US2373979A - Esterified tall oil treatment - Google Patents

Description

. Patented Apr."-17, 1945 Ernest Segessemann, Newark, N.

J assignor to National Oil Products Company, Harrison, N. J., a corporation of New Jersey No Drawing. Application January 1, 1942, Serial No. 425,348

2' Claims. (01. zoo-97.5)-

This invention relates in general to the prox duction of valuable products from tall oil, and

more particularly to a process of separating tall oil into its main constituents, i. e. fatty'and resinic acid substances. The present invention is especially directed to the recovery of valuable ester products from esterified tall oil without subjecting the same to any extensive'degree of hydrogenation,.my copending application Serial No. 309,703, now Patent No. 2,305,498 of which this is a continuation in part, being directed to a generally similar process during which non-esterified tall oil is subjected to hydrogenation to varying extents; my copending application Serial No. 425,347 filed herewith being directed to similar processes in which the tall oil is both esterified and hydrogenated to varying extents; and my copending application Serial No. 425,346 filed herewith being directed to a similar process in which tall oil is neither hydrogenated nor esterifled to any considerable extent.

Tall oil or talloel, which literally means pine oil," is the resinous and fatty by-product obtained chiefly in the production of paper pulp from resin-bearing woods by the so-called sulphate process. In the sulphate process wood is digested with an alkaline liquor containing sodium sulphate, during which process tall oil accumulates in the form of its sodium soap on the surface of the waste liquor. The main constituents of this oil, after acidification, comprise'resinic acids and fatty acids, the latter consisting mainly of oleic, linoleic and linolenic acids, each of which are valuable commodities in substantially-pure form. Various processes have been proposed in an attempt to efiect separation of tall oil into its main constituents, i, e. fatty acids and resinic acids. One process comprises esterifying the fatty acids in tall oil with a low boiling alcohol and separating the resulting fatty ester from the free resin acids by distillation or by alkali extraction. Another known process comprises esterifylng the fatty acids with a polyhydric alcohol and distilling off the resinic acids. According to another process, both the fatty acids and the resinic acids are esterifled with a polyhydric alcohol and the resin esters are then catalytically split and the liberated reslnic acids distilled off. While the foregoing and other known processes have been employed with varying degrees of success, they all exhibit certain disadvantages, primarily in that only partial separation is effected. Moreover, the fatty acid fraction obtained by these processes, consisting mainly of a, mixture of oleic, linoleic and linolenic acids, is not particuv the form of esters.

larly suitable for a wide variety of industrial uses. Usually having an iodine value of about to 130, this fatty acid fraction (or its esters) shows some drying properties, but these drying properties are not pronounced enough for a drying oil of good quality. On the other hand, this fatty acid fraction is too highly unsaturated to find extensive application in some of the largest fat-consuming industries, namely the soap industry and in the manufacture of specialties for the textile and tanning trades, the bulk of fats used in these industries being of more highly saturated type.

The general object of this invention is to obviate the foregoing and other disadvantages.

A specific object of the invention is to provide an improved and more efficient process for separating tall oil into its main constituents.

A further object of the invention is to provide an improved process for recovering from tall oil the more saturated fatty constituents thereof so that the same can be adapted to a wide industrial use. Still another object is to recover from tall oil a more highly unsaturated fraction capable of many technical applications.

Other objects will in part be obvious and will in part appear hereafter.

The foregoing and other objects are accomplished according to the broader aspects of the invention whereby tall oil is treated with esterifying agents to convert the fatty acids therein to The tall oil in its esterified form is then dissolved in a suitable solvent and subjected to temperatures suiiiciently low to efiect precipitation of a certain fraction of the fatty esters thereof. In general, if lower temperatures are employed, a larger proportion of the more unsaturated fatty ester will be precipitated, and conversely, if higher temperatures are employed, a larger proportion of these more unsaturated fatty esters are retained in solution, and only the more saturated esters such as oleic esters, are precipitated. The said precipitated fraction is then removed by filtration, centrifuging or any other known means of separating an insoluble solid from a liquid. The resinic constituents in admixture with the more highly unsaturated fatty esters remaining in the solvent may be recovered by dis tilling off the solvent- The tall oil or its esters employed in accordance with the process of the invention may be in thecrudeor distilled state and they may be subjected to someslight degree of hydrogenation before being subjected to the chilling and separating steps. However it is not intended to cover in this application the treatment of tall '01] or esters which have been subjected to any considerable degree of hydrogenation, this subject matter being disclosed and claimed in my copending applications Serial Nos. 309,703 and 425,347 above referred to. Accordingly, the filtrate obtained upon separation of the precipitated fatty esters will also contain fatty esters of the more highly unsaturaed type, mostly linoleic and linolenic esters. These higher unsaturated fatty materials may then be separated from the-rosin by alkali extraction of the rosin, or by methods disclosed in my copending applications, Serial Nos. 217,974 and 303,536, filed July I, 1938 and November 9, 1939, respectively. Alternatively. the mixture of rosin constituents and higher unsaturated fatty esters may be used as such in the preparation of other products such as drying oils, which is to form the subject matter of another application.

This invention accordingly comprises the sev The solubility of the highly unsaturated esters such as linoleic and linolenic esters is somewhat comparable to the rosin acids and they tend to remain in solution along with the rosin acids during the chilling operation during which the oleic esters precipitate out. Such a result in certain cases is desirable, i. e. to remove the oleic eral steps and the relation of one or'more of such steps with respect to each of the others thereof, which will be exemplified in the process hereinafter disclosed, and the scope of the invention will be indicated in the claims.

In carrying out the process of the invention, the first step involves the treatment of tall oil to convert the fatty acids therein to the form of esters. Preferably, the fatty acids are converted to esters of monohydric, rather than polyhydric, alcohols since otherwise mixed fatty and resin esters may be formed and a less sharp separation of fatty. from resinic constituents may result. Preferably also, the alcoholic constituents introduced by esterification should be derived from the lower alcohols containing from 1 to 5 carbon atoms for best results. The esterification may be carried out to varying extents, for instance only the fatty acids in the tall oil may be converted to the form of esters, or alternatively a greater or less proportion of the rosin acids'may likewise be esterified. Any suitable esterification reagents and processes may be employed, for instance, refluxing the tall oil with an appropriate alcohol in thepresence of an esterification catalyst, or treating the tall 011 at high temperatures and pressures with an alcohol.

The esterified tall oil is next dissolved in a suitable solvent therefor which is characterized by the property of retaining the resinic acids or derivatives thereof in solution at low temperatures and permitting the fatty acids or derivatives. thereof to precipitate out at low temperatures. Examples of such solvents include, inter alia, petroleum hydrocarbons such as gasoline, kerosene, heptane, mineral spirits, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; alcohols such as ethyl alcohol, methyl alcohol, isopropyl alcohol, etc.; ketones such as acetone, ethyl methyl ketone, cyclohexanone, etc.; chlorinated hydrocarbons such as ethylene dichloride, trichlorethylene, etc.

The step of dissolving the tall oil in a solvent has been described as subsequent to the esterification step; obviously this order may be reversed, and the esterification carried out after the tall oil has been dissolved. In certain cases, where an alcohol is employed as the solvent, this alcohol may itself act as the esterifying agent. Accordingly, in the specification and claims to follow, it is to be understood that the recitation, in any order, of these steps is to lee-construed to mean the combination of these two steps indifferently in any order, unless the contrary is explicitly indicated.

esters and recover the mixture remaining in the solvent, which comprises essentially the rosin constituents and. linoleic and linolenic esters. From this latter mixture the unsaturated fatty esters may be separated from the rosin acids by any suitable process, including those aforementioned. Moreover, this mixture of rosin constitucuts and unsaturated fatty ester may be used in the preparation of other products such as drying oils, which is to form the subject matter of another application.

After the esterified tall oil has been obtained in the form of its solution in a suitable solvent, the temperature of the solution is decreased to obtain the desired degree of precipitation of fatty acids or esters thereof. By actual experiment, a'temperature range of about 5 C. to '70" C. will accomplishw this result. It is obvious, of course, that temperatures outside of this range may also be operative to carry out the objects of the invention. The degree of cooling will be varied according to the nature of the solvent used and according to the form in which the fatty and resinous materials occur. The degree of cooling will be further varied according to the product desired, lower temperatures being required when it is desired to remove a larger portion of the fatty esters, particularly the more hig y unsaturated. fatty esters such as linoleic esters from the solution. Theprecipitated fatty esters are removed from the solution byany suitable means including centrifuging and filtration. The precipitated products after removal are preferably washed with a suitable solvent, e. g. the same solvent as used in the process, and preferably at substantially the same temperature at which the precipitating operation was carried out.

For a fuller understanding of the nature and objects of the, invention, reference should be had to the following example, which is given merely to illustrate the invention and is not to be construed in any limiting sense.

Example parts of the methyl ester of tall 011 containing 25% free rosin were dissolved in 400 parts of acetone, and the solution chilled to 15 C. for 12 hours. The resultant precipitate was separated from the solution by filtration, yielding 10 parts of fatty methyl esters having an iodine I value of 125.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the abovedescriwion shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention, which as a matter of language might be. said to fall therebetween.

Having described my invention what I claim as new and desire to secure by Letters Patent is: p l. A process for treating tall oil which comprises esterifying the same so as to produce lower alcohol esters of the fatty acids in said tall oil;

lowering the temperature of the esteriiied tall oil in the presence of acetone so as to eflect a separation thereof into a fatty ester fraction insoluble in said acetone at the lowered temperature and a solution of constituents soluble in said acetone at the lowered temperature; and separating the insoluble fatty ester fraction from said solution.

2. A'process for treating tall oil which comalcohol esters of the fatty acids in said tall oil: dissolving the esterified tall oil in acetone; 10 erin: the temperature of the resulting solution so as to .eflect a separation thereof into a fatty ester fraction insoluble in said acetone at the lowered temperature and a solution of constitu-' ents soluble in said acetone at the lowered temperature; and separating the insoluble fatty ester fraction from the residual solution.

ERNEST SEGEBSEMANN.