JPH01228825A - Manufacturing method of uniaxially stretched film - Google Patents

Abstract

PURPOSE:To contrive thickness equalization and homogenization of a longitudinal and lateral directions of the title film by a method wherein both side fringes of a thermoplastic film is removed by stretching uniaxially the same with a roll in the longitudinal direction and after the same is heat-treated with a heating roll in succession the same is wound up while performing oscillation. CONSTITUTION:A thermoplastic resin film (a) extruded through a T die 2 fitted to an extruding machine is stretched in a longitudinal direction with a pair of high speed rolls 5, 5' after passing through between a pair of low speed rolls 4, 4' through a cooling roll 3. Both side fringes of the film (a) are cut off in a slitlike state with a slit razors 8, 8' between pairs of nip rolls 6, 6' and 7, 7'. The film (a) passed through between the nip rolls 7, 7' is heated between heating rolls 9a, 9a' and cooled by passing through between cooling rolls 9c, 9c' after heating while turning around the lower side part of a heating roll 9b. Then the film (a) is wound up round a wind-up shaft 11 while oscillating a wind-up machine 10 in the direction of the film (a) and a thermoplastic resin longitudinal and uniaxially-stretched film (b) is manufactured.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a uniaxially stretched film that can produce a longitudinally uniaxially stretched film of a thermoplastic resin with uniform thickness and homogeneity in the longitudinal and lateral directions at a high yield. This relates to a manufacturing method.

(Prior art) Films uniaxially stretched in the shrinkage direction are suitable for packaging, taking advantage of various properties such as high strength, high elasticity, easy tearability, and heat shrinkability among the various properties due to molecular orientation that acts only in the longitudinal direction. It is widely used as packaging materials for films, strings, bands, etc., and its properties such as piezoelectricity, high dielectricity, and polarization are used to produce industrial materials such as piezoelectric elements, capacitor elements, and polarizing elements. It is widely used, especially for electronic devices, and is also expected to be used as a negative layer.

However, when a longitudinally uniaxially stretched film is used as a packaging material, for example in the case of strings, bands, etc., local variations in the width direction of the film are not a problem;
It is sufficient that the band as a whole reaches the target values for strength and elasticity in the longitudinal direction, but in the case of films used as industrial materials, especially materials for electronic equipment, it is necessary to use the entire surface of the film. Local variations in the width direction become a major problem.

In other words, there is a demand for a film that has uniform properties such as strength, elasticity, heat shrinkage, piezoelectricity, dielectricity, and polarization in the width direction, and has a uniform thickness. The challenge is how to manufacture it at a high rate.

Conventionally, longitudinally uniaxially stretched film is plasticized using an extruder;
The thermoplastic resin film extruded into a film form from a T-die or annular die is cooled and solidified to form a flat unstretched film, then passed through a heated low-speed roll, then passed through a high-speed roll that is usually cooled, and then passed through a low-speed roll. Due to the speed difference between the rolls and high-speed rolls, uniaxial stretching is carried out in the longitudinal direction,
Subsequently, the material is heat-treated by a group of heated rolls and a group of cooled rolls while being contracted in the longitudinal direction, and then wound into a long length over the entire width by a winder. Thereafter, the wound long film is cut to the required width and length.

However, when an unstretched film having a uniform thickness in the width direction is uniaxially stretched with a low speed roll and a high speed roll, the unstretched film is stretched in the machine direction while decreasing the film width in the width direction. The resulting uniaxially stretched film is several times thicker at both side edges than other parts, and the thickness in the width direction is non-uniform.

That is, with respect to the cross section of the film (A) before stretching shown in FIG. 2, as shown in FIG. 3, the thickness of both side edges (B) and (B) is larger than that of the other portions.

In this way, when a film with uneven thickness in the width direction is heat-treated and then wound into a long length across its entire width, the wound film (
In c), since the thickness of both edges of the film is large, stronger stress is applied to the parts closer to both edges of the film, and smaller stress is applied toward the center, and there is almost no stress applied near the center. (See Figure 4).

Due to these circumstances, the only part of the produced uniaxially stretched film that has homogeneous properties and uniform thickness in the width direction is the central part, and the yield of the desired film that is homogeneous and uniform in thickness is low and only a small amount can be obtained. The drawback is that the production yield is significantly low.

Therefore, in order to improve the disadvantage that the thickness of both side edges of the film after stretching is large, only the both side edges of the film in the stretching process are held between rubber rolls on low-speed rolls, and the unstretched film is stretched. Measures have been proposed to reduce changes in width in the width direction.

Although this method significantly improves the thickness of both side edges of the film and improves the production yield to 1 as compared to the conventional method, it cannot be said that the production yield is sufficient. However, since both edges of the film during the stretching process are pinched, the stretching start point in the longitudinal direction on the low-speed rolls becomes uneven in the width direction, resulting in a disadvantage that the uniformity in the longitudinal direction is deteriorated.

In addition, as another means to improve the problem that the thickness of both side edges of the film becomes large after stretching, after heat treatment with a heated roll, only the thickest parts of the film's both side edges are rolled before winding. Measures are proposed.

In the case of such a method, when the product is wound into a long length, the MW is partially thickened locally at a certain position in the width direction, which cannot be avoided in the case of uniaxial stretching in the longitudinal direction.
In the case of long winding of 100 m or more, minute thickness parts that are within the allowable range of thickness non-uniformity for a sheet gradually accumulate, [! The stress effect on the film portion differs depending on the accumulation of minute thick portions, and even if it appears to be uniform in the width direction, the film characteristics are actually non-uniform in the width direction.

Furthermore, after heat-treating with a heated roll, a large part of the thickness of both side edges of the film is removed before winding, and while shaking the winding roll of the winding machine from side to side in a direction perpendicular to the stretching direction of the film, In other words, a method has been proposed in which, while oscillating, the unavoidably local minute thick portions at certain positions in the width direction are dispersed to the left and right, thereby making the stress in the width direction uniform during winding. .

Although this method has been recognized as a considerable improvement over conventional methods and is suitable for use as packaging materials, it is also useful for cutting the wound film into desired widths and lengths for use as materials for electronic devices. When used, a similar problem occurs, although to a lesser extent, when the film is thick at both ends. That is, as shown in FIG.
D) is in uneven contact with the heating roll (E), so wrinkles are likely to occur, the quality is non-uniform, and the production yield is low, so it is not a fully satisfactory film, especially as a material film for electronic devices. Ta.

(Problem to be solved by the invention) Depending on the conventional method, it has not been possible to produce a thermoplastic resin uniaxially stretched film that is uniform in thickness and homogeneity in the vertical and horizontal directions and is fully satisfactory as a material film for electronic devices. There was a problem.

(Means for Solving the Problems) As a result of intensive research and consideration, the present invention provides a means for obtaining a film with uniform thickness and homogeneity in the longitudinal and transverse directions by using a unique method for producing a thermoplastic resin uniaxially stretched film. According to claim (1), a thermoplastic resin film is rolled uniaxially stretched in the length direction, and then both side edges are cut off.
A method for producing a uniaxially stretched film, characterized in that the film is then heat-treated with a heating roll and then wound up while being oscillated; Then pass it between nip rolls and cut both side edges into slits.
The running film is passed between the next nip rolls, the slitted side edges are removed, and the running film is passed through the heating rolls of the heat treatment roll group, then the cooling rolls, and then wound onto the winder while being oscillated. This is a unique method for producing uniaxially stretched film.

(Example) An example of the present invention will be described with reference to the apparatus shown in FIG.

The thermoplastic resin film <a) extruded from a T-die 2 attached to an extruder 1 is uniaxially stretched via a cooling roll 3.

That is, the extruded thermoplastic resin film (a) passes between a pair of low-speed rolls 4.4' consisting of a metal roll 4 and a rubber roll 4°, and then passes between a metal roll 5 and a rubber roll 5.
' is guided between a pair of high-speed rolls 5, 5' consisting of a pair of nip rolls 6, 5', and stretched in the length direction by a high-speed roll 5.5' rotating at a higher speed than a low-speed roll 4.4'. .6' and then the next nip roll 7.7
'Lead between. Nip roll 6.6' and nip roll 7'
, 7', both side edges of the film (a) are cut into slits by slit razors 8, 8'.

The film (a) exiting between the nip rolls 7 and 7' is then guided to a group of heat treatment rolls 9.

The heat treatment roll group 9 includes a pair of upper and lower heating rolls 9a and 9a' consisting of a metal roll 9a and a rubber roll 9a'.
,! :, a pair of upper and lower cooling rolls 9c, 9c' consisting of a heating roll 9b, a metal roll 9c and a rubber roll 9c'.
Thus, the film (a) that has passed between the nip rolls 7 and 7' is heated between the heating rolls 9a and 9a', heated while going around the lower side of the heating roll 9b, and then heated by the cooling rolls 9c and 9a'. cooled by passing through the
10 is a direction perpendicular to the direction of the winding shaft 11, that is, the length direction of the film (a), in other words, the direction of the film (a)
The film (a) is wound around the winding shaft 11 while being oscillated in a reciprocating direction in the width direction of the film, thereby producing a longitudinally uniaxially stretched thermoplastic resin film (b).

The process of cutting both side edges of the film (a) into slits is carried out after the high-speed rolls 5, 5', particularly preferably between at least one of the high-speed rolls 5, 5' and the heat treatment rolls 9a, 9a'. A pair of nip rolls 6.6', 7, and 7' are provided, each of which is made of a rubber roll,
Both side edges of the film (a) are slit between the nip roll 6.6' and the nip roll 7.7', and the heat treatment roll group 9
The side edge cuts are removed between the side nip rolls 7.7' and the first heat treatment roll 9a.

A pair of upper and lower front nip rolls 6.6' and a pair of upper and lower rear nip rolls 7.7' cut the slits on both side edges of the film.
What is done between the stretching process and the heat treatment process is
Because the molecular orientation of the thermoplastic resin is not sufficiently fixed or the crystal orientation is not sufficiently fixed, high shrinkage stress exists in the stretched film, so if a double roll is not provided, delicate problems may occur during stretching. This is because the vibration may cause slit errors and breakage of the film.

In addition, it is important to remove the slitted side edge portions before the stretched film (a) contacts the first heating roll. This is because it is necessary to simultaneously contact the heating roll in a straight line due to the uniformity in the width direction. For this reason, it is particularly preferable to have the heating roll 9a' pressed by the first heating roll 9a, and if the slitted side edges and the traveling film portion are sandwiched at the nip position by the first heating roll 7. Even if you use a soft rubber nip roll,
Both side edges of the running film are cut off and the running film becomes thicker, making it impossible to uniformly contact the heating roll in a straight line. It is important to remove the slitted side edges from 1'fl before contacting the first heating roll, and since both side edges of the film are slit before heat treatment, as shown in Figure 6, The entire width of the film contacts the heating roll 9a uniformly and simultaneously, resulting in uniform quality, and the entire width extending between both side edges shown in FIG. 6 becomes a product, significantly increasing the production yield.

Circumferential speed S1 of the high-speed roll and circumferential speed S of the first heating roll
Regarding the relationship between
．． 2 or less. If S2/S1 is less than 0.9, the stretched film in the section where both side edges are not cut between the two pairs of nip rolls 6.6' and 7.7' will relax unevenly in the width direction. Therefore, it is undesirable.

The width of the slits at both side edges is desirably 2 meters or more, preferably 5 meters or more, and if the slit width is less than 2 meters, the thickness of both side edges of the running film is thicker than other parts. Since the width of the thick side edge portions decreases by more than 50% in the width direction during the stretching process, the moment they first come into contact with the heating roll, they exhibit different elongation and contraction behavior in both the width and length directions from other portions. This is not preferable because the film running on the first heating roll does not contact uniformly and in a straight line, and slitting errors are more likely to occur.

Furthermore, regarding the heat treatment using heating rolls, it is preferable to nip the running film when it comes into contact with the first heat treatment roll, and it is also preferable to nip it when the running film comes into contact with the cooling roll located at the end of the heat treatment roll group. Preferably, this means that the heated film expands in the width direction due to thermal expansion, and if it is brought into contact with the cooling rolls without being nipped, it will contract by the amount due to the expansion in the width direction, causing the running film to This is because irregular wrinkles occur and a uniform film cannot be obtained.

In addition, when a single heating roll is used as a means for shrinking the film running in the longitudinal direction during heat treatment, a speed difference is set between the heating roll and the cooling roll following this heating roll, and the speed of the cooling roll is changed. If there are two or more heating rolls, the speed of the first heating roll and subsequent heating rolls may be the same or slower than the previous heating roll.

The rate of shrinkage due to the speed difference between the heating roll 9a and the cooling roll 9c is selected depending on the amount of heat shrinkage required for the desired product, but in order to improve the dimensional stability of the desired product, it is 0.5. % or more and 15% or less, preferably 3% or more and 10% or less.

Further, the heat treatment temperature is preferably the same or higher than the stretching temperature in order to improve the dimensional stability of the product to be obtained.

Furthermore, regarding the winding means, the reciprocating distance of the reciprocating motion of the winder for reciprocating left and right is preferably 2 or more, preferably 5 or more, and more preferably 10 mm.
With the above, if the reciprocating distance is less than 2, minute thick parts within the range of thickness non-uniformity allowed for the target product will gradually accumulate, and the thick parts will be spread out from side to side. Dispersion becomes impossible, and a uniform stretched film cannot be obtained. In addition, the speed of reciprocating left and right can be set by considering the relationship between the reciprocating distance, the film winding speed, and the surface condition of the film. It is desirable that the reciprocating process be a uniform motion.

Thermoplastic resins used in the present invention include polyolefin polymers and copolymers such as low-density polyethylene, high-density polyethylene, and polypropylene, as well as fluororesin polymers and copolymers such as polycarbonate, polyester, polyamide, and polyvinylidene fluoride. However, it goes without saying that the thermoplastic resin is not limited to this and other thermoplastic resins may be used. It may also be in the form of a single-layer film made by mixing two or more types of resin, or it may be made into a multilayer film by plasticizing and kneading two or more different thermoplastic resins in different extruders and then using a feed block method or a multi-manifold method. It may also be a multilayer film extruded from a die.

In the present invention, a known method for uniaxial stretching in the longitudinal direction using a speed difference between a low speed roll and a high speed roll is employed, and stretching conditions such as a stretching temperature and a stretching ratio suitable for a thermoplastic resin are adopted.

Although the thickness of the film is not particularly limited, it is preferable that the thickness of a single layer is 100 μm or less, particularly 50 μm or less, if the film is a single layer film, or if the thickness of the entire multilayer film is a multilayer film.

Furthermore, the method of the present invention is suitable for use in cases where the protective layer film is peeled off after stretching as disclosed in Japanese Patent Publication No. 60-6220, and an ultra-thin film of several microns or less as an intermediate layer is manufactured. be.

Furthermore, although the width of the film is not limited, the smaller the width of the film, the greater the effect of the present invention.

Next, an example of the method of the present invention will be described, but the present invention is not limited to this example.

(An embodiment in which the method of the present invention is not applied) An example of an embodiment in which the method of the present invention is applied will be described with reference to FIG.

Polypropylene (Mitsubishi Polypropylene MFR = 5.5g
/10 minutes, density 0.90g/mouth 3, melting point 168℃) 2
Plasticized in a 150 mm diameter extruder at 30°C, and separately made from PVDF (
KYNAR manufactured by Pennwalt, MFR=5.5g/10
min, density 1°8g/♂, melting point 171°C) at 230°C, 2
Plasticized with a 0φ extruder, extruded from a multi-manifold type T-die with a three-layer structure in a three-layer state of polyglopylene/PVDF/polypropylene, cooled and solidified by contacting with a cooling roll 3 heated to 70°C, and then 100+u+φ, 12
0℃ low speed roll 4.4' and 1100IIφ, 30℃,
A stretched film with a width of 400 IuI, which was uniaxially stretched 5 times in the longitudinal direction between 10 m/lin high speed rolls 5, 5', was provided between the high speed rolls 5, 5' and heating rolls 9a, 9a'. A slit razor 8.8' is used to slit both side edges of the running film (a) by 7 intervals between the nip rolls 6.6' and 7, 7'.
, remove the slitted side edges between '7' and heating rolls 9a, 9a', and continue to roll the film into 30011
1Iφ, 130°C, 10m/nin heating roll 9a,
The film (a) produced by a nip roll 7.7'' with a diameter of 100mm was brought into contact with the nip roll 7.7゜ of 100mm diameter against 9a' in a straight line, and then brought into contact with the heating roll 9b for 2/3 of a turn.
The cooling roll 9c is pressed by a cooling roll 9c' shaped like a nip roll of 50+u+φ so as to contact the cooling roll 9C of 9.4 m/nin in a straight line at 0°C.

9 c', continue to the left and right 101WI11.2
The film was oscillated on the winding shaft 11 for 1000 m under the oscillation condition of reciprocating from left to right in a straight line in 0 minutes.

From the 1000 m long film thus wound up, we cut several pieces into 100 m lengths with several different widths, and while peeling off the 15 μm polypropylene film from both layers,
The middle layer is a 0.9μ PVDF uniaxially stretched film with a diameter of 6
After winding the film into a 1.5-inch aluminum tube, it was rewound and the sagging condition of the film was observed. In the case of 330 cm or more, sagging was observed near both side edges of the film.
When the width was 30 mm or less, a uniaxially stretched film in the contraction direction was obtained which was uniform in thickness and homogeneity in both the longitudinal and transverse directions.

(Comparative Example 1) In the above-mentioned example, when the film was wound under the same conditions except that both side edges of the film were not slit between the high-speed roll and the heating roll, the winding state became unstable after 500 m. At this point, the winding process was stopped, and the intermediate layer 0.9 μ uniaxially stretched PVDF film was wound onto a 6-inch diameter aluminum tube under the same conditions as in the example, then rewound and the sagging state of the film was observed. As a result, 20 O
When the slit width was greater than the rntn width, sagging was observed near both ends of the film, and when the slit width was 200 mm or less, it was considered to be of uniform thickness and homogeneity.

(Comparative Example 2) In Comparative Example 1, the obtained heat-treated stretched film was cut off at 7 stops from both side edges of the film immediately before being wound up, and then wound up for 1000 m under the same conditions as in the example. After winding the stretched film thus wound into an aluminum tube with a diameter of 6 inches, the 0.9μ PVDF uniaxially stretched film of the intermediate layer was wound up under the same conditions as in the practical example, and then rewound and the state of the film was observed. As a result, 280
When the width was greater than the gap width, sagging was observed near both side edges of the film, and when it was less than 280ffi+11, it was uniform in thickness and homogeneity.

From these results, it is clear that the production yield of a thermoplastic resin film having uniform thickness and homogeneity in the longitudinal and lateral directions is much superior to that of the conventional method.

(Effects of the Invention) According to the method of the present invention, a uniaxially stretched film that is uniform in thickness and homogeneity in the contraction direction and the transverse direction can be produced at a high yield.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an example of a device to which the method of the present invention is applied;
FIGS. 2, 3, 4, and 5 are explanatory views of the main parts according to the conventional method, respectively, and FIG. 6 is an explanatory view of the main parts according to the present invention. 3.9e, 9c'...Cooling roll, 4.4'...Low speed roll, 5,5'...High speed roll, 6.6', 7
．． 7'... Nip roll, 9... Heat treatment roll group,
9a. 9a', 9b... heating roll, 10... winding machine, (
a)...Thermoplastic resin film. Patent applicant Mitsubishi Yuka Co., Ltd. $2, $3, 4, B, 5, 6, sub

Claims (2)

[Claims] (1) A uniaxial film that is characterized in that a thermoplastic resin film is uniaxially stretched in the length direction by a roll, then both side edges are cut off, then heat treated with a heated roll, and then wound up while being oscillated. Stretched film manufacturing method. (2) The thermoplastic resin film is uniaxially stretched in the longitudinal direction by rolls, then passed between nip rolls to cut both side edges into slits, passed between the next nip rolls, the slitted side edges removed, and then run. A method for producing a uniaxially stretched film, characterized in that the film is passed through a heating roll of a group of heat treatment rolls, then a cooling roll, and then wound onto a winder while being oscillated.