JPH0788931A - Method and apparatus for producing thermoplastic resin sheet or film - Google Patents

Abstract

PURPOSE:To produce a thermoplastic resin sheet or film made excellent in appearance characteristics such as glossiness or surface smoothness regardless of thickness by preheating a metal endless belt. CONSTITUTION:The film like thermoplastic resin 2 extruded from a T-die 1 in a molten state is cooled while pressed between a casting drum 3 and the corrosion-resistant endless metal belt 4 fitted over at least three metal rolls having horizontal axial lines and having flexibility imparted thereto under definite tension in a circular arc shape to be formed into a sheet. At this time, the belt 4 is preheated in the long section of the upstream region of the casting drum by a heating device A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a thermoplastic resin sheet or film suitable for packaging foods, stationery such as files, various packaging cases, various industrial applications and the like.

[0002]

2. Description of the Related Art Air knife method and polishing roller method are known as methods for producing the thermoplastic resin sheet or film.

[0003]

In the former air knife method, since a sheet or film is manufactured by press-bonding a film-like molten resin onto a cast drum with air pressure blown from a nozzle, fluctuations in the thickness of the sheet surface to which air is blown However, the smoothness cannot be maintained, and one side of the sheet or film is cooled by air, so rapid cooling cannot be performed. As a result, there is a drawback that a sheet or film excellent in surface smoothness and thickness accuracy cannot be formed. The upper limit of the pressure force of this air is about 3000 mm of water column, and since there is only one point of pressure contact with air, the production speed of a sheet or film of commercial value is about 20 m / min. Therefore, the air knife method is mainly used for producing a thin sheet or film having a thickness of about 0.2 to 0.5 mm, which does not require the appearance characteristics of the sheet or film, but the thickness is about 0. Not suitable for producing thick sheets of 7 mm or more. The latter polishing roller method is a method in which a sheet of molten resin is sandwiched between a pair of metal rollers to produce a sheet, but the contact between the pair of rollers completes the shaping of the sheet thickness and surface texture at the same time. When the take-up speed is as low as about 4 m / min or less, a sheet with excellent surface smoothness can be obtained, but when the take-up speed is about 6 m / min or more, the shaping of the sheet cannot be followed and a sheet with commercial value is obtained. I will not be able to. In addition, since a wavy wave is generated in a thin sheet having a thickness of about 0.4 mm or less, it becomes impossible to produce a sheet having a commercial value. The object of the present invention is to solve the above-mentioned problems of the prior art, to cool the front and back surfaces of a sheet or film to almost the same temperature, and to provide excellent heat characteristics such as gloss and surface smoothness, regardless of the thickness. It is an object of the present invention to provide a method and a device therefor capable of producing a plastic resin sheet or film at high speed.

[0004]

In order to solve the above-mentioned problems, a specific invention is a film-shaped thermoplastic resin extruded in a molten state from a T-die and a cast drum and three metal rollers having at least horizontal axes. It is characterized in that it is cooled to a sheet shape while being pressed in an arc shape with a corrosion-resistant metal endless belt that is applied with a certain tension and imparts flexibility, and the upstream side area of the cast drum is long. A method for producing a thermoplastic resin sheet or film is characterized in that the belt is preheated in a section.

In order to solve the above-mentioned problems, two metal rollers are arranged in the vicinity of the cast drum in this method invention at intervals in the circumferential direction, and at least a metal roller peripheral surface near the T die is disposed. A metal drum covered with a heat-resistant rubber or an elastomer having elasticity is pressed against the cast drum with the metal roller covered with the metal roller, and the metal endless belt and the cast drum are connected between these two metal rollers. It is characterized in that the thermoplastic resin is cooled while being pressed to form a sheet.

In order to solve the above-mentioned problems, the invention of this apparatus is such that, on the downstream side of the extrusion nozzle of the T-die, there is a cast drum which receives the thermoplastic resin extruded from this nozzle in its gap, and a cast drum which is located above this cast drum. One metal roller is arranged as a pair, and the first metal roller is equipped so as to be able to move toward and away from the cast drum, and the cast drum and the first metal roller are approached from each other. A second metal roller that is in contact with the peripheral surface of the cast drum is disposed on the downstream side in the rotation direction of, and the metal is formed between these two metal rollers and the third metal roller under a constant tension. In the area between the first and second metal rollers, the metal endless belt is engaged with the endless belt, and the metal endless belt runs along the peripheral surface of the cast drum. The first metal roller has a sickle property and is for covering the surface of the metal endless belt with the cast drum, and the surface of the first metal roller is coated with heat-resistant rubber or elastic elastomer. A heating device for preheating the metal endless belt is arranged in a long section of the leading area between the roller and the third metal roller, and axes of the three metal rollers are horizontal. Alternatively, a film manufacturing device is used.

In order to solve the above-mentioned problems, the cast drum of the present invention has a structure which is heated from the inside, and the surface roughness is preferably 0.5 μm or less. In order to solve the above problems, it is desirable that the metal endless belt of the present invention is made of SUS, carbon steel or a titanium alloy. In order to solve the above-mentioned problems, the heating device of the present invention is a rectangular tube-shaped heat insulating cover having a top plate, a bottom plate and a pair of side plates that surround the running area over the entire length, and the running inside the heat insulating cover. It is preferable that the far-infrared heaters are arranged side by side on the top plate and the bottom plate portion at intervals along the front and back surfaces of the metal endless belt in the region.

The polypropylene resin, which is one of the crystalline thermoplastic resins used in the present invention, is a crystalline propylene homopolymer or a copolymer of propylene with one or more comonomers other than propylene, such as ethylene and butene. Crystalline copolymers and mixtures thereof are used. These polypropylene resins include antioxidants, lubricants, antistatic agents, slip agents, anti-blocking agents, UV absorbers, nucleating agents, transparency improvers, organic peroxides, pigments, inorganic materials such as talc and calcium carbonate. In some cases, a system filler, an organic filler such as wood powder or synthetic fiber, another resin or rubber such as polyethylene or ethylene propylene rubber may be appropriately added and used. Further, other thermoplastic resins include polyethylene, polystyrene, and AB.
S, polyethylene terephthalate, polybutylene terephthalate, polyamide, polycarbonate, vinyl chloride or the like can be used. The sheet or film manufacturing method and apparatus described above are also applicable to the manufacturing of multilayer sheets or laminated sheets. If necessary, the sheet or film thus produced is directly introduced into a water tank for secondary cooling, and then the cooling liquid adhering to the sheet surface is removed, and then the heat distortion temperature of the thermoplastic resin using this sheet. When the heat treatment is performed in the temperature range of -40 ° C to the heat distortion temperature + 15 ° C, the transparency of the crystalline thermoplastic resin increases.

[0009]

EXAMPLES Next, typical examples of the apparatus invention according to claims 3 to 6 will be described below. In FIG. 1, 1
Is a T-die, and on the downstream side of the extrusion nozzle of the T-die 1, a cast drum 3 for receiving a molten polypropylene resin 2 which is a kind of thermoplastic resin extruded from the nozzle in its gap and a position above the cast drum 3. The first metal rollers 5 are arranged as a pair, and the first metal rollers 5 are provided so as to be able to approach and separate from the cast drum 3. A second metal roller 6 that is in contact with the peripheral surface of the cast drum 3 on the downstream side in the rotation direction of the cast drum 3 from the approach point between the cast drum 3 and the first metal roller 5 is arranged. The metal endless belt 4 is engaged between the two metal rollers 5 and 6 and the third metal roller 7 under a certain tension. The metal endless belt 4 has flexibility to run along the peripheral surface of the cast drum 3 in the area between the first and second metal rollers 5 and 6, and the metal endless belt 4 is attached to the cast drum 3. The surface of the first metal roller 5 for pinching is covered with heat-resistant silicone rubber or elastic elastomer.
The coating thickness is 5 to 15 mm, and the rubber hardness of the elastomer used is 55 to 85 degrees. Further, the first
A heating device A for preheating the metal endless belt 4 from the front and back sides is arranged in the traveling area 10 between the metal roller 5 and the third metal roller 7, and the three metal rollers 5, 6,
The axis of 7 is horizontal. The heating device A includes a rectangular tube-shaped heat insulating cover 11 having a top plate, a bottom plate, and a pair of side plates that surround the running area 10 over the entire length, and the metal endless belt 4 in the running area 10 in the heat insulating cover 11. The far-infrared heaters 12 are arranged side by side on the top plate and the bottom plate at intervals along the front and back surfaces of the above. A hot air blowing nozzle may be used instead of the far infrared heater 12. The cast drum 3 has a structure in which it is heated from inside by heating oil or the like, and has a surface roughness of 0.
The thickness is 5 μm or less, preferably 0.3 μm or less. The metal endless belt 4 is made of SUS, a kind of carbon steel or titanium alloy, and SUS is preferable from the viewpoint of corrosion resistance.

The surface roughness of the metal endless belt 4 in contact with the molten resin is 0.5 μm or less, preferably 0.
This metal endless belt 4 is preferably 3 μm or less.
Is used as a belt by welding a thin metal plate, it is necessary to prevent the unevenness of the weld joint from affecting the sheet. When the thickness of the metal endless belt 4 is thin, unevenness is likely to occur in the connecting portion, and when it is thick, the flexibility of the metal endless belt 4 is lost and use is hindered. Therefore, the thickness of the metal endless belt is 0.5 to 1.2 mm. The degree is appropriate.

Next, the operation of the apparatus of the embodiment will be described in the above
A description will be given below together with a representative embodiment of the manufacturing method invention described in claim 2. First, the state where the first metal roller 5 is brought close to the peripheral surface of the cast drum 3 is set, and the T
The film-shaped polypropylene resin 2 extruded in a molten state from the die 1 is supplied between the metal endless belt 4 and the cast drum 3 which are engaged with the first metal roller 5, and then the cast drum 3 and the first drum The second metal rollers 5 and 6 and the metal endless belt 4 lead to the arc-shaped pressing portion 8 formed by the cast drum 3 and the metal endless belt 4. At this time, the variation in the molding thickness of the film-shaped polypropylene resin 2 is absorbed by the silicone rubber or the elastomer coated on the first metal roller 5. Further, the gap between the pressing portions 8 formed by the metal endless belt 4 which is engaged between the cast drum 3 and the first and second metal rollers 5 and 6 is mechanically caused by vertical displacement of the cast drum 3 or the like. Can be adjusted (not shown). The thickness of the product sheet or film 9 is finally set by setting the gap size of the pressing portion 8. At this time, the metal endless belt 4 moves in the traveling area 10 between the first and third metal rollers 5 and 7,
For example, the heating device A heats it to 120 ° C to 140 ° C.

Therefore, the molten resin is used as the metal endless belt 4.
The temperature of the primary cooling sheet 9 that has been cooled from the both sides substantially evenly between both sides and the casting drum 3 and then sent out from the arc-shaped pressing portion 8 varies from the heat distortion temperature of the polypropylene resin to the softening temperature (test method). Is set in accordance with JIS K-6758 and a load of 1 kgf, and the same shall apply hereinafter). If the temperature is lower than the heat deformation temperature, a sheet having excellent transparency and gloss cannot be obtained, and if the temperature is higher than the softening temperature, the sheet is too soft and peelability from the cast drum 3 or the metal endless belt 4 is deteriorated. However, fine scratches may frequently occur on the surface of the sheet, or wrinkles may occur in the sheet in the step of introducing the sheet into a water tank (not shown), so that a good sheet may not be formed.

If necessary, the first metal roller 5'is completely separated from the cast drum 3, and the film-shaped polypropylene resin 2 is guided to the pressing portion 8 to adjust the thickness of the resin 2. The fluctuation may be absorbed by the flexibility of the metal endless belt in the compression portion 8 (see FIG. 2).
In this case, the peripheral surface of the first metal roller 5'may not be covered with rubber or an elastic elastomer.

[0014]

According to the manufacturing method of the present invention, the metal endless belt is sufficiently preheated in a relatively long section of the upstream side of the cast drum even during high speed molding, and the circle It is possible to obtain a thermoplastic resin sheet or film having excellent appearance characteristics such as gloss and surface smoothness in which the front and back surfaces of the sheet or film are cooled from both sides in the arcuate pressure portion and are maintained at approximately the same temperature. .
Further, the product sheet or film can be manufactured with high quality from thin products to thick products, and the production speed can be increased several times faster than the conventional method. Therefore, the sheet or film obtained by the production method of the present invention is suitable for packaging such as food packaging and pharmaceutical packaging, for stationery, packaging cases such as cosmetics and household items, and industrial materials. In particular, in the method invention described in claim 2, in addition to the above effects,
The heat-resistant rubber or the elastomer having elasticity on the peripheral surface of the first metal roller can sufficiently absorb the variation in the thickness of the sheet or film and improve the thickness accuracy. According to the apparatus invention described in claim 3, the manufacturing method according to any one of claims 1 and 2 can be implemented, and equivalent effects can be obtained. In the device invention described in claim 4, in addition to the effect of the device invention described in claim 3, the transferability of the thermoplastic resin sheet or film can be enhanced, and the surface smoothness of this sheet or film can be enhanced. . In the device invention described in claim 5, in addition to the effect of the device invention described in claims 3 to 4, the corrosion resistance of the metal endless belt can be enhanced. In the device invention described in claim 6, in addition to the effect of the device invention described in claim 3, the structure of the heating device is simplified, and the front and back surfaces of the metal endless belt can be reliably preheated.

An experimental example will be described below. Experimental Example 1 A polypropylene resin sheet was manufactured using the apparatus shown in FIG. At this time, the polypropyrin resin used was Chisso Polypro XF1893 (manufactured by Chisso Corporation) having a density of 0.90 g / m ³ and a melt flow rate of 1.8 g / 10 min. The resin temperature is 240 ℃
With T-die extruder (extruder cylinder diameter 100m
m, L / D = 36, die width 550 mm, die lip interval 1.2 mm). The extruded molten resin was passed through the apparatus shown in FIG. 1 to obtain a polypropylene resin sheet having a thickness of 0.3 mm.

The sheet manufacturing conditions are as follows. Metal endless belt made of SUS, thickness 0.8 mm, width 600 mm, surface roughness 0.3 μm, preheating temperature by heating device 120 ° C.
Set cast drum width 650mm, surface roughness 0.3μm, preheat temperature 1
Set to 20 ° C. 1st metal roller Silicone rubber with rubber hardness of 65 degrees is 10mm thick
Coating Arc-shaped clamping part Length 60 cm, interval set to 0.3 mm Sheet take-up speed Cast drum and metal endless belt set to the same speed of 5 m / min The polypropylene resin sheet thus obtained is
It had excellent gloss and surface smoothness, and had no streaks, wrinkles, or waviness, and had excellent appearance characteristics.

Experimental Example 2 A polypropylene resin sheet having a thickness of 1.0 mm was manufactured under the same manufacturing conditions as in Experimental Example 1 except that the sheet take-up speed was 10 m / min. This sheet was also excellent in various characteristics similar to those of Experimental Example 1, that is, excellent in gloss and surface smoothness, and free of streaks, wrinkles, and waviness, and thus excellent in appearance characteristics.

Experimental Example 3 A polypropylene resin sheet having a thickness of 0.3 mm was manufactured under the same manufacturing conditions as in Experimental Example 1 except that the sheet take-up speed was 20 m / min. This sheet was also excellent in various properties similar to those in Experimental Example 1, that is, excellent in gloss and surface smoothness, and free from streaks, wrinkles, corrugations, and the like, and excellent in appearance properties.

Experimental Example 4 A polypropylene sheet having a thickness of 0.3 mm was produced under the same production conditions as in Experimental Example 1 except that the sheet take-up speed was 40 m / min. This sheet also has excellent gloss and surface smoothness.
Since it had no streaks, wrinkles, or waviness, it had excellent appearance characteristics.

Experimental Example 5 Using the apparatus shown in FIG. 2, the same T-die extrusion apparatus as in Experimental Example 1 was used, and the thickness was 1.0 m under the same manufacturing conditions.
m polypropylene resin sheet was produced. At this time, the first metal roller is separated from the peripheral surface of the cast drum, and the peripheral surface of the first metal roller is not covered with the silicone rubber. Therefore, in the arcuate pressing portion other than the second metal roller, the molten resin is held only by the peripheral surface of the cast drum and the metal endless belt, and is pressed by the tension applied to the metal endless belt and the restoring force of the metal endless belt. To be done. In this case, the length of the arcuate pressing portion is set to 40 cm. The sheet thus obtained had excellent gloss and surface smoothness, was free of streaks, wrinkles, and waviness, and had good appearance characteristics.

Experimental Example 6 Using the apparatus shown in FIG. 2 as in Experimental Example 5, a polypropylene resin sheet having a thickness of 0.3 mm was manufactured under the same manufacturing conditions as in Experimental Example 4. The sheet thus obtained was also excellent in glossiness and surface smoothness, free from streaks, wrinkles, and wavy, and had good appearance characteristics.

Comparative Example 1 The first metal roller 5 was used without using the metal endless belt of FIG.
The air knife is arranged at the position of No. 2, and the same resin as in Experimental Example 1 is used, and the sheet pulling speed is 10 m / min.
A 3 mm polypropylene resin sheet was produced. The gloss and surface smoothness of this sheet were slightly poor, and vertical wrinkles were generated.

Comparative Example 2 The same resin as used in Experimental Example 1 was used in a T-die extruding apparatus (extruder cylinder diameter 100 mm, L / D = 36, T-die width 600).
mm, die lip spacing 1.5 mm)
Extruded at 40 ° C., the extruded molten resin was subjected to a polishing roller temperature of 80 ° C., and a polypropylene resin sheet having a thickness of 0.3 mm was manufactured at a sheet take-up speed of 5 m / min. This sheet had good gloss and surface smoothness, but wavy. The characteristic values used in the experimental examples and comparative examples were measured by the following test methods. Melt flow rate: JIS K-6758 (23
0 ° C, load 2.16 kgf) Density: JIS K-6758 Surface smoothness, gloss: Visual observation Streaks, wrinkles, corrugations: Visual observation

[Brief description of drawings]

FIG. 1 is an explanatory view showing one embodiment of an apparatus for carrying out the method of the present invention.

FIG. 2 is an explanatory diagram showing another aspect.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 T-die 2 Membrane polypropylene resin 3 Cast drum 4 Metal endless belt 5 1st metal roller 6, 7 2nd, 3rd metal roller 8 Arc-shaped pinching part 9 Product sheet or film A Heating device

Claims (6)

[Claims] 1. A film-shaped thermoplastic resin extruded in a molten state from a T-die is interlocked with a cast drum and three metal rollers having at least horizontal axis lines, and a constant tension is applied to impart flexibility. A thermoplastic resin sheet or film characterized by preheating the belt in a long section in the upstream side region of the cast drum when the sheet is formed by cooling while pressing in an arc shape with a corrosive metal endless belt. Manufacturing method. 2. The two metal rollers are arranged in the vicinity of the cast drum at intervals in the circumferential direction, and at least the metal roller peripheral surface near the T-die has heat-resistant rubber or elastic elastomer. And the preheated metal endless belt is pressed against the cast drum by the coated metal roller, and the thermoplastic resin is cooled while sandwiching the thermoplastic resin between the two metal rollers by the metal endless belt and the cast drum. The sheet or film manufacturing method according to claim 1, wherein the sheet or film is produced. 3. A casting drum, which receives the thermoplastic resin extruded from this nozzle in its gap, and a first metal roller located above this casting drum, are arranged as a pair on the downstream side of the extrusion nozzle of the T die. Yes, this first
The metal roller of the cast drum is provided so as to be able to approach and separate from the cast drum, and in the rotation direction of the cast drum from the approach point of the cast drum and the first metal roller, the metal roller of the Second to contact
The metal endless belt is engaged under a constant tension between these two metal rollers and the third metal roller, and the area between the first and second metal rollers is arranged. In the above, the metal endless belt has flexibility to run along the peripheral surface of the cast drum, and the surface of the first metal roller for pressing the metal endless belt on the cast drum is made of heat-resistant material. A heating device is provided which is coated with rubber or an elastomer having elasticity and which preheats the metal endless belt over substantially the entire length of the traveling area between the first metal roller and the third metal roller. The apparatus for producing a thermoplastic resin sheet or film, wherein the axis of the two metal rollers is horizontal. 4. The apparatus for producing a crystalline thermoplastic resin sheet or film according to claim 3, wherein the cast drum has a structure heated from the inside and has a surface roughness of 0.5 μm or less. 5. The apparatus for producing a thermoplastic resin sheet or film according to claim 3, wherein the metal endless belt is made of one of SUS, carbon steel and titanium alloy. 6. The heating device comprises a rectangular tube-shaped heat insulating cover having a top plate, a bottom plate and a pair of side plates that surrounds the running area over the entire length, and the metal endless belt in the running area in the heat insulating cover. 4. The thermoplastic resin sheet or film manufacturing apparatus according to claim 3, comprising a far-infrared heater arranged in parallel on the top plate and the bottom plate at intervals along the front and back surfaces.