JP2022056854A - Liquid crystalline polyester multifilament and manufacturing method thereof - Google Patents

Abstract

To provide a liquid crystalline polyester multifilament achieving mechanical properties such as high strength and high elastic modulus, and high heat resistance not having been achieved in the prior arts and suitable for general industrial materials and the uses which require designability and visibility.SOLUTION: A liquid crystalline polyester multifilament is characterized by that values showing fiber colors are an L value of 64-86, a (a) value of -6 to 6, and a (b) value of 15-36. A manufacturing method of the liquid crystalline polyester multifilament is characterized by that a resin pellet with gas volume generated by heating at +40°C of a melting point suppressed to 1000 ppm or under is used as a raw material, and residence time of the liquid crystalline polyester resin melting in a spinning machine on melting spinning is set to be 40 minutes or under.SELECTED DRAWING: None

Description

The present invention relates to a liquid crystal polyester multifilament. More specifically, the present invention relates to a liquid crystal polyester multifilament that can be suitably used for general industrial material applications and applications that require design and visibility.

The liquid crystal polyester fiber is made of a liquid crystal polyester resin having a rigid molecular structure, and in melt spinning, the molecular chains are highly oriented in the fiber axis direction, and after the fibers are formed, they are subjected to high temperature and long time heat treatment for melt spinning. It is known that the highest strength and elasticity among the fibers obtained in the above are exhibited. It is also known that the liquid crystal polyester fiber has improved heat resistance and dimensional stability because the molecular weight of the liquid crystal polyester fiber is increased by the heat treatment and the melting point is also increased. Such liquid crystal polyester fibers are suitable for general industrial material applications such as ropes, slings, fishing nets, nets, meshes, woven fabrics, fabrics, sheet-like materials, belts, tension members, various reinforcing cords, resin reinforcing fibers and the like. Can be used for.

Japanese Unexamined Patent Publication No. 08-260242 Japanese Unexamined Patent Publication No. 03-137225 Japanese Patent Application Laid-Open No. 2003-147638 JP-A-2007-196516

However, although the above-mentioned liquid crystal polyester fiber generally has high mechanical properties such as high strength and high elastic modulus, it is difficult to dye or color it, so that it has design properties such as various textiles and woven and knitted fabrics. The use was limited in applications where visibility was required. In recent years, warm colors (red, orange) have been used for textile applications for outdoor tent fabrics, which require design and innovation, and for construction work ropes and safety belt belts, which require workers to ensure visibility. , Yellow, etc.), and the development of high-strength and high elastic modulus fibers is desired.

In order to solve such a problem, in Patent Document 1, in order to obtain a liquid crystal polyester fiber having high strength and elastic modulus and excellent dyeability, the polymer composition and fiber structure constituting the fiber are adjusted. Therefore, there is no contraction stress peak at 50 ° C to 250 ° C, the ratio of the contraction stress value at 50 ° C to the contraction stress value at 200 ° C, and the dyeing parameters are controlled within a certain numerical range, and blue dyeing is performed. The latter b value is set to -5 or less. Certainly, in Patent Document 1, although a fiber having a certain degree of strength and elastic modulus and having excellent dyeability which has not been conventionally obtained is obtained, a polymer in which an ethylene unit is copolymerized in order to exhibit the above-mentioned characteristics is obtained. In addition to adopting the structure, a small amount of diethylene glycol is added to the polymer. As described above, when a flexible structure (such as an ethylene unit) is introduced into the polymer, the dyeability is improved, but it is disadvantageous for increasing the strength of the fiber, and as a result, the strength of the obtained fiber is as described in the examples. The maximum is only about 21 g / d (≈18.5 cN / dtex), which is insufficient for application to general industrial applications in which high-strength fibers are preferably used. In addition, the final product is a liquid crystal polyester fiber having a b value of -5 or less.

Patent Document 2 relates to an aromatic polyester fiber that is colored and has high strength and high elastic modulus. Colored by using an aromatic polyester capable of forming an anisotropic molten phase in the core component A and an aromatic polyester containing 0.1 to 3.0% by weight of a colorant in the sheath component B to form a composite fiber. Obtained the raw fiber. Certainly, in Patent Document 2, colored fibers having high strength and high elastic modulus are obtained, but since a composite fiber structure is adopted in order to achieve both mechanical properties and coloring, a long-term period is certainly obtained. At the time of use, the interface peeling between the core polymer and the sheath polymer causes deterioration of mechanical properties such as strength and abrasion resistance and deterioration of fluff quality, which is insufficient for general industrial use. Further, in Patent Document 2, only composite fibers having a black color or a gray diameter as described in Examples and Comparative Examples are obtained.

Further, Patent Document 3 contains a liquid crystal polyester resin (a) having a predetermined amount or more of structural units produced from p-hydroxybenzoic acid, terephthalic acid or isophthalic acid as a dicarboxylic acid component, and ethylene glycol as a glycol component. The polyester resin (b) is mixed with a predetermined composition to obtain a polyester resin composition for pearl-like fibers, which is characterized by having a color tone L value of 65 or more. Certainly, in Patent Document 3, a fiber having a pearl-like texture having excellent thermal stability, high strength and a strong whiteness is obtained, and is suitable as a fiber for clothing. However, in order to exhibit the above-mentioned characteristics, the liquid crystal polyester resin (a) and the polyester resin (b) containing an ethylene unit are mixed, and the mixing ratio thereof is dominated by the polyester resin (b). In the example, about 97 wt% is polyester resin (b), that is, liquid crystal polyester resin is added in a small amount, and a flexible structure (ethylene unit, etc.) is introduced in most of the polymer, so that the high-strength fiber is Not obtained. The strength level of the pearl-like texture fiber actually obtained in Patent Document 3 is less than 6 cN / dtex, and although it can be used for clothing, it is not suitable for general industrial use in which high-strength fiber is used. It is enough. Further, in Patent Document 3, although the L value is 65 or more, the liquid crystal polyester fiber having yellowness as in the present invention has not been obtained.

Further, Patent Document 4 suppresses deterioration of the retained heat of the resin in the flow path from the front surface of the screw tip of the extruder to the die when the polyarylate resin composition is produced by the melt-kneading method in the extruder, and is extremely It is an object of the present invention to provide a method for producing a resin composition having a good color tone, which does not contain a resin discolored to. Certainly, in Patent Document 4, in order to produce a resin composition having a good color tone, the shape of the screw tip portion of the extruder is set to be asymmetrical with respect to the rotation axis, and is suitable for the resin flow at the screw tip portion. By generating a high level of turbulence, the generation of heat-deteriorated resin can be minimized. However, although it is effective to optimize the polymer flow path structure in the screw to reduce the retention portion, the residence time is not controlled, and it depends on the low molecular weight substance and unreacted monomer contained in the resin used. The effect of suppressing the thermal decomposition reaction of the polyarylate resin cannot be obtained. Further, Patent Document 4 relates to a method for producing a resin composition, does not mention fibrosis of a polyarylate resin, and does not obtain a yellowish liquid crystal polyester fiber as in the present invention.

Further, in general industrial material applications, heat resistance after dry heat treatment tends to be required for the purpose of reducing deterioration of product physical properties during heat treatment in manufacturing textile products, but in any of Patent Documents 1 to 4. However, there is no mention of heat resistance after dry heat treatment.

As described above, the prior art has high mechanical properties such as high strength and high elastic modulus and high heat resistance, which can be suitably used for general industrial material applications and applications requiring designability and visibility. No yellowish liquid crystal polyester multifilament has been obtained.

Therefore, in the present invention, high mechanical properties such as high strength and high elastic modulus and high heat resistance that can be suitably used for general industrial material applications and applications that require designability and visibility, which have not been achieved by the prior art, are provided. It is an object of the present invention to provide a liquid crystal polyester multifilament having and having a yellowish color.

In order to solve the above problems, the present invention has the following configuration. That is, the present invention is a liquid crystal polyester multifilament characterized in that the L value representing the color of the fiber is 64 to 86, the a value is -6 to 6, and the b value is 15 to 36.

In addition, resin pellets in which the amount of gas generated by heating at a melting point of + 40 ° C. is suppressed to 1000 ppm or less are used as raw materials, and the residence time of the molten liquid crystal polyester resin in the spinning machine during melt spinning is within 40 minutes. This is a method for manufacturing the liquid crystal polyester multifilament described above.

Since the liquid crystal polyester multifilament of the present invention has high mechanical properties such as high strength and high elastic modulus and has yellowness, it is used for general industrial materials and various textiles and woven and knitted fabrics that are required to have designability and visibility. It can be suitably used for various purposes. Further, since the yellowish liquid crystal polyester multifilament of the present invention also has excellent heat resistance, there is little deterioration in product physical properties during heat treatment when manufacturing high-order processed products, and the general industrial material use and design properties are small. -In addition to applications that require visibility, it can also be suitably used for applications such as fiber-reinforced resin products and resin molded products.

The liquid crystal polyester multifilament of the present invention and a method for producing the same will be described in detail below.

The method for producing a liquid crystal polyester multifilament of the present invention is as long as a liquid crystal polyester multifilament having an L value of 64 to 86, an a value of -6 to 6, and a b value of 15 to 36, which represent the color of the fiber, can be obtained. , But not limited to, preferred embodiments are described below.

The liquid crystal polyester used in the present invention refers to a polyester that exhibits optical anisotropy (liquid crystal property) when it is heated and melted. This can be certified by placing a sample made of liquid crystal polyester on a hot stage, heating it in a nitrogen atmosphere, and observing the presence or absence of transmitted light of the sample with a polarizing microscope.

Examples of the liquid crystal polyester used in the present invention include a polymer of aromatic oxycarboxylic acid (a), a polymer of aromatic dicarboxylic acid and aromatic diol, and a polymer of aliphatic diol (b), the above (a) and the above (b). ) And the like, and among them, a polymer composed only of aromatics is preferable. Polymers composed only of aromatics exhibit excellent strength and elastic modulus when made into fibers. Further, a conventionally known method can be used for the polymerization formulation of the liquid crystal polyester.

Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid (p-hydroxybenzoic acid and the like), hydroxynaphthoic acid and the like (6-hydroxy-2-naphthoic acid and the like), or alkyl, alkoxy and halogen substitutions thereof. The body etc. can be mentioned.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyetanedicarboxylic acid, diphenylethanedicarboxylic acid and the like, or alkyl, alkoxy and halogen substitutions thereof. The body etc. can be mentioned.

Further, examples of the aromatic diol include hydroquinone, resorcin, dihydroxybiphenyl, naphthalene diol and the like, or alkyl, alkoxy, halogen substituents and the like thereof, and examples of the aliphatic diol include ethylene glycol, propylene glycol and butane diol. , Neopentyl glycol and the like.

In addition to the above-mentioned monomers, the liquid crystal polyester used in the present invention can be further copolymerized with other monomers to the extent that the liquidity is not impaired, and examples thereof include adipic acid, azelaic acid, sebacic acid, and dodecandioic acid. Examples thereof include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, polyethers such as polyethylene glycol, polysiloxanes, aromatic iminocarboxylic acids, aromatic diimines, and aromatic hydroxyimines.

Preferred examples of the liquid crystal polyester obtained by polymerizing the above-mentioned monomer and the like used in the present invention include a liquid crystal polyester in which a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthic acid component are copolymerized, a p-hydroxybenzoic acid component and 4 , 4'-Dihydroxybiphenyl component and isophthalic acid component and / or terephthalic acid component copolymerized liquid crystal polyester, p-hydroxybenzoic acid component and 4,4'-dihydroxybiphenyl component, isophthalic acid component, terephthalic acid component and hydroquinone Examples thereof include liquid crystal polyester in which components are copolymerized.

In the present invention, a liquid crystal polyester composed of the structural units (I), (II), (III), (IV) and (V) represented by the following chemical formula is particularly preferable. In the present invention, the structural unit refers to a unit that can form a repeating structure in the main chain of a polymer.

This combination results in the molecular chain having adequate crystallinity and non-linearity, i.e., a melt-spinnable melting point. Therefore, the fiber has good yarn-making property at a spinning temperature set between the melting point of the polymer and the thermal decomposition temperature, a fiber having a relatively uniform value in the longitudinal direction is obtained, and the fiber has an appropriate crystallinity. The strength and elastic modulus can be increased.

Further, in the present invention, it is preferable to combine components composed of diols which are not bulky and have high linearity, such as structural units (II) and (III). By combining this component, the molecular chain in the fiber has an orderly and less disturbed structure, and the crystallinity is not excessively increased and the interaction in the direction perpendicular to the fiber axis can be maintained. As a result, in addition to high strength and elastic modulus, excellent wear resistance can be obtained.

The above-mentioned structural unit (I) is preferably 40 to 85 mol%, more preferably 65 to 80 mol%, still more preferably 68 to 75 mol% with respect to the total of the structural units (I), (II) and (III). .. By setting it in such a range, the crystallinity can be set in an appropriate range, high strength and elastic modulus can be obtained, and the melting point is also in a range where melt spinning is possible.

The structural unit (II) is preferably 60 to 90 mol%, more preferably 60 to 80 mol%, still more preferably 65 to 75 mol% with respect to the total of the structural units (II) and (III). Within such a range, the crystallinity does not increase excessively and the interaction in the direction perpendicular to the fiber axis can be maintained, so that the wear resistance can be improved.

The structural unit (IV) is preferably 40 to 95 mol%, more preferably 50 to 90 mol%, still more preferably 60 to 85 mol% with respect to the total of the structural units (IV) and (V). By setting it in such a range, the melting point of the polymer becomes an appropriate range, the spinning property is good at the spinning temperature set between the melting point of the polymer and the thermal decomposition temperature, the single fiber fineness is fine, and the fiber is fine in the longitudinal direction. A relatively uniform fiber can be obtained.

It is preferable that the sum of the structural units (II) and (III) and the sum of (IV) and (V) are substantially equimolar. The term "substantially equimolar" as used herein means that the dioxy unit and the dicarbonyl unit constituting the main chain are present in equal molar amounts, and the terminal structural unit may not necessarily be equimolar because one of them may be unevenly distributed. It means that it may be.

A particularly preferable range of each structural unit of the liquid crystal polyester used in the present invention is as follows. The preferable range of each structural unit is the range when the total of the structural units (I), (II), (III), (IV) and (V) is 100 mol%. The liquid crystal polyester fiber of the present invention is suitably obtained by adjusting the composition so as to satisfy the above conditions within this range.

Structural unit (I) 45-65 mol%
Structural unit (II) 12-18 mol%
Structural unit (III) 3-10 mol%
Structural unit (IV) 5-20 mol%
Structural unit (V) 2 to 15 mol%
The polystyrene-equivalent weight average molecular weight (hereinafter, Mw) of the liquid crystal polyester used in the present invention is preferably 30,000 or more, and more preferably 50,000 or more. By setting Mw to 30,000 or more, it is possible to have an appropriate viscosity at the spinning temperature and improve the spinning property, and the higher the Mw, the higher the strength, elongation and elastic modulus of the obtained fiber. Further, from the viewpoint of improving fluidity, Mw is preferably less than 250,000, more preferably less than 150,000. The Mw referred to in the present invention is a value obtained by the method described in the examples.

The melting point of the liquid crystal polyester used in the present invention is preferably in the range of 200 to 380 ° C., more preferably 250 to 350 ° C., still more preferably 290 to 340 ° C. from the viewpoint of ease of melt spinning and heat resistance. Is. The melting point referred to in the present invention is a value obtained by the method described in Examples.

Further, other polymers can be added or used in combination with the liquid crystal polyester used in the present invention as long as the effects of the present invention are not impaired. Addition / combination means mixing polymers with each other, partially mixing one component with two or more components, or using another polymer with multiple components, or using it entirely. To say. Examples of other polymers include polyesters, vinyl polymers such as polyolefins and polystyrenes, polycarbonates, polyamides, polyimides, polyphenylene sulfides, polyphenylene oxides, polysulfones, aromatic polyketones, aliphatic polyketones, semi-aromatic polyesteramides and polyethers. Polymers such as ether ketone and fluororesin may be added, and polyphenylene sulfide, polyether ether ketone, nylon 6, nylon 66, nylon 46, nylon 6T, nylon 9T, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene na. Preferable examples include phthalate, polycyclohexanedimethanol terephthalate, polyester 99M and the like. When these polymers are added or used in combination, it is preferable that the melting point of the liquid crystal polyester is within ± 30 ° C. so as not to impair the yarn-making property, and also to improve the strength and elastic modulus of the obtained fiber. The amount to be added / used in combination is preferably 50% by weight or less, more preferably 5% by weight or less, and most preferably no other polymer is added / used in combination.

The liquid crystal polyester used in the present invention includes various metal oxides, inorganic substances such as kaolin and silica, colorants, matting agents, flame retardants, antioxidants, and ultraviolet absorbers, as long as the effects of the present invention are not impaired. It may contain a small amount of additives such as an ultraviolet absorber, a crystal nucleating agent, a fluorescent whitening agent, an end group encapsulant, and a compatibilizer. Further, in order to improve the strength and elastic modulus of the obtained fiber, the amount of these additives added is preferably 10% by weight or less, more preferably 5% by weight or less, and further preferably 3% by weight or less with respect to the liquid crystal polyester. It is preferable, and it is most preferable that no additive is substantially added.

The method for obtaining a yellowish liquid polyester multifilament characterized by having an L value of 64 to 86, an a value of -6 to 6, and a b value of 15 to 36, which represent the color of the fiber of the present invention, is Although not limited in any way, an important point of the present invention is to suppress thermal deterioration and excessive polymerization reaction of the raw material liquid polyester resin before fiberization in the production of the liquid crystal polyester multifilament. be.

That is, in the present invention, as a result of investigating and diligently examining factors that affect the color (L value, a value, b value) of the liquid crystal polyester multifilament produced from the liquid crystal polyester resin, the liquid crystal polyester multifilament is produced. It has been found that the amount of low molecular weight substances contained in the liquid crystal polyester resin used as a raw material and the residence time of the melted liquid crystal polyester resin in the spinning machine at the time of melt spinning affect the color of the liquid crystal polyester multifilament obtained. That is, in the present invention, the amount of low molecular weight substances contained in the liquid crystal polyester resin used as a raw material for producing the liquid crystal polyester multifilament is controlled, and the amount of gas generated under heating at a melting point of + 40 ° C. is 1000 ppm or less. By using a polyester resin and controlling the residence time of the molten liquid crystal polyester resin in the spinning machine during melt spinning so that the residence time is within 40 minutes, the L value indicating the color of the fiber is 64 to 86, a value. However, it was found that a liquid crystal polyester multifilament having a yellowish color, which was not obtained by the prior art, can be stably obtained with -6 to 6 and a b value of 15 to 36. By using a liquid crystal polyester resin having a gas amount of 1000 ppm or less generated under heating at a melting point of + 40 ° C. as a raw material, the amount of low molecular weight substances such as unreacted monomers and by-products contained in the liquid crystal polyester resin is small, and the amount of low molecular weight substances is small. Since the residence time of the liquid crystal polyester resin in the spinning machine during melt spinning is within 40 minutes, it is considered that the thermal decomposition reaction and excessive polymerization reaction of the liquid crystal polyester resin due to low molecular weight substances could be suppressed at high temperature. As described above, it is important to suppress the thermal decomposition reaction and the excessive polymerization reaction of the liquid crystal polyester resin due to the low molecular weight substance in the molten resin in order to obtain the yellowish liquid crystal polyester multifilament of the present invention.

The amount of gas generated when the liquid crystal polyester resin is heated to a melting point of + 40 ° C. is essential to be 1000 ppm or less, preferably 900 ppm or less, more preferably 800 ppm or less, and more preferably 700 ppm or less. More preferred. By setting the content to 1000 ppm or less, it is possible to reduce the amount of low molecular weight substances such as unreacted monomers and by-products contained in the liquid crystal polyester resin, and as a result, the liquid crystal polyester resin due to the low molecular weight substances at the time of melt spinning of the liquid crystal polyester resin. The yellowish liquid polyester multifilament having an L value of 64 to 86, an a value of -6 to 6, and a b value of 15 to 36, which can suppress the thermal decomposition reaction and the excessive polymerization reaction of the present invention, is preferable. can get. If it exceeds 1000 ppm, the L value, a value, and b value of the liquid crystal polyester multifilament are out of the above range, and the desired yellowing of the present invention cannot be obtained.

Regarding the liquid crystal polyester resin used for manufacturing the liquid crystal polyester multifilament, the method for reducing the amount of gas generated under heating at a melting point of + 40 ° C. to 1000 ppm or less is described.
Although not limited in any way, for example, in the production of liquid crystal polyester resin, the ratio and the amount of monomer components used in the polymerization reaction are variously adjusted, and the temperature and pressure reducing degree at the time of the polymerization reaction and their retention times are variously adjusted. Therefore, low-molecular-weight substances such as unreacted monomers and by-products contained in the liquid crystal polyester resin are reduced, and the amount of gas generated under heating at a melting point of + 40 ° C. is 1000 ppm or less. Further, when the liquid crystal polyester resin used for melt spinning is dried before melt spinning, it is also a problem that the amount of gas generated under heating at a melting point of + 40 ° C. is 1000 ppm or less by drying at a high temperature for a long time under reduced pressure. not. In the present invention, in consideration of productivity, when the liquid crystal polyester resin used for melt spinning is dried before melt spinning, the amount of gas generated under heating at a melting point of + 40 ° C. is determined by drying at a high temperature for a long time under reduced pressure. It was set to 1000 ppm or less. When drying the chips (pellets) of the liquid crystal polyester resin at a high temperature, it is preferable to keep the chips moving so that the chips do not fuse with each other. There is no problem in driving the drying device itself to rotate.

In melt spinning of liquid crystal polyester multifilament, a usual method can be used as a basic melt extrusion method, but it is preferable to use an extruder type extruder in order to eliminate the ordered structure generated during polymerization. The extruded polymer is weighed by a known weighing device such as a gear pump via a pipe, passes through a filter for removing foreign matter, and then is guided to a base. At this time, the temperature from the polymer pipe to the base (spinning temperature) is preferably not less than the melting point of the liquid crystal polyester and not more than the thermal decomposition temperature, more preferably not more than the melting point of the liquid crystal polyester + 10 ° C and not more than 400 ° C, and more preferably the liquid crystal polyester. It is more preferable that the melting point of the above temperature is +20 ° C. or higher and 370 ° C. or lower. It is also possible to adjust the temperature from the polymer pipe to the base independently. In this case, the discharge is stabilized by raising the temperature of the portion close to the base to be higher than the temperature on the upstream side thereof.

The residence time of the molten liquid crystal polyester resin in the spinning machine at the time of melt spinning is indispensable to be 40 minutes or less, preferably 30 minutes or less, more preferably 20 minutes or less, and 10 minutes or less. Is more preferable. If the residence time exceeds 40 minutes, the liquid crystal polyester resin melted in the spinning machine undergoes thermal decomposition and an excessive polymerization reaction. Therefore, the L value, a value, and b value of the obtained liquid crystal polyester multifilament are the values of the present invention. It is out of the range, and the desired yellowing of the present invention cannot be obtained. Further, in order to suppress the thermal decomposition reaction and the excessive polymerization reaction of the liquid crystal polyester resin due to the unreacted monomer and the low molecular weight substance contained in the liquid crystal polyester resin to be used, a short residence time is preferable, but the residence time is short. If it is too much, melting defects and melting spots of the liquid crystal polyester resin itself will occur, so it is preferable to shorten it within the range where stable spinning is possible. Regarding the residence time of the molten liquid crystal polyester resin in the spinning machine, the liquid crystal polyester multifilament is discharged from the spinneret after the liquid crystal polyester resin chips (pellets) are charged into the chip supply section of the extruder. It's time to. Therefore, the value is obtained by dividing the polymer flow path volume (cm3) in the spinning machine and the polymer discharge amount (cm3 / min) of the spinning machine.

The method for keeping the residence time of the molten liquid crystal polyester resin in the spinning machine at the time of melt spinning within 40 minutes is not limited in any way, but for example, the volume of the polymer flow path in the spinning machine can be minimized or the polymer discharge of the spinning machine can be performed. There is no problem in setting the amount high.

Further, in the melt spinning of the liquid crystal polyester multifilament of the present invention, usually, for the purpose of reducing energy cost and improving productivity, a large number of mouthpiece holes are drilled in one mouthpiece, so that each mouthpiece hole is ejected and narrowed. It is better to stabilize the behavior.

In order to achieve this, it is preferable to reduce the hole diameter of the mouthpiece hole and increase the land length (the length of the straight pipe portion of the mouthpiece hole). However, from the viewpoint of effectively preventing clogging of the holes, the hole diameters are preferably 0.03 mm or more and 1.00 mm or less, more preferably 0.05 mm or more and 0.80 mm or less, and further preferably 0.08 mm or more and 0.60 mm or less. .. From the viewpoint of effectively preventing the pressure loss from increasing, the L / D defined by the quotient of the land length L divided by the hole diameter D is 0.5 or more, preferably 3.0 or less, preferably 0.8 or more. 5 or less is more preferable, and 1.0 or more and 2.0 or less are further preferable.

Further, in order to improve the productivity of the multifilament, the number of holes in one mouthpiece is preferably 10 or more and 500 or less, more preferably 10 or more and 400 or less, and further preferably 10 or more and 300 or less. It is preferable that the introduction hole located directly above the mouthpiece hole is a straight hole having a diameter of 5 times or more the diameter of the mouthpiece hole in that the pressure loss is not increased. It is preferable to taper the connection part between the introduction hole and the base hole in order to suppress abnormal retention, but it is preferable to make the length of the tapered part less than twice the land length without increasing the pressure loss and stabilizing the streamline. It is preferable to make it.

The polymer discharged from the mouthpiece hole passes through the heat insulating region and the cooling region to be solidified into a filament, and then is taken up by a roller (godet roller) rotating at a constant speed. If the heat insulating region is excessively long, the silk-reeling property is deteriorated, so that it is preferably up to 400 mm from the base surface, more preferably up to 300 mm, and further preferably up to 200 mm. It is also possible to raise the atmospheric temperature in the heat insulating region by using a heating means, and the temperature range is preferably 100 ° C. or higher and 500 ° C. or lower, and more preferably 200 ° C. or higher and 400 ° C. or lower. Although an inert gas, air, water vapor or the like can be used for cooling, it is preferable to use a parallel or annular air flow from the viewpoint of reducing the environmental load.

The pick-up speed is preferably 50 m / min or more, more preferably 300 m / min or more, still more preferably 500 m / min or more in order to improve productivity. Since the liquid crystal polyester used in the present invention has a suitable spinnability at the spinning temperature, the take-up speed can be increased. The upper limit is not particularly limited, but in the liquid crystal polyester used in the present invention, it is about 3,000 m / min from the viewpoint of spinnability.

The spinning draft defined by the quotient obtained by dividing the take-up speed by the discharge line speed is preferably 1 or more and 500 or less, more preferably 5 or more and 200 or less, and further preferably 12 or more and 100 or less. Since the liquid crystal polyester used in the present invention has suitable spinnability, the draft can be increased, which is advantageous for improving productivity. The discharge line velocity (m / min) used in the calculation of the spinning draft is defined by the quotient obtained by dividing the discharge amount per single hole (m ³ / min) by the single hole cross-sectional area (m ² ). Since it is a value and the take-up speed (m / min) is divided by the discharge line speed, the spinning draft is a dimensionless number.

In the present invention, from the viewpoint of improving spinnability and productivity, it is preferable to set the polymer discharge rate per spinning pack to 10 to 2,000 g / min in order to obtain the above spinning draft, preferably 20 to 1,000 g / min. It is more preferable to set it, and it is further preferable to set it to 30 to 500 g / min. By spinning at a high discharge rate of 10 to 2,000 g / min, the productivity of the liquid crystal polyester is improved.

The winding can be a package in the shape of cheese, pan, cone or the like using a normal winding machine, but it is preferable to use a cheese winding package in which the winding amount can be set high.

In melt spinning of liquid crystal polyester multifilament, it is common to apply a spinning oil to the spun yarn with an oiling roller or the like to focus the multifilament, take it up with a roller or the like, and then wind it up with a winder without stretching. Is. By focusing the multifilament spun yarns in this way, the take-up property is improved and a package without unwinding can be obtained.

In the liquid crystal polyester multifilament, it is preferable to perform solid phase polymerization after melt spinning to form a filament.

When solid-phase polymerization is carried out in the form of a package, fusion is easy. To prevent this, it is necessary to form a package on the bobbin with a winding density of 0.30 g / cm ³ or more and carry out solid-phase polymerization. preferable. Here, the winding density is calculated from the occupied volume Vf (cm ³ ) of the package obtained from the external dimensions of the package and the dimensions of the bobbin as the core material, and Wf / Vf (g / cm ³ ) from the weight Wf (g) of the fiber. Value. If the winding density is excessively small, the tension in the package will be insufficient, so the contact area between the fibers will increase and fusion will increase, and the package will collapse, so the volume is preferably 0.30 g / cm ³ or more. It is more preferably .40 g / cm ³ or more, and further preferably 0.50 g / cm ³ or more. The upper limit is not particularly limited, but if the winding density is excessively large, the adhesion between the fibers in the inner layer of the package increases and the fusion at the contact point increases. Therefore, the upper limit is preferably 1.50 g / cm ³ or less. .. In the present invention, it is more preferable to set the winding density to 0.30 to 1.00 g / cm ³ from the viewpoint of reducing fusion and preventing unwinding.

A package with such a winding density has good process passability and can simplify the process. For example, it is possible to directly wind the liquid crystal polyester after melt-spinning to form a package having the above-mentioned winding density, and it is possible to improve the process passability. Further, when adjusting the yarn weight at the time of solid phase polymerization, it is also possible to rewind the package once wound by melt spinning to form a package having the above winding density. In order to adjust the shape of the package and control the winding density, the contact rolls that are normally used are not used, and the surface of the package is wound in a non-contact state. Winding with a controlled winder is also effective. In these cases, the take-up speed is preferably 3000 m / min or less, particularly 2000 m / min or less, in order to adjust the package shape. The lower limit is preferably 50 m / min or more from the viewpoint of productivity.

The bobbin used to form the package may be any cylindrical shape, and when the bobbin is wound as a package, it is attached to a winder and rotated to wind up the fibers to form the package. In the solid phase polymerization, the package can be treated integrally with the bobbin, but it is also possible to remove only the bobbin from the package and treat it. When the bobbin is treated while being wound around the bobbin, the bobbin must withstand the solid phase polymerization temperature, and is preferably made of a metal such as aluminum, brass, iron, or stainless steel. Further, in this case, it is preferable that the bobbin has a large number of holes because solid phase polymerization can be efficiently performed. When the bobbin is removed from the package for processing, it is preferable to attach an outer skin to the outer surface of the bobbin. Further, in either case, it is preferable to wind a cushion material around the outer surface of the bobbin and wind the liquid crystal polyester melt-spun filament on the cushion material. The material of the cushion material is preferably felt made of organic fibers such as aramid fibers or metal fibers, and the thickness is preferably 0.1 mm or more and 20 mm or less. The cushion material can be used instead of the above-mentioned outer skin.

The fiber weight of the package may be any weight as long as the winding density is within the range of the present invention, but 0.01 kg or more and 11 kg or less are preferable in consideration of productivity. The thread length is preferably 10,000 m or more and 2 million m or less.

In order to prevent fusion during solid phase polymerization, it is a preferred embodiment to attach an oil agent to the surface of the filament. These components may be attached between melt spinning and winding, but in order to improve the adhesion efficiency, they may be attached at the time of rewinding, or a small amount may be attached at the time of melt spinning and further added at the time of rewinding. It is preferable to do so.

The method of adhering the oil agent may be guide lubrication, but in order to adhere the fibers uniformly, it is preferable to use a metal or ceramic kiss roll (oiling roll).

As a component of the oil agent, it is better to have high heat resistance because it is not volatilized by high temperature heat treatment in solid phase polymerization, and ordinary inorganic particles, fluorine compounds, siloxane compounds (dimethylpolysiloxane, diphenylpolysiloxane, methylphenylpolysiloxane, etc.) ) And a mixture thereof and the like are preferable. The ordinary inorganic particles in the present invention include, for example, minerals, metal hydroxides such as magnesium hydroxide, metal oxides such as silica and alumina, chloride chlorides such as calcium carbonate and barium carbonate, calcium sulfate and barium sulfate and the like. In addition to the sulfate compound of, carbon black and the like can be mentioned.

Further, these components may be solid-adhered or directly applied with an oil agent, but emulsion application is preferable for uniform application while optimizing the amount of adhesion, and water emulsion is particularly preferable from the viewpoint of safety. Therefore, it is desirable that the components are water-soluble or easily form a water emulsion. Among them, a mixed oil containing mainly a water emulsion of a siloxane compound and silica or silicate added thereto is inactive under solid phase polymerization conditions. It is preferable because it has an effect on slipperiness in addition to the effect of preventing fusion in solid phase polymerization. When a silicate is used, a phyllosilicate having a layered structure is particularly preferable. Examples of phyllosilicates include kaolinite, haloyite, serpentine, silicate nickel ore, smectite, pyrophyllite, talc, mica, etc. Among these, talc, considering availability. It is most preferable to use mica.

The amount of the oil agent attached to the fiber is preferably large in order to suppress fusion, preferably 0.5% by weight or more, and more preferably 1.0% by weight or more when the whole fiber is 100% by weight. On the other hand, if the amount is too large, the fibers are sticky and the handling is deteriorated, and the process passability is deteriorated in the subsequent process. Especially preferable. The amount of oil attached to the fiber refers to a value obtained by the method described in Examples.

Solid-phase polymerization can be carried out in an atmosphere of an inert gas such as nitrogen, an atmosphere of an oxygen-containing active gas such as air, or under reduced pressure, but the equipment can be simplified and the oxidation of fibers or deposits can be prevented. Therefore, it is preferable to carry out in a nitrogen atmosphere. At this time, the atmosphere of the solid phase polymerization is preferably a low humidity substance having a dew point of −40 ° C. or lower.

As for the solid phase polymerization temperature, it is preferable that the maximum temperature reached is -80 ° C or higher with _respect to the melting point (T _m1 ) of the liquid crystal polyester filament to be subjected to solid phase polymerization. By setting the temperature to a high temperature near the melting point, solid phase polymerization can proceed rapidly and the strength of the fiber can be improved. Further, it is preferable that the maximum temperature reached is less than T _m1 in order to prevent fusion. Further, since the melting point of the liquid crystal polyester filament rises with the progress of the solid phase polymerization, the solid phase polymerization temperature is raised to about the melting point (T _m1 ) + 100 ° C. of the liquid crystal polyester filament to be subjected to the solid phase polymerization according to the progress state of the solid phase polymerization. be able to. It is more preferable to raise the solid phase polymerization temperature stepwise or continuously with respect to time because fusion can be prevented and the time efficiency of solid phase polymerization can be improved.

The solid phase polymerization time is preferably 5 hours or more at the maximum temperature reached, and more preferably 10 hours or more in order to sufficiently increase the strength, elastic modulus, and melting point of the fiber. The upper limit is not particularly limited, but the effects of increasing the strength, elastic modulus, and melting point are saturated with the elapsed time, so that about 100 hours is sufficient, and a short time is preferable for increasing productivity, and about 50 hours is not a problem.

For the package after solid phase polymerization, it is preferable to rewind the package after solid phase polymerization again to increase the winding density in order to improve the transport efficiency. At this time, in order to prevent the solid phase polymerization package from collapsing due to unwinding when the filament is unwound from the solid phase polymerization package, and further to suppress fibrillation when peeling off a slight fusion, the solid phase polymerization package is used. It is preferable to unwind the yarn by so-called pre-emption, in which the yarn is unwound in the direction perpendicular to the rotation axis (fiber circumferential direction) while rotating. Further, it is preferable that the solid phase polymerization package is rotated by active driving instead of free rotation because the tension at which the yarn is separated from the package can be reduced and fibrillation can be further suppressed.

Here, in order to form a liquid crystal polyester multifilament package, a package in the form of a pan, a drum, a cone, or the like can be used, but from the viewpoint of productivity, a drum winding package that can secure a large winding amount can be used. Is preferable.

Further, in the liquid crystal polyester multifilament of the present invention, in order to improve the process passability in the case of a high-order processed product, it is better to impart a focusing property to the multifilament, and various finishing oils are applied according to the purpose. Is a preferred embodiment.

It is essential that the L value representing the color of the fiber of the liquid crystal polyester multifilament of the present invention is 64 to 86, preferably 66 to 86, more preferably 68 to 86, and even more preferably 70 to 86. By setting the value to 64 to 86, the liquid crystal polyester multifilament having an appropriate brightness and the yellowness of the present invention can be obtained. If it is less than 64, the blackness becomes too strong, and if it exceeds 86, the whiteness becomes too strong, so that the yellowish liquid crystal polyester multifilament of the present invention cannot be obtained. The L value refers to a value obtained by the method described in the examples.

It is essential that the a value representing the color of the fiber of the liquid crystal polyester multifilament of the present invention is -6 to 6, preferably -5 to 6, more preferably -4 to 6, and even more preferably -3 to 6. .. By setting the value to -6 to 6, a liquid crystal polyester multifilament having an appropriate reddish green tint and the yellowness of the present invention can be obtained. If it is less than -6, the greenness becomes too strong, and if it exceeds 6, the redness becomes too strong, so that the yellowish liquid crystal polyester multifilament of the present invention cannot be obtained. The a value refers to a value obtained by the method described in the examples.

It is essential that the b value representing the color of the fiber of the liquid crystal polyester multifilament of the present invention is 15 to 36, preferably 17 to 36, more preferably 19 to 36, and even more preferably 21 to 36. By setting the value to 15 to 36, a liquid crystal polyester multifilament having an appropriate yellowish blue tint and having the yellowness of the present invention can be obtained. If it is less than 15, the bluish tint becomes too strong, and if it exceeds 36, the yellowish tint becomes too strong, so that the liquid crystal polyester multifilament having the yellowness of the present invention cannot be obtained. The b value refers to a value obtained by the method described in the examples.

The single fiber fineness of the liquid crystal polyester multifilament of the present invention is preferably 1 to 30 dtex. Further, it is more preferably 1 to 20 dtex. By reducing the fineness of the single fiber to 1 to 30 dtex, uniform cooling to the inside of the single fiber is possible after ejection, the yarn-making property is stable, and it becomes easy to obtain a liquid crystal polyester multifilament with good fluff quality, and heat treatment is performed. The surface area of the fiber that sometimes comes into contact with the outside air increases, which is advantageous for high strength and high elasticity. Further, since the yarn of the liquid crystal polyester multifilament of the present invention having a single fiber fineness of 1 to 30 dtex is flexible, it is excellent in high-order process passability, and when used for woven fabrics, the filling rate of the yarn is excellent. High density and improved storability. In the present invention, the quotient obtained by dividing the total fineness by the number of single fibers is defined as the single fiber fineness (dtex).

The number of single fibers (number of filaments) of the liquid crystal polyester multifilament of the present invention is preferably 10 to 500, more preferably 10 to 400, and even more preferably 10 to 300. By setting the number of single fibers to 10 to 500, the productivity of the multifilament can be improved, and the surface area of the fiber exposed to the outside air during the heat treatment becomes large, so that the solid phase polymerization reaction is promoted and the strength and elastic modulus vary. A liquid crystal polyester multifilament having reduced and uniform physical properties can be obtained. Further, the sample obtained by spinning may be split or combined to form a liquid crystal polyester multifilament having 10 to 500 single fibers. The number of single fibers refers to a value obtained by the method described in the examples.

The total fineness of the liquid crystal polyester multifilament of the present invention is preferably 100 to 3,000 dtex, more preferably 150 to 2,500 dtex, and even more preferably 200 to 2000 dtex. By setting the value to 100 to 3,000 dtex, it is suitable for industrial material applications in which the process passability is high and the amount of raw yarn used is extremely large. Further, the sample obtained by spinning may be split or combined to obtain a liquid crystal polyester multifilament having a total fineness of 100 to 3,000 dtex. The total fineness refers to a value obtained by the method described in the examples.

The strength of the liquid crystal polyester multifilament of the present invention after solid phase polymerization is preferably 15.0 cN / dtex or more, more preferably 17.0 cN / dtex or more, and even more preferably 19.0 cN / dtex or more. Having a strength of 15.0 cN / dtex or more, it is suitable for industrial material applications where high strength and light weight are required. The upper limit of the strength is not particularly limited, but the upper limit that can be reached in the present invention is about 30.0 cN / dtex. The strength referred to in the present invention refers to the breaking strength in the strong elongation / elastic modulus measurement described in the examples.

The elongation of the liquid crystal polyester multifilament of the present invention after solid phase polymerization is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less. Since the elongation is 5.0% or less, it is difficult to stretch when stressed from the outside, and the dimensional change when lifting a heavy object is small, so that it can be suitably used. The lower limit of the elongation is not particularly limited, but the lower limit that can be reached in the present invention is about 1.0%. The elongation referred to in the present invention refers to the elongation at break in the strong elongation / elastic modulus measurement described in the examples.

The elastic modulus of the liquid crystal polyester multifilament of the present invention after solid phase polymerization is preferably 300 cN / dtex or more, more preferably 500 cN / dtex or more, and even more preferably 700 cN / dtex or more. Since the elastic modulus is 300 cN / dtex or more, the dimensional change when subjected to stress is small and it is suitable for industrial material applications. The upper limit of the elastic modulus is not particularly limited, but the upper limit that can be reached in the present invention is about 1,000 cN / dtex. The elastic modulus referred to in the present invention refers to the elastic modulus in the strong elongation / elastic modulus measurement described in the examples.
Further, the yellowish liquid crystal polyester multifilament of the present invention controls the amount of low molecular weight substances contained in the liquid crystal polyester resin as a raw material used in producing the liquid crystal polyester multifilament, and is generated under heating at a melting point of + 40 ° C. It can be obtained by using a liquid crystal polyester resin having a gas amount of 1000 ppm or less and controlling the residence time of the molten liquid crystal polyester resin in the spinning machine at the time of melt spinning so that the residence time is within 40 minutes. Since the liquid crystal polyester multifilament manufactured by the above manufacturing method has few low molecular weight substances remaining in the fiber and thermal decomposition products derived from the liquid crystal polyester resin, the liquid crystal polyester multifilament is unlikely to undergo thermal decomposition during dry heat treatment (of the fiber). (Small deterioration of physical properties) and excellent heat resistance. The heat resistance of the liquid crystal polyester multifilament was determined by the method described in the examples, and was evaluated by the strength retention rate of the raw yarn after the dry heat treatment at 280 ° C. × 1 hr. The strength retention of the raw yarn after the dry heat treatment of the liquid crystal polyester multifilament of the present invention at 280 ° C. × 1 hr is preferably 50 to 100%, more preferably 60 to 100%, still more preferably 70 to 100%. Since the raw yarn strong retention rate after dry heat treatment at 280 ° C. × 1 hr is 50 to 100%, the deterioration of product physical properties during heat treatment when manufacturing high-order processed products is small, and the general industrial material use and designability are small. -In addition to applications that require visibility, it can also be suitably used for applications such as fiber-reinforced resin products and resin molded products. In the processing process of applying various resins and chemicals to the textile product manufactured of the liquid crystal polyester multifilament at the time of higher-order processing for the purpose of imparting functionality, and in the processing process of compounding with other materials, the above-mentioned Since heat treatment in a temperature range up to about 280 ° C. is common, a liquid crystal polyester multifilament having yellowness of the present invention and excellent strength retention after dry heat treatment at 280 ° C. × 1 hr can be preferably used. ..

The liquid crystal polyester multifilament of the present invention thus obtained has an L value of 64 to 86, an a value of -6 to 6, and a b value of 15 to 36, which represent the color of the fiber, and has a general industrial material use and designability. It can be suitably used for applications of high-order processed products that require visibility. Applications that require design and visibility include, for example, various woven and knitted fabrics, textiles, tent fabrics, speaker cones, ropes for construction work, belts for safety belts, and the like. Liquid crystal polyester multifilaments having such yellowness, high strength, high elasticity, heat resistance, dimensional stability, vibration damping, chemical resistance, low moisture absorption characteristics, high wet strength, etc. are various general. It can also be used for industrial materials. Examples of general industrial material applications include ropes, slings, fishing nets, nets, meshes, woven fabrics, fabrics, sheets, belts, tension members, civil engineering / building materials, sports materials, protective materials, rubber reinforcement materials, and various types of reinforcement. Examples include cords, fiber materials for reinforcing resins, electrical materials, acoustic materials, and the like.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The definition of the characteristics used in the main text of the specification and the examples, and the measurement and calculation methods for each physical property are shown below.

(1) Melting point After observing the heat absorption peak temperature (T _m1 ) observed when the temperature rise condition is measured from 50 ° C to 20 ° C / min in the differential calorimetry performed by a differential scanning calorimeter (DSC2920 manufactured by TA 1nstruments). The heat absorption peak temperature observed when the temperature is maintained at a temperature of about T _m1 + 20 ° C. for 5 minutes, cooled to 50 ° C. at a temperature lowering rate of 20 ° C./min, and measured again under the heating condition of 20 ° C./min ( T _m2 ) was used as the melting point. The same operation was performed twice, and the average value of the two times was taken as the melting point T _m2 (° C.) of the liquid crystal polyester.

(2) Amount of gas generated under heating at a melting point of + 40 ° C. A sample of about 100 mg was placed in a heating tube and placed in a tube furnace set at a melting point of + 40 ° C. under a nitrogen stream (100 mL / min.). The generated gas was collected by a carbo trap attached to the outlet side of the heating pipe. After collecting the heating generated gas for 8 hours, the carbo trap was removed. At the time of measurement, the carbo trap is attached to a heat desorption device (TDU), the temperature is rapidly raised to 300 ° C to desorb the components adsorbed on the carbo trap, and the desorption gas is introduced into the GC / MS for measurement. bottom. The total amount of desorbed gas (ppm) was calculated using a calibration curve prepared from a toluene standard solution.

(3) Polystyrene-equivalent weight average molecular weight (molecular weight)
A mixed solvent of pentafluorophenol / chloroform = 35/65 (weight ratio) is used as a solvent, and the liquid crystal polyester is dissolved in the mixed solvent while stirring at 120 ° C. for 20 minutes. At this time, the concentration of the liquid crystal polysell is adjusted to 0.04% by weight, and the sample is used for GPC measurement. This was measured using a GPC measuring device manufactured by Waters, and Mw was determined by polystyrene conversion. The same operation was performed twice, and the average value of the two times was taken as the weight average molecular weight (Mw).
Column: ShodexK-G (1)
Shodex K-806M (2)
ShodexK-802 (1)
Detector: Differential refractometer detector RI (2414 type)
Temperature: 23 ± 2 ° C
Flow rate: 0.8 mL / min Injection amount: 0.200 mL.

(4) Moisture content The measurement was performed by a potentiometric titration method using a Karl Fischer Moisture Meter (AQ-2100) manufactured by Hiranuma Sangyo Co., Ltd. The average value of 3 trials was used.

(5) Oil agent concentration When the weight of the solution in which the oil agent was dispersed was W0 and the weight of the oil agent was W1, the product obtained by multiplying the quotient of W1 divided by W0 by 100 was defined as the oil agent concentration (% by weight).

(6) Amount of oil agent adhered After removing 100 m of fiber with a measuring machine and measuring the weight, the fiber was immersed in 100 ml of water and washed for 1 hour using an ultrasonic cleaner. The skein after ultrasonic cleaning is dried at a temperature of 60 ° C. for 1 hour, and the weight is measured. Weight%).

(7) Total fineness The positive fineness was measured with a predetermined load of 0.045 cN / dtex by the JIS L 1013 (2010) 8.3.1 A method to obtain the total fineness (dtex).

(8) Number of single fibers Calculated by the method of JIS L 1013 (2010) 8.4.

(9) Single fiber fineness The value obtained by dividing the total fineness by the number of single fibers was defined as the single fiber fineness (dtex).

(10) Strong elongation and elastic modulus JIS L 1013 (2010) 8.5.1 Measured under the constant speed elongation conditions shown in the standard time test. The sample was a Tensilon UCT-100 manufactured by Orientech, and the gripping interval (measurement test length) was 250 mm and the tensile speed was 50 mm / min. The elongation (elongation at break) was calculated from the elongation of the point showing the stress (strong) at break in the load (stress) -elongation curve. The strength was calculated by dividing the stress (strength) at break in the load (stress) -elongation curve by the total fineness. The elastic modulus was calculated from the slope at the 0.5% elongation point on the load (stress) -elongation curve in the tensile test. The stress (strong) at break in the fiber is also generally called the raw yarn strength.

(11) L value, a value, and b value indicating the color of the fiber A sample for color measurement was prepared by circling the obtained fiber around a plate so as to have a thread-like pitch of 0.5 cm and a width of 4.5 cm. Then, the measurement was performed using a color difference meter CR-400 manufactured by Konica Minolta. The L value represents the brightness (brightness) of the color, ranging from 0 to 100 (black when close to 0, white when close to 100), and the larger the number, the brighter the color. The a value represents a reddish-green hue (plus side is reddish, negative side is greenish). The b value represents a yellowish-blue hue (yellowish on the plus side and bluish on the minus side).

(12) Suitability for high-order processed products that require design and visibility For the obtained liquid crystal polyester multifilament, the L value representing the color of the fiber is 64 to 86, the a value is -6 to 6, and the b value is. If it satisfies 15 to 36 and has yellowness, it can be applied to applications where designability and visibility are required. On the other hand, the L value, a value, and b value indicating the color of the fiber are out of the above range. Therefore, if it does not have yellowness, it is marked as x for applications that require design and visibility.

(13) Heat resistance The heat resistance of the obtained liquid crystal polyester multifilament is evaluated by the raw yarn strength retention rate after the dry heat treatment of 280 ° C. × 1 hr, and the yarn strength X (N) before the heat treatment and 280 ° C. × 1 hr. Using the raw yarn strength Y (N) after the dry heat treatment, the raw yarn strength retention rate (%) = (Y / X) × 100 after the dry heat treatment of the following formula 280 ° C. × 1 hr.
Calculated from.

[Example 1]
870 parts by weight of p-hydroxybenzoic acid, 327 parts by weight of 4,4'-dihydroxybiphenyl, 157 parts by weight of isophthalic acid, 292 parts by weight of terephthalic acid, 89 parts by weight of hydroquinone in a 5 L reaction vessel equipped with a stirring blade and a distillate. And 1433 parts by weight of acetic anhydride (1.08 equivalent of the total phenolic hydroxyl group) was charged, and the temperature was raised from room temperature to 145 ° C. in 30 minutes while stirring in a nitrogen gas atmosphere, and then the reaction was carried out at 145 ° C. for 2 hours. Then, the temperature was raised to 330 ° C. in 4 hours. The polymerization temperature was maintained at 330 ° C., the pressure was reduced to 1.0 mmHg (133 Pa) in 1.5 hours, the reaction was continued for another 20 minutes, and the polycondensation was completed when a predetermined torque was reached. Next, the inside of the reaction vessel was pressurized to 1.0 kg / cm ² (0.1 MPa), and the polymer was discharged into a strand-like substance via a mouthpiece having one circular discharge port having a diameter of 10 mm, and pelletized by a cutter.

This liquid crystal polyester resin consists of 54 mol% of p-hydroxybenzoic acid unit, 16 mol% of 4,4'-dihydroxybiphenyl unit, 8 mol% of isophthalic acid unit, 15 mol% of terephthalic acid unit, and 7 mol% of hydroquinone unit. The melting point was 315 ° C., the melt viscosity measured at a temperature of 330 ° C. and a shear rate of 1,000 / sec using a high-grade flow tester was 30 Pa · sec, and Mw was 145,000. ..

Using this liquid crystal polyester resin, vacuum drying (decompression degree: 0.1 Pa) was performed at 200 ° C. for 48 hours to remove water and oligomers. At this time, the water content of the liquid crystal polyester was 5 ppm, and the amount of gas generated under heating at a melting point of + 40 ° C. was 950 ppm. The liquid crystal polyester resin dried and strengthened under these high temperature conditions was melt-extruded with a uniaxial extruder (heater temperature 290 to 340 ° C.), and the polymer was supplied to the spinning pack while being weighed with a gear pump. At this time, the spinning temperature from the extruder outlet to the spinning pack was 335 ° C. In the spinning pack, the polymer is filtered using a metal non-woven fabric filter with a filtration accuracy of 15 μm, and the discharge rate is 100 g / min (0.33 g / min per hole) from a mouthpiece having 300 holes with a pore diameter of 0.13 mm and a land length of 0.26 mm. Minutes) to eject the polymer. The residence time of the molten liquid crystal polyester resin in the spinning machine in the melt spinning was 27 minutes.

A liquid crystal polyester multifilament cooled and solidified at room temperature immediately after discharge is adhered with an oil agent (polydimethylsiloxane (“SH200-350cSt” manufactured by Toray Dow Corning) is a 5.0% by weight water emulsion) using an oiling roller. All 300 filaments were taken up with a 600 m / min Nelson roller. The spinning draft at this time is 29. The amount of the oil adhering to the oil was 1.5% by weight. The multifilament taken by the Nelson roller was directly wound into a cheese shape using a feather traverse type winder via a dancer arm. The spinnability in melt spinning was good, and a liquid crystal polyester multifilament with a total fineness of 1667 dtex and a single fiber fineness of 5.6 dtex could be stably spun without yarn breakage, and a 4.0 kg roll package of yarn was obtained. ..

The fibers are unwound from this spinning package in the vertical direction (perpendicular to the fiber circumferential direction), and the winding machine (SSP-WV8P type precision winder manufactured by Kozu Seisakusho Co., Ltd.) with a constant speed is used at 400 m / min. I rewound it. A stainless steel bobbin was used as the core material for rewinding, the tension at the time of rewinding was 0.005 cN / dtex, the winding density was 0.50 g / cm ³ , and the winding amount was 4.0 kg. Furthermore, the package shape is a taper end winding with a taper angle of 65 °.

The obtained rewound sample was heated from room temperature to 240 ° C. using a closed oven, held at 240 ° C. for 3 hours, then heated to 290 ° C., and further held at 290 ° C. for 20 hours. Solid phase polymerization was carried out. As for the atmosphere in solid phase polymerization, dehumidified nitrogen was supplied at a flow rate of 100 L / min and exhausted from the exhaust port so that the inside of the refrigerator was not pressurized.

The solid-phase polymerization package obtained in this way is attached to a feeding device that can be rotated by an inverter motor, unwinding is performed while feeding the fibers in the lateral direction (fiber circumferential direction) at 200 m / min, and the fibers are wound into a product package by a winder. As a result, it was unwound with almost no resistance and no thread breakage occurred. The fiber physical characteristics are as shown in Table 1. The liquid crystal polyester multifilament obtained in Example 1 has high mechanical properties (high strength, high elastic modulus) shown in Table 1, and has an L value of 64 to 86 and an a value of -6, which indicate the color of the fiber. Since the values of ~ 6 and b are 15 to 36 and the color is yellowish, it can be suitably used for high-order processed products that require design and visibility. Furthermore, the strength retention rate of the raw yarn after dry heat treatment at 280 ° C. × 1 hr is 56%, which is excellent in heat resistance, and the deterioration of product physical properties during heat treatment when manufacturing high-order processed products is small, and it is a general industry. In addition to material applications and applications that require design and visibility, it could be suitably used for applications such as fiber-reinforced resin products and resin molded products.

[Examples 2 to 6], [Comparative Examples 1 to 3]
A liquid crystal polyester multifilament was obtained in the same manner as in Example 1 except that the drying conditions of the liquid crystal polyester resin used for melt spinning were changed.

[Examples 7 to 9], [Comparative Examples 4 to 6]
A liquid crystal polyester multifilament was obtained in the same manner as in Example 1 except that the polymer discharge amount and the winding speed at the time of melt spinning were changed to adjust the polymer residence time in the spinning machine.

[Examples 10 to 17]
Example 1 except that the number of holes in the mouthpiece, the amount of polymer discharged, and the take-up speed during melt spinning were changed to adjust the polymer residence time in the spinning machine, the total fineness of the obtained liquid crystal polyester multifilament, and the single fiber fineness. A liquid crystal polyester multifilament was obtained in the same manner as in the above.

[Example 18]
As the liquid crystal polyester resin, a liquid crystal polyester resin having a p-hydroxybenzoic acid unit of 73 mol% and a 6-hydroxy-2-naphthoic acid unit of 27 mol% was used in the same manner as in Example 1. A multifilament was obtained.

The fiber physical characteristics of Examples 1 to 18 are shown in Tables 1 and 2, and the fiber characteristics of Comparative Examples 1 to 6 are shown in Table 3.

As is clear from the examples in Tables 1 and 2, the amount of low molecular weight substances contained in the liquid crystal polyester resin used as a raw material for producing the liquid crystal polyester multifilament is controlled, and the gas generated under heating at a melting point of + 40 ° C. By using a liquid crystal polyester resin having an amount of 1000 ppm or less, controlling the residence time of the molten liquid crystal polyester resin in the spinning machine during melt spinning, and keeping the residence time within 40 minutes, the L value indicating the color of the fiber is shown. The value was 64 to 86, the a value was -6 to 6, and the b value was 15 to 36. A yellowish liquid crystal polyester multifilament, which was not obtained by the prior art, was stably obtained. As described above, the yellowish liquid crystal polyester multifilament of the present invention has high mechanical properties such as high strength and high elastic modulus, and also has yellowness, so that it can be used for general industrial materials such as ropes and slings. , Various textiles, woven and knitted fabrics, etc., could be suitably used for applications requiring design and visibility. Furthermore, since the raw yarn strong retention rate after dry heat treatment at 280 ° C. × 1 hr is excellent in heat resistance of 50 to 100%, the deterioration of product physical properties during heat treatment when manufacturing high-order processed products is small, and it is general. In addition to industrial material applications and applications that require design and visibility, it could be suitably used for applications such as fiber-reinforced resin products and resin molded products.

On the other hand, as is clear from the comparative examples in Table 3, the amount of low molecular weight substances contained in the liquid crystal polyester resin as a raw material used for producing the liquid crystal polyester multifilament, that is, the amount of gas generated under heating at a melting point of + 40 ° C. When a liquid crystal polyester resin exceeding 1000 ppm is used, or when the residence time of the melted liquid crystal polyester resin in the spinning machine during melt spinning exceeds 40 minutes, the liquid crystal polyester resin melted in the spinning machine is thermally decomposed or excessive. The L value, a value, and b value of the obtained liquid crystal polyester multifilament are out of the range of the present invention, the desired yellowing of the present invention cannot be obtained, and the drying temperature is 280 ° C. × 1 hr. The strong retention rate of the raw yarn after the heat treatment was less than 50%, which was inferior in heat resistance.

The liquid crystal polyester multifilament of the present invention has high mechanical properties such as high strength and high elastic modulus, and has an L value of 64 to 86, an a value of -6 to 6, and a b value of 15 representing the color of the fiber. Since it is ~ 36, it has a yellowish color. Therefore, it can be suitably used for general industrial materials, various textiles and woven and knitted fabrics that require design and visibility. Further, since the yellowish liquid crystal polyester multifilament of the present invention also has excellent heat resistance, there is little deterioration in product physical properties during heat treatment when manufacturing high-order processed products, and the general industrial material use and design properties are small. -In addition to applications that require visibility, it can also be suitably used for applications such as fiber-reinforced resin products and resin molded products.

Claims (8)

A liquid crystal polyester multifilament having a yellowish color, characterized in that the L value representing the color of the fiber is 64 to 86, the a value is -6 to 6, and the b value is 15 to 36. The liquid crystal polyester multifilament according to claim 1, wherein the liquid crystal polyester is a total aromatic polyester resin. The liquid crystal polyester multifilament according to claim 1 or 2, wherein the raw yarn strong retention rate after a dry heat treatment at 280 ° C. × 1 hr is 50 to 100%. The liquid crystal polyester multifilament according to any one of claims 1 to 3, wherein the liquid crystal polyester comprises the structural units (I), (II), (III), (IV) and (V) represented by the following chemical formulas.

The ratio of the structural unit (I) is 40 to 85 mol% with respect to the total of the structural units (I), (II) and (III), and the ratio of the structural unit (II) is the structural unit (II) and (III). 1 to any of claims 1 to 4, wherein the ratio of the structural unit (IV) is 40 to 95 mol% with respect to the total of the structural units (IV) and (V). The liquid crystal polyester multifilament described. It is characterized by using resin pellets in which the amount of gas generated by heating at a melting point of + 40 ° C. is suppressed to 1000 ppm or less as a raw material, and the residence time of the molten liquid crystal polyester resin in a spinning machine during melt spinning is within 40 minutes. The method for producing a liquid crystal polyester multifilament according to any one of claims 1 to 5. A high-order processed product manufactured from the liquid crystal polyester multifilament according to any one of claims 1 to 5. A fiber-reinforced resin product or a resin molded product produced from the liquid crystal polyester multifilament according to any one of claims 1 to 5.