DE1495955A1 - Resin manufacturing process - Google Patents

Description

The invention relates to an improved method for making linear polyesters. In particular, it concerns a Process that can be carried out batchwise or continuously to produce high molecular weight linear polyesters of high quality to manufacture.

At the moment, high molecular weight linear polyesters are produced on an industrial scale using the transesterification process, uo are e.g. in the production of high polymer linear J'olyäthylenterephthalats the dimethyl ester of terephthalic acid with an excess of ethylene glycol in the presence of an urn fermentation catalyst at a temperature of about 185 to Heated 25O ° n under atmospheric pressure until about the theoretical Men ^ e methyl alcohol has been released. The over-Mohit ^ nige Glycol is then distilled off and the remaining product, which is the Blycoleuter, by condensation

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reaction with elimination of the glycol polymerized by the bisglyicol ester with a catalyst at increased Temperature and heated under reduced pressure until a high molecular weight product has formed.

For example, polymeric ethylene terephthalate can be prepared by heating terephthalic acid with ethylene glycol to form the magnesium glycol ester, which can then be polymerized by heating in the presence of a catalyst under reduced pressure to form a high molecular weight product. "This method, however, can not be successfully carry out on a large industrial scale, / is required with / ithylenglykol heating at elevated temperature, and also the use of a large excess glycol v eil for the esterification of terephthalic acid. It has also been attempted, polyethylene terephthalate tn '. "It can be prepared by reacting ethylene glycol with terephthalic acid under positive pressure at elevated temperature, but this process has the disadvantages that a large excess of glycol must be used and part of the glycol is converted into polyether glycol and other products. The polyether glycols are incorporated into the polymer molecules. However, it is known that ether bonds in the polyester chain lower the softening point of the polyester resin and contribute to the instability of the high molecular weight, linear polyethylene terephthalate.

Polymeric ethylene terephthalate can also be produced

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by heating terephthalic acid with ethylene glycol in the presence of a low molecular weight polyethylene terephthalate polymer _B at atmospheric pressure. Only a limited concentration of ethylene glycol can be used in this process. Accordingly, if the ethylene glycol concentration used in this process is too high, the maximum temperature attainable in the reaction mixture is too low to allow the reaction to proceed quickly enough because of the cooling effect of the evaporating glycol. The concentration of the glycol is limited so that the temperature that can be achieved in the mixture can be high enough to maintain the reaction. At such a temperature, however, the glycol will evaporate from the mixture. When it is returned to the rectification column and drips into the mixture, it distills away, suddenly cools and freezes part of the mixture, making stirring difficult and slowing the reaction rate. The production of a high molecular weight linear polyester from free acids and glycol using the above atmospheric-free process has not been attractive up to now, because the reaction of the free acid with the glycol is slow and the difficulties outlined above arise when the process is carried out «

The object of the present invention is to provide an improved one Process for the production of linear polyesters. Another goal is a process for making linear polyesters

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that of free dicarboxylic acids and free glycol as reactants is assumed. Another goal is a practical process for the technical production of high polymer, linear polyesters ,, Another object of the invention is a process in which only a minimum amount of catalyst is used and the resulting high molecular weight, linear polyester resin contains only a small amount of catalyst residues. Another object of the invention is a method in which the Eeaktionstexlnehmer are exposed to the catalysts for a minimum time, so that undesirable Side reactions are reduced to a minimum. Further objects will emerge from the following description of the invention emerged.

According to the invention, linear polyesters are produced, by making a free !!! carboxylic acid with a glycol in a solvent that is a low molecular weight, linear polyester is reacted at a pressure of about 1.4 to 70 atmospheres to form a low molecular weight, linear polyester product, which has an average degree of polymerization of about 1.4 to 10. This low molecular weight polymer can then through Condensation reaction are polymerized.

The present process can advantageously be carried out continuously by continuously free Dicarboxylic acid and glycol are added to molten, low molecular weight, linear polyester resin, they can be converted and continuously a lot of low molecular weight polyester resin

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draws, which corresponds approximately to the amount of acid and glycols added. Higher molecular weight, linear polyesters can be produced continuously by continuously adding free dicarboxylic acid and glycol to molten, low molecular weight, linear polyester resin there and lets them react while continuously stripping low molecular weight resin and the withdrawn resin is placed in a polymerizer, where it is continuously polymerized into high molecular weight resin and the high molecular weight linear polyester resin is then withdrawn from the polymerizer.

The process according to the invention is illustrated by the following examples.

example 1

387.35 kg of terephthalic acid, 44.45 kg of isophthalic acid and 23b, 45 liters of ethylene glycol were placed in a reaction vessel containing 861.82 kg of molten low molecular weight ethylene terephthalate / ethylene isophthalate mixed polyester (in a ratio of 90/10) with an average degree of polymerization of about 1, 7 contained. The vessel was sealed and placed under a bridge of 3.5 atmospheres with nitrogen gas. The temperature of the mixture was raised to 260 ⁰ C. The water vapor which formed was distilled from the system at such a rate that the pressure in the system remained at about 3.5 atmospheres as above. After a reaction time of two hours, the mixture became clear, from which it emerged that all of the phthalic acids had reacted.

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The process described in Example 1 can be carried out continuously by turning the reactants - instead of in fractions - is added continuously and low molecular weight polymer is continuously removed. This Processes can be combined with a polymerization and in this way an efficient, economical, continuous one Process for the production of high molecular weight polyester, which is used for the production of fibers and films suitable is. This is explained below.

In the accompanying drawing an apparatus for the continuous implementation of the method is shown. When the continuous process is started, about one third of the heated reaction vessel 1 is low molecular weight Polyethylene terephthalate filled.

The reaction vessel is pressurized from 2.1 to 70 atmospheres with nitrogen gas. Then, the low molecular weight polymer is heated to 250 to 26O ⁰ G by means of a fixed to the shaft 3 the stirrer 2 - V'elle is driven by the motor 4 - stirred. The storage vessel 5 is used to store terephthalic acid. From this storage vessel 5 the terephthalic acid is brought into the heated conversion vessel 1 by means of a screw conveyor 6 through line 7. A storage vessel 8 is used to store ethylene glycol. This ethylene glycol is introduced from the storage vessel through the control valve 9 and line 10 into the heated conversion vessel 1. Terephthalic acid and ethylene glycol are continuously

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Nuierlich and at the same time introduced in approximately stoichiometric proportions to low molecular weight polymer with the to produce the desired degree of polymerization. The water released in the esterification reaction is evaporated. Of the Water vapor passes together with the ethylene glycol vapor in the reflux condensation device 11, where the ethylene glycol is condensed and returned to the reaction vessel 1. The water vapor is passed through line 12 at the top of the condenser 11 withdrawn in such an amount that the pressure in the system is maintained. It arises with a lower molecular weight Polyester exiting the heated reaction vessel 1 at about the same rate as the reactants be introduced into the heated reaction vessel 1, withdrawn by means of the Re ^ elventils 13 through line 14 and is passed to the polymerization kettle 15, into which daa low molecular weight polyester resin introduced at one end, polymerized during the change through the reaction vessel and the resulting high molecular weight resin peeled off the other end 'we ;. Polymerization catalyst stored in storage vessel 16, is continuously introduced into the polymerization kettle 15 through the control valve 17 via line 18. Glycol released in the polymerization reaction and released water vapor is released from the polymerization kettle withdrawn through the condenser 19 and sent to the glycol recovery plant 20, from which the glycol again-

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is won. The polymerization vessel is operated under reduced pressure generated by a vacuum system; this vacuum system (not shown) is connected to the condenser 19. From the polymerization kettle is then through Valve 21 and line 22 high molecular weight polyester resin removed and sent to another (not shown) plant, in which it can be stored or processed into tapes, films or other products.

The invention has been illustrated particularly with regard to the use of terephthalic acid and ethylene glycol as reactants. But it can also be used for production of polyesters made from other acids and other glycols «For example, instead of terephthalic acid, other acids can be used ..

The invention is accordingly applicable to the production of polyesters and mixed polyesters from various dicarboxylic acids and various glycols. Examples of acids that can be used are aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, p, p ^f -diphenyldicarboxylic acid and 2,6-naphthalic acid; cycloaliphatic dicarboxylic acids such as hexahydroterephthalic acid; and aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, etc. In the same manner, polyesters can be prepared with other glycols. Examples of such glycols are the polymethylene glycols with 2 to 10 methylene groups, such as ethylene glycol, propylene glycol, tetramethylene glycol, hexa-

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methylene glycol and decamethylene glycol, the cyelohexanediols, Cyclohexanedimethanol, di-ß-hydroxyethoxybenzene and 2,2-Bi- [4- (ß-hydroxyethoxy) phenyl] propane and similar types of glycols. The invention can be used to produce mixed polyesters can be used by reacting one or more acids with one or more glycols.

The invention is particularly suitable for the production of mixed polyesters of terephthalic acid, such as the ethylene terephthalate-ethylene isophthalate mixed polyester with terephthalic acid as the main amount of the acid component, e.g. the 90/10, 80/20, 70/30 and 60/40 mixed polyesters, i.e. those mixed polyesters which, based on the total acid component, 90 to 60 moles of terephthalic acid and 10 to 40 moles of isophthalic acid contain.

The process can be carried out over a wide temperature range. The temperature for the esterification reaction should be at least as high as the melting temperature of the low molecular weight polyester resin used, but not so high that a major degradation reaction occurs with a consequent reduction in the desired properties. The temperature can accordingly be in a suitable manner between 150 and 300 ⁰ O, which depends on the melting temperature of the low molecular weight polymer used, and will preferably be in the range from 220 to 260 ⁰ O. The ratio of moles of oil to deif moles of dioarboxylic acid used is in the range of about 1.7: 1 to 1.05: 1. When terephthalic acid as

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Reactants used and the process is ^{carried out at about 250 0} C, the ratio of glycol to terephthalic acid can have any of the values indicated in the above range and produce satisfactory results.

The pressure used for the esterification reaction will vary with the temperature used and should generally be at least as high as the vapor pressure of the most volatile glycols in the reaction mixture at the temperature used. The pressure applied will be less than the vapor pressure of water at the temperature at which the reaction occurs. Accordingly, the pressure in an appropriate ^{l 'r} else may be 1.4 to 70 atmospheres, and will preferably be employed in atmospheres Eereich 2.1 to 7.

The process can be carried out by placing the reaction vessel with the mixture of glycol and acid together charged with the low molecular weight polyester resin and heated the mixture until the low molecular weight resin melts and the substances react. However, the preferred procedure is to first melt the low molecular weight resin and then introducing the acid and the glycol and allowing them to react with one another. The process can be batch or continuous be performed. For reasons of effectiveness and economy, it will be carried out continuously preferred.

The linear low molecular weight polyester resin initially used as a solvent is a linear polyester,

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which has an average degree of polymerization of about 1.4 to 10. This polyester can have the same degree of polymerization like the end product or have a different degree of polymerization, i.e. it can have a higher or have lower degree of polymerization because of the Degree of polymerization of the end product through the quantities and proportions from acid to glycol added to the system. The one used as a solvent at the beginning Low molecular weight, linear polyester usually consists of units of the same acid and the same glycol, which in a mixture be reacted with the low molecular weight polyester. If necessary, however, it can also consist of units of acids and / or “lycoles that are different from those with which it is later reacted in a mixture.

The average degree of polymerization for both the initial low molecular weight polyester and the The low molecular weight product produced is in the range from 1.4 to 10, preferably 1.6 to 5. The polyester molectiles have the general structure

H (GA) _n GH,

where H is hydrogen, G is a glycol unit or a glycol residue, A is a dicarboxylic acid unit or a carboxylic acid residue and η is a number from 1.4 to 10, ^ as low molecular weight So polyester resin has an average molecular weight of about 300 to 2000. If this resin is either batchwise or continuously in the presence of a polymerization catalyst

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sators is polymerized to a high polymer is the product is a high polymer linear polyester resin having an intrinsic viscosity of at least 0.40; in the generally it is in the range from 0.50 to 1.20.

The initial low molecular weight linear polyester can be polymerized by the bisglycol ester or after any other suitable method.

The above has shown that the invention provides an effective continuous process for the production of high molecular weight linear polyester resin, ie a resin having an intrinsic viscosity of at least 0.40, generally above 0.50. The procedure and conditions for the production of the low molecular weight resin produced in the first stage are explained above. The condensation or polymerization reaction in the production of the high molecular weight resin from the low molecular weight resin is carried out at elevated temperature under reduced pressure in the presence of a suitable polymerization catalyst in a manner known per se. The reaction is therefore preferably carried out in the absence of oxygen and generally in an atmosphere of an inert gas such as nitrogen or the like. It is under reduced pressure, generally below 10 mm Hg and usually at or below 1 mm Hg, at a temperature ^{between 260 and 290 ° C}

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lying temperature carried out, although of course - like known - other temperatures and pressures can also be used.

The method according to the invention offers many advantages, both technically and economically. The free acids are cheaper than the dialkyl esters; So you save when using the free acids - instead of the dialkyl ester as was previously the case - Significant costs · Then there is no lower alkyl alcohol as a by-product; and there the excess on The glycol used is kept to a minimum, the recovery and loss of glycol is considerably reduced. The reaction takes place quickly} the complete conversion of the raw material to the high polymer can already take place in three hours can be achieved. In addition, the polyesters produced by this process have intrinsic vis-

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cosities that are one / es higher than those caused by transesterification normally received. In addition to these advantages, the polyester product contains much less catalyst residue, than that produced by the dermesterification process Polyester resins is the case. No catalyst is needed in the initial esterification reaction, though optionally catalysts such as zinc acetate, manganoacetate and alkali metal alcoholates can be used. One and only the catalyst actually required is the polymerization or condensation catalyst, which is best made of a material

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rial, such as antimony trioxide, zinc borate, black lead, lead acetate, magnesium oxide or any other condensation catalyst

While certain embodiments and details have been set forth for the purpose of illustrating the invention, it will be understood that many changes and modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

_ Patent claims -

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Claims (6)

7 Jan Pat ent test marriage: 1. Process for the production of a polyester, characterized in that there is a glycol and a dicarboxylic acid in a ratio of 1.7: 1 to 1.05: 1 (glycol to acid) to a preformed, low molecular weight polyester from this glycol and this acid and the mixture at one above the melting point of the low molecular weight polyester lying temperature at a pressure lying between about 1.4 and 70 atmospheres and reacted. 2. The method according to claim 1, characterized in "that there is ethylene glycol as the glycol and terephthalic acid as the acid used. 3. The method according to claim 1 or 2, characterized in that the v ^r water vapor formed in the reaction is continuously withdrawn at such a rate that the pressure in the system is kept constant, and that an amount of low molecular weight polyester is continuously withdrawn, which is about corresponds to the amount of glycols and acid added. 4. The method according to claim 1, 2 or 3, characterized in that aan progress the polymerization reaction lets the polyester formed have an average degree of polymerization of 1.4-10. 009808/1695 U95955 5. The method according to any one of the preceding claims, characterized in that there is added to the withdrawn low molecular weight Polyester is a polymerization catalyst and the low molecular weight polyester by condensation polymerized to a high molecular weight polyester. 6. A process for the production of a high molecular weight linear polyester, characterized in that one (a) at least one acid from the group terephthalic acid, Isophthalic acid and naphthalenedicarboxylic acid- (2,6) and (b) ethylene glycol in the molar ratio of glycol to acid, such as 1.7: 1 are a low molecular weight linear Polyesfer, the mixture at a up to 260 ⁰ C lying in Pereich from the melting point of the low molecular weight linear polyester at a temperature: 1 to 1.05 from 2.1 to 70 atmospheres "pressure ranging and reacted, the water formed during the reaction is distilled off to such an extent that the pressure in the system remains constant, a condensation polymerization catalyst is added and then the mixture is brought to a temperature of about? 65 heated Hg at a "pressure of about 1 mm to 28O ⁰ C and reacted has arisen to a high molecular weight linear polyesters. l-> ie patent attorney » Dipl.-Ing.WM _G issner DipUnq. H. T 009808/1695