JP2000117827A - Forming method and device by using crystalline thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost forming method and a forming device, with which a molding without mold shift, drawing shift and deformation can be obtained at the forming of a crystalline thermoplastic resin sheet. SOLUTION: This forming method is one for forming a foamed or non-foamed crystalline thermoplastic resin sheet S thermally softened in advance. At a heating mold part A, the crystallinity on of the sheet is enhanced and thermoformed into a predetermined shape. Next, at a cooling mold part B, the formed sheet S is allowed to cool without employing a cooling mold. The forming and letting cool are executed within the heating mold part A and the cooling mold part B under the state that the portion in the formed sheet S except the position of a molding, which is trimmed after forming, is pressingly held by a clamping member 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method and a molding apparatus using 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 A thermoforming method for a crystalline thermoplastic resin sheet, for example, a crystalline polyethylene terephthalate, is well known, and a multistage molding method is generally employed. The multi-stage molding die is composed of a heating die heated to 160 to 180 ° C and a heating die of 20 to 180 ° C.
There are a pair of cooling dies cooled to 60 ° C., and the arrangement is such that the heating dies and the cooling dies are arranged in this order.

[0003] The molding method is to heat the sheet in an oven,
It is softened and heated to a temperature just before crystallization is promoted, and is conveyed by a chain to a mold portion serving as a molding zone. Then, after heating and molding with a heating mold until it is sufficiently crystallized, the mold is once released from the heating mold, and the molded article is transported by a chain to a cooling mold located in the next zone, where it is cooled. The molded article obtained by heat molding is subjected to cooling molding. The sheet softening heating, the crystallization molding heating, and the cooling molding were performed by this repetition to obtain a heat-resistant crystallized molded product.

However, when a molded article formed by a heating mold is conveyed to a cooling mold, variations in the feeding of the conveyor chain and shrinkage of the molded portion between the time when the mold is released and the time when the molded article is sent to the cooling mold are finished. In addition, displacement occurs due to the inertia force of stretching, chain conveyance, and the like, and the molded product is displaced due to cooling and pressing. When a mold shift occurs, the edge line when molding with a heating mold is the same as the molding line when molding with a cooling mold.
A molded product that is heavily displaced and obtained is obtained, and the appearance is reduced. Furthermore, since the molded product is trimmed according to the shape molded by cooling with the cooling mold and commercialized, the shape molded with the heating mold when heated and cooked in an oven or microwave oven in practical use Since the information is memorized, a double-shifted edge line clearly appears, the appearance is further deteriorated, and a portion formed only by the cooling mold is generated near the trimming, which may cause a large deformation.

[0005]

In order to solve the above-mentioned problem, Japanese Unexamined Patent Publication No. Hei 6-134854 discloses a method of providing a clamp having a hole penetrating a heating mold, holding a portion to be trimmed of a sheet and pressing and holding it. ing. Thereby, the effect of suppressing the shrinkage deformation, stretching, etc. of the molded product can be confirmed,
When a cooling mold is provided in the next step, it is difficult to completely eliminate the double molding, and the above practical problem is not completely improved. In addition, if the cooling process is not carried out in the next step and the natural cooling is performed simply, the pitch shift occurs between the molding shots due to shrinkage of the molded part formed by the heating mold before the trimming, and during trimming, Misalignment occurs, and the appearance of the molded product is inevitably reduced.

When focusing only on a mold for forming a crystalline thermoplastic resin sheet, usually a heating mold and a cooling mold are often provided, but the thermal expansion of the heating mold and the heating mold and the cooling mold are often performed. It is necessary to consider the difference in mold thermal expansion between molds and to consider heat conduction to other members.
Since a mold is required in one mold, it is a complicated and expensive molding mold.

[0007] The present invention provides an inexpensive molding method and a molding apparatus capable of obtaining a molded article free from the above-mentioned mold displacement, displacement, and deformation when molding a crystalline thermoplastic resin sheet. The purpose is to:

[0008]

According to a first aspect of the present invention, there is provided a molding method using a crystalline thermoplastic resin sheet according to the present invention. A method of molding a crystalline thermoplastic resin sheet of the above, in the heating mold portion to increase the crystallinity and heat molding to a predetermined shape, and then in the cooling unit is allowed to cool without using a cooling mold, In the heating mold section and the cooling section, the heat forming and cooling are performed in a state in which a portion of the molded sheet, which is outside the molded product position to be trimmed after molding, is pressed and held by a clamp member. is there.

In the molding method according to the first aspect of the present invention, the above-mentioned problems caused by the misalignment are eliminated because the double pressing by the heating mold and the cooling mold having the same shape as in the prior art is eliminated. Is eliminated. In addition, the part outside the position of the molded product that is trimmed after molding (non-molded part in three dimensions)
By holding only the press with the clamp member of the cooling unit, the surroundings can be cooled in a fixed state until the molded product is allowed to cool down naturally, so that pitch variations in shots can be suppressed, and Non-defective products can be obtained.

According to a second aspect of the present invention, as a forming method, a clamp member configured to press and hold a formed sheet is formed of a single member from a heating mold portion to a cooling portion. It is characterized by the following.
According to the second aspect of the present invention, since the temperature variation of the clamp holding by the clamp member in the heating mold portion and the cooling portion is uniform without variation, it is possible to obtain a molded product that is free from displacement due to trimming and deformation.

According to a third aspect of the present invention, as a forming method, a clamp member which presses and holds a sheet is a clamp member whose temperature is adjusted to be equal to or lower than a glass transition point of the formed sheet. It is. According to the third aspect of the present invention, the temperature of the portion to be trimmed after molding is adjusted to the glass transition point or lower by the clamp member, and the molding is held by pressing to heat only the molding portion of the molding sheet that comes into contact with the heating mold. Since the non-molded portion of the sheet can be crystallized and molded at a temperature equal to or lower than the glass transition point of the sheet, it is possible to suppress poor mold release and misalignment of trimming.

Next, the molding apparatus for the crystalline thermoplastic resin sheet of the present invention is an apparatus for molding a foamed or non-foamed crystalline thermoplastic resin sheet which has been heated and softened in advance. So, I. Heating mold part that increases the crystallinity and heat-forms into a predetermined shape. II. Cooling unit that performs cooling without using a cooling type III. In the above-mentioned heating mold part and the cooling part, of the molded sheet, a part outside the molded article position to be trimmed after molding is constituted by a clamp member capable of being simultaneously pressed and held.

In the molding apparatus according to the fourth aspect of the present invention, since the cooling section naturally cools the heating mold section without using the cooling mold, a problem caused by the mold displacement which has been a concern in the past. The point is eliminated. Moreover, the above-described clamp member can eliminate the deviation of trimming.

According to a fifth aspect of the present invention, there is provided a molding apparatus according to the present invention, wherein the clamp member for press-holding the formed sheet includes a heating mold part position to a cooling part position, and a cooling part position to a heating mold part position. It is characterized in that a cooling water pipe is provided so as to meander outside the position of the molded product. The cooling water pipe described in claim 5 can form a water passage, and can control the temperature by the water flowing, and can eliminate the temperature variation of the clamp holding between the heating mold part and the cooling part and make it uniform. It is possible to eliminate the slippage of trimming after molding.

Further, in the forming apparatus according to the present invention, as the clamp member for press-holding the sheet as described in claim 6, an apparatus in which a portion from a heating mold portion to a cooling portion is formed by one member is used. As the clamp member for press-holding the sheet as described in the above item or claim 7, a member whose temperature is adjusted to be equal to or lower than the glass transition point of the formed sheet is used. 2 and 3 have the advantages described above.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a molding method using a crystalline thermoplastic resin sheet according to the present invention will be described with reference to the drawings, together with a molding apparatus used for carrying out the method. FIG. 1 shows an outline of a molding apparatus, which comprises a heating mold section A serving as a first station and a cooling section B serving as a second station. A plurality of molds 10 and 10 'are provided vertically and horizontally so that a plurality of molded products can be formed by heating at the same time, and the heating getters 11 and 11' and the heater base 1 are formed.
2, 12 '. Reference numerals 30 and 30 'denote adapter plates serving as mounting members made of one member common to the cooling section B side.
Heating getters 11 and 11 'are connected to 0', and no cooling mold is provided in the cooling section B, and the adapter plates 30 and 30 '
Are connected to the cooling getters 21 and 21 '.

Numerals 40 and 40 'denote upper and lower clamp members.
FIG. 2 shows one of the upper and lower clamp members 40 and 40 'which can press and hold a portion of the molded sheet S outside the molded product position to be trimmed after molding. The clamp members 40 and 40 'have openings 41 in the heating mold portion A at portions corresponding to the heating molds 10 and 10', and the cooling portion B has openings 42 in the same form.

The above-mentioned clamp members 40 and 40 'are composed of a series of members from the heating die portion A to the cooling portion B. However, the heating die portion A and the cooling portion B are formed as separate clamp members. May be implemented. Clamp member 4 described above
In one or both of 0 and 40 ', the outer position of the molded article position is set so as to extend from the position of the heating mold part A to the position of the cooling part B, and further from the position of the cooling part B to the position of the heating mold part A. The meandering cooling water pipe P is arranged as shown in FIG.
Denotes a cooling water inlet, P2 denotes a cooling water outlet, and P3 is a hole for convenience when processing the cooling water pipe P. Blind processed.

When the clamp members 40 and 40 'are passed through the cooling water pipe P, the heating die portion A and the cooling portion B can be alternately and uniformly passed. Is preferably adjusted to a glass transition point or lower. The above-described clamp members 40 and 40 'are composed of a series of members from the heating mold part A to the cooling part B. However, the heating mold part A and the cooling part B may be constituted by separate clamp members.

In order to form a crystalline thermoplastic resin sheet S, for example, a crystalline polyethylene terephthalate sheet by using the above-described molding apparatus, preheating is performed by heating in an oven in a preheating zone (not shown).
In the heating mold part A, the degree of crystallinity is increased by the heating molds 10 and 10 ′ and heat molding into a predetermined shape is performed. Then, after releasing the mold, the molded sheet S is conveyed and cooled in the cooling part B (using a cooling mold). Without cooling), and in the heating mold section A and the cooling section B, portions of the molded sheet S outside the molded article position to be trimmed after molding (non-molded parts in three dimensions) are simultaneously clamped by the clamp member 40. , 40 'perform the above molding and cooling while holding the press.

After cooling, the molded article portion of the molded sheet is trimmed to provide each molded article.
Further, the molding method and apparatus of the present invention can be applied to a molding die for crystallizing not only a polyethylene terephthalate sheet but also another crystalline thermoplastic resin sheet such as polybutylene terephthalate. In addition, the molding method and apparatus 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.

[0023]

EXAMPLE A molding test was performed using the conventional molding dies X and Y and the devices A and B according to the present invention according to the following specifications.
The conventional mold X is a multi-stage mold having both a heating mold and a cooling mold, and Y is a prior art disclosed in Japanese Patent Laid-Open No. 6-134.
854 ", a multi-stage mold incorporating a temperature-controlled clamp, wherein A divides the clamp into a heating zone and a cooling zone, and the clamp is formed by two members outside the position of the molded product to be trimmed out of the molded sheet. In the case where the portion is pressed and held, B is a case where the clamp is formed by one member. <Molding test specifications (1)> Molded sheet Crystalline polyethylene terephthalate sheet Sheet weight 912 g / m ² Sheet thickness 0.7 mm Heating mold temperature 180 ° C Clamping temperature 60 ° C Heating mold number of molding 5 width x 4 flows Total 20 pcs Molded size Die diameter φ88 mm Diameter φ74 mm Bottom diameter φ64 mm Depth 35 mm (1)-The following items were investigated for the trimmed containers after molding.

[0024]

[Table 1] (1)-The above container was put into a hot air convection oven preheated to 200 ° C for 15 minutes, and the following items were reexamined.

[0025]

[Table 2] <Molding test specifications (2)> Molded sheet Crystalline foamed polyethylene terephthalate sheet Sheet weight 400 g / m ² Sheet thickness 1.1 mm Secondary thickness after heating 1.9 mm Heating mold temperature 180 ° C Clamping temperature 60 ° C Heating Molded number 4 width × 2 flow 8 total Molded product size Die diameter Long side max 205mm × Short side max 132mm Depth 27mm (2)-The following items were investigated for the trimmed container after molding.

[0026]

[Table 3] (2)-The container was put into a hot air convection oven preheated to 200 ° C for 15 minutes, and the following items were re-examined.

[0027]

[Table 4]

[0028]

As described above, according to the molding method using the crystalline thermoplastic resin sheet of the present invention, the conventional double press using a heating mold and a cooling mold is not required. Therefore, all the problems caused by the misalignment are eliminated.
Further, the molded sheet can be cooled in a fixed state until the molded article is naturally cooled by pressing and holding only the part outside the molded article position to be trimmed after molding by the clamp member of the cooling unit. Therefore, it is possible to suppress a variation in pitch in a shot, and to provide a good molded product without a deviation in trimming.

[Brief description of the drawings]

FIG. 1 is an overall schematic front view.

FIG. 2 is a plan view of one of the upper and lower mold parts.

FIG. 3 is a plan view of a clamp member showing an arrangement example of a water pipe;

[Explanation of symbols]

 A Heating mold part 10, 10 'Heating mold 11, 11' Heating getter 12, 12 'Heater base B Cooling part 21, 21' Cooling getter 30, 30 'Adapter plate 40, 40' Clamp member P Cooling water pipe P1 Inlet P2 outlet P3 blind

Claims (7)

[Claims] 1. A method for molding a foamed or non-foamed crystalline thermoplastic resin sheet which has been softened by heating in advance, wherein the heating mold portion has a higher degree of crystallinity and is heat-molded into a predetermined shape. In the cooling section, the cooling is performed without using the cooling mold, and the heating mold section and the cooling section are pressed and held by a clamp member at a portion outside the molded article position to be trimmed after molding. A molding method using a crystalline thermoplastic resin sheet, wherein heating and cooling are performed. 2. The crystalline thermoplastic resin according to claim 1, wherein the clamping member for press-holding the formed sheet is formed of a single member from the heating mold section to the cooling section. Forming method by sheet. 3. The molding method according to claim 1, wherein the clamping member for holding the sheet by pressing is a member whose temperature is adjusted to a glass transition point of the molded sheet or lower. 4. An apparatus for forming a foamed or non-foamed crystalline thermoplastic resin sheet which has been heated and softened in advance, comprising: Heating mold part that increases the crystallinity and heat-forms into a predetermined shape. II. Cooling unit that performs cooling without using a cooling type III. A crystalline thermoplastic resin sheet characterized by being constituted by a clamp member capable of simultaneously pressing and holding a part outside a molded article position to be trimmed after molding among molded sheets in the heating mold part and the cooling part. Molding equipment. 5. A clamp member for press-holding a formed sheet, meandering at an outside position of a molded product position so as to pass from a heating mold portion position to a cooling portion position, and further from a cooling portion position to a heating mold portion position. A molding device for a crystalline thermoplastic resin sheet, comprising: a cooling water pipe arranged in a vertical direction. 6. The crystallinity according to claim 4, wherein the clamp member for holding the sheet by press is formed of a single member from the heating die to the cooling part. Molding device using thermoplastic resin sheet. 7. The crystalline thermoplastic according to claim 4, wherein the clamp member for holding the sheet by pressing is a member whose temperature is adjusted to be equal to or lower than the glass transition point of the molded sheet. Molding equipment using resin sheet.