US2049888A - Bleaching agent and process for making same - Google Patents

Description

Patented Aug. 4, 1936 UNITED STATES PATENT OFFICE SAIVIE Souren Z. Avedikian, New York, N. Y.

No Drawing. Application December 18, 1933, Serial No. 702,963

9 Claims. (or. 8- 2) This invention relates to bleaching agents and processes for making them, and relates particularly to the manufacture of powdery bleaching agents from aldehydes and acid halogenides.

An aldehyde is a member of that group of organic compounds which contain a group in the molecule, and an acid halogenide is a compound having the formula of an organic acid but with the OH group of the -COOH group replaced by a halogen. The term aldehyde as used in this specification also includes substituted aldehydes, which are aldehydes in which one or more of the H atoms of the molecule issreplaced by other atoms or groups such as halogens, nitro groups, hydroxyl groups, or organic radicals. Likewise, the term acid halogenidef as used herein includes substituted acid halogenides, and also includes mixtures which produce acid halogenides.

In order to obtain convenient and efilcient mixing of a bleaching agent and a milling product, the bleaching agent must be in the form of a fine powder which effectively permeates through the entire mass to be bleached.

Bleaching powders made from aldehydes and acid halogenides in conjunction with halogenatlng agents, basic bodies, and persalts have been proposed for use in bleaching flour and other milling products, but the bleachin powders prepared from these constituents by known methods are not of the desired strength and the amount required makes the bleaching expensive, and makes the percentage of bleaching agent in the final product higher than desirable.

The known methods of making powdery bleaching agents from aldehydes and acid halogenides are not satisfactory because they make no provision for controlling the chemical reaction which occurs during the mixing operation, or soon after. Unless it is controlled, this reaction between the active ingredients of the. mixture is attended by a heatingand fuming of the mixture, which turns dark, is partially decomposed, and loses almost all of its bleaching power. Efforts to increase the strength of the bleaching agent by increasing the percentage of active ingredients in the mixture have beenattended by this heating and fuming reaction, and destruction of the value of the mixture as a bleaching agent.

It has also been diflicult, with existing methods, to produce a product which can be finely ground and can be prevented from forming caked aggregates.

It is an object of this invention to provide an improved powdery bleaching agent, of the class containing aldehydes and acid halogenides as the 5 active ingredients, which has a stronger bleaching action than the bleaching agents of the prior art, and which permeates more readily through a powdery mass to bejbleached.

Another object of the invention is to provide 10 an improved method for making bleaching agents from aldehydes and acid halogenides without risk of heating and fuming of the mixture and consequent destruction of its value as a bleaching agent. The bleaching agent made in accordance with this invention can be ground to a fine texture and has special utility in bleaching flour and other milling and plant products.

It has been customary to produce a dry powdery mass directly upon addition of the active ingredicuts to the diluents or basic bodies, or other substances serving a similar purpose, but this procedure accelerates the reaction between the active ingredients to such an extent as to bring about partial decomposition, rendering the product unsatisfactory for use. The reaction can be retarded or prevented by using less active ingredients in proportion to the diluents or basic body, but the diluents decrease the final strength of the bleaching agent.

I have discovered that a bleaching agent of greater strength than those of the prior art can be obtained by mixing an aldehyde and an acid halogenide, at least one of which is liquid, with thickening powder comprising a diluent powder, as, for example, a ground siliceous body, and/or a powdered basic body in such quantities that the mixture has the consistency of a thick paste, and allowing the mixture to dry to a solid which is thereafter ground to a powder. The term paste is used in this specification in its broad sense to describe a thick semi-solid consistency which is not necessarily sticky. The aldehyde and acid halogenide are preferably mixed in proportion to 5 their molecular weights.

In preparing bleaching agents according to this invention, the mixture of an aldehyde and acid halogenide is added to a diluent powder, preferably a heavy, ground siliceous substance. 50 Talc or an aluminum silicate is suitable. I believe that this inert ingredient serves to decrease the reactivity of the liquid ingredients and serves to retard their reaction. Another unexpected res lt is that the heavy siliceous substance makes the final powdery bleaching agent permeate more readily through the substance to be bleached.

A basic body is one capable of neutralizing an acid, and unless the mixture contains a basic body, it is likely to leave the flour, or other substance, acid after the bleaching reaction. In order to completely neutralize the acid in practice it is necessary to have some excess of basic body over that theoretically required. Where acid properties of the bleached product are not objectionable, the bleaching agent can be made from an aldehyde and acid halogenide mixed with the diluent powder, and without any basic body.

According to the preferred embodiment of my invention, the process is carried out by mixing a quantity of heavy, ground siliceous substance with an aldehyde and an acid halogenide, at

least one, and preferably both, of which are liquid. The amount of liquid added is sufficient to make the consistency of the mixture liquid.

The basic body in powder form is add-ed to the mixture slowly and distributed with a rapid mixing and kneading motion until the mixture reaches the consistency of a thick paste having a uniform distribution of the various substances in each other. It is important to limit the amount of powder added so that the mixture does not become partially dry during the mixing operation. More'of the basic body can be added when the mixing and subsequent drying is in a cool dry atmosphere. The mixing and drying can be performed in contact with the air and is preferably carried out in a dry atmosphere and at a room temperature between 20-35 C.

The mixture after reaching the consistency of a paste is spread in a thin layer on a drying floor or trays and allowed to stand until dry. The temperature during the drying should not exceed 60-65 C. The mixture dries into a hard mass in from 6 to 60 hours, the time depending on the temperature, the amount of liquid in the mixture, and the thickness of the mass on the drying floor or trays. 7

After the mixture has hardened and the odor of the acid halogenide has disappeared, the mass is broken up and ground to an impalpable powder. Unless the drying is complete it is not possible to obtain a sufiiciently fine degree of pulverization. After drying completely, the mixture made according to the method described can be ground to any desired degree of fineness. An advantage of using a hard siliceous body as the diluent is that such a diluent is harder than the basic body and reaction product and with any given amount of grinding remains somewhat coarser than the other constituents of the mixture. This heavier powder in the finished bleaching agent causes it to permeate more readily through flour or other ground substances in which the bleaching agent is used and thus promotes rapid and thorough mixing.

The basic body added to the mixture to bring it to the consistency of a paste is usually not more than 60% to 80% of the-quantity of basic body desirable in the final bleaching agent. This deficiency is made up by adding additional basic body to the original mixture after it is dry. It is advantageous to add this additional basic body during the final grinding operation so that this operation may serve to thoroughly mix the added basic. body with the mixture being ground.

The process of this invention can be carried out with a basic body substituted for the siliceous body and the mixture brought to the consistency of a paste as described, but the final bleaching agent obtained does not permeate through a powdery mass to be bleached in the same way as when the mixture contains a hard siliceous body. The most desirable proportion of siliceous body seems to be between 20% and of 'the total weight of the final bleaching agent.

A mixture of two or more substances which are inert in the mixture can be employed as the diluent body, and a mixture of two or more aldehydes or acid halogenides can be substituted for the single substances described. I prefer to use a single siliceous body, aldehyde, and acid halogenide, with a mixture of two basic substances, but the basic body may be a single compound.

An illustrative example of the invention will now be described in detail, with benzaldehyde as the aldehyde, benzoyl chloride as the acid halogenide, aluminum silicate as the siliceous body, and a mixture of sodium carbonate and calcium carbonate as the basic body. Good results are obtained when the combined weight of aldehyde and acid halogenide is from 20% to 35% of the total weight of the final bleaching agent. In making 100 kilograms of bleaching powder, 12.9 kilograms of benzaldehyde is mixed with 17.1 kilograms of benzoyl chloride. This ratio is proportional to the molecular weights of the substances and is desirable because it gives a product which does not contain an excess of either of the active ingredients and which can be more easily dried and well ground. The benzaldehyde and benzoyl chloride are well mixed and added to from 20 to 50 kilograms of aluminum silicate, and the mixture stirred until the solid is completely wetted by the liquid and the mixture is of liquid consistency. The mixing is done in a vessel exposed to the atmosphere.

A mixture containing equal amounts of calcium carbonate and sodium carbonate is then added until the mass reaches the consistency of a thick paste. This basic body is added slowly with constant stirring of the liquid to obtain uniform distribution of the solid throughout the mass. The paste sets and dries after standing from 6 to hours, depending on its consistency, the thickness of the mass, and the temperature at which the drying takes place. The temperature of drying should not exceed 60-65 C.

The paste is spread out as thin as practicable on a drying floor or trays so that each kilogram of paste covers approximately 0.05-02 square meters of surface. The paste is allowed to remain thus spread out and partly covered until it becomes hard and dry. The product is then broken up and ground to a fine powder. Additional calcium carbonate and sodium carbonate are added during or after this final grinding to bring the basic body of the mixture to a value somewhat in excess of that theoretically required to neutralize the acid present after a bleaching reaction. The bleach obtained is exceptionally strong and remarkably rapid in action. One part of this bleaching powder for every 7000 parts of flour is sufficient to obtain satisfactory bleaching of the flour. The heavy particles of the aluminum silicate cause'the bleach particles to penetrate through the flour to be bleached when intimately mixed with it, thus rendering the bleaching action uniform and rapid throughout the mass.

In place of benzaldehyde and benzoyl chloride, analogous compounds of the aliphatic, aromatic,

and alicyclic series can be substituted in the process above described. With some modifications in the mixing operations and apparatus employed, it is possible to use volatile aldehydes such as acetaldehyde, and volatile acid halogenides such as acetyl chloride. The use of oxalyl chloride as an acid chloride is of importance in that it is a derivative of a dibasic acid and thus one molecular weight of it is equivalent to two molecular weights of halogenides of monobasic acids and the proportionate amount of active liquid ingredients required in the bleaching agent is less than required in the case of a monobasic acid chloride.

Some examples of substituted aldehydes are ortho-, meta-, and para-chlorobenzaldehyde, ortho-, meta-, and para-nitro benzaldehyde, the corresponding brom benzaldehydes, chloracetaldehyde, and vanillin. Some specific examples of acid halogenides are acetyl bromide and oxalyl bromide. The substituted acid halogenides which can be employed include, ortho-, meta-, andparachlorobenzoyl chloride, ortho-, meta-, and paraacetyl chloride or bromide, and benzoyl bromide.

In addition to the carbonates of sodium and calcium as basic bodies, the oxides, peroxides,

hydroxides, carbonates, bicarbonates, and other basic compounds of sodium, potassium, lithium, magnesium, and calcium and other metallic elements can be used, singly or in combinations of two or more.

Minute quantities, one part in 3000 to one part in 10,000, of manganese, nickel, cobalt, iron, or copper salts, such as their benzoates, when added to the bleaching agent accelerate its action considerably.

I claim:

1. In the process of making a powdery bleaching agent, the steps which comprise forming a liquid mixture of an aldehyde and an acid halogenide, adding thereto a sufficient quantity of a solid basic body to form a paste, and causing the mixture to dry.

2. The process for making a powdery bleaching agent, for bleaching flour and other milling and plant products, which comprises mixing an aldehyde and an acid halogenide, at least one of which is a liquid, with a ground inert diluent body and a solid basic body to form a mixture having the consistency of a paste, causing the mixture to dry, and then grinding it to a powder.

3. The process for making a powdery bleaching agent, for bleaching flour and other milling and plant products, which comprises mixing an aldehyde and an acid halogenide, at leastone of which is a liquid, with a ground inert body to obtain a mass of liquid consistency, adding to this mass sufficient quantity of a powdery an aldehyde and an acid halogenide to a ground siliceous body, adding to this mixture a powdered basic body until the mixture reaches'the consistency of a thick paste, causing the paste to dry and harden by spreading it in a thin layer over a supporting surface, at a temperature not.

exceeding 65 C., and thereafter breaking up the hardened mass and grinding it to powder.

5; The process of making a powdery bleaching agent, for bleaching flour and other milling and plant products, which comprises the steps of adding to a liquid mixture of benzoyl chloride and benzaldehyde a suflicient quantity of a solid basic body to form a paste, causing the mixture to dry, at least one of the steps being carried out in the presence of air, and then grinding the mixture to a powdery mass.

6. The process of making a powdery .bleaching agent, for bleaching flour and other milling and plant products, which comprises the steps of adding to a liquid mixture of chlorbenzoyl chloride and benzaldehyde a suflicient quantity of a solid to dry, at least one of the steps being carried out in the presence of air,- and then; grinding the mixture to a powdery mass.

'7. The process of making a powdery bleaching agent for bleaching flour and other milling and plant products which process includes the steps of adding to a liquid mixture of an aldehyde and an acid halogenide a sufllcient quantity of a solid basic body 'to form a paste, and causing the mixture to dry, at least one of the steps being carried out in the presence of air, and then grinding the mixture to a powdery mass.

8. The product obtained by the method of claim 1.

9. The product obtained by the method of claim '7.

SOUREN Z. AVEDIKIAN.

basic body to form a paste, causing the mixture 35