US 1859414 A
Description (OCR text may contain errors)
@atented May 24, 1932 UNITED STATES PATENT OFFICE I EARL P. STEVENSON, OF NEWTON, AND HARRY A. BURON, 013 BOSTON, MASSACHUSETTS, ASSIGNORS TO THE RICHARDSON COMPANY, OF LOCKLAND, OHIO, A CORPORATION OF OHIO No Drawing. Application filed May 31,
Our invention relates to the preparation of pulps containing desired proportions of water insoluble binder substances and which can be felted into sheets upon conventional types of paper board and felt making machinery. Among the binder substances of the type noted are to be enumerated coal tars, asphalts, bitumens, and in general heat plastic materials. The fibrous ingredients may be any of to those which, in pulp form, are suitable for paper making. a
It is an object of our invention to provide a modification of the premix process described in our co-pending application for patcut, Serial No. 314,551, filed October 23, 1928,
to which reference is hereby made for a description of the ultimate product which it is desired to form. This product with respect to a particular type of binder, can be described as a bituminous, fibrous stock in aqueous suspension, wherein the asphalt or other bitumen is uniformly dispersed in the form of discrete particles having in general a globular or spherical form. This result is secured without the use of any emulsifying agent, such as colloidal clay. The discrete particles of binder substance are not rendered non-adhesive by a surface coating of an adsorbed emulsifying agent.
The present modification is primarily concerned with the mechanics of our premixing process above referred to, and particularly with the first step. in which fibers wet with water are dispersed in a gummy or viscous binder, of which asphalt is one example. In carrying out this process it is essential to keep the fibers moistened with water during the mastication with binder substance, and thereby to prevent a complete coating of the fibers with said binder substance. It is a characteristic of such fibrous compositions that they can be dispersed in water.
The present improvement is specifically addressed to the handling of waste fibrousmaterials such as rags, which can not be used directly in the preferred procedure set forth in ouroriginal application, but require for adaptation thereto, a pre-treatment such as cutting, and fibration in a'beater. For such 60 products as asphalt roofing (particularly PROCESS OF FORMING PULPS 1929. Serial No. 361606.
other ends which do not concern alone the use of a rag stock for the fiber base. One of these objects is to shorten materially the time previously required for pre-mixing a heat-fusible binder and a fibrous material to secure an association capable of ready reduction to an aqueous pulp suitable for fabrication into sheets on a paper machine.
Another object is to improve the quality of x the pulp so made, by securing a more uniform distribution of binder, with particular reference to the size of particles. objects are to secure a more complete disintegration of the fibrous material used into its elementary fibers,-in order thereby to min1- mize the time necessary for refining the ultimate pulp in either the beater or the jordan or both, to reduce the cost of premixing especially in the item of power, and to provide a semi-automatic operation.
Another advantage is to extend the practical application of our premixing process to heat fusible binders which are so viscous at temperatures readily obtainablein an open mixer and in the presence of water as to be practically unworkable therein. Examples of such binders are asphalts having a ball and ring softening point of approximately 200 F. and higher. Shellac is another such material.
In place of the open Werner-Pfleiderer mixer previously described as the preferred apparatus for premixing, a steam jacketed closed mixer fitted with a mechanically 0perated ram serving to close the top of the mixer and to force the charge positively into working contact with the mixing mechanism, is now recommended- Such an apparatus is examplified by that described in the Banbury United States Patent No. 1,200,070 dated October 3, 1916.
This type of apparatus makes it possible to eflectively use a high input power, and
Yet other 4 thereby to achieve a directly therein.
I Generally it will structures such as heavy kraft paper,
is a more or less adhesive,
,rial may "beater without resorting to this intermediate the action is largely -material which is passing 'binder is not carried to 7 material shortening in the premixing time. Where thirty minutes are generally required'in the open type of mixer, two to three minutes are here sufli cient.
We have also discovered, when using this type of mixer, that rags can be handled In a typical operation wet rags can be directly charged into the beater, followed by the addition of the binder, which need not be previously liquefied. A binder such as asphalt when in a viscous state, assists directly in the disintegration of the rags to a non-structural mass in which the fibers are liberated. In like manner strong fibrous I asphalt saturated and coated rag felt, partially digested wood such as sulfite tailings and the like can be utilized to advantage and with over-all economy. In some cases it may be desirable to introduce the binder before the fibrous material, though in general we prefer to reverse this procedure. The material delivered from the above step gummy mass of intimately mixed binder and fibers which latter, while appearing to be completely masticated and coated by the binder, are yet in acondition for the ready assimilation of water. The step of breaking down this mass into a watery pulp may be carried on in the same mixer; but we prefer to transfer the material at this stage to another mixer.- A Werner-Pfleiderer is well adapted to the next operation.
The amount of water added in the second step is immaterial as to the upper limit."
be found desirable to employ heat at this stage, thoughwith certain types of asphalts or other binders, this may be unnecessary. In some instances the mate- -be added directlyto a paper mill stage 'of'pulping. Otherwise the procedure at this point is that more fully described in the co-pending application hereinabove referred to.
The advanta es' which are inherent in this modification 0 our premix process are attributable to mixing under a mechanically imposed pressure. In the open type of mixer restricted to that material which at any 'ven time is directly in contact with the mixing blades, and to that directly between the blades and the bottom of the mixer. Power is inefliciently used in tumbling the mass around, and the filming out o the a desired degree. It is to'thisbetter distribution of binderthat we attribute the greater uniformity of the and the more intimate asso- .1
ciation of binder and fiber which we attain-v The foregoing process is'ideally adapted the preparation of bituminous pulps.
ultimate pulp softening point above 190 Various types of as halts have been successfullyhandled, an pulps made therewith show under the microscope spherical particles of asphalt ranging in diameter.between'.045 and .002 millimeters, with the average between .015 and .006 millimeters. A few of the particles may be adherent to the fibers; but the majority appear to exist as discrete particles. If the asphalt used is one that is normally adhesive, a tendency toward agglomeration may be apparent. Consequently we prefer to use asphalts which are at least semi-solid at' ordinary or normal temperatures; We have asphalts having a penetration as high as 30 at 771005, but we prefer those slightly harder for reasons not wholly concerned with the premixing operation.
The intense mechanical operation usually results in a considerable heating of the mixer contents which will not be found disadvan-' tageous'. In the handling of certain binders it is not, therefore, necessary to apply any external heat to the mixer as through the steam jacket provided for this pur ose,the internally generated-heat being su cient to cause the binder to flow under the imposed pressure. In other cases it may be found advantageous to both heat the mixer and add the binder in a molten'state. This improved process of premixing is not necessarily limited with respect to consistency and temperature of binder during mixing.
The resulting pulp will be utilizable in any regular paper making operation, and in the final product the binder, if it is plasticizable by heat, will be uniformly dispersed with relation to the final dried product.
Sheets containing in excess of 75% of asphalt can be made more readily by this process.
Having thus described our invention, we claim as new and desire to secure by Letters Patent, isz
.1. A process of preparing a bituminous pulp, which consists in mechanically mixing wet fibrous material composed of bitumen and fiber in a closed compartment, and under pressure, and thereafter transferring said material to another mixer where it is reduced to a pulp through hydration with.water assisted by a mechanical agency.
2. A process of preparing a fibrous composition capable of reduction to a pulp by mechanical agency, which consists-in subJecting, under pressure, a mass of wet fibrous material and a heatplasticizable binder to the kneading action of mixing lades revolving in a closed compartment, substantially as described 3. A process of preparing a fibrous'composition capa le of being .fe ted on a screen, which comprises subjecting under heat and pressure a mass of wet'cellulose fibers and a heat-fusible binder having a ball and ring what F., to the masti- 13o p .a closed compartment substantially as described, while maintaining the fibers through out the mixingcycle in a moistened condition,
and thereafter reducing the resulting Wet fibrous mass to a pulp by mechanical dispersion in water. y v
4. A process of preparing a fibrous composition capable" of being felted on a screen, which comprises-subjecting under heat and pressure a mass of wet cellulose fibers and a bitumen having a ball and ring softening point above F. to the masticating action of mixing blades revolving in a closed compartme'nt substantially as described, while maintaining the fibers throughout the mixin g cycle in a moistened condition, and thereafter reducing the resulting wet fibrous mass to a pulp by mechanical dispersion in water.
5. A process of preparing a fibrous composition which comprises subjecting under pressure, fibrous material and water to the mechanical action of mixing bladesrevolving in a closed compartment, until at least a semipulped mass is obtained adding a binder, and continuing said action until a fibrous mass is obtained capable of reduction to a pulp by a mechanical agency, on the addition thereto of sufiicient water.
6. The process of preparing a bituminous pulp from rags which consists in first adding wet rags to a closed mixer as described, adding thereto a bitumen, continuing the mixing until a substantially homogeneous mass is obtained, thereafter removing the resulting mass to another mixer, addin water and re-v ducing said mass to the condition of a pulp suitable for handling in a beater.
7. That process of producing a pulp which comprises simultaneously liberating the fibers of wetted rag stock and distributing a bitumen therethrough in minute uncoated particles, by mixing rags and bitumen in the presence of water in a closed mixer under pressure.
EARL P. STEVENSON. HARRY A. BURON.