DE1154936B - Process for the production of polyurethane foams - Google Patents

Description

Process for the production of polyurethane foams It is known Polyurethane foams by polyaddition of polyhydroxyl compounds and polyisocyanates using fluorinated chlorinated hydrocarbons as propellants. In general, one proceeds here in such a way that first the polyhydroxyl compound mixed with the fluorinated chlorohydrocarbon, this mixture if necessary nor substances that accelerate the formation of polynrethane, such as tertiary amines and others suitable substances, added and the mixture thus obtained then with the polyisocyanate implements.

The heat released during the exothermic polyaddition reaction causes evaporation of the fluorinated chlorinated hydrocarbons contained in the mixture, whereby the mass is foamed during the hardening.

The above-mentioned polyhydroxyl compounds are in most cases around polyester or polyether with at least two free, reactive ones Hydroxyl groups. The former are generally by esterification of polybasic ones Carboxylic acids, for example adipic acid or phthalic acid, with glycols, for example n-butylene glycol, or triol compounds. In contrast, it is with the Polyethers to more or less branched polyglycols, e.g. B. polypropylene glycol. Propoxylated diamines are also used as polyhydroxyl compounds in contrast to the polyester or polyether compounds described above even without the use of other tertiary amines, it has its own reaction accelerator Have an effect when mixed with polyisocyanates.

As is known, suitable fluorinated chlorinated hydrocarbons are those whose boiling points are between + 50 and 850 C, especially monofinortrichloromethane and difluorodichloromethane.

Suitable tertiary amines as catalysts include triethylenediamine, Triethylamine, N-methylmorpholine, N-ethylmorpholine or tetramethylbutanediamine. Further Possible additives are also, for example, tin octoate or dibutyltin dilaurate, which also have a catalyzing effect, and also fire retardants such as dichloroethyl phosphate or diammonium phosphate, and emulsifying compounds, for example silicone oils. Foam stabilizers and dyes are also often added.

The polyisocyanate compounds used are in particular 2,4-toluene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate or mixtures thereof.

In practice, the individuals involved are responsible for mixing Components different procedures are common.

So it is z. B. in the block foaming of flexible polyurethane foams It is customary for all individual components to be sent separately to a common mixing head give and this there immediately before the exit of the reaction mass by a high-speed Mix stirrer.

There is a long way to go when it comes to foam-molding, especially rigid foam common, the polyhydroxyl compounds with the fluorinated chlorinated hydrocarbon to premix and also feed this mixture to a mixing device, in to which the polyisocyanate is added. Immediately before the entry of the fluorinated Chlorinated hydrocarbons added polyhydroxyl compound in the mixing device the mixture of the accelerating tertiary is in the supply line Amines and the other additives are metered in.

With another processing method, all components involved in the reaction including the fluorinated chlorinated hydrocarbon, but without the polyisocyanate, premixed and in this form of a mixer fed, in which the reaction takes place with foam formation with the polyisocyanate.

Often this results in the need to consist of the mixture from the polyhydroxyl compounds, the fluorinated chlorohydrocarbon and optionally the tertiary amines as catalysts and other common additives, via a to be stored for a longer period of time, for example because it work break has not been used up completely.

In these cases it has been shown that when storing such Mixture shows a significant decrease in activity after a relatively short time is to be observed, especially if the storage of this mixture in vessels or Pipelines made of iron or copper alloys are made. The mixture takes one unwanted dark color and is already after a storage of only a few Days have become so unresponsive that a reaction time that is several times longer, i. H. Foaming time, is required. In unfavorable cases it is even at all it is no longer possible to use the mixture stored in this way by adding polyisocyanate To implement polyurethane foams.

There has now been a method of making polyurethane foams from polyhydroxyl compounds, polyisocyanates, fluorinated chlorinated hydrocarbons and optionally tertiary amines as catalysts and other customary additives found, which is characterized in that mixed with epichlorohydrin mixtures from polyhydroxyl compounds, fluorinated chlorohydrocarbons and optionally tertiary amines as catalysts and other conventional additives in per se be known Way to be foamed after addition of polyisocyanate.

The mixtures stabilized by means of epichlorohydrin are also after longer storage times are still very good for the production of polyurethane foams suitable by adding polyisocyanates, even if they stored in metal vessels and pipes containing iron or copper alloys have been.

The epichlorohydrin is added to the above mixture to be stabilized in small amounts, expediently in amounts between 1 and 5%, preferably 2.5 and 3.5 o / o based on the weight of the fluorinated chlorohydrocarbon. However, these additional amounts are only to be regarded as guidelines and can be used if necessary can also be significantly exceeded or undercut.

The epichlorohydrin can be added to the finished polyisocyanate-free mixture, but also added to one or more components of the mix before mixing will. The epichlorohydrin is preferably added to the fluorinated chlorohydrocarbon before adding it to the reaction mixture.

It is therefore possible to use the mixtures of polyhydroxyl compounds described above, fluorinated chlorinated hydrocarbons, catalytically active tertiary amines and to store other usual additives for a longer period of time, if this is due to equipment or manufacturing reasons should be necessary. If not excessively Long storage times can thereby reduce the quality of the mixtures stored from such polyurethane foams to be produced and the foaming time to practically be kept unchanged.

The invention is illustrated by the following example.

Example a) A mixture consisting of 80 g of a polyester compound with reactive free OH groups, 20 g of a propoxylated diamine compound with free OH groups, 40 g of monofinortrichloromethane, 0.6 g of a mixture of tertiary Amines, 3 g of additives regulating cell formation, were placed in a brass jar Stored at 400 C for 2 days. Following this, this mixture was 125 g Stirred diisocyanate.

The resulting foam was compared to a foam from a freshly prepared reaction mass has a strong brown discoloration. The foaming time was elongated about five times, and the resulting foam had a about twice as high density (about 60 g / l freely foamed) compared to a foam of a freshly prepared mixture. b) A mixture of the same Composition, as described under a), in a brass vessel for 6 days stored at 400 ° C. and then stirred with 125 g of the diisocyanate gave a dark brown colored mass that no longer foamed.

The activity of this mixture was completely lost during storage. c) A mixture of the same composition as described under a) was made according to the invention additionally mixed with 1.2 g of epichlorohydrin and again in brass vessels 400 C stored. After 2 resp.

This mixture was stirred with 125 g of the diisocyanate each time for 6 days and assess the formation of the foam.

The mixture, stored for 2 days, gave a foam that stood out from practically no difference to such a freshly prepared reaction mixture. The mixture, which had been stored for 6 days, produced a difference compared to the freshly prepared mixture only slightly impaired foam. The foaming time was only about 50% extended and the density of the foam increased by only about 20%.

Claims (1)

PATENT CLAIM: Process for the production of polyurethane foams from polyhydroxyl compounds, polyisocyanates, fluorinated chlorinated hydrocarbons and optionally tertiary amines as catalysts and other customary additives, characterized in that mixed with epichlorohydrin mixtures of polyhydroxyl compounds, fluorinated chlorohydrocarbons and optionally tertiary amines as catalysts and other conventional additives in a manner known per se after adding polyisocyanate be foamed.