US1865192A - Method of making structural material - Google Patents

Description

June 28, 1932. w. R. KAPPEs METHOD OF MAKING STRUCTURAL MATERIAL Filed March 26. 1931 2 $heets sheet l TTORNEY June 28, 1932. A w. KAPPES I 1,865,192

METHOD OF MAKING STRUCTURAL MATERIAL Filed March 26, 1931 2 Sheets-Sheet 2 INVENTOR ATTORN EY Patented June 28, 1932 UNITED STATES PATENT OFFICE WALTER RAYMOND KAPPES, 0]? DAEMON T, PENNSYLVANIA, ASSIGNOR TO ALUMINUM COMPANY Oi AMERICA, 0]? PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN SYLVAIN'IA.

METHOD OF MAKING STRUCTURAL MATERIAL Application filed March 26, 1931. Serial No. 525,481.

This invention relates to a process for the production of improved insulating material of the type known as pulp board or fiber board.

An object of the invention is to produce a fibrous material which is light and porous and has improved heat and sound insulating properties. The term structural units as used throughout the specification and claims relates to blocks, boards, sheets or other desirable forms of material suitable for the formation or lining of walls, floors, buildings, containers or other structures where it is desirable that they be resistant to either heat or sound.

A further object of the invention is to produce such porous structural units from materials consisting primarily of pulp or fiber, such as wood pulp, porn stalk, bagasse, jute, flax, hemp or other plant fiber, or other fibrous cellulosic material or asbestos fiber or rock wool or similar inorganic fibrous materials.

I have found that highly porous fibrous structures may be produced by incorporating in a pulp pr fiber mass a small amount of a material capable of, reacting with a reagent to produce agas, which gas will exert a leavening eifect upon the pulp mass so as to able particularly for heat or-sound insulat-.

form therein minute bubbles of gas and to produce in the finally shaped and dried mass an extremely light and porous structure suit in purposes.

' n practicing my invention, I prepare a pulp mass of the nature above described by mixing any suitable fiber stock in a beater or other mixing apparatus with a suflicient amount of water or other solution to'render the ulp more or less coherent and sufliciently uid for satisfactory handling. Such masses as may be thus or similarly formed are referred to herein and in the appended claims as pulped mass. To the pulp mass thus formed, I add and incorporate uniformly thefiein a small amount of a leavening agent, i. e., a substance which is capable of producing, by reaction with a suitable rea cut, a relatively large amount of gas.

is leavening substance may be either a metal which is capable of reacting with an acid or an alkali, or a chemical compound which is capable of reacting with a suitable reagent to produce the gaseous evolution de sired. But in the practice of my invention, I have found it generally preferable to use as the leavening agent a metal in the form of a powder and to act upon the metal pow der with an alkali or an acid. Although a chemical compound, such as for instance, calcium carbonate, may be used as a leavening agent to produce the results of my invention, I have found the use of a metal powder to be superior to the use of chemical compounds; for it is desirable from a roduction standpoint, as will hereinafter e explained, that the start of the leavening action in the pulp mass be dela ed slightly from the time that the gas producing agents are added and, furthermore, that the evolution of gas extend over a relatively long interval of time. A metal powder incorporated in the pulp mass is, I have discovered, a material which more readily meets these conditions than a chemical compound in that the metal powders are somewhat slower to react with the acid or alkali which is added to produce the leavening eflfect and, because of their slowness of action, aflord a sufiicient opportunity for forming the pulp and obtaining the maximum leavening effect in the pulp mass. Moreover, the reaction between metal powder and acids and alkalies is capable of a more positive regulation of the speed of gas evolution than are mixtures of chemical compounds and reagents capable of acting upon them to form a gas.

Among the metal powders which may be used as leavening agents for this purpose are finely divided aluminum, zinc, and magnesium. In the practice of my invention, I have found that in relation to these and other metals, the most satisfactory and commercially practical method of producing a leavening effect in the pulp mass is to add the pulp mass and the gas produced by the addition of either an acid or alkali material, and magnesium will give satisfactory results under the same conditions when treated with an acid. It is preferred, however, to use finely divided aluminum with a sub uent treatment with an alkali for this com ination lends itself most readilyito the problems of the speed of the gas evolution as outlined above.

The amount of leavening agent, whether metal -or compound, which shouldbe incorporated in the pul mass to obtain the best results will vary with the metal or compound to be used and with the amount of leavening action which it is desired to obtain. The necessary amount may be readily predetermined by experiment. Amounts of finely divided aluminum corresponding in weight to about 5 per cent of the dry weight of the fiber stock present in a paper pulp mass have been found to be satisfactory. The amount of leavening action which takes place in the pulp mass is directly a function of the amount of the leavening agent, whether it be metal powder or a chemical com ound, incorporated therein and when it is esired to obtain a highly porous, relatively bulky finished product, higher percentages of the leavening agent should be used than when it is desired to (produce a product which is not so light an rous and somewhatstifi'er and stronger. enerally, the most desirable tipe of product is obtained b incorporating t 2 to 3 per cent by weig t of aluminum powder in the pulp mass.

The metal or compound may be incorrated either with the fiber stock before ating or with the liquid pulp mass. I prefer, however, to add the leavening agent to the prepared pulp mass, as a more even distribution throughout the pulp mass is thereby obtained and the leavening action is consequently more uniform and a uniform and satisfactory product is obtained.

After the pulp mass containing the leavening agent has been prepared, it is treated with a reagent which will react with the leavening agent to produce the desired leavening action. ThlS reagent is preferably an acid or an alkali which will produce a positive gas producing reaction with the. metal or compound used. Where the nature of the pulped material prohibits the use of such reagents, a reagent of another type, such as mercuric chloride, will produce the desired effect. In general, depending u on the nature of the pul material an the desired speed and v0 ume of gas evolution, any reagent which will produce, with the metal or campound incorporated in the pulped mass, a gas evolution may be satisfactorily used if it is not inherently destructive of the final result desired.

The reagent is readily handled in the'form of a solution or suspension in water. When added to the .pulp mass in this form, an even distribution throu hout the pulp mass may be readily obtaine .The amount of reagent to be added may be readily predetermined b calculating the amount required to react wit the amount of leavening agent added to the pulped mass. The solution of the reagent should be of such a concentration that too sirable, however, to use an excess of the reagent over the amount required for complete reaction. But the excess of reagent should not in any case be great since the excess left in the pulp mass after the reaction is completed may have a modi 'ng effect on the fibers in the pulpimass w ich will substantially change the physical properties of the final product. It is preferred, therefore, to use the reagent in an ,amount suin'cient to give only a slight excess over that r uired to react with the metal or compoun previously incorporated in the pulp mass.

When, as in the preferred practice of my invention, finelydivided aluminum is added to the pulp mass and the mixture treated with an alkaline reagent to produce a leavenin gas, there are certain alkaline reagents to preferred. I have found that a solution of 'caustic soda will be satisfactory in those instances where ra id handling of the pulp mass is feasible. here the rapldhandlingof the pulp is not feasible,I prefertouse some less active alkaline reagent, and, for this purpose, I have found a suspension of lime in water to be most satisfactory. When such a reagent is used, the evolution of gas is slow in startin and proceeds slowly and regularly, thus a ording a reasonable mterval for handling and formin the pulp mass'before the leavenin action as reached its maximum. The maximum advanta e of the leavening action is thus secured an a more porous product is obtained. A further advantage accruing from the use of milk of lime arises from the fact that the hydrate of calcium, being only weakly basic, has very little, if an modifymg efl'ect upon the fibrous materia The reagent can, therefore, be used in reasonably largeexcess if desired without danger of injuring the final product. In fact, it has been found that the product may be materiall improved for some purposes by using are atively large amount of milk of lime in treating the pulp mass. The lime deposited in the fibers from the suspension as a binding quality which renders the finished product stronger and more rigid and also more fire resistant. In the formation of the pulp mass into hght, porous structural units, a reasonablemix should then be transferred to the forming apparatus without delay as it is preferable that any violent handling of the mass be avoided while the principal part of the leavemng action is proceeding. The forming apparatus should be of such a type that the principal part of the water content may be removed from the leavened pulp mass either by drainage or by suction or pressure. In so removing the water, care must be taken, when either suction or pressure is used, that such suction or pressure be very light, otherwise the entrapped gas bubbles may be removed from the leavened mass, causing the whole mass to collapse into a dense and relatively non-porous form.

In practicing my invention, I may employ an apparatus such as illustrated in the accompanying drawings, but it will be understood that this mechanism is shown by" way of illustration only, and various other convenient means may be employed to accomplish the results herein described.

Inthe drawings, Fig. 1 represents in perspectrve view a simple form of apparatus for carrying out my invention;

Flg. 2 represents in perspective view a po- Frgus lilock formed in the apparatus shown in ig. 3 represents in diagrammatic form an arrangement by means of which my invention may be practiced'on a commercial scale;

Fig. 4-represents a vertical section on the line 1-4 of Fig. 3.

In 1, a simple form of apparatus is shown by means of which suitable structural units of pulp mass may be formed. A shallow tray 14 having a perforated bottom 15 of X fine screen is positioned above-a vacuum hood 16. The pulp mass containing the leavenin material may be cured onto thetray an permitted to stan for a short time until the leavening action has become vigorous throughout the mass. The excess liquid is then removed'from the pulp mass by applymg a slight vacuum beneath the pulp mass and the tray may then be transferred to an oven to completely dry the pulp cake thus formed. By careful handlin the pulp cake.

may be removed from thes allow tray before drying in the oven if desired.

By means of this apparatus, a stiif block of highly porous, fibrous-material as shown in Fig. 2 is produced. K q

Figs. .3 and 4 represcntiin diagrammatic form an apparatus in which such structural units may be produced, in accordance with my invention, on a commercial scale.

Apulp mass containing a leavening agent,

and in quantity suflicient to fill a form of the desired shape, such as form 6, is run into a rotary mixer 1 through the chute 2. A suitable quantity of'reagent is then added to the mixer 1 from the tank 3 by means of the pipe 4, a valve 5 being provided in the pipe line 4 to regulate the quantity of reagent. The pulp mass and the alkali solution are mixed for a suitable period in the rotarymixer 1 and the mixture is then discharged into the form 6, the dot-and-dash line indicating the discharging position of the rotary mixer. The form 6 is provided with a perforated bottom similar to that shown at 2 in Fig. 1.

Forms 6 are supported upon a suitable endless conveyor consisting of roller chains 9, and are provided with supporting members 10 which are adapted to ride upon the cross links in the conveyor chains 9 as shown in detail in .Fig. 4. Rotatably mounted idler rollers 11 are positioned to support the conveyor chains intermediate. the drive sprockets.

A form 6, after having been filled, moves to a second station where, if it is desired to limit the thickness of the block to be formed, a perforated cover 7 of predetermined weight may be placed on the surface of the mixture in the form. The form is then moved to a third stat-ion and positioned over the vacuum hood 8 where the liquid is removed from the pulp mass by means of a slight vacuum produced by the vacuum apparatus 12. From this point, the form passes on to the drying oven 13 where the pulp mass is thoroughly dried.

Successive forms are placed on the conveyor and filled and carried intermittently through the successive stations as described,

and pouring into a form a batch of the pulp mass.

The results which may be. obtained in thepractice of my invention are illustrated in the following examples. To 300 grams of a pulp mass, there was added,0.5 gram of a milk of lime prepared by adding 100 grams of lime to one liter of water. As soon as the gas was evolved vigorously, a light suction was applied to the mass. This suction was continued until all the excess water had been removed from th'epulp. The pulp cake was then transferred toan oven and dried thoroughly. The resulting product was a very light, porous block which was quite firm. The dried block had a wei ht of 45 grams and an average thickness of 0.5 inch and a bulk of about 25 cubic inches.

To another batch of 300 grams of wet pulp, 1.0 gram of finely divided aluminum powder was added. This'mixture was treated with 100 cc. of milk of lime andformed into.

a dried block as in the preceding experiment. The dried block resulting from this experiment had a weight of grams and a thickness of 0.75 inch and a bulk of about 40 cubic inches. V In a third experiment, 2.0 grams of aluminum powder were added to 300 grams of the wet pulp mass and the mixture was treated with 100 cc. of milk of lime. A dry block was formed of this mass as in the preceding e riments. The resultin product had a weight of 52 grams and a t ickness of 1.375 inches.

It will be readily apparent from these examples that the porosity and thickness of the insulating product may be regulated by the amount of metal powderor chemical compound used to produce the leavening gas.

-As an example of the results obtained when the amount of lime used is material- 1y increased, a milk of lime containing 200 grams of lime in 600 cc. of water was prepared. This suspension was added to 400 grams of wet pulp mass containing 2 grams of aluminum powder. The resulting mixture was formed and dried as usual. The product obtained was a orous block which was quite strong and rigld. It weighed 27 5 grams and had a thickness of. 1.75 inches.

I claim:

1. The method of making light, porous structural units from pulped masses prising mixing with a pulped mass about 2 to 3 per cent of aluminum powder and a predetermined quantity of an alkaline reagent.

2. The method of making light, porous structural units from pulped masses, comprising mixing with a pulped mass a predetermined quantity of metallic powder and a reagent capable of reacting with the metallic powder to produce a leavening gas.

- 3. The method of making light, porous structural units from pulped prising mixing with a'pulped mass a predetermined quantity of a a predetermined quantity of an alkaline reagent.

4. The. method of making light, porous structural units from pulped masses, comprising mixing with a pulped mass a predetermined quantity of aluminum powder, and

treating the mixture thus formed with a reagent capable of reacting with said powder to 1 form a leavening gas."

5. A method of making light, porous structural units from pulped masses, comprising adding to the pulped mass a solid leavening agent and a reagent capable of reacting with said leavening agent to form a leavening gas.

6. 'The method of making light, porous structural units from p'ulped masses, comprising mixing with a pulped mass 0." predetermined quantity of metallic powder and an amount of a reagent capable of reacting with said powder to form a leavening gas in exmasses, com:

uminum powder and prising forming a pulpedmass, incorporatmg m sald mass a solid leavening agent, treating the mixture thus formed with a reagent capable of reacting with said leavening agent to form a leavenmg gas, and placing the final mixture in a form.

' W. RAYMOND KAPPES.

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