JPH01162816A - Novel polyethylene fiber - Google Patents

Abstract

PURPOSE:To provide high-strength and high-modulus polyethylene fiber having each specific weight-average molecular weight, single fiber strength, single fiber initial modulus, dynamic viso-elastic parameters and creep, also unobservable for structure with long period using the small angle X-ray scattering technique. CONSTITUTION:The objective fiber with low creep, suitable as an industrical fibrous material, obtained by melt spinning of high-density polyethylene with a weight-average molecular weight of >=700,000. This fiber has the following characteristics: 1, creep at 50 deg.C under a load of 4.5g/d for 24hrs....<=2.0% 2, single fiber strength...>=40g/d 3, single fiber initial modulus...>=1,200g/d 4, structure with long period by the small angle X-ray scattering measurement... unobserrable 5, gamma-dispersion peak height in tandelta determined by the dynamic viscoelasticity measurement...<=0.020 (pref. <=0.016) 6, dynamic storage modulus E' at 100 deg.C...>=600g/d 7, single fiber fineness...pref. <=3de.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel polyethylene fiber having high strength and 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 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. 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,
Ropes made of 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.A. DeBoer, H.J. Vandenberg, and A.J. Pennings; Polymer No. 25
Volumes 513-519 (1984) [J, d
E. Boer, H. J. van den.
Berg, A-J, Pennings; 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. Zarani 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 novel polyethylene fiber useful as an industrial fiber material that has high strength, high elastic modulus, and low creep.

(Means for solving the problems) The present invention has the following features: (1) The weight average molecular weight is 700,000 or more, and the
．． Creep of 2.0% or less when placed under a load of 5 g/d for 24 hours, single yarn strength of 40 g/d or more, 12
It has a single filament initial elastic modulus of 0.00 g/d or more, and no long-period structure is observed in small-angle X-ray scattering measurements, and the height of the tan δ γ dispersion peak in dynamic viscoelasticity measurements is 0.020. and the dynamic viscoelastic modulus E' is 10
A novel polyethylene fiber characterized by having a value at 0°C of 600 g/d or more; (2) a novel polyethylene according to item (1) above, characterized by having a single fiber fineness of 3 d or less; fibers.

The polyethylene used in the present invention includes 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, 1f polymers such as vinyl monomers that can be copolymerized with ethylene, or copolymerized two or more types, or a small amount of polyolefins such as polypropylene and polybutene-1. It may also be mixed with polyethylene.

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

Generally, the higher the molecular weight, the fewer defects such as molecular chain ends inside the fiber, and the higher the strength. Therefore, in order to obtain a single fiber strength of 40 g/d or higher, polyethylene with a weight average molecular weight of 70°C or higher is required. It is necessary to use Also,
The higher the molecular weight, the less macroscopic movement of the molecular chains will occur and the creep can be reduced, but it is necessary to use polyethylene with a weight average molecular weight of 70° C. or higher in order to achieve low creep as described below.

The polyethylene fiber in the present invention has a temperature of 4.
．． Creep when placed under a load of 5 g/d for 24 hours must be 2.0% or less, preferably 1.5% or less, and more preferably 1.0% or less.

Creep varies depending on the measurement ambient temperature and the magnitude of the load, and its value increases as the temperature and load increase. Also, creep increases with time under load. However, the present inventors showed that 4
．． Creep when placed under a load of 5 g/d is 2.
It has been found that fibers with a content of 0% or less pose no practical problem as industrial fiber materials.

The single yarn strength of the polyethylene fiber in the present invention is 40g/
d or more, preferably 45 g/d or more, more preferably 5 g/d or more
0 g/d or more is required, and the initial elastic modulus of the single yarn is 1
It is necessary to set it to 200 g/d or more, preferably 1400 g/d or more, and more preferably 1600 g/d or more.

The strength and elastic modulus of the single yarn are each 40 g/d or more, 120
If it is 0 g/d or more, it can be used as an industrial fiber material without any practical problems.

The polyethylene fiber of the present invention must not have a long-period structure in small-angle X-ray scattering measurements.

In this small-angle X-ray scattering measurement, the long-period structure is g = the fiber that is wetted shows that there is a large structural difference between the crystalline part and the amorphous part. In other words, this indicates that the molecular chains within the fiber have not been substantially completely extended. Therefore, the single yarn strength does not exceed 40 g/d and the initial elastic modulus of the single yarn does not exceed 1200 g/d.

In the polyethylene fiber of the present invention, the height of the tan δ γ dispersion peak (peak near -130°C) in dynamic viscoelasticity measurement is 0.020 or less, preferably 0.016 or less, more preferably 0.013 or less. There is a need,
The value of dynamic elastic modulus E' at 100'C is 600 g/d or more, preferably 800 g/d or more, more preferably 10
00 g/d or more.

γ dispersion peak of tan δ in dynamic viscoelasticity measurement (-1
The height of the peak (around 30° C.) reflects the quantitative proportion of the amorphous portion, and the lower the peak height, the less the amorphous portion. On the other hand, the dynamic elastic modulus E' decreases from low to high temperatures, but the higher the degree of crystallinity and orientation, that is, the higher the integrity of the fiber structure, the higher the value maintained even at high temperatures.

Therefore, if the γ dispersion peak height of tan δ in dynamic viscoelasticity measurement is greater than 0.020 or the dynamic elastic modulus E'
YC fibers with a value of less than 600 g/d at 100° C. have low crystallinity and orientation, and have an incomplete fiber structure.

Therefore, the single yarn strength does not exceed 40 g/d and the initial elastic modulus of the single yarn does not exceed 1200 g/d.

Generally, the lower the fineness of a fiber, the higher its mechanical properties tend to be. Therefore, the polyethylene fiber of the present invention also has a single yarn fineness of 3 in order to easily achieve high strength and high elastic modulus.
It is preferably d or less, more preferably 2d or less.

The novel polyethylene 1 agricultural fiber of the present invention can be provided, for example, by the following manufacturing method.

First, a polyethylene solution having a weight average molecular weight of 70° C. or higher is prepared.

However, if the molecular weight of polyethylene becomes too high, the viscosity of the polyethylene solution becomes too high, and in order to carry out spinning, it is necessary to extremely reduce the polyethylene 1 ratio of the spinning dope. Therefore, the weight average molecular weight force'<100
If it exceeds 0,000, the productivity will be low and the production cost will be high, which may make it difficult to produce industrially.

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 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 selected, a range of 1 to 15% is suitable.

The above polyethylene solution is discharged in the form of fibers using an ordinary gear pump and a spinning nozzle, and is cooled and solidified to form an m-phase ratio. So-called wet-dry spinning, in which the yarn is coagulated after being passed through a gaseous bath, and gel spinning, in which the solution extruded from the nozzle is cooled to form a rubbery gel yarn, which is extruded from the nozzle. The spinning method described in JP-A-61-113813 (hereinafter referred to as gel wet spinning), in which the resulting solution is introduced into a bath consisting of a cooling agent and a coagulant to gel and solidify, can be applied. The method is not limited.

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, not only the tensile strength of the entire filament will decrease, but also the adhesiveness with the resin will decrease.
This is because problems such as a decrease in the power utilization rate during heating may occur.

The undrawn polyethylene yarn spun by the above-mentioned method is irradiated with ultraviolet rays either as it is or after it has been drawn to 20 times or less. When irradiated with ultraviolet rays, some of the molecules in the amorphous portion are crosslinked, and it is thought that this crosslinked portion connects the crystals or fibrils in the final drawn yarn, thereby significantly suppressing creep.

At this time, fibers with a draw ratio exceeding 20 times have a very high degree of crystallinity and have a small amount of amorphous parts, so when irradiated with ultraviolet rays, crosslinking is difficult to occur in the amorphous, and therefore the crosslinked part of the final drawn yarn is low, and creep is high.

It is preferable that the illuminance of the ultraviolet rays to be irradiated is in the range of 30 to 1000"vV/m2, and the irradiation time is in the range of 0.5 to 250 minutes. If these ranges are exceeded, the amount of ultraviolet rays irradiated will be too large, resulting in poor results. The mechanical properties of polyethylene fibers may deteriorate, and below these ranges,
Because the amount of irradiation is too small, the effects of UV irradiation are difficult to see.

The polyethylene fibers irradiated with ultraviolet rays by the above method are subsequently stretched 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. It is difficult for polyethylene fibers with a total draw ratio of 20 times or less to have a single fiber strength of 40 g/d or more.

The stretching temperature for polyethylene fiber stretching is 80-15
Preferably, the temperature is in the range of 5°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 bottle.

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. Note that tensile strength, initial elastic modulus, creep, dynamic viscoelasticity, and small-angle X-ray scattering 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 curve It was determined from the slope at the origin.

Creep measurement conditions Measurement atmosphere: 50℃ Load: 4.5g/d Incidentally, creep was determined using the following formula.

L9: Initial length immediately after applying a load to the sample) L: Length measured with a load applied to the sample for 24 hours Dynamic viscoelasticity measurement conditions Equipment: Toyo Baldwin DDV-II type Vibration frequency: 110Hz Heating rate = 3℃/min Small-angle X-ray scattering (photography) Measurement conditions Equipment: Ru-200 type X-ray source manufactured by Rigaku Denki Co., Ltd.:
CuKa ray (using Ni filter) X-ray output: 50
KV, 150mA Slit system: 0.3mmφ Camera radius: 400mm Exposure time: 120 minutes Film: Kodak DEF-5 Long period is small angle
It was determined using Bragg's equation from the position of the interference point (or interference line) on the meridian of the line scattering image. If no interference point (or interference line) appears on the meridian, a long period is not recognized.

(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.5. A 0% by weight polyethylene solution was prepared.

After passing this solution through an air layer of 5 mm distance g1 from a nozzle with a hole diameter of 1 mm and 10 holes at 170°C, a spinning bath with a two-layer structure consisting of water in the upper layer and trichlorotrifluoroethane in the lower layer is formed. After cooling, 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 N (water) was 80 m.
m, the thickness of the lower layer (trichloride trifluoride ethane) is 230 mm
And so.

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 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 illumination intensity of 800 W/T1'' for 1 hour.

Next, the one-stage drawn yarn after being irradiated with ultraviolet rays was further stretched 6.5 times using a hot plate at 145° C., and as a result, a drawn yarn with the following yarn 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 γ dispersion peak height of tan δ: 0.012 E' at 100°C: 1180 g/d long period
A load of 4.5 g/d was applied to this drawn yarn and it was left at 50° C. for 24 hours, but the creep was as small as 0.19%.

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

The resulting stretched system had a strength of 56 g/d and a Young's modulus of 1830.
It showed high physical properties of g/d, but the creep was high at 3.2%. Other physical properties are as follows.

γ dispersion peak height of tan δ: 0.009 E' at 100°C: 1420 g/d long period
: Not observed (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 drawn yarn 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%.

(Effects of the Invention) As described above, the novel polyethylene fiber of the present invention has high strength and high modulus of elasticity, and has low creep, so it is very useful as an industrial fiber material.

Claims (2)

[Claims] (1) Weight average molecular weight is 700,000 or more, and at 50℃
．． Creep of 2.0% or less when placed under a load of 5 g/d for 24 hours, single yarn strength of 40 g/d or more, 12
It has a single filament initial elastic modulus of 00 g/d or more, and no long-period structure is observed in small-angle X-ray scattering measurements, and the height of the tan δ γ dispersion peak in dynamic viscoelasticity measurements is 0.020 or less. and a dynamic viscoelastic modulus E' at 100° C. of 600 g/d or more. (2) The novel polyethylene fiber according to claim (1), characterized in that the single yarn fineness is 3d or less.