INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1927
87
Impregnating Wood with Paraffin'" By Leon W. Eberlin and Alosco 11.1. Burgess RESEARCH LABORATORY, EASTMAX KODAKCo., ROCHESTER, N. Y.
T
HE experiments here described were undertaken to
obtain an impregnated wood that would withstand the action of acid and alkaline solutions with a minimum absorption of moisture and consequent swelling. The most suitable kind of wood, impregnant, and method of impregnation were sought. Gamble3 has published an interesting article on impregnating cedar, fir, and yellow pine with creosote, but his materials and methods were not applicable to the problem at hand. The impregnation of wood with sulfur has also been reported.' Experimental Maple, pine, cypress, oak, fir, and spruce were the woods tested. Cresol, Vaseline, paraf?in oil, linseed oil, and paraffin, singly and in combination, were the impregnants. Some of the wood received no treatment before being impregnated. Some was first dried, some was so:tked in water, and some was extracted to remoye the resins. An impregnator, using both vacuum and pressure, was used for several experiments, but the "open-tank" method was used for most of them. The idea of an "open-tank" method was taken from the following method devised by the Forest Products Laboratory a t Madison, Wis., for the moisture-proofing of wood for instrument cabinets: Immerse green sapwood in paraffin a t 135' C. (275' F.) for 2 hours, follow by 30 minutes in paraffin at 71.0"C. (160' F.), remove, and wipe excess paraffin from the surface. Standard size samples, 204 by 100 by 11 mni., were used. They were weighed before and after impregnation and the percentage of impregnant absorbed, based on the dry weight of the wood, was calculated. After being impregnated each sample was immersed for 48 hours in an agitated solution of 5 per cent sulfuric acid, removed, wiped thoroughly, and weighed. The percentage increase in weight, or absorption, based on the weight of the impregnated sample, was calculated. Measurements before and after the absorption test in dilute sulfuric acid were made and the amount of swelling was noted. More than one hundred experiments were conducted. The best results were obtained with cypress and spruce that had been soaked in water for 12 hours before impregnation with paraffin. The wood was impregnated with paraffin for 2 hours at 127' C. (260' Fa),and then for 30 minutes at 71.0" C. (160' F.). It was then removed and the surfaces were wiped free from excess paraffin with a cloth. Some of the samples of wood thus treated increased as little as 2.8 per cent in weight and showed a swelling less than 1 per cent when immersed for 48 hours in the dilute acid. Effect of Preliminary Treatment of Samples Drying the wood before impregnating was unsuccessful, apparently because many of the cells collapsed, thus making it impossible to attain the same degree of impregnation as with the undried wood. 1
Received September 27, 1926.
* Communication No. 283 from the Research Laboratory Rodak Company. I J . Elec. Western Ind., 55, 325 (1926). 4 Chrm. Met. Eng., 33, 354 (1926).
of Eastman
Soaking the mood in mater before impregnating resulted in a higher degree of impregnation. The apparent explanation for this is that the cells or pores become swollen and remain open until the hot paraffin displaces the water which is vaporized a t the temperature of the paraffin bath. Extraction of the resins with sodium carbonate solution was unsuccessful. It resulted in most cases in a warping of the wood and in many cases in splitting. Working the impregnated wood had no appreciable effect on the percentage of moisture absorbed in the 48-hour test in the acid solution. Practical Application of Results In actual practice, good results were obtained by keeping the pieces of wood separate and immersing them at 127132' C. (260-270" F.) for 3 to 4 hours, followed by 30 minutes a t 71" C. (160' F.). The average percentage of paraffin absorbed by 33 pieces was 124, based on the original weight. The pieces were soaked for a t least 12 hours in water a t room temperature before impregnating. To obtain the 124 per cent impregnation, it was important that wood of fairly open grain be used. With fine-grain spruce it was often practically impossible to obtain a degree of impregnation exceeding 15 per cent of the original weight of the pieces. However, it was later shown that it is not so important to obtain open-grain pieces as a t first appears, provided the temperature of the paraffin is gradually raised to 135' C. (275' F.). Spruce not kiln-dried and not soaked in water was successfully impregnated by the following modification of the foregoing method: (Kiln-dried wood usually contains 3 t o 4 per cent moisture, which on ordinary exposue to air increases t o 6 to 7 per cent. Wood which has not been kiln-dried contains 15 to 20 per cent moisture.) Place the wood in the paraffin tank a t 71" C. (160' F.) and raise the temperature to 105' C. (220" F.), which requires about 30 minutes. Then slowly raise the temperature to about 135' C. (275' F.),which requires 3 to 4 hours. When all effervescence due to the escape of the last traces of air and moisture has ceased, remove the wood, which has sunk in the tank, and place it in the other tank a t 71 ' C. (160' F.). After it has stood for 30 minutes, remove it and wipe the surfaces free from excess paraffin. The success of this method appears to depend upon gradually increasing the temperature of the paraffi to 135' C. (275' F.). When the operation is carried out in this way, selection to obtain open-grain pieces is unnecessary, but it is important that wood containing 15 to 20 per cent or more of moisture be used. Spruce impregnated with paraffin in this manner was found by actual practice to withstand the action of acid and alkaline solutions very satisfactorily. Pieces of cypress and spruce measuring up to 1.8 meters by 20 cm. by 5 cm. (6 feet by 8 inches by 2 inches), as well as pieces of maple 1.8 meters by 10 cm. by 10 cm. (6 feet by 4 inches by 4 inches) have been thoroughly impregnated with paraffin in this way. Good results may also be obtained in impregnating pine, provided that pieces free from pitch are used. At present vertical tanks heated by a steam coil and insulated with a magnesia-asbestos lagging are being used
INDUSTRIAL A N D ENGIXEERIIVG CHEitlISY’Kl‘
88
1‘01. 19, No. 1
Summary
for impregnating. There is no reason to believe that horizontal tanks could not be used, however. In a large number of observations on the wood as it was removed from the impregnating bath, no oozing or kickback of the paraffin was noted. No evidences of cold flow of the paraffin in pieces of wood impregnated with this material have been seen. Rapid surface cooling is undesirable, as the paraffin congeals on the surface of the wood and subsequently flakes or chips off, contaminating the solutions in which the wood is used.
An impregnated wood which will withstand the action of acid and alkaline solutions has been found. A practical method for the large-scale impregnation of spruce with paraffin has been worked out. Contrary to the general opinion that better results are obtained by drying wood before impregnation, it was found that for impregnation with paraffin and similar substances the degree of impregnation was enhanced by the presence of 15 to 20 per cent or more of moisture in the wood.
Plasticity of Finishing Limes’ By Herman T. Briscoe and Frank C. Mathers DEPARTMENT OB CHEMISTRY.
INDIANA
UNIVERSITY,
BLOOMINGTON, IND.
In order t h a t hydrated lime may be classed as a plastic “finishing lime,” it must so react with water as to produce a putty which spreads easily under the trowel without sticking and pulling. Plastic lime makes possible the application of a n even, smooth “white coat” without undue labor on the part of the plasterer. Only a very few hydrated limes will yield plastic putties when they are soaked in water. It is of interest, therefore, to determine the effect of various conditions of calcination and hydration upon the plastic properties of the hydrated limes. Calcination may be made a t too low a temperature as well as a t too high a temperature. Under laboratory conditions, a temperature of 1050’ to 1150’ C. has been found most satisfactory for the production of plastic limes. The plastic properties of hydrated limes that are produced from stones treated with solutions of alkali metal
salts, particularly sodium chloride, before burning, are much more satisfactory t h a n the properties of limes made from the untreated stones. The sodium chloride treatment renders the quicklime softer and much more inactive. The rate of its hydration may, therefore, be regulated by the proper addition of salt to the stone. Hydration of lime in steam, treatment of the hydrated lime with steam, drying plastic putties, and hydration of the quicklime with relatively large amounts of water result in decreased plasticity. I t is believed t h a t plasticity is due to hydration, particularly hydration of magnesia, which takes place during the soaking of the lime in water. Evidence in support of this view is found in the results of experiments which deal with the losses of various plastic and non-plastic hydrates when heated to certain temperatures and the gain in weight which these same limes undergo when they are allowed to stand in contact with water.
T IS unfortunate that the term “plasticity” has been
produced from dolomites or highly magnesian limestones of northwestern Ohio. Other limestones, although they have almost exactly the same chemical composit,ion and in some cases even belong to the same geological formations, the Niagara, are not calcined to give limes that are suitable for this purpose. No high calcium stone is a t present used to produce a dry hydrated lime that is suitable for finish purposes. All quicklimes, however, yield fairly plastic putties when they are slaked with sufficient water to produce the putty without the formation of the intermediate dry form. KO dry hydrate yields a plastic putty immediately after it is mixed with water. Plasticity increases with time of soaking. The purpose of this investigation was to determine the relation between various properties of quicklimes and their hydrates and the plasticity or working qualities of the plaster putties made by soaking the dry hydrated limes in water, and to deduce probable theories to account for the difference in the plastic properties of such putties.
* . . . . ... ......
I
so generally used in the description of the working
qualities of putties made by soaking limes in water previous to their use as finish coats of plaster. It has long been used in a very definite sense in the description of clays and similar materials. It seems desirable that the definition of plasticity discussed by Bancroft2 be retained to describe that property which permits certain substances to be molded under pressure, and that in the case of lime putties we should substitute for plasticity an exact description of the properties of the plasters which either do or do not make them desirable finishing lime putties. For various reasons, however, it seems best to use the term “plasticity” in this paper as it is used today in the lime industry. Emley3 has defined a plastic lime putty as one in which the internal friction is not sufficiently great to make it “sticky” or so low as to make it “sandy.” Plastic putty does not dry out quickly when it is applied to an absorbent surface. It does not stick to the trowel nor does it drag or pull in resistance to the force which the plasterer exerts in spreading it, but may be spread evenly and smoothly without very great internal friction or resistance to forces that tend to deform it. The lime industry is without much definite information on the subject of plasticity. The plastic f i s h i n g limes are 1
Received July 6, 1926. “Applied Colloid Chemistry,” p. 154, McGraw-Hill Book Co. Inc.,
1921. a
J . Am. Ceram. SOC.,19, 523 (1917).
Experimental The list of dolomites studied includes stones from the quarries of various manufacturers of plastic and non-plastic hydrated limes. Commercial quicklimes and hydrates were also generously supplied by the manufacturers. Laboratory samples of quicklimes were obtained by burning the stones in crucibles heated by gas flames or in electric furnaces made by wrapping alundum tubes with resistance
