Title:
DISINTEGRATION PROCESS FOR FIBROUS SHEET MATERIAL
United States Patent 3750962
Abstract:
A process for continuously converting dried cellulosic fibrous sheet material into a dispersion of individual fibers in air. The fibrous sheet is advanced into a disintegrating device wherein the end of the sheet is repeatedly impacted at a predetermined velocity by one or more impacting elements at a critical distance from the support elements for the sheet. The fibrous sheet is entirely disintegrated into individual fibers at relatively high rates.
Application Number:
05/182796
Publication Date:
08/07/1973
Assignee:
The Procter & Gamble Company (Cincinnati, OH)
International Classes:
D01G9/06; D01G11/04; D21B1/06; D01G9/00; D01G11/00; D21B1/00; (IPC1-7): B02C13/08
Field of Search:
241/18,27,28,280
Primary Examiner:
Custer Jr., Granville Y.
Claims:
What is claimed is
1. A process for disintegrating dried cellulosic fibrous sheet material comprising the steps of feeding a fibrous sheet into a disintegrator comprising a casing, supporting said sheet in a slotted opening terminating in a sheet support in said casing, moving a plurality of impacting elements having tips so that the tips move at a velocity of at least about 6,000 feet per minute, and impacting said tips against the end of the fibrous sheet so that impact is substantially normal to the plane of the sheet whereby said fibrous sheet is disintegrated into individual fibers, the tips of said impacting elements moving past the sheet at a distance from the end of the sheet support of from about 0.023 in. to about 0.050 in., said distance being from about 0.023 in. to about 0.035 in. when said sheet material is advancing into said disintegrator at a speed of less than about 100 fpm. and said distance being from about 0.023 in. to about 0.050 in. when said sheet material is advancing into said disintegrator at a speed of greater than about 100 fpm.
2. The process of claim 1 wherein the velocity of said tips is at least about 12,000 feet per minute.
3. The process of claim 1 wherein the distance from the sheet support to said tips is from about 0.027 in. to about 0.033 in.
4. The process of claim 3 wherein the cellulosic sheet material is fed into the disintegrator at a rate of from about 30 fpm to about 100 fpm.
5. The process of claim 4 wherein the dried cellulosic material is a drylap having a thickness of from about 0.04 in. to about 0.06 in.
6. The process of claim 3 wherein the dried cellulosic material is a drylap having a thickness of from about 0.04 in. to about 0.06 in.
7. The process of claim 6 wherein the moisture content of the drylap is less than about 7 percent.
8. The process of claim 3 wherein the velocity of said tips is less than about 30,000 feet per minute.
9. The process of claim 3 wherein the moisture content of the drylap is less than about 7 percent.
Description:
FIELD OF THE INVENTION
This invention relates to the art of disintegrating fibrous sheet material. More particularly, it relates to a process whereby a dried cellulosic fibrous sheet is impacted under predetermined operating conditions to cause progressive disintegration of the sheet into individual fibers.
PRIOR ART
A similar process is disclosed in U.S. Pat. No. 3,519,211 where a different distance from the impacting element to the support elements is specified. Said patent is incorporated herein by reference.
OBJECTS OF THE INVENTION
The principal object of the present invention is to improve the operation of the prior art device of U.S. Pat. No. 3,519,211.
Another object of the present invention is the provision of a process for disintegrating dried cellulosic fibrous sheet material into individual cellulose fibers in such a way as to minimize the scorching and burning of the fibers.
Still another object of the present invention is the provision of a disintegration process for fibrous sheet material which increases the capacity and efficiency of the previously known processes and apparatus of this kind without need for artificial cooling.
SUMMARY OF THE INVENTION
The nature and substance of the invention can be briefly summarized as comprising a process for converting dried cellulosic fibrous sheet material into a dispersion of individual fibers in air. The fibrous sheet material is fed inwardly to a disintegrating device having a plurality of impacting elements. The fibrous sheet is advanced continuously between support elements for the sheet such that its end is disintegrated by the impact of the tips of the impacting elements on the free end of the sheet at a distance of from about 0.020 in. to about 0.050 in. from the end of the support elements. The sheet is advanced at a relatively constant rate between successive impacts. The fibers are freed from the cellulosic sheet whereupon they are dispersed in air and conducted away from the impact zone of disintegration by way of unobstructed passageways.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawing in which the Figure is a side elevation cross-section of the disintegration apparatus.
Referring now to the drawing, a preferred embodiment of the process will be described with particular reference to the disintegration of a dried cellulosic fibrous sheet. The invention is particularly useful in disintegrating wood-fiber "drylap" material of the kind found in commerce. Such "drylap" sheets are typically between about 100 and about 200 pounds 1,000 ft. 2 basis weight, and generally have a caliper of at least about 0.04 inch or greater, e.g., from about 0.04 to about 0.06. A drylap sheet of this type usually has a moisture content of less than about 10 percent, e.g., about 7 percent, although lower and higher moisture contents can be used. It has been found that the method of the invention produces better results if the initial moisture content is as low as possible. In fact, a moisture content of about 1 percent was found to produce best results.
As used herein, the term dried cellulosic fibrous sheet describes any type of fibrous-sheet material capable of disintegration by the process of the invention. On the other hand, a drylap sheet will be understood to mean a wood-fiber material of the above described characteristics to which the invention is preferably applied.
Referring now to the FIGURE, a roll 11 of drylap sheet material is unrolled into a web of sheet material 12 which is advanced to the disintegrator 13.
The sheet 12 is fed radially into the disintegrator 13. For this purpose, a pair of metering infeed rolls 14 and 15 are mounted on one side of the disintegrator 13. A motive power source which may typically be an electric motor is connected to the rolls in a conventional manner, to provide a driving force.
The disintegrator 13 comprises a casing 16 having a generally cylindrical bore. The internal configuration of the casing 16 is not critical to the practice of the invention and it will be understood that a cylindrical bore is shown in the preferred embodiment only as a matter of convenience. A shaft 18 is journaled in the casing such that one end extends outside the casing to permit coupling the shaft in some conventional manner to a motive source such as an electric motor. The motor continuously drives the shaft 18.
The casing 16 is provided with a slotted inlet opening 19 to receive the drylap sheet 12. A relatively large discharge outlet 20 is provided in the bottom of the casing 16. An air inlet opening 21 is provided near the discharge outlet 20 to permit air to be forced into the casing at a slight positive pressure from a suitable blower (not shown) or the like, for the purpose of preventing recycling of the fibers through the disintegrator. Additional air inlets 21a can be provided as necessary to carry out the function of adjusting the air flow.
One such system is disclosed in the copending application of Kenneth B. Buell entitled APPARATUS AND PROCESS FOR PREPARING AIRFELT, Ser. No. 182,795 filed concurrently herewith and incorporated herein by reference.
Rotors 22 are keyed to the shaft 18 and are provided with a plurality of teeth 23 extending radially outwardly which serve as impacting elements 24. A critical small clearance is provided between the teeth 23 and the supports for the sheet 12 at the inner end 19a of the inlet opening 19. The inner end 19a forms a sheet support for the sheet 12.
With the above arrangement of the parts of the apparatus, successive teeth 23 impact the ends of the sheet 12 as the rotor 22 is turned. The path of travel and the manner of supporting the teeth 23 is not critical to the practice of the invention. The only necessary requirement is that the teeth 23 are moved such that their tips 24 impact the sheet 12 with at least one force component normal or perpendicular to the free ends of the sheets as the tips move past the sheet support 19a.
It has now been found that the clearance between the tips 24 and the edge of the sheet support 19a should be maintained within a range of from about 0.023 in. to about 0.050 in. Preferably, this clearance is from about 0.027 in. to about 0.033 in. and most preferably about 0.028 in. The gap range below about 0.035 is especially desirable with dry lap feed rates of from about 30 - 100 fpm where with this gap distance range there is essentially no scorching. With larger gap sizes there is scorching with these drylap feed rates unless auxilliary cooling means, e.g., a water spray, are provided; and with gaps smaller than about 0.023 in. the disintegration quality is much poorer. With higher feed rates gap sizes closer to 0.050 in. can be used since the short residence time in the heat generation zone will minimize scorching, but above 0.050, even with high feed rates, disintegration quality is significantly poorer. This gap size appears to be independent of the drylap, etc., which is used insofar as scorching is concerned, but good disintegration is dependent on the thickness of the drylap. The thicker the drylap, the larger the gap necessary for good disintegration.
The impact on the free end of the sheet material is preferably controlled by turning the rotor such that the impact velocity of the tips 24 is at least about 6,000 feet per minute, although an impact speed of at least about 12,000 feet per minute is preferred. About 15,500 feet per minute has been found to be a most desirable impact velocity. Velocities in excess of about 30,000 feet per minute are not practical with presently available materials.
The individual disintegrated fibers which have been disengaged from the sheet 12 are removed from the impact zone whereupon they are dispersed and discharged from the casing 16 by air flow and/or the velocity imparted to the fibers by the teeth 23. The air flow is generated, at least in part, by rotation of the rotor, although it can be supplemented significantly by forced air flow into the casing from the inlet 21. The individual fibers are removed at the discharge outlet 20 from where they can be conducted to a suitable collecting device.
The practice of the present process and apparatus results in the production of individual fibers in essentially the same size as they are derived originally from the pulping process prior to the manufacture of the fibrous sheet material being disintegrated. Such individual fibers may typically be somewhat contorted and flattened cylinders of about 10-15 microns diameter and about 2,500 microns in length.
The preferred design of the tip 25 of the impacting elements 22 is set forth in the copending application of Kenneth B. Buell referred to hereinbefore.
While the present illustration of the invention describes the feeding of one sheet into the disintegrator, it will be understood, of course, that the invention can be practiced with the infeeding of two sheets or three or more sheets. The only structural changes that would be needed under such varying circumstances are in the number of pairs of infeed rolls and the provision of corresponding openings in the disintegrator casing for receiving the sheet material.
While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention and it is intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.