CS204523B1 - Method of making the tubular foils from the polyolefines - Google Patents

Description

A description of the invention

REPUBLIC OF COPYRIGHT CERTIFICATE 204523 (11) (B,)

(61) (23) Show priority (22) Registered 05 02 79 (21) (PV 764-79) (51) Int. Cl.3B 29 F 3/08

OFFICE OFFICE

AND DISCOVERIES (40) Posted on 31 07 80 (45) Published 29 10 8? (75)

Author of the Invention ZVONÍČEK JOSEF ing., SÝKORA STANISLAV ing. CSc.,

MALÍK KAREL ing. CSc., VALÁŠEK JIŘÍ ing. And VÁŇA JOSEF, GOTTWALDOV (54)

A method for producing tubular films of polyolefins

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the production of polyolefin tubes.

Tubular films of thermoplastic polymers are commonly produced by extrusion of melt through a polymeric circular die, blow molding and cooling. By blowing and drawing the film at a rate higher than the extrusion speed, a longitudinal transverse orientation occurs. Foil cooling is most often ensured by blowing its outer surface with cold air. The cooled film is flattened, withdrawn and wound. The disadvantage of blown tubular films is the fact that the inner surfaces adhered to each other adhere to one another, so that it is difficult to handle e.g. A friction coefficient of at least 0.5 or less is required to provide a good slip of the film surface. This value is usually achieved only on the outer surfaces of the foils, while the coefficient of friction is usually 0.75-1.

It has been found that the cause of the different friction coefficients on both surfaces is the difference in diffusion of low molecular weight polymer blends (up to 1000 molecular weight), monomer residues, and film surface additives.

Diffusion studies have shown that the diffusion rate for melts is significantly higher than for solid polymers. The values found are from 10 " to 10 " in the case of melts, the order of magnitude being higher for solid polymers. In the present state of the art, this condition is only ensured on the outer side of the tubular foil, which is blown by cold air, but the air essentially only maintains the pressure required to increase the diameter of the foil inside the foil, but cooling is considerably less intense than on the outer The amount of diffused material here is substantially higher, with virtually all low molecular weight substances remaining on the inner surface and forming a sticky layer, in addition to the amount of low molecular weight substances on the surface, the surface profile is also applied to the foil. the small cooling surface shows only slight unevenness, which also increases the tendency of the surfaces to adhere to each other.

Blown films of polyolefins, especially polyethylene, are used extensively for the manufacture of bags, bags, and bags where filling of the inner surfaces is considerably hindered. The elimination of this drawback is the main purpose of the present invention.

This purpose is accomplished by a process wherein the cooling rate of the two surfaces of the extruded film ranges from 120 to 250 ° C / min and the heat flow when cooling from 1600 to 10,000W / m 2 sec, calculated on the film surface after blowing. A lower cooling rate is not sufficient to make the coefficient of friction of the inner surfaces lower 2 0 4 5 2 3

Claims (1)

2 than 0.5. However, with even quicker cooling, the surface of the film is so rough that it adversely affects the mechanical properties of the film (strength) and, in particular, its wettability. Another favorable consequence of the process of the present invention is the possibility of increasing the extrusion speed. While in the external cooling, the film temperature between the flattening rollers must be less than 50 ° C, with double-sided cooling, the film can already be folded at 65-70 ° C. the performance of all equipment. The following examples are provided to illustrate the invention. EXAMPLE 1 A film having a thickness of 0.05 mm and a composite width of 600 mm was extruded from the branched polyethylene. The temperature of the extruder barrel was 140-160 UC, the extrusion head temperature was 160-170 DEG C. The extruded film was cooled by blowing the outside and inside with cool air. 20% of the total quantity) and also only from the outside. Cooling speed achieved by double-sided blasting: 140 ° C / sec (5800 W / m 2 sec heat flow), PftEDMET Friction coefficient production method for inner and outer 0.15-0.5 s polyolefin coefficients extrudes spraying at a specific power of 2-4 kg / hr on 1 cm slots and extruded melt-blowing only 72 ° C / sec (thermal flow 3250 W / m 2 sec). The friction coefficient of the inner surface was reduced from 0.8 to 0.25, and the films made according to the invention were hardly adherent. The output increased from 175 kg / hr to 250 kg on external cooling. Example 2 A film of the same thickness and width was produced from the same material as in Example 1 on another apparatus. The outside cooling rate was 79 ° C / sec (3550 W / m 2 sec flux). By introducing double-sided cooling, the cooling rate was increased to 206 ° C / min (2900 W / m2sec heat flux), while the output increased 1.9 times. Example 3 For the production of self-supporting bags, a 0.25 mm thick film of 560 mm width was extruded from the polyethylene. The heat flow from the outside was 2600 W / m2sec. By providing internal cooling, the heat flux of 4600 W / m 2 sec increased, the power increased by 1.5X. Friction coefficient differences were proportional to the difference in flux. SUMMARY OF THE INVENTION The nina is cooled on both sides by external and internal blowing, wherein the cooling rate is 120 - 250 ° C / min and the thermal flow during cooling is 1600 10,000 W / m 2 sec calculated on the film surface after blowing. 204523