JPH0437861B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a high molecular weight polyolefin molded product, and more particularly, a method for producing a high molecular weight polyolefin molded product such as a fiber or film having high strength and high elastic modulus with excellent splitting resistance, knot strength and tear strength. Regarding. 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 have significant vertical cracking or splitting, and when trying to obtain tow/bleb legs or cloth using a normal loom or knitting machine, the fibers are damaged due to bending and friction when passing through guide pulleys, guide rolls, kite ribs, etc. The disadvantage was that the actual 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 polyolefins obtained by conventional methods. Molding of a high molecular weight polyolefin characterized by molding a gel-like molded product, removing the solvent in the gel-like molding, impregnating a styrenic monomer in the gel-like molding, and then heating and stretching it. It is a method of manufacturing something. The high molecular weight polyolefin used in the present invention is a crystalline olefin homopolymer or copolymer with a weight average molecular weight of 500,000 or more, preferably 1,000,000 or more, particularly preferably
2,000,000 or more, such as polyethylene, polypropylene, ethylene-propylene copolymer,
Examples include polybutene-1, polymethylpentene-1, and polyoxymethylene. Among these, polyethylene or polypropylene having a weight average molecular weight of 2,000,000 or more is preferred. In addition, the styrene monomer used in the present invention rapidly undergoes radical polymerization during the process of impregnating, heating, and stretching a gel-like molded product formed from a solution of a high-molecular-weight polyolefin, which will be described later, after removing the solvent. Examples include progressive styrene 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 groups such as fluorine, chlorine, bromine, and iodine. Examples include those substituted with halogen, and among these, ortho, meta or para substitutions are preferred. Among the above styrenic monomers, ortho,
Meta- or para-methylstyrene is preferred, and para-methylstyrene or a mixture of ortho- or meta-methylstyrene mainly consisting of para-methylstyrene is particularly preferred in terms of reactivity and vapor pressure. In addition, these styrene monomers are used as a mixture of two or more types or as a mixture with other polymerizable monomers such as isocyanuric acid, vinylnaphthalene, vinylpyridine, vinylcaprolactam, etc. mainly composed of styrene monomers. be able to. The solution of high molecular weight polyolefin in the present invention is prepared by heating and dissolving the high molecular weight polyolefin in a solvent. The solvent at this time is
The material can sufficiently dissolve the polymer, such as saturated aliphatic hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, or mixtures thereof. Suitable examples include paraffin oil, aliphatic or cyclic hydrocarbons such as decane, undecane, dodecane, and tetralin, and mineral oil fractions whose boiling points correspond to these hydrocarbons. The heating dissolution is carried out at a temperature at which the polyolefin completely dissolves in the solvent, which is higher than the temperature at which it gels during dissolution. The temperature varies depending on the solvent used, but is generally between 140 and 250.
℃ range. Further, the concentration of polyolefin present in the solution is 1 to 15% by weight, preferably 4 to 15% by weight.
It is 8% by weight. Next, a gel-like molded product of polyolefin is molded from this heated and dissolved solution. This gelation method involves applying the polyolefin solution to an appropriately selected die, for example, a die having holes with a circular, elliptical, X-shaped, or Y-shaped cross section for forming fibers, or a die for forming films, bands, etc. One example is a method of extruding using a hole having a rectangular cross section. The extruded gel-like molded product is cooled at a rate of at least 50°C/min to a temperature below the gelling temperature, preferably from 15 to 25°C, in a water bath, an air bath, or an extraction solvent. The resulting gel-like molded product contains the solvent used to dissolve the polyolefin, and therefore requires a solvent removal treatment. Methods for removing the solvent in the gel-like molded product include evaporation and removal of the solvent by heating the gel-like molded product;
Alternatively, removal of the solvent by extraction using a volatile solvent may be mentioned, but in order to remove the solvent without significantly changing the structure of the gel-like molded product, extraction removal using a volatile solvent is preferable. It is preferable to remove the solvent in the gel molded product to 1% by weight or less. Examples of this volatile solvent include pentane,
Hydrocarbons such as hexane, hebutane, toluene,
Examples include chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as trichlorotrifluoroethane, ethers such as diethyl ether and dioxane, and alcohols such as methanol and ethanol. The gel-like extrusion containing the volatile solvent from which the solvent has been extracted is dried under conditions that remove the volatile solvent and leave a substantially intact solid network polymer or containing the volatile solvent. impregnated with styrenic monomer. Impregnation of a polymerizable styrenic monomer (hereinafter referred to as monomer) into a gel-like molded product that has been desolvated is performed by immersing the molded product in the monomer in the presence or absence of a reaction initiator. This is achieved by doing. A reaction initiator is preferably added to effect effective polymerization, such as benzoyl peroxide,
lauroyl peroxide, azobisisobutyronitrile, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t- butylperoxy)hexyne-3, di-t-butyl peroxide, and the like. The amount of the reaction initiator added is not particularly limited, but is usually 0.005 to 5 parts by weight per 100 parts by weight of the monomer. The temperature of the monomer at this time exceeds the freezing point of the monomer,
Furthermore, it is economically preferable to carry out the reaction at a temperature until the gel-like molded product dissolves into the monomer, specifically at a temperature in the range of 90°C after the freezing point, particularly at a room temperature of 20 to 25°C. If the temperature of the monomer is below the freezing point, the monomer will not be impregnated into the gel-like molded product, while at high temperatures exceeding 90°C, the gel-like molded product will dissolve into the monomer,
This is not preferred because the polymerization rate increases significantly and the monomer evaporates. In addition, the immersion time of the gel-like molded product in the monomer is selected depending on the amount of monomer added by polymerization in the gel-like molded product in the heating stretching of the gel-like molded product described below. Ru. The preferred amount of polymer added by polymerization in the gel molded product is
0.5-25% by weight, particularly preferably 1-5% by weight
is within the range of If the amount of polymer added is less than 0.5% by weight, the fiber splitting resistance, knot strength, tear strength, etc. of the 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. unfavorable to Next, the gel-like molded product impregnated with the monomer is heated and stretched in one or more stages. The temperature at this time must be such that the monomer impregnated into the gel-like molded product is polymerized and the gel-like molded product can be sufficiently oriented. Specifically, it is preferable to conduct the heating at a temperature between the softening point and the melting point of the gel-like molded product, particularly just below the melting point.
In the case of polypropylene, the temperature is preferably 110 to 160°C. If the temperature during stretching exceeds the melting point,
This is because the gel-like molded product cannot be oriented, and on the other hand, below the softening point, the monomer is not sufficiently polymerized, and the stretching ratio necessary to obtain a high-strength and high-elastic molded product cannot be obtained. unfavorable to The tensile strength and elastic modulus of a molded product 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 stretched molded product is heat-treated and dried to remove unreacted monomers. 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. A high molecular weight polyolefin 1 and a non-volatile solvent 2 are supplied to a mixing tank 3 and made into a slurry by a stirrer 4. This slurry is continuously sent through a tube 5 to a heated stirring tank 6 and stirred by a stirring plate 7 to form a uniform solution. This solution is sent to a spinning die 9 by a gear pump 8 and subjected to solution spinning. The extruded solution 10 is immediately cooled and gelled in a cooling tank 11 to become a yarn 12. The gelled fibers 12 are supplied by rolls 13 to an extraction tank 15 using a volatile solvent 14 to extract and remove the nonvolatile solvent, and then sent by rolls 16 to a drying chamber 17 to obtain dry gel fibers 18 (xerogel). The dry gel fiber 18 is rolled into a roll 19
The film is sent through a monomer 20 dipping tank 21, impregnated with monomer, and led to a stretching process. monomer 20
The gel fiber 22 containing the rolls 23, 25, 2
Cylindrical heating machines 24, 26 with different temperatures at 7, 29,
The gel fibers are supplied to the gel fibers 28 or wound up, and stretched in three stages while changing the temperature. At the same time, the monomers contained in the gel fibers are polymerized to form a polymer of monomers between the oriented crystals of the stretched fibers 30. let Stretched fiber 30
is dried in a heat setting tank 31, passed through a roll 32, and wound up on a winder 33. As described above, according to the method of the present invention, the splitting resistance, knot strength and tear strength of a stretched product obtained from a high molecular weight polyolefin can be significantly improved without impairing the high elasticity and high strength. For example, the fibers obtained by the method of the present invention are suitable for ropes, cables, etc. that are subject to strong friction and twisting, and are resistant to buckling, so they are suitable for applications such as single yarns and nets. In addition, it can be used for secondary processing of tow, prepreg, cloth, etc. using normal techniques, expanding its use as a reinforcing material for composite materials. Examples of the present invention are shown below. The test method is as follows. (1) Tensile modulus, strength: Using an Instron type tensile tester, the distance between the cracks was 25 mm, and the tensile speed was 5 mm/
It was determined from a tensile test of fibers at a temperature of 25°C. (2) Knot strength: The fibers were tied once and determined by the above tensile test. (3) Resistance to splitting: A fiber with one end fixed is wrapped once each 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): The drawn fiber was extracted with chloroform, and the content was determined from the weight of the dissolved portion. In addition, PPMS was confirmed by infrared analysis. Example 1 Polyethylene having a weight average molecular weight of 2.4 million was added to liquid paraffin (Crystal 322 (trade name) manufactured by Etsuo Oil Co., Ltd.) to form a 4.0% by weight liquid mixture. 0.125 parts by weight of 2,6-di-t-butyl-p-cresol and tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate] per 100 parts by weight of this mixed solution. 〕methane
0.25 parts by weight were added and mixed at room temperature to prepare an emulsion liquid. This emulsion liquid was filled into an oil jacketed autoclave equipped with a stirrer, heated to 200°C, and stirred for 2 hours to obtain a solution. This solution was spun at 200° C. using a conical die with a spinning diameter of 2 mm at a speed of 6 cm ³ /min. The spun fibers were placed 5 cm below the spinning die at 15 to 20℃.
The fibers were rapidly cooled through a water bath to obtain gel-like fibers. This gel-like fiber was continuously wound onto a bobbin with a diameter of 3.5 cm at a speed of 1.2 m/min. A bobbin of gel-like fibers was immersed in methylene chloride kept at room temperature to extract liquid paraline from the gel-like fibers. After two extractions of 8 hours each, the methylene chloride was evaporated to obtain dry gel-like fibers. The dried gel-like fibers were immersed for 2 hours in paramethylstyrene containing 4% by weight of a reaction initiator (benzoyl peroxide) at 23°C. The gel-like fiber impregnated with para-methylstyrene containing this reaction initiator is stretched at the first stage using a 2m long cylindrical heating tube with an oil jacket.
115℃, drawing speed 2.0m/min, winding speed 4.0m/min,
In the second stage, the drawing temperature is 125℃ and the drawing speed is 2.0m/
The winding speed is 10.0 m/min, and the third stage is the stretching temperature of 135°C, the drawing speed is 2.0 m/min, and the winding speed is 8.0 m/min.
The fiber was drawn in 3 stages with a draw ratio of 40.4. Table 1 shows the properties of the fibers obtained by heat-treating the drawn fibers at 60°C for 24 hours. Examples 2 to 15 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 dry gel fiber and the stretching ratio were changed. Table 1 shows the properties of this drawn fiber.
Also listed. Comparative Example 1 The dried gel-like fiber obtained in Example 1 was
Using a 2m long cylindrical heating tube with an oil jacket,
The first stage is a drawing temperature of 125℃ and a drawing speed of 2.0m/
12.5m/min, winding speed 12.5m/min, second stage stretching temperature 135℃, drawing speed 2.0m/min, winding speed 4.0m/min.
A drawn fiber was obtained in the same manner as in Example 1, except that the two-step drawing was carried out at a draw ratio of 12.5. 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] Examples 16-20 The dried gel-like fibers obtained in Example 1 were
A drawn fiber was obtained in the same manner as in Example 1 except that it was immersed in paramethylstyrene containing 5% by weight of divinylbenzene. The properties of this drawn fiber are shown in Table 2.

[Table] * Polymer of paramethylstyrene and divinylbenzene.
Example 21 In Example 1, polypropylene with a weight average molecular weight of 2.5 million was used instead of polyethylene, and the concentration was 8.
% by weight liquid paraffin solution was prepared, and the gel-like fibers impregnated with para-methylstyrene were stretched at a stretching temperature of 115°C and a drawing speed in the first stage.
2.0m/min, winding speed 4.0m/min, second stage stretching temperature 135℃, drawing speed 2.0m/min, winding speed
Stretching was carried out in the same manner as in Example 1, except that the stretching temperature was 155°C, the drawing speed was 2.0 m/min, and the winding speed was 3.0/min, and the stretching ratio was 15.5 at 10.0 m/min and the third stage. Obtained fiber. The properties of this drawn fiber are shown in Table 3. Comparative Example 7 The dried gel-like fiber obtained in Example 21 was
Using a 2 m long cylindrical heating tube with an oil jacket, the first stage was drawn at a drawing temperature of 135°C and a drawing speed.
2.0m/min, winding speed 20.m/min, second stage stretching temperature 155℃, drawing speed 2.0m/min, winding speed
A drawn fiber was obtained in the same manner as in Example 21, except that the drawing was carried out in two stages at 4.2 m/min and the drawing ratio was 15.3. The properties of this drawn fiber are also listed in Table 3.

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic side view showing an embodiment of the manufacturing method of the present invention.

Claims (1)

[Claims] 1 Molding a gel-like molded product from a solution of a high molecular weight polyolefin, removing the solvent in the gel-like molding, impregnating a styrene monomer in the gel-like molding, and then heating and stretching. A method for producing a high molecular weight polyolefin molded product, characterized by: