US2117432A - Process and apparatus for impregnating fibrous sheet material - Google Patents

Description

M y 17, 1938 v c. E. Lmsco'rr 2,117,432

PROCESS AND APPARATUS FOR IMPREGNATING FIBROUS SHEETMATERIAL Filed Feb. 7, 1935 'INVENTOR 7 6747/71? M7460 ATTORNEY Patcnted'May 17, loss Um'rso STATES ffj 2,117,432

PATENT orr cl:

PROCESS AND AIPABATUS FOR MEG- .NATING I'IBROUS SHEET MATERIAL chemia.

Linscott, Bidgcwood, 11.3., assisnor to United States Rubber Company, N. Y., a corporation of New Jersey New Yorlr,

Application rm 1, 1935, Serial No. am 3.0lahns. (cl. si-ss) woven or knitted fabrications of thread and yarn are commonly impregnated with rubber compositions, such as rubber latex, by passing the material throush a tanlr of the latex and thence ,between squeeze rolls. In such a process, especially where light weight and wide fabrics are interstices of the material is displaced by the impregnating composition, creating large amounts of ,undesirable foam in the impregnating fluid.

Furthermore, when it has been desired to coat 1' both sides of a fabric by conventional spreader methods, it has been necessary-to coat first one side and dry the material, then to coat theother side and dry again, a minimum of two spreader operations thus being required.

The present invention relates to the impregnation of fibrous sheet material with fluid rubber compositions without the use of squeeze rolls, thereby eliminating the disadvantages incident to that method of impregnation. It also provides a process and apparatus whereby flbrous sheet material may be impregnated, and coated on both faces in one operation by'direct application of a fluid rubber composition to one face only of the sheet material. It also makes it possible to use, with only minor changes, the same type of machines for latex impregnation as for conventional latex spreading.

In the coating of fabrics on one side only with latex according to common practice, trouble is frequently experienced due to the tendency of the latex to strike through the fabric at various points rubber over the entire upper and lower faces in a single spreading operation.

According to the present invention, the fluid rubber composition is applied directly, to the upper surface only of the travelling flbrous sheet material. and is caused to penetrate into and through sheet material to provide a coating on both sides thereof. A convenient method of accomplishing this is by, means of one or more spreading devices and rollers frictionally engag-- ing the upper face of the sheet material, the rollers preferably rotating in the direction opposite to the direction of travel of the material. It is also possible to use a stationary roll or a roller driven in the same direction as the travel of the material and driven either by the moving fabric itself or by external means. The roller itself may be a part of the means for applying the composition as well as the means for driving it into the travelling material. The penetration of the composition into and through the sheet material is also aided by the hydrostatic pressure of a bank of the fluid rubber composition maintained upon the material between the rollers and spreading devices. The composition is then distributed as desired and excess composition removed to the extent desired by a suitable arrangement of wiper and scraper knives frictionally engaging the upper and lower faces-of the sheet material.

It is desirable that the rubber composition or the fibrous sheet material, or both, have such characteristics that the sheet material is readily wetted by theiiuid composition, in order to facilitate the penetration of the composition into and through the sheet material. For this purpose either the rubber composition, or the sheet material, or both, may be treated with a suitable hols.

The drawing illustrates more or less diagrammatically one type of-apparatus for impregnating fibrous sheet material.

Referring more particularly to the figure, which is merely exemplary of the invention and illustrates a present preferred embodiment thereof, the fibrous sheet material I, in the form of a woven fabric, for example, is unwound from the roll 2 and drawn under tension through the impregnating means and drier to be described below and onto a windup roll 3. The fabric as it advances from the roll 2 passes under a smooth-faced roller 4 rotating as shown by the arrows in a direction opposite to the direction of travel of the fabric and thence under a spreading device such as doctor I. The surface of the roller 4 frictionally engages the upper surface of the fabric and drives into the same the latex 5 which is provided between the roller and the spreading device in the form of a pool or bank fed from the latex supply 6 and confined by the upper surface of the fabric i, the roller 4, the doctor I, and by stops or guides 8 situated on each side of the fabric between the roller 4 and spreader l. Latex from the pool or bank 5 is driven into and through the advancing fabric by virtue of the rotation of the roller 4 and the pressure of the tensioned fabric against the roller, these actions being supplemented by the hydrostatic pressure of the bank 5. The result of this process is that both the threads or yarns constituting the fabric become coated or impregnated, and a substantial part of the latex strikes through the interstices over the entire area of the fabric and exudes upon the under side of the fabric in the form of small globules or buttons or extending fingers adhering to the fabric. In order to minimize or nullify any tendency of surface tension or capillarity to draw the exuded latex back into the body of the fabric, it is preferred that the fluid latex composition have a relatively high viscosity and yield value, preferably at least several times the values for uncompounded normal latex. Concentrated latices are therefore suitable, and may if desired be further thickened by various known means. The spreader I regulates the thickness of the layer of fluid rubber composition retained on the upper surface of the fabric, which composition may be subsequently smoothed out or partially scraped off, as desired, by means of one or more scraper knives 9 arranged at suitable angles along the path of travel of the fabric. Thus, by permitting a relatively small amount of latex to be retained on the upper side of the fabric as it emerges from under the spreading device I, or by removing the excess of latex by means of scrapers 9, the amount of latex remaining on the upper side of the fabric may be so regulated that the individual threads of the fabric, coated with rubber,

stand out in relief, with the latex webbing across the interstices to form saucer-shaped depressions which are closed at the bottom, between the threads. In other words, the film deposited on the upper face of the fabric may be continuous, but irregular in contour, following the weave of the fabric. Or a greater amount of the latex may be retained on the upper face of the fabric so as to provide a smooth, even coating. The fluid rubber composition which exudes upon the under side of the fabric may be smoothed.out and distributed evenly over the under side of the fabric by wiper knives l arranged at a suitable sloping angle to the fabric. After the desired smoothing operations, the fabric may be passed through a drying tunnel conventionally shown at H and then wound up as at 3, the coated fabric being drawn through the drying tunnel under sufficient tension to hold the fabric out of contact with the present invention with a vulcanizable latex composition as follows:

Rubber (as twice creamed latex 66%) 100 Formaldehyde 2, Sodium isopropyl naphthalene sulfonate- 1. 25, Water 5. 0

Oleic acid g 2. 0 2,2-di-p-phenylol-propane 2 0 Water 18.0 Ammonium hydroxide -(28%) 5.0

Stearic acid .25

Bleached Montan wax 1 Casper w 75 Water 6. 0 Ammonium hydroxide (28%) 5 Whiting 5.0 Sulfur 1. 25 Zinc dimethyl dithiocarbamate .65 Zinc oxide .1 Sodium isopropyl naphthalene sulfonate .1 Oleic acid 1 Ammonium hydroxide 1 Water, 4. 5

This composition was compounded by mixing the various materials, the ingredients being added to the latex in groups as indicated above, the liquids as emulsions and the solids as a paste, and the whole diluted with water to a water content of 50%. The various ingredients of such a latex composition may be, varied as well known in the art or other latex compositions substituted, the above composition being merely cited as one example of a latex composition that has been found satisfactory for the purpose. A so-called 4.75 cotton sheeting (4.75 running yards per pound of 39 inch width), having a thread count of 68 x 72 (threads per inch of warp and weft, respectively) was fed under considerable tension at about 24 feet per minute under a smooth steel roller two inches in diameter rotating about 70 revolutions per minute in a direction opposite to the direction of travel of the fabric. A reservoir or bank of the latex equal to or greater than the height of the roller was provided on the upper surface of the fabric on the egress side of the roller and confined by the roller and by aspreading device or doctor situated two inches from the roller along the path of travel of the fabric. the fabric passed under the roller and spreading device, the under side of the fabric became covered with exuded globules of latex which had struck through the interstices of the fabric. The coatings on the upper and lower surfaces were smoothed out by scraper knives and the thus impregnated and coated fabric was dried in a drying tunnel at 200-220 F. Further coats of latex, as desired, were applied to either or both sides in the usual manner and the finished fabric vulcanized at 225 F. for 45 minutes.

Various modifications of the illustration in the drawing may be resorted to. For example, the fluid rubber composition may first be applied to the surface of the travelling sheet material by means of a spreading device and after such application the sheet material may be passed under a rotating roller such as roller 4 to drive the composition into the material. If desired,

anus:

the roller, the rubber composition being confined only by the roller and the surface of the inclined sheet material and the stops at the sides of thefabric, and being carried from the reservoir or bank on theupper surface of the fabric and flowing down the inclined fabric by gravity, as shown in the McGavack Patent 1,946,090, to form a smooth coherent coating. The spreading device, if used in conjunction with the roller 4, as shown at I, or if used to apply the fluid rubber composition to the sheet material prior to passage under the roller 4, may take the form of a conventional doctor, as shown, or may take the form of a grooved spreading device, as shown in the patent to Charles Dennison No. 1,975,195. It is possible to obtain even better impregnation by having a bank of latex in front of as well as behind the rotating roll 4. It is also possible to place the blade 1 ahead of bank 5 between the two. It is ewise possible to confine the bank of latex between two rolls, one placed at I as at present and'one replacing the doctor I.

Various other modifications will occur to those skilled in the art and it is not intended to limit the invention other than as set forth in the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. A process for impregnating textile sheet material with an aqueous dispersion of rubber comprising advancing the material, applying the 4 and confine the aqueous dispersion of rubber to one surface of the material and driving the dispersion univ formly into and through the material, so that it exudes upon the opposite surface thereof, and distributing the dispersion which has been extruded through the interstices of the material smoothly and uniformly over the opposite surface of the material to form a continuous film thereover. A 2.-A process for impregnating textile sheet "material with an aqueous dispersion of rubber comprising treating either or both of the sheet material and the dispersion so that the sheet material is readily wetted by said dispersion, advancing the material, applying the aqueous dispersion of rubber to one surface of the material and driving the dispersion uniformly into and through the material to the opposite surface thereof, and distributing the dispersion which has been extruded through the interstices of the material smoothly and uniformly over the opposite surface of the material to form a continuous film thereover.

3. A process for impregnating fabric with an aqueous dispersion of rubber, said fabric and dispersion being mutually wettable, which com prises applying the aqueous dispersion of rubber, driving the dispersion uniformly into and through the fabric to the opposite surface thereof, and distributing the dispersion which has been extruded through the interstices of the fabric smoothly and uniformly over the opposite surface of the material to form a continuous film thereover.

Images