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 pulp suspensions in papermaking.
• sticky contaminations can considerably disrupt the production process and negatively influence the quality of the paper produced.
• the stickies get into the paper manufacturing process when the used paper contains glue 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.
• the stickies are in a compact form, they can be removed relatively easily mechanically with the help of sorting machines. As a rule, the stickies are not only available 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, 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 felts, dry felts, drying cylinders, smoothing rolls, calender rolls and, moreover, also in the finished paper, which causes web breaks in the paper machine and a deterioration in the paper quality Holes, stains, markings come (see HL Baumgarten, Das Textil, 1984, 38, Issue 10A, pp. V121 - V125). HLBaumgar ⁇ ten notes that adhesive contaminants in industrial and institutional Publications have been described as the biggest problem of waste paper recycling for years. Even minimal amounts of glue can still tear on paper and printing machines, making cleaning stoppages necessary. Baumgarten explains: "If 2 g of adhesive is applied to 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 the coating of 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 come 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. Liability is achieved by pressing the surfaces of the parts to be bonded together.
• a large number of base materials in combination with corresponding additives, for example tackifying resins, plasticizers or antioxidants, are customary as base polymers.
• Typical base polymers include natural rubber, butyl rubber, styrene-butadiene copolymers (SBR rubber), acrylonitrile copolymers, polychloroprene, polyisobutylene, polyvinyl ether, acrylates, polyester, polyurethane, silicones.
• the polymers which are suitable for forming the adhesive layer are present as solid particles in an aqueous dispersant.
• 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.
• an aggregation and an associated sedimentation of the polymer particles are counteracted by adding protective colloids or emulsifiers to the system.
• hot melt adhesives also called “hot melts”
• thermoplastics These substances have the property b ?. . Warm to soften, making them flowable. When they cool down, they solidify again.
• polymers which are used as hot-melt adhesives include polyamides, copolyamides, polyaminoamines, saturated polyesters and ethylene-vinyl acetate copolymers.
• Primary stickies are understood to mean those sticky contaminants which, due to their high resistance to wet grinding, tion are not dispersed. 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 the waste paper processing, which is brought about by thermal, chemical and mechanical influences. This means that even impurities which are still in a rather coarse form at the beginning of the reprocessing can be more or less reduced in size when the waste paper is reprocessed.
• the processes in the hot shredder of waste paper processing result in dispersion of sticky contaminants.
• stickies with a low melting point are liquefied and then finely dispersed. Even crumbly or brittle stickies disintegrate into very small particles.
• the particle size of the dispersed stickies then ranges from coarsely dispersed to colloidal to molecularly disperse.
• Van der Waals forces Small solid particles that touch or between which there is a very small distance attract each other due to molecular interactions.
• the van der Waals forces working towards agglomeration come in an alkaline environment - i.e. the milieu typical of waste paper processing - but generally not to the advantage, since the particles are surrounded by an electrical double layer which is responsible for the mutual repulsion of the particles charged in the same direction.
• the paper machine is usually operated in a neutral or slightly acidic environment, as a result of which the repelling negative forces are reduced.
• the drainability of the pulp suspensions that were made using waste paper is generally poor.
• 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, polyaines or polyacrylamides and modified natural products such as cationic starch.
• the mode of action of the retention agents is based on the addition of fine substances and fillers to the paper fibers.
• An important mechanism is that polyelectrolytes with a sufficient chain length can bridge the distance between two particles and thus cause agglomeration.
• cationic polyelectrolytes e.g. cationic starch, suitable as a catcher for anionic contaminants (Wochenblatt für Textilfabrikation 1993, pages 163-170).
• the object of the present invention was therefore to develop a method for controlling the settling of adhesive contaminants which appear negatively as secondary stickies in the paper machine.
• This method should generally be applicable to a wide variety of types of adhesive contaminants, but in particular to pressure sensitive adhesives, dispersion adhesives and hotmelt adhesives.
• the sticky control it had to be demanded that the sticky control not be at the expense of increased losses of fibers and fillers.
• This object is achieved according to the invention by a method for controlling the settling of adhesive contaminants from paper pulp suspensions. sions in paper production, with the paper stock suspension immediately before the first and / or further flotation stages - based on otro paper stock - 0.2 to 3.0% by weight of water glass and / or 0.05 to 1.0% by weight .-% of a fatty acid with essentially 12 to 22 carbon atoms or its salt with mono- to trivalent cations added.
• "Ootro paper stock” is understood to mean, as is customary in paper technology, oven-dry paper stock.
• the present invention therefore relates to a process for controlling the settling of adhesive contaminants from paper stock suspensions in paper manufacture, which is characterized in that the paper stock suspension is in each case immediately before the first and / or further flotation stages. based on otro paper stock - 0.2 to 3.0 wt .-% water glass and / or 0.05 to 1.0 wt .-% of a fatty acid with essentially 12 to 22 carbon atoms or their salt with a up to trivalent cations.
• components i) and / or ii) are added is a critical feature for the success of the process according to the invention.
• the fact that components i) and / or ii) are to be added immediately before the first and / or further flotation stages implies that they get into the flotation without being subjected to strong shear forces beforehand. Such shear forces occur at various points in the course of papermaking. Examples of this are the waste paper pulper, the so-called pulper, or sorting devices connected to it.
• Adherence to the above-mentioned parameters essential to the invention guarantees that the adhesive contaminants which are present in finely divided form in the aqueous paper pulp suspensions used and which can lead to secondary stickies largely result from the System are removed.
• Another advantage of the method according to the invention is that the reduction in the content of adhesive contaminants does not come at the expense of an increased loss of fibers and fillers. Rather, the method according to the invention achieves an additional advantage in reducing the loss of fibers and fillers.
• the paper stock suspensions used are made from waste paper or paper products which contain waste paper components.
• the type of water glass is not critical in itself. However, soda and / or potassium water glass are preferred.
• a mixture of components i) and ii) is used.
• the weight ratio of the two components is not critical per se, but it is preferred to set a weight ratio of 0.5: 1 to 10: 1. Again, it is preferred to use component i) in excess compared to component ii); a weight ratio of components i) and ii) of 3: 1 to 5: 1 is very particularly preferred.
• the two components i) and ii) are used in combination with an alkali hydroxide.
• the alkali hydroxide preferably sodium and / or potassium hydroxide, is preferably used in an amount of 0.05 to 2.0% by weight, based on the dry paper stock.
• the presence of alkali hydroxide further reduces the loss of fibers and fillers, which is of great importance for the economy of the process.
• component ii) it is crucial that it is present - at least partially - in the respective flotation cell in the form of a relatively sparingly soluble soap.
• cationic polymers such as polyacrylamides, polyethyleneimines, polyamidamines or cationic starches and inorganic compounds such as aluminum sulfate.
• the method according to the invention is generally applicable to a wide variety of 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 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.
• Water glass "Water glass 37/40" (Na2Si ⁇ 3), from Henkel / Düsseldorf.
• the dichloromethane extract served as an indirect measure for determining the proportion of adhesive impurities in paper suspensions. This is obtained by filtering a sample of the paper stock suspension to be investigated, drying the residue and determining the constituents soluble in dichloromethane, which are essentially adhesive contaminants, by extraction.
• a 500 ml sample was taken from a well-mixed paper stock suspension and passed through a filtering device consisting of a Buchner funnel with a diameter of 15 cm, a large suction bottle and a paper bottle. round filter, filtered. After the filtration, it was checked visually in each case whether the filtrate had no turbidity. If turbidity could still be seen, the filtrate was filtered again using the same filter. The round filter was dried together with the filtered cake in the warming cabinet and then weighed.
• the dried fabric cake was then transferred together with the round filter into a Soxhlet extractor with a ground-in cooler and a connected 500 ml standing flask with a ground neck. After adding 400 ml of dichloromethane, the mixture was extracted with heating for 6 hours. After the end of the extraction, the extract solution was concentrated by distillation until it was just liquid. The flask was then dried in a drying cabinet at a temperature of (105 * 2) ⁇ C to constant weight and then as in 2.2. described weighed. From the values found, the dichloromethane extract DCM was calculated in% - based on the dry weight of the sample weight - as follows:
• waste paper was pulpered at a consistency of 12 otro with 1% water glass, 0.5% sodium hydroxide solution, 0.5% hydrogen peroxide and 0. 33% Olinor 042 - all percentages related to otro paper stock - opened. After the subsequent coarse sorting, a volume corresponding to 200 kg of dry paper stock was pumped into a chest and, after determination of the stock density, was diluted with circulating water to 1.3% stock density.
• the additives to be investigated were then metered in, a fabric sample was taken and the flotation was then carried out for 30 minutes.
• the pulp suspension circulated from the chest over the flotation cell to a subsequent second chest back to the first chest. After the end of the flotation, the entire amount of substance was pumped back into the first * chest and another substance sample was taken. From the material samples obtained before and after the flotation, the dichloromethane extract is determined, as indicated above, and the total loss of filler and fibers is also determined via the material density and the level of the laid paper.

Landscapes

• Paper (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Sampling And Sample Adjustment (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=6487641

Family Applications (1)

Country Status (10)

Families Citing this family (5)

Family Cites Families (1)

• 1993
  • 1993-05-10 DE DE4315449A patent/DE4315449A1/de not_active Withdrawn
• 1994
  • 1994-05-02 JP JP6524889A patent/JPH08509789A/ja active Pending
  • 1994-05-02 ES ES94916917T patent/ES2098951T3/es not_active Expired - Lifetime
  • 1994-05-02 CA CA002162668A patent/CA2162668A1/fr not_active Abandoned
  • 1994-05-02 DE DE59402082T patent/DE59402082D1/de not_active Expired - Fee Related
  • 1994-05-02 AT AT94916917T patent/ATE150119T1/de not_active IP Right Cessation
  • 1994-05-02 EP EP94916917A patent/EP0698141B1/fr not_active Expired - Lifetime
  • 1994-05-02 WO PCT/EP1994/001389 patent/WO1994026973A1/fr active IP Right Grant
  • 1994-05-02 DK DK94916917.1T patent/DK0698141T3/da active
• 1995
  • 1995-11-08 FI FI955377A patent/FI955377A0/fi not_active Application Discontinuation
• 1997
  • 1997-05-19 GR GR970401136T patent/GR3023487T3/el unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events