US2832693A - Liquid rosin size containing anti-stratifying and viscosity decreasing agent - Google Patents

Description

tates LIQUID ROSIN SiZE CUNTAINING ANTI-STRATI- FYING AND VISCOSITY DECREASING AGENT John F. Gorham, Orono, Maine, Edward Strazdins, Stamford, Conn., William C. Hopkins, Valdosta, Ga., and John G. Senese, Jr., South Charleston, W. Va., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application February 25, 1954 Serial No. 412,645

7 Claims. (Cl. 106-233) of the sizes, and substantially prevents stratification of the sizes on storage.

Rosin sizes have their principal use in the manufacture of paper. These sizes are manufactured on a large commercial scale by heating a natural or modified rosin above its melting point, forming a hot caustic solution from water and an alkali metal alkali such as potassium or, more commonly, sodium hydroxide or carbonate, and reacting the alkali solution with the rosin. The rosins referred to are organic acids. Neutralization of these acids by the caustic takes place within a few hours, the product being a viscous soap dispersion. In this process, the amount of water employed is controlled so that the size contains between about 50% and 80%-85 of solids, on the one hand to avoid sizes as dilute that they cannot be shipped economically, and on the other hand to avoid sizes so concentrated and, therefore, viscous that they cannot be pumped.

The amount of alkali employed in this manufacture is at least about 60% of that required for complete neutralization so that the size contains about 40% of free rosin acids, 21 lower amount of alkali yielding a size which contains so much free rosin acids that it cannot be suc cessfully diluted for application to paper. On the other hand, the amount of alkali may be sufiicient to completely neutralize the rosin, and this yields satisfactory sizes.

In commercial practice, liquid rosin sizes generally contain between 60% and 80% of solids by weight, thus minimizing shipping costs while providing a product having a pumpable viscosity at a temperature of about 60-70 C., this being the standard temperature at which sizes are handled within paper mills. Moreover, sufficient alkali is used to cause at least 65 %75 neutralization of the rosin, this amount insuring that the rosin possesses excellent dilutability in water while maintaining consumption of alkali and the viscosity of the product at minimum practical values.

Frequently, liquid rosin sizes are stored by the manufacturer before they are shipped in tank cars, and these sizes are further stored by paper manufacturers before use. It is known that during these periods of storage liquid rosin sizes of the commercially practicable types mentioned, that is, sizes containing from about 5% to 25% of free rosin acids and about 60% to 80% of solids, stratify on storage and separate into two layers. The bottom layer is more viscous than the upper layer. Hence, when a liquid rosin size has been prepared of maximum pumpable viscosity, allowance being made for the increase in viscosity which normally takes place on aging, storage of the size resultsin separation of a bottom layer which is beyond the range of normal pumpability and which,

2,832,693 Patented Apr. 29, 1958 "ice therefore, can be removed from the storage tank only with difiiculty.

A further disadvantage is that the upper layer is usually darker in color than the lower layer, and this introduces a problem of color control in the manufacture of paper.

Stratification of liquid rosin size often becomes evident in the laboratory in 3-5 hours and, in the case of rosin stored in large commercial tanks, in about 3 days. The phenomenon is not spontaneously reversible and homogeneity can be restored only by thorough mixing of the contents of the tank.

The discovery has now been made that liquid rosin sizes of the composition mentioned are much improved in terms of decreased viscosity by a dissolved content of between about /1 and 6% of alkali metal nitrate, based on the solids content of the size, that from about /2% to about 2% inhibits Stratification, and that Stratification is substantially completely prevented by the presence therein of between about 2% and about 6% by weight of dissolved alkali metal nitrate based on the weight of solids in the size. It has further been found that separation of the sizes into phases takes place when more than about 6% to 8% of the nitrate salt is present, the alkali metal nitrate in this instance acting to salt out the rosin soap resulting also in an actual increase in viscosity of the size.

From the foregoing it will be seen that the subject matter of the present invention broadly comprises a liquid rosin size of about 5% to 25% free rosin acids content containing about 60% to solids by weight, said size being improved by the presence ofan effective amount between about /2% and 6% based on the weight of the solids, of an alkali metal nitrate dissolved therein.

The amount of alkali metal nitrate which should be present within the range mentioned to prevent stratilication varies with the type of rosin employed, the solids content of the size, the amount of free rosin acids in the size, and the temperature of the size. As a result, the minimum effective amount can best be determined in each instance by laboratory trial. In general, with regard to liquid rosin sizes of the composition mentioned, we have found that fortified rosin sizes of low solids content but containing an intermediate amount of free rosin acids show the greatest and most rapid stratification, and that with regard to these sizes, higher temperatures favor Stratification. For example, a fortified rosin size containing 60% or 70% solids and 15% of free rosin acids is particularly prone to stratify and requires somewhat more of the nitrate salt for stabilization at the upper normal storage temperature of 80 C. than does ordinary rosin size containing 80% solids and 15% free rosin acids at the lower normal storage temperature of 50 C.

It is a particular advantage of the present invention that the presence of only a small amount of alkali metal nitrate very greatly decreases the viscosity of the sizes often to only a small fraction of the values which they would otherwise possess. Since the viscosity of liquid rosin sizes increases as their temperature falls, and since rosin sizes are normally stored in heated storage tanks, this means that rosin in such tanks can be stored at lower temperatures than would otherwise be the case while still preserving the size at pumpable viscosity. It is the curtomary practice of paper mills to store rosin size in tanks maintained at a temperature between about 60-70 C. The presence of an alkali metal nitrate permits the same sizes to be stored at a temperature about 20 C. lower without increase in viscosity, thus permitting substantial economy in the heat supplied.

It is a further advantage that the alkali metal nitrate does not in any way alter the color of the size or affect the usefulness of the size in the manufacture of paper.

Freshly prepared liquid rosin size, when stored at normal temperatures within the range of 50-80 C. in-

mally produced on a very large industrial scale creases rapidly in viscosity during the course of about the first seven days, the viscosity at that time often being several times that of the initial viscosity of the material. Thereafter the viscosity of the size generally remains at or near the high value reached towards the end of the first week of storage. It is a further most important advantage that the action of the alkali metal nitrate is a permanent one, the stabilized sizes of the present invention having a much lower viscosity during and after this period than corresponding sizes containing none of the nitrate.

In the manufacture of the liquid rosin sizes to which the present invention is directed, numerous forms of resin are currently employed and include gum rosin, wood rosin, and tall oil rosin, the latter being a new development in the rosin field for which standards have been promulgated by the U. S. Department of Agriculture. Moreover, rosins may be employed which contain a minor amount, e. g. to 40% by weight of the Diels-Alder adducts formed by reacting a naturally-occurring rosin with maleic anhydride or similar material. These rosins and the sizes prepared therefrom, generally respectively termed fortified rosins and fortified rosin sizes are disclosed broadly in U. S. Patent Nos. 2,628,918 and 2,385,794.

It will be understood that liquid rosin sizes, in addition to the foregoing, commonly contain a number of other materials. Included are the lower aliphatic alcohols and rosin esters therewith since rosin size may be prepared from the latter. Moreover, natural rosins contain small amounts of unsaponifiable materials including lignin and sterols. Sizes containing these materials undergo stratification on storage and an alkali metal nitrate is advantageously employed therewith.

The alkali metal nitrate may be introduced at any desirable point in the manufacture of the rosin size. For example, it may be dispersed into the molten rosin itself or may be dissolved in the liquid size subsequent to its preparation. Since, however, liquid rosin size is norit has been found most convenient to dissolve the nitrate in the water in which the alkali metal alkali is dissolved. In this manner uniform distribution of the anti-Stratification agent is most readily effected, and separate metering of the agent becomes unnecessary.

In the present specification, the term percent free rosin acids is used to designate the proportion of the rosin acids, as found by titration, which are not neutralized by the alkali-metal alkali during manufacture of the size.

The invention will be more particularly described with reference to the examples which follow, which are intended only to illustrate specific embodiments of the invention and which are not to be construed as limitations thereon.

Example 1 The effect of sodium nitrate in inhibiting stratification and decreasing the viscosity of a liquid fortified rosin size is illustrated as follows.

A liquid fortified rosin size was prepared by heating 15,000 pounds of M grade gum rosin to 150 C. and slowly adding 600 pounds of maleic anhydride. Reaction of the maleic anhydride was complete in 3 hours at about 170-180 C., the product being fortified rosin containing the Diels-Alder rosin maleic anhydride product.

In a separate vessel 1,800 pounds of sodium hydroxide was dissolved in 23,700 pounds of water and the mixture heated to 95 C. The molten fortified rosin and the hot caustic solution were separately but simultaneously pumped into a cook tank and the mixture agitated by agitation of live steam from the bottom. Reaction of the caustic was complete in 2 hours. The resulting size 4 had a free rosin acids content of 15% and a solids content of 70%.

Six samples were withdrawn. To five was added sufiicient of an approximately saturated hot aqueous sodium nitrate solution to provide sodium nitrate as shown in the table. The sixth sample was left untreated as control. The viscosities of the samples were then determined at 55 C. and 71 C. The samples were then stored at C. for 48 hours and observed for stratification.

Stratification was deemed to take place when two distinct layers could be observed. The samples were rated on an arbitrary scale on which 4 indicates bad Stratification, 1 indicates acceptably slight Stratification,

and 0 indicates no noticeable stratification. Results are as follows:

Viscosity (on) Stratifica- Percent at tion on Size NaNOa 1 Storage for 48 Home at 55 0. 71 C 71 0.

None 16,600 3,340 4 o. 5 10, 900 1, 635 4 1. 0 7, 780 1, 2+ 1.5 7,200 1,154 1+ 2.5 2, 800 1,000 0 3.0 2, 300 602 0 1 Based on solids content of size.

These tests show that the presence of a very minor amount of sodium nitrate caused a major decrease in viscosity, and that about 2% substantially prevented Stratification.

Example 2 The effect of potassium nitrate upon the viscosity and stratification of rosin size is illustrated by the following.

A fortified rosin size containing 70% solids and 19% free rosin acids was made by the method of Example 1, the amount of caustic being decreased to 1,720 pounds, and a control sample and a potassium nitrate-containing sample were prepared and tested as described in Ex- 1 Based on the weight of solids in the size. 1 Centipoises.

In this case the amount of stratification was very minor, the lower layer being less than one-tenth the weight of the upper. The data indicate that the maximum viscosity of the size which contained potassium nitrate was lower than the initial viscosity of the control sample.

We claim:

1. A liquid rosin size of from about 5% to 25% free rosin acids content containing between about 60% and 80% of solids by weight, said size containing an elfective amount between about /2% and 6%, based on the weight of said solids, of a dissolved alkali metal nitrate as agent decreasing the viscosity of the size.

2. A size according to claim 1 wherein the nitrate is sodium nitrate.

3. A liquid rosin size according to claim 1 containing a rosin-maleic anhydride adduct.

4. A liquid rosin size of from about 5% to 25% free rosin acids content containing between about 60% to 80% of solids by weight, said size being inhibited against stratification on storage by the presence of an effective 7. A liquid rosin size according to claim 6 containing amount between about 2% and 6%, based on the weight a rosin-maleic anhydride adduct. of said solids, of a dissolved alkali metal nitrate.

5. A liquid rosin size according to claim 4 containing References Cited in the file of this Patent a rosin-maleic anhydride adduct. 5 UNITED STATES PATENTS 6. A liquid rosin size of about 15% free rosin acids 2 content containing about 70% of solids by weight, said gggig :32? gfif' g size containing an effective amount between 16% and n 6%, based on the weight of said solids, of a dissolved FOREIGN PATENTS alkali metal nitrate as agent decreasing the viscosity 10 15,269 Great Britain 1897 of the size. v

Claims (1)

1. A LIQUID ROSIN SIZE OF FROM ABOUT 5% TO 25% FREE ROSIN ACIDS CONTENT CONTAINING BETWEEN ABOUT 60% AND 80% OF SOLIDS BY WEIGHT, SAID SIZE CONTAINING AN EFFECTIVE AMOUNT BETWEEN ABOUT 1/2% AND 6%, BASED ON THE WEIGHT OF SAID SOLIDS, OF A DISSOLVED ALKALI METAL NITRATE AS AGENT DECREASING THE VISCOSITY OF THE SIZE.