US2364965A - Dry rosin size - Google Patents

Description

E. A. GE ORGI DRY ROSIN SIZE Dec. 12, 1944.

Filed May 14, 1941 MOISTURE 6 R o E G A D N U M D E m K a m on Patented Dec. 12, 1944 DRY ROSIN SIZE Edmund A. Georgi, Wilmington, Del., assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application May 14, 1941, Serial No. 393,485 3 Claims. (01. 260-105) This invention relates dry saponified rosin size, and in particular concerns a non-caking dry rosin size prepared from B wood rosin.

In the selective solventand selective absorbent processes of wood rosin refining, a large proportion of the color bodies and some of the asolineinsoluble material originally present in the rosin are obtained as a resinous by-product which is known in the art as B wood rosin or as Belro resin. This product is a hard, dark-colored,

amorphous material which is characterized by the a following approximate analysis:

It may be saponified with caustic alkali and.

thereafter sprayor drmn-dried in the known manner to form a dry product, which is comparable to dry saponified refined rosin in paper sizing value, and which is suitable for use in kraft or other dark-colored stock where color requirements are not particularly stringent. Such size, however, differs from dry sizes prepared from refined rosin in that it has an inherent tendency to cake or solidify upon storage underpressure, as for example when bags of the size are stacked one above another in a warehouse. Thisproperty constitutes a serious disadvantage since its detracts from the appearance of the product and renders it so diflicult to dissolve in water that it is entirely unacceptable to many paper manufacturers. The phenomenon is observed even when the size is packed in moisture-vapor proof bags, and hence cannot be attributed entirely to moisture absorbed from the atmosphere. For this reason, the term inherent caking is herein employed to distinguish the present type of caking from that which is observed in refined rosin dry sizes and which is due entirely to absorption of moisture from the air.

It is accordingly an object of this invention to provide dry 3 wood rosin sizes which are substant y free from inherent caking or solidification during storage.

Another object is to provide dry B wood rosin sizes which have substantially the same storage and. solubility characteristics as dry sizes prepared from refined rosin.

A further object is to provide a simple and economical method for the preparation of such noncaking dry B wood rosin sizes.

Other objects will be apparent from the following description of the invention, and various advantages not specifically referred to herein will occur to those skilled in the art upon employment of the .invention in practice.

In accordance with the above-mentioned objects, I have found that the inherent tendency of dry B wood rosin size to cake upon storage under pressure is .due to the residual moisture content of the size, and that inherent caking of the size may be substantially eliminated by reducing its residual moisture content below a certain predetermined value.

' In the single figure of the accompanying drawing, the curve is that obtained by plotting the moisture content of dry B wood rosin size samples against the change in density observed when the samples are stored for 24 hours under constant pressure at a temperature of 125 F. Since the latter value is directly proportional to the inherent tendency of the size to cake or solidify, thecu-rveillustrates. the relationship between inherent caking and moisture content. It will be readily seen from the curve that there is a definite moisture content value, namely, about 3.8 per- .cent by Weight, above which the size cakes very readily andlbelow which substantially no inherent caking occurs. This value is relatively independent of slight variations in the free rosin or free alkali content of the size, as well as variations in the pressure and temperature at which the may be prepared simply by subjecting the product prepared in the usual manner to a irying treatment in an oven unil the deiired low moisture content is attained. For example, the B wood rosin may be saponi- 46 fied with aqueous sodium hydroxide at an elevated temperature and pressure, and the prodict thereafter spray-dried .in the usual manner, e., by discharging into an atmospheric drying chamber maintained at a relative humidity below 50 about 78 percent, e. g., 20-50 percent, as described percent or less by heating in an tray-drier or in U. S. Patent No. 2,134,911. The product so obtained will have a moisture content of about 4.5-7.0 percent by weight and may be further dried to the desired low moisture content of 3.8

other suitable device. Alternatively, the saponified product may be drum-dried in the known manner to obtain a product having the usual moisture content, and the latter then reduced to the desired value in a rotary-drier or the like.

Ordinarily, however, it is preferable that, if at all possible, a desired product be prepared by a one-step process. I have found that this may be accomplished in the present case by employing a spray-drying process which differs from that employed for the preparation of refined rosin dry sizes only as regards certain of the operating conditons. For example, whereas in preparing refined wood rosin dry sizes it is cus tomary to heat the mixture of rosin and aqueous sodium hydroxide to a temperature of about 225-375 F., usually about 350 F., and under a pressure of about 100-125, usually about 115, pounds prior to spray-drying, in preparing the improved dry B wood rosin sizes of the present invention it is desirable to employ somewhat more stringent conditions, e. g., temperatures between about 375 and about 425 F. and pressures between about 125 and about 250 pounds. Also, it has been found preferable to employ somewhat more drastic drying conditions within the spray-drying chamber, namely, a temperature between about 200 and about 220 F. and a relative humidity of less than about percent, preferably 4-8 percent. By operating under such conditions, employing substantially chemically equivalent amounts of sodium hydroxide and rosin, a substantially neutral dry B wood rosin increase of 54.7 lbs/cu. ft. A sample of refined rosin dry size of 7.8 per cent moisture content showed a density increase of only 0.5 lb./cu. ft.

It will be understood that many variations may be made in the above-described procedure without departing from the purview of the invention. Thus, for example, the proportion of sodium hydroxide may be increased or decreased to prepare sizes having high free alkali or high free rosin contents, respectively. Also, alkalies other than sodium hydroxide, e. g., potassium hydroxide, may be employed for the saponification. Likewise, if desired, various additon agents, such as antioxidants, waxes, etc., may be added before, during, or afterthe saponification reaction to prepare a variety of sizes having modified propsize of only 1.0-1.5 percent moisture content may T Example erties as a result of the presence of such addition agents. Many other variations in dry size manufacture are Well-known in the art and, if desired, may be applied in practice of the present invention.

While the dry B wood rosin sizes herein described are substantially free from what has been termed inherent caking, i. e., they display little or no tendency to cake or solidify spontaneously upon storage under substantially moisture-free conditions, like other hygroscopic substances they are capable of caking by reason of gradual absorption of water-vapor from a moist atmosphere. Accordingly, when such sizes are to be stored for extended periods of time under more or less humid climatic conditions, they should be packaged in such manner as to exclude the access of moisture vapor.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regards the methods herein disclosed or the materials employed,

Approximately 40 pounds of B wood rosin was melted and charged into a vertical autoclave, the bottom half of which was encased in an oiljacket. The rosin was heated to a temperature of 300 F. and under the corresponding autogenic pressure by circulating he'ated oil through the jacket of the autoclave, after which 10.8 pounds of a 39 percent by weight aqueous sodium hydroxide solution was forced into the autoclave under pressure. The mixture was heated to a temperature of 400 F. over a period of 20 minutes while maintaining a pressure of about 215 lbs. gauge, after which it was allowed to discharge into an atmospheric drying chamber maintained at a temperature of about 200 F. and a relative humidity of about 10 percent. The dry B wood rosin size so prepared contained about 1.0 percent by weight moisture and about 1.4 percent by weight of free rosin, and had an approximate density of about 6.3 lbs./cu. ft. A /2- pound sample of this product was tested for inherent caking by placing under a 9 lb. weight in a cylnder of 5.5 inch daimeter. The entire cylinder and contents were held at a temperature of 125 F. for 24 hours, after which the size sample was found to have a density of about 6.5

lbs. /cu. ft., amounting to a 0.2 lb./ou. ft. increase in density. In contrast, a dry B wood rosin size sample which contained 3.9 per cent moisture showed an increase in density of 13.5 1bs./cu,ft.

when subjected to this test, and a sample containing 5.4 per cent moisture showed a. density provided the step orsteps stated by any of the following claims be employed, or the product defined by any of the following claims be obtained.

What I claim and desire to protect by Letters Patent is:

1. The method of preparing a dry resin size which comprises heating a mixture of a resin, said resin being obtained as a by-product in the refining of FF wood rosin to a pale grade of wood rosin and characterized by an acid number from about 100 to about 130, a saponification number from about 140 to about 200, an unsaponiflable content from about 10 to about 20 per cent, a drop melting point from about C. to about C. and a gasoline-insoluble content from about 35 to about 75 per cent, and a substantially chemically equivalent amount of aqueous sodium hydroxide at a temperature between about 375 and about 425 F. and under a pressure between about and about 200 pounds gauge until reaction is substantially complete, discharging the reaction mixture while under said pressure and at said temperature into a zone maintained at substantially atmospheric pressure and at a relative humidity below about 10 per cent,

whereby there is produced a substantially neutral dry resin size having a moistureicontent below about 3.8 per cent by weight.

2. The method of preparing a dry resin size which comprises heating a mixture of a resin, said resin being obtained as a by-product in the refining of FF wood resin to a pale grade of wood rosin and characterized by an acid number from about 100 to about 130, a saponification number from about to about 200, an unsaponifiable content from about 10 to about 20 per cent. a.

drop melting point from about 85 C. to about 95 C. and a gasoline-insoluble content from about 35 to about 75 per cent, and a substantially chemically equivalent amount of aqueous sodium hydroxide to a temperature of about 400 F. and under a pressure of about 215 pounds gauge, and thereafter discharging the mixture into a zone maintained at a temperature of about 200 F; at a relative humidity below about 10 per cent, and at substantially atmospheric pressure,whereby there is produced a substantially neutral dry resin size having a moisture content between about 1.0 and about 2.0 per cent by weight.

3. The method of preparing a dry resin size which comprises heating a mixture of a resin, said resin being obtained as a by-product in the refining of FF wood rosin to a pale grade of wood rosin and characterized by an acid number from about 100 to about 130, a saponification and about 200 pounds gauge until reaction is,

substantially complete, discharging the reaction mixture while under said pressure and at said temperature into a zone maintained at substantially atmospheric pressure and at a relative humidity below about 10 per cent, whereby there is produced a substantially neutral dry resin size having a moisture content below about 3.8 per cent by weight.

EDMUND A. GEORGI.

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