JPS61282416A - Plastic wire and production thereof - Google Patents

Abstract

PURPOSE:To obtain plastic wires capable of plastic deformation, by melting ultrahigh-molecular weight polyethylene in a screw extruder, extruding the melt through a die having a specific value of (L/D) or more, annealing the extruded wires, taking off the annealed wires and drawing the taken off wires at a specific draw ratio. CONSTITUTION:Whitened plastic wires, having >=4dl/g, preferably 8-30dl/g intrinsic viscosity [eta] and >=20kg/m<2>, preferably >=50kg/mm<2> tensile strength (TS) at the breaking point and obtained by melting ultrahigh-molecular weight polyethylene in a screw extruder, extruding the melt through a die having >=10 (L/D), annealing the resultant extruded wires and drawing the annealed wires at 8-30 draw ratio. The bending return angle (theta) is <=20 degrees, prefer ably <=10 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a plastic wire, and particularly to a plastic wire that can be bent like a wire or plastically deformed by twisting and knotting.

[Conventional technology]

For example, iron wire is used for a variety of purposes, including tying fruit bags in orchards and arranging grape trellises.

However, since such wires are made of iron, although they are inexpensive, they tend to rust and cannot withstand long-term use.

Therefore, in order to overcome rust, it may be possible to use plastic wire as a substitute for wire.

[Problem that the invention seeks to solve]

However, the plastic wires currently on the market are made of nylon or polypropylene, which are elastic and cannot be plastically deformed like wire, so they can be tied together by simply twisting them like wire. I can't.

The present invention was made in view of these points, and a technical object thereof is to provide a plastic wire that can be plastically deformed and a method for manufacturing the same.

[Means for solving problems]

In order to solve the above technical problem, the present invention takes the following technical measures.

That is, it is made of ultra-high molecular weight polyethylene, has an intrinsic viscosity [η] of at least 4 dQ/g and a tension at break of at least 20 kg/n+IIl',
It has become white due to the stretching effect, and the bending return angle θ is 2.
A plastic wire with a temperature of 0 degrees or less was used.

As for its manufacturing method, first, the ultra-high molecular weight polyethylene is melted using a screw extruder, extruded through a die with at least L/D of IO, and the extruded strand is slowly cooled and taken out at a draft ratio of at least 1. Form a wire yarn.

Next, the wire yarn is drawn at a drawing ratio of 8 to 30 times to form the plastic wire.

[Effect]

Due to the stretching effect, the ultra-high molecular weight polyethylene is oriented in the stretching direction and crystallized, separated into fine fibers, and whitened. Therefore, when the wire is bent or twisted, deformation due to the stress occurs due to the displacement between the fibers, and even if the stress is removed, the wire will not recover to its original straight shape due to elastic force.

By the way, the ultra-high molecular weight polyethylene used here is
For example, the intrinsic viscosity [η] measured at 135°C in a decalin solvent is 4 d12/g12°C, and melt fluorate (MF'R: ASTM D 123B).

F) A homopolymer of ethylene or a combination of ethylene and other α-olefins, such as propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc., with a rate of 0.01 g/10 min or less It is a crystalline ultra-high molecular weight polyethylene that is a random or block copolymer mainly composed of ethylene.

Further, this plastic wire is obtained by drawing a wire yarn formed by the method described below using the ultra-high molecular weight polyethylene as a raw material, and has an intrinsic viscosity [η] of at least 4 dl/g1, preferably 8 to 8. 30
dQ/g, and at least the shaft tension at break (T
S) is 20 kg/l111 or more, preferably 50 kg#
+m'' or more, moreover, the stretching effect is so-called whitening, and the bending return angle θ is 20 degrees or less, preferably 1
It is below 0 degrees. Here, the bending return angle θ means that the plastic wire is
As shown in the figure and FIG. 4, it refers to the return angle after being bent 180 degrees or 90 degrees and left for 10 minutes.

Here, those whose limiting viscosity [η] is less than 4 dQ/g are:
The average molecular chain is short, and the tensile strength does not increase even if the stretching ratio is increased. In addition, the shaft tension at the breaking point is 20
If it is less than "kg/mm", the strength as a plastic wire is insufficient and it may not be possible to use it as a substitute for wire.

Also, the outer diameter of this plastic wire is generally 0.4
With a diameter of 3.5+l1 mφ, it can be used not only as a single wire but also as a wire with a thick outer diameter made by twisting a plurality of single wires together.

If the outer diameter is less than 0.4 mmφ, it is technically possible to form the yarn, but the productivity of the raw yarn is low and it is not practical.

On the other hand, if the diameter exceeds 3.5 mm, the equipment cost for the stretching device becomes enormous and it is also impractical in terms of use.

To manufacture this plastic wire, it is first necessary to shape the wire yarn.

The method involves melting the ultra-high molecular weight polyethylene in a screw extruder, preferably a screw extruder equipped with a fluted cylinder (barrel). Next, L/D is at least 10, preferably 15 or more, more preferably 30 to 6
After extrusion from a die of 0.0°C, the extruded strand is slowly cooled at a draft ratio of at least 11, preferably 12 to 30, preferably in a cooling tube (0.3 to 5 m) into which air at 15 to 80°C can be blown. In this method, the material is slowly cooled under conditions where the material is allowed to pass through. As a result, the outer diameter becomes 2 to 1.
A wire yarn with excellent drawability of 0+nmφ is obtained.

Here, the draft ratio is the ratio between the extrusion speed of the resin at the die exit and the take-off speed by the take-off machine when extrusion molding the raw wire yarn.

By the way, unlike general-purpose polyethylene, the melt of ultra-high molecular weight polyethylene is a rubber-like lump, so L/
In a die with D less than 10, the melt is not completely uniformly fused before being extruded from the die, resulting in a wire yarn with poor drawability, so it is difficult to obtain a plastic wire with sufficient strength by drawing. Can not.

On the other hand, the upper limit of L/D is not particularly limited, but it is practically 10
It is preferably 0 or less. Note that the shape of the die is usually cylindrical, and the L/D of the die is correlated with productivity, and the larger the L/D, the higher the production rate (pulling rate) can be.

If the molten strand extruded from the die is rapidly cooled, that is, cooled in a water circulation tank or the like, vacuum bubbles are generated in the core of the strand, and the degree of crystallinity is low, resulting in a yarn with poor drawability.

Further, the extrusion temperature of ultra-high molecular weight polyethylene is not particularly limited as long as it is higher than the melting point of the resin and lower than the decomposition temperature of the resin.

The preferable conditions for the wire yarn forming temperature are: extruder temperature of 180 to 350°C, die inlet to middle part temperature of 180 to 300°C, die middle part to die outlet temperature of 135 to 160°C. is within the range of

Through the above process, a wire yarn having an outer diameter of 2 to 10 ma+φ and having excellent drawability can be obtained. As a method for obtaining a plastic wire from this raw yarn, both dry stretching and wet stretching are possible, but wet stretching is preferable in terms of heat transfer efficiency and temperature control accuracy.

The stretching temperature is usually the melting point of ultra-high molecular weight polyethylene +15°C.
Below, preferably 80 to 150°C, more preferably 1
00 to 150°C. Even if the drawing temperature exceeds the melting point +15°C, the wire will be drawn, but there is a risk that a wire with high strength and whitening will not be obtained. On the other hand, if the drawing temperature is too low, although the wire will be whitened, a wire with high strength will not be obtained. There is a possibility that it is not.

Furthermore, although single-stage stretching is possible, multi-stage stretching is preferable because it allows the stretching ratio to be increased and a high-strength drawn yarn can be obtained.

The optimal stretching conditions when performing two-stage stretching as a multi-stage stretching method, for example, are as follows.

That is, in the first stage, the raw yarn is stretched at a temperature of 80°C to 13°C.
It is stretched at a stretching ratio of 4 to 8 times at 5°C.

In the second stage, the film is stretched at a stretching temperature of 140° C. to 150° C. and a stretching ratio of 2 times to 5 times. The first stage of stretching and the second stage of stretching are used to stretch the film by a total of 8 to 30 times, preferably 10 to 30 times.

The resulting plastic wire becomes white as the molecules are oriented in the stretching direction and crystallize due to the stretching effect.

As shown in FIG. 5, the apparatus for producing ultra-high molecular weight polyethylene yarn includes a grooved cylinder 2 and a compression ratio of 1 to 2.5, preferably 1.3 to 1.8, from the extruder l side. An extruder 11 consisting of a screw 3 having a diameter of at least IO1, preferably 15
Above, more preferably 30 to 60, and the ratio of the cross-sectional area Sl of the die inlet 4 to the cross-sectional area S of the die outlet 5 (S r/
S and a collection machine 10.

The grooves 12r of the grooved cylinder 2 stably supply the ultra-high molecular weight polyethylene powder to the compression section 22. Further, if the compression ratio of the screw 3 is less than 1.0, the compression stress of the resin against the cylinder wall surface is small, the extrusion amount becomes unstable, and appearance defects are likely to occur due to surging phenomenon or poor deaeration. On the other hand, if it exceeds 2.5, the resin temperature will abnormally rise due to clogging phenomenon in the compression part 22 and frictional heat, and the molecular weight of the resin will decrease significantly due to thermal decomposition, resulting in loss of product physical properties such as friction coefficient and friction resistance. This is not desirable as it will cause problems.

The compression ratio of the screw 3 is the ratio of the groove depth at the hopper mouth of the screw 3 to the groove depth at the tip of the screw.

Further, the L/D of the extruder 1 is usually in the range of 7 to 32, preferably 20 to 26. If L/D is less than 7, there is a risk that the ultra-high molecular weight polyethylene powder will be supplied to the cylindrical die 6 without being completely melted.

If the L/D of the cylindrical die 6 is less than 10, the ultra-high molecular weight polyethylene melt will not be completely melted before being extruded from the die, resulting in a yarn with poor drawability.

Note that L/D of the cylindrical die 6 is the ratio of the length from the cylindrical die inlet 4 to the cylindrical die outlet 5 to the inner diameter of the cylindrical die outlet 5. Further, if the ratio of S l/S t is in the range of 1 to 5, there is no particular problem, but if the ratio of S l / S t is less than 1, the internal pressure is insufficient and the melt of ultra-high molecular weight polyethylene is insufficiently fused. The appearance (shape) of the extruded strand is poor, and the yarn does not have excellent drawability. On the other hand, when it exceeds 5, shear failure flow tends to occur in the melt, which necessitates low-speed extrusion.

The length of the slow cooling cylinder 9 is not particularly limited as long as it is long enough to cool the molten strand extruded from the cylindrical die 6 without being rapidly cooled, but is usually 0.3 to 5 m, preferably 1 to 5 m. The range is 3m.

If the length is less than 0.37n, the molten strand may not be slowly cooled when the take-off speed is increased. The air ring 7 at the inlet 8 of the molten strand of the slow cooling tube 9 is for feeding hot air at a temperature of usually 15 to 80°C, preferably 30 to 50°C into the slow cooling tube 9 to gradually cool the molten strand. be.

This manufacturing apparatus may further include a sizing die on the inlet side of the molten strand of the slow cooling cylinder 9 to regulate the size and slow cooling.

〔Effect of the invention〕

Since the plastic wire of the present invention is plastically deformable, it can be twisted like wire, and can be used as a substitute for wire, for example, for tying bags to fruits in orchards or creating grape trellises.
Alternatively, it can be used as a substitute for wire in all fields where wire is conventionally used, except in cases where it is heated, including the construction of fences surrounding orchards.

Moreover, unlike wire, it does not rust, making it highly durable.
It has the advantage of not breaking due to plastic deformation and can withstand repeated use.

〔Example〕

Hereinafter, an example of the present invention will be described in more detail as Experimental Example 1 while comparing it with Comparative Example I, but the present invention is not limited to this example.

In the apparatus for producing a drawing yarn (strand) shown in FIG. 5, an ultra-high molecular weight polyethylene drawing yarn (strand) was manufactured using an apparatus having the following specifications.

Screw diameter: 20mmφ screw Screw rotation speed: 22 Screw compression ratio
=1.8 Die length: 240mm.

Die exit inner diameter: 6mmφ die L/D
: 40Sl/S!
: IJ(n) = 16.5d(2/gSM
F R: O, less than 1g/lomin, melting point = 136
°C and bulk density: 0.45 g/cm3 ultra-high molecular weight polyethylene powder (Product name: HIZEX MILLION ■240
M, manufactured by Mitsui Petrochemical Industries, Ltd.), the extruder, die base (Dl) and die end (D) were set at 320°C, 200°C and 140°C, respectively, and the screw rotation speed was 5 Orpm. set to 1.5m/min with a pick-up machine.
By drawing at a speed of , an ultra-high molecular weight polyethylene yarn for drawing having an outer diameter of 4.0 mm was produced.

Next, this yarn was drawn in a triethylene glycol liquid drawing tank by 6 times (1st stage: 133°C), 8 times (1st stage: 133°C), 10 times (1st stage = 133°C), 12 times (1st stage) Eye: 133℃ 6 times, 2nd row: 144℃
2x) 18x (1st stage: 133℃ 6x, 2nd stage: 14
The film was stretched 24 times (1st stage: 6 times at 133°C, 2nd stage: 3 times at 144°C).

In addition, as a comparative example, [η): 2.6 dQ/g, M
Using polyethylene (general purpose polyethylene) with F R: O, l1g/10m1n, melting point: 131°C, and bulk density: 0.956g/-cm', the extruder temperature was set at 220°C.
A drawn yarn was produced under the same conditions except that

The physical properties of each drawn yarn obtained were measured by the following method. The results are shown in Table 1.

Density: ASTM D 1505 (without annealing) Diameter size 2 Micrometer tensile test: Yonekura Instron type universal testing machine (C
ATY-1001ZS) Tensile speed: 200+nm/min, between chucks: 200
Under the conditions of mm, the tension at break (kg/mm") and Young's modulus (kg/mm").

Elongation (%) was determined.

Return angle: (1) The product was bent 180 degrees and the return angle θ was measured 10 minutes later.

(2) It was bent 90 degrees and the return angle θ was measured 10 minutes later.

Table 1 shows that in Experimental Example 1, if the stretching ratio is 8 times or more, or even 10 times or more, a plastic wire with a small return angle θ during bending and excellent tension at the breaking point can be obtained. I understand.

Also, what about general-purpose polyethylene? It is clear that even if the return angle θ is reduced, a small return angle θ cannot be obtained.

(Hereafter, margin)

[Brief explanation of the drawing]

Figures 1 and 2 show one plastic wire of the present invention.
A diagram showing the return angle θ when bent 80 degrees, FIGS. 3 and 4 are diagrams showing the return angle θ when bent 90 degrees, and FIG. 5 shows the ultra-high molecular weight polyethylene yarn according to the present invention. FIG. ■...Extruder, 2...Grooved cylinder, 3...Screw, 4...Die inlet, 5...Die outlet,
6. Cylindrical die, 7. Air ring, 8. Strand population, 9. Annealing tube, IO. Taking machine.
21...Groove portion, 22...Compression portion. Figure 1 @Figure 2

Claims (3)

[Claims] (1) It is made of ultra-high molecular weight polyethylene, has an intrinsic viscosity [η] of at least 4 dl/g, has a tension at break of at least 20 kg/mm^2, is white, and has a bending return angle θ of 20 degrees. A plastic wire characterized by: (2) After melting ultra-high molecular weight polyethylene with an intrinsic viscosity [η] of at least 4 dl/g in a screw extruder,
The wire yarn is extruded from a die with an L/D of at least 10, at a draft ratio of at least 1, and the extruded strand is slowly cooled and taken out, and the wire yarn is formed with a drawing ratio of 8 to 30.
A method for producing a plastic wire characterized by stretching it twice. (3) After the wire yarn is drawn to a drawing ratio of 4 to 8 times, it is further drawn to a drawing ratio of 2 to 5 times, and the entire wire is drawn to a drawing ratio of 8 to 30 times. 2. Method for producing plastic wire as described in Section 1.