JPH01162818A - Production of polyethylene fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber of high strength and high modulus, low in creep, by heat treatment, at specified temperatures, of a high-molecular weight polyethylene solution incorporated with an organic compound having two or more vinyl groups 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, incorporated with pref. 2-20wt.% of an organic compound having two or more vinyl groups (pref. soluble in the solvents for polyethylene, e.g., diarylphthalate, triaryl isocyanurate, divinylbenzene) is heat treated at temperatures at or higher than the swelling temperature of said polyethylene followed by spinning and then hot drawing of the resultant undrawn yarn pref. at 100-160 deg.C, 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 cellulose, 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 producing polyethylene fibers that satisfy this requirement, a method is disclosed in JP-A-55-107506, in which a solution of high molecular weight polyethylene is spun, cooled, and the obtained gel-like filament is hot-stretched to a high magnification. Kaisho 58-522
This is disclosed in Publication No. 8, 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. Useful notes are awaited for materials such as wood and concrete reinforcement materials.

However, although the high-strength, high-modulus polyethylene fibers obtained by the above method have high strength, they have the disadvantage of high elongation under load, that is, high creep, similar to energized polyethylene fibers. For industrial use'a
When these high-strength, high-modulus polyethylene fibers are used as fiber materials, many problems occur. For example, lobes made of these fibers tend to gradually stretch under load. Furthermore, when these fibers are used as tension members for optical fibers and the like, the tension members that are supposed to bear tension progress over time. As a result, tension is applied to the optical fibers, etc. that should be supported by the tension members.
This may result in a decrease in its aqueous performance or even lead to breakage.

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] describes a method in which dried Kel-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) 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 a solution of polyethylene having a weight average molecular weight of 700,000 or more mixed with an organic compound having two or more vinyl groups, after heat treatment at a temperature equal to or higher than the swelling temperature of the polyethylene. The present invention provides a method for producing polyethylene fibers, which comprises spinning the resulting undrawn yarn 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 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. It is necessary to use polyethylene.

In the method of the present invention, first, a solution of polyethylene having a weight average molecular weight of 700,000 or more is prepared by mixing an organic compound having two or more vinyl groups.

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 above 100°C, so low boiling point solvents are not preferred. Suitable solvents include decalin,
Examples include xylene, tetralin, nonane, decane, n-varafine, kerosene, paraffin oil, and the like.

Materials that are solid at room temperature, such as solid, paraffin wax and naphthalene, may also be used.

There is no particular limit to the weakness of the polyethylene solution, and the solution viscosity will be appropriate from the viewpoints of uniformity during dissolution, ejection stability during spinning, spinnability, thread runnability, and spinnability during drawing. However, a range of 1 to 15% by weight is appropriate.

The organic compound having two or more vinyl groups 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 diaryl phthalate, Those that can be dissolved in the above-mentioned polyethylene solvents, such as triaryl isocyanurate, divinylbenzene, ethylene dimethacrylate, and methacrylic anhydride, are preferred.

The amount of the organic compound having two or more vinyl groups varies depending on the type of compound, heat treatment temperature, etc., and is not particularly limited, but it is suitably in the range of 1 to 25% by weight, particularly preferably 2 to 20% by weight, based on polyethylene. It is.

If the mixing amount of the organic compound having two or more vinyl groups is small, crosslinking of polyethylene will be difficult to occur, and the creep suppressing effect will be reduced. In addition, if the mixing amount of an organic compound having two or more vinyl groups is too large, the degree of crosslinking will be too strong and the viscosity of the solution will become high, making spinning difficult, and orientation and crystallization by stretching will be inhibited, resulting in high strength. , it becomes difficult to obtain a drawn yarn with a high elastic modulus.

An organic compound containing two or more vinyl compounds can be mixed into the polymer solution by adding it to the solvent at the same time as the polymer, or by mixing it into the polyethylene solution at an appropriate time before spinning. .

In addition, in the method of the present invention, an organic peroxide can be used simultaneously with an organic compound having two or more vinyl groups. However, in this case, it is appropriate that the amount of organic peroxide be equal to or less than the amount of the organic compound having two or more vinyl groups. This is because if the amount of organic peroxide is large, the degree of crosslinking becomes too strong, which may inhibit orientation and crystallization during stretching.

In the present invention, after preparing a polymer solution containing a mixture of organic compounds having two or more vinyl groups, it is necessary to heat-treat the solution at a temperature higher than the swelling temperature of the polyethylene used in the solution before spinning.

During this heat treatment, an organic compound having two or more vinyl groups is reacted to crosslink 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, if the heat treatment temperature is set higher than the swelling temperature of polyethylene, the viscosity of the polyethylene solution used for spinning will be slightly higher than that of a non-crosslinked polyethylene solution, but it will maintain appropriate spinnability and will be used for normal spinning and spinning. Subsequent stretching is possible.

In addition, the swelling temperature in the present invention refers to the combination of polymer and solvent used for spinning, and when the polymer is immersed in the solvent for 15 minutes, the weight fraction (swelling degree) of the solvent absorbed by the polymer relative to the dry polymer is, This is the temperature at which the temperature increases to 400%.

The above heat treatment needs to be continued for a sufficient time for the organic compound having two or more vinyl groups to react, but this time varies depending on the type of compound, heat treatment temperature, etc., and the appropriate time can be determined by prior experimentation. can be easily determined.

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 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. 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 better to remove the extractant by drying the extracted threads.
This is preferable because it 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. In addition, the degree of inhibition of orientation and crystallization due to stretching is also small.

In addition, although this undrawn polyethylene yarn can be drawn by cold drawing, in this case, it is not possible to obtain polyethylene fibers with high strength and high elastic modulus that can be used as a material for industrial grade ♀1 without any problems. .

There is no particular limitation on the stretching temperature in the hot stretching of this undrawn polyethylene yarn, but 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 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,
Polyethylene fibers with a single yarn Young's modulus of 1000 g/d or more and a creep of 2% or less when kept under a load of 1/10 of the breaking strength at 20°C for 60 days can be easily obtained, and the single yarn strength is 40g/d or more, single yarn Young's modulus 140
1/ of the breaking strength at 0 g/d or more and at 20°C
It is also possible to obtain polyethylene fibers having a creep of less than 1% when subjected to a load of 10% for 60 days.

(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, 65% relative humidity 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: Strength and elongation curve It was determined from the slope at the origin.

Creep measurement conditions Measurement atmosphere: 20° C. 1 Relative humidity 65% Load: Breaking strength of 1710 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.

L2: 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 5. High-density polyethylene and 10% by weight of triallylisocyanate of this polyethylene were dissolved in kerosene at a temperature of 180°C, and heat treated at the same temperature for 90 minutes with stirring.5. 0% by weight
A polyethylene solution was prepared.

Note that the swelling temperature of the combination of polymer and solvent used here was 107°C.

After passing this solution through a 5 mm distance of air from a nozzle with a hole diameter of 1 mm and 10 holes at 170°C, a two-layer structure consisting of water in the upper layer and trichlorotrifluoroethane in the lower layer is spun. After cooling in a bath, it was coagulated and bundled to obtain a coagulated thread. The temperature of the spinning bath was 10°C, and the thickness of the upper layer (water) was 80°C.
mm, the thickness of the lower layer (trichloride trifluoride ethane) is 230 m
It was set as m.

Further, the coagulated yarn was taken 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 8 times using a hot plate at 135°C. After stretching it, I rolled it up with wine goo.

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

6 under a load of 1/10 of the breaking strength of this drawn yarn at 20°C.
The creep when worn for 0 days was 0.48%. In addition, other physical properties are as follows.

Single yarn fineness: 1.5 d Single yarn tensile strength: 150 g/d Single yarn initial elastic modulus: 1600 g/d (Comparative example 1
) Spinning, extraction, and drying were carried out in exactly the same manner as in Example 1, except that triallylisocyanurate was not added and the magnification of the first-stage drawing subsequent to spinning was 12 times, to obtain a single-stage drawn yarn. 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 58 g/d and a Young's modulus of 1820 g.
/d, but the breaking strength was 1/1/2 at 20°C.
Creep is 4.4 when worn for 60 days under a load of 10.
The value was as high as 0%.

(Comparative Example 2) Linear high-density polyethylene with a weight average molecular weight of 150,000 and this polyethylene were dissolved in kerosene containing 10% by weight of triallyl isocyanurate at a temperature of 170°C, and stirred for 90 minutes to obtain 15% by weight of the polyethylene. A polyethylene solution was prepared. Note that the swelling temperature in the combination of the polymer and solvent used here was 93°C.

This solution was spun in the same manner as in Example 1, and the dried yarn was wound with a wine goose without being stretched.

Next, the obtained undrawn yarn was heated for 30 minutes using a hot plate at 135°C.
Stretched twice. This stretching system had low physical properties such as strength of 13 g/d and Young's modulus of 410 g/d due to the low molecular weight of the polymer. Furthermore, when a load of 1/10 of the breaking strength was applied and left at 20°C, creep exceeded 5% at 38 stitches.

(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 (1)

[Claims] A solution of polyethylene having a weight average molecular weight of 700,000 or more mixed with an organic compound having two or more vinyl groups is heat-treated at a temperature equal to or higher than the swelling temperature of the polyethylene, and then spun,
A method for producing polyethylene fibers, which comprises hot drawing the obtained undrawn yarn.