Core resin composition and core

Abstract

The present invention provides a core resin composition that exhibits high heat resistance and enables the production of cores that do not deform even under the molding conditions of super engineering plastics. It also provides a core made using the core resin composition. The present invention relates to a core resin composition containing a polyvinyl alcohol resin, which contains a particulate filler, and the total surface area A per unit mass of the core resin composition of the particulate filler represented by the following formula (1) is 10 m 2 / g or more. A: Total surface area of ​​particle filler per unit mass of core resin composition (m 2 / g) B: Average particle size of particle filler (m) D: Content of particle filler in resin composition for core (% by mass) E: Density of particle filler (g / m 3 ) [Number 1] JPEG0007797751000007.jpg14156

Description

[Technical Field]

[0001] The present invention relates to a resin composition for a core and a core. [Background technology]

[0002] Conventionally, in order to obtain molded articles with complex internal structures by injection molding, the use of cores made of water-soluble resin compositions has been considered. For example, a core having a shape corresponding to the complex internal structure is placed inside a mold and injection molded. Then, by removing the core from the obtained molded article, a molded article with a complex internal structure can be obtained. From the viewpoint of reducing environmental impact, the use of water-soluble resins as resins for the cores has been considered. For example, Patent Document 1 discloses a core resin containing a polyvinyl alcohol resin and an easy-release agent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 157375 Summary of the Invention [Problem to be solved by the invention]

[0004] Furthermore, in recent years, from the viewpoint of weight reduction, studies have been conducted to replace the materials of parts of automobiles and the like with super engineering plastics (super engineering plastics) that have excellent heat resistance. As a result of extensive research, the inventors of the present invention have discovered that, because the molding temperature of super engineering plastics is higher than that of general-purpose thermoplastic resins, when a core resin such as that described in Patent Document 1 is used, the core resin will deform during molding. If the core resin deforms during molding, it becomes a problem that a molded body having the desired shape cannot be obtained.

[0005] An object of the present invention is to provide a core resin composition that exhibits high heat resistance and enables the production of cores that do not deform even under the molding conditions of super engineering plastics, and to provide a core made using the core resin composition. [Means for solving the problem]

[0006] The present disclosure (1) provides a core resin composition containing a polyvinyl alcohol resin, which contains a particulate filler, and the total surface area A per unit mass of the core resin composition of the particulate filler represented by the following formula (1) is 10 m 2 / g or more.

number

[0007] The inventors investigated the addition of a particulate filler to a resin composition for a core and discovered that by combining a polyvinyl alcohol resin with a particulate filler and setting the total surface area of ​​the particulate filler within a predetermined range, high heat resistance could be achieved, leading to the completion of the present invention.

[0008] <Polyvinyl alcohol resin> The core resin composition contains a polyvinyl alcohol resin. By using a polyvinyl alcohol resin, it can be easily removed from the molded body by, for example, immersing it in water.

[0009] The degree of polymerization of the polyvinyl alcohol resin is preferably not more than 4000. When the degree of polymerization is not more than 4000, the resin can exhibit sufficient solubility in water. The degree of polymerization is more preferably 180 or more, further preferably 200 or more, even more preferably 220 or more, and is preferably 3400 or less, more preferably 2300 or less, further preferably 1200 or less, even more preferably 900 or less. The degree of polymerization can be determined, for example, by measuring polyvinyl acetate before saponification by gel permeation chromatography (GPC) or by measuring the viscosity of an aqueous solution in accordance with JIS K6726.

[0010] The saponification degree of the polyvinyl alcohol resin is preferably 72 mol % or more and 99.8 mol % or less. By setting the content within the above range, the solubility in water can be sufficiently exhibited. The saponification degree is more preferably 80 mol% or more, even more preferably 87 mol% or more, even more preferably 92 mol% or more, particularly preferably 95 mol% or more, more preferably 99.5 mol% or less, even more preferably 99 mol% or less. The saponification degree can be measured, for example, by a method in accordance with JIS K 6726. The saponification degree indicates the proportion of units that are actually converted into vinyl alcohol units among vinyl ester units that can be converted into vinyl alcohol units by saponification. The degree of saponification can be controlled, for example, by adjusting the saponification conditions, that is, the hydrolysis conditions.

[0011] The weight average molecular weight (Mw) of the polyvinyl alcohol resin is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 14,000 or more, especially more preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, especially preferably 40,000 or less, especially more preferably 32,000 or less, and most preferably 24,000 or less. When two or more polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) of the entire polyvinyl alcohol resin is calculated based on the weight average molecular weight of each resin and its weight fraction, and is obtained by summing the values ​​obtained by multiplying the weight average molecular weight of each polyvinyl alcohol resin by its weight fraction. When two or more polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 14,000 or more, particularly more preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 40,000 or less, particularly more preferably 32,000 or less, and most preferably 24,000 or less.

[0012] The number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 4,000 or more, more preferably 4,500 or more, and even more preferably 5,000 or more, and is preferably 90,000 or less, more preferably 60,000 or less, and even more preferably 30,000 or less.

[0013] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 1.0 or more, more preferably 1.2 or more, even more preferably 1.4 or more, even more preferably 1.6 or more, and is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.5 or less, even more preferably 2.0 or less. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) can be determined, for example, by gel permeation chromatography (GPC), by measuring polyvinyl ester before saponification by GPC, by measuring polyvinyl ester obtained by re-esterifying polyvinyl alcohol resin by GPC, or by measuring the viscosity of an aqueous solution in accordance with JIS K 6726. For example, columns such as TSKgel (Tosoh Corporation), PLgel (AMR Corporation), KF-806, KF-807 (Shodex Corporation) and the like can be used using polystyrene as a standard.

[0014] The polyvinyl alcohol resin preferably has a viscosity of 30 mPa s or less in a 4% by mass aqueous solution, which provides fluidity suitable for injection molding and water solubility suitable for use as a core. The viscosity of the 4 mass % aqueous solution is preferably 3 mPa·s or more, more preferably 5 mPa·s or more, and is preferably 20 mPa·s or less, more preferably 10 mPa·s or less. The viscosity of the 4% by mass aqueous solution can be measured, for example, by a method in accordance with JIS K 6276 3.11.1 rotational viscometer method.

[0015] The polyvinyl alcohol resin may be an unmodified polyvinyl alcohol resin or a modified polyvinyl alcohol resin, where the modified polyvinyl alcohol resin refers to a polyvinyl alcohol resin having structural units other than vinyl ester units and vinyl alcohol units. Examples of the modified polyvinyl alcohol resin include those modified with a hydrophilic modifying group such as a sulfonic acid group, a pyrrolidone ring group, an amino group, a carboxyl group, etc. These hydrophilic groups include not only the functional groups but also their salts such as sodium salts and potassium salts.

[0016] The content of structural units having a modifying group in the polyvinyl alcohol resin is preferably 1 mol% or more, more preferably 3 mol% or more, and particularly preferably 5 mol% or more, and is preferably 20 mol% or less, more preferably 15 mol% or less, and particularly preferably 12 mol% or less.

[0017] The content of the polyvinyl alcohol resin in the core resin composition is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 65% ​​by mass or more, and is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. The polyvinyl alcohol resin may contain multiple types of polyvinyl alcohol resins with different degrees of polymerization, saponification, etc. When the polyvinyl alcohol resin contains multiple types of polyvinyl alcohol resins, the content of the polyvinyl alcohol resins represents the total content of the multiple types of polyvinyl alcohol resins.

[0018] The polyvinyl alcohol resin can be obtained by polymerizing a vinyl ester to obtain a polymer, and then saponifying the polymer, i.e., by hydrolysis, in accordance with a conventionally known method. An alkali or an acid is generally used as a saponification catalyst.

[0019] Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, and vinyl benzoate.

[0020] The method for polymerizing the vinyl ester is not particularly limited, but examples thereof include solution polymerization, bulk polymerization, and suspension polymerization.

[0021] Examples of polymerization catalysts used in polymerizing the vinyl ester include 2-ethylhexyl peroxydicarbonate (TrigonoxEHP manufactured by Tianjin McEIT Co., Ltd.), 2,2'-azobisisobutyronitrile (AIBN), t-butyl peroxyneodecanoate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di-cetyl peroxydicarbonate, and di-s-butyl peroxydicarbonate. One type of the polymerization catalyst may be used alone, or two or more types may be used in combination.

[0022] The polyvinyl alcohol resin may be a saponified polymer of a vinyl ester and another unsaturated monomer. The other unsaturated monomers include monomers other than the vinyl esters and having an unsaturated double bond such as a vinyl group. Specific examples include olefins, (meth)acrylic acid and its salts, (meth)acrylic acid esters, unsaturated acids other than (meth)acrylic acid, their salts and esters, (meth)acrylamides, N-vinylamides, vinyl ethers, nitriles, vinyl halides, allyl compounds, vinylsilyl compounds, isopropenyl acetate, sulfonic acid group-containing compounds, and amino group-containing compounds.

[0023] Examples of olefins include ethylene, propylene, 1-butene, and isobutene. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of unsaturated acids other than (meth)acrylic acid, and salts and esters thereof include maleic acid and salts thereof, maleic acid esters, itaconic acid and salts thereof, itaconic acid esters, methylenemalonic acid and salts thereof, and methylenemalonic acid esters. Examples of (meth)acrylamides include acrylamide, n-methylacrylamide, N-ethylacrylamide, and N,N-dimethylacrylamide. Examples of N-vinylamides include N-vinylpyrrolidone. Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether. Examples of nitriles include (meth)acrylonitrile. Examples of vinyl halides include vinyl chloride and vinylidene chloride. The allyl compounds include allyl acetate and allyl chloride. Examples of the vinylsilyl compound include vinyltrimethoxysilane. Examples of sulfonic acid group-containing compounds include (meth)acrylamidoalkanesulfonic acids such as (meth)acrylamidopropanesulfonic acid and salts thereof, and olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid and salts thereof. Examples of the amino group-containing compound include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0024] <Particle filler> The core resin composition contains a particulate filler. By including a particulate filler, heat resistance can be improved.

[0025] In the core resin composition, the total surface area of ​​the particle filler per unit mass of the core resin composition calculated by the following formula (1) is 10 m 2 / g or more.

number

number

[0026] The total surface area of ​​the particulate filler per unit mass can be adjusted by the average particle size of the filler, the density of the filler, and the amount of the filler blended. The surface area of ​​the particulate filler is calculated from the average particle size, density, and blending amount of the primary particles, but the particle shape is not necessarily limited to spherical. Other than spherical shapes, for example, plate-like, needle-like, rugby-like, hollow, porous, etc. are possible, and the particulate filler may have a higher-order structure in which multiple such shapes are connected or overlapped.

[0027] The average particle size of the particulate filler is preferably 1 nm or more and 100 nm or less. By setting the average particle size within this range, the surface area of ​​the filler in the resin composition for a core can be kept within a certain range, and the resin composition can be provided with the necessary heat resistance. The average particle size is preferably 2 nm or more, more preferably 3 nm or more, even more preferably 4 nm or more, more preferably 70 nm or less, even more preferably 50 nm or less, and even more preferably 30 nm or less. Furthermore, the average particle size is particularly preferably 5 nm or more, and particularly preferably 29 nm or less. By setting the average particle size within the above range, the particulate filler and the polyvinyl alcohol resin can be easily kneaded and mixed. The average particle size of the particulate filler can be measured, for example, by a particle size distribution measuring device.

[0028] The density of the particle filler is 0.5 g / cm 3 More than 0.7g / cm is preferable. 3 More preferably, 0.9 g / cm 3 More preferably, 1.1 g / cm 3 More than 22 g / cm is particularly preferred. 3 Less than 13 g / cm is preferred 3 Less than 6g / cm is more preferable. 3 More preferably, 4.5 g / cm 3 The following are particularly preferred: The density can be measured, for example, by an electronic densitometer, etc. Regarding the density of the particulate filler, even when the particulate filler is a hollow particle or a porous particle, the particle density is adopted taking into consideration the volume including the cavities and pores inside the particle.

[0029] Examples of materials for the particulate filler include metals, metal oxides, ceramics, carbon materials, glass, etc. Furthermore, resin particles having a melting point of 200° C. or higher can also be used as the particulate filler. Examples of the metal oxide include titanium oxide, aluminum oxide, calcium oxide, lithium oxide, molybdenum oxide, vanadium oxide, zinc oxide, nickel oxide, cesium oxide, iron oxide, etc. Other examples include diamond, boron nitride, aluminum nitride, gold, silver, copper, platinum, palladium, silicon carbide, etc. Examples of the carbon material include carbon black, graphite, and diamond. Among these, titanium oxide and carbon black are preferred from the viewpoints of cost performance, availability, etc. Examples of the resin having a melting point of 200° C. or higher include polyethylene terephthalate, polyamide, aromatic polyamide (aramid), polyimide, polyether ether ketone (PEEK), and the like. As the material for the particulate filler, a particulate filler having high hydrophilicity is preferred from the viewpoint of water solubility, and among these, metal oxides are more preferred, with titanium oxide being even more preferred.

[0030] The content of the particulate filler in the core resin composition is preferably 5% by mass or more and 70% by mass or less. By setting the content within this range, heat resistance can be improved. The content of the particulate filler is more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 19% by mass or more, more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less.

[0031] In the core resin composition, the total surface area of ​​the particulate filler per 1 g of the polyvinyl alcohol resin is set to 10.5 m from the viewpoint of heat resistance. 2 / g or more is preferable, and 16.5m 2 / g or more is more preferable, and 23.5m 2 / g or more is more preferable, and 29m 2From the viewpoint of heat resistance, it is not necessary to determine a preferable upper limit, but when molding into a core, a certain level of fluidity and plastic deformability is required, so the total surface area of ​​the particulate filler per 1 g of the polyvinyl alcohol resin is preferably 200 m 2 / g or less, and 150m 2 / g or less is more preferable, and 100m 2 However, as long as the particle filler has sufficient deformability to be molded into a core, the upper limit of the total surface area of ​​the particle filler is not limited to this.

[0032] <Easy-to-peel agent> The core resin composition may contain an easy-release agent. By including the easy-release agent, the core resin can be more easily removed from the molded body.

[0033] As the easy-peeling agent, for example, a glycerin fatty acid ester compound can be used. Examples of the glycerin fatty acid ester compounds include monoglyceride stearic acid ester, monoglyceride oleic acid ester, and diglyceride lauric acid ester.

[0034] The content of the easy-release agent in the core resin composition is preferably 0.1% by mass or more and 2% by mass or less. By setting the content within this range, the surface smoothness of the inside of the obtained molded product can be sufficiently improved. The content of the easy-release agent is more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, more preferably 1.6% by mass or less, even more preferably 1.1% by mass or less.

[0035] <Plasticizer> The core resin composition may contain a plasticizer. By including a plasticizer, moldability can be improved.

[0036] The plasticizer may be, for example, a polyhydric alcohol. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, polyethylene glycol, polypropylene glycol, erythritol, xylitol, sorbitol, and mannitol.

[0037] The content of the plasticizer in the core resin composition is preferably 0.1% by mass or more and 10% by mass or less. By setting the content within this range, good extrusion and injection moldability and good water solubility can be achieved. The content of the plasticizer is more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and more preferably 7% by mass or less, even more preferably 5% by mass or less.

[0038] <Crosslinking agent> The core resin composition may contain a crosslinking agent. Examples of the crosslinking agent include oxoacids, boron compounds, divalent or higher metal hydroxides, diamines, polyamines, etc. Metal salts of the above acids may also be used.

[0039] Examples of the oxoacid include boric acid, silicic acid, phosphorous acid, polycarboxylic acid, and hydroxycarboxylic acid. The polycarboxylic acid is preferably an acid having two or more carboxyl groups, and the hydroxycarboxylic acid is preferably an acid having two or more carboxyl groups. Metal salts of the above acids are also acceptable. Among the above oxoacids, boric acid is particularly preferred. The use of boric acid makes it possible to obtain a core resin composition that has sufficient water resistance during processing and can be easily removed with warm water when removal becomes necessary. Examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid. In addition to the boric acid exemplified as the oxoacid, examples of the boron compound include salts of boric acid. The boron compound may also be a hydrate. Examples of the salts of boric acid include borax, alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as calcium salts and magnesium salts, aluminum salts, and organic amine salts such as triethylamine, triethanolamine, morpholine, piperazine, and pyrrolidine. Among these, boric acid and borax are preferred.

[0040] Examples of the polycarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, poly(meth)acrylic acid, etc. Of these, succinic acid is preferred. Examples of the hydroxycarboxylic acid include glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, cytosine acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineraidic acid, cerebronic acid, quinic acid, shikimic acid, hydroxybenzoic acid, salicylic acid, creosote acid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orsellinic acid, gallic acid, mandelic acid, benzilic acid, atrolactic acid, mellotic acid, phloretic acid, coumaric acid, umbellic acid, caffeic acid, ferulic acid, sinapic acid, and hydroxystearic acid. Of these, malic acid and citric acid are preferred. Examples of the divalent or higher metal hydroxides include calcium hydroxide, magnesium hydroxide, barium hydroxide, aluminum hydroxide, iron hydroxide, zinc hydroxide, manganese hydroxide, and copper hydroxide. The above crosslinking agents may be used alone or in combination of two or more. Among these, the crosslinking agent preferably contains any one of a divalent or higher metal hydroxide, a boron compound, or an acid having two or more carboxyl groups, and more preferably any one of a divalent or higher metal hydroxide, boric acid, or an acid having two or more carboxyl groups. Furthermore, the crosslinking agent is more preferably a divalent or higher metal hydroxide, a boron compound, or an acid having two or more carboxyl groups, and even more preferably a divalent or higher metal hydroxide, boric acid, or an acid having two or more carboxyl groups.

[0041] <Other> The core resin composition may also contain other additives such as antioxidants, colorants, antifoaming agents, ultraviolet absorbers, and preservatives.

[0042] As the antioxidant, known antioxidants can be used, such as phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, sulfur-containing antioxidants, etc. Also, antioxidants having both a phenolic functional group and a phosphorus-based functional group in one molecule can be used.

[0043] Examples of the phenol-based antioxidant include acrylate compounds such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate and 2,4-di-t-amyl-6-(1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)phenyl acrylate, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2 '-Methylene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(6-t-butyl-m-cresol), 4,4'-thiobis(3-methyl-6-t-butylphenol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)methane, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxo Alkyl-substituted phenolic compounds such as saspiro[5,5]undecane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane, or triethylene glycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate), 6-(4-hydroxyphenyl)-2-methyl-2-propanol, and triazine group-containing phenolic compounds such as 6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3,5-dimethylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3-methyl-5-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine, and 2-octylthio-4,6-bis-(3,5-di-t-butyl-4-oxyanilino)-1,3,5-triazine.

[0044] Examples of the phosphorus-based antioxidant include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2-t-butyl-4-methylphenyl) phosphite, tris(cyclohexylphenyl) phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, or monophosphite compounds such as 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene; and diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12 to C15) phosphite) 4,4'-isopropylidene-bis(diphenyl monoalkyl(C12 to C15) phosphite), 1,1,3-tris(2-methyl-4-di-tridecyl phosphite-5-t-butylphenyl)butane, or tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphite.

[0045] The antioxidant having both a phenolic functional group and a phosphorus functional group in one molecule is not particularly limited, but examples thereof include phosphite compounds having a phenol skeleton. Specifically, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]dioxaphosphepine, 2,10-dimethyl-4,8-di-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphene, 2,4,8,10-tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]dibenzo[d,f][1,3,2]dioxaphosphene, 2,4,8,10-tetra-t-pentyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphene, )propoxy]-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,10-dimethyl-4,8-di-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,4,8,10-tetra-t-pentyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-dibenzo[d,f][1,3, 2]dioxaphosphepin, 2,10-dimethyl-4,8-di-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyloxy)-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyloxy)-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,10-dimethyl-4,8-di-t-butyl-6[3-(3-methyl-4-hydroxy-5-t-butylphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,10-di-t-pentyl-4,Examples include 8-di-t-butyl-6[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphocin and 2,4,8,10-tetra-t-butyl-6-[2,2-dimethyl-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-dibenzo[d,f][1,3,2]dioxaphosphepine.

[0046] The content of the antioxidant in the core resin composition is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and even more preferably 0.7% by mass or more, and is preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.2% by mass or less.

[0047] The core resin composition preferably has a melt flow rate (MFR) of 35 g / 10 min or less at 230°C under a load of 10 kg. By setting the MFR within this range, the resin composition exhibits high heat resistance, making it possible to produce a core that does not deform even under high-temperature conditions such as those used to mold super engineering plastics. The MFR is preferably 25 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. The lower limit of the MFR is not particularly limited, but it is sufficient if the molding can be performed using a molding machine for molding the core, and depends on the capacity of the molding machine. The MFR can be measured, for example, by a method in accordance with ASTM D 1238 under conditions such as an initial weight of 7.5 g and a measurement time interval of 0.25 minutes.

[0048] The melt flow rate (MFR) under the above conditions of 230°C and 10 kg load can be adjusted by the composition and amount of polyvinyl alcohol resin, the type and amount of particulate filler, the average particle diameter, the total surface area, fillers of various other shapes, crosslinkers, plasticizers, mold release agents, etc. Fillers of various other shapes include plate-like, needle-like, rugby-like, fibrous, and higher-order structures in which primary particles are linked (for example, chain-like, agyuroramate-like, layer-like), etc.

[0049] The core resin composition can be obtained by mixing, for example, a polyvinyl alcohol resin, a particulate filler, and other additives that are added as needed, such as a release agent, a plasticizer, and an antioxidant. The method for mixing the above components is not particularly limited, and examples thereof include a method of mixing using a known kneading device, a method using an extrusion molding machine, etc. Alternatively, a method of mixing in the cylinder of an injection molding machine may be used.

[0050] The form of the core resin composition is not particularly limited, and may be, for example, pellets, powder, or the like.

[0051] A core can be produced by molding the core resin composition. A core made using the above-mentioned core resin composition also constitutes one aspect of the present invention. The molding method is not particularly limited, but examples thereof include injection molding.

[0052] The core can be used to produce a molded body. There are no particular restrictions on the material that is molded together with the core to form the composite, but because the resin composition for the core has particularly excellent heat resistance, it is possible to prevent melting and deformation even when using super engineering plastics that are molded at high temperatures as the material.

[0053] Examples of the super engineering plastics include highly heat-resistant plastics such as fluororesins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polyphenylsulfone (PPSU), polysulfone (PSF), polyethersulfone (PES), polyarylate (PAR), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE). By using the above super engineering plastic, a molded article having excellent heat resistance, durability, and mechanical strength can be obtained.

[0054] By removing the core from the composite, a molded body having a hollow portion can be obtained. The core can be removed, for example, by immersing the composite in water or warm water.

[0055] The shape of the molded article may be a straight shape, or may be various shapes such as an L-shape, an S-shape, a T-shape, etc. For example, an L-shaped or S-shaped molded article can be used as a joint. Examples of the molded article having a hollow portion include a joint for an in-vehicle pipe, a housing for an electronic device, and the like. [Effects of the Invention]

[0056] According to the present invention, it is possible to provide a core resin composition that exhibits high heat resistance and enables the production of cores that do not deform even under the molding conditions of super engineering plastics, and also to provide a core made using the core resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0057] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0058] (Synthesis Example 1) [PVA1 (saponification degree 98.4 mol%, weight average molecular weight 15,000)] A reactor equipped with a thermometer, stirrer, and condenser was charged with 2,000 parts by mass of vinyl acetate monomer and 200 parts by mass of methanol. Nitrogen gas was then blown in for 30 minutes to replace the atmosphere, and the reactor was then heated to 60°C for 30 minutes. Next, 456.5 parts by mass of 2,2'-azobisisobutyronitrile (a polymerization initiator) was added, and the reaction was allowed to proceed at 60°C for 4 hours. After the reaction time, the reaction solution was cooled. After cooling, the polymerization rate was measured by H-NMR, and found to be 99%. Next, the remaining vinyl acetate monomer was removed together with methanol under reduced pressure while adding additional methanol, yielding a methanol solution containing 50% by mass of polyvinyl acetate. A methanol solution of sodium hydroxide was added to this methanol solution to provide a sodium hydroxide content of 0.07 mol% relative to the vinyl acetate, and saponification was carried out at 40°C. The resulting solid was pulverized, washed with methanol, and dried to obtain PVA1. The degree of saponification of the resulting PVA1 was measured according to JIS K6726. The weight-average molecular weight of the polyvinyl alcohol resin was determined by gel permeation chromatography using an LF-804 (Shoko) column to measure the weight-average molecular weight in terms of polystyrene. The resulting saponification degree and weight-average molecular weight were 98.4 mol% and 15,000, respectively. The viscosity of a 4% by mass aqueous solution of the resulting polyvinyl alcohol resin was measured using a rotational viscometer (Toki Sangyo Co., Ltd., model "TVB-10") according to JIS K 6276 and was found to be 3.5 mPa s.

[0059] (Synthesis Example 2) [PVA2 (saponification degree 88.0 mol%, weight average molecular weight 30,000)] PVA2 having a degree of saponification, a weight-average molecular weight, and a 4% by mass aqueous solution viscosity of 88.0 mol %, 30,000, and 5.3 mPa s, respectively, was obtained by performing the same operations as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 4.2 parts by mass, and the amount of the methanol solution of sodium hydroxide added was changed so that the amount of sodium hydroxide was 0.02 mol % relative to the vinyl acetate.

[0060] (Synthesis Example 3) [PVA3 (saponification degree 98.4 mol%, weight average molecular weight 22,000)] PVA3 having a degree of saponification, a weight-average molecular weight, and a 4% by mass aqueous solution viscosity of 98.4 mol %, 22,000, and 6.9 mPa s, respectively, was obtained by performing the same operations as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 22.9 parts by mass, and the amount of the methanol solution of sodium hydroxide added was changed so that the amount of sodium hydroxide was 0.07 mol % relative to the vinyl acetate.

[0061] The following particle fillers and antioxidants other than the polyvinyl alcohol resin were used. Titanium dioxide 1: Ishihara Sangyo Kaisha, Ltd. TTO-51(A), average particle size 20 nm, density 3.7 g / cm 3 Titanium dioxide 2: Ishihara Sangyo Kaisha, Ltd. PF-690, average particle size 210 nm, density 4.0 g / cm 3 Carbon black 1: TOKABLACK #5500 manufactured by Tokai Carbon Co., Ltd., average particle size 25 nm, density 1.9 g / cm 3 Carbon black 2: Seast TA manufactured by Tokai Carbon Co., Ltd., average particle size 122 nm, density 1.9 g / cm 3 Antioxidant: Sumitomo Chemical Co., Ltd., Sumilizer GP Easy-peel agent: Monoglyceride stearate ester, Kao Electrostripper TS-5 The average particle size of the particle filler was taken from the catalog value. The density was measured using an Accupyc II1345 manufactured by Shimadzu Corporation.

[0062] Example 1 Polyvinyl alcohol resin, particle filler, and antioxidant were mixed to obtain the formulation shown in Table 1, and the mixture was pelletized at an extrusion temperature of 190°C to 220°C using a Toshiba Machine processing machine "TEM26SX" to obtain pellets of the resin composition for cores.

[0063] Examples 2 to 8 The polyvinyl alcohol resin, particle filler, and antioxidant were mixed to obtain the formulation shown in Table 1, and pellets of a resin composition for a core were obtained in the same manner as in Example 1.

[0064] Example 9 Polyvinyl alcohol resin, particle filler, antioxidant and easy-release agent were mixed to obtain the formulation shown in Table 1, and pellets of a resin composition for a core were obtained in the same manner as in Example 1.

[0065] (Comparative Example 1) Pellets of a resin composition for a core were obtained in the same manner as in Example 1, except that no particulate filler was added and the polyvinyl alcohol resin and antioxidant were mixed to obtain the formulation shown in Table 1.

[0066] (Comparative Examples 2 to 3) The polyvinyl alcohol resin, particle filler, and antioxidant were mixed to obtain the formulation shown in Table 1, and pellets of a resin composition for a core were obtained in the same manner as in Example 1.

[0067] (Evaluation method) The obtained resin composition for a core was evaluated by the following methods, and the results are shown in Table 1.

[0068] (1) Total surface area of ​​particle filler The total surface area of ​​the particulate filler per unit mass of the core resin composition was calculated based on the following formula (1).

number

[0069] (2) Melt flow rate (MFR) Using a melt index tester No. 120-FWP (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the melt flow rate (MFR) of the core resin composition was measured according to a method in accordance with ASTM D 1238 under the conditions of an initial weight of the core resin composition of 7.5 g, 230°C, a load of 10 kg, and a measurement time interval of 0.25 minutes.

[0070] (3) Heat resistance A 10 mm diameter SUS304 steel ball was heated to 300°C, and the pellets were cooled to room temperature (20°C) and molded into a plate of core resin composition. The ball was then placed on the plate for 1 minute to measure the diameter (mm) of the depression that formed. Evaluation was carried out with the following criteria: less than 2 mm was marked "◎", 2 mm to 3 mm was marked "〇", and 3 mm or more was marked "×".

[0071] (4)Water-soluble 2 g of the obtained core resin composition was placed in a basket-shaped stainless steel 200-mesh net and dissolved in 1000 g of 90°C hot water in a 1 L beaker with a rotor rotating at 500 rpm for 60 minutes. The stainless steel net was then removed from the hot water and dried in a hot air circulating oven at 80°C for 24 hours. The solubility (mass%) of the core resin composition was calculated from the initial weight of the stainless steel net (W0), the weight of the sample placed in the basket (S1), and the weight of the dried stainless steel net including the undissolved portion of the core resin composition (W1). Dissolution rate (mass%)=(S1-(W1-W0))÷S1×100(mass%)

[0072] [Table 1] [Industrial Applicability]

[0073] According to the present invention, it is possible to provide a core resin composition that exhibits high heat resistance and enables the production of cores that do not deform even under the molding conditions of super engineering plastics, and also to provide a core made using the core resin composition.

Claims

1. A core resin composition containing a polyvinyl alcohol resin, Contains particle filler, The total surface area A per unit mass of the resin composition for a core of the particulate filler represented by the following formula (1) is 10 m ２ / g or more, The polyvinyl alcohol resin has a weight average molecular weight (Mw) of 200,000 or less, a degree of saponification of 72% or more and 99.8% or less, and a viscosity of a 4% by mass aqueous solution of 30 mPa·s or less. [Equation 1] A: total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) B: average particle diameter (m) of particle filler D: Content (mass%) of particle filler in the resin composition for core E: density of particle filler (g / m ３ )

2. 2. The resin composition for a core according to claim 1, wherein the average particle diameter of the particulate filler is 1 nm or more and 100 nm or less.

3. 3. The resin composition for a core according to claim 1, wherein the content of the particulate filler is 5% by mass or more and 70% by mass or less.

4. The resin composition for a core according to claim 1 or 2, containing 0.1% by mass or more and 2% by mass or less of an easy-release agent.

5. The resin composition for a core according to claim 1 or 2, containing 0.1% by mass or more and 10% by mass or less of a plasticizer.

6. The resin composition for a core according to claim 1 or 2, which is in the form of pellets.

7. A core made using the resin composition for a core according to claim 1 or 2.

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