Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
  • C08B37/0057—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Xylans, i.e. xylosaccharide, e.g. arabinoxylan, arabinofuronan, pentosans; (beta-1,3)(beta-1,4)-D-Xylans, e.g. rhodymenans; Hemicellulose; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F218/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
  • C08F218/02—Esters of monocarboxylic acids
  • C08F218/04—Vinyl esters
  • C08F218/08—Vinyl acetate
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
  • D21C5/02—Working-up waste paper
  • D21C5/025—De-inking
  • D21C5/027—Chemicals therefor
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/64—Paper recycling

Definitions

• This invention relates to a process for de-inking paper pulp and to materials used in the process.
• the detached ink particles must be emulsified to a sufficient extent to prevent redeposition on the fibres but at the same time, the emulsions produced must not be so stable that carrier particles required to raise the ink particles to the surface have difficulty in attracting the ink from the emulsions.
• the carrier itself must have the required affinit for the ink and be suitable for rapid transport to the surface of the pulp by the air and the carrier and ink must form a foam or scum at the surface.
• the foam must have characteristics suited to efficient mechanical removal in particular it should not incorporate significant quantities of fibres, since otherwise the overall efficiency will be reduced.
• Flotation de-inking indicates that the complex processes are finely balanced and unsatisfactory results can easily occur if any imbalance occurs in these processes. It has been found the the level of calcium ions which it is necessary to add to the pulp much exceeds that required to insolubilize the sodium soap and it is also found that the addition of synthetic anionic and non-anionic surfactants in addition to the added sodium soaps serve to reduce the speed with which the carrier particles can transport the ink to the surface foam. Also the production of foam is dependant upon the pH value and a minimum level of 8-8.5 is generally needed for satisfactory results.
• the hemicellulose fraction is a mixture of polysaccharides based mainly on xylose and a small proportion of side-chain carboxyl groups. This hemicellulose is soluble in alkaline but insoluble in acid and is therefore found only, in pulps prepared under acid conditions.
• the added material intended both as a surfactant and as a foaming agent should resemble natural hemicelluloses as far as possible and thus contain a high proportion of hydroxyl and a low proportion of carboxyl groups in a linear polymeric structure.
• One suitable co-polymer is made from vinyl acetate and acrylic or maleic acid and the co-polymer is made by removing acetate residues by transesterification with methanol in the presence of sodium methoxide (made by adding sodium to methanol). It is found that such co-polymers have specific properties necessary for foaming at high calcium levels (say 250 p.p.m) in alkaline solutions.
• AZBN Azo-bis-isobutyronitrile
• the polymers prepared were characterised by the following two methods: a) By infra-red spectroscopy: the polymer was dissolved in water and a film cast on a silver chloride plate. The water was evaporated in an oven. The spectrum was run on a Perkin-Elmer 157G grating infra-red spectrometer. b) A weighed amount of each polymer was dissolved in 250 ml. of methanol and the solution was titrated with standardised potassium or sodium hydroxide, using phenolphthalein as indicator. The percentage by weight of acid monomer in the polymer was then calculated from this titration.
• Example 1 Reactants: 50gm. vinyl acetate, 30gm. hydroxypropyl methacrylate, 5gm maleic acid, 20ml. iso-propanol. Solvent: 100ml toluene. Initiator: 0.3gm. AZBN. The reactants were heated at 85°C under reflux for three hours. The isolation of the intermediate and the methanolysis were then performed and the product was precipitated by the addition of petroleum ether. Yield 21gm. Acid content of intermediate: 15.1% and of the product: 6.2%, Example 2 Reactants: 50gm. vinyl acetate, 30gm. of hydroxy propyl methacrylate 6.9gm.
• Example 3 Reactants: 50gm. of vinyl acetate, 30gm of hydroxy-propyl methacrylate, 2gm. of acrylic acid, 20ml. of iso-propyl alcohol. Solvent: 100ml. of toluene. Initiator: 0.3gm. of AZBN. The reactants were heated under reflux at 83°C for two hours. . The product prepared by the general method proved difficult to extract: on adding toluene and petroleum ether still no product was precipitated. A little glacial acetic acid and a little water were added and the product separated slowly with stirring. Yield 5.6gm. Acid content of intermediate: 9.6%, of product: 9.7%,.
• Example 4 Reactants: 50gm.
• Example 5 Reactants: 50gm. of vinyl acetate, 25gm. of methyl acetate, then 0.15gm. of maleic acid dissolved in 25gm. more of methyl acetate added dropwise. Initiator: 0.3gm of AZBN. The mixture was heated under reflux for one hour while the acid was added, and the heating was continued for a further hour. Approx. 20ml methanol and 1ml. of 40% sodium hydroxide solution were then added. The mixture was heated under reflux for 30 minutes, at the end of which time the product had precipitated out. This was filtered and washed with acetone before being dried in an oven. Yield 6.7gm. Acid content of product: 2.0%,
• Example 6 Reactants: 50gm. of vinyl acetate, 25gm. of methyl acetate, Initiator: 0.3gm. of AZBN. These reactants were heated under reflux for four hours. During the first two hours the following were run in dropwise: 25mg. of methyl acetate, 0.15gm. of maleic acid, 0,2gm of AZBN, After four hours approximately 20 ml. of methanol, and 1-2ml. 40% sodium hydroxide solution were added. This produced a considerable amount of heat and some of the solution blew out of the top of the condenser. The solution was cooled in an ice bath before heating under reflux for 30 minutes. Yield 6gm. Acid content of product 2.1%.
• Example 7 Reactants: 50gm. of vinyl acetate, 25gm. of methyl acetate and then 0.1gm. acrylic acid and 25gm, methyl acetate. These added dropwise over the first three hours. Initiator: 0.3gm. AZBN. The mixture was heated under reflux for four hours before being cooled in an ice-bath. 200ml. of methanol and 2ml. of 40% sodium hydroxide solution, were added. The mixture was then heated to reflux for half an hour, the product was precipitated and was filtered and dried. Yield 4.6gm. Acid content of product: 1.9%.
• Example 8 Reactants: 50gm. of vinyl acetate, 25gm. of methanol, 25gm.
• Example 9 Reactants: 50gm. of vinyl acetate. Solvent: 100ml of methyl acetate. Initiator: AZBN 0.3gm. These reactants were heated under reflux for four hours. After two hours, 0.3gm. of AZBN and 20ml. of toluene were added. The solution was then cooled somewhat, and approximately 250ml. of petroleum ether were added with stirring. The liquid was decanted off and discarded. 300ml of methanol was added with heating and stirring to dissolve the polymer. After adding some methoxide the solution was heated under reflux for half an hour. The product was filtered and dried in the usual way. Yield 10.5gm.
• the first stage was to pulp the sample of newsprint : this was performed..in a standard pulp evaluation disintegrator. 2 litres, 40o-45°C of warm water, 0.7gm. of the polymer, 1.0gm. of sodium hydroxide and 4.0gm, of sodium metasilicate were added to the pulper. The mixture was then stirred for a count of 500 on a counter fitted to the pulper to ensure that the polymer had dissolved; each unit on the counter is equivalent to 25 revolutions of the stirrer shaft - 50 revolutions per second. 2ml. of 100 volume hydrogen peroxide solution was then added. The solution was further agitated. 2gm. of calcium chloride was then added with stirring. 70gm. of newsprint was added, the counter was set at 3,000 and the disintegrator started. The contents of the pulper were checked after 100 on the counter, to see if there had been any separation of ink from the pulp.
• the contents of the pulper were again checked and then transferred to the bucket.
• the pulper was rinsed with hot water, which was added to the contents of the bucket. The latter was then made up to the volume of the flotation tank with cold water.
• the flotation tank was a cylindrical cell of 7.5 litres capacity, constructed of stainless steel, which incorporated a multi-pored base bubbler attached to a pressurised air supply, and an overhead stirrer with a butterfly blade system.
• the soap solution was placed in the flotation tank and the pulp transferred to it.
• the air flow was adjusted to a rate of 0.95 litres/min. and the stirrer motor was switched on, running at a rate of approximately 1,200 revolutions/min.
• the froth was removed by manual scraping with a palette knife from the top of the tank for 20 minutes
• the froth removed was checked to see: a) the extent of fibre removal and b) whether the ink was being removed as large or small particles, or not at all.
• the de-inked pulp was then formed into handsheets: a sample of 1,500ml. was taken out of the flotation tank (through the tap on the side). The water was then drained off in a 60-mesh sieve and the resultant pulp was then thickened, most of the remaining water being pressed out. The pulp was then re-diluted to 1,500ml.
• the diluted pulp was then made into three handsheets, each of 500ml. using a filter tank and a press. In each case, some water was run into the filter tank and 500ml. of pulp were poured in at the same time. The tank was then emptied, leaving a film of paper on the mesh. Two sheets of blotting paper and then a 7" diameter metal disc were placed on top of this. Then using a heavy, metal roller, the sheet was rolled seven times. The blotters plus sample were placed on the press for the first pressing: two blotters were placed on the press, then the two blotters plus sample (sampla facing upwards), and then a 6" diameter metal plate.
• Trial 1 No polymer Clean (after Small, light Fair (50.6) added 100 on the bubbles slow counter), some to form, some ink stuck to fibre, not all sides of the ink removed. bucket at the end of trial.
• Trial 4 1.5gm. NaOH in Slight separGood foaming, Good (56.3) each stage ation of ink largish, light at 100 on the bubbles, ink counter, cleacame off quickner at end of ly, foam quicker trial. to form than in trial 3. Little fibre loss.
• Trial 6 As Trial 5, Considerable More foam Quite good but with inky scum than trial 5 (55.0) polymer separated. quicker formation of same type of foam. Most ink removed by 15 minutes.
• Trial 9 No peroxide, Inky scum sepComparable to Fair (49.9) soap in pulper arated out. trial 8.
• Trial 1 No polymer .Slightly inky Not very good; Fair (52.0) used. 1.5gm. scum separaseemed to reNaOH in pulted. move, little ink. ping stage. Some fibre removed.
• Trial 2 1.5gm. NaOH Slight foamMore foam than Good (54.5) in pulping ing on top trial 1, did stage not seem to remove a lot of ink. Some fibre loss.
• Trial 4 4gm. CaCl 2 in Reasonably Not very great. Quite good flotation clean. Some ink re(53.3) stage moved at first, little at end of trial. Some fibre loss.
• Trial 6 6gm. CaCl 2 and Reasonably Good foaming. Good (56.8) 2gm. NaOH in clean Good removal flotation stage of ink as fine particles. Little fibre removal.
• Trial 2 0.7gm. interMuch the same Very light foam Quite good mediate used as trial 1. but ink seemed to (52.7) 1.5gm. NaOH be removed. Pulp in each stage. at end of trial was grey. Little fibre loss.
• Trial 1 1.5gm. NaOH Reasonably Poor, unstable Good (55.1) used in each clean after and slow to form stage. 0.7gm. 100 on the foam. Some fibre intermediate counter; removed. Little used. large partink being removed icles of ink towards the end separated at of trial. the end of trial.
• Trial 2 1.5gm. NaOH in Quite clean Rather poor foamQuite good each stage. ing - slow to (54.7) form and unstable. Considerable ink removed at start still removiiig at end. Little fibre loss.
• Trial 3 Also 2.1gm. Some ink parVery poor, 2gm. Fair (51.5) polymer in ticles separ- NaOH + 8gm. CaCl 2 , lotation ted after 100 added then foamed stage. 2gm. on the counter; very well, but
• Trial 2 1.5gm. NaOH More foam at Much the same as Good (55.6) in each stage. top than trial 1 but trial 1. seemed to remove ink more efficiently; foaming better near end.
• Trial 3 1.5gm. NaOH Considerable Quite good, ink Quite good in each foam on top removed as fine (53.4) stage. at end. particles. Ink still caning off at end. Some fibre removed.
• Trial 2 As trial 1, Some ink Foam-free parExcellent but no CaCl 2 particles ticulate scum. (60.2) added. separating 4gm. CaCl 2 towards end. added: then foam generation still much lighter than trial 1. Ink still highly particulate. Differences Contents of Foaming in Handsheets from general pulper tank (Reflectance)
• CaCl 2 used. about 5 minutes after 6gm. CaCl 2 added then quite good foaming.
• Trial 5 Much the same Much the same Very good but 1.0gm. as trial 3. as trial 4. (56.7)
• Trial 1 1.5gm. NaOH Considerable Good, ink Fair (52.9) in each inky scum removed as fine stage. after 100 on particles, sane the counter, fibre loss. little less at end ink being removed of trial. but still good foaming at end of trial.
• the polymers were characterised by their acid numbers, the amount by weight of acid monomer as a percentage in the product, and by their infra-red spectra. In practice the infra-red spectra appeared very much the same in all cases. All the polymers showed a strong absorbance at a wavelength of about 3500cm -1 ; this is characteristic of the -OH group. There was a peak in the spectra of the intermediates .which became almost negligible in the spectra of the final products. This peak (at a wavelength of 1575cm -1 ) did not appear in any of the spectra of the monomers on their own, but it did appear in the pure poly (vinyl alcohol) spectrum. It could perhaps be attributed to a carboxyl group.
• Example 1 (acid content 6.2%), had twice the level of hydroxypropyl methacrylate at the start as compared to earlier Examples, not described. It was found that a higher sodium hydroxide level in each of the pulping and flotation stages gave a much better paper product. These levels were generally used in the production of all handsheets. The best results were obtained by trial 7, with 0.7gm. polymer and the soap added in the pulper, which gave very good handsheets with a reflectance of 56.4. The trial was repeated with no peroxide and gave poor handsheets with a reflectance of 49.9. This shows that the peroxide is necessary; but merely adding a large amount of bleach to obtain good handsheets does not give adequate results. Also, if the soap is added to the pulper instead of to the flotation tank, the ink tends to separate in the pulper and sticks to its side and to the bucket during transfer to the flotation tank.
• Example 2 (acid content 13.7%), was prepared similarly to Example 1, except that acrylic acid was used instead of maleic acid. This also gave quite good results, but only after the addition of extra calcium chloride in the flotation stage.
• Example 3 (acid content 9.7%), contained a smaller amount of acrylic acid than Example 2. This proved particularly difficult to isolate, and after that it gave a very poor performance as de-inking additive.
• Example 4 including maleic acid as opposed to acrylic acid, and also some trichloroacetic acid which might become trapped in the polymer structure, was then prepared. De-inking trials were then run with both the product and the intermediate and both gave very poor results. Models for maleic and acrylic acids when incorporated in a co-polymer are succinic and propionic acids, respectively. pK for propionic acid is 4.87, and for succinic acid pKa (1) is 4.16 and pKa(2) is 5.61.
• Example 5 Due to the poor performance of these "high-acid" polymers only a trace of acid was added to the co-polymer of later Examples. Both Examples 5 and 6 had a small amount of maleic acid added as a solution in methyl acetate from a dropping-funnel. To produce Example 5 the first stage was heated under reflux for two hours whereas this polymerisation lasted four hours in Example 6. Example 5 (acid content 2.0%), produced quite good results; it was interesting to note that 0.7gm, of additive produced the same amount of foa m as 0.25gm., but removed the ink more efficiently, Example 6, (acid content 2.1%), gave excellent results, But it was thought that the calcium level was too high and some trials were performed with different calcium levels. These produced particularly good handsheets; probably the best results so far have come from Example 6.
• Example 7 and 8 were much the same as Example 5 and 6 but contained small amounts of acrylic acid Cadded dropwise). Neither of these products, though, proved to be as good an additive as Example 6,.
• Example 7, (acid content 1.9%), did not produce a large amount of foam and little ink seemed to be removed, though the handsheets were reasonable. In the second trial, though foaming well, poor handsheets resulted.
• Example 8 (acid content 2.1%), gave a good foam but poor handsheets were produced. Generally, ink removal was not satisfactory,
• the polymers which performed the best in flotation de-inking as an additive were those with some acid present in the chain, but not too much.
• the polymers which seemed to work best were those with about 2% of acid by weight in the polymeric chain.

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• 1979
  • 1979-11-27 JP JP50203979A patent/JPS55501147A/ja active Pending
  • 1979-11-27 WO PCT/GB1979/000202 patent/WO1980001085A1/en unknown
• 1980
  • 1980-06-03 EP EP79901574A patent/EP0020601A1/de not_active Withdrawn

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