RU2309210C2 - Method for processing of white resin sediments - Google Patents

Abstract

FIELD: production of paper and paper products in pulp-and-paper industry.

SUBSTANCE: method involves adding effective amounts of at least one cation-active polymer coagulant or inorganic coagulant with following adding of material consisting of microparticles, wherein pulp contains cellulose produced at least partly from processed paper products. Coagulant used is of natural or synthetic origin. Material based on microparticles is, for example, bentonite clay, network polymer, colloidal silicon, or polysilicate.

EFFECT: increased efficiency in reducing of white resin sedimentation.

17 cl, 2 dwg, 2 ex

Description

BACKGROUND OF THE INVENTION

Organic deposits in the papermaking system can cause losses in efficiency and reduce the quality of the finished paper due to stains, holes and tears. These organic deposits arise from naturally occurring resins in the wood itself or from synthetic materials such as adhesive, melt or latex found in recycled cellulosic mixtures. These deposits are hydrophobic and accumulate water during processing. These deposits may coarsen and get stuck on the surfaces of the paper machine or in a sheet of paper. Deposits formed from wood are called “wood resin”, while deposits from artificial materials are called “Velcro” or “white resin”. White resin is specific for coating binder crystal lattices such as styrene butadiene rubber (SBR) and polyvinyl acetate.

Papermaking, in its simplest sense, involves making pulp from wood, making a slurry of pulp and water, and forming a pulp matrix that is pressed and dried to form paper. At a crucial stage in the preparation, a cellulose / water suspension (paper composition) is formed in the form of a matrix on a wire mesh of a paper machine. Excess water and finely divided substances (white water) pass through the matrix onto the wire and are reused. The formed mesh is then advanced to a press and a drying machine section, where the matrix becomes paper.

Defective paper is a term used in paper production to describe paper that does not meet regulatory standards and cannot be sold for this reason. This paper is usually reused internally for fiber recovery, but it can also be sold to other industries as a source of fiber. Defective paper may be coated with a layer, the coating being applied to the base of the paper web as it is manufactured. Defective coated paper is referred to as coated defective paper. Paper waste is a term used in paper production to describe paper that has been used by a consumer. It is often referred to as "post-consumer waste." This paper is often collected and reused in production for fiber regeneration. Paper waste can be coated with a layer, the coating being applied to the paper substrate as it is processed. Coated paper waste is referred to as coated paper waste. Recycled coated paper may be paper scrap or waste. In recent years, many paper manufacturers have experienced reuse of coated paper, as substances that would not normally be present in the initial set of fibers used to make the base of the paper web are introduced into the coatings.

Coatings typically include various pigments and binders. Typical pigments used include many types of clay, calcium carbonate, titanium dioxide and other special fillers. White resin problems are believed to be caused mainly by binders, which include latex polymers derived from styrene butadiene and polyvinyl acetate resins, and natural binders such as starch.

Problems with white resin have been known for some time in paper manufacturing. White resin is a sticky light gray substance that is detected as deposits on metal surfaces in the area of the wet end part, the molding press or in the area of the drying device of the paper machine. It is called “white” to distinguish it from brown or black resin, which is formed from the substances contained in wood. White resin is also found in the white water system. From time to time, deposits of char are charred, forming black deposits in the area of the drying device of the paper machine. It has been shown that the problem with white resin is caused by the relatively high use of coated paper in the load in the industries faced with the problem. When coated paper is again converted to pulp, the clay or minerals and latex included in the coatings do not disperse easily in the pulp, but form agglomerates that result in white resin. White resin may coat equipment or create defects in the paper if it is transported with cellulose in a paper machine. Long machine downtime, frequent cleaning, paper sheet defects such as holes and increased number of cracks in the sheet are costly problems associated with deposits of white resin. Equipment cleaning is really implied, as deposits can be found on films, register rolls, in vacuum chambers, drying drums and drying cloth and throughout the length of the press cloth.

Various solutions have been proposed to overcome the problem with white resin. Several deposition chemicals are currently being applied or evaluated by papermaking. By trapping and dispersing small latex particles in the sheet, the problem of white resin can be controlled. More specifically, the latex particles should be attached to the fibers immediately passing through the re-pulp breaker. At this point, the latex particles are small and have an anionic structure and therefore they can exit the system as part of a paper web. Due to the anionic nature of both latex particles and fibers, an additive having a low molecular weight and strong cationic charge is best suited for this purpose. However, a single additive may not be enough to hold the latex particles in the paper sheet, and the use of a retention aid compatible with the additive may be important for successful control of the white resin.

Synthetic polymers are the most effective, known, anti-deposition additives for white resin. They have a high content of cationic groups, giving them the opportunity to create a strong electrostatic bond between the fibers, latex particles and the additive. When charged, the fiber will transport the latex particles to the end of production with the aid of a delaying excipient, and the particles will become part of the finished paper. It was shown that polyglycol with an average molecular weight, polymers based on aminoglycol or polyethyleneimine are useful in reducing the amount of white resin.

Some of the processing methods to solve problems associated with white resin are described in the sources below.

US Pat. No. 5,131,982 (to Michael R. St. John) describes the use of polymers and copolymers containing diallyldimethylammonium chloride (DADMAC) for treating cellulose fibers recycled from recycled waste paper coated to make them suitable for paper production.

US Pat. No. 4,997,523 (to Pease et al.) Describes the use of tetrafunctional alkoxidiamine in combination with phosphate, phosphonate or phosphoric acid to minimize the deposition of white resin on paper-making equipment.

US Pat. No. 4,643,800 (to Maloney et al.) Describes the use of a nonionic hydroxyethylene glycol based surfactant in which one terminal hydroxyl group is replaced by an aliphatic or alkyl aromatic group and the other two hydroxyl end groups are replaced by a polyoxypropylene group or a benzyl ether residue, in combination with a polyelectrolyte dispersant with an average molecular weight of 500-50000 to remove and disperse impurities from the secondary fiber during processing for repetition nogo use.

There are some drawbacks to the use of polymers for controlling white resin. Polymers are generally not cost effective. For example, polyethyleneimine (PEI), a tertiary amine polymer, is an effective additive in the control of white resin, but it is quite expensive to use.

There are other solutions used to control white tar. In the past, talc was commonly used, and it is still sometimes used to control deposits. As a surface-active filler, in order to control deposits, talc acts by reducing the stickiness of the area around the resin particle so that it cannot adhere to the paper-making equipment. However, this only involves a temporary solution to the resin problem, which reappears as processing continues. Talc does not attach latex particles to the fibers, and therefore, when exposed to shear forces, new adhesive areas appear that cause deposits. Additives that react with the surface of a resin particle to make it less sticky (tackifiers) also offer a temporary solution to the problem of controlling white resin. The published patent application US 20001/0023751 describes a method for reducing sticky impurities using polyvinyl alcohols and bentonite. Polyvinyl alcohol acts as a masking agent for particles. The problem is the need to use excess amounts of polyvinyl alcohols. Bentonite absorbs excess polyvinyl alcohol.

SUMMARY OF THE INVENTION

The present invention is a deposition control system consisting of an inorganic or organic (natural or synthesized) coagulant and microparticle material (synthetic or natural) such as bentonite clay, cross-linked polymer, colloidal silicon, polysilicate or borosilicate, for pulp, containing white resin / Velcro. The order of addition of these two components is essential to preserve the benefits of reducing the amount of white resin in papermaking technology. The coagulant may be added to the pulp breaker or tub for thick pulp and pulp, and the microparticle material may be added at the outlet of the pulp breaker or tub before diluting the pulp.

DETAILED DESCRIPTION OF THE INVENTION

The results of numerous turbidimetric measurements are shown in figure 1. The turbidity of the circulating water (filtrate) is an indicator of the latex emulsion particles being maintained in a colloidal state or an indicator of purity. By using polyamine as the sole component, a reduction in turbidity is achieved compared to untreated coated paper. However, the addition of material based on microparticles and a coagulant provides a significant reduction in turbidity of the water. These data show that more white resin / sticky particles remain in the pulp and paper rather than recycle in the papermaking system. These laboratory results demonstrate that the coagulant / microparticle system significantly reduces the accumulation of white resin / sticky in the papermaking process.

The present invention is a deposition control system consisting of an inorganic or organic (natural or synthesized) coagulant and microparticle material (synthetic or natural) such as bentonite clay, cross-linked polymer, colloidal silicon, polysilicate or borosilicate, for pulp, containing white resin / Velcro.

The coagulant may be an inorganic or organic (natural or synthetic) substance. Examples of suitable organic coagulants are a polymer with a low molecular weight and high charge density, a polymer that is usually a homopolymer of repeating cationic groups or a copolymer containing at least 80 wt.% Cationic monomer and 0-20 wt.% Acrylamide or other non-ionic monomer. Cationic groups can be formed from diallyldimethylammonium chloride and dialkylaminoalkyl (meth) acrylates and - acrylamides (usually in the form of a quaternary ammonium salt or acid addition salts). The quaternary ammonium salt of dimethylaminoethyl acrylate or the quaternary ammonium salt of methacrylate is often particularly preferred. Alternatively, the coagulant may be a condensation polymer, such as a polymer of dicyandiamide, polyamine or polyethyleneimine. Inorganic coagulants (such as alum, lime, iron (III) chloride and iron (II) sulfate may be used.

Cationic coagulants that may find use in this aspect of the invention include well known, commercially available, low to medium molecular weight, water soluble polyalkylene polyamines, including those prepared by reacting an alkylene polyamine with a difunctional alkyl halide. Substances of this type include condensation polymers obtained by the reaction of ethylene dichloride and ammonia-ethylene dichloride, ammonia and a secondary amine such as dimethylamine, epichlorohydrin-dimethylamine, epichlorohydrin-dimethylamine-ammonia, polyethyleneimines and the like. In some cases, cationic starch can be used as a coagulant. Inorganic coagulants, for example alum and polyaluminium chloride, can also be used according to the invention. The rate of use of inorganic coagulants is usually from 0.005 to 1 wt.% Based on the dry weight of the fiber in the load.

A preferred coagulant is a cationic polyelectrolyte, i.e. poly [diallyl di (hydrogen or lower alkyl)] ammonium salt having an average molecular weight of more than 300,000 but less than 2,000,000.

Microparticle materials can be synthetic or natural. Examples of suitable microparticle-based materials are swellable clay materials, cross-linked polymer, colloidal silicon, borosilicate or a suspension of microparticle-based anionic material selected from bentonite, colloidal silicon, polysilicate microgel, polysilicic acid microgel and cross-linked water soluble microemulsion.

Microparticle-based materials are widely used in the manufacture of paper making as retention aids, especially for high-grade paper. One such system utilizes swellable clay to provide an improved combination of retention and wetting as described in US Pat. Nos. 4,753,710 and 4,913,775, the disclosures of which are incorporated by reference herein below. In the method disclosed by Langley et al., A high molecular weight cationic linear polymer is added to an aqueous paper pulp suspension before the suspension is sheared, followed by the addition of swellable clay such as bentonite after shearing. Shear deformation, as a rule, is provided by one or several stages of the paper manufacturing method - cleaning, mixing and pumping, and shear destroys large flakes formed with a high molecular weight polymer into micro flakes. Further agglomeration occurs when bentonite clay particles are added.

Other microparticle programs are based on the use of colloidal silicon as a microparticle in combination with cationic starch, such as described in US Pat. Nos. 4,388,150 and 4,385,961, the disclosures of which are incorporated by reference in this specification, or a combination of cationic starch, flocculant and flint sol, such as described both in US Pat. No. 5,098,520 and in US Pat. No. 5,185,062, the disclosures of which are also incorporated by reference in this specification. US Pat. No. 4,643,801 discloses a method for producing paper using a high molecular weight anionic, water-soluble polymer, dispersed silicon and cationic starch.

Moreover, the microparticle is obtained from borosilicates, preferably aqueous solutions of colloidal particles of borosilicate have a molar ratio of boron to silicon from 1: 1000 to 100: 1 and, as a rule, from 1: 100 to 2: 5. The retention aid may be a borosilicate colloid, whose chemistry is similar to that of borosilicate glass. This colloid, as a rule, is obtained by the interaction of an alkali metal salt of a boron-containing compound with silicic acid under conditions leading to the formation of a colloid. Borosilicate particles can have a size covering a wide range, for example, from 1 nm (nanometer) to 2 μm (2000 nm) and preferably from 1 nm to 1 μm.

The microparticle can be inorganic, for example, colloidal silicon (such as described in US Pat. No. 4,643,801), polysilicate microgel (such as described in EP-A-359552), polysilicic acid microgel (such as described in EP-A-348366 ), their variants modified with aluminum. In particular, systems can be used that are described in US Pat. Nos. 4,927,498, 4,954,220, 5,167,891 and 5,279,807 and put into serial production by Ciba Specialty Chemicals and Dupont under the trade name Partikol.

Microparticle anionic organic materials can also be used. For example, anionic organic polymer emulsions are suitable. The emulsified polymer particles may be insoluble due to the formation of a copolymer, for example a water-soluble anionic monomer and one or more insoluble monomers, such as ethyl acrylate, but preferably the polymer emulsion is a cross-linked microemulsion of a water-soluble monomer substance, for example, as described in US Pat. Nos. 5,167,755, and 527. and put into serial production by Ciba Specialty Chemicals under the trade name Polyflex.

The particle size of the microparticle material is typically less than 2 μm, preferably less than 1 μm, and most preferably less than 0.1 μm.

The amount of material in the form of microparticles (dry weight calculated on the dry weight of the suspension of cellulose) is usually at least 0.03% and usually at least 0.1%. It can rise, for example, to 1.6 or 2%, but, as a rule, is less than 1%.

A preferred microparticle material is swellable clay, especially swellable clay from the smectite family. Preferred members of the smectite family include bentonite, montmorillonite, saponite, hectorite, beidilite, nontronite, fuller’s earth, and mixtures thereof. A swellable clay component containing mainly bentonite is particularly preferred. Bentonite must be in a highly swollen activated form, and in practice this means that it must be in the form of a monovalent salt of bentonite, such as sodium bentonite. Although there are several natural sources of sodium bentonite, most bentonites are alkaline earth metal bentonites, typically calcium or magnesium bentonites. A common practice is to activate alkaline earth metal bentonite by ion exchange of calcium or magnesium to sodium or another alkali metal or ammonium ion. Typically, this is accomplished by exposing bentonite to an aqueous solution of sodium carbonate, although other activating agents are known. Varieties of swellable clay are natural substances and are commercially available.

Appropriate fibers for producing pulp all have the qualities commonly used for this purpose, for example, pulp, bleached and unbleached pulp, and pulp and paper fiber mixtures from all annual plants. Wood pulp includes, for example, wood fibers, thermomechanical cellulose (TMP), chemothermomechanical cellulose (CTMP), compressed wood fiber, semi-cellulose, high yield industrial pulp and wood pulp (RMP). Examples of suitable celluloses are sulphate, sulphite and soda pulp. Unbleached pulps, which are also referred to as carriers of unbleached kraft pulp, are preferably used. Suitable annual plants for the production of pulp and paper pulp are, for example, rice, wheat, sugarcane and kenaf.

The pulp is obtained using paper waste alone or as a mixture with other fibers. Waste paper includes coated paper waste, which, due to the content of binders used in the coating and printing ink, leads to the formation of a white resin. The claimed fibers and pulps can be used individually or in a mixture with each other. Binders arising from pressure-sensitive sticky labels and envelopes, and binders from gluing book roots, as well as melts, lead to the formation of Velcro.

The present invention is particularly suitable for papermaking systems that utilize pulp obtained from a substantial amount of recycled paper or scrap paper. The value of a significant amount will vary depending on the system and the type of recycled recycled or rejected paper, but it will differ in that a significant amount of white resin is present in the product streams to significantly affect the operating conditions. In general, at least 10% of the pulp must be obtained from a recycled or defective paper product in order to cause the formation of significant amounts of white resin.

The deposition control method is introduced into the papermaking system by adding thick or liquefied pulp and paper pulp to the technology in the papermaking method. An important aspect of this method is the regulation of the time of addition of each component. The method requires the addition of a cationic coagulant, followed by an anionic particle. Without going into theory, it is believed that the preliminary addition of a cationic coagulant improves the adsorption of white resin using anionic microparticles. In addition, it is believed that the cationic coagulant is absorbed on resins (wood, white and Velcro), which are predominantly anionic or non-ionic, leading them at least partially to the cationic state. Now bentonite, containing increased adsorbed amounts of resin, is retained in the paper during its formation. The result is reduced amounts of resin in the resulting product. In a preferred embodiment, the coagulant is added to the pulp breaker or pulp tub for pulp and paper pulp, while the microparticle material is added at the outlet of the pulp breaker or tub to dilute the pulp and paper pulp.

The invention is further described by the following non-limiting examples. The examples illustrate the invention, which is characterized only by the attached claims.

Example 1

Coated paper sheets were pulped in a laboratory pulp breaker. A 400 ml aliquot of pulp and paper pulp with a consistency of 1% was stirred at 1000 rpm. A coagulant with a polyamine structure and bentonite microparticles were added at intervals of 1 min with stirring. Polyamine was added in an amount of 1, 1.5 or 2 pounds per ton, as usual, then bentonite in an amount of 4, 6 or 8 pounds per ton. After processing, the pulp and paper pulp was filtered through a 100 mesh sieve and the filtrate was measured for turbidity. Each sample of the filtrate was prepared by dilution with 1:14 deionized water. A Hach 2100P portable turbidimeter was used for analysis and the results were recorded in nephelometric turbidity units (NTUs). The results are shown in figure 1

Example 2

Sheets of coated paper were pulped. A 400 ml aliquot of pulp and paper pulp with a consistency of 2.5% was stirred at 1000 rpm. A coagulant with a structure of either polyamine, poly (diallyldimethylammonium chloride) (polyDADMAC), or polyaluminium chloride (PAC) and bentonite microparticles were added at intervals of 1 min with stirring. The coagulant was added in an amount of 1 pound per ton, as is customary, then bentonite in an amount of 4, 6 or 8 pounds per ton. The coagulant was also added as a single component in an amount of 1 or 2 pounds per ton, as is customary. After processing, the pulp and paper pulp was filtered through a 100 mesh sieve and the filtrate was measured for turbidity. Each sample of the filtrate was prepared by dilution with 1:14 deionized water. A Hach 2100P portable turbidimeter was used for analysis and the results were recorded in nephelometric turbidity units (NTUs).

results

The results of turbidimetric measurements for each treatment are shown in figure 2. Turbidity of the circulating water (filtrate) can serve as an indicator of the latex emulsion particles remaining in the colloidal state or an indicator of purity. By using polyamine or polyDADMAC as a single component at 1 or 2 pounds per ton, a reduction in turbidity is achieved compared to untreated coated paper. However, the addition of bentonite with various coagulants reduces the turbidity of the water. A significant reduction in turbidity was observed when comparing 1 pound per ton, as is customary, polyamine or coagulant PAC + bentonite to 2 pounds per ton, as is customary.

Claims (17)

1. A method of producing paper, comprising adding to the pulp an effective amount to reduce the deposition of white resin of at least one cationic polymer coagulant or inorganic coagulant, followed by the addition of material consisting of microparticles, where the paper pulp contains cellulose obtained at least partially from recycled paper products. 2. The method according to claim 1, where the material based on microparticles is selected from the group consisting of swellable clay, cross-linked polymer, colloidal silicon, borosilicate or a suspension of anionic material consisting of microparticles selected from bentonite, colloidal silicon, polysilicate microgel, polysilicon microgel acids and cross-linked microemulsions of a water-soluble monomer substance and mixtures thereof. 3. The method according to claim 2, where the material containing microparticles is an anionic material. 4. The method according to claim 2 or 3, where the material containing microparticles is a swellable clay from the family of smectites. 5. The method according to claim 2, where the material containing microparticles is a mineral consisting essentially of bentonite, montmorillonite, saponite, hectorite, beidilite, nontronite, fuller earth and mixtures thereof. 6. The method according to claim 1, where the material containing microparticles is a mineral consisting mainly of bentonite. 7. The method according to claim 1, where the cationic polymer coagulant is a homopolymer containing repeating cationic groups, or a copolymer of at least 80 wt.% Cationic monomer and 0-20 wt.% Acrylamide or other non-ionic monomer. 8. The method according to claim 7, where the cationic groups are obtained from diallyldimethylammonium chloride and dialkylaminoalkyl (meth) acrylates and acrylamides or their quaternary ammonium salts. 9. The method of claim 8, where the cationic groups are a quaternary ammonium salt of dimethylaminoethyl acrylate or methacrylate. 10. The method according to claim 1, where the coagulant is a polymer of dicyandiamide, polyamine or polyethyleneimine. 11. The method according to claim 1, where the coagulant is selected from the group consisting of alum, lime, iron (III) chloride, polyaluminium chloride, iron (II) sulfate, and mixtures thereof. 12. The method according to claim 1, where the coagulant is a polyalkylene polyamine obtained by the interaction of alkylene polyamine with a difunctional alkyl halide. 13. The method according to claim 1, where the coagulant is a cationic polyelectrolyte, i.e. poly [diallyl di (hydrogen or lower alkyl)] ammonium salt, the average molecular weight of more than 300,000, but less than 2,000,000. 14. The method according to item 13, where the material consisting of microparticles, is a mineral consisting mainly of bentonite. 15. A paper product obtained according to the method according to any one of claims 1-5 or 7-13. 16. A paper product obtained according to the method according to claim 6. 17. A paper product obtained according to the method of claim 14.

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