US2684726A - Wetting agent - Google Patents

Description

July 27, 1954 PL EBAUGH ETAL WETTING AGENT Original Filed Oct. 12, 1945 INVENTORS PAUL EBAUGH BY LEON T. PIEKARSKI Patented July 27, 1954 WETTIN G AGENT Paul Ebaugh, State College, Pa., and Leon T. Piekarski, Schenectady, N. Y., assignors to the United States of America as represented by the Secretary of the Navy Application May 27, 1949, Serial No. 95,867

(01. ISL-0.5)

2 Claims.

This invention relates to wetting agents and is particularly directed to a wetting agent which is effective for rubber surfaces to be immersed in water.

In the use of transducers for underwater sound signaling it is frequently desirable to provide a rubber face for the transducer diaphragm which is in direct contact with the water since rubber compounds can be prepared to have essentially the same sound transmission characteristics as water. One of the difliculties which has been encountered in the calibration and use of rubber-faced transducers is the fact that air bubbles cling to the surface of the transducer as it is immersed in the water and are likely to remain there for a long period of time. While the air bubbles are present the sound transmission and receiving characteristics of the transducer cannot be taken accurately since the air-water and air-rubber interfaces represent definite barriers for the transmission of sound waves.

It has been the practice to scrub the transducers prior to immersion and to use certain wetting agents which were calculated to disperse the air bubbles. In some instances this procedure has not been eiiective because the wetting agents do not remain on the surface of the rubber but become dissolved in the water leaving the face of the transducer in imperfect contact with the medium.

The present invention has for its primary object to overcome the diiiiculty above set forth and to provide a wetting agent which becomes adsorbed on the rubber surface to present a continuous hydrophilic surface to the water.

Another object of the invention is to provide an actively charged wetting agent which will increase the interfacial tension between a rubber surface and a surrounding liquid medium.

Other objects and advantages of the invention will become apparent from the following description in which a preferred form of the invention is disclosed and from the accompanying drawing, the single figure of which shows a typical embodiment of the features of the present invention.

With reference now to the figure, a cup-shaped casing l of steel or the like has its open end covered with a vibratile diaphragm 2 of steel or other suitable material. Diaphragm 2 is held in place on the casing by a suitable means such as a clamping ring 3 and bolts 4. To produce or utilize vibrations of diaphragm 2, magnetostrictive devices =5-5 are attached to diaphragm 2 and surrounded in part by coils 1-4. Coils 'l-7 are operative with electrical connections (not shown) which are brought through suitable water tight feed-through devices placed in the wall of casing I.

Surrounding the foregoing assembly is a corrosion resistant layer or coating i! of rubber which may be applied by one of several conventional Ways, typically by vulcanization.

Adsorbed on the external surface of the coating 9, particularly that portion thereof which covers the diaphragm 2, is a thin layer it of triethanolamine acetate. This layer is of such minute thickness as to be impossible to show to reasonable proportion in the figure, however due to a phenomenon involving surface adsorption, this material remains on the surface of the rubber for prolonged periods of time and provides a Vast improvement in the wettability characteristics of the rubber coating.

The wetting agent of the present invention relies for its effectiveness on the fact that neutral materials such as rubber acquire a negative charge when immersed in an aqueous medium. A wetting agent which is initially positively charged or cation-active will absorb on the negatively charged rubber face and cause the rubber face to become completely wetted. One compound which has been found satisfactory for this purpose is triethanolamine acetate which can be prepared by mixing one part of acetic acid to two and one half parts by weight of triethanolamine. An excess of acetic acid may be used without detrimental effect.

Triethanolamine has the structural formula:

OH-CHr-CHz OHCH2CH2--N OH-CHPCHI This substance when combined with acetic acid (CH3COOH) results in an acetate having the following structural formula:

In aqueous media the hydrogen is closely held because the nitrogen is in a pentavalent state and the salt dissociates into the acetate radical and the positively charged ammonium complex. This latter adsorbs onto the surface of the rubber and forms a hydrophilic surface thereon. The rubber surface, so coated, is readily wetted by water due to the presence of the hydrophilic hydroxyl radicals in the compound which have become adsorbed.

In use the rubber surface is cleaned to assure the removal of oily materials and thoroughly rinsed to assure the absence of anionic compounds such as soaps and mild cleaning acids. The presence of an anionic compound will, of course, reduce the effectiveness of the triethanolamine wetting agent.

While the present invention has been found effective the advantages gained by its use can be increased if temperature equilibrium can be established between the transducer and water prior to immersion. However, the immersion of a warm transducer in cold water will result, when first prepared as above suggested, in the presence of small bubbles having a contact angle with the rubber surface which is so large that slightly mechanical agitation will release the bubbles. Thus even a very warm transducer which has been coated with our Wetting agent is usually cleaned of all air bubbles simply by rotating it or otherwise moving it in water immediately after immersion.

Acetic acid is the preferred source of hydro gen ions, but other acids such as formic, hydrobrornic and hydrochloric acids may be used in the same manner.

While the present invention is particularly effective on rubber surfaces it may also be used on other surfaces which acquire a similarly negative charge when immersed in water, such as synthetic rubber, artificial resins, glass and sulphur. While a specific compound has been disclosed, other compounds of an equivalent nature may be used without departing from the invention as defined in the appended claims.

This application is a division of application Serial No. 622,078, filed October 12, 1945, for Wetting Agent, but now abandoned.

What is claimed is:

1. A transducer unit for underwater sound signalling, comprising a sound actuatable diaphragm, a rubber coating on said diaphragm having normally a negative charge when immersed in water, and a coating of triethanolamine acetate on said rubber coating, said triethanolamine acetate coating disassociating into an acetate radical and a positively charged ammonium complex which adsorbs on said rubber coating thereby to present a continuous hydrophilic surface to an aqueous medium.

2. A transducer unit for underwater sound signalling, comprising a sound actuatable diaphragm, a coating on the diaphragm surface of rubber-like material having normally a negative electric charge when immersed in Water, and an additional coating on the rubber-like material coating of a compound having a positively charged hydroxyl containing radical, said compound being formed of triethanolamine and any one or" the acid group consisting of acetic acid, formic acid, hydrochloric acid and hydrobromic acid, said additional coating adsorbing on said rubber-like material thereby to present a continuous hydrophilic surface to said water.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,176,326 Sutline Mar. 21, 1916 1,890,158 Lindstaedt Dec. 6, 1932 2,094,609 Kritchevsky Oct. 5, 1937 2,200,184 Morgan May 7, 1940 2,206,517 Stefiens July 2, 1940 2,214,646 Walker Sept. 10, 1940 2,279,860 Crawford Apr. 14, 1942 2,421,079 Narcus May 27, 1947 2,444,507 Hanson July 6, 1948 2,496,060 Mell et al Jan. 31, 1950

Claims (1)

1. A TRANSDUCER UNIT FOR UNDERWATER SOUND SIGNALLING, COMPRISING A SOUND ACTUATABLE DIAPHRAGM, A RUBBER COATING ON SAID DIAPHRAGM HAVING NORMALLY A NEGATIVE CHARGE WHEN IMMERSED IN WATER, AND A COATING OF TRIETHANOLAMINED ACETATE ON SAID RUBBER COATING, SAID TRIETHANOLAMINE ACETATE COATING DISASSOCIATING INTO AN ACETATE RADICAL AND A POSITIVELY CHARGED AMMONIUM COMPLEX WHICH ADSORBS ON SAID RUBBERCOATING THEREBY TO PRESENT A CONTINUOUS HYDROPHILIC SURFACE TO AN AQUEOUS MEDIUM.

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