US2235462A - Manufacture of an improved tall oil - Google Patents

Description

Patented 18,1941

This invention rent to a processor resume crude tall oil. lit is well known in the wood pulpin: that when the black liquor obtainedi'rom the pulping of coniferous woodby v the sulphate procws is evaporated, a scum. com-' mcnly mown as tall oilsoep, separates and floats upon the of theblack liquor; scum is not present on the liquors o-s t y obtained before the evaporation step, but]: pro; du' probably by'a salting out erect, the liquor becomes concentrated. In present puoctice the scum of tall ,oil soap is skimmed oil of the;

evaporated black liquor sndeither used as to produce crude sodium salts of tell oil or more frequently the scum is treeted'totformfcrude (chemical constituents of the exudation are comtall oil. The crude tell oil soepis usually treeted withdilutesolutions of sulphuric acid or sodium acid sulphate to liberatethis crude tall oil;

In orderto facilitate the sepamtlon'ofthe mixq ture into two layers, ,the,use of with the aoidto increase" thedens'ityof the I water leyer iscommon practice; Aiter the acid.

f hasreaeted the crude tall oil is theupper layer and can beseparated-from the lower aqueouszs sodimn sulphate layer byodeoantstion or any other suitable means commonly used in the'chem-' icaiindustries. i

Crude tall oil, prepared in the above manner,

, is of limited usefulness in industrial imitation.

an It posseses the "foul odor typicalof suljphwte black liquors; "it, of darkcolor;

and. an even greater; objection is its tendency to vpartially, P oducing-is thick couspastedifilcult to pump anddiulcultfto re- I move t omshlpping' 'contalners. Mllstendency to crystallize varies depending upon the" history of the wood from which it originates Conse quently, crude tall oil lacks uniformity in chemical composition'and physical characteristics.

It is the purpose {of ithisinvention to provide 9, simple economical process by which taliofl can a e mn e m w mi e hy ical appearance with an improved odorsnd colori'as compared to the crude oilnow found in commerce. The improvedtall oil producedin accordence with'in P c to be deswlbedhemmatter has been found to be free of those cryfs talline which occurin the crude prod- H v q q q crude tall on showsmoreorystalformaltion than does the untreated product. r 0

not and consequently is a smooth uniform oily Pro uct. 'It*'is" capable of standing in storage I indefinitely without crystallization."

'To understand the advantages offered by this 7 invention it is essential to appreciate the lack of uniformity found in tall oll resultinz from the 5 variations inthe kind or woodused in the Q88, and more panticularlyfrom mum in the history of this, wood. when southern pine is 1 pulped by the'sulphate process promptly after it is cut green, yields a tall oildifterent from' that produced the, loss are puiped after I they have been out and exposed to air for months. When apine tree is out it exudes resmous matter in an attemptto seal the wound. This necessarily places "a. large portion of the resinous contentlof'tl'lewood in withthelo' air. and utter longexposure the air penetrates the ,wood and oxidizes some of the constituents plex and of many types, the'che'mical changes by oxidation srenot entirely understood.

Experience has 'proyed'also that in the of fattyacids to the resin acids is considerably b1813 thanin the tall oilobtained by pulping wood whichhas been cut inthe winter when' the sap is out of the tree. Because of these variations me the wood used, crude m1 oil so: u

' wood; These variations have retarded the ingo dustrial application of. crude tall oil.

Experimentation has shown that sbietlcacid toh'ydrOXyabieticacid under mild 0x1- dlzinmconditions. This can occur to a certain extent'when the coniferous woods'tends exposed u to air utter being, cut. Hydroxyebietic acid is less soluble .in fatty acid than is abietic and consequently. it tends to crystallize out of crude tall oil. crystals probably act as a. nuclei for the crystal growth of other resinous P oducts 0 present in the nude telloil. In' any event hydmxyebietic acid is believed'to accountfonthe partial solidiflwtlon of crude tall oijldue to'crys- It is one of the objects of this invention to eliminate the presence '-of hydroxyabietic acid and other oxidized analogous orilrelated' com pounds and derivatives bychemlcally processing the crude tall oil; 11 heat the crude telloil, -'at u r wood cutln the spring of the year the ratio a first rather slowly, to drive oil water which is not chemically bound and some low-boiling odorous I then continue the heating progressively until a maximum temperature of 250450" 0. has been attained. I usually pre fer to maintain a temperature of at least about 300 for atleast an hour inor'der that the chemical reactionswhich occur during may be substantially completed. Care is taken that the tall oil does notcome in contact with air during the heating operation and. that the vaporized products are removed. After the mei chanicaily held water has been driven away the volatile products coming from the heated tall oil show an increasing volume of vapor as the temperature rises. This vapor is substantially all water, formed by pyrolysis, and also contains sulphur bodies coming from the ligninand other sulphur compounds always present in crude tall. oil as impurities. I

A variety of procedures may be employed in the heating operation as'will be apparent to one 7 skilled in the art. I have found it advantageous toheatthetalloilintwosi:ages,firsttoaternperature in the neighborhood of 100 C. to remove free water and readily vaporizable con- "stituents and then to about 325' C. to effect the chemical changes described. Each heating stage advantageously is accompanied by a flow! U ing of the heated material. in a thin layer over a splash plate or the like to facilitate the re-' moval of volatile constituents. In some in.- stances I have found it desirable to maintain a temperature of 325 C. for aboutil hours.

Ifthetalloilisdryatthestartthelossof' tall oil as a result of theheat treatment gener found to be changed from a yellowish-,brownto an iridescent green, 9. color similar to that ob-' served in petroleum lubricating oils. Also the odor is decidedly improved'because of the subally does notexceed 5%.

The heating of the crude tall'dl-rmlts in a product which will be found to havaehanged chemically and physically in characteristics. In the first place, its color after cooling will be stantial loss ofsulphur compounds found in crude tall oil. a burnt or charred organic substance. This odor, I believe,.is due to the charring of small traces of lignin usually present in tall 011. Although it is not necessary in carrying out my process, I may remove this burnt fodor by, treatment with hydrogen in the presence of a catalyst in the usual manner common in hydrogenation of oils. While one may continue the treatment with sufficient hydrogen to hydrogenate the fat-.

ty and resin acids, as well as the odorous materials, this is not essential as, the odorous materials appear to be converted to non-odorous products rapidly by hydrogen treatment. I also appreciate the possibility of removing these odorous materials by many of the known methods used in the art,- such as superheated steam, activated carbon, etc. Filtration for the removal of solid matter is not necessary. .The constituents which normally result in the deposition of solids j from crude tall oil apparently are destroyed or rendered more soluble or removed by. distillation during the heating andvaporizing treatment described.

Probably the major change which occurs in crude tall oil when processedas described is the lowering of the resin acid contentof the oil and the simultaneous substantial increase in the unsaponifiable content in the oil. Merely, as a mat- The derived odor is suggestive of V asssaes ter of possible explanation I ofler the following theory to account for this chemical change during the process. Hydrozvabietic acid has been found to be unstable at temperatures of 200' C. and higher. It 'is believed that the oxidized products in crude tall oil, among'which is probably hydroxyabietic acid, become dehydrated during the heating process. This produces anhydrohydronabietic acids and possibly po ymerized or isomerized colophonic acids. Evidence indicates that some of the carbonyl groups of'these resin type acids are destroyed in the heating process. Any one ofthe above conditions would account for the lower acid number found on theheated product, as well as the increased unsaponiflable value. It appears also that abietic acid if present probably is converted to the more stable pyroabietic acid.

The following table shows the changes produced by the above described heating and va- Theimproved'odor, together with the relatively increasedpel' cntage of fatty acids, has rendered the, product suitable for use in the manufacture of such commercialarticles as soaps, printinginks,

greases, rubber compounds, etc, where the crude tall oil hasnever been found adaptable. I

After deodorizlng with hydrogen as described above theproduct' hasa definitely sweet fatty odor fax-more desirable than the foul odor of the crudetalloil.

The product is characterized physically, by its improved odor compared to tail oil and by its freedom from any tendency to crystallize'o'n standing. Chemically it appears to be, most distinctly characterized by its freedom from hydroxy abietic acid.

I claim:

1. Process'for the production of refined tall oil which is a smooth. uniform, oily liquid capable of prolonge'dstanding without crystallization which consists in raising the temperature'of, crude tall oil from coniferous wood to a maximum between about 250 C.'and about 350 C., said heating operation'serving to vaporize and expel mechanically associated water, water produced by Pyrolysis, low boiling odorous materials and sulfur'compounds,

. the loss by vaporization from tall oil which is dry at the beginningof the heating operation generally not exceeding 5 and separating the residual liquid from the vaporized materials.v

2. Process as defined in claim 1 in which the crude tall 011' is first heated slowly todrive of! mechanically associated water and some low boiling odorous materials and then is heated progressively to a'maximum temperature of 250-350 C. and the heating iscontinued at said temperature for a time suflicient to permit completion of chemical reactions occurring at said temperature.

' 3. Processes defined in claim 1 in which the heating at said maximum temperature is carried out at atleastabout 300 C. for at leastabout 1 hour.. y

4. Process as defined in claim 1 inwhich the heating at said maximum temperature is atabout 325 C. for about 3 hours.

l needed:

1 in whiclialr isaboutfos aby weight or the weight of the dry "crude tail oil and containing the organic products oi p rroiysiaot the hydroxy abietic acid content of the crude tall oil. 1

8. Refined tall 011 as defined in claim '1 having,

as compared with crude tail oil lower acid number, saponification number, resin acid content and iodine number and higher fatty' acid content and unsaponifiabie content. 9. Refined tall oil as substantially free of hydroxy abietic acid. HAROLD R. 'MURDOCK'.

defined in claim v being 10