US2479857A - Drying oils - Google Patents

Description

Patented Aug. 23, 1949 DRYING OILS Latlmer D. Myers, Cincinnati, Ohio, and James W. Ritz, Bergenfield,

Industries, Inc., tion of Ohio N. Cincinnati, Ohio, a corpora- J., assignors to Emery No Drawing. Application January 26, 1945,

' Serial No. 574,818

6 Claims. (Cl. 260-4043) This invention relates to a process of improving the film forming properties of drying and semi-drying oils such as those used in the manufacture of paints, varnishes, printing inks and the like. This application is a continuation in part of our copending application, Serial No. 475,- 282, filed February 9, 1943 which is now aban-' cloned.

Among the unsaturated acids which are found in the commoner vegetable oils' are oleic acid which contains one double bond, linoleic acid having two double bonds, and linolenic acid having three double bonds; in certain fish oils and the like some higher molecular weight unsaturated acids suchas clupanodonic are also present. These oils may be classified as being of the non-drying, semi-drying or the drying type. Drying oils are different from the non-drying oils in that they contain higher percentages of linoleic and linolenic acid. They are characterized, in fact, in that they contain unsaturated acids in suificient quantity and degree of unsaturation that the oils are capable of forming dry films when exposed to air. Thus, for example, the familiar drying properties of linseed oil are attributed to the relatively large amounts of both linoleic and linolenic acid which are present in it.

Cotton seed oil, on the other hand, contains little or no linolenic acid but it does contain a substantial quantity of linoleic acid and it therefore is classified as a semi-drying oil. But in addition to the doubly and triply unsaturated acids all of the glyceride oils contain the singly unsaturated acid, oleic, and some saturated acids such as stearic and palmitic. None of these contribute to the drying properties. Thus, palm oil consisting essentially of the solid palmitic acid and singly unsaturated oleic acid is a non-drying oil.

One of the most important of the desirable characteristics which a drying oil may possess is the speed with which a film of it will dry upon exposure to the air. The oils usually are cooked when paints and varnishes and printing inks are made and the speed with which the drying oil will form a homogeneous polymerized product when cooked with a resin is of great importance to the varnish maker. Inasmuch as all oils tend to become dark when they are cooked over long periods of time, an oil which cooks rapidly also permits the varnishes of lighter color to be made. On the other hand, it is desirable that the dry film be resistant to moisture inasmuch as the preservation of the surface is one of the primary reasons for applying the protective coating. The films also must be durable and have such degree of elasticity and flexibility that they do not chip easily. Some of the drying and semi-drying oils which are presently available possess some of these characteristics, and some possess other of the characteristics but none of the naturally occurring oils display all of these desirable properties to best advantage, and the primary objective of the present invention has been to provide a method by which the drying, film forming, moisture resistance and flexibility properties of naturally occurring oils may be improved.

It is also an object of the invention to provide a process for improving drying oils such that the time required to cook an oil into a varnish may be shortened.

In pending application entitled Treatment of glyceride oils, Serial No. 464,792 which is now Patent No. 2,440,667, there has been disclosed a method whereby the properties of a dryin oil may be improved by heating the oil to the distillation temperature of monobasic fatty acids in the presence of high boiling dibasic acids.

Briefly, we have found the properties of a natural drying or semi-drying oil may be improved by distilling the less saturated fatty acids from the oil, simultaneously replacing them in their linkages with the glycerides by polymer forming fatty acids which, when polymerized, are of higher boiling points than the undesirable acids. In order to accomplish this displacement and distillation, however, it is necessary first to polymerize the polymer forming fatty acids to prevent them from being distilled with the fatty acids less inclined to form polymers. Some of this polymerization must take place in the oil being treated to fix its more polymerizable components, but polymerization must also be effected in respect to thepolymer forming acids which are added to replace the less desirable acids which are to be removed by distillation.

Thus, a batch of polymer forming acids may be polymerized or partially polymerized before bein added to the oil to be treated or the polymerization can be accomplished after addition to the oil to be treated, at the same time polymerization is going on in the oil. Also, both the acids to be added to the oil and the oil itself can be subjected separately to polymerization to any desired degree before intermixture and distillation. If the polymer forming fatty acids are polymerized before being added to the oil, they consist mainly, we believe, of dibasic acids but may also contain tri or higher polybasic acids.

For convenience, they are referred to in this specification as dimer acids, and they are prepared from drying or semi-drying oils by methods which are described at a later point in the specification.

Our theory is that the polymer forming acids tend to react at two points, namely, at their double bonds and at their acid ends, thus forming complex molecules of relatively high boiling points which do not distill when the saturated fatty acids and the mono unsaturated fatty acids are subjected to distillation conditions. Thus, the invention comprises establishing an excess acidity in a drying oil, the excess acidity constituted by polymer forming fatty acids, effectin polymerization of the bodies to be retained in the finished oil and distilling off the fatty acids less inclined to form polymers.

In the process of the present invention the neutral or substantially neutral drying or semidrying oil which is to be treated is heated at a temperature of from 250 to 315 C. with these dimer acids for a period of from one-half hour to four hours, depending upon the degree of polymerization of the dimer acids, the quantity employed, the neutral oil being treated and the temperature. The heating preferably is carried out in an atmosphere of an inertgas and in a vessel equipped for vacuum distillation. At the end of the heating period, which is necessary to permit reaction of the polymerized acids with the neutral oil, and to polymerize the polymerizable components of the oil, a vacuum is applied and the monobasic saturated and low iodine value acids which have been liberated during the reaction are removed by distillation. The distillation is continued until the acid number of the residual oil has dropped to a sufliciently low value. The heating period prior to distillation is quite important not only to react the polymerized acids with the oil but also to polymerize the drying acid radicals in the oil, so that they become doubly attached, i. e., both to the glycerine part of the molecule and to one another at the points of greatest unsaturation.

The drying oils obtained by this process display greatly improved properties when compared to the untreated oils. The drying time is considerably shortened, the time required to cook varnishes is reduced generally to less than half the time required to cook a varnish from the untreated oil, and films produced have better water resistance and elasticity.

The polymerized acids required for the practicing of our process may be obtained by any one of several methods; such as by polymerizing the glyceryl esters, followed by splitting; by polymerizing the free acids, or by polymerizing and then saponifying and acidulating the monohydric alocohol esters of the fatty acids. The dimer acids may be freed from monomer acids prior to use or may be used admixed with monomer acids.

A convenient and, in most cases, the preferred method of preparing the dimer acids consists of heating an oil having substantial quantities of poly-unsaturated acids until a high degree of polymerization is obtained. The time and temperature required for this reaction are interdependent and also depend upon the nature of the oil used and its content of unsaturated acids.

oils is considerably greater than the oils usually used for the purpose of varnish manufacture. However, this condition can readily be obtained by those skilled in the bodying of oils.

, When polymerized the viscous oils containing dimer acid compounds are split into their components by heating at elevated temperatures with water in an autoclave under pressure or by alkali saponification, followed by acidification.

The glycerine is removed by known methods and the product remaining consists of the dimer acids admixed with some monobasic acids which are chiefiy of the non-drying type. This mixture of polymerized and non-polymerized acids may now be added directly to the oil to be improved or it may be subjected to distillation conditions so as to remove the monobasic acids and obtain the dimers in a substantially pure state. While either step may be employed we have found that sharper segregations of the non-drying acids are obtained by treating oils With the substantially pure dimers. The method described does not necessarily require the use of corrosion resistant metals for the construction of the treating vessels and light colored products are obtained.

If difliculty is experienced in handling the viscous product the fatty acids themselves may be polymerized instead of polymerizing the oil. In this case, the oil may be split in the unbodied state, the fatty acids recovered, if necessary, distilled, and the acids then polymerized. The product so obtained usually is considerably less viscous than that obtained by polymerizing the oil.

In the case of oils containing a large quantity of highly unsaturated acids the best results are obtained by polymerizing the oil as far as possible without yielding a gel. The viscosity of these i This method may also be preferred if it is desirable to utilize fatty acids obtained from low grade oil such as foots. However, this method does require the use of corrosion resistant equipment for at the temperature required for polymerization these acids attack ordinary metals such as iron, producing undesirable soaps.

Still a third method is to polymerize the methyl esters of the semi-drying or drying fatty acids and recover the dimer acids as hereinbefore described. In addition to the use of noncorrosion resistant equipment this method also has the advantage that lower temperatures can be used for distilling the monomeric acids from the dimer acids. An objection to the method is that the methyl esters are somewhat difiicult to split.

The choice of oils from which the dimer acids may be prepared is not critical but may-include any fatty oil having substantial quantities of poly-unsaturated acids. It is to be noted that the invention is not limited to the use of dimer acids obtained from one oil to the improvement of the same oil for it is generally possible by practicing this process to improve any drying or semi-drying oil by treating with dimer acids obtained from any other drying or semi-drying oil. Having obtained the dimer acids, they are added to the oil which is to be treated and are cooked with it as previously described.

The quantity of dimers which may be added to the oil is determined by the degree of improvement desired andthe percentage of non-polymerizable acids contained in the oil to be treated. For example, considerably more dimer, acids are required to effect a removal of the non-drying constituents of sardine oil than would be necessary to displace those in linseed oil. Generally, the addition of 5% of the dimer acids is suflicient to noticeably improve the oil, although larger quantities, at times as high as 50% by weight. of the oil to be treated, are frequently employed, especially if the oil contains considerable amounts of non-drying constituents.

It has been observed that the longer the reace as naphthenate drier. The varnish was then compared with a like varnish made from bodied lingsegd oil. The following diflerences/ were no e tion period at substantially constant temperature between the dimer acids and the glyceride the sharper is the segregation of the non-drying acids. This is revealed by the lower iodine value of the distillate. The limit on the reaction time is governed by the viscosity desired in the com-- pleted oil and as a result heavy bodied oils obtained by this process may exhibit slightly better properties than less viscous oils treated in a similar manner.

While We cannot state a full and complete explanation of the reasons underlying this improvement, it is believed that during the reaction period, prior to distillation, and while the oil is being heated with the dimer acids, cross esterification occurs between the polymerized acids and the neutral oil and monobasic acids are displaced or liberated. These monobasic acids are predominantly acids of a low degree of unsaturation as the more highly unsaturated acids are fixed in the glyceride molecule by polymerization. The fact that the dimer acids are di or higher polybasic acids may result in the formation of polymers similar to those produced in alkyd resin formation. When distillation is started the monobasic acids are distilled and any equilibrium which may have existed andwhich may have tended to prevent complete reaction of the dimer acids with the neutral oil is disturbed by removal of the monobasic acids, whereupon further reaction may proceed between the dimer acids and the neutral oil. The removal of the monobasic acids, which, in efiect, are only diluents so far as drying is concerned, leaves a residue enriched in drying components.

From the foregoing explanation of the fundamentals of the'process and from the following detailed examples, those skilled in the art readily will comprehend the modifications to which the process is susceptible.

Example I.Impromng linseed oil with linseed dimers 96 parts of distilled linseed fatty acids having an I. V.=l81.0 obtained by Twitchell splitting alkali refined linseed oil were polymerized in a still for seven hours at 300 C. under an atmosphere of carbon dioxide and then subjected to distillation under a vacuum of 10 mm. Hg to remove 43 parts of the non-polymerized acids with an iodine value of 87.5. To the 53 parts of the viscous residue were added 212 parts of alkali refined linseed oil and the mass heated to 300 C. in an atmosphere of C02 and held at that temperature for one hour and 50 minutes. The pressure was gradually reduced until nearly all of the uncombined fatty acids were removed, leaving a light colored residue having a viscosity of 47.0 poises and an acid number of 2.2. This oil was cooked into a 30 gallon varnish with a rosinmodified maleic resin to a viscosity of 2.0 poises when thinned with equal parts of mineral spirits and .4 per cent lead and .1 per cent cobalt added Ewample H.Improving soybean oil with sardine oil dimers 350 parts of refined sardine oil were heated under an atmosphere of carbon dioxide for 12 hours at 270 C. after which the temperature was increased to 290 C. and the oil polymerized for an additional 5 hours. The oil, which had attained a viscosity of 28.0 poises, was then pressure-split in an autoclave at 500 pounds pressure for 4 hours. After removing the sweet water and drying the fatty acids, there was obtained 303.3 parts of the viscous material having an acid number of 187.4. These were transferred to a vacuum still where the non-polymerized acids were removed by distillation under 6 mm. of mercury and at a temperature range of from 245-313 C. The distillate was a white solid representing 50.8% by weight of the stock and having an acid number of 212 and an iodine value of 45.9 (Hanus). The. residue was a very viscous, tacky liquid with an acid number of 103.6.

To the acids in the still were added 745 parts of refined soyabean oil and the mixture heated for one hour at 300 C. and then slowly distilled under a vacuum of 5 mm. of mercury at 280 to 315 C. to remove those non-drying acids of the soyabean oil displaced by the dimer sardine oil acids. Evidence of their non-drying characteristics was the iodine value of 108.2 obtained on the distillate. The completed drying oil had attained a viscosity of 26.0 poises during the treatment and its acid number had decreasedto 5.6.

A varnish prepared from the above oil by cooking with a modified phenolic resin, thinning with varnolene, and having .1% lead and 2% cobalt as naphthenates, was compared against a similar varnish made by using refined soyabean oil which had been heat polymerized to 28.0 poises. The following chart indicates the improvement ob-- tained by employing the treated oil.

384 parts of linseed oil were heat bodied under a carbon dioxide atmosphere until they reached the viscosity of 80.0 poises when the polymerized mass was split by heating in an autoclave at 520 pounds pressure until the acid number of the fatty acids was 186.0. The fatty acids obtained by splitting the bodied oil were dried and 300 parts were mixed with 680 parts of refined soyabean oil and the mass heated in a still to 300 C. 'while a stream of carbon dioxide was passed through. After 1 hours at this temperature the uncombined fatty acids which were predominantly of a non-drying nature were removed by-di s tillaticn under a vacuum. These fatty acids had an iodine value of 101.1 (Hanus) and they represented 135.1 parts of the original mix. The residue was a rather dark oil with a viscosity of 95.0 poises and an acid number of 8.5.

When made into a varnish of the same type as shown in Example 11 this oil revealed the following improvements over a similar varnish prepared with refined soyabean oil bodied to 95.0 oises.

Time required to cook to viscosity Effect of boiling water-l hour Minutes Treated Oil Varnish. Bodied Soyabean Oil Varnish.

Slight Whitening. Considerable Whiten- From the foregoing description of the principles of the invention and the detailed examples illustrating the typical practice of it, those skilled Example IV 500 parts of alkali refined linseed oil and 165 parts of distilled linseed fatty acids were mixed and heated to 300 C. and held at this temperature for two hours in an atmosphere of inert gas.

The fatty acids were then removed by distilling at a temperature starting at 235 C. and ending at 315 C. under 2 mm. vacuum.

168 parts of distillate were obtained, having a free fatty acid of 93.1 calculated as oleic acid and an iodine value of 136.5. The residue had a free fatty acid content as oleic acid of 1.1% and a vis cosity of 36.2 poises. A portion of this oil was cooked into a 20-gallon varnish at a temperature of 580 F. using a modified phenolic resin. The cooking time was 46 minutes. A similar varnish quired 70 minutes to cook to a varnish.

The treated oil tested alone was practically dry in 64 hours while linseed oil still showed some tackiness after 64 hours. The dried oil films were tested by immersing in boiling water for 15 minutes; the processed oil showed only a slight blueness whereas the bodied linseed showed some whitening.

The varnish prepared from the treated oil was dry in 18 hours whereas the varnish prepared from the untreated oil still showed slight tackiness after that time. The processed oil showed no trace of whitening when examined immediately was prepared using a bodied linseed oil; this reafter immersion for 15 minutes in boiling water.

The. varnish prepared from the untreated oil showed whitening of the film.

In the example above linseed acids have been added to linseed oil. The acids employed need heating the oil with a polymer of fatty acids hav-.

ing, before their polymerization, the same number of carbon atoms per molecule as the nondrying fatty acids which are desired to be removed from the said oil, and then distilling from the said oil non-drying fatty acids which have been liberated by the said polymer acids.

2. The method of removing non-drying fatty acid from linseed oil to improve the drying properties thereof, said method comprising heating id linseed oil with a polymer of unsaturated fatty acids having, before their polymerization, the same number of carbon atoms per molecule as the non-drying fatty acids which are desired to be removed from the said linseed oil, and then distilling from the said linseed oil non-drying fatty acids which have been liberated by the said polymer acids.

3. The method of treating soybean oil to improve the drying properties thereof, said method comprising heating said soybean oil with a polymer of fatty acids having, before their polymerization, the same number of carbon atoms as the non-drying fatty acids which are desired to be removed from the said soybean oil, and then distilling from the said soybean oil the fatty acids which have been liberated by the said polymer acids.

4. The method of removing non-drying fatty acid from sardine oil to improve the drying properties thereof, said method comprising heating said sardine oil with a polymer of fatty acids having, before their polymerization, the same number of carbon atoms as the non-drying fatty acid radicals which are desired to be removed from the said sardine oil, and then distilling 01f non-drying fatty acids which have been liberated by the said polymer acids.

5. The method of removing non-drying fatty acid radicals from a fatty oil of the class consisting of drying and semi-drying oils, to improve the drying properties thereof, said method compris ing heating said oil with from about 5 to 50% by weight of polymer of unsaturated fatty acids having, before their polymerization, the same number of carbon atoms as the non-drying fatty acid radicals which are desired to be removed from the said oil, and then distilling from the said oil non-drying fatty acids which have been liberated by the said polymer acid.

6. A method of improving the drying properties of a fatty oil of the class consisting of drying and semi-drying oils by removing non-drying fatty acid radicals therefrom, said method comprising adding to said fatty oil heat polymerizable fatty acids having the same number of carbon atoms per molecule as the non-drying fatty acids which are desired to be removed from the oil, then heating the oil at sufiicient temperature and for sufficient time to polymerize the added fatty acids in the oil, whereby the polymerized fatty acids become capable of displacing nonfrom the oil non-drying fatty acids which have 10 been liberated by the said polymerized fatty acids. Numbe; Name Date 2,192, 92 Barsky Dec. 5, 1999 LATIMER MYERS- 2,317,915 Jenkins 1 Apr. 27, 1943 JAMES RITZ- 2,919,507 Krumbaar May 12,1943 5 2,341,239 Percy Feb. 8, 1944 REFERENCES CITED 2,347,562 Johnston Apr. 25, 1944 The following references are of record in the HER REFEREN me of this patent: I I d 8: E 2h J 1941 CES 86-89 11 ng. em., an. P es U STATES PATENTS 1O Ind. & Eng. Chem., Jan. 1939, pages 114 11a. Number Name Date Ind. & Eng. Chem, May 1940, pages 694-7.

2,040,461 Bonney May 12, 1936 Ind. & Eng. Chem, June 1940, pages 802- 9. 2,050,930 De Groote Aug. 11, 1936 Ind. & Eng. Chem., July 1940, pages 963-9.