JPH1058536A - Thermoforming device of thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finely control heat treatment of a material cloth and condition of thermoforming and obtain a molding having excellent heat resistance, excellent appearance, and excellent impact resistance, by connecting a holding tool at a peripheral edge of a thermoplastic resin sheet movably in the space direction and the longitudinal direction. SOLUTION: A thermoforming mold 5, a vacuum pump 20 which sucks air and patterns a material cloth 2 by the thermoforming mold 5, an air pressure box 21, and a plug 22 are provided. In a heating mechanism 4, an upper heater 4a and a lower heater 4b are provided at a position adjacent to the thermoforming mold 5, so as to heat the material cloth 2 uniformly from the upper and lower parts. After the heat treatment is completed, the heating mechanism 4 moves in the horizontal direction so as to deviate from the up-and-down position of the material cloth 2, and the thermoforming mold 5 is raised so as to attach its upper edge 5a to the bottom face of the material cloth 2. When the thermoforming mold 5 is attached to the base material, the air in the thermoforming mold 5 is discharged by the vacuum pump 20 and the material cloth 2 is sucked to the inside face of the thermoforming mold for molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a molded article made of a thermoplastic resin sheet having excellent heat resistance and impact resistance. More specifically, the present invention relates to a thermoplastic resin sheet thermoforming apparatus capable of forming a molded product of a conventional thermoplastic resin, particularly a polyester having excellent physical properties, stably with high productivity.

[0002]

2. Description of the Related Art Molded articles made of a thermoplastic resin sheet are:
Since it can be processed into various shapes, it is used for various purposes. For example, molded articles made of a polyester sheet are excellent in thermoformability, gas barrier properties, mechanical strength, and the like, and are widely used for packaging containers such as cups and trays. However, polyester has a low second order transition point (about 70% in the case of polyethylene terephthalate).
C), there is a disadvantage that such a molded article is deformed when exposed to a high temperature such as 60 to 100C.

[0003] In order to solve such problems, various methods have been conventionally attempted. But those results were not always satisfactory. For example, Japanese Patent Publication No. 44-5108 discloses that after a polyethylene terephthalate film is formed, it is heated at 140 to 220 ° C. in a mold.
By heat-treating the molded article at the temperature of
A method for improving heat resistance is disclosed. However, this method has a drawback that the molded article is deformed during the heat treatment and the impact resistance of the obtained molded article is reduced. The decrease in impact resistance in this method is presumed to be due to the fact that polyethylene terephthalate crystals tend to be spherulite in the heat treatment by this method, and thus the molded article becomes brittle.

Japanese Patent Application Laid-Open Nos. 54-43971, 54-43972 and 55-17516 describe that a polyester sheet is biaxially stretched and oriented, and then thermoformed. And a method of heat-treating the obtained molded article. These methods have a small effect when molded using a sheet with a low degree of orientation, and have poor appearance of the molded article due to poor deep drawability when molded with a sheet with a high degree of orientation. Becomes Thus, attempts by these methods have not always yielded satisfactory results.

Japanese Patent Application Laid-Open No. Sho 50-21051 discloses that an unstretched polyester sheet is stretched 1.5 to 3.0 times uniaxially in a temperature range of 70 to 100 ° C. and then stretched 90 to 90 times.
There is disclosed a method in which heat shaping is performed in hot water at ~ 95 ° C, followed by thermoforming, and then heat setting in a mold at a temperature of 130 ° C to 150 ° C. Japanese Patent Application Laid-Open No. 61-254326 discloses that an unstretched polyester sheet is simultaneously stretched 1.5 to 3.0 times in a biaxial direction in a temperature range of 70 to 100 ° C. using a biaxial stretching machine. 70 to 12 later
80-100 ° C after heat shrinking in the temperature range of 0 ° C
And then heat-setting at a temperature of 180 to 250 ° C. in a mold.

However, even with these methods, the improvement of the physical properties is not sufficient, and the appearance of the molded product is poor, the effect of improving the heat deformation is small, or the impact resistance of the molded product is reduced. However, satisfactory results have not always been obtained by these methods. As a method other than the above method, after the unstretched polyester sheet is thermoformed, the unstretched polyester sheet is placed in a molding die.
A method of removing the strain without heat-treating the molded article in a low temperature range such as 140 ° C. without crystallizing the molded article is also considered. Not the way to go.

[0007]

SUMMARY OF THE INVENTION The present invention is capable of precisely controlling the conditions of heat treatment and thermoforming of a raw material, has excellent heat resistance and appearance of a molded product, and has impact resistance and mechanical strength. It is an object of the present invention to provide an apparatus capable of stably producing a molded article having excellent characteristics in high productivity.

[0008]

The present invention has been intensively studied for the development of a thermoforming method having further excellent physical properties. As a result, heat treatment conditions before thermoforming are important, and in particular, shrinkage during heat treatment is controlled. Has been found to be important, leading to the present invention. That is, the present invention includes a plurality of grippers for gripping the peripheral edge portion of the thermoplastic resin sheet, and the gripping mechanism in which the grippers are connected so as to be movable in the interval direction and the front-back direction of the grippers has a thermal mechanism. An object of the present invention is to provide a thermoforming apparatus for a thermoplastic sheet, which is provided along a side of a plastic sheet and is provided with a heating mechanism and a thermoforming mechanism. The conventional thermoforming apparatus is a method of forming into a target shape in one step. On the other hand, the novel thermoforming apparatus of the present invention is a novel molding apparatus for subjecting at least a uniaxially stretched thermoplastic resin sheet to heat shrinkage under control and then forming it into a desired shape.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is an apparatus for stretching a thermoplastic resin sheet in at least one direction, heat-treating the sheet, and then thermoforming. The thermoplastic resin is not particularly limited, polyethylene,
Polyolefin such as polypropylene, polyamide, polyester, polystyrene and the like can be used, but a crystalline thermoplastic resin is preferable, and polyester is particularly preferable.

The thermoforming apparatus of the present invention can stretch an unstretched thermoplastic sheet using the thermoforming apparatus, and can perform thermoforming after stretching. However, it is also possible to use a stretched sheet that has been stretched in at least one direction in advance. When using a stretched sheet that has been stretched in advance, the method for producing the sheet is not particularly limited, and a known method can be employed. For example, there is a method in which stretching in the longitudinal direction is first performed by a roll, and then, if necessary, stretching in the transverse direction is performed by a tenter. However, in the present invention, it is preferable not to perform the heat fixing step which is usually performed. The sheet may be a uniaxially stretched sheet or a biaxially stretched sheet, or may be a stretched sheet manufactured by rolling using a roll.

Although the thickness of the raw material is not limited,
Generally, 0.01-5 mm, preferably 0.05-3
mm. The thermoforming device of the present invention will be described in detail with reference to FIG. 1. The thermoforming device 1 holds a raw material 2 made of a thermoplastic resin sheet by holding a peripheral portion of the raw material 2 horizontally. 3, a heating mechanism 4 for heating the web, and a thermoforming mechanism 6 having a thermoforming die 5. As shown in FIGS. 2 and 3, the gripping mechanism 3 is provided with a plurality of gripping tools 7, 7 for gripping a peripheral portion of the web 2, and a plurality of gripping tools 7 are provided along the sides of the web 2. .

In the figure, four gripping mechanisms 3a, 3b, 3c, 3d are provided along each side of the quadrilateral raw material 2. The gripping members 7, 7 of the gripping mechanism 3 are connected so as to be movable in the interval direction and the front-back direction of the gripping members 7, 7 in order to extend or contract the raw material 2. The mechanism shown in FIG. 5 can be used as the connecting mechanism 8 that can move the grippers 7, 7 in the interval direction and the front-back direction. The mechanism of FIG.
Having a first guide rail 9 and a second guide rail 10, and a first sliding body that moves along the guide rail. 11 and 11, the second guide rail 10 is provided with a second
Are provided.

Further, the grippers 7, 7 and the first sliding body 11,
11 is connected in a zigzag manner by rods 13
The grippers 7, 13 and the first sliding bodies 11, 11 are pivotally connected by shafts 14, 15 so as to change the angle. Similarly, the rods 16, 16 of the first sliding bodies 11, 11 and the second sliding bodies 12, 12 are
To form a parallelogram which can be deformed by the gripper 7, the two first sliding bodies 11, 11 and the second sliding body 12.

Therefore, by moving one or both of the first guide rail 9 and the second guide rail 10 in parallel, the first guide roll 9 and the second guide roll 1 are moved.
0, the first sliding body 11, 1
1 is narrowed, and as a result, the spacing between the gripping tools 7 is reduced, and the gripping tools 7, 7 protrude in the direction of the raw material 2 to reduce the widthwise width of the raw material 2. Become.

The thermoforming apparatus 1 of the present invention has a thermoforming mechanism 6.
have. In the present invention, thermoforming means a method of forming a heated sheet-like raw material along a forming die, and means for making the raw material along the forming die include:
A method such as vacuum, pressurized air, or a combination of these with mechanical means such as a plug, or a press molding method in which the material is pressed by a pressing die can be employed.

FIG. 1 includes a thermoforming die 5, a vacuum pump 20, a compressed air box 21, and a plug 22 for sucking air and shaping the raw material 2 by the thermoforming die 5.
The heating mechanism 4 is provided with an upper heater 4a and a lower heater 4b at positions adjacent to the thermoforming die 5, and is configured to uniformly heat the raw fabric 2 from above and below.

When performing thermoforming using the thermoforming apparatus 1 of the present invention, first, as shown in FIG. 4 (A), the periphery of the raw material 2 is gripped by gripping tools 7 provided on four gripping mechanisms 3a to 3d. , 7 and hold it horizontally. When an unstretched thermoplastic sheet is used as the raw material 2, the heaters 4a and 4b are moved horizontally to the upper and lower positions of the raw material 2 to uniformly heat the raw material 2 from the upper and lower sides to reach the drawing temperature. When the distance between the first guide rail 9 and the second guide rail 10 is reduced by moving the first guide rail 9 and / or the second guide rail 10 in parallel, the gripper 7,
As shown in FIG. 4B, 7 widens the gap between the gripping tools 7, 7, and the gripping tools 7, 7 recede to the opposite side of the web 2,
The web 2 is stretched in the vertical and horizontal directions. The stretched raw material 2 is further heated and heat-treated.

Along with this heat treatment, the web 2 is shown in FIG.
As shown in (B), the contraction is performed under the control by the regulation by the gripping tools 7 and 7. The contraction is achieved by horizontally moving the first guide rail 9 and / or the second guide rail 10 as shown in FIG. 5B, thereby increasing the distance between the first guide rail 9 and the second guide rail 10. The grippers 7, 7 are moved in the direction of contraction, and the material 2 is gradually contracted.
The state shown in FIG.

The heat treatment temperature is the melting point Tm ° C. of the thermoplastic resin.
Hereinafter, the temperature is preferably (Tm-140) ° C. or higher,
The temperature is more preferably Tm ° C or lower and (Tm-120) ° C or higher, particularly preferably Tm ° C or lower and (Tm-100) ° C or higher. Heat treatment temperature is (Tm-140) ℃
When the heat treatment temperature exceeds Tm ° C., the impact resistance of the finally obtained molded product is unfavorably deteriorated.

After the heat treatment is completed, the heating mechanism 4 moves in the horizontal direction and moves off the upper and lower positions of the raw material 2. Next, the thermoforming die 5 is moved up and its upper edge 5a is attached to the lower surface of the web 2. When the thermoforming die 5 is attached to the raw material, the air in the thermoforming die 5 is exhausted by the vacuum pump 20, and the raw material 2 is formed by vacuum forming in which the raw material 2 is sucked into the inner surface of the thermoforming die, as shown in FIG. Become.

Alternatively, instead of or in combination with vacuum forming, air pressure forming may be adopted in which the upper part of the raw material 2 is covered with a compressed air box 21 and formed by feeding compressed air. Further, the plug 22 is used together with these vacuum and compressed air.
It is also possible to adopt a plug assist method that assists with. In addition, instead of vacuum forming and pressure forming, press forming by pressing with a set of dies may be employed.

The temperature of the mold is not particularly limited, and can be appropriately changed depending on the required degree of heat resistance of the finally obtained molded article. For example, when heat resistance is required only in a region at a temperature lower than around 100 ° C., the temperature of the mold may be set to about 30 ° C. by using water cooling or the like.
In the case where heat resistance around ℃ is required, heat treatment may be performed in a mold at a high temperature of, for example, about 200 ℃. By applying the production method of the present invention described above, excellent physical properties,
In particular, a molded article made of a thermoplastic resin sheet having dramatically improved heat resistance can be obtained. The method of the present invention is applicable to any method for producing molded articles, and examples thereof include packaging containers such as cups and trays and transport containers such as luggage.

[0023]

The method for producing a thermoplastic resin molded article of the present invention is an epoch-making method for improving heat resistance without impairing other characteristics. The method of the present invention is a method for forming a thermoplastic resin sheet capable of dramatically improving the physical properties of a molded product, and includes, for example, any molded products such as packaging containers such as cups and trays and transport containers such as luggage. Applicable to manufacturing method.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a thermoforming device of the present invention.

FIG. 2 is a plan view showing a gripping mechanism.

FIG. 3 is a side view showing a gripping mechanism.

FIG. 4 is an explanatory view showing a thermoforming step using the apparatus of the present invention.

FIGS. 5A and 5B are plan views showing a coupling mechanism of the gripper, wherein FIG. 5A shows a state before contraction and FIG. 5B shows a state after contraction.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 thermoforming device 2 raw material (thermoplastic resin sheet) 3 gripping mechanism 4 heating mechanism 5 thermoforming die 6 thermoforming mechanism 7 gripping tool 8 connecting mechanism 9 first guide rail 10 second guide rail 20 vacuum pump 21 compressed air Box 22 plug

Claims (4)

[Claims] A gripping mechanism comprising a plurality of grippers for gripping a peripheral portion of a thermoplastic resin sheet, wherein the grippers are connected so as to be movable in an interval direction and a front-rear direction of the grippers. An apparatus for thermoforming a thermoplastic sheet, comprising a plurality of heating mechanisms and a thermoforming mechanism provided along a side of the sheet. 2. A heat treatment mechanism according to claim 1, wherein said heat treatment mechanism has a unit cross-sectional area of 1: 1.
^{2. The} thermoforming apparatus for a thermoplastic resin sheet according to claim 1, wherein the thermoplastic resin sheet is thermally contracted under a low tension of 0 kg / cm ² or less. 3. The apparatus for thermoforming a thermoplastic resin sheet according to claim 1, wherein the thermoplastic resin sheet is a polyester sheet. 4. The thermoplastic sheet according to claim 1, wherein the thermoforming device sequentially performs stretching of the thermoplastic resin sheet, shrinkage of the thermoplastic resin sheet by heat treatment, and thermoforming. Thermoforming equipment.