JP2014001467A - Method for producing flame retardant polyester fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a flame-retardant polyester fiber having high strength and excellent productivity.SOLUTION: There is provided a method for producing a flame-retardant polyester fiber by applying treatment liquid having a solid concentration of 20 wt.% or more and comprising a flame retarder and oil components to polyester fiber at a processing speed of 100 m/min or more and drying the fiber. Preferably, the solid concentration of the flame retarder in the treatment liquid is 10 wt.% or more, the oil components include a smoothing agent, an antistatic agent, and an emulsifier, and aging treatment and refining treatment are performed after preliminary drying.

Description

  The present invention relates to a method for producing a flame-retardant polyester fiber, and further relates to a method for producing a high-performance and efficient flame-retardant polyester fiber.

  Polyester fibers are used in various applications because they have many excellent properties. However, since the raw material polyester polymer itself has combustibility classified as “flammable”, it basically has the property of burning in air. Therefore, various techniques have been developed in order to impart high flame retardancy to polyester fibers.

  For example, as a method for increasing the flame retardancy of polyester fibers, a method of adding a flame retardant into a polymer and a method of copolymerizing a flame retardant monomer or polymer with a polymer chain constituting the polymer have been known for a long time. (Patent Document 1, Patent Document 2, etc.).

  However, when such a flame retardant polymer is used, there is a problem that the polymer itself is expensive, and sufficient stretching cannot be performed in the middle of the process, so that the strength of the inherent polyester fiber cannot be exhibited sufficiently. Especially in industrial material applications where high strength is required, the field of use is limited.

  On the other hand, a method for imparting flame retardancy to a polyester fiber by post-processing is known. As the post-processing step, a method of treating a flame retardant mainly at the stage of woven or knitted fabric is mainly used. For example, a method of exhausting or adhering a phosphorus-based flame retardant to a fiber by a bathing method or a padding method ( Patent Document 3) is known.

However, in this post-processing method, it is easy to obtain polyester fibers that have been sufficiently stretched and strengthened, but low-speed processing such as batch processing is the mainstream. It was a difficult method.
Development of an efficient method for producing flame-retardant polyester fibers having high strength inherent in polyester fibers and high productivity has been desired.

Japanese Patent Laid-Open No. 50-56488 JP 52-47891 A JP 2007-77539 A

  An object of the present invention is to provide a method for producing a flame-retardant polyester fiber that is high in strength but excellent in productivity.

In the method for producing a flame-retardant polyester fiber of the present invention, a treatment liquid having a solid content concentration of 20% by weight or more comprising a flame retardant and an oil component is applied to the polyester fiber at a processing speed of 100 m / min or more and dried. It is characterized by.
Further, the solid content concentration of the flame retardant in the treatment liquid is 10% by weight or more, the oil component contains a smoothing agent, an antistatic agent and an emulsifier, and aging treatment and refining treatment can be performed after preliminary drying. preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the flame retardant polyester fiber excellent in productivity while being high intensity | strength is provided.

  The method for producing a flame-retardant polyester fiber according to the present invention is a method in which a high-concentration treatment liquid containing a flame retardant containing 20% by weight or more containing a flame retardant is applied to a polyester fiber at a high processing speed of 100 m / min and dried. is there.

  Here, the polyester fiber used in the present invention is a polyester fiber melted from a polyester polymer and discharged from a spinneret. Furthermore, at the time of application | coating of a process liquid, it is preferable that it is a polyester fiber after a extending process. The polyester polymer to be spun is not particularly limited as long as it is a general-purpose polyester polymer. Among them, the main repeating unit of the polyester is ethylene terephthalate, ethylene-2,6-naphthalate, trimethylene terephthalate, trimethylene-2,6- It is preferably selected from the group consisting of naphthalate, butylene terephthalate, butylene-2,6-naphthalate. In particular, it is preferably made of polyethylene terephthalate having excellent physical properties and suitable for mass production. Further, it may be a copolymer containing a suitable third component in the polyester polymer.

  In the present invention, it is a method of applying a treatment liquid containing a flame retardant to a polyester fiber obtained by melting and discharging such a polyester polymer from a spinneret. It is preferable to apply a treatment liquid to the stretched polyester fiber.

  Further, the present invention applies a treatment liquid comprising a flame retardant and an oil component to the polyester fiber, but the application step may be immediately after stretching, but in the step of rewinding the subsequent polyester fiber, the treatment liquid is applied. It is preferable to give. Since the drying process can be carried out immediately after the application, it is more excellent in process passability.

  The treatment liquid used in the present invention is composed of a flame retardant and an oil component, but it is essential that the treatment liquid is a high-concentration treatment liquid having a solid concentration of 20% by weight or more. And as this process liquid, it is preferable that a smoothing agent, an antistatic agent, and an emulsifier are included as oil agent components other than a flame retardant. Further, the treatment liquid is preferably an aqueous solution in which a flame retardant component and an oil component are dispersed in water.

  As the flame retardant, any flame retardant generally used for the purpose of exhausting into polyester fibers in post-processing can be used, and a phosphorus compound is particularly preferable. Preferred flame retardants include, for example, 1,2,3,4,5,6-hexabromocyclohexane, 1,2,3,4-tetrabromocyclooctane, 1,2,5, which are halogenated cycloalkane compounds. 6,9,10-hexabromocyclododecane, 1,2-bis (3,4-dibromocyclohexyl) 1,2-dibromoethane, or those in which bromine of these compounds is substituted with chlorine, or aromatic phosphoric acid Triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris (t-butylated phenyl) phosphate, tris (i-propylated phenyl) phosphate, phosphinic acid compound which are ester flame retardants (2-carboxyethyl) methylphosphinic acid, (2-carboxyethyl Phenylphosphinic acid or cyclic anhydrides thereof, derivatives such as ethylene glycol adducts, phosphazene compounds such as phenoxyphosphazene, propoxyphosphazene, diaminophosphazene, etc., cyclic compounds, linear compounds, and phenylene groups, Compounds cross-linked with a bisphenylene group or the like as a cross-linking group, 10-benzyl-9,10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-propyl-9, which is a phosphaphenanthrene compound 10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-2,5-dihydroxyphenyl-9,10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide 10-4-hydroxy Phenyl-9,10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-2,5-dimethylphenyl-9,10-di-hydro-9-oxa-10-phosphaphenanthrene -10-oxide or the like can be used. In particular, in recent years, interest in the environment has increased, and it is more preferable to use phosphorus compounds. Further, the above flame retardants can be used alone or in combination.

  On the other hand, the treatment liquid used in the present invention is a high-concentration treatment agent, but it is preferable that the oil component contains a smoothing agent, an antistatic agent and an emulsifier. As these oil agent components, those used in the production process of ordinary polyester fibers can be used, for example, rapeseed oil, mineral oil, fatty acid esters as a smoothing agent, higher alcohols or ethylene oxide as an emulsifier. As the (EO) adduct and antistatic agent, various anionic and cationic surfactants can be used.

  And in the manufacturing method of the flame-retardant polyester fiber of this invention, although the processing liquid of 20 weight% or more of solid content which consists of said flame retardant and oil agent component is provided to polyester fiber, Furthermore, as solid content density | concentration of a processing liquid Is preferably 30% by weight or more and 70% by weight or less. By using such a high-concentration treatment liquid, it is possible to increase the amount of the treatment liquid applied to the fiber, and thus the amount of the flame retardant, and by satisfying other requirements such as subsequent drying treatment, high flame retardancy is imparted. Polyester fiber could be obtained.

  The solid content concentration of the flame retardant in the treatment liquid of the present invention is preferably 10% by weight or more of the flame retardant, usually 50% by weight or less, more preferably 25% by weight or more and 35% by weight or less. On the other hand, the solid content concentration of the oil component in the treatment liquid is preferably 10% by weight to 50% by weight, and more preferably 12% by weight to 35% by weight. When the amount of the flame retardant is less than 10% by weight, it tends to be difficult to impart sufficient flame retardancy to the polyester fiber. Conversely, when the amount is too large, the viscosity tends to be too high, particularly when the treatment liquid is an aqueous solution. It is in. The present invention secures the amount of adhesion to the fiber by increasing the viscosity of the treatment liquid, but if the treatment liquid becomes too viscous, spots will occur in the adhesion of the agent to the fiber, and post-processes such as yarn-forming properties The passability tends to deteriorate. On the other hand, when there are too few other oil agent components, especially when the treatment liquid is an aqueous dispersion, the water ratio in the treatment liquid becomes high, and there is also a problem that it becomes difficult to dry the polyester fiber after the treatment liquid adheres. . On the contrary, when the amount of the oil component is excessive, the viscosity of the treatment liquid tends to increase and adhesion spots tend to occur.

  Moreover, as a process liquid used with the manufacturing method of this invention, it is preferable that the pH exists in the range of 6.0-10.0. Furthermore, it is preferable that it is the range of 7.0-9.5. By adjusting to such pH, the dispersibility of the solid component in the treatment liquid is improved, and more stable process stability can be ensured. On the other hand, when it deviates from this range to the acidic side or the alkaline side, the dispersibility of the solid component is lowered, and the adhesion to the fiber tends to occur.

  Now, in the manufacturing method of this invention, it is necessary to provide the polyester fiber with the process liquid which disperse | distributed said flame retardant component and the other oil agent component. The process of applying the treatment liquid to the polyester fiber may be performed at the stage where the polyester fiber is in an undrawn yarn, that is, before the drawing process, and may be performed between drawing and winding. The drawn yarn may be wound once and then applied when rewinding. Furthermore, in the manufacturing method of this invention, it is preferable to heat a fiber immediately before providing a process liquid. By preheating the fiber, the final flame retardant exhaust rate can be increased.

  In the production method of the present invention, the treatment liquid is applied at a speed of 100 m / min or more as a processing speed. However, it is necessary to prepare conditions that allow the treatment liquid to be sufficiently dried. In particular, when the treatment liquid is an aqueous solution, it is necessary to cope with it carefully. For example, it is necessary to adjust the concentration of the treatment liquid, or to adjust the processing speed and the amount of agent attached to the polyester fiber. Furthermore, the processing speed is preferably 100 m / min or more and 4000 m / min or less, and more specifically, 100 m / min or more and 500 m / min or less in the rewinding process or the like, and 400 m / min or more and 700 m / min or less before the stretching process. After stretching, it is preferably 100 m / min or more and 4000 m / min or less. In the production method of the present invention, by using a high-concentration treatment liquid having a solid content concentration of 20% by weight or more, effective treatment can be performed even at a high processing speed of 100 m / min or more. On the other hand, if the processing speed becomes too fast, the amount of agent attached to the polyester fiber will be insufficient, and the amount of flame retardant attached will tend to be difficult to obtain sufficient flame retardancy, and the amount of other oil component will be attached. In some cases, the yarn-forming property may be impaired due to the decrease in. On the other hand, when the speed is less than 100 m / min, not only the production efficiency is lowered, but also the amount of the treatment agent attached to the fiber is excessively increased, and the processability, particularly the processability of post-processing such as yarn forming and weaving deteriorates. .

  In the manufacturing method of this invention, it is preferable that the adhesion amount of a process liquid is the range of 10-100 weight% (Wet) with respect to fiber weight. Moreover, as solid content adhesion amount, it is preferable that it is 10-30 weight% (Dry), and also it is optimal that it is the range of 15-25 weight% (Dry). If the amount of adhesion is too small, the effect is reduced, and if it is too large, drying of the fiber becomes difficult and tends to cause stickiness.

  Further, the preferable adhesion amount for each component is an adhesion amount of 2 to 30% by weight of a flame retardant component such as a phosphorus compound and 1 to 10% by weight of other oil component with respect to the fiber weight. It is preferable. Further, it is preferable that the flame retardant is 10 wt% or more and 20 wt% or less, and the oil component is 5 wt% or more and 8 wt% or less. If the amount of flame retardant attached is too small, there is a tendency that sufficient flame retardancy cannot be imparted. Conversely, if the amount is too large, the fiber itself becomes sticky, and the post-processing processability such as yarn-making and weaving is remarkably high. It tends to get worse. On the other hand, if the adhesion amount of the oil component is too small, the yarn-making property tends to be impaired. Conversely, if the amount is too large, the fiber itself becomes sticky, and the post-processing processability such as yarn-making and weaving tends to deteriorate. It is in.

  Further, in order to obtain a high-strength flame-retardant polyester fiber, it is preferable that the polyester polymer is melted and cooled slowly using a heated spinning cylinder when discharged from the spinneret. The polyester polymer immediately after being discharged from the spinneret tends to be oriented immediately, and single yarn breakage is likely to occur, but it can be effectively prevented by delayed cooling. After the molten polymer composition is discharged from the spinneret and molded, it is further stretched, so that highly efficient production can be performed, and stretching after spinning makes it possible to obtain stretched fibers with higher strength. is there.

  In the flame retardant polyester fiber production method of the present invention, the polyester fiber thus provided with the treatment liquid is dried. The drying treatment at this stage may be such that the treatment liquid on the fiber does not easily adhere to others. The drying temperature is 120 ° C. or higher and 300 ° C. or lower, and more preferably 150 ° C. or higher and 260 ° C. or lower. The higher the processing speed, the higher the drying temperature. The drying equipment may be a contact type such as a hot roller or a non-contact type such as a hot air dryer, and the drying time will be approximately depending on the drying equipment and processing speed. Therefore, it is important to set an appropriate drying temperature. Usually, a processing time of about 0.1 to 30 seconds is employed. Moreover, it is preferable to perform this drying process rapidly after providing a processing agent.

  Further, the flame-retardant polyester fiber obtained by the production method of the present invention after drying is preferably subjected to aging treatment at the end. Here, the aging treatment is preferably a dry heat treatment of 50 ° C. or more, and more preferably a treatment in a temperature range of 60 ° C. to 200 ° C. The treatment time is preferably in the range of 1 to 5 days if the aging temperature is less than 100 ° C, and 10 to 60 minutes if the aging temperature is 100 ° C or higher. This treatment may be continued after drying, but is preferably performed after twisting the flame-retardant polyester fiber or processing it into a woven fabric in order to prevent loss of shape. Furthermore, it is preferable that the flame-retardant polyester fiber of the present invention is refined after the aging treatment. By performing such treatment, the flame-retardant polyester fiber of the present invention can ensure extremely high flame retardancy.

  There is no particular limitation on the single yarn fineness of the flame-retardant polyester fiber obtained by the production method of the present invention. However, from the viewpoint of yarn production or physical properties such as strength and flexibility, 0.1 to 100 dtex / filament In particular, 1 to 20 dtex / filament is preferable. The total fineness is not particularly limited, but is preferably 10 to 10,000 dtex, and particularly preferably 250 to 6,000 dtex. In addition, as the total fineness, for example, 2 to 10 yarns may be spun during spinning or drawing, or after the end of each, so that two fibers of 1,000 dtex are combined to a total fineness of 2,000 dtex. Is possible.

  Furthermore, in the method for producing a flame-retardant polyester fiber of the present invention, it is also a preferable aspect that the polyester fiber as described above is used as a multifilament and twisted. By twisting the multifilament fiber, the strength utilization rate in the fiber structure is finally averaged and the fatigue property is improved. The number of twists is preferably in the range of 50 to 1000 turns / m, and may be obtained by combining the lower and upper twists. The number of filaments constituting the yarn before being combined is preferably 50 to 3000. By using such a multifilament, fatigue resistance and bending resistance are further improved.

  The strength of the flame retardant polyester fiber obtained by the production method of the present invention as described above is preferably 4.0 to 10.0 cN / dtex. Furthermore, it is preferably 5.0 to 9.5 cN / dtex. When the strength is too low, the durability tends to be inferior when the strength is too high. In addition, when production is performed with a very high strength, yarn breakage tends to occur in the yarn making process, and there is a tendency for quality stability to be problematic. The dry heat shrinkage at 150 ° C. is preferably 1 to 15%. If the dry heat shrinkage rate is too high, the dimensional change during processing tends to increase, and the post-processing process of the fiber structure such as woven fabrics, knitted fabrics, nonwoven fabrics, ropes and strings using flame-retardant polyester fibers and the product itself Dimensional stability is affected.

  Usually, in the case of a flame-retardant polyester fiber using a polymer with a flame retardant added or copolymerized, when trying to develop the above strength, a single yarn breakage occurs during stretching, and in some cases, the yarn breaks. It was difficult to increase the strength. According to the present invention, since the flame retardant can be applied regardless of the stretching of the fiber, sufficient strength can be obtained and flame retardancy can also be imparted.

  And finally as content of the phosphorus atom contained in the flame-retardant polyester fiber obtained by the manufacturing method of this invention, it is 0.2 to 1.5 weight% with respect to the total fiber weight. preferable. Furthermore, it is preferable that it is 0.6 to 1.2 weight%. If the phosphorus content is less than 0.2% by weight, it tends to be difficult to obtain sufficient flame retardancy. Conversely, even if the phosphorus content is more than 1.5% by weight, it is very difficult. No improvement in flammability is expected. Here, sufficient flame retardancy refers to flame retardancy that conforms to the 45 degree method and the coil method specified in JIS L 1091. If it is flame retardant that complies with the 45-degree method and the coil method, even when it is used for interiors such as curtains, decoration materials such as tents, and woven nets for civil engineering, it will be sufficient in the event of an emergency. Can be expressed.

  Regarding the mechanism by which the present invention can impart flame retardancy very effectively, currently there is no speculation, but the flame retardant component present in the oil component layer adhering in large quantities to the polyester fiber surface is preferably subjected to drying treatment or This is thought to be because the aging treatment performed thereafter exhausts the relaxed amorphous portion of the polyester fiber and effectively retains the flame retardant inside the polyester fiber polymer. Since the exhausted flame retardant is held at a high concentration in the outer layer of the polyester fiber, when the fiber burns, it becomes easy to form a coated char on the fiber surface, and high flame retardant performance is expressed. . This is an effect that was not obtained when a resin was used instead of the oil component as in a normal post-processing treatment.

  Further, when a scouring step is added at the end, there is an effect of washing off the flame retardant and oil component remaining on the polyester fiber surface. Even if a trace amount of the flame retardant or oil component remains on the surface of the polyester fiber, combustion may be accelerated during combustion. Excess components on the fiber surface can be removed by scouring. Usually, when weaving or the like is performed, scouring is often performed, but in that case, it is not necessary to separately perform the smelting step in the present invention, and the number of processing steps is the same as the conventional number.

  The present invention will be further described in the following examples, but the scope of the present invention is not limited by these examples. Various characteristics were measured by the following methods.

(A) Strong elongation of the fiber and intermediate unloading,
It measured according to JIS L-1013 using the tensile load measuring device (Shimadzu Corporation autograph). In addition, intermediate | middle unloading represented elongation at the time of the intensity | strength of 4 cN / dtex.

(A) Dry heat shrinkage rate In accordance with JIS L 1013, after leaving in a room where temperature and humidity are controlled at 20 ° C. and 65% RH for 24 hours, heat treatment is performed in a dryer at 150 ° C. for 30 minutes in a no-load state. Calculated from the difference in length.

(C) Flame retardancy Conforms to JIS L 1091. In the 45 degree micro burner method, a 350 mm × 250 mm polyester woven fabric is tilted 45 °, heated by a micro burner for 1 minute, and after flame time (seconds), residual dust time (seconds), and carbonized area (cm ² ) are measured. . Acceptance judgment flame retardancy was evaluated as acceptable or less after flame time 3 seconds and 5 seconds or less afterglow time and carbide area 30 cm ² or less. On the other hand, the coil method measures the number of times of flame contact necessary to burn a fiber bundle having a mass of 1 g and a length of 100 mm inclined at 45 ° by 90 mm in the fiber axis direction. The pass / fail judgment of flame retardancy was set to 3 or more times of flame contact. What passed both of these two measurements was considered to achieve the object of the present invention.

[Example 1]
Polyethylene terephthalate resin was melted to a polymer melting temperature of 295 ° C. or higher, spun from a spinneret having a diameter of 0.4 mm and 96 holes, and provided through a cylindrical heating zone heated to 300 ° C. with a length of 200 mm provided directly under the base. Next, cooling air adjusted to 20 ° C. and 65% RH was blown onto the spun yarn from a cylindrical chimney with a blowing distance of 500 mm, delayed cooling, and after applying a spinning oil, it was taken up by a roller at a speed of 550 m / min. . The discharged yarn was continuously stretched and heat-set without being wound once to obtain a multifilament of 1100 dtex / 96 filaments. The strength of this product was 7.85 cN / dtex, the elongation was 16.0%, the dry heat shrinkage was 11.5% (150 ° C. × 30 min), there was no fuzz defect, and the yarn production was excellent.
The polyester fiber was rewound at a speed of 200 m / min. In the rewinding process, the polyester fiber was preheated with a non-contact heater at 200 ° C., and then a treatment liquid having a solid content concentration of 35% by weight of flame retardant and 15% by weight of oil was applied. The flame retardant component in the treatment liquid was a phosphaphenanthrene compound, and the oil component was an aqueous solution of pH 7.2 consisting of a smoothing agent, an antistatic agent and an emulsifier. Subsequently, drying was performed on a take-up roller at 180 ° C. for a treatment time of 2 seconds. The polyester fiber was provided with 18% by weight of flame retardant and 8% by weight of oil component.
Using the obtained flame-retardant polyester fiber for warp and weft, a plain woven fabric having a woven density of 25 / inch × 25 / inch was obtained. After weaving, aging treatment (heat treatment) was performed at 180 ° C. for 30 minutes, followed by scouring and drying. The adhesion amount of the phosphorus component was 0.9% by weight. Flame retardant evaluation based on JIS L 1091 was performed using the obtained woven fabric. The results are shown in Table 1.

[Example 2]
In the spinning process, the treatment liquid used in Example 1 of 35% by weight of flame retardant and 15% by weight of oil was applied instead of the spinning oil, and the drawing conditions were finely adjusted. Except that the application of was omitted, it was carried out in the same manner as in Example 1 to obtain a flame-retardant polyester fiber. About this fiber, the process liquid containing a flame retardant was provided at a speed | rate of 550 m / min before extending | stretching.
The obtained flame-retardant polyester fiber has a strength of 7.85 cN / dtex, elongation of 16.0%, dry heat shrinkage of 11.5% (150 ° C. × 30 min), a flame retardant of 12% by weight, and an oil component. 6% by weight was applied.
Next, as in Example 1, a plain woven fabric was obtained, followed by aging treatment and refining treatment. The evaluation results are also shown in Table 1.

[Example 3]
After extending | stretching the processing liquid used in Example 1 of 35 weight% of flame retardants, and 15 weight% of oil agents, it carries out similarly to Example 1 except omitting the rewinding process of Example 1, and provision of a processing liquid, A flame retardant polyester fiber was obtained. About this fiber, the process liquid containing a flame retardant was provided at a speed of 2830 m / min after drawing.
The strength of the obtained flame-retardant polyester fiber was 7.85 cN / dtex, elongation 16.0%, dry heat shrinkage 11.5% (150 ° C. × 30 min), flame retardant 8%, oil 4% Was granted.
Next, as in Example 1, a plain woven fabric was obtained, followed by aging treatment and refining treatment. The evaluation results are also shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, except that the treatment liquid of 35% by weight of the flame retardant and 15% by weight of the oil of Example 1 was treated with a treatment liquid having a pH of 7.3 of 5% by weight of flame retardant and 2% by weight of the oil. Implemented to obtain a flame-retardant polyester fiber. The obtained polyester fiber was provided with 1% by weight of a flame retardant and 1% by weight of an oil.
Next, as in Example 1, a plain woven fabric was obtained, followed by aging treatment and refining treatment. The evaluation results are also shown in Table 1.

[Comparative Example 2]
A flame-retardant polyester fiber was obtained in the same manner as in Example 1 except that the rewinding step and application of the treatment liquid in Example 1 were omitted. No flame retardant was applied to this polyester fiber, and only 0.5% by weight of the spinning oil was applied.
Next, as in Example 1, a plain woven fabric was obtained, followed by aging treatment and refining treatment. The evaluation results are also shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was performed except that the rewinding speed of Example 1 was changed to 80 m / min. In addition to being inferior in production efficiency, the amount of treatment liquid deposited was too large, and process passability in post-processing such as yarn-making and weaving deteriorated.

Claims (4)

  A method for producing a flame-retardant polyester fiber, comprising applying a treatment liquid having a solid content concentration of 20% by weight or more comprising a flame retardant and an oil component to a polyester fiber at a processing speed of 100 m / min or more and drying.   The method for producing a flame retardant polyester fiber according to claim 1, wherein the solid content concentration of the flame retardant in the treatment liquid is 10% by weight or more.   The method for producing a flame retardant polyester fiber according to claim 1 or 2, wherein the oil component contains a smoothing agent, an antistatic agent and an emulsifier.   The method for producing a flame-retardant polyester fiber according to any one of claims 1 to 3, wherein an aging treatment and a refining treatment are performed after the preliminary drying.