KR100572086B1 - Polyamide tape and preparation thereof - Google Patents

Abstract

The present invention provides a polyamide biaxially oriented film having a longitudinal elongation of 250 to 400%, a transverse elongation of 50 to 200%, a density of 1.1218 to 1.1369 and a crystallinity of 25 to 35%, and slitting and uniaxially stretching the fracture or fibrillation. Provided are polyamide tapes that are particularly useful for wool bags, with strengths of at least 6 g / d and at most 30% elongation without developing.

Description

Polyamide tape and preparation method             

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide tape, and more particularly, to a polyamide tape having a high strength without causing breakage or fibrillation, which is used for the production of bags containing wool and the like.

Conventionally, wool bags have been used by weaving a sack using a tape uniaxially stretched from high density polyethylene (HDPE), polypropylene (PP), or the like as a flat filament. However, in the process of moving and loading wool packed with high-density polyethylene, a small amount of PP and HDPE pieces are mixed with wool, causing dye differences in dyeing wool products. Polyamide-based stretched tapes, which are not recognized as dyeing irregularities, are used for the production of wool bags.

For example, according to Japanese Patent Application No. 57-38143, a polyamide-based polymer is used to form an inflation film or T-die film, slitting at a predetermined width interval with respect to the film's advancing direction, and uniaxially stretching in dry or wet heat. Polyamide tapes having a strength of 3.0 to 6.0 g / denier (g / d) are proposed.

The reason why the strength of the tape is adjusted to 3.0 to 6.0 g / d is to prevent the breakage and fibrillation of the tape even in the sampler work that occurs during the inspection of the contents of the wool packing harness woven with the stretched tape. This is because when the tape breaks at a strength of 3.0 g / d or less of the tape and rises to 6.0 g / d or more, the orientation is excessive and fibrillation occurs.

However, the above degree of strength is somewhat unsuitable as a pleated polyamide tape, and the user's demand for higher strength polyamide tape is intensified.

Accordingly, the present invention is to provide a polyamide tape having a higher strength while preventing breakage or fibrillation.

In order to solve the above problems, the present inventors have specifically designed the state of the biaxially stretched polyamide film before slitting in the form of a tape, so that a polyamide tape having high strength and high resistance to fracture or fibrillation can be obtained. It became possible to manufacture.

Therefore, according to the present invention, the polyamide biaxially stretched film having a longitudinal elongation of 250 to 400%, a transverse elongation of 50 to 200%, a density of 1.1218 to 1.1369, and a crystallinity of 25 to 35% is slitted. Polyamide tapes having a stretch strength of 6 g / d or more and an elongation of 30% or less are provided.

In addition, according to the present invention, as a method for producing the polyamide tape, an unstretched amorphous sheet obtained by extruding and quenching a polyamide resin is subjected to a cold crystallization temperature (Tcc) or more than a glass transition temperature (Tg). After stretching at a temperature of 1.1 to 2.0 times in the longitudinal direction and 2.0 to 3.5 times in the transverse direction at the following temperature, heat treatment is performed at a temperature of stretching temperature not less than 180 ° C. to obtain a polyamide biaxially stretched film, and then slitting it in a tape form. There is provided a method for producing a polyamide tape characterized by uniaxial stretching at a draw ratio of 3.0 to 7.0 times in the longitudinal direction.

Hereinafter, the present invention will be described in more detail.

According to the present invention, if the state of the biaxially stretched polyamide film before slitting into a tape form is designed to have a longitudinal elongation of 250 to 400%, a transverse elongation of 50 to 200%, a density of 1.1218 to 1.1369 and a crystallinity of 25 to 35%, The polyamide tape after slitting and uniaxial stretching can be made to have a strength of 6 g / d or more and an elongation of 30% or less while having high resistance to fracture or fibrillation.

As a polyamide resin to be used as a raw material, for example, polyamide 6, polyamide 66, polyamide 6 and other polyamide salts and the like copolymerized with a small amount of the copolymer, polyamide 6 and other polyamide resins and the like can be used. Examples of the polyamide salts include polyamide salts of hexamethylenediamine and adipic acid or isophthalic acid, and polyamide salts of metakisylenediamine and adipic acid. The polyamide may also contain a small amount of known additives such as various antiblocking agents, antistatic agents and stabilizers within a range that does not impair its properties.

Hereinafter, a method for producing a polyamide tape according to the present invention will be described with reference to a preferred embodiment. The present production method is carried out in the process of preparing unoriented amorphous sheets, biaxial stretching, slitting and uniaxial stretching.

First, an unoriented amorphous sheet is produced by extruding and quenching a polyamide resin according to a conventional method.

The present invention has a major feature in biaxially stretching an unoriented amorphous sheet. According to the present invention, biaxial stretching is performed by stretching the unoriented amorphous sheet 1.1 to 2.0 times in the longitudinal direction and 2.0 to 3.5 times in the transverse direction at a temperature of Tg or more and Tcc or less, and then performing heat treatment at a temperature of stretching temperature or more and 180 degrees C or less. An amide biaxially oriented film is obtained.

As such, the MD stretching ratio in the biaxial stretching is 1.0 times smaller than the TD stretching ratio, so that the MD orientation is suppressed in preparation for uniaxial stretching, and at the same time, the polymer chains that are stretched in the transverse direction are formed only when the microstructure is formed in the TD preferred orientation. Therefore, when uniaxial re-stretching is rotated in the longitudinal direction to bring the effect of increasing the MD orientation. This increase in orientation has a great effect on the increase in final strength after uniaxial stretching.

During biaxial stretching, the heat treatment temperature is limited to 180 ℃ above the stretching temperature. When the heat treatment is performed at a temperature higher than 180 ° C. during biaxial stretching, the structure is broken during uniaxial stretching by slitting such a biaxially stretched film with a tape, and thus the strength is not maintained and fracture occurs, and the stretchability is very poor. This is because strong crystals are formed when heat treatment is performed at a temperature of 180 ° C. or higher during biaxial stretching.

Due to the crystallization characteristics of the polyamide, a weak γ-crystal is formed below the boundary of approximately 150 ° C., and a strong α-crystal is formed above. In the subsequent process after film production, weak γ-crystals should be mainly produced at 150 ° C. or lower in order to be able to stretch while maintaining dimensional stability. Since the γ-crystal becomes a crystal transition to a strong α-crystal at a temperature of 150 ° C. or more, the heat treatment temperature is set to generate more γ-crystals than α-crystals under possible processing conditions. Since the α-crystallization is easy at a temperature of 180 ° C. or higher, the heat treatment temperature is set to 180 ° C. above the stretching temperature at which stretching is possible.

Next, the biaxially stretched film is then slitted in the form of a tape having a width of preferably 3 mm to 50 mm, more preferably 10 mm to 25 mm.

Next, the film obtained by slitting is uniaxially stretched into a polyamide tape having a desired physical property. At this time, the uniaxial stretching ratio is preferably 3 to 7 times, preferably 4 to 6 times. The higher the uniaxial draw ratio is, the higher the strength is, which is advantageous for the quality of the product, but it is difficult to draw more than 7 times in practice, and less than 3 times it is difficult to obtain the desired strength.

The present invention will be described in more detail by the following examples. However, the embodiments are only examples of the present invention and the present invention is not limited thereto.

Various performance evaluations of the films and processability of the films prepared in Examples and Comparative Examples of the present invention were carried out by the following measuring method.

* Tensile Elongation (%): measured according to ASTM D-882. Tensile elongation is expressed as a percentage of the strain length divided by the initial length. The measurement conditions are as follows.

Device Model-Instron 1123

Measuring condition-drawing speed 300㎜ / min,

Grip distance 100 mm, temperature 23 ℃,

Relative Humidity 50%

Specimen Size-Width 10㎜, Length 150㎜

* Density: Measured using density gradient tube method according to ASTM D-1507.

* Crystallinity: It was calculated by the following formula.

ρ _s: density of sample, ρ _a : density of amorphous region, ρ _c : density of crystal region

Ρ _a is 1,084 and ρ _c is 1,235 based on polyamide α-crystal.

 * Hot air shrinkage: Measured by dimensional change after standing at 150 ° C. for 30 minutes according to JIS C-2318, and substituted by the following formula.

Hot air shrinkage (%) = strain length / initial length × 100

[Examples 1-3 and Comparative Examples 1-4]

The molten polyamide was extruded through an annular die at 260 ° C. and quenched to form an amorphous tubular sheet. The unstretched sheet was heated to 80 ° C. in the stretched section and air was introduced into the tube. Simultaneous biaxial stretching was performed under the conditions indicated. Next, the film was stretched 5 times in the longitudinal direction after slitting in a tape form. The elongation, heat shrinkage and crystallinity of the biaxially stretched film, and the strength and elongation of the final product were measured in the same manner as described above. The results are shown in Table 1.

  division Exam conditions Biaxially oriented film characteristics Tape properties Elongation ratio (%) Heat treatment temperature (℃) Elongation (%) Hot Air Shrinkage Crystallinity (%) density Strength (g / d) Elongation (%) MD TD MD TD MD TD Example 1 1.15 3.00 130-150 340.2 89.7 7.75 4.86 28.34 1.1268 6.20 21 Example 2 1.50 3.00 130-150 302.4 95.7 7.35 4.25 28.03 1.1263 6.30 23 Example 3 1.75 3.00 150-180 290.2 82.5 4.83 3.75 29.75 1.1289 6.50 20 Comparative Example 1 3.00 3.00 160-210 145.7 140.8 1.20 1.05 42.05 1.1475 Breaking Breaking Comparative Example 2 1.50 3.00 190-210 291.0 80.3 2.60 1.25 32.18 1.1326 3.60 25 Comparative Example 3 1.00 1.00 No heat treatment 338.4 328.8 0.75 0.90 27.28 1.1252 4.90 53 Comparative Example 4 2.60 3.00 180-215 162.5 162.5 1.10 0.75 43.70 1.1500 Breaking Breaking

As can be seen from the results of Table 1 above, controlling the state of the biaxially stretched film according to the present invention has excellent resistance to fracture or fibril, and has physical strength of 6.0 g / d or more and elongation of 30% or less. It is possible to provide a very useful polyamide tape, especially for wool bags.

Claims (3)

In the polyamide tape, the strength of the polyamide biaxially stretched film having a longitudinal elongation of 250 to 400%, the transverse elongation of 50 to 200%, the density of 1.1218 to 1.1369, and the crystallinity of 25 to 35% by uniaxially stretching the polyamide tape is 6 g / d or more. , Polyamide tape with elongation of 30% or less. In the production of polyamide tape, the unstretched amorphous sheet obtained by extruding and quenching the polyamide resin is stretched 1.1 to 2.0 times in the longitudinal direction and 2.0 to 3.5 times in the transverse direction at a temperature of Tg or more and Tcc or less, and then the stretching temperature is 180 or more. A method for producing a polyamide tape, characterized in that the polyamide biaxially stretched film is subjected to heat treatment at a temperature of not more than C to obtain a polyamide biaxially stretched film, and then slitted in the form of a tape, and then uniaxially stretched at a draw ratio of 3.0 to 7.0 times in the longitudinal direction. The polyamide tape according to claim 2, wherein the biaxially stretched film simultaneously satisfies the longitudinal elongation of 250 to 400%, the transverse elongation of 50 to 200%, the density of 1.1218 to 1.1369 and the crystallinity of 25 to 35%. Way.