JPH01162815A - 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 irradiating ultraviolet light on the (un)drawn yarn produced by spinning a solution of high-molecular weight polyethylene followed by drawing at high draw ratio. CONSTITUTION:(A) Undrawn yarn produced by spinning a solution of polyethylene with a weight-average molecular weight of >=700,000 (pref. >=2,000,000) or (B) the drawn yarn produced by drawing said undrawn yarn by a factor of >=20 (pref. 1.5-15) is irradiated with ultraviolet light pref. at an illuminance of 30-1,000W/m<2> for 0.5-250min, followed by drawing at pref. 100-155 deg.C so that the total draw ratio exceeds 20, 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 fiber materials that are lightweight, have high strength, and have high modulus of elasticity in order to meet the demands for energy saving and high functionality in products that use these industrial fiber materials.

As a method for manufacturing polyethylene fibers that satisfies this requirement, a method was proposed in Japanese Patent Application Laid-Open No. 5-11301, in which a solution of high molecular weight polyethylene is spun, cooled, and the obtained gel-like fibers are hot-drawn to a high magnification.
It is disclosed in JP-A No. 5-107506, Japanese Unexamined Patent Publication No. 58-5228, etc.

Due to its characteristics, 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, various rubber reinforcement materials, and reinforcement of various resins. It is expected to be useful as a concrete reinforcement material.

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 tension member that is responsible for 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.G. Vandenberg, and A.G. Bennings; Polymer No. 25
Volume (1984) pages 513-519 [J, de
Boer, H.J., van den B.
erg+ A, J, Pennjngs; POLYM
ER, Vol, 25 (1984), P, 513-51
[9] describes 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. Furthermore, JP-A-61-29322
No. 9, the purpose of which is to improve heat resistance, describes a method of impregnating a polyethylene gel-like material with a crosslinking agent and molding the material. 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) An object of the present invention is to provide a method for producing polyethylene fibers that have high strength, high elastic modulus, and low creep and are useful as industrial fiber materials.

(Means for Solving the Problems) The present invention provides undrawn yarn or undrawn yarn obtained by spinning a solution of polyethylene having a weight average molecular weight of 700,000 or more.
The present invention relates to a method for producing polyethylene fibers, which comprises irradiating a drawn yarn drawn to 0 times or less with ultraviolet rays, and then drawing it until the total drawing ratio exceeds 20 times.

The polyethylene used in the present invention may include a small amount of propylene, for example, 10 mol% or less, within a range that does not impair the effects of the present invention.
Other alkenes such as butylene, pentene, hexene, 4-methylpentene, or one or more vinyl monomers that can be copolymerized with ethylene, or a small amount of polyolefin such as polypropylene or polybutene-1. may be mixed with polyethylene.

The molecular weight of the polyethylene used in the method of the present invention is j4fl
It is necessary that the average molecular weight is 700,000 or more, preferably 1,500,000 or more, and more preferably 20,075 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, it is necessary to have a weight average molecular weight of 700,000 or more. It is necessary to use polyethylene.

Further, since the higher the molecular weight, the greater the effect of reducing creep, the weight average molecular weight is required to be 700,000 or more.

Solvents used to form solutions of polyethylene of the present invention include, but are not limited to, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and mixtures thereof. It's not a thing. Normally, even with these solvents, polyethylene does not dissolve at temperatures below 60°C and is often heated to temperatures above 100°C, so solvents with low boiling points are not preferred. Suitable solvents include decalin, xylene, tetralin, nonane, decane, n-
Examples include paraffin, kerosene, and paraffin oil. 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 in the present invention, and the solution viscosity is determined to be appropriate from the viewpoints of uniformity during dissolution, ejection stability during spinning, spinnability, thread runnability, and spinnability during drawing. 1 to 15
A range of weight percent is suitable.

Note that the spinning temperature in solution spinning is selected so as to provide an appropriate solution viscosity in terms of ejection stability during spinning, spinnability, and the like. This temperature varies depending on the type of solvent, the molecular weight of polyethylene, and the concentration of polyethylene, but it is usually 120~
A range of 250°C is suitable.

In the method of the present invention, the above polyethylene solution is discharged in the form of fibers using an ordinary gear pump and a spinning nozzle,
The spinning methods are dry spinning, wet spinning, and dry-wet spinning, in which the solution extruded from a nozzle is passed through a gas section, then introduced into a coagulation bath and coagulated into yarn. , so-called gel spinning, in which the solution extruded from the nozzle is cooled to form a rubbery gel thread, and the solution extruded from the nozzle is introduced into a bath consisting of a cooling agent and a coagulant to gel and coagulate. 1986-
The spinning method described in Japanese Patent No. 113813 (hereinafter referred to as gel wet spinning) can be applied, but 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 fibers 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. If the residual solvent in the yarn is removed using an extractant, drying is possible.
Even if hot stretching is performed, no fusion occurs between single yarns.

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 polyethylene undrawn yarn spun in the present invention can be used as it is, or - 20 times or less, preferably 1.5 to 2 times
After stretching 0 times, more preferably 1.5 to 15 times,
It is necessary to irradiate it with ultraviolet light. When irradiated with ultraviolet light, some of the molecules in the amorphous portion crosslink. It is thought that creep is significantly suppressed because this crosslinked portion connects the crystals or fibrils in the final drawn yarn. However, fibers with a draw ratio exceeding 20 times have a very high degree of crystallinity and a small amount of amorphous parts, so crosslinking does not easily occur within the amorphous part when irradiated with ultraviolet rays, and therefore the crosslinked part of the final drawn yarn is low, and creep is high.

The illumination intensity of the ultraviolet rays to be irradiated is preferably in the range of 30 to 100 OW/nr, and more preferably in the range of 50 to 800 W/tn'. Also, the irradiation time was 0. The range is preferably 5 to 250 minutes, and more preferably 0.5 to 180 minutes. When these ranges are exceeded, the amount of ultraviolet rays irradiated becomes too large, and the mechanical properties of the resulting polyethylene fibers may deteriorate. Furthermore, below these ranges, the amount of irradiation is too small, making it difficult for the effects of ultraviolet irradiation to appear.

In the present invention, it is necessary to stretch the polyethylene fibers irradiated with ultraviolet rays until the total stretching ratio exceeds 20 times.

The total stretching ratio as used herein refers to the ratio at which the polyethylene fiber is substantially stretched from an undrawn yarn to a final drawn yarn.

Polyethylene fibers with a total draw ratio of 20 times or less have low strength and modulus of elasticity, and are unsatisfactory as industrial fiber materials.

Although there is no particular limitation on the drawing temperature in drawing the polyethylene fibers in the present invention, the range is preferably 80 to 155°C, more preferably 100 to 155°C. In addition, examples of the heating medium during stretching include a heating roll, a hot plate, a heated gas bath, a heated liquid bath, and a heating pin, but the present invention is not limited to these.

Note that the stretching before and after the ultraviolet irradiation may be performed in one stage or in multiple stages.

(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 = 60°C Load: vi breaking force 1/10 Note that the breaking strength here means the product of single yarn tensile strength and fineness. In addition, creep was determined using the following formula.

Le: Length immediately after applying a load to the sample (initial length) L: Length measured after applying a load to the sample for 24 hours and with the load closed (Example 1) Linear high-density polyethylene was dissolved in kerosene at a temperature of 180° C. to prepare a 5.0 Ju 1% polyethylene solution.

After passing this solution through a 5 mm distance from a nozzle with a hole diameter of 1 mm and 10 holes at 170°C, the upper layer is 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 mm.
The thickness of the lower N (trichloride trifluoride ethane) was 230 mm.

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

The coagulated thread is then passed through an extraction bath consisting of trichlorotrifluoroethane at 5°C to extract the kerosene remaining in the thread,
After drying, it was stretched 9 times using a hot plate at 135° C. and then wound up with a winder.

This single-stage drawn yarn was irradiated with ultraviolet rays at an illuminance of 800 W/ln' for 1 hour.

Next, the one-stage drawing system after irradiation with ultraviolet rays was further drawn 6.5 times using a hot plate at 145° C., and as a result, a drawn yarn with the following physical properties was obtained.

Single yarn fineness: 0.93 d Single yarn tensile strength: 51 g/d Single yarn initial elastic modulus: 1760 g/d A load of 1/1O of the breaking strength was applied to this drawn system and it was left at 50°C for 24 hours, but there was no creep. ．． The percentage was small at 22%.

(Comparative Example 1) A single-stage drawn yarn obtained in exactly the same manner as in Example 1 was drawn 7 times using a hot plate at 145° C. without irradiating it with ultraviolet rays.

The obtained drawn yarn has a strength of 56 g/d and a Young's modulus of 1830.
Although it exhibited high physical properties of g/d, its creep was high at 3.5%.

(Comparative Example 2) Linear high-density polyethylene with a weight average molecular weight of 150,000 was dissolved in kerosene at a temperature of 170°C, and stirred for 90 minutes.
A wt% polyethylene solution was prepared.

This solution was spun and extracted in the same manner as in Example 1, and the dried yarn was stretched 7 times using a hot plate at 130° C. and wound up with a winder.

This one-stage drawn yarn was irradiated with ultraviolet rays under the same conditions as in Example 1, and then stretched five times using a hot plate at 135°C. This stretching system had low physical properties such as strength of 14 g/d and Young's modulus of 420 g/d due to the low molecular weight of the polymer. Moreover, the creep exceeded 5%.

(Comparative Example 3) A yarn spun, extracted, and dried in the same manner as in Example 1 was stretched 26 times using a hot plate at 135°C.

This one-stage stretching system was irradiated with ultraviolet rays at an illuminance of 800 W/- for a period of 1 hour.

Next, the single-stage drawn yarn after irradiation with ultraviolet rays was further drawn twice using a hot plate at 145° C., and as a result, a drawn yarn with the following physical properties was obtained.

Single yarn fineness: 1. 02d Single yarn tensile strength: 54 g/d Single yarn initial elastic modulus: 1810 g/d However, the creep of this drawn yarn was as large as 2.4%.

(Effects of the Invention) As described above, according to 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.

Claims (4)

[Claims] (1) Undrawn yarn obtained by spinning a polyethylene solution with a weight average molecular weight of 700,000 or more, or a drawn yarn obtained by stretching the undrawn yarn to 20 times or less, is irradiated with ultraviolet rays, and then the total stretching ratio is 20 times. A method for producing polyethylene fibers, characterized by stretching the fibers until the fibers exceed (2) Adjust the illuminance of the ultraviolet rays to 30 to 1000 W/m^
2. A method for producing polyethylene fibers according to claim (1). (3) The method for producing polyethylene fibers according to claims (1) and (2), wherein the ultraviolet irradiation time is 0.5 to 250 minutes. (4) Stretching ratio of undrawn yarn to 1.5 before irradiation with ultraviolet rays
Claims (1) to (20) to 20 times
3) The method for producing polyethylene fibers according to item 3).