JPH06102847B2 - Plastic wire and method for producing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic wire, and more particularly to a plastic wire that can be plastically deformed such as bent like a wire or twisted knot.

[Conventional technology]

For example, in orchards, iron wire is used for various purposes such as a knot of fruits and a shelf for grapes.

However, since such a wire is made of iron, it has a drawback that it is inexpensive but easily rusts and cannot withstand long-term use.

Therefore, in order to overcome rust, it is conceivable to use a plastic wire as a substitute for the wire.

[Problems to be solved by the invention]

However, currently commercialized plastic wires are made of nylon or polypropylene, and since they both have elasticity and cannot undergo plastic deformation like wires, they are tied together simply by twisting like wires. I can't.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a plastically deformable plastic wire and a manufacturing method thereof.

[Means for solving problems]

The present invention has adopted the following technical means in order to solve the above technical problems.

That is, after melt-molding, the outer diameter obtained by stretching is composed of an ultra-high molecular weight polyethylene wire having a diameter of 0.4 to 3.5 mm, and the intrinsic viscosity number [η] is at least 4 dl / g and the tensile strength at break is at least 20 kg / mm ^2. Then, a plastic wire having a bending return angle θ of 20 degrees or less was used.

As its production method, first, an ultrahigh molecular weight polyethylene having the intrinsic viscosity number is melted by a screw extruder,
Extruded from a die having an L / D of at least 10, and gradually extruding and extruding the extruded strand having a draft ratio of 1 to form a wire raw yarn.

Next, the plastic wire is formed by drawing the wire raw yarn at a draw ratio of 8 to 30 times.

[Action]

Due to the stretching effect, the ultra-high molecular weight polyethylene is oriented and crystallized in the stretching direction, 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 original linear shape is not recovered by the 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 decalin solvent is 4dl / g or more, and the melt florate (MFR: A
STM D 1238, F) is a homopolymer of ethylene of 0.01 g / 10 min or less or ethylene and other α-olefins such as propylene, 1-butene, 1-hexene, 1-octene,
It is a crystalline ultra-high molecular weight polyethylene which is a random or block copolymer mainly composed of ethylene such as 4-methyl-1-pentene.

Further, this plastic wire is obtained by drawing a wire raw yarn formed by the method described below using the above-mentioned ultra high molecular weight polyethylene as a raw material, and at least the intrinsic viscosity [η] is 4 dl / g, preferably 8 To 30 dl / g and at least the tensile strength at break (TS) of 20 kg / mm ²
As described above, it is preferably 50 kg / mm ² or more, and there is also what is called whitening due to the stretching effect, and the folding back angle θ is 20 degrees or less, preferably 10 degrees or less. Here, the bending return angle θ means that the plastic wire is 18 as shown in FIG. 1 and FIG. 2 or FIG. 3 and FIG.
The angle of return after bending for 0 or 90 degrees and leaving for 10 minutes.

Here, when the intrinsic viscosity [η] is less than 4 dl / g, the average molecular chain is short and the tensile strength does not increase even if the stretching ratio is increased. If the tensile strength at break is less than 20 kg / mm ² , the strength as a plastic wire is insufficient and it may not be used as a substitute for wire.

The outer diameter of this plastic wire is generally 0.4 to 3.5 mmφ, and it can be used not only as a single wire but also as a wire having a thick outer diameter in which a plurality of single wires are combined.

Those with an outer diameter of less than 0.4 mmφ are technically moldable, but the productivity of the raw yarn is low and not practical.

On the other hand, when the diameter exceeds 3.5 mm, the equipment cost of the stretching device is enormous, and the practicality is poor.

In manufacturing this plastic wire, it is first necessary to form the raw wire yarn.

In the method, the ultra high molecular weight polyethylene is melted by a screw extruder, preferably a screw extruder equipped with a grooved cylinder (barrel). Then at least L / D is 1
After extrusion through a die of 0, preferably 15 or more, more preferably 30 to 60, at least a draft ratio of 1, preferably 1.
2 to 30, and the extruded strands are gradually cooled, preferably a cooling cylinder (0.3 to 5
This is a method of slowly cooling under conditions that allow m) to pass through. Thus, a wire raw yarn having an outer diameter of 2 to 10 mmφ and excellent in drawability is obtained.

Here, the draft ratio is the ratio between the extrusion speed of the resin at the die exit and the take-up speed of the take-out machine when the raw wire yarn is extrusion-molded.

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

On the other hand, although the upper limit of L / D is not particularly limited, it is preferably 100 or less for practical use. The shape of the die is usually a cylinder, and the L / D of the die correlates with the productivity. The larger the L / D, the higher the production rate (pulling rate) can be.

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

The extrusion molding 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. In addition, the preferable condition of the wire raw yarn forming temperature is that the temperature of the extruder is 180 to 350.
C., the temperature at the die inlet to the middle is 180 to 300.degree. C., and the temperature at the die middle to the outlet is 135 to 160.degree.

By the above, a wire raw yarn having an outer diameter of 2 to 10 mmφ and excellent in drawability can be obtained. The method for obtaining the plastic wire from the raw yarn may be either dry drawing or wet drawing, but the wet method 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 or lower, preferably 80 to 150 ° C, more preferably 100 to 15
It is 0 ° C. Even if the drawing temperature exceeds the melting point + 15 ° C., the wire may be drawn, but a high strength wire may not be obtained. On the other hand, if the drawing temperature is too low, a high strength wire may not be obtained.

Although it is possible to carry out single-stage drawing, the multi-stage drawing method is preferable because the draw ratio can be increased and a high strength drawn yarn can be obtained.

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

That is, in the first stage, the yarn is drawn at a drawing temperature of 80 to 135 ° C.
The film is stretched at a stretch ratio of 4 to 8 times below. Then, the second stage is stretched at a stretching temperature of 140 ° C. to 150 ° C. at a stretching ratio of 2 to 5 times. Then, the stretching in the first stage and the stretching in the second stage are performed 8 to 30 times as a whole, preferably 10 to 30 times.

The plastic wire obtained as a result is preferably whitened because the molecules are oriented and crystallized in the stretching direction due to the stretching effect.

As shown in FIG. 5, the apparatus for producing the ultra-high molecular weight polyethylene raw yarn comprises an extruder 1 side, a grooved cylinder 2 and a screw 3 having a compression ratio of 1 to 2.5, preferably 1.3 to 1.8. Extruder 1, which has at least L / D attached to the tip of the extruder 1 of 10, preferably 15 or more, more preferably 30 to 60, and the cross-sectional area S ₁ of the die inlet 4 and the die outlet 5. The ratio (S ₁ / S ₂ ) to the cross-sectional area S ₂ is 1 to 5, preferably 1.5
It is composed of a cylindrical die 6 in the range of 3.0 to 3.0, an air ring 7 or a sizing die (not shown) at the inlet portion 8 of the strand, and an annealing cylinder 9 and a take-up machine 10.

The groove portion 21 of the grooved cylinder 2 stably supplies the ultra high molecular weight polyethylene powder to the compression portion 22. Further, when the compression ratio of the screw 3 is less than 1.0, the pressure force of the resin to be pressed against the cylinder wall surface is small, the amount of extrusion becomes unstable, and the appearance is likely to occur due to a surging phenomenon or poor degassing. On the other hand, 2.
If it exceeds 5, the resin temperature abnormally rises due to the clogging phenomenon or frictional heat in the compression section 22, the molecular weight of the resin is significantly reduced due to thermal decomposition, and problems such as deterioration of the friction coefficient and physical resistance of the product physical properties occur. Not preferable.

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 screw tip.

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

When the L / D of the cylindrical die 6 is less than 10, the melt of the ultrahigh molecular weight polyethylene is not completely melted before being extruded from the die, resulting in a yarn having poor drawability.

The L / D of the cylindrical die 6 is the ratio of the length L from the cylindrical die inlet 4 to the cylindrical die outlet 5 and the inner diameter D of the cylindrical die outlet 5. Also, if the S ₁ / S ₂ ratio is in the range of 1 to 5, there is no particular problem, but if the S ₁ / S ₂ ratio is less than 1, the internal pressure will be insufficient and the melt of ultra high molecular weight polyethylene will be insufficiently fused. , The appearance (shape) of the extruded strand is poor, and a raw yarn having excellent drawability cannot be obtained. On the other hand, if it exceeds 5, a shear fracture flow is liable to be generated in the melt, so that low speed extrusion is unavoidable.

The length of the slow cooling cylinder 9 is not particularly limited as long as it is a length sufficient to cool the molten strand extruded from the cylindrical die 6 before it is rapidly cooled, but is usually 0.3 to 5 m, preferably 1 to 3 m. It is a range. If the length is less than 0.3 m and the take-up speed is increased, the molten strand may not be gradually cooled. The air ring 7 at the inlet portion 8 of the melt strand of the slow cooling cylinder 9 is normally 15 to 80 ° C, preferably 30 to 50 ° C in the slow cooling cylinder 9.
This is for blowing in the warm air of to slowly cool the molten strand.

In this manufacturing apparatus, a sizing die may be provided on the inlet side of the melted strand of the puncture slow cooling cylinder 9 to regulate the size and slow cooling.

〔The invention's effect〕

Since the plastic wire of the present invention is plastically deformable, it can be twist-knotted like a wire, and as a substitute for the wire, for example, a bag knot or a grape shelf for fruits in an orchard, or a fence surrounding the orchard. Including the creation of
It can be used as a substitute for wire in all fields where wire is conventionally used except when heated.

Moreover, unlike wires, it does not rust and is highly durable.
It has the advantage that it does not break due to plastic deformation and can withstand repeated use.

〔Example〕

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

In the apparatus for producing a stretching raw yarn (strand) shown in FIG. 5, an ultrahigh molecular weight polyethylene stretching raw yarn (strand) was produced using an apparatus having the following specifications.

Screw diameter: 20 mmφ Effective screw length (L / D): 22 Screw compression ratio: 1.8 Die length: 240 mm Die outlet inner diameter: 6 mmφ Die L / D: 40 S ₁ / S ₂ : 1.8 [η] = 16.5dl / g , MFR: less than 0.01g / 10min, melting point: 136 ℃
And bulk density: 0.45 g / cm ³ of ultra-high molecular weight polyethylene powder (trade name: Hi-Zex Million 240M, manufactured by Mitsui Petrochemical Co., Ltd.), extruder, die base (D ₁ ) and die end (D ₂ ) Setting temperature of 320 ℃, 200 ℃ and 14 ℃ respectively
Set it to 0 ° C, set the screw rotation speed to 50 rpm, and use a take-up machine.
By drawing at a speed of 1.5 m / min, an ultra-high-molecular-weight polyethylene drawing raw yarn having an outer diameter of 4.0 mmφ was produced.

Then, this raw yarn is 6 times (1st stage: 133 ° C) 8 times (1st stage: 133 ° C) 10 times (1st stage: 133 ° C) 12 times (1st stage) in a drawing tank of triethylene glycol liquid : 133 ℃ 6 times, 2nd step: 144 ℃ 2 times) 18 times (1st step: 133 ℃ 6 times, 2nd step: 144 ℃ 3 times) 24 times (1st step: 133 ℃ 6 times, 2 steps Eyes: 144 ° C 3 times).

In addition, as a comparative example, [η]: 2.6 dl / g, MFR: 0.11 g / 10 mi
A drawn yarn was produced under the same conditions except that the extruder temperature was 220 ° C. using polyethylene (general-purpose polyethylene) having n, melting point: 131 ° C. and number density: 0.956 g / cm ³ .

The physical properties of the obtained drawn yarns were measured by the following methods. The results are shown in Table 1.

Density: ASTM D 1505 (no annealing) Diameter: Micrometer Tensile test: Yonekura Instron type universal testing machine (CATY-1
001ZS) The tensile strength at break (kg / mm ² ), Young's modulus (kg / mm ² ), and elongation (%) were determined under the conditions of tensile speed: 200 mm / min, chuck distance: 200 mm.

Return angle: (1) The return angle θ was measured after bending 180 degrees and after 10 minutes.

(2) 90 degree bending, and the return angle θ after 10 minutes was measured.

From Table 1, it can be seen that in Experimental Example 1, when the stretch ratio is 8 times or more, and further 10 times or more, a plastic wire having a small return angle θ at the time of bending and an excellent tensile strength at break can be obtained. . It is also clear that general-purpose polyethylene cannot obtain a small return angle θ in any case.

[Brief description of drawings]

1 and 2 show the plastic wire of the present invention.
The figure which shows the bending return angle (theta) at the time of bending by 0 degree, 3rd
Figures and 4 show the bending return angle when bent 90 degrees.
And FIG. 5 is a sectional view of an apparatus for producing an ultrahigh molecular weight polyethylene raw yarn according to the present invention. 1 ... Extruder, 2 ... Grooved cylinder, 3 ... Screw, 4 ... Die inlet, 5 ... Die outlet, 6 ... Cylindrical die, 7 ... Air ring, 8 ... Strand inlet,
9 ... Slow cooling cylinder, 10 ... Take-up machine, 21 ... Groove part, 22 ... Compression part.

Claims (3)

[Claims] 1. An outer diameter obtained by stretching after melt molding is 0.4.
To 3.5 mmφ ultra high molecular weight polyethylene wire, intrinsic viscosity number [η] is at least 4 dl / g, tensile strength at break is at least 20 kg / mm ² , whitening, bending return angle θ is 20 degrees or less A plastic wire characterized by being. 2. Ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of at least 4 dl / g is melted by a screw extruder and then extruded from a die having at least L / D of 10 and extruded at a draft ratio of 1 at least. The raw yarn having an outer diameter of 2 to 10 mmφ formed by gradually cooling the drawn strand is drawn at a draw ratio of 8 to 30 to obtain the raw yarn having an outer diameter of 0.4.
A method for manufacturing a plastic wire, which comprises processing a wire having a diameter of 3.5 mm to 3.5 mm. 3. The wire raw yarn is drawn at a draw ratio of 4 to 8 times, then drawn at a draw ratio of 2 to 5 times, and drawn at a draw ratio of 8 to 30 times as a whole. 2. The method for producing a plastic wire according to claim 2.