JPH06138321A - Polyvinylalcohol based polymer film - Google Patents

Abstract

PURPOSE:To provide a PVA based polymer film which shows only a low degree of curling at the time of dipping it in water or leaving it to stand in air. CONSTITUTION:The polyvinylalcohol based polymer film features that the average crystallinity (Xc) by the X ray transmission method is in the range of 50 to 75wt.% and the absolute value of the difference of the crysallinity index (DELTAA) between one surface and the other surface of the film is below 0.05, and also the absolute value of the difference of the crystal size (DELTAD) between one surface and the other surface of the film by the X ray reflection method is below 1.5nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol polymer film suitable for use as an optical film such as a polarizing film or a retardation film, or a film for fiber packaging.

[0002]

2. Description of the Related Art Conventional polyvinyl alcohol (hereinafter, referred to as
It is called "PVA". The) -based polymer film was produced by a casting method (solution casting method) (see, for example, Japanese Patent Publication No. 51-23981). Conventional PV
The method for producing an A-based polymer film is as follows: a PVA-based polymer chip is dissolved to obtain a stock solution, and the stock solution is a surface of a casting substrate such as a drum or belt-type film forming machine that rotates from the slit-shaped opening. After casting and casting, the film was obtained by drying or heat treatment, if desired.

[0003]

However, the conventional PVA polymer film has the following problems. 1) When the film is immersed in water, the film bends (hereinafter referred to as "curl"). 2) The film curls when the film is left in the air.

When manufacturing a polarizing film or a retardation film, if both ends of the film are greatly curled by immersion in water, roll
The folds of the ears occur at the lars, making manufacturing impossible. Further, in the case of making a bag for fiber packaging, if the film is largely curled by leaving it in the air, it will be difficult for the bag-making machine to start.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide a PVA-based polymer film having a small degree of curling when the film is immersed in water or when the film absorbs moisture. And

[0006]

Means for Solving the Problems As a result of extensive studies to achieve the above object, a film obtained by casting an undiluted solution of an aqueous PVA polymer solution on the surface of a casting substrate and drying it In the method for producing a PVA-based polymer film obtained by peeling from the substrate for use, by selecting the drying conditions and the heat treatment, the crystallinity index and the crystal size of the front and back surfaces of the PVA-based polymer film The structural difference is small, and as a result,
Film cover when immersed in water or left in the air
And found that the

That is, the present inventors have found that the average crystallinity (Xc) by the X-ray transmission method is 50 to 75% by weight, the crystallinity index (Ab) on one side of the film represented by the following formula and the other. Absolute value of difference in crystallinity index (Af) of surface (△ A) 0.0
5 or less, and the absolute value of the difference between the crystal size of one surface of the film by the X-ray reflection method and the crystal size of the other surface (Δ
D) A polyvinyl alcohol-based polymer film having a thickness of 1.5 nm or less was found. ΔA = | Ab −Af | where Ab: A of the infrared absorption spectrum of one surface of the film
Crystallization band (11 by TR method (total reflection absorption measurement method)
Relative intensity at 40 cm ⁻¹ ) A f: A of infrared absorption spectrum of the other surface of the film
Relative intensity of crystallization band (1140 cm ^-1 ) by TR method

In the present invention, the average crystallinity (Xc) of the PVA polymer film is 50 to 75% by weight (hereinafter,
Sometimes called "wt%". ), And 55 to 65 wt% is more preferable. (Xc) is 50
If it is less than wt%, the degree of swelling becomes too large for optical use and it becomes easy to dissolve in water, which makes it difficult to handle in the manufacturing process of the optical film. Further, in the field of fiber packaging, the hygroscopicity becomes large and the stiffness of the film becomes weak. On the other hand, when (Xc) is larger than 75 wt%,
In optical applications, the swelling property becomes too low and the stretchability deteriorates. Further, in fiber packaging applications, workability such as heat sealability and flexibility are deteriorated.

Crystallinity index (Ab) and crystallinity index (A
f) is determined by the ATR method of infrared absorption spectrum (total reflection absorption measurement method), and is 2 μm from the surface of the film.
It is an amount proportional to the crystallinity of the depth region up to a certain degree. The crystal size (D) is (10) parallel to the film surface.
It is the crystal size D ₍₁₀₀₎ of the ₍ 0) plane and is determined by X-ray reflection method measurement.

In the present invention, the surface of the PVA-based polymer film which is in contact with the drum or belt of the film forming machine (hereinafter referred to as "
It is called "b side". The absolute value (ΔA) of the difference between the crystallinity index (Ab) and the crystallinity index (Af) of the surface of the film opposite to the b-plane (hereinafter referred to as “f-plane”), and the film. It is preferable that the absolute value (ΔD) of the difference between the crystal size (D) on the b-plane and the crystal size (D) on the f-plane of the film is small. That is, it is necessary that (ΔA) is 0.05 or less and (ΔD) is 1.5 nm or less.
A) 0.05 or less and (ΔD) 1 nm or less are more preferable. If (△ A) is greater than 0.05 or (△ D)
Is less than 1.5 nm, the angle (θ) of the curl during immersion in water becomes larger than 90 degrees, which is not preferable.

The curl angle (θ) of the film when immersed in water (hereinafter referred to as "curl angle in water") is the maximum angle taken during 5 minutes when the film is immersed in water at 30 ° C. -Le angle. This underwater curl angle (θ)
Is important when the PVA polymer is stretched in water during the production of the optical film. The water curl angle (θ) of the PVA-based polymer of the present invention is preferably 90 degrees or less. When the underwater curl angle (θ) is larger than 90 degrees, both ends of the film curl and the folds of the ears occur at the rollers, making it impossible to produce an optical film. In the case of a packaging film, it is difficult for the film to be applied to the bag making machine. The definition of the above parameters and the details of the measuring method will be described later.

Examples of plasticizers for PVA type polymers include glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol and polyethylene glycol.
And polyhydric alcohol plasticizers such as polypropylene and polypropylene glycol, and mixtures thereof. Glycerin is preferred among these polyhydric alcohol plasticizers. The plasticizer may or may not be added, but when the plasticizer is added, it is preferable to add about 2 to 20 parts by weight to 100 parts by weight of the PVA polymer.

The degree of polymerization of the PVA polymer used in the present invention is not particularly limited, but it is preferably 1,000 or more, more preferably 1,000 to 20,000, even more preferably 1,500 to 10,000, still more preferably 3,000 to 10,000.
The degree of saponification of the PVA polymer is not particularly limited, but is preferably 80 mol% or more, more preferably 90 mol% or more,
Even more preferably 95 mol% or more.

The PVA polymer of the present invention can be obtained by saponifying a polymer of vinyl ester monomer. As vinyl ester-based monomers, vinyl formate,
Vinyl acetate, vinyl propionate, vinyl valerate,
Examples thereof include vinyl caprate, vinyl laurate, vinyl stearate, vinyl 2,2,4,4-tetramethylvalerate, vinyl benzoate, vinyl pivalate, vinyl versatate, and vinyl butyl ether. Among these, vinyl acetate, vinyl propionate, vinyl pivalate and vinyl versatate are preferably used alone or as a mixture.

As the stereoregularity of the PVA type polymer, those having an atactic structure are generally used.
Those rich in syndiotactic or isotactic structures can also be used.

It is also possible to copolymerize the above-mentioned vinyl ester-based monomer with a copolymerizable monomer. Examples of the copolymerizable monomer include acrylic acid, methacrylic acid, itaconic acid, and anhydride. Maleic acid, N
-Vinylpyrrolidone and the like. The content of these copolymerizable monomers is preferably 10 mol% or less, more preferably 5 mol% or less.

The thickness of the PVA polymer film obtained by the present invention is preferably 20 to 100 μm. There is no particular limitation on the length and width of the PVA-based polymer film of the present invention. The lower limit of the width is preferably 50 cm or more, more preferably 80 cm or more, and particularly preferably 100 cm or more. The upper limit of the width is preferably 3 m or less,
It is more preferably 2.5 m or less. The length is preferably 1 m or more, more preferably 10 m or more.

The PVA polymer film of the present invention can be obtained, for example, by the following method. (1) When the drying temperature is about 80 to 120 ° C., after the film is peeled off, the rolls are sequentially heat-treated on both sides of the film at a temperature of 130 to 180 ° C. or on both sides of the film at a temperature of 130 to 180 ° C. The structure on both sides of the film is made uniform by performing hot air heat treatment.

(2) When the drying temperature is about 125 to 170 ° C., when the film is peeled off from the casting substrate, a large surface difference has already occurred in the front and back structures of the film. This surface difference is 100 after peeling the film.
Both sides of the film are relaxed by performing a relatively gentle heat treatment at about 120 ° C. However, in this case, if severe heat treatment conditions of 130 ° C. or higher are adopted,
The surface difference between the front and back surfaces of the film is rather increased.

A belt type film forming machine or a drum type film forming machine can be used as the casting substrate in the case of producing the PVA polymer film of the present invention. FIG. 1 shows a belt-type film forming machine 11 used for producing the PVA-based polymer film of the present invention. This belt type film forming machine 11 has a die 10. PV for die 10
A stock solution L composed of an A-type polymer aqueous solution is supplied. The die 10 has a slit-shaped opening that is long in the width direction (direction perpendicular to the paper surface of FIG. 1), and the stock solution L has a uniform thickness in the width direction from the opening and is used as a casting base material. It is poured out on 13.

The belt-type film forming machine 11 has the endless belt 13 which runs while being stretched between a pair of rollers 12 and 12. The stock solution flowing out from the die 10 is placed on the belt 13. It is cast and dried. The belt 13 is made of, for example, a stainless steel, and its outer peripheral surface is mirror-finished. Partition walls 14 that partition the space in the traveling direction of the belt 13 are provided on the outer circumference and the inner circumference of the belt 13, respectively.
The outer peripheral surface and the inner peripheral surface of the belt 13 are provided with 80 to 17 from a warm air blower (a warm air blower is omitted in the drawing).
Hot air H of 0 ° C. is blown to accelerate the drying of the stock solution. In the most downstream zone 14A, film F
May be cooled by the air C at room temperature.

A peeling roller is provided near the roller 12 on the right side.
The film F dried to a predetermined water content is peeled off from the belt 13 by the peeling roller 15. The film F is wound on a winder 19 after passing through a heat treatment machine 16, a humidity controller 17, and an inspection machine 18. The heat treatment machine 16 blows hot air of about 100 to 170 ° C. onto the film F to change the crystallinity of the film F and the like. The humidity controller 17 is for adjusting the water content of the film F to, for example, about 5% by weight. The inspection machine 18 is for inspecting physical defects, foreign matter, thickness, moisture and the like.

FIG. 2 shows a drum type film forming machine 21. In the figure, the stock solution L is quantitatively supplied to the die 10, a film is formed on a drum type roll 22, and dried by a drying roll 23 to produce a PVA-based film F. Film F
Goes through the heat treatment machine 16, the humidity controller 17, and the inspection machine 18,
Winded up by winder 19.

[0024]

The present invention will be described more specifically in the following examples. The physical properties of the films in the following examples and comparative examples were measured by the following methods.

Average crystallinity (Xc): Wide-angle X-ray diffractometer RAD-γC type manufactured by Rigaku Denki Co., Ltd. was used, and X-rays generated at 40 kV and 100 mA as a radiation source were monochromatic with a graphite monochrometer. The converted CuKα1 ray was used, and a scintillation counter was used as a detector. Slit system is DS 2 mmφ, SS 0.5 degree, RS 0.15 mm
The equipment conditions of While rotating the sample at 76 rpm, the measurement was performed by a transmission method at a scan speed of 1.0 degree / minute in a range of a scan angle 2θ = 5 to 35 degrees.
The obtained diffraction curve is analyzed by Johnson's method (AMHindeleh,
DJJohnson, Polymer, 15, 697 (1974).) Was used for computer analysis, and the crystallinity was calculated as the area ratio of the diffraction peak by the crystal to the surface line of the total scattering curve. The calculated crystallinity is an average crystallinity over the entire depth of the film.

Crystal size (D): Wide angle X-ray diffractometer RAD-γC type manufactured by Rigaku Denki Co., Ltd.
CuKα1 rays obtained by monochromating X-rays generated at kV and 100 mA with a graphite monochrometer were used, and a scintillation counter was used as a detector. The slit system adopts the apparatus conditions of DS 0.5 degree, SS 0.5 degree, RS 0.15 mm, and scanned at 0.5 degree / minute. The half value width B (10) of the peak of the surface index (100) obtained by the above reflection method
The crystal size in the thickness direction of each sample film was calculated from the value of 0) using the following Scherrer's formula. D (100) = Kλ / Bo (100) cos θ (100) where K = 0.9 and λ = 0.15405 nm,
Bo (100) is the spread (radian) of the slit-corrected diffraction curve obtained by Jones' method, and θ (1
00) is the Bragg angle (degrees).

Crystallinity index (Ab) and (Af) of the film surface: An infrared spectrophotometer (manufactured by JEOL Ltd.) was used to measure the surface of the PVA film by the ATR method (total reflection absorption measurement method). It was measured. As the ATR prism, KRS-5 manufactured by JEOL Ltd. having an incident angle of 45 degrees was used.
In the infrared absorption spectrum of PVA, the intensity ratio of the absorption band intensity at 1140 cm ⁻¹ , which is well known as a crystallization band, to the absorption band intensity at 1425 cm ⁻¹ was defined as the crystallinity index. However, 1140 cm ^-1 and 1425 cm ^-1
The base line of each band when calculating the band intensities was drawn as shown in FIG. It is well known that the value of the crystallinity index thus obtained is proportional to the crystallinity of a PVA-based film (NAPeppas, Makromol. Che.
m., 178 vol. 595 (1977).). The value of the crystallinity index obtained here is an amount proportional to the crystallinity of the surface region up to about 2 μm from the film surface (Tasumi Mitsuo, FT-
The basics and facts of IR, Tokyo Kagaku Dojin (1986)). The value of the crystallinity index varies somewhat depending on the amount of moisture absorption of the film, but in this measuring method, the film was conditioned under the environment of a temperature of 22 ° C. and a relative humidity of 40%.

Underwater curl angle (θ) of the film: a rectangular shape cut out in a length of 34 cm in the film forming direction (MD direction) at the time of film forming of the film shown in FIG. 4 and a length of 3.4 cm in the direction perpendicular thereto. With respect to the film sample 31, a load of 300 g / cm ² was uniformly applied in the long side direction B of the rectangle in the short side direction C of the rectangle, and the film sample 31 was immersed in water at 30 ° C. The straight line 34 connecting the curved edge 32 in the short side direction C and the curved start point 33 forms an angle with the plane of the central portion 35 of the film sample 31 in the short side direction C, and 5 after the film is immersed in water.
The maximum value taken during the period was defined as (θ).

Example 1 100 parts by weight of PVA (polymerization degree: 1750, saponification degree: 99.9 mol%), glycerin: 12 parts by weight, water as a solvent was further added, and the water content was 60% wb (weight% in wet base, the same applies hereinafter). The homogeneous stock solution of is quantitatively supplied to the die 10 of FIG.
A film having a thickness of 75 μm and a width of 1 m was manufactured by the drum type film forming machine 21 and heat-treated by a heat treatment machine. The main manufacturing conditions are shown below. Die: T-type slit die Die temperature 100 ° C Drum type film forming machine: Cast roll Diameter 2m Rotation speed 5m / min Roll temperature 85 ° C Drying time 62 seconds Water content at film peeling 30wt% Heat treatment machine: Hot air hot air Temperature 160 ° C. Treatment time 35 seconds Water content of exit film 1.8 wt% Water content of film after humidity conditioning 6.5 wt% Physical properties of the film thus obtained are shown in Table 1. This film has a small difference in structure such as crystallinity index on the front and back surfaces of the film, and has a small underwater curl angle (θ).

Table 1 shows Examples 2 and 3 and Comparative Examples 1 and 2 in which the raw material PVA (stock solution) and the production conditions were changed. In Examples 2 and 3 and Comparative Examples 1 and 2, the thickness was 75 μm.
A film having a width of m and a width of 1 m was produced and heat-treated with a heat treatment machine.

[0031]

[Table 1]

[0032]

EFFECTS OF THE INVENTION According to the present invention, it is possible to reduce the difference in structure between the front and back surfaces of the film. Therefore, when the film is immersed in water or left in the air, the water absorption surface on the front and back surfaces of the film is reduced. As a result of the small difference, it is possible to reduce the curl angle when immersed in water and left in the air. Therefore, in both cases of underwater stretching when producing an optical film and when applied to a bag-making machine when producing a fiber packaging bag, the curled end does not get caught on the machine. Thus, the process passability when processing a film is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a film manufacturing apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing another example of a film manufacturing apparatus according to the present invention.

FIG. 3 is a diagram showing how to draw the base lines of the crystallization band and the reference (reference) band when determining the relative intensities of the crystallization bands in the infrared absorption spectrum by the ATR method.

FIG. 4 is a perspective view showing a method for measuring an underwater curl angle (θ).

[Explanation of symbols]

11 ... Belt type film forming machine, 21 ... Drum type film forming machine, 31 ...
Film sample, 32 ... Edge, 33 ... Starting point, 34 ... Straight line,
35 ... central part, A ... flow direction, B ... long side direction, C ... short side direction.

Front page continuation (72) Inventor Hiroaki Hayase, 892 Sakusui-shi, Saijo City, Ehime Prefecture, Kuraray Co., Ltd. (72) Inventor Yoshiaki Mukai, 892, Sakusui-shi, Saijo City, Ehime Prefecture

Claims (1)

[Claims] 1. An average crystallinity (X
c) 50 to 75% by weight, the crystallinity index (Ab) on one side of the film represented by the following formula and the crystallinity index (A on the other side of the film
f) absolute value (ΔA) of 0.05 or less, and absolute value of difference (ΔD) between the crystal size of one side of the film by the X-ray reflection method and the crystal size of the other side (ΔD) 1.5 nm The following is a polyvinyl alcohol-based polymer film. ΔA = | Ab −Af | Ab: A of the infrared absorption spectrum of one surface of the film
Crystallization band (11 by TR method (total reflection absorption measurement method)
Relative intensity at 40 cm ⁻¹ ) A f: A of infrared absorption spectrum of the other surface of the film
Relative intensity of crystallization band (1140 cm ^-1 ) by TR method