Resin composition for cores

Abstract

The present invention provides a resin composition for cores, which allows production of a core that exhibits high heat resistance and does not melt or deform even under molding conditions for super engineering plastics. The present invention pertains to a resin composition for cores, which contains a polyvinyl alcohol resin. The resin composition contains a particle filler (X) and a scale-like, sheet-like, or layer-like compound (Y). The total surface area A of the particle filler (X) per unit mass of the resin composition for cores as represented by formula (1) is at least 10 m2 / g. A: The total surface area (m2 / g) of the particle filler (X) B: The average particle diameter (m) of the particle filler (X) D: The contained amount (mass%) of the particle filler (X) in the resin composition for cores E: The density (g / m3) of the particle filler (X)

Description

Resin composition for core

[0001] This invention relates to a resin composition for cores.

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

[0003] International Publication No. 2021 / 157375

[0004] In recent years, from the perspective of weight reduction, there has been research into replacing the materials used in automobile and other parts with super engineering plastics (super engineering plastics) that have excellent heat resistance. As a result of diligent research, the present inventors have found 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 deforms during molding. When the core resin deforms during molding, the problem is that a molded body with the desired shape cannot be obtained.

[0005] The present invention aims to provide a resin composition for cores that exhibits high heat resistance and can produce cores that do not melt or deform even under the molding conditions of super engineering plastics.

[0006] Disclosure 1 is a core resin composition comprising a polyvinyl alcohol resin, a particulate filler (X), and a flake-like, plate-like, or layered compound (Y), wherein the total surface area A per unit mass of the core resin composition of the particulate filler (X) represented by the following formula (1) is 10 m². ２ This is a resin composition for cores with a concentration of 1 / g or more. A: Total surface area of ​​particle filler (X) (m²) ２( / g) B: Average particle diameter of particle filler (X) (m) D: Content of particle filler (X) in the core resin composition (mass%) E: Density of particle filler (X) (g / m ３ Disclosure 2 is a core resin composition of Disclosure 1, wherein the flake-like, plate-like, or layered compound (Y) is a layered silicate compound. Disclosure 3 is a core resin composition of Disclosure 2, wherein the layered silicate compound is mica. Disclosure 4 is a core resin composition of Disclosure 1, 2, or 3, wherein the total content of the particle filler (X) and the flake-like, plate-like, or layered compound (Y) is 20% by mass or more and 60% by mass or less. Disclosure 5 is a core resin composition of Disclosure 1, 2, 3, or 4, wherein the average particle diameter of the particle filler (X) is 1 nm or more and 100 nm or less. Disclosure 6 is a core resin composition of Disclosure 1, 2, 3, 4, or 5, wherein the polyvinyl alcohol resin has a degree of polymerization of 4000 or less, a degree of saponification of 72.0 mol% or more and 99.8 mol% or less, and a viscosity of 4% by mass aqueous solution of 150 mPa·s or less. Disclosure 7 is a core resin composition according to Disclosures 1, 2, 3, 4, 5, or 6, containing 0.1% by mass or more and 2.0% by mass or less of an easy-release agent. Disclosure 8 is a core resin composition according to Disclosures 1, 2, 3, 4, 5, 6, or 7, wherein the polyvinyl alcohol resin has a degree of polymerization of 200 to 1000, a degree of saponification of 85 mol% to 99.5 mol%, and a viscosity of a 4% by mass aqueous solution of 2 mPa·s to 15 mPa·s. The present invention will be described in detail below.

[0007] In light of general knowledge, simply increasing the total amount of particle filler (X) is considered an effective method for improving the heat resistance of the core. However, if the total amount is simply increased, the melt viscosity rises sharply, making it difficult to knead the resin composition or to mold it using an injection molding machine. In other words, even if the heat resistance is improved, the original purpose of the resin composition for the core cannot be achieved. Therefore, the inventors diligently studied the addition of particle filler to the resin composition for the core and found that by combining polyvinyl alcohol resin with particle filler, setting the total surface area of ​​the particle filler within a predetermined range, and further adding flake-shaped, plate-shaped, or layered compounds, it is possible to simultaneously solve problems such as heat resistance, kneadability, and moldability, and to suppress melt deformation even under the molding conditions of super engineering plastics. This led to the completion of the present invention.

[0008] <Polyvinyl alcohol resin> The above core resin composition contains polyvinyl alcohol resin. By using polyvinyl alcohol resin, the core can be easily removed from the molded body by immersion in water or other means.

[0009] The degree of polymerization of the above polyvinyl alcohol resin is preferably 4000 or less. When the degree of polymerization is 4000 or less, it can fully exhibit good solubility in water. The degree of polymerization is more preferably 180 or more, even more preferably 200 or more, even more preferably 220 or more, preferably 3400 or less, more preferably 2300 or less, even more preferably 1200 or less, even more preferably 1000 or less, and particularly preferably 900 or less. The degree of polymerization can be determined, for example, by measuring polyvinyl acetate before saponification using gel permeation chromatography (GPC) or by measuring the viscosity of the aqueous solution in accordance with JIS K6726.

[0010] The degree of saponification of the above polyvinyl alcohol resin is preferably 72.0 mol% or more, and preferably 99.8 mol% or less. By keeping it within this range, sufficient solubility in water can be achieved. The degree of saponification is more preferably 80.0 mol% or more, even more preferably 85.0 mol% or more, even more preferably 87.0 mol% or more, particularly preferably 92.0 mol% or more, most preferably 95.0 mol% or more, more preferably 99.5 mol% or less, and even more preferably 99.0 mol% or less. The degree of saponification can be measured, for example, by a method in accordance with JIS K6726. The degree of saponification indicates the proportion of vinyl ester units that can be converted to vinyl alcohol units by saponification and are actually converted to vinyl alcohol units. The degree of saponification can be controlled, for example, by adjusting the saponification conditions, i.e., the hydrolysis conditions.

[0011] The weight-average molecular weight (Mw) of the above 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, preferably 150,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, and even more preferably 40,000 or less.

[0012] The number-average molecular weight (Mn) of the above polyvinyl alcohol resin is preferably 4000 or more, more preferably 4500 or more, even more preferably 5000 or more, preferably 90000 or less, more preferably 60000 or less, and even more preferably 30000 or less.

[0013] The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the above polyvinyl alcohol resin is preferably 1.0 or higher, more preferably 1.2 or higher, even more preferably 1.4 or higher, even more preferably 1.6 or higher, preferably 5.0 or lower, more preferably 4.0 or lower, even more preferably 3.5 or lower, and even more preferably 2.0 or lower. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) can be determined, for example, by measuring by gel permeation chromatography (GPC), measuring the polyvinyl ester before saponification by GPC, measuring the polyvinyl ester obtained by re-esterifying the polyvinyl alcohol resin by GPC, or by measuring the viscosity of the aqueous solution in accordance with JIS K6726. For example, polystyrene can be used as the standard, and columns such as TSKgel (Tosoh Corporation), PLgel (AMR Corporation), KF-806, KF-807 (Shodex Corporation) can be used.

[0014] The above polyvinyl alcohol resin preferably has a viscosity of 150 mPa·s or less when used in a 4% by mass aqueous solution. A viscosity of 150 mPa·s or less when used in a 4% by mass aqueous solution provides fluidity suitable for injection molding and appropriate water solubility when used as a core. The viscosity of the above 4% by mass aqueous solution is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, even more preferably 5 mPa·s or more, more preferably 20 mPa·s or less, even more preferably 15 mPa·s or less, and even more preferably 10 mPa·s or less. The viscosity of the above 4% by mass aqueous solution can be measured, for example, by a method conforming to JIS K 6276 3.11.1 rotational viscometer method.

[0015] The polyvinyl alcohol resin described above may be an unmodified polyvinyl alcohol resin or a modified polyvinyl alcohol resin. Here, a modified polyvinyl alcohol resin means a polyvinyl alcohol resin having constituent units other than vinyl ester units and vinyl alcohol units. Examples of the modified polyvinyl alcohol resin include those modified with hydrophilic groups such as sulfonic acid groups, pyrrolidone ring groups, amino groups, and carboxyl groups. These hydrophilic groups also include sodium salts, potassium salts, and other salts of the functional groups described above.

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

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

[0018] The above polyvinyl alcohol resin is obtained by polymerizing vinyl esters according to conventionally known methods, and then saponifying, i.e., hydrolyzing, the polymer. Generally, alkalis or acids are used as saponification catalysts.

[0019] Examples of the vinyl esters mentioned above 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, and examples thereof include solution polymerization method, bulk polymerization method, suspension polymerization method, and the like.

[0021] Examples of the polymerization catalyst used when polymerizing the above vinyl ester include 2-ethylhexyl peroxydicarbonate ("Trigonox EHP" manufactured by Tianjin McEIT), 2,2'-azobisisobutyronitrile (AIBN), t-butyl peroxyneodecanoate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di-cetyl peroxydicarbonate, di-s-butyl peroxydicarbonate, and the like. The above polymerization catalyst may be used alone or in combination of two or more.

[0022] The above polyvinyl alcohol resin may be a saponified product of a polymer of a vinyl ester and another unsaturated monomer. Examples of the other unsaturated monomer include monomers other than the above vinyl ester and having an unsaturated double bond such as a vinyl group. Specifically, for example, 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, amino group-containing compounds, and the like can be mentioned.

[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, their salts, and esters include maleic acid and its salts, maleic acid esters, itaconic acid and its salts, itaconic acid esters, methylenemalonic acid and its salts, 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. Examples of allyl compounds include allyl acetate and allyl chloride. Examples of vinylsilyl compounds include vinyltrimethoxysilane. Examples of sulfonic acid group-containing compounds include (meth)acrylamide alkanesulfonic acids such as (meth)acrylamidepropanesulfonic acid and their salts, olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and metaallylsulfonic acid, or their salts. Examples of amino group-containing compounds include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0024] <Particle Filler (X)> The above core resin composition contains particle filler (X). By including particle filler (X), heat resistance can be improved.

[0025] In the above resin composition for neutrons, the total surface area A of the above particle filler (X) per unit mass of the resin composition for neutrons calculated by the following formula (1) is 10 m ２ / g or more. A: Total surface area of the particle filler (X) (m ２ / g) B: Average particle diameter of the particle filler (X) (m) C: Amount of the resin composition for neutrons (g) D: Content of the particle filler (X) in the resin composition for neutrons (mass%) E: Density of the particle filler (X) (g / m ３ )

[0026] The above formula (1) is explained by the following formula (2). That is, the above total surface area A is calculated by multiplying the surface area per particle filler (X) (m ２ )(4π×(B / 2) ２ ) by the number of particle fillers (X) per 1 g of the resin composition for neutrons. Also, the number of particle fillers (X) per 1 g of the resin composition for neutrons is the content of the particle filler (X) per 1 g of the resin composition for neutrons (g)(C(g)×D(mass%) / 100÷C(g)) divided by the mass per particle filler (X) (g)(density × average volume per particle filler (X)=E×4 / 3π(B / 2) ３ ). Regarding the density of the above particle filler (X), even when the particle filler (X) is hollow particles or porous particles, the particle density considering the volume including cavities and pores inside the particles is adopted. Since it is important not to consider the area of dents and pore parts for the total surface area A of the above particle filler (X), in the above formula (2), the particle filler (X) is approximated as a sphere to calculate the total surface area A of the particle filler (X) per unit mass of the resin composition for neutrons. By setting the total surface area A to 10 m ２ / g or more, the heat resistance can be sufficiently increased, and a resin composition for neutrons that does not melt or deform even under the molding conditions of super engineering plastics can be obtained. The above total surface area A is preferably 15 m ２ / g or more, more preferably 20 m ２ / g or more, still more preferably 23 m ２ / g or more, and even more preferably 28 m ２A value of 1 / g or more is even more preferable. Furthermore, the total surface area A is 560 m². ２ Preferably less than / g, 200m ２ More preferably less than / g, and 75m ２ It is even more preferable to have a value of 55m or less per g. ２ It is even more preferable that the amount be less than or equal to 40m ２ A value of less than or equal to / g is particularly preferred. Note that one type of particle filler (X) may be used, or two or more types with different average particle sizes or materials may be used in combination. When two or more types are used in combination, the total surface area A can be calculated for each particle filler (X) using formula (1) above, and then summed up.

[0027] The total surface area A of the particle filler (X) per unit mass can be adjusted by the average particle diameter, density, and amount of particle filler (X) used. Furthermore, while the surface area of ​​the particle filler (X) is calculated from the average particle diameter, density, and amount of primary particles, the particle shape is not necessarily limited to spherical. Other shapes include needle-shaped, rugby-shaped, hollow, and porous forms, and these may also have a higher-order structure consisting of multiple connected or overlapping particles. Note that the particle filler (X) is different from the flaky, plate-shaped, or layered compounds (Y) described later.

[0028] The average particle diameter of the above particle filler (X) is preferably 1 nm or more, and preferably 100 nm or less. By setting it within this range, the surface area of ​​the particle filler (X) in the core resin composition can be kept within a certain range, and the heat resistance required for the resin composition can be imparted. The average particle diameter is more preferably 2 nm or more, even more preferably 3 nm or more, even more preferably 4 nm or more, even 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 diameter is particularly preferably 5 nm or more, and particularly preferably 29 nm or less. By setting it within this range, the particle filler (X) and the polyvinyl alcohol resin can be easily kneaded and mixed. The average particle diameter of the above particle filler (X) can be measured, for example, by a particle size distribution analyzer or the like.

[0029] The density of the above particle filler (X) is 0.5 g / cm³. ３ The above is preferable, and 0.7 g / cm³ ３ The above is more preferable, 0.9 g / cm³ ３ The above is even more preferable, 1.1 g / cm³ ３ The above is particularly preferred, at 22.0 g / cm³. ３ The following is preferable: 13.0 g / cm³ ３ The following is more preferable: 6.0 g / cm³ ３ The following is even more preferable: 4.5 g / cm³ ３ The following is particularly preferred. The density can be measured, for example, by an electron hydrometer. Regarding the density of the particle filler (X), even if the particle filler (X) is a hollow particle or a porous particle, the particle density is adopted that takes into account the volume including cavities and pores inside the particle.

[0030] Examples of materials for the particle filler (X) include metals, metal oxides, ceramics, carbon materials, and glass. Resin particles with a melting point of 200°C or higher can also be used as the particle filler (X). Examples of metal oxides include titanium oxide, aluminum oxide, calcium oxide, lithium oxide, molybdenum oxide, vanadium oxide, zinc oxide, nickel oxide, cesium oxide, and iron oxide. Other examples include diamond, boron nitride, aluminum nitride, gold, silver, copper, platinum, palladium, and silicon carbide. Examples of carbon materials include carbon black, graphite, and diamond. Among these, titanium oxide and carbon black are preferred from the viewpoint of cost performance and availability. Examples of resins with a melting point of 200°C or higher include polyethylene terephthalate, polyamide, aromatic polyamide (aramid), polyimide, and polyetheretherketone (PEEK).

[0031] The content of the particle filler (X) in the resin composition for the core is preferably 5% by mass or more, and preferably 70% by mass or less. Heat resistance can be improved by setting it within this range. The content of the particle filler (X) 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, and even more preferably 35% by mass or less.

[0032] <Flake-like, plate-like, or layered compound (Y)> The above core resin composition further contains a flake-like, plate-like, or layered compound (Y). By including the flake-like, plate-like, or layered compound (Y), heat resistance can be further enhanced while ensuring sufficient kneadability and moldability.

[0033] The density of the above-mentioned flaky, plate-like, or layered compound (Y) is 1.5 g / cm³. ３ The above is preferable, 1.8 g / cm³ ３ The above is more preferable, specifically 2.4 g / cm³. ３ The above is even more preferable, 2.5 g / cm³ ３ The above is even more preferable, 4.2 g / cm³. ３ The following is preferable: 3.7 g / cm³ ３ The following is more preferable: 3.5 g / cm³ ３ The following is even more preferable: 2.9 g / cm³ ３ The following is even more preferable. The density can be measured, for example, by an electronic hydrometer. Regarding the density of the flake-like, plate-like, or layered compound (Y), even if the flake-like, plate-like, or layered compound (Y) is hollow or porous, the density is adopted that takes into account the volume including the internal cavities and pores.

[0034] Examples of the above-mentioned flaky, plate-like, or layered compound (Y) include layered silicate compounds. Examples of the above-mentioned layered silicate compounds include kaolin minerals such as kaolin and delamikaolin, talc, mica, pyrophyllite, smectite, vermiculite, chlorite, septechlorite, serpentine, stilpnomelane, and montmorillonite. The mica may be a natural mineral or synthetic mica. Examples of mica include muscovite, sericite, phlocopite, biotite, fluorinated phlocopite (synthetic mica), red mica, soda mica, vanadine mica, illite, tin mica, paragonite, brittle mica, potassium tetrasilicate mica, sodium tetrasilicate mica, sodium teniolite, and lithium teniolite. In particular, for the purpose of imparting heat resistance, it is desirable that the melting point is 350°C or higher and that it is chemically stable at 350°C. As the layered silicate compound, mica is preferred, and fluorophlogopite and sodium tetrasilicon mica are more preferred. Many of the above-mentioned flake-like, plate-like, or layered compounds (Y) are very brittle or have low strength and change shape significantly during kneading, making it difficult to specify the shape in the core resin composition. However, for example, those with an average particle diameter of 1 to 500 μm and an aspect ratio of 5 to 3000 are suitably used. Furthermore, an average particle diameter of 2 to 200 μm is more preferred, and 3 to 100 μm is even more preferred. An aspect ratio of 10 to 2000 is more preferred, and 20 to 1500 is even more preferred. However, since the shape also changes significantly depending on the kneading state, it is not limited to the above ranges, and it is particularly important that it is flake-like, plate-like, or layered, with layered compounds such as mica being particularly suitable.

[0035] The content of the above-mentioned flake-like, plate-like, or layered compound (Y) in the above-mentioned core resin composition is preferably 3% by mass or more, and preferably 50% by mass or less. By setting it within the above range, the heat resistance can be further improved. The content of the above-mentioned flake-like, plate-like, or layered compound (Y) is more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0036] In the resin composition for the core described above, the ratio of the content of the particle filler (X) to the content of the flake-like, plate-like, or layered compound (Y) is preferably 9:1 to 1:9, more preferably 8:1 to 1:4, even more preferably 6:1 to 1:2, and particularly preferably 5:1 to 1:1. Furthermore, the total surface area A (m²) determined by the shape and content of the particle filler (X) is also specified. ２ The ratio A / F calculated from the content F (mass%) of particle filler (Y) in the core resin composition (per g) is preferably 0.1 to 200, more preferably 0.2 to 150, even more preferably 0.4 to 100, and particularly preferably 0.5 to 15. Within this range, a high level of both moldability when injection molding as a core and heat resistance when used as a core can be achieved.

[0037] In the resin composition for the core described above, the density ratio of the particle filler (X) to the flake-like, plate-like, or layered compound (Y) (particle filler (X) / flake-like, plate-like, or layered compound (Y)) is preferably 0.119 or higher, more preferably 0.200 or higher, even more preferably 0.300 or higher, preferably 14.700 or lower, more preferably 7.220 or lower, and even more preferably 2.500 or lower.

[0038] In the resin composition for the core described above, the total content of the particle filler (X) and the flake-like, plate-like, or layered compound (Y) is preferably 20% by mass or more, and preferably 60% by mass or less, in order to achieve a high level of both moldability when injection molding as a core and heat resistance when used as a core. Furthermore, the total content is more preferably 25% by mass or more, more preferably 50% by mass or less, even more preferably 30% by mass or more, and even more preferably 40% by mass or less.

[0039] <Removable Agent> The above core resin composition may contain a removable agent. Including a removable agent makes it easier to remove the core resin from the molded article.

[0040] As the above-mentioned easy-release agent, for example, a glycerol fatty acid ester compound can be used. Examples of the above-mentioned glycerol fatty acid ester compound include monoglyceride stearate, monoglyceride oleate, and diglyceride laurate.

[0041] The content of the release agent in the resin composition for the core is preferably 0.1% by mass or more, and preferably 2.0% by mass or less. By setting it within this range, the surface smoothness of the inside of the resulting molded article can be sufficiently improved. The content of the release agent is more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1.6% by mass or less, and even more preferably 1.1% by mass or less.

[0042] <Plasticizer> The resin composition for the core described above may contain a plasticizer. Including a plasticizer can improve moldability.

[0043] Examples of the plasticizers mentioned above include polyhydric alcohols. Examples of polyhydric alcohols 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, mannitol, and the like.

[0044] The content of the plasticizer in the resin composition for the core is preferably 0.1% by mass or more, and preferably 10.0% by mass or less. This range allows for good extrusion and injection moldability and good water solubility. The content of the plasticizer is more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less.

[0045] <Crosslinking Agent> The above core resin composition may contain a crosslinking agent. Examples of the above crosslinking agent include oxo acids, boron compounds, divalent or higher metal hydroxides, diamines, polyamines, etc. A metal salt of the above acid may also be used.

[0046] Examples of the oxoacids mentioned above 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 acids may also be used. Among the oxoacids, boric acid is particularly preferred. Using boric acid allows for a core resin composition that has sufficient water resistance during processing but can be easily removed with hot water when necessary. Examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid. In addition to the boric acid listed above, other boron compounds include, for example, salts of boric acid. Furthermore, the boron compound may be a hydrate. Examples of boric acid salts 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.

[0047] Examples of the polycarboxylic acids mentioned above include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and poly(meth)acrylic acid. Among these, succinic acid is preferred. Examples of the hydroxycarboxylic acids mentioned above include glycolic acid, lactic acid, tartaric acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, citomalic acid, citric acid, isocitric acid, leucic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineradicic acid, cerebronic acid, quinic acid, shikimic acid, hydroxybenzoic acid, salicylic acid, creosoteic acid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orceric acid, gallic acid, mandelic acid, benzyl acid, atrolactinic acid, melilotic acid, floretic acid, coumaric acid, umbellic acid, caffeic acid, ferulic acid, sinapic acid, and hydroxystearic acid. Among these, malic acid and citric acid are preferred. Examples of the above-mentioned metal hydroxides with a valency of 2 or higher include calcium hydroxide, magnesium hydroxide, barium hydroxide, aluminum hydroxide, iron hydroxide, zinc hydroxide, manganese hydroxide, and copper hydroxide. The above-mentioned crosslinking agent may be used alone or in combination of two or more types. In particular, the above-mentioned crosslinking agent preferably contains any of the following: a metal hydroxide with a valency of 2 or higher, a boron compound, or an acid having two or more carboxyl groups. It is even more preferable that the above-mentioned crosslinking agent is a metal hydroxide with a valency of 2 or higher, a boron compound, or an acid having two or more carboxyl groups, and even more preferable that it is a metal hydroxide with a valency of 2 or higher, boric acid, or an acid having two or more carboxyl groups.

[0048] <Other> The resin composition for the core described above may also contain other additives such as antioxidants, colorants, defoamers, UV absorbers, and preservatives.

[0049] As antioxidants, known antioxidants such as phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, and sulfur-containing antioxidants can be used. Furthermore, antioxidants containing both phenolic and phosphorus-based functional groups within a single molecule can also be used.

[0050] Examples of the above phenolic antioxidants include acrylate compounds such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 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, and 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-tetraoxy Suspiro[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 alkyl-substituted phenol compounds such as triethylene glycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate), 6-(4-H Examples include triazine group-containing phenolic compounds such as droxy-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, or 2-octylthio-4,6-bis-(3,5-di-t-butyl-4-oxyanilino)-1,3,5-triazine.

[0051] Examples of the phosphorus-based antioxidants mentioned above include triphenyl phosphite, diphenylisodecyl 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, Alternatively, examples include monophosphite compounds such as 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12-C15) phosphite), 4,4'-isopropylidene-bis(diphenylmonoalkyl(C12-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.

[0052] Antioxidants possessing both phenolic and phosphorus functional groups within a single molecule are not particularly limited, but examples include phosphite ester compounds having a phenol skeleton. Specifically, these include 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]dioxaphosfepine, 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]dioxaphosphosine, and 2,4,8,10-tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl] )propoxy]dibenzo[d,f][1,3,2]dioxaphosfepine, 2,4,8,10-tetra-t-pentyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, 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]dioxaphosphosine, 2,4,8,1 0-Tetra-t-pentyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, 2,4,8,10-Tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-dibenzo[d,f][1,3,2]dioxaphosfepine, 2,10-dimethyl-4,8-di-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyl Xy)-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, 2,4,8,10-tetra-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyloxy)-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, 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]dioxaphosphosine, 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]dioxaphosphosine 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]dioxaphosfepine.

[0053] The content of the antioxidant in the above-mentioned core resin composition is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, even more preferably 0.7% by mass or more, preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.2% by mass or less.

[0054] The resin composition for the core described above preferably has a melt flow rate (MFR) of 35 g / 10 min or less under conditions of 230°C and a 10 kg load. By keeping it within this range, it is possible to produce a core that exhibits high heat resistance and does not deform even under high-temperature conditions such as those for molding super engineering plastics. The MFR is more preferably 25 g / 10 min or less, even 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 as long as it can be molded by a molding machine for molding the core, and depends on the capabilities of the molding machine. The MFR can be measured, for example, by a method in accordance with ASTM D 1238.

[0055] 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 particle filler (X), the average particle size, the total surface area, the type and amount of flake-like, plate-like, or layered compound (Y), crosslinking agents, plasticizers, release agents, etc.

[0056] The resin composition for the core described above can be obtained by mixing, for example, a polyvinyl alcohol resin, a particulate filler (X), a flake-like, plate-like, or layered compound (Y), and other additives as needed, such as release agents, plasticizers, and antioxidants. The method of mixing the above components is not particularly limited, but examples include mixing using a known kneading apparatus or using an extrusion molding machine. Alternatively, mixing may be done in the cylinder of an injection molding machine.

[0057] A core can be produced by molding the above-mentioned core resin composition. The molding method is not particularly limited, but examples include injection molding.

[0058] The above-mentioned core can be used to manufacture a molded body. The material that is molded together with the above-mentioned core to form a composite is not particularly limited, but since the above-mentioned 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.

[0059] Examples of the above-mentioned super engineering plastics include highly heat-resistant plastics such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyimide (PI), polyamide imide (PAI), polyetherimide (PEI), polyphenyl sulfone (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-mentioned super engineering plastics, molded articles with excellent heat resistance, durability, and mechanical strength can be obtained.

[0060] A molded body having a hollow portion can be obtained by removing the core from the above composite. One method for removing the core is to immerse the composite in water or hot water.

[0061] The shape of the molded body described above may be straight, or it may be L-shaped, S-shaped, T-shaped, or various other shapes. For example, L-shaped, S-shaped, or similar molded bodies can be used as joints. Examples of molded bodies having a hollow section include automotive piping joints and electronic equipment housings.

[0062] According to the present invention, it is possible to provide a resin composition for cores that exhibits high heat resistance and can be used to manufacture cores that do not melt or deform even under the molding conditions of super engineering plastics.

[0063] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0064] (Synthesis Example 1) [PVA1 (Degree of Saponification 88.0 mol%, Degree of Polymerization 500)] In a reactor equipped with a thermometer, stirrer, and condenser, 2000 parts by mass of vinyl acetate monomer and 200 parts by mass of methanol were added, and nitrogen gas was blown in for 30 minutes to purge the reactor with nitrogen. The reactor was then heated at 60°C for 30 minutes. Next, 4.2 parts by mass of 2,2'-azobisisobutyronitrile, which is a polymerization initiator, was added, and the reaction was carried out at 60°C for 4 hours. After the reaction time was completed, the reaction solution was cooled. After cooling １The polymerization rate was measured by 1H-NMR and found to be 99%. Next, under reduced pressure, the remaining vinyl acetate monomer was removed along with methanol, with methanol being added as needed, to obtain a methanol solution containing 50% by mass of polyvinyl acetate. To this methanol solution, a methanol solution of sodium hydroxide was added to a concentration of 0.02 mol% of sodium hydroxide relative to vinyl acetate, and saponification was carried out at 40°C. The obtained solid was pulverized, washed with methanol, and dried to obtain PVA1. The degree of saponification of the obtained PVA1 was measured according to the method in accordance with JIS K6726. The degree of polymerization of the polyvinyl alcohol resin was determined by measuring the viscosity of the aqueous solution according to JIS K6726. As a result, the degree of saponification and the degree of polymerization were 88.0 mol% and 500, respectively. The viscosity of the 4% by mass aqueous solution of the obtained polyvinyl alcohol resin was measured using a rotational viscometer (TVB-10, manufactured by Toki Sangyo Co., Ltd.) in accordance with JIS K 6276, and was 5.3 mPa·s.

[0065] (Synthesis Example 2) [PVA2 (Degree of Saponification 98.0 mol%, Degree of Polymerization 300)] By performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 456.5 parts by mass and the amount of methanol solution of sodium hydroxide added was changed to 0.07 mol% of the amount of sodium hydroxide relative to vinyl acetate, PVA2 was obtained with a degree of saponification, degree of polymerization, and viscosity of a 4% aqueous solution of 98.0 mol%, 300, and 3.5 mPa·s, respectively.

[0066] (Synthesis Example 3) [PVA3 (Degree of Saponification 98.0 mol%, Degree of Polymerization 450)] By performing the same procedure 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 methanol solution of sodium hydroxide added was changed to 0.07 mol% of the sodium hydroxide relative to vinyl acetate, PVA3 was obtained with a degree of saponification, degree of polymerization, and viscosity of a 4% aqueous solution of 98.0 mol%, 450, and 6.9 mPa·s, respectively.

[0067] The following were used as particulate fillers (X) other than polyvinyl alcohol resin, flaky, plate-like, or layered compounds (Y), and antioxidants: <Particulate filler (X)> Titanium dioxide 1: TTO-51A manufactured by Ishihara Sangyo Co., Ltd., average particle size 20 nm, density 3.7 g / cm³ ３ Titanium dioxide 2: PF-690, manufactured by Ishihara Sangyo Co., Ltd., average particle size 210 nm, density 4.0 g / cm³ ３ Carbon Black 1: Manufactured by Tokai Carbon Co., Ltd. TOKA BLACK #5500, average particle size 25 nm, density 1.9 g / cm³ ３ Carbon Black 2: SEAST TA, manufactured by Tokai Carbon Co., Ltd., average particle size 122 nm, density 1.9 g / cm³ ３ <Scaly, plate-like, or layered compounds (Y)> Mica 1: Sodium tetrasilicon mica, manufactured by Topy Industries, Ltd. DMA350NC, density 2.7 g / cm³ ３ Mica 2: Fluorinated mica, manufactured by Topy Industries, Ltd., PDM9LX, density 2.8 g / cm³ ３ <Antioxidant> Sumitomo Chemical Co., Ltd., SumiLizer GP <Easy-to-remove agent> Glycerol monostearate: Kao Corporation, Electro Stripper TS-5 The average particle size of the particle filler (X) was taken from the catalog value. The density was measured using Shimadzu Corporation, AccuPic II 1345.

[0068] (Example 1) Polyvinyl alcohol resin, particulate filler (X), flake-shaped, plate-shaped or layered compound (Y), and antioxidant were mixed in the proportions shown in Table 1, and pelletized using a Toshiba Machine Co., Ltd. processing machine "TEM26SX" at an extrusion temperature of 190°C to 220°C to obtain pellets of the core resin composition.

[0069] (Examples 2-9) Polyvinyl alcohol resin, particulate filler (X), flake-like, plate-like or layered compound (Y), antioxidant and release agent were mixed in the proportions shown in Table 1 to obtain pellets of core resin composition in the same manner as in Example 1.

[0070] (Comparative Example 1) A pellet of the core resin composition was obtained in the same manner as in Example 1, except that no particle filler (X) or flake-like, plate-like, or layered compound (Y) was added, and the polyvinyl alcohol resin and antioxidant were mixed to the formulation shown in Table 2.

[0071] (Comparative Examples 2-7) Polyvinyl alcohol resin, particle filler (X), and antioxidant were mixed in the proportions shown in Table 2, and pellets of core resin composition were obtained in the same manner as in Example 1.

[0072] (Comparative Example 8) Polyvinyl alcohol resin, particulate filler (X), flake-shaped, plate-shaped or layered compound (Y), and antioxidant were mixed in the proportions shown in Table 2, and pellets of the core resin composition were obtained in the same manner as in Example 1.

[0073] (Evaluation Method) The obtained core resin compositions were evaluated by the following method. The results are shown in Tables 1 and 2.

[0074] (1) Total surface area A of particle filler (X) The total surface area A of particle filler (X) per unit mass of core resin composition was calculated based on the following formula (1). A: Total surface area of ​​particle filler (X) (m²) ２ ( / g) B: Average particle diameter of particle filler (X) (m) D: Content of particle filler (X) in the core resin composition (mass%) E: Density of particle filler (X) (g / m ３ )

[0075] (2) A heat-resistant SUS304 steel ball with a diameter of 10 mm was heated to 300°C and placed on a core resin composition formed from pellets at room temperature (20°C) for 1 minute. The diameter (mm) of the indentation that formed was measured. Although the heat resistance evaluation measures the diameter of the indentation in the deformed area, the deformation volume caused by the heated steel ball differs by the cube of that value. Therefore, even a small difference in diameter can result in a very large difference in deformation volume, and thus a significant difference in heat resistance.

[0076]

[0077]

[0078] According to the present invention, it is possible to provide a resin composition for cores that exhibits high heat resistance and can be used to manufacture cores that do not melt or deform even under the molding conditions of super engineering plastics.

Claims

1. A core resin composition containing polyvinyl alcohol resin, comprising a particulate filler (X) and a flake-like, plate-like, or layered compound (Y), wherein the total surface area A per unit mass of the core resin composition of the particulate filler (X) represented by the following formula (1) is 10 m². ２ A resin composition for cores having a concentration of 1 / g or more. A: Total surface area of ​​particle filler (X) (m²) ２ ( / g) B: Average particle diameter of particle filler (X) (m) D: Content of particle filler (X) in the core resin composition (mass%) E: Density of particle filler (X) (g / m ３ ) 2. The core resin composition according to claim 1, wherein the flaky, plate-like, or layered compound (Y) is a layered silicate compound.

3. The core resin composition according to claim 2, wherein the layered silicate compound is mica.

4. The core resin composition according to claim 1, 2, or 3, wherein the total content of the particulate filler (X) and the flake-like, plate-like, or layered compound (Y) is 20% by mass or more and 60% by mass or less.

5. The core resin composition according to claim 1, 2, or 3, wherein the average particle diameter of the particle filler (X) is 1 nm or more and 100 nm or less.

6. The core resin composition according to claim 1, 2, or 3, wherein the polyvinyl alcohol resin has a degree of polymerization of 4000 or less, a degree of saponification of 72.0 mol% or more and 99.8 mol% or less, and a viscosity of 4% by mass aqueous solution of 150 mPa·s or less.

7. The core resin composition according to claim 1, 2, or 3, comprising 0.1% by mass or more and 2.0% by mass or less of an easy-release agent.

8. The core resin composition according to claim 1, 2, or 3, wherein the polyvinyl alcohol resin has a degree of polymerization of 200 to 1000, a degree of saponification of 85 mol% to 99.5 mol%, and a viscosity of 4% by mass aqueous solution of 2 mPa·s to 15 mPa·s.

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