US3098598A - Dairy wax composition - Google Patents

Description

United States Patent Office 3,098,598 DAIRY WAX COMPOSITION George A. Weisgerber, Cranford, and Arthur J. Reinsch,

Middletown, NJ., assignors to Esso Research and Engmeering Company, a corporation of Delaware N Drawing. Filed June 1, 1061, Ser. No. 114,004 8 Claims. (Cl. 229--3.1)

The present invention is concerned with a new and improved wax composition and more particularly relates to the use of such a composition in the coating of paperboard milk cartons and the like. In accordance with the present invention, a superior dairy wax composition is formulated without utilizing residual microwaxes and using high quality waves secured from distillates. By utilizing the waxes of this character, greater flexibility and better wax distribution is secured, thereby producing a high quality waxed container. The wax composition of the present invention is secured by utilizing a conventional refined paraffin wax in conjunction with critical quantities of particular microcrystalline waxes which have been pro duced from various distillates.

In the refining of hydrocarbon oils such as petroleum oils, it is known to segregate paraffin waxes from socalled paraffin distillates, waxy lubes and the like. The overhead or paraffin distillate cfraction for example has a boiling range of about 580 F. to 850 F. and a viscosity of about 80 S.U.S. at 100 F. A heavy lubricating oil distillate side stream, for example, has a boiling range of about 800 F. to 1000 F. and a viscosity of about 50-70 S.U.S. at 210 F. The residuum comprises all the hydrocarbons boiling above this range and, for example, has a viscosity from about 150 to 200 S.U.S. at 210 F. Crystalline or parafiin waxes produced from the paraffin distillates have melting points which range rfrom about 120 F. to 150 F. This type of wax is characterized by large well-formed crystals that can be readily separated from the oil. Furthermore, this type of wax generally contains a relatively small amount of oil and can be refined with comparative case.

The segregation of these waxes is secured by a number of processes. For example, it is known to chill the selected wax containing fraction in order to secure crystallization of the wax and to remove the wax crystals from the oil by filtering, centrifuging and the like. It is also known to use various dewaxing solvents such as liquid normally gaseous hydrocarbons, such as propane, as well as other solvents, such as methyl ethyl ketone, methyl isobutyl ketone, and the like. It is also known to utilize in dewaxing operations solvent mixtures wherein one solvent comprises a wax precipitating solvent while the other comprises a solvent having a high solubility for oil. A solvent mixture of this character, for example, comprises 40% by volume of toluene and 60% by volume of methyl ethyl ketone In utilizing a mixture of this character, it has been thepractice to add the mixture in toto or incrementally to the waxy distillate as it is being chilled. In dewaxing operations, it is also known to use various filter aids and other agents in order to render the dewaxing and filtering operations more eflicient.

The wax segregated from the hydrocarbon oil, usually termed slack wax, contains from about 10% to 40% of oil. The slack wax is refined usually by conventional sweating to produce crude scale wax in a manner to reduce the oil content to less than about by weight. The slack wax may be distilled to obtain the desired boiling mange wax prior to sweating, if desired. This crude scale wax generally has an oil content of about 2% to 3% by weight. In order to remove this oil from the scale wax to produce a refined wax, such as a refined paraliin, having an oil content below about .5 usually below about 3%, various procedures have been proposed and employed.

Alternatively, the slack wax may be processed by a solvent deoiling process, to remove oil from the wax. In this, the wax is dissolved in such solvents as methyl isobutyl ketone, methyl ethyl ketonc, or mixtures of methyl ethyl ketone and toluene in a ratio of approximately to 25, respectively. The wax solution is cooled to produce crystallization and the crystallized wax is removed by a process such as filtration. The filter cake of crystallized wax may be washed with cold solvent to remove occluded oil solution. The wax so produced may be an unfinished refined paraffin wax or an unfinished microcrystalline wax, depending on the nature of the slack wax feed, and on the selection of crystallization conditions. After oil removal from the wax, it is subjected to a finish ing process such as clay percolation or hydrofining. In the latter, the process involves treating the unfinished wax with hydrogen gas at a rate of about 0.5-1.0 volume of wax per hour, at 500-800 p.s.i., at 500-600 F., in contact with cobalt molybdate catalyst. Or, at lower pressures such as 200 p.s.i., a nickel catalyst may be used. The hydrogen treated wax product is greatly improved with respect to color, odor and purity.

It is also known in the art to segregate microcrystalline waxes from residual oils. As pointed out heretofore, these crystalline waxes are normally produced from residuums which boil above about 1000 F. and have viseosities in the range from 150 to 200 S.U.S. at 210 F. These microcrystalline waxes are characterized by very minute crystalline forms and which melt in the range from about 145 -F. to 190 F. These microcrystalline waxes from residual oils are of a relatively high melting point and of different crystalline structure. The microcrystalline waxes may be prepared from any of the paraffin or mixed base crude oils. The undistilled residue may be treated with sulfuric acid and neutralized to remove the tarry matter and unsaturated hydrocarbons. The undistilled residue also may be deasphalted. The treated stock, containing a fairly high percentage of wax, as evidenced by a very high pour point, may be dewaxed by blending with a dewaxing solvent, such as propane, methyl ethyl ketonebenzol, or petroleum naphtha and chilled, and filtered or centrifuged to separate the Waxy fraction from the residual lubricating oil solution.

This dewaxing operation produces a wax fraction containing some oil and solvent. The wax after removal of the solvent has 13. melting point of from about to 180 F. The wax may be again put in solution with more solvent or naphtha and chilled and filtered or recentrif-uged to further reduce the oil content. The wax which separates in either of these operations is referred to as crude microcrystalline wax. The wax separated in the second crystallization process afiter stripping to remove solvent is fairly dry and of a low oil content. This wax should not be confused with petroleum jellies which contain large amounts or oil. The crude microcrystalline wax may be again put into solution with naphtha and filtered thnough clay or an equivalent material in order to improve its color. The clay filtered solution is distilled to remove the naphtha, the residue being a refined petrolatum wax having a melting point within the range of about to F. Alternatively, the microcrystalline wax may be hydrogen treated to improve its color and odor, such as by hydrofining at about 600 F., 600 p.s.i. of hydrogen, using cobalt molybdate catalyst. The source of the crude oil and the oil content or the refined microcrystalline prodnot will affect the melting point of the final wax product. The refined microcrystalline wax, sometimes called amorphlous wax, is as pointed out, of a very small crystal structure.

It is also known in the art to segregate microcrystalline Patented July 23, 1963 waxes from distillate lubricating oils. These distillate type micnocrystalline waxes differ in characteristics from the residual type micnocrystalline waxes hereinbefore described. Thus, the distillate waxes are lower in viscosity and are generally finished to a higher degree of purity, such as freedom from color and odor. Furthermore, the distillate microorystalline waxes have two advantages over the residual microcrystalline waxes from the standpoint of ease of manufacture. Namely, first, the distillable nature of the wax makes it possible to manufacture specific microcrystalline wax fractions for use in specific product applications; and, second, the distillate waxes can be more readily and more economically refined with respect to color and odor than can the residual microcrystalline waxes. These features of distillate microcrystalline wax (low viscosity, high purity, select fractionation, economy of finishing) have been found to be of particular value in the present invention.

The distillate microcrystalline waxes are manufactured fnom distilled waxy lubricating oil fractions from crude oil. These fractions will vary with regard to distillation range, depending upon the desired viscosity grade of the lubricating oil ultimately produced. Thus, a number of fractional cuts may be taken across the lubricating oil distillation range, to produce different lubes. The entire range may cover 'a distillation from about 6S01180 F. (760 mm. basis). Each of the fractional waxy lubricating oil cuts is processed to remove the waxy components by a process such as dewaxing by solvent crystallization. As hereinbefiore described, this comprises dissolving the waxy distillate in such solvents as methyl ethyl ketone, methyl isobutyl ketone and mixtures of methyl ethyl ketone and toluene, cooling the solution to cause crystallization of the wax, then filtering to separate the lubricating oil and the slack Wax. The slack wax is then processed to further remove oil from it by a procedure such as solvent deoiling. In this operation, the excess oil is removed from the slack wax, by the solvent crystallization technique, while, at the same time, the solvent and temperature conditions are controlled to :achieve a fractional crystallization of the wax fraction. Thus, a slack wax may be crystallized first at a relatively high temperature to separate the most crystalline, paraffi-nic and high melting wax components present in the slack wax as the solid phase. The melting point may range from 140 to 190 F depending on the properties of the slack wax feed and the crystallization temperature. The filtrate phase is then further cooled to cause a second crystallization of the wax which is microcrystalline in nature, and of lower melting point than the first wax cut. Waxes in this fraction vary from 125l40 F. melting point. By selection of the solvent composition and crystallization temperature, the exact properties of the separated wax can be controlled. The

filtrate from the second crystallization contains the oil which was removed from the wax fractions. Both the first and second fractions of wax contain about 0.2 to 1.5% oil, this generally being 0.3 to 1.0% oil. These deoiled wlax fractions may then be finished to the desired degree of purity with respect to color and odor by one of several methods, such as the hydrogen treating (hydrofining) or adsorption (clay percolation) methods previously described. As a final manufacturing operation, the paraffin or microcrystalline wax may be distilled again to further separate specific wax fractions.

In compositions of the current invention, it is particularly important that microcrystalline waxes of the distillate type rather than microcrystalline waxes of the residual type, be employed as components in the dairy wax coating formulations.

It is also known in the art that the wax formulations used for milk carton coating are among the most critical of all wax applications from a quality standpoint. The quality of the wax coating is under continuous close scrutiny by the dairy operators, milk distributors, retail stores, and the ultimate users. For example, it is known that waxes exist on the market which have good performance quality in one or two aspects, but which also have certain quality weaknesses. The overall quality for dairy waxes is controlled by a number of rigid tests. One test is the flaking test which measures the degree to which wax particles will flake off the canton and adulterate the milk. Other rigid tests for wax for milk coated cantons are the bottom wax accumulation test, the bottom wax flowing test, the cold flexibility test, the consumption test, as well as the appearance of the coating, the dye coverage, and the rubaolf.

However, the most important diactors are those that concern the very undesirable flaking, since the excessive wax floats in the milk and is of immediate deep concern to the users. Flaking is a prime cause of customer complaint. The flaking test procedures are as follows for Waxed milk cartons after passing through the waxing machine and after filling with a liquid at 38 F., the normal filling temperature.

METHOD A Five to ten filled test cartons are each dropped eight times from a height of 7 inches onto a rail frame, i.e. a group of rods spaced apart, 4" long for /2 gallon cartons and 3 long for quart cartons. The displaced flakes are filtered out, washed, dried and weighed.

METHOD B Same as Method A except that the cartons are dropped onto a metal plate slightly greater than the size of the carton bottom, having the corners of the plate turned up (dog-earred) to a height of A METHOD C Thirty-six filled test cartons are each dropped twice from a height of 5 inches onto the corner plate described in Method B for half gallons. For quarts, the 36 cartons are dropped 6 times from a height of 5 inches.

The bottom wax accumulation test is a visual rating of the relative amount of wax that has run down the sides of the carton and has gathered inside of the carton at the bottom. The accumulation is rated as light, moderate, or heavy. Greater accumulation tends to lead to more flaking.

The bottom wax flowing test determines the amount of molten or semi-molten wax that flows across the bottom of the carton due to the vigorous motion of the carton as it travels through the cooling or wax hardening section of the dairy machine. The molten lava-like flow does not re-fuse with the main body of wax, but tends to solidify separately from the main coating, in the form of a thin sliver or overlayer on the bottom, in the corners, or washed up the sides. This overlayer is very readily displaced if the carton receives a mechanical shock due to rough handling. Flowing is a phenomenon depending very much on the machine type, and on the routing of the carton within the cooling chamber. In some machines flowing does not occur and is not contributory to flaking. In other machines, where flowing can occur, it becomes an extremely serious problem. Flowing is evaluated by visual observation of the inside coating of the carton and the displaced flakes.

The cold flexibility test determines cold flexibility rather than brittleness. Cold flexibility is desired in the wax coatings in order to resist mechanical shock. The cold flexibility is evaluated by cutting off the bottom of a test carton which has been filled with liquid at 38 F., and rapidly flexing the bottom through an angle of about degrees. The rating of poor to very good is made on the basis of audible brittleness, the degree of cracking and the separation of ruptured flakes from the bent paperboard.

Consumption is the rate of wax usage per thousand cartons, measured by weighing cartons before and after waxing. High wax consumption generally tends to produce high wax accumulation and flowing and high flaking.

Also, a reasonable amount of consumption must always be maintained in order to achieve a uniform protective covering of the paperboard.

In accordance with the present invention, a conventional refined paraflin wax is used in conjunction with 5 The microcrystalline waxes are secured from distillate critical amounts of various microcrystalline waxes prolube oil petrolatums by recrystallization techniques utilizduced from distillate sources. These waxes of the presing a solvent comprising methyl ethyl ketone and methyl ent invention have outstanding and unusual advantages isobutyl ketone. over other commercial dairy waxes. The waxes of the Microcrystalline wax A was secured by treating a dispresent invention avoid or minimize the bottom accumutillate waxy lubricating oil stream of about SAE 30 with lation and flowing, and impart desirable cold flexibility, a solvent at a temperature of 20 F. with approximately leading to an overall reduction in the level of the flaking. 3 volumes of solvent to one volume of oil. Under these The wax of the present invention will also have better conditions, a slack wax was produced and separated from performance by reason of better cold flexibility characthe lubricating oil. The slack was then redissolved in teristics. about 6 volumes of solvent to one volume of wax and Thus, avery important part of this invention is that these Cooled. to to achieve qystalli'zatiom Under these characteristics are achieved Without utilizing residual conditlons, melting Paint Parafi'in Wax Was microwax o overhead waxes are used Advantages removed. The filtrate was further cooled to a temperature are thereby realized with regard to purity, availability and of F with treatment 3 Volumes of solvent to one cost. While the residuals can be further purified, this Volume of WaX, cfystalllze microcfystalline WaX has not been widely done, and the added cost largely Microcrystalline wax B was secured by treating a waxy excludes the resulting highly purified microcrystalline wax lubricating oil distillate of SAE 60 with 5 volumes of. from dairy wax for the competitive market. Overheads solvent to one volume of waxy lubricating oil distillate are inherently cleaner and are more susceptible to conat a temperature of F. Under these conditions, a ventional finishing methods. 25 slack wax was produced which was then redissolved with Thus, the present invention comprises the use of overheat in about 6 volumes of solvent to one volume of wax head waxes, without residuals; the use of specially preplus oil feed and cooled to about 96 F. The wax fraction pared, solvent crystallized overhead wax of a relatively precipitated comprised crude microcrystalline wax B. flexible type, (the wax is prepared by deeper deoiling -i.e. The filtrate was further cooled with 7 volumes. of sollower temperature than has previously been used to make vent to one volume of wax plus oil feed. At the temperadairy wax components); and the use of a special high ture of 48 F., the crude microcrystalline wax 10 was congealing point overhead wax to reduce bottom accollected. cumulation and flowing. The crude microcrystalline waxes were finished by In cases where control of accumulation and flowing are hydrogen treating at 600 F. and 600 p.s.i., using cobalt desired or necessary, it is seen further that the congealing point of the preferred dairy wax should be about 140 F. minimum, and preferably about 145 F.

The refined paraffin wax is secured as described heretofore and comprises a deoiled slack wax to produce a refined wax having an oil content less than about 3% by weight.

molybdate catalyst to improve their quality with respect to color, \odor, and purity. The inspections of the respective wax fractions are listed in Table I; I

Table I TYPICAL WAX COMPONENT INSPECTIONS Identity Microcrystalline A B C Refined base wax Description Second crystalli- First crystalli- Second crystallization from zation from ration from Ketone (MIBK) MIBK deoiling MIBK deoiling deoiling of SAE of SAE slack of SAE 60 slack 30 slack wax wax wax Gongealing pt, F 1% 139 1 128. Viscosity at 210 F., cs 6.5 11.0... 11.4 3.8. Distillation, F. at-

Pressure 10 1 1 10.

5 an) am 610 502,

98 71 688 MR 62L Width of distillation at 595%, F 216 at 10 mm... 150 at 1 mm 255 at 1 mm..." 135 at 10 mm.

The waxes of the present invention are characterized by having the following constituents.

The high quality of the Wax composition of the present invention may be readily appreciated by the following examples wherein the various w ax compositions were Percent by Weight 65 tested utilizing several field tests and full-scale machines.

Constituents Range Preferrcd Test location Machine model Criticality Refined par'affin wax (about 3% oil) -90 F, quart Bottom wax accumulation. Microcrystalline A 8-12 0, 36 gallon" Accumulation and flo ing, Microcrystalline 3.. 3-12 5 S. 3 gallon Accumulation. Microcrystalline C 3-7 5 Polyethylene (7,000 molecular Weight) 1-2.0 .5 Polyethylene (12,000 molecular Weight) 1-2.0 .5 Oxidation inhibitor 00031001 -0005 The results of these test are shown in the fOHQWlHg Table II.

Table II DAIRY WAX CONTAINING MIOROCYSTALLINE WAXES A, B, C IMPROVES FLEXIBILITY, REDUCES FLAKING AND ELIMINATES FL-OWING [Test arrangement: Location L, machine 0, wax temperature 180 F.]

Test I II III IV Base plus 0.57 12,000 molecular weight oomposltmn polyethylene plus 0.5% 7,000 molecular weight polyethylene plus microcrystal- Cmpe line wax mive 4 B 7A 4 B 107A "7 B conimer' 17 A, ,o cia wax 03% O0 05% OD Consumption, lbs/1,000 otn 42.0 40.6 42.0.- 42.3. Flaking, gm./1,000 ctn.:

Method A 9 4 22. MethodB 2'; 17 10 24. Method 0 0.8 0.2 3.3. Co1dfiexibility Very good". Very good... Very good Good. Flowing Yes Verylittle... Np Yes. Bottom wax accumulation Moderate--- Lt.tomod Light Heavy Oongealing point, F. 13 141 1 5.

From the above it is apparent that formulation I gives fairly good performance, similar to a highly rated commercial wax IV, but with the disadvantage that bottom wax accumulation and flowing occur. This is very markedly reduced by adding 3-5 of C, and the better wax distribution directly reduces flaking, as measured by the several test techniques. In this arrangement, where flowing is critical, the full formulation with C is required.

I Additional tests were carried out with the following results.

From the above it is apparent that the improved wax V gives less accumulation, better flexibility, and less flaking. In this machine, flowing is not critical. However, even in the absence of flowing, wax V is better than wax VI.

Additional tests were carried out in a machine where flowing was not critical. From the examination of the following data, it is apparent that wax C shows continued general advantage over two highly rated commercial waxes.

Table IV NEW DAIRY WAX IS SUPERIOR TO COMPETITIVE PRODUCTS [Test arrangement: Location D, machine S] Test No VII VIII IX Composition III IV Competitive commercial wax Consumption, lbs/1,000 ctn 48.7 48.9 55.3. Flaking, gin/1,000 0th.:

MethodA 9 0 22. MethodB 13 G6 18. Cold flexibility Good Poor. Bottomwaxflowing No No No. Bottom wax accumula Moderate- Heavy Heavy.

From the above it is apparent that, in still another machine where flowing is not critical, the wax composition of the present invention shows excellent advantages over two highly rated commercial waxes.

Thus, the presentinvention is concerned with an improved wax composition which is particularly desirable for coating of dairy cartons which comprises a base parafiin wax used in conjunction with critical amounts of disrillate micnocrystalline waxes.

While the wax compositions of [the present invention were particularly developed and designed to serve as coatings for milk cartons, it will be appreciated that these wax compositions will also find useful application in other fields. Thus, paper or paperboard products coated with Waxes of the current'invention can be effectively used for packaging of orange juice, grape juice, cottage cheese, frozen food, and the like. In such applications, the excellent coven'ng quality of :the wax, its flexibility at low temperature, resistance to thermal or mechanical shock, good purity qualities and so forth, are of particular value. Similarly, the Wax may be used as a direct coating of foodstuffs or other items, without paper, where the packaged material is to be subjected to conditions of low temperature, mechanical shock, and the like.

What is claimed is:

1. An improved wax coating composition which comprises essentially a refined paraflin wax present in a con- CGIHIFMIOH from about to by weight, a first overhead microcrystallline wax present in a concentration of from about 8 i 12% by weight, said first overhead microcrystalline wax having a congealing point of about F., a 5% distillation temperature at 10 mm. pressure of about 490 F. and a 95% distillation temperature of about 706 F., a second overhead microcrystalline wax present in a concentration from about 3 to 12% by weight, said second overhead microcrystalline wax having a congealing point of about 182 F., a 5% distillation temperature at 1 pressure of about 509 F. and a 95% distillation temperature of about 659 F., and a third overhead microcrystalline wax present in a concentration of from about 3 to 7% by weight, said third overhead microcrystalline wax having a congealing point of about 136 F., a 5% distillation temperature at 1 mm. pressure of about 436 F. and a 95% distillation temperature of about 661 F.

2. An improved wax covered canton which comprises in combination a paper carton having adhered thereto a wax composition as defined by claim 1.

3. The composition of claim 1 wherein said refined parafiin wax is present in aconcentration of about 79% by weight, wherein said first overhead microcrystalline wax is present in 'a concentration of about 10% by weight, wherein said second overhead microcrystalline 9 wax present in a concentration of about 5% by weight, and wherein said third overhead microcrystalline wax is present in a concentration of about 5% by weight.

4. The composition as defined by claim 3 wherein said composition comprises about 1% of polyethylene.

5. The composition as defined by claim 4 wherein said polyethylene comprises about 0.5% by weight of a polyethylene of about 7,000 molecular weight and about 0.5% by Weight of a polyethylene of about 12,000 molecular weight.

6. The method of preparing improved wax coating compositions comprising treating a waxy lube distillate with solvent thereby precipitating a wax having a melting point of about 155160 F. and thereafter cooling the filtnate to crystallize a first microcrystalline wax, treating a second waxy lube distillate with solvent to precipitate a slack wax therefrom and thereafter deoiling said slack wax to produce a second mlicrocrystalline wax, thereafter cooling the filtrate from the said second microcrystalline wax to precipitate a third microcrystalline wax and then mixing minor amounts of the above first, second and third microcrystalline waxes with a major amount of a refined paraffin wax.

7. The method of claim 6 wherein an additional minor amount of a polyethylene is present.

8. The method of claim 6 wherein the first waxy lube distillate has an SAE viscosity of about 20 to 40 and the second waxy lube distillate has an SAE viscosity of about References Cited in the file of this patent UNITED STATES PATENTS 2,733,225 Smith Ian. 31, 1956 15 2,967,817 Marple et al. Jan. 10, 1961 2,988,528 Tench et a1. June 13, 1961 FOREIGN PATENTS 597,090 Canada Apr. 26, 1960

Claims (1)

1. AN IMPROVED WAX COATING COMPOSITION WHICH COMPRISES ESSENTIALLY A REFINED PARAFFIN WAX PRESENT IN A CONCENTRATION FROM ABOUT 70 TO 90% BY WEIGHT, A FIRST OVERHEAD MICROCRYSTALLINE WAX PRESENT IN A CONCENTRATION OF FROM ABOUT 8 TO 12% BY WEIGHT, SAID FIRST OVERHEAD MICROCRYSTALLINE WAX HAVING A CONGEALING POINT OF ABOUT 130* F., A 5% DISTILLATION TEMPERATURE AT 10 MM. PRESSURE OF ABOUT 490*F. AND A 95% DISTILLATION TEMPERATURE OF ABOUT 706*F., A SECOND OVERHEAD MICROCRYSTALLINE WAX PRESENT IN A CONCENTRATION FROM ABOUT 3 TO 12% BY WEIGHT, SAID SECOND OVERHEAD MICROCRYSTALLINE WAX HAVING A CONGEALING POINT OF ABOUT 182*F., A 5% DISTILLATION TEMPERATURE AT 1 MM. PRESSURE OF ABOUT 509*F. AND A 95% DISTILLATION TEMPERATURE OF ABOUT 659*F., AND A THIRD OVERHEAD MICROCRYSTALLINE WAX PRESENT IN A CONCENTRATION OF FROM ABOUT 3 TO 7% BY WEIGHT, SAID THIRD OVERHEAD MICROCRYSTALLINE WAX HAVING A CONGEALING POINT OF ABOUT 136*F., A 5% DISTILLATION TEMPERATURE AT 1 MM. PRESSURE OF ABOUT 436*F. AND A 95% DISTILLATION TEMPERATURE OF ABOUT 661*F.