JP7819922B2 - Curable resin composition - Google Patents

Description

The present invention relates to a curable resin composition.

To prevent the spread of fire in the event of a fire, flame retardancy has been promoted for automobile components, home appliances, electronic materials, sporting goods, building materials, containers for storing flammable liquids, and other products.

In recent years, the electronics field has made remarkable progress, particularly in the miniaturization, lightening, and increasing density of electronic devices. This has led to increasing demands for thinner, multi-layered, and higher-definition electronic materials, including printed wiring boards and light-emitting diodes (LEDs). These electronic materials also require flame retardancy.

In addition, improved flame retardancy is also required for containers that store flammable liquids in order to improve safety.

Patent Document 1 discloses a flame-retardant resin composition containing (A) a polymeric compound, (B) ammonium polyphosphate, (C) aluminum hydroxide and/or magnesium hydroxide, (D) a polyhydric alcohol, (E) a compound having a melamine skeleton, and (F) hollow ceramic beads and/or expanded graphite.

Japanese Patent Application Laid-Open No. 2021-14513

However, the flame-retardant resin composition of Patent Document 1 has the problem that the flame retardancy of the film obtained from this flame-retardant resin composition is insufficient. Furthermore, the flame-retardant resin composition of Patent Document 1 has the problem that it has high viscosity, making it difficult to apply to electronic materials.

The present invention provides a curable resin composition that has excellent coatability, can be easily applied to substrates, particularly electronic materials, and can impart flame retardancy to the substrate or improve the flame retardancy of the substrate.

The curable resin composition of the present invention contains a curable resin, a feldspar, a non-ferrous metal hydroxide, and a phosphate ester.

[Curable resin]
The curable resin includes one-component curable resins and two-component curable resins. One-component curable resins include resins that are cured by introducing a crosslinked structure due to moisture, light irradiation, or heat. Two-component curable resins include resins that are cured by mixing a base resin and a curing agent to introduce a crosslinked structure.

[One-component curable resin]
Examples of the one-component curable resin include a polymer having a hydrolyzable silyl group, a polymer having a hydrolyzable isocyanate group, and a photocrosslinkable polymer, and it is preferable that the one-component curable resin contains a polymer having a hydrolyzable silyl group.

In the presence of water, polymers containing hydrolyzable silyl groups hydrolyze the hydrolyzable groups of the hydrolyzable silyl groups to form silanol groups (≡SiOH). The silanol groups then undergo dehydration condensation to form crosslinked structures. In the presence of water, polymers containing hydrolyzable isocyanate groups form urea bonds (-NHCONH-) while generating carbon dioxide, forming crosslinked structures.

A hydrolyzable silyl group is a group formed by bonding one to three hydrolyzable groups to a silicon atom. The hydrolyzable groups of the hydrolyzable silyl group are not particularly limited, and examples include hydrogen atoms, halogen atoms, alkoxy groups, acyloxy groups, ketoximate groups, amino groups, amide groups, acid amide groups, aminooxy groups, mercapto groups, alkenyloxy groups, and oxime groups.

Among these, alkoxysilyl groups are preferred as hydrolyzable silyl groups because of their mild hydrolysis reaction. Examples of alkoxysilyl groups include trialkoxysilyl groups such as trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, and triphenoxysilyl; dialkoxysilyl groups such as propyldimethoxysilyl, methyldimethoxysilyl, and methyldiethoxysilyl; and monoalkoxysilyl groups such as dimethylmethoxysilyl and dimethylethoxysilyl.

A hydrolyzable isocyanate group is an isocyanate group that can form a urea bond (-NHCONH-) by hydrolysis.

[Polymer having hydrolyzable silyl group]
The polymer having a hydrolyzable silyl group is not particularly limited, and examples thereof include polyalkylene oxides having a hydrolyzable silyl group, acrylic polymers having a hydrolyzable silyl group, silicone resins having a hydrolyzable silyl group, urethane resins having a hydrolyzable silyl group, and polyolefin resins having a hydrolyzable silyl group. The polymer having a hydrolyzable silyl group preferably contains a polyalkylene oxide having a hydrolyzable silyl group. The polymer having a hydrolyzable silyl group may be used alone or in combination of two or more.

[Polyalkylene oxide having a hydrolyzable silyl group]
In the polyalkylene oxide having a hydrolyzable silyl group, the hydrolyzable silyl group is preferably an alkoxysilyl group, more preferably a dialkoxysilyl group, more preferably a dimethoxysilyl group, and more preferably a propyldimethoxysilyl group.

The polyalkylene oxide having a hydrolyzable silyl group preferably has an average of 1 to 4 hydrolyzable silyl groups per molecule. When the number of hydrolyzable silyl groups in the polyalkylene oxide having a hydrolyzable silyl group is within the above range, the flame retardancy of the cured product of the curable resin composition is improved. The polyalkylene oxide having a hydrolyzable silyl group preferably has a hydrolyzable silyl group at at least one of the two ends of its main chain.

The average number of hydrolyzable silyl groups per molecule in a polyalkylene oxide having hydrolyzable silyl groups can be calculated based on the concentration of hydrolyzable silyl groups in the polyalkylene oxide determined by ^1H -NMR and the number average molecular weight of the polyalkylene oxide determined by GPC.

Preferred examples of polyalkylene oxides constituting the polyalkylene oxide having a hydrolyzable silyl group include polymers whose main chain contains repeating units represented by the general formula: -(R-O) _m- (wherein R represents an alkylene group having 1 to 14 carbon atoms, and m represents the number of repeating units and is a positive integer). The main chain skeleton of the polyalkylene oxide may be composed of only one type of repeating unit, or may be composed of two or more types of repeating units.

In the present invention, an alkylene group is a divalent atomic group formed by removing two hydrogen atoms bonded to two different carbon atoms in an aliphatic saturated hydrocarbon, and includes both linear and branched atomic groups.

Examples of the alkylene group include an ethylene group, a propylene group [--CH(CH ₃ )--CH ₂ --], a trimethylene group [--CH ₂ --CH ₂ --CH ₂ --], a butylene group, an amylene group [--(CH ₂ ) ₅ --], and a hexylene group.

Examples of the main chain skeleton of polyalkylene oxide include polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetramethylene oxide, polyethylene oxide-polypropylene oxide copolymer, and polypropylene oxide-polybutylene oxide copolymer. Of these, polypropylene oxide is preferred. Polypropylene oxide reduces the viscosity of the curable resin composition, improving its coatability and allowing the curable resin composition to be applied accurately to narrow coating areas.

The number average molecular weight of the polyalkylene oxide having a hydrolyzable silyl group is preferably 3,000 or more, more preferably 10,000 or more. The number average molecular weight of the polyalkylene oxide having a hydrolyzable silyl group is preferably 50,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. When the number average molecular weight of the polyalkylene oxide is 3,000 or more, the polyalkylene oxide does not easily thermally decompose into lower molecular weight compounds, and the cured product of the curable resin composition has excellent flame retardancy. When the number average molecular weight of the polyalkylene oxide is 50,000 or less, the coatability of the curable resin composition is improved, allowing it to be applied accurately to the desired location on the substrate.

In the present invention, the number average molecular weight of a polyalkylene oxide having a hydrolyzable silyl group refers to the polystyrene-equivalent value measured by GPC (gel permeation chromatography).

The number average molecular weight of the polyalkylene oxide having a hydrolyzable silyl group can be measured, for example, using the following measuring device and under the following measuring conditions.
Measuring device: TOSOH Corporation, product name "HLC-8121GPC/HT"
Measurement conditions Column: TSKgelGMHHR-H(20)HT x 3
TSKguardcolumn-HHR(30)HT x 1
Mobile phase: o-DCB 1.0mL/min
Sample concentration: 1 mg/mL
Detector: Bryce type refractometer
Standard material: Polystyrene (TOSOH Corporation, molecular weight: 500-8420000)
Elution conditions: 145℃
SEC temperature: 145℃

Commercially available polyalkylene oxides having hydrolyzable silyl groups can be used. For example, examples of polyalkylene oxides having hydrolyzable silyl groups include those manufactured by Kaneka Corporation under the trade names "MS Polymer S-203," "MS Polymer S-303," "MS Polymer S-303H," "Silyl Polymer SAT-200," "Silyl Polymer SAT-350," and "Silyl Polymer SAT-400." Examples of polyalkylene oxides having hydrolyzable silyl groups include those manufactured by Asahi Glass Co., Ltd. under the trade names "Excestar ESS-3620," "Excestar ESS-2420," "Excestar ESS2410," and "Excestar ESS3430."

A polyalkylene oxide with a polypropylene oxide main chain and (methoxymethyl)dimethoxysilyl groups at the ends of the polypropylene oxide is commercially available from Kaneka Corporation under the product name "HS-2."

A polyalkylene oxide with a polypropylene oxide main chain and an isopropyldimethoxymethylsilyl group at the end of the polypropylene oxide is commercially available from Kaneka Corporation under the product name "SAX720."

[Acrylic polymer having hydrolyzable silyl group]
As the hydrolyzable silyl group contained in the acrylic polymer having a hydrolyzable silyl group, an alkoxysilyl group is preferred, a trialkoxysilyl group is more preferred, and a trimethoxysilyl group is particularly preferred, because the hydrolysis reaction is mild.

In an acrylic polymer having a hydrolyzable silyl group, the average number of hydrolyzable silyl groups per molecule is preferably one or more, more preferably two or more. In an acrylic polymer having a hydrolyzable silyl group, the average number of hydrolyzable silyl groups per molecule is preferably four or less, more preferably 2.5 or less. When the number of hydrolyzable silyl groups is one or more, the flame retardancy of the cured product of the curable resin composition is improved. When the number of hydrolyzable silyl groups is four or less, the viscosity of the curable resin composition is reduced, improving coatability, allowing the curable resin composition to be applied accurately to narrow application areas. Furthermore, when the curable resin composition is applied to the application area, the curable resin composition flows smoothly at the application area, providing excellent leveling properties. It is preferable that the acrylic polymer having a hydrolyzable silyl group has a hydrolyzable silyl group at at least one of the two ends of its main chain.

An acrylic polymer having hydrolyzable silyl groups may be used in combination with an acrylic polymer not having hydrolyzable silyl groups. In this case, the total number of hydrolyzable silyl groups per molecule for both polymers is preferably 0.3 or more, more preferably 0.5 or more. When the number of hydrolyzable silyl groups is 0.3 or more, the curability of the curable resin composition is improved. On the other hand, the total number of hydrolyzable silyl groups per molecule for both polymers is preferably 2.0 or less, more preferably 1.8 or less. When the number of hydrolyzable silyl groups is 2.0 or less, the viscosity of the curable resin composition is reduced, improving coatability. This allows the curable resin composition to be applied accurately to narrow application areas. Furthermore, when the curable resin composition is applied to the application area, the curable resin composition flows smoothly at the application area, providing excellent leveling properties.

The method for introducing hydrolyzable silyl groups into acrylic polymers is not particularly limited, and examples include a method in which unsaturated groups are introduced into a copolymer of monomers that make up the main chain skeleton, and then hydrosilylation is carried out by reacting the copolymer with a hydrosilane having a hydrolyzable silyl group.

The average number of hydrolyzable silyl groups per molecule in the acrylic polymer having hydrolyzable silyl groups is calculated based on the concentration of hydrolyzable silyl groups in the acrylic polymer having hydrolyzable silyl groups determined by ^1H -NMR and the number average molecular weight of the acrylic polymer having hydrolyzable silyl groups determined by GPC.

The main chain skeleton of the acrylic polymer having a hydrolyzable silyl group is preferably a copolymer of monomers containing methyl (meth)acrylate and butyl (meth)acrylate, more preferably a copolymer of monomers containing methyl methacrylate and butyl acrylate, and even more preferably a copolymer of monomers containing methyl methacrylate and n-butyl acrylate. An acrylic polymer having a hydrolyzable silyl group whose main chain skeleton is the above copolymer improves the flame retardancy of the cured product of the curable resin composition. Note that (meth)acrylate refers to methacrylate and/or acrylate.

In the acrylic polymer having a hydrolyzable silyl group, the content of the methyl (meth)acrylate component is preferably 3% by mass or more, and more preferably 5% by mass or more. In the acrylic polymer having a hydrolyzable silyl group, the content of the methyl (meth)acrylate component is preferably 70% by mass or less, and more preferably 50% by mass or less. When the content of the methyl (meth)acrylate component is 3% by mass or more, the viscosity of the curable resin composition is reduced, improving coatability, allowing the curable resin composition to be applied accurately to narrow application areas. In addition, when the curable resin composition is applied to the application area, the curable resin composition flows smoothly at the application area and exhibits excellent leveling properties. When the content of the methyl (meth)acrylate component is 70% by mass or less, the viscosity of the curable resin composition is reduced, improving coatability, allowing the curable resin composition to be applied accurately to narrow application areas.

In the acrylic polymer having a hydrolyzable silyl group, the content of the butyl (meth)acrylate component is preferably 30 to 97% by mass, and more preferably 50 to 95% by mass. By having a butyl (meth)acrylate component content of 30% by mass or more, the viscosity of the curable resin composition is reduced, improving coatability and allowing the curable resin composition to be applied accurately to narrow application areas.

In acrylic polymers having hydrolyzable silyl groups, the monomers used in the polymer constituting the main chain skeleton may include methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate, as well as other monomers. Examples of other monomers include styrene derivatives such as styrene, indene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, p-chloromethylstyrene, p-methoxystyrene, p-tert-butoxystyrene, and divinylbenzene; compounds having a vinyl ester group such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl benzoate, and vinyl cinnamate; maleic anhydride, N-vinylpyrrolidone, N-vinylmorpholine, methacrylonitrile, acrylonitrile, acrylamide, methacrylamide, N-cyclohexylmaleimide, N-phenylmaleimide, N-laurylmaleimide, N-benzylmaleimide, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, tert-amyl vinyl ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, 2-chloroethyl vinyl ether, ethylene glycol butyl vinyl ether, trimethylsilyl vinyl ether, methyl ... Examples of vinyloxy group-containing compounds include ethylene glycol methyl vinyl ether, (4-vinyloxy)butyl benzoate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, butane-1,4-diol divinyl ether, hexane-1,6-diol divinyl ether, cyclohexane-1,4-dimethanol divinyl ether, di(4-vinyloxy)butyl isophthalate, di(4-vinyloxy)butyl glutarate, di(4-vinyloxy)butyl succinate, trimethylolpropane trivinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether, cyclohexane-1,4-dimethanol monovinyl ether, diethylene glycol monovinyl ether, 3-aminopropyl vinyl ether, 2-(N,N-diethylamino)ethyl vinyl ether, urethane vinyl ether, and polyester vinyl ether. These monomers may be used alone or in combination.

The polymerization method for acrylic polymers having hydrolyzable silyl groups is not particularly limited, and known methods can be used, including various polymerization methods such as free radical polymerization, anionic polymerization, cationic polymerization, UV radical polymerization, living anionic polymerization, living cationic polymerization, and living radical polymerization.

The weight-average molecular weight of the acrylic polymer having a hydrolyzable silyl group is preferably 1,000 to 50,000, more preferably 2,000 to 30,000, and particularly preferably 3,000 to 15,000. An acrylic polymer having a hydrolyzable silyl group with a weight-average molecular weight within the above range reduces the viscosity of the curable resin composition, improving coatability and allowing the curable resin composition to be applied accurately to narrow application areas. Furthermore, when the curable resin composition is applied to the application area, it flows smoothly at the application area, providing excellent leveling properties.

[Silicone resin having hydrolyzable silyl groups]
A silicone resin refers to a polymer having a main chain formed by repeating siloxane bonds (-Si-O-). A silicone resin having hydrolyzable silyl groups has a plurality of hydrolyzable silyl groups in the main chain of the silicone resin. A silicone resin having hydrolyzable silyl groups preferably has hydrolyzable silyl groups at both ends of the main chain of the silicone resin. The hydrolyzable silyl groups contained in a silicone resin having hydrolyzable silyl groups are preferably oximesilyl groups, and more preferably ketoximesilyl groups.

[Urethane resin having hydrolyzable silyl group]
A urethane resin refers to a polymer having a main chain formed by repeating urethane bonds (-NHCOO-). A urethane resin having a hydrolyzable silyl group has a plurality of hydrolyzable silyl groups in the main chain of the urethane resin. The urethane resin having a hydrolyzable silyl group preferably has the hydrolyzable silyl group at both ends of the main chain of the urethane resin.

[Polyolefin resin having hydrolyzable silyl group]
Examples of polyolefin resins include polyethylene resins and polypropylene resins. The polyolefin resin having hydrolyzable silyl groups has a plurality of hydrolyzable silyl groups in the main chain of the polyolefin resin. The polyolefin resin having hydrolyzable silyl groups preferably has hydrolyzable silyl groups at both ends of the main chain of the polyolefin resin.

[Polymer having hydrolyzable isocyanate group]
Examples of polymers having hydrolyzable isocyanate groups include urethane resins having hydrolyzable isocyanate groups. Urethane resins refer to polymers having a main chain formed by repeating urethane bonds (-NHCOO-). Urethane resins having hydrolyzable isocyanate groups have multiple hydrolyzable isocyanate groups in the main chain of the urethane resin. Urethane resins having hydrolyzable isocyanate groups preferably have hydrolyzable isocyanate groups at both ends of the main chain of the urethane resin. Urethane resins include polyether-based urethane resins made from polyether polyol as a raw material and polyester-based urethane resins made from polyester polyol as a raw material, but either of these may be used.

[Photocrosslinkable polymer]
A photocrosslinkable polymer has photocrosslinkable groups in its molecules, and when irradiated with light such as ultraviolet light, chemical bonds are formed between the molecules, forming a crosslinked structure and curing the polymer.

The photocrosslinkable group may be one that forms a chemical bond upon irradiation with light. The photocrosslinkable group is not particularly limited, and examples include thiol groups, glycidyl groups, oxetanyl groups, vinyl groups, (meth)acryloyl groups, benzophenone groups, benzoin groups, and thioxanthone groups. Benzophenone groups, benzoin groups, and thioxanthone groups are preferred, and benzophenone groups are more preferred. Note that (meth)acryloyl refers to methacryloyl or acryloyl.

The main chain structure of the photocrosslinkable polymer is not particularly limited, and examples include polyolefin resins, acrylic resins, epoxy resins, and cyanoacrylate resins. Examples of methods for introducing photocrosslinkable groups into the main chain include polymerizing a monomer composition containing a photocrosslinkable group-containing monomer.

The photocrosslinkable group-containing monomer is not particularly limited, and examples include glycidyl (meth)acrylate, 4-hydroxybutyl acrylate glycidyl ether, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, 4-(meth)acryloyloxyethoxy-4'-methoxybenzophenone, 4-(meth)acryloyloxy-4'-bromobenzophenone, and 4-(meth)acryloyloxyethoxy-4'-bromobenzophenone, with 4-(meth)acryloyloxybenzophenone and 4-[2-((meth)acryloyloxy)ethoxy]benzophenone being preferred. The UV-crosslinkable group-containing monomer (D) may be used alone or in combination of two or more types. Note that (meth)acryloyloxy means methacryloyloxy or acryloyloxy.

[Two-component curable resin]
The two-component curable resin is not particularly limited, and examples thereof include isocyanate-based polymers and glycidyl-based polymers.

Isocyanate-based polymers are two-component curable resins consisting of a base resin containing polyisocyanate and a curing agent containing polyol. By mixing the base resin and curing agent and causing the polyisocyanate and polyol to react, urethane bonds are formed, crosslinking occurs, and the resin hardens.

Examples of polyisocyanates include araliphatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Examples of araliphatic diisocyanates include diphenylmethane diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene, 1,4-bis(1-isocyanato-1-methylethyl)benzene, ω,ω'-diisocyanato-1,4-diethylbenzene, and urethane prepolymers having isocyanate groups at both ends.

Examples of aliphatic diisocyanates include hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate.

Examples of alicyclic diisocyanates include isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate.

Examples of polyols include polyurethane polyols, polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, and castor oil-based polyols.

Glycidyl polymers are two-component curable resins consisting of a base resin containing an epoxy resin and a curing agent. Epoxy resins are not particularly limited, but examples include bisphenol A epoxy resins obtained by reacting bisphenol A with epichlorohydrin, bisphenol F epoxy resins obtained by reacting bisphenol F with epichlorohydrin, and hydrogenated versions of these, glycidyl ester epoxy resins, novolac epoxy resins, urethane-modified epoxy resins, nitrogen-containing epoxy resins such as triglycidyl isocyanurate, and rubber-modified epoxy resins containing polybutadiene or NBR.

The curing agent is not particularly limited, and examples include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, imidazole-based curing agents, and polymercapran-based curing agents.

Examples of amine-based curing agents include aliphatic polyamines such as polyoxypropylenetriamine, diethylenetriamine, and triethylenetetramine, and aromatic polyamines such as metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and 2,4,6-tris(dimethylaminomethyl)phenol.

Examples of acid anhydride curing agents include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, HET anhydride, and dodecenyl succinic anhydride. Examples of polyamide curing agents include dimer acid.

[Feldspars]
The curable resin composition contains a feldspar. By containing a feldspar in the curable resin composition, a cured product of the curable resin composition has excellent flame retardancy. The feldspar contains feldspar and feldspar spheroid, and feldspar spheroid is preferred. The feldspars may be used alone or in combination of two or more.

Examples of feldspars include alkali feldspars such as orthoclase, sanidine, microcline, and anorthoclase; and plagioclases such as albite, oligoclase, andesine, albite, anorthite, and anorthite.

Examples of feldspars include nephelines such as kalsilite and cancrinite, nepheline syenite, leucite, sodalite, hauyne, lazurite, nosean, and melilite, with nepheline syenite being preferred. Note that nepheline syenite is sometimes referred to as syenite.

The average particle size of the feldspars is preferably 0.1 μm or more, more preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The average particle size of the feldspars is preferably 50 μm or less, more preferably 25 μm or less, and even more preferably 15 μm or less. When the average particle size of the feldspars is 0.1 μm or more, the cohesive strength of the curable resin composition before curing is improved, allowing the curable resin composition to be applied accurately to narrow coating areas. When the average particle size of the feldspars is 50 μm or less, the feldspars can be uniformly dispersed in the curable resin composition, imparting excellent mechanical strength to the cured product of the curable resin composition and providing stable, excellent flame retardancy to the coated object over a long period of time. The average particle size of the feldspars is a value measured by image analysis using a transmission electron microscope. Specifically, 100x magnification photographs of feldspars are taken using a transmission electron microscope, 50 randomly selected feldspars are selected, the diameter of each feldspar is measured, and the arithmetic mean of the diameters of each feldspar is taken as the average particle size of the feldspar. Note that the diameter of the feldspar refers to the diameter of the smallest circle that can surround the feldspar.

The feldspar content in the curable resin composition is preferably 1 part by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and more preferably 80 parts by mass or more, per 100 parts by mass of curable resin. The feldspar content in the curable resin composition is preferably 800 parts by mass or less, more preferably 600 parts by mass or less, more preferably 450 parts by mass or less, more preferably 300 parts by mass or less, more preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and more preferably 80 parts by mass or less, per 100 parts by mass of curable resin. When the feldspar content is within the above range, the cured product of the curable resin composition has excellent flame retardancy, and the viscosity of the curable resin composition is reduced, improving coatability and allowing the curable resin composition to be applied accurately to narrow coating areas.

[Non-ferrous metal hydroxides]
The curable resin composition contains a non-ferrous metal hydroxide. By containing the non-ferrous metal hydroxide in the curable resin composition, a cured product of the curable resin composition has excellent flame retardancy. The non-ferrous metal hydroxides may be used alone or in combination of two or more.

The non-ferrous metal hydroxide is not particularly limited, and examples include aluminum hydroxide, magnesium hydroxide, dawsonite, calcium aluminate, dihydrate gypsum, calcium hydroxide, zinc hydroxide, nickel hydroxide, copper (II) hydroxide, and chromium (III) hydroxide. Aluminum hydroxide and magnesium hydroxide are preferred, as the endothermic effect exerted by non-ferrous metal hydroxides during thermal decomposition improves the flame retardancy of the cured product of the curable resin composition.

The average particle size of the non-ferrous metal hydroxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more. The average particle size of the non-ferrous metal hydroxide is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The average particle size of the non-ferrous metal hydroxide refers to the particle size D50 at which the cumulative frequency of particles from the smaller particle size side in the volume-based particle size distribution measured by laser diffraction is 50 mass%.

The content of the non-ferrous metal hydroxide in the curable resin composition is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of curable resin. The content of the non-ferrous metal hydroxide in the curable resin composition is preferably 250 parts by mass or less, more preferably 200 parts by mass or less, and even more preferably 150 parts by mass or less, per 100 parts by mass of curable resin. When the content of the non-ferrous metal hydroxide is within the above range, the cured product of the curable resin composition has excellent flame retardancy, and the viscosity of the curable resin composition is reduced, improving coatability and allowing the curable resin composition to be applied accurately to narrow coating areas.

[Phosphate ester]
The curable resin composition contains a phosphate ester. Due to the inclusion of the phosphate ester in the curable resin composition, a cured product of the curable resin composition has excellent flame retardancy. The phosphate ester may be used alone or in combination of two or more.

The phosphate ester is not particularly limited, but examples include monophosphate ester, condensed phosphate ester, etc.

Monophosphate esters are phosphate esters containing one phosphorus atom in the molecule. Monophosphate esters are not particularly limited, and examples include trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, and tri(2-ethylhexyl)phosphate; halogen-containing phosphate esters such as tris(β-chloropropyl)phosphate; trialkoxy phosphates such as tributoxyethyl phosphate; aromatic ring-containing phosphate esters such as tricresyl phosphate, trixylenyl phosphate, tris(isopropylphenyl)phosphate, cresyl diphenyl phosphate, and diphenyl(2-ethylhexyl)phosphate; and acidic phosphate esters such as monoisodecyl phosphate and diisodecyl phosphate. Aromatic ring-containing phosphate esters are preferred as monophosphate esters, with tricresyl phosphate being preferred.

Condensed phosphate esters are phosphate esters that contain multiple phosphorus atoms in the molecule. There are no particular limitations on the condensed phosphate esters, but examples include aromatic condensed phosphate esters such as trialkyl polyphosphate, resorcinol polyphenyl phosphate, bisphenol A polycresyl phosphate, and bisphenol A polyphenyl phosphate.

Phosphate esters have excellent compatibility with curable resins, reduce the viscosity of the curable resin composition, improve coatability, and allow the curable resin composition to be applied accurately to narrow application areas. Therefore, trimethyl phosphate, triethyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, resorcinol polyphenyl phosphate, bisphenol A polycresyl phosphate, and bisphenol A bisdiphenyl phosphate [formula (V)] are preferred, with trigresyl phosphate, resorcinol polyphenyl phosphate [formula (II)], cresyl di-2,6-xylenyl phosphate [formula (III)], tris(chloropropyl) phosphate [formula (IV)], bisphenol A polycresyl phosphate, and bisphenol A bisdiphenyl phosphate [formula (V)] being more preferred.

The phosphate ester is preferably liquid at 20°C and 1 atmosphere (0.101 MPa). Liquid refers to a state in which the ester does not have a fixed shape, is fluid, and has a substantially fixed volume.

When the phosphate ester is liquid, the viscosity of the phosphate ester is preferably 1 mPa·s or more, more preferably 50 mPa·s or more, and even more preferably 500 mPa·s or more. The viscosity of the phosphate ester is preferably 30,000 mPa·s or less, more preferably 10,000 mPa·s or less, and even more preferably 5,000 mPa·s or less. The viscosity of the phosphate ester is the value measured using a Brookfield type B viscometer specified in JIS K7117.

The content of the phosphate ester in the curable resin composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, more preferably 5 parts by mass or more, more preferably 15 parts by mass or more, more preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and more preferably 40 parts by mass or more, per 100 parts by mass of the curable resin. The content of the phosphate ester in the curable resin composition is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and more preferably 80 parts by mass or less, per 100 parts by mass of the curable resin. When the content of the phosphate ester is 1 part by mass or more, the cured product of the curable resin composition has excellent flame retardancy, and the viscosity of the curable resin composition is reduced, improving coatability and allowing the curable resin composition to be applied accurately to narrow coating areas. When the content of the phosphate ester is 300 parts by mass or less, the curability of the curable resin composition is improved.

In the curable resin composition, the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate esters [(total content of feldspars and non-ferrous metal hydroxides)/(content of phosphate ester)] is preferably 2.0 or greater, and more preferably 2.5 or greater. In the curable resin composition, the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate esters [(total content of feldspars and non-ferrous metal hydroxides)/(content of phosphate ester)] is preferably 20 or less, more preferably 15 or less, more preferably 12 or less, more preferably 10 or less, more preferably 8 or less, more preferably 6 or less, more preferably 4 or less, and more preferably 3.5 or less. When the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate esters [(total content of feldspars and non-ferrous metal hydroxides)/(content of phosphate ester)] is 2.0 or greater, the film strength of the cured product of the curable resin composition is improved. When the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate esters in the curable resin composition [(total content of feldspars and non-ferrous metal hydroxides) / (content of phosphate ester)] is 20 or less, the film strength of the cured product of the curable resin composition is improved.

[Glass frit]
The curable resin composition preferably contains glass frit. The glass frit acts as a binder to bind the combustion residue of the curable resin and feldspars in the combustion residue of the cured product of the curable resin composition, and the combustion residue has excellent strength. Therefore, the combustion residue of the curable resin composition is stably present at the coated portion of the substrate, and can impart excellent flame retardancy to the substrate.

Examples of glasses constituting the glass frit include phosphate glass, borate glass, bismuth oxide glass, silicate glass, and sodium oxide glass, with phosphate glass and borate glass being preferred, and phosphate glass being more preferred. These glass frits can be obtained by adjusting _the composition ratios of _B2O3 , _P2O5 , _ZnO , _SiO2 , _Bi2O3 , _Al2O3 , _BaO , CaO, _MgO , _MnO2 , _ZrO2 , _TiO2 , _CeO2 , _SrO , _V2O5 , _SnO2 , Li2O, _Na2O , _K2O , CuO, _{Fe2O3 ,} and the _like .

The content of glass frit in the curable resin composition is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of curable resin. The content of glass frit in the curable resin composition is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of curable resin. When the content of glass frit is 5 parts by mass or more, the combustion residue of the cured product of the curable resin composition has excellent strength and is stably present at the coated area of the coated substrate, thereby imparting excellent flame retardancy to the coated substrate. When the content of glass frit is 200 parts by mass or less, the viscosity of the curable resin composition is reduced, improving coatability and allowing the curable resin composition to be coated accurately into narrow coating areas.

[Silanol condensation catalyst]
The curable resin composition may contain a silanol condensation catalyst, which is a catalyst for promoting a dehydration condensation reaction between silanol groups formed by hydrolysis of the hydrolyzable silyl groups contained in the curable resin when the curable resin has hydrolyzable silyl groups.

Silanol condensation catalysts include organotin compounds such as dibutyltin diacetylacetonate, 1,1,3,3-tetrabutyl-1,3-dilauryloxycarbonyl distannoxane, dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, dibutyltin phthalate, bis(dibutyltin laurate) oxide, dibutyltin bis(acetylacetonate), dibutyltin bis(monoester maleate), tin octoate, dibutyltin octoate, dioctyltin oxide, dibutyltin bis(triethoxysilicate), bis(dibutyltin bistriethoxysilicate) oxide, and dibutyltin oxybisethoxysilicate; and organotitanium compounds such as tetra-n-butoxytitanate and tetraisopropoxytitanate, with organotin compounds being preferred. These silanol condensation catalysts may be used alone or in combination.

A preferred silanol condensation catalyst is 1,1,3,3-tetrabutyl-1,3-dilauryloxycarbonyl-distannoxane. Using such a silanol condensation catalyst makes it easy to adjust the curing rate of the curable resin composition.

The content of the silanol condensation catalyst in the curable resin composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass or more, per 100 parts by mass of curable resin. The content of the silanol condensation catalyst in the curable resin composition is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of curable resin. When the content of the silanol condensation catalyst in the curable resin composition is 0.1 parts by mass or more, the curing rate of the curable resin composition can be increased, and the time required to cure the curable resin composition can be shortened. When the content of the silanol condensation catalyst in the curable resin composition is 10 parts by mass or less, the curable resin composition has an appropriate curing rate, and the storage stability and handleability of the curable resin composition can be improved.

[Dehydrating agent]
The curable resin composition preferably further contains a dehydrating agent, which can prevent the curable resin composition from being cured by moisture contained in the air or the like during storage.

Examples of dehydrating agents include silane compounds such as vinyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, phenyltrimethoxysilane, and diphenyldimethoxysilane; and ester compounds such as methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate. These dehydrating agents may be used alone or in combination. Of these, vinyltrimethoxysilane is preferred.

The content of the dehydrating agent in the curable resin composition is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the curable resin. The content of the dehydrating agent in the curable resin composition is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the curable resin. When the content of the dehydrating agent in the curable resin composition is 0.5 parts by mass or more, the effects obtained by the dehydrating agent are fully obtained. Furthermore, when the content of the dehydrating agent in the curable resin composition is 20 parts by mass or less, the curable resin composition has excellent curability.

[Other additives]
The curable resin composition may contain other additives such as a thixotropic agent, an antioxidant, an ultraviolet absorber, a pigment, a dye, an anti-settling agent, an aminosilane coupling agent, a thixotropic agent, a plasticizer, and a solvent, within the range that does not impair the physical properties of the curable resin composition. Among these, the thixotropic agent, the ultraviolet absorber, and the antioxidant are preferred.

The curable resin composition preferably contains an aminosilane coupling agent. Use of an aminosilane coupling agent can improve the rubber elasticity and adhesiveness of the cured product of the curable resin composition. An aminosilane coupling agent refers to a compound that contains, in one molecule, a silicon atom to which an alkoxy group is bonded and a functional group containing a nitrogen atom.

Specific examples of aminosilane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N'-bis-[3-(trimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(triethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(methyldimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(trimethoxysilyl)propyl]hexamethylenediamine, and N,N'-bis-[3-(triethoxysilyl)propyl]hexamethylenediamine. These aminosilane coupling agents may be used alone or in combination.

Among these, preferred aminosilane coupling agents include 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltriethoxysilane, with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane being more preferred.

The content of the aminosilane coupling agent in the curable resin composition is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the curable resin. When the content of the aminosilane coupling agent is within the above range, the rubber elasticity and adhesiveness of the cured product of the curable resin composition can be improved.

The thixotropic agent may be any agent capable of imparting thixotropy to the curable resin composition. Preferred examples of thixotropic agents include hydrogenated castor oil, fatty acid bisamide, and fumed silica.

The content of the thixotropy-imparting agent in the curable resin composition is preferably 0.1 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the curable resin. The content of the thixotropy-imparting agent in the curable resin composition is preferably 200 parts by mass or less, and more preferably 150 parts by mass or less, per 100 parts by mass of the curable resin. When the content of the thixotropy-imparting agent in the curable resin composition is 0.1 parts by mass or more, thixotropy can be effectively imparted to the curable resin composition. Furthermore, when the content of the thixotropy-imparting agent in the curable resin composition is 200 parts by mass or less, the curable resin composition has an appropriate viscosity, improving the handleability of the curable resin composition.

Examples of UV absorbers include benzotriazole-based UV absorbers and benzophenone-based UV absorbers, with benzotriazole-based UV absorbers being preferred. The content of the UV absorber in the curable resin composition is preferably 0.1 parts by mass or more per 100 parts by mass of the curable resin. The content of the UV absorber in the curable resin composition is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the curable resin.

Examples of antioxidants include hindered phenol antioxidants, monophenol antioxidants, bisphenol antioxidants, and polyphenol antioxidants, with hindered phenol antioxidants being preferred. The content of the antioxidant in the curable resin composition is preferably 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more, per 100 parts by mass of curable resin. The content of the antioxidant in the curable resin composition is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of curable resin.

[Light stabilizer]
The curable resin composition preferably contains a hindered amine light stabilizer, which can provide a curable resin composition that can maintain excellent rubber elasticity for a longer period of time after curing.

Examples of hindered amine light stabilizers include a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, dibutylamine/1,3,5-triazine/N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine) and N-(2,2,6,6- Examples include polycondensates of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], and polycondensates of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol.

Preferred examples of hindered amine light stabilizers include NOR-type hindered amine light stabilizers. NOR-type hindered amine light stabilizers can provide a curable resin composition that inhibits deterioration in rubber elasticity over time after curing.

NOR-type hindered amine light stabilizers have an NOR structure in which an alkyl group (R) is bonded to a nitrogen atom (N) contained in a piperidine ring skeleton via an oxygen atom (O). The alkyl group in the NOR structure preferably has 1 to 20 carbon atoms, more preferably 1 to 18, and particularly preferably 18. Examples of the alkyl group include linear alkyl groups, branched alkyl groups, and cyclic alkyl groups (saturated alicyclic hydrocarbon groups).

Examples of linear alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, and n-decyl groups. Examples of branched alkyl groups include isopropyl, isobutyl, sec-butyl, and tert-butyl. Examples of cyclic alkyl groups (saturated alicyclic hydrocarbon groups) include cyclopentyl, cyclohexyl, and cyclooctyl groups. Furthermore, the hydrogen atoms constituting the alkyl group may be substituted with halogen atoms (e.g., fluorine, chlorine, and bromine atoms) or hydroxyl groups.

NOR-type hindered amine light stabilizers include those represented by the following formula (I):

When using a NOR-type hindered amine light stabilizer, it is preferable to use it in combination with a benzotriazole-based UV absorber or a triazine-based UV absorber. This makes it possible to provide a curable resin composition in which the decrease in rubber elasticity over time after curing is more significantly suppressed.

The content of the hindered amine light stabilizer in the curable resin composition is preferably 0.01 parts by mass or more, and more preferably 0.1 parts by mass or more, per 100 parts by mass of the curable resin. The content of the hindered amine light stabilizer in the curable resin composition is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the curable resin.

[Curable resin composition]
The curable resin composition can be produced by mixing a curable resin, feldspar, a non-ferrous metal hydroxide, and a phosphate ester with additives added as needed. The curable resin composition may be in the form of a suspension or emulsion by being suspended or emulsified in an aqueous solvent. The curable resin composition may also be in the form of a solution by being dissolved in a solvent. Examples of aqueous solvents include water, alcohols such as ethyl alcohol, methyl alcohol, and isopropyl alcohol. Examples of solvents include xylene, toluene, and acetone.

By using a combination of feldspars, non-ferrous metal hydroxides, and phosphate esters, the curable resin composition exhibits excellent flame retardancy in its cured form. Furthermore, because the viscosity of the curable resin composition is kept low, it has excellent coatability and can be applied precisely to desired locations on the substrate. This is particularly true for precise application to the narrow, specified coating locations on electronic materials, which are becoming increasingly miniaturized.

As a result, the curable resin composition can be applied with high precision to predetermined locations on the substrate without affecting the performance of the substrate, particularly electronic materials. The curable resin composition can impart or improve excellent flame retardancy to the substrate, particularly electronic materials and/or electronic devices containing electronic materials.

Furthermore, by adjusting the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate ester (total content of feldspars and non-ferrous metal hydroxides / content of phosphate ester) in the curable resin composition to a specified range, the cured product of the curable resin composition will have excellent film strength (impact resistance). By applying the curable resin composition to a substrate that requires impact resistance, a cured product of the curable resin composition with excellent impact resistance can be formed on the surface of the substrate. Even when an impact force is applied to the substrate, the cured product of the curable resin composition will not suffer damage such as cracks, and the excellent flame retardancy imparted to the substrate can be stably maintained.

The substrate to be coated is not particularly limited, but examples include electronic devices, electronic materials, and storage containers (synthetic resin containers, metal containers, etc.).

Electronic devices include, but are not limited to, car navigation systems, mobile phones, smartphones, game consoles, digital cameras, televisions, DVD players, electronic dictionaries, calculators, hard disk recorders, personal computers, video cameras, printers, liquid crystal displays, plasma displays, radios, and electronic musical instruments.

As electronic devices become smaller and lighter, the electronic materials that make up these devices are also becoming smaller. Examples of such electronic materials include, but are not limited to, printed wiring boards, light-emitting diodes (LEDs), light-emitting diode mounting boards, flexible copper-clad laminates, bonding sheets, touch panels, and sensor substrates.

Storage containers include, but are not limited to, containers for flammable liquids (e.g., organic solvents, organic compounds, gasoline, diesel, kerosene, etc.).

The method for applying the curable resin composition to the desired coating location on the substrate is not particularly limited, and examples include application methods using a brush and application methods using known application equipment.

The viscosity of the curable resin composition is preferably 500 mPa·s or more, more preferably 1000 mPa·s or more, and even more preferably 3000 mPa·s or more. The viscosity of the curable resin composition is preferably 200,000 mPa·s or less, more preferably 100,000 mPa·s or less, and even more preferably 50,000 mPa·s or less. The viscosity of the curable resin composition is measured using a BH-type viscometer under conditions of 23°C, 10 rpm, and rotor No. 5.

The curable resin composition applied to the substrate is cured to produce a cured product. The curable resin can be cured using known methods (e.g., supplying moisture, irradiating with ultraviolet light or other light, heating, etc.) depending on the type of curable resin.

The cured product of the curable resin composition generates a strong combustion residue when burned by the heat of a fire. This combustion residue remains stably disposed at the coated area even in the event of a fire, demonstrating excellent flame retardancy.

The curable resin composition of the present invention has excellent coatability due to its low viscosity, and can be applied accurately and easily to desired locations on substrates, particularly electronic materials, without impairing the functionality of the substrate.

The cured product produced by curing the curable resin composition has excellent flame retardancy, and can impart or improve the flame retardancy of the coated object, particularly electronic materials and/or electronic devices made from electronic materials.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these.

The following raw materials were used in producing the curable resin compositions of the Examples and Comparative Examples.

[Curable resin]
Polyalkylene oxide having a hydrolyzable silyl group (polyalkylene oxide having a main chain skeleton made of polypropylene oxide and a dimethoxysilyl group at the end of the main chain, number average molecular weight: 38,000, manufactured by Kaneka Corporation, trade name "Excestar S303H")

[Feldspars]
Feldspar (Nepheline syenite, average particle size: 5 μm, manufactured by Shiraishi Calcium Co., Ltd., product name "Nespar")

[Non-ferrous metal hydroxides]
Aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., product name "BF013", average particle size: 1 μm)
Magnesium hydroxide (manufactured by Konoshima Chemical Co., Ltd., product name "Magseeds S", average particle size: 1 μm)

[Phosphate ester]
Tricresyl phosphate (monophosphate ester, trade name "TCP" manufactured by Daihachi Chemical Industry Co., Ltd., viscosity: 58 mPa s)
Cresyl di-2,6-xylenyl phosphate (monophosphate ester, manufactured by Daihachi Chemical Industry Co., Ltd., trade name "PX-110", viscosity: 1200 mPa s)
Tris(chloropropyl)phosphate (monophosphate ester, manufactured by Daihachi Chemical Industry Co., Ltd., trade name "TMCPP", viscosity: 69 mPa s)
Resorcinol polyphenyl phosphate (condensed phosphate ester, manufactured by Daihachi Chemical Industry Co., Ltd., trade name "CR-733S", viscosity: 800 mPa s)
Bisphenol A bisdiphenyl phosphate (condensed phosphate ester, manufactured by Daihachi Chemical Industry Co., Ltd., trade name "CR-741", viscosity: 2300 mPa s)

[Glass frit]
Glass frit (phosphate-based glass, "VY0144" manufactured by Nippon Frit Co. _, Ltd., main components: _P2O5 , _AI2O3 , and _R2O , _where R is an alkali metal atom, softening point: 404°C)

[Other additives]
Polypropylene glycol (plasticizer, manufactured by AGC, product name "Exenol 3020")
Silanol condensation catalyst (dibutyltin diacetylacetonate, manufactured by Nitto Kasei Co., Ltd., trade name "U220H")
Dehydrating agent (vinyltrimethoxysilane, product name "KBM1003" manufactured by Shin-Etsu Chemical Co., Ltd.)
Aminosilane coupling agent (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, product name KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.)

(Examples 1 to 11, Comparative Examples 1 to 3)
The curable resin, feldspar, non-ferrous metal hydroxide, phosphate ester, glass frit, polypropylene glycol, silanol condensation catalyst, dehydrating agent, and aminosilane coupling agent were mixed in the amounts shown in Table 1 using a planetary mixer under a vacuum atmosphere for 60 minutes until uniform, thereby obtaining a curable resin composition.

The flame retardancy, post-combustion hardness, coatability, and viscosity of the resulting curable resin composition were measured as follows, and the results are shown in Table 1.

The film strength of the resulting curable resin composition was measured as follows, and the results are shown in Table 1.

(Flame retardant)
A test sheet with a thickness of 1.5 mm was prepared using the curable resin composition and aged for 7 days at 23° C. The test sheet was cut into a flat rectangular shape measuring 15 mm long x 130 mm wide x 1.5 mm thick to prepare five test pieces.

The test was conducted based on the UL94V-0 standard. Specifically, one horizontal end of the test specimen was held using a clamp and the test specimen was hung vertically. Next, a flame was applied to the other horizontal end (bottom end) of the vertically hung test specimen using a burner for 3 seconds, and after the burner was temporarily removed from the test specimen, the other horizontal end of the test specimen was again applied to the same flame for 3 seconds using the burner to measure flame retardancy. Evaluation was based on the following criteria.
A: For each test specimen, the afterflame time after two flame contacts was within 10 seconds, and the total afterflame time for the five test specimens was within 50 seconds. Furthermore, no test specimen continued to glow for 30 seconds or more after the second flame contact.
B: For each test specimen, the afterflame time after two flame contacts was within 10 seconds, and the total afterflame time for five test specimens exceeded 50 seconds. Furthermore, no test specimen continued to glow for 30 seconds or more after the second flame contact.
C: For each test specimen, the afterflame time after two flame contacts was within 10 seconds, and the total afterflame time for five test specimens exceeded 50 seconds. Furthermore, there was a test specimen that continued to glow for 30 seconds or more after the second flame contact.
D: All test pieces were burned down to the clamp, and none of A to C was applicable.

(Hardness after combustion)
The curable resin composition was cured for one week in an atmosphere of 23°C and 50% relative humidity to produce a cured product. 100 g of the cured product of the curable composition was prepared as a test piece. The test piece was placed in a combustion furnace. The test piece was burned in the combustion furnace at 600°C for 30 minutes. Immediately after the end of combustion, the combustion residue obtained by burning the test piece was left in an atmosphere of 23°C for one hour. Next, the rubber elasticity of the combustion residue was measured using a type A durometer at a measurement temperature of 23°C in accordance with JIS K6253 using Shore A. Evaluation was performed based on the following criteria.
A: The rubber hardness was 30 or more.
B: The rubber hardness was 20 or more and less than 30.
C: The rubber hardness was 10 or more and less than 20.
D: The rubber hardness was less than 10 or was too brittle to be measured with an A-type durometer.

(Coatability)
The curable resin composition was filled into a volumetric syringe and attached to an air-operated dispenser (Performus X100, manufactured by Nordson Corporation), and the coatability was measured. Substrates on which coating grooves with widths of 0.5 mm, 1.0 mm, and 2.0 mm were formed were prepared. The coating grooves with widths of 0.5 mm, 1.0 mm, and 2.0 mm were referred to as "coating grooves 1 to 3," respectively.

The curable resin composition was applied to each of the coating grooves having widths of 0.5 mm, 1.0 mm, and 2.0 mm by operating an air dispenser at 23°C and an air pressure of 0.6 MPa. Evaluation was performed based on the following criteria.
A: All coating grooves 1 to 3 were coated cleanly. B: Coating grooves 2 and 3 were coated cleanly, but coating groove 1 was not coated cleanly.
C: Coating groove 3 was coated cleanly, but coating grooves 1 and 2 were not coated cleanly.
D: None of coating grooves 1 to 3 could be coated cleanly.

(viscosity)
The viscosity of the curable resin composition was measured using a BH type viscometer under conditions of 23°C, 10 rpm, and rotor No. 5.

(film strength)
The curable resin composition was applied to a thickness of 3 mm on the release-treated surface of the release-treated substrate, and then the curable composition was aged for 1 month in an environment of 23°C and a relative humidity of 50%. The cured product of the curable resin composition was peeled off from the substrate.

The cured product of the curable composition was cut into No. 3 dumbbell specimens in accordance with JIS K6251. Tensile tests were conducted using the resulting specimens at a tensile speed of 200 mm/min. In the tensile test, the strength at the point when the specimen broke was measured, and this strength was taken as the coating strength.

Claims (4)

A curable resin composition comprising a curable resin, feldspar, a non-ferrous metal hydroxide, and a phosphate ester. The curable resin composition according to claim 1, characterized in that the curable resin composition contains a polyalkylene oxide having a hydrolyzable silyl group. The curable resin composition according to claim 1 or 2, characterized in that the non-ferrous metal hydroxide contains aluminum hydroxide. The curable resin composition according to claim 1 or 2, characterized in that the mass ratio of the total content of feldspars and non-ferrous metal hydroxides to the content of phosphate ester (total content of feldspars and non-ferrous metal hydroxides / content of phosphate ester) is 2.0 or greater.