JPH08174646A - Manufacture of thermoplastic polyester resin foamed molding - Google Patents

Abstract

PURPOSE: To provide a method, by which a molded article having high mechanical strength and no locally scattering of mechanical strengths in the article can be obtained and which is suitable for deep forming at the manufacturing of a foamed molding out of a thermoplastic polyester resin sheet. CONSTITUTION: This manufacturing method has a process for adding an inert gas as a foaming agent to a thermoplastic polyester resin sheet, a process for bringing keep plates 3 in close contact with both the sides of the sheet 11 under the state being held in a vacuum former 1, a process for bringing a male heating mold 5 in close contact through holes provided on the keep plates 3 with the sheet 11 so as to selectively expand the portions contacting with the mold 5 of the sheet 11 and, at the same time, to vacuum-form the sheet through minute holes provided on the mold 5 and process, in which vacuumizing is stopped and a molded article 12 obtained in the previous process is separated from the mold 5 in order to cool down the article 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic polyester resin foam molded article.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a thermoplastic resin foam-molded article, a primary foam sheet is fixed with a clamp or the like, and the sheet is sandwiched between male and female heating dies, and in-mold foaming (secondary A method of foaming) to obtain a desired molded article is generally known.

In order to obtain a large number of molded products, a method is known in which a partition plate for pressing the contoured portion of each molded product is sandwiched between a male mold and a female mold. (For example, JP-A-58-193123).

Further, in order to produce a thermoplastic polyester resin foam-molded article, a foamed sheet is prepared by various known methods, preheated until the foamed sheet is softened, and then,
A method is known in which a heating die of a vacuum forming machine is used to impart heat resistance by causing crystallization by heat at the same time as forming, and a cooling die is used to make the appearance shape uniform (Plastics , Vol. 43, No. 6, p. 121-12.
6, 1992). As a method for producing a foamed sheet, a method for producing a thermoplastic polyester resin foamed sheet having fine bubbles and having no stripes using a circular die (for example, JP-A-4-229423) is known. There is.

[0005]

However, since any of the above-mentioned conventional methods uses the already-foamed primary foamed sheet, even if it is strongly pressed by a clamp or a partition plate, that portion will not be removed. It does not become non-foaming.
For this reason, there is a drawback that the contour portion of the obtained molded product is weak against a lateral force or an upward force. In particular, when the foaming ratio of this contour portion was 5 times or more, insufficient mechanical strength was unavoidable no matter how the shape of the molded product was modified.

Further, when a molded article such as a cup is manufactured by a conventional method, the sheet corresponding to the side surface of the cup is stretched during molding and the bubbles are distorted into an elliptical shape. There was a problem that the dynamic strength became uneven depending on the part.

Further, even if an attempt is made to perform deep drawing by a conventional method, since the primary foamed sheet has a small elongation, the foamed sheet may not be able to withstand the stretching at the time of molding and the foamed sheet may be broken. Therefore, it has been difficult to perform deep drawing by the conventional method.

The present invention has been made in view of the above problems, and when a foamed molded product is manufactured from a thermoplastic polyester resin sheet, the mechanical strength is high and the mechanical strength varies depending on the part of the molded product. An object of the present invention is to provide a method capable of obtaining a molded product that does not have any shape and suitable for deep drawing.

[0009]

The method for producing a thermoplastic polyester resin foam-molded article according to the present invention comprises a step of incorporating an inert gas as a foaming agent in a thermoplastic polyester resin sheet, and a vacuum forming machine for the sheet. Holding it inside and crimping a holding plate having a shape corresponding to the contour of the molded product on both sides of the sheet and provided with a hole into which a mold is inserted; A step of pressing the sheet through the holes provided in the plate to selectively foam the portion of the sheet in contact with the mold, and vacuuming from the fine holes provided in the mold to form the sheet. And a step of stopping the evacuation, separating the mold from the molded product obtained in the step, and then cooling the molded product.

The present invention will be described in more detail below. In the method of the present invention, first, the thermoplastic polyester resin sheet is made to contain an inert gas as a foaming agent.

Examples of the thermoplastic polyester resin used here include polyethylene terephthalate, polybutylene terephthalate, and various polymer alloys composed of a base resin of these and polycarbonate, among which polyethylene terephthalate is particularly preferable.

The thermoplastic polyester resin includes a crystallization nucleating agent, a crystallization accelerating agent, an aeration nucleating agent, an antioxidant, an antistatic agent, an anti-ultraviolet agent, a pigment and a dye as long as the original properties of the resin are not impaired. , Various additives such as lubricants may be added.

Examples of the inert gas contained in the thermoplastic polyester resin include helium, nitrogen, carbon dioxide and argon. Among these inert gases, carbon dioxide is particularly preferable because the content in the resin can be increased.

In the present invention, in order to prepare a thermoplastic polyester resin sheet containing an inert gas as a foaming agent, for example, the method described in USP-4473665 can be used. In this method, a thermoplastic polyester resin sheet formed by controlling an extruder to have a uniform thickness is wound into a roll, which is housed in a high-pressure container and impregnated with an inert gas under high pressure. Further, for example, the method disclosed in JP-A-4-268345 can be used. This method is a thermoplastic polyester resin containing an inert gas by injecting an inert gas as a foaming agent into a thermoplastic polyester resin in a molten state in an extruder and cooling while completely suppressing foaming of the resin. A sheet is prepared. Whichever method is used, the resin sheet is not yet foamed at this stage.

Next, the sheet containing the inert gas is held in a vacuum forming machine, and a mold having a shape corresponding to the contour portion of the molded article (the peripheral portion of the opening of the molded article) is held on both sides of the sheet. Press the pressing plate with the hole into which is inserted. The holding plate may be provided with only one hole, or may be provided with a plurality of holes so that a large number of molded products can be taken. The pressing force of the pressing plate to the sheet is preferably 10 kg / cm ² or more. The temperature of the holding plate at the time of pressure bonding must be below the softening temperature of the resin sheet. This is because when the temperature of the pressing plate becomes higher than the softening temperature of the resin sheet, foaming starts at the same time as the pressure bonding, so that the non-foamed state of the pressure bonded portion cannot be maintained. In addition, as the number of moldings increases,
Since the temperature of the holding plate rises due to the radiant heat of the heating mold,
Cooling is performed by using a refrigerant or the like so that the pressing plate at the time of pressure bonding is always below the softening temperature of the resin sheet. It should be noted that it is permissible that the temperature of the holding plate becomes slightly higher than the softening temperature of the resin sheet after pressure bonding of the heating die in the subsequent step.

Next, a male heating die is pressed against a resin sheet containing an inert gas through a hole provided in the holding plate to selectively foam the portion of the sheet in contact with the die, and A sheet is formed into a desired shape by drawing a vacuum from the fine holes provided in the mold. At this time, the conditions such as the heating temperature and the heating time by the heating mold are appropriately set according to the degree of deep drawing of the target molded product.

Finally, the evacuation is stopped, the mold is separated from the molded product obtained in the above step, and the molded product is cooled,
The target molded article is manufactured. In the method of the present invention, both sides of an unfoamed thermoplastic polyester resin sheet are pressed by a pressing plate only by containing an inert gas as a foaming agent, and a male heating die is passed through a hole provided in the pressing plate to form a sheet. Since it is pressure-bonded to, and the part in contact with the mold is selectively foamed,
It is possible to obtain a molded product in which the contour portion (the peripheral portion of the opening of the molded product) pressed by the holding plate is non-foamed.
In this way, since the contour of the molded product is non-foamed, it has high mechanical strength and is deformed by the lateral force received when grasped by hand or the force applied when the contour is wrapped with another resin. Become very strong against. Further, it is not necessary to devise such as folding back the end portion to increase the strength of the contour portion.

Further, in the method of the present invention, since vacuum forming is carried out simultaneously with foaming by heating, the thermoplastic polyester resin sheet having a large plasticizing effect is subjected to elongation at the time of molding and elongation accompanying bubble growth at the time of foaming, so that the sheet is formed. It can be stretched significantly. Therefore, the method of the present invention is very suitable for deep drawing. Moreover, since an excessive deformation force is not applied to the sheet at the time of vacuum forming, there is almost no deformation or collapse of bubbles, and a foam-molded product having no variation in mechanical strength can be obtained.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a view showing the structure of a vacuum molding machine used to manufacture a thermoplastic polyester resin foam-molded article in the following examples.
A plurality of support columns 2 are attached to the upper and lower inner surfaces of the vacuum forming machine 1 so as to be vertically movable.
The upper and lower holding plates 3 are supported by. These pressing plates 3 have a shape corresponding to the contour portion of the molded product, and are provided with holes into which molds are inserted. The hole of the holding plate 3 is, for example, 2
It is arranged in 3 rows x 6 rows so that 6 pieces can be taken. A holding table 4 is attached to an inner lower surface of the vacuum forming machine 1 so as to be vertically movable, and a male heating die 5 is held on an upper end thereof. A thermoplastic polyester resin sheet 11 is sent from a roll containing an inert gas as a foaming agent into the vacuum molding machine 1 and undergoes predetermined steps according to the method of the present invention to form, for example, a cup-shaped foam. The molded product 12 is manufactured.

Example 1 A polyethylene terephthalate resin (manufactured by Unitika Ltd., trade name: C-0312) containing a crystallization nucleating agent was dried at 140 ° C. for 5 hours in a dehumidifying dryer. This resin was supplied to an extruder, melt-kneaded, and then extrusion-molded into a sheet having a thickness of 0.5 mm, and this polyethylene terephthalate resin sheet was wound on a roll. Next, the polyethylene terephthalate resin sheet roll is placed in a high-pressure container, and 60 kg as a foaming agent is placed in the container.
Carbon dioxide gas of / cm ² was filled. The sheet roll was impregnated with carbon dioxide gas for 24 hours and then taken out from the high-pressure container.

This sheet roll was set outside the vacuum forming machine 1 as shown in FIG. The sheet 11 was sent into the vacuum forming machine from the roll body, and the support columns 2 were operated to press the pressing plates 3 onto the upper and lower surfaces of the sheet 11. In this state, the holding table 4 is operated to press the male heating die 5 heated from below to 240 ° C. to the pressing plate 3 through the 6 holes provided in 2 rows × 3 steps to the sheet 11 to press the sheet. A portion of 11 that was in contact with the mold 5 was selectively foamed, and vacuum was drawn from the fine holes provided in the mold 5 to form a sheet. Then
After the evacuation was stopped and the mold 5 was separated from the molded product, the molded product was cooled to manufacture a cup-shaped foam molded product 12 having an opening diameter to depth ratio of 2: 1 and an internal volume of 200 cc. .

When the cross sections of the side surface and the bottom surface of the obtained molded product were observed with a scanning electron microscope (SEM), no deformation of the bubble shape was observed in any part. Dumbbell-shaped samples were punched from the side and bottom of the molded product, and the tensile strength was measured.
Almost no difference was found in the strength of both.

Further, when the molded product was filled with 150 cc of water and the contour portion (the peripheral portion of the upper opening) was grasped and lifted by hand, the deformation ratio of the opening was measured, and the deformation ratio was 3% or less, which was very low. It was a small one.

Comparative Example 1 The same polyethylene terephthalate resin as in Example 1 was treated in exactly the same manner as in Example 1 and a 0.5 mm thick polyethylene terephthalate resin sheet was wound on a roll and impregnated with carbon dioxide gas. .

The obtained sheet roll is passed through a hot air circulation type foaming furnace, heated to a sheet surface temperature of 220 ° C. to be foamed, and a polyethylene terephthalate resin having fine bubbles uniformly foamed. A foamed sheet was produced.

The obtained polyethylene terephthalate resin foam sheet was molded by using a general vacuum molding machine having a heater and a molding die, and the ratio of the opening diameter to the depth was 2: 1 and the internal volume was 200 cc. A cup-shaped foam molded article was produced.

In the obtained molded product, the thickness of the side surface portion was 1/3 or less of that of the bottom surface portion. When observing the cross sections of the side surface and the bottom surface of this molded product with a scanning electron microscope (SEM), the shape of the bubbles in the cross section of the side surface was an elliptical shape that was flatly stretched. When a dumbbell-shaped sample was punched from each of the side surface and the bottom surface of the molded product and the tensile strength was measured, the strength of the side surface was ¼ or less that of the bottom surface, which was extremely low. in this way,
It was found that the strength of the side surface portion was reduced as a result of the thin side surface portion and the deformation of the bubbles contained in the side surface portion.

Further, when the molded product was filled with 150 cc of water and the contour part (the peripheral part of the upper opening) was grasped and lifted by hand, the deformation ratio of the opening part was measured, and the deformation ratio was 25%.
Then, it was about 8 times larger than that of Example 1.

Example 2 Polyethylene terephthalate resin (manufactured by Unitika Ltd., trade name: SA-1206)
Was dried in a dehumidifying dryer at 140 ° C. for 5 hours. This resin and 0.5% by weight of crystallization nucleating agent talc (manufactured by Nippon Talc Co., Ltd., trade name: Microace K-1) were fed to an extruder and melt-kneaded, and then 0.5 mm thick. The polyethylene terephthalate resin sheet was wound into a roll by extrusion molding. Next, the polyethylene terephthalate resin sheet roll was housed in a high-pressure container, and the container was filled with 60 kg / cm ² carbon dioxide gas as a foaming agent. The sheet roll was impregnated with carbon dioxide gas for 24 hours and then taken out from the high-pressure container.

This sheet roll was set on the outside of the vacuum forming machine 1 as shown in FIG. 1, and in exactly the same manner as in Example 1, according to the method of the present invention, the ratio of the opening diameter to the depth was 2: 1 and the internal volume was. A 200 cc cup-shaped foam molded article 12 was produced.

When the cross sections of the side surface and the bottom surface of the obtained molded product were observed with a scanning electron microscope (SEM), no deformation was observed in the bubble shape in any part. Dumbbell-shaped samples were punched from the side and bottom of the molded product, and the tensile strength was measured.
Almost no difference was found in the strength of both.

Further, when the molded product was filled with 150 cc of water and the contour part was grasped and lifted by hand, the deformation ratio of the opening was measured, and the deformation ratio was 4% or less, which was very small. On the other hand, for comparison, when the deformation rate of the opening was measured in the same manner as above for the molded product having the foamed contour portion, which was produced from the sheet that was primary-foamed by the conventional method, the deformation rate was 40%. It was very big.

Example 3 A polybutylene terephthalate resin (trade name: 1401-X04, manufactured by Toray Industries, Inc.) was dried at 140 ° C. for 5 hours in a dehumidifying dryer. This resin was supplied to an extruder, melt-kneaded, and then extrusion-molded into a sheet having a thickness of 0.5 mm, and this polybutylene terephthalate resin sheet was wound on a roll. Next, the polybutylene terephthalate resin sheet roll was housed in a high-pressure container, and the container was filled with 60 kg / cm ² carbon dioxide gas as a foaming agent. The sheet roll was impregnated with carbon dioxide gas for 24 hours and then taken out from the high-pressure container.

According to the method of the present invention, the opening diameter was set in the same manner as in Example 1 except that this sheet roll was set outside the vacuum forming machine 1 as shown in FIG. 1 and the temperature of the heating mold was set to 200 ° C. And a depth ratio of 2: 1 and an internal volume of 200 cc, a cup-shaped foam molded article 12 was manufactured.

When the cross sections of the side surface and the bottom surface of the obtained molded product were observed with a scanning electron microscope (SEM), no deformation was observed in the bubble shape in any part. Dumbbell-shaped samples were punched from the side and bottom of the molded product, and the tensile strength was measured.
Almost no difference was found in the strength of both.

Further, when the molded product was filled with 150 cc of water and the contour part was grasped and lifted by hand, the deformation ratio of the opening was measured, and the deformation ratio was 2% or less, which was very small. On the other hand, for comparison, when the deformation rate of the opening was measured in the same manner as above for the molded product having the foamed contour portion, which was produced from the sheet that was primary-foamed by the conventional method, the deformation rate was 35%. It was very big.

[0037]

As described above in detail, the use of the method of the present invention makes it possible to produce a thermoplastic polyester resin foam-molded article having high mechanical strength and no variation in mechanical strength depending on the molded article. It can also be suitably applied to deep drawing.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a vacuum forming machine used for carrying out a method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum forming machine, 2 ... Supporting pillar, 3 ... Pressing plate, 4 ... Holding stand, 5 ... Heating mold, 11 ... Thermoplastic polyester resin sheet, 12 ... Foam molded article.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C08L 67:00 (72) Inventor Mitsunori Okada 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A step of containing an inert gas as a foaming agent in a thermoplastic polyester resin sheet, holding the sheet in a vacuum forming machine, and forming a shape corresponding to a contour portion of a molded article on both sides of the sheet. A step of crimping a pressing plate provided with a hole into which a pressing die is inserted; and a male heating die is crimped to the sheet through a hole provided in the pressing plate and brought into contact with the die of the sheet. While selectively foaming the formed portion, the step of forming a sheet by drawing a vacuum from the fine holes provided in the mold, and stopping the vacuuming,
And a step of cooling the molded product after separating the mold from the molded product obtained in the above step, and a method for producing a thermoplastic polyester resin foam-molded product.