US2378882A - Manufacture of articles from liquid dispersions - Google Patents

Description

June19, 1945. I HABIB El AL 2,378,882

MANUFACTURE OF ARTICLES 1 30M LIQUID DISPERSIQNS I Filed Nov. 16, 1943 3nventors= AND GozwoNl'l GOTT Patented June 19, 1945 MANUFACTURE OF ARTICLES FROM LIQUID DISPERSIONS Emile E. Habib and Gordon E. Gott,

Arlington,

Mass., assignors to Dewey and Almy Chemical Company, North Cambridge, Mass., a' corporation of Massachusetts Application November 16, 1943, Serial No. 510,443

4 Claims.

The present invention relates to the manufacture of meteorological, radiosonde, and emergency life-saving balloons, and more particularly to an improvement; in a dipping type process used in manufacturing these articles.

Balloons which are used to carry aloft weather recording instruments are quite large. The common sized balloon of this type is about three feet in diameter before ascension and expands during flight to 12 feet or more. Because of this requirement, such balloons had, until the recent past, been made by a casting procedure, as distinguished from a dipping procedure. In this casting process a sensitized latex dispersion is cast in a rotating, hollow, spherical mold im-' mersed in a hot water bath. The process is slow and, especially when used with chloro butadiene- 1,3, the preferred material for certain military balloons, is too sensitive to slight variations in time and temperature, and consequently requires too precise control for effective and economic factory use. This difficulty has, to a large extent, recently been over-come by introduction of a dipping type process, in which the formed deposit is st iipped from the mold while it is still sufficiently soft from the presence of water to be capable of plastic (as distinguished from elastic) deformation, washed and then inflated while still plastic to permanently increase its size and make it more nearly spherical. This dipping process is described in detail in our co-pending application, Serial No.

510,442, filed on the same day as the present application. In practicing this process on a factory scale, it was found that a substantial percentage of the balloons burst during the inflation treatment before reaching the desired size. Investigation showed that the uninflated gel of specimens which burst was of uniform auge over its entire area within extremely close tolerance limits, so close that the failures during inflation could not be accounted for on the basis of variations inwall thickness alone. Further investigation led to the discovery that any droplets of water'remaining on the surfaces.

of the plastic gel from the washing following dipping were immediately absorbed into the. material during inflation. It was then discovered.

from a study of the fragments of the burst specimens, that failure had occurred in those areas into which excess water had been absorbed. It is not possible to avoid wetting the gels, because they must be washed to remove the coagulant which remains on their inner surface. It is not possible to avoid local accumulations of water by drying the gels before inflation, because it is essential that the gels be still In accordance with the present invention, the

percentage of failures in the manufacture of meteorological balloons by the coagulant dipping process referred to above is substantially reduced by removing'any local accumulation of water from the surfaces ofthe plastic gel which is to be stretched during inflation before the inflation step is carried out. The invention will be more fully understood from a reference to th accompanying drawing, in which Figure 1 is a sectional view of a dipping mold with the rubber deposit thereon;

Figure 2 is an elevation, partly broken away, of the stripped gel deposit;

tion on the inflation nozzle; and

Figure 4 is similar to Figure 3, but shows a later stage in the inflation step.

In practicing the present invention, a coagulant bath and a dipping bath of compounded rubber dispersion are made up according to established practice in the dipping art. The following examples are illustrative of suitable coagulant and dipping compounds.

Example 1.For a meteorological balloon made from a polymerized chloroprene-1,3 latex compound. I

A dipping compound is made up in accordance Figure 3 shows in section the wet gel inposi V with the following formula:

Parts by weight I of solids 7 Polymerized chloroprene-1,3 dispersion- (neoprene type 571) 100.00 Dibutyl sebacate emulsion 15.00 NH: (as ammonium hydroxide) 0.28 Hard clay (Suprex brand) 7.00

Dispersing agent (formaldehyde conden-' sation product of naphthalene sul- The dibutyl sebacate emulsion has the following formula:

. Parts by weight Zinc dibutyl dithiocarbamate The formula for the casein solution is as follows:

Example 2.-For a life-saving (captive) The casein solution and; coagulant have the composition described in Example I.

Example 3.For a'balloon made from natural rubber latex; the dipping compound has the following composition: r

' Parts by weight 0 of solids Rubber latex (60% solids) 100.00 Potassiumhydroxide 1 1.75 Zinc stearate 1.00

Symmetrical 'di-beta naphthyl para phenamount will va with different latices. Suiiieient should be used to give e dispersion a viscosity suitable for dipping.

The ingredients are added in the order stated.

In manufacturing balloons by the preferred form of ,the present process, a conventional balloon mold II is dipped in the coagulant to form a coating -ll of coagulant on its surface. The coated mold is then dipped in the bath of rubber dispersion, allowed to dwell therein for the time necessary .to build up a rubber gel deposit I! of the desired thickness, and then withdrawn and held for a short time in still air-at room temperature to .permit coagulant to diffuse throughout the deposited layer i2 and complete coagulation of the very thin layer of mmlated dispersion which adheres to the outer surface of the coagulated gel I! as it is withdrawn as The excess water on the inside surface of the balloon which collects during inflation at the botover an'inflation nozzle l5, arranged in a ver-' tical position and having its orifice facing upwardly. A support forthe soft gel is provided adjacent the inflation nozzle; As shown in Figure,'3, the support takes the form of a ring ll surrounding the nozzle oriiice and supp rted by arms .20 mounted at their lower ends on the nozale. Anyeircess liquid on, the outside surface of the balloon will flow downwardly onto the neck, and most of it will drain away oi the end of the bal- 2g neck. Excess water -on the inside surface will hon hydrogen Parts by weight likewise drain downwardly and collect at It in' -Polymerized -chloroprene-l,3 dispe ion the l a i t nozzle. Air under (neoprene type 571) 10090 a low pressure is then discharged through the 'Ammonia (as ammonium hydroxide) 0.2a nozzle into e e si e it to expand. As it Hard clay (Suprex brand) 7.00 25 ,expands, the rubber material undergoes plastic Dispersirig agent ;formaldehyde-condensag z z g gmi n r a tlg flm :33 woduct naphthalene sulphonic 0J4 contract to its original size as would an ordinary Zinc'oxlde (Kadox) 5.00 W balloon- Phenyl'beta naphthylamine 2.00 so when 8 1 has been fully expanded, it is Casein'solution- (10%) 0.35 n the x d condition which perms-- nently increases its size. The envelopes are then A I 114.77. deflated and may be subsequently vulcanized, if

desired, in air at 212 F.

. tom, will be in. contact with the gel only at its neck. The neck is stretched, much less severely ylene diamine 1.00 Formaldehyde" condensation product of naphthalene sulphonic acid. 0.24

Titanium dioxide 1.00

- Sulphur 1.10

duringthe inflation than is the body'portion; consequently excess water at this point does no harm.

The inflation nozzle may be arranged, it desired, to permit the excess water which drains from the inside surface of the balloon to flow out the noule. For example, a trap may beprovided in the air line just below the nozzle.

The hivention may be practiced also by swabbing or wiping the excess. water from the surface of the gel before it is inflated, although we have found this procedure to be less convenient than the method described above. The swabs or cloths used for wiping should preferably be dusted with tale to prevent scufllng the gel.

It will be appreciated by those skilled in the art that the present invention is applicable to the manufacture or other dipped goods than meteorological and similar balloons. The process is applicable tothe manufacture of any object which lends itself to manufacture by the coagulant dipping process of our application 8e No. 510,442, referred toabove.

While the herein described process is particularly applicable tothe polymerized halogen butadiam-1,3 and natural rubber illustrated in the examples, we believe it to be applicable to other elastomeric materials capable of being made in speciflcationandintheclaimswehaveusedthc .word rubber" in an inclusive sense.

We claim:

1. The method or making a hollow. rubber object having an opening which comprises dipping a coagulant-coated mold of smaller size than the object into a liquid dispersion or rubber, withdrawing the mold from the dispersion with a layer of rubber gel thereomstripping the gel from the mold while the gel is still plastic from the presv ence of water. removing free water from the surv face or the gel and enlarging the plastic gel to object into a liquid dispersionoi natural rubber,

withdrawing the mold from the dispersion with a layer 01' natural rubber gel thereon, stripping the gel from the mold while the gel is still plastic the dispersion with a layer of polymerized chloro butadiene-l,3 thereon, stripping the gel from the mold while the gel is still plastic from the presence of water, removing free .water from the surface of the gel, and enlarging the plastic gel to the desired size by inflating it while it is still plastic from the'presence of water interstitially' present in the gel, and thereafter drying the gel.

4. The method of making a hollow rubber object having an opening which comprises dipping acoagulant-coated mold of smaller size than the from the presence of water, removing free water from the surface of the gel, and enlarging the plastic gel to the desired size by inflating it while it is stfll plastic from the presence of water interstitially present in the gel, and thereafter drying the gel. 3. The method of making a hollow rubber object having an opening which comprises dipping a coagulant-coated mold of smaller size than the object into a liquid dispersion of polymerized chloro butadiene-1,3, withdrawing the mold from desired size 01' the finished object into a liquid dispersion of rubber to deposit' a layer of rubber gel thereon, withdrawing the mold from the dispersion with the layer of gel thereon, stripping the gel from the mold while the gel is still plastic from the presence of water, and removing free water from the surface of the gel and enlarging the gel to the desired size by inflating it in inverted position with its opening downward whileit is still plastic from the presence of water interstitially present in the gel, and thereafter drying the gel. EMILE E. HABIB.

GORDON E. GO'I'I'.

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