JPH048215B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an easily splittable uniaxially stretched oriented material. More specifically, the present invention includes:
Before embossing thermoplastic film,
The present invention relates to a method for producing an easily splittable uniaxially stretched oriented material, which is characterized by performing a roll rolling process, and which is unlikely to cause irregular local splitting or stretch breakage during the subsequent stretching process. Generally, a uniaxially stretched oriented material has a property of being extremely easy to tear substantially in the direction of stretching. This property often has an adverse effect on the secondary processability of the uniaxially stretched oriented product or the physical properties of the final product. Particularly in tape yarns and the like, random tearing substantially along the stretching direction is a major factor in reducing strength. However, by mechanically providing a large number of grooves parallel to the stretching direction of the uniaxially stretched oriented body, the cracks will inevitably run along the grooves. Even if tearing occurs due to external mechanical force, the tape yarn itself is only fragmented in parallel along the striped grooves, and the strength of the entire tape yarn is not significantly reduced. In addition, the easily splittable uniaxially stretched oriented material has a large number of thin grooves in the stretching direction of the uniaxially stretched oriented material. If the fibers are completely separated along the grooves, it is possible to easily produce single fibers of small denier without implementing sophisticated and complicated forming methods such as melt spinning. Conventionally, as a method and apparatus for producing an easily splittable uniaxially stretched oriented material having such advantages, there are those disclosed in Japanese Patent Publication No. 50-973, and the like.
This is usually called the REF (Roll Emboss Film) process. This method and apparatus include a film forming process for producing a raw film including an extruder, a take-off machine, etc., an embossing process for imprinting strips on the raw film, a stretching process for uniaxially stretching the embossed film, and a tape yarn. It consists of a winding process, and usually a slitter with suitable blades is installed between the embossing process and the stretching process, and after the embossed film is made into a tape shape, it is uniaxially stretched to create an easily splittable tape or tape. It manufactures yarn. In order to increase the strength of the easily splittable film or split single fibers through such a process, the stretching ratio in the uniaxial stretching process may be increased. However, as the stretching ratio increases,
During stretching, fiber splitting along the grooves tends to occur locally and irregularly, and stretching breaks occur at the split locations, making it difficult to obtain a uniform film or tape yarn. The present invention was made as a result of intensive studies to solve these problems, and has made it possible to significantly improve strength without causing local splitting during stretching. It is something. That is, (A) a supplying step of supplying a thermoplastic resin film, (B) a rolling step of rolling the film so as to orient it vertically and uniaxially in the length direction in a solid state, and (C) the above-mentioned rolling step. An embossing step in which the treated film is passed through an embossing roll to imprint strips parallel to the length direction, and (D) the film with the strips stamped thereon is further uniaxially stretched to form an easily splittable uniaxial film. This relates to a method for producing an easily splittable uniaxially stretched oriented body, comprising a stretching step to form a stretched oriented body, and (E) a winding step of winding up the easily splittable uniaxially stretched oriented body. be. Thermoplastic resins used in the present invention include polyethylene, polypropylene, polybutene-1,
Homopolymers such as poly-4-methylpentene-1, other α-based polymers mainly composed of ethylene and propylene
- Polyolefin resins such as olefins or copolymers with polar monomers, polyamide resins such as nylon-6, nylon-6, nylon-6, nylon-12, and nylon-11, and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. , polystyrene resins, polyvinylidene chloride resins, polyvinyl chloride resins, polyvinyl alcohol resins, saponified ethylene-vinyl acetate copolymers, and mixtures thereof, as long as they are crystalline thermoplastic resins. There is no particular restriction on the type of raw material resin. In the method of the present invention, the roll rolling treatment for vertically uniaxially oriented in the length direction may be performed by any known method and is not particularly limited, but it is necessary to perform the rolling treatment at a temperature lower than the melting point of the thermoplastic resin. It is. That is, for crystalline resins, the temperature is below the crystal melting point, preferably about 60°C lower than the crystal melting point, and for polystyrene resins, polyvinyl chloride resins, polymethacrylic acid resins, polyester resins, etc. For resins with poor crystallinity at room temperature, such as, it is preferable to perform the treatment near the glass transition point of the resin. Furthermore, the film may be preheated before rolling if necessary. The rolling ratio (film thickness before rolling/film thickness after rolling) in the above rolling process is not particularly limited, but is preferably about 1.05 to 5 times, more preferably about 1.2 to 4 times. This rolling ratio is
When it is less than 1.05 times, the effect of roll rolling is not significant. On the other hand, if the rolling ratio exceeds 5 times, there is a concern that the hardness of the rolled film will increase, making it difficult to deform the film during the subsequent embossing process. The above rolling ratio is determined in consideration of the uniaxial stretching ratio after embossing. For example, using the target magnification (roll rolling magnification x uniaxial stretching magnification after embossing) as a guide, some trial-and-error tests are conducted on the relationship between the target magnification and product strength to find the most suitable conditions. The distribution between the roll rolling ratio and the uniaxial stretching ratio is not particularly limited, as the optimal ratio is determined depending on the implementation conditions, and it also changes depending on the type of resin, rolling conditions, uniaxial stretching conditions, etc. do not have. In addition, the raw film to be subjected to roll stretching is T
It may be manufactured by a known molding method such as a die method or an inflation method. In particular, in the method of the present invention, remarkable advantages are exhibited when the above-mentioned inflation film is used. In other words, the inflation method requires simple equipment and is the most advantageous film forming method;
The film has a large thickness deviation in the width direction and is flattened into a tube shape. When such an inflation film with a large thickness deviation in the width direction is subjected to the above-mentioned embossing process, the degree of embossing differs depending on the position in the width direction, and the grooves become shallow and deep, resulting in an overall This results in non-uniformity, resulting in locally irregular fiber splitting and stretching breakage. In addition, since the inflation film is in the form of two tube-shaped layers, it must be cut open to form a single film and supplied to the embossing process, but this is usually not carried out industrially. At such film running speeds, it is quite difficult to cut a tube-shaped flattened film into one piece without causing wrinkles or the like. However, in the method of the present invention, by rolling the blown film, it is possible not only to level the film in the width direction and significantly reduce the uneven thickness, but also to reduce uneven thickness of the film. By rolling the stacked flattened films as they are, they are completely integrated and can be processed in the same manner as a single film. By performing roll rolling before embossing as in the present invention, it is possible to significantly improve the strength of the product without causing local splitting, and furthermore, it is possible to prevent stretching breakage. Many improvements are achieved, including a significant improvement in stretchability, such as no embossing, and a reduction in embossing unevenness caused by the bending of the embossing roll. The invention will be explained in more detail below by means of the illustrated apparatus and embodiments. Figure 1 is an explanatory diagram of the REF process.
Figures 2a to 2c are cross-sectional views of the film in each step, and Figure 2d is a cross-sectional view of a single fiber. In FIG. 1, a thermoplastic resin film 1 is supplied from a film forming process A, which is a supply process, to a rolling roll 2 in a rolling process B, where it is pre-rolled and then supplied to an embossing process C. The rolling treatment in rolling step B is performed by a conventional method, and the rolling ratio is preferably in the range of 1.05 to 5 times, as described above. In the embossing process C, the thermoplastic resin film 1 whose thickness has been made uniform by rolling is compressed by a plain roll 4 and an embossing roll 5 to perform an embossing process. Thermoplastic resin film 1
The cross section changes as shown in FIG. 2a to FIG. 2b. Embossed thermoplastic resin film 1
is further cut into tape shapes by a slitter 7. In the next stretching process D, a low speed roll 8, a stretching hot plate 9
(or a heated roll oven, etc.), and a high-speed roll 10, the progress of the tape-shaped thermoplastic resin film 1 was suppressed to some extent by the low-speed roll 8, and the thermoplastic resin film 1 was appropriately heated by a stretching hot plate 9. Thereafter, the thermoplastic resin film 1 heated by the high-speed roll 10 is stretched and transferred forward while being stretched. In this way, the easily splittable tape 13 of the present invention
[Fig. 2c] is manufactured, sent to a winding process E, and wound around a large number of winders 12a to 12e to be manufactured into a product. In addition, if necessary, the easily splittable tape 1
An external force such as twisting or ironing is applied to the fibers 3 to form a single fiber 14 as shown in FIG. 2d for use.
Note that reference numerals 3, 6, and 11 in the figure are guide rolls. The following examples and comparative examples were carried out using the apparatus described above. Examples 1-1 to 1-6 Isopolypropylene (MI: 4.0, density: 0.91)
Using the air-cooled inflation method,
A tube-shaped flattened film with a thickness of approximately 55 μm and a fold diameter of 450 mm was obtained. Next, this film was passed through a preheating roll in a flat state, and was narrowly pressed with a pair of rolling rolls of 250φ x 500Lmm, and rolled at a rolling temperature of 120°C and a rolling ratio of 1.1 to 5.5 to obtain various rolled films. . Both of the two layers of film after rolling were strongly blocked and looked like a single T-die film. Thread grooves (depth
240φ×600Lmm stamped with 200μ, density 80 pieces/in)
The rolled film was introduced into an embossing device consisting of an embossing roll and a plain roll (for backup) to obtain an embossed film having a cross section as shown in FIG. 2b. The embossing temperature at this time was 130°C. Next, this embossed film was cut into a tape shape using a slitter so that the product fineness was 1000 denier, and uniaxially stretched on a hot plate having a length of 1500 mm. The stretching temperature is about 130°C. The stretching ratio at this time was determined according to each rolling ratio so that the target ratio (total ratio) was 12 times. The degree of local fibers during stretching in the above process,
The state of stretching breakage and product strength were measured. The results are shown in Table 1. In this example, even though the target magnification was high, all of the obtained products were in a uniform state and there was no stretching breakage, indicating that they could be manufactured in a stable state. In addition, strip grooves of a predetermined depth were uniformly imprinted on all tape yarns. Furthermore, even though the tube-shaped flattened film is used as is, it can be processed in exactly the same way as when using a single T-die film, and the product does not separate into two pieces. Ta. However, in the case of Example 1-1, the effect of rolling is small, and in the case of Example 1-6, the rolling ratio is high, so the rolled film tends to tear in the length direction, causing tearing during embossing. were seen here and there. Examples 2-1 to 2-7 Tests were conducted in the same manner as in Example 1, except that the target magnification was 10 times, and products were obtained. The same tendency as in Example 1 was observed in the effect of rolling. In addition, only in Examples 2-7, an original film (thickness about 110 μm) made by the T-die method was used. The above test results are shown in Table 1. Examples 3-1 to 3-6 Polyethylene terephthalate ([η] 0.75, density: 1.41, melting point: 255°C) was used, the temperature of the rolling process was about 90°C, the temperature of the embossing process was about 110°C,
The test was conducted in the same manner as in Example 1, except that the temperature of the stretching treatment after embossing was about 90°C. The original film used was made by the T-die method. The results are shown in Table 2. The effect of roll rolling showed exactly the same tendency as in Example 1. Comparative Examples 1-1 to 1-5 In Comparative Examples 1-1 to 1-4, original films obtained by the T-die method were used, and in Comparative Example 1-5, original films obtained by the inflation method were used, An easily splittable tape yarn was obtained without rolling treatment. Since no stretching process is applied, the target magnification is equal to the value of the uniaxial stretching after embossing process, from 6x to
It was varied over a 12-fold range. The rest is the same as in Example 1. The thickness of the T-die film is approximately
110μ, inflation film thickness is approximately 55μ
And so. When the target magnification is 10x and 12x, due to the high-magnification stretching, irregular and localized fiber splitting is observed throughout the obtained tape yarn, and there are many stretching breaks, making stable production difficult. I couldn't do it. Furthermore, when looking at the cross section of the embossed film in the width direction before stretching, it was found that striped grooves of uniform depth were not imprinted, and that the emboss roll and plain roll were bent by the pressing force. The tape yarns obtained did not have good splitting properties if they passed through the center of the roll, but on the contrary, the tape yarns located closer to the ends had better splitting properties. This tendency is observed in Comparative Example 1
-1 and 1-2 were exactly the same. In the case of Comparative Examples 1-5, the embossed state was uneven due to poor thickness accuracy of the original film, and the obtained tape yarn was seen to be locally separated into two pieces. As described above, it is extremely difficult to obtain a product with high magnification and high strength using conventionally known methods that do not involve roll rolling. The above results are shown in Table 2. Comparative Example 2 Comparative Example 2 was carried out in the same manner as in Comparative Example 1, except that a tensile stretching method was used instead of the roll rolling method. During the above-mentioned stretching, at a stretching ratio of at least 1.1 times to 5.5 times, irregularly island-shaped unstretched portions were always generated, and a uniform stretched film could not be obtained. Therefore, it was impossible to apply uniform embossing to this film. In addition, when stretched at a magnification of 4 times or more, tearing tends to occur in the length direction during embossing, making it impossible to continue stable embossing. The stretching method carried out here is a close roll stretching method in which stretching is carried out between two adjacent rolls while preventing width reduction as much as possible.The roll spacing is 1 mm, and the roll size is 250φ for both the low speed roll and high speed roll.
It is 500Lmm. Even if this stretching method is replaced with a long-range stretching method that is widely used for tape yarns, etc., it is thought that the difficulty will only be doubled. As described above, it has been found that it is impossible to replace the roll rolling before embossing with the tensile stretching method. Comparative Example 3 A test was conducted in the same manner as in Example 3, except that an easily splittable tape yarn was obtained without going through the rolling process. Although the obtained tape yarn was of better quality than that of polypropylene, local splitting was observed. Further, the cross section of the embossed film in the width direction showed the same tendency as Comparative Example 1.

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a step explanatory diagram of the REF process, and Figures 2 a to d are cross-sectional views of the film in each step, where a is a rolled film, b is an embossed film,
c is a cross-sectional view of an easily splittable tape and d is a cross-sectional view of a single fiber after splitting. 1: thermoplastic resin film, 2: rolling roll,
3, 6, 11: Guide roll, 4: Plain roll, 5: Emboss roll, 7: Slitter, 8:
Low speed roll, 9: Stretching hot plate, 10: High speed roll,
12a to 12e: winder, 13: easily splittable tape, 14: single fiber.

Claims (1)

[Scope of Claims] 1 (A) a supplying step of supplying a thermoplastic resin film; (B) a rolling step of rolling the film in a solid state so as to vertically uniaxially orient it in the longitudinal direction; (C) An embossing process in which the film subjected to the above rolling process is passed through an embossing roll to imprint strips parallel to the length direction; (D) the film with the strips imprinted thereon is further uniaxially stretched; Production of an easily splittable uniaxially stretched oriented body, comprising a stretching step to form an easily splittable uniaxially stretched oriented body, and (E) a winding step of winding up the easily splittable uniaxially stretched oriented body. Method. 2. The method for producing an easily splittable uniaxially stretched oriented material according to claim 1, wherein the thermoplastic film is obtained by pinching and flattening a tubular film formed by inflation molding. 3. Claim 1 or 2, wherein the rolling magnification of the roll rolling process is from 1.05 times to 5.0 times.
A method for producing an easily splittable uniaxially stretched oriented material as described in 2.