JPH0465426A - Production of polyester - Google Patents

Abstract

PURPOSE:To obtain a polyester having excellent quality in high productivity by using a water-containing recovered 1,4-butanediol as a part of stock glycol and adjusting the water content in the total raw material to or below a prescribed level before the reaction. CONSTITUTION:A polyester is produced by using a stock glycol composed mainly of 1,4-butanediol. In the above process, the water-containing 1,4-butanediol distilled and recovered in the production process is used as at least a part of the stock glycol and the amount of water in the total raw material composition is adjusted to <=0.5 wt.% (preferably <=0.3 wt.%). The water-content is preferably adjusted to + or -0.03% of the present water-content level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing polyester. More specifically, by reusing 1,4-butanediol containing distilled and recovered water, we stabilized the reaction behavior when manufacturing polyester, improved productivity, and achieved stable quality with no variation from product to product. This invention relates to a method for producing polyester.

(Prior art) 1,4-butanediol (hereinafter referred to as 14-BD)
Bis-4-hydroxybutyl terephthalate and/or bis-4-hydroxybutyl terephthalate and/or Alternatively, a polyester represented by polybutylene terephthalate (hereinafter referred to as PBT) can be obtained by a transesterification reaction to obtain a low polymer thereof (hereinafter referred to as BHT), followed by a polycondensation reaction at high temperature and under high vacuum. Unreacted 1 distilled and recovered during the above reaction,
4- The distillate containing B and D as main components can be reused in subsequent transesterification reactions, either directly or after purification if necessary, by using recovered glycol alone or in combination with fresh glycol. It is being done. Normally, the distillate containing unreacted 1,4-BD as a main component recovered during the polycondensation reaction contains water produced by side reactions such as dehydration of the diol and ring-closing reaction during the reaction. Contains.

(Problem to be solved by the invention) However, when recovered Glyfur (recovered 1.4-BD) is used as at least a part of the raw material glycol in the next transesterification reaction, the activity of the reaction catalyst is inhibited by the water contained. In addition, the reaction time and reaction rate are not constant from batch to batch due to variations in the amount of water, and the color tone, acid value, amount of tetrahydrofuran by-product, etc. of the reactants are also not constant, which affects production efficiency, economics, and product performance. Not good in terms of appearance.

In addition, in order to complete the transesterification reaction within a specified time, measures such as raising the reaction temperature or adding a large amount of catalyst are often used at manufacturing sites, but the water contained in the raw material Glyfur is If the amount was not constant, it was difficult to predict the reaction temperature and the amount of catalyst to be added. For this reason, for example, due to a sudden increase in the distillation rate, DMT sublimate distilled out together with methanol solidifies and adheres in distillation lines such as rectification towers, cooling pipes, pipes, and side pipes, causing blockages in the reaction vessel. This may cause an abnormal increase in internal pressure, or when these are removed, the contents may boil due to the sudden pressure release, and furthermore, the contents distilled due to bumping may solidify and become clogged in the distillation line. , an extremely undesirable phenomenon occurs from the viewpoint of safe and stable operation.

The purpose of the present invention is to use recovered 1.4-BD containing water in part or all of the raw material glycol when producing polyester using glycol whose main component is 1.4-BD. In order to achieve stable productivity and stable performance, we aim to stabilize the distillation start time, change in distillation amount over time, final distillation rate, reaction completion time, amount of THF by-product, acid value of the product, etc. To provide a polyester manufacturing method to obtain a product.

(Means for Solving the Problems) The present inventors have conducted intensive studies to solve the problems, and as a result, have completed the present invention.

That is, the present invention has the following features: 1. When producing polyester using Glyfur, whose main component is 1.4-7 tanediol, as a raw material glycol, 1. Contains water distilled and recovered during production.
A method for producing polyester, characterized in that 4-butanediol is used as at least a part of the raw material glycol, and the content of water in the total raw material composition before the start of the reaction is adjusted to 0.5% by weight or less. and 2. When carrying out the method for producing polyester according to claim 1 continuously or batch by batch, the water content in the total raw material composition before the reaction is the water content set when producing the reference polyester. A method for producing polyester is characterized in that the polyester is adjusted within a range of ±0.03% by weight.

The raw material glycol used in the method of the present invention is 14-B
The main target is ethylene glycol,
Propylene glycol, neopentylene gellicol, hexamethylene glycol, decamethylene glycol, cyclohexanediol, polyoxyethylene glycol,
One type or two or more types of polyoxytetramethylene glycol and the like may be mixed, and can be arbitrarily selected depending on the purpose.

In the present invention, at least a part of the raw material glycol includes 1, which is distilled and recovered during the production of polyester.
4-BD is used. The recovered diol may be used without purification, or may be subjected to distillation, filtration, precipitation, adsorption, decolorization,
It may be used after adding additives, etc., and is not particularly limited.

The alkyl ester component of difunctional carboxylic acid used in the reaction with the glycol component mentioned above is mainly dimethyl terephthalic acid, but also includes isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, etc. Examples include alkyl esters of aromatic dicarboxylic acids such as oxybenzoic acid, aromatic oxyacids such as oxybenzoic acid, aliphatic dicarboxylic acids such as adipic acid, sepatic acid, etc., and one or more of these may be mixed. It's okay. The alkyl ester mentioned above may include one or more of ethyl ester, propyl ester, butyl ester, hydroxyethyl ester, hydroxypropyl ester, hydroxybutyl ester, etc., with the main target being methyl ester. .

In the present invention using recovered 1,4'-BD, first, the water content in the total raw material composition in the reaction vessel before the start of the transesterification reaction is reduced to 0.5% by weight or less, preferably 0.3%.
Adjust to below weight%. If the water content before the start of the transesterification reaction exceeds 0.5% by weight, the reaction time will be significantly delayed, resulting in an increase in the amount of tetrahydrofuran by-product, coloring of the product, increase in acid value, and inhibition of the polycondensation reaction. The negative effects such as
This departs from the purpose of the present invention.

In addition, the water content in the total raw material composition before the reaction when performing the polyester production method continuously or batch by batch is closely related to the water content set when producing the reference polyester. be. The range of deviation from the standard water content varies depending on the type of glycol component and difunctional carboxylic acid alkyl ester component used and the ratio of the used components, but it is ±0.03% by weight, preferably ±0. A range of 0.01% by weight is preferable. That is, the set value of the water content can be any value of 0.5% by weight or less, but around that value ±0.03% by weight, preferably ±0.
Adjust within the range of 01%.

If it exceeds the range of ±0.03% by weight, the distillation behavior and product characteristics such as distillation start time, time-dependent change in distillation amount, final distillation rate, and reaction completion time during transesterification reaction will be affected. This deviates from the purpose of the present invention, which is to ensure stable productivity.

The method for adjusting the water content in the total raw material composition before the start of the reaction is not particularly limited, and any suitable method may be used. For example, 1.4-BD containing water distilled off and recovered during the polycondensation reaction can be used directly without distillation purification, or if necessary, after distillation purification to a predetermined purity, the water content within the scope of the present invention can be used. The difunctional carboxylic acid alkyl ester components may be mixed in such a manner that the difunctional carboxylic acid alkyl ester components are mixed, and if necessary, new glycol may be mixed to adjust the ratio. The content may be adjusted within the range.

The raw material composition in the reaction vessel before the start of the transesterification reaction is substantially composed of a glycol component using some or all of the recovered 1,4-BD and a difunctional carboxylic acid alkyl ester component, and a catalyst etc. are added to advance the reaction.

The catalyst used in the method of the present invention is a known reaction catalyst, and organic titanium compounds are particularly preferred. Examples of the organic titanium compound include (R,O), T i (OR2)4-1 (however, R
3. R7 represents an aliphatic group, alicyclic group, or aromatic hydrocarbon group having 1 to 10 carbon atoms, and n represents a number of 1 to 3 (including a minority). ) and a titanate ester having a cyclic ester structure containing a Ti atom.

Specifically, titanic acid methyl ester, tetra-n-
propyl ester, tetra-n-butyl ester, tetraisopropyl ester, tetraisobutyl ester,
These include tetra-tert-butyl ester, cyclohexyl ester, phenyl ester, benzyl ester, or mixed esters thereof. Among these, tetra-n-propyl ester, tetra-n-butyl ester, tetraisopropyl ester and the like are particularly preferred. These organic titanium compounds can be used alone or in combination of two or more.

The amount of the organic titanium compound added is usually 0.005 to 05% by weight, preferably 0.005% by weight based on the produced polymer.
It is in the range of 1 to 02 f%. If the amount added is less than 0.005% by weight, the effect as a catalyst for transesterification or polycondensation reaction will be insufficient, and especially in transesterification, the reaction time will be prolonged and the amount of by-product of tetrahydrofuran will tend to increase. is recognized. On the other hand, if the amount added is more than 0.5% by weight, not only the catalytic effect becomes saturated, but also the resulting polymer tends to have disadvantages such as decreased transparency and decreased physical properties, which is not preferable.

The organic titanium compound may be added all at once or in portions before or after the adjustment of the water content in the raw material composition, which is a means of the present invention. These organic titanium compounds can be added as a polycondensation reaction catalyst at once or in portions after the end of the transesterification reaction and before the polycondensation reaction, if necessary.

In addition, in the present invention, in order to further increase the transesterification reactivity and further suppress the by-product of tetrahydrofuran, monoalkyltin compounds, monoaryltin compounds,
Organic tin compounds such as dialkyltin compounds, diaryltin compounds, trialkyltin compounds, triaryltin compounds, and tetraalkyltin compounds can also be added. In that case, the amount added is 0 to the generated polymer.
The amount is preferably about 0.01 to 0.5% by weight.

The molar ratio of glycol component/bifunctional carboxylic acid alkyl ester component used during the transesterification reaction is 2.0 or less,
Preferably, it is desirable to set it as 1.05-18. 2.0
If it exceeds 1.4-BD, a large amount of by-product tetrahydrofuran is likely to be produced due to the decomposition of 1.4-BD, which is unfavorable from an economic point of view such as an increase in raw material cost.

In addition, at this time, the transesterification reaction is started by setting the molar ratio of the Glyfur component to the ester component to 0.4 to 1.3, and then the remaining glycol of the total required amount is added to complete the transesterification reaction. You can also do it. In addition, the temperature conditions for the transesterification reaction are 130°C to 24°C.
A temperature range of 0°C is preferable, and at higher temperatures, 1.4-B
The amount of tetrahydrofuran as a by-product due to the decomposition of D tends to increase. Further, this temperature may be maintained at a constant temperature from the start of the transesterification reaction until its completion, or the reaction temperature may be raised at any time from the start of the reaction.

Furthermore, the reaction pressure conditions are usually 200 to 760 mm.
Although the reaction is carried out within the HH range, it is effective to carry out the reaction under reduced pressure in order to suppress the decomposition of 1.4-BD and the hydrolysis of the organic titanium compound. Incidentally, the reaction pressure at this time may be started in a slightly reduced pressure state, and a method may be adopted in which the degree of pressure reduction is increased from the middle of the reaction.

The atmosphere for the transesterification reaction is preferably an atmosphere of an inert gas that does not contain oxygen.

If oxygen is included in the atmosphere, coloring is likely to occur.

The transesterification product thus obtained is subsequently subjected to a polycondensation reaction, and the polycondensation conditions are as follows:
There are no particular limitations, and reaction conditions commonly used in the production of PBT can be used as they are. (
For example, the temperature is 230°C to 250°C, the pressure is 1 mmHg or less, etc.) Furthermore, the polycondensation reaction may be partially or entirely carried out in a solid phase. Further, part or all of it may be performed continuously.

In addition, various additives such as matting agents, optical brighteners, stabilizers, ultraviolet absorbers, flame retardants, antistatic agents, crystal nucleating agents, etc. may be added as appropriate within the range that does not impair the properties of PBT. You may.

(Example) Hereinafter, the present invention will be specifically described with reference to Examples. In addition, in the examples, parts mean parts by weight. In addition, water was determined using a Karl Fischer moisture meter (manufactured by Kyoto Denshi Kogyo Co., Ltd.), and tetrahydrofuran was determined using a gas chromatograph (manufactured by Takasugi Seisakusho).

Acid value is 16
After dissolving at 0° C., the solution was titrated with a 50/I NKOH/benzyl alcohol solution while hot using bromothymol blue as an indicator, and expressed in units of mgKOH/g.

Example 1 Recovery 1 containing 607.2 parts of dimethyl terephthanic acid, fresh 1.4-BD with the composition ratio shown in Table 1, and water in a two-part reaction vessel equipped with a rectifier, a stirrer, and a torque meter. .4
-I prepared the BD. At that time, the mixing ratio of new 1.4-BD and recovered 1.4-BD was adjusted so that the water content of the contents before transesterification was within the range of 0.16±0.03% by weight. , and adjusted by adding water as necessary. After adjusting the water content, the inside of the reaction vessel was made into a nitrogen atmosphere, the internal temperature was raised to 145°C at normal pressure, 0.097 part of tetra-n-butyl titanate was charged, and the temperature was raised to 210°C for 3 hours. The methanol distillate containing tetrahydrofuran and water as a by-product was distilled off from the rectification column while gradually raising the temperature, and a transesterification reaction was carried out. (Performed in 10 batches. The water content after adjustment was 0.161% on average for 10 batches and 2 batches, and the standard deviation was 0.018%.) The reaction end point in each batch was The time point was 3 hours after the addition of butyl titanate. The time from catalyst addition to the start of distillation, percentage of methanol amount in the distillate relative to theoretical distilled methanol amount (i.e., transesterification reaction rate),
Then, the acid value of the product was measured and the results are shown in Table 1. The standard deviation indicating the dispersion was 3.0 minutes for the distillation start time, 0.18% for the transesterification reaction rate, and 0.013 mgKOH/g for the acid value of the product.

Next, 0.292 parts of tetra-n-butyl titanate was added to the transesterification product of each batch according to a conventional method at a vacuum level of 0, 5 mm Hg and a temperature of 250°.
A polycondensation reaction was carried out at C, and when a predetermined torque value was reached, the reaction was terminated and the polymer was taken out. The polycondensation reaction time, acid value of the polymer, and THF by-product rate (expressed as a percentage of the number of moles of DMT charged) from the start of the transesterification reaction to the end of the polycondensation reaction for each batch are as shown in Table 1. there were. The standard deviation of each value is 1.2 minutes for the polycondensation reaction time and 0.014 mgKOH/g for the acid value of the polymer.
The THF by-product rate was 0.007%.

Example 2.3 and Comparative Example 1 As shown in Table 2, Example 2.3 and Comparative Example 1 are the same as No. of Example 1 except that a predetermined amount of water was added before starting the transesterification reaction. 1 (No. 1 in Table 1).

In Comparative Example 1, where the water content of the contents before starting the transesterification reaction exceeds 0.5%, it took more than 2 hours to start distillation after adding the catalyst, and the transesterification reaction rate was as low as 57%. The acid value of the transesterification product is also 2.32 mg
The value was as high as KOH/g.

When this transesterification product was subjected to polycondensation reaction according to a conventional method, there was a large amount of DMT sublimate and the predetermined torque value was not reached. The acid value of the produced polymer is 5.5
The product had a high THF by-product rate of 5 mgKOH/g and 98%, and the color of the polymer was dark brown.

Comparative Example 2 In Comparative Example 2, the width of the water content range after adjusting the content before starting the transesterification reaction was set to 0.16± for N092 and later.
The same procedure as in Example 1 was carried out except that the amount exceeded 0.03% by weight. (Performed in 10 batches. The average water content after adjustment was 0.161% by weight and standard deviation of 0.058% in 10 batches.) As shown in Table 3, the standard deviation showing the variation is: Distillation start time: 7.3 minutes, transesterification reaction rate: 0.58
%, acid value of transesterification product, 0.037 mg
KOH/g, polycondensation reaction time: 2.7 minutes, acid value of polymer: 0.081 mgKOH/g, THF by-product rate: 0
．． It was 21%.

It is understood that, compared to Comparative Example 2, Example 1 has smaller variations in all items.

(Effects of the Invention) The polyester manufacturing method of the present invention uses recovered 1.4-BD containing water in the raw material glycol, but it is possible to improve the distillation start time, the change in distillation amount over time, the final distillation rate, and the reaction rate. Since it is possible to stabilize the completion time, the amount of THF by-product, the acid value of the product, etc., that is, to stabilize the productivity, it is possible to obtain a product with stable performance with little variation from product to product.

Claims (1)

[Scope of Claims] 1. When producing polyester using a glycol containing 1,4-butanediol as a main component as a raw material glycol, 1,4-butanediol containing water distilled and recovered during production is used. Used as at least a part of the raw material glycol,
And the water content in the total raw material composition before the start of the reaction is 0.
．． A method for producing polyester, which comprises adjusting the content to 5% by weight or less. 2. When carrying out the method for producing polyester according to claim 1 continuously or batch by batch, the water content in the total raw material composition before reaction is determined by the water content set when producing the reference polyester. A method for producing polyester, which comprises adjusting the content within a range of ±0.03% by weight.