JPH086205B2 - Molecularly oriented molded product of ultra-high molecular weight ethylene / propylene copolymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molecularly oriented molded product of an ultrahigh molecular weight ethylene / propylene copolymer, and more specifically, it has a novel crystal melting property and a mechanical property. Oriented molecular body of ultra-high molecular weight ethylene / propylene copolymer excellent in physical properties, heat resistance and creep resistance, particularly fiber.

(Prior art) Molding ultra high molecular weight polyethylene into fiber, tape, etc.,
By stretching this, it is already known to obtain a molecularly oriented molded article having a high elastic modulus and a high tensile strength.For example, JP-A-56-15408 discloses a dilute solution of ultra-high molecular weight polyethylene. Spinning and stretching the resulting filaments is described. Further, JP-A-59-130313 describes that an ultra-high-molecular-weight polyethylene and a wax are melt-kneaded, and this kneaded product is extruded, cooled and solidified, and then stretched. Further, JP-A-59-187614. Describes that the melt-kneaded product is extruded, drafted, cooled and solidified, and then stretched.

(Problems to be Solved by the Invention) By molding ultra-high molecular weight polyethylene in the form of fibers and subjecting it to strong stretching, the elastic modulus and tensile strength can be increased with an increase in the draw ratio. Stretched fibers are excellent in mechanical properties such as high elastic modulus and high tensile strength, light weight, water resistance, weather resistance, etc., but their heat resistance is such that the melting point of polyethylene is generally in the relatively low range of 120 to 140 ° C. The restriction that it is inside is fundamentally escaped, and when using ultra high molecular weight polyethylene fiber at high temperature,
It has the drawback that the strength retention is significantly reduced and the creep is significantly increased.

Therefore, an object of the present invention is to provide an ultra-high molecular weight polyethylene-based molecularly oriented molded product having novel crystal melting properties and having markedly improved heat resistance and creep resistance.

Another object of the present invention is to exhibit remarkably high strength retention and elastic modulus retention even when subjected to high temperature thermal history such as heat treatment at 170 ° C. for 5 minutes, and low creep at high temperature. It is an object of the present invention to provide an ultra-high molecular weight polyethylene-based molecularly oriented molded product whose level is suppressed.

(Means for Solving Problems) The inventors of the present invention have found that an ultrahigh molecular weight ethylene / propylene copolymer obtained by copolymerizing propylene with ethylene in a limited small amount is extruded and stretched. When I did
It has extremely excellent stretchability compared to ordinary homopolymers of ultra-high molecular weight polyethylene, and is capable of imparting effective molecular orientation by stretching at high magnification; this ultra-high molecular weight ethylene-propylene The molecular orientation-molded product of the copolymer has novel molecular orientation crystal characteristics with an improvement phenomenon of melting temperature, which is not observed in conventional polyethylene stretched products, and this molecular orientation-molded product is 170 ° C. It was found that even when heat-treated for 5 minutes, the mechanical properties at high temperature are such that the strength and elastic modulus are hardly reduced, or conversely, these values are improved. Further, it was also found that this molecularly oriented molded product has a significantly improved creep resistance while retaining the high strength and high elastic modulus peculiar to the stretched molded product of ultra-high molecular weight polyethylene.

According to the present invention, the intrinsic viscosity [η] is at least 5 dl / g
A propylene content is an average molecular weight molded product of an ultra-high molecular weight ethylene / propylene copolymer having an average of 0.5 to 15 carbons per 1000 carbon atoms, and the molded product was measured with a differential scanning calorimeter in a restrained state. At this time, it has at least two crystal melting endothermic peaks and is at least as high as the original crystal melting temperature (Tm) of the ultrahigh molecular weight ethylene-propylene copolymer required as the main melting endothermic peak at the time of the second heating.
Molecular orientation characterized by having at least one crystal melting endothermic peak (Tp) at a temperature 20 ° C. higher, and having a heat quantity based on this crystal melting endothermic peak (Tp) of not less than 15% based on the total heat of melting A shaped body is provided.

(Operation) According to the present invention, an ultrahigh molecular weight ethylene / propylene copolymer obtained by copolymerizing a limited amount of propylene with ethylene can be stretched at a higher ratio than a homopolymer of ultrahigh molecular weight polyethylene. It is possible, and it is based on the surprising finding that the molecular orientation molded body by this stretching has a markedly improved melting point of the polymer chains constituting it, under restrained conditions.

In the present specification, the restraint state or the restraint condition means
No positive tension is applied to the molecularly oriented molded body,
It means that the ends are fixed so that free deformation is prevented.

The melting point of a polymer is associated with melting of crystals in the polymer and is generally measured as an endothermic peak temperature associated with melting of crystals in a differential scanning calorimeter. This endothermic peak temperature is constant if the type of polymer is determined, and after that,
For example, it hardly changes due to the stretching treatment or the like, and even if it varies, even the stretching heat treatment, which is well known as the most varying case, moves to a high temperature side of about 15 ° C. at most.

The attached drawings FIG. 1 is an ultrahigh molecular weight ethylene / propylene copolymer used in the present invention, FIG. 2 is a highly drawn filament of this copolymer, FIG. 3 is a normal ultrahigh molecular weight polyethylene raw material, and FIG. 4 is It is an endothermic curve by a differential scanning calorimeter about each of the highly drawn filaments of this ultra-high molecular weight polyethylene, and the endothermic curve of the highly drawn filaments was measured under the constraint conditions of the filaments. For the composition of each polymer and the processing conditions of the filament, refer to the examples described later. The endothermic curves of the raw material powders in FIGS. 1 and 3 were measured by the method described in ASTM D 3418 in order to erase various histories during polymerization.

From these results, the drawn filament of ordinary ultra-high molecular weight polyethylene shows an endothermic peak associated with crystal melting at a temperature of about 150 ° C., which is about 15 ° C. higher than the starting ultra-high molecular weight polyethylene. You can see the ultra high molecular weight ethylene propylene.

In the molecular oriented molded product of the present invention, by using a copolymer of ethylene with a small amount of propylene, the introduction of the comonomer component of the polymer chain generally causes a decrease in crystallinity and a decrease in melting point. The melting point of the molecularly oriented molded article is equal to or higher than the melting point of the molecularly oriented molded article of ultra-high molecular weight polyethylene, and the creep resistance is improved as described later. The facts turn out to be truly surprising.

In the molecular orientation molded article of the present invention, the reason why the shift of the crystal melting temperature to the high temperature side becomes large and the reason why the stretching performance can be improved by incorporating a small amount of the propylene comonomer are:
Although not fully clarified yet, it is estimated as follows from the analysis of the above-mentioned measurement results. That is, it is considered that the molecular orientation molded body of ultra-high molecular weight polyethylene has a structure in which a large number of polymer chains alternately pass through the crystal part and the amorphous part and the polymer chains are oriented in the stretching direction. In a molecular oriented molded product obtained by introducing a small amount of propylene into high-molecular-weight polyethylene by copolymerization, the introduced propylene chain part, that is, the part where the side chain is formed, selectively becomes an amorphous part, and this amorphous part is It is believed that a portion of the repeating ethylene chain becomes an oriented crystal part. At this time, the side chain portion introduced at an average number of 0.5 to 15 per 1000 carbon atoms in the polymer chain is concentrated in the amorphous portion, whereby the oriented crystallization of the repeating ethylene chain portion is rather regular and good. It progresses to a large size, or the entanglement between the molecular chains increases in the amorphous parts at both ends of the oriented crystal part, and the polymer chains become difficult to move,
It seems that the melting temperature of the oriented crystal part increases.

Further, it is recognized that the stretchability is improved by the softening effect due to the presence of a small amount of propylene branched chains.

The molecular orientation molded article according to the present invention has substantially no decrease in strength or elastic modulus as compared with an unheated one even when heat-treated at 170 ° C. for 5 minutes, and if anything, the strength and elastic modulus are rather low. It has the feature of improving rather than untreated one. Furthermore, this molecularly oriented molded article is also excellent in creep resistance at high temperatures, and the creep (CR ₉₀ ) obtained by the method described in detail below is 1/2 or less of that of a normal ultra-high molecular weight polyethylene oriented molded article, In particular, it has a surprising characteristic that it is 1/3 or less, and the creep rate ε _90-180 (sec ^-1 ) is smaller than that of the oriented polymer of ultra-high molecular weight polyethylene by one digit. It is considered that the remarkable improvements in these properties are derived from the novel microstructure of the oriented crystal part described above.

It is important that the ethylene / propylene copolymer used in the molecularly oriented molded product of the present invention contains propylene in an amount of 0.5 to 15, especially 0.1 to 10 per 1000 carbon atoms in the polymer chain. That is, the ultra-high molecular weight ethylene copolymer using propylene as a comonomer provides the advantage that it can be stretched at a higher ratio than ultra-high molecular weight polyethylene, and can be stretched at a higher ratio. Therefore, the elastic modulus and the tensile strength can be further improved. It is also very important that this propylene is contained in the above amount, and when this content is less than the above range, almost no effect of increasing the crystal melting temperature due to molecular orientation is observed, and more than the above range. If it is too large, the melting point of the ethylene / propylene copolymer itself tends to decrease, and at the same time, the effect of increasing the crystal melting temperature due to molecular orientation and the improvement of the elastic modulus tend to decrease.

It is also important that the ethylene / propylene copolymer has an intrinsic viscosity [η] of 5 dl / g or more, particularly 7 to 30 dl / g from the viewpoint of mechanical properties and heat resistance of the molecularly oriented molded product. That is, since the molecular terminals do not contribute to the fiber strength and the number of the molecular terminals is the reciprocal of the molecular weight (viscosity), it can be seen that the one having a large intrinsic viscosity [η] gives a high strength.

The molecular orientation molded article of the present invention is at least as high as the main crystal melting temperature (Tm) of the ultrahigh molecular weight ethylene / propylene copolymer, which is determined as the main melting endothermic peak at the time of the second heating.
Having at least one crystal melting endothermic peak (Tp) at a temperature higher by 20 ° C., and the amount of heat based on this crystal melting endothermic peak (Tp) per total heat of fusion is 15% or more, preferably 20% or more, particularly 30 % Or more is important from the viewpoint of heat resistance of the molecularly oriented molded article, that is, retention of strength and elastic modulus at high temperature and creep resistance at high temperature.

That is, an oriented molded product that does not have a crystal melting endothermic peak (Tp) in a temperature region higher than Tm by 20 ° C. or even if it has a crystal melting endothermic peak in this temperature region, the endothermic amount based on it is the total melting heat amount. 170 for molecularly oriented compacts below 15%
When heat-treated at 5 ° C. for 5 minutes, the strength retention and elastic modulus tend to decrease substantially, and creep and creep rate during heating tend to increase.

(Description of preferred embodiments) The present invention will be described below in the order of the raw material, the production method, and the target product for easy understanding.

Raw Material The ultrahigh molecular weight ethylene / propylene copolymer used in the present invention is obtained by slurry-polymerizing ethylene and propylene as a comonomer in the presence of a Ziegler catalyst, for example, in an organic solvent. The amount of propylene comonomer used should provide a propylene content in the polymer chain in the above mentioned range per 1000 carbons. Further, the ultrahigh molecular weight ethylene / propylene copolymer used should have a molecular weight corresponding to the above-mentioned intrinsic viscosity [η].

When the propylene content is 0.5 / 1000 carbon atoms or less, it is not possible to form an effective structure for improving the creep resistance property. Conversely, when the propylene content exceeds 15/1000 carbon atoms, The crystallinity is remarkably reduced, and a high elastic modulus cannot be obtained.

<Quantification of Propylene Component> The propylene component in the ultrahigh molecular weight ethylene / propylene copolymer in the present invention was quantified with an infrared spectrophotometer (manufactured by JASCO Corporation). That is, the absorbance of 1378 cm ^-1 which represents the deformation vibration of the methyl group of the captured propylene in the ethylene chain is measured in advance now ¹³
It is a value measured by converting it into the number of methyl branches per 1000 carbon atoms with a calibration curve prepared using a model compound with a C nuclear magnetic resonance apparatus.

Manufacturing Method In the present invention, a diluent is blended with the above components in order to enable melt molding of the ultrahigh molecular weight ethylene / propylene copolymer. As such a diluting agent, a solvent for the ultra high molecular weight ethylene copolymer or various waxes having compatibility with the ultra high molecular weight ethylene copolymer are used.

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

Specific examples of such a solvent include n-nonane and n-nonane.
Decane, n-undecane, n-dodecane, n-tetradecane, n-octadecane or liquid hydrocarbon, aliphatic hydrocarbon solvent such as kerosene, xylene, naphthalene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, benzyl Benzene, dodecylbenzene, bicyclohexyl, decalin, methylnaphthalene, aromatic hydrocarbon solvents such as ethylnaphthalene or hydrogenated derivatives thereof, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,2,
Examples thereof include halogenated hydrocarbon solvents such as 3-trichloropropane, dichlorobenzene, 1,2,4-trichlorobenzene and bromobenzene, and mineral oils such as paraffin type process oil, naphthene type process oil and aromatic type process oil.

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

Since the aliphatic hydrocarbon compound is mainly a saturated aliphatic hydrocarbon compound, it is usually called a paraffin wax having a molecular weight of 2000 or less, preferably 1000 or less, more preferably 800 or less. Specific examples of these aliphatic hydrocarbon compounds include docosane, tricosane,
N- with 22 or more carbon atoms such as tetracosane and triacontane
Alkanes or mixtures with lower n-alkanes containing them as a main component, so-called paraffin wax separated and purified from petroleum, and low molecular weight polymers obtained by copolymerizing ethylene or ethylene with other α-olefins.・
Low-pressure polyethylene wax, high-pressure polyethylene wax, ethylene copolymer wax or wax such as medium / low-pressure polyethylene, high-pressure polyethylene whose molecular weight has been reduced by thermal degradation, and oxides or maleic acid modification of these waxes Oxidized waxes, maleic acid-modified waxes and the like.

As the aliphatic hydrocarbon compound derivative, for example, one or more, preferably one or two, at the terminal or inside of the aliphatic hydrocarbon group (alkyl group, alkenyl group),
Particularly preferred is a compound having a functional group such as a carboxyl group, a hydroxyl group, a carbamoyl group, an ester group, a meltcapto 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 Is 200
To 800 fatty acids, aliphatic alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones and the like.

Specifically, as a fatty acid, capric acid, lauric acid,
Myristic acid, palmitic acid, stearic acid, oleic acid, lauric alcohol as a fatty alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, capric amide as a fatty acid amide, laurinamide, palmitinamide, stearyl amide, stearyl acetic acid ester as a fatty acid ester, etc. Can be illustrated.

The ratio of ultra-high molecular weight ethylene copolymer to diluent also varies with these types, but is generally up to 3:97.
It is advisable to use it in a weight ratio of from 80 to 20:20, in particular from 15:85 to 60:40. 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 roughness of the molded product is remarkable, and stretch breakage easily occurs. On the other hand, when the amount of the diluent is more than the above range, the melt-kneading becomes difficult and the stretchability of the molded product becomes poor.

Melt kneading is generally carried out at a temperature of 150 to 300 ° C., particularly 170 to 270 ° C., and if the temperature is lower than the above range, the melt viscosity is too high, which makes melt molding difficult, and is higher than the above range. In particular, due to thermal degradation, the molecular weight of the ultra high molecular weight ethylene copolymer is lowered, and it becomes difficult to obtain a molded product having a high elastic modulus and a high strength. The compounding may be performed by dry blending using a Henschel mixer, a V-type blender, or the like, or may be performed by melt mixing using a single-screw or multi-screw extruder.

Melt molding is generally performed by melt extrusion molding. For example, by melt-extruding through a spinneret, a filament for stretching is obtained, and by extruding through a flat die or a ring die, a stretching film or sheet or tape is obtained, and further by extruding through a circular die, A stretch blow molding pipe (parison) is obtained. The invention is particularly useful for producing drawn filaments, in which case the melt extruded from the spinneret can be drafted, i.e., stretched in the molten state. Extrusion speed V ₀ of the molten resin in the die / orifice and winding speed V of the unstretched uncooled material
The ratio can be defined as the draft ratio as follows.

Draft ratio = V / V ₀ (2) The draft ratio can be usually 3 or more, preferably 6 or more, depending on the temperature of the mixture, the molecular weight of the ultrahigh molecular weight ethylene copolymer, and the like.

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 a preform for stretch blow molding by injection molding. The molded product can be cooled and individualized by forced cooling means such as air cooling and water cooling.

The unstretched molded product of the ultrahigh molecular weight ethylene copolymer thus obtained is stretched. The degree of the stretching treatment is, of course, such that molecular orientation in at least uniaxial direction is effectively imparted to the ultrahigh molecular weight ethylene copolymer of the molded product.

The stretching of the ultra-high molecular weight ethylene copolymer molded body is preferably carried out at a temperature of generally 40 to 160 ° C, particularly 80 to 145 ° C. As a heat medium for heating and holding the unstretched molded body at the above-mentioned temperature, any of air, steam, and a liquid medium can be used. However, a solvent capable of eluting and removing the above-mentioned diluent as a heat medium and having a boiling point higher than the melting point of the molded body composition, specifically decalin, decane, kerosene, etc. By performing the above, it is possible to remove the above-mentioned diluent, and it is possible to eliminate unevenness in stretching during stretching and achieve a high stretching ratio, which is preferable.

Of course, means for removing the excess diluent from the ultra high molecular weight ethylene copolymer is not limited to the above method, hexane, heptane, hot ethanol, chloroform, a method of stretching after treating with a solvent such as benzene, Hexane,
The method of treating with a solvent such as heptane, hot ethanol, chloroform, benzene, etc. can also effectively remove the excess diluent in the molded product and obtain a stretched product with high elastic modulus and high strength.

The stretching operation can be performed in one stage or in multiple stages of two or more stages. The stretching ratio generally depends on the desired molecular orientation and the effect of improving the melting temperature accompanied therewith, but generally 5 to
Satisfactory results can be obtained by carrying out the stretching operation so that the stretching ratio is 80 times, particularly 10 to 50 times.

In general, multi-stage drawing of two or more steps is advantageous, and the drawing operation is performed while extracting the diluent in the extrusion-molded product at a relatively low temperature of 80 to 120 ° C in the first step, and in the second and subsequent steps,
It is preferable to continue the stretching operation of the molded body at a temperature of 120 to 160 ° C. and a temperature higher than the first stage stretching temperature.

In the case of uniaxial stretching operation such as filament, tape or uniaxial stretching, tensile stretching may be performed between rollers having different peripheral speeds, and in the case of biaxially stretched film, longitudinal stretching may be performed between rollers having different peripheral speeds. Along with performing the tensile stretching, the tensile stretching is also performed in the transverse direction using a tenter or the like. Biaxial stretching by the 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 molecular orientation molded body thus obtained can be heat-treated under restrained conditions, if desired. This heat treatment is generally carried out at a temperature of 140 to 180 ° C, especially 150 to 175 ° C, for 1 to 20 ° C.
It can be carried out for minutes, in particular for 3 to 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.

Molecularly oriented molded product As described above, the ultra high molecular weight ethylene according to the present invention
The molecularly oriented molded product of a propylene copolymer has at least one crystal melting peak (Tp) at a temperature that is at least 20 ° C. higher than the crystal melting temperature (Tm) of the copolymer, and per unit of heat of fusion. The heat of fusion based on this crystal melting peak (Tp) is 15% or more, preferably 20% or more, and particularly 30% or more.

Original crystalline melting temperature of ultra high molecular weight ethylene copolymer (T
m) is, once this molded body is completely melted and then cooled,
It can be determined by a method of relaxing the molecular orientation in the molded body and then raising the temperature again, that is, a second run in a so-called differential scanning calorimeter.

To further explain, in the molecular orientation molded product of the present invention, there is no crystal melting peak in the crystal melting temperature range of the above-mentioned copolymer, or if there is, there is very little tailing or shoulder. Nothing more.
The crystal melting peak (Tp) is generally in the temperature range Tm + 20 ° C to Tm
It usually appears in the + 50 ° C. region, and this peak (Tp) often appears as a plurality of peaks within the above temperature range.

These crystal melting peaks or shoulders (Tp) in the high temperature region act to remarkably improve the heat resistance of the molecularly oriented molded product of the ultra-high molecular weight ethylene / propylene copolymer, and the high temperature heat It is considered to contribute to the strength retention rate and elastic modulus retention rate after the history.

The melting point and the heat of crystal fusion in the present invention were measured by the following methods.

The melting point was measured by a differential scanning calorimeter as follows. As the differential scanning calorimeter, DSC II type (manufactured by Perkin Elmer) was used. The sample was constrained in the orientation direction by winding about 3 mg around an aluminum plate having a thickness of 4 mm × 4 mm and a thickness of 0.2 mm. Then, the sample wound around the aluminum plate was enclosed in an aluminum pan to obtain a measurement sample. The same aluminum plate used for the sample was sealed in a normally empty aluminum pan to be placed in the reference holder, and the heat balance was maintained. First, the sample was kept at 30 ° C. for about 1 minute, and then heated up to 250 ° C. at a rate of 10 ° C./min to complete the first melting point measurement at the time of temperature rise. Subsequently, the sample was held at 250 ° C. for 10 minutes, then cooled at a cooling rate of 20 ° C./min, and further held at 30 ° C. for 10 minutes. Next, the second heating was carried out at a heating rate of 10 ° C./min to 250 ° C., and the melting point measurement at the second heating (second run) was completed. At this time, the maximum value of the melting peak was taken as the melting point.
When it appears as a shoulder, a tangent line was drawn between the inflection point on the low temperature side and the inflection point on the high temperature side of the shoulder, and the intersection was taken as the melting point.

Also, from the melting point (Tm) of the original crystal melting point (Tm) of the ultra-high molecular weight ethylene copolymer, which is obtained by connecting the points of 60 ° C and 240 ° C of the endothermic curve to the straight line (baseline) and the main melting peak at the second heating A vertical line is drawn at a point higher by ℃, the low temperature side surrounded by these is based on the original crystal melting (Tm) of the ultra high molecular weight ethylene copolymer, and the high temperature side is the function of the molded product of the present invention. It was based on the crystal melting (Tp) that developed, and the heat of fusion of each crystal was calculated from these areas.

The degree of molecular orientation in the 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 the drawn filament of the ultrahigh molecular weight ethylene copolymer of the present invention, for example, Yukichi Kure, Teruichiro Kubo: Industrial Chemistry Journal Vol. 39, 992 (1939), the degree of orientation according to the half width,
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.

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.

The drawn filament of the ultra-high molecular weight ethylene / propylene copolymer of the present invention has a strength retention of 90% or more, particularly 95% or more, and an elastic modulus retention after being subjected to a thermal history of 170 ° C. for 5 minutes. It has an excellent heat resistance of 90% or more, especially 95% or more, which is not observed in conventional drawn filaments of polyethylene.

In addition, this drawn filament is outstandingly excellent in creep resistance at high temperatures, and the load is 30% breaking load,
Creep, determined as the elongation (%) after 90 seconds at an ambient temperature of 70 ° C, is 7% or less, especially 5% or less, and the creep speed (ε, sec ^-1 ) after 90 seconds to 180 seconds is 4%. × 10 ^-4 sec
^-1 or less, particularly 2 × 10 ^-4 sec ^-1 or less.

Furthermore, the molecular orientation molded product of the ultrahigh molecular weight ethylene / propylene copolymer according to the present invention is also excellent in mechanical properties, for example, in the form of a stretched filament, 20 GPa or more, particularly 30 GPa or more elastic modulus, 1.2 GPa or more, In particular, it has a tensile strength of 1.5 GPa or more.

(Effect of the Invention) The molecularly oriented molded article of the ultrahigh molecular weight ethylene / propylene copolymer of the present invention is excellent in the combination of heat resistance, creep resistance and mechanical properties. Thus, by utilizing this characteristic, the molecularly oriented molded article of the present invention is useful as a packaging material such as a packing tape, in addition to industrial textile materials such as high density multifilament, strings, ropes, woven fabrics and nonwoven fabrics. Is.
In addition, a molded product in the form of a filament is made of epoxy resin,
When it is used as a reinforcing fiber for various resins such as unsaturated polyester and synthetic rubber, it is clear that the heat resistance and creep resistance are significantly improved as compared with the conventional ultra high molecular weight polyethylene drawn filament. Ah
In addition, since this filament has high strength and low density, it is particularly lighter than a molded product using a conventional molded product using glass fiber, carbon fiber, boron fiber, aromatic polyamide fiber, aromatic polyimide fiber, or the like. It is effective because it can be converted. Similar to composite materials such as glass fiber, UD
(Unit Directional) Laminated board, SMC (Sheet Molding Com)
It can be used for molding processes such as pound) and BMC (Bulk Molding Compound), and is expected to be used for various composite materials in the fields of light weight and high strength such as automobile parts, boat and yacht structures, and electronic circuit boards. .

Example 1 <Polymerization of Ultra High Molecular Weight Ethylene / Propylene Copolymer> A slurry polymerization of an ethylene / propylene copolymer was carried out using a Ziegler type catalyst and n-decane 1 as a polymerization solvent. The composition of ethylene and propylene in molar ratio is 98.2:
Monomer gas in a ratio of 1.84 was continuously fed so that the pressure in the reactor was kept constant at 5 kg / cm ² , and the polymerization was completed at 70 ° C. for 2 hours. The yield of the ultra-high molecular weight ethylene-propylene copolymer powder obtained was 171 g and the intrinsic viscosity (decalin: 135 ° C).
Is 7.65 dl / g, and the propylene content by infrared spectrophotometer is 10
The number was 6.7 per carbon atom.

<Preparation of Ultra-High Molecular Weight Ethylene / Propylene Copolymer Stretched Alignment> Ultra-high molecular weight ethylene / propylene copolymer powder described above
20 parts by weight and paraffin wax (melting point = 69 ° C., molecular weight =
490 g / mol) 80 parts by weight of the mixture was melt-spun under the following conditions.

0.1 part by weight of 3,5-di-tert-butyl-4-hydroxytoluene was added as a process stabilizer to 100 parts by weight of a mixture of ultra-high molecular weight ethylene / propylene copolymer powder and paraffin wax. Next, the mixture was melt-kneaded at a set temperature of 175 ° C. using a screw type extruder (screw diameter 25 mm, L / D = 25, manufactured by Thermoplastics Co., Ltd.). Subsequently, the melt was melt-spun with a spinning die having an orifice diameter of 2 mm attached to the extruder.

The extruded melt was taken with a draft ratio of 38 times with an air gap of 180 cm, cooled in air and solidified to obtain an unstretched fiber. Further, the unstretched fiber was stretched under the following conditions.

Two-stage stretching was performed using three godet rolls. At this time, the heat medium in the first drawing tank was n-decane, and the temperature was 11
The heating medium in the second stretching tank was 0 ° C., triethylene glycol was used, and the temperature was 145 ° C. The effective length of each tank is 50 cm
Met. At the time of drawing, the rotational speed of the first godet roll was set to 0.5 m / min and the rotational speed of the third godet roll was changed to obtain an oriented fiber having a desired draw ratio. The rotation speed of the second godet roll was appropriately selected within a range in which stable stretching was possible. Almost all the paraffin wax mixed in the initial stage was extracted into n-decane during stretching. Thereafter, the oriented fibers were washed with water, dried at room temperature under reduced pressure for a day and night, and subjected to measurement of various physical properties. The stretching ratio was calculated from the rotation speed ratio of the first godet roll and the third godet roll.

<Measurement of Tensile Properties> Modulus of elasticity and tensile strength were measured at room temperature (23 ° C) using a Shimadzu DCS-50M type tensile tester.

At this time, the sample length between the clamps is 100 mm and the pulling speed is 100
It was mm / min (100% / min strain rate). The elastic modulus was calculated using the initial elastic modulus and the slope of the tangent line. The fiber cross-sectional area required for the calculation was calculated from the weight with a density of 0.960 g / cc.

<Measurement of creep resistance> Using a thermal stress strain measurement device TMA / SS10 (manufactured by Seiko Denshi Kogyo Co., Ltd.), the creep characteristics were measured using a sample length of 1 cm, an ambient temperature of 70 ° C, and a load of 30% of the breaking load at room temperature. Was performed under accelerated conditions of a weight corresponding to The following two values were obtained to quantitatively evaluate the amount of creep. That is, the sleep elongation% after 90 seconds after loading is CR ₉₀ , and the average creep rate (sec ⁻¹ ) ε from 90 seconds to 180 seconds.

<Tensile elastic modulus and strength retention rate after heat history> The heat history test was performed by leaving it in a gear oven (perfect oven: manufactured by Tabai Seisakusho).

The sample had a length of about 3 cm, and was folded back on a stainless steel frame provided with a plurality of pulleys at both ends to fix both ends of the sample. At this time, fix both ends of the sample so that the sample does not sag.
The sample was not actively tensioned. The tensile properties after thermal history were measured based on the description of the measurement of tensile properties described above.

 Table 1 shows the tensile properties of the stretch-oriented fibers.

The differential scanning calorimeter of Sample 1 shows the first endothermic characteristic curve in FIG. 2 and the second (second run) endothermic characteristic curve in FIG.

The original crystal melting peak was 128.4 ° C, and the Tp ratio to the total crystal melting peak area was 49.0%. The creep resistance was CR ₉₀ = 4.6% ε = 3.33 × 10 ^-5 sec ^-1 . The creep characteristics of Sample 1 are shown in FIG. Further 170
The elastic modulus retention rate after heat history at 5 ° C for 5 minutes was 104.5%, and the strength retention rate was 108.2%, showing no deterioration in performance.

Example 2 <Polymerization of Ultra High Molecular Weight Ethylene / Propylene Copolymer> As in Example 1, a Ziegler type catalyst was used and slurry polymerization of an ethylene / propylene copolymer was performed using n-decane 1 as a polymerization solvent. Monomer gas with a composition ratio of ethylene and propylene in the molar ratio of 99.5: 0.55 was continuously fed so that the pressure in the reactor was kept constant at 5 kg / cm ² , and the polymerization was completed at 70 ° C. in 3 hours. . The yield of the ultra-high molecular weight ethylene-propylene copolymer powder obtained was 146 g, the intrinsic viscosity [η] (decalin, 135 ° C) was 10.4 dl / g, and the propylene content by infrared spectrophotometer was 1.4 per 1000 carbon atoms. It was an individual.

<Preparation of Ultra-High Molecular Weight Ethylene-Propylene Copolymer Stretched Oriented Product> Using the ultra-high molecular weight ethylene-propylene copolymer powder obtained by the above-mentioned polymerization, a stretch-oriented fiber is prepared by the method described in Example 1. did. At this time, the conditions different from Example 1 were that the set temperature during melt spinning was 190 ° C. and the draft ratio during spinning was 35 times.

 Table 2 shows the tensile properties of the stretch-oriented fibers.

FIG. 6 shows the first endothermic (first run) endothermic characteristic curve of Sample 2 by the differential scanning calorimeter, and FIG. 7 shows the second endothermic characteristic curve (second run).
Original ultra high molecular weight ethylene / propylene copolymer sample 2
The crystalline melting peak was 131.7 ° C, and the Tp ratio to the total crystalline melting peak area was 57.4%. The creep resistance was CR ₉₀ = 4.0% and ε = 1.44 × 10 ^-4 sec ^-1 . Sample 2
Fig. 9 shows the creep characteristics of. Furthermore, the elastic modulus retention rate for heat history at 170 ° C. for 5 minutes was 104.4%, and the strength retention rate was 107.9%, and as in Example 1, no deterioration in performance was shown.

Comparative Example 1 Ultrahigh molecular weight polyethylene (homopolymer) powder (intrinsic viscosity [η] = 7.42 dl / g, decalin, 135 ° C.): 20 parts by weight and paraffin wax (melting point = 69 ° C., molecular weight = 490): 80 parts by weight The mixture was melt-spun and stretched by the method of Example 2 to obtain oriented stretched fibers. Table 3 shows the tensile properties of the obtained stretched and oriented fibers.

The endothermic characteristic curve of the ultrahigh molecular weight polyethylene stretch-oriented fiber sample 3 observed by the differential scanning calorimeter at the first heating (first run) is shown in FIG. 4, and at the second heating (second run). FIG. 8 shows the endothermic characteristic curve obtained by the observation. The original crystal melting peak of the ultra high molecular weight polyethylene sample 3 was 135.1 ° C, and the Tp ratio to the total crystal melting peak area was 8.8%. Creep resistance is CR ₉₀
= 12.0% and ε = 1.07 × 10 ⁻³ sec ⁻¹ . The creep characteristics of Sample 3 are shown in FIG. 9 together with Sample 1 and Sample 2. Furthermore, the elastic modulus retention rate after thermal history at 170 ° C for 5 minutes is 80.4
%, The strength retention rate was 79.2%, and the elastic modulus and strength decreased due to thermal history.

[Brief description of drawings]

1 is an endothermic characteristic curve of the ultrahigh molecular weight ethylene / propylene copolymer powder used in Example 1 measured by a differential scanning calorimeter, and FIG. 2 is an ultrahigh molecular weight ethylene / propylene copolymer obtained in Example 1. Endothermic characteristic curve by the differential scanning calorimeter in the restrained state of the drawn oriented fiber, FIG. 3 is an endothermic characteristic curve by the differential scanning calorimeter of the ultra high molecular weight polyethylene powder used in Comparative Example 1, and FIG. 4 is in Comparative Example 1. Endothermic characteristic curve of the obtained ultra-high molecular weight polyethylene stretched and oriented fiber in a restrained state by a differential scanning calorimeter, Fig. 5 is an endotherm when the sample of Fig. 2 is subjected to the second temperature rise measurement (second run). Characteristic curve, FIG. 6 is an endothermic characteristic curve of the ultra-high molecular weight ethylene / propylene copolymer stretched and oriented fiber obtained in Example 2 by a differential scanning calorimeter in a restrained state, and FIG. 7 shows the sample of FIG. Second temperature rise measurement 8 is an endothermic characteristic curve when the sample of FIG. 4 is subjected to a second temperature rise measurement, and FIG. 9 is an example 1, an example 2 and a comparative example. The creep characteristic curve of the stretch-oriented fiber of each polymer obtained in 1 is shown.

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Claims (2)

[Claims] 1. A molecular orientation molded article of an ultrahigh molecular weight ethylene-propylene copolymer having an intrinsic viscosity [η] of at least 5 dl / g and an average propylene content of 0.5 to 15 per 1000 carbon atoms. When the molded body is constrained and measured by a differential scanning calorimeter,
Having at least two crystalline melting endotherms,
Ultrahigh molecular weight ethylene-propylene copolymer, which is determined as the main melting endothermic peak during the second temperature rise, is at least 20 ° C higher than the original crystal melting temperature (Tm) of the polymer.
It has one crystal melting endothermic peak (Tp), and the calorific value based on this crystal melting endothermic peak (Tp) per total heat of fusion is 15
% Or more, a molecular orientation molded article. 2. The ultrahigh molecular weight ethylene / propylene copolymer has an average propylene content of 1.0 to 10 per 1000 carbon atoms.
The molecularly oriented molded article according to claim 1, which is a single piece.