MODERN WAX TECHNOLOGY

TEE importance of wax in industry has steadily in- creased ever since man first learned from nature of its value in protecting and beautifying the things that he has made. The use of wax as a protective agent dates back several thousand years to ancient times when the Egyptians employed it for protection of their paintings, their mummies, and in various ways in the building of their pyramids. The uses of wax have increased since these early t i e s and as early as the first of the 16th century wax was known to he used on floors to protect and to increase their beauty. Beeswax was the most important wax a t this time. The methods of applying the wax were crude. After passing through an evolu- tionary period, wax has attained an important position in industry, not only as a protective agent for floors but also as a major constituent in dental compounds, cos- metics, pharmaceutical preparations, stencils and inks, adhesives, lubricants, polishes, photography, and numerous other important classifications.

Waxes occur in nature in various forms. The har- vesting and refining of these waxes is a study in itself. The three major classes of the natural waxes are the vegetable waxes, animal waxes, which include the in- sect waxes, and the mineral waxes. There are other minor classes that do not have the importance of the above mentioned, that is, gum-resin waxes and micro- organism waxes. Many materials now classi6ed as waxes are not true waxes but are so classed because of their waxy appearance or nature. From a chemical standpoint quite a few of the commonly regarded waxes would not live up to the definition of a true wax: a compound chiefly composed of fatty acid esters of monohydric alcohols of high molecular weight, con- taining some free fatty acids, sterols, or hydrocarbons.

The production of wax is a natural reaction which is not dependent on man. The waxes in the vegetable class occur mainly as coatings on plant leaves and stems, on berries of certain shrubs, and on grasses, with some of the rarer waxes appearing on flowers, roots, and fruit of other plants. Most of the trees or plants from which these waxes are obtained grow wild in dif- ferent sections of the world.

The value of any wax to industry is dependent on its availability in quantities, the ease of its gathering and refining, and the properties it possesses. Probably the most important property of a wax to be considered is its hardness. Industry is continually trying to find harder waxes than the ones now available.

VEGETABLE WAXES

Carnauba. Probably the most important wax in

HUBERT W. JENKINS and HAROLD B. FRIEDMAN Zep Manufacturing Corp. Atlanta, Georgia

the vegetable class is the well-known carnauba (k*- nofi-ba) wax obtained from the leaves of a palm which grows almost exclusively in Brazil. This tree grows wild mostly along the banks of rivers and lakes. Its growth is very slow and even after fifty years it rarely attains a height of more than forty feet. Like most palms, the bark is rough and scaly and the leaves grow from long stems in a fan shape. The wax forms a continuous film over the surface of the leaves and serves to conserve moisture for the preservation of the tree during the dry seasons. The wax is harvested during the dry season by native workers, usually share-crop- pers, who cut the trees with long sickle-like knives. The stems are cut from the leaves and the leaves are carefully transported to one of their local drying ter- races where they are sun-dried. The wax is loosened by the drying and the leaves are then taken to he threshed in a shed where there is no air stirring. The leaves are first shredded with special knives which cut the ribs apart and allow the leaf to be ripped apart to loosen the wax. The leaves are then beaten across sawhorses to remove all the wax dust.

Since the dust is so light there can be no passage of air through the shed that would result in a loss of wax. Three workers can handle about 4000 leaves per day. The dust from the leaves is then melted down and strained to remove some of the impurities. A full five-gallon can of powder will usually melt down to about a quart of molten wax. After the wax hardens it is broken into lumps and shipped to the coast for re- fining and export. The yield of wax varies with the age of the tree, the locality, and the amount of rain that season. Less wax is produced during a rainy season than during a dry season. The average yield per leaf is about five grams. Since there are usually less than twenty leaves cut from a tree per year it takes about five carnauba palms to produce one pound of wax per year. There are about 50 to 75 million trees produc- ing. Of this, about 75 per cent of this production goes to the United States.

There are two different classes of carnauha wax with several grades of each class. About 30 per cent of the total production is obtained from the olho leaf. This is the young unopened leaf that grows upward from the center of the palm. A very small amount of almost pure wax known as "flower" is obtained from the melt of this leaf. Most of the remaining wax is very light in color and is known as Yellow No. 1 and Yellow No. 2. There is some inferior wax recovered from the residue of this purer wax. The remaining 70 per cent of the wax is produced from the palha or open leaves of the

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palm. The wax obtained is a darker color ranging from a greenish yellow to almost black. From the palha leaves are obtained the different grades known as North Country wax. There are several grades of wax from the palha leaves which are classed according to the color or the moisture content. North Country Chalky wax has about ten per cent of water added dur- ing the refining process. The greatest advantage of the wax from the olha leaf over that from the palha leaf is in the color, the chemical and physical constants of both being about the same.

Carnauba wax is the hardest wax known and has an average melting point of 84°C. One of the biggest uses is in water-emulsion floor waxes, with leather dressings and shoe polishes following closely.

The carnauba tree is versatile, not only is it important for its wax production but also for the many uses found for the bark, wood, leaves, and roots of the tree. The wood is hard and resists attack by water. It is useful in building and lasts a long time when nsed as pilings and bridges. The leaves are used for thatching roofs and for making window shades and hats. The roots find use in certain medicines and the young shoots are used for food and for making a kind of vinegar.

Ourieuri. Another wax that has become available in the last few years is ouricuri wax, which resembles carnauba wax to some extent in its physical character- istics. This wax is obtained from the under side of the leaves of a tall palm tree which grows in the north- eastern states of Brazil. The wax is scraped from the leaves with a knife and the powder is caiefully col- lected. The powder is melted, poured into forms, and cooled. 'The process of collecting resembles that for carnauba but is much cruder and as a result much of the ouricuri shipped has a large amount of impurities. Onrieuri is used as a substitute in some industries for carnauba but due to its high resin content it is not always a too desirable replacement. In generaa, ouricuri is a dense, hard, brittle wax with a melting point of about 83'C. Unlike most other vegetable waxes, which have a lag of about 50" between the melting point and the setting point, this wax has a lag of about 12'. Reports indicate that A refined grade of ouricuri is available. One reason that this wax is more difficult to refine is that its higher density will not allow the trash to sink to the bottom as other waxes do. The refining is done by digesting the scrapings in a caustic soda solution with the aid of steam. The wax, relatively free from vegetable matter, then rises to the top. The refined wax has a lower saponification value than the crude grade. Like carnauba, this wax can be used to increase the melting point of paraffin and other low-melting waxes. A large amount is nsed in inks and carbon paper with smaller amounts appearing in polishes and shoe creams.

Cauassh Wax . A newcomer to the wax field, cauassd, was discovered recently by Knaggs (4) while on a wax-hunting expedition. This wax forms on the big leaves of a plant that grows on the Amazon River near GurupB, Brazil. Preliminary investigations indi-

cate that this wax may he the carnauba substitute that the industry has been looking for, although it may be a long time before it becomes available for use. The big leaves are cut off and allowed to dry in the sun. The wax flakes off and is then melted down and poured into molds or containers. The physical properties re- semble carnauba in that it is hard, brittle, and has approximately the same melting point and oil reten- tion. When used as a polish and buffed the cauassd wax gives a very good luster. Although the yield of carnauba is higher, the big leaves of the cauassd can survive more clippings, can be harvested a t any time during the year, and are much easier to grow. It is quite possible that since the cauassd can be cultivated easily the plant may he grown on plantations in Brazil.

Candelilla. Candelilla wax is obtained from a msh- like weed that grows in the dry regions of northern Mexico and southern Texas. Most of the production is from MexicE, where the weed grows wild. The plants occur in bunches of leafless, reedlike stems 2 to 4 feet high and about ' / r inch in diimeter. The wax forms a coating on the entire plant except the root. The plants are pulled up by hand or cut off a t the ground and taken by wagon or burro to the nearest extraction works. Two methods are used to recover the wax. The older process is to boil the weeds in acidulated water in tanks capable of holdmg about 500 pounds of the weeds. The plants are kept below the surface of the water and as the temperature is raised the molten wax rises to the surface where it is skimmed off and transferred to lead-lined tanks. The crude wax is then remelted and kept a t the boiling point to remove all the water. After all the water is removed the wax is drawn off into pans where it is permitted to settle. The trash and dirt settle to the bottom and are scraped off. The wax is then remelted and resettled, after which it is heated again to reduce the moisture content to less than 1 per cent. After being cooled in pans it is broken up and sacked up for the market. The yield of wax from the weeds is usually about 21/2 per cent.

The more modern way of recovering the wax is by a solvent process. The plants are first allowed to dry, then they are pulverized and put into solvent tanks con- taining petroleum benzine and the wax is dissolved. The solution is then filtered and distilled. The sol- vent is recovered and used again. The remaining wax is refined and cooled ready to ship.

Candelilla is very hard and brittle. It is com- posed of about 50 per cent hydrocarbons with smaller amounts of alcohols and esters. I t is used in some polishes and as an insulating material. It does not emulsify or saponify as easily as carnauba. The melting point is about 68%.

Sugarcane Wax . Since the first of the twentieth century attention has been focused on the refining and usage of sugarcane wax for commercial use. Investi- gations proved that this wax can be produced reason- ably and that it is a good competitor for other high melting waxes. During a period of about ten years, starting in 1916, a wax recovery plant in Natal, Union

184 JOURNAL OF CHEMICAL EDUCATION

of South Africa, shipped several thousand tons of sugarcane wax. Due to a decreased demand for the wax the plant was closed and not until lately has there been any attempt to produce the wax commercially.

The wax occurs as a thin white layer on the exterior of the stem of the sugarcane with most of it being close to the nodes. Although the amount present varies greatly it rarely exceeds 0.5 per cent of the weight of the cane. It is known that the conditions under which the cane is grown affect the amount of wax, but it is not known why the wax occurs. When the cane is being milled, about 40 per cent of the wax is loosened and stays in the juice as suspended matter. The rest of the wax remains in the bagasse and would have to be recovered from that. Several methods have been pro- posed to extract the wax from the cane: extraction by hot water before milling of the cane; extraction from the filter cake by solvents; extraction from the bagasse by digesting with caustic; and extraction from the juice by centrifuging. Probably the best method would be to use a selective solvent treatment on the filter cake and to extract the wax along with the fatty material present. The fatty material could then be removed by another solvent treatment which would leave the wax. The solvent would have to be removed and reused or the cost of the operation would be pro- hibitive. The wax recovered from this type of opera- tion is hard and rather dark in color. In order to in- crease its usefulness it would have to be refined to a lighter color. Refining of the wax may be carried on by an alcohol treatment. The wax is digested with alcohol and the extracts treated with decolorizing agents and filtered. The wax is then recovered by dis- tillation, giving a light-colored hard wax. The alcohol insoluble matter is dark-colored and seems to be a kind of pitch.

The melting point of this wax is usually around 78°C. It is hard and has a relatively low saponification num- ber. It has been estimated that about 60 million pounds of crude wax are discarded annually in a11 of the cane-raising sections. With the research being carried on a t the present, it seems that the time is not far away when this wax will find its place and be used in industry as a competitor for carnauba wax. Sugar- cane wax can be produced in Cuba, Argentina, East India, South Africa, Australia, and the United States.

Esparto Wax. Esparto wax is produced from es- parto grass, a tough grass that is found principally in Libya, Tunisia, Algeria, and Southern Spain. The plant consists of a cluster of stems with feathery leaves grdwing out from them. Roving bands of Arabs gather the grass and sell it a t several different stations where it is shipped to Scotland. The grass is dewaxed and used in papermaking. Due to the small amount of wax recovered from the grass, it had not been profit- able for the individual manufacturer to try to recover the wax. However, a central plant was set up and all the manufacturers sent the dust obtained from the wax to this mill. The wax is extracted with solvents on the principle of the Soxhlet extractor, the solvent is dis-

tilled off and the wax recovered. The average yield is about three pounds of wax from a ton of grass. Esparto wax is a hard, ea.sily saponifiable wax with a melt,ing point of about 76'C. I t is much used in polishes due to the hard, lustrous finish which it leaves. It is com- posed of about 65 per cent esters, 20 per cent alcohols and hydrocarbons, the remainder being free wax acids.

Japan Wax. Japan wax resembles a fat more than it does a wax. It is obtained from the berries of a small sumac-like tree which grows in Japan and China. The wax occurs as a coating on the kernel of the berry or nut. A tree produces during a span of about 100 years and has a yield of 30 to 150 pounds of nuts per year. The nuts yield about 15 per cent crude wax. The wax melts a t about 50%. and finds many uses in industry in candles, rubber vulcanization, polishes, and in textile finishes. About 9000 tons of the wax are produced each year in Japan and China.

Cotton Wax. A small amount of wax has been ex- tracted from raw cotton fiber by a solvent extraction process. Some work has been done in investigating the properties and constants of cotton wax and there is a possibility that this wax may some day be of com- mercial value. The crude wax has a dark color wit,h a disagreeable odor. The color may be lightened and the odor reduced by refining with activated carbon or fuller's earth. The wax melts a t about 70°C. and has about the same consistency of beeswax. It is com- posed mainly of esters and alcohols. Probably the reason that so little work has been done previously on this wax is the small yield, about 0.4 to 0.7 per cent. However, a variety of Arkansas green lint cotton has been reported containing from 14 to 17 per cent wax. Investigation has shown that this wax should meet the requirements of a medium-high melting wax since it is compatible with other waxes and resins and can be compounded into many of the products for which wax is used.

Miscellaneous Minor Waxes. Small quantities of wax have been extracted from the leaves of the tea shrub but due to the small amount produced there has been no demand for it in industry.

There are several other waxes in the vegetable class which have been studied in the laboratory but which have not been produced in large enough quantities to warrant investigation for use in industry. Some of these waxes occur as coatings on flowers, fruits, seeds, and berries.

MINERAL WAXES

Parafin. In the mineral wax class occurs probably the most familiar and most widely used of all, paraffin wax. This wax is obtained from a crude petroleum fraction known as paraffin distillate. This distillate is obtained from a residue which remains after the pe- troleum has been distilled to yield its naphtha and burning-oil content. The wax distillate is treated with sulfuric acid then washed with water and caustic soda. During this processing the mixture is kept liquid by steam coils and settling takes place. The

APRIL. 1949 185

mixture is then chilled to form crystals of paraffin. This mixture is then filtered under pressure in re- frigerated rooms and the oil which drains off is used as a lubricating oil. If a refined paraffin wax is desired the cake is melted, solidified, and submitted to higher pres- sure a t elevated temperature. Further refinements are possible by washing with solvents and filtering through filter mediums. A process of sweating re- moves most of the remaining oil in the wax.

The yield of paraffin wax from petroleum is usually from 3 to 6 per cent, depending on the source of the oil. By far the largest use of paraffin is for coating paper or paper products, with the remainder being largely used in candles or other applications. It is used to adulter- ate some of the higher priced waxes, mainly ozokerite. Paraffin wax is a mixture of hydrocarbons and is not a true wax, but due to its waxy appearance and nature it is classed as such. Different grades of paraffin melt from 40 to 60°C.

After the paraffin wax distillate has been removed there is left in the still a residue consisting of heavy lubricating oil, asphalt, and microcrystalline wax. The asphalt is removed by treatment with sulfuric acid or solvents. A petrolatum is obtained from the residue by diluting with solvents, chilling, and cen- trifuging. Another solvent is then added to the petrolatum and the mixture heated, then cooled to pre- cipitate the w&-which is then filtered through canvas. The oil content of microcrystalline wax is usually a great deal higher than that of paraffin wax. Paraffin wax has a large crystal structure as compared to a very small crystalline structure for microcrystallime. The microcrystalline is much more plastic than paraffin and has a higher melting point ranging from 60' to 90°C.

Montan Wax. Montau wax is a bituminous wax which occurs in certain types of coal and lignite in cen- tral Germany. The coal is mined and the wax ex- tracted with various solvents. The solvents are dis- tilled off and the wax remains as a hard mass. It is very hard, brittle, and dark brown in color but can be refined to give a light-wax resembling beeswax. It con- tains a fairly large amount of resinous material. In the crude form Montan wax melts a t about 8OoC., but after bleaching the melting point is lowered. Due to its hardness, good results are obtained in polishes and printing ink.

Ozokerite. Ozokerite is a hydrocarbon wax which is mined mostlv in eastern E u r o ~ e from veins of wax that usually occur within 25 y a r h of the surface of the earth. Some mining of the wax has been done in Utah and Texas. It resembles paraffin wax in ap- pearancle and composition but is not as brittle or as slippery as paraffin. Much of the ozokerite is adulter- ated with paraffin wax to reduce its cost but if it is desired to increase the melting point a small amount of carnauba is added. It is useful in solvent type polishes, candles, and insulation.

Ceresin Wax. Much of the ozokerite mined is freed from impurities to give a light-colored ceresin wax,

although a mixture of paraffi wax and beeswax is also known as ceresin. Due to the adulteration of nearly all ceresin wax it is difficult to assign to it a definite composition. When obtained from ozokerite it varies in color from yellow to white, according to the degree of bleaching. The ceresin is filtered and agitated while cooling to form a cloudy product. The uses for this wax are much the same as for paraffi or ozokerite.

ANIMAL AND INSECT WAXES

Beeswax. In this group beeswax is by far the oldest and most used. The use of this wax has been traced hack to the early Egyptians, possibly even earlier. It was thought a t one time that it had certain holy powers which account for its use in religious candles. The wax is produced by the worker bees as a digestive secre- tion formed in the stomach from the honey and the flower pollen. It is exuded as a liquid and hardens to a scale. It is then removed by the bees, worked to a paste and used for the construction of the honeycomb. The comb is melted, strained, and the honey removed by centrifuging. The wax can be bleached by shred- ding and then allowing it to remain in the sun for a period of time. The color of the crude wax depends largely on the color of the flower that the bee has been visiting but the bleached wax is usually white or light yellow. The wax melts a t ahout 6Z°C. and is com- posed chiefly of cerotic and melissic acids with the cor- responding alcohols. Beeswax is used in many in- dustries and its production and distribution is almost world-wide.

Chinese Insect Wax . Chinese insect wax is deposited on the leaves and stems of certain types of ash and privet trees in China. The insects do not breed in the same districts as the trees and the larvae have to be transported about 200 miles to the area where these particular trees grow. The branches of the tree are covered with the deposit from the insects until there is a continuous crust over the tree. The insects must then find another tree or die. The wax is scraped from the branches, thrown into boiling water and the clean wax skimmed from the top and cast into molds. It takes about 1500 insects to produce 1 to 2 g. of wax. It is used extensively in the manufacture of candles and as coatings on paper and cloth.

Shellac Wax. Shellac wax is obtained from shellac which is deposited in a manner similar to that for the Chinese wax. The wax is removed by a selective sol- vent treatment and is very useful as an insulating ma- terial.

Spermaceti Wax . One of the chief animal waxes is spermaceti, which is obtained from the head of sperm whales. The whales have huge oil-filled cavities in their heads which are carefully emptied by the whalers. After standing for a period of time, the wax in the oil begins to crystallize out in needle-like crystals. The mass is submitted to heavy pressure to remove the oil from the wax. It has a melting point of about 43°C. and becomes rancid on aging. The standard candle for measuring light intensity uses spermaceti because of the

186 JOURNAL OF CHEMICAL EDUCATION

bright flame it gives. The wax is a source of cetyl alco- hol. As pointed out by Knaggs, it is interesting to note that the chemical composition of spermaceti, which is recovered from the largest mammal, is about the same as Chinese insect wax, which is deposited by the smallest wax-producing insect.

Other Waxes. There are many more waxes that are not of commercial value because of the small amounts available. Some of these are obtained from the petals of flowers or fruits.

CONCLUSION

The future of waxes .is very good if the past is any indication. It has been said that we live on a film of wax, which is very true if one stops to consider that it is Found as a covering on most of the floors we walk over, and as a beautifying and protective agent on our shoes as well as being used directly or indirectly in nearly every occupat,ion or industry that we come in contact with.

Up to the past few yeam, the substitutes that chem- ists have had to offer could not compare with the

carnauba or other hard waxes, but now there are several synthetics that offer some of the same properties as these waxes with some more desirable qualities of their own. A synthetic wax is a t au advantage over some natural waxes with about the same qualities, because of its uniformity, lack of impurities, and controlled manu-. facture. It is quite possible that the research going on now will show some very important uses for sugarcane wax, which might give carnauba some competition in the polish field.

(1) BALCA, R. T., "Wax and Fatty By-Products from Sugar Cane," Technologics1 Report Series No. 3, Sugar Research Foundation. Inc.. New York. 1947. , ,

(2) BENNETT, H., "Commercial Waxes," Chemioal Publishing~ Company, Ine., New York, 1944.

(3) JOHN, W. D., "Modern Polishes and Specialties," Chemical Publishing Company, Inc., New York, 1947.

(4) KNAGGS, N. S., "Adventures in Man's First Plastir," Reinhold Publishing Corp., New York, 1947.

(5) WAZTA, A. H., "The Chemistry and Technology of Wsxrs," Reinhold Publishing Corp., New York, 1947.