JP2000102977A - Method for producing thermoplastic resin film - Google Patents

Abstract

[PROBLEMS] To provide a method for efficiently producing a thermoplastic resin film by a simultaneous biaxial tenter stretching method. SOLUTION: This is a method for producing a thermoplastic resin film using a simultaneous biaxial stretching type tenter, wherein the simultaneous biaxial stretching is performed under a temperature condition in which the temperature of the stretching step is lower than the temperature of the preheating step by 10 ° C. or more. A method for producing a thermoplastic resin film, comprising:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin film by simultaneously biaxially stretching a raw sheet of thermoplastic resin by a simultaneous biaxial tenter stretching method. The present invention relates to a method for producing a thermoplastic resin film having excellent shrinkage performance by axial stretching.

[0002]

2. Description of the Related Art Stretched films of thermoplastic resins, particularly stretched films of polypropylene, are excellent in mechanical properties, chemical resistance, transparency, water vapor permeability, etc., even though their raw materials are relatively inexpensive. It is used in a wide range of fields, such as miscellaneous goods and industrial use.

[0003] Stretched thermoplastic resin films used in such applications are required to have shrinkage characteristics according to the respective applications, and for example, low-temperature shrinkage or isotropic shrinkage is required. As a method for producing a film having these shrinkage characteristics, for example, a tubular simultaneous biaxial stretching method has been conventionally used. In the simultaneous tubular biaxial stretching method, a thermoplastic resin melt-plasticized is extruded into a tubular raw material in an extruder, rapidly cooled, heated to a predetermined temperature, and then taken up while expanding in a bubble shape. In this method, the raw material is biaxially stretched at the same time in the MD (vertical direction) and TD (horizontal direction) by increasing the speed in the direction. In addition,
The stretched film is heated again and heat set.

[0004] The tubular simultaneous biaxial stretching method is effective as an industrial stretching method for exhibiting low-temperature shrinkage and isotropic shrinkage, but has a low processing speed and low productivity.
This method has problems that the film thickness accuracy is low and a film having a uniform thickness cannot be obtained, and a high degree of skill is required for stretching.

As a stretching method which can avoid these problems, there is a sequential biaxial tenter stretching method. this is,
The thermoplastic resin melt-plasticized in an extruder is extruded into a sheet-shaped raw material, rapidly cooled, stretched in the MD direction while being heated by passing through a plurality of heating rolls, and further guided to a tenter to a predetermined temperature. Under the following conditions. This method generally has a higher processing speed and higher productivity than the tubular stretching method. Further, the thickness accuracy of the obtained film is high. However, this method uses MD stretching and T
Since the D stretching is not performed at the same time, and the stretching methods of the MD stretching and the TD stretching are different, the resulting film has anisotropy in terms of mechanical properties and shrinkage characteristics. In addition, the sequential biaxial tenter stretching method is inferior to the tubular stretching method in terms of ease of low-temperature stretching, and in particular, it is difficult to perform stretching at a low temperature in the TD stretching step, so that the low-temperature shrinkage property of the film is hardly exhibited. . Also in the tenter stretching method, a simultaneous biaxial stretching type is known, and is mainly used for biaxial stretching of nylon. However, conventionally, simultaneous biaxial stretching type tenters have not been used industrially in the processing of resins other than nylon, because the structure of the equipment is complicated, the processing speed is low, and the productivity is low. It is not used as a means for imparting the shrinkage characteristic of

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently producing a thermoplastic resin film by a simultaneous biaxial tenter stretching method. Another object of the present invention is to provide a stretched thermoplastic resin film having excellent shrink performance and thickness accuracy.

[0007]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies on a stretching method using a simultaneous biaxial stretching type tenter. It has been found that the object of the present invention is achieved by biaxial stretching, and the present invention has been completed.

That is, the present invention relates to a method for producing a thermoplastic resin film using a simultaneous biaxial stretching type tenter, wherein the temperature of the stretching step is 10 ° C. with respect to the temperature of the preheating step.
This is a method for producing a thermoplastic resin film, characterized in that the film is simultaneously biaxially stretched under a low temperature condition. Hereinafter, the present invention will be described in detail.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The thermoplastic resin used in the present invention is:
There is no particular limitation, for example, ethylene resin,
Propylene resin, polybutene, styrene resin, polyester, polyamide, polycarbonate resin, poly (4-methylpentene-1) resin, and the like. Among these, ethylene-based resins, propylene-based resins, and olefin-based resins such as polybutene are preferred. Among them, propylene-based resins are relatively inexpensive but have mechanical properties, chemical resistance, transparency, and water vapor permeability. It is more preferable since it is excellent in such properties as shrink film.

[0010] The propylene-based resin is a polymer containing propylene as a main component, and its type is not particularly limited. As the propylene-based resin, for example, propylene homopolymer,
A propylene-α-olefin copolymer is exemplified. α
-As the olefin, for example, ethylene, butene-1,
One or more α-olefins such as hexene-1 can be used. Further, the copolymer may be any of a random copolymer and a block copolymer.

The ethylene resin is a polymer containing ethylene as a main component, and there is no particular limitation on the type of the ethylene resin. Examples of the ethylene-based resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-4-methylpentene-1 copolymer, and ethylene-ethylene.
Ethylene-α such as hexene-1 copolymer, ethylene-octene-1 copolymer and ethylene-decene-1 copolymer
-Olefin copolymers, and furthermore, ethylene-based copolymers of ethylene with unsaturated compounds such as conjugated dienes and non-conjugated dienes or copolymer components such as acrylic acid, methacrylic acid and vinyl acetate. These ethylene resins may be those modified with an acid, for example, a polymer graft-modified with an α, β-unsaturated carboxylic acid, an alicyclic carboxylic acid, or a derivative thereof.

Next, the stretching method using the simultaneous biaxial stretching type tenter of the present invention will be described. The stretching method includes an extrusion step, a preheating step, a stretching step, and a heat setting step. First, in the extrusion process of the raw sheet, a known casting facility can be applied. A known T-die is used as a die, and the thermoplastic resin melt-kneaded by an extruder is extruded from the T-die and taken up by a cooling roll to cool and solidify the raw sheet. In this step, the thermoplastic resin may be guided from a plurality of extruders to a multilayer T-die to obtain a multilayer raw sheet. Further, a water cooling system in which a cooling roll portion is immersed in a water bath can be used. The extrusion process may be integrated with a process group after the preheating process described below, or may be independent.

Next, the obtained raw sheet is guided to a simultaneous biaxial stretching type tenter, and a preheating step, a stretching step, and a heat setting step are performed. The simultaneous biaxial stretching type tenter has a large number of clips that grip the raw sheet symmetrically along the center line in the MD direction so that the clips that can grip the rail can go around on the rail, and the clips grip both ends of the raw sheet at the entrance. And a step of extending the clip (rail) to the left and right while the distance between the clips on the rail gradually widens (stretching step), and a width after the step is extended. Or 5 to 10 from the width after spreading
% (A heat setting step). Further, in the heat setting step, relaxation can be performed in the MD direction. Note that the heat setting step referred to herein is a generic term for a step after passing through a stretching step, and in this step, it may be subdivided into, for example, a relaxation step and a cooling step. Thus, the raw sheet is simultaneously stretched in the MD and TD directions in the tenter. At this time, the start and end points of stretching in both the MD and TD directions do not necessarily need to coincide. Generally, each of the above-mentioned steps has a structure capable of independently controlling the temperature, and in each step, the temperature may be further divided into a plurality of temperature control sections.

[0014] In the prior art, the above preheating step,
In the stretching step and the heat setting step, a method of controlling the temperature to substantially the same temperature is adopted. The present invention is characterized in that the temperature of the stretching step is lower than the temperature of the preheating step. That is, the temperature of the stretching step is lower than the temperature of the preheating step by 10 ° C. or more, preferably 20 ° C. or more, and simultaneous biaxial stretching is performed under these conditions. When the preheating step and the stretching step are divided into a plurality of temperature control zones, the average value of the temperatures of the respective steps is applied.

The temperature in the heat setting step can be arbitrarily set as required. However, considering the dimensional stability of the stretched film, a temperature equal to or lower than the temperature in the stretching step by 20 ° C. It is preferred that

The stretching machine used in the stretching of the present invention is not particularly limited as long as it is a tenter stretching machine of a simultaneous biaxial stretching system, and a device using a mechanism such as a pantograph or a screw as a running system of the clip, or A device using a linear motor or the like can be used. Above all, devices where the clip drive system is a linear motor drive system,
Since the productivity is high and the degree of freedom of the stretching conditions is high, it is extremely useful in practicing the present invention. As an apparatus using a linear motor, for example, L.
ISM tenters.

[0017]

Hereinafter, the present invention will be described based on examples.
The present invention is not limited to these examples.

The methods for measuring physical properties in the examples and comparative examples were as follows. (1) Heat shrinkage rate In a silicone oil bath maintained at a predetermined temperature, MD,
A film sample cut into a square having a length of 9 cm in each of the TD directions was immersed for 5 seconds, and the dimensions x of the film taken out of the bath were measured for MD and TD.
The obtained dimension x (cm) is substituted into the following equation, and the heat shrinkage s
(%) Was calculated for each of the MD and TD directions.
Silicon oil bath temperature is 110 ℃ and 120 ℃
Were measured for two levels. s (%) = (1−x / 9) × 100

Example 1 Propylene-terpolymer resin (Sumitomo Noblen FL85)
1, MFR = 6.5 g / 10 min) was formed using a T-die film forming machine manufactured by Chugai Tec Corporation. Specifically, a propylene terpolymer resin is melt-kneaded at 250 ° C. with an extruder having an L / D of 32 at 50 mmφ, extruded from a T-die (600 mm width) controlled at 250 ° C., and taken up by a chill roll at 10 ° C. And solidified into a 300 μm-thick raw sheet. Next, the raw material was simultaneously biaxially stretched by a desktop stretching machine manufactured by Toyo Seiki. Specifically, the raw sheet was set on a table-top stretching machine controlled at 100 ° C., preheated for 5 minutes, and the MD of the raw sheet was immediately set to 50 ° C. by opening the lid of the stretching machine and opening the lid of the stretching machine. Direction and TD direction.
Simultaneous biaxial stretching was performed at a magnification of 5 times. Stretching speed is MD direction,
It was 1 m / min both in the TD direction. The heat shrinkage of the obtained stretched film was measured. Table 1 shows the results.

Comparative Example 1 In Example 1, after preheating at 100 ° C. for 5 minutes, 100 ° C.
The film was stretched in the same manner as in Example 1 except that the film was simultaneously stretched biaxially while maintaining the above. The heat shrinkage of the obtained stretched film was measured. Table 1 shows the results.

[0021]

Table 1--------------------------------------------------------------------------------------------------------------------- −−−−−−−−−−−−−−−−−−−−−− Heat shrinkage (%) MD / TD MD / TD 110 ° C 37/35 11/10 120 ° C 51/49 33/31 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0022]

As described above, according to the present invention, a method for efficiently producing a thermoplastic resin film by the simultaneous biaxial tenter stretching method can be provided. Further, the present invention can provide a stretched thermoplastic resin film having excellent shrink performance and thickness accuracy.

Claims (5)

[Claims] 1. A method for producing a thermoplastic resin film using a simultaneous biaxial stretching type tenter, wherein the simultaneous biaxial stretching is performed under a temperature condition in which the temperature of the stretching step is lower than the temperature of the preheating step by 10 ° C. or more. A method for producing a thermoplastic resin film. 2. The method for producing a thermoplastic resin film according to claim 1, wherein the temperature in the stretching step is lower than the temperature in the preheating step by 20 ° C. or more. 3. The method for producing a thermoplastic resin film according to claim 1, wherein the thermoplastic resin is an olefin resin. 4. The method according to claim 1, wherein the thermoplastic resin is a propylene-based resin. 5. The method for producing a thermoplastic resin film according to claim 1, wherein the clip driving method of the simultaneous biaxial stretching type tenter is a linear motor driving method.