US4086129A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for controlling the intrinsic viscosity of sulfite pulp
Assignee: International Telephone and Telegraph Corp
•
Filing: 1975-11-03
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Granted: 1978-04-25
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Expires: 1995-11-03
Abstract
Abstract A process for accurately controlling the intrinsic viscosity of sulfite pulp at the termination of a digestion operation comprising predetermining the duration of digestion time required to obtain a given pulp intrinsic viscosity for a range of initial weight ratios of combined SO2 to wood, determining during the digestion operation the initial weight ratio of combined SO2 to wood by measuring the rate of change of absorbance in the digestion cooking liquor and terminating the digestion operation at a time corresponding to the predetermined time required to obtain the given pulp intrinsic viscosity at the aforesaid combined SO2 to wood ratio.
Inventors
- 👤 Romeo John Conca
- 👤 John Patrick Gray
- 👤 Tod Hunter Sloan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 12:37
CPC Classifications
D; D21; D21C; D21C3/00; D21C3/22; D21C3/228; Y; Y10; Y10T; Y10T436/00; Y10T436/18; Y10T436/186
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
156 words
A process for the preparation of sulfite pulp of a given controlled intrinsic viscosity comprising predetermining the rate of change in light absorbance in digestion cooking liquor required to obtain a given pulp intrinsic viscosity for a range of initial weight ratios of combined SO 2 to wood, digesting particulate wood in the presence of sulfite cooking liquor, measuring the rate of change in light absorbance in the cooking liquor as the digestion proceeds comparing the thus measured rate of change of light absorbance with the predetermined rate of change of light absorbance for the given pulp intrinsic viscosity, determining from said comparison the initial weight ratio of combined SO 2 to wood, adjusting the time, temperature and pressure of the digestion operation to obtain the given controlled intrinsic viscosity at the aforesaid initial weight ratio of combined SO 2 to wood, and terminating the digestion operation in accordance with the adjusted time, temperature and pressure.
Claim 2
Dependent Claim
156 words
A process for the preparation of sulfite pulp of a given controlled intrinsic viscosity comprising predetermining the rate of change in light absorbance in digestion cooking liquor required to obtain a given pulp intrinsic viscosity for a range of initial weight ratios of combined SO 2 to wood, digesting particulate wood in the presence of sulfite cooking liquor, measuring the rate of change in light absorbance in the cooking liquor as the digestion proceeds comparing the thus measured rate of change of light absorbance with the predetermined rate of change of light absorbance for the given pulp intrinsic viscosity, determining from said comparison the initial weight ratio of combined SO 2 to wood, adjusting the time, temperature and pressure of the digestion operation to obtain the given controlled intrinsic viscosity at the aforesaid initial weight ratio of combined SO 2 to wood, and terminating the digestion operation in accordance with the adjusted time, temperature and pressure.
Claim 3
Dependent Claim
31 words
The process of claim 1 in which the time of digestion is predetermined and the pressure and temperature of the digestion operation are adjusted to obtain the given pulp intrinsic viscosity.
Claim 4
Dependent Claim
29 words
The process of claim 1 in which the pressure and temperature are predetermined and the duration of the digestion operation is adjusted to obtain the given pulp intrinsic viscosity.
Claim 5
Dependent Claim
27 words
The process of claim 1 in which the rate of change of light absorbance is measured by spectrophotometric analysis of a sample stream of the cooking liquor.
References Cited (Backward Citations)
US2615339A
Cited
GB747108A
Cited
US3555204A
Cited
US3748044A
Cited
US3941649A
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US3837217A
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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) | 1981-04-24 | 1981-10-24 | 1982-04-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-24 | 1985-10-24 | 1986-04-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-24 | 1989-10-24 | 1990-04-25 | $7700.00 | Window Closed / Lapsed |