IL44902A

IL44902A - Hydrophilic polyurethane foams

Info

Publication number: IL44902A
Application number: IL44902A
Authority: IL
Original assignee: Montedison Spa
Priority date: 1973-05-30
Filing date: 1974-05-28
Publication date: 1977-06-30
Also published as: NL7407077A; FR2231704A1; DE2425707A1; IL44902A0; IT988808B; FR2231704B1; BE815682A; GB1466712A

Description

44902/2 D"¾'sm»n insn s is 'as Hydrophilic polyxirethane foams MONTEDISON S.p.A.

Co 42792 The present invention relates to open-cell hydrophilic polyurethane foams.

It is known how to render polyurethane foams hydrophilic by adding the polymeric materials, while the reaction between the polyol reactant and isocyanate reactant is taking place, with added substances having the function of imparting hydrophilic properties to the foams. Various types of materials have been suggested to this purpose, among them, for example , wood powder, vegetable fibres, cellulose and its derivatives, such as carboxy-methyl-cellulose and the like.

This operation method presents some drawbacks, among which, in particular, those due to processing difficulties during casting and those connected with the low homogeneity of the foams thus obtained.

Furthermore, if such added materials are added before the polyol component, sedimentation phenomena may occur during storage, which would jeopardize. the success of the molding operation.

It is also known from French Patent Specification No. 2,079,194 to prepare hydrophilic polyurethane foams from mixtures of low molecular weight difunctional or. higher functional aliphatic and/or cycloaliphatic polyols having molecular weight of up to 500 and higher molecular weight polyols having molecular weights of 500 to 5,000, polyisocyanates., water and, auxiliary agents.

We have discovered that . a similar polyurethane forming reaction mixture leads to foams having greater water absorption provided that the low molecular weight higher functional polyol, having a molecular weight up to 500, be Thus the object of the present invention is open-cell hydrophilic polyurethane foams consisting of the product ' ^ obtained by reacting a mixture containing: 50 to 90 parts by weight of one or more trifunctional polyols having a molecular weight ranging from 500 to 3000, preferably around 1000; 10 to 50 parts by weight of one or more trifunctional polyols having a molecular weight lower than 500; preferably, but not necessarily; up to 10 'parts by weight of one or more polyols with a functionality from 2 to 6 and a molecular weight up to 1000; 1 to 5 parts by weight of water, and 0.1 to 2 parts by weight of silicone surfactants; 0.1 to 5 parts by weight of an amine-type catalyst; and finally preferably, but not necessarily, up to 50 parts by weight of one or more foaming agents consisting, of halogen derivatives of saturated or unsaturated hydrocarbons having a. low number of carbon atoms; with one or more organic isocyanates wherein, according to this invention, the trifunctional polyol having a molecular weight lower than 500 is of the amine type and consists preferably of trialkanolamines , in which the alkyl group contains from 2 to 4 carbon atoms and the total amount of the organic isocyanates is such as to provide between 40 and 80% of the number of equivalents of isocyanate (-NCO) groups necessary to react with all the reactive hydrogens of the polyols and water. The number of equivalents of isocyanate groups provided by the isocyanate used as compared with the number of isocyanate groups necessary to react with all the The oams , according to this invention have a density ί varying from 12 to 100 kg/cu.m, depending upon the contents of water and of foaming agent; they are of the open-cell semirigid type and highly hydrophilic, as can be inferred from the high water absorption value, generally exceeding 0.500 g/cu.cm, after a ten-minute immersion in water.

The hydrophilic foams according to this invention have a wide application. Particularly advantageous is their employment as a substrate for cultivation of plants in very warm and dry climates, since said foams, owing to their particular hydrophilic characteristics, prevent a too rapid evaporation of the water used to wet the cultivations.

The polyols having a molecular weight of from 500 to 3000, to be employed as components of the polyurethane foams according to this invention, may be selected from a wide range of compounds. Particularly satisfactory results are attained with polyols prepared from glycerol and/or trimethylolpropane and/or triethanolamine with; lower alkylene oxides, such as ethylene oxide and propylene oxide. Also the polyol with functionality from 2 to 6 may be selected from a wide range of compounds.

Particularly advantageous results are achieved by using polyols prepared from sorbitol and lower alkylene oxides, such as ethylene oxide and propylene oxide.

The organic ieocyanates too may be selected from a wide range of cycloaliphatic, aliphatic and/or aromatic dl-or polyfunctional derivatives including polymers.

Particularly suited are 2,4- and/or 2 , 6-toluidenediiso-cyanate, 4 ,4-diphenyl-methane diisocyanate and polyphenyl-polymethylene-polyisocyanates . ' The. foaming agents too may be selected from a wide range of compounds. Very interesting results are attained by using chlorofluoromethanes and chlorofluoroethanes , of which trichlorofluoromethane is preferred.

The reaction of the mixture consisting of the polyols, water and, optionally, the halogenated hydrocarbon foaming agent, and the isocyanic component, in the presence of amino-type catalysts and silicone surfactants, is preferably carried out at room temperature using apparatus and methods which are conventional and well-known to those skilled in the art.

The following examples are given to better illustrate, without however limiting the essential features of the present invention.

EXAMPLE 1 a) A mixture composed of: - a polyol having a molecular weight equal to 1000, obtained from glycerol and propylene oxide with a hydroxyl number = 170 83,00 parts by weight - trifunctional aminopolyol consisting of triethanolamine 12,70 - water 4,30 - silicone surfactants (Silicone DC 190- Dow Corning, U.S.A.) 0,85 - triethylamine 0,60 - halogenated hydrocarbon foaming agent 44902 2 was reacted with a polymeric organic isocyanate consisting of polyphenyl-polymethylene-polyisocyanate in such an amount^ as to have an isocyanate index equal to 76 with respect to polyols and water.

The reaction was carried out at room temperature.

An open-cell semirigid urethane foam with a density of 20 kg/cu.m and of the hydrophilic type, as resulting from the absorption of 0.620 g of water per cu.cm of resin after a 10-minute immersion, was thus obtained. b) For comparison the preceding test was repeated, but using glycerol instead of triethanolamine (in the same amount) . A polyurethane foam with a density of 20 kg/cu.m was obtained, but with hydrophilic characteristics quite inferior to those of the foam prepared according to a) , as may be inferred from a water absorption value equal to 0.250 g/cu.cm. after a 10-minute immersion. c) Again for comparison the test according to a) was repeated, but using, in the place of polyol obtained from glycerol and propylene oxide, an identical amount of hexafunctional polyol, prepared by the reaction of sorbitol and propylene oxide and having a molecular weight of 1000 and a hydroxy! number equal to 490.

A substantially hydrophobic polyurethane foam having a density of 20 kg/cu.m. and a very low water absorption value (0.05 g/cu.cm.) after a ten-minute immersion was thus obtained. 44902/2 EXAMPLE 2 By o erating under the same conditions as in exampl 1, a mixture composed ofs -T a polyol having a molecular weight = 1000, obtained by the reaction of glycerol and propylene oxide with a hydroxyl number equal to 170 60 parts by weight - triethanolamine 20 " " n - hexafunctional polyol from the reaction of sorbitol and propylene oxide and having a molecular weight = 700 and a hydroxyl number equal to 490 20 w - water 4 " " " - silicone surfactant (silicone DC 190) 1 " a n - triethylamine 0.6 " n " was reacted at room temperature with polyphenyl-polymethylene-polylsocyanate in such amount as to have an isocyanate index equal to 50.

An open-cell polyurethane foam with a density of 49 kg/cu.m and being highly hydrophilic, as shown by the high water absorption value (0.930 g/cu.m) after a 10-minute immersion, was thus obtained.

Claims

44902/2 CLAIMS:

1. Open-cell hydrophilic polyurethane foams consisting of the product obtained by reacting a mixture containing: - 50 to 90 parts by weight of one or more trifunctional poiyols having a molecular weight ranging from 500 to 3000, preferably around 1000; - 10 to 50 parts by weight of one or more trifunctional poiyols having a molecular weight lower than 500; preferably, but not necessarily, - up to 10 parts by weight of one or more poiyols with a functionality from 2 to 6 and a molecular weight up to 1000; - 1 to 5 parts by weight of water - 0.1 to 2 parts by weight of silicone surfactants; - 0.1 to 5 parts by weight of an araine-type catalyst; and finally preferably, but not necessarily, up to 50 parts by weight of one or more foaming agents consisting of halogenated derivatives of saturated or unsaturated hydrocarbons having a low number of carbon atoms; with one or more organic isocyanates , characterized in that said trifunctional polyol having a molecular weight lower than 500 is of the amine type and preferably consists of trialkanolamines, i which the alkyl groups contain from 2 to 4 carbon atoms, and in that the total amount of the isocyanates used is such as to provide between 40 and 80% of the number of isocyanate groups necessary to react with all the reactive hydrogens of the poiyols and water.

2. Open-cell hydrophilic polyurethane foams, substantially as described and exemplified hereinbefore.