WO2001063050A1

WO2001063050A1 - An organic coagulant composition for treating coated broke

Info

Publication number: WO2001063050A1
Application number: PCT/US2001/005231
Authority: WO
Inventors: F. Kenneth Henderson; Craig W. Vaughn; Dennis Davis
Original assignee: Calgon Corporation
Priority date: 2000-02-24
Filing date: 2001-02-16
Publication date: 2001-08-30
Also published as: AU2001238483A1

Abstract

Coated broke is treated with an organic coagulant composition comprising preferably a branched polyamine and a copolymer comprising an acrylamide and a DADMAC in a preferred weight percent ratio of 50 to 50 based on the weight of the copolymer. The weight ratio of the branched polyamine to the copolymer ranges from 1:4 to 4:1 in a blended composition which is added to the coated broke slurry so the white pitch attaches to the fiber in the furnish thereby reducing the tendency for the coating binders and pigments of the coated broke to accumulate resulting in deposits on the paper making machinery which ultimately can result in defects in the formed paper. The average weight molecular weight of the branched polyamine and the DADMAC ranges from 500,000 to 7 million and that of the acrylamide is from 3 to 7 million.

Description

AN ORGANIC COAGULANT COMPOSITION FOR TREATING COATED BROKE

FIELD OF THE INVENTION

The invention pertains to a composition comprised of organic coagulants for treating coated broke so that the

"pitch" or sticky material in the coated broke attaches to the fiber in the stock or furnish used in making paper products, thereby reducing the tendency for the coating binders and pigments of the coated broke to accumulate resulting in deposits on the paper making machinery and associated parts thereof.

BACKGROUND OF THE INVENTION

In the manufacture of paper, broke is re-pulped and reused as part of the paper furnish, along with virgin or fresh pulp. "Broke" is a term used in the paper industry that refers to materials, such as fibers, fillers, and additives, used in the paper making process, which is internally recycled for use in the process. The material used in a coating formulation for coating a paper product in a paper mill that is internally recycled and reused in the mill is referred to as "coated broke" . Coated broke generally is comprised of starch and/or latex or styrene butadiene rubber (SBR) polyvinyl acetate (PVA) binders; pigments, such as titanium dioxide (Ti0₂) , kaolin clay, and calcium carbonate (CaC0₃) and combinations thereof; and fiber. When recycled, the coated broke is re-pulped and added to the paper furnish, along with fresh pulp, i.e. pulp that had not been previously used. Coated broke, before being treated, generally contains "white pitch" which is a white sticky deposit derived from the binder materials (starch, latex, styrene butadiene rubber, and polyvinyl acetate) and the coating pigments or fillers used in the coating formulation.

If the coated broke is left untreated, the coating binders of the coated broke generally accumulate resulting in white sticky deposits on several parts of the paper machine, such as the wire mesh belts, wires, foils, press rolls, press felts and chests. Also, these deposits can occur in the stock lines, i.e. pipes that 5 carry the stock (pulp, pigments and process additives) from the pulp chests (tanks) to the headbox of the paper machine. This accumulation can cause weak areas or holes in the paper, build-up of residues and sticky masses, and clogging of felts and the like in the

]0 manufacture of paper. Occasionally these deposits appear in the formed paper as brown lumps or patches (dirt specks or stickies) .

These deposits then require either a machine shutdown in order to remove the deposits off of the

15 machine parts, and/or requires a cleaning program whereby the paper machine parts, particularly, the wires and press felts are either continuously or batch cleaned chemically or mechanically.

. Pitch is the name given by paper manufacturers to

20 the natural substance that is derived from colloidally dispersed components of wood resin of the wood pulp. Both the white pitch and the natural pitch in the paper furnish are typically controlled in the paper process by one of three processes. These processes are:

25 1) dispersion; 2) attachment; or 3) detackification.

Dispersion is the process that involves the adding of a dispersant to the stock or the furnish at the point in which the stickies or pitch are liberated into the stock system. The attachment process involves attaching the

30 negatively charged pitch to the fiber in the paper furnish with a low molecular weight cationic polymer. The detackification process involves adding an agent that coats the surface of the pitch in order to make the pitch non-sticky.

35 As discussed herein above, coated broke generally is comprised of those materials used in the coating formulation, i.e. binders; fillers or pigments, i.e. titanium dioxide (Ti0₂) , kaolin clay, calcium carbonate and combinations thereof; fines; and fibers. This coated broke is added to a paper furnish which also is comprised of a fresh supply of pigments, fines and fibers to form a wet paper web which then is formed into a paper sheet .

The net charge on the binders and pigment particles in the coated broke is generally highly anionic, i.e. very negative. Since the retention aid system may comprise a polyelectrolyte (synthetic polymer) with a cationic or anionic charge, these polyelectrolytes will react with both the coated broke and the pigments, fines and long fibers of the paper furnish. The anionic charge and surface area in the coated broke is sufficient to overwhelm the retention aids before the retention aids have a chance to react with the entire paper furnish.

The binder and pigment particles of the coated broke must therefore be neutralized and fixed to the fines and fiber in the coated broke so that the retention aid will be available to react with the remainder of the paper furnish (pigments, fines and long fiber) . The attachment or fixation process discussed herein above is where the stickies or pitch, both white and natural along with the pigments are fixed to the fines and fibers of the coated broke by the polymer added to treat the coated broke . In the attachment process discussed herein above, the white and natural pitch is caused to attach itself to the fines and fibers of both the recycled portion (coated broke), and the fresh portion of the paper furnish. In the past, the coated broke had been treated with an organic coagulant, such as diallyl dimethyl ammonium chloride (DADMAC) , polyamine, and an inorganic coagulant such as alum and polyaluminum chloride (PAC) , polyethyleneimine, or blends thereof in order for the white pitch to attach itself to the fines and fibers. These chemistries were added to the coated broke soon after the pulping process so as to reduce the degree of accumulation of the binders and/or pigments, and therefore, reduce the tendency for large sticky deposits to attach or fix themselves to the associated parts of the paper machine, such as the chest walls, foils and press rolls.

5 An example of the use of DADMAC is disclosed in U.S.

Patent No. 5,131,982 assigned to Nalco Chemical Company. The method allows the recycling of paper waste containing binders, etc. that generally interfere in the manufacture of paper. The coated broke is repulped into an aqueous

10 slurry and a polymer consisting of at least 20 wt. % of a diallyl dimethyl ammonium chloride (DADMAC) monomer is admixed with the slurry. An embodiment encompasses the use of a copolymer of DADMAC and acrylamide having a weight ratio of about 2:1 to about 1:2 or of about 3:1 to

15 about 1:3.

U. S. Patent No. 4,997,523 assigned to Betz discloses a method for treating coated broke in a paper mill repulping operation by the addition of an effective amount of a tetrafunctional alkoxylated diamine and

!0 phosphate, phosphoric acid or its salt. These additives are useful for treatment of coated broke containing styrene butadiene and/or polyvinyl acetate binders. About 99% of the coated broke particles are reduced to 100 to 200 microns.

!5 U.S. Patent No. 5,466,338 assigned to Nalco Chemical

Company discloses the treatment of repulped coated broke slurry, which allows the slurry to be recycled as cellulose fiber to a paper making machine. The treatment involves the addition of a water soluble polymer

10 dispersion that is formed by polymerizing a water soluble mixture comprising at least one cationic monomer and a methacrylamide in an aqueous solution of a polyvalent anion salt.

Some of these known methods discussed above for

15 treating coated broke generally relate to coated broke comprising a latex and/or a starch as the binder and a coating pigment including titanium dioxide. It has been found that these known methods of treating a coated broke containing the rutile form of titanium dioxide in the coating pigment in the coating formulation may be generally ineffective in controlling white pitch. This has been theorized that this may be due to the fact that the rutile form of titanium dioxide is processed by different dispersants with more anionic charge and in higher amounts of dispersants than that of the anatase form of titanium dioxide (Ti0₂) . Therefore, some or all of the above disadvantages occur in the manufacture of a basic paper web made from repulped coated broke.

The inventors theorized that the coated broke comprising the anatase form of titanium dioxide may have less anionic dispersant as a result of its processing than does the rutile form of titanium dioxide. This theory was confirmed by chemical analysis wherein it was found that the anatase form of titanium dioxide contained 0.1% anionic dispersant, whereas the rutile form of titanium dioxide contained 0.5% anionic dispersant. The inventors believe that this additional amount of anionic dispersant in the rutile form of titanium dioxide may tend to make the titanium dioxide particles more difficult to be retained in the paper web during the papermaking process even though the rutile form of titanium dioxide is only a very small part, i.e. about 3 parts per 115 parts of the coating formulation in the coated broke .

There is, therefore, a need to provide a treatment program for treating recycled coated broke which has been repulped to a slurry for the purpose of recycling it as cellulose fiber to the paper machine, particularly when the coating formulation in the coated broke includes a titanium dioxide pigment regardless of whether the titanium dioxide comprises either the anatase form and/or the rutile form.

Although some of the know methods for controlling pitch involve the use of one or more polymers, or a composition of polymers or copolymers, the inventors have found an improved method and composition for controlling white pitch in recycled cellulose fibers obtained from coated broke recycle that has not been considered in the prior art.

SUMMARY OF THE INVENTION

The invention relates to controlling at least white pitch in the manufacture of a paper sheet which is formed from a pulp containing fresh pulp and recycled coated broke. The invention may have particular application in the instance where the coated broke includes the rutile form and/or the anatase form of titanium dioxide as a coating pigment. In the invention, the coated broke slurry which is to be added to fresh fiber for use in manufacturing paper is formed by beating and repulping coated broke in aqueous slurry and admixing an organic coagulant composition into the coated broke slurry. The organic coagulant composition comprises at least a first polymer and a second polymer or copolymer, which, preferably, are blended together before the composition is added to the coated broke slurry. The two polymers, i.e. a first polymer and a second polymer, comprise at least three monomers. The first polymer is, preferably, a cationic monomer and is selected from the group consisting of a branched polyamine and a DMDAAC. The second polymer preferably is a copolymer comprising a nonionic monomer and a cationic monomer, and preferably is a copolymer with a 50:50 wt . % ratio of acrylamide: dimethyl diallyl ammonium chloride (DMDAAC) based on the weight of the second polymer in the organic coagulant composition. The ratio of the first polymer, which preferably is a branched polyamine, to the second polymer ranges from about 1:4 to about 4:1 on a weight basis of the organic coagulant composition. These two polymers can be blended together and then admixed into the coated broke in the repulping process in order to coagulate the white pitch and the binder components of the coated broke onto the fibers of coated broke. This treated coated broke is then added to the fresh fiber pulp. The first polymer, whether a branched polyamine or a DADMAC, has an average weight molecular weight ranging between about 500,000 to about 3 million, and preferably is about 1 to 2 million. With regard to the second polymer, the acrylamide has an average weight molecular weight ranging from about 3 to about 7 million, and preferably, is about 4 to about 5 million, and the DADMAC monomer has an average weight molecular weight ranging from about 500,000 to about 3 million, and preferably is about 1 to 2 million. The cationic monomer of the copolymer of the invention, in addition to diallyl dimethyl ammonium chloride (DADMAC) , may be selected from the group consisting of dialkyl diallyl ammonium monomer, quaternary dialkyl diallyl ammonium, methacryloxyethyl trimethyl ammonium chloride, acrylamido propyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride (AETAC) , methacrylamido propyl trimethyl ammonium chloride, quaternized derivatives of N,N- dimethyl amino ethyl methacrylate, dimethyl amino ethyl acrylate, and dibutyl amino ethyl methacrylate. The nonionic monomer, in addition to the acrylamide (AM) , may be selected from the group consisting of N-vinylamide, N- alkylacrylamide, vinyl acetate, acrylate esters, diacetone acrylamide, and N,N-dialkylacrylamide, vinyl pyrrolidone, and vinyl alcohol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term "active basis" means a concentration of additives based on the solids in the stock solution. The term "effective amount" refers to that amount necessary to bring about a desired result; for example, the amount needed to improve retention or attachment of the white pitch and its components, i.e. binders and pigments, of a recycle coated broke to the fines and fibers of the recycle coated broke. The invention provides a process and an organic coagulant polymer composition for treating recycled coated broke which has been repulped to a slurry for the purpose of recycling it as cellulose fiber and pigment to the paper machine. The invention may have particular application when the coated broke comprises a coating formulation which includes a pigment which includes the rutile form and/or the anatase form of titanium dioxide.

The invention comprises adding the organic coagulant polymer composition to the coated broke slurry for the purpose of fixing the white pitch onto at least the fibers of the slurry. The composition of the invention is an organic coagulant composition that comprises at least two polymers with at least three monomers. The first polymer is a cationic monomer and is selected from a group consisting of a branched polyamine and a diallyl dimethyl ammonium chloride (DADMAC) polymer. The second polymer preferably is a copolymer comprising a nonionic monomer and a cationic monomer, and preferably is a copolymer of acrylamide and dimethyl diallyl ammonium chloride (DMDAAC) in a weight percent ratio ranging from about 15:85 to about 85:15, and preferably about 50:50 based on the weight of the second polymer in the organic coagulant composition. The ratio of the first polymer, which preferably is a branched polyamine, to the second polymer ranges from about 1:4 to about 4:1 on a weight basis of the organic coagulant composition. These two polymers are preferably blended together either in dry form or solution form and then admixed into the coated broke in the repulping process in order to coagulate the white pitch and the binder components of the coated broke onto the fibers of coated broke.

The branched polyamine useful in accordance with the present invention has an average weight molecular weight ranging from about 500,000 to about 3 million, and more preferably, ranging from about 1 to about 3 million, and most preferably is about 1 to about 2 million. The branched polyamine is present in an amount between about 10 weight percent to about 40 weight percent based on the weight of the organic coagulant composition, and more preferably is about 17.5 weight percent to about 35 weight percent. An example of a branched polyamine, which may be used in the composition of the invention, is a low molecular weight coagulant about 50% active in solution form which is polymer I listed herein below which is available under the trade name ECCat™ 2060 from ECC International Inc., GA.

The copolymer of the second polymer of the composition of the invention preferably comprises acrylamide and diallyl dimethyl ammonium chloride (DADMAC) polymer in a weight percent ratio ranging from about 15:85 to about 85:15 based on the weight of the second polymer in the composition of the invention and preferably, is about 50 weight percent acrylamide to 50 weight percent DADMAC, or about 30.7 mole percent acrylamide to about 69.3 mole percent DADMAC. The acrylamide portion preferably has an average weight molecular weight ranging from about 3 to about 7 million, and preferably is about 4 to about 5 million. The DADMAC portion preferably has an average weight molecular weight ranging from about 500,000 to about 3 million, and more preferably, from about 1 to 3 million, and most preferably is about 1 to about 2 million. The acrylamide is present in an amount between about 30 weight percent to about 40 weight percent, and preferably is about 32.5 to about 41.25 weight percent based on the weight of the organic coagulant composition of the invention. The DADMAC is present in an amount between about 30 weight percent to about 40 weight percent, and preferably is about 32.5 to about 41.25 weight percent based on the weight of the organic coagulant composition. An example of a 50 wt %/50 wt % acrylamide/DADMAC useful in accordance with the present invention is a copolymer available under the trade name ECCat™ 777 from ECC International Inc., Georgia, and is listed below as polymer A. These polymers A and I are constituted in the organic coagulant compositions of the invention which are represented below as N, 0, P, and Q and which are used in the Examples .

The cationic monomer of the copolymer of the invention, in addition to diallyl dimethyl ammonium chloride (DADMAC) , may be selected from the group consisting of dialkyl diallyl ammonium monomer, quaternary dialkyl diallyl ammonium, methacryloxyethyl trimethyl ammonium chloride, acrylamido propyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride (AETAC) , methacrylamido propyl trimethyl ammonium chloride, quaternized derivatives of N,N- dimethyl amino ethyl methacrylate, dimethyl amino ethyl acrylate, and dibutyl amino ethyl methacrylate. The nonionic monomer, in addition to the acrylamide (AM) , may be selected from the group consisting of N-vinylamide, N- alkylacrylamide, vinyl acetate, acrylate esters, diacetone acrylamide, and N,N-dialkylacrylamide, vinyl pyrrolidone, and vinyl alcohol. Preferably, the composition of the invention comprises branched polyamine and a copolymer of acrylamide and DADMAC in a weight ratio of the composition ranging from about 1:4 to about 4:1 of polyamine :acrylamide/DADMAC copolymer, and preferably ranging from about 3:1 to about 1:3 of branched polyamine : acrylamide/DADMAC copolymer in the organic composition.

The amount of composition comprising the polyamine polymer : acrylamide/DADMAC copolymer that has been found effective for fixing the white pitch to the fiber ranges from a concentration of about 0.01 pounds active composition of the invention per ton of coated broke solids up to and including about 20 pounds active composition per ton of total broke solids.

Preferably, the treatment levels range from between about 0.02 pounds composition per ton total coated broke solids to about 19.0 pounds composition per ton total coated broke solids. Most preferably, the effective treatment ranges between about 0.03 pounds composition per ton to about 18.5 pounds composition per ton total coated broke solids. Each source of coated broke can and does have its own character therefore the treatment level demand for the blended composition of the invention to treat the white pitch does vary with the source of coated broke.

The first polymer and the second polymer of the organic coagulant composition as described herein preferably are blended together and this blend is added after the pulper in a broke fiber recycle stream and prior to any holding chest or storage vessel, or preferably this composition of the invention may be added after the re-pulped coated broke slurry has been retained .in a holding chest and before or during the time this coated broke fiber slurry is being pumped to a blend chest for the purpose of blending this coated broke fiber source with other fiber sources such as from raw wood fibers prior to us in making base paper sheet . The addition of the organic coagulant composition preferably is after the holding chest in a broke recycle process used to re-pulp coated broke forming a broke fiber slurry and prior to the blending of this re-pulped coated broke fiber slurry with the other fiber sources in the blend chest used to store paper fiber slurries prior to use in the manufacture of paper sheet .

Even though a preferred method is for both polymers of the invention to be blended into a composition prior to being added to the coated broke slurry, there may be some instances, where the first polymer and the second polymer are added to the coated broke slurry within a few seconds or minutes of each other and in a varying order without distracting from the scope and spirit of the invention.

Evaluation of Coagulants and Coagulant Blends

A study was performed to evaluate different coagulants and coagulant compositions, including the organic coagulant composition of the invention. This study was done to determine which coagulants and/or coagulant compositions effectively attached the white pitch (coating binder) and coating pigments (titanium dioxide, calcium carbonates, and kaolin clay) to the fibers instead of agglomerating and depositing out onto the various paper machine parts. In view of the variable nature of the coated broke, testing was done on several occasions to determine which treatment gave the most consistent performance. These tests are more fully described and explained in the examples below.

The study was done on coated broke obtained from an alkaline coated fine paper machine of a commercial paper mill. The coated broke contained polyvinyl acetate (PVAC) starch that caused extreme white pitch deposits on the foils under the wire of the paper machine. The deposits had a tendency to build up so quickly that the mill workers attending the paper machine used a scraper to remove the PVAC off of the foils while the paper machine was still running. This procedure, referred to as "flossing the foils", had to be repeated several times in the paper mill during a single shift operation.

General Experimental Procedure Of Testing Filter Turbidity

A filtrate turbidity test was performed to evaluate the performance of the several coagulants and/or coagulant compositions including the organic coagulant composition of the invention to retain the coated broke materials, i.e. attach colloidal and fine particles of the coated broke onto the fiber, during a filtration process. The test procedure was as follows:

1. The coated broke obtained from the paper machine of the commercial paper mill was diluted with tap water to 1.0% consistency so that the coagulants to be tested could be mixed into the stock. If available, the same water used to dilute the stock in the pulper can be used to dilute the coated broke.

2. 350 ml to 500 ml of diluted coated broke was poured into a one liter square jar and mixed for 60 to 90 seconds at 1200 rpm with a Britt Jar type mixer (from Electro Craft) which is a variable speed mixer with three paddle blades having a 2-inch diameter.

3. The coagulants or coagulant blends were added to the coated broke and mixed for an additional minute.

4. The coated broke was poured through a 500 ml graduated drainage tube fitted on the bottom with a 100 mesh screen which acts to separate the fiber and fines of the coated broke from the colloidal suspended materials. The tube was inverted 5 times to ensure that the coated broke and coagulant or coagulant blend were homogenous . The bottom stopper was removed and the top air vent opened to permit free drainage of the filtration through the mesh screen. The first 50 ml of the filtrate, being the most turbid, were collected, and turbidity tests were performed on these filtrate samples. Instead of a drainage tube, the treated coated broke can be filtered through coarse filter paper or centrifuged for a short duration to separate the cloudy solution from the long fiber and/or fines.

5. The turbidity of each filtrate sample was measured. Turbidity represented as percent transmittance for these treated samples and polymer dosages are shown in Tables 1-6. The polymer dosages ranged from 0.25 to about 10 pounds active coagulants/coagulant composition per ton total coated broke solids. Method of Measuring Turbidity A Bausch & Lo b Spectronic 21 spectrophotometer (420 nm) was used to measure filtrate transmittance which was considered as being proportional to the concentration of suspended materials in the filtrate samples. The transmittance corresponds to turbidity, but is measured on a percent (%) scale instead of turbidity units, i.e. NTU. The "higher" filtrate transmittance level represents the coagulant and/or coagulant blend and dose that attaches the most colloidal and fine particles onto the fiber in the coated broke. The spectrophotometer absorbance reading is related to the percent transmittance of the instrument by the following equation:

% Photo A = 100% - %T. (1)

The transmittance is related to the turbidity exponentially by the formula: I_{t =} exp ( - xl) (2)

where 1 is the path length of the cell through which the measurement is taken, and τ is the turbidity.

As the above U.S. Patent No. 5,466,338 discloses, a standard phototester is used to measure filtrate turbidity that was taken to be proportional to the concentration of suspended solids. The so-called "absorbance" of the phototester (spectrophotometer) is inversely proportional to percent transmittance and is not directly proportional to turbidity, but is a measure of the quantity of suspended solids in the filtrate.

The percent transmittance (%T) is defined in the normal way as the transmitted light intensity through a particular measuring cell divided by the incidence light intensity. In the absence of absorption and under ideal conditions, the transmittance is related to the turbidity, exponentially by formula (2) above. The teachings of U.S. Patent No. 5,466,338 for determining percent transmittance are incorporated herein by reference.

Method of Measuring Cationic Demand

In some Examples below, cationic demand in units of μeq/L, was determined using a Mutek Particle Charge Detector in accordance with standard procedure.

EXAMPLES

The following Examples are not intended to limit the scope of the invention in any way. In the Examples, the following commercial or experimental polymers or polymer compositions were used:

A A copolymer in a 8% active solution formed of 50% by weight acrylamide (AM) and 50% by weight DADMAC. (4-5 MM MW)

B Coagulant formed of 33% active polyaluminum chloride sulfate.

C Coagulant 10/1 wt/wt active polyaluminum chloride/polyamine blend in solution form. (1-2 MM MW) . Being 28% active.

D Coagulant 20/1 wt/wt active polyaluminum chloride/DADMAC blend in solution form. Being 30% active. (10-1000 M MW)

E Coagulant formed of 50% active aluminum chlorohydrate . F A terpolymer in solution form being

8.0% active formed of 45% by acrylamide; 5% by weight acrylic acid; and 50% by weight DADMAC, where 5% of the acrylamide is post hydrolyed to acrylic acid. (4-5MM MW) .

G Coagulant in solution form being 8.0% active of melamine formaldehyde.

H Melamine formaldehyde treated clay.

I Low molecular weight coagulant in solution form formed of branched

Polyamine. (1-2 MM MW DMA- ephichlorohydrin) . Being 50% active.

J Low molecular weight coagulant in solution form of polyethyleneimine . Being 25% active. (0.5-1.0 MM MW) .

K Low molecular weight coagulant in solution form of modified poly-

Ethyleneimine. Being 25% active. (1-2 MM MW) .

L Low molecular weight coagulant in solution form of polyethyleneimine.

Being 25% active. (0.5-1.0 MM MW) .

M A copolymer in dry form 100% active formed of 50% by weight AM and 50% by weight DADMAC. (4-5 MM MW) . N Coagulant 1.5/1 wt/wt active polyamine/acrylamide/DADMAC copolymer blend in solution form. Being 16.1% active. The acrylamide/DADMAC copolymer is formed of 50 weight % acrylamide and 50 weight % DADMAC.

O Coagulant 2.0/1 wt/wt active polyamine/acrylamide/DADMAC copolymer blend in solution form. Being 18.2% active. The acrylamide/DADMAC copolymer is formed of 50 weight % acrylamide and 50 weight % DADMAC.

P Coagulant 2.5/1.0 wt/wt active polyamine/acrylamide/DADMAC copolymer blend in solution form. Being 20.0% active. The acrylamide/DADMAC copolymer is formed of 50 weight % acrylamide and 50 weight % DADMAC.

Q Coagulant 3.0/1 wt/wt active polyamine/acrylamide/DADMAC copolymer blend in solution form. Being 21.6% active. The acrylamide/DADMAC copolymer is formed of 50 weight % acrylamide and 50 weight % DADMAC.

R Low molecular weight coagulant in solution form formed of DADMAC. (1-2

MM MW) Being 20% active.

Example 1 500 milliliters of coated broke containing the rutile form of titanium dioxide in a kaolin clay pigment in the coated broke were mixed at 1200 rpm for 90 seconds. The several polymers were added separately at 30 seconds apart or were added simultaneously (but not blended together) to the coated broke slurry. The type and dosage of the polymers, the manner in which the polymers were added i.e. Product 1 followed by Product 2, and the percent transmittance are shown in Table 1. The tests in Table 1 do not include any of the organic coagulant compositions of the present invention. These tests were performed to demonstrate the percent transmittance values obtained when using single polymers or dual polymer compositions that are not the present invention for comparison purposes to those percent transmittance values obtained in later Examples herein including the organic coagulant composition of the invention. When polymer A is combined with either polymer B or polymer C (test Nos . 11-15 and 35), the percent transmittance value ranges from 11.7 to 34.7. In order to obtain the percent transmittance value of 34.7 (test No. 35), the dosages of polymers A and B were 4.5 pounds/ton active compared to test No. 12 where the dosages were 3 pounds/ton active. In test No. 12, the percent transmittance value was 19.6 which is little more than half the value of test No. 35, i.e. 34.7 compared to 19.6.

Table !

No. 5 Paper Machine White Pitch Study

Coating Formulation Change from Anatase to Rutile Date 6/12/97

Mixing Sequence: 500 ml coated broke mixed at 1200 rpm for 90 sec. First additive at 0 sec, second additive added at 30 sec. Example 2 Five grades of coated broke were treated either with a single polymer or with two polymers in varying dosages of 0.25, 0.5, 0.75, and 1.00 pounds active per ton. These five grades of coated broke along with percent transmittance values are shown in Table 2. The five grades of coated broke included 80 pounds of a No. 1 coating precipitated calcium carbonate pigment containing the anatase form of Ti0₂; 80 pounds of a No. 1 coating precipitated calcium carbonate pigment containing the rutile form of Ti0₂; 80 pounds of a coating kaolin clay containing the anatase form of Ti0₂; 80 pounds of a coating kaolin clay containing the rutile form of Ti0₂; and the same coated broke used in Example 1 above which is a kaolin clay with a rutile form of Ti0₂ (No. 5 Coated Broke) .

Table 2 shows that some of the higher percent transmittance values were obtained for the anatase form of titanium dioxide of the precipitated calcium carbonate coated broke that was treated with polymers A and I (test Nos . 19 through 22) which polymers A and I were added separately. Polymers A and I are components of the organic coagulant composition of the invention but were added in different ratios than those constituted in compositions N, O, P, and Q of the invention. Table 2 also shows that for the No. 5 coated broke some of the higher percent transmittance values were obtained when using polymers A and I (test Nos. 19 through 21) .

Table 2. No. 5 PM Coated Broke

Example 3 Coated broke from the No. 5 paper machine was tested with different polymers and dosages. The results are shown in Table 3. In test Nos. 1 through 17, only one polymer was used, including polymer A, a component of the organic coagulant composition of the invention. Test Nos. 18 through 36 involve polymers I and A which are both components of the second polymer of the composition of the invention. However, these polymers I (Product 1) and A (Product 2) were added to the coated broke separately but at the same time. That is, the two polymers were not blended together before being added to the coated broke. Test Nos. 37 through 52 involve polymers I and M, polymer M being a dry polymer (a dry polymer version of solution Polymer A) which constitutes the second polymer of the composition of the invention.

The results of this Example 3 show that overall there is an improvement in the percent transmittance values when both polymers I and A (constituting the composition of the invention) are added to the coated broke compared to when polymers I and A are added singularly, i.e. test Nos. 5 to 9 and 13 to 17 compared to test Nos. 18 through 36.

Table 3. No. 5 PM Coated Broke Application New Coagulant Evaluation Date: 08/01/97

Mixing Sequence: First and second additive added to coated broke and mixed @1200 rpm 60 sec.

Example 4

Coated broke from the No. 5 paper machine discussed in Examples 1-3 was tested with different ratio blends of the organic coagulant compositions of the invention (N, O, P, and Q) and the results are shown in Table 4. The consistency of the coated broke was 1% and was mixed for 60 seconds at 1200 rpm. The Brookfield viscosity for compositions N, O, P, and Q was 12,300 cps, 12,000 cps, 12,150 cps, and 11,900 cps, respectively. Blended ratios were 1.5:1; 2.0:1; 2.5:1; and 3.0:1. The dosages are given in both pounds/ton active and pounds/ton product. Pounds/ton product represents the given concentration of the product .

This testing was done to compare the percent transmittance values for the blended polymers of the invention to those values for the polymers of the invention when they were not blended but added simultaneously to the coated broke slurry. From Table 4, it can be seen that the 2:1 active blend ratio gave the highest percent transmittance at 6.8 for Test No. 14. This 2:1 ratio blend of the composition of the invention gave an improvement in percent transmittance compared to test Nos. 29 and 31, 33-36 of Table 3 whereby the polymers of the composition were added individually (not blended) and simultaneously to the coated broke at the same ratio and dosage. Overall, the polymers of the composition of the invention result in comparable percent transmittance values when the polymers are either blended together before being added to the coated broke or are added to the coated broke individually but simultaneously.

Table 4.

No. 5 PM Coated Broke Application

New Coagulant Evaluation (Blended Product)

Mixing Sequence: Blended product added to 1.0% coated broke and mixed for 60 sec. @ 1200 rpm. Example 5

Fresh coated broke from the No. 5 paper machine was tested at the mill site with polymers A, B, I, and J and also with blended polymer compositions N, O, and P of the invention. The results are shown in Table 5. Polymers A and I, as indicated herein above, are components of the compositions of the invention. In test Nos. 4 and 10, polymers A and B were blended together and immediately added to the coated broke slurry since previously in this experiment the blend of these two polymers A and B formed a gel if allowed to set longer than sixty seconds.

The active blend of the compositions of the invention (test Nos. 7-9) produced higher percent transmittance values compared to when only one polymer was added to the coated broke (test Nos. 2, 3 and 5) .

Table 5. No. 5 P.M. Coated Broke In-mill Test Data

Polymers B and A were blended together then immediately added to the coated broke. The blend of polymers A and B forms a gel if allowed to set for 60 sec. Example 6

Table 6. Allentown Coated Broke Treatment Test Data (PVA binder)

Sample size 300 ml, 1.0% consistency Mix Time 60 sec. at 1200 rpm.

Coated broke from a commercial mill site different from the mill where the coated broke was obtained for Examples 1-5 above was tested. The sample sizes were 300 ml at 1% consistency and were mixed for 60 seconds at 1200 rpm. This Example tests individual polymers A, B, E, I, and R (A and I being components of the composition of the invention) and compositions of the invention, N, O, P, and Q. This coated broke contained about the same amount of rutile form of titanium dioxide as that of the prior Examples 1-5.

It can be seen that composition Q of the invention at a 3:1 active blend ratio gave the best performance in percent transmittance values. Comparing compositions N, O, and P of the invention of Table 6 to these compositions of Table 5, one can see that equivalent blend ratios on different types of coated broke can result in different percent transmittance values. For example, test Nos. 13, 14, and 15 of Table 6 resulted in different percent transmittance values for the same polymer compositions of test Nos. 9, 8, and 7 respectively of Table 5.

As stated herein above, percent transmission is a measure of retention (colloidal particle retention) . Higher percent transmittance equates to better retention of the colloidal material in the coated broke slurry. If the colloidal retention is low, then the percent transmittance will also be low.

The last columns of Tables 5 and 6 show the amount of anionic charge in the coated broke that was neutralized by the various polymers and dosages. The lower the cationic demand the closer the coated broke charge is to zero.

While the invention has been described herein above, it is to be clearly understood that the same are susceptible to numerous changes apparent to one skilled in the art. Therefore, the invention is not to be limited to the details shown and described but it is to be construed to cover all obvious forms and modifications, which are within the spirit and scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A process for treating coated broke to minimize the deposition of white pitch on paper making equipment so as to reduce paper sheet defects, comprising: adding to a coated broke slurry in a paper mill repulping operation an organic coagulant composition comprising an admixture of (a) a first polymer selected from the group consisting of a branched polyamine and diallyl dimethyl ammonium chloride (DADMAC) and (b) a second polymer which is a copolymer comprising a nonionic monomer and a cationic monomer.

2. A process of Claim 1 wherein said copolymer of said second polymer comprises an acrylamide and a diallyl dimethyl ammonium chloride (DADMAC) in a weight percent ratio ranging from about 15:85 to about 85:15 based on the weight of said second polymer in said composition.

3. A process of Claim 2 wherein said weight percent ratio of said acrylamide and diallyl dimethyl ammonium chloride of said copolymer of said second polymer is about 50:50 based on the weight of said second polymer in said composition.

4. A process of Claim 1 wherein the weight ratio of said first polymer to said second polymer ranges from about 1:4 to about 4:1 based on the weight of said organic coagulant composition.

5. A process of Claim 3 wherein said first polymer is a branched polyamine and has an average weight molecular weight ranging from about 500,000 to about 3 million, and said acrylamide portion of said second polymer has an average weight molecular weight ranging from about 3 to about 7 million and said diallyl dimethyl ammonium chloride portion of said second polymer has an average weight molecular weight ranging from about 500,000 to about 3 million.

6. A process of Claim 5 wherein said branched polyamine has an average weight molecular weight ranging from about

1 million to about 2 million, said acrylamide portion has an average weight molecular weight ranging from about 4 to about 5 million, and said diallyl dimethyl ammonium chloride portion has an average weight molecular weight ranging of about 1 million to about 2 million.

7. An organic coagulant composition for treating coated broke, said composition comprising: an admixture of (a) a first polymer which is a cationic monomer selected from the group consisting of a branched polyamine and diallyl dimethyl ammonium chloride (DADMAC) and (b) a second polymer which is a copolymer comprising a nonionic monomer and a cationic monomer.

8. An organic coagulant composition of Claim 7 wherein said__.copolymer of_ said second polymer comprises an acrylamide and a diallyl dimethyl ammonium chloride (DADMAC) in a weight percent ratio ranging from about 15:85 to about 85:15 based on the weight of said second polymer in said composition.

9. An organic coagulant composition of Claim 8 wherein said weight percent ratio of said acrylamide and diallyl dimethyl ammonium chloride of said copolymer of said second polymer is about 50:50 based on the weight of said second polymer in said composition.

10. An organic coagulant composition of Claim 7 wherein the weight ratio of said first polymer to said second polymer ranges from about 1:4 to about : 1 based on the weight of said organic coagulant composition.

11. An organic coagulant composition of Claim 9 wherein said first polymer is a branched polyamine and has an average weight molecular weight ranging from about 500,000 to about 3 million, and said acrylamide portion of said second polymer has an average weight molecular weight ranging from about 3 to about 7 million and said diallyl dimethyl ammonium chloride portion of said second polymer has an average weight molecular weight ranging ^' from about 500,000 to about 3 million.

12. An organic coagulant composition of Claim 11 wherein said branched polyamine has an average weight molecular weight ranging from about 1 million to about 2 million, said acrylamide portion has an average weight molecular weight ranging from about 4 to about 5 million, and said diallyl dimethyl ammonium chloride portion has an average weight molecular weight ranging from about 1 million to about 2 million.

13. A process for forming a paper sheet containing cellulose fiber derived from repulped coated broke containing white pitch, the steps comprising: repulping the coated broke in slurry form; adding to the slurry an organic coagulant composition comprising an admixture of (a) a first polymer selected from the group consisting of a branched polyamine and diallyl dimethyl ammonium chloride (DADMAC) and (b) a second polymer which is a copolymer comprising a nonionic monomer and a cationic monomer; and forming the sheet .

14. A process of Claim 13 wherein said copolymer of said second polymer comprises an acrylamide and a diallyl dimethyl ammonium chloride (DADMAC) in a weight percent ratio ranging from about 15:85 to about 85:15 based on the weight of said second polymer in said composition.

15. A process of Claim 14 wherein said weight percent ratio of said acrylamide and diallyl dimethyl ammonium chloride of said copolymer of said second polymer is about 50:50 based on the weight of said second polymer in said composition.

16. A process of Claim 13 wherein the weight ratio of said first polymer to said second polymer ranges from about 1:4 to about 4:1 based on the weight of the composition.

17. A process of Claim 15 wherein said first polymer is a branched polyamine and has an average weight molecular weight ranging from about 500,000 to about 3 million, and said acrylamide portion of said second polymer has an average weight molecular weight ranging from about 3 to about 7 million and said diallyl dimethyl ammonium chloride portion of said second polymer has an average weight molecular weight ranging from about 500,000 to about 3 million.

18. A process of Claim 17 wherein said branched polyamine has an average weight molecular weight ranging from about 1 million to about 2 million, said acrylamide portion has an average weight molecular weight ranging from about 4 to about 5 million, and said diallyl dimethyl ammonium chloride portion has an average weight molecular weight ranging from about 1 million to about 2 million.