Field of the Invention

This invention relates to a bleaching composition for fading an at least partially non- synthetic fabric. The bleaching composition is used nonaqueously to produce a faded look to a garment. More particularly, the bleaching composition contains a castable cementitious material such as plaster, activated with a bleaching agent, wherein the composition is prepared by mixing the plaster, the bleaching agent and the water and allowing it to set in molds. Following release from the molds, the cast, bleach impregnat¬ ed plaster, is dry tumbled with the fabric to be faded.

Background of the Invention

Potassium permanganate (KMnO^, the preferred active bleaching ingredient in the bleaching composition, is an odorless, dark purple salt, forming crystals or granules with a blue metallic luster and a sweetish, astringent taste. It is soluble in water (to about 6% at room temperature), decomposed by alcohol, acids and many organic solvents and reducing agents. It is used in water treatment, waste treatment, air pollution treatment, in the metal plating industry, and in processing food. In the textile industry it is used to prevent wool felting and to improve the wool's luster, strength and level dyeing character¬ istics, and as an oxidizing agent to bleach cotton, rayon, and jute.

Industrial plasters and gypsum cements are the preferred castable cementing agents. The term "cementing agent" as used herein is to be construed broadly to mean a dry powder made from silica, alumina, lime, iron oxide, gypsum, clay, magnesia or the like, which hardens when mixed with water.

Plaster has been used for thousands of years in model and mold making. The term "plaster" once referred only to "plaster of paris", but is now used to describe a variety of materials in the calcium sulfate family as set forth more fully below and in the referenced documents. Today, it is also used for tool making and molding in the aircraft, automo¬ tive, foundry and plastic industries. Both wet and dry blending are done with various chemicals, powders and granular materials for a variety of purposes. These include: talc, kaolin, ball clay, perlite, sand, vermiculite, wood fiber, foam, glass/polymer fibers, iron oxide, resins, asphalt, starches, dyes, pigments, polymers, and powdered glue.

However, plaster has not heretofore been used in the garment treatment industry to fade dyed fabrics.

The term "cement" generally means any material used to bind other materials together; however, it is most often used to describe any powdery material which, when mixed with water into a plastic state, will harden in place and in so doing act as a binder between other materials such as between particles of sand and gravel in concrete. Portland cement is the most widely used type of cement.

Cement, when known as portland cement, is a gray powder that when mixed with water and allowed to stand will "set" to rocklike hardness. Cement makes up about 20%

of concrete, the remainder being aggregate. As is generally known to persons skilled in the art of plaster casting, from 75 to 80% of the raw material for cement manufacture is limestone, which yields lime (CaO); the rest is clay or shale, which yields silica (SiO^, alumina (AI ₂ O _g ), and iron oxides. A few impure limestones contain all of these oxides in just the right proportion and can be used alone.

Gypsum is a whitish mineral which occurs naturally in sedimentary rocks and which, after special processing, hardens when mixed with water. It is used as the main ingredient in Plaster, Gypsum Board, and similar products. It is not suitable for exterior use since moisture causes deterioration of its cementing capability. Chemically, gypsum is hydrous calcium sulphate having the approximate chemical formula CaSO ₄ ^* 2H ₂ 0, having a water content of about 20%. In manufacture, about three-fourths of this chemically combined water is removed from the gypsum rock by means of a controlled calcining (burning to powder) process. In the case of plaster, water is added at the job site, just prior to application, thereby causing the material to crystallize (set) and thereby revert to ^' its original chemical composition.

The gypsum of commerce is a white to gray sedimentary rock composed of the mineral gypsum, which is hydrous calcium sulfate (CaSO ₄ ^■ 2H ₂ O). Beds commonly occur between strata of dolomite or shale. A related material, anhydrite (CaSO,,), is present in some deposits. Small amounts of crude gypsum are used in portland cement to retard the setting time, but at least 90% of gypsum is converted to plaster. After quarrying and crushing, the gypsum is heated (calcined) to ~17§C, at which temperature it loses 75% of its combined water. The resulting hemihydrate, or plaster of Paris, is finely ground, mixed with water, and spread, cast, or molded. It sets to a dense, rocklike mass of intergrown crystals. Gypsum plaster may also be mixed with a fine aggregate, such as sand or expanded periite, and applied as an interior coating to concrete block, lath, or other backing.

To form plaster, gypsum is finely ground and calcined to produce a powder with uniform chemical and physical properties. In manufacturing the powder, a portion of the chemically controlled water is removed by calcination, as indicated by the following reaction:

CaSO ₄ ^• 2H ₂ O + heat— CaSO ₄ ^■ i H ₂ O + 11 H ₂ O

[gypsum] [plaster]

Since this reaction is reversible, adding water to plaster forms gypsum as follows: CaSO ₄ ^• H ₂ O + 11 H ₂ O — CaS0 ₄ ^• 2H ₂ O + heat

[plaster] [gypsum]

Industrial plasters and gypsum cements differ chiefly in the size and shape of crystals formed during the manufacturing process. This difference in crystalline structure

has the following effects: industrial plasters require 65 to 160 pounds of water per 100 pounds of plaster to make a workable slurry; gypsum cements require 22 to 45 pounds of water to gain good workability. Products using the smallest amounts of water set up to form a harder, stronger and denser solid. Both plasters and gypsum cements come in a variety of species, which vary in their consistency (parts of water by weight per 100 parts of plaster by weight), setting time, hardness, percent expansion, compressive strength, density, resistance to water absorp¬ tion and workability. These products and their characteristics are set out more fully in a U.S. Gypsum Company publication IG-504, available from U.S. Gypsum, 101 South Wacker Drive, Chicago, Illinois 60606. Publication IG-504 is incorporated herein by reference.

The present nonaqueous method for bleaching at least partially non-synthetic textiles, such as cotton denim, to produce a faded look, uses a bleaching solution made up of an active agent such as a 1 - 10% solution of potassium permanganate or up to 14% sodium hypochlorite soaked in volcanic rock or pumice. This is the "stone-wash" method. The volcanic rocks are about 2 inches in diameter, which reduce in diameter when used to about \ inch. They are made up of a hard silica with sharp edges and abrade the work piece. Before the fabric is placed into the tumbler, it must be pre- washed to remove the starch and excess dye and then dried or left damp. This is called desizing. It is done with a commercially available enzyme stripper. The bleach activated rocks are put into a tumbler with the garments and tumbled for 15 - 60 minutes, depend¬ ing upon the look required.

In addition to the abrasive nature of pumice, 10 - 20% "seconds" result when the bleach activated rocks "burn" holes in the damp fabric. The stone-wash method is expensive because the rocks get ground up as they collide with each other, the tumbler, and the fabric. Tests results show that this method reduces the tensile strength of the denim when compared to using the activated cement casts as disclosed herein. Furthermore, expensive stainless steel cylinders are required to withstand the pounding. As many as 10 - 15% of the garments treated are rejected as seconds due, in part, to "hot spots" or large, white, bleached-out spots where the denim doesn't look uniform. This occurs when an individual rock gets jammed up against a fabric and is not allowed to circulate but remains in contact with the piece of fabric for an extended period of time. In addition, inconsistent results occur when comparing one batch of fabric to a second batch for the same machine. The weight of the rocks can overload the machines. To achieve the looks set forth in Table II, 11 to 6 pounds of impregnated pumice per pound of garment is required. The disclosed composition produces the same look with

to 1 pounds of composition per pounds of garment. Further, the abrasion of the volcanic rocks reduce the useful life of the drum.

U.S. Patent Application No. 07/117,664 (of which this application is a continuation in part) filed November 5, 1987 discloses a bleaching composition comprising a powder carrier activated with a bleaching agent such as a potassium permanganate solution, which composition is used to "dry-tumble" with a dyed fabric to produce a faded look.

U.S. Patent No. 4,740,213 (April 26, 1988, Francesco Ricci) discloses a method in which cloth to be faded is brought into dry contact with pumice granules that impreg¬ nated with a chemical bleaching agent such as hypochlorite. This is the stone wash method described above.

U.S. Patent No. 4,243,391 (Puchta, et al) relates to a method for bleaching washed textiles in a laundry drier with an aqueous solution of hydrogen peroxide and a guaternary ammonium salt. The textiles are subject to mechanical agitation and hot air flow at a temperature of 55°C to 80°C for at least 5 minutes. U.S. Patent No. 1,533, 917 (Kaiser) relates to a process of bleaching fabrics which involves impregnating a first sheet (e.g. blotting paper) with oxalic acid and a second sheet with sodiuπv bisulfite. The fabric is placed between the first and second sheets and bleached by gaseous sulfur dioxide liberated from the second sheet upon contact with an aqueous acidic stream. U.S. Patent No. 4,575,887 (Viramontes) discloses a method for abrading fabrics in a washing machine with small sized pumice sand particles.

U.S. Patent No. 4,391,723 (Baron, et al) discloses a controlled release bleach product which is contained within a polyester pouch.

U.S. Patent No. 3,048,546 (Lake, 1962) reveals a bleaching compound which is a solid composition of monopersulfate with a chloride salt used to increase the bleaching and cleansing actions of the monopersulfate (the active ingredient). It also discloses an "abrasive filler" of ground quartz flour, sodium tripolyphosphate, detergent and a perfume. The monopersulfate is used as the active ingredient in a bleaching compound, a bleach¬ ing and scouring composition, and a cleanser for hard-to-remove stains from porcelain sinks and bowla

U.S. Patent No. 4,655,953 (Oakes, 1987) discloses a detergent bleach made up of peroxide, a manganese, and a sodium salt having a specified pH range. The composi¬ tion is prepared to launder and bleach stained or soiled fabrics in a liquid at relatively low temperatures. Oakes' invention combines peroxide bleach and manganese, rendering the bleach effective for bleaching at lower temperatures if the pH range is proper.

U.S. Patent No. 4,130,392 (Diehl et al, 1978) discloses a "dry bleaching" method for bleaching (without use of an aqueous bath) in which damp fabrics are placed in a

dryer with a dry, activated bleaching composition. The method discloses a solid peroxygen bleach activated by certain additives and employed in an automatic dryer to remove stains under heat. The Diehl patent presents a method for removing stains from fabric using an automatic dryer and commingling pieces of damp fabric by tumbling under heat, together with an effective amount of a particular bleaching composition, preferably contained in a porous, polyurethane pouch.

Summary of the Invention

It js the purpose of this invention to overcome the problems that arise during the nonaqueous bath bleaching ("dry bleaching" or "dry tumbling") of an at least partially nonsynthetic fabric. Briefly stated, it is the purpose of this invention to provide activated cement casts which will uniformly and consistently fade the fabric when tumbled there¬ with. It is to be understood that the term "activated" is to be construed broadly to mean combined with a bleaching agent capable of dying an at least partially nonsynthetic dyed fabric, e.g. cotton denim.

It is the further object of this invention to provide for a bleaching composition comprised of a bleaching agent mixed with a castable material, e.g. plaster or gypsum cement.

It is the further object of this invention to provide a cement and bleaching agent mix to produce casts for use in a tumbler with an at least partially nonsynthetic dyed fabric, to produce uniform and consistent fade.

It is a further object of this invention to provide for a method of mixing and preparing the casts and for a method of using the casts to fade an at least partially non- synthetic dyed fabric. Other advantages of this invention are set below as part of the specifications, or will be apparent therefrom.

Brief Description of the Photographs

Fig. 1 illustrates blue denim faded with one embodiment of the claimed composi- tion.

Fig. 2 illustrates blue denim faded with a second embodiment of the claimed composition.

Fig. 3 illustrates blue denim faded with a third embodiment of the claimed composi¬ tion. Fig. 4 illustrates unbleached new blue denim and is included for comparison.

Description of the Preferred Embodiment

The compositions, the mix and the methods herein described are used for fading, bleaching or removal of dye from an at least partially nonsynthetic fabric to change its color and/or appearance by "dry bleaching" or "dry tumbling" as more fully described below.

The garment work piece is usually faded by the manufacturer before sale to the public. A number of different effects may be achieved such as: "frost" look (for cordu¬ roy), "cracked" look, "ice" look (few or no "cracks" with very low contrast between cracks and background), black sky effect ("ice" look on black dyed fabric), or "bright white" effect (uniform white background also called a "super ice" look). Each look differs from the others in the extent of fade, the uniformity of fade and the presence or absence of "cracks" (weblike, Ughter colored streaks), and in the amount of contrast between the color of the cracks and the background color. They all differ from the undyed fabric - Fig. 4 (blue denim), which is included for comparison. This description will be segregated into three parts: the make up of the various bleaching compositions, the manner in which the bleaching compositions are made, and the method for using the bleaching compositions to fade or bleach a fabric.

In general, the casts are produced by first mixing dry potassium permanganate or other bleaching agent and/or agents with water at or above room temperature to form a solution. The castable powder is then measured out by weight. The powder is then soaked and mixed with the solution, poured into molds and dried.

The preferred active bleaching ingredient in the compositions is potassium perman¬ ganate (KMnO^. This chemical is known in the art as a strong oxidizing agent and is useful to bleach fabrics. The potassium permanganate is dissolved in water. It is then mixed with the plaster, cement or other castable material, poured into molds and allowed to harden. Following this, the casts are removed and the cubes used to fade the fabric in a manner more fully set forth below.

A good general working knowledge of plaster and gypsum cements may be obtained from the United States Gypsum Company publication IG-453. That publication is incorporated herein by reference.

The following general comments will apply to all of the embodiments of the composition set forth below. The term "cube" or "pellets" will be used interchangeably to describe the end product of the mixing of the ingredients; the cast. These terms are not to be considered in a limiting sense as they describe merely one shape of mold used to cast the mix. In fact, a variety of shapes and sizes of molds may be used to produce individual "cubes", "pellets", "sticks", "stars", "blocks", etc.

The plaster can be worked in four main ways: mixed as a fluid slurry, it can be cast or sprayed; worked in a plastic state by screeding or template forming; pressed between dyes as a semi-wet powder; and carved or machined as a solid. The preferred embodiment of the composition uses the plaster mixed as a fluid slurry with a bleaching agent water solution (e.g., potassium permanganate). Compressive strength (and hardness), absorption, and density can vary depending upon the type of plaster used and controlling the amount of mixing water (as set forth more fully below).

An ideal plaster mix is one in which the plaster particles are completely dispersed in the water to produce a uniform, homogeneous slurry. Water used in mixing plaster should be as pure as possible - water that is drinkable is probably suitable for mixing plaster. The addition of bleaching salts, such as potassium permanganate, may result in efflorescence in which hard spots form on the cast surfaces, which results in variable absorption properties and finishing casts. However, this does not effect the use of the cast produced for the purposes of fading a dyed textile. Gypsum has a maximum solubility between 70° and 100° Fahrenheit; variations in water temperature affect setting time, and can cause difficulty in control of mixing time.

The water to plaster ratio (consistency) is the amount of water used with a definite amount of plaster. For example, a 70 consistency mix would mean 70 parts of water by weight per 100 parts of plaster by weight. Consistency is always specified by weight. When less water is used in a mix the setting time may be faster, and the plaster will not be as fluid, which may cause air bubbles in the cast pieces.

The density, hardness, strength, and durability of plaster casts are intimately related to the quantity of water used in the mix. The harder the pellet or cube produced, the more durable it is in the dry tumbling process, and the less loss results. Therefore, it is important that the recommended solution (water) to plaster ratio be followed for best results.

Soaking removes air and allows each plaster particle to be saturated with the solution, making it easier to disperse during mixing. Always add plaster to the liquid (not liquid to piaster) to avoid excessive air entrapment. The plaster will slowly sink into the solution and become almost completed wetted after 30 seconds to 2 minutes. It is then ready to be mixed.

Mixing the plaster slurry is the most important step in producing plaster casts with maximum strength, hardness and other important properties. Mixing disperses plaster particles in the water. The strength of the plaster is directly related to mixing, since there is a direct relationship between energy input during mixing and the strength developed in the cast. Where, as here, high strength is a consideration, longer mixing times are desirable. However, care must be taken not to mix into the setting stage of the plaster

since this decreases strength. Generally, the batch size should be controlled so as to permit pouring to be completed within 5 minutes after the slurry has been mixed. To mix plaster properly for uniform casts, follow these steps: 1. Weigh plaster and solution accurately for each mix. 2. Follow timed soaking and mixing cycles.

3. Use a mechanical mixer and mixing bucket of proper size and design.

Sift or strew plaster into water slowly and evenly. Allow plaster to soak 1 to 2 minutes. Then mix as required - generally 30 seconds to 2 minutes - to obtain a creaming of the slurry. When mixing batches over 5 pounds, it is best to use mechanical mixing. A high speed, direct drive propeller mixer with a mixing shaft set at an angle of 15° from the vertical is preferred. The propeller should clear the bottom of the container by 1 inch - 2 inches and the shaft should be about halfway between the center and side of the container. Propeller rotation should force mix downward. The equipment should be kept clean to avoid accelerated setting of the plaster. Use the following as a guide.

For small batches (up to 50 pounds slurry): J or 1/3 horse power direct drive 1750 rpm motor, 3 inch, 3 blade, 25° pitch propeller. For medium batches (50 - 100 pounds slurry): i horse power direct drive 1750 rpm motor; 4 inch or 5 inch, 3 blade, 25° pitch propeller. Other methods of mixing, such as continuous mixing, are described more fully in United States Gypsum Company publication IG-543.

Once the mix begins to cream and set up, it should be poured into the molds. Molds can be made of a variety of materials - either plastic or flexible molds. Preferred molds are flexible. Flexible molds may be made of gelatin, latex, coal compounds, hot melt, polysulfide, urethane elastomers and other materials having good strength and elas- ticity.

The plaster casts should be dried following pouring. They may be air dried. In the preferred embodiment, the pellets or cubes are air dried. In alternate embodiments, they may be placed into a burner to dry at a temperature below that which will calcine the cast (generally, about 115°F). The calcination temperatures for the various plaster and gypsum cement mixes are set forth in the above referenced publication.

In general, a i- 10% solution of potassium permanganate is prepared. The 6% potassium permanganese solution represents saturation at room temperature. A pellet made from a 6% potassium permanganese solution is more active than one of a lower percentage. Activity of a pellet may be further increased by adding solid potassium permanganese crystals to the plaster before combining with the solution.

An example of an active pellet composition is one prepared by combining the following:

1. 16 pounds of 6% potassium permanganate solution, premixed;

2. 24 pounds of United States Gypsum Company No. 1 pottery grade plaster;

3. 1.6 pounds of industrial grade, free flowing potassium permanganate (pp) crystals, sifted into the piaster. After strewing the plaster and potassium permanganese crystals into the solution and soaking for about 2 minutes in a 5 gallon pail, the mix is mechanically mixed for about 60 seconds until a good consistency is reached. The mix is then poured immedi¬ ately into flexible molds shaped generally like ice cubes and allowed to set up or "cure" for approximately 12 minutes. Following curing, the molds are inverted and the individual cubes knocked out with rubber mallets or the like.

The table below summarizes the various combinations of cement and bleaching agents tested. As can be seen from the table, solution strength ranged from 1% to 6% for potassium permanganese mixed in consistency range of about 50 to 60. However, consistency may range from 30 - 80 (producing a harder to softer pellet, respectively). Another plaster cementing agent is HYDROCAL gypsum. HYDROCAL is the registered trademark of United States Gypsum Company and is in the Calcium Sulfate family. Low expansion HYDROCAL such as HYDROCAL A-ll contain 3 - 8% Portland cement. HYDRO-STONE, a super-strength HYDROCAL contains 2 - 55% portland cement, but with a higher proportion of portland cement (above 10%), reactions with the potassium permanganate solution may occur.

TABLE l-A illustrates the use of specific members of the United States Gypsum Company plaster "family." The complete family and the members' physical characteristics may be found in publication IG-504 on pages 5 - 7. The solutions are prepared and combined with the dry mix at room temperature, as set forth above. The consistencies illustrated are close to the minimum, but which allow the mixing of the composition as a slurry. The pellets illustrated in TABLE l-A are softer than those illustrated in Table ll-A, the gypsum cement "family."

In TABLE l-A compositions, 3 and 3a, and 6 and 6a are produced with the same concentration of bleaching agent but different mixing procedures. In examples 3 and 6, the solution is prepared then combined with the dry mix. In 3a and 6a, the potassium permanganese powder or crystals is combined with the dry mix, which is then combined with water. In the former, the pellet produced is more active, producing a greater degree of fade even though the concentration of potassium permanganese is the same. In 10a, the effect is similar, but one is starting with a saturated solution of potassium perman- ganese and combining it with the plaster-potassium permanganese dry mix.

TABLE l-A

PART A PART B PART C

Solution Total Dry Mix Total Total

Example l-^O Mn0 ₄ Part A Powder KMnO, Part B A + B

1 13.86 .14 14.00 26.00 0.00 26.00 40.00

2 13.72 _28 14.00 26.00 0.00 26.00 40.00

3 13.58 .42 14.00 26.00 0.00 26.00 40.00

3a 13.58 0.00 13.58 26.00 .42 26.42 40.00

4 13.44 .56 14.00 26.00 0.00 26.00 40.00

5 13.30 .70 14.00 26.00 0.00 26.00 40.00

6 13.16 .84 14.00 26.00 0.00 26.00 40.00

6a 13.16 0.00 13.16 26.00 .84 26.84 40.00

7 13.16 .84 14.00 26.00 .40 26.40 40.40

8 13.16 .84 14.00 26.00 .80 26.80 40.80

9 13.16 .84 14.00 26.00 1.20 27.20 41.20

10 13.16 .84 14.00 26.00 1.60 27.60 41.60

10a 13.16 0.00 13.16 26.00 2.44 28.44 41.60

11 13.16 .84 14.00 26.00 2.00 28.00 42.00

12 13.16 .84 14.00 26.00 2.40 28.40 42.40

13 13.16 .84 14.00 26.00 2.80 28.80 42.80

14 13.16 .84 14.00 26.00 3.20 29.20 43.20

15 13.16 .84 14.00 26.00 3.60 29.60 43.60

16 13.16 .84 14.00 26.00 4.00 30.00 44.00

17 13.16 .84 14.00 26.00 4.40 30.40 44.40

18 13.16 .84 14.00 26.00 4.80 30.80 44.80

19 13.16 .84 14.00 26.00 5.20 31.20 45.20

20 13.16 .84 14.00 26.00 5.60 31.60 45.60

21 13.16 .84 14.00 26.00 6.00 32.00 46.00

22 13.16 .84 14.00 26.00 6.40 32.40 46.40

23 13.16 .84 14.00 26.00 6.80 32.80 46.80

24 13.16 .84 14.00 26.00 7.20 33.20 47.20

The plaster used in TABLE l-A is preferably one of the following: #1 Pottery Plaster, Industrial Plaster PC, Puritan Pottery Plaster, #1 Casting Plaster, or Molding Plaster.

The following TABLE l-B illustrates the use of specific members of the United States Gypsum Company family of gypsum cements. The members of this family are listed on the referenced pages of IG-504. These may be mixed in a lower consistency than illustrated to produce a harder pellet.

TABLE l-B

PART A PART B PART C

Solution Dry Mix

Total Gypsum Total Total

Example H.0 KMnO, Part A Cement KMn0 ₄ Part B A + B

1 11.88 .12 12.00 28.00 0.00 28.00 40.00

2 11.76 .24 12.00 28.00 0.00 28.00 40.00

3 11.64 .36 12.00 28.00 0.00 28.00 40.00

3a 11.64 0.00 11.64 28.00 .36 28.36 40.00

4 11.52 .48 12.00 28.00 0.00 28.00 40.00

5 11.40 .60 12.00 28.00 0.00 28.00 40.00

6 11.28 .72 12.00 28.00 0.00 28.00 40.00

6a 11.28 0.00 11.28 28.00 .72 28.72 40.00

7 11.28 .72 12.00 28.00 .40 28.40 40.40

8 11.28 .72 12.00 28.00 .80 28.80 40.80

9 11.28 .72 12.00 28.00 1.20 29.20 41.20

10 11.28 .72 12.00 28.00 1.60 29.60 41.60

10a 11.28 0.00 11.28 28.00 2.32 30.32 41.60

11 11.28 .72 12.00 28.00 2.00 30.00 42.00

12 11.28 .72 12.00 28.00 2.40 30.40 42.40

13 11.28 .72 12.00 28.00 2.80 30.80 42.80

14 11.28 .72 12.00 28.00 3.20 31.20 43.20

15 11.28 .72 12.00 28.00 3.60 31.60 43.60

16 11.28 .72 12.00 28.00 4.00 32.00 44.00

17 11.28 .72 12.00 28.00 4.40 32.40 44.40

18 11.28 .72 12.00 28.00 4.80 32.80 44.80

19 11.28 .72 12.00 28.00 5.20 33.20 45.20

20 11.28 .72 12.00 28.00 5.60 33.60 45.60

21 11.28 .72 12.00 28.00 6.00 34.00 46.00

22 11.28 .72 12.00 28.00 6.40 34.40 46.40

23 11.28 .72 12.00 28.00 6.80 34.80 46.80

24 11.28 .72 12.00 28.00 7.20 35.20 47.20

The gypsum cement used in the composition illustrated in TABLE l-B is preferably one of the following: HYDROCAL White, or Statuary HYDROCAL.

TABLE l-C illustrates compositions which contain bleaching agents from the chlorine family. In Example 1, one of the following bleaching agents are used, the active ingredient being s-tria zinetriones: ACL 59, ACL 60, and ACL 90, or calcium hypochlo¬ rite. A dry mix is prepared which is then combined with water. In Example 2, the 15% bleach is a 15% sodium hypochlorite solution. The sodium hypochlorite is mixed with the water, then the dry mix added thereto.

TABLE l-C

PART A PART B PART C

Solution Dry Mix

15% Total Total Total

Example HjO Bleach Part A Plaster Oxidizer Part B A + B

1 9.60 0.00 9.60 24.00 6.40 30.40 40.00

2 3.20 6.40 9.60 24.00 0.00 24.00 33.60

The plaster used in the preparation of the composition listed in TABLE IC is preferably one of the following: #1 Pottery Plaster, Industrial Plaster PC, Puritan Pottery Plaster, #1 Casting Plaster, or Molding Plaster.

The Oxidizer used is preferably one of the following: ACL 59, ACL 60, ACL 90, Calcium Hypochlorite, or Sodium Chlorite.

Soak time for all of the above compositions is 1 - 2 minutes, mix time is 30 seconds to 2 minutes and the mold shapes are } inch to 2 inch round or cubes. The drying time is about 10 to 15 minutes.

The following chemicals may be substituted in any of the compositions for potassi- um permanganese: sodium hypochlorite, calcium hypochlorite, ACL 90+, 60, 59, or 56. ACL is the registered trademark of Monsanto Industrial Chemicals Company. The ACL compounds are a source of dry, stable, available chlorine for use in bleaching. They are further described in publication MIC-5-030, available through Monsanto, which publication is incorporated herein by reference. In pouring the slurry into molds, a squeegee is handy to spread the mix into each mold until they are filled, with the excess scraped onto the adjacent mold sheet. The curing time will be determined by the size of the mold and the ambient temperature and humidity. In addition, it takes less time for the more active pellets to "set up" than the less active. If you try to knock the casts out of the molds before they are ready, they may crumble in the molds. Finally, instead of mixing a pourable slurry, a wet powder mix can be "stamped" into molds. In this manner, the consistency of the mix may be

decreased to about 30. When the pellets are made with the preferred methods, about 2.0% loss occurred between the mixing and the finished, bagged pellets.

Safely handling the compositions described above requires adherence to the following guidelines: do not get in eyes, on skin, on clothing; do not take internally; use with adequate ventilation and employ respiratory protection; when handling, wear chemical splash goggles, face shield, rubber gloves, and protective clothing; wash thoroughly after handling or contact; keep container closed; and keep away from acids (to avoid possible violent reaction).

Use of the Pellets in the Dry-Tumbling Process

In general, a preferred method of using the casts is to insert the garments into a tumbler with the casts and tumble for a period of time. The tumbling causes repeated contact between the pellets and the garments, thereby bleaching the dye out of the fabric.

There are a number of factors, the variation of which alter the degree of fade in a tumbled fabric. These factors include: the strength of the composition (activity), the moisture content of the fabric, the length of time that the garment is tumbled, the amount of pellets used, and the pH of the fabric. A hard pellet produces less "waste" as it decreases in size from one run to the next.

A softer pellet produces a "whiter" or more faded look but produces more loss. The user may also decrease extraction, increase tumbling time, or use more rock to get a whiter or more faded look.

If a fabric has a high or a low pH, it may inhibit the action of the bleaching agent used and may have to be neutralized in the prerinse before tumbling. The pH of most denim does not inhibit the bleaching action of potassium permanganate.

Probably the most frequent fabric which is the subject of bleaching is blue cotton denim, which is often prefaded by the manufacturer or contractor before it is sold to the public. This "faded" look is at present enjoying much popularity. Therefore, this discus- sion which sets forth a method of use of a bleaching composition is directed to such work piece.

Denim is usually prewashed in a soap or detergent to remove starch and other substances (desizing). Following the prewash, the wet garment is prerinsed in water and spun (extracted) for a period of time. This spinning extracts the rinse water from the garment. However, for certain faded looks the garment is removed from the rinse dripping wet (without any extraction), and directly inserted into the tumbler with the bleaching composition. When the tumbling begins with a saturated (nonextracted)

garment, more bleaching results (and produces a more faded garment). The extraction of water prior to placing the fabric in the tumbler decreases the amount of bleaching, if all other variables are kept constant. For example, differences in the garment's final appearance can be discerned between dripping wet (most faded) and a ten minute extraction, at one minute intervals therebetween. Preferably, a 15 second to 2 minute extraction is used for blue denim, to produce a uniform ice look.

For decreasing the "cracks" in the garment, a period of drying may be introduced following the extraction step. This will remove even more water than the extraction step.

It is helpful to shake out and lay flat or drape the garments following prerinse. This allows folds or creases to unfold before tumbling. Sometimes a folded garment will not unfold during tumbling, and the portion covered by the fold or crease will not receive enough bleaching.

The bleaching ability (activity) of the pellets is determined, in part, by their potassi¬ um permanganate content. Figs. 1 - 3 illustrate different looks achieved on blue denim (Fig. 4) with three different compositions from TABLE l-A prepared under the same conditions.

Depending on the size and weight of the garments, \ to 1 pounds of pellets per pound of garment is placed in the tumbler. For example, a medium weight garment, when tumbled with .75 pounds of a pound of pellet gives a faded look to the fabric. However, the same fabric tumbled with 1.50 pounds of pellets per pound of the same weight garment produces a more white look.

Garments are tumbled at ambient temperature for two to 30 minutes, again depending upon the extent of "fade" desired. The longer the tumbling period, the greater the fade - to a point. Test results indicate that almost all combinations produce their greatest effect within 20 - 30 minutes, regardless of the extraction of the garment.

The following Table II illustrates the use of the pellets in a dry tumbling process and the look achieved. Variation of the garments, pellets, extraction and tumble time will effect the look.

A number of mold shapes were used including: cubes with sharp edges about to 2 inches on a side; cubes with rounded edges, spheres, cylinders, and bullet shapes. Test results indicate that the shape of the pellet has a slight effect on the loss incurred per run. In a test run with 100 pounds of jeans and 100 pounds of new pellets in a tumbler for 20 minutes, a 20% loss in pellet weight resulted. Twenty pounds of new pellets were added to the 80 pounds of "used" pellets to do another run of jeans. The pellet used in this test is similar to Example 10 from TABLE l-B above.

The tumblers used to produce the stone wash look are designed to carry volcanic rocks with about a 2 inch length. Tumblers are commercial grade and capacity spin

TABLE II

Pellet

Composition Weight/ (Seconds) (Minutes)

Look Example Garment Garment Extraction Tumble

Achieved Table l-A Weight Tvoe Time Time

Fig. 2 r ark 1 1.15 Blue Denim 45 20

Fig. 3 4 1.15 Blue Denim 45 20

Fig. 1 Light 10 1.15 Blue Denim 45 20

washers, such as the Washex, or others known in the art. However, since water is not used during tumbling, that apparatus is usually disconnected. The pellets wear down as they are tumbled and the powder produced will escape through holes in the drum. Sometimes curved plates or other liners may be used, attached to the inside curvature of the carrier, to prevent loss of powder or produce a duller look.

Following tumbling, the garments are rinsed to remove the bleaching chemicals or detritus remaining on the fabric. The rinse is preferably done in a neutralizing solution or antichlor. One such neutralizing solution is prepared by mixing 70% sodium metabisulfite (the active neutralizer) and 30% sodium sulfite anhydrous and works effectively to neutralize potassium permanganate. Following neutralization, the garment is washed and rinsed. These two steps complete the removal of any foreign chemicals from the garment.

An Additional Preferred Embodiment Enzymes are a group of proteins which catalyze a variety of typically biochemical reactions. Enzyme preparations have been obtained from natural sources, such as bacterial or fungal sources, and have been adapted for a variety of chemical applications. Enzymes are classified based on the substrate target of the enzymatic action. The enzymes useful in this embodiment involve cellulase, which degrades cellulose, a high molecular weight natural polymer made of polymerized glucose. Cellulose is a major structural component of fibers used to produce textiles, including cotton, linen, jute, and rayon, among others.

Cellulase is the active ingredient of an aqueous based composition used to produce a stone wash look to denim fabric in U.S. Patents No. 4,832,864 (Olson 1989) and No. 4,912,056 (Olson 1990). That method differs from the present method in that it utilizes an aqueous bath containing the enzyme and into which the work piece is soaked and, optionally, mechanically agitated. In Applicants' invention the cellulase enzyme is

captured in a castable powder which is dry tumbled with the denim. No aqueous bath is needed or desired.

In place of the oxidizers described above, a cellulase enzyme may be used. The cellulase will attack the cellulose cotton fibers in the denim to create a look similar to a stone wash look. That is, the use of an oxidizer such as those disclosed above (potas¬ sium permanganate, etc.), produces more of an acid wash look while the use of a cellulase enzyme produces more of a stone wash look. Any of the castable powders listed above are suitable for combining with the cellulase enzyme. For example, Hydrocal 2000 can be combined with an aqueous solution containing cellulase enzymes and allowed to harden to produce an enzyme "nugget." Hydrocal /enzyme combinations in the range of 75-78% Hydrocal and 25-22% water-containing cellulase enzyme (10%) have produced a satisfactory stone wash type look when tumbled with denim fabric, but the strength of the enzyme concentration may be varied above or below these ranges. An example of the ratios used to prepare a 40-pound batch of 75/25 mix is as follows: 30 pounds of Hydrocal powder combined with a 10-pound premixed liquid portion made from mixing 4 pounds of cellulase enzyme with 6 pounds of water.

A source of liquid cellulase enzyme is "Rapidase GL" (a trademark of International Biosynthetic, P. O. Box 75436, Charlotte, North Carolina 28275, United States of Ameri¬ ca). A source of powdered cellulase enzyme is Novo Laboratories, Inc., P. O. Box 30955, Hartford, Connecticut 06150, United States of America, who manufactures the cellulase enzyme under the trademark "Denimax T." Another enzyme (powder) that is effective is Dytolase 300 by Genencor, 180 Kimble, S. San Francisco, California 94080, United States of America.

To make the enzyme pellets, follow the method as set forth above with the oxidizers, except the mix is usually stirred about twice as long before it begins to cream and set up. Then the mix is poured into the molds. The enzyme nugget generally sets up 4-5 times slower than the oxidizer nuggets, unless accelerators are used.

The method of tumbling the denim products with the cellulase based nuggets is similar to the method of tumbling the products with the oxidizer based nuggets. Howev- er, in the pre-rinse cycle (before the garments are tumbled with the enzyme nugget), an acid is added to bring down the pH of the garments to the 4.4 to 5.5 level, for more effective enzymatic action. Citric acid effectively serves this purpose. By reducing the pH of the garments to the 4.4 to 5.5 level, an enzyme can more effectively attack the cellulose based cotton fiber. A tumbling time of 10-30 minutes can be used and the amount of enzyme nuggets per unit garment weight can be varied to achieve different variations of the stone-wash look.

Following tumbling, the garments are rinsed to remove the chemicals or enzyme remaining on the fabric. However, in the preferred method of using the enzyme nugget, citric acid (or other acid) is added to the first post-wash rinse cycle to increase the effectiveness of the remaining cellulase in attacking the cellulose fiber. For example, about two ounces of powdered citric acid may be added per ten gallons of rinse water to effectively promote additional and enzymatic action during the first post-tumbling rinse cycle. This is optional, however, and the user may wish to forego the post-tumbling acidification.

The second and third rinse cycles are clear water rinses of about three minutes duration. Following this is a fourth post-tumbling cycle in which the garments are washed in a soap solution for approximately five minutes. Following the soap cycle is a fifth and sixth clear water rinse, approximately about two minutes' duration. Finally, there is a last post-tumbling clear water and softener rinse of three to four minutes' duration. Following the rinse cycle the garments are extracted and/or dried as further set forth in the method described above for use with the oxidizer based pellets.

Although the invention has been described with reference to a specific embodiment and method, this description is not meant in a limiting sense. Various modifications of the disclosed compositions and methods will become apparent to those skilled in the art upon reference to these specifications. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.