US2033885A - Impregnating pitch and process and product utilizing it - Google Patents

Description

roamed Mar. 10, 1936 UNITED STATES IMPREGNATING PITCH AND PROCESS AND PRODUCT UTILIZING I'I.

Ira Derby, Indianapolis, Ind.,- assignor to PER! C. Reilly, IIIMDQIIS, Ind.

No Drawing.

3 Claims.

My invention relates to the impregnation of cellulosic fibrous material and products,- such as paper, cloth, wood-pulp sheets and-conduit, roofing paper, and fibrous insulating materials,.as.

' well as wood itself, with water-proofing compounds ofipitchy character, such as coal-tar pitch, water-gas-ta.r pitch, and/or petroleum pitch, and various mixtures of pitches; to the process of impregnation involved; to the special impregnating materials used; and to the final impregnated materials, more especially impregnated conduit. v V

It is the object of my'invention to increase the absorption if such pitchy material into the fibrous materials to be impregnated, so that. a greater amount of the pitchy material may betaken into the pores of the f fibrous material; toserve the o multiple purpose of increasing the water-imperviousness, of increasing both the dielectricstrength 29 the strength, .of decreasing the 1owermrbr dielectric'strength under water-absorption conditions, and of improving the appearance of the treated material.

This invention is based on the discovery that the absorption of pitch by cellulosic fibrous ma- 'terlals maybem'arkediy increased in rate and extent, and "water-imperviousness promoted, by the coniointfuse with the pitch. to be absorbed of phenolic tar-acid. By phenolic tar-acid I mean such phenolic bodiesas those which normally occur in coal-tar, and their analogs, homologs, and isomerldes, lwhether o1 synthetic or other origin. That is, tar-Y-acids which I use in any particu- 5 sources than coa1- tar.-

ong the phenolictar-acids which are suit able, either-in thecrude or the refined state, are

acid oil) I 3-- ar ms rl e d 4 Qrtho-cresol 5.]Para-bresol A 6. Meta-cresolfl= i e J. 1, "tilxylenols t Q 9 .iHig h-boilingjtar-acids 10.' Low-teniperature tar-acids i V 11 Qrtho-phenyl phenol 1 12. Alpha-naphthol la Beta-naphthol 4 14. Pymr ws i l6. of oils with the tar acids or. with mixtures of tar-acids, whether the oil is a tar oil or some other kind ofoilsuch lar case may actuallybe. derived from,other i are desirably dried before impregnation.

2. variously composite tar- 7. Mixtures of cresols, asof metaci'esol and Application December 18, 1931, Serial No. 581,987

In carrying out my invention I may use any suitable impregnating pitch; and I use with it a phenolic tar-acid material such as referred to above. The pitch vI prefer is a water-gas-tar pitch which melts between and C. The 5 additional material may be mixed with the pitch, and-the mixture applied as a unit in a single impregnating process; or the additional material may be preliminarily applied to the fibrous material to be impregnated, and the pitchy materlal applied subsequently. The temperature used for impregnation should be sufiiciently high to make the impregnating materials flow fairly freely, and should be as highas conveniently pos- 'sible withoutcauslng deterioration of either the treated or the treating materials. In practice,

the impregnating temperature is well 'over' C., but ,usually under, 200 C.; and for most pitches a satisfactory. impregnating temperature is about .to (2. The impregnation may be made by simply/soaking the fibrous material for a suitable time, or-may be made under pressure to obtain greater penetrationin shortened time.

I will describe my invention particularlywith 25 reference to the impregnation of electric conduits, of the type made of news-print paper-pulp or wood-pulp; and from that it will be clearly apparent how my invention is used on other types of cellulosic fibrous material.

These conduits are commonly from about 2 to 8 inches across, in length of from 3 to 12 feet, with walls of from y inchto inch in thickness, or thereabouts. After 'being formed; these conduits For many years it has been the custom; to im-' pregnate these conduits with pitch, by immersing themin a pitch bathfor 7 or8 hours and then I allowing them to cool, with the pitch. bath m'airitained at a temperature of about 150 to 185? (140+ The normal mean absorption of pitch has been in the nemhborhood of 1* i0%"to' %[of1the weight of the untreated conduit; A conduit so treatedis fairly water-impervious, but, not much was is to be desired. 'Whentested, forflli water absorption by being immei sed in water at 21 C. for 48 hours the mean absorp ion of water I,

is ordinarily found to be from 5,% to 15% of the weight of the pitch-treated conduit. When such absorption of water occurs in a conduitin actual use, the resultant lowering of dielectric strength 9 is very pronounced. ordinarily to about 40%, to 60%.

Instead of using the sim a pitcnihat has heretofore been used for impregnation, I use, i such pitch together with some one or" more of,

the phenolic tar-acids above referred .to as the impregnating material. The quantity. of taracid used may be relatively small in on to the quantity of. pitch. In most instmces it-is' suflicient to use as little as from 1% to 3% taracid as reckoned on the weight of the pitch used; although in some instances it is desirable to use more tar-acid than that for best results, up to 8% or 10% in the case of beta-naphthol for instance, while in others it is possible to get good results with less, for instance as little as 0.2% in the case of crude composite tar-acids from taracid oil. In any case, it is desirable to use enough of the phenolic tar-acid to cause an increase in the total quantity of pitch which will be absor Bed by the cellulosic fibrous material (the conduit) in a given time under specified conditions.

It is found that with conduit thus impregnated, so that a greater amount of pitch is absorbed, the water-imperviousness of the conduit is markedly increased over that of previously known conduits, the proportionate increase varying with the nature and amount of the tar-acids used. The pitch absorption by the use of the tar-acids may be increased by as much as 40% or 50% in some instances, over that of the unmodified pitch; and the mean water absorption of the conduit so impregnated with the modified pitch under the test for absorption by immersion in water for 48 hours at 21 C., may easily be reduced to below 3% of the weight of the treated conduit, and in most cases below 1% thereof. In many instances, with this water-absorption test, we have been able to get a mean absorption below 0.5% of the weight of the treated conduit. Thus the lowering of water-absorption under given conditions is of the order of 40% to 90%, and even more in some instances, as compared to previous commercial pitch-treated conduits.

The following table shows some results that were actually obtained by the use of water-gastar pitch melting between 50 C. and 80 C. and

containing the indicated percentages of various phenolic tar-acids Percentage Percentage absorption water sbso The material added to the pitch of mm on in ma hours at 21 0.

Percent Percent 0.5 crude composite tar-acids 228 0. 32 l. crude composite tar-acids; 251 0. 27 2. a crude composite tar-acids; 271 0. 15

' 22! 0. 2i 2% 0. 40 246 0. B 242 0. 00 248 0. 05 henol 228 0. 7

2. undo com to tau-acids 1g i ttaa'anuazi (I'll ecom treatment) m4 1. 1

aoeaees The treatments shown in the above table, except the last two, were all for 7% hours, the first '7 hours at 160 C. and the last hour at 182 C.; which conforms to standard practice in impregnating conduits. The last two lines of the table, however, show that in my process it is possible to use a. shortenedtreatment, for there the treatments were for totals of only 4% hours and 1 hour respectively, at 160 C. I

Thus a marked increase in the amount of pitch absorbed, and/or a great saving in impregnating time, may be obtained in impregnating processes by the use of my modified pitch. The saving in impregnating time is especially marked when the impregnation is carried only to the extent of previous iml s ations.

In the examples shown in the table given above the treatment is made by mixing the pitch and the indicated phenolic tar-acid, and impregnating'the conduit in a single impregnating treatment. However, I have also gotten good results by treating the conduit first with the phenolic tar-acid and subsequently impregnating with the pitch. In the latter case, the treatment of the conduit with the tar-acid may be in any convenient way, as by dipping, brushing, or spraying, using either the tar-acid alone, the tar-acid dissolved in a solvent (such as benzol'), or the tar-acid made into an emulsion (even with water). The amount of tar-acid used is so small in comparison to the pitch that when it is applied preliminarily it is not in sumcient amount to make a complete impregnation by itself of the treated material; but it somehow combines with and modifies the subsequently applied pitch so that the penetration of the latter is facilitated.

With the impregnation by modified pitch as above outlined; I not only get an increase in the .amount of absorption of the treating material,

and a decreased amount of water-absorption under similar water-exposure conditions, but I also get an increase in the dielectric strength of the conduit, an increased mechanical strength, a decrease in the proportionate lowering in dielectric strength under given water-exposure conditions, and an improved appearance. The surface of the conduit which has been treated with my modified pitch is usually a uniform lustrous black on both inner and outer surfaces, with a thin but even outer seal coating instead of the thick irregular outer coating seen in those previous conduits in which it has been sought to obtain a seal coat. If preferred, a dull surface may be obtained, for instance if phenol or meta-cresol is used as the pitch-modifying agent.

Although I have primarily described my invention for electric conduit, in which telephone or telegraph or similar conductors are placed, my invention is applicable to various other cellulosic fibrous materials. For instance, fabric insulation can be impregnated in the manner described above for conduit. 80 can wood; although it is desirable to dry the wood first, so that penetration into the wood may not be interfered with by moisture in the wood-pores. The wood that is treated may have been previously creosoted if desired. I have also used the same impregnating materials and processes for vegetable-fiber plates or sheets. such as various wall-boards, fibrousbase tiles, etc. These are merely examples of the materials to which my invention is applicable.

I claim as my invention: v 1. The process of treating relatively inflexible prefabricated cellulosic fibrous material, which consists in impregnating it with water-gas-tar pitch containing from 0.2% to 10.0% of phenolic tar-acid.

2. An impregnating pitch of the class consisting of coal-tar pitch and water-gas-tar pitch, containing between 0.2% and 10.0% phenolic taracid, for impregnating relatively inflexible prefabricated cellulosic fibrous material such as conduit.

3. An impregnating pitch comprising watergas-tar pitch melting between 50 and 80 C., to which has been added phenolic tar-acid, for impregnating relatively inflexible prefabricated cellulosic fibrous material such as conduit.

IRA H. DERBY.