Pitch Or Stickies Control Agent

Europaisches Patentamt J European Patent Office © Publication number: 0 569 085 A1 Office europeen des brevets

© Priority: 05.05.92 US 878637 © Applicant: CALGON CORPORATION 26.02.93 US 23988 Route 60-Campbell's Run Road Robinson Township Pennsylvania 15205(US) @ Date of publication of application: 10.11.93 Bulletin 93/45 @ Inventor: Richardson, Paul F. 250 Twin Hill Drive © Designated Contracting States: Mt. Lebanon, PA 15216(US) AT BE DE FR GB SE

© A method for inhibiting the deposition of pitch or stickies on and/or for removing pitch or stickies from the surfaces of pulping and papermaking machinery by adding an effective amount of a melamine formaldehyde-type polymer to a pulp slurry or furnish in contact with said machinery.

Rank Xerox (UK) Business Services (3. 10/3.6/3.3. 1) 1 EP 0 569 085 A1 2

BACKGROUND OF THE INVENTION and paper machines, and (3) reduces pulp brightness and brightness stability. The composition and The present invention relates to the use of amount of pitch deposited on pulping and paper- melamine aldehyde-type polymers to inhibit and/or making machinery and in the final paper vary with control pitch or stickies deposition in pulping and 5 the time of the year the trees are harvested, the papermaking processes. More particularly, this in- type of wood, and the type of the pulping process vention relates to inhibiting the deposition of pitch used. For example, wood pulped from trees cut in on machinery used in pulping and papermaking the early spring and fall generally contains more processes and to the removal of pitch from ma- pitch than wood pulped from trees cut at other chinery used in pulping and papermaking pro- io times during the year. Pitch deposited in softwood cesses. This invention further relates to inhibiting Kraft mills tends to have a relatively larger abietic the deposition of stickies on machinery used in acid to fatty acid-ester ratio than pitch found in secondary fiber pulping and papermaking pro- hardwood Kraft mills, and pitch deposit problems cesses and to the removal of stickies from machin- are generally somewhat more severe in sulfite ery used in secondary fiber pulping and paper- 75 mills. The sulfite pulping process removes only making processes. about one half of the resins and fatty esters leaving Pitch, stickies and tackies continue to be a a considerable portion of these materials encap- problem in pulp and paper mills. It is believed that sulated within the cellulose fibers. However, these the problems caused by the build up of pitch or encapsulated materials are released by the shear- stickies and tackies on pulp and papermaking ma- 20 ing forces of pulping and papermaking processes chinery and in the final paper cost the pulp and and thus pitch deposits are more prevalent in the paper industry many millions of dollars per year in stock preparation area and on the paper machine. lost production. Pitch, as used herein, maybe gen- Pitch problems can be quite bothersome in me- erally defined as any resin-based deposit of widely chanical pulp mills, including groundwood, TMP, varying composition originating in the extractive 25 CTMP, and semi-chemical pulping processes, par- fraction of wood. The extractive fraction of wood is ticularly those that utilize softwoods. This is be- one of the four principal components of wood. The cause there is little chemical degradation of the other three are cellulose, lignin, and hemicellulose. fatty acid esters and resin esters. Therefore, those The extractive fraction is defined as a complex materials are not washed out and tend to remain mixture of substances which are soluble in water, 30 dispersed in the aqueous system of the pulping alcohol, benzene, ether, and/or acetone. The ex- process. tractive fraction, which generally makes up from Stickies and tackies are a major problem in about 3% to 10% of the weight of wood, contains secondary fiber pulp and papermaking operations such components as low molecular weight car- because, like pitch, they (1) agglomerate and also bohydrates, terpenes, aromatic and aliphatic acids, 35 occlude other matter to form visible "dirt" in the alcohols, tannins, color substances, proteins, lig- final paper, (2) plate out and collect on machinery nins, alkaloids, and soluble lignins. used in pulping and papermaking process such as The term "stickies" and "tackies", as used screens, filter refining requipment, pulp washers, herein, are interchangeable terms that primarily in- and paper machines, and (3) reduce pulp bright- clude synthetic contraries found in secondary fiber. 40 ness and brightness stability. The composition and For example, stickies and tackies include, but are amount of stickies deposited on pulping and paper- not limited to, ink residuals, tars, latexes and heat making machinery and in the final paper vary with melt contaminants found in secondary fiber. As the type of secondary fiber used in the pulping such, stickies and tackies are distinct from pitch, operation. As used herein, the term "secondary which, as defined above, includes any resin-based 45 fiber" includes any paper fiber used for a second deposit of widely varying constituency originating time in the production of a paper end-product. in the extractive fraction of wood. The constituents Sources of secondary fiber include, but are not of pitch are naturally occurring, as opposed to the limited to, tissue, fine paper, boxboard, linerboard, synthetic compounds that comprise stickies. While footboard and newsprint. Each of these sources pitch and stickies cause similar problems in paper- 50 generally contains unique impurities, such as inks, making operations, they are distinct both in terms colors, fillers, strength resins and/or coatings, which of their origin and their composition. means that the stickies composition and concentra- Pitch is a major problem in pulp and paper- tion can vary widely from one secondary fiber to making because it (1) agglomerates and also oc- another. cludes other matter to form visible "dirt" in the final 55 The presence of calcium carbonate in the pul- paper, (2) plates out and collects on machinery ping process exacerbates the problem of pitch used in pulping and papermaking process such as and/or stickies deposition on pulp and papermaking screens, filters refining equipment, pulp washers, machinery. Crystallized calcium carbonate can pro-

2 3 EP 0 569 085 A1 4 vide nucleation sites for precipitated metal soaps sitive adhesives to binders and coatings for inks or thereby producing hydrophobic particles which co- wet strength resins. Polymeric examples include, alesce with other particles to form a pitch deposit. for example, polyethylenes, polybutadiene- There have been many attempts over the years styrenes, polyvinylacetates and polyacrylates. to eliminate pitch or stickies problems by adding 5 control agents to pulping and/or papermaking pro- SUMMARY OF THE INVENTION cesses. While more thorough pulp washing may help to reduce pitch or stickies problems, the most The instant invention is directed to the inhibi- common methods of treatment involve the addition tion of pitch or stickies deposits on and to the of dispersants or adsorbant fillers to the furnish. io removal of pitch or stickies deposits from pulping For example, treatments may involve the use of and/or papermaking machinery, particularly wet- alum, talc, anionic pitch-control agents such as end papermaking machinery, comprising adding to polynaphthalene sulfonates or modified lignosul- a pulp slurry or paper furnish in contact with said fonates, cationic pitch control agents such as poly- machinery an effective amount of a designated quaternary ammonium polymers, methylcellulose is melamine formaldehyde-type polymer. derivatives and nonionic surfactants. None of these treatments are believed to be particularly effective. DETAILED DESCRIPTION OF THE INVENTION Examples of the use of poly quaternary ammonium polymers as pitch control agents can be More particularly, the present invention relates found in U.S. Pat. No. 3,582,461. The '461 patent 20 to a method for inhibiting pitch deposition on discloses the use of water soluble dicyandiamide- papermaking equipment or machinery, and/or for formaldehyde condensates to prevent pitch deposi- removing existing pitch deposits from such equip- tion on machinery used in pulping and paper- ment or machinery, comprising adding to a furnish, making processes. By contrast, the instant inven- stock or papermaking stream containing pitch tion utilizes water insoluble acid colloids. 25 which contacts said equipment or machinery an Examples of attempts to control pitch with oth- effective amount of a melamine formaldehyde-type er types of compounds or processes are found in polymer. U.S. Pat. Nos. 3,812,055; 3,895,164; 3,896,046; The present invention also relates to a method 3,992,249; 4,313,790. for controlling and/or inhibiting stickies and/or tac- Zirconium chemicals have also been used to 30 kies deposition on secondary fiber papermaking control pitch. See, for example, U.S. Pat. No. equipment or machinery, and/or for removing exist- 4,950,361. ing stickies/tackies deposits from such equipment The instant melamine formaldehyde-type poly- or machinery, comprising adding to a secondary mers are widely used in water treatment, particu- fiber furnish, stock or papermaking stream contain- larly in the treatment of paint spray booths. See, for 35 ing stickies or tackies which contacts said equip- example, U.S. Pat. Nos. 4,656,059, 4,629,572, ment or machinery an effective amount of a 4,935,149 and 5,068,279. melamine formaldehyde-type polymer. However, the use of melamine formaldehyde- An effective amount of a melamine type polymers to control pitch or stickies deposi- formaldehyde-type polymer must be used. As used tion in papermaking is not known or suggested in 40 herein, the melamine formaldehyde-type polymer the art. is a polymer comprising: (a), melamine or a substi- As indicated above, the present invention re- tuted melamine; and (b) a compound described by lates to the inhibition and/or control of pitch or the following formula: stickies in papermaking operations. While pitch is defined as the material comprising naturally occur- 45 ring resinous materials and gums liberated during o the screening, heating and refining processes that II occur during papermaking, stickies are defined as R, - C - Rj synthetic additives which enter into paper furnishes. More particularly, stickies are defined as 50 adherent deposits caused by organic materials wherein Ri and R2, which may be the same or used in paper and board converting operations different, are selected from the group consisting of which are typically introduced into paper machine H and straight or branched C1 -4 alkyl groups. The furnishes with recycled fibers. The word "stickies" preferred compounds of (b) comprise aldehydes, is derived from the fact that the resultant deposits 55 with methanal (formaldehyde), ethanal and pro- stick to wires, felts, and other parts of paper ma- panal being especially preferred; the most pre- chine. Stickies are a diverse mixture of synthetic ferred aldehyde is formaldehyde. Also, moderate materials ranging from hot-melt and pressure-sen- amounts of additional moieties, including, for exam-

3 5 EP 0 569 085 A1 6 pie, urea and/or dicyandiamide, may be present in being treated at a preferred dosage of at least the melamine formaldehyde-type polymers of this about 0.01 lb. polymer per ton of dry fiber, on an invention. active polymer basis. More preferably, the dosage Irrespective of the presence of additional should be maintained between about 0.40 lb/ton to moieties, however, the mole ratio of component (a) 5 about 10.0 lb/ton. The melamine formaldehyde- to component (b) should range from about 1:1 to type polymer can be added at any convenient about 1 :6, with the preferred ratio being from about location, but is preferably added so as to allow the 1:1 to 1:3. The most preferred mole ratio is about 1 maximum contact between melamine mole of melamine or a derivative thereof to about 2 formaldehyde-type polymer and the pitch or stic- to 2.5 moles of an aldehyde. Thus, the most pre- io kies. For example, the melamine formaldehyde- ferred polymer is prepared from melamine and type polymer may be added to brown stock wash- formaldehyde with the mole ratio of melamine to ers, deckers, high density chests or machine dilu- formaldehyde being about 1 :2 to about 1 :2.5. tion chests. Also, multiple points of addition may The instant melamine-formaldehyde polymers dilution chests. Also, multiple points of addition are insoluble in water. They are therefore best is may be used. utilized in acidic solutions wherein the melamine polymer is stabilized in a fine colloidal state of EXAMPLES suspension. Calgon's product CA-289, which has a pH of about 1.6 to about 2.1, is an example of the Example 1 - Paner Mill Trial - Pitch Control preferred form. This product contains 8% active 20 melamine-formaldehyde polymer in an acidic aque- Calgon product CA-289 was fed to a small ous solution. Any acid can be used to prepare the storage chest after the outside brown stock high melamine aldehyde acid suspension, although hy- density chest of a bleached softwood Kraftmill. The drochloric acid is preferred. Also, other stabilizing trial used fresh wood chips. The stock, after treat- agents, such as alcohols, can be used. 25 ment, went through the screening room and even- The percent by weight of active melamine tually to the bleach plant. The feed rate ranged polymer in a stabilized (acidic) suspension or solu- from 2 to 10 lb of 8%, by weight, active polymer tion should range from about 0.1% to about 20%, per ton of furnish. This equates to a feed rate of preferably 1% to about 15%, and most preferably about 0.16 to about 0.8 lb per ton, on an active about 4% to about 12%, due to cost and product 30 polymer basis. stability considerations. The pH should be suffi- Visual observations during the trial of the ciently low to keep the melamine aldehyde-type screens room and the reject cleaner - cones in the polymer in a fine colloidal suspension. bleach plant indicated that they were virtually free The molecular weight of the melamine of pitch. Further, pulp staining demonstrated a sig- aldehyde-type polymer is not critical. However, the 35 nificant decrease in the amount of loose pitch in preferred molecular weight ranges from about 500 the system i.e., colloidal and sheared off encap- to about 50,000, and the most preferred molecular sulated pitch. The pitch plate deposition in the weight ranges from about 500 to about 5,000. As screened room decreased slightly (8%) after the noted above, suitable melamine aldehyde-type trial. polymers are commercially available from Calgon 40 The Uhle boxes in the press section of the Corporation, under the tradenames CA-289 and paper machine were cleaned one day before and WT-2511. These products have molecular weights one day after the colloidal melamine formaldehyde of about 2,200. trial. No pitch or scale deposits were found in the An effective amount of the melamine Uhle boxes. This treatment replaced an effective formaldehyde-type polymer should be added to or 45 AZC program. maintained in the furnish, papermaking or secondary fiber stream being treated. The melamine Example 2 - Mixed Office Waste - Stickies Control polymer interacts with the pitch or stickies contained in such streams, thereby inhibiting pitch or A melamine-formaldehyde acid colloid, com- stickies deposition and/or removing existing pitch 50 mercially available from Calgon Corporation, was or stickies deposits from the surface of paper- fed to a secondary fiber furnish prepared from a making equipment. As used herein, the term mixed office waste containing 3% by weight fiber, "effective amount" refers to that amount of deinking chemicals, ink solids and bleach. The melamine formaldehyde-type polymer which polymer dosage, on an active basis, was .65 achieves the desired inhibition or removal of pitch 55 pounds/ton. Hand sheets were then prepared from or stickies for a given system. the treated and untreated furnishes. The untreated The melamine polymer can be applied intermit- hand sheeets contained large tacky particle with tently or continuously to the papermaking stream fiber attached to them. The treated hand sheets

4 7 EP 0 569 085 A1 8

contained smaller, non tacky particles with fewer O fibers attached. These tests demonstrated the abil- II ity of the polymer to impede agglomeration of the R1 - C - FL, stickies particles. These tests also demonstrated the ability of CA-289 polymer to render the sur- 5 faces of the stickies non-tacky. wherein Ri and R2, which may be the same or different, are selected from the group consist- Claims ing of H and straight or branched C1 -4 alkyl groups. 1. A method for inhibiting pitch deposition on 10 pulping and papermaking equipment or ma- 8. The method of Claim 7, wherein b) is formal- chinery comprising adding to a furnish, stock dehyde. or papermaking stream containing pitch which contacts said equipment or machinery, an ef- 9. The method of Claim 7, wherein the mole ratio fective amount of a melamine formaldehyde- 15 of a):b) is about 1:1 to about 1:6. type polymer. 10. The method of Claim 8, wherein the mole ratio 2. The method of Claim 1, wherein said of a):b) is about 1:1 to about 1:6. melamine formaldehyde-type polymer comprises (a), melamine or a substituted melamine; and (b) a compound described by the following formula:

O II R1 - C - Rj

wherein R1 and R2, which may be the same or different, are selected from the group consist- 30 ing of H and straight or branched C1 -4 alkyl groups.

3. The method of Claim 2, wherein b) is formaldehyde. 35

4. The method of Claim 2, wherein the mole ratio of a):b) is about 1:1 to about 1:6.

5. The method of Claim 3, wherein the mole ratio 40 of a):b) is about 1:1 to about 1:6.

6. A method for inhibiting stickies deposition on secondary fiber pulping and papermaking equipment or machinery comprising adding to 45 a secondary fiber furnish, stock or papermaking stream containing stickies which contacts said equipment or machinery, an effective amount of a melamine formaldehyde-type polymer. 50

7. The method of claim 6, wherein said melamine formaldehyde-type polymer comprises (a), melamine or a substituted melamine; and (b) a compound described by the following formula: 55

5 Patent J) European iUROPEAN SEARCH RErUKl )ffice !P 93 20 1240

>OCUMENTS CONSIDERED TO BE RELEVAIN I citation of document with indication, where appropriate, Application pint. rategoryl of relevant passages o claim ci.s ) S-A-3 582 461 (LIPOWSKI ET AL.) -iu the whole document * I21C9/08 I21H17/51 E-A-l 546 237 (BADISCHE ANILIN-& ODA-FABRIK AG) the whole document *

IS-A-5 068 279 (MORSE) the whole document *

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The present search report has been drawn up for all claims Place of search THE HAGUE 23 AUGUST 1993 dUNuT uai le CATEGORY OF CITED ducumenis I : ineory or principle unoenying mv uivciiuuu E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure A : member of the same patent family, corresponding P : intermediate document document