DE10009649A1 - Open celled rigid polyurethane foam, useful for vacuum panels, is prepared from di/polyisocyanates with castor oil glycerol ester and polyether polyols and dimethylamino-N-methyl-ethanolamine catalyst. - Google Patents

Abstract

An open celled rigid polyurethane foam is prepared by reaction of di- and/or polyisocyanates with 5-30 pts.wt. castor oil glycerol ester and 1-30 pts.wt. of a polyether polyol having a hydroxyl number of 50-300 in the presence of 0.1-5 pts.wt. dimethylamino-N-methyl -ethanolamine catalyst. An open celled rigid polyurethane foam (I) is prepared by reaction of (A) di- and/or polyisocyanates with (B) compounds having isocyanate reactive hydrogen atoms in the presence of (C) propellant (D) catalysts, processing aids and additives whereby (B) comprises (wrt 100 pts. wt. (B), (C) and (D)) (B1) 5-30 pts.wt. castor oil glycerol ester (B2) 1-30 pts.wt. of a polyether polyol having a hydroxyl number of 50-300, prepared by reaction of a di to tetravalent alcohol or aromatic amine with at lest one alkylene oxide and (D) comprises 0.1-5 pts.wt. dimethylamino-N-methyl -ethanolamine.

Description

The invention relates to open-cell rigid polyurethane foams, which have a high open cell structure in the marginal zone.

Rigid foams can be used in many technical fields, for example as a heat insulation material.

EP-A-905 159 discloses a process for the manufacture of open cellular isocyanate-based foams and their use for the production of vacuum panels, being as with isocyanate reactive compounds prefer esterification products from fat acids and polyfunctional alcohols are used.

In the manufacture of vacuum panels for use e.g. B. in refrigeration cabinets, district heating pipe insulation, truck bodies is one high open-cell nature of the rigid foam used Lich. The methods described in the prior art lead usually to rigid foams that are a partially closed Have edge zone. Consequently, this edge zone must be separated and be discarded, which leads to economically disadvantageous material ver lust leads. The formation of cavities is also disadvantageous in the continuous production of rigid polyurethane foam fen according to the double belt process.

The object of the present invention was therefore to open one cellular rigid polyurethane foam with few cavities ready to deliver, which has a high open cell of the edge zone and thus, for example, advantageous for the production of Vacuum panels can be used.

The task could be solved by implementing di and / or polyisocyanates containing reactive hydrogen atoms Compounds comprising castor glycerol esters and a polyether polyol (A) with a hydroxyl number of 50-300 in the presence of Dimethylamino-N-methylethanolamine as a catalyst or cocata lysator.

The invention accordingly relates to a process for producing open-cell rigid polyurethane foams by reacting the components

• a) Di- and / or polyisocyanates with  
• b) having hydrogen atoms reactive toward isocyanates Compounds in the presence of the components
• c) blowing agent,
• d) catalysts, auxiliaries and / or additives,

characterized in that, based on 100 parts by weight of Components b), c) and d), component b)

• 1. 5-30 parts by weight of castor glycerol ester and
• 2. 1 to 30 parts by weight of a polyether polyol (A) with one Hydroxyl number of 50-300, prepared by reacting one di- to tetravalent alcohol or aromatic amine at least one alkylene oxide,

and component d) 0.1 to 5 parts by weight of dimethylamino-N-methyl includes ethanolamine.

The invention further relates to those using this method manufactured open-cell rigid polyurethane foams as well their use in the manufacture of vacuum panels.

In the context of this invention, an edge area is defined as an edge area understood by foam bodies, usually a few centimeters is thick.

Under high open cell of the rigid foam is in the frame understood such a high open cell in this invention, that the rigid foam as the core material for vacuum panels can be used. There is usually an open for this cellularity of at least 85%, preferably of at least 90%, particularly preferably of at least 95% is necessary. The open Cellularity of the polyurethane foam obtained is more common determined according to ASTM D 2856-87, method B).

The b1) castor glycerol ester according to the invention is usually used Made from castor oil and glycerin and has a hydroxyl Number from 250 to 500, preferably from 300 to 450. The compo nente b1) is used in an amount of 5-30 parts by weight before add 10 to 20 parts by weight, based on 100 parts by weight of Components b), c) and d) used.

The b2) polyether polyol (A) according to the invention has a hydroxyl number from 50 to 300, preferably 100 to 250, more preferably 100 to 200, and is implemented by implementing a two- to four-valued  Alcohol or aromatic amine with at least one Alkylene oxide produced. Examples of a two- to four-valued alcohol are ethylene glycol, glycerin, trimethylolpropane, tri methylolethane, dipropylene glycol, dieethylene glycol. Is preferred trimethylolpropane and glycerol are particularly preferred Trimethylolpropane. As a two- to four-valent aromatic Amine can be used, for example, toluenediamine. As Alkylene oxide can be, for example, ethylene oxide, propylene oxide or a mixture of these can be used. Propylene oxide is preferred. Component b2) is used in an amount of 1-30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of components b), c) and d) used.

The following can be said in detail about the other components:

• a) The organic di- and / or polyisocyanates come per se known aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyvalent isocyanates in Question, if necessary, according to generally known methods can be modified.

The following may be mentioned as examples: alkylene diisocyanates with 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecane diisocyanate, 2-ethyl-tetramethylene-diisocyanate-1,4, 2-methyl pentamethylene diisocyanate 1,5, tetramethylene diisocyanate 1,4 and preferably 1,6-hexamethylene diisocyanate; cycloaliphatic Diisocyanates such as cyclohexane-1,3- and -1,4-diisocyanate as well any mixtures of these isomers, 1-isocyanato-3,3,5-tri methyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate and the corresponding the isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures and preferably aromatic di- and polyisocyanates, such as. B. 2.4- and 2,6-tolylene diisocyanate and the corresponding isomers mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and the corresponding mixtures of isomers, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates, polyphenyl polymethylene poly isocyanates, mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and polyphenyl polymethylene polyisocyanates (raw MDI) and mixtures of crude MDI and tolylene diisocyanates. The organic di- and polyisocyanates can be used individually or in form of mixtures can be used.

Have proven particularly useful as organic di- and / or polyiso cyanates and are therefore preferably used in the manufacture development of rigid polyurethane foams: mixtures of toluene diisocyanates and raw MDI or mixtures of modified,  Organic polyisocyanates containing urethane groups with a NCO content of 33.6 to 15 wt .-%, especially those based of tolylene diisocyanates, 4,4'-diphenylmethane diisocyanate, Di phenylmethane diisocyanate isomer mixtures or crude MDI and ins special crude MDI with a diphenylmethane diisocyanate isomer content of 30 to 80 wt .-%, preferably from 30 to 55 wt .-%.

So-called modified polyvalent iso are also common cyanate, d. H. Products made by chemical conversion of organic Di- and / or polyisocyanates are obtained used. Example ester, urea, biuret, allophanate, Carbodiimide, isocyanurate, uretdione and / or urethane groups containing polyisocyanates. The modified polyisocyanates can NEN mixed with each other or with unmodified polyisocyanates become.

• a) As compounds with hydrogen atoms which are reactive toward isocyanates and which are used together in component b) with components b1) and b2) according to the invention, compounds which have two or more reactive groups selected from OH groups, SH- Groups, NH groups, NH ₂ groups and CH-acidic groups, such as. B. β-diketo groups in the molecule.

Appropriately, those with a functionality of 2 to 8, preferably 2 to 6, and a molecular weight of 300 to 8000, preferably from 400 to 4000 used. Have proven z. B. polyether polyamines and / or preferably polyols, selected from the group of polyether polyols, polyester polyols, polythioether polyols, polyester amides, hydroxyl groups containing polyacetals and hydroxyl-containing aliphatic Polycarbonates or mixtures of at least two of the above Polyols. Polyester polyols and / or are preferably used Polyether polyols. The hydroxyl number of the polyhydroxyl compounds is usually 200 to 850 and preferably 280 to 650.

Suitable polyester polyols can, for example, from organic Dicarboxylic acids with 2 to 12 carbon atoms, preferably ali phatic dicarboxylic acids with 4 to 6 carbon atoms, and polyhydric alcohols, preferably diols, with 2 to 12 carbons atoms, preferably 2 to 6 carbon atoms become. Examples of suitable dicarboxylic acids are: Succinic acid, glutaric acid, adipic acid, suberic acid, azelaine acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, Phthalic acid, isophthalic acid and terephthalic acid. The dicarbon Acids can be used individually or in a mixture with one another  be used. Instead of the free dicarboxylic acids also the corresponding dicarboxylic acid derivatives, such as. B. Dicarbon acid esters of alcohols with 1 to 4 carbon atoms or Dicarboxylic anhydrides are used. Examples of two and polyhydric alcohols, especially diols are: ethanediol, Diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, Glycerin and trimethylolpropane.

To produce the polyester polyols, the organic, e.g. B. aromatic and preferably aliphatic, polycarbonate acids and / or derivatives and polyhydric alcohols catalyst free or preferably in the presence of esterification catalyst ren, suitably in an atmosphere of inert gas, such as. B. Nitrogen, carbon monoxide, helium, argon and the like. a., in the melt at temperatures of 150 to 250 ° C, preferably 180 to 220 ° C optionally under reduced pressure to the desired Acid number, which is advantageously less than 10, preferably is less than 2, be polycondensed.

The organic polyols are used to produce the polyester polyols Polycarboxylic acids and / or derivatives and polyhydric alcohols advantageously in a molar ratio of 1: 1 to 1.8, preferably 1: 1.05 to 1.2 polycondensed.

The polyester polyols obtained preferably have one Functionality from 2 to 4, in particular 2 to 3, and one molecule lar weight from 300 to 3000, preferably 350 to 2000 and ins special 400 to 600.

However, polyethers are used in particular as polyols polyols by known methods, for example by anionic polymerization with alkali hydroxides, such as. B. Sodium or potassium hydroxide or alkali alcoholates, such as. B. Sodium methylate, sodium or potassium ethylate or potassium iso propylate, as catalysts and with the addition of at least one Starter molecule, the 2 to 8, preferably 2 to 6, reactive Contains hydrogen atoms bound, or by cationic Polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate u. a. or bleaching earth, as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the Alkylene radical can be produced.

Suitable alkylene oxides are, for example, tetrahydrofuran, 1,2- or 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately can be used in succession or as mixtures. As starter molecules  for example: water, organic Dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and Terephthalic acid, aliphatic and aromatic, optionally N-mono-, N, N- and N, N'-dialkyl substituted diamines with 1 to 4 carbon atoms in the alkyl radical, such as mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, tri ethylene tetramine, 1, 3-propylene diamine, 1,3- or 1,4-butylene diamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylene diamine.

Other suitable starter molecules are: alkanolamines, such as e.g. B. ethanolamine, N-methyl and N-ethylethanolamine, dialkanol amines such as B. diethanolamine, N-methyl and N-ethyl-diethanol amine, and trialkanolamines, such as. B. triethanolamine, and ammonia. Polyvalent, in particular bivalent, trihydric and / or higher alcohols, such as ethanediol, Propanediol-1,2 and 1,3, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, penta erythritol, and sucrose, sorbitol and sorbitol.

The polyether polyols, preferably polyoxypropylene and polyoxy propylene-polyoxyethylene-polyols, have a functionality of preferably 2 to 6 and in particular 2 to 4 and molecular weight weights from 300 to 8000, preferably 400 to 1500 and in particular 420 to 1100 and suitable polyoxytetramethylene glycols Molecular weight up to approximately 3500.

Polymer-modified polyols are also suitable as polyether polyols Polyether polyols, preferably graft polyether polyols, ins especially those based on styrene and / or acrylonitrile in situ polymerization of acrylonitrile, styrene or preferably Mixtures of styrene and acrylonitrile, e.g. B. in weight ratio 90: 10 to 10: 90, preferably 70: 30 to 30: 70, in purpose moderately the aforementioned polyether polyols analogous to the Anga ben of German patents 11 11 394, 12 22 669 (US 3 304 273, 3 383 351, 3 523 093), 11 52 536 (GB 10 40 452) and 11 52 537 (GB 987 618) and polyether polyol dispersions, the disperse phase, usually in an amount of 1 to 50% by weight, preferably 2 to 25% by weight, included: e.g. B. polyureas, polyhydrazides, tert-amino groups bound containing polyurethanes and / or melamine and the z. B. are described in EP-B-011 752 (US 4 304 708), US-A-4 374 209 and DE-A-32 31 497.

The polyether polyols can just like the polyester polyols used individually or in the form of mixtures. Furthermore, Use the graft polyether polyols or polyester polyols  as well as the hydroxyl-containing polyester amides, polyacetals, Polycarbonates and / or polyether polyamines are mixed.

The open-cell rigid polyurethane foams can be with or without Use of chain extension and / or crosslinking with be manufactured. To modify the mechanical Properties, e.g. B. the hardness, but the addition of Chain extenders, crosslinking agents or given if mixtures of them also prove to be advantageous. As chains extenders and / or crosslinking agents are used diols and / or triols with molecular weights less than 400, preferably example, from 60 to 300. For example, ali phatic, cycloaliphatic and / or araliphatic diols with 2 to 14, preferably 4 to 10 carbon atoms, such as. B. Ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-, p-dihydro xycyclohexane, diethylene glycol, dipropylene glycol and preferably 1,4-butanediol, 1,6-hexanediol and bis (2-hydroxyethyl) hydro quinones, triols such as 1,2,4-, 1,3,5-trihydroxycyclohexane, glycerin and trimethylolpropane and low molecular weight hydroxyl groups Polyalkylene oxides based on ethylene and / or 1,2-propylene oxide and the aforementioned diols and / or triols as starter molecules.

Provided for the production of rigid foams based on isocyanate Chain extenders, crosslinking agents or mixtures of which are used, they are conveniently used in one Amount up to 20 wt .-%, preferably from 2 to 8 wt .-%, based on the weight of component b).

In a preferred embodiment, component b) in addition to the b1) castor glycerol ester and the b2) polyether polyol (A) additionally b3) a two to tetravalent polyether polyol (B). The polyether polyol (B) has a hydroxyl number of 450 to 700, preferably from 500 to 600 and can consist of a two to four quality alcohol and at least one alkylene oxide become. The polyether polyol (B) from trimethylol is preferred propane and propylene oxide. The polyether polyol (B) is in an amount of 10 to 50 parts by weight, preferably 30 to 45 Parts by weight, based on 100 parts of components b), c) and d) used.

• a) Water is preferably used as blowing agent, which by reaction with the isocyanate groups carbon dioxide splits off. The water content is in particular 0.1 to 4, preferably 0.3 to 3, in particular 0.5 to 2 parts by weight, based on 100 parts by weight of components b), c) and d).

In addition to water, physically active propellants can also be used tel can be used. In particular, low boiling Hydrocarbons, lower monofunctional alcohols, acetals or also partially halogenated hydrocarbons, so-called HCFCs, used. Low-boiling cyclic and acyclic saturated hydrocarbons with up to 12 carbons atoms of matter, individually or in any mixtures which can be used, especially pentanes, where both Mixtures of the pentane isomers as well as the pure isomers can be set. The amount of hydrocarbons is included 1 to 30 parts by weight, preferably 1 to 10 parts by weight, ins special 1 to 5 parts by weight, based on 100 parts by weight of Components b). c) and d).

It is also advantageous to use perfluorobin as a co-blowing agent applications. Perfluoroalkanes are used in particular, preferably n-perfluoropentane, perfluorohexane, n-perfluoroheptane, n-perfluorooctane. The perfluoro compounds can be used individually or in Form of mixtures can be used. Preferably, the Use in an amount of 0.1 to 6 parts by weight, based on the sum of components b) to d).

Because the perfluoro compounds are insoluble in the polyol component they are mostly emulsified in this component. As Emulsifiers are preferably used (meth) acrylates, where especially those with fluorine-containing side chains Use come, for example fluorinated alkyl esters.

• a) As a catalyst for the production of Hart according to the invention Foams are 0.1 to 5 parts by weight, preferably 0.5 up to 3 parts by weight of dimethylamino-N-methyl-ethanolamine (Dabco T), based on 100 parts by weight of component b), c) and d) used. Furthermore, in the Component d) as catalysts, in particular such compounds applications that react to the reaction Compounds (b) containing hydrogen atoms with the poly Accelerate isocyanates (a) strongly. Are preferred for this tertiary amines, tin and bismuth compounds, alkali and Alkaline earth metal carboxylates, quaternary ammonium salts, s-hydroxy triazines and tris (dialkylaminomethyl) phenols.

Tertiary amino alcohols of the general formula are particularly preferred

R ₁ R ₂ NR ₃ OH,

wherein R ₁ and R ₂ aliphatic or cycloaliphatic groups with 1 to 15 carbon atoms or R ₁ and R ₂ together form a single cycloaliphatic ring with 3 to 15 carbon atoms and the nitrogen atom in the ring and R _{3 is} an aliphatic chain with 1 to 15 carbon atoms.

The carbon chains or rings of R ₁ , R ₂ and R ₃ can also contain heteroatoms, such as sulfur or, in particular, oxygen atoms in the chain. Preferably, R ₁ and R ₂ , including the nitrogen atom, form a piperidine, pyrrolidine, imidazole, morpholine structure, an alkaloid of the pyrrolidine-piperidine type or a bicyclic compound, e.g. B. an azanorbornane.

Examples of preferred catalysts are N, N, N, N-trimethyl-N-hydroxyethyl-bisaminoethyl ether, 2,2-dimor pholinodiethyl ether (DMDEE), dimethylethanolamine (DMEA) and N- (3-dimethylaminopropyl) N, N-diisopropanolamine.

The foams of the present invention can also be Isocyanu Council structures included. For the production of isocyanurate structure Ren in the foam, the usual catalysts are used such as metal carboxylates, e.g. potassium acetate, and others Substances such as those found in the plastics manual, vol. VII, Polyurethanes, 3rd edition 1993, on page 108.

The catalysts and mixtures of these are usually described in an amount of 0.1 to 10 parts by weight, preferably 1 to 5 Parts by weight, based on 100 parts by weight of components b), c) and d) used.

Other auxiliaries and additives are, for example, surfaces active substances, foam stabilizers, cell regulators, flame retardants agents, fillers and hydrolysis inhibitors.

Further information on the above and other starting materials are the specialist literature, for example the monograph of H.J. Saunders and K.C. Frisch, "High Polymers", Volume XVI, Poly urethanes parts 1 and 2, publisher Interscience Publishers 1962 and 1964 or the Plastic Handbook, Volume VII, Polyurethane, Carl Hanser Verlag Munich, Vienna, 1st, 2nd and 3rd editions 1966, 1983 and Can be seen in 1993.

To produce the rigid polyurethane foam according to the invention the di- and / or polyisocyanates with the opposite Compounds containing isocyanate-reactive hydrogen atoms and possibly partially to react with themselves brings. Components b) to d) are usually used  the implementation of the so-called polyol component. If necessary, components b2) and b3) mixed before adding more reactive hydrogen atoms pointing compounds to component b) are combined.

The conversion ratio of component a) to components b), c) and d) is usually chosen so that an excess of Component a) is present. In general, the foaming will an index of greater than 100, in particular greater than 110.

The combination of the polyol component with the polyisocyanate can in the simplest case by stirring. However, it is common carry out the foaming mechanically. The com components in mixing heads and then inserted into a mold brings. In a preferred embodiment, the polyure than rigid foam continuously using a double belt process (see Becker, Braun "Plastic Handbook 7, Polyurethane", Page 272).

The method according to the invention leads to a particularly low void formation in the resulting foam.

The foams according to the invention mostly have an open cell core of 90 to 100%, preferably 95 to 100%. The open cell at the edge is also 80 to 100%, preferably over 90%. The density of the rigid foam is usually 30 to 100 kg / m ³ , preferably 45-70 kg / m ^3, in particular 50 to 65 kg / m ³ . The foams according to the invention are preferably used for filling voids, which are then evacuated, such as walls and / or doors of refrigerators, storage units, truck bodies, district heating pipes or sandwich elements, in particular as core material for vacuum insulation units. For this purpose, the foam cores are evacuated and z. B. sealed with a film and sealed permeation ver.

According to the method of the invention, it is possible to open-cell Rigid polyurethane foams that are special are characterized by a high open cell structure of the marginal zone, whereby less material has to be discarded. Another advantage of Foams according to the invention lie in the low shrinkage dung in, for example, a production on a double belt.

The invention is illustrated by the examples below become.  

Examples

The following starting materials are used:

Polyols

• 1. OH number 470, ethylenediamine based polyether Propylene oxide
• 2. OH number 485, sucrose, glycerol started polyether Base propylene oxide
• 3. OH number 550, trimethylolpropane started polyether Base propylene oxide
• 4. OH number 385, castor glycerol ester
• 5. OH number 400, glycerin-started polyether based Propylene oxide
• 6. OH number 175, trimethylolpropane started polyether on Ba sis propylene oxide
• 7. OH number 175, polyether started polyether based Propylene oxide

Catalysts

• 1. Dabco® AN20 from Air Products
• 2. Dimethylamino-N-methylethanolamine (DABCO® T)
• 3. Jeffts® ZF10 from Huntsman
• 4. Jeffcat® DMDEE from Huntsman
• 5. Jeffcat® DMEA from Huntsman
• 6. Jeffcat® DPA from Huntsman

Stabilizers

• 1. Tegostab® B8919 from Th.Goldschmidt
• 2. Tegostab® B8870 from Th.Goldschmidt
• 3. Ortegol® 505 from Th.Goldschmidt

Isocyanates Lupranat® M20 NCO content 31.5 (raw MDI)

Component A (consisting of components b) to d)) and compo component B (consisting of component a) were identified with the index 110 foamed up to 140. The foaming took place on the double belt instead of. Belt speed was between 2-6 m / min with shift thickness up to 150 mm.  

The foam sheets obtained were sawn, i.e. H. the deck layers sawn off a maximum of 1 mm, 2 cm, 3 cm / or a test specimen taken from the core for an open cell test (OZ). The open cell (OZ) of the polyurethane foam obtained was according to ASTM D 2856-87, method B) in the core, right on the edge and determined at a distance of 2 cm or 3 cm from the edge. The Check for blowholes was carried out visually.

In all examples the bulk density was between 54-70 g / l Start times 10-15 sec and setting times 45-70 sec.

Examples 1 to 5 contain a composition according to the invention of components A and B, which contain comparative examples 6 to 11 a composition of component A that is outside the Limits of entitlement. The information in Tables 1 and 3 are Parts by weight.

Table 1 shows the compositions of the components used A of Examples 1 to 5.

Table 1

Table 2 shows the properties of the test specimens of Examples 1 until 5

Table 2

Table 3 shows the compositions of the components used A of comparative examples 6 to 11.

Table 3

Table 4 shows the properties of the test specimens of the comparison examples 6 to 11.

Table 4

Claims (10)

1. Process for the production of open-celled rigid polyurethane foams by reacting the components

• a) Di- and / or polyisocyanates with
• b) compounds containing hydrogen atoms which are reactive toward isocyanates in the presence of the components
• c) blowing agent
• d) catalysts, auxiliaries and / or additives,

characterized in that, based on 100 parts by weight of components b), c) and d), component b)

• 1. 5-30 parts by weight of castor glycerol ester and
• 2. 1 to 30 parts by weight of a polyether polyol (A) having a hydroxyl number of 50-300, prepared by reacting a di- to tetravalent alcohol or aromatic amine with at least one alkylene oxide,

and component d) comprises 0.1 to 5 parts by weight of dimethylamino-N-methylethanolamine. 2. The method according to claim 1, characterized in that the Polyether polyol (A) by reaction of trimethylolpropane, Glycerol, toluenediamine or mixtures thereof with at least an alkylene oxide is produced. 3. The method according to any one of claims 1 or 2, characterized records that propylene oxide is used as the alkylene oxide. 4. The method according to any one of claims 1 to 3 characterized records that the polyether polyol (A) has a hydroxyl number of 100 to 250.   5. The method according to any one of claims 1 to 4, characterized records that component d) 1 to 4 parts by weight of dimethyla mino-N-methyl-ethanolamine, based on 100 parts by weight of Components b), c) and d). 6. The method according to any one of claims 1 to 5, characterized records that component b), based on 100 parts by weight of components b), c) and d), 10 to 20 parts by weight Castor glycerol esters and 5 to 20 parts by weight of the poly ether polyol (A). 7. The method according to any one of claims 1 to 6, characterized in that component b), based on 100 parts by weight of components b), c) and d), additionally

• 1. 10 to 50 parts by weight of a dihydric to tetravalent polyether polyol (B) having a hydroxyl number of 450-700.

8. The method according to any one of claims 1 to 7, characterized records that the process is continuous and with a dop pelband is performed. 9. Open-cell rigid foams, producible according to one of the types sayings 1 to 8. 10. Use of the foams according to claim 9 as core material for vacuum panels.