US1993148A - Method of defibering lignocellulose material - Google Patents

Description

Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE" Ma'mon or DEFIBEBING LIGNO- CELLULOSE MATERIAL.

Judson A. De Oew, Mount Vernon, N. I.

No Drawing. Application March 29, 1932, Serial No. 601,883

2 Claims.

5 various methods have been devised for grinding other ligno-cellulose materials than wood into a fibrous pulp. I have developed methods of doing, this in machines of the Jordan type by operating the machine on a partially disintegrated fibre at high consistency by using either vacuum at the outlet or pressure at the'inlet to accelerate the flow of stock and obtain the greatest output at the highest density.

In the operation of these refiningprocesses I have discovered a means of improving these processes and operating at still higher density by a preliminary treatment of the fibrous mate rial to reduce the viscosity of the mass before the refining action is allowed to take place. The treatment of a ligno-cellulose product is different from/that which would be used in the refining or hydration of a cellulose material. In treating cellulose it is desirable to keep the product cold as a means of accelerating the absorption of water. In the treatment of a ligno-cellulose like wood or any other lignified fibre, the absorption of water is accelerated by heat-also the binding action of the individual fibres to each other is reduced and the viscosity of the pulp mass is lowered.

I have discovered that in a partially defibered ligno-cellulose material like wood pulp, if heated rapidly in the presence of water to relatively high temperature, preferably above the boiling point, a permanent change takes place in the relative strength of adhesion of the fibres to each other and the resistance of individual fibers to breakage so that they are more easily separated without breaking by a mechanical treatment. This lowering of the binding action is carried further if the fibrous material undergoes a kneading or mixing action during the heat treatment. in order to carry out this process efiicientiy the material must be disintegrated into coarse fibre bundles but not into individual fibres. It is then possible to provide a quick and uniform heat treatment to bring about the physical change in the rigidity of the fibers without decomposition or discolorization of the lignocellulose.

In treating the material all excess water is removed and it is then treated in a mixing or kneading device where it can be steamed or heated to the required extent. The equipment used may be any mechanical kneading machine (01. sz-zc;

or a mixing tank with an agitator. The temperature and time factors are controlled so that the material becomes permanently softened with the minimum of chemical change and the formation of little or no coloring matter. Attempts have been made to accomplish this resultby boiling wood blocks or chips before the grinding treatment but in this case the heating action is not uniform or complete and coloring matter is formed from local decomposition of material that is heated too long. It is necessary therefore that the ligno-cellulose must be partially defibered or broken up into fibre groups before this treatment is applied. As a means of economizing in the amount of heat required, I prefer to steam the material ratherthan boil it, removing the steam condensate during the operation so that any slight amount of coloring matter formed will not be absorbed into the fibres. As an example of the operation of this process, a treatment of ground wood screenings would be carried out as follows: I I

It may be treated either in a pulping machine of the ordinary'type which has a kneading action but no grinding action, and steamed during the treatment. It may be mixed in a tank with slow moving agitators and steam applied or it may be steamed in a, revolving digestor and treated by a batch process. I In any of these treatments there is little or no defibering action but the viscosity of the material is lowered and the character of the ligno-cellulose changed, and after this treatment it is passed through a refiner where by attrition or grinding action the fibres are pulled apart and not cut into fragments as would happen if the ligno-cellulose were treated while the fibres were in their original hardened rigid condition. After the material -is partially defibered by the refining machine, it is passed through or over a screen to remove the individual fibres and the rejected fibre bundles are again dewatered and brought back for further treatment.

In the processes already known to the industry where such materials are being refined, the product is always treated cold or if any heat is applied it is done within the refining machine. If, however, the refining action and the heat treatment are applied simultaneously, only a slight advantage is obtained because a definite time factor is required in the heat treatment and this treatment must precede the refining action. A preliminary heating and kneading such as described in this specification where no chemical disintegration of the fibres takes place before the/ refining action, is a new step in pulp refining.

With a lowered viscosity resulting from this treatment, I am able to pass the material through the refiner at consistencies of 10% or over, which is a density unheard of in refining operations. By lowered viscosity is meant increasing the flowability of the pulp without dilution, or at the same density.

The' refining machine I prefer to use is one of the Jordan type although there are numerous types of refiners that might beu'sed.

The results of this process are wood fibres having a structure closely resembling the original fibres, with more pliability and strength than any wood fibremade heretofore without chemical treatment.

It is understood that the-present disclosureis for the purpose of illustration only, and'that the invention is not limited thereto. To those skilled in the art, many modifications of the invention "will be readily apparent, and it will also be obvious may be used without other parts of the device may be used without other parts thereof, many such combinations of the parts readily suggesting themselves. Therefore, it should be, and is to be distinctly understood that for a definition of the limitations'of the invention, reference must be had to the appended claims.

What is claimed is,

1. In the treating and defibering of ligno-cellulose material, the method which comprises employing the material to be treated in the form of fiber-bundles typified by wood screenings from which excess water has: been substantially removed, applying steam to the material while ef-' fecting a kneading or slow agitative action applied to the material under conditions for permitting the steam to reach all portions of the material undergoing treatment and until the material becomes permanently softened; said steaming operation being carried out under conditions whereby there is little or no defibrating action, until the viscosity of the material is lowered so that the fiowability of, the mass of material is increased, and until the character of the ligno-cellulose is sufilciently changed so that the individual fibers thereof may be more readily separated, the steam operation also being accompanied by the removing from the mass of a substantial portion of the steam condensed during the steaming operation so that any slight amount of coloring matter formed will not be absorbed into the fibers, and after the steaming operation passing the softened fiber bundlesto and through a refining operation -during which attrition or grinding action is car-- ried out on the fiber bundles whereby the fibers of eachv particular bundle are pulled apart without being'cut into fragments as would be the case if the ligno-cellulose were subject to attrition or grinding while the fiber bundles were in their original hardened or relatively rigid condition.

2. In the treating and defibering of ligno-cellulose material, the method which comprises employing the material to be treated in the form of fiber bundles typified by wood screenings from which excess water is substantially eliminated, applying steam to the material while under the efiect of kneading or slow agitation and thus under conditions for the steam to reach the several fiber bundles undergoing treatment and until the material constituting said fiber bundles becomes permanently softened, the steaming operation being carried out under conditions whereby there is little or no defibrating action, until the viscosity of the material is lowered so that the fiowability thereof is increased, and until the character of the ligno-cellulose is sufficiently changed so that the individual fibers may be more readily separated, there also being a removing of the steam condensed in the mass during the steaming operation thereof so that any slight amount of coloring matter formed will not be absorbed into and by the fibers, after the steaming operation passing the softened bundles to and through a refining operation during which attrition or grinding action is carried out on the fiber bundles whereby the individual fibers are pulled apart without being cut into fragments, and screening the treated product or resulting mass to separate out individual fibers that are recovered along one path and to obtain rejected fiber bundles that are de-watered and returned along another path for, repeated treatment.

JUDSON A. Dr: CEW.