US2072686A - Composition of matter and method of making the same - Google Patents

Description

Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE COMPOSITION OF MATTER AND METHOD OF MAKING THE SAME,

No Drawing. Application December 16, 1935, Serial No. 54,714

10 Claims.

This invention relates to fibrous compositions which, as prepared, are in plastic condition and become hard on setting, and is concerned more particularly with a novel composition of the type described containing fibrous material and a bituminous binder which diiiers from, and is superior to, similar prior compositions in its physical characteristics. The new material has a low thermal-conductivity and a low susceptibility to temperature changes and is non-absorbent and fire-resistant. It can be made rigid without being brittle, so that it can be nailed and cut or sawn without difliculty, and it is of low specific weight and great durability. Moreover, it can be produced at low cost, and for these several reasons, it is applicable to the manufacture of numerous articles, such as roofing elements, conduits, battery boxes, and various others.

The improved qualities of the new composition flow from the unusual characteristics of the fibrous constituent, the individual fibres of which are of uncommon length and have an extraordinary amount of fibrillae thereon. These characteristics of the fibres are the result of a novel method employed, in the manufacture of the new composition, for reducing the fibrous substance and mingling the fibres thereof with the binding material. This new method makes possible the production of the new composition in plastic form without any considerable preliminarytreatment of the materials employed and, in particular, from waste fibrous substances. The invention, accordingly, comprehends both the new composition and the new method by which that composition may be made most expeditiously and in the best form.

The composition of the invention consists primarily of fibres which are matted and interlaced together and are coated, impregnated, and bound together by a suitable bituminous binder, which is preferably asphalt of a melt point selected in accordance with the use to which the composition is to be put. The proportions of the fibrous material and binder employed in making the composition depend upon the characteristics which the composition is to have, and in some instances, where the nature of the fibrous material employed requires it for best results, or where a final product of special characteristics is desired, additional substances such as other binding materials, neutralizing agents, etc. may also be employed.

The fibrous constituents of the new composition may be derived from various substanceshaving a fibrous structure with individual fibres of substantial length, such for example as wood, bagasse,

vegetable stalks, etc., and the material used is preferably one which has not beensubjected to a defibering operation by the use, for example, of chemicals or steam, prior to its use in the manufacture of the new product. Wood, and in particular, waste wood in the form of small pieces or chips, is therefore preferred, both because the fibres thereof are relatively long and in their natural state, and because of its low cost.

In producing the new composition in accordance with the method of the invention, a quantity of a fibrous substance such as wood in the form of chips or a smaller size, together with a relatively small amount of water, is fed under pressure to an internal mixer. The mixer is first used to effect the reduction of the wood to a coarsely fibrous condition, that action being aided by the frictional heat developed within the mixing chamber, which acts in conjunction with the water present to soften the fibrous mass and break down the substances which bind the fibres together. The amount of water employed in the initial reducing operation should be as small as is practicable, since an excessive amount interferes'with the final reduction which is carried on in the presence of the binding agent. Preferably, the weight of the water fed into the mixer with the wood is less than half that of the wood, and a part of this water is driven off during the mixing op erations,

The internal mixer which I prefer to use for the purpose is one which contains one or more rotating members operating to subject the mass to a smearing action against the walls of the mixing chamber, and I have found that the mixer known commercially as the Banbury mixer is admirably adapted for the purpose. The preliminary reduction of the fibrous material to coarsely fibrous condition can be effected in a short time in such a mixer, and ordinarily, only the fibrous material and the water need be present in the mixing chamber. However, with some fibrous substances, such as resinous wood, the reducing operation is facilitated by the addition of a small amount of lime or other sim ilar alkaline materials which assist in breaking down the substances binding the fibres together. The alkaline material employed, such as lime, also acts upon the constituents of the lightin in the wood to form compounds insoluble in water which act as emulsifying agents in the final reducing operation carried on when the binding material has been added to the fibrous material.

ually fed into the mixing .chamber,. either in fluent form or as a solid, the amount so lntro-- duced being about equal in weight to that of the fibrous material. The mixing then continues until the coarse fibrous material is reduced substantially to single fibre units. During such reduction, the action of the mixer causes the water and asphalt to combine to form a water-inasphalt emulsion, the emulsification being promoted by the lignin, resins, etc., in the wood, and by the water-insoluble compounds produced when polyvalent alkaline material, such as lime, has been added. The production" of the emulsion referred to is thus not only the result of the useof the particular mixer described which operates with a smearing action, but also of the action of the substances naturally present in the wood. Mixing together water, asphalt, and fibrous substances such as paper, from which the natural compounds, such as lignin, resins, etc. have been removed, in an ordinary mixer does not result in the formationof such an emulsion, and the defibering is not as effective and does not produce fibres of the same sort as those resulting from the action of such an emulsion upon a natural fibrous substance, such as wood.

The water-in-asphalt emulsion, produced as above described, contains a relatively small amount of water derived at least in part from the water on the surfaces of the fibres. This emulsion, which is of great tenacity and develops unusually high hydraulic shear, accordingly, wets the fibres, and the mechanical action of the mixer with its smearing effect assisted by the hydraulic shear applied to the fibres by the emulsion causes the fibre bundles to be torn apart. tially single fibre condition with the individual fibres carrying unusually large amounts of fibrillae, and these fibres are thoroughly distributed through the emulsion and wet thereby.

As an example of the production of one form of the new composition, the following may be given: About 175 pounds of wood in the form of chips having a size of about 1" x 7;" x 54;" is fed into a Banbury mixer with about 10 gallons of water, and when lime is used, it is added at this time and in the proportions of about 2 pounds of lime to about pounds of wood. The charge is fed to the mixing chamber and is conditioned therein under pressure of an airoperated ram, and pressure is maintained in the mixing chamber throughout the operation of the machine so that although the'temperature within the chamber may rise to about 220 F., the amount of water driven ofi may be controlled. As the mixer operates, the rotating members thoroughly mix the charge, and at the same time, force it against and along the inner walls of the mixing chamber with a smearing action. Operation of the mixer, under the conditions described, results in a rapid reduction of the wood to a coarsely fibrous condition, and the fibrous material so produced is heated and softened.

. At the same time, the lime reacts with the lignin in the wood to form compounds insoluble in water, these compounds promoting the formation of the water-in-asphalt emulsion, previously referred to.

After the desired reduction has taken place, the binding material is added, and for the charge of wood referred to, an equivalent weight, that is, about pounds, of the binding material is slowly added. The material employed for that purpose may be an oxidized asphalt, such as one The wood is thus reduced to substanhaving a melt point of 220 to 235 C. The amount of asphalt introduced into themixture at this stage of the operation is somewhat critical, and it should not exceed the weight of the fibrous material in the charge to any substantial extent, since an excess of the binding material, is found to reduce the efiiciency of the mixer and the effectiveness of the hydraulic shear applied through the binding material.

Upon the addition of the asphalt,the emulsion of water in asphalt is formed and the hydraulic shear effect previously mentioned is obtained,

resulting in the production of individual fibres,

with large amounts of fibrillae. Since the unusual characteristics of the final product are to a considerable extent caused by the large amount of fibrillae on the fibres, it is important that the final reduction of the fibrous material be carried on in the presence and by the aid of the emulsion mentioned. It is therefore important that water be present in the mixing chamber during the final reduction, so that such an emulsion may result, but the amount of water must be kept as low as possible in order that the emulsion may be tenacious and the high hydraulic shear may be developed. Accordingly, if too great an amount of water is introduced into the mixing chamber during the initial reduction, the reducing operations will have to be carried on for a longer time so that the excess water may be driven off and the desired tenacious emulsion is obtained.

Upon completion of the final mixing and reducing operation, the resulting mass consists of soft, moist fibres intimately mixed with, uniform- 1y distributed through, and wet by the water-inasphalt emulsion, and this mass may be considered the basic product which can then be converted into other products of varying characteristics by admixture therewith of further quantities of binding material and other substances. For some purposes, the basic product may be used without such admixture, but ordinarily, a final product is obtained by introducing an additional relatively smaller quantity of binding material into the mixing chamber and thoroughly mingling it with the mass present therein.

In the basic product, the fibres are moist, soft, and pliable, and the asphalt is in emulsion form sothat the mass is plastic and may be readily shaped by extrusion, pressing, or rolling. When the moisture evaporates, the emulsion breaks down, the asphalt sets, and the fibres lose their pliability and softness and become stiff. Since the fibres have been shaped while soft and moist, they retain the shape into which they have been formed without initial strain. The contraction of the fibres during such drying strengthens the interlacing of the fibrillae, and this increases the rigidity of the final product and eliminates any tendency toward plastic flow. The elimination of water from the emulsion and the fibres also insures that the fibres will be thoroughly coated with and bound together by the binder.

to use only wood, asphalt, and water as the components of the mixer feed, in most cases, the addition of a polyvalent alkaline material such as lime, in a relatively small amount such as 2 pounds per 100 pounds of charge, is usually desirable, since it reacts with resinous substances in the wood to produce water insoluble compounds, sometimes referred to as insoluble soaps which aid in the emulsification of the water in the binder, improve the Waterproof qualities of the finished product, and lessen its tendency to soften under heat. The formation of such soaps is at the expense of those materials in the wood which bind the fibres together, and the breaking down of those binding substances by means of the alkaline material referred to facilitates the defibering of the wood and results in the production of a softer fibre which in turn makes possible a better interlacing of fibres throughout the fibrous structure.

While I have given a specific example of the new composition produced by the use of approximately equal amounts of fibrous material and the binder, it is to be understood that such proportions may be departed from to a considerable extent, as for example, the binding material may vary from 50% to 70% by weight of the total, and the fibrous material may vary from to 50% by weight. When the amount of binding material used exceeds the quantity of fibrous materiaLthe excess is-added, as described, after the final reduction of the fibrous material in the presence of the binding material. The quantity of water employed will also vary, but will ordinarily approximate 50% by weight of the fibrous material. As the purpose of the water is both to facilitate the reduction of the fibrous material, and also to combine with the binding material to form the emulsion, the quantity of water used will depend to some extent on the moisture content of the fibrous material, and more or less will be introduced as required to efiect the proper reduction and to obtain the desired tenacious emulsion. l

In the new composition, the fibres are substantially homogeneously distributed through the binder, and while the composition is plastic so long as the emulsified condition of the binder persists, it sets and hardens upon elimination of the water, acquires strength and rigidity, and becomes non-liquefiable by heat. Also, by reason of the peculiar characteristics of the fibres, the composition does not stretch under its own weight to any substantial extent when subjected to a temperature above that of the melt point of the binding agent present in it.

The size' of the individual fibres in the new composition and the characteristics of the fibres depend to some extent on the nature of the fibrous substances employed, but in all instances, the individual fibres have an extraordinary number of fibrillae and the fibre length is relatively high, ranging in the case of wood, from 1 5" to Such fibres are noticeably different both in length and in the amount of fibrillae thereon from fibres made from the same fibrous substances but by other methods as, for example, by boiling with chemicals, or by steam, and these differences are particularly noticeable when the fibres produced by the method of this invention are compared under the microscope with fibres derived from the same type of Wood but by other defibering operations.

I claim:

1. A composition of matter comprising a bituminous binding medium, natural wood fibres distributed therethrough substantially uniformly and homogeneously in the form substantially of relatively long individual fibres having a large amount of fibrillae thereon, said fibres being interlaced and coated and bound together by said binding medium, and a polyvalent alkaline sub stance present, at least in part, in" combination with the lignin derived from said fibres and forming therewith water-insoluble compounds.

2. A composition of matter comprising a bituminous binding medium, water, and a stabilizing substance combined to form a stabilized emulsion in which the binding medium is in the continuous phase and the water is in the disperse phase, and fibrous material is distributed substantially uniformly and homogeneously through said emulsion in the form substantially of individual fibres having fibrillae thereon in large amount, said fibres being interlaced and Wet by and bound together by said binding medium.

3. A composition of matter comprising asphalt, natural wood fibres distributed therethrough substantially uniformly and homogeneously, lignin derived from said Wood, and water, said fibres being present in the form substantially of individual fibres having fibrillae thereon in large amount, said individual fibres being interlaced and wet by and bound together by said asphalt, said water and asphalt being present in combination in the form of an emulsion in which the asphalt is present in the continuous phase and the Water is present in the disperse phase.

4. A composition of matter which comprises asphalt and water combined to form a water-inasphalt emulsion, natural wood disintegrated to the form substantially of individual fibres, distributed substantially uniformly and homogeneously through said emulsion, said fibres having a large amount of fibrillae thereon and being interlaced and coated and bound together by said emulsion, and a relatively small quantity of a polyvalent alkaline substance combined at least in part with the lignin of the wood.

5. A method of making a composition of matter which comprises, disintegrating wood in the form of small pieces by subjecting it in the presence of water; to a mixing and smearing action carried on in an internal mixer, adding a relatively small quantity of a polyvalent alkaline substance to the mass under treatment, said substance being a stabilizer of: emulsions of water and bituminous binding media in which emulsions the water is in the internal phase, adding a bituminous binding medium to the reduced mass, and continuing the disintegration of the Wood in the presence of the bituminous binding medium until the binding medium and water have formed an emulsion in which the water is present in the internal phase and the fibrous material is substantially completely reduced. and substantially uniformly and homogeneously distributed through said emulsion.

6. A composition of matter comprising substantially individual fibres derived from the disintegration of natural wood, water, a bituminous binding medium, said water and binding medium being present in the'form of an emulsion in which the water is in the internal phase, and a relatively small quantity of an agent stabilizing such emulsions, said agent being derived at least in part from said wood, said fibres being moist and distributed substantially uniformly and homogeneously through said emulsion and superficially wet thereby.

7. A composition of matter comprising substantially individual fibres derived from the disintegration of natural wood, the lignin from said wood, a relatively small quantity of lime at least in part combined with said lignin, water, and a bituminous binding medium, the said water and binding medium being present in the form of an emulsion in which the water is in the internal phase, said fibres being moist internally and being substantially uniformly and homogeneously distributed through said emulsion and superficially wet thereby.

8. A method of making a composition of matter which comprises subjecting natural wood in the form of small pieces, water, a relatively small quantity of lime, and a quantity of asphalt approximately equal to the weight of the wood to mechanical mixing to cause the asphalt and water to form an emulsion in which the water is present in the internal phase, the formation of said emulsion being promoted by the lime and the lignin derived from said wood, and continuing the mixing action to complete the disintegra tion of said wood to the form substantially of individual fibres, and to distribute said fibres substantially uniformly and homogeneously through said emulsion, said fibres being superficially Wet by said emulsion.

9. A method of making a composition of matter comprising subjecting a woody substance, in the presence of water and a polyvalent alkaline material, to a mixing and smearing action to effeet a substantial reduction of the fibrous material, said alkaline material combining chemically with the lignin from said substance to form 'a water insoluble compound, adding a. bituminous binding medium and continuing the mechanical action to produce, under the influence of the said compound, an emulsion of the binding medium and water with the water in the internal phase, and to complete the disintegration of said woody substance to the form substantially of individual fibres distributed substantially uniformly and homogeneously through said emulsion, the emulsifi cation removing thefree water from the surface of the fibres and thereby enabling the emulsion to thoroughly coat the fibres.

10. A method of making a composition of matter which comprises mechanically disintegrating a fibrous material in the presence of water, adding a bituminous binding medium and a relatively small quantity of an agent capable of stabilizing emulsions of said binding medium and water in which emulsions the binding medium is in the continuous phase, continuing the mechanical treatment of the mass to convert the binding medium and water into an emulsion in which the binding medium is in the continuous phase and the water is in the disperse phase, and carrying on the disintegration of the fibrous material in the presence of the emulsion until the fibrous substance is substantially in the form of individual fibres distributed through said emulsion and superficially wet thereby.

THOMAS ROBINSON.