Method for chemically modifying amorphous cellulose

Abstract

The present invention relates to a method for chemically modifying amorphous cellulose and cellulose chemically modified thereby, wherein the method comprises the steps of: performing an ultrasonic pulverization process on a mixed solution including cellulose, NaOH, and distilled water to pretreat at least a portion of the crystalline region of cellulose into an amorphous region, thereby obtaining amorphized pretreated cellulose; and performing a shear mixing process on a mixture including the pretreated cellulose, acetone, and acrylonitrile to obtain cellulose in which at least a portion of the amorphous cellulose is modified with cyanoethyl cellulose (CEC).

Description

Chemical modification method of amorphous cellulose

[0001] The present invention relates to a method for chemically modifying amorphous cellulose capable of low-temperature and high-speed processing, and to cellulose chemically modified according to this method.

[0002] With the recent advancement of polymer chemical materials, cellulose is increasingly being applied as a cutting-edge material across the entire plastic composite industry. This trend is driven by its excellent mechanical properties as well as the advantage of being a biomass extracted from plants, which is why it is combined with synthetic resins and compounds in composites.

[0003] Cellulose is a component extracted from wood pulp, but it is difficult to apply it directly; therefore, it is used as a polymer and composite material. To this end, technology is being developed to modify the physicochemical properties of cellulose by modifying the -OH groups of its functional groups, thereby enabling its composite formation with heterogeneous materials.

[0004] Korean Patent Publication No. 10-2022-0143608 relates to a method for modifying the surface of cellulose using an electrochemical reaction. While the technology achieves a high surface modification rate through an electrochemical reaction using a TEMPO catalyst, there is a problem that modification occurs only on the surface.

[0005] In addition, Korean Patent Publication No. 10-2016-0000919 relates to the hydrophobic modification of the surface of cellulose using radiation and composite materials utilizing the same. While this technology enables the hydrophobic modification of cellulose into silane groups and composite formation with polymer resins within a short period of time in an environment free from high temperature, high pressure, and chemical additives, it has the disadvantage of requiring the use of radiation equipment.

[0006] The present invention is intended to provide a method for modifying cellulose capable of low-temperature and high-speed processing, and cellulose chemically modified according to this method.

[0007] The above and other objects and advantages of the present invention will become apparent from the following description describing preferred embodiments.

[0008] The present invention provides a method for chemically modifying amorphous cellulose, comprising the steps of: performing an ultrasonic grinding process on a mixed solution containing cellulose, NaOH, and distilled water to pre-treat at least a portion of the crystalline region of the cellulose into an amorphous region to obtain amorphous pre-treated cellulose; and performing a shear mixing process on a mixture of the pre-treated cellulose, acetone, and acrylonitrile to obtain cellulose in which at least a portion of the amorphous cellulose is modified into cyanoethyl-cellulose (CEC).

[0009] In addition, the present invention provides cellulose chemically modified according to the chemical modification method.

[0010] In addition, the present invention provides a polymer composite material comprising the chemically modified cellulose.

[0011] According to the present invention, a portion of the crystalline region of cellulose is pretreated into an amorphous region through an ultrasonic grinding process under room temperature and atmospheric pressure conditions, and the amorphous cellulose is chemically modified to obtain modified cellulose with a high modification introduction rate.

[0012] However, the effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below.

[0013] FIG. 1 is a flowchart of a cellulose modification process according to one embodiment of the present invention.

[0014] Figure 2 is the FT-IR analysis result of cellulose before modification, and Figure 3 is the FT-IR analysis result of cyanoethyl cellulose after modification of Example 7.

[0015] The present invention will be described in detail below.

[0016]

[0017] The present invention relates to a method for chemically modifying amorphous cellulose, comprising the steps of: performing an ultrasonic grinding process on a mixed solution containing cellulose, NaOH, and distilled water to pre-treat at least a portion of the crystalline region of the cellulose into an amorphous region to obtain amorphous pre-treated cellulose; and performing a shear mixing process on a mixture of the pre-treated cellulose, acetone, and acrylonitrile to obtain cellulose in which at least a portion of the amorphous cellulose is modified into cyanoethyl-cellulose (CEC).

[0018] Cellulose consists of 70% crystalline regions and 30% amorphous regions. The crystalline regions have a high density of cellulose structures.

[0019] Modification is difficult in crystalline regions because strong intermolecular and intramolecular hydrogen bonds form a dense network, preventing modifying functional groups from penetrating these regions.

[0020] Therefore, cellulose requires a pretreatment to convert crystalline regions into amorphous regions in order to increase the modification rate and yield (degree of substitution (DS)).

[0021] The method for pre-treating amorphous regions of cellulose according to the present invention comprises the step of performing an ultrasonic grinding process on a mixed solution comprising cellulose, NaOH, and distilled water to modify at least a portion of the crystalline regions of cellulose into amorphous regions, thereby obtaining amorphous pre-treated cellulose.

[0022] The cellulose contained in the above mixed solution is untreated cellulose.

[0023] The above-mentioned pretreated cellulose may have a degree of amorphousness of 55% or more, preferably 65% ​​or more.

[0024] Through the ultrasonic grinding process, a portion of the crystalline region of cellulose is modified into an amorphous region by destroying the hydrogen bonding structure formed between cellulose molecules through localized physical vibrations.

[0025] In this invention, the degree of amorphousness was improved by controlling the temperature, pressure, time, and pH of the ultrasonic grinding process.

[0026] In one embodiment of the present invention, the ultrasonic grinding process may be carried out for 30 to 50 minutes under conditions of room temperature-atmosphere pressure (25℃-1 bar) and pH 10.0 or higher.

[0027] The above NaOH acts as a catalyst in the cellulose amorphous pretreatment process.

[0028] The degree of amorphousness can be improved by increasing the amount of NaOH added.

[0029] In one embodiment of the present invention, the degree of amorphousness was compared according to the NaOH content, and when the NaOH content was 0.01 wt% and the pH was 10.0 to 10.5, ultrasonic grinding was performed for 30 to 50 minutes at room temperature and atmospheric pressure (25℃-1 bar), and the degree of amorphousness was 65% or more.

[0030] Many environmental byproducts can be generated during the process of neutralizing alkalinity caused by the addition of NaOH. Experimental results showed that when the NaOH content is 0.11 wt% (pH 12.5), there is a problem in that environmental byproducts are generated excessively compared to the effect of increasing amorphousness.

[0031] Accordingly, it is preferable that the above NaOH content is 0.01 to 0.05 weight% and the pH is 10.0 to 10.5.

[0032] The above-mentioned mixed solution containing cellulose, NaOH, and distilled water may be shear-mixed prior to the ultrasonic grinding process.

[0033] Shear mixing can be carried out at 100 to 250 rpm.

[0034] The method for pre-treating amorphous regions of cellulose according to the present invention further comprises the step of performing a shear mixing process on a mixture of pre-treated cellulose, acetone, and acrylonitrile to obtain cellulose in which at least a portion of the amorphous cellulose is modified into cyanoethyl-cellulose (CEC).

[0035] The above-mentioned pretreated cellulose may be dried to evaporate moisture and then dispersed again in a solvent.

[0036] The acrylonitrile above modifies the -OH groups of cellulose to -CN to form cyanoethyl-cellulose (CEC).

[0037] The above acetone acts as a solvent for insoluble acrylonitrile.

[0038]

[0039] The higher the degree of amorphousness of the above-mentioned pretreated cellulose, the higher the modification introduction rate.

[0040] In one embodiment of the present invention, shear mixing may be carried out at 150 to 300 rpm for 30 to 240 minutes under conditions of 30 to 60°C and a pH of 10.0 or higher.

[0041] Preferably, in one embodiment of the present invention, the shear mixing may be carried out for 50 to 70 minutes at 200 to 300 rpm under conditions of 35 to 60°C and pH 10.0 to 10.5.

[0042] The above amorphous cellulose may have a cyano group modification introduction rate (DS) of 1.3 or higher, preferably 1.4 or higher.

[0043] In addition, the present invention provides cellulose chemically modified according to the above method.

[0044] The chemically modified cellulose mentioned above may be one in which at least a portion of amorphous cellulose is esterified and cyanoethylated to be modified into cyanoethyl-cellulose (CEC).

[0045] In addition, the present invention provides a polymer composite material comprising the chemically modified cellulose.

[0046] According to the present invention, chemically modified cellulose can be combined with synthetic resin compounds and utilized as a polymer composite material across various industries.

[0047]

[0048] Hereinafter, the structure of the present invention and the resulting effects are to be explained in more detail through specific embodiments and comparative examples. However, these embodiments are intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[0049] Ingredients

[0050] Cellulose: Daejeong Chemical Co. Micro Cellulose, Crystalline (20-100㎛)

[0051] NaOH: Samjeon Sunyak Co. Sodium Hydroxide

[0052] Shear Mixer: MTOPS MS3060D

[0053] Ultrasonic Grinder: BIO KONVISIONQ BKNE-1000

[0054]

[0055] <Examples 1 to 4>

[0056] Pretreatment of the cellulose crystalline region was carried out using a Shear Mixer and an ultrasonic grinder under the composition, temperature, pressure, and dispersion conditions listed in Table 1 below.

[0057] <Comparative Examples 1 to 6>

[0058] Pretreatment of the cellulose crystalline region was carried out using a Shear Mixer with the composition, temperature, pressure, and dispersion conditions listed in Table 1 below.

[0059] Classification Composition (wt%) Temperature Pressure Dispersion Condition Alkalinity Degree of Amorphousness Cellulose Distilled Water NaOH ℃ bar Shear Mixer (rpm) Ultrasonic Grinder (kHz) Time (min) pH% Comparative Example 15 Residue 0.07 160 3320 -480 11.246 Comparative Example 25 Residue 0.01 160 3320 -480 10.232 Comparative Example 35 Residue 0.07 25 1320 -480 11.436 Comparative Example 45 Residue 0.00 325 1200 12.44 09.353 Comparative Example 55 Residue 0.01 25 1200 12.42 10.2 59 Comparative Example 65 Remaining amount 0.01 25 1200 12.4 60 10.07 1 Example 15 Remaining amount 0.01 25 1200 12.4 40 10.36 9 Example 25 Remaining amount 0.11 25 1200 12.4 40 12.57 1 Example 35 Remaining amount 0.01 60 1200 12.4 40 10.26 9 Example 45 Remaining amount 0.01 25 1200 23.9 40 10.27 4

[0060]

[0061] <Experimental Example 1> Evaluation of Amorphous Degree

[0062] XRD measurements were performed on the cellulose pretreated in Examples 1 to 4 and Comparative Examples 1 to 6, and the degree of crystallinity (CI) was calculated using the Segal method with the following formula.

[0063] [Degree of Crystallization]

[0064]

[0065] CI: Crystallinity Index, expressed as a percentage

[0066] I CR : Maximum intensity of the crystallinity peak in the XRD pattern of cellulose

[0067] I am : Minimum intensity of the amorphous region in the XRD pattern of cellulose

[0068] Next, the degree of amorphousness (%) was calculated using the formula “100 - degree of crystallization (%)”, and the results are shown in Table 1 above.

[0069]

[0070] As shown in Table 1 above, when pretreated according to the conventional cellulose pretreatment (amorphous) composition ratio and conditions (high temperature (160℃), high pressure (3 bar), strong alkali (pH 11.2), 8 hours) as in Comparative Example 1, the degree of amorphousness was 46%, which is an average level.

[0071] As in Comparative Example 2, when pretreated under weak alkaline conditions (pH 10.2), high temperature (160℃), and high pressure (3 bar), the degree of amorphousness was low at 32%.

[0072] As in Comparative Example 3, the process was carried out under room temperature and atmospheric pressure conditions, and when pretreated under conventional strong alkaline conditions (pH 11.4), the degree of amorphousness was low at 36%.

[0073] Comparative Example 4 was a case where an ultrasonic grinder (200 rpm, 40 min) was applied under conditions of 0.003 wt% NaOH (pH 9.3), room temperature, and atmospheric pressure, and the degree of amorphousness was low at 53.

[0074] In the case of Example 1 (0.01 wt% NaOH, applied to an ultrasonic grinder) and Example 2 (0.11 wt% NaOH, applied to an ultrasonic grinder), the degree of amorphousness was found to be 69 and 71, respectively.

[0075] As a result of comparing Example 3 (hot water bath at 60°C) and Example 4 (room temperature at 25°C), it was confirmed that the degree of amorphousness is excellent even under room temperature conditions.

[0076] In the case of Comparative Example 5 (dispersion time 20 minutes), the degree of amorphousness was low at 59, and in the case of Comparative Example 6 (dispersion time 60 minutes), the degree of amorphousness increased to 71, but the increase in the degree of amorphousness was not significant compared to the increase in dispersion time. From this, it was confirmed that the optimal dispersion time is 40 minutes.

[0077] When the ultrasonic grinder intensity was increased to 23.9 (kHz) as in Example 4, the degree of amorphousness increased, but there was no significant difference from Example 1.

[0078] <Examples 5 to 11>

[0079] Chemical modification of amorphous cellulose, including the preparation of cyanoethyl cellulose (CEC), was carried out using a Shear Mixer under the composition and modification conditions listed in Table 2 below. Figure 2 shows the FT-IR analysis results of cellulose before modification, and Figure 3 shows the FT-IR analysis results of cyanoethyl cellulose after modification in Example 7.

[0080] <Comparative Examples 7 to 10>

[0081] Chemical modification of amorphous cellulose, including the preparation of cyanoethyl-cellulose (CEC), was carried out using a Shear Mixer under the composition and modification conditions listed in Table 2 below.

[0082] Classification Composition (wt%) Modification Condition Alkalinity Modification Intake Rate Pretreatment Cellulose Acetone Distilled Water Acrylonitrile NaOH Temperature (°C) Shear Mixer (rpm) Time (min) pHDS Value Comparative Example 7 10 (Comparative Example 1) 50 50 90.1 27 0 240 48 0 11.4 0.88 Comparative Example 8 10 (Comparative Example 1) 50 50 90.1 24 0 240 48 0 11.3 0.64 Comparative Example 9 10 (Comparative Example 1) 50 50 90.1 24 0 240 60 11.3 0.44 Comparative Example 10 10 (Example 1) 50 50 90.0 24 0 240 60 9.3 0.96 Example 5 10 (Example 1) 50 50 90.0 64 0 240 60 10.2 1.41 Example 6 10 (Example 1) 505090.12402406011.41.29 Example 710 (Example 1) 505090.06252406010.11.02 Example 810 (Example 1) 505090.06602406010.21.36 Example 910 (Example 1) 505090.06402404010.11.17 Example 1010 (Example 1) 505090.064024012010.21.39 Example 1110 (Example 1) 505090.064024018010.01.42

[0083]

[0084] <Experimental Example 2> Evaluation of Modification Introduction Rate

[0085] For the cellulose modified in Examples 5 to 11 and Comparative Examples 7 to 10, the degree of substitution was calculated using the DS calculation method based on elemental analysis and is shown in Table 2.

[0086] [Modification Introduction Rate]

[0087]

[0088] The above modification introduction rate refers to the number of substituted modification functional groups, in this case -CN groups, per 1 repeating unit of cellulose. Since there are 3 -OH groups per 1 repeating unit of cellulose, the maximum DS value is 3.0.

[0089] Table 2 above shows the results of cyanoethyl group modification performed on the cellulose pretreated in Comparative Example 1 and Example 1.

[0090] From the results of Examples 5 and 6, it can be seen that the modification rate varies depending on the amount of NaOH added and the pH conditions, and that a high modification rate of DS value 1.4 or higher can be achieved when the optimal pH value is 10.

[0091] In both Example 7 and Example 8, which were conducted by changing the temperature from Example 5 to room temperature (25℃) and medium temperature (60℃), the modification introduction rate was lower compared to Example 5, so it can be seen that the optimal temperature is 40℃ and if the optimal temperature is not maintained, the modification introduction rate decreases.

[0092] When comparing the results of Examples 9, 10, and 11, which were conducted by adjusting the modification time (40, 120, 180 min) in Example 5, Example 9, with a modification time of 40 min, had the lowest modification introduction rate, and in the case of Example 10, with a modification time of 120 min, and Example 11, with a modification time of 180 min, there was no increasing trend in the modification introduction rate compared to Example 5, with a modification time of 60 min.

[0093] Comparative Examples 7 to 9 were modified using the pretreated cellulose of Comparative Example 1 under conditions of 0.12 wt% NaOH input and pH 11. Although Comparative Example 7, which was modified at a temperature of 70°C, had a relatively higher modification rate than Comparative Example 8, which was modified at 40°C, all were 1 or less. In cases where the modification time was short, such as Comparative Example 9, the modification rate was very low. In the case of Comparative Example 10, modification was performed on the pretreated cellulose of Example 1, but the modification was carried out under conditions of pH 9.3, resulting in a low modification rate of 0.96.

[0094]

[0095] [National R&D projects that supported this invention]

[0096] [Project ID] 2410001114

[0097] [Project No.] RS-2024-00431408

[0098] [Ministry Name] Ministry of Trade, Industry and Energy

[0099] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0100] [Research Project Name] Materials and Components Technology Development Project (Package Type)

[0101] [Research Project Title] Manufacturing Technology for High-Performance Gel Electrolytes with High-Strength, High-Elasticity Structure

[0102] development

[0103] [Project Executing Organization Name] R&F Chemical Co., Ltd. [Lead Organization]

[0104] [Research Period] July 1, 2024 ~ December 31, 2027

Claims

1. A step of obtaining amorphous pre-treated cellulose by performing an ultrasonic grinding process on a mixed solution containing cellulose, NaOH, and distilled water to pre-treat at least a portion of the crystalline region of the cellulose into an amorphous region, and A method comprising the step of performing a shear mixing process on a mixture of the above-mentioned pretreated cellulose, acetone, and acrylonitrile to obtain cellulose in which at least a portion of the amorphous cellulose is modified into cyanoethyl-cellulose (CEC). Chemical modification method of amorphous cellulose.

2. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the above ultrasonic grinding is carried out for 30 to 50 minutes under conditions of room temperature-atmosphere pressure (25℃-1 bar) and pH 10.0 or higher.

3. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the above ultrasonic grinding is carried out for 30 to 50 minutes under conditions of room temperature-atmosphere pressure (25℃-1 bar) and pH 10.0 to 10.

5.

4. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the pretreated cellulose has a degree of amorphousness of 55% or more.

5. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the pretreated cellulose has a degree of amorphousness of 65% or more.

6. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the above shear mixing is carried out for 30 to 240 minutes at 150 to 300 rpm under conditions of 30 to 60°C and pH 10.0 to 10.

5.

7. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the amorphous cellulose has a cyano group modification introduction rate (DS) of 1.3 or higher.

8. In Paragraph 1, A method for chemically modifying amorphous cellulose, wherein the amorphous cellulose has a cyano group modification introduction rate (DS) of 1.4 or higher.

9. Cellulose chemically modified according to the chemical modification method of any one of paragraphs 1 to 8.

10. In Paragraph 9, The chemically modified cellulose above is cellulose in which at least a portion of amorphous cellulose is modified into cyanoethyl-cellulose (CEC).

11. A polymer composite material comprising chemically modified cellulose in accordance with paragraph 9.

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