Flame-retardant resin composition and electronic device

Abstract

To provide a flame-retardant resin composition reduced in a use ratio of petroleum resources while maintaining flame retardancy and mechanical strength, a flame-retardant resin housing, and an electronic equipment.SOLUTION: A flame-retardant resin composition of the present invention is a flame-retardant resin composition containing a thermoplastic resin, and a polysaccharide, where the polysaccharide includes an acidic polysaccharide comprising one or more selected from the group consisting of a polysaccharide having an acidic functional group, a derivative of a polysaccharide having an acidic functional group modified at a part other than the acidic functional group, and a salt of these, and the total number of the acidic functional group and the salt thereof per monosaccharide in the acidic polysaccharide is within the range of 0.2-1.5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant resin composition. matter More specifically, the present invention relates to a flame-retardant resin composition that uses a flame retardant with a low content of petroleum resources, and yet maintains flame retardancy and strength in the resulting molded product. matter The present invention also relates to an electronic device using a part manufactured using the flame-retardant resin composition. [Background technology]

[0002] It is known to blend polysaccharides as flame retardants into resin compositions (see, for example, Patent Document 1). Polysaccharides are compounds whose basic skeleton is a cyclic structure containing a large number of hydroxyl groups. When heated during combustion, they undergo dehydration condensation, generating water vapor, which provides a flame retardant effect by absorbing a large amount of heat, cooling the combustion gas, diluting the combustion gas, blocking oxygen, and so on. Furthermore, it is expected that the carbonization of polysaccharides after dehydration forms a coating (char (carbonized layer)) with an insulating effect, thereby providing flame retardancy. However, when polysaccharides are dispersed in a resin composition, compatibility with the resin and the dehydration reaction caused by heating during resin mixing make it difficult to achieve flame retardancy.

[0003] Furthermore, a flame retardant obtained by modifying a polysaccharide is known in which a phosphate ester structure is bonded to a hydroxyl group in a cellulose molecule (see, for example, Patent Document 2). The addition of the phosphate ester structure to cellulose in this flame retardant involves adding part of the structure of a phosphate flame retardant to the cellulose structure, and since this utilizes the flame retardant mechanism of phosphate flame retardants, the flame retardancy increases depending on the ratio of phosphorus in the material. As a result, the phosphorus concentration is relatively low compared to general phosphate flame retardants, and therefore the effect as a flame retardant is limited.

[0004] Further known flame retardants for use in resin compositions include biodegradable flame retardants having a hydroxy group and a carboxy group in the molecule, such as tartaric acid, citric acid, gluconic acid, lactic acid, malic acid, and gallic acid (see, for example, Patent Document 3). However, the biodegradable flame retardants exemplified in Patent Document 3 have low melting points and decomposition temperatures, and therefore, in molded articles obtained by, for example, injection molding a heat-molten resin composition into a mold, it is difficult for the flame retardant to remain as a constituent component of the molded article, resulting in a problem of reduced flame retardancy of the molded article. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-77215 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-031230 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-213149 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to provide a flame-retardant resin composition that uses a flame retardant with a low content of petroleum resources, while maintaining flame retardancy and strength in the resulting molded product. matter and to provide electronic devices using parts manufactured using the flame-retardant resin composition. [Means for solving the problem]

[0007] In the course of investigating the causes of the above problems in order to solve the above problems, the present inventors discovered that by using as a flame retardant an acidic polysaccharide consisting of one or more selected from polysaccharides having acidic functional groups, derivatives thereof, and salts thereof, wherein the total number of acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide falls within a specific range, the amount of petroleum resources contained in the flame retardant in a flame-retardant resin composition can be reduced, and furthermore, flame retardancy and strength can be maintained in molded articles obtained using the flame-retardant resin composition, thereby arriving at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; the content of the acidic polysaccharide relative to the total amount of the flame-retardant resin composition is within a range of 5 to 40 mass %, The acidic polysaccharide includes at least one selected from alginic acid, alginate, carrageenan, pectin, xanthan gum, and gellan gum, or a cross-linked polysaccharide obtained by cross-linking at least one selected from these. An electronic device characterized in that a molded article made of a flame-retardant resin composition is used as a component.

[0009] 2. 2. The electronic device described in item 1, wherein the flame-retardant resin composition is characterized in that the total number of the acidic functional groups and their salts per monosaccharide unit in the acidic polysaccharide is in the range of 0.6 to 1.2.

[0010] 3. 3. The electronic device according to item 1 or 2, wherein the flame-retardant resin composition has an acidic functional group that is a carboxy group or a sulfo group.

[0012] 4. 4. The electronic device according to any one of items 1 to 3, wherein the flame-retardant resin composition is characterized in that the derivative of the polysaccharide having an acidic functional group is a cross-linked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are cross-linked.

[0013] 5. 5. The electronic device according to any one of items 1 to 4, wherein the flame-retardant resin composition is characterized in that the derivative of the polysaccharide having an acidic functional group is a crosslinked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked with epichlorohydrin.

[0015] 6. 6. The electronic device according to any one of items 1 to 5, wherein the flame-retardant resin composition further contains a metal hydroxide in an amount of 5 to 20 mass % relative to the total amount of the flame-retardant resin composition.

[0016] 7. 7. The electronic device according to item 6, wherein the flame-retardant resin composition contains aluminum hydroxide particles having an average primary particle diameter in the range of 10 to 100 nm as the metal hydroxide.

[0017] 8. 8. The electronic device according to any one of items 1 to 7, wherein the flame-retardant resin composition is characterized in that the thermoplastic resin is a polyolefin-based resin.

[0018] 9. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; An electronic device using, as a component, a molded article of a flame-retardant resin composition, wherein the derivative of a polysaccharide having an acidic functional group is a crosslinked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked with epichlorohydrin.

[0019] 10. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; A flame-retardant resin composition characterized in that the derivative of a polysaccharide having an acidic functional group is a cross-linked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are cross-linked with epichlorohydrin. [Effects of the Invention]

[0020] According to the above-mentioned means of the present invention, a flame-retardant resin composition is obtained which uses a flame retardant with a low content of petroleum resources, and yet maintains flame retardancy and strength in the resulting molded product. matter It is also possible to provide electronic devices using parts manufactured using the flame-retardant resin composition.

[0021] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0022] It is believed that the acidic polysaccharide contained in the flame-retardant resin composition of the present invention undergoes a dehydration condensation reaction upon heating more rapidly than polysaccharides that do not have acidic functional groups, due to the presence of acidic functional groups or salts thereof (hereinafter, these are also collectively referred to as "acidic functional groups, etc.") in the structure. Therefore, compared to general neutral polysaccharides that do not have acidic functional groups, such as cellulose, water vapor is generated more rapidly and, at the same time, film formation on the resin surface is promoted by the promotion of carbonization, resulting in improved flame retardancy.

[0023] In the present invention, the total number of acidic functional groups per monosaccharide unit of the acidic polysaccharide is 0.2 or more, thereby ensuring flame retardancy in the resulting molded article that is durable for practical use. Furthermore, the total number of acidic functional groups per monosaccharide unit is 1.5 or less, thereby ensuring strength in the resulting molded article that is durable for practical use. If the total number of acidic functional groups per monosaccharide unit exceeds 1.5, particularly in highly hydrophobic thermoplastic resins, intermolecular hydrogen bonding due to the acidic functional groups becomes significant in the resin, resulting in shrinkage during molding. This reduces the strength or strength uniformity of the molded article. Furthermore, warpage due to shrinkage during molding is likely to occur, making the resin composition unsuitable for use in molding housings, for example. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic perspective view of a large-sized copying machine as an example of application of a molded article made from the flame-retardant resin composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The flame-retardant resin composition of the present invention is a flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, wherein the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having acidic functional groups, derivatives of the polysaccharides having acidic functional groups modified at sites other than the acidic functional groups, and salts thereof, and wherein the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is in the range of 0.2 to 1.5. This characteristic is a technical characteristic common to the following embodiments.

[0026] In an embodiment of the present invention, from the viewpoint of exerting the effects of the present invention, the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is preferably within the range of 0.6 to 1.2, and the acidic functional groups are preferably carboxy groups or sulfo groups.

[0027] As an embodiment of the present invention, from the viewpoint of exhibiting the effects of the present invention, it is preferable that the content of the acidic polysaccharide is within a range of 5 to 40% by mass relative to the total amount of the flame-retardant resin composition.

[0028] In an embodiment of the present invention, the polysaccharide derivative having an acidic functional group is preferably a crosslinked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked. Furthermore, the polysaccharide derivative having an acidic functional group is preferably a crosslinked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked with epichlorohydrin. Compared to non-crosslinked polysaccharides, crosslinked polysaccharides have improved heat resistance to heating during molding to obtain a molded article from a flame-retardant resin composition. In other words, since crosslinked polysaccharides are less reactive during molding, molded articles can be obtained from the flame-retardant resin composition with reduced loss of flame-retardant effect.

[0029] In an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the acidic polysaccharide comprises at least one selected from alginic acid, alginate, carrageenan, pectin, xanthan gum, and gellan gum, or a crosslinked polysaccharide obtained by crosslinking at least one selected from these.

[0030] In an embodiment of the present invention, from the viewpoint of exerting the effects of the present invention, the flame-retardant resin composition preferably further contains a metal hydroxide in an amount of 5 to 20 mass % relative to the total amount of the flame-retardant resin composition.Furthermore, the flame-retardant resin composition of the present invention preferably contains, as the metal hydroxide, aluminum hydroxide particles having an average primary particle diameter of 10 to 100 nm.

[0031] In one embodiment of the present invention, the thermoplastic resin is a polyolefin resin, whereby the effects of the present invention are more significantly exhibited.

[0032] The flame-retardant resin casing of the present invention is a flame-retardant resin casing made using a flame-retardant resin composition, characterized in that the flame-retardant resin composition is the flame-retardant resin composition of the present invention described above.

[0033] The electronic device of the present invention is characterized in that it uses a molded article made of the flame-retardant resin composition of the present invention as a component.

[0034] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0035] [Flame-retardant resin composition] The flame-retardant resin composition of the present invention is a flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, wherein the polysaccharide comprises an acidic polysaccharide consisting of one or more selected from polysaccharides having acidic functional groups, derivatives of polysaccharides having acidic functional groups in which sites other than the acidic functional groups have been modified, and salts thereof, and is characterized in that the total number of the acidic functional groups and their salts per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5.

[0036] Hereinafter, an acidic polysaccharide consisting of one or more selected from polysaccharides having acidic functional groups, derivatives of polysaccharides having acidic functional groups in which sites other than the acidic functional groups have been modified, and salts thereof, wherein the total number of the acidic functional groups and salts thereof per monosaccharide unit is within the range of 0.2 to 1.5, will also be referred to as "acidic polysaccharide (A)".

[0037] The flame-retardant resin composition of the present invention contains a thermoplastic resin and an acidic polysaccharide (A). In the flame-retardant resin composition of the present invention, the acidic polysaccharide (A) functions as a flame retardant. In addition to the thermoplastic resin and the acidic polysaccharide (A), the flame-retardant resin composition of the present invention can optionally contain various additives that are generally contained in flame-retardant resin compositions. Each component of the flame-retardant resin composition of the present invention will be described below.

[0038] (thermoplastic resin) The thermoplastic resin contained in the flame-retardant resin composition of the present invention may be any known thermoplastic resin without any particular limitation. Examples of the thermoplastic resin include polyolefin resins, polystyrene resins, polycarbonate resins, aromatic polyester resins, polyphenylene sulfite resins, polyamideimide resins, polyetheretherketone resins, polyethersulfone resins, polyimide resins, polyvinyl chloride resins, polyamide resins, polyacetal resins, acrylic resins, polystyrene thermoplastic elastomers, polyolefin thermoplastic elastomers, polyurethane thermoplastic elastomers, 1,2-polybutadiene thermoplastic elastomers, ethylene-vinyl acetate copolymer thermoplastic elastomers, fluororubber thermoplastic elastomers, and chlorinated polyethylene thermoplastic elastomers.

[0039] Furthermore, the thermoplastic resin contained in the flame-retardant resin composition of the present invention can be a thermoplastic resin generally considered to be a biodegradable resin. Examples of biodegradable thermoplastic resins include aliphatic polyesters, polyamino acids, polyvinyl alcohols, polyalkylene glycols, and copolymers containing these. As the thermoplastic resin, one of the above resins may be used alone, or two or more may be used in combination.

[0040] The polystyrene resins include polystyrene resins, syndiotactic polystyrene resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), and the like.

[0041] Examples of aromatic polyester resins include aromatic polyesters having a structure in which an aromatic dicarboxylic acid or its ester derivative component is linked to a diol component such as an aliphatic diol or an alicyclic diol via an ester reaction. Specific examples include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene-1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, and copolymer polyesters such as polyethylene isophthalate / terephthalate, polybutylene terephthalate / isophthalate, and polybutylene terephthalate / decanedicarboxylate.

[0042] Examples of biodegradable thermoplastic aliphatic polyesters include polyoxyacids, which are (co)polymers of oxyacids, and polycondensates of aliphatic diols and aliphatic dicarboxylic acids. Examples of polyoxyacids include poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), random copolymers of L-lactic acid and D-lactic acid, and polylactic acids such as stereocomplexes of L-lactic acid and D-lactic acid, polycaprolactone, polyhydroxybutyric acid, and polyhydroxyvaleric acid. Examples of polycondensates of aliphatic diols and aliphatic dicarboxylic acids include polyethylene succinate, polybutylene succinate (PBS), and polybutylene adipate.

[0043] The use of a biodegradable thermoplastic resin as the thermoplastic resin is preferred from the viewpoint of reducing the environmental impact. Alternatively, a biodegradable thermoplastic resin may be used in combination with a non-biodegradable thermoplastic resin to obtain a thermoplastic resin that combines the advantages of both.

[0044] The thermoplastic resin preferably contains a polyolefin resin as a main component. The content of the polyolefin resin in the thermoplastic resin is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the thermoplastic resin. In the flame-retardant resin composition of the present invention, it is particularly preferable that the thermoplastic resin consists solely of a polyolefin resin.

[0045] The content of the thermoplastic resin in the flame-retardant resin composition of the present invention is the amount obtained by excluding the contents of the acidic polysaccharide (A) and other various additives that may be optionally contained from the flame-retardant resin composition.

[0046] <Polyolefin resin> Polyolefin resins are homopolymers or copolymers polymerized using olefins as the main monomer component. In this specification, "olefin" refers to an aliphatic chain unsaturated hydrocarbon having one double bond.

[0047] Here, the main component constituting the resin (polymer) refers to a component that accounts for 50% by mass or more of all the monomer components constituting the polymer. Polyolefin-based resins are homopolymers or copolymers containing olefins in an amount of preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass of all the monomer components.

[0048] The olefin copolymer includes a copolymer of an olefin with another olefin, or a copolymer of an olefin with another monomer copolymerizable with the olefin. The content of the other monomer in the polyolefin resin is preferably 30% by mass or less, more preferably 0 to 20% by mass, of the total monomer components.

[0049] The olefin is preferably an α-olefin having 2 to 12 carbon atoms. Examples of the olefin include ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-octene, and 1-decene. When polymerizing the polyolefin resin, one type of olefin may be used alone, or two or more types may be used in combination.

[0050] Examples of other monomers copolymerizable with olefins include cyclic olefins such as cyclopentene and norbornene, and dienes such as 1,4-hexadiene and 5-ethylidene-2-norbornene. Furthermore, monomers such as vinyl acetate, styrene, (meth)acrylic acid and its derivatives, vinyl ether, maleic anhydride, carbon monoxide, and N-vinylcarbazole may also be used. When polymerizing polyolefin-based resins, the above-mentioned other monomers may be used alone or in combination of two or more. Note that "(meth)acrylic acid" refers to at least one of acrylic acid and methacrylic acid.

[0051] Specific examples of polyolefin-based resins include polyethylene resins whose main component is ethylene, such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE); polypropylene-based resins whose main component is propylene, such as polypropylene (propylene homopolymer), ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer, and ethylene-propylene-diene copolymer; polybutene; and polypentene.

[0052] Specific examples of polyolefin resins include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, polyketone, and copolymers produced with metallocene catalysts. Also included are chemically modified versions of these polymers, such as ionomer resins, saponified EVA, and olefin elastomers produced by dynamic vulcanization in an extruder.

[0053] As the polyolefin-based resin, polyethylene-based resin and polypropylene-based resin are preferred, and polypropylene-based resin is more preferred. The stereoregularity of the propylene-derived structure in the polypropylene-based resin may be any of isotactic, syndiotactic, and atactic. As the polypropylene-based resin, polypropylene is more preferred.

[0054] The thermoplastic resin may contain one type of polyolefin resin or two or more types of polyolefin resins. Commercially available thermoplastic resins may be used.

[0055] (Acidic polysaccharide (A)) The acidic polysaccharide (A) is one or more selected from polysaccharides having acidic functional groups, derivatives thereof (wherein sites other than the acidic functional groups are modified), and salts thereof, and is an acidic polysaccharide in which the total number of acidic functional groups and salts thereof per monosaccharide unit is within the range of 0.2 to 1.5.

[0056] In this specification, "polysaccharide" is a general term for substances formed by dehydration condensation of many monosaccharide molecules via glycosidic bonds. The number of types of monosaccharides that serve as constituent units of polysaccharides is one or more. The monosaccharide is preferably a pentose or a hexose, and more preferably a hexose. The degree of polymerization of polysaccharides is, for example, 50 to 20,000, preferably 200 to 1,500, and more preferably 200 to 1,100.

[0057] Derivatives of polysaccharides having acidic functional groups are derivatives in which sites other than the acidic functional groups of the polysaccharide have been modified. In this specification, unless otherwise specified, the term "derivatives of polysaccharides having acidic functional groups" is used in the above sense. Derivatives of polysaccharides having acidic functional groups include compounds in which atoms at sites other than the acidic functional groups of the polysaccharide have been replaced with different atoms or substituents, and compounds obtained by binding the sugar chains of the polysaccharide to other compounds or other molecules of the polysaccharide via functional groups other than the acidic functional groups originally possessed by the polysaccharide, such as hydroxyl groups. Derivatives of polysaccharides having acidic functional groups include cross-linked polysaccharides, which will be described later.

[0058] In the present invention, polysaccharides having acidic functional groups, their derivatives, and salts thereof are collectively referred to as "acidic polysaccharides." The total number of acidic functional groups and their salts per monosaccharide unit in an acidic polysaccharide is hereinafter also referred to simply as the "number of acidic functional groups." Acidic polysaccharide (A) is an acidic polysaccharide having a number of acidic functional groups in the range of 0.2 to 1.5.

[0059] The acidic polysaccharide (A) may consist of one or more selected from polysaccharides having acidic functional groups, derivatives thereof, and salts thereof. When the acidic polysaccharide (A) consists of one type of acidic polysaccharide, the number of acidic functional groups of the acidic polysaccharide is in the range of 0.2 to 1.5. When the acidic polysaccharide (A) consists of two or more types of acidic polysaccharides, the number of acidic functional groups of each acidic polysaccharide does not have to be in the range of 0.2 to 1.5, as long as the number of acidic functional groups of the acidic polysaccharide (A) is in the range of 0.2 to 1.5. It is preferable that the number of acidic functional groups of each of the two or more types of acidic polysaccharides constituting the acidic polysaccharide (A) is in the range of 0.2 to 1.5.

[0060] From the viewpoint of further enhancing the effects of the present invention, the number of acidic functional groups in the acidic polysaccharide (A) is preferably within a range of 0.6 to 1.2, and particularly preferably within a range of 0.6 to 1.0.

[0061] In the present invention, the number of acidic functional groups in the acidic polysaccharide can be calculated, for example, by the following method.

[0062] [Method for measuring the number of acidic functional groups] When determining the number of acidic functional groups of an acidic polysaccharide contained in a flame-retardant resin composition, the acidic polysaccharide is first extracted from the flame-retardant resin composition by an appropriate method, and the molecular structure of the polysaccharide constituting the sugar chain of the extracted acidic polysaccharide is identified by thermogravimetric analysis, infrared spectroscopy (IR), or the like.

[0063] The number of acidic functional groups per monosaccharide unit in acidic polysaccharides is measured using the ashing method. Approximately 0.7 g of sample (acidic polysaccharide) is accurately weighed, wrapped in filter paper, and placed in a magnetic crucible. It is then thoroughly ashed at 600°C. After cooling, it is transferred to a 500 mL beaker, and approximately 250 mL of water and 35 mL of 0.05 mol / L sulfuric acid are added. The mixture is boiled for 30 minutes and then cooled. Phenolphthalein indicator is added, and the excess acid is back-titrated with 0.1 mol / L potassium hydroxide. The number of acidic functional groups is calculated using the following formula (1):

[0064] Number of acidic functional groups=Mc×A / (10000-Ma×A) Formula (1) The meanings of the symbols in formula (1) are as follows: A: Volume of 0.05 mol / L sulfuric acid consumed by the combined alkali in 1 g of sample [mL] Mc: Chemical formula weight per monosaccharide structure of polysaccharides in the sample Ma: Formula mass of alkali salt of acidic functional group

[0065] Examples of the acidic functional group possessed by the acidic polysaccharide (A) include a carboxy group (-COOH), a sulfo group (-SO3H), a thiocarboxy group (-CSOH), a sulfino group (-SO2H), and a sulfeno group (-SOH), with a carboxy group and a sulfo group being preferred. The acidic functional group may be an acidic functional group having a sulfo group, for example, an acidic functional group (-O-SO3H) in which a sulfo group is bonded to an oxygen atom. Examples of salts of the acidic functional group include salts with alkali metals such as Li, Na, and K, salts with alkaline earth metals such as Mg, Ca, Sr, and Ba, and alkyl(ammonium) salts (e.g., RN + -(wherein R is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, provided that at least one of R is an alkyl group) salts are exemplified.

[0066] The molecular weight of the acidic polysaccharide (A) is preferably in the range of 10,000 to 250,000, more preferably in the range of 20,000 to 80,000, as a weight average molecular weight based on polystyrene determined by gel permeation chromatography (GPC).

[0067] Examples of the acidic polysaccharide (A) include acidic polysaccharides having naturally occurring acidic functional groups or the like (acidic functional groups or salts thereof) and having an acidic functional group number in the range of 0.2 to 1.5. Alternatively, the acidic polysaccharide (A) may be an acidic polysaccharide obtained by introducing acidic functional groups or the like into a polysaccharide having no acidic functional groups so that the acidic functional group number is in the range of 0.2 to 1.5. Furthermore, the acidic polysaccharide (A) may be an acidic polysaccharide obtained by introducing or separating acidic functional groups from a naturally occurring acidic polysaccharide having an acidic functional group number outside the range of 0.2 to 1.5 so that the acidic functional group number is in the range of 0.2 to 1.5.

[0068] Examples of derivatives include compounds in which atoms at positions other than the acidic functional groups, such as hydrogen atoms, of the naturally occurring acidic polysaccharides or acidic polysaccharides having acidic functional groups introduced therein are replaced with substituents such as halogen atoms or hydrocarbon groups. Other examples include ester derivatives and ether derivatives obtained by reacting hydroxy groups originally present in the sugar chains of the acidic polysaccharides with compounds having functional groups reactive with hydroxy groups. Similarly, when the acidic polysaccharides have functional groups other than hydroxy groups, the functional groups may be reacted with other compounds to form derivatives. The derivatives may also be crosslinked polysaccharides, as described below. In the present invention, among these derivatives, derivatives having an acidic functional group number in the range of 0.2 to 1.5 can be used as the acidic polysaccharide (A).

[0069] When the acidic polysaccharide (A) is a combination of two or more acidic polysaccharides as described above, the number of acidic functional groups of each of the combined acidic polysaccharides does not necessarily have to be in the range of 0.2 to 1.5. The individual acidic polysaccharides may be selected so that the number of acidic functional groups in the combined acidic polysaccharide (A) is in the range of 0.2 to 1.5.

[0070] Examples of acidic polysaccharides include pectin, alginic acid, propylene glycol alginate, carboxymethylcellulose, xanthan gum, gum arabic, karaya gum, psyllium, xylan, arabic acid, tragacanthic acid, khava gum, linseed acid, cerulonic acid, lichenin uronic acid, gellan gum, rhamsan gum, welan gum, carrageenan, glycosaminoglycans (e.g., hyaluronic acid, chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate, keratin sulfate, and heparin) and their salts.

[0071] In the present invention, among the above acidic polysaccharides, acidic polysaccharides having an acidic functional group number in the range of 0.2 to 1.5 can be used as the acidic polysaccharide (A).

[0072] Among these, the acidic polysaccharide (A) is preferably at least one selected from alginic acid, alginate salts, carrageenan, pectin, xanthan gum, and gellan gum (however, when used alone, the number of acidic functional groups is 0.2 to 1.5) from the viewpoint of heat resistance stability when mixed into the resin composition.

[0073] The number of acidic functional groups in alginic acid, carrageenan, pectin, xanthan gum, and gellan gum can also be determined from their molecular structure. For example, the structure of alginic acid is shown in formula (A) below. As shown in formula (A), the acidic functional group possessed by alginic acid is a carboxyl group (-COOH). From the molecular structure in formula (A), the number of acidic functional groups in alginic acid can be determined to be 1.0.

[0074] [ka]

[0075] For example, there are three types of carrageenan: κ-carrageenan, whose molecular structure is represented by the following formula (C1); ι-carrageenan, whose molecular structure is represented by the following formula (C2); and λ-carrageenan, whose molecular structure is represented by the following formula (C3). As shown in formulas (C1) to (C3), the acidic functional group possessed by carrageenan is a sulfo group, more specifically, an acidic functional group (-O-SO3H) in which a sulfo group is bonded to an oxygen atom. In formulas (C1) to (C3), the acidic functional group is in an ionized state (-OSO3 - ) is described in

[0076] From the molecular structure in formula (C1), the number of acidic functional groups of κ-carrageenan can be determined to be 0.5. From the molecular structure in formula (C2), the number of acidic functional groups of ι-carrageenan can be determined to be 1.0. In formula (C3), R is typically H (30%) or SO3 - (70%), and from the molecular structure in formula (C3), the number of acidic functional groups of λ-carrageenan can be determined to be 1.35.

[0077] [ka]

[0078] Among the above-mentioned acidic polysaccharides, carboxymethyl cellulose is an acidic polysaccharide obtained by introducing acidic functional groups into cellulose. The number of acidic functional groups of carboxymethyl cellulose is adjusted to fall within the above range by adjusting the production conditions, and the carboxymethyl cellulose is used as the acidic polysaccharide (A) in the present invention.

[0079] Carboxymethyl cellulose can be produced by a known production method, specifically, a method described in JP 2000-34301 A, which includes a step of reacting cellulose with an alkali at a temperature of 20 to 50°C to produce alkali cellulose, and a step of reacting alkali cellulose with monochloroacetic acid to produce carboxymethyl cellulose.

[0080] Alternatively, according to another method, for example, the method described in JP 2012-12553 A, carboxymethyl cellulose can be produced by mixing cellulose, an alkaline agent, and monohaloacetic acid or a salt thereof, and then heating the mixture to 40 to 90°C to cause a reaction.

[0081] In either method, the number of acidic functional groups in the resulting carboxymethyl cellulose can be adjusted by adjusting the amount of monochloroacetic acid or monohaloacetic acid added to cellulose. The structural formula of carboxymethyl cellulose can be represented, for example, by the following general formula (CMC). In formula (CMC), each R is independently H or CH2COOH. Carboxymethyl cellulose in which, on average within the molecule, 0.2 to 1.5 R in formula (CMC) are CH2COOH can be used as the acidic polysaccharide (A).

[0082] [ka]

[0083] Examples of acidic polysaccharides in which acidic functional groups or the like have been introduced into cellulose include, in addition to carboxymethyl cellulose, carboxyalkyl cellulose (e.g., having 2 to 3 carbon atoms), sulfoethyl cellulose, hydroxypropyl methyl cellulose acetate succinate, etc. Furthermore, acidic polysaccharides in which acidic functional groups or the like have been introduced into polysaccharides other than cellulose that do not have acidic functional groups or the like, such as starch, agarose, guar gum, etc., so that the number of acidic functional groups is in the range of 0.2 to 1.5, can also be used in the present invention.

[0084] Further, as the acidic polysaccharide (A), crosslinked polysaccharides (when used alone, the number of acidic functional groups is 0.2 to 1.5) can be used as derivatives of the above-described acidic polysaccharides.

[0085] As used herein, the term "crosslinked polysaccharide" refers to a compound having a structure in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked. Crosslinked polysaccharides can be obtained, for example, by crosslinking hydroxy groups between at least different polysaccharide molecules using a crosslinking agent. The resulting crosslinked polysaccharide may include a structure in which two hydroxy groups are bonded via a crosslinking agent within the same molecule, as long as the crosslinking occurs between different molecules. The types of crosslinked polysaccharide molecules may be the same or different.

[0086] The crosslinked polysaccharide used in the present invention is a crosslinked product of an acidic polysaccharide, and the acidic polysaccharide used for crosslinking can be any of the acidic polysaccharides exemplified above, without any particular limitation. The acidic polysaccharide used to produce the crosslinked polysaccharide is preferably at least one selected from alginic acid, alginate salts, carrageenan, pectin, xanthan gum, and gellan gum. As the acidic polysaccharide, one of these may be used alone, or two or more may be used in combination.

[0087] The crosslinking agent used to obtain a crosslinked polysaccharide from an acidic polysaccharide may be a compound having two or more functional groups reactive with a hydroxy group. Examples of the functional group possessed by the crosslinking agent include an epoxy group, a chloro group, a silyl group, an isocyanate group, and an acid anhydride. Examples of the crosslinking agent include epichlorohydrin, hexamethylene diisocyanate, and tetraethyl silicate, with epichlorohydrin being preferred.

[0088] Crosslinking of acidic polysaccharides using epichlorohydrin can be carried out, for example, by the reactions shown in the following formulas (I-1) and (I-2). In each formula, the symbol "*" indicates the bond between the acidic polysaccharide and the sugar skeleton. Formula (I-1) is carried out under alkaline conditions. In formula (I-1), the epoxy ring of epichlorohydrin opens and reacts with the OH group of a polysaccharide molecule to obtain intermediate (P). Furthermore, according to formula (I-2), the terminal chloro group derived from epichlorohydrin in intermediate (P) reacts with the OH group of another polysaccharide molecule, crosslinking the two polysaccharide molecules via the linking group -CH2-CH(OH)-CH2-.

[0089] Although the reactions represented by formulas (I-1) and (I-2) have been described above as intermolecular reactions, the reactions represented by formulas (I-1) and (I-2) may occur in parallel within a single molecule. Furthermore, the final reaction product may contain the same terminal —CH—CH(OH)—CH—Cl as in intermediate (P).

[0090] [ka]

[0091] The degree of crosslinking in the crosslinked polysaccharide can be adjusted by the amount of crosslinking agent added to the acidic polysaccharide. It is preferable that the weight average molecular weight of the polymer (A) is in the same range as the preferable range of the weight average molecular weight of the polymer (A).

[0092] Theoretically, the number of acidic functional groups in the resulting crosslinked polysaccharide is the same as that of the acidic polysaccharide used as the raw material. However, the acidic functional groups may react during production, and the number of acidic functional groups in the resulting crosslinked polysaccharide is usually smaller than that of the acidic polysaccharide used as the raw material. Therefore, when a crosslinked polysaccharide is synthesized and used in the present invention, the number of acidic functional groups in the resulting crosslinked polysaccharide is measured by the above-mentioned method, and a crosslinked polysaccharide that falls within the range of the present invention is used.

[0093] In the flame-retardant resin composition of the present invention, the content of the acidic polysaccharide (A) is preferably within a range of 5 to 40 mass % relative to the total amount of the flame-retardant resin composition, and more preferably within a range of 20 to 30 mass %. When the content of the acidic polysaccharide (A) in the flame-retardant resin composition is within the above range, it is easy to achieve both the development of flame retardancy and the maintenance of strength in the obtained molded article.

[0094] (Other flame retardants) The flame-retardant resin composition of the present invention contains an acidic polysaccharide (A) as a flame retardant. The flame retardant may consist solely of the acidic polysaccharide (A), or may contain other flame retardants (also simply referred to as "other flame retardants") other than the acidic polysaccharide (A) as long as the effects of the present invention are not impaired. Examples of other flame retardants include polysaccharides other than the acidic polysaccharide (A), metal hydroxides, condensed phosphate esters, and intumescent flame retardants.

[0095] As the other flame retardant, a metal hydroxide is preferred from the viewpoint of enhancing the flame retardant effect of the acidic polysaccharide (A) and from the viewpoint of containing a small amount of petroleum resources.

[0096] When the flame retardant contains a metal hydroxide as another flame retardant, the content thereof is preferably in the range of 5 to 20 mass %, more preferably in the range of 5 to 10 mass %, based on the total amount of the flame retardant resin composition. If the content of the metal hydroxide in the flame retardant resin composition is within the above range, it is easy to achieve a higher level of both flame retardancy and maintenance of strength in the obtained molded article.

[0097] Examples of the metal hydroxide include aluminum hydroxide and magnesium hydroxide, with aluminum hydroxide being particularly preferred.

[0098] The metal hydroxide is preferably in the form of particles. The particle shape is not particularly limited, and examples include spherical, spindle-shaped, plate-shaped, scale-shaped, needle-shaped, and fibrous shapes. The average primary particle diameter of the metal hydroxide particles is preferably in the range of 10 nm to 100 μm, and more preferably in the range of 10 to 100 nm. The average primary particle diameter of the metal hydroxide particles is, for example, the volume-based median diameter (D50). The volume-based median diameter (D50) can be measured, for example, by a laser diffraction / scattering method using an LA-960S2 (manufactured by HORIBA) or the like.

[0099] The metal hydroxide particles may be surface-modified with a surface modifier, if necessary. Examples of surface modifiers that can be used for the surface modification include alkylsilazane compounds such as hexamethyldisilazane (HMDS), alkylalkoxysilane compounds such as dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, methyltrimethoxysilane, and butyltrimethoxysilane, chlorosilane compounds such as dimethyldichlorosilane and trimethylchlorosilane, silicone oil, silicone varnish, and various fatty acids. These surface modifiers may be used alone or in combination of two or more.

[0100] (Other additives) Examples of additives other than the flame retardant that can be optionally contained in the flame-retardant resin composition of the present invention include antioxidants, fillers, crystal nucleating agents, etc. The content of the other additives in the flame-retardant resin composition of the present invention is within a range that does not impair the effects of the present invention, for example, within a range of about 0 to 30% by mass, preferably within a range of 0 to 20% by mass, relative to the total amount of the flame-retardant resin composition. The total amount is preferably 30% by mass or less.

[0101] (Production of flame-retardant resin composition) The flame-retardant resin composition of the present invention can be obtained by melt-kneading a thermoplastic resin, an acidic polysaccharide (A), and other flame retardants (preferably metal hydroxides) that may be contained as needed, and other components. The melt-kneading method is not particularly limited, and any known melt-kneading method can be used.

[0102] Specific examples include a method in which the components are premixed in advance using various mixers such as a tumbler or a high-speed mixer known as a Henschel mixer, and then melt-kneaded using a kneading device such as a Banbury mixer, a roll, a plastograph, a single-screw extruder, a twin-screw extruder, or a kneader. Among these, a production method in which the components are melt-kneaded using an extruder is more preferred because of its high production efficiency, and a production method in which a twin-screw extruder is even more preferred. The components are melt-kneaded using an extruder, the kneaded mixture is extruded into a strand shape, and the kneaded mixture extruded into a strand shape can then be processed into a form such as pellets or flakes.

[0103] It is preferable to thoroughly dry each component before premixing. The drying temperature is not particularly limited, but is preferably 60 to 100°C. The drying time is not particularly limited, but is preferably 2 to 6 hours. Furthermore, drying under reduced pressure is preferable because it facilitates the drying process. The drying may be performed again after premixing.

[0104] The temperature during melt kneading is, for example, 150 to 280°C and is appropriately selected depending on the thermoplastic resin used. When a polyolefin resin, for example, a polypropylene resin, is used as the thermoplastic resin, the temperature during melt kneading is preferably 180 to 270°C, more preferably 190 to 230°C. The temperature during melt kneading corresponds to the cylinder temperature of a kneading device such as a twin-screw extruder. When multiple temperatures are set in the cylinder of the kneading device, the cylinder temperature refers to the temperature of the highest cylinder. The kneading pressure is not particularly limited, but is preferably 1 to 20 MPa.

[0105] The discharge rate from the kneading device during melt-kneading is not particularly limited, but is preferably 10 to 100 kg / hr, more preferably 20 to 70 kg / hr, in order to ensure sufficient melt-kneading.

[0106] The kneaded product melted and kneaded by the kneading device as described above is preferably cooled after being extruded from the kneading device. The cooling method is not particularly limited, and examples of the cooling method include a method of immersing the kneaded product in water at 0 to 60°C to cool it with water, a method of cooling it with gas at -40 to 60°C, and a method of contacting it with metal at -40 to 60°C.

[0107] The flame-retardant resin composition of the present invention can be in various forms such as powder, granules, tablets, pellets, flakes, fibers, and liquid.

[0108] According to the flame-retardant resin composition of the present invention, it is possible to produce molded articles that maintain flame retardancy and strength while using an acidic polysaccharide (A), a flame retardant with a low petroleum resource content.

[0109] Here, flame retardancy is a type of flame resistance, and refers to the property of burning slowly but continuing to burn to a certain extent. Flame resistance is evaluated by standards such as JIS and ASTM, but the UL standard is generally given particular importance. The UL standard is established by the American company Underwriters Laboratories and is evaluated by the same company.

[0110] When a molded article molded from the flame-retardant resin composition of the present invention is evaluated using a test piece of a predetermined size according to the above-mentioned UL standards, it is preferably evaluated as passing in UL94HB, more preferably passing in UL94V-2, and even more preferably passing in UL94V-0.

[0111] Furthermore, by using the flame-retardant resin composition of the present invention, a molded article having the above-mentioned sufficient flame retardancy, good appearance, and excellent mechanical strength such as bending strength can be obtained by a conventional molding method described below.

[0112] (molded product) A molded article can be produced using the flame-retardant resin composition of the present invention. This molded article can provide a flame-retardant product. When producing a molded article, the flame-retardant resin composition can be melted and molded in various molding machines. The molding method can be appropriately selected depending on the shape and application of the molded article, and examples thereof include injection molding, extrusion molding, compression molding, blow molding, calendar molding, and inflation molding. Furthermore, sheet- or film-shaped molded articles obtained by extrusion molding, calendar molding, or the like can also be subjected to secondary molding such as vacuum molding or pressure molding.

[0113] Molded articles formed from the flame-retardant resin composition of the present invention are not particularly limited, and examples thereof include electric and electronic components, electrical components, exterior components, and interior components in the fields of home appliances and automobiles, as well as various packaging materials, household goods, office supplies, piping, and agricultural materials.

[0114] [Flame-retardant resin housings and electronic devices] The present invention can provide a molded article produced using the flame-retardant resin composition of the present invention as a flame-retardant resin housing. The article housed in the flame-retardant resin housing is not particularly limited. Examples of the flame-retardant resin housing include housings for various machines and devices, and other housings generally made of flame-retardant resins.

[0115] The present invention provides an electronic device characterized by using the above-mentioned molded article as a part. The electronic device is not particularly limited, but examples thereof include office automation equipment such as computers, scanners, copiers, printers, facsimile machines, and multifunction machines called MFPs (Multi Function Peripherals) that combine the functions of these machines, as well as digital printing systems for commercial printing.

[0116] Molded articles made from the flame-retardant resin composition of the present invention are preferably used as exterior parts for electronic devices. An example of a large-sized copying machine shown in FIG. 1 will be described. FIG. 1 is a schematic perspective view of large-sized copying machine 10. As shown in FIG. 1, large-sized copying machine 10 is exteriorly covered with exterior parts G1 to G9. Molded articles made from the flame-retardant resin composition of the present invention can be used for such exterior parts. [Example]

[0117] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0118] [Preparation of flame-retardant resin composition] As constituent materials of the flame-retardant resin compositions in the examples, the following thermoplastic resins and flame retardants (polysaccharides, metal hydroxides, etc.) were prepared.

[0119] (thermoplastic resin) The following commercially available thermoplastic resins were prepared: 1. Polyolefin resin High-density polyethylene (PE): HI-ZEX (HDPE) 1300J (product name, manufactured by Prime Polymer Co., Ltd.) Polypropylene resin (PP): Prime Polypro J715M (product name, manufactured by Prime Polymer Co., Ltd.)

[0120] 2. Other thermoplastic resins Polylactic acid resin (PLA): Terramac TE-8303 (product name, manufactured by Unitika Ltd.)

[0121] (metal hydroxide) Aluminum hydroxide 1 (represented as "Al(OH)3-1" in Table II): KH-101 (product name, manufactured by Hayashi Kasei Co., Ltd., primary particle diameter 0.9 μm) Aluminum hydroxide 2 (represented as "Al(OH)3-2" in Table II): Nano aluminum hydroxide (product name, manufactured by EM Japan, primary particle diameter 50 nm) Magnesium hydroxide (represented as "Mg(OH)2" in Table II): Magseeds S-4 (product name, manufactured by Konoshima Chemical Co., Ltd., primary particle diameter 0.8 μm, surface coated with silane coupling agent)

[0122] (polysaccharide) The polysaccharides used were polysaccharides A1 to A9 and polysaccharides Cf1 and Cf2, which were commercially available products shown in Table I or obtained in the following synthesis examples. Polysaccharides A1 to A9 are polysaccharides that can be used in the flame-retardant resin composition of the present invention, while polysaccharides Cf1 and Cf2 are polysaccharides for comparative examples that are not suitable for the flame-retardant resin composition of the present invention.

[0123] [Table 1]

[0124] (Synthesis Example 1: Production of Polysaccharide A5) A 5 L flask was charged with 2,500 parts by mass of isopropyl alcohol, 180 parts by mass of water, and 100 parts by mass of powdered cellulose (cellulose, powder, 38 μm filtration product (Fujifilm Wako Pure Chemical Industries, Ltd.); polysaccharide Cf1) and stirred at room temperature. 56.1 parts by mass of sodium hydroxide dissolved in 60 parts by mass of water was added to the flask and stirred at 35°C for 1 hour. After stirring at 35°C for 1 hour, a mixture of 63.4 parts by mass of monochloroacetic acid and 45 parts by mass of isopropyl alcohol was added dropwise and stirred at 65°C for 2 hours to allow the mixture to react.

[0125] The resulting reaction solution was cooled to room temperature, removed, and 1,000 parts by mass of 70% aqueous methanol solution and 3.7 g of acetic acid were added and stirred to neutralize excess sodium hydroxide. 3,000 parts by mass of 70% aqueous methanol solution was then added, stirred, and the slurry was filtered, washed with acetone, and dried to obtain 123 parts by mass of carboxymethylcellulose as polysaccharide A5. The number of acidic functional groups in polysaccharide A5 was determined to be 0.61.

[0126] (Synthesis Example 2: Production of Polysaccharide A6) A 5 L flask was charged with 2,500 parts by mass of isopropyl alcohol, 180 parts by mass of water, and 100 parts by mass of powdered cellulose (cellulose, powder, 38 μm filtration product (Fujifilm Wako Pure Chemical Industries, Ltd.); polysaccharide Cf1) and stirred at room temperature. 21.6 parts by mass of sodium hydroxide dissolved in 25 parts by mass of water was added to the flask and stirred at 35°C for 1 hour. After stirring at 35°C for 1 hour, a mixture of 11.6 parts by mass of monochloroacetic acid and 15 parts by mass of isopropyl alcohol was added dropwise and stirred at 65°C for 2 hours to allow the mixture to react.

[0127] The resulting reaction solution was cooled to room temperature, removed, and 1,000 parts by mass of 70% aqueous methanol solution and 0.1 g of acetic acid were added and stirred to neutralize excess sodium hydroxide. 3,000 parts by mass of 70% aqueous methanol solution was then added, stirred, and the slurry was filtered, washed with acetone, and dried to obtain 103 parts by mass of carboxymethylcellulose as polysaccharide A6. The number of acidic functional groups in polysaccharide A6 was confirmed to be 0.20.

[0128] (Synthesis Example 3: Production of Polysaccharide A7) A 3-L flask was charged with 50 parts by mass of polysaccharide A2 (calcium alginate) shown in Table I, 500 parts by mass of ethanol, and 100 parts by mass of water, and the mixture was stirred. To this was added 16.8 parts by mass of calcium hydroxide, and the mixture was stirred at 30°C for 1 hour. A mixture of 30 parts by mass of epichlorohydrin and 150 parts by mass of ethanol was then added dropwise to the flask, heated to 50°C, and stirred for 3 hours while maintaining the temperature at 50-60°C. Next, an aqueous calcium hydroxide solution (16.8 parts by mass of calcium hydroxide, 100 parts by mass of water) was added dropwise, and the mixture was stirred for 1.5 hours. 30 parts by mass of epichlorohydrin was added to the mixture, and the mixture was stirred for an additional 2 hours.

[0129] The resulting reaction solution was cooled to room temperature, filtered, and washed with water until the pH of the wash was approximately neutral. After drying, 52.1 parts by mass of crosslinked polysaccharide A2 was obtained as polysaccharide A7. The number of acidic functional groups in polysaccharide A7 was confirmed to be 0.80.

[0130] (Synthesis Example 4: Production of Polysaccharide A8) Except for using 50 parts of polysaccharide A4 (carrageenan (ι type)) shown in Table I instead of polysaccharide A2, 46.5 parts by mass of epichlorohydrin-treated crosslinked polysaccharide A4 was obtained as polysaccharide A8 in the same manner as in Synthesis Example 3. The number of acidic functional groups in polysaccharide A8 was confirmed to be 0.30.

[0131] (Synthesis Example 5: Production of polysaccharide Cf2) A 5 L flask was charged with 2,500 parts by mass of isopropyl alcohol, 180 parts by mass of water, and 100 parts by mass of powdered cellulose (cellulose, powder, 38 μm filtration product (Fujifilm Wako Pure Chemical Industries, Ltd.); polysaccharide Cf1) and stirred at room temperature. A solution of 160 parts by mass of sodium hydroxide in 150 parts by mass of water was added to the flask and stirred at 35°C for 1.5 hours. After stirring at 35°C for 1.5 hours, a mixture of 180 parts by mass of monochloroacetic acid and 130 parts by mass of isopropyl alcohol was added dropwise, and the mixture was stirred and reacted at 65°C for 3 hours.

[0132] The resulting reaction solution was cooled to room temperature, removed, and 1,000 parts by mass of 70% aqueous methanol was added and stirred. The excess sodium hydroxide was neutralized by adding acetic acid. 3,000 parts by mass of 70% aqueous methanol was then added and stirred. The slurry was filtered, washed with acetone, and dried to obtain 152 parts by mass of carboxymethyl cellulose as polysaccharide Cf2. The number of acidic functional groups in polysaccharide Cf2 was confirmed to be 1.7.

[0133] (Preparation of Flame-Retardant Resin Composition) As a pre-drying step before kneading, the thermoplastic resin and the flame retardant (polysaccharide, metal hydroxide, etc.) were each dried for 4 hours at 80° C. Then, the components were weighed out in the ratios (mass%) shown in Table II and dry-blended.

[0134] Next, the mixture obtained by dry blending was fed at 10 kg / hour from the raw material inlet (hopper) of a twin-screw extruder kneader (KTX-30; Kobe Steel, Ltd.), and melt-kneaded under conditions of a cylinder temperature of 190°C and a screw rotation speed of 200 rpm. After kneading, the molten resin was cooled in a water bath at 30°C and then pelletized in a pelletizer to obtain flame-retardant resin compositions 1 to 17. Flame-retardant resin compositions 1 to 15 correspond to the flame-retardant resin compositions of the present invention, and flame-retardant resin compositions 16 and 17 are comparative examples.

[0135] <Evaluation> The flame-retardant resin compositions 1 to 17 obtained above were evaluated by the following evaluations 1 to 3. The results are shown in Table II together with the composition of the flame-retardant resin compositions and the cylinder temperature set during molding.

[0136] (Evaluation 1: Evaluation of exterior part fabrication) Each of the resulting pellet-shaped flame-retardant resin compositions 1 to 17 was dried in a hot air circulation dryer at 80°C for 5 hours. After drying, an injection molding machine (J1300E-C5 manufactured by The Japan Steel Works, Ltd.) was used to mold a simulated molded product representing the exterior part G8 of the large-size copier shown in Figure 1 at a cylinder temperature and mold temperature of 80°C as shown in Table II, and a sample was taken from the center. The appearance of the obtained samples was visually observed and evaluated according to the following criteria. A rating of Fair or better was considered to be satisfactory for practical use.

[0137] ◎: No defects in appearance. Good: There is slight warping on the exterior, but it is at a level that can be addressed by modifying the mold, and there is no problem with the product. △: Warping is visible on the exterior, but this can be improved by modifying the mold and reviewing molding conditions that reduce productivity. ×: Severe warpage is observed, and there is no prospect of improvement by modifying the mold or changing the molding conditions.

[0138] (Rating 2: Flame retardant) Each of the obtained pellet-shaped flame-retardant resin compositions 1 to 17 was dried at 80°C for 4 hours, and then molded using an injection molding machine (J55ELII, manufactured by The Japan Steel Works, Ltd.) with the cylinder set temperature and mold temperature set to 50°C as shown in Table II to obtain strip-shaped test pieces measuring 125 mm in length, 13 mm in width, and 1.6 mm in thickness.

[0139] The resulting test specimens were then conditioned for 48 hours in a temperature-controlled room at 23°C and 50% humidity, and then subjected to a flame retardancy test in accordance with the UL94 test (flammability test for plastic materials for equipment components) established by Underwriters Laboratories (UL). The test was first conducted using the UL94V test method, and for materials that did not achieve V-2 in UL94V, the UL94HB test was conducted to confirm the flame retardancy ranking. The flame retardancy was then evaluated based on the following evaluation criteria. △, meaning that a flame retardancy of HB or higher was considered to be a pass.

[0140] ◎:V-0 (passed) ○: V-1 or V-2 (pass) △:HB (passed) ×: Out of specification (also failed the HB test)

[0141] (Rating 3: Bending strength) Each of the obtained pellet-shaped flame-retardant resin compositions 1 to 17 was dried at 80°C for 4 hours, and then molded using an injection molding machine (J55ELII, manufactured by The Japan Steel Works, Ltd.) with the cylinder set temperature and mold temperature set to 50°C as shown in Table II to obtain test pieces measuring 80 mm in length, 10 mm in width, and 4.0 mm in height.

[0142] After 300 shots were discarded, 100 consecutive shots were molded. The flexural strength variation XTS (%) of the 100 molded products obtained was calculated using the formula below and evaluated according to the following criteria. A rating of △ or higher was deemed acceptable for practical use.

[0143] XTS(%)=(TRmax-TRmin) / (TRav)×100 In the above formula, TRmax represents the maximum bending strength (MPa) of 100 molded articles, TRmin represents the minimum bending strength (MPa) of 100 molded articles, and TRav represents the average bending strength (MPa) of 100 molded articles. Here, the bending strength of the molded articles is a value measured based on JIS K7171.

[0144] ◎: TRav is 20 MPa or more and XTS is less than 0.5% ○: TRav is 20 MPa or more and XTS is 0.5% or more and less than 5% △: TRav is 20 MPa or more and XTS is 5% or more and less than 15% ×: TRav is less than 20 MPa or XTS is 15% or more

[0145] [Table 1]

[0146] Table II shows that the flame-retardant resin composition of the present invention maintains flame retardancy and strength while reducing the amount of petroleum resources used in the resulting molded articles. Flame-retardant resin composition 9, which contains a polysaccharide with 1.4 acidic functional groups, exhibits severe shrinkage of the molded articles and a large variation in bending strength of the molded test pieces. [Explanation of symbols]

[0147] 10: Large copy machine G1 to G9: Exterior parts

Claims

1. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; the content of the acidic polysaccharide relative to the total amount of the flame-retardant resin composition is within the range of 5 to 40 mass %, An electronic device characterized in that a molded article of a flame-retardant resin composition is used as a component, wherein the acidic polysaccharide contains at least one selected from alginic acid, alginate salts, carrageenan, pectin, xanthan gum, and gellan gum, or a crosslinked polysaccharide obtained by crosslinking at least one selected from these.

2. The electronic device described in Claim 1, characterized in that the flame-retardant resin composition has a total number of acidic functional groups and their salts per monosaccharide unit in the acidic polysaccharide in the range of 0.6 to 1.

2.

3. The electronic device described in claim 1 or claim 2, characterized in that the flame-retardant resin composition has an acidic functional group that is a carboxy group or a sulfo group.

4. The flame-retardant resin composition is an electronic device described in any one of claims 1 to 3, characterized in that the derivative of the polysaccharide having the acidic functional group is a cross-linked polysaccharide in which the hydroxy groups in the sugar chains of two or more polysaccharide molecules are cross-linked.

5. The flame-retardant resin composition is an electronic device described in any one of claims 1 to 4, characterized in that the derivative of the polysaccharide having the acidic functional group is a cross-linked polysaccharide in which the hydroxy groups in the sugar chains of two or more polysaccharide molecules are cross-linked with epichlorohydrin.

6. An electronic device described in any one of claims 1 to 5, characterized in that the flame-retardant resin composition further contains a metal hydroxide in a range of 5 to 20 mass% relative to the total amount of the flame-retardant resin composition.

7. The electronic device described in Claim 6, characterized in that the flame-retardant resin composition contains aluminum hydroxide particles having an average primary particle diameter in the range of 10 to 100 nm as the metal hydroxide.

8. An electronic device described in any one of claims 1 to 7, characterized in that the flame-retardant resin composition and the thermoplastic resin are polyolefin-based resins.

9. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; An electronic device using, as a component, a molded article of a flame-retardant resin composition, wherein the derivative of a polysaccharide having an acidic functional group is a crosslinked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are crosslinked with epichlorohydrin.

10. A flame-retardant resin composition containing a thermoplastic resin and a polysaccharide, the polysaccharide comprises one or more acidic polysaccharides selected from polysaccharides having an acidic functional group, derivatives of the polysaccharides having an acidic functional group in which a site other than the acidic functional group has been modified, and salts thereof; the total number of the acidic functional groups and salts thereof per monosaccharide unit in the acidic polysaccharide is within the range of 0.2 to 1.5; A flame-retardant resin composition characterized in that the derivative of a polysaccharide having an acidic functional group is a cross-linked polysaccharide in which hydroxy groups in the sugar chains of two or more polysaccharide molecules are cross-linked with epichlorohydrin.

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