DE2603498B2 - Further development of the process for the production of crosslinked, elastic, open-cell foams containing urethane groups - Google Patents

Description

40

NHR ²

in which R ^{1 is} a CH ₃ , NHr, NHR ³ or NRr radical, where R ^{3 is} an alkyl radical with 1 to 4 carbon atoms and R ^{2 is} a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms or ethylene urea or tetramethylammonium bromide or tetraethylammonium iodide in the aqueous solution of the crystalline crosslinking agent completely or partially dissolves and this solution is thus dispersed in the polyether polyol

2. The method according to claim 1, characterized in that a dispersion is used which Urea has been added.

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Foams containing urethane groups are activated by reacting polyisocyanates with Obtained polyols containing hydrogen atoms. Such foams are widely used, e.g. B. on in the field of insulation, for the production of structural elements or for upholstery purposes.

For many of these uses are open-cell {, 5 ge foam systems desired. Closed cell foams show reduced elastic behavior and tend to shrinkage during manufacture, Desired is. t further, d & ß open-cell, elastic Foams can be varied in their load-bearing capacity or their hardness as far as possible over a wide range can. A foam body can have a desired hardness by increasing the degree of crosslinking, by increasing the rgum weight or by increasing the Polyisocyanate content of the formulation are given. Among these possibilities, the increase in the degree of crosslinking is technically and economically the most important most advantageous. Both to increase the density as well as the polyisocyanate content higher amounts of starting materials are required, which makes the production of the foams less economical There is also an increase in the polyisocyanate content also for reasons of the resulting increased tendency to flammability and toxicity as well as the the hard grip of the foams is not advantageous

To achieve a higher degree of networking garden according to the current state of the art: a polyurethane foam formulation, low molecular weight, polyfunctional Added compounds which are soluble in the polyols containing active hydrogen atoms. Accordingly, the crosslinking agents can react immediately after the foaming reaction has started step. The possibility of the crosslinking density arbitrarily to increase, is limited in this method that, depending on the rest Constituents of the foam formulation, the crosslinking density at the point in time at which the foams their maximum height of rise and normally then the cell opening begins to be already too high to the To allow the process of cell opening to occur.

The result is foams that are highly networked, but have a large part of closed cells or are completely closed. Show such foams decreased elasticity behavior and tend due to their high closed-cell content after production to shrinkage.

These disadvantages are overcome according to the method of patent application P 25 07 161.8-44.

This patent application relates to a process for the production of crosslinked, elastic, open-celled urethane groups containing foams by reacting polyether polyols with a hydroxyl equivalent weight of 700 to 5000, polyisocyanates, water, catalysts, optionally low molecular weight compounds having two or more active hydrogen atoms and one which are soluble in the polyether polyols Molecular weight up to 750 as crosslinking agent in an amount of up to \ J5 hydroxyl equivalent, based on one hydroxyl equivalent of the polyether polyol, and optionally organic blowing agents and emulsifiers or stabilizers with the additional use of crystalline crosslinking agents that are only slightly soluble or insoluble in the polyether polyol to be foamed at room temperature from the group sorbitol, tri · or hexamethylolmelamine, glucose, sucrose, erythritol, mixtures or hydrates of these compounds or their partial esters or ethers in an amount from 0.1 to 5.0 hydroxyl equivalent, based on one hydroxyl equivalent of the polyether polyol to be foamed, in the form of a dispersion of these crystalline crosslinking agents in the polyether polyol.

This makes it possible to provide foams which contain urethane groups and which have a high Crosslink density and, as a result, correspondingly increased hardness values, but at the same time a

contain a small proportion of closed cells and are therefore highly elastic and do not tend to shrink after production.

With increasing additives used there Crosslinking agent, the elongation at break and tear resistance of the foams formed is somewhat reduced, the tensile strength, however, increases

The compression deformation, the drop in hardness after 500,000 load changes (pressure drop), the fatigue behavior and the aging properties and the rebound resilience, on the other hand, are hardly noticeable influenced

It was found, however, that such dispersions of crystalline crosslinkers in the polyether polyols become increasingly viscous over the course of a few days and sometimes even solidify. It was therefore necessary to use these dispersions as soon as possible after their preparation to use. -

It has now been found that this disadvantage can be avoided by further training the Method of the patent application P 25 07 161.8-44 a such dispersion of the crystalline crosslinking agent in the polyether polyol used has been prepared is by adding 0.5 to 50% by weight, based on the Amount of water in the foaming formulation, a compound of the general formula

R ¹

O = C

NHR ²

in which R ^{1 represents} a CH ₃ , NHr, NHR ³ or NRr radical where R ^{3 is} an alky radical rut I to 4 carbon atoms and R ^{2 is} a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms or ethylene urea or tetramethyl or tetraethylammonium bromide or iodide completely or partially dissolves in the aqueous solution of the crystalline crosslinking agent and this solution is dispersed in the polyether polyol

The compounds of the general groups dissolved in the dispersion in the process according to the invention formula

R ¹

O = C

NHR ²

Ethylene urea, tetramethylammonium bromide or tetraethylammonium iodide degrade water associates.

This also has the effect that the reaction of the isocyanate groups with the water in the Foaming approach is included selectively accelerated so that the propellant gas is already in an early stage Stage of the urethane formation reaction is available and the water as quantitatively as possible with the Isocyanate groups reacts In addition, this counteracts the observation that the crystalline Polyols bind parts of the water contained in the foaming and the foaming reaction only are available with a delay.

The inventive method is the Cream time shortened, by which one understands the time that

elapsed until the reaction mixture as a result of

incipient CO _r formation takes on a creamy appearance

Preferred among the aforementioned compounds are the more hydrophilic substances, i. H. those in Water are more soluble than in the organic components of the reaction mixture to be foamed. The use of urea is particularly preferred,

The invention is explained in more detail by the following example;

A mixture consisting of

100.00 parts by weight

1, S6 weight parts
2.00 parts by weight
1.00 part by weight
0.40 parts by weight
6.00 parts by weight

1.00 part by weight
10.00 parts by weight

a polyoxyalkylene triol started with glycerol, which is made up of 84% by weight of propylene oxide and 16% by weight of ethylene oxide and has an OH number of 35
Water,
Glycerine,
Triethylenediamine,
Dimethylethanolamine,
a dispersion of 25 wt .-% sorbitol and 7 wt .-% urea in esters started with glycerol polyoxyalkylene triol, which is made up of 84 wt .-% of propylene oxide and 16 wt .-% of ethylene oxide and an OH number of 35 " wherein the dispersion contains 14% by weight of water

a polyether-polysiloxane block copolymer
Trichlorofluoromethane

is with 51.5 parts by weight of a mixture of 65 Parts by weight of 2,4- / 2,6-toluene diisocyanate (isomer ratio 80:20) and 35 parts by weight of crude Piphenylmethane diisocyanate in an open box brought to reaction The result is an open-cell, non-shrinking foam with a height of 28.5 cm. The cream time is 10 seconds, the rise time 105 seconds.

A reaction mixture which has the aforementioned composition but differs in that

so that the sorbitol dispersion does not contain any urea also results in an open-cell, non-shrinking one Foam. However, it only reaches a height of 27 cm and the cream time is 15 seconds Climbing time 135 seconds.

The technical progress of the. is achieved with the present invention is additionally thereby proves that the urea-containing dispersion of sorbitol in polyether polyol still after several weeks, During the entire observation period, it remained uniformly fluid while the urea-free one Preparation initially becomes increasingly viscous within three days. The crystalline portion of the The dispersion is finally so coarse that the polyether polyol preparation solidifies after a week.

Claims (1)

Claims; 1, Further training of the procedure for Manufacture of cross-linked, elastic, open-ended materials Foams containing urethane groups by reacting polyether polyols with a Hydroxyl equivalent weight of 700 to 5000, polyisocyanates, water, optionally in the polyether polyols soluble low molecular weight compounds with two or more active hydrogen atoms and a molecular weight up to 750 as a crosslinking agent in an amount up to 1.5 Hydroxyl equivalent based on one hydroxyl equivalent of the polyether polyol, and optionally organic blowing agents and emulsifiers or stabilizers with additional use more crystalline, in the polyether polyol to be foamed at room temperature only sparingly soluble or insoluble crosslinking agents from the group Sorbitol, tri- or hexamethylolmelamine, glucose, Sucrose, erythritol, mixtures or hydrates of these Compounds or their partial esters or ethers in an amount of 0.1 to 5.0 hydroxyl equivalents, based on a hydroxyl equivalent of the foaming polyether polyol, in In the form of a dispersion of these crystalline crosslinking agents in the polyether polyol according to patent application P 25 07161.8-44, characterized in that that such a dispersion of the crystalline crosslinking agent in the polyether polyol used, which has been prepared by 0.5 to 50 wt .-%, based on the amount of Water in the foaming, a compound of the general formula R ¹