DE2801578A1 - Polybutylene glycol carboxylic acid di:ester(s) - made by polymerisation of purified THF in the presence of carboxylic acid (anhydride) and catalyst - Google Patents

Abstract

Polybutyleneglycol carboxylic acid diesters R-CO-O-(-CH2CH2CH2CH2-O-)n-CO-R' (I) (in which R and R1 are alkyl, COOH-contg. opt. unsaturated aliphatic gp. or COOH-contg. aromatic gp. and n is a 2-200) are made by first treating tetrahydrofuran with strong mineral acids, organic sulphonic acids, silica gel and/or fuller's earth. The treated THF is then polymerised in the presence of >=1 carboxylic acid or carboxylic acid anhydride and a polymerisation catalyst to form the (I). The pretreatment of the THF removes traces of impurities present in technical THF and gives higher rates of polymerisation, reproducible molecular weights and avoidance of discoloured prods. The (I) can be transesterified e.g. with methanol to give the corresponding dihydroxy cpds., which are useful raw materials for the prodn. of polyurethanes.

Description

Process for the polymerization of tetrahydrofuran

The invention relates to a process for the production of polybutylene glycol carboxylic acid diesters of the formula R-CO-O R-CO-O - (- CH2CH2CH2CH2-O -) - nCO-R 'by polymerization of tetrahydrofuran in the presence of carboxylic anhydrides and fuller's earth with a water content smaller than 3% by weight as a catalyst.

The polymerization of tetrahydrofuran (THF) with the help of oxonium ions as catalysts is due to the fundamental work of H. Meerwein and co-workers (Angew. Chem. 72 (1960), 927) has become generally known.

The catalysts used are either preformed compounds or those which are generated in situ, used. The following preformed ones are described, for example Trialkyloxonium salts as catalysts: (C2H5) 30 SbC16; (C2H5) 30 BF4 (C2H5) 3 ° FeC14 (C2H5) 3 ° A1C14 Suitable components which form oxonium ions in the reaction medium, are mainly Lewis acids, such as BF3, AlCl3, SnCl4, SbCl5> FeC13 or PF5, the together with ethylene oxide, propylene oxide, epichlorohydrin, orthoesters and acetals, -Chlorether, benzyl chloride, trivinyl methyl chloride, acetyl chloride or ß-propiolactone can be used as well as inorganic hydrogen acids, such as HC104, HBF4, HS03F, HS03C1, H2SnCl6, HJ03, HSbC16 or HFeCl4, which together with carboxylic acid anhydrides, Carboxylic acid chlorides, SOC12, POC13 and Benzenesulfonic acid chloride can be used, and finally, more recently, aluminum alkyl compounds in combination with epichlorohydrin or water.

The production of low molecular weight diacetates from di- and polybutylene glycols with a degree of polymerization of 2 to a maximum of 10 in the presence of bleaching earth as a catalyst is described in XT-AS 12 26 560. Called as bleaching earth aluminum hydrosilicates or aluminum magnesium hydrosilicates of the type are used ontmorrillonits, which can be activated by acids. The bleaching earths have opposite Catalyst systems of the Oxoniuiaionen type have the advantage that they are much cheaper and are very easy to use.

Another advantage that should not be underestimated is the toxicological one Integrity of the bleaching earth. In contrast, many of the described and technical actually used catalyst systems as dangerous and toxicologically not be regarded as unobjectionable.

From this list of the known types of catalysts that in no way claims to be complete, only the most important describes previously known systems, it becomes clear that it is a confusing one A variety of catalysts are used to convert tetrahydrofuran to polybutylene glycol, also called polytetrahydrofuran (PTHF), can be polymerized. Still have but only a few catalysts achieved industrial importance. Because only them make it possible to produce polymers that have chemical and physical properties meet the market requirements.

Even the person skilled in the art is therefore not in a position to use what is known so far to derive an optimal catalyst easily. The ones currently in technology The catalysts used are derived from BF3, FS03H, HCl04 and oleum, whereby as Additional promoters olefin oxides, acetyl chloride, acetic anhydride and Reten can be used. In general, however, the defect is liable to these procedures indicate that the so-called catalysts are not catalytically effective in the strict sense but in relation to the resulting macromolecule in a stoichiometric ratio can be used. For the production of a molecule of PTHF, at least one Catalyst molecule consumed. As a result, the PTHF production does not take place only expensive, but also has a significant environmental impact. In US Patent For example, 3,358,042 describes a method in which about 2 molecules per molecule of PTHF HS03F must be used as a catalyst. The polymer primarily obtained must then be worked up by hydrolysis to turn it into a catalyst-free To convert polyether diol. The catalyst then appears quantitatively as NaF and Na2S04 in wastewater. For the production of 100 parts of polymer, 30 up to 40 parts of salt load can be accepted.

Even when using fuller's earth as a catalyst according to DT-AS 12 26 560 environmental problems have to be overcome, since the amount available per catalyst quantity Amount of PTHF is limited. A maximum of 40 parts of PTHF can be produced per part of fuller's earth are, however, already technically unsustainable long response times in purchase must be taken. Another disadvantage is that with the method described only low molecular weight diacetates of polybutylene glycol, the upper limit of the Molecular weight is about 800.

The object of the present invention was the polymerization of TijF in relation to the rate of polymerization and molecular weight setting to improve, i.e. to make products available that have a degree of polymerization from n = 2 to n = arbitrarily large.

The present invention is therefore a method for Production of polybutylene glycol carboxylic acid diesters of the formula R-Ci) -O-OH2OH 1> 2OH2OnOOR in which R and R1 are identical or different and are an alkyl radical, a carboxyl-containing, optionally ethylenically unsaturated aliphatic Radical or an aromatic radical containing carboxyl groups and n is an integer mean from 2 to 200, by polymerization of tetrahydrofuran in the presence of Carboxylic anhydrides and fuller's earth as a catalyst, which is characterized is that the fuller's earth has a water content of less than 3 wt.

Bleaching earths or fuller's earths belong to the crystallographic Nontmorrillonites. These are colloidal, hydrous aluminum hydrosilicates, which occur naturally and in which aluminum ions are partly due to iron or magnesium can be replaced. The ratio of silica to the oxides of 2- or 5-valent Metals in these minerals is mostly 4: 1. The commercial products, which are mostly activated by acid treatment and have a water content of 4 to 8 Ges., based on the total weight, are to a large extent as Catalysts for refining edible oils, fats and mineral oils, adsorbents and fillers used.

In the common areas of application, bleaching earths unfold in Consistent with the recommendations of manufacturers, their maximum effectiveness when they come in the commercially available, water-containing form for use. It was therefore Surprisingly and in no way predictable that during the polymerization of THF Much better results can be obtained if instead the commercial, water-containing minerals anhydrous or, in particular, essentially anhydrous bleaching earth can be used as a catalyst. The anhydrous bleaching earth show a higher catalytic activity in relation to the rate of polymerization, the achievable conversion and the number of catalyst used. It is also advantageous that with the catalysts according to the invention, in particular polybutylene glycol carboxylic acid diesters Polybutylene glycol diacetates are obtained, the degree of polymerization of which n = 2 upwards can be set arbitrarily depending on the reaction conditions. With With the aid of the polymerization process according to the invention, diesters of polybutylene glycols are obtained with degrees of polymerization from n = 2 to n = 200, preferably from n = 5 to 50, in particular produced from n = 12 to 36, i.e. polymers which, after hydrolysis hydroxyl-containing PTHF with molecular weights of approximately 150 to 15,000, preferably from 400 to 4,000, especially from 1,000 to 3,000. PTHF with these high molecular weights are required in the end products, e.g. in the production of polyurethanes, a sufficiently high level of mechanical properties to create. The use of PTHF with molecular weights less than 500 is consistent limited to solving specific problems.

Another advantage of the method according to the invention is that that the catalysts are not in dissolved form as in the conventional process are present in the reaction product and are costly due to laborious washing and precipitation processes must be separated, but by common physical separation methods, such as filtration or centrifugation, can be isolated. Surprisingly it was found that the separated, substantially anhydrous bleaching earths can be used again for any number of further polymerizations. So can according to the method according to the invention without difficulty per part substantially anhydrous fuller's earth up to 1,000 or more parts of diester des Polybutylene glycol are polymerized. If, on the other hand, you use the commercially available, water-containing bleaching earths, it is not possible in an economically justifiable manner to use the separated catalyst again for further reactions, since its Activity decreases very quickly with each further use. In this you agree the environmental friendliness of the new polymerization process, which is considered to be significant technical progress is to be assessed, since it is not necessary to have large amounts of salt load, which are obtained, for example, by the process of US Pat. No. 3,358,042, to master, still need larger quantities of used fuller's earth catalysts by organic If components are contaminated, they should be disposed of. In contrast to the conventional quasi - catalytic polymerization processes must be the process according to the invention be classified as genuinely catalytic because - as already stated - the catalyst can be used any number of times.

Suitable bleaching earths are in particular aluminum hydrosilicates or Aluminum nagnesium hydrosilicates of the montmorillonite type, which are produced by acid can be activated and e.g. under the name 1? Tonsil1? are in trade. For the production the ore in the substantially anhydrous bleaching earths according to the invention are commercially available water-containing bleaching earths at temperatures from 1000 to 2000 C, preferably from 110 to 150 ° C, in 1 to 8 hours, preferably 2 to 4 hours at normal pressure or preferably dehydrated under reduced pressure. According to the invention as catalysts usable, essentially anhydrous bleaching earths have water contents of less than 3% by weight, preferably from 0.001 to 1.5% by weight, and in particular from 0.1 to 1.0% by weight. For the polymerization of the THF, only small amounts of essentially anhydrous bleaching earths required.

Beneficial results are obtained when they are related on the total polymerization batch in an amount of 1 to 20 wt., Preferably 5 to 10 wt., V, is used. Of course, larger and smaller quantities can also be used will. This hardly affects the properties of the polymers obtained. Only the reaction speed, which is directly proportional to the first food the amount of catalyst used is affected.

The essentially anhydrous bleaching earth only contains in the presence of the promoter carboxylic acid anhydride their catalytic effect. Advantageously one uses such carboxylic acid anhydrides, which differ from aliphatic or aromatic, poly- and / or preferably monocarboxylic acids having 2 to 12, preferably 2 to d carbon atoms derive. Examples include anhydrides of aliphatic carboxylic acids with 2 to 12 carbon atoms, such as butyric anhydride, valeric anhydride, Caprons acid anhydride, caprylic anhydride, pelargonic anhydride and preferably Propionic anhydride and acetic anhydride, anhydrides of aromatic and aliphatic Polycarboxylic acids, especially dicarboxylic acids, such as phthalic anhydride and naphthalic anhydride and preferably succinic acid and maleic anhydride. For price reasons and reasons acetic anhydride is preferred for easy accessibility. Of course Mixed anhydrides and mixtures of the abovementioned anhydrides can also be used.

As already mentioned, diesters can be prepared by the process according to the invention of polybutylene glycol with any degree of polymerization. The degree of polymerization is essentially determined by the carboxylic acid anhydride concentration the polymerization mixture. The lower the selected carboxylic anhydride concentration is, the higher molecular weights are achieved and vice versa. Since the degrees of polymerization also of the properties of the essentially anhydrous Bleaching earth be determined, it is generally required for a particular fuller's earth dfe acid anhydride concentration to determine the desired molecular weight results. Since the type of substantially anhydrous fuller's earth used has less influence on the molecular weight than the carboxylic acid anhydride concentration, For example, the following values should be given here as a guide.

At a carboxylic anhydride concentration of, for example, 70 to The THF becomes d0 mol percent at a polymerization temperature of 300 to 400C converted almost quantitatively into the diester of dibutylene glycol. If you turn one Carboxylic acid anhydride concentration of about 3 mol percent, a polymer is obtained with a degree of polymerization n = 25 to 30.

For the production of diesters of polybutylene glycols with degrees of polymerization from 12 to 36 at e.g. 300C, which is especially produced by hydrolysis in PTHF transferred and used for the production of polyurethanes, has become a Carboxylic acid anhydride concentration, especially acetic anhydride concentration, of 12 up to 0.5 mol percent, preferably from 9 to 1.5 mol percent, particularly well proven, so that it is preferably polymerized in this concentration range.

The polymerization is generally carried out at temperatures from OOC to 700C carried out. On the one hand, the reaction rate is below 200C decreases very sharply and the reaction conversion becomes low above 60.degree. C., is preferred polymerized at temperatures of 20 to 500C. The polymerization times are depending on the temperature and catalyst concentration used, approximately 1 to 20 hours, preferably 2 to 10 hours.

After the polymerization has taken place, the reaction is carried out by separating off the Catalyst stopped. The separation can be done with the help of common physical separation methods, for example by filtration or centrifugation take place. Reaction solutions are obtained which, in addition to diesters of polybutylene glycol Depending on the reaction conditions used, a further 0 to 50% by weight, based on the total weight the reaction solution, may contain unreacted THF. Since the so obtained Reaction solution apart from the diester of polybutylene glycol only volatile components, namely, carboxylic acid anhydride and unreacted THF, it is sufficient to be separated off by distillation, if appropriate under reduced pressure.

The separated, substantially anhydrous bleaching earths can can be used again as catalysts without further pretreatment.

The polybutylene glycols obtained according to the invention, the contain bonded carboxylic acid residues as end groups, can be in a known manner by transesterification, for example with methanol in accordance with US Pat. No. 2,499,725 and Journal of American Chemical Society, Vol 70, page 1842 into the corresponding dihydroxy compounds convict.

The polytetrahydrofurans obtained in this way, which are preferably Having molecular weights of about 1,000 to 3,000 are eminently suitable for the production of polyurethanes, especially polyurethane elastomers, casting resins i.a.

The following examples are intended to explain the process according to the invention in more detail explain without limiting it. The parts mentioned are parts by weight; they behave to parts by volume as kilograms to liters.

Example 1 A mixture of 2,160 parts is made in a stirred tank Tetrahydrofuran and 102 parts of acetic anhydride heated to 40 ° C and 226 parts a commercial bleaching earth (R monsil Optimum FF, Süd-Chertiie AG, Munich) added, the water content of which by drying at 13000 in # hours to 0.01 wt., was reduced. The immediately onset exothermic reaction is by cooling at 400C held. A conversion of 58% by weight is achieved after just 2 hours. Of the The catalyst is separated off by filtration. From the colorless reaction solution a colorless polybutylene aglycol diacetate is obtained by distilling off the unreacted THF with a molecular weight of 1,900 (calculated from the saponification number).

The bleaching earth sold by the company Süd-Chemie, Munich, is used onsil Optimum extra (mex) T ?, a polymer from I obtained molecular weight 2,300.

A polymerization carried out under the same experimental conditions with the fuller's earth "ViIP 24/48" from Mid-Florida Mining Company, U.S.A., their Water content by drying at 110 ° C and 30 Torr for 8 hours from 5% to 0.06 " was decreased, gave a polymerization conversion of 41% and a polymer with a molecular weight of 3,000.

Example 2 If the procedure is analogous to the information in Example 1, use is made however, instead of 102 parts, 306 parts of acetic anhydride are obtained after d hours a polymerization conversion of 73,.

The polymer obtained has a molecular weight of 750 (determined from the saponification number).

Example 3 504 parts of tetrahydrofuran and 2142 parts of acetic anhydride are in the presence of a commercial bleaching earth (Tonsil Optimum FF), their Water content by drying at 1200C in 30 hours to 0.005 total, based on the total weight, reduced, polymerized at 40 ° C for 12 hours. After that it was the catalyst separated off. The THF was found to be complete by distillation was polymerized.

After the unreacted acetic anhydride has been distilled off, one obtains a polybutylene glycol diacetate with a molecular weight of 300.

Example 4 Proceed as described in the example 1 and polymerizes 2 160 parts of tetrahydrofuran with 102 parts of acetic anhydride in the presence of 226 parts of Tonsil Optimum FF, the water content of which was previously obtained by drying at 11500 was reduced to less than 0.1% over 24 hours. One achieves the polymerization result given in Example 1.

The separated catalyst is used again for the polymerization of 2,160 parts of tetrahydrofuran and 102 parts of acetic anhydride are used at 40 ° C. The result obtained does not differ from the first polymerization attempt.

Even after the catalyst has been reused 20 times under the same conditions The test result remains constant under the reaction conditions.

Example 5 The procedure is analogous to that of Example 1, used however, 130 parts of a commercially available bentonite as a catalyst (trade product Catalyst; 10 from the company Süd-Chemie, Munich), which previously reached 120 in 12 hours 0C to a water content of less than 0.1 wt., Ó was dried. oh one The reaction time of 0 hours is the polymerization by filtering off the catalyst stopped. The polymer obtained has an average molecular weight of 1 800, calculated from the saponification number. The polymerization conversion was 58 total%.

Corresponding results are achieved with the commercially available bentonites KSF catalyst and KP 10 catalyst (trade names of the Süd-Chemie company, Munich), provided that this was previously reduced to one in 24 hours at temperatures of 1200C Water content of 0.02 wt. Or -0.008 total; to be dried.

COMPARATIVE EXAMPLE A mixture of 2 160 parts of tetrahydrofuran and 102 parts of acetic anhydride heated to 40 ° C. and in the presence of 226 parts of a commercial fuller's earth (commercial product Tonsil Optimum FF der Süd-Chemie, Munich), which has a water content of 5 wt. P, based on the Total weight, polymerized. After a pole, immersion time of 2 hours a degree of conversion of tetrahydrofuran of 21% by weight is achieved. The molecular weight of the polytetrahydrofuran acetate obtained is 2,500. Even after a polymerization time of 32 hours, the degree of conversion is only 24% by weight, the molecular weight of the polytetrahydrofuran diacetate obtained 2,450.

If you use the same commercial fuller's earth with a water content of 6.3% by weight, based on the total weight, as a polymerization catalyst, see above obtained after a polymerization time of 32 hours a Pol: rrerisat with a Molecular weight of 2,900 with a degree of conversion of 19% by weight.

The catalyst is removed from the polymerization batches by filtration separated and re-used for the polymerization, so one reaches in the renewed Implementation a degree of conversion of 15% by weight and a molecular weight of the polymer from 3 100.

The comparative examples show that those which have not been pretreated are commercially available Bleaching earth with a water content greater than 3 total weight, based on the total weight, have lower catalytic activity and poor in polymerization deliver reproducible results.

Claims (6)

Claims 1. A process for the preparation of polybutylene glycol carboxylic acid esters of the formula R-CO-O - (- CH2CH2CH2CH2-O -) - nCO-R¹, in which R and R1 are identical or different are and an alkyl radical, a carboxyl group-containing, optionally ethylenic unsaturated aliphatic radical or an aromatic containing carboxyl groups The remainder and n are an integer from 2 to 200, by polymerization of tetrahydrofuran in the presence of carboxylic anhydrides and bleaching earth as a catalyst, thereby characterized in that the fuller's earth has a water content of less than 3% by weight. 2. The method according to claim 1, characterized in that the bleaching earth has a water content of 0.001 to 1.5 wt. 3. The method according to claim 1, characterized in that the bleaching earth Is used in amounts of 1 to 20 wt., Based on tetrahydrofuran. 4. The method according to claim 1, characterized in that the Fuller's earth used as a catalyst after the end of the polymerization of the reaction mixture separated and used again as a polymerization catalyst. 5. The method according to claim 1, characterized in that as Carboxylic acid anhydride used acetic anhydride. 6. The method according to claim 1, characterized in that the polymerization is carried out at temperatures of 20 to 50 0C.