US2486459A - Urea-formaldehyde condensates having detergent properties - Google Patents

Description

Patenied Nov. 1, 1949 UREA-FORMALDEHYDE CONDENSATES HAVING DETERGENT PROPERTIES Louis B. Bock, Huntingdon Valley, and James L. Ralney, Abington, Pa., assignors to ltiihm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application January 25, 1946,, Serial No. 643,482

This invention relates to surface-active or capillary-active agents. It relates to the preparation of materials which have high detergent action under a wide variety of conditions. More specifically, it relates to the preparation and use of polymeric, water-soluble detergents which have high molecular weights and contain within each molecule a multiplicity of hydrophobic and hydrophilic groups or portions so arranged and balanced as to become oriented at an interface.

It is generally recognized that surface-active agents, as, for example, alkali-metal soaps or quaternary ammonium compounds, exist in water in the form of micelles. While the exact nature of such micelles is not established. there is evidence that they are electrically charged aggregates of molecules. For example, when a sodium soap of a fatty acid is dispersed in water, it dissociates into positively charged sodium ions and into negative ions. Some of the latter apparently form aggregates with soap molecules and, as a result, negatively charged micelles are produced.

' Because the micelles carry a negative charge, this type of soap is known as an anion-active detergent. In contrast, detergents of the type of quaternary ammonium compounds ield positively charged micelles in aqueous solution and, hence, are known as cation-active soaps or agents. This conception of the formation of micelles is based on measurements of freezing points, vapor pressures, and electrical conductivities of aqueous dispersions of surface-active agents. It is further 7 Claims. (Cl. 260-70) recognized that surface activity is related to the formation of such micelles and to the orientation of the micelles at an interface.

The individual molecules in colloidal micelles are held together only by physical forces or by weak secondary valences; and, as a result, the extent of micelle formation depends upon the prevailing conditions, and it is affected by such factors as the concentration of the surface-active agent, the presence of electrolytes, solvents, and other surface-active agents, and also upon the temperature. Thus, dilution of the solution, elevation of the temperature, or a change in the amount of any salts which may also be present in solution favor the reversion of micelles into simple molecules and/or ions with the formation of true solutions. As an example, synthetic detergents known heretofore have no value at very low concentrations or in very hot water because under these conditions the micellar structure reverts, the molecules then exist in true solution, and, as a result, detergency is lost. The necessity of using relatively high concentrations plus the higher cost of synthetic detergents combines to make the use of such detergents uneconomical and often impractical. Furthermore, the materials are inefiective in marry laundering operations wherein extremel hot water is used in order to accelerate the removal of soil.

The products of this invention difler from and have advantages over-detergents known heretofore in that their effectiveness is not dependent upon the formation of loosely bound micelles. By the process of this invention, watersoluble macromolecules are synthesized in which all of the bonds between atoms are primary valence links and, hence, are strong and are not affected by such factors as concentration and temperature. Furthermore, the synthetized macromolecules contain balanced hydrophilic and hydrophobic group so positioned in the macromolecule that orientation can and does occur readily at an interface.

The products of this invention are water-soluble, surface-active, polymeric detergents comprising sulfonated condensates of urea, formaldehyde, and an aliphatic alcohol containing from six to eighteen carbon atoms. They may be made by a series of well-deflned steps. First, a condensate of urea, formaldehyde, and an aliphatic alcohol of six to eighteen carbon atoms is prepared. It is commonly believed that durin this condensation methylol derivatives of the urea, are first formed and that, subsequently, polymerization occurs with the splitting out of some formaldehyde and the formation ofmacromolecules containing urea units or residues joined by methylene bridges. Simultaneously, some of the methylol groups are etherifled by the alcohol with the result that the macromolecules contain some N-methylene alkyl ether groups which may be represented as CH2-OR, in which R is an alkyl group of six to eighteen carbon atoms obtained from the alcohol. Such CH2-0- R groups impart hydrophobic properties to the macromolecules. Some of the methylol groups of the macromolecules are then sulfonated by means of a water-soluble salt of sulfurous acid. As a. result, N-methylene sulfonate groups are formed in the macromolecule. These may be represented as -CH2-SO3M, in which M is one equivalent of a metal, such as sodium, Whose sulfurous acid salt it water-soluble. Such sulfonate groups impart hydrophilic properties to the macromolecules.

The resultant products may be considered to have three functional portions. Thus, they contain (1) as the hydrophobic portion, the

group in which R is the hydrocarbon group of six to eighteen carbon atoms from the alcohol, (2) as the hydrophilic portion, the methylene sulfonate groups, CH2SO3M, and (3) as the polymeric portion, th urea units or residues joined by methylene bridges. The number and size or the other groups and the number or sul- 3 fonate groups are so balanced as to assure solubility in water and also orientation of the macromolecules at an interface. At the same time, the polymeric nature of the product provides such a high molecular weight that the product is in fact a macromolecule which imparts capillaryor surface-activity to a solution, as do micelles of ordinary soaps, but which is stable and is not dissociated as are the micelles of customary detergents under severe conditions frequently encountered in actual use.

The above discussion is for purposes of theoretical explanation only, and it must be understood that the so-called three portions of the macromolecule are not independent of one another but are all combined in onelarge molecule which functions as a concerted whole.

Although the polymeric detergents of greatest interest are those prepared from urea, it is to be understood that some of the urea may be replaced by other compounds known to react with formaldehyde in a manner similar to urea, such as thiourea, guanidine, melamine, and monosubstituted acyl-, alkyl-, and aralkyl-ureas.

Formaldehyde may be used in the form of an aqueous solution, such as Formalin, or in its polymeric forms, e. g. paraformaldehyde, or, at least in part, in a form such as hexamethylene tetramine or formals which yield formaldehyde under the conditions of the reaction. Other aldehydes,

such as acetaldehyde, benzaldehyde, and fufuraldehyde, may be used in minor amounts in conjunction with the formaldehyde.

The suitable aliphatic alcohols which are employed may be straight-chained, branch-chained, or alicyclic, as typified by cyclohexanol, n-hexyl alcohol, Z-ethyl butanol, heptanol-2, 2-ethylhexanol, capryl alcohol, 5-ethylnonanol-2, 7- ethyl 2 methylundecanol-i, octadecanol, and isomers of these. In all cases, however, they must contain a minimum of six and a maximum of eighteen carbon atoms. Alcohols having fewer than six carbon atoms do not impart sumclent hydrophobic properties to the compounds made therewith and, as a result, such compounds do not orient at an interface or have detergent properties. Not only must the alcohols contain at least six carbon atoms, but it is, in fact, preferred that they contain at least eight carbon atoms. On the other hand, alcohols containing more than eighteen carbon atoms impart such hydrophobic characteristics that the products made therewith are not water-soluble and are, therefore, of no value as detergents.

The metal salts of sulfurous acid employed in accordance herewith include bisulfites per se, sulfltes which yield bisulfites under the conditions of the detergent-forming reaction, and mixtures of such sulfltes and bisulfltes. While bisulfites form sulfonate groups in the reaction directly, sulfites of particular utility are those which yield sulfonate groups indirectly, for example, by hydrolysis to the bisulflte, exemplified as follows:

Since, in the reaction which results in the new detergents, bisulfltes are immediately used up as they are added or formed, the reaction exemplifled above goes to the right.

The alkali metal salts of sulfurous acid are preferred in most instances. From the standpoint of cost and availability, sodium salts, especially sodium metabisulfite of commerce, are particularly useful. It is essential that the metal salt of sulfurous acid be soluble in water, and it is further essential that the polymeric detergent made therefrom be water-soluble also. While alkali metal salts of sulfurous acid can be used in the process of this invention, sulfurous acid itself and the ammonium salts thereof cannot be used. The acid merely accelerates the condensation of the urea and formaldehyde and causes the condensate to gel and become insoluble without any sulfonation having taken place. As is well known, ammonium salts react with formaldehyde and thereupon liberate sulfurous acid, which acts in the objectionable manner described.

The use of a bisuliite per se results in a lower pH than does the use of a sulflte per se. When polymerization of the urea-aldehyde-alcohol condensate tends to proceed rapidly together with the sulfonation reaction, it is often desirable to employ sultltes, at least in part, in order to take advantage of their higher pH and their retarding action on the rate of polymerization. In other cases where simultaneous polymerization and sulfonation is desired, it is preferred to use the bisuliites, since they impart a lower pH which accelerates polymerization.

The ratios of the urea. aldehyde, alcohol, and salt of sulfurous acid employed are very important. Each reagent, as well as the amount thereof used, contributes to the final properties of the product.

For example, the ratio of aldehyde to urea is critical, because the aldehyde provides the connecting links between the urea units and also forms alkylol groups on the urea nucleus which are etherified by the alcohol and sulfonated by the salt of sulfurous acid. A ratio of 1.75 to 3.0 mols of aldehyde per mol of urea may be used. A preferred ratio, however, is 1.9 to 2.2 mols of aldehyde per mol of urea.

The amount of aliphatic alcohol containing six to eighteen carbon atoms which reacts should be between about 0.3 and 1.0 mol per mol of urea. The theoretical maximum amount of 1.0 is rarely employed, and a ratio of about 0.4 to about 0.8 mol per mol of urea is much preferred. In many instances, an excess of alcohol is employed in the reaction mixture with the urea and aldehyde, but all of it does not react. The limits given above are for reacted alcohol, and it-is understood that each macromolecule must contain at least one CHa-OR group in which R represents an alkyl group obtained from the alcohol of six to eighteen and, preferably, eight to eighteen carbon atoms. a

As in the case of the aliphatic alcohol, the maximum amount of sulflte salt which can theoretically be reacted in the preparation of the polymeric detergents is one mol per mol of urea. This amount, however, cannot be used in practice and smaller amounts, up to a ratio of 0.5 mol per mol of urea, are employed. A ratio of 0.15 mol of sulfite is the operable minimum, and ratios from about 0.25 to about 0.5 mol are much preferred. The optimal ratio will depend to some extent upon the degree of polymerization of the urea-formaldehyde condensate and to an even greater extent upon the number of carbon atoms in the aliphatic alcohol which is used in the etherification. Higher ratios of sulflte are required as the number of carbon atoms in the alcohol increases from six to eighteen. It is essential that suflicient sulfite salt be reacted with the urea-formaldehyde-alcohol condensate to impart water solubility and that each macromolecule of the surface-active agent contain at least one sulfonate group.

It is essential, furthermore, that the product be polymeric. In order to have detergent properties, the compounds must contain at least three urea units or residues joined by methylene bridges. Actually, it is preferred that the compounds be more highly condensed and thus contain more than three such urea units in each macromolecule. In general, the detergent properties of the compounds as measured by whiteness-retention in laundering tests increases as the degree of condensation increases. The maximum degree of condensation, or the maximum average number of urea units in the macromolecules, is limited only by the requirement that the -flnal product be soluble in water.

The polymeric detergents of this invention are readily prepared by a variety of procedures. In the preferred method, a condensate of the urea, the aldehyde, and a lower aliphatic alcohol, such as ethanol, propanol, or butanol, is prepared in the customary way, usually at or near refluxing temperature and a pH of 4.0 to8.0. This condensate is then heated together with a higher alcohol. Transetherification takes place, and the alkyl group of the lower alcohol is replaced by the alkyl group of the higher alcohol. This method is particularly desirable when alcohols having eight or more carbon atoms are used. In the case of the alcohols of six and seven carbon atoms, it is often more convenient to react them directly with the urea and aldehyde and thus avoid the transetherification step. To the urea-aldehyde-alcohol condensate is added a water-soluble salt of sulfurous acid, preferably in the form of an aqueous solution. Sulfonation of the condensate takes place and is carried at least to the point where the product is watersoluble.

During the sulfonation reaction, the ureaaldehyde-alcohol condensate may continue to condense. As a result, there are two reactions occuring simultaneously: one, polymerization, and the other, sulfonation; and care may be required to prevent the polymerization reaction from proceeding too rapidly. This can be done by lowering the temperature or, preferably, by raising the pH.

The products of this invention may be described as water-soluble polymeric materials comprising a condensate of (a) urea, (b) formaldehyde, and (c) a saturated, aliphatic alcohol containing from six to eighteen carbon atoms, said condensate containing an average of at least three, and preferably at least seven, urea units joined by methylene bridges and each molecule of said condensate containing at least one sulfonate group and at least one -CH2OR group in which R represents an alkyl group of six to eighteen carbon atoms obtained from said alcohol, the number of said sulfonate and CH2OR groups being so balanced that orientation of said condensates in aqueous solution takes place at an interface. Or they may be described as water-soluble, surface-active polymeric detergents comprising a sulfonated condensate of urea, formaldehyde, and an aliphatic alcohol of six to eighteen carbon atoms and being the product of condensing (a) urea with (b) formaldehyde in an amount from about 1.75 to about 3.0 mols per mol of urea and (c) said alcohol in an amount from about 0.4 to about 0.8 mol per mol of urea, and sulfonating said condensate with a water-soluble salt, preferably an alkali metal salt, of sulfurous acid in an amount from 0.15 to about 0.5 mol per mol of urea, and each molecule of said condensate containing at least three urea units or residues joined by methylene bridges.

The preparation of these detergents may be readily understood from a consideration of the following illustrative examples.

Example 1 (a) A condensate of urea, formaldehyde, and capryl alcohol was made as follows: Into a threenecked vessel, equipped with thermometer, agitator, and reflux condenser fitted with a water separator containing a mixture of equal quantities of butanol and xylol, were charged (a) 22 mols of formaldehyde in the form of a 37% aqueous solution having a pH of 7.2-8.0, (b) 20 mols of butanol, (c) 10 mols of urea, and (d) 180 grams of xylol (30% of weight of the urea). The mixture was heated to refluxing temperature andv held there for one hour. Atthis point, formic acid was added in an amount equal to 2% of the weight of urea. Heating was continued for six hours, during which time water was removed continuously. The product at this stage had a viscosity at 25 C. of Z4 on the Gardner-Holdt scale.

(1)) Seven and one-half mols of capryl alcohol was then added, and the mixture was heated to C. Butanol was distilled off, and heating was continued at 110- 115 C. until the product had a viscosity of X when measured at 25 C.

(0) Two hundred grams of the above caprylatecl urea-formaldehyde resin was mixed with 25 grams of sodium met-abisulflte dissolved in 25 grams of water, and the mixture was refluxed at 105 C. for five hours. At the end of this time, a sample of the product dispersed readily in water to give a solution which foamed readily. To the main portion of the product was then added 100 grams of xylol. Heating was continued, and water was-separated. After one and one-half hours, the temperature had risen to C. and 22 grams of water had been separated and collected. The product was cooled and unreacted bisulfite salt was filtered off. The filtrate was then heated at 100 C. and 10 mm. pressure, and 165 grams of a paste was obtained which had good detergent properties. The paste, however, contained some free capryl alcohol, which was removed by steam-distillation. The final purified product, which was dried at 100 C. under vacumm, was a white solid. -It was analyzed and was found to contain an average of one methylene sulfonate group, CHzSOaNa, and 3.5 methylene capryl ether groups, CH2OCaHn, for every '7 urea residues.

This material was'surface-active and was particularly well suited as a detergent, as shown by Launder-O-Meter tests.

, Example 2 A dodecylated and sulfonated urea-formaldehydecondensate was prepared in the manner described above.

(a) A mixture of grams of the condensate of the urea-formaldehyde and butanol prepared in part (a) of Example 1 and 60 grams of lauryl alcohol was heated to boiling, and butanol was distilled off. Heating was continued until the product had a viscosity of Z at 25 C. At this point, '75 grams of a 50% solution of sodium metabisulflte in water was added together with 100 grams of xylene. The mixture was refluxed for six hours without water separation, after which water removal was begun. After fortyfive minutes of heating at 104-105 C. thirtytwo grams of water had been removed. In order to facilitate filtering, one hundred grams of toluene was added and excess unreacted bisulfite salt was removed by filtration. The clear solution was then stripped at 100 C. and 20 mm. pressure. A clear, amber, sticky solid, weighing 150 grams, was obtained. This material dispersed readily in water to give a foamy solution. It was an excellent detergent. Analysis showed that the product contained 2.2 methylene sulfonate groups and 2.8 methylene dodecyl ether groups,

for every seven urea residues.

.All of the products of this invention function as capillary-active or surface-active agents. As such, they become oriented at an interface, lower the surface tension of water, and cause more rapid wetting of surfaces such as the surfaces of fibers as measured by the standard Draves sinking test. Their outstanding property is their effectiveness as detergents. In this capacity, as measured by wash tests and laundering tests, they are outstanding and are far superior to soaps and to many synthetic detergents known heretofore.

As detergents the products described herein may be used in hard water or in water of high salt content. Their advantage over synthetic detergents disclosed in the prior art resides in the fact that they are not micellar but are in fact macromolecules which do not revert as do micelles. Thus, they are excellent detergents at very low concentrations or at very high temperatures where former synthetic detergents failed.

They are uncommonly advantageous in the' laundering of cotton fabrics and in the scouring of wool, sized, dyed, and printed fabrics in general. They may be used for preparing dispersions of oil in water or dispersions of polymerizable materials prior to the polymerization thereof. Also, they serve to break water-ln-oil emulsions such as are encountered in oil fields. And they have been found to be very satisfactory in the treatment of leather, in the dispersion of pigments, and as assistants in dyeing.

The products of this invention are particularly useful when used in conjunction with other capillary-active agents, including fatty acid soaps and synthetic detergents such as those shown in United States Patents 2,115,192 and 2,143,759. Such combinations have extraordinarily high degrees of wetting and detergent properties.

We claim:

1. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and an unsubstituted saturated aliphatic monohydric alcohol containing six to eighteen carbon atoms prepared by sulfonating by heating a condensate of one mole of urea, 1.75 to 3.0 moles of formaldehyde, and 0.4 to 0.8 mole of a saturated unsubstituted aliphatic alcohol containing six to eighteen carbon atoms with 0.15 to 0.5 mole of a water-soluble metal salt of sulfurous acid.

2. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and an unsubstituted saturated aliphatic monohydric alcohol containing eight to eighteen carbon atoms prepared by sulfonating by heating a condensate of one mole of urea, 1.9 to 2.2 moles of formaldehyde, and 0.4 to 0.8 mole of a saturated unsubstituted aliphatic alcohol containing eight to eighteen carbon atoms with 0.15 to 0.5 mole of a water-soluble metal salt of sulfurous acid.

3. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and an unsubstituted saturated aliphatic monohydric alcohol containing six to eighteen carbon atoms prepared by sulfonating by heating a condensate of one mole of urea, 1.75 to 3.0 moles of formaldehyde, and 0.4 to 0.8 mole of a saturated unsubstituted aliphatic alcohol containing six to eighteen carbon atoms with 0.15 to 0.5 mole of a water-soluble alkali metal salt of sulfurous acid.

4. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and octanol prepared by sulfonating by heating a condensate of one mole of urea, 1.75 to 3.0 moles of formaldehyde, and 0.4 to 0.8 mole of octanol with 0.15 to 0.5 mole of a water-soluble metal salt of sulfurous acid.

5. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and octanol prepared 'by sulfonating by heating a condensate of one mole of urea, 1.9 to 2.2 moles of formaldehyde, and 0.4 to 0.8 mole of octanol with 0.15 to 0.5 mole of a sodium salt of sulfurous acid.

6. Surface-active, polymeric compositions com I prising a water-soluble, sulfonated condensate of urea, formaldehyde, and dodecanol prepared by sulfonating by heating a condensate of one mole of urea, 1.75 to 3.0 moles of formaldehyde, and 0.4 to 0.8 mole of dodecanol with 0.15 to 0.5 mole of a water-soluble metal salt of sulfurous acid.

7. Surface-active, polymeric compositions comprising a water-soluble, sulfonated condensate of urea, formaldehyde, and dodecanol prepared by sulfonating by heating a condensate of one mole of urea, 1.9 to 2.2 moles of formaldehyde, and 0.4 to 0.8 mole of dodecanol with 0.15 to 0.5 mole of a sodium salt of sulfurous acid.

LOUIS H. BOCK. JAMES L. RAINEY.

REFERENCES CITED The following references are of record in the Sweden July 10, 1945