JPS59227422A - Preparation of traverse uniaxially stretched film - Google Patents

Abstract

PURPOSE:To improve traverse stretchability without losing the physical properties of a traverse uniaxially streched film, by stretching a thick film to a traverse axis direction after lightly rolling the same to a longitudinal axis direction in a solid phase state. CONSTITUTION:It is necessary that a thick film is subjected to rolling treatment to reduce and uniformize the thickness thereof and rolling magnification is set to a range of 1.1-2.5. If the rolling magnification is smaller than said range, rolling effect is hardly recognized and, contrarily, when larger than said range, the longitudinal tearing property of a film becomes remarkable. Therefore, it is necessary that the rolling magnification by a roll is set to 2.5 or less and, at the same time, traverse uniaxial stretching magnification is set to 4 or more. By preliminarily applying light rolling in a longitudinal direction as mentioned above, traverse uniaxial stretching treatment can be drastically stabilized and facilitated.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a transversely uniaxially stretched body.

More specifically, the present invention provides a transversely uniaxially stretched body, which is characterized in that an original film made of a thermoplastic resin is roll-rolled in a solid state in the vertical axis direction, and the film is further stretched four times or more in the horizontal axis direction. The present invention relates to a method for producing a homogeneous and good horizontally uniaxially stretched film or horizontally uniaxially stretched splitting material without causing stretch breakage or stretching unevenness during film stretching.

A long film that is axially stretched in the width direction (horizontal direction) is
It is easy to cut and is used in products such as adhesive tapes. In addition, the horizontally uniaxially stretched body is -
It is used as a cross-oriented laminate or as a packaging material strengthened in the vertical and horizontal directions by laminating with an axially stretched longitudinally-axially stretched film.

On the other hand, by cross-laminating split films obtained by splitting longitudinally and transversely uniaxially stretched films in the stretching direction, a reinforced network that can be called a type of nonwoven fabric can be obtained. Such a net-like material is used as a reinforcing material for other types of packaging materials by bonding it with paper, aluminum foil, etc., or it is used alone as a reinforced mesh material having air permeability.

Conventionally, the method for obtaining the transversely-axially stretched body as described above is generally to grasp both ends of the raw film,
The tenter method, in which stretching is carried out by gradually expanding the distance between the two gripping portions mechanically, or the JP-A-55-
No. 85522, Japanese Patent Application Laid-open No. 128427/1985,
As described in Japanese Unexamined Patent Publication No. 55-101424, etc., a method and an apparatus thereof have been proposed in which a film is introduced between a pair of pulleys and stretched so as to form a stretching axis trace that widens at the end.

However, in these conventional methods, when transverse uniaxial stretching is performed, unstretched portions may occur due to slight thickness unevenness, or breakage such as stretch breakage during stretching may occur due to slight unevenness or portions of the original film. This tends to occur, and in order to perform a good stretching process, highly accurate control and management of the forming conditions, stretching conditions, etc. of the original film is required.

For example, JP-A-52-47070, JP-A-54-
As described in Japanese Patent Laid-Open No. 71173, Japanese Patent Laid-Open No. 55-65522, etc., the current situation is that strict precision is required for setting and controlling the conditions.

In view of the current situation, the present invention was developed based on various studies.
When transversely uniaxially stretching a thermoplastic resin film obtained by a general-purpose appropriate forming method, it is possible to perform a slight longitudinal roll rolling treatment in advance without impairing the physical properties of the resulting transversely-axially stretched product. It was discovered that the lateral stretchability could be significantly improved, and the present invention was completed.

That is, in the present invention, an original film made of a thermoplastic resin is roll-rolled in a solid state in the vertical axis direction at a rolling ratio of 1.1 to 2.5, and the film is further stretched 4 times or more in the horizontal axis direction. The present invention relates to a method for producing a structurally axially stretched body, characterized in that:

The above-mentioned rolling in a solid state means rolling in a temperature range lower than the melting point or softening point of the thermoplastic resin, and the rolling temperature is 5°C or more lower than the melting point of the thermoplastic resin, and 60°C lower than the melting point of the thermoplastic resin. It is preferable that the temperature is not lower than 2°C.

If the rolling temperature is higher than the above range, the adhesiveness between the film and the rolling roll will increase, which is disadvantageous.On the other hand, if the rolling temperature is too low, the required rolling blade will become too large.
This is undesirable because the rolling rolls must be made more powerful.

The original film needs to be rolled to reduce its thickness and make it uniform. The rolling ratio is 1.1 as mentioned above.
When the rolling ratio is smaller than this range, almost no effect of rolling is observed, and on the other hand, when the rolling ratio is larger than the above range, the longitudinal cracks in the film are weak. This becomes noticeable and results in an increase in stretch breakage during lateral stretching.

In other words, making the rolling ratio larger than 2.5 means that
Folds between the oriented crystals of the film tend to occur, causing longitudinal tearing, which actually reduces the transverse stretchability, or the resulting transversely uniaxially stretched film takes on biaxially stretched characteristics, and the original transversely uniaxially stretched film As a result, physical properties deteriorate. Therefore, at the same time as reducing the rolling ratio by rolls to 2.5 or less,
It is necessary to set the horizontal uniaxial stretching ratio to 4 or more.

Furthermore, it is not even expected that a thermoplastic resin film treated with the above-mentioned rolling ratio and transverse uniaxial stretching ratio would behave in the same way as the physical properties of a conventional transversely-axially stretched product.
This is completely new knowledge. For example, when using another tensile force-based stretching method instead of roll rolling, such as the close roll stretching method, it is difficult to achieve longitudinal stretching of 2.5 times or less, and unlike roll rolling, when horizontal uniaxial stretching is used, In addition, there is no effect on leveling out the uneven thickness that causes unstretched parts, and
Many problems arise, such as the occurrence of a zigzag bead, which requires trimming, and an increase in loss, and the improvement effect aimed at by the present invention cannot be obtained.

As described above, the present invention dramatically stabilizes and facilitates the transverse uniaxial stretching process, which has conventionally been difficult to stabilize, by performing slight longitudinal roll rolling in advance. becomes possible. In addition, the physical properties of the obtained stretched body are equivalent to or better than those of the conventional transversely stretched body, so the transversely stretched body obtained by the method of the present invention is different from the usual biaxially stretched body. They are different.

Conditions that further enhance the effects of the present invention include preparation conditions during melt molding of the original film. In other words, in an appropriate film-forming method, by rolling a raw film formed under so-called quenching conditions, in which the cooling time for transition from a molten state to a solid state is extremely short, the transverse axis stretchability is even more remarkable. This will be improved.

The above-mentioned cooling conditions are expressed by the average temperature drop rate from the time when the resin is melt-extruded from the die lip and cooling is started until solidification. It is desirable to use rapid cooling conditions such that the temperature decrease rate is 15°C/second or more, preferably 20°C/second or more.

General film forming methods that satisfy these conditions include:
A film forming method using a casting roll in which molten resin is extruded from a flat die onto a cooling roll and taken off as it solidifies, or a water-cooled inflation method in which bubbles extruded from an annular die are directly contacted with cooling water to solidify and then taken off. Examples include a membrane method, but of course the present invention is not limited to the above two methods.

Another method for further exerting the effects of the present invention is to use a flattened two-ply tube-shaped film obtained by a blown film molding method as an original film as it is. That is, by continuously introducing the tube of blown film from the film forming process into the roll rolling process, it is possible to obtain a transversely stretched body that is exactly the same as that obtained from a single original film. This provides two major advantages in terms of production efficiency, equipment efficiency, etc.

Normally, when using a single sheet of raw film, it is common to use the casting film described above or to cut out a blown film, but the former casting film has edge beads, which are removed during the trimming process. etc., which complicates the process, reduces production efficiency, or causes losses.

On the other hand, when using the latter blown film, it is necessary to cut the tube-shaped film, but it is difficult to cut continuously and the cutting speed cannot be increased. It has been difficult to make the inflation process and stretching process continuous.

In addition, in order to solve the above-mentioned difficulties, we flattened the tubular film obtained by the inflation method.
It is conceivable to use a film consisting of layers as the base film. However, even if this two-layer film is directly horizontally stretched under conventional conditions, the stretched product will not be satisfactory, and some parts of the stretched film will separate into two sheets, or some parts will be strongly bronched. Phenomena such as being combined into one sheet occur, and you can only obtain one in a halfway state.

On the other hand, in the present invention, the compressive force due to roll rolling is
The stacked film blocks to a high degree and behaves in the same way as a single film in the subsequent steps, and the resulting stretched product does not have any peeling parts and is no different from that obtained from a single film. It becomes something that does not change. This means that
This is further advantageous in the production of a splitting body, which will be described later.

The transversely-axially stretched body in the present invention refers to a film, a tape,
This method includes splittable bodies and the like, and its effects are particularly remarkable as a method for producing transversely-axially stretched splittable bodies.

In general, the stretched splitting material is used as a cross-laminated net structure in which vertically-axis and horizontally uniaxially stretched splittings are superimposed, or as a reinforced laminate in the form of a nonwoven fabric. The above-mentioned transversely uniaxially stretched splitting body is obtained by splitting the raw film in advance and then laterally stretching it. Splitable fibers are made up of thin filaments, and are easily broken during transverse stretching, and unstretched portions also tend to remain. Very difficult.

The method of the present invention is also effective against the above-mentioned inhibitory factors that make transverse stretching difficult.

That is, the method for producing a transversely-axially stretched splitting body in the present invention is achieved by inserting a splitting process between the roll rolling process and the horizontal uniaxial stretching process.

” - In the splitting process, parallel to the width direction of the film,
Alternatively, make slits in a staggered pattern.

The fiber splitting method may be a method using a file or the like, but the most preferable method is a method using a heating blade as disclosed in Japanese Patent Laid-Open No. 58-51114.

When a film that has been lightly rolled in the longitudinal direction as in the present invention is split by the heating blade method described above, the shrinkage force (moves) in the direction perpendicular to the cut line, and at the same time it is separated by the edge, the cut line Since the fibers tend to separate from each other, the fibers are completely split, and the above-mentioned phenomena such as breakage during horizontal axis stretching are eliminated.

In other words, when the film is melted and cut when exposed to heat, the heat causes the fused edges to contract and separate from each other, forming a smooth cut edge without any notches, resulting in undesirable conditions such as uncut edges. will all disappear. As a result, the subsequent transverse stretching is stabilized, and no breakage or unstretched portions occur.

As a method in which the features of the present invention are clearly exhibited, there is a method of manufacturing a splitting body using a flattened tubular film obtained by a blown film forming method, similar to the method of manufacturing a horizontally uniaxially stretched film described above. . Obtaining a transversely-axially stretched split fiber body using a blown film causes stretching breakage and unstretched portions as described above.
This has traditionally been extremely difficult. However, according to the method of the present invention, together with the blocking effect caused by roll rolling, the split edges of the fibers split by the above-mentioned thermal force are completely welded, and there is no peeling during stretching or unstretched portions. The desirable result is that this does not occur.

Thermoplastic resins to which the method of the present invention can be applied include low, medium,
Homopolymers such as high-density polyethylene, isotactic polypropylene, polybutene-1, poly-4-methylpentene-1, etc.; copolymers containing ethylene or propylene as a main component with other α-olefins, such as ethylene-1; Propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, or propylene-butene-1 copolymer, or ethylene-drunken vinyl Polyolefin resins such as copolymerization, nylon-6, nylon-
6, 8, polyamide resins such as nylon-11 and nylon-12, polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyvinyl chloride resins, polyvinylidene chloride resins, and mixtures containing at least one thereof. Among these, crystalline resins having stretchability are particularly preferred.

In the present invention, usual additives such as antioxidants, ultraviolet absorbers, pigments, carbon black, and inorganic fillers may be added to the resin.

Further, as the raw film, it is also possible to use a composite film such as a coextruded laminated film in which different or similar resins are simultaneously extruded, or a laminated film in which different resin films are laminated together.

As mentioned above, the present invention has the following advantages compared to the conventional method for producing a transversely stretched body.

(1) A simple rolling process that does not require precise temperature control and evens out uneven thickness of the original film, improves subsequent stretchability, and prevents unstretched areas and stretch breaks. Uniform stretching is possible.

(2) Through the rolling process, in addition to regular films, various types of raw films such as multilayer films and flattened blown films can be used, and transversely-axially stretched splitting bodies can also be easily produced. It is possible.

(3) A flattened tubular film consisting of two layers formed by the inflation molding method can be used as the base film,
Since it can be continuously supplied directly from the film manufacturing process, it is possible to increase production efficiency and loading differential rate.

The transversely stretched body produced by the method of the present invention can be used for the above-mentioned cross-oriented laminates, reinforced nets, reinforcing materials for other types of packaging materials, adhesive tapes, heat-shrinkable films, etc.
It can be widely used for industrial materials, packaging materials, etc.

The present invention will be explained in more detail below using experimental examples, but the present invention is not limited to these examples unless it departs from the gist of the present invention.

Example High density polyethylene (MI: 1. (+, density: 0.95
B, melting point: 127°C), by the inflated film forming method and casting roll method, 400 m
Original films of m width and various thicknesses were obtained. This film was rolled at a temperature of 110°C at various rolling ratios,
Both films were made into films with a thickness of 0.1 mm, and were horizontally stretched. In the horizontal axis stretching process, JP-A-55-126427
The transverse stretchability was examined by stretching at a stretching speed of 40 m/win and a near-stretching ratio using an apparatus that shows a divergent stretching locus as disclosed in the above publication.

The results are shown in Table 1.

The evaluation criteria for lateral stretchability are as follows.

XX: Breakage, unstretched portions occur, continuous stretching for less than 1 minute Stretched in this state, the film strength was as follows: tensile speed: 300 mm/win and grip interval: 3001
The strength at break at 11111 is shown.

As shown in Table 1, it can be seen that those without roll rolling and those with a rolling ratio outside the range of 1.1 to 2.5 (Experimental Example 1.2.4) have poor transverse stretchability. Also,
It can be seen that it is better to increase the film forming cooling rate of the original film.

Example polypropyl l/7 (Ml: 1.5, density: 0.
90, melting point = 187°C), and the roll rolling temperature was changed to 130'0.

The results are shown in Table 2. As can be seen from the table, similar results are obtained for polypropylene film.

EXAMPLES In Experimental Examples 1 to 6, a fiber splitting process was provided between the roll rolling process and the horizontal axis stretching process. In the splitting process, JP-A-58
Thermal force (IB of the blade, g
: 250 to 280°C) to form a split film in which cuts were made at intervals of 2m+n in the transverse direction of the film. Regarding this, the transverse stretchability was examined by straining in the same manner as in Experimental Examples 1 to 6. The results are shown in Table 3.The transverse stretching speed was 1 to 2 times per hour when continuous stretching was performed.
It is shown by the maximum stretching speed at which the condition occurs several times. Therefore, the higher the stretching speed, the better the stretching property is.

The splitting body strength was determined by bundling approximately 10 splitting bodies after horizontal axis stretching, tensile speed: 300 mm/win, and gripping interval = 30.
A value was obtained by dividing the maximum breaking strength at 0ff1m by the number of bundles, and this value was converted into strength per denier.

As can be seen from the results shown in Table 3, according to the method of the present invention, the drawing speed of the split fibers can be significantly increased.

Table 1 Table 2 Table 3

Claims (5)

[Claims] (1) A raw film made of thermoplastic resin is rolled at a rolling ratio of 1
．． 1 to 2.5. A method for producing a transversely uniaxially stretched product, which comprises subjecting the film to solid-state tyrol rolling in the longitudinal direction, and further stretching the film four times or more in the transverse direction. (2) The method for producing a transversely uniaxially stretched body according to claim 1, wherein a splitting process is added between the roll rolling process and the transversely stretching process. (3) A method for producing a horizontally uniaxially stretched body according to claim 1 or 2, which uses a film molded at an average cooling rate of 15° C./sec or more during molding as the raw film. . (4) Horizontal uniaxial stretching according to any one of claims 1 to 3, characterized in that the roll rolling treatment is performed at a temperature from 5°C to 60°C lower than the melting point of the thermoplastic resin. How the body is manufactured. (5) The method for producing a transversely uniaxially stretched body according to any one of claims 1 to 4, wherein the IJX film is obtained by flattening a tubular film obtained by a blown film molding method.