US2675745A - Protection of dispersed asbestos - Google Patents

Description

l. J. NOVAK 2,675,745 PROTECTION OF DISPERSED ASBESTOS FIBERS ON PAPERMAKING MACHINES Filed Sept. 10, 1949 April 20, 1954 Patented Apr. 20, 1954 PROTECTION OF DISPERSED ASBESTOS FIBERS ON'PAPERMAKING MA'CHINES Izador J. Novak, Trumbully-Cozm' asslgnor to Raybestos-Manhattan, Ina, Passaic, N. L, a corporation of New J ersey- Application September 10, 1949, Serial No. 114,949

Claims.

This invention relates to improvements in the production of felted sheets or webs of fibrous asbestos with generally conventional paper-making apparatus when employing slurries of individualized and dispersed asbestos produced in accordance with my co-pending application, Ser. No. 66,552, filed December 21, 1948, now Patent No. 2,626,213.

More particularly, the present invention relates to the maintenance and protection of the asbestos fibers in such dispersed condition, as distinguished from a flocked or clotted condition while on the foraminous or porous forming or conveying components of the paper-making machine, such as the Fourdrinier wire or felts thereof.

As more fully described in my aforesaid copending application, the asbestos dispersions with which the present invention is concerned are prepared by opening and individualizing the fibers of Chrysotile asbestos by subjecting macroscopic bundles or agglomerates thereof (which terms are intended to include mechanically fiberized asbestos) to mild mechanical action, such as stirring or agitation, while immersed in water containing an organic detergent surface-active material adsorbable on the asbestos and capable of forming an alkaline dispersion therewith, the amount of detergent being in excess of that adsorbed on the asbestos and suflicient to form and preserve or maintain the dispersion in a stable manner. Typical examples of such dispersing agents are Aerosol OT (dioctyl sodium sulfosuccinate), sodium oleate, and others more fully particularized in my said co-pending application. Treatment of the asbestos in this manner causes separation, individualization, dissemination and unclotting of the asbestos fibers, and converts them to single fibers or fascicular fiber bundles instead of the predominantly clotted and tangled multiple fiber groups known to prior wet or dry asbestos practice. The fibers in such dispersion are in a lubricated, slippery, relatively slidable condition and composed predominantly of asbestos fibers of unit size, or fibro-colloidal diameter, that is, of a diameter of from about 200 to about 500 Angstrom units.

As further set forth in my aforesaid co-pending application, for each surface-active agent, there concentrated agent. However, in addition to the .minimum amount required and adsorbed by the asbestos, a further concentration should remain in the liquid for the purpose of dispersin the previously opened fibers, Thus, I have found that beyond the amount necessary to satisfy the fibers, a certain concentration of the agent in theliqui'd phase is necessary to maintain a stable dispersion. As further described and illustrated in my aforesaid c'o-pending application, the concentration of the agent in the aqueous phase necessary to maintain the asbestos dispersion over and be-' yondthat which is adsorbed by the asbestos is in the case of Aerosol OT about 035% and for sodium oleate is .047%. These dispersions act in many respects like emulsions or dispersions of other substances in that even though a dispersion may contain an excess of dispersing agent in the liquid phase, dilution thereof by plain water in a rapid manner may cause precipitation or flocculation of the fibers. Further, the addition of water in an amount so as to reduce the concentration of the protective agent or minimum amount required for dispersion will cause flocculation or precipitation of the fibers. As is evident from the foregoing, these surface-active agents are actually colloidizing agents for asbestos in an aqueous vehicle since they reduce the asbestos to colloidal size particles and hold said particles in colloidal dispersion.

An object of the present invention to prevent the shocking of the dispersions employed, and to prevent flocking or precipitation of the fibers on the paper-making machine so as to permit felting of the fibers in their individualized dispersed condition whereby webs or sheets of much greater toughness and flexibility can be produced, as compared to dry webs or sheets composed of heretofore conventional or clotted asbestos fibers. It is a further object of the present invention to prevent clotting or precipitation of dispersed fibers in the paper-making appurtenances such as Wires or felts so as to prevent their becoming clotted with asbestos fibers such as, for example, as might occur in carrying out the conventional water washing of a Fourdrinier wire on its return 'run.

For the purpose of illustration and not limitation, the following is an example of a methodfor forming an asbestos dispersion, generally described in my aforesaid co-pending application, and the sheeting thereof on a paper-making machine:

A slurry was prepared for making an asbestos tissue by adding 312 lbs. of 25% AerosolO'I' in water to .1000 gallons of water and dissolving same therein. Then 212 lbs. of 3B spinning grade Chrysotile asbestos was added and on stirring for four hours produced a smooth slurry at 2 /2% asbestos concentration. This was further diluted by adding water slowly to the 2 /2 slurry in the volume proportion of 9 parts of 2 /2% slurry to 47 machine at 85 ft. per minute producing a tissue weighing about 0.7 grams per square foot, having a thickness of about .00035 inch. This tissue was well formed, smooth, uniform in fiber distribuand line 3| to white water filter chest 32. This filter chest may, as illustrated, be a cylinder or decker type of save-ah employing a wire-covered cylinder. The filtered white water is removed therefrom through line 33, valve 34 and pump 35 and delivered through line 36 to the screen spray 31.

As an alternative, I may employ a fresh aqueous solution containing a requisite amount of asbestos dispersing agent, supplied from the tank 38 by means of line 39 and valve 40 through pump 35 and line 36 to spray 31. In such case, the asbestos dispersing agent need not necessarily be .the same one contained in the fiber dispersion,

tion, tough, strong, stretchy, and highly oriented in the machine direction. On its return run the Fourdrinier wire was continuously washed with filtered white water recovered in the operation.

In this manner, the screen was continuously freed trates methods and means in connection there- W with for washing the Fourdrinier wire with watercontaining dispersing agent in accordance with the present invention.

Referring to the drawing, a dilute slurry of dispersed and individualized asbestos is supplied from the stock chest to the head box I l wheref-rom it is picked up onto the Fourdrinier wire 12 by means of the suction formation roll [3. The Fourdrinier wire in conventional manner passes over the vacuum boxes Id and the felted asbestos .web on the wire 12 is transferred therefrom as it passes over the drive roll I5 bymeans of the pick- .up felt l6 as the latter passes over the suction pick-up roll I]. The felt I6 is thereafter transferred from the web to drying means (not shown) such as, for example, a Yankee dryer.

The white water from the drainage trays l8 and i9 may be collected through line and valve 2! to the white water tank 22 together with white water collected from the suction formation roll 13, vacuum boxes Hi and suction pick-up roll I! by means of pump 23 and line 24. This white water may in whole or part be returned for use as make-up liquid through the pump 25, line 26, valve 21 and line 28 which may lead to suitable stock preparation tanks, or, in the alternative, if desired, discharged.

As i conventional, the Fourdrinier wire l2 in its lower return run as it passes over rolls 29 is subjected to washing to clean the wire by removing accumulations thereon. As previously "described and in accordance with the present invention, washing of the Fourdrinier wire on its return run is accomplished by means of water containing asbestos dispersing agent. In accordance with the preferred embodiment of themes- .ent invention, such dispersing agent-containing water is the white water recovered as hereinbefore described. Thus, all or part of thewhlte water from line 26 may be directed through valvefiflbut still one, or a mixture of asbestos dispersing agent, as described in my aforesaid co-pending application, capable of protecting the asbestos fibers from clotting. If desired, the solution collecting in the pan l9 may be discharged therefrom through line l2, valve 4| and line 42. As a further alternative, instead of discharging the solution from line 42 to waste, the discharge from line 42 may be recovered for use as slurry makeup or, as a further alternative, the discharge from line 42 may be directed by means, not shown, to tank 38 for direct recirculation thereof.

It will thus be seen that by proceeding in accordance with the preferred method, that is, by employing the white Water recovered in the usual manner as the solution for washing the screen, an adequate amount of dispersing agent in the wash water will already be present since such amount was present in the slurry water for maintaining the dispersion, and in commercial practice the dispersing agent is generally contained therein in exces so as to have insured stability of the original dispersion.

As further indicated from the foregoing, if desired, wash water may be employed which is not necessarily recovered white water. In such instance, the wash solution should contain an adequate amount of dispersing agent, such as will not cause precipitation of fibers and entanglement thereof on the screen, th amount being related to the character of the agent employed as hereinbefore pointed, out. In the event the agent employed in this wash water solution is the same as the agent employed in preparing the original dispersion, it may be combined with the wash water. In the alternative, that is to say, for example, if the dispersing agent employed in the wash water is other than the agent employed in preparin the original asbestor dispersion, it may be wasted after use or recirculated in a separate but continuous wash system, as hereinbefore described in accordance with the description of the apparatus.

Although I have particularly described the present inmprovement in connection with the washing of a Fourdrinier screen, it willbe understood that my invention is of like effect in respect to other endless forming or conveying surfaces employed in paper-making machines which are intermittently or continuously washed. That is to say, washing operations of surfaces on which my individualized and dispersed asbestor-fibers are deposited prior to drying should not'.. be

washed with clear water, or water deficientin an amount of dispersing agent adequate to maintain the fibers in their desired dispersed individualized condition.

I claim as my invention:

'1. A method which comprises forming a fibrous asbestos web from an aqueous alkaline colloidal dispersion of individualized chrysotile asbestos fibers containing organic chrysotile asbestos colloidizing agent both adsorbed on the fibers and in the aqueous phase maintaining said dispersion, upon an endless continuously moving foraminated surface, continuously stripping the formed Web therefrom, and washing said surface, after removal of the web, with an aqueous dispersionmaintaining solution of asbestos colloidizing agent.

2. A method which comprises forming a fibrous asbestos web from an aqueous alkaline colloidal dispersion of individualized chrysotile asbestos fibers containing organic chrysotile asbestos colloidizing agent both adsorbed on the fibers and in the aqueous phase maintaining said dispersion, upon an endless continuously movin foraminated surface, continuously stripping the formed web therefrom, and Washing said surface after removal of the Web with a fresh aqueous solution of said colloidizing agent of a concentration substantially equal to that of the aqueous phase of said dispersion.

3. A method which comprises forming a fibrous asbestos web from an aqueous alkaline colloidal dispersion of individualized chrysotile asbestos fibers containin organic chrysotile asbestos colloidizin agent both adsorbed on the fibers and in the aqueous phase maintaining said dispersion, upon an endless continuously moving foraminated surface, continuously stripping the formed web therefrom, and Washin said surface after removal of the Web, with white water containing said colloidizing agent recovered in the process.

4. A method which comprises forming a fibrous inated. surface, continuously stripping the formed web therefrom, collecting colloidizing agent-containing white Water separated in the process and filterin same, and Washing said foraminated surface, after removal of the web therefrom, with said filtered white water.

5. In a method of making a fibrous asbestos web wherein an aqueous alkaline colloidal dispersion of individualized chrysotile asbestos fibers containin organic chrysotile asbestos colloidizin agent both adsorbed on the fibers and in the aqueous phase maintaining said dispersion, is deposited on an endless continuously moving foraminated surface and the excess aqueous solution removed therefrom through said surface to form a fibrous web thereon, the improvement which comprises collecting and filtering a portion of said aqueous solution and Washing said foraminated surface therewith in the path of its return travel.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,302,313 Coppage Apr. 29, 1919 1,907,616 Tucker May 9, 1933 2,068,219 Badollet Jan. 19, 1937 2,182,274 Baker et a1. Dec. 5, 1939 2,217,005 Clapp Oct. 8, 1940 2,220,386 Badollet Nov. 5, 1940 FOREIGN PATENTS Number Country Date 481,705 Great Britain Mar. 16, 1938 OTHER REFERENCES Chemistry of Pulp and Paper Making by Sutermeister, 3rd Ed. (1941), pgs. 407-411, pub. by John Wiley and Sons, New York.

Morrison, Paper Industry and Paper World, May 1943, p. 192.

Claims (1)

1. A METHOD WHICH COMPRISES FORMING A FIBROUS ASBESTOS WEB FROM AN AQUEOUS ALKALINE COLLOIDAL DISPERSION OF INDIVIDUALIZED CHRYSOTILE ASBESTOS FIBERS CONTAINING ORGAINC CHRYSOTILE ASBESTOS COLLOIDIZING AGENT BOTH ADSORBED ON THE FIBERS AND IN THE AQUEOUS PHASE MAINTAINING SAID DISPERSION, UPON AN ENDLESS CONTINUOUSLY MOVING FORAMINATED SURFACE, CONTINUOUSLY STRIPPING THE FORMED WEB THEREFROM, AND WASHING SAID SURFACE, AFTER REMOVAL OF THE WEB, WITH AN AQUEOUS DISPERSIONMAINTAINING SOLUTION OF ASBESTOS COLLOIDIZING AGENT.

Images