JPH01162817A - Production of polyethylene fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber of high strength and high modulus, low in creep, thus useful as an industrial fibrous material, by heat treatment at specified temperatures of a high-molecular weight polyethylene solution incorporated with an organic peroxide followed by spinning and then hot drawing of the resultant undrawn yarn. CONSTITUTION:A solution of polyethylene with a weight-average molecular weight of >=700,000 (pref. >=2,000,000), incorporated with pref. 0.05-10wt.% of an organic peroxide (e.g., di-t-butyl peroxide, pref. soluble in the solvents for polyethylene) is heat-treated at temperatures at or higher than the swelling temperature of said polyethylene followed by spinning. The resultant undrawn yarn is then put to hot drawing pref. at 100-160 deg.C by a factor of >=25, thus obtaining the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing polyethylene fibers having high strength, high modulus of elasticity, and low creep.

(Prior Art) Polyethylene fibers have excellent properties as industrial fiber materials, such as being light, having excellent chemical resistance, and being relatively inexpensive.

In recent years, there has been a demand for glue fiber materials that are lightweight, have high strength, and have high elastic modulus in order to meet the demands for energy saving and high functionality of products that use them as industrial fiber materials.

As a method for producing polyethylene fibers that satisfy this requirement, a method is disclosed in JP-A-55-107506 in which a high molecular weight polyethylene solution α is spun, cooled, and the obtained gel-like filament is hot-stretched to a high magnification. , Japanese Patent Publication No. 58-52
This is disclosed in Publication No. 28 and the like.

The high-strength, high-modulus polyethylene fibers obtained by these methods can be used for industrial fiber applications that require particularly high strength and high modulus, such as lobes, slings, and various silica rubbers. It is expected to be useful for i7 reinforcement materials, various resin reinforcement materials, concrete reinforcement materials, etc.

However, although the high-strength, high-modulus polyethylene fibers obtained by the above method have high strength, they have the same drawback as ordinary polyethylene fibers of high elongation under load, that is, high creep. Therefore, when these high-strength, high-modulus polyethylene fibers are used as industrial fiber materials, many problems occur. For example,
Lobes using these fibers have the problem of gradually stretching under load. In addition, when these fibers are used as tension members for optical fibers, etc.,
The Hegi tension member that carries the tension progresses over time. As a result, tension is applied to the optical fibers and the like that should be supported by the tension members, which may reduce their functionality or cause them to break.

Therefore, if the creep characteristics of high-strength, high-modulus polyethylene fibers as described above can be improved, their use as industrial fiber materials will be greatly expanded.

Crosslinking treatment is known as a method for improving the creep properties of polyethylene.

JP-A No. 60-59172 describes a method of applying radiation to a drawn polyethylene yarn, and JP-A No. 60-240433 describes a method of subjecting a gel-like film or tape to crosslinking treatment by irradiating radiation before or during stretching. has been done. However, in these methods, when irradiating with radiation, not only crosslinking but also molecular chain scission occurs at the same time, resulting in an unavoidable decrease in strength.

Also, J. DeBoer, H.J. Vandenberg, and A.J. Pennings; Polymer No. 25
Volume 513-519 [J, de Boer,
H, J. van'de Berg.

A. J. Pennings; POLYMER, V.

1.25. P, 513-519 disclose a method in which dried gel-like fibers are impregnated with a crosslinking agent dissolved in a solvent, the solvent is blown off, and then a crosslinking treatment is performed simultaneously with stretching. Further, JP-A-61-293229 describes a method of impregnating a polyethylene gel with a crosslinking agent and molding the material, the purpose of which is to improve heat resistance. However, in these methods, crosslinking progresses during stretching or molding, which inhibits orientation and crystallization, making it difficult to obtain high strength and high elastic modulus.

Therefore, crosslinked polyethylene fibers obtained by the above-described method generally do not have sufficient mechanical properties for many industrial fiber applications.

(Problems to be solved by the present invention) The purpose of the present invention is to have high strength and high modulus of elasticity useful as an industrial fiber material.
Another object of the present invention is to provide a method for producing polyethylene fibers with low creep.

(Means for Solving the Problems) The present invention provides that the weight average molecular weight of the mixed organic peroxide is 7.
The present invention provides a method for producing polyethylene fibers, which comprises heat-treating a solution of polyethylene of 0,000 or more at a temperature equal to or higher than the swelling temperature of the polyethylene, and then hot-drawing the spun and wide-banded undrawn yarn.

In the present invention, polyethylene refers to a small amount of propylene, butylene, pentene, hexene, for example, 10 mol% or less,
One or more types of vinyl monomers copolymerizable with other alkenes such as 4-methylpentene or ethylene may be copolymerized.

The weight average molecular weight of the polyethylene used in the method of the present invention needs to be 700,000 or more, preferably 1,500,000 or more, and more preferably 2,000,000 or more.

In general, the higher the molecular weight, the fewer defects such as molecular chain ends inside the fiber, and the higher the strength.In order to obtain polyethylene fiber that can be used as an industrial fiber material without any problems, the weight average molecular weight is 700,000 or more. polyethylene must be used.

In the method of the present invention, first, a solution of polyethylene having a weight average molecular weight of 700,000 or more and mixed with an organic peroxide is prepared.

Solvents used to form the solution of polyethylene include, but are not limited to, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and mixtures thereof. . Normally, even with these solvents, polyethylene does not dissolve at temperatures below 60°C and is often heated to temperatures above 100°C, so low boiling point solvents are not preferred. Suitable solvents include decalin, xylene, tetralin, nonane, decane, n-paraffin, kerosene, paraffin oil, and the like.

Moreover, those that are solid at room temperature such as paraffin wax and naphthalene can also be used.

There is no particular limitation on the polyethylene concentration of the polyethylene solution, and the solution viscosity is determined to be appropriate from the viewpoints of uniformity during dissolution, ejection stability during spinning, spinnability, yarn runnability, and spinnability during drawing. However, a range of 1 to 15% double bases is appropriate.

The organic peroxide used in the present invention is not particularly limited as long as it can crosslink polyethylene in a polyethylene solution by heat treatment at a temperature higher than the swelling temperature of polyethylene, but di-t-butyl peroxide, di-t-butyl peroxide, G
cumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2°5-di(t-butylperoxy)hexane-3,
t-Butylperoxy-2-ethylhexanoate, 1
, 1-bis(t-butylperoxy)3°3.5-)limethylcyclohexane, t-butylperoxyisopropyl carbonate, benzoyl peroxide, and the like which are soluble in the above-mentioned polyethylene solvents are preferred.

The amount of organic peroxide mixed varies depending on the type of organic peroxide, heat treatment temperature, etc., and is not particularly limited, but is preferably 0.02 to 15% by weight based on polyethylene, particularly preferably 05
A range of ~10% is appropriate.

If the amount of organic peroxide mixed is small, crosslinking of polyethylene will be difficult to occur, and the creep suppressing effect will be reduced. Also,
If a large amount of organic peroxide is mixed, the degree of crosslinking becomes too strong, which increases the viscosity of the solution and makes spinning difficult. Orientation and crystallization during stretching are inhibited, resulting in drawn yarn with high strength and high elastic modulus. It becomes difficult to obtain.

The organic peroxide may be mixed into the polymer solution by adding it to the solvent at the same time as the polymer, or it may be mixed at an appropriate time before spinning (during the polyethylene solution).

Furthermore, there is no problem in using a crosslinking aid that is commonly used to promote crosslinking together with an organic peroxide.

In the present invention, after preparing a polymer solution mixed with an organic peroxide, it is necessary to heat-treat the solution at a temperature equal to or higher than the swelling temperature of the polyethylene used in the solution before spinning.

This heat treatment causes the organic peroxide to react and crosslinks the polyethylene, but if the temperature is set above the swelling temperature, the crosslinking will proceed with the polyethylene molecules spread out.

Therefore, compared to the bulk case, each polyethylene molecule has fewer contact points with neighboring molecules, and the degree of crosslinking is reduced. Therefore, although the viscosity of an organic peroxide-mixed polyethylene solution heat-treated above the swelling temperature of polyethylene is slightly higher than that of a non-crosslinked polyethylene solution, it maintains appropriate spinnability and can be used for normal spinning and subsequent spinning. Stretching is possible.

In addition, the swelling temperature in the present invention refers to the temperature at which the weight fraction (swelling degree) of the solvent absorbed by the polymer relative to the dry polymer when the silk is immersed in a polymeric solvent for 15 minutes is the , 400%.

The above heat treatment needs to be continued for a sufficient time for the organic peroxide to react, but this time varies depending on the type of organic peroxide, heat treatment temperature, etc., and it is easy to determine the appropriate time by prior experimentation. You can decide.

In the method of the present invention, the above-mentioned polyethylene solution is discharged in the form of tTJJlt using an ordinary gear pump and a spinning nozzle, and is cooled and solidified to form fibers. After the solution is passed through a gaseous region, it is introduced into a coagulation bath and coagulated into threads using the so-called dry-wet spinning process.The solution extruded from the nozzle is cooled to form a rubbery gel thread. The spinning method described in JP-A-61-113813 (hereinafter referred to as gel wet spinning), in which the solution extruded from a spinning nozzle is introduced into a bath consisting of a cooling agent and a coagulant to gel and solidify, can be applied. However, the method is not particularly limited to these methods. However, it is preferable to apply gel wet spinning because it is easy to obtain polyethylene filaments with high tensile strength and polyethylene multifilaments with less fusion between single filaments. This is because if there is a lot of fusion between single filaments in polyethylene multifilament, problems such as not only the tensile strength of the entire filament will decrease, but also the adhesiveness with the resin will decrease, and the strength utilization rate during heating will decrease. It is from.

When the solvent remains in the yarn spun by the above method, it is preferable to extract the remaining solvent with an extractant. This is because if the residual solvent in the yarn is removed by a method such as drying or hot stretching, fusion between single yarns may occur when the solvent evaporates. The residual solvent in the yarn is removed using an extractant and the yarn is dried.
Even if hot stretching is performed, no inter-filament fusion occurs.

Note that it is preferable to remove the extractant from the extracted yarn by drying, since this improves the spinning properties in the subsequent hot stretching step.

The undrawn polyethylene yarn obtained by the above method needs to be subsequently subjected to hot drawing.

Usually, crosslinked polymers have a three-dimensional network structure, so even unoriented polymers can hardly be stretched. However, since the crosslinked undrawn yarn obtained by the method of the present invention has a very slight degree of crosslinking, a high drawing ratio can be employed. Furthermore, the degree of inhibition of orientation and crystallization due to stretching is also small.

Further, although this undrawn polyethylene yarn can be drawn by cold drawing, in this case, it is not possible to obtain a polyethylene fiber with high strength and high elastic modulus that can be used as an industrial fiber material without any problems.

Although there is no particular limitation on the drawing temperature in the hot drawing of this undrawn polyethylene yarn, it is preferably in the range of 80 to 160°C, more preferably 100 to 160°C. In addition, examples of the heating medium during stretching include, but are not limited to, a heating roll, a hot plate, a heated gas bath, a heated liquid bath, and a heating bottle.

The stretching ratio in hot stretching is suitably set to 10 times or more, preferably 20 times or more, and more preferably 25 times or more so as to obtain high strength and high elastic modulus. Note that the stretching may be performed in one stage or in multiple stages.

When the method of the present invention is applied, the single yarn strength is 30 g/d or more,
Single yarn Young's modulus of 1000 g/d or more and 20°
60 days under a load of 1/10 of the breaking strength at C.
It is easy to obtain polyethylene fibers that have a creep of 2% or less when broken, and have a single yarn strength of 40 g/d or more, a single yarn Young's modulus of 1400 g/d or more, and under a load of 1/10 of the breaking strength at 20°C. The creep for 60 days is 1
% or less can also be obtained.

(Example) Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In addition, tensile strength, initial elastic modulus, and creep were measured under the following conditions.

Tensile strength and initial elastic modulus measurement conditions Measurement atmosphere: 20°C, relative humidity 65% Equipment: Tensilon UTM-4 tensile tester manufactured by Toyo Baldwin Co., Ltd. Sample: Single yarn 250 mm Tensile speed: 300 mm/min Initial elastic modulus Double strength elongation It was determined from the slope at the origin of the curve.

Creep measurement conditions Measurement atmosphere: 20° C. 1 Relative humidity 65% Load: 1/10 of breaking strength Note that breaking strength here means the product of single yarn tensile strength and fineness. In addition, creep was determined using the following formula.

L8: Length immediately after applying a load to the sample (initial length) L: Length measured after applying a load to the sample for 60 days (Example 1) Straight chain with a weight average molecular weight of 3 million high-density polyethylene and 1% by weight of 2,5-dimethyl-2 of this polyethylene.
,5-di(t-butylperoxy)hexane in kerosene
The polyethylene solution was dissolved at a temperature of 80°C and heat-treated at the same temperature for 90 minutes with stirring to prepare a 5% by weight polyethylene solution.

The swelling temperature of the combination of polymer and solvent used here was 107°C. Also, 2,5-dimethyl-2,5
Since the half-life of -di(t-butylperoxy)hexane at 180°C is about 1 minute, it is considered that the decomposition has already been completed in the solution.

After passing this solution through an air layer at 170°C and a distance of 5 mm from a nozzle with a hole diameter of 1 mm and 10 holes, the upper layer was water,
After cooling in a two-layer spinning bath in which the lower layer was composed of trichlorotrifluoroethane, the mixture was coagulated and bundled to obtain a coagulated yarn. The temperature of the spinning bath was 10°C, and the thickness of the upper layer (water) was 80 m.
m, the thickness of the lower layer (trichloride trifluoride ethane) is 230 mm
And so.

Further, the coagulated yarn was pulled off at a rate of 7.5 m/min.

The coagulated thread was then passed through an extraction bath of trichlorotrifluoroethane at 5°C to extract the kerosene remaining in the thread, and after drying, it was heated 10 times using a hot plate at 135°C. After stretching it, it was wound up with a winder.

This one-stage drawn yarn was further stretched five times using a hot plate at 145°C, and the yarn physical properties were as follows.

Single yarn fineness: 1.3 d Single yarn tensile strength: 51 g/d Single yarn initial elastic modulus: 1640 g/d A load of 1/10 of the breaking strength was applied to this drawn system and it was left at 20°C for 60 days, but the creep was , was small at 27%.

(Comparative Example 1) Same as Example 1 except that 2,5-dimethyl-2,5-cy(t-butylperoxy)hexane was not added and the magnification of the first drawing step following spinning was 10 times. A yarn was similarly spun, extracted, dried, mulled, and drawn in one stage. This single-stage drawn yarn was further drawn six times using a hot plate at 145°C.

The obtained drawn yarn has a strength of 56 g/d and a Young's modulus of 1780 g.
/d, but the breaking strength was 1/1/2 at 20°C.
Creep is 4.2 when kept under a load of 10 for 60 days.
It was a high value of 7%.

(Comparative Example 2) Linear high-density polyethylene with a weight average molecular weight of 150,000 and 1% by weight of 2,5-dimethyl-2,
17 5-di(t-butylperoxy)hexane in kerosene
A 15% by weight polyethylene solution was prepared by dissolving at a temperature of 0° C. and stirring for 90 minutes. Note that the swelling temperature of the polymer and solvent used here in the silk combination was 93°C.

This solution was spun and extracted in the same manner as in Example 1, and wound into a winder without being drawn into a dry yarn.

Next, the obtained undrawn yarn was heated to 35°C using a hot plate at 135°C.
Stretched twice. This drawn yarn had low physical properties such as strength of 14 g/d and Young's modulus of 440 g/d due to the low molecular weight of the polymer. Furthermore, when left at 20° C. under a load of 1/10 of the breaking strength, the creep exceeded 5% on the third day.

(Effects of the Invention) As described above, by the method of the present invention, it is possible to obtain a novel polyethylene fiber that has high strength and high modulus and has low creep, which is useful as an industrial fiber material.

Shrines and temples, knights.

Claims (1)

[Claims] A solution of polyethylene with a weight average molecular weight of 700,000 or more mixed with an organic peroxide is heat-treated at a temperature higher than the swelling temperature of the polyethylene, and then spun, and the resulting undrawn yarn is hot-stretched. Method for producing polyethylene fiber.