WO2011110528A1

WO2011110528A1 - Method for producing polyols using basic catalysis

Info

Publication number: WO2011110528A1
Application number: PCT/EP2011/053394
Authority: WO
Inventors: Thomas Ostrowski; Anne-Kathrin Merten; Achim LÖFFLER; Hermann Graf
Original assignee: Basf Se
Priority date: 2010-03-09
Filing date: 2011-03-07
Publication date: 2011-09-15

Abstract

The present invention relates to a method for producing polyetherols in the presence of basic catalysts, characterized in that propylene oxide (PO) and/or ethylene oxide (EO) is used, the added contents of which • of aldehydes, expressed by the contents determined gas chromatographically or titrimetrically using the bisulfite method and calculated for proprionaldehyde, do not exceed the value of 300 ppm and • of allyl alcohol which are determined gas chromatographically, do not exceed the value of 2500 ppm and • of water, determined by Karl-Fischer titration, do not exceed the value of 1700 ppm, and • of acid, expressed by the contents determined by acid-base titration and calculated for acetic acid, do not exceed the value of 100 ppm and • of carbon dioxide, determined by KOH titration, do not exceed the value of 500 ppm.

Description

Process for the preparation of polyols with basic catalysis

Description Background:

The invention relates to a process for the preparation of polyether alcohols (polyetherols) by catalyzed addition of alkylene oxides to solid starter substances, primarily sucrose, and the use of these polyether alcohols for the preparation of polyurethanes (PUR), in particular PUR foams.

The preparation of polyether alcohols by anionic polymerization of alkylene oxides has long been known. For more details, for example, the Plastics Handbook, Volume VII, polyurethanes, Carl-Hanser-Verlag, Munich, 1st edition 1966, edited by Dr. med. R. Vieweg and dr. A. Höchtlen, as well as 2nd edition 1983 and 3rd edition 1993, edited by Dr. med. G. Oertel, or M. Szycher, Szycher's Handbook of Polyurethanes, CRC Press, New York 1999, ch. 5 "Polyols" are removed.

The addition of the alkylene oxides is usually carried out using catalysts. For this purpose, mainly basic, and in particular alkaline catalysts are used in the art. Basic compounds such as alkali and alkaline earth hydroxides are among the standard catalysts in the preparation of polyether alcohols; Potassium hydroxide (KOH) is the most widely used.

The preparation of polyether alcohols is described in M. Lonescu, "Chemistry and Technology of Polyols for Polyurethanes", Rapra Technology, 2005.

Frequently used alkylene oxide starting materials for the preparation of polyether alcohols are propylene oxide (PO) and / or ethylene oxide (EO). In practice, it is a constant task to improve the quality of the products, to optimize the process and to ensure plant safety.

Disturbances in the process can occur if the at least one alkylene oxide used, in particular propylene oxide (PO) and / or ethylene oxide (EO), has too high a content of by-products (impurities). Impurities can also by the starting substances, eg. For example, alcohols may be added to the process. however, the present disclosure is particularly concerned with impurities in the alkylene oxide starting materials, such as e.g. EO and PO.

For example, aldehydes that can occur in PO from both the epichlorohydrin and the SM / PO and MTBE-PO (SM = styrene monomer, MTBE = methyl tert-butyl ether) processes can cause interference in several ways :

a) under the influence of the basic catalyst, a series of aldol condensations can occur which lead to colored compounds and worsen the color number of the polyol,

b) with low molecular weight glycols, in particular dipropylene glycol and glycerol, as present in the starter mixture, cyclic acetals can form, which are difficult or impossible to remove in the workup. Because they bind the hydroxyl groups of the starter molecules, they reduce the functionality of the final product and / or deactivate some of the starter molecules, resulting in a polyol having a different OH number. As an unreactive substance, they deceive a lower OH number (the OH number is based on the initial weight, "dilution effect".) When using the polyol batch in polyurethane formulations, quality problems can occur because of the too low OH number the desired ratio of NCO to OH functionality is no longer correct.

c) Not in the synthesis, but in the application of the polyurethane prepared therefrom, the odor attributable to aldehydes and their derivatives can be disturbing.

Allyl alcohol, which can be formed by rearrangement of the PO, acts as a monofunctional starter and lowers the functionality of the polyol. Deviations in OH number and viscosity are the result, as well as deviations in the properties of the polyurethanes produced therefrom.

Water as a ubiquitous impurity (if present in unknown amounts) acts as a bifunctional starter and alters functionality, with consequences as indicated for allyl alcohol.

Acid can be present as a mineral acid (for example as hydrochloric acid in the case of PO from the epichlorohydrin process) and / or as an organic carboxylic acid (in the case of PO from the SM / PO or MTBE / PO process). Mineral acid deactivates the basic catalysts used in polyol synthesis, especially when treated with tert. Amine catalysts are co-catalysed, as they are less active compared to the (alkaline) alkali metal hydroxides. Carboxylic acids act similarly, but additionally as monofunctional ler starter. The primary alkoxylated carboxylic acid can be saponified again by the basic catalyst in the presence of traces of water so that diols are formed with release of the carboxylic acid, leading to altered functionality. Acetic acid therefore has almost the same effect as the equivalent amount of water.

Carbon dioxide reacts with the basic catalyst to form inorganic carbonates and partly deactivates it. With ethylene or 1,2-propylene glycol as a starter, base carbonates form cyclic carbonates with zero functionality. The resulting polyol then does not have the intended functionality, and the OH number is too high, since the carbon dioxide consumes propylene oxide, which is then not available for the chain structure.

The object of the invention was thus to improve the basic catalyzed preparation process for polyols with at least one alkylene oxide, such as propylene oxide and / or ethylene oxide, as starting materials so that the above-mentioned problems are avoided; In this case, particular attention was paid to the KOH-catalyzed process.

pictures

Figure 1 shows an example of the OH number of a polyol as a function of the content of allyl alcohol in PO.

Figure 2 shows an example of the viscosity of a polyol as a function of the content of allyl alcohol in PO.

Description of the invention:

The problem has been solved according to the invention in that alkoxylations are carried out only with (at least) one alkylene oxide, in particular PO and / or EO, whose added content (s) of the following impurities do not exceed the following defined threshold values:

^■ content of aldehydes, expressed by gas chromatography or titrimetry determined by the disulphite method and calculated for propionaldehyde

Contents, of <300 ppm, preferably <120 ppm, more preferably <60 ppm

^■ content of allyl alcohol, which is determined by gas chromatography, of <2500 ppm, preferably <1700 ppm, particularly preferably <1000 ppm

^■ Content of water, determined by Karl Fischer titration, of <1700 ppm, preferably of <500 ppm, more preferably <200 ppm ^■ content of the acid, in the form of mineral acid and / or organic acid, expressed by the acid-base titration and calculated specific for acetic acid content of <100 ppm, preferably <40 ppm, particularly preferably <20 ppm

Content of carbon dioxide, which is determined by KOH titration, of <500 ppm, preferably <200 ppm, more preferably <100 ppm

In this case, all of the abovementioned limits for the added contents of the contaminants are met.

This means z. B. that when using only a propylene oxide as alkylene oxide starting compound both the content of aldehydes in propylene oxide does not exceed the value of 300 ppm as well as the content of carbon dioxide in the propylene oxide does not exceed the value of 500 ppm. If, for example, propylene oxide and ethylene oxide are used as starting alkylene oxide compounds, this means inter alia that both the added content of aldehydes in the propylene oxide and in the ethylene oxide does not exceed the value of 300 ppm and the added content of allyl alcohol in the propylene oxide and in ethylene oxide does not exceed the value of 2500 ppm.

The invention accordingly provides a process for the base-catalyzed preparation of polyetherols, characterized in that at least one alkylene oxide, in particular propylene oxide (PO) and / or ethylene oxide (EO), is used whose or their added contents a) are expressed on aldehydes the contents determined by gas chromatography or by titration with the bisulfite method and calculated for propionaldehyde, the value of 300 ppm and

b) the value of allyl alcohol, which is determined by gas chromatography

2500 ppm and

c) on water, determined by Karl Fischer titration, the value of 1700 ppm and d) of acid, expressed by acid-base titration and calculated for acetic acid contents, the value of 100 ppm and

e) of carbon dioxide determined by KOH titration shall not exceed the value of 500 ppm.

The process according to the invention for preparing polyetherols in the presence of basic catalysts is preferably carried out using a propylene oxide (PO) and / or an ethylene oxide (EO) whose added contents of aldehydes, expressed by gas chromatography or titrimetry with the bisulfite Determined and propionaldehyde calculated levels, do not exceed the value of 120 ppm.

In a further preferred embodiment of the process according to the invention for the preparation of polyetherols in the presence of basic catalysts, the process is carried out such that a propylene oxide (PO) and / or an ethylene oxide (EO) is used whose added contents of allyl alcohol are determined by gas chromatography , do not exceed the value of 1000 ppm. In a further preferred embodiment of the process according to the invention for preparing polyetherols in the presence of basic catalysts, the process is carried out such that a propylene oxide (PO) and / or an ethylene oxide (EO) is used whose added contents of water, determined by Fischer titration, the value of 500 ppm, preferably not exceed 200 ppm.

In a further preferred embodiment of the process according to the invention for the preparation of polyetherols in the presence of basic catalysts, the process is carried out such that a propylene oxide (PO) and / or an ethylene oxide (EO) is used whose added contents of acid, expressed by the Acid-base titration determined and calculated for acetic acid contents, the value of 40 ppm not exceed.

In a further preferred embodiment of the process according to the invention for preparing polyetherols in the presence of basic catalysts, the process is carried out such that a propylene oxide (PO) and / or an ethylene oxide (EO) is used, whose added contents of carbon dioxide, which are carbonated by Titration, do not exceed the value of 200 ppm.

In a further preferred embodiment of the process according to the invention for the preparation of polyetherols in the presence of basic catalysts, the process is carried out so that only EO is used and wherein the content of water, determined by Karl Fischer titration, the value of 70 ppm, preferred Does not exceed 50 ppm. The analyzes of the respective contaminants were carried out as follows:

^■ Aldehyde content, disulfite method: Houben-Weyl, Method. d. Org. Chemie Bd. 2, Analyt. Method., Thieme Verl. Stuttgart 1953, P. 463/464 (Maßanaly.

^■ Aldehyde content (DNPH + HPLC (DNPH = 2,4-dinitrophenylhydrazine = HPLC = High Performance Liquid Chromatography)): VDI 3862 Part 2; the disulfite method becomes disturbed in the presence of ketones. The DN PH method is therefore used assuming further impurities in the form of ketones, such as acetone.

^■ Allyl alcohol and carbon dioxide by gas chromatography: analogous to DIN 51405; or carbon dioxide via KOH titration. Assuming further impurities in the form of additional acids, carbon dioxide is determined by gas chromatography.

^■ acetic acid for acid-base titration: DIN EN 62021 -2 (. Colorimetr) or DIN (DIN = German Industrial Standard) 12634 (. Potentiometric)

^■ Water content according to Karl Fischer: DIN EN 13267 The following starters are suitable for the process, for example:

a) mono- and polyhydric alcohols having functionality F = 1-8, for example MEG (monoethylene glycol), DEG (diethylene glycol), TEG (trietylene glycol), PEG (polyethylene glycol); MPG (monopropylene glycol), DPG (dipropylene glycol), TPG (tripropylene glycol), PPG (polypropylene glycol); PTHF (polytetrahydrofuran), glycerol, glycerol alkoxilate with molecular weight <10000, TMP (trimethylolpropane), TME, (trimethylolethane), NPG (neopentyl glycol), allyl alcohol alkoxylate with molecular weight <1000, sugars and sugar derivatives such as sucrose or sorbitol, bisphenol A, Bisphenol F, pentaerythritol, degraded starch, water, mixtures thereof;

b) mono- and polyhydric amines (aliphatic and aromatic), such as ethylenediamine,

Triethanolamine or the various isomers of toluenediamine such as 2,4-, 2,6- or vic-TDA,

c) hydroxycarboxylic acids, hydroxyaldehydes, hydroxyketones; Tridecanol N and polymers thereof; Esters of acrylic acid and methacrylic acid with difunctional alcohols such as HEA (hydroxyethyl acrylate), HPA (hydroxypropyl acrylate), HEMA (hydroxyethylmethyl acrylate), HPMA (hydroxypropyl methacrylate), vinyl ethers such as HBVE (hydroxybutyl vinyl ether); isoprenol; polyester polyols; lower alkoxylates of the abovementioned starters, in particular sucrose, sorbitol; polyesterols,

d) vegetable oils with hydroxyl groups or vegetable oils into which hydroxyl groups have been introduced by chemical modification, such as soybean oil or castor oil.

The starters can be submitted to the beginning of the reaction or possibly also added during the process.

The alkylene oxides used are preferably selected from the group comprising ethylene oxide and propylene oxide.

The basic catalysts are preferably selected from the group comprising alkali metal hydroxides and alkaline earth metal hydroxides and the mono-, di- or trihydric amines; particularly preferred is potassium hydroxide.

The process can be carried out as a random or as a block copolymerization using different alkylene oxides. For example, EO / PO Mixtures are randomly polymerized by EO and PO are fed as a mixture, or polymerized in blocks by first pure PO and then pure EO is closed or vice versa. For example, the inventive method can be carried out in a stirred tank, wherein the stirred tank can be equipped with at least one internal and / or at least one external heat exchanger.

The addition of the total amount of the catalyst can be carried out at the beginning of the reaction or in portions over the reaction time. Likewise, it is possible to proceed with the starter substance (s).

The process according to the invention can be carried out as a batch, semibatch or continuous process.

The reaction of the starting substance with the alkylene oxides is carried out at the customary pressures in the range between 0.1 and 1.0 MPa and the usual temperatures in the range between 80 and 160 ° C. The dosing of the alkylene oxides is usually followed by a post-reaction phase to completely react the alkylene oxides. The Rohpolyetheralkohol thus obtained is freed of unreacted alkylene oxide and volatile compounds by distillation or stripping, preferably under vacuum, dehydrated and worked up by acid neutralization and separation of the resulting salts. If amines are used as catalysts, they can remain in the polyol.

The subject of the process according to the invention for the preparation of polyetherols in the presence of basic catalysts are also the polyetherols which can be prepared using the process according to the invention.

The polyether alcohols which can be prepared by the process according to the invention can preferably be reacted with polyisocyanates to give polyurethanes.

The use of the polyether alcohols according to the invention in the production of polyurethanes allows accurate prediction of the properties of the final product, since the polyether alcohols according to the invention due to the absence of undesirable side reactions with impurities or impurities in the production process have well-defined and predictable properties. Thus, the tailor-made production of polyurethanes with certain properties is possible. In addition, only when using the polyether alcohols according to the invention some desired in polyurethanes specifications such. B. the lowest possible color can be achieved. The use of the polyetherols which can be prepared according to the invention for adjusting PUR (polyurethane) foams is particularly preferred.

Examples:

In the following the invention is illustrated by means of selected examples. However, the examples are not intended to limit the scope of the invention in any way; they are illustrative only. A) trial:

In a 300 mL stainless steel autoclave, 5.4 g of glycerol were submitted, 1.33 g 45proz. added aqueous potassium hydroxide solution, the vessel was sealed, heated to 120 ° C with stirring and maintained under a vacuum of 20 mbar for 1 h. Subsequently, a nitrogen pressure of 1 bar was set. Over a period of about 5 hours 194.6 g of pure propylene oxide were added via a pressure line at 1 10- 130 ° C. If the pressure remained constant, it was cooled, vacuum was applied briefly, this was removed and 1.25 g of 85% strength. Phosphoric acid with stirring at room temp. added. After 30 minutes, vacuum was applied and at the same time a slight stream of nitrogen was introduced. Subsequently, the batch was filtered through a plate filter. Thereafter, the OH number and the viscosity were determined.

OH number: 42.1 mg KOH / g

Viscosity: 670 mPa ^* s / 25 ° C

The OH number and the viscosity are determined by standard methods which are familiar to the person skilled in the art.

By the term "pure propylene oxide" is meant a propylene oxide which contains impurities or impurities only up to the following upper limits:

^■ aldehydes (as propionaldehyde) <60 ppm

^■ allyl alcohol <1700

^■ Water <500 ppm

^■ Acid (as HOAc) <20 ppm

■ Carbon dioxide <100 ppm

B) Experiments with Propionaldehyde Contamination:

1 . Experiment A) was repeated, but after the introduction of nitrogen 0.973 g of propionaldehyde (corresponding to 5000 ppm, based on 194.6 g of crude PO) were added and 193.6 g of pure PO were added. OH number: 30.2 mg KOH / g

Viscosity: 960 mPa ^* s / 25 ° C

2. The experiment was carried out as approach B1, but with 0.389 g of propionaldehyde (corresponding to 2000 ppm based on 194.6 g of crude PO) and 194.3 g of pure PO. The aldehyde was metered with a syringe through a septum into the reaction vessel.

OH number: 37.4 mg KOH / g

Viscosity: 840 mPa ^* s / 25 ° C

3. In further approaches, the amount of propionaldehyde was successively reduced. The OH number and viscosity were graphically plotted against the amount of propionaldehyde and the value of the amount of propionaldehyde for which OH number and viscosity were within the error limits identical to those of Experiment A was determined by extrapolation. This value was about 300 ppm.

C) Experiments with Allyl Alcohol Contamination:

Experiment A) was repeated, but after the introduction of nitrogen, 0.973 g of allyl alcohol (corresponding to 5000 ppm, based on 194.6 g of crude PO) were added and 193.6 g of pure PO were added.

The further experiments were carried out in analogy. The results are summarized in Table 1:

Table 1 :

To determine the maximum allowable amount of allyl alcohol contamination, the OH number and viscosity were plotted against this amount, and a curve fit was made using a least squares compensation polynomial as indicated in FIG.

Based on this, the maximum permitted amount of allyl alcohol was determined. The reason for this was the requirement that the OH number and viscosity should be within the limits of measuring accuracy should not deviate from the comparative batch without contamination. The measurement accuracy for the OH number was one unit (ie 1 mg KOH / g), for the viscosity ± 3% of the measured value (rotational viscometer, at 660 mPa ^* s therefore about 20 mPa ^* s). This resulted in the maximum amount of 500 ppm.

Figure 1 shows the curve for the OH number, Figure 2 for the viscosity.

D) Experiments with water contamination: See Table 2. The procedure was as under A), but after the nitrogen supply, the amounts of water indicated in Table 2, column 1, were added. The PO used contained 250 ppm of water. The amount of water added was chosen to give the total amounts listed in Table 2, column 2. Table 2:

The maximum permissible quantity was determined as described in B). The amount was thus 500 ppm.

However, it is known to the person skilled in the art that even in the case of contaminant water, generally even at higher contents in the alkylene oxide used, tolerable quality losses in the product still result for some applications. E) Experiments with acetic acid contamination:

See Table 3. Procedure as in A), but after the nitrogen supply the amounts of glacial acetic acid given in Table 3 were added. Table 3:

Acetic acid acetic acid pure PO OH number [mg viscosity [ppm] [g] [g] KOH / g] [mPa ^* s / 25 ° C]

5000 0.973 193.6 53.9 510 Acetic acid acetic acid pure PO OH number [mg viscosity [ppm] [g] [g] KOH / g] [mPa ^* s / 25 ° C]

1500 0,292 194,3 45,7 620

500 0.097 194.5 43.3 645

250 0.049 194.6 42.70 650

0 0.000 194.6 42.1 660

The maximum permissible quantity was determined as described in B). The amount was thus 100 ppm. F) Experiments with carbon dioxide contamination:

See Table 4. The experiments were carried out as in A), but after feeding nitrogen, the amounts of carbon dioxide shown in Table 4 were introduced through a septum into the reactor with a gas tight syringe.

Table 4:

By gas chromatography, it was possible to detect propylene carbonate in the polyol with 5000 ppm carbon dioxide in the polyol.

The maximum permissible quantity was determined as described in B). This resulted in 500 ppm. The experiments thus show the advantages of the method according to the invention over the conventional methods.

The above-mentioned problems in conventional processes, ie using more contaminated with impurities alkylene oxides as starting materials are avoided in the process according to the invention. For example, there is no marked discoloration due to aldol condensation caused by a too high content of aldehydes, or undesirable and unpredictable property changes. tions of the polyols - and thus the producible from polyurethanes flow to high levels of allyl alcohol in the alkylene oxides used

Claims

claims

1) A process for the preparation of polyetherols in the presence of basic catalysts, characterized in that propylene oxide (PO) and / or ethylene oxide (EO) is used, their added contents

1 a) to aldehydes, expressed by the gas chromatographic or titrimetric determined by the bisulfite method and calculated for propionaldehyde contents, the value of 300 ppm and

1 b) of allyl alcohol, which are determined by gas chromatography, the value of 2500 ppm and

1 c) of water, determined by Karl Fischer titration, the value of 1700 ppm and

1 d) of acid, expressed by the acid-base titration determined and calculated for acetic acid contents, the value of 100 ppm and

1 e) of carbon dioxide, which are determined by KOH titration, do not exceed the value of 500 ppm.

2) Process for the base-catalyzed preparation of polyetherols according to claim 1, characterized in that a propylene oxide (PO) and / or ethylene oxide (EO) is used, the added levels of aldehydes, expressed by gas chromatography or by titrimetry with the bisulfite method and levels calculated for propionaldehyde do not exceed 120 ppm.

3) Process for the base-catalyzed preparation of polyetherols according to claim 1 or 2, characterized in that a propylene oxide (PO) and / or an ethylene oxide (EO) is used, the added contents of allyl alcohol, which are determined by gas chromatography, the value of 1000 ppm do not exceed.

4) Process for the base-catalyzed preparation of polyetherols according to any one of claims 1 -3, characterized in that a propylene oxide (PO) and / or an ethylene oxide (EO) is used whose added levels of water, determined by Karl Fischer titration, do not exceed the value of 500 ppm, preferably 200 ppm. 5) A process for the base-catalyzed preparation of polyetherols according to any one of claims 1 -4, characterized in that a propylene oxide (PO) and / or an ethylene oxide (EO) is used, the added levels of acid, expressed by the acid-base Titration determined and calculated for acetic acid contents, not exceed the value of 40 ppm. 6) Process for the base-catalyzed preparation of polyetherols according to any one of claims 1-5, characterized in that a propylene oxide (PO) and / or an ethylene oxide (EO) is used, the added levels of carbon dioxide, which are determined by KOH titration, do not exceed the value of 200 ppm.

7) Method according to one of claims 1-6, wherein the basic catalyst is selected from the group comprising alkali hydroxides and alkaline earth hydroxides, preferably potassium hydroxide.

8) Method according to one of claims 1-7, wherein only EO is used and wherein the content of water, determined by Karl Fischer titration, does not exceed the value of 70 ppm, preferably 50 ppm. 9) Polyetherols, preparable by the process of any of claims 1-8.

10) Use of the polyetherols according to claim 9 for the preparation of polyurethanes.