US2167606A - Process for producing aerated cementitious compositions and articles - Google Patents

Description

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LRGHHIHH raten ted July 25, 1959 UNITED STATES PATENT OFFICE PROCESS FOR PRODUCING AERATED CE- IIENSTITIOUS COMPOSITIONS AND ARTI- Conrad Grard Francois Cavadino, Rochester, England, assignor to Gyproc Products Limited, London, England, a. British limited-liability company, and himself No Drawing. Application November 17, 1937, Se-

rial No. 175,031. In Great Britain August 18,

8 Claims.

This invention relates to hydraulic cements with a quick set and hardening suc s or an cement cements of the hi h alumina series th e oxychlorides of zinc an n-a nesi'a' a"n1 to such mm ars and t i their two oxygens neutralize each other and 5 in which aeratioh e. g. e-rasrtnon 01' pores, v v xy en as, a d wh n ch m a d. a s voids cc] 5 or gaps s aecom s e y means-o the first class, is present. this evolution is of evolvl en as from solid um greatly increased intensity, a phenomenon simi- Tfii'ng hgas n ppositely polar conditions. lar to that as with the electrolysis of water when 10 In addition to the ordinary state in which the acidified water contains a little chromic acid 10 oxygen is known with its u ual t l properand more ozone is obtained than without it. ties it also exists in another state, that of allo- Manganese P e with hydrogen Pe tropic oxygen or as it is generally called, ozone. wh l te a so belongs o t e seco d class.

It is also known that certain peroxides such as o es oxy en but not ap d y. Al o t us those belonging to the class of the peroxide of dealing with peroxides in both cases the oxygen 15 manganese, or the latters permanganates of the as i is v v must be different in its p p alkali metals such as the potas ium permangaties. In the electrolytic decomposition of wanate and the like, the peroxide of lead and also l t y n w h pp at the P v the chromic anhydride commonly called chromic pl m pole has ozonic properties and has been acid, or the latters salts such as potassium difound to possess t e s e P w Of c ouring 20 chromate and the like, on the one hand and strychnia as the oxygen (ozone) liberated by those belonging to the class of peroxides of basulphuric aci f om the peroxid of a e e rium and sodium on the other, contain oxygen or from the latter's permanganates of the alkali which produces ozonic eilects but of which the me als, f m p r x f l d nd from ohr mic oxygen of each individual class possesses difieracid, or the latters salts such as potassium di- 25 ent properties. The peroxides of lead and of chromate and the like. The 0 en of this class manganese produce chlorine with hydrochloric of peroxides and of chromlc acid and its salts acid and liberate oxygen when heated. Chromic has thus been considered to be an electr acid when added to the acidified water in the tj ve ele m ent, per contra the oxygen of the perelectrolytic decomposition of water increases the oxides of the second class as electrmpgsitiyg ele- 30- production of ozone and it transforms camphene ments. into camphor with evolution of oxygen. Peroxide The evolution of oxygen gas can be accomof manganese gives a blue colour to the precipiplished by mixing a compound such as hydrogen tated resin of guaiacum and turns aniline (on peroxide and alkali peroxide with manganese paper) brown. It does not produce peroxide of peroxide in this process. However, the manga- 35 hydrogen but when mixed with the latter even nese peroxide itself does not undergo any change, at a strength of only three per cent by volume but merely exercises a catalytic action resulting it decomposes it with slow liberation of oxygen in the liberation of oxygen from the other pergas. With sulphuric acid it produces a rich seoxides present. In this process, manganese per- 40 ries of purple colours with strychnia. Barium oxide remains after completion of the aeration 40 peroxide similarly treated does not produce the as a black residue which may entirely spoil the results above described but it does produce hycolor of the resulting composition. drogen peroxide with hydrochloric acid without If the manganese peroxide in the above deliberating chlorine; its oxygen in its action on scribed process is replaced by potassium perman- 5 alkaline iodides and in its bleaching properties ganate which is able to liberate the active oxyresembles ozone. Sodium peroxide by the action gen of the hydrogen peroxide, for example, the 01' water evolves oxygen and also produces hypotassium permanganate undergoes a chemical drogen peroxide. Generally the oxygens of each change in the process. However, the chemical one individual class exercise no action upon each reaction involved leaves an insoluble, voluminous,

other when treated with an acid but when a greenish-brown residue of potassium manganate 50 peroxide of the first class is brought into conand manganous oxide which also seriously aftact with one ot the second class oxygen gas fects the color of the resulting product. may be evolved abundantly andwith great ra- According to my invention I mix barium erpidity even with almost explosive violence either oxide and man anese eroxide in a e y oby'the use of an acid such as for example hydrogeth'e'r an corpora e mixture with a 55 chloric or even without the use of an acid. For instance when a mixture of manganese peroxide of the first class with barium peroxide of the second class is treated with hydrochloric acid cement such as for example laster of Paris. To this mix of plaster of Paris and perofiaes of barium and manganese I add ater in the usual manner and proportion an s e mix to a thick and creamy consistency and then add thereto a reagent solution containin chromic acid and hydrochloric acid to promote the evolution o ox en a mm the peroxides con"- ame erein. ereafter stir the whole mass rapidly and thoroughly either by hand or mechanically when a powerful aeration of a few seconds duration sets up in the mass which I then rapidly pour into moulds which may be of metal, wood, paper and the like. By varying the percentage of the reagent solution the aeration may at will be either intensified, retarded and/or accelerated and if so required iiavbe stabilizedTbythaddition of a small quantity of a's'ein,'r in soap, saponin, albumen and the like.

decomposed into a soluble manganese salt leaving no residue to cause discoloration of the article produced. Potassium permanganate when used in conjunction with barium peroxide in the presence of hydrochloric acid is also decomposed into soluble salts presenting a clear solution with no residue whatsoever.

The method followed by the present invention aims at evolving oxygen gas and using it forthwith .,,it.,a'.,liiscfitffstate, e. g. directly and immediately on its evdliition and in its full power of action therefore without wasting any of its energy resulting in an economical commercial application.

I do not bind myself to the use of manganese peroxide alone for I may also use in its stead its permanganates of the alkali metals such as the potassium permanganate and the like. Nitric acid may be used instead of hydrochloric acid.

As an example the following compounding weights and volumes per 6800 lbs. of aerated plaster of Paris will illustrate the process.

(a) 45 lbs. of barium peroxide and 3 lbs. of manganese peroxide are thoroughly mixed together for a short while by preference in a small ball mill. Thereafter 4 lbs. and 13 ounces of this mix are thoroughly mixed in the usual manner with 6800 lbs. of dry plaster of Paris. The plaster of Paris thus prepared is then drawn on a belt in the usual manner through a water bath in order to soak it with water to a workable consistency and to convey it in the state of a semi-fluid mass to the mixer. Immediately before the said semi-fluid mass reaches the mixer I add thereto about 24 gallons of a solution consisting of:

Commercial hydrochloric acid gallons 3 Water do 22 Chromic acid ounces 27 The semi-fluid mass thus prepared n'ow passes through a powerful beater-mixer for a few seconds duration when an equally distributed powerful aeration of the plaster mass results through the evolution and dispersion of oxygen gas in its nascent state. 4

I do not limit myself to the weights and volumes as given in the example for it should be understood that by varying their ratios the aeration may at will be either intensified, retarded and/or accelerated.

I have, however, found that to obtain a thorough homogeneous mix of such a small quantity as 4 lbs. and 13 ounces of barium and manganese peroxide mix with 6800 lbs. of dry plaster of Paris is a rather troublesome operation. I therefore give preference to the execution of the aeration principle in the following manner which consists in using solutions only instead of partly a dry powder mix and partly a solution. To this effect I split the 3 gallons of commercial hydrochloric acid solution in 22 gallons of water as stated in the aforementioned example sub (b) into two parts each of 1 gallons of commercial hydrochloric acid and 11 gallons of water. In one half part, e. g. 12% gallons hydrochloric acid solution I dissolve 4% lbs. of barium peroxide. In the second half part of 12 gallons of hydrochloric acid solution I dissolve 27 ounces of chromic acid and 5 ounces of manganese sulphate instead of 5 ounces of manganese peroxide which latter with hydrochloric acid would produce chlorine which is to be avoided. In other words I substitute the latter by the former.

The two solutions are prepared separately in two vats or containers suitable for the purpose and the adding of each of them at the rate of about 1 gallon per 5 minutes to the semi-fluid plaster mass immediately before it reaches the mixer proceeds in the same manner -as hereinbefore stated with the difference however that the barium peroxide solution is added to it a little distance apart from the chromic acid solution so that the two do not enter into contact but upon entering the beater-mixer where the energetic action of the latter instantly promotes in the same manner a' powerful aeration due to the evolution and dispersion of oxygen gas in a "nascent state. Here again I do not bind myself exclusively to the aforementioned weights and volumes which'may be varied to suit the degree of aeration one wishes to attain.

In that part of the 12 /2 gallons commercial hydrochloric acid solution which contains 2'7 ounces of chromic acid and 5 ounces of manganese sulphate, I can advantageously substitute for both the 27 ounces of chromic acid together with the 5 ounces of manganese sulphate, solely 22 ounces of a chromic acid salt such as for instance potassium dichromate or 16 ounces of an alkali metal permanganate of the manganese peroxide such as potassium permanganate, but since potassium permanganate is the more economical I therefore give preference to the use of potassium permanganate. Moreover, when using potassium permanganate, the aeration bubbles which form at the moment of the evolution of the gas are much more infinites mal in size but far greater in number, e. g. they lend themselves to a far greater dis persion throughout the cement mass or slurry in which they are imprisoned thereby forming a cellular product of higher technical value and eificiency. This is of great importance for instance when plaster of Paris cement slurry is poured into paper moulds such as is the case with plaster boards. If the aeration pores or cells are relatively large and fewer in number, the boards will lose in strength but when they are structured so as to represent a multitude of homogeneously interspersed but contiguous microscopic voids or COATING R PLASTIC.

cells, the boards will be stronger and have higher thermal and acoustical value.

The liquid reagents per 6800 lbs. glastgr per hour herebefore described may thus also be composed on the one hand of 11 gallons of water, 1

gallons of commercial lggrgehloric acid and 4 lbs. of b a rium peroxide dissolved therein, and on the other errrgsnans of water, 1 gallons of commercial hydrochloric acid and 16 ounces of tassium permanganate or 22 ounces of potassium dicfiromate dissolved therein. The two solu ions are en ready to be used.

I do not bind myself exclusively to the aforementioned weights and volumes which may be varied to suit the degree of aeration one wishes to obtain.

When using Portland cement or cements of the high alumina series or of the oxychlorides of zinc or of the magnesia series the proportion of cementitious material is the same as hereinbefore described.

I claim:

1. Process for producing aerated cementitious compositions and articles made therefrom, comprising the steps of mixing together cementitious material, barium peroxide, an acid substance selected from the group consisting of hydrochloric acid, nitric acid and the mixtures of hydrochloric with nitric acid, a compound selected from the group consisting of manganese peroxide, the alkali metal permanganates, chromic acid and the chromic acid salts, and suflicient water to form a semi-fluid mixture, and stirring the mixture to promote dispersion throughout the semi-fluid mixture of the evolved oxygen, the proportions of the several reagents being such as to result in the evolution of oxygen in a nascent form.

2. Process for producing aerated cementitious compositions and articles made therefrom, comprising the steps of intimately mixing cementitious material, barium peroxide, and manganese peroxide with a quantity of water sufilcient to bring the mixture into a semi-fluid state, then adding an acid substance selected from the group consisting of hydrochloric acid, nitric acid, and the mixtures of hydrochloric with nitric acid and stirring to promote dispersion throughout the semi-fluid mixture of the evolved oxygen, the proportions of the several reagents being such as to result in the evolution of oxygen in a nascent form.

3. Process for producing aerated cementitious compositions and articles made therefrom, as claimed in claim 1, in which an alkali metal per- 55 manganate is admixed to said acid substance,

before the latter is added to said semi-fluid mixture.

4. Process for producing aerated cementitious compositions and articles made therefrom, as

claimed in claim 1, in which a chromic acid is admixed to said acid substance, before the latter is added to said semi-fluid mixture.

5. Process for producing aerated cementitious compositions and articles made therefrom, as claimed in claim 1, in which a chromic acid salt is admixed to said acid substance, before the latter is added to said semi-fluid mixture.

6. Process for producing aerated cementitious compositions and articles made therefrom, comprising the steps of dissolving barium peroxide in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and mixtures of hydrochloric with nitric acid, dissolving an alkali metal permanganate in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and the mixtures of hydrochloric with nitric acid, adding the two solut ons separately to a semi-fluid mass consisting of cementitious material and water, and stirring the mixture to promote dispersion throughout the semi-fluid mass of the evolved oxygen, the proportions of the several reagents being such as to result in the evolution of oxygen in the nascent form.

'7. Process for producing aerated cementitious compositions and articles made therefrom, comprising the steps of dissolving barium peroxide in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and mixtures of hydrochloric with nitric acid, dissolving a chromic acid in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and the mixtures of hydrochloric with nitric acid, adding the two solutions separately to a semi-fluid mass consisting of cementitious material and water, and stirring the .mixture to promote dispersion throughout the semifluid mass of the evolved oxygen, the proportions of the several reagents being such as to result in the evolution of oxygen in the nascent form.

8. Process for producing aerated cementitious compositions and articles made therefrom, comprising the steps of dissolving barium peroxide in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and mixtures of hydrochloric with nitric acid, dissolving a'chromic acid salt in a diluted acid substance selected from the group consisting of hydrochloric acid, nitric acid and the mixtures of hydrochloric with nitric acid, adding the two solutions separately to a semi-fluid mass consisting of cementitious material and water, and stirring the mixture to promote dispersion throughout the semi-fluid mass of the evolved oxygen, the proportions of the several reagents being such as to result in the evolution of oxygen in the nascent form.

CONRAD GERARD FRANCOIS CAVADINO.