MXPA97006074A - Use of mixtures of dispersion polymers and coagulants for the treatment of damaged paper revest - Google Patents

Abstract

The present invention relates to an improved process for the manufacture of paper comprising the formation of an aqueous cellulose slurry from papermaking and the addition of a mixture of a water soluble dispersion polymer and a coagulant to the slurry for increase retention and / or drainage. After the addition of the polymers, the slurry is purged to form a sheet and the sheet is

Description

SO OF MIXES OF DISPERSION POLYMERS AND COAGULANTS FOR THE TREATMENT OF DAMAGED PAPER Background of the Invention 1. Field of the Invention The invention relates to the field of papermaking, and in particular, to a papermaking process -perfected using hydrophobic dispersion polymers to increase the retention of fibers in the paper sheet. 2. Description of the Previous Technique In papermaking an aqueous cellulose suspension or slurry is formed on a sheet of paper. The cello lósica slurry is generally diluted to a consistency (percent by weight of dry solids in the slurry) of less than 1 percent, and often below 0.5 percent, before the paper machine, while the finished sheet it has less than 6 percent by weight of water. Therefore, the dehydration aspects of papermaking are extremely important for the efficiency and cost of manufacturing.

Ref. 025403 An important aspect in the manufacture of paper is the retention of finishing compounds on and within the entire fiber being formed during the manufacture of paDel. The papermaking finish contains particles that range in size from approximately 2 to 3 millimeters in cellulose fibers to the measurement of fillings of only a few microns. Within this range are the fine cellulosics, mineral fillers (used to increase the opacity, brightness and other characteristics of paper) and other small particles that would generally, without the inclusion of one or more retention additives, pass through the spaces (pores) between the cellulosic fibers in the entire fiber that is being formed. One method of improving the retention of cellulosic fibers, mineral fillers and other compounds in the whole fiber is the use of a coagulant / flocculent system, added before the paper machine. In this system, a coagulant, for example a synthetic cationic polymer of low molecular weight or a cationic starch, is first added for the finishing, said coagulant generally reduces the negative surface charges present in the particles in the finish, particularly in fine cellulosics. and mineral fillers, and - hence the agglomeration of said particles. The coagulant is followed by the addition of a folate. The flocculant is general. A high molecular weight synthetic anionic polymer which bridges the particles and / or agglomerates, from one surface to another, linking the particles in large agglomerates. The presence of said large agglomerates in the finish increases the retention. The agglomerates are filtered out of the water in the fiber network, where the different non-agglomerated particles would pass in a large quantity.

A system employed to provide an improved combination of retention and dehydration is described in U.S. Pat. Nos. 4,753,710 and 4,913,775, inventors Langley et al., Issued respectively on June 28, 1988 and April 3, 1990, the disclosures of said patents are incorporated herein by reference. In summary, said method adds to the aqueous cellulosic suspension of the prime papermaking a linear cationic polymer of high molecular weight before the cutting of the suspension, followed by the addition of bentonite after cutting. The cut is generally given by one or more of the cleaning, mixing and pumping stages of the papermaking process, and the cut breaks up the large flocs -formed by the high molecular weight polymer in microflocks and the subsequent agglomeration. it is followed with the addition of the bentonite clay particles.

Another system uses the combination of cationic starch followed by colloidal silica to increase the amount of material retained in the network by charge neutralization and adsorption of smaller agglomerates. This system is described in U.S. Pat. No. 4,388,150, inventors Sunden et al .. issued on June 14, 1983.

Greater retention of fines and fillers allows a reduction in the cellulose fiber content of the paper that is formed. The lower quality pulps are used to reduce papermaking costs, the retention aspect in papermaking becomes more important because the fines content of these lower quality pulps is generally larger than that of pulps of higher quality.

Greater retention of fine components, fillers and other slurries reduces the amount of such substances lost in white water and therefore reduces the amount of waste material, the cost of waste disposal and the adverse environmental effects therein.

As described in the Langley patents, paper or paperboard is generally made from a suspension or slurry of cellulosic material in an aqueous medium, said slurry being subjected to one or more steps, said steps being generally a cleaning step, a mixing stage and a pumping stage, and then the suspension is drained to form a sheet, which is then dried to the desired, and generally low water concentration. As disclosed in these patents, the cationic polymer generally has a molecular weight of at least 500,000, and preferably the molecular weight is greater than 1,000,000 and may be greater than 5,000,000, for example in the range of 10 to 30 million or greater. The cationic polymer is substantially linear; it can be totally linear or - this can be slightly reticulated as long as this structure is still substantially linear compared to the globular structure of the cationic starch. Preferably - the cationic polymer has a relatively high charge density of for example about 0.2 and preferably at least about 0.35, and more preferably about 0.4 to 2.5 or greater, equivalents of cationic nitrogen per kilogram of or grouper. When the polymer is formed by polymerization of a cationic monomer, an ethylenically unsaturated monomer, optionally with other monomers, the amount of cationic monomer will normally be above 2 mole percent and usually above 5 mole percent, and preferably above 10 percent mole. 100 mole, based on the total moles of monomer used in the polymer fortification. The amount of the cationic polymer employed in the process, in the absence of any substantial amount of cationic binder, is typically at least 0.3% based on the dry weight of the slurry, and preferably 0.6% in the substantial absence of the cationic binder and 0.5 percent in the presence of the cationic binder, same base, which is from 1.1 to 10 times, and usually from 3 to 6 times, the amount of cationic polymer that would be used in conventional processes (2 polymers), and so both "an excess amount" of cationic polymer is considered. The cationic polymer is preferably added to the thin paper, preferably to the cellulosic slurry having a consistency of 2 percent or less, and at most 3 percent. The cationic polymer can be added to the prediluted slurry, or it can be added to the slurry together with the dilution of water.

In the paper and pump manufacturing industry, the fraction of paper products which do not comply with the minimum commercial specifications and therefore can not be sold, is called damaged paper. The damaged paper, which usually consists of scraps or cuttings from the form network is a valuable source of fibers, and are returned to be used again in a manufacturing operation. paper to the - same or another mill. The damaged paper derived from the paper which contains coating is referred to as "coated coated paper". The coating is applied to the paper to improve the surface uniformity which positively influences the printability, and, in some cases, provides a uniform, shiny, opaque coating to cover the "unattractive" base sheet. The mills which make use of a relative proportion - high paper coated coated in the finish confront several problems due to the presence of the coating in its recycled finish.

The coated materials contained in the coated coated paper have ten (10) to about forty (40) percent by weight of the total solids in the finished paper. Typically, 80 to 90 percent of the dry formulation by weight coating is composed of pigments, and 5 to 20 percent binders. Coating formulations often contain a wide variety of compounds and are customary to meet stringent requirements with respect to both, the same coating paper and the handling properties of the coating dispersion.

Pigments typically used in the paper coating include, various types of clays, various types of calcium carbonates, and titanium dioxide. Other types of white pigments include white satin extenders, barium sulfate, zinc oxide, talc, plastic pigments, alumina trihydrate and titanium dioxide. Colored organic or inorganic pigments are also used in some cases.

LJS coating binders fall within three classifications: starches, proteins and synthetics. Protein binders are either casein, soy extract, or animal supplements. Synthetic binders are significantly latexes based on vinyl alcohol, styrene butadiene, vinyl acetate and acrylic polymers.

The mills which make use of damaged paper re dressed in their finish experience problems of sticky deposits that originate from binding materials in combination with pigments and fillers. These deposits, often referred to as "white paste mix", can be found along the wet end, the pressure section, and the drying section of a paper mill. They can cause operational problems such as holes or spots in the paper, felt filler, paper machine and coating breaks, and insed deposits of empty boxes, drying cylinders and sorted rolls. The consequence is unproductive downtime - frequent failure of the machine and loss of fluidity, and also occasional loss of efficiency of chemical additives such as retention aids.

Previously, the cationic solution polymers derived from dimethylamine reagents of epichlorohydrin (EPI-DMA), ammonium diallyldimethyl chloride (DADMAC), and ethylene dichloride ammonia (EDC / N) have been used to treat coated coated paper (JE Pearson; MR St. John "Proper Selection of Polymeric Coagulant for Coated Broke Treater and Consequences of Selection on Overall Wet End Chemistry", Tappi paper manufacturers conference 1995, p. 523). The goal of the treatment of the damaged paper coated with these polymers, referred to as "coagulants", is attached to the white paste mixture in the paper fibers - while the particles of the paste are still small and still did not have the changes to combine the agglomerates in the form dp deposit. The coagulants also act to neutralize the dispersion effects of the coatings, which are detrimental to the retention. In addition, the coagulants help retain fine coating pigments, which results in improved ash retention. The treatment-of the damaged paper coated with coagulants is supposed to be based on a mechanism of charge neutralization and is often described as cationization of damaged paper. However, it has shown that other aggregation mechanisms, such as the load-balancing and bridging mechanism, can play a role in determining polymer activity.

In addition to the use of coagulants, Pearson has been claimed in U.S. Pat. No. 5,466,388, the disclosure of which is incorporated herein by reference, -that the high molecular weight dispersion polymers with the charge density much lower than that of -the coagulants, can be successfully used to treat -the damaged paper coated by coagulation of the white paste mixture. These dispersion polymers often have the advantage of requiring much less elaborate feeding equipment and will be more effectively mixed in the pumping system as compared to high molecular weight emulsion polymers.

Brief Description of the Invention An improved manufacturing process is described which consists of the formation of an aqueous paper-making cellulosic slurry and the addition of a binder of a water-soluble dispersion polymer and a coagulant to the slurry to increase retention-and / or drainage. The water soluble polymer which consists of: (a) a first cationic monomer represented by the following formula (I): where 1 is H or CH-, each of "y. is an alkyl group having one to three carbon atoms: A is an oxygen atom or NH: B is an alkylene group of 2 to 4 carbon atoms or a hydroxypropylene group: and X is an anionic counterion, and / or a second cationic monomer represented by the following general formula (II): where R, is H or CH ^: each of R ,. and R, is an alkyl group having one to two carbon atoms: R-, is H or an alkyl group of one to two atoms: A is an oxygen atom or NH: B is an alkyl group of 2; to 4 carbon atoms or a hydroxypropylene group: and X is an anionic counterion: and (b) the (meta) acrylamide in an aqueous solution of a polyvalent anion salt, wherein the polymerization is carried out in the presence of either a high molecular weight multivalent cation consisting of a water soluble polymer containing at least one monomer of formula (II) or an alkyl ester of acrylic acid. After the addition of the polymers, the stem is purged to form a leaf, and the leaf is dried.

Brief description of the drawings FIG. 1 is a graph comparing turbidity reduction data for a solution polymer referred to as "coagulant", dispersion polymers, and mixtures of the two polymers as described in the present invention.

FIG. 2 is a graph comparing the turbidity reduction data for a solution polymer referred to as "coagulant", dispersion polymers, and mixtures of the two polymers as described in the present invention.

Description of the Preferred Modalities It has now been revealed that the products obtained by mixing a high molecular weight dispersion polymer and a high load coagulant shows an improved retention activity in papermaking compared to the only ones made by themselves. Both the high molecular weight and the charge are characteristic of the polymer which has previously been found to be important for the coagulation of white pastes. Surprisingly, a synergistic effect is obtained by mixing the compounds and the ease of these products to coagulate fibers in a slurry of papermaking is greater than that obtained with the two compounds - added at the same time but separately for the finishing of paper making.

These mixtures, similar to their compounds do not require the elaboration of feeding equipment used by emulsion polymers. The mixed composition can also be applied to the finishing treatment of old papers containing adhesives and de-inked fiber.

The mixture contains from 5 to 95 weight percent dispersion polymers as a product. Most preferred mixtures contain 25 to 75 weight percent dispersion polymer as the product, although the weight percent polymer dispersion contained in the mixture which is efficient to treat the slurry of the manufacturing Paper depends on the nature of the grout itself.

The mixture is added to the slurry in an amount of almost 0.1 kilograms of product per tonne of total damaged paper solids up to approximately 5 kilograms of product per tonne of product of total discharged paper solids. More preferably the effective treatment ranges are between 0. 25 kilograms of product per ton of total solids in the leach- ing up to approximately 3 kilograms per ton, although the demand for the treatment level for the mixtures may vary with the type of slurry to be treated.

Preferably, the dispersion polymer and coagulant are mixed as above concentrated products until diluted for use levels and added to the slurry. Alternatively the dispersion polymer and coagulant can be diluted separately and then added to the slurry.

The coagulants of the invention are preferably selected from the group consisting of epichlorohydrin dimethylamine, diallyldimethyl ammonium chloride, polyaluminium chloride, alum, polyethyleneimine, diayandiamide, ethylene dichloride ammonia and mixtures thereof.

The following examples are presented to describe the embodiments and utilities of the invention and are not intended to limit the invention unless otherwise stated in the claims appended thereto.

Examples The coated coated paper slurry was prepared in the laboratory through dry damaged paper pulp in Synthetic Chicago Tap Water # 13 for 1 hour and 45 minutes using a high consistency pulp, and successively disintegrated in a standard 10,000 to 45000 revolutions according to the type of paper damaged.

The measurements of intrinsic viscosity / reduced viscosity (RSV / IV) were carried out by a capillary viscometer under standard conditions (0.125 M NaNOg, 30 ° C). The RSV is the reduced specific viscosity of the polymer at 0.045 wt% of weight. The IV of the polymer is the intercept of the best calculated line of the RSV points at 3 different concentrations by weight of polymer. The viscosity of the mixtures was calculated on the basis of percent by weight dispersion polymer present in the mixture. Said calculation allows the measurement of those viscosity changes of the dispersion polymer ex periented in this mixture with the coagulant.

The polymers were diluted to 0.2-0.4% by product by test. The activity of the polymer was tested on the wet coated damaged paper carton collected from the paper mill or on the prepared coated paper slurry prepared in the laboratory from dry damaged paper as above. A simple turbidity test used to evaluate polymer activity. To 200 ml of paper damaged in a 400 ml crusher, stirred at 500 rpm using a Britt Jar mixer, the polymer dispersion mixtures and solution polymer or individual compounds were added for 10 seconds. In any case, the stirring was interrupted for 30 seconds, and the mixture was filtered through a 100 mesh screen at the same volume of the filtrate each time. By this method, the retention of coated damaged paper particles results from the activity of the polymer and no filtration through the medium filter. The filtering turbidity was measured by a standard turbidity meter (2100 N Turbidimeter by Hach Company) calibrated Formazin Primary Standard as suggested by the manufacturer. Retention was expressed in terms of% turbidity reduction of the damaged paper filtrate with no treated polymer (white).

Example 1 Polymer A: Polymer of EPI-DMA solution Polymer B: 90/10 AcAm / DMAEA-BCQ Polymer C: 50/50 mix of polymer A / polymer B Polymer D: 25/75 mix of polymer A / polymer B Polymer E: 75 / 25 mixture of polymer A / polymer B Table I The dose curves based on turbidity reduction for polymers A, B, C, D, and E are presented in Figure 1. The polymers in the example were calculated as product in pe, and their doses are based on the dry weight of damaged paper-coated. Figure 1 clearly shows that polymer C, polymer D and polymer E, which are mixtures of polymer A and B in various proportions, show the highest% turbidity reduction per product dose. In particular, polymers C, D and E have a high raas efficiency (retention obtained at a fixed polymer dose) than polymers A - and B individually. The activity of the mixtures depends on the proportion in% weight of their product components, the optimum point depends on the nature of the treated coated damaged paper. Furthermore, it was found that the retention activity of the polymers A and B added separately to the damaged paper is lower than those polymers C, D and E, in which, the 2 products are premixed. In particular, the addition of lKg / tonne of polymer C produces a turbidity reduction of 76.6%, while the polymer A and the polymer B are added to the raismo time, but separately, to the damaged paper at a dose of 0.5Kg. / ton each, gives a turbidity reduction of only 53.5%. The addition of polymer E at a dose of 2 kg / tonne produces a turbidity reduction of 92.8%, while the individual addition of polymer A (1.5 kilograms / ton) and polymer B (0.5 kilo-grams / ton) to the damaged paper reduces turbidity to only 88.8%.

As can be seen from the viscosity data reported in Table I, the viscosity of polymer B varies when this polymer is present in the mixtures with polymer A. Therefore, the viscosity data suggest the existence of specific interactions between polymer A and dispersion of pre-blended polymer B. These interactions may explain - the increase in retention activity observed for the mixture compared to the retention activities produced by the 2 compounds added at the same time but separately to the damaged paper.

Example 2 Table II Polymer A: Polymer of EPI-DMA solution Polymer F: 65/25/10 AcAm / DMAEA-BCO / DMAEA-MCQ Polymer G: 75/25 Polymer A / Polymer F mix The polymers A, F and G were tested on the wet-damaged paper used in the mill immediately after this collection. As shown in Figure 2, polymer G, which is a mixture of coagulant A and dispersion polymer F, has considerably greater efficiency and efficacy than those of the only compounds in the mixture, polymers A and F. The polymers in the example are calculated as product-weight, and their dose is based on the dry weight of the coated damaged paper.

Also in this case, the viscosities of the dispersion polymer which has been mixed with the polymer A is different from that dispersion polymer only. (Table II). This change in viscosity indicates the presence of interactions between the coagulant and the dispersion polymer. These interactions can explain the benefits of the retention activity obtained by using the mixtures on the only products only.

Example 3 The activity of 4 polymers was tested in a coated coated paper slurry. Polymer A is a polymer of EPI-DMA solution; polymer B is a dispersion polymer -90/10 Ac Ap./DMAEA-BC0; polymer H is a 50/50 mixture of polymer A and polymer H and J have the same composition but differ in the method of preparation. The polymer H was prepared by mixing the polymer A B as concentrated products. This mixture was diluted to a working concentration of 0.285% by weight before the test. Polymer J was prepared by mixing diluted solutions of polymer A and polymer B at 0.285% by weight. Polymers H and J have the same activity. Both products out perform their unique compounds. Additionally, these mixtures, apart from representing their unique compounds, are added at the same time but separately to the damaged paper. These results suggest that the dispersion - coagulant polymer interactions involved in explaining the increase in the mixtures are favored without taking into account the concentration of the dispersion and coagulant polymer.

The changes can be made in the composition, operation and arrangement of the method of the present invention described herein without departing from the concept and scope of the invention as defined in the following claims:

Claims (6)

1. A papermaking process, characterized in that it consists of: the formation of an aqueous cellulose slurry for the manufacture of paper; adding a mixture of: a water-soluble dispersion polymer, the water-soluble polymer is formed by polymerization of a water-soluble mixture, comprising: (a) a first cationic monomer represented by the following formula ( I): wherein R. is H or CH ", each of R" and R ~ is an alkyl group having from 1 to 3 carbon atoms; A is an oxygen atom or NH; B is an alkylene group having 2 to 4 carbon atoms or a hydroxypropylene group; and X is an anionic counterion, and / or a second cationic monomer represented by the following general formula (II): wherein R is H p CH- ,; each of R ,. and R, is an alkyl group having 1 to 2 carbon atoms; R? is H or an alkyl group of 1 to 2 carbon atoms; A is an oxygen atom or NH; B is an alkylene group having 2 to 4 carbon atoms or a hydroxypropyl group; and X is an anionic counterion; and (b) the (meta) acri lick in an aqueous solution of a polyvalent anion salt; wherein the polymerization is carried out in the presence of either a high molecular weight multivalent cation comprising a water soluble polymer containing at least one monomer of formula (II) or an alkyl ester of acrylic acid; and a cationic coagulant; drain the suspension to form a sheet; and dry the sheet.

2. The method according to claim 1, characterized in that the mixture contains from 5 to 95 weight percent of dispersion polymer as a product.

3. The method according to claim 2, characterized in that the mixture contains from 25 to 75 weight percent of dispersion polymer as a product.

4. The method according to claim 1, characterized in that the mixture is added to the coated paper-coated slurry in an amount of about 0.1 kilograms of product per ton of paper solids damaged to about 5.0 kilograms of product per ton. of total damaged paper solids.

5. The method according to claim 4, characterized in that the mixture is added to the coated paper slurry in an amount of about 0.25 kilograms of product per tonne of total paper solids discharged up to about 3.0 kilograms per tonne of solid paper. - two paper damaged.

6. The method according to claim 1, characterized in that the cationic coagulant is selected from the group consisting of epichlorohydrin dimethylamine, diallyl dimethyl anion chloride, polyaluminium chloride, alum, polyethylenimine, dicyandiamide, ethylene dichloride ammonia and of them.