DE3233251A1 - Asymmetric polyether-polyols, process for their preparation, and their use for polyurethane plastics - Google Patents

Abstract

Asymmetric polyether-polyols having a functionality of from 3 to 8, a hydroxyl number of from 15 to 112 and preferably a compatibility index of less than 50 DEG C are obtained by reacting a) one mol of a polyoxyalkylene glycol having a hydroxyl number of from 15 to 200 with b) from 0.1 to 2 mol of an epoxyalcohol of the formula <IMAGE> in which R<1> and R<2> are identical or different and are a hydrogen atom or a -CH2OH radical, x is an integer from 0 to 9 and y is 0 or 1, preferably glycidol, and subsequent c) alkoxylation of the resultant trifunctional to octafunctional intermediate c) in the presence of basic catalysts until the hydroxyl number mentioned has been reached. The asymmetric polyether-polyols are particularly suitable for the production of open-cell polyurethane foams.

Description

'' Asymmetric polyether polyols, process for their production

Position and its use for polyurethane plastics The manufacture of polyether polyols through polymerization of alkylene oxides, which attach to a starter molecule with Zerewitinoff active hydrogen atoms in the presence of basic catalysts add is known. The basic catalysts are usually alkali metal hydroxides or alcoholates used for polyether polyols with hydroxyl numbers up to 28 in Amounts up to a maximum of 0.06 mol per equivalent of Zerewitinoff active hydrogen atom of the starter molecule can be used. Polyether polyols with free hydroxyl groups are obtained, some of which have terminal alcoholate groups due to the basic reaction medium wearing. For the further use of the polyether polyols, e.g. for the production of Polyurethanes, it is necessary to remove the alcoholate residues of the polymers, for example by neutralization with acids, into free hydroxyl groups.

Activated polyether polyols are usually made by addition from ethylene oxide to polyoxypropylene glycols or polyoxyethylene-polyoxypropylene glycols produced, the oxyethylene and oxypropylene groups in the copolymers can be arranged randomly or in blocks. This is the reactivity of the polyether polyol by the amount of polymerized ethylene oxide in the end block certainly.

A high content of oxyethylene groups, which is necessary because of the reactivity in the polyether polyol can interfere with the foam properties. So tend Poly Urethane foams made from oxyethylene groups are rich in polyether polyols for the formation of closed foam cells.

Furthermore, the mechanical property level deteriorates in the presence from moisture, as the foams are too hydrophilic.

According to DE-OS 30 30 737 it was achieved by reducing the ethylene ether content in the polyoxyethylene end block and by increasing the catalyst concentration at the same time before the final ethoxylation to produce polyether polyols, which are used in the Reaction with organic polyisocyanates foams with a larger number of open cells result. However, it was also found that the hardness of flexible polyurethane foams impaired by a reduction in the ethylene ether content in the polyether polyol will. It is also known that by increasing the ethylene ether content in the end block of a polyether-polyol, the compatibility index (CI) becomes larger and the closed-cell structure of a polyurethane foam produced with it increases sharply.

The use of epoxy alcohols, especially glycidol, for the production of polyether or polyester polyether polyols is not new either. To Information in GB-PS 973 958 is mixtures of epoxy alcohols and alkylene oxides added together to a starter molecule. In this way, polyether-polyol mixtures are made obtained with a desired hydroxyl content and molecular weight, however differentiate the individual molecules with regard to their molecular weight.

DE-OS 25 39 108 describes the production of polyoxypropylene glycols with reduced double bond content, without the content of hydroxyl end groups noteworthy Changes, by polymerization of propylene oxide in the presence from 0.1 to 3 mole percent glycidol.

According to US Pat. No. 3,483,169, hydroxyl or carboxyl groups are disclosed Copolymers by copolymerizing epoxides and cyclic anhydrides on a Starter molecule in special proportions and under certain reaction conditions manufactured.

The object of the present invention was to provide polyether polyols to develop an ethylene ether content comparable to that of commercially available polyether polyols in the end block and also have a very low tolerance index. The polyether polyols should be used in the production of polyurethane, semi-rigid, soft or integral foams are effective in opening cells or reducing foam pressure, the internal foam pressure showing a low value over a long period of time should (flat course of the internal foam pressure curve in the internal foam pressure-time diagram).

This object was surprisingly achieved with the aid of asymmetrical polyether polyols with a functionality of 3 to 8 and a hydroxyl number of 15 to 112, which are obtained by reacting a) one mole of a polyoxyalkylene glycol with a hydroxyl number of 15 to 200 with b) 0.1 to 2 moles of an epoxy alcohol of the formula in which R1 and R2 are identical or different and 1 is a hydrogen atom or a methylol radical, x is an integer from 0 to 9 and y is 0 or 1 and subsequent c) alkoxylation of the tri- to octa-functional intermediate (c) up to the aforementioned Hydroxyl number.

Asymmetrical polyether-polyols are in the sense of ore in dung polyether-polyols with a functionality of 3 to 8 and a different equivalent weight of the individual ligands.

The asymmetric polyether polyols according to the invention have the The advantage that they have the same compared to commercially available polyether polyols Functionality and hydroxyl number as well as the same weight ratio of ethylene ether have a lower compatibility index CI for alkylene ether groups in the molecule. The compatibility index CI, also called the cloud point, is among the known ones Polyether polyols of the prior art are sharply defined and usually lie over 5000. The polyether polyols according to the invention, however, have either a sharply defined cloud point less than 500C or a relatively broad one Cloud point range from less than 200C to a maximum of 600C, which means that in In this area the turbidity does not occur suddenly, but increases continuously. The compatibility index CI or cloud point is determined by mixing of 100 g of a solution of 50 parts by weight of water and 50 parts by weight of isopropanol with 3 g of polyether polyol and heating the solution at a rate of 300 per minute until clouding occurs.

In this connection it should be noted that the compatibility index usually with increasing molecular weight with the same functionality and constant Weight ratio of ethylene ether to other alkylene ether units decreases or with the same molecular weight and the same functionality with increasing ethylene ether content can be increased.

The products also show an excellent cell-opening effect, i.e. a decrease in internal foam pressure in the production of polyurethane, semi-rigid, Soft and integral skin foams.

For the preparation of the asymmetric polyether polyols according to the invention Usable starting materials and catalysts must be carried out as follows: a) Suitable Polyoxyalkylene glycols with a hydroxyl number of 15 to 200, preferably 20 up to 100 and especially from 35 to 70 can be prepared by reaction of one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene chain and a molecular weight of 44 to 250, preferably 44 to 72 with a starter molecule, that contains two reactive hydrogen atoms bonded.

Examples of alkylene oxides that may be mentioned are tetrahydrofuran, epichlorohydrin, styrene oxides, cyclohexene oxide, l-cyclohexyl ethylene oxide, which may be substituted on the phenyl group, 1,2- and 2,3-butylene oxide, 1,3-propylene oxide and preferably 1,2-propylene oxide and Ethylene oxide. The alkylene oxides can be used individually, alternately one after the other or as Mixtures can be used. For example, the starter molecule can initially 1,2-propylene oxide and then the ethylene oxide polymerizes, or initially 'the copolymerized all of the 1,2-propylene oxide in admixture with part of the ethylene oxide and the remainder of the ethylene oxide is subsequently unpolymerized or initially incrementally some of the ethylene oxide, then all of the 1,2-propylene oxide, and then the remainder of the ethylene oxide are polymerized. Of course, only 1,2-propylene oxide can also be used or ethylene oxide are polymerized onto the starter molecule.

Possible starter molecules are, for example: water, amino alcohols such as ethanolamine, N-alkyldialkanolamines such as N-methyl and N-ethyldiethanolamine, diglycol ethers such as diethylene glycol and dipropylene glycol and diols with 2 to 10 carbon atoms, preferably 2 to 6 Carbon atoms such as ethylene glycol, 1,2-, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol and 1,10-decanediol. Preference is given to using water, ethylene glycol, diethylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol and 1,6-hexanediol. B) As starting component b) epoxy alcohols of the formula is used, in which R1 and R2 are identical or different and denote a -CH20H- radical or preferably a hydrogen atom, x is an integer from 0 to 9, preferably 0 to 3 and in particular 0 and y is 1 or preferably 0.

'The following are examples of epoxy alcohols: 1,2-epoxy-butan-4-ol, 1,2-epoxy-3-methylol-butan-4-ol, 1,2-epoxy - 3,3-dimethylol-butan-4-ol, 1,2-epoxy-pentan-5-ol, 1,2-epoxy-4-methylol-pentan-5-ol, 1,2-epoxy-4, 4-dimethylol-pentan-5-ol, 1,2-epoxy-hexan-6-ol, 1,2-epoxy-5-methylol-hexan-6-ol, 1,2-epoxy-5,5-dimethylol-hexan-6-ol, 1,2-epoxy-heptan-7-ol, 1,2-epoxy-octan-8-ol, 1,2-epoxy-decan-10-ol, 1,2-epoxy-dodecan-12-ol, 1,2-epoxy-II-methylol-dodecan-12 -oil, 1,2-epoxy-II, II-dimethylol-dodecan-12-ol and preferably glycidol (1,2-epoxy-propan-3-ol).

The epoxy alcohols can be used either individually or in the form of mixtures can be used.

To produce the tri- to octafunctional, preferably tri- to tetrafunctional intermediates are per mole of polyoxyalkylene glycol (a) 0.1 to 2 moles, preferably 0.5 to 1.5 moles, and especially about 1 mole of epoxy alcohol (b) reacted.

c) The intermediate product obtained is then known per se Way in the presence of basic catalysts up to a hydroxyl number of 15 to 112, preferably 25 to 55 and in particular from 25 to 35 alkoxylated. Preferred are used as alkylene oxides, ethylene oxide, 1,2-propylene oxide or mixtures thereof used, in particular such asymmetric polyether polyols are produced based on the total weight of polymerized alkylene oxide groups 5 to 40% by weight, preferably 10 to 30% by weight, of polymerized ethylene oxide groups bound Contain, of which in turn 5 to 30 wt.%, Preferably 10 to 20 wt.% Terminal are bound. The asymmetric polyether polyols according to the invention have measured by the aforementioned method, a compatibility index CI or cloud point from less than 20 to 50 ° C, preferably from less than 20 to 40 ° C dead a turbidity range from less than 200 ° C. to a maximum of 9600 ° C., preferably from 35 to 580C.

The polyoxyalkylene glycols (a) suitable as starting materials can be prepared in the presence of acidic or, preferably, basic catalysts. Likewise, the addition of the epoxy alcohols (b) and the final alkoxylation are carried out (c) the intermediates carried out in the presence of acidic or basic catalysts, the use of basic catalysts is preferred.

Examples of acidic catalysts are: strong mineral acids with pKa values from -5 to +4 such as perchloric acid, hydrochloric acid, sulfuric acid, phosphoric acid, organic sulfonic acids, such as toluenesulfonic acid and ion exchangers with sulfonic acid groups, Lewis acids, e.g.

BF3, All3, SnCl4, FeCl3, PF5 or SbCl5 and fuller's earth.

Polytetrahydrofurans containing hydroxyl groups are preferably made by Polymerization of tetrahydrofuran in the presence of acetic anhydride with antimony pentachloride or substantially anhydrous fuller's earth as a catalyst and then Transesterification produced. The reaction temperatures for the polymerization with acidic Catalysts are usually between 10 and 1200C, preferably 30 and 660C.

As basic catalysts, e.g. in amounts of 0.03 to 1.0 mol, preferably from 0.06 to 0.2 moles per equivalent hydroxyl group of the polyoxyalkylene glycols (a) or intermediates (c) are used, for example: Alkali alkoxides with 1 to 4 carbon atoms in the alkyl radical, such as sodium methylate, Sodium and potassium ethoxide, potassium isopropoxide and potassium butoxide, alkaline earth hydroxides, like: .B. Calcium hydroxide and preferably 9 wise alkali hydroxides, such as lithium and especially sodium and potassium hydroxide.

In particular, the asymmetric polyether polyols are advantageous Prepared as follows: The polyoxyalkylene glycols (a) are made with acidic catalysts at temperatures up to 1200C and reaction times of 0.5 to 5 hours or preferably in the presence of basic catalysts with an epoxy alcohol (b) or a Reacted epoxy alcohol mixture to the tri- to octafunctional intermediates.

For this purpose, the polyoxyalkylene glycols (a) with the basic catalyst added and partially converted into the corresponding alcoholate. Depending on the used The catalyst is then optionally formed water or low-boiling alcohol, expediently distilled off under reduced pressure and at temperatures of 90 to 15,000, preferably 100 to 130 ° C., the epoxy alcohols to the same extent as they react, for example in 0.5 to 8 hours, preferably 1 to 2 hours Atmospheric pressure or optionally under increased pressure at 1.1 to 20 bar, preferably 1.1 to 7 bar entered. After the reaction has ended, the unreacted epoxy alcohol becomes distilled off under reduced pressure, for example at 10 to 20 mbar. The implementation is expediently, like the subsequent alkoxylation, in the presence a gas which is inert under the reaction conditions, for example nitrogen.

Thereafter, the intermediate product (c) formed, optionally after Introducing additional basic catalyst and separating off the water formed or alcohol, under the above reaction conditions with 1,2-propylene oxide, mixtures of 1,2-propylene oxide and ethylene oxide or ethylene oxide alkoxylated, preferably with the proviso that for the formation of terminal ethylene ether groups is finally ethoxylated.

After the hydroxyl number required according to the invention has been reached, the excess alkylene oxides, preferably ethylene oxide under reduced pressure distilled off, the asymmetric polyether polyols formed with inorganic ones Acids, such as sulfuric acid, hydrochloric acid or phosphoric acid, react acidic Salts such as potassium hydrogen phosphate, organic acids such as citric acid, Tartronic acid or other neutralized ion exchangers and using known methods cleaned.

According to a preferred embodiment, the preparation of the polyoxyalkylene glycols (a), the reaction with the epoxy alcohols and the subsequent alkoxylation in several stages carried out in the same reaction vessel. In a preliminary stage, first from the mentioned difunctional starter molecules and alkylene oxides in the presence of basic catalysts by known methods with polyoxyalkylene glycols (a) Hydroxyl numbers of 15 to 200 produced, which after removal of excess Alkylene oxide directly, i.e. in the same reaction vessel, according to the invention Process to asymmetric polyether polyols are implemented.

The asymmetric polyether polyols according to the invention have functionalities from 3 to 8, hydroxyl numbers from 15 to 112, cloud points up to 500C or cloud areas up to 600cm The content of primary hydroxyl groups is on average 50 bs 95% by weight.

'The products are used to manufacture polyurethane plastics used. They are particularly suitable for the production of polyurethane, semi-hard, Soft foams and integral skin foams, including a mixture of the inventive asymmetric polyether polyols and conventional polyether polyols are used can.

EXAMPLES 1 TO 5 General Manufacturing Instructions The inventive asymmetric polyether polyols were produced in 2 precursors and 3 reaction stages, However, depending on the technical conditions, the alkoxylation is still can subdivide more reaction stages.

1st precursor: 134.2 parts by weight of dipropylene glycol were in a reactor submitted and with 14.7 parts by weight of an 85% strength by weight aqueous potassium hydroxide solution mixed. This mixture was used to separate the resulting from the alcoholate formation Water heated to 1050C for 2 hours under reduced pressure (10-20 mbar).

2nd precursor: The 1,2-propylene oxide was the reaction mixture at a temperature of 105 ° C and a pressure of up to a maximum of 7 bar in 2 to 7 hours incorporated. After a post-reaction time of about 1.5 hours this did not happen converted 1,2-propylene oxide stripped off under reduced pressure.

1st reaction stage: to the obtained polyoxypropylene glycol were 74 parts by weight of glycidol (1 mole per mole of polyoxypropylene '-glycol) metered in at 105 ° C. in 1.5 hours. After the reaction was over, it did not work converted glycidol is separated off under reduced pressure (10 to 20 mbar) in 1.5 hours.

2nd reaction stage: the intermediate product obtained was treated with 1,2-propylene oxide propoxylated analogously to the instructions for precursor 2. After the reaction was over, it became unreacted 1,2-propylene oxide is distilled off under reduced pressure (10 to 20 mbar).

3rd reaction stage: 740 parts by weight of ethylene oxide were added to the reaction mixture incorporated at 105 ° C under a pressure of up to a maximum of 7 bar in 4 hours. After finished Reaction was the unreacted ethylene oxide under reduced pressure (10 to 20 mbar) distilled off, the reaction mixture mixed with a magnesium silicate and the alkaline magnesium silicate is filtered off.

Comparative Example A For the separation of the alcoholate formation The resulting water was a mixture of 1.84 parts by weight of glycerol and 147 parts by weight an 85% strength by weight aqueous potassium hydroxide solution for 2 hours under reduced Pressure (10 to 20 mbar) heated to 1300C.

To the reaction mixture were added at a temperature of 1050C and a pressure up to a maximum of 7 bar in 5 to 6 hours 4160 parts by weight of 1,2-propylene oxide added. After a post-reaction time of 4 hours, this was not converted 1,2-propylene oxide is distilled off under reduced pressure.

740 parts by weight of ethylene oxide were then added to the reaction mixture 1050C and incorporated under a pressure of up to 7 bar in 3 hours. To complete After the ethoxylation, the reaction mixture was kept at 105 ° C. for 4 hours the unreacted ethylene oxide is distilled off, the reaction mixture with a Treated magnesium silicate and filtered off the alkaline magnesium silicate.

The order in which the structural components are added in a schematic form and the characteristics determined on the end products obtained are in the tables la and 1b combined.

Table 1a Examples 1 2 3 4 5 2nd precursor: 1,2-propylene oxide [parts by weight] 516 1030 2050 3080 4360 Reaction time [hours] 2 3 5 6 7 Hydroxyl number of the obtained Polyoxypropylene glycol 180 98 54 38 28 2nd reaction stage: 1,2-propylene oxide [parts by weight] 3880 3350 2310 1280 reaction time [hours] 6 6 5 4 hydroxyl number of the obtained Polyoxypropylene triols 42 42.5 41.5 42 41.5 Table 1b examples Order of addition of the L1 L2 L3 f OHZ CI Appearance build-up components wt.% Wt.% Weight% [° C] EO + PO EO + PO EO + PO 1 II2-PO (10) -Glycid [1] -PO (75) -EO (15) 40 30 30 3 36 30-58 clear 2 II2-PO (20) -Glycid [1] -PO (65) -EO (15) 46.6 26.6 26.6 3 35 36.8 clear 3 II2-PO (40) -Glycid [1] -PO (45) -EO (15) 60 20 20 3 35 <20 weak opacity 4 II2-PO (60) -Glycid [1] -PO (25) -EO ( 15) 73.3 13.3 13.3 3 35 <20 turbidity 5 II2-PO (85) -Glycid [1] -EO (15) 90 5 5 3 35 <20 strong haze Comparative Example A Glyc-PO (85) -EO (15) 33.33 33.33 33.33 3 35 56 clear In Tables Ib and 2b the following abbreviations have been used 9 used: II2 dipropylene glycol PO: 1,2-propylene oxide EO: ethylene oxide (X): x% by weight PO or EO based on the total weight of the alkylene oxides Glycid: Glycidol (1,2-epoxy-propan-3-ol) [Y]: y Mol Glyc: Glycerin L1: Ligand 1 L2: Ligand 2 L3 Ligand 3 functionality OHZ: Hydroxyl number CI: Compatibility index Examples 6 to 8 The asymmetric polyether polyols were prepared analogously to the general preparation procedure for Examples 1 to 5.

The structural components used and their quantities, the process parameters as well as the sequence of the addition of structural components in schematic form and the The characteristic data determined on the end products are summarized in Tables 2a and 2b.

Table 2a Examples 6 7 8 Comparative Examples B C D 1st preliminary stage: Dipropylene glycol [g] 175.6 231.4 268.4 - - -Glycerol [g] - - - 120 92 145 85% strength by weight aqueous KOH [g] 16.5 16.47 10.07 16.5 9.5 8 reaction temperature [° C] 105 105 105 105 105 105 pressure [mbar] 15 15 15 15 15 15 2nd precursor: 1,2-propylene oxide [g] 4036.8 3984 2405 5503 3370 2850 Response time [hours] 6 5 4.5 6 5 6 max. Pressure [bar] 6.5 6.0 5.5 5.5 6 5.5 hydroxyl number 38 46 86 41 48 87 1st reaction stage: glycidol [g] 96.9 127.7 148.2 - - -Mol glycidol / mole dipropylene glycol 1 1 1 - - reaction time [Hours] 1 1.5 1 - - -Reaction temperature [° C] 105 105 105 - - - Cont. Table 2a Examples 6 7 8 Comparative Examples B C D 2nd reaction stage: 1,2-propylene oxide [g] 1345 1660 1002 - - -Hydroxyl number 42 50.5 88 - - -3. Reaction stage: ethylene oxide [g] 1345 996 601 1375 595 503 maximum pressure [bar] 5 5.5 4.5 5 4.5 4.5 reaction time [Hours] 2 2 1.5 2 2 1.5 hydroxyl number 36 42 76 37 45 74 Tabel 2b Examples Order of addition of the L1 L2 L3 f OHZ CI Appearance of structural components Wt% wt% wt% [° C] EO + PO EO + PO EO + PO 6 II2-PO (60) -Glycid [1] -PO (20) -EO (20) 73.3 13.3 13.3 3 36 <20 slightly cloudy 7 II2-PO (60) -Glycid [1] -PO (25) -EO (15) 73.3 13.3 13.3 3 42 <20 slightly cloudy 8 II2-PO (60) -Glycid [1] -PO (25) -EO (15) 73.3 13.3 13.3 3 73 45-58.7 slightly cloudy comparative examples: B Glyc-PO (80) -EO (20) 33.33 33.33 33.33 3 36 61 clear C Glyc-PO (85) -EO (15) 33.33 33.33 33.33 3 45 55 clear D Glyc-PO (85) -EO (15) 33.33 33.33 33.33 3 70 61 clear Examples 9 to 13 and comparative examples E to H Production of semi-rigid polyurethane foams: A component: Mixture from a polyether polyol, 8.4 parts by weight of a polyether polyol based on ethylene diamine propylene oxide with a hydroxyl number of 770, 0.3 parts by weight of dimethylethylenediamine and 1.8 parts by weight Water.

B component: Mixture of diphenylmethane diisocyanates and polyphenyl - polymethylene polyisocyanates.

100 parts by weight of the A component and 50 parts by weight of the B component were mixed intensively with a stirrer for 10 seconds and to determine the foaming characteristics (Start and rise time) in an open cup and to measure the foaming pressure filled into an open pressure nut tube and left to foam there.

The foaming data were determined analogously to the publication by R. Jannings, Instrumental Analysis of the Performance Characteristics of Rigid Urethane Foaming Systems, in J. Cell. Plastic May / June 1969, pages 159 to 172.

The polyether polyols used and their amounts as well as those determined Start and rise times, the gel point and the maximum foam pressure are in the table 3 summarized. Table 3.

Examples of polyether-polyol according to the start-rise-gel point max Example amount time time [parts by weight] [sec] [sec] [sec] mbar 9 3 89.5 34 150 116 64 10 6 89.5 36 143 111 33 11 7 89.5 40 127 110 15 12 8 89.5 37 153 112 51 13 A 71.6 and 5 17.9 33 156 130 37.5 comparative examples E A 89.5 39 178 169 275 F B 89.5 37 179 171 193 G C 89.5 37 153 149 214 H D 89.5 38 163 118 118 tThe Examples 9 to 13 and Comparative Examples E to H show that in the production of semi-rigid polyurethane foams by using the inventive asymmetric polyether polyols or their mixtures with conventional polyether polyols a significant maximum reduction in foaming pressure is achieved.

7th

Claims (10)

Patent claims 1. Asymmetrical polyether polyols with a functionality of 3 to 8 and a hydroxyl number of 15 to 112, obtained by reacting a) one mole of a polyoxyalkylene glycol with a hydroxyl number of 15 to 200 with b) 0.1 to 2 Moles of an epoxy alcohol of the formula in which R1 and R2 are identical or different and denote a hydrogen atom or a -CH2011 radical, x is an integer from 0 to 9 and y is 0 or 1 and subsequent c) alkoxylation of the tri- to octafunctional intermediate (c) bis formed to the hydroxyl number mentioned. 2. Asymmetric polyether polyols according to claim i, characterized in that that the products have a compatibility index CI or cloud point lower than TOOC or have a turbidity range of less than 200C to 6o0C. 3. Asymmetric polyether polyols according to claim 1, characterized in that that the products contain terminal ethylene ether blocks bound. 4. Asymmetrical polyether polyols according to claim 1, characterized in that that the products contain 5 to 40% by weight of polymerized ethylene oxide groups, based on the weight of polymerized alkylene oxide groups, with 5 to 30% by weight the polymerized ethylene oxide groups are arranged at the end. 5. Asymmetrical polyether polyols according to claim 1, characterized in that that glycidol is used as the epoxy alcohol for the reaction. 6. Process for the preparation of asymmetric polyether - polyols with a functionality of 3 to 8 and a hydroxyl number of 15 to 112, characterized in that a) one mole of a polyoxyalkylene glycol with a hydroxyl number of 15 to 200 with b) 0 , 1 to 2 moles of an epoxy alcohol of the formula in which R1 and R2 are identical or different and represent a hydrogen atom or a methylol radical, x is an integer from 0 to 9 and y 0 or 1 are converted and the tribis octafunctional intermediate c) formed is alkoxylated in the presence of a basic catalyst up to the hydroxyl number mentioned . 7. The method according to claim 6, characterized in that the tri- to octafunctional intermediate formed is ethoxylated or alkoxylated and finally ethoxylated. 8. The method according to claim 6, characterized in that one pro Mole of polyoxyalkylene glycol (a) used approximately 1 mole of epoxy alcohol (b). 9. The method according to claim 6, characterized in that as Epoxy alcohol (b) glycidol used. 10. Use of the asymmetric polyether polyols for the production of polyurethane plastics, especially open-cell polyurethane, semi-rigid, Soft and integral foams.