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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
  • D21H23/06—Controlling the addition
  • D21H23/14—Controlling the addition by selecting point of addition or time of contact between components
• • 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
  • D21H21/06—Paper forming aids
  • D21H21/10—Retention agents or drainage improvers
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch

Definitions

• This invention relates to the production of paper which is strengthened by starch
• Various processes for making paper, and for making paper strengthened by starch, are described in, for instance, WO95/33096, which is incorporated herein by reference
• Processes which are currently of particular interest in paper making comprise providing a celluiosic thin stock suspension, flocculating this suspension, shea ⁇ ng the flocculated suspension, reflocculating the sheared suspension by adding an aqueous reflocculating composition, draining the suspension through a wire to form a wet sheet, and drying the sheet
• the flocculation is generally caused by the use of a natural or synthetic polymeric retention aid and the reflocculation is generally caused by the use of an aqueous suspension of bentonite or other anio ⁇ ic microparticulate material
• One conventional treatment comprises applying a solution of substantially fully cooked starch to the sheet before final drying It is also known to apply partially or wholly uncooked starch in this position and to cook it du ⁇ ng the drying It is also known to include substantially uncooked starch in the aqueous suspension before drainage, for instance as a result of being added with the polymeric retention aid or with the aqueous reflocculating composition
• the substantially uncooked starch may have been slightly cooked so as to facilitate its final cooking, but most or all of the cooking is conducted during the drying stage thereby converting the substantially uncooked starch to substantially fully cooked starch in the final sheet
• substantially fully cooked starch is added to the suspension after the suspension has been flocculated, and preferably after the flocculated suspension has been sheared
• the aqueous reflocculating composition comprises the substantially fully cooked starch
• the aqueous reflocculating composition preferably comprises an aqueous dispersion of anionic microparticulate material
• the substantially fully cooked starch may be precooked to its substantially fully cooked state and then the cooked starch and the anio ⁇ ic microparticulate material may be blended to form the final dispersion containing both For instance the starch mav be cooke ⁇ and then mixe ⁇ with an aqueous dispersion of the microparticulate material
• the reflocculating composition is made by mixing substantially uncooked starch with an aqueous dispersion of the microparticulate material and cooking the starch in that dispersion If necessary or desirable, the resultant dispersion may then be diluted with water It seems that cooking the starch in the presence of the microparticulate material generates a particularly desirable structure within the reflocculating composition
• Preferred anionic particulate materials are swelling clays such as silica, colloidal silicic acid and colloidal silicas, polysilicate and polysilicic acid microgels and aluminium modified versions of these, and organic microparticles, for instance all as described in WO95/33096
• Another reflocculating composition that can be used is an aqueous solution of a polymer which is generally counte ⁇ onic to the polyme ⁇ c retention aid which was used for causing the initial flocculation of the celluiosic thin stock suspension, and in particular it can be a material as described in WO98/29604
• the starch must be fully cooked p ⁇ orto drainage, and preferably prior to addition to the aqueous celluiosic thin stock suspension, by which we mean that the starch granules must have burst and become substantially fully gelatinised Naturally it is usually necessary to maintain the starch under some degree of agitation during cooking, as is conventional
• substantially no uncooked starch is included in the suspension which is drained, and thus it is not necessary to rely on cooking of the starch during drying of the sheet
• the starches which can be used can be any of the conventional starches such as cationic, anio ⁇ ic or amphote ⁇ c starches and can be derived from, for instance, com wheat, potato or tapioca or may be recovered starch in another embodiment of the invention, the aqueous reflocculating composition can contain as its essential component, merely cooked starch which is sufficiently counte ⁇ onic to the sheared celluiosic floes for it to act as a reflocculating composition
• the cooke ⁇ starch which best meets this requirement is usually amphote ⁇ c cooke ⁇ starch
• the invention also provides a novel paper making process in which the reflocculation of the sheared suspension is achieved merely by adding cooked amphote ⁇ c or other suitable starch, without the customary anionic microparticulate material Such processes give satisfactory retention and drainage properties despite the absence of the microparticulate material
• the amount of starch which is to be added will be selected having regard to the degree of strength that is required and having regard to the other components in the suspension Generally it is at least 0 5 and usually at least 1 % by weight and can be as much as 10 or 15% by weight, based on the dry weight of the celluiosic thin stock
• the polymeric retention aid which is used can be cationic starch but is generally a synthetic polymer
• the synthetic polymer can comprise a combination of low and high molecular weight polymers, as is known, but generally the final polymeric retention aid which is added is a synthetic polymer having intrinsic viscosity at least 4dl/g
• the synthetic polymer can be non-ionic, anionic or cationic, but is usually cationic
• the retention aid is a synthetic cationic polymer of intrinsic viscosity of at least 4dl/g
• the cationic polymers may be copolymers of acrylamide with for instance diallyl dimethyl ammonium chlo ⁇ de or dialkylaminoalkyl (meth) -acrylate or -acrylamide polymers (usually as acid addition or quaternary ammonium salt) Suitable mate ⁇ als are described in, for instance WO95/33096 and in the documents to which it refers
• the process can be used to generate any weight of paper, including paper board, and so may be low weight or high weight
• the invention is of particular value in relatively low weight materials since it is in these materials that it can be difficult to achieve adequate cooking of uncooked starch during the drying stage
• the invention is of particular value in the production of sheets of below 150 grams per square metre but it can also be applied to higher weight sheets and boards
• Chelating agent may be incorporated in the reflocculating composition and/or queous phase in which the starch is to be cooked, if the water is hard.
• the following examples illustrate the invention.
• the burst strength (in KPA) depended on the reflocculating composition
• the reflocculating composition consisted of an aqueous dispersion of bentonite alone or with anionic potato starch
• the burst strength when the bentonite was used alone was 299KPA
• the burst strength when the anionic potato starch was cooked in the bentonite dispersion was 352 and the burst strength when the anio ⁇ ic starch was cooked and added after the shearing but before the bentonite was 322
• Example 1 was repeated and varying the reflocculating composition When bentonite was added alone the burst strength was 169 The burst strength when precooked anionic starch was included in the bentonite dispersion was 281 The burst strength when the anionic starch was cooked in the bentonite was 350 The burst strength when the anionic starch was precooked and added after the shearing, but in the absence of any bentonite du ⁇ ng the process was 308
• Free drainage test was earned out on a packaging grade paoer furnish de ⁇ ved from waste using a cooolymer of acrylamide with dimethylaminoethyl acrylate, methyl chloride quaternary ammonium salt of intrinsic viscosity in excess of 12dl/g as the retention aid and either bentonite or cooked starch as the reflocculating composition
• the free drainage was measure ⁇ in seconds for 100ml 200ml ana 300ml drained respectively and shown in Table 1.
• Example 4 was repeated except using a newsprint stock derived from 70% deinked waste and 30% mechanical pulp. The results are shown in table 4. Table 4

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Citations (3)

• 1998
  • 1998-08-16 ID IDW20010408A patent/ID28511A/id unknown
  • 1998-08-28 GB GBGB9818917.8A patent/GB9818917D0/en not_active Ceased
• 1999
  • 1999-08-09 TW TW088113687A patent/TW499527B/zh active
  • 1999-08-16 JP JP2000571073A patent/JP2002525448A/ja active Pending
  • 1999-08-16 HU HU0103273A patent/HUP0103273A2/hu unknown
  • 1999-08-16 CN CN99810194A patent/CN1314962A/zh active Pending
  • 1999-08-16 SK SK272-2001A patent/SK2722001A3/sk unknown
  • 1999-08-16 PL PL99346277A patent/PL346277A1/xx unknown
  • 1999-08-16 KR KR1020017002424A patent/KR20010072977A/ko not_active Application Discontinuation
  • 1999-08-16 BR BR9913146-3A patent/BR9913146A/pt not_active Application Discontinuation
  • 1999-08-16 CA CA002340641A patent/CA2340641A1/en not_active Abandoned
  • 1999-08-16 WO PCT/EP1999/005999 patent/WO2000012819A1/en not_active Application Discontinuation
  • 1999-08-16 AU AU57357/99A patent/AU5735799A/en not_active Abandoned
  • 1999-08-16 EP EP99944410A patent/EP1109972A1/en not_active Withdrawn
• 2001
  • 2001-02-27 NO NO20010985A patent/NO20010985L/no not_active Application Discontinuation

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