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
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect
  • D21H23/765—Addition of all compounds to the pulp
• • 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
  • D21H17/47—Condensation polymers of aldehydes or ketones
  • D21H17/49—Condensation polymers of aldehydes or ketones with compounds containing hydrogen bound to nitrogen
  • D21H17/51—Triazines, e.g. melamine
• • 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
  • D21H17/54—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 nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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

Definitions

• This invention relates to the manufacture of paper, and is particularly concerned with making paper of improved dry strength.
• cellulose fibres are deposited as a layer from an aqueous suspension, and the layer is subsequently de-watered, consolidated and dried.
• a melamine acid colloid which is an acidic solution of an aminoplast resin of relatively high formaldehyde content
• this treatment also gives a good improvement in dry strength.
• use of such a resin leads to a concentration of free formaldehyde in the working atmosphere which is coming to be regarded as unacceptably high.
• the present invention provides a method which can be employed to produce paper of usefully improved dry strength, without generating an unacceptable level of free formaldehyde in the working atmosphere.
• a method of making paper by depositing cellulose fibres as a layer from an aqueous suspension, and de-watering said layer of cellulose fibres, in which method, to improve the dry strength of the paper product, the cellulose fibres are treated successively with a cationic polymer not derived from .formaldehyde and an anionic polymer which is an aminoplast resin whose repeating unit is anionic.
• This property in the repeating unit of being 'anionic' arises from the presence in the unit of an acidic group in salt form e.g. -O.SO 2 - or -S0 3 -.
• the cation of the salt is of no particular importance, provided that it does not interfere with the ready solution or dispersion of the salt in water. It is therefore conveniently an alkali metal ion such as that of sodium or potassium, or an organic cation, e.g. N(CH 3 ) 4 + , which is small in comparison with the repeating unit.
• treatment of the cellulose fibres is carried out by successively adding the cationic non-formaldehyde polymer and the anionic polymer to the aqueous suspension from which the cellulose fibres are deposited.
• the polymers dissolve or disperse in the aqueous suspension, and become successively deposited on the fibres.
• the anionic aminoplast resin is preferably one derived by condensation of (A) melamine (B) formaldehyde (C) an alkali metal salt of sulphurous acid.
• A melamine
• B formaldehyde
• C an alkali metal salt of sulphurous acid.
• formaldehyde employed in the condensation is used in an amount of 1.75-4 moles per mole of melamine.
• the anionic aminoplast resin is suitably used in an amount forming 0.1-5% by weight of the cellulose fibres.
• the cationic non-formaldehyde polymer used in the method of the invention is preferably one whose repeating unit is cationic as a result of the presence in the unit of an amino group in salt form bound to aliphatic carbon atoms.
• the polymer is preferably a polyamide, suitably one of the kind described in British Patent Specification 865727, that is to say one derived by the condensation of a C 3 - C 10 saturated aliphatic dibasic acid (e.g. malonic, succinic, adipic, azelaic acid) and a polyalkylene polyamine containing 2-8 alkylene groups (e.g. diethylene triamine, triethylene tetramine, tetraethylene pentamine, dipropylene triamine), followed by reaction of the condensate with epichlorhydrin.
• Such cationic polymers are conventionally employed to impart wet strength to paper.
• the cationic polymer is suitably used in an amount forming 0.1-5% by weight of the cellulose fibres.
• Bleached sulphite cellulose pulp (Modocrown) was beaten to a freeness of 32° Schopper-Riegler and then diluted to a cellulose fibre concentration of 1.5% by weight.
• This aqueous suspension of cellulose fibres was then brought to a pH of 6 with dilute sulphuric acid, and cationic polymer and anionic polymer were successively added to it with stirring, each polymer being in solution in water and being added in an amount forming 2% by weight (resin solids) of the cellulose fibre content of the suspension.
• the cationic polymer was a polyamide condensate obtained from diethylene triamine (2.1 moles), adipic acid (2 moles) and epichlorhydrin (2.5 moles), following generally the procedure of Example 1 in British Patent Specification 865727, and containing a repeating unit which was predominantly
• the anionic aminoplast resin was a condensate obtained from melamine (1 mole), formaldehyde (3 moles) and sodium metabisulphite (enough to provide 1 mole of sulphite radical, S032-), following generally the procedure of Example 1 in British Patent Specification 751501, and containing a repeating unit which was predominantly
• the aqueous suspension was left for 1/2 hour and then diluted to a cellulose fibre concentration of 0.3% by weight.
• This diluted suspension was then used to make handsheets of 60g./m 2 , using an entirely conventional apparatus (Papermakers Association Standard Apparatus for Pulp Evaluation), and the handsheets were air-dried and then heated at 127°C for 10 ninutes to develop dry strength fully.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Making Paper Articles (AREA)
• Diaphragms For Electromechanical Transducers (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10523537

Family Applications (1)

Country Status (5)

Cited By (1)

Citations (4)

• 1982
  • 1982-07-21 EP EP82303814A patent/EP0071392A1/fr not_active Withdrawn
  • 1982-07-23 ZA ZA825294A patent/ZA825294B/xx unknown
  • 1982-07-27 FI FI822624A patent/FI822624L/fi not_active Application Discontinuation
  • 1982-07-27 JP JP57131080A patent/JPS5823997A/ja active Pending
  • 1982-07-27 NO NO822573A patent/NO822573L/no unknown

Patent Citations (4)

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