JPH04209817A - High strength polyethylene fiber having creep resistance - Google Patents

Abstract

PURPOSE:To provide the subject fiber comprising PE polymer having an ultrahigh mol.wt. and having specific strength, specific elastic modulus, specific creep rate, and good creep resistance. CONSTITUTION:The objective fiber comprising a polymer consisting mainly of an ultrahigh mol.wt. PE having a viscosity-average mol.wt. of >=500000, preferably >=1500000, and having a strength of >=25g/d, an elastic modulus of >=800g/d, and a creep rate of <=5X10<-6> sec<-1> under a load of 9g/d at 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to high strength polyethylene fibers having very good creep resistance.

[Conventional technology]

In recent years, attempts have been made to obtain polyethylene fibers with high strength and high elastic modulus using so-called ultra-high molecular weight polyethylene, which has a viscosity average molecular weight of several hundred thousand to several million, as a raw material. Polyethylene fibers having very high strength and elastic modulus have been developed (see, for example, JP-A-56-15408 and JP-A-55-107506).

The reason why ultra-high molecular weight polyethylene was first developed to be highly strong as a flexible polymer material is that its secondary structure is extremely simple; however, polyethylene does not have hydrogen bonds between its molecular chains. The drawback was that it was easy to greep. These drawbacks have severely limited the range of use of polyethylene fibers in applications where loads are applied for long periods of time.

Conventionally, as an attempt to improve the creep resistance of polyethylene II apa, studies have been made to introduce crosslinks between molecular chains by means such as thermal means or electron beam irradiation, with or without adding a crosslinking agent. However, it is extremely difficult to introduce crosslinking while maintaining the high strength of polyethylene fibers, and it is currently impossible to achieve both creep resistance and high strength.

Furthermore, JP-A No. 61-28911 states that the creep resistance of polyethylene fibers is improved by post-stretching or heat treatment, but due to the very slow stretching and complicated process, economic efficiency and productivity are low. There was a problem from this point of view.

[Problem to be solved by the invention]

As a result of extensive studies, the inventors of the present invention have found that the less disordered the crystal structure of polyethylene fibers and the less impurities other than polyethylene, the better the creep resistance, and have completed the present invention.

Therefore, an object of the present invention is to provide a high-strength polyethylene fiber having high strength, high modulus of elasticity, and unprecedentedly excellent creep resistance, and a method for producing the same. Means for Achieving] The present invention consists essentially of a polymer whose main component is ultra-high molecular weight polyethylene with a viscosity average molecular weight IL of 500,000 or more, and a degree of perfectness of 25! %/d or more, and a polyethylene fiber having an elastic modulus of 800 g/d or more, a creep-resistant high-strength polyethylene whose creep rate under a load of 50°C and 9y-/d is 5 x 10""5ee-' or less It is a fiber.

The present invention will be explained in detail below.

In order to produce fibers with high strength and high elastic modulus using ultra-high molecular weight polyethylene, which is a flexible polymer and has a viscosity average molecular weight of 500,000 or more, how can the molecular chains be aligned long and uniformly? However, since the polyethylene molecule itself is actually flexible, crystallization progresses with the molecular chains intertwined with each other and the molecular chains folded. It is difficult to produce moth fibers using melt extrusion technology. Such folds and molecular terminals exist as amorphous parts, but when 2n is incorporated into the crystal, they become defects within the crystal. High-strength polyethylene stretched products, especially 4
Regarding the structure of ila, a model that assumes that it is a single-layer system in which amorphous parts (defects) are unevenly distributed in the crystal is becoming popular, but as a method to quantitatively describe such crystal disorder, the Hoseman plot (FlosemannPl
ot).

The inventor investigated in detail the relationship between this g value, other defects in the crystal, impurities other than polyethylene, and creep characteristics, and found that the more disordered the crystal, the more the residual solvent and additives It has been found that the more impurities there are, the worse the creep resistance is. The cause of this is not clear, but the dominant factor may be that disorder within the crystal causes weaker intermolecular forces and promotes slippage between molecular chains, or that dislocations that cause these defects to move together with creep are the dominant factors. Presumed.

From this point of view, as described below, we have discovered a method for producing ultra-high molecular weight polyethylene that has not been considered until now, has more perfect T crystals, and does not contain impurities.
We succeeded in obtaining high-strength polyethylene fiber vertebrae that have creep resistance that has not been available in the past. here! J key n
It all comes from the truth! The ultra-high molecular weight polyethylene*i produced by the above-mentioned ultra-high molecular weight polyethylene*i not only has improved creep resistance, but also maintains the high strength and high elastic modulus inherent to ultra-high molecular weight polyethylene fibers.

The polyethylene-based polymer used in the present invention may be polyethylene alone or ethylene and other α
- It may be a copolymer with an olefin such as propylene, butene, etc., or it may be a blend of a polyethylene homopolymer and these polyethylene copolymers. Introducing methyl and ethyl w'@ flanks into the main chain of the polymer is effective in improving creep resistance, but 3
If 11@ increases too much, the stretchability during the production of bottle fibers will be significantly lowered, and physical properties such as strength will be significantly lowered, which is not preferable.

Therefore, from the viewpoint of high strength and high elastic modulus, which are the objectives of the present invention, the side chain components introduced by the polyethylene copolymer that can be used or the polyethylene copolymer mixed as a blend should not be too large, such as methyl groups or ethyl groups. It is preferable that it is not bulky, and the content rate is 1 per 1000 earthen carbon.
It is preferable that it is below.

The above-mentioned polyethylene-based polymer used in the present invention needs to have a viscosity average molecular weight of 500,000 or more, preferably 1,000,000 or more, and more preferably 1,500,000 or more.

Such ultra-high molecular weight is an essential requirement for producing high-strength polyethylene fibers, and this has the effect of reducing defects originating from the molecular ends due to the low range of molecular ends due to the high molecular weight.

As mentioned above, it is difficult to produce high-strength polyethylene fibers using a polymer whose main component is ultra-high molecular weight polyethylene as described above using the normal melt spinning method. For this reason, one suitable method is, for example,
There is a method generally known as a "gel spinning method" using a solvent, as disclosed in Japanese Patent No. 5-107506. According to this gel spinning method, polyethylene fibers having a strength of 2511/d or more and an elastic modulus of 80 Gli/d or more can be obtained. However, it has the disadvantage of poor creep resistance. This is due to the presence of defects and impurities within the fiber crystals, as described above.

Therefore, it has been found that the following is important in order to reduce defects and impurities in the crystal of ** as much as possible and improve creep resistance.

First, in order to obtain polyethylene fibers with excellent creep resistance according to the present invention, residual components other than the polyethylene-based polymer contained in the polyethylene fibers, specifically solvents and additives, must be 1 o o o pp
It was found that it is important that the distance be less than m. When the residual component exceeds 1000 pp-, the creep resistance deteriorates significantly.

Since the gel spinning method is suitable for the production of polyethylene fibers according to the present invention, a large amount of solvent is necessarily used as described below. Therefore, the residual component is mainly the solvent used. If additives other than those for cutting are also used, the residual components including these must be kept at 1000 ppm or less. Such non-cutting additives include antioxidants that are added during the fiber manufacturing process to prevent molecular degradation. However, when producing the polyethylene fibers of the present invention, the heating atmosphere is maintained in a substantially oxygen-free state in a screw extruder when mixing and dissolving a mixture of a solvent and a polymer component, specifically at 150 wH.
It has been found that if the pressure is reduced to P or less, the same effect can be obtained without using snow formation prevention. Therefore, it is preferable not to use antioxidants. It is also preferable not to use other common additives as much as possible.

In the method of the present invention, as mentioned above, the viscosity average molecular weight is 50
Using a polymer whose main component is over 10,000 polyethylene,
In order to perform spinning using the gel V yarn method, a mixture of the above polymer components and a solvent is used as a raw material mixture for spinning. The ratio of the polymer component to the solvent varies depending on the molecular weight of the polymer component and the type of solvent used, but it is usually 95 to 20 parts by weight of the solvent to 5 to 20 parts by weight of the polymer component.

As for the solvent that can be used, the ratio of the residual component, that is, the solvent component and the additive in the finally formed fiber is as described above.
10001)1)! 1 or less, it is essential to use a volatile solvent whose melting point is lower than the melting point of the polymer component, whose boiling point is 15°C or more higher than the core temperature of the polymer component, and preferably at a temperature of 15°C or less. It is best to use one that is not much higher than ℃.

Solvents that can be used vary depending on the molecular weight of the raw material polyethylene, and include, for example, decalin, tetralin, dichlorobenzene, naphthalene, and mixtures thereof.

In the present invention, in principle, it is preferable to use a mixture consisting only of the above-mentioned ultra-high molecular weight polymer component and a solvent as the spinning saliva.

In the method of the present invention, a t1-mixture containing the above-mentioned polymer component and solvent component is passed through a screw extruder for 150 m
The mixture is supplied under a reduced pressure of tmg or less, after which the seeds are thoroughly mixed and dissolved, and after being extruded from a spinning nozzle, the obtained gel-like unrolled yarn is heated to remove the solvent,
The undrawn yarn is stretched simultaneously with the heating or by tearing it apart.

The undrawn yarn obtained after the above extrusion was heated to 90°C or higher,
Preferably, the heating is carried out at 100 to 130° C. for a residence time of 0.5 minutes or more, preferably 0.7 minutes or more. Further, the stretching may be carried out 3 times or more, preferably 4 times or more.

When producing polyethylene fibers using a mixture of a polymer containing ultra-high molecular weight polyethylene as a main component and a solvent, removing the solvent is described in, for example, JP-A-58-5228.
However, the purpose of this invention is to improve the operability of the subsequent stretching process, and no consideration is given to residual solvent at all. Therefore, no consideration is given to improving creep resistance.

The polyethylene 44 according to the present invention is required to have a small amount of residue as described above, and also to have IIa in which the crystal grooves in the tungsten are well-defined and less disordered. For example, X-Ray Diff is a measurement method that expresses crystal disorder.
ration Methods impoiymer
5science, ? , 4 2 4, L
E. Alexander.

Robert K., Krieger Publishing
ing Cotspany, Inc.

Wide-angle
semann Plot). The fiber according to the present invention has a g value of 0.035 or less and has very little structural disorder, which is considered to be one of the reasons for the low creep property.

The most important factor in creating a structure with less turbulence is the melting conditions inside the screw, and the g value is 0.
．． It is necessary to select a screw rotation speed and temperature that will achieve sufficiently uniform heating so that the temperature is 0.035 or less.

Also, the degree of solution is important, and the fraction of polymer components is 5-20%, preferably 5-12.5tt! It is important that the time is 1s. As the humidity increases, molecular entanglement increases, resulting in defects within the crystal.

As mentioned above, the present invention provides a method for reducing the residual amount of other components in the polyethylene magnet to be formed. It has excellent creep resistance only due to the synergistic effect of having an IT fraction of 11,000 pp or more and a y value of 0.035 or less according to Hoseman plot.

That is, the polyethylene 4 according to the present invention has a strength of 25 g/d or more that conventional ultra-high molecular weight polyethylene fibers, 8
Possesses an elastic modulus of 009/d or more, and also has an elasticity of 97% at 50°C.
Creep rate measured under 7/d load (CRY 50
) is less than 5 x 10-@5ec-' and has excellent creep resistance.

[Effect]

According to the present invention, the residual components, especially solvents and additives, in the fiber made from a polymer whose main component is ultra-high molecular weight polyethylene are reduced to 10001) I) 1 m or less, and the crystal structure is made less disordered. By doing so, a high-strength polyethylene resin with excellent creep resistance can be obtained.

[One Practical Example] The present invention will be explained below by giving one practical example. The method of measuring the g value and the creep rate was as follows.

Method for measuring g-Ra7The 9 values used in this specification are, for example, X-Ra7Dif
Fraction Methods in I'oly
mer 5science.

P,424,L,K,Alexander,Rob
ert E, rieger Publishing C
The measurement is carried out using a method known as the Hosemann plot described in OA+Pany, Inc. The method is as follows. Wide angle X* perpendicular to the axis
Measure the diffraction curve (for details on the appropriate method at this time, especially various corrections such as scattering angle, etc., please refer to "X
(See “Trenches Crystallography (Supervised by Isamu Nita)”).

The integrals @B of the (110) and (220) peaks of the obtained scattering curve are calculated, and B, 1. and B□.

shall be. However, each of these B values includes the peak spread b that is unique to the device, so it is corrected as follows (indicated by B□). The squared value of B thus corrected is calculated as the surface index ( h) to the fourth power. The I value can be calculated from the slope and intercept of the straight line passing through the image point using the following equation.

B”= 1 a”X (1/ N”+ III:'f
h') Here, B=integral width (degree) a: Interplanar spacing of crystal lattice (degree) N: Number of repetitions of lattice within microcrystal Creep rate
al Polymer 5science Volume 22, No. 5
61 (1961). This method is based on the strain rate when the change in strain rate over time after a load is applied to the sample is constant, or when the rate of change is the lowest, that is, the plateau creep (P
deformation speed (lateau creep). In particular, the creep rate (CRV50) in this specification is 50
9. onto a yarn sample adjusted to a temperature of ℃. Apply a load of F/d. The length of the original sample is 1. (m), the length after 2 hours is 1
．． (cm), and the length after 22 hours is I, -), then C
RV 50 (5ee-') is given by the following formula.

CRY 50”(IL)/(20x3600x1.)
Example 1 5 parts by weight of ultra-high molecular weight polyethylene with a viscosity average molecular weight of 1.9 million and 95 parts by weight of decalin were mixed and heated at a temperature of 210°C.
Kneaded and dissolved using a 300 rpm screw extruder,
It was extruded through an orifice with a diameter of 0.5. At this time, the pressure from the ultra-high molecular weight polyethylene solution preparation tank to the extruder was maintained at substantially 150 saaHJiE. The extruded filament is cooled by air flow and 30x
The film was drawn off at a drawing speed of 1/2 min, and then stretched 6 times in an open air chamber adjusted to 100°C. In this case, the average residence time of the filament in the oven was 0.95 minutes. Note that the average residence time (Tr) is expressed by the following formula.

Tr=2L/(VO+RxVO) (Q) where L: Open length - 1vO: Supply speed (m/min) R=Stretching ratio This yarn was subsequently stretched 5 times in a heated atmosphere at a temperature of 100°C, the final volume. The sampling rate was 100 wL/min. The strength of the obtained drawn yarn was 37 g/d, and the elastic modulus was 1580.
It was excellent at 9/d. Furthermore, as a result of analyzing the extract from this drawn yarn using methods such as gas chromatography, it was found that the amount of residue other than the remaining bokethylene was 55 ppm.
Met. The I value, creep rate, and residual solvent fraction are shown in Table 2 below.

Comparative Examples 1 and 2 and Examples 2 to 4 Yarns were produced using the same manufacturing method as in Example 1, except that the screw rotation speed and melting temperature (screw temperature) were changed as shown in Table 1 below. However, when the final stretching ratio was low, stretching was performed at the possible ratio. In Comparative Example 2, paraffin wax (non-volatile) was used as a solvent.

Table 1 Example 5 Ultra-high molecular weight polyethylene with viscosity average molecular @ 1.9 million
A yarn was produced in the same manner as in Example 1, except that the amount of 0 parts by weight and the amount of decahydronaphthalene were 90 parts by weight. The physical properties of the finished yarn are excellent with a strength of 35 g/d% and an elastic modulus of 17209/d.
It was ours.

Comparative Example 3 Ultra-high molecular weight polyethylene with a viscosity average molecular weight of 1.9 million
A yarn was produced in the same manner as in Example 1, except that the amount of 0 parts by weight and the amount of decahydronaphthalene were 70 parts by weight. However, 2
In the second stage of stretching, although the stretching was only possible up to 3 times, a stretched product having physical properties of tensile strength of 31 p/d and elastic modulus of 11209/d was obtained.

Comparative Example 4 A thread was produced in the same manner as in Example 1, except that ultra-high molecular weight polyethylene with a viscosity average molecular weight of 400,000 was used. The physical properties of the obtained yarn include strength 18, p/d, and elastic modulus 800.
It was 9/d, which was unsatisfactory.

Comparative Example 5 A yarn was produced using the same polymer and polymer aKb as in Example 1, and under the same yarn spinning conditions. However, when making the polymer dope, add an antioxidant (trade name: Yoshinox BHTJ, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) to the polymer in an amount of 1 part by weight, and from the dope to the screw supply section,
It was placed under a substantially atmospheric atmosphere. The physical properties of the obtained wA resin are as follows: strength: 3 sy/as; elastic modulus: 1623. It was p/d.

Comparative Example 6 Ultra-high molecular weight polyethylene 15 with a viscosity average molecular weight of 1.9 million
Paraffin wax (melting point 48-5
An undrawn yarn was prepared by extruding a mixture of 85 parts by weight (0°C) and 11 parts by weight under actual conditions of 9'll. This undrawn yarn was drawn five times in an n-hexane drawing tank while extracting paraffin.

Subsequently, the film was stretched 6 times in an open atmosphere at 143°C. The physical properties of the obtained fibers are as follows: strength: 33.9/d%
Elastic modulus x3z3. It was F/d.

Comparative Example 7 The same method as in Example 1 was followed, except that one stage of stretching in three directions was performed with an open zone length of 50 seconds. The residence time Tr in the open state was 0.47 minutes.

The strength was 34 g/d and the elastic modulus was 1390@/d, which were good.

G case and creep speed Table 2 shows the gffi and G of the yarns made in each example and comparative example.
Residual fraction other than polyethylene determined by ClH5 method and 5
It shows the creep rate under a load of 9 i/d at 0°C. In this case (the i value exceeds 0.03 or the residual component is 1000
ppaI) or if the selected conditions are unfavorable due to insufficient dissolution and mixing to form a homogeneous mixture,
It can be seen that the creep rate becomes very large.

Table 2

Claims (1)

[Claims] 1. Consists of a polymer whose main component is ultra-high molecular weight polyethylene with a viscosity average molecular weight of 500,000 or more, and has a strength of 2.
A polyethylene fiber having an elastic modulus of 5 g/d or more and an elastic modulus of 800 g/d or more, characterized in that the creep rate under a load of 9 g/d at 50°C is 5 x 10^-^6 sec^-^1 or less. Creep resistant high strength polyethylene fiber. 2. The polyethylene fiber according to claim 1, wherein the weight fraction of residual solvents and additives other than the polyethylene-based polymer is 1000 ppm or less. 3. The polyethylene according to claim 1 or 2, wherein the polyethylene-based polymer consists only of polyethylene, a copolymer of ethylene and another α-olefin, or a blend of polyethylene and a polyethylene copolymer. fiber. 4. Obtained by wide-angle X-ray measurement of polyethylene fibers (
110) The polyethylene fiber according to any one of claims 1 to 3, which has a g value of 0.035 or less obtained from a Hosemann plot of a surface index and its higher-order peak group.