JPH01162819A - Production of novel polyethylene fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber of high strength and high modulus, low in creep, by spinning a solution of polyethylene with a specified molecular weight which has been made by blending two kinds of polyethylene differing in molecular weight from each other followed by hot drawing of the resultant undrawn yarn. CONSTITUTION:A solution of polyethylene with a weight-average molecular weight of 700,000 to 4,000,000 which has been prepared by blending 5-50wt.% of polyethylene having a weight-average molecular weight of >=5,000,000 with a second polyethylene having a weight-average molecular weight of >=600,000 (pref. >=1,500,000) is spun followed by hot drawing of the resultant undrawn yarn 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 a novel polyethylene fiber having high strength, high modulus of elasticity, and low creep.

(Prior Art) Polyethylene fiber has excellent properties as an industrial cellulose material, 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 elastic modulus in order to meet the demands for energy saving and high functionality of products that use them as industrial la fiber materials.

As a method for producing polyethylene fibers that meet this requirement, Japanese Patent Laid-Open No. 55'-107506 discloses a method 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. Publication, JP-A-58-5
It is disclosed in Publication No. 228 and the like.

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 ropes, slings, various rubber reinforcement materials, and reinforcement materials for various resins. It is expected that it will 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.

Even in the above method, it is believed that in principle, if the molecular weight of the polyethylene used is increased, the creep of the resulting fibers will be reduced. However, if the solution used for spinning has a polymer concentration within a practical range, the higher the molecular weight of the polymer, the higher the viscosity. This makes spinning difficult or makes it impossible to increase the drawing ratio.

For example, the viscosity at 170°C of 5% by weight solutions of polyethylene with different molecular weights using kerosene as a solvent ()1), the maximum drawing ratio (in) of undrawn yarn obtained from those solutions,
A comparison of the physical properties of the drawn yarn is shown in the following table (the spinning and drawing conditions were the same).

μ (pojse) 300 5100 20,000 or more
210
60 18 strength (
g/d) 48 56 28 Elongation (
%) 4.6 4.7 5.1 Initial modulus of elasticity Also, the drawn yarn obtained from the polyethylene with a weight average molecular weight of 6 million listed in the above table was subjected to a load of 5 g/d at 20°C for 60 days. The creep rate was as high as 2.4%, which was a problem for use as an industrial fiber material. This is thought to be because, as shown in the table above, the viscosity of the polyethylene solution is high, so the maximum draw ratio is reduced, and only drawn yarns with low integrity of the internal structure of the fibers can be obtained. Therefore, even if polyethylene fibers are obtained by the method disclosed in JP-A-55-107506 using high molecular weight polyethylene, polyethylene fibers having high strength, high elastic modulus, and low creep cannot be obtained.

Now, when fibers with high creep are used as industrial fiber materials, many problems arise. For example, lobes using these fibers have the problem of gradually stretching under load. Furthermore, when these fibers are used as a tension member such as an optical fiber, the tension member that is supposed to bear 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 polyethylene fibers with high strength, high elastic modulus, and low creep can be obtained, 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. Bennings; Polymer No. 25
Volume 513-519 [J, de Boer,
HoJ, 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 have insufficient mechanical properties for many industrial textile applications.

(Problems to be Solved by the Present Invention) An object of the present invention is to provide a novel method for producing polyethylene fibers that have high strength, high modulus, and low creep and are useful as industrial fiber materials. .

(Means for Solving the Problems) The present invention combines polyethylene with a weight average molecular weight of 5 million or more into polyethylene with a weight average molecular weight of 600,000 or more.
The present invention provides a novel method for producing polyethylene fibers, which comprises spinning a solution of polyethylene with a weight average molecular weight of 700,000 to 4,000,000 mixed at 50%, and hot drawing the resulting 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 two types of vinyl monomers copolymerizable with other alkenes such as 4-methylpentene or ethylene.
Fi! The above may be copolymerized.

The weight average molecular weight of the main component of polyethylene used in the method of the present invention must be 600,000 or more, preferably 1,000,000 or more, and more preferably 1,500,000 or more.

In general, as the number of low molecular weight molecules increases, creep tends to increase because these low molecular weight molecules also function as a leachable agent in the drawn yarn. For this reason, when polyethylene having a weight average molecular weight of less than 600,000 is used, the resulting polyethylene fibers exhibit large creep, making them unsuitable for use as industrial fiber materials.

In the present invention, the molecular weight of the polyethylene to be mixed with the polyethylene having a weight average molecular weight of 600,000 or more, which is the main component, must have a weight average molecular weight of 5,000,000 or more. This is because mixing a polymer with a very high molecular weight suppresses the stagnation of molecules and reduces creep, but polyethylene with a weight average molecular weight of less than 5 million has little effect in reducing creep.

In the present invention, the amount of polyethylene having a weight average molecular weight of 5 million or more needs to be 5 to 50% of the total amount of polyethylene.

This is because if the mixing amount of polyethylene with a weight average molecular weight of 5 million or more is less than the above range, the effect of reducing creep will be small, and if it is too large, the viscosity of the solution will increase, making spinning difficult, or This is because a high magnification cannot be achieved and polyethylene fibers with high strength and high modulus of elasticity cannot be obtained.

In the method of the present invention, first, a polyethylene solution is prepared by mixing polyethylene having a weight average molecular weight of 5 million or more with polyethylene having a weight average molecular weight of 600,000 or more.

The weight average molecular weight of the polyethylene after mixing the above polymers is required to be 700,000 to 4,000,000.

In general, the higher the molecular weight! ! In order to obtain polyethylene fibers that can be used without any problems as industrial fiber materials, it is necessary to use polyethylene with a weight average molecular weight of 700,000 or more, since defects such as the ends of internal chains within the fibers are reduced and the strength is increased. There is.

However, when the weight average molecular weight exceeds 4 million, the viscosity of the polyethylene solution used for spinning becomes extremely high, making spinning difficult and making it impossible to obtain a high drawing ratio, resulting in high-strength, high-modulus polyethylene fibers. can't get it.

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,
Examples include xylene, tetralin, nonane, decane, n-paraffin, kerosene, paraffin oil, mineral 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 limit to 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. Although it is selected, a range of 1 to 15% by weight is suitable, and a range of 3 to 10% by weight is more preferable.

Although the viscosity of the polyethylene solution used in the present invention is slightly higher than that of a polyethylene solution in which polyethylene with a weight average molecular weight of 5 million or more is not mixed, it maintains appropriate spinnability and can be subjected to normal spinning and subsequent drawing. It is.

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 and then introduced into a coagulation bath to solidify the yarn. 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. Unexamined Japanese Patent Publication No. 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 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 threads in polyethylene multifilament, problems such as a decrease in the tensile strength of the entire filament, a decrease in adhesiveness with the scale or resin, and a decrease in the strength utilization rate during heating occur. 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, adhesion 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 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 undrawn polyethylene yarn obtained by the above method needs to be subsequently subjected to hot drawing.

This undrawn polyethylene yarn can also be drawn by cold drawing, but in this case, it is not possible to obtain polyethylene fibers with high strength and high elastic modulus that can be used as industrial textile materials 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 is 1
It may be performed in stages or in multiple stages.

The polyethylene fiber obtained by the method of the present invention has high strength and high modulus of elasticity, and has low creep because the polyethylene molecules with very high molecular weight suppress the sliding between molecules or fibrils within the fiber. ing.

Therefore, in the method of the present invention, the single yarn strength is 30 g/d or more,
The single yarn Young's modulus is 1000 g/d or more, and the creep is 1 when worn for 60 days under a load of 5 g/d at 20°C.
．． 5% or less polyethylene fibers can be easily obtained, and the single yarn strength is 40 g/(1 or more, single yarn Young skewer 1 ton).
It is also possible to obtain polyethylene fibers which have a polyethylene fiber of roog/d or more and a creep of 1% or less when worn for 60 days at 20° C. under a load of 5 g/d.

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

Weight average molecular weight measurement conditions measurement method Nigel permeation chromatography equipment Nigel permeation chromatograph, GPC-150C ('vVAT
ER8) Column: 5hodex A-80M, 1 wood Showa Denko) Solvent 20-dichlorobenzene (added with 0.1% ionol) Flow rate: 1ml/min Temperature: 135°C Sample concentration: 0.01% Filtration: 2- Using a 5μ sintered filter Injection waste: 0.4ml Detector: Differential refractive index detector Molecular weight calibration: Monodisperse polystyrene tensile strength, first IVI elastic skewer Measurement conditions Measurement atmosphere: 20°C, relative humidity 65% Equipment: Toyo Baldwin Co., Ltd. Tensilon UTM-4, tensile tester sample:
Single yarn 250 mm Tensile speed: 300 mm/min Periodic modulus: Obtained from the slope at the origin of the strength and elongation curve.

Creep measurement conditions Measurement atmosphere: 20°C1 relative humidity 65% Load: 5
g/d In addition, creep was calculated|required by the following formula.

L: Length immediately after applying a load to the sample (initial length of 11 nm) L: Length measured with a load applied to the sample for 260 days (Example 1) Weight average molecular weight is 6 million 5. A mixture of 2 million linear high-density polyethylene in a ratio of 1:4 was dissolved in kerosene at a temperature of 190°C; 5. A polyethylene solution containing % ON was prepared. Note that the weight average molecular weight of this mixed polyethylene was 3 million.

After passing the above solution through an air layer at 180°C for a distance of 5 mm from a nozzle with a hole diameter of 1 mm and a number of holes of 10, 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 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 is then passed through an extraction tower made of trichloride trifluoroethane at 5°C to extract the kerosene remaining in the thread, and after drying, it is heated 8 times using a hot plate at 135°C. After stretching it, I rolled it up and rolled it up.

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

Single yarn fineness: 1.3 d Single yarn tensile strength: 56 g/d Single yarn initial concavity modulus: 18'00 g/d Further, the creep of this drawn yarn was as small as 0.53%.

(Comparative Example 1) Linear high-density polyethylene having a weight average molecular weight of 3 million was dissolved in kerosene at a temperature of 180°C to prepare a 5.0% by weight polyethylene solution.

This solution was spun and extracted in the same manner as in Example 1, dried, and then stretched 10 times to obtain a single-stage drawn yarn.

This one-stage drawn yarn was further drawn 6 times using a hot plate at 145° C. to obtain a 60 times drawn yarn using l·-tal.

This drawn yarn has a strength of 56 g/d and a Young skewer of 1780 g/d.
It showed high physical properties, but the creep was high at 2.1%.

(Comparative Example 2) A 1:10 mixture of linear high-density polyethylene with weight average molecular weights of 6 million and 150,000 was dissolved in kerosene at a temperature of 180°C to prepare a 10% by weight polyethylene solution.

The weight average molecular weight of this mixed polyethylene was 650,000. This solution was spun in the same manner as in Example 1.
The extracted and dried yarn was wound up with wine goo without stretching.

Next, the obtained undrawn yarn was heated to 52°C using a hot plate at 145°C.
Stretched twice. This drawn yarn had low physical properties such as strength of 16 g/d and Young Hata's strength of 560 g/d because the molecular weight of the main component polymer was low. Also, 1/10 of the strength of jealousy at 20℃
When the load was applied and left for 3 days, the creep exceeded 5%.

(Comparative Example 3) Linear high-density polyethylene having a weight average molecular weight of 6 million was dissolved in kerosene at a temperature of 180°C and stirred for 90 minutes to prepare a 5.0% by weight polyethylene solution.

This polyethylene solution was spun in the same manner as in Example 1, but it could only be stretched 6 times by stretching subsequent to spinning.

Further, the obtained single-stage drawn yarn was drawn using a hot plate at 145° C., but it could only be stretched up to 3 times, and the single yarn strength of the drawn yarn was as low as 28 g/d.

In addition, creep also showed a high value of 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, high elastic modulus, and low creep and is useful as an industrial fiber material.

＞r#Koshi Karato

Claims (1)

[Claims] Undrawn yarn obtained by spinning a solution of polyethylene with a weight average molecular weight of 700,000 to 4 million by mixing 5 to 50% polyethylene with a weight average molecular weight of 5 million or more to polyethylene with a weight average molecular weight of 600,000 or more. A novel method for producing polyethylene fibers, which comprises hot drawing.