US2688598A - Compositions of alcohols with hydrophilic gum colloids - Google Patents

Description

Patented Sept. 7, 1954 UNITED STATES ATENT OFFICE COMPOSITIONS F ALC OHOLS WITH HYDROPHILIC GUM COLLOIDS ration of Delaware No Drawing. Application November 6, 1950, Serial No. 194,398

6 Claims. 1

This invention relates to methods and agents for increasing the viscosity of polyhydric alcohols such as ethylene glycol, propylene glycol, glycerine and diethylene glycol, and for imparting viscosity to the lower monohydric alcohols such as methanol, ethanol and isopropanol.

The rimary purpose of the invention is to increase and control the viscosity of the polyhydric and other alcohols, thereby rendering them more useful and valuable in various utilizations.

A purpose of the invention is to increase the viscosity of a glycol without the introduction of insoluble solids or other deleterious foreign matter.

A purpose of the invention is to control the penetration of printing inks having an alcohol vehicle, thus improving the coverage and color value of the ink.

A purpose of the invention is to control the penetration of special varnishes having vehicles which consist of or contain material proportions of an alcohol.

A purpose of the invention is to provide an alcoholic antifreeze compound having an extremely low freezing point together with sufficient viscosity to make it highly resistant to leakage through hose and gasket connections.

A purpose of the invention is to improve the gloss of printed wall papers which are sprayed after printing with a dilute solution of a transparent lacquer.

A purpose of the invention is to provide a hydraulic pressure fluid of any desired high viscosity which will not freeze even at very low temperature.

A purpose of the invention is to provide a lubricant for plug cocks and the like, and for pump packings, which is free from hydrocarbons, is insoluble in oils and is stable at elevated temperatures.

The water-soluble salts of alginic acid with the alkali metals, ammonium and magnesium are wholly insoluble in the monohydric and polyhydric alcohols. The sodium salts of cellulose glycolic acid (carboxymethyl cellulose) and of tragacanthic acid are acohol-soluble in only a very slight degree. These observations are true also for most of the alkylamine and alkylolamine derivatives of these acids.

I have discovered, however, that certain selected members of these groups of bases, and also certain of the lower quaternary ammonium hydroxides (those having not more than ten carbon atoms in the molecule) form, with the above named acids, salts which have such degree of alcohol-solubility as to render them highly useful and valuable for the various purposes above named.

The acids and bases which I have found to be adapted to the production of useful alcohol-soluble salts are listed in Table 1 below, which also gives the combining weight of each and a reference letter or numeral by which the reactant is identified in a later appearing table of properties of the salts.

TABLE 1 Identification of reactants gg??? Name of Acid A Al iuic 205 B Ce lulose glycolic 275 C Tra amnfhin 760 Reference Comb.

Numeral Name of Base Wt Trlbutylamine Phenyltrimethylammonium hydroxide 163 Benzyltrimethylammonium hydroxide. 167 Di-n-butylamine 129 Triisopropanolamine 191 Diisopropanolamine 133 Butylaminc 73 Tetraethanolammonium hydroxide" 211 All other amines and alkylolamines with which I have experimented, and all of the gum acids other than those above named, either react too little or yield a product of too low alcohol solubility to be useful. The above selections of materials for reaction are based solely on experiment with a large number of substances in each class and have no present theoretical basis.

Alginic acid is obtainable commercially in a state of considerable purity, but tragacanthic' and cellulose glycolic acids are best prepared by acidification of the corresponding gums.

The acidification of gum tragacanth may be performed in an aqueous medium containing sufficient alcohol to prevent the gum from passing into solution, as for example three parts ethanol or isopropanol to two parts water. Dilute hydrochloric acid is suitable for this purpose and the liberated gum acid should be washed free from chlorides with aqueous alcohol.

The method just described does not work so well in preparing cellulose glycolic acid from commercial sodium carboxymethyl cellulose (sodium cellulose glycolate) as the product thus obtained is usually insoluble and nonreactive with the amines. This difficulty may be avoided by acidifying an aqueous solution of the sodium salt to about pH 2.5, and precipitating and washing the liberated gum acid with alcohol.

The reaction between acid and base is brought about by simple admixture with the addition of enough water or dilute alcohol to maintain the mass at a workable consistency. It is mildly exothermic and ordinarily will go to completion rapidly, with agitation but without the application of external heat. Many of the products are hygroscopic and are best dried in thin layers at from 160 to 190 F., and are then ground to pass a screen of say 40 mesh, or other mesh as may seem desirable. It is preferable to adhere closely to the stoichiometric proportions, as an excess of the acid tends to reduce the solubility of the salt; i. e., the proportion of the salt which is soluble, not the amount which will dissolve. An excess of the base, on the other hand, tends to increase drying difliculty.

The behavior of the quternary ammonium salts of alginic acid has been more thoroughly investigated than that of the other salts produced by combinations of the above reactants. I propose, therefore, first to describe the solubilities of the alginates and then to provide in tabulated form certain solubility data for the remaining salts which will permit general comparisons of properties to be made.

The ability to impart viscosity to the alcohols, which is the most useful characteristic of the above amine and quaternary ammonium alginates, is not displayed by the alkali metal and ammonium alginates. The latter, when in solid form, are readily soluble in water but are insoluble in an aqueous solution containing as little as 25% of a monohydric alcohol such as ethanol or isopropanol. Or, if one of these previously known alginates is dissolved in water and ethanol added to the aqueous solution, viscosity begins to be lost (by fractional precipitation of the algin) at an alcoholzwater ratio of about 30:70, and the alginate is completely precipitated when this ratio reaches about 50:50.

By contrast, the benzyland phenyltrimethylammonium alginates are completely soluble in a lower alcohol (monohydric or polyhydric) containing a mere trace of water and are not precipitated from aqueous solution by the addition of alcohol in substantially any proportion. For example, these alginates dissolve completely and yield a clear solution in 95% ethanol (5% water), and dissolve in 100% ethanol to produce a solution of only slight graininess. Thus it is possible to prepare solutions of these alginates in solvents containing water, a monohydric alcohol and/or a polyhydric alcohol in any desired proportion, or a solution which is entirely free from water.

The solutions thus obtained will also tolerate the addition of a considerable proportion of a nonpolar solvent which is miscible with alcohol. Thus, for example, the addition of an equal volume of benzol to a solution of a quaternary am monium alginate in alcohol (ethanol) fails to precipitate the algin or to make any greater reduction in the viscosity of the solution than that normally produced by dilution.

Glycol solutions of the quaternary ammonium alginates may be diluted with other glycols, such as triethylene glycol, or solvents such as acetone, Carbitol (diethylene glycol monoethyl ether) or Cellosolve (ethylene glycol monoethyl ether) without causing separation of the algin or reducing its'usefulness in solution, even when added in large proportion. This fact is of importance in the fabrication of special varnishes in which a wide variety of solvents are used to dissolve the resins on which the varnish is based.

The alginates of the first four bases (bases 1 to 4 of Table 1) are soluble in the monohydric alcohols, ethylene glycol, glycerine, propylene glycol and diethylene glycol. The alginates of bases 5 to 8 of the table are insoluble in propylene and diethylene glycol, but soluble in the remaining alcohols of this group.

The viscosity of an alcohol solution of one of these salts will vary with the initial viscosity of the alcohol, with the specific viscosity-producing characteristic of the individual salt, and with the percentage of the salt in solution, as well as with the degree of polymerization of the acid from which the salt was made. Table 2 gives a partial idea of these relations in the case of a single salt (of base 2 of Table 1) with an alginic acid having, in the form of the sodium salt, a viscosity in 1% aqueous solution of 250 centipoises.

TABLE 2 Viscosity relations with difierent solvents As would be foreseen, the products realized in the use of different combinations of acid and base are not of equal value as regards solubility, clarity of solution and viscosity-building characteristic, though all are of such quality as to be useful and valuable. The available data as to the properties of these products are set forth in abbreviated form in Table 3 following.

In this table the letter and numeral in the first column indicate, by reference to Table 1, the combination of acid and base used in forming the salt (e. g., A-l is the tributylamine salt of alginic acid, 0-5 is the triisopropanolamine salt of tragacanthic acid, etc.). The symbol S indicates sodium (e. g., A-S is the sodium salt of alginic acid), the notations regarding the sodium salts being inserted for comparison only,

The alcohol tolerance of the second column indicates the maximum percentage of ethanol, as referred to the total liquid quantity, that may be present in an aqueous liquid in which the product will dissolve to such etxent as to thicken the solution appreciably; the appearance in the third column is that of a 2% solution of the salt in ethylene glycol, and the viscosity is that of the same 2% solution, in centipoises, at 26 C.

Alcohol Clear, smooth flo 45 Only a trace soluble i 75 Trace, insoluble, smooth flow- 75 do 500 75 do 500 70 8 Gradual decrease in prop'or- 9? 50 tion soluble. 300 40 25 Only small amount soluble 05 The figures in the above table appear to support the following generalizations:

1. The solubilities of the salts of any one base with alginic or cellulose glycolic' acid are substantially equal while the tragacanthates are somewhat less fully soluble in glycol;

2'. The viscosities, at equal concentration, of glycol solutions of the salts of any one base are highest for the alginates, materially lower for the cellulose glycolates and still lower for the tragacanthates. The latter probably approach the limit of utility as regards ability to increase viscosity;

3. The solubilities and the viscosities, respectively, are approximatel equal for the salts of the first five bases with either alginic Or cellulose glycolic acid and for the salts of the first three bases with tragacanthic acid, but are progressively poorer when the remaining bases are substituted in the order named.

ALCOHOL SOLUTIONS AS SOLVENTS AND VEHICLES The above described solutions of the gum acid salts have a wide range of compatibilities. For example, a solution of triisopropanolamine alginate in ethylene glycol Will tolerate up to one weight part of ethanol, cellosolve (ethylene lycol monoethyl ether), methyl cellosolve (ethylene glycol monomethyl ether) or methyl carbitol (diethylene glycol monomethyl ether); up to two parts of acetone, isopropanol, carbitol (diethylene glycol monoethyl ether), methanol or triethylene glycol, and from four to six weight parts of propylene glycol or diethylene glycol. Solutions of the quaternary ammonium alginates are even more tolerant of the above diluents and will accept from one-half to one weight part of an aromatic solvent such as benzene. The solutions thus produced are ordinarily clear and smooth flowing but may occosionally be thixotropic, gelatinizing on standing and becoming free-flowing when stirred.

The solutions are compatible with moderate proportions of alkali metal and ammonium salts but will be salted out by excessive additions of water-soluble salts when water is present in the solution. Strong acids precipitate the organic acids, and soluble salts of polyvalent metals precipitate insoluble metallic salts. The quaternary ammonium salts are strongly basic and are compatible with the alkalis While the amine and alkylolamine salts are weakly basic and may be decomposed in. alkaline solution with liberation of the base.

Solutions of any of the above named salts in ethylene glycol or glycerol may be used to replace .the unmodified alcohol when used as the entire or partial vehicle or solvent in printing inks, varnishes and lacquers, thus increasing viscosity and film thickness, reducing penetration, and producing improvements in color value and gloss which often cannot be obtained in any other manner.

The increase in viscosity produced by even a slight addition of the alcohol-soluble gum salt will often permit the substitution in a vehicle of a less costly alcohol. For example, a 2% solution in ethylene glycol of the A-3 salt of Table 3 has a viscosity exceeding that normal to glycerol, and an 0.25% solution of the A5 salt in ethanol or propanol has a viscosity equal to that normal to ethylene glycol. type may be made, without detriment to the properties of the composition and with a material saving in cost.

In instances in which, for reasons other than viscosity, the preferred solvent is propylene glycol or diethylene glycol (as in the instance of steam set printing inks), the choice of salts'is limited to those of the diand tributylamines and the quaternary ammonium hydroxides.

Because of the great diiierences between the normal viscosities of the various alcohols, between the viscosity-producing abilities of the various salts and between the requirements for increase in viscosity in different usages, the quantity of the salt to be dissolved in the alcohol will vary over an extremely Wide range, for example from 0.1% to 20% by weight. In most instances, however, the range will be much narrower, as for example from 0.25% to 3% by weight.

HYDRAULIC PRESSURE FLUIDS The practical utility of a hydraulic fluid used to transmit high pressures is to a large extent dependent on a viscosity sufliciently high to minimize leakage at glands and packed joints and past the impellers of pressure pumps.

For use at normal temperatures, glycerol has a high viscosity when relatively free from water, and petroleum oils may be had in any desired viscosity.

For use at temperatures slightly below normal atmospheric, e. g., 6 to -12 C}, ethylene and diethylene glycol are available, having sufiicient viscosities for all but the higher range of pressures.

For safety at the very low temperatures encountered by high level aircraft, the freezing points of the glycols and glycerol are much too high, and the dilution with a solvent which produces a major depression in the freezing point, such as water, a monohydric alcohol or other nonviscous, alcohol-miscible solvent, produces a sharp lowering of the viscosity.

For example, the freezing point of ethylene glycol is depressed from 12 to 49 C. by dilution with water to a 60% glycol concentration, the viscosity being simultaneously lowered from about 17 cps. to about 5 cps. Dilution of the glycol with an equal volume of ethanol depresses the freezing point below C. and makes substantially the same reduction in viscosity.

Numerous substitutions of this The addition to the 60/40 aqueous dilution or to the 50/50 ethanol dilution of 0.25% by weight of the A- salt of table 3 brings the viscosity of each back to substantially the original viscosity of the glycol, while addition of 1% of the same salt raises the viscosity of the ethanol dilution to '78 cps., nearly five times that of the undiluted glycol. The presence of the salt has in itself a perceptible but unimportant effect in lowering the freezing point.

This procedure is capable of general application to the glycols and glycerol. By judicious selection of the glycol, dilution with water to produce a moderate or with a monohydric alcohol to an extreme depression of the freezing point, and restoration of the viscosity to the original or any desired higher level by the addition of one of the named salts, a hydraulic pressure fluid adapted to use at any naturally occurring temperature and at any required pressure may be produced.

LUBRICANTS The conditions encountered in the use of plug cock lubricants and lubricants for high pressure air compressor cylinders are burdensome and, so far as I am aware, no wholly satisfactory product for either of these purposes has heretofore been developed. The lubricant, to be prefectly adapted to such uses must be inherently nonvolatile under the conditions of use, must be free from volatile diluents or vehicles (including water) and must be stable when maintained at elevated temperatures over long periods.

For example, when held continuously at a temperature of 250 F. for thirty days, the lubricant may darken in color but there should be no carbonization or separation of solid matter. The lubricant must be completely insoluble in gasoline, hot oils or other hydrocarbons, and chlorinated hydrocarbons. It must preferentially wet.

metallic surfaces in the presence of gasoline or other liquid hydrocarbons. Finally, the viscosity must be sufiicient to maintain a lubricating film between the mating metallic surfaces of a plug cock or compressor cylinder and to resist displacement by the fluid pressure to which the film is subjected.

The lower polyhydric alcohols (specifically, ethylene, diethylene and propylene glycol and glycerol) are stable to heat but have as such too little lubricating value because of their relatively low viscosity and their steep viscosity vs. temperature curve. Various thickening agents have been employed in the attempt to increase the lubricating value of these alcohols, but in each instance of which I am aware some major difficulty has been encountered.

Agar displays some solubility in the polyhydric alcohols but the solution does not preferentially wet metallic surfaces. Sodium carboxymethyl cellulose swells in contact with the alcohols but does not dissolve and the insoluble particles tend to carbonize or harden and to cause scoring. Sodium alginate, as an aqueous paste, has been blended with glycerol for use as a plug cock lubricant, but as this salt (like all of the metallic alginates) is wholly insoluble in the alcohol, the product is merely a dispersion of water-swollen, gelatinous particles in an alcohol vehicle. On heating, or with the "passage of time, the algin particles separate from the alcohol and the composition loses its wetting power and to a large degree its lubricating value.

The solutions in the lower polyhydric alcohols of the salts listed in Table 3 behave as true solutions, even when free from water; they are equal to oils of corresponding viscosity in lubricating properties, and neither separate nor carbonize under the conditions above set forth. They have a low viscosity index and are not displaced from metallic surfaces by gasoline or other liquid hydrocarbons, in which they are completely insoluble. These solutions are of the highest degree of utility, not only as plug cock lubricants but also for lubricating pump rod or valve stem packings in machinery handling gasoline, kerosene, hot oils and molten asphalts, as air cylinder lubricants in air compressors, and in similar locations in which hydrocarbon or fatty lubricants are dangerous or unsatisfactory.

Following i an example of the manufacture of a very heavy lubricant for plug cocks. A quantityo of the A-5 salt of Table 3 (triisopropanolamine alginate) equal to 10% of the weight of lubricant to be produced was placed in a steamjacketed stirring vessel and enough commercial ethanol (about strength) to produce a thin liquid layer over the upper surface of the solid granules was added. The mass was then gently stirred until air bubbles ceased to come to the surface.

Glycerine at 96% strength was then added to make up the total weight, low pressure steam was applied to the jacket and the mass stirred slowly and carefully, to avoid the entrainment of air bubbles, until the solid grains had passed into solution and the mass became clear. About three hours heating was required, though this time will depend to some extent on the size of the batch.

The product on cooling was a clear substance which appeared to be solid though it would flow very slowly and was actually an extremely viscous liquid. The purpose in the addition of ethanol is solely to cause the disengagement of air from between the grains and this step may be omitted and the glycerol fed onto the dry salt granules if the temperature is raised slowly and great care exercised in the blending.

A similar general procedure may be followed in the manufacture of a lubricant of any lower viscosity, it being possible to adjust the viscosity to suit the requirement by selection of the polyhydric alcohol and the salt, and by controlling the proportion of salt dissolved in the alcohol. While viscous lubricants can be made with the use of any of the salts of Table 3, it is preferable to restrict the proportion of solids in the product by utilizing the alignates or cellulose glycolates of the bases numbered from 1 to 5 in the table, these salts having the greatest viscosityenhancing effect per unit of weight.

For obvious reasons, the proportion of the salt in any given lubricant may vary over an extreme- 1y wide range, as for example from 5% to 20% of the total weight of a semisolid plug cock lubricants and from 1% to 15% in more fluent lubricants. These lubricants should be substantially water-free, that is, the alcohols employed should be of at least 95% concentration and no additional water should be introduced into the composition.

These products are neutral or slightly basic and show no tendency to corrode polished metal surfaces. Any additives such as colloidal graphite, wetting agents, finely ground talc and the like, adapted to meet special conditions, may be incorporated and will remain in suspension.

It will be understood that the above described compositions of alcohol and a gum acid salt need not consist solely of these two components, but that this composition may function as a vehicle or solvent for other materials. Thus, a printing ink will always contain coloring matter and usually a gum or resin; a lacquer will contain a large proportion of a resin and a smaller proportion of coloring matter, and a varnish will contain resins and solvents of greater volatility than the alcohol.

I claim as my invention:

1. A composition consisting essentially of a viscous solution of an alcohol selected from the group consisting of methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerol, and of a salt consisting of a radical R and a radical HP, in which R is the anion of a hydrophilic, colloidal, gum acid selected from the group consisting of alginic, cellulose glycolic and tragacanthic acids and R is the cation of an organic base selected from the group consisting of di-n-butylamine, tributylarnine, phenyltrimethylammonium hydroxide and benzyltrimethylammonium hydroxide; the weight proportion of said salt to said alcohol being within the range from 0.1% to 20%; said salt being substantially free from extraneous salts, and said solution containing less than five volume per cent of water and being substantially free from undissolved residue of said salt.

2. A composition as recited in claim 1 in which the proportion of said salt is within the range from .25% to 3% of the total weight of said composition.

3. A hydraulic pressure fluid consisting essentially of a polyhydric alcohol of relatively high viscosity; a nonviscous monohydric alcohol in quantities sufficient to depress the freezing point of said polyhydric alcohol to a desired degree and to eifect a material reduction in its viscosity, and a salt consisting of a radical R and a radical R in which R is the anion of a hydrophilic, colloidal, gumacid selected from the group consisting of alginic, cellulose glycolic and tragacanthic acids and R is the cation of an organic base selected from the group consisting of butylamine, diisopropanolamine, triisopropanolamine 10 and tetraethanolammonium hydroxide, di-nbutylamine, tributylamine, phenyltrimethylammonium hydroxide and benzyltrimethylammo nium hydroxide; said salt being present in a quantity at least sufiicient to ofiset said reduction in viscosity of the polyhydric alcohol.

4. A composition consisting essentially of a viscous solution of an alcohol selected from the group consisting of methanol, ethanol, isopropanol, ethylene glycol, and glycerol, and of a salt consisting of a radical R. and a radical R in which R is the anion of a hydrophilic, colloidal, gum acid selected from the group consisting of alginic, cellulose glycolic and tragacanthic acids and R is the cation of an organic base selected from the group consisting of butylamine, diisopropanolamine, triisopropanolamine, and tetraethanolammonium hydroxide; the weight proportion of said salt to said alcohol being within the range from 0.1% to 20%; said salt being substantially free from extraneous salts, and said solution containing less than five volume per cent of water and being substantially free from undissolved residue of said salt.

5. A composition as recited in claim 4 in which said salt is a triisopropanolamine alginate.

6. .A composition as recited in claim 4 in which the proportion of said salt is within the range from .25% to 3% of the total Weight of said composition.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,087,549 Powers et al. July 20, 1937 2,158,485 Preble May 16, 1939 2,184,564 Oxley et al. Dec. 26, 1939 2,264,388 Lamprey Dec. 2, 1941 2,455,961 Walker Dec. 14, 1948 2,461,502 Moe Feb. 8, 1949 OTHER REFERENCES Hollabaugh et al., Ind. and Eng. V. 37, Oct. 1945, pages 943-947. (Copy in Patent Office Science Library.)

Claims (1)

1. A COMPOSITION CONSISTING ESSENTIALLY OF A VISCOUS SOLUTION OF AN ALCOHOL SELECTED FROM THE GROUP CONSITING OF METHANOL, ETHANOL, ISOPROPANOL, ETHYLENE GLYCOL, DIETHYLENE GLYCOL, PROPYLENE GLYCOL, AND GLYCEROL, AND OF A SALT CONSISTING OF A RADICAL RA, AND A RADICAL RB, IN WHICH RA IS THE ANION OF A HYDROPHILIC, COLLOIDAL, GUM ACID SELECTED FORM THE GROUP CONSISTING OF ALGINIC CELLULOSE GLYCOLIC AND TRAGACANTHIC ACIDS AND RB IS THE CATION OF AN ORGANIC BASE SELECTED FROM THE GROUP CONSISTING OF DI-N-BUTYLAMINE, TRIBUTYLAMINE, PHENYLTRIMETHYLAMMONIUM HYDROXIDE AND BENZYLTRIMETHYLAMMONIUM HYDROXIDE; THE WEIGHT PROPORTION OF SAID SALT TO SAID ALCOHOL BEING WITHIN THE RANGE FROM 0.1% TO 20%; SAID SALT BEING SUBSTANTIALLY FREE FROM EXTRANEOUS SALTS, AND SAID SOLUTION CONTAINING LESS THASN FIVE VOLUME PER CENT OF WATER AND BEING SUBSTANTIALLY FREE FROM UNDISSOLVED RESIDUE OF SAID SALT.