US 3873417 A
A neutralized solution of polymer prepared by the free radical polymerization of an alpha, beta unsaturated acid, e.g., acrylic acid with small amounts of an alkyl ester an alpha, beta unsaturated acid and allyl alcohol when added to an aqueous pulp slurry at a rate of less than one percent polymer solids by weight of pulp present yields improved pitch and pigment dispersion and deposit control.
Description (OCR text may contain errors)
United States Patent Otrhalek et al.
[ Mar. 25, 1975 PITCH AND PIGMENT DISPERSANT IN AQUEOUS PULP SLURRIES  Inventors: Joseph V. Otrhalek, Dear-born,
Mich.; Gunther II. Elfers, Mutterstadt, Germany  Assignee: Bast Wyandotte Corporation,
 Filed: Jan. 31, 1974 ] App]. No.: 438,385
 US. Cl. 162/168, l62/DIG. 4, 260/17.4 CL, 260/174 R, 260/80.75
 Int. Cl. C08f 15/40, D2lh 3/44  Field of Search 260/8075, 17.4 CL; 162/168, DIG. 4
 References Cited UNITED STATES PATENTS 2,765,229 10/1956 McLaughlin 162/168 2,957,853 10/1960 Chapin et al. 260/8075 3,081,219 3/1963 Drennen et al. 3,748,220 7/1973 Gard 162/168 Primary Examiner-Morris Liebman Assistant ExaminerEdward Woodberry.
Attorney, Agent, or Firm-Bernhard R. Swick; Joseph D. Michaels; Robert E. Dunn  ABSTRACT 11 Claims, No Drawings PITCH AND PIGMENT DISPERSANT IN AQUEOUS PULP SLURRIES BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to the control of pitch and pigment deposits and dispersions in aqueous pulp slurries by the use of a solution of a neutralized copolymer having a high alpha, beta unsaturated carbonyl acid content.
2. Description of the Prior Art The problem of pitch and pigment control in papermaking has previously been recognized. The pitch in the fibers of wood pulps is associated with naturally occurring lighin dispersing agents. Cooking and mechanical agitation which occur during the pulping by the sulfite process liberates pitch and natural dispersing agents. But, the natural dispersing agents liberated along with the pitch are inadequate to keep the pitch from depositing, as a result of the mechanical work on the fibers, on the equipment employed in beating, hydrating, refining, bleaching, and even onthe wire used for forming the sheet. Because of the tendency of the pitch to agglomerate within the pulp suspension or deposit on the surfaces of the wire or other equipment and then to break free in the form of particles of considerable size, the pitch frequently causes the formation of spots or holes in the sheet formed or may adhere to the wire or press rolls or drier rolls and cause tearing of the sheet. This results in occasional tearing of the sheet during formation or in the production of sheets with numerous imperfections. Among other consequences involved are the expense of cleaning the machinery frequently either with solvents or steam, and the loss of production during cleaning and during relacing operations caused by breakdown of the sheet.
Various systems have been employed heretofore for controlling the pitch in the making of paper from sulfite pulps whether bleached or unbleached or from ground wood pulps. One way of controlling pitch heretofore employed is the introduction of diatomaceous earth, bentonite, or the like for the purpose of introducing finely divided particles which adhere to the pitch and reduce the tackiness of its surface. Other expedients involve the addition of dispersing agents or sequestering agents. US. Pat. No. 2,399,489 discloses the use of sodium carbonate. This patent also discloses polyphosphates such as sodium hexa-meta-phosphate have been employed. They have appreciable value when the pulp treated has a pH of about 3.5 to 4.5; but when the pulp is nearer the neutral state such as at a-pH from 5.5 to 7, the beneficial effect is slight. Various dispersing agents have been employed such as the sodium salt of sulfonated formaldehyde/naphthalene condensates, but these agents have decreased effects at neutral pH values. They also are precipitated by cationic materials,
such as alum and cationic urea-formaldehydepolyamine wet-strength resins, so that pitch control suffers and the wet-strength efficiency of such resins is reduced when the latter materials are added to the pulp, as in the beating stage. US. Pat. No. 3,081,219 discloses the use of a polymeric N-vinyl lactam to prevent the deposition of pitch during papermaking.
There have also been suggestions to employ a mixture of an organic solvent for the pitch in conjunction with a dispersing agent, but these procedures involve the additional expenses of the organic solvent and of compounding the emulsifier therewith.
SUMMARY OF THE INVENTION In accordance with this invention there is provided a composition for controlling the deposit of pitch and/or pigments in an aqueous slurry of cellulosic fibers consisting essentially of an alkali neutralized terpolymer produced by the free radical polymerization of from about 60 to about 88 parts by weight of at least one alpha, beta unsaturated acid containing three to four carbon atoms, from about 6 to about 28 parts by weight of at least one alkylate of an alpha, beta unsaturated acid containing three to four carbon atoms, said alkylate containing from one to l8'carbon atoms, and from about 4.5 to about 20 parts by weight of allyl alcohol, the total of said parts being 100. Also provided is a method for controlling the deposit of said pitch and/or pigment in an aqueous slurry comprising adding to said slurry an aqueous solution containing from about 20 to about weight percent polymer-solids of the above described polymer composition and in an amount of polymer solids of up to one percent by weight of pulp or cellulosic fiber solids in the slurry.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The terpolymer of this invention is an alkali neutralized free radical polymerized polymer containing an alpha, beta unsaturated acid andalkylate of an alpha,
' about 88 parts and, more preferably, from about 75 to about 88 parts.
The alkylates contained in the terpolymer of this invention are esters of the acids employed herein and again the preferred acids are acrylic and methacrylic acids. The alkyl portion contains from one to 18 carbon atoms and, more preferably, from one to 10 carbon atoms and includes linear or normal alkyl, branched alkyl, hydroxyalkyl and cycloalkyl. Illustrative of the alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, 2-ethylhexyl, cyclohexyl, nonyl, octyl, dodecyl and stearyl. Based on 100 parts the alkylated acid is present in the terpolymer in an amount from about 6 to about 28 parts and, more preferably, from about 6 to about 15 parts.
The third component of the terpolymer is allyl alcohol which is present, based on 100 parts, in an amount from about 4.5 parts to about 20 parts and preferably from about 6 to about 15 parts by weight.
The terpolymer is prepared by free radical polymen ization in an aqueous medium at a temperature just above the freezing temperature up to the reflux temperature of the aqueous reaction mixture, more practical operating temperatures are in the range of about 50C. to about 100C., a range of about 60C. to about 90C. being particularly preferred. Polymerization in accordance with this invention can be carried out at atmospheric to autogenous pressures. The polymerization is generally conducted for a period of 2 to 8 hours and a period of 3 to 5 hours is very satisfactory. The foregoing details, catalyst discussed below and other details are well known to those skilled in the polymer arts and for the sake of brevity need not be discussed further.
It has been found preferable to prepare an aqueous solution of acid, ester and alcohol and charge the solution incrementally to the reaction vessel along with incremental additions of an aqueous solution of the catalyst at such a rate so as to evenly maintain the desired reaction temperature. The solids content of the reaction system can range from about 20 to about 50 percent by weight. Thirty percent has been found to be very satisfactory from the point of view of low enough viscosity to permit easy handling of the resulting polymer solution.
Any of the compounds known to generate free radicals and which are soluble at effective concentrations in the aqueous polymerization medium may be used as the polymerization catalyst in practicing this invention. Examples of useful polymerization catalysts include the alkali metal and ammonium persulfates, perborates, or percarbonates, hydrogen peroxide, organic peroxides such as benzoyl peroxide, cumene hydroperoxide, tertiary butyl peroxide, tertiary butyl perbenzoate, acetyl benzoyl peroxide, tertiary butyl peracetate and tertiary butyl peroxyisobutyrate. Ammonium, potassium and sodium persulfates are particularly preferred. Organic peroxides may be used in combination with these inorganic peroxidic catalysts. Azonitrile compounds such as described in U.S. Pat. No. 2,471,959 can be used also as a polymerization catalyst for the polymers of this invention.
Generally, the proportion of polymerization catalyst is in the range of 0.1% to 8.0% based on the weight of acid and alkylate charged, and preferably from 1% to 3%.
The catalyst can also be a peroxidic catalyst activated with a reducing agent to provide a redox system. Examples of useful reducing agents include water-soluble bisulfites, such as sodium metabisulfite, sulfites, hydrosulfites, and thiosulfates. The redox system may be further activated by the presence of polyvalent metal ions, e. g., ferrous ions at concentrations of the order of magnitude of several parts per million, or with tertiary amines which are soluble in the reaction mixture.
The proportion of reducing agent included in the polymerization catalyst combination ordinarily ranges up to 3% based on the weight of the monomers and preferably is in the range of 0.02% to 1% on this basis. In the inorganic redox system of persulfate and bisulfite, the weight ratio can vary from 1 to parts of persulfate per part by weight of bisulfite.
The polymerization product has an acid pH and can be neutralized with alkaline materials such as ammonia or ammonium hydroxide, monoand dialkylamines containing one to six carbon atoms in each alkyl group and alkali metal hydroxides, e.g., potassium hydroxide or sodium hydroxide, that form water-soluble neutralization products. Preferably, the neutralizing agent will be ammonia, ammonium hydroxide, potassium hydroxide or sodium hydroxide. The neutralizing agent is added to the polymer solution until a final pH of about 7.5 to about 8.5 is obtained. Thus neutralized, the poly mer solution has improved storage stability and possible metal corrosion problems in the storage container are minimized.
The resulting polymer solution is adjusted as necessary to have a polymer total solids content of between about 20 and about 50 weight percent. The polymer solution is a true solution in comparison to the polymer solutions known in the prior art which are only emulsions. It is believed that the high acid content of the invented polymers materially contributes to this condition.
The deposit of pitch and/or pigments in cellulosic fiber (or pulp) slurries occurs throughout the paper manufacturing process. For the purpose of this invention, it is convenient to use the term pitch as embracive of pitch per se and the other gums, resins and resins which result from the production of cellulosic fibers by the pulping step of paper manufacture. The pitch in the fibers of wood pulps is associated with naturally occurring lignin dispersing agents. Cooking and mechanical agitation which occur during the pulping by the Kraft, ground wood or sulfite process liberates the pitch. But, the natural dispersing agents liberated with the pitch are inadequate to keep the pitch from depositing as a result of the mechanical work on the fibers, on the equipment employed in beating, hydrating, refining, bleaching, and even on the wire used for forming the sheet. Because of the tendency of the pitch to agglomerate within the pulp suspension or deposit on the surfaces of the wire or other equipment and then to break free in the form of particles of considerable size, the pitch frequently causes the formation of spots or holes in the sheet formed or may adhere to the wire or press rolls or drier rolls and cause tearing of the sheet. This results in occasional tearing of the sheet during formation or in the production of sheets with numerous imperfections. Among other consequences involved are the expense of cleaning the machinery frequently either with solvents or steam, and the loss of production during cleaning and during re-lacing operations caused by breakdown of the sheet. Pigments such as clay or calcium carbonate for color and/or smoothness and titanium dioxide or zinc oxide for color are also added at or after the bleaching step to-obtain the desired properties for the paper being made. These pigments have a tendency to agglomerate and settle out producing uneven spots in the resulting paper, tears and wasting of materials.
To avoid the foregoing problems, it has been found advantageous to add to the various fiber slurries small amounts of the previously described aqueous polymer solution of this invention. The amount to be added will vary according to the amount of pitch and/or pigment to be dispersed with the fiber slurry at that particular stage in the paper manufacture. It has been found that even under the most adverse condition an amount by weight of polymer solids in the polymer solution equal to one percent of the fibers present is sufficient to disperse the pitch and/or pigment present. In conditions normally encountered in paper manufacture, an amount from about 0.2 to about 0.8 percent by weight is satisfactory. The actual amount to be added, of
course, will vary depending on the source and type of cellulosic fiber pulp as well as the stage of manufacture since at certain steps all the pulp liquor is drained off and a different aqueous liquor then added.
It has been further found that efficiency of the dispersant of this invention can be enhanced when the dispersant is used in hard water or when calcium or magnesium is supplied by process additives such as bleach.
This enhancement is achieved by the use of chelating agents well known in the soap and detergent art and the water treatment art. The chelating agent is used in an amount from 5 to 25 percent by weight of the invented polymer dispersant added. The term invented polymer dispersant includes the invented polymer, chelating agent, surfactant hereinafter described and water. Typically a beneficial amount of chelating agent would be 9 percent by weight. Included within the class of chelating agents are polyphosphates, e.g., sodium tripolyphosphate, gluconates, e.g., sodium gluconate, glucoheptonates, e.g., sodium glucoheptonate, potassium glucoheptonate, the alkali metal salts of nitrilotriacetic acid, the alkali metal salts of ethylenediaminetetraacetic acid and diethylenediaminepentaacetic acid, and the like. For the sake of brevity, reference is made to an article in Encyclopedia of Chemical Technology, 2nd Edition, Interscience Publishers, New York, N.Y., Volume 6 (1965), pages I through 24, which further describes chelating agents suitable for this invention and which is hereby incorporated herein by reference. The chelating agents in combination with the polymer dispersants of this invention have an unexpected synergistic effect on increasing pitch dispersion in hard water, i.e., with water having a hardness of 20 grains per gallon or more.
In addition to the foregoing chelating agents, the effectiveness of the invented polymer dispersants when used on ground wood pulp can also be enhanced by the use of nonionic surfactants. However, with the preferred compositions of this invention the amount of enhancement added by the surfactant is minimal. The surfactant is added in an amount of from 1 to 25 percent by weight of the invented polymer dispersant added. The nonionic surface active agents which are advantageously employed in the compositions of the invention are generally the polyoxyalkylene adducts of hydrophobic bases wherein the oxygen/carbonatom ratio inthe oxyalkylene portion of the molecule is greater than 0.40. Those compositions which are condensed with hydrophobic bases to provide a polyoxyalkylene portion having an oxygen/carbon atom ratio greater than 0.40 include ethylene oxide, butadiene dioxide and glycidol, mixtures of these alkylene oxides with each other and with minor amounts of propylene oxide, butylene oxide, amylene oxide, styrene oxide, and other higher molecular weight alkylene oxides. Ethylene oxide, for example, is condensed with the hydrophobic base in an amount sufficient to impart water dispersibility or solubility and surface active properties to the molecule being prepared. The exact amount of ethylene oxide condensed with the hydrophobic base will depend upon the chemical characteristics of the base employed and is readily apparent to those of ordinary skill in the art relating to the synthesis of oxyalkylene surfactant condensates. For the sake of brevity, reference is made to U.S. Pat. No. 3,793,221 of co-pending application, Ser. No. 288,772, filed Sept. 13, 1972, of.
ide, the ethylene oxide being present in amounts equal to 5 to 25 moles of ethylene oxide per mole of alkyl phenol. This group of surfactants is exemplified by octylphenoxy polyethoxyethanol.
The following examples are included to illustrate the preparation of the dispersants of the present invention and the use thereof but are not to be considered limiting. Unless otherwise noted, all parts are by weight and all temperatures are in degrees Centigrade.
The evaluation of the pitch dispersants is carried out in the following laboratory test equipment, which simulates the actual conditions in the pulp and paper mill: Two 3% X 2% X 0.032 inch copper panels are attached at the bottom (horizontally) and inthe middle (vertically) to a brass rod of 8 inches length and one-quarter inch diameter. This plunger-like device is then moved up and down-in 1,000 ml of 3.5 percent by weight consistency pulp at room temperature at a constant frequency of approximately 4 oscillations per second for 16 hours. An Atlab laboratory shaker can be used as auxiliary equipment to move the plunger in the way described above. The amount of pitch which is deposited on the plunger is determined by weighing the plunger before and after removal of the pitch. Common solvents, such as acetone or benzene-ethanol mixtures can be employed for the removal of the pitch from the plungers. The pitch deposit is expressed as percent of extractable pitch deposited. The extractable pitch is determined according to Technical Association of Paper and Pulp Industries Standard Procedure T6M-59. The pitch dispersants are evaluated by the addition of varying amounts of dispersant to the pulp and comparison of the amounts of deposited pitch with a control.
EXAMPLE 1 A l-liter, three-neck flask equipped with stirrer, thermometer, addition funnels, reflux condenser and heat exchange equipment was charged with 236 g. water. A mixture of 207 g. acrylic acid, 23 g. butyl acrylate, and 11.5 g. allyl alcohol (solution I) and 115 g. of a 6% aqueous potassium persulfate solution (solution 11) were added concurrently to the water at 85C. over 3 /2 hours. The reaction product was then neutralized with 175 g. 28% aqueous ammonia. A clear viscous solution was obtained (Brookfield viscosity: 1,800 cps). The product was evaluated as a pitch dispersant employing equipment and procedures described above. Excellent results were obtained when a sulfite process pulp was used. Without the use of the dispersant, a pitch deposit of 1 percent by weight was obtained. The
addition of dispersant (0.05 percent by weight of poly- EXAMPLE 2 A 5-liter, three-neck flask equipped with stirrer, thermometer, addition funnels, reflux condenser and heat exchange equipment was charged with 1,230 g. water. A mixture of 1,035 g. acrylic acid, g. butyl acrylate, and 115 g. allyl alcohol (solution I) and 575 g. of a 6% aqueous potassium persulfate solution (solution II) were added concurrently to the water at 80-85C. over 3 hours. The reaction product was then neutralized with 1,150 g. 50% aqueous sodium hydroxide solution. A clear viscous solution having a total active solids of 30% was obtained, which exhibited a pH of 7.7, Brookfield viscosity 3,040 cps (Spindle No. 4, 6O r.p.m.), and a density of 1.25. (The pitch dispersant properties of this product is tabulated as Sample 2A in Tables I, ll and 11] below).
A mixture of 30 g. of the above product, 18 g. Belzak BL-SO brand of sodium glucoheptonate (50% aqueous solution) and 5 2 g. water formed a clear brown solution containing 18% active solids, i.e., 9% polymer product solids and 9% sodium glucoheptonate. This blended product showed excellent performance as a pitch dispersant for a commercial lot of ground wood pulp in extremely hard water (40 grains/gallon) in contrast to an aqueous solution of the neutralized terpolymer prepared in this Example (Sample 28 in Tables I, 11 and Ill below).
Table l 40 Grain Hard Water Ground Wood Pulp Percent Polymer Solids Added Percent Pitch (Based on Weight Extractable Dispersant Dry Pulp) Pitch Deposited None 0.75
Table 11 Water Percent Effective' Hardness, Dispersant Dispersant Grains/Gallon 23 2A 5 7 l 6 80 l 72 l 28 32 -65 30 89 5 4O lOO Commercial production lot from State of Wisconsin W 100 percent equals no deposit. 0 equals amount of deposit with no dispersant. negative value indicates any of deposit in excess of deposit with no dispersant.
Table 111 Commercial production lot from State of Washington m 100 percent equals no deposit. 0 equals amount of deposit with no dispersant.
The usage of extremely small amount of dispersant in Table 11 and 111 shows in exaggerated detail the effects of minute amounts of the dispersants of this invention.
EXAMPLE 3 Following the procedure of Example 1 a dispersant was prepared based on 82 parts of acrylic acid, 9 parts of methyl methacrylate and 9 parts of allyl alcohol. The total solids of the polymer solution was 30 percent and the solution was neutralized with a percent sodium hydroxide solution. The solution had a viscosity of 2,560 cps. The Brookfield viscosity of a percent by weight dispersion of calcium carbonate to which had been added 0.75 percent of the terpolymer of this example was 2,450 cps. When the slurry is added after the bleaching step of paper making the tendency to agglomerate and settle out and thus be objectionable is avoided.
EXAMPLE 4 Following the procedure of Example 1 a dispersant was prepared based on 64 parts of acrylic acid, 27 parts of hydroxy methacrylate and 9 parts of allyl alcohol. The polymer solution solids and neutralization was the same as in Example 3. The solution viscosity was 2,648 cps. The Brookfield viscosity of a 70 percent dispersion of calcium carbonate to which had been added 0.75 percent of the terpolymer dispersant of this example was 2,950 cps.
Still other useful dispersants of this invention are pre-. pared as indicatedin Table IV below.
Table IV Parts Example Parts Alkylatc Parts All 1 Neutralizing No. Acid (a) Acid Monomer (c) Alkylatc Alco 01 Agent (b) 5 A 80 E 15 5 C 6 M G 10 15 C 7 M 82 F 9 9 D 8 A 82 G 10 8 C (a) A Acrylic M Methacrylic C Ammonium hydroxide, 28% solution D Sodium hydroxide, 50% solution E Z-ethyl hexyl acrylate F butyl acrylate G ethyl acrylate The foregoing examples and methods have been described in the foregoing specification for the purpose of illustration and not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art based on this disclosure. These are intended to be comprehended as within the scope of this invention.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
l. A composition for controlling the deposit of pitch and/or pigments in an aqueous slurry of cellulosic fibers consisting essentially of an alkali neutralized terpolymer produced by the free radical polymerization in water of a. from about 60 to 88 parts by weight of at least one alpha, beta unsaturated acid containing three to four carbon atoms,
b. from about 6 to 28 parts by weight of at least one alkylate of an alpha, beta unsaturated acid containing three to four carbon atoms, said alkylate containing from one to 18 carbon atoms, and
c. from about 4.5 to about 20 parts by weight of allyl alcohol, the total of said parts being 100.
2. The composition of claim 1 wherein the acid is acrylic acid or methacrylic acid.
3. The composition of claim 2 wherein the acid is acrylic acid.
4. The composition of claim 1 wherein the alkylate is an alkyl acrylate or an alkyl methacrylate.
5. The composition of claim 4 wherein the alkylate is butyl acrylate.
6. The composition of claim 5 wherein the acid is acrylic acid.
7. The composition of claim 1 containing from about to about 88 parts of an alpha, beta unsaturated acid, from about 6 to about 15 parts of an alkylate of an alpha, beta unsaturated acid and from about 6 to about 15 parts of allyl alcohol.
8. The composition of claim 7 containing about 82 parts acrylic acid, about 9 parts butyl acrylate and about 9 parts allyl alcohol.
9. A method for controlling the deposition of pitch or pigment from an aqueous slurry of cellulosic fibers comprising adding to saidslurry an aqueous solution v containing from about 20 to about 50 weight percent polymer solids of the polymer of claim 1 and in an amount of polymer solids up to 1 percent by weight of cellulosic fibers in the slurry.
10. The method of claim 9 wherein the acid isacrylic acid.
ll. The method of claim 10 wherein the composition contains about 82 parts acrylic acid, about 9 parts butyl acrylate and about 9 parts allyl alcohol.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 5,875, +1? DATED Z March 25, 1975 I INVENTORtS) Joseph V. Otrhalek and Gunther Elfers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown beiow:
Column 9, claim 1, line 24, the expression the total of said parts Being 100. should begin at the left-hand margin of the column on a separate line.
Signed and sealed this 27th day of May 1.975.
C. MARSHALL DANN RUTH C. MASON I Commissioner of Patents Attesting Officer and Trademarks