MOLDABLE CELLULOSE FIBER BASED MATERIAL

Abstract

The present invention relates to a method for manufacturing modified cellulose fibers for a moldable cellulose fiber based material, said method comprising: a) providing a chemical or semi-chemical wood pulp comprising cellulose fibers, and optionally subjecting the pulp to alkaline extraction to obtain an alkaline extracted pulp; and b) subjecting the pulp or the alkaline extracted pulp of step a) to a chemical treatment with an alkaline solution and/or an organic solvent to obtain a treated pulp or treated alkaline extracted pulp comprising modified cellulose fibers for a moldable cellulose fiber based material. The invention further relates to a moldable cellulose fiber based material comprising at least 70% by dry weight of modified cellulose fibers obtainable by the method.

Claims

1. A method for manufacturing modified cellulose fibers for a moldable cellulose fiber based material, said method comprising: a) providing a chemical or semi-chemical wood pulp comprising cellulose fibers; and b) subjecting the pulp of step a) to a chemical treatment with an alkaline solution, an organic solvent, or both to obtain a treated pulp comprising modified cellulose fibers for a moldable cellulose fiber based material.

2. The method according to claim 1, wherein the moldable cellulose fiber based material is a moldable cellulose fiber based web material.

3. The method according to claim 1, wherein said chemical or semi-chemical wood pulp is a softwood pulp.

4. The method according to claim 1, wherein the pulp is subjected to an alkaline extraction before step b), wherein said alkaline extraction comprises: a1) contacting the pulp with an alkaline extraction solution for 1-360 minutes, and, a2) removing the alkaline extraction solution to obtain an alkaline extracted pulp.

5. The method according to claim 4, wherein said alkaline extraction solution comprises a NaOH, KOH or Mg(OH).sub.2 solution.

6. The method according to claim 5, wherein the concentration of said alkaline extraction solution is in the range of 0.5-4 M.

7. The method according to claim 1, wherein said chemical treatment comprises: b1) contacting the pulp of step a) with an alkaline solution, an organic solvent, or both for at least 5 minutes, and, b2) removing the alkaline solution and the organic solvent to obtain the treated pulp.

8. The method according to claim 1, wherein said chemical treatment comprises contacting the pulp of step a) with a mixture of an alkaline solution and an organic solvent.

9. The method according to claim 8, wherein said alkaline solution is a NaOH, KOH or Mg(OH).sub.2 solution.

10. The method according to claim 9, wherein the concentration of said alkaline solution is in the range of 0.5-4 M.

11. The method according to claim 8, wherein said organic solvent is a polar organic solvent.

12. A method for manufacturing a moldable cellulose fiber based material, said method comprising: a) providing the treated pulp according to claim 1; and b) forming the treated pulp into a moldable cellulose fiber based material.

13. The method according to claim 12, wherein the moldable cellulose fiber based material is a moldable cellulose fiber based web material.

14. The method according to claim 12, wherein the treated pulp has not been dried before the moldable material has been formed.

15. A moldable cellulose fiber based material comprising: at least 70% by dry weight of modified cellulose fibers obtained by the method according to claim 1.

16. The moldable cellulose fiber based material according to claim 15, comprising: at least 80% by dry weight of modified cellulose fibers obtained by the method according to claim 1.

17. The moldable cellulose fiber based material according to claim 16, wherein 100% of the cellulose fibers in the moldable cellulose fiber based web material are modified cellulose fibers obtained by the method according to claim 1.

18. The moldable cellulose fiber based material according to claim 15, comprising less than 30% by dry weight of added polymer.

19. The moldable cellulose fiber based material according to claim 15, wherein the moldable cellulose fiber based material is a moldable cellulose fiber based web material.

20. The moldable cellulose fiber based web material according to claim 19, wherein said moldable cellulose fiber based web material has a 2D elongation at least 10% higher than the 2D elongation of a corresponding cellulose fiber based web material wherein the cellulose fibers are unmodified.

21. The moldable cellulose fiber based web material according to claim 15, wherein the moldable cellulose fiber based web material a basis weight in the range of 50-500 g/m.sup.2.

22. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] FIG. 1 shows CCD camera images of (a) a conventional, untreated softwood pulp, and (b) the inventive moldable pulp.

[0079] FIG. 2 is a diagram showing stress-strain curves of conventional, untreated softwood pulp, mechanically treated pulp, and the inventive moldable pulp.

[0080] FIG. 3 is a schematic representation showing the 2D formability tester used for measuring the formability strain and strength of the modified sheets.

[0081] FIG. 4 shows the 2D tension vs. strain curves to different pulps.

EXAMPLES

Example 1—Alkaline Extraction of Cellulose Pulp

[0082] Softwood kraft cellulose pulp (SE SW) was first extracted with 2.5 M NaOH (100 g NaOH/L) at 20-25° C. for 1 h in pulp consistency 10 wt %. The extracted pulp was washed by filtering and pH was adjusted to pH 8-9. The dry matter content of extracted pulp was approximately 35 wt %. The yield of extracted pulp was 86.5% (average of four extraction batches, +1-1.3%). This cellulose pulp, referred to herein as Reference 1, was then used as a starting material for the chemical treatment.

Example 2—Chemical Treatment of Alkaline Extracted Cellulose Pulp

[0083] 1500 g of Reference 1 pulp was weighed and added into a 60 L reaction flask with 14000 ml of water and with 13000 ml of 90% aqueous tert-butanol. Then 1220 g of 50% NaOH solution was added to adjust the molarity of NaOH to 1.1-1.5 M in respect of the total amount of water in the reaction mixture. The reaction mixture was stirred for 48 h at 45° C. The reaction mixture was then neutralized with 400 ml of concentrated sulfuric acid diluted with water to 1/10 before addition into the reactor. The samples were filtrated and washed carefully with 10 L of 100% ethanol, and finally 3×20 L of water to remove organic solvents and salts. The obtained chemically treated kraft cellulose pulp is referred to herein as Reference 2.

Example 3—Chemical Treatment of Non-Extracted Cellulose Pulp

[0084] Softwood kraft cellulose pulp as used in Example 1, was used as the starting material. 500 g of the starting material was weighed and added into a 60 L reaction flask with 4000 ml of water and with 3000 ml of 90% aqueous tert-butanol. Then 400 g of 50% NaOH solution was added to adjust the molarity of NaOH to 1.1-1.5 M in respect of the total amount of water in the reaction mixture. The reaction mixture was stirred for 48 h at +45° C. The reaction mixture was then neutralized with 130 ml of concentrated sulfuric acid diluted with water to 1/10 before addition into the reactor. The samples were filtrated and washed carefully with 3 L of 100% ethanol, and finally 3×10 L of water to remove organic solvents and salts. The obtained chemically treated non-extracted pulp is referred to herein as Reference 3.

Example 4—Preparation of Laboratory Sheets by Foam Forming

[0085] The foam formed laboratory sheets were prepared as follows:

1. Foam was produced by mixing the cellulose pulp, with water, surface active agent (SDS), and optional additives, until the air content of foam was ˜60-70%. Also retention aids or fixative were used in some trial points. The basis weight was 200 g/m.sup.2.
2. Foam was poured into a hand sheet mold.
3. Sheet was formed to the screen by removing the foam with a vacuum.
4. Sheet was removed with the wire from the mold and pre-dried by transferring wire on a special suction table by using an exhauster. The suction table has a suction slit, width 5 mm, and it sucks air through the sheet with 0.2 bar vacuum.
5. No wet pressing was done.
6. The pre-dried sheets were dried overnight. The drying shrinkage was restrained.

Example 5—Analysis of Hand Sheets

[0086] Formability strain and strength of modified sheets were measured using a 2D formability tester developed by VTT in Jyväskylä, Finland. The 2D formability tester is shown in FIG. 3. The objective of the 2D formability tester is to simulate the thermoforming process in 2D-scale. The unit is equipped with a double-curved heated press (1) and bottom support (2) (allowing for temperatures up to 250° C.) and blank holders (3,4). Typically, a paper with a grammage range from 80 to 250 g/m.sup.2 can be preheated to the die temperature within 0.5-0.7 s. In practice, this means that the temperature of the paper at the moment of forming is close to that of the die.

[0087] The testing proceeds as follows: the two blank holders (3,4) fix a paper sample (20-30 mm wide and more than 100 mm long). The press (1) is then moved into contact with the sample and retained still for 0.5 s in order to preheat the sample. Then, the press continues a downward movement until breakage of the sample. Displacement and load of the press is measured by a displacement sensor (5) and load sensor (6) respectively. The velocity of the forming press was 1 mm/s. The formability strain and strength of the samples was measured as an average value collected from 7 samples at die temperature of 90-140° C.

[0088] The geometry of the press surface, as well as the geometry of the sample holder was taken into account when calculating the 2D formability strain value. The sample holders have an absolute blank holding, so no slipping of the sample took place during the test.

[0089] The results of the measurements are presented in FIG. 4 and in Table 1.

TABLE-US-00001 TABLE 1 Formulation 2D strain, % 100% Ref. 2 + SDS without additives 10.5 100% Ref. 2 + SDS with additives 14.3  50% Ref. 2 + 50% SE SW pulp + SDS 10.7 with additives 100% Ref. 3 + SDS with additives 14.5 100% SE SW + SDS without additives 5.4 Additives = 30% polyurethane (Impranil DL 519, Covestro) and 600 g/tn CPAM (Perform PC 435, Solenis) and microparticles (Perform 7200, Solenis)