WO1990002832A1

WO1990002832A1 - Chlorine bleach compositions with reduced fabric dye attack

Info

Publication number: WO1990002832A1
Application number: PCT/US1989/003762
Authority: WO
Inventors: Ralph S. Webber
Original assignee: Olin Corporation
Priority date: 1988-09-01
Filing date: 1989-08-30
Publication date: 1990-03-22
Also published as: AU4205889A

Abstract

Chlorine bleaching granules for colored fabrics which minimize fabric dye attack and fabric damage. This is accomplished in a bleaching granule for preventing dye attack of fabrics during bleaching, the granule comprising an alkali metal chloroisocyanurate and a buffering agent where the active alkalinity of the granule is from about -0.5 to about 0.

Description

CHLORINE BLEACH COMPOSITIONS WITH REDUCED FABRIC DYE ATTACK

This invention relates to chlorine bleaching granules for colored fabrics which minimize fabric dye attack and fabric damage.

Chlorine bleaches are known for their ability to economically remove unwanted stains from fabrics. However many fabric dyes are unstable in high concentrations of chlorine bleaching agents and experience a shift in color and/or a loss of color. Further, natural fabrics such as cotton and wool can be damaged by high chlorine concentrations.

To control the release of chlorine from chlorine-containing bleaching agents such as alkali metal dichloroisocyanurates, bleach particles have been coated or encapsulated with a variety of materials.

U.S. Patent 3,112,274, issued November 26, 1983 to J. H. Morgenthaler et al teaches a process for coating particles of polychlorocyanurate with inorganic salts. Dry particles of the polychlorocyanurate in a fluidized bed are sprayed with inorganic compounds including sulfates, phosphates, borates, and carbonates, to produce coated particles having a weight ratio of coating material to polychlorocyanurate of 1:3 to 5:1. In a related process, R. B. Hudson in U.S. Patent 3,650,961, issued March 21, 1972, teaches spraying an aqueous slurry of core particles of a chlorocyariurate into a fluidized bed of hydratable, particulate inorganic salts.

More recently, hard spherical bleaching particles were formed of an agglomerated mixture containing an alkali metal dichloroisocyanurate, an alkali metal tripolyphosphate and a binding agent, having a melting point in the range of 85° to 125°F, such as soap or- a fatty acid, i.e. lauric acid. The particles produced are encased in the binding agent which, as taught in U.S. Patent 4,707,160, issued November 17, 1987 to K. W. Chun et al, represents 10 to 30 percent by weight of the particle.

While the above references teach coated bleach formulations which are said to prevent pin holing and other severe attacks to fabrics when used in laundry applications, there is no teaching of preventing or minimizing dye attack under conditions of direct contact with high concentrations of the bleaching particles. Now it has been found that dye attack and fabric damage can be effectively prevented or minimized by controlling the active alkalinity of the bleach component.

These and other advantages are accomplished in a bleaching granule which comprises an alkali metal chloroisocyanurate and a buffering agent wherein the active alkalinity of the granule is from about -0.5 to about 0.

More in detail, the novel composition of the present invention includes as the bleaching agent an alkali metal dichloroisocyanurate. Suitable alkali metal dichloroisocyanurates include, for example, sodium dichloroisocyanurate and hydrates thereof, potassium dichloroisocyanurate and hydrates thereof, and mixtures of these alkali metal dichloroisocyanurates. Any suitable amount of the alkali metal dichloroiso¬ cyanurates may be used in the granules. For example, the granules may contain from about 10 to about 90 percent by weight of the alkali metal dichloro¬ isocyanurates.

The second component of the novel composition of the present invention is a buffering agent. Suitable buffering agents are alkaline compounds which are water soluble and have an active alkalinity, expressed as percent Na_0, in the range of from 0 to about +10. Examples of these buffering agents include dialkali metal phosphates such as disodium or dipotassium phosphate, tetraalkali metal pyrophosphates including tetra sodium or tetra potassium pyrophosphate, alkali metal tripolyphosphates and hydrates thereof, alkali metal bicarbonates, alkali metal tetraborates and hydrates thereof, and mixtures thereof. Preferred as buffering agents are those alkaline compounds having an alkalinity in the range of from about 0 to about +5. Alkali metal bicarbonates and alkali metal tripolyphosphates are exemplary of the preferred embodiments of the buffering agents.

The novel granular composition of the present invention containing a buffering agent having an active alkalinity in the range of 0 to +5 may include amounts of the buffering agent up to about 90 percent by weight of the granule, and preferably from about 10 to about 50 percent by weight of the granule. Where the buffering agent has an active alkalinity in the range of from about +5 to about +10, suitable amounts include those up to about 25 percent by weight of the granule. Up to about 10 percent by weight of the granule may be provided by alkaline compounds having an alkalinity in the range of +10 to about +15 such as liquid alkali metal silicates.

Similarly, acidic buffering agents having alkalinities in the range of from about -25 to about 0, for example, mono-alkali metal phosphates such as monosodium phosphate or weak organic acids such as citric acid, may be incorporated in the granules in amounts up to about 5 percent by weight. Additional components which may be incorporated in the granules include neutral salts such as alkali metal chlorides or alkali metal sulfates.

As used in the specification, the active alkalinity (or free alkali) of buffering agents and other components of the bleaching granule is expressed as the percent of Na_0 and may be determined by known methods such as the procedure in section 21 of Method D460-84 of the American Society for Testing Materials. The granular composition of the present invention may be produced in any suitable manner which homogeneously incorporates the alkali metal dichloroisocyanurate and the buffering agent. For example, in one method the dry ingredients are thoroughly mixed and compacted using compacting methods such as tabletting, briquetting or chilsonating. The compacted forms are milled or crushed and the granules produced screened to provide particles which suitably dissolve when added to a washing machine or are comparable in size to any detergent compositions with which they may be admixed. When used, for example, in commercial or home washing machines, the novel bleaching granules of the present invention may be added separately or admixed with detergent compositions containing surfactants, soaps, builders, enzymes, and filler materials, among others.

Bleaching granules of this invention are employed in amounts which provide a wash solution with from about 10 to about 200 parts per million of available chlorine for white fabrics. For colored fabrics, suitable amounts are in the range of from about 10 to about 50 parts per million.

When dissolved in water, a solution of the bleaching granules of the present invention has a pH which is generally in the range of from about 7.4 to about 8.5.

The following examples will more fully illustrate embodiments of the invention without being limited thereby. All parts and percentages referred to herein and in the appended claims are by weight unless otherwise indicated.

3326C

EXAMPLES 1-12

Blends of sodium dichloroisocyanurate dihydrate, the buffering agent, and any additional additives were obtained as particles less than 60 mesh (U.S. Sieve - 250 microns). These blends were well mixed and compacted into 3 to 5 gram tablets using a Carver laboratory hydraulic press and 1-inch diameter molds. The tablets were crushed and coarse ground using a ceramic mortar and pestle, then sieved through a 16 mesh (U.S. Sieve - 1190 microns). Material remaining on the screen was reground and resieved. Material passing through the 16 mesh screen was sieved through a 60 mesh screen. Granules remaining on the 60 mesh screeen were retained as final product. Material passing through the 60 mesh screen was retabletted, reground, etc. The process was repeated until 90 to 95 percent of the starting material was converted to -16/+60 mesh granules.

The granules were mixed with water at 40°C. to form pastes having an available chlorine concentration of 140,000 ppm (Procedure 21, ASTM D460) . The pastes were applied to 3" x 3" swatches of 100 percent cotton denim which had been dyed indigo and allowed to stand 90 seconds. The swatches were then rinsed with warm water and allowed to dry. The change in brightness of the treated swatches was measured and CIE (Commission International de l'Eclairage) L*a*b values determined using a Hunterlab ColorQUEST model 1200CQ Spectrocolorimeter coupled to an IBM-XT computer and calibrated to a D65 illuminate and 10° observer angle. The results for bleaching granules providing a minimum color shift and minimum color lightening is given in Table I below. TABLE I

Examples

Component (% by wt.) J_ a Ji_¬ ll 12

Sodium dichloroiso¬ 90 75 90 50 10 75 10 90 50 75 56 86 cyanurate dihydrate

Disodium phosphate 10 25

Sodium bicarbonate 10 10 90 25 19

Sodium tripolyphosphate 15 25 10 15

Sodium metasilicate 10 10

Sodium sulfate 21.2 80 21.65 25 25

Monosodium phosphate 3.8 3.35

Sodium tetraborate . lOE.2O 14

Active alkalinity -0.36 -0.30 -0.27 -0.22 -0.20 -0.20 -0.13 -0.12 -0.10 -0.07 -0.05 0.00

Change in brightness 5.34 10.39 5.83 5.16 1.74 8.28 6.85 8.62 3.27 3.28 5.11 10.59 pH 7.70 8.05 7.52 8.58 7.79 8.41 7.99 8.00 8.42 7.75 7.69 8.16

Claims

WHAT IS CLAIMED IS:

1. A bleaching granule characterized by an alkali metal dichloroisocyanurate and a buffering agent wherein the active alkalinity of the granule is from about 0 to about -0.5.

2. The bleaching granule of claim 1 characterized in that the buffering agent has an active alkalinity in the range of from about 0 to about +10.

3. The bleaching granule of claim 2 characterized in that the buffering agent is selected from the group consisting of dialkali metal phosphates, tetraalkali metal pyrophosphates, alkali metal tripolyphosphates and hydrates thereof, alkali metal bicarbonates, alkali metal tetraborates and hydrates thereof, and mixtures thereof.

4. The bleaching granule of claim 1 characterized in that the alkali metal dichloroisocyanurate is present in the granule in amounts of from about 10 to about 90 percent by weight.

5. The bleaching granule of claim 4 characterized in that the alkali metal dichlorocyanurate is sodium dichloroisocyanurate and hydrates thereof.

6. The bleaching granule of claim 5 characterized in that the buffering agent has an active alkalinity in the range of from about 0 to about +5.

7. The bleaching granule of claim 6 characterized in that the buffering agent is present in the granule in amounts up to about 90 percent by weight.

8. The bleaching granule of claim 7 characterized by incorporating a neutral salt selected from the group consisting of alkali metal chloride, alkali metal sulfate, and mixtures thereof.

9. The bleaching granule of claim 7 characterized in that the buffering agent is an alkali metal bicarbonate.

10. The bleaching granule of claim 7 characterized iri that the buffering agent is an alkali metal tripolyphosphate.

11. The bleaching granule of claim 5 characterized in that the buffering agent has an active alkalinity in the range of from about +5 to about +10 and is present in amounts up to about 25 percent by weight of the granule.

12. The bleaching granule of claim 5 characterized in that a liquid alkali metal silicate having an alkalinity in the range of from about +10 to about +15 is present in amounts up to about 10 percent by weight of the granule.

13. The bleaching granule of claim 5 characterized in that an acidic buffering agent having an alkalinity in the range of from about -25 to about 0 is present in an amount up to about 5 percent by weight of the granule.

14. The bleaching granule of claim 8 characterized in that the neutral salt is an alkali metal sulfate. -il¬

ls. A process for producing bleaching granules characterized by: : a) blending particles of an alkali metal dichloroisocyanurate and a buffering agent to form a homogeneous mixture, b) compacting the homogeneous mixture to provide compacted forms, and c) crushing the compacted forms to produce granules.

16. The process of claim 15 characterized in that the compacting is selected from the group consisting of tabletting, briquetting or chilsonating.