CN102275317A

CN102275317A - Three-stage stretching process for cast film

Info

Publication number: CN102275317A
Application number: CN2011102302337A
Authority: CN
Inventors: 刘文艺
Original assignee: CHONGQING HETAI PLASTIC CO LTD
Current assignee: Chongqing runjiah and Limited by Share Ltd
Priority date: 2011-08-12
Filing date: 2011-08-12
Publication date: 2011-12-14
Anticipated expiration: 2031-08-12
Also published as: CN102275317B

Abstract

The invention discloses a three-stage stretching process for a cast film and belongs to the field of manufacturing of thin films and sheets. The process comprises the following steps of: mixing materials, extruding, casting pieces, preheating, performing three-stage stretching, quenching and sizing, cooling and annealing, embossing, performing corona treatment, trimming and winding. On the basis of the conventional two-stage stretching process, one stage of stretching is added in the three-stage stretching process; as longitudinal expansion amplitude is enlarged, the aperture ratio of the thin film is increased, the micropore diameter is increased and the transverse permeability is higher; furthermore, the thin film manufactured by employing the three-stage stretching process has high air permeability and smaller thickness difference.

Description

Three grades of drawing processes of casting films

Technical field

The present invention relates to three grades of drawing processes of a kind of casting films, belong to the making field of film and sheet material.

Background technology

Develop rapidly along with national economy, brought unprecedented opportunity to develop for the flexible package industry, plastic sheeting is as the important foundation material in the flexible package, and its demand every year, the amplification with 20% constantly increased, and developing high performance composite plastic film has become one of development trend; The tape casting is to utilize thermoplastic to produce one of method of plastic sheeting, its casting films of producing is transparent, high strength, face is strong, heat sealability and kink property are good, and this method speed of production is fast, material loss is few, become the main flow of producing high performance thin film in recent years, but traditional The tape casting all is that film is carried out secondary drawing, after having drawn, shortcomings such as the film thickness differs greatly, and it is inhomogeneous laterally to breathe freely have and point out in the document, it is constant to fix other process conditions, change the longitudinal stretching multiple, can control the aperture and the percent opening of film, but not have the people specifically to implement.

Summary of the invention

The invention is intended to provide the uniform casting films of a kind of longitudinal stretching three grades of drawing processes.

Purpose of the present invention can reach by following measure: three grades of drawing processes of casting films, and its technical process is:

1) batch mixing: masterbatch resin and returning charge are mixed;

2) extrusion molding: mixed raw material is extruded behind the extruder fusion plastification;

3) casting sheet: the raw material after the fusion is cast to cooling formation film on the casting roller through T type head;

4) preheating: the film behind the above-mentioned casting sheet is heated by preheat roll;

5) three grades of stretchings: the preheating rear film is undertaken three times by draw roll stretch;

6) typing of quenching: will be through the film after three grades of stretchings by the setting roll typing of quenching;

7) cooling annealing: will cool off by chill roll through the film after the typing;

8) embossing: will carry out embossed through the film after the supercooling annealing;

9) corona: the film after the embossed is carried out sided corona treatment;

10) cut edge: the film behind the corona is carried out rim charge cut, rim charge returns the batch mixing step;

11) rolling: the film after rim charge cut flattens by wind-up roll and batches.

The technique scheme difference with the prior art is: resin raw material is after the casting sheet stretches, acquisition has stable microporous membrane, this micropore can see through steam, water can not pass through in certain hydraulic pressure, the aperture of micropore and percent opening are indexs of film good air permeability, and traditional secondary drawing ventilated membrane, after having drawn, vertically thickness differs greatly, shortcomings such as it is inhomogeneous to breathe freely, three grades of drawing processes disclosed by the invention increase one-level and stretch on the basis of original secondary drawing, because vertically expanding becomes big, improved the percent opening of film, increased micropore size, laterally rate of perviousness becomes big, and the film of being made by these three grades of drawing processes is ventilative good, and thickness difference is less.

Further, reduce the thin film crystallization degree for carrying, improve the transparency of film, the temperature of described T type head is 230 ℃～250 ℃, and the temperature of chill roll is 25 ℃;

Further, in order to reduce breakage rate, improve drawing effect, the gap between the described draw roll is 1～3mm.

Description of drawings

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments:

Fig. 1 is the schematic flow sheet of the embodiment of three grades of drawing processes of casting films of the present invention.

The specific embodiment

As shown in Figure 1: three grades of drawing processes of a kind of casting films, its technical process is:

1) batch mixing: HDPE master batch (high density polyethylene (HDPE)) and returning charge are mixed;

2) extrusion molding: above-mentioned mixed raw material is added single screw extrusion machine, and this single screw extrusion machine front end is a T shape mouth mould, and described extruder temperature is controlled to be 260 ℃, and T shape head temperature is 250 ℃;

3) casting sheet: the HDPE colloidal sol body after the above-mentioned fusion is cast to cooling formation HDPE film on the casting roller through T type head, and described casting roller diameter is 600mm, and the temperature of casting roller is controlled to be 25 ℃;

4) preheating: by three preheat roll heating, the preheat roll temperature is controlled to be 60 ℃ with the HDPE film behind the above-mentioned casting sheet;

5) three grades of stretchings: will carry out little gap single-point longitudinal stretching by four draw rolls through HDPE film after the preheating, four draw rolls form three times and stretch, the adjusting extensibility is 1:1, minimum clearance between the adjacent draw roll is 3mm, like this, the HDPE film longitudinal extension after stretching through three times three times;

6) typing of quenching: will be through the HDPE film after three grades of stretchings by the typing of quenching of three setting rolls, the temperature of setting roll is controlled to be 50 ℃;

7) cooling annealing: the HDPE film after the typing of will quenching cools off by three chill rolls, and the temperature of chill roll is controlled to be 18 ℃;

8) embossing: will carry out embossed through the HDPE film after the supercooling annealing;

9) corona: the HDPE film after the embossed is carried out two-sided sided corona treatment, and described HDPE film surface wetting tension reaches 38 dyne;

10) cut edge: the HDPE film behind the corona is cut edge by the rim charge cutting machine, and the HDPE rim charge returns the batch mixing step;

11) rolling: the HDPE film after rim charge cut flattens by wind-up roll and batches.

By above technology, use three grades of stretchers and technology, the parameter of the HDPE film of acquisition is:

1, thickness: 60um ± 1, thickness deviation is less than 3.5%;

2, horizontal rate of perviousness: divide horizontal 8 points to detect gained data (the g/m 24h of unit): 2112,2119,2204,2200,2178,2155,2084,2093; Gained data fit 2100 ± 100g/m 24h standard;

3, the longitudinal thickness deviation is less than ± 1gsm.

The above only is the detailed description of preferred embodiment of the present invention, is not to be used for limiting the present invention, and the embodiment of all similar variations of doing according to creation spirit of the present invention all should be contained among the present invention.

Claims

1. three of casting films grades of drawing processes, its technical process is:

Batch mixing: masterbatch resin and returning charge are mixed;

Extrusion molding: mixed raw material is extruded behind the extruder fusion plastification;

Casting sheet: the raw material after the fusion is cast to cooling formation film on the casting roller through T type head;

Preheating: the film behind the above-mentioned casting sheet is heated by preheat roll;

Three grades of stretchings: the preheating rear film is undertaken three times by draw roll stretch;

The typing of quenching: with the film after stretched by the setting roll typing of quenching;

Cooling annealing: will cool off by chill roll through the film after the typing;

Embossing: will carry out embossed through the film after the supercooling annealing;

Corona: the film after the embossed is carried out sided corona treatment;

Cut edge: the film behind the corona is carried out rim charge cut, rim charge returns the batch mixing step;

Rolling: the film after rim charge cut flattens by wind-up roll and batches.

2. three grades of drawing processes of casting films according to claim 1 is characterized in that: the temperature of described T type head is 230 ℃～250 ℃, and the temperature of casting roller is 25 ℃～35 ℃.

3. three grades of drawing processes of casting films according to claim 1 is characterized in that: the gap between the described draw roll is 1～3mm.