JPH0149143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing a glycol solution of a 5-metal sulfoisophthalic acid compound. For more details, see 5
- A method for preparing a highly concentrated glycol solution of 5-metal sulfoisophthalic acid and/or its dialkyl ester, which is suitable for producing a modified polyester copolymerized with a metal sulfoisophthalic acid component.

A known method is to copolymerize a 5-metal sulfoisophthalic acid component to modify polyesters such as polyethylene terephthalate and polybutylene terephthalate, for example to improve dyeability and water absorption. Alternatively, a method is widely used industrially in which the dialkyl ester is made into a glycol solution, foreign substances are removed by filtration, etc., and then added to the polyester synthesis reaction system for copolymerization. However, these 5-metal sulfoisophthalic acid compounds have low solubility in glycol; for example, dimethyl 5-sodium sulfoisophthalate dissolves at most around 7% by weight in ethylene glycol at room temperature. However, if you try to add a large amount of 5-metal sulfoisophthalic acid component to achieve a sufficient effect, excess glycol will be added to the polyester synthesis reaction system, resulting in a large amount of free glycol in the system. Therefore, the amount of diethylene glycol by-produced increases, the softening point of the polymer decreases, and entrainment of monomers to the outside of the system increases. Furthermore, extra thermal energy and time are required to drive off excess glycol, which is disadvantageous in terms of energy and production costs.

The present inventor attempted various studies on methods for dissolving dimethyl 5-sodium sulfoisophthalate in ethylene glycol at a high concentration.
For one thing, if the solution is heated and dissolved, solidification and precipitation will occur and fluidity will be lost when the temperature of the solution drops, making it impractical.Additionally, the method of adding the solution to the polyester reaction system at a high temperature will cause the solution to deteriorate due to high temperature retention. This is difficult due to quality issues and equipment issues, and furthermore, if it is added before the start of the transesterification reaction, the internal temperature of the reaction mixture will increase due to the addition of a high temperature solution, so adding the transesterification reaction catalyst is difficult. This resulted in operational problems such as rapid transesterification and bumping, which made it impossible to use this method.
The present inventor further attempted to prepare a glycol ester of 5-sodium sulfoisophthalate by reacting dimethyl 5-sodium sulfoisophthalate and ethylene glycol in advance. Specifically, dimethyl 5-sodium sulfoisophthalate was introduced into ethylene glycol, heated in the presence of a catalyst, and the methanol produced was distilled off to cause a transesterification reaction. however,
In this case, the reaction takes a long time of 5 to 6 hours,
Furthermore, the viscosity of the resulting reactant increases, resulting in a marked deterioration in handling properties, and furthermore, a separate transesterification reactor is required to carry out this reaction, making it impossible to adopt this method due to cost considerations.

The inventor of the present invention has conducted intensive studies to create a highly concentrated ethylene glycol solution of dimethyl 5-sodium sulfoisophthalate that is easy to handle and has excellent handling properties in a very short time, and has surprisingly found that 5-sodium sulfoisophthalate By simply adding dimethyl acid into ethylene glycol and treating it in the presence of a transesterification catalyst at a temperature of 110 to 120°C for 1 to 2 hours without distilling off methanol, precipitation and solidification will not occur even if the temperature is lowered to room temperature. This method provides a clear solution that does not generate
- It was discovered that a highly concentrated solution of about 40% by weight of sodium dimethyl sulfoisophthalate can be obtained in a low viscosity state with good handling properties, and based on this knowledge, further extensive studies were conducted, and the present invention was completed. It is.

That is, in preparing a highly concentrated glycol solution of 5-metal sulfoisophthalic acid and/or its dialkyl ester, the present invention involves transesterifying 5-metal sulfoisophthalic acid and/or its dialkyl ester with glycol in the presence of a transesterification catalyst. This is a method for preparing a glycol solution of a 5-metal sulfoisophthalic acid compound, which is characterized by heating under total reflux.

The metal of 5-metal sulfoisophthalic acid and its dialkyl ester used in the present invention is not particularly limited, but alkali metals or alkaline earth metals are preferable, and alkali metals are particularly preferable. Further, as the dialkyl ester, one in which the alkyl group is a lower alkyl group having 1 to 4 carbon atoms is preferable. Particularly preferred examples of such 5-metal sulfoisophthalic acid compounds include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, dimethyl 5-sodium sulfoisophthalate, and 5-potassium sulfoisophthalate. dimethyl,
Examples include dimethyl 5-lithium sulfoisophthalate.

As the glycol used in the present invention, any glycol can be used, but preferably alkylene glycols having 2 to 6 carbon atoms, ie, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, and hexamethylene glycol are used. Particularly preferred is at least one glycol selected from ethylene glycol and tetramethylene glycol. For practical applications, it is particularly preferred to choose the same glycol as the glycol component constituting the base polyester with which the 5-metal sulfoisophthalic acid component is to be copolymerized.

The ratio of the above-mentioned 5-metal sulfoisophthalic acid compound to glycol can be selected arbitrarily, but if the amount of 5-metal sulfoisophthalic acid compound used is too large, the viscosity of the final solution will increase. 5.
- The concentration of the metal sulfoisophthalic acid compound in the glycol solution is preferably 7 to 50% by weight based on the solution.

In the present invention, a transesterification catalyst must be present in order to dissolve the above-mentioned 5-metal sulfoisophthalic acid compound in glycol. Any transesterification catalyst can be used as the transesterification catalyst. In particular, metals such as calcium, magnesium, strontium, lithium, sodium, potassium, zinc, manganese, lead, titanium, cobalt, tin, cerium, hydrides,
Carbonates, borates, halides, oxides, hydroxides, aliphatic and aromatic monobasic and dibasic acid salts, organic complex compounds, alcoholates, etc. are used. Particularly preferred examples of such transesterification catalysts include calcium acetate, magnesium acetate, cobalt acetate, lithium acetate, sodium acetate, potassium acetate, zinc acetate, manganese acetate, titanium acetate, cerium acetate, zinc benzoate, titanium tetraisopropoxide, and the like. can be given.
If the amount of the transesterification catalyst used is too small, it will be difficult to dissolve the 5-metal sulfoisophthalic acid compound in glycol beyond its solubility, whereas if it is too large, the catalyst metal of 5-metal sulfoisophthalic acid will be dissolved. Since salt tends to be produced as a by-product, the amount is preferably in the range of 0.1 to 10 mol % based on the 5-metal sulfoisophthalic acid compound. When producing a polyester copolymerized with a 5-metal sulfoisophthalic acid component by a transesterification method, the above-mentioned glycol solution of the 5-metal sulfoisophthalic acid compound is added before the transesterification reaction of copolymerization, The above-mentioned transesterification catalyst present in the solution may also be used as a catalyst for the transesterification reaction in producing the copolyester.

In the method of the present invention, in order to dissolve the above-mentioned 5-metal sulfoisophthalic acid compound beyond its solubility in glycol, it is sufficient to make the above-mentioned transesterification catalyst exist and heat it under total reflux. There is no need to distill the components out of the system to advance the esterification reaction or transesterification reaction to convert the 5-metal sulfoisophthalic acid compound into 5-metal sulfoisophthalic acid di(hydroxyalkyl) ester. This is not appropriate since it results in an increase in viscosity. Heating conditions vary depending on solution concentration, etc., but usually the temperature is 80-180℃.
The temperature range is preferably from 100 to 140°C. The time can range from 30 minutes to 3 hours.

By doing this, a glycol solution of a highly concentrated 5-metal sulfoisophthalic acid compound can be easily obtained in a state with good handling properties at room temperature.
- It becomes possible to produce a polyester copolymerized with a large amount of a metal sulfoisophthalic acid component in high quality and with good productivity.

Further explanation will be given below with reference to Examples. Parts and % in Examples indicate parts by weight and % by weight, respectively.

Example 1 80 parts of ethylene glycol, 20 parts of dimethyl 5-sodium sulfoisophthalate and 0.092 parts of sodium acetate trihydrate (1.0 mol % based on dimethyl 5-sodium sulfoisophthalate) were placed in a dissolution tank equipped with a reflux condenser. and heated to 120°C for 30 minutes under normal pressure.
The temperature was increased to 0.degree. C. and kept at this temperature for an additional 60 minutes under stirring. Then, it was cooled to room temperature to obtain a colorless and transparent solution. No precipitation was observed in this solution even after one year had passed.

100 parts of dimethyl terephthalate, 75 parts of a 20% ethylene glycol solution of the above dimethyl 5-sodium sulfoisophthalate (molar ratio of ethylene glycol to dimethyl terephthalate 1.88, 9.8 mol% of dimethyl 5-sodium sulfoisophthalate to dimethyl terephthalate) , 0.03 part of manganese acetate tetrahydrate (0.024 mol% based on dimethyl terephthalate) was charged into a transesterification tank, and the temperature was raised from 140°C to 230°C over 4 hours under a nitrogen gas atmosphere, and the generated methanol was removed from the system. The transesterification reaction was carried out while distilling off. The resulting product is then treated with orthophosphoric acid.
0.027 part of a 56% aqueous solution (0.030 mol % based on dimethyl terephthalate) and 0.04 part of antimony trioxide were added and transferred to a polymerization can. Then over an hour
Depressurize from 760mmHg to 1mmHg for 1 hour at the same time.
The temperature was raised from 230°C to 285°C over 30 minutes. 1mm
Under reduced pressure below Hg, polymerization was carried out for an additional 30 minutes at a polymerization temperature of 285°C for a total of 2 hours to obtain a copolymer having an intrinsic viscosity of 0.415 and a softening point of 245°C.

Example 2 In place of the sodium acetate trihydrate used in preparing the ethylene glycol solution of dimethyl 5-sodium sulfoisophthalate in Example 1, 0.079 parts of manganese acetate tetrahydrate (0.48 parts based on dimethyl 5-sodium sulfoisophthalate) was added. A pale yellow transparent solution was obtained in the same manner as in Example 1 except that mol %) was used. No precipitation was observed in this solution even after one year had passed.

100 parts of dimethyl terephthalate, 30 parts of ethylene glycol, 38 parts of a 20% ethylene glycol solution of the above dimethyl 5-sodium sulfoisophthalate (5.0 parts of dimethyl 5-sodium sulfoisophthalate)
Mol% vs. dimethyl terephthalate, manganese acetate 4
0.024 mol % aqueous salt to dimethyl terephthalate) was charged to the transesterification vessel (total ethylene glycol to dimethyl terephthalate molar ratio charged 1.88).
Transesterification and polycondensation reactions were carried out in the same manner as in Example 1 without adding a separate transesterification catalyst. A copolymer with an intrinsic viscosity of 0.450 and a softening point of 253.5°C was obtained.

Comparative Example In preparing the ethylene glycol solution of dimethyl 5-sodium sulfoisophthalate in Example 1, the same procedure as in Example 1 was carried out except that sodium acetate trihydrate was not used. A transparent solution was obtained at 120°C, but precipitation occurred during cooling. A similar dissolution test was conducted using various amounts of dimethyl 5-sodium sulfoisophthalate and ethylene glycol, and as a result, the maximum concentration at which a clear solution could be obtained without precipitation at room temperature was 7%.

Using this 7% glycol solution, a polyester was produced by copolymerizing a 5-sodium sulfoisophthalic acid component in the same proportion as in Example 1. That is, in place of 75 parts of the 20% glycol solution used in Example 1, 213.6 parts of the above 7% ethylene glycol solution of dimethyl 5-sodium sulfoisophthalate (molar ratio of ethylene glycol to dimethyl terephthalate 6.2, 5-sodium sulfoisophthalate) Example 1 was repeated except that 9.8 mol % of dimethyl acid to dimethyl terephthalate was used. The resulting copolymer had an intrinsic viscosity of 0.413 and a softening point of 204°C.

In this comparative example, the softening point of the copolymer obtained was too low, so 0.069 parts of sodium acetate trihydrate was added as an ether bond formation inhibitor at the start of the transesterification reaction, and the rest was the same as in the above comparative example. I went to The resulting copolymer had an intrinsic viscosity of 0.413 and a softening point of 231°C.

Claims (1)

[Claims] 1. When preparing a highly concentrated glycol solution of 5-metal sulfoisophthalic acid and/or its dialkyl ester under heating, a transesterification catalyst is used to transesterify 5-metal sulfoisophthalic acid and/or its dialkyl ester with glycol. A method for preparing a glycol solution of a 5-metal sulfoisophthalic acid compound, characterized in that the solution is prepared under total reflux.