Low molecular weight cellulose derivative composition and method for producing the same

Abstract

A low-molecular-weight cellulose derivative composition having a weight-average molecular weight of 40,000 or less, which is less colored and has excellent stability, is provided by producing a low-molecular-weight cellulose derivative at low cost and with high purity. [Solution] The low-molecular-weight cellulose derivative composition is provided by a method for producing the low-molecular-weight cellulose derivative composition, which comprises adding a radical generator to a solution in which a cellulose derivative is dissolved in an organic solvent, obtaining a low-molecular-weight cellulose derivative by a radical reaction, and then adding a radical scavenger.

Description

[Technical Field]

[0001] The present invention relates to a composition containing a low-molecular-weight cellulose derivative having a weight-average molecular weight of 40,000 or less and a radical scavenger. [Background technology]

[0002] Cellulose derivatives, which are made from chemically modified cellulose, a biomass material, are being reexamined in light of sustainability and waste issues. Cellulose derivatives have long been developed as semi-artificial polymers, and have excellent thickening, water absorption, and water retention properties, making them widely used in a variety of applications, including food additives, feed additives, cosmetics, thickeners, viscosity modifiers, binders, adhesives, inks, binders for various pastes and slurries, films, various components, and water absorption and retention agents. Furthermore, the thermotropic and lyotropic liquid crystallinity exhibited by the rigidity of the polymer chains is expected to lead to applications as high-performance materials.

[0003] As for cellulose derivatives, various types have been developed, such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, cellulose acetate (acetyl cellulose, diacetyl cellulose, triacetyl cellulose, etc.), cellulose acetate propionate, cellulose acetate butyrate, and nitrocellulose, as seen in Non-Patent Document 1, for example.

[0004] In addition, materials with various molecular weights are required depending on the application. For example, ethyl cellulose has excellent solution viscosity characteristics, making it useful as a binder for printing compositions used in the manufacture of electronic components. With the advancement of miniaturization in electronic components, the metal and ceramic particles contained in the printing compositions used tend to become finer. However, this fineness increases the viscosity of the printing composition, posing a problem of reduced printability. To solve this problem, it is necessary to lower the molecular weight of ethyl cellulose, but this is limited by production costs and quality issues. For example, the lowest weight-average molecular weight of commercially available ethyl cellulose is approximately 44,000, posing a challenge in reducing the viscosity of printing compositions.

[0005] Commercially available cellulose derivatives are available in a variety of molecular weights and grades. Their production methods include hydrolyzing (depolymerizing) raw cellulose with oxidation or acid to reduce its molecular weight, followed by etherification or esterification, or hydrolyzing (depolymerizing) the cellulose derivative with acid. Furthermore, cellulose derivative grades with different molecular weights can be obtained by fractionating the cellulose derivatives based on their solubility in water or organic solvents. These reactions require a neutralization reaction because of the use of acid, and water washing is required to remove the resulting salt. This purification process has presented challenges, including reduced yields and high costs due to the difficulty of recovery, as well as insufficient purification, which can lead to problems with purity and quality. To address these challenges, a technique has been proposed in which cellulose derivatives are powdered and then depolymerized with acidic gases such as hydrogen chloride (hydrogen halide) to reduce their molecular weight (Patent Documents 1-4). However, this method also faces challenges such as coloration, safety issues, the need for large-scale equipment, and the high cost of the equipment. Hydrogen chloride is absorbed by the water contained in the cellulose derivative, resulting in acidity and a continuous decrease in molecular weight, as well as residual hydrochloric acid, which limits its application. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Toyozo Hamada, "Synthesis and Use of Cellulose Derivatives and Acetic Acid / Acetic Acid Derivatives," Chemistry and Education, Chemical Society of Japan, 2023, Vol. 71, No. 8, pp. 330-333 [Patent documents]

[0007] [Patent Document 1] Special Publication No. 48-41037 [Patent Document 2] Special Publication No. 60-9041 [Patent Document 3] Special Publication No. 2002-531594 [Patent Document 4] Special Publication No. 2008-500426 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a low-molecular-weight cellulose derivative composition with little coloration and excellent stability, which is produced by a new method for producing a low-molecular-weight cellulose derivative that solves the problems of safety, cost, purity, and stability in the prior art, and also relates to a method for producing the same. [Means for solving the problem]

[0009] The present inventors have found that radical generators, which are generally used as polymerization initiators for polymers, cleave glycosidic bonds in cellulose derivatives. Furthermore, the presence of residual radical generators has been found to cause further cleavage of glycosidic bonds, resulting in a decrease in the average molecular weight of the degraded cellulose derivative over time. However, this problem has been solved by adding a specific amount of another additive to the degraded cellulose derivative to prepare a low-molecular-weight cellulose derivative composition, leading to the present invention.

[0010] That is, the present invention provides a cellulose derivative composition containing a cellulose derivative having a weight-average molecular weight of 40,000 or less and a radical scavenger in an amount of 50 to 500 ppm relative to the cellulose derivative. Also, the cellulose derivative in the cellulose derivative composition is ethyl cellulose. Also, the cellulose derivative but does not have a hydroxyl group A radical generator is added to a solution of the cellulose in an organic solvent to obtain a low molecular weight cellulose derivative, and then a radical scavenger is added. 50 to 500 ppm based on the amount of low molecular weight cellulose derivative after radical reaction The present invention relates to a method for producing a low molecular weight cellulose derivative composition to be added. [Effects of the Invention]

[0011] The low-molecular-weight cellulose derivative composition of the present invention contains a low-molecular-weight cellulose derivative having a weight-average molecular weight of 40,000 or less, a molecular weight not found in commercially available products, and is excellent in stability. Furthermore, the cellulose derivative composition of the present invention does not suffer from discoloration, and is therefore useful as a blend, similar to conventional cellulose derivatives. Furthermore, the production method of the present invention does not require special equipment or processes, and produces almost no by-products or impurities, making it a production method with excellent productivity and safety. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Low-molecular-weight cellulose derivatives and methods for producing same> Cellulose derivative raw materials Examples of cellulose derivatives include methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, cellulose acetate (acetyl cellulose, diacetyl cellulose, triacetyl cellulose, etc.), cellulose acetate propionate, cellulose acetate butyrate, nitrocellulose, etc. Among these, ethyl cellulose, which has good viscosity characteristics, is useful because it can be used in a wide range of applications.

[0013] Cellulose derivatives are produced from pulp through various chemical reactions, such as esterification and etherification. Because alkalis and acids are used in the production process, water or water-containing solvents are often used to remove them, i.e., for purification. To adjust molecular weight, acids such as hydrogen chloride are sometimes used to sever the polymer chains. Therefore, cellulose derivatives with low molecular weights are highly hydrophilic or water-soluble, making purification difficult and limiting the lower molecular weight limit.

[0014] The cellulose derivative used as a raw material in the present invention is preferably one with as low a molecular weight as possible, and commercially available cellulose derivatives with a weight average molecular weight of 44,000 to 60,000 are preferably used.

[0015] Low molecular weight cellulose derivative composition Next, the composition will be described in detail. The low-molecular-weight cellulose derivative composition of the present invention comprises a low-molecular-weight cellulose derivative having a weight-average molecular weight of 40,000 or less and a radical scavenger in an amount of 50 to 500 ppm relative to the low-molecular-weight cellulose derivative. In the following description, the term "cellulose derivative" refers to one having a current weight-average molecular weight of 44,000 or more, and the term "low-molecular-weight cellulose derivative" refers to one having a weight-average molecular weight of 40,000 or less.

[0016] Radical scavengers are agents that energetically stabilize radicals, and so-called hindered phenols and hindered amines are used. Examples include hydroquinone (abbreviation: HQ), hydroquinone monomethyl ether (abbreviation: HQME), 3,5-dibutyl-4-hydroxytoluene (abbreviation: BHT), butylhydroxyanisole (abbreviation: BHA), and product names such as the Irganox series manufactured by BASF and the KEMINOX series manufactured by Chemipro Chemical.

[0017] The low-molecular-weight cellulose derivative composition of the present invention may contain an organic solvent. The organic solvent is preferably one that dissolves the cellulose derivative, and examples thereof include ethyl acetate, butyl acetate, hexyl acetate, tetrahydrofuran, dioxane, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, toluene, xylene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethyl lactate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate (butyl carbitol acetate), diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol butyl ... Examples of the organic solvent include ethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol monomethyl ether acetate, propylene glycol dimethyl ether, propylene glycol diacetate, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, dihydroterpineol acetate, ethyl alcohol, isopropyl alcohol, butyl alcohol, benzyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, terpineol, dihydroterpineol, etc. Only one organic solvent may be used, or two or more organic solvents may be used in combination.

[0018] In the case of a composition containing an organic solvent, the concentration of the low-molecular-weight cellulose derivative is preferably in the range of 1% by mass to 80% by mass, although the optimum concentration may be selected depending on the application and is not limited to this range.

[0019] Method for producing a low-molecular-weight cellulose derivative composition The method for producing a low-molecular-weight cellulose derivative composition is described in detail below. As mentioned above, the only cellulose derivatives currently available on the market have a weight-average molecular weight of about 44,000 or more. Therefore, the key point is to convert these cellulose derivatives with a weight-average molecular weight of 44,000 or more into low-molecular-weight cellulose derivatives with a weight-average molecular weight of 40,000 or less using the method described below.

[0020] The organic solvent used in the production of the low-molecular-weight cellulose derivative composition of the present invention can be the same as the organic solvent used as the solvent for the low-molecular-weight cellulose derivative composition of the present invention. As will be described later, in order to optimize the reaction conditions, the organic solvent used in the production method of the low-molecular-weight cellulose derivative composition of the present invention should not have a hydroxyl group. It is necessary.

[0021] The radical generator referred to in the present invention means any compound capable of generating radicals in a reaction system by interacting with substances in the system, such as azo-based or peroxide-based compounds and metal compounds.

[0022] As the radical generator, various azo-based and peroxide-based compounds can be used. Examples of azo-based compounds include azobisbutyronitrile (AIBN) and V-601, VR-110, and V-70 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Examples of peroxide-based compounds include benzoyl peroxide (BPO) and various peroxides manufactured by NOF Corporation, such as Perocta-based, Perhexa-based, Percumyl-based, Permenta-based, Perbutyl-based, and Peroyl-based compounds. It is well known that these peroxides generate radicals at lower temperatures when amines such as anilines and pyridines are added (so-called redox systems).

[0023] Various metal compounds that are thought to generate radicals through redox reactions can also be used as radical generators. Examples include copper compounds with carboxylic acid ligands, such as copper acetate, copper propionate, copper isobutyrate, copper bis(cyclohexanebutyrate), copper caproate, copper 2-ethylhexanoate, and copper laurate, as well as copper chloride, zinc acetate, zinc butyrate, nickel acetate, nickel isobutyrate, and nickel cyclohexanebutyrate. Because these metal compounds have limited solubility in organic solvents, long-chain carboxylic acid compounds, amines, and crown ethers may be added to improve their solubility.

[0024] In the reaction between the cellulose derivative and the radical generator, the cellulose derivative is dissolved in the organic solvent, and the radical generator is added to the solution, followed by heat treatment, etc. Alternatively, the reaction can be carried out at a low temperature below room temperature without heating, for example, by adding a reducing agent such as an amine to the peroxide radical generator as described above.

[0025] The radical generator used in the present invention may be any of the compounds mentioned above, but peroxides and metal compounds are particularly preferred. Both are easy to handle and do not cause side reactions, which greatly reduces the effort required to remove by-products.

[0026] The reaction solution is prepared so that the solids concentration of the cellulose derivative is in the range of 1 to 50% by mass, and a radical generator is added in an amount of 0.01 to 20% by mass relative to the mass of the cellulose derivative. The reaction is then carried out at a heating temperature of 30 to 200°C for 1 to 48 hours. It is also desirable to remove oxygen from the reaction system to increase the efficiency of polymer chain scission by radicals. Oxygen removal is typically achieved using an inert gas such as nitrogen or argon gas.

[0027] The radical cleavage reaction is affected by the amount and type of radical generator used, the reaction temperature, and the type of organic solvent used. Therefore, by optimizing conditions such as the amount added, heating temperature, and time, it is possible to efficiently obtain a product with the target molecular weight. In particular, in the reaction, it is effective to use an organic solvent that does not have a hydroxyl group and to use a peroxide or metal compound as the radical generator in order to shorten the reaction time.

[0028] After the reaction is complete, filtration can be carried out using a general filter or the like to remove trace amounts of insoluble matter and metal compounds that have been produced. It is also preferable to remove metal ions using a filter with a metal-capturing function.

[0029] The molecular weight of the low-molecular-weight cellulose derivative in the low-molecular-weight cellulose derivative composition of the present invention is a weight-average molecular weight of 40,000 or less, preferably in the range of 10,000 to 40,000. These molecular weights are values ​​measured using gel permeation chromatography (GPC) and converted into standard polystyrene.

[0030] The low-molecular-weight cellulose derivative composition can be obtained by adding a radical scavenger to the solution after the completion of the reaction to produce the low-molecular-weight cellulose derivative. The amount of radical scavenger added must be 50 to 500 ppm relative to the low-molecular-weight cellulose derivative in the low-molecular-weight cellulose derivative composition. If the amount is less than 50 ppm, the stabilizing effect is insufficient. If the amount is more than 500 ppm, the low-molecular-weight cellulose derivative composition becomes discolored, which may make it unsuitable for use as a blend containing the low-molecular-weight cellulose derivative. A more desirable range is 50 to 300 ppm.

[0031] The low-molecular-weight cellulose derivative composition of the present invention may be in a solution state or in a solid state from which the solution has been removed. It can be used in the optimal form depending on the application. Furthermore, when in a solution state, the effect of the radical scavenger is more pronounced, and the molecular weight is stabilized. To obtain a solid state, methods such as heat drying, reduced-pressure heat drying, precipitation and drying of the cellulose derivative using water or a solvent, and spray drying can be applied. Furthermore, the low-molecular-weight cellulose derivative composition in a solid state can be dissolved in a solvent different from the original solvent to obtain a solution state.

[0032] The low-molecular-weight cellulose derivative composition of the present invention is expected to be applicable to various binders, pressure-sensitive adhesives, adhesives, thickeners, viscosity modifiers, dispersants, liquid crystal materials, structural members, and the like.

[0033] As an example, application to a compound containing dispersed inorganic particles will be described below. Various pastes or slurries containing inorganic particles and an organic solvent with the low-molecular-weight cellulose derivative composition of the present invention as a binder can be used as formulations for producing electronic components and electronic equipment members. Although there is no clear distinction between pastes and slurries, they are distinguished mainly from each other in terms of viscosity, with the former having a higher viscosity.

[0034] For example, a compound containing metal particles or ceramic particles can be suitably used as a paste or slurry for forming circuits and electrode patterns, dielectric layers, phosphor layers, etc. for various electronic components.

[0035] Examples of inorganic particles contained in the paste or slurry include conductive particles, ceramic particles, glass particles, pigments, and phosphor particles. Examples include metals such as gold, silver, copper, platinum, palladium, nickel, aluminum, tungsten, and iron; alloys containing any of the above metals, such as silver-palladium alloys; metal oxides such as ITO; and carbon powder. Examples of ceramics include magnetic ceramics such as barium titanate, titanium oxide, alumina, zirconia, aluminum nitride, silicon nitride, boron nitride, silicon carbide, and ferrite. Examples of glass include those containing silicon dioxide (usually those containing silicon dioxide as the main component), and the melting point thereof is not particularly limited. The particle diameter of the inorganic particles is usually in the range of 20 nm to 1 mm. Only one type of inorganic particles may be used, or two or more types may be used in combination.

[0036] The organic solvent contained in the formulation may be one or more of the organic solvents listed above. The organic solvent is a solvent capable of dissolving the low-molecular-weight cellulose derivative, and preferably has a high boiling point when used as a printing paste.

[0037] The composition may further contain additives as needed. Additives include surfactants, viscosity modifiers, antifoaming agents, leveling agents, stabilizers, plasticizers, wetting agents, pigments, polymer particles, etc. The additives may be used alone or in combination of two or more. The blend may also contain polymers other than the copolymers described above.

[0038] The ratio of the inorganic particles (total content when two or more types of inorganic particles are contained) to the binder (low-molecular-weight cellulose derivative) in the blend is typically 100:1 to 100:50 by mass, and preferably 100:5 to 100:30 from the viewpoints of the viscosity of the copolymer composition and the dispersibility of the inorganic particles. The content of the organic solvent (total content when two or more types of organic solvents are contained) is typically 100 to 10,000 parts by mass per 100 parts by mass of the binder. When the copolymer composition contains additives, the content thereof (total content when two or more types of additives are contained) is typically 0.1 to 30 parts by mass per 100 parts by mass of the binder.

[0039] The inorganic particles, the copolymer dissolved in the organic solvent, and additives used as needed are mixed using various dispersing devices such as a three-roll mill, a ball mill, a media mill, a homogenizer, etc., and the inorganic particles are uniformly dispersed to prepare the blend.

[0040] After applying the formulation to a substrate or the like, subsequent baking volatilizes the organic solvent and thermally decomposes the binder, thereby forming a layer or pattern formed by inorganic particles. Examples of methods for applying the composition include screen printing, die coating printing, doctor blade printing, roll coating printing, offset printing, gravure printing, flexographic printing, inkjet printing, dispense printing, casting, and dip coating, with screen printing and dip coating being preferred. The layer or pattern obtained by baking is usually composed of a sintered body of inorganic particles.

[0041] Although a formulation containing inorganic particles is shown as an example, the application of the present invention is not limited thereto. As described above, the low molecular weight cellulose derivative composition of the present invention is useful in a wide range of applications. [Example]

[0042] Example 1 20 parts by mass of ethyl cellulose STD-4 (manufactured by The Dow Chemical Company; number average molecular weight by GPC: 14,200; weight average molecular weight: 45,000) was dissolved in 80 parts by mass of ethyl acetate. The solution was stirred in a glass container and heated to 75°C using a heating device. After the temperature reached 75°C, 0.4 parts by mass of the peroxide Perocta O (manufactured by NOF Corporation) was added, and the mixture was reacted and treated for 8 hours under reflux at a heating temperature of 77°C to 80°C. The molecular weight of the solution after the reaction was measured by GPC, and it was found that the number average molecular weight was 11,000 and the weight average molecular weight was 24,500, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0009 parts by mass of hydroquinone (HQ) (approximately 50 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a 30 μm mesh to obtain a composition. The solution viscosity of the composition was measured using a Brookfield viscometer (similar measurements were made below), and was found to be approximately 80% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0043] Example 2 The reaction was carried out under the same conditions as in Example 1, except that the peroxide was changed to Perocta O (manufactured by NOF Corporation) and the same amount of benzoyl peroxide was added. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 11,000 and a weight average molecular weight of 25,000, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0018 parts by mass of hydroquinone (HQ) (approximately 100 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a mesh to obtain a composition. The solution viscosity of the composition was approximately 80% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0044] Example 3 The experiment was carried out under the same conditions as in Example 1, except that the type of peroxide was changed to Perbutyl O (manufactured by NOF Corporation). The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 12,000 and a weight average molecular weight of 26,000, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0036 parts by mass of hydroquinone (HQ) (approximately 200 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a 30 μm mesh to obtain a composition. The solution viscosity of the composition was approximately 40% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0045] Example 4 A similar reaction was carried out under the same conditions as in Example 1, except that butyl carbitol acetate was used in place of ethyl acetate and the heating temperature was set to 100°C. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 13,000 and a weight average molecular weight of 27,000, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0018 parts by mass of hydroquinone (HQ) (approximately 100 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a mesh to obtain a composition. The solution viscosity of the composition was approximately 70% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0046] Example 5 A similar reaction was carried out under the same conditions as in Example 1, except that butyl carbitol acetate was used in place of ethyl acetate and the heating temperature was set to 100°C. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 13,000 and a weight average molecular weight of 26,000, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0036 parts by mass of hydroquinone monomethyl ether (HQME) (approximately 200 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a mesh to obtain a composition. The solution viscosity of the composition was approximately 75% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0047] Example 6 20 parts by mass of cellulose acetate butyrate (CAB-551-0.01: manufactured by Eastman Chemical Company, number average molecular weight by GPC: 16,000, weight average molecular weight: 50,000) was dissolved in 80 parts by mass of ethyl acetate. The solution was stirred in a glass container and heated to 75°C using a heating device. After the temperature reached 75°C, 0.4 parts by mass of the peroxide Perocta O (manufactured by NOF Corporation) was added, and the mixture was reacted and treated for 8 hours under reflux at a heating temperature of 77°C to 80°C. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 12,000 and a weight average molecular weight of 30,000, which was a low molecular weight. The yield based on the solid content measurement was about 90%. After the reaction, 0.0009 parts by mass of hydroquinone (HQ) (approximately 50 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a 30 μm mesh to obtain a composition. The solution viscosity of the composition was approximately 75% lower than that of a CAB-551-0.01 solution in the same solvent and at the same concentration.

[0048] Example 7 20 parts by mass of ethyl cellulose STD-4 (manufactured by The Dow Chemical Company, number average molecular weight by GPC: 14,200, weight average molecular weight: 45,000) was dissolved in 80 parts by mass of butyl carbitol acetate. The solution was stirred in a glass container and heated to 100°C using a heating device. After the temperature reached 100°C, 0.4 parts by mass of copper (II) acetate, a metal compound, was added, and the mixture was reacted and treated at 100°C for 10 hours. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 12,000 and a weight average molecular weight of 26,000, which was a low molecular weight. The yield based on the solid content measurement was about 85%. After the reaction, 0.0017 parts by mass of hydroquinone (HQ) (approximately 100 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a 30 μm mesh to obtain a composition. The solution viscosity of the composition was approximately 80% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0049] Example 8 20 parts by mass of ethyl cellulose STD-4 (manufactured by The Dow Chemical Company, number average molecular weight by GPC: 14,200, weight average molecular weight: 45,000) was dissolved in 80 parts by mass of dihydroterpineol acetate. The solution was stirred in a glass container and heated to 100°C using a heating device. After the temperature reached 100°C, 0.4 parts by mass of copper(II) isobutyrate, a metal compound, was added, and the heating temperature was increased to 100°C, allowing the mixture to react and treat for 10 hours. The molecular weight of the solution after the reaction was measured by GPC, and it was found to have a number average molecular weight of 12,000 and a weight average molecular weight of 26,500, which was a low molecular weight. The yield based on the solid content measurement was about 85%. After the reaction, 0.00765 parts by mass of hydroquinone monomethyl ether (HQME) (450 ppm relative to the cellulose derivative) was added as a radical scavenger to the solution, which was then dissolved and filtered through a 30 μm mesh to obtain a composition. The solution viscosity of the composition was approximately 75% lower than that of the STD-4 solution in the same solvent and at the same concentration.

[0050] <Evaluation of stability over time> Examples 1 to 8 and Comparative Examples 1 to 3 were prepared using the same method as Example 1, but without the radical scavenger hydroquinone (HQ), and with HQ added at approximately 45 ppm and 550 ppm, respectively. Furthermore, Comparative Example 4 was prepared using the same method as Example 7, but without the radical scavenger hydroquinone (HQ). The stability over time of each sample was evaluated. The stability over time was evaluated by sealing each sample in a solution state in a glass container and heating it at 50°C for 14 days. The weight-average molecular weight before and after heating was measured, and the rate of change (%) was calculated and evaluated. The degree of coloration of each sample after heat treatment was also visually evaluated.

[0051] These results are shown in Table 1. In the table, samples with an absolute value of the rate of change in weight-average molecular weight after heating at 50°C for 14 days of less than 5% are marked with an O, and samples with an absolute value of the rate of change greater than 5% are marked with an X. Samples marked with an "X" have a large rate of change and poor stability over time.

[0052] The coloring evaluation was a visual sensory evaluation, and those that were noticeably colored and unsuitable for use as a compound were marked with "X." "O" means there was almost no coloring, and "△" means the degree of coloring was intermediate between O and X, and both "△" and "O" were judged to be suitable for use as a compound.

[0053] [Table 1]

[0054] It was found that heating at 50°C reduced the molecular weight of all samples to some extent over time. However, comparison with the comparative examples confirmed clear improvements depending on the amount of radical scavenger added. Furthermore, when a large amount was added, as in Comparative Example 3, no molecular weight reduction occurred, but the excess radical scavenger was oxidized, causing the low molecular weight cellulose derivative composition to turn yellowish-brown. This discoloration severely limits the use of low molecular weight cellulose derivatives as additives and makes them unsuitable for general use. Color evaluation was performed after 14 days of heating at 50°C, and the comparative example sample showed significant discoloration within a few days of heating. Furthermore, Example 8 did not show as much discoloration as Comparative Example 3, making it usable for most compounding applications, but its application to transparent materials is limited. From the above, it was found that the low molecular weight cellulose derivative composition of the present invention is a low molecular weight cellulose derivative with potential for a wide range of applications and excellent stability over time.

[0055] Furthermore, the method for producing a low-molecular-weight cellulose derivative composition of the present invention does not use strong acids as in conventional methods and causes almost no side reactions, so that the desired composition can be obtained efficiently and in high yield without requiring special equipment or complicated processes.

Claims

1. A low molecular weight cellulose derivative composition comprising a low molecular weight cellulose derivative having a weight average molecular weight of 40,000 or less and a radical scavenger in an amount of 50 to 500 ppm relative to the low molecular weight cellulose derivative.

2. 2. The low molecular weight cellulose derivative composition according to claim 1, wherein the cellulose derivative is ethyl cellulose.

3. A method for producing a low-molecular-weight cellulose derivative composition containing a low-molecular-weight cellulose derivative with a weight-average molecular weight of 40,000 or less and a radical scavenger, the method comprising adding a radical generator to a solution in which the cellulose derivative is dissolved in an organic solvent having no hydroxyl groups, obtaining a low-molecular-weight cellulose derivative by a radical reaction, and then adding the radical scavenger in an amount of 50 to 500 ppm relative to the amount of the low-molecular-weight cellulose derivative after the radical reaction.

4. 4. The method for producing a low-molecular-weight cellulose derivative composition according to claim 3, wherein the radical generator is a peroxide or a metal compound.

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