# US 4,391,670 A · Low energy TMP furnish of improved strength by ozonation and press drying

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- Number: US 4,391,670 A
- Document ID: US4391670A
- Status: Granted
- Kind: A
- Application number: 06/309,295
- Filed: 1981-10-07
- Granted: 1983-07-05
- Earliest claimed: 1981-10-07
- Assignees: International Paper Company
- Inventors: Richard B. Phillips
- Web page: https://patentgrep.com/patent/US4391670A

## CPC

- D21C 9/1073: {with O3 (closed, see D21C9/153)}
- D21C: PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR

## Abstract

Press dried paper sheets from certain ozonated high yield pulps are disclosed. Such sheets show substantially improved strength over comparable sheets prepared from non-ozonated pulps and over non-press dried sheets from ozonated pulps.

## Claims

### Claim 1

A process for the preparation of linerboard from thermomechanical, high temperature mechanical and semichemical mechanical pulps comprising:
(a) treating mechanical pulp selected from thermomechanical, semi-chemical mechanical, high temperature mechanical, or mixtures thereof with ozone;
(b) forming a sheet having from about 30% to about 60% consistency from the ozone treated pulp of step a above; and
(c) press drying the sheet formed in step b above at high temperatures and pressure until at least about 10% to about 15% moisture content is attained.

### Claim 2 (depends on 1)

A process as defined in claim 1 wherein the mechanical pulp is a mixture of thermomechanical pulp and high temperature mechanical pulp.

### Claim 3 (depends on 2)

A process as defined in claim 2 wherein the thermomechanical pulp comprises southern softwood thermomechanical pulp and the high temperature mechanical pulp comprises southern hardwood high temperature mechanical pulp.

### Claim 4 (depends on 1, 2)

A process as defined in claims 1, 2, or 3 wherein the mechanical pulp comprises from about 40% to about 60% by weight southern softwood thermomechanical pulp.

### Claim 5 (depends on 1, 2)

A process as defined in claims 1, 2, or 3 wherein the mechanical pulp comprises from about 40% to about 60% by weight southern hardwood high temperature mechanical pulp.

### Claim 6 (depends on 1)

A process as defined in claim 1 wherein the mechanical pulp comprises 60% by weight southern softwood thermomechanical pulp and 40% by weight southern hardwood high temperature mechanical pulp.

### Claim 7 (depends on 1)

A process as defined in claim 1 wherein ozone consumption by the mechanical pulp is about 2.5% to 10% by weight.

### Claim 8 (depends on 1)

A process as defined in claim 1 wherein cationic starch is added to the sheet formed in step b.

### Claim 9 (depends on 8)

A process as defined in claim 8 wherein about 0.5% to 5% by weight cationic starch is added at the wet end during sheet formation.

### Claim 10 (depends on 7)

A process as defined in claim 7 wherein ozone consumption is about 5% by weight.

### Claim 11 (depends on 9)

A process as defined in claim 9 wherein about 1.0% cationic starch is added.