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
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/44—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups cationic
  • D21H17/45—Nitrogen-containing groups
• • 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
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
  • D21H11/04—Kraft or sulfate 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • 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
  • D21H17/31—Gums
  • D21H17/32—Guar or other polygalactomannan gum
• • 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
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
  • D21H17/43—Carboxyl groups or derivatives thereof
• • 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
  • D21H21/14—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 characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
  • D21H21/20—Wet strength agents

Definitions

• the invention relates to the preparation of paper and paperboard by the deposition of wood pump from an aqueous slurry and, more particu­larly, relates to the improvement in the moist compressive strength of such paper products.
• paper paperboard and similar water-laid paper webs
• a cellulose fiber suspension which may contain rosin size and mineral constituents (fillers) depending on the product desired, is deposited and drained on a continuously moving wire cloth.
• the free water passes through the paper web which undergoes further processing to yield the desired paper product.
• Paperboard cartons which are stored or stacked under conditions of high humidity (90+%) absorb a high level of moisture of approximately 14-17%. This absorbed moisture causes the cartons, especially those near the bottom of the stack, to buckle or yield with the stack tumbling and causing damage to the contents.
• U.S. 3,597,314 discloses a process for dewatering aqueous cellulose fiber suspension in the formation of paper by adding to the suspension from 0.05 to 4% of a water soluble polymer consisting essentially of units derived from N-vinyl-N-methylformamide having 60-100% of the formic acid radicals of the polymer split off by acid hydrolysis.
• CMC carboxymethyl cellulose
• PAE poly(aminoamide) epichlorohydrin
• the present invention provides a means for increasing the moist compressive strength of a paper product prepared by depositing cellulose fiber from an aqueous slurry.
• the improvement comprises adding to the aqueous slurry of cellulose fiber an effective amount of a moist compres­sive strength additive consisting essentially of poly(vinyl acetate-­vinylamide), preferably in combination with an anionic polymer, such as carboxymethyl cellulose in a ratio of 0.5 to 5 parts by weight cationic polymer to one part anionic polymer.
• the vinyl acetate units of the poly(vinyl acetate-vinylamide) are at least 75 mole%, preferably 90 mole%, hydrolyzed to vinyl alcohol units and the vinylamide units are hydrolyzed to provide the polymer with 1-50 mole% vinylamine units.
• the means for improving the moist compressive strength of paper products is incorporated into the wet-end stage of the papermaking process.
• An amount of additive composition effective to increase the moist compressive strength of the paper product for example 0.1 to 3 wt% based on cellulose fibers, is added to the aqueous slurry of cellulose fiber, such as wood pulp.
• the added composition consists essentially of a poly(vinyl alcohol-vinylamine) [P(VOH-VAm)]. preferably in combination with a carboxymethyl cellulose (CMC).
• the most preferred composition will contain 0.5-5 parts of P(VOH-VAm) per part of anionic polymer, pre­ferably about 2 parts P(VOH-VAm) per part anionic polymer.
• the P(VOH-VAm) is a poly(vinyl acetate-vinylamide) in which the vinyl acetate units are hydrolyzed to at least 75 mole%, preferably 90+ mole%, to vinyl alcohol units and most preferably about 99+ mole% hy­drolyzed, i.e. fully hydrolyzed.
• the amount of the vinylamide units in the polymer which should be hydrolyzed depends on the mole ratio of poly(vinyl acetate) to poly(vinylamide), but should be sufficient to give at least 1 mole% vinylamine units based on total polymer, preferably 3 to 30 mole%, and most preferably 6 to 12 mole%.
• the P(VOH-VAm) com­ponent in the additive composition may contain amounts of unhydrolyzed vinylamide and/or vinyl acetate units.
• Suitable P(VOH-VAm) polymers will contain about 1-50 mole%, preferably 3-30 mole% vinylamine units with the remainder being vinyl alcohol units and, in the case where the polymer is less than fully hydrolyzed. amounts of vinylamide and vinyl acetate units.
• the molecular weight of P(VOH-VAm) can range from 6,000 to 300,000, preferably 10,000 to 100,000.
• the process for preparing P(VOH-VAm) suitable for use in the present invention is the same as the well known process for making polyvinyl acetate and hydrolyzing it to polyvinyl alcohol with merely the incor­poration of a vinylamide monomer into the polymerization reaction.
• the vinylamide monomer may be a vinylacetamide or preferably a vinylform­amide, especially N-vinylformamide.
• the moist strength additive composition preferably includes an anionic polymer such as anionic starch, carboxy­methyl guar, polyacrylic acid, partially hydrolyzed polyacrylamide or most preferably CMC.
• anionic polymer such as anionic starch, carboxy­methyl guar, polyacrylic acid, partially hydrolyzed polyacrylamide or most preferably CMC.
• the degree of carboxymethyl substitution in the CMC can range from 0.2 to 1.2 and the molecular weight can range from 10,000 to 300,000.
• the amount of the moist strength additive composition added to the slurry of cellulose fibers is about 0.1-3 wt% based on fiber and is pre­ferably about 0.2-2 wt%.
• the P(VOH-VAm) is added to the slurry before the addition of the anionic polymer. If the two components are mixed together before adding them to the slurry, a gummy mixture results. It is preferred to add the P(VOH-VAm) and the anionic polymer as aqueous solutions.
• the P(VOH-VAm) being cationic is absorbed by the anionic cellulose fibers and, especially with addition of the anionic polymer, electrostatic bonds are formed leading to polyelectrolyte com­plexes which enhance the strength of the fiber matrix through stronger interfiber bonds.
• the treated paper is better able to with­stand compaction forces, e.g. when cartons formed from such treated com­ponents are stacked under conditions of high humidity and high moisture content. Yet the interfiber bonds can still be broken during typical repulping processes.
• the handsheets were formed on a 100 mesh monel wire, couched onto blotter stock, pressed 5 min at 50 psig, and dried 7 min on a steam drum at 220°F.
• Control handsheets were formed from untreated pulp and from pulp treated with the additives as shown in Tables 1 and 2. After conditioning at 50% RH and 73°F, the handsheets were tested for basis weight, wet tensile, and dry and moist compressive strength. Moist com­pressive strength and wet tensile factors were determined by dividing the value of the treated sheet by that of the untreated controls.
• Table 1 shows the amount of cationic and anionic additives in the fiber slurry as well as the performance data for the paper product prepared from a com­mercial southern pine pulp formulation at pH 7-9.
• the Runs in Table 2 used a fiber slurry maintained at pH 4.5 throughout the sheetmaking process through addition of dilute sulfuric acid.
• WT. (Mn x 103) BASIS WT COMPRESSIVE STRENGTH MOIST COMPRESSIVE STRENGTH FACTOR WET TENSILE FACTOR % AMINE FUNCTIONALITY % HYDROXYL FUNCTIONALITY STFI.
• the wet tensile level produced by the P(VOH-VAm) was lower than normally achieved through the use of PAE wet strength resins in combina­tion with CMC and suggests that P(VOH-VAm)-treated papers may be more readily repulped which is a desirable property.
• a repulpability study was conducted using various handsheet sets made with (a) no additive (blank control), pH 4.5; (b) PAE (1%), pH 4.5; (c) PAE (1%) and CMC (0.4%), pH 4.5; (d) P(VOH-VAm) (1%), pH 4.5; (e) P(VOH-VAm) (1%), pH 7-8; and (f) P(VOH-VAm) (1%) and CMC (0.4%), pH 7-8.
• the P(VOH-VAm) had 6% amine functionality and a molecular weight of 130,000.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (4)

Cited By (8)

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Citations (6)

• 1989
  • 1989-04-07 EP EP89106140A patent/EP0337310A1/fr not_active Withdrawn
  • 1989-04-12 FI FI891730A patent/FI891730A/fi not_active Application Discontinuation
  • 1989-04-13 NO NO89891527A patent/NO891527L/no unknown
  • 1989-04-14 JP JP9329389A patent/JPH026686A/ja active Pending

Patent Citations (6)

Non-Patent Citations (1)

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