JP2003003326A - Polybutylene terephthalate resin monofilament - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polybutylene terephthalate resin monofilament that has reduced filament breakage in the production line with the production efficiency increased and has improved quality because of increased uniformity in strength and thickness, when the polybutylene terephthalate resin monofilament is produced from the polymer formed through the continuous polymerization process. SOLUTION: The monofilament is produced by using the polybutylene terephthalate resin obtained through the continuous polymerization process and has <=20/100 m<2> fish eyes of >=20 μm sizes in the film thickness of 50 μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polybutylene terephthalate resin monofilament. More specifically, the present invention, in a monofilament formed by molding a polybutylene terephthalate resin obtained by a continuous polymerization method, by using a polybutylene terephthalate resin with less foreign matter, to suppress yarn breakage in the production line The present invention relates to a polybutylene terephthalate-based resin monofilament capable of improving production efficiency and having uniform strength and thickness and improved quality.

[0002]

2. Description of the Related Art Polybutylene terephthalate resins are
It has been widely used in the field of injection molding as an engineering plastic since it has a higher crystallization rate than polyethylene terephthalate-based resin and is excellent in moldability and has excellent mechanical properties and electrical properties. Furthermore, in recent years, polybutylene terephthalate resin has a good balance of strength and flexibility, low water absorption,
It has been recognized as a raw material for polyester monofilaments because of its high specific gravity and chemical resistance. By the way, a method for producing a polybutylene terephthalate resin is a transesterification reaction between a dicarboxylic acid ester component containing an ester derivative of terephthalic acid such as dimethyl terephthalate as a main component and a diol component containing 1,4-butanediol as a main component. And a direct polymerization method through a direct esterification reaction between a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component. After the polymerization reaction (oligomerization), there are a batch polymerization process in which a polycondensation reaction for increasing the molecular weight is performed in a batch system, and a continuous polymerization process in which an esterification reaction to a polycondensation reaction are continuously performed. From the viewpoint of manufacturing cost, the continuous polymerization process is considered to be overwhelmingly advantageous. However, when the polymerization is carried out by a continuous polymerization process, since the polymerization plant is continuously operated for a long time (several months to 1 year or more), the long-term retention product in the system becomes highly viscous and becomes a main product. The viscosity difference between the two becomes extremely large, and as a result, it becomes an unmelted substance during molding to become a foreign substance, or the esterification reaction catalyst deteriorates during the reaction to become insoluble and precipitate to form an agglomerate and become a foreign substance. Sometimes. These ultra-high-viscosity substances and precipitates become apparent when formed into a thin film, and become fine foreign substances called fish eyes. Further, in a monofilament, this fish eye causes an unfavorable situation such as breakage during stretching in the monofilament manufacturing process, uneven yarn diameter, partial reduction in yarn strength, and the like. .

[0003]

Under the above circumstances, the present invention is directed to a monofilament formed by molding a polybutylene terephthalate resin obtained by a continuous polymerization method, which suppresses yarn breakage in a production line. Thus, the object is to provide a polybutylene terephthalate-based resin monofilament having improved quality, uniform strength and thickness, and good quality.

[0004]

Means for Solving the Problems As a result of intensive studies to develop a polybutylene terephthalate resin monofilament having the above-mentioned preferable properties, the present inventor has found that when it is made into a film, a fish eye having a certain size or more is obtained. It has been found that the object can be achieved by using a polybutylene terephthalate resin whose number is less than or equal to a specific value and which has few foreign matters, and the present invention has been completed based on this finding. That is, according to the present invention, (1) the number of fish eyes having a size of 20 μm or more in a film having a resin thickness of 50 μm obtained by the continuous polymerization method is 2
Polybutylene terephthalate-based resin monofilament obtained by using 0/100 cm ² or less of polybutylene terephthalate-based resin, (2) Polybutylene terephthalate-based resin spun by melt extrusion method, and the resin The polybutylene terephthalate-based resin monofilament according to item 1, which has been stretched at a temperature not higher than the melting point of 1.5 times or more, (3) having a fineness of 50 to 1800.
The polybutylene terephthalate-based resin monofilament according to the first or second aspect, which is 0 dTex, (4) The first and second aspects in which the linear breaking strength is 2.0 cN / dTex or more.
Or a polybutylene terephthalate resin monofilament according to item 3 and (5) the cross section is circular, elliptical, rectangular, star-shaped, "tree" type, "ki" type, "L" type, "↑" type or The polybutylene terephthalate-based resin monofilament according to any one of items 1 to 4, which has a shape obtained by combining these shapes.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polybutylene terephthalate resin monofilament of the present invention uses a polybutylene terephthalate resin obtained by a continuous polymerization method as a raw material. Examples of the polybutylene terephthalate resin include terephthalic acid and / or its ester derivative,
For example, a dicarboxylic acid component containing methyl ester, ethyl ester, propyl ester, etc. as a main component and 1,4-
A polyene obtained by subjecting a butanediol-based diol component to a continuous esterification reaction mainly in the presence of an esterification reaction catalyst, followed by a continuous polycondensation reaction, and then extracting from a polymer extraction die. Butylene terephthalate resin can be used. Here, the terephthalic acid and / or terephthalic acid ester derivative as the dicarboxylic acid component accounts for 50 mol% or more of the total dicarboxylic acid component, preferably 80 mol% or more, and 95 mol% or more. Is more preferable.
Further, 1,4-butanediol as a diol component accounts for 50 mol% or more of the total diol component, preferably 80 mol% or more, and 95 mol%.
It is more preferable to occupy the above. In the present invention, examples of dicarboxylic acid components other than terephthalic acid include phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4 ′.
-Diphenyl ketone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, 4,4'-diphenyl sulfone dicarboxylic acid, aromatic dicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1 Alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid Examples thereof include acids and the like, and their esters with methyl, ethyl, propyl alcohol and the like. These may be used alone or in combination of two or more.

On the other hand, examples of diol components other than 1,4-butanediol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, 1,3-propanediol, polytetramethylene ether glycol, and 1,5-pentanediol. ,
Neopentyl glycol, 1,6-hexanediol,
Aliphatic diols such as 1,8-octanediol, 1,2
-Cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-
Alicyclic diols such as cyclohexane dimethylol, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis (4'-hydroxyphenyl) propane, aromatic diols such as bis (4-hydroxyphenyl) sulfone, etc. Is mentioned. These may be used alone or in combination of two or more. Further, for example, glycolic acid, m-hydroxybenzoic acid,
Hydroxycarboxylic acids and alkoxycarboxylic acids such as p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid and p-β-hydroxyethoxybenzoic acid,
And monofunctional components such as stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid and benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid,
One or more selected from trifunctional or higher polyfunctional components such as trimethylolethane, trimethylolpropane, glycerol and pentaerythritol and esters thereof may be used as a copolymerization component. The polybutylene terephthalate resin in the present invention is a resin obtained by continuously polymerizing a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component. Is preferable, and a resin obtained by continuously polymerizing terephthalic acid and 1,4-butanediol as main raw materials is particularly preferable. As the polybutylene terephthalate resin in the present invention, the intrinsic viscosity [η] measured in a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1) at a temperature of 30 ° C. is in the range of 0.6 to 3.0 dl / g. Are suitable for forming monofilaments and are therefore preferable. If this [η] is less than 0.6 dl / g, the strength of the obtained monofilament may not be sufficiently exerted, and if it exceeds 3.0 dl / g, the motor load becomes high when extruding a monofilament having a small diameter, and the resulting monofilament is extruded. Becomes unstable, the worst motor stops,
Resin leakage may occur from the joints of the extruder, which is not preferable. A more preferable range of intrinsic viscosity is 0.8
To 1.7 dl / g, and more preferably 0.85 to
It is in the range of 1.3 dl / g. In the monofilament of the present invention, as the polybutylene terephthalate resin, the number of fish eyes having a size of 20 μm or more in a film having a resin thickness of 50 μm is 20/100 cm.
² or less, preferably 10/100 cm ² or less, more preferably 5/100 cm ² or less are used. The resin of which the number of fish eyes exceeds 20/100 cm ² cannot achieve the object of the present invention. The method for producing the polybutylene terephthalate resin used in the present invention is basically based on the conventional continuous production method for the polybutylene terephthalate resin. That is, the dicarboxylic acid component containing terephthalic acid and / or its ester derivative as a main component and the diol component containing 1,4-butanediol as a main component are mixed at high temperature in a single or a plurality of esterification reaction tanks. The esterification reaction is carried out under pressure under stirring, and the resulting oligomer as the esterification reaction product is transferred to the polycondensation reaction tank, and the presence of the polycondensation reaction catalyst is reduced at a high temperature in one or more polycondensation reaction tanks. This is a method of continuously performing the polycondensation reaction below. As a method for producing the polybutylene terephthalate-based resin in the present invention, a method of continuously polymerizing directly using a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component is preferable. , Terephthalic acid and 1,
A method in which 4-butanediol is used as a main raw material and continuous direct polymerization is more preferable. The resin obtained by the polycondensation reaction is usually continuously transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted in a strand form, while being cooled with water or after water cooling, and then cut with a cutter to form pellets. , A chip-like granular body.

Typical examples of the esterification reaction catalyst in the above production method include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. For example, in the case of tetrabutyl titanate, the amount used is usually selected in the range of 30 to 300 ppm, preferably 50 to 200 ppm, as titanium atom with respect to the theoretical yield of the polybutylene terephthalate resin. Further, as the esterification reaction catalyst, in addition to the titanium compound, for example, a tin compound, a magnesium compound, a calcium compound or the like can be used. Further, as the polycondensation reaction catalyst, the esterification reaction catalyst added during the esterification reaction can be used subsequently as the polycondensation reaction catalyst. In this case, it is not necessary to add a new catalyst. The same catalyst as the esterification reaction catalyst added during the reaction may be further added. In the esterification reaction and / or polycondensation reaction, in addition to the catalyst, orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, and phosphorus compounds such as esters and metal salts thereof, sodium hydroxide, and benzoic acid. Reaction aids such as alkali metal or alkaline earth metal compounds such as sodium acidate, magnesium acetate, calcium acetate, 2,6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl)
Propionate] and other phenol compounds, dilauryl-3,3′-thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate) and other thioether compounds, triphenylphosphite,
Tris (nonylphenyl) phosphite, tris (2,
Antioxidants such as phosphorus compounds such as 4-di-t-butylphenyl) phosphite, paraffin wax, microcrystalline wax, polyethylene wax, long-chain fatty acids typified by montanic acid and montanic acid esters and esters thereof, silicone oil Other additives such as a release agent may also be present. In case of multi-stage continuous polymerization plant,
As the second-stage polycondensation tank, a horizontal reaction tank equipped with a stirring device having a horizontal rotating shaft is often used. In the reaction tank, it is usually 235 to 280 ° C., preferably 235 to 265.
Temperature of ℃, usually less than 1333Pa, preferably 667P
The polycondensation reaction is further advanced with stirring under a reduced pressure of a or less. In the present invention, in the continuous production method of the polybutylene terephthalate-based resin described above, in order to remove foreign matters and reduce fish eyes, the outlet of the polymer extraction die from the outlet of the first esterification reaction tank It is desirable to install a filter in the main product flow path between and to pass the main product through the filter.

Here, the filter medium constituting the filter may be any of metal wind, laminated metal mesh, metallic non-woven fabric, porous metal plate and the like, but from the viewpoint of filtration accuracy, laminated metallic mesh or metallic non-woven fabric is preferable. Also,
The shape of the filter may be any type such as a basket type, a disc type, a leaf disc type, a tube type, a flat type cylindrical type, and a pleat type cylindrical type, but when filtering an oligomer having a low melt viscosity, Is preferably a tube type or a flat cylindrical type from the viewpoint of cleanability, etc., and when filtering a prepolymer or polymer having a high melt viscosity, from the viewpoint of pressure resistance and processing flow rate per unit area, leaf disk type Alternatively, a pleat type cylindrical type is preferable. Further, the absolute filtration accuracy of the filter is preferably in the range of 0.5 to 50 μm from the viewpoint of filtration efficiency and the like, and 0.5 to 30 μm when the oligomer having a low melt viscosity is filtered.
Is more preferable, and the range of 5 to 50 μm is more preferable when filtering a prepolymer or polymer having a high melt viscosity. Here, the shape of the filter may be any type such as a flat type, a cylinder type, and a candle type. The absolute filtration accuracy is preferably in the range of 0.5 to 50 μm from the viewpoint of filtration efficiency and the like. In the monofilament of the present invention, it is preferable to use the polybutylene terephthalate resin from which the foreign matter is removed in this way. Figure 1
2 is a flow chart showing an example of the continuous production method of the polybutylene terephthalate resin according to the present invention, which is a dicarboxylic acid containing terephthalic acid and / or its ester as a main component prepared in the raw material preparation tank 1. A raw material mixture containing a component and a diol component containing 1,4-butanediol as a main component, the first stage esterification tank 2,
Then, it is supplied to the second stage esterification tank 3 to cause an esterification reaction to generate an oligomer. Next, this oligomer is transferred to a first-stage polycondensation tank (for example, a vertical reactor) 4 and then to a second-stage polycondensation tank (for example, a horizontal reactor) 5 to further advance the polycondensation reaction to obtain a polymer. After being generated, the polymer is transferred to a polymer extraction die 6 to extract the polymer, and a pelletizer 7 forms pellets, chips, or the like. Further, the filter may be installed anywhere from the outlet of the first stage esterification tank 2 to the outlet of the polymer extraction die 6, or may be installed at one place or a plurality of places. Particularly, the effective installation location for removing foreign matter is to install the location from the outlet of the second stage esterification tank 3 to the outlet of the polymer extraction die 6, and more preferably the second stage polycondensation tank 5 It is to be installed in a place from the outlet to the outlet of the polymer extraction die 6. In the present invention, the polymerization apparatus and the polymerization conditions are not limited to the above, and the point is to install foreign matter by installing a filter in the flow path of the main product of the polybutylene terephthalate resin that is continuously produced. It is important to obtain a polybutylene terephthalate-based resin that is removed to give a monofilament with a reduced fish eye number.

With respect to the polybutylene terephthalate type resin obtained by the continuous polycondensation method, resins having various intrinsic viscosities can be obtained mainly by changing the operating conditions of the second stage polycondensation tank. Alternatively, when it is necessary to reduce tetrahydrofuran, which is a main side reaction product, the resin particles obtained by the continuous polymerization method are treated under an inert gas atmosphere and / or under a reduced pressure of about 13 to 1333 Pa, Usually 5 to 50 ° C below the melting point of the resin, preferably 1 below the melting point
It is also possible to perform a solid phase polycondensation reaction by heat treatment at a temperature of 0 to 40 ° C. lower than that of the other particles, usually for about 5 to 20 hours while performing fluidization so that the particles do not stick to each other.
Even in the case of solid-phase polymerization in the polycondensation reaction of the polybutylene terephthalate-based resin in the present invention, if the filter is not installed in the production of the resin for the solid-state polymerization, the obtained polymer contains many foreign substances that cause fish eyes. When the monofilament is included, the stretching breakage frequently occurs in the stretching step in the monofilament manufacturing step, the diameter of the product may vary in the foreign matter portion in the monofilament having a small diameter even if it is successfully stretched, and the tensile strength may decrease due to the foreign matter effect.
The monofilament of the present invention can be obtained by forming the polybutylene terephthalate resin thus obtained into a monofilament by a known method. For example, the raw material resin is continuously supplied to a single-screw extruder, continuously extruded in a filament shape from a nozzle at the tip end while being melted, and once cooled and solidified with water or air at about 3 to 50 ° C.
At this time, if the temperature is too high, it is not preferable because the molten resin is crystallized and the stretching is not properly performed or whitening occurs. Cooling with cold water at 5 to 20 ° C. is preferable. Subsequently, hot water set to a temperature near the glass transition temperature of the resin,
Reheat the monofilament in the steam or air tank, using the speed difference of the drive rolls installed before and after the tank,
The stretching treatment is preferably 1.5 times or more, and more preferably 1.8 to 6 times. The temperature is about 40 to 280 ° C., and it is important to carry out the stretching treatment at a low temperature when the yarn diameter is small and at a high temperature when the yarn diameter is large. From the viewpoint of stabilizing the temperature, warm water heating is preferable at a low temperature, steam heating at about 100 ° C., and hot air heating at a temperature higher than that. This stretching treatment is usually carried out in two or three stages, in which case it is desirable to make the stretching temperature at the second stage higher than the first stage or at the third stage higher than the second stage. After that, in order to prevent post-shrinkage, the glass transition temperature, specifically 6
A stable monofilament can be obtained by heat-treating the monofilament stretched with hot air in a tank at 0 ° C to 280 ° C. All such stretching treatments are performed at a temperature equal to or lower than the melting point of the polybutylene terephthalate resin. When forming the monofilament, known additives such as phenol-based, phosphorus-based, sulfur-based, amine-based antioxidants, dyes and pigments for coloring, fluorescent whitening agents for beautifully coloring, and flexibility Plasticizers and oils to impart, UV absorbers to prevent deterioration by UV when used as monofilaments, metal soaps such as calcium stearate and sodium stearate to maintain biteability in extruders May be added.

These additives can be used by blending them with the raw materials at the time of film forming, or by appropriately diluting a master batch prepared in advance to a high concentration at the time of forming. When the additives are directly blended with the raw materials, ethylene glycol or polyhydric alcohol esters, which are liquid at room temperature, called a spreading agent, and a surfactant may be used together. It is also possible to make them flexible by using a large amount of these. In addition, even if the surface of the molded monofilament is coated with a silicone-based or fluorine-based lubricant, a surfactant for the purpose of preventing static electricity or imparting flexibility, dyeing treatment with a polyester dye or pigment or printing treatment is performed. I do not care. Although the fineness of the monofilament is not particularly limited, it is 50 to 18000 dTe that the effect of improving the stretch breakage and the unevenness of the wire diameter is great in reducing the fish eye.
In the range of x, the improvement effect is more effectively recognized in the range of 70 to 15000 dTex, and more preferably 100 to
It is a monofilament in the range of 9000 dTex. d
Tex is a weight (g) of 10,000 m (meters) of monofilament, which is a small value when the diameter of the monofilament is small and a large value when it is thick.
The cross-sectional shape of this monofilament is not particularly limited, but in addition to circular shape, oval shape, rectangular shape, star shape, “wood” shape, “ki”
A shape, an “L” shape, an “↑” shape, or a shape obtained by combining these shapes is also effective. Further, the monofilament of the present invention preferably has a linear breaking strength of 2.0 cN / dTex or more. A more preferable linear breaking strength is 2.1 cN / dTex or more.

[0011]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Production Example 1 Production of PBT-1 FIG.
Using the same production equipment as shown in, the raw material preparation tank 1 was supplied at a ratio of 1.8 mol of 1,4-butanediol to 1 mol of terephthalic acid, and the temperature was 230 ° C. and the pressure was 0.10113.
While being transferred to the first stage esterification tank 2 adjusted to MPa, 3.14 parts by weight of tetrabutyl titanate was supplied to 100 parts by weight of the raw material, and the esterification reaction was performed with stirring for a residence time of 2 hours, An oligomer having an esterification reaction rate of 87.3% was obtained. Subsequently, the oligomer was transferred to a second stage esterification tank 3 adjusted to a temperature of 240 ° C. and a pressure of 0.10113 MPa, and the esterification reaction was further promoted for 1 hour under stirring to obtain an esterification reaction rate of 98.0. % Oligomers, the oligomers at a temperature of 250 ° C. and a pressure of 6.
Transfer to the first-stage polycondensation tank 4 adjusted to 65 kPa, and
A polycondensation reaction was carried out for a time to obtain a prepolymer having an intrinsic viscosity of 0.24 dl / g. Subsequently, the absolute filtration accuracy of 20 is provided in the middle of the pipe for transferring the prepolymer to the second-stage polycondensation tank 5.
After passing through a pleat type cylindrical type filter using a laminated metal mesh having a thickness of μm as a filter medium, a temperature of 260
C., transferred to the second-stage polycondensation tank 5 adjusted to a pressure of 66.5 Pa, and further proceeded the polycondensation reaction with stirring for a residence time of 4 hours to obtain a polymer having an intrinsic viscosity of 1.20 dl / g. The polymer is extracted by a gear pump and the die 6
To a pelletizer 7
Polybutylene terephthalate resin pellets (PBT-1) were produced by cutting with 1. to obtain pellets.

Here, the esterification reaction rate and the intrinsic viscosity were measured by the following methods, respectively. Esterification reaction rate The obtained oligomer is dissolved in N, N-dimethylformamide, and the acid value is measured by conducting titration with an ethanolic aqueous solution of 0.1 mol% potassium hydroxide to measure the acid value [X
(Meq / g)] was calculated by the following formula. Esterification reaction rate = [(9.083-X) /9.083]
The viscosity of the solution was dissolved in a mixed solvent at a concentration of 1.0 g / dl of × 100 intrinsic viscosity resulting polymer phenol / tetrachloroethane (1/1 by weight) at 30 ° C. using an Ubbelohde viscometer It was determined by measuring. The obtained polybutylene terephthalate resin pellets were supplied to a single-screw extruder equipped with a T-die and having a cylinder temperature of 270 ° C., melt-extruded into a film, and then cooled to a temperature of 58 to 62 ° C. by metal cooling. By rapidly cooling with a roll, a film having a thickness of 50 μm was obtained. When the number of fish eyes was measured by the method shown below, 6.
3 pieces / 100 cm ² . Number of fish eyes About the obtained film, 10 cm square (100 cm ² )
The area of 5 was observed with a stereoscopic microscope at a magnification of 50 times, the number of fish eyes having nuclei with a size of 20 μm or more at each location was counted, and the average value was calculated. Production Example 2 Production of PBT-2 Polybutylene terephthalate resin pellets were produced in the same manner as in Production Example 1 except that no filter was used. At that time, the esterification reaction rate of the oligomer at the outlet of the first-stage esterification tank was 87.3%, and the esterification reaction rate of the oligomer at the outlet of the second-stage esterification tank was 9%.
8.2%, the intrinsic viscosity of the prepolymer at the outlet of the first-stage polycondensation tank is 0.25 dl / g, and finally the intrinsic viscosity of the polymer is 1.21 dl / g of polybutylene terephthalate resin (PBT). -2) was obtained. The number of fish eyes in the resin film was 35.2 / 100 cm ² , and the appearance was shark skin.

Example 1 PBT-1 was charged into a 30 mm single-screw extruder, and about 260
After melt-extruding at 0 ° C, it was continuously extruded from a die having 20 circular nozzles of 1.5 mmφ and cooled at 5 ° C in water while being drawn at a take-up speed of 20 m / min. Then, as the first stage stretching treatment, it is stretched 2.5 times in 60 ° C. warm water, as the second stage stretching treatment, it is 1.44 times in 165 ° C. hot air, and as the heat treatment, it is 0.975 times stretched in 155 ° C. hot air. It was relaxed (2.5%) to obtain a monofilament having a diameter of about 0.2 mm (490 dTex). The monofilament was molded for 3 hours, but no troubles due to stretch breakage (thread breakage) occurred. When the tensile properties of this monofilament were confirmed at n = 10, the linear breaking strength was 2.4 cN / dTex.
(Maximum value 2.8 cN / dTex, minimum value 2.2 cN / dT
ex, deviation = 0.18), elongation is 59%, Young's modulus is 2
It was 260 MPa. Comparative Example 1 A monofilament was molded in the same manner as in Example 1 except that PBT-2 obtained without using a filter was used instead of using PBT-1. The monofilament was molded for 3 hours, but 20
It was confirmed that in 15 of these, stretch breakage occurred a total of 74 times and production stability was poor. When the tensile properties of this monofilament were confirmed at n = 10, the linear breaking strength was 1.7.
cN / dTex (maximum value 2.8 cN / dTex, minimum value 1.1 cN / dTex, deviation = 0.72), elongation 45
%, Young's modulus was 2260 MPa, the frequency of stretching and rupture was increased as compared with Example 1, and it was confirmed that the variation was large due to the decrease in strength and the large deviation.

[0014]

According to the present invention, by using as a raw material a polybutylene terephthalate resin obtained by a continuous polymerization method with a small amount of foreign matter, yarn breakage in a production line can be suppressed and production efficiency can be improved. At the same time, it is possible to provide a polybutylene terephthalate-based resin monofilament having uniform strength and thickness and improved quality.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a continuous method for producing a polybutylene terephthalate resin according to the present invention.

[Explanation of symbols] 1 raw material preparation tank 2 1st stage esterification tank 3 2nd stage esterification tank 4 1st stage polycondensation tank 5 Second stage polycondensation tank 6 Polymer extraction die 7 pelletizer

Claims (5)

[Claims] 1. A polybutylene terephthalate resin obtained by a continuous polymerization method, wherein the number of fish eyes having a size of 20 μm or more in a film having a resin thickness of 50 μm is 20/100 cm ² or less. A polybutylene terephthalate-based resin monofilament characterized in that 2. The polybutylene terephthalate resin monofilament according to claim 1, which is obtained by spinning a polybutylene terephthalate resin by a melt extrusion method and stretching the resin at a temperature not higher than the melting point of the resin by a factor of 1.5 or more. 3. The polybutylene terephthalate-based resin monofilament according to claim 1, which has a fineness of 50 to 18000 dTex. 4. The polybutylene terephthalate resin monofilament according to claim 1, 2 or 3, which has a linear breaking strength of 2.0 cN / dTex or more. 5. The cross section is circular, oval, rectangular, star-shaped, "tree".
The polybutylene terephthalate-based resin monofilament according to any one of claims 1 to 4, which has a mold shape, a "ki" shape, an "L" shape, an "↑" shape, or a combination of these shapes.