JPS6339941A - Production of ultrahigh-molecular weight polyolefin mixture - Google Patents

Abstract

PURPOSE:To obtain the title mixture excellent in extrudability, etc., by mixing an ultrahigh-MW polyolefin powder with a low-melting flow improver at a temperature from the m.p. of the latter to the m.p. of the former, solidifying the mixture by cooling and grinding the solid. CONSTITUTION:An ultrahigh-MW polyolefin powder (A) (e.g., ultrahigh MW polyethylene powder) of an intrinsic viscosity >=5dl/g is mixed under agitation with a normally solid flow improver (B) having a m.p. lower than the m.p. of component A (e.g., paraffin wax). This mixture is solidified by cooling and ground to obtain the purpose ultrahigh-MW polyolefin mixture. The obtained mixture excels in storage stability and handleability and can be suitably used as a material for fibers, etc., having a high modulus and a high tensile strength.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a homogeneous ultra-high molecular weight polyolefin mixture with excellent extrudability. More specifically, extrusion moldability, stretchability, storage stability, suitable for obtaining a drawn ultra-high molecular weight polyolefin product having high elastic modulus and high 4I tensile strength,
This invention relates to a method for producing a homogeneous mixture consisting of an ultra-high molecular weight polyolefin with excellent transport properties and a fluidity improver that is solid at room temperature. [Conventional technology] Ultra-high molecular weight polyolefin is molded into fibers, tapes, etc.
By stretching this, it has a high elastic modulus. It is already known that a molecularly oriented molded product having high tensile strength can be obtained. For example, Japanese Patent Application Laid-Open No. 15408/1983 describes spinning a dilute solution of ultra-high molecular weight polyoleain and drawing the resulting filament. has been done. However, polyolefins with large molecular weights are extremely poorly soluble in solvents, making it difficult to obtain a highly concentrated homogeneous solution.
This is despite the fact that the general description in the publication states that a 1 to 50% by weight solution is used. In that example, at most about 8 weight ffi% 1 molecular weight is 1
This is clear from the fact that only a method using a solution with an extremely low concentration of 3 weight arcs has been disclosed for substances exceeding 1,000,000 yen. In practical application of this method, there are problems such as processing of a large amount of solvent and productivity, so there is a desire to develop a spinning technique from a highly concentrated solution of ultra-high molecular weight polyolefin. As a method for producing a homogeneous solution of an ultra-high molecular weight polyolefin, a room temperature liquid solvent and an ultra-high molecular weight polyolefin are mixed and stirred at a temperature below the dissolution temperature of the ultra-high molecular weight polyolefin to form a suspension, and then the ultra-high molecular weight polyolefin is mixed and stirred. A method of making a homogeneous solution by supplying it to an extruder kept at a melting temperature (JP-A-61-73743, JP-A-61-892)
No. 32) has been proposed. However, in a method such as this method in which a room temperature liquid is used as a solvent, if stirring is stopped during mixing of the solvent and the ultra-high molecular weight polyolefin, the ultra-high molecular weight polyolefin will precipitate, resulting in a non-uniform suspension. It requires constant stirring and is difficult to store in advance as a suspension. Furthermore, when a suspension containing a solvent is kneaded and extruded using a single-screw extruder, the suspension and the screw rotate together, and the solvent and ultra-high molecular weight polyolefin are partially separated in the extruder, resulting in a uniform solution. There is a possibility that it will not happen. In fact, all of the examples described in JP-A-61-89232 are examples using a two-wheel screw extruder, and compared to the case where a normal single-screw extruder is used, the filament is non-uniform and the drawability is poor. This is described in Example C. On the other hand, a method using a fluidity improver that is solid at room temperature such as paraffin wax as a fluidity improver for ultra-high molecular weight polyolefin (JP-A-59-130515, JP-A-6
No. 0-197752, etc.] have been proposed. It has also been found that by employing this method, a molded article can be produced using a single-screw extruder commonly used for extrusion molding. However, even if such a method is used, the ultra-high molecular weight polyolefin may not be sufficiently dispersed when using a single-screw extruder depending on the pretreatment conditions when mixing the ultra-high molecular weight polyolefin and the fluidity improver that is solid at room temperature. It has been found. In other words, if an ultra-high molecular weight polyolefin and a fluidity improver that is solid at room temperature are simply mixed in a solid state using a Henschel mixer or the like, there is a risk that they will not be melted and mixed sufficiently uniformly using a single-screw extruder. 60-19
It was described in Publication No. 7752. In the method of leaving a powder mixture of an ultra-high molecular weight polyolefin and a fluidity improver at a temperature above the melting point of the ultra-high molecular weight polyolefin, the ultra-high molecular weight polyolefin also melts and the viscosity of the mixture becomes extremely high. . As described in the publication, Bamba IJ-
It is necessary to uniformly melt and knead using a melt mixer such as a mixer. Moreover, once the melt-kneaded mixture is solidified, a slight phase separation occurs, and the solidified blend has the ability to stretch, which leads to high performance even when it is melted again, probably because the molecules of the ultra-high molecular weight polyolefin become entangled. Therefore, it is necessary to immediately feed the melt-kneaded mixture to an extruder or the like, and it is difficult to store it as a premix in advance. [Problems to be Solved by the Invention] In view of this situation, the present inventors have developed an extrudability modifier comprising an ultra-high molecular weight polyolefin and a fluidity improver that is solid at room temperature and has a melting point lower than the melting point of the ultra-high molecular weight polyolefin. The present invention was achieved as a result of various studies aimed at developing a method for producing a homogeneous mixture with excellent storage stability, stretchability, transportability, etc. [Means for Solving the Problems] That is, the present invention provides a powder of an ultra-high molecular weight polyolefin (A) having an intrinsic viscosity [η] of 5 al/g or more and an ultra-high molecular weight polyolefin (A) that is solid at room temperature and has a melting point. (lower melting point than the melting point of the fluidity improver...) at a temperature above the melting point of the fluidity improver CB) and below the melting point of the ultra-high molecular weight polyolefin (A) with stirring, and the mixture is cooled to solidify and then pulverized. Features extrusion moldability. The present invention provides a method for producing a homogeneous ultra-high molecular weight polyolefin composition having excellent storage stability, stretchability, transportability, etc. [Function] The ultra-high molecular weight polyolefin (A) used in the present invention has an intrinsic viscosity [η] of 5al measured at 135°C in a decalin solvent.
/g or more, preferably 7 to 30 dA? /g. Although it is possible to easily prepare a homogeneous mixture with an intrinsic viscosity [η] of less than 5 d//g, it tends to be difficult to achieve high elastic modulus and high strength properties because the molecular chain is short. The upper limit of the intrinsic viscosity [η] is not particularly limited, but is 30 dl.
/g, the melt viscosity is too high even when the fluidity improver (B) is added, and extrusion moldability tends to be poor. The ultra-high molecular weight polyolefin in the present invention is. Examples include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene. Among these, ethylene homopolymers or ethylene-based copolymers of ethylene and other α-olefins with high crystallinity are preferred since they can achieve high elastic modulus and high tensile strength. The fluidity improver used in the present invention is a low molecular weight compound that is solid at room temperature and has excellent dispersibility with ultra high molecular weight polyolefins whose melting point is lower than the melting point of ultra high molecular weight polyolefins, and is preferably an aliphatic hydrocarbon. It is a compound or its derivative. The aliphatic hydrocarbon compounds are mainly saturated aliphatic hydrocarbon compounds, specifically n-alkanes having 22 or more carbon atoms such as tocosan, tricosane, tetraphsan, and triafunthane, or lower lower alkanes containing these as main components. Mixture with n-alkane So-called paraffin wax purified by 1 minute from petroleum, medium/low pressure polyethylene wax, which is a low molecular weight polymer obtained by copolymerizing ethylene or ethylene and other α-olefins, high pressure process Polyethylene wax, ethylene copolymer wax, wax made by reducing the molecular weight of polyethylene such as medium/low-pressure polyethylene, high-pressure polyethylene, etc., oxides of these waxes, oxidized waxes such as maleic acid-modified products, and maleic waxes. Examples include acid-modified wax. Also, as aliphatic hydrocarbon compound derivatives. For example, aliphatic hydrocarbon groups (alkaline groups, alkenyl groups)
1 or more terminal or internal G9. Preferably 1 or 2, particularly preferably 1, carboxyl group, hydroxyl group, carbamoyl group, nischyl group, meltcapto group, carbonyl group, etc. A compound having a group having 10 or more carbon atoms, preferably a carbon number Examples include fatty acids, fatty alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones and the like. The fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; the fatty alcohols include myristyl alcohol, cetyl alfur, and stearyl alcohol; and the fatty acid amides include caprinamide. Laurinamide, palmitinamide, and stearyl. Examples of amides and fatty acid esters include stearyl acetate and the like.The fluidity improver (B) used in the present invention is preferably the aliphatic hydrocarbon compound or its derivative; To the extent that the object of the present invention is not impaired, the derivatives are soft bodies, specifically, monomer sources that are usually used as tackifying resins in the fields of adhesive tapes, paints, and hot melt adhesives, and that are polymerized. Depending on the difference, the following resins: 1 For example, the C4 fraction obtained by decomposition of petroleum, naphtha, etc., a mixture of these, or any fraction of these 1 For example, isoprene and 1,6-pentadiene in the C5 fraction are the main raw materials. Aliphatic hydrocarbon resin 1 An aromatic hydrocarbon resin whose main raw materials are styrene derivatives and indenes in the C9 fraction obtained by cracking petroleum, naphtha, etc. Any fraction of the 0 -C fraction. Aliphatic/aromatic copolymerized hydrocarbon resin made by copolymerizing C9 fraction with C9 fraction, alicyclic hydrocarbon resin made by hydrogenating aromatic hydrocarbon resin.Structure containing aliphatic, alicyclic, and aromatic. Synthetic terpene-based hydrocarbon resin, ° A terpene-based hydrocarbon resin made from α, β-pinene in turpentine oil. Coumarone-indene hydrocarbon resin made from indene and styrene in coal tar-based naphtha. , low molecular weight styrene resin and rosin carbonization may be used. The mixing amount of the ultra high molecular weight polyolefin (A) powder and the fluidity improver (B) is usually 1.
The powder of A) is 10 to 80% by weight, preferably 20
60% by weight, in other words, the fluidity improver (B) is 2% by weight.
It ranges from 0 to 90% by weight, preferably from 40 to 80% by weight. The powder of ultra-high molecular weight polyolefin (A) contains a fluidity improver (B) which melts even at a temperature below its melting point.
) to some extent and swells, so the fluidity improver (B
) If the amount is less than 20% by weight, heat it. There is a risk that sufficient fluidity to achieve uniformity cannot be ensured during mixing and stirring, and the melt viscosity of the mixture is high, making extrusion molding difficult. On the other hand, if the fluidity improver (B) exceeds 90 weight fig, there is a possibility that the mixture cannot be pulverized to form a granular mixture with excellent transportability. The method of the present invention comprises the ultra-high molecular weight polyolefin (A)
powder and the fluidity improver CB) are combined into a fluidity improver (B).
) and below the melting point of the ultra-high molecular weight polyolefin (A), the mixture is cooled and solidified, and then pulverized. Ultra-high molecular weight polyolefin (A
) and the fluidity improver (Bl), after mixing both in a predetermined amount, the system is heated to a temperature above the melting point of the fluidity improver (B) and below the melting point of the ultra-high molecular weight polyolefin (A). The fluidity improver (B) alone may be dissolved by heating to a high temperature and mixed by stirring, or the powder of the ultra-high molecular weight polyolefin (A) may be added to a system in which only the fluidity improver (B) has been dissolved in advance. If the temperature of the system at the time of stirring and mixing is below the critical point of the fluidity improver CB), the dispersibility is poor because it is a solid-solid mixture. If the temperature exceeds the melting point of the polyolefin, the ultra-high molecular weight polyolefin will melt and the viscosity of the system will increase rapidly, making stirring difficult. The temperature of the system during stirring of the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B) is preferably from the melting point of the fluidity improver (E) +10°C to the melting point of the ultra-high molecular weight polyolefin (the ultra-high molecular weight polyolefin) -20°C. It is ℃. Powder of ultra-high molecular weight polyethylene (A) and fluidity improver (
After stirring and mixing B), should it be cooled in the system? Alternatively, the mixture is cooled and solidified by taking it out of the system at room temperature or out of the prefecture where it has been cooled.1 The method of the present invention has a small difference between the melting point of the fluidity improver (B) and the temperature of the system at the time of stirring and mixing. Since the powder of high molecular weight polyolefin (A) is in an unmolten state, it also acts as a binder for the crystallization of the fluidity improver (B).
A mixture in which the powder of ) is evenly dispersed solidifies in a uniformly dispersed state without phase separation.◎ The mixture that is cooled and solidified is a hard ultra-high molecular weight polyolefin (
Since the powder of A) is solidified with a brittle fluidity improver (Bl), it can be crushed very easily using a Henschel mixer, blade mixer, crusher, etc. By melt extrusion molding using a machine, it can be formed into homogeneous filaments, sheets, T-die films, pipes, rods, tapes, blown films, etc. Also, the pulverized mixture obtained by the method of the present invention Although a sufficiently homogeneous molded product can be obtained using a single-screw extruder, this does not exclude forming methods using other extrusion molding machines such as a twin-screw extruder. -Die films, pipes, rods, tapes, blown films, etc. have excellent stretchability because the fluidity improver CB) is homogeneously dispersed in the ultra-high molecular weight polyolefin (A). ), and by removing the fluidity improver from the molded product before, during, or after stretching, a high elastic modulus can be achieved. A drawn ultra-high molecular weight polyolefin having high tensile strength can be easily produced. A heat-resistant stabilizer and a weather-resistant stabilizer are used when mixing the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B). Compounding agents such as pigments, dyes, and inorganic fillers that are normally added to polyolefins may be added to the extent that they do not impair the purpose of the present invention. [Effects of the Invention] By employing the method for producing an ultra-high molecular weight polyolefin mixture of the present invention, the powder of ultra-high molecular weight polyolefin (A) is uniformly dispersed and has excellent storage stability and handling properties in a solid state at room temperature. A mixed mixture can be obtained. Moreover, this mixture can be easily extruded using a general-purpose single-screw extruder. In addition, the extruded molded product is homogeneous and has excellent stretchability, so ultra-high molecular weight polyethylene mixtures have a high elastic modulus and
Suitable as a raw material for high tensile strength fibers. d 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 unless the gist thereof is exceeded. Example 1 Preparation of mixture> Ultra-high molecular weight polyethylene ([η] depth 15°-5dj?/
g) Powder blend 55% by weight of a fluidity improver (paraffin wax; melting point = 69°C 1 molecular weight = 460) against 45% by weight, then put it into a flask and heat it to 90°C to dissolve the fluidity improver. Ta. On this occasion. α for 100% by weight of the mixture as a process stabilizer;
One portion of BHT (3,5-di-tert-butyl-4-hydrocitluene) was added. After this, the system is 9
Stir and mix the mixture while maintaining it at 0°C,
It was made into a slurry state. The slurry mixture was then spread on a metal vat and cooled to solidify. Continuing with Hensielmi noon (manufactured by Mitsui Miike Seisakusho, type FM10B)
) for 22 minutes. The prepared mixture was in the form of granules with an average particle size of about imm. Preparation of drawn product of ultra-high molecular weight polyethylene> The granular mixture prepared by the above method was melt-spun and then drawn under the following conditions. Melting, kneading, and spinning were performed using a spinning device equipped with a 25 mmφ extruder (manufactured by Thermoplastics) and a die with a nozzle diameter of 2 mm. The melting, kneading section and spinning die of the extruder were maintained at 230°C. At this time, auxiliary transport operations such as forced feeding and shaking of the mixture charged into the extruder hopper to a portion of the screw were not particularly performed. The extruded molten mixture was taken out in an air gap of 1.8 ffl at a draft ratio of 58.1 times, and was cooled and solidified to form an undrawn yarn. The fineness of this undrawn yarn was 470 denier. . Then, stretching was performed using a three-stage stretching device equipped with four godet rolls. The first and second stages contain 13 n-tecan.
In the third stage, triethylene glycol was used as the heat medium. The temperature of each stretching tank is 120°C for the first tank, second tank, and third tank.
The temperatures were 130°C and 137°C, and the effective length of the tank was 501 cm. During stretching, the feed speed of the first godet roll was set to in/min, and the second. The rotational speeds of the third and fourth godet rolls were appropriately selected within a range that allowed stable operation. Here, the drawing ratio was calculated from the ratio of the rotational speed of the first godet roll to the final godet roll. Table 1 shows the drawing ratio, tensile modulus, and tensile strength of the prepared fiber samples. The tensile strength and elongation at break were measured using an Instron universal testing machine model 1123.

[Manufactured by Instron] at room temperature (23
℃). At this time, the sample length was 100 mm and the tensile strength was 100 mm/min. Tensile modulus was calculated using stress at 2% strain. Further, the 1a fiber cross-sectional area required for calculation was calculated by measuring the weight and length of the fiber, assuming the density of polyethylene as 0.96 y/l:m. Further, Table 2 shows the fineness and uniformity of elongation at break of the samples. The sample at this time was 1! ! Measured using 100 samples taken out in sequence from a continuous fiber sample of 1 length,
I did the calculations. Table 2 The ratio of standard deviation to average fineness and average elongation at break was 13.9% and 13.4%, respectively. The spinning stability and drawing stability during the preparation of the drawn fiber were both excellent, and the fiber had high performance even though it was started from a mixture with a high fraction of ultra-high molecular weight polyethylene (45% by weight). . In addition, the intrinsic viscosity ([η]) of the drawn fiber is 1
4.2417 g, and it was found that the sample had almost no thermal degradation.
/g) 50% by weight of paraffin wax (melting point = 69°C 1 molecule fi = 46035050% by weight) was blended with powder. Then, by the method described in Example 1. Mixing, stirring, and granulation were performed.Continued Melting, intermixing, and spinning were performed in the same manner as described in Example 1. Then, drawing was performed to obtain drawn fibers of ultra-high molecular weight polyethylene. Table 3 shows the drawing ratio, tensile modulus, and tensile strength of the prepared fiber samples. Table 3 The uniformity of the fineness and elongation at break of the samples is shown in Table 4. Table 4 The ratio of standard deviation to the average fineness and average elongation at break is 12.2% and 11.0%, respectively. As in Example 1, the spinning stability and drawing stability were excellent, and the drawn fibers also had high performance. In addition, the intrinsic viscosity of the drawn fibers ([η
]) was 7.20 tsl/g, and it was found that the sample was hardly thermally degraded.O Comparative Example 1 Ultra-high molecular weight polyethylene ([η) = 15.5 a#
/g) to 40% by weight, paraffin wax (i
After powder-blending 60% by weight of 1 molecule fi = 460) at 170°C, the mixture was left in the open at 170°C for 30 minutes to swell the paraffin wax in the mx molecular weight polyethylene. At this time, the mixture 100% is used as a process stabilizer.
00% by weight α, 5-fold weight BIT (3+5-''
;-tart-butyl-4-hydroxytoluene) was added. This mixture was kneaded using a Prabender mixer for 10 minutes at a jacket temperature of 170° C. and 4FJk of 100 rpm. The mixture is transparent in the molten state;
It was uniform. Next, this mixture was crushed into a sheet shape using a press molding machine heated to 170° C., and a pressed sheet having a thickness of 5 mm was formed using a cooling press. Thereafter, it was made into pellets using a sheet pelletizer (product name: Yukon, manufactured by Horai Tekkosho). The obtained pellet-like mixture was used to prepare drawn fibers by the method described in Example 1. This mixture has poor spinnability,
The draft ratio remained at 2x. Table 5 shows the stretching ratio, tensile modulus, and tensile strength of the sample. Table 5 Further, the uniformity of the fineness and elongation at break of the samples is shown in Table 6. The ratio of standard deviation to the average fineness and average elongation at break was 25.3% and 17.1%, respectively. Due to poor spinnability and low draft during spinning, the draw ratio reached up to 22.5 times, but the 1 elastic modulus and 1 strength were extremely low values. In addition, the intrinsic viscosity [η] of the stretched sample is 9.2
0417 g, and a decrease in molecular weight due to heat was observed. In addition, #J&fiber strength and uniformity of elongation at break were determined in Example 1.
．． 2 It can be seen that the quality is inferior in both cases. Comparative Example 2 Ultra-high molecular weight polyethylene ([η) = 7.42 ag
/g 750% by weight, paraffin wax CM point = 69°C 1 molecular weight (460): 50. % by weight was powder blended in solid form. Furthermore, 0.1 weight% of BHT (3,5-jet) is added to 100% by weight of the mixture.
art-butyl-4-hydroxytoluene) was added uniformly throughout. Subsequently, the mixture powder was charged into the extruder hopper of the spinning apparatus described in Example 1. Further, melting, kneading, and spinning were performed by the method described in the same example. At this time, the mixed powder that was put into the hopper did not easily fall off and was likely to form a bridge state. Therefore, by pushing the mixed powder lumps into the screw groove as an auxiliary, starvation feed state was prevented and stable extrusion was achieved. Table 7 shows the stretching ratio, tensile modulus, and tensile strength of the prepared ionized sample. Table 7 Also, Table 8 shows the fineness of the sample and the uniformity of elongation at break.
It was shown to. Table 8 The ratio of standard parrot deviation to average fineness and average elongation at break was 32.1% and 22.5%, respectively. As in Examples 1 and 2, it can be seen that although fibers with high elastic modulus and high strength can be prepared, the quality is inferior.

Claims (1)

[Claims] (1) A powder of an ultra-high molecular weight polyolefin (A) having an intrinsic viscosity [η] of 5 dl/g or more and a fluidity improver (B) that is solid at room temperature and has a melting point lower than that of the ultra-high molecular weight polyolefin (A). A method for producing an ultra-high molecular weight polyolefin mixture, which comprises stirring and mixing at a temperature above the melting point of the fluidity improver (B) and below the melting point of the ultra-high molecular weight polyolefin (A), cooling the mixture to solidify it, and then pulverizing it. .