US1958470A - Method of making free rosin emulsions - Google Patents

Description

Patented May 15, 1934 UNITED STATES METHOD OF MAKING FREE ROSIN EMULSIONS Judson A. De Cew, Mount Vernon, N. Y.-

No Drawing. Application November 24, 1931, Serial No. 577,149

4 Claims.

Rosin soap emulsions containing free rosin have always been made by making a rosin soap by partial saponification and in the form of a concentrated aqueous product containing over solids.

This product when required for use is made into a dilute emulsion by passing the hot soap or size through an emulsifying device with water or steam or both, as disclosed in many patents, and also methods well known in the art.

These rosin soaps are generally made from rosin and sodium carbonate NaCos, this alkali being better suited in this boiling process than a stronger alkali because it reacts slowly giving ofif the acid gas CO2 during the boiling operation and does not carry the saponiiication to such a degree as to solidify the product during the boiling process.

It is the purpose of this invention to prepare direct from the rosin a dilute rosin soap containing free rosin, so that the emulsifying system can be eliminated and the size can be made in the mill in a dilute condition all ready to use.

This is accomplished by dissolving the rosin directly in a large volume of water containing a suflicient amount of caustic alkali to produce the kind of free rosin size desired when all of the rosin is dissolved.

I am aware that a dilute rosin soap containing no free rosin has been made with cold dilute caustic alkali by a continuous process. It is evident that a cold dilute caustic solution will not produce a free rosin size as the rate of solution is very slow so that it will contain free alkali instead of free rosin.

In order to have accurate control of the composition I use the batch system and I accelerate the reaction by heat so that the alkali will not only dissolve the amount of rosin acids to neutralize the alkali but the soap formed will also dissolve an additional amount of rosin even in its dilute state so that a free rosin emulsion is produced in one operation.

My method of operation is to fill a tank, hav ing an agitator of some kind, with hot water having a temperature of from 120 to 180 F., and add to this water while it is being agitated both the caustic alkali and crushed rosin. As these materials are added to the hot water the rosin dissolves in the alkali and in 'the soap formed until an opalescent or milky emulsion is formed on cooling. In this way a dilute size containing as high as 50% free rosin can be formed.

In making a rosin size with a hot dilute caustic solution a Wider range of concentration of alkali is possible than with a cold solution because the soap formed doesnot salt out of the hot solution as it -does With a cold one. This range, however, has its limitations as far as strength is concerned, for if the caustic alkali is over 6% NaOI-I it will make a size about 50% solids and this always jells in the tank from over saponification so that it cannot be circulated or mixed or handled in a commercial manner. It is necessary for safety of operation that the strength of the alkali be under 4% NaOI-I but inasmuch as it is desirable to use the soap at a concentration of under 10% and as the stronger the alkali the darker the size for a given temperature, it is much better practice to use alkali of about 1% NaOH or less. When it is desired to have a very light colored size the dilution is extreme.

This process may be carried out continuously by adding a stream of crushed rosin to a stream of hot dilute caustic soda and allowing this mixture to flow through a pipe or into a tank in which the right amount of saponification may take place. The temperature of the solution can be controlled to suit the time of saponification.

The advantages of this process of making rosin size emulsions in one operation are-many as all of the apparatus required is a tank with agitation or pump circulation and feeding devices, and by using hot caustic soda instead of sodium carbonate, there is practically no frothing during the saponification and all of the disadvantages of making a concentrated size with caustic alkali are avoided, such as jelling and discoloration.

It has not heretofore been known in the art that a high free rosin size emulsion can be made by direct saponification of rosin in a highly diluted caustic alkali. And it has always been considered necessary to first make a concentrated soap, which would act as a solvent for more rosin, and which required special equipment tomake into a good emulsion. This fact is proven by many patents that have been issued on the methods of emulsifying a free rosin size.

In practice, I would use a hot aqueous solution of caustic soda containing lb. NaOI-l to 100 lbs. of water to make a free rosin emulsion of about 3% rosin size, or a solution containing Z2 lb. NaOI-I per 100 lbs. of Water would make a 6% solution of size which could be further diluted after saponification to a concentration of 2% by adding cold water. Since the object of this invention is to produce a size containing free rosin, it is necessary to use proportions of rosin and caustic soda in which the caustic soda is less than 12% of the weight of the rosin because this proportion will completely saponify the rosin. All proportions less than 12% will therefore produce a free rosin size. Any quantity of rosin can be used depending upon the free rosin desired in the emulsion.

One advantage in making a rosin size by the use of caustic soda instead of soda ash is the fact that the finished size never contains dissolved bicarbonates or CO2 in solution, which make the solutions unstable, and which are always present in a size with sodium bicarbonate.

The advantage of using a dilute solution and at moderate temperatures is that saponification takes place without polymerization of the rosin and discolorization of the size.

I claim:

1. The method of making rosin size emulsion containing free rosin which comprises blending rosin and caustic soda in hot water between 120 and 180 F. to form a dilute emulsion, the caustic soda used being less than 4 percent of the water used and less than 12 percent of the rosin used. 2. The method of making a dilute solution of rosin size containing free rosin which consists in mixing rosin and caustic soda wherein the caustic soda has less than 4 percent NaOH in hot water whose temperature lies between 120 and 180 F. and stirring the mixture until the required amount of rosin is dissolved.

3. The method of making a dilute solution of free rosin size which comprises mixing rosin, caustic soda and water under the conditions wherein one-quarter of a pound of caustic is used to 100 pounds of water and the caustic is less than 12 percent of the weight of the rosin, and the temperature of the water lies between 120 F. and 180 F., to produce an emulsion having about 3 percent rosin size.

4. The method of making a dilute solution of free rosin size which comprises mixing rosin, caustic soda and water under the conditions wherein one-half of a pound of caustic is used to 100 pounds of water and the caustic is less than 12 percent of the weight of the rosin, and the temperature of the water lies between 120 F. and 180 F., to produce an emulsion having about 6 percent rosin size.

JUDSON A. DE CEW.