JP3026231B2 - Method for producing high-strength polyolefin tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength polyolefin tape by rolling a polyolefin sheet or film in the width direction in advance and then uniaxially stretching it in the take-off direction. .

[0002]

2. Description of the Related Art As a method for producing a tape-shaped material such as a uniaxially-stretched tape or band of polyolefin, a method in which a rolling step and a uniaxially-stretching step are used in combination, that is, before a uniaxially-stretching in a take-off direction, a widthwise direction. Rolling method is known.

[0003] This manufacturing method is disclosed in, for example, Japanese Patent Application Laid-Open No. 53-2
As described with reference to FIG. 2 and described with reference to FIG. 2, first, a thermoplastic resin is extruded in a molten state from a mold 22 attached to the tip of an extruder 21, and the obtained extrudate 23 is cooled. 24, quenched and solidified, then preheated by a preheating device 25, passed through the rolling rolls 26, 26 and rolled into a belt shape, and then drawn rolls 27, 2
7 and stretched in the length direction, and these rolling and stretching were repeated at least twice or more to reduce the length of the extrudate 23 by 5 times.
This is a method of stretching by a factor of 10 to form a molecular orientation in the length direction and the width direction. 28 is a guide roll, 29 is a cooling tank for cooling the extruded product 23 after stretching, and 30 is an extruded product 2
No. 3 winder.

In this manufacturing method, 1
Before the axial stretching, the material is rolled in the width direction, so that the effectiveness of this rolling is recognized. That is, according to the same publication, the extrudate 23 is rolled in the width direction.
The strength in the width direction is improved, longitudinal cracks along the take-off direction are prevented, and the strengths in the width direction and the take-up direction are balanced without being biased to one side.

[0005]

However, the rolling effect in the width direction in the above manufacturing method is not as high as expected, and the longitudinal cracking resistance of the obtained extrudate 23, that is, the tape-like material, is greatly improved. In fact, the mechanical strength in the width direction and the take-off direction is not so well-balanced because the former mechanical strength is not improved.

This is considered to be due to the following reasons. That is, the extrudate 23 that has passed through the rolling rolls 26 and rolled into a belt shape contracts in the width direction due to elastic recovery due to its properties, and the effective rolling ratio in the width direction is lower than expected. For this reason, it is considered that the longitudinal cracking resistance of the extrudate 23 is not improved as much as expected, and the molecular orientation of the thermoplastic resin due to the subsequent uniaxial stretching is insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and it is an object of the present invention to provide a method for producing a high-strength polyolefin tape-like material having a large mechanical strength in a take-up direction as well as in a width direction. With the goal.

[0008]

The present invention provides a method for producing a high-strength polyolefin tape-like material having a width of 1 mm to 1 mm.
After passing a 0 mm polyolefin sheet or film between two rolling rolls at a temperature equal to or lower than the melting point of the polyolefin, the sheet is rolled by a pressure roll to a roll by 1.1 to 5 times in the width direction. This is a method of rolling and then uniaxially stretching in the take-off direction.

The polyolefin used in the present invention is:
Ethylene homopolymers, essentially crystalline ethylene resins such as copolymers of ethylene and α-olefins, propylene homopolymers and propylene and ethylene or other α-olefins
An essentially crystalline propylene-based resin such as a copolymer with an olefin. In addition, an appropriate amount of additives such as an antioxidant, a lubricant, and a coloring agent are included as necessary.

As a method for producing a polyolefin sheet or film before rolling, there are a method of extrusion molding with a T die and a method of molding by inflation molding with an annular die, and any method may be employed depending on the purpose.

In the case of manufacturing using a T-die, a sheet or film having a uniform thickness continuous in the width direction is extruded and then adjusted to an appropriate width by slitting in the take-off direction, and the subsequent rolling process is performed. Or the exit width in the width direction of the T-die may be adjusted so as to obtain a sheet or film having an appropriate width, and the above-described slitting step may be omitted. In the latter case, it is productionally efficient to simultaneously form a plurality of sheets or films by using a T-die that can simultaneously obtain a plurality of sheets or films having an appropriate width.

On the other hand, in the case of manufacturing by inflation molding, after the tubular sheet or film is flattened at the time of taking off, the width end is cut open to separate the sheet or film into a total of two upper and lower sheets. It is appropriate to slit to width.

The effect of rolling the polyolefin sheet or film rolled by the rolling rolls in the width direction depends on the width of the sheet or film. The width of the polyolefin sheet or film that can be rolled in the width direction is such that the smaller the smaller, the larger the upper limit of the effective rolling ratio in the width direction becomes.However, when the width is less than 1 mm, the width of the sheet or film is adjusted by slitting, Even if a sheet or film having an appropriate width is directly extruded, it is difficult to implement it industrially. On the other hand, when the width of the polyolefin sheet or film exceeds 10 mm, a large pressing force is required for the rolling roll, and it is difficult to industrially make the rolling ratio in the width direction an effective size. The reason why the width of the polyolefin sheet or film is 1 mm to 10 mm is as described above.

In order for the rolling effect when the polyolefin sheet or film is rolled in the width direction to be effective, it is necessary to perform rolling at an appropriate temperature determined by the material properties of the sheet or film. That is, the appropriate temperature range of the polyolefin sheet or film is a temperature equal to or lower than the melting point of the polyolefin, and more specifically, is equal to or lower than the melting point of the polyolefin sheet or film to the melting point minus 50 ° C, preferably, the melting point minus 5 ° C to the melting point. It is in the range of minus 30 ° C.

In the width direction rolling of the polyolefin sheet or film having an appropriate width obtained by the above-mentioned method, the sheet or film preferably adjusted to an appropriate temperature in advance is preferably used.
It is performed by passing between one or more pairs of rolling rolls adjusted to an appropriate surface temperature.

Unless the polyolefin sheet or film rolled by the above-mentioned rolling roll is cooled to a temperature lower than its melting point and at least lower than the melting point minus 60 ° C., the effective rolling ratio in the width direction is reduced by elastic recovery. Therefore, immediately after the rolling, it is necessary to maintain the adhesion to the rolling roll after the nip point and to prevent the shrinkage in the width direction due to the elastic recovery.

According to the present invention, the shrinkage in the width direction is reduced by one or a plurality of pressure rolls arranged so as to minimize the air gap after rolling. Is pressed against a rolling roll. Thereafter, the surface temperature is adjusted to the melting point of the polyolefin or lower and at least minus 60 ° C. or lower, and is prevented by passing through a cooling roll equipped with the same pressure roll as described above. It is desirable for the above-mentioned pressure roll to minimize the air gap after rolling (the distance until the pressure is pressed after rolling).

As described above, the rolling ratio in the width direction is 1.
An appropriate range is 1 to 5 times. If it is less than 1.1 times, the effect cannot be recognized, and if it is 1.1 times or more, the mechanical strength of the tape-like material obtained by uniaxial stretching is improved. This effect is maximized in the vicinity of about 2 times, and when the rolling ratio is further increased, the effect gradually decreases,
If it exceeds 5 times, almost no effect is observed, or it becomes worse rather than not rolling. The draw ratio in the width direction is limited to the above range for such a reason.

The uniaxial stretching in the take-off direction is performed by a method widely used for uniaxial stretching of polyolefin, that is, between two or more pairs of nip rolls having different peripheral speeds in an appropriate temperature range. The stretching ratio at this time is about 4 to 10 times. Following the uniaxial stretching described above, in order to improve the dimensional stability of the stretched tape in the take-off direction, annealing can be performed under tension in the take-off direction, which is generally widely used.

[0020]

The polyolefin tape immediately after rolling, which has passed through the nip point of the rolling roll, tends to shrink in the width direction by elastic recovery as it is, but in the present invention, the tape is crimped to the rolling roll by a pressure roll. Therefore, the shrinkage is prevented, and the effective rolling ratio in the width direction is not reduced. For this reason, the strength in the width direction of the obtained polyolefin tape-like material is improved, and the vertical cracking resistance is improved. Further, for the same reason, the molecular orientation of the polyolefin is facilitated by the subsequent uniaxial stretching, so that the strength of the tape-like material in the take-off direction is improved.

[0021]

EXAMPLES Example 1 Density 0.954 g / cm ³ , MF
Using high density polyethylene (Mitsubishi Yuka Co., Ltd. “Mitsubishi Polyethylene-HD, YH430”) with 0.8 g / 10 min, high-density polyethylene sheet 2 mm wide and 0.35 mm thick by T-die method Sheet) was extruded. This raw sheet was rolled in the width direction using the apparatus shown in FIG. 1 in the following steps, then uniaxially stretched in the take-off direction, and annealed to produce a polyethylene tape.

First, the apparatus will be described with reference to FIG.
Is a raw sheet or film, and 2, 3 have a surface temperature of 120.
120 mmφ metal rolling rolls adjusted to 0 ° C., sheets or films rolled by rolling rolls 2 and 3 are rolling rolls 4 and 5,
A 50 mmφ free rotation rubber pressure roll for preventing a reduction in the effective rolling ratio in the width direction due to elastic recovery is provided in contact with the rolling roll 3. 6 is a 120 for cooling the rolled raw sheet or film.
mmφ metal rolls, 7 and 8 are 50 mmφ free rotation rubber pressure rolls having the same effect as the pressure rolls 4 and 5, and 9 is a 120 mmφ metal cooling roll. The surface temperature of both rolls 6 and 9 is adjusted to 50 ° C. 10,1
Reference numerals 1, 12, and 13 denote two pairs of nip rolls each having a different peripheral speed for uniaxial stretching and each having a diameter of 120 mmφ, and 10 is adjusted to a surface temperature of 110 ° C. Nip roll 1
The uniaxial stretching ratio is adjusted by the peripheral speed difference between 0, 11 and 12, 13. Reference numerals 10 and 12 denote metal rolls.
Reference numeral 3 denotes a freely rotating rubber roll. Reference numerals 15 and 16 denote nip rolls of 120 mmφ, and reference numeral 14 denotes an annealing oven provided between two pairs of nip rolls 12, 13 and 15, 16 at the same peripheral speed.

Next, the manufacturing process will be described. (1) The raw sheet 1 is passed between the two rolling rolls 2 and 3 and then pressed to the rolling roll 3 by the two pressing rolls 4 and 5 to increase the width 3.4 times in the width direction. Rolled. (2) The raw sheet 1 rolled to 3.4 times is cooled by the cooling rolls 6 and 9 and the pressure rolls 7 and 8 while being cooled by two pairs of nip rolls 10, 11, 12 and 13 in the take-off direction. The film was uniaxially stretched by a factor of 0.5. (3) The uniaxially stretched tape was guided to an annealing oven for annealing.

The resulting polyethylene tape had a tensile strength at break of 1.03 Gpa and an elongation at break of 15%.

(Example 2) The width of the raw sheet was 4.0 mm,
The rolling ratio in the width direction was 2.0 times, and the other conditions were the same as in Example 1. The resulting tape-shaped material had a tensile strength at break of 0.97 Gpa and a breaking elongation of 20%.

(Embodiment 3) The width of the raw sheet is 9.0 mm,
The rolling ratio in the width direction was set to 1.2 times, and other conditions were the same as in Example 1. The obtained tape-shaped material had a tensile breaking strength of 0.88 Gpa and a breaking elongation of 18%.

Comparative Example 1 A tape was obtained under the same conditions as in Example 1 except that the rolling step in the width direction was omitted. The obtained tape-shaped material had a tensile strength at break of 0.60 Gpa and an elongation at break of 25%.

Comparative Example 2 A tape was obtained under the same conditions as in Example 1 except that the width of the raw sheet was 4.0 mm and the rolling step in the width direction was omitted. The obtained tape-shaped material had a tensile strength at break of 0.55 Gpa and an elongation at break of 26%.

(Comparative Example 3) Rolling in the width direction was attempted under the same conditions as in Example 1 except that the width of the raw sheet was 12 mm, but the rolling ratio in the width direction exceeded 1.04 times. And the mechanical strength after uniaxial stretching could not find any significant difference as compared with the case where the rolling step was omitted.

Example 4 Density 0.90 g / cm ³ , MF
A raw sheet having a width of 2 mm and a thickness of 0.35 mm was extruded by a T-die method using R 0.5 g / 10 min polypropylene (Mitsubishi Yuka Corporation "Mitsubishi Polypro, MA8").
This raw sheet is rolled in the width direction using the apparatus shown in FIG. 1 in the same process as in Example 1, and then uniaxially stretched between two pairs of nip rolls 10 to 13 having different peripheral speeds in the take-off direction. Then, annealing was performed to produce a polypropylene tape. However, the surface temperature of the rolling rolls 2 and 3 was 150 ° C., the rolling ratio in the width direction was 3.5 times, and the surface temperature of the cooling rolls 6 and 9 was 60 ° C. The surface temperature of the roll 10 was 130 ° C., and the roll 10 was uniaxially stretched 8.5 times in the take-off direction. The tensile breaking strength of the tape after annealing was 1.01 Gpa, and the breaking elongation was 16
%Met.

(Example 5) The width of the raw sheet was 4.0 mm,
The rolling ratio in the width direction was set to 2.0 times, and other conditions were the same as in Example 4. The resulting tape-shaped material had a tensile strength at break of 0.93 Gpa and a breaking elongation of 18%.

(Example 6) The width of the raw sheet was 9.0 mm,
The rolling ratio in the width direction was set to 1.2 times, and other conditions were the same as in Example 4. The obtained tape-shaped material had a tensile strength at break of 0.85 Gpa and a breaking elongation of 17%.

Comparative Example 4 A tape was obtained under the same conditions as in Example 4 except that the rolling step in the width direction was omitted. The obtained tape had a tensile strength at break of 0.63 Gpa and an elongation at break of 25%.

Comparative Example 5 A tape was obtained under the same conditions as in Example 4, except that the width of the raw sheet was 4.0 mm and the rolling step in the width direction was omitted. The obtained tape-shaped material had a tensile breaking strength of 0.58 Gpa and a breaking elongation of 27%.

(Comparative Example 6) Rolling in the width direction was attempted under the same conditions as in Example 4 except that the width of the raw sheet was 12 mm, but the rolling ratio in the width direction exceeded 1.03 times. And the mechanical strength after uniaxial stretching could not find any significant difference as compared with the case where the rolling step was omitted.

[0036]

As described above, according to the present invention, a polyolefin sheet or film is passed between two rolling rolls at a temperature equal to or lower than the melting point of the polyolefin, and then pressure-bonded to a rolling roll by a pressure roll. As a result, a high-strength polyolefin tape having high mechanical strength not only in the width direction but also in the take-off direction can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus used in an embodiment.

FIG. 2 is a configuration diagram of an apparatus used for manufacturing a conventional thermoplastic resin tape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polyolefin sheet 2,3 Rolling roll 4,5 Compression roll 10-13 Nip roll

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B29C 55/02-55/18 B29D 7/00

Claims (1)

(57) [Claims] 1. A polyolefin sheet or film having a width of 1 mm to 10 mm at a temperature not higher than the melting point of the polyolefin,
After passing between two rolling rolls, the roll is rolled to 1.1 to 5 times in the width direction by pressure bonding to a rolling roll with a pressing roll, and then uniaxially stretched in the take-off direction. For producing a high-strength polyolefin tape.