Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control

Definitions

• the invention relates to a method for controlling the settling of adhesive contaminants from paper stock suspensions in paper manufacture.
• stickies In the field of processing waste paper, sticky contaminants, commonly referred to as stickies, can significantly disrupt the production process and negatively affect the quality of the paper produced.
• the stickies get into the paper manufacturing process when the waste paper used contains adhesive spots, adhesive tapes or finished products such as coated, laminated or coated papers or cardboards.
• the resin of the wood and its interaction with paper auxiliaries can also form adhesive contaminations.
• stickies are in compact form, they can be removed relatively easily mechanically with the aid of sorting machines. As a rule, however, the stickies are not only in a compact form, they are also contained in dispersed form in the pulp and are very difficult to remove in this form. In recent times, therefore, the increasing use of waste paper in paper production and the narrowing of the water cycles have led to an increasing increase in the proportion of stickies in the cycle.
• Stickies not only cause a number of problems or faults in paper production, but also in paper processing. Because of their stickiness, deposits form on machine parts, tube walls, screens, wet felting, dry felting, drying cylinders, smoothing rollers, calender rollers and, moreover, also in the finished paper. which leads to web breaks in the paper machine and a deterioration in paper quality due to holes, stains, markings (cf. HI. Baumgarten, Das Textil, 1984, 38. Issue 10A, pp. V121 - V125). HL-Baumgarten notes that sticky soiling has been described in industry and institute publications as the biggest problem of waste paper recycling for years. Even minimal amounts of adhesive can still cause tears on paper and printing machines, so that cleaning stoppages are necessary. Baumgarten explains: "If 2 g of adhesive are applied at a well-chosen point in the paper machine, several 100 kg of paper can be rejected" (loc. Cit., Page V122, right column).
• stickies come from the resin of wood, auxiliaries for paper production, binders for coating paper and cardboard, adhesives for paper processing, printing ink binders and materials for paper processing. Of particular importance in the context of the task of the present invention are those adhesive contaminants which originate from the resin of the wood and the adhesives used in paper processing.
• the resins present in the cellulose and wood pulp contain a proportion of about 1-5% by weight of so-called harmful resins. These can be in a colloidal unbound form or adhere to the paper fibers.
• harmful resins can be in a colloidal unbound form or adhere to the paper fibers.
• the adhesives used in paper processing can be divided into three groups: the pressure sensitive adhesives, the dispersion adhesives and the hot melt adhesives.
• the pressure sensitive adhesives are permanently adhesive and permanently adhesive products. Adhesion is achieved by pressing the surfaces of the parts to be bonded.
• a large number of base materials in combination with corresponding additives, e.g. tackifying resins, plasticizers or antioxidants.
• Typical base polymers include Natural rubber, butyl rubber, styrene-butadiene copolymers (SBR rubber), acrylonitrile copolymers, polychloroprene, polyisobutylene, polyvinyl ether, acrylates, polyesters, polyurethanes, silicones.
• the polymers which are suitable for forming the adhesive layer are present as solid particles in an aqueous dispersion medium.
• the base monomers are first emulsified in an aqueous phase and then polymerized therein, a technique known as emulsion polymerization.
• the polymer is then in the form of small particles with different particle sizes, which can vary in the range from molecularly disperse to coarsely disperse.
• a joint storage and an associated one Sedimentation of the polymer particles counteracted by adding protective colloids or emulsifiers to the system.
• hot melt adhesives also called “hot melts”
• thermoplastics These substances have the property of softening when heated, which makes them flowable. When they cool down, they solidify again.
• polymers which are used as hot-melt adhesives are polyamides, copolyamides, polyaminoamines, saturated polyesters and ethylene-vinyl acetate copolymers.
• Primary stickies are adhesive contaminants that are not dispersed due to their high resistance to wet grinding. They are therefore in a compact form and are easy to excrete.
• the existence of the secondary stickies stems from the fact that the adhesive contaminations are subject to a change in their particle size in the course of waste paper processing, which is brought about by thermal, chemical and mechanical influences. This means that even impurities that are still in a rather coarse form at the start of the reprocessing can be reduced to a greater or lesser extent in the reprocessing of waste paper.
• the processes in the hot shredder used to process waste paper result in dispersion of sticky contaminants.
• stickies with a low melting point are liquefied and then finely dispersed. Also crumbly or brittle Stickies break up into very small particles. The particle size of the dispersed stickies then ranges from coarse to colloidal to molecular.
• Van der Waals forces Small solid particles that touch each other or between which there is a very small distance pull due to molecular interactions, the so-called Van der Waals forces, on.
• the van der Waals forces acting on an agglomeration generally do not come into play in the alkaline milieu - ie the milieu typical for waste paper processing - since the particles are surrounded by an electrical double layer which is responsible for the mutual repulsion ⁇ ß are responsible in the same charged particles.
• the paper machine is usually operated in a neutral or slightly acidic environment, as a result of which the repelling negative forces are reduced.
• retention aids The drainability of the pulp suspensions that were made using waste paper is generally poor. In practice, aids are therefore often used which are referred to as drainage or retention aids.
• retention agents as substances that bind fine fibers and fillers to the long paper fibers (long fibers). This binding of the short fibers and the fillers to the long fibers prevents a kind of fleece formation of the fine materials, which makes dewatering of the paper pulp suspension difficult. In this way, retention agents improve the drainability by binding the fine substances to the long fibers.
• the retention aids can be divided into three groups. A distinction is made between inorganic products such as aluminum sulfate or sodium aluminate, synthetic products such as polyethyleneimines, polyamines or polyacrylamides and modified natural products such as cationic starch.
• the mode of action of the retention agents is based on the deposition of fine substances and fillers on the paper fibers.
• An important mechanism here is that polyelectrolytes with a sufficient chain length can bridge the distance between two particles and thus cause agglomerate formation. For example, JLHemmes et al. Report that cationic polyelectrolytes, for example cationic starch, are suitable as scavengers for anionic interfering substances (Wochenblatt für Textilfabrikation 1993, pages 163-170).
• This object was achieved according to the invention by a process for controlling the settling of sticky contaminants (stickies) from paper pulp suspensions during paper manufacture, the pulp suspension being metered in with an effective amount of a derivative of native starch.
• the present invention therefore relates to a process for controlling the settling of sticky impurities (stickies) from paper pulp suspensions during paper manufacture, which is characterized in that an effective amount of a derivative of native starch is metered into the paper pulp suspension.
• the method according to the invention is generally applicable to the most varied types of adhesive contaminants. However, it is particularly suitable for solving the problems caused by pressure-sensitive adhesives, dispersion adhesives and hotmelt adhesives.
• the method according to the invention relates to those pulp suspensions which have been produced from waste paper or from paper products which contain waste paper components.
• a derivative of native starch means those products which are accessible by chemical derivatization of native starch. Degradation products one Thermal, hydrolytic or enzymatic cleavage of native starch do not fall under this definition.
• the type of chemical derivatization is not subject to any particular restriction, but the products of esterification, etherification, acetylation of native starch and cationized starch are preferred as starch derivatives.
• the type of native starch which is used to produce the degradation products suitable according to the invention is not subject to any particular restriction.
• Potato starch, corn starch, rice starch or canna starch can be used as starting materials.
• Another object of the present invention is the use of derivatives of native starch to control the settling of sticky contaminants (stickies) from paper stock suspensions in paper manufacture.
• cationic starch is a common dewatering agent in papermaking and that cationic polymers are generally used as dewatering and / or retention agents: "It is standard practice to include cationic polymers in the stock that is to be drained in order to improve drainage and / or retention "(p.2, lines 12-13). It is also stated that inorganic substances, such as aluminum oxide, talc or bentonite, which can minimize the problems associated with adhesive contaminations, are often added to the preparation for drainage: “... the normal way of preparing it for drainage is by adding inorganic material, such as alum, talc or bentonite, at the pulping or thick stock stages. These treatments can have the effect of minimizing the problems due to pitch and other sticky materials "(S.2, lines 6-9) .
• the method according to the invention is suitable in principle for checking the setting and sticking of stickies of different types and thus also of different chemical and physico-chemical nature.
• the advantages of the method according to the invention are particularly evident in the case of stickies based on pressure-sensitive adhesives and hotmelt adhesives.
• the derivatives of native starch according to the invention can be metered in at any point in the entire paper-making process. They are metered in either in the form of solid particles or in the form of an aqueous solution or dispersion.
• the effective amount of derivatives of native starch required in each case depends on the extent to which the waste paper or paper types to be processed, which contain waste paper constituents, contain sticky contaminants.
• the derivatives of native starch according to the invention are used in an amount in the range from 0.001 to 5.0% by weight, preferably 0.1 to 1.0% by weight, based on the fiber material.
• MHPC methylhydroxypropyl cellulose
• MHPC 50 Aqualon
• AcKS acetylated starch
• the detacking test used here is known in principle to the person skilled in the art from the American patent application US 4,886,575 and the above-mentioned article by B.Brattka (loc. Cit. P.311).
• the method consists in immersing a selected adhesive tape in an aqueous solution with the substance to be tested. The tapes are then glued together under defined conditions and then the (still existing) adhesive strength is determined in a universal testing machine.
• the peeling force is to be seen as an indicator of the ability of the respective polymer to exert a controlling influence on the stickie formation: the lower the measured force, the better the polymer prevents the tapes from sticking to one another and thus preventing them from sticking together Agglomeration of adhesive particles that ultimately cause sticky problems.
• the values given in the tables each represent mean values from five measurements. Comparative Verse 1

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• 1993
  • 1993-04-08 DE DE19934311600 patent/DE4311600A1/de not_active Withdrawn
• 1994
  • 1994-03-30 CA CA002160103A patent/CA2160103A1/en not_active Abandoned
  • 1994-03-30 JP JP6522679A patent/JPH08508792A/ja active Pending
  • 1994-03-30 WO PCT/EP1994/000998 patent/WO1994024367A1/de not_active Application Discontinuation
  • 1994-03-30 EP EP94913087A patent/EP0693147A1/de not_active Withdrawn
• 1995
  • 1995-10-04 FI FI954722A patent/FI954722A/fi not_active Application Discontinuation

Non-Patent Citations (1)

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