JPS599022A - Preparation of oriented film of acrylonitrile polymer - Google Patents

Abstract

PURPOSE:To obtain oriented film excellent in mechanical strength, transparency and thickness uniformity by stretching hydrous coagulated film of acrylonitrile polymer laterally in a tenter at a specified temperature, then, longitudinally in rolls at a specified temperature. CONSTITUTION:Hydrous coagulated film of acrylonitrile copolymer comprising acrylonitrile copolymer or homopolymer containing acrylonitrile of 60wt% or more is stretched laterally in a tenter under a condition of moisture contents of 10-50wt% (to the weight of dry polymer), ambient temperature 100-180 deg.C. Then, the film is stretched longitudinally at the moisture content lower than that at the transversely stretching time under 5-40wt% and in rolls having a surface temperature 70-150 deg.C to obtain biaxially oriented film of the titled compolymer. The moisture content of the hydrous coagulated film is adjusted by various drying methods using hot air, infrared rays, hot rolls etc. It is preferable to dip a hydrous original sheet into hot water of 50-90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a biaxially stretched film of an acrylonitrile polymer having excellent mechanical properties and uniform thickness.

Films of acrylonitrile-based polymers, especially high nitrile-containing polymers, cannot be easily oriented ((), and the production of biaxially stretched films is not easy.
No. 26582, Japanese Patent Publication No. 1974-7458, Japanese Patent Publication No. 1983-
Although it is described in Publication No. 142673, etc., there are problems with residual solvent in the stretched film and instability of stretching conditions, making it difficult to put it into practical use in terms of sanitary physical properties and thickness uniformity. .

The present inventors focused on the plasticizing effect of water on acrylonitrile-based polymers at high temperatures, and created biaxial sheets (hereinafter referred to as hydrated original fabrics) obtained by film-coagulation of a solution of acrylonitrile-based polymers. After many studies on the stretching method, we found that the stretching of a water-containing raw fabric by contact heating using a metal plate or metal roll has particularly low stretching stress (even raw fabric with a relatively low moisture content can be easily stretched, and it is possible to easily stretch a raw fabric with a sequential 2 We discovered that axial stretching is also possible, and furthermore, using a general-purpose roll tenter sequential biaxial stretching device, we performed tenter horizontal stretching under a specific temperature condition, and then roll longitudinal stretching under a specific temperature condition. By carrying out stable biaxial stretching, it was possible to obtain a stretched film with excellent mechanical strength, transparency, and uniformity of original size.

That is, in the present invention, a water-containing coagulated film of an acrylonitrile polymer is transversely stretched in a tenter under conditions of a water content of 10 to 50% by weight (relative to dry polymer weight) and an ambient temperature of 100 to 18Q°C, and then 5 to 50% by weight. The surface temperature is 70~ at a water content (relative to dry polymer weight) lower than that during lateral stretching of 40% by weight.
The present invention relates to the manufacturability of a biaxially stretched film of an acrylonitrile polymer, which is longitudinally stretched using rolls at 150°C.

The present invention will be explained in detail below.

The acrylonitrile polymer used in the present invention is:

It is an acrylonitrile copolymer or homopolymer containing 60% or more of acrylonitrile by breath.

Monomers used in the copolymerization include acrylic esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, feyol acrylate, octyl acrylate, etc. Acid esters such as methyl methacrylate, ethyl methacrylate, globyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, phenyl methacrylate, octyl methacrylate, etc., vinyl halides such as vinyl chloride, vinyl bromide, fluoride Vinyl, vinylidene chloride, vinylidene fluoride, etc., vinylamides such as acrylamide, methacrylamide, N-methylacrylamide, N-vinylpyrrolido, etc., vinyl esters such as vinyl acetate, vinyl propionate, vinyl lactate, etc., vinyl aromatic compounds such as styrene, vinyl Naphthalene, vinylpyridine, etc., vinyl carboxylic acids such as acrylic acid, methacrylic acid, unsaturated dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, etc., unsaturated dicarboxylic acid anhydrides such as itaconic anhydride, maleic anhydride, etc. , arylsulfonic acid or methallylsulfone (9) 1 Salts of these, methacrylonitrile, olefin examples, t is ethylene, globylene, etc. Polymers in which two or more of these monomers are copolymerized with acrylonitrile Both polymers and mixtures of these polymers are possible.

If the acrylonitrile content of the copolymer is less than 60% by weight, depending on the strain of the copolymer monomer, l of water = J
The ffi effect is reduced, making it difficult to stretch, and the properties expected of an acrylonitrile polymer film, such as ganne barrier properties and weather resistance, are insufficient. On the other hand, acryloni)
When the IJ content approaches 100%, that is, close to that of a homopolymer (the stretching stress increases and uniform stretching becomes difficult, but some amount of By supplementing the plasticizing effect, it is possible to perform uniform stretching.The upper limit of the acrylonitrile content that allows uniform stretching without such auxiliary means is 98% by weight.

The water-containing raw fabric of acrylonitrile polymer referred to in the present invention is
Generally, it is convenient to produce by the so-called wet coagulation method as described below. That is, a coagulated film is obtained by casting an acrylonitrile polymer solution onto the surface of a belt or drum, or extruding it into a sheet or tube shape from a slit die, and coagulating and forming the solution in an aqueous coagulating bath.

Solvents used to create the polymer solution include dimethylformamide, dimethylsulfoxide, N-dimethylformamide, N-methyl-β-cyanethylformamide,
There are aqueous solutions of inorganic acids such as α-cyanoacetamide, acetonitrile, γ-butyrodicton, nitric acid, sulfuric acid, zinc chloride, and sodium thiocyanate.

The polymer concentration in the polymer solution is preferably io]ki% or more for producing a dense stretched film, but conversely, the higher the polymer concentration, the higher the viscosity of the solution, and the more difficult it is to defoam, irradiation, etc. It becomes difficult.

Casting and extrusion of the polymer solution can be performed using known methods (.

As the aqueous coagulation bath used for coagulation, it is convenient to use water or an aqueous solution of the solvent used for solution preparation.In this case, it is best to increase the solvent concentration of the aqueous solution within the range where coagulation occurs. This is advantageous in producing films.

Generally, the concentration tends to be higher in organic solvents than inorganic solvents; for example, nitric acid is preferably 20 to 40% by weight, and dimethylformamide is preferably 30 to 60%. Furthermore, the higher the polymer concentration in the polymer solution, the denser the film can be obtained even if the solvent concentration in the coagulation bath is lowered.

Washing with water or warm water can be used to remove the solvent in the coagulated film. It is convenient for the degree of solvent removal to be incomplete in view of the plasticizing effect of the residual solvent during stretching, but it is preferable to be sufficient in view of the physical properties and uses of the resulting film.

The water-containing raw fabric thus obtained usually contains 50 to 400% by weight (based on the dry polymer weight) of water.

The water-containing raw fabric of the acrylonitrile polymer of the present invention can also be produced by the following method. That is, as described in Japanese Patent Publication No. 46-7458 and Japanese Patent Publication No. 49-20625, a film is formed by casting using a volatile organic solvent, and after evaporating the solvent to some extent with hot air, water or A method of replacing and removing residual solvent with hot water, or JP-A-48-
As described in Japanese Patent No. 49839, it can also be produced by a method in which the IJ group of an acrylonitrile polymer is hydrated with water to a semi-molten state, and then extruded into, for example, high-temperature, high-pressure steam -F.

The biaxial stretching can be carried out by adjusting the moisture content and temperature of the water-containing raw fabric within a certain range, and using a general-purpose roll-tenque sequential biaxial stretching apparatus.

The moisture content of the hydrous raw fabric can be adjusted using hot air, infrared rays, far infrared rays,
Drying methods such as steam, hot plates, and hot rolls can be used, but in any case, it is preferable to avoid rapid drying as it tends to cause devitrification and porosity in the original fabric. . Among these, drying with hot air has a relatively low drying efficiency, but can provide a stretched film that is transparent and has excellent mechanical strength. Further, as an efficient and uniform dehydration drying method, a method of immersing a water-containing raw fabric in hot water of 50 to 90°C can be used. This method is particularly effective for dewatering warp with high moisture content, for example, 250
By immersing a raw fabric having a water content of 10% by weight in hot water at 80°C for about 30 seconds, it can be uniformly dehydrated and dried to a water content of about 80% by weight. If the temperature of the hot water is higher than 90° C., the raw film becomes porous (devitrification becomes thick) due to dehydration, and it is difficult to recover the dense state even by subsequent heating, and the physical properties of the film, especially the mechanical strength, decrease. Further, if the temperature is lower than 50°C, the effect of dehydration and drying is small.

Roll tenter sequential stretching can be performed under the following conditions. That is, the moisture content is adjusted in advance by the method described above, and first, the original fabric is horizontally stretched at a moisture content of 10 to 50% by weight and an ambient temperature of 100 to 180°C, and then horizontally stretched to a moisture content of 5 to 40% by weight. Longitudinal stretching is performed using rolls with a surface temperature of 70 to 150° C. and a lower water content than that during stretching.

Regarding tenku stretching, if the moisture content of the original fabric is lower than 10% by weight or the ambient temperature is lower than 100C, the stretching stress is high and stretching breaks are likely to occur. On the other hand, if the moisture content of the original film exceeds 50% by weight, the stretching stress becomes high (and the stretched film becomes porous (devitrification), and it is difficult to devitrify the film by subsequent heating or stretching, which is undesirable. Also,
When the ambient temperature exceeds 180°C, it becomes difficult to adjust the water content uniformly. Generally, the most preferable raw fabric moisture content in tenter stretching is 15-35% by weight, and the ambient temperature is 110-35% by weight.
The temperature is 350°C.

For roll stretching, the moisture content is lower than 5% by weight;
Alternatively, if the roll surface temperature is lower than 70°C, the stretching stress is high (stretching breaks easily). Also, if the water content exceeds 40% by weight, thin devitrification occurs in the stretched film and the mechanical strength of the film also decreases. Furthermore, when the roll surface temperature exceeds 150°C, unevenness (
It is easy to cause devitrification (scale-like) (and the stability of stretching decreases. Generally, the most preferable φ in roll stretching is
The conditions are: moisture content 10-30% by weight, roll surface temperature 80\
The temperature is 120°C.

Note that general-purpose roll tenter sequential biaxial stretching equipment is usually provided with a preheating section at the front of each stretching zone of the rolls and tenter, and this can be used to adjust the moisture content and preheat. I can do it.

The stretching ratio must be at least 1.5 times, preferably 20 to 4.0 times, in both the longitudinal and transverse directions in order to obtain a stretched film with good mechanical properties. Note that after stretching,
It is also possible to perform heat setting treatment as necessary to improve thermal dimensional stability and mechanical properties, and surface treatment to improve static prevention, adhesion, printability, etc. .

Examples are shown below. Note that % and parts in the examples are based on weight unless otherwise specified.

Example: 16 parts of an acrylonitrile polymer consisting of 96% acrylonitrile and 4% methyl acrylate was dissolved in 84 parts of 70% nitric acid at 0°C, and after degassing under reduced pressure, a slit width of 300B was prepared.
The sample was extruded into a 30% nitric acid coagulation bath at 0° C. through a T-die with a slit gap of 1.51111+l and taken out at a speed of 1 m/ynry+, and then the solvent was removed by washing in a water washing bath. The resulting water-containing raw fabric with a thickness of 400 μm and a water content of 200% was passed through a tunnel-type hot air drying oven at 80° C. to adjust the water content, and first subjected to transverse stretching with a tenter, and then longitudinal stretching with rolls.7.
It's C. Stretching is 3.2 times the original warped length at °C and horizontally.
It was performed at a magnification of 25 times vertically. Table 1 shows the stretching conditions, stretching state, thickness uniformity and physical properties of the stretched film. In addition,
Since the tenter-stretched film is easily split, the edges were not trimmed and roll-stretched as it was, and then tensioned and heat-set using hot rolls.

(Left below) Example 2 The water-containing raw fabric obtained in Example 1 was soaked in hot water at 65°C for 60 minutes.
immersed for seconds, dehydrated and dried to a moisture content of 130%, and then
The moisture content was adjusted to 55% in a tunnel type hot air drying oven at 80° C., and tenter transverse stretching and then roll longitudinal stretching were performed. Tenter stretching was carried out at a ratio of 2.8 times with a water content of the original film at the time of stretching of 32% and a hot air temperature of 125°C in the stretching machine.Next, roll stretching was performed to reduce the water content of the l-axis stretched film to 18% during stretching. The test was carried out at a roll surface temperature of 95° C. and a magnification of 25 times.

Furthermore, after that, tension heat fixation was performed at 180° C. for 20 seconds.

The obtained film had excellent thickness uniformity (transparency) and mechanical strength as shown below.

Thickness uniformity (R/:i) Near [%] Transparency (haze): o, s [%] Tensile strength:
13.6 (FviD), 12.8 (TD) (Ki, /=
=%) Tensile elongation: 18 (MD), 28 (TD) C%]
In addition, products that were immersed in hot water at 95°C, dehydrated and dried to a water content of 72%, and then similarly dried with hot air and sequentially stretched biaxially with tenter rolls had the following properties such as transparency and physical properties. It was inferior in terms of quality.

Transparency (haze): z, 4 [%] Tensile strength: 10. fi (MD), 10.2 (TD) ky/rtd] Tensile elongation: 12 (MD), 16 (TD)
)C%] Example 3 60 parts of an acrylonitrile-based polymer consisting of 88% acrylonitrile and 12% vinyl acetate and 40 parts of ethylene carbonate were uniformly mixed at 30°C using a Henschel mixer.
It was extruded into a strand at 150° C. using a axial screw extruder, and pelletized using a pelletizer. This pellet was extruded into a sheet through a T-die at 155° C. using a twin-screw extruder to obtain an original fabric having a thickness of 140 μm. Next, this raw fabric was immersed in hot water at 80° C. to remove the solvent of ethylene carbonate to 3%, thereby obtaining a devitrified water-containing raw fabric with a moisture content of 48%. This water-containing raw fabric is heated to 120℃ using a hot air dryer to adjust the moisture content and thermally densify it (devitrification recovery).
Then, using a tenter stretching machine, the atmospheric temperature at the time of stretching was 105°C, the water content was 32%, and horizontal stretching was carried out at a magnification of 3.0 times, and then using a roll stretching machine, the roll surface temperature was 12%.
Longitudinal stretching was carried out at a 0'C1 water content of 10% and a magnification of 25 times. Stretching is stable and uniform, and the film is transparent with good thickness uniformity of 12 μm.
I got a film of. The physical properties of the film heat-set for a fixed length with hot air at 180° were as follows.The heat-set film had less than 0.5% of residual solvent and water.

Transparency (haze): 1.6C%] Tensile strength = 15.2 (MD), ts, o (rD) [k
#/wF) Tensile elongation: 38 (MD), 45 (T"D)
C%] Patent applicant Asahi Kasei Industries, Ltd.

Claims (3)

[Claims] (1), acryloni) A hydrous coagulated film of IJ-based polymer is transversely stretched in a tenter under conditions of a water content of 10 to 50% by weight (relative to dry polymer weight) and an ambient temperature of 100 to 180°C, and then The surface temperature is 70-15 at a lower moisture content (relative to dry polymer weight) than that during lateral stretching of ~40%
A method for producing a biaxially stretched film of an acrylonitrile polymer, which comprises longitudinally stretching using rolls at 0°C. (2) The manufacturing method according to claim 1, wherein the water content of the water-containing coagulated film is adjusted by hot air drying. (3) Adjust the water content of the water-containing coagulated film from 50 to 90.
Claims: 1. The manufacturing method according to claim 1, which is carried out by dehydration by immersion in hot water at a temperature of 0.degree. C., or a combination thereof with hot air drying.