阅读说明：本技术 制造纳米纤维素材料的方法，包括至少两个纤维素原料的脱纤维阶段和至少一个中间分级阶段 (Process for manufacturing nanocellulose material, comprising at least two defibration stages of cellulosic raw material and at least one intermediate fractionation stage ) 是由 马科斯·亨里克·卢西亚诺·西尔韦拉 歌蒙诺·安德雷德·西凯拉 比比亚娜·罗贝罗·鲁比尼 赫洛伊 于 2019-07-17 设计创作，主要内容包括：本发明涉及一种基于使用来自预处理或机械脱纤维的纤维素浆料流(部分精制/脱纤维的浆料)的分级与机械脱纤维阶段的组合制造纳米纤维素材料的方法,其中良料级分和废料级分都可被传送到稠度调节阶段,以在另一个不同的脱纤维阶段之前。例如,如果良料被传送到第二脱纤维阶段之前的稠度调节,而废料被传送到稠度调节的另一独立阶段以返回到机械脱纤维的第一阶段。(The present invention relates to a method for manufacturing nanocellulose material based on the use of a combination of fractionation from a pretreated or mechanically defibered cellulose pulp stream (partially refined/defibered pulp) and a mechanical defibering stage, wherein both a good fraction and a waste fraction can be passed to a consistency adjustment stage to precede another different defibering stage. For example, if the accept is passed to consistency conditioning before the second defibering stage, while the reject is passed to another separate stage of consistency conditioning to be returned to the first stage of mechanical defibering.)

1. A process for the production of nanocellulose material from a cellulosic feedstock, comprising at least two defibration stages of said cellulosic feedstock.

2. The method of making nanocellulose material of claim 1, wherein the fractionation stage occurs between pretreatment, defibration, and post-treatment.

3. Process for the manufacture of nanocellulose material according to claim 1 or 2, comprising the following phases:

(a) providing a cellulosic feedstock;

(b) performing a first defibering stage of the feedstock;

(c) carrying out at least a first selection/classification phase of the particles;

(d) passing the particle stream from the waste fraction of (c) to stage (b);

(e) passing the particles of the good fraction from stage (c) to stage (f);

(f) performing a second defibering stage of the feedstock;

(g) recovering nanocellulose material from stage (f).

4. A method according to claim 3, further selection/ranking stages being provided after stage (c).

5. The method of claim 4, providing an additional defibering stage after stage (b).

6. The method according to claim 5, comprising a consistency adjustment stage after at least one defibration stage.

7. The method according to claim 6, comprising a consistency adjustment stage after at least one selection/classification stage.

8. The method of claim 3, wherein the nanocellulose material is microfibrillated cellulose and/or nanocellulose.

9. Process for the manufacture of nanocellulose material according to claim 1 or 2, comprising the following phases:

(a) providing a cellulosic feedstock;

(b) performing a first defibering stage of the feedstock;

(c) subjecting the particles passing through a 50-350 mesh screen to at least one first selection/classification stage;

(d) passing the particle stream from the waste fraction of (c) to stage (b);

(e) passing the particles of the good fraction from (c) to stage (f);

(f) performing a second defibering stage of the feedstock;

(g) recovering nanocellulose material from stage (f).

10. The process of claim 9 wherein the sieve of stage (c) is a 75 mesh sieve.

11. The process of claim 9 wherein the sieve of stage (c) is a 200 mesh sieve.

12. The process according to any one of claims 9 to 11, wherein the stream of the waste fraction from stage (d) is partially passed to stage (b).

13. The method of claim 12, wherein a stream of the waste fraction from stage (f) is fed back to stage (f) or passed to stage (b).

14. The method of claim 13, further selection/ranking stages being provided after stage (c).

15. The method of claim 14, providing an additional defibering stage after stage (b).

16. The method according to claim 15, comprising a consistency adjustment stage after at least one defibration stage.

17. The method according to claim 16, comprising a consistency adjustment stage after at least one selection/classification stage.

18. A process for enriching a nanocellulose material, comprising at least one stage of feeding back a defibration product from a defibration stage to the same defibration stage or to a previous defibration stage to provide a nanocellulose material.

Technical Field

The present invention generally relates to a method for the manufacture of nanocellulose based on the use of a combination of fractionation and mechanical defibration stages on a cellulose pulp stream from a refining process (partially refined/defibered pulp).

Background

Nanocellulose is defined as a cellulose sample comprising cellulose particles having at least a nanometric size (1-100 nm). The shape and composition of which depend mainly on the conditions and the manufacturing process. Based on composition and dimensional properties, nanocellulose can be classified as: (1) cellulose Nanocrystals (CNC), also known as cellulose whiskers; (2) cellulose Nanofibrils (CNF) and (3) Bacterial Cellulose (BC).

The process for making nanocellulose may involve mechanical defibration, which may be performed as a single stage of the procedure, or in combination with biological and/or chemical processes (e.g., pre-treatment or post-treatment stages). Thus, the manufactured nanocellulose-like products are typically a mixture of CNF, CNC and microfibrillated cellulose (MFC), part of these fractions depending on the process technology and application conditions, which are factors defining the final quality of the product. Furthermore, the type of raw material used to make nanocellulose is also a determining factor in the final quality of the product.

The nanocellulose production process may be based on pre-treatment (chemical, mechanical or biological) followed by mechanical refining, or by a single stage (usually mechanical defibration). Enzymatic pre-treatment or chemical oxidation, such as the TEMPO process (2, 2, 6, 6-tetramethylpiperidin-1-oxyl radical mediated oxidation) (Habibi Y, Chanzy H, Vignon MR: TEMPO-mediated surface oxidation of cellulose fibers 2006,13: 679-. A more complete description can be found in Janardhnan S., Sain MM, Isolation of cellulose microfibers-an enzymatic apreach, BioResources,2006,2: 176-.

An article published in Tanaka et al (Tanaka a., houoni, j.,v. Pirkonem P. nanocell chromatography with mechanical fractionation, Normal pulp and paper research project, 2012,27: 689-.

Furthermore, Osong and co-workers (Osong, SH, Norgren, S., Engstrand, P., An apple to product no-ligno-cellulose from mechanical Pulp fibers materials, Nordic Pulp and Paper Research Journal,2013,28: 472-. On the other hand, the same authors demonstrated that a similar process for a Bleached Kraft Pulp (BKP) sample consisting of 75/25 pine/spruce (conifer) did not yield similar results and had to adopt a lower consistency to perform mechanical defibration by high pressure homogenization, probably due to the higher cellulose content in the BKP fines fraction compared to that obtained with TMP.

BR112014000862 a2 discloses a method of manufacturing nanocellulose material, comprising fractionating a cellulose raw material in the presence of an acid and mechanically treating cellulose-rich solids to form cellulose fibrils and/or cellulose crystals. Therefore, it does not disclose the treatment of distributed comminution after a fiber size selection/fractionation (fractionation) or continuous comminution (fibril removal) stage.

Application US 6024834A discloses a method of fractionating cellulose fibers by subjecting a first mixture of cellulose fibers to an effective fractionating medium to fractionate the first mixture of cellulose fibers into a second mixture of cellulose fibers and a third mixture of cellulose fibers, wherein the second mixture of cellulose fibers has a fiber dispersion value of greater than about 20 mg/100 m and a fiber average length value of greater than about 0.9 mm. This document also does not disclose a comminution process distributed after the fibre size selection/classification or continuous comminution stage.

To date, no methods for making nanocellulose have been proposed to allow for the use of fractionation stages between pretreatment, defibration and post-treatment.

The present invention provides for combining at least one fractionation single-step operation after at least one defibration stage to provide a uniform flow for defibration, pre-treatment or post-treatment, which results in higher quality nanocellulose in morphology and rheology.

Disclosure of Invention

In contrast to the prior art, the present invention provides a method using a fractionation unit (single-step operation) between single-step operations of defibration and/or pre-or post-treatment. Thus, for all forms of embodiment, such single-step operations are optimized in terms of the quality (morphology and rheology) of the nanocellulose produced and in terms of exhibiting gains related to the energy consumption in the mechanical process. By using a classification stage in the nanocellulose manufacturing process, the defibration stage is performed with a more uniform sample flow in terms of particle size and, therefore, the manufactured nanocellulose will have a greater uniformity in terms of nanofibril size distribution.

Drawings

FIG. 1A is a schematic representation of the application of fractionation to nanocellulose characterization;

FIG. 1B is a schematic illustration of nano-ligno-cellulose making samples with low fiber content;

FIG. 2A is a schematic diagram of one embodiment of a fractionation application method in the fabrication of nanofibrillated Cellulose (CNF) and/or microfibrillated cellulose (MFC);

FIG. 2B is a schematic diagram of one embodiment of a fractionation application method in the manufacture of nanofibrillated Cellulose (CNF) and/or microfibrillated cellulose (MFC) by different types of refining;

FIG. 3 is an embodiment of the present invention including a selection/classification stage and fiber feedback between two pulverizing stages;

FIG. 4 is an embodiment of the present invention including a selection/classification stage and fiber feedback between two pulverizing stages for use in a variety of processes;

FIG. 5 is an embodiment of the present invention including two selection/classification stages and fiber feedback after two pulverizing stages for use in multiple processes;

FIG. 6 is an embodiment of the present invention comprising two successive selection/classification stages and fiber feedback, both between the two pulverizing stages, for multiple processes;

FIG. 7 is an embodiment of the present invention including a selection/classification stage and fiber feedback between two pulverizing stages for use in a variety of processes;

FIG. 8 is an embodiment of the present invention including a selection/classification stage and fiber feedback between two consistency adjustment stages for a variety of processes;

FIG. 9 is an embodiment of the present invention comprising two successive pulverizing stages for a variety of processes;

FIG. 10 is an embodiment of the present invention comprising two successive pulverizing stages for multiple processes;

FIG. 11 is an embodiment of the present invention including a selection/classification stage and fiber feedback after two defibration adjustment stages;

FIG. 12 is an embodiment of the present invention including multiple selection/sizing and fiber feedback stages, after multiple defibration adjustment stages;

figure 13 shows the fines length distribution (%) for each fines range;

figure 14 shows the fines length distribution (%) for each fines range;

fig. 15 shows the fiber thickness distribution (%) for each fines range (μm);

FIG. 16 shows the change in viscosity versus shear Rate (RPM) where the curve for sample A overlaps the curve for sample B;

fig. 17 shows scanning electron microscope images of unfractionated samples (a and D), waste (B and E), and classified good (C and F) after 5 grinding passes;

FIG. 18 shows the dynamic viscosity curves of the fractionated and unfractionated samples after 5 mill passes (A) and 10 mill passes (B);

FIG. 19 shows the dynamic viscosity curves of the fractionated and unfractionated samples;

fig. 20 shows the dynamic viscosity curves of microfibrillated cellulose samples produced by disc milling (both fractionated and unfractionated).

Detailed Description

The present invention provides a process, unlike the literature, the authors propose the use of a classification unit between single-step operations of defibration and/or pre-or post-treatment. Thus, for all examples, this single-step operation will be optimized in terms of the homogeneity (in morphological terms and unique rheological characteristics) of the nanocellulose produced. More specifically, they suggest the use of a classification stage in the nanocellulose manufacturing process and in this way, the defibration stage will be performed with a sample flow that is more uniform in terms of particle size and, therefore, the nanocellulose produced will have a higher quality and uniformity in terms of particle size distribution (fig. 2A).

Furthermore, the proposed embodiments allow manufacturing different types of CNFs and/or MFCs, as shown in the embodiments of the methods shown in fig. 2B, 4, 5, 6, 7, 8, 9, 10 and 12.

In particular, the present invention relates to a process for the manufacture of nanocellulose material from a previously partially defibered cellulose raw material. Preferably, the cellulosic raw material may be a pulp originally derived from coniferous or hardwood, more particularly eucalyptus, or pine, or birch or beech, a bleached kraft pulp (BEKP) derived from eucalyptus or agro-industrial waste, such as bagasse and rice or wheat straw, obtained by: kraft pulp slurry; or sulfite pulping; or steam explosion; or blasting the fibers with ammonia; or dilute acid hydrolysis; or alkaline hydrolysis; or oxidation alkali treatment; or enzyme treatment; or organic solvent treatment. However, there is no limitation on the cellulosic material provided at the start of the process (stage a).

The process for manufacturing nanocellulose material, object of the present invention, occurs between pre-treatment, defibration and post-treatment and comprises at least two stages, one being fractionation of the cellulose raw material and the other defibration of the cellulose raw material, possibly with at least one further mechanical defibration stage or chemical pre/post-treatment stage with consistency adjustment stage. The output of at least one of the defibering stages comprises returning the fibers to itself or to the same stage. For example, if the first defibering stage outputs a first batch of fibers, they may be partially or completely returned to that stage. Also, such fibers may be conveyed integrally to a second defibering stage, which outputs a second batch of fibers, which may be partially returned to the second stage or the first stage.

The process, object of the present invention, therefore comprises a first defibering stage (stage b) of the raw material, followed by a first selection/classification stage (stage c). Preferably, the selection/classification is performed by passing the particles through a sieve of 50 to 350 mesh size, e.g. up to 200 mesh size, referred to as the good fraction. The granules selected without passing through the sieve, called the waste fraction, are then (stage d) fed back to stage b, i.e. they will be again subjected to a crushing stage, followed by selection/classification (stage c). The particles of the good fraction from stage (c) are conveyed (stage e) to a second defibering stage (stage f). After repeated defibering of the fibrils of the good fraction, the result (stage g) is the nanocellulose material from stage f.

The method, object of the present invention, also comprises an additional selection/classification stage. After the selection/ranking stage (e.g. stage c), at least one further selection/ranking stage may be considered.

Furthermore, the process may have a further defibering stage after the defibering stage (b).

In addition, the method (object of the invention) may comprise a consistency adjustment stage after at least one defibering stage or after at least one selection/classification stage.

Furthermore, a variant of the process for manufacturing nanocellulose material may comprise the following stages:

(a) providing a cellulosic feedstock;

(b) subjecting the feedstock to a first defibering stage;

(c) carrying out at least a first selection/classification phase of the particles;

(d) passing the particle stream from the waste fraction of (c) to stage (b);

(e) passing the particles of the good fraction from (c) to stage (f);

(f) performing a second defibering stage of the feedstock;

(g) recovering nanocellulose material from stage (f).

This variant preferably transfers the waste fraction of stage (d) partially to stage (b). Also preferably, the waste fraction from stage (f) may be fed back to stage (f) or passed to stage (b). Furthermore, such a process may provide an additional selection/classification stage after stage (c) and an additional defibration stage after stage (b).

In general, the method, object of the present invention, may also comprise a consistency adjustment stage after at least one selection/classification stage.

The nanocellulose material is preferably microfibrillated cellulose, nanofibrillated cellulose or cellulose nanocrystals.

Thus, the process is a process for enriching a nanocellulose material, wherein the use of a fractionation stage takes place between pretreatment, defibration and post-treatment, comprising at least one selection/fractionation stage, the defibration product from the defibration stage going to the same or a previous defibration stage to provide a nanocellulose material, or to a further defibration stage.

Example 1

The process of the present invention occurs between pretreatment, defibration and post-treatment according to the process depicted in fig. 2A. Eucalyptus bleached kraft pulp slurry suspended at 4% consistency (solids content) was subjected to a disc refining process at 57.93 ± 1.43 ℃ for 6.0 hours until reaching either an L-fines content of 70.30% (length-based fines) or an a-fines content of 33.35% (area-based fines). The resulting material was then subjected to a classification process in a Bauer mcnet apparatus using a 200 mesh screen/sieve. As a result of the fractionation stage, a mass recovery of about 43% was obtained in the waste fraction (fraction collected in another stream that did not pass through the screen in the fractionation), a mass recovery of 56% was obtained in the good fraction, with 22% and 94% L-fines for the waste and good fractions, respectively. Both fractions were thickened (consistency adjusted) on a wire (550 mesh) resulting in a consistency of 21.28% for the waste fraction and 17.73% for the good fraction, as shown in the method of fig. 2A.

The classified materials (waste and good fractions) as well as MFC samples with a fines-L content of 70.30% were then diluted to a consistency of 1% and subsequently defibrated by using 10 grindings in Masuko (Supermasscolloider-MKCA6) using an ultrafine 120# MKGC (silicon carbide-SiC) grindstone. For comparison of the morphology of the samples, the L-fines, fiber length and fiber width profiles (%) are shown in fig. 13, 14 and 15, respectively.

As shown in fig. 13, the massuko fractionated and processed samples showed gains in the increase of fine particle fraction in the smaller particle size range (1-23 μm) compared to the other very similar ranges of stages. On the other hand, the use of fractionation between the defibering processes (refining and grinding) resulted in an increase in the percentage of fractions of smaller length range (200-. Still in terms of morphology, the method of fig. 2A provides a reduction in fiber width and a more uniform sample (greater correlation between height and width of the bottom of the curve) (fig. 15).

As shown in fig. 16, a positive effect was also observed on the rheological behavior of the samples, indicating a huge gain in the thixotropic properties of the nanofibrillated cellulose produced according to the process shown in fig. 2A.

The benefits of the proposed method can also be determined in the results of table 1, where the gain in area content of fines can be perceived, as well as the gain in energy consumed in the final mechanical process.

Table 1: average of fines content based on area and energy expended in final defibration of samples

Example 2

The process of the present invention occurs between pretreatment, defibration and post-treatment according to the process depicted in fig. 2A. Eucalyptus bleached kraft pulp slurry suspended at 4% consistency (solids content) was subjected to a disc refining process at 57.93 ± 1.43 ℃ for 6.0 hours until reaching either an L-fines content of 70.30% (length-based fines) or an a-fines content of 33.35% (area-based fines). The resulting material was then subjected to a classification process in a Bauer mcnet apparatus using a 200 mesh screen/sieve. As a result of the fractionation stage, a mass recovery of about 43% was obtained in the waste fraction (fraction collected in another stream that did not pass through the screen in the fractionation), a mass recovery of 56% was obtained in the good fraction, with 22% and 94% L-fines for the waste and good fractions, respectively. Both fractions were thickened (consistency adjusted) on a wire (550 mesh) resulting in a consistency of 21.28% for the waste fraction and 17.73% for the good fraction, as shown in the method of fig. 2A.

The classified materials (waste fraction and good fraction) were then diluted to a consistency of 1% and subsequently defibered by using an ultrafine 120# mkka (alumina-Al 2O3) grindstone in Masuko (supermascolider-MKCA 6) using 10 grindings. To compare the morphology of the samples after the milling process, fig. 17 shows an image obtained by scanning electron microscopy. As shown in the MEV plot, the highest level of agglomeration can be determined after grinding the filaments in the unfractionated sample and the sized waste, compared to the sized good sample.

In addition, as shown in fig. 18, a positive effect was also observed in the rheological behavior of the samples, indicating that there is a huge gain in the thixotropic properties of the nanofibrillated cellulose produced according to the method shown in fig. 2A for different times in the grinding phase.

Example 3

The process of the present invention occurs between pretreatment, defibration and post-treatment according to the process depicted in fig. 2A. Bleached eucalyptus kraft pulp stock (BEKP) suspended at 4% consistency (solids content) was subjected to a disc refining process (18.66km/rev) at 57.93 ± 1.43 ℃ for 6.0 hours until an L-fines content (length based fines) of 69.89% was reached. The resulting material was then diluted to a solids content of 3.5% and subjected to a classification process using a pressurized basket with a 75 mesh screen (200 μm). In this case, the classification is carried out after dilution of the suspension to a consistency of 3.5%, with a reject rate per volume of 40% at a rotor speed of 12m/s and an average transit speed of 0.07 m/s.

As a main result of the fractionation, as shown in table 2, it can be seen that the separation of the particles occurs according to their respective sizes, which is reflected in the average length value of the fibers in each fraction as well as the respective fines content. In addition, the consistency values are also different, the good fraction being more diluted (consistency 2.81%) than the fraction obtained in the waste (consistency 3.91%).

Table 2: fines content and average fiber length data for standard and graded samples.

The efficiency of the fractionation process in improving the quality of the microfibrillated cellulose suspension is also demonstrated in the corresponding dynamic viscosity curve (thixotropic behaviour), as shown in figure 19.

The suspension produced in the graded good was refined with a 12 inch disk having a cut length of 95.5km/s (3.82 km/rev). For comparison, the BEKP samples were disk refined using two 12-inch disk refining stages, wherein the disk used in the two successive refining stages had cut lengths of 44.25km/s (1.77km/rev) and 95.5km/s (3.82 km/rev). In this case, the first stage produces a sample of fines with a length content of 65% or fines with an area content of 34.1%. The refined samples (standard BEKP and classified good) were analyzed for fines content (fines defined as particles smaller than 80 μm, fibers defined as other particles), the results are shown in table 3, showing the gain obtained by refining discs using classification between defibration stages, and showing the milled defibration of example 1.

Table 3: data on fines content of standard and fractionated samples.

In addition to the results of the morphological analysis, there was also a gain in the thixotropic properties of the nanofibrillated cellulose produced according to the method shown in fig. 20.