KR100322954B1 - Manufacturing method of thermoplastic polyester - Google Patents

Abstract

The present invention is a method for producing a thermoplastic polyester by polycondensing a dihydroxy compound with a dicarboxylic acid or an ester or ester-forming derivative thereof, wherein the alkali metal per kg of polyester is calculated based on the alkali metal or alkaline earth metal. At least one first step of adding the compound or alkaline earth metal compound in an amount of 1 to 10 mmol; And at least one additional step of carrying out the solid phase condensation reaction.

Description

Process for producing thermoplastic polyester

The present invention relates to a process for preparing thermoplastic polyesters by multistep polycondensation of dihydroxy compounds with dicarboxylic acids, their esters or ester forming derivatives.

Processes of the type mentioned above are being modified on a large scale worldwide, in particular for producing polyalkylene terephthalates.

In order to increase the molecular weight, solid phase postcondensation reactions were often carried out in at least two stage reactions.

There is a need for long residence times required for the purposes of the present invention and related to the thermal stresses in which polyester is applied resulting in the formation of unwanted specks and gels.

The presence of alkali metal compounds in polycondensation reactions to increase the crystallinity or the rate of crystallization of polyesters is known and is disclosed, for example, in EP-A-215 364 and EP-A 29 285. According to EP-A 29 285, the amount of alkali metal compound added is about 0.1 to 2% by weight, or 0.02 to 1 mole per kilogram of polyester (EP-215,364). However, this relatively large amount in the final product also has disadvantages for some applications.

It is an object of the present invention to provide a process for the preparation of polyesters of the type described above, which provides a substantially speck-free, gel-free product and reduces the total time of the polycondensation reaction.

In the process for producing thermoplastic polyesters by multi-step polycondensation of dihydroxy compounds with dicarboxylic acids, their esters or ester forming derivatives, the inventors have at least one first step an alkali metal compound or an alkaline earth metal. It is found that the above object can be achieved according to the method of the present invention which calculates the compound as an alkali metal or an alkaline earth metal and adds it in an amount of 1 to 10 mmol per kg of polyester and performs a solid phase condensation reaction in at least one weight step. It became.

In the novel process of the invention, high molecular weight, substantially unspecified, gel-free polyesters can be obtained at shorter polycondensation times, especially in solid phase condensation reactions.

The dihydroxy compounds used may be aliphatic, aromatic or cycloaliphatic diols.

The above compounds are particularly preferably aliphatic diols having 2 to 20 carbon atoms, especially 2 to 12 carbon atoms, and having 2 to 12 carbon atoms, especially 2 to 6 carbon atoms.

Examples include ethanediol (ethylene glycol), 1,3-propanediol, 1,4-butanediol, cyclohexanediol, hydroquinone, resorcinol, and bisphenol A, among which ethanediol and 1,4-butanediol This is particularly preferred.

The dicarboxylic acids used may preferably be aliphatic and / or aromatic dicarboxylic acids having 4 to 20 carbon atoms, in particular 4 to 12 carbon atoms.

Examples include isophthalic acid, phthalic acid, terephthalic acid, alkyl substituted derivatives of these acids, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, There are sebacic acid, azelaic acid and decandicarboxylic acid, of which isophthalic acid and terephthalic acid or mixtures thereof are particularly preferred.

In the above, it has been proved that polyalkylene terephthalate, polyalkylene isophthalate or copolymers of acidic terephthalic acid and isophthalic acid can be produced particularly advantageously by the process of the invention.

In addition to the aforementioned components, the polyesters prepared according to the invention may contain further units, for example derived from hydroxycarboxylic acids, in relatively small amounts, preferably less than 10 mol%, based on the particular monomer component. have.

In the novel process of the present invention, the alkali metal compound or alkaline earth metal compound is calculated (calculated based on alkali metal or alkaline earth metal) in a known manner in the first step while the starting monomers are reacted in a known manner. 1 to 10 mmol, preferably 2 to 7 mmol, in particular 2.5 to 5 mmol, per kg.

Theoretically, inorganic and organic compounds of alkali metals are preferred, preferably Li, Na or K, particularly preferably sodium compounds.

Examples of suitable inorganic compounds of alkali or alkaline earth metals, preferably sodium, are the corresponding silicates, phosphates, phosphites, sulfates, or preferably carbonates, bicarbonates and hydroxides.

Organic compounds of alkali metals and alkaline earth metals, preferably sodium, preferably contain up to 30 carbon atoms and include the corresponding salts of (cyclo) aliphatic, araliphatic or aromatic carboxylic acids having 1 to 4 carboxyl groups do. Examples thereof include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, caprylic acid, stearic acid, cyclohexanecarboxylic acid, succinic acid, adipic acid, suberic acid, 1,10-decanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, terephthalic acid, 1,2,3-propanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, trimellitic acid, 1,2,3,4-cyclopentane Alkali metal salts of tetracarboxylic acid, pyromellitic acid, benzoic acid, substituted benzoic acid, dimer acid and trimer acid, and neutral or partially neutralized montan wax salts or montan wax ester salts (montanates). Salts with other types of acid radicals, for example alkali metal paraffin sulfonates, alkali metal olefin sulfonates and alkali metal arylsulfonates, or phenolates and alcoholates such as methanolates, ethanolates or glycolates It can be used for the invention. Sodium carbonate, sodium bicarbonate, sodium hydroxide, mono- and polycarboxylic acids, in particular aliphatic mono- and polycarboxes having from 2 to 18 carbon atoms, preferably from 2 to 6 carbon atoms, and having up to 4 carboxyl groups, preferably up to 2 carbon atoms. It is preferable to use an acid and sodium alcoholate having 2 to 15 carbon atoms, preferably 2 to 8 carbon atoms. Examples of particularly preferred members are sodium acetate, sodium propionate, sodium butyrate, sodium oxalate, sodium malonate, sodium succinate, sodium methanolate, sodium ethanolate and sodium glycolate. Sodium methanolate is particularly preferred and it is particularly useful to use in amounts of 2.5 to 5 mmol, calculated on the basis of sodium. Mixtures of different alkali metal and alkaline earth metal compounds may also be used.

The alkali metal or alkaline earth metal, or alkali metal compound or alkaline earth metal compound is generally added at any time in the first step of the polyester synthesis by the esterification / polycondensation process, preferably the transesterification / condensation process. If a transesterification / polycondensation process is used, the addition at the start of the transesterification reaction is particularly preferred. Esterification / polycondensation processes and transesterification / polycondensation processes are well known and are described, for example, in Ullman's Encyklopaedie der technischen chemie (4th edition) 19 (1980), 61-88.

Example

In the preparation of polyesters from dimethyl terephthalate and 1,4-butanediol in the transesterification / polycondensation process, during the transesterification reaction, 4 kgol of sodium (1 kg of polyester formed in complete stoichiometric reaction) in the form of sodium methanolate Based on the amount), and then condensation in the melt or solution first, and then the product is subjected to a solid phase condensation reaction in the second step.

Compared to the reaction carried out without sodium methanolate under the same conditions, the molecular weight increased substantially more rapidly, and the product obtained had substantially less speck and gel components.

Claims (4)

As a method for producing a thermoplastic polyester by multicondensation of a dihydroxy compound with a dicarboxylic acid, an ester or an ester forming derivative thereof, In at least one first step, the alkali metal compound or alkaline earth metal compound is added in an amount of 1 to 10 mmol per kilogram of polyester, as calculated based on the alkali metal or alkaline earth metal; In at least one further step, a solid phase condensation reaction. The method according to claim 1, wherein the alkali metal compound used is an alkali metal organic compound. The method according to claim 1, wherein the alkali metal compound used is an alcoholate. The method according to claim 1, wherein the alkali metal compound used is sodium methanolate.