US3878038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Stiff light-weight paper
Assignee: Feldmuehle Anlagen und Produktion GmbH
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Filing: 1972-03-16
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Granted: 1975-04-15
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Expires: 1992-03-16
Abstract
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.
Inventors
- 👤 Fritz Opderbeck
- 👤 Volker Franzen
- 👤 Guido Dessauer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:18
CPC Classifications
D; D21; D21H; D21H19/00; D21H19/10; D21H19/12; D21H17/00; D21H17/20; D21H17/33; D21H17/34; D21H17/36; D21H19/14; D21H19/20; G; G03; G03G; G03G7/00; Y; Y10; Y10T; Y10T428/00; Y10T428/31504; Y10T428/31725; Y10T428/3175; Y10T428/31754; Y10T428/31761; Y10T428/31768; Y10T428/31772; Y10T428/31775; Y10T428/31942; Y10T428/31949; Y10T428/31964
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
184 words
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 70 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, AND 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.
Claim 2
Dependent Claim
184 words
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 70 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, AND 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.
Claim 3
Dependent Claim
39 words
A stack as set forth in claim 1, wherein said surface layer contains a protein in an amount of 10 percent to 60 percent of the weight of said polymer in the condensation product present in said surface layer.
Claim 4
Dependent Claim
18 words
the viscosity of said remainder of said mixture being kept constant by said discharging of said major portion,
Claim 5
Dependent Claim
18 words
the viscosity of said remainder of said mixture being kept constant by said discharging of said major portion,
Claim 6
Dependent Claim
122 words
the viscosity of said applied remainder being sufficient to retain most of said mixture in a surface layer of said web while holding the amount of said mixture in a core layer of said web to not more than 12% by weight, the remainder of said core layer consisting essentially of said cellulose fibers; e. heating the coated web to an elevated temperature until the water therein is evaporated, said temperature and the amount of said formyl groups of said precondensate being sufficient to cross-link said polyvinyl alcohol during said heating; and f. directly and releasably superimposing a portion of said coated web on the surface layer of another portion of said web after said evaporation of water from said other portion.
Claim 7
Dependent Claim
122 words
the viscosity of said applied remainder being sufficient to retain most of said mixture in a surface layer of said web while holding the amount of said mixture in a core layer of said web to not more than 12% by weight, the remainder of said core layer consisting essentially of said cellulose fibers; e. heating the coated web to an elevated temperature until the water therein is evaporated, said temperature and the amount of said formyl groups of said precondensate being sufficient to cross-link said polyvinyl alcohol during said heating; and f. directly and releasably superimposing a portion of said coated web on the surface layer of another portion of said web after said evaporation of water from said other portion.
Claim 8
Dependent Claim
33 words
A stack as set forth in claim 1, wherein said condensation product further includes cyanamide, sodium cyanamide, or calcium cyanamide in an amount of 10 to 50% of the weight of said precondensate.
Claim 9
Dependent Claim
26 words
A stack as set forth in claim 1, wherein said sheet has two of said surface layers, said core layer being received between said surface layers.
Claim 10
Independent Claim
114 words
A method of preparing a laminar paper which comprises: a. separately feeding respective aqueous dispersions of polyvinyl alcohol having a molecular weight of 30,000 to 90,000 and of a pre-condensate of urea or melamine with formaldehyde as a source of formyl groups to a mixing zone; b. mixing said dispersions in said zone; c. discharging a major portion of the resulting mixture from said zone to waste; d. continuously applying to at least one face of a web consisting essentially of cellulose fibers a coating of the remainder of said mixture in an amount corresponding to 1.5 to 3.0 grams of solids in said mixture per square meter of said at least one face,
Claim 11
Independent Claim
114 words
A method of preparing a laminar paper which comprises: a. separately feeding respective aqueous dispersions of polyvinyl alcohol having a molecular weight of 30,000 to 90,000 and of a pre-condensate of urea or melamine with formaldehyde as a source of formyl groups to a mixing zone; b. mixing said dispersions in said zone; c. discharging a major portion of the resulting mixture from said zone to waste; d. continuously applying to at least one face of a web consisting essentially of cellulose fibers a coating of the remainder of said mixture in an amount corresponding to 1.5 to 3.0 grams of solids in said mixture per square meter of said at least one face,
Claim 12
Dependent Claim
56 words
A method as set forth in claim 5, wherein said web contains water and is prepared prior to said applying by straining an aqueous suspension of said cellulose fibers of a major portion of the water content thereof, and collecting the fibers on a foraminous carrier, said suspension having a pH value of 7.2 to 9.7.
Claim 13
Dependent Claim
17 words
A method as set forth in claim 5, wherein said web is sized prior to said coating.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |