JPH0350007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyester fibers for knitted fabrics that have appropriate strength and elongation, excellent flexibility and dyeability, and good processability. As is well known, polyester fibers (hereinafter abbreviated as PES fibers) are industrially produced in large quantities due to their excellent fiber properties, and are widely used for various purposes. This PES fiber has conventionally been used as yarn for knitting and fabrics by spinning at a spinning speed of 1500 m/min or less to obtain a spun yarn, which is then drawn and heat treated in a separate process. However, in recent years, ultrahigh-speed spinning has attracted attention as a streamlined process for manufacturing PES fibers at lower cost. In other words, increase the spinning speed to 5000
m/min or more, the drawing step can be omitted and practically usable PES fibers (referred to as ultra-high speed spun fibers) can be produced all at once. The PES fibers obtained in this way have recently become commercially available as spinners that can be used at speeds of 5,000 m/min or higher have become commonplace, and PES fibers (hereinafter referred to as stretched (abbreviated as "thread") has become cheaper to obtain. Furthermore, in terms of fiber properties, it was reported in JP-A No. 57-16914 that PET drawn yarn can significantly improve the drawback that when used for knitting and weaving, the hand becomes harder than other materials due to its high Young's modulus. etc. have been proposed.
However, on the other hand, ultra-high speed spun fibers have a very small shrinkage rate of 2-3% in boiling water, so there is not enough shrinkage in the processing process of knitted fabrics, so wrinkles cannot be corrected or the texture of knitted fabrics is affected. A drawback has also been found in that it becomes paper-like. On the other hand, Japanese Patent Application Laid-Open No. 16914/1983 proposes an improvement in which the heat shrinkage rate can be appropriately increased by subjecting the running yarn to tension treatment during the ultra-high speed spinning process. However, in this case, although the above-mentioned drawbacks are corrected by improving the heat shrinkage rate, the inherent low dyeability of PES fibers is improved by ultra-high speed spinning, but is not lost by tension treatment. There is a tendency to On the other hand, in order to improve the dyeability of PES fibers, particularly polyethylene terephthalate fibers (hereinafter referred to as PET fibers), fibers made from a melt mixture of polyethylene terephthalate and polybutylene terephthalate have been proposed in Japanese Patent Publication No. 51-27777. Here, we have achieved dyeability comparable to that of 100% polybutylene terephthalate fiber (abbreviated as PBT fiber), but the level of Young's modulus of the fiber is lower than PET drawn yarn, but higher than PET ultra-high speed spun fiber. It cannot be said that it has sufficient softness. In view of the problems of conventionally known technology, the inventors of the present invention have conducted intensive studies on the production of polyester fibers for knitting fabrics that have appropriate strength and elongation, excellent flexibility and dyeability, and favorable processing steps. , the present invention has been achieved. In other words, the main point of the present invention is that polyethylene terephthalate (hereinafter abbreviated as PET) 55
~75% by weight and polybutylene terephthalate (less than
PBT (abbreviated as PBT) 45 to 25% by weight is mixed and melt extruded, and when spinning at a winding speed of 5000 m/min or more, the maximum temperature of the melt extrusion section is set to 280°C or more and 305°C or less, and the polymer is discharged from the start of melting. By setting the residence time to 7 minutes or more and 20 minutes or less, the strength is 3.5 g/d or more, the elongation is 60% or less, and the Young's modulus is 50 or more.
75g/d, boiling water shrinkage rate 6-10% and Tg
The present invention relates to a method for producing polyester fibers having good dyeability at 60 to 70°C. Next, the present invention will be explained in detail. With this invention
The mixing ratio of PET and PBT is PET55-75% by weight.
PBT is 45-25% by weight. If the PET ratio is
If the PBT ratio is less than 55% by weight, that is, if the PBT ratio is 45% by weight or more, the Young's modulus of the fiber will be less than 50 g/d, and the fabric will become too soft when made into a knitted fabric. It's not good because it's completely gone. In addition, the melting point of the fiber is 255℃, which is the melting point of PBT fiber.
The problem is that the heat resistance is low, and the processing conditions for knitted fabrics that are normally applied to PET fibers cannot be applied.
On the other hand, when the PET ratio exceeds 75% by weight,
In other words, when the PBT ratio is less than 25% by weight, it becomes impossible to achieve a boiling water shrinkage rate of 6% or more for polyester fibers, which is an extremely important aspect of the present invention. Fibers with a boiling water shrinkage rate of less than 6% are difficult to wind up as a uniform and stable package during spinning and winding at ultra-high speeds of 5,000 m/min or higher, which is a problem in fiber manufacturing, and there are also problems in producing knitted fabrics using these fibers. Various troubles occur during the manufacturing process. for example,
If the relaxation process does not allow sufficient shrinkage and the subsequent heat setting fails to sufficiently remove the wrinkles caused by relaxation, the resulting knitted fabric will swell if the wrinkles are removed by excessively pulling and setting the fabric. For example, it becomes nothing more than a paper-like product with no On the other hand, if the boiling water shrinkage rate exceeds 10%, there will be too much shrinkage during the processing process for producing knitted fabrics, resulting in the problem that, for example, in fabrics where grains are to be formed, the grains will be insufficient. Therefore, the mixing ratio of PET and PBT is 55 to 75% by weight of PET and 45 to 25% by weight of PBT, and the boiling water shrinkage rate is 6 to 10%.
becomes. Next, the PET used in the present invention is polyethylene terephthalate in which 90 mol% or more of the repeating units are polyethylene terephthalate, and within that range, the acid component terephthalic acid and the glycol component ethylene glycol may be replaced with a modifying component. . Also,
Regarding PBT, as long as 90 mol% or more of the repeating units are polybutylene terephthalate, the acid component terephthalic acid and the glycol component butylene glycol may be replaced with the modifying component within that range. The strength and elongation of the fibers are preferably 3.5 g/d or more and the elongation is 60% or less from the viewpoint of not causing any practical problems. Next, another important point of the polyester fiber of the present invention is that the Young's modulus is 50 to 75 g/d. Generally, polyester fibers, that is, PET drawn yarn, have a Young's modulus of about 100 to 120 g/d, so the texture of the resulting knitted fabric becomes stiff.In order to avoid this, in the present invention, the Young's modulus of the fiber is 75 g/d or less. It must be. This makes it possible to completely eliminate the rough and stiff feel of the knitted fabric. However, when the Young's modulus is less than 50 g/d, the knitted fabric is too soft to be used as a polyester product, resulting in a low-quality product with no stiffness, which is undesirable. Therefore,
It is important that the fiber Young's modulus is 50 to 75 g/d. Furthermore, an important point for the polyester fiber of the present invention is that it exhibits good dyeability at a Tg (glass transition point) of 60 to 70°C. Normally, PET fibers have a Tg of over 70°C and are highly crystalline, so high-pressure dyeing or carrier dyeing is required to dye them to a high degree with disperse dyes. For this reason, the dyeing process for polyester fibers generally consumes a lot of energy and has a high dyeing cost. However, the fibers of the present invention, which have a Tg of 70° C. or less, can be dyed to a high degree even under normal pressure dyeing without a carrier, and can achieve dyeing performance comparable to that of high pressure dyeing of PET fibers. However, when Tg becomes less than 60℃, PET fiber loses its good shape stability.
In practical use of knitted fabric products, problems such as easily losing their shape and wrinkles tend to occur, which is a disadvantage. From this point of view, it is necessary that the fiber of the present invention has a Tg of 60 to 70°C. Here, the Tg of the fiber is measured using a differential calorimeter (DSC).
Measured in _N2 gas. The temperature increase of the sample is
The temperature was 10°C/min. Next, the method for producing polyester fiber of the present invention will be explained. The important points regarding the manufacturing method of the present invention are:
Mixing PET and PBT, melt extrusion, spinning winding speed
The objective is to obtain polyester fibers having predetermined fiber physical properties by spinning at a speed of 5000 m/min or more. PET and PBT
The mixture is based on the prescribed mixing ratio i.e. PET55~75
The polymer is mechanically mixed in the form of chips before being fed to a screw-type extruder so that the weight% and PBT are 45-25% by weight, and then melt extrusion is performed using a screw-type extruder. However, they are mixed even in a molten state, and then spun at ultra-high speed to form fibers.
In this melt extrusion, or mixing process in the molten state,
It is thought that PET and PBT undergo a transesterification reaction, and by controlling the degree of this reaction appropriately, it is thought that the various physical properties of the fiber targeted by the present invention will be exhibited. That is, PET and PBT
It is a mixture of fibers that can be spun at high speeds of 5000 m/min or more, has a fiber strength of 3.5 g/d or more, and an elongation of 60% or less.
Young's modulus 50~75g/d, boiling water shrinkage rate 6~10%,
Tg60~70℃ can be achieved. The degree of transesterification reaction between PET and PBT is greatly influenced by melt mixing conditions, especially temperature and time. It is extremely important to control them appropriately so that both can be kept at a stage where they only partially react. In other words
The first point is to keep the maximum temperature at the melt-extrusion section of the mixed polymer of PET and PBT in the form of chips from 280°C to 305°C. If the maximum temperature of this part does not reach 280℃, use PET
The rate of the transesterification reaction of PBT is slow, and the desired mixing state cannot be achieved with the melt extrusion time taken in normal melt spinning. On the other hand, the maximum temperature of the melt extrusion section is
When the temperature exceeds 305℃, the transesterification reaction rate of PET and PBT increases, and at the same time, the thermal decomposition of PET and PBT also proceeds rapidly, making the melt viscosity of the polymer extremely low, not to mention ultra-high speeds of 5000 m/min or more.
Spinning at a normal spinning speed of 1000 to 1500 m/min also becomes difficult. Therefore, the maximum temperature of the melt extrusion section is
The temperature should be 280°C or higher and 305°C or lower, preferably 285°C or higher and 300°C or lower. Next, the second point is to control the residence time from the start of melting to polymer discharge, which has a large effect on the reaction between PET and PBT, to within 7 minutes or more and within 20 minutes. If the residence time is less than 7 minutes
The transesterification reaction between PET and PBT does not proceed sufficiently,
The kneading of both polymers is also insufficient and a predetermined mixed state cannot be achieved. Even if the maximum temperature of the melt extrusion section is increased with the intention of compensating for this, this is not preferable because the thermal decomposition of PET and PBT will occur rapidly at the same time. On the other hand, if the residence time exceeds 20 minutes, the transesterification reaction between PET and PBT will proceed too much, making it impossible to achieve the desired mixing state. In other words, the fiber
Tg no longer reaches 60℃. It may be possible to compensate for this by lowering the temperature of the melt extrusion section, but this would raise the melt viscosity of the polymer to a high level, which would tend to reduce spinnability and reduce ultra-high speed spinning speeds of 5000 m/min or higher. . Therefore, the residence time from the start of melting to polymer discharge is preferably 7 minutes or more and 20 minutes or less, preferably 10 minutes or more and 15 minutes or less. Actually, the Tg determined by DSC of mixed polyester is 60~
It is necessary to control the temperature within the range of 70℃. if
When PET and PBT undergo a complete transesterification reaction and become a random copolymer, the Tg will be 50 to 55°C in this composition range. The mixture of the invention has a Tg
The temperature is 60 to 70°C, therefore, no random copolymerization occurs, and the ester is only formed to the extent that most of the block copolymerization part, a small amount of unreacted part, and the random copolymerization part are mixed. It is thought that the exchange reaction is not progressing. When polymers in such a mixed state are spun at ultra-high speeds of 5000 m/min or higher, the strength and elongation remain comparable to that of PET ultra-high speed spun fibers, and the Young's modulus is comparable to that of PET fibers and PBT fibers.
Although the boiling water shrinkage rate is between that of fibers, it is at a higher level than when PET and PBT are individually spun at high speed (both 2 to 3%), that is, 6 to 6%.
10% can be achieved. Thus, 5000 for PET alone and PBT alone
This fact is completely unexpected from ultrahigh-speed spinning at a spinning speed of m/min or more, and greatly enhances the practicality of the fiber of the present invention. The reason for this is not necessarily clear, but the transesterification reaction between PET and PBT occurs during melt mixing, but the extent of the transesterification remains at a partial stage and does not reach the stage of complete random copolymerization. Because there is also a randomized part, the crystallinity of the fiber as a whole is lower than that of a fiber obtained by ultrahigh-speed spinning of a single component, and as a result, the spinning strain generated during ultrahigh-speed spinning is not restricted in the crystalline region. It is thought that this caused the boiling water shrinkage rate to increase as a result. Further, it is considered that this decrease in crystallinity contributes synergistically to the improvement in the dyeability of the fiber of the present invention in conjunction with the already mentioned decrease in Tg. In any case, the low shrinkage of polyester ultra-high speed spun fibers has been a very big problem because if it is processed in the same process as normal polyester drawn fibers, the above-mentioned troubles will occur. This almost negates the other merits of ultra-high speed spun fibers, such as the fact that they can be streamlined by omitting the drawing process. Moreover, there has never been a method to improve this low shrinkage property by ultra-high-speed spinning while maintaining ultra-high-speed spinnability comparable to that of PET alone, and maintaining strength and elongation comparable to that of polyester drawn yarn. The present invention has achieved this goal. If the spinning winding speed does not reach 5000 m/min, it will not be possible to achieve the specified physical properties, especially an elongation of 60% or less, only by the spinning process that is the gist of the present invention, and the boiling water shrinkage rate will be less than 10%. However, it becomes impossible to achieve a 6 to 10% value with good post-processability. Therefore,
The spinning winding speed is 5000 m/min or more, preferably 5500 m/min.
It is preferable to set the speed at m/min or more. According to the present invention, polyester fibers for knitting and fabrics made of a mixture of PET and PBT and having appropriate strength, elongation, excellent flexibility and dyeability, and good post-processing properties can be produced at low cost through a spinning process alone. Obtainable. This completely eliminates the problem that conventional drawn PET yarns have a rough and hard texture when used for knitted fabrics due to their high Young's modulus.
Furthermore, because PET drawn yarn has a high Tg and high crystallinity, high-pressure dyeing or carrier dyeing was required to achieve high-quality dyeing, but it is now possible to achieve high-quality dyeing using normal pressure dyeing without a carrier. Therefore, the fiber of the present invention can be widely used for polyester knitted fabrics. EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. In addition, the intrinsic viscosity [η] of the polyester referred to in the present invention is tetrachloroethane/phenol=
Measurements were taken at 30°C using a 1/1 mixed solvent. The strength, elongation, and Young's modulus of the fibers were measured using an Instron tensile tester at a sample length of 5 cm and a tensile speed.
It was determined by conducting a tensile test under the conditions of 20 cm/min and initial load of 1/20 g/d. The boiling water shrinkage rate was determined by free-processing a 40 cm sample in boiling water at 100° C. for 60 seconds, and measuring the length of the sample under a load of 1/20 g/d before and after the treatment. Example 1 A screw-type extruder with a diameter of 30 mm and a mouth hole diameter of 0.25
mm, a spindle hole length of 0.5 mm, a spindle with 32 holes installed, and a constant discharge rate of 40 g/min, the mixing ratio of PET chips with [η] = 0.71 and PBT chips with [η] = 0.80, and the spinning winding speed. Table 1 shows the fiber properties of polyester fibers obtained by spinning with various changes in the maximum temperature of the melt extrusion section and the residence time from the start of melting to polymer discharge. No. 1 and No. 2 are the fiber manufacturing conditions of the present invention and the polyester fibers of the present invention obtained thereby. These fibers had moderate strength and elongation, excellent flexibility and dyeability. This was subjected to the same weaving and post-processing steps as ordinary polyester drawn fibers to produce a polyester fabric. The processability was almost the same as that of ordinary drawn polyester fibers, and no troubles occurred. In addition, the obtained fabric does not have the rough and stiff feel that is characteristic of fabrics made from polyester drawn fibers, but does not have the loose feel of fabrics made from polyamide fibers, does not lose its shape during practical use, and is in good condition. It had a nice texture. Furthermore, although the dyeing was carried out using a disperse dye under normal pressure, the dyeability level was the same as that of ordinary polyester fabrics dyed under high pressure. On the other hand, examples No. 3 to No. 11 are all polyester fibers obtained under conditions outside the fiber manufacturing conditions of the present invention, but all of them satisfy the excellent characteristics of the polyester fiber of the present invention. isn't it. Using these (except for No. 6 because no yarn could be obtained due to poor spinnability), a polyester fabric was produced through the same weaving and post-processing steps as for ordinary polyester drawn fibers. In these cases, the weaving and post-processing properties are lowered, the dyeability of the obtained woven fabric is insufficient, and the texture is poor, which is lower than the product of the present invention. It was hot. 【table】

Claims (1)

[Claims] 1. When mixing 55 to 75% by weight of polyethylene terephthalate and 45 to 25% by weight of polybutylene terephthalate and performing melt extrusion and spinning at a spinning winding speed of 5000 m/min or more, the maximum temperature of the melt extrusion section should be set to 280 m/min or higher.
℃ or more and 305℃ or less, and the residence time from the start of melting to polymer discharge is 7 minutes or more and 20 minutes or less. Strength is 3.5 g/d or more and elongation is 60.
% or less, Young's modulus 50 to 70 g/d, boiling water shrinkage rate 6
~10% and a Tg of 60 to 70°C.