JPH0782606A - Composition for forming polyethylene fiber - Google Patents

Abstract

PURPOSE:To obtain a composition for forming a polyethylene fiber having stable productivity, high strength and high modulus of elasticity. CONSTITUTION:This composition for forming a polythylene fiber is obtained by blending an ethylene/propylene copolymer (A) having >=300,000 weight- average molecular weight and a propylene content of 0.3-2 on the average shown as the number of side chains based on 1,000 carbons with an ethylene/ propylene copolymer (B) having >=800,000 weight-average molecular weight and a propylene content of 0.3-3 shown as the number of side chains based on 1,000 carbons in the molecular weight ratio of the component (B/A) of >=1.5 and the weight ratio of the component (A):(B)=50:50 to 95:5. A high-strength polythylene fiber is obtaines at a low draw ratio and the polythylene fiber is excellent even in the maximum achievable strength.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for molding a novel polyethylene fiber having stable productivity, high strength and high elastic modulus.

[0002]

2. Description of the Related Art Polyethylene fibers are light and have excellent chemical resistance and are relatively inexpensive, and have excellent properties as an industrial fiber material. In recent years, there has been a demand for a fiber material that is lightweight, has high strength, and has a high elastic modulus in order to respond to energy saving and high functionality of products using it as an industrial fiber material. As a method for producing a polyethylene fiber satisfying this requirement, a fiber material having very high strength and elastic modulus is prepared from a high molecular weight or ultra high molecular weight polyethylene having a weight average molecular weight of hundreds of thousands to several millions as a raw material. It has been developed (for example, JP-A-56-15408 and JP-A-55-107506).

The high-strength, high-modulus polyethylene fibers obtained by the method disclosed in the above-mentioned prior art are used for industrial fiber applications requiring particularly high strength and high modulus due to their properties, such as ropes, slings, and various types. It is expected to be useful as a rubber reinforcing agent, a reinforcing agent for various resins, a concrete reinforcing agent, and the like, and in some fields, practical application is progressing.

However, in the above method, in order to realize high strength and high elastic modulus, stretching is carried out at a draw ratio of 80% or more with respect to the limit draw ratio to realize high strength and high elastic modulus. Therefore, it cannot be said that the stability of production in producing fibers is very good, and as a result, the production cost is increased.

The following methods are available for producing a stretched filament or a stretched tape having a high strength and a high elastic modulus from ultrahigh molecular weight polyethylene. (A) Japanese Patent Publication No. 60-47922: Concentrations 1 to 3
A 0 wt% hot polyolefin solution is spun. (B) JP-A-60-101032: An aggregate of gel-like particles obtained by dissolving a polyethylene solution is compression-molded at a temperature not higher than the melting temperature. (C) JP-A-58-217322: A single crystal aggregate mat obtained from a polyethylene solution having a concentration of 1% or less is extruded at 70 to 135 ° C. (D) Japanese Examined Patent Publication No. 60-53690: A melt-molded product of ultra-high molecular weight polyethylene is stretched at a temperature of 150 ° C or higher. (E) JP-A-63-265619: A polyethylene mixture having a concentration of 51 to 90% is molded by applying pressure at a temperature lower than its melting point, and then hot drawing is performed.

According to the method disclosed in Japanese Patent Laid-Open No. 63-265619, the stretching ratio is 15 to 16 times and the strength is 1.4 to 1.6 GPa in order to realize high strength and high elastic modulus. Even with 28 times the strength, only a strength of 2.0 GPa was obtained. Further, although the limit draw ratio is not specified, the draw ratio at which the highest strength is obtained is considered to be the limit draw ratio at which stable stretching can be performed, and therefore the limit draw ratio itself is also considered to be low.

In most of these inventions, a single raw material is used as the raw material, and even if any dispersant is used for the uniformity of the raw material, the dispersant is extracted at the stretching stage in order to develop the strength. Therefore, the formability changes depending on the number of entangled molecular chains. As a prescription for suppressing and improving this, it is stated that the concentration of polyethylene is made as low as possible at the stage of obtaining the first undrawn yarn. However, this method cannot be said to be a method for producing polyethylene fibers, which aims to reduce the production capacity, consequently improve the moldability, and achieve high strength and high elastic modulus.

Further, as proposed in Japanese Patent Laid-Open No. 177036/1982, the molecular weight is 5000 to 2000.
A production method is known in which 10 to 60 parts by weight of low molecular weight polyethylene of 0 is added to 100 parts by weight of ultra high molecular weight polyethylene. It cannot be drawn at a magnification, and as a result, it is not possible to obtain a monofilament having high strength and high elastic modulus.

As a blend of two kinds of ultra high molecular weight polyethylene, JP-A-64-38439 discloses a viscosity average molecular weight of 500,000 or more and 100 carbon atoms in the main chain.
Ultra-high molecular weight polyethylene having less than 2 branches per 0, and a main chain carbon atom with a viscosity average molecular weight of 500,000 or more 1
It is disclosed that a molded product obtained from a blended product with an ultrahigh molecular weight polyethylene having 4 or more branches per 000 is highly resistant to creep.

Further, in Japanese Patent Application Laid-Open No. 1-162819, polyethylene having a weight average molecular weight of 5,000,000 or more is replaced with polyethylene having a weight average molecular weight of 600,000 or more by 5 to 5.
A polyethylene fiber having a high strength and a high elastic modulus and low creep by spinning a solution of 0% mixed polyethylene having a weight average molecular weight of 700,000 to 4,000,000 and thermally stretching the obtained undrawn yarn. Is disclosed.

As seen in these prior arts, it is known to combine a plurality of ethylene polymers to form a polyethylene fiber having high strength, high elastic modulus and creep resistance. In all of these techniques, the purpose is to improve the mechanical strength, and no attempts have been made to find a composition that improves moldability and enables high stretching.

[0012]

In view of the above, the present invention is divided into a structure mainly responsible for improving the moldability of polyethylene used as a raw material and a structure for exhibiting high strength and high elastic modulus. To improve the moldability or productivity in drawing and to obtain a new finding that a composition for polyethylene fiber having high strength and high elastic modulus can be obtained by mixing these as raw materials. I arrived. Therefore, an object of the present invention is to provide a composition for improving the moldability or productivity in stretching and molding a polyethylene fiber having high strength and high elastic modulus.

[0013]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object and comprises two kinds of ethylene / ethylene having a specific weight average molecular weight and propylene content.
It is characterized in that a propylene copolymer is mixed at a specific ratio. That is, according to the present invention, the weight average molecular weight is 300,000 or more and the propylene content is 10 carbon atoms.
An ethylene / propylene copolymer (A) having an average of 0.3 to 2 in terms of the number of side chains per 00, a weight average molecular weight of 800,000 or more, and a propylene content of 100 carbon atoms.
An ethylene / propylene copolymer (B) having an average of 0.3 to 3 in terms of the number of side chains per 0;
And the molecular weight ratio (B / A) of (B) is 1.5 or more, (A):
There is provided a polyethylene fiber molding composition having a high strength, a high elastic modulus and a very excellent moldability, which is mixed in a ratio of (B) = 50: 50 to 95: 5 (weight ratio).

[0014]

[Detailed Description of the Invention]

< Ethylene / Propylene Copolymer (A) > The raw material ethylene / propylene copolymer (A) used in the composition of the present invention uses a Ziegler catalyst and contains ethylene and propylene as a comonomer, for example, an organic solvent. Obtained by slurry polymerization in. When, for example, an ethylene homopolymer is used instead of the ethylene / propylene copolymer (A), there arises a disadvantage that the stretchability is extremely poor in the preparation of the molecular oriented body.

This ethylene / propylene copolymer (A)
Has a weight average molecular weight of 300,000 Kg / Kmol or more, preferably 500,000 Kg / Kmol or more. That is, since the molecular ends do not contribute to the fiber strength and the number of the molecular ends is the reciprocal of the molecular weight, the higher the molecular weight, the higher the strength. This weight average molecular weight is 135 ° C for the decalin solution.
From the intrinsic viscosity [η] at, for example, the Chang equation (J.
Polymer Sci. , Vol. 36, 91 (19
59)), and can be directly measured by GPC / LALS or the like.

In the present invention, the propylene content of the ethylene / propylene copolymer (A) is changed to the methyl side chain of propylene introduced into the ethylene chain in order to obtain excellent moldability, strength and elastic modulus. It is desirable that the average number is 0.3 to 2, preferably 0.3 to 1 per 1000 carbon atoms in the main chain, expressed as the number observed as

The number of such methyl group side chains can be quantified by using an infrared spectrophotometer. That is, it represents the bending vibration of the methyl group incorporated in the ethylene chain.
The absorbance at 78 cm ^-1 was measured, and this absorbance was quantified by converting it into the number of methyl branches per 1000 carbon atoms with a calibration curve prepared in advance using a model compound with a ¹³ C nuclear magnetic resonance apparatus (NMR). Can be done. Of course, it is also possible to directly quantify by ¹³ C NMR.

< Ethylene / Propylene Copolymer (B) >
In the present invention, the ethylene / propylene copolymer (B) is used as a raw material together with the above-mentioned ethylene / propylene copolymer (A).

This ethylene / propylene copolymer (B)
Can be obtained by slurry polymerization, for example, in an organic solvent using a Ziegler type catalyst as in the case of the copolymer (A). When, for example, an ethylene homopolymer is used instead of the ethylene / propylene copolymer (B), there arises a disadvantage that the stretchability is extremely poor in the preparation of the molecular oriented body.

This ethylene / propylene copolymer (B)
Has a weight average molecular weight of 800,000 Kg / Kmol or more, preferably 1,000,000 Kg / Kmol or more. That is,
Since the molecular ends do not contribute to the fiber strength and the number of the molecular ends is the reciprocal of the molecular weight, the higher the molecular weight, the higher the strength.

Also in this copolymer (B), the propylene content of this ethylene / propylene copolymer (B) is introduced into the ethylene chain in order to obtain excellent moldability, strength and elastic modulus. The average number of carbon atoms in the main chain is 0.3 to 3, preferably 0.3 to 1.5 per 1,000 carbon atoms in the main chain, expressed as the number of methyl side chains of propylene.
It is desirable to be individual.

Quantification of this number can be carried out using an infrared spectrophotometer, as in the case of the copolymer (A). That is, the absorbance at 1378 cm ^-1 , which represents the bending vibration of the methyl group incorporated in the ethylene chain, was measured, and this absorbance was measured by a calibration curve prepared using a model compound in advance by a ¹³ C nuclear magnetic resonance apparatus (NMR). Quantification can be performed by converting the number of methyl branches per 1000 carbon atoms. Of course, it is also possible to directly quantify by ¹³ C NMR.

The most important technical features of the present invention are:
By blending the copolymer (A) having excellent stretch moldability and the copolymer (B) having excellent mechanical properties such as strength and elastic modulus under appropriate conditions, the moldability and tensile properties can be improved. The point is to find a raw material composition having an appropriate composition distribution suitable for obtaining a well-balanced polyethylene fiber.

That is, the composition of the present invention can have an appropriate composition distribution and molecular weight distribution by blending two kinds of copolymers having different weight average molecular weights but having similar compositions. A polyethylene fiber having excellent moldability and tensile properties can be obtained.

Polyethylene fiber molded using the composition of the present invention comprises the above-mentioned copolymers (A) and (B),
When the molecular weight ratio of (A) and (B) is 1.5 or more, (A):
(B) = 50:50 to 95: 5 (weight ratio), preferably 70:30 to 90:10 (weight ratio), the blended mixture is melt-molded, and the resulting molded body is stretched. It can be manufactured by For example, when the amount of the copolymer (A) used is more than the above range, the tensile properties tend to be poor, and when it is less than the above range, the moldability tends to deteriorate.

In this melt molding, a diluent is used together with the above copolymers (A) and (B). As such a diluent, a solvent for the high molecular weight ethylene copolymer and various wax-like substances having dispersibility in the high molecular weight ethylene copolymer are preferably used.

The solvent is preferably a solvent having a boiling point not lower than the melting point of the polymer, more preferably not lower than the melting point + 20 ° C.

Specific examples of the solvent include n-nonane, n-decane, n-undecane, n-dodecane and n-
Aliphatic hydrocarbon solvents such as tetradecane, n-octadecane or liquid paraffin, kerosene, xylene, naphthalene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, benzylbenzene, dodecylbenzene, bicyclohexyl, decalin, methyl Aromatic hydrocarbon solvents such as naphthalene and ethylnaphthalene or hydrogenated derivatives thereof, 1, 1, 2,
2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,2,3, -trichloropropane, dichlorobenzene, 1,2,4, -trichlorobenzene,
Examples thereof include halogenated hydrocarbon solvents such as bromobenzene, paraffin-based process oils, naphthene-based process oils, and aromatic-based process oils.

As the wax, an aliphatic hydrocarbon compound or its derivative is used.

The aliphatic hydrocarbon compound is mainly composed of a saturated aliphatic hydrocarbon compound and usually has a molecular weight of 2
000 or less, preferably 1000 or less, more preferably 800 or less, which is called paraffin wax. Specific examples of these aliphatic hydrocarbon compounds include n-alkanes having 22 or more carbon atoms such as docosane, tricosane, tetracosane, and triacontane, or mixtures with lower n-alkanes containing these as the main components, and separation and purification from petroleum. So-called paraffin wax, low molecular weight polymer obtained by copolymerizing ethylene or ethylene or other α-olefin, polyethylene wax for medium / low pressure method, polyethylene wax for high pressure method, ethylene copolymer wax or medium / low pressure method Examples thereof include waxes obtained by reducing the molecular weight of polyethylene such as polyethylene and high-pressure polyethylene by thermal degradation, oxides of these waxes, oxidized waxes such as maleic acid-modified waxes, and maleic acid-modified waxes.

The aliphatic hydrocarbon compound derivative is, for example, one or more, preferably 1 or 2, and particularly preferably 1 at the terminal or inside of the aliphatic hydrocarbon group (alkyl group, alkenyl group). A compound having a functional group such as a carboxyl group, a hydroxyl group, a carbamoyl group, an ester group, a mercapto group and a carbonyl group, having 8 or more carbon atoms, preferably 12 to 50 carbon atoms, or a molecular weight of 130 to 2000, preferably 200 to 8
00 fatty acid, fatty alcohol, fatty acid amide, fatty acid ester, aliphatic mercaptan, aliphatic aldehyde,
Examples thereof include aliphatic ketones.

Specifically, as the fatty acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, as the aliphatic alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and as the aliphatic amide, capric amide. , Laurinamide, palmitinamide, stearylamide, and stearyl acetic acid ester as an aliphatic ester.

The ratio of the high molecular weight polyolefin to the diluent varies depending on their kind, but is generally 3:97 to 80:20, and particularly 15:85 to 6.
It is preferable to use it in a weight ratio of 0:40. When the amount of the diluent is lower than the above range, the melt viscosity becomes too high, which makes melt-kneading and melt-molding difficult, and the surface of the molded article is significantly roughened. On the other hand, if the amount of diluent is more than the above range,
After all, melt-kneading becomes difficult, and the stretchability of the molded product becomes poor.

Melt kneading is generally 150 to 300.
It is desirable to carry out at a temperature of ℃, especially 170 to 270 ℃, at a temperature lower than the above range, the melt viscosity is too high, it becomes difficult to melt molding in the next step, and if it is higher than the above range, Due to the thermal degradation, the molecular weight of the high molecular weight polyolefin is lowered, and it becomes difficult to obtain a molded product having a high elastic modulus and high strength. The blending may be performed by dry blending with a Henschel mixer, a V-type blender, or the like, or by melt mixing using a single-screw or multi-screw extruder.

The melt molding is generally carried out by melt extrusion molding. For example, a filament for stretching is obtained by melt extrusion through a spinneret, and a tape for stretching is obtained by extruding through a flat die or a ring die. At this time, the melt extruded from the spinneret can be drafted, that is, stretched in a molten state. The ratio between the extrusion speed V ₀ of the molten resin in the die orifice and the winding speed V of the unstretched material that has been cooled and solidified can be defined as the draft ratio by the following equation. Draft ratio = V / V ₀ Such a draft ratio varies depending on the temperature of the mixture and the molecular weight of the high molecular weight ethylene polymer, but is usually 3
Or more, preferably 6 or more.

The unstretched molded product of high molecular weight polyethylene thus obtained is stretched. The stretching operation can be performed in one stage or in multiple stages of two or more stages. The stretching operation can be carried out so that the stretching ratio is 2 to 10 times, particularly 3 to 8 times. The temperature of the drawing tank is set to 105 to 147 ° C. in the case of carrying out one step, and the temperature of the first drawing tank is set to 105 in the case of carrying out in two or more steps.
It is desirable that the temperature of the subsequent drawing tanks adjacent to each other be set to 1 ° C. or higher, preferably 2 to 10 ° C.

As described above, the stretching operation is carried out using a heat source such as a heat medium, an oven, a hot plate, far infrared rays, or microwave irradiation. In particular, a method using a heat medium is preferable. It is preferable and recommended because it allows accurate and stable temperature control. Examples of the heat medium include n-decane,
Examples include triethylene glycol, paraffin-based process oil, silicone oil and the like.

The high molecular weight polyethylene fibers thus obtained can be heat-treated under restraint conditions if desired.
This heat treatment is generally 140 to 180 ° C., especially 15
At a temperature of 0 to 175 ° C. for 1 to 20 minutes, especially 3
It can be carried out for 10 minutes. The heat treatment further promotes the crystallization of the oriented crystal part, which leads to the shift of the crystal melting temperature to the high temperature side, the improvement of the strength and the elastic modulus, and the improvement of the creep resistance at high temperature.

The process of molecular orientation in the molded body can be known by X-ray diffraction method, birefringence method, fluorescence polarization method and the like. In the case of the stretched filaments of the high molecular weight ethylene polymer of the present invention, for example, Yukichi Kure and Kouichiro Kubo: Industrial Chemistry Magazine No. 3
Vol. 9, p. 929 (1939), the degree of orientation according to the full width at half maximum, that is, the formula In the formula, H ° is the half width (°) of the intensity distribution curve along the Debye ring of the strongest paratropic plane on the equator line. It is desirable in terms of mechanical properties that the molecular orientation is such that the degree of orientation (F) defined by is 0.90 or more, particularly 0.95 or more.

[0040]

EFFECTS OF THE INVENTION According to the present invention, there is provided a raw material composition for improving the formability or productivity in drawing and obtaining a polyethylene fiber having an excellent balance of formability and strength.

[0041]

EXAMPLES The present invention will be described below with reference to examples, which are for explaining the preferred embodiments of the present invention. As long as the technical idea of the invention is not exceeded, the present invention It is not limited.

<Examples 1 to 3＞ <Raw materials> Ethylene / propylene copolymer (A)
And the weight average molecular weight is 7.3 × 10. ^Five And
The carbon content is expressed as the number of side chains per 1000 carbons and is flat.
Use an average of 1.0.

Further, ethylene / propylene copolymer (B)
The weight average molecular weight is 1.5 × 10 ⁶ and the average propylene content is 1.0, which is represented by the number of side chains per 1000 carbon atoms.

The above copolymers (A) and (B) were mixed in the weight ratio shown in Table 1 below to prepare raw materials 1 to 3.

<Spinning-Drawing Step> After melting, paraffin wax (trade name: Lubax, manufactured by Nippon Seiro, melting point = 69 ° C.) kept at 90 ° C. and each raw material were mixed at a weight ratio of 20:80. Melt spinning was performed under the following conditions.

First, 3,5-dimethyl-tert-butyl-4-hydroxytoluene was added to this mixture as a process stabilizer in an amount of 0.1 to 3100 parts by weight of raw materials.
It was compounded in parts by weight. Next, co-rotating twin-screw extruder (Plastics Engineering Laboratory: screw diameter = 3)
9 mm, L / D = 42), and the set temperature is set by the supply unit 9
0 ° C., 195 ° C. in other parts, and screw rotation speed 100 r. p. m. Melt kneading was carried out with a residence time of 5 minutes. Subsequently, the obtained mixed melt was extruded and spun through a die having a orifice of 2.0 mm and 100 holes (temperature: 175 ° C.). The spun fiber was taken at a draft ratio of 45 times with an air gap of 150 cm, and cooled and solidified with air at room temperature to obtain an undrawn yarn.

The 100 spun raw yarns thus obtained were wound and drawn under the following conditions to obtain drawn fibers.

That is, two-stage drawing was carried out by using four godet rolls in a drawing tank using n-decane as a heating medium.
The temperature of the first drawing tank was 105 ° C, and the temperature of the second drawing tank was 115 ° C.

The stretching ratio at this time was 6.0 times in the first stretching tank and 1.25 times in the second stretching tank, and the effective length of the tank was the first.
Both the drawing tank and the second drawing tank had a length of 6 m.

At the time of drawing, the rotational speed of the first godet roll was set to 5 m / min, and the rotational speeds of the second and third godet rolls were appropriately changed to obtain a drawn fiber having a desired draw ratio. In addition, a drying zone having a temperature of 110 ° C. and an effective length of 50 m was provided between the third godet roll and the fourth godet roll, and the amount of n-decane in the fiber was adjusted to 1% by weight with respect to the high molecular weight polyethylene fiber, and then wound. I took it.

<Redrawing Step> The drawn fiber wound as described above was subjected to two-step drawing using three godet rolls in a drawing tank using triethylene glycol as a heating medium. At this time, the temperature of the third stretching tank was 145 ° C, and the temperature of the fourth stretching tank was 148 ° C. The draw ratio is the ratio of the yarn feeding speed to the winding speed, and the fiber having a desired draw ratio was obtained by changing the rotation speed of the final godet roll. The effective length of the tank was 5 m in both the third drawing tank and the fourth drawing tank. The yarn feeding speed was 37.5 m / min.

The limiting stretch ratio and the tensile properties (the maximum strength and the stretch ratio that gives a strength of 2.5 GPa) of the obtained stretched fiber were measured, and the results are shown in Table 2.

The tensile strength, tensile modulus and elongation at break of the obtained drawn fiber were measured at room temperature (23 ° C.) using an Intesco universal testing machine 2005 type (manufactured by Intesco).
The sample length between the clamps is 254 mm and the pulling speed is 254
mm / min. However, the tensile modulus is the initial modulus. The fiber cross-sectional area required for the calculation was obtained by measuring the weight and length of the fiber with the density of polyethylene being 0.96 g / cm ³ .

[0054]

< Comparative Example ><Rawmaterial> As a raw material, an ethylene / propylene copolymer having a weight average molecular weight of 7.3 × 10 ⁵ and a propylene content of 1000 side chains per 1000 carbon atoms is represented. An average of 1.0 pieces was used.

<Spinning-Drawing Step> High-molecular-weight polyethylene fibers were spun and drawn in the same manner as in the examples.

<Redrawing Step> The high molecular weight polyethylene fiber was redrawn in the same manner as in the example. Table 3 shows the physical properties of the obtained yarn.

[0058]

As is clear from the results of Examples and Comparative Examples, when a blended product of two specific types of ethylene / propylene copolymers is used as a raw material, high strength can be obtained at a low draw ratio, so that the moldability is improved. Is much better than a single source. Further, it is understood that the blended raw material also exceeds the ultimate strength.

Claims (1)

[Claims] 1. An ethylene / propylene copolymer (A) having a weight average molecular weight of 300,000 or more and a propylene content of 0.3 to 2 on average in terms of the number of side chains per 1000 carbon atoms, An ethylene / propylene copolymer (B) having a weight average molecular weight of 800,000 or more and a propylene content of 0.3 to 3 on average in terms of the number of side chains per 1000 carbon atoms; Molecular weight ratio of (B) (B / A)
Is 1.5 or more, and (A) :( B) = 50: 50 to 9
A polyethylene fiber molding composition, which is mixed in a ratio of 5: 5 (weight ratio).