JPS6143445B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical field) The present invention relates to a method for spinning polyester fiber,
More specifically, the present invention relates to a polyester fiber spinning method suitable for high-speed stretching and simultaneous false twisting. (Prior Art) Polyesters, represented by polyethylene terephthalate, have many excellent properties and are therefore widely used in various applications, particularly in fibers. Polyester fibers are usually melt-spun, drawn,
It is ready for use after heat setting. In recent years, advances in spinning technology have made it possible to significantly increase the take-up speed during melt spinning from the conventional 1000 to 1500 m/min to 2000 m/min or more, and even 4000 m/min. The intermediately oriented yarn obtained at a spinning take-off speed of 2000 to 4000 m/min is subjected to simultaneous drawing and false twisting ( (Hereinafter, it may be referred to as DTY processing.) In recent years, this application has made remarkable progress and is becoming the mainstream of silk reeling technology. Moreover, recently the machining speed has increased to 700
High-speed DTY machining at m/min is also becoming common. However, when the spinning take-off speed is increased to 2,000 m/min or higher, especially 3,000 m/min or higher, yarn breakage during spinning (hereinafter sometimes referred to as spinning yarn breakage) tends to increase, as well as the resulting intermediate orientation. Even if the yarn is subjected to the high-speed DTY processing, yarn breakage during processing (hereinafter sometimes referred to as processed yarn breakage) is likely to occur frequently, which may affect the productivity of the spinning and processing processes, and further reduce the processed yarn that is the final product. The disadvantage is that the quality of both materials tends to deteriorate. In order to eliminate these drawbacks, attempts have been made to optimize the spinning conditions, such as spinning temperature, cooling air volume, and cooling air temperature, and to improve the structure of the spinning tube and spinneret nozzle, but these measures have their limits. Yes, we cannot expect any major improvements. Also, JP-A-50-124, JP-A-51-
No. 112860 and Japanese Patent Application Laid-Open No. 134925/1983, as polyester to be subjected to high-speed spinning, a large amount of lithium compound and/or calcium compound is added in the polyester manufacturing process, and particles made of lithium and/or calcium are It has been proposed to use precipitated polyesters. In the above-mentioned publication, according to this method, yarn breakage is reduced, and even if the obtained intermediately oriented yarn is drawn and then subjected to false twisting at a processing speed of 100 m/min, yarn breakage during drawing is reduced. It is stated that it is possible to obtain processed yarn in a small amount and at an even cost. However, when the inventors experimented with this method, they found that when polyester obtained by a method of precipitating particles in the polymer was subjected to high-speed spinning and then subjected to DTY processing, the precipitated particles aggregated and became coarse. It becomes particles and easily causes yarn breakage and processing yarn breakage, and furthermore, the processing speed is 700m/
It was also found that high-speed DTY processing for 10 minutes resulted in frequent yarn breakage, making it unsuitable for practical use. (Object of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks, and to produce an intermediately oriented yarn that can be spun stably with very little occurrence of yarn breakage even when the take-up speed during spinning is 2000 to 4000 m/min. High speed DTY with processing speed of 700m/min
It is an object of the present invention to provide a method for spinning polyester fibers which can be stably processed with almost no yarn breakage even when subjected to processing. (Structure) The present inventors conducted studies to achieve this objective, and found that polyester has a property that it is difficult to crystallize compared to polyethylene, polyamide, etc., but the take-up speed during melt spinning is 2000 m/min. If the speed exceeds 3000 m/min, molecular orientation will occur and crystallization will occur. It has been found that the above-mentioned drawbacks occur due to the large degree of deterioration. Based on the above findings, the present inventors further investigated the crystallization behavior of polyester during high-speed spinning, and found that the antimony compound used as a polymerization catalyst for polyester acts as a nucleating agent for polyester. Although this antimony compound is not sufficient, it has been found that it has the effect of suppressing crystallization during molecular orientation during high-speed spinning. In addition, compounds that have a greater crystallization inhibiting effect than the antimony compounds are alkali metal carboxylates and calcium carboxylates represented by sodium acetate, potassium acetate, lithium acetate, etc., and these alkali metal salts are It has been found that even if the amount added is so small that it cannot be precipitated as particles in the resulting polyester, a sufficient crystallization inhibiting effect can be achieved. Furthermore, we repeatedly investigated this crystallization suppressing effect and the crystallization behavior of the polyester produced, and found that as the diameter of the spherulites that are produced at the cooling crystallization peak measured with a differential scanning calorimeter becomes smaller, the molecular The polyester pellets were prepared in advance in an acetic acid aqueous solution to suppress crystallization during orientation, and more importantly, the crystal nuclei that have the effect of suppressing crystallization during molecular orientation must interact with the polyester molecular chains. This was discovered by measuring the spherulite nuclei of polyester after heat extraction. That is, it has been found that the smaller the polyester spherulite diameter after heating and extracting polyester pellets with an acetic acid aqueous solution, the greater the effect of suppressing crystallization during molecular orientation. The present invention was completed as a result of further studies based on these findings. That is, the present invention is produced by polycondensing a transesterification product of a lower alkyl ester of a difunctional carboxylic acid, mainly terephthalic acid, and a glycol, mainly ethylene glycol, in the presence of a polycondensation catalyst. 2000~4000 polyester
During melt spinning at a take-up speed of m/min, the polyester is subjected to a polycondensation reaction using an antimony compound as a polycondensation catalyst, and at any stage before the polycondensation reaction is completed, as a crystallization inhibitor. 0.05 mol% of at least one metal carboxylate selected from the group consisting of lithium, sodium, potassium, and calcium, based on the bifunctional carboxylic acid component constituting the polyester.
A polyester obtained by adding the following, and the diameter of spherulites measured with a differential scanning calorimeter is 20 μm
This is a method for spinning polyester fiber, characterized in that it uses a polyester that is less than or equal to Specifically, to measure the diameter of spherulites generated at the cooling crystallization peak measured with a differential scanning calorimeter (DSC), a granular polymer weighing approximately 50 mg is placed in an aluminum capsule of a calorimeter. The temperature was increased at a rate of 20°C/min, and after passing through the glass transition peak, crystallization peak, and melting point peak, the temperature increase was stopped at 305°C, and after holding at this temperature for 5 minutes, the calorimeter was switched off. Turn off and under nitrogen flow (0.6/
(min) Cool at a rate of 9°C/min, and when the peak of the cooling crystallization peak that appears during cooling is reached, the sample is quickly taken out and rapidly cooled in ice water, then sliced into approximately 10μ thin pieces using a microtome. None, use a polarizing microscope to measure the diameter of the spherulites at 500x magnification. Hereinafter, the diameter of the spherulite produced at this cooling crystallization peak will be simply referred to as the spherulite diameter. The polyester referred to in the present invention mainly refers to polyethylene terephthalate consisting of a terephthalic acid component and an ethylene glycol component, but a portion (usually 20 mol% or less) of the terephthalic acid component is replaced with another difunctional carboxylic acid component. It may be a substituted polyester, or a polyester in which a part (usually 20 mol% or less) of the ethylene glycol component is replaced with another diol component. Furthermore, the polyester may be copolymerized or mixed with various additives, such as dye-facilitating agents, flame retardants, antistatic agents, hydrophilic agents, colorants, etc., as necessary. Such polyester is a polyester obtained by a so-called transesterification method, and in the case of polyethylene terephthalate, it is as follows.
A lower alkyl ester of terephthalic acid such as dimethyl terephthalate is transesterified with ethylene glycol to form a glycol ester of terephthalic acid and/or a low polymer thereof, and then heated under reduced pressure until a predetermined degree of polymerization is reached. It is produced by a method of carrying out a polycondensation reaction using an antimony compound as a polymerization catalyst. As such an antimony compound, antimony oxide is preferable, and antimony trioxide is particularly preferable. In the polyester used in the present invention, an aliphatic monocarboxylate of at least one metal selected from the group consisting of lithium, sodium, potassium, and calcium is added as a crystallization inhibitor before the polycondensation reaction of the polyester is completed. A polyester obtained by adding 0.05 mol% or less to the difunctional carboxylic acid component constituting the polyester at any stage, and having a spherulite diameter of less than 20 μm. If a polyester with a spherulite diameter of 20 μm or more is used, crystallization will proceed rapidly with molecular orientation when melt spinning is carried out at a drawing speed of 2000 m/min or more, which is the object of the present invention. high speed
It is not possible to spin polyester fiber without yarn breakage, which can minimize yarn breakage during DTY processing. Although there is no need to particularly limit the lower limit of the spherulite diameter, a diameter of 1 μm or more is usually used. On the other hand, when we examine the crystallization behavior under molecular orientation in more detail, we find that crystal nuclei that interact with polyester molecular chains have a particularly large effect on suppressing crystallization during molecular orientation. Among polyesters with a spherulite diameter of less than 20 μm, pellets of this polyester are particularly
A polyester having a spherulite diameter of less than 30 μm after being boiled for 4 hours at a H ₂ O mixing ratio of 70/30% by volume is preferred. In this way, in order to obtain a polyester with a spherulite diameter of 20 μm, at least one metal carboxylate selected from the group consisting of lithium, sodium, potassium, and calcium is added as a crystallization inhibitor during the polycondensation reaction of the polyester. It can be obtained by adding it before completion. At this time, it is important that the amount of the crystallization inhibitor added is 0.05 mol% or less based on the difunctional carboxylic acid component constituting the polyester, that is, the dialkyl ester of the difunctional carboxylic acid used as the raw material for the polyester. It is. Here, even if more than 0.05 mol% of the crystallization inhibitor is added, the crystallization inhibitory effect almost reaches saturation, and on the other hand, foreign matter in the polymer increases, causing yarn breakage and processing yarn breakage. Otherwise, in addition to causing an increase in pack pressure, the decomposition reaction causes the polyester to become colored. The carboxylic acid salts of lithium, sodium, potassium, and calcium used as such crystallization inhibitors are preferably glycol-soluble aliphatic monocarboxylic acid salts, especially acetate salts, and the lower limit of the amount added is set at the time of high-speed spinning. In relation to the crystallization suppressing effect, the content is preferably 0.001 mol%. In such a method for producing polyester used in the present invention, a method using a homogeneous solution of antimony oxide and aromatic carboxylic acid or a reaction product of both as a polycondensation catalyst, or a method in which antimony oxide is added as a polycondensation catalyst and further aromatic A method of adding a group carboxylic acid is preferred. Examples of the aromatic carboxylic acids used here include terephthalic acid, isophthalic acid, benzoic acid, p-toluic acid, and salicylic acid, and alkyl esters of these can also be used. A homogeneous solution of antimony oxide and aromatic carboxylic acid has a ratio of 1 to 1 for antimony oxide and this antimony oxide.
It is prepared by heating 100 times the molar amount of aromatic carboxylic acid in a solvent while stirring. The solvent used at this time may be any solvent as long as it does not adversely affect the polyester reaction system, but ethylene glycol is particularly preferred. Furthermore, as the reaction product of antimony oxide and aromatic carboxylic acid, antimony salts of aromatic carboxylic acids are preferred. Furthermore, when aromatic carboxylic acid and antimony oxide are added separately, and when antimony oxide is added after the completion of the transesterification reaction, the aromatic carboxylic acid is 1 to 100 times the amount of antimony oxide. It is preferable to add molar amount. The polyester thus obtained has a small amount of foreign matter in the polymer and a spherulite diameter of less than 20 μm, more preferably a polyester having a spherulite diameter of less than 30 μm after the acetic acid aqueous solution treatment at a drawing speed of 2000 μm.
m/min or more, especially 3000 m/min or more, yarn breakage hardly occurs during melt spinning, and even when the obtained fiber is subjected to high-speed DTY processing at a processing speed of 700 m/min, almost no yarn breakage occurs. In addition, when the spinning take-off speed exceeds 4000 m/min, the obtained polyester fibers are extremely highly oriented, and even if such fibers are subjected to DTY processing, processing yarn breakage occurs frequently. In contrast to the polyester used in the present invention as described above, the polyesters that have been commonly used in the past are:
a first step reaction in which dimethyl terephthalate and ethylene glycol are heated in the presence of a transesterification catalyst such as manganese acetate to cause a transesterification reaction to produce a glycol ester of terephthalic acid and/or a low polymer thereof; 0.03-0.04 mol% as a polycondensation catalyst in the reaction product of the first stage
It is produced by a second-stage reaction in which antimony trioxide (component to terephthalic acid) and a phosphorus compound are added as a stabilizer, and the mixture is heated under reduced pressure to undergo polycondensation.
The polyester obtained in this way has a spherulite diameter of
20~30μm, spherulite diameter after acetic acid aqueous solution treatment is 30~40
.mu.m, and if such a polyester is used, the object of the present invention cannot be achieved. Furthermore, a method for producing polyester using a germanium compound such as germanium dioxide as a polycondensation catalyst is also known. However, if such a germanium compound is used according to a conventional method, for example, after the first stage reaction is completed, 0.02 to 0.01 mol% (based on the terephthalic acid component) of the germanium compound and phosphorus compound are added and the polymerization reaction is carried out. In this case, the polyester obtained has a spherulite diameter of 40 to 60 μm, which also fails to achieve the object of the present invention. (Function) According to the spinning method of the present invention, the spinning take-off speed is 2000.
There are few foreign substances in the polyester subjected to high-speed spinning of ~4000 m/min, and as a result of suppressing crystallization during molecular orientation during high-speed spinning, intermediately oriented yarns with high orientation and low crystallinity can be obtained without yarn breakage. Even if the intermediately oriented yarn is subjected to high-speed DTY processing at a processing speed of 700 m/min, it can be stably processed without yarn breakage. (Effects of the Invention) According to the present invention, it is possible to improve both the productivity of the spinning process for producing the intermediately oriented yarn and the DTY processing process of the intermediately oriented yarn obtained, as well as the quality of the processed yarn that is the final product. , further machining speed 700m/
Stable machining is possible even during high-speed DTY machining. (Example) Next, the present invention will be explained in further detail by giving examples. In the examples, parts are parts by weight, and [η] is the intrinsic viscosity determined from the value measured at 30°C in an orthochlorophenol solvent. The L value and b value, which represent the color tone of the polymer, are values measured using a Hunter type color difference meter, and the larger the L value, the more the whiteness is improved, and the larger the b value, the stronger the yellowish tinge. It shows. In addition, 100 yarns (2.5Kg) were broken during spinning.
Winding) Indicated by the number of yarn breaks during winding. Example 1 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol, 0.31 part of manganese acetate as a transesterification catalyst [25 mmol% (hereinafter referred to as mmol%) to dimethyl terephthalate], and 0.10 part of sodium acetate as a crystallization inhibitor ( 15 mmol% of dimethyl terephthalate) was charged into a reactor equipped with a stirrer, a rectification column, and a methanol distillation condenser, and heated from 140°C to 230°C, while distilling methanol produced as a result of the reaction out of the system. A transesterification reaction was carried out. 3 hours after the start of the reaction, the internal temperature was 230℃
320 parts of methanol were distilled out. Here, 0.18 parts of trimethyl phosphate (25 mmol% to dimethyl terephthalate) was added as a stabilizer,
After reacting for 10 minutes, add 0.44 parts of antimony trioxide (30 mmol% to dimethyl terephthalate) as a polymerization catalyst.
was added, and further 2.91 parts of titanium dioxide was added as a matting agent, and the reaction was allowed to proceed for 20 minutes to complete the transesterification reaction. Next, the obtained reaction product was transferred to a polymerization reactor equipped with a stirrer and a glycol condenser, and the polycondensation reaction was carried out while gradually raising the temperature from 230°C to 285°C and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. I let it happen. Total polycondensation reaction time 3 hours 30 minutes [η] 0.64, softening point 263.0℃, hue L value 71.0, b value
7.7. Polyethylene terephthalate with a spherulite diameter of 10 μm without treatment and 15 μm after extraction with acetic acid aqueous solution was obtained. This polymer was spun at a spinning temperature of 290℃ and a discharge amount of 38g/
cooling air velocity 15 m/min (26°C, relative humidity 70
%), and an intermediate orientation system of 115 denier/36 filaments was wound at a take-up speed of 3000 m/min. This intermediately oriented yarn has a △n (birefringence) of 0.055, a hot water shrinkage rate (shrinkage rate after 30 minutes of treatment in 60℃ hot water) of 60%, and a strength of 2.8.
g/denier and elongation of 130%, and there were no yarn breakages during spinning. Next, a high-speed false twisting machine using a urethane disc was used at a stretching ratio of 1.53 times and a heater temperature.
A processed yarn of 75 denier/36 filaments was wound at 220°C and at a yarn speed of 700 m/min. No processing yarn breakage was observed. In addition, the types and amounts of the transesterification catalyst, crystallization inhibitor, and polycondensation catalyst added here, as well as the physical properties and spherulite diameter of the obtained polymer, as well as the physical properties of intermediate orientation, spinning yarn breakage, and processing yarn breakage. The results are also shown in Table 1. Examples 2 to 6, Comparative Examples 1 to 4 The amount of transesterification catalyst added, the type and amount of crystallization inhibitor added, and the type and amount of polycondensation catalyst added in Example 1 were changed as shown in Table 1. The same procedure as in Example 1 was carried out except for the following. The physical properties and spherulite diameter of the obtained polymer, the physical properties of the intermediately oriented yarn, the spinning yarn breakage, and the processing yarn breakage are also listed in Table 1. As is clear from Table 1, by performing melt spinning using the polymer specified in the present invention, spinning and DTY processing could be performed stably without occurrence of either spinning yarn breakage or processing yarn breakage.

【table】

[Table] Comparative Example 5 Using the polymer obtained in Example 1,
Spinning temperature 290℃, discharge rate 40g/min, cooling air velocity
15m/min (26℃, relative humidity 70%), take-up speed 5000
A 75 denier/24 filament yarn was melt spun at m/min. The obtained filament had a Δn of 0.11, an elongation of 58%, and a strength of 40 g/denier. this thread
When DTY processing was performed, there were an extremely high number of broken threads, 17. Example 7 In Example 1, 0.10 parts of sodium acetate (15
Polycondensation reaction was carried out in the same manner as in Example 1, except that dimethyl terephthalate (mmol %) was added at the same time as antimony trioxide, and the resulting polyester was subjected to spinning and simultaneous stretching and false twisting in the same manner as in Example 1. The obtained polyester had a [η] of 0.64 and a softening point of
The temperature was 262.8°C, the hue L value was 70.8, the b value was 7.6, and the spherulite diameter was 9 μm untreated and 14 μm after extraction with acetic acid aqueous solution. Furthermore, there were no yarn breakages during spinning, and no yarn breakage was observed.

Claims (1)

[Claims] 1. Polycondensation reaction of a lower alkyl ester of a difunctional carboxylic acid, mainly terephthalic acid, and a glycol, mainly ethylene glycol, in the presence of a polycondensation catalyst. When melt-spinning the resulting polyester at a take-up speed of 2000 to 4000 m/min, the polyester is subjected to a polycondensation reaction using an antimony compound as a polycondensation catalyst, and at any stage before the polycondensation reaction is completed. , at least 0.05 mol% or less of a metal carboxylate selected from the group consisting of lithium, sodium, potassium and calcium is added as a crystallization inhibitor to the bifunctional carboxylic acid component constituting the polyester. A method for spinning polyester fibers, characterized in that the obtained polyester is used, and the diameter of spherulites measured with a differential scanning calorimeter is less than 20 μm. 2. A polyester in which the diameter of spherulites is less than 30 μm when measured with a differential scanning calorimeter after forming the polyester into pellets and boiling the pellets in a 70% by volume acetic acid aqueous solution for 4 hours. A method for spinning polyester fiber according to claim 1. 3. The method for spinning polyester fibers according to claim 1, wherein the amount of the crystallization inhibitor added is 0.001 mol% or more based on the bifunctional carboxylic acid component constituting the polyester.