JPH10212345A - Production of polyester excellent in moldability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a product reduced in the formation of foreign matter such as a sublimate in melting and being excellent in molding stability and quality by melt-reacting a polyester consisting of repeating ethylene terephthalate units and prepared by using an antimony compound as the catalyst with a cyclic acid anhydride, cutting the reaction product into chips and bringing the chips into contact with heated water or heated steam. SOLUTION: A polyester mainly consisting of repeating ethylene terephthalate units and prepared by using an antimony compound as the catalyst is reacted by melt kneading with 0.01-3.0 equivalents, per equivalent of the terminal hydroxyl groups, of a cyclic acid anhydride represented by the formula (wherein A is a divalent aromatic or aliphatic organic group), the reaction product is cut into chips, and the chips are brought into contact with heated water or heated steam. The contact with heated water is performed by immersing the chips in hot water of usually 80-150 deg.C for 2-5hr. The contact with heated steam is performed usually by contacting them with steam at 80-150 deg.C or an inert gas (or air) containing steam for 2-10hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the stability during molding and the quality of a molded product, which is excellent in thermal stability and low in generation of foreign substances such as sublimates during melting. The present invention relates to a method for producing a polyester having excellent moldability and capable of obtaining fibers having excellent quality by suppressing foreign matters deposited around a die.

[0002]

2. Description of the Related Art Polyester represented by polyethylene terephthalate has many excellent physical properties.
It is widely used for resins, films, etc., and its fiber application is not limited to clothing but its application range is extremely wide for industrial textile applications. These polyesters are usually processed into various products by melt molding.For example, in the case of fibers, the polyester is melted, discharged from a die to form a fibrous form, and then subjected to a stretching heat treatment to form a practical fiber. ing.

However, in this melt spinning, the polymerization catalyst used for producing the polyester, particularly the antimony compound, tends to accumulate as a foreign matter around the spinneret with the lapse of spinning, damaging the fiber or preventing the flow of the fiber. It may be disturbed or fall off and mixed as foreign matter in the fiber.
Eventually, it has a serious drawback that it causes yarn breakage, lowering the yield and lowering the product quality. As a method for improving the moldability by reducing the generation of sublimates due to the polymerization catalyst during melt molding of polyester, for example, for melt spinning, a polyester chip is treated with water in advance to reduce the polymerization catalyst. A deactivation method (Japanese Patent Application Laid-Open No. Hei 7-286046) and a method of adding a phosphonium sulfonate compound during the production of polyester (Japanese Patent Application Laid-Open No. Hei 6-9767) have been proposed, but their effects are insufficient. It is. As another method, attempts have been made to apply a release agent such as a silicon compound or the like in advance around the spinneret or to change the material of the spinneret. However, a sufficient effect has not yet been recognized.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to reduce the generation of foreign substances such as sublimates at the time of melting and to improve the stability of molding processing. An object of the present invention is to provide a method for producing a polyester, which is excellent and can obtain a product having excellent quality.

[0005]

Means for Solving the Problems Foreign matter deposited at various places during melt molding of polyester impairs moldability and lowers the quality of the obtained molded product. For example, in the case of melt spinning, It accumulates as spinneret foreign matter around the spinneret. The foreign matter is mainly composed of an antimony compound used as a polymerization catalyst for polyester and a sublimable organic compound which is a by-product of polyester. In particular, the antimony compound has an important role as a foreign matter in a base. Therefore, in order to suppress the generation of foreign matter, it is necessary to stabilize the antimony compound.

The inventors of the present invention have made intensive studies on the reduction of foreign matter generation from such a viewpoint. As a result, the concentration of terminal hydroxyl groups in the polyester was reduced, and the demonstrating treatment of the antimony polymerization catalyst was carried out. The present inventors have found that generation of foreign matter is suppressed, and have reached the present invention.

In other words, according to the present invention, "a polyester having a main repeating unit of ethylene terephthalate using an antimony compound as a polymerization catalyst is represented by the following formula (Chemical Formula 2) based on the content of terminal hydroxyl groups of the polyester. At least one kind of cyclic acid anhydride to be used.
A method for producing a polyester having excellent moldability, which comprises melting and mixing 0 equivalents, reacting, cutting into chips, and then bringing the cut chips into contact with heated water or heated steam.

[0008]

Embedded image

Wherein A is a divalent aromatic or aliphatic organic group. ]] Is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester referred to in the present invention is
The main repeating unit is a polyester composed of ethylene terephthalate, preferably polyethylene terephthalate, but in a small proportion, for example, 15 mol% or less, preferably 10 mol%, based on all acid components constituting the polyester.
Below, particularly preferably 5 mol% or less of a copolymer component may be contained. As the preferably used copolymer component, for example, isophthalic acid, naphthalenedicarboxylic acid,
Diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, p-oxybenzoic acid, adipic acid, sebacic acid,
Dicarboxylic acid components such as succinic acid; poly (oxyalkylene) glycols such as propylene glycol, tetramethylene glycol, diethylene glycol and polytetramethylene glycol; cyclohexanedimethanol; ethylene oxide adduct of bisphenol-A; ethylene oxide adduct of bisphenol-S And the like.

The intrinsic viscosity of the polyester (measured at 30 ° C. using orthochlorophenol as a solvent) is not particularly limited, but is preferably in the range of 0.5 to 0.8.

[0012] Further, the polyester targeted by the present invention is:
Although an antimony compound is used as a polymerization catalyst, the antimony compound may be a conventionally known one, and most commonly, antimony trioxide, antimony acetate and the like are used. Of course, other than the antimony compound, a titanium compound, a germanium compound, a tin compound, a zinc compound, or the like may be used in combination as a polymerization catalyst. If the amount of the antimony compound in the polyester is too small, the polymerization rate during the melt polymerization of the polyester will be slow. It is preferable that the amount is as small as possible, for example, 10 to 50 mmol%, particularly 20
~ 30 mmol% is suitable.

In the polyester, various modifiers usually blended with the polyester, for example, a matting agent, an antistatic agent, a heat stabilizer, a light stabilizer, a flame retardant, so long as the object of the present invention is not impaired. Even if a coloring agent, an antioxidant, a dyeing assistant, etc. are added, there is no problem.

In the present invention, at least one of a cyclic acid anhydride represented by the following formula (Formula 3) is added to the above-mentioned polyester.
It is necessary to melt and react the seed with 0.01 to 3.0 equivalents, preferably 0.05 to 1.0 equivalent, based on the terminal hydroxyl group content of the polyester. When the mixing amount of the cyclic acid anhydride is less than the above range, the foreign matter suppressing effect aimed at by the present invention is insufficient, while when it exceeds the above range, it is accompanied by a thermal decomposition reaction or sublimation of the acid anhydride. It is not preferable because contamination of equipment and problems in quality of the obtained polyester are easily caused.

[0015]

Embedded image

In the formula, A represents a divalent aromatic or aliphatic organic group. Such cyclic acid anhydrides include, for example, phthalic anhydride, trimellitic acid, pyromellitic acid, naphthalenedicarboxylic anhydride, aromatic carboxylic anhydrides such as diphenyldicarboxylic anhydride, succinic anhydride, cyclohexanedicarboxylic anhydride These may be used in combination of two or more.

In order to cause the cyclic acid anhydride to undergo a melt reaction with the polyester, it may be added and melted and mixed at a later stage of the polyester polymerization reaction or at any stage from the end of the polymerization reaction to the formation of chips. Note that since the latter stage of the polyester polymerization reaction is generally carried out at a high temperature, it is necessary to devise a method particularly when a compound that easily evaporates is used. For example, there can be mentioned a method in which once the compound is added, the pressure is once increased, the reaction is carried out for a predetermined time, and then the polymerization reaction is continued again if necessary.

Depending on the conditions under which the cyclic acid anhydride is melt-mixed and reacted with the polyester, undesirable phenomena such as an increase in sublimable substances may occur.
It is important to optimize conditions such as reaction temperature, reaction time, degree of vacuum, and stirring conditions (such as stirring effect and shearing force).

In the present invention, it is essential that the cyclic acid anhydride is melt-mixed and reacted as described above, cut into chips, and then the cut chips are brought into contact with heated water or steam. is there. As a result, the active antimony element in the polyester is changed to an inactive form, and the generation of sublimates during melt molding is suppressed. As a result, the stability during molding and the quality of the resulting molded product are improved. I do.

Here, the effect of contact between the polyester chips and the heating water is too small if the temperature is too low, and if the temperature is too high, hydrolysis of the polyester is likely to occur. On the other hand, if the contact time is too short, the effect is reduced, and if it is too long, hydrolysis of the polyester is likely to occur. For this reason, a temperature of 8
It is preferable to carry out by immersing in hot water of 0 to 150 ° C. for 2 to 5 hours.

On the other hand, the contact between the polyester chips and the heated steam is usually carried out at a temperature of 80 to 150 ° C. with steam or an inert gas (or air) containing steam for 2 to 10 hours.
It is preferably carried out by contacting for 2 to 5 hours.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
In the examples, parts are parts by weight, and each evaluation item is measured according to the following method.

<Intrinsic Viscosity IV> The intrinsic viscosity was measured at 30 ° C. using orthochlorophenol as a solvent.

<Hue L value, b value> The values are measured using a Hunter type color difference meter. The larger the L value, the whiter the color. The lower the b value, the lower the yellow tint.

<Evaluation of Sublimation Property> Forty parts of the polyester is put in a stainless steel cylindrical container (inner diameter: 50 mm), and a stainless steel lid with a cooling jacket to which an aluminum plate can be detached is attached. The container was placed in a bath at 305 ° C. while conducting cooling water, and the container was heated for 3 hours at a pressure of 0.1 to 0.3 mmHg, and the weight of the material accumulated on the aluminum plate was measured. In addition, the amount of antimony element therein was quantitatively analyzed.

<Terminal hydroxyl group content> Measured by an alkali titration method according to a conventional method.

<Height of spinneret foreign matter> The polyester dried at 140 ° C. is melted at 295 ° C. and discharged at a discharge rate of 15 g / min from a spinneret having 36 spinning nozzles having a hole diameter of 0.3 mm at a winding speed of 2,000 m. After spinning for 2 days at
The height of the spinneret foreign matter deposited around the spinning nozzle was measured.

Examples 1-3 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol and 0.31 part of manganese acetate tetrahydrogen were stirred with a stirrer, a rectification column and a condenser.
, And the mixture was heated from 140 ° C. to 230 ° C., and subjected to a transesterification reaction while distilling off methanol produced as a result of the reaction. After the internal temperature reached 230 ° C., 0.22 parts of trimethyl phosphate was added and reacted for 10 minutes. Then, 0.44 parts of antimony trioxide was added as a polymerization catalyst, and 2.91 parts of titanium dioxide was glossed. Added as eraser. After reacting for 20 minutes, it is transferred to a polycondensation reactor and
While gradually increasing the temperature from 30 ° C. to 290 ° C., the polymerization reaction was carried out while reducing the pressure from normal pressure to a high vacuum of 1 mmHg. When the intrinsic viscosity becomes about 0.64 as viewed from the stirring power, the vacuum is broken with nitrogen, and then, while stirring, phthalic anhydride is added in an amount shown in Table 1 and pressurized to 1 atm with nitrogen. A stirring reaction was performed for 10 minutes. The obtained polyester was discharged from the reactor at 290 ° C. under nitrogen gas pressure, cooled with water, and cut into chips.

Next, the obtained chip was brought into contact with heated water under the conditions shown in Table 1, then air-dried, and further heated at 160 ° C. for 6 hours.
Circulation heat treatment was performed with heated air for hours. Table 1 shows the evaluation results of the quality and the spinnability of the obtained polymer.

Comparative Examples 1-2 Polyester chips obtained by polycondensation in the same manner as in Example 1 except that phthalic anhydride was not added were brought into contact with heated water under the conditions shown in Table 1, and then air-dried. Further, circulating heat treatment was performed with heated air at 160 ° C. for 6 hours. Table 1 shows the evaluation results of the quality and the spinnability of the obtained polymer.

Comparative Example 3 A polyester chip obtained by polycondensation in the same manner as in Example 1 was dried with heated air at 160 ° C. for 6 hours. Table 1 shows the evaluation results of the quality and the spinnability of the obtained polymer.

[0032]

[Table 1]

[0033]

According to the production method of the present invention, even when an antimony compound is used as a polymerization catalyst, the concentration of terminal hydroxyl groups (glycol groups) is reduced by reacting a cyclic acid anhydride with terminal hydroxyl groups, and at the same time heating water or Since the activity of the antimony element is reduced by heating steam, a polyester having excellent thermal stability can be obtained, and the generation of various foreign substances including a sublimable substance is suppressed during melt molding. As a result, for example, in the case of melt spinning, the accumulation of foreign substances around the spinneret is significantly reduced, the stability of the spinning and drawing step is improved, and polyester fibers having good quality can be obtained with high productivity. Also, in the field of resins and films, it is possible to efficiently obtain products with improved moldability and less foreign matter.

Claims (4)

[Claims] 1. A polyester having a main repeating unit of ethylene terephthalate using an antimony compound as a polymerization catalyst and a cyclic acid anhydride represented by the following formula (Chem. 1) based on the terminal hydroxyl group content of the polyester. Excellent formability characterized by melting and mixing at least one of the components in an amount of 0.01 to 3.0 equivalents and reacting, cutting into chips, and then bringing the cut chips into contact with heated water or steam. Method of producing polyester. Embedded image [Wherein A is a divalent aromatic or aliphatic organic group. ] 2. The process according to claim 1, wherein the cyclic acid anhydride is phthalic anhydride. 3. The temperature of the heated water or steam is 80-1.
The method for producing a polyester excellent in moldability according to claim 1 or 2, wherein the temperature is 50 ° C. 4. The contact time to heated water or heated steam is 2
The method for producing a polyester excellent in moldability according to any one of claims 1 to 3, which is for 5 to 5 hours.