Background of he Invention

1 Field of the Invention

The present invention relates to a process for enhancing ash removal white removing pπnting inks from substrates containing them More particularly, the invention comprises reducing ash from process fiber typically mixed office waste, when removing inks by using a flotation deinking process wherein a nonionic surfactant is utilized.

2. Technology Description

Several technologies have been proposed in the art for effectively removing ink from substrates. While these methods have been successful in their purpose, further consideration could be made with respect to reducing ash from the resulting processed paper fibers To typically reduce the ash content of fibers which have been subjected to deinking processes, one or more wash stages is typically required.

Typical ash reduction when using conventional chemicals in flotation deinking is approximately 20-30%. To reduce the ash level to 50% or more, the above-suggested wash stages and other post flotation procedures are required. It would be desired if a chemical agent could be utilized in combination with the deinking flotation procedure to reduce ash content to a level of 50% or less of its original value to render subsequent washing and post flotation procedures unnecessary

Brief Summary of the Invention

in accordance with the present invention a novel process for reducing ash content while demkmg ink containing waste is provided which reveals a surprising beneficial effect by utilizing nonionic surfactants duπng the flotation deinking process The novel process provides an environmentally friendly, cost effective way to both remove inks from substrate and significantly decrease the ash content of the resulting fibers

One embodiment of the present invention provides a process for reducing the ash content of fiber while simultaneously removing ink from the fiber comprising the steps of

(a) forming a slurry by pulping paper containing inks in an aqueous medium including one or more nonionic surfactants and

(b) subjecting the slurry produced in step (a) to a flotation cell having an aqueous medium, wherein the nonionic surfactant is selected to reduce the ash content by at least fifty percent of its original amount

In particularly preferred embodiments the nonionic surfactant present in step (a) is an alkoxylated fatty alcohol

An object of the present invention is to provide a process which is effective in reducing the ash content during a deinking process

This, and other objects will readily be apparent to those skilled in the art as reference is made to the detailed description of the preferred embodiment

Detailed Descπption of the Preferred Embodiment

In describing the preferred embodiment, certain terminology will be utilized for the sake of clarity. Such terminology is intended to encompass the recited embodiment, as well as all technical equivalents which operate in a similar manner for a similar purpose to achieve a similar result.

The present invention provides a novel process for reducing ash content by at least fifty percent of its original amount while using flotation processing

The overall process generally comprises pulping or maceration of the wastepaper and ink removal by a flotation system. A screening or coarse cleaning stage or stages can be utilized to remove contaminants such as glass, stone, metal and staples A centrifugal cleaning stage or stages can be utilized to remove light weight materials such as plastics. Typical deinking processes are described in Fergusen. LD , "Deinking Chemistry: part 1 "

July 1992 TAPPI Journal pp. 75 to 83; Ferguson, LD . "Deinking Chemistry: part 2" August

1992 TAPPI Journal pp 49-58, and Spieibauer, J.L "Deinking System Overview", Voith, Inc.

Appletoπ, WI , pp. 1-9. To the extent necessary for completion, these references are expressly incorporated herein by reference. It has been discovered that the specific process of the present invention may be successfully used to significantly decrease the ash content of the resulting treated stock.

The first step of the invention is directed to forming a slurry by pulping paper containing inks in an aqueous medium including one or more nonionic surfactants. The type of paper which may be selected for pulping includes any which may be subjected to flotation type deinking procedures. Examples of such paper include flexographically printed waste, newsprint, filled and unfilled papers and paper boards and mixed office waste, with mixed office waste being the most preferred starting material. The percentage of stock in the pulper is between about 10 and about 20 percent with amounts between about 12 and about 18 being more preferred and an amount of about 16 being particularly preferred for commercial use

The pH of the aqueous medium of the pulper is maintained between about 4 to about 10, more preferably between about 6 to about 10, and most preferably between about 6 5 to about 10 Maintenance of the pH is accomplished by adding one or more acidic or basic agents to the pulper Agents which may be selected include any of those commonly known in the art which are capable of raising or lowering the pH to the desired range Examples of basic agents include, but are not limited to the following materials of NaOH NH ₄ OH KOH Na ₂ C0 ₃ K ₂ C0 ₃ , and mixtures thereof Examples of acidic agents include HCl H ₂ S0 , HN0 ₃ H ₃ P0 ₄ and mixtures thereof Particularly preferred agents are NaOH or H ₂ S0 ₄ As would readily be understood by one skilled in the art the amount of basic or acidic agent added to the pulper is that which would yield the desired pH

Also present in the aqueous medium of the pulper is one or more nonionic surfactants The surfactants function to disperse the ink into the aqueous medium during pulping and demonstrate surprising efficiencies in reducing the ash content of the resulting product Nonionic surfactants suitable for use are higher (greater than C ₈ ) aliphatic alcohol alkoxylates, higher aromatic alcohol alkoxylates fatty acid amides of alkanolamiπes, fatty acid amide alkoxylates, block or random copolymers of ethylene and propylene oxide, higher (greater than C ₈ ) alcohol polyethylene polypropylene block or random adducts and mixtures thereof Specific examples of surfactants which may be used in accordance with the present invention include the following classes of chemicals

1 ) a fatty alcohol having a carbon number of from about 8 to about 22, alkoxylated with ethylene oxide and propylene oxide, as represented by formula (I)

R-0-(CH ₂ CH ₂ 0) _x -(CH ₂ CH(CH ₃ )-0) _y -H (I), wherein R is a straight-chain or branched alkyl group having a carbon number of from about 8 to 22, x represents the number of oxyethylene groups per molecule and is in the range of from about 3 to about 25, and y represents the number of oxypropylene groups per molecule and is in the range of from about 1 to about 10 Examples of commercially available

products are sold under the InkMaster™ and Antarox" trademarks by Rhόne- Poulenc Inc.;

2) a fatty alcohol having a carbon number of from about 8 to about 22, alkoxylated with ethylene oxide and propylene oxide, as represented by formula (II)

R-0-(CH ₂ CH ₂ 0) _x -(CH ₂ CH(CH ₃ )-0) _y -(CH ₂ CH ₂ 0) _x -(CH ₂ CH(CH ₃ )-0) _y -H (I!),

wherein R is a straight-chain or branched alkyl group having a carbon number of from auout 8 to about 22, x and x which may be the same or different, represents the number of oxyethylene groups per molecule and is in the range of from about 2 to about 25, and y and y', which may be the same or different represents the number of oxypropylene groups per molecule and is in the range of from 0 to about 10 Examples of commercially available products are sold under the InkMaster " trademark by Rhόne-Poulenc Inc

It is believed that the following other surfactants which may be practiced within the scope of the present invention include'

3) an aromatic alcohol such as phenol having alkyl chaιn(s) with a carbon number of from about 8 to about 20. alkoxylated with ethylene oxide, as represented by formula (III).

R^-<OCH _a CH _Λ -OH «„„. R' wherein R and R' independently are H or an alkyl group which is branched or straight-chain having a carbon number of from about 8 to about 14; and x is the number of oxyethylene groups per molecule and is in the range of from about 1 to about 20. Examples of commercially available products are

InkMaster™, Igepal ^® , and Alkasurf ^® , products sold by Rhόne-Poulenc Inc.;

4) fatty amide of alkanolamide of formula (IV)

R-C(0)-N-R' (IV), dr wherein R' and R" may be the same or different and are H or CH ₂ CH ₂ OH or

CH ₂ CH(CH ₃ )-OH and R is a fatty alkyl group having a carbon number of from about 8 to about 20 Examples of commercially available products are Alkamide ^® products sold by Rhόne-Poulenc Inc ,

5) an alkoxylated fatty acid amide of alkanolamide of formula (V)

R- C(0)-N-(CH ₂ CH ₂ 0) _x -H

(CH ₂ CH ₂ 0) _x -H (V) wherein R is a fatty alkyl group having a carbon number of from about 8 to about 20, and x represents the number of oxyethylene groups per molecule and is in the range of from about 2 to about 10 Examples of commercially available products are Alkamide ^® products sold by Rhόne-Poulenc Inc ,

6) a propylene glycol alkoxylate of formula (VI)

HO-(CH ₂ CH ₂ O) ₀ (CH ₂ CH(CH ₃ )-0) _m (CH ₂ CH ₂ 0) _p -H (VI) wherein o and p are the number of oxyethylene groups per molecule and are in the range of from about 3 to about 15 and m is the number of oxypropylene groups per molecule and is in the range of from about 25 to about 40 Examples of commercially available products are Antarox ^® products sold by

Rhόne-Pouienc Inc and products having a CTFA designation of Poloxamer,

7) a block or random copolymer of ethylene and propylene oxide of formula

(VII)

HO (CH(CH ₃ )CH ₂ 0) _m (CH ₂ CH ₂ 0) _p (CH(CH ₃ )CH ₂ 0) _n H (VII) wherein m and n are the number of oxypropylene groups per molecule and are in the range of from about 10 to about 25 and p is the number of oxyethylene groups per molecule and is in the range of from about 5 to about

25. Examples of commercially available products are Antarox ^® products sold by Rhόne-Poulenc Inc. and products having a CTFA designation of Meroxopol;

8) an ethoxylated fatty alcohol of formula (VIII)

RO(CH ₂ CH ₂ 0) _x -H (VIII) wherein R is a fatty alcohol; and x represents the number of oxyethylene groups per molecule and is in the range of from about 1 to about 20 Examples of commercially available products are Rhodasurr products sold by Rhόne-Poulenc Inc.

More preferred nonionic surfactants within the above classes include

1 ) Those of Formula (I) wherein R is a straight-chain or branched alkyl group having a carbon number of from about 16 to 20, x represents the number of oxyethylene groups per molecule and is in the range of from about 10 to about 20, and y represents the number of oxypropylene groups per molecule and is in the range of from about 4 to about 8 A commercial example of such a nonionic surfactant is InkMaster ¹ " 750. or wherein R is a straight- chain or branched alkyl group having a carbon number of from about 8 to 14, x represents the number of oxyethylene groups per molecule and is in the range of from about 3 to about 12, and y represents the number of oxypropylene groups per molecule and is in the range of from about 1 to about 6 A commercial example of such a nonionic surfactant is InkMaster™ 770, sold by Rhόne-Poulenc. ,

2) Those of Formula (II) wherein R is a straight-chain or branched alkyl group having a carbon number of from about 16 to about 20. x and x' represents the number of oxyethylene groups per molecule and is in the range of from about 4 to about 10, and y and y' represents the number of oxypropylene groups per molecule and is in the range of from about 1 to about 5; A commercial

example of such a nonionic surfactant is lnkMaster ^{l l} 780 sold by Rhόne- Poulenc ,

3) Those of Formula (III) wherein R and R is H or a branched or straight-chain having a carbon number of from about 8 to about 14 and x is the number of oxyethylene groups per molecule and is in the range of from about 8 to about 12 A commercial example of such a nonionic surfactant is inkMaster ^I 730,

4) Those of Formula (IV) wherein R' and R are H or CH ₂ CH ₂ OH or CH ₂ CH(CH ₃ )-OH and R is a fatty alkyl group naving a carbon number of from about 8 to about 14

5) Those of Formula (V) wherein R is a fatty alkyl group having a carbon number of from about 8 to about 14 and x represents the number of oxyethylene groups per molecule and is in the range of from about 4 to about

8,

6) Those of Formula (VIII) wherein R is a fatty alcohol having a carbon number from about 12 to about 18, and x represents the number of oxyethylene groups per molecule and is in the range of from about 5 to about 15 A commercial example of such a nonionic surfactant is Rhodasurfji BC720 sold by Rhόne-Poulenc Inc

Of the above, the use of the following classes of nonionic surfactants is particularly suggested those of Formula (I) and (I!) as defined above

The amount of surfactant present in the aqueous medium of the pulper ranges from about 0 05 to about 3 0 percent by weight based upon the dry weight of all paper added to the pulper with amounts ranging from about 0 05 to about 0 5 percent being more preferred and amounts ranging from about 0 07 to about 0 3 percent being even more preferred

Optionally present in the aqueous medium of the pulper are commonly known deinking additives added in amounts recognized by those skilled in the art Such additives include, but are not limited to, bleaches, sodium silicate, chelants dispersants other than the defined nonionic surfactant, enzymes detergent builders, other detergents and the like

It is important to maintain an appropriate pulp slurry temperature during pulping Determining the appropriate temperature range is within the skill of an artisan Generally the range is from about 40°C to about 65°C preferably from about 45°C to about 60°C and most preferably from about 48°C to about 55°C

The activation period is the time needed to allow substantially all of the paper fibers in the pulp slurry to come into contact with the aqueous medium Conditions such as the degree of dilution of the pulp slurry and the utilization of agitation can effect the amount of time needed The determination of the appropriate amount of time needed is within the skill of an artisan Generally, this time period can range from about 5 to about 90, preferably from about 10 to about 60 and most preferably from about 15 to about 45 minutes

Once the paper added to the pulper has been sufficiently slurried in the aqueous medium, the slurry is transferred to a flotation cell

The pH of the flotation cell is maintained between about 6 to about 10 more preferably between about 7 to about 9, and most preferably between about 7 to about 8 This pH often is the pH of the slurry which is provided to the flotation cell If necessary to provide the desired pH profile, one or more of the acidic or basic agents which have been described in connection with the pulping step may be added in amounts to yield a pH in the flotation cell as defined above

Optionally present in the flotation cell is one or more nonionic surfactants as defined above with respect to the pulping step The amount of nonionic surfactant present is that which yields the same percentages as that present in the pulping step (i e , between about 0 05 to about 3 0 percent by weight of the paper added to the pulper) Often it is not necessary to add

additional nonionic surfactant as that which is present in the slurry produced in the pulper is sufficient for functioning in the flotation cell although additional nonionic surfactant may be added

Other materials which may be added to the flotation cell which are considered optional include foam enhancing chemicals, poiyelectrolytes enzymes pH adjusting chemicals and mixtures thereof

The slurry is maintained in the flotation cell for a time temperature and rate of agitation necessary to produce a foam which contains a significant amount of the removed ink Such process conditions are preferably those operating conditions which are defined by the manufacturer of the flotation cell Such conditions typically comprise treating the slurry at about 40°C to about 50°C for about 1 to about 30 minutes injecting air into the cell in an amount sufficient to disperse air bubbles throughout the mixture, with good agitation and without becoming so turbulent as to dislodge ink from the air bubbles This amount of injection is typically about 1 cell volume of air per minute The concentration of the paper fibers is about 0 5 to about 2 0% of the cell

Once flotation has been completed, the foam which forms above the slurry in the flotation is removed by methods known in the art such as by froth vacuum, mechanical paddle etc From the remaining slurry, paper can be produced which has a high level of brightness and in accordance with the invention, significant reduction of ash content

Up until the present invention utilizing a single step flotation deinking process would typically result in a reduction of about 20-30% when typical pulp and flotation chemistries are used Typical chemistries include nonionic surfactants which are long chain alkyl (i e , greater than 12 carbon atoms) fatty ester ethylene oxide/propylene oxide alkoxylates or C _{12 16} α-olefin sulfonates blended with polyglycol (propylene oxide capped with ethylene oxide) The method for determining ash is set forth as TAPPI Standard T 211 om-93 As a result, subsequent processing steps are needed to further reduce the ash content By stark comparison the use of the nonionic surfactant in accordance with the claimed invention is capable of reducing the

ash content by at least 50% as measured by the above standard More specifically, the use of the nonionic surfactant can enable a reduction of ash content of greater than about 55% more preferably greater than about 60% and most preferably greater than about 65%

The invention is described in greater detail by the following non-limiting examples

EXAMPLES 1-7 and COMPARATIVE EXAMPLES 8-9

Wastepaper:

The wastepaper comprises a mixture of 65% white laser ledger and 35% colored mixed office waste (MOW) The 35% MOW component is approximately 90% colored material and the remaining 10% includes old newspaper, old magazine and unbleached brown bags The groundwood content is approximately 10%

Process Sequence:

The process sequence includes high consistency pulping (16%) where three 2000 lb pulper batches are defibered and repulped for 40 minutes Each batch is pumped into a dump chest where the consistency is reduced to ~4% Chemical addition is accomplished by addition to the high consistency pulper or by addition to the lower consistency dump chest A series of cleaning and screening steps follows the pulping first high density centrifugal cleaning and then screening through 1 4 mm holes and 0 15 mm slots The pulp is then diluted further to 1 % consistency in an intermeduite chest prior to flotation Flotation consists of primary flotation with reject froth vacuum followed by secondary flotation Flotation accepts then proceed through two stages of forward centrifugal cleaning and then fine screening (0 1 mm slots) The pulp is further processed by washing and thickening into wet-lap with a twin-wire

press Wash and press rejects are clarified using a DAF unit and DAF effluent is used as make-up water in each stage of the deinking process

The following conditions are used to conduct the evaluation

Example 1 InkMaster™ 750 nonionic surfactant addition (0 125 %) to pulper at 16% consistency, pulper temperature of 130°F pH=7

Example 2 Same as Example 1 except 300 ml/ton of a demkmg enzyme (Novo Nordisk SP342) added to pulper, pH=7

Example 3 InkMaster™ 750 nonionic surfactant added (0 125%) to dump chest at 4% consistency, pulper temperature of 130°F, pH of pulper is 7 2 pH of dump chest is 7 0

Example 4 InkMaster™ 750 nonionic surfactant added (0 125%) and 450 ml/ton of a deinking enzyme (Novo Nordisk SP342) addition to dump chest at 4% consistency, pulper temperature of 130°F dump chest temperature of 108°F, pH of pulper is 7 2 pH of dump chest is 7 0

Example 5 Same as Example 4 except pulper temperature of 145°F dump chest temperature of 130°F, pH of pulper is 7 1 , pH of dump chest is 7 0

Example 6 Same as Example 2 except InkMaster™ 750 (0 10%) and 450 ml/ton of a deinking enzyme (Novo Nordisk SP342) are preblended and added to pulper at 1 1 % consistency, pH=7 1

Example 7 InkMaster™ 750 nonionic surfactant addition (0 075 %) to pulper at 16% consistency, pH=9 5

Comparative Example 8 Same as Example 7 except the surfactant added (0 10%) is a C ₁₈ fatty ester ethylene oxide/propylene oxide alkoxylate manufactured by Lion Industπes, Inc

Comparative Example 9 Same as Example 6 except the surfactant added (0 125%) is a C ₁₂ . ₁₆ α-olefin sulfonate blended with polyglycol (propylene oxide capped with ethylene oxide) sold under the trade name Buckman BRD 2340

Results:

The ash removal across flotation and ash flotation rejects for each of the above Examples is shown in the table below

Significant ash reduction (50-67%) is achieved across flotation in all runs involving the inventive process InkMaster™ 750 is surprisingly well suited for ash reduction Ash levels of <2% with single flotation/single wash are achieved at a high system yield of -74% Competitive chemistries typically result in ash removal levels of 10-30% Ash flotation rejects in the inventive examples are on the order of about 40-60% whereas the comparative examples are on the order of about 10-30% These results are significant for those mills requiring multiple wash stages and/or post flotation stages to meet ash reduction targets Conventional tissue deinking mills employ a double wash/single flotation process to achieve <2% ash and typically achieve yields of 60-65% Use of InkMaster™ 750 or other nonionic surfactants as defined in the present invention for ash reduction may therefore allow single pass flotation and avoid the use of additional processing sequences that would adversely impact fiber yield

Having described the invention in detail and by reference to the preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims