Background of the Invention

The present invention relates to commercial, printable and convertible paper, and certain specialty papers, made from fibers reclaimed from 100% cotton denim scrap material from clothing manufacturing as well as to paper pulps and methods for making such paper and pulps and in particular to such papers and pulps made from denim scrap that contains color dye.

In the United States alone, hundreds of millions of pounds of 100% cotton denim scrap (cloth from the manufacture of clothing) are stuffed into already choked landfills every year. Every million pounds of such denim scrap relegated to the dump represents a year's harvest from 1,000 acres of cotton. Thus, essentially, hundreds of thousands of acres of cotton are being plowed under in the United States every year along with the water and energy required to grow and harvest that equivalent quantity of cotton. When the entire world's disposal of denim scrap is accounted for, the numbers are staggering and the damage to the earth incalculable.

A relatively minuscule amount of this denim scrap has been used in the past and is being used today to make electrical insulating paper, gaskets, currency paper, and calender paper (from which burnishing calender rolls are made). The rest is treated as waste.

Cotton denim is a heavy, Z-twist cloth of the basic twill weave in which the filling threads are woven over one warp yarn and under two or more others (producing a diagonal pattern). Both the weave and the twisted threads that characterize cotton denim give it a toughness that has made it the material of choice for blue jeans, overalls and other clothing requiring durability. The world famous Levi's® jeans are all made of 100% cotton denim. Most denim used today to make clothing is made from premium grades of cotton which are particularly coveted in the making of paper.

Prior to the present invention, and in spite of the fact that for hundreds of years all paper was made from 100% cotton, cotton denim has never been considered a suitable material for the manufacture of printable, convertible papers and fine stationery. The conventional wisdom has always been that fibers reclaimed from 100% cotton denim would produce a paper unsuitable for printing and writing because it lacked essential characteristics, such as the porosity essential to receive ink. It was also believed that paper made from denim fibers could not be convertible into envelopes and other stationery products because its tough fibers would not permit folding and cutting on standard equipment. It is also the belief that dyed denim (such as that used to make blue jeans) requires such drastic processing (cooking) in caustic and bleach that the fibers would be too severely damaged to be usable to produce quality paper.

Based on these industry paradigms, fiber from denim scrap material has been used only to make paper for non-stationery and non-printing uses such as in the manufacture of calender rolls for burnishing paper and other materials. The toughness of the calender paper made from 100% denim makes it suitable for the abrasive work of calender rolls, but it is not printable or convertible paper and thus supports the paradigms that 100%

10 denim paper is not printable or otherwise suitable for stationery products. The use of denim to make paper gasket material where toughness and durability are the qualities required, further

- .- supports the belief that fine stationeries and the like cannot be made from reclaimed denim fibers.

Currency paper which is known to use fibers from cotton denim and which is printable, is a mixture of denim with other 0 cotton materials, such as cotton underwear cuttings and cotton linter (unspun cotton fibers from seeds). All denim fibers have never been used in currency paper in the belief that without the linter and other cotton rags the paper would not be printable or

25 able to absorb other chemicals (such as wet-strength additives). The present invention teaches how a wide variety of high quality printable and convertible papers can be made from reclaimed fibers from 100% cotton denim scrap material and

30 opens the way for hundreds of millions of pounds of denim scrap to be rescued from landfills, and converted into the same amount of

paper per million pounds of scrap that would otherwise require 8,000 thirty year-old trees. The potential exists from the present invention for saving more than a million mature trees a year in the United states alone.

In addition, the various paper products made according to the present invention from 100% cotton denim scrap material have qualities that make them superior to the same products made from wood pulp, wood pulp and cotton or other cotton or cotton blend materials.

The manufacture of paper has essentially remained unchanged since it was first made by Ts'ai Lun in China in 150 A.D. Woven cotton cloth (rag) is macerated to defiber the material and hydrated to form a pulp from which the paper is made. The pulp is applied to a mould (by either dipping or pouring) allowing the fibers to reform in an interlocking relationship into thin sheets as the pulp is dewatered and dried.

Over the centuries since the invention of paper, the major advances have been in the machines for making pulp from rag, in machines for making long lengths of paper from pulp, and in the use of chemicals in the making of pulp. It was discovered long ago that the maceration process for turning cotton rags into paper pulp was enhanced by the use of caustics, such as lye, soda ash and other alkaline chemical equivalents. The use of bleach (chlorine) was introduced in the 19th century to remove any coloration from the

original cotton rags or the water. It is now a standard industry¬ wide practice in making pulp for paper out of cotton scrap material to cook the material at elevated temperatures and pressures in caustic solutions and bleach to achieve as white - colorless- a pulp as possible. When paper other than white is to be made, color dyes are added to the bleached- white pulp. In addition to the cost that these chemicals add to the paper making process, they also pose an environmental hazard in the form of large quantities of toxic waste water.

All but a small fraction of the denim scrap from the manufacture of clothing is heavily dyed dark blue or black. This characteristic dark dye component is one more reason why scrap denim has been considered undesirable and thus overlooked as a suitable paper making material. The present invention includes paper pulps and methods for making paper pulps from denim scrap material; papers made from fibers reclaimed from denim scrap material and methods for making same; and various products constructed from papers made from the fibers reclaimed from denim scrap material. Summary of the Invention

In the present invention denim scraps from the manufacture of blue jeans and other clothing is turned into high quality stationery papers and other printable and convertible papers by altering the standard paper making process so as to take advantage

of the inherent paper making qualities of the fibers that make up the scrap material. In addition, dye present in the scrap material is preserved and used to color the paper.

First the denim scrap material is transformed into pulp. It is a common practice in the art of making cotton paper for a pulper to prepare pulp for use by paper mills. The pulper transforms the cotton scrap to a pulp that is "half way" to being suitable for making paper. At this stage the pulp is partially dewatered and becomes what is referred to in the art as "half-stuff. The half-stuff is delivered to the mill where the pulp is rehydrated and refined until it is ready to be made into paper. Some paper mills do their own pulping in which case the pulp may never technically become half- stuff since the dewatering and rehydrating steps might not be necessary. Paper pulp is an aqueous solution of typically 4 to 6 % by weight of fibers. Prior art processes for making pulp from cloth include chemical as well as mechanical maceration of the scraps to free the fibers into solution and to hydrate the fibers. The pulping process as now practiced includes cooking the fibers in bleach and high levels of caustic (above pH 11) at elevated temperature and pressure. The bleach and caustic break down the fibers and strip the dye from the fibers.

In the present invention, pulp from 100% cotton denim scrap material from the manufacture of blue jeans and the like is

made by mechanical maceration only with very little or no caustic being used and in some cases without bleach. Even when caustic is used, it is not for the purpose of conditioning the fibers since its use is limited to such low pH levels ( pH 11 or below) as to have virtually no effect on the structure of the fibers. The absence of traditional levels of caustic from the cooking process, permits the fibers to retain their strength and inherent characteristics for

10 forming printable and convertible papers. Thus, when the low (or no) caustic cooking process of the present invention is used in making pulp, and the pulp process finished in essentially the same

- .. way as other all cotton fiber pulps, the paper made from that pulp is as fully printable, convertible and useful as other cotton papers.

Pulp made according to the present invention without bleach retains the color of the dye in the reclaimed scrap material. 0 Because caustic is either not present at all or at lower levels than those used in the prior art, the color dye that comes along with the cloth is not discolored (yellowed or browned) as would occur if cooked in traditional levels of caustic. Thus, the dye of the cloth is

25 usable as a commercial coloring for the paper. And while limiting the levels of caustic in the cooking process protects the dye, the elevated temperatures and pressures of that process frees the dye from the fibers permitting it to be evenly redistributes throughout

30 the fibers, dying any undyed fibers and over-dying any fibers of a color other than the dominant color. Thus, color paper made from

pulp according to the present invention is printable and convertible and has a uniform, repeatable color without an undesirable yellow or brown film or cast.

Even bleached pulp made according to the present invention at limited levels of caustic benefit by having a brighter and more uniform whiteness due to the absence of caustic cooked fibers.

Varying shades of color are attainable by mixing pulp made according to the present invention without bleach with pulp made according to the present invention with bleach (stripping the color from the fibers to make them white). The colors achieved by mixing varying percentages of bleached and unbleached pulps are uniform and repeatable. The presence of the unbleached fibers processed according to the present invention, even in small amounts (3% to 10%, for example), gives the paper added strength and durability (both dry and wet). Thus, the unbleached pulp made according to the present invention can also be added to other paper making materials (cotton or non-cotton) to give them color as well as added strength and durability.

Papers of the present invention are those that contain fibers reclaimed from denim scrap material which have not been cooked in high levels of caustic. The invention includes paper formed from cotton fibers from 100% cotton denim scrap from the manufacture of clothing and the like that have not been cooked in high levels of caustic wherein the paper fibers: (a) are all 100% cotton denim

fibers that have not been bleached; (b) are 100% cotton denim fibers that have been bleached; (c) are 100% cotton denim fibers some of which have been bleached and some of which have not been bleached (in varying proportions as desired to achieve a particular shade of color); or (d) are less than 100% cotton denim fibers, bleached and/or unbleached.

Paper made according to the present invention can, in addition to being printable and convertible, be of unusual strength, both wet and dry (without the addition of a wet-strength agent commonly added to prior art papers) . This available strength factor permits papers to be made that out- perform similar paper made using prior art processes. For example, tractor feed paper can be made without plastic reinforcing in the area of the margin holes where it is now required and used; photo archive pH neutral paper can be made that will retain its integrity far longer than conventional archive papers; corrugated can be formed that has far greater strength-to-weight ratios than corrugated made from traditional kraft papers; pattern paper can be made that can be recycled along with denim scrap material (presently the wood fiber pattern paper must be hand separated from the denim scrap before it is processed); as well as many other papers that require strength, durability and high quality finish.

Accordingly it is an object of the present invention to reclaim 100% cotton scrap denim from the manufacture of clothing and transform it into useful paper and paper making products.

It is another object of the present invention to make paper pulp, including half-stuff, from 100% cotton denim fiber from manufacturing waste from clothing production.

Yet another object of the present invention is make a variety

10 of printable and convertible paper products from 100% cotton denim waste material from the manufacturing of clothing and the like.

, -. A further object of the present invention is to make a variety of specialty paper products that require exceptional strength and durability from 100% cotton denim fibers from the scrap material reclaimed from the manufacture of clothing and the like. 0 Another object of the present invention is to make colored paper pulp and paper products using only the dye present in the 100% cotton denim manufacturing scrap material used as the source of the fibers. 5 Preferred Embodiments A. Pulp (dyed or bleached)

100% cotton dyed denim scrap from the manufacture of clothing is cut into particle size of about one square inch (on

30 average) by a 75 hp Taylor Stiles cutter.

10,000 pounds of particle size scrap is fed into a Kamyr continuous digester along with 4,200 gallons of hot water and heated to 310 degrees F for 2 to 3 hours under pressure of 60 to 65 psi.

At this point the prior art teaches the addition to the digester of a caustic solution of sodium hydroxide (first diluted 50/50 with water) to bring the pH level in the digester to above 11 (in some cases to as high as 14). In the preferred embodiment of the present invention no caustic is added. Low levels of caustic can be helpful, however, in keeping some processing machinery clean and unclogged (especially where color pulp is being made) . As long as the pH level of the denim does not at any time exceed 11 (preferably 9) the color of the dye will not take on an unwanted dulling (brown or yellow) and the bleached pulp will be whiter and brighter.

After the initial 2 to 3 hour cook, the pressure is relieved in the digester and an additional 2,000 gallons of water are added to rinse the cooked denim. The pressure in the digester is then allowed to build back to between 60 and 65 psi (this takes about thirty minutes) and remain there for 36 minutes.

The cooked denim is then removed from the digester and dumped onto a concrete staging area where it cools and sits for 24 hours at ambient temperature.

Page 12 submitted later, but not taken into account for the purposes of international processing.

blue (or other color depending on the color of the denim used to make the half-stuff). The inclusion of as little as 3% unbleached pulp to 97% bleached pulp produces a paper with a definite blue color. As more pulp with the original dye is added to any mixture, the blue color deepens. By carefully controlling the percentages of bleached and unbleached pulp used, the same colors can be consistently repeated. And the colors will not be dulled with a yellow or brown cast.

The fibers are pre-beaten in the pulper for about 30 minutes to hydrate, soften and fray the fibers. The duration of pre-beating needs to be controlled so that the fibers are softened and frayed to increase their bonding qualities, but not to the point of weakening the fibers and turning them into "mush".

The fibers are then processed in a Jones Bertrum beating ^uni t for approximately 50 minutes to cut the fibers (reduce their length) and further hydrate them.

The fibers are next processed in three successive Jones-3000 Double Disk refiner s for further fiber length sizing and hydration. These refiners are loaded at 290KW, 170KW and 70 amps, in that order.

The pulp in now ready for delivery to the head box of a Rice Barton Fourdrinier papermaking machine wire where it is dewatered resulting in a formed web or sheet of fiber. Each formed web is then transferred to a carry felt and passed through press

rolls where additional water is removed and through steam heated dryer cans for final water removal. Each dried web or sheet is then passed through several nips of a calendar stack to achieve the desired sheet smoothness and caliper. Finally each sheet is then wound on a machine reel core to provide a roll of paper for converting.

Having thus described the invention, what is claimed is: