US2425200A - Modifying drying oils - Google Patents

Description

Patented Aug. 5, 1947 MODIFYING DRYING on.s

Floyd G. Nessler, Rocky River, and Charles E.

Penoyer, Garfield Heights, Ohio, assignors to The Sherwin-Williams Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application May 5, 1943, Serial No. 485,722

12 Claims. (Cl. 260-398) This invention relates to drying and semi-drying oils for use in synthetic resins and in paints, varnishes, enamels, lacquers, and other coating compositions. More particularly, the invention relates to animal and vegetable glyceride oils containing unsaturated long chain fatty acid radicals in the molecule.

The principal object of the invention is to increase the drying speed and improve the film forming characteristics of certain drying and semi-drying oils.

Another object of the invention is to increase the speed with which certain oils may be heat bodied.

Still another object of the invention is to increase the drying and bodying speed and improve the film forming characteristics of certain oils by a simple and economical procedure that does not require any highly specialized types of apparatus or expensive reagents.

Another object of the invention is to transform certain low grade drying oils, of which there is an abundant domestic supply, into acceptable replacements for such high grade oils as Chinawood, oiticica, and dehydrated castor, of which the domestic supply is at present extremely limited.

Other objects and advantages of the invention will become apparent from thefollowing detailed description thereof.

It has been the practice in the past to import into this country the great bulk of various fast drying oils, such as China-wood oil and oiticica oil, needed for their particularly valuable film forming characteristics. The very great utility of these oils in the field of protective coatings is believed to be due to a particular type of unsaturation within the oil structure. This is commonly referred to as a conjugated system of double bonds (e. g., -CH=CH-CH=CH--). Some oils imported for use in coating materials are not suited for use in their natural state and are processed in this country for the purpose of developing the desired drying qualities. Castor oil, for example, imported principally from India and Brazil, is dehydrated here in such a way as to develop within the oil structure a system of conjugated double bonds; As a result of this, the castor oil is converted from a non-drying oil into.the valuable, fast drying, film forming, dehydrated castor oil so widely used in the protective coatings industry.

The above mentioned imported oils are not always available in sufllcient quantities to meet the large demand for manufacturing high quality protective coatings. Also,-for obvious reasons, it is undesirable to be without a domestic supply of any product which is essential to the uninterrupted satisfactory operation of an industry. By means of our invention we are enabled to improve the drying and bodying speeds and film forming characteristics of relatively high quality drying oils as well as to improve those properties of the poorer quality oils. The improvements are obtained when the oils are used as film forming vehicles, both with and without driers.

Oils treated by our process, when heated to the usual bodying temperatures, body in a very much shorter time than do the untreated oils. This is very desirable as a time saving factor in the manufacture of coating compositions. Our treated oils also dry much more rapidly than the .untreated oils, thus greatly increasing their value as film forming vehicles. They are very highly compatible with both natural and synthetic resins, and, therefore, are of exceptional value in the manufacture of varnishes, lacquers, enamels, printing inks, linoleum, and the like. Varnish films prepared from these oils demonstrate, in addition to fast drying, very good adhesion and flexibility, excellent resistance to the aotionof soap and alkali, and a high degree of durability on exposure to the weather. Also, our process permits a considerable degree of control of variations in the individual properties of our new oils. This control enables the operator to produce an oil which will best conform with the requirements of a particular formulation or usage.

The large bulk of drying and semi-drying oils produced in this country are of a class possessing isolated, or non-conjugated, double bonds (e. g., CH=CHCH2CH=CH). Because of the isolated positions of the double bonds, these oils dry relatively slowly and, when dry, lack some of the desirable film characteristics. The principal oils of this type are linseed oil and soya bean oil. Other oils of this class are fish, hempseed, cottonseed, sunflower seed, walnut, and fiax screenings oils. Perilla oil, which is an imported oil, may also be mentioned as an important member of this group, though, in its untreated condition, it is superior to any of those mentioned above.

We have found that-when the slower drying, isolated double bond, domestic oils, such as linseed oil or soya bean oil, are treated with activating reagents of the low molecular weight,

saturated, aliphatic acid anhydride class, such heating of the oil.

3 to their performance as fllnrjorming vehicles. The class of anhydrides includedhere are those which resplt from-the'removal of one molecule of water, jointly, from two like molecules of a straight chain, low molecular weight, monocarboxylic acid, or from two molecules of different, straight chain, low molecular weight, monocarboxylic acids, or mixtures of either or both of these types. Both of these last two classes of anhydride reagents are contemplated by the term "mixed anhydride-s, as used herein.

Our new process consists essentially of heating an oil of the class typified by linseed .oil to a point within the approximate temperature range of 240 toiidOflCkirFari inert atmosphere, if desired, such as one of carbon dioxide or nitrogen. The oil is then treated with an organic acid anhydride, such as acetic anhydride, by any one of the procedures hereinafter described, for example, by passing vapors of the anhydride through the heated oil. The anhydride vapors, having passed through the oil, may be recycled directly, or they may be removed from the zone of reaction, condensed, redistilled, and the vapors again passed through the oil as a continuation of the treatment. It is most convenient to perform this operation at, or near, atmospheric pressure. However, if desired, it may be performed under either substantially increased or substantially reduced pressure. As a variation, the first addition of acid anhydride may be madeat a lower temperature than 240 C., either just preceding or during the Furthermore, it is unnecess ry to vaporize the acid anhydride as a preliminary step before adding it to the heated oil. It is only necessary to maintain the temperature of the heated oil during the main period of treatment within the approximate range of 240 to 340 C. The required time of treatment decreases as the temperature employed in the process increases.

Using due precautions, an acid anhydride which boils at a temperature lower than the temperature at which the oil is to be treated may be added directly to the hot oil at a controlled rate. Provided, that the pressure is not permitted to increase unduly, the anhydride will vaporize, and the vapors may be made to pass through the mass of oil. These vapors may then be led into a surface condenser and the condensed liquid may be returned to the feed vessel for recycling. The rate and continuity of the addition must then be such that the available supply of heat to the oil will be adequate to maintain the temperature at a point which will permit a sufficiently rapid reaction. This form of treatment may be conducted at or near atmospheric pressure, or, if desired, under'reduced pressure, or at a pressure which has been increased but which is not so high that the boiling point of the anhydride exceeds the operating temperature of the oil.

If it is preferred to operate in such a manner that the anhydride is not vaporized, provision may be made for developing a pressure sufficiently high that the boiling point of the anhydride does exceed the oil temperature. If the anhydride 'boils at a temperature higher than the temperature of the oil under the conditions of the treatment, an ordinary reflux condenser is *all that is required to return, in liquid form, any such small amount of anhydride as may vaporize from the oil during the treatment. Reduced pressures may be employed, if desired, in order to progressively withdr aw the anhydride in 4 the form of a vapor during the course of the treatment.

Of the above operating methods, it is our preferred practice to pass anhydride vapors through the hot oil and in some manner recycle the anhydride, in the vapor phase, through the oil. As a matter of convenience, we have found it desirable to condense the vapors as they emerge from the reaction zone and then redistill the condensate so that the vapors may again be passed through the oil as a continuation of the treatment. The oil may be pre-bodied slightly with heat prior to the anhydride treatment; or, if the anhydride treatment is conducted at a temperature below 280' C., the oil temperature may be raised, for example to 300 C., at the conclusion of the treatment and held there for a period of time,'such as for one or two hours, in order to polymerize or body the oil to a desired viscosity. This latter operation may be conducted in a vessel open to the air, although, to obtain the lightest colored product and to aid in scrubbing out the last traces of the anhydride reagent, it is good practice to pass carbon dioxide, nitrogen, or other inert gas through the oil during the bodying treatment. After a certain period of use, which will depend somewhat on the chosen operating conditions, the anhydride reagent will be found to have lost some of its potency. The reagent may be reactivated by mere purification, or by any desired method of regeneration.

We have found that the color of the treated oil is somewhat lighter if S0: has been bubbled into the oil with the anhydride during the treatment. However, the use of SO: simultaneously with the anhydride vapor tends to reduce the efilciency of the treatment in accomplishing the principal objects of the invention.

This process lends itself to both the batch and the continuous type of operation. Convenient apparatus for conducting a batch operation may consist of a vessel in which to boil or vaporize the reagent, a vapor line from this vessel ending in a blowing coil at the bottom of a second vessel containing th hot oil to be treated, a surface condenser connected to the upper portion of the reaction vessel containing the oil for receiving vaporized reagent, a receiving tank in which the reagent condensate is collected, and a line with an interposed pump for conveying the condensate back to the first vessel for recycling.

Apparatus for conducting a continuous operation may consist of a vessel in which to vaporize the reagent, a vapor line passing through a superheater to the base of a bubble tower of conventional design, a surface condenser connected with the top of the bubble tower, a receiving tank for the condensate, a line with an interposed pump and heat exchanger for conveying th condensate back to the boiler, a feed oil storage tank connected through a heat exchanger to the top of the tower, and a treated oil receiving vessel con-- nected with the base of the tower. In this equipment, the vapors from the boiler are superheated and mad to enter the tower at its base. They then rise and bubble through the preheated oil which enters at the top of the tower and flows downward over the shelves, counter-current to the flow of the anhydride vapors. The many bubble caps arranged upon the superimposed shelves within the tower aid enormously in establishing suflicient interface between the vapor and the oil to promote a rapid reaction. The oil discharged at the base of the tower may be considered to have received sufficient treatment, or

it may be returned to the tower for timber re- Example 1 1,500 gm. of alkali refined linseed oil, having an iodine value of 183, a viscosity of 0.43 poises at 76 F., and a color index of 5 to 6 on the Gardner scale, was placed in a flask and heated to 260 C. under an atmosphere of C02, created by constantly bubbling the CO2 into the oil through a blowing coil so that the ascendin gas replaces substantially all the air in the flask. On reaching the temperature of 260 C., acetic anhydride vapor was substituted for the CO2 and passed continuously into the oil at the rate of 28 gm. per minute for 4 hours while maintaining th temperature of 260 C. Then CO2 was substituted for th acetic anhydride and the temperature raised to and held at 300 C. for 1 hour. The oil was then allowed to cool while the CO2 atmosphere was still maintained. Throughout the treatment, the oil was mechanically agitated to increase the vapor-oil interface and to prevent local overheating.

The resulting treated oil had a color index of between 10 and 11 on the Gardner scale and a viscosity of 24.3 poises at 75 F. This oil is identified as oil A for reference purposes.

The same alkali refined oil was heat-bodied in an open kettle to a viscosity of 22.7 poises at 75 F. without subjecting it to the above treatment. This oil is identified as oil B for reference purposes.

A commercial grade (Dehydrol made by The Sherwin-Williams Company) of high quality dehydrated castor oil was prepared having a viscosity of 23.8 poises at 75 F. This oil is identified as oil C" for reference purposes.

The same drier (0.03% Co and 0.3% Pb as naphthenates) was added to a sample of each of oils A, B, and C, and clear films prepared from the samples were spread on glass plates and allowed to dry at 65 F. The films made from the three oils set to touch as follows:

Sample From the above table it will be seen that oil A,

- treated by our new process, dried almost twice as Example 2 Following the same general procedure of Ex. ample 1, but with the CO2 and acetic anhydride introduced through an open end tube, rather than through a blowing coil, and with no mechanical agitation, 500 gm. of the same oil used in Example 1 was heated under CO: to 340 0., at which point acetic anhydride vapor was substituted in part for the CO: at the approximate rate of 25 gm. per minute. The acetic anhydride treatment was continued for thirty minutes while maintaining the temperature of the oil at 340 C. CO: was then introduced at the original rate in place of the acetic anhydride vapor during cooling of the 011', all heating being discontinued. The higher treating temperature. combined with the efl'ects of the anhydride treatment, made further bodying unnecessary, the resulting oil having a viscosity of 38 poises at 75 F. The color index of the oil was between 13 and 14 on the Gardner scale. This 011 is identified as "oil A."

As in Example 1, two comparison oils were prepared: the same linseed oil (untreated) bodied to a viscosity of 39.9 poises at 75 F. (*011 B") and the same grade and brand of dehydrated castor oil as in Example 1, bodied toa viscosity of 39.9 poises at 75 F. (oil C).

Using the same drier as in Example 1, clear films prepared from the three oils and spread on glass plates to dry in air at78 F. set to touch as follows:

It will be noted that our new treatment pro.- duced a very marked improvement in drying time, though the comparison above is not quite as favorable as that in Example 1. However, by reason of the higher treating temperature, the relatively high viscosity of 39.9 poises was reached after only 30 minutes of anhydride treatment and without any further bodying being required. Compared with oils B and C, oil A was found to be capable of further heat bodying at a much faster rate. The less favorable drying speed comparison in this case may be attributed to the fact that bodying proceeded so fast during treatment at the high temperature of 340 C. that only a 30 minute anhydride treating time was feasible.

- Example 3- Using the same apparatus and physical procedure of Example 2, 500 gm. of the same oil used in Example 1 was heated under CO2 to 250 0., at which point the vapors of a, mixture of equal parts of acetic and propionic anhydrides were substituted for the CO2 at the approximate rate of 25 gm. per minute. The anhydride treatment was continued for 2 hours and 55 minutes while maintaining the oil at 250 C. CO2 was then substituted for the anhydride vapors, and the temperature of the oil was raised to 300 C. and held for 1 hour. After cooling with continued CO2 treatment, the resultingoil had a color index of slightly more than 12 on the Gardner scale and a viscosity of 10.7 poises at 75 F. This oil is identified as "oil A."

Two comparison oils were produced: the same linseed oil (untreated) and the same grade and brand of dehydrated castor oil referred to in Example 1, both bodied to the same viscosity as the treated oil of this example. These comparison oils are identified as oil B" and "oil C," respectively. I

Using the same drier as in Example 1, clear films prepared from the three oils and spread on 7 glass plates to dry in air at 80 F, set to touch as follows:

Time in minutes From the above it will be seen that oil A was materially faster drying than oil B, though not as fast as 011 C.

This example illustrates the use of a mixture of acetic and propionic anhydrides.

Example 4 Using the same apparatus and physical procedure of Example 2, 500 gm. of the same oil used in Example 1 was heated under C: to 316 C., at which point the vapor or propionic anhydride was substituted for the CO2 at the approximate rate of 25 gm. perminute. The anhydride treatment was continued for 20 minutes while maintaining the oil at 316 C. CO: was then substituted for the propionic anhydride for 5 minutes while maintaining the temperature of 316 C., after which the oil was allowed to cool under C02. The resulting oil had a color index of 11 on the Gardner scale and a viscosity of 27 poises at 75 F.

Two comparison oils were produced: the same linseed oil (untreated) and the same grade and brand of dehydrated castor oil referred to in Example 1, both bodied to the same viscosity as the treated oil of this example. These comparison oils are identified as "oil B" and oil C, respectively.

' Using the same drier as in Example 1, clear films prepared from the three oils and spread on glass plates to dry in air at 78 F. set to touch as follows:

Time in Sample minutes Oil A 100 Oil B i 210 Oil C 110 Example 5 Example 4 was repeated using butyric instead of propionic anhydride, treating at 340 C. for 20 minutes, and bodying at the same temperature under CO2 for minutes. The resulting oil had a color index of 14 on the Gardner scale and a viscosity of 285.0 poises at 77 F.

This oil bodied so rapidly during the high temperature anhydride treatment that comparison with other oils as to drying time was not feasible. It is apparent from a comparison of the viscosity obtained in this example (285.0 poises at 77) with the viscosity obtained in other examples using acetic anhydride as the reagent, that the butyric anhydride treatment produces an extremely fast bodying oil.

Example 6 Using the same apparatus as in Example 2 except that a. reflux condenser was employed at the start instead of a surface condenser, 200 gm. of the same oil used in Example 1 was heated with 200 gms. of caproic anhydride for 4 hours at 260 C. The reflux condenser was then replaced by a surface condenser, and the oil was blown with CO: for 3 hours at 260 C. The temperature was next raised to 300 C. for ,5 hour, and then the oil was allowed to cool, all the while continuing the blowin with C02. The resulting oil had a color index of 16.5 on the Gardner scale and a viscosity of 47.8 poises at 75 F. This oil is designated oil A."

Two comparison oils were produced: the same linseed oil (untreated) and the same grade and brand of dehydrated castor oil referred to in Example 1, both bodied to the same viscosity as the treated oil above. These comparison oils are identified as "oil B" and oil 0," respectively.

In this instance, the drying tests, conducted as in Examples 1, 2, and 3, showed no improvement in the drying of oil A over oil B, both drying at the same speed, and oil A was considerably darker in color than oil B. However, oil A bodied faster than either oil B or oil C.

Example 7 Following the procedure of Example 1 and,

using the same apparatus, 1500 gm. of fish oil having an iodine value of 192, a viscosity of 0.5 poise at 77 F., and a color index of 7 to 8 on the Gardner scale was heated to 260 C. under CO2. On reaching the temperature of 260 C., acetic anhydride vapor was substituted for the CO: at a rate of approximately 26 gm. per minute and passed continuously into the oil for 4 hours and 25 minutes while maintaining the temperature of 260 C. Then CO2 was substituted for the acetic anhydride, and the temperature was raised to 300 C. and held there for 35 minutes. The oil was then allowed to cool while the CO2 atmosphere was maintained. The oil was agitated throughout the treatment as in Example 1.

The resulting treated oil had a color index of slightly higher than 15 on the Gardner scale and a viscosity of 32.5 poises at 75 F. This oil is identified as oil A.

When compared with an untreated product of the same oil bodied to the same viscosity (oil B), by means of the same drying test and using the same driers as in the foregoing examples, oil A dried in minutes and oil B in 465 minutes. While oil A does not compare very favorably in drying speed with a dehydrated castor oil of the same viscosity, the improvement over the untreated fish oil (oil B) is very pronounced, and the drying rate of oil A is superior to that of a good grade of linseed oil of the same viscosity.

Oil A was very fast bodying as indicated by its gelation time of 382 minutes when subjected to the modified Browne heat test, whereas oil B, when subjected to the same test, was still fluid after 9 hours of heating.

Example 8 Following the procedure of Example 1 and using the same apparatus, 1,500 gm. of Perilla oil having an iodine value of 206, a viscosity of 0.4 poise at 77 F., and a color index of about 6 on the Gardner scale was heated to 260 C. under CO2. On reaching the temperature of 260 C., acetic anhydride-vapor was substituted for the CO2 at a rate of approximately 26 gm. per min- 9 ute and passed continuously into the oil for 4 hours and 25 minutes while maintaining the temperature of 260 G. Then CO: was substituted for theacetic anhydride, and the temperatur was raised to 300 C. and held there for 43 minutes. The oil was then allowed to cool while the CO2 atmosphere was still maintained. The oil was agitated throughout the treatment as in Examarse Oil A 65 Oil B 95 Oil C 85 Without the addition of driers, the time required for these oils to set to touch was as follows:

Sample 33}:

Oil A 16. 5 Oil B 39. 0 Oil 0 17.5

When subjected to the same modified Browne heat test referred to above, the time required for the same three oils to gel was as follows:

teas

Oil A 38 Oil B 154 Oil C 84 The remarkable improvement in 'Perilla oil when treated in accordance with this example is apparent from the foregoing data, the treated oil being both very fast drying and very fast bodying.

Example 9 poise at 77 F. The mixture of oils was heated to 260 C. under CO2, and, on reaching this temperature, acetic anhydride vapor was substituted for the CO2 at a rate of about 25 gm. per minute. The anhydride treatment was continued for 4 hours and 30 minutes while maintaining the temperature of 260 C. CO: was then substituted for the anhydride, and the temperature was raised to 300 C. and held there for 3 hours. The oil was then allowed to cool while the CO2 atmosphere was still maintained, Agitation was employed throughout the treatment as in Exampie 1.

Theresulting treated oil had a. color index of 10 to such an extent as to compare favorably with a highv grade drying oil, such as dehydrated castor oil, but it dried about 25% faster than the same mixture bodied to the same viscosity without re-' ceiving the anhydride treatment. The treated oil also demonstrated somewhat faster bodying than the untreated oil.

Example 10 1,500 gm. of alkali refined linseed oil, having an iodine value of 183, a viscosity of 0.43 poise at 76 F., and a color index of 5 to 6 on the Gardner scale, was prebodied by heating it to 307 C. and

holding it there for 1 hour under a C02 atmosphere created by bubbling the gas through the oil. Due to heat bleach the color index of the oil was dropped to between 2 and 3 on the Gardner scale. The temperature of the oil was then allowed to drop to 260 C., and acetic anhydride vapor was substituted for the CO: at a rate of about 25 gm. per minute. The acetic anhydride treatment was continued for 4 /2 hours while maintaining the temperature of the oil at 260 C. CO2 was then substituted for the acetic an-v hydride, and the temperature was raised to 300 C. for 30 minutes. The oil was then allowed to cool while retaining the CO2 atmosphere.

The resulting treated oil had a color index of about 13 on the Gardner scale and a viscosity of 39.9 poises at 75 F. This oil is identified as oil A. i

The same alkali refined oil was heat bodied to the same viscosity without subjecting it to the anhydride treatment. This oil is identified as oil B." The same grade and brand of dehydrated castor oil used in Example 1 was bodied to 39.9 poises at 75 F.

Using the same driers and conducting the same film drying test as in Example 1, films made from these three oils set to touch at 75 F. as follows:

This example illustrates that a marked improvement in drying speedis also obtained by the use of our process in treating aprebodied oil.

It is to be understood that the results of the drying tests in any on of the foregoing examples should not be compared with the results in any other example. Since the various examples represent experiments run on different days and at dififerent times of year, atmospheric and light conditions, in addition to the drying temperature, must be taken into account.

We have shown by the foregoing examples that considerable variation in the reagents used and in the mode of treating th oils is possible. It will be apparent from the data given, therefore, that our invention is not limited to any of the specific conditions illustrated and that one may depart widely from those conditions and still obtain the advantages of our invention. In the Y appended claims it is our intention to cover such slightly under 16 on the Gardner scale and a viscosity of 23.8 poises at F.

The drying speed of this oil was not improved variations as will naturally occur to those skilled as a reagent to improve the drying properties of certain types of oils, it ha not to our knowledge been used for our purposes in treating oils of the type disclosed herein, nor for performing the same kind of chemical transformation. In U. S. Patent No. 2,212,385, issued to Brod, the treatment of raw castor oil with acetic anhydride is disclosed. The treatment consists of causing the acetic anhydride to esterify the hydroxyl groups in the fatty acid chains of this oil and then, by the application of heat, splitting off acetic acid, thus creating new double bonds in the acid chains. In U. S. Patent No. 2,210,305, issued to Rheineck, the treatment of oiticica and po-yoak oils with acetic anhydride is disclosed. These oils contain ketone groups in the fatty acid chains which, according to the disclosure, react with the acetic anhydride to change the chemical structure of the oil.

The oils to which the present invention relates are non-hydroxylated oils and do not possess a ketone group in their acid chains. Since they lack these characteristics 'of the oils treated by Brod and Rheineck, they are not susceptible to the types of reactions taught by either of those patentees. Instead, under the conditions which we have prescribed, a difierent type of reaction necessarily takes place. and Rheineck can use other acetyl reagents than the anhydride form, we have found that our process is dependent upon the use of an anhydride, and that the acid or salt forms of the reagents which we have disclosed fail to produce corresponding improvements. Because of the special characteristics of the oils treated by Brod and by Rheineck, their results do not suggest the use of their respective processes for treating other types of oils, nor do their disclosures shed any light upon the nature of the chemical change which we bring about in practicing our invention. Our own investigations, likewise, have not disclosed any reliable explanation for the novel results which we achieve, and no such explanation is offered.

What we claim as our invention and desire to secure by Letters Patent is:

1. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. and intimately contacting the oil at such a temperature with an anhydrideof saturated, aliphatic, mono-carboxylic acid having up to five carbon atoms for a time suilicient to effectv such modification of the oil by contact with the anhydride.

2. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. under an inert atmosphere and intimately contacting the oil at such a temperature with an anhydride of saturated, aliphatic, mono-carboxylic acid having up to five carbon atoms for a time sufficient to effect such modification of the oil by contact with the anhydride.

3. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the Moreover, while Brod oil to a temperature in the range of 240 to 340 C. and passing through the oil at such a temperature a stream of vaporized anhydride of saturated, aliphatic, mono-carboxylic acid having up to five carbon atoms for a time sufficient to effect such modification of the oil by contact with the anhydride.

4. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C.

and intimately contacting the oil at such a tem-.

perature with acetic anhydride for a time willcient to effect such modification of the oil by contact with the anhydride.

5. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. under an inert atmosphere and intimately contacting the oil at such a temperature with a. stream of vaporized acetic anhydride for a time sufllcient to effect such modification of the oil by contact with the anhydride. Y

6. The method of modifying a non-hydroxylated. non-ketonic type of drying oil having non-conjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. and intimately contacting the oil at such a temperature with propionic anhydride for a time suiilcient to effect such modification of the oil by contact with the anhydride.

7. The method of modifying a non-h'ydroxylated, non-ketonic type of drying oil having non-conjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. under an inert atmosphere-and intimately contacting the oil at such a temperature with a stream of vaporized propionic anhydride for a time sufllcient to eflect such modification of the oil by contact with the anhydride.

8. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. and intimately contacting the oil at such a temperature with butyric anhydride for a time sufiicient to effect such modification of the oil by contact with the anhydride.

- 9. The method of modifying a non-hydroxylated, non-ketonic type of drying oil having nonconjugated double bonds to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. under an inert atmosphere and intimately contacting the oil at such a temperature with a stream of vaporized butyric anhydride for a time suflicient to effect such modification of the oil by contact with the anhydride.

10. The method of modifying linseed oil to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed, comprising heating 'the oil to a temperature in the range of 240 to 340 C. and intimately con- 13 tacting the oil at such a temperature with an anhydride of saturated, aliphatic, mono-carboxylic acid having up to flve carbon atoms for a time sufiicient to effect such modification of the oil by contact with the anhydride.

11. The method of modifying Perilla oil to improve the oil as, to at least one of the characteristics of drying speed and heat bodying speed, comprising heating the oil to a temperature in the range of 240 to 340 C. and intimately contacting the oil at such a temperature with an anhydride of saturated. aliphatic, mono-carboxylic acid having up to five carbon atoms for a time sufficient to efiect such modification of the oil by contact with the anhydride.

12. The method of modifying soya bean oil to improve the oil as to at least one of the characteristics of drying speed and heat bodying speed,

14 comprising heating the oil to a temperature in the range of 240 to 340 C. andintimately contacting the oil at such a temperature with an anhydride of saturated, aliphatic, mono-carboxylic acid having up to five carbon atoms for a time uflicient to efiect such modification of the oil by contact with the anhydride.

FLOYD G. NESSLER.

CHARLES E. PENOYER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I