DE2301691A1 - PROCESS FOR INCREASING THE VELOCITY OF VERESTERIFICATION IN THE PRODUCTION OF POLYHYDROXY POLYESTERS - Google Patents

Description

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¹¹ M. 197J

Process for increasing the rate of esterification in the manufacture of polyhydroxypolyesters

It is known to produce polyesters containing hydroxyl groups from dibasic carboxylic acids and dihydric alcohols Polycondensation at elevated temperature and other suitable conditions with molecular weights of about 4oo to 5ooo to manufacture. The acid component is usually used, for. B. adipic acid or phthalic acid, as a diol component z. B. ethylene glycol, diethylene glycol, propylene glycol (1,2), Butanediol (1,4), neopentyl glycol or hexane

Such hydroxyl-containing polyesters have been long as valuable starting components in the production of polyurethane plastics by the isocyanate polyaddition process known and have been produced on a large scale for many years. In large-scale manufacturing processes an optimal space-time yield is of the utmost practical importance.

As has now surprisingly been found, it is possible to reduce the rate of esterification in the production of as Starting component for the production of polyurethanes

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suitable polyhydroxypoly esters by those known to calibration Polycondensation of polybasic acids with polyvalent ones Alcohol exi to increase quite considerably when in the polycondensation reaction 2 ~ Met! Iyi-propanediol - (1,3) as alcohol component (with; ν is used, with this increased esterification rate ig k: e it goes; naturally an increased space-time yield hand in hand.

The present invention thus relates to a process for increasing the rate of esterification during production of polyhydroxypoly esters of the OH number range 3o 5oo by polycondensation of polyhydric alcohols with polybasic carboxylic acids or carboxylic acid anhyarides, which is characterized in that the polyhydric alcohols 2-methyl-propaned iol - (1,3) alone or in a mixture with a maximum 90 mole percent, based on the total alcoholic component, of other poly oils is used.

The present invention also relates to the polyesters obtainable by this process.

In addition to the surprising technical advantage of an increased space-time yield according to the process according to the invention the polyhydroxypolyesters produced with (co) use a number of notable advantages:

1. The products of the process show in comparison to corresponding polyhydroxypolyesters, in the manufacture of which 2-methylpropanediol (1,3) propylene glycol (1,2), butanediol (1,4) and / or neopentyl glycol was used instead of γοη , have a much lower viscosity, which can be of crucial importance for many special fields of application, in particular for their suitability as polyhydroxy components in the production of polyurethane paints and "polyurethane high-solid coatings".

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2. In comparison with corresponding polyhydroxy polyesters produced without 2-methyl-propanediol (1,3), the products of the process have show a lower tendency to crystallize, which in no way corresponds to the already published in the Journal of Polymer Science, Volume XVIII, pages 215-226 (1955) described melting point lowering must conform. This lesser A tendency to crystallization is unnecessary, which is normally required in the case of the polyhydroxy polyesters of the prior art Melting of the products stored at room temperature or below room temperature before processing. The melting or storage of the polyhydroxypolyester Experience has shown, however, that higher temperatures lead to a change in the quality and discoloration of the polyhydroxy poly ester.

3. The polyhydroxypolyesters obtainable according to the process according to the invention also show the aromatic solubility mentioned in the Journal for Practical Chemistry, 155 , pages 129-163, (1940) for polyesters based on sebacic acid and 2-methyl-propanediol- (1, 3). This fact, too, is of decisive importance for the suitability of the process products in the production of solvent-based polyurethane paints, especially since the branched polyhydroxy polyesters obtainable according to the process according to the invention also have a compared to the corresponding branched polyhydroxy polyesters usually made with propylene glycol (1,2) show significantly increased aromatic solubility.

4 · In comparison with the corresponding polyhydroxypolyesters, the products of the process exhibit Production instead of 2-methyl-propanediol- (1,3) Butanediol (1.4 ·) and / or neopentyl glycol was used, a much less discoloration, which for many

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Areas of application, especially for their suitability as polyhydroxy component for the production of polyurethane elastomers, Paints, threads and foams are a weighty argument.

5. The Ereatz of Neopeiityl Glycol or Mixtures of Neopentyl Glycol with butanediol (1,4) by the essential 2-methylpropanediol (1,3) "brings for the technical Carrying out the esterification with essential simplifications: One can use mixtures of neopentyl glycol and butanediol (1,4) advantageously replaced by 2-methylpropanediol (1,3), which, as only one diol component must be added, the storage and metering simplified and can be carried out better. One of the biggest There are problems with using neopentyl glycol, however its tendency to sublimation, causing valves, pipes and distillation columns with this high-melting point Block diol and cause malfunctions. Finally, when using neopentyl glycol The acid number of the polyhydroxypolyester is difficult to lower below 2, which is important for polyurethane production is unfavorable.

The process according to the invention is carried out in accordance with the processes known per se for the production of polyhydroxypolyesters by polycondensation of polycarboxylic acids with polyvalent ones Alcohols at temperatures from 100 to 25o ° C., preferably from 120 to 220 ° C., optionally in the presence per se known esterification catalysts and / or water entrainers, which remove the water of reaction from the reaction mixture remove, for example, by azeotropic distillation, optionally carried out under reduced pressure.

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Essential to the invention for carrying out the method of the invention is the (co-) use of 2-Methylpropandiol- (1,3) as the alcohol component. In general, the proportion of this component, which is essential to the invention, is 10-100 mol percent, preferably 25-1oo mol percent, based on the total amount of the polyol components used in the process according to the invention.

Raise the essential 2-methyl-propanediol- (1,3) can be any polyols known per se in the production of polyhydroxy polyesters with a preferably below 2oo molecular weight can also be used. Examples of such polyols are ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, Neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, Diethylene glycol, triethylene glycol, trimethylolethane, trimethylolpropane, Glycerin, pentaerythritol, etc. Preferably, in addition to the essential 2-methyl-propanediol (1,3) Ethylene glycol and / or 1,6-hexanediol and / or trimethylolpropane used.

Polycarboxylic acids to be used with preference in the process according to the invention are preferably dicarboxylic acids or their anhydrides, such as. B. adipic acid, phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, maleic acid or maleic anhydride.

The process according to the invention allows the rate of esterification to be increased in the production of preferably linear polyhydroxy polyesters with an OH number range of 3o - 28o, preferably 40 - 18o, with only diols or a maximum of 0.2 moles of triol per mole of diol being present in the polyol component. The method according to the invention allows

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Cl

furthermore, an increase in the rate of esterification in the production of branched polyhydroxypolyesters of the OH number range 15o - 500, preferably 18o - 44o, where in the polyol component per mole of diol more than 0.2 moles, preferably 0.3 ~ 7 moles of higher than dihydric alcohol are present.

The acid number of all, including the branched, according to the invention Process accessible polyhydroxypoly ester can be kept below 15 »that of the polyhydroxy polyesters with few or no branches without any particular difficulty will.

example 1

a) A mixture of 1,4oo g (1o, 47 mol) trimethylolpropane, 1,953 g (21.7o mol) 2-methylpropanediol- (i, 3), 2,830 g (19.4o Mol) adipic acid, 167 g (1.13 mol) phthalic anhydride and 35.3 g (0.36 mol) maleic anhydride is initially without Vacuum under inert gas up to a sump temperature of 195 C. condenses until no more water passes over. Then vacuum is applied and condensation continues at this temperature as long as until the acid number has fallen below 4. A total of 22 hours are required for this. Then 243 g are distilled Excess 2 ~ methylpropanediol- (1,3) from - accordingly a consumption of 1.71o g = 18.97 mol. To test the compatibility with aromatics, 5o g of a 50 or 80 wt. A solution of the polyester in butyl acetate is titrated with xylene until it becomes cloudy.

b) For comparison, a mixture of 1,4oo g (1o, 47 mol) of trimethylolpropane, 1,674 g (22, o5 mol) of propylene glycol (1,2), 2.83ο g (19.4o mol) adipic acid, 167 g (1.13 mol) phthalic anhydride and 35 »3 g (0.36 mol) of maleic anhydride as in Example 1 a) condensed until the acid number fell below 4 is. This is achieved after 27 hours. Finally distilled

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one 264 g of excess propylene glycol (1,2) from - accordingly a consumption of 1.41ο g = 18.97 mol.

By replacing the propylene glycol (1,2) with the one according to the invention 2-Methylpropanediol- (1,3) is thus achieved a reduction in the reaction time from 100 to 81 time units.

Table 1

Example 1a) 1b)

Acid number

OH number

Iodine color number viscosity (2o ° C) (7o # ig in ethyl glycol acetate) Compatibility with aromatic compounds 5o in butyl acetate 8o in butyl acetate

1.2 4th 2, o 4th 225 cP 215 cP • z _ _% G 3 - G 219
t) G 4oo G 18o Ho 145 8o

3 4th 2o5 cP 3 - G 22o G 2o7 1o5

Example 2

A mixture of 312 g (2.33 moles) trimethylolpropane, 8oo g (8.9o moles) 2-methylpropanediol- (1,3), 77o g (5.26 moles) adipic acid and 321 g (2.17 mol) of phthalic anhydride is esterified as in Example 1 until the acid number is below 4 has fallen. Then the excess 2-methylpropanediol (1,3) is distilled and lets the polyester cool down. The consumption of 2-methylpropanediol- (1,3) is calculated as follows 700 g = 7.76 moles.

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Example 3

a) A mixture of 3o11 g (33.4o mol) of 2-methylpropanediol- (1,3) and 4,4oo g (3o, 1o mol) of adipic acid is initially under normal pressure esterified for 15 hours while passing through a weak, constant stream of carbon dioxide. In this time lets the sump temperature can be increased evenly from 125 ° C to 2oo ° C. Then 48 mg of titanium tetrabutoxide are added, a vacuum is applied and the esterification is carried out at a constant 200.degree End. The pressure applied is reduced to 30 torr over the course of 14 hours. The polyester shows after this time an acid number of 0.9 and an OE number of 50.8 and that's it.

b) For comparison, a mixture of 3o11 g (33.4o mol) Butanediol (1, 4) and 4,4oo g (3o, 1o mol) of adipic acid under the same conditions as in Example 3 a) initially for 15 hours under normal pressure, then esterified under vacuum after adding 48 mg of titanium tetrabutoxide. After a total of 29 hours is a pressure of 30 torr was also applied. However, the acid number of the polyester at this point is still 4.1 and only falls below 1 after a total of 35 hours. The OH number is then 50.6.

By replacing butanediol- (1,4) with the one according to the invention 2-Methylpropanediol- (1,3) is thus achieved a reduction in the esterification time from 100 to 83 time units.

A corresponding polyester made from propylene glycol (1,3) and Adipic acid requires a reaction time of 35 hours under the same conditions, a corresponding polyester from ethylene glycol and adipic acid 37 hours. When using neopentyl glycol as a diol component, can be among these Conditions that do not drop below 2 even after a much longer reaction time.

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Example 4

a) To produce a 2-methylpropanediol (1,3) -ethylene glycol-adipic acid mixed ester, 1.696 g (18.82 mol) of 2-methylpropanediol- (1,3), 1167 g (18.82 mol) of ethylene glycol and 4 -972 g (34.05 mol) of adipic acid first esterified under normal pressure while passing through a weak, constant stream of carbon dioxide for 15 hours. The reaction temperature is allowed to rise steadily from 125 ° C. to 200 ° C. during this time. Then a vacuum is applied, the pressure being reduced to 30 Torr over the course of 16 hours, and the esterification is carried out at a constant 200 ° C. to the end. After a total of 51 hours the acid number is 0.8, the OH number 55.3 and the iodine color number 1. The polyester has a viscosity of 57o cP at 75 ° C. and a viscosity of 13,862 cP at 20 ° C. In Einfriertest both at -5 ⁰ C as well as at -15 ° C for 3oo hours, the crystallization half-time is not yet reached. After thawing to room temperature, the liquid polyester shows no visible sediment. This means that these polyesters can be stored for days at -15 ⁰ C without significant amounts of the polyester to crystallize. The pour point of this polyester is -23 ⁰ C.

b) For comparison, a mixture of 1,691 g (18.8o mol) Butanediol (1,4), 1,167 g (18.82 mol) ethylene glycol and 4,932 g (33.73 mol) adipic acid under the same conditions esterified as in Example 4 a). However, this polyester only reaches after a total reaction time of 60 hours an acid number of 0.8 and an OH number of 55, ο the specification. This polyester is much more discolored with an iodine color number of 3 than that produced according to Example 4 a) Polyester. The viscosity is 631 cP at 75 ° C. The pour point is + 10 ° C, the solidification point of the crystallized Polyester at + 30 ° C.

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The replacement also effects a corresponding effect in a mixed ester from butanediol- (1,4) through 2-methylpropanediol- (1,3) one Reduction of the esterification time from 100 to 85 time units.

Example 5

This example illustrates the shortening of the reaction time when replacing feopentyl glycol with 2-methylpropanediol- (1,3). For this purpose, a mixture of 1.o42 g (11.59 mol) of 2-methylpropanediol (1.3), 2.56 g (21.7o mol) of hexanediol (1.6) and 4212 g (28.85 mol) of adipic acid is used esterified as in Example 4 a) initially under normal pressure, then under a pressure which is steadily reduced to 30 torr until the acid number has fallen below 1. This is achieved after a total of 46 hours. The acid number is then 0.9 and the OH number is 67.4. The polyester has at 75 ⁰ C a viscosity of 38o cP at 5o ° C to a viscosity of 1.11o cP.

If, instead, an appropriate mixture of neopentyl glycol, hexanediol (1,6) and adipic acid is esterified under the same conditions, an acid number of 0.9 is only achieved after a total of 65 hours. The OH number is then 67.6, viscosity at 75 ⁰ C 4O5 cP at 5o ° C 1.25o cP.

By replacing the neopentyl glycol with the 2-methylpropanediol (1,3) according to the invention, there is thus a reduction the esterification time from 100 to 71 time units. This corresponds to an increase in the capacity of an esterification apparatus by $ 41

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Example 6

A mixture of 138 g (1.533 mol) of 2-methylpropanediol- (1,3), 53o g (3.95o mol) trimethylolpropane and 676 g (4.395 mol) Hexahydrophthalic anhydride is first esterified without vacuum until a bottom temperature of 180 ° C is reached. spell a vacuum is applied and the esterification is carried out until an acid number of 3.6 is reached. The clear polyester then has an OH number of 262. A 5o wt .- # solution in ethylglycol acetate shows a viscosity of 139 cP at 20 ° C, a 65% strength by weight solution in xylene-ethylglycol acetate (1: 1) 1,824 cP. The latter solution does not reveal any larger jellyfish after a day.

Example 7

A mixture of 1.17og 2-methylpropanediol- (1,3) (13.0 mol), 1.84o g ethylene glycol (29.7 mol) and 5.69og adipic acid (39.0 mol) is first without vacuum under carbon dioxide up to a bottom temperature of 2oo C condensed until no more water passes over. A vacuum is then applied and condensation continues until the acid number has dropped below 1. The liquid polyester then has the following key figures: OH number: 54; Iodine color number: 1; Viscosity (75 ⁰ C: 698 CP; viscosity (2o ° C): 17,7oo cP. In the freezing test, the crystallization ^{half-life at -5 0} C is 10.5 hours, at -15 ° C 4.2 hours. The pour point is - 13 ⁰ C.

Example 8

A mixture of 3 · 67ο g of 2-methylpropanediol- (1,3) and 5 · 15ο g Adipic acid is first esterified without a vacuum in about 9 hours up to a temperature of 200 ° C, until there is no more water overdistilled. Then 60 mg of titanium tetrabutylate are added, applies vacuum and condenses at 2oo ° C until the acid number has dropped below 1. This is after overall

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reached about 40 hours. The OH number is then 54 and the iodine color number 1. The polyester is liquid at room temperature and does not show any crystal formation even after three months of storage at 20 ° C. The pour point of the polyester is -18 ⁰ G.

Comparison :

Analogously to Example 8, a polyester from butanediol (1,4) and Adipic acid produced. The polyester is under the same conditions after a total running time of about 49 hours done. The OH number is then 51, the iodine color number 5-7. The solidification point of this polyester is around 49 ° C.

Example 9

A mixture of 2.64og of 2-methylpropanediol- (1,3) (29.3 mol) and 3.65og of adipic acid (25.0 mol) is first under normal pressure, later in vacuo for a total of about 42 hours to an acid number of o, 9 esterified. The OH number is 76, the iodine color number 1-2. The polyester is liquid at room temperature and shows no signs of crystal formation even after three months of storage at about 20 ° C. The viscosity is 363 cP at 75 ° C and 9.76o cP at 20 ° C. Pour point -18 ⁰ C.

For comparison, a polyester according to US Pat. No. 3,094,510 is initially made by esterifying 1,352 g of 1,4-butanediol (15.0 mol), 1,576 g of neopentyl glycol (15.1 mol) and 3,800 g of adipic acid (26.o mol) produced under normal pressure, later in a vacuum at about 200 ° C. During the esterification, the neopentyl glycol carried out by sublimation from the reaction flask into the fractionating column must be continuously returned. After a total running time of about 48 hours, the acid number has only dropped to 1.5. The OH number is 73, the iodine color number 5. The polyester is liquid also at room temperature, but has a higher viscosity at 75 ⁰ C with 456 eP and at 2o C with 12,880 cP. Pour point -15 ° C.

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Table 2,

example

OH number Acid number ^{Iodine color number Viscosity 75 0} C Viscosity 2o ° C Pour point Reaction time

Examples 1o to

In principle, these examples are carried out in the same way as Example 8. A) g of 2-methylpropanediol (1,3) and b) g adipic acid. The catalyst used is c) mg of tin (II) chloride, furthermore, if appropriate, d) g of 2-methylpropanediol (1,3) followed up.

Tabel

9 comparison 76 73 o, 9 1.5 1 - 2 363 cP 456 cP 9.76o cP 12.88ο cP -18 ⁰ C -15 ° C 42 hours 48 hours

Example 1o 11 12 13 14

OH number Acid number ^{Iodine color number Viscosity 75 0} C cP Viscosity 2o ° C cP State of aggregation at 2o ° C

Pour point
* Even after three months of storage at room temperature there are no

Crystal seeds visible.
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2.85ο 2,755 2.47ο 2,455 2.42ο 3.65ο 3.65ο 3.65ο 3.65ο 3.65ο 48.8 49.6 56, o 62, o 54, o 51 5o 55 - - 131 113 55 45 37 o, 9 o, 7 o, 7 o, 9 o, 9 2 1-2 1-2 1 2 165 268 566 1,049 1.7o8 3,993 5.105 15.48ο 28.53ο 53.21. flow
sig *
-27 ° C flow
sig *
-23 ⁰ C flow
sig *
-2o ° C flow
sig *
-13 ⁰ C flow
sig *
-14 ⁰ C

Example 15

A mixture of 1.14og of 2-methylpropanediol (1,3), 2.82og of hexanediol (1.6) and 4.68ο g of adipic acid is initially condensed without vacuum and later with vacuum at 200 ° C until the acid number has dropped below 1 is. The OH number is then 64, the iodine color number 1-2. The polyester is at 75 ⁰ C a viscosity of 4o2 cP and solidified at about 26 ⁰ C.

comparison

If, according to Example 15, _{the same molar amount of neopentyl glycol is used instead of 2-methylpropanediol (1 f} 3), a polyester with an iodine color number of 3-4 which solidifies at 40 ° C. is obtained. The viscosity at 75 ^° C. is 459 cP.

Examples 16 to 21

These mixed polyesters are produced in the same way as described in Example 15. The amounts used and Characteristic data of the polyesters are compiled in Table 4.

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Table 4 16 17th (sr *
19th 20th 21 example 555 372 18th 1,237 62o 795 a) 2.1o3 1.4o6 49o 1,655 3.28ο - b) - - 1,863 - - 1.23ο c) 2,628 1,839 - 3.65ο 4.37ο 3.65ο d) 134 1o8 2,628 52 67 75 OH number o, 9 o, 9 8o o, 9 o, 8 o, 9 Acid number 2 2 o, 9 4th 3 2 Iodine color number 17OcP 2 578cP 385cP 387cP Viscosity 75 ⁰ C 276cP

a) = g 2-methylpropanediol- (1,3)

b) = g hexanediol- (1.6)

c) = g ethylene glycol

d) = g adipic acid

Esterification catalyzed

Example 22

A mixture of 2-5.2oo g Methylpropandiol- (1.3), 475 g trimethylolpropane and 8.3oo g adipic acid is first esterified without vacuum at 195 ⁰ C, until no more water is distilled. Then 65 mg of titanium tetrabutoxide, 16 mg of ammonium molybdate and 17 mg of iron powder are added, a vacuum is applied and esterification is carried out until the acid number reaches about 1. The OH number is 55, the iodine color number of 2. The polyester is liquid at room temperature and has 75 ⁰ C a viscosity of 2.o2o cP.

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Example 25

A mixture of 59o g of trimethylolpropane, 154 g of 2-methylpropanediol (1,3), 254 g of ethylene glycol and 817 g of phthalic anhydride is first esterified in the mixture without a vacuum up to a temperature of 19o ° C until no more water passes over. The condensation is then continued under vacuum for 12 hours. 74 g of phthalic anhydride are then added and the mixture is condensed under vacuum until the acid number has dropped to about 14. After a total of 30 hours, the acid number is 13.7 and the OH number is 39o. The bright polyester has a viscosity of from 3.72o cP at 75 ⁰ C.

Example 24

A mixture of 516 g of trimethylolpropane, 151 g of ethylene glycol, 4o g of 2-methylpropanediol (1,3) and 623 g of phthalic anhydride are condensed up to a sump temperature of 19o C, initially under normal pressure, then under vacuum until the acid number has dropped to about 13 . Then 4.0 g of Soligen zinc and 0.025 g of Soligen lead are added and the mixture is stirred for a further 2 hours at 150 ° C. The acid number is 12.8, the OH number is 4o3. The polyester has a viscosity of 13.63o cP at 75 ⁰ C; the viscosity of the 70% strength solution in ethyl glycol acetate is 1,728 cP at 20 ° C.

Example 25

A mixture of 64o g of 2-methylpropanediol- (1,3), 563 g Trimethylolpropane, 1.o66 g of adipic acid and 134 g of phthalic anhydride are heated to about 151 ° C. and a little xylene is added and esterified with azeotropic distillation of the water of reaction, until the acid number of a xylene-free sample has dropped below 3. Then the xylene is completely distilled off. The OH number is 2o9, the viscosity of a 7o wt .- ^ solution in ethyl glycol acetate at 20 ° C is 311 cP.

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Example 26 * Γ

A mixture of 138 g (1.533 moles) of 2-methylpropanediol- (1,3), 265 g (1.975 moles) of trimethylolpropane, 214 g (2.815 moles) of propylene glycol- (1,2), 328 g (2.130 moles) of hexahydrophthalic anhydride and 315 g (2.130 mol) of phthalic anhydride are esterified first for 15 hours without vacuum until a sump temperature of 180 ° C. is reached, then under vacuum at this temperature for a further 15 hours. The practically colorless, plastic polyester then has the following characteristics: acid number 2.8; OH number 262; Iodine color number 2; Viscosity at 75 ⁰ C 17 794 cP; Viscosity of a 50% strength by weight solution in ethyl glycol acetate at 20 ° C. 53.7 cP; Viscosity of a 65% strength by weight solution in xylene-ethylglycol acetate (1: 1) 503 cP.

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Claims (4)

Claims Process for increasing the rate of esterification in the production of polyhydroxy polyesters in the OH number range 3o - 5oo by polycondensation of polyhydric alcohols with polybasic carboxylic acids or carboxylic acid anhydrides, characterized in that the polyhydric alcohols are 2-methylpropanediol (1,3) alone or in a mixture with a maximum of 90 mole percent, based on the total alcoholic component, of other poly oils is used. 2. Process for increasing the rate of esterification in the production of predominantly linear polyhydroxy polyesters of the OH number range 3o - 28o according to claim 1, characterized in that the carboxylic acids or carboxylic acid anhydrides difunctional carboxylic acids or anhydrides difunctional carboxylic acids and as polyhydric alcohols Diols or mixtures of triplets and diols are used which contain a maximum of 0.2 moles of triol per mole of diol. 3. Method of increasing the rate of esterification in the manufacture of branched polyhydroxy polyesters of the OH number range 15o - 5oo according to claim 1, characterized in that the carboxylic acids or carboxylic acid anhydrides dibasic carboxylic acids or anhydrides of dibasic carboxylic acids and as polyhydric alcohols Mixtures of higher than dihydric alcohols and dihydric alcohols are used, which more than 0.2 moles of a higher than dihydric alcohol per mole of dihydric alcohol. Le A H 784 - 18 - 409832/0909 4. According to claims 1 to 3 obtainable polyhydroxy polyester. Le A14 784 - 19th 409832/0909