MX2012009972A - Method for producing polyurethane hard foam materials. - Google Patents

Abstract

The invention relates to a method for producing polyurethane hard foam materials by reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms reactive with two isocyanate groups in the presence of c) foaming agents, characterized in that the compounds having at least two hydrogen atoms reactive with two isocyanate groups comprise at least one polyether alcohol b1) having a functionality of 2-8 and a hydroxyl number of 200-800 mg KOH/g, said alcohol having been produced by building up alkylene oxides b1b) on compounds having at least two hydrogen atoms reactive with alkylene oxides b1a), referred to below as starting substances, using an amine b1c) as a catalyst.

Description

METHOD FOR PRODUCING HARD POLYURETHANE FOAM MATERIALS Description The invention relates to a process for preparing rigid polyurethane foams by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups in the presence of blowing agents.

Rigid polyurethane foams have been known for a long time and are used predominantly in heat and cold insulation, eg, in refrigeration appliances, in hot water storage systems, in municipal heating pipes or in the construction of buildings. , for example in interleaved elements. A summarized overview of the production and use of rigid polyurethane foams for example in Kunststoff-Handbuch, volume 7, Polyurethanes edition 1966, edited by Dr. R. Vieweg and Dr. A. Hochtlen, and 2nd edition 1983, edited by Dr. Günter Oertel, and 3rd edition 1993, edited by Dr. Günter Oertel, Carl Hanser Verlag, Municha, Vienna.

Blowing agents used for the production of rigid polyurethane foams were used mainly as chlorofluorocarbons (CFCs), preferably trichlorofluoromethane. However, these blowing gases had an adverse impact on the environment.

Hydrocarbons, preferably pentanes, have now become the most-used successors of CFCs. EP-A-421 269 discloses the use of cyclopentane and / or cyclohexane, optionally in admixture with other hydrocarbons, as blowing agents.

However, these blowing agents differ from the halogenated blowing agents in several aspects. They are less compatible with the other constituents of polyurethane systems. This leads to rapid separation of the components comprising blowing agents.

Not much blowing agent can be incorporated in the components. Therefore, alkane blown foams usually have a higher density than foams blown with CFCs.

Therefore, there is a need to reduce the density of the foams to save material without, however, sacrificing the thermal conductivity of the mechanical properties of the polyurethanes. When hollow spaces such as cooling apparatus housings are filled with foam, the hollow space must be filled uniformly, that is, the liquid reactive components will flow in all parts of the hollow space. If the flow capacity of the foam is sufficient, the hollow spaces having a large volume and / or complicated geometry need to be overfilled with foam so that the pressure buildup can ensure even distribution of the foam. The better the hollow spaces fill the reactive liquid components, the smaller the amount of rigid polyurethane foam needed to completely fill the hollow space with foam. As a result, the rigid polyurethane foam in the hollow space has a lower density, leading to a reduction in the weight of the final products, for example refrigeration appliances, as well as material savings.

The flowability of the foam herein is to be understood as referring to the flow behavior of the reaction mixture of the polyisocyanate and the compound having at least two hydrogen atoms reactive with isocyanate groups. The flow capacity is usually determined by the determination of the distance covered by the reaction mixture. This can be done by introducing the reaction mixture into a flexible tube of polymer film, hereinafter referred to as the tube test, or into a standardized elongated mold, for example a so-called Bosch lance and determining the length of the article of mold thus formed.

The flow capacity of the reaction mixtures is typically determined by the flow factor. The flow factor is the ratio of the minimum fill density to the foam-free wrap density, and is determined by the Bosch lance method. The minimum filling density is obtained by varying the weight of the impact and corresponds to the minimum density needed to completely fill a Bosch lance for a given free wrap density.

An object of the present invention is to provide a process for preparing rigid polyurethane foams wherein the polyol components have better solubility for the hydrocarbons used as blowing agents. The improved processing properties must also be achieved, very particularly an improved flowability. In addition, foams that have good mechanical properties and low thermal conductivities must be obtained.

The inventors of the present have found that this object is achieved, surprisingly, by the use of polyols prepared by the addition of alkylene oxides on compounds having at least two active hydrogen atoms in the presence of at least one compound having at least one amino group as a catalyst.

The compounds prepared by the addition of alkylene oxides on compounds having at least two active hydrogen atoms in the presence of at least one compound having at least one amino group as a catalyst are known.

US 20070203319 and US 20070199976 disclose polyether alcohols obtained by the addition of alkylene oxides by means of dimethylethanolamine on initiator substances comprising solid compounds at room temperature. However, the polyurethanes obtained using these polyols are not described. Nor does this document include any indication for the properties of the polyols described in the preparation of foams and their effects on the properties of the foams.

The invention provides a method for preparing rigid polyurethane foams, comprising reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms reactive with isocyanate groups in the presence of c) blowing agents, wherein said compounds having at least two hydrogen atoms reactive with isocyanate groups b) comprise at least one polyether alcohol bl) having a functionality of 2-8 and a hydroxyl number of 200-800 mgKOH / g, obtained by the addition of an alkylene oxide to blb) on a compound having at least two hydrogen atoms bla), hereinafter also known as initiator substances, reactive with alkylene oxide by the use of an amine ble) as a catalyst The polyether alcohol bl) can be used as the sole compound of component b).

Preferably, the polyether alcohol b) is used in an amount of 10-90% by weight, based on the weight of component b).

Preferably, the component having at least two hydrogen atoms reactive with alkylene oxides used to prepare the polyether alcohol b1) comprises a mixture comprising at least one blai compound which is solid at room temperature. The blai compound preferably has a functionality of at least 3, most preferably at least 4, most preferably still 3-8 and most preferably still 4-8.

Blai compounds of this type are known and are frequently used in the manufacture of polyether alcohols, particularly those for use in rigid polyurethane foams. The blai compounds are preferably selected from the group comprising trimethylolpropane, pentaerythritol, glucose, sorbitol, mannitol and sucrose, polyhydric phenols, resols, for example oligomeric condensation products of phenol and formaldehyde, oligomeric condensation products of aniline and formaldehyde (MDA). , toluene diamine (TDA) and condensates of Mannich phenols, formaldehyde and dialkanolamines, and also melamine and also mixtures of at least two of the listed alcohols.

In a preferred embodiment of the invention, the blai compound) is selected from the group comprising sucrose, sorbitol and pentaerythritol, most preferably sucrose or sorbitol. In a particularly preferred embodiment of the invention, bla) is sucrose).

The aromatic amines used as blai compounds are very particularly selected from the group comprising toluene diamine (TDA) or diphenylmethane diamine (DA) or polymeric MDA (p-MDA). In the case of ADD, it is very particularly 2,3- and 3,4-isomers, also known as local ADT, that are used.

Further useful starting substances include compounds bla) having at least two hydrogen atoms reactive with alkylene oxides comprising at least one blaii compound, which is liquid at room temperature.

In a preferred embodiment of the invention, the initiator substance of component bl) comprises a liquid compound at room temperature blaii) comprising hydrogen atoms reactive with alkylene oxides as well as the compound blai). The compound blaii) may comprise alcohols or amines. These have very particularly 1 to 4 and preferably 2 to 4 hydrogen atoms reactive with alkylene oxides. The component blaii) is particularly selected from the group comprising glycerol, mono-functional alcohols of 1-20 carbon atoms, ethylene glycol and its higher homologs and propylene glycol and its higher homologs, hydroxyalkylamines, such as monoethanolamine, diethanolamine, triethanolamine, and also reaction products thereof with propylene oxide. Glycerol is used in particular.

The liquid alcohols at room temperature (blaii), as mentioned, may also comprise compounds having a hydrogen atom reactive with alkylene oxides and 1-20 carbon atoms. Monofunctional alcohols are preferred herein, such as methanol, ethanol, propanol, octanol, dodecanol.

In a further embodiment of the invention, the initiator substance of component bl) comprises a mixture of at least one solid amine at room temperature blai) and a liquid alcohol at room temperature blaii).

The solid amines at room temperature blai), as indicated above, may preferably comprise MDA and polymeric MDA. The liquid alcohols at room temperature blaii) may then preferably comprise ethylene glycol and its higher homologs and propylene glycol and their higher homologs. The concentrations of amine homologs in p-MDA depend on the conditions of the procedure. In general, the distribution (in percent by weight) is as follows: MDA of two rings: 50-80% by weight Three-ring MDA: 10-25% by weight Four-ring MDA: 5-12% by weight MDA of five and more rings: 5-12% by weight A preferred p-MDA mixture has the composition: MDA of two rings: 50% by weight Three-ring MDA: 25% by weight Four-ring MDA: 12% by weight MDA of five and more rings: 13% by weight An additional preferred p-MDA mixture has the composition: MDA of two rings: 80% by weight MDA of three rings: 10% by weight MDA of four rings: 5% by weight MDA of five and more rings: 5% by weight In a further preferred embodiment of the invention, the initiator substance of component bl) comprises a mixture of at least one solid alcohol at room temperature (blai)) and a liquid alcohol at room temperature (blaii)). The solid alcohols at room temperature (blai) preferably comprise sugar alcohols glucose, sorbitol, mannitol and sucrose very particularly characterized above, very particularly sucrose. The liquid alcohols at room temperature (blaii) preferably comprise mono-functional alcohols of 1-20 carbon atoms, ethylene glycol and its higher homologs, propylene glycol and its higher homologs, hydroxyalkylamines, such as monoethanolamine, diethanolamine, triethanolamine and also analogues thereof. based on propylene oxide, and glycerol, very particularly glycerol. The initiator substance of component b) can also comprise water. When water is used, the amount very particularly is not more than 25% by weight, based on the weight of the initiator substance of the component bl).

The alkylene oxide blb) preferably comprises propylene oxide, ethylene oxide, butylene oxide, isobutylene oxide, styrene oxide and mixtures of two or more thereof. Preferably, the propylene oxide, ethylene oxide or mixtures of propylene oxide and ethylene oxide are used as alkylene oxide blb). It is particularly preferable to use propylene oxide as alkylene oxide blb).

The catalyst ble), as mentioned, comprises an amine other than the blaii component). This amine can comprise primary, secondary or tertiary amines and also aliphatic or aromatic amines, very particularly tertiary. In a further embodiment, aromatic heterocyclic compounds having at least one, preferably a, nitrogen atom in the ring may be of importance.

The amines ble) are preferably selected from the group comprising trialkylamines, very particularly trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylalkylamines, very particularly dimethylethanolamine; dimetiletoxietanolamina, dimethylcyclohexylamine, dimethylethylamine, dimethylbutylamine, aromatic amines, very particularly dimethylaniline, dimethylaminopyridine, dimethylbenzylamine, pyridine, imidazoles (very particularly imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, 5-methylimidazole, 2-ethyl-4-methylimidazole , 2, 4-dimethylimidazole, 1-hidroxipropilimidazol, 2, 5-trimetilimidazol, 2-ethylimidazole, 2-ethyl-4-methylimidazole, N-phenylimidazole, 2-phenylimidazole, 4 -phenylimidazole, guanidine, alkylated guanidines, (most particularly 1,1,3,3-tetramethylguanidine), 7-methyl-l, 5, 7-triazabicyclo [4.4.0] dec-5-ene, amidines (very particularly 1,5-diazobicyclo [4.3.0] ??? -5-ene, 1, 5-diazabicyclo [5.4.0] undec-7-ene.

It is also possible to use mixtures of at least two of the mentioned amines as catalysts.

The catalyst ble) is dimethylethanolamine in a preferred embodiment of the invention.

The catalyst ble) is an imidazole, in a preferred embodiment of the invention.

The amine is preferably used in an amount of 0.01-5.0% by weight, preferably 0.05-3.0% by weight and most preferably 0.1-1.0% by weight based on the overall batch. The overall batch is to be understood as the amount of all the starting compounds used for the preparation of the polyether alcohol.

In order to prepare the polyether alcohols (b), the constituents of the initiator substance mixture (b) and b) are typically introduced into the reactor and mixed together. Then the mixture is subjected to inertia in it. Subsequently, the alkylene oxide is metered.

The addition reaction of the alkylene oxides is preferably carried out at a temperature between 90 and 150 ° C and a pressure between 0.1 and 8 bar. The dosage of the alkylene oxides is typically followed by a post-reaction phase to complete the reaction of the alkylene oxides.

The conclusion of the dosage of the alkylene oxides is typically followed by a post-reaction phase in which the reaction of the alkylene oxide is brought to completion. This is followed by a post-reaction phase, if necessary. This is typically followed by distillation to remove volatile compounds, which is preferably carried out under reduced pressure.

The amine catalysts ble) can remain in the polyether alcohol. This simplifies the process of preparation thereof, since the removal of catalysts, which is necessary when oxides and alkali metal hydroxides are used, is no longer necessary. This leads to an improvement in space-time performance. Removal of salt by filtration forms a filter cake. The order of polyol in the filter cake generally reaches a certain percentage. Improved space-time performance and avoided filter loss lead to reduced manufacturing costs.

A combination of alkali metal hydroxide catalysts and amine catalysts is also useful. This is particularly an option for preparing low hydroxyl number polyols. The products obtained can be treated in a similar way to polyols catalyzed by alkali metal hydroxide. Alternatively, they are also treated by performing the neutralization step with an acid. In this case, it is preferable to use carboxylic acids such as for example lactic acid, acetic acid or 2-ethylhexanoic acid.

The aminic catalysts ble) as such can be alkoxylated in the course of the reaction. The alkoxylated amines, therefore, have a higher molecular weight and reduced volatility in the subsequent product. Due to the remaining self-reactivity of the alkoxylated amine catalysts, incorporation into the polymer scaffold occurs during the subsequent reaction with isocyanates. The self-reactivity of the formed tertiary amines provides the polyols with a self-reactivity that can be usefully exploited in certain applications.

Without wishing to be bound by any theory, it is believed that the polyether alcohols obtained using amines as catalysts have a construction that differs from the construction of polyether alcohols obtained using other catalysts. This different molecular construction has advantages in the manufacture of polyurethanes.

Therefore, the polyols of the invention have distinct advantages in polyurethane applications, particularly in the process of manufacturing polyurethane foams.

As mentioned, the polyether alcohols b) are used in the manufacture of polyurethanes.

The starting materials used for this can be described very particularly as follows: The organic polyisocyanates contemplated are preferably aromatic polyfunctional isocyanates.

Specific examples are: 2,4- and 2,6-tolylene diisocyanate (TDI) and the corresponding isomeric mixtures, 4,4'-, 2,4'- and 2, 2'-diphenylmethane diisocyanate (MDI) and the corresponding isomeric mixtures, mixtures of diisocyanates of 4,4'- and 2,4'-diphenylmethane and in the manufacture of rigid polyurethane foams, particularly mixtures of diisocyanates of 4,4'-, 2,4'- and 2, 2 ' -diphenylmethane and polyphenyl polymethylene polyisocyanates (crude MDI).

The polyether alcohols b) of the present invention are typically used in admixture with other compounds having at least two hydrogen atoms reactive with isocyanate groups.

Useful compounds together with the polyether alcohols bl) and having at least two isocyanate-reactive hydrogen atoms include particularly polyether alcohols and / or polyester alcohols having OH numbers in the range of 100 to 1200 mgKOH / g. .

The polyester alcohols used together with the polyether alcohols b) are usually prepared by condensation of polyfunctional alcohols, preferably diols, having 2 to 12 carbon atoms and preferably 2 to 6 carbon atoms, with polyfunctional carboxylic acids having 2 to 12 carbon atoms, for example succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid and preferably italic acid, isophthalic acid, terephthalic acid and the isomeric naphthalenedicarboxylic acids.

The polyether alcohols used together with the polyether alcohols bl) usually have a functionality between 2 and 8 and very particularly from 3 to 8.

Particular preference is given to the use of polyether alcohols prepared by known methods, for example by anionic polymerization of alkylene oxides in the presence of catalysts, preferably alkali metal hydroxides.

The alkylene oxides are usually mostly ethylene oxide and / or propylene oxide, preferably pure 1,2-propylene oxide.

The initiator molecules used are in particular compounds having at least 3 and preferably from 4 to 8 hydroxyl groups or having at least two primary amino groups in the molecule.

By means of starter molecules having at least 3 and preferably from 4 to 8 hydroxyl groups in the molecule, it is preferable to use trimethylolpropane, glycerol, pentaerythritol, sugar compounds such as for example glucose, sorbitol, mannitol and sucrose, polyhydric phenols, resoles, for example oligomeric condensation products of phenol and formaldehyde, condensation products of aniline and formaldehyde, toluene diamine and condensates of Mannich phenols, formaldehyde and dialkanolamines and also melamine.

The polyether alcohols have a functionality of preferably 3 to 8 and hydroxyl numbers of preferably 100 mgKOH / g to 1200 mgKOH / g and very particularly 120 mgKOH / g to 570 mgKOH / g.

Using difunctional polyols, for example polyethylene glycols and / or polypropylene glycols, having a molecular weight in the range of 500 to 1500 in the polyol component, the viscosity of the polyol component can be adapted.

Compounds having at least two isocyanate-reactive hydrogen atoms also include the optionally used chain extenders and interleavers. Rigid polyurethane foams can be manufactured with or without the use of chain extenders and / or interlacing agents. The addition of chain extension agents, difunctional, trifunctional and higher function crosslinking agents or optionally mixtures thereof, may prove to be advantageous for modifying the mechanical properties. The chain extenders and / or crosslinking agents used are preferably alkanolamines and very particularly diols and / or triols having molecular weights below 400, preferably in the range of from 60 to 300.

Chain extenders, crosslinking agents or mixtures thereof are advantageously used in an amount of 1% to 20% by weight and preferably 2% to 5% by weight, based on the polyol component.

Polyurethane foams are typically manufactured in the presence of a blowing agent. The blowing agent used can preferably be water, which reacts with isocyanate groups by removal of carbon dioxide. An additional frequently used chemical blowing agent is formic acid, which reacts with isocyanate releasing carbon monoxide and carbon dioxide. The so-called physical blowing agents can also be used in addition to or in place of chemical blowing agents. Physical blowing agents usually comprise compounds at room temperature that are inert to the feed components and vaporize under the conditions of the urethane reaction. The boiling point of these compounds is preferably below 50 ° C. Physical blowing agents also include compounds that are gaseous at room temperature and are introduced into and / or dissolved in the feed compounds under pressure, examples being carbon dioxide, alkanes, very particularly low boiling alkanes and fluoroalkanes, preferably alkanes, very particularly low boiling alkanes and fluoroalkanes.

Physical blowing agents are usually selected from the group consisting of alkanes and / or cycloalkanes having at least 4 carbon atoms, dialkyl ethers, esters, ketones, acetals, fluoroalkanes having from 1 to 8 carbon atoms and tetraalkylsilanes which they have 1 to 3 carbon atoms in the alkyl chain, very particularly tetramethylsilane.

Examples are propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, cyclopentane, cyclohexane, dimethyl ether, methyl ethyl ether, methylbutyl ether, methyl formate, acetone and also fluoralkanes which can be degraded in the troposphere and therefore they are harmless to the ozone layer, such as trifluoromethane, difluoromethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2, 3-pentafluoropropene, l-chloro-3, 3, 3-trifluoropropene, 1,1,1,2-tetrafluoroethane, difluoroethane and 1,1,1,3,3,3-heptafluoropropane, and also perfluoroalkanes, such as C3F8, C4F10, C5F12, C6F14 and C7F17. Particular preference is given to hydrocarbons, preferably pentanes, very particularly cyclopentane. The aforementioned physical blowing agents can be used alone or in any desired combination with one another.

A mixture of physical and chemical blowing agents can be used in a preferred embodiment of the invention. Particular preference is given to mixtures of physical blowing agents and water, very particularly hydrocarbons and water. Among the hydrocarbons, they are the pentanes - and of those especially the cyclopentane - which are particularly preferred.

The manufacture of polyurethanes can be carried out, if necessary, in the presence of catalysts, flame retardants and also auxiliary substances and / or added as usual.

Particular additional aspects relating to the starting compounds used can be found, for example, in Kunststoffhandbuch, volume 7"Polyurethane", edited by Günter Oertel, Carl-Hanser-Verlag Munich, 3rd edition, 1993.

Rigid PU foams are preferably used as a thermally insulating intermediate layer in mixed elements and for filling hollow spaces in refrigeration apparatus housings, very particularly refrigerators and freezers with foam and as an outer cover of hot water storage tanks. The products are also useful for insulating heated materials, such as motor covers and pipe shells.

Its use particularly in the manufacture of mixed or interleaved elements constructed of a rigid PU foam and at least one outer layer of a rigid or elastic material such as paper, polymeric film, aluminum foil, metal foils, glass veils or particle table is known. Also known is the filling of hollow spaces in household appliances such as refrigeration appliances, for example refrigerators or freezers or hot water storage systems, with rigid PU foam as a thermal insulator. Additional uses are insulated tubes consisting of an inner metal or plastic tube, an insulating polyurethane layer and an outer polyethylene jacket. Isolation is also possible for large storage containers or transport vessels, for example for storage and transport of liquefied liquids or gases in the temperature range of 160 ° C to -160 ° C. Heat and cold insulating rigid PU foams suitable for these purposes, as will be known, are obtained by reaction of organic polyisocyanates with one or more compounds having at least two isocyanate-reactive groups, preferably polyester- and / or polyether- polyols, and also typically by the joint use of chain extenders and / or crosslinking agents in the presence of blowing agents, catalysts and optionally auxiliaries and / or substance added. An appropriate choice of reactive components makes it possible to obtain rigid PU foams having a low thermal conductivity index and good mechanical properties.

A summary overview of the production of rigid PU foams and their use as an outer layer or preferably a core layer in mixed elements and their use as an insulating layer in cooling or heating technology was published for example in Polyurethane, Kunststoff-Handbuch, volume 7 , 3rd edition 1993, edited by Dr. Günter Oertel, Carl Hanser Verlag, Munich, Vienna.

The following examples illustrate the invention.

Polyol synthesis: Example 1: Preparation of polyols of the invention: 2, 3 and 5 Polyol 2 A pressure reactor of 250 1 equipped with shaker, jacket heating and cooling, dosing devices for solid and liquid substances and alkylene oxides and also devices for nitrogen inertization and a vacuum system was heated to 80 ° C and was repeatedly inerted . 18.38 kg of glycerol and 1.26 kg of DMEOA were emptied therein and the agitator was started. Then, sucrose (191.6 kg) was introduinto the reactor and the temperature was raised to 95 ° C. The mixture was reacted with 54.0 kg of propylene oxide at 95 ° C. After a time after the 30 minute reaction, an additional 0.64 kg of DMEOA was added. The temperature was then raised to 112 ° C and 116 kg of propylene oxide was added. The 3 hour post-reaction took place at 112 ° C. The product was separated at 105 ° C (vacuum, nitrogen) for 2 hr to obtain 352 kg of product having the following parameters: Hydroxyl number 444 mg KOH / g Viscosity 15300 mPas Water content 0.013% pH 9.7 Polyol 3 pressure reactor of 600 1 equipped with shaker, jacket heating and cooling, dosing devices for solids and liquids and alkylene oxides and also devices for nitrogen inertization and a vacuum system was heated to 80 ° C and was repeatedly inerted. 52.8 kg of glycerol and 6.0 kg of dimethylethanolamine were introduced into the reactor and the stirrer was started. Then, the sucrose (191.6 kg) was introduced into the reactor and the temperature was raised to 95 ° C. The mixture was reacted with 195.0 kg of propylene oxide at 105 ° C. The temperature was then raised to 112 ° C and the product was reacted with an additional 352.7 kg of propylene oxide. The 3 hour post-reaction took place at 112 ° C. The propylene oxide still present was separated in a stream of nitrogen to obtain 770 kg of product having the following parameters: Hydroxyl number 455 mg KOH / g Viscosity 14800 mPas Water content 0.03% pH 9.8 Polyol 5 A pressure reactor of 600 1 equipped with agitator, jacket heating and cooling, dosing devices for solids and liquids and alkylene oxides and also devices for nitrogen inertization and a vacuum system was heated to 75 ° C and was repeatedly inerted . 47.00 kg of glycerol and 3.09 kg of dimethylethanolamine were introduced into the reactor and the stirrer was started. Then, the sucrose (154.75 kg) was introduced into the reactor and 157.50 kg of PO were dosed at a temperature of 75 ° C to 95 ° C.

After the 30 minute reaction at 105 ° C, an additional 1.55 kg of DMEOA and 254.50 kg of PO were added. The 2 hour post-reaction took place at 105 ° C. The propylene oxide still present was separated in a stream of nitrogen to obtain 593 kg of the product.

Hydroxyl number 468 mg KOH / g Viscosity 21300 mPas Water content 0.016% pH 10.2 Example 2: Preparation of the comparative polyols: 1 and 4 Polyol 1: A pressure reactor of 50 1 equipped with shaker, jacket heating and cooling, dosing devices for solids and liquids and alkylene oxides and also devices for nitrogen inertization and a vacuum system was heated up to 90 ° C and was repeatedly inerted . 2.87 kg of glycerol, 0.188 kg of 48% KOH solution and 0.065 kg of water were introduced and the agitator was started. Then, sucrose (9.48 kg) was added. The temperature was raised to 105 ° C and 7.53 kg were added. After a reaction time of 1 hr the temperature was raised to 112 ° C and the remaining PO (19.85 kg) was dosed. The obtained polyetherol was hydrolyzed with water, neutralized with phosphoric acid, filtered, and separated under vacuum to obtain 39.1 kg of product.

Hydroxyl number 450 mg KOH / g Viscosity 19500 mPas Water content 0.07% pH 9.2 Polyol 4 A pressure reactor of 50 1 equipped with shaker, jacket heating and cooling, dosing devices for solids and liquids and alkylene oxides and also devices for nitrogen inertization and a vacuum system was heated up to 90 ° C and was repeatedly inerted . 4.00 kg of glycerol, 0.245 kg of 48% KOH solution and 0.049 kg of water were introduced and the agitator was started. Then, sucrose (13.16 kg) was added and 11.7 kg of PO were dosed at 105 ° C. After a post-reaction of 3 hr, the temperature was raised to 112 ° C and the remaining PO (22.3 kg) was dosed. The obtained polyetherol was hydrolyzed with water, neutralized with phosphoric acid, filtered and separated under vacuum to obtain 41.5 kg of the product.

Hydroxyl number 477 mg KOH / g Viscosity 22300 mPas Acid number 0.012 mg KOH / g Water content 0.023% pH 10.2 Methods: Viscosity measurements: The viscosity of polyols and polyol blends, unless otherwise indicated, was determined at 25 ° C using a Rheotec RC 20 rotary viscometer with CC 25 DIN spindle (screw diameter: 12.5 mm, internal diameter of cylinder measuring: 13.56 mm) at a shear rate of 50 1 / s.

Hydroxyl number The hydroxyl numbers were determined in accordance with DIN 53240.

Thermal conductivity: The thermal conductivity was determined in accordance with DIN 52616. To produce the test specimens, the polyurethane reaction mixture was emptied into a mold measuring 200 x 20 x 5 cm (10% overfill) and after a few hours, any Test specimen measuring 20 x 20 x 2 cm was cut in half.

Resistance to compression: The compressive strength was determined in accordance with DIN 53421 / DIN EN ISO 604 Determination of solubility in pentane: 50 g of polyol or polyol mixture was introduced into a 100 mL glass vessel. An amount of cyclopentane was added. Subsequently, the glass container was sealed, vigorously stirred for 5 minutes and then allowed to stand for one hour. Subsequently, the appearance of the sample was inspected. When the sample is clear, the test is repeated with more cyclopentane. When the mixture is cloudy, the test is repeated with less cyclopentane. In this manner, the maximum amount of cyclopentane soluble in the polyol or mixture of polyols is determined. This amount is the solubility of pentane of the polyol or mixture of polyols. The accuracy of this method is 1%.

Foam production for mechanical tests: The foaming experiments were carried out using the following base formulation: 100 parts by weight of polyol (or mixture of polyols) 2.4 parts by weight of stabilizer (Tegostab® B 8467 from Evonik) 0. 85 parts of water Gew. YOU. Wasser dimethylcyclohexylamine cyclopentane Polymeric MDI (Lupranat M20® from BASF SE) The foams are produced at an isocyanate index of 100. The amounts of dimethyl-cyclohexylamine and cyclopentane were determined in such a way that, in a beaker test involving 50 g of total initial weight, a stirring time of 10 sec. and also a settling time of 55 sec, an empirical density with free foaming of 35 g / L was obtained. In a second test, the components were thoroughly mixed with each other by means of a laboratory stirrer and introduced into a cube-shaped steel mold for foaming (500 g of reaction mixture, mold volume: 11.4 L). The fully reacted foam samples were molded after 20 min and stored for 3 additional days under standard conditions. The density was determined at ISO 845 and the compressive strength at ISO 604.

The table gives an overview of the polyols used.

Table 1: General view of the polyols used and solubilities of pentane (V = Comparative Examples) Fn: average functionality Table 2 presents a comparison of the properties of a system based on sucrose and a polyol.

Table 2: Foam formulations based on sucrose-based polyols (V = comparative example) pep - parts by weight Tables 3 and 4 give an overview of the systems obtained with polyol blends.

Table 3: Foam formulations based on mixtures of polyols in which the sucrose-based polyols are the main constituent of the mixture (V = comparative example) Table 4: Foam formulations based on mixtures of polyols in which the sucrose-based polyols are the main constituent of the mixture (V = comparative example) Comments regarding Tables 2-4: The amine-catalyzed polyols show better utilization of the cyclopentane used as the blowing agent. A foam having the same empirical density could be produced using a smaller amount of cyclopentane. Due to the autocatalytic properties of the amine-catalyzed polyols, the amount of catalyst used can be reduced. The improved pentane solubility and the reduced viscosity were obtained not only from the exclusive use of amine-catalyzed polyols (table 2), but also from mixtures comprising said polyols (tables 3 and 4). The mechanical properties are the same.

Foaming on the machine Established starting materials were used to prepare a polyol component. The polyol component was mixed with the required amount of isocyanate established in a Puromat® HD30 at high pressure (Elastogran GmbH), to obtain an isocyanate index of 110. The reaction mixture was injected into molds measuring 200 cm x 20 cm x 5 cm or 40 cm x 70 cm x 9 cm and allowed to foam therein. The properties and parameters of the foams were reported in Tables 5 and 6.

Table 5: Composition of foam for foaming machine Table 6: Properties The post-expansion was determined using a box mold that measures 70 x 40 x 9 cm as a function of demolding time and degree of overpacking (OP) by measuring the heights of the boxes after 24 hr. The surface quality was determined by visual determination of the frequency and intensity of surface alterations (0 = reference, + = lower number of alterations and also lower intensity of surface alterations compared to the reference).

Summary of results Comments regarding tables 5 and 6: Although the functionality and number of OH are the same, the viscosity of the polyol catalyzed by D EOA is less than 3000 raPas. This is significant and also manifests itself in an equally lower viscosity of the polyol component and also in the flow factor and an improved surface quality (reduced number of hollow spaces). All other properties important for rigid foams for this use are comparable.

Claims (15)

1. A process for preparing rigid polyurethane foams, comprising reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms reactive with isocyanate groups in the presence of c) blowing agents, wherein said compounds having at least two hydrogen atoms reactive with isocyanate groups b) comprise at least one polyether alcohol bl) having a functionality of 2-8 and a hydroxyl number of 200-800 mgKOH / g, obtained by the addition of an alkylene oxide to blb) on a compound having at least two hydrogen atoms bla), hereinafter also known as initiator substances, reactive with alkylene oxide by the use of an amine ble) as a catalyst

2. The process according to claim 1, wherein said polyether alcohol bl) is used in an amount of 10-90% by weight, based on the weight of component b).

3. The process according to claim 1, wherein said compound bla) having at least two hydrogen atoms reactive with alkylene oxides used for the preparation of said polyether alcohol b1) comprises a mixture comprising at least one compound blai) which is solid at room temperature.

4. The process according to claim 1, wherein said blai compound is selected from the group comprising pentaerythritol, glucose, sorbitol, mannitol, sucrose, polyhydric phenols, resols, condensates of aniline and formaldehyde, toluene diamine, condensates of phenols from Mannich, formaldehyde and dialkanolamines, melamine and also mixtures of at least two of the mentioned compounds.

5. The process according to claim 1, wherein said blai compound is selected from the group comprising sucrose, sorbitol and pentaerythritol.

6. The process according to claim 1, wherein said compound bla) having at least two hydrogen atoms reactive with alkylene oxides used to prepare said polyether alcohol bl) comprises a mixture comprising at least one blaii compound) which is liquid at room temperature.

7. The process according to claim 1, wherein said compound blaii) is selected from the group comprising glycerol, mono-functional alcohols of 1-20 carbon atoms, ethylene glycol and its higher homologs and propylene glycol and its higher homologs, hydroxyalkylamines, such as monoethanolamine, diethanolamine, triethanolamine and also reaction products thereof with propylene oxide.

8. The process according to claim 1, wherein said compound bla) comprises a mixture of at least one blai compound which is solid at room temperature and at least one blaii compound) which is liquid at room temperature.

9. The process according to claim 1 using an amine other than the amine of blai) as said ble catalyst).

10. The process according to claim 1, wherein said ble) catalyst is selected from the group comprising trialkylamines, aromatic amines, pyridine, imidazoles, guanidines, alkylated guanidines, amidines.

11. The process according to claim 1, wherein said ble) catalyst is dimethylethanolamine.

12. The process according to claim 1, wherein said catalyst is ble) is imidazole.

13. The process according to claim 1, wherein said ble catalyst is used in an amount of 0.01-5.0, preferably 0.05-3.0% and most preferably 0.1-1.0% by weight, based on the total batch, to prepare said component bl).

14. The process according to claim 1, which uses hydrocarbons as the blowing agent.

15. A rigid polyurethane foam obtainable according to any of claims 1-14.