US2345009A - Compressed composition and products and the like - Google Patents

Description

[.Adllllllu @15- COMMONS CROSS REFERENCE COATlNG R PLAS'HC 7 Patented Mar.28,1944 2,345,009

COMPRESSED COMPOSITION AND PRODUCTS AND THE LIKE Charles H. Schuh, Ridgewood, N.

mesne assignments, to Carbide and Y., assignor, by Carbon Chemicals Corporation, New York, N. Y., a corporation of New York No Drawing. Original application October 25,

1935, Serial No.

46,742. Divided and this application December 15, 1937, Serial No. 179,867

6 Claims.

This invention relates to compressed products and more particularly to light weight non-metallic products, and is a division of my copending application Serial No. 46,742, filed October 25, 1935, now Patent No. 2,156,309, issued May 1939.

Prior rigid thermal insulating materials may be divided into three classes, to wit: (1) the porous type, such as blown molten limestone commercially known as Rock cork, which is characterized by the presence of large visible voids, (2) the various fiber boards composed of large coarse wood, cane, and other fiber or cellulosic material matted and pressed together with or without binder, and (3) corkboard, either in its natural form or made from granulated cork baked under pressure with or without binder. Natural cork, being the bark of a tree, is obtained in sheets of limited thickness and of nonuniform size and shape and is an expensive product. It is therefore not used in the natural state to any extent for insulating board. Instead, the trimmings from various trades employing natural cork and as may be otherwise obtained are granulated and this granulated cork is formed into boards usually one foot by three feet by two inches in thickness. It is to be noted that the granulated cork employed for this purpose consists largely of granules of considerable size, much of it being coarser than ten mesh. These granules may be formed into corkboard by mixing with an asphalt binder and pressing into shape. The use of a binder, however, greatly decreases the insulating efliciency and also increases the weight considerably. The discovery that these granules can be united into a board by simply baking under pressure was a very important invention commercially and practically all corkboard has been made by this process. The product, however, has been expensive.

In preparing cork for various uses in the trade. V

the exterior rough surface of the bark is ground 05 and in so doing a fine, reddish brown powder i obtained which naturally contains asmall amount of impurities such as sand, etc. This is practically a waste produce and can be purchased today at a very low price per ton. Heretofore. there has been no successful attempt to produce an insulating board from any such material as this. The general problem of producing a board, and particularly one of light weight, from a fine powdered material presents various serious obstacles. Although many attempts have been made to improve these materials, particularly those of group (3) ,none, as far as I am aware,has

been wholly satisfactory, practical and successful when carried into practice on an industrial scale.

I have discovered that it is possible to produce a desirable board or sheet of material from a fine powdered material without the use of any so-called binder material or with the use of such a small percentage of same as to make its pres ence entirely unobjectionable from the standpoint of increase in density, increase in thermal conductivity, and even increase in cost. T0 attain this object, I employ a process which is based upon a fundamentally new concept in the procedure for the production of this type of product.

The object of the invention is to obtain a nonmetallic material of very light weight which has valuable thermal and acoustical insulating properties.

A further object of the'invention is to obtain a highly efllcient insulating material of light weight and low cost.

It is also within the contemplation of the in-.- vention to obtain an efficient insulating material of light weight which has a fine uniform structure and is free from large visible voids and large coarse fiber such as occur in prior porous insulating materials and fiber board.

The invention likewise contemplates utilizing in the production of light weight products raw materials which are now practically waste prodnets and very low in cost.

Other objects will become apparent from the following description of preferred embodiments of the invention.

In carrying my invention into practice, I prefer to employ a very dilute solution or dispersion containing (1) a binding agent, such as, for example, a /z% latex or a /z% aqueous resinous dispersion, (2) a filter aid, and (3) what I call a medium of extension. The general procedure is to intimately mix these three fundamental components to form a dilute aqueous suspension, filter the same without disturbing the matrix as it is formed, then gradually subject the matrix to a predetermined pressure without breaking its continuous bonded structure, and finally dry the matrix. The operations are simple and easily carried into practice and are adaptable to large scale volume production resulting in low manufacturing cost,

By the expression medium of extension, as referred to hereinabove, I mean a substance which, when added to an aqueous dispersion of a powdered material, will produce a very large bulk of practically non-settling precipitated substance so that a slurry is obtained which, when subjected to filtration, will readily form a matrix of large volume maintaining the particles of powdered material in such relation to each other as to produce a characteristic orientation and physical structure. I have found that finely pulped fibrous material, such as finely pulped newspaper or wood pulp, in which the average individual fiber is less than approximately 0.08 of an inch in length, makes an excellent extension medium. The use of about to about of such a substance, together with about 75% to about 85% of the powdered material, if properly dispersed in an aqueous medium will, when subjected to filtration, begin to form a matrix at a remarkably low density of the dispersed material, in fact, values as low as 4 lbs. per cu. ft. have been obtained. Such a matrix is easily compressed and this makes possible a. wide range of densities in the finished product. The important thing, however, is to have the density before compression as low as possible.

I have found that a properly processed fibrous material as described hereinabove in connection with its use as a medium of extension, likewise acts as an excellent filter aid. This material therefore performs the dual function of acting as a filter aid and medium of extension.

It is to be observed that merely mixing the three basic components mentioned hereinabove, filtering, and drying does not necessarily produce the desired result. Several problems and difliculties arise which I have discovered can only be overcome by using these components within certain critical ranges of composition. For example, it has been found that if too large a percentage of medium of extension is employed, the shrinkage and warping during drying is excessive, which is a serious problem. On the other hand, too small a percentage results in a product too high in density. Then again, an inadequate percentage of filter aid or medium of extension acting as such, causes filtration difiiculties and makes it impossible to retain the matrix in its shape and form while pressure is applied. Moreover, the presence of small quantities of substances in aqueous solution, which may be advantageous for certain reasons, will often act as colloidal stabilizers and entirely prevent the filtration process from being carried out. Thus, the use of 3% sodium silicate or glue or other commonly used materials as binding agents when used herein will, in many cases, make filtration practically impossible to carry out. The use of the foregoing proportions (3% sodium silicate or glue or other stabilizing agent) is to be avoided whenever filtration diificulties are encountered.

It is also to be noted that the present invention embodies not only the establishment of certain critical ranges of composition, but moreover sets forth certain important factors of control and embodies a procedure whereby a desired result can be obtained and any such obstacles as mentioned hereinabove entirely avoided. This is of considerable practical importance because of the variety of products which it is posible to produce and the exactness with which it becomes possible to meet the requirements in any given product. For example, in standard corkboard used in refrigeration, high thermal efiiciency is extremely important but high tensile strength is not, whereas in insulating wallboard for building construction high tensile strength is required and the thermal efficiency is not so critically important. Furthermore, by appropriate compression of the matrix during processing, a comparatively high strength material may be obtained which might serve as a substitute for linoleum or even leather. The invention, therefore, does not contemplate simply the production of a corkboard substitute or a linoleum substitute, or a leather substitute, etc, but rather contemplates a product in the process of making which certain factors of control are set up and a general basic procedure followed, whereby the properties of the finished product are kept under control and can be varied at will to produce, for example, a high degree of flexibility, a rigid or even brittle product, a super light weight product, a medium weight product, high or low tensile strength, a high or low moisture absorption product, etc., and in each case the density of the product, comparatively speaking, is low due to the novel microcel structure of the material. Moreover, the microcel structure is preserved at all densities and unless the matrix has been greatly condensed the volume of nonvisible voids will be at least 40% of the total volume of the structure.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative examples will be given.

Example No. 1

To about 1000 pounds of a /2 latex dispersion, about 20 pounds of newspaper are added and subjected to high speed mechanical disintegration until the average individual fiber is about or less than approximately 0.08 inch in length. To this medium of extension, about 40 pounds of finely ground regranulated cork are added with high speed mixing. The mixture is run into molds which in their simplest form are rectangular boxes, the bottoms of which are filter screens of approximately 16 mesh. It is essential to fill the form quickly and agitate the mixture while still very dilute so as to obtain a uniform suspension in the mold and, once the matrix is formed, it must not be disturbed by further mixing. This latter point is important because in filling a form with a dilute aqueous mixture, as used herein, to the depth required, a considerable washing efl'ect is encountered, tending to disturb and wash out the matrix which is formed immediately adjacent to the filter screen during the filling process. If such local washing out is allowed to occur during filling, the slabs will have holes and regions of decreased thickness when finished, even though the molds are apparently absolutely evenly filled at the end of the filling operation. By noting the above precaution, an even and uniform slab can be made.

After the major portion of the liquid has filtered off, a cover made of 16 mesh screen and fitting accurately inside the mold, is placed on the material and a slight pressure is applied. It has been found that a pressure as little as about 2 to about 4 pounds per square inch is suflicient to produce the result required in this present case. The pressed slabs will still contain 400% to 600% aqueous liquid calculated on the dry weight of the material used. The slabs are then removed from the forms by inverting them onto another screen and are placed in a dryer. The filtrate is, of course recovered and used for subsequent batches. The dried material will have a density of approximately 7 to 9 pounds per cubic foot, which is lower than corkboard itself and a thermal conductivity of approximately 0.24. Those skilled in the art will readily understand how unit opera- IUD.

UUIYWUOI l lune,

hot medium of extension while it is vigorously tions of the above type may be conducted on a continuous scale.

In the above illustration, it is advisable to have the cork as finely powdered as practicable, certainly less than about ten mesh and preferably about 50 to about 200 mesh. This is contrary to prior methods of corkboard manufacture wherein large granules are used. The use of an extension medium as herein described in the manufacture of a corkboard is a novel feature of the process. The establishment of a critical range of composition, namely, about 20 to about 50% medium of extension, with the optimum value established at about 25%, is an important factor of control. The formation of a greatly extended matrix under filtration and its gradual compression without interrupting its continuous physical structure, is another important principle of the invention.

Example No. 2

To produce a building board, the procedure used in Example No. 1 is followed but different materials are used. Thus, about 1000 pounds of about 1 to about 3% sodium silicate solution, about 48 pounds of a medium of extension (dry weight), and about 62 pounds of finely powdered exterior portion of corkboard are used. These boards are usually thinner than for refrigeration use, say about to about 1", and a greater compression, say approximately 5 to 20 pounds per square inch is used. The finished material will have a density of approximately 12 to 20 pounds per cubic foot, and a thermal conductivity of approximately 0.29 to 0.35. The tensile strength is approximately 150 to 400 pounds per square inch. This makes an excellent low cost insulating building board. Moreover, the obvious advantage of using a cork base in an insulating board is extremely important from the point of view of the public.

Example No. 3

board. The boards are made still thinner, about of an inch for, say, sole leather substitute or flooring material, and a still higher compression is used, sufficient to reduce the aqueous content to about 100 to 150%. A strong, flexible, physically uniform structured material having a fine texture, free from visible voids, or cork granules, or visible fiber, is obtained. For certain purposes, hardening agents, such as sodium silicate, various resins, etc., may be added. Of course, in using latex, it may be compounded according to well known principles with the use of anti-oxidants, accelerators, etc.

I have found that the addition of a small percentage of dispersed wax to the medium of extension will entirely eliminate any capillary action in the finished product and will render it internally waterproof. For many products, this is extremely important. I have found that this wax may be satisfactorily incorporated by slowly pouring the melted wax into the'hot medium of extension under high speed agitation; for instance, an aqueous dispersion of the medium of extension may be raised to a temperature above the melting point of paraihn, say about 130 F. or more, and molten paraffin poured slowly into this Cal agitated as by a high speed mixer.

In waterproofing my new light weight products, I have made an important discovery. I have found that an extremely effective paraflin preparation can be made which is both very practical and very economical to prepare and to use in a form in which it is obtained. In making my paraflin preparation, I pour hot, melted paramn into boiling water containing a dispersing agent, preferably a small amount of soap and then subject the mixture to high speed mixing while making the addition, The agitation is continued for several minutes while the mixture is cooled and a thick white paste is obtained comprising dispersed particles of paraiiin and an aqueous vehicle containing a dispersing agent, preferably soap. Soluble soap stock can be used in an amount less than 10% of the weight of the paraffin. Water may be used in an amount from about to about of the weight of the paraflin. From a commercial point of view, it is preferred to use a cheap soluble soap stock such as rosin laundry soap stock and the like. This paraffin paste distributes itself in practically a dispersed form when mixed into a dilute aqueous mixture of the other ingredients even when cold. Only about 4% to about 6% of this paraffin paste is required to destroy all capillary action in my new light weight products and render them water repellent. It is also to be pointed out that various resinous materials, rosin, shellac, gums, and natural and synthetic resins, can likewise be made into a similar paste for use in these light weight products.

While in each of the foregoing examples, powdered cork is employed as a basic material, it is possible to substitute other powdered materials such as wood flour or the like in this general process and obtain new materials of practical commercial importance, all of which have a similar physical microcel structure, and a resultant comparatively low density. This new microcel structure is produced when and only when the number of particles of powdered material bears a certain relation to the volume of extension medium present. I have found a simple, practical empirical expression of this relation to be as follows: percent of extension medium (that is, the percent of the total dry weight of the composition which is extension medium) equals 900 divided by the density of the powdered material in pounds per cubic foot. Thus, if the density of the powdered material is 90 (as for certain rock flour), the percent of extension medium used should be 10%. Using wood flour having a density of 30 pounds per cubic foot, 30% extension medium should be used. For a mixture of various flours having a density of 60, 15% medium of extension should be used. Using the waste product cork flour herein referred to having a density of 25 pounds per cubic foot, 36% extension medium should be used. Naturally, however, the percentage of extension medium used may be varied over a small range before the desired structure will show signs of breaking down and sometimes it becomes necessary to shift somewhat away from the calculated percentage. Thus, in Example No. 3, 45% extension medium is used instead of 36%, but the extension medium is also acting as a filter aid and unless at least 45% is used in this case, filtration and compression is practically impossible to carry out. In general, the range of allowable variation might be expressed as follows: percent extension medium should fall between 450 divided by the density of the powdered material and 1800 divided by that density. When this allowable variation is exceeded, the breakdown in physical structure is evidenced by the formation of layers of cleavage perpendicular to the direction of compression. Likewise, a parallel matting of the material takes place similar to that found, for example, in cardboard. The greater the compression the more serious the breakdown. Thus, again, it is important to work under the large dilution described herein and filter gradually without disturbing the matrix, otherwise a non-uniform, weak, inferior structure is obtained comprising large nodules of material, loosely connected together with resultant cleavages around these aggregates.

It is to be noted that natural cork itself has a microcel structure, hence its low density. Finely ground regranulated cork has a density of only approximately 6 pounds per cubic foot. In using this material, as in Example No. l, a special case is encountered regarding the application of the empirical formula given above and a correction must be made due to the exceptional structure of these cork particles. The values given in the example have been found to work out in practice. This exception does not hold for the waste cork fiour referred to in Example No. 2, which has a density of 25 pounds per cubic foot.

The present invention embodies the use of latex as a binding agent in this particular combination and method of procedure, when the finished product is desired to have a high degree of flexibility. The invention contemplates the use of small amounts of sodium silicate as a binding agent in this combination and process, when low cost is of vital importance and also where additional stifiness is required. This latter quality may also be obtained by use of appropriate resins. The invention likewise contemplates the use of wax to destroy capillary action in the finished product, as herein specified. Other well known waterproofing agents, such as soaps, oxychloride of zinc, etc.. may, of course, be added without departing from the spirit of the invention.

Although the present invention has been described in connection with certain preferred embodiments, it is to be understood that variations and modifications can be resorted to as those skilled in the art will readily understand. These variations and modifications are to be within the purview of the spirit of the present invention and within the scope of the appended claims. Thus in the specification and claims, the term powdered materials may include such powdered materials as cork, wood flour, bark, limestone, diatomaceous earth, pumice stone, tripoli, fullers earth, resins. sulphur, asphaltum, stone, marble, alumina, etc., etc. The substances forming the medium of extension may comprise such fibrous materials as cellulose fiber, cotton, wool, paper, wood, cane fiber, straw, jute, rags, felt, kapok, asbestos, mineral wool, etc. The binding agents may comprise latex, glue, sodium silicate, and dispersed resins, including prepared resinous pastes such as the prepared resins referred to in connection with the especially prepared parafin herein described.

I claim:

. 1. A self-sustaining, light weight, compressed, substantially non-metallic, cellular, thermal insulating composition of substantially uniform physical character, comprising as to its principal components finely divided, substantially waterinsoluble particles and finely pulped fibers, the

average individual fiber of which is about 0.08 inch in length, said fibers maintaining said particles in a fine, substantially uniform, continuously bonded, microcellular structure having a multiplicity of microscopic voids and having said particles, fiber and voids in substantially uniform volumetric distribution and said fibers arranged in substantially all directions; the proportion of said particles to fiber in said composition being such that the structure of said composition is substantially free of layers of cleavage perpendicular to the direction of compression and of parallel matting of the fiber characteristic of cardboard.

2. A self-sustaining, light weight, compressed, substantially non-metallic, cellular, particulatefiber, thermal insulating composition of substantially uniform physical character, comprising principally finely divided, substantially waterinsoluble particles and finely pulped fiber about 0.08 inch in length and including a small amount of water repellent material; said fiber maintaining said particles in a fine, substantially uniform, continuously bonded microcellular structure having a multiplicity of microscopic voids at least 40% of the total volume of said structure; said composition having said particles, fiber and voids in substantially uniform volumetric distribution and said fibers arranged in substantially all directions, and the proportion of said particles to fiber in said composition being such that the structure thereof is substantially free of layers of cleavage perpendicular to the direction of compression and of parallel matting of the fiber characteristic of cardboard, and said water repellent substance being in amount as not to detrirnentally affect the said percentage of voids.

3. A compressed self-sustaining, uniformly microcellular non-metallic thermal insulating composition having a density not exceeding twenty pounds per cubic foot; said composition comprising short fibers not exceeding 0.08 inch in length, powdered material, and a smaller amount of binder, said fibers constituting from 20% to 50% by weight of the composition; said composition being particularly characterized by random orientation of said fibers, such short length and random orientation of said fibers imparting to said composition a uniform structure substantially free from the layers of cleavage and parallel matting of fiber characteristic of cardboard.

4. A compressed self-sustaining, uniformly microcellular non-metallic thermal insulating composition having a density not exceeding twenty pounds per cubic foot; said composition comprising short cellulosic fibers not exceeding 008 inch in length, powdered cork, and a smaller amount of binder, said fibers constituting from 20% to 50% by weight of the composition; said composition being particularly characterized by random orientation of said fibers, such short length and random orientation of said fibers imparting to said composition a uniform structure substantially free from the layers of cleavage and parallel matting of fiber characteristic of cardboard.

5. A compressed self-sustaining, uniformly microcellular non-metallic thermal insulating com position having a density not exceeding twenty pounds per cubic foot; said composition comprising short cellulosic fibers not exceeding 0.08 inch in length, powdered cork, and a smaller amount of rubber latex binder, said fibers constituting from 20% to 50% by weight of the composition; said composition being particularly characterized by random orientation of said fibers, such short length and random orientation .of said fibers imzairizilsm EEEEE EEEEEEEEE 2,345,009 '5 7 5 parting to said composition a uniform structure repellent material in the form of a dispersed wax,

said fibers constituting from 20% to 50% by weight of the composition; said composition being board. particularly characterized by random orienta- 6. A compressed self-sustaining, uniformly mi- 5 tion of said fibers, such short length and random crocelluiar non-metallic thermal insulating comorientation of said fibers imparting to said compoposition having a density not exceeding twenty sition a uniform structure substantially free from E pounds per cubic foot; said composition compristhe layers of cleavage and parallel matting oi fiber ing short cellulosic fibers not exceeding 0.08 inch characteristic of cardboard. in length, powdered cork, a smaller amount of 10 rubber latex binder, and a small amount of watersubstantially free from the layers of cleavage and parallel matting of fiber characteristic of card- CHARLES H. SCHUH.