US2156309A - Method of producing compressed products - Google Patents

Description

Patented May 2. 1939 I I 2,156,309

UNITED s-TATEs PATENT: OFFICE.

METHOD OF PRODUCING COMPRESSED v 'PRODUCTS Charles Schuh, Brooklyn, N. Y., assignor, by

mesne assignments, to Bakelite Building Products 00., Inc., New York, N. Y., a corporation of Delaware No Drawing. Application October 25, 1935, Se-

rial No. 46,742. Renewed July 11, 1938 12 Claims. (on. 18-48) This invention relates to compressed products aware, has been wholly satisfactory, practical and a method of producing the same, and more and successful when carried into practice on an particularly to a new method for the production industrial scale. of lightweight non-metallic products and to\the I have discovered that it is possible to produce products resulting therefrom; a desirable board or sheet of material from a 5 Prior rigid thermal insulating materials mayv fine powdered'material without the use of any be divided into three classes, to wit: (1)' the so-called binder material or with the use of such porous type, such as blown molten limestone a small percentage of same as to make its prescommerciaiiy known as Rock cork, which is ence entirely unobjectionable from the standcharacterized bythe presence of large visible point of increase in density, increase in thermal 10 voids, (2) the various fibre boards composed of conductivity,-and even increase in cost. To atlarge coarse wood, cane, and other fibre or cellutain this object, I employ a process which is losic material matted and pressed together with based upon a fundamentally new concept in v -or without bindenand (3) corkboard, either in the procedure for the production of this type of its natural form or made from granulated cork product. 15 baked under pressure with or without binder. The object of the invention is to obtain a non- Natural cork being the bark of a tree is obtained metallic material of super light weight which in sheets of limited thickness andofnon-uniformhas valuable thermal and acoustical properties.- size and shape and is an expensive product. It A further object of the invention is to obtain 2c is therefore not used in the natural state to any a highly efficient insulating material of light extent for. insulating board. Instead the trimweight and low cost. a mings from various trades employing natural cork It-is also within the contemplation of the inand as may be otherwise. obtained are granuvention to obtain an efilcient insulating matelated and this granulated cork is formedint'o rial of light weight which has a finenniform boards usually one ioot by three feet by two structure and is free from large visible'voids and 25 inches in thickness. It is to be noted that the large coarse fibre such as occur in prior porous granulated cork employed for this purpose coninsulating materials and fibre board.

sists largely of granules of considerable size, The invention likewise contemplates the promuch of it being coarser than'ten mesh. These vision of utilizing in thel production of, light granules may be formed into corkboard by mixweight products raw materials which are now ing with an asphalt binder and pressing into practically waste products-and very low in cost. shape. The use of a binder, however, greatly Other objects will become apparent from the decreases the insulating emclency and also infollowing description of preferred embodiments creases the weight considerably. The discovery of the invention.

that these granules can be united into a board In carrying my invention into practice,-I prefer 35 bysimply baking under pressure was a vefiimto employ a very dilute solution or dispersion P nt invention ommer ially and practically containing (1) abinding agent, such as for examall corkboard has been made by this process.- pie, a latex or a /l aqueous resinous dis- The product, however, has been expensive; persion, a filter aid. a d what I call a '49 In preparing cork for various uses m't trader medium-of extension. The general procedure is '40 to intimately mix these three fundamental components to form a dilute aqueous suspension,

der is obtained which'naturaH contai filter the same withoutdisturbing the matrix as y small it is formed, then gradua y Subject 15118 matrix ampunt of impurities such as sand, etc, This to Y v is practically a waste product and can, a predetermined pressure withoutbreaking 45 c] may at a very low price per ton its continuous bonded structure, and finally dry tofore there has been no successful att ein t to the matrix operations are simple and 6d 1 1 boa f y p easily carried into practice and are adaptable to pr an a g m n such large scale volume production resulting in low terial as this. The general problem of producing f tu i cost 8- b a d, dpa tl i i y 9 01 light W By the expression medium of extension, as

g f om a fine p w m t i l p s various referred to hereinabove, I mean a substance seriousobstacles. Although many attempts have which-when added to an aqueous dispersion of a been made to improve thes materials,- particu-- powdered material will produce a very large bulk "the exterior rough surface of the bark is ground oil and in so doing ayflne, reddish flbrown powe larly those of group "(3), n ne, as far as I am of practically non-settling precipitated substance 5 so that a slurry is obtained which when ,subiected-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 stiucture. I have found that finely pulped fibrous material, such as finely pulped newspaper or wood pulp, in which the average individual fibre is less than approximately 0.03.

of an inch in length, makes an excellent exten- 'sion medium. The use of about 15% to about 25% 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 tohave the minimum value of the densities obtainable as low as possible. i

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 aidand medium of extension.

It is to be observed that merely mixing the three basic components mentioned hereinab'ove, filter- 8. and drying does not necessarily produce the desired result. Several problems and diillculties arise which I have discovered can only be ove'r come 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. Onthe other hand, too

small a percentageresults in a product too high in density. Then again, an inadequate percentage of filtefiaid 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 or 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 carrledout. Thus, the use or 3% sodium silicate or glue or other commonly used materialsas binding agents when used herein will in many cases make filtration 55 Practically imposnble to carry out. The use of the foregoing proportions is to beavoided.

It is also to be noted that thepresent invention embodies not only the establishment of certain critical ranges of composition but moreover sets forth certain important factors of control and em as a procedure whereby a predetermined ult canbe obtained and any such obstacles as mentioned hereinabove entirely avoided. This is of considerable practical importance because of the variety of products which are possible to produce and the exactness with which it becomes possible to meet the requirements in any given product. Fbr example,in-

standard corkboard used in refrigeration high thermal emciency is extremely important but high tensile strength is not, whereas in insulating wallboard for building construction high tensile,

strength is required and the thermal efliciency is notso'critically important. Furthermore by appropriate on 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

rathevcontemplates a process in 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, amedium densities and unless the matrix has been greatly condensed, the volume of non-visible voids will be at least 40% of the total volume of the structure.

- For thepu rpose of giving thoseskilled m the arta better understanding of the invention, the following illustrative examples will be given.

Example No. 1

To about 1000 pounds of a latex dispersion, about 20 pounds of newspaper are added and subjected to high speed mechanical distintegration until the average individual fibre is about or less than approximately 0.08 inch in length. To thismedium 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 tothe depth required, a considerable washing effect 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 ofdecreased thickness when finished even though the slabsare 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 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 operations of the above type may be conducted on a continuous scale.

In theabove 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 anotherimportant principle of the invention.

Example No. 2

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 I 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.

I Ezcample No. 3

materials used are about 1000 pounds of 15% latex dispersion, about 60 pounds of a medium of extension (dry weight), and about 60 pounds of finely powdered exterior bark portion of cork-.

board. The boards are made still thinner, about of an inch for say sole leather substitute or flooring material, and astill higher compression is used, suflicient 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 fibre, 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

I have found that theaddition of a small percentage of dispersed wax'to the mediumof extension will entirely eliminate any capillary action in the finished product and will renderit 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.

' In waterproofing my new light weight products, I have made an important discovery. I have found that an extremely effective paraffin 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 persed particles of paraffin and. an aqueous ve- I hicle containing a dispersing agent, preferably soap. Less than about 10% of soluble soap stock can be used to the weight of the paraffin. From about 100% to about 150% of water may be used ,to the weight' of the parafiin. .From a commercial point of view it is preferred touse a cheap soluble soapstock such as rosin laundry soap stock and the like. This paraflln paste distributes itself in practically a dispersed form in a dilute aqueous mixture even when cold. Only about 4 to about 6% of this paramn paste is required to destroy all capillary action in my new light weight products and render them waterrepellent. 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 fdregoing 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 haves. similar physical Microcell structure, and a resuIta-nt comparative low density. This new Microcell structure is produced when and only when the number of particles of powdered material bears a certain relation to the volume ofex' te ion medium present. I have found a simple, pr ctical empirical expression of this relation to be as followsz-per cent of extension medium, (per cent of total dry weight of composition), equals 900 The same general procedure as described in connection with Example No. 1 is followed. The

divided by the density of the powdered material. Thus, if .the density of the powdered material is 90 (as for certain rock flour) 'the per cent 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 toshift somewhat away from the calculated percentage. 1 Thus, in Example No. 3,

extension medium is used instead of 36%, but' In general, the range of 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 thebreakdown. 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 Microcell" structure, hence its low density.

Finely ground regranulated cork has a density of approximately only 6 poundsper 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 exceptionfdoes not hold for the waste cork flour referred to in Example No. 2,

which has a density of 25 pounds percubic 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 bination and process, when low cost is of vital importance and also where additional stiffness 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 theinvention.

Although the presentinvention has been-described in connection with certain preferred em bodiments, 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, pumic'e stone, tripoli, fuller's of sodium silicate as abinding agent in this coml which comprises intimately mixing finely ground exterior. P rtions of natural cork bark, a filter aid, an extension medium, and a dispersed binding agent in a liquid, said natural cork bark being about 50 to 90% of the total dry weight of said mixture exclusive of the said binding agent, filtering said mixture without breaking the matrix previously formed, compressing said matrix to a desired density without breaking the continuous bonded structure thereof and including further expression of the liquid-phase, and subsequently drying said matrix to form a light weight product.

3. The process of forming light weight, compressed, substantially non-metallic products which comprises intimately mixing wood flour, a filter aid, an extension medium, and a dispersed binding agent in a liquid, said wood flour being about 50 to 90% of the total dry weight of said mixture exclusive of the said binding agent, fildispersed binding agent, a finely powdered, light weight, water insoluble material substantially inert with respect to'said binding agent, and a finely pulped fibrous material of the group consisting of newspaper stock, wood pulp stock and asbestos pulp stock having individual fibres less than about 0.08 inch in length, said fibrous material being adapted to perform the dual function of a filter aid and of ainedium of extension and constituting about 10 to 50% of the total dry-weight exclusive of they binding agent, filtering said mixture without breaking the matrix previously formed, compressing said matrix to .adesired density without breaking the continuous bonded structure thereof including further expression of the liquid phase, and subsequently drying said matrixto form a light weight product.

5. The process of forming light weight compressed products which comprises intimately mixing in water a filter aid, an extension medium, dispersed rubber in the form of latex as a binding agent constituting about to 5% of the mixture in the aqueous phaseand finely powdered, light weight, water insoluble materialsubstantially inert with respect .to said binding agent, filtering said mixture without breaking the matrix previously formed, compressing said matrix to a desired density without breaking the con-- tinuous bonded structure thereof including'further expression of the liquid phase, and subse- 1. The process of forming lightweight substantially non-metallic products which comprises intimately mixing finely ground regranulated cork, a filter aid, and extension medium.

and a dispersed binding agent in a liquid, said regranulated cork being about 60 to 90% ofthc totaldry weight of said mixture exclusive of the said binding agent, filtering said mixture without breaking the matrix previously formed, compressing said matrix to a desired density without- 'bre king the continuous bonded structure there- 01' nd including, further expression of the liquid phase, and subsequently drying said matrix to form a light weight product.

2. The process of forming light weight, compressed, substantially, non-metallic products quently drying said matrix whereby a low strength light weight compressed product is obtained.

6. The process of forming light weight compressed products which comprises intimately mixing in water a filter aid, an extension medium,

dispersed rubber in the form of latex as a binding-agent constituting about 15% to 25% of the mixture in the aqueous phase and finely powdered,light weight, water insoluble material substantially inert with respect to said binding agent,

expression of the liquid phase, and subsequently drying said matrix whereby a high strength light weight compressed product is obtained.

7. The process of forming light weight compressed products which comprises intimately mixing in water a. filter aid, an extension medium, finely ground dispersed resinous material as a binding agent, and finely powdered, light weight, water insoluble material substantially inert with respect to saidibinding agent, said binding agent constituting about /g% to of the mixture in the aqueous phase for obtaining low strength products and to 25% of the mixture for-obtaining high strength products, filtering said mixture without breaking the matrix previously formed, compressing said matrix to a desired density without breaking the continuous bonded structure thereof including further expression of the liquid phase, and subsequently drying said matrix to form a light weight compressed product.

8. The process of forming light weight compressed products which comprises intimately mixing in water a finely pulped fibrous material for filter aid and extension medium constituting about 40% to 60% of the mixture exclusive of a binding agent, a binding agent of sodium silicate,- and finely powdered, light weight, water insoluble material substantially inert with respect to said binding agent, said binding agent constituting about /2 to 5% of the mixture in the aqueous phase for obtaining low strength products and to 25% of the mixture for obtaining high strength products, filtering said mixture without breaking the matrix previously formed, compressing said matrix to a desired density without breaking the continuous bonded structure thereof including further expression of the liquid phase, and subsequently drying said matrix to form a light-weight compressed product.

9. In the production of light weight materials,

- the improvement which comprises embodying an extension medium in an aqueous mass containing a finely powdered, light weight, substantially water-insoluble material for producing an enlarged uniform dispersion of said material in an aqueous mixture, whereby such abnormally large volumetric dispersion of said powdered material will be maintained during filtration and compression and also during subsequent drying of said mixture to produce light weight materials.

10. The process of forming light weight products which comprises intimately mixing in a liquid an extension medium, a dispersed binding agent, a. finely powdered, light weight, water insoluble material substantially inert with respect to said binding agent, filtering said mixture without breaking the matrix as formed, compressing said matrix to a desired density without breaking the continuous bonded structure thereof in eluding further expression of the liquid phase,

and subsequently drying said matrix toform a light weight product. V

11. The process of vforming light weight products which comprises forming an intimate aqueous mixture containing a dispersed binding agent, a finely powdered, light weight, water insoluble material-substantially inert with respect to said binding agent, and a finely pulped fibrous material having individual fibers less than about 0.08

inch in length, said fibrous material being adapted to perform the dual function of a filter aid and of a medium ofextension and constituting about 10 to 50% of the total dry weight exclusive of the binding agent, filtering said mixture without breaking the matrix as formed,

compressing said matrix to a desired density 7 without breaking the continuous bonded structure thereof including further expression of the liquid phase, and subsequently drying said compressed matrix to form a light weight product.

12. The process of forming light weight products which comprises intimately mixing an extension medium and a dispersed binding agent in a hot liquid, slowly pouring melted wax into said hot mixture under 'high speed agitation, adding a finely powdered, light weight, water in.- soluble material substantially inert with respect to said binding agent, filtering said mixture without breaking the matrix as formed, compressing said matrix to a desired density without breaking the continuous bonded structure-thereof including further expression of the liquid phase, and subsequently drying said matrixto form a light weight and substantially waterproof product.

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