US3639284A

US3639284A - Bleaching composition

Info

Publication number: US3639284A
Application number: US850225A
Authority: US
Inventors: Alfred Long; Duane L Sawhill
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1969-08-14
Filing date: 1969-08-14
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01

Abstract

Bleaching compositions, substantially free from ''''pinholing'''' textiles are prepared by mixing calcium hypochlorite, sodium tripolyphosphate and diluent salts in particulate form and in specified ratios, compacting to form aggregates, disintegrating the aggregates to form homogeneous granules and sizing the granules.

Description

United States Patent Long et al.

1 5] Feb. 1, 1972 [54] BLEACHING COMPOSITION [72] Inventors: Alfred Long, New Haven; Duane L.

Sawhill, Orange, both of Conn.

[73] Assignee: Olin Corporation [22] Filed: Aug. 14, 1969 [211' Appl. No.: 850,225

3,110,678 11/1963 Shaffett ..252/l87 X 3,154,495 10/1964 Robson et al. ..252/99 3,234.14] 2/1966 Robson ..252/ l 87 3,338,671 8/l967 Marshall et al. ..252/99 X Primary Examiner-Mayer Weinblatt Att0rney-Gordon D. Byrkit, Donald F. Clements, Richard S, Strickler, Robert H. Bachman, Donald R. Motsko and Thomas P. ODay [5 7] ABSTRACT Bleaching compositions, substantially free from pinholing" textiles are prepared by mixing calcium hypochlorite, sodium tripolyphosphate and diluent salts in particulate form and in specified ratios, compacting to form aggregates, disintegrating the aggregates to form homogeneous granules and sizing the granules.

8 Claims, No Drawings BLEACHING COMPOSITION This invention relates to the production of calcium hypochlorite bleach compositions which are stable, dust-free, uniform in composition and not susceptible to segregation of the components. The product comprises calcium hypochlorite with diluent salt characterized in that each particle is of substantially the same composition. The product is further characterized in being substantially free from the pinholing frequently caused in washing textiles using strong, solid bleaches.

The preparation of mixtures of calcium hypochlorite and diluent salts is well known. For this purpose, solid high test calcium hypochlorite compositions are usually mixed with inert salts or extenders, soda ash, quicklime, and modifiers. These mechanical mixtures, however, are subject to segregation in storage and shipment because of the different density of the component particles. When a portion of the material is removed from a container after storage or shipment it may differ in composition materially from other portions removed from the same container. Some particles may be nearly all solid calcium hypochlorite substantially free from diluents and these particles, in contact with cloth, cause pinholes.

Dry household bleaches based on calcium hypochlorite are used under conditions which the manufacturer or blender cannot control. Despite specific directions, the consumer frequently adds dry bleach to the washing machine after the clothes have been added. Under these conditions some particles of calcium hypochlorite sink through the wash water and are retained in folds of cloth. in this position they dissolve slowly with relatively little circulation of water and give rise to a small volume of liquid containing very much more available chlorine than that present in the solution around it. Calcium hypochlorite dissolves fairly rapidly to make solutions of 50,000 or more parts per million of available chlorine. In water at 140 F. this does not result in immediate visible damage. However, after and cycles of wear and washing, fibers once exposed to this strong bleach solution disintegrate and leave a pinhole. Clothes dyed with a bleach-sensitive dry are changed to white at the point where the particle of calcium hypochlorite was in contact with it.

Dry bleaches improperly formulated tend to form lumps if a substantial amount of the bleach is dumped into the wash water. Once a lump has formed it takes several minutes to dissolve. Clothes contacting the surface of this lump before solution is complete are bleached over irregular areas as the lump moves in relation to the cloth. A large lump caught in folds of cloth can produce a large hole. Ingredients which are lumpforming when improperly blended with calcium hypochlorite include sodium tripolyphosphate, sodium silicate and sodium sulfate. Synthetic detergents under some conditions also contribute to lump formation. The novel stable, dry bleach composition of calcium hypochlorite and diluent salts of this invention is fast dissolving, does not form lumps under adverse conditions of use, does not segregate and greatly reduces the hazard of pinhole formation.

The composition of this invention is composed of particles containing calcium hypochlorite in intimate admixture with a diluent salt, the particles being of uniform size and uniform composition. Substantially all of the particles contain the same percent of available chlorine. The compositions have the relatively high density of about 1.3 to 1.5 when packed in bulk.

The compositions of this invention provide marked advantages over compositions hitherto available. The compositions contain no particles of 70 percent available chlorine as do prior compositions and thus do not have the attendant disadvantages. The calcium hypochlorite is evenly distributed throughout each particle and each particle is suitably diluted with inert salts so that pinhole" formation hazards are greatly reduced and at the same time formulations with markedly reduced chances of lumping when dissolved are made possible. Also, physical segregation is eliminated due to the nature of the admixture of the calcium hypochlorite with the diluent salt in a particle form. The high density compositions of this invention are particularly useful in bleach formulations.

THE PRIOR ART US. Pat. No. 2,963,440 describes the advantages of limiting dry bleach compositions to 10 percent available chlorine and the undesirable pinholing properties of mechanical mixtures containing granules of calcium hypochlorite having more than about 25 percent available chlorine even though such granules are diluted with other granules to form a composition containing not over 10 percent available chlorine. This patent discloses and claims the method of diluting HTH with inert diluent salts in a wet way, forming the mixture, drying and screening.

US. Pat. No. 2,959,554 describes the problems of preparing solid bleach compositions based on calcium hypochlorite and polyphosphates. The patent teaches (1) the necessity of sufficient polyphosphate in such mixtures to sequester the calcium; (2) the problem of lumping when such mixtures are added to water; (3) the resulting problem of fpinholing" when such lumps lodge in folds of cloth; (4) the selection of polyphosphates which do not deleteriously affect the stability of calcium hypochlorite. This patent discloses and claims mechanical mixtures of sodium tripolyphosphate in the form of hollow beads with calcium hypochlorite, each suitably sized, the weight ratio of tripolyphosphate to calcium being from 25:1 to 100.1.

US. Pat. No. 3,234,141 discloses the advantages of Chilsonating mixtures of calcium hypochlorite and sodium sulfate with or without other diluent salts, crushing and screening the resulting tablets.

THE CQMPOSITION OF THE INVEN'ITON The invention provides a solid bleaching composition in the form of discrete particles at least percent of which pass 10 mesh and are retained on 40-mesh US. Standard screens, substantially each of said particles consisting essentially of calcium hypochlorite, sodium tripolyphosphate and at least one solid, anhydrous diluent alkali metal salt having a cation selected from the group consisting of sodium and potassium and an anion selected from the group consisting of metasilicate, carbonate, bicarbonate, chloride, pyrophosphate acid pyrophosphate phosphate, acid phosphate and mixtures thereof;

a. the weight ratio of saidsodium tripolyphosphate to said calcium hypochlorite being from 2.9:1 to 8.6: l;

b. the weight ratio of said diluent salt to calcium hypochlorite being from0.4:1 to 4:1; and

c. the weight ratio of the total of sodium tripolyphosphate plus diluent salts to calcium hypochlorite being from 2.9:] to 13:].

THE CALCIUM HYPOCHLORITE For the purposes of the present invention, commercial calcium hypochlorite preparations are generally suitable. Commercial calcium hypochlorite as generally sold contains at least 70 percent available chlorine and usually contains at 71 to 73 percent. The general range of the usual impurities is given in table 1, column 1. A typical composition of HTH," a leading commercial product, is given in column 2.

The commercial HTH brand of calcium hypochlorite (granular) typically has a minimum (loose packed) density of about 0.79 and a maximum (shaken) density of about 0.83. It is suitable for use according to the present invention as well as finer grades of HTH." The screen analyses (US. Standard screens) of exemplary grades of HTH are shown in table ll.

TABLE ll Weight percent By the term calcium hypochlorite" in the present specification and claims is meant true calcium hypochlorite a compound of the formula, Ca(OC1) Various preparations contain varying amounts of Ca(OCl) as indicated in table I and elsewhere herein.

Commercial HTH containing about 70 percent available chlorine and 70 percent of true calcium hypochlorite is suitably used for the purposes of this invention, taking into account, in calculating proportions, that 1.0 part by weight of HTH contains 0.7 part by weight of calcium hypochlorite. Other calcium hypochlorite compositions containing more or less available chlorine are also suitable, taking into account the available chlorine content in calculating proportions.

THE SODIUM TRIPOLYPHOSPHATE Commercial sodium tripolyphosphate, suitably in the form of spray-dried beads, granular or powdered is used in preparing the compositions of the present invention.

The weight ratio of sodium tripolyphosphate to HTH" should be not less than 2.1, equivalent to 2.9 parts of sodium tripolyphosphate per part of Ca(OC1) in order adequately to sequester the calcium. The ratio of sodium tripolyphosphate to HTH is preferably not more than 6:1, equivalent to 8.6 parts of sodium tripolyphosphate per part of Ca(OC1) in order to maintain the available chlorine content of the product at convenient levels.

DlLUENT SALTS Diluent Salts" means salts other than the calcium hypochlorite and the sodium tripolyphosphate which are incorporated incidentally with these ingredients or additionally incorporated.

Commercial calcium hypochlorite always contains varying amounts of sodium chloride and other components as shown in table I. It is to be understood that the compositions of this invention include the miscellaneous minor amounts of salts normally appearing in commercially available calcium hypochlorite and sodium tripolyphosphate. The sodium chloride, including other lesser impurities, in commercial calcium hypochlorite usually amounts to about 0.3 part per 0.7 part of Ca(OCl) equivalent to 0.4 diluent salts, per part of Ca(OC1) The total of diluentsalts, including sodium chloride, cannot usually be less than about 3 parts per 0.7 part of Ca(OCl) equivalent to 4 parts per part of Ca(OCl) More diluent salt reduces the available chlorine content of the compositions below levels useful in bleaching compositions.

Suitable diluent salts in the compositions of this invention are the following sodium and potassium salts:

Sodium metasilicate Potassium metasilicate Sodium chloride Potassium chloride Sodium carbonate Potassium carbonate Sodium bicarbonate Potassium bicarbonate Disodium acid pyrophosphate Potassium pyrophosphate Monosodium phosphate Disodium phosphate Trisodium phosphate Monopotassium phosphate Dipotassium phosphate Tripotassium phosphate Sodium or potassium metasilicate, when used in the compositions of this invention, is suitably the dry, solid product of commerce.

The weight ratio of sodium silicate to HTH" is suitably up to 1:1, equivalent to l.4:l of Ca(OCl The acidic salts, particularly sodium bicarbonate, disodium acid pyrophosphate, sodium bisulfate and monosodium ortho phosphate and the corresponding potassium salts are particularly useful in reducing the alkalinity of the compositions of this invention. Preferably the pH of a 0.25 percent aqueous solution of these compositions at 25 C. is from about 9 to l l. The diluent salts buffer the solution in this range and maintain the stability of the hypochlorite.

The weight ratio of total of sodium tripolyphosphate and diluent salts to HTHf is not greater than about 9: l, equivalent to a ratio of sodium tripolyphosphate and diluent salts to calcium hypochlorite of 13:1, in order to have a minimum of 7 percent available chlorine in the product. A maximum available chlorine content is obtained using 2 parts by weight of sodium tripolyphosphate per part of HTH" and no other components. This is equivalent to 2.9 parts by weight of sodium tripolyphosphate to one part of calcium hypochlorite. The resulting product contains about 23 percent available chlorine.

THE PROCESS OF THE INVENTlON The process of the invention consists of the steps of homogeneously mixing to form aggregates, crushing and screening the aggregates to separate a fraction of discrete particles at least percent of which pass 10 mesh and are retained on 40-mesh US. Standard screens.

The compaction of the granular or powdered components is accomplished by available means which form aggregates of the well-mixed granular or powdered components. Especially useful for compaction are tabletting machines, compression rolls and the Chilsonator" of US. Pat. No. 3,255,285. In tabletting machines, pressures of 20,000 to 100,000 pounds per square inch are used, preferably 60,000 to 80,000 pounds per square inch. The resulting tablets, of any desired size and shape, are hard, dense and do not readily crumble to allow separation of granules of the original components. The Chilsonated" product is also hard, dense and does not readily crumble to release granules consisting essentially of the original components.

The resulting aggregates are disintegrated, for example, by crushing using available means, including grinders, jaw crushers and the like. The thus granulated product is sorted, for example, by screening, to separate the final product having the desired mesh size. Oversize is recrushed and recycled and the undersize is recycled to the compacting operation.

Compaction prevents fabric attack by regulating the solubility rate of the resulting granules of the bleach formulation. This prevents high, localized concentrations of hypochlorite ion in solution and thus avoids pinholing.

The optimum solubility time for the individual granules is preferably in the range of l to 6 minutes. The variables which control the solubility times are:

a. Granule size b. Granule density c. Diluent salt A mixture of granular sodium tripolyphosphate, granular calcium hypochlorite and granular salt diluent compacts better and harder than the respective powders. The resulting aggregates are disintegrated to form granules which are sized to to 40 mesh. The resulting granules have the desired solubility time of l to 6 minutes in hot water at 130 to 140 F. Granules finer than 40 mesh tend to lumpand these lumps cause pinholes in the fabric. Granules much coarser than 10 mesh dissolve too slowly.

ADVANTAGES OF THE INVENTION The most important advantage of the compositions of this invention is that pinholing is substantially completely avoided even under careless or otherwise adverse conditions of use in washing and bleaching, particularly in domestic washing machines.

Another advantage of the product of this invention is that all of the available chlorine is not released at once. In a washer having a 12 minute wash cycle, it is desireable that all of the available chlorine be released before the end of the cycle but it is also desirable that not all the available chlorine be released the moment the bleach is added.

In the compositions of the present invention, and in normal use, over 60 percent of the bleach is released in the first two minutes and over 90 percent is released at the end of six minutes which is the halfway point of a 12-minute wash cycle.

At least 90 percent of the particles of the composition of the present invention are in the l0 +40 mesh size. Larger particles tend to be slower dissolving. Smaller particles in greater amounts tend to pinhole more frequently. The fine particles are undesirable since they may cause the user to sneeze or cough when pouring or handling the product. For these reasons, the preferred range or particle size is -10 +40 mesh.

TEST PROCEDURES Washing-All washes were carried out in a Mark XII Whirlpool top-loading machine having a total capacity of l6 gallons. Water temperature was l30-135 F. in all tests. In each test, pieces of unbleached broadcloth 36x48 inches in size were used. To the water was added the cloth, one ounce of a commercial alkylaryl sulfonate type detergent (Tide") and 120 grams of the dry bleach composition. The wash cycle consisted of 12 minutes and the total cycle for fill, wash, rinse, and spin was 40 minutes.

After each washing, the cloths were dried in a whirlpool Mark XI] electric clothes dryer at 140 F. for 30 minutes.

Brightness and whiteness-Bleaching efficiency was determined by measurements commonly used in the textile industry. A piece of cloth after the washing, bleaching and drying operations was ironed lightly with a steam iron and subjected to light-reflectance readings with a Model 610 Photovolt Reflection Meter. Readings in percent reflectance were taken with blue, amber and green filters. Each recorded reading was an average of three or four individual readings taken on each swatch backed by three similar swatches. The reflectance readings were taken automatically at 45 to the incident light beam. From the percent reflectance readings, brightness and whiteness were calculated as follows:

Brightness (blue and amber and green filter readings)/3 whiteness 4 blue filter readings3 green filter readings The brightness and whiteness figures are purely empirical and have no units. They closely represent what the human eye perceives. The larger the number, the brighter or whiter the fabric. Brightness values over 80 are considered good and whiteness values over 70 are considered to be good.

EXAMPLE I The following mixture:

200 lbs. HTI-I" granular l 100 lbs. sodium tripolyphosphate granular 100 lbs. sodium metasilicate granular was blended for 30 minutes in a ribbon blender and Chilsonated ata pressure of 10,000 pounds per lineal inch on the rolls of a Chilsonator manufactured by the Fitzpatrick Company in Chicago, Ill., Model 7 LX 10D under the following conditions:

Chilsonator roll speed I8 r.p.m.

Chilsonator morot load lO-IS Amp.

Chilsonator roll pressure l.200-2200 lbs. total (pulsating) Horiz.-fecd screw speed 160 r.p.rn.

Vert.-l'eed screw load 4 amps HoriL'feed screw 1.4 amps The product was crushed and screened to separate a fraction in the -10 +40 mesh range. It contained 9.4 percent available chlorine. The pH of the wash water containing I20 g. of this product with l ounce of Tide and 20 test cloths was 10.6. Twenty washings, bleachings and dryings were performed as described above and the bleaching efficacy was determined as before with the following results:

Brightness whiteness Original 73.5 41.5 After 20 washes 86.5 75.3

The bleach was effective and no pinholing was observed.

Dissolving rates of the product of example I were determined by agitating 10 grams of granules of the product in 5 liters of water at various temperatures and analyzing the solution at various times for each component. The data of table III were obtained:

The data show complete solution of all but the sodium tripolyphosphate at washing temperatures (130 F.) in 2 to 3 minutes. At the lower temperature of F., the metasilicate is shown to dissolve fastest and the tripolyphosphate slowest. However, even at 80 F. all the components dissolve completely within a 12 minute washing cycle.

EXAMPLE II A mixture of:

lbs. granular HTl-I 400 lbs. granular sodium tripolyphosphate 200 lbs. granular sodium metasilicate was blended and Chilsonated" as described in example I.

The product was crushed and screened to separate the l0 +40 mesh range. The available chlorine content of the Chilsonated" product was 9.1 percent.

Test washes were performed as described above under Test Procedures." The pH of the wash water, measured 6 minutes after addition of the bleach, was I L8.

The cloths were dried in a Mark XII Whirlpool electric clothes dryer after each washing and the brightness and whiteness determined by the procedures described above under Test Procedures" with the following results:

Brightness whiteness Original 73.5 41.5 After 20 washes 88.4 78.4

The bleach was highly effective and no pinholes were observed.

EXAMPLE III A mixture of the following (parts by weight):

1.00 l-lTH" granular 5.25 Sodium tripolyphosphate granular 0.25 Sodium metasilicate granular 0.50 Disodium dihydrogen pyrophosphate granular was blended and Chilsonated as described in example I at pressures of 10,000 pounds per linear inch. The product was crushed and screened to separate the l .+40 mesh range Available chlorine in the product was 9.7 percent. The pH of the wash water containing 120 g. of the product with 1 ounce of Tide and 20 test cloths was 9.7. After washing, the test cloths had a brightness of 83 and a whiteness of 64. The bleach was effective and no pinholing was observed.

The rates of release of available chlorine of the products of examples I, II and III were measured when an amount of product sufficient to provide 200 parts per million of available chlorine was agitated in 16 gallons of water at 130 to 135 F. The data of table IV were obtained:

TABLE IV Percent oftotal Product of Available chlorine released Example I Product of Example Ill Product of Example I] 1 minute 2 minutes 3 minutes 4 minutes 5 minutes The product of example Ill released available chlorine faster initially than the products of examples I and II but the rate or the product of example ll became equal to and greater than the rate for the product of example Ill after 2.5 minutes. All three products released more than 90 percent of their available chlorine in less than 5 minutes.

EXAMPLE IV TABLE V Time Minute Minimum Maximum 7 97 B 98 I00 9 99 I00 l0 I00 I00 What is claimed is:

1. A solid calcium hypochlorite bleaching composition in the form of discrete particles at least 90 percent of which pass 10 mesh and are retained on 40-mesh US. Standard Screens, substantially each of said particles consisting essentially of calcium hypochlorite sodium tripolyphosphate and at least one solid, anhydrous diluent alkali metal salt havin a cation selected from the group consisting of sodium an potassium and an anion selected from the group consisting of metasilicate, carbonate, bicarbonate, chloride, pyrophosphate, acid pyrophosphate, phosphate, acid phosphate and mixtures thereof;

a. the weight ratio of said sodium tripolyphosphate to said calcium hypochlorite being from 2.9:1 to 8.6: l.

b. the weight ratio of said diluent salt to calcium hypochlorite being from 0.4:] to 4: l and c. the weight ratio of the total of sodium tripolyphosphate plus diluent salts to calcium hypochlorite being from 2.921 to 13:1.

2. A composition as claimed in claim 1 in which said diluent salts are sodium chloride and sodium metasilicate, the weight ratio of sodium chloride to calcium hypochlorite being about 0.421, the weight ratio of said metasilicate to calcium hypochlorite being about 0.8:1 and the weight ratio of sodium tripolyphosphate to calcium hypochlorite being about 8:1.

3. A composition as claimed in claim 1 in which said diluent salt is sodium chloride, the weight ratio of sodium chloride to calcium hypochlorite being about 04:1 and the weight ratio of sodium tripolyphosphate to calcium hypochlorite being about 3.5: I.

4. Process of preparing the bleaching composition as claimed in claim 1 which consists of the steps of (l) mixing particulate calcium hypochlorite, sodium tripolyphosphate and said diluent salt in said ratios, (2) compacting the thus prepared mixture to form aggregates, (3) disintegrating said aggregates to form granules and (4) sizing said granuels to separate the said bleaching composition having at least 90 percent through l0 mesh and retained on 40'mesh US. Standard screens.

5. Process as claimed in claim 4 in which said calcium hypochlorite contains from 70 to 74.5 percent of available chlorine.

6. Process as claimed in claim 4 in which said compacting produces aggregates which have the form of tablets.

7. Processes as claimed in claim 4 in which the oversize separated from said sizing is further disintegrated and recycled to said compacting.

8. Process as claimed in claim 4 in which the undersize separated from said sizing is recycled to said compacting.

Claims

2. A composition as claimed in claim 1 in which said diluent salts are sodium chloride and sodium metasilicate, the weight ratio of sodium chloride to calcium hypochlorite being about 0.4:1, the weight ratio of said metasilicate to calcium hypochlorite being about 0.8:1 and the weight ratio of sodium tripolyphosphate to calcium hypochlorite being about 8:1.
3. A composition as claimed in claim 1 in which said diluent salt is sodium chloride, the weight ratio of sodium chloride to calcium hypochlorite being about 0.4:1 and the weight ratio of sodium tripolyphosphate to calcium hypochlorite being about 3.5:
4. Process of preparing the bleaching composition as claimed in claim 1 which consists of the steps of (1) mixing particulate calcium hypochlorite, sodium tripolyphosphate and said diluent salt in said ratios, (2) compacting the thus prepared mixture to form aggregates, (3) disintegrating said aggregates to form granules and (4) sizing said granuels to separate the said bleaching composition having at least 90 percent through 10 mesh and retained on 40-mesh U.S. Standard screens.
5. Process as claimed in claim 4 in which said calcium hypochlorite contains from 70 to 74.5 percent of available chlorine.
6. Process as claimed in claim 4 in which said compacting produces aggregates which have the form of tablets.
7. Processes as claimed in claim 4 in which the oversize separated from said sizing is further disintegrated and recycled to said compacting.
8. Process as claimed in claim 4 in which the undersize separated from said sizing is recycled to said compacting.