JPH046740B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for preparing a paraffin wax melt that can produce fibers, films, etc. having high elastic modulus and high strength from ultra-high molecular weight polyethylene. .

[Conventional technology and its problems]

It is well known that by spinning ultra-high molecular weight polyethylene and then stretching it, a stretched product with high strength and high modulus of elasticity can be obtained. For example, Japanese Patent Application Publication No. 55
As in JP-A-107506, JP-A-56-15408, or JP-A-58-5228, ultra-high molecular weight polyethylene is made into a dilute solution with a concentration of about 2 to 10% by weight, then spun and stretched to a high ratio. A certain method and JP-A-Sho
No. 59-130313, in a composition in which ultra-high molecular weight polyethylene is blended with a specific paraffin wax, ultra-high molecular weight polyethylene is added at a concentration of 15 to 15%.
A method has been proposed in which the composition is melt-extruded in a range of 80% by weight and then stretched, and this method has achieved some results. In addition, in order to obtain such a stretched product with high strength and high modulus, it is first necessary to prepare a uniform solution of a high molecular weight polymer such as ultra high molecular weight polyethylene using an appropriate solvent. method has been proposed. For example, as in JP-A-60-40133, a gel-like substance is precipitated while slowly cooling a solution of ultra-high molecular weight polyethylene, and the gel-like substance is removed from the gel-like substance in the form of a film and a solid lump. A method has been proposed in which a substance is stirred to form a spherulite gel and then dispersed again in a solvent. However, when this method is used, it not only produces a large amount of unnecessary film-like and solid gel-like substances, but also requires re-dissolution, making the operation complicated and making it difficult to effectively utilize ultra-high molecular weight polyethylene. There are some problems, such as not being able to get it.

Also, a method of cooling and concentrating a dilute solution of ultra-high molecular weight polyethylene and then redissolving it (Japanese Patent Laid-Open No. 59-223307)
is proposed.

Similar methods are also found in the literature. (B. Kalb and A. G. Pennings; Journal of Materials Science, 15
(Vol., pp. 2584-2590 (1980)) However, these methods require complicated operations and involve exposure to high temperatures twice for long periods of time, which may lead to a decrease in molecular weight.

After humidifying the ultra-high molecular weight polyethylene as a raw material with a solvent at a temperature below the swelling temperature or above the low-temperature wet temperature and below the melting point of polyethylene, it is heated as it is or brought into contact with the heated solvent quickly, and then gently stirred. A method has been proposed for preparing a homogeneous solution of ultra-high molecular weight polyethylene by adding .

(Japanese Patent Publication No. 60-22010, Japanese Patent Publication No. 59-232123) In both of these methods, the rate of penetration of the thermal solvent into the polyethylene is increased by pre-wetting or swelling the ultra-high molecular weight polyethylene. The aim is to prepare a homogeneous solution in a very short time and at a high concentration by avoiding the formation of . However, its uniformity and high concentration vary greatly depending on the solvent used, and liquid paraffin, which has relatively low swelling performance, is not described in the examples, and is generally used as a solvent for polyethylene. Examples are only given for p-xylene, decahydronaphthalene, etc., which have high swelling ratios. Even when a relatively uniform solution is prepared using these solvents, since these solvents are liquid at room temperature, there may be fluctuations in the winding tension, fusion of the wet gel, or winding when winding onto a bobbin after spinning. The gel used for stretching may become non-uniform due to changes in the physical properties of the inner and outer layers of the bobbin due to differences in solvent desorption over time after drawing.
In addition, the wet gel is soft and must be handled with care, and its cross-sectional shape is irregular, resulting in problems such as uneven denier in the final stretched product.

[Problem that the invention seeks to solve]

The inventors of the present invention have conducted intensive research on a method for producing a stretched product with high strength and high elastic modulus using ultra-high molecular weight polyethylene, and as a result, it has been possible to prepare a solution with excellent uniformity even at a high concentration of ultra-high molecular weight polyethylene. Furthermore, it is easy to handle and maintain high quality without fluctuations in the solvent content during the period from spinning the solution to stretching. We considered this to be essential for producing stretched products and conducted repeated research.

[Means for solving problems]

In other words, using paraffin wax, which is solid at room temperature and has excellent compatibility with ultra-high molecular weight polyethylene, as a solvent for dissolving ultra-high molecular weight polyethylene makes it easier to handle the undrawn yarn after spinning and to make it easier to wind. It is especially excellent for producing stretched products with stable quality continuously, as there is almost no fluctuation in solvent content due to etc., and ultra-high molecular weight polyethylene is uniformly and quickly compatible with paraffin wax. The optimal method is to use paraffin wax that has been heated and melted in advance, and ultra-high molecular weight polyethylene that has been dispersed or wetted with a liquid organic compound that is compatible with the paraffin wax. It has been found that the melt obtained by mixing these is very uniform.

That is, the present invention provides a method for preparing a melt of paraffin wax containing ultra-high molecular weight polyethylene having a weight average molecular weight of at least 1 x 10 ⁶ or more,
A paraffin wax containing ultra-high molecular weight polyethylene, which is characterized by mixing paraffin wax that has been heated and melted in advance and the ultra-high molecular weight polyethylene that has been dispersed or wetted with a liquid organic compound that is compatible with the paraffin wax. A method for preparing a tuxu melt is provided.

The ultra-high molecular weight polyethylene used in the present invention is ethylene or ethylene and a small amount of other α-polyethylene.
-olefins, such as propylene, butene-1,
Among polyethylenes obtained by polymerizing 4-methylpentene-1, hexene-1, etc. using a transition metal catalyst such as so-called 4-glar polymerization,
Those having a weight average molecular weight of 1×10 ⁶ or more are used. Those having a weight average molecular weight of less than 1×10 ⁶ are easy to dissolve, but they tend to be difficult to obtain high performance even when stretched. There is no particular regulation regarding the upper limit, but it tends to be difficult to obtain a practical melt if it exceeds 1×10 ⁷ .

The paraffin wax used in the present invention includes:
It is solid at room temperature, is mainly composed of saturated aliphatic hydrocarbon compounds, has a melting point of 40 to 120°C, preferably 45 to 70°C, and has a molecular weight of 2000 or less, preferably 1000 or less, specifically: , n-alkanes with 22 or more carbon atoms such as docosane, tricosane, and tetracosane, or lower n-alkane mixtures containing these as main components, paraffin wax separated and refined from petroleum, ethylene or ethylene and other α-olefins. Medium-low pressure polyethylene wax, high-pressure polyethylene wax, which is a low molecular weight polymer obtained by copolymerization, or wax whose molecular weight has been reduced by thermal degradation of medium-low pressure polyethylene or high-pressure polyethylene, and oxides of these waxes. Alternatively, oxidized waxes such as maleic acid-modified waxes, maleic acid-modified waxes, etc. may be mentioned.

The mixing ratio of ultra-high molecular weight polyethylene and paraffin wax in the present invention is not particularly limited, but preferably the mixing ratio of ultra-high molecular weight polyethylene and paraffin wax is 3:97 to 50:50, more preferably 5:50. The range is from 95 to 30:70, more preferably from 5:95 to 15:85. When the amount of ultra-high molecular weight polyethylene is less than 3% by weight, the strands formed after spinning the melt are brittle and unsuitable for drawing. Furthermore, if the ultra-high molecular weight polyethylene exceeds 50% by weight, the viscosity of the paraffin wax melt will be extremely high, resulting in poor moldability and stretchability.

The liquid organic compound that is compatible with the paraffin wax used in the present invention is not particularly limited as long as it can disperse or wet the ultra-high molecular weight polyethylene; In order to disperse the ultra-high molecular weight polyethylene and to penetrate the heated paraffin wax into the ultra-high molecular weight polyethylene particles, organic compounds having specific solubility parameter ranges and viscosity ranges are naturally required. Preferably, the solubility parameter range is from 7.3 to 9.3, and the viscosity at 20° C. is preferably 3 c.p or less. Aliphatic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, n-nonane and n-decane, and aromatics such as toluene, xylene, butylbenzene, cyclohexylbenzene, dodecylbenzene, decalin, tetralin and cyclohexane. Examples include group hydrocarbon compounds, hydrogenated derivatives thereof, and halogen derivatives. Two or more of these may be used as a mixture in any proportion. The solubility parameter here is defined as the square root of the evaporation energy per unit volume. If the evaporation energy is expressed as △E [cal/mole] and the molecular volume of the substance is expressed as V [cc], then The solubility parameter δ is expressed by the following formula.

δ=(△E/V) ^1/2 The temperature of the heated and melted paraffin wax in the present invention is not particularly limited as long as the temperature in the system after mixing can be maintained at a temperature higher than the melting point of the ultra-high molecular weight polyethylene. The temperature is preferably 140°C or higher and lower than the decomposition temperature of the ultra-high molecular weight polyethylene and paraffin wax, and more preferably 150°C or higher and 270°C or lower. The temperature of the paraffin wax is
If the temperature is lower than 140°C, the dispersion of the ultra-high molecular weight polyethylene or the penetration of the wetting liquid into the heated paraffin wax is insufficient, and the ultra-high molecular weight polyethylene is difficult to uniformly swell. Therefore, even if you continue spinning as is,
Alternatively, even when spinning is performed after passing through an extruder, it is difficult to obtain a uniform strand, and it is difficult to perform sufficient stretching to achieve high performance.

On the other hand, if the temperature exceeds the decomposition temperature, the molecular weight of the ultra-high molecular weight polyethylene decreases, and a stretched product with high performance cannot be obtained even after stretching.

In the present invention, the method of mixing the heated and melted paraffin wax and the ultra-high molecular weight polyethylene dispersed in or wetted with the liquid organic compound to form a melt includes stirring the heated and melted paraffin wax. A method of adding dispersed or wet ultra-high molecular weight polyethylene therein, or a method of adding the heated and melted paraffin wax into the dispersed or wet ultra-high molecular weight polyethylene while stirring, and the heated melting. Examples include a method in which the paraffin wax and the ultra-high molecular weight polyethylene in a dispersed or wet state are brought into contact at the same time and then fed into an apparatus capable of heating and kneading, but the method is not particularly limited.

In addition, in preparing a paraffin wax melt with a high concentration of ultra-high molecular weight polyethylene, after heating the ultra-high molecular weight polyethylene dispersed or wet in the liquid organic compound to a temperature below the boiling point of the liquid organic compound, A method of mixing with the paraffin wax heated and melted, or a method of passing the thus prepared mixture through an extruder can also be used.

The method of dispersing or wetting the ultra-high molecular weight polyethylene in the liquid organic compound in the present invention is not particularly limited as long as the ultra-high molecular weight polyethylene and the liquid organic compound can be mixed in an amount equal to or about three times the amount of the ultra-high molecular weight polyethylene. It is desirable that the ultra-high molecular weight polyethylene is dispersed or wetted without settling. For this purpose, a method of adding a viscosity improver or mixing while applying ultrasonic vibration is also used.

Japanese Unexamined Patent Application Publication No. 1983-1980 on a method for obtaining highly drawn products of ultra-high molecular weight polyethylene using paraffin wax.
Publication No. 130313 has been proposed. However, methods for uniformly mixing the paraffin wax and the ultra-high molecular weight polyethylene include mixing using a Henschel mixer, V-blender, etc., or melt-kneading and granulating using a single-screw or multi-screw extruder after mixing ( However, if the amount of ultra-high molecular weight polyethylene is less than 15 parts by weight, sufficient stretching cannot be achieved (Comparative Example 3 of the cited specification) because the uniformity is not sufficient. ) results have been obtained. One of the reasons why a uniform paraffin wax melt of relatively low to high concentration ultra-high molecular weight polyethylene can be prepared by mixing the paraffin wax and the ultra-high molecular weight polyethylene using the method of the present invention. One reason is that the molten ultra-high molecular weight polyethylene powder is sufficiently swollen before being fused together, and is uniformly dispersed after swelling to form a uniform melt. To this end, it is important that the liquid organic compound that disperses or wets the ultra-high molecular weight polyethylene has compatibility with the paraffin wax at high temperatures, and that the liquid organic compound that disperses or wets the ultra-high molecular weight polyethylene has compatibility with the paraffin wax at high temperatures, and that the liquid organic compound that disperses or wets the ultra-high molecular weight polyethylene quickly exceeds its melting point after mixing. at a temperature at which the ultra-high molecular weight polyethylene is sufficiently swollen in the paraffin wax by raising the temperature;
It is important that the paraffin wax is heated and melted.

The ultra-high molecular weight polyethylene and paraffin wax used in the present invention may contain conventional polyolefins such as heat stabilizers, weather stabilizers, pigments, dyes, lubricants, and small amounts of inorganic fillers, to the extent that the purpose of the present invention is not impaired. Among the various additives that are used, those that do not significantly inhibit the stretching may be used.

〔Effect of the invention〕

By using the paraffin wax melt containing the ultra-high molecular weight polyethylene of the present invention, in each step, compared to the case where a stretched product having high strength and high modulus is obtained using a solution obtained by a conventional method, Extremely low recovery loss of raw materials, and ultra-high molecular weight polyethylene concentration up to 50% by weight
Not only can it be used in a wide range of applications, improving productivity, but it can also be adjusted in an extremely short time with relatively gentle kneading, and the melt can be safely and stably continuously extruded. This can prevent various non-uniformities after spinning.

The unstretched product obtained by spinning the paraffin wax melt of ultra-high molecular weight polyethylene obtained by the method of the present invention is solid at room temperature, highly flexible, and easy to handle. It also has high storage stability. Moreover, the drawn product obtained by drawing this has high strength and high elastic modulus, and can be used in a wide range of fields, making it an extremely useful product industrially.

(Examples) Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Ultra-high molecular weight polyethylene (Sanhuain)
UUH900, weight average molecular weight 3.3×10 ⁶ ) was weighed so that the final concentration was 5% by weight, and after adding n-heptane in an amount twice the weight of ultra-high molecular weight polyethylene at room temperature, the mixture was thoroughly stirred. An ultra-high molecular weight polyethylene slurry made into a thriller was obtained. Meanwhile, in another container, put a predetermined amount of paraffin wax (melting point = 52
~54℃, molecular weight = 350) was heated and melted at 190℃,
A stirring device was attached, and 0.2% di-tert-butyl paracresol was added to the heated and melted paraffin wax which was stirred at 60 revolutions based on the weight of the paraffin wax.

The previously prepared ultra-high molecular weight polyethylene slurry was quickly poured into the stirred hot paraffin wax while stirring to prevent sedimentation, and the mixture was continuously heated to maintain a temperature of 190°C.
After injection, the ultra-high molecular weight polyethylene particles swelled rapidly, and the so-called ``Weisenberg effect'' was observed, in which the paraffin wax melt rose along the stirring rod. At this point, stirring was stopped and the mixture was allowed to stand for 5 minutes, resulting in an extremely uniform paraffin wax melt. The melt contained a considerable amount of bubbles due to the evaporation of n-heptane, but when extruded into water through a spinning tube (nozzle diameter 1.0 mmφ) heated to 170°C after degassing, unevenness in shape and breakage of the spun fibers were observed. I was able to wind it up without any problems. The wound paraffin wax strand was flexible and could be easily stretched up to 8 times even at room temperature. Further, no wax leaching during spinning, no denier unevenness in the inner and outer layers of the winding bobbin, etc. were observed.

Example 2 Using the same polyethylene as in Example 1, it was weighed so that the final concentration was 8% by weight, and twice the amount of n-decane was added to the weight of the ultra-high molecular weight polyethylene at room temperature. Thereafter, an ultra-high molecular weight polyethylene slurry was obtained by thoroughly stirring and turning into a thriller. Meanwhile, in a separate container, add a predetermined amount of paraffin wax (melting point
After heating and melting 69℃ molecular weight = 460) to 200℃,
A stirring device was attached, and the temperature was kept at 180°C while stirring. Ditertiary butyl paracresol in an amount of 0.2% based on the weight of the paraffin wax was added to the hot paraffin wax, and the ultra-high molecular weight polyethylene slurry prepared earlier was added thereto in the same manner as in Example 1 to form a uniform paraffin wax. A wax melt was obtained. After degassing in the same manner as in Example 1, the fibers were extruded into water through a spinning tube (nozzle 1 mmφ) heated to 180° C., and then wound at various draft rates. The highest draft rate was 15x. When the obtained strand was stretched in n-decane heated to 130°C, it was possible to stretch it to a stretching ratio of 40 times.

Example 3 Using the same polyethylene as in Example 1, it was weighed so that the final concentration was 20% by weight, and heated at 100°C.
After adding n-decane in an amount equal to the weight of the heated ultra-high molecular weight polyethylene, the mixture was sufficiently stirred to prepare an ultra-high molecular weight polyethylene slurry. Meanwhile, in a separate container, add a predetermined amount of paraffin wax (melting point 42-44
After melting the mixture by heating to 220°C (molecular weight = 300°C), a stirring device was attached and the mixture was mixed in the same manner as in Example 1 to obtain a paraffin wax melt. Since this melt had a very high viscosity, it was supplied to a single-screw extruder preset at 180°C and extruded into water through a die with a spinning diameter of 2 mm to obtain an unstretched product. Using the obtained strands, after extracting the residual paraffin wax in n-decane heated to 130°C or using boiling n-hexane, the strands were stretched in an oven at 130°C. It was possible to stretch it up to 22 times.

Comparative Example 1 10 g of polyethylene similar to Example 2 and 190 g of paraffin wax (melting point = 52-54°C, molecular weight = 350)
was placed in a container at the same time, and after melting the paraffin wax, it was rapidly heated to 200°C while stirring, and stirring was continued while maintaining that temperature. However, even after 20 minutes had passed after reaching the set temperature, the mixture remained extremely non-uniform as it remained separated into two phases: a molten mass of ultra-high molecular weight polyethylene and a solution diluted from the predetermined concentration. After that, stirring was continued for an additional 60 minutes, but no homogenization occurred. An attempt was made to spin this melt by transferring it to a spinning tube preheated to 180°C, but only the molten paraffin wax flowed out of the nozzle, making spinning impossible.

Comparative Example 2 Using the same polyethylene as in Example 1, it was weighed so that the final concentration was 5% by weight, and twice the amount of decalin was added to the weight of the ultra-high molecular weight polyethylene at room temperature. 0.2% di-tert-butyl para-cresol based on the weight of the polymer was added and stirred to wet the polyethylene particles. Meanwhile, a predetermined amount of decalin was heated to boiling in another container, and the hot decalin was quickly poured into the container containing the polyethylene particles, which had been moistened with decalin, while stirring. The polyethylene particles absorbed decalin and swelled without association, and a viscous solution was obtained over time. Add this solution in advance
A gel-like fiber containing a large amount of decalin was obtained by extruding it into water from a spinning tube heated to 150°C. However, during spinning, a considerable amount of decalin leaches out into the cooling tank and onto the take-up bobbin, and if the decalin is left to be wound on the take-up bobbin while still containing decalin, the moist gel-like fibers will fuse together, causing problems during the drawing process. This caused thread breakage. Further, the obtained drawn yarn had a non-uniform cross section and large denier unevenness due to the difference between the inner and outer layers of the winding bobbin.

Example 4 Ultra-high molecular weight polyethylene
1900, Hercules, weight average molecular weight 5.1×10 ⁶ )
A paraffin wax melt containing ultra-high molecular weight polyethylene was prepared by mixing in the same manner as in Example 3. Using this melt,
It was extruded into water from a spinning tube (nozzle diameter: 2 mm) heated to 180°C, and a continuous strand with no paraffin wax seeping out and a uniform strand diameter was obtained. When the obtained strand was stretched in an n-decane bath heated to 130°C,
It was possible to stretch to a stretching ratio of 30 times.

Example 5 Using the same polyethylene as in Example 1, an equal amount of liquid paraffin preheated to 100°C was added to 100 parts by weight of the ultra-high molecular weight polyethylene, and the mixture was thoroughly stirred to obtain wet ultra-high molecular weight polyethylene powder. made a slurry cake. Separately, prepare paraffin wax (melting point: 42-44°C, molecular weight: 300) heated and melted at 230°C, and mix both at the same time so that the final concentration of the ultra-high molecular weight polyethylene is 30% by weight. It was then fed to the extruder. The temperature of the extruder was maintained at 200°C, and the residence time in the extruder was 3 minutes. The resulting paraffin wax melt containing the ultra-high molecular weight polyethylene was very viscous and had properties similar to those of a molten polymer. When a die having a nozzle with a nozzle diameter of 2 mm was attached to the above extruder and spinning was carried out, winding was possible at a maximum draft rate of 50 times, and no defects such as strand breakage were observed.

When the obtained strand was stretched in n-decane heated to 130°C, it was possible to stretch the strand to a stretching ratio of 10 times even at a maximum draft ratio of 50.

Claims (1)

[Claims] 1 Paraffin wax heated and melted in advance,
A paraffin containing ultra-high molecular weight polyethylene, characterized in that it is mixed with ultra-high molecular weight polyethylene having a weight average molecular weight of at least 1×10 ⁶ or more, which is dispersed or wetted with a liquid organic compound that is compatible with the paraffin wax. Method for preparing wax melt.