Method for modifying modified cellulose, method for producing modified modified cellulose, method for producing modified modified cellulose film, modified modified cellulose, modified modified cellulose film, and modified cellulose molded article.

Abstract

The present invention provides a method for modifying modified cellulose that can modify modified cellulose while maintaining its quality and mechanical properties, a method for producing modified modified cellulose, a method for producing a modified modified cellulose film, modified modified cellulose, a modified modified cellulose film, and a modified cellulose molded article. [Solution] A method for modifying modified cellulose, which involves contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher.

Description

[Technical Field]

[0001] This disclosure relates to a method for modifying modified cellulose, a method for producing modified modified cellulose, a method for producing a modified modified cellulose film, modified modified cellulose, a modified modified cellulose film, and a modified cellulose molded article. [Background technology]

[0002] In recent years, the application of modified cellulose, a biodegradable biomass material that takes the environment into consideration, has been explored. Non-patent document 1 discloses that a cellulose acetate membrane, a type of modified cellulose, was subjected to supercritical carbon dioxide treatment at 50°C to obtain a cellulose acetate membrane with improved selective gas permeability.

[0003] On the other hand, other technologies utilizing supercritical carbon dioxide are known. For example, Patent Document 1 discloses that a resin composition with excellent color tone and lightfastness was obtained by mixing polyphenylene ether and supercritical carbon dioxide, lowering the melting point or glass transition temperature by 10°C to 200°C, and then injection molding the mixture. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-263858 [Non-patent literature]

[0005] [Non-Patent Document 1] Colin A. Scholes, Shinji Kanehashi, “Polymeric membrane gas separation performance improvements through supercritical CO2 treatment”, Journal of Membrane Science 566 (2018) 239-248 [Overview of the project] [Problems that the invention aims to solve]

[0006] Modified cellulose is modified by annealing at high temperatures, such as 200°C or higher under vacuum, which promotes crystallization. By controlling the higher-order structure of crystallization, the modified cellulose exhibits superior properties. However, high-temperature processing of modified cellulose has led to problems such as yellowing, decomposition, and degradation. It is also known that adding plasticizers to modified cellulose can promote crystallization at lower temperatures, but this reduces the biodegradability and mechanical properties of the modified cellulose.

[0007] This disclosure is made in view of the above, and relates to a method for modifying modified cellulose that can modify modified cellulose while maintaining quality and mechanical properties, a method for producing modified modified cellulose, a method for producing a modified modified cellulose film, modified modified cellulose, a modified modified cellulose film, and a modified cellulose molded article. [Means for solving the problem]

[0008] This disclosure includes the following aspects: <1> A method for modifying modified cellulose, which involves contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher. <2> The contact temperature is 55°C to 190°C. <1> A method for modifying modified cellulose as described in [reference]. <3> The modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose. <1> or <2> A method for modifying modified cellulose as described in [reference]. <4> The modified cellulose is cellulose acetate. <1> ~ <3> A method for modifying modified cellulose as described in any one of the following. <5> The modified cellulose and the supercritical carbon dioxide are brought into contact under a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours. <1> ~ <4> A method for modifying modified cellulose as described in any one of the following. <6> A method for producing modified cellulose, comprising contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher. <7> The contact temperature is 55°C to 190°C. <6> A method for producing modified cellulose as described above. <8> The modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose. <6> or <7> A method for producing modified cellulose as described above. <9> The modified cellulose is cellulose acetate. <6> ~ <8> A method for producing modified cellulose as described in any one of the following. <10> The modified cellulose and the supercritical carbon dioxide are brought into contact under a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours. <6> ~ <9> A method for producing modified cellulose as described in any one of the following. <11> A method for producing a modified cellulose membrane, comprising contacting the modified cellulose membrane with supercritical carbon dioxide at a temperature of 55°C or higher. <12> The contact temperature is 55°C to 190°C. <11> A method for producing a modified cellulose membrane as described above. <13> The modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose. <11> or <12> A method for producing a modified cellulose membrane as described above. <14> The modified cellulose is cellulose acetate. <11> ~ <13> A method for producing a modified cellulose membrane as described in any one of the following. <15> The method for producing a modified modified cellulose film according to any one of <11> to <14>, wherein the modified cellulose film and the supercritical carbon dioxide are brought into contact with each other at a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours. <16> Modified modified cellulose obtained by the method for producing modified modified cellulose according to any one of <6> to <10>. <17> Modified modified cellulose film obtained by the method for producing a modified modified cellulose film according to any one of <11> to <15>. <18> A modified cellulose molded body formed using the modified modified cellulose according to <16> or the modified modified cellulose film according to <17>.

Effects of the Invention

[0009] According to the present disclosure, there are provided a method for modifying modified cellulose capable of modifying modified cellulose while maintaining quality and mechanical properties, a method for producing modified modified cellulose, a method for producing a modified modified cellulose film, modified modified cellulose, a modified modified cellulose film, and a modified cellulose molded body.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a graph showing a differential scanning calorimetry (DSC) curve of a modified cellulose film treated with supercritical carbon dioxide under each temperature condition. [Figure 2] FIG. 2 is a graph showing a DSC curve of a modified cellulose film heat-treated at 230°C. [Figure 3] FIG. 3 is a graph showing the crystallinity of a modified cellulose film treated with supercritical carbon dioxide under each temperature condition. [Figure 4] FIG. 4 is a graph showing the tanδ of a modified cellulose film treated with supercritical carbon dioxide under each temperature condition. [Figure 5] FIG. 5 is a graph showing a WAXD pattern of a modified cellulose film treated with supercritical carbon dioxide under each temperature condition. [Figure 6]Figure 6 is a graph showing the WAXD pattern of a modified cellulose film heat-treated at 230°C. [Figure 7] Figure 7 is a graph showing the length L110 of the (110) plane of microcrystals in modified cellulose films treated with supercritical carbon dioxide at various temperature conditions. [Figure 8] Figure 8 shows photographs of the appearance of modified cellulose membranes heat-treated at 230°C and modified cellulose membranes treated with supercritical carbon dioxide under various temperature conditions. [Figure 9] Figure 9 is a graph showing the UV-vis spectra of modified cellulose films heat-treated at 230°C and modified cellulose films treated with supercritical carbon dioxide under various temperature conditions. [Modes for carrying out the invention]

[0011] One embodiment of this disclosure is described in detail below. However, this disclosure is not limited to the embodiment described below. In the following disclosure, the components (including elemental steps, etc.) are not essential unless otherwise explicitly stated. The same applies to numerical values ​​and their ranges, and they do not limit this disclosure.

[0012] In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the lower and upper limits, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, the content of each component in the composition means the total content of the multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component are present in the composition. Where multiple elements are listed using "or" or "or," unless otherwise explicitly stated, this does not preclude selecting multiple elements in combination, provided that it does not result in a technical inconsistency. Even if an element is expressed in the singular form in this disclosure, unless otherwise explicitly stated, this does not preclude the existence of multiple elements unless it would result in a technical inconsistency. In this disclosure, the various exemplary embodiments described separately may be combined to form new embodiments, provided they do not contradict each other. When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0013] ≪Methods for modifying modified cellulose≫ The method for modifying modified cellulose according to this disclosure involves contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher.

[0014] According to the method for modifying modified cellulose described herein, modified cellulose can be modified while maintaining its quality and mechanical properties. As mentioned above, modified cellulose is modified by annealing at high temperatures, such as 200°C or higher, which promotes crystallization. However, high-temperature treatment has resulted in problems such as yellowing, decomposition, and deterioration. On the other hand, according to the modified cellulose modification method of this disclosure, by utilizing supercritical carbon dioxide, crystallization of modified cellulose can be promoted under milder conditions at lower temperatures of 55°C or higher. It is believed that the supercritical carbon dioxide causes swelling and plasticization by dissolving in the modified cellulose, thereby inducing the growth of the crystalline phase of the modified cellulose and thus modifying it. Furthermore, the modified cellulose obtained by the modified cellulose modification method of this disclosure maintains its quality and mechanical properties, and can be said to have become highly functional. This disclosure is not limited in any way to the estimation mechanism described above.

[0015] <Modified cellulose> In this disclosure, modified cellulose (also referred to as cellulose derivative) is cellulose in which some of the hydroxyl groups of cellulose have been chemically modified.

[0016] Modified cellulose may be included alone or in combination of two or more types. The modified cellulose is preferably at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose.

[0017] Examples of acylated cellulose include cellulose acetate. Examples of alkyl etherified cellulose include methylcellulose, ethylcellulose, propylcellulose, and butylcellulose. Examples of hydroxyalkyl etherified cellulose include hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxypropylethylcellulose. Examples of carboxyalkyl etherified cellulose include carboxymethyl cellulose and carboxyethyl cellulose.

[0018] From the viewpoint of having excellent affinity for carbon dioxide and readily undergoing cold crystallization, acylated cellulose is preferred as the modified cellulose. Acylated cellulose is cellulose in which some of the hydroxyl groups contained in cellulose are acylated. The acylated cellulose may contain one or more types of acyl groups. As the acyl group, an aliphatic acyl group (R-CO-; R is an aliphatic group, preferably having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms) is preferred, an acetyl group, a propanoyl group, or a butanoyl group is more preferred, and an acetyl group is particularly preferred. From the standpoint of having excellent affinity for carbon dioxide and readily undergoing cold crystallization, modified cellulose is more preferably cellulose acetate.

[0019] Examples of cellulose acetate include acetylcellulose, diacetylcellulose, and triacetylcellulose, with triacetylcellulose being preferred.

[0020] The degree of substitution in the modified cellulose is preferably 0.1 to 3.0, more preferably 1.0 to 3.0, even more preferably 2.0 to 3.0, particularly preferably 2.5 to 3.0, and most preferably 2.8 to 3.0. The degree of substitution indicates the average number of hydroxyl groups in the glucose unit, which is the repeating structural unit in modified cellulose, where the hydrogen atoms constituting the hydroxyl group have been replaced by substituents. Therefore, the upper limit of the degree of substitution in typical modified cellulose is 3.0.

[0021] The degree of substitution is, 1 This can be determined by methods such as 1H-NMR. A specific method is, for example, the method described in Cellulose Communication, 1999, Vol. 6, pp. 73-79.

[0022] Generally, the lower the degree of substitution of modified cellulose, the smaller the free volume and the more densely the modified cellulose film tends to become due to the effect of hydroxyl groups, and the more easily plasticizes under high-pressure conditions.

[0023] From the viewpoint of having an appropriate melt viscosity for a composition containing modified cellulose and excellent physical properties of the formed product using the composition, the number average molecular weight (M) of the modified cellulose is considered to be appropriate. n The value of ) is preferably 5,000 to 500,000, more preferably 10,000 to 200,000, and even more preferably 30,000 to 100,000.

[0024] From the viewpoint of having an appropriate melt viscosity for a composition containing modified cellulose and excellent physical properties of the formed product using the composition, the weight-average molecular weight (M) of the modified cellulose is considered.w The value of ) is preferably 5,000 to 500,000, more preferably 10,000 to 300,000, and even more preferably 100,000 to 200,000. In this disclosure, the number-average molecular weight and weight-average molecular weight can be determined by gel permeation chromatography (GPC) (using commercially available standard polystyrene as a standard sample).

[0025] From the viewpoint of ensuring that the melt viscosity of the composition containing modified cellulose is appropriate and that the strength and heat resistance of the formed product using the composition are excellent, the weight-average degree of polymerization of the modified cellulose is preferably 30 to 5,000, more preferably 50 to 3,000, and even more preferably 100 to 1,000. In this disclosure, the weight-average degree of polymerization is determined from the weight-average molecular weight by the following procedure. First, the weight-average molecular weight of modified cellulose is measured in polystyrene equivalent using GPC. Next, the degree of polymerization of cellulose acylate is determined by dividing by the molecular weight of the constituent units of modified cellulose.

[0026] The external form of the modified cellulose used for modification is not particularly limited. The modified cellulose may be in the form of powder, flakes, liquid, film, membrane, plate, string, or lump. From the viewpoint of promoting crystallization of the modified cellulose, it is preferable that the modified cellulose be in the form of a membrane.

[0027] <Supercritical carbon dioxide> Supercritical carbon dioxide is carbon dioxide that has exceeded its critical point (critical temperature of 31.0°C and critical pressure of 7.4 MPa).

[0028] Examples of methods for producing supercritical carbon dioxide include liquid pressurization and gas pressurization. In the liquid pressurization method, liquid carbon dioxide, which has been sufficiently cooled in a chiller, is pressurized and simultaneously heated using a plunger-type or diaphragm-type pump to reach a supercritical state of 31.0°C or higher and a pressure of 7.4 MPa or higher, thereby obtaining supercritical carbon dioxide. According to the gas pressurization method, gaseous carbon dioxide is pressurized using pressurized nitrogen gas or air to bring it to a supercritical state at a temperature of 31.0°C or higher and a pressure of 7.4 MPa or higher, thereby obtaining supercritical carbon dioxide.

[0029] Furthermore, the liquid pressurization method requires the fluid to be liquid before pressurization, necessitating a cooling mechanism to maintain a constant liquid state between the carbon dioxide cylinder and the pump. Additionally, the liquid pressurization method carries the risk of cavitation occurring within the pump, potentially reducing pressurization capacity. Therefore, when producing small amounts of supercritical carbon dioxide, the gas pressurization method is preferable. On the other hand, when producing large amounts of supercritical carbon dioxide, the liquid pressurization method is preferable because it allows for wide-ranging and highly accurate control of the production volume and requires less frequent maintenance.

[0030] <Processing conditions> (contact) The method for modifying modified cellulose according to this disclosure involves contacting the modified cellulose with supercritical carbon dioxide. The detailed method of contact is not particularly limited, and for example, the modified cellulose may be exposed to supercritical carbon dioxide.

[0031] (temperature) The temperature at which modified cellulose is brought into contact with supercritical carbon dioxide is 55°C or higher. This temperature promotes crystallization of the modified cellulose, thereby modifying it. The temperature at which modified cellulose and supercritical carbon dioxide are brought into contact is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, even more preferably 100°C or higher, even more preferably 120°C or higher, even more preferably 140°C or higher, and particularly preferably 160°C or higher, from the viewpoint of further promoting the crystallization of modified cellulose and increasing the degree of crystallinity. The temperature at which modified cellulose and supercritical carbon dioxide are brought into contact is preferably 190°C or lower, more preferably 180°C or lower, even more preferably 170°C or lower, even more preferably 160°C or lower, and even more preferably 150°C or lower, from the viewpoint of ensuring excellent colorlessness and transparency of the modified cellulose, no change in shape due to modification, and excellent mechanical properties. The temperature at which modified cellulose is brought into contact with supercritical carbon dioxide is, for example, 55°C to 190°C. According to the modified cellulose modification method of this disclosure, the degree of crystallinity and crystalline morphology of the modified cellulose can be controlled by the contact temperature (i.e., the higher-order structure can be controlled), so the contact temperature can be set according to the desired degree of crystallinity and crystalline morphology.

[0032] (pressure) From the viewpoint of maintaining the supercritical state of supercritical carbon dioxide while considering safety, and modifying modified cellulose while maintaining better quality and mechanical properties, the pressure at which modified cellulose and supercritical carbon dioxide are brought into contact is preferably 7.4 MPa to 100 MPa, more preferably 10 MPa to 50 MPa, and even more preferably 15 MPa to 30 MPa.

[0033] (time) The time for contacting the modified cellulose with supercritical carbon dioxide is not particularly limited and may be adjusted as appropriate depending on the form of the modified cellulose. From the viewpoint of sufficiently impregnating the modified cellulose with supercritical carbon dioxide, the contact time for the modified cellulose with supercritical carbon dioxide is preferably 1 minute to 24 hours, more preferably 1 hour to 12 hours, and even more preferably 1 hour to 8 hours, for example, when the modified cellulose is a modified cellulose film with a thickness of 1 μm to 1000 μm.

[0034] (Decompression) In the modified cellulose modification method of this disclosure, it is preferable to further reduce the pressure after bringing the modified cellulose and the supercritical carbon dioxide into contact under predetermined conditions. The rate of the reduced pressure treatment is not particularly limited and may be, for example, 1 MPa / min to 1000 MPa / min or 10 MPa / min to 100 MPa / min.

[0035] <Additives> In the method for modifying modified cellulose according to the present disclosure, the modified cellulose and supercritical carbon dioxide may be brought into contact at a temperature of 55°C or higher in the presence of an additive. The additive may be included individually or in combination of two or more types. Examples of additives used for modification include plasticizers, stabilizers (e.g., oxidation resistance improvers, heat resistance improvers, and metal deactivators), polymerization inhibitors, flame retardants, and flame retardant aids.

[0036] Examples of plasticizers include polyester-based plasticizers, glycerin-based plasticizers, polycarboxylic acid ester-based plasticizers, polyalkylene glycol-based plasticizers, and epoxy-based plasticizers.

[0037] <Characteristics of modified cellulose> The modified cellulose method disclosed herein yields modified cellulose. The modified cellulose is modified by crystallization. From the viewpoint of structural stabilization and long-term stability, the crystalline form of the modified cellulose is preferably a CTAII orthorhombic system. The crystalline morphology of modified cellulose can be confirmed by wide-angle X-ray diffraction (WAXD).

[0038] From the viewpoint of structural stabilization, temporal stability, and crystallinity, the degree of crystallinity of the modified cellulose is preferably 30% to 50%, more preferably 35% to 50%, and even more preferably 40% to 50%. The degree of crystallinity of modified cellulose can be calculated using the following formula (1).

[0039]

number

[0040] Length L of the (110) plane of the modified cellulose crystal. 110 From the viewpoint of structural stabilization and stability over time, a wavelength of 4.5 nm to 7.0 nm is preferred, 5.0 nm to 7.0 nm is more preferred, and 5.5 nm to 7.0 nm is even more preferred. Length L of the (110) plane of the modified cellulose crystal. 110can be calculated from the following formula (2) (Scherrer formula).

[0041] [Number]

[0042] The glass transition temperature (T g ) of the modified modified cellulose may be 190°C to 200°C. The melting point (T m ) of the modified modified cellulose may be 295°C to 305°C (peak top). The crystallization temperature (T cc ) of the modified modified cellulose may be 210°C to 215°C (peak top). T g T m and T cc can be measured by a differential scanning calorimeter (DSC).

[0043] <<Method for producing modified modified cellulose>> The method for producing the modified modified cellulose of the present disclosure brings the modified cellulose into contact with supercritical carbon dioxide at a temperature of 55°C or higher.

[0044] Regarding the modified cellulose, supercritical carbon dioxide, the treatment conditions of the modified cellulose and supercritical carbon dioxide, additives, and the properties of the modified modified cellulose in the method for producing the modified modified cellulose of the present disclosure, the descriptions including definitions, examples, and preferred embodiments are the same as each description described in the item of <<Method for modifying modified cellulose>> of the present disclosure.

[0045] <<Method for producing modified modified cellulose film>> The method for producing the modified modified cellulose film of the present disclosure brings the modified cellulose film into contact with supercritical carbon dioxide at a temperature of 55°C or higher.

[0046] The descriptions of the modified cellulose, supercritical carbon dioxide, treatment conditions for the modified cellulose and supercritical carbon dioxide, additives, and properties of the modified cellulose in the method for producing the modified cellulose membrane of this disclosure, including definitions, examples, and preferred embodiments, are the same as those described in the section on "Method for Modifying Modified Cellulose" of this disclosure. However, the modified cellulose used in the method for producing the modified cellulose membrane described herein, and the form of the modified cellulose obtained, are in the form of a modified cellulose membrane.

[0047] The method for forming a modified cellulose film using modified cellulose is not particularly limited. For example, a modified cellulose film can be obtained by preparing a modified cellulose solution using a solvent, filtering it, casting the solution, and drying the solvent.

[0048] The content of modified cellulose relative to the total volume of the modified cellulose solution may be 0.1% to 30% by mass, 0.5% to 20% by mass, or 1% to 10% by mass, from the viewpoint of ease of solution casting.

[0049] Examples of solvents used in preparing modified cellulose solutions include methanol, ethanol, isopropanol (IPA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, tetrahydrofuran (THF), diester of succinic acid and triethylene glycol monomethyl ether, acetone, methyl ethyl ketone (MEK), acetonitrile, dichloromethane, chloroform, toluene, acetic acid, and water.

[0050] The thickness of the modified cellulose membrane is not particularly limited and may be adjusted as appropriate depending on the application. The thickness of the modified cellulose membrane may be 1 μm to 1000 μm, 5 μm to 500 μm, or 10 μm to 100 μm.

[0051] Modified Cellulose The modified cellulose of this disclosure is obtained by the method for producing the modified cellulose of this disclosure.

[0052] The descriptions of the modified cellulose in this disclosure, including the method for producing the modified cellulose and the properties of the modified cellulose, are the same as those described in the section on "Method for Producing Modified Cellulose" in this disclosure, including definitions, examples, and preferred embodiments.

[0053] Modified cellulose membrane The modified cellulose membrane according to this disclosure is obtained by the method for producing the modified cellulose membrane according to this disclosure.

[0054] The descriptions of the modified cellulose membrane of this disclosure, the method for producing the modified cellulose membrane of this disclosure, and the properties of the modified cellulose, including definitions, examples, and preferred embodiments, are the same as those described in the section on "Method for producing the modified cellulose membrane" of this disclosure. However, the modified cellulose used in the method for producing the modified cellulose membrane described herein, and the form of the modified cellulose obtained, are in the form of a modified cellulose membrane.

[0055] Modified Cellulose Molded Body The modified cellulose molded articles of this disclosure are formed using the modified modified cellulose or modified modified cellulose membrane of this disclosure.

[0056] The modified cellulose molded articles of this disclosure may be formed using a resin composition containing the modified modified cellulose of this disclosure, or a resin composition containing modified modified cellulose derived from the modified modified cellulose film of this disclosure. The resin composition may further contain other components. Other components include polymers other than modified cellulose, plasticizers, fillers, flame retardants, stabilizers (antioxidants and UV absorbers, etc.), mold release agents (fatty acids, fatty acid metal salts, oxy fatty acids, fatty acid esters, aliphatic partially saponified esters, paraffin, low molecular weight polyolefins, fatty acid amides, alkylene bis-fatty acid amides, aliphatic ketones, fatty acid lower alcohol esters, fatty acid polyhydric alcohol esters, fatty acid polyglycol esters, and modified silicones, etc.), antistatic agents, flame retardant additives, processing aids, drip inhibitors, antibacterial agents, antifungal agents, and colorants (dyes and pigments, etc.).

[0057] The content of the modified cellulose of this disclosure relative to the total amount of the resin composition is not particularly limited and may be 1% to 99% by mass, or 10% to 50% by mass.

[0058] The modified cellulose molded article of this disclosure may be obtained by heating the resin composition and molding it using various molding methods. Examples of molding methods include injection molding, extrusion molding, and blow molding. The heating temperature is preferably 160°C to 300°C, and more preferably 180°C to 260°C.

[0059] ≪Applications≫ The modified cellulose of this disclosure can be used as a barrier material, a film (e.g., a deflection protective film and a display protective film), a pharmaceutical excipient, a filtration aid, a food additive, a dispersant, and a viscosity modifier. [Examples]

[0060] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0061] Modification of cellulose by supercritical carbon dioxide treatment <Modified cellulose> As modified cellulose, we prepared cellulose acetate with the following chemical formula.

[0062] [ka]

[0063] The details of the prepared cellulose acetate are as follows: Cellulose acetate: LT-35 (manufactured by Daicel Corporation, triacetylcellulose) Substitution degree: 2.93 Number average molecular weight (M n ): 86,000 Weight average molecular weight (M w ): 176,000 Weight average degree of polymerization (n): 385

[0064] <Film forming> Modified cellulose membranes were prepared using a solution casting method with dichloromethane as the solvent. More specifically, a 3% by mass modified cellulose solution was prepared using dichloromethane, filtered, and cast into a glass petri dish. Next, it was dried at room temperature for 2 days, and then vacuum-dried at 35°C for 24 hours and 100°C for 24 hours to remove residual solvent. The resulting modified cellulose film had a thickness of 50 μm to 80 μm.

[0065] <Supercritical carbon dioxide treatment> The resulting modified cellulose membrane was exposed to supercritical carbon dioxide for 8 hours under conditions of a pressure of 25 MPa and temperatures of 35°C, 50°C, 55°C, 120°C, or 150°C. After exposure, the membrane was subjected to a reduced pressure treatment from the supercritical state at 37.7 MPa / min.

[0066] Modification of cellulose by heat treatment at 230°C For comparison, a modified cellulose film obtained by the same procedure as described above was heat-treated at 230°C.

[0067] Untreated modified cellulose membrane For comparison, modified cellulose membranes obtained using the same procedure as described above were left untreated and considered as untreated modified cellulose membranes.

[0068] ≪Rating≫ The modified cellulose membranes treated with supercritical carbon dioxide, modified cellulose membranes heat-treated at 230°C, and untreated modified cellulose membranes were evaluated as follows.

[0069] <Differential Scanning Calorimeter (DSC)> Figure 1 shows the differential scanning calorimeter (DSC) curves (1st scan) of modified cellulose films treated with supercritical carbon dioxide at 35°C, 50°C, 55°C, 120°C, or 150°C. Because the modified cellulose films are not fully crystallized at the time of film formation, the glass transition temperature (T) is not fully developed. g It is known that cold crystallization occurs in a temperature range 10°C higher than 193°C. For comparison, Figure 2 shows the DSC curves (1st scan) of an untreated modified cellulose membrane (as-cast in Figure 2) and a modified cellulose membrane heat-treated at 230°C (heated in Figure 2). From the DSC curves, the T of the untreated modified cellulose membrane is shown. g The temperature is 193±0.5℃, cold crystallization temperature (T cc ) is 211.7±0.1℃, melting point (T m The temperature was 300 ± 0.2°C. From the DSC curve of the modified cellulose film heat-treated at 230°C, it was found that complete crystallization occurred upon heating at 230°C.

[0070] Next, the degree of crystallinity was calculated based on the above formula (1). Figure 3 shows the crystallinity of modified cellulose films treated with supercritical carbon dioxide at various temperatures. The crystallinity of the untreated cellulose film (as-cast in Figure 3) was 30.0%, while the crystallinity of the modified cellulose film heat-treated at 230°C was 50.3±0.1% (not shown).

[0071] Supercritical carbon dioxide is generally used to plasticize polymer materials. g This reduces the temperature. However, according to Figure 1, after the reduced pressure treatment, under all temperature conditions of the supercritical carbon dioxide treatment, T gThe performance was comparable to that of the untreated modified cellulose film, indicating that the effects of plasticization were almost negligible. Furthermore, in crystalline and semi-crystalline polymers, crystal packing improved with crystallization, and T increased with increasing temperature of supercritical carbon dioxide treatment. m It has been reported that T increases, but in this disclosure, T is present at all temperature conditions of supercritical carbon dioxide treatment. m No changes were observed.

[0072] Furthermore, as shown in Figures 1 and 3, the supercritical carbon dioxide treatment at 35°C or 50°C did not change the cold crystallization temperature or degree of crystallinity, and was similar to that of the untreated cellulose membrane. On the other hand, as shown in Figure 3, crystallization was promoted and the degree of crystallinity increased during supercritical carbon dioxide treatment at temperatures above 55°C. More specifically, as shown in Figures 1 and 3, supercritical carbon dioxide treatment at 55°C slightly reduced the size of the cold crystallization peak and increased the crystallinity to 30.8%. Supercritical carbon dioxide treatment at 120°C reduced the size of the cold crystallization peak and increased the crystallinity to 36.3±0.5%. Furthermore, supercritical carbon dioxide treatment at 150°C further reduced the size of the cold crystallization peak and increased the crystallinity to approximately 39.7±1.3%. Furthermore, as shown in Figures 2 and 3, in the modified cellulose film heat-treated at 230°C, the cold crystallization peak disappeared, and the degree of crystallinity was 50.3 ± 0.1%. This is because the plasticization of supercritical carbon dioxide improved the mobility of the amorphous material, and the T of the modified cellulose film during supercritical carbon dioxide treatment at 120°C and 150°C cc and T g This is thought to be because it has decreased significantly.

[0073] <Dynamic Viscoelasticity Measurement (DMA)> T g Furthermore, to evaluate the degree of crystallinity, tanδ was evaluated from dynamic viscoelasticity (DMA) measurements. A METTLER TOLEDO DMA1 was used as the measuring instrument. The measurement conditions were under air, measurement frequency of 1 Hz, tensile mode, heating rate of 5°C / min, and temperature range of 50°C to 250°C. The tanδ obtained from the measurements is shown in Figure 4.

[0074] According to Figure 4, modified cellulose membranes treated with supercritical carbon dioxide at 35°C or 50°C, which had a similar degree of crystallinity to untreated modified cellulose membranes, exhibited similar tanδ intensity to the untreated modified cellulose membrane. On the other hand, the tanδ of modified cellulose membranes treated with supercritical carbon dioxide, particularly at 120°C or 150°C, showed a significant decrease in tanδ intensity with increasing treatment temperature. Generally, the intensity of tanδ decreases with increasing crystallinity, so, similar to the results from DSC, it was found that cold crystallization was further promoted with increasing supercritical carbon dioxide treatment temperature.

[0075] <Wide-angle X-ray diffraction measurement (WAXD)> To evaluate the changes in crystal morphology associated with crystallization, wide-angle X-ray diffraction (WAXD) measurements were performed. A Rigaku SmartLab (Cukα, λ=1.5418Å, 45kV, 200mA) was used. Measurement conditions were scan speed=5° / min, and the measurement range was 2θ=5°~60°. Furthermore, the regularity of the crystal was evaluated from the size of the hkl plane of the microcrystals calculated using the above formula (2). The WAXD patterns obtained from the measurements are shown in Figure 5. For comparison, Figure 6 shows the WAXD patterns of an untreated modified cellulose film (as-cast in Figure 6) and a modified cellulose film heat-treated at 230°C (heated in Figure 6). The WAXD pattern of the modified cellulose film heat-treated at 230°C, which was completely crystallized, showed sharp crystal peaks.

[0076] Modified cellulose exists in three crystalline forms: CTAI (monoclinic), CTAII (orthorhombic), and CTAIII (orthorhombic). However, during the solution casting process, a conversion occurs between these crystalline forms, and after film formation, the corresponding crystalline form becomes CTAII (orthorhombic). As shown in Figure 5, the crystalline morphology of modified cellulose films treated with supercritical carbon dioxide at 35°C or 50°C was similar to that of untreated modified cellulose films. On the other hand, the WAXD patterns of modified cellulose films treated with supercritical carbon dioxide at 55°C, 120°C, and 150°C showed a significant change in crystalline morphology as the treatment temperature increased, with each crystal peak becoming sharper and the full width at half maximum (FWHM) decreasing. However, the WAXD pattern of the modified cellulose film heat-treated at 230°C, which was completely crystallized, showed even sharper crystal peaks, suggesting that the modified cellulose film treated with supercritical carbon dioxide at 150°C was not completely crystallized. Alternatively, it is possible that fine crystals can be obtained through crystallization at low temperatures using supercritical carbon dioxide treatment.

[0077] Furthermore, the values ​​calculated from the above formula (2) for the (110) plane of the microcrystal are shown in Figure 7. According to Figure 7, the length L of the (110) plane of the microcrystal 110 In supercritical carbon dioxide treatment at temperatures above 55°C, the amount increased significantly with increasing treatment temperature. This suggests that the increase in treatment temperature promoted an increase in the regularity of crystal size. Alternatively, it is possible that the size of a single crystallite increased in a temperature-dependent manner.

[0078] <Quality> To evaluate the quality of the modified cellulose membrane under each condition, we checked for colorlessness, transparency, and changes in shape.

[0079] (colorless and transparent) Figure 8 shows photographs of the appearance of the modified cellulose membrane under each condition. Untreated modified cellulose membranes were colorless and transparent. Modified cellulose membranes treated with supercritical carbon dioxide remained colorless and transparent under all temperature conditions. On the other hand, modified cellulose membranes heated at 230°C turned yellow.

[0080] The light transmittance was further evaluated using ultraviolet-visible spectroscopy (UV-vis). The results are shown in Figure 9. Compared to modified cellulose films heat-treated at 230°C, modified cellulose films treated with supercritical carbon dioxide at 55°C, 120°C, or 150°C maintained superior transmittance to a wider range of wavelengths of light, i.e., they were colorless and transparent.

[0081] (Shape change) Furthermore, as can be seen from Figure 8, the modified cellulose membrane treated with supercritical carbon dioxide showed no significant shrinkage or change in shape under any temperature conditions. In other words, the shape of the modified cellulose membrane treated with supercritical carbon dioxide was the same as that of the untreated modified cellulose membrane. On the other hand, the modified cellulose membrane heated at 230°C underwent shrinkage and deformation.

[0082] Furthermore, Figure 8 shows that even when the modified cellulose membrane was treated with supercritical carbon dioxide, the modified cellulose membrane did not become brittle and was able to maintain its shape.

[0083] <Mechanical properties> To evaluate the mechanical properties of the modified cellulose membrane under each condition, tensile strength and fracture strain were measured.

[0084] (Tensile strength) Tensile strength was measured using Shimadzu Corporation's EZ-SX at a temperature of 25°C and a tensile speed of 1 mm / sec. The results are shown in Table 1. The supercritical carbon dioxide-treated modified cellulose membrane showed tensile strength that was comparable to that of the untreated modified cellulose membrane at all temperature conditions.

[0085] (Fracture strain) Fracture strain can be measured using Shimadzu Corporation's EZ-SX at a temperature of 25°C and a tensile speed of 1 mm / sec. The results are shown in Table 1. The supercritical carbon dioxide-treated modified cellulose membrane showed a fracture strain that was comparable to that of the untreated modified cellulose membrane at all temperature conditions.

[0086] Furthermore, the modified cellulose membrane heat-treated at 230°C exhibited inferior tensile strength and fracture strain compared to the modified cellulose membrane treated with supercritical carbon dioxide.

[0087] [Table 1]

[0088] Based on the above, the modified cellulose modification method of this disclosure allows for the modification of modified cellulose while maintaining its quality and mechanical properties by contacting the modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher.

Claims

1. A method for modifying modified cellulose, which involves contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher.

2. The method for modifying modified cellulose according to claim 1, wherein the temperature at which contact occurs is 55°C to 190°C.

3. The method for modifying modified cellulose according to claim 1 or claim 2, wherein the modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose.

4. The method for modifying modified cellulose according to claim 1 or claim 2, wherein the modified cellulose is cellulose acetate.

5. A method for modifying modified cellulose according to claim 1 or claim 2, comprising contacting the modified cellulose with the supercritical carbon dioxide under a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours.

6. A method for producing modified cellulose, comprising contacting modified cellulose with supercritical carbon dioxide at a temperature of 55°C or higher.

7. The method for producing modified cellulose according to claim 6, wherein the contact temperature is 55°C to 190°C.

8. The method for producing modified cellulose according to claim 6 or claim 7, wherein the modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose.

9. The method for producing modified cellulose according to claim 6 or claim 7, wherein the modified cellulose is cellulose acetate.

10. A method for producing modified cellulose according to claim 6 or claim 7, comprising contacting the modified cellulose and the supercritical carbon dioxide under a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours.

11. A method for producing a modified cellulose membrane, comprising contacting the modified cellulose membrane with supercritical carbon dioxide at a temperature of 55°C or higher.

12. The method for producing a modified cellulose film according to claim 11, wherein the contact temperature is 55°C to 190°C.

13. The method for producing a modified cellulose membrane according to claim 11 or claim 12, wherein the modified cellulose is at least one selected from the group consisting of acylated cellulose, nitrocellulose, sulfated cellulose, alkyl etherified cellulose, hydroxyalkyl etherified cellulose, and carboxyalkyl etherified cellulose.

14. The method for producing a modified cellulose membrane according to claim 11 or claim 12, wherein the modified cellulose is cellulose acetate.

15. A method for producing a modified cellulose membrane according to claim 11 or claim 12, comprising contacting the modified cellulose membrane with the supercritical carbon dioxide under a pressure of 7.4 MPa to 100 MPa for 1 minute to 24 hours.

16. Modified modified cellulose obtained by the method for producing modified cellulose according to claim 6.

17. A modified cellulose membrane obtained by the method for producing a modified cellulose membrane according to claim 11.

18. A modified cellulose molded article formed using the modified modified cellulose described in claim 16 or the modified modified cellulose membrane described in claim 17.

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