Modified microfibrillated cellulose comprising non-inorganic material, process for obtaining said modified microfibrillated cellulose, and use thereof

Abstract

The invention relates to a modified microfibrillated cellulose comprising highly fibrillated cellulose and non-inorganic material with high conductivity, high cationic demand, and high viscosity even after freezing or drying treatments. The invention also relates to a process for obtaining the modified cellulose by subjecting highly fibrillated cellulose and non-inorganic material to mechanical treatments. Use of the modified microfibrillated cellulose of the invention is related to applications in the manufacture of paper, textiles, paints and coatings, cement, mortar, and in household and personal care products.

Description

[0001] Modified microfibrillated cellulose comprising non-inorganic material, process for obtaining said modified microfibrillated cellulose and its use.

[0002] FIELD OF THE INVENTION

[0003]

[0001] The invention relates to a modified microfibrillated cellulose comprising highly fibrillated cellulose (HFC) and a non-inorganic material with high conductivity, high cation demand, and high viscosity even after freeze-drying treatments. The invention also relates to a process for obtaining the modified microfibrillated cellulose (MMFC) by subjecting a highly fibrillated cellulose and a non-inorganic material to mechanical treatments. The use of the modified microfibrillated cellulose of the invention relates to applications in the manufacture of paper, textiles, paints and coatings, cement, mortar, and in household and personal care products.

[0004] BACKGROUND

[0005]

[0002] Industries and the market are increasingly seeking environmentally friendly alternatives and renewable sources for the development of their products. Cellulose derivatives are important materials to contribute to this search, as they can be applied in different products as a primary raw material or as an additive to promote good properties and a focus on sustainability in a wide range of applications.

[0006]

[0003] Various biomass sources have been used to extract cellulose, for example, hardwood, softwood, sugarcane bagasse, and others. The characteristics and morphology of cellulose depend on the biomass source and the processes used to extract it. The cellulose obtained from extractions is commonly isolated or transformed into derivative materials according to the modification process applied.

[0004] Cellulose modification is traditionally used depending on the objective of the final application and the advantages sought by developers to meet performance expectations. These modifications can be done in different ways, such as chemical, mechanical, or biological methods, resulting in products with different characteristics.

[0007]

[0005] Non-inorganic materials can be combined with cellulose through different physical or chemical interactions to create modified celluloses with different chemical and mechanical properties. An example of a non-inorganic material is carboxymethylcellulose (CMC), which can be irreversibly bonded to the surface of the cellulose fiber, resulting in changes in surface charges and, consequently, changes in the behavior and properties of the fiber.

[0008]

[0006] Document WO2015 / 166141 discloses a method for producing a microfibrillated cellulose suspension using additives and a homogenizer or fluidizer. Although microfibrillated cellulose is obtained by mechanical means, the starting cellulose is an untreated pulp, to which additives are added before mechanical treatment, where this additive can be removed at the end of the process, as it is not definitively bound to the fiber.

[0009]

[0007] The present invention, on the other hand, provides a process for obtaining a modified microfibrillated cellulose that starts from a refining treatment, obtaining a highly fibrillated cellulose with specific characteristics and combining it with other mechanical treatments, adding a non-inorganic material at a determined stage of the mechanical fibrillation process. The modified microfibrillated cellulose exhibits an irreversible bond with a non-inorganic material, creating a new resulting product with unique mechanical and physicochemical properties.

[0008] There are different challenges in the manufacture of microfibrillated cellulose regarding process performance, the inclusion of additives, and also regarding the properties of the microfibrillated cellulose obtained in the process. Some of these challenges are described below.

[0010]

[0009] Regarding process performance, a significant challenge is the limitation on the use of mixing and pumping systems due to the high viscosity and low fluidity of microfibrillated cellulose during its manufacture. The formation of the fiber network promotes gel-like behavior, even at low consistencies, and this characteristic is unfavorable to the material's fluidity. Furthermore, it can influence the maximum solids content that can be used in the production of the material.

[0011]

[0010] Regarding microfibrillated cellulose obtained in the processes, one of the challenges is the loss of physicochemical properties of this microfibrillated cellulose after freezing or drying treatments, which are desirable or susceptible treatments applied to the product due to logistics and transportation. When dried or frozen, the fibers shrink due to the decrease in surface tension, and the existing pores collapse and disappear. Once rewetted, the pores regenerate only partially, resulting in the loss of the original structure, stiffening, and a reduction in the fiber's ability to retain water.

[0012]

[0011] Furthermore, another important challenge is the formation of granules when spreading microfibrillated cellulose on a surface. This technical problem is called the rolling effect and is an undesirable effect for some applications, as it can give the final application product a poor spreadability appearance.

[0013]

[0012] Regarding the use of additives in processes, a very common challenge is the pre-preparation of additives, which requires prior steps using various equipment or resources. For example, the difficulty in diluting carboxymethylcellulose, as it is not easily diluted in water or mixed with other ingredients, and the need for a prior preparation step before it is added to the manufacture of microfibrillated cellulose.

[0014]

[0013] Given the challenges outlined and other challenges related to the manufacture of microfibrillated cellulose, there is a need for a product that promotes flow in pumping and mixing systems, mitigating problems with equipment and process blockages during product manufacturing, and also a product that eliminates the need for pre-preparation of additives, saving time and costs for the manufacturer. In addition, there is a need for a product with satisfactory physical and chemical properties even after treatments such as freezing or drying, and that also mitigates the rolling effect to allow application in different end products.

[0015] SUMMARY OF THE INVENTION

[0016]

[0014] One objective of the present invention is to provide a process for obtaining a modified microfibrillated cellulose, first treating the cellulose pulp with a non-chemical technology, obtaining a highly fibrillated cellulose, subjecting it to mechanical treatments and adding a non-inorganic material to the medium at a determined stage after previous mechanical treatment steps.

[0017]

[0015] In one embodiment of the present invention, the process for obtaining modified microfibrillated cellulose comprises the steps of: a) subjecting a cellulose pulp to a refining treatment to produce highly fibrillated cellulose; b) subjecting the highly fibrillated cellulose from step a) to a mechanical treatment system and applying energy up to about 20 MWh / ton, preferably up to 8 MWh / ton; c) adding a non-inorganic material to the mechanical treatment system and applying energy up to about 10 MWh / ton, preferably up to 2 MWh / ton; d) discharging the product obtained in step c).

[0018]

[0016] In an optional embodiment of the present invention, the process comprises a dehydration step after step a) and / or step c).

[0019]

[0017] The process of the present invention starts from a cellulose pulp, wherein this cellulose pulp may originate from different production processes or treatments such as chemical, mechanical or enzymatic treatments, and is refined to obtain a highly fibrillated cellulose.

[0020]

[0018] After subjecting a cellulose pulp to a refining treatment, the highly fibrillated cellulose obtained has about 80% to 100% of the fiber length in a length-weighted distribution below 200 µm and about 2% to about 6% consistency, preferably about 4%.

[0021]

[0019] The mechanical treatment system comprises a shearing apparatus selected from the group consisting of a high shear mixer, grinder, colloid mill, homogenizer or microfluidizer.

[0022]

[0020] The added non-inorganic material is selected from the group consisting of cellulose derivatives (methylcellulose, hydroxypropylcellulose, carboxymethylcellulose), pectin and sodium alginate, preferably carboxymethylcellulose, and is added at a rate of about 1% to 20% of the total amount of highly fibrillated cellulose, based on dry mass, preferably at a rate of about 5% to 15%. The added non-inorganic material is in powder form or diluted in water, wherein when added in powder form it has about 90% to 100% solids content and in diluted form it has about 10% solids content. The product obtained in step d) has a solids consistency of about 1.0 to 20.0%, preferably about 5.5%.

[0023]

[0021] Another objective of the present invention is to provide a modified microfibrillated cellulose comprising a highly fibrillated cellulose and a non-inorganic material in which the viscosity range is from about 500 mPa.s to about 10 mPa.s, even after freeze-dry treatments, the conductivity range is from about 150 to about 2000 uS / cm, the cation demand range is from about 40 to about 1400 peq / L and exhibits reduced rolling formation.

[0024]

[0022] Modified microfibrillated cellulose also exhibits greater water retention.

[0025]

[0023] The modified microfibrillated cellulose of the invention has about 30% to about 85% of the fibers in a length-weighted distribution from about 20 µm to about 80 µm, wherein the fiber length distribution in the length-weighted distribution is as follows: i. 20 µm to 40 µm: about 15% to 40%; ii. 40 µm to 60 µm: about 10% to 25%; iii. 60 µm to 80 µm: about 5% to 20%.

[0026]

[0024] The non-inorganic material comprised in the modified microfibrillated cellulose of the invention is selected from the group consisting of cellulose derivatives (methylcellulose, hydroxypropylcellulose, carboxymethylcellulose), pectin and sodium alginate, preferably carboxymethylcellulose.

[0027]

[0025] The present invention is also related to the use of modified microfibrillated cellulose in the manufacture of paper, textiles, paints and coatings, cement, mortar and in household and personal care products.

[0028] FIGURES

[0029]

[0026] Figure 01 shows the viscosity behavior of highly fibrillated cellulose after freeze-dry treatments, as detailed in Example 1.

[0030]

[0027] Figure 02 shows the viscosity behavior of the modified microfibrillated cellulose after freeze-dry treatments, as detailed in Example 1.

[0031]

[0028] Figure 03 refers to the cation demand measurements of the modified microfibrillated cellulose from Example 2.

[0032]

[0029] Figure 04 refers to a graph of conductivity measurements of the modified microfibrillated cellulose from Example 3.

[0033]

[0030] Figure 05 refers to an image of highly fibrillated cellulose spread on a surface as detailed in Example 4.

[0034]

[0031] Figure 06 refers to an image of modified microfibrillated cellulose spread on a surface as detailed in Example 4.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036]

[0032] The process of the present invention combines a highly fibrillated cellulose and a non-inorganic material, subjecting them to a sequence of steps and parameters that results in a modified microfibrillated cellulose with unexpected mechanical properties and strength behavior. The combination of steps and parameters as per the sequence established in the process of the present invention allows for the elimination of the dilution step of the non-inorganic material when it is added in powder form.

[0037]

[0033] One embodiment of the present invention is a process for producing a modified microfibrillated cellulose, which process comprises the steps of: a) subjecting a cellulose pulp to a refining treatment to produce a highly fibrillated cellulose; b) subjecting the highly fibrillated cellulose from step a) to a mechanical treatment system and applying energy up to about 20 MWh / ton, preferably up to 8 MWh / ton; c) adding a non-inorganic material to the mechanical treatment system and applying energy up to about 10 MWh / ton, preferably up to 2 MWh / ton; d) discharging the product obtained in step c).

[0038]

[0034] In one embodiment, the dehydration step that is commonly required in cellulose manufacturing is performed optionally, since the previous steps and the characteristics of the resulting modified microfibrillated cellulose promote greater product consistency, allowing the product to be discharged directly after the mechanical treatment step. The exclusion of the dehydration step can bring benefits such as savings in processing time, equipment costs, and processing costs, for example, energy, water, and system costs.

[0039]

[0035] The highly fibrillated cellulose supplied in step a) is characterized by having more than 80% of the fiber length in a length-weighted distribution below 200 µm and a consistency between 2% and 6%.

[0040]

[0036] The cellulose pulp from step a) can be derived from different production processes or treatments, such as treatments selected from the group consisting of chemical, mechanical or enzymatic treatments, and is subsequently refined to obtain a highly fibrillated cellulose. It can be extracted from various sources, including, but not limited to, softwood, hardwood, soybeans, cotton, sugarcane and wheat straw. Cellulose pulp can be obtained from wood using processes such as kraft pulping, sulfite pulping and organosolv pulping. Cellulose pulp can be bleached, semi-bleached or unbleached and can also be a soluble pulp.

[0041]

[0037] In one embodiment of the invention, the mechanical treatment system of step b) is preferably a shearing apparatus selected from the group consisting of a high shear mixer, grinder, colloid mill, disc and cone refiner, homogenizer or microfluidizer. The energy applied to the system is up to about 20 MWh / ton, since this energy range promotes physical modifications in the highly fibrillated cellulose, making it suitable to react with the non-inorganic material that will be added in the next step, allowing a synergistic interaction between the materials, resulting in a modified microfibrillated cellulose with good and unexpected physical properties.

[0042]

[0038] The non-inorganic material may be selected from the group consisting of cellulose derivatives (methylcellulose, hydroxypropylcellulose, carboxymethylcellulose), pectin and sodium alginate, preferably the non-inorganic material is carboxymethylcellulose. The non-inorganic material is added to the mechanical treatment system in a proportion of about 1% to 20% of the amount of highly fibrillated cellulose, based on dry mass, preferably in a proportion of 5% to 15%. The non-inorganic material may be added in powder form or diluted in water, where the powder form has about 90% to 100% solids content and the diluted form has from about 1.0% to 10% solids content, preferably 5.5%.

[0043]

[0039] In one embodiment of the invention, when the non-inorganic material is added in powder form, the prior dilution step of the non-inorganic material is not required, allowing the non-inorganic material to be added directly to the mechanical treatment system. Dilution of the non-inorganic material is a common step in the industry, and eliminating this step can bring benefits such as savings in time, equipment costs, and processing costs, for example, energy, water, and system costs. This can simplify the process.

[0044]

[0040] During the development of the present invention, non-inorganic material was added at different stages of the process, including the simultaneous addition of highly fibrillated cellulose and non-inorganic material in the mechanical treatment system. The resulting modified cellulose did not exhibit satisfactory physical and mechanical properties. This shows that the stage of addition of the non-inorganic material and the characteristics of the highly fibrillated cellulose at the time of this addition are important points to achieve the optimized form of the modified microfibrillated cellulose.

[0045]

[0041] After the addition of the non-inorganic material, the mechanical treatment system continues to operate until it reaches approximately 10 MWh / ton of energy and a modified microfibrillated cellulose is obtained, with a solid consistency ranging from 2.0 to 10.0%, preferably 5.5%.

[0046]

[0042] The characteristics of highly fibrillated cellulose combined with the non-inorganic material, the interaction between these materials, the sequence of steps, the setting of parameters and the type of treatment applied, in this case shearing, promoted an optimized process, with clear and unexpected technical advantages for the processing and for the product obtained from it.

[0047]

[0043] During the invention process, it was possible to increase the consistency of the modified microfibrillated cellulose due to improvements in the product's rheology, which promotes better product flowability and pumpability. According to the results presented in Example 5, the flow point of the modified cellulose is less than 5 Pa, promoting a lower flow point compared to highly fibrillated cellulose, thus increasing the process flowability.

[0048]

[0044] Another embodiment of the present invention is a modified microfibrillated cellulose comprising a highly fibrillated cellulose and non-inorganic material wherein the modified microfibrillated cellulose has viscosity ranging from about 500 mPa.s to about 10 mPa.s, conductivity ranging from about 150 to about 2000 uS / cm, cation demand ranging from about 40 to about 2000 peq / L and exhibits low rolling formation.

[0049]

[0045] As shown in Example 4, the rolling effect is resolved by using modified cellulose. To measure this property, a 0.5 ml volume of the sample is applied to the center of a circle drawn on the forearm. Using a finger, circular movements are performed clockwise, and the number of rotations required for the appearance of rolling is counted, with a maximum limit of 100 rotations. A consistent movement rate was maintained for all samples; for example, two rotations per second. The result was measured by the number of circular movements required for the appearance of rolling. The modified microfibrillated cellulose did not form granules even after 100 circular movements, while the highly fibrillated cellulose formed granules with 10 circular movements.

[0050]

[0046] Modified microfibrillated cellulose also exhibits greater water retention.

[0051]

[0047] One of the most challenging problems faced in the processing or transport of microfibrillated cellulose is the hornification effect, which causes losses in the physicochemical properties of cellulose due to the formation of cross-links between cellulose fibrils by hydrogen bonds, after treatments such as drying and freezing, which cannot be broken by swelling forces during rewetting. As in some applications drying or freezing treatments are required or likely due to technical, transport or logistical issues, when the dried or frozen cellulose needs to be redispersed, the losses of properties are very clear.

[0052]

[0048] The modified microfibrillated cellulose of the present invention preserves the properties of the product even after drying or freezing processes, maintaining the viscosity and rheology of the product, mitigating or significantly reducing the hornification effect on the fibers, as shown in Example 1.

[0053]

[0049] Due to its enhanced advantages and the preservation of its physical and chemical properties, modified microfibrillated cellulose can be used in the manufacture of paper, textiles, paints and coatings, cement, mortar, and in household and personal care products.

[0054] EXAMPLES

[0055]

[0050] The examples presented in the present invention are not exhaustive, are intended to illustrate the invention and should not be used as a basis for limiting it.

[0056] Example 1

[0057]

[0051] In this example, the viscosity of the modified microfibrillated cellulose was measured after applying freeze-dry treatments.

[0058]

[0052] Viscosity measurements were taken at a shear rate between 10 s 1 and 2,000 s 1 , in samples at a concentration of 0.85% solids in aqueous medium, using an oscillatory rheometer with concentric cylinder geometry.

[0053] The results are presented in Table 1 and Figures 01 and 02, comparing the viscosity behavior after freezing and drying of the HFC without being modified by the process of the present invention and the viscosity behavior of the MMFC obtained from the present invention. The measurements shown in Table 1 were made at a shear rate of 130 s⁻¹. 1 .

[0059]

[0054] As can be seen in the graph and Table 1, compared to highly fibrillated cellulose which lost properties after freeze-dry treatments, the modified microfibrillated cellulose of the present invention maintained the viscosity and, consequently, the rheological properties of the product, which is a very important advantage for the final applications of MMFC.

[0060] Table 1

[0061] Example 2

[0062]

[0055] In this example, the cation demand of HFC and MMFC was measured by diluting the material to 1.5% dry matter content with ultrapure water and subjecting the sample to titration in a particle charge detector.

[0063]

[0056] The results are presented in Table 2 and Figure 03, where it can be observed that the modified microfibrillated cellulose showed an increased cation demand of up to 30 times when compared to highly fibrillated cellulose.

[0064] Table 2

[0065] Example 3

[0066]

[0057] In this example, the conductivity of modified microfibrillated cellulose (MMFC) was measured using a conductivity meter.

[0067]

[0058] Table 3 and Figure 4 show the increase in conductivity of the modified microfibrillated cellulose when compared to highly fibrillated cellulose.

[0068] Table 3

[0069] Example 4

[0070]

[0059] In this example, the rolling effect was evaluated. The rolling effect occurs when a product is applied to a surface through friction or circular movements, and the formation of small granules on that surface can be observed. It is an undesirable effect for some applications, as it can give the appearance of poor spreadability of the final application product.

[0071]

[0060] The evaluation of the rolling effect is done visually. Figure 05 shows the highly fibrillated cellulose, before being modified by the process of the present invention, spread on a forearm surface and Figure 06 shows the modified microfibrillated cellulose spread on the same surface.

[0072]

[0061] To perform this evaluation, a 0.5 ml volume of the sample is applied to the center of a circle drawn on the forearm. Using a finger, circular movements are performed clockwise, and the number of rotations required for the appearance of rolls is counted, with a maximum limit of 100 rotations. A consistent movement rate was maintained for all samples; for example, two rotations per second. The result was measured by the number of circular movements required for the appearance of rolls.

[0073]

[0062] Table 4 shows the number of circular movements required for the appearance of rolling by the spreading of highly fibrillated cellulose and modified microfibrillated cellulose. Table 4

[0074]

[0063] As can be observed, the modified microfibrillated cellulose did not form granules even after 100 circular movements, demonstrating that the modified cellulose solves the problem caused by the rolling effect.

[0075] Example 5

[0076]

[0064] This example describes the fiber length in the length-weighted distribution of modified microfibrillated cellulose using a fiber image processing fiber analyzer. According to the results obtained, a range of about 30% to about 85% of the modified microfibrillated cellulose has a length in the length-weighted distribution of about 20 pm to about 80 pm.

[0077]

[0065] More specifically, the modified microfibrillated cellulose exhibits a length-per-fiber distribution weighted by length as follows: i. 20 pm to 40 pm: approximately 15% to 40%; ii. 40 pm to 60 pm: approximately 10% to 25%; iii. 60 pm to 80 pm: approximately 5% to 20%.

[0078] Example 6

[0079]

[0066] In this example, the pour point of the samples was measured to evaluate the fluidity of the process. The pour point is the minimum force that must be exceeded for the sample to flow; therefore, the lower the pour point, the easier it is to pump the material.

[0080]

[0067] Table 5 shows the reduction in the Pour Point of modified microfibrillated cellulose when compared to highly fibrillated cellulose.

[0081] Table 5

[0082]

[0068] According to the results obtained, the MMFC Pour Point is 45% lower than the HFC Pour Point, demonstrating the increased fluidity of the process.

Claims

CLAIMS 1. Modified microfibrillated cellulose, characterized in that it comprises highly fibrillated cellulose and non-inorganic material, wherein the modified microfibrillated cellulose has a viscosity ranging from about 500 mPa.s to about 10 mPa.s, conductivity ranging from about 150 to about 2000 uS / cm, cation demand ranging from about 40 to about 2000 peq / L and exhibits low rolling formation.

2. Modified microfibrillated cellulose, according to claim 1, characterized in that the highly fibrillated cellulose has about 80% to 100% of fibers in the length-weighted distribution below about 200 µm.

3. Modified microfibrillated cellulose, according to claim 1, characterized in that the non-inorganic material is selected from the group consisting of cellulose derivatives (methylcellulose, hydroxypropylcellulose, carboxymethylcellulose), pectin and sodium alginate, preferably carboxymethylcellulose.

4. Modified microfibrillated cellulose, according to claim 1, characterized in that the fiber length distribution in the length-weighted distribution is as follows: i. 20 pm to 40 pm: about 15% to 40%; ii. 40 pm to 60 pm: about 10% to 25%; iii. 60 pm to 80 pm: about 5% to 20%.

5. Modified microfibrillated cellulose, according to claim 1, characterized in that it has conductivity preferably ranging from 500 to 1500 uS / cm and / or cation demand preferably ranging from 250 to 1400 peq / L.

6. Process for obtaining modified microfibrillated cellulose as defined in Claim 1, characterized in that it comprises the steps of: a) subjecting a cellulose pulp to a refining treatment to produce a highly fibrillated cellulose; b) subjecting the highly fibrillated cellulose from step a) to a mechanical treatment system and applying energy up to about 20 MWh / ton; c) adding a non-inorganic material to the mechanical treatment system and applying energy up to about 10 MWh / ton; and d) discharging the product obtained in step c).

7. Process according to claim 6, characterized in that it optionally comprises a dehydration step after step a) and / or step c).

8. Process according to claim 6, characterized in that the cellulose pulp originates from a process selected from the group consisting of chemical, mechanical or enzymatic treatments.

9. Process according to claim 6, characterized in that the refining treatment in step a) is preferably a mechanical treatment.

10. Process according to claim 6, characterized in that the highly fibrillated cellulose obtained in step a) has about 80% to 100% fibers in the length-weighted distribution below 200 µm.

11. Process according to claim 6, characterized in that the highly fibrillated cellulose obtained in step a) has a consistency of about 2% to about 6%, preferably about 4%.

12. Process according to claim 6, characterized in that the mechanical treatment system of step b) occurs in a shearing apparatus selected from the group consisting of a high shear mixer, grinder, colloid mill, disc and cone refiner, homogenizer or microfluidizer.

13. Process according to claim 6, characterized in that the non-inorganic material added in step c) is selected from the group consisting of cellulose derivatives (methylcellulose, hydroxypropylcellulose, carboxymethylcellulose), pectin and sodium alginate, preferably carboxymethylcellulose.

14. Process according to claim 13, characterized in that the non-inorganic material is added in step c) at a ratio of about 1% to 20% of the total amount of highly fibrillated cellulose, based on dry mass, preferably at a ratio of about 5% to 15%.

15. Process according to claim 13, characterized in that the added non-inorganic material is in powder form or diluted in water.

16. Process, according to claim 15, characterized in that the non-inorganic material added in powder form has a solids content of about 90% to 100% and in diluted form has a solids content of about 1% to 10%.

17. Process, according to claim 6, characterized in that the product obtained by step d) has a solids consistency of about 1.0 to 20.0%, preferably about 5.5%.

18. Use of the modified microfibrillated cellulose defined in claim 1, characterized by the fact that it is used in the manufacture of paper, textiles, paints and coatings, cement, mortar and in household and personal care products.

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