Inorganic-organic plastic - Patent Review 3981831

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It is known to produce polyurethane and polyurea plastics form organic polyisocyanates and organic compounds which contain active hydrogen atoms. The properties of this class of polymers can be widely varied. Among the properties which are particularly highly valued in these substances are their high strength, elasticity and wear resistance. However, their thermostability, and, in particular, their long term endurance of temperatures above 120.degree.C, is only moderate. Moreover, the use of these products as building and constructional elements is restricted by their unfavorable fire resistance characteristics. Although these characteristics may be improved by adding flame retarding agents, the mechanical properties are usually adversely affected thereby.

It is known to produce inorganic silica gel plastics from aqueous solutions of alkali metal silicates by the action of (potential) acids. These materials have gained importance especially in their use as putties and surface coatings. Lightweight foam plastics based on water glass have also been produced. These products have high dimensional stability when heated and are completely incombustible, but they are brittle and have relatively little strength. These foams are unable to withstand substantial loads and crumble under pressure.

It would be extremely desirable to combine the advantageous properties of inorganic and organic plastics materials and, at the same time to suppress the negative properties.

Accordingly, there has been no lack of effort to produce combination organic-inorganic plastics but the objective has so far not been achieved.

For example, in one such attempt, polyurethanes have been mixed with active silicic acid and a filler and then vulcanized. A certain reinforcing effect is observed, similar to that obtained when highly active carbon black is used, namely the tensile strength and modulus increase and the elongation at break decreases. The addition of silica, however, does not fundamentally alter the overall properties of the material, probably because the material is a two-phase system in which only the polyurethane forms a coherent phase in which the silica is merely embedded as an incoherent phase. The incoherent zones have diameters of the order of from 3 to 100.mu.. Therefore, one is dealing with relatively coarse heterogenous diphasic systems. The interaction between the two phases is only slight, both on account of the relatively small interfaces and on account of the widely differing chemical nature of the two phases.

It has also been proposed to use silicic acid in a microfibrous form. A greater reinforcing effect is thereby obtained due to the specific morphology but, on the other hand, the incoherent zones are inevitably larger so that the chemical interaction between the two phases, if anything decreases. The fundamental character of a coarse heterogeneous two-phase synthetic resin remains.

It has also been proposed to react an aqueous solution of an alkali metal silicate (water glass) with a low molecular weight polyisocyanate, e.g. 4,4'-diphenylmethane diiosocyanate. In most cases, this reaction gives rise to foams in which the water present causes the isocyanate phase to react, the resulting carbon dioxide foaming up inside the mass and some of the carbon dioxide reacting with the surrounding aqueous silicate phase, this reaction being accompanied by gelling of the interface.

This reaction is preferably carried out with the water glass in excess so that the resulting mixture is an emulsion of the isocyanate in a coherent silicate solution. Therefore, the resulting foam has the character of a silicate foam which contains incoherent, foamed polyurea zones. The properties of such a foam do not differ substantially from those of a pure silicate foam. In fact, the foams obtained in this way are brittle and are only able to withstand slight mechanical loads.

Similar effects are also obtained with other isocyanates, e.g. cyclohexylisocyanate, phenylisocyanate, hexamethylene diisocyanate, diphenylmethane-2,4-diisocyanate, tolylene diisocyanate and also adducts of these isocyanates with low molecular weight glycols, e.g. ethylene glycol, propylene glycol, butane-1,4-diol, hexane-1,6-diol, neopentyl glycol, glycerol and trimethylolpropane. Although the organic isocyanate group containing component which is added to the silicate solution acts as a hardener, it has little influence on he properties of the resulting foam and frequently even has an adverse effect. The organic component obviously exists mainly as a filler in the finished silicate structure.

Alternatively, if an excess of diisocyante is used, the polyurea foams obtained have an incoherent silicate phase dispersed therein. Therefore, the properties are mainly those of a polyurea foam filled with silica, so that the products are highly combustible and extremely brittle.

If one proceeds in accordance with this teaching, (DOS No. 1,770,384), it is observed that mixtures of aqueous sodium silicate solutions and diphenylmethane diisocyanate form only relatively coarse emulsions. This disadvantage may, however, be greatly reduced by the recommended addition of emulsifiers or foam stabilizers which enable more finely divided and more stable primary emulsions to be obtained.

Nevertheless, the overall properties are unsatisfactory and in particular the combination plastics obtained are very brittle and have little strength. From previous results it must be concluded that combination plastics based on silicates and organic materials have no decisive advantages over purely organic or purely inorganic materials.

It is an object of this invention to provide a process for making substantially homogeneous inorganic-organic plastics having properties which are an improvement over either wholly organic or wholly inorganic plastics. Another object of this invention is to provide an organic-inorganic plastic having high strength, elasticity, dimensional stability when heated and good flame resistance.

The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a process for making inorganic-organic plastics wherein an organic polyisocyanate, an aqueous solution of an alkali metal silicate or aqueous silica sol and an organic amphiphilous compound having 1 to 9 carbon atoms, a molecular weight of 32 to about 400, and containing a hydroxyl group or at least one other hydrophilic or polar group are mixed together to form a sol which reacts to form a xerosol.

A process has now been found which enables macroscopically completely homogeneous inorganic-organic plastics to be obtained which constitute solid/solid xerosols similar to the known ABS plastics. The novel composite materials obtained in this way are extremely high quality plastics whose properties show improvements over wholly organic as well as wholly inorganic materials. In particular, they are distinguished by their high strength, elasticity, dimensional stability when heated and flame resistance.

It has now surprisingly been found that inorganic-organic plastics characterized by high strength, elasticity, dimensional stability to heat and flame resistance are obtained when organic polyisocyanates are substantially uniformly mixed with aqueous solutions of alkali metal silicates and/or aqueous silica sols in the presence of at least one special organic amphiphilous compound which contains from 1 to 9 carbon atoms, the resulting sol being left to react to form a xerosol. These compounds have the character of additives or carriers but are not emulsifiers, protective colloids or surface active agents.

The addition according to the invention of amphiphilous low molecular weight compounds has a desirable influence on the colloid chemical character of the primary emulsion formed by mixing the reactants and substantially improves the properties of the inorganic/organic plastics obtained as end-product.

In particular, the additive component according to the invention has the effect of increasing the phase interface and improves the foaming properties as well as resulting in products which have a higher compression strength and a better cell structure.

In many cases, sufficient foaming for technical purposes is not obtained without the addition of these amphiphilous compounds. These effects are extremely surprising in view of the fact that the compounds used are not surface active agents in the usual sense, in other words they are neither emulsifiers nor wetting agents. As is well known, wetting agents contain hydrophobic C.sub.10 -C.sub.30, and in particular C.sub.12 -C.sub.18, chains and by virtue of this property they form mycellae in an aqueous medium.

It has already been proposed to add substances of this type, e.g. commercial emulsifiers, to combinations of isocyanates and water glass.

The addition of emulsifiers, e.g. in the form of alkyl-aryl sulphonates, in fact also results in an increase in the interface area and hence, for example, an increase in the reaction velocity.

In addition to the desired effect, however, these emulsifiers produce numerous disadvantages, especially if added in larger amounts:

1. they favor the formation of oil-in-water (O/W) emulsions instead of water-in-oil (W/O) emulsions which have much more suitable properties;

2. they impair the quality of the cell structure;

3. they have a marked deleterious effect on the mechanical properties and in particular on the compression strength.

The conventional emulsifiers appear to reduce the interaction between organic and inorganic phases due to concentration at the interface.

On the contrary, short chain amphiphilous compounds used according to this invention rather tend to reinforce this interaction.

An exact explanation for this surprising effect has not yet been found but is is assumed that a type of carrier effect takes place rather as in the case of lyotropic substances. The products which are preferably added to the isocyanate component may be solubilized therein with the hydrophobic radical while hydrophilic molecular portions enable the interaction with the aqueous phase to take place. The effect therefore corresponds, more or less, to a modification of the non-polar polyisocyanate with hydrophilic or polar groups. Compared with a modification in the normal sense, however, the difference resides in the fact that, in the present case, the "modification" comes about as a solubilizing action by way of side valencies.

No chemical reaction need take place between the amphiphilous additive and the polyisocyanate in order that the above-described effects may occur.

If a reaction with isocyanate is possible, e.g. in the case of alcohols, carboxylic acids or sulphonic acids, the additive is advantageously added only shortly before the two main components are mixed or, alternatively, it may first be mixed with the silicate component. This ensures that most of the amphiphilous component added is in its free form at the time when mixing is carried out.

The possibility of a certain activity in the form of the modified isocyanate even after the reaction with the isocyanate cannot be excluded but since the hydrophilic character of the urethane group is considerably weaker than that of the hydroxyl group and, moreover, the functionality of the isocyanate is reduced in a chemical reaction, such a reaction should be excluded as far as possible in the present process, and this may easily be achieved by the procedural measures indicated above.

It is particularly advantageous to use the amphiphilous compounds according to the invention in combination with very small quantities of conventional emulsifiers. By means of such combinations, it is possible to utilize the effect which emulsifiers have of increasing the area of the interface without the above-mentioned disadvantages of emulsifiers having any effect.

The process is particularly easy to carry out with prepolymers which contain isocyanate end groups, these prepolymers being preferably from organic polyisocyanates.

The organic amphiphilous compounds used according to the invention enable such a homogeneous distribution of the organic and aqueous inorganic phase to be achieved that sols in which the disperse phase has particle dimensions of from 20 nm to 20.mu. and preferably from 50 nm to 1.mu. are obtained, so that the chemical interactions increase by orders of magnitude and new types of composite materials are obtained. In particular, the addition of the amphiphilous organic compound according to the invention also enables a colloidal fibrous structure to be produced so that the two phases may exist as coherent systems. This means that a macroscopically homogeneous and, in many cases, even a microscopically homogeneous, composite material is obtained which combines the advantages of both inorganic and organic plastics.

This invention therefore, provides a process for producing inorganic-organic plastics which are characterized by high strength, elasticity, dimensional stability and flame resistance, and which consist of a polyurea- polysilicic acid composite material existing as a colloidal xerosol, by mixing:

a. an organic, preferably aromatic polyisocyanate or polyisothiocyanate;

b. an aqueous silicate solution and/or an aqueous silica sol; and

c. an organic additive;

and, optionally, also other auxiliary agents and additives, and leaving the resulting system to react, characterized in that the organic additive (c) is an amphiphilous compound which contains from 1 to 9 carbon atoms, has a molecular weight of from 32 to 400 and contains one OH group or at least one other hydrophilic and/or polar group.

The proportion, by weight, of component (a) to component (b) is preferably from 70:30 to 20:80, and the quantity of component (c) is from 1 to 30 percent, by weight, preferably from 2 to 20 percent, by weight, based on component (a).

In the process according to the invention, therefore, novel plastics are produced from at least three components:

1. an organic polyisocyanate;

2. an aqueous alkali metal silicate solution and/or a silica sol; and

3. one of the above-mentioned organic amphiphilous compounds containing 1 to 9 carbon atoms.

Component (a)

a. Any suitable organic polyisocyanate may be used according to the invention including aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates such as those described e.g. by W. Siefken in Justus Liebigs Annalen der Chemie, 562 pages 75 to 136, for example, ethylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, (U.S. Pat. No. 3,401,190), hexahydrotolylene-2,4- and -2,6-diisocyanate and any mixtures of these isomers, hexahydrophenylene-1,3- and/or 1,4-diisocyanate, perhydrodiphenylmethane-2,4'- and/or 4,4'-diisocyanate, phenylene-1,3 and -1,4-diisocyanate, tolylene-2,4- and 2,6-diisocyanate and any mixtures of these isomers, diphenylmethane-2,4'- and/or 4,4'-diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate, polyphenyl-polymethylene polyisocyanates of the kind which may be obtained by anilineformaldehyde condensation followed by phosgenation and which have been described e.g. in British Pat. Specification No. 874,430 and 848,671, perchlorinated arylpolyisocyanates such as those described e.g. in German Auslegeschrift No. 1,157,601 polyisocyanates which contain carbodiimide groups as described in German Pat. No. 1,092,007, the diisocyanates described in U.S. Pat. No. 3,492,330, polyisocyanates which contain allophanate groups as described e.g. in British Pat. No. 994,890, in Belgian Pat. No. 761,626 and in published Dutch patent application No. 7,102,524, polyisocyanates which contain isocyanurate groups as described e.g. in German Pat. Nos. 1,022,789 and 1,027,394 and in Britsh Pat. Nos. 1,091,949, 1,267,011 and 1,305,036, polyisocyanates which contain urethane groups as described e.g. in Belgian Pat. No. 752,261 or in U.S. Pat. No. 3,394,164 polyisocyanates which contain acylated urea groups according to U.S. Pat. No. 3,517,139, polyisocyanates which contain biuret groups as described e.g. in German Pat. No. 1,101,394, in British Pat. No. 889,050 and in French Pat. No. 7,017,514 polyisocyanates prepared by telomerization reactions as described e.g. in Belgian Pat. No. 723,640, polyisocyanates which contain ester groups such as those mentioned e.g. in British Pat. Nos. 956,474 and 1,086,404 and in U.S. Pat. Nos. 3,281,378 and 3,567,763 and reaction products of the above-mentioned isocyanates with acetals according to German Pat. No. 1,072,385.

The distillation residues which are obtained from the commercial production of isocyanates and still contain isocyanate groups may also be used, optionally dissolved in one or more of the above-mentioned polyisocyanates. Mixtures of the above-mentioned polyisocyanates may also be used.

It is generally preferred to use commercially readily available polyisocyanates, e.g. tolylene-2,4- and -2,6-diisocyanate and any mixtures of these isomers, ("TDI"), polyphenyl-polymethylene-isocyanates obtained by aniline-formaldehyde condensation followed by phosgenation, ("crude MDI"), and polyisocyanates which contain carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups, imide groups or biuret groups, ("modified polyisocyanates").

If the amount of component (c) added is not sufficient for the required extremely finely divided emulsions, especially if quantities below 1%, by weight, based on the total solids content, are used, one may, of course, add organic polyisocyanates which are modified with ionic groups, for example, with carboxyl and/or carboxylate groups and/or sulphonic acid groups and/or sulphonate groups. A certain proportion of non-ionic hydrophilically modified organic polyisocyanates may, of course, also be included.

Reaction products of from 50 to 99 mols of aromatic diisocyanates with from 1 to 50 mol of conventional organic compounds with a molecular weight of, generally, from about 400 to about 10,000 which contain at least two hydrogen atoms capable of reacting with isocyanates may also be used. While compounds which contain amino groups, thiol groups or carboxyl groups may be used, it is preferred to use organic polyhydroxyl compounds, in particular compounds which contain from 2 to 8 hydroxyl groups, especially those with a molecular weight of from about 800 to about 10,000 and preferably from about 1,000 to about 6,000, e.g. polyesters, polyethers, polythioethers, polyacetals, polycarbonates or polyester amides containing at least 2, generally from 2 to 8 but preferably from 2 to 4 hydroxyl groups, of the kind known for producing homogeneous and cellular polyurethanes.

The hydroxyl group-containing polyesters may be, for example, reaction products of polyhydric alcohols, preferably dihydric alcohols, with the optional addition of trihydric alcohols, and polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or their mixtures may be used for preparing the polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may be substituted, e.g. with halogen atoms, and may be unsaturated. Examples include: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, endomethylene tetrahydropthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids such as oleic acid, optionally mixed with monomeric fatty acids, dimethylterephthalate and bis-glycol terephthalate. Any suitable polyhydric alcohol may be used such as, for example, ethylene glycol, propylene-1,2- and -1,3-glycol, butylene-1,4 - and -2,3-glycol, hexane-1,6-diol, octane1,8-diol, neopentyl glycol, cyclohexanedimethanol-(1,4-bis-hydroxymethylcyclohexane), 2-methyl-propane-1,3-diol, glycerol, trimethylol propane, hexane-1,2,6-triol, butane-1,2,4-triol, trimethylol ethane, pentaerythritol, quinitol, mannitol and sorbitol, methylglycoside, diethylene glycol, triethylene glycol, tetraethyleneglycol, polyethyleneglycols, dipropyleneglycol, polypropylene glycols, dibutylene glycol and polybutylene glycols. The polyesters may also contain a proportion of carboxyl end groups. Polyesters of lactones, such as .epsilon.-caprolactone, or hydroxycarboxylic acids, such as .omega.-hydroxy-caproic acid, may also be used.

The polyethers with at least 2, generally from 2 to 8 and preferably 2 or 3 hydroxyl groups used according to the invention are known and may be prepared e.g. by the polymerization of epoxides, e.g. ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin, each with itself, e.g. in the presence of BF.sub.3, or by addition of these epoxides, optionally as mixtures or successively, to starting components which contain reactive hydrogen atoms such as alcohols or amines, e.g. water, ethylene glycol, propylene-1,3- or -1,2-glycol, triemthylolpropane, 4,4'-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine or ethylenediamine. Sucrose polyethers such as those described e.g. in German Auslegeschriften Nos. 1,176,358 and 1,064,938 may also be used according to the invention. It is frequently preferred to use polyethers which contain predominantly primary OH groups, (up to 90% by weight, based on the total OH group content of the polyether). Polyethers modified with vinyl polymers such as those which may be obtained by polymerizing styrene or acrylonitrile in the presence of polyethers, (U.S. Pat. Nos. 3,383,351; 3,304,273; 3,523,093 and 3,110,695 and German Pat. No. 1,152,536), and polybutadienes which contain OH groups are also suitable.

By "polythioethers" are meant, in particular, the condensation products of thiodiglycol with itself and/or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols. The products obtained are polythio-mixed ethers, polythioether esters or polythioether ester amides, depending on the cocomponent.

The polyacetals used may be, for example, the compounds which may be obtained from glycols, e.g. diethylene glycol, triethylene glycol, 4,4'-dihydroxy-diphenyldimethylmethane, hexanediol, and formaldehyde. Polyacetals suitable for the invention may also be prepared by the polymerization of cyclic acetals.

The polycarbonates with hydroxyl groups used may be of the known kind, e.g. those which may be prepared by reacting diols, e.g. propane-1,3-diol, butane-1,4-diol and/or hexane- 1,6-diol or diethyleneglycol, triethylene glycol or tetraethylene glycol, with diarylcarbonates, e.g. diphenylcarbonate or phosgene.

The polyester amides and polyamides include, e.g. the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, diamines, polyamines and mixtures thereof.

Polyhydroxyl compounds which already contain urethane or urea groups, modified or unmodified natural polyols, e.g. castor oil, carbohydrates and starches, may also be used. Addition products of alkylene oxides with phenolformaldehyde resins or with urea-formaldehyde resins are also suitable for the purpose of the invention.

Examples of these compounds which are to be used according to the invention have been described e.g. in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", published by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32 to 42 and pages 44 to 54 and Volume II, 1964, pages 5 to 6 and 198 to 199 and in Kunststoff-Handbuch, Volume VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Munich, 1966, e.g. on pages 45 to 71.

If the polyisocyanate or the prepolymer which contains NCO groups has a viscosity above 2000 cP at 25.degree.C, it may be advantageous to reduce the viscosity thereof by mixing it with:

1. the organic amphiphilous compound to be used according to the invention;

2. a low viscosity organic polyisocyanate; and/or

3. an inert blowing agent or solvent.

Component (b)

By "aqueous solutions of alkali metal silicates" are meant the solutions of sodium and/or potassium silicate in water which are normally known as "water glass". Crude commerical solutions which may in addition contain other substances, e.g. calcium silicate, magnesium silicate, borates or aluminates, may also be used. The molar ratio of Me.sub.2 O/SiO.sub.2 (Me = metal) is not critical and may vary within the usual limits but is preferably between 4 to 1 and 0.2 to 1. If the water content of the plastics first obtained by the reaction with organic components is of minor importance, either because it has no disturbing effect or because it may easily be removed by drying, then neutral sodium silicates may well be used, which may be prepared from 25% to 35%, by weight, solutions. It is preferred, however, to use from 20% to 54%, by weight silicate solutions and these cannot be obtained at a viscosity below 500 poises which is necessary for trouble-free working unless they are sufficiently alkaline. Ammonium silicate solutions may also be used but they are less advantageous. The solutions may be true solutions or colloidal solutions.

The choice of concentration depends mainly on the desired end-product. Compact materials or materials with closed cells are preferably prepared with concentrated silicate solutions which may, if necessary, be adjusted to a low viscosity by the addition of alkali metal hydroxide. Solutions with concentrations of from 40% to 70%, by weight, may be prepared in this way. On the other hand, for producing open-celled, lightweight foams it is preferred to use silicate solutions with concentrations of from 20% to 54%, by weight, in order to obtain low viscosities, sufficiently long reaction times and low unit weights. When finely divided inorganic fillers are used in substantial quantities, it is also preferred to use silicate solutions with concentrations of from 20% to 54%.

Component (c)

According to the invention component (c) consists of organic amphiphilous compounds containing from 1 to 9 carbon atoms and having a molecular weight of from 32 to about 400, preferably from 32 to 150, which contain one OH group and/or at least one other hydrophilic and/or polar group. This other hydrophilic and/or polar group is preferably a functional group corresponding to one of following general formulae; --SH, --CH.sub.2 Cl, --CH.sub.2 --Cl, --CH.sub.2 Br, --CH.sub.2 I, --CN, --NO.sub.2, --COCl, --COBr, --SO.sub.2 Cl, --COOH, --SO.sub.3 H, --COO.sup.-, --SO.sub.3 .sup.-, --OR, ##EQU1## wherein R denotes a methyl or ethyl group.

Component (c) may contain an OH group and/or from 1 to 6, preferably 1 or 2 of these other groups.

The following are examples of component (c):

1. Alcohols, thioalcohols, phenols and thiophenols:

methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butyl alcohol and the isomeric pentanols, hexanols and heptanols, cyclohexanol, methylcyclohexanol, benzyl alcohol, cyclohexano-methanol, methallylalcohol, butylmercaptan, phenols, e.g. phenol and the cresols, thiophenols and thiocresols. Alcohols with from 1 to 4 carbon atoms are preferred, particularly methanol.

2. Halomethyl compounds:

ethyl chloride, ethyl bromide, ethyl iodide, n-propyl chloride, n-propylbromide, n-propyliodide, isopropyl chloride, isopropyl bromide, isopropyl iodide, butyl chloride, butyl bromide, butyl iodide, C.sub.3 -C.sub.6 -halogenated methyl compounds, benzyl halides, e.g. benzyl chloride or benzyl bromide, hexahydrobenzylhalides, e.g. cyclohexanomethyl chloride, epichlorohydrin, 2-ethyl-2-chloromethyl-oxetane and 2-ethyl-2-chloro-methyloxetane.

Halogenated methyl compounds which contain from 4 to 7 carbon atoms are particularly preferred.

3. Nitriles:

acetonitrile, propionitrile, butyronitrile, benzonitrile, tolunitrile, hexahydrobenzonitrile, acrylonitrile, allylnitrile, methallylnitrile, methacrylonitrile.

4. Esters:

methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, the methyl and ethyl esters of propionic, butyric, pentanoic, hexanoic and heptanoic acid and the corresponding isomeric compounds, for example isobutyric acid, and 2,4,6-tribromophenylacetate.

5. Ethers and Thioethers:

methyl ethyl ether, cyclohexyl methyl ether, methyl butyl ether, phenol methyl ether, thiophenol methyl ether, cresol methyl ether, tetrahydrofuranomethyl-methyl ether.

6. Ketones:

methyl ethyl ketone, methyl-isopropyl ketone, methyl-isobutyl ketone, methyl-isoamyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl-t-butyl ketone, methyl-furanyl ketone, methyl-tetrahydrofuranyl ketone, methyl-heptyl ketone, ethylhexyl ketone, acetophenone, .omega.-chloroacetophenone and propiophenone.

7. Nitro compounds: nitromethane, nitroethane, nitrohexane, nitrobenzene, chlorinated nitrobenzenes, nitrocyclohexane, brominated nitrobenzenes, benzyl nitrate and nitrotoluene.

8. Carboxylic acid chlorides, carboxylic acid bromides, sulphonic acid chlorides:

acetyl chloride, propionic acid chloride, acetyl bromide, acid chlorides of C.sub.4 -C.sub.6 carboxylic acids, but also methanesulphonic acid chloride, benzenesulphonic acid chloride, p-toluenesulphochloride, o-toluenesulphochloride, carbamic acid chlorides, e.g. t-butyl carbamic chloride, and phenylcarbamic chloride.

9. Carboxylic acids:

formic acid, acetic acid propionic acid, butyric acid, isobutyric acid, pentanoic acid, hexane carboxylic acid, heptane carboxylic acid, cyclohexane carboxylic acid, benzoic acid, toluic acid.

10. Sulphonic acids:

methanesulphonic acid, ethanesulphonic acid, butanesulphonic acid benzenesulphonic acid, 2-toluenesulphonic acid, 4-toluenesulphonic acid, chlorosulphonic acid esters and sulphonic acid esters e.g. methanesulphonic acid methyl ester, methane sulphonic acid ethyl ester and chlorosulphonic acid methyl ester.

The carboxylic acids and/or sulphonic acids may be partially or completely neutralized, for example with alkali metal and alkaline earth metal hydroxides, e.g. sodium hydroxide, potassium hydroxide, barium hydroxide, or magnesium hydroxide, or by the addition of amines, e.g. trimethylamine, triethylamine, methylmorpholine, pyridine, dimethylaniline, or metal alcoholates e.g. sodium t-butanolate, or potassium isopropanolate. Metal oxides, hydroxides or carbonates, either in the solid form or suspended in diluents, may also be used for neutralization. Calcium oxide, magnesium oxide, calcium carbonate, magnesium carbonate and dolomite, for example, are particularly suitable.

Non-volatile higher molecular weight tertiary amines are also particularly useful in this neutralization because they do not evaporate in the subsequent reaction with the alkali metal silicate solution. Amines of this type are, in particular, the alkoxylation products of primary or secondary amines, and also polyesters or polyacrylates which contain tertiary nitrogen atoms as well as the known condensation products based on epichlorohydrin and polyamines of the kind used, for example, for wet strengthening paper. Polycondensation products of weakly basic or sterically hindered amines are preferred because an excessively high increase in viscosity may otherwise occur when using polyamines.

11. Aldehydes:

formaldehyde, acetaldehyde, propionaldehyde, butyl aldehyde, pentanals, hexanals, heptanals, octanals and their simple substitution products, semi-acetals and full acetals.

12. Components (c) according to this invention may also comprise compounds which contain phosphorus, for example trimethyl phosphite, trimethylphosphate, triethylphosphite, triethyl phosphate, diethylphosphite, diethylphosphate, dimethylphosphite, dimethylphosphate, thiophosphoric acid-O,O-dimethyl ester, thiophosphoric acid trimethylester, or thiophosphoric acid-O,O-dimethyl ester chloride.

The preparation of the inorganic-organic plastics according to this invention is simple to carry out. Basically, all that is necessary is to mix the three starting components homogeneously. The mixture then, in most cases, hardens at once. The mixtures are typical finely divided emulsions or sols. They are not optically clear but usually opaque or milky-white. The subsequent xerosol appears to be preformed in them.

Two of the three components (a), (b) and (c) may be premixed, optionally with heating, or all three components may be mixed together, optionally with heating.

Component (c) is preferably premixed with component (a). Alcohols, phenols, carboxylic acids and sulphonic acids are preferably added to a mixture of all the other components or premixed with component (b).

The mixture of the three components is not stable. The so-called "pot life" during which the mixtures are in a workable state depends mainly on the chemical nature of the organic components of the syst