US 3582461 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
3,582,461 PITCH CONTROL IN PULP AND PAPERMAKING PROCESSES Stanley A. Lipowski, Livingston, and James F. Hern,
Newark, N.J., assignors to Diamond Shamrock 'Corporation, Cleveland, Ohio No Drawing. Filed Feb. 14, 1968, Ser. No. 705,298 Int. Cl. D21h 3/52 US. Cl. 16272 7 Claims ABSTRACT OF THE DISCLOSURE Water soluble dicyandiamide-formaldehyde condensates are used in controlling the pitch which forms during pulp and papermaking processes. A condensate which is the reaction product of dicyandiamide and formaldehyde is effective in controlling the pitch which is liberated during pulp and papermaking processes.
This invention relates to a method of controlling the pitch which forms in pulp and papermaking processes.
One of the frequently occurring problems in pulp and paper manufacture is caused by pitch, viz, the collection of resinous materials and gums on pulp handling equipment or paper machine parts. Pitch is liberated from the pulp during the screening, beating and refining processes and tends to accumulate as a colloidal suspension of negatively charged, insoluble sticky dark colored particles which form lumps. These particles cause trouble by collecting on mill equipment, by filling in the wires of paper machines thereby producing holes in the finished paper or by collecting on the felt or machine parts as sticky, dark colored lumps. Troublesome pitch comes mostly from resins or resinous matter in the fibers themselves. Once pitch becomes attached to the machine parts, the only way it can be removed is by scrubbing with gasoline, kerosene or special cleaning compounds. In some paper mills, special solvents are sprayed on the return side of the wire and on the felt return to remove pitch. All of these methods have proven costly and have not destroyed or prevented the formation of pitch during the pulp and papermaking processes.
In the past, it has been found that the best way to remove pitch is to prevent its formation during the papermaking or pulping processes. In the pulping process, this has been accomplished by adding various pitch control agents, e.g., chemical sequestrants, dispersing agents or surface active agents to the pulp during washing, screening and/or bleaching operations. Another common practice for controlling pitch deposits in pulp and paper mill operations is to add talc (magnesium silicate) or 'bentonite (montmorillonite) which adheres the pitch to the fibers thereby preventing pitch deposition. The main disadvantages of this practice are (1) high amounts of these materials are required (many times in excess of 0.5% by weight of the dry pulp weight), (2) incompatibility with other additives and materials used in the papermaking processes (sizing chemicals and the like), and (3) also the pitch may remain with the fibers during the pulping 3,582,461 Patented June 1, 1971 operation when these materials are used and the pitch may deposit out during the refining operation in the papermaking process.
In the papermaking process, the pitch control agents are normally added at the beater or prior to the refining operation. These agents have produced a material reduction of the pitch that collects on the paper felt and machine parts during the pulp and papermaking operation. Use of these pitch control agents has resulted in very little shutdown time in the operation of paper machines and in a decided improvement in screening conditions and pulp cleanliness as well as improved quality pulps. Some effective and commonly used pitch control agents in pulp manufacture for controlling pitch include napthalene sulfonic acid-formaldehyde condensates such as those disclosed by Dr. Poschmann in Pulp and Paper Magazine of Canada 60:T 1091 14 (1959) and the xylene sulfonic acid-formaldehyde condensates such as those described in US. Pat. No. 3,154,466-Nothum, patented Oct. 27, 1964. While use of these anionic aryl sulfonic acid-formaldehyde condensates in pulp and paper manufacture has proven to be an effective, low cost method of dispersing pitch, in many mills there is still a need for improved pitch control agents. During the past few years, there has been a strong trend toward closing up white water systems in papermaking operations. This change entails reuse of water which has been removed from the sheets during formation rather than discharging this water into streams and adding to pollution problems. When dispersant types of pitch control agents have been used, the pitch remains dispersed in the aqueous phase and continues to build up in the system as the waters are continually reused, reaching a point eventually where pitch breakout and deposition occurs. Hence, there is now an important need for a pitch control agent which is effective in small amounts and which will allow the pitch to be carried out of the system with the fibers so that the pitch will not remain in the system where it will eventually become a problem.
It is an object of this invention to provide an improved method of controlling pitch formation during the pulp and papermaking processes. A further object is to provide a more effective pitch control agent for preventing pitch from collecting on paper felt, wires and other machine parts during the pulping and papermaking processes. Still another object is to provide an improved method of making paper pulp whereby improved cleanliness in the mill equipment, in the pulp and in the paper is achieved. Other objects of this invention will become apparent from the detailed description given herein. However, it is intended that the detailed description and specific examples do not limit this invention, but merely indicate preferred embodiments.
A new class of pitch control agents for use in pulp and papermaking processes has been discovered. These agents are characterized as water soluble cationic amino last resins which are dicyandiamide-formaldehyde condensates. The dicyandiamide-formaldehyde condensates are condensates of the amino resin base, dicyandiamide, and formaldehyde as well as condensates of dicyandiamide and formaldehyde along with other amino resin bases which form water soluble cationic aminoplast resins. These agents differ from the anionic aryl sulfonic-formaldehyde condensates described above in that they are cationic in nature, i.e., they are positively charged, whereas the anionic condensates are anionic in nature, i.e., they are negatively charged. These cationic aminoplast resins control pitch formation during pulp and papermaking and prevent its collection on the processing equipment.
These cationic resins bring about the attachment of the pitch, in the form of discrete particles, to pulp fibers so that the pitch particles are uniformily distributed on the fibers. Paper produced from such pulp does not contain objectionable dark spots or specks of pitch and does not stick to the press rolls during manufacture. These improved pitch control agents are suitable for use in all methods of pulping, that is, sulfate, sulfite, semi-chemical, groundwood, reclaimed fibers and the like. Their use brings about substantial reductions in the amount of pitch which accumulates on the wires and other parts of the papermaking machine. This is particularly evident in that breaks caused by press roll sticking are markedly reduced. Reduction in breaks caused by press roll sticking is particularly important because press roll sticking can cause breaks and press roll unwrapping which results in thirty minute or longer downtimes. Us of these water soluble condensates has resulted in a marked reduction in the downtime in the papermaking operation and a decided improvement in screening conditions an pulp cleanliness as well as improved quality pulps and papers. As indicated above, the most important advantage of the process using these water soluble condensates lies in the greater elimination of difficulties caused by pitch in the production of paper and in the operation of the paper machines.
In the improved process of this invention, a pitch controlling quantity of a water soluble dicyandiamideformaldehyde condensate is added to the pitch containing pulp. Generally, the pitch control agent is added to the pulp prior to the screening or refining operations so that it may be mixed with the pulp for a period of from about 30 to about 60 minutes to obtain the maximum pitch controlling elfect. The optimum amount of pitch control agent which will be required varies because the process concerns itself with natural products (wood pulp) which contain varying amounts of pitch. For most purposes, the condensates should be added to the pulp prior to screening or refining operations in pulping and in papermaking processes in amounts of from about 0.2% to about 100% based on the weight of the pitch present in the dry pulp to effectively reduce the amount of pitch formed during the papermaking operation. These condensates can be added in greater amounts than 100% without detracting from any of their beneficial properties as pitch control agents. Since no additional beneficial results in pitch control were noted with concentrations in excess of 100%, it is not usually practical or economical to utilize larger amounts of these agents. The condensates may be added to the system in the form of a dry powder or as about 35% to 55% by weight aqueous water solution, but preferably as a 1% to by weight aqueous solution so that mixing with the pulp or papermaking furnish is rapid.
Water soluble dicyandiamide-formaldehyde condensates useful in controlling pitch are reaction products of the amino resin base, dicyandiamide, and formaldehyde as well as reaction products of dicyandiamide, at least one other amino resin base and formaldehyde. The other amino resin bases are materials such as guanidine, guanylurea, urea, thiourea, biuret, melamine, ammeline, ammelide, cyanuric acid, guanamies as well as their mixtures and derivatives. The other amino base should contain reactive hydrogen groups capable of reaction With formaldehyde and/or free methylol groups. Hence, by the expression dicyandiamide-formaldehyde condensate is meant those condensates obtained from dicyandiamide with or without at least one other amino resin base and formaldehyde or a formaldehyde liberating material, with or without etherification of the free methylol groups. Reactive methylol groups in the condensates can be etherified by reaction with an alkanol such as methanol, ethanol, npropanol, n-butanol or the like to obtain stabilized condensates. tEtherified condensates have longer shelf lives and improved stabilities and are a preferred embodiment.
Useful dicyandiamide-formaldehyde condensates include the reaction products of about one mole of dicyandiamide, about 0 to about 2 moles of one or a mixture of an additional amino resin base and about 2 to about 15 moles of formaldehyde. Formaldehyde includes formaldehyde in the form of 30 to 40% aqueous solutions, 30 to 55% alcohol solutions using alcohols such as methanol, nbutanol, i-butanol or the like, polymeric forms such as paraformaldehyde, trioxane, hexamethylene tetramine or the like as well as chemical compounds such as acetals which will liberate formaldehyde. These condensates can be prepared by any procedure which provides for reaction between formaldehyde and amino resin base so that a water soluble condensate is obtained. Reaction between the amino resin base and formaldehyde can be carried out under acid and alkaline conditions, i.e., the reaction is either acid catalyzed or alkaline catalyzed. Acid conditions usually involve a pH of from about 1.0 to about 3.5 and water soluble organic mono and polycarboxylic acids, including the corresponding hydroxy acids, are used to attain these conditions. Typical acids are acetic acid, formic acid, butyric acid, oxalic acid, malonic acid, glutaric acid, citric acid, lactic acid, glycolic acid and the like. Alkaline conditions usually involve a pH of from about 9 to about 11 and water soluble alkaline materials are used to attain these conditions. Examples of alkaline materials are alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide and other materials such as ammonium hydroxide, borax, water soluble alkali metal carbonates such as sodium carbonate, potassium carbonate or the like.
The acid catalyzed reaction is exothermic and heat is usually initially applied to initiate reaction. Reaction generally occurs at temperatures within the range of about 55 C. to about C.
The alkaline catalyzed reaction is endothermic and heat is applied to maintain a temperature of reflux which varies between 98 C. to 102 C. without pressure. Higher temperatures can be used with pressures greater than atmospheric pressure.
In etherifying the free, reactive methylol groups, the alcohol is used in equimolar amounts with respect to the methylol groups. Temperatures of about 50 C. up to the reflux temperature of the mixture are used in the etherification. The number of free methylol groups are determined by the Delong method (Rec. trav. chim. 72:653, 654 (1953).
One particularly useful condensate is the reaction product of one mole of dicyandiamide, 0.5 mole of urea and three moles of formaldehyde in the presence of 0.2 mole of formic acid as catalyst followed by etherification With methanol of the free, reactive methylol groups in the reaction product. This condensate is an acid catalyzed condensate and is a preferred embodiment. Procedures which yield acid catalyzed condensates are described in US. Pat. No. 2,990,397Fetscher et al., June 27, 1961 and in U.S. Pat. No. 3,106,541Lipowski et al., Oct. 8, 1963, said procedures being incorporated by reference herein. Another useful acid catalyzed condensate is the reaction product of one mole of dicyandiamide, three moles of formaldehyde, one mole of urea and 0.2 mole of formic acid followed by etherification with methanol of the free reactive methylol groups. Still another useful condensate is the reaction product of one mole of dicyandiamide, three moles of formaldehyde and 0.2 mole of formic acid followed by etherification with methanol of the free reactive methylol groups. Alkaline catalyzed condensates are also useful as pitch control agents. One useful alkaline catalyzed condensate is the reaction product of one mole of dicyandiamide and four moles of formaldehyde using sodium hydroxide solution as a catalyst wherein sufficient catalyst is added to obtain a reaction mixture having a pH of about 9. These condensates are added to the pulp or papermaking furnish to control pitch formation and should not afiect other properties of pulp or paper produced from the furnish.
These condensates are useful in controlling pitch formation in kraft or sulfite bleach plants, groundwood mills, paper mills or the like. They are effective at concentrations of about 0.75 lb. per ton dry resin on dry fiber in keeping systems clean and preventing pitch deposition in a paperboard mill. Likewise they are efiective at one lb. per ton dry resin on dry fiber weight in preventing press roll sticking and picking problems in a paper mill producing fine printing papers. The condensates are also effective at 0.5 lb. per ton in pitch control in a paper mill producing highly refined light weight paper grades.
For a fuller understanding of the nature and objects of this invention, reference may be made to the following examples. These examples are given merely to illustrate the invention and are not to be construed in a limiting sense. All parts, proportions, percentages and quantities are by weight unless otherwise indicated. The term g. and C. are used to indicate grams and degrees centigrade respectively in these examples.
EXAMPLE I 84 g. (1 mole) of dicyandiamide, 243 g. (3 moles) of 37% by weight inhibited aqueous formaldehyde solution, 10.2 g. (0.2 mole) of formic acid 90% active were charged to a 1-liter four neck glass reaction flask equipped with an agitator, thermometer and condenser. The inhibited formaldehyde solution contained 8% by weight of the methanol as an inhibitor. The resulting reaction mixture was agitated and heated gradually over 30 minutes to 60 C. Agitation was continued for one hour while the temperature was maintained constant at 60 C. Then the temperature of the mixture was gradually raised to its boiling point. The exothermic reaction, which occurred when the temperature was raised above 60 C., was controlled by intermittent cooling. The boiling point of the reaction mixture was reached after about 45 minutes of heating and the mixture was boiled for two hours. The reaction mixture was then cooled to 70 C., 30 g. (0.5 mole) of urea was added to the reaction mixture and the mixture was boiled for 30 minutes and then cooled to 50 C. 33 g. of methanol was added to the reaction mixture to etherify free methylol groups and the mixture was agitated for 30 minutes at 50 C. and then cooled to room temperature. The resulting reaction product was a dicyandiamide-formyldehyde condensate, that is, a cationic aminoplast resin in the form of a water white syrup containing 45% by weight solids. The product was soluble in water at all dilutions. The pH of a by weight solution of the product was 7.2.
EXAMPLE II 84 g. (1 mole) of dicyandiamide, 243 g. (3 moles) of a 37% by weight uninhibited aqueous formaldehyde solution, 10.2 g. (0.2 mole) of formic acid 90% active were charged into a 1-liter four neck glass reaction flask equipped with an agitator, thermometer and condenser. The reaction mixture was agitated and gradually heated over 30 minutes to 60 C. Agitation was continued for one hour while the reaction temperature was maintained constant at 60 C. Then the temperature was gradually raised from 60 C. to the boiling point of the reaction mixture. The exothermic reaction, which occurred when the temperature was raised above 60 C., was controlled by intermittent cooling. The boiling point of the reaction mixture was reached after about 45 minutes of heating and the mixture was boiled for 1.5 hours. At the end of this period, the reaction mixture had become very viscous and was close to the gelation point. The reaction mixture was cooled rapidly to C. and 60 g. (1 mole) of urea was added. Then the reaction mixture was reheated to its boiling point where the viscosity of the reaction mixture dropped rapidly and substantially. The reaction mixture was then boiled for 15 minutes and cooled to 60 C. 40 g. of methanol was added to etherify the free methylol groups present in the dicyandiamide-formaldehyde condensate and the reaction mixture was agitated for 30 minutes to complete etherification of the free methylol groups. The reaction mixture was then cooled to room temperature. The reaction product was a dicyandiamide-formaldehyde condensate, that is, a cationic aminoplast resin in the form of a water white syrupcontaining 55% by weight solids and had a higher viscosity than the condensate obtained in Example I above. The product was soluble in water at all dilutions. The pH of a 5% by weight solution of the product was 7.0. The product had a free formaldehyde content of about 0.2% by weight and had an unlimited shelf life.
EXAMPLE III 84 g. (1 mole) of dicyandiamide, 243 (3 moles) of 37% by weight uninhibited aqueous formaldehyde solution, 12 g. (0.235 mole) of formic acid active were charged into a 1-liter four neck flask equipped with an agitator, thermometer and condenser. The mixture was agitated for 1.5 hours at room temperature. External heat was applied to the reaction mixture and the mixture was heated to 60 C. over a one hour period. The reaction temperature was gradually raised from 60 C. to the boiling point of the mixture. The exothermic reaction, which occurred when the temperature was raised above 60 C., was controlled by intermittent cooling. The boiling point of the reaction mixture was reached after 1.33 hour of heating. The mixture was boiled for 10 minutes and then cooled rapidly to 55 C. 50 g. of methanol was added to etherify free methylol groups and the mixture was agitated without external heating or cooling until the tem perature of the mixture dropped to 25 C. The resulting reaction product was a water soluble dicyandiamideformaldehye condensate in the form of a clear water soluble syrup containing 41% by weight solids.
EXAMPLE IV 84 g. (1 mole) of dicyandiamide, 324 g. (4 moles) of 37% by weight uninhibited aqueous formaldehyde solution were charged into a 1-liter four neck flask equipped with an agitator, thermometer and condenser. The pH of the mixture was adjusted to 9.0 by the addition of two drops of 50% by weight aqueous sodium hydroxide solution. The alkaline reaction mixture was then heated over 15 minutes to its reflux temperature (102 C.). The reaction mixture was refluxed for 3 additional hours. At the end of this period, the reaction mixture had become very viscous and was cooled to 80 C. 60 g. (1 mole) of urea, g. of methanol and g. of water were added to the mixture and the mixture was stirred without external cooling or heating until the reaction temperature was 25 C. The resulting product was a water soluble dicyandiamideformaldehyde condensate. The pH of the product was adjusted to 6.8 by the addition of 4.5 g. of 50% by weight sulfuric acid. The resulting product was a clear, water soluble syrup containing 32% by weight solid.
EXAMPLE V The procedure given below was used to evaluate the pitch control properties of the following Pitch Control Agents (Compound No.):
I-Xylene sulfonic acid-formalydehyde condensate described in Example 1 of U.S. Patent 3,154,466Nothum.
II-Naphthalene sulfonic acid-formaldehyde condensate described in Example III of U.S. Patent 3,154,466, Northum.
IIINaphthalene sulfonic acid-formaldehyde condensate described in Example III of U.S. Patent 3,154,466, Northum.
IVDicyandiamide-formaldehyde condensate described in Example I above.
V-Dicyandiamide-formaldehyde condensate described in Example 11 above.
VI-Dicyandiamide-formaldehyde condensate described in Example III above.
VIIDicyandiamide formaldehyde condensate described in Example IV above.
15 g. of alpha cellulose shreds is charged to 600 cc. of hot water at about 50 C. in a 1-liter beaker placed on a heated water bath. The alpha cellulose is chosen as the pulp source because it is substantially free of pitch. Alpha cellulose sheets are shredded and charged in the form of shreds. The mixture is agitated with a high speed agitator equipped with cutting blades until the shreds of alpha cellulose are converted to pulp. Then the compound to be tested as a pitch control agent is added in the desired quantity to the pulp mixture and the mixture agitated for minutes. The pitch, which is the sap from the Balsam Fir tree, is dispersed in acetone. Usually about 0.7 to about 0.8 gram of the pitch is dispersed in 30 ml. of acetone. The sap dispersion is added to the agitated heated pulp mixture and the pitch remains in the pulp mixture in the form of a dispersion. The pulp mixture is then heated to 75 to 80 C. with agitation and agitated for one hour. After one hour at 75 to 80 C. agitation is discontinued. The agitator is removed, rinsed with warm water, dried for about 30 minutes in an oven at 120 C., cooled and weighed to determine the quantity of pitch remaining on the agitator, that is, the increase in weight of the agitator. The percent of pitch remaining on the agitator is determined by the following formula:
Pitch Percent By Wt. Deposited on agitator Increase in weight of agitator Results obtained with each of the compounds as well as the blank in accordance with the above procedure are set forth in Table I below. The small differences in the amounts of pitch and pitch control agent in Table I which. were used in the tests and which are reproduced therein are considered to be statistically insignificant in that they present minor variations within experimental limits.
The pitch control agents shown in Table I are those listed above as Material No. I through VII. The term Blank means that a pitch control agent was not used. Pitch g. represents the weight of pitch added to g. of alpha cellulose. Pitch control agent g. represents the weight of the particular agent which was added to the pulp mixture. Pitch control agent percent weight based on pitch represents the weight percent of pitch control agent based on the Weight of pitch used. Pitch g. deposited on agitator represents the weight of pitch which remained on the agitator after rinsing, drying, and cooling. Pitch percent by wt. deposited on agitator represents the percent of pitch remaining on the agitator as determined by the formula given above.
It is clear from the data in Table I that the dicyandiamide-formaldehyde condensates (Material Nos. IV through VII) are effective pitch control agents. These dicyandiamide-formaldeh'yde condensates bring about the attachment of pitch to pulp so that the pitch particles are uniformly distributed on the fibers as evidenced by clear beaker walls and little if any pitch deposited on the agitator.
The efiicacy of the pitch control agents of the present invention was further demonstrated on a full plant scale in several successive pulping and papermaking operatiOns. These demonstrations appear as follows:
EXAMPLE VI A paperboard mill producing bleached paperboard grades using bleached sulfite fiber and a furnish containing rosin size and alum was plagued with pitch problems for many years. Immediately before the trial with the pitch control agents disclosed in this invention, this mill had been adding a surfactant, sequestrant type pitch control agent at the rate of about 2 lbs. per ton of dry fiber at the stock chest prior to refining and another 2. lbs. per ton after refining. Pitch control with this application had been sporadic with intermittent control and deposition problems on mill equipment, Fourdrinier wires, press rolls, etc.
The sporadic results were believed to be the result of white water reuse at this mill and build up of dispersed pitch in the system until periodic deposition occurred. The pitch control agent described in Example I of the present invention was diluted to 5% solids with water and introduced into the system at the rate of 0.75 lb./ton dry resin on dry fiber, one half being added at the stock chest prior to refining and the remainder immediately after refining. This application rate was continuous over a three month period with the system remaining clean and no deposition of pitch occurring at any point in the system subsequent to the application.
EXAMPLE VII A paper mill producing various grades of fine printing papers had a long history of press roll sticking and picking problems resulting in considerable lost production time because of paper breaks and shut downs for clean up of sticking materials at the first press section of their Fourdrinier paper machine. Immediately prior to a trial with the condensates and process of this invention, the mill was using up to 5 lbs. per ton of dry fiber of a naphthalene sulfonic acid-formaldehyde condensate which was added to the pulper prior to refining. This condensate permitted the mill to operate their machines for longer durations between shut downs (1 to 2 days), but did not prevent press roll build up and sticking. Furnish here was a blend of bleached sulfate and sulfite pulps, rosin size, alum and titanium dioxide. The pitch control agent described in Example I of the present invention was introduced into the pulper at the rate of 1 lb. per ton (dry resin on dry fiber weight) and has been used continuously for a 5 month period with no press roll picking or sticking problems.
EXAMPLE VIII A paper mill producing highly refined light weight paper grades using a furnish containing sulfate, sulfite and groundwood pulps along with rosin size, alum and filler pigments had a continuing pitch problem. During the past few years this mill has been maintaining pitch control using surfactant type pitch control agents. The pitch control agent described in Example I of the present invention was introduced into the stock chest prior to refining at the rate of 0.5 lb. per ton (dry resin on dry fiber weight) which represented a cost reduction of 50% over normal surfactant use. This pitch control agent has been used at this application level continuously for a 4 month period with no pitch deposits anywhere in the system.
TABLE I Pitch control Pitch, agent, percent Pitehcontrol percent P1tch,g. by wt.,
agent Pitch by wt., depositdeposit- (Compound control based on ,ed on ed on N o.) Pitch,g. agent, g. pitch agitator agitator Remarks Blank 0.752 0 0.256 34.0 Very sticky beaker walls. Heavy pitch deposit on agitator.
I 0.750 0.500 66.6 0.086 11.3 No pitch deposit on beaker walls. Smooth beaker walls. Substantial pitch deposit on agitator.
IT 0.750 0.500 66.6 0.121 16.1 Slightly sticking beaker walls. Substantial pitch deposit on agitator.
III 0. 755 0.500 66. 3 0. 206 27. 3 Very sticky beaker walls. Heavy pitch deposit on agitator.
IV O. 750 0. 495 66. 0 0 0 Very clean beaker walls. No pitch deposit on agitator.
V 0.833 0.510 61.2 0 0 Do.
V 0.732 0.223 30.4 0.017 2.3 Clean beaker walls.
Slight pitch deposit on agitator.
VI 0. 759 0. 430 56. 7 0 0 Very clean beaker walls. No pitch deposit on agitator.
VII 0.750 0.502 67.0 0.015 2.0 Cleanbeaker walls.
Slight pitch deposit on agitator.
What is claimed is:
1. In pulp and papermaking processes, the improvement which comprises adding to the pulp from about 0.2% to about 100% of a water soluble cationic dicyandiamide formaldehyde condensate based on the weight of pitch present in the pulp to prevent deposition of pitch on machinery used in said processes.
2. The process of claim 1 where said improvement comprises (a) adding said condensate to said pulp, and thereafter (h) screening said pulp, said screening taking place at least thirty minutes after said condensate is added to said pulp.
3. The process of claim 1 wherein said condensate is the reaction product of from about one mole of the amino resin base, dicyandiamide, from about 0 to about 2 moles of at least one other amino resin base and from about 2 to about moles of formaldehyde.
4. The process of claim 3 wherein said condensate is etherified by reaction with an alkanol.
5. The process of claim 3 wherein said condensate is the reaction product of one mole of dicyandiamide, 0.5 mole of urea and three moles of formaldehyde in the presence of 0.2 mole of formic acid as catalyst followed by etherification with methanol of the free, reactive methylol groups in the reaction product.
6. The process of claim 3 wherein said condensate is the reaction product of one mole of dicyandiamide and three moles of formaldehyde in the presence of 0.2
mole of formic acid as catalyst followed by etherification with methanol of the free, reactive methylol groups in the reaction product.
7. The process of claim 3 wherein said condensate is the reaction product of one mole of dicyandiamide, one mole of urea and four moles of formaldehyde in the presence of aqueous sodium hydroxide solution as catalyst.
References Cited UNITED STATES PATENTS S. LEON BASHORE, Primary Examiner F. FREI, Assistant Examiner US. Cl. X.R.