JPH0616796A - Production of flame-retardant polyester - Google Patents

Abstract

PURPOSE:To obtain a flame-retardant polyester useful for fibers excellent in whiteness and productivity by copolymerization of the recurring units of ethylene terephthalate and a prescribed amount of a specific phosphorus compound under specialized conditions. CONSTITUTION:The copolymerization of the recurring units mainly comprising the ethylene terephthalate unit with 0.5 to 3.0wt.% (based on the P atomic weight) of a phosphorus compound of the formula (R1, R4 are 1 to 21 C alkyl, aryl, monohydroxyalkyl, H; R2 is 1 to 6 C alkyl, aryl; R3 is 1 to 10 C alkylene) is effected together with an antimony compound, a cobalt compound and a titanium compound in such amounts (based on the terephthalic acid component in millimole %) as they satisfy the expressions: (i) 3<=T<=10, (ii) 15<=S<=30, (iii) 3<=C <=15, (iv) 40<=4T+2C+S<=100 where T, S and C are titanium, antimony and cobalt compounds) to prepare oligomers. Then, the polycondensation reaction of the oligomers is carried out in the presence of a catalyst to give the objective polyester.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a flame-retardant polyester. More specifically, it relates to a method for producing a flame-retardant polyester suitable for obtaining a fiber having both high flame retardancy and good hue with high productivity.

[0002]

2. Description of the Related Art In recent years, along with an increase in safety orientation, it is required to impart a high degree of flame retardancy to polyester fibers. To meet such demands, (1) a method of copolymerizing a flame retardant component during polyester production, (2) a method of incorporating a flame retardant in the stage from polyester production to spinning, and (3) a polyester fiber containing a flame retardant A method of treating with the treating agent contained therein has been proposed.

[0003] Among these methods, from the viewpoints of reducing the feeling of the fiber, the deterioration of the spinnability due to the bleeding of the flame retardant at the time of spinning, and the deterioration of the flame retardancy in the post-processing or washing of the fiber (1 (2) is preferable, and as the flame retardant, a phosphorus compound is said to be preferable in terms of safety because it is difficult to generate a toxic gas such as a halogen gas during combustion.

[0004]

However, in the method of copolymerizing a trifunctional ester-forming compound such as a phosphoric acid ester as a phosphorus compound (Japanese Patent Publication No. 49-22958, etc.), a polyester having a good whiteness is obtained. However, when the copolymerization ratio is increased, gelation is likely to occur, so that a sufficient amount cannot be copolymerized and the flame retardance becomes insufficient. On the other hand, when a specific bifunctional ester-forming phosphorus compound is used, With the method of copolymerization (Japanese Patent Publication No. 53-13479), the amount of copolymerization can be increased without the problem of gelation, so that sufficient flame retardancy can be obtained, but the polymerization rate during polyester production is slow and the hue is good. There was a problem that it was difficult to obtain a good polyester.

The present invention solves the above-mentioned problems of the prior art and provides a method for producing a polyester having high flame retardancy and good hue, which is suitable for producing a flame retardant polyester fiber with high productivity. It is intended to be provided.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that when a specific bifunctional phosphorus compound is copolymerized with polyester, a specific polycondensation catalyst is combined in a specific amount. It was found that the problems of flame retardancy and polymer hue can be solved at the same time by using the above-mentioned materials, and thus the present invention has been accomplished.

That is, according to the present invention, the ethylene terephthalate unit is the main repeating unit, and the following (I)
The phosphorus compound represented by the formula has a phosphorus atomic weight of 0.5 to
In producing a polyester copolymerized by 3.0% by weight, an antimony compound, a cobalt compound and a titanium compound are added as polycondensation catalysts in an amount that simultaneously satisfies the following formulas (a) to (d). Flame retardant polyester manufacturing method,

[0008]

[Chemical 2]

(In the formula, R ₁ and R ₄ each have 1 to 2 carbon atoms.
1 alkyl group, aryl group, monohydroxyalkyl group or hydrogen atom, R ₂ represents an alkyl group or aryl group having 1 to 6 carbon atoms, and R ₃ represents an alkylene group having 1 to 10 carbon atoms) (a) 3 ≦ T ≦ 10 (b) 15 ≦ S ≦ 30 (C) 3 ≦ C ≦ 15 (d) 40 ≦ 4T + 2C + S ≦ 100 (In the formula, T, S and C are titanium compounds and antimony compounds respectively added as a polymerization catalyst. And the amount of addition of the cobalt compound to the terephthalic acid component (representing mmol%) are provided.

The present invention will be described in detail below. The polyester referred to in the present invention mainly comprises a polyester having an ethylene terephthalate unit as a main repeating unit and a difunctional phosphorus compound represented by the following general formula (I) as a flame retardant component. Other copolymerization components may be copolymerized within a range that does not impair the purpose.

[0011]

[Chemical 3]

In the formula, R ₁ and R ₄ are an alkyl group having 1 to 21 carbon atoms, an aryl group, a monohydroxyalkyl group,
Or a hydrogen atom, R ₂ is an alkyl group having 1 to 6 carbon atoms or an aryl group, and R ₃ is an alkylene group having 1 to 10 carbon atoms. Specific examples preferably used include, for example, (2-carboxyethyl) methylphosphinic acid, an ester of (2-carboxyethyl) methylphosphinic acid and ethylene glycol, (2-carboxyethyl) ethylphosphinic acid, (2-methoxycarbonyl). Ethyl) methylphosphinic acid, [2-β-hydroxyethoxycarbonyl) ethyl] methylphosphinic acid, (2
-Methoxycarbonylethyl) methyl phosphinate and the like can be mentioned. Even if these are used alone,
They may be used in combination, or may be those obtained by further condensing these compounds.

The copolymerization amount of such a phosphorus compound is such that the phosphorus atom content in the obtained polyester is 0.3 to 3.0% by weight, preferably 0.6 to 2.0% by weight. If the copolymerization amount of the phosphorus compound is less than the above range, the flame retardancy is poor, whereas if it exceeds the above range, the physical properties of the polyester are greatly deteriorated, which is not preferable.

Next, in order to copolymerize the phosphorus compound with polyester, it may be added at any stage of the polyester production. However, since the polycondensation time is prolonged in the latter stage of the polycondensation reaction, the esterification reaction or ester It is desirable to add during the period from when the exchange reaction is substantially completed to the beginning of the polycondensation reaction. Further, the phosphorus compound may be previously dispersed and dissolved in a diol component or another solvent, or may be added after being heated and reacted with the diol component in advance.

The present invention is most characterized in that, when the polycondensation reaction is carried out after the addition of the phosphorus compound, an antimony compound, a cobalt compound and a titanium compound are used together in a specific ratio as a polycondensation catalyst. That is,
It is important to use it in a ratio that satisfies the following expressions (a) to (d). (A) 3 ≦ T ≦ 10 (b) 15 ≦ S ≦ 30 (C) 3 ≦ C ≦ 15 (d) 40 ≦ 4T + 2C + S ≦ 100

Here, T, S, and C are the amounts of the titanium compound, antimony compound, and cobalt compound added as the polymerization catalyst, respectively, and represent the ratio (mmol%) to the terephthalic acid component. When the addition amount of the titanium compound is less than the above range, the polycondensation reaction rate becomes slow, while when it exceeds the above range, the color tone of the obtained polymer is lowered (the b value by a Hunter color difference meter becomes high), which is preferable. Absent.

If the amount of the antimony compound added is less than the above range, the polycondensation reaction becomes slow, while if it exceeds the above range, the L value of the polymer obtained by a Hunter color difference meter decreases, which is not preferable. When the amount of the cobalt compound added is less than the above range, the b value becomes high with respect to the color tone of the polymer to be obtained, while when it exceeds the b value, the b value tends to be too low and the L value tends to decrease, which is preferable. Absent.

Further, when T, S and C do not satisfy the above formula (d) and 4T + 2C + S is less than the above range, the polycondensation reaction rate becomes insufficient. It is not preferable because the color tone deteriorates.

In the present invention, the time for adding the polycondensation catalyst is not particularly limited as long as it is before the start of the polycondensation reaction, and it may be carried out according to a conventionally known method. For example,
Manganese acetate was added as a transesterification catalyst using dimethyl terephthalate and ethylene glycol, and the transesterification reaction was carried out while gradually raising the temperature. The obtained reaction product was subjected to the polycondensation with the phosphorus compound represented by the above formula (1). It can be produced by adding a catalyst and then gradually raising the temperature to a high vacuum of 1 mmHg or less and raising the temperature to carry out a polycondensation reaction at a temperature of 250 to 300 ° C.

In the method for producing a flame-retardant polyester according to the present invention, generally used additives such as tetraethylammonium hydroxide which is an ether bond inhibitor, titanium dioxide which is a matting agent, and other difficult additives. It is also possible to add a combustion aid, carbon black, an antistatic agent, a heat stabilizer, etc. in combination.

[0021]

In the past, a method of copolymerizing a difunctional ester-forming phosphorus compound with polyethylene terephthalate in order to satisfy both high flame retardancy and mechanical properties at the same time has been disclosed, for example, in Japanese Patent Publication No. 53-13479. It is proposed in the gazette and the like. However, the phosphorus compound used here is presumed to have a low copolymerizability with polyethylene terephthalate, and the polycondensation reaction time of the antimony polycondensation catalyst used alone when polycondensing polyethylene terephthalate alone is long. If a polyester having a long length and a sufficiently high degree of polymerization is to be obtained, there is a problem that the color tone of the polymer is deteriorated (the L value measured by a Hunter color difference meter becomes low and the b value becomes large).

On the other hand, in the production method of the present invention, although the detailed reason is not clear, the polycondensation reaction rate is improved by using the compounds of titanium, antimony and cobalt in a specific ratio, Combined with the effect of shortening the polycondensation reaction time, the color tone of the resulting polymer is significantly improved.

Therefore, from the flame-retardant polyester according to the present invention, for example, polyester fibers having excellent mechanical properties, good whiteness and high flame retardancy can be easily obtained, and its industrial value is high. It is extremely large.

[0024]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the part in an Example shows a weight part. Various characteristics were evaluated by the following methods.

(1) Intrinsic viscosity [η] Measured at 30 ° C. with orthochlorophenol as a solvent,
The relative viscosity was determined by a conventional method.

(2) Color tone (L value, b value) The L value and the b value representing the color tone of the polymer are values measured by using a Hunter color difference meter, and the larger the L value, the higher the whiteness. The larger the b value, the stronger the yellowish tint. That is, the larger the L value and the smaller the b value, the better the color tone.

(3) Phosphorus content Fluorescent X-rays derived from the phosphorus atom of the obtained polymer were measured and calculated from the emission intensity thereof.

(4) Flame retardance The limiting oxygen index (LOI value) was measured and evaluated according to a conventional method.

[0029]

Example 1 100 parts of dimethyl terephthalate, 54 parts of ethylene glycol, 0.063 parts of calcium acetate (69
mmol% to dimethyl terephthalate) and cobalt acetate 0.
Charge 013 parts (10 mmol% with respect to dimethyl terephthalate) to a reactor equipped with a stirrer, a rectification column and a methanol distillation condenser, gradually raise the temperature from 140 ° C., and distill the methanol produced as a result of the reaction out of the system. The transesterification reaction was performed while letting it out. The internal temperature is 220 after 3 hours from the start of the reaction.
C. was reached and 33 parts of methanol was distilled off. Here, 0.058 parts of trimethyl phosphate as a stabilizer (80 mm
ol% to dimethyl terephthalate) and after 10 minutes 0.072 parts antimony trioxide (20 mmol% to dimethyl terephthalate) and titanium acetate 0.0045 parts (5 mmol%)
Dimethyl terephthalate) was added, and after 10 minutes, 6.0 parts of a product obtained by reacting 2-carboxyethylmethylphosphinic acid as a phosphorus compound with ethylene glycol (1: 1 weight ratio) by heating was added, After a further 10 minutes, 0.07 part of titanium oxide was added. Next, the obtained reaction product was transferred to a reactor equipped with a stirrer and a glycol distillation condenser, and the polycondensation reaction was performed while gradually raising the temperature from 230 ° C to 282 ° C and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. Was done. Track the melt viscosity of the reaction system,
The polycondensation reaction was terminated when [η] reached 0.660.

The time required for the polycondensation reaction was 210 minutes, and there was no problem in productivity. Further, the color tone of the obtained polymer was as good as L value 65.0 and b value 4.1,
The phosphorus content was 0.685% by weight.

Subsequently, the obtained polymer was spun according to a conventional method at a spinning temperature of 285 ° C. and wound at a speed of 1500 m / min to obtain an unstretched yarn. Each undrawn yarn was bundled into a tow of about 500,000 denier in terms of drawn yarn. At a liquid bath temperature of 75 ° C. so that the residual elongation of the drawn yarn becomes about 30%,
Liquid bath drawing was performed at a draw ratio of 3.5 to 4.5 times. Subsequently, a constant length heat treatment was performed on a heating drum at 165 ° C. for about 5 seconds, crimping was applied, and after drying at 120 ° C., a short fiber was obtained by cutting into 38 mm. Using this short fiber, a spun yarn is made by a usual method to make a plain weave with a basis weight of 250 g / m ² ,
Table 1 shows the flame retardancy evaluation results of the fabrics which were heat-set at 0 ° C for 1 minute with a constant length.

[0032]

Examples 2 to 5 and Comparative Examples 1 to 8 Polymers were obtained in the same manner as in Example 1 except that the polycondensation catalyst used was changed as shown in Table 1. The results are also shown in Table 1.

[0033]

[Table 1]

Claims (1)

[Claims] 1. A polycondensation catalyst for producing a polyester in which an ethylene terephthalate unit is a main repeating unit and a phosphorus compound represented by the following formula (I) is copolymerized in an amount of 0.5 to 3.0% by weight as a phosphorus atom weight. As a method for producing a flame-retardant polyester, an antimony compound, a cobalt compound, and a titanium compound are added in an amount satisfying the following formulas (a) to (d) at the same time. [Chemical 1] (In the formula, R ₁ and R ₄ are each an alkyl group having 1 to 21 carbon atoms, an aryl group, a monohydroxyalkyl group or a hydrogen atom, R ₂ is an alkyl group having 1 to 6 carbon atoms or an aryl group, R ₃ Represents an alkylene group having 1 to 10 carbon atoms) (a) 3 ≦ T ≦ 10 (b) 15 ≦ S ≦ 30 (C) 3 ≦ C ≦ 15 (d) 40 ≦ 4T + 2C + S ≦ 100 (wherein T , S and C represent the addition amount (mmole%) of the titanium compound, antimony compound and cobalt compound added as the polymerization catalyst to the terephthalic acid component, respectively)