JPH04214405A - Draw-formed material of polypropylene having ultra-high molecular weight and its use - Google Patents

Abstract

PURPOSE:To provide a draw-formed material of a polypropylene having ultra- high molecular weight and excellent tensile properties, especially tensile strength without deteriorating the intrinsic thermal properties, creep resistance and high breaking energy of ultra-high molecular weight polypropylene fiber and to provide an elastomer for energy-regeneration composed of the draw-formed polypropylene having ultra-high molecular weight. CONSTITUTION:The objective draw-formed polypropylene having ultra-high molecular weight and a tensile strength of >=0.5GPa is composed of 85-99.5 pts.wt. of an ultra-high molecular weight polypropylene having an ultimate viscosity [eta] of >=5dl/g and 0.5-15 pts.wt. of a polyethylene having an ultimate viscosity [eta] of >=2dl/g. The objective energy-regeneration elastomer is composed of the above draw-formed polypropylene having ultra-high molecular weight.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultra-high molecular weight polypropylene stretched molded article, and more particularly to an ultra-high molecular weight polypropylene stretched molded article which is prepared by a spinning/drawing method and has excellent properties.

The present invention also relates to an elastic body for energy regeneration comprising the above-mentioned stretched and oriented ultra-high molecular weight polypropylene body.

0003

[Technical background of the invention] By forming ultra-high molecular weight polyethylene into fibers or tapes, etc., and stretching this,
It is already known that stretched molded bodies with high elastic modulus and high tensile strength can be obtained, and numerous patents have been published. For example, in Japanese Patent Application Laid-Open No. 56-15408,
A method related to the so-called gel spinning/ultra-stretching method is disclosed in which a dilute solution of ultra-high molecular weight polyethylene is spun and then the resulting filaments are stretched. Furthermore, Japanese Patent Application Laid-Open No. 58-5228 discloses that after preparing a dilute solution of an ultra-high molecular weight thermoplastic crystalline polymer using a non-volatile solution and forming a xerogel fiber by spinning this,
A method of stretching is shown. This method is basically the same as the gel spinning/ultra-stretching method described above, but when ultra-high molecular weight polyethylene is used as the ultra-high molecular weight thermoplastic polymer, the elastic modulus is 100 GPa or more, Furthermore, it is possible to obtain a stretched molded article having a high elastic modulus and high strength and a tensile strength of 3 GPa or more.

[0004] As described above, in the case of ultra-high molecular weight polyethylene, a method for producing fibers with high elastic modulus and high tensile strength using a dilute solution as a medium has almost been established, and the principle thereof has not yet been established. Journal of the Japanese Society of Rheology (Matsuo, Vol. 13, No. 1, P4-15, 19
85) is explained in detail. According to this paper,
In order for the manufactured fiber to exhibit high elastic modulus and high tensile strength, it must have so-called "extended chain crystals" in which the molecular chains have been extended to a certain extent.
``Extended Chain Crystal'' states that an ultra-high molecular weight molecular chain can be formed by an ultra-stretching method with a much larger stretching ratio than the conventional stretching ratio (6 to 12 times). This super-stretchability is thought to be achieved by the presence of molecular entanglement between crystals of the undrawn yarn before drawing, that is, lamellae and adjacent lamellae. .

[0005] The above paper also states that (1) in an ultra-dilute solution, ultra-high molecular weight polyethylene cannot form entanglement, so there is no interaction between molecules, and as a result, it does not exhibit stretchability; In a concentrated solution, the number of entanglements is too large, so the molecules become entangled with each other, and as a result, they do not exhibit stretchability. It has been reported that defects occur when the crystal becomes an extended chain crystal. Therefore, in order to obtain fibers with high elastic modulus and high tensile strength, it is necessary to minimize this number of entanglements, and for this purpose, polymers with ultra-high molecular weights are used as raw materials. It is preferred to draw undrawn fibers prepared from a dilute solution of this ultra-high molecular weight polymer. Further, it is preferable to use an ultra-high molecular weight polymer as a raw material in this way since the resulting high-strength fiber naturally has defects at the molecular ends. This principle is supported by the experimental results in this report and by many other researchers.

On the other hand, a number of studies have been conducted to obtain fibers with high elastic modulus and high tensile strength for polypropylene, and the various preparation methods that were successful for polyethylene described above have been appropriately improved for polypropylene. has been added and applied.

[0007] Here, when comparing the theoretical strength of polypropylene and polyethylene, polypropylene has a strength of 18 GPa.
(“Textiles and Industry” Vol. 40, P. 407-418,
(1984), whereas polyethylene has a strength of 32 GPa, and theoretically polypropylene has about half the strength of polyethylene. Furthermore, as the current strength of high-strength polyethylene fibers has reached approximately 6 GPa according to the report by Matsuo et al., it is believed that polypropylene can sufficiently reach a strength of approximately half this, that is, approximately 3 GPa. Conceivable.

[0008] Here, as a conventionally known method for producing high-strength polypropylene fibers, first, as an example of applying the zone stretching method, which was successful in polyethylene, to polypropylene, there is a report by Koki et al. (Journal of Appl.
ied Polymer Science, Vol. 2
8, pp. 179-189, 1983), which involves heating a 1-2 mm section of fiber prepared in advance using a conventional melt-spinning method using a local heating furnace, and then stretching the section to obtain super-stretched fibers. This is the way to do it. According to this method, when polypropylene with a molecular weight of 475,000 is used, polypropylene fibers having an elastic modulus of 16.9 GPa and a tensile strength of 0.74 GPa are obtained.

[0009] Furthermore, as an example of applying the above-mentioned gel spinning/ultra-stretching method to polypropylene, Peguy and Ma
nley report (Polymer Communica
tions, Vol. 25, P39-42, 1984
), and according to this method, Smith and Lem
An example of ultra-high molecular weight polyethylene (Jo
urnal of Polymer Bulletin
, Vol. 1,733,1979), 0.75
Polypropylene fibers having an elastic modulus of 36 GPa and a tensile strength of 1.03 GPa were obtained by gel spinning and super-stretching using a solution of ~1.5% W/W.

Furthermore, the above-mentioned Japanese Patent Application Laid-open No. 58-5228 also discloses an example of polypropylene similar to the example of polyethylene described above, and has an intrinsic viscosity of 1
The elastic modulus is 23.9 GPa from a 6% weight concentration solution of ultra-high molecular weight polypropylene of 8 dl/g (molecular weight 3.3 million).
and has successfully produced polypropylene fibers with a tensile strength of 1.04 GPa.

However, when such conventional methods for preparing high-strength polypropylene fibers were investigated, it was found that the elastic modulus and tensile strength of the drawn polypropylene yarn or tape were 7 to 10 GPa and 0.5 GPa, respectively.
The tensile strength is 5 to 1.04 GPa, and compared to the above-mentioned value of 3 GPa, the actual situation is that the tensile strength has hardly been improved.

[0012] As an example of success in improving this tensile strength, there is a report by Kanemoto et al. (Japan Society of Textile Science and Technology, 1985 Annual Conference Research Presentation Proceedings), in which ultra-high molecular weight polypropylene with a molecular weight of 3.6 million was used. The tensile strength is 2.3GP.
An ultra-high molecular weight polypropylene stretched molded article having a. This method is roughly divided into the following three steps. [First step]: A so-called solvent cast film is prepared by evaporating the solvent from a 1% by weight or less ultra-high molecular weight polypropylene solution. This process is considered to be the same in principle as the preparation process for gel fibers and xerogel fibers described above. [Second step]:
The cast film is sandwiched between polyethylene burettes and subjected to solid phase extrusion in a pseudo-melt state. At this time, the cast film is solid state stretched by passing through a conical die, and the solid state drawing ratio (EDR) is about 6 times. [Third step]: By subjecting the solid phase extruded film to normal tension stretching, solid phase stretching ratio x tensile stretching ratio =
Stretched at about 72 times, the above-mentioned tensile strength is about 2.3GP
A high-strength polypropylene fiber was obtained.

The reason why the superstretched molded product of Kanemoto et al., which was prepared by the same principle as the gel spinning/superstretching method, has significantly improved tensile strength is due to the above-mentioned [
2nd step]. In other words, passing through a conical die and solid-state stretching in a burette is in principle subjected to tensile stretching deformation, so it is the same deformation as the tensile stretching performed in the gel spinning/superstretching method. The major difference is that no matter how weak or brittle the sample is, the burette can be inserted into the sample from both sides in a tough manner and the sample can be stretched without being damaged or broken.

In other words, when attempting to prepare polypropylene fibers by the gel spinning/ultra-drawing method, it is thought that fatal defects are imparted to the drawn fibers during low-magnification drawing in the tensile drawing operation, which affects the ability to achieve high strength. . That is, the structure of gel fibers prepared from polypropylene is fundamentally different from gel fibers obtained from polyethylene, and the structure of gel fibers prepared from polypropylene is fundamentally different from that of normal gel fibers until they become oriented to some extent, increasing fiber strength and being able to withstand drawing operations. It is not suitable for tensile stretching, and even if the tensile stretching stress exceeds the fiber strength at the initial stage of stretching and the stretching is apparently possible, at least a fatal flaw occurs in increasing the strength of the stretched fiber. There is.

Therefore, as described above, sandwiching ultra-high molecular weight polypropylene fibers in a buret and subjecting them to solid phase drawing using a conical die is a reasonable method for increasing the strength of the fibers, but Sandwiching molecular weight polypropylene fibers in a buret and solid-phase drawing with a conical die is extremely disadvantageous in terms of productivity and cost when manufacturing fibers continuously from ultra-high molecular weight polypropylene, that is, from the standpoint of industrialization. I have to say that it is.

In view of these points, the present inventors developed a polypropylene fiber having excellent thermal properties, creep resistance, and high breaking energy by using a spinning/drawing method, which is superior in terms of productivity and cost. As a result of intensive research to obtain this method, it was found that ultra-high molecular weight polypropylene requires a much longer time to cool and crystallize after the spinning solution is discharged from the spinning nozzle than ultra-high molecular weight polyethylene. It has been found that the moldability of ultra-high molecular weight polypropylene is extremely difficult.

[0017]

OBJECTS OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above, and aims to overcome the inherent thermal properties, creep resistance, and high breaking energy of ultra-high molecular weight polypropylene fibers. The object of the present invention is to provide an ultra-high molecular weight polypropylene stretched molded article having excellent tensile properties, especially tensile strength, without impairing properties.

Another object of the present invention is to provide an elastic body for energy regeneration comprising the above-mentioned stretched ultra-high molecular weight polypropylene body.

[0019]

SUMMARY OF THE INVENTION The ultra-high molecular weight polypropylene stretched molded article according to the present invention comprises 85 to 99.5 parts by weight of ultra-high molecular weight polypropylene (A) having an intrinsic viscosity of at least 5 dl/g and 0.5 to 15 parts by weight of polyethylene (B) having a tensile strength of at least 0.5 GPa or more.

[0020] Furthermore, the elastic body for energy regeneration according to the present invention contains 85 to 99.5 parts by weight of ultra-high molecular weight polypropylene (A) having an intrinsic viscosity [η] of 5 dl/g or more and /g or more polyethylene (B)0
．． The ultra-high molecular weight polypropylene stretched and oriented molded article has a tensile strength of 0.5 GPa or more.

[0021] Here, the polyethylene (B) as described above is preferably an ultra-high molecular weight polyethylene having an intrinsic viscosity of at least 5 dl/g or more.

[0022]

DETAILED DESCRIPTION OF THE INVENTION The ultra-high molecular weight polypropylene stretched molded article and energy regeneration elastic body according to the present invention will be explained in detail below.

The ultra-high molecular weight polypropylene stretched molded article according to the present invention is obtained by spinning and spinning an ultra-high molecular weight polypropylene composition consisting of ultra-high molecular weight polypropylene and polyethylene.
It is a molded body obtained by spinning and stretching using a stretching method.

Ultra-high molecular weight polypropylene (A) The ultra-high molecular weight polypropylene used in the present invention has an intrinsic viscosity [η] of at least 5 dl/g, preferably 10 dl/g or more, as measured in a decalin solvent at 135°C. If the intrinsic viscosity [η] is less than 5 dl/g, there will be a tendency that a stretched molded product with excellent tensile strength cannot be obtained due to insufficient molecular chain length. On the other hand, the upper limit of the intrinsic viscosity [η] is not particularly limited, but if it exceeds 30 dl/g, the solubility becomes poor and the viscosity of the dope becomes extremely high at high concentrations, resulting in unstable spinning due to causes such as melt fracture. There is a tendency to become inferior in gender.

The ultra-high molecular weight polypropylene used in the present invention is a propylene homopolymer obtained by coordination anionic polymerization, or a small amount (for example, 10
propylene-based copolymers of other α-olefins such as ethylene, 1-butene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-octene, 1-decene, etc.) Copolymers are used.

Polyethylene (B) The polyethylene used in the present invention plays a role in accelerating the crystallization rate of ultra-high molecular weight polypropylene when the ultra-high molecular weight polypropylene is stretched. It is desirable that such polyethylene has an intrinsic viscosity [η] of at least 2 dl/g, preferably 5 dl/g or more, more preferably 10 dl/g or more, as measured at 135° C. in a decalin solvent. This intrinsic viscosity [η] is 2dl
If it is less than /g, there will be a tendency that the effect of accelerating the crystallization rate cannot be sufficiently exerted due to insufficient interaction between molecules of polyethylene and ultra-high molecular weight polypropylene. On the other hand, the upper limit of the intrinsic viscosity [η] of polyethylene is not particularly limited, but if it exceeds 30 dl/g, it will have poor solubility;
There is a tendency that a gel-like substance is formed in the spinning dope, resulting in poor spinning stability.

The polyethylene in the present invention is an ethylene homopolymer obtained by coordination anionic polymerization, or ethylene and a small amount (for example, 10 mol % or less) of other α-olefins, such as propylene, 1-butene, 4-methyl -1- An ethylene copolymer containing pentene, 1-pentene, 1-hexene, 1-octene, 1-decene, etc. is used.

As described above, in the ultra-high molecular weight polypropylene composition composed of ultra-high molecular weight polypropylene and polyethylene, the polyethylene plays a role of accelerating the crystallization rate of the composition, but the ultra-high molecular weight polypropylene containing the diluent The crystallization rate of the composition, ie, the spinning dope, can be measured using a differential scanning calorimeter as follows.

[0029] First, the spinning dope is heated and dissolved in a sealed solution cell made of silver, and this cell is attached to a sample holder of a high-sensitivity differential scanning calorimeter. As the high-sensitivity differential scanning calorimeter, for example, a high-sensitivity differential scanning calorimeter SS10 model manufactured by Seiko Electronics Industries, Ltd. can be used. After the sealed cell is attached to a differential scanning calorimeter, the temperature of the sealed cell is rapidly raised to a spinning temperature of about 130 to 240°C. The sealed cell is held at this temperature for a sufficient period of time (for example, 15 minutes) to restore the state to the state at which the spinning dope was prepared.

Next, this sealed cell was rapidly cooled using liquid nitrogen as a refrigerant, and the time (
T) is measured, and the crystallization rate is quantitatively evaluated based on this time.

For example, when a spinning stock solution at 150° C. is rapidly cooled to a temperature of 60° C., the time (T) until the exothermic peak accompanying crystallization appears is 60 seconds or less, preferably 30 seconds or less, particularly preferably 10 seconds. It is as follows.

[0032] The crystallization rate of the ultra-high molecular weight polypropylene composition according to the present invention can be determined by visually checking the position of the whitening point (frosting point) of the spinning stock solution when the spinning stock solution is flowed down in a cooling atmosphere or into a refrigerant. It can also be easily and qualitatively measured.

Composition In the ultra-high molecular weight polypropylene stretched molded article obtained from the ultra-high molecular weight polypropylene composition according to the present invention, the ultra-high molecular weight polypropylene is contained in an amount of 85 to 99.5 parts by weight, preferably 90 to 99 parts by weight, and more preferably Polyethylene is used in an amount of 95 to 99 parts by weight, and polyethylene in an amount of 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight.

If the amount of polyethylene exceeds 15% by weight, the mechanical properties at high temperatures of the obtained ultra-high molecular weight polypropylene stretched molded product (molecularly oriented product) tend to decrease, while if the amount is less than 0.5% by weight Then, when the ultra-high molecular weight polypropylene is stretched, the crystallization rate of the ultra-high molecular weight polypropylene tends to be too slow, resulting in poor moldability. In addition, when the melting point of the ultra-high molecular weight polypropylene stretched molded article (molecularly oriented body) obtained from the ultra-high molecular weight polypropylene stretched molded article (molecularly oriented body) obtained from the composition for forming an ultra-high molecular weight polypropylene stretched molded article according to the present invention, it was found that the polyethylene portion was in a relatively low temperature region (around 130°C). It has an independent peak. From this, it can be understood that if the amount of polyethylene is too large, the mechanical properties at high temperatures of the obtained ultra-high molecular weight polypropylene stretched molded article will deteriorate.

Manufacturing method [Dissolution and mixing] In the present invention, first, a fluidity improver is mixed into a composition consisting of ultra-high molecular weight polypropylene and polyethylene as described above to obtain a spinning stock solution, and the composition is made into a spinning solution. do. Such a fluidity improver is a solvent that can dissolve the ultra-high molecular weight polypropylene, preferably a solvent that can dissolve the ultra-high molecular weight polypropylene, and has a boiling point higher than the melting point of the ultra-high molecular weight polypropylene, more preferably a melting point +2.
A solvent having a boiling point of 0° C. or higher is used.

Specifically, such solvents include n
- Nonane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-octadecane or aliphatic hydrocarbon solvents such as liquid paraffin and kerosene; xylene,
Aromatic hydrocarbon solvents such as naphthalene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, pentylbenzene, dodecylbenzene, bicyclohexyl, decalin, methylnaphthalene, ethylnaphthalene, etc. or hydrogenated derivatives thereof; 1,1,
2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,2,3-trichloropropane,
dichlorobenzene, 1,2,4-trichlorobenzene,
Halogenated hydrocarbon solvents such as bromobenzene; mineral oils such as paraffinic process oils, naphthenic process oils, and aromatic process oils are used.

In the present invention, various waxes having dispersibility in ultra-high molecular weight polypropylene can also be used as fluidity improvers. Further, as the above-mentioned waxes, aliphatic hydrocarbon compounds or derivatives thereof are used.

[0038] Specifically, the aliphatic hydrocarbon compounds used as waxes are mainly saturated aliphatic hydrocarbon compounds, and usually have a molecular weight of 2,000 or less, preferably 10
A paraffin wax having a molecular weight of 0.00 or less, more preferably 800 or less is used.

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 containing these as main components with lower n-alkanes; So-called paraffin wax separated and refined from petroleum, medium/low polyethylene wax which is a low molecular weight polymer obtained by copolymerizing ethylene or ethylene with other α-olefins, high-pressure polyethylene wax, ethylene copolymer wax, or Medium/low pressure polyethylene,
Waxes obtained by reducing the molecular weight of polyethylene such as high-pressure polyethylene by thermal degradation, oxides of these waxes, oxidized waxes modified with maleic acid, waxes modified with maleic acid, and the like are used.

Examples of aliphatic hydrocarbon compound derivatives include aliphatic hydrocarbon groups (alkyl groups, alkenyl groups)
A compound having one or more, preferably 1 to 2, particularly preferably 1, functional group such as a carboxyl group, hydroxyl group, carbamoyl group, ester group, mercapto group, or carbonyl group at the terminal or inside of the carbon Number 8 or more, preferably carbon number 12-50 or molecular weight 130-2
000, preferably 200 to 800 fatty acids, aliphatic alcohols, aliphatic amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones, and the like.

Specifically, the aliphatic acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; the aliphatic alcohols include lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol; and the fatty acid amides include capric acid. Examples of fatty acid esters include amide, lauramide, palmitinamide, stearylamide, and stearyl acetate.

Among these fluidity improvers, waxes that are solid at room temperature are preferred in terms of storage and transportation properties. As the fluidity improver used in the present invention, a low softening point hydrocarbon polymer having a softening point of 50 to 120°C is used, as long as it does not impair the purpose of the present invention. Specifically, adhesive tapes are usually used as a tackifying resin. , paints, and hot melt adhesives, and depending on the monomer source to be polymerized, the following resins, such as C4 fraction and C5 fraction obtained by decomposing petroleum, naphtha, etc. or any fraction thereof, such as aliphatic hydrocarbon resins whose main raw materials are isoprene and 1,3-pentadiene in the C5 fraction, obtained by cracking petroleum, naphtha, etc. in the C9 fraction. Aromatic hydrocarbon resins whose main raw materials are styrene derivatives and indenes, aliphatic/aromatic copolymerized hydrocarbon resins made by copolymerizing arbitrary fractions of C4 and C5 fractions and C9 fractions, aromatic carbonization Alicyclic hydrocarbon resin obtained by hydrogenating hydrogen resin, synthetic terpene hydrocarbon resin with a structure containing aliphatic, alicyclic and aromatic groups, and terpene resin made from α,β-pinene in turpentine oil. Hydrocarbon resin, coumaron-indene hydrocarbon resin made from indene and styrene in coal tar naphtha, low molecular weight styrene resin, rosin hydrocarbon resin, etc. are added as a mixed fluidity improver. It can also be used.

The blending ratio of the ultra-high molecular weight polypropylene composition and the fluidity improver varies depending on the type of blending, but generally speaking, the weight ratio is 1:99 to 1.
It is desirable that the ratio is 5:85, preferably 3:97 to 10:90. If the amount of the fluidity improver is less than the above range, the viscosity of the spinning dope will become too high, which will not only make dissolving and mixing and spinning difficult, but also cause the resulting fiber to have a markedly rough surface and be prone to stretch breakage. There is a tendency to on the other hand,
If the amount of the fluidity improver is greater than the above range, the spinnability during spinning and the drawability of the fibers tend to be poor.

[0044] The melting and mixing of the ultra-high molecular weight polypropylene composition and the fluidity improver is generally carried out at a temperature of 110°C to 300°C, preferably 130°C to 240°C, although it varies depending on the type of fluidity improver used. If melting and mixing is performed at a temperature lower than this range, the ultra-high molecular weight polypropylene composition and the fluidity improver will not be completely dissolved or dispersed, and as a result, a uniform unstretched molded article will be obtained by spinning. There is a tendency to become unable to do so. On the other hand, if the melting and mixing is carried out at a temperature higher than the above range, the molecular weight of the ultra-high molecular weight polypropylene in particular decreases due to thermal degradation, which tends to make it difficult to obtain a high-strength stretched molded article.

Such melting and mixing can be carried out using a mixer equipped with heatable stirring blades, or can also be carried out using a single-screw or multi-screw extruder. In addition, when preparing the above-mentioned spinning dope, it is desirable to incorporate a stabilizer in order to prevent thermal deterioration of ultra-high molecular weight polypropylene and polyethylene. Stabilizers that can be used in this case include, for example, 3,5-di-tert-butyl-4-hydroxytoluene and tetrakis[methylene-3-(3,5-di-tert-
Butyl-4-hydroxyphenyl)propionate]
Methane and the like can also be used. [Spinning] Spinning of the spinning dope is generally performed by extrusion molding. That is, a filament for drawing is obtained by extruding the spinning solution through a spinneret, a film, sheet or tape for drawing is obtained by extruding it through a flat die, and a drawing film or sheet or tape is obtained by extruding it through a circular die. A pipe for hollow fiber molding is obtained. The present invention is particularly useful in the production of drawn filaments, in which case drafting (ie, stretching in solution) can also be applied to the solution extruded from the spinneret. The spinning stock solution extruded in this manner can be cooled by air cooling or forced cooling means such as a refrigerant such as water, methanol, ethanol, acetone, etc. to further increase the crystallization rate. [Stretching] The unstretched molded article of ultra-high molecular weight polypropylene thus obtained is subjected to a stretching treatment. The extent of this stretching treatment may be such that the ultra-high molecular weight polypropylene in the molded article is effectively given molecular orientation in at least one axial direction.

The stretching of the ultra-high molecular weight polypropylene molded body is generally carried out at a temperature of 40°C to 230°C, particularly 80°C to 200°C. As the heat medium, air, water vapor, or a liquid medium can be used. Furthermore, prior to stretching, the fluidity improver added in advance can be extracted and removed from the unstretched molded body using a solvent or the like. Furthermore, as a heat medium for heating and holding the unstretched compact, a solvent that can extract and remove the fluidity improver and has a boiling point higher than the stretching temperature, specifically, decane, decalin, kerosene, etc. is used. It is preferable to carry out the stretching operation using the above-mentioned resin because it becomes possible to extract and remove the above-mentioned fluidity improver, eliminate stretching unevenness during stretching, and achieve a high stretching ratio. Note that even if such a heating medium does not have the effect of removing the fluidity improver, the fluidity improver in the molded product can be removed by, for example, treating the stretched molded product in a solvent. Needless to say.

[0047] The stretching operation can be carried out either in one stage or in multiple stages of two or more stages. In addition, the stretching ratio depends on the desired molecular orientation and the accompanying effect of increasing the melting temperature, but is generally 5 to 200 times, particularly 1
It is preferable to carry out the stretching operation so that the stretching ratio is 0 to 100 times.

[0048] In the above-mentioned stretching operation, multistage stretching of two or more stages is generally advantageous, and the first stage stretching is preferably carried out at a relatively low temperature of 60°C to 120°C. Further, in the second and subsequent stages of stretching, it is preferable to perform the stretching operation of the molded body at a temperature of 120°C to 230°C, and at a temperature higher than the first stage stretching temperature. Here, in the second and subsequent stages of stretching, it is preferable that at least one stage of the stretching operation be performed at a temperature of 165° C. or higher. Furthermore, during the stretching operation, a part of the polyethylene contained in the unstretched molded product may be removed in the form of scum from the stretched molded product, but the polyethylene has already been crystallized from ultra-high molecular weight polypropylene. It is actually preferable to remove the polyethylene contained in the unstretched molded body after it has fulfilled its promoting function. [Heat Treatment] The stretched molded product thus obtained can be heat treated under restrictive conditions or under some shrinkage conditions, if desired. The shrinkage condition referred to here is an operation opposite to the above-mentioned stretching, and the stretching ratio is 0.92 times or more, preferably 0.95 times or more. Heat treatment is generally 14
At temperatures of 0°C to 220°C, especially 150°C to 200°C, 0
．． It is preferable to carry out the heating for 5 to 10 minutes, particularly for 1 to 5 minutes. This heat treatment moves the crystal melting temperature of the stretched molded product to a higher temperature side, and also improves the creep resistance at high temperatures. This is considered to be because the heat treatment further progresses crystallization of the oriented crystal portions that were previously formed in the stretched compact.

Stretched molded article The stretched molded article obtained from the ultra-high molecular weight polypropylene composition as described above has a composition of ultra-high molecular weight polypropylene having an intrinsic viscosity [η] of at least 5 dl/g.
5 to 99.5% by weight and an intrinsic viscosity [η] of at least 2
dl/g of polyethylene in an amount of 0.5 to 15% by weight, and has a tensile strength of at least 0.5 GPa or more, preferably 0.8 GPa or more. Further, the melting point of the ultra-high molecular weight polypropylene stretched molded product obtained by the present invention is 170°C or higher, preferably 180°C or higher, when measured by a differential scanning calorimeter under restraint conditions.
It is more preferably 190° C. or higher, and has heat resistance that is not seen at all in conventional drawn polypropylene fibers.

[0050] Here, the melting point is determined using a differential scanning calorimeter according to the following procedure. In other words, the differential scanning calorimeter is
Approximately 3 samples were collected using a PerkinElmer DSCII model.
The orientation of the sample is restricted by winding the sample onto an aluminum plate of 4 mm x 4 mm and 0.2 mm thick. Next, the sample wound around this aluminum plate is enclosed in an aluminum pan, and this is used as a measurement sample. In addition, the same aluminum plate used for the sample is sealed in a normally empty aluminum pan to be placed in the reference holder, which is a comparison sample, to maintain a thermal balance between the two. After holding the sample at 30°C for about 1 minute, the sample is heated to 250°C at a rate of 10°C/min. The maximum endothermic peak position determined by this measurement is taken as the melting point of the sample.

[0051] When such melting point measurements are carried out, no independent melting peak of polyethylene is observed in the ultra-high molecular weight polypropylene stretched molded product according to the present invention, but after this melting point measurement, the temperature is lowered to room temperature and the melting point is measured again. In the so-called second run, a single polyethylene melting peak appears. This is one of the characteristics of the present invention, and shows that the polyethylene itself is highly oriented by the spinning and drawing operations, and that at least the polyethylene does not cause defects in the fibers.

Further, the degree of molecular orientation of the ultra-high molecular weight polypropylene stretched molded article according to the present invention can be measured by an X-ray diffraction method, a birefringence method, a fluorescence polarization method, or the like. For example, the degree of orientation according to the half width (Japanese Industrial Chemistry, Vol. 39, P.
．． 992, 1939) F is

[0053]

[Math 1]

It is represented by: In this equation, H° is the half of the intensity distribution curve along the Debye ring of the strongest paratropic plane on the equator (generally (110) plane reflection in the case of polypropylene) among the X-ray diffraction reflections. price range (°). From the viewpoint of the mechanical properties of the resulting fibers, it is preferable that the molecules are oriented so that the degree of orientation F expressed by this formula is 0.90 or more, particularly 0.95 or more.

[0055] Applications The ultra-high molecular weight polypropylene stretched molded article according to the present invention is
It has excellent heat resistance, creep resistance, mechanical properties, etc.
The stretched molded product is useful as industrial textile materials such as high-strength multifilaments, strings, ropes, woven fabrics, and nonwoven fabrics, as well as packaging materials such as packing tapes. In addition, when the filament-shaped molded product is used as a reinforcing fiber for various resins such as epoxy resins and unsaturated polyesters, and synthetic rubber, it has a higher heat resistance than conventional ultra-high molecular weight polyethylene drawn filaments and polypropylene drawn filaments. Significant improvements are achieved in this regard. Furthermore, since this filament has high strength and low density, it can be particularly lightweight compared to conventional molded products using glass fiber, carbon fiber, boron fiber, aromatic polyamide fiber, aromatic polyimide fiber, etc. It is valid. Similar to composite materials using glass fiber etc., UD (Unit Direct
tional) laminate, SMC (Sheet Mold)
ing Compound), BMC (Bulk Mo
It is expected to be used as a variety of composite materials in lightweight, high-strength fields such as automobile parts, boat and yacht structures, and electronic circuit boards.

Further, the ultra-high molecular weight polypropylene stretched molded article according to the present invention can be preferably used as an elastic body for energy regeneration. When energy is externally applied to the elastic body for regeneration made of the stretched ultra-high molecular weight polypropylene body as described above, this energy can be stored in the elastic body for regeneration, and this accumulated energy can be used for regeneration. It can be taken out from the elastic body and used. The energy regeneration rate of the energy regeneration elastic body made of such a stretched ultra-high molecular weight polypropylene body does not decrease even if it is used repeatedly.

The amount of energy stored in the energy regeneration elastic body can be measured and evaluated by various methods. For example, a simple method may be to measure the amount of stored energy when a load corresponding to, for example, 50% of the stress required for rupture is applied, and to evaluate based on this value. In other words, if the vertical axis is set as stress and the horizontal axis is set as elongation on a recording paper during a tensile test, a perpendicular line is drawn from the part of the stress-strain curve that corresponds to the 50% load at rupture, and this perpendicular line and the horizontal The area surrounded by the axis and the stress/strain curve corresponds to this amount of stored energy. According to this measuring method, the amount of stored energy of the energy regeneration elastic body made of the ultra-high molecular weight polypropylene stretched molded product according to the present invention is at least 1 kgfm/g or more, preferably 2 kgfm/g or more.
gfm/g or more, preferably 2.5 kgfm/g or more.

[0058]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way as long as the gist thereof is not exceeded.

[0059]

Examples 1 to 5 [Preparation of spinning dope] Ultra-high molecular weight polypropylene powder, polyethylene powder and decalin at a desired mixing ratio were charged into a separable flask equipped with a condenser. At this time, as a process stabilizer, 3,5-di-tert-butyl-4
- Hydroxytoluene was added in an amount of 0.1% by weight based on the total of ultra-high molecular weight polypropylene and polyethylene. Thereafter, while stirring, the temperature of the system was kept at room temperature, and nitrogen gas was bubbled for about 30 minutes to remove oxygen dissolved in the system. Furthermore, the temperature of the system was heated to 110° C. under stirring to moisten the powder. When the state inside the system was continuously observed, it was found that after about 8 minutes at 110° C., a viscous slurry-like suspension was formed, and wetting was completed. Next, when the temperature of the system was heated to 140° C. and stirring was continued, a transparent solution was obtained in about 10 minutes, and a solution of an ultra-high molecular weight polypropylene-polyethylene composition was obtained. This solution was left standing at 140° C. for about 1 hour to obtain a spinning stock solution. A sample for measuring the crystallization rate was sampled from this state. [Spinning] The solution of the ultra-high molecular weight polypropylene composition prepared as described above was spun under the following conditions to obtain fibers. That is, the solution was extruded at a temperature of 140° C. using a plunger type extruder equipped with a spinning nozzle of 2 mmφ. The extruded solution was taken at room temperature under an air gap of about 30 cm, and then introduced into an acetone bath.
A crystallized fiber was obtained by performing a crystallization operation. At this time, the solution was taken up in a state close to free fall, and drafting was not actively performed. The whitened and crystallized fibers were wound onto a bobbin, dried under reduced pressure at room temperature, and subjected to the next drawing process. [Stretching] The fibers prepared by the method described above were drawn under the following conditions to obtain oriented drawn yarn. That is, using four godet rolls, n-decane was used as the heating medium in the first stage, and Flusol P (heating medium manufactured by Thermal Kagaku Kogyo) was used as the heating medium in the second and subsequent stages, and three-stage stretching was performed in a stretching tank. Ta. At this time, the temperature inside the first drawing tank was 110°C, the temperature inside the second drawing tank was 140°C, the temperature inside the third drawing tank was 165°C, and the effective length of each tank was 50°C.
It was cm. During stretching, the rotational speed of the first godet roll was set to 0.5 m/min, and the desired stretching ratio was obtained by changing the rotational speed of the fourth godet roll. Further, the rotational speeds of the second and third godet rolls were appropriately selected within a range that allowed stable stretching. However, the stretching ratio was determined by the rotation ratio of the first godet roll and the fourth godet roll. The elastic modulus and tensile strength were measured at room temperature (23° C.) using Autograph DCS-50 manufactured by Shimadzu Corporation. The sample length between the clamps at this time was 100 mm, and the pulling speed was 100 mm/min. However, the elastic modulus was calculated using the initial elastic modulus and the slope of the tangent. Also,
The fiber cross-sectional area required for calculation is based on the fiber density of 0.910g.
/cc, and calculated from the weight of the sample.

Table 1 shows the sample number, sample composition, and crystallization rate. As mentioned above, the crystallization rate in the table is the rapid temperature drop when the temperature was rapidly lowered from 140°C to 60°C using a differential scanning calorimeter. It was expressed as the time (sec) from the start to the appearance of the crystallization peak (exotherm). In either case, it can be seen that the crystallization rate is faster and the forming stability during spinning is excellent compared to the results of comparative examples (Table 3) described later. Further, Table 2 shows various physical properties of drawn fibers obtained by drawing each sample having the composition shown in Table 1 under the above-mentioned conditions. Compared to the results of comparative examples (Table 4) described later, it can be seen that the fibers have extremely well-balanced heat resistance and mechanical properties.

[0061]

[Comparative Examples 1 to 5] Drawn fibers were prepared in the same manner as described in Example 1. Table 3 shows sample numbers, sample compositions, and crystallization rates. When the crystallization rate is slow (for example, 10 seconds or more), the formability during spinning is extremely poor;
Furthermore, the uniformity of the diameter of the fibers was poor, and if the crystallization rate was extremely slow, it was not possible to form them into fibers. Also,
Table 4 shows the physical properties of fibers obtained by drawing the samples shown in Table 3 in the same manner as in Example 1 described above. Said Example 1
It can be seen that the heat resistance and mechanical properties are inferior to that of .

Furthermore, Tables 2 and 4 show the amount of stored energy measured by the method described herein.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

[Table 4]

Claims (4)

[Claims] Claim 1: The intrinsic viscosity [η] is at least 5 dl/
Ultra-high molecular weight polypropylene (A) 85 to 9 g or more
9.5 parts by weight and an intrinsic viscosity [η] of at least 2 dl/
An ultra-high molecular weight polypropylene stretched molded article, characterized in that it comprises 0.5 to 15 parts by weight of polyethylene (B) having a tensile strength of at least 0.5 GPa or more. 2. The ultra-high molecular weight polypropylene stretched molded article according to claim 1, wherein the polyethylene (B) is an ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of at least 5 dl/g or more. 3. 85 to 99.5 parts by weight of ultra-high molecular weight polypropylene having an intrinsic viscosity [η] of 5 dl/g or more;
Polyethylene 0 whose intrinsic viscosity [η] is 2 dl/g or more
．． 5 to 15 parts by weight, and has a tensile strength of 0.5 GPa or more. 4. The polyethylene has an intrinsic viscosity [η]
The elastic body for energy regeneration comprising a stretched and oriented ultra-high molecular weight polypropylene body according to claim 3, wherein the elastic body is ultra-high molecular weight polyethylene having an elasticity of 5 dl/g or more.