US 3312648 A
Description (OCR text may contain errors)
United States Patent ()fifice 3,312,648 Patented Apr. 4, 1967 3,312,648 COMPOSITIQN CONTAINING WAXES AND PGLYETHYLENE Arnold L Gnttman, Chicago, and John Pozllipnik, Palos Heights, 101., assignors to Sinclair Research, Inc., Wilmington, Del., a corporation of Delaware N Drawing. Filed Aug. 9, 1962, Ser. No. 215,788
2 Claims. (ill. 260-285) This invention relates to a new wax composition particularly useful in the manufacture of wax-coated paperboard containers.
Wax compositions have found increasingly extensive use in recent years for coating paper and paperboard materials as, for instance, milk and juice cartons. In certain of these applications, especially those wherein the wax coating is applied to the inside of the containers, it has become highly desirable that the wax composition meet the following requirements:
(a) The wax coating must posses exceptional flexibility and toughness at 40 F. in order to preclude cracking and flaking under shock loads which occur when the filled cartons are roughly handled;
(b) The wax should substantially enhance the flexural strength of the paperboard in order to minimize bulging of the carton panels under the hydrostatic pressure of its contents;
(0) The fiow out properties of the wax should be such that under the conditions of application the coating will be smooth and provide essentially complete coverage of all surfaces;
(d) The wax composition should not be tacky to the extent that causes dilficulty in opening any closures prior to filling of the cartons;
(e) The wax composition should have a high enough congealing point so that it will not flow When the coated cartons are exposed to ambient storage temperatures as high as 130 F., and
(f) The wax composition must have no objectionable odor and taste and must in all other ways meet safety requirements.
Heretofore, attempts toward the formulation of a wax composition that meets all of the above requirements have failed. For example, a blend of certain wax components designed to meet one or more of the requirements quite often has been found to create additional or adverse effects upon other desirable properties so that the Wax composition fails one or more of the other requirements. A particularly severe problem, for example, has been meeting the low temperature crack resistance and carton durability requirements. Until the present invention, compositions of the prior art to our knowledge have been unable to meet these latter requirements while still having desirable viscosity and flow and minimum tackiness.
We have now discovered a wax composition containing a plurality of wax components of defined properties which, when combined in particular proportions, provide a product that meets all of the above requirements. Each component of our composition makes its contribution to the end product in such a way that it does not adversely affect physical and functional properties fundamentally contributed by the other components and is apparently able to do this because of its particular properties, defined concentrations and the relationship it holds to the combination of all the components.
The novel wax composition is comprised essentially of about 35 to 50% of paraffin wax, about 20 to 35% of a relatively high viscosity isoparafiin-naphthenic wax, about to 20% of a relatively hard microcrystalline wax, hereinafter designated microcrystalline wax A, about 10 to 20% of a relatively soft microcrystalline wax, hereinafter designated microcrystalline wax B, and about 0.5
to 2% of a low molecular weight, branched chained polyethylene. These percentages are by weight. This composition can be applied to paperboard container by any manner known to the art as, for example, by dipping the container in a vat of the melted wax composition, for instance maintained at a temperature of about 170 to 220 F., withdrawing the coated containers from the vat and cooling with air. The composition is particularly suited for application of a wax liner to the container. The coating can be sprayed into the container or the container filled with the melt wax composition, emptied and then cooled. Paperboard presently employed in the packaging industry such as sized and calendered paperboard produced by the cylinder or Fourdrinier process and having a low moisture content, i.e. about 5%, is an example of the base material that can form the carton. The base carton material can also be formed by laminating two or more plies of paper, foil, and other films using polyethylene or other materials as the adhesive. Furthermore, the carton material can have an extrusion coated plastic film on the outside for water proofness. It is preferable that the innermost layer of the carton material be made of paper so as to allow sufficient penetration of the wax composition to strengthen and water-proof the carton.
The parafiin wax component of the present invention is composed of essentially straight chain crytalline pa-raflins and has a melting point in the range of about 125-l35 F. (ASTM D87-57), and a viscosity SUS at 210 F. (ASTM D446-53) of about 35 to 40. It is preferably a fully refined parafiin wax, i.e. essentially tasteless and odorless and contains a maximum oil content of about 1.0% (ASTM D721-56T). These essentially straight chain parafiin waxes are obtained from parafiin-containing crude petroleum oils such as mixed base crudes by procedures well known to the art. The preferred paraffin wax is a 127-130 F. (ASTM D87-57) melting point wax. Blends of different melting point waxes of this essentially straight chain type are permissible so long as the physical properties of the blend fall Within the ranges defined above. The parafiin wax component of the present invention functions to improve the modulus of rupture and it is adjusted to control the viscosity and melting point of the complete composition of this invention.
The high viscosity isoparafiin-naphthenic wax component of our composition is a flexible, low melting point, non-normal or non-straight chain paraffin-type Wax, present for instance, in heavy lube distillate slack wax. It can be obtained, for instance, by solvent deoiling the foots oil fraction resulting from the solvent deoiling of heavy lube distillate slack Wax. These slack Waxe are those used in the production of the higher melting point paraflin waxes, for example, of about l45-160 F. melting point. The foots oil Wax thus obtained is characterized by a relatively high visicosity for its low melting point, a soft and pliable nature and an exceptionally good low temperature flexibility. Listed below are the approximate requirements which are met by an isoparaflin-naphthenic wax satisfactory for us in the composition of the present invention:
Molecular weight (average) 450 min. Melting point, ASTM D87-57 120 F. or even F.
Viscosity at 210 F. SUS, ASTM D446-53 42-50. Oil content, ASTM D721-56T 2.0 max. Refractive index n 1.4400 min. Penetration at 77 F. (ASTM Dl321-57T) 40-100.
This wax, while crystalline in nature, often contains roughly equal amounts of isoparaflins and alkyl cycloparaflins with a minor amount (e.g. about 20%) of n-parafiins, as determined by mass spectrometer, gas chromatgoraphy and n, d, M ring analysis of material fractionated by urea treating. The concentration of the isoparafiin-naphthenic wax component in the novel wax composition is about to by weight. Addition of higher percentages would considerably increase the viscosity of the finished blend. Concentrations of less than about 20% by weight are usually in'eifective.
The relatively hard microcrystalline wax A component of the present invention has a petrolatum melting point of about 160 to 180 F.; a 100 gram needle penetration (ASTM D5-52) at 77 F. of about 15 to 40; a viscosity (ASTM D446-53) at 210 F., SUS of about 75 to 90; a refractive index (11 of 1.4470 minimum; and an oil content (ASTM D-72l-56T) of about 2% maximum. This microcrystalline wax component can be obtained by deoiling of petrolatum produced by the conventional deasphalting, and solvent dewaxing of residual oils obtained from mixed base or Mid-Continent crude oils. The addition of this microcrystalline wax component has proved particularly beneficial in improving the durability of the wax-coated carton.
The second microcrystalline wax component of the present invention, that is microcrystalline wax B, is considerably softer and mor flexible than the above described microcrystalline wax A component. Microcrystalline wax B has a petrolatum melting point (ASTM Dl2749) ot about,l30-l60 F.; a cone penetration (ASTM D937) at 77 F. of about -100; a viscosity at 210 F. ofabout 65 to 100 SUS; a refractive index 115 of 1.4490 minimum and an oil content (ASTM D721-56T) of 5 maximum. Whereas microcrystalline wax A is added to improve the container durability, that is, prevent leakage and provide a stronger carton under severe abuse conditions, microcrystalline wax B is added mainly to improve resistance to cracking and flaking at low temperatures and to a lesser degree to improve durability. Microcrystalline wax B is considerably richer in cycloparafiins that microcrystalline wax A, the cycloparaffin content of the wax including both non-condensed and condensed cycloalkanes usually being at least about 25% by weight. This microcrystalline wax component can b obtianed from Pennsylvania and Mid-Continent petrolatum and can be best described as a heart cut of the parent petrolatum resulting from the removal of both the most oily components and the most crystalline, leaving the desired microcrystalline wax fraction. This fraction is generally obtained by various combinations of deoiling procedures using selective solvents such as for example, a mixture of methyl ethyl ketone, toluene and benzene. Because of it tacky nature the concentration of microcrystalline wax B is limited to about 20% by weight maximum. The proportions of microcrystalline wax A to microcrystalline wax B can generally b varied within the range of about 2 to 1 and 1 to 2, but a ratio of '1 to 1 is preferred. It is important to emphasize that use of either of the microcrystalline wax components A or B alone in the wax composition does not result in a suitable final wax composition.
The polyethylene component of the wax composition is a low molecular weight polyethylene, that is, a polyethylen having an average molecular weight of about 1500 to 7000 and which in addition is highly branched. The degree of branching of polyethylene is closely re- 'lated to the density of the solid polymer with the highly branched polymers having the lowest density. Polyethylenes suitable for use in the present invention have a density of about 0.88 to 0.91. We have found that the essentially straight-chained polyethylenes even in th low molecular weight ranges are unsuitable for use in the present invention. The polyethylene component is employed to further enhance the low temperature flexibility and toughness of the finished blend. Without the polyethylene component the wax composition does not have suflicient flexibility and toughness to preclude cracking and flaking under shock loads. The concentration of the branched-chain polyethylene component may be varied from about 0.5 to 2.0% by weight but about 1.0 to 1.25% i preferred. The polyethylene may be a copolymer where the monomer other than ethylene is a minor portion, 'e.g. up to about 10%, of the total monomers. As an example, a ethylene-vinyl acetate copolymer, about 4 to 5% vinyl acetate, has been found to be satisfactory.
Other ingredients may be added toour wax composition in minor amounts so long as they do not unduly 'deleteriously affect the desired properties of th wax composition. These additional ingredients may be for example, defoamers, antioxidants, other waxes, etc.
The following examples are included to illustrate preparation of the wax components and the final wax composition.
Example I By conventional vacuum distillation of a Mid-Continent crude, a waxy light lube distillate was prepared having a 10- 90% distillation range of 660790 F. at 760 mm. pressure. This distillate was dearomatized by conventional phenol treating and dewaxed to produce +l0 F. pour point oil by conventional solvent dewaxing by low temperature precipitation from MEK-toluene solution. The resultant slack wax was subjected to two successive solvent deoiling steps, using conventional MEK-toluene deoiling, at 50 F. temperatures to produce a first foots oil, a second foots oil, and ahard, oil-free n-paraffinicwax of 130 F. melting point designated as paraffin wax A.
Example II Another component wax was prepared by processing a waxy medium lube distillate, similar in source to that of Example I and having a 10-9-0% distillation range of 7 -8 80 F. Techniques described in Example I were used to produce a hard, highly n-paraffinic wax of 143 F. melting point designated as parafiin wax B.
Example III A waxy heavy lube distillate similar in source to that of Example I but having a 10-90% distillation range of '01 050 F. was processed using the same techniques and sequence used in Example I to produce a hard, oilfree wax of 152.5 F. melting point designated as paraffin wax C. The two foots oils produced were combined and solvent deoiled at 10 F. to produce a rejected oily filtrate and a substantially oil free fonts wax of 119.4 melting point, rich in both iso-parafiins and naphthenic (cyclo alkanes) parafiins. This foots wax is designated Non- Straight Chain Distillate Paraffin Wax.
Example IV By conventional vacuum distillation of a mixed-base crude the fractions-boiling below 1050 F. were substantially removed. The residual stock was deasphalted by conventional propane extraction. The deasphalted oil was then dearomatized by conventional phenol treating, and dewaxed at 8 F. by conventional solvent dewaxing, employing a 5050 mixture of MEK-toluene as the solvent. The resultant petrolatum was deoiled by conventional MEK-toluene deoiling at 35-50 F. temperature to produce microcrystalline wax A of 169 F. petrolatum melting point and a first foots oil. This first foots oil was deoiled by conventional MEK-toluene solvent deoiling at l020 F. temperature to produce the soft, flexible microcrystalline wax B of 143 F. M.P.
The physical properties of the various component waxes are presented in Table I.
TABLE I.TESTS ON WAX COMPONENTS Various finished wax blends were prepared by combining the component waxes and filtering the blends through ASTM D938-60.
2 Obtained using a Brookfield Viscosimeter with Ultra-Low adapter.
3 Tackiness, Viscosity, M of R. M of R, Viscosity.
Melting Point, Percent activated bauxite in order to remove traces of colored or 011 malodorous 1mpurit1es. Polyethylene, where used, was ASTM ASTM D37 57 ASTM D938 60 DTQHBT then added to yield the final composition. The various blends thus formed were sub ected to a variety of tests and Parafiin Wax A 11 the blends and test results are set forth in Table II. Parafifin Wax B 0.0 Paraflin Wax C 0.51 N on-Straight Chain Distillate Parafiin W 119. 4 1. 4s
Viscosity at Penetration at Refractive l5 210 F. (SUS) 77 F. ASTM Index, on"
ASIM D5-52 D446-53 Paraflin Wax A 37. 0 0 1. 42665 Parafiin Wax B. 40. 4 8 1. 43030 Paraffin Wax C 47. 3 15 1 43640 Non-Straight Chain Distillate Paraflin ax 48. 4 64 1. 44070 Microcrystalline ax 85. 3 24 1. 44980 Microcrystalline Wax B 95. 2 116 1. 45380 TABLE II Finished Blend N o 1 2 3 4 5 6 7 8 9 10 Composition, Weight Percent:
Paratlin Wax A 25 40 40 45 Parafiin Wax B 40 25 Paralfin Wax C 40 Non-Straight Chain Distillate Parafiin Wax 50 30 30 30 30 30 30 30 30 25 Microcrystalline Wax A 15 15 15 Microcrystalline Wax B 50 30 30 30 20 20 15 15 15 15 Polyethylene A (Density 0.89, M01. Wt.
4,000) +1. 25 +1. 25 +1.25 +1.25 +1.25 Polyethylene B (Density 0.92, M01. Wt.
00 +1.25 Monsanto PC-1344 Foam Inhibitor,
p.p.m +60 BHI Oxidation Inhibitor, p.p.m +10 +10 Properties:
Congealing Point, F 125.0 129. 0 125.0 139. 0 144.0 140. 0 Viscosity 2 at:
210 F., cp 8. 98 5. 93 6.61 7.11 4. 90 5. 51 4. 5. 74 5. 61 5.32 175 F., cp 15. 45 9. 07 10. 38 11. 31 7.14 7. 48 6. 99 8. 71 8. 34 7. 96 145 F., op 10. 54 11.0 10.21 13. 86 17. 50 12.24 Modulus of Rupture at 40 F., p.s.i 266 342 336 420 672 681 650 697 692 733 Beam Deflection at max. load at 40 F.,
iHOheSXIO 145 131 125 128 106 145 123 Drop Test. Pass Pass Fail Pass Pass Pass Wax Flow-out on Carton Panels Eric. .G. Exc. .G. Poor Exc. Simulated Dairy Abuse Test. 55 80 Reasons for Rejection M of R Drop Flow- Test out Finished Blend N o 11 12 13 14 15 16 17 18 19 20 Composition, Weight Percent:
Parafiin ax A 40 35 20 40 40 50 50 40 40 40 Paraffin Wax B 20 Paraflin Wax C 5 10 N on Straight Chain Distillate Paraifin Wax 25 25 30 30 30 30 20 30 30 30 Microcrystallinc Wax A 15 15 15 20 10 20 15 15 15 15 Microcrystalline Wax B 15 15 15 10 20 15 15 15 15 Polyethylene A (Density 0.89, M01. Wt.
4,000) +1.25 +1.25 +1.25 +1.25 +1- 25 +1. 25 +1.25 +0. 5 +1. 0 +2. 0 Pglggghylene B (Density 0.92, M01. Wt. Monsanto PC-l344 Foam Inhibitor".-- BHI Oxidation Inhibitor Properties:
Congealing Point, F 141. 0 142. 0 140.0 138.0 132.0 139.0 138.0 137. 5 138.0 139.0 Viscosity 2 at:
210 F., e 5.58 5. 71 6.06 5. 65 5. 93 4. 86 5. 11 5. 30 5. 54 6.08 175 F., op- 8.28 8. 43 9.13 8. 58 8.97 7.14 7. 53 7. 83 8.10 9. 08 F., op 14. 06 15.26 14. 64 13. 61 14. 11 10. 98 11. 12 12. 08 12. 66 15. 22 Modulus of Rupture at 40 F., p.s.i 720 726 720 749 722 847 795 660 676 704' Beam Deflection at max. load at 40 F.,
inches 10-= 127 122 130 103 111 80 122 120 130 143 Drop Test Pass Pass Pass Botder- Pass Fail Border- Border- Pass Pass line line line Wax Flow-out on Carton Panels V.G. Fair Good 40 Good V. V.G. Good Simulated Dairy Abuse Test Reasons for Rejection.
5 Flexibility, Viscosity, M of R:
6 Low viscosity.
7 Low Abuse Test Rating.
8 Flexibility, Drop Test.
Examination of the data of Table II reveals the following:
Blends 1 through 4 illustrate that the addition of paraffin wax components to the non-normal and microwax B components increases the modulus of rupture but decreases flexibility. Blend 5 shows that the addition of low molecular weight, branched chain polyethylene results in a substantial improvement of modulus of rupture and flexibility but its viscosity is too low for good coverage. In blend 6 the viscosity was increased by adding par-aflin wax B but the blend did not perform well commercially from the standpoint of carton durability and exhibited a low dairy abuse rating. Blend 8, a composition of the present invention met all of the requirements and on commercial test-ing was found to result in markedly improved carton durability. Blend 9 illustrates that straight chain polyethylene adversely atfects the flow-out properties of the wax. High molecular weight polyethylenes would be expected to show the same tendency. That a combination of pa-raflin waxes may be used is shown by blends ll, 12 and 13. Also, that the use of microcrystalline Wax A or B alone results in an inferior composition is shown by comparing blends 6 and 16 with blend 8.
The criteria used in the evaluation of the various blends included the following for the reasons stated.
(1) Congealing p0int.-The congealing point partially controls the flow out and carton coverage properties of the liner wax. A congealing point range of about 130 140 F. is thought to be the most suitable for the conditions of commercial application.
(2) Viscosity.-The viscosity of the wax at the higher temperatures (175 F. and 210 F.) is related to'such functional properties as Wax consumption, penetration into the paperboard and wax film continuity. The viscosity in the region of the congealing point has bearing on the flow-out properties of the wax. This refers to the ability of the wax to form a well distributed, smooth film of reasonably uniform thickness.
(3) Modulusof rupture (M of R) and beam deflecti0n.-Tl1e M of R is ameasure of the flexural strength of the Wax and the deflection at maximum load relates to flexibility. These properties correlate to some extent with the ability of the wax to withstand mechanical impact required in a durable carton. The modulus of rupture and beam reflection tests were conducted as follows:
Approximately 118 grams of chipped or shaved wax was placed into a Pyrex pan and 700 grams of deionized boiling water was added. The pan was covered to avoid possible effects of drafts and permitted to stand and cool for 4 hours. The resulting wax slabs were removed and the edges trimmed to leave a piece about 9 inches by 3 inches. Strips 3 inches by /2 inch wide were cut from the above slab and permitted to age at least one hour at test temperature. The test temperature employed was 40 F. and the strips tested on an Instron Tensile Tester for modulus of rupture and flexibility. Six specimens were tested with the water side down and six specimens with the air side down. The modulus of rupture for each specimen was calculated using the following formula:
0.0066W be Where S =modulus of rupture in psi.
W=l0ad at fracture (or maximum load) in grams. b=width of specimen in inches.
t=thickness of specimen in inches.
a The deflection of the wax beam at rupture or at maximum load in the case of flexible specimens was determined from the plot on the chart as follows:
erosshead speed Deflection Where C -C =chart travel in inches between point of initial load and point at rupture or maximum load.
The modulus of rupture and beam deflection are reported as averages of the 12 separate determinations.
(4) Drop test.-This is a more direct measure of the durability of the wax as applied to the carton. The drop test is conducted as follows:
At least 3 waxed cartons are filled with 3233 F. water (containing no unmelted ice) and conditioned for 5 minutes. Each carton is then dropped once from a height of 4 inches onto a flat plate guiding the carton between vertical rails so that the bottom of the carton strikes the plate squarely. The cartons are then drained and filled with a Malachite Green dye solution (49% by weight isopropyl alcohol, 49% by weight tap Water and 2% by weight water soluble Malachite Green). The dye is left in for 2. minutes and then drained and rinsed. The bottom Wax fillets of the carton are inspected for signs of cracking. In order to pass there must be no cracks in the fillets.
(5 F low-out 0n panels.While the wax film on the carton surf-aces is in the liquid state it flows under the influence of gravity. The flow pattern must be such that at the moment of solidification there is no excessive accumulation of wax either on the panels or on the bottom of the carton.
-(6) Simulated dairy abuse test.This test is conducted by filling the Wax cartons with milk or orange juice at 40 F. The cartons are sealed and placed into standard carrying cases. The cased cartons are then dropped 8 times from a height of 2 inches onto a platform. The same cartons .are placed on the platform which is slammed horizontally against a rigid stop. This is done twice. The intent is to simulate the type of damage that occurs when a case is slid along the floor of the delivery truck and strikes other cases. The same cartons are bounced rapidly on a cam actuated platform which has A inch vertical movement. This simulates the bouncing of the cartons in a truck traveling on a rough road. The abused cartons are then rated as follows:
The abused cartons are placed in a 40 F. cooler for 7 days in the case of milk and 20 days in the case of orange juice. During the storage period the cartons are examined daily by a panel of four men. The panel rates the cartons for bulge, leakage and softening or raggy feel. A numerical rating of is a perfect score and a minimum acceptable rating is about 65 to 70. The results of the tests are set forth in Table II. We claim: 1. A wax composition consisting essentially of (a) about 35 to 50% by weight of paraflin wax having a melting point in the range of about 125-135" F. and a viscosity SUS at 210 F. of about 35 to 40; (b) about 20 to 35% by weight of an isoparaflinnaphthenic wax having a melting point in the range of about to F.; a viscosity SUS at 210 F. of about 42 to 50, an average molecular weight of about 450 minimum, a refractive index 11 of about 1.4400 minimum and a penetration at 77 F. of about 40* to 100; (c) about 10 to 20% by Weight of a microcrystalline wax having a petrolatum melting point in the range of about 160 to 180 F., a 100 gram needle pene- References Cited by the Examiner tration at 77 F. 0f about to 40, a viscosity SUS UNITED STATES PATENTS 225 2 and a refractwe m ex 2,808,382 10/1957 Jakaitis.
(d) about 10 to by weight of a microcrystalline 3,0139% 13/1961 fablan 260 28'5 Wax having a petrolatum melting point of about 1962 l30-l60 F., a cone penetration at 77 F. of about OTHER REFERENCES 50400, a viscosity SUS at 210 F. of about to Ward]: Chemistry and Technology of Waxes,
3 a refractive index of 14490 minimum and second edition, Reinhold Publishing corporation, New having a cycloparafiin content of at least about 25%; 10 York pages 417, 430 and and (e) about 0.5 to 2% by Weight of a branched chain MORRIS LIEBMAN, Primar Examiner,
polyethylene having a molecular weight of about I 1500 to 7000 and a density of about 0.88 to .91. ALEXANDER BRODMERKEL Exammer' 2. A paperboard carton coated with the wax composi- 15 KOLASCH, AMERNI'CK, tion of claim 1. Asslstant Exammers.