US1738776A - Aqueous dispersions and process of making same - Google Patents

Description

Patented -Detail), 1929 isa-176 LESTER xmscnnaann, or LEONIA, NEW Jansen AQUEOUS DISPEBSIONS AND PROCESS OF MAKING SAME Ho Drawing.

undergoing dispersion together with a certain quantity of material functioning as a dispersin medium. In actual commercial practice, a arge bulk supply of finished product is constantly maintained in the apparatus of which the agitating mechanism forms a part,

and the material to be dispersed is fed to this apparatus in fluidcondition while a separate stream comprising an-aqueous suspension of dispersing medium is simultaneously led into the mass undergoing agitation, suitable provision being made for continuously or intermittently withdrawing the dispersed material from the apparatus.

In order to produce dispersions of this:

character which shall be capable of admixture with electrolytes without destroying the character of the product as a dispersion, it is essential to employ as the dispersing agent materials or-conibinations of materials which are relatively inert chemically and incapable of entering into any reaction with or being reacted upon by the specific electrolyte which may be proposed for admixture with the product. It will be appreciated in this connection, where the dispersing agent is such '4 that a specific electrolyte may react therewith and impair on destroy its dispersive or protective properties, that under such conditions the dispersive agent may nolonger be able to function, with the result that the aqueous.

t dispersed condition of the system is destroyed and the dispersion is then said to be broken.

, For the purpose of providing dispersive media which shall be relatively inert to such action, and which possess other desirable advantages, there have been employed certain Application filed October 6, 1927. Serial No. 224,526.

organic and inorganic powders, insoluble in, though readily Wetted with, water and capable of swelling or being treated so as to swell more or less and assumea plastic condition in the presence of water. Of this class of materials, clays, metallic silicates and oxides, casein and other proteins, starch, etc. are examples, althou h clays are generallypreferred and have ound extensive application in this field, since ,they are comparatively 30 inexpensive and possess to the largest extent the inertness and other properties necessary to produce the desired product.

It has been found that certain of these mineral powder types of dispersive media, for instance, certain kinds of clays and metalllc oxides, are sometimes deficient in suspendmg power, so that while they are capable of exercising their function in the production of the dispersions, they are, on the other hand, 7 more or less unable to effect a sufliciently fine dispersion to retain the entire mass of dispersed particles in suspension in the aqueous phase over long periods of time, with the result that the particles gradually settle out to a greater or less extent.

Emulsions made with various types of emulsifying agents in which the dispersed particles, among other conditions, are not sufliciently fine, are prone to settle out. It is 30 sometimes diflicult to secure fine dispersion either because of the type of emulsifying agent used, the viscosity of the mass, temperatures, character of equipment, or the like. The purpose of the present invention is to se treat dispersions which have been made, or are being made under such unfavorable con-' ditions as might impair their suspendability, in such a manner as to render them suspendable despite their large particle size.

The present invention is particularly concerned with dispersions made with dispersive media which are open to the foregoing obj ections, and is directed to methods of treatment whereby such dispersons may be converted into products of improved and relatively permanent suspendability.

The invention further comprehends methods for treating dispersive media of the aforesaid character and which ordinarily give rise to non-suspendable products in such manner as to render them capable of producing more highly suspendable dispersions.

In its broadest aspect, the invention proceeds upon the principle of forming a cellular or gel-like structure in the dispersed product. The lnventlon is embodied invariou s modes of procedure which are hereinafter to be deof gel which'has been found to be practical in carrying out the principles-of the inven- 'tion, and that the broad concept is not to be regarded as restricted or limited to this particular type of gel.

One convenient method by which silica gels may be formed is to treat an aqueous solution of sodium silicate with ammonium chloride or hydrochloric acid whereby there is precipitated a highly gelatinous mass composed largely of silicic acid. The character of the gel thus formed depends upon the concentration of the silicate solution employed as well as that of the reagent with which the silicate is treated to form the silica gel.

It seems to be characteristic of silica gels as thus produced that when they are agitated or stirred, they are disru ted into more or less grainy particles distri uted in irregular and non-homogeneous fashion throughout the mass, and, particularly when the silicate concentration has been relatively low, a large quantity of free water appears after the gel has been agitated. With high concentrations of silicate and more rigid gels, the gel 1s not destroyed although it may be broken up and the separate portions of the rigid gels subsequently coalesce upon standing. ()n the other hand, it has been observed that where silica gels are formed, in dispersions of the type here referred to, the gelled dispersion thereby produced, possesses the unique property of being able-to regain its gel character upon standing quiet for a short time subsequent to having had the gel formation thereof converted to liquid as by stirring or otherwise. This phenomenon, i. e., to liquety by stirring and reassume gel structure on standing, does not occur with silica gels, per so, made from aqueous solutions of equal sodium silicate concentration.

By virtue of this peculiar behavior of dispersions having gels formed therein, ithecomes possible to prepare such dispersions and rely upon the gelled condition of the aqueous continuous phase to maintain the dispersed particles in suspension, even after the product has been subjected to stirring action or similar influence whereby the gel is temporarilydissipated. since upon permitting the product to remain in a quiescent state for ling and the rapidity with which the gelling 4 action takes place. Generally, the lower the hydrogen ion concentration of the gelled dispersion, the greater the concentration of sodium silicate must be, and vice versa. f

In one mode of carrying out the invention, there mayfirst be prepared an aqueous dispersion of bituminous material such as steam refined Mexican asphalt having a melting point of, say 100 to 200 E, more or less, using ordinary brick making clay as the dis persing agent. This dispersion may beeffected in any desired manner, for instance, in accordance with the 'methods disclosed in United States Letters Patent No. 1,302,810. Such dispersion may be composed of, say, 5055%- of the asphalt, 5 to 10% of clay dispersing agent, and the balance water. To a suitable quantity of the dispersion thus produced, there may be added about 1.8%, more or less, by weight of commercial 4A% sodium silicate solution. Hydrochloric acid in quantities sufficient to bring the hydrogen ion concentration to a pH value say, 3.0 to 3.8, more or less, may be then added to the silicate treated dispersion, with. the result that a gel formation takes place in situ in the dispersion, and this gelv structure exerts a protective action on the dispersed particles and serves to retain them in relatively permanent suspension."

The invention .may also be carried out by a somewhat modified procedure in which the silicate treatment is applied to the dispersing agent prior to effecting the dispersion therewith. In this procedure, it is preferable that the concentration of silicate and acid be such that no gelling takes place in the aqueous-- The concentration may delay the formation of the gel untilafter the.

dispersing action has been completed. Accordingly, illustrating such a procedure, say 20 parts, more or less, of brick making clay may be mixed with, say, '100 parts of water containing. say. 5 parts. more or less,

of .the commercial 44% sodium silicate soiution. Sufiicient hydrochloric acid may he then added to the mixture to bring the hydrogen ion concentration thereof to a pH value of, say, 2.0 to 2.3. more or less. At this pH value, substantially no gelling takes place but the aqueous suspension is of a sirupy consistency which functions efiiciently as the I water. and irreversible. Upon allowing this heavy productto stand, it assumes a gel con dition, and it may be beaten or stirred out,

if necessary, to convert the mass into a viscous body of desired consistency, and thereafter, by permittlng the beaten out mass to remain quiescent, the gel will reform in the mass,

as already described, and function to maintain the product in suspension.

Should it benecessary or desirable to thin out the heavy dispersion as withdrawn from the dispersing apparatus, this may be done with water, or with an aqueous solution of sodium silicate and hydrochloric acid, al

though in order to favor the ready formation of the silica gel in the dispersed mass, it is preferable to employ the sodium silicate solution containing the hydrochloric acid. so Eor this purpose, and to thus thin out the dispersion made as above described with the silicate-treated clay dispersing media, there may be added to the heavy dispersion an aqueous solution composed of about, 2.2% sodium silicate, more or less, acidified with hydrochloric acid to a pH value of about 3.0,

more or less. This solution may be employed in such quantities as are necessary to bring about the desired fluidity in the product. As a further illustration of the foregoing procedure with another material possessing relatively poor suspending power, a Ken tucky ball clay may be employed as the dispersing agent. With this substance, however, -it has been found that for more successful results it is necessary to use lower concentrations of the sodium silicate, and also to operate at' a pH value different from the 3.0 to 3.5 value used inconnection with the preceding clay, since at this value with the Kentucky clayit is more difficult to carry on the rigid and does not beat out easily to. the desired body and viscosity. Hence, in order to disperse a material such as Mexican asphalt, the dispersive media may preferably comprise 20 parts, more or less, of the Kentucky clay and 100 parts of water containing approximately 3 .parts, 'more or less, of

t the commercial 44% sodium silicate solution,

and acidified with hydrochloric acid to a pH value of, say, 6.0 to 6.5, more or less. With 'suchdispersive media, the'asphalt may be dispersed more readilyand the gel formed in the dispersion may be easily beaten or Ldispersing action and the gel formed is too.

stirred out to a homo eneous body of desired consistency, the gel eing subsequently reformed upon allowing the product to remain quiet, and as long as the gelled condition exists in the product, the dispersed particles are enabled to remain in suspension. The. product as thus produced is capable, Without any further treatment for the modification of its pH value, of drying to a film which is highly resistant to permeation by Water.

Ammonium chloride and other equivalent materials may be used instead of hydrochloric acid, if desired.

By the use of the term gel or gelled in the claims I intend to define an emulsion possessed of the unique property of being able to regain its gelled character by standing quiet for a short time subsequent to having had the gelled formation thereof converted to liquid with a slight amount of stirring and without the use of a diluent or substantial quantities thereof. I

I claim as my invention:

1 1. An aqueous gelled'dispersion of a waterproofing material, the aqueous phase containing silica in gelled form.

2. An aqueous gelled dispersion of a Waterproofing material, the aqueous phase being in the form of a gel.

3. A product of the character described, comprising a waterproofing material, dispersed in a gelled aqueous vehicle.

4. A product of the character described, comprising a dispersion, the continuous phase of which is in the form of a gell, the internal phase of said dispersion comprising a waterproofing material.

5. A product of the character described, comprising a waterproofing material dispersed in an aqueous vehicle, said product being characterized by its ability to gel on standing.

6. A gelled product comprising a waterproofing material dispersed in an aqueous vehicle, the gel condition of said product being dispelled by agitating action, said product being characterized by its ability to return to the gel condition upon standing quiet after being subjected to such action as has been suflicient to dispel the gel condition there- 7. -A product of the character described, comprising a waterproofing material dispersed in water, and containing substances for causing a gelled formation in the aqueous phase thereof.

8:A product of the character described, comprising a water-proofing material dis- .persed inwater, and containing substances for causing the formation of silica gel in the product. K

persedwaterproofing particles whereof tend tea settle out of suspension, the step which 9. In the production of dispersions, thedis- I comprises forming a gel in situ in the dispersion.

10. In the production of dispersions, the dispersed waterproofing particles whereof tend to settle out of suspension, the step which comprises forming a silica gel in situ in the dispersion.

11. The method of treating aqueous dispersions whereby to in creasethe ability of the dispersed waterproofing particles thereof to remain in suspension, which comprises combining with the aqueous dispersiona material capable of inducing a gel formation in theaqueous phase thereof.

2. The method of treating dispersions whereby to increase the ability of the dispersed Waterproofing particles thereof to remain in suspension, which comprises comv bining with the dispersion a material capable of inducin av silica el formation in the a: a:

dispersion,

13. In the production of dispersions, the steps which comprise combining with a mineral powder dispersing medica, substances capable of producing a gel formation in the dispersion, and effecting dispersion of a waterproofing material, with said combined mixture. g

In testimony whereof I afiix my signature.

' LESTER KIRSCHBRAUN.