US2355605A - Extraction of drying oil - Google Patents

Description

Aug. 15, 1944.

R. F. RUTHRUFF ET AL 2,355,605

EXTRACTION OF DRYING OIL Filed April l, 1941 3 ShetS-Sheet l Aug. 15, 1944.

KEY

R. F. RUTHRUFF ET AL EXTRACTION OF DRYING OIL Filed April 10, 1941 KUIZ.

F: FURFURAL 3 Sheets-Sheet 2 I+ (SMALL) Invenoms Aug. 15, 1944.

R. F. RUTHRUFF ET AL EXTRACTION DRYING OIL Filed April 10, 1941 5 Sheets-Sheet 3 GOL/D5 Patented Aug. l5, 1944 EXTRACTION F DRYING OIL Robert F. Butliruff and Donald F. Wilcock, Chloago, lll., assigner-s to The Sherwin-Williams gohllnpany. Cleveland, Ohio, a. corporation of application April 1o. 1941, serial No. 381,846

26 Claims.

Thepresent invention relates to the recovery or treatment of natural and artificial drying oils such as fish oil, linseed oil, soya bean oil, dehydrated` castor oil, cottonseed oil, tung oil, and many other oils. to provide a fraction thereof having improved drying or other qualities.

Vegetable and animal drying oils comprise generally a mixture of triglycerides of saturated and unsaturated higher fatty acids in mixed or single acid glyceride form with or without free fatty acids. The common fatty acid components of the glycerides of the better known vegetable oils are stearic, oleic, linoleic and linolenic acids. Animal oil glycerides contain in addition higher fatty acid components. Only the unsaturated fatty acid components contribute drying quality, particularly those derived from linoleic and linolenic acids. 'I'he capacity for drying is represented by an analytically determined "iodine number. The iodine number is higher, the greater the degree of unsaturation, which in general induces more rapid drying and harder oil films.

The invention may be applied to drying oils already isolated, or it may be applied to-materials containing drying oils, such as cotton seed meal, soya bean meal, and other sources of such oils, or material impregnated with such oils. Since the invention depends upon the use of materials which are complete solvents for oil when used in adequate amounts for a given temperature, or selective solvents when used in limited amounts, or at a lower temperature, it is immaterial to the invention whether an isolated oil or an oil-impregnated material, or an'oil solution is the originally available material.

The preferred aspect of the invention is the treatment of isolated oils. Since the drying oils are most useful in their drying nature, for paints. varnishes and the like. the invention is described with particular emphasis on securing oil fractions of improved drying quality. However, thoseskilled in the art will readily perceive4 that the operations may be performed and varied in order better to attain other speciilc objectives.

Llnseed oil is naturally a satisfactory drying oil, yet its drying capacity may be increased by a suitable fractionation. Soya bean oil gives limited satisfaction as a drying oil, having naturally a lower iodine number than linseed oil. Its drying capacity may be increased by suitable fractionation. Many uses of soya bean oil do not require drying properties. Although its increasing availability at reasonable costs makes it desirable for drying-oil uses, yet in 1939 only 7.5% of the production was so used. Thepresent inventionJ is 6b (Cl. E60-428.5)

especially useful to fractionate soya bean oil into a fraction of increased iodine number, and a fraction of decreased iodine number. Given a low cost process for fractionation, the raw oil may be split for its drying and non-drying fields `of use; with advantage in the drying field, and with or without advantage in the non-drying field. In the latter ileld, sometimes the drying quality is disadvantageous.

Since the invention is particularly adaptable in its economic aspects, pecuniary and national, for treating soya bean oil, it ls herein described and illustrated with reference to soya bean oil, without being limited thereto.

In the concern for fractionating vegetable drying oil, a practice well established in the petroleum field has been turned to. It is well known to treat petroleum oil with a selective solvent capable of 'forming two liquid phases under chosen conditions for that end.- Thus, the parafiinic-rich oils and the aromatic-and-naphthenicrich oils have been concentrated in the two liquid phases. 'Ihis has been practiced with lubricating oil distillate. The process is known generally as solvent extraction. It produces as one liquid phase, the extract which is largely the solvent with an extracted content representing the more aromatic and naphthenic components of the original oil; and as the second liquid phase the "raflinate which is the more paraiilnic components of the oil containing a small dissolved content of the solvent. Solvent is distilled away from the two separated phases.

Numerous solvents have been so used with vegetable and animal drying oils, and extract and raflinate fractions obtained having respectively increased and decreased iodine numbers, indicating theoretically in the formerl case improved drying qualities. However, in actual per; formance such extract fractions of higher iodine number have been inferior to the original untreated oil, taking a much longer time to dry. Alike unexepected result has been that the ramnate fractions of lower iodine number dried much quicker than the original oil. Based on the iodine to treat the solution to secure a fraction of theoriginal oil.

It is a particular object of the invention to treat a'furfural solution containing drying oil to a selective oil-extracting solvent.

It is also an object of the present invention to recover from drying oils a fraction which has an iodine number increased over the iodine number of the original oil, and a shorter drying period than the original oil.

Corollary objectives are to produce a fraction of drying oil which has less capacity for drying, and to provide a raffinate drying oil which has either a lengthened or a shortened drying time in comparison with the original oil.

It is another object of the invention to produce a drying oil having less than the natural proportion of anti-oxidants to oil.

A particular object of the invention is to secure a soya bean source oil having improved drying characteristics compared to the natural soya bean oil.

Various other and ancillary objects and advantages of the invention will become apparent from the following description and explanation of the I invention, which is given in connection with the accompanying drawings in which:

Fig. 1 represents a number of graphs showing data pertaining to the treatment or extraction of soya bean oil with furfural at 20 C.

Fig. 2 is a diagrammatic representation of the preferred process of extracting drying oil with furfural, extracting the furfural extract with hydrocarbon, recovering two fractions of oil, and recovering the hydrocarbon and the furfural.

Fig. 3 is a diagrammatic arrangement of process and apparatus for carrying out the preferred process of Fig. 2, in a continuous manner.

Fig. 4 is a diagrammatic representation of modifications of the process as set forth in Fig. 2, the dotted lines of the figure representing a portion of Fig. 2, to which the said modications apply.

It has heretofore been suggested that drying oils may be improved in drying qualities by selective solvent extraction with a furan compound, such as furfural. Attempts to use furfural at normal temperatures for such purpose have been successful to split the oil into a fraction of higher iodine number, and a fraction of lower iodine number than that exhibited by the oil charged. The procedure in general is as follows:

The oil is thoroughly brought into contact with furfural in proportion to permit a separation into two liquid phases at a desired temperature. Furfural in the extract and in the railinate is distilled off, and the resulting oils analyse with higher iodine number from the extract and lower iodine number from the raffinate. But these are respectively worse and better than the original oil in time of drying,

By investigation, it was determined that the furfural also extracts certain substances natural to the oil, and herein referred to as "anti-oxidants, along with the high-iodine number extract oil, leaving the rafiinate oil deficient in antioxidants. This clearly explained the unexpected differences in drying times of the two oils resulting from the solvent extraction treatment.

The anti-oxidants natural tothe oil are believed to include at least certain phosphati'des, which includes so-called lecithin in the case of soy bean oil. The so-called lecithin is a well known antioxidant. The present invention is not concerned with the constitution of the anti-oxidants, and whatever they are, they are referred to by source and. function, for example, as natural anti-oxidants.

A study of the drying times of oil fractions has shown that furfural is highly selective of the natural anti-oxidants, and so much so, that a very light extraction with furfural, that is, using a low ratio of furfural to oil,'will remove a major portion of them, while extracting but a very minor part of the oil. This has been determined by nding that such a light extraction, leaving the rafilnate oil substantially unchanged in amount and in iodine number, compared to the charge, greatly reduces the drying time of the raillnate oil compared to the charged oil.

Therefore, it is one aspect of the invention that the drying oil may be given a light extraction with furfural to extract the natural anti-oxidants selectively, with little extraction of oil.

Attempts were made to operate a process by first giving such a light extraction with furfural, then an effective oil-splitting extraction with furfural, and distillation of the furfural from the extract and the raillnate. The oil thus obtained from the raflinate was expectedly quicker-drying than the natural oil, yet it had a lowered iodine number. However, surprisingly, the oil obtained from the extract was slower-drying than the natural oil, yet having a higher iodine number, in spite of the fact that substantially all of the natural antioxidants were removed from the original oil in the first and light extraction with furfural.v

This presented a further problem of shortening the drying time of the extract-oil over that of the charged oil, whereby the extract oil could be improved in drying time as well as in capacity.

Further investigation taught that the process employed was creating anti-oxidant material from the furfural. It was observed that upon distillation of the furfural extract fraction, by direct heat under a vacuum, or by direct heat while introducing steam, the oil became colored, and the more colored the oil, the slower its drying time. It was determined that there is formation of a black tar or gum in thus distilling the furfural extract. Either such product or an accompanying product exercised an anti-oxidant action on the extract oil residue of distillation. Thus,` the simple application of the petroleum oil technique, using furfural on drying oil, worked disadvantages in effecting the presence in the oil fraction having high-iodine number, of natural and formed anti-oxidants.

The invention is further related to modification of the process to avoid the presence of these anti-oxidants. In doing this, the natural antioxidants may be disposed of by the light-extraction as above set forth. The formed antioxidants may be avoided in the extract oil, either by removal or by the prevention of their formation. Where removal is employed, the natural anti-oxidants need not be removed by the light furfural extraction, but may be retained for removal with the formed anti-oxidants. When the formation of anti-oxidants is avoided, the natural anti-oxidants may or may not be removed by a selective extraction, according to the process employed to avoid the formation of the antioxidants resulting from a distillation of furfural from the extract phase.

vRemoval of anti-oxidants from the extract oil may be effected by a physical process such as contact with an adsorbent, such as activated charcoal, adsorbent clay, active magnesia, Magnesolf tricalcium phosphate, or contact with a solution, such as of sodium bisulflte, or a light extraction with a limited volume of furfural. The term Magnesol is a trade name of a product sold by the Westvaco Chlorlne Products poration, oi' New York city, New York, of which product the active material is a synthetic magnesium silicate. All oi these remove both kinds of anti-oxidants, except that the sodium blsuliite solution removes only formed-anti-oxidants.

Prevention of the formation ot anti-oxidants from turtural may be eilected by chilling'the furiural extract to a point where two liquid phases result, the extract being high in furfural which has high aillnity for any natural anti-oxidants. Residual iuriural in the ranlnate of this chilling may be distilled of! with little if any amount of anti-.oxidant formation. This procedure involves low yield o! extract oil for the processing and material required.

A second method, which is partially eective. is to dilute the furiural extractant of the .process with an agent which forms a mixed solvent of substantially the same extracting value. Such a mixture is one having 60 volumes o! i'urfural and 40 volumes of acetone. The extract is distilled. but there being less furfural, less anti-oxi- .dant is formed. In other words, prevention is eilected by reducing the amount o! furfural involved in proportion tot extract oil recovered.

A third method which is the preferred one, is

assaoos y Corinto a hydrocarbon extract, which is distilled to remove the hydrocarbon and yield the improved quicker-divins higher iodine-number drying oil. The rafllnate oi' the turfural extraction and the residual iurtural phase of the hydrocarbon extraction (containing anti-oxidants and a slight amount of a high-iodine number oil) are combined and .subjected to an exhaustive hydrocarbon extraction. This removes substantiallyl all oil and anti-oxidants in a hydrocarbon solution, leaving a furfural phase which, with or without purifying distillation, may be reused.

I! the original oil is lightly extracted with iur-` fural to remove natural anti-oxidants, then selectively extracted to provide iurfural extract and rainate, then the hydrocarbon extraction is eito extract the furfural extract with an appropriate solvent which is selective of the extract oil while being'sufilciently immiscible with the furiural and poorly selective for any natural antioxidants dissolved in the furi'ural. Further, such solvent should be one which is distillable from the extract oil without forming anti-oxidantl The paratilnic hydrocarbons in liquid form are such solvent. Suitable ones are propane, the butanes, petroleum ether (largely pentanes and hexanes), n-heptane, higher hydrocarbons, and "VMP" naphtha, which includes such higher hydrocarbons. The latter is the most efdoient in the preierred process. One important feature resides in the degree to which the hydrocarbon extraction is carried out. A severe extraction removes both natural anti-oxidants and oil from thefuriural extract, and a light extraction removes oil selectively leaving anti-oxidants. Thus, a hydrocarbon extraction may be carried out lightly in the presence of iurfural to retain the anti-oxidants in the furfural, or exhaustively to remove the anti-oxidants from the furfural. A light extraction which leaves in the ,furfural the anti-oxidants also leaves a small amount of some high-iodine number oil. In a cyclic process the light extraction is carried out to secure the improved drying oil, and an exhaustive extraction is carried out to produce a residual oil with its natural antioxidants for non-drying uses of the oil. Thus, the process is operable to split a drying oil containing natural anti-oxidants, into a fraction of higher-iodine number and lowered-to-no antioxidant content, and a fraction with the residual oil and the residual or all of the anti-'oxidant content, or in another variation little or none of the anti-oxidants.

Accordingly, the preferred process of the present invention is a plural solvent extraction process. The 'raw drying oil may be optionally freed of natural anti-oxidants by a light extraction' with furfural. As given in detail below, this is omitted in the preferred practice. 'I'he natural oil, with its anti-oxidants is` then to be split by solvent extraction with i'urfural to produce iur- !-ural extract and rafilnate The iurfural extract is given a light extraction with liquid parailln hydrocarbon. selectively to remove some oil content fected exhaustively, thus to secure all the oil. f

'Ihe preferred process as above described may be carried out batchwise, or in continuous extracting and tower-distilling equipment common in the petroleum industry for like process steps. The selection of proportions of materials and the extent to which any step may be carried, are largely matters of judgement, based on conditions, equipment, degree of separation desired, andvdegree of improvement in drying time desired. The following information pertains to such operation.

Since drying oils vary in their specific composition, and in their response to solvent extraction at different temperatures, it is not possible to give data for various oils atall temperatures. However, this is readily obtainable by simple determination. The following discussion is pertinent to extraction with furfural of natural soya bean oil at normall temperatures in the vicinity of 20 C. This temperature has been chosen for the preferred operation of the process for soya -bean oil to avoid special heating and chilling in the extraction process.

Fig. l is a plot of data obtained by extracting soya bean oil with various proportions by volume of furfural to oil at normal temperature. `The oil and solvent, are well mixed and allowed to separate in two liquid phases. Each phase is distilled to secure the oil content, and each oil specimen is analysed for its iodine number. The l original oil has an iodine number of 131.5 (Wijs method).

Axis I0 represents the volumes of furfural to vlegend Iodine number of extracted oil.

Curve I6 is a plot of the iodine numbers of the unextracted or railinate oil when furfural is used in the'amounts indicated along axis I0, with the legend Iodine number of raiilnate oil.

Curve I1 represents the percent of phase separation," that is. percent by volume Aof the oilV plus furfural taken, found in the lower or extract layer.

Curve I8 represents the percent by volume of the original oil which is in the extract.

Reading the graphs at the point 4 on axis I0, it is indicated that with 4 volumes of furfural to lvolume of oil, 20% of the oil is extracted, 80% of the total extraction mass is the liquid extract phase. and 20% is the raillnate phase. The ex-l tract oil has an iodine number of 143, or 11.5 points above the raw oil: and the raffinate oil has an iodine number of 128.6, or 2.9 points below the original oil.

'I'he graphs further show that the maximum iodine number is attained using 1 tot 2 volumes of furfural to 1 volume of oil, with from 5% to by volume or weight of the oil extracted. The extraction of oil high iodine number remains selective for much greater use of furiural with increased yield of extract, as shown by the continued higher location of curve l5.

Darme Tun:

The oils have been tested for drying time by a procedure which delays drying comparably, in order to accentuate the data for comparison. 6 cc. of oil, to which a standard drier is added is mixed with 5 gms. of ferrite yellow pigment. Thev latter is a retarder of drying, especially in the earlier stages of the drying action. The paste is spread on a plate in a uniform lm by a doctor blade, and exposed to standard, or to the same, conditions where comparisons are made. 'I'he plate is weighed at frequent intervals and the Weight plotted against time. The time required for increase in weight to begin is well known as the induction period (herein called A). The total time, called B herein, to attain a maximum weight is the time required to form a hard dry film. By calling the A-time for raw oil A0, a simultaneous comparison of A for a fraction obtained from a raw oil and the Ao of the raw oil itself, as a ratio of A to Ao, gives a significant value D used herein.

Table 1 represents a comparison of drying values of soya bean extract and raffinate oil obtained at the point 1.5 on the axis I0 of Fig. 1, and of the original charge of oil.

of highest iodine number takes longer to dry than the original oil and also the rafnate oil; and that the railinate oil dries quicker than the raw oil, in spite of its having lost the more drying components. As stated heretofore, these facts result from removal of natural anti-oxidants from the raiiinate oil, and placing them with formed anti-oxidants into the extract oil.

HYDxooAaBoN Ex'rRACTIoN 1 volume of soya bean oil having an iodine number of 130.4, and an induction period A of 73 hours, was extracted with 8 volumes of furfural.` 'Ihe extract oil was about 42% of the original charged oil. The extract oil had an iodine number of 140.4 while the raiiinate oil had an iodine number of 123.3. The extract phase was divided into two parts, and extracted with petroleum ether and VMP naphtha, at about C., respectively. About 1 volume of hydrocarbon to 3 volumes of extract phase was used. This is about 25.8 volumes of solvent (naphtha plus furfural) to 1 volume of extract oil. In the respec.- tive hydrocarbon extractions 84% and 87% of the extract oil was removed into the hydrocarbon phase. Oil of high iodine number remains in the residual furfural phase. However, it may be extracted by further treatment with hydrocarbon solvent. Where a ilrst hydrocarbon-extraction removed oil of 140.2 iodine number, the second hydrocarbon-extraction removed oil with iodine number of 155.3. But this oil, for reasons a1- ready given, is rich in natural anti-oxidants.

In the above two parallel hydrocarbon extractions. the results are closely identical, as shown in Table 2.

From the foregoing table, and the data on the original oil, it is seen that the ilrst extraction with furfural removes 42% of the original oil. The second extraction, with hydrocarbon, removes from this roughly or 36% of the original oil, as useful quick-drying oil, comparable as follows with the raw oil:

Table 3 Comparable induction period A in `hours Dryin ratio of new to raw Yield, Iodine numpercent ber Raiivlv soya been o New improved drying fraction.

PROCEDURE Fig. 2 represents diagrammatically the relation of steps, whether conducted batchwise or in a continuous process. Block 20 represents a natural drying oil containing a fraction of higher iodine number (indicated as I+), a fraction of lower iodine number (indicated as I-), and natural anti-oxidants (indicated as AO). Block 2| indicates the step of lightly extracting the oil of block 20 with a solvent selective of the anti-oxidants AO, using such a small amount of solvent that an inappreciable amount of oil is extracted. Suitable solvents are furfural, the described 60-40 furfural-acetone, and others. The preferred solvent is furfural because that amount dissolved by the oil does not effect a mixture of the solvent so used with the furfural which is usedin a subsequent step. Such a light extraction provides a furfural extract 22 containing the anti-oxidants AO. As indicated by the broken lines 23 and 24 to and from block 2 l, this extraction 2l is optional and preferably omitted, where it is permissible to provide the final fraction of oil having lowered iodine number with an anti-oxidant content for non-drying uses.

The line 25 leading from block 20 to block 26 indicates the preferred subjection of the oil of block 20 to a furfural (from supply '21) extraction 216, which of course, may also be practiced on the rafllnate from the light extraction 2 I.

'I'he extraction 26 is carried out with an amount of furfural which will yield two liquid phases 28 and 29 at a suitable separating temperature. The oil and furfural, as for example in a proportion assaeos chosen from a data-chart such as Fig. 1, may be mixed at the separating temperature to eifect an extraction, or be mixed at a higher temperature, and then cooled to a temperature at which a desired proportion of liquid phases, indicated by blocks 28 and 29, is eected.

'I'he liquid phase 23 is represented by legends in block 23 indicating that it is' the furfural (F) extract, with oil of higher iodine number (I+), and with anti-oxidants (AO) wherethe preferred path 20-25-26 is followed. The liquid phase 29 is the rafiinate phase indicated as containing `a small amount (f) of furiural dissolved therein, and oil of lowered iodine number (I-) Parailin hydrocarbon solvent liquid (from supply 30) is used for a light extraction indicated by block 3|, of the extract phase 26, giving a hydrocarbon extract phase 32 and a railinate phase 33. The extract phase 32 contains hydrocarbon (HC) and the desired oil of high iodine number (I+). Since the hydrocarbon predominates, it may be reduced in quantity or all removed by a distillationin still 34, yielding hydrocarbon 35 to be returned to supply 30, and the desired fraction 36 of high-iodine number oil with vless than, or substantially free from its natural proportion of natural anti-oxidants, according toy the exact manner selected to perform the steps to this point. The retention of hydrocarbon with drying oil permits use of such a mixture in some formulations.

ffural extraction 26, to givecombined raflinates indicated at 33, containingthe-oil ofv lower iodine number (I-) of block 29, furfural, and antioxidants. Although a small amount of oil of high iodine number (I+) is mixed with this, the resultant oil mixture is still oil of lower iodine number (I-) because it is all the oil remaining after removal of the oil (I+) of block 36.

The combined rainates are extracted at 40 exhaustively with parafiin lwdrocarbon liquid, as from -the supply 30, giving an extract phase 4| and a raffinate phase 42,' which is furfural. Thismay be returned to supply 21, or redistilled at 43 and then returned to said supply. The extractphase 4| predominates in hydrocarbon, and carries oil of lower iodine number (I), that small quantity of oil of high iodine number which is found' in ramnate 33 of the light hydrocarbon extraction, and anti-oxidants (AO) of s-aid ralnate 33. This extract 4| may be distilled at 44 to remove some or all of the hydrocarbon as distillate 45, return- 4 able to supply 30, and yield the oil fraction 46 havins iodine number below that of the original oil '20, in association with natural anti-oxidants iny greater than natural proportion, and preferably substantially all of the anti-oxidants or the orisinal oil 20.

CONTINUOUS Paocsss Aun APPARATUS Raw oil from supply 53, is led by connection 59 into the lower end of tower 52, into the upper end oi' which line 60 brings furfural from supply 50. These liquid streams tend to flow away from their points oi introduction toward the respective opposite ends of the tower, whereby they thoroughly mix. and effect the extraction. desired. Thus, furfural extract gathers at the bottom of tower-52, from which it is drawn oil in line 6| to the upper end of tower 53. Also, rainate oil gathers at the top of tower 52, from which it is drawn off in line 62 to the upper end of tower 54.

. Naphtha for the light extraction is drawn from' -combining of the raiilnate with rafiinate material from line 62 is eil'ected. v

Naphtha for the exhaustive hydrocarbon extraction is drawn from supply 5| by line 63-66 to enter the lower end of tower 54, wherein it flows against the combined rafilnates of the furfurai andlight naphtha extractions. The raffinate which results from this is furfural, drawn from the bottom of tower 54 and led by line 61 to the furfural supply 50. The hydrocarbon extract is led from the top of tower 54 by line 68, to the second naphtha still tower 56. From the two naphtha stills 55 and 56, naphtha distillate is returned to the supply 5| by the respective lines 10 and 1|. f

From the rst'naphtha still 55 the residue of oil having high-iodine number is drawn off at the .bottom as indicated at 12. From the second naphtha still 56, the residue of oil having low iodine number and anti-oxidants, is drawn off, as indicated at 13.

In order to point out the materials of the same character, in Figs. 2 and 3, the following Table 4 is given, in which the number given is the designating character or line connection.

Table 4 Material, or composition or process Fig. Fig. 3

Raw oil Furiural extractiom...

Furiural raiilnate. Light hgxdrocarbon extraction. Hy oearbon extract Hydrocarbo raiiina Exhaustive hydrocarbon extractie Hydrocar trac Hydrooar n raffinate (iuriural) Oil-high iodine number Oil-low iodine number plus anti-oxidants easeeassease adesaacsema liquid paraiiin hydrocarbons have a selective action, when used in limited quantity, to extract oil selectively from a furfural solution of drying oil and natural anti-oxidants of drying oil. Although such solutions are described above as made preferably by selectively extracting drying oil withv furfural, it is to be understood that the whole oil may be dissolved in furfural, which has a high ailinity for the anti-oxidants. Since the liquid parafiin hydrocarbon may be used to select Oil from furfural solution and to leave anti-oxidants dissolvedinfurfural, it is readily understandable that it is possible to extract oil from such solution faster than anti-oxidants can be extracted. Thus, itis possible to produce a fraction of oil, regardless of its iodine number, which has less than the natural proportion of antioxidants to oil. For example, raw oil may be dissolved in furfural, then extracted selectively with paraflln hydrocarbon liquid, short of the point of completion where the anti-oxidants in the extract have the natural proportion of antioxidants to oil in the extract.

The process is subject to a number of variations to secure the improved drying oil of either low or high iodine numberwith less than the natural proportion of anti-oxidants to oil, or substantially none at all. These variations are represented in Fig. 4, the dotted lines being used to show the portion carried over from Fig. 2, with reference to which the modifications are illustrated. The numbers applied to Fig. 2 and the legends are carried over into Fig. 4. The heavy lines of Fig. 4 represent various modifications, and it is to be understood that these include independent variations, all included in one diagram for convenience. The principles employed having been disclosed, each variation will be clearly understood by reference to the chart.

MODIFICATION No. 1

In the light hydrocarbon extraction 3|, the rafnate furfural 33 may be split into two portions designated 80 and 8|. Each contains largely furfural (F), anti-oxidants (AO) and a small amount of oil (I+). One portion 8| is mixed (line 82) with the raillnate 29, at 38, for the processing as in Fig. 2. The portion 8| alternatively may be processed in any other way, as indicated by line 83. The portion 80 is returned (line 84) to the furfural extraction 26, thus increasing the proportion of anti-oxidants to oil involved in said extraction, but also increasing to a small extent the oil of high iodine number present in raflinate 33 as taken into portion 80. This amounts to using in extraction 26 some furfural containing dissolved anti-oxidants, which is permitted by reason of the high selectivity Of'furfural for them.

MODIFICATION No. 2

nate 29, when exhaustively extracted with hydrocarbon at 40.

MODIFICATION NO. 3

The furiural-extract oil 28, containing antioxidants may be taken along line 86 and exhaustively extracted at 81 with paramn hydrocarbon liquid, whereby there are obtained a hydrocarbon extract 88, and a raiiinate furfural 89. The extract 88 contains the oil (I+) and antioxidants (AO) dissolved in hydrocarbon. The extract is passed over solid adsorbent, such as activated charcoal, adsorbent clay, activated magnesia, Magnesol, tricalcium phosphate, and like materials, which remove large amounts of anti-oxidant and but a small amount of oil. The adsorption step is indicated at 90, giving solid residue 9|, and useful hydrocarbon solution 92 of oil (I+). This may be reduced in hydrocarbon content, as 1n still 83 to give a concentrate V91| of oil (I+), and recovered hydrocarbon 95.

MODIFICATION No. 4

The above described exhaustive extraction 81 with hydrocarbon, may be practiced on the raftlnate furfural 33, as shown by lead line 91, connecting suchI rainate 33 and extraction 81. Thus, the oil (I+) in furfural extract 28, is divided into the oil (I+) of block 32, and oil (I+) recovered at 94. Thesemay be combined in the hydrocarbon solution stage, as indicated by line 98, or elsewhere, or not combined at all.

MODIFICATION No. 5

The furfural extract 28 is treatedl as by direct, vacuum or steam distillation, represented by block |00, to remove Iurfural |02, and yield a residue |03 of oil (I+) with anti-oxidants (AO) present in the furfural extract 28. These will be natural anti-oxidants, and according to the method Vof removal, may include formed antioxidants. The residue |03 is then extracted lightly with furfural at |05, selectively to remove anti-oxidants and a small amount of oil, as a light furfural extract ||0, leaving a raffinate phase |06, containing oil (I+) and a small amount of dissolved furfural (j). This amount (f) is so small that it can safely be distilled of! at |01 without danger from too much formed antioxidants, to give oil (I+) as shown at |08, and recovered furfural |09. The extract phase ||0 is rich in anti-oxidants (AO) and poor in oil (I+).

In this modification, the removal |00 of furfural (F) may be so incomplete that two phases result, one of which is furfural dissolving the anti-oxidants, whereby the said light furfural extraction |05 is eiIected by this incompletion of removal of furfural.

MODIFICATION No. 6

It is of course to be understood that in all these modiiications, the step 2l (a light selective extraction for anti-oxidants) may be practiced, whereby the anti-oxidants present are materially reduced in proportion to oil to be treated.

LINsEED OIL Although the invention has its preferred application to those drying oils which are of lower iodine, number than linseed oil, it is to be understood that linseed oil may be improved by securing fractions thereof according to the invention herein described. The fractions may be either higher or lower in iodine number than the original linseed oil, and in either fraction the natural proportions of anti-oxidants to oil may be reduced or removed. Thus a fraction may be improved by (1) added capacity to dry, (2) by shorter drying time, or (3) both.

A linseed oil is used having an iodine number of 175.1, an induction period A of 18 hours, and a drying time B of 39 hours. It was extracted according to step 26 (Fig. 2), with a ratio of 6.6 volumes of furfural to 1 volume of oil at 19 C. In the furfural extract was found 56.2% of the original oil. The extract phase wasv divided into three parts, each differently treated as follows:

Pafrt 1.-The extract was stripped of furfural by vacuum distillation, followed and completed by use of fire heat'and steam. The residue of oil had an iodine number of 185.9, and an induction period A of 51 hours. This shows the presenceof anti-oxidants, which as it will appear about 27% by volume of the original oil.

Part 3.-The extract was extracted at 19 C. with 0.22 volume of VMP naphtha to 1 volume of extract, with 76% by volume of the oil content going into the naphtha extract phase. 'I'his oil has an iodine number of 183.9, an induction period A of 1.5 hours, and a drying time B of hours. The oil is better in both capacity to dry and in drying time, than the original oil. It represents a fraction of about 43% by volume o! the original oil.

The oil in ranates of the above extractions have properties as follows:

Extraction by- Naph- Naph- Furfural tha,2part tha,3part Iodine No 161. 2 194. 2 192. 3 Induction period A liours.. 7 Drying time B ..do.- 27

'drocarbon extract phase containing oil of said higher iodine number and free from its natural proportion of said anti-oxidants, and reducing the Y hydrocarbon content of lsaid phase to secure said tion therefrom having a higher iodine number and a shorter drying time than the untreated oil which comprises lightly extracting the oil with furfural to leave substantially al1 the oil and to remove substantially all the anti-oxidants natural to the oil, again extracting the drying oil with sulcient furfural to provide a liquid furiural extract yphase containing an appreciable fraction of the oil having higher iodine number than the original oil and a liquid rafllnate oil phase, extracting the said extract phase with a parailln hydrocarbon solvent to form a residual furfural phase and a hydrocarbon phase containing oil of said higher iodine number substantially free of natural anti-oxidants, and reducing the hydrocarbon content of said last phase to secure said fraction.

4. The method of claim l in which natural drying oil is employed containing natural anti-oxidants and in which the said furfural extraction is preceded by a relatively lighter extraction with v furfural whereby anti-oxidants enter the -earlier liquid furfural phase.

5. The method of treating drying oil to split it into two -fractions having iodine numbers relatively higher and lower than the untreated oil o the said extract phase with a paraiiin hydrocartraction of more natural anti-oxidants by the inbon solvent to form a residual furfural phase retaining some oil and a hydrocarbon phase containing said quicker-drying oil of higher iodine number, removing hydrocarbon from said phase to secure the rst of said desired oil fractions,

combining the rainate oil phase and the said phase, extracting oil from the said extract phase with a paramn hydrocarbon solvent to form a residual furfural railinate phase and a hydrocarbon extract phase containing oil vof said higher iodine number, and reducing the hydrocarbon content of said phase to secure saidv traction while lowering the proportion of said hydrocarbon to oil, whereby the distillation of furfural in the presence of oil is avoided, with the avoidance tract phase which contains the natural anti-oxi-- dants o'i' the oil and to provide a liquid raffinate oil phase, incompletely extracting oil from the f; said extract phase with a parailln hydrocarbon solvent to form a residual Iurfural raffinate phase containing anti-oxidants and some oil and a hyresidual furfuralphase, exhaustively extracting the oil in said combined phases with a paraiiin hydrocarbon solvent whereby to form a furfural phase and a hydrocarbon phase containing oil of lowered iodine-number, and removing hydrocarbon from said last mentioned phase to secure the secondof said desired oil fractions.

6. The method of claim 5 in which natural drying oil is employed containing natural antioxidants, whereby said anti-oxidants enter the furfural extract and remain with the furf-ural phase of the first hydrocarbon extraction and then enter the hydrocarbon phase of the second hydrocarbon extraction, whereby they appear vin the oil fraction having an iodine number below that of the original oil. e

7. The method of claim 5 in which drying oil is employed from which natural anti-oxidants have been removed.

8. The method of claim 5 in which natural drying oil is employed containing natural antioxidants in which the said furfural extraction is preceded by a relatively lighter extraction with furfural whereby anti-oxidants enter the rst liquid furfural phase.

9. The method of treating drying oil containing natural anti-oxidants to secure a fraction therefrom having a higher iodine number and a less proportion of natural anti-oxidants than the untreated oil, which comprises lightly extracting the oil with furiural to remove anti-oxidants into a relativeiy small volume of furfural extract and leave a large volume of railinate oil, extracting the said raflinate oil with sulcient furfural to provide a second liquid furfural extract containing desired oil of higher iodine number, and extracting all of said oil from said second furfural extract with a parafiin hydrocarbon liquid to secure a hydrocarbon solution of said desired fraction.

10. The method of treating drying oil to remove therefrom a fraction of higher iodine number, which comprises moving in intimate contact with each other counter-current streams of drying oil and of furfural whereby to extract into the furfural a fraction of the oil and to provide a stream of furfural extract, moving in intimate contact with each other counter-current streams of said furfural extract and of paraiiin hydrocarbon liquid to provide a stream of furfural retaining oil and to provide a stream of hydrocarbon solution of said oil of said higher iodine number, and removing hydrocarbon from said hydrocarbon solution to secure an oil concentrate having a higher iodine number than the original oil.

11. The method of treating drying oil having natural anti-oxidants to secure a fraction therefrom having a higher iodine number which comprises moving in intimate contact with each other counter-current streams of drying oil and of furfural whereby to extract into the furfural a fraction of the oil and to provide a stream of furfural extract, moving in intimate contact with each other counter-current streams of said furfural extract and of parain hydrocarbonliquid to provide a stream of hydrocarbon solution of extracted oil of said higher iodine number and to provide a stream of furfural containing the remainder of said oil of the furfural extract and the natural anti-oxidants of the original oil, and removing hydrocarbon from said hydrocarbon solution to secure an oil concentrate having a higher iodine number than the original oil.

12. The method of treating drying oil having natural anti-oxidants to split it into two fractions A having iodine numbers relatively higher and lower than the untreated oil and with the oil of higher iodine number having a shorter drying time than the original oil, which comprises moving in intimate contact with each other counter-current streams of drying oil and of furfural whereby to extract into the furfural a fraction of the oil and to provide a stream of furfural extract, moving in intimate contact with each other countercurrent streams of said furfural extract and of parailin hydrocarbon liquid whereby to extract a portion of the oil into said hydrocarbon to provide a stream of hydrocarbon solution of extracted oil having said higher iodine number and to provide a stream of furfural containing the remainder ofv said oil and the natural anti-oxidants of the original oil, removing hydrocarbon from said hydrocarbon solution to secure an oil concentrate having a higher iodine number than the original oil and less than the natural proportion of anti-oxidants to oil, combining the raffinate streams of the first and second countercurrent actions, moving the combined stream of the said raflinates and a stream of parailn hydrocarbon liquid in intimate contact with each other in counter-current relation exhaustively to remove extract oil into hydrocarbon solution and to remove attendant anti-oxidants into hydrocarbon solution in providing a stream of said hydrocarbon solution, and removing hydrocarbon from said solution whereby to secure an oil concentrate having an iodine number lower than the original oil and containing greater than the natural proportion of anti-oxidants to oil.

13, The method of treating drying oil containing natural anti-oxidants, which comprises dissolving said oil in furfural, and extracting a portion of the dissolved oil in said furfural by treatment with a paraffin hydrocarbon liquid to form two liquid phases, one being a hydrocarbon solution of oil, and the other being a furfural solution of oil and anti-oxidants, said portion of oil so extracted being such that any natural antioxidants extracted from the furiural solution with said portion are less in proportion to the said portion than in the original drying oil, and removing hydrocarbon from said hydrocarbon solutionto secure an oil concentrate having 1ess than the natural proportion of anti-oxidants to oil.

14. The method of treating drying oil to secure a fraction thereof, which comprises extracting the drying oil with suilcient furfural to provide a liquid furfural extract phase and a liquid rafilnate phase, exhaustively extracting the furfural extract phase with a paraffin hydrocarbon liquid solvent to provide a liquid hydrocarbon extract phase containing oil and to provide a rallinate furfural phase, and removing hydrocarbon from said hydrocarbon extract phase to secure an oil concentrate having an iodine number greater than that of the original oil,

15. The method of treating drying oil to secure a fraction thereof, which comprises extracting the drying oil with sufficient furfural to provide a liquid furfural extract phase and a liquid rafnate phase, and extracting the ralnate phase with a paraflln hydrocarbon liquid solvent to provide a liquid hydrocarbon extract phase containing oil and to provide a railnate furfural phase.

16. The method of treating drying oil to secure a fraction thereof, which comprises extracting the drying oil with sufcient furfural to provide a liquid furfural extract phase and a liquid rafnate phase, and exhaustively extracting the raflinate phase with a paraln hydrocarbon liquid solvent to provide a liquid hydrocarbon extract phase containing oil and to provide a raliinate furfural phase.

17. The method of treating drying oil containing natural anti-oxidants to secure a fraction thereof, which comprises extracting the drying oil with suilicient furfural to provide a liquid fura fraction thereof, which comprises extracting the drying oil with suiicient 4furfural to provide a liquid furfural extract phase and a liquid raffinate phase, extracting the furfural extract phase lightly with a parailin hydrocarbon liquid while selecting a lower proportion of anti-oxidants to extracted oil than characterizes the original oil to provide a liquid hydrocarbon extract phase containing oil and to provide a rafnate furfuralV phase containing oil and natural anti-oxidants, splitting the railinate furfural phase into two portions, mixing one portion with an additional quantity of said original drying oil and using said mixture with additional furfural to provide a second furfural extract phase and a second liquid railnate phase.

19. The method of treating drying oil to secure a fraction thereof, which comprises extracting the drying oil with sulcient furfural to provide a liquid furfural extract phase and a liquid rafnate phase, whereby the furfural phase contains oil of iodine number higher than that of the original oil, extracting the furfural extract phase with a parain hydrocarbon liquid solvent to provide a hydrocarbon extract having a portion of oil having an iodine number greater than that of the original oil, whereby said portion is substantially free from furfural, and removing hydrocarbon from said hydrocarbon extract phase to provide an oil concentrate having an iodine number greater than that of theoriginal oil.

20. The method of treating drying oil containing natural anti-oxidants which comprises treating it with a quantity of organic liquid incompletely miscible with it, which liquid is a solvent i'or the anti-oxidants and a selective solvent for a fraction of the oil having a higher iodine number than the original oil, whereby to provide a liquid extract phase containing anti-oxidants and said fraction both dissolved in said organic liquid, and to provide a raiilnate phase containing a second fraction of oil having an iodine number lower than that of the original oil, extracting a portion of the dissolved oil in said liquid extract phase by treatment with a paraffin hydrocarbon liquid to form two liquid phases, one being a hydrocarbon solution containing said portion oi' oil, and the other being a solution of oil and anti-oxidants in said organic liquid, said portion of oil so extracted being such that any natural anti-oxidants extracted from the said liquid extract phase with said portion are less in proportion to said portion than the proportion in the original oil of natural anti-oxidants to oil, and removing hydrocarbon from said hydrocarbon solution to secure an oil concentrate `having less tliilan the natural proportion of anti-oxidants to 21. The method of treating drying oil containing natural anti-oxidants which comprises lightly and incompletely extracting the oil with a. small quantity of organic liquid which is a solvent for natural anti-oxidants and a selective solvent for a fraction of the oil having a higher iodine number than the original oil, whereby to provide a liquid extract phase containing a small fraction of the original oil and anti-oxidants both dissolved in said organic liquid, and to provide a raillnate phase containing a large proportion of the original oil as a second fraction having a lower iodine number than the original oil, the quantity of organic liquid being such as to' provide said second fraction of oil as one having a lower iodine number, a less drying time, and a less induction period than the original oil.

22. The method of treating drying oil containing natural anti-oxldantswhich comprises lightly and incompletely extracting the oil with a small quantity of organic liquid which is a solvent i'or natural anti-oxidants and a selective solvent for a fraction of the oil having a higher iodine number than the original oil, whereby to provide a liquid extract phase containing a small fraction of the original oil and anti-oxidants both dissolved in said Organic liquid,

raffinate phase containing a large proportion of the original oil as a second fraction having a. lower iodine number than the original oil, the quantity of organic liquid being such as to provide said second fraction of oil as one having a lower iodine number, and a less drying time than the original oil, and a substantially zero-time induction period in terms of hours.

23. The method of treating drying oil `containing natural anti-oxidants which comprises lightly and incompletely extracting the oil with a small quantity of an organic liquid prodominating in furfural content, which liquid is a solvent for said anti-oxidants and a selective solvent for a fraction of the oil having a higher iodine number than the original oil, whereby to provide a liquid extract phase containing a small fraction of the original oil and anti-oxidants both dissolved in said organic liquid, and to provide a raiiinate phase containing a large proportion of the original oil as a second fraction having a lower iodine number than the original oil, the quantity of organic liquid being such as to provide said second fraction of oil as one having a lower iodine number, a less drying time, and a less induction period than the original oil.

24. The method of treating drying oil containing anti-oxidants which comprises lightly and incompletely extracting the oil with a small quantity of furfural, whereby to provide a liquid 'furfural extract phase containing a dissolved small fraction of the original oil having an iodine number greater than that of the original oil and containing dissolved anti-oxidants, and to provide a ratlinate phase containing a large proportion of the original oil as a second fraction having a lower iodine number than the original oil, the quantity of furfuralbeing such as to provide said second fraction of oil as one having a lower iodine number, a less drying time, and a less induction period than the original oil.

25. The method of treating drying oil containing natural anti-oxdants which comprises lightly and incompletely extracting the oil with and to provide a 1l a small quantity of furfural, whereby to provide a liquid furfural extract phase containing a dissolved small fraction of the original oil having an iodine number greater than that of the original oil and containing dissolved anti-oxidants, and to provide a raiilnate phase containing a large Proportion of the original oil as a second fraction having a lower iodine number than the original oil, the quantity of furfural being such as to provide said second fraction of oil as one having a lower iodine number and a less drying time than the original oil, and a. substantlally zero-time induction period in terms of hours.

26. The method of treating natural drying oil containing natural anti-oxidants which comprises lightly extracting the oil with a small quantity of furfural to leave substantially all the oil and to remove substantially all the anti-oxidants natural to the oil, whereby to secure one fraction comprising a solution in furfural of a small amount of oil of higher iodine number than the original oil and substantially all the anti-oxidants of the original oil, and a second fraction comprising the remainder of the oil with an iodine number lower than that of the original oil with furfural dissolved therein, said second fraction being substantially free from natural anti-oxidants.

ROBERT F. RU'IHRUFF. DONALD F. WILCOCK.

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