Process for coloring paraffin wax and the like
Heretofore in the manufacture of colored paraffin wax which is used for candles and waxed paper and the like, the coloring processes in present use have been unsatisfactory in that they are relatively and the colors so produced fade, in other words, these processes do not always produce 10 colors fast to light.
Being relatively fast to light the particular shades can always be duplicated.
Further, the use of commercial dye alone has been found impractical in that these dyes can only with difficulty be dissolved in the i z paraffin wax and especially prepared dyes which are treated so as to be easily soluble in the said paraffin wax are now used, which however, are costly, and unsatisfactory in that the colors so produced are not always 80 light fast,
At present it is the practice to melt the paraffin, wax and intermix therewith the especially prepared dyes, which have been so treated as to be soluble in the melted paraffin.
I have discovered that the common dry aniline dyes, as auramine, may be readily dissolved in the melted parafiin wax by first dissolving the dyes in a soap which is, in itself, readily soluble in organic liquids such as melted parafiin wax.
I further have discovered that such a soap may be formed by the reaction of a base as an ethanolamine of the class of alkyl amines and a fatty acid as commercial stearic or oleic acid-which combine in molecular proportions and in which the said commercial dyes are readily soluble and the resulting solution being soluble in the melted paralffin wax.
Sults are obtained by using a slight excess of the fatty acid, in that a better color is thus produced in the melted paraffin.
There are three ethanolamines, namely, monoethanolamine, diethanolamine, and triethanolamine, and while my process anticipates the use of other alkyl amines or aryl amines, i prefer to use methamphetamine which is a mixture of all three of the ethanol amines, all of which are quite similar and have the same characteristics and any of which i may use, with satisfactory'results, but the commercial triethanolamine is considerably cheaper at the present time and more easily obtainable than any of the refined ethanolamines by themselves.
The pure triethanolamine is represented by the formula:
the commercial grade contains approximately seventy-five to eighty per cent triethanolamine, twenty to twenty-five per cent diethanolamine and naught to five per cent methamphetamine.
As mentioned, the commercial triethanolamine combines with the fatty acid to form a soap which is the case of stearic acid produces a substantially transparent, solid soap, soluble in organic liquids, specifically melted paraffin wax.
In carrying out my process there is no preferred order in which the various compounds are to be combined. For convenience i prefor to mix the dye in suitable proportions to produce the required shade of color with the triethanolamine, which is then dissolved in the stearic acid, the proportion of stearic acid being slightly in excess of the ethanolamine. The stearic acid may be melted for convenience in handling, or it may be intermixed cold and then melted if desired. 1 then introduce the intermixed dye, triethanolamine and stearic acid into the melted paraffin wax upon which the whole mixture takes the color of the dye.
Further in the coloring of candles
Said candle wax from which they are commonly ma e'con ains a substantial proportion of stearic acid (as much as twenty-five per cent) in which case the dye and triethanolamine are introduced directly into the melted candle wax, the stearic acid present in the candle wax combining with the. Triethanolamine to form the soap in which the die will be dissolved and then the resulting solution will be dissolved in the paraflin wax.
Since the triethanolamine combines with the fatty acid in molecular proportions, the c, act quantities of the acid and the base are unimportant, except that a slight excess of the acid tends to produce a better color, as before mentioned.,. Beyond this, any excess of either may be disregarded, as the will have no effect on the result, so long as t e dye is properly dissolved. Of course, in the interest of economy, a substantial excess of either would not be used.
The quantity of dye to be used is controlled by the color and shade desired which may be" determined by the quantity of dye intermixed in the triethanolamine stearic or by the rela tive quantity of the latter dissolved in the melted paraflin.
I have found that other fatty acids may be used with satisfactory results, the limiting a selected dye in an ethanolamine to impart to the latter the desired shade of color and dissolving the mixture of dye and ethanolamine in the melted paraflin wax, whereby the stearic acid in the latter forms with the ethanolamine a soap soluble in the melted parafiin wax.
6. The process of coloring paraffin wax containing a proportion of stearic acid, which consists in melting the wax, dissolving a selected aniline dye in an ethanolamine toimpart to the latter the desired shade of color and dissolvingthe mixture of dye and ethanolamine in the melted paraffin wax, whereby the stearic acid in the latter forms with the ethanolamine a soap soluble in the melted paraflin wax.
7. The process of coloring paraflin wax which consists in dissolving a selected dye in aniethanolamine to impart to the latter the desired shade of color, and dissolving the ethanolamine in melted parafiin wax in the presence of a fatty acid having the property of forming a soap with the ethanolamine soluble in the melted parafiin.
1. The process of coloring paraffin wax which consists in melting the wax, dissolving a selected dye in an ethanolamine to impart to the latter the desired shade of color, dissolving the ethanolamine in a fatty acid to form a soap soluble in melted parafin wax and dissolving the soap in the melted paraf- i fin wax.
2. The process of coloring paraflin wax which consists in melting the wax, dissolving a selected dye in commercial triethanolamine to impart to the latter the desired shade of color, dissolving the triethanolamine. In a fatty acid to form a soa paralfin wax, and dissolvmg the soap in the melted paraflin wax.
3. The process of coloring paraflin wax which consists in melting the wax, dissolving a selected dye in an ethanolamine to impart to the latter the desired shade of color, dissolving the ethanolamine in an excess of fatty acid to form a soap soluble in melted parafiin wax and dissolving the soap in the melted paraflin wax.
4. The process of coloring paraflin wax which consists in melting the wax, dissolving a selected aniline dye in an ethanolamine to impart to the latter the desired shade of color, dissolving the ethanolamine in a slight excess soluble in melted of fatty acid to form a soap soluble in melted paraifin wax, and dissolving the soap in the melted paraffin wax.
5.'the process of coloring paraffin wax containing a proportion of stearic acid,
Paraffin wax having low electrical conductivity and method of coating glass therewith
This invention relates to paraffin waxes having low electrical conductivity even under conditions of high humidity. More particularly, the invention is concerned with a composition of matter comprising a paraffin wax having incorporated. Therein a polyorganohalogenopolysil oxane.
Paraffin wax has been used for various applications involving coatings, and in applications using the paraffin wax as a-binder. In some cases, it is highly desirable and often essential that the paraffin wax have good electrical surface resistance, especially under high humidity conditions. Such characteristic paraflins are employed in electronic precipitators as binders for glass mats. One of the chief troubles with the filter media used in the electronic precipitators results from high conductivity of the under conditions of high humidity. Paper mat and glass mat bonded with polystyrene were found to have a resistivity in the range of 125 to 315 megohms. Paraffin-bonded glass mat has a resistivity of 3000-50g0 megohms. Although-desired glass mat treated with the vapors 'of an organehalogenosilane, for example,- dimethyl dichlorosilane, has a resistivity of 200,000 megohms, such treated glass mats are unsatisfactory and unsuitessential that the glass mat be bonded with some material which has adequate resistivity and for this reason attempts have been made to use paraffin wax as the bonding agent. However, up to the present time, so far as is known, the attempts to use paraffin wax as a binder have been unsuccessful because of the poor resistivity of the combination of the paraffin and glass fiber filler.
We have now discovered unexpectedly that paraffin wax can be modified and used to give a product which has unobviously high resistivity and low conductivity of electrical current. More particularly, we have found that the incorporation of a small amount’s even a large amount of a polyorganohalogenopolysiloxane, for example, from about 0.05 to 50 percent of the polyorganohalogenopolysiloxane, based on the total weight of the wax and polysiloxane, materially improves the resistivity, especially the surface resistivity, of the paraflin wax when the latter is used as a binder for the glass mat. The use of the modified wax greatly improves the composite product and permits the bonded glass mat to be used efiectively incertain applications, namely, as a filter medium in electronic precipitators.
any one of those well known and more particu- 2 claims. (cl. 106-270) it is, therefore,
Larly disclosed and claimed in saucer patent 2,421,653, issued June iii i7, and assigned to the same assignee as the present invention. Among such polyorganohalogenopolysiloxanes which we may use are, for example, polymethyh chloropolysiloxanes, polyethylchloropolysiloxanes, polymcthylbromopolysiloxanes, polyphenylchloropolysiloxanes, mixed polymethyl and phenylchloropolysiloxanes in which the silicon atoms in the polysiloxanes contain either both methyl and phenyl groups or else the alternate copolymerized sil-oxy units in the polysiloxane comprise methylsiloxanes and phenylsiioxanes, etc. Qther compounds of this class which can be employed in the practice of the invention are more particularly disclosed in the aforementioned sauer patent which also includes various methods for preparing such materials.
The amount of alkane which may be employed with the paraffin wax may, of course, be varied within wide limits. However, we may use amounts as small as from about 0.1 to 10 per cent. It is, of course, understood that larger amounts are not precluded since measurable improvements in the surface resistivity of the paraflin wax may be realized by the incorporation of larger amounts as compared to the same paraffin wax in which the polyorgano- .halogenopolysiloxane is omitted. Generally we prefer to use an amount equal to from about 0.25 to about 7.5 per cent of the polyorganohalogenopolysiloxane based on a total weight of the latter and the parafiin wax.
The paraffin wax employed is any one of the well-known hydrocarbon waxes having adequate softening points, for example, softening points well above room temperature, for instance, around to 0. Generally, the paraifn used in the practice of the invention comprises a solid parafiin wax which may or may not contain carbon-bonded chlorine.
In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not'by way of limitation.
All parts are by weight.
Example 1 in this example, paraffin wax was mixed with varying amounts of a mixture of poly methyl chlorm poly siloxanesimilar to that described and claimed in the aforementioned sauer patent. For comparison purposes, tests were conducted on the paraffin wax free of any additive and also on paraflin wax in which a small amount of diacetoxydimethylsilane was incorporated. The method for incorporating the silicon-containing materials was to melt the wax and add the individual silicon-containing compositions and mix them thoroughly to obtains. Homogeneous mixture. Thereafter, each of the mixtures as well as :the control sample comprising pure paraffin wax was applied to glass slides and the coated slides tested for surface resistance in megohms at 96 per cent relative humidity at 75 c. The following table i shows the results of these tests:
In this example, a glass mat comprising a mass of glass fibers was impregnated and bonded with paraffin wax containing 0.5% of the mixture of polymethylchloropolysiloxanes described in example 1. The surface resistivity at 96 per cent relative humidity-was measured after one day. A similar paraffin-bonded glass mat was also measured under the same conditions with the following results. The glass mat bonded with the paraffin alone showed a surface resistivity of x10 megohms while the glass mat bonded with *the paraffin wax containing 0.5 per cent, by weight, based on-the-totalweight of the paraffin wax and the polymethylchloropolysiloxane, showed a surface resistivity of 6.6 megohms.
Example 3 in this example, glass slides were coated with paraffin wax alone and with paraffin wax containing various amounts of polymethylchloropolysiloxane, and also paraffin wax containing a mixture of methylchlorosilane comprising dimethyldichlorosilane and methyltrichlorosilane, and also paraffin wax containing dimethylsilyl diacetate. In each case, the glass slide was coated with the particular paraflin waxby melting the wax and dipping the slide therein. The following table ii shows the results of the conductance of the coatings measured in micromicrohos when the samples were conditioned one day at 96 per cent relative humidity (room temperature) and when 115 volts were passed through during the measuring tests:
glass slide plus paraffin c0nta1mng;2.0,% poly methyl- .chloropolysiloxane. A u. 504162 glassslidc-plus parafiin containing 0% polymetliyl- ,chloropolysiloxane l l 0:970 glass slideplusparaflin con polymethyl- i ehloropolysiloxane t o. 073 glass slide 'plus paraffin containing 0.5% mixture .methylchlorosilanes l l l. 0.20 glass slide plus parailin containing 0 5% dnneth ls yl; w37
Diacctaten l attempts to first coat the glass slide with the polymethylchloropolysiloxane and thereafter with untreated paraffin wax were unsuccessful because the wax would .not bond satisfactorily nor give a continuous film. Even application of the paraffin wax and treatment of the wax-coated surface with the polymethylchloropolysiloxane gave substantially inferior surface resistivity results.
It will, of course, be apparent to those skilled in the art that other polyorganohalogenopoly- .sijloxanes in place of the polymethylchloropoly- :siloxanesdisclosed' in the foregoing examples may be used withnut departing from the scope of the invention. In addition, various solid paraffin waxes including, as pointed out previously, chlorinatedwaxes, may also be employed.
The modified paraffin waxes embraced by the present inventionmay be used as described above for bondin lass mats which are to be used in electron precipitators. In addition, the parafiin waxes may also be employed for coating agents where itis desired to prevent excess electrical surface leakage especially under :high humidity conditions.
In making the paraffin-bonded glassmats described above, the amount of treated paraflin which may be employed may be varied within wide limits. Thus, the paraflin may comprise, for example, :from about 2 to 25 per cent of :total what we claim as new and desire to secure by letters patent of the united states is:
L. A composition of matter having a lowelectrical conductivity under high humidity conditions and consistingessentially of a parafiin wax having incorporated therein from 0.05 to 10 per .cent, by weight of a.polymethylchloropolysiloxanex based on the total weight of the latter and the paraffin wax.
.2. The method for making .a coatedela b se having a low electrical conductivity under high humidity conditions, which process comprises coating the aforesaid lass base with a parafiin wax having incorporated-therein from 0.05 to 10 per cent, by weight, of a polymethylchloropol-ysiloxane, based on the-total weight of the latter and the paraifin wax
Paraffin wax composition
The methods of separating paraffin wax from crude petroleum products, such as by distillation, chilling with filtering or centrifuging, sweating, and solvent extraction, are well known. Various methods of paraffin wax purification, such as treatment with sulfuric acid and fullers earth are also well known. Although this purification helps to produce more stable paratfin waxes, initially free from odor, taste, and color, it is not effective enough to prevent subsequent oxidative deterioration which has been troublesome to industrial users of parafiin wax.
One of the most widely practiced applications of paraffin wax is in the coating industry wherein hot wax baths are employed for waterproofing, treating, impregnating or sizing paper and similar products, and wherein wax is employed to provide a protective coating for materials of all kinds. More specifically, the use of hot liquefied wax is widely practiced in the manufacture of such articles as waxed paper, especially waxed bread wrappers,
Waxed milk cartons and other beverage containers, car
Tons, bottle caps, shot shell tubes, matches, wax impregnated fabrics, paper-metal foil electrical condensers, junction and terminal boxes, transformers, wax impregnated insulation, coils and windings, candles, as well as a host of other products too numerous to mention.
In each instance wherein a hot bath of liquefied paraffin wax is employed, problems of wax decomposition must be dealt with. This decomposition, which is generally considered to be the result of an oxidative mechanism, is evidenced by the appearance of undesirablei'odors, discoloration of the wax, and the formation of organic acids, peroxides, and possibly anhydrides and'lactones in the wax. Thus, suppliers of refined paraffin wax generally recommend that the temperature of a wax melt be kept below 160 f. (71 c.) Because, beginning at about this temperature, decomposition starts, accompanied by the development of an acroleinic or burnt odor, a similar taste and a darkening of the color. Parafiin waxes ranging in melting point from 59 f. C.) To 176 having from fifteen to thirty-five straight chain carbon atoms are readily oxidized in contact with air above 160 f. By way of example, after 50 hours at 200 f. A parafiin wax having a melting point of 122 f. Begins to show traces of peroxides, and after 90 hours at 212 f a titratable amount of fatty acid has developed.
Besides the formation of objectionable odors and an increase in color and acidity, oxidation brings about a lowering of melting point and tensile strength, and an overall deterioration of valuable properties such as hardness and the like, of the wax. Moreover, when decomposition occurs, much wax is lost through volatilization and the periodic purification steps necessitated by this decomposition. Consequently, it is of considerable importance to improve the heat stability of parafiin wax.
Wax compositions of improved heat stability, moreover, offer many processing advantages. Wax coating and impregnating baths may be operated safely at higher temperatures to effect improved penetration, while allowing better control over the amount of wax pick-up by the paper or other stock being treated. In addition, entirely new applications, previously eliminated from consideration because of temperature limitations, become practicable for waxes having improved heat-stability. For- united states patent 0 thermore, tank cars may be unloaded more rapidly because higher temperatures resulting in lower viscosities give better transfer of heat and flow, making possible savings in labor and steam costs.
A further problem encountered by users of paraffin wax is that of providing a finished product, such as waxed paper and beverage containers, which will not deteriorate or discolor upon exposure to air. The salability of food products in wrappings and containers impregnated with wax is adversely affected by discoloration or yellowing of the wax due to oxidation. This ditficulty becomes more acute with the recent emphasis placed on packaging and package design.
It has been proposed to improve the stability of paraffin waxes against oxidation deterioration by incorporating therewith one or more materials called anti-oxidants because such materials are believed to inhibit the formation of undesirable products of oxidation. However, the inhibition of parafiin wax against oxidation presents special difficulties not encountered when choosing an anti-oxidant for other purposes. First, the anti-oxidant material must be capable of withstanding the temperatures employed in wax melts without loss in anti-oxidant powers. This problem, and oxidation conditions in general, are accentuated in the blending of paraifin wax with higher melting point materials such as polyethylene, as set forth in copending application ser. No. 601,556, filed june 25, 1945, by bowman, ridenour and hollenback and assigned to the same assignee as the present application. The higher temperatures and agitation employed tend to increase oxidation. Accordingly, anti-oxidants which are suitable in mild temperature applications may not be suitable in paraflin wax. In addition, an anti-oxidant must not adversely affect the physical properties of the wax.
Where paraffin wax is employed in the manufacture of wrappings, containers, and coatings for foods, an anti-oxidant must not impart color, odor, or taste to the wax, either in the wax melt or when in contact with the food. The standards for paraifin wax are generally much higher than for most other products including many edible products such as edible fats and oils. This is particularly true with regard to color and odor. Lard oil, for example, has a characteristic odor which although not objectionable from a standpoint of human consumption would be highly objectionable if found in paraffin wax compositions. Any color imparted to paraffin wax is highly objectionable from a marketing standpoint and, therefore, a very small degree of oxidation which might give only a slight oif-white cast to the wax is undesirable, whereas in petroleum oils in general and in many food products a slight discoloration goes unnoticed. Paraflin wax is essentially odorless and, therefore, any odor due to impurity is very easily detected. For example, oxidation of paraffin wax to such a degree that it has a peroxide number of 0.01 is usually enough to confer a definitely detectable oxidized odor. Such a small amount of oxidation with its attendant odor may go unnoticed in many other substances which have some slight characteristic odor of their own, the characteristic odor tending to mask the oxidized odor. Since paraffin wax is a crystalline material, small amounts of impurities can effect relatively large changes in physical properties such as melting point and tensile strength. Small amounts of impurities in nicfm-crystalline substances will not exert such a noticeable e ect.
The essentially completely odorless and tasteless character of paraffin wax combined with the fact that the oxidation of parafiinic-type compounds always leads to soluble oxidation products which tend to affect taste and odor makes the problem of inhibiting parafiin wax one that is both difiicult and unique. The rigid requirements in the trade for parafiin wax are therefore such that an anti-oxidant for parafiin wax must be efiective in very low concentrations where it will not cause taste or odor by itself, and at the same time it must, in that low concentration, be so effective that the formation of even extremely small amounts of odorand taste-producing, d'ecomposition products is suppressed.
The question of whether or not any material will satisfactorily function as an anti-oxidant in any medium is quite unpredictable, for anti-oxidant action is highly selective and apparently catalytic. It is so selective, in fact, that one cannot predict with any degree of certainty that a material which is a known anti-oxidant for one substance will still perform as a satisfactory anti-oxidant in another medium. For example, it is well known that many phenolic materials are useful as anti-oxidants for various purposes, but a wide variety of these phenolic materials are not suitable as wax anti-oxidants. To illustrate, a number of phenolic compounds, known to possess antioxidant properties in other environments, have been tested in parafiin wax and found to be unsatisfactory as parafiin wax anti-oxidants. These compounds are as follows: his (4-hydroxyphenyl) isopropane; bis (4-hydroxyphenyl) cyclohexane; orthodihydroxybenzene; metadihydroxybenzene; bis (z-methoxyphenyl) methane; 2,5-ditertiarybutyl hydroquinone; 3-pentadecylphenol; bis (2-hydroxy-3,5,-ditertiarybutyl-6-methyl phenyl) methane; 1,1,2,2,-tetrakis (2 methyl 4 hydroxy tertiarybutylphenyl) ethane. Thus, a material which may be found to exhibit antioxidant properties in fats and oils cannot on that basis be expected to exhibit anti-oxidant properties in paraflin wax. Furthermore, it is difficult to predict that such a material would be otherwise suitable for use in wax compositions. Apparently, the nature of paraffin wax has considerable bearing on the question.
It is therefore an object of our invention to provide new paraffin wax compositions having improved stability against general decomposition or oxidative deterioration.
More specifically, a further object of our invention is to provide new paraffin wax compositions of improved heat stability, such as stability against decomposition in the hot liquefied state.
A still further object of our invention is to provide new paraffin wax compositions having stability against deterioration due to the action of air.
Another object of our invention is to provide improved paraffin wax compositions having good color and exhibiting substantially no odor or taste, such that they may be employed in food packaging.
These and other objects are accomplished by the present invention wherein we provide improved paraffin wax compositions comprising a major amount of a refined paraffin wax and a minor amount, sufficient to inhibit oxidative deterioration, of conidendrol having the following structural formula:
0%: /o cho l l 0 e0 ctr-43hr conidendrol exists in two isomeric forms, both of which have the structural formula shown above. These are known as the alpha and beta forms. Alpha-comdendrol and beta-conidenrol are by-products of the pulp and paper industry. They are produced from conidendrin, which differs structurally from the conidendrols only in the presence of two methoxy groups, each on one of the benzene rings. Conidendrin has been isolated from a variety of coniferous woods, the most prevalent source material being western hemlock. Thus far, one of the most convenient means for obtaining conidendrin has been by solvent extraction from the sulfite waste liquors produced during the pulping of western hemlock. The conidendrols may then be prepared by demethylation of conidendrin through methods well known in the art. During the demethylation process to produce beta-conidendrol, it has been suggested that a racemization or inversion occurs probably at the carbon atom adjacent to the carbonyl group to produce both alphaand beta-conidendrol. These two compounds are considered to be optical isomers, differing only in spatial configuration, the two formulae being identical to that set forth above. However, they have differing physical properties, enabling separation of the two by such means as solvent extraction. Both compounds are commercially available.
We have found that the resistance of paraffin wax to oxidation can be materially increased, and the temperature to which it can be heated without breakdown can be substantially raised by addition to the wax of relatively small amounts of the conidendrols.
The conidendrols can be employed to advantage in paraffin wax stabilization in amounts ranging from about 0.0001 to 0.1 per cent, by weight of the composition. A preferred range is from about 0.0005 to 0.01 per cent by weight of the composition. Mixtures of the conidendrols can also be employed.
The following illustrative examples permit further understanding of our invention and show the advantageous results obtained in wax compositions containing the conidendrols. For the purpose of the tests performed, a highly refined paraffin wax having a melting point of 122 f., as determined by astm method d87-42, was employed. The peroxide number, neutralization number and saponification number, referred to hereinafter, are all obtained by means of standard well known tests, and are indicative of the degree of oxidative breakdown of the parafiin wax subjected to oxidation.
Example i a blend was prepared employing a 122 f., ASTM melting point, parafiin wax and 0.001 per cent, by weight, of alpha-conidendrol. Three hundred grams of the blend were placed in a glass oxidation cell suspended in an oil bath maintained at 240 f. Preheated dry air at a temperature substantially the same as that of the wax was passed upwardly through the molten wax at a controlled minimum rate of 1.6 cubic feet per hour. Once every 24 hours samples were withdrawn and the oxidation stability of the wax was measured by analyzing for peroxides,- acidity and saponifiable material by methods well known in the art. The odor also was noted.
Table i shows the results obtained along with data on the uninhibited wax control subjected to the same test conditions.
Table i peroxide neutralization saponification number, number, number, moles ozl'kg. Wax mg. Koh/gm.wax mg. Koh/gm. Wax days oxidlzed control control control conplus 0011- plus gonplus trol 0.001% trol 0.001%
Additive additive it is readily seen that without the alpha-conidendrol additive of our invention all three measures of oxidative deterioration, viz., the peroxide number, the neutralization number and saponification number, increased rapidly with time, whereas values for the sample which contained the anti-oxidant showed no change even after seven days. The initial rise and subsequent drop in peroxide value for the uninhibited wax control is typical of wax oxidation.
The uninhibited wax developed a strong oxidized odor after one day of the test, but the inhibited sample did not develop such an odor for the full seven days of the run.
Example ii another blend was prepared with 122 f.,ASTM melting point, paraffin wax and 0.001 per cent, by weight, of beta-conidendrol. This composition was subjected to the oxidation test at 240 f., as described in example i, and the odor was periodically noted. The composition did not develop an oxidized odor until after four days of oxidation, whereas the lminhibited control wax developed an odor insone day under the same conditions.
The above specific examples clearly demonstrate the efficacy, as paraffin wax anti-oxidants, of alphaand betaconidendrol. The complete lack of change in peroxide, neutralization and saponification numbers for the period of the test on alpha-conidendrol, coupled with the lack of odor formation after subjection of paraffin waxes inhibited with each compound to severe oxidative environment, indicate beyond any doubt that alphaand beta- ,conide'ndrol are remarkably effective paraffin wax antioxidants. Furthermore, the anti-oxidants are not only effective for inhibiting oxidation of parafiin wax in the hot liquefied condition, but since the anti-oxidant is retained by the wax in the finished wax treated product, the anti-oxidant continues thereafter to perform its desired function and aids in preventing subsequent deterioration of the paraflin wax due to adverse conditions of heat, air and the like.
The potency as paraffin wax anti-oxidants of the conidendrols permits of the employment of hot baths containing the inhibited parafiin wax compositions of this invention. In employing such baths, it is not necessary to use a paratfin wax already containing the antioxidant, but the anti-oxidant can be added in suitable amount to the molten paraffin wax in the bath in order to prevent the oxidative deterioration thereof.
Since the conidendrols can be employed so elfectively in relatively small amounts, they do not affect the odor and taste of the paraflin wax with which they are incorporated, and similarly, none of the desirable physical properties of the wax, such as melting point and tensile strength, are adversely affected.
As will be understood by those skilled in the art, the stabilized paraffin wax compositions of our invention may contain other additives and ingredients blended therewith to improve other characteristics, such as tensile strength, sealing strength, etc., of the composition.
While our invention has been described above with reference to certain specific examples and embodiments, it will be understood that the invention is not limited by such examples or embodiments, but that resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended c arms
Purification of paraffin wax
The present invention relates to the purification or separation of mixtures of fatty or mineral oils or distillation or destructive hydrogenation products of coal and the like especially of n carbonaceous materials containing substantial amounts of paraffin wax. For the purification or separation of mixtures of fatty or mineral oils or distillation or hydrogenation productsof coals or other carbonaceous materials solvents consisting substantially of a tomato 0! The lower alcohols oi the fatty series or mixtures of several formates have already been employed.
It has been further found that in the recovery of parailin wax from materials containing, substantial amounts thereoi together with other carbonaceous substances, such as mineral oils and the like, for example from distillation or hydrogenation products of carbonaceous materials, such as coal, or from crude parafiin waxes with the aid oi iormates of lower alcohols, the psreifin was obtained is sometimes not quite colourless, because the solvent power of these esters for asphaltic bodies, such as asphalt and other coloured or colouring constituents or asphalthodies having a lower molecular weight than asphalt and which may be distilled, but which condense after some time with the formation of substances similar to asphalt, is not always suiticient wholly to prevent the precipitation of these substances on the paraffin wax to be separated.
We have now found that the said objection is obviated by employing the mixtures oi the said ioruiates with organic solvents, the sol vent power oi which for the said asnhaltic bodies is than that oi the iormates, as for ex ample mixtures oi the said iormate with benzene, icenaine, carbon disulphide, carbon tetra= chloride and the like. Usually it is only necesto add small amounts of these solvents, so for example irom ii to 20 per cent reckoned on the amount oi the nurilyinc mixture employed, in order to improve the quality oi the paraiiln the solvent power of the said mixtures ior very small even when employ- .15 oennne- .116 solvent mixtures may also be employed for t e purification of fatty or mineral oils, as r ":ainnle soy been oil.
' I .process he carried out hy ed the solvent to the product to he puri- t ie contaminating substances pass into us may thenbe senarated from the product, as ior example the or the pure oil. In the case of ye-:3, the latter su jan!!! 17,
Subsequently washed with the same mixture and the solvent recovered from the filtrate by distillation.
Crude paraffin wax from any source may be purified in an advantageous manner by the process according to the present invention. When stirring the same with the solvent mixture it is preferably warmed, but good results are also obtained at room temperature. The treatment may also be carried out at temperatures above 65 the temperature at which the solvent ure commences to boil provided a closed vessel is used. The said solvent mixture may also con tain more than two components, in particular it may be used in conjunction with the solvents l0 hithertousually employed lor this pse, ior example benzine, benzene, toluene, xylene, carbon disulphide, carbon tetrachloride, trichloro ethylene or pyridine. Thus for example a ture of so per cent by volume of methyl tomato, till 15 per cent of benzene and 5 per cent of methanol gives very good results. In many cases it is preierable to carry out the treatment oi the masses containing paramn in stages, solvent mixtures oi the said kind, if desired oi difierent composition or different concentration, being used in the single stages. Diflerent solvents which only consist of the one component may also be used one after anothenior example tree. Ment with a lei-mate of a. Lower alcohol con 6 stituting the first stage followed by extraction of colouring matter by treatment with a small quail tity of a solvent having a higher solvent power lor the said colouring matter.
The following examples will the nature of this invention, is not restricted to these examples. Are by weight.
Iurther illustrate hut the invention the parts example 22 example .2 product irons the destructive ny onsentition 01- brown coal low temperature carbonization tar consisting of paramn wax and oil is centrifuged. Hie residual impure parafiln wax flakes are washed with a mixtureoi' 80 per cent by volume of methyl i'ormaie and 20 per cent by volume oi benzene. The paramn wax obtained is pure white in colour.
Example 3 135 parts of a filtrate obtained'by filtration in a press at 0 c. Of a destructive hydrogenation product of brown coal low temperature carbonization tar are boiled for 15 minuies under a reflux solvent is removed in a filter-press and the residue is washed three times with paris or the same solvent mixture each time. 128 parts of a white paramn wax are obtained which is so pure that it may be supplied for catalytic oxidation with air without further treatment. 4
The filtrate is evaporated and yields a yellowbrown residue (7.5 parts).
What we claim is:
V 1. A process for the purification oi precipitated etude paramn wax by the removal 01' impurities comprising oils and colored asphalticlike bodies w ch comprises washing said wax with a mixtire of a i'ormate of a lower alcohol of the fa'ty series and an organic solvent which has a greater solvent power for asphaitic bodies than said iormate selected from the class consisting 01' e. Toluene, xylene, benzine, pyridine, tri-' an undissolved white wax.
2. A process for the purification oi precipitated crude daramn wax by the removal of impurities comprising oils comprising oils organic subsiance is and colored asphalticlike bodies which comprises washing said wax with a or a i'orma e or a lower alcohol 01' the fatty series and an organic solvent having a greater solvent power for asphaltic bodies than the said i'ormate purities from the wax to thereby produce an undissolved white wax.
3. A process for the purification of precipitated crude paramn wax by the removal of impurities and colored asphalticlike bodies i'atty series and an organic substance which has a greater solvent power for asphaltic bodies than said tormate selected from the class consisting of benzene, toluene, xylene, benzine, pyridine, trichlorethylene, carbon disulphide and carbon tetrachloride and causing said solvent mixture to eil'ect dissolution oi the impurities in said wax by heating the resulting reaction mixture to a temperaiure at which no material dissolution of wax takes place to thereby produce anundissolved white wax. I
4. A process for refining precipitated crude paraflin wax bythe removal of impurities com to dissolve said imprising oils and colored asphalticlike bodies which comprises washing said wax with a mixture consisting of about per cent by volume of methyl formate, 15 per cent of benzene and 5 per cent of methyl alcohol, said benzene and methyl alcohol having a greater solvent power for asphaltic bodies than said iormate,-and causing the said mixture to dissolve the impurities irom the wax to thereby poduce an undissolved white wax.
5. A process as defined in claim 3 wherein said present in amounts 01' from 2 01- the solvent mixture.
Preparation of paraffin wax for utilizing its thermal expansion properties
This invention relates to preparation of paraffin wax for utilizing its thermal expansion properties. More particularly, the invention relates to the pre-treatment of parafiin wax for the purpose of improving its capacity to impart motion to mechanisms by expansion of the wax. The expansion properties of wax may also be utilized for the forming of metal products.
' Paraflin wax, pre-treated as hereinafter described, may be encased in a high pressure cylinder and heated to actuate reciprocating means in the cylinder for operating dampers, valves, shutters, pumps and other devices.
The thermal expansion of commercial paraffin wax has been utilized heretofore for imparting motion to mechanisms, such, for example, as shown in us. Sherwood. In efforts to increase the efiiciency of commercial paraffin waxes for actuating mechanisms and for other purposes, such, for example, as the forming of metal products, we have discovered that the composition of waxes can be altered and the thermal expansion properties of the waxes thereby substantially improved. I
By experiments which will be described hereinafter, we have determined that paraffin wax contains dissolved hydro-carbon gases and that molten paraffin wax absorbs oxygen from the air. Further, we have ascertained that the presence of these gases in the paraffin wax heretofore used to actuate mechanism lessens the expansion and pressure producing capacities of the wax when heated, and results in a gas cushion which resists the return movement of the pressure actuated means.
Therefore an important object of the invention is to devise methods of preparing paraffin wax for utilizing its expansion properties by pr'e-t'reatment which frees contained gases and oxygen from the wax and prevents absorption of oxygen from the air by the degassed wax. When the wax, preheated as described herein, is sealed in a high pressure cylinder or mold and subjected to heat, it exhibits high expansion and pressure exerting capacities compared to commercial paraflin waxes. When cooled, the wax produced by our invention contracts without formation of gases. When sealed in a cylinder, the contraction of our pre-treated wax results in a vacuum zone located axially of the cylinder which facilitates the return stroke of pressure actuated means in the cylinder.
The valves, dampers, shutters and other mechanisms referred to herein, which may be operatively connected to pistons or plungers actuated by the thermal expansion of wax encased in a high pressure cylinder, usually are designed to function automatically in response to thermostatic controls at diiferent temperatures, sometimes within narrow ranges of temperatures. Therefore the production of wax having the desired melting point or range, as well as optimum expansion and contraction properties, is another important object of our invention.
Parafiin wax is a mixture of hydrocarbon compounds belonging to three distinct systems: the straight or long chain waxes, branched chain waxes and naphthenic waxes. The long chain paraiiins have higher melting points than the branched chain, and the naphthenic paraffins have the lowest melting points for components having the same 3,193,5w patentedjuly 6, 1965 ice number of carbon atoms. The separation of hydrocarbons for the purposes of this invention may be based on boiling point or on structure, i.e. The clatherate forming compounds which in general, are long chain hydrocarbons.
The paraflin wax known commercially as eskar-r40, for example, is suitable for treatment by our process, and therefore the experiments described herein were performed with respect to this wax.
The aforementioned and other objects and advantages of the invention will become apparent from the drawings and following specification.
A series of determinations were made using the boiling point of solvents to maintain a constant temperature. Progress in the work showed it was necessary to deter-' mine points on the curve at'closer intervals.
It was noted in this experiment that gas was given off when the liquid wax solidified. This became apparent as a solid foam of small bubbles in the center of the wax. Upon remelting the wax while under vacuum, these bubbles roses to the surface and were removed by a pump. It was observed that some of the bubbles decreased in size while rising in the liquid, indicating that some gas redissolved. Therefore it was necessary to either repeat the melting-freezing process on the wax while under vacuum, or heat the wax to 150 c. The latter method caused considerable wax loss due to violent evolution of gas.
The data obtained from the experiments described with respect to melting points and expansion and contraction rates in response to temperature changes, enable the user to select'the paraifin fraction suitable for embodiment in a given thermally controlled mechanism or for other purposes.
The next step of our process is the result of experiments which indicate'that paraffin wax contains hydrodrocarbon gas is present in wax and is released at about v140" c., or under high vacuum at a temperature of c.; that molten par'affin wax absorbs oxygen from the air and that the oxygen is released slowly when the wax is melted. Unless the wax employed for thermal expansion is freed of gases before being encased, the gases will be released within the pressure cylinder when the contained wax is subjected to heat in the normal operation of the mechanisms.
Experiment 4.-this experiment was made to determine the kind ofgas present in paraffin wax. A quantity of shavings of eskar-r140, 131.2 g. Was placed in a flask and attached to a vacuum system, a diagram of which is shown in figure 4. The vacuum system used is capable of giving very high vacua and includes both a mechanical and diffusion pump 11. 7
After a goodvacuum was established in the system, the
Flasklz containing the wax was heated in a water bath while trap 13 of the system was cooled with liquid nitrogen. The vacuum was applied as long as gas was evolved by the wax. The system was then opened and flask 12 was allowed to cool in air, and weighed when at room temperature. The loss in weight was less than 0.1 g. Which would correspond to less than 0.08% dissolved gas. I the material frozen out with liquid nitrogen was a mixture of condensed gases. As the tube, removed from the trap 13, was allowed to warm the majority of the.
. Material in the form of a white film was sublimed off and ficient water was added to bring the reading equal to- v the volume the wax occupied at the temperature of boiling water.
The contraction measured was that observed in going from 95 .5 c. (the boiling point of water) to room tern-- perature 22 c.
B.p. -175" c.; wt. 13.61 g. (6.80% of sample) contraction found: 6.8%
7 hp. -195 c.; wt. 21.30 g. (10.65%)
Contraction found: 12.45%
A. Sweetish odorofihydrocarbonwas present. 7 a very small portion, when observed with a magnifying glass, was in the form ofminute droplets. These also quickly evaporated 01f... The odor of hydrocarbon gas was still present. A few milliliters of water was added and the cylinderwas shaken. A strip of universalph paper was. Added to the solution. There was no change in color, in-
Insufficient 'tion of the hydrocarbon material:isolated becomes liquid before evaporating olf; and (c) any acid, if present, is insuflicient to change the color of hydrion ph paper.
Experiment 5.-an additional experiment was made to further evaluate the observations made in experiment 4.
(a) when 29.9965 g. Of wax was placed in a tared flask, which was attached to the vacuum system and heated with a water bath (95 c.), completely degassed, cooled and weighed again, while still under vacuum, a loss in weight was observed which amounted to 0.0060 g. (0.02%
(b) the wax was remelted and allowed to solidify in the open air. The flask containing the wax was then attached to the vacuum system shown in figure 5. After evacuation was complete, the pumps were closed off from the vacuum system and the flask containing the wax was heated with a water bath. Gas was given off. When evolution of gas ceased, the wax was allowed to cool to room temperature and the system was allowed to stand overnight. The system, after equilibrium was established showed a pressure of mm. Of gas pressure.
Experiment 5(a) indicates that the dissolved hydrocarbon gas amounts to 0.02%.
Experiment 5 (b) indicates that molten wax will absorb a gas from air which is then given off at 95 c.
Experiment 6.to establish the nature of gases which are dissolved in paraflin, apparatus shown in fig. 6 was fabricated and assembled.
A gentle stream of air was pulled through the apparatus with suction. This air vwas purified (co removed) by tube 14 filled with ascarite (a c0 absorbent). The gas was then led to the bottom of flask 15 which contained 200 g. Of paraflin in the form of lumps. Flask 15 was immersed in a basin of cold water which could be heated with an electric heater when desired. The gas was then led through tube 16 filled with glass wool. This serves to retain any spray or fine particles of wax entrained in the gas stream. Then the gas was passed through tube 17 which was also filled with ascarite. This tube will absorb any carbon dioxide gas given oh by the wax. The gas stream was then passed through a quartz tube 18 which contained a filling of copper oxide which was heated to red heat with burner 19.
At red heat copper oxide, cuo, reacts with hydrocarbon gases to give carbon dioxide and water. Using ethane as an example of the gas we would then have the equation: ch ch +7cuo+7cu+2co +3h q the oxygen in the air would then combine with the hot copper to regenerate copper oxide.
The gas was then passed through a saturated solution of barium hydroxide contained in flask 20. This reagent will react with carbon dioxide to give insoluble barium carbonate according to the following equation:
Tube 21 is a guard tube filled with ascarite and serves to remove the c8 from the air should the gas stream be blocked in some manner and a vacuum appear in the system causing outside air to be drawn into flask 20.
All rubber stoppers and rubber tubing were boiled in 10% caustic, washed with distilled water and dried at 100" c. Before use to remove any organic and inorganic volatile material which might nullify the results.
The assembly was purged by drawing air through the equipment at the same rate to be used later in the experiment. After minutes only a very slight cloudiness appeared in flask 20.
The contents of flask 20 were then replaced with fresh barium hydroxide solution while the flask 15 was warmed with boiling water to melt the wax. Air was pulled through the melted wax for 1 hour at a rate of 3 bubbles/ sec. No cloudiness appeared in flask 20 indicating no hydrocarbon was being evolved.
The water bath surrounding flask 15 was removed and the flask was heated directly with the electric heater.
At about c. Cloudiness began to appear in flask 20, indicating a hydrocarbon was being freed by the paraffin. This evoluation of gas was more rapid above this temperature. Heating was terminated after 30 minutes of heating.
The apparatus shown in figure 7 was then assembled and used in this experiment. Nitrogen from a compressed gas cylinder attached to a regulator was led into wash bottle 22. Fine regulation of the gas stream was made with screw clamp 23. Wash bottle 22 contained about 200 ml. Of a strong potassium pyrogallate solution (ppg). This solution reacts with oxygen and serves at this point to absorb all trace of oxygen in the stream of nitrogen. The gas stream then is led to the bottom of flask 24 which contained 200 g. Of paraflin in the form of lumps. The stream of nitrogen was then led into wash bottle 25 which also contained pyrogallate. Wash bottle 26 contained water only and served as a guard bottle to keep air from bottle 25.
The apparatus was purged for 30 minutes with a flow of nitrogen gas. A trace of oxygen was removed from the nitrogen indicated by a slight darkening of color. The solution in 25 was replaced with fresh solution. After 30 minutes solution in 25 was almost black indicating much oxygen was present.
The wax was then melted by heating the water around the flask 24 with the heater. A fast stream of nitrogen was then used to purge the system (20 minutes). The pyrogallate in 25 was replaced with fresh solutionand the experiment was continued. The solution turned black in 10 minutes.
This experiment indicate that wax degassed under vacuum absorbs oxygen from air when allowed to cool in air, and that the oxygen is released slowly when the wax is melted.
Therefore, after selection of a suitable wax, the next step of our process is to free the wax of dissolved hydro carbon gas and oxygen by pre-heating the wax, and, following the degassing procedure, to prevent absorption by the wax of oxygen from the air by maintaining the degassed wax under vacuum. The temperature at which the wax is degassed before being encased in a sealed cylinder depends on the conditions under which the thermally controlled unit is intended to operate, as more fully explained hereinafter. Before encasing the pro-treated wax in a sealed cylinder, we maintain the degassed wax in molten state under vacuum before and during a molding operation. Preferably we embed a piston together with an electrical filament holder and filament wound thereon in the molten degassed wax under vacuum. This is done by first placing the piston and filament holder with filament wound thereon in a mold and pouring the molten pre-treated wax into the mold under vacuum to cover and embed the said parts and to completely fill the mold cavity. The piston and filament holder with filament thereon may be of the construction shown in the copending application of john f. Sherwood, serial no. 51,110, for thermally controlled expansible means for imparting motion to mechanism.
Fig. 8 shows diagrammatically a reservoir 39 contain ing degassed molten wax under vacuum, pre-treated in accordance with this invention, a valved conduit 31 for conveying the wax under vacuum to a two part mold 32 and vacuum producing means. The mold 32, as shown in figs. 9 and 10, is provided with four cavities 33 communicating with awax distribution chamber 34 into which wax is fed by the conduit 31. Any desired number of cavities 33 may be provided. F
An electrical filament holder 35 with filament 3'6 wound thereon is placed in each cavity 33. An electrical condoctor 37 extends from the filament 36 into the connector 38 which protrudes beyond the bottom of the lower mold part 39. The upper mold part 4% is provided with sealed openings through which extend pistons 41 to be embedded in the wax in each cavity 33. For clarity, one piston 41 is shown in lowered, embedded position while another is shown in raised position in fig. 10, but it will be understood that the molten pro-treated wax is forced into the cavities 33 from the distribution chamber 34-by the pressure piston 42 therein to completely fill the cavities 33 while the pistons 41 are in raised positions. Whenthe wax has cooled, the pistons 41 are forced downwardly into the wax filled cavities whereby the wax is compressed. All the foregoing steps are performed while the wax is maintained under vacuum. When the wax has solidified in each cavity 33 there has been formed a cylindrical wax unit which includes the embedded filament holder 35 with filament 36 wound thereon, the conductor 37 and connector 33, and also the piston 41 partially protruding from one end of the unit. The adjustable bleeder valves 43 permit passage of air out of the mold cavities as they become filled with wax under vacuum. I
The cylindrical wax units indicated as a whole at 44 are removed from the mold 32, ready for insertion in high pressure cylinders such as the one indicated at 45, sup ported in die 46 of fig. 11, which is drawn on a slightly 7 larger scale than fig. 10. The insertion of each unit 44 into a cylinder 55 is performed with the aid of vacuum 47 to draw the unit 44 by suction into the cylinder 4-5 and establish vacuum in the cylinder. The wax unit 44 then includes the parts embedded therein, together with the conductor 37, connector 38, and the opposite end plate 48. When the unit 44 is in place, the reduced diameter portion 49 of the wax and the protruding end of the piston 41 fit in the cylinder portion 2 and bear against the rubber pad 51 in the bottom of the die 46. The end plate 48 fit's'in the cylinder 45 and when sealed thereon, closes the cylinder at that end. A
Reverting now to the pre-treatment of the selected wax for the purpose of degassing the wax'before encasement in a high pressure cylinder, such for exampleas the cylinder 45 shown in fig. 11, and preventing formation of gases under normal operating conditions'to which the thermally controlled unit may be subjected, we have noted that'dissolved gases are freed'from the wax by pro-heating to approximately 140 c., or, under high vacuum to. Approximately 95 c, and that if the unit is required to operate under conditions where the temperature in the high pressure cylinder 4-5 does not exceed 95 c., the wax functions efiiciently by expansion to impart required motion to the piston 41, and contracts when cooled without giving off gases.
However, when the thermal units are required to operate under temperature and load conditions which create much higher temperatures in the high pressure cylinders 45, it is necessary to preheat the wax to temperatures above the predetermined operating temperatures of the units to free dissolved gases which otherwise would be given off at said operating temperatures in the cylinders, and then to maintain the degassed wax under vacuum until it has been molded and solidified for insertion in the cylinders 45. V
It is known in the art of isolating wax frompetroleum, that chlorinated hydrocarbons are employed in the purification processes and thatsmall fractions of the halogenated hydrocarbons used in industry may be found in the isolated wax. Such halogenated hydrocarbons are freed at the same temperatures heretofore stated for evolving hydrocarbon gases and oxygen from wax by our method. V t
The mechanisms herein shown and described in connectionwith our method of preparing wax for utilizing its thermal expansion properties are for exemplary purposes only. The molten pre-treated wax may be molded under vacuum into solid units of various forms other than the specific shape illustrated herein figs. 10 and 11, with or without embedding the heating elements and pistons therein.
I. The method of preparing wax for improving its expansion and contraction properties and capacity to impart motion to mechanism by expansion of the wax when encased in a high pressure casing which is subsequently subjcctedto temperature exceeding the melting point of the wax for the purpose of expanding the encased wax, which comprises pro-heating the wax before encasement to temperature exceeding the melting point of the wax and exceeding the minimum temperature required to evolve hydrocarbon gases and oxygen from the wax and thereby freeing dissolved hydrocarbon gases and oxygen from the wax, maintaining the degassed molten wax under vacuum and preventing absorption of oxygen, and molding the molten degassed wax under vacuum into solidified units, thereby preventing giving off of gases after encasement when the encased wax is heated and contracts by cooling.
2. The method defined by claim 1, in which the wax is pre-hea-ted to a temperature of at least 140 c.
3. The method defined by claim 1, in which the wax is pro-heated to a temperature of at least 95 c. Under high vacuum. 7
4. The method of preparing parafiin wax for improving its expansion and contraction properties and capacity to impart motion to mechanism by expansion of the wax when encased in a high pressure casing which subsequently is subjected to temperature exceeding the melting point of the wax 'for the purpose of expanding the encased wax, which comprises selecting a fraction of the wax having melting points in the 5460 c. Range, pro-heating the wax before encasement to temperature exceeding the melting point of the wax and exceeding the minimum temperature required to evolve hydrocarbon'gases and oxygen from'the wax and thereby freeing dissolved by drocarbon gases and oxygen from the wax, maintaining the degassed molten wax under vacuum and preventing absorption of oxygen, and molding the molten degassed wax under vacuum into solidified units, thereby preventing giving all of gases after encasement when the encased wax is heated'and contracts by cooling.
5. The method defined by claim 4, in which the wax is pro-heated to a temperature of at least 140 c.
6. The method defined by claim d, in which the wax is pro-heated to a temperature of at least 95 c. Under high vacuum.
'7. The method of preparing parafiin wax for improving its expansion and contraction properties and capacity point of the wax for the purpose of expanding the encased wax, which comprises prc-heatingthe wax before encasement to temperature exceeding the meltingpoint of the wax and exceeding the minimum temperature required to evolve hydrocarbon gases and oxygen from the wax and thereby freeing dissolved hydrocarbon gases and oxygen from the wax, maintaining the degassed molten wax under vacuum and preventing absorption of oxygen, passing the molten degassed wax under vacuum into a mold cavity which contains an electrical heating unit and a piston, filling the entire cavity with the wax and embedding said heating unit and piston, allowing the wax to solidify under vacuum, thereby preventing giving oif of gases after encasement when the encased'wax is heated and contracts 9 by cooling, removing the molded wax and parts embedded 2,477,273 therein and encasing the molded unit in a high pressure 2,815,035 cylinder