There is a problem that the shrinkage and deformation of the sheet and molded product are large. Therefore, it is preferable to leave the sheet at a normal temperature during which the inert gas remaining on the sheet is released (10 days or more), or as another method, to leave the sheet in an atmosphere at 50 ° C. for 48 hours to remove the inert gas.

<Molding device>
FIG. 1 is a diagram showing an outline of the molding apparatus 100, and FIG. 2 is a simplified plan view illustrating the position and size of each part of the molding apparatus 100 of FIG. FIG. 3 is a block diagram illustrating each configuration connected to the control unit.
As shown in FIG. 1, the molding apparatus 100 includes a conveyance supply unit 1, a preheating unit 2, a molding unit 3, a cooling unit 4, and a control unit 5 (see FIG. 3). The forming apparatus 100 is arranged in the order of the preliminary heating unit 2, the forming unit 3, and the cooling unit 4 from the upstream side in the conveyance direction of the sheet S conveyed by the conveyance supply unit 1. The forming apparatus 100 heats, forms, and cools different portions of the sheet S by the preheating unit 2, the forming unit 3, and the cooling unit 4 while intermittently conveying the sheet S by the conveyance supply unit 1. Can be performed almost simultaneously.

(Conveying supply unit)
As shown in FIGS. 1 and 2, the conveyance supply unit 1 conveys the sheet S to the preheating unit 2, the forming unit 3, and the cooling unit 4. The conveyance supply unit 1 includes a shaft 11, a spike chain 12, and a cutter 13.
The shaft 11 is mounted with a sheet S winding, and rotatably supports the sheet S winding. Accordingly, the shaft 11 is disposed on the most upstream side in the conveyance direction of the sheet S.
The spike chain 12 feeds the sheet S from the winding and intermittently conveys the sheet S. The spike chain 12 is arranged along the conveying direction of the sheet S, and is arranged above both opposing edges along the conveying direction of the sheet S.
The cutter 13 is for individually cutting the molded products molded by the molding unit 3 and cooled by the cooling unit 4 one by one. Therefore, the cutter 13 is disposed downstream of the cooling unit 4 in the conveyance direction of the sheet S.

(Preheating part)
As shown in FIGS. 1 and 2, the preheating unit 2 is a place where the sheet S fed out from the winding is first guided, and preheats the sheet S before forming. The preheating unit 2 heats the sheet S conveyed by the spike chain 12 from the upper surface side and the lower surface side. The preheating unit 2 includes far infrared heaters 21 and 22 and a radiation thermometer 23.
The far-infrared heaters 21 and 22 are arranged at a certain interval above and below the sheet S conveyed together. The far-infrared heater 21 is disposed so as to face the upper surface of the conveyed sheet S, and heats the sheet S from the upper surface side. The far infrared heater 22 is disposed so as to face the lower surface of the conveyed sheet S, and heats the sheet S from the lower surface side.
As shown in FIG. 2, the far-infrared heaters 21 and 22 are formed in a rectangular shape in plan view, and are sized to cover the area of the sheet S necessary for one molding.
The radiation thermometer 23 is disposed on the surface of the far infrared heater 21 facing the sheet S, and measures the temperature near the surface of the sheet S.

  The far-infrared heaters 21 and 22 are connected to the control unit 5 (see FIG. 3) and controlled by the control unit 5. That is, the control unit 5 controls the amount of current that flows through the far-infrared heaters 21 and 22 based on the measured temperature value from the radiation thermometer 23 so that the sheet S is maintained at a temperature at which it can be molded. . In this way, temperature control by the control unit 5 is performed so that the temperature of the space between the far infrared heaters 21 and 22 is maintained at a temperature at which the sheet S is softened into a formable state. This temperature is set in advance and stored in a memory in the control unit 5.

(Molding part)
As shown in FIGS. 1 and 2, the forming unit 3 is arranged on the downstream side in the transport direction of the sheet S in the preheating unit 2. The forming unit 3 is formed by sandwiching the heated sheet S from above and below. Here, the forming method is a known method such as vacuum forming.
The molding unit 3 includes a cavity 31, a core 32, molding die drive units 33 and 34, and flat plate molding die units 35 and 36.

The cavity 31 is disposed above the conveyance path of the sheet S. That is, the cavity 31 is arranged at a position facing the core 32 with the sheet S interposed therebetween. The cavity 31 is fixed to the base 37. The cavity 31 is formed in a concave shape that is complementary to the core 32. A heater 31 a is embedded in the cavity 31 and is heated to a temperature at which the sheet S is thermally deformed under temperature control by the control unit 5.
The core 32 is disposed below the conveyance path of the sheet S. That is, the core 32 is disposed at a position facing the cavity 31 with the sheet S interposed therebetween. The core 32 is fixed to the base 38. The core 32 is formed in a convex shape that is complementary to the cavity 31. A heater 32 a is embedded in the core 32 and is heated to a temperature at which the sheet S is thermally deformed under temperature management by the control unit 5.

The mold drive unit 33 moves the base 37 along the vertical direction. That is, the mold drive unit 33 serves as a drive source that allows the cavity 31 provided on the base 37 to be brought into and out of contact with the sheet S.
The mold drive unit 34 moves the base 38 along the vertical direction. That is, the mold drive unit 34 serves as a drive source that allows the core 32 provided on the base 38 to be brought into and out of contact with the sheet S.
The mold drive units 33 and 34 are connected to the control unit 5, and the drive is controlled by the control unit 5.

The flat plate mold part 35 is provided on the base 37. The flat plate mold part 35 is provided in the vicinity of the cavity 31, and when the sheet S is formed by the cavity 31 and the core 32, around the molded product part P1 (see FIG. 1) that becomes a molded product. The suppression part P2 (refer FIG. 1) which suppresses the force added to the said molded article part P1 can be shape | molded. The lower end part of the flat plate mold part 35 and the lower end part of the cavity 31 are formed at the same height. Thereby, the flat plate mold part 35 can perform planar shaping | molding as a suppression part.
The flat plate mold part 36 is provided on a base 38. The flat plate mold portion 36 is provided in the vicinity of the core 32, and when the sheet S is formed by the cavity 31 and the core 32, the molded product portion P1 is formed around the molded product portion P1 to be a molded product. It is possible to form the suppressing portion P2 that suppresses the force applied to the. The upper end portion of the flat plate mold portion 36 and the bottom portion of the core 32 are formed at the same height. Thereby, the flat plate mold part 36 can perform planar shape as a suppressing part.
The flat plate mold portions 35 and 36 are preferably formed so as to extend over almost the entire width of the sheet S so as to extend in a direction orthogonal to the conveying direction of the sheet S. Thereby, the rigidity of the whole sheet | seat S can be improved and the molded article part P1 can be protected from the force added to the molded article part P1.
Since the flat plate mold portions 35 and 36 also serve to cool the sheet S in the vicinity of the molded product portion P1 which is a molded product in the sheet S, a flow path of water or oil is provided in the flat plate mold portions 35 and 36. It is preferable to set and flow and keep the temperature as low as about 40 ° C. If the temperature of the flat plate mold portions 35 and 36 exceeds the thermal deformation temperature of the sheet P, the effect of increasing the rigidity of the sheet S cannot be obtained, and the force applied to the molded product portion P1 by thermal deformation is not obtained. It cannot be suppressed.

(Cooling section)
As shown in FIGS. 1 and 2, the cooling unit 4 is disposed on the downstream side in the conveyance direction of the sheet S in the forming unit 3. The cooling unit 4 cools the sheet S by blowing wind on the formed sheet S from above and below.
The cooling unit 4 includes two air blows 41 and 42.
The air blow 41 is disposed above the conveyance path of the sheet S. That is, the air blow 41 cools the sheet S by blowing air from the upper surface side to the sheet S.
The air blow 42 is disposed below the conveyance path of the sheet S. That is, the air blow 42 cools the sheet S by blowing air from the lower surface side to the sheet S.
The air blows 41 and 42 are connected to the control unit 5, and the drive is controlled by the control unit 5.

(Control part)
As shown in FIG. 3, the control unit 5 controls each drive unit of the molding apparatus 100.
The control unit 5 includes a known CPU, ROM, RAM, and the like.
The control unit 5 includes far-infrared heaters 21 and 22, a radiation thermometer 23, a heater 31 a that heats the cavity 31, a heater 32 a that heats the core 32, mold drive units 33 and 34, and a spike chain that drives the spike chain 12. The drive unit 15, the cutter drive unit 16 that drives the cutter 13, and the air blows 41 and 42 are connected.

<Method for producing foamed polyethylene terephthalate sheet molding>
FIG. 4 is a flowchart showing a method of manufacturing a molded product using the sheet S.
As shown in FIG. 4, when manufacturing a molded product from the sheet S, the spike chain 12 of the conveyance supply unit 1 is driven, the sheet S is unwound and conveyed toward the preheating unit 2 (step). S1).
The sheet S conveyed to the preheating unit 2 is heated until it is softened into a formable state by the far infrared heaters 21 and 22 under temperature control by the radiation thermometer 23 and the control unit 5 (step S2).
The sheet S heated until it is softened to a formable state by the far infrared heaters 21 and 22 is conveyed to the forming unit 3 by the spike chain 12.

In the molding unit 3, the control unit 5 drives the molding die driving units 33 and 34 to sandwich the sheet S between the cavity 31 and the core 32, and molding the molded product part P <b> 1 according to the shape of the cavity 31 and the core 32. Is performed (step S3). Simultaneously with the formation of the sheet S by the cavity 31 and the core 32, the flat suppression part P2 is formed around the portion to be the molded product of the sheet S by the flat plate forming part 35 and the flat plate forming part 36 (step). S3).
Here, since the molding of the planar suppressing portion P2 is performed using the flat plate molding die portions 35 and 36 adjusted to a temperature lower than that of the cavity 31 and the core 32, it is heated by the preheating portion 2 and the molding portion 3. This is done while cooling the sheet S.
The sheet S formed in the forming unit 3 is conveyed to the cooling unit 4 by the spike chain 12.

In the cooling unit 4, the control unit 5 drives the air blows 41 and 42 to cool the sheet S from the upper surface and the lower surface (step S4).
The sheet S cooled in the cooling unit 4 is cut into one molded part P1 by the cutter 13 (step S5).
A molded product is manufactured from the sheet S by the above processing.

<Action and effect>
As described above, according to the method of manufacturing a molded product manufactured from the sheet S, the molded product portion P1 of the high crystallinity sheet S is formed when the high crystallinity sheet S is formed by the cavity 31 and the core 32. Since the planar suppressing portion P2 is formed around the periphery, the planar suppressing portion P2 can suppress the shrinkage and distortion of the sheet S of high crystallinity generated during heating or molding.
Thereby, since the shaping | molding die which cools the molded article part P1 after shaping | molding becomes unnecessary, the cost concerning shaping | molding can be suppressed. Moreover, since the shrinkage | contraction and distortion of the sheet | seat S of high crystallinity degree can be suppressed, the fall of the quality of a molded product can be suppressed.
As a result, the yield is improved and the productivity is greatly improved.

<Others>
The present invention is not limited to the above embodiment. For example, the suppressing portion P2 is not limited to the flat shape forming by the flat plate forming die portions 35 and 36, and the uneven shape may be formed on the surface of the sheet S. Moreover, the shape and size of the flat plate mold portions 35 and 36 are arbitrary and can be freely changed.
Further, as shown in FIG. 5, an annular flat plate forming mold portion 60 surrounding the periphery of each core 32 is formed on the base 38, and when the sheet S is formed, the planar suppressing portion is surrounded so as to surround the periphery of the forming portion. Molding may be performed. If comprised in this way, even if the sheet | seat S will shrink | contract or distort after a shaping | molding, it can absorb with the planar suppression part which exists around, and suppresses the fall of the quality of a molded product. Can do.
In this case as well, the suppressing portion is not limited to the flat shape, and the concave portion may be formed on the surface of the sheet S.
Here, the concave / convex shape may be formed in any shape as long as the concave / convex shape is formed on the surface of the sheet. That is, if the sheet is formed into a concavo-convex shape or a flat shape, distortion and shrinkage of the molded product portion can be suppressed, the forming method is not limited, and the shape of the suppressing portion is not limited.

DESCRIPTION OF SYMBOLS 1 Conveying supply part 2 Preheating part 3 Molding part 4 Cooling part 5 Control part 100 Molding apparatus P1 Molded product part P2 Control part S Sheet (foamed polyethylene terephthalate sheet)

Claims (4)

Heating until the high crystallinity foamed polyethylene terephthalate sheet is softened into a moldable state;
A foamed polyethylene terephthalate sheet having a high crystallinity heated until it is softened into a moldable state is molded with a mold heated to a heat distortion temperature, and the molded product part is formed around the molded product part that becomes a molded product. Forming a restraining portion that suppresses the force applied to the
A method for producing a foamed polyethylene terephthalate sheet molded article, comprising:   The method for producing a foamed polyethylene terephthalate sheet molded product according to claim 1, wherein the molding of the suppressing portion is performed by forming a concavo-convex shape or a planar shape around a molded product portion to be a molded product.   The foamed polyethylene terephthalate according to claim 1 or 2, wherein when the foamed polyethylene terephthalate sheet having a high crystallinity is molded by the molding die, the suppressing portion is molded so as to surround the periphery of the molded product portion. Manufacturing method of sheet molded product.   The said control part is shape | molded, cooling the foamed polyethylene terephthalate sheet | seat of the high crystallinity heated, Manufacture of the foamed polyethylene terephthalate sheet molded product as described in any one of Claims 1-3 characterized by the above-mentioned. Method.

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