Systems and methods for producing microcrystalline cellulose

Abstract

A system for producing microcrystalline cellulose (MCC) is disclosed. A system is further disclosed that provides a new method for producing MCC by using mixing in a two-stage reactor system that allows for control of product average particle size and particle size distribution.

Description

[Technical field]

[0001] The present disclosure relates to a system for producing microcrystalline cellulose (MCC). The present disclosure further relates to a system that provides a new method for producing MCC by using mixing in a two-stage reactor system that allows for the adjustment of product average particle size and particle size distribution. [Background technology]

[0002] Microcrystalline cellulose (MCC) is a cellulosic product that has particle-like physical properties quite different from the raw material chemical pulp from which it is produced. Chemical pulp has a fiber-like structure, meaning a high length / thickness ratio, and in the MCC production process, it is converted into a particle-like product using an acid hydrolysis process.

[0003] The intensity of the hydrolysis process affects the product properties. The more chemicals used, the longer the residence time of the hydrolyzed material in the reactor, or the more concentrated the reaction slurry, the higher the hydrolysis intensity. This means that by varying the intensity of the acid hydrolysis in the MCC production process, different types of MCC products can be produced.

[0004] It is a well-known fact in chemical engineering science that mass transfer affects the efficiency of chemical reactions. Poor mass transfer leads to the formation of concentration gradients and slow reaction rates. This can occur, for example, in the acid hydrolysis process when MCC is produced.

[0005] The mixing phenomenon equalizes concentration gradients in one or more reactors by converting a heterogeneous mixture of materials into a homogeneous form. This can result in an increase in reaction rate, for example in MCC acid hydrolysis, which means a more efficient manufacturing process. Since mixing is a physical unit process, it also affects the product by mechanical means.

[0006] Thus, in MCC production, product properties are the result of a combination of several factors: chemical charge, process concentrations, time, temperature, mass transfer and physical stresses.

[0007] US Patent 2,978,446 discloses a method for producing MCC, in which acid is added to a reactor all at once and the reactor is started. No mixing during the hydrolysis reaction is mentioned. After hydrolysis, intense mechanical mixing / shearing lasting one hour is used to modify the product to create a viscous gel. US Patent 7,037,405 discloses a method for producing MCC using acid, and no mixing during the acid hydrolysis process is mentioned. Acid is added to the reactor all at once. This patent teaches the use of a harsh mechanical refiner after hydrolysis to produce very small MCC particles with a particle size range of 1.0-10.0 μm. WO 02 / 057540 discloses a method for producing MCC using undried pulp material and mixing the reacting slurry during the hydrolysis reaction. Acid is added to the reactor all at once. US 2012 / 0135505 discloses a process for making MCC where compressed cellulose feedstock is hydrolyzed using acid(s). The reaction slurry is stirred during the hydrolysis procedure and the acid is added to the reactor all at once. This patent does not teach the effect of mixing on the final product. US 4,391,973 discloses a MCC process where cellulose feedstock is hydrolyzed using acid(s) and the reaction mixture is stirred during the hydrolysis process, without mentioning the effect of mixing on the final product. WO 2019 / 095024 discloses the use of two separate reactors to make MCC. The pressure is reduced to atmospheric pressure between the reactors and washing of the intermediate product is performed. Acid is added to reactor 1 and reactor 2. Mixing during the hydrolysis process is not mentioned.

[0008] None of the known methods show the fact that the product properties can be adjusted by using very short mixing during or after hydrolysis. None of the known MCC manufacturing methods show the combination of split acid addition to the hydrolysis system. By carrying out the hydrolysis process of cellulose material in two stages, for example in a two-reactor system, and by carrying out multiple acid additions at several places in the reactor system, the process efficiency is higher and the yield is increased, as shown by Battista in the experiments of mild and severe hydrolysis with two-stage hydrolysis (Battista, OA, Hydrolysis and crystallization of cellulose, IND ENG CHEM, vol. 42, No. 3, 502-507).

[0009] Considering the known processes, there is a need for new methods to produce MCC that can vary the product properties using simple process solutions. Summary of the Invention

[0010] A method for producing microcrystalline cellulose (MCC) is disclosed. The method comprises: a. acid hydrolyzing a pulp mixture in a reactor to obtain a hydrolyzed process mixture; b. mixing the hydrolyzed process mixture to form MCC; Includes.

[0011] A system for preparing MCC is disclosed. The system may include at least one reactor.

[0012] Disclosed is microcrystalline cellulose (MCC) obtainable by the disclosed method or system.

[0013] The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate various embodiments. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a system for producing MCC according to the present disclosure, the system including one reactor. [Diagram 2] FIG. 1 is a schematic diagram of one embodiment of a system for producing MCC according to the present disclosure, the system including two reactors. [Diagram 3] FIG. 13 shows the values ​​of d-ratio after mixing MCC1 using a cut-off type mixer with different rpm and mixing times. [Figure 4] FIG. 1 shows the particle size distribution of MCC1 before mixing. [Diagram 5] FIG. 1 shows particle size distribution of MCC1 after mixing for 15 seconds using 15000 rpm. [Figure 6] FIG. 1 shows the d-ratio values ​​after mixing of MCC2 using a shear generating mixer at rpm 5000 at a temperature of 80° C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A method for producing microcrystalline cellulose (MCC) is disclosed. The method comprises: b. acid hydrolyzing the pulp mixture in a reactor to obtain a hydrolyzed process mixture; c. mixing the hydrolyzed process mixture to form MCC; may include:

[0016] 1 and 2 show exemplary embodiments of the process using a single reactor system or a two reactor system. In certain embodiments, mixing in the system can occur in one or several locations, and acid can be added to the system in one or several locations.

[0017] At an early stage in the process system is a pulp suspension that is used as a raw material to produce microcrystalline cellulose (MCC). In one embodiment of the invention, the acid (3) used in the MCC production can be added to the suspension at an early stage before the pulp enters the pumping vessel (2) or the like. The purpose of the pumping vessel is to balance the incoming pulp suspension flow before it enters the successive process stages. Alternatively, the pumping vessel can act as a mixing vessel if the addition of acid is done before the suspension or pulp enters it.

[0018] The pulp used to make MCC can be any suitable type of bleached chemical pulp, such as kraft pulp, prehydrolyzed kraft, sulfite pulp, semi-chemical pulp, mechanical pulp, non-wood pulp, reclaimed fiber, or any combination thereof. The pulp can be made from hardwood, softwood, grass, straw, waste paper, bamboo, or any combination thereof.

[0019] In certain embodiments, the consistency of the pulp prior to introduction into the pumping vessel can be about 2-50% by weight, about 3-45% by weight, or about 5-30% by weight.

[0020] In certain embodiments, the consistency of the pulp before being introduced into the first reactor can be about 2-30 wt%, about 3-25 wt%, or about 5-20 wt%, or about 8-15 wt%. In one embodiment, the consistency of the pulp before being introduced into the first reactor can be about 10 wt%.

[0021] The pulp suspension (1) is fed from a pumping vessel (2) to a process line (14). A booster pump (4) is used to pump the heated pulp suspension to the hydrolysis reactor to maintain the desired hydrolysis temperature and pressure. Process steam (5) used to heat the pulp to the hydrolysis temperature is fed to the process line either before or after the booster pump. In one embodiment of the present invention, the acid (3) used in the MCC production process can be added to the process line before and / or after the booster pump (4) in the process line (14).

[0022] In one embodiment, process steam is used to heat the pulp suspension to about 80-185° C., or 90-175° C., or 100-165° C., or 120-160° C. In one embodiment, process steam is used to heat the pulp suspension to about 130-160° C.

[0023] In certain embodiments, the acid hydrolysis of the pulp to form MCC can be carried out according to the methods disclosed in patent applications WO 2011 / 145600 or WO 2011 / 145601.

[0024] The heated and acidified pulp suspension enters the first reactor (7) where the cellulose in the pulp suspension is hydrolyzed, which means it is depolymerized, i.e. the degree of polymerization (DP) is reduced. During the hydrolysis process, local concentration gradients can occur, which can result in a decrease in the reaction rate, i.e. the efficiency of hydrolysis. In this kind of situation, the process will not work optimally and will not produce a uniform product. The pulp suspension can be mixed in the reactor to increase the uniformity of the material flow, eliminate the concentration gradients, better mix the chemicals, and increase the hydrolysis efficiency and product uniformity.

[0025] In one embodiment, the mixing can occur anywhere in the reactor before the materials exit or in a premixer (6) located before the entry point of the reactor. In the premixer and reactor, the chemical pulp fibers have not yet been hydrolyzed into microcrystalline cellulose and still have the chemical and physical properties of cellulose or pulp. This means that the cellulose does not meet the definition of microcrystalline cellulose as defined by the Food and Agriculture Organization of the United Nations.

[0026] In one embodiment, mixing occurs in reactor (7) using a mixer (8). In one embodiment, the process mixture is mixed in at least one reactor during the hydrolysis process. Mixing in the reactor or reactors helps to produce a homogenous process mixture to improve the efficiency of the hydrolysis.

[0027] In one embodiment, mixing can also take place at the output of the hydrolysis reactor, or in the process line after the output of the reactor in a mixer (9), or at the end of the process line (27) before removal of the MCC (13) in a mixer (10).

[0028] In certain embodiments, the mixing in any of the aforementioned mixers can be independently described by one of the following alternatives: 1. If the pulp suspension fibers have not been converted to microcrystalline cellulose (i.e., not hydrolyzed) and are still at least partially in a solid fibrous form described by a high degree of polymerization, the mixing effect is the production of a homogenous mixture. 2. If the hydrolysis process is already complete and a) the pulp has been hydrolyzed to microcrystalline cellulose in a chemical, but not necessarily physical, sense (meaning the pulp and / or MCC particles are still loosely bound or agglomerated in a fiber-like form) or b) the pulp has been hydrolyzed to microcrystalline cellulose in both a chemical and physical sense (meaning the pulp is fully hydrolyzed), the effect of mixing is to break down the material into particle-like MCC and / or adjust the properties of the final product, such as particle size distribution.

[0029] In certain embodiments, the produced MCC may flow through a process line (17) for further processing, such as washing, drying, and packing, etc. In one embodiment, the hydrolyzed process mixture from the first reactor is fed to a second reactor for further hydrolysis.

[0030] In certain embodiments, the material stream is directed to a second hydrolysis reactor after exiting the first hydrolysis reactor. In one embodiment, the material stream still at least partially in fibrous form is directed to the second hydrolysis reactor. In one embodiment, the process mixture is mixed at least once between the first reactor and the second reactor.

[0031] In certain embodiments, the hydrolysis process continues in a second hydrolysis reactor (19). The process and reactions in the second reactor are similar to those in the first reactor described above.

[0032] During the hydrolysis process in the second reactor, local concentration gradients may occur, resulting in a decrease in the reaction rate, i.e. the efficiency of hydrolysis. In this kind of situation, the process will not work optimally and will not produce a uniform product. The pulp suspension can be mixed in the reactor to increase the uniformity of the material flow, eliminate the concentration gradients, better mix the chemicals, and increase the hydrolysis efficiency and product uniformity.

[0033] In one embodiment, mixing can occur anywhere in the reactor (19) using a mixer (23) before the material exits the reactor, where the chemical pulp fibers have not yet been hydrolyzed to microcrystalline cellulose and still possess the chemical and physical properties of cellulose or pulp.

[0034] In certain embodiments, the mixing in any of the aforementioned mixers can be independently described by one of the following alternatives: 1. If the pulp suspension fibers have not been converted to microcrystalline cellulose (i.e., not hydrolyzed) and are still at least partially in a solid fibrous form described by a high degree of polymerization, the mixing effect is the production of a homogenous mixture. 2. If the hydrolysis process is already complete and a) the pulp has been hydrolyzed to microcrystalline cellulose in a chemical, but not necessarily physical, sense (meaning the pulp and / or MCC particles are still loosely bound or agglomerated in a fiber-like form) or b) the pulp has been hydrolyzed to microcrystalline cellulose in both a chemical and physical sense (meaning the pulp is fully hydrolyzed), the effect of mixing is to break down the material into particle-like MCC and / or adjust the properties of the final product, such as particle size distribution.

[0035] In one embodiment, mixing can also occur at the outflow of the material from the second hydrolysis reactor using mixer (24) or in the process line directly following the reactor using mixer (25).

[0036] In certain embodiments, mixing of the pulp or process mixture may occur at one or more independently selected points in the process prior to entering the first reactor, the first or second reactor, the outlet of the first or second reactor, a point in the process line between the first and second reactors, and / or the outlet of the process.

[0037] In one embodiment, the process includes premixing of the process mixture or pulp before entering the first reactor, and one or more additional mixing steps at a point in the process independently selected from the first or second reactor, the exit point of the first or second reactor, a point in the process line between the first and second reactors, and / or the exit point of the process.

[0038] In certain embodiments, acid may be added to the pulp or process mixture at one or more points in the process. In one embodiment, acid is added to the pulp or process mixture at least in the process line (14) before or after the booster pump (4). In certain embodiments, acid may be added to the process mixture in the mixer (9) as it exits the first reactor and / or before entering the second reactor (15). In one embodiment, acid is added to the process mixture between the first and second reactors.

[0039] In one embodiment, process steam (5) used to heat the pulp to hydrolysis temperatures is fed into the process line either before or after the booster pump. In one embodiment, additional process steam (16) is fed into the process line between the first and second reactors.

[0040] In one embodiment, the added steam heats the process mixture to a temperature of about 80-185° C., or 90-175° C., or 100-165° C., or 120-160° C. In one embodiment, the added steam is used to heat the pulp suspension to a temperature of about 130-160° C.

[0041] An acid is added to the process mixture to hydrolyze the pulp into microcrystalline cellulose. In one embodiment, the acid is selected from the group consisting of mineral acids and organic acids. The acid used may be a mineral acid. In one embodiment, the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, or any mixture thereof.

[0042] In one embodiment, the acid is added to the process mixture in an amount of 0.2 to 10% by weight based on the amount of solids.

[0043] High shear mixers used for mixing applications in the pulp and paper industry have the ability to break down the fiber network that forms when the pulp consistency is increased to levels of 6-15%, more typically when pulp is processed in the consistency range of 8-13%. For example, at a 10% consistency, pulp forms groups of fibers called flocs, the sizes of which range from 2-20 mm. A single fiber floc consists of tens of thousands of fibers. Breaking the fiber network is essential to process single fibers or microflocs or to obtain chemicals that come in contact with the fibers.

[0044] In one embodiment, the mixture is about 0.01 to 15.0 x 10 6 W / m 3 In certain embodiments, the mixing is performed at a low intensity of 0.01 to 1.0 × 10 6 W / m 3 Or high strength 1.0~15.0×10 6 W / m 3 In one embodiment, the mixing can be carried out using about 1.0-5.0×10 6 W / m 3 This is done by dissipating energy.

[0045] In one embodiment, the mixing time is 0.1 to 180 seconds. In a specific embodiment, the mixing time is 0.1 to 30.0 seconds, or 0.1 to 10.0 seconds, or 0.1 to 5.0 seconds.

[0046] In one embodiment, the process mixture is thoroughly mixed in the first reactor to achieve complete hydrolysis of the cellulose in the pulp. Once hydrolysis is complete, the hydrolyzed pulp is removed from the first reactor and mixed for a short period of time to homogenize the product MCC. In one embodiment, mixing occurs immediately upon removal of the hydrolyzed process mixture from the reactor. In one embodiment, additional mixing occurs after removal of the process mixture from the reactor.

[0047] In certain embodiments, the MCC is formed in a semi-batch or continuous manner. In certain embodiments, the MCC is formed in a continuous manner.

[0048] In one embodiment, the hydrolyzed process mixture is removed from the first reactor and mixed for a short period to provide a thoroughly mixed intermediate process mixture that is fed to the process line (17). In one embodiment, the feeding of the intermediate process mixture is controlled by a valve (12).

[0049] In one embodiment, the process mixture may be mixed immediately prior to removal from the process line using mixers (10, 25) to produce an MCC product with desired properties.

[0050] After removal from the process line, the MCC product may be subjected to processing steps such as drying.

[0051] In certain embodiments, the flow of the process mixture in the process lines and / or between the reactors can be controlled using pumps (4, 11, 26) and valves (12, 18).

[0052] The methods of the present disclosure have the additional utility of enabling the production of MCC having small particle size and narrow particle size distribution.

[0053] A system for producing MCC is also disclosed. In one embodiment, the system for producing MCC implements the method described above. The system for producing MCC includes at least one reactor. In one embodiment, each reactor in the system includes at least one mixer. In one embodiment, the system includes a first reactor in which a hydrolysis process is carried out. In a particular embodiment, the system includes at least a first and a second reactor. Pulp is fed into the system from a pumping vessel (2) connected to the first reactor by a process line (14).

[0054] In one embodiment, the process line includes a means for supplying an acid to the pulp. In one embodiment, the process line includes a means for supplying an acid to the pulp and a means for supplying steam to the pulp. In one embodiment, the system includes at least one pump for transporting the process mixture. In one embodiment, the process line also includes a mixer (6) for mixing the pulp and the acid to form a homogenous process mixture. In one embodiment, the system includes at least one mixer outside of the at least one reactor.

[0055] From the process line, the process mixture is fed into a first reactor. After a predetermined residence time in the first reactor, the process mixture is removed from the first reactor. In one embodiment, the process mixture is mixed for a short period of time after being removed from the first reactor. In one embodiment, the system includes at least one mixer at the outlet of each of the at least one reactor.

[0056] In one embodiment, the process mixture removed from the first reactor is subsequently mixed briefly upon removal from the first reactor to form the MCC composition, which is sent to a second process line (17). In certain embodiments, the second process line includes pumps and / or valves to control the flow of the MCC composition from the first reactor. In one embodiment, the second process line is a process line that is connected to the MCC composition removal system (18) where the MCC composition is removed from the system (MCC アウト, 13) to mix the MCC composition. In one embodiment, the system includes at least one mixer in the process line.

[0057] In one embodiment, the system for producing MCC includes a second reactor (19) connected to the first reactor by a second process line (17). In certain embodiments, the second process line includes a pump and / or a valve for controlling the flow of the process mixture from the first reactor. In certain embodiments, the second process line includes a means for adding steam (16) to the process mixture to heat the process mixture prior to the second reactor. In one embodiment, the second process line includes a means for adding an acid (15) to the process mixture.

[0058] In one embodiment, the acid is added to the process mixture between the first and second reactors. In one embodiment, the acid (20) can be added to the process mixture in connection with mixing the process mixture leaving the first reactor. In one embodiment, the second process line includes a valve (12) for controlling the flow of the process mixture to the second reactor. In one embodiment, the second process line includes a mixer (10) for briefly mixing the process mixture immediately prior to entering the second reactor. In one embodiment, the system includes a means for adding the acid to the process mixture and / or the process line.

[0059] In the second reactor, the hydrolysis of the cellulose contained in the process mixture is completed to form the MCC composition. In one embodiment, the second reactor includes a mixer (23) to ensure complete mixing of the process mixture and complete hydrolysis of the cellulose. After a certain residence time in the second reactor, the formed MCC composition is removed. In one embodiment, the MCC composition is mixed for a short time as soon as it is removed from the second reactor and fed to a third process line (21). In one embodiment, the third process line includes a mixer (25) that mixes the process mixture before it is removed from the system (22). In a particular embodiment, the third process line includes a pump and / or a valve to control the flow of the MCC composition from the system.

[0060] In certain embodiments, the system operates in a semi-batch or continuous mode, hi certain embodiments, the system operates continuously.

[0061] Once the MCC composition is removed from the system, any final treatments may be applied to it, non-limiting examples of which include removing water from the MCC composition, drying the MCC, and / or sorting by particle size the MCC formed in the process or system.

[0062] The disclosed system has the additional utility of enabling the production of MCC having small particle size and narrow particle size distribution.

[0063] Using the method or system of the present disclosure, it is possible to produce MCC with uniform size distribution and small particle size. By adjusting the various mixing steps, it is possible to adjust the particle size of the produced MCC to a desired value and provide an MCC product with a narrow and uniform size distribution.

[0064] Disclosed herein is an MCC obtained by the above method. Disclosed herein is an MCC obtained by the above system using the above method.

[0065] The MCC product formed using the methods or systems described herein may have an average particle size of about 10-250 μm. In certain embodiments, the MCC has an average particle size of 20-200 μm, 25-150 μm, 30-100 μm, or 35-75 μm.

[0066] The formed MCC may have a d10 of less than 30 μm, a d50 of less than 60 μm, and a d90 of less than 300 μm. In certain embodiments, the MCC has a d10 of less than 28 μm, or less than 26 μm, or less than 24 μm, or less than 22 μm, or less than 20 μm, a d50 of less than 55 μm, or less than 50 μm, or less than 45 μm, or less than 40 μm, or less than 35 μm, or less than 30 μm, and a d90 of less than 275 μm, or less than 250 μm, or less than 225 μm, or less than 200 μm, or less than 175 μm.

[0067] The d ratio of the MCC formed may be in the range of 1.0 to 6.0. In certain embodiments, the d ratio of the MCC is less than 6.0, or less than 5.5, or less than 5.0, or less than 4.5, or less than 4.0.

[0068] By varying the mixing speed and mixing time of one or more of the mixes in the described methods, it is possible to control both the size and size distribution of the MCC formed in the process.

[0069] The D values ​​(d10, d50 and d90) indicate what percentage (10%, 50% or 90%) of the particles are above a certain micrometer size. The d ratio is

number

[0070] In one embodiment, the MCC products of the present disclosure can be used in pharmaceutical applications, cosmetics, food and beverage applications, or any combination thereof as further disclosed.

[0071] The MCC products described herein have the added advantage of having both a small particle size and a narrow particle size distribution as compared to MCC produced by other processes.

[0072] The MCC compositions described herein have the added advantage of having both a small particle size and a narrow particle size distribution as compared to MCC produced by other processes. EXAMPLES

[0073] Reference will now be made in detail to the various embodiments.

[0074] The following description discloses several embodiments in detail to enable one skilled in the art to utilize the embodiments based on the present disclosure. Not every step or feature of the embodiments is described in detail, and many of the steps or features will be apparent to one skilled in the art based on this specification.

[0075] The following examples describe how blending, when performed during or after the hydrolysis reaction, affects the properties of the MCC product. Definitions: The d values ​​(d10, d50, and d90) indicate what percentage (10%, 50%, or 90%) of the particles are below a particular micrometer size. The d ratio is

number

[0076] Example 1 Effect of mixing on MCC particle size distribution after hydrolysis. Hardwood-based chemical pulp was used as the raw material to prepare two microcrystalline cellulose products, MCC1 and MCC2, whose particle size d values ​​and d ratios are shown in Table 1. [Table 1]

[0077] The mean particle size of MCC1 and MCC2 were 55.2 μm and 50.8 μm, respectively. The acid hydrolysis process used mild reaction conditions, so the d90 values ​​remained at high levels of 359.7 (MCC1) and 280.5 (MCC2). The d-ratio was 6.2 for MCC1 and 5.2 for MCC2. Thus, both products had very broad particle size distributions. Both products were washed to neutral pH after hydrolysis.

[0078] Blending experiments were carried out on the MCC product in order to adjust the mean particle size, and especially the width of the particle size distribution, to achieve much lower d-ratios.

[0079] A high shear mixer was used to mix MCC1 using a concentration of 5% after the hydrolysis process. The rpm value of the mixer was varied and mixing times ranging from 5 s to 635 s were used.

[0080] Figure 3 shows the value of the d-ratio after mixing MCC1 using different rpm and mixing times. A cut-type mixer was used as the mixer. Figure 3 shows that even after a short 5-15 s mixing, the d-ratio value decreases by about 40%. When using a high rpm, the d90 value of MCC decreases from 359.7 μm to 230.9 μm after 5 s and to 178.7 μm after 15 s. This means that the fraction of larger particles decreases, the d-ratio decreases, and the particle size distribution becomes narrower. Figure 4 shows the particle size distribution of MCC1 before mixing, and Figure 5 shows the particle size distribution of MCC1 after 15 s mixing.

[0081] The effect of mixing on size distribution is evident when using short mixing after hydrolysis. Short mixing removes the trimodal shape of the distribution and transforms it into a more uniform distribution form. At the same time, the average particle size decreases from 55.2 μm to 42.3 μm.

[0082] Figure 6 shows the effect of mixing on MCC2. The mixing concentration used was 10%, the MCC-water slurry was heated to 80°C before mixing, and 5000 rpm was used. The mixer device used was a shear generating mixer as compared to the previous case.

[0083] Figure 6 shows that a short 15 second period is sufficient to reduce the d-ratio from 5.2 to 3.2, a reduction of almost 40%. The d90 value, which indicates the fraction of larger particles, is 280.5 μm before mixing and decreases to 124.9 μm after 15 seconds. At the same time, the average particle size decreases from 50.8 μm to 34.9 μm.

[0084] Example 2 Effect of mixing during hydrolysis on MCC particle size distribution. To see the effect of mixing during acid hydrolysis in MCC production, a Lodige DVT5 reactor was used. The reactor was equipped with a heating jacket and steam was used as the heat carrier. The diameter of the Lodige reactor chamber was 200 mm, the height was 230 mm, and the volume of the reactor was 7.2 dm 3 From the control unit it was possible to adjust the rpm of the chopper (diameter 50 mm, max. rpm 3000, max. achievable peripheral speed 7.9 m / s) and the mixing blades (diameter 190 mm, max. rpm 250, max. achievable peripheral speed 2.5 m / s). The chopper mixer was a fluidizing mixer used to impart high shear forces to the reacting slurry, whereas the blades were for stirring. A reactant concentration of 10%, a sulfuric acid dosage of 1.5%, a temperature of 150° C. and a P-factor of 30 were used for the MCC production. Table 2 shows the obtained particle sizes of the three test points. [Table 2]

[0085] From Table 2, it can be seen that by increasing the mixing intensity, the produced particle size becomes smaller, the particle size distribution becomes narrower, and the d ratio becomes smaller.

[0086] It is obvious to those skilled in the art that with the advancement of technology, the basic idea can be realized in various ways. Therefore, the embodiments are not limited to the above examples, instead, they may vary within the scope of the claims.

[0087] The above-mentioned embodiments can be used in any combination with each other. Some embodiments may be combined to form further embodiments. The method, system or MCC composition disclosed herein may include at least one of the embodiments described herein above. It will be understood that the benefits and advantages described above may relate to one embodiment or to several embodiments. The embodiments are not limited to those that solve any or all of the problems described or those that have any or all of the benefits and advantages described. It will be further understood that a reference to "an" item refers to one or more of those items. The term "comprising" is used herein to mean including the feature(s) or operation(s) that follows it without excluding the presence of one or more additional features or operations.

Claims

1. A method for preparing microcrystalline cellulose (MCC), comprising the steps of: a. acid hydrolyzing a pulp mixture in a reactor to obtain a hydrolyzed process mixture; b. mixing the hydrolyzed process mixture to form MCC, wherein the process mixture is mixed in the at least one reactor during the hydrolysis process, and the mixing is between about 1.0 and 15.0×10 ６ W / m ３ and a mixing time of 5 to 180 seconds; Including, The method wherein the d ratio of the MCC formed is less than 6.

0.

2. 10. The method of claim 1, wherein one mixing occurs immediately upon removal of the hydrolyzed process mixture from the reactor.

3. 10. The method of claim 1, wherein additional mixing occurs after removing the process mixture from the reactor.

4. The method of claim 1 , wherein the MCC is formed continuously.

5. 10. The method of claim 1, wherein the hydrolyzed process mixture from the first reactor is fed to a second reactor for further hydrolysis.

6. 6. The method of claim 5, wherein an acid is added to the process mixture between the first reactor and the second reactor.

7. 6. The method of claim 5, wherein the hydrolyzed process mixture removed from the first reactor is mixed prior to being fed to the second reactor.

8. 6. The method of claim 5, wherein the process mixture is mixed at least once between the first reactor and the second reactor.

9. 2. A system for preparing MCC according to the method of claim 1, comprising at least one reactor, said system comprising at least one mixer in each of said at least one reactor, and mixing is performed at a rate of about 1.0 to 15.0×10 ６ W / m ３ and including means for adding acid to said process mixture and / or process line.

10. 10. The system of claim 9, wherein the system includes at least one pump for transporting the process mixture.

11. The system of claim 9 , wherein the system includes at least one mixer external to the at least one reactor.

12. 10. The system of claim 9, wherein the system includes at least one mixer at an outlet of each of the at least one reactor.

13. The system of claim 9 , wherein the system includes at least one mixer in the process line.

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