JPH0465512A - Molecular oriented formed polyethylene having excellent creep resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molecularly oriented molded article, particularly a fiber, which has excellent creep properties and is obtained from a blend of a high molecular weight ethylene/α-olefin copolymer.

(Prior art) In recent years, there have been active attempts to mold high-strength fibers using high-molecular weight or ultra-high molecular weight polyethylene as a raw material, with weight average molecular weights ranging from hundreds of thousands to several million. materials have been developed that have
No. etc.).

The reason why high molecular weight polyethylene was first made highly strong as a visible polymer is that its secondary structure is extremely simple.On the other hand, polyethylene does not have hydrogen bonds between molecules, etc. Moreover, since the repeating units are simple and there is no steric hindrance, slippage between molecular chains easily occurs, resulting in a tendency to creep. These drawbacks have limited the use of high molecular weight polyethylene, particularly in applications where static loads are applied for long periods of time.

Conventionally, attempts have been made to improve the creep properties of high-molecular-weight polyethylene by irradiating it with electron beams to form crosslinks between molecular chains to suppress slippage between the molecular chains. There is a problem in that it is difficult to carry out crosslinking while maintaining the .

Furthermore, the following techniques are known for obtaining polyethylene fibers with improved creep properties from a blend of two different types of polyethylene.

JP-A No. 1-148807 discloses that an ultra-high molecular weight ethylene homopolymer and an ultra-high molecular weight ethylene/α-olefin (carbon number 3 or more) copolymer are combined in a manner that the total content of a-olefin is Contained in a ratio such that the number of side chains per 1000 carbon atoms is on average 0.2 to 5.0, and the overall intrinsic viscosity [n] is 5 di
Disclosed is a polyethylene-based stretched molded article having a composition having a molecular weight of at least /g. It is described that in this stretched molded article, initial elongation is mainly improved, but creep resistance is secondarily improved.

JP-A-64-38439 discloses ultra-high molecular weight polyethylene having a viscosity average molecular weight of 500,000 or more and less than 2 branches per 1000 carbon atoms in the main chain, A creep-resistant, high-strength polyethylene molding comprising a blend of ultra-high molecular weight polyethylene having four or more branches per 1000 carbon atoms is disclosed.

JP-A-1-162819 discloses that polyethylene with a weight average molecular weight of 5 million or more is used as a polyethylene with a weight average molecular weight of 60
A polyethylene solution with a weight average molecular weight of 700,000 to 4,000,000 is mixed in a proportion of 5 to 50%, and the resulting undrawn yarn is hot-stretched. A method for producing polyethylene fibers with low creep is disclosed.

In JP-A No. 63-275711, the intrinsic viscosity [η]
is at least 5 di/g, and the content of total olefins is an average of 1 to 15 carbon atoms per 1000 carbon atoms. A molecularly oriented molded article, particularly a fiber, is disclosed. In this copolymer, two or more α-olefins are used, and the first monomer is an α-olefin selected from propylene and butene-1.
The remaining comonomer is selected from a-olefins having 4 or more carbon atoms.

(Problems to be Solved by the Invention) Both of the above-mentioned prior art techniques address the disadvantages of high-modulus, high-strength polyethylene oriented molded products (especially fibers), namely, their creep resistance compared to other high-performance fibers such as aramid fibers. Although the purpose of these methods is to improve the disadvantage that they are inferior in terms of quality, they have a problem in that they have poor stretchability and it is extremely difficult to achieve high stretching ratios. Also some of these prior art.

Depending on the method, there is also the problem that an ultra-high molecular weight polyethylene polymer having a weight average molecular weight of 100 or more must be used.

Therefore, an object of the present invention is to provide a molecularly oriented molded article, particularly a fiber, which has a better balance between strength and creep resistance than the prior art described above, and also has excellent stretchability.

(Means for Achieving the Object) The molecularly oriented molded article of the present invention has a weight average molecular weight of 300,000 or more, and an average propylene content of 0.3 to 0.3 to 1,000 in terms of the number of side chains per 1000 carbon atoms. The ethylene/propylene copolymer (A) has a weight average molecular weight of 300,000 or more and an α-olefin content of 10 carbon atoms.
The average number of side chains per 0.00 is 0.3 to 4.
A composition obtained by mixing a copolymer (B) of ethylene, which is 1, and an α-olefin having 4 or more carbon atoms, in a ratio of (A): (B) = 10:90 to 90:10 on a weight basis. It consists of

(Preferred Embodiment of the Invention) Ethylene/Propylene Copolymer (A) The raw material ethylene/propylene copolymer (A) used in the present invention is a mixture of ethylene and propylene, which is a comonomer, using a Ziegler catalyst, such as an organic Obtained by slurry polymerization in a solvent. When, for example, an ethylene homopolymer is used instead of the ethylene/propylene copolymer (A), there arises the disadvantage that the stretchability is extremely poor when preparing a molecularly oriented product.

The weight average molecular weight of this ethylene/propylene copolymer (A) is 300,000 kg/kmol or more, preferably 500,000 kg/kmol or more. That is, the molecular ends do not contribute to fiber strength, and the number of molecular ends is the reciprocal of the molecular weight, so the larger the molecular weight, the higher the strength. This weight average molecular weight is determined by the intrinsic viscosity [n
], for example, Chang's equation (J, Polymer
Sci., Vol. 36.91 (195911), and GPC-LAL
It can also be directly measured using S or the like.

In the present invention, this ethylene/propylene copolymer (
The propylene content of A) is on average 0.3 to 2 per 1000 main chain carbon atoms, expressed as the number of methyl side chains of propylene introduced into the ethylene chain;
The number is preferably 0.3 to 1.

The number of methyl group side chains can be determined using an infrared spectrophotometer. That is, 1378 cm-, which represents the bending vibration of the methyl group incorporated into the ethylene chain.
' Measure the absorbance of 13C in advance.
Quantification can be performed by converting into the number of methyl branches per 1000 carbon atoms using a calibration curve created using a model compound using a nuclear magnetic resonance apparatus (NMR). Of course, it is also possible to directly quantify by 13ONMR.

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

This ethylene/α-olefin copolymer (B) is produced by using a Ziegler catalyst in the same way as the copolymer (A).
For example, it can be obtained by slurry polymerization in an organic solvent. As the comonomer α-olefin, those having 4 or more carbon atoms, preferably 4 to 18 carbon atoms, and more preferably 4 to 10 carbon atoms, are used alone or in combination of two or more. Specifically, butene-1,4-methylpentene-1 and hexene-1 are preferably used, and butene-1 is most preferably used.

The weight average molecular weight of this ethylene/α-olefin copolymer (B) is 300,000 kg/km or more, preferably 5
00,000 kg/kwol or more, more preferably in the range of 500,000 to 1,500,000 kg/kwol.

Also, in this copolymer (B), in order to have excellent creep resistance and stretchability, the α-olefin content is observed as the number of propylene α-olefin side chains introduced into the ethylene chain. It is desirable that the average number is 0.3 to 4, preferably 1 to 4 per 1000 carbon atoms in the main chain.

As with the copolymer (A), this number can be determined by measuring the absorbance at a wavelength appropriate for the type of side chain using an infrared spectrophotometer.
It is also possible to quantify directly with R.

The most important technical feature of the present invention is that by blending a copolymer (A) with relatively excellent stretchability and a copolymer (B) with relatively excellent creep properties under appropriate conditions, The advantage is that it is possible to obtain a raw material with an appropriate composition distribution and to obtain a polyethylene molecularly oriented molded product with a high balance between tensile properties and creep properties.

The molecularly oriented molded product obtained by the present invention has excellent stretchability compared to systems with a relatively narrow composition distribution (for example, the terpolymer shown in JP-A No. 63-275711), and as a result, It shows high tensile properties and has a relatively wide composition distribution (for example, JP-A-64-38439
The copolymer corresponding to (B) of the present invention, as shown in the above publication, has relatively superior creep properties compared to a kettle (system containing branched side chains).

That is, by blending two copolymers,
It is very important to have an appropriate composition distribution in order to obtain a molecularly oriented molded product with excellent tensile properties and creep properties.

The molecularly oriented molded article of the present invention contains the above-mentioned copolymers (A) and (B) in a ratio by weight of (A): (B) mil O: 90 to 90:10.
Preferably, it can be produced by melt-molding a blend blended at a ratio of 10:90 to 80:20 and stretching the obtained molded product. For example, if the amount of the copolymer (A) used is more than the above range, the creep resistance tends to be poor, and if it is less than the above range, the stretchability tends to decrease.

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

The solvent preferably has a boiling point higher than the melting point of each copolymer, more preferably higher than the melting point +20°C. Specifically, n-nonane, rhodecane, n-undecane, n-dodecane, n-tetradecane, n-octadecane or liquid paraffin, aliphatic hydrocarbon solvents such as kerosene, xylene, naphthalene, tetralin, butylbenzene, p - Aromatic hydrocarbon solvents such as cymene, cyclohexylbenzene, diethylbenzene, pentylbenzene, dodecylbenzene, bicyclohexyl, decalin, methylnaphthalene, ethylnephthaline, etc. or hydrogenated derivatives thereof, 1.1.2.2-tetrachloroethane, Pentachloroethane, hexachloroethane, 1.2.3-
Trichloropropane, dichlorobenzene, 1.2.4-
Examples include halogenated hydrocarbon solvents such as trichlorobenzene and bromobenzene, and mineral oils such as paraffinic process oils, naphthenic process oils, and aromatic process oils.

As waxes, aliphatic hydrocarbon compounds or derivatives thereof are used. These aliphatic hydrocarbon compounds are mainly saturated aliphatic hydrocarbon compounds.
Usually the molecular weight is 2000 or less, preferably 1000 or less,
More preferably, it is a so-called paraffin wax having a molecular weight of 800 or less. Specifically, these aliphatic hydrocarbon compounds include n-alkanes having 22 or more carbon atoms such as tocosan, tricosane, tetracosane, and triacontane, mixtures of these with lower n-alkanes as main components, and separation and refinement from petroleum. So-called paraffin wax,
Medium/low pressure polyethylene wax, high pressure polyethylene wax, ethylene copolymer wax, medium/low pressure polyethylene, high pressure polyethylene, etc., which are low molecular weight polymers obtained by copolymerizing ethylene or ethylene with other α-olefins. Examples include waxes obtained by reducing the molecular weight of polyethylene by thermal degradation, oxides of these waxes, oxidized waxes modified with maleic acid, and waxes modified with maleic acid. Further, as the aliphatic hydrocarbon compound derivative, for example, one or more derivatives, preferably one or two, particularly preferably one
A compound having a functional group such as a carboxyl group, a hydroxyl group, a carbamoyl group, an ester group, a mercapto group, or a carbonyl group with carbon atoms of 18 or more, preferably 12 or more carbon atoms.
50 or molecular weight 130-2000, preferably 200
~800 fatty acids, fatty alcohols, fatty acid amides,
Examples include fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, and aliphatic ketones. Specifically, fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, and fatty alcohols include lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol,
Examples of the fatty acid amide include caprinamide, urinamide, valmitinamide, stearylamide, and examples of the fatty acid ester include stearyl acetate.

The ratio of the high molecular weight ethylene copolymer blend to the diluent varies depending on the type of these, but - shot-wise, it is from 3:97 to 80:20, especially 15:85.
It is preferable to use a weight ratio of 60:40 to 60:40. If the amount of diluent is lower than the above range, the melt viscosity will be high (
It becomes too much, making it difficult to mix wires and melt forming.
The surface of the molded product is markedly rough, and stretching breaks are likely to occur. On the other hand, if the amount of the diluent is larger than the above range, melt mixing becomes difficult and the stretchability of the molded product becomes poor.

Melting crosstalk is generally 150 to 300°C, especially 170°C.
It is preferable to carry out the process at a temperature between 270°C and 270°C; if the temperature is lower than the above range, the melt viscosity will be too high and melt molding will be difficult; if the temperature is higher than the above range, the high molecular weight ethylene copolymer will be The molecular weight of the aggregate decreases, making it difficult to obtain a molded article with high elastic modulus and high strength. still,
The respective copolymer components and diluent components may be blended by dry blending using a Henschel mixer, V-type blender, or the like, or by melt mixing using a single-screw or multi-screw extruder.

Melt molding is generally performed by melt extrusion. For example, melt extrusion through a spinneret yields drawn filaments, extrusion through a flat or ring die yields drawn films, sheets or tapes, and circular extrusion produces drawn filaments.
By extruding through a die, a stretch blow molding pipe (parison) is obtained. The invention is particularly advantageous for the production of drawn filaments, in which case the melt extruded from the spinneret can also be subjected to drafting, ie, drawing in the molten state. ■ Extrusion speed of molten resin in the die orifice. The draft ratio can be defined by the following formula:

Draft ratio = V/V.

This draft ratio depends on the temperature of the mixture, the molecular weight of the high molecular weight ethylene copolymer used, etc., but it can usually be 3 or more, preferably 6 or more.

Of course, melt molding is not limited to extrusion molding, and in the case of manufacturing various stretch-molded containers and the like, it is also possible to manufacture preforms for stretch-blow molding by injection molding.

The molded product can be solidified by forced cooling means such as air cooling or water cooling.

The unstretched molded body made of the high molecular weight ethylene copolymer blend obtained by The molecular orientation is effectively imparted.

The stretching of the molded body consisting of a high molecular weight ethylene copolymer blend is generally carried out at 40 to 160°C, in particular at 80 to 160°C.
Preferably, it is carried out at a temperature of 45°C. As a heat medium for heating and maintaining the unstretched molded body at the above temperature, air, steam, or a liquid medium can be used. However, as a heating medium, a hot medium that can elute and remove the diluent mentioned above and whose boiling point is higher than the melting point of the molded article composition, specifically, decalin, decane, kerosene, etc., is used for stretching. Preferably, the operation is carried out. This makes it possible to remove the diluent described above, eliminate stretching unevenness during stretching, and achieve a high stretching ratio.

Note that the means for removing excess diluent from the high molecular weight ethylene molded composition is not limited to the above-mentioned method, but may include a method in which an unstretched material is treated with a solvent such as hexane, heptane, hot ethanol, chloroform, benzene, etc., and then stretched; Alternatively, by treating the stretched product with a solvent such as hexane, heptane, hot ethanol, chloroform, or benzene, excess diluent in the molded product can be effectively removed and a stretched product with high elastic modulus and high strength can be obtained. Obtainable.

The stretching operation can be performed in one stage or in multiple stages of two or more stages. The stretching ratio depends on the desired molecular orientation and the accompanying effect of increasing the melting temperature, but it is satisfactory if the stretching operation is carried out at a stretching ratio of 5 to 80 times, particularly 10 to 50 times. Get the desired results. Usually, it is advantageous to use multiple stages of two or more stages; in the first stage, the stretching operation is carried out while extracting the diluent in the extrudate at a relatively low temperature of 80 to 120°C, and in the second and subsequent stages, the stretching operation is carried out at a relatively low temperature of 80 to 120°C. Preferably, the stretching operation of the molded body is continued at a temperature of 160° C., which is higher than the first-stage stretching temperature.

In the case of uniaxial stretching operations such as filament, tape or uniaxial stretching, tension stretching is performed between rollers with different circumferential speeds (and in the case of biaxially stretched films, tension stretching is performed in the longitudinal direction between rollers with different circumferential speeds). In addition to performing bow stretching, tensile stretching is also performed in the transverse direction using a tenter or the like. Biaxial stretching using an inflation method is also possible.Furthermore,
In the case of a three-dimensional molded product such as a container, a biaxially stretched molded product can be obtained by a combination of tensile stretching in the axial direction and expansion stretching in the circumferential direction.

The molecularly oriented molded product thus obtained can be heat-treated under restrictive conditions if desired. This heat treatment can be carried out generally at a temperature of 110 to 180°C, particularly 150°C to 175°C, for 1 to 20 minutes, particularly 3 to 10 minutes. By this heat treatment, the crystallization of the oriented crystal portions in the molded article further progresses, resulting in a shift of the crystal melting temperature to a higher temperature side, an improvement in strength and elastic modulus, and an improvement in creep resistance at high temperatures.

The molecularly oriented molded product of the present invention formed as described above has a crystal melting temperature (T+s) of at least 15
At least two crystal melting endotherms (
), and this endothermic peak (Tp
) are close to each other. Furthermore, the heat of fusion based on the endothermic peak of crystal melting (Tp) is 40% or more, preferably 50% or more, and particularly preferably 60% or more based on the total heat of fusion.

The original crystalline melting temperature (Tm) of the ultra-high molecular weight ethylene/α-olefin copolymer composition is determined by completely melting the molded body composition and cooling it to relax the molecular orientation in the molded body. It can be determined by raising the temperature again (so-called second run in a differential scanning calorimeter).

To explain further, in the molecularly oriented molded article of the present invention, there is no crystal melting endothermic peak at all in the original crystal melting temperature range of the aforementioned molded article composition, or even if it exists, it exists with a very slight tailing. It's nothing more than that. In the present invention, the crystal melting temperature peak (Tp) generally appears in the temperature range Tm+15°C to Tm+25°C, and this peak (Tp) is formed as multiple peaks close to each other within the above temperature range. It appears.

These peaks in the high temperature region (Tp) significantly improve the heat resistance of the molded product of the high molecular weight ethylene/α-olefin copolymer composition, and also reduce the strength retention and elastic modulus after high-temperature thermal history. This seems to contribute to the retention rate.

Incidentally, the melting point and the heat of crystal fusion were measured by the following method.

The melting point was determined using a differential scanning calorimeter as follows.

A DSCn type (manufactured by PerkinElmer) was used as a differential scanning calorimeter. The sample is approximately 3mg 4nueX4+++m
The wire was wound around an aluminum plate having a thickness of 0.2 mm and constrained in the orientation direction by fixing both ends. Next, the sample wrapped around an aluminum plate was sealed in an aluminum pan and used as a measurement sample. In addition, the normally empty aluminum pan placed in the reference holder was filled with the same aluminum plate used for the sample to maintain balance. First, the sample was held at 30°C for about 1 minute,
Thereafter, the temperature was increased to 190° C. at a temperature increase rate of 1OT/min, and the melting point measurement at the first temperature increase was completed. Continued 1
Hold at 90℃ for 10 minutes, then heat at 20℃/5hi
The temperature was lowered at a temperature lowering rate of n, and the sample was further held at 30°C for 10 minutes. Next, the temperature was raised for the second time to 190°C at a heating rate of 10"C/win, and at this time, the melting point measurement during the second heating (second run) was completed. At this time, the maximum value of the melting peak was When it appeared as a shoulder, a tangent was drawn between the inflection point on the low-temperature side of the shoulder and the inflection point on the immediately high-temperature side, and the intersection was determined as the melting point.

Also, connect the 60°C and 180°C lines of the endothermic curve, and the straight line (
Draw a perpendicular line to a point 15°C higher than the original crystalline melting temperature (Tm) of the ultra-high molecular weight ethylene copolymer composition, which is determined as the main melting peak during the second temperature increase, and draw a perpendicular line to the lower temperature side surrounded by these. The part is based on the crystal melting inherent to the ultra-high molecular weight ethylene copolymer composition, and the high temperature example part is based on the crystal melting that expresses the function of the molded article of the present invention, and the heat of crystal fusion for each is as follows: Calculated from these areas.

The degree of molecular orientation in a molded article can be determined by an X-ray diffraction method, a birefringence method, a fluorescence polarization method, or the like. In the case of drawn filaments of the ultra-high molecular weight ethylene copolymer composition of the present invention, for example, Yukichi Go, Teru Kubo: Industrial Chemistry Magazine Vol. 39,
The degree of orientation according to the half-width described in detail on page 992 (1939), that is, the degree of orientation F = (90°-H' /2)
/90° In the formula, Ho is the half-width (°) of the intensity distribution curve along the Debye ring of the strongest paratropic surface on the equator.

The degree of orientation (F) defined by is 0.90 or more, especially 095
It is desirable from the point of view of mechanical properties that the reciprocation is as described above.

In addition, this drawn filament has extremely excellent creep resistance under high temperatures, with a creep rate of 15% or less, measured as elongation (%) after 90 seconds at a 30% breaking load and an ambient temperature of 70°C. , especially less than 10%, and the creep rate after 90 seconds to 180 seconds (5ec-
'l is 5 x to -'5ec-' or less, especially 3
It is under 10-' 5ec-TJ.

Furthermore, the molecularly oriented molded product of the present invention also has excellent mechanical properties, for example, in the form of a drawn filament, the molecularly oriented molded product has a
In particular, it has an elastic modulus of 60 GPa or more and a tensile strength of 1.5 GPa or more, especially 2.0 GPa or more.

(Example) Example 1 The ethylene/propylene copolymer (A) has a weight average molecular weight of 5.3xlO' and a propylene content of 0.5 on average in terms of the number of side chains per too many carbon atoms. Use what is.

Moreover, as an ethylene/α-olefin copolymer (B),
The weight average molecular weight is 5.3X 105, butene-1
An ethylene/butene-1 copolymer with an average content of 2.1 side chains per 1000 carbon atoms is used.

The above copolymers (A) and (B) were mixed in the following weight ratio to prepare raw materials No. 3.

Paraffin wax (melting point 69°C, molecular weight 4
90) at a weight ratio of 30:70, and melt spinning was performed under the following conditions.

First, 1 part by weight of 3.5 dimethyl-tert-butyl-4-hydroxytoluene was added to this mixture as a process stabilizer based on 100 parts by weight of the copolymer (A). Then, using a screw extruder, set temperature 19
The mixture is mixed with hot water at 0°C, and then the melt is passed through a spinning die with an orifice diameter of 2 mm attached to an extruder (
Melt spinning was carried out at a temperature of 180'c).

Next, the spun fibers were taken through an air gap of 180 cm at a draft ratio of 33 times, and cooled and solidified in air to obtain undrawn fibers.

Furthermore, the undrawn fibers were drawn in three stages using a spinning godet roll to obtain oriented fibers. At this time, the heat medium in the first drawing tank and the second drawing tank was n-decane, and the temperatures were 1]'O<0>C and 120<0>C, respectively. The heating medium in the third drawing tank is triethylene glycol, and the temperature is 143
℃. In addition, the effective length of the Nobu-naka type is 50 cm. During the stretching, the rotational speed of the first godetroll was set to 0.5 m/min, and the rotational speed of the fourth godetroll was changed to obtain fibers with a desired drawing ratio.

The rotation speeds of the second and third godet rolls were appropriately selected within a range that allowed stable stretching. Most of the initially mixed paraffin wax was extracted in the first drawing tank and the second drawing tank. The stretching ratio was calculated from the rotational speed ratio of the first godet roll and the fourth godet roll.

The tensile properties (elastic modulus, tensile strength) and creep rate of the obtained drawn fibers were measured, and the results are shown in Table 1.

The elastic modulus and tensile strength were measured at room temperature (23°C) using a Tensilon RTM-100 tensile tester manufactured by Orientic.
) was measured. The sample length between the clamps at this time is 100m
m, and the tensile speed was 100 mna/l1in.

The elastic modulus is the initial elastic modulus, which was determined from the slope of the tangent to the stress-strain curve. The fiber cross-sectional area required for calculation is density 0.960
It was calculated from the weight as g/cc.

The creep test was carried out using a thermal stress strain measuring device TMA/SS 100 (manufactured by Seiko Electronics Co., Ltd.) under accelerated conditions with a sample length of 5 mm, an ambient temperature of 70°C, and a load equivalent to 30% of the breaking load at room temperature. I did it.

The creep rate was determined as the average deformation rate (sec-') from 90 seconds to 180 seconds after the start of loading.

Table 1 Also, the first endothermic characteristic curve measured by differential scanning calorimeter of the drawn fiber obtained from the original Fll is shown in Fig. 1, and the second
The endothermic characteristic curve of the second run is shown in FIG.

The original crystal melting peak was at 131°C.

Comparative Example 1 Weight 1 average molecular weight is 5.3X 105, butene-1
An ethylene/butene-1 copolymer having an average content of 1.0 side chains per 1000 carbon atoms was used as raw material 4.
used as.

Further, an ethylene/propylene copolymer having a weight average molecular weight of 5.3×10 5 and a propylene content of 0.5 on average in terms of the number of side chains per 1000 carbon atoms was used as the raw material 5.

Each raw material was mixed with paraffin wax in the same manner as in Example 1, and melt-spun and drawn to obtain drawn fibers.

The properties of the drawn fibers obtained were measured in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 Also, Section 3 shows the relationship between the strength of the drawn fibers obtained from the above raw materials 1 to 5 and the reciprocal of the creep rate. From FIG. 3, it is understood that the drawn fibers of the present invention obtained from raw materials 1 to 3 have a higher balance of both properties than the drawn fibers obtained from raw material 4.5.

Comparative Example 2 The ethylene/propylene copolymer (A) had a weight average molecular weight of 5. I is 5.5X10
5, and the butene-1 content is 5.5 on average in terms of the number of side chains per 1000 carbon atoms.
1 copolymer is used.

Raw materials 6 to 8 were prepared by mixing the above copolymers (A) and (B) at the weight ratio shown below.

This raw material was mixed with paraffin wax (melting point: 69° C., molecular weight: 490) at a weight ratio of 30:70, and the mixture was spun and drawn in the same manner as in Example 1 to obtain fibers. The tensile properties and creep rate of the drawn fibers obtained were measured and the results are shown in Table 3.

Table 3 In addition, FIG. 3 shows the relationship between the strength of the drawn fibers obtained from the above raw materials 1 to 8 and the reciprocal of the creep rate. From FIG. 3, it is understood that the fibers of the present invention obtained from raw materials 1 to 3 have a higher balance of both properties than the drawn fibers obtained from raw materials 4 to 8.

Example 2 The ethylene/propylene copolymer (A) has a weight average molecular weight of 9.9 XIO' and an average propylene content of 0.5 side chains per 1000 carbon atoms. Also, as the ethylene/α-olefin copolymer (B), the weight average molecular weight is 1.08X 1
0' and an ethylene/butene-1 copolymer having an average butene-1 content of 2.5 in number of side chains per 1000 carbon atoms is used.

Raw material 9 was prepared by mixing the above copolymers (A) and (B) at a weight ratio of 70:30. This raw material was mixed with paraffin wax (melting point 69° C., molecular weight 490) at a weight ratio of 20:80, and the mixture was spun and drawn in the same manner as in Example 1 to obtain fibers. The tensile properties and creep rate of the drawn fibers obtained were measured, and the results are shown in Table 4.

Further, the first endothermic characteristic curve of the drawn fiber obtained from raw material 9 measured by a differential calorimeter is shown in FIG. 4, and the second endothermic characteristic curve is shown in FIG.

The original crystal melting peak was at 132°C.

Comparative Example 3 Weight average molecular weight is 1.03X105, carbon number is 1
An ethylene/propylene/butene-1 ternary co-Topolymer having an average number of side chains of 1.4 per 000 was used as raw material 10. This raw material is paraffin wax (melting point 6
(9°C, molecular weight: 490) at a weight ratio of 20:80, and was spun and drawn in the same manner as in Example 1 to obtain fibers. The tensile properties and creep rate of the drawn fibers obtained were measured, and the results are shown in Table 4.

It is understood from Table 4 that the drawn fibers of the present invention obtained from raw material 6 have better tensile properties and creep properties than the fibers obtained from terpolymerized raw material 7. Ru.

(Effects of the Invention) According to the present invention, a molecularly oriented molded product, especially fiber, which has an excellent balance of strength and creep resistance and also has excellent stretchability, is obtained from a high molecular weight ethylene copolymer. .

[Brief explanation of the drawing]

FIG. 1 is an endothermic characteristic curve of drawn fibers obtained from raw material 1 in Example 1 measured by a differential scanning calorimeter in a restrained state. FIG. 2 is an endothermic characteristic curve obtained when the sample shown in FIG. 1 was subjected to a second temperature increase measurement (second run). Figure 3 shows raw materials 1 to 8 in Examples and Comparative Examples.
Figure 4 shows the relationship between the strength of the drawn fiber obtained from raw material 9 and the reciprocal of the creep rate. curve. FIG. 5 is a graph showing the second endothermic characteristic curve. Patent applicant Mitsui Petrochemical Industries, Ltd. Figure 1 Figure 2 Temperature (0C) Temperature (0C) Figure 3 Reciprocal of creep rate (seconds) Figure 4 Temperature ('C)

Claims (3)

[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; The weight average molecular weight is 300,000 or more, and α
- A copolymer (B) of ethylene and an α-olefin having 4 or more carbon atoms, with an average olefin content of 0.3 to 4 side chains per 1000 carbon atoms,
On a weight basis, (A):(B)=10:90 to 90:
A polyethylene molecularly oriented molded article consisting of a composition mixed at a ratio of 10:1. (2) When the crystal melting temperature (Tm) is measured under restrained conditions using a differential scanning calorimeter, it is at least 15% lower than the original main crystal melting temperature of the composition, which is determined as the main heat of fusion peak during the second temperature rise. The polyethylene molecularly oriented molded article according to claim 1, which has at least two closely related crystal melting endothermic peaks in a high temperature region. (3) Claim (1) or (2) wherein the ethylene/α-olefin copolymer (B) is an ethylene/butene-1 copolymer.
) The polyethylene molecularly oriented molded product described in