Claims
- 1. A process for manufacturing high strength kraft sack or bag paper having improved tensile energy absorption, comprising:
- forming on a paper machine at least two separate moist layers of kraft sack or bag paper pulp;
- couching said layers together and pressing to form a single pressed web; and
- drying said pressed web partly by free drying and partly by cylinder drying, the part of the drying performed by said free drying being within a dry solids content range of from about 55% to about 85% by weight and permitting sufficient free shrinkage of the web to provide substantially increased stretch at break in the cross direction, and the part of said drying not performed by free drying being performed by cylinder drying.
- 2. A process as in claim 1, wherein during said free drying the web is glazed by passing through one or more glazing nips.
- 3. A high strength kraft sack or bag paper having improved strength properties as manufactured by the process of claim 1.
- 4. A process for manufacturing high strength kraft sack or bag paper having improved tensile energy absorption, comprising:
- forming on a paper machine at least two separate moist layers of kraft sack or bag paper pulp;
- couching said layers together and pressing to form a single pressed web;
- drying said pressed web partly by free drying and partly by cylinder drying, the part of the drying performed by said free drying being within a dry solids content range of from about 55% to about 85% by weight and permitting sufficient free shrinkage of the web to provide substantially increased stretch at break in the cross direction, and the part of said drying not performed by free drying being performed by cylinder drying; and
- creping or micro-creping said web before said free drying.
- 5. A process as in claim 1 or claim 4, wherein the amounts of said pulp layers are sufficient to provide a paper grammage within the range of from about 60 to about 150 g/m.sup.2.
- 6. A process as in claim 1 or claim 4, wherein the resultant kraft sack or bag paper has a stretch at break in the machine direction of at least about 2.5% and a stretch at break in the cross direction of at least about 5%.
- 7. A process as in claim 4, wherein the resultant kraft sack or bag paper has a stretch at break in the machine direction of from about 3% to about 12%.
- 8. A process as in claim 1, wherein said pressed web is partially dried by cylinder drying, the partially dried web is micro-creped, and the drying of said web is completed first by free drying within a dry solids content range of from about 55% to about 85% by weight and finally by cylinder drying.
- 9. A process as in claim 1 or claim 4, wherein said free drying is effected in a fan dryer.
- 10. A high strength kraft sack or bag paper having improved strength properties as manufactured by the process of claim 4.
- 11. A high strength kraft sack or bag paper having a grammage of about 100 g/m.sup.2 and a tensile energy absorption index of about 3 J/g in the cross direction as manufactured by the process of claim 4.
- 12. A process as in claim 1 or claim 4, wherein said pulp layers are formed on a multi-wire paper machine with each layer supported on its own wire.
- 13. A process as in claim 1 or claim 4, wherein said free drying is effected by blowing a stream of hot air onto said web while said web is suspended or supported in air.
- 14. A process as in claim 4, wherein said paper machine has wire, press, and drying sections, and after said layers are couched together the web is wet creped in the press section of the machine.
- 15. A process as in claim 1 or claim 4, wherein said pressed web is partially dried by cylinder drying, and the drying of said web is completed first by free drying within a dry solids content range of from about 55% to about 85% by weight and finally by cylinder drying.
Priority Claims (1)
Number |
Date |
Country |
Kind |
8301804 |
Mar 1983 |
SEX |
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Parent Case Info
This application is a continuation of application Ser. No. 593,954, filed Mar. 27, 1984, now abandoned.
US Referenced Citations (4)
Non-Patent Literature Citations (1)
Entry |
Casey, Pulp and Paper, vol. II, (1980), vol. III, (1983) pp. 1044-1052, 2360,2361. |
Continuations (1)
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Number |
Date |
Country |
Parent |
593954 |
Mar 1984 |
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