US2951028A - Wax compositions comprising 3-15% of a paraffin wax with a melting point of 125-135deg. f. and 85-97% of a paraffin wax with a melting point of 138-147deg. f. - Google Patents

Description

States John D. Tench, Prospect Park, Pa., Seymour W. Ferris, Mount Holly, N.J., and Irl N. Duling, Newtown Square, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed Feb. 12, 1958, Ser. No. 714,675

3 Claims. (Cl. 208-21) This invention relates to a new wax composition especially suitable for coating fibrous sheet materials and fibrous containers designed for packaging food products.

Waxes and wax compositions have long been used for coating fibrous sheet materials and containers designed for packaging foods such as cereals, breads, frozen foods and the like. Such Waxes or wax compositions must possess certain properties in order to be suitable for this purpose. For example, the wax must impart a pleasing appearance to the package and it must not cause blocking. A primary requisite for a wax used for coating fibrous materials for packaging many types of foods is that it must impart low water vapor permeability to the fibrous material. By water vapor permeability, hereinafter designated W.V.P., is meant the resistance of the coated material to the passage of water vapor therethrough, and is measured as the quantity of water in grams passing through a square meter of coated material in 24 hours from an atmosphere of about 90% humidity to an atmosphere of about 5% humidity, the temperature being maintained at about 100 F. (T.A.P.P.I. test T464m-45); good resistance is evidenced by a low W.V.P. value. As illustrative of .water vapor resistance of the coating products heretofore described, a product having good resistance will generally permit from 0.5 to 5.0 grams of water to pass through a square meter of the coated material in 24 hours, whereas a material having poor water vapor resistance will gen erally permit from 20 to 30 grams or more of Water to pass in the same test. Coated materials having poor W.V.P. are not suitable for packaging food products, since such products are spoiled by contacting moisture which passes through the packaging material. Although several waxes are known which impart good W.V.P. characteristics to sheet materials, when the coated sheet material is creased, the W.V.P. value is greatly increased, say to a value of 60 to 200 or more. Since it is frequently necessary to crease coated sheet materials in order to package products, e.g. frozen food products, sheet materials coated with these waxes are unsuitable for such use. Accidental creasing of the wrapper may also cause spoilage of packaged foods. Also, waxes having good W.V.P. characteristics are generally soft waxes, -i.e., waxes having high penetrations and low blocking temperatures, and hence, especially because of the low blocking temperatures, are not suitable for the uses herein described. The addition of a soft Wax to a relatively hard wax to improve the W.V.P. thereof is generally unsuccessful because the soft wax imparts poor blocking characteristics to the composition. A wax-coated packaging material having a blocking temperature of below 110 F. is considered to be unsuitable for coating packaging materials. Blocking temperature, as used herein is determined by ASTM D1465-57T. The W.V.P. of a creased, wax-coated sheet material is determined by creasing the coated sheet material in accordance with T.A.P.P.I. test T465sm-52, and then testatet lice

Patented Aug. 30, 1960 composition effective for coating fibrous sheet materials which, even when severely creased, presents good resistance to the passage of water vapor, which has good blocking characteristics, and which has certain other ad-v vantageous properties which make itespecially suitable for the stated use. A further object is to provide a process for the preparation of such wax compositions. Other objects and their achievement in accordance with the present invention will be apparent hereinafter.

It has now been found that by blending two paraffin waxes having specific properties in certain amounts, the W.V.P. of a sheet material coated therewith is remarkably low, being far below the values observed with either of the wax constituents, good blocking characteristics are obtained, and the wax composition possesses other properties so that it is especially suitable for coat ing fibrous sheet materials designed for packaging food products and the like, I

The first paraffin wax component of the present composition is prepared from petroleum, and must have a melting point of from 138 F. to 147 F., a penetration of F. of from 19 to 24, and a viscosity at 210 F. of from 37 to 43 SUS (Saybolt Universal Seconds). A sheet material coated with the first parafiin wax will have a W.V.P. of from about-l to 3 when uncreased, but when creased the value increases substantially to 70 or more.

As used herein, the melting points are determined by ASTM D87-42, penetrations by ASTM D5-52 and viscosities (SUS) by ASTM D446-53.

This first panaffin wax is prepared from a slack wax which may be from the dewaxing of lubricating oil or from topping a high wax content crude petroleum. The slack wax is distilled under vacuum, and the fraction distilling in the range of from about 398 F, to 534 F. at 2 mm. of mercury pressure is collected. The distillate fraction is dissolved in a solvent which is preferably a mixture of methyl ethyl ketone and benzene in about equal parts by volume, dissolution being at a temperature of from about F. to F. with about 4 parts by volume of the solvent per part of the wax, fraction being used. The solution is slowly cooled to a temperature of from about 57 F. to 63 F. and the wax precipitated at this temperature is separated. The separated wax is advantageously washed with the same material as used for dissolving the wax at the temperature of the precipitation, and the wax then recovered from the solvent. This wax forms the first parafiin wax of the present invention.

The second paraffin wax must have a melting point of from 125 F. to 132 F., a penetration (at 100 F.) of above about 100, and a viscosity (at 210 F.) of from 36 to 42. The second paraffin wax, when used to coat a fibrous sheet material, exhibits a W.V.P. of about 7, say from about 3 to 10, and when creased, of about 44. However, it is not suitable for use in packaging food products because it readily blocks both in the form of wax slabs and when formed as a coating on packaging materials, the blocking temperature being 90 F. The parafiin wax meeting these specifications may be made by two methods. In the first method of preparing the described parafiin wax, a slack wax such as from the dewaxing of lubricating oil, which may contain about 30% oil, is vacuum distilled and the fraction distilling between about 390 F. and 565 F. at

2 mm. of mercury pressure is collected. This fraction is dissolved in a solvent, preferably a mixture of methyl ethyl ketone and benzene in about equal volumes, dissolution being at a temperature of from about 165 F. to 195 F. and about 6 parts by volume per part of the wax fraction being used. The solution is slowly cooled to a temperature of from 75 F. to 83 F. and the wax which precipitates at this temperature is separated as by filtration. The solution separated from the precipitated wax is further slowly cooled to a temperature of from 25 F. to 33 F. and the Wax which precipitates at this temperature is separated and forms the second paraffin wax of the present compositions. Preferably the wax after separation from the solution is washed such as with a solvent employed for dissolution preferably at the same temperature of filtration, namely from 28 F. to 32 F., and the wax is then recovered.

An alternate method of preparing the second paraffin wax of the present invention which provides considerable flexibility in obtaining the desired wax product is to separate from slack wax two distillate fractions, one distilling in the range of from about 390 F. to 475 F., at 2 mm. of mercury pressure and a second fraction distilling in the range of from about 450 F. to 565 F. at 2 mm. of mercury pressure. As usually occurs, the initial boiling point of the second fraction will overlap the endpoint of the first-mentioned distilled fraction. The lower boiling distillate fraction is dissolved in a solvent as above described, about 6 parts by volume of solvent per part of the wax fraction being used, and the solution cooled to a temperature of from 25 F. to 33 F. The wax which precipitates at this temperature is separated by filtering. The higher boiling distillate fraction is dissolved in the solvent as above described, about 4.5 parts of solvent per part of the wax fraction being used, and the solution slowly cooled to a temperature of from 72 F. to 82 F. The wax which precipitates at this temperature is separated as by filtering and the remaining solution is further slowly cooled to a temperature of from 25 F. to 33 F. The wax precipitating at this latter temperature is separated as by filtering. The two distillate waxes so-prepared are combined to form the second paraffin wax of the present invention. Considerable flexibility is obtained since the blending may be in various proportions so that the properties of the resulting wax mixture is within the limits above described for the second paraifin wax. If desired, the two Waxes can be washed, preferably with an additional quantity of the solvent used at the temperature of the final precipitation and separated from the solvent prior to blending, or the wet waxes may be combined and simultaneously so washed and separated. In general, from about 69% to 75% of the wax mixture will consist of wax from the lower boiling distillate fraction since, as has been found, such mixture gives a wax having properties within those defined for the second paraffin wax of the invention.

It is essential in order to realize the advantages of the invention that the wax composition consist essentially of from 3% to 15% by weight of the second paraffin wax, the remainder of the composition, i.e., from 97% to 85%, being the first paraifin wax. The two parafiin waxes can be advantageously combined by heating an appropriate mixture thereof to above the melting points, stirring the molten waxes to form a homogeneous mixture, and cooling. The wax composition of the invention will have a melting point of from 139" F. to 142 F., a viscosity (at 210 F.) of from 39.5 to 40.5 SUS, and a penetration (at 110 F.) of from about 35 to 55.

In order to demonstrate a specific embodiment of the present invention and the advantages thereof, two paraffin waxes were prepared as follows: The first parafiin wax component of the present composition was prepared by topping a high wax content crude to about 38% bottoms. The bottoms were charged to a vacuum distillation operation, operating at 2 mm. of mercury pressure 4- and the fraction distilling between about 398 F. and 534 F. was collected. This. fraction was dissolved in a solvent consisting of a mixture of about 60% methyl ethyl ketone and about 40% benzene at a temperatureof about 180 F., 4 parts by volume of the solvent per part of the wax fraction being used. The resulting solution was slowly cooled to 60 F. and the wax precipitated at this temperature was separated, washed with an additional quantity of the solvent at a temperature of 60 F. and then recovered from the solvent. This first parafiin wax had a melting point of 142 F., a viscosity (at 210 F.) of 40 SUS and a penetration (at 100 F.) of 21. The second parafiin wax was prepared from slack wax from the dewaxing of lubricating oil and containing about 30% oil was distilled at a pressure of 2 mm. of mercury, a distillate fraction boiling in the range of from about 390 F. to 475 F. and another distillate fraction boiling in the range of from about 450 F. to 565 F. were collected. The lower boiling fraction was dissolved in a mixture of methyl ethyl ketone and benzene at an elevated temperature of about 170 F. The solution was slowly cooled to 28 F. and the Wax was filtered, washed with additional solvent at 28 F., and the wax recovered. The higher boiling distillate fraction was dissolved in a similar solvent as above described and the resulting solution cooled to F. The wax precipitated was separated by filtering and the filtrate was further cooled to 30 F. The wax separating at this latter temperature was separated by filtering and was washed with an additional quantity of solvent at 30 F. and the wax then separated from solvent. The two so-formed waxes were blended in quantities such that the final composition contained 72% of wax from the lower boiling distillate and 28% from the higher boiling distillate to form the second paratfin wax of the invention. The resulting wax prodnot had a melting point of 127 F., a viscosity (at 210 F.) of 39.0 and a penetration (at F.) of about 100.

Blends of two waxes were prepared by heating together at a temperature above the melting points and mixing to form a homogeneous composition. The resulting compositions were then tested for W.V.P., both flat (uncreased), and creased, and for blocking temperature. The results obtained are shown in the following table, which also shows, for comparative purposes, values for the individual components of the blend:

1st Wax 2nd Wax 90% 1st Wax 77% 1st Wax 10% 2nd Wax 23% 2nd Wax W.V.P. (Flat) l. l 7 0. l5 W.V.P. (Creasod) 73 44 30 34 Blocking Temp.

As shown by these data, combining the two paratfin waxes within the limits herein described results in a composition having W.V.P., both uncreased and creased, far below the same values observed for the individual waxes, and in general the W.V.P. of the composition will be below one half the W.V.P. of any component thereof. Also, adding the soft second wax to the first wax, within the defined limits, does not alter appreciably the blocking temperature. However, adding an amount greater than 15% of the second wax substantially lowers the blocking temperature, as shown by the data. When less than 3% of the second wax is used, the W.V.P. value is not substantially improved. The composition illustrating a preferred embodiment of the invention, i.e., the composition consisting essentially of 90% of the first wax and 10% of the second wax, had a melting point of F., and a viscosity (at 210 F.) of 40.

It does not appear that other waxes can be substituted for either of the components without defeating the purposes of the invention. It is also not possible to alter thepreparation of the first parafiin wax to include relatively soft wax components therein such as is observed in the second paraflin Wax to obtain the same results. For example, a wax corresponding to the first paraffin Wax was prepared except that the temperature of filtration was lowered to about 33 F. The resulting wax product had a penetration (at 100 F.) of about and a W.V.P. when creased of 62.

The invention claimed is:

1. A wax composition consisting essentially of from 3% to 15% of a paraflin wax having a melting point of from 125 F. to 132 F., a penetration at 100 F. of above about 100, a viscosity at 210 F. of from 36 to 42 SUS and a W.V.P. (water vapor permeability, T.A.P.P.I. Test No. T464 m-45) of from about 3 to 10, and from 97% to of a parafiin Wax having a melting point of from 138 F. to 147 F., a penetration at F. of from 19 to 24, a viscosity at 210 F. of from 37 to 43 SUS, and a W.V.P. of from about 1 to 3.

References Cited in the file of this patent UNITED STATES PATENTS 2,624,501 Ferris Ian. 6, 1953 2,670,323 Hunter et a1 Feb. 23, 1954 2,734,365 Ferris et a1 Feb. 14, 1956 2,825,635 Dooley et a1 Mar. 4, 1958

Claims (1)

1. A WAX COMPOSITION CONSISTING ESSENTIALLY OF FROM 3% TO 15% OF A PARAFFIN WAX HAVING A MELTING POINT OF FROM 125*F. TO 132*F., A PENETRATION AT 100*F. OF ABOVE ABOUT 100, A VISCOSITY AT 210*F. OF FROM 36 TO 42 SUS AND A W.V.P. (WATER VAPOR PERMEABILITY, T.A.P.P.I. TEST NO. T464 M-45) OF FROM ABOUT 3 TO 10, AND FROM 97* TO 85% OF A PARAFFIN WAX HAVING A MELTING POINT OF FROM 138*F. TO 147*F., A PENETRATION AT 100*F. OF FROM 19 TO 24, A VISCOSITY AT 210*F. OF FROM 37 TO 43 SUS, AND A W.V.P. OF FROM ABOUT 1 OF 3.