JP2849513B2 - Molding mold for crystalline thermoplastic resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a crystalline thermoplastic resin sheet to be crystallized in order to add heat resistance to a molded article.

[0002]

2. Description of the Related Art Conventionally, crystalline thermoplastic resin sheets,
For example, a thermoforming method for a non-foamed sheet among crystalline polyethylene terephthalate sheets is well known, and is generally a two-stage molding method using a heating mold and a cooling mold. In many cases, an oven heating method that is not in contact with a sheet has been adopted.

It is known that the amount of heat required for crystallization affects the molding cycle of both non-foamed and foamed crystalline polyethylene terephthalene sheets. Change. However, the temperature of the heating mold could not be raised above a certain level due to the relationship with the mold release. 160 ° C ~ 180 ° at present
It was crystallized with C, and it took about 8 seconds to crystallize from 20% to 25%. In particular, in the case of a foamed sheet, since it is a foam, thermal conductivity is poor, a long time is required for crystallization, productivity is poor, and cost is high.

Therefore, a foamed or non-foamed crystalline polyethylene terephthalate sheet is heated and softened in advance, and the sheet is thermoformed and crystallized in a heating mold provided in two or more sets in series. By cooling, a crystallization time is divided into two or more, and a molding apparatus with improved productivity is provided (JP-A-4-85019).
Reference).

[0005]

By the way, the above-mentioned plurality of heating dies are fixed to a single heating plate having a built-in heating means (such as a cartridge heater) for heating the heating dies. Usually, this heating plate was fixed to the base at a plurality of locations on the peripheral edge. For this reason, when the heating plate thermally expands, the position of the heating mold fixed to the heating plate also changes accordingly. Therefore, the relative positions of the core mold and the cavity mold that constitute the heating mold also shift, and the clearance between the two becomes uneven, and the thickness of the molded product becomes uneven. In particular, the heating plate is subject to thermal deformation that is difficult to predict because deformation is restricted at a plurality of locations.

On the other hand, when the sheet is released from the heating mold after the molding or when the sheet is conveyed to the cooling mold, a non-molded portion of the sheet (not in contact with the heating mold but in contact with the heating plate). Part) shrinks and deforms or elongates, the releasability deteriorates, and the pitch of the molded product is not constant. Also in this case, the precision of the molded product is deteriorated. An object of the present invention is to solve the above technical problems and to provide a molding die for a crystalline thermoplastic resin sheet capable of performing molding with high accuracy.

[0007]

In order to achieve the above object, a mold for forming a crystalline thermoplastic resin sheet according to the present invention comprises a foamed or non-foamed crystalline thermoplastic resin sheet which has been heated and softened in advance. A plurality of sets of dies to be crystallized, a heating die composed of an upper die and a lower die, an upper die mounting plate with a plurality of upper dies, a lower die mounting plate with a plurality of lower dies, and each mounting plate A molding die provided with heating means provided respectively, a part of each of the mounting plates facing each other is fixed to a vertically movable press base, and the other part is a plate surface of the mounting plate. And is slidably supported on the press base so as to allow free thermal expansion in the direction along.

In addition, a pair of clamps which are movable vertically in relation to each mounting plate, have through holes for penetrating the heating mold, and hold the trimmed portion of the sheet during molding. A plate may be provided, and a cooling path may be provided inside the clamp plate.

[0009]

According to the above-described mold for forming a crystalline thermoplastic resin sheet, each mounting plate can freely expand in the direction along the plate surface, centering on a part fixed to the press base. it can. Moreover, since the portions of the mounting plates facing each other are fixed, the pair of upper and lower dies mounted on each mounting plate is displaced from the fixed portion due to expansion. Are equal. Therefore, the clearance between the upper mold and the lower mold in the clamped state can be made uniform regardless of the thermal expansion at the time of molding.

In the case where a clamp plate having the above cooling path is provided, only the molded portion of the sheet that comes into contact with the heating mold is heated and crystallized during molding, and the non-molded portion of the sheet (trimmed portion) is formed. Portion) can be cooled to a temperature that does not cause crystallization. Therefore, at the time of mold release or the like, the mold releasability or sheet transportability does not deteriorate due to shrinkage and deformation of the non-molded portion of the sheet.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 2 is a schematic view showing a molding process of a crystalline polyethylene terephthalate sheet as a crystalline thermoplastic resin sheet. Referring to FIG. 3, reference numeral A denotes a preheating softening zone, in which the crystalline polyethylene terephthalate sheet S is preheated to about 120 ° C. to 140 ° C. by oven heating using infrared heaters 10, 10 ′ and the like. The preheating may be performed by sandwiching and contacting the crystalline polyethylene terephthalate sheet S with a plurality of sets of preheating plates (not shown) provided vertically and horizontally.

B is a thermoforming crystallization zone,
A plurality of sets of heating molds 20 and 20 ′ at a temperature of ° C to 185 ° C are provided vertically and horizontally to heat-mold and crystallize the crystalline polyethylene terephthalate sheet S. C is a cooling zone,
A plurality of sets of cooling dies 30, 30 'are provided vertically and horizontally at 35 ° C (only one set is shown in the figure for simplicity), and the formed and crystallized sheet is cooled and collected as a molded product. .

The crystalline polyethylene terephthalate sheet includes a non-foamed sheet and a sheet expanded 2 to 10 times. In the above-mentioned use device, the sheet is fed to each zone without error using a high-precision feeding mechanism (not shown). FIG. 1 shows a molding die P according to the present embodiment, which is arranged in the heat molding crystallization zone B. Referring to FIG. 1, a molding die P includes a plurality of sets of a lower die 20 as a core die and an upper die 20 ′ as a cavity die as a heating die, and a lower die mounting plate 3 and an upper die, respectively. It is mounted vertically and horizontally on the mounting plate 3 'so that a plurality of molded products can be molded at the same time.

A portion of the molding die P relating to the lower die 20 is a press cylinder 1, a press base 2 fixed to a rod 1a of the press cylinder 1 and moved up and down, and fixed to the press base 2. A mold base 2A in which the cooling path 11 is built, and the mold base 2A
The lower mold mounting plate 3 in which only the central portion is fixed via the column 6 and the other portions are slidably supported in the direction of the plate surface by the slide support means 7, and a biasing cylinder with respect to the mold base 2A. 5, and has a through hole 4a through which the heating dies 20, 20 'can be penetrated, and a portion ST (see the hatched portion in FIG. 3) of the sheet S which is trimmed at the time of molding will be described later. And a lower clamp plate 4 which is held between the upper clamp plate 4 'and the lower clamp plate 4'.

The portion relating to the upper die 20 'of the molding die P has substantially the same configuration as the portion relating to the lower die 20 arranged vertically symmetrically, and includes a press base 2' and a die base 2A. , An upper mold mounting plate 3 ', an upper clamp plate 4', a biasing cylinder 5 ', a column 6', a slide support means 7 ', and a cooling path 11'. Mold base 2A, 2
Cooling dies 30, 30 'having the same size and the same pitch as the heating dies 20, 20' in the heated state are fixedly attached to A 'via a pair of upper and lower mounting plates. Thus, the line configuration is such that the heat molding and the cooling can be performed simultaneously by the vertical movement of the press cylinder 1. In addition, the clamp plates 34, 34 'for the cooling dies 30, 30'.
Are provided independently of the clamp plates 4, 4 'for the heating dies 20, 20'. This is the heating mold 20, 20 '
The temperature of the clamp plates 4, 4 'for the cooling molds 30, 3
20 to 50 than the temperature of the clamp plates 34 and 34 'of 0'.
If these clamp plates are integrated, the temperature will be non-uniform, and it will be difficult to predict thermal expansion, which will be described later.

The mounting of the lower die mounting plate 3 and the die base 2A will be described in more detail. The central portion of the lower mold mounting plate 3 is fixed by columns 6, and the vertical direction and the horizontal direction are regulated with respect to the mold base 2A. The slide support means 7 is attached to the L-shaped member 71 fixed to the end of the lower mold mounting plate 3 and the mold base 2A, and is slidably engaged with the L-shaped member 71. And a cross-sectional U-shaped member 72. By the operation of the slide support means 7, the end of the mold mounting plate 3 can be freely changed in distance from the fixed portion when the lower mold mounting plate 3 expands thermally. The same applies to the relationship between the upper mold mounting plate 3 'and the mold base 2A'. In each of the mounting plates 3, 3 ', the central portions facing each other are fixed. As a material of each of the mounting plates 3 and 3 ′, a non-ferrous metal having excellent heat conductivity such as aluminum (including an alloy) or brass can be exemplified. Each of the mounting plates 3, 3 'incorporates an electric heating sheath heater 8, 8' as a heating means.

The clamp plates 4 and 4 'are used to hold the sheet S
And assists the mold release operation of the molded product. Clamp plates 4, 4 'are heated molds 20, 20'
And the mounting plates 3 and 3 'can be moved up and down without contact. Cooling paths 9, 9 'through which cooling water flows are arranged in a meandering manner inside the clamp plates 4, 4'. The cooling paths 9, 9 'are connected to the clamp plates 4, 4'.
Pipes may be embedded in the
It may be constituted by the hole itself provided in 4 '. Further, the cooling paths 9 and 9 ′ may be arranged in a grid. Further, the clamp plates 4, 4 'themselves may be constituted by a porous member.

When the mold is clamped, the pair of clamp plates 4, 4 'are sandwiched between the upper and lower mounting plates 3, 3'. In consideration of thermal expansion, the thickness of the clamp plates 4 and 4 'is set to be thin by a thermal expansion allowance (about 0.5 to 0.6%). According to this embodiment, each of the mounting plates 3, 3 'can expand freely around the central portion fixed to the mold bases 2A, 2A'.
The pair of upper mold 20 'and lower mold 20 attached to 3' have the same amount of displacement from the central portion due to expansion. Therefore, regardless of the thermal expansion during molding,
The clearance between the upper die 20 'and the lower die 20 in the clamped state can be made uniform. Since the clearance can be made uniform, a highly accurate molded product having a uniform thickness can be obtained.

Further, since the clamp plates 4, 4 'are cooled by the cooling water flowing through the cooling passages 9, 9', a non-molded portion (trimming) of the sheet which comes into contact with the clamp plates 4, 4 'at the time of molding. The portion ST) to be crystallized can be cooled to a temperature that does not cause crystallization. Therefore, at the time of release, due to shrinkage deformation of the non-molded portion of the sheet,
There is no possibility that the releasability and the sheet transportability are deteriorated.
Therefore, a more accurate molded product can be obtained, and the molding efficiency can be improved. The mold bases 2A and 2A 'also receive heat from the mounting plates 3 and 3', and when the mold bases 2A and 2A 'expand due to this heat, the position of the column 6 as a fixed point shifts. There is a risk of doing this. However, since the mold bases 2A and 2A 'are also cooled by the cooling passages 11 and 11' to prevent thermal expansion, there is no such a fear as described above. Also,
The air cylinders 5, 5 'may be cooled. That is, it is preferable to cool as much as possible except for the heating molds 20 and 20 'which require heating.

FIGS. 4 to 6 show another embodiment of the present invention. Referring to these figures, the present embodiment is shown in FIG.
1 is different from the embodiment of FIG. 1 in that the heating dies 20, 20 'are vertically and horizontally mounted on one mounting plate 3, 3' in the embodiment of FIG. 1, but in this embodiment, a plurality of rows of mounting plates 3a are provided. , 3b, and 3c, and a plurality of heating dies 20 were attached to each row. The mounting plates 3a, 3b, 3c of each row are fixed only at the center,
Both ends are slidably supported by slide means 7.

The present embodiment specifically shows that the mounting plate can be appropriately divided and used according to the size and the number of the heating dies. In particular, with reference to FIG. 5, each of the lower mold mounting plates 3a, 3b, 3c includes only the lower mold 20 arranged along a direction orthogonal to the arrow IV. That is, the lower mold 20 is arranged only in one direction.
Therefore, only the one-way expansion needs to be considered, and the clearance adjustment between the upper mold 20 ′ and the lower mold 20 can be performed more easily. Note that, even if each of the mounting plates 3a, 3b, 3c in FIG. 5 has the die 20 arranged in the direction along the arrow IV, the same operation and effect can be obtained. Cooling molds 30, 30 'attached to the mold base
Since the mounting plate on which is mounted is originally cooled, there is no need to divide the mounting plate, and the mounting plate may be integrated.

The present invention is not limited to the above-described embodiment, but may employ a system in which heating oil is circulated as the heating means, instead of the sheathed heaters 8 and 8 '. Further, the fixing position of the mounting plate is not limited to the central portion, and the end portion may be fixed. Even in this case, the amount of thermal expansion centering on the fixed portion can be easily calculated, and it is possible to easily set such that a good clearance is generated at the time of molding.

Further, the molding die of the present invention can be applied not only to a polyethylene terephthalate sheet but also to a molding die for crystallizing other crystalline thermoplastic resin sheets. In addition, the molding die of the present invention can be applied to match molding, vacuum, compressed air, and plug assist molding.

In addition, various design changes can be made without changing the gist of the present invention. Test A molding test was performed according to the following specifications using a test example including the same apparatus as the example in FIG. 1 and a comparative example including the conventional apparatus. 1) Test contents Sheet specification: crystalline foamed polyethylene terephthalate sheet Sheet weight: 400 g / m ² Sheet thickness: 1.5 mm Secondary thickness after heating: 3.1 mm Mounting plate dimensions for heating mold: 370 × 600 Clamp plate Dimensions: 370 × 600 Heating die mounting plate temperature: 180 ° C. Clamp plate temperature: 40 ° C. Heating die number: 5 × 3 = 15 Cooling die number: 5 × 3 = 15 Molded product size Diameter: 82 mm Bottom Diameter: 70mm Depth: 35mm 2) Test result

[0025]

[Table 1]

As described above, in the test examples, it was proved that a variation in the thickness of the molded product and a small pitch shift between the molded products were small, and a molded product with high accuracy was obtained.

[0027]

As described above, according to the mold for molding a crystalline thermoplastic resin sheet of the present invention, regardless of the thermal expansion during molding, the upper mold and the lower mold in the clamped state can be interposed between the upper mold and the lower mold. Since the clearance can be made uniform, a highly accurate molded product having a uniform thickness can be obtained.

In the case where the clamp plate having the cooling path is provided, the non-molded portion (the portion to be trimmed) of the sheet can be cooled to a temperature at which crystallization does not occur during molding. At the time of release or the like, there is no possibility that the releasability and the sheet transportability are deteriorated due to shrinkage and deformation of the non-molded portion of the sheet. Therefore, a more accurate molded product can be obtained, and the molding efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a mold for forming a crystalline thermoplastic resin sheet according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a molding step.

FIG. 3 is a plan view of a sheet during molding.

FIG. 4 is a sectional view of a main part of a molding die according to another embodiment.

FIG. 5 is a plan view of a lower die and a lower die mounting plate.

FIG. 6 is a view taken in the direction of the arrow IV in FIG. 5;

[Explanation of symbols]

 S Crystalline polyethylene terephthalate sheet ST Trimmed portion 20, 20 'Heating mold 2, 2' Press base 2A, 2A 'Mold base 3 Lower mold mounting plate 3' Upper mold mounting plate 4 Lower clamp plate 4 'Upper clamp Plates 4a, 4a 'Through holes 8, 8' Electric heating sheath heater (heating means) 9, 9 'Cooling path

Claims (2)

(57) [Claims] 1. A heating mold comprising a plurality of sets of an upper mold and a lower mold and a plurality of upper molds for crystallizing a foamed or non-foamed crystalline thermoplastic resin sheet heated and softened in advance. An upper die mounting plate, a lower die mounting plate on which a plurality of lower dies are mounted, and a molding die including a heating means provided on each mounting plate, wherein a part of each of the mounting plates facing each other is Is fixed to a vertically movable press base, and the other parts are slidably supported by the press base to allow free thermal expansion in a direction along the plate surface of the mounting plate. A molding die for a crystalline thermoplastic resin sheet, characterized by the following. 2. A pair of clamps which are vertically movable relative to each mounting plate, have through holes for penetrating a heating die, and hold a trimmed portion of a sheet during molding. 2. A mold for forming a crystalline thermoplastic resin sheet according to claim 1, wherein a plate is provided, and a cooling path is provided inside the clamp plate.