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
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/12—Coatings without pigments applied as a solution using water as the only solvent, e.g. in the presence of acid or alkaline compounds
• • 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
  • D21H17/36—Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G7/00—Selection of materials for use in image-receiving members, i.e. for reversal by physical contact; Manufacture thereof
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
  • Y10T428/3175—Next to addition polymer from unsaturated monomer[s]
  • Y10T428/31754—Natural source-type polyamide
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
  • Y10T428/31761—Next to aldehyde or ketone condensation product
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
  • Y10T428/31768—Natural source-type polyamide [e.g., casein, gelatin, etc.]
  • Y10T428/31772—Next to cellulosic
  • Y10T428/31775—Paper
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31942—Of aldehyde or ketone condensation product
  • Y10T428/31949—Next to cellulosic
  • Y10T428/31964—Paper

Definitions

• ABSTRACT Light-weight paper can be made as stiff as paper of 50% greater weight or more without loss of folding endurance by coating its surfaces with a freshly prepared mixture of polyvinyl alcohol or an analogous polyol or polyamine and a source of formyl groups such as a water-soluble precondensate of formaldehyde with melamine or urea in an aqueous solution viscous enough to prevent full penetration of the paper.
• the product has a core layer of low bulk density and surface layers of much greater density and toughness and can be processed successfully in xerographic and like copying equipment not normally capable of handling very light paper.
• This invention relates to paper. and particularly to paper suitable for use in xerographic copying machines and like equipment. and to a method of preparing the same.
• At least one surface layer of preferred paper of the invention predominantly consists of a condensation product of a polymer having a molecular weight greater than 2,000. and preferably of 30.000 to 90,000, and having available hydroxyl or amino groups in each of its repeating units. with a source of available formyl groups which cause cross linking of the polymer.
• the condensation reaction is performed on or in the outermost portion of the core layer so that the predominantly polymeric surface layer is bound to the cellulosic core layer by cellulose fibers extending into the surface layer.
• the laminar structure of the paper is obtained by coating at least one face of a paper web consisting essentially of cellulose fibers with an aqueous mixture of the polymer and of the source of formyl groups in an amount corresponding to 1.5 to 3.0 grams of solids in the mixture per square meter of the coated face or faces.
• the condensation mixture must have adequate viscosity to prevent penetration of the core layer. Not more than about 12% by weight of the core layer should consist of the condensation product, and it is not normally practical to prevent penetration of the core layer by less than 3% of the condensation product.
• the condensation mixture may be provided with an inert thickener, such as bentonite, which does not enter into the reaction, or the base paper forming the core layer may be sized to impede penetration by the aqueous condensation mixture.
• an inert thickener such as bentonite
• Suitable polymers soluble or dispersible in water and having available hydroxyl or amino groups in their repeating monomer units include polyvinyl alcohol. particularly polyvinyl alcohol practically free from acid moieties such as residual acetate. starch. ethoxylated starch. and related starch derivatives including products of oxidation and partial enzymatic hydrolysis. also polymerized hydroxyalkyl esters of acrylic and methacrylic acid. acrylamide and methacrylamide. also copolymerizates of the acrylic monomers mentioned with olefinically unsaturated compounds. such as ethylene. propylene. vinyl acetate. and vinyl chloride.
• the surface layer in the paper of the invention may additionally contain proteins such as casein. soybean protein, gelatin. in amounts not exceeding of the weight of the polymer described above. A significant increase in stiffness isachieved with 10% protein, but folding endurance is impaired by proteins in amounts exceeding 60% of the polymer because the surface layer is embrittled.
• the source of a formyl group capable of reacting with the hydroxyl or amino groups of the polymer may be a lower alkanal or a substance which. in the presence of the polymers, yields alkanals.
• the sources of available formyl groups thus include formaldehyde, acetaldehyde. glyoxal, but also hexamethylenetetramine. and the water-soluble. liquid precondensates of formaldehyde with melamine and urea which are staple articles of commerce and contain at least the equivalent of one mole formaldehyde per amino group in the urea or melamine.
• Cyanamide sodium cyanamide. or calcium cyanamide. when present in the condensation mixture applied to the base paper. enhance the cross-linking effect of the aldehyde and significantly increase the bond strength between the polymer predominating in the surface layer and the cellulose which is the essential component of the core layer.
• the condensation reaction can be accelerated. if so desired. by the presence of catalysts such as sodium chloride, ammonium chloride, hydrogen chloride, or Lewis acids.
• catalysts such as sodium chloride, ammonium chloride, hydrogen chloride, or Lewis acids.
• the viscosity of the condensation mixture must be adequate to preventpenetration of the core layer, and is controlled most effectively by suitably selecting the molecular weight or degree of polymerization of the polymer having available hydroxyl or amino groups.
• the condensation mixture preferably should be capable of being applied to a paper web in continuous operation by the conventional equipment of the paper industry. particularly coating equipment. and must be capable of being applied in a thin, uniform layer since the condensation product should not usually amount to more than ten percent of the weight of the base stock per surface layer.
• the necessary reproducible properties of the condensation mixture can be achieved under industrial conditions only if the polymer and the cross-linking agent are mixed immediately prior to being applied to the base stock. or by applying the polymer and the I cross-linking agent sequentially, the more viscous polymer solution preferably being applied first.
• the lastmentioned procedure is advantageous in preventing the formation of hardened condensates in the equipment if the machinery has to be stopped.
• the papers of the invention having surface layers predominantly consisting of the afore-described condensation products may be written or printed upon like good bond papers and have satisfactory opacity even when weighing only g/m
• the surface layers have sufficient electric conductivity to prevent a build-up of electrostatic charges and the resulting difficulties in separating sheets of a stack of papers of the invention from each other. Because the surface layers contain at least some cellulose fibers, they do not form a continuous film impermeable to air, and sheets of the paper can be fed by conventional suction equipment.
• the condensation products are thermally stable. do not turn yellow at elevated temperature, and the surface layers lack abrasiveness which might cause accumulation of dust and dirt in the processing equipment.
• the stiffness of the paper of the invention and its resistance to buckling are not impaired by the relatively high operating temperatures of many types of copying equipment which do not permit the use of thermoplastic coatings.
• the bonding of the condensation product to the cellulose and other important. but less critical mechanical properties of the paper of the invention are particularly good when the base stock employed is prepared from aqueous stuff having an alkaline reaction. and preferably a pH of 7.2 to 9.7. ln such paper, the hydroxyl groups in the cellulose are most readily available for bonding to the condensation products of the invention.
• EXAMPLE 1 Pulp prepared from coniferous wood and from hardwood was ground in a weight ratio of '60 parts to 40 parts to a drainage rate of 38S.R. and 6 parts calcium carbonate were added as a filler.
• An alkylketene dimer (Aquapel.
• Hercules Incorporated and a cationic polyamide resin (Kymene 557, Hercules Incorporated) were added to the stuff as sizing agent and retention aide respectively, the pH was adjusted to 7.8-8.0, and a paper web was formed on a Fourdrinier type paper machine in the usual manner, the consistency of the initial cellulose fiber suspension and the speed of the machine being such as to normally produce paper having a weight of 50 g/m Near the dry end of the machine, the sized paper web containing approximately 93% airdry matter was coated on both sides on a doctor blade coater to a dry weight of 1.5-1.7 g/m with a homogeneous aqueous composition having a viscosity of 34 cp at 40C and prepared by mixing equal volumes ofa 120 g/l solution of commercial polyvinyl alcohol of high viscosity, 99.9% saponified, and of a 120 g/l solution of a commercial melamine formaldehyde precondensate containing an excess of formaldeh
• the two solutions were continuously pumped to a small mixing vessel from which they entered the trough of the coater, the dwell time in the mixing vessel and the trough being held to a minimum by permitting much of the mixture to overflow to waste so that very little condensation took place before the mixture was applied to the paper web, and its viscosity was uniform at the time of application.
• the condensation reaction took place in the dryer section of the paper machine at about 125C.
• the treated paper had a bulk density of 0.58-0.60 g/cm. When its section was inspected by the unaided eye or at low magnification, three distinct layers were clearly visible, but microscopic examination showed a minor, though significant amount of cellulose fibers in the surface layers and a small amount of condensation product in the core layer.
• the bulk density of the surface layers was approximately I, whereas that of the core layer was approximately 0.45.
• the stiffness of the laminar product was 4-6 gem in the direction of web travel and 2.2-3.2 gcm at right angles to that direction as determined according to German standard method DIN-Norm 6723.
• the stiffness of the paper of the invention thus corresponded to that normally expected from a paper weighing 80-90 g/cm It was processed without difficulty on a xerographic copying machine adjusted for handling paper sheets of the heavier weight.
• EXAMPLE 2 20 Parts (weight) fine groundwood pulp having a drainage rate of -82S.R. and bleached was ground with 40 parts long-fibered sulfate pulp. and combined with 25 parts hardwood pulp and 15 parts de-inked waste paper to a stuff having a drainage rate of 35-40S.R. Rosin size and alum were added for fully sizing the paper which was formed at pH 4.5-4.8.
• Example 1 an aqueous composition was applied to the almost dry paper web on a doctor blade coater on both faces.
• the composition was mixed immediately prior to application as described in Example 1, and consisted, on a dry basis, of 50 parts (weight) bone gelatine, 50 parts of the polyvinyl alcohol of high viscosity employed in Example 1, 25 parts ureaformaldehyde precondensate, and 0.5 part sodium bentonite, also enough water manually controlled to permit application of a uniform coating varying in dry weight between 1.5 and 3.0 g/m per side in successive runs, while the base stock amounted to about 45 g/m
• the papers so produced were generally similar in their structure and their properties to the paper described in Example 1.
• the stiffness values increased with increasing weight of the surface layers to three times the corresponding values for the base stock.
• the stiffness-reducing effect of the groundwood in the stuff and of the acidic medium was balanced by the stiffnessenhancing effect of the gelatine in the coating.
• the amount of condensation product in the core layer varied with the viscosity of the coating solution between 3 and 12%.
• Example 2 All the papers produced in Example 2 were run successfully on the xerographic copying machine referred to in Example 1.
• EXAMPLE 3 A paper web was formed on the above-mentioned paper machine in a conventional manner from stuff prepared from 40 parts long-fibered sulfate pulp, 50
• composition was cured at the highest temperature available on the dryer section used. and the coated paper was reeled while still hot to complete the cure. whereby each turn of coated paper in the reel was directly and releasably superimposed on the surface layer of another turn.
• papers weighing 35-7O g/m were produced and had the necessary properties enumerated above.
• the surface layers of the several papers prepared in Examples 2 and 3 had bulk densities close to 1.0 and slightly higher. while the densities of the core layers varied between 0.4 and 0.75.
• the stiffness values varied between twice and three times the corresponding values for the untreated base stock.
• Sulfate pulp generally gives better results than groundwood or sulfite pulp, but some pulp other than sulfate pulp is acceptable as exemplified in Example 2.
• the melamine and urea precondensates with formaldehyde are preferred sources of available formyl groups although formaldehyde and acetaldehyde may be used in corresponding amounts.
• the free aldehydes react with the polyvinyl alcohol at so high a rate that it is difficult to maintain desired and uniform operating conditions whereas the precondensates yield formaldehyde at a slow and readily reproducible rate.
• Hexamethylenetetramine is intermediate in its decomposition and reaction rate between the free aldehydes and the preferred precondensates.
• the polyvinyl alcohol referred to in Examples 1 to 3 had a degree of polymerization of 1700-1800 and a viscosity of 44 centipoise at C in 4% aqueous solution as determined with a Brookfield viscosimeter at 100 r.p.m. of a No. 2 spindle.
• a polymer of lower viscosity may be employed either at higher concentrations or in combination with thickeners such as the bentonite mentioned.
• Polyvinyl alcohol may be replaced at least partly in the above Examples by other polymers having a molecular weight of at least 2,000 and at least one available hydroxyl or amino group in each repeating monomer unit such as those mentioned above.
• the properties of the surface layer or layers may also be modified by varying the ratio of hydroxyl or amino groups in the polymer to the formyl groups in the crosslinking agent.
• the weight ratio may be chosen between one and nine parts polyvinyl alcohol per part of the precondensate.
• a stack of sheets of laminar structure each sheet consisting essentially of cellulose fibers and a condensation product of water-soluble polyvinyl alcohol and a water-soluble precondensate of formaldehyde with melamine or urea. the weight ratio of said polyvinyl alcohol to said precondensate in said condensation product being between 1:1 and 9:1.
• said sheet having a weight of 35 to grams per square meter, a core layer of said sheet consisting essentially of said cellulose fibers and not more than 12 percent by weight of said condensation product.
• the sheet having at least one surface layer consisting essentially of said condensation product in an amount of 1.5 to 3.0 grams per square meter of said surface layer and being bound to said core layer by cellulose fibers extending from said core layer into said surface layer, the mechanical strength. stiffness. and bulk density of said surface layer being substantially greater than the corresponding properties of said core layer, the molecular weight of said polyvinyl alcohol being at least 2000. each sheet being directly and releasably superimposed on said surface layer of another sheet.
• condensation product further includes cyanamide, sodium cyanamide, or calcium cyanamide in an amount of 10 to 50% of the weight of said precondensate.
• a method of preparing a laminar paper which comprises:

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Paper (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Laminated Bodies (AREA)

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• 1971
  • 1971-03-18 DE DE2113216A patent/DE2113216C3/de not_active Expired
• 1972
  • 1972-03-06 LU LU64906D patent/LU64906A1/xx unknown
  • 1972-03-07 NO NO714/72A patent/NO140236C/no unknown
  • 1972-03-07 NL NL7203036A patent/NL7203036A/xx not_active Application Discontinuation
  • 1972-03-14 FI FI673/72A patent/FI56871C/fi active
  • 1972-03-15 AT AT218672A patent/AT332729B/de not_active IP Right Cessation
  • 1972-03-16 IT IT12538/72A patent/IT953389B/it active
  • 1972-03-16 IE IE340/72A patent/IE36771B1/xx unknown
  • 1972-03-16 BE BE780776A patent/BE780776A/fr not_active IP Right Cessation
  • 1972-03-16 DK DK122972A patent/DK142770C/da not_active IP Right Cessation
  • 1972-03-16 US US235412A patent/US3878038A/en not_active Expired - Lifetime
  • 1972-03-16 FR FR7209248A patent/FR2129726A5/fr not_active Expired
  • 1972-03-16 SE SE7203381A patent/SE387144B/xx unknown
  • 1972-03-17 CA CA137,377A patent/CA944597A/en not_active Expired
  • 1972-03-17 BR BR1563/72A patent/BR7201563D0/pt unknown
  • 1972-03-17 CH CH394472A patent/CH549689A/xx not_active IP Right Cessation
  • 1972-03-17 ES ES400872A patent/ES400872A1/es not_active Expired
  • 1972-03-18 JP JP47028019A patent/JPS5836119B1/ja active Pending
  • 1972-03-18 GB GB4861571A patent/GB1396891A/en not_active Expired

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