JPH04370234A - Production of split yarn - Google Patents

Abstract

PURPOSE:To obtain high-strength split yarn composed of ultra-high molecular weight polyethylene. CONSTITUTION:The subject method is a method for producing split yarn including a step for slitting a film of ultra-high molecular weight polyethylene having >=5dl/g intrinsic viscosity (eta), drawing the resultant slit film at 100-150 deg.C temperature in at least the longitudinal direction at a draw ratio of at least >=2 times and providing a drawn tape and a step for cooling the aforementioned drawn tape to <=80 deg.C and then splitting the cooled tape at 0.5-4.0 splitting ratio (roll peripheral speed/tape speed).

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 ultra-high molecular weight polyethylene split yarn.

0002

BACKGROUND OF THE INVENTION Ultra-high molecular weight polyethylene has superior impact resistance, abrasion resistance, chemical resistance, tensile strength, etc. compared to general-purpose polyethylene, and is expected to be used as an engineering plastic.

[0003] However, this ultra-high molecular weight polyethylene has poor moldability and is difficult to mold using the molding methods (extrusion molding, injection molding) used for ordinary polyethylene and polypropylene.

[0004] In view of these points, the present applicant and others have proposed various film manufacturing techniques and stretching techniques for ultra-high molecular weight polyethylene. For example, Japanese Unexamined Patent Application Publication No. 122736/1982 by the present applicant proposes a method for producing a film, and Japanese Patent Application Unexamined Publication No. 203816/1982 proposes a method for stretching this film.

[0005]

[Problems to be Solved by the Invention] By the way, the above-mentioned prior art does not mention defibration technology, and the technical problem is how to defibrate the stretched tape obtained by the above-mentioned prior art. It had become.

[0006] The present invention has been made in view of these points, and its object is to provide a technique for realizing a split yarn made of ultra-high molecular weight polyethylene.

[0007]

[Means for Solving the Problems] The present invention provides a film of ultra-high molecular weight polyethylene having an intrinsic viscosity (η) of 5 dl/g or more when producing a split yarn.
A step of slitting the film into a width of mm and stretching the slit film at least twice in the longitudinal direction at a temperature of 100°C to 150°C to obtain a stretched tape, and stretching the stretched tape at 80°C.
After cooling to below, defibration ratio (roll circumferential speed/tape speed)
The method includes a step of defibrating at a fiber density of 0.5 to 4.0.

[0008]

[Operation] The ultra-high molecular weight polyethylene used in the present invention has an intrinsic viscosity (η) of 5 when measured at 135°C in a decalin solvent.
dl/g or more, preferably 8 to 25 dl/g, and the melt flow rate (MFR: ASTM D1238, F) is 0.
．． 01g/10min or less of ethylene homopolymer or ethylene and other α-olefins such as propylene,
It is a crystalline copolymer mainly composed of ethylene, such as 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene.

The split yarn of the present invention is obtained by producing the ultra-high molecular weight polyethylene by the method described below, and has an intrinsic viscosity (η) of 5 dl/g or more, preferably 7 to 25 dl/g, and a tensile strength. Usually 30 with a strength of 7 g/denier or more, preferably 10 g/denier or more
~20,000 denier, preferably 100-5,000 denier split yarn.

[0010] The method for producing a split yarn of the present invention includes:
First, a film is produced from ultra-high molecular weight polyethylene having an intrinsic viscosity (η) of 5 dl/g or more, and then the film is slit and then at least doubled in the longitudinal direction at a temperature of 100°C to 150°C. or more, preferably 4 to 10
Stretch it twice to obtain a stretched tape.

Next, after cooling the stretched tape to 80° C. or lower, the defibration ratio (roll circumferential speed/tape speed) is 0.5 to 4.
．． 0, preferably 1.0 to 2.0.

[0012] There are the following methods for producing the film used for stretching. In the first method, the intrinsic viscosity (
Ultra-high molecular weight polyethylene with η) of 5 dl/g or more is melted in a screw extruder, preferably a screw extruder equipped with a grooved cylinder (barrel), and then at least L/D in which the mandrel rotates with the rotation of the screw.
is 5 or more, preferably 10 or more, more preferably 20 or more
After extrusion through a tube die of 70 mm, gas is blown into the molten tubular film to achieve a swelling ratio of 1.1 to 2.
Expand to 0 times, preferably 1.5 to 12 times and melting point -5
A film is obtained which heat shrinks by 10% or more in the transverse direction at a temperature of .degree.

[0013] If the intrinsic viscosity (η) is less than 5 dl/g, the mechanical strength such as tensile strength at break or impact strength is insufficient, and when heat-shrinked, the film softens and loses its shape. It ends up. Furthermore, because of the low melt viscosity, twisting due to co-rotation of the melt of ultra-high molecular weight polyethylene and the mandrel in the tube die and uneven thickness due to deflection of the mandrel are likely to occur, resulting in non-uniform moldability.

[0014] A melt of ultra-high molecular weight polyethylene has an extremely high viscosity compared to a melt of general-purpose polyethylene;
Because it is a rubber-like viscous material, a tube die with an L/D of less than 5 does not completely homogeneously fuse the melt before extruding from the die, so gas is trapped inside the tubular film extruded from the die. When blowing into the tube, the tube does not expand uniformly or breaks, making it impossible to obtain a good film.

[0015] The tube mandrel must be rotated as the extruder screw rotates. The number of rotations of the mandrel does not necessarily have to be the same as the number of rotations of the screw.

The gas blown into the tubular film is usually air, but nitrogen or the like may also be used. Melting point -5℃
A film with a transverse heat shrinkage rate of less than 10% at a temperature of 10% can have a tensile strength of 7 g/denier or more, but the longitudinal tear strength may be less than 150 g/mm. Moreover, if the stretching ratio is less than 2 times, there is a possibility that the tensile strength will not be 7 g/denier or more.

[0017] The film used for stretching can also be produced by continuously carving out the outer shell of a round bar obtained by compression molding or extrusion with a knife, or by adding a fluidity improver such as wax. There is a T-die film forming method obtained from ultra-high molecular weight polyethylene.

[0018] However, the method of cutting with a knife does not allow obtaining an undefined length of the original fabric for stretching. Furthermore, the T-die film molding method requires a complicated molding process. Therefore, from the point of view of economy, it is preferable that the raw material used for the stretched tape be a tubular film.

[0019] Furthermore, in the defibration process, if defibration is performed at a temperature exceeding 80°C, defibration becomes difficult and there is a possibility that undefibration or non-uniform defibration occurs. In addition, if the defibration ratio is smaller than the above value, the fibers will become rough;
If the mesh is large, the mesh becomes fine and feathery, and the strength tends to decrease.

[0020] The defibration treatment is performed using a porcupine cutter, a spiral cutter, or the like. Here, since the stretched tape of ultra-high molecular weight polyethylene obtained in the above step has high strength, defibration treatment with a porcupine cutter is preferable.

[0021] At this time, the porcupine needle is at 0 in the width direction.
．． It is preferable to plant the needles at intervals of 5 to 2 mm and 1 to 10 mm in the flow direction in a staggered or spiral pattern in the flow direction. Further, the length of the needle tip is preferably 1 to 10 mm.

[0022]

Effects of the Invention The split yarn obtained by defibrating the drawn ultra-high molecular weight polyethylene of the present invention has extremely high strength, and the strength is further increased by twisting. In addition, since it becomes fine fibrous by the defibration process, it has an excellent texture and can be effectively used for fiber materials that require high strength, mountain climbing ropes, and the like.

[0023]

EXAMPLES Next, the present invention will be explained based on examples, but it goes without saying that the present invention is not limited to the following examples unless it departs from the gist thereof. (Production process of ultra-high molecular weight polyethylene film) Ultra-high molecular weight polyethylene powder ((η): 13.8 dl/g, M
FR: less than 0.01g/10min, melting point: 136°C,
Bulk density: 0.45 g/cc) was used to connect 3 dies consisting of outer die/mandrel = 20/17 mmφ.
0mmφ extruder, cylinder temperature 280℃, die temperature 1
The temperature was set at 70°C, the screw rotation speed was set to 15 rpm, and compressed air was introduced from the 6 mmφ gas flow path extending inside the screw and inside the mandrel of the tube die while drawing at a speed of 1.2 m/min with pinch rolls. Blow in to inflate the tube to a size that makes contact with the cooling ring inner diameter 82mmφ (swelling ratio = 4.1), folding width 128mm.
An ultra-high molecular weight polyethylene film having a thickness of 60 μm was produced. The heat shrinkage rate of this film at 131° C. was 20.4% in the transverse direction and 10.6% in the longitudinal direction. (Manufacture of ultra-high molecular weight polyethylene stretched tape) The film was slit in the longitudinal direction to a width of 10 mm, and this was used as a raw material. Next, this original fabric was stretched 4 times and 6 times (one-stage stretching), respectively, in a stretching tank containing a triethylene glycol solution at 120°C. (Defibration treatment of stretched tape) After cooling the stretched tape obtained above and bringing the temperature of the stretched tape itself to 80°C or less,
It was defibrated using a porcupine cutter.

The properties of the split yarn thus obtained are shown in Table 1 together with other comparative examples.

[0025]

[Table 1]

Claims (1)

[Claims] Claim 1: A film of ultra-high molecular weight polyethylene with an intrinsic viscosity (η) of 5 dl/g or more is slit,
A step of stretching this slit film at least twice or more in the longitudinal direction at a temperature of 150°C to 150°C to obtain a stretched tape, and cooling the stretched tape to 80°C or less, followed by a fibrillation ratio (
A method for producing a split yarn, comprising a step of defibrating at a roll circumferential speed/tape speed of 0.5 to 4.0.