Binder composition based on plant fibers and mineral fillers, preparation and use thereof

Abstract

A method for preparing a binder composition containing water, plant fibers and mineral fillers, wherein the method comprises: preparing a suspension of plant fibers and mineral fillers in water, the weight ratio between the plant fibers and the mineral fillers being comprised between 99/1 and 2/98, refining this suspension, and obtaining a binder composition wherein the refined fibers have a mean size of between 10 and 700 μm, and wherein the refined fibers, at least partially, embed the refined mineral fillers,
wherein refining is carried out in the absence of any grinding medium made of ceramic or metal.

Claims

1. A method for preparing a binder composition containing water, plant fibers and mineral fillers, wherein the method comprises the following steps: preparing a suspension of plant fibers and mineral fillers in water, the weight ratio between the plant fibers and the mineral fillers being comprised between 99/1 and 2/98, refining this suspension, obtaining a binder composition wherein the refined fibers have a mean size of between 10 and 700 μm, and wherein the refined fibers, at least partially, embed the refined mineral fillers, wherein refining is carried out in the absence of any grinding medium made of ceramic or metal.

2. The method of claim 1, wherein refining is carried out between parallel refiner discs.

3. The method of claim 1, wherein refining is carried out between parallel discs, and stopped after 10 to 80 passes.

4. The method of claim 1, wherein fibers are enzymatically treated before refining the suspension.

5. The method of claim 1, wherein after refining, the binder composition has a concentration of plant fibers and mineral fillers of between 5 and 500 g per liter of water.

6. The method of claim 1, wherein the method further comprises after preparation of the suspension of plant fibers and mineral fillers in water and before refining the suspension a fractionating step and an enzymatic treatment.

7. A method for preparing a composition a binder composition containing water, plant fibers and mineral fillers, wherein the method comprises the following steps: preparing a suspension of plant fibers and mineral fillers in water, the weight ratio between the plant fibers and the mineral fillers being comprised between 99/1 and 2/98, refining this suspension, obtaining a binder composition wherein the refined fibers have a mean size of between 10 and 700 μm, and wherein the refined fibers, at least partially, embed the refined mineral fillers, wherein fibers are enzymatically treated before refining the suspension, wherein, refining is carried out between parallel discs, and stopped after 10 to 80 passes between parallel discs.

8. The method of claim 7, wherein refining is carried out through 2 to 6 pairs of discs.

9. The method of claim 7, wherein refining is carried out through parallel pairs of discs having a same inter-discs gap.

10. The method of claim 9, wherein refining is carried out through parallel pairs of discs, wherein the inter-discs gap decreases over the 10 to 80 passes.

11. The method of claim 7, wherein after refining, the binder composition has a concentration of plant fibers and mineral fillers, of between 5 and 500 g per liter of water, and wherein refining is carried out in the absence of any grinding medium made of ceramic or metal.

12. The method of claim 7, wherein a fractionating step of the fibers is carried out before the enzymatic treatment of the fibers.

13. A method for preparing a composition a binder composition containing water, plant fibers and mineral fillers, wherein the method comprises the following steps: preparing a suspension of plant fibers and mineral fillers in water, the weight ratio between the plant fibers and the mineral fillers being comprised between 99/1 and 2/98, refining this suspension, obtaining a binder composition wherein the refined fibers have a mean size of between 10 and 700 μm, and wherein the refined fibers, at least partially, embed the refined mineral fillers, wherein fibers are enzymatically treated before refining the suspension, wherein, refining is carried out between parallel refiner discs, in the absence of any grinding medium made of ceramic or metal, wherein, after the refining step, water is partially evaporated to concentrate the binder composition.

14. The method of claim 13, wherein the binder composition has a concentration of plant fibers and mineral fillers, of from 5 to 500 g per liter of water.

15. The method of claim 14, wherein the concentration of plant fibers and mineral fillers in the binder composition is from 10 to 100 g per liter of water.

16. The method of claim 15, wherein the concentration of plant fibers and mineral fillers in the binder composition is from 20 g to 50 g per liter of water.

17. The method of claim 13, wherein refining is carried out through a series of 2 to 6 pairs of discs.

18. The method of claim 13, wherein refining is carried out through a series of parallel pairs of discs having a same inter-discs gap.

19. The method of claim 13, wherein refining is carried out through a series of parallel pairs of discs, wherein the inter-discs gap decreases over the passes between the parallel pairs of discs.

20. The method of claim 13, wherein a fractionating step of the fibers is carried out before the enzymatic treatment of the fibers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the fiber length distribution of the binding composition according to the invention vs a composition obtained by grinding (area weighted fiber length).

(2) FIG. 2 shows mean fiber lengths of the binding composition according to the invention vs a composition obtained by grinding.

EXAMPLES

(3) The binding composition according to the invention (GP) has been compared to a composition resulting from the grinding of fibers in the presence of mineral fillers (CE).

(4) 1/ Preparation of the Composition According to the Invention

(5) Plant fibers are treated as follows in the presence of mineral fillers: Preparation of a paper pulp (Helico pulper): 160 kg plant fibers+1300 liter of water at 63° C. for 15 minutes, Enzymatic treatment in a bioreactor: 30 minutes at 50° C., Filtering (Buchner) (% C retention=4.96%), Refining (16 inches) for 180 minutes, with an overall specific energy of 600 kWh per ton of fibers and fillers.

(6) Table 1 summarizes the different treatments carried out in order to prepare the GP0, GP2 and GP3 compositions (softwood+CaCO.sub.3 simultaneously refined).

(7) TABLE-US-00001 TABLE 1 Conditions for preparing the composition according to the invention (GP0, GP2, GP3). Composition Pulper Enzymatic treatment % C Refining GP0 Industrial 30 minutes at 50° C. 4,96% 180 minutes GP2 Lab 30 minutes at 50° C.   2% 190 minutes GP3 Lab 30 minutes at 50° C.   2% 120 minutes

(8) GP0, GP2 and GP3 have a mineral filler of 2.00; 18.60 and 45.40 wt % respectively, with respect to the dry weight of the GP compositions. The amount of mineral fillers corresponds to the ash content after treatment of the composition at 425° C.

(9) 2/ Counter-Example (CE)

(10) The composition according to the invention has been compared to a composition (CE) comprising fibers and mineral fillers that have been simultaneously grinded.

(11) The CE composition comprises softwood fibers and CaCO.sub.3 mineral fillers. It has an ash content of 53.6 wt % at 425° C.

(12) 3/ Properties of the GP Compositions Vs CE

(13) The size distribution of the GP compositions (refining) has been compared to the CE composition resulting from a grinding process.

(14) These analyses have been carried out with a MorFi instrument (Techpap). Only fibers and fillers having a size of at least 80 μm have been considered.

(15) According to FIG. 1 (area weighted fiber length), the GP0 composition has a narrow size distribution centered at about 174 μm. Less than 15% of the fibers of GP0 have a size of 335 μm or more.

(16) The composition according to counter-example CE has 30% of its fibers of 335 μm or more. The size distribution of the GP composition is therefore definitely more homogeneous than that of the CE composition, as also demonstrated by the various length measurements (see FIG. 2).

(17) FIG. 2 shows indeed mean fiber lengths of the binding composition according to the invention vs a composition obtained by grinding. The mean fiber arithmetic length (L(n)), the mean length-weighted fiber length (L(l)) and the mean area-weighted length (L(w)) are respectively calculated according to the following formula:

(18) $\begin{array}{ccc}L\left(n\right)=\frac{\underset{i}{.Math.}{n}_i{l}_i}{\underset{i}{.Math.}{n}_i}& L\left(l\right)=\frac{\underset{i}{.Math.}{n}_i{l}_i^2}{\underset{i}{.Math.}{n}_i{l}_i}& L\left(w\right)=\frac{\underset{i}{.Math.}{n}_i{l}_i^3}{\underset{i}{.Math.}{n}_i{l}_i^2}\end{array}$
4/ Papermaking Involving the Compositions According to the Invention and the CE Composition

(19) Paper sheets (90 g/m.sup.2) have been formed with a dynamic sheet former. 5 wt % (dry weight) of a GP or CE composition (see “Added composition” line in Table 2) have been added to a paper pulp containing plant fibers (softwood) that have been refined at 25° SR (see “Initial pulp” line in Table 2).

(20) Additional mineral fillers have been added as shown in Table 2 so as to reach a total of 15 wt % (see “Added CaCO.sub.3” and “Total CaCO.sub.3” lines in Table 2).

(21) TABLE-US-00002 TABLE 2 Paper pulp compositions-Properties CE GP0 GP2 GP3 Added Fibers (wt %) 2.68 0.10 0.93 2.27 composition Fillers (wt %) 2.32 4.90 4.07 2.73 Initial Added CaCO.sub.3 (wt %) 12.32 14.90 14.07 12.73 pulp Softwood fibers 82.68 80.10 80.93 82.27 (wt %, 25° SR) Final Total CaCO.sub.3 (wt %) 15.00 15.00 15.00 15.00 pulp Total softwood fibers 85.00 85.00 85.00 85.00 (wt %) Ash content 5.10 6.70 11.90 11.60 in the formed sheet (425° C.), wt % Ash retention, wt % 34.00 44.67 79.33 77.33 Bulk, cm.sup.3/g 1.51 1.44 1.46 1.49 Tensile index, N*m/g 60.5 65.3 55.3 54.2 TEA, N.m/mm.sup.2 0.215 0.263 0.244 0.245 Burst index, kPa.m.sup.2/g 6.30 6.70 5.75 5.66 Scott bond, J/m.sup.2 385.9 490.4 409.1 369.2 Air permeability, 6.2 2.2 2.8 3.1 cm.sup.3/m.sup.2.Pa.s Opacity, % 84.5 85.3 90.0 89.2

(22) The sheets of paper made from GP compositions have a greater filler retention than the CE composition (see “Ash retention” line). Refined fibers that embed refined fillers (GP2 and GP3 composition) also promote the retention of added fillers.

(23) The filler content ranges from 5.1 (CE) to 11.9% (GP2). As shown by examples CE and GP0 (similar ash content), the amount of mineral fillers can drastically change the properties of the sheet of paper. Indeed, GP0 affords an improvement of 8% of the Tensile index (65.3 vs 60.5), an improvement of 22% of the TEA (Tensile Energy Absorption; 0.263 vs 0.215), and an improvement of 27% of the Scott bond (bond strength, 490.4 vs 385.9).

(24) In view of the above, the composition according to the invention clearly affords improved properties as compared to prior art compositions resulting from the grinding of plant fibers in the presence of mineral fillers. It also improves the filler retention.