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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/59—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon
• • 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
• • 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
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/13—Silicon-containing compounds
• • 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

• the present invention relates to a method of deinking printed wastepaper.
• Printing on paper is typically accomplished using one of two types of ink, namely, impact ink, which is physically pressed onto the paper, and non-impact ink, which is attracted to a charged image and is then transferred to the paper.
• Impact inks are typically wet inks, for example letterpress inks, offset litho inks, photogravure inks and flexographic inks.
• letterpress inks are generally composed of carbon black pigment in a mineral oil vehicle and are used in, for example, newspaper printing.
• Offset litho inks tend to contain more pigment than letterpress inks and contain drying oils such as linseed or alkyl resins.
• Flexographic inks are used in similar processes to letterpress inks but are water-based and contain emulsified ink in an alkali soluble binder. Such inks may easily be dislodged, but may form extremely fine particles that are difficult to capture and remove.
• Non-impact inks e.g. toners
• toners are generally dry, powdered inks and are used in laser printing, photocopying and facsimile machines and generally comprise thermoplastic resins and pigment.
• the wastepaper is disintegrated (pulped) by mechanical agitation in an aqueous medium to separate the ink and impurities from the paper fibre and disintegrate the ink into particles of approximately 0.1 to 1000 ⁇ m.
• a grey slurry is thus obtained in which the ink is present in a finely dispersed form.
• the impurities for example, plastic, aluminium foil, stones, screws, staples, paper clips etc., are removed during a large number of screening steps.
• ink detachment of non-impact, e.g. photocopy, paper can normally be achieved in neutral conditions
• other printed paper ink detachment is routinely accomplished at alkaline pH levels using alkali hydroxides, alkali silicates, oxidative-working bleaches and surfactants at temperatures between 30 and 50° C.
• anionic and nonionic tensides are used as surfactants, for example, soaps, ethoxylated fatty alcohols and/or ethoxylated alkyl phenols (see, for example, EP 0013758).
• the ink particles are then removed from the fibre slurry by washing and/or flotation. Smaller ink particles are removed by washing, and larger ink particles and stickies (i.e. glue residues and adhesives) are removed by flotation. During flotation, air bubbles are blown into the pulp. The dispersed ink particles become attached to the air bubbles, which carry the ink particles to the surface. The resultant foam is then skimmed from the surface. Subsequent steps involve heating the pulp to evenly distribute stubborn ink particles and screening the pulp to separate the damaged, short or weak fibres. The remaining clean pulp is then pressed between rollers into sheets and dried.
• the alkaline conditions used in traditional deinking methods cause water-soluble and/or colloidal solids and finely dispersed solids to contaminate the process water, for example, fillers, fine fibres and stickies. If these contaminants are insufficiently removed during washing, they can be concentrated by subsequent washings and reintroduced to the paper fibre, causing a loss of brightness in the resultant paper. Effluent containing the aforementioned chemicals conventionally used in deinking methods is also environmentally undesirable.
• the present invention seeks to provide a method of deinking wastepaper which can overcome disadvantages of conventional deinking methods.
• a method of deinking printed paper comprising pulping the paper to form an aqueous slurry, adding a deinking additive to the paper, and removing detached ink by flotation, wherein the additive comprises an organo-modified siloxane comprising units of the formula: [R 1 a Z b SiO (4-a-b)/2 ] n
• each R 1 is independently selected from a hydrogen atom, an alkyl, aryl, alkenyl, aralkyl, alkaryl, alkoxy, alkanoyloxy, hydroxyl, ester or ether group;
• each Z is independently selected from an alkyl group substituted with an amine, amide, carboxyl, ester, or epoxy group, or a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 ;
• n is an integer greater than 1;
• a and b are independently 0, 1, 2 or 3;
• R 2 is an alkylene group or a direct bond
• R 3 is a group as defined for R 1 or Z above;
• p and r are independently an integer from 1 to 6;
• q and s are independently 0 or an integer such that 1 ⁇ q+s ⁇ 400;
• each molecule of the organo-modified siloxane contains at least one group Z.
• Z is preferably a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 , more preferably wherein p and/or r are independently 2, 3 or 4, i.e. a group comprising ethylene, propylene, and/or butylene oxide groups.
• p and/or r are independently 2, 3 or 4, i.e. a group comprising ethylene, propylene, and/or butylene oxide groups.
• q and s are each independently integers from 10 to 30, more preferably 15 to 25 (for example 18).
• p is 2
• r is 3
• q and s are both 18.
• R 2 may be an alkylene group, for example having from 1 to 6 carbon atoms (i.e.
• R 3 may be a group as defined hereinabove for R 1 or z, and is preferably a hydrogen atom or a hydroxyl group.
• Z may be an alkyl group substituted with an amine, amide, carboxyl, ester, or epoxy group, for example an alkyl group having from 1 to 6 carbon atoms, i.e. a substituted methyl, ethyl, propyl, butyl, pentyl or hexyl group.
• Z is a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3
• R 3 is preferably a hydroxyl or alkanoyloxy group.
• siloxane molecule Preferably, 2 to 20 mole percent of silicon atoms in the siloxane molecule are substituted by a group Z, more preferably 5 to 16 mole percent.
• the siloxane preferably has a hydrophilic/lipophilic balance (HLB) in the range of 5.0 to 7.3.
• HLB hydrophilic/lipophilic balance
• the molecular weight of the siloxane is preferably in the range of 1,000 to 500,000, more preferably 10,000 to 100,000.
• a particularly preferred siloxane for use in the present invention is a hydroxy-endcapped linear polydimethylsiloxane having an HLB of 5.9 to 6.3, in which 10 to 12 mole percent of silicon atoms are substituted by Z groups of the formula —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 , in which p is 2, r is 3 and q and s are both 18, R 2 is an alkylene group having from 1 to 6 carbon atoms or a direct bond, and R 3 is a hydrogen atom or a hydroxyl, ester or ether group.
• the additive used in the present invention may comprise further components, in addition to the organo-modified siloxane.
• the additive may further comprise one or more components selected from a polydimethylsiloxane, an organic polyether, and a fatty acid.
• Suitable organic polyethers include those of the formula R 4 —(OC p H 2p ) q (OC r H 2r ) s —R 5 in which R 4 and R 5 are selected from a hydrogen atom, hydroxyl, alkyl and alkoxy groups, and p, q, r and s are as defined hereinabove.
• Suitable fatty acids include saturated and unsaturated monobasic aliphatic carboxylic acids, for example having from 8 to 22 carbon atoms, such as lauric, myristic, palmitic, stearic, arachidic, behenic, lignoceric, palmitolic, oleic, linoleic, linolenic, and arachidonic acids.
• the additive may be in the form of an emulsion, for example the organo-modified siloxane may be a gum based self-emulsifying siloxane.
• the additive may be added to the paper before, during or after pulping.
• the amount of additive to be added to the paper is preferably within the range 0.1 to 1 wt % of the paper, more preferably 0.1 to 0.5 wt %.
• the additive may, for example, be added to the paper neat, as an emulsion, or in solution, for example an aqueous solution.
• the method of the present invention is preferably performed at substantially neutral pH, although the method may be performed under alkaline pH.
• the pulping and ink removal steps of the present invention may be performed as is conventional, as will be familiar to a person skilled in the art and described hereinabove.
• the paper may be pulped to form an aqueous slurry having a consistency of, for example, from 1 to 10% (for example, 1 to 5%) at a temperature of between 30 and 50° C., for example 35 to 45° C. Consistency is defined as wt % of pulp solids in the fibre suspension.
• Ink removal may be performed in a suitable flotation cell (for example, a Denver Lab flotation cell) at a suitable temperature, for example between 30 and 50° C. (e.g. 35 to 45° C.), and number of revolutions per minute, for example from 500 to 1000 rpm.
• An additional advantage associated with the method of the present invention is that when used to treat flexographic printed waste, the process water is relatively clear, whereas with known deinking methods it is generally black. Moveover, the present method produces pulp of improved brightness.
• Steps a) and b) above were repeated using the siloxane used in Example 1 (Siloxane 1) and the siloxanes defined in Table 4 (Siloxanes 2 to 8) on fresh and aged wastepaper.
• Table 4 also contains viscosity data for each of the siloxanes.
• the experiment was also carried out using the commercially available fatty acid based deinking preparation used in Example 1. The results are shown in Table 2 (fresh wastepaper) and Table 3 (aged wastepaper) below. Whiteness was evaluated according to DIN 53145 Part 1.
• Steps a) and b) above were repeated using the siloxane used in Example 1 (Siloxane 1) and two of the siloxanes defined in Table 4 (Siloxanes 4 and 7).
• the experiment was also carried out using the commercially available fatty acid based deinking preparation used in Example 1. The results are shown in Table 5 below. Whiteness was evaluated according to DIN 53145 Part 1.
• Steps a) and b) of Example 1 were repeated using the siloxane used in Example 1 (Siloxane 1), but were performed on 100% flexographic paper. In addition, 0.10 wt % sodium hydroxide and 1.20 wt % sodium silicate were added to the slurry.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Silicon Polymers (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Paints Or Removers (AREA)
• Treatment Of Liquids With Adsorbents In General (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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Citations (9)

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