Means for protecting sheaths of electric cables, pipes, and other metal articles agaist corrosion

June 4, 1940. _T. l. osborne ετ al 2,203,232

MEANS FOR PROTECTING SHEATHS OF ELECTRIC CABLES, PIPES, AND OTHER METAL ARTICLES AGAINST CORROSION

Filed May 11, 1938

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Wrappings of ce//u/osic materia/ of which tee fibres are coated wr'te ce//u/ose rosinate and of which rhe interstices are seated by water- excluding compound.

Fig. 2.

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Thomas Lloyd Qseoerra and Harold Sohn Hll&amp;ock

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Patented June 4,1940

2,203,232

UNITED STATES PATENT OFFICE

2/203,232

MEANS FOR PROTECTING SHEATHS OF ELECTRIC CABLES, PIPES, AND OTHER METAL ARTICLES AGAINST CORROSION

Thomas Lloyd Osborne and Harold John Allcock, Belvedere, Kent, England, assignors to Callender’s Cable and Construction Company Limited, London, England, a British company Application May 11, 1938, Serial No. 207,301 In Great Britain May 27, 1937 (CL 91—68) conductor I surrounded by a body of dielectric 2 and a seamless lead or lead alloy sheath 3. Surrounding the sheath 3 are two wrappings 4 and 5 of cellulosic material, for instance, paper or cotton tape, of which the fibres are coated S with a film of cellulose rosinate and of which the interstices between the coated fibres are sealed by a water excluding compound. The wrappings 4 and 5 are so arranged that the small gap between successive turns of file wrap- IS ping 4 are bridged by the turns of the wrapping 5. Over the wrapping 5 is a wrapping of fabric material 6, for instance, hessian, on which is arranged a single layer of wire armouring 7 in the usual manner.

The rosin required for the formation of the - water resistant film on the fibres of the material used in the construction of the improved protective covering may in general be applied in any way which brings it into intimate contact 23 with the fibres of the paper or fabric. This is, of course, subject to the qualification that the method does not involve the use of any material which disadvantageous^ affects the paper or fabric, either in its structure or in its proper- gg ties required for its subsequent use. The resin may, for instance, be applied in solution or In the form of a suspension. A solution may, for instance, be made by the aid of trichlozefiiylene, alcohol or other organic solvent for rosin, g'C Satisfactory results are obtained, if the solution strength is such as to leave about 5 parts &amp;y weight of rosin in 100 parts by weight of paper or fabric. The paper or fabric is soaked in the solution or suspension, for instance, by running as it through a bath of the solution or suspension, and the solvent or suspension medium may be removed by drying in air or under a pressure less than atmospheric pressure. In the case of paper the rosin may be incorporated in the process of manufacturing the paper, for instance, during the beating stage. Conveniently a rosinsized paper containing about 5% by weight of rosin may be employed.

The rosin-containing material thus produced 4g or obtained is treated in accordance with the invention by heat drying it under vacuum until the reaction has been completed or substantially completed. A suitable treatment comprises drying rosin-containing material for a period vary- sq ing from about 20 to about 50 hours at a temperature of about 120° C. at an absolute pressure which at the end of the process is not greater than 1 mm. of mercury. This treatment also has the advantage that it leaves the. paper or fabric 55

Claims.

This invention is concerned with the production of wrappings, of impregnated paper and cotton and other textile fabrics formed of natural cellulosic materials, such as are used for 5 protecting sheaths of electric cables, pipes and other metal articles against corrosion and proceeds from the discovery that when natural cellulosic material is subjected to a vacuum and heat in the presence of rosin it undergoes a chem10 leal change on the surface which appears to be an esterification, cellulose rosinate being produced. This reaction, which is accompanied by the production of water that must be removed for the reaction to continue, can be employed, as 15 described and claimed in the specification of copending United States application, Serial No. 207,299 filed on May 11, 1938, for the purpose of making paper or fabric resistant to water.

In accordance with the present invention we 90 provide a cable sheath, pipe or other metal body with a protective covering comprising one or more wrappings of a material, consisting of paper or cotton or other fabric formed from natural cellulosic material, of which the fibres 9-, have been coated with a film of cellulose rosinate by drying the material by subjecting it to heat and a vacuum in the presence of rosin and of which the passages between the coated fibres have been sealed by impregnating the vacuum 30 dried material with a water excluding compound. The coating of cellulose-rosinate on the fibres reduces the water absorptive capacity of the material and to a large' extent overcomes the difficulty experienced with existing cover35 ings formed of paper or fabric impregnated with a water excluding compound which merely fills the passages between the fibres, of preventing the passage of moisture through the fabric by way of the fibres themselves. In the case of 40 paper and felted fabric, the cellulose rosinate coating also has. the advantage of giving it the power to resist the softening and disintegrating action of water.

The accompanying drawing shows by way of 45 example a length of a lead sheathed electric cable furnished with a corrosion resistant protective covering constructed in accordance With the invention. In the drawing

Figure 1 is a perspective view of the protected 50 cable from which portions of the component parts have been removed to expose the construction thereof, and

Figure 2 is a cross-sectional view, on an enlarged scale, of the cable shown in Figure 1.

₅₅ The illustrated cable comprises a stranded .dry and with little tendency to take up moisture. The treatment can therefore be applied to the paper or fabric while to rolls and need not Immediately precede the process of impregnating with water excluding compound. The flexibility of the material is not' affected by the treatment.

The sealing of the passages between the coated fibres is effected by impregnating the vacuum dried material with a water excluding com- ' 10 pound in the usual way. As examples of water excluding compounds. are mentioned pitch, tar, bitumen and oil compounds. These materials penetrate into the paper or fabric and adhere to the surface thereof.

. The improved protective covering has greatly improved resistance to the penetration of moisture and to the softening effect of any moisture which does penetrate into it. An .indication of this is provided by comparing the tensile strength 20 of ordinary paper impregnated with bitumen and then saturated'with, water with a similar grade of paper vacuum dried in the presence of rosin in accordance with the invention and subsequently impregnated with bitumen and then saturated with water. The following figures have been obtained for a particular grade of paper.

<td> 89</td><td> Sample</td><td> Breaking load after soaking in water at S0° C. for 24 hours</td>

<td> 35</td><td> Ordinary paper impregnated with bitumen________ Paper vacuum dried in the presence of rosin and afterwards impregnated with bitumen__________</td><td> Pounds 6.25 10. 0</td>