DE10319242A1 - Starting compounds for the production of polyurethanes - Google Patents

Abstract

The invention relates to starting compounds for the production of polyurethanes, characterized in that they can be prepared by reacting oligomers of formaldehyde containing hydroxyl groups.

Description

object the invention are new starting compounds for the production of polyurethanes and a process for their manufacture.

Polyurethane as well as their production have long been known and in many cases in described in the literature. They are usually manufactured by reacting polyisocyanates with compounds containing at least two hydrogen atoms reactive with isocyanate groups.

As Compounds with at least two reactive with isocyanate groups Hydrogen atoms are mostly used in polyols. The biggest technical The polyether alcohols and the polyester alcohols are important here.

polyester alcohols are common by reacting at least difunctional alcohols with at least difunctional carboxylic acids manufactured.

The Polyether alcohols are generally made by adding alkylene oxides obtained on OH- or NH-functional starter compounds.

there the price of the usual Polyols from the starter compounds used and those used Alkylene oxides, especially propylene oxide and ethylene oxide, determined.

A much cheaper The starting compound for the production of polyols would be formaldehyde. As is well known, formaldehyde reacts with itself to form oligomers, the terminal Have hydroxyl groups. However, this reaction usually leads to one Mixture of oligomers and polymers with different chain lengths, the be in equilibrium with formaldehyde. Connections with a such a broad molecular weight distribution are, however, for production useless of polyurethanes. Another disadvantage of these connections is their lack of stability. After a short time, the oligomers and Polymers.

In DD 247 223 describes a process for the preparation of polyether alcohols in which a mixture of formaldehyde condensates, known as formose, and other compounds having active hydrogen atoms is reacted with alkylene oxides. In this process too, the formose has a broad molecular weight distribution.

ab.In EP 1 063 221 describes a method for the preparation of formaldehyde oligomers of the general formula (I) with a narrow molecular weight distribution, starting from formaldehyde. The implementation follows the general equation

from.

there can through drainage of formaldehyde solutions Formaldehyde oligomers of the general formula (I) with n = 2 to 19, preferably 2-9 become. These solutions can contain up to 80% oligo-formaldehyde, there is no free water in front. It is possible, individual fractions, i.e. Oligomers with certain chain lengths, by means of specifically carried out Procedure, in particular by means of distillation. The oligomers are reacted with other substances, whereby one here the defined cleavage which uses oligomers to formaldehyde.

The resulting oligomer mixture of usually 2-9 formaldehyde units like polyoxymethylene, is unstable. Form within 2 hours themselves alongside higher molecular weight Compounds (paraformaldehyde), water and monomolecular hydrated Formaldehyde.

It is desirable the cost of raw materials for the production of polyurethanes, especially the polyols.

Surprisingly it was found that formaldehyde and its oligomers in a simple manner as a starting substance for Manufacture of polyurethane raw materials can be used.

object the invention are accordingly starting compounds for production of polyurethanes, hereinafter also referred to as polyurethane raw materials, can be produced by reacting oligomers containing hydroxyl groups of formaldehyde.

object The invention is also a process for the production of polyurethane raw materials Implementation of the hydroxyl groups of oligomers of formaldehyde.

As Formaldehyde oligomers are mixtures of compounds of general formula (I), where n is an integer from 2 to 19, in particular from 2 to 9 is used.

The Preparation of the compounds of general formula (I) can be according to known methods. So it is possible to go through the oligomers known polymerization of trioxane, a cyclic reaction product of formaldehyde. This process is known from the literature. It is preferably used for the production of polyoxymethylene (POM) and is for example in Römpp Chemistry lexicon described. This process is for manufacturing of the polyurethane raw materials according to the invention, however not preferred, since preferably high molecular weight reaction products arise.

In a preferred embodiment of the invention, the oligomers according to the in EP 1 063 221 described process, wherein the subsequent reaction of the oligomers with aniline described in this document is dispensed with.

The The oligomers of formaldehyde are produced here by from a solution in which there is a balance between formaldehyde and its oligomers there are certain fractions to be separated. This separation is preferably carried out by distillation, usually using a film evaporator, in particular by means of a thin film evaporator. Suitable operating conditions for the film evaporators are generally a temperature between 10 and 230 ° C, preferably between 10 and 150 ° C, at an absolute pressure between 0.5 mbar and 2 bar. For the separation an aqueous formaldehyde solution Temperatures between 20 and 100 ° C preferred at normal pressure.

The thus separated fractions of oligomers of formaldehyde have mostly a very narrow molecular weight distribution. They are, as stated above, for one certain time stable in storage and should be processed during this time be a change to avoid their composition.

in principle could for the separation of certain oligomers from the reaction mixture dispensed and this directly for the production of the starting compounds be used for the production of polyurethanes. The disadvantage here is that this Mix great Contains amounts of free formaldehyde and water, causing it to become substantial Side reactions come.

The Oligomers of the general formula (I) described can in principle even without further treatment as starting compounds for the preparation of polyurethanes can be used. If the implementation is immediate following their separation, degradation reactions that lead to the release of formaldehyde are avoided. However, the terminal hydroxyl groups are preferably reacted Oligomers.

at the conversion of the oligomers to starting compounds for the preparation The terminal hydroxyl groups of polyurethanes are converted.

In one embodiment the invention will be the terminal Hydroxyl groups reacted with alkylene oxides to form polyether alcohols. The implementation is usually done as in the known production of polyether alcohols using the usual alcoholic starter substances.

Depending on the number of formaldehyde units, the hydroxyl number of the oligomers is between 1436 mg KOH / g at n = 2 and 389 mg KOH / g at n = 9. Since the oligomers are anhydrous after the separation, there is a drying step between the separation of the oligomers and theirs Reaction with the alkylene oxides is not more necessary.

How common in technology, the oligomers of formaldehyde are reacted with the alkylene oxides in the presence of catalysts. As usual, basic catalysts can be used Compounds such as amines, basic metal oxides and metal hydroxides, especially potassium hydroxide can be used.

Multimetal cyanide compounds, also referred to as DMC catalysts, are preferably used as catalysts. Such connections have long been known and are described, for example, in EP 654 302 or in EP 862 947 described. The advantage of using DMC catalysts is, on the one hand, that they can remain in the product after the reaction, and, on the other hand, that, unlike basic catalysts, they do not promote the cleavage of the oligomers.

As Alkylene oxides can the usual ones for this and known compounds are used. The biggest technical Ethylene oxide and propylene oxide, individually or in any mixtures can be used with each other. At the The two alkylene oxides can be used with ethylene oxide and propylene oxide together in a so-called statistic or one after the other in so-called alkylene oxide blocks be dosed.

The The type and amount of the dosed alkylene oxides depends in particular on the use of the polyether alcohols. For the use in rigid foams has the polyether alcohols short Chains on. The hydroxyl number of such polyether alcohols is mostly in the range between 300 to 600, in particular between 400 and 500 mg KOH / g. Propylene oxide is preferably used as the alkylene oxide used.

For use Long-chain polyether alcohols are mostly used in flexible foams used. The hydroxyl number of these polyether alcohols is usually in the range between 30 and 120 mg KOH / g, preferably in the range between 30 and 60 mg KOH / g. Mixtures are mostly used as alkylene oxides used from ethylene oxide and propylene oxide. For certain areas of application, for example for the production of cold molded foams, a pure ethylene oxide block is added to the end of the polyether chain.

at the use of DMC catalysts for the production of the polyether alcohols is preferably propylene oxide or statistical as alkylene oxide Mixtures of propylene oxide and ethylene oxide are used. In a special embodiment this process is carried out in a statistical mixture of ethylene oxide and Propylene oxide during the ratio of the dosage of the two alkylene oxides changed to one another in the mixture, such as described in WO 01/44347.

By this process variant can by using oligomers of different molecular weights, diols produced in a wide range of molecular weights in a simple manner be that have a narrow molecular weight distribution.

The Oligomers of formaldehyde can alone or in a mixture with other H-functional starting substances with the Alkylene oxides are implemented. As additional starting substances preferably at least two-functional alcohols, such as glycerol, Trimethylolpropane, ethylene glycol, propylene glycol and their higher homologues be used.

The Implementation of the starting substance with the alkylene oxides is generally at the usual pressures for this Range between 0.1 and 1.0 MPa and the usual temperatures in the range between 80 and 140 ° C carried out. A post-reaction phase usually follows the metering of the alkylene oxides to complete Reaction of the alkylene oxides. In an advantageous embodiment of the method according to the invention is at the beginning of the post-reaction phase, preferably immediately after completion of the Dosing of the alkylene oxides, the reaction mixture again catalyst, especially amine catalyst added.

To the addition of the alkylene oxides, the polyether alcohols are mostly a short distillation treatment to separate volatile substances Subjected to impurities. If necessary, the polyether alcohol subsequently be filtered to remove any solid contaminants to remove. If basic compounds are used as catalysts are carried out after the addition of the alkylene oxides the removal of the catalyst. This can be done through neutralization with acids or by using adsorbents. In connection the salts or the adsorbents are then passed through Filtration removed.

In a particular embodiment of the process according to the invention, the reaction of the oligomers of formaldehyde with the alkylene oxides can also be carried out continuously, in particular using DMC catalysts. The separated oligomer mixture and the alkylene oxide and the catalyst are continuously fed to a reactor and the polyether alcohol formed is continuously removed from the reactor. Such continuous processes are for example in DD 203 235 and WO 98/03571. The continuous reaction can be carried out, for example, in tubular reactors, stirred tanks or loop reactors. In this embodiment of the process according to the invention, the continuous production of the polyether alcohols by reaction of the oligomers with alkylene oxides can be directly connected to the separation of the oligomers which is also carried out continuously

The polyether alcohols obtained in this way can easily be prepared by conventional methods Process with isocyanates to be implemented as polyurethanes. there can the polyether alcohols according to the invention alone or preferably in a mixture with other compounds with additional ones Alcohols, especially short-chain polyfunctional alcohols, Polyether and / or polyester alcohols, preferably polyether alcohols, be used. Short-chain alcohols are usually two- or polyfunctional alcohols with a molecular weight in the range between 62 and 400 g / mol, such as ethylene glycol, propylene glycol and their higher Homologues or glycerin used.

As Polyether alcohols and polyester alcohols can be the usual ones for this purpose and known compounds are used. They mostly have a molecular weight Mn of over 400 g / mol, preferably in the range between 400 and 15000 g / mol. These polyols are prepared by customary and known processes, in the case of polyester alcohols, by the implementation of multifunctional ones Alcohols with polyfunctional carboxylic acids, in the case of polyether alcohols by addition of alkylene oxides to H-functional starter substances. Depending on the nature of the desired polyurethanes, the reaction is optionally carried out in the presence of catalysts, blowing agents and conventional Auxiliaries and / or additives.

In a further embodiment In the present invention, the oligomers of formaldehyde after their separation from the reaction mixture with isocyanates converted to prepolymers.

For this become the terminal ones Hydroxyl groups of the oligomers separated as described above of the general formula (I) reacted with isocyanates. Because the oligomers are only stable in storage for a limited time, the implementation must also be immediate subsequent to the separation of the oligomers if a Product with a narrow molecular weight distribution should be obtained.

at Excessive storage of the oligomers occurs next to one Broadening of the molecular weight distribution also leads to the formation of Formaldehyde and water in the oligomer mixture. This is though the formaldehyde formed is principally removed by stripping can be detrimental to the further processing of the oligomers to prepolymers, since it is too undesirable Side reactions leads.

By the reaction of all the hydroxyl groups of the oligomers becomes their cleavage completely suppressed. The Prepolymers are stable in storage and can be processed like Prepolymers from others commonly used in polyurethane chemistry Polyols.

The Reaction of the hydroxyl group-containing oligomers with the isocyanates takes place according to the usual Manufacturing method for Prepolymers containing isocyanate groups. This is the oligomer reacted with at least such an amount of isocyanate, the for a complete Sales of the hydroxyl groups of the oligomers is sufficient. The implementation can be in the presence of usual Urethane formation catalysts take place. This is usually the isocyanate compound, optionally in the presence of a catalyst, at a temperature from 40 to 100 ° C, preferably 50 to 80 ° C, submitted. With stirring the oligomer mixture is metered in, then the reaction mixture is left if necessary, until complete Conversion, usually up to 2 hours, after-reacting at 60 to 140 ° C., preferably at 80 to 100 ° C.

The NCO content of the prepolymers depends on the molar mass of the oligomers, the excess used of isocyanate, the reaction time, the residence time, the reaction temperature and the catalysts used.

Usually the NCO content of the prepolymers is in the range between 10 to 30% by weight, preferably 15 to 25% by weight.

The Oligomers of formaldehyde can individually or in a mixture with other compounds with at least two hydrogen atoms reactive with isocyanate groups with the isocyanates be implemented. The components that are shared with the oligomers of the formaldehyde can be reacted with isocyanates to form prepolymers can, are especially alcohols. Depending on the intended use of the Prepolymers can different alcohols in an amount of 0 to 90 wt .-%, preferred 0 to 60 wt .-%, each based on the sum of the oligomers of Formaldehyde and the other compounds with at least two Isocyanate reactive hydrogen atoms are used.

For the most Applications are considered additional Alcohols short-chain multifunctional alcohols, polyether and / or Polyester alcohols, preferably polyether alcohols, are used. As short-chain alcohols mostly become bifunctional or multifunctional Alcohols with a molecular weight between 62 and 400 g / mol, such as ethylene glycol, propylene glycol and their higher homologues or glycerin used.

As Polyether alcohols and polyester alcohols can be the usual, closer up above described are used. It is also possible to use the polyether alcohols, by the addition of alkylene oxides to oligomers of the general Formula (I) were prepared together with the oligomers of Implement formaldehyde with isocyanates.

As Isocyanates come for the inventive method all isocyanates with two or more isocyanate groups in the molecule are used. You can both aliphatic isocyanates, such as hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI), or preferably aromatic Isocyanates, such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) or mixtures of diphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanates (P-MDI), preferably TDI and MDI, can be used. It is also possible, To use isocyanates, which through the incorporation of uretdione, isocyanurate, Allophanate, uretonimine and other groups have been modified. These connections are common also called modified isocyanates.

The prepolymers produced in this way with compounds containing at least one, preferably at least two have hydrogen atoms reactive with isocyanate groups in the molecule, processed into polyurethanes. Depending on the type of used Polyols and isocyanates can the prepolymers for rigid foams, flexible foams, adhesives, Coatings or elastomers are processed.

The The invention is illustrated by the following examples.

example 1

A formalin with a formaldehyde content of 37 wt .-% was by means of thin-film evaporator at 80 ° C Wall temperature and 120 mbar to a theoretical formaldehyde content evaporated from 73 wt .-%. The solution was at 80 ° C stored and processed within an hour. 961 g of this solution was in a pilot plant autoclave with 38.4 g of dimethylcyclohexylamine are added and 1010 g of propylene oxide are metered in at 100 ° C. in the course of 6 hours. Subsequently let one react the reaction mixture for 2 hours at the same temperature. After that, became volatile Components removed in vacuo. The remaining liquid reaction product had a hydroxyl number of 685 mg KOH / g and a water content of 0.011% by weight. A GPC investigation showed oligomeric products with a molecular weight in the range of 100-500 g / mol. By means of investigations by means of gas chromatography and coupled mass spectroscopy (GC-MS) showed that adducts consist of 2 molecules of propylene oxide and 2 molecules Formaldehyde.

Example 2

A formalin with a formaldehyde content of 37 wt .-% was by means of thin-film evaporator at 80 ° C Wall temperature and 120 mbar to a theoretical formaldehyde content evaporated from 73 wt .-%. The solution was at 80 ° C stored and processed within an hour. 1110 g this solution 70 g of potassium hydroxide were added in a pilot plant autoclave and metered in 1600 g of propylene oxide within 9 h. The liquid reaction product had a hydroxyl number of 868 mg KOH / g and a water content of 0.014% by weight. An examination using gel permeation chromatography showed oligomeric products with a molecular weight in the range of 100 - 500 g / mol. GC-MS showed that adducts consist of 2 molecules of propylene oxide and 2 molecules Formaldehyde.

Claims (16)

Starting compounds for the production of polyurethanes, characterized in that they react by reacting hydroxyl groups containing oligomers of formaldehyde can be produced. Compounds according to Claim 1, characterized in that the oligomers of formaldehyde used are those of the general formula (I), where n is an integer between 2 and 19

Compounds according to claim 1, characterized in that by reacting the hydroxyl groups of the oligomers of Formaldehyde can be produced with alkylene oxides. Compounds according to claim 3, characterized in that as alkylene oxides, ethylene oxide, propylene oxide or mixtures of Ethylene oxide and propylene oxide can be used. Compounds according to claim 1, characterized in that by reacting the hydroxyl groups of the oligomers of Formaldehyde can be produced with isocyanates. Compounds according to claim 5, characterized in that they have an NCO content have in the range of 10 to 30 wt .-%. Compounds according to claim 5, characterized in that they have an NCO content have in the range of 15 to 25 wt .-%. A method of making compounds according to claim 1, characterized in that the hydroxyl-containing Oligomers of formaldehyde are implemented. The method of claim 8, comprising the steps a) Preparation of oligomers of formaldehyde with the general formula (I) b) reaction of the hydroxyl groups of the oligomers of formaldehyde. A method according to claim 9, characterized in that in step a) the oligomers by distillation from an aqueous formaldehyde solution be separated. A method according to claim 10, characterized in that the distillation is a thin film distillation is. A method according to claim 9, characterized in that a reaction with alkylene oxides is carried out in step b). A method according to claim 9, characterized in that a reaction with isocyanates is carried out in step b). A method according to claim 9, characterized in that steps a) and b) are carried out continuously. Process for the production of polyurethanes, thereby characterized in that compounds according to claim 3 with isocyanates be implemented. Process for the production of polyurethanes, thereby characterized in that compounds according to claim 5 with compounds implemented with at least two groups reactive with isocyanates become.