JP2015086254A - Injection molding method, injection-molded article and resin composition therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method enabling a molded article with good quality to be manufactured even when a resin composition containing cellulose ester is injection molded, an injection molded article and a resin composition suitable for injection molding.SOLUTION: A method for manufacturing an injection-molded article is provided in which a resin composition containing (a) cellulose ester and (b) a fluorene-based compound having a 9,9-bisaryl fluorene skeleton, a weight percentage of (a) the cellulose ester (cellulose triacetate or the like) and (b) the fluorene-based compound, namely the former/the later being 90/10 to 70/30; and 0.01 to 0.5 pts.wt. of (c) a stabilizer based on 100 pts.wt. of the total of (a) the cellulose ester and (b) the fluorene-based compound is pelletized by being melted and kneaded under a condition of a pelleting temperature of 240 to 290°C and an average residence time of 10 to 600 seconds, then is injection-molded.

Description

  The present invention relates to a resin composition containing a cellulose ester as a resin component, a method for injection molding the resin composition, and an injection molded body.

  Cellulose esters are excellent in optical properties and heat resistance, but have a low thermal flowability because of their close thermal decomposition temperature, melting point or softening point, and low melt flowability, and are not suitable for injection molding. Therefore, the cellulose ester is usually formed into a film by a casting method (casting method) and used for an optical film or the like. However, although it is desired to reuse defective products and unnecessary products generated in the optical film preparation process, cellulose ester is not sufficiently recycled because of poor thermoformability.

  In JP 2007-51304 A (Patent Document 1), as a composition suitable for melt molding such as injection molding, 100 parts by weight of cellulose acetate having an acetyl group substitution degree of 0.9 to 2.9, A resin composition containing two to five parts by weight of glyceryl acylate as a plasticizer and 5 to 200 parts by weight of an organic filler is described. However, since this composition contains a low molecular weight plasticizer, the plasticizer may bleed out from the molded article. Furthermore, when a resin composition containing a cellulose ester is injection-molded, only a molded product that is yellowed or browned and whose mechanical strength is significantly reduced can be obtained. In particular, when the degree of acetylation of cellulose acetate increases, the properties of the injection molded product are significantly impaired.

  In order to improve the moldability of cellulose ester, JP 2009-40868 (Patent Document 2) proposes a method of modifying cellulose ester with a dibasic acid. Japanese Patent Laid-Open No. 2012-255142 (Patent Document 3) discloses a cellulose acetate ether in which a predetermined polymer compound residue (acrylic polymer having a glycidyl group) is bonded to a hydroxyl group of cellulose acetate to form an ether group. Disclosed is a resin composition containing a compound and a stabilizer selected from phosphites, hindered phenols, hindered amines, and sulfur compounds. However, in these methods, it is necessary to modify the cellulose ester, and the properties of the modified cellulose ester derivative are also reduced as compared with the cellulose ester.

  In Japanese Patent Application Laid-Open No. 2012-212252 (Patent Document 4), a composition containing cellulose triacetate and 9,9-bis (hydroxy (poly) alkoxyaryl) fluorenes is melt-mixed, formed into a film, and stretched. Obtaining excellent films is described. In this document, phosphorous antioxidant is added to 100 parts by weight of a composition of cellulose triacetate / 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene = 95/5 to 80/20 (weight ratio). It is described that 3 parts by weight of the agent is added and melt-kneaded, the pellet-like composition is hot pressed to prepare a film, and the resulting film is stretched. Further, JP 2011-144344 A (Patent Document 5) describes plasticizing a cellulose derivative (such as cellulose acetate) with a fluorene-based compound (such as 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene). It describes that a molded body can be produced while improving compoundability, moldability and / or workability by making it into a melt and kneaded. This document also describes that a stabilizer selected from a phenol compound, an amine compound, a phosphorus compound, a sulfur compound, and an epoxy compound is contained (claim 10). In Examples, a composition containing 190 parts by weight of cellulose acetate, 10 parts by weight of 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, and 2 parts by weight or 6 parts by weight of a stabilizer is melt-kneaded. An example of preparing a sheet by hot pressing the pellet-like composition is described, and it is described that when kneaded under a nitrogen gas flow, there is little coloring and high transparency.

  However, these resin compositions require a large amount of stabilizer. Therefore, the stabilizer may bleed out from the molded product, and the characteristics (such as mechanical characteristics) of the molded product are likely to be deteriorated. In particular, when the resin composition is injection-molded, the molded product is greatly colored and bubbles are generated in the molded product, or the stabilizer is vaporized or decomposed, deteriorating the appearance quality and characteristics of the molded product, and reducing the working environment. To lose.

JP 2007-51304 A (Claims) JP 2009-40868 A (Claims) JP 2012-255142 A (Claims) JP 2012-211252 A (Claims, Examples) JP 2011-144344 A (Claims, Examples 7 to 9)

  Accordingly, an object of the present invention is to provide an injection molding method capable of producing a high-quality molded product even when a resin composition containing a cellulose ester as a resin component is injection molded, and an injection molded product molded by this method and injection molding. Another object of the present invention is to provide a resin composition.

  Another object of the present invention is an injection molding method capable of producing a uniform injection molded product with little coloration even when the acylation degree (for example, acetylation degree) of the cellulose ester is high, and the injection molded product obtained by this method And providing a resin composition suitable for injection molding.

  Still another object of the present invention is to provide an injection molding method capable of preventing foaming and embrittlement and capable of stably injection-molding an injection-molded product having high mechanical strength even when the injection molding temperature fluctuates, and a resin composition therefor. It is to provide.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have determined that even if the system is easy to be colored by hot melt molding, in which the stabilizer content is low and the acylation degree of the cellulose ester is high. When pellets or compounds prepared under the above conditions are used, stable injection molding can be achieved, and when injection molding is performed under predetermined conditions, coloring can be suppressed, and homogeneous and high mechanical strength injection molded products can be stably manufactured. As a result, the present invention has been completed.

  That is, in the method of the present invention, a resin composition containing (a) a cellulose ester (such as cellulose triacetate) and (b) a fluorene compound having a 9,9-bisarylfluorene skeleton is pelletized or formed under specific conditions. Compounded and injection molded. From the viewpoint that the pelletization temperature at which uniform pellets or compounds can be obtained (resin temperature of the die part where the uniform pellets or compounds can be molded) can be lowered by melt kneading of the resin composition, (b) of the fluorene compound Although the larger the blending amount, the better. On the other hand, the larger the blending amount of the (b) fluorene compound, the lower the physical properties of the resulting molded article. Moreover, deterioration of the resin component can be suppressed by the stabilizer. Therefore, in the resin composition, the weight ratio of (a) cellulose ester and (b) fluorene compound is the former / the latter = 90/10 to 70/30 (for example, 87.5 / 12.5 to 75 / 25) degree, and (c) 0.001 to 0.5 parts by weight of a stabilizer (for example, 0.01 to 0.5 parts by weight) with respect to 100 parts by weight of the total amount of (a) cellulose ester and (b) fluorene compound. 0.3 parts by weight) may be included. (A) The cellulose ester may be (a1) cellulose triacetate having an average substitution degree of 2.5 to 3, and (b) the fluorene-based compound may be (b1) 9,9-bis (hydroxyaryl) fluorenes and / or Alternatively, (b2) 9,9-bis (hydroxyalkoxyaryl) fluorenes may be used. The stabilizer (c) is at least one selected from (c1) a combination of a hindered phenol antioxidant and a phosphorus antioxidant, and (c2) a hindered phenol phosphorus antioxidant. May be.

  Such a resin composition can be injection-molded after being melt-kneaded and pelletized under the conditions of a pelletization temperature of 240 to 290 ° C. and an average residence time of 10 to 600 seconds. In this method, the resin composition is preferably pelletized by melt-kneading under conditions of a pelletization temperature of 250 to 285 ° C. and an average residence time of 10 to 240 seconds from the viewpoint of suppressing decomposition. When injection molding is performed through such a pelletizing step, a high-quality pellet can be obtained without circulating an inert gas, and a high-quality injection-molded product can be prepared by injection molding using this pellet.

  Moreover, in the said resin composition, since (a) cellulose ester (cellulose triacetate etc.) and (b) fluorene type compound have high compatibility, it is compared with (a) cellulose ester (cellulose triacetate etc.) before pelletization. As a result, the melting point of the pellet is lowered. Therefore, in this invention, the said fat composition is melt-kneaded at the melt-kneading temperature T, and a pellet-shaped composition is prepared (compounding), The said pellet is made into temperature lower than the melt-kneading temperature T of the said pelletization. Injection molding is possible. That is, the pellets having the above composition can be molded at a temperature lower than (a) the decomposition temperature range of cellulose ester (about 290 ° C.).

The present invention also includes an injection molded product molded by the injection molding method. This injection molded product is less colored. For example, in an injection molded product having a thickness of 4 mm, the yellow index may be about 5 to 150. The injection-molded product has high mechanical strength. For example, in a test piece having a width of 10 mm × length of 80 mm × thickness of 4 mm, the tensile modulus is 2 to 5.5 MPa, the tensile strength is 70 to 120 MPa, and the bending strength is 80 to 140 MPa. The Izod impact strength may be about 60 to 100 kJ / m ² .

  The present invention further includes a resin composition suitable for pre-pelletization and injection molding, that is, (a) a cellulose ester and (b) a fluorene-based compound having a 9,9-bisarylfluorene skeleton, The weight ratio of (a) cellulose ester (cellulose triacetate etc.) and (b) fluorene compound is the former / the latter = 90/10 to 70/30, and (a) the cellulose ester and (b) the fluorene compound. And (c) a resin composition containing 0.01 to 0.5 parts by weight of a stabilizer with respect to 100 parts by weight in total.

  In the present specification, the “pelletized resin composition” may be referred to as “pellet” or “compound”, and both are used synonymously. The “residence time” is calculated by dividing the resin amount [g] filled in the extruder by the resin discharge amount [g / min] per minute, and means an average residence time. “Melt-kneading temperature T” refers to the maximum value of the cylinder temperature when pelletizing the resin composition, and “pelletizing temperature” refers to a temperature at which uniform pellets can be produced from the resin composition, for example, an extruder It means the resin temperature of the die part where the melt-kneaded material can flow uniformly from the die connected to the die and can be continuously extruded.

  In the present invention, even when a resin composition containing a cellulose ester as a resin component is injection-molded, a resin composition pelletized under a predetermined condition is injection-molded, so that a high-quality molded product can be produced. Moreover, even if the acylation degree (for example, acetylation degree) of a cellulose ester is high, a uniform injection molded product with little coloring can be manufactured. Furthermore, foaming and embrittlement in injection molding can be prevented, and an injection molded product with high mechanical strength can be manufactured.

FIG. 1 is a graph showing the relationship between the “BPEF” content and the pelletization temperature. FIG. 2 is a graph showing the relationship between the residence time in the extruder and the transmittance of the pellet molded product.

  The resin composition of the present invention is suitable for injection molding and contains a cellulose ester as a resin component, a predetermined fluorene compound, and a stabilizer.

[Cellulose ester]
Cellulose esters include cellulose acetate such as cellulose diacetate (DAC) and cellulose triacetate (TAC); cellulose C _3-5 acylate such as cellulose propionate and cellulose butyrate; cellulose acetate propionate (CAP) and cellulose acetate butyrate Cellulose acetate C _3-5 acylate such as rate (CAB) may be used. These cellulose esters can be used alone or in combination of two or more.

  Preferred cellulose esters are cellulose acetate, especially cellulose triacetate. The average substitution degree of the cellulose ester (for example, cellulose acetate) may be 2 to 3 (average acylation degree 48 to 63%), particularly 2.5 to 3 (average acylation degree 58 to 63%). In the present invention, even cellulose acetate having a high degree of average substitution (or degree of acetylation) (for example, cellulose triacetate having an average degree of acetylation of 58 to 63%, particularly 60% or more) can be injection-molded and has little coloration. Uniform and high mechanical strength injection molded products can be produced. In addition, a cellulose acetate can be used individually or in combination of 2 or more types.

The resin component may be composed of a cellulose ester, and is composed of a combination of cellulose acetate (particularly cellulose triacetate) and other cellulose esters [for example, cellulose C _3-5 acylate, cellulose acetate C _3-5 acylate, etc.]. May be. The ratio of cellulose acetate (particularly cellulose triacetate) may be, for example, 50 to 100% by weight, preferably 75 to 100% by weight, and more preferably 80 to 100% by weight, based on the entire resin component.

  In the present invention, by using together with a fluorene compound, the melt flowability of the cellulose ester can be greatly improved, and it can be compounded by melt kneading, and the molded product can be injection molded with high accuracy.

[Fluorene compounds]
(B) The fluorene compound only needs to have a 9,9-bisarylfluorene skeleton, and is a resin having a fluorene compound as a polymerization component (for example, a thermoplastic resin such as a polyester resin, or a thermosetting resin such as an epoxy resin). A low molecular fluorene compound, for example, a compound represented by the following formula (1).

(In the formula, A represents an aromatic hydrocarbon ring; X ¹ represents a hydroxyl group, an epoxy-containing group, a mercapto group, an amino group or an N-substituted amino group; R ¹ represents an alkylene group; R ² represents Alkyl group, cycloalkyl group, aryl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, alkylthio group, cycloalkylthio group, arylthio group, aralkylthio group, acyl group, alkoxycarbonyl group, A halogen atom, a nitro group, a cyano group or an N-substituted amino group; R ³ represents an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a hydroxyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group; Group, mercapto group, alkylthio group, cycloalkylthio group, arylthio group A group, an aralkylthio group, an acyl group, an alkoxycarbonyl group, a halogen atom, a nitro group, a cyano group, an amino group or an N-substituted amino group; k is 0 or an integer of 1 or more; Represents an integer; n and p are the same or different and represent an integer of 0 to 4)
In the fluorene compound represented by the formula (1), details of the ring A, the alkylene group R ¹ , the substituents R ² and R ³ , the repeating unit k, and the coefficients m, n, and p corresponding to the number of substituents Can refer to Patent Literature 4 and Patent Literature 5.

  For example, the aromatic hydrocarbon ring represented by ring A includes a benzene ring, a condensed polycyclic aromatic hydrocarbon ring (for example, a condensed bicyclic hydrocarbon ring such as an indene ring or a naphthalene ring, an anthracene ring, or a phenanthrene. A condensed tricyclic hydrocarbon ring such as a ring). The position of the bond of ring A with respect to the 9-position of fluorene is not particularly limited. For example, in the naphthalene ring, the 1-position (1-naphthyl group), 2-position (2-naphthyl group) and the like may be used. .

X ¹ is, for example, a hydroxyl group, an epoxy-containing group (such as an epoxy group or a glycidyloxy group), a mercapto group, an amino group, or an N-substituted amino group [for example, an N-monoC _1-4 alkylamino such as a methylamino group. Group, N, N-diC _1-4 alkylamino group, N-monohydroxy C _1-4 alkylamino group such as hydroxyethylamino group, N, N-dihydroxy C _1-4 alkylamino group, etc.] it can.

Examples of the alkylene group represented by the group R ¹ include C _2-6 alkylene groups such as ethylene group, propylene group, trimethylene group, 1,2-butanediyl group, and tetramethylene group. Preferred alkylene groups are C _2-4 alkylene groups (eg C _2-3 alkylene groups), especially ethylene groups. The types of oxyalkylene groups bonded to the two rings A may be different but are usually the same in many cases. In addition, when k is an integer of 2 or more, in each oxyalkylene unit bonded to two rings A, the type of alkylene group may be different but is usually the same in many cases. In the two rings A, the type of the group R ¹ may be different, but is often the same. Each coefficient k can be selected from a range of about 0 to 15 (for example, 0 to 10), 0 to 6, preferably 0 to 4 (for example, 0 to 3), more preferably 0 to 2, particularly 0 or 1.

The substitution position of the group — (OR ¹ ) _k —X ¹ in ring A is not particularly limited. For example, when ring A is a benzene ring and m is 1, the bonding position (position 1) with position 9 of the fluorene skeleton On the other hand, it may be any of 2-position, 3-position or 4-position, and when m is 2, the substitution positions are 2-position, 4-position, 3-position, 5-position, 3-position and 4-position. There may be. When ring A is a naphthalene ring, it may be substituted with a benzene ring directly bonded to ring A or a benzene ring adjacent to this benzene ring.

Examples of the alkyl group represented by R ² and R ³ include C _1-6 alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and t-butyl group (preferably C _1-4 An alkyl group, more preferably a C _1-3 alkyl group, particularly a methyl group or an ethyl group, and a cycloalkyl group include a C _5-8 cycloalkyl group such as a cyclopentyl group and a cyclohexyl group (preferably a C _{5- 6} cycloalkyl group) and aryl groups include, for example, phenyl group, alkylphenyl group (mono or dimethylphenyl group such as tolyl group, 2-methylphenyl group and xylyl group), and C _6-10 such as naphthyl group. an aryl group. Examples of the aralkyl group, a benzyl group, such as C _6-10 aryl -C _1-4 alkyl group such as a phenethyl group can be exemplified.

Examples of the alkoxy group represented by R ² and R ³ include C _1-6 alkoxy groups such as methoxy group, ethoxy group, propoxy group, n-butoxy group, t-butoxy group (preferably C _1-4 alkoxy group, More preferably, a C _1-3 alkoxy group and the like can be exemplified. The cycloalkoxy group includes a C _5-8 cycloalkyloxy group such as a cyclohexyloxy group, and the aryloxy group includes a C _6- group such as a phenoxy group. Examples of the ₁₀ aryloxy group and aralkyloxy group include C _6-10 aryl-C _1-4 alkyloxy groups such as benzyloxy group. Examples of the alkylthio group, cycloalkylthio group, arylthio group and aralkylthio group represented by R ² and R ³ include groups corresponding to the alkoxy group, cycloalkoxy group, aryloxy group and aralkyloxy group.

Examples of the acyl group represented by R ² and R ³ include C _2-7 acyl groups such as an acetyl group (C _2-5 acyl group) and the like, and examples of the alkoxycarbonyl group include C ₂ such as a methoxycarbonyl group. Examples include _1-4 alkoxy-carbonyl groups. Examples of the halogen atom represented by R ² and R ³ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The N- substituted amino group represented by R ² and R ^3, similarly to the X ^1, N- monosubstituted amino group [e.g., methylamino, N- mono-C _1-6 alkylamino such as ethylamino group Group (N-mono C _1-4 alkylamino group etc.), N-monohydroxy C _1-6 alkylamino group such as hydroxyethylamino group (N-monohydroxy C _1-4 alkylamino group etc.) etc.], N , N-disubstituted amino group [diC _1-6 alkylamino group such as N, N-dimethylamino group ( _diC1-4 alkylamino group etc.), N, N-diacylamino group etc.].

In the two rings A, the types of the groups R ² may be the same or different, and when the ring A has a plurality of groups R ² , the types of R ² may be the same or different. The type of the group R ³ may be the same or different in the two benzene rings, and when the benzene ring has a plurality of groups R ³ , the type of R ³ may be the same or different. Furthermore, each of the coefficients n and p may preferably be an integer of 0 to 3, more preferably 0 to 2. In the two rings A, the coefficients n may be different from each other, but are often the same. The coefficient p may also be the same or different between the two benzene rings of the fluorene skeleton.

A preferred fluorene compound is a compound having the following ring A, alkylene group R ¹ , substituents R ² and R ³ , repeating unit k, coefficients m, n and p in the formula (1).

Ring A: benzene ring or naphthalene ring (1-naphthalene ring, 2-naphthalene ring, etc.)
X ¹ : hydroxyl group, epoxy-containing group, amino group, or N-monosubstituted amino group; preferably hydroxyl group R ¹ : linear or branched C _2-4 alkylene group; preferably linear or branched chain C _2-3 alkylene group (ethylene group or propylene group)
R ² : linear or branched alkyl group, aryl group, linear or branched alkoxy group, halogen atom or cyano group; preferably C _1-6 alkyl group, phenyl group, halogen atom or cyano group; More preferably a linear or branched C _1-4 alkyl group or a phenyl group; particularly a linear or branched C _1-3 alkyl group R ³ : a linear or branched alkyl group, an aryl group, Hydroxyl group, linear or branched alkoxy group, mercapto group, linear or branched alkylthio group, halogen atom, cyano group, amino group or N-monosubstituted amino group; preferably linear or branched chain C _1-6 alkyl group, hydroxyl group, halogen atom, cyano group, amino group or N-mono C _1-6 alkylamino group; more preferably linear or branched C _1-4 alkyl group, hydroxyl group ; In particular, a linear or branched C _1-3 alkyl group k: an integer of 0 to 10; preferably an integer of 0 to 3; more preferably an integer of 0 to 2 (for example, 0 or 1).
m: 1 or 2; preferably 1
n and p: an integer of 0 to 3; preferably an integer of 0 to 2; more preferably 0 or 1.

  A typical fluorene compound is at least one selected from (b1) 9,9-bis (hydroxyaryl) fluorenes and (b2) 9,9-bis (hydroxy (poly) alkoxyaryl) fluorenes. May be.

(B1) As 9,9-bis (hydroxyaryl) fluorenes, in the formula (1), ring A is a benzene ring, k is 0, X ¹ is a hydroxy group, and m is 1 to 3, for example, 9,9-bis (hydroxyphenyl) fluorene (such as 9,9-bis (4-hydroxyphenyl) fluorene), 9,9-bis (mono or di C _1-4 alkyl-hydroxyphenyl) fluorene (9,9- Bis (3-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (3,5-dimethyl-4-hydroxyphenyl) fluorene, etc.), 9,9-bis (C _6-10 aryl-hydroxyphenyl) fluorene (9,9-bis (3-phenyl-4-hydroxyphenyl) fluorene, etc.), 9,9-bis (di to trihydroxyphenyl) fluorene (9,9- Scan (3,4-dihydroxyphenyl) fluorene etc.); A is a naphthalene ring in the formula (1), k is 0, X ¹ is hydroxy group, compounds wherein m is 1-3, for example, in the above compounds, the ring A compound in which A is a naphthalene ring, for example, 9,9-bis (hydroxynaphthyl) fluorene (such as 9,9-bis (6-hydroxy-2-naphthyl) fluorene) can be exemplified.

(B2) As 9,9-bis (hydroxy (poly) alkoxyaryl) fluorenes, in the formula (1), A is a benzene ring, k is 1 or more (for example, 1 to 4), X ¹ is a hydroxy group, Compounds in which m is 1 to 3, for example, 9,9-bis (hydroxyC _2-4 alkoxyphenyl) fluorene (9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (such as “BPEF”) 9,9-bis (mono- or di-C _1-4 alkyl-hydroxy C _2-4 alkoxyphenyl) fluorene (such as 9,9-bis [3-methyl-4- (2-hydroxyethoxy) phenyl] fluorene), 9,9-bis (C _6-10 aryl - hydroxy C _2-4 alkoxyphenyl) fluorene, 9,9-bis [di or tri (hydroxy C _2-4 alkoxy) phenyl] fluorene] Etc.; the formula (1) A naphthalene in ring, k is 1 or more (e.g., 1 to 4), X1 is a compound hydroxy group, m is 1 to 3, for example, 9,9-bis [hydroxy C _{2 -4} alkoxynaphthyl] fluorene (such as 9,9-bis [6- (2-hydroxyethoxy) -2-naphthyl] fluorene).

  These fluorene compounds may be used alone or in combination of two or more.

  The weight ratio of (a) cellulose ester and (b) fluorene compound can be selected according to the type of cellulose ester, melt fluidity, injection moldability, and properties of the injection molded product. / 10 to 70/30, preferably 87.5 / 12.5 to 75/25, more preferably about 85/15 to 80/20, and 87.5 / 12.5 to 77.5 / 22.5. (For example, about 87.5 / 12.5-82.5 / 17.5) may be sufficient. When the amount of the fluorene compound is small, the melt fluidity and the injection moldability are lowered, and when it is too much, not only the appearance quality of the injection molded product but also the mechanical strength is liable to be lowered.

  In addition, when there is little content of a fluorene type compound, high temperature is required for melt-kneading and it will become easy to decompose | disassemble a cellulose ester. On the other hand, when a predetermined amount of fluorene compound is contained, the melt viscosity can be lowered, and the kneading and molding temperature can be lowered to perform injection molding. In particular, when the melting start temperature (or melting point) is exceeded, high melt fluidity is exhibited even in a temperature range slightly higher than the melting start temperature (or melting point), and even when the melting start temperature (or melting point) is exceeded, the melt viscosity is Does not fluctuate much (low temperature response). Therefore, when a pellet-shaped resin composition previously melt-kneaded is used, it can be stably injection-molded at a temperature lower than the melt-kneading temperature and even when the injection molding temperature fluctuates. When the cellulose ester is cellulose triacetate, the melting point of the composition in which the weight ratio of cellulose ester and BPEF is 90/10 is about 282 ° C., and the melting point of the composition in which the weight ratio is 80/20 is The melting point of the composition having a weight ratio of about 273 ° C. and a weight ratio of 70/30 is about 264 ° C.

[Stabilizer]
In the present invention, even if the resin composition contains a small amount of a stabilizer, a high-quality molded product can be produced by injection molding under predetermined conditions. Examples of the stabilizer include phenol compounds, phosphorus compounds, amine compounds, sulfur compounds, and the like. Preferred stabilizers are antioxidants and / or heat stabilizers (heat stabilizers). The antioxidant may function as a heat stabilizer (heat stabilizer) depending on the type.

  Examples of phenolic compounds (phenolic antioxidants) include hindered phenolic compounds having a t-butyl group and a phenolic hydroxyl group, such as (t-butylphenol) propionic acid esters [(octadecyl-3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate (“IRGANOX 1076” manufactured by BASF), 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] ("IRGANOX 259"), triethylene glycol bis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate] ("IRGANOX 245"), pentaerythrityl tetrakis [3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) Propionate] ("IRGANOX 1010"), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, 3,9-bis {2- [3- (3-t -Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane, N, N′-bis [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine and the like]]; alkanebis or tris (tert-butylphenol) [2,2′-methylenebis (6-tert-butyl-4-methyl) ) Phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, etc.]; tris (t-butylphenol) Benzene [1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy) benzene ("IRGANOX 1330"), 1,3,5-trimethyl-2 , 4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene and the like]; tris (t-butylphenol) isocyanurates [tris (3,5-di-t-butyl-4- Hydroxybenzyl) isocyanurate ("IRGANOX 3114"), tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione Etc.]; hindered phenol compounds having a (meth) acryloyl group, such as 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl ] -4,6-di-t-pentylphenyl acrylate ("SUMILIZER GS" manufactured by Sumitomo Chemical Co., Ltd.), 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) Examples include -4-methylphenyl acrylate.

  Examples of phosphorus compounds (phosphorus antioxidants and phosphorus heat stabilizers) include hindered phenol phosphorus antioxidants having a t-butylphenyl group, such as diethyl (3,5-di-t-butyl-4). -Hydroxybenzyl) phosphonate ("IRGAMOD 295" manufactured by BASF), ethyl di (3,5-di-t-butyl-4-hydroxybenzyl) phosphonate ("IRGAFOS 38"), 6- [3- (3-t -Butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenzo [d, f] [1,3,2] dioxaphosphine (Sumitomo Chemical Co., Ltd.) Manufactured by "SUMILIZER GP"); phosphorous antioxidants having a t-butylphenyl group such as tris (2,4-di-t-butylphenyl) phosphine Ito ("IRGAFOS 168" manufactured by BASF), tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphite, 3,9-bis (octadecyloxy) -2,4,8, 10-tetraoxa-3,9-diphosphaspiro [5,5] undecane (“ADEKA STAB PEP-8” manufactured by Adeka), 3,9-bis (2,6-di-t-butyl-4-methylphenoxy) -2 , 4,8,10-tetraoxa-3,9-diphosphaspiro [5,5] undecane ("Adekastab PEP-36 / 36A"), 2,2-methylenebis (4,6-di-t-butylphenyl) 2- Examples thereof include ethylhexyl phosphite (“ADK STAB HP-10”). Phosphorus compounds include phosphorus heat stabilizers such as aryl phosphites (triphenyl phosphate, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, etc.); aryl phosphines (Tri-2,4-dimethylphenylphosphine, tri-2,4,6-trimethylphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tri-o-anisyl Phosphine, tri-p-anisylphosphine, etc.).

  Examples of amine compounds (or amine antioxidants) include hindered amine compounds (HALS) [tetracarboxylic acid piperidyl esters (for example, 1,2,3,4-butanetetracarboxylic acid tetrakis (2,2, 6,6-tetramethyl-4-piperidyl) ester, 1,2,3,4-butanetetracarboxylic acid tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) ester, etc.); poly [[ 6-[(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) Imino]] and the like]; naphthylamine compounds (such as phenyl-α-naphthylamine); diphenylamine compounds (such as p-isopropoxydiphenylamine); p Phenylenediamine-based compound (N, such as N'- diphenyl -p- phenylenediamine), and the like.

  As sulfur compounds (sulfur antioxidants), thioether antioxidants such as 3,3′-thiobispropionic acid dilauryl ester, 3,3′-thiobispropionic acid dioctadecyl ester, 2,2 Thiobispropionic acid esters such as bis [[3- (dodecylthio) -1-oxypropoxy] methyl] propane-1,3-diylbis [3- (dodecylthio) propionate] (“AO-412S” manufactured by Adeka); Examples thereof include an antioxidant having a t-butylphenol group, such as 4,4′-thiobis (3-methyl-6-t-butylphenol).

  These stabilizers may be used alone or in combination. Preferred stabilizers are hindered phenolic antioxidants and phosphorus antioxidants, and in particular, (c1) hindered phenolic antioxidants (including hindered phenolic phosphorus antioxidants) and phosphorous oxidations. A combination with an inhibitor (for example, a phosphorus compound having a t-butylphenyl group) and (c2) a hindered phenol phosphorus antioxidant are preferred. In the combination (c1), the ratio (weight ratio) between the hindered phenol compound and the phosphorus compound is, for example, the former / the latter = 5/95 to 95/5 (for example, 10/90 to 70/30). , Preferably 15/85 to 60/40, more preferably about 20/80 to 50/50 (for example, 30/70 to 35/65). Such a combination (c1) stabilizer can be prepared, for example, by mixing “IRGANOX 1010” and “SUMILIZER GP” in the above ratio.

  (C2) The hindered phenol phosphorus antioxidant can be obtained, for example, as “SUMILIZER GP” as described above.

  Preferred stabilizers include phosphorus-containing antioxidants (hindered phenol phosphorus antioxidants (for example, “SUMILIZER GP”), phosphorus antioxidants having a t-butylphenyl group) that are excellent in hydrolysis resistance. In many cases.

  The proportion of the stabilizer is, for example, 0.001 to 0.5 parts by weight (for example, 0.01 to 0.5 parts by weight), preferably 0 with respect to 100 parts by weight of the total of the cellulose ester and the fluorene compound. 0.01 to 0.4 parts by weight, more preferably 0.05 to 0.3 parts by weight (for example, 0.1 to 0.3 parts by weight), or 0.03 to 0.1 parts by weight. It may be a degree. When the proportion of the stabilizer is too small, the injection molded product tends to be colored or non-uniform molded product (for example, a molded product in which bubbles are mixed), and when it is too large, the mechanical properties of the molded product are deteriorated.

[Other ingredients]
The resin composition of the present invention is a conventional additive such as a light stabilizer (UV absorber, light stabilizer), a flame retardant, a flame retardant aid, an antistatic agent, etc. Plasticizers, impact modifiers, fillers, reinforcing agents, dispersants, antibacterial agents, lubricants and the like may be contained. These additives may be used alone or in combination of two or more.

[Preparation of injection molding pellets and injection molding method]
In the present invention, by using the fluorene compound in combination, the cellulose ester can be melt-kneaded with high melt fluidity even if the acylation degree is high, and as the content of the fluorene compound increases, the melt fluidity is improved, Even if the residence time in the extruder is long, deterioration (decomposition, etc.) of the cellulose ester can be suppressed. Therefore, in a highly crystalline cellulose ester (particularly cellulose triacetate) and a cellulose ester (particularly cellulose triacetate) whose thermal decomposition temperature is close to the melting point or softening point, a resin composition containing a fluorene compound is melt-kneaded in advance. (Compounded), a resin composition (or pellets, compound, pellet-shaped resin composition) having a reduced molding temperature (or melt viscosity) is prepared, and the pellet is heated to a temperature lower than the decomposition temperature of the cellulose ester ( It is preferable to perform injection molding at a molding temperature. The resin composition is usually pelletized or compounded by melt-kneading at a resin temperature (pelletizing temperature) of a die part capable of stably forming uniform pellets. In addition, a conventional kneader, for example, an extruder (single screw or twin screw extruder or the like) can be used for preparing the compound by melt kneading.

  The melt-kneading temperature T of the resin composition in the extruder may be about 260 to 310 ° C (eg, 265 to 305 ° C), preferably 270 to 300 ° C, and more preferably about 275 to 295 ° C. The pelletization temperature is 240 to 290 ° C. (for example, 250 to 290 ° C.), preferably 250 to 285 ° C. (for example, 250 to 280 ° C.), more preferably 255 to 285 ° C. (for example, 255 to 280 ° C.). It may be about 260 to 285 ° C. (for example, 270 to 285 ° C.). When the kneading temperature is low, it is difficult to prepare uniform pellets or compounds, and when the kneading temperature or pelletizing temperature is too high, the cellulose ester is likely to deteriorate. In particular, when melt kneading or processing at a temperature of 290 ° C. or higher, cellulose ester (cellulose acetate and the like) is decomposed and an organic acid (acetic acid and the like) is rapidly generated. However, when the weight ratio of (a) cellulose ester and (b) fluorene compound is the ratio (for example, the former / the latter = 90/10), the decomposition of the cellulose ester can be suppressed even at a temperature of 290 ° C. Therefore, pellets can be stably prepared even when the melt-kneading temperature T and / or the pelletizing temperature is 290 ° C. On the other hand, if the pelletization temperature is too low, resin discharge from the die becomes unstable and clogging is likely to occur.

  In the present invention, the average residence time of the resin composition in the extruder can be increased, and the average residence time can be selected from a range of about 10 to 600 seconds (for example, 20 to 400 seconds). It may be about -240 seconds (for example, 15 to 220 seconds), preferably 20 to 180 seconds (for example, 25 to 150 seconds), more preferably about 30 to 120 (for example, 35 to 90 seconds) seconds. If the residence time is too long, the cellulose ester is deteriorated and the properties of the injection molded product are deteriorated.

  Further, the pellet (compound) may be prepared by melt-kneading in an atmosphere of inert gas (helium, nitrogen, argon, etc.) or flowing, but in the present invention, the inert gas may not be circulated. , Coloring of the pellet (compound) can be effectively suppressed.

  If necessary, a pelletizer may be used for pelletizing the resin composition.

  The pellets (compounds) thus prepared are preferably dried and used for injection molding.

  The injection molding temperature may be not less than the melting point of the pellet and not more than the decomposition temperature of the cellulose ester, but is 5 to 30 ° C. higher than the melting point of the pellet, preferably 5 to 20 ° C. (for example, 7 to 20 ° C.), more preferably about 5 to 15 ° C. (for example, 10 to 15 ° C.).

  In addition, the pelletization can lower the melting point of the pellet and improve the melt fluidity. Therefore, the injection molding temperature should be lower than the melt-kneading temperature T for the pelletization. The temperature may be about 2-30 ° C. (T- (2-30) ° C.), preferably T- (5-25) ° C., more preferably about T- (10-20) ° C.

  The injection molding pressure is not particularly limited, and may be, for example, about 0.5 to 100 MPa, preferably 1 to 80 MPa, and more preferably about 5 to 50 MPa. The gate resin pressure is not particularly limited, and may be, for example, about 0.1 to 3 MPa, preferably about 0.3 to 2 MPa. The mold clamping force is, for example, 0 to 1 t, preferably 0.1 to It may be about 0.8t. The gate position and the number of gates can be selected according to the type of injection molded product.

  The mold temperature is not particularly limited, and may be, for example, about 20 to 100 ° C., preferably about 30 to 80 ° C. (for example, 40 to 70 ° C.).

  Injection molding includes injection molding, injection compression molding, two-color molding, in addition to normal injection molding in which a resin composition is injected into a mold and cooled by an injection molding machine such as an inline screw injection molding machine. It also includes molding techniques that apply injection molding such as sandwich molding and gas assist molding.

  In the present invention, even if the cellulose ester is contained, the resin composition exhibits high melt fluidity, so that it can be efficiently injection-molded and the molding cycle can be shortened.

[Injection molded products]
Since the injection-molded article of the present invention contains a cellulose ester and a fluorene compound, it is excellent in characteristics such as optical characteristics, heat resistance, solvent resistance, and water resistance. In particular, even an injection-molded product containing cellulose ester as a resin component is less colored and highly transparent. For example, in an injection molded product having a thickness of 4 mm, when measured with a spectrophotometer (manufactured by Hitachi, HITACHI “U-3010”), the yellow index is, for example, 5 to 150 (for example, 7 to 135), preferably 5 It is about -130 (for example, 8-120), More preferably, it is about 5-100 (for example, 10-80).

Furthermore, the injection-molded article of the present invention has excellent mechanical properties. For example, in a test piece having a width of 10 mm, a length of 80 mm, and a thickness of 4 mm, the tensile elastic modulus is, for example, 2 to 5.5 MPa, preferably 2 The tensile strength is, for example, 70 to 120 MPa, preferably 80 to 110 MPa, more preferably 90 to 100 MPa, about 5.0 to 5.0 MPa, more preferably about 3 to 4.5 MPa (for example, 3.3 to 4.3 MPa). The degree and bending strength may be, for example, about 80 to 140 MPa, preferably about 100 to 135 MPa, and more preferably about 110 to 130 MPa. Further, the Izod impact strength of the test piece may be, for example, about 60 to 100 kJ / m ² , preferably 70 to 98 kJ / m ² , and more preferably about 80 to 95 kJ / m ² . The above-mentioned mechanical properties include properties of injection molded products of resin compositions that contain cellulose esters, fluorene compounds, and stabilizers and that do not contain components that affect the mechanical properties (fillers, reinforcing agents, etc.). It is.

  The form of the injection molded product is not particularly limited, and may be a rod shape, a spherical shape, a plate shape, a frame shape, a case or container shape, a housing shape, or the like.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Comparative Examples 1-5
Triacetylcellulose ("LT55" manufactured by Daicel Corporation) and 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd., hereinafter simply referred to as "BPEF") Of the former / the latter = 95/5 weight ratio, and 3000 ppm of antioxidant is mixed with 100 parts by weight of the total amount of triacetylcellulose and “BPEF”, and the same direction twin screw extruder (melt kneading) Pellet samples were prepared under different conditions of residence time at a temperature of 290 ° C. (residence time: 222 seconds (Comparative Example 1), 107 seconds (Comparative Example 2), 81 seconds (Comparative Example 3), 58 seconds (Comparison) Example 4), 43 seconds (Comparative Example 5)).

  As an antioxidant, 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [ 1,3,2] dioxaphosphine (“SUMILIZER GP” manufactured by Sumitomo Chemical Co., Ltd.) 2000 ppm and pentaerythrityltetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (BASF “IRGANOX1010” manufactured by the company) 1000 ppm was used.

  In the preparation of the pellet sample of the resin composition, the resin temperature (pelletizing temperature) of the die part was 292 ° C.

Examples 1-3
Triacetylcellulose ("LT55" manufactured by Daicel Corporation) and "BPEF" are used in a ratio of the former / the latter = 90/10 weight ratio, and the total amount of triacetylcellulose and "BPEF" is 100 parts by weight. In addition, 3000 ppm of the same antioxidant as in Comparative Example 1 was mixed, and pellet samples were prepared under different conditions of residence time in the same-direction twin screw extruder (melt kneading temperature 290 ° C.) (Retention time: 330 seconds (implementation) Example 1), 165 seconds (Example 2), 73 seconds (Example 3)). In the preparation of the pellet sample of the resin composition, the resin temperature (pelletizing temperature) of the die part was 279 ° C.

Examples 4-5
Triacetyl cellulose ("LT55" manufactured by Daicel Corporation) and "BPEF" are used at a ratio of the former / the latter = 80/20 weight ratio, and the total amount of triacetyl cellulose and "BPEF" is 100 parts by weight. In addition, 3000 ppm of the same antioxidant as in Example 1 was mixed, and pellet samples were prepared under different conditions of residence time in the same-direction twin screw extruder (melt kneading temperature 290 ° C.) (retention time: 560 seconds (implementation). Example 4) 133 seconds (Example 5)). In the preparation of the pellet sample of the resin composition, the resin temperature (pelletizing temperature) of the die part was 253 ° C.

  And the pellet ("BPEF" 5 weight%) obtained in Comparative Examples 1-5, the pellet of Examples 1-3 ("BPEF" 10 weight%), and the pellet of Examples 4-5 ("BPEF" 20 weight%) %), The relationship between the “BPEF” content and the pelletization temperature was examined. The result shown in FIG. 1 was obtained.

  The pellets obtained in Comparative Examples 1 to 5 and Examples 1 to 5 were hot-pressed at 290 ° C. to form a 150 μm sheet (pellet molded product), and then the obtained sheet (pellet molded product) When the transmittance (wavelength 350 nm) was measured and the relationship between the residence time in the extruder and the transmittance was examined, the results shown in FIG. 2 were obtained.

  From these results, as the amount of “BPEF” added increases, the molding temperature can be lowered, and when the content of “BPEF” is 10% by mass or more, the residence time in the extruder is long. However, it was found that decomposition is difficult to occur.

Example 6
85 parts by weight of triacetyl cellulose ("LT55" manufactured by Daicel Corporation), 15 parts by weight of "BPEF", and 3000 ppm of the same antioxidant as in Example 1 were mixed, and the same direction twin screw extruder (melt kneading temperature) The mixture was melt kneaded and compounded at 290 ° C. and an average residence time in the extruder: about 30 seconds to obtain pellets having a BPEF content of 15% by weight.

Comparative Example 6
Pellets having a BPEF content of 15% by weight were obtained in the same manner as in Example 1 except that the average residence time in the extruder was about 5 minutes.

  The pellets obtained in Example 6 and Comparative Example 6 were each injection molded (injection molding temperature 280 ° C., mold temperature 60 ° C.) with a small injection molding machine (“HM-7DENKEY” manufactured by Nissei Plastic Industry Co., Ltd.) No. 2 dumbbell test piece (half size) [tensile test piece (1BA type)] and strip type test piece [bending test piece (10 mm × 80 mm × 4 mm)] were prepared.

  Then, the tensile strength characteristics of the tensile test piece were measured according to JIS K 7161, the bending strength of the bending test piece was measured according to JIS K 7171, and the Izod impact strength of the bending test piece was measured according to JIS K 7110. Moreover, the yellow index (YI) was measured with the spectrophotometer (Hitachi "U-3010" by Hitachi, Ltd.) in the said bending test piece. The results are shown in Table 1.

  The mold specimen obtained in Comparative Example 1 contained bubbles, had a high YI, and was very brittle. Moreover, when the tensile test, the bending test, and the impact test of the obtained test piece were implemented, it was a very low physical property. On the other hand, the injection-molded test piece obtained in Example 1 is slightly colored without containing bubbles or the like (YI = 18), and has high homogeneity and high transparency. Mechanical properties (tensile properties, bending properties, impact properties) were shown.

Comparative Example 7
Pellets were prepared according to Example 7 of Patent Document 5. That is, the composition containing 190 parts by weight of triacetyl cellulose used in Example 1, 10 parts by weight of “BPEF”, and 2 parts by weight of a stabilizer [manufactured by Ciba Japan Ltd., trade name “IRGANOX B215”] Pellets were prepared by melt kneading and compounding in a directional twin screw extruder (melt kneading temperature 285 ° C., average residence time in the extruder: about 5 minutes). The obtained pellet was injection-molded at 290 ° C. using the same injection molding machine as in Example 6 to prepare a test piece similar to that in Example 6. The test piece cracked.

  In the present invention, since it can be injection-molded even if it contains cellulose ester as a resin component, various molded products such as optical components (eg, lenses, prisms, etc.), biodegradable molded products (various cases, housings, containers, etc.) ) Is efficiently produced.

Claims (8)

  A method of injection molding a resin composition comprising (a) cellulose ester and (b) a fluorene compound having a 9,9-bisarylfluorene skeleton, wherein (a) cellulose ester and (b) fluorene The weight ratio with respect to the compound is the former / the latter = 90/10 to 70/30, and (c) a stabilizer relative to 100 parts by weight of the total amount of (a) cellulose ester and (b) fluorene compound. A method of injection molding after melting and kneading a resin composition containing 0.001 to 0.5 parts by weight under conditions of a pelletization temperature of 240 to 290 ° C. and an average residence time of 10 to 600 seconds.   (A) The cellulose ester is (a1) cellulose triacetate having an average substitution degree of 2.5 to 3, and (b) the fluorene compound is (b1) 9,9-bis (hydroxyaryl) fluorenes and / or (b2) 9,9-bis (hydroxyalkoxyaryl) fluorenes, wherein (c) the stabilizer is (c1) a combination of a hindered phenol antioxidant and a phosphorus antioxidant, and (c2) a hindered phenol The method according to claim 1, wherein the method is at least one selected from phosphorus-based antioxidants.   The weight ratio of (a) cellulose triacetate and (b) fluorene compound is former / latter = 87.5 / 12.5 to 75/25, and (a) cellulose triacetate and (b) fluorene compound The resin composition containing 0.01 to 0.3 part by weight of the stabilizer (c) with respect to the total amount of 100 parts by weight of the pelletizing temperature 250 to 285 ° C. and the average residence without passing an inert gas. The method according to claim 1 or 2, wherein the pelletization is performed under conditions of a time of 10 to 240 seconds.   The method according to claim 1, wherein the resin composition is melt-kneaded at a melt-kneading temperature T to prepare pellets, and the pellets are injection-molded at a temperature lower than the melt-kneading temperature T.   An injection-molded article molded by the method according to claim 1.   The injection molded product according to claim 5, wherein the yellow index is 5 to 150 at a thickness of 4 mm. In a test piece having a width of 10 mm, a length of 80 mm, and a thickness of 4 mm, the tensile elastic modulus is 2 to 5.5 MPa, the tensile strength is 70 to 120 MPa, the bending strength is 80 to 140 MPa, and the Izod impact strength is 60 to 100 kJ / m ² . The injection-molded product according to claim 5 or 6.   A resin composition comprising (a) a cellulose ester and (b) a fluorene-based compound having a 9,9-bisarylfluorene skeleton, which is previously pelletized and injection-molded, and comprises (a) a cellulose ester and ( b) The weight ratio with the fluorene compound is the former / the latter = 90/10 to 70/30, and (c) with respect to 100 parts by weight of the total amount of (a) cellulose ester and (b) fluorene compound. ) A resin composition containing 0.001 to 0.5 parts by weight of a stabilizer.

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