JPS5957720A - Manufacture of thermoplastic resin sheet or film - Google Patents

Abstract

PURPOSE:To obtain inexpensively the titled product excellent in transparency, surface gloss and homogeneity, by introducing a thermoplastic resin that is melted and extruded from a T-die into a slit from upstream that has a specified constitution and into which water is allowed to run. CONSTITUTION:The slit 4 has such a constitution that a pair of rotating endless belts 3, 3' are opposed with a gap therebetween, water is allowed to run down in the gap, and the opposed surfaces of the endless belts 3, 3' are moved in the same direction as the running direction of the water. The thermoplastic resin 2 that is extruded from the T-die into the form of a film in the molten state is led from upstream into the slit 4 to be cooled. further, generally, the cooled resin 2 is cooled in cooling water in a water receiving tank 12 to provide the intended item. Preferably, the temperature of the cooling water is 2-30 deg.C. EFFECT:Even a high quality thick sheet or the like can be formed at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing thermoplastic sheets or films.

Conventionally, the chill roll method, the water cooling method, and the like are known as methods for making a T-Guy quenched sheet or film of a thermoplastic resin. However, during high-speed molding, the chill roll method can introduce air between the roll and the molten resin film, and the adhesion between the roll and the molten resin film is poor, resulting in uneven thickness and wrinkles. However, there are drawbacks such as occurrence of curling due to the difference in cooling between the front and back surfaces of the molten resin film, and a decrease in transparency and surface gloss due to insufficient rapid cooling. In addition, in the water cooling method, heat dissipation from the molten resin film occurs locally on the cooling water surface, resulting in swelling spots due to boiling of the water surface, uneven cooling due to ripples and shaking of the water surface, uneven thickness due to insufficient cooling, and haze spots. It has the disadvantage that it causes unevenness and reduction in surface gloss and transparency, and high-speed formation cannot be performed.

Incidentally, the water cooling method has the advantage of being able to cool sheets etc. more efficiently than the roll method. Therefore, as methods to improve the drawbacks of the water cooling method described above, there are methods such as (1) cooling the molten resin film with a cooling water flow flowing on both sides, and (2) introducing the molten resin between rollers with slits provided in the cooling tank. Proposed. However, even with these methods, properties such as transparency and high-speed moldability of the sheet cannot be fully satisfied.

Motoyama N11 d: has already proposed a method for producing thermoplastic resin sheets or films that eliminates these drawbacks (71-!1' No. 357-55291, 57
No. 86475) is an object of the present invention to provide a method for producing a thermoplastic resin sheet or film such as kJ-23i.

The present invention is a slit in which a thermoplastic resin in the form of a film extruded from a T-die in a molten state is formed by a pair of rotating endless belts facing each other with a gap between them. A slit that moves the opposing surface of the endless belt in the same direction as the flow direction of the water,
This is a method for producing a thermoplastic resin sheet or film, characterized in that the thermoplastic resin sheet or film is introduced from upstream to downstream.

The thermoplastic resin used as a raw material for sheets and films in the present invention is not particularly limited, and examples thereof include polyolefins (polyethylene, polypropylene, etc.), polystyrene, polyvinyl chloride, etc. Crystalline thermoplastic resin 1iW, which had problems with surface properties and the like, can also be used without causing such problems. In addition, the sheets and films of the present invention include multilayer sheets and films,
In addition, silica, talc, para-tertiary butyl,
Also included are those to which a nucleating agent such as fric acid, aluminum, and dibenzylidene sorbitol is added.

Hereinafter, the method of the present invention will be explained with reference to the drawings. FIGS. 1 and 2 are explanatory diagrams showing aspects of an apparatus for carrying out the method of the present invention.

A pair of rotating endless bells through which cooling water flows to extrude a film-like thermoplastic resin 2 in a molten state from a T-die 1! 1
．． 3' is introduced into the slit 4 from the upstream direction. There is no particular restriction on the material of the endless belt 3°6', but metal such as stainless steel, rubber, etc.
It is preferable to use a fabric coated or impregnated with a resin having excellent heat resistance and smoothness, such as a fluororesin.

A pair of endless bells) 5.5' are each sai tv, moving roll 5
．． 5' and rotates on the roll. The slit 4 is formed by making a pair of such rotating endless bells 5, 5' face each other with a space between them. During this time, cooling water is flowing through the slit 4, and a pair of endless bells 3.5' facing 7 and 1 d, the above-mentioned cold It is moving in the same direction as the water flow. In other words, according to Fig. 1.2, both the χ and 1 facing surfaces tit are moving in the same downward direction as the water flow direction, so there is no! /jiff bell) 5 rotates to the right, and the endless belt 3' rotates to the left.

Here, the width of the slit 40 varies depending on various conditions, and is -1
Define ζ-, difficulty is 1, but usually 05-10
Door, preferably 05-5 +ll [. In addition, the distance between the slit and the die (air gap) and the length of the slit vary depending on various conditions, but the former is usually 50 to 250 mm.
Q. The latter is 50-2 Bam. Note that if the rolls are made variable, the h + air gap between the slits and the length of the slits can be made arbitrary by appropriately changing the position of the rolls.

In addition, there is no particular restriction on the drive means of the ia peltro 5', and as shown in the first part, the power of the motor 6 etc. is transmitted to the drive σt) J roll 5 via the chain 7 etc. f; (driving the drive roll 5' by a car or the like (not shown), and driving the endless bell by this drive roll 5.5') 3
, 3', or other known driving means may be used.

The supply of cooling water is through a cooling water supply nozzle (or slit) 8.8' as shown in FIG.
Any type of water tank 9, 9' as shown in FIG. 2 may be used.

The film-like thermoplastic resin 2 is cooled by cooling water as it passes through the water flow slit 4 from upstream to downstream. On both sides of the slit 4, a pair of rotating endless belts 5.5' Since the 7λ is moving in the same direction as the cooling water flow direction, cooling is performed uniformly and efficiently. Mugen Peltolo here.

The rotational speed (Vv) of 3' varies depending on various conditions such as the flow rate of cooling water, but the general rule is 5 to 5 Q m/m1n, and it is different from the molding speed (v8) of the thermoplastic resin sheet or film. Well, the following range 1! (It is preferable to select by ().

10 Vs > Vv :> 02Vs The rotational speed (Vv) of the endless belt is determined by the sheet or film forming speed (
7), the rotation of the endless belt should be determined appropriately depending on the width of the sheet or IT film, the spacing of the slits, the initial velocity of the cooling water (1η), etc. If J(Vv) is outside the above conditions, the transparency of the sheet or film will deteriorate,
This is not desirable because it causes haze spots to appear.

In the figure, to and to' are backup rolls, +1.
II' is a tension roll.

The film-like resin thus cooled is sent to the water receiving tank 12. The water receiving tank 12 is provided with a guide roll 15 as shown in the figure, and after the film-like resin is cooled by cooling water in the water receiving tank 12, it is taken up by the take-up roll 14 via the guide roll 15. In addition, the guide roll 16
Regarding 17J: Positioning the resin film at the center of the slit is effective in preventing curling, but it can also be used as a transfer roll to transfer the mirror surface of the roll to the resin film.

The temperature of the cooling water used in the present invention is 2 to 50°C.
A suitable surfactant may be added if necessary to improve wetting of the resin film.

No. 213/, 1, 15 is an overflow plate, 16 is a cooler, 17
is a pump.

According to the improved water cooling method of the present invention, even when manufacturing sheets or films using crystalline thermoplastic resin as raw material, it is possible to obtain sheets, etc. that are unoriented and have excellent transparency and gloss. can. In addition, the resulting sheets are free from uneven thickness, wrinkles, curls, etc., and have excellent homogeneity. Furthermore, the method of the present invention has features such as being able to obtain relatively thick sheets of high quality by high-speed molding, and being able to be manufactured at low cost.

The sheets and films obtained by the method of the present invention have good transparency and surface gloss as described above, and are therefore suitable for packaging foods, medicines, and the like. In addition, pressure molding,
It can also be used as a raw fabric for solid-phase forming, such as roll pressing forming and stretched cedar pots.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example polypropylene (density o91 P/c1d, melt index 2.0y-710';)) was made of 7Ji? l7
1A/ffi 2B (J-Cte T-die extrusion device 1°t (extruder 60m+nj, L/]) = 28
.

Die width 55[]m+n, grip opening +mm)
wo) Extruded using T1.

3. The extruded molten resin is placed in a pair of rotating endless bells as shown in FIG. ! The cooling water formed by l' is introduced into the slit 4 formed by r, and the average thickness is 0.
Two pieces of polypropylene sheets were obtained. Note that the conditions are as follows. This polypropylene film had excellent transparency without haze spots or waving.

Manufacturing conditions Molding MI! IJ 25 tn/min.

Air gap +20mm Cooling water temperature 18℃ Slit width 5 tran Slit length +SO water level 5 ff Rotation speed of 11m endless belt 25 nI/mj-n.

Comparative Example 1 In Example 1, the endless bevel was
, C The procedure was carried out according to Example 1 except that polypropylene (polypropylene)', 1? ! )is. This polypropylene sheet had poor appearance.

Comparison 11 Example 2 Example 1 In Example 1, a gap of 5 mm is used instead of an endless belt.
Example 1 except that a molten resin film was introduced between the rolls.
A polypropylene sheet with an average thickness of 0.2 mm was obtained. This polypropylene sheet had poor appearance, such as haze spots, and was also poor in transparency.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing aspects of an apparatus for carrying out the method of the present invention. 1...T-die, 2...Membrane thermoplastic resin.

Claims (1)

[Claims] (+1 A slit formed by making a pair of rotating endless belts face each other with a gap in the film-like thermoplastic resin extruded in a molten state from T-Gui, allowing water to flow down into the gap, and A method for producing a thermoplastic resin sheet or film, which comprises introducing the belt from upstream to downstream into a slit through which water flows, which is formed by moving the opposing surface of a belt in the same direction as the water flow direction.