US4718982A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Densification and heat treatment of paperboard produced from SCMP and other sulfite pulps
Assignee: International Paper Co
•
Filing: 1985-08-23
•
Granted: 1988-01-12
•
Expires: 2005-08-23
Abstract
Abstract Both the wet strength and the folding endurance of SCMP and sulfite paperboard are improved by subjecting the board to steps of densification and high temperature treatment during its production.
Inventors
- 👤 Roy S. Swenson
- 👤 F. Keith Hall
- 👤 Donald M. MacDonald
- 👤 Michael Ring
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 22:31
CPC Classifications
D; D21; D21F; D21F11/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
125 words
A method of minimizing the degradation of paperboard produced from semichemical-mechanical pulp while improving its wet strength by heat treatment, comprising steps of forming a wet web of cellulose fibers from an aqueous suspension of fibers; then, without first drying the web, press drying said wet web, by compressing it sufficiently to produce a product having a density of at least 700 kg/m 3 and drying the product until its water content by weight is less than 10%; and then heat treating the product at an internal temperature of at least 420° F. (216° C.) for a time sufficient to increase both the wet strength and folding endurance thereof as compared to a like product heat treated at the same temperature, but not press dried.
Claim 2
Independent Claim
125 words
A method of minimizing the degradation of paperboard produced from semichemical-mechanical pulp while improving its wet strength by heat treatment, comprising steps of forming a wet web of cellulose fibers from an aqueous suspension of fibers; then, without first drying the web, press drying said wet web, by compressing it sufficiently to produce a product having a density of at least 700 kg/m 3 and drying the product until its water content by weight is less than 10%; and then heat treating the product at an internal temperature of at least 420° F. (216° C.) for a time sufficient to increase both the wet strength and folding endurance thereof as compared to a like product heat treated at the same temperature, but not press dried.
Claim 3
Dependent Claim
23 words
The method of claim 1, wherein said internal temperature is in the range of 420° F. (216° C.) to 572° F. (300° C.).
Claim 4
Dependent Claim
15 words
The method of claim 1, wherein said internal temperature is about 450° F. (232° C.).
Claim 5
Dependent Claim
29 words
The method of claim 1, wherein said densification includes applying sufficient pressure to the paper to produce density in range of 700-900 kg/m 3 prior to said heating step.
Claim 6
Dependent Claim
11 words
The method of claim 1, wherein said paper product is linerboard.
Claim 7
Dependent Claim
22 words
The method of claim 5, wherein said paperboard has a basis weight in the range of 125 to 464 g/m 2 .
Claim 8
Dependent Claim
18 words
The method of claim 5, wherein said paperboard has a basis weight of about 203 g/m 2 .
Claim 9
Dependent Claim
24 words
A paperboard of high wet strength and high folding endurance, produced according to any of claims 2, 3, 4, 5, 6, 7 or 1.
Claim 10
Dependent Claim
26 words
A paperboard as in claim 8, having a wet strength of at least 6 lb/in, and satisfying a folding endurance test of at least 10 cycles.
Claim 11
Dependent Claim
27 words
The method of claim 1, wherein said heat treating step is for a duration sufficient to produce a wet strength of at least 15 pounds per inch.
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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) | 1991-01-11 | 1991-07-13 | 1992-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-11 | 1995-07-13 | 1996-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-11 | 1999-07-13 | 2000-01-12 | $7700.00 | Window Closed / Lapsed |