US2904482A - Irradiation of wax - Google Patents

Description

United States Patent IRRADIATION F WAX Herman L. Thwaites, Clark, and James F. Black, Roselle,

N.J., assignors to Esso Research and Engineering Company, a corporation 'of Delaware No Drawing. Application January 27, 1956 Serial No. 561,948 I 3 Claims. (Cl. 204-154) This invention relates to wax and more particularly relates to the irradiation of petroleum waxes and to the irradiated wax products. Still more particularly, the present invention relates to the process of subjecting crystalline petroleum waxes to high intensity ionizing radiation from an atomic pile whereby the normal parafiin content of the wax is charged.

Waxes such as those obtained from'petroleum are employed extensively as coatings for paper and paper cartons. The particular end uses of these waxes dictate the desired properties or characteristics of the waxes. For example, waxes which are employed in coating paper (e.g., to make bread wrappers and the like) should be relatively hard and have a high normal paralfin content. On the other hand, waxes which are employed for coating paper cartons (e.g., milk and food cartons) should be relatively flexible and have a lower normal paraffin content and a higher isoparaflin content. Although the normal paraflin content of petroleum waxes can be varied to a certain extent by refining methods, frequently it is necessary to employ different crude oils as sources for different types of waxes. The necessity, therefore, of segregating and processing two or more different types of crude oil specifically for wax manufacture complicates petroleum processing, particularly in a small refinery. It would, therefore, be highly desirable to develop a simple, inexpensive and effective method for modifying the properties, and more particularly the normal paraffin content, of waxes derived from a given crude oil.

In accordance with the present invention, a novel method has now been found for modifying the properties of agive'n wax and more particularly for changing the normal paraffin content of such wax. This method of the present invention comprises subjecting the wax to high intensity ionizing radiation whereby thenormal paraffin content of the wax is changed. The present invention is most eliectively carried out when subjecting petroleum wax to the radiation from an atomic pile. It has been found that relatively low radiation dosages will increase the normal paraffin content of the wax, whereas relatively high radiation dosages will decrease the normal parafiin content of the wax. Thus by means of the present invention it is possible to simply and effectively modify theproperties of the Wax by irradiation to make, if desired, either a hard wax useful as a paper coafingor to make a more flexible wax useful for coating paper cartons. In accordance with the preferred method of' the present invention, the wax is irradiated prior to its: conventional finishing steps such as the final! deoiling step and/or final distillation step.

The present method is particularly applicable to petroleum waxes,: especially to crystalline waxes melting Within the range of about 100 to 165 F., e.g., 120

2,904,482 Patented Sept. 15, 1959 to 150 F. The waxes which may be irradiated in ac cordance with the present invention may be (1) refined waxes having oil contents below about 0.5% by Weight, (2) crude scale waxes having oil contents in the range of about 0.5 to 5% by weight or (3) relatively high oil content waxes, such as slack waxes from plate and frame presses or petrolatum from solvent deWaXing plants, having oil contents in the range of about 5 to 50% by weight. These petroleum waxes may be ob tained from a variety of crude oils such as, for example, East Texas, Panhandle, Louisiana, San Joaquin, Mid-Continent, Pennsylvania, etc. Generally the crystalline paraffin waxes will contain 1) about to 97% by weight of normal (straight chain) paraflins, (2) about 3 to 16% by weight of iso (branched chain) paraflins and (3) about 0 to 15% by weight of naphthe'nes (saturated cyclic rings.

The above-described waxes are subjected to high intensity ionizing radiation and more particularly to high intensity radiation comprising neutrons and gamma rays. In the preferred embodiment of the invention, the waxes are subjected to the radiation from an atomic pile (or nuclear reactor) which consists essentially of gamma rays and neutrons. Generally the gamma ray fluxes from atomic piles will be about 10 to 6x10 usually about 10 to 3 1O roentgens per hour. The neutrons in the pile are of two general types, namely, slow (thermal) neutrons and fast neutrons. Slow neutrons are generally considered to be those neutrons having an energy of less than about 100 electron volts. The present process is most effectively carried out employing fast neutrons, that is, neutrons having an energy more than about 100 electron volts. Generally these fast neutrons will have an energy in the range of about 100 to 2x10 usually an energy in the range of about 3 10 to 1 10 electron volts. The fast neutron flux will generally be in the range of about 10 to 10 usually about 10 to 10 neutrons/cm. /sec. The slow (thermal) neutron flux existing in the atomic piles generally will be in the range of about 10 to 10 usually about 10 to 10 neutrons/cm. /sec. Beta rays are also produced in an atomic pile. However, as beta rays have low penetration, they are absorbed principally in the metals which clad the fissionable fuel elements. Therefore, these rays are relatively insignificant as compared to the gamma rays and neutrons.

The irradiation may be carried out on either a batch or continuous basis. More specifically, for example, a batch operation can be carried out simply by exposing the wax in a container to the high intensity ionizing radiation. To carry out a continuous process, the wax in liquid form may be pumped through pipes disposed in the atomic pile. The wax may be irradiated at a temperature of about 0 to 400 F., preferably about 60 to 300 F. It will usually be most convenient to carry out the irradiation at about atmospheric pressure although it will be understood that higher (e.g., l to 10 atmospheres) or lower pressures may be employed if desired. The irradiation may be carried out in the presence or absence of air or may be carried out in an inert atmosphere such as nitrogen.

The present process has a number of advantages over conventional processes. More particularly, these advantages include: 1) The present process may be conveniently carried out at atmospheric temperatures'and pressures. (2) The products of the present invention are free from contaminants such as catalyst residues and the like. In addition, the present process minimizes undesirable side reactions. (3) The present process afiords a high degree of process control since controlled radiation dosages can be readily effected. (4) The present process is readily adaptable to a continuous operation.

The time of irradiation will depend primarily upon the degree of conversion desired as well as the radiation dosage rate available. Actual times may vary from a matter of a few seconds up to a week or longer. As has been stated heretofore, relatively low radiation dosages are employed to increase the normal parafiin content of the wax to produce a harder wax. Generally, radiation dosages of about 0.001 to 3, preferably about 0.1 to 1 megaroentgens of gamma rays and about 3 x10 to 10 preferably 3X10 to 3X10 fast neutrons/cm. will be employed for this purpose. When employing such radiation dosages, the slow neutron dosage will be about 3X10 to 10 usually about 3 10 to 10 slow neutrons/cmF. On the other hand, when it is desired to decrease the normal paraffin content (and increase the isoparafiin content), the radiation dosage should be about 3 to 500, preferably about 10 to 200 megaroentgens of gamma rays and about 10 to 2x10 preferably 3 10 to 10 fast neutrons/cmfi. When using such radiation dosages, the slow neutron dosage will be about 10 to 2X10, usually about 3X10 to 10 slow neutrons/cmfi.

Upon completion of the irradiation in accordance with the present invention the irradiated wax product may be employed per se. However, if desired, the irradiated wax product may be further processed by conventional techniques. For example, the irradiated wax product may be subjected to distillation, preferably vacuum distillation, to cut a product of desired melting point or melting point range. Further, the irradiated wax product may be deoiled by conventional deoiling techniques including sweating and solvent deoiling, which processes are Well known in the art. In the preferred embodiment of the present invention, the Wax is irradiated prior to one or more of its usual finishing steps such as deoiling and/or distillation. In this way, any small amounts of undesirable side reaction products formed during the irradiation may be separated from the irradiated wax product. For example, when preparing a refined wax product to be used for coating paper or paper cartons, a crude scale wax (about 0.5 to weight percent oil) may be irradiated in accordance with the present invention and then deoiled in a solvent (methyl ethyl ketone or propane) deoiling unit (or sweaters) to produce the refined wax product (less than about 0.5 weight percent oil). As another example of this preferred modification of the present invention, a refined wax, which in the normal course of events is to be subjected to vacuum distillation, is irradiated in accordance with the present invention prior to the final vacuum distillation step. Similarly, if desired, petrolatum or slack wax may be irradiated in accordance with the present invention and then subsequently processed through the normal wax refining steps (such as solvent deoiling and/or sweating and/or vacuum distillation) to prepare a finished wax product such as crude scale wax or refined wax.

The invention will be more fully understood by reference to the following example. It is pointed out, however, that the example is given for the purpose of illustration only and is not to be construed as limiting the scope of the present invention in any way.

EXAMPLE A refined petroleum wax having a melting point of l32/134 F. was irradiated in accordance with the pres ent invention. This refined wax contained about 0.14 weight percent oil and was obtained from San Joaquin crude by the following conventional processing steps, namely, distillation followed by solvent deoiling (methyl ethyl ketone-toluene mixture) for oil content reduction and sweating for melting point separation. This wax con- 4 tained about 92.5 weight percent normal paralfins, about 6.0 weight percent isoparaflins and about 1.5 weight percent naphthenes.

Samples of this wax, which were contained in 10 cc. quartz ampules, were subjected at about F. to irradiation from an atomic reactor. The intensity of radiation at the time of these tests was about 0.69 megaroentgen per hour gamma radiation, a slow neutron flux of 9 x10 neutrons/cm. sec. and a fast neutron flux estimated at about 10 neutrons per cm. /sec. Samples of the wax after 1, 3, 8 and 168 hours of irradiation were then evaluated, the results of which are summarized below.

Pile irradiation of a fully refined parafifn wax It will be noted that significant changes in the melting point and viscosity of the Wax were achieved after as little as one hour of in-pile irradiation. The melting point of the wax decreased generally during the irradiation period whereas the viscosity of the wax decreased during the first hour of exposure and increased thereafter. This discontinuity in viscosity is due to the destruction of small concentrations of radiation-sensitive isoparaffins and to the resultant formation of normal paraffins during approximately the first hour of irradiation. Then after approximately the first hour under the present irradiation conditions, the normal parafiin content is decreased and the isoparaflin content is increased. A comparison of the viscosity and melting points shown in the above table with those values for pure compounds indicates that these desirable results are obtained.

The process of the present invention, as demonstrated above, is important since the proportions of isoparafiins present in a wax, even though small, have a marked influence on the end use characteristics of waxes. By means of the present invention, the branched parafiin wax content of a petroleum wax or wax feedstock may either be reduced or increased depending upon the quantity of radiation employed. Such a method can thus provide greater flexibility in the types of Waxes that can be produced and in the feedstocks which can be used as a source for producing refined waxes.

In a corresponding experiment, the above-identified 132/ 134 F. refined wax was subjected solely to gamma radiation. A radiation dosage of about 5.5 megaroentgens of gamma radiation was found to have no measurable eflect on either melting point or viscosity.

What is claimed is:

1. A process for treating refined petroleum wax which comprises subjecting said wax to ionizing radiation comprising fast neutrons of intensity of at least about 10 neutrons per cm. per second and gamma rays of intensity of at least about 10 roentgens per hour the total radiation dosage being in the range of 0.001 to 3 megaroentgens of gamma rays and about 3 10 to 10 fast neutrons per cm. sufficient to significantly alter the normal parafiEin content of said wax.

2. A process which comprises subjecting petroleum wax having a melting point in the range of to F. to high intensity ionizing radiation consisting essentially of mixed gamma-neutron radiation from a nuclear reactor for a time sufficient to significantly alter the nor mal parafiin content of said wax, the total radiation dosage being in the range of 0.001 to 3 megaroentgens of gamma rays and in the range of 3X10 to 15 fast neutrons per cmP.

References Cited in the file of this patent f UNITED STATES PATENTS McClinton OTHER REFERENCES Apr. 24, 1956 Lawton et al.: Nature, vol. 172, pages 76, 77, July Charlesby: Proc. Roy. Society" (London), vol. 222A,

10 pages 6074, Feb. 23, 1954.

Claims (1)

1. A PROCESS FOR TREATING REFINED PETROLEUM WAX WHICH COMPRISES SUBJECTING SAID WAX TO IONIZING RADIATION COMPRISING FAST NEUTRONS OF INTENSITY OF AT LEAST ABOUT 108 NEUTRONS PER CM.2 PER SECOND AND GAMMA RAYS OF INTENSITY OF AT LEAST ABOUT 104 ROENTGENS PER HOUS THE TOTAL RADIATIONS DOSAGE BEING IN THE RANGE OF 0.001 TO 3 MEGAROENTGENS OF GAMMA RAYS AND ABOUT 3X1011 TO 1015 FAST NEUTRONS PER CM.2 SUFFICIENT TO SIGNIFICANTLY ALTER THE NORMAL PARAFFIN CONTENT OF SAID WAX.