Cellulose ester composition

Abstract

To provide a cellulose ester composition containing a plasticizer having high compatibility, and a method for producing the same.SOLUTION: The cellulose ester composition contains a cellulose ester and a plasticizer. The solubility parameter of the cellulose ester and the solubility parameter of the plasticizer satisfy either (a) or (b). (a) A distance Ra between coordinates obtained by plotting a dispersion force term, a dipole-dipole force term, and a hydrogen bonding force term of solubility parameters of the cellulose ester and a dispersion force term, a dipole-dipole force term, and a hydrogen bonding force term of solubility parameters of the plasticizer in a Hansen space is less than 8.5. (b) The coordinate distance Ra is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to cellulose ester compositions and methods for making the same. [Background technology]

[0002] Many cellulose esters have poor thermal melting properties due to hydrogen bonds caused by residual hydroxyl groups in the molecular chain. In particular, the lower the substitution degree of cellulose ester, the higher the melting temperature tends to be. In addition, when the substitution degree of cellulose ester is increased, its crystallinity increases, so that the solubility and melting property tend to decrease. Conventionally, efforts have been made to improve processability by adding a plasticizer to cellulose ester to lower the melting temperature.

[0003] For example, Chinese Patent Application Publication No. 111138721 (Patent Document 1) discloses a biodegradable film containing acetyl cellulose and a plasticizer, and Japanese Patent No. 5865195 (Patent Document 2) discloses a cellulose ester composition containing a plasticizer containing a phosphate ester of a specific structure.

[0004] Japanese Patent Laid-Open Publication No. 2019-26699 (Patent Document 3) discloses a resin composition containing cellulose acylate and a polyether derivative having one or more carbon-carbon unsaturated bonds (excluding aromatic groups) in the molecule. Japanese Patent No. 6626894 (Patent Document 4) discloses a water-soluble cellulose acetate resin composition containing cellulose acetate having a total acetyl substitution degree of 0.4 to 1.4 and polyvinyl alcohol having a saponification degree of 50 mol% or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Chinese Patent Application Publication No. 111138721 [Patent Document 2] Patent No. 5865195 [Patent Document 3] Japanese Patent Application Publication No. 2019-26699 [Patent Document 4] Patent No. 6626894 Summary of the Invention [Problem to be solved by the invention]

[0006] Cellulose esters such as cellulose acetate are materials with excellent mechanical and optical properties and are used in various technical fields. In recent years, attempts have been made to change the type of substituent, degree of substitution, degree of polymerization, etc. of cellulose esters in order to improve properties according to various applications and to develop further new applications. In order to facilitate thermoforming of these cellulose esters, plasticization by blending a plasticizer is desired. However, conventionally known plasticizers are limited to those obtained empirically, making it difficult to apply them to various cellulose esters with different degrees of substitution, polymerization, etc.

[0007] When selecting a plasticizer suitable for cellulose esters with varying degrees of substitution depending on the application and performance, the number of plasticizers and their combinations to choose from is enormous. In particular, blending two or more plasticizers requires extensive trial and error. No technology has yet been proposed for efficiently obtaining a composition in which a cellulose ester and a plasticizer are compatible and have the desired properties.

[0008] An object of the present disclosure is to provide a cellulose ester composition containing a highly compatible plasticizer and a method for producing the same. [Means for solving the problem]

[0009] The Hansen Solubility Parameter (HSP) is an index for evaluating the affinity between different materials, and is generally expressed by dividing it into three dimensions: the dispersion force term δd, the dipole-dipole force term δp, and the hydrogen bonding force term δh. As a result of extensive research, the present inventors have found that for a desired cellulose ester, an optimal plasticizer or a combination thereof can be efficiently selected from a vast variety of substances based on the Hansen solubility parameter determined by the Hansen sphere method, and have thus completed the present disclosure.

[0010] That is, the cellulose ester composition according to the present disclosure contains a cellulose ester and a plasticizer, and the solubility parameters of the cellulose ester and the plasticizer satisfy either (a) or (b) below. (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

[0011] Preferably, in the composition, the cellulose ester and the plasticizer are compatible. The plasticizer may be a mixture of two or more plasticizers.

[0012] Preferably, the content of the plasticizer is 5% by weight or more and 40% by weight or less.

[0013] Preferably, the cellulose ester is cellulose acetate.

[0014] The molded article of the present disclosure is formed from any of the cellulose ester compositions described above.

[0015] The method for producing a cellulose ester composition of the present disclosure includes a first step of obtaining the dispersion term, dipole-dipole term, and hydrogen bonding term of the solubility parameters of a cellulose ester by the Hansen dissolving sphere method, and a second step of selecting a plasticizer that satisfies either the following (a) or (b) and mixing it with the cellulose ester: (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

[0016] In this manufacturing method, the plasticizer may be a mixture of two or more plasticizers. [Effects of the Invention]

[0017] The cellulose ester composition according to the present disclosure contains an optimum plasticizer depending on the type of cellulose ester. According to the production method of the present disclosure, an optimum plasticizer can be efficiently selected based on the solubility parameters of the cellulose ester and the plasticizer, thereby obtaining a cellulose ester composition suitable for thermoforming. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a conceptual diagram showing the relationship between a cellulose ester and a plasticizer in the Hansen space for a cellulose ester composition according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present disclosure will be described in detail below based on preferred embodiments, with appropriate reference to the drawings. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0020] In the present specification, the range "X to Y" means "X or more and Y or less," and unless otherwise noted, all tests were carried out at room temperature (20°C ± 5°C).

[0021] [Cellulose ester composition] The cellulose ester composition according to the present disclosure includes a cellulose ester and a plasticizer, and the solubility parameters of the cellulose ester and the plasticizer satisfy either (a) or (b) below. (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

[0022] The distance Ra between the coordinates of the Hansen solubility parameters (HSP) of the cellulose ester and the plasticizer is calculated by the following formula. Ra = {(δd2-δd1) 2 +(δp2-δp1) 2 +(δh2-δh1) 2} 1 / 2 In the formula, δd1, δp1, and δh1 are the dispersion term, dipole-dipole term, and hydrogen bond term of the Hansen solubility parameter of the cellulose ester, respectively, and δd2, δp2, and δh2 are the dispersion term, dipole-dipole term, and hydrogen bond term of the Hansen solubility parameter of the plasticizer, respectively. From the dispersion term, dipole-dipole term, and hydrogen bond term, the solubility parameter δt(1) of the cellulose ester and the solubility parameter δt(2) of the plasticizer are calculated using the following formula: δt(1)=(δd1 2 +δp1 2 +δh1 2 ) 1 / 2 δt(2)=(δd2 2 +δp2 2 +δh2 2 ) 1 / 2

[0023] Figure 1 is a conceptual diagram showing a three-dimensional space (Hansen space) with the HSP dispersion force term δd, dipole-dipole force term δp, and hydrogen bond force term δh as axes. The distance Ra in this specification is the distance between the coordinates of the cellulose ester (δd1, δp1, δh1) and the organic solvent (δd2, δp2, δh2) plotted on this Hansen space, and is shown as a double-headed arrow Ra in Figure 1. Hereinafter, the distance Ra between the coordinates may be simply referred to as "distance Ra."

[0024] In the cellulose ester composition of the present disclosure, in which the cellulose ester and the plasticizer satisfy either (a) the distance Ra is less than 8.5, or (b) the distance Ra is 8.5 or more and 12.7 or less, and δt(2) is 22.0 or more, the plasticizer is compatible with the cellulose ester, regardless of the degree of substitution of the cellulose ester. In this cellulose ester composition, the plasticizer imparts good plasticity to the cellulose ester. This cellulose ester composition is suitable for thermoforming.

[0025] In the present disclosure, the term "compatible" means that the cellulose ester and the plasticizer have affinity with each other, and the plasticizer is dispersed uniformly in the cellulose ester. Specifically, it means that no cloudiness or turbidity is observed when a molten mixture of the cellulose ester and the plasticizer is visually observed.

[0026] In the cellulose ester composition of the present disclosure, the dispersion term, dipole-dipole term and hydrogen bond term of cellulose ester can be determined by Hansen dissolved sphere method.Specifically, cellulose ester is put into a number of organic solvents whose dispersion term, dipole-dipole term and hydrogen bond term are known, and then solubility is evaluated.The dispersion term, dipole-dipole term and hydrogen bond term of all organic solvents used are plotted on Hansen space, and a sphere (Hansen sphere) is obtained that includes the plot of the organic solvent that dissolves cellulose ester and does not include the plot of the organic solvent that does not dissolve cellulose ester, and its central coordinates are the dispersion term, dipole-dipole term and hydrogen bond term of cellulose ester.The radius of this Hansen sphere is called interaction radius R0.

[0027] [Cellulose ester] The cellulose ester has an acyl group as a substituent. Examples of the acyl group include an acetyl group, a propionyl group, a butyryl group, a carboxyl group, a carboxymethyl group, a 2-hydroxyethyl group, a 2-hydroxypropyl group, and a methyl group. In applications requiring high biodegradability, the substituent of the cellulose ester is preferably an acetyl group, a propionyl group, or a butyryl group, and more preferably an acetyl group. The cellulose ester may have two or more types of acyl groups. The cellulose ester may contain a substituent other than an acyl group, as long as the effects of the present disclosure are not impaired.

[0028] Specific examples of the cellulose ester contained in the cellulose ester composition of the present disclosure include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, etc. In the present disclosure, the cellulose ester may be cellulose acetate.

[0029] (Total degree of substitution) In the cellulose ester composition of the present disclosure, the total degree of substitution DS of the cellulose ester is not particularly limited. A desired total degree of substitution can be selected depending on the application. For example, from the viewpoint of obtaining good biodegradability, the total degree of substitution of the cellulose ester is preferably 2.6 or less, more preferably 2.5 or less, more preferably 2.4 or less, and particularly preferably 2.3 or less. From the viewpoint of excellent mechanical properties, the total degree of substitution of the cellulose ester is preferably 1.9 or more, more preferably 2.0 or more, and particularly preferably 2.1 or more.

[0030] The degree of substitution of cellulose ester can be measured by the following method. For example, it can be measured by NMR according to the method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)). That is, the free hydroxyl groups of cellulose ester are acylated with a carboxylic acid anhydride in pyridine. The type of carboxylic acid anhydride used here should be selected depending on the purpose of analysis. For example, butyric anhydride is suitable for analyzing the degree of butyric substitution of cellulose acetate, and acetic anhydride is suitable for analyzing the degree of butyryl substitution of cellulose butyrate. The obtained sample is dissolved in deuterated chloroform and 13C-NMR spectrum is measured. For example, when the substituent is an acetyl group, the carbon signals of the acetyl group appear in the region from 169 ppm to 171 ppm in the order of 2nd, 3rd, and 6th positions from the high magnetic field. For another example, when a cellulose ester having a propionyl group or a cellulose ester not having a propionyl group is treated with propionic anhydride to analyze the degree of propionyl substitution, the signals of the carbonyl carbon of the propionyl group appear in the same order in the region from 172 ppm to 174 ppm. The total degree of substitution of cellulose ester treated with carboxylic anhydride by Tezuka's method or a method similar thereto is 3.0, so if the sum of the areas of the carbonyl carbon signals of the acyl groups originally possessed by the cellulose ester and the carbonyl signals of the acyl groups introduced by the carboxylic anhydride treatment is normalized to 3.0, and the abundance ratio of each acyl group at the corresponding positions (in other words, the area ratio of each signal) is calculated, this can be determined as the degree of acyl substitution at the 2nd, 3rd, and 6th positions of the glucose ring in the cellulose ester. Needless to say, the only substituents containing acyl groups that can be analyzed by this method are those that do not correspond to the carboxylic anhydride used in the treatment for analysis. In addition, 13 In addition to C-NMR, 1 It can also be analyzed by H-NMR.

[0031] (Number-average molecular weight, weight-average molecular weight and molecular weight distribution of cellulose ester) In the cellulose ester composition of the present disclosure, the number-average molecular weight Mn, weight-average molecular weight Mw, and molecular weight distribution Mw / Mn of the cellulose ester are not particularly limited, and the desired molecular weight and molecular weight distribution can be selected depending on the application. For example, from the viewpoint of obtaining a molded article with excellent tensile properties, the molecular weight is preferably 100,000 or more, more preferably 120,000 or more. From the viewpoint of obtaining an appropriate melt viscosity, the weight-average molecular weight of the cellulose ester is preferably 1,500,000 or less, more preferably 1,200,000 or less. From the viewpoint of obtaining good biodegradability, the weight-average molecular weight is preferably 1,000,000 or less, more preferably 800,000 or less, and even more preferably 500,000 or less. From the viewpoint of high durability, the molecular weight distribution is preferably 1.0 to 5.0, more preferably 1.3 to 4.0, and particularly preferably 1.5 to 3.0.

[0032] The number-average molecular weight, weight-average molecular weight, and molecular weight distribution of cellulose ester can be determined by a known method. Specifically, they are determined by size exclusion chromatography (GPC) measurement using the following apparatus and conditions (GPC-light scattering method). Equipment: Shodex GPC "SYSTEM-21H" Solvent: Acetone Columns: 2 GMHxl (Tosoh), guard column (TSKgel guard column HXL-H manufactured by Tosoh) Flow rate: 0.8ml / min Temperature: 29℃ Sample concentration: 0.25% (wt / vol) Injection volume: 100μl Detection: MALLS (multi-angle light scattering detector) (Wyatt, "DAWN-EOS") MALLS correction standard material: PMMA (molecular weight 27600)

[0033] [Plasticizer] In this specification, the term "plasticizer" refers to a compound that enhances the plasticity or melt fluidity of cellulose ester. In the cellulose ester composition of the present disclosure, the type of plasticizer is not particularly limited. For a cellulose ester having a desired degree of substitution and degree of polymerization, a plasticizer that satisfies either (a) a distance Ra of less than 8.5, or (b) a distance Ra of 8.5 to 12.7 and a solubility parameter δt(2) of 22.0 or more can be appropriately selected and used.

[0034] The dispersion, dipole-dipole, and hydrogen bonding terms of the solubility parameters of plasticizers can be obtained by referring to known databases. Alternatively, each term of the solubility parameters can be estimated using commercially available software based on the chemical structure of the plasticizer.

[0035] The plasticizer contained in the cellulose ester composition may be a mixture of two or more kinds, as long as it satisfies either (a) the distance Ra is less than 8.5, or (b) the distance Ra is 8.5 or more and 12.7 or less, and the solubility parameter δt(2) of the plasticizer is 22.0 or more. When two or more kinds of plasticizers are contained, the solubility parameter δt(2) is calculated as a weighted average of the HSP of each plasticizer.

[0036] The plasticizer contained in the cellulose ester composition of the present disclosure may be selected from, for example, ester compounds, ether compounds, epoxy compounds, sugars, etc. The selected plasticizer may be an aliphatic compound or an aromatic compound. It may also be linear, branched, or cyclic. The plasticizer may have a substituent such as a hydroxyl group, a halogen group, an alkyl group, an alkoxyl group, or an amino group.

[0037] Specific examples of plasticizers include diethyl phthalate, triethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, trimellitic acid and thi(2-ethylhexyl) ), methyl-O-acetylricinoleate, triacetin, diacetin, monoacetin, polycaprolactone triol, polyethylene glycol, triethylene glycol, triethylene glycol diacetate, polyethylene glycol dibenzoate, tripropylene glycol dimethyl ether, triethylene glycol butyl methyl ether, polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, octaacetylsucrose, sorbitol, etc. The cellulose ester composition may contain other plasticizers not specified herein, as long as the effects of the present disclosure are obtained.

[0038] (Plasticizer content) From the viewpoint of easy thermoforming, the amount of plasticizer in the cellulose ester composition of the present disclosure is preferably 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 15% by weight or more. From the viewpoint of excellent formability, the amount of plasticizer is preferably 40% by weight or less, more preferably 35% by weight or less, and particularly preferably 30% by weight or less. When two or more plasticizers are used in combination, the total amount is adjusted to be within the above-mentioned range.

[0039] [Other additives] The cellulose ester composition may further contain additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property adjusters, fluorescent brighteners, flame retardants, lubricants, hydrolysis inhibitors, and water repellents, as long as the effects of the present disclosure are not impaired.

[0040] [Method of producing cellulose ester composition] The method for producing a cellulose ester composition of the present disclosure includes a first step of obtaining the dispersion term, dipole-dipole term, and hydrogen bonding term of the solubility parameters of a cellulose ester by the Hansen dissolving sphere method, and a second step of selecting a plasticizer that satisfies either the following (a) or (b) and mixing it with the cellulose ester: (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

[0041] By selecting a plasticizer that satisfies either (a) a distance Ra of less than 8.5, or (b) a distance Ra of 8.5 to 12.7 and a solubility parameter of the plasticizer of 22.0 or more, a plasticizer compatible with a cellulose ester having a desired degree of substitution and polymerization can be obtained. This production method allows the production of a cellulose ester composition of the present disclosure that contains a highly compatible plasticizer and is suitable for thermoforming. Other additives may be further added to the cellulose ester composition within a range that does not impair the effects of the present disclosure.

[0042] According to the manufacturing method of the present disclosure, in the first step, the dispersion term, dipole-dipole term and hydrogen bond term of the solubility parameter of a conventionally unknown cellulose ester are determined.By using the solubility parameters of this cellulose ester, in the second step, a plasticizer that satisfies either (a) distance Ra is less than 8.5, or (b) distance Ra is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more can be selected, thereby efficiently obtaining the optimal plasticizer that is compatible with the cellulose ester, regardless of the type of cellulose ester, and without requiring extensive trial and error.

[0043] According to the production method of the present disclosure, it is possible to obtain a cellulose ester composition containing a plasticizer having excellent compatibility with cellulose esters having different degrees of substitution, polymerization, etc., which have not been selectable due to the limited types of plasticizers used in the past. This makes it possible to change the type of cellulose ester so as to obtain desired properties depending on the application, thereby improving the degree of freedom in development.

[0044] (First step) The first step is to calculate the dispersion term, dipole-dipole term, and hydrogen bond term of the solubility parameter of the cellulose ester using the Hansen dissolving sphere method.

[0045] Specifically, a dissolution test is first conducted by placing the cellulose ester to be tested in several organic solvents with known dispersion, dipole, and hydrogen bond terms, and classifying the organic solvents into those in which the cellulose ester dissolves and those in which it does not. Next, the dispersion, dipole, and hydrogen bond terms of all organic solvents used in the dissolution test are plotted in a three-dimensional space (Hansen space) with δd, δp, and δh as axes. A sphere (Hansen sphere) is then determined that contains organic solvents that dissolve the cellulose ester but does not contain organic solvents that do not dissolve the cellulose ester. The radius of this Hansen sphere is the interaction radius R0, and its central coordinates are the dispersion, dipole, and hydrogen bond terms of the cellulose ester.

[0046] In the first step, the solubility of cellulose ester is evaluated as "soluble" when no precipitate or no cloudiness is observed in the organic solvent by visual observation, and as "insoluble" when precipitate or cloudiness is observed. In addition, commercially available software can be used to calculate the Hansen ball. As the dispersion term, dipole-dipole term and hydrogen bond term of the organic solvent, values ​​from known databases can be used. In addition, the dispersion term, dipole-dipole term and hydrogen bond term can be calculated from the chemical structure of the organic solvent using commercially available software.

[0047] (Second step) The second step is to select a plasticizer based on the coordinate distance Ra between the cellulose ester and the plasticizer in the Hansen space and the solubility parameter of the plasticizer, and then mix the plasticizer with the cellulose ester.

[0048] When the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester are (δd1, δp1, δh1), and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer are (δd2, δp2, δh2), the distance Ra between these coordinates can be calculated by the following formula. Ra = {(δd2-δd1) 2 +(δp2-δp1) 2 +(δh2-δh1) 2} 1 / 2

[0049] The solubility parameter δt(2) of the plasticizer is calculated by the following formula: δt(2)=(δd2 2 +δp2 2 +δh2 2 ) 1 / 2 In the formula, δd2, δp2 and δh2 2 are the dispersion term, dipole-dipole term, and hydrogen bonding term of the plasticizer, respectively. Values ​​from a known database may be used for the dispersion term, dipole-dipole term, and hydrogen bonding term of the plasticizer. Alternatively, the dispersion term, dipole-dipole term, and hydrogen bonding term may be calculated from the chemical structure of the plasticizer using commercially available software.

[0050] In this manufacturing method, a plasticizer is selected that satisfies either (a) the distance Ra of less than 8.5, or (b) the distance Ra of 8.5 or more and 12.7 or less, and the solubility parameter δt(2) of the plasticizer is 22.0 or more. This plasticizer has excellent compatibility with cellulose esters having desired physical properties. According to this manufacturing method, by using the distance Ra of the coordinate system and the solubility parameter δt(2) of the plasticizer as indicators, a highly compatible plasticizer can be efficiently selected.

[0051] In the second step, two or more plasticizers may be mixed with the cellulose ester. The solubility parameter of the mixture containing two or more plasticizers is calculated as a weighted average of the solubility parameters of the individual plasticizers. By combining multiple plasticizers so that the solubility parameter and coordinate distance Ra of the mixture satisfy either (a) the distance Ra is less than 8.5, or (b) the distance Ra is 8.5 to 12.7, and the solubility parameter of the mixture is 22.0 or more, a combination of plasticizers compatible with the desired cellulose ester can be easily and efficiently obtained.

[0052] As long as the effect of the present disclosure can be obtained, the method of mixing cellulose ester and plasticizer in the second step is not particularly limited.For example, the cellulose ester composition of the present disclosure can be obtained by melt-kneading cellulose ester and selected plasticizer.After mixing cellulose ester and plasticizer, melt-kneading can also be performed.By mixing before melt-kneading, the plasticizer and cellulose ester can be more uniformly blended in a short time, and thus a homogenized cellulose ester composition can be efficiently obtained.

[0053] A known mixer such as a Henschel mixer can be used to mix the cellulose ester and the plasticizer. Either dry mixing or wet mixing may be used. When using a mixer such as a Henschel mixer, the temperature inside the mixer is preferably a temperature at which the cellulose ester does not melt, for example, 20°C or higher but lower than 200°C.

[0054] An extruder such as a twin-screw extruder is used to melt-knead the cellulose ester and the plasticizer. From the viewpoint of uniformity of the kneaded mixture and suppression of thermal degradation, the kneading temperature (cylinder temperature) of the extruder is preferably 170°C or higher and 230°C or lower. When melt-kneading is performed using a twin-screw extruder, the kneading temperature (also referred to as the cylinder temperature) may be 200°C. The kneaded mixture may be extruded in the form of strands from a die attached to the tip of the twin-screw extruder, and then hot-cut into pellets. In this case, the die temperature may be about 220°C.

[0055] The amount of plasticizer blended in the cellulose ester composition of the present disclosure is preferably 5% by weight or more and 40% by weight or less. When two or more plasticizers are blended, the total amount is preferably adjusted to 10% by weight or more and 40% by weight or less.

[0056] The cellulose ester composition may contain known additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property adjusters, fluorescent brighteners, flame retardants, lubricants, hydrolysis inhibitors, water repellents, etc., within the range that does not impair the effects of the present invention. In this case, it is preferable to blend the cellulose ester and plasticizer so that the total content of the cellulose ester and plasticizer in the cellulose ester composition is 90% by weight or more.

[0057] [Application] In the cellulose ester composition of the present disclosure, the desired cellulose ester and plasticizer are compatible with each other. The cellulose ester composition of the present disclosure has plasticity suitable for thermoforming, so it can be melt-molded at a relatively low temperature. The cellulose ester composition of the present disclosure has appropriate fluidity when melted, so it can also be suitably applied to injection molding. Molded articles containing cellulose ester can be obtained from this cellulose ester composition. Preferred molded articles include films and sheets. The cellulose ester composition of the present disclosure can be applied to the production of films or sheets by, for example, injection molding and melt film formation. Furthermore, it can be made into a thin film by stretching or inflation molding after melt extrusion.

[0058] The cellulose ester composition according to the present disclosure can be suitably used as a material for, for example, tableware, packaging containers, trays, agricultural materials, fishing materials, office automation parts, construction materials, medical parts, home appliance parts, automotive components, daily necessities, stationery, eyeglass frames, and the like. [Example]

[0059] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0060] [Test 1] In Test 1, the HSP of cellulose ester was calculated using the Hansen solubility sphere method. Specifically, the cellulose ester (cellulose acetate) shown in Table 1 and the organic solvents with known HSP shown in Table 2 were prepared. The degree of substitution, number average molecular weight, weight average molecular weight, and molecular weight distribution of the cellulose ester are shown in Table 1 as DS, Mn, Mw, and Mw / Mn. The Hansen solubility parameter δ of the organic solvent was calculated. t (1) is shown in Table 2.

[0061] First, 0.5 g of cellulose acetate CA1 (total degree of substitution 2.9, number-average molecular weight 105,930, weight-average molecular weight 274,854, molecular weight distribution 2.59) was collected and dried at 105°C for 2 hours, then allowed to cool to room temperature in a desiccator. It was then added to 50 ml of acetone and stirred with a stirrer for 3 hours, after which its solubility was evaluated. If it was not dissolved, it was stirred for another 3 hours and the solubility was evaluated again. The solubility was visually observed, and a clear solution with no precipitate was evaluated as dissolved (score 1), whereas a cloudy solution or the presence of a precipitate was evaluated as insoluble (score 0).

[0062] The solubility of each of the organic solvents listed in Table 2 was evaluated in the same manner, and then the HSPs of solvents with a score of 1 and those with a score of 0 were all plotted on Hansen space. Based on the HSPs of each plotted solvent, a virtual sphere (Hansen sphere) was determined that encompassed the HSPs of solvents that showed solubility but not the HSPs of solvents that did not show solubility. The central coordinates of the Hansen sphere (δd1, δp1, δh1) were calculated, and the Hansen solubility parameter δt(1) of this cellulose acetate was calculated using the following formula. δt(1)=(δd1 2 +δp1 2 +δh1 2 ) 1 / 2

[0063] For the cellulose esters CA2 and CA3 shown in Table 1, the interaction radius R0 and HSP (δd, δp, δh) were similarly calculated to determine the Hansen solubility parameter δt(1). The results are shown in Table 3. In Table 3, R0 is the interaction radius of the cellulose ester (the radius of the Hansen sphere).

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] [Test 2] In Test 2, a cellulose ester composition was prepared by selecting a plasticizer for the cellulose ester based on the Hansen solubility parameters of the cellulose ester and the plasticizer.

[0068] Specifically, cellulose acetate (CA1) with a degree of substitution of 2.9 and HSP (δd1 = 18.8, δp1 = 12.6, δh1 = 8.1, δt(1) = 24.0) was dried at 105°C for 2 hours and then allowed to cool to room temperature in a desiccator. It was then dry-blended with the plasticizers listed in Table 4 in a 1:1 weight ratio, dried at 80°C for at least 3 hours, and further stirred and mixed using a Henschel mixer to obtain a mixture of cellulose acetate and plasticizer. The resulting mixture was fed into a twin-screw extruder (manufactured by Ikegai Corporation, product name "PCM30", cylinder temperature: 200°C, die temperature: 220°C), melt-kneaded, and extruded to obtain a cellulose ester composition. The compatibility of the resulting cellulose ester composition with the cellulose acetate (CA1) and plasticizer was evaluated using the evaluation method described below. The evaluation results are shown in Table 4.

[0069] Similarly, cellulose acetate (CA2) with a substitution degree of 2.4 and HSP (δd1=18.9, δp1=10.4, δh1=7.7, δt(1)=22.9) and cellulose acetate (CA3) with a substitution degree of 2.2 and HSP (δd1=18.9, δp1=12.6, δh1=7.9, δt(1)=24.2) were used to prepare cellulose ester compositions, and their compatibility with plasticizers was evaluated. The results are shown in Table 4.

[0070] In Table 4, R a is the distance between the solubility parameters of cellulose acetate (δd1, δp1, δh1) and the solubility parameters of the plasticizer (δd2, δp2, δh2) in the Hansen space, calculated using the following formula: R a ={(δd2-δd1) 2 +(δp2-δp1) 2 +(δh2-δh1) 2} 1 / 2 The HSP (δd2, δp2, δh2) of the plasticizer was calculated by the JKU-HSP method with reference to the non-patent document Araki, S., et.al., H., Journal of Membrane Science, 2016, 514, 458-466. δt(2) was calculated using the following formula: δt(2)=(δd2 2 +δp2 2 +δh2 2 ) 1 / 2

[0071] [Compatibility evaluation method] Cellulose acetate and a plasticizer were mixed in a solid state using a Henschel mixer, and melt-kneaded using a Brabender at 210°C to evaluate the compatibility of the resulting cellulose ester composition. Table 4 shows that a transparent mass formed after cooling after melt-kneading was evaluated as compatible (score 1), and a powdery mass that did not solidify after melt-kneading was evaluated as incompatible (score 0).

[0072] [Table 4]

[0073] As shown in Table 4, diethyl phthalate and octaacetylsucrose, which have an Ra of less than 8.5, are compatible with cellulose esters. In addition, triethyl citrate, polycaprolactone triol (molecular weights 550 and 300), polyethylene glycol (PEG200 and PEG400), triethylene glycol, polyethylene glycol monomethyl ether 200, and triethylene glycol monomethyl ether, which have an Ra of 8.5 to 12.7 and a δt(2) of 22.0 or more, are compatible with cellulose esters.

[0074] The results in Table 4 show that, regardless of the degree of substitution or molecular weight of the cellulose ester, the combination of a plasticizer and a cellulose ester that satisfies either (a) Ra less than 8.5, or (b) Ra between 8.5 and 12.7 and δt(2) greater than or equal to 22.0 exhibits excellent compatibility. These evaluation results clearly demonstrate the superiority of the present disclosure. [Industrial Applicability]

[0075] The cellulose ester composition and the method for producing the same described above can be applied to cellulose esters other than cellulose acetate.

Claims

1. Contains a cellulose ester and a plasticizer, A cellulose ester composition, wherein the solubility parameter of the cellulose ester and the solubility parameter of the plasticizer satisfy either the following (a) or (b): (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.

5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

2. 2. The cellulose ester composition according to claim 1, wherein the cellulose ester and the plasticizer are compatible with each other.

3. 3. The cellulose ester composition according to claim 1, wherein the content of the plasticizer is 5% by weight or more and 40% by weight or less.

4. 4. The cellulose ester composition according to claim 1, wherein the plasticizer is a mixture of two or more plasticizers.

5. 5. The cellulose ester composition according to claim 1, wherein the cellulose ester is cellulose acetate.

6. A molded article formed from the cellulose ester composition according to any one of claims 1 to 5.

7. a first step of obtaining the dispersion term, dipole-dipole term, and hydrogen bonding term of the solubility parameter of the cellulose ester by the Hansen dissolving sphere method; a second step of selecting a plasticizer that satisfies either the following (a) or (b) and mixing it with the cellulose ester; The method for producing a cellulose ester composition comprising the steps of: (a) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is less than 8.

5. (b) The distance Ra between the coordinates obtained by plotting the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the cellulose ester and the dispersion force term, dipole-dipole force term, and hydrogen bonding force term of the solubility parameter of the plasticizer in Hansen space is 8.5 or more and 12.7 or less, and the solubility parameter of the plasticizer is 22.0 or more.

8. The method for producing a cellulose ester composition according to claim 7, wherein the plasticizer is a mixture of two or more plasticizers.

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