JPH0218216B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent fiber splitting resistance, knot strength, and tear strength by molding a gel-like molded product from a solution of high molecular weight polyethylene using a styrene monomer as a solvent and heating and stretching this molded product. The present invention relates to a method for manufacturing high molecular weight polyethylene molded products such as fibers or films having high strength and high elasticity. A method for producing fibers with high elastic modulus and high strength using ultra-high molecular weight polyethylene as a raw material is described, for example, in the literature of AJ.
It is described in JP-A No. 107506, Japanese Unexamined Patent Publication No. 58-5228, etc. These methods involve dissolving ultra-high molecular weight polyethylene in a non-volatile solvent at high temperature, performing solution spinning to obtain a gel-like fiber, and then drawing this, or The fiber is obtained by extracting the solvent with a volatile solvent and hot stretching it to the appropriate elastic modulus and strength. However, although these methods make it possible to obtain fibers with high elasticity and strength from ultra-high molecular weight polyethylene, these fibers are subject to properties specific to highly oriented and crystallized chain polymers. In other words, as the degree of orientation increases, the elastic modulus and strength in the direction of the orientation axis asymptotically approach the crystal elastic modulus and strength, but anisotropy occurs in the strength and the elastic modulus and strength in the direction perpendicular to the orientation axis become relatively weak. . Therefore,
These fibers are severely cracked or split in the vertical direction, and when trying to obtain tow, preplex, or cloth using a normal loom or knitting machine, the fibers are bent and rubbed as they pass through guide pulleys, guide rolls, guide ribs, etc. The problem was that the fibers were separated into fine fibers, making it difficult to operate the device. In order to improve these drawbacks, for example, Japanese Patent Application Laid-Open No. 169521/1983 discloses a method of coating a filament of ultra-high molecular weight polyolefin with a polymer having the crystallinity of ethylene or propylene to prevent fibrillation of the fiber. There is a description of coated fibers. However, since this coated fiber uses a polymer to coat the filament, it is difficult to impregnate the micropores in the filament with the polymer, and the prevention of fibrillation of the filament is done from the surface, so it is difficult to improve the fiber splitting resistance. It wasn't enough. The present invention aims to improve these drawbacks of molded products having high strength and high elasticity obtained from high molecular weight polyethylene obtained by conventional methods, and the method for producing high molecular weight polyethylene molded products of the present invention In this method, a solution is prepared by dissolving high molecular weight polyethylene in a styrene monomer, a gel-like molded product is molded from this solution, and this molded product is heated and stretched. The high molecular weight polyethylene used in the present invention is a crystalline ethylene homopolymer or a copolymer of ethylene and 10 mol% or less of α-olefin, and has a weight average molecular weight of 5×10 ⁵ or more;
Preferably, those having an ultra-high molecular weight of 1×10 ⁶ or more, particularly 2×10 ⁶ or more are preferred. Ordinary polyethylene having a molecular weight of less than 5×10 ⁵ is not preferred because a molded product with high strength and high elasticity cannot be obtained. In addition, the styrene monomer used in the present invention is styrene, which is contained in a gel-like molded product formed from a solution of high molecular weight polyethylene and rapidly undergoes radical polymerization during the heating and stretching process. or its derivatives. Styrene derivatives include styrene, alkyl groups such as methyl, ethyl, isopropyl, and t-butyl, vinyl groups, cyclohexyl groups, amino groups, oxy groups, methoxy groups, cyan groups, and other fluorine, chlorine, bromine, and iodine groups. Examples include those substituted with halogen, and among these, ortho, meta or para substitutions are preferred. Among the above-mentioned styrenic monomers, ortho-, meta-, or para-methylstyrene is preferred, and para-methylstyrene or a mixture of ortho- or meta-methylstyrene mainly containing para-methylstyrene is particularly preferred from the viewpoint of reactivity and vapor pressure. Moreover, these styrene monomers can be used as a mixture of two or more types or a mixture of a styrene monomer and another polymerizable monomer. Examples of mixtures of styrenic monomers and other polymerizable monomers include paramethylstyrene and unsaturated carboxylic acids such as maleic acid, acrylic acid, and methacrylic acid or derivatives thereof, isocyanuric acid, vinylnaphthalene, and vinylpyridine. Or a mixture with vinyl caprolactam or the like. The solution of high molecular weight polyethylene using a styrenic monomer as a solvent in the present invention is prepared by heating and dissolving high molecular weight polyethylene in the above styrenic monomer. The dissolution temperature varies depending on the solvent used, but is generally 100 to 160°C, preferably 120°C.
~140℃ range. Also, the amount of high molecular weight polyethylene present in the solution is 1 to 15% by weight, preferably 4 to 8% by weight. In addition, in dissolving the above-mentioned high molecular weight polyethylene, some of the styrenic monomers undergo radical polymerization due to heating, so
It is preferable to add a polymerization inhibitor. Examples of polymerization inhibitors include t-butylcatechol,
Examples include diphenylpicrylhydrazyl and p-benzoquinone. These are added in an amount of 0.05 to 10.0% by weight, preferably 0.5 to 5.0% by weight. Next, a polyethylene gel-like molded article is molded from this high molecular weight polyethylene dissolved solution. This gelation method involves applying the high molecular weight polyethylene solution to an appropriately selected die, for example, a die having holes with a circular, oval, X-shaped, or Y-shaped cross section for forming fibers, or a die such as a film, a band, etc. For molding, there is a method of extruding using a hole having a rectangular cross section. The extruded gel-like molded product is
Below the gelling temperature in a water bath, air bath, etc., preferably 15
Cool at a rate of at least 50°C/min to a temperature of ~25°C. The resulting gel-like molded product contains styrenic monomers when dissolved in high-molecular-weight polyethylene, and in particular, those using a polymerization inhibitor undergo radical polymerization of styrenic monomers during heating and stretching of the gel-like molded product, which will be described later. In order to prevent this, it is preferable to remove the polymerization inhibitor contained in the gel-like molded product. This removal method can be easily accomplished by immersing the gel-like molded product in a water bath. In addition, in heating and stretching the gel-like molded product, in order to promote radical polymerization of the styrene monomer in the gel-like molded product, the gel-like molded product is treated with a reaction initiator, such as potassium persulfate or ammonium persulfate, at a concentration of 0.1. It is preferred to treat with an aqueous solution of ~1.0% by weight. Next, the gel-like molded product containing the styrene monomer is heated and stretched in one or more stages. The temperature at this time must be such that the styrene monomer contained in the gel-like molded product undergoes radical polymerization to form a polymer, and the gel-like molded product can be sufficiently oriented. Specifically, stretching is preferably carried out from the softening point of the gel-like molded product to the melting point, particularly just below the melting point, for example at a temperature of 80 to 140°C, preferably 100 to 140°C. If the stretching temperature exceeds the melting point, the gel-like molded product cannot be oriented sufficiently;
If the temperature is below the softening point, the styrenic monomer will not be sufficiently polymerized, and the stretching ratio required to obtain a molded article with high strength and high elasticity cannot be obtained, which is not preferable. The tensile strength and elastic modulus of a molded article are approximately proportional to the stretching ratio, so when increasing the strength, it is necessary to increase the stretching ratio, and the stretching ratio is at least 10, preferably 20 or more. The amount of the styrenic monomer added by polymerization to the stretched molded product is in the range of 0.5 to 25% by weight, preferably in the range of 1 to 5% by weight. The amount of polymer added is
If it is less than 0.5% by weight, the fiber splitting resistance, knot strength, tear strength, etc. of the stretched molded product will not be improved, while if it exceeds 25% by weight, the high elasticity and high strength of the molded product will be impaired, which is not preferable. The amount of polymer added above is the amount of polymerization inhibitor added to the styrenic monomer,
It can be adjusted by adjusting the amount of reaction initiator added to the gel-like molded product or the stretching conditions of the gel-like molded product. The process of the invention can be carried out in batch and continuous processes. Next, an example of an apparatus for continuous production using the method of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing an example of an apparatus for producing fibers according to the method of the present invention. High molecular weight polyethylene 1, styrenic monomer 2
and polymerization inhibitor 3 are supplied to a mixing tank 4 and made into a slurry by an agitator 5. This slurry is continuously sent through a tube 6 to a heating stirrer 7 and stirred by a stirring plate 8 to form a uniform solution. This solution is sent to a spinning die 10 by a gear pump 9 and subjected to solution spinning. The extruded solution 11 is immediately cooled and gelled in a cooling tank 12 to become a yarn 13. This yarn 13 is
In order to remove the polymerization inhibitor contained in the yarn, it is supplied to a water tank 15 by a roll 14, and further supplied to a water tank 17 containing a reaction initiator by a roll 16, and then led to a stretching process. The gel fibers 18 treated with the reaction initiator are rolled on rolls 19, 21, 23.
The gel fibers are supplied to cylindrical heating machines 20, 22, and 24 with different temperatures, and stretched in three stages while changing the temperature. At the same time, the gel fibers are wound up with rolls 25, and the styrene monomer contained in the gel fibers is polymerized and stretched. fiber 26
A styrene-based monomer is formed between the oriented crystals.
The drawn fiber 26 is dried in a heat setting tank 27, passed through a roll 28, and wound up on a winder 29. The present invention is constructed as described above, and the obtained stretched polyethylene product has excellent splitting resistance, knot strength, and tear strength, as well as high strength and high elasticity. Furthermore, since the method of the present invention does not use a plurality of solvents, the steps can be simplified compared to conventional methods, and the dissolution temperature is low, making it easy to operate and moreover economically advantageous. Also,
Since the stretched polyethylene product constitutes a styrenic monomer between oriented crystals, it is possible to further improve splitting resistance, knot strength and tear strength compared to the conventional method of coating fibers. Furthermore, the molded products obtained by the method of the present invention, such as polyethylene drawn fibers, are suitable for ropes and cables that are subjected to strong friction and twisting, and are resistant to buckling, so they are suitable for applications such as single yarns and nets. Furthermore, since it can be secondary-processed into tow, preplex, cloth, etc. using normal techniques, it expands the use of composite materials as reinforcing materials. Examples of the present invention are shown below. The test method is as follows. (1) Tensile modulus, strength; using an Instron type tensile testing machine, the chuck distance was 25 mm, and the tensile speed was 5.
It was determined from a fiber tensile test at mm/min and a temperature of 23°C. (2) Knot strength: The fibers were tied once and determined from the above tensile test. (3) Resistance to splitting: A fiber with one end fixed is wrapped once around two metal rods arranged in parallel at 5 cm intervals at orthogonal angles, and the other end is wrapped with a
The load was doubled and the metal rod was moved vertically and parallelly at a speed of 60 times/minute over a distance of 5 cm, and the number of times the fibers were cut was determined. (4) Content of polyparamethylstyrene (PPMS): Extracted the drawn fiber with chloroform and determined from the weight of the dissolved portion. In addition, PPMS was confirmed by infrared analysis. Example 1 Polyethylene with a weight average molecular weight of 2.4 million was added to paramethylstyrene to make a 4.0% by weight mixed solution,
Add to this a polymerization inhibitor (t-butylcatechol) 5.0
A chiller was prepared by adding % by weight and mixing at room temperature. This chiller was packed into an oil jacketed autoclave equipped with a stirrer, heated to 125°C, and stirred for 3 hours to obtain a solution. This solution was spun using a gear pump and a conical die with a diameter of 2 mm at a temperature of 125° C. and a spinning speed of 6 cm ³ /min. This spun fiber was placed 3 cm below the spinning die.
The mixture was rapidly cooled by passing it through a water bath at ℃ to obtain a gel-like fiber. This gel-like fiber was continuously wound onto a bobbin having a diameter of 35 mm at a speed of 1.2 m/min. This gel fiber containing paramethylstyrene is
Using a 2m long cylindrical heating tube with an oil jacket, the first stage was drawn at a stretching temperature of 105℃ and a feed rate of 2.0m/
minutes, winding speed 14.0m/min, second stage stretching temperature
125℃, feeding speed 2.0m/min, winding speed 6.0m/min and third stage stretching temperature 135℃, feeding speed 2.0
m/min, and the winding speed was 3.3 m/min, and the stretching ratio was
34.7 fibers were obtained. Table 1 shows the properties of this drawn fiber.
It was shown to. Examples 2 to 5 Stretched fibers were obtained in the same manner as in Example 1, except that the amount of polyparamethylstyrene (hereinafter referred to as PPMS) added to the fibers and the stretching ratio were changed. The properties of this drawn fiber are also listed in Table-1. Comparative Example 1 Polyethylene with a weight average molecular weight of 2.4 million was mixed with liquid paraffin [Crystal 322 manufactured by Etsuo Oil Co., Ltd.]
(trade name)] and 4.0% by weight.
Per 100 parts by weight of this mixture, 0.125 parts by weight of 2.6-di-t-butyl-P-cresol and 0.25 parts by weight of tetrakis[methylene-3-(3.5-di-t-butyl-4-hydroxyphenyl)-propionate]methane. A chiller was prepared by adding and mixing at room temperature. This chiller was packed into an oil jacketed autoclave equipped with a stirrer, heated to 200°C and stirred for 2 hours to obtain a solution. Add this solution to 200
The fibers were spun at a speed of 6 cm ³ /min using a conical die with a spinning diameter of 2 mm. The spun fibers were passed through a 15-20°C water bath placed 5 cm below the spinning die to be rapidly cooled to obtain gel-like fibers. 1.2m/1.2m of this gel fiber
It was continuously wound onto a 35 mm diameter bobbin at a speed of 1 minute. A bobbin of gel-like fibers was immersed in methylene chloride kept at room temperature, and liquid parine was extracted from the gel-like fibers. After two extractions of 8 hours each, the methylene chloride was evaporated to obtain dry gel-like fibers. The obtained dried gel-like fibers were drawn using a 2 m long cylindrical heating tube with an oil jacket, at a first stage stretching temperature of 125°C, feeding speed of 2.0 m/min, and winding speed of 12.5°C.
Stretching was carried out in the same manner as in Example 1, except that the second stage was a two-step stretching at a stretching temperature of 135° C., a feeding speed of 2.0 m/min, and a winding speed of 11.7 m/min, and the stretching ratio was 36.5. Obtained fiber. The properties of this drawn fiber are also listed in Table-1. Comparative Examples 2 to 6 Stretched fibers were obtained in the same manner as in Comparative Example 1, except that the stretching ratio of the dry gel fiber was changed. The properties of this drawn fiber are also listed in Table-1.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a specific example of an apparatus for producing fibers by the method of the present invention.

Claims (1)

[Claims] 1. A method for producing a high-molecular-weight polyethylene molded product, which comprises dissolving high-molecular-weight polyethylene in a styrene monomer to prepare a solution, molding a gel-like molded product from this solution, and heating and stretching this molded product. .