JP2006322098A - Method for producing polyethylene naphthalate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing high tenacity polyethylene naphthalate fibers, by which spinning and drawing are carried out stably. <P>SOLUTION: The invention relates to the method for producing the polyethylene naphthalate fibers comprising drawing the filaments obtained by melt spinning a polymer comprising the polyethylene naphthalate as principal component, wherein the drawing is carried out by preheating the filaments with a preheating roller with average surface temperature of 170-190°C and having ≤7°C of maximum deviation of the surface, for 1.50-2.50 sec. The drawing is preferably carried out through a multi-stage drawing, the drawing rate in a first stage drawing is 4.5-6.0 times, and the spinning rate is 450-1200 m/min and the winding rate is ≥2500 m/min, and the fineness of the monofilament is 4.0-8.0 dtex and the total fineness of the fibers is 560-2200 dtex. The preheating roller is preferably a jacket roller enclosing heat transfer medium and the roller has 150-250 mm of diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing polyethylene naphthalate fiber, and more particularly to a method for producing polyethylene naphthalate fiber which has good productivity and is optimally used for industrial materials.

  Polyethylene naphthalate fiber can be used for production of polyethylene terephthalate fiber, which is widely used as a fiber for industrial materials, and can be used almost as it is. In recent years, its application fields have expanded dramatically. For example, various industrial materials, especially tire cords, power transmission belts, rubber hoses, and conveyances that take advantage of the excellent properties of polyethylene naphthalate fibers, such as high strength, high modulus, heat resistance and chemical resistance, and dimensional stability. It is suitably used as a reinforcing material for a belt for use.

  However, polyethylene naphthalate has a problem that the molecular chain is rigid, has a glass transition temperature higher than that of polyethylene terephthalate fiber, and is very brittle in the glass state, so that it is very difficult to stretch. Synthetic fibers improve the physical properties by aligning the molecular orientation in the drawing process, so the polyethylene naphthalate polymer, which is difficult to draw, has insufficient performance and productivity compared to the high performance inherent in polyethylene terephthalate fibers. There was a problem of becoming.

  In particular, in recent polyester fiber production methods, a high-productivity direct spinning drawing method in which a spinning process and a drawing process are continuous is often employed. In this case, the drawing speed is high and the drawing load increases. As compared with another stretching method in which the yarn is once wound after melt spinning and then stretched, there has been a problem that more yarn breakage occurs during stretching.

  On the other hand, many proposals regarding the spinning stage of polyethylene naphthalate fiber have been made. For example, Patent Document 1 discloses a method of obtaining high toughness by adjusting the temperature and length of a heating cylinder immediately after melt spinning, and Patent Document 2 performs stretching of three or more stages to improve the elastic modulus in a high temperature atmosphere. A method is disclosed. However, although both methods have achieved the purpose of improving the physical properties of the fiber when the optimum conditions are taken, there are problems in stable production such as yarn breakage during drawing, and the high potential of polyethylene naphthalate polymer is high. There was a problem that it could not always be demonstrated.

JP-A-6-128810 JP-A-10-88422

  In view of such a current situation, the present invention is to provide a production method capable of stably spinning and stretching high-strength polyethylene naphthalate fibers.

  The method for producing polyethylene naphthalate fiber according to the present invention comprises a fiber obtained by melt spinning a polymer mainly composed of polyethylene naphthalate, having a surface average temperature of 170 to 190 ° C., the maximum temperature of the surface. The film is stretched after preheating for 1.50 to 2.50 seconds with a preheating roller having a deviation of 7 ° C. or less. Furthermore, the drawing process is multistage drawing, the first stage draw ratio is 4.5 to 6.0 times, the spinning speed is 450 to 1200 m / min, and the winding speed is 2500 m / min or more. It is preferable that the single yarn fineness of the fiber after drawing is 4.0 to 8.0 dtex and the total fineness is 560 to 2200 dtex. Moreover, it is preferable that the preheating roller to be used is a heat medium enclosure type jacket roller, and the diameter of a preheating roller is 150-250 mm.

  According to the present invention, there is provided a production method capable of stably spinning and stretching high-strength polyethylene naphthalate fibers.

The production method of the present invention relates to a method in which a synthetic fiber obtained by melt spinning a polymer is preheated and then drawn.
Here, the melt-spun polymer used in the present invention is not particularly limited as long as it has polyethylene naphthalate as a main component, and generally has ethylene-2,6-naphthalate as a repeating unit, Preferably, ethylene-2,6-naphthalate occupies 80 mol% or more, more preferably 90 mol% or more of all repeating units. The polyethylene naphthalate used in the present invention is generally synthesized by polycondensing naphthalene-2,6-dicarboxylic acid or an ester-forming derivative thereof with ethylene glycol in the presence of a catalyst under appropriate reaction conditions. . If it is a small amount, it may be a copolymer containing other components in addition to such polyethylene naphthalate. Suitable other components to be copolymerized include (a) a compound having two ester-forming functional groups; For example, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid and dimer acid; alicyclic dicarboxylic acids such as cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid and hexahydroterephthalic acid; phthalic acid, isophthalic acid and naphthalene Aromatic dicarboxylic acids such as -2,7-dicarboxylic acid and diphenyldicarboxylic acid; carboxylic acids such as diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid and sodium 3,5-dicarboxybenzenesulfonate; Glycolic acid, p-oxybenzoic acid, p Oxycarboxylic acids such as oxyethoxybenzoic acid; propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, bisphenol A, etc. An oxy compound, or a functional derivative thereof: a carboxylic acid, an oxycarboxylic acid, a compound having a high degree of polymerization derived from the oxy compound or a functional derivative thereof, or (b) a compound having one ester-forming functional group, For example, benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyalkylene glycol and the like can be mentioned. Furthermore, (c) a compound having three or more ester-forming functional groups, such as glycerin, pentaerythritol, and trimethyl, can be used within the range where the polymer is substantially linear. It goes without saying that matting agents such as titanium dioxide and stabilizers such as phosphoric acid, phosphorous acid and esters thereof may be contained in the polyester.

  The polymer mainly composed of polyethylene naphthalate used in the production method of the present invention is preferably a polymer whose intrinsic viscosity is increased by solid phase polymerization before melt spinning. In particular, when using fibers for industrial materials that require high strength, performance such as high strength, high elastic modulus, and high durability is required. The viscosity is preferably in the range of 0.65 to 0.90. When the intrinsic viscosity is less than 0.65, it tends to be difficult to obtain sufficient strength and toughness for industrial materials, and conversely, when it is higher than 0.90, the viscosity at the time of melting becomes extremely high. There is a tendency for yarn breakage during spinning to increase.

  A conventionally known method can be used as the method of solid phase polymerization. This method is broadly divided into two types, batch type and continuous type, which can be selected as needed. The former is preferable in that it can produce a relatively small lot without any loss, and the latter is preferable for a large lot. This is preferable because production can be performed efficiently.

  The polymer obtained is melt-spun, and a conventionally known method can be used for this method. For example, a polyethylene naphthalate chip is melted to a temperature equal to or higher than the melting point by an extruder and then discharged from a spinneret. The spinning speed at this time is preferably 450 to 1200 m / min. It is preferable that the spun fiber is further drawn without being wound up and then drawn into a drawn yarn after further applying an oil agent.

  And the manufacturing method of the polyethylene naphthalate fiber of this invention is the surface average temperature of 170-190 degreeC, and the maximum deviation of the surface temperature is 7 degrees C or less about the fiber obtained by melt-spinning in this way. This is a method in which stretching is essential after preheating with a preheating roller for 1.50 to 2.50 seconds.

  At this time, in the production method of the present invention, it is extremely important to strictly control the surface temperature distribution of the preheating roller, and the maximum deviation of the surface temperature must be 7 ° C. or less, preferably 5 ° C. or less. is there. When the maximum temperature deviation is greater than 7 ° C., for example, when the temperature distribution in the longitudinal direction of the roller is locally high, crystallization of the yarn passing through the region is likely to occur, which may cause yarn breakage in the process. . Also, if the average temperature is set so that the highest temperature is the optimum temperature so that yarn breakage is unlikely to occur, the draw ratio cannot be increased due to insufficient preheating, resulting in insufficient fiber strength. Or it may cause the yarn to break by forcibly drawing. Since the fiber passes a plurality of times on the preheating roller, the temperature deviation in the longitudinal direction is particularly important in the production method of the present invention, and the temperature deviation in the longitudinal direction is preferably within 5 ° C.

  As a method for making the surface temperature distribution of the roller uniform, a technique of arranging a plurality of heat pipes enclosing a heat medium in a balanced manner on the roller shaft is generally used, but in order to keep the temperature deviation within 7 ° C. It is preferable to further provide a jacket chamber in which a heat medium is sealed inside the roller. The type of the heat medium can be appropriately selected according to the use temperature range, but water (water vapor) is generally used. Furthermore, in order to make the temperature distribution of the roller even more uniform, it is also a preferable means to enclose the roller in a heat insulating box with high heat insulation or to increase the internal temperature positively by arranging a heating source in the heat insulating box. .

  In the present invention, it is essential that the undrawn yarn is preheated at a high temperature of 170 to 190 ° C. and for a time as long as 1.50 to 2.50 seconds with the temperature-controlled preheating roller. Crystallization is induced at a temperature higher than 190 ° C., and the crystallized portion is difficult to be stretched. As a result, the fiber is partially stretched in the length direction, and the frequency of yarn breakage increases. Further, when the temperature is lower than 170 ° C., the slip of the molecular chain is insufficient, and the degree of molecular orientation at the time of stretching does not increase, so that improvement of fiber physical properties due to stretching cannot be obtained. Further, when the preheating time is shorter than 1.5 seconds, there is a large variation in the preheating state between the filaments constituting the fiber yarn and in the length direction, and the diameter of the fiber is locally reduced at the time of drawing. Since the neck point moves and the fixing of the neck point is not smooth, the stretching degree is partially different, and the frequency of occurrence of yarn breakage increases. On the other hand, when heating in the above-mentioned temperature range for a time longer than 2.5 seconds, the occurrence frequency of yarn breakage increases to induce crystallization, as in the case of high temperature.

  The preheating time can be adjusted by the number of yarns wound on the preheating roller and the peripheral speed of the roll. However, since the peripheral speed of the roller is largely limited by the draw ratio and the winding speed, a method of increasing / decreasing the number of wrinkles is preferable. Therefore, it is preferable to use a Nelson roller as the preheating roller. When the Nelson roller is used, the number of wrinkles can be changed within a certain range by changing the angles of the left and right rollers. However, in order to ensure a long preheating time as in the present invention, it is preferable to employ a large roller among the rollers usually used for the production of polyester fiber, because the thread pitch becomes too narrow just by adjusting the angle of the roller. . For example, the diameter is preferably 150 to 250 mm, and the length is preferably 300 to 1000 mm.

  In the production method of the present invention, the preheating conditions are so narrow that the importance of preheating conditions in the stretchability of polyethylene naphthalate fibers is not so large as that of polyethylene terephthalate fibers, which are general-purpose fibers. The inventors have found that there is an optimum point and have reached the present invention. Polyethylene naphthalate fiber has a glass transition temperature of about 113 ° C., which is higher than that of polyethylene terephthalate fiber. Even though it is necessary to preheat the yarn to a high temperature, the oriented undrawn yarn of polyethylene naphthalate molecules that are rigid is At temperatures above the glass transition temperature, crystallization is very likely to occur compared to polyethylene terephthalate molecules.

  In the production method of the present invention, the stretching step is multi-stage stretching, and the first stage draw ratio is preferably 4.5 to 6.0 times, and more preferably 4.8 to 5.5 times. It is preferable. By stretching at such a high magnification, neck stretching can be completed in the first stage and the unstretched portion can be eliminated, so that high-strength fibers tend to be easily obtained. Furthermore, it is preferable that the variation in strength (CV%) between the single yarns after the first stage drawing is less than 10%. When each single fiber is sufficiently drawn by the production method of the present invention, it is possible to reduce the strength variation between the single yarns in this way, and since there is no weak single yarn, the yarn breakage in the drawing process is reduced. It became possible to make it.

  In order to obtain sufficient fiber strength, the total draw ratio is preferably 5.0 to 6.0 times. The final winding speed is preferably 2500 m / min or more. The upper limit is 5000 m / min or less, and usually 3500 m / min or less. Thus, when spinning and drawing at high speed, the number of yarn breaks tends to increase, and thus the present invention is particularly effective.

  Moreover, as the single yarn fineness of the finally obtained fiber after drawing, it is preferably in the range of 4.0 to 8.0 dtex, and the total fineness is preferably in the range of 560 to 2200 dtex, and the filament constituting the yarn The number is preferably 120 to 300 filaments. In the case of such a filament composed of multifilaments, it is possible to more effectively prevent yarn breakage in the manufacturing process by applying the present invention. The fiber strength is preferably 7 cN / dtex or more, and more preferably in the range of 8 to 12 cN / dtex.

  When such a production method of the present invention is used, the stretching conditions are controlled to be very uniform, so that the strength of the resulting fiber can be obtained, of course, in the production process, particularly in the stretching process in the second and subsequent stages. The number of thread breaks can be reduced.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these specific examples. In addition, the measuring method used for evaluation of this invention is as follows.
(1) Intrinsic viscosity The resin or fiber was dissolved in a mixed solvent of phenol and orthodichlorobenzene (volume ratio 6: 4), and the viscosity was determined from the viscosity measured at 35 ° C.

(2) Strength and single yarn strength variation Measured with an autograph manufactured by Shimadzu Corporation in accordance with JIS L-1070.
For the single yarn strength variation, 50 single yarns were taken out from multifilaments at the same location, the strength was measured, and CV% was calculated based on the standard deviation. Sampling was performed at two points after the one-stage stretching, which is an intermediate step, or after the stretching step.

(3) Roller surface temperature Among the rollers having a total length of 500 mm, an effective length 450 mm portion which is a portion in contact with the fiber on the roller surface is 10 points at intervals of 50 mm and 4 points every 90 degrees on the circumference. The surface temperature of the points was measured with a thermocouple thermometer, and the average temperature and the maximum deviation (difference between the maximum value and the minimum value) were calculated.

[Example 1]
A polyethylene-2,6-naphthalate chip having an intrinsic viscosity of 0.76 is discharged from a spinneret having a circular spinning hole with 250 holes and a hole diameter of 0.6 mm at a polymer temperature of 316 ° C. and a discharge amount of 333 g / min. Then, after cooling and solidifying with cold air, a spinning oil agent was applied and taken up at a speed of 484 m / min. The obtained undrawn yarn is continuously supplied to the drawing process without being wound once, and is a Nelson roller (preheating roller) composed of a heating medium enclosing jacket roller in which water is enclosed as a heating medium having a surface temperature deviation of 3 ° C. After preheating for a predetermined time, the film was stretched in two stages so that the one-stage magnification was 5.0 times and the total stretching ratio was 6.2 times. Thereafter, it was heat-set at 240 ° C. and wound at a winding speed of 3000 m / min to obtain a drawn yarn of 1100 dtex / 250 filament.
At this time, the CV% of the single fiber strength variation after the first-stage drawing was 8%. Table 1 shows preheating conditions, drawn yarn strength, single fiber strength variation, and the number of yarn breaks per unit production.

[Example 2]
Spinning and drawing were performed in the same manner as in Example 1 except that the preheating temperature and time were changed.
Table 1 shows preheating conditions, drawn yarn strength, single fiber strength variation, and number of yarn breaks per unit production.

[Comparative Example 1]
Spinning and drawing were performed in the same manner as in Example 1 except that the preheating temperature was changed.
At this time, the CV% of the single fiber strength variation after the first-stage drawing was 11%. Table 1 shows preheating conditions, drawn yarn strength, single fiber strength variation, and number of yarn breaks per unit production.

[Comparative Examples 2 and 3]
Spinning and drawing were performed in the same manner as in Example 1 except that the preheating temperature and time were changed.
Table 1 shows preheating conditions, drawn yarn strength, single fiber strength variation, and number of yarn breaks per unit production.

[Comparative Example 4]
A drawn yarn was obtained under the same conditions as in Example 1 except that a normal preheating roller having a temperature of 180 ° C. and a surface temperature deviation of 15 ° C. was used as the preheating roller.
Table 1 shows preheating conditions, drawn yarn strength, single fiber strength variation, and number of yarn breaks per unit production.

Claims (7)

  A fiber obtained by melt-spinning a polymer mainly composed of polyethylene naphthalate has a surface average temperature of 170 to 190 ° C., and a maximum temperature deviation of the surface is 7 ° C. or less. A method for producing polyethylene naphthalate fiber, which is preheated for 50 to 2.50 seconds and then drawn.   The method for producing a polyethylene naphthalate fiber according to claim 1, wherein the drawing step is multistage drawing, and the draw ratio of the first stage is 4.5 to 6.0 times.   The method for producing polyethylene naphthalate fiber according to claim 1 or 2, wherein the single yarn fineness of the drawn fiber is 4.0 to 8.0 dtex, and the total fineness is 560 to 2200 dtex.   The method for producing a polyethylene naphthalate fiber according to any one of claims 1 to 3, wherein the spinning speed is 450 to 1200 m / min.   Winding speed is 2500 m / min or more, The manufacturing method of the polyethylene naphthalate fiber of any one of Claims 1-4.   The method for producing a polyethylene naphthalate fiber according to any one of claims 1 to 5, wherein the preheating roller is a heat medium-sealed jacket roller.   The method for producing polyethylene naphthalate fiber according to any one of claims 1 to 6, wherein a diameter of the preheating roller is 150 to 250 mm.