JPH0733437B2 - Method for producing flame resistant polyester - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improved process for making flame resistant polyesters.

(Prior Art) Generally, polyester, especially polyethylene terephthalate, has excellent mechanical properties and chemical properties. Therefore, in addition to fibers for clothing, industrial use, films for magnetic tape, photography, capacitors, etc., or Widely used for molded products such as bottles.

By the way, in recent years, there has been an increasing demand for flame resistance of synthetic fibers and various plastic products from the viewpoint of fire prevention. In particular, polyester is used in large amounts in clothing, carpets, curtains, vehicle seats, etc. The establishment of measures is urgent.

Heretofore, various methods for imparting flame resistance to polyester have been proposed, and it is said that the method of incorporating a phosphorus compound into the polyester is effective.

For example, in Japanese Examined Patent Publication No. 55-41610, it is specified as a flame resistance-imparting substance that does not deteriorate the physical properties of molded articles or the operability when producing polyesters used for flame resistant fibers and films. A method of adding and copolymerizing the phosphorus compound of No. 1 has been proposed, but in this method, in order to produce a polyester having a high degree of polymerization, the phosphorus compound to be added is previously prepared as a compound having a divalent ester-forming functional group. However, the production cost of the phosphorus compound to be added is high, and the production is extremely difficult depending on the structure of the phosphorus compound, which eventually leaves an economic problem.

Further, Japanese Patent Publication No. 56-9178 proposes a method of blending a phosphorus compound having a specific structure with a polyester. In this method, a functional group for depolymerizing the polyester, such as PH bond, is proposed. The phosphorus compound having a group has a problem in that it is not practical because it significantly lowers the degree of polymerization of the polyester or blocks the ends of the polyester, thereby lowering the physical properties of the resulting polyester.

Further, in Japanese Patent Laid-Open No. 62-172017, a polyester preliminarily copolymerized with an unsaturated compound (referred to as a prepolymer) is added.
A method for producing a flame resistant polyester by reacting a phosphorus compound having a specific PH bond has been proposed.

However, under the conditions specifically disclosed in this publication, there are variations in the polymerization reaction rate and the ultimate viscosity reached in each production batch, and the obtained polyester becomes a little three-dimensional, and the operation during molding into fibers, films, etc. However, there is a problem in that the properties are deteriorated and the physical properties of the obtained fiber or film are impaired.

(Problems to be Solved by the Invention) The present invention improves the method disclosed in JP-A-62-172017 and economically produces a polyester having excellent flame resistance and without deterioration of physical properties. It is intended to provide a way to do.

(Means for Solving the Problems) The gist of the present invention is as follows.

During the production of polyalkylene terephthalate, the unsaturated compound having an ester-forming functional group is added at a ratio of 1 to 10 mol% with respect to the total acid components constituting the polyester, and the reaction is performed at a temperature not exceeding 260 ° C. When the intrinsic viscosity of the obtained copolyester becomes 0.25 to 0.48,
Add a phosphorus compound represented by the following formula at a ratio of 0.7 to 1.0 times equivalent to the unsaturated bond of the unsaturated compound, and perform polycondensation reaction at a temperature not exceeding 270 ° C until the intrinsic viscosity becomes 0.5 or more. A method for producing a flame-resistant polyester, characterized by:

(R ¹ and R ² are C1-20 alkyl group, C6-20 aryl group, C1
It is the same or different group selected from an alkoxy group of -20 and an aryloxy group of C6-20, and R ¹ and R ² may form a ring with each other. In addition, n is 0 or 1. ) In the present invention, as a base polyester for producing a copolyester, a polyalkylene terephthalate represented by polyethylene terephthalate and polybutylene terephthalate is used. If necessary, isophthalic acid, 4-hydroxybenzoic acid, 5 -Sodium sulfoisophthalic acid, adipic acid, trimellitic acid, diethylene glycol, propylene glycol, 1,4-cyclohexanedimethanol, pentaerythritol, etc. may be contained in a small amount as a copolymerization component.

The unsaturated compound having an ester-forming functional group in the present invention is not particularly limited, but a compound having 1 to 4, preferably 2 carboxyl groups or hydroxyl groups is preferable. Specifically, unsaturated dicarboxylic acid compounds composed of dicarboxylic acids such as fumaric acid, maleic acid, mesaconic acid, citraconic acid, glutaconic acid, itaconic acid or their anhydrides or esters, or 2-butene-1,4-diol. Unsaturated diol compounds such as unsaturated diols such as 1,3-butene-1,2-diol and their esters are mentioned, and maleic anhydride is most preferable.

In the present invention, the proportion of the unsaturated compound having an ester-forming functional group to be copolymerized with the polyester is 1 to 10% by mole, preferably 2 to 8% by mole, and most preferably 2% by mole, based on the total acid components constituting the polyester. ~ 5 mol%. If this copolymerization ratio is too small, the effect of copolymerization will not be substantially exhibited, while if it is too large, some three-dimensionalization has already occurred at the stage of prepolymer production, and the properties of the resulting polyester are significantly deteriorated. , Both cannot obtain excellent polyester.

In the present invention, the prepolymer can be produced by a conventionally known polyester production method, for example, a method of transesterification or esterification followed by polycondensation.

Further, the unsaturated compound having an ester-forming functional group is
May be added before transesterification or esterification reaction,
After transesterification or esterification reaction, it may be added at the stage of producing the prepolymer.

However, the preferred method is to add an unsaturated compound to the polyester forming raw material and carry out the transesterification or esterification reaction under pressure. According to this method, the operation is simple, the scattering of the unsaturated compound can be prevented, and when the unsaturated compound is a dicarboxylic acid compound, the decarboxylation reaction can be suppressed.

In the present invention, specific examples of the phosphorus compound include the following (a) to (m), and the most preferable phosphorus compound is a compound represented by the following formula.

(The benzene ring consists of halogen atoms, C1-20 alkyl groups, C6
It may be substituted with a -20 aryl group, a C1-20 alkoxy group and a C6-20 aryloxy group. ) In the present invention, the amount of the phosphorus compound to be reacted with the prepolymer is required to be 0.7 to 1.0 times the equivalent of the unsaturated bond of the unsaturated compound. If the amount of phosphorus compound is less than this, three-dimensionalization proceeds as the intrinsic viscosity increases, and the excellent properties inherent to polyester are impaired. On the other hand, if the amount of phosphorus compound is greater than this, the intrinsic viscosity does not increase and high polymerization is achieved. I can't get the same degree of polyester.

In the present invention, it is necessary to add the phosphorus compound at a time when the prepolymer has an intrinsic viscosity of 0.25 to 0.48, preferably 0.35 to 0.48.

If added at the time when the intrinsic viscosity is less than 0.25, the intrinsic viscosity is unlikely to increase, while if added at the time when the intrinsic viscosity exceeds 0.48, three-dimensionalization of the polyester tends to occur.

Further, in the present invention, first, a polycondensation reaction is performed under reduced pressure at a temperature not exceeding 260 ° C. until a prepolymer having a predetermined intrinsic viscosity is obtained, and a phosphorus compound is added to the obtained prepolymer. However, it is suitable to carry out the polycondensation reaction under reduced pressure at a temperature not exceeding 270 ° C. If these reaction temperatures are too high, the polyester tends to become three-dimensional.

More specifically, the preferable conditions are as follows. An unsaturated compound is added to a polyalkylene terephthalate forming raw material, and transesterification or esterification is performed under pressure, and then 25% under reduced pressure.
A polycondensation reaction is carried out at a temperature of about 5 to 260 ° C to obtain a prepolymer having an intrinsic viscosity of about 0.45, and the reaction system is added under normal pressure to slightly pressure under a nitrogen gas, and a phosphorus compound is added for 5 to 60 minutes, preferably Ten~
The reaction is carried out for 30 minutes under stirring, and then the polycondensation reaction is carried out under a reduced pressure of 0.01 to 10 torr at a temperature of 260 to 270 ° C until a highly polymerized polyester having an intrinsic viscosity of 0.5 or more is obtained. Is preferred.

Depending on the type of phosphorus compound, the intrinsic viscosity may once drop due to the addition of the phosphorus compound, but the subsequent polycondensation reaction yields a polyester with a high degree of polymerization.

The polycondensation reaction is carried out in the presence of a catalyst, and as the catalyst, conventionally used metal compounds such as antimony, germanium, tin, titanium and cobalt or organic sulfonic acid compounds are used.

The catalyst is added in an amount of 1 × 10 ^{-5 to} 5 × 10 ^-2 mol, preferably 5 × 10 ^-5 , per mol of the acid component constituting the polyester.
˜5 × 10 ⁻³ mol, more preferably 1 × 10 ^{−4 to} 5 × 10 ⁻⁴ mol.

Further, since the phosphorus compound in the present invention may have a slight reducing property, the use of a catalyst weak in a reducing atmosphere such as antimony may not be preferable.

In the present invention, additives such as a stabilizer such as a hindered phenol compound, a fluorescent agent, a color improving agent such as a dye, and a pigment such as titanium dioxide may coexist.

(Operation) After introducing an unsaturated bond into the main chain of polyester,
When a polyester in which a phosphorus atom is pendantly bonded to the main chain of the polyester is obtained by reacting a phosphorus compound having a -H bond, stoichiometrically, the equivalent number of unsaturated bonds and the P- Ideally, the number of equivalents of H bonds is equal.

However, when it is carried out industrially, a part of the added unsaturated compound is scattered, the unsaturated bond is cleaved by thermal decomposition, or the P—H bond of the phosphorus compound reacts with the end group of the polyester. Since the ends of the polyester are closed, the polyester may become three-dimensional, or a polyester with a high degree of polymerization may not be obtained.

For this reason, in the past, in order to obtain a polyester having a high degree of polymerization, even if the physical properties of the polyester are reduced to some extent by three-dimensionalization, the amount of the phosphorus compound is made small and the intrinsic viscosity of the prepolymer is increased. Was taken. Further, in order to increase the intrinsic viscosity, it is said that it is preferable to raise the temperature of the polycondensation reaction.

However, according to the method of the present invention, the temperature of the polycondensation reaction is kept low, and the phosphorus compound is added to the prepolymer having a relatively low intrinsic viscosity in an equivalent number of the P--H bond close to the equivalent number of the unsaturated bond. It was found that the three-dimensionalization of the polyester can be suppressed and a polyester with a high degree of polymerization can be obtained by the reaction.

In the method of the present invention, the reaction temperature is kept low,
Since the intrinsic viscosity of the prepolymer is reduced, it is necessary to lengthen the reaction time a little, but a polyester having a sufficiently high degree of polymerization can be obtained with a reaction time that does not hinder industrial implementation.

(Example) Next, an Example is given and this invention is described.

In the examples, the intrinsic viscosity of the polyester [η]
Is the value measured at a temperature of 20.0 ° C using an equal weight mixture of phenol and ethane tetrachloride as the solvent.

The content of phosphorus atoms in the polyester was quantified by the fluorescent X-ray method.

In addition, flame resistance was measured by using a spinning tester according to a conventional method.
Spin at a spinning speed of 1,400 m / min and draw at a draw speed of 630 m / min so that the residual elongation is 30%.
When 1 g of the material was rolled into a length of 10.0 cm and inserted into a wire coil with a diameter of 10.0 mm, held at an angle of 45 degrees, and ignited by a micro burner with a diameter of 0.64 mm from the lower end to extinguish the fire source, Ignition was repeated again, and the number of ignitions required until all the samples burned out was determined and expressed as the number of ignitions (referred to as the number of flame contact) for 5 samples.

Furthermore, prior to the flame resistance measurement, the strength of the fiber is measured,
The strength characteristics were evaluated in the following four stages.

A: Strength 4.5 g / d or more B: Strength 4.0 to less than 4.5 g / d C: Strength 3.0 to less than 4.0 g / d D: Strength less than 3.0 g / d Example 1 Bis (β-hydroxyethyl terephthalate) and its oligomer A slurry of terephthalic acid [TPA] and ethylene glycol [EG] (EG / TPA molar ratio 1.6) was continuously supplied to the esterification reaction tank containing [BHET] at 255 ° C.
At an average residence time of 6 hours, the esterification reaction was carried out to continuously obtain BHET having an esterification reaction rate of 95%.

After transferring the obtained BHET to a polymerization tank, the temperature was raised to 260 ° C, and a mixed melt of maleic anhydride [MA] and EG at about 50 ° C (molar ratio of MA / EG 1 / 0.8) was added to MA was added so that the amount of MA would be 2.5 mol% with respect to the acid component constituting the polyester, and pressurized with nitrogen gas to 800 torr, and the esterification reaction was carried out at 260 ° C for 45 minutes.

Then, as a catalyst, germanium dioxide 2.5 × 10 ^-4 mol
/; Acid component mole was added as an EG solution, and the pressure of the reaction system was gradually reduced to 75 Torr at 0.3 torr, and polymerization condensation was performed for 90 minutes under these conditions. (At this point, [η] of polyester is
It was 0.45. ) At this point, the reaction system was pressurized with nitrogen gas to 800 torr and the phosphorus compound of formula (h) [9,10-dihydro-9-
The melt of oxa-10-phosphaphenanthrene-10-oxide (HCA)] at about 120 ° C is 2.0 mol% (MA / HCA molar ratio 1 / 0.8) based on the acid component of the polyester. And stirred at 260 ° C for 20 minutes. Then, the pressure of the reaction system was gradually reduced to 30 torr after 30 minutes, and polycondensation was performed for 4 hours under these conditions.

Examples 2 to 5 and Comparative Examples 1 to 3 Polyesters were obtained in substantially the same manner as in Example 1 except that the addition amount of MA and HCA and the [η] of the prepolymer when adding HCA were changed.

In Comparative Example 2, [η] increased only to 0.46.

Example 6 and Comparative Example 4 As the phosphorus compound, the compound of the above formula (d) (Example 6)
Alternatively, a polyester was obtained in the same manner as in Example 1 except that triphenyl phosphate (Comparative Example 4) was used.

Examples 7 to 9 Similar to Example 1 except that maleic acid (Example 7), itaconic acid (Example 8) or 2-butene-1,4-diol (Example 9) was used as the unsaturated compound. To obtain polyester.

Table 1 collectively shows characteristic values and the like of the polyesters obtained in the above Examples and Comparative Examples.

Example 10 A mixture of dimethyl terephthalate [DMT] and 1,4-butanediol [BD] (molar ratio of BD / DMT of 2.0) and tetrabutyl titanate 2.4 × 10 ⁻⁴ mol / mol of acid component as a catalyst were autoclaved. It was charged into the flask and transesterified at 240 ° C.

Then, MA was added to the acid component of the polyester to 2.5
Mol of tetrabutyl titanate 2.6 × 10 ⁴ mol / mol of acid component was added, and the pressure of the reaction system was gradually reduced to 75 Torr to 0.3 Torr and polymerized at 240 ° C. for 90 minutes. . ([Η] of polyester at this point is 0.48
Met. ) Thereafter, Example 1 was repeated except that the polycondensation reaction temperature was changed to 240 ° C.
A polyester was obtained in the same manner as in.

The obtained polyester had an intrinsic viscosity of 0.80, a melting point of 233 ° C, and a phosphorus residual rate of 99%. Further, the number of flame contacts of the fiber from this polyester was 3.2 times, and the strength characteristics were rank B.

(Effects of the Invention) According to the present invention, it is possible to economically and stably produce a polyester having substantially no three-dimensional structure, no deterioration in strength properties, and excellent flame resistance. Is possible.

Claims (4)

[Claims] 1. When producing a polyalkylene terephthalate, an unsaturated compound having an ester-forming functional group is added at a ratio of 1 to 10 mol% with respect to the total acid components constituting the polyester, and the temperature exceeds 260 ° C. When the intrinsic viscosity of the obtained copolyester reaches 0.25 to 0.48, the phosphorus compound represented by the following formula is added at a ratio of 0.7 to 1.0 times equivalent of the unsaturated bond of the unsaturated compound Added in, 270
A method for producing a flame-resistant polyester, which comprises carrying out a polycondensation reaction at a temperature not exceeding ℃ until the intrinsic viscosity becomes 0.5 or more. (R ¹ and R ² are C1-20 alkyl group, C6-20 aryl group, C1
It is the same or different group selected from an alkoxy group of -20 and an aryloxy group of C6-20, and R ¹ and R ² may form a ring with each other. In addition, n is 0 or 1. ) 2. The polyalkylene terephthalate-forming component and the unsaturated compound are reacted with each other, and the polyalkylene terephthalate-forming component and the unsaturated compound are esterified or transesterified under pressure, and then polycondensed.
The method described. 3. The method according to claim 1, wherein the unsaturated compound is maleic anhydride. 4. The method according to claim 1, wherein the phosphorus compound is a compound represented by the following formula. (The benzene ring consists of halogen atoms, C1-20 alkyl groups, C6
It may be substituted with a -20 aryl group, a C1-20 alkoxy group and a C6-20 aryloxy group. )