PRODUCT CONTAINING AN ANIONIC CELLULOSE DERIVATIVE AND ITS USE IN PAPER INDUSTRY

Abstract

A product includes a microfibrillated cellulose composition, a starch derivative, and an anionic cellulose derivative, as a combined preparation for simultaneous or separate use. The anionic cellulose derivative has a number average molecular weight comprised between 300000 g/mol and 800000 g/mol, and a degree of substitution comprised between 0.3 and 0.65. Additionally, a paper sheet includes the product as an additive to increase the initial wet web strength and/or dry tensile strength of the paper sheet.

Claims

1. A product comprising: a microfibrillated cellulose composition, a starch derivative, and an anionic cellulose derivative having a number average molecular weight comprised between 300000 g/mol and 800000 g/mol, and a degree of substitution comprised between 0.3 and 0.65, as a combined preparation for simultaneous or separate use.

2. The product of claim 1, wherein the microfibrillated cellulose of the microfibrillated cellulose composition is not chemically modified nor physically modified.

3. The product of claim 1, wherein the starch derivative is a cationic starch.

4. The product of claim 1, wherein the degree of substitution of the anionic cellulose derivative is comprised between 0.45 and 0.5.

5. An admixture composition comprising: an aqueous pulp mixture, a microfibrillated cellulose composition, a starch derivative, and an anionic cellulose derivative having a number average molecular weight comprised between 300000 g/mol and 800000 g/mol, and a degree of substitution comprised between 0.3 and 0.65.

6. The admixture composition of claim 5, wherein the aqueous pulp mixture comprises at least 80 wt % of short fibers, relative to a total weight of fibers.

7. The admixture composition of claim 5, wherein the microfibrillated cellulose of the microfibrillated cellulose composition is not chemically modified nor physically modified.

8. The admixture composition of claim 5, wherein the starch derivative is a cationic starch.

9. The admixture composition of claim 5, wherein the degree of substitution of the anionic cellulose derivative is comprised between 0.45 and 0.5.

10. The admixture composition of claim 5, further comprising a retention system.

11. The admixture composition of claim 10, wherein the retention system comprises at least one cationic polyacrylamide.

12. The admixture composition of claim 5, wherein an amount of microfibrillated cellulose composition is comprised between 0.3 wt % and 5 wt %, based on a dry solid content of the microfibrillated cellulose composition relative to a dry solid content of the aqueous pulp mixture.

13. The admixture composition of claim 5, wherein an amount of starch derivative is comprised between 0.1 wt % and 2 wt %, based on a dry solid content of the starch derivative relative to a dry solid content of the aqueous pulp mixture.

14. The admixture composition of claim 5, wherein an amount of anionic cellulose derivative is comprised between 0.05 wt % and 0.3 wt %, based on a dry solid content of the anionic cellulose derivative relative to a dry solid content of the aqueous pulp mixture.

15. A method for preparing the admixture composition of claim 5, comprising: providing the aqueous pulp mixture, and admixing to the aqueous pulp mixture, the microfibrillated cellulose composition, the starch derivative, and the anionic cellulose derivative, and.

16. The method of claim 15, wherein the aqueous pulp mixture has a solid content of less than 3% of a total solids content in the aqueous pulp mixture.

17. The method of claim 15, wherein the retention system of the admixture composition comprises at least one of cationic polyacrylamide and silica.

18. A method for preparing a paper product, comprising: providing an aqueous pulp mixture, admixing to the aqueous pulp mixture, a microfibrillated cellulose composition, a starch derivative and an anionic cellulose derivative, to form the admixture composition of claim 5, and forming a wet sheet by draining the admixture composition, and.

19. The method of claim 18, wherein the anionic cellulose derivative is added to the aqueous pulp mixture at least 10 minutes before a wet sheet formation.

20. A paper product comprising a microfibrillated cellulose composition, a starch derivative, and an anionic cellulose derivative having a number average molecular weight comprised between 300000 g/mol and 800000 g/mol, and a degree of substitution comprised between 0.3 and 0.65.

21. A paper sheet comprising the product of claim 1, as an additive to increase at least one of an initial wet web strength and a dry tensile strength of the paper sheet.

22. The method of claim 15, further comprising admixing a retention system.

23. The method of claim 16, wherein the aqueous pulp mixture has a solid content of less than 3% of a total solids content in the aqueous pulp mixture.

24. The method of claim 20, further comprising admixing a retention system to form the admixture composition.

Description

EXAMPLE 1: EVALUATION OF IWWS OF HAND SHEETS PREPARED FROM BIRCH PULP

[0110] 1.1 Pulping of Birch Furnish

[0111] Birch pulp were refined with Voith Sulzer-refiner to a Schopper-Riegler (SR) value of 22, determined according to the method set forth in ISO 5267-1 Pulps—Determination of drainability—Part 1: Schopper-Riegler method. The consistency (or solid content) of the disintegrated pulp was 3 wt %. The pulp was further diluted with water prior to sheet formation to a solid content of 0.5 wt % with respect to the total weight of the aqueous pulp mixture.

[0112] 1.2 Preparation of Hand Sheets

[0113] The laboratory hand sheets were prepared with dynamic sheet former (TechPap). The chemicals were added to the pulp system in the following order:

[0114] 1. Anionic cellulose derivative: ECA (Nouryon); chemically modified cellulose having anionic carboxymethyl substituents with a degree of substitution comprised between 0.45 and 0.5 and a number average molecular weight of about 500 000 g/mol.

[0115] 2. Cationic starch (Raisamyl)

[0116] 3. Sugar beet originated microfibrillated cellulose composition (MFC) having a cellulose content of 49 wt %, based on dry solid content of the MFC, and a solid content of 18.6 wt %, based on the total weight of the MFC; the Brookfield viscosity of a 1 wt % MFC aqueous solution is 0.106 Pa.Math.s at 100 rpm, and 0.192 Pa.Math.s at 50 rpm (a V75 vane spindle was used for the measurement)

[0117] 4. Cationic polyacrylamide (CPAM): Fennopol K3400 (Kemira Oyj)

[0118] 5. Silica microparticles: Fennosil 2180 having a 6.5 wt % concentration (Kemira Oyj).

[0119] The normal delay time to add these chemicals is the following: cationic starch is added 30 s after ECA, MFC is added 60 s after ECA, CPAM is added 70 s after ECA and silica is added 80 s after ECA, the sheet formation occurring 90 s after the addition of ECA.

[0120] The sheet average grammage was 100 g/m.sup.2.

[0121] After the sheet formation, the sheets were placed between plotting papers and pressed with a lab nip press under 5 bar pressure. The pressing was repeated twice after which the sheets were cut in 15 mm×150 mm cross direction (CD) and machine direction (MD) pieces. The pieces were placed into a plastic minigrip bag to avoid changes in the solid content prior the initial wet web strength (IWWS) measurements.

[0122] 1.3 Measurement of the Solid Content, IWWS and Dry Tensile Strength

[0123] The solid content of the pressed sheets was measured with placing a sample into 150° C. dryer for 10 minutes and measuring the weight loss of the dried paper pieces.

[0124] Dry tensile strength was measured on dried sheets.

[0125] Dry tensile strength was measured by using method ISO 1924-3.

[0126] IWWS was measured with tensile strength measuring equipment similarly to the dry tensile strength, except that the sheets were not dried. Each test point measurement was repeated with 8 separate paper slices per machine direction and 6 per cross direction.

[0127] 1.4 Results

[0128] The results for the different tested compositions are indicated in Table 1 below, wherein percentages of ECA, cationic starch, MFC, CPAM and silica are expressed as weight percentages based on the dry solid content of the component with respect to the dry solid content of the aqueous pulp mixture.

[0129] Compositions 5 and 6 are compositions according to the invention, whereas compositions 1-4 are comparative compositions. ECA was added either with normal delay time (90 seconds between addition of ECA and sheet formation) for compositions 1-5, or with long delay time (30 minutes between addition of ECA and sheet formation) for composition 6.

TABLE-US-00001 TABLE 1 ECA Cationic MFC CPAM Silica IWWS Solid content Dry tensile Test (%) Starch (%) (%) (%) (%) (N) (wt %) (Nm/g) 1 — — — 0.02 0.2 2.191 35.11 51.56 2 — 0.5 — 0.02 0.2 2.394 36.65 64.16 3 — 0.5 1.0 0.02 0.2 2.372 37.86 63.86 4 0.2 0.5 — 0.02 0.2 2.358 37.02 64.01 5 0.2 0.5 1.0 0.02 0.2 2.421 37.01 63.04 6 0.2 0.5 1.0 0.02 0.2 2.529 36.79 65.4

[0130] The results show that, for a similar solid content, the birch sheets obtained from the compositions 5 and 6 according to the invention have the higher IWWS, while a combination of starch with either ECA (composition 4) or MFC (composition 3) leads to sheets having an IWWS less than sheets obtained with addition of starch only (composition 2).

[0131] Furthermore, the compositions 5 and 6 according to the invention show a significant increase of the dry tensile strength with respect to the reference sheet (composition 1).

[0132] Consequently, the results show that the compositions according to the invention are able to highly increase the IWWS, as well as the dry tensile strength.

EXAMPLE 2: EVALUATION OF IWWS OF HAND SHEETS PREPARED FROM EUCALYPTUS PULP

[0133] 1.1 Pulping of Eucalyptus Furnish

[0134] Eucalyptus pulp was obtained by following the method described in point 1.1 of Example 1.

[0135] 1.2 Preparation of Hand Sheets

[0136] Hand sheets were obtained according to point 1.2 of Example 1, except that eucalyptus pulp was used instead of birch pulp, and a different MFC was used. This MFC is a sugar beet originated MFC having a cellulose content of 69 wt %, based on dry solid content of the MFC, and a solid content of 7.7 wt %, based on the total weight of the MFC; the Brookfield viscosity of a 1% MFC aqueous solution is 0.940 Pa.Math.s at 100 rpm, and 1.725 Pa.Math.s at 50 rpm (a V75 vane spindle was used for the measurement).

[0137] 1.3 Measurement of the Solid Content, IWWS and Dry Tensile Strength

[0138] The solid content, the IWWS and the dry tensile strength were measured according to the procedure described in Example 1.

[0139] 1.4 Results

[0140] The results for the different tested compositions are indicated in Table 2 below, wherein percentages of ECA, cationic starch, MFC, CPAM and silica are expressed as dry weight percentages with respect to the solid content of the aqueous pulp mixture.

[0141] Composition 15 is a composition according to the invention, whereas compositions 7-14 are comparative compositions.

[0142] ECA was added with normal delay time (90 seconds between addition of ECA and sheet formation) for all compositions.

TABLE-US-00002 TABLE 2 ECA CMC Cationic MFC CPAM Silica IWWS Solid content Dry tensile Test (%) (%) Starch (%) (%) (%) (%) (N) (wt %) (Nm/g)  7 — — — — 0.02 0.2 2.6031 35.662 46.969  8* — — — — 0.02 0.2 2.9700 35.688 48.871  9 — — 0.5 — 0.02 0.2 2.5519 37.179 57.775 10 0.2 — — — 0.02 0.2 2.7734 37.946 49.389 11 — 0.2 — — 0.02 0.2 2.6309 35.336 47.582 12 — — — 1.0 0.02 0.2 2.9509 36.176 50.199 13 — — 0.5 1.0 0.02 0.2 2.5615 36.397 60.460 14 — 0.2 0.5 1.0 0.02 0.2 2.7554 36.364 60.924 15 0.2 — 0.5 1.0 0.02 0.2 2.9045 35.662 63.798 *The pulp was obtained from a weight ratio of 90/10 eucalyptus/softwood (long fibers)

[0143] The results show that, for a similar solid content, the sheet obtained from composition 15 according to the invention (comprising a combination of MFC, starch and ECA) has an increased IWWS, as well as an increased dry tensile strength, with respect to the reference eucalyptus sheet (composition 7).

[0144] In addition, the sheet obtained from composition 15 reaches a value close to the comparative sheet made from 90/10 eucalyptus/softwood (composition 8), and has an increased dry tensile strength compared to this sheet (composition 8), resulting in better overall properties than the comparative sheet made from 90/10 eucalyptus/softwood.

[0145] On the contrary, the eucalyptus sheets obtained from any one of the comparative compositions 9, 10, 12 (comprising only one of ECA, cationic starch or MFC) do not combine both a high IWWS and a high dry tensile strength.

[0146] In addition, the improvement in terms of both IWWS and dry tensile strength is not as high when CMC is used instead of ECA (comparison of compositions 10 and 11, and of compositions 14 and 15).

[0147] The composition according to the invention allows obtaining sheets from 100% eucalyptus pulp having an IWWS close to a sheet made from 90/10 eucalyptus/softwood (good runability), but also a better dry tensile strength (better handling properties) than said sheet.