US 3278377 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent Ofitice 3,278,377 Patented Oct. 11, 1966 3,278,377 WGOD PRESERVATHVE COMPOSITION Anthony P. Ferrucci, Jr., Villa Park, Ill, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware N Drawing. Filed Mar. 12, 1964, Ser. No. 351,527 2 Claims. (Cl. 167-38.6)
This invention relates to wax-containing compositions. More particularly, the invention relates to Waxand oilcontaining compositions which are very useful for the treating and preservation of wood.
All wood of any commercial importance is subject to deterioration after cutting, and the degree and kind of deterioration depends on the type of use to which the wood is put. There are, of course, a number of natural agencies of wood deterioration, among which are wood-destroying (decay-producing) fungi, wood-staining fungi, molds, wood-boring insects such as termites, powder-post beetles and carpenter ants, marine borers such as ship worms, martesia, limnoria, sphaeroma and chelura, and the different kinds of deterioration which are normally referred to as weathering.
Among the most effective and economical materials known for general use in the protection of wood against all forms of wood-destroying agencies are coal-tar creosote and mixtures of coal tar and coal-tar creosote. Coaltar creosote is produced by distillation of coal tar which consists of the condensable liquids made by carbonization of bituminous coal at elevated temperatures. It is comprised principally of liquid and solid aromatic hydrocarbons and contains appreciable quantities of tar acids (e.g., pyridines, quinolines, acridines) and tar bases (e.g., phenols, cresols). Creosote usual-1y has a boiling range Width of at least 125C, the initial boiling point being in the range of ISO-200C, the final boiling point being in the range 300450C. The higher boiling portions of creosote may contain appreciable amounts of fluorene, anthracene and phenanthrene.
Creosote-coal tar solutions are frequently used in place of creosote alone primarily to reduce the preservative cost. Such solutions may be either a solution of coal tar in distillate oil (creosote) or a so-called coal-tar distillate oil. They are comprised of at least 50% coal tar and should contain no more than 3 by volume water and no more than 24% weight benzene insolubles, this amount being directly related to the amount of coal tar in the solution.
There are, of course, many other closely related wood preservatives. Among these is water-gas tar and watergas tar creosote which is produced by distillation of water-gas tar, a by-product in the manufacture of watergas from petroleum oils. Water-gas tar and water-gas tar creosote are not, however, considered to be as effective as coal-tar creosote. Wood-tar creosote, produced by distillation of wood tar, is an effective wood preservative. However, it is more expensive than coal-tar creosote and not quite as effective as coal-tar creosote. Petroleum oils have occasionally been tried as wood preservatives; however, they possess very low toxic properties when used alone. Consequently, their use has been limited to diluents for other preservative oils such as coal-tar creosote and solvents for toxic chemicals such as pentachlorophenol.
Coal tar and coal-tar creosote (hereinafter referred to as creosote) preservatives are applied to wood by a wide variety of processes. For example, non-pressure processes are used as brushing, spraying, dipping, steeping and cold soaking. The most widely used processes for treating wood with preservatives are those which are conducted under pressure. In such pressure processes,
the wood is impregnated in a closed vessel with the preservative, usually in the liquid form, at pressures up to, say, 250 psi. and temperatures on the order of 180- 220F. By using such pressure processes, the degree of penetration of the preservative into the wood is maximized as well as retention of the treating agent. There are many variants to the pressure process; for example, the wood may first be subjected to a vacuum before pressure impregnation to exhaust air from the wood. On the other hand, in other treating processes air is deliberately forced into the wood prior to impregnation in order to facilitate removal of excess preservative and to reduce bleeding and dripping of the preservative upon the completion of the treatment.
In any of these processes, however, it is desired to obtain (1) complete and thorough penetration of the wood preservative with the wood,
(2) adequate retention of the preservative within the wood, and
(3) minimum amounts of bleeding of the preservative from the wood upon subsequent exposure to outdoor weather conditions.
In the treatment of wood with preservatives, it is important that retention of the preservative in the wood be high in order to provide a reserve against depletion by leaching and evaporation. By retention is meant the net amount of treating solution which is retained in the wood after impregnation. Retention is usually measured at the time of treatment by determination of the consumption of treating solution, allowing, of course, for any other known non-retentive losses. The minimum amount of retention depends on many factors-the type of wood, the type of service to which the wood is to be put, and the kind of preservative used. Illustrative of the required minimum retention, however, is 5-10 pounds per cubic foot which is specified by the railroads for impregnation of railroad ties with coal-tar creosote-containing compositions.
Equally important is the degree of penetration of the preservative into the wood. Obviously, in order to assure more nearly complete protection of the wood, penetration of the preservative should be complete (100%). With most preservatives, including coal-tar creosote, however, penetration is less than complete and minimum values are specified, depending on the preservative and the properties of the wood. Though with some woods it is impossible to obtain complete penetration, it is nevertheless desirable to obtain the highest possible degree of penetration.
Penetration is usually measured by making incremental borings or hit holes in the wood a sufiicient distance from the end of the treated piece of wood to escape the effect of end penetration. Such borings are observed as to penetration promptly after boring. In the case of dark colored preservatives, the degree of penetration is determined by visual observation of the depth of color change in the wood. When oils are used which do not perceptively change the color of the wood, reagents are used to induce color-producing reactions with the oil, thereby facilitating visual observation of the penetration of the preservative.
Applicant has now discovered a unique coal-tar creosote-containing wood-preservative composition which retains the desirable preservative properties of coal-tar creosote while having greatly improved penetration properties. More specifically, applicants wood-preservative composition consists essentially of 15 to by volume normally liquid creosote, 0 to 45% by volume normally liquid coal tar, the volumetric ratio of creosote to coal tar being at least 1.0:1, 7 to 66.5% by volume Wax and 0.5 to 21.0% by volume of a high-boiling paraffinic petroleum oil, the volumetric ratio of wax-to-oil being from about 2.3:1 to about 19: 1. Within the foregoing limits, it is preferred that the volumetric ratio of creosote to coal tar be at least about 1.5 :1 and the volumetric ratio of wax to oil from about 4:1 to about 9:1.
As the wax component of the preservative composition, it is preferred to use a low-melting-point petroleum paraffinic distillate wax such as that obtained from the dewaxing of petroleum lubricating oil stocks. By low melting point is meant an ASTM D87 wax melting point of less than 135 F. and preferably no greater than 120 F. The minimum melting point will not, however, be lower than 95 F. In some instances where the amount of oil in the wax is high, the wax or the wax-oil mixture which is used in the invention may not have a distinct melting point, in which case its point of phase change is measured by the ASTM D938 Congeal Point. Such oily waxes and wax-oil mixtures have been found to be particularly suitable in the composition of the invention. It is preferred that the wax contain no substantial amounts of microcrystalline or amorphous wax, which is normally present in all except certain specially refined residual waxes. It is also preferred that the preservative composition contain at least 10% by volume wax and, still more preferably, at least by volume wax.
As the oil component of the composition of the invention, it is preferred to employ a high-boiling paraflinic petroleum oil, preferably one containing at least 80% paratfinic hydrocarbons and less than aromatic hydrocarbons. High-boiling oils containing at least 90% parafiinic hydrocarbons are preferred, especially those oils the paraffins in which contain a high degree of side-chain branching. By the term high-boiling oil is meant an essentially hydrocarbon oil no more than about 5% of which boils below 600 F. when heated at one atmosphere pressure. Thus it is intended to include within this definition oils Within the boiling and viscosity range of distillate lubricating oils which, of course, are substantially vaporizable at 600 F. only at below atmospheric pressures. The above-described oils, which are useful in the compositions of the invention may be derived from parafiinic, naphthenic or mixed-base crudes. Thus, they frequently will contain 1530% of naphthenic (cycloparaffinic) components. Within the above-mentioned limits regarding paraffins and aromatics, however, the amount of naphthenes is not especially important. The relatively non-polar characteristics of petroleum lubricating oils are, however, greatly to be desired.
It is preferred that both the oil and wax be of comparatively low average molecular weight, i.e., from 280 to no more than 420 and still more preferably no more than about 340.
Both the wax and the oil may be fully or only partially refined. They may also be obtained from either the same or different crude oil fractions. Not infrequently, it is possible to obtain the wax and oil in the correct proportions from the same fraction. For example, the soft wax product obtained by solvent de-oiling of crude wax obtained by solvent dewaxing of high-viscosity-index distillate lubricating oils is particularly suitable without further adjustment of composition. In addition, certain crude or slack waxes obtained by dewaxing distillate lubricating oils are likewise frequently suitable. More rarely, certain undewaxed distillate lubricating oil stocks containing very high amounts of wax can also be used. Conversely, highly refined waxes and oils can likewise be employed. The customary refining treatments of such Waxes and oils, e.g., hydrotreating, acid treating, percolation, etc. have no adverse effect on their efiicacy in the compositions of the invention.
The compositions and their unique character will better be understood by reference to the following examples:
Example I Four charges of wooden railroad crossties, each containing over 500 ties, were treated with Wood preservative in a commercial scale pressure-treating facility. Two of the charges were treated with a conventional woodpreservative composition consisting of 60% creosote and 40% coal tar. The remaining two charges were treated under the same operating conditions with a waxand oilcontaining wood-preservative composition in accordance with the invention. The waxand oil-containing preservative consisted of by volume of 60/40 creosote-coal tar mixture and 15 by volume of soft wax byproduct produced from the solvent dewaxing of a H.V.I. distillate lubricating stock oil. The soft wax contained about 29% by volume oil. The over-all composition of the waxand oil-containing preservative was therefore as follows:
Creosote percent v. 51.0 Coal tar do 34.0 Wax do 10.7 Oil do 4.3 Creosote-coal tar ratio volume 1521 Wax-oil ratio do 2.5:1
All four charges of crossties were treated to refusal, i.e., until no more preservative was taken up by the Wood. The treating temperature was l85200 F. The results are tabulated in the following table:
Table L-Commereial Scale Treatment of Railroad Crossties with Conventional Prescrvative versus Wax-Oil-Containing Preservative Preservative Composition- Creosote 60 60 51 51 Goal Tar 40 4O 34 34 Wax 10. 7 10. 7 Oil 4. 3 4. 3 Preservative Properties:
Specific Gravity at 60 F 1. 106 1.106 1.068 1.068 Viscosity, SSU at- F 42. 2 42. 2 46. 6 46. 6 F 30. 0 36.0 40. 0 40. 0 210 F 34. 3 34. 3 34. 2 34. 2 Pour Point, F +5 +5 +80 +80 Number of Crossties e 556 551 509 567 Species:
Red Oak, percent 86 83 80 83 White Oak, percent. 17 20 17 Retention, lbs./lt. 8. 45 7. 92 9. 04 Penetration, percent b White Oak 1O 20 20 Red Oak 30-50 100 100 5 Dimensions of all crossties 7 x 9 x 8. Penetration determined by 5 long borings taken through 9" dimension.
The results of the foregoing test are quite striking because of the complete penetration obtained with the wax-oil-creosote composition as compared with the mere 30-50% penetration obtained with the conventional creosote-coal tar preservative composition. The results were especially noteworthy in that complete penetration was obtained on the crossties made of white oak which is classified by the US. Dept. of Agriculture Forest Service in Agriculture Handbook No. 40 as being Heart wood very difficult to penetrate. It is also noteworthy that greater penetration was obtained with the wax-oilcreosote composition despite the fact that the viscosities of the two compositions were almost identical. The foregoing data also indicate that the compositions of the invention are of significant economic advantage in that at least twice as much penetration of the Wood (ergo protection of the wood) was obtained with only 3.57% more treating solution.
Example 11 Two charges of railroad crossties containing an equal number of crossties made from Engelmann spruce were treated separately at the same operating conditions. One charge was treated with a standard solution of pentachlorophenol in petroleum oil, the other was treated with the creosote-Wax-oil composition of Example I. Upon examination of the treated crossties it was found that the pentachlorophenol-oil solution had penetrated an average of only inch, whereas the creosote-Wax-oil composition had penetrated an average of greater than /2 inch. The Engelmann spruce ties used in this test were of particularly close grain and dense cell structure, hence the low penetrations. Ordinarily, suchwood would not be usable for crossties because of the virtual impossibility of treating it adequately with existing preservatives and processing means. However, the eight times greater penetration obtained with the composition of the invention, even though only /2 inch, is sufficient to give adequate preservative action. Thus, in effect, some woods, heretofore unusable, can be upgraded in economic value by the superior penetration capability of the wax-creosote-oil composition of the invention.
In the foregoing examples, the properties of the oil, wax and oil-wax mixture were as follows:
TABLE IL-PROPERTIES OF OIL WAX AND OIL-WAX MIXTURE Wax Oil Oily Wax Viscosity, SSU at 210 F 35. 3 37. 8 36. 1 Average Molecular Weight 322 322 322 Melting Point (D87), F 112 Congeal Point (D939), F 105 It is to be noted that the characterization of hydrocarbons as oil or as wax depends in part upon the meth- 0d by which they are produced. That is, in the dewaxing of oils or the deoiling of waxes, whether or not a particular fraction is contained in the wax fraction or in the oil fraction depends upon the process conditions by which they are separated. In order to have a datum plane for this purpose, the following standardized deoiling procedure is used to characterize the oils and waxes referred to herein:
The hydrocarbon material is dissolved in a 60/ 40 (by volume) mixture of methyl ethyl ketone and toluene and cooled to 0 F. The cooled material is then filtered. The resultant filter cake is redissolved in warm fresh solvent and recrystallized by cooling again to 0 F. and filtered. The recrystallized cake is washed with additional solvent and repulped but not redissolved by mixing the washed cake with cold (0 F.) solvent and filtered to remove the solvent. Additional cold solvent is finally used to wash the repulped and filtered wax, and the wax is washed. Each of the oil fractions is then recombined, either before or after solvent removal if the properties and weight of the oil are to be determined. The solvent to feed volumetric ratios employed are as follows:
Repulping Wash 1: 1
I claim as my invention:
1. A wood preservative composition comprising (a) at least about 51% by volume of coal tar creosote, (b) at least about 34% by volume of coal tar, (c) at least about 10% to 66.5% by volume of low melting point parafiinic wax obtained by solvent deoiling of crude wax obtained by solvent dewaxing of high viscosity index petroleum distillate lubricating oil stocks, said wax being further characterized as having no substantial amounts of microcrystalline or amorphous wax, an ASTM D87 wax melting point of between about F. and F. and an average molecular weight of from 280 to no more than 420; (d) at least about 3.621% by volume of high-boiling paraflinic oil containing at least 80% by volume of parafiinic hydrocarbons and no more than 20% by volume aromatic hydrocarbons, said oil being further characterized as having no more than about 5% of an essentially hydrocarbon oil which boils below 600 F. when heated at one atmosphere pressure, an average molecular Weight of from about 280 to about 340, and
the relatively non-polar characteristics and viscosity range of petroleum distillate lubricating oils derived from paraffinic, naphthenic, or mixed-base crudes.
2. In the art of impregnation of wood and improvement which consists essentially of the step of impregnating wood with the composition of claim 1 thereby to obtain an improved degree of penetration of said wood.
References Cited by the Examiner UNITED STATES PATENTS 1,041,604 10/1912 Dehnst 117-149 1,556,570 10/1925 Coolidge 117-116 1,648,294 11/1927 Coolidge 117-149 1,648,295 11/ 1927 Coolidge 117-92 1,976,221 10/1934 Goodwin et a1 167-387 2,078,570 4/1937 Holmes 167-387 2,296,401 9/1942 Perkins 16738.7 2,310,194 2/ 1943 Harvey 196-50 2,892,261 6/1959 Hutchinson 34-95 2,907,684 10/1959 Partansky 117-149 3,061,508 10/1962 Morriss et a1. 167-42 OTHER REFERENCES Chem. Abstracts 20: 3550 (2), 3551 (4), (1926). Chem. Abstracts 30: 8558 (7), 8560(8), (1936). Chem. Abstracts 57: 1130c (1962).
LEWIS GOTTS, Primary Examiner.
ELBERT L. ROBERTS, Examiner.
S. K. ROSE, Assistant Examiner.