NO155917B - PROCEDURE AND DEVICE FOR CLIFTING FIBER PLATES. - Google Patents

Description

Process for the production of polyurethane foam.

This invention relates to improvements in the production of polymers, and more particularly polyurethane foam. in

It is known to produce polyurethane foam by the reaction of organic polyisocyanates and polyethers containing hydroxyl groups under such conditions that a 1 foam-forming gas is developed. Polyethers which have been proposed for use in such reactions include products containing hydroxyl groups obtained by the reaction of polyhydric alcohols with alkylene oxides, especially propylene oxide. A number of methods for 1 gas evolution are known, but the method that has been particularly used in recent years, particularly in the production of rigid polyurethane foams, is the use of an inert liquid with a low boiling point, e.g. a halogenated hydrocarbon, which evaporates during the exothermic, polyurethane-forming reaction, resulting in the formation of a cellular product. Although the low-boiling liquids commonly used are freely miscible with propylene oxide-based polyethers with low hydroxyl functionality, such as the polyoxypropylene triols obtained by the reaction of propylene oxide with trihydric alcohols, some difficulty may be encountered when polyoxypropylene polyols with higher functionality are used . In the case of propylene oxide condensates that contain more than 3 hydroxy groups per molecule, one thus often finds that there is an upper limit to the quantity ratio of low-boiling liquid,

which can be mixed homogeneously with polyethylene

pure. Above this limit, some of said liquid separates as another phase, and mixing the desired proportions of polyurethane foam-forming components is made difficult.

It has now been found that this difficulty can be avoided or made minimal by using a reaction product of a polyhydric alcohol which has from 4 to 8 hydroxyl groups per molecule, and an alkylene oxide having from 4 to 8 carbon atoms per molecule. In particular, it has been found that the proportion of low-boiling liquid that can be mixed homogeneously with these reaction products is considerably higher than is the case with the corresponding reaction products of propylene oxide. The mixing of the polyurethane foaming components in the desired proportions is thereby made easier due to the reduced tendency for said liquid to separate from the polyether. Furthermore, due to this higher compatibility between gas developing agent and polyether, it is often possible to use a polyether with a higher hydroxyl content than would be possible for a propylene oxide-based product, and thus obtain rigid polyurethane foams with improved mechanical properties. In particular, the foams have a better structure and are less brittle than foams made from propylene oxide-based polyethers.

According to the present invention, a method is thus provided for the production of polyurethane foam by the reaction of an organic polyisocyanate with a polyether containing a hydroxyl group under such conditions that a foam-forming gas is developed, characterized in that the polyether is used as a reaction product of a polyhydric alcohol having from 4 to 8 hydroxyl groups per molecule, and an alkylene oxide having from 4 to 8 carbon atoms per molecule.

The foaming gas can be developed in a number of different ways. For example the gas may be carbon dioxide developed by the reaction of a certain amount of the organic polyisocyanate with water incorporated in the reaction mixture. As stated above, however, the method according to the invention is of particular value when the gas is developed by incorporating a low-boiling, inert liquid into the reaction mixture which evaporates during the exothermic, polyurethane-forming reaction.

Suitable, inert, low-boiling liquids are liquids which are inert to the polyurethane foam-forming components and have boiling points of not more than 75°C at atmospheric pressure, and preferably between 40 and 50°C. Examples of such liquids are halogenated hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, dichlorotetrafluoroethane, 1:1:2-trichloro-1:2:2-trifluoroethane, dibromodifluoromethane, monobromotrifluoroethane, methylene chloride, vinyl chloride and vinylidene chloride . Mixtures of these low-boiling liquids with each other and/or with other substituted or unsubstituted hydrocarbons can also be used. Such liquids are usually used in amounts of from 1 to 100 percent, preferably 5 to 60 percent, based on the weight of the polyether.

Water is usually used in amounts of from 1 to 10 percent based on the weight of the polyether, when used as a gas developing agent.

The polyethers used in the method according to the invention can be produced by the reaction of a polyhydric alcohol which has from 4 to 8 hydroxyl groups per molecule, with an alkylene oxide having from 4 to 8 carbon atoms per molecule, and will normally have the same number of hydroxyl groups per molecule like the polyhydric alcohols from which they are prepared.

Suitable alkylene oxides having from 4 to 8 carbon atoms per molecule, includes 1:2-butylene oxide, 2:3-butylene oxide, amyl enoxide and styrene oxide. Mixtures of such oxides can be used.

Suitable polyhydric alcohols which have

from 4 to 8 hydroxyl groups per molecule, includes tetrahydric alcohols, e.g. erythritol, pentaerythritol and methylglucoside, pentahydric alcohols, e.g. arabitol, xylitol, glucose, mannose and galactose, hexavalent alcohols, e.g. dipentaerythritol, sorbitol, mannitol, dulcitol and iditol, and alcohols with even higher functionality, e.g. sucrose and lactose. Mixtures of such polyhydric alcohols can be used.

The advantages of these reaction products compared to propylene oxide reaction products in terms of improved compatibility with gas-evolving agents such as halogenated hydrocarbons are particularly marked in the case of reaction products of polyhydric alcohols having at least six hydroxyl groups per molecule, e.g. sorbitol, and especially in the case of reaction products of alcohols with higher functionality, e.g. sucrose. The molecular weights of the reaction products have a considerable effect on their compatibilities with said gas developing agents. In this connection, the method according to the invention is particularly suitable when the reaction product of the alkylene oxide and the polyhydric alcohol has a molecular weight of from 75 to 150 units per hydroxyl group.

Particularly noteworthy are the polyethers produced by the reaction of butylene oxide with sucrose having molecular weights of from 600 to 1200, and butylene oxide reaction products of sorbitol having molecular weights of from 450 to 900. These polyethers are more compatible than the corresponding propylene oxide reaction products with gas-evolving agents such as halogenated hydrocarbons, and gives rigid polyurethane foams with excellent mechanical properties.

Methods for the production of polyethers by reaction of alkylene oxides with polyhydric alcohols are well known and can be used for the production of the polyethers used in the method according to the present invention. The polyhydric alcohol group has 4-8 hydroxyl groups per molecule, can thus be reacted with the alkylene oxide which has 4-8 carbon atoms per molecule, in the presence of a basic catalyst such as potassium hydroxide. The general reaction conditions can be as described in the state of the art, e.g. a temperature of from 50 to 150°C, preferably between 90 and 120°C, and pressure of up to 5.6 kg/cm<2> can be used. As many of the polyhydric alcohols that have from 4 to 8 hydroxyl groups per molecule, are solids or highly viscous liquids at the reaction temperatures usually used, it is particularly appropriate to carry out the reaction in the presence of a solvent for the polyhydric alcohol. Water is a particularly suitable solvent, but organic solvents, e.g. dimethylsulfoxide, can optionally be used. When water is used as a solvent for the polyhydric alcohol, the alkylene oxide acid addition can be carried out in two stages, unreacted water and low molecular weight oxyalkylation products of the water being removed from the reaction mixture at an intermediate point to reduce the contamination of the product with materials of low functionality.

Examples of suitable organic polyisocyanates for use in the method according to the invention include aliphatic diisocyanates such as hexamethylene diisocyanate, cycloaliphatic diisocyanates such as dicyclohexylmethane diisocyanate and aromatic diisocyanates such as tolylene-2:4-diisocyanate, tolylene-2:6-diisocyanate , diphenylmethane-4:4'-diisocyanate, 3-methyl-diphenylmethane-4:4'-diisocyanate, m- and p-phenylene diisocyanates, chlorophenylene-2:4-diisocyanate, naphthalene-1:5-diisocyanate, diphenyl -4:4'-diisocyanate, 3:3'-dimethyldiphenyl-4:4'-diisocyanate and diphenyl ether-4:4'-diisocyanate. Triisocyanates which can be used include aromatic triisocyanates such as tolylene-2:4:6-triisocyanate and diphenyl ether-2:4:4'-triisocyanate. Examples of other suitable organic polyisocyanates include the reaction products of an excess of diisocyanate with a polyhydric alcohol such as trimethylolpropane. Urethedion dimers and isocyanurate polymers of diisocyanates such as tolylene-2:4-diisocyanate can also be used. Mixtures of polyisocyanates can be used. Examples of particularly suitable mixtures include polyisocyanate compositions obtained by phosgeneration of the mixed polyamine reaction products of formaldehyde and aromatic amines such as aniline and orthotoluidine.

The production of polyurethane foam can be carried out by the general methods which are fully described in the state of the art. Thus, the materials can be mixed continuously or discontinuously, and part or all of the organic polyisocyanate can first be reacted with part or all of the polyether before the final reaction to give a foam is carried out in the second step. However, it is generally preferred to carry out the foam production in a single-step reaction between the organic polyisocyanate and the polyether in the presence of a gas-evolving agent.

Possibly, it can also to the poly-

urethane foam-forming reaction mixture, a catalyst is added. Suitable catalysts are well known in the art and include basic compounds of all types, but particularly tertiary amines. Examples of suitable tertiary amines include triethylamine, dimethylbenzylamine, dimethylphenylethylamine, tetramethyl-1:3-butanediamine, triethylenediamine, N-alkyl morpholines, N-alkylpyrrolidines and fully N-substituted 4-aminopyridines such as 4 -dimethyl-aminopyridine. Other suitable catalysts include basic and non-basic organic compounds of metals, e.g. dibutyltin dilaurate, dibutyltin diacetate, ferric acetylacetonate, manganese acetylacetonate, tin(II) carboxylates such as tin(II) octoate, and lead carboxylates such as lead acetate and lead octoate. Mixtures of catalysts are often particularly appropriate.

As fully described in the state of the art, the general methods for producing polyurethane foam can include introducing different additives such as surfactants into the polyurethane foam-forming mixture. Suitable surfactants include silicone liquids and in particular siloxane-oxyalkylene block copolymers. Oxyethylated phenols and oxyethylated fatty alcohols are examples of other surfactants that can be used. Block copolymers of ethylene and propylene oxides can also suitably be added. The polyurethane foam-forming reaction can be further modified by introducing other known additives such as foam stabilizers, e.g. ethylcellulose, colorants, fillers, plasticizers, flame retardants such as tri(|3-chloroethyl)phosphate or antimony oxide, and antioxidants such as tertiary butylcatechol.

The following examples, in which all parts and percentages are by weight, shall serve to further illustrate the invention.

Example 1

Production of sucrose-butylene oxide condensate.

A mixture of 1074 parts of sucrose, 430 parts of water and 6.75 parts of potassium hydroxide is added to an autoclave and slowly heated with stirring to 100°C. 867 parts of 1:2-butylene oxide are then added at a temperature of 100°C and a pressure of 2.1-2.8 kg/cm<2>. After the addition is complete, unreacted water and butylene glycol are removed by heating to 100°C under a pressure of 20 mm of mercury for 2'/2 hours. To the resulting intermediate is added 9 parts of potassium hydroxide in 18 parts of water, the mixture is heated at 100°C for half an hour, and the water is then removed by distillation at 100°C under 20 mm pressure. A further 1150 parts of butylene oxide are then added at 100°C and 2.1-2.8 kg/cm<2> overpressure. Remaining potassium hydroxide catalyst is neutralized by heating condensate with a sufficient excess of glacial acetic acid at 100°C for half an hour and then removing unreacted acetic acid by heating at 100°C under 20 mm pressure for half an hour. The polyether obtained has a hydroxyl value of 553 mg KOH/g and a viscosity at 25°C of 1422 poise.

Test for compatibility with trichloromonofluoromethane. 50 parts of the sucrose-butylene oxide condensate described above are mixed with successive portions of trichloromonofluoromethane, each portion being 5 parts, until a total of 100 parts of trichloromonofluoromethane have been added. The two components are easily mixed together, and a clear, homogeneous solution is obtained for all the mixing ratios used.

The experiment is repeated with 50 parts of a sucrose-propylene oxide condensate with

hydroxyl value 522 mg KOH/g. After only 20 parts of trichloromonofluoromethane have been added, a cloudy mixture is obtained, and addition of a total of 40 parts of trichloromonofluoromethane gives a heterogeneous mixture from which undissolved trichloromonofluoromethane separates as another phase on standing.

Production of foam.

To 150 parts of the sucrose-butylene oxide condensate described above are added 1.5 parts of a siloxane-oxyalkylene copolymer, commercially available under the name "Silicone 1520", 4 parts of a solution of 1 part triethylenediamine in 2 parts hexane-triol, commercially available under the name "Dabco 33", and 75 parts trichloromonofluoromethane. The whole is mixed carefully, and then 210 parts of a diphenyl-methane-diisocyanate composition obtained by phosgenation of crude diaminodiphenylmethane containing approx. 15 percent polyamines (mainly triamines) produced by condensation of aniline with formaldehyde in the presence of hydrochloric acid. The entire mixture is thoroughly stirred for 40 seconds. Expansion of the mixture is complete after another 100 seconds, and a non-brittle, rigid foam with a density of 0.034 g/cm<3 > and a fine texture is obtained.

Another foam is prepared in the same way from 150 parts of a sucrose-propylene

oxide condensate with a hydroxyl value of 522 mg KOH/g, 1.5 parts of the siloxane-oxyalkylene copolymer mentioned above, 6 parts of the triethylenediamine solution mentioned above, 75 parts of trichloromonofluoromethane and 214 parts of the diphenylmethane diisocyanate composition mentioned above. This foam has a considerably coarser texture than the foam produced from the sucrose-butylene oxide condensate, and is somewhat brittle.

Example 2

Production of sucrose-butylene oxide condensate.

A mixture of 1074 parts of sucrose, 430 parts of water and 6.75 parts of potassium hydroxide is reacted with 867 parts of 1:2-butylene oxide as described in Example 1. The resulting intermediate is then treated with 11.1 parts of potassium hydroxide and 22 parts of water as described in the previous example, and is then reacted with a further 1524 parts of butylene oxide. Remaining potassium hydroxide catalyst is neutralized with acid as before. The obtained polyether has a hydroxyl value of 485 mg KOH/g and a viscosity at 25°C of 529 poise.

Test for compatibility with trichloromonofluoromethane. 50 parts of the above-mentioned sucrose-butylene oxide condensate with a hydroxyl value of 485 mg KOH/g are mixed with successive portions of trichloromonofluoromethane as described in example 1. Completely homogeneous solutions are obtained at all mixing ratios up to 100 parts of trichloromonofluoromethane.

By repeating the experiment with 50 parts of a sucrose-propylene oxide condensate with a hydroxyl value of 479 mg KOH/g, it is possible to add up to 45 parts of trichloromonofluoromethane without the formation of cloudiness, but when 60 parts are added, a heterogeneous mixture is obtained from which undissolved trichloromonofluoromethane is separated by standing.

Production of foam.

Foam is prepared in the same way as described in example 1, from 150 parts of the sucrose-butylene oxide condensate with a hydroxyl value of 485 mg KOH/g as described above, 1.5 parts of the siloxane-oxy-alkylene copolymer as described above, 4 parts of the triethylenediamine solution as described above, 45 parts of tris-((3-chloroethyl) phosphate, 75 parts of trichloromonofluoromethane and 198 parts of the diphenylmethane diisocyanate composition as described above. The foam is fine textured and not brittle, and has a density of 0.034 g/cm3.

Another foam prepared from 150 parts of a sucrose-propylene oxide condensate

with a hydroxyl value of 479 mg KOH/g, where all other components are otherwise as described above, is somewhat brittle.

Example 3 Production of sorbitol butylene oxide condensate.

A mixture of 740 parts of sorbitol, 317 parts of water and 4.8 parts of potassium hydroxide is reacted with 676 parts of 1:2-butylene oxide in the same manner as described in Example 1. The resulting intermediate is then reacted with 9.4 parts of potassium hydroxide and 20 parts of water which described in example 1, and is then reacted with a further 1828 parts of butylene oxide. Remaining potassium hydroxide catalyst is neutralized with acetic acid as before. The obtained polyether has a hydroxyl value of 470 mg KOH/g and a viscosity at 25°C of 112

poise.

Production of foam.

Foam is prepared in the same way as in example 1 from 150 parts of the sorbitol-butylene oxide condensate described above, 1.5 parts of the siloxane-oxyalkylene copolymer described above, 6 parts of the triethylenediamine solution described above, 45 parts of tri((5-chloroethyl) phosphate, 75 parts of trichloromonofluoromethane and 201 parts of the diphenylmethane diisocyanate composition as described above.The foam had a fine texture and was not brittle and had a density of 0.032 g/cm<3>.

Claims (2)

1. Process for the production of polyurethane foam by reaction of an organic polyisocyanate with a polyether containing hydroxyl groups under such conditions that a foam-forming gas is developed, characterized in that the polyether is used as a reaction product of a polyhydric alcohol which has from 4 to 8 hydroxyl groups per molecule, and an alkylene oxide, which has from 4 to 8 carbon atoms per molecule. 2. Process for the production of polyurethane foam as stated in claim 1, characterized in that a polyether is used which has a molecular weight of from 75 to 150 units per hydroxyl group and which is a reaction product of butylene oxide and sucrose or sorbitol.