Fibrillated blend of lyocell low DP pulp

Abstract

A fibrillated blend of lyocell and cellulosic pulp having a degree of polymerization of 200 to 1000 as measured by ASTM Test 1795-96, a method of making the blend and materials which incorporate the blend.

Claims

1. A fibrillated blend of lyocell and cellulosic pulp having a degree of polymerization of 200 to 1000 as measured by ASTM Test 1795-96, the lyocell and cellulosic pulp having been fibrillated together to form a fibrillated blend, wherein at least a portion of the lyocell fiber has a length of 3 to 12 mm, and wherein the lyocell is from 25 to 75 weight percent of the blend.

2. The blend of claim 1 wherein at least one of the lyocell or the cellulosic pulp contains lignin.

3. The blend of claim 1 wherein the blend is hydrophobic.

4. The blend of claim 1 wherein the blend has been treated with an additive.

5. The blend of claim 4 wherein the additive is selected from surfactants, dispersants, nanoclay, carbon black, silica and lignin or lignin derivatives.

6. A material comprising a fibrillated blend of lyocell and cellulosic pulp having a degree of polymerization of 200 to 1000 as measured by ASTM Test 1795-96, the lyocell and cellulosic pulp having been fibrillated together to form a fibrillated blend, wherein at least a portion of the lyocell has a length of 3 to 12 mm, and wherein the lyocell is from 25 to 75 weight percent of the blend.

7. The material of claim 6 wherein at least one of the lyocell or the cellulosic pulp contains lignin.

8. The material of claim 6 wherein the blend is hydrophobic.

9. The material of claim 6 wherein the blend has been treated with an additive.

10. The material of claim 9 wherein the additive is selected from surfactants, dispersants, nanoclay, carbon black, silica and lignin derivatives.

11. The material of claim 6 further comprising polyvinyl alcohol, cellulose ether, polyurethane, polylactic acid, polystyrene-co-butyl acrylate, water soluble polymers, nonwovens, adhesives, water borne coatings or starch based materials.

12. The material of claim 6 further comprising thermoplastic or thermoset or gel materials.

13. The material of claim 6 further comprising elastomeric materials or rubber.

14. The fibrillated blend of lyocell and cellulosic pulp of claim 1, wherein the cellulose pulp has a degree of polymerization of 300 to 800 as measured by ASTM Test 1795-96.

15. The fibrillated blend of lyocell and cellulosic pulp of claim 14, wherein the cellulose pulp has a degree of polymerization of 400 to 750 as measured by ASTM Test 1795-96.

Description

EXAMPLES

(1) In the following examples Weyerhaeuser Peach® pulp is used as an example of a low DP pulp. Examples of high DP pulps are Weyerhaeuser fluff pulps NB 416, FR 416, FR 516 and LV bleached. UB unbleached pulp is an example of a low DP pulp containing lignin. LV is a highly carboxylated pulp (30 meq/loogram) using Weyerhaeuser Longview pulp as starting pulp and the method described in U.S. Pat. No. 6,524,348.

(2) The following two examples show the manufacture of a lyocell/low DP pulp blend using a low energy hydropulper and a high energy disintegrator.

Example 1: Use of Hydropulper (90 Minutes)

(3) A 2.75 wt % consistency solution with water (56.5 kg), 6 mm lyocell fibers (0.91 kg at 92% solids), and never-dried Peach® pulp (3.65 kg at 23% solids) was added to a 40 gallon lab hydropulper. The hydropulper was turned on and ran for 90 minutes. A “typical” hydropulper would run at about 700 rpm. The energy in the hydropulper is 25 kwh per ton of blend. Dried Peach® can be used too.

Example 2: Use of Disintegrator (90 and 180 Minutes)

(4) A 1.2 wt % consistency solution with water (1.94 kg), 6 mm long lyocell fibers (13.2 g at 92% solids), and never-dried Peach® pulp (52.2 g at 23% solids) was added to a standard British Disintegrator (Tappi T227 om-94). The Disintegrator was turned on and ran at 3000 rpm for 90 and 180 minutes. The energy in the disintegrator is 175 kwh per ton of blend. The pulps may be dry or never dry. Dry wood pulps include fluff NB 416, FR 416, Peach® pulp and unbleached pulp (UB). Table 1 shows that highly fibrillated cellulose blend from 6 mm long lyocell and Peach® pulp had lower freeness than lyocell/NB 416 or lyocell/FR 416 blends with the same lyocell/pulp blend ratio made under the same refining condition. A highly fibrillated cellulose blend from 6 mm long lyocell and unbleached pulp with DP of 760 and lignin content of 1.9% also had low freeness. It is believed that low freeness indicates more fines. Fines are particles having a size less than 250 microns.

(5) TABLE-US-00001 TABLE 1 Freeness of cellulose pulp and lyocell fiber blend with high fibrillation Freeness (CSF, ml) of the slurry Composition Lyocell/ Lyocell/ Lyocell/pulp Lyocell/UB* Peach NB416 Lyocell/FR416 British Disintegrator (consistency: 1.2%, 90 minutes, example 2)  0/100 696 >700 704  5/95 630 25/75 190 290 330 50/50 108 (6.68)** 68 (6.30)** 106 (7.32)** 94 75/25 44 58 58 95/5  49 55 54 100/0  36 (1.90)** British Disintegrator (consistency: 1.2%, 180 minutes, example 2) 50/50 0 22 0 (100% lyocell) Hydropulper (consistency: 3%, 90 minutes, example 1) 50/50 38 75 *UB = unbleached kraft pulp, **Hemicellulose (xylan and mannan).

Example 3: Properties of Refined Lyocell/pulp Blend

(6) This example shows that a refined Peach®/lyocell blend or a refined unbleached low DP pulp/lyocell blend will generate more fines during refining than a refined high DP pulp/lyocell blend as shown in Table 2. The high DP pulps are LV bleached and NB 416. The extra fines from pulp, higher population and shorter low DP fibers in their blend with lyocell will enhance lyocell fibril dispersion in the blend and reduce mechanical entanglement among lyocell fibrils due to extra dilution and spacing among long lyocell fibrils. The blend may contain from 25 to 75 weight % lyocell and 75 to 25 weight percent low DP pulp. At high lyocell content (95/5 lyocell/NB416), the blend may have higher fines, but lower population than lyocell/Peach of same composition (table 2), but this extra fines from lyocell/NB416 is possibly from over-fibrillated lyocell fiber. This will not benefit the utilization of lyocell fibrils for composite applications. Lyocell/Peach with 95/5 ratio also had high fine than 75/25 ratio. Again, fines from lyocell do not imply higher dispersion. High lyocell ratio in blend will have high entanglement even it is high fines. This indicated that a proper lyocell/pulp ratio is important and only fines from pulp will benefit dispersion for these blends with proper lyocell/pulp ratio.

(7) In this example, lyocell alone or lyocell was combined with the different pulps in the ratios shown and the blends were fibrillated either in a British disintegrator or a hydropulper for the times shown. The blends were in aqueous solution at the consistencies disclosed in Example 1 for the hydropulper and example 2 for the British disintegrator. The resulting material was tested for the fiber properties shown.

(8) TABLE-US-00002 TABLE 2 Properties of refined lyocell fiber or its 50/50 blend with pulp Lyocell (8 mm) Yes Yes Yes Yes Yes Pulp used No LV NB416 UB Peach Pulp bleached yes yes no yes DP (fibrillated blend) 589 1100*    1140 690 542 Fiber Properties FQA British disintegrator (90 minutes, example 2) Fibers per gram, million 22.1 8.6  11.0 14.4 15.6 LWAFL, mm 2.26 2.18 2.48 2.13 2.12 Fiber Coarseness, mg/100 m 11.3 20.8  16.2 14.4 15.7 Kink Index 2.29 1.4  2.4 2.5 3.1 Curl Index 0.35 0.19 0.38 0.39 0.42 WWAFL, mm 3.75 3.31 3.81 3.64 3.60 LW Fines, % 14.0 7.1  9.2 11.0 11.9 Fiber Properties FQA Hydropulper (90 minute, example 1) Fibers per gram, million LWAFL, mm 2.22 1.45 Fiber Coarseness, mg/100 m Kink Index 2.22 2.26 Curl Index 0.24 0.28 WWAFL, mm 3.43 2.96 LW Fines, % 9.2 22.6 Properties of refined lyocell fiber blend with pulp Lyocell (L)/Pulp L/NB416 L/Peach ® L/Peach ® L/Peach ® L/Peach ® ratio 95/5 95/5 75/25 50/50 25/75 Fiber Properties FQA 90 minutes refining (example 2) Fibers per gram, million 13.4 17.3  19.9 15.6 16.7 LWAFL, mm 2.55 2.68 2.23 2.12 2.02 Fiber Coarseness, mg/100 m 12.7 12.8  11.8 15.7 15.5 Kink Index 3.3 3.3  3.3 3.1 2.8 Curl Index 0.56 0.59 0.54 0.42 0.33 WWAFL, mm 4.19 4.19 3.74 3.60 3.19 LW Fines, % 13.8 12.9  11.7 11.9 11.0 LV is a paper grade pulp from Longview pulp mill Weyerhaeuser with 30 meq/100 gram of carboxyl groups. *estimated DP is 1100.

Example 4: Suspension Stability of Refined Lyocell/pulp Blend

(9) One method of showing dispersion is showing the turbidity stability of the blend in water using EPA method 180.1. The following table gives a comparison among fibrillated lyocell, a blend of fibrillated lyocell and Peach® pulp having a DP of 700, and a blend of fibrillated lyocell and NB 416 pulp having a DP of 1500.

(10) TABLE-US-00003 TABLE 3 Turbidity (11 reading in half minute) of the suspension in water (0.003%) Sample Lyocell/NB Lyocell Lyocell/Peach ® 416 Blend 50/50 50/50 Standard deviation (STDEV) 2.25 0.29 8.56

(11) In this test for slurry stability, half minute time is used to record turbidity of the slurry. Stable slurry will have low turbidity variability (lower standard deviation). The stability of the lyocell/low DP blend has far greater stability than the lyocell alone or the lyocell and higher DP pulp.

(12) The following table provides more suspension stability data for other samples. As can be seen, suspension from Lyocell/Peach® blend at 50/50 ratio still has the highest suspension stability (the lowest standard deviation).

(13) It is known that charged nanocellulose surface improves nanocellulose dispersion but a blend of lyocell with high carboxyl group pulp with high DP (the LV fiber) did not show good stability (a high standard deviation). This may be the result of a poor generation of fines

(14) TABLE-US-00004 TABLE 4 Turbidity (25 reading in one minute) of the suspension in water (0.003%) Lyocell/Pulp 50/50 50/50 50/50 50/50 Pulp Peach ® FR416 LV Peach ® additive no no no no STDEV 0.26 0.58 0.84 0.13

(15) Another method is to determine the time it takes to filter a specified amount of water from a water/cement mix. The longer it takes to filter the specified amount of water the better the dispersion of the fiber. The three materials used in the first test as well as a low DP pulp sample were used. The filtration times in seconds were: low DP pulp alone, 55 seconds; lyocell alone 101 seconds; lyocell/high DP (1500 DP) 50/50 blend 103 seconds; and lyocell/low DP (700 DP) 50/50 blend 178 seconds. Again the low DP blend showed better dispersion.

(16) Applicant is unsure why the low DP pulp provides better dispersion. The properties of the fibers were checked with FQA (Jeremy Meyers and Hiroki Nanko TAPPI Spring 2005 Technical Conference, pages 1-8) to see if there was an attribute that might cause the dispersion. Table 5 has a comparison of fiber properties.

(17) TABLE-US-00005 TABLE 5 Fiber properties FR 416 FR 516 NB 416 Peach ® Fluff Fluff fluff Chemical Properties Viscosity, mPa * s 22 78 70 224 DP 700 1148 1110 1498 R-10, % 81.5 86.9 86.6 87.5 R-18, % 85.7 87.4 87.2 87.8 Carboxyl group, meq/100 g 4.65 3.3 Fiber Properties FQA Fibers per gram, million 5.7 4.9 5.2 4.6 LWAFL, mm 2.24 2.55 2.44 2.67 Fiber Coarseness, mg/100 m 20.8 21.2 20.3 21 Kink Index 2.2 1.8 1.7 1.4 Curl Index 0.22 0.18 0.18 0.14 WWAFL, mm 3.13 3.44 3.31 3.4 LW Fines, % 6.2 5.2 5.3 4.4

(18) It can be seen that the viscosity (Tappi T-230) and DP of Peach® pulp are lower than the others. The R-10 and R-18 (Tappi T-235 cm-00) of Peach® pulp are slightly lower than the others. The Carboxyl groups of Peach® pulp are higher than NB 416. The number of fibers per gram of Peach® pulp is higher than the others. The LWAFL (length weighted average fiber length) of Peach® pulp is lower than the others. The kink and curl index of Peach® pulp are higher than the others. The WWAFL (weight weighted average fiber length) of Peach® pulp is lower than the others and the LW fines [length weighted, under 0.2 mm] of Peach® pulp is higher than the others. Upon disintegration (Tappi T227 om-94), Peach® pulp has much lower fiber length, higher population and much higher fines than the FR 416 refined under same condition (Table 6).

(19) TABLE-US-00006 TABLE 6 Refining performance of Peach and fluff pulp FR 416 FR 416 Peach ® Peach ® Chemical Properties Refining time (minute) 5 90 5 90 5 90 5 90 Freeness 751 704 749 696 Fiber Properties FQA Fibers per gram, million 6.8 7.0 9.7 12.8 LWAFL, mm 2.54 2.59 2.44 2.47 2.16 2.20 2.05 2.05 Fiber Coarseness, mg/100 m 20.1 19.7 18.0 17.2 Kink Index, 1/mm 1.8 1.6 2.2 1.9 2.3 2.1 3.0 2.7 Kink number, 1/mm 0.9 0.8 1.0 0.9 1.1 1.0 1.3 1.1 Curl Index 0.16 0.12 0.19 0.16 0.19 0.16 0.25 0.21 WWAFL, mm 3.30 3.53 3.20 3.24 3.02 3.10 2.75 2.79 LW Fines, % 5.8 5.7 5.8 5.6 7.9 8.6 6.4 8.1