US2761814A - Process for the preparation of paraffin wax products - Google Patents

Description

B. G. POST Sept. 4, 1956 PROCESS FOR THE PREPARATION OF PARAFFIN WAX PRODUCTS Filed Deo. 20, 1954 mmhzm N. mmh-...JE

:Quixo BENJAMIN G. POST asT HIS AGENT PROCESS FOR THE PREPARATION OF PARAFFIN PRODUCTS Benjamin G. Post, Bellaire, Tex., assigner to Shell De- 4 velopment Company, New York, N. Y., a corporationk of Delaware Application December 20, 1954, Serial No. 476,190

4 Claims. (Cl. 196-17) The present invention relates to improvementsin processes or preparation of superior wax products. More particularly, the invention pertains to an improved method of solvent dewaxing and deoiling at relatively low de-y oiling temperatures whereby paran waxes having; improved low temperature properties are obtained;

The method of the present invention is superior to various processes heretofore proposed for'the preparation of paraliin waxes especiallysuitable for use as milk carton waxes and the like. Paran waxes prepared by prior processes normally exhibit poor low temperature propertica-especially with respect to exibility as evidenced by both bending and fracture-resistance tests at relatively lowtemperatures or, at least, by having poor properties in one of these respects.

Paraiiin waxes are normally a mixture of hydrocarbons predominating in those having substantially straight-chain configurations together with minor amounts of materials relatively low deoiling temperatures. The product so obhaving branched chains and naphthenes with only minor portions of olens (if any). They are to be diiferentiated inl properties and in predominating configurations from the so-called microcrystalline or amorphous waxes normally obtained from residual oil fractions. type of waxes predominate in highly branched congurations, as well as, cyclic or polycyclic molecules which impart to the microcrystalline wax a structure which is apparently non-crystalline to the naked eye. 'Ihese mi- `crocrystalline waxes may be combined with paran'waxes to impart certain desirable properties thereto but it is necessary to employ relatively large amounts in the order of -40% of a microcrystalline wax in order to impart improved low temperature properties to parain waxes. In utilizing such large proportions of microcrystalline waxes, the blocking point of the wax composition is undesirably depressed. Moreover, as data given later in this disclosure show, the low temperature properties of such wax blends are not satisfactory with respect to flexibility and fracture, especially when normal (i. e., at least 40 F. or higher) deoiling temperatures are employed.

The low temperature properties of paraiin waxes may be improved according to prior art processes by utilizing variations of complicated alternatives to the basic step of dewaxing a waxy lubricating oil. The eiort in the past has been to isolate a whole parain wax from a relatively low-boiling lubricating oil fraction and combine it with a desired fraction of a higher boiling wax fraction obtained from another lubricating oil cut and thereafter deoiling the mixture at relatively high deoiling temperatures. The process involved in isolating a particular portion of a paraiin wax is undesirable due to the fact that numerous processing steps and equipment are involved. While the waxes so produced may be desirable with respect to one function or another, the benefit so gained is counterbalanced by the complication of the defining process and the low temperature properties possessed by wax products obtained by the process of the present invention have not thereby. been attained.

It is an object of the present invention to provide a The latter Ftented Sept. 4, 1956 ice process for the preparation of improved paratlin wax products. It is a further object of this invention to pro-v v1de paran wax products having improved low tempera-z ture properties. It is a particular object of this invention to provide a process for the preparation of wax products having improved low temperature properties. It is a special object of this invention to provide a process for.

the isolation of paraiin waxes having improved flexibility characteristics at low temperatures. become apparent during the following discussion.

tionated into waxy lubricating oil fractions such thatthe waxes contained thereinhave a carbon atom contentper molecule varying no more than about 15 carbon atoms; At least two of these fractions are separately subjected to dewaxing operations whereby substantially wax-free lubricating oil fractions are obtained from each, together with at least two slack wax fractions. Substantial portions of each of these slack wax fractons as defined hereinafter are combined and then subjected to deoiling at tained comprises a substantially purified, i. e., deoiled, parain wax product having improved low temperaturel properties not obtainable by other methods known in the art. perature below about 33 F. and preferably in the order of about` 15-30" F. The use of the low deoiling temperature combined with the speciiied` relationship of the wax cuts as defined more fully hereinafter for the pur` pose of purifying the particular mixture of paran waxes appears to be the key to obtain the improvedproductsj having excellent low temperature flexibility characteristics. Alternatively, the slack waxes may be deoiled separately. at the low deoiling temperatures and thereafter coinf vbined. The waxes to be combined are to be chosen so that the wax having the higher melting point'has an average molecular weight from about 50 to 150 higher than that of the lower melting wax.

For the purpose of this invention, a waxy oil is dened asv a high viscosity index solvent-extracted oil derived from crude petroleum containing parainic compounds which are normally solid at room temperature. The per- .centage of such petroleum parain wax may vary from 42 to 50% in waxy rainates obtained from solvent treat-4 It is preferred that.. waxy ra'inates obtained from solvent treating distillate ing distillate fractionsV or residua.

lubricating fractions be utilized.

The slack waxes obtained by dewaxing usually contain between aboutV 10 and about 60% of a 0 F. pour point lubricating oil, although the oil content may be as loW as 2-3%. applied especially to full-range parathn'waxes having a relatively low average melting point modified with full. range waxes from higher boiling waxy lubricating oils,

the latter waxes having an average molecular weight between about 60 and about 100 greater than that of the lower melting point Wax cut. By full-rangeV waxes is meant the entire wax mixture separatedby dewaxing of awaxy lubricating oil substantially without any of the Wax members having been later segregated from said mixture.,

Preferably, these parain waxes are obtainedfrom lowj boiling and intermediate boiling waxy lubricating oils'` The waxes in the low boiling distillates as well as in the, intermediate distillates cover allV types of configurations but predominate in both cases innormal or straight-chain paranic hydrocarbons with minor proportions of slightly branched hydrocarbons and naphthenes or other configurations. Consequently, it will be understood that the Other objects will` By a low deoiling temperature is meant a tem,

ln its preferred version, the present process is combination of low melting parain wax obtained from relatively low boiling waxy lubricating oils with fractions f of slack wax obtained from intermediate boiling waxy lubricating oil distillates results in compositions having a full range of all of the wax configurations involved and The exact proportion'of each of these configurations has not been determined to date. Therefore, it can only be said at the present time thatV the configurations appear to Vhavev been balanced `by the method of preparation in such a manner asto result in obtaining improved low temperatureflexibility and other properties. A secondary advantage, which is nonethelessl an important commercial consideration, is the fact that-the waxesso produced do not inherentlyl entail the production of other less desirable wax products which must be worked off, or disposed of,

infother means such asby being sent to a'cracking unit or the like. There is no necessity, furthermore, for increas-l ing lubricating oil manufacture to any extent for the purpose of improving the waxes bythe present process. The process entails, on the contrary, the full utilization of waxes in'products bearingva premium price rather than necessitating a dispersal of undesirable fractions into chan# nels bearing no appreciable cost advantage.

In carrying out the improved process of the present invention, the dewaxing and deoiling operations are acinvention, the lower melting component employed as the wax to be modified by addition thereto of other slack waxes comprises that contained in the lowest boiling lubricating oil cut and containing waxes having anaverage melting point particularly in the range of 1Z0-125 F. AMP (American melting point, as defined in ASTM D87-42). The preferred higher melting wax component has an average of 13S-140 F. AMP, while the products most suitable for wax cartons andthe like have an average melting point of 13G-135 F. More generally, the present process may be applied to any parainwax obtained from the lubricating oildistillates but the effect is found when employing waxes having the above average melting point as a major component.

Wax isolated from a waxy lubricating oil of intermediate boiling range is preferably utilized in conjunction with the lower molecular weight waxes, although higher boiling range material may be so employed, The cut utilized preferably has the narrow boiling range (less than 1 5. carbon atoms spread) similar in'range to that' of the Ilc` wer boiling-waxylubricating oil and containing paraffin waxes exhibiting the samel spread in carbon atom content' as detailed above. For the purposev of obtaining wax prod! ucts having optimum low temperature properties, itis preferred that the slack waxes [obtained from two or'more lubricating oil distillates by dewaxing operation be combined in a proportion of about 30-50% by weight ofthe complished by chilling the waxy lubricating oils, preferl ably in the presence of oil solvents or diluents including,

for example, ketones, such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, etc.; alcohols, such'as ethyl alcohol, isopropyl alcohol, normal propyl alcohol and the like; petroleum naphthas, halo# genatedhydrocarbons, such as ethylene dichloride and trichloro ethylene; esters, such as ethyl acetate; ethers, such as diethyl ether and isopropyl ether; liquefied normally gaseous hydrocarbons, such as ethane, ethylene, propane, propylen'e, lbutane, isobutane, etc. eous diluents, such as methyl ether, methyl chloride and dichlorodifluoro methane, or mixtures thereof. The normally gaseous diluents serve to dissolve and dilute the oil and also to chill the mixture when the diluent is evaporated under reduced pressure. Ordinarily, mixtures of solvents or diluents, such as benzene, containing known proportions of methyl ethyl ketone are employed.

Solvent dewaxing step can be carried out by the various known methods wherein the primary object of the step is to obtain a substantially completely dewaxed lu Other normally gasf lower boilingslack wax to about 70-50% by weightof higher boiling slack waxes and the proportions of Vdeoiled waxes in the iinal products should be in thisy range as well. Still more preferably, the slack waxes are combined in such a ratio that the proportion of lower boiling paraffin waxes obtained from the lower boiling lubricating oil distillate after the deoiling operation following the combination of the slack waxes is between about 30 to about 50 weight per cent while the higher boiling parain waxes are present in an' amount between about 70 and 1 about 50 weight per cent.

As'stated hereinbefore, each of the waxy oils should contain waxes having a range of no more than about 15 carbon atoms between the wax molecules having highest and lowest molecular weights.

The dewaxing'step is still more preferably carried out on fractionsof waxy lubricating oil distillates having a relatively, narrow boiling range, such that the major'proportion'of parat-lin hydrocarbon waxes contained therein have av range of carbon atoms per molecule of not more than about 4 and preferably not more than 2 or 3, such that the vmelting-point of the highest melting isomeric parain wax in said fraction is lower than the melting point of the lowest melting normal paraffin wax therein. In general, it will be satisfactory if at least 90% of the isomeric lowest melting normal paraffin wax therein.

In accordance with a particular phase of the presentY For deoiling the slack wax combinations, it is essentialto employ relatively low deoiling temperatures if wax products having optimum low temperature propertiesfare desired. Preferably, the slack wax charge prior to'coolingis admixed with at least a substantial portion of the' solvent or diluent, such as at least l volumeV of solvent to 4 volumes of wax up to about l0 volumes of solvent for each volume of slack wax. Then the mixture is preferably heated to about 20-50 F. above the average melting point of the waxy material in order to dissolve the oil' and at least a substantial proportion of the wax in the deoiling solvent. During the subsequent chilling of the waxsolventoil mixture, additional solvent, such as 1'-5 or more volumes per volume of wax charge, may be added,

as desired. After the mixture has been cooled to'the proper relatively low wax deoiling temperature of below about 32 F. and preferably in the order of l0-30 F.,

vthe oil-free wax is separated from the foots oil in a suitable manner, such as-by a continuous filter. The wax product contains less than about 1% and preferably less than 0.5% oil. In` accordance with this invention, it has been found to be essential to deoilthe slack waxes, either before or after their combination, at temperatures below about 32 F., since higher deoiling temperatures provide oil-free waxes having poor ex and shatter resistance. The reasons for this are not clear, but it is to be emphasized that low deoiling temperatures alone arenot suiiicent to provide the desired type of waxes suitable' for use at low temperatures; it is necessary to utilize the two types of wax fractions defined hereinbefore, combined in the ratios already specified, and deoiled as just stated.

Referring to the drawing,v the waxy' lubricating oil i is 'drawn through pump Z'from tank 1 'into a distillation' column 3 wherein the waxy oil is split by distillationinto.

type from source 6. rIhe binary liquid mixture is then sent to separator 7, from which the solution of aromatics and solvent therefor is withdrawn and the remaining high viscosity index waxy lubricating oil is passed through line 8 and mixed therein with the dewaxing solvent obtained, for example, from the solvent recovery area 9. 'I'his mixture is then passed through a heater 10 and warmed to such a point that homogeneous solution is obtained. The latter is then subjected to a chilling operation in chiller 11 for the purpose of precipitating slack wax and obtaining a solution of dewaxed lubricating oil. 'Ihis mixture is separated in filter 12, the solution of dewaxed oil being pumped by pump 13 to a stripping column or similar piece of apparatus for the recovery of solvent in solvent recovery area 9. The solvent so recovered may be returned to the system, for example, into line 8. The dewaxed oil isolated during solvent recovery is sent by means of pump 14 to storage 15.

At least one other waxy lubricating oil cut from the distillation column 3 is processed through a similar series of steps in the same or a parallel set of apparatus in order to isolate a slack wax to be combined with the slack wax from cut A. This set of apparatus need not be detailed since the steps are substantially identical to those carried out on cut A and are shown in the figure as area 16. The slack wax so derived is pumped to the blend tank 17 together with a substantial portion of the slack wax obtained from cut A. Deoiling solvent from solvent recovery 18 is inserted in the lines to the blend tank or in the blend tank itself. The mixture is then pumped by means of pump 19 through heater 20 for the purpose of forming a homogeneous single phase system which is then conducted by means of line 21 to chiller 22 wherein the system is cooled to the relatively low deoiling temperature as specied hereinbefore.

The chilled mixture is passed to filter 23 wherein the deoiled puried wax product is separated from the solution of foots oil. The latter solution is passed by means of pump 24 to solvent recovery area 18 wherein the solvent is recovered and recycled to the system and the foots oil sent for further processing. The deoiled wax is sent by means of pump (or conveyer) 25 to the solvent recovery area where residual amounts of the deoiling solvent are removed in the area 26 to separate both the solvent and the wax product.

Having described a general but preferred set of apparatus and operating steps for the preparation of the subject wax products, the following specific example constitutes a utilization of the general process:

Example I Distillation of a Texas crude oil resulted in Cuts A and B, each comprising wax and oil. A lube oil of 100 SSU at 100 F. would finally be obtained from Cut A and a lube oil of 250 SSU at 100 F. would be obtained from Cut B. Both streams were mixed with solvents (2 parts of methyl ethyl ketone and l part of benzene to 1 part by volume of oil), cooled to 0 to +10 F. and iiltered. The slack waxes from each were combined in a 60% of A and 40% of B ratio, redissolved in the same solvent mixture, cooled and subjected to deoiling at +30 F. The resulting product passed bend and fracture tests defined hereinafter and had a melting point of 126 to 128 F. This wax was flexible enough to be satisfactory for milk containers and was obtained in 12% higher yield than by usual operations.

In contrast to the above described process, a method of manufacture that consisted of following the same procedure described above up to the final deoiling step, but from then on deoiled at 35 F. in one case and 45 F. in another case produced two wax products which would not pass the bend test and were unsatisfactory for milk containers.

The Bend Test recognized by milk carton manufacturers as one of the two tests of a wax satisfactory for coating of milk cartons is conducted as follows: A sample of the wax is cast into a cake 0.5 inch thick and is bent at a temperature of 77 F. In order to pass the test, the cake of wax must bend noticeably before breaking at this temperature.

The Fracture Test, which is recognized by carton manufacturers as the second basic criterion, requires that of 1/s inch film of the wax not crack when chilled from 104 F. by plunging into 40 F. water.

Example II The following table illustrates the benefits of thepresent invention and the necessity for avoiding the normal dewaxing temperatures. It also shows that combined (Sample G) or separate (Sample F) low temperature deoiling does not affect the quality of the eventual product.

Deoiling Bend Frac- Sample Wax Source Temp., Test ture F. Test A; Slack Wax from intermediate 45 Fail..- Pass.'

lube oil cut. v B do 35 Fail-.. Pass. C Slack Wax from low viscosity 45 Fail.-- Fail.

lube oil cut. ID -do 35 Fail.-- Fail. E -do 15 Fai1-- Fail.

60% slack Wax from intermediate 15 F lube oil cut. Pass-- Pass.

40% slack wax from low viscos- 30 ity lube oil cut. ZJlac wax from intermediate l1 e 0 C11 G""" 1i402', slack Wax from 10W viscos- 30 Pass Pass' ity lube oil cut.

I claim as my invention: l. The process of segregating a substantially oil free paraffin Wax having improved low temperature exibility which comprises distilling a solvent extracted waxy lubricating oil into a plurality of high viscosity index lubricating fractions waxy lubricating oil fractions, dewaxing one of said fractions to produce a substantially wax-free lubricating oil and a first slack wax which on deoiling would yield a first lower melting point wax, separately dewaxing a second of said waxy high viscosity index fractions to produce a substantially wax-free 1ubricating oil and a second slack wax which on deoiling would yield a second higher melting point Wax with an average molecular Weight from about 50 to about 150 units higher than that of said iirst wax, and solvent deoiling the slack waxes ata temperature below about 32 F. and above 10 F. toproduce a parain wax product having an average melting point in the range of 140" F. and improved low temperature ilexibility properties, the product containing 30-50% of wax from the rst slack wax and 50-70% of wax from the second slack wax, said waxes being combined together subsequent to the separate dewaxing steps.

2. The process of segregating a substantially oil free paraffin wax having improved low temperature flexibility which comprises distilling a waxy lubricating oil into a plurality of waxy lubricating oil fractions, solvent extracting said fractions to produce waxy high viscosity i11- dex lubricating oil fractions, dewaxing one of said fractions to produce a substantially wax-free lubricating oil and a lirst slack wax, which on deoiling would yield a wax with an average melting point in the range of 120/ F. AMP, separately dewaxing a second of said waxy high viscosity index fractions immediately above the boiling range of the first fraction so treated to produce a substantially Wax-free lubricating oil and a second slack wax which on deoiling would yield awax with an average melting point in the range of 135 F. AMP, combining substantial proportions of the slack waxes so produced and solvent deoiling the combined slack waxes at a temperature below about 32 F. and above 10 F. to produce a paran wax having an average Y Y wax-free lubricating oil and a first slack wax which on deoiling would yield a wax with an average melting point in the range of 1Z0/125 F. AMP, separately dewaxing a second of said waxy high viscosity index fractions to produce a substantially wax-free lubricating oil and a second slack wax which on deoiling would yield a wax with an average melting point in the range of 135/ 140 F. AMP, combining substantial proportions of the slack waxes so produced in a ratio of 30v to 50 volumes of the first slack wax to 70 to 50 volumes of the second slack wax and solvent deoiling the combined slack waxes at a temperature below about 32 F. and above 10 F. to produce a parafhn wax having an average melting point in the range of 130/ 135 F. AMP and improved low temperature flexibility properties. Y

4. The process of segregating an improved oil free wax having improved low temperature flexibility compris'- ing the steps of fractionating a waxy oil stock into a plurality of relatively narrow boiling waxy lubricating oil fractions', solvent extracting said fractions to produce high viscosity index waxy lubricating oil fractions, sepavrately dewaxing at least two of said fractions to produce substantially wax free lubricating oils and slack waxes from each fraction so treated, combiningV at least sub"l stantial portions of the slack waxes from at least two of such fractions, and solvent deoiling the mixture so Vformed at a temperature below about 32 F. and above 10 F to produce a paraffin wax having improved low temperature flexibility,

References Cited in the le of this patent UNITED STATES PATENTS

Claims (1)

1. THE PROCESS OF SEGREGATING A SUBSTANTIALLY OIL FREE PARAFFIN WAX HAVING IMPROVED LOW TEMPERATURE FLEXIBILITY WHICH COMPRISES DISTILLING A SOLVENT EXTRACTED WAXY LUBRICATING OIL INTO A PLURALITY OF HIGH VISCOSITY INDEX LUBRICATING FRACTIONS WAXY LUBRICATING OIL FRACTIONS, DEWAXING ONE OF SAID FRACTIONS TO PRODUCE A SUBSTANTIALLY WAX-FREE LUBRICATING OIL AND A FIRST SLACK WAX WHICH ON DEOILING WOULD YIELD A FIRST LOWER MELTING POINT WAX, SEPARATELY DEWAXING A SECOND OF SAID WAXY HIGH VISCOSITY INDEX FRACTIONS TO PRODUCE A SUBSTANTIALLY WAX-FREE LUBRICATING OIL AND A SECOND SLACK WAX WHICH ON DEOILING WOULD YIELD A SECOND HIGHER MELTING POINT WAX WITH AN AVERAGE MOLECULAR WEIGHT FROM ABOUT 50 TO ABOUT 150 UNITS HIGHER THAN THAT OF SAID FIRST WAX, AND SOLVENT DEOILING THE SLACK WAXES AT A TEMPERATURE BELOW ABOUT 32* F. AND ABOVE 10* F. TO PRODUCE A PARAFFIN WAX PRODUCT HAVING AN AVERAGE MELTING POINT IN THE RANGE OF 120140* F. AND IMPROVED LOW TEMPERATURE FLEXIBILITY PROPERTIES, THE PRODUCT CONTAINING 30-50% OF WAX FROM THE FIRST SLACK WAX AND 50-70% OF WAX FROM THE SECOND TO THE SEPARATE DEWAXING STEPS.

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