JP2000202901A - Method for molding thermoplastic resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate a molding speed without transferring a surface shape of a hot plate or a mold when molded by bringing a heating means into non- contact with a thermoplastic resin sheet, and separating the means from a molding means using a mold. SOLUTION: A heating means is separated from a molding means of a mold, and is brought into non-contact with a thermoplastic resin sheet. That is, the heating means 3 has a pair of heaters 5 opposed through a thermoplastic resin sheet conveyor 4, and is separated from a vacuum molding machine 2 having a mold 8, and is brought into non-contact with the sheet 9. A thermoplastic resin molding is further improved at its appearance and impact resistance by preferably being molded normally by a contraction stress of 1.5 to 4.0 kg/cm2. As the sheet, a biaxially oriented transparent polystyrene resin sheet is effectively used. As a result, shapes of pores provided at the mold are not transferred, and when molded, a heat treatment can be conducted in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a molded article thermoformed from a thermoplastic resin sheet such as a packaging container material.

[0002]

2. Description of the Related Art Thin-walled molded articles such as packaging container materials are often produced by thermoforming in which a thermoplastic resin sheet is heated and softened and molded using a mold. Above all, vacuum forming and pressure forming are often used. However, since these are heated to a temperature at which they can be molded on a hot plate provided at a position facing the mold during molding with a mold, the surface shape of the hot plate such as small holes for air blowing during compressed air molding is reduced. In the case of transfer onto the sheet surface or in the case of vacuum forming, the shape of the small holes provided in the mold for sucking the sheet is transferred, and this has been a major problem in appearance, especially in the case of a transparent molded product.

[0003] In addition, when the thickness of the sheet is large, the heating time is prolonged. However, in thermoforming, a thermoplastic resin sheet is heated on a hot plate provided at a position opposed to a mold.
Overall, molding speed slows.

Further, there is another problem that when heated by directly contacting the hot plate, the shrinkage stress increases and the impact resistance is low.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a molding method in which the surface shape of a hot plate or a mold is not transferred during molding and the molding speed is high.

[0006]

According to a first aspect of the present invention, there is provided a method for molding a thermoplastic resin molded article, comprising a heating means and a molding means for a molded article thermoformed from a thermoplastic resin sheet. In the molding method, the heating unit is not in contact with the thermoplastic resin sheet, and is separated from the molding unit using a mold.

[0007] By using a non-contact heating means for the thermoplastic resin sheet, the surface shape of the hot plate is transferred to the sheet surface, or in the case of vacuum forming, the shape of the small holes provided in the mold is transferred. Is eliminated, and problems in appearance are eliminated. Further, since the heating means is separated from the molding means by the mold, the heat treatment can be performed in parallel with the molding by the mold, so that the molding speed is increased.

A thermoplastic resin molded article according to a second aspect of the present invention is formed by the method for molding a thermoplastic resin molded article according to the first aspect.

[0009] By molding by the molding method of the first aspect, it is possible to obtain a molded article having a beautiful appearance and improved impact resistance.

The thermoplastic resin molding of the present invention is characterized in that
As described in the above, preferably, the normal shrinkage stress (JIS
1.5 kg / cm ^{2 to} 4.0 kg /
cm ² is good.

Usually, when the shrinkage stress is in the above range, appearance and impact resistance are further improved.

According to the method of molding a thermoplastic resin molded article of the present invention, the problem of appearance is solved. The effect on the plastic resin molding is great.

[0013] Further, the thermoplastic resin molded article is preferably a thermoplastic resin molded article.
As described in (1), when the thermoplastic resin molded article is formed from a rubber-modified polystyrene resin sheet, the impact resistance is further improved.

According to a sixth aspect of the present invention, there is provided a molding apparatus for thermoforming a molded article from a thermoplastic resin sheet, wherein the thermoplastic resin sheet is provided upstream of molding means using a mold. Heating means is provided for heating the thermoplastic resin sheet without contacting it.

By thermoforming using the apparatus of the present invention, the surface shape of the hot plate is not transferred to the sheet surface, and in the case of vacuum forming, the shape of the small holes provided in the mold is not transferred. In addition, the problem of appearance is solved, and furthermore, at the time of molding with a mold, heat treatment can be performed in parallel,
The molding speed increases.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. 1 to 3 show an example of an embodiment of the molding method of the present invention, but the present invention is not limited to this. FIG. 1 is a schematic cross-sectional view showing the configuration of a molding apparatus comprising a heating means and a molding means using a mold for a thermoplastic resin molded article by the molding method of the present invention, FIG. 2 is an explanatory view of a molding process, and FIG. It is a perspective view of an example of the molded object (lid of the packaging container material) formed by the molding method of the present invention.

The apparatus 1 shown in FIG. 1 includes a vacuum forming apparatus 2 which is a forming means using a mold, a heating apparatus 3 (heating means) installed on the upstream side in the thermoplastic resin sheet conveying direction, and a thermoplastic resin sheet. It is mainly composed of the transport device 4.

The heating device 3 has a pair of heaters 5 and 5 facing each other with the thermoplastic resin sheet conveying device 4 interposed therebetween, and is not in contact with the thermoplastic resin sheet. The heating device 3 heats the thermoplastic resin sheet prior to thermoforming, prior to molding with a mold.

The vacuum forming apparatus 2 has a mold 8 for sucking and molding the conveyed heated thermoplastic resin sheet. The mold 8 has a plurality of small holes 10 for sucking air, making the gap between the thermoplastic resin sheet 9 and the mold 8 a negative pressure, and sucking the thermoplastic resin sheet. The small hole 10 is connected to a suction pump (not shown).

The thermoplastic resin sheet transporting device 4 transports the thermoplastic resin sheet 9 in the horizontal direction, and comprises an endless belt and a roll.

The vacuum forming by the forming method of the present invention is performed as follows (FIG. 2). The transparent polystyrene resin sheet 9 (thermoplastic resin sheet) conveyed by the conveying device 4 is heated to a moldable temperature by the heater 5 in the heating device 3 (FIG. 2A). After that, it is further transported into the vacuum forming device 2 by the transport device 4 [FIG.
(B)], the air in the molding apparatus is sucked through the small holes 10 of the mold 8, and the transparent polystyrene resin sheet 9 is sucked into the mold 8 (FIG. 2 (c)). [FIG. 2 (d)]. By blowing air from the small holes 10, the molded body 11 is separated from the mold 8, and the molding is completed.

In the present invention, if the heating means can be heated to a moldable temperature in a state in which the heating means is separated from the molding means by a mold and is not in contact with the thermoplastic resin sheet, the heating method and apparatus are provided. The configuration is not particularly limited.

In the present invention, as a molding means using a mold, a molding means in a commonly known method such as vacuum molding and air pressure molding can be used, and the molding method and apparatus configuration are not particularly limited except that there is no heating means. Not done.

The thermoplastic resin molded article molded by the molding method of the present invention is excellent in appearance and impact resistance, but preferably has a normal shrinkage stress (measured in accordance with JIS) of 1.5 k.
By molding so as to be g / cm ^{2 to} 4.0 kg / cm ² , appearance and impact resistance are further improved.

The thermoplastic resin sheet to be subjected to the molding method of the present invention is not particularly limited, and polystyrene resin, polypropylene resin, and the like generally used for thermoforming.
Although a polyethylene-based resin or the like can be used, the effect of the present invention appears particularly effectively in a biaxially stretched transparent polystyrene-based resin sheet.

Further, when the biaxially stretched transparent polystyrene resin sheet is a rubber-modified polystyrene resin sheet,
The impact resistance is further improved. The content of the rubber-modified polystyrene resin sheet is preferably about 0.5 to 20% by weight based on the whole resin.

Example 1 A biaxially stretched transparent polystyrene resin sheet (trade name: B-OPS, manufactured by Daicel Chemical Industries, Ltd.) was roughly 100 mm × 150 m by using a molding apparatus having the structure shown in FIG.
A rectangular parallelepiped packaging container material lid of mx 20 mm was formed. The heating conditions were 120 ° C. and 15 seconds, and the vacuum forming conditions were a mold temperature of 60 ° C. and a degree of vacuum of 100 TDrr.
As a result, the heating time can be performed in parallel with the vacuum forming,
The time required for vacuum forming excluding the heating time is 7.5 sec.
c, which had no transfer of the shape of the vacuum hole or the like in appearance. Further, the shrinkage stress was 2.0 kg / cm ² .

Comparative Example 1 Using a molding apparatus having the structure shown in FIG. 5, a packaging container material lid having the same shape as in Example 1 was molded from the same biaxially stretched transparent polystyrene resin sheet as in Example 1. The vacuum forming conditions were as follows: the heating condition was a hot plate at a temperature of 120 ° C., and the heating time was 9 s.
ec was performed in the same manner as in Example 1. As a result, the time required for vacuum forming was longer than in Example 1, and the appearance was inferior to Example 1. The shrinkage stress was measured in the same manner as in Example 1, and was found to be 5.0 k.
g / cm ² .

[0029]

According to the method for molding a thermoplastic resin molded article of the present invention, the obtained molded article is transferred to the surface of the hot plate by using a heating means which is not in contact with the thermoplastic resin sheet. In the case of vacuum molding or vacuum molding, the shape of the small hole provided in the mold is not transferred, and the problem in appearance is solved. Further, since the heating means is separated from the molding means by the mold, the heat treatment can be performed in parallel with the molding by the mold, so that the molding speed is increased.

The molded article of the thermoplastic resin obtained by the molding method of the present invention usually has a shrinkage stress (measured according to) of 1.
By a ^{5kg / cm 2 ~4.0kg / cm 2} ,
Appearance and impact resistance are further improved.

The method of molding a thermoplastic resin molded article of the present invention eliminates problems in appearance, and has a great effect on a thermoplastic resin molded article molded from a biaxially stretched transparent polystyrene resin sheet.

Further, when the thermoplastic resin molded article is a thermoplastic resin molded article molded from a rubber-modified polystyrene resin sheet, the impact resistance is further improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a configuration of a molding apparatus for performing thermoforming of a thermoplastic resin molded article by a molding method of the present invention.

FIGS. 2 (a) to 2 (d) are explanatory views of a molding step according to the molding method of the present invention.

FIG. 3 is a perspective view of an example of a molded article (a lid of a packaging container material) molded by the molding method of the present invention.

FIG. 1 is a schematic cross-sectional view showing another example of the configuration of a molding apparatus for thermoforming a thermoplastic resin molded article by the molding method of the present invention.

FIG. 5 is a schematic cross-sectional view showing a configuration of a molding apparatus for performing thermoforming of a thermoplastic resin molded article by a conventional molding method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Forming apparatus of this invention 2 Vacuum forming apparatus 2 'Compressed air forming apparatus 3 Heating apparatus 4 Thermoplastic resin conveying apparatus 5 Heater 8 Mold 9 Sheet (Either a cut sheet or a roll sheet, but a roll sheet in this case) 10 Small hole 11 Molded body 12 Hot plate

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 25:04 F term (Reference) 4F071 AA12X AA22 AA22X AA77 AF54Y AG28 AH04 BB08 BC01 4F201 AA13 AC03 AH56 AH58 AR20 BA04 BC01 BC02 BC12 BD07 BN01 BN50 4F208 AA13 AC03 AH56 AH58 AR20 MA01 MA02 MB01 MC01 MG01 MH06 MH10 MH30

Claims (6)

[Claims] 1. A molding method for a molded article thermoformed from a thermoplastic resin sheet, comprising a heating means and a molding means using a mold, wherein the heating means is not in contact with the thermoplastic resin sheet, and A method for molding a thermoplastic resin article, which is separated from a molding means. 2. A thermoplastic resin molded article formed by the method for molding a thermoplastic resin molded article according to claim 1. 3. The thermoplastic resin molded article according to claim ² , wherein the shrinkage stress (measured in accordance with JIS) is generally 1.5 kg / cm ^{2 to} 4.0 kg / cm ² . 4. A molded article made of a biaxially stretched transparent polystyrene resin sheet.
The thermoplastic resin molded article according to the above. 5. The thermoplastic resin molded article according to claim 4, wherein the biaxially stretched transparent polystyrene resin sheet is a rubber-modified polystyrene resin sheet. 6. A molding apparatus for thermoforming a molded article from a thermoplastic resin sheet, wherein a heating means for heating the thermoplastic resin sheet upstream of a molding means using a mold, wherein the heating means is not in contact with the thermoplastic resin sheet, is provided. A molding apparatus for a thermoplastic resin molded article, characterized in that: