JP2598293B2 - Manufacturing method of uniaxially stretched film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a uniaxially stretched film capable of producing a longitudinally uniaxially stretched film of a thermoplastic resin having a uniform thickness and uniformity in a machine direction and a high yield in a high yield. The present invention relates to a film manufacturing method.

(Conventional technology) A longitudinal uniaxially stretched film is used for packaging by utilizing, for example, high strength, high elasticity, easy tearing property, heat shrinkage property, etc. among various properties due to molecular orientation acting only in the longitudinal direction. Widely used as packaging materials for films, strings, bands, etc.In addition, among its characteristics, industrial materials such as piezoelectric elements, capacitor elements, polarizing elements, etc. In particular, it is widely used for electronic devices, and further utilization is expected.

However, when the longitudinal uniaxially stretched film is used as a packaging material, for example, in the case of a string, band, or the like, local variation in the width direction of the film is not a problem,
As long as the target values for the strength and elasticity in the vertical direction of the cord and the band as a whole have been reached, in the case of films for industrial use, especially for electronic devices, the entire surface of the film is used. Local variation in the width direction becomes a serious problem.

That is, there is a demand for a film having uniform properties such as strength, elasticity, heat shrinkage, piezoelectricity, dielectric properties, and polarizing properties in the width direction of the film, and a uniform thickness of the film. The issue is how to manufacture at a high rate.

Conventionally, a longitudinally uniaxially stretched film is plasticized by an extruder, a thermoplastic resin film extruded into a film shape from a T die or an annular die is cooled and solidified into a flat unstretched film, and then passed through a heated low-speed roll. Then, usually through a high-speed roll that is normally cooled, uniaxially stretched in the longitudinal direction due to the speed difference between the low-speed roll and the high-speed roll, and subsequently contracted in the longitudinal direction by a heated roll group and a cooled roll. Then, it is heat-treated and subsequently wound up in a full length by a winder. Thereafter, the wound long film is cut into a required width and length.

However, when an unstretched film having a uniform thickness in the width direction is uniaxially stretched by a low-speed roll and a high-speed roll, the unstretched film is stretched in the longitudinal direction while reducing the film width in the width direction. In the obtained uniaxially stretched film, the thickness of both side edges of the film is several times as large as that of the other portions, and the thickness in the width direction is not uniform. That is, with respect to the cross section of the film (a) before stretching shown in FIG.
As shown in FIG. 3, the thickness of both side edges (b) and (b) is larger than other portions.

As described above, when a film having a non-uniform thickness in the width direction is heat-treated and then wound into a long length over the entire width, the wound film (c) has a large thickness at both side edges of the film. The closer to the sides, the stronger the stress applied, the smaller the stress toward the center, and almost no stress is applied near the center (see FIG. 4).

Under these circumstances, the only part having uniform properties and uniform thickness in the width direction is the central part of the produced uniaxially stretched film, and the desired film having uniform and uniform thickness is low in yield and small in quantity. However, there is a disadvantage that the production yield is significantly low.

Therefore, in order to improve the disadvantage that the thickness of the side edges of the stretched film becomes large, only the side edges of the film being stretched are clamped by rubber rolls on a low-speed roll, and the unstretched film is stretched. Means for reducing changes in the width direction and width at the time have been proposed.

Such a means improves the degree of increase in the thickness of the film side edges as compared with the conventional method, and the production yield accompanying this is slightly improved. In addition, since both sides of the film in the stretching process are sandwiched, the starting point in the longitudinal direction on the low-speed roll becomes non-uniform in the width direction, and the uniformity in the longitudinal direction is deteriorated.

Also, as another means to improve the point where the thickness of both side edges of the film after stretching becomes large, after heat treatment with a heating roll, only the portion where the thickness of both side edges of the film is large before winding is taken up. Means of taking have been proposed.

In the case of such a means, a locally and extremely minutely thick portion at a certain position in the width direction, which cannot be avoided in the case of uniaxial stretching in the longitudinal direction when wound up in a long length, that is, as one sheet of a target product, In the case of a long winding of 100 m or more, the extremely small thickness part within the allowable thickness non-uniformity range gradually accumulates, and the stress action on the film part differs due to the accumulation of the very small thick part. At first glance, there appears to be a drawback that various characteristics in the width direction become non-uniform, even though they may appear to be uniform in the width direction.

Furthermore, after heat treatment with a heating roll, before winding up, after cutting off a large part of the thickness on both sides of the film,
While oscillating the take-up roll of the winder to the left and right in the direction perpendicular to the film stretching direction, that is, while oscillating, disperse the inevitable local minutely thick part at a certain position in the width direction to the left and right. Means for winding while uniformizing the stress in the width direction during winding has been proposed.

Such a means has a considerable improvement effect as compared with the conventional method, and there is no problem for packaging materials, but the wound film is cut into a desired width and length as a material for electronic devices. In the case of using the film, a problem similar to the case where the both ends of the film are thick, though to a lesser extent, occurs. That is, as shown in FIG. 5, the portions (d) near the both side edges of the film are in uneven contact with the heating roll (e).
Wrinkles are likely to occur and the quality is heterogeneous and the production yield is low,
In particular, the film was not a satisfactory film as a material film for electronic devices.

(Problems to be Solved by the Invention) According to the conventional method, it has not been possible to produce a uniaxially stretched thermoplastic resin film which is uniform and uniform in the longitudinal and lateral directions and is sufficiently satisfactory as a material film for electronic equipment. There was a problem.

(Means for Solving the Problems) As a result of intensive studies and investigations, the present invention provides a unique means for producing a uniaxially stretched thermoplastic resin film and a means for obtaining a uniform and uniform film in the machine and transverse directions. Claim (1) is to uniaxially stretch the thermoplastic resin film in the longitudinal direction of the roll, cut off both side edges, and then heat-treated by a heating roll, and then wind up while oscillating. A method for producing a uniaxially stretched film, wherein the thermoplastic resin film is uniaxially stretched in a roll in the longitudinal direction, and then passed between nip rolls to cut both side edges into slits. After passing through the next nip roll, the slit side edges are removed, and the running film is passed through the heating rolls of the heat treatment rolls and then through the cooling rolls. This is a method for producing a uniaxially stretched film, wherein the film is wound around a winding machine while the film is being stretched.

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

The thermoplastic resin film (a) extruded from the T-die 2 mounted on the extruder 1 is uniaxially stretched through a cooling roll 3.

That is, the extruded thermoplastic resin film (a) passes between a pair of low-speed rolls 4, 4 'composed of a metal roll 4 and a rubber roll 4', and then a pair of high-speed rolls composed of a metal roll 5 and a rubber roll 5 '. The high-speed roll 5, which is guided between the rolls 5 and 5 'and rotates at a higher speed than the low-speed rolls 4 and 4'.
It is stretched in the length direction by 5 'and then passed between a pair of nip rolls 6, 6' and guided between the next nip rolls 7, 7 '. Between the nip rolls 6, 6 'and the nip rolls 7, 7', both side edges of the film (a) are cut into slits by slit razors 8, 8 '.

The film (a) having passed between the nip rolls 7, 7 'is subsequently led to a group of heat treatment rolls 9.

The heat treatment roll group 9 includes a metal roll 9a and a rubber roll.
A pair of upper and lower heating rolls 9a, 9a 'comprising 9a', a heating roll 9b, and a pair of upper and lower cooling rolls 9c, 9c 'comprising a metal roll 9c and a rubber roll 9c', are provided between the nip rolls 7, 7 '. The film (a) passed through is heated rolls 9a, 9a '
Between the cooling rolls 9c, 9c ', and then cooled while passing around the lower side of the heating roll 9b.
Next, the winding machine 10 is moved in the direction of the winding shaft 11, that is, the film (a).
The film (a) is wound around the winding shaft 11 while being oscillated in a direction orthogonal to the length direction of the film, in other words, in a direction in which the film (a) reciprocates in the width direction of the film (a). A uniaxially stretched film (b) is manufactured.

The step of cutting both side edges of the film (a) into a slit shape is preferably performed after the high-speed rolls 5, 5 ', and more preferably at least one of the high-speed rolls 5, 5' and the heat treatment rolls 9a, 9a '. A pair of nip rolls is provided with two pairs of nip rolls 6, 6 ', 7, 7' composed of rubber rolls, and nip rolls 6,
Slit both side edges of the film (a) between 6 ′ and nip rolls 7 and 7 ′, and nip rolls 7 and 7 on the heat treatment roll group 9 side.
Between the 7 'and the first heat treatment roll 9a, cut off both side edges.

The slits on both side edges of the film are formed between the pair of upper and lower front nip rolls 6 and 6 ′ and the pair of upper and lower rear nip rolls 7 and 7 ′. Because the molecular orientation of the film is not fixed enough or the crystal orientation is not fixed enough, there is a high shrinkage stress in the stretched film. This is because a mistake may occur and the film may be broken.

Before the stretched film (a) comes into contact with the first heating roll, it is important to remove the slit side edge portions because the film is in contact with the first heating roll when the film comes into contact with the first heating roll. This is because it is necessary to simultaneously contact the heating roll on a straight line due to the homogeneity in the width direction. For this reason, it is particularly preferable to press the heating roll 9a 'against the first heating roll 9a, and if the slits on both sides and the running film portion are clamped at the nip position by the first heating roll 9a. ,
Even if a soft rubber nip roll is used, both sides of the running film are cut off at both sides, and both sides of the film run thick, and it is impossible to make uniform contact with the heating roll in a straight line. Under such circumstances, it is important to remove both side edges that have been slit before contacting the first heating roll, and since both sides of the film are slit before heat treatment, as shown in FIG. It comes into contact with the heating roll 9a uniformly and simultaneously, resulting in uniform quality. The entire width between both side edges shown in FIG. 6 becomes a product, thereby significantly increasing the production yield.

Peripheral speed of the high speed roll S ₁ and the peripheral speed of the first heating roll S ₂
Relationship with the, S ₂ / S ₁ is desirably 0.9 to 1.5, preferably at S ₂ / S ₁ is 0.95 or more and 1.2 or less, still more preferably S ₂ / S ₁ is 1.0 to 1.2. If S ₂ / S ₁ 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 ′, 7, 7 ′ is unevenly relaxed in the width direction. Therefore, it is not preferable.

The slit width of the side edges is preferably 2 mm or more,
When the slit width is preferably 5 mm or more and the slit width is less than 2 mm, the thickness of both side edges of the running film is thicker than other portions, and the thick side edges have a width of 50% or more in the width direction in the stretching process. As it decreases, at the moment it comes into contact with the first heating roll, it shows different elongation and shrinkage behavior in the width direction and the length direction with other parts, and the film running on the first heating roll comes into uniform and straight contact. Disappears,
It is not preferable because a slit mistake easily occurs.

Further, for the heat treatment by the heating roll, it is preferable to nip when the traveling film comes into contact with the first heat treatment roll, and also to nip when the traveling 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, so if it is brought into contact without being nipped by the cooling roll, it contracts by an amount due to the expansion in the width direction, causing the running film to shrink. This is because irregular wrinkles occur and a uniform film cannot be obtained.

When a single heating roll is used as a means for shrinking the film running in the vertical direction during the heat treatment, a speed difference is provided between the heating roll and a cooling roll following the heating roll, and the speed of the cooling roll is adjusted. May be made slower than the heating roll. When two or more heating rolls are used,
The speed of the subsequent heating roll from the first heating roll may be the same as or lower than the speed of the preceding heating roll.

The rate of shrinkage due to the difference in speed between the heating roll 9a and the cooling roll 9c is selected according to the required shrinkage of the target product, but in order to improve the dimensional stability of the product to be obtained, it is required to be 0.5% or more. %, Preferably 3% or more and 10% or less.

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

Furthermore, as for the winding means, the reciprocating distance of the oscillation for reciprocating the winding machine right and left is preferably 2 m.
m or more, preferably 5 mm or more, more preferably 10 mm or more, and when the reciprocating distance is less than 2 mm, minutely thick portions within the range of thickness non-uniformity allowed as a target product are gradually increased. As a result, it becomes impossible to disperse the thick portion to the left and right, and a uniform stretched film cannot be obtained. The reciprocating speed can be set in consideration of 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 performed at a constant speed.

Examples of the thermoplastic resin in the present invention include polyolefin polymers and copolymers such as low-density polyethylene, high-density polyethylene, and polypropylene; and polymers and copolymers of fluororesins such as polycarbonate, polyester, polyamide, and polyvinylidene fluoride. In Although,
It is a matter of course that other thermoplastic resins may be used without limitation, and the film-shaped molten resin extruded from the T-die lip in a molten state is one kind of thermoplastic resin, or two or more kinds. May be in the form of a single-layer film obtained by mixing the above resins, and two or more different thermoplastic resins are plasticized by different extruders, extruded from a feed block method or a multi-manifold type multilayer die after kneading. It may be a multilayer film.

A known means is employed for the longitudinal uniaxial stretching method based on the speed difference between the low-speed roll and the high-speed roll in the present invention,
Stretching conditions such as a stretching temperature and a stretching ratio suitable for the thermoplastic resin are employed.

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

Further, the method of the present invention is suitable for use, for example, in the case where the protective layer film is peeled after stretching as described in JP-B-60-6220, and an ultrathin film having a thickness of several μ or less as an intermediate layer is produced. is there.

Furthermore, the width of the film is not limited, but 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 only this example.

(One Embodiment to which the Method of the Present Invention is Applied) An example of an embodiment to which the method of the present invention is applied will be described with reference to FIG.

Polypropylene (Mitsubishi polypropylene MFR = 5.5g / 10
Min., Density 0.90 g / cm ³ , melting point 168 ° C) plasticized at 230 ° C, 50mmφ extruder, and separately PVDF (KYNAR, MFR manufactured by Penwald)
= 5.5 g / 10 min, density 1.8 g / cm ³ , melting point 171 ° C) at 230 ° C, 20
After being plasticized by a φ extruder and extruded from a three-layered multi-manifold type T-die in a three-layer state of propylene / PVDF / polypropylene, and contacted with a cooling roll 3 at 70 ° C. to be cooled and solidified, then to 100 mmφ, 120 mm ℃ low speed roll 4,
A 400 mm wide stretched film stretched uniaxially 5 times in the longitudinal direction between 4 'and 100 mmφ, 30 ° C., 10 m / min high-speed rolls 5,5' is rolled with high-speed rolls 5,5 'and heating rolls 9a, 9a'. Between two pairs of nip rolls 6, 6 'and 7, 7'
8 'each side edge of the film (a) running is slit by 7 mm, and the nip rolls 7, 7' and the heating rolls 9a, 9
Remove both side edges that have been slit between a ′ and the film and continue heating rolls 9a, 9 at 300 mmφ, 130 ° C., 10 m / min.
The film (a) coming out of the nip rolls 7, 7 'of 100 mmφ is brought into contact with a' in a straight line, and then the heating roll 9b
After making contact with the cooling roll 9c at 200mmφ, 30 ° C, 9.4m / min in a straight line, press the cooling roll 9c with a 50mmφ nip roll-shaped cooling roll 9c '.
After passing between c and 9c ', the wire was oscillated under the oscillation condition of reciprocating right and left in a straight line in 10 minutes left and right in 20 minutes, and wound up on the winding shaft 11 by 1000 m.

From the 1000m long film wound up in this way, cut several pieces to 100m length with several widths,
μ while removing the polypropylene film.
After winding a 0.9μ PVDF uniaxially stretched film into an aluminum tube with a diameter of 6 inches, the film was rewound and the sagging state of the film was observed. When the film was 330 mm or more, sagging was observed near both side edges of the film. However, when the width was 330 mm or less, a uniform uniaxially stretched film in the longitudinal direction was obtained in both the longitudinal and transverse directions.

(Comparative Example 1) In the above embodiment, the film was wound under the same conditions except that the both side edges of the film were not slit between the high-speed roll and the heating roll, and the winding state became unstable at 500 m. At this point, the winding was stopped, and the 0.9 μm PVDF uniaxially stretched film of the intermediate layer was wound on a 6-inch-diameter aluminum tube under the same conditions as in the example of the embodiment, then unwound, and the sagging state of the film was observed. In the case of a slit width of 200 mm or more, slack was observed near both ends of the film, and a film having a width of 200 mm or less was uniform and uniform.

(Comparative Example 2) In Comparative Example 1, both side edges of the obtained heat-treated stretched film were each 7 mm just before winding.
It was excised and subsequently wound up 1000 m under the same conditions as in the example of implementation. The rolled stretched film was wound on a 6-inch diameter aluminum tube with a 0.9 μm PVDF uniaxially stretched film of the intermediate layer under the same conditions as in the example, and then unwound, and the slack state of the film was observed. When the width was 280 mm or more, slack was observed near both side edges of the film, and when the width was 280 mm or less, the film was uniform and uniform.

From these results, it can be understood that the production yield of the thermoplastic resin film having a uniform thickness and uniform thickness in the vertical and horizontal directions is much superior to that of the conventional method.

(Effects of the Invention) According to the method of the present invention, a uniform and uniform uniaxially stretched film in the longitudinal and transverse directions can be produced with high yield.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an example of an apparatus to which the method of the present invention is applied,
2, 3, 4, and 5 are explanatory views of main parts in the case of the conventional method, and FIG. 6 is an explanatory view of main parts in the case of the present invention. 3,9c, 9c '… Cooling roll, 4,4'… Low speed roll, 5,
5 ': High-speed roll, 6, 6', 7, 7 '... Nip roll, 9
... heat treatment rolls, 9a, 9a ', 9b ... heating rolls, 10 ...
... winder, (a) ... thermoplastic resin film.

Continuation of front page (56) References JP-A-60-257220 (JP, A) JP-A-61-8325 (JP, A) JP-A-60-104313 (JP, A) JP-A-62-87320 (JP) JP-A-51-46372 (JP, A) JP-A-61-160222 (JP, A) JP-A-58-153616 (JP, A)

Claims (2)

(57) [Claims] The present invention is characterized in that a thermoplastic resin film is uniaxially stretched in a roll in a longitudinal direction, subsequently, both side edges are cut off, heat-treated by a heating roll, and then wound up while oscillating. A method for producing a uniaxially stretched film. 2. A thermoplastic resin film is uniaxially stretched in the length direction of a roll, then passed between nip rolls to cut both side edges into slits, passed through the next nip roll, and removed slit side edges. A method for producing a uniaxially stretched film, wherein a running film is wound on a winding machine while being oscillated through a heating roll of a heat treatment roll group, and subsequently through a cooling roll.