Cellulose mixed fatty acid ester and method for producing the same

Abstract

This invention provides a novel cellulose-mixed fatty acid ester and a method for producing the same. [Solution] A cellulose mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, In the aforementioned cellulose mixed fatty acid ester, some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring are substituted with acetyl groups. The ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or greater. A cellulose-mixed fatty acid ester in which the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms is 0.5 or more.

Description

[Technical Field]

[0001] This disclosure relates to cellulose mixed fatty acid esters and methods for producing the same. [Background technology]

[0002] In recent years, with serious environmental pollution and excessive carbon emissions, attention to the circular economy has been increasing. In this context, derivatives made from biomass-derived cellulose are promising due to their abundant cellulose yield. Cellulose derivatives are expected to be biodegradable, which could help solve problems such as marine pollution caused by plastics. However, cellulose derivatives are poor at thermoforming. Therefore, it is necessary to improve the thermoforming properties of cellulose acetate and other materials using plasticizers. Furthermore, cellulose acetate lacks the flexibility of polyethylene, so flexibility is desired.

[0003] Long-chain fatty acid esters have also been proposed as cellulose acylates. For example, Non-Patent Literature 1 describes the synthesis of cellulose esters having linear aliphatic acyl substituents from C12 (lauric acid) to C20 (eicosanoic acid) under a solvent of p-toluenesulfonic acid / carboxylic acid mixed anhydride. These cellulose long-chain fatty acid esters exhibited broad crystallization and melting transitions in the range of -19 to +55°C due to the crystallinity of the side chains, indicating a problem with heat resistance.

[0004] Patent Document 2 proposes a thermoplastic biodegradable plastic characterized by a substitution degree of benzyl or alkaloyl groups greater than 0 and less than 3, for the purpose of providing a thermoplastic biodegradable plastic. In this document, it is stated that lauroylated cellulose has a substitution degree of 2.5 to 2.8 and a melting point of 110 to 122°C. Patent Document 3 describes esterification by reacting cellulose or other polysaccharides with organic acids or organic acid salts in an organic solvent in the presence of sulfonyl chloride. The examples describe the introduction of valeric acid, octanoic acid, lauric acid, stearic acid, benzoic acid, p-aminobenzoic acid, and glycine as substituents. While such materials have excellent thermoplasticity, they lack heat resistance. Furthermore, the degree of polymerization tends to decrease easily, resulting in insufficient strength.

[0005] It has also been proposed to produce mixed fatty acid esters using cellulose acetate as a starting material. Patent Document 4 proposes a method for producing cellulose esters using acyl anhydride and trifluoroacetic anhydride. In Example 20 of this document, cellulose acetate propionate is synthesized from cellulose acetate with propionic anhydride without a sulfuric acid catalyst.

[0006] Cellulose mixed fatty acid esters with limited substitution at positions 2, 3, and 6 of the glucose ring have also been proposed. Patent document 5 describes the synthesis of cellulose acetate with a high degree of substitution at positions DS2 and 3 by reacting trifluoroacetic anhydride and trifluoroacetic acid as a solvent and acylating agent. Subsequently, mixed fatty acid esters are synthesized in a single step reaction using cellulose as a raw material in a similar manner. (Table 3 Examples 3, 4, 5) However, this fatty acid ester does not disclose mixed fatty acid esters composed of acetyl groups and long-chain fatty acid esters.

[0007] Furthermore, Patent Document 6 discloses a cellulose acetate with an acetyl substitution degree of 2.7 or less, where the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position in the total acetyl substitution degree is 2.0 or more. However, these documents neither describe nor disclose the preferential introduction of acetyl groups at the 2nd and 3rd positions of the glucose ring of the cellulose ester, and the introduction of an aliphatic acyl group with 3 to 24 carbon atoms at the 6th position of the glucose ring. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2002-322201 [Patent Document 2] Japanese Patent Publication No. 2000-119302 [Patent Document 3] Japanese Patent Application Publication No. 1-249801 [Patent Document 4] Japanese Patent Application Publication No. 6-32801 [Patent Document 5] Special Publication No. 2020-515682 [Patent Document 6] WO2021 / 117113 publication [Non-patent literature]

[0009] [Non-Patent Document 1] James et al,15 July 1996,Novel cellulose derivatives. IV. Preparation and thermal analysis of waxy esters of cellulose Materials Science, Chemistry Journal of Polymer Science Part B [Overview of the project] [Problems that the invention aims to solve]

[0010] For example, cellulose diacetate has thermoplasticity, but its melting point is close to its thermal decomposition temperature. In addition, since the cellulose backbone is rigid, the extensibility at the time of melting is insufficient. For this reason, in practical use, a plasticizer is used to impart thermoplasticity at melting to cellulose esters such as cellulose diacetate.

[0011] However, even when a plasticizer is used, it is difficult to reduce the melt viscosity to a level usable for injection molding due to insufficient melt fluidity. In addition, since the plasticizer is a low-molecular-weight substance, the mechanical strength of the resulting molded article is insufficient. Attempts have also been made to introduce long-chain fatty acid esters to lower the melting point of cellulose esters. However, the improvement of plasticity and melt fluidity brought by the lowering of the melting point and the decrease in heat resistance caused by the lowering of the melting point are in a trade-off relationship. No cellulose ester that has the melt fluidity required for injection molding and other molding methods requiring high melt fluidity and also has high heat resistance has been proposed.

[0012] The main object of the present disclosure is to provide a novel cellulose mixed fatty acid ester and a method for producing the same. Means for Solving the Problem

[0013] The inventors of the present disclosure have conducted intensive studies to solve the above problems. As a result, they found that by mainly introducing acetyl groups to the 2- and 3-positions of the glucose ring of cellulose, and further introducing a long-chain aliphatic acyl group having 3 to 24 carbon atoms to the 6-position of the remaining glucose ring of cellulose, both heat resistance and melt fluidity can be achieved. They also found that a novel cellulose mixed fatty acid ester can be obtained by acylating the hydroxy groups of cellulose acetate having a predetermined degree of acetyl substitution with a fatty acid having 3 to 24 carbon atoms.

[0014] The present disclosure has been completed through further studies based on such findings. Effect of the Invention

[0015] This disclosure provides novel cellulose-mixed fatty acid esters and methods for producing the same.

[0016] Furthermore, this disclosure provides a cellulose mixed fatty acid ester and a method for producing the same, which achieve both excellent heat resistance and excellent moldability.

[0017] Furthermore, this disclosure provides a cellulose-mixed fatty acid ester with excellent tensile strength and a method for producing the same. [Brief explanation of the drawing]

[0018] [Figure 1] These are the reaction equations between cellulose acetate (cellulose diacetate (CDA)) and various carboxylic acids in Examples 1-7. [Figure 2] This graph shows the XRD measurement results in Examples 1-7. [Figure 3] This shows the reaction process between cellulose acetate (cellulose diacetate (CDA)) and various carboxylic acids in Examples 8 and 9. [Figure 4] This graph shows the XRD measurement results of the cellulose mixed fatty acid ester compound films (heated at 250°C and 260°C) and powder obtained in Example 1. [Figure 5] This graph shows the tensile breaking strength and tensile breaking elongation measured for each film obtained in the examples. [Figure 6] This graph shows the tensile elongation at break and tensile modulus of elasticity measured for each film obtained in the examples. [Figure 7] This graph shows the melting peak temperature (°C) and glass transition temperature (°C) of the cellulose mixed fatty acid ester compound film obtained in each example, and the cellulose acetate (CDA) film used as the raw material. [Figure 8] These are photographs of the films of the cellulose mixed fatty acid ester compounds obtained in each example. [Figure 9] These are photographs of injection-molded sheets of cellulose-mixed fatty acid ester compounds obtained in each example. [Modes for carrying out the invention]

[0019] Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments.

[0020] In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Alternatively, the upper and lower limits, upper and lower limits, or lower and lower limits described separately may be combined to form numerical ranges. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0021] [Cellulose mixed fatty acid ester] The cellulose mixed fatty acid esters of this disclosure are cellulose esters containing an acetyl group (acetic acid group) and an acyl group other than an acetyl group. The cellulose mixed fatty acid esters of this disclosure encompass the following first, second, and third embodiments.

[0022] The cellulose mixed fatty acid ester and its manufacturing method described herein will be described in detail below. In the following descriptions, matters specific to the first, second, and third embodiments will be clearly indicated as relating to which embodiment. On the other hand, matters common to the first, second, and third embodiments will be described in relation to the present disclosure, and descriptions for each individual embodiment will be omitted.

[0023] Furthermore, the degree of substitution, molecular weight, glass transition temperature, melting peak temperature, thermal decomposition temperature, and tensile properties of the cellulose mixed fatty acid ester of this disclosure are values ​​obtained by the measurement methods described in the examples.

[0024] (First aspect) A cellulose mixed fatty acid ester according to a first aspect of this disclosure is a cellulose mixed fatty acid ester comprising an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms.

[0025] In the cellulose mixed fatty acid ester according to the first embodiment, some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring of the cellulose mixed fatty acid ester are substituted with acetyl groups.

[0026] In the cellulose mixed fatty acid ester according to the first embodiment, the ratio τ of the sum of the acetyl substitution degrees at positions 2 and 3 to the acetyl substitution degree at position 6 is 1.8 or more. Furthermore, in the first embodiment, the degree of substitution of aliphatic acyl groups having 3 to 24 carbon atoms is 0.5 or more.

[0027] The cellulose mixed fatty acid ester according to the first embodiment, having the above characteristics, is a novel cellulose mixed fatty acid ester that can exhibit effects such as achieving both excellent heat resistance and excellent moldability.

[0028] From the viewpoint of more favorably exhibiting the effects of the invention according to the first embodiment, the lower limit of the number of carbon atoms in the acyl group can be 3, 4, 5, 7, 8, 10, or 12. The upper limit of the number of carbon atoms in the acyl group can be selected from 24, 22, 20, 18, 16, or 14. These upper and lower limits of the number of carbon atoms in the acyl group can be combined as appropriate. When the number of carbon atoms in the acyl group is in the range of 3 to 5, the melting point decreases as the number of carbon atoms increases. On the other hand, the thermal decomposition temperature of cellulose acylate is known to be around 240°C. Therefore, decomposition will begin when the thermoforming temperature reaches around 240°C. On the other hand, from the viewpoint of melt fluidity, the difficulty in thermoforming with cellulose acetate lies in the need to heat it sufficiently above the melting point to ensure fluidity. For this reason, attempts have been made to add plasticizers or to lower the melting point by using long-chain carboxylic acid esters. In this respect, in the present disclosure, the melting point is around 171°C when there are 3 carbon atoms, so the effect of lowering the melting point is sufficient.

[0029] In this disclosure, the effect of melting point reduction is lower when the carbon number is 7 or more, preferably 8 or more. Conversely, even when creating cellulose mixed fatty acid esters of carboxylic acids with 7 to 8 or more carbon atoms, the reduction in melting point can be suppressed. That is, a certain level of heat resistance can be maintained.

[0030] In the melt molding of cellulose acylates containing cellulose-mixed fatty acid esters, some fatty acid esters may decompose. In the case of propionic acid esters with three carbon atoms, the propionic acid produced by thermal decomposition can be problematic as it resembles the odor of rotting garbage. Similarly, butyric acid (four carbon atoms), pentanoic acid (five carbon atoms), and hexanoic acid (six carbon atoms) may be perceived as having an animalistic odor. Enanthic acid (heptanoic acid) with seven carbon atoms also has a foul odor reminiscent of decaying matter.

[0031] Since the melting point is lowered, the thermoforming temperature can be reduced, and therefore the cellulose-mixed fatty acid ester of this disclosure also reduces odor generation. However, even trace amounts of these substances can sometimes produce an odor, and in terms of both odor and the effect of lowering the melting point, caprylic acid (C8) and capric acid (C10) are preferred. Lauric acid (C12) and myristic acid (C14) are abundant in coconut oil and palm kernel oil, and biomass raw materials are readily available. Furthermore, they are also superior in terms of odor when decomposed.

[0032] Stearic acid with 18 carbon atoms can be obtained from animal fats or vegetable oils. Furthermore, films obtained from these mixed fatty acid esters can have a lower yield strength and a lower modulus of elasticity. Therefore, stearic acid is a viable option when a more flexible molded product is desired. Myristic acid, with its mild odor and abundance in coconut oil and palm kernel oil, is also a strong option. It can produce flexible molded products similar to those obtained with stearic acid with 18 carbon atoms.

[0033] The range of carbon atoms in the long-chain fatty acid esters of the mixed fatty acid esters of this disclosure is as follows: For aliphatic acyl groups with 3 to 24 carbon atoms, 3 to 24, 4 to 24, 5 to 24, preferably 5 to 20, more preferably 6 to 20, even more preferably 7 to 18, and even more preferably 7 to 12, 8 to 18, and 8 to 14 carbon atoms are superior in terms of odor. It is also preferable that the cellulose mixed fatty acid esters according to the second and third embodiments described later contain aliphatic acyl groups that satisfy the above carbon atoms.

[0034] To obtain the effects described herein, the ratio τ is preferably 1.8 or higher, more preferably 1.9 or higher, and even more preferably 2.0 or higher.

[0035] The technical significance of ratio τ in this disclosure is as follows: Generally, polymers exist in three states depending on the temperature: glassy, ​​rubbery, and molten. The transition point from the glassy state to the rubbery state is the glass transition point (temperature) Tg, which is closely related to heat resistance in the case of crystalline polymers. The transition point from the rubbery state to the molten state is the melting point Tm.

[0036] In thermoplastic polymers, micro-Brownian motion is frozen in the glassy state. At temperatures above the glass transition point, micro-Brownian motion, or thermal motion within the molecule, occurs, resulting in a rubbery state. At this point, the polymer's molecular backbone can rotate in place.

[0037] In cellulose acylates, for example, cellulose acetate (CA) has a high melting point. This is due to its molecular structure. The acetyl groups in cellulose acetate strengthen the intermolecular hydrogen bonds. Therefore, a lot of thermal energy is required to melt the crystalline structure of cellulose acetate, resulting in a high melting point. Furthermore, its main chain is not easily bent, resulting in low thermal fluidity during melting. Here, the thermal decomposition temperature is determined by the primary structure of the polymer, so in the case of cellulose acetate, the melting point is close to the thermal decomposition temperature.

[0038] In general polymer thermoforming, increasing the thermoforming temperature facilitates thermal fluidity; however, this is difficult with cellulose acetate because its melting point and thermal decomposition temperature are close together. To mitigate this, cellulose long-chain fatty acid esters were also considered. In this case, acetic anhydride is generally used in combination to esterify the cellulose, resulting in a cellulose mixed fatty acid ester. However, it was found that introducing long-chain fatty acid esters to lower the melting point of the mixed fatty acid ester lowers the melting point, and furthermore, a sub-melting peak is observed in the temperature range below 100°C, impairing its heat resistance. (Non-patent document 1)

[0039] The inventors of this disclosure found that introducing acetyl groups at the 2nd and 3rd positions of the glucose ring of cellulose in cellulose-mixed fatty acid esters mitigates the decrease in melting point. Furthermore, they discovered that introducing a long-chain fatty acid ester at the 6th position of the glucose ring of cellulose relaxes the binding of the molecular chain during melting, thereby increasing melt fluidity, which led to the invention of this disclosure. This technical concept is parameterized by τ.

[0040] τ is the ratio of the sum of the acetyl substitution degrees at positions 2 and 3 to the acetyl substitution degree at position 6. A τ of 1.8 or greater means that the acetyl substitution degree at position 6 can be set to 0 by selecting a method for producing cellulose acetate. For example, cellulose acetate can be completely hydrolyzed, dissolved in a solvent, triphenylacetic acid can be added to protect the substituent at position 6, and then acetylated. This method yields a product in which the hydroxyl groups at positions 2 and 3 are completely acetylated. In this way, the substitution degree at position 6 is zero, so τ can be set to ∞. Furthermore, given the mechanism of action of this disclosure, it is desirable for the substitution degree of the acetyl groups at positions 2 and 3 to be as high as possible, and for the substitution degree of the acetyl group at position 6 to be as low as possible.

[0041] In the manufacturing process described in Patent Document 5, cellulose is treated with trifluoroacetic anhydride in trifluoroacetic acid, and then an acyl donor or acyl donor precursor is added to obtain cellulose acetate with approximately 34 to 43 carbon atoms. However, the total degree of substitution is approximately 1.4 to 1.7.

[0042] In general methods for synthesizing cellulose acetate, as described in Patent Document 6, cellulose acetate with a τ of 2.0 or higher, for example, around 2.1 to 2.3, can be obtained by adjusting the conditions during hydrolysis.

[0043] Furthermore, it is preferable that the cellulose mixed fatty acid esters according to the second and third embodiments described later also satisfy the ratio τ.

[0044] As described above, the value of τ can be increased by decreasing the degree of acetyl group substitution at the 6th position. However, in order to avoid using special solvents in the synthesis of cellulose acetate, the lower limit of τ is 2.0 or higher, more preferably 2.1 or higher, and even more preferably 2.3 or higher.

[0045] As mentioned above, the upper limit of τ can be increased by reducing the degree of substitution at position 6, so a specific numerical range is not set, but for example, it is 10,000 or less, more preferably 1,000 or less, even more preferably 100 or less, and particularly preferably 50 or less.

[0046] Furthermore, from the viewpoint of more favorably exhibiting the effects of the invention according to the first embodiment, the acetyl groups at the 2,3 positions in the cellulose mixed fatty acid ester may be at least 1.5, preferably 1.8, more preferably 1.9, and even more preferably 2.0.

[0047] When the degree of acetyl group substitution at positions 2 and 3 is low, aliphatic acyl groups with 3 to 24 carbon atoms may bond to the remaining hydroxyl groups. As the number of such aliphatic acyl groups with 3 to 24 carbon atoms at positions 2 and 3 increases, the melting point decreases and the heat resistance decreases.

[0048] The fact that the hydroxyl groups at the 2nd and 3rd positions of glucose are acetyl groups suppresses the free movement of the molecular chain when heated, thus conferring heat resistance.

[0049] The effect of the aliphatic acyl group having 3 to 24 carbon atoms in this disclosure is to ensure the fluidity of the rigid cellulose backbone by securing voids between molecular chains when the constraints on the molecular chains are released (i.e., during melting). Therefore, it is more effective for the aliphatic acyl group having 3 to 24 carbon atoms to be bonded to the 6th position of the glucose ring, which is spatially distant from the backbone of the cellulose acylate. In this sense, when τ is high, the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms is preferably 0.5 or higher. Depending on the value of τ, hydroxyl groups at the 2nd and 3rd positions of glucose may also be present, so the upper limit of the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms may be 1 or higher. That is, the upper limit of the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms at the 6th position of the glucose ring is 1, but since it is conceivable that the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms may be present at the 2nd and 3rd positions of glucose, it may be 1 or higher. However, such a configuration is undesirable. The reason is that aliphatic acyl groups with 3 to 24 carbon atoms at the 2nd and 3rd positions of glucose reduce heat resistance. Considering these points, the degree of substitution of aliphatic acyl groups with 3 to 24 carbon atoms is preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.7 or more, and also preferably 1.1 or less, more preferably 1.0 or less, more preferably 0.9 or less, and even more preferably 0.8 or less, with a preferred range being 0.5 to 1.0. The objective of the present invention can be more favorably achieved when the degree of substitution of aliphatic acyl groups with 3 to 24 carbon atoms is in the range of 0.6 to 0.9.

[0050] Furthermore, it is preferable that the cellulose mixed fatty acid esters relating to the second and third embodiments described later also satisfy the said degree of substitution.

[0051] From the viewpoint of more favorably exhibiting the effects of the invention according to the first embodiment, it is more preferable that the cellulose mixed fatty acid ester according to the first embodiment also possesses the characteristics of the cellulose mixed fatty acid ester according to the second and / or third embodiment described later.

[0052] Specifically, in the first embodiment, from the viewpoint of achieving both excellent heat resistance and excellent moldability, it is preferable that the glass transition temperature Tg is 120°C to 180°C and the melting peak temperature Tm is 160°C to 270°C, similar to the second embodiment. Furthermore, in the first embodiment, from the viewpoint of excellent tensile strength, it is also preferable that, similar to the third embodiment, when the cellulose mixed fatty acid ester is made into a film, the tensile breaking strength of the film, measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is 20 MPa to 60 MPa.

[0053] (Second aspect) The cellulose mixed fatty acid ester according to the second aspect of this disclosure is a cellulose mixed fatty acid ester that, like the first aspect, contains an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms.

[0054] The cellulose-mixed fatty acid ester according to the second embodiment has a glass transition temperature Tg of 120°C to 180°C and a melting peak temperature Tm of 160°C to 270°C. That is, similar to the first embodiment of this disclosure, the temperature range of Tm and Tg is set to a specific range by controlling the degree of substitution and substituents at the 2, 3, and 6 positions of the glucose ring. This ensures fluidity during melting while maintaining heat resistance. Considering the technical concept of this disclosure, various variations can be considered in setting the degree of substitution and substituents at the 2, 3, and 6 positions of the glucose ring. For example, a high melting point can be created by using acetyl and propionyl groups at the 2 and 3 positions of the glucose ring. Then, a relatively short long-chain fatty acid, such as caprylic acid ester, can be added to the remaining 6 position. In this case, although it is not the first embodiment, heat resistance and fluidity during melting are ensured by controlling the glass transition temperature Tg and melting peak temperature Tm, which is the technical concept of this disclosure. A glass transition temperature (Tg) within a specific range means that, in the rubbery state, the molecular backbone easily rotates in place due to micro-Brownian motion, or thermal motion within the molecule. A relatively high glass transition temperature (Tg), while keeping the temperature (Tm) relatively low, ensures appropriate fluidity during melting.

[0055] The cellulose-mixed fatty acid ester according to the second embodiment, which possesses the above characteristics, is also a novel cellulose-mixed fatty acid ester and can exhibit effects such as achieving both excellent heat resistance and excellent moldability.

[0056] From the viewpoint of more favorably exhibiting the effects of the invention according to the second embodiment, the glass transition temperature Tg is preferably 120°C or higher, more preferably 125°C or higher, even more preferably 130°C or higher, and also preferably 180°C or lower, more preferably 170°C or lower, and even more preferably 160°C or lower. Preferred ranges include 120-180°C, 120-170°C, 120-160°C, 125-180°C, 125-170°C, 125-160°C, 130-180°C, 130-170°C, and 130-160°C. It is also preferable that the cellulose mixed fatty acid esters according to the first embodiment described above and the third embodiment described below also satisfy these glass transition temperature Tg values.

[0057] Furthermore, from the viewpoint of more favorably exhibiting the effects of the invention according to the second embodiment, the melting peak temperature Tm is preferably 160°C or higher, more preferably 165°C or higher, even more preferably 170°C or higher, and also preferably 270°C or lower, more preferably 265°C or lower, even more preferably 260°C or lower. Preferred ranges include 160-270°C, 160-265°C, 160-260°C, 165-270°C, 165-265°C, 165-260°C, 170-270°C, 170-265°C, and 170-260°C. It is also preferable that the cellulose mixed fatty acid esters according to the first embodiment described above and the third embodiment described later also satisfy these melting peak temperatures Tm.

[0058] From the viewpoint of more favorably exhibiting the effects of the invention according to the second embodiment, it is more preferable that the cellulose mixed fatty acid ester according to the second embodiment also possesses the characteristics of the cellulose mixed fatty acid ester according to the first embodiment and / or the third embodiment described later.

[0059] Specifically, in the cellulose mixed fatty acid ester according to the second embodiment, it is preferable that, as in the first embodiment, some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring of the cellulose mixed fatty acid ester are substituted with acetyl groups. Furthermore, from the viewpoint of excellent tensile strength, in the cellulose mixed fatty acid ester according to the second embodiment, as in the third embodiment, it is also preferable that, when the cellulose mixed fatty acid ester is made into a film, the tensile breaking strength of the film, measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is between 20 MPa and 60 MPa.

[0060] (Third aspect) The cellulose mixed fatty acid ester according to the third aspect of this disclosure has a tensile breaking strength of 20 MPa to 60 MPa when the cellulose mixed fatty acid ester is used as a film, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min. Furthermore, the tensile modulus is preferably 1.5 GPa or less, more preferably 1.4 GPa or less, 1.3 GPa or less, 1.0 GPa or less, or 0.9 GPa or less.

[0061] Furthermore, the elongation at break is 10% or more for a 100 μm film, more preferably 20% or more, 30% or more, or 40% or more.

[0062] The main chain of cellulose and its derivative polymers has a linear structure in which β-D-glucose units are linked by β(1→4) glycosidic bonds. This bonding creates a very stable linear structure in cellulose molecules. This structure is highly strong and rigid. However, this rigidity makes cellulose and its derivative polymers susceptible to impact.

[0063] Cellulose derivatives (e.g., cellulose acetate and cellulose ether) also basically retain this linear main chain structure, but different functional groups are introduced into the side chains. This changes the physicochemical properties of cellulose, making it adaptable to a variety of applications. However, in cellulose mixed fatty acid esters, when long-chain fatty acids are introduced at the 2, 3, and 6 positions of the glucose ring, these fatty acids form an associated structure. Such a structure becomes a mechanical weakness, resulting in a brittle polymer rather than a flexible one. However, as disclosed herein, by limiting the substituents and their types at the 2, 3, and 6 positions of the glucose ring, it is possible to ensure strength, low elastic modulus, and high elongation at break.

[0064] The cellulose-mixed fatty acid ester according to the third embodiment, which possesses the above characteristics, is also a novel cellulose-mixed fatty acid ester and, for example, may have excellent tensile strength.

[0065] From the viewpoint of more favorably exhibiting the effects of the invention according to the third embodiment, the tensile breaking strength of the film is preferably 20 MPa or more, more preferably 25 MPa or more, even more preferably 30 MPa or more, and also preferably 60 MPa or less, more preferably 55 MPa or less, and even more preferably 50 MPa or less. Preferred ranges include 20-60 MPa, 20-55 MPa, 20-50 MPa, 25-60 MPa, 25-55 MPa, 25-50 MPa, 30-60 MPa, 30-55 MPa, and 30-50 MPa. It is also preferable that the cellulose mixed fatty acid ester according to the first and second embodiments described above also satisfy these tensile breaking strengths.

[0066] From the viewpoint of more favorably exhibiting the effects of the invention according to the third embodiment, it is more preferable that the cellulose mixed fatty acid ester according to the third embodiment also possesses the characteristics of the cellulose mixed fatty acid ester according to the first embodiment and / or the second embodiment described above.

[0067] Molecular weight is also an important factor in the third aspect of this disclosure. In the synthesis of cellulose acetate, the hydroxyl groups at positions 2, 3, and 6 in the glucose ring undergo esterification and de-esterification. This is an equilibrium reaction of esterification. Esterification generates water in the reaction system, and this water then undergoes de-esterification (hydrolysis). Since the β(1→4) glycosidic bond is also an ester bond, it undergoes a de-esterification reaction. This reaction is irreversible. Therefore, depending on the esterification conditions, the β(1→4) glycosidic bond is cleaved and the molecular weight decreases. The degree of molecular weight decrease can also be determined by the molecular weight distribution. In general, in the reaction of cellulose long-chain fatty acid esters, the molecular weight tends to decrease, and as the amount of low molecular weight increases, Mn tends to decrease more easily than Mw, so the molecular weight distribution becomes larger. In this disclosure, the molecular weight distribution can be approximately Mw / Mn of 1.5 to 2.5.

[0068] Specifically, the cellulose mixed fatty acid ester according to the third embodiment is preferably a cellulose mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, similar to the first and second embodiments. Furthermore, for the cellulose mixed fatty acid ester according to the third embodiment, similar to the first embodiment, it is preferable that some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring of the cellulose mixed fatty acid ester are substituted with acetyl groups. Also, from the viewpoint of achieving both excellent heat resistance and excellent moldability, it is preferable that the cellulose mixed fatty acid ester according to the third embodiment has a glass transition temperature Tg of 120°C to 180°C and a melting peak temperature Tm of 160°C to 270°C, similar to the second embodiment.

[0069] Preferred embodiments of the cellulose mixed fatty acid ester of this disclosure (even more preferred embodiments common to the first, second, and third embodiments described above) are described below.

[0070] From the viewpoint of more favorably exhibiting the effects of the invention disclosed herein, the total substitution degree DS of the cellulose mixed fatty acid ester of the invention disclosed herein total It is preferable that the total degree of substitution DS is 3.total When expressed as a number to two decimal places, it is preferably 2.80 or higher, more preferably 2.90 or higher, and even more preferably 2.94 or higher.

[0071] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, the number-average molecular weight (Mn) of the cellulose mixed fatty acid ester is preferably 70,000 or more, more preferably 75,000 or more, even more preferably 80,000 or more, and also preferably 100,000 or less, more preferably 95,000 or less, even more preferably 90,000 or less, with preferred ranges including approximately 70,000 to 100,000, approximately 75,000 to 95,000, and approximately 80,000 to 90,000.

[0072] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, the weight-average molecular weight (Mw) of the cellulose mixed fatty acid ester is preferably 150,000 or more, more preferably 15.5 or more, even more preferably 16 or more, and also preferably 180,000 or less, more preferably 175,000 or less, even more preferably 170,000 or less, with preferred ranges including approximately 150,000 to 180,000, approximately 155,000 to 175,000, and approximately 160,000 to 170,000.

[0073] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, the molecular weight distribution (Mw / Mn) of the cellulose mixed fatty acid ester is preferably 1.8 or higher, more preferably 1.85 or higher, even more preferably 1.9 or higher, and also preferably 2.1 or lower, more preferably 2.05 or lower, even more preferably 2.0 or lower, with preferred ranges including 1.8 to 2.1 and 1.9 to 2.0.

[0074] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, the 5% thermal decomposition temperature T of the cellulose mixed fatty acid ester is specified. d5% The temperature is preferably 330°C or higher, more preferably 335°C or higher, even more preferably 340°C or higher, and also preferably 360°C or lower, more preferably 355°C or lower, even more preferably 350°C or lower. Preferred ranges include 330-360°C and 340-350°C.

[0075] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, the 50% thermal decomposition temperature T of the cellulose mixed fatty acid ester is specified. d50% The temperature is preferably 360°C or higher, more preferably 365°C or higher, even more preferably 370°C or higher, and also preferably 400°C or lower, more preferably 395°C or lower, even more preferably 390°C or lower. Preferred ranges include 360-400°C and 370-390°C.

[0076] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, when the cellulose mixed fatty acid ester of the present disclosure is made into a film, the modulus of elasticity of the film, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is preferably 0.7 GPa or higher, more preferably 0.8 GPa or higher, even more preferably 0.9 GPa or higher, and also preferably 1.5 GPa or lower, more preferably 1.4 GPa or lower, and even more preferably 1.3 GPa or lower. Preferred ranges include approximately 0.7 to 1.5 GPa, 0.8 to 1.4 GPa, and 0.9 to 1.3 GPa.

[0077] Furthermore, from the viewpoint of more favorably exhibiting the effects of the present invention, when the cellulose mixed fatty acid ester of the present disclosure is made into a film, the tensile elongation at break of the film, measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, and also preferably 40% or less, more preferably 37% or less, even more preferably 35% or less, with preferred ranges including 5-40%, 7-37%, and 9-35%.

[0078] The cellulose-mixed fatty acid esters of this disclosure can, for example, achieve both excellent heat resistance and excellent moldability. Therefore, the cellulose-mixed fatty acid esters of this disclosure can be used in a variety of applications, such as packaging and building materials.

[0079] [Method for producing cellulose mixed fatty acid esters] The method for producing the cellulose mixed fatty acid ester of the present disclosure, encompassing the first, second, and third embodiments described above, is not particularly limited. The cellulose mixed fatty acid ester of the present disclosure can be suitably produced, for example, by a method comprising the step of acylating the hydroxyl groups of a cellulose acetate having a predetermined degree of substitution using a fatty acid having 3 to 24 carbon atoms.

[0080] Specifically, the method for producing a cellulose mixed fatty acid ester according to this disclosure comprises the following steps 1) to 3), wherein the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or more. 1) A process of synthesizing primary cellulose acetate by acetylating each hydroxyl group of cellulose. 2) A step of hydrolyzing the primary cellulose acetate to synthesize a secondary cellulose acetate in which the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions is 1.8 or more. 3) A step of acylating at least a portion of the remaining hydroxyl groups of the secondary cellulose acetate using a fatty acid having 3 to 24 carbon atoms in the presence of a carboxylic anhydride.

[0081] The present manufacturing method is characterized by comprising a step of acyling the hydroxyl groups of a cellulose acetate having a predetermined degree of substitution using a fatty acid having 3 to 24 carbon atoms. Here, the cellulose acetate having a predetermined degree of substitution is specifically a cellulose acetate in which some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring are substituted with acetyl groups, and the ratio τ of the sum of the acetyl substitution degrees at positions 2 and 3 to the acetyl substitution degree at position 6 is 1.8 or more. In other words, the present manufacturing method is characterized in that the sum of the acetyl substitution degrees at positions 2 and 3 of the cellulose acetate acylated with a fatty acid having 3 to 24 carbon atoms is higher than the acetyl substitution degree at position 6. By using such a cellulose acetate having a predetermined degree of substitution as a raw material and acyling it using a fatty acid having 3 to 24 carbon atoms, the cellulose mixed fatty acid ester of this disclosure can be suitably produced.

[0082] The degree of acetyl substitution in the cellulose acetate used as a raw material is preferably 2.0 or higher, more preferably 2.1 or higher, and even more preferably 2.2 or higher. It is also, for example, 4000 or less, preferably 2.5 or less, more preferably 2.4 or less, and even more preferably 2.3 or less, with a preferred range being 2.0 to 2.5. In the cellulose acetate used as a raw material, it is sufficient that some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring are substituted with acetyl groups, and may be further substituted with other fatty acids, but it is preferable that only acetyl groups are substituted for the hydroxyl groups.

[0083] Furthermore, the total degree of substitution of the cellulose acetate used as a raw material is preferably 1.5 or higher, more preferably 1.7 or higher, even more preferably 1.8 or higher, and also preferably 1.9, 2.0, 2.1, and more preferably 2.5 or lower, more preferably 2.3 or lower.

[0084] The number-average molecular weight (Mn) of the cellulose acetate used as a raw material is preferably 30,000 or more, more preferably 40,000 or more, even more preferably 50,000 or more, and also preferably 100,000 or less, more preferably 90,000 or less, even more preferably 80,000 or less, with a preferred range being around 50,000 to 80,000.

[0085] Furthermore, the weight-average molecular weight (Mw) of the cellulose acetate used as a raw material is preferably 80,000 or more, more preferably 90,000 or more, even more preferably 100,000 or more, and also preferably 150,000 or less, more preferably 140,000 or less, even more preferably 130,000 or less, with a preferred range being around 100,000 to 130,000.

[0086] Furthermore, the molecular weight distribution (Mw / Mn) of the cellulose acetate used as a raw material is preferably 1.0 or higher, more preferably 1.5 or higher, even more preferably 1.8 or higher, and also preferably 3.0 or lower, more preferably 2.5 or lower, even more preferably 2.2 or lower, with a preferred range being 1.8 to 2.2.

[0087] Furthermore, the 5% thermal decomposition temperature T of the cellulose acetate used as a raw material d5% The temperature is preferably 300°C or higher, more preferably 320°C or higher, even more preferably 340°C or higher, and also preferably 400°C or lower, more preferably 380°C or lower, even more preferably 360°C or lower. Preferred ranges include 300-400°C and 340-360°C.

[0088] Furthermore, the 50% thermal decomposition temperature T of the cellulose acetate used as a raw material d50% The temperature is preferably 340°C or higher, more preferably 350°C or higher, even more preferably 360°C or higher, and also preferably 420°C or lower, more preferably 410°C or lower, even more preferably 400°C or lower. Preferred ranges include 340-420°C and 360-400°C.

[0089] Furthermore, when the cellulose acetate used as the raw material is made into a film, the tensile breaking strength of the film, measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is preferably 40 MPa or more, more preferably 50 MPa or more, even more preferably 60 MPa or more, and also preferably 120 MPa or less, more preferably 110 MPa or less, even more preferably 100 MPa or less, with a preferred range being 60 to 100 MPa.

[0090] Furthermore, when the cellulose acetate used as the raw material is made into a film, the elastic modulus of the film, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is preferably 1.5 GPa or higher, more preferably 1.7 GPa or higher, even more preferably 2.0 GPa or higher, and also preferably 4 GPa or lower, more preferably 3.5 GPa or lower, even more preferably 3.0 GPa or lower, with a preferred range being 2.0 to 3.0 GPa.

[0091] Furthermore, when the cellulose acetate used as the raw material is made into a film, the tensile elongation at break of the film, measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and also preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, with a preferred range being 3 to 10%.

[0092] The cellulose acetate described above is publicly known, and the cellulose acetate used as a raw material can be manufactured according to the instructions in, for example, Patent Document 5 or Patent Document 6.

[0093] Regarding methods for acylating the hydroxyl groups of cellulose acetate using fatty acids with 3 to 24 carbon atoms, known methods for reacting the hydroxyl groups of cellulose acetate with fatty acids can be employed. For example, methods such as reacting cellulose acetate with fatty acids with 3 to 24 carbon atoms in the presence of trifluoroacetic anhydride, or reacting cellulose acetate with fatty acids with 3 to 24 carbon atoms in the presence of dimethylacetamide can be used.

[0094] The fatty acid with an aliphatic acyl group having 3 to 24 carbon atoms that is reacted with cellulose acetate preferably has 3 to 24 carbon atoms, more preferably 3 to 20 carbon atoms, and even more preferably 3 to 18 carbon atoms.

[0095] The cellulose mixed fatty acid ester produced by the method for producing cellulose mixed fatty acid esters of this disclosure may be subjected to purification, drying, and other processes by known methods.

[0096] [Molded body] The molded articles of this disclosure are formed by molding the cellulose mixed fatty acid ester of this disclosure as described above. As described above, the cellulose mixed fatty acid ester of this disclosure can achieve both excellent heat resistance and excellent moldability. Therefore, the molded articles of this disclosure have excellent heat resistance and can be easily manufactured by heating and pressurizing the cellulose mixed fatty acid ester of this disclosure.

[0097] The shape of the molded article of this disclosure is not particularly limited and can be appropriately selected depending on the application. Specific examples of the shape of the molded article of this disclosure include film-like, sheet-like, plate-like, and dumbbell-shaped articles.

[0098] The temperature at which the cellulose mixed fatty acid ester of this disclosure is molded into the molded article of this disclosure varies depending on the shape of the molded article, but is, for example, 150°C or higher, preferably 170°C or higher, and also, for example, 280°C or lower, preferably 230°C or lower, with a preferred range being around 170 to 230°C.

[0099] Furthermore, the pressure applied when molding the cellulose mixed fatty acid ester of this disclosure into a molded article of this disclosure varies depending on the shape of the molded article, but is, for example, 1 MPa or more, preferably 5 MPa or more, and also, for example, 80 MPa or less, preferably 60 MPa or less, with a preferred range being around 5 to 60 MPa. [Examples]

[0100] The present disclosure will be explained in more detail below with reference to examples. In the following examples, cellulose diacetate synthesized based on the description in Patent Document 6 was used as the cellulose acetate powder (cellulose diacetate (CDA)). The characteristics of the cellulose diacetate used are as follows.

[0101] (Characteristics of cellulose acetate powder) Total degree of acetyl substitution: 2.2-2.3 Substitution distribution of acetyl groups: 0.6-0.8 at the 6-position of the glucose ring, 0.8-1.0 at the 2-position, and 0.6-0.8 at the 3-position Number average molecular weight (Mn): 5.3×10 4 Weight average molecular weight (Mw): 11.1×10 4 Molecular weight distribution (Mw / Mn): 2.1 5% thermal decomposition temperature (T d5% ): 342°C 50% thermal decomposition temperature (T d50% ): 371°C Glass transition temperature (Tg): 213°C Melting peak temperature (Tm): 247°C

[0102] [Preparation of cellulose mixed fatty acid ester compound] In Examples 1 to 7, cellulose acetate (cellulose diacetate, CDA) was reacted with various carboxylic acids respectively by the following procedure to prepare a cellulose mixed fatty acid ester compound (see the reaction scheme in Figure 1).

[0103] (Example 1) 200 mL of trifluoroacetic anhydride (TFAA) and 50 mL of propionic acid were mixed at 50°C for 10 minutes. Then, 10 g of the cellulose acetate powder was added. After all the cellulose acetate powder was dissolved (about 10 minutes), the mixture was further stirred at 50°C for 2 hours to react cellulose acetate with propionic acid. After the reaction, the solution was slowly poured into 1.8 L of a mixed solvent of methanol and water, wherein the volume ratio of methanol to water was 5:1. The obtained precipitate was collected by filtration, and the precipitate was washed again with 1.8 L of a mixed solvent of methanol and water (volume ratio of methanol to water: 5:1), followed by filtration. Next, chloroform was added to the obtained precipitate, methanol was added to the solution obtained after filtration, and a precipitate was obtained. This precipitate was washed twice with methanol and water. The precipitate was further washed with water and freeze-dried. Through the above procedure, a cellulose mixed fatty acid ester compound, in which hydrogen atoms of hydroxyl groups of cellulose are substituted with acetyl groups and propionate groups, was obtained.

[0104] (Example 2) A cellulose mixed fatty acid ester compound was obtained in the same manner as in Example 1, except that hexanoic acid was used instead of propionic acid, in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and hexanoate groups.

[0105] (Example 3) A cellulose mixed fatty acid ester compound was obtained in the same manner as in Example 1, except that heptanoic acid was used instead of propionic acid, in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and heptanoic acid (heptanoate) groups.

[0106] (Example 4) A cellulose mixed fatty acid ester compound was obtained in the same manner as in Example 1, except that octanoic acid was used instead of propionic acid, in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and octanoic acid (octanoate) groups.

[0107] (Example 5) A cellulose mixed fatty acid ester compound was obtained in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and decanoate groups, in the same manner as in Example 1, except that decanoic acid was used instead of propionic acid.

[0108] (Example 6) A cellulose mixed fatty acid ester compound was obtained in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and myristate groups, in the same manner as in Example 1, except that myristic acid was used instead of propionic acid.

[0109] (Example 7) Except for using stearic acid instead of propionic acid, a cellulose mixed fatty acid ester compound was obtained in the same manner as in Example 1, in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and stearic acid groups.

[0110] [Measuring the degree of substitution] The degree of substitution (DS) of the cellulose mixed fatty acid ester compounds obtained in each example was determined by nuclear magnetic resonance spectroscopy using a nuclear magnetic resonance spectrometer (JNM-A500, 500 MHz, JEOL Ltd., Tokyo, Japan) with tetramethylsilane as the internal reference. 1 The measurement was performed by 1HNMR. The measurement solvent was chloroform- d1 The solution concentration was set to 2.5 mg / mL. The degree of substitution (DS) of the acetyl group of the cellulose acetate (CDA) used as the raw material was determined. AC For the following, TFA-d1 was used as the measurement solvent, and the measurement was performed in the same manner as a reference example. Degree of substitution of acetyl group (DS AC ) and the degree of substitution of carboxyl groups other than acetyl groups (DS Al The result was calculated using the following formula: DS AC =(Ib / 3) / (Ic / 7) DS Al =(Ia / 3) / (Ic / 7) Ia represents the area of ​​the peak for the methyl group of the carboxyl group (0.75-1.05 ppm), Ib represents the area of ​​the peak for the methyl group of the acetyl group (1.85-2.15 ppm), and Ic represents the area of ​​the peak for the pluton of the glucose ring (3.2-5.3 ppm). The results are shown in Tables 1 and 2.

[0111] [Table 1]

[0112] In Table 1, DS total This is the total degree of substitution.

[0113] [Table 2]

[0114] [Measurement of molecular weight] The molecular weights (number-average weight Mn, weight-average molecular weight Mw, and molecular weight distribution Mw / Mn) of the cellulose mixed fatty acid ester compounds obtained in each example, and the cellulose acetate (CDA) used as the raw material, were measured by gel permeation chromatography (GPC) using a Shimadzu 10AVP system. All measurements were performed at 40°C using polystyrene gel columns (Shimadzu Simpack GPC-80MC x 2 and GPC-8025C), with chloroform as the solvent and a flow rate of 0.8 mL / min. The concentration of the measurement solution was 2.5 mg / mL. The results are shown in Table 3.

[0115] [Table 3]

[0116] [Measurement of pyrolysis temperature] Thermogravimetric analysis (TGA) of the cellulose-mixed fatty acid ester compounds obtained in each example was performed using a thermogravimetric analyzer (TGA-50, Shimadzu Corporation). All tests were conducted in a temperature range of 100 to 550°C under a nitrogen atmosphere at a heating rate of 20°C / min. The results are shown in Table 4.

[0117] [Table 4]

[0118] [Measurement of glass transition temperature and melting peak temperature] The melting peak temperatures (°C) of the cellulose mixed fatty acid ester compounds obtained in each example, and the cellulose acetate (CDA) used as the raw material, were measured by differential scanning calorimetry (DSC). A Seiko DSC6200 / EXSTAR6000 instrument was used for the measurements. The sample was first cooled to 0°C, and then heated to 300°C at a scan rate of 100°C / min (first heating scan). Immediately afterward, it was rapidly cooled to -50°C at a rate of 200°C / min and maintained for 2 minutes. The second heating scan was performed from -50°C to 300°C at a scan rate of 100°C / min, and a stable thermogram was recorded. The glass transition temperature results are shown in Table 5. The melting peak temperature results are shown in Table 6.

[0119] [Table 5]

[0120] [Table 6]

[0121] [Film manufacturing] Films were produced by hot pressing the cellulose-mixed fatty acid ester compounds obtained in each example, along with the cellulose acetate (CDA) used as the raw material. Specifically, the samples were placed at intervals on a polytetrafluoroethylene sheet (PTFE, 10 × 10 cm), preheated at 2 MPa for 1 minute, and then heated at 15 MPa for 2 minutes to obtain films with a thickness of 0.1-0.2 mm. The hot pressing temperature for each sample was increased in 5°C increments starting from a temperature 20°C above the glass transition temperature, until the minimum temperature required for hot pressing was finally determined. Photographs of the films of the cellulose-mixed fatty acid ester compounds obtained in each example are shown in Figure 8.

[0122] [Tensile test of film] Tensile tests were performed on each of the films obtained above using an EZ testing machine (Shimadzu Corporation, Japan), and stress-strain curves were obtained for all molten films. The initial height was 10 mm, and the tests were performed at a strain rate of 10 mm / min. Each film was prepared as a sample with dimensions of 30 mm × 5 mm, and at least eight samples were tested. The measurement results (average values) for tensile breaking strength, tensile elongation at breaking, and elastic modulus are shown in Table 7, Figure 5, and Figure 6. As shown in Figures 5 and 6, as the length of the aliphatic acyl group side chain increased, the tensile strength decreased from 77 MPa to 28 MPa, and the elastic modulus decreased from 2.3 GPa to 0.75 GPa. As the length of the aliphatic acyl group side chain increased, the elongation rate increased, and the film became softer.

[0123] [Table 7]

[0124] [X-ray diffraction measurement of film] The crystal structures of each film obtained above were recorded using an X-ray diffractometer (XRD, Miniflex600, Rigaku) ​​with monochromatic CuKα rays (λ=0.15059nm) at 40kV and 15mA. The 2theta scan range was 5-45°, the step size was 0.05°, and the speed was 10° / min. The results are shown in Table 8. Figure 2 shows a graph of the XRD measurement results. From the graph in Figure 2, it was confirmed that the CDA-Pr film showed crystalline structures, while all the other films had amorphous structures. Figure 4 shows graphs of the XRD measurement results for the films (heated at 250°C and 260°C) and powder of the cellulose mixed fatty acid ester compound obtained in Example 1. The CDA-Pr film showed crystalline structures, while all the other films had amorphous structures. CDA-Pr crystallization occurred at 240-250°C. There were some crystals at 260°C.

[0125] [Injection molding] Each of the films obtained above was cut to prepare pellets. 4g of pellets were placed in a cylinder, preheated for 10-15 minutes, and then injection molded at 600 bar to obtain sheets. Table 8 shows the feasibility of injection molding and the processing temperature. Photographs of the injection-molded sheets of cellulose-mixed fatty acid ester compounds obtained in each example are shown.

[0126] [Table 8]

[0127] [Production of Cellulose Mixed Fatty Acid Ester Compounds] (Example 8) 1.5 g of the cellulose acetate powder was dissolved in 40 mL of dimethylacetamide (N,N-Dimethylacetamide, DMAc) at 70°C. 7.2 g of pyridine (Py) and 20 g of propionic anhydride were mixed with the resulting solution and reacted at 70°C for 24 hours to produce a cellulose mixed fatty acid ester compound (see the reaction equation in Figure 3). The reaction solution was slowly poured into 500 mL of a methanol-water mixture (methanol to water volume ratio 5:1). The resulting precipitate was filtered, washed again with 500 mL of methanol-water mixture (methanol to water volume ratio 5:1), and filtered again. Next, chloroform was added to the precipitate, and methanol was added to the filtered solution to obtain a precipitate. This precipitate was washed twice with methanol and water. The precipitate was further washed with water and freeze-dried. By following the above procedure, a cellulose mixed fatty acid ester compound was obtained in which the hydrogen atoms of the hydroxyl groups of cellulose were replaced with acetate groups and propionic acid groups.

[0128] (Example 9) A cellulose mixed fatty acid ester compound was obtained in the same manner as in Example 8, except that hexanoic acid anhydride was used instead of propionic anhydride, in which the hydrogen atoms of the hydroxyl groups of cellulose were substituted with acetate groups and hexanoic acid groups.

[0129] [Measurement of degree of substitution, molecular weight, thermal decomposition temperature, and glass transition temperature] The degree of substitution, molecular weight, thermal decomposition temperature, and glass transition temperature (Tg) of the cellulose-mixed fatty acid ester compounds obtained in Examples 8 and 9 were measured in the same manner as in Examples 1 and 2. The measurement results, along with those from Examples 1 and 2, are shown in Table 9.

[0130] [Table 9]

[0131] As shown in Table 9, although the methods for producing the cellulose mixed fatty acid ester compound differ between Examples 1 and 2 and Examples 8 and 9, it can be seen that the resulting cellulose mixed fatty acid ester compounds possess similar physical properties.

[0132] [Measurement of the melting peak temperature of the film] The melting peak temperatures (°C) of the cellulose mixed fatty acid ester compound films obtained in each example, and the cellulose acetate (CDA) film used as the raw material, were measured by differential scanning calorimetry (DSC). A Seiko DSC6200 / EXSTAR6000 instrument was used for the measurements. The sample was first cooled to 0°C, and then heated to 300°C at a scan rate of 100°C / min (first heating scan). Immediately afterward, it was rapidly cooled to -50°C at a rate of 200°C / min and maintained for 2 minutes. The second heating scan was performed from -50°C to 300°C at a scan rate of 100°C / min, and a stable thermogram was recorded. The results are shown in Figure 7. As shown in Figure 7, an endothermic peak appeared in the 1st run, which is considered to be the melting temperature. This temperature change trend is similar to the change in the glass transition temperature.

[0133] As described above, this disclosure provides inventions in the following embodiments. Item 1. A cellulose mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, In the aforementioned cellulose mixed fatty acid ester, some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring are substituted with acetyl groups. The ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or greater. A cellulose mixed fatty acid ester in which the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms is 0.5 or more. Item 2. Total degree of substitution DS of the cellulose mixed fatty acid ester. total However, the cellulose mixed fatty acid ester described in item 1 is between 2.5 and 3.0. Item 3. The cellulose mixed fatty acid ester according to item 1 or 2, wherein the number-average molecular weight (Mn) of the cellulose mixed fatty acid ester is 70,000 or more and 100,000 or less. Item 4. The cellulose mixed fatty acid ester according to any one of items 1 to 3, wherein the weight-average molecular weight (Mw) of the cellulose mixed fatty acid ester is 150,000 or more and 180,000 or less. Item 5. The cellulose mixed fatty acid ester according to any one of items 1 to 4, wherein the molecular weight distribution (Mw / Mn) of the cellulose mixed fatty acid ester is 1.8 or more and 2.1 or less. Item 6. A cellulose mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, The glass transition temperature Tg is between 120°C and 180°C. A cellulose-mixed fatty acid ester having a melting peak temperature Tm of 160°C to 270°C. Item 7. 5% thermal decomposition temperature T of the cellulose mixed fatty acid ester. d5% However, the cellulose mixed fatty acid ester described in any one of items 1 to 6 is 330°C or higher. Item 8. 50% thermal decomposition temperature T of the cellulose mixed fatty acid ester. d50% However, the cellulose mixed fatty acid ester described in any one of items 1 to 7 is 360°C or higher. Item 9. Cellulose mixed fatty acid ester, A cellulose-mixed fatty acid ester, when formed into a film, has a tensile breaking strength of 20 MPa or more and 60 MPa or less, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min. Item 10. The cellulose mixed fatty acid ester according to Item 9, wherein the modulus of elasticity, as measured by the tensile test, is 0.7 GPa or more and 1.5 GPa or less. Item 11. The cellulose mixed fatty acid ester according to item 9 or 10, wherein the tensile elongation at break of the film, as measured by the tensile test, is 5% or more and 40% or less. Item 12. The glass transition temperature Tg is between 120°C and 180°C. A cellulose mixed fatty acid ester according to any one of items 1 to 5 or 9 to 11, wherein the melting peak temperature Tm is 160°C or higher and 270°C or lower. Item 13. 5% thermal decomposition temperature T of the cellulose mixed fatty acid ester. d5% However, the cellulose mixed fatty acid ester described in any one of items 9 to 11 is 330°C or higher. Item 14. 50% thermal decomposition temperature T of the cellulose mixed fatty acid ester. d50% However, the cellulose mixed fatty acid ester described in any one of items 9 to 11 is 360°C or higher. Item 15. The cellulose mixed fatty acid ester according to any one of items 1 to 8, wherein, when the cellulose mixed fatty acid ester is used as a film, the tensile breaking strength of the film, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min, is 20 MPa or more and 60 MPa or less. Item 16. The cellulose mixed fatty acid ester according to Item 15, wherein the modulus of elasticity, as measured by the tensile test, is 0.7 GPa or more and 1.5 GPa or less. Item 17. The cellulose mixed fatty acid ester according to item 15 or 16, wherein the tensile elongation at break of the film, as measured by the tensile test, is 5% or more and 40% or less. Item 18. A method for producing a cellulose mixed fatty acid ester, comprising the steps 1) to 3) below, wherein the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or greater. 1) A process of synthesizing primary cellulose acetate by acetylating each hydroxyl group of cellulose. 2) A step of hydrolyzing the primary cellulose acetate to synthesize a secondary cellulose acetate in which the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions is 1.8 or more. 3) A step of acylating at least a portion of the remaining hydroxyl groups of the secondary cellulose acetate using a fatty acid having 3 to 24 carbon atoms in the presence of a carboxylic anhydride.

Claims

1. A cellulose-mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, In the aforementioned cellulose-mixed fatty acid ester, some of the hydroxyl groups at positions 2, 3, and 6 of the glucose ring are substituted with acetyl groups. The ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or greater. A cellulose-mixed fatty acid ester in which the degree of substitution of the aliphatic acyl group having 3 to 24 carbon atoms is 0.5 or more.

2. Total substitution degree DS of the cellulose mixed fatty acid ester total The cellulose mixed fatty acid ester according to claim 1, wherein the ratio is 2.5 to 3.

0.

3. The cellulose mixed fatty acid ester according to claim 1 or 2, wherein the number-average molecular weight (Mn) of the cellulose mixed fatty acid ester is 70,000 or more and 100,000 or less.

4. The cellulose mixed fatty acid ester according to claim 1 or 2, wherein the weight-average molecular weight (Mw) of the cellulose mixed fatty acid ester is 150,000 or more and 180,000 or less.

5. The cellulose mixed fatty acid ester according to claim 1 or 2, wherein the molecular weight distribution (Mw / Mn) of the cellulose mixed fatty acid ester is 1.8 or more and 2.1 or less.

6. A cellulose-mixed fatty acid ester containing an acetyl group and an aliphatic acyl group having 3 to 24 carbon atoms, The glass transition temperature Tg is between 120°C and 180°C. A cellulose-mixed fatty acid ester having a melting peak temperature Tm of 160°C or higher and 270°C or lower.

7. The 5% thermal decomposition temperature T of the cellulose mixed fatty acid ester d5% The cellulose mixed fatty acid ester according to claim 6, wherein the temperature is 330°C or higher.

8. The 50% thermal decomposition temperature T of the cellulose mixed fatty acid ester. d50% The cellulose mixed fatty acid ester according to claim 6 or 7, wherein the temperature is 360°C or higher.

9. A cellulose mixed fatty acid ester, The cellulose-mixed fatty acid ester, when used as a film, has a tensile breaking strength of 20 MPa or more and 60 MPa or less, as measured by a tensile test under the conditions of a temperature of 25°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min.

10. The cellulose mixed fatty acid ester according to claim 9, wherein the modulus of elasticity, as measured by the tensile test, is 0.7 GPa or more and 1.5 GPa or less.

11. The cellulose mixed fatty acid ester according to claim 9 or 10, wherein the tensile elongation at break of the film, as measured by the tensile test, is 5% or more and 40% or less.

12. A method for producing a cellulose mixed fatty acid ester, comprising the steps 1) to 3) below, wherein the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions to the acetyl substitution degree at the 6th position is 1.8 or more. 1) A process of synthesizing primary cellulose acetate by acetylating each hydroxyl group of cellulose. 2) A step of hydrolyzing the primary cellulose acetate to synthesize a secondary cellulose acetate in which the ratio τ of the sum of the acetyl substitution degrees at the 2nd and 3rd positions is 1.8 or more. 3) A step of acylating at least a portion of the remaining hydroxyl groups of the secondary cellulose acetate using a fatty acid having 3 to 24 carbon atoms in the presence of a carboxylic anhydride.

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