JPS6126569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyester, particularly a method for producing polyester suitable for producing a blow molded article or a precursor molded article thereof.

Conventionally, polyvinyl chloride has been widely used as a hollow molded body. However, in recent years, problems with the toxicity of vinyl chloride monomers have arisen, and there is a need to develop alternative materials. Polyester is known as one such material, and polyethylene terephthalate is particularly promising. .

Such polyesters are usually produced by transesterifying a lower alkyl ester of terephthalic acid such as dimethyl terephthalate with ethylene glycol in the presence of a transesterification catalyst, and then polycondensing the resulting transesterification product in the presence of a polycondensation catalyst. It is produced by a reaction and is widely used in fibers, films, etc. due to its excellent properties.

However, when such a polyester is used to mold a hollow molded article, such as a bottle, it becomes cloudy and has the disadvantage that it is difficult to obtain a good product. This clouding is particularly noticeable in thick-walled parts of the molded product and in parts where the cooling rate is relatively slow.

Conventionally, improvements in the color tone and transparency of polyester have been studied for use in fibers or films, but no problem has been raised regarding the clouding described above.

The inventors of the present invention have focused on the fact that this clouding is caused by the catalyst used in the production of polyester, that is, the clouding is due to the crystallization promoting effect of insoluble fine particles generated by the catalyst. As a result of intensive studies on catalysts that do not have a The inventors have discovered that the above drawbacks can be overcome by using a combination of the above germanium compounds and adding this germanium compound at a specific stage during the polyester production reaction, and have thus arrived at the present invention.

That is, in the present invention, a lower alkyl ester of a difunctional carboxylic acid, mainly terephthalic acid, and a glycol, mainly ethylene glycol, are transesterified in the presence of a transesterification catalyst, and then the transesterification product is converted into a germanium compound. In producing polyester by polycondensation reaction in the presence of a manganese compound, a manganese compound is used as a transesterification catalyst, and the germanium compound is added to the transesterification reaction at a stage where the transesterification reaction rate exceeds 80% and reaches 95%. This is a method for producing polyester characterized by adding.

The alkyl esters of difunctional carboxylic acids used in the present invention mainly refer to dialkyl esters of terephthalic acid, especially lower alkyl esters having 1 to 4 carbon atoms.
(below) may be replaced with a lower alkyl ester of a difunctional carboxylic acid other than terephthalic acid. Examples of such difunctional carboxylic acids other than terephthalic acid include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylmethanedicarboxylic acid, diphenyl etherdicarboxylic acid, and diphenoxyethanedicarboxylic acid. , aromatic dicarboxylic acids such as β-hydroxyethoxybenzoic acid, aliphatic dicarboxylic acids such as sebacic acid, adipic acid, and oxalic acid, and aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

Glycol mainly refers to ethylene glycol, and some of it may also include other glycols such as tetramethylene glycol, trimethylene glycol, polyoxyethylene glycol, cyclohexane-1,4-dimethanol, 2,2-bis(4'- Aliphatic, alicyclic, or aromatic glycols such as β-hydroxyethoxyphenyl)propane and bis(4-β-hydroxyethoxyphenyl)sulfone may be substituted.

In the present invention, the manganese compound used as a transesterification catalyst for the lower alkyl ester of difunctional carboxylic acid and glycol may be any manganese compound having transesterification ability, such as manganese carboxylates, halides, Among them, particularly preferred are aliphatic or aromatic carboxylates of manganese such as manganese acetate, manganese propionate, manganese salicylate, and manganese benzoate.
Two or more such manganese compounds may be used in combination. If, for example, calcium acetate or magnesium acetate is used instead of such a manganese compound, even if a germanium compound is used as a polycondensation catalyst and its addition is carried out at a predetermined stage described below, the desired molding time will not be achieved. Clouding cannot be prevented.

The amount of the manganese compound used is suitably in the range of 0.01 to 0.06 mol % based on the lower alkyl ester of difunctional carboxylic acid used as the raw material for the polyester. Moreover, arbitrary conditions are employed for the transesterification reaction carried out in the presence of the manganese compound. For example, the transesterification reaction between dimethyl terephthalate and ethylene glycol is usually carried out by heating to 140 to 250° C. under normal pressure or slightly increased pressure and distilling off the generated methanol.

The germanium compound used as a polycondensation catalyst in the present invention may be any germanium compound having polycondensation catalytic ability, such as crystalline germanium dioxide, amorphous germanium dioxide, germanium oxide such as germanium monoxide, germanium methoxide, Examples include germanium alkoxides such as germanium butoxide, germanium halides, and the like. Among them, germanium oxide and germanium alkoxide are preferred. Furthermore, various methods have been proposed to increase the solubility of germanium compounds in polyester, and soluble germanium compounds obtained by any of these methods can be used. Two or more such germanium compounds may be used in combination.

In the present invention, such a germanium compound is added especially before the transesterification reaction rate exceeds 80% and reaches 95% in the transesterification reaction. If it is added before the reaction rate reaches 80%, self-condensation of ethylene glycol will be promoted in the reaction mixture, and a large amount of ether bonds will be formed in the resulting polyester, resulting in a significant decrease in the softening point of the polyester product. Moreover, the thermal stability of the hollow molded product obtained by molding this material is significantly deteriorated. Furthermore, if the polyester is added after the transesterification reaction rate is higher than 95%, when the resulting polyester is molded into a blow molded product, clouding will become significant and the object of the present invention cannot be achieved. In particular, it is preferable to add it when the transesterification reaction rate reaches a range of 85 to 95%. In addition, the transesterification reaction rate as used in the present invention is indicated by the ratio of the amount of alkanol distilled from the reaction system to the theoretical amount.

The amount of the germanium compound to be used is suitably in the range of 0.001 to 0.1 mol % based on the lower alkyl ester of the difunctional carboxylic acid used as the raw material for the polyester.

After adding the germanium compound, the subsequent transesterification reaction is completed, and then a polycondensation reaction is performed. There is no need to adopt special conditions for the remaining transesterification reaction, and the transesterification conditions described above can be used as they are. In addition, there is no need to use special conditions for the polycondensation reaction.
Any method can be adopted. For example, in the case of polyethylene terephthalate, the above-mentioned transesterification product of dimethyl terephthalate and ethylene glycol is usually prepared under reduced pressure at a temperature above its melting point of 300 ml.
The polycondensation reaction may be carried out by heating to a temperature below .degree. C. and distilling off the generated glycol.

In carrying out the present invention, other polycondensation catalysts such as titanium compounds and antimony compounds may be used in combination with the germanium compound without departing from the purpose of the present invention. 0.001-0.01 mol% based on lower alkyl ester of functional carboxylic acid
It is preferable to use these titanium compounds together.

The above polycondensation reaction can be further carried out in the coexistence of a phosphorus compound, and this is also preferred. Examples of the phosphorus compound used here include phosphoric acid, phosphorous acid, or mono-, di-, or tri-(alkyl, aryl, or cycloalkyl) esters thereof, and specific examples of such esters include monomethyl phosphate, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate,
Examples include hydroxyethyl dimethyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite and the like. It is preferable to use these phosphorus compounds in an amount such that the resulting polyester contains 10 to 200 ppm of phosphorus atoms, and the timing of addition is from the time when the transesterification reaction is substantially completed to the beginning of the polycondensation reaction. Between is preferable.

Further, a cobalt compound may be used for the purpose of improving the color tone of the obtained polyester. The cobalt compound used here is preferably a cobalt aliphatic carboxylate such as cobalt acetate, or a cobalt halide such as cobalt chloride. The amount used is preferably in the range of 0.001 to 0.03 mol% based on the lower alkyl ester of difunctional carboxylic acid used as the raw material for the polyester.

Furthermore, a monofunctional compound such as benzylbenzoic acid, phenolsulfonic acid metal salt, γ-hydroxypropanesulfonic acid metal salt, etc. may be bonded to the terminal end of the obtained polyester, and the thermoplasticity of the obtained polyester is substantially impaired. 3 within the range
It is also possible to copolymerize a polyfunctional compound such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid, etc. In addition, optional additives such as heat stabilizers, oxidation stabilizers, ultraviolet absorbers, colorants, matting agents, fluorescent whitening agents, mold release agents, and antistatic agents may be added to the obtained polyester as necessary. , a printability agent, etc. may be added.

The polyester obtained by the method of the present invention can be melt-molded or melt-molded in combination with other molding methods such as vacuum forming, blow molding, etc. to produce a hollow molded body or its precursor molded body with good thermal stability. It can be easily molded without causing any damage. In addition,
The hollow molded body referred to in the present invention refers to a bottle, cup, pack, etc. that directly packages or contains food and drink or cosmetics.
A molded body having a hollow shape such as a bag or a tray, and its precursor molded body is a molded body that can be formed into a hollow shape by molding or processing, or a hollow body formed by combining with another molded body. It is a molded article that can be formed, and representative examples thereof include packaging films, pack films, textured sheets, and inner plugs of containers.

The present invention will be explained in further detail by giving examples below.
In the examples, parts are parts by weight, and [η] is the intrinsic viscosity determined from the viscosity measured at 35° C. using orthochlorophenol as a solvent. The color tone was expressed by the L value and b value obtained by heat-treating the polymer at 200°C for 20 minutes in a nitrogen stream to crystallize it, and then measuring the surface color with a Color Machine CM-20 model (manufactured by Color Machine Co., Ltd.). . The L value indicates brightness, and the higher the value, the higher the brightness.The higher the b value is on the (+) side, the more yellow it is, and the higher it is on the (-) side, the more blue it is. shows. The softening point was measured by the penetration method. Thermal stability is determined by molding a bottle, measuring the internal volume of the resulting bottle, and then
After being completely immersed in a water tank kept at ℃ and left for 8 hours, it was taken out, and the internal volume was measured again to determine the rate of decrease, that is, the shrinkage rate.

Example 1 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol, and 0.37 parts of manganese benzoate as a transesterification catalyst (based on dimethyl terephthalate)
0.025 mol%) was charged into a reactor equipped with a stirrer, a rectification column, and a methanol distillation condenser.
The methanol produced as a result of the reaction is distilled out of the system by heating from °C to 230 °C, and a transesterification reaction is carried out. When 290 parts of methanol has been distilled out (transesterification reaction rate: 90%), crystalline germanium dioxide is 0.30 parts. parts (for dimethyl terephthalate)
0.06 mol%) was added to proceed with the transesterification reaction, and the internal temperature reached 230°C within 3 hours after the start of the reaction.
320 parts of methanol were distilled off. At this point, the transesterification reaction was completed. After adding 0.20 parts of trimethyl phosphate (0.03 mol% based on dimethyl terephthalate) as a stabilizer, the reaction mixture was transferred to a reactor equipped with a stirrer and an ethylene glycol distillation condenser, and the temperature was gradually increased from 230°C to 280°C. The polycondensation reaction was carried out while raising the temperature to 1 mmHg and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. A polymer with [η] 0.65 was obtained in a total polycondensation reaction time of 3 hours and 30 minutes. The softening point of this polymer is 260.4℃, and the color tone is L.
The value was 82.0, and the b value was -4.1.

The obtained polymer was molded into a 3 oz.
A preform with a length of 160 mm, a wall thickness of 25 mm, and a weight of 38 g was molded. Molding conditions are cylinder set temperature
265℃ (polymer temperature at nozzle part 275℃), injection pressure 500-600Kg/cm ² G, polymer cycle 35 seconds,
The injection mold and core temperature were 20-30°C (water cooling).
The obtained preform was amorphous.
After preheating this preform for 50 to 70 seconds in a heating cylinder maintained at 240 to 280°C, it has a beverage container-shaped cavity with a body diameter of 94 mm, a height of 288 mm, and a mouth diameter of 28 mm. The preform is transferred to a blowing mold maintained at a predetermined mold temperature and stretched in the axial direction with a stretching rod, at the same time at a rate of 3 to 9 kg.
Compressed air of cm ³ ·G was blown into the preform to expand it in the circumferential direction to form a bottle with an internal volume of about 1.5 liters. The blowing time was 1 to 3 minutes.
The resulting bottle had good transparency and no cloudy areas were observed. Also, the shrinkage rate of the bottle is 0.2%
It was hot.

For comparison, the same procedure as in the above Example was carried out except that the crystalline germanium dioxide was added after the end of the transesterification reaction (at the time when the methanol distillation amount was 320 parts). [η] of the obtained polymer is
0.623, the softening point was 260.2°C, the color tone was L value 81.5, b value -4.5, and the shrinkage rate of the obtained bottle was 0.5%, but the 2 mm wall thickness of the mouth part was noticeably cloudy. It had no commercial value.

Example 2 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol, 0.306 parts of manganese acetate (0.025 mol% relative to dimethyl terephthalate) as a transesterification catalyst, and 0.062 parts of cobalt acetate (0.005 mol% relative to dimethyl terephthalate) as a color toner. ) was charged into a reactor equipped with a stirrer, a rectification column, and a methanol distillation condenser, and heated from 140°C to 230°C to cause a transesterification reaction while distilling methanol produced as a result of the reaction out of the system. % of methanol has been distilled off (transesterification reaction rate: 85%)
%) of crystalline germanium dioxide (0.030 mol% relative to dimethyl terephthalate),
The transesterification reaction was further progressed, and the transesterification reaction was completed when 320 parts of methanol had been distilled off. Here trimethyl phosphate as stabilizer
After adding 0.20 parts (0.03 mol % based on dimethyl terephthalate) and 0.085 parts titanium butoxide (0.005 mol % based on dimethyl terephthalate), the reaction mixture was transferred to a reactor equipped with a stirrer and an ethylene glycol distillation condenser. 230℃ to 285
The polycondensation reaction was carried out while gradually raising the temperature to .degree. C. and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. A polymer having [η] 0.665 was obtained in a total polycondensation reaction time of 3 hours and 30 minutes. The softening point of this polymer is 261.4℃,
The color tone had an L value of 83.1 and a b value of -4.5.

The obtained polymer was treated in the same manner as in Example 1 to 1.5
When a small bottle was molded, the resulting bottle had good transparency and no cloudy parts were observed.
The shrinkage rate of the bottle was good at 0.3%.

For comparison, the same procedure as in the above example was carried out except that crystalline germanium dioxide was added at the same time as manganese acetate before the start of the transesterification reaction.
[η] of the obtained polymer was 0.660, and the softening point was
The temperature was 250.1°C, and the color tone was L value 82.3 and B value -3.6. The obtained bottle had good transparency and no cloudy parts were observed, but the shrinkage rate reached 10% and was not of commercial value. Ta.

Example 3 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol, and 0.306 parts of manganese acetate as a transesterification catalyst (0.025 parts per dimethyl terephthalate)
mol%) into a reactor equipped with a stirrer, a rectification column and a methanol distillation condenser, and the mixture was heated from 140°C.
The methanol produced as a result of the reaction was heated to 230°C and the transesterification reaction was carried out while distilling the methanol out of the system. When 290 parts of methanol was distilled out (transesterification reaction rate 9.0%), germanium butoxide was formed.
Adding 0.546 parts (0.03 mol% based on dimethyl terephthalate) and further proceeding with the transesterification reaction,
The transesterification reaction was terminated when 320 parts of methanol had been distilled off. Here, 0.60 parts of trimethyl phosphate (0.09 mol% relative to dimethyl terephthalate) and 0.085 parts of titanium butoxide (0.005 mol% relative to dimethyl terephthalate) were added as stabilizers, and the reaction mixture was then transferred to a stirrer and an ethylene glycol distillation condenser. Transfer to a reactor equipped with
Polycondensation reaction was carried out while gradually raising the temperature from 230°C to 285°C and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. Total polycondensation reaction time: 3 hours and 30 minutes [η]
A polymer of 0.655 was obtained. This polymer had a softening point of 260.8°C, a color tone of L value 80.0, and b value -1.3.

The obtained polymer was treated in the same manner as in Example 1 to 1.5
When a small bottle was molded, the resulting bottle had good transparency and no cloudy parts were observed.
The shrinkage rate of the bottle was good at 0.2%.

For comparison, 0.75 parts of magnesium acetate (0.07 parts for dimethyl terephthalate) was used instead of manganese acetate.
The same procedure as in the above example was carried out except that mol %) was used. The [η] of the obtained polymer was 0.651, the softening point was 261.7°C, the color tone was L value 81.2, b value -3.1, and the shrinkage rate of the obtained bottle was good at 0.2%. The 2 mm thick part of the tube was extremely cloudy and had no commercial value.

Furthermore, for comparison, 0.616 parts of calcium acetate (for dimethyl terephthalate) was used instead of manganese acetate.
The same procedure as in the above example was carried out except that 0.07 mol %) was used. [η] of the obtained polymer is 0.666,
The softening point was 261.4°C, the color tone was L value 82.3, b value -2.8, and the shrinkage rate of the obtained bottle was good at 0.3%, but the 2 mm wall thickness of the mouth part was noticeably cloudy. It had no commercial value.

Claims (1)

[Claims] 1. A transesterification reaction is carried out between an alkyl ester of a difunctional carboxylic acid, mainly terephthalic acid, and a glycol, mainly ethylene glycol, in the presence of a transesterification catalyst, and then the transesterification product is transesterified with germanium. In producing polyester by polycondensation reaction in the presence of a compound, a step in which a manganese compound is used as a transesterification catalyst and the germanium compound is transesterified until the transesterification reaction rate exceeds 80% and reaches 95%. A method for producing polyester characterized by adding. 2. The method for producing polyester according to claim 1, wherein the manganese compound is a manganese carboxylate. 3. The method for producing polyester according to claim 1 or 2, wherein the germanium compound is at least one germanium compound selected from the group consisting of germanium oxides and alkoxides. 4 The germanium compound is added when the transesterification reaction rate in the transesterification reaction is 85% or more95
Claims 1 to 3 that are in stages of % or less
A method for producing polyester according to any one of paragraphs. 5. The method for producing polyester according to any one of claims 1 to 4, wherein the polyester is for use in a blow molded product or a precursor molded product thereof.