Resin composition

Abstract

The present invention provides a resin composition with which suppression of excessive flow deformation and suppression of deformation speed at ultrahigh temperatures can be achieved while preventing thermal deformation at high temperatures, and a core having excellent water solubility can be produced. The present invention is a resin composition containing a polyvinyl alcohol resin and a filler, wherein the filler contains a water-soluble filler having a solubility of at least 10 g per 100 mL of 80°C water, and the content of the water-soluble filler with respect to the resin composition is 5-40 mass% inclusive.

Description

resin composition

[0001] This invention relates to a resin composition.

[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 technology that uses a resin composition containing polyvinyl alcohol resin and an easy-release agent as a core resin (core resin composition).

[0003] International Publication No. WO2021 / 157375

[0004] However, when using a core resin such as that described in Patent Document 1, while deformation during thermal melting can be suppressed, there is a problem in that the time required for dissolving and removing the core increases. The efficiency of core dissolution and removal is an important factor that directly affects productivity, and there is a need for a core resin that combines heat resistance and water solubility.

[0005] The present invention aims to provide a resin composition that can prevent thermal deformation at high temperatures, suppress excessive flow deformation and deformation rate at ultra-high temperatures, and produce cores with excellent water solubility.

[0006] Disclosure 1 is a resin composition containing a polyvinyl alcohol resin and a filler, wherein the filler contains a water-soluble filler having a solubility of 10 g or more in 100 mL of water at 80°C, and the content of the water-soluble filler in the resin composition is 5% by mass or more and 40% by mass or less. Disclosure 2 is the resin composition according to Disclosure 1, wherein the filler contains only a filler having a melting point of 350°C or more and 5000°C or less. Disclosure 3 is a resin composition according to Disclosure 1, wherein the filler contains a non-water-soluble filler having a solubility of less than 10 g in 100 mL of water at 80°C, and the total surface area A per unit mass of the resin composition of the non-water-soluble filler represented by the following formula (1) is 10 m².２ The above is the resin composition described in Disclosure 1 or 2. A: Total surface area of ​​non-water-soluble filler (m²) ２ ( / g) B: Average particle size of non-water-soluble filler (m) D: Content of non-water-soluble filler in resin composition (mass%) E: Density of non-water-soluble filler (g / m) ３ Disclosure 4 is a resin composition according to any one of Disclosures 1 to 3, wherein the water-soluble filler contains at least one selected from the group consisting of alkali metals and alkaline earth metals. Disclosure 5 is a resin composition according to any one of Disclosures 1 to 4, wherein the water-soluble filler has an average particle size of 0.1 μm or more and 500 μm or less. Disclosure 6 is a resin composition according to any one of Disclosures 1 to 5, wherein the polyvinyl alcohol resin has a degree of polymerization of 4000 or less, a degree of saponification of 72 mol% or more and 99.8 mol% or less, and a viscosity of a 4% by mass aqueous solution of 150 mPa·s or less. Disclosure 7 is a resin composition according to any one of Disclosures 1 to 6, which contains an antioxidant of 0.1% by mass or more and 2% by mass or less. Disclosure 8 is a resin composition according to any one of Disclosures 1 to 7, containing 0.1% to 2% by mass of an easy-release agent and 0.1% to 10% by mass of a plasticizer. Disclosure 9 is a resin composition according to any one of Disclosures 1 to 8, used for making cores in injection molding. The present invention will now be described in detail.

[0007] The inventors investigated adding fillers to resin compositions, but discovered that simply adding fillers resulted in a significantly greater decrease in the water solubility of the core than would have been predicted from the blending ratio. They found that this decrease in water solubility was due to the hydrophobic filler covering the surface of the resin composition, making it difficult for the resin to come into contact with water. Therefore, the inventors found that by combining a polyvinyl alcohol resin with a predetermined water-soluble filler and setting the content of the water-soluble filler in the resin composition within a predetermined range, it is possible to prevent thermal deformation at high temperatures while suppressing excessive flow deformation and deformation speed at ultra-high temperatures, thereby improving water solubility. Furthermore, they found that excellent water solubility could be achieved while suppressing melt deformation even under molding conditions for super engineering plastics, thus completing the present invention.

[0008] <Polyvinyl alcohol resin> The above resin composition contains polyvinyl alcohol resin. By using polyvinyl alcohol resin, it can be easily removed from the molded article 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, more preferably 3400 or less, even more preferably 2300 or less, even more preferably 1200 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 K 6726.

[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 87.0 mol% or more, even more preferably 92.0 mol% or more, particularly 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 K 6726. 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 mass-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 mass-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 above mass-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 K 6726. 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 3 mPa·s or more, more preferably 5 mPa·s or more, more preferably 100 mPa·s or less, and even more preferably 50 mPa·s or less. The viscosity of the above 4% by mass aqueous solution can be measured, for example, by a method in accordance with JIS K 6726 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 unit having a modifying group in the above polyvinyl alcohol resin is preferably 1 mol% or more, more preferably 3 mol% or more, particularly preferably 5 mol% or more, preferably 20 mol% or less, more preferably 15 mol% or less, and particularly preferably 12 mol% or less.

[0017] The content of the above polyvinyl alcohol resin in the above resin composition is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 65% by mass or more, preferably 85% by mass or less, more preferably 75% by mass or less, and still more preferably 70% by mass or less. The above polyvinyl alcohol resin may contain a plurality of types of polyvinyl alcohol resins having different degrees of polymerization, saponification degrees, etc. When the above polyvinyl alcohol resin includes a plurality of types of polyvinyl alcohol resins, the content of the above polyvinyl alcohol resin represents the total content of the plurality of types of polyvinyl alcohol resins.

[0018] The above polyvinyl alcohol resin is obtained by polymerizing a vinyl ester to obtain a polymer, then saponifying, i.e., hydrolyzing, the polymer according to a conventionally known method. An alkali or an acid is generally used as the saponification catalyst.

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

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

[0021] Examples of polymerization catalysts used when polymerizing the above vinyl ester include 2-ethylhexyl peroxydicarbonate (Tianjin McEIT's "TrigonoxEHP"), 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 of these polymerization catalysts may be used alone, or two or more may be used in combination.

[0022] The polyvinyl alcohol resin described above may be a polymer of a vinyl ester and another unsaturated monomer that has been saponified. Other unsaturated monomers include monomers other than the vinyl ester described above that have an unsaturated double bond such as a vinyl group. Specifically, 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, amino group-containing compounds, and the like.

[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] <Filler> The above resin composition contains a filler. In particular, by including a water-soluble filler, water solubility can be improved without impairing heat resistance. The above filler is classified into water-soluble fillers and water-insoluble fillers. In the present invention, a filler with a solubility of 10 g or more in 100 mL of water at 80°C is defined as a water-soluble filler, and a filler with a solubility of less than 10 g in 100 mL of water at 80°C is defined as a water-insoluble filler.

[0025] Preferably, the above filler contains only fillers having a melting point of 350°C or higher and 5000°C or lower. Having the melting point of the filler within this range further enhances heat resistance. A more preferable lower limit for the melting point is 450°C, an even more preferable lower limit is 600°C, a particularly preferable lower limit is 700°C, a more preferable upper limit is 1600°C, an even more preferable upper limit is 1200°C, and a particularly preferable upper limit is 950°C.

[0026] <Water-soluble filler> The above filler contains a water-soluble filler whose solubility in 100 mL of water at 80°C is 10 g or more. To determine the solubility, add a slightly excessive amount of the water-soluble filler to 100 mL of water at 80°C until it no longer dissolves, stir with a magnetic stirrer for 2 hours, and then take approximately 10 g of the supernatant of the dissolved aqueous solution into an aluminum dish. Then dry it in a 95°C oven for 3 hours. Weigh the pre-measured weight of the empty aluminum dish, the weight of the aqueous solution inside, and the weight after drying to determine the weight of the supernatant, the weight of the solute, and the weight of the solvent. Then, refer to the density of water at 80°C to calculate the solubility in 100 mL of water at 80°C.

[0027] The content of the water-soluble filler in the above resin composition is 5% by mass or more and 40% by mass or less. By setting it within this range, it is possible to prevent thermal deformation at high temperatures, suppress excessive flow deformation and deformation rate at ultra-high temperatures, and improve water solubility. The content of the water-soluble filler is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 19% by mass or more, preferably 38% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

[0028] In this invention, by combining a polyvinyl alcohol resin with a predetermined water-soluble filler and setting the content of the water-soluble filler in the resin composition within a predetermined range, it is possible to improve water solubility without impairing heat resistance. The reason why it is possible to improve water solubility in this way is thought to be that the water-soluble filler dissolves before the polyvinyl alcohol resin, thereby increasing the surface area of ​​the polyvinyl alcohol resin that comes into contact with water.

[0029] Examples of materials for the above-mentioned water-soluble filler include those containing at least one selected from the group consisting of alkali metals and alkaline earth metals. Examples of alkali metals include lithium, sodium, potassium, rubidium, and cesium. Examples of alkaline earth metals include calcium, strontium, barium, and radium. The alkali metals and alkaline earth metals may be used individually or in combination of two or more. It is preferable to use salts or halides of alkali metals and alkaline earth metals as the water-soluble filler. Examples of acids constituting the salts include organic acids, inorganic acids, and their acid anhydrides and derivatives. Organic acids, inorganic acids, and their acid anhydrides and derivatives may also be used as water-soluble fillers. Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, and carbonic acid. Examples of the above organic acids include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malic acid, tartaric acid, citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, oleic acid, and p-toluenesulfonic acid. Furthermore, at least one of the halogens selected from the group consisting of sodium halides and potassium halides is preferred. Specific examples of the above water-soluble fillers include sodium chloride, potassium chloride, calcium chloride, potassium nitrate, copper sulfate, anhydrous aluminum potassium sulfate, anhydrous sodium sulfate, sodium carbonate, sodium acetate, and citric acid.

[0030] The water-soluble filler preferably has a melting point of 90°C or more and 5000°C or less. When the melting point of the water-soluble filler falls within the above range, heat resistance can be further improved. A more preferable lower limit of the melting point is 100°C, and a more preferable upper limit is 2000°C. A still more preferable lower limit is 160°C, a still more preferable upper limit is 1600°C, an even more preferable lower limit is 300°C, an even more preferable upper limit is 1200°C, a particularly preferable lower limit is 500°C, a particularly preferable upper limit is 1000°C, a particularly more preferable lower limit is 700°C, and a particularly more preferable upper limit is 950°C. However, when a mixture of a plurality of fillers is used, the average value thereof corresponding to the weight fraction is defined as the melting point specified in the present application.

[0031] The average particle diameter of the water-soluble filler is preferably 0.1 µm or more and 500 µm or less. By setting the average particle diameter within the above range, it is possible to achieve both prevention of thermal deformation at high temperatures, suppression of flow deformation and deformation rate at ultra-high temperatures, and water solubility at a high level. The average particle diameter is more preferably 1 µm or more, still more preferably 5 µm or more, particularly preferably 10 µm or more, more preferably 400 µm or less, still more preferably 300 µm or less, and particularly preferably 250 µm or less. The average particle diameter of the water-soluble filler can be measured, for example, by a particle size distribution analyzer or the like.

[0032] The density of the water-soluble filler is 1 g / cm ３ or more, preferably, 1.4 g / cm ３ or more, more preferably, 1.7 g / cm ３ or more, still more preferably, 1.9 g / cm ３ or more, particularly preferably, 8 g / cm ３ or less, preferably, 6 g / cm ３ or less, more preferably, 4 g / cm ３ or less, still more preferably, 3 g / cm ３ or less, particularly preferably. The density can be measured, for example, by an electronic hydrometer or the like.

[0033] <Non-water-soluble filler> The above filler contains a non-water-soluble filler whose solubility in 100 mL of 80°C water is less than 10 g. By including the above non-water-soluble filler, heat resistance can be increased. The above solubility is calculated by adding a slightly excessive amount of the non-water-soluble filler to 100 mL of 80°C water until it no longer dissolves, stirring with a magnetic stirrer for 2 hours, and then taking about 10 g of the supernatant of the dissolved aqueous solution into an aluminum dish. Then drying it in a 95°C oven for 3 hours. The solubility is calculated by weighing the weight of the empty aluminum dish (which has been measured in advance), the weight of the aqueous solution placed inside, and the weight after drying.

[0034] In the above resin composition, the total surface area of ​​the non-water-soluble filler per unit mass of the core resin composition, calculated by the following formula (1), is 10 m². ２ It is preferable that the amount is 1 / g or more. A: Total surface area of ​​non-water-soluble filler (m²) ２ (g) B: Average particle size of non-water-soluble filler (m) C: Amount of resin composition (g) D: Content of non-water-soluble filler in resin composition (mass%) E: Density of non-water-soluble filler (g / m ３ )

[0035] The above equation (1) is explained by the following equation (2). In other words, the total surface area is the surface area (m²) of each non-water-soluble filler. ２ ) (4π × (B / 2) ２ The number of non-water-soluble fillers per gram of the resin composition is calculated by multiplying the amount of non-water-soluble fillers per gram of the resin composition (g) (C (g) × D (mass%) / 100 ÷ C (g)) by the mass per non-water-soluble filler (g) (density × average volume per non-water-soluble filler = E × 4 / 3π (B / 2) ３It is calculated by dividing by ). Regarding the density of the non-water-soluble filler mentioned above, even if the non-water-soluble filler 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. Since it is important that the total surface area of ​​the non-water-soluble filler does not take into account the area of ​​depressions and pores, in formula (2) above the non-water-soluble filler is approximated as a sphere and the total surface area of ​​the non-water-soluble filler per unit mass of resin composition is calculated. Total surface area is 10 m ２ By setting the amount to 1 / g or more, the heat resistance can be sufficiently enhanced, resulting in a resin composition that does not melt or deform even under the molding conditions of super engineering plastics. The total surface area is 15 m². ２ Preferably 20 m ２ More preferably 23m / g or more. ２ More preferably 28m / g or more. ２ A value of 58m or more is particularly preferred. ２ Preferably less than / g, and 51m ２ More preferably less than / g, and 45m ２ It is even more preferable to be less than or equal to 41m ２ A value of less than or equal to / g is particularly preferred. In particular, a total surface area of ​​10 m² ２ By setting the amount to 1 / g or more, it is possible to achieve extremely high heat resistance, such as a deflection temperature of 160°C or higher, an MFR of 230°C, and a load of 21.6 kg, resulting in a minimum of 30 g / 10 min. Note that one type of non-water-soluble filler 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 can be calculated by determining the total surface area of ​​each non-water-soluble filler using formula (1) above and then summing them up.

[0036] The total surface area of ​​the non-water-soluble filler per unit mass can be adjusted by the average particle diameter, density, and amount of the non-water-soluble filler. Furthermore, while the surface area of ​​the non-water-soluble filler 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 higher-order structures formed by multiple connected or overlapping particles.

[0037] The average particle size of the above-mentioned water-insoluble filler is preferably 1 nm or more, and preferably 200 nm or less. By setting it within this range, the surface area of ​​the water-insoluble filler in the resin composition can be kept within a certain range, and the heat resistance required for the resin composition can be imparted. The average particle size is more preferably 2 nm or more, even more preferably 3 nm or more, even more preferably 4 nm or more, even more preferably 150 nm or less, even more preferably 70 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 it within this range, the water-insoluble filler and the polyvinyl alcohol resin can be easily kneaded and mixed. The average particle size of the above-mentioned water-insoluble filler can be measured, for example, by a particle size distribution analyzer or the like.

[0038] The density of the above non-water-soluble filler 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 electronic hydrometer. Regarding the density of the non-water-soluble filler, even if the non-water-soluble filler 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.

[0039] Examples of materials for the above-mentioned water-insoluble filler include metals, metal oxides, non-metallic oxides, ceramics, carbon materials, and glass. Resin particles with a melting point of 200°C or higher can also be used as the water-insoluble filler. Examples of the above-mentioned metal oxides include titanium oxide, aluminum oxide, calcium oxide, lithium oxide, molybdenum oxide, vanadium oxide, zinc oxide, nickel oxide, cesium oxide, and iron oxide. Examples of the above-mentioned non-metallic oxides include silicon dioxide (SiO₂).２ Examples include the following. 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, diamond, etc. 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, polyether ether ketone (PEEK), etc.

[0040] The content of the water-insoluble filler in the above resin composition 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 water-insoluble 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, and even more preferably 35% by mass or less.

[0041] <Flake-like or plate-like compounds> The above resin composition may further contain flake-like or plate-like compounds. By including flake-like or plate-like compounds, the heat resistance can be further enhanced. In this invention, the flake-like or plate-like compounds are different from the above-mentioned water-soluble fillers and non-water-soluble fillers.

[0042] The density of the above-mentioned flaky or plate-like compound 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, 4.2 g / cm³. ３ The following is preferable: 3.5 g / cm³ ３ The following is more preferable: 3.0 g / cm³ ３ The following is even more preferable. The density can be measured, for example, by an electronic hydrometer or the like.

[0043] Examples of the above-mentioned flake-like or plate-like compounds 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 a 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 providing heat resistance, it is desirable that the melting point is 350°C or higher and that it is chemically stable even at 350°C. As the layered silicate compound, mica is preferred, and fluorinated mica and sodium tetrasilicon mica are more preferred.

[0044] The content of the flake-like or plate-like compound in the above resin composition is preferably 3% by mass or more, and preferably 50% by mass or less. Heat resistance can be further improved by setting it within this range. The content of the flake-like or plate-like compound 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.

[0045] In the above resin composition, the ratio of the content of the water-insoluble filler to the content of the flake-like or plate-like compound 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. Within this range, it is possible to achieve a high level of both moldability when injection molding as a core and heat resistance when used as a core.

[0046] In the above resin composition, the density ratio of the non-water-soluble filler to the flake-like or plate-like compound (non-water-soluble filler / flak-like or plate-like compound) 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.

[0047] In the above resin composition, the ratio of the content of the water-soluble filler to the water-insoluble filler is preferably 1:8 to 10:1, more preferably 1:6 to 2:1, even more preferably 1:4 to 1:1, and particularly preferably 1:3 to 1:2.

[0048] In the above resin composition, the total content of the non-water-soluble filler and the flake-like or plate-like compound 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 weight or more, and even more preferably 40% by weight or less.

[0049] <Removable Agent> The above resin composition may contain a removable agent. Including a removable agent makes it easier to remove the core resin from the molded article.

[0050] 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.

[0051] The content of the release agent in the above resin composition 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 inside 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.

[0052] <Plasticizer> The above resin composition may contain a plasticizer. Including a plasticizer can improve moldability.

[0053] 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.

[0054] The content of the plasticizer in the above resin composition 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.

[0055] <Crosslinking Agent> The above 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. Alternatively, a metal salt of the above acid may also be used.

[0056] 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.

[0057] 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.

[0058] <Other> The above resin composition may also contain additives such as antioxidants, colorants, defoamers, UV absorbers, and preservatives.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The content of the antioxidant in the above resin composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, particularly preferably 0.7% by mass or more, preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.2% by mass or less.

[0064] The above resin composition preferably has a melt flow rate (MFR) of 30 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 cores that exhibit high heat resistance and do not deform even under high-temperature conditions such as those for molding super engineering plastics. The above 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 cores, and depends on the capabilities of the molding machine. The above MFR can be measured, for example, by a method in accordance with ASTM D 1238.

[0065] 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 fillers (water-soluble fillers, non-water-soluble fillers), average particle size, total surface area, the type and amount of flake-like or plate-like compounds, crosslinking agents, plasticizers, release agents, etc.

[0066] The above resin composition preferably has a deflection temperature of 160°C or higher, as measured by a predetermined method. This range allows for the production of cores that exhibit high heat resistance and do not deform even under high-temperature conditions such as those used for molding super engineering plastics. A deflection temperature of 162°C or higher is more preferable, and 165°C or higher is even more preferable. While there are no particular upper limits to the deflection temperature, 230°C or lower is preferred. The deflection temperature can be measured, for example, by ASTM D 648.

[0067] The deflection temperature mentioned above can be adjusted by the composition and amount of polyvinyl alcohol resin, the type and amount of fillers (water-soluble fillers, non-water-soluble fillers), the average particle size, the total surface area, the type and amount of flake-like or plate-like compounds, crosslinking agents, plasticizers, release agents, etc.

[0068] The above resin composition can be obtained by mixing, for example, a polyvinyl alcohol resin, a water-soluble filler, a water-insoluble filler, a flake-like or plate-like compound, 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.

[0069] The above resin composition is preferably used for the production of cores in injection molding (resin composition for cores). This more preferably achieves the effects of high heat resistance and excellent water solubility. Cores can be produced by molding the above resin composition for cores. The molding method is not particularly limited, but examples include injection molding.

[0070] 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 has particularly excellent heat resistance, it is possible to prevent melting and deformation even when using super engineering plastics (super engineering plastics) that are molded at high temperatures as the material.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] According to the present invention, it is possible to provide a resin composition that can prevent thermal deformation at high temperatures, suppress excessive flow deformation and deformation rate at ultra-high temperatures, and produce cores with excellent water solubility.

[0075] 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.

[0076] (Synthesis Example 1) [PVA1 (Degree of Saponification 98.0 mol%, Degree of Polymerization 300)] 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 １ The 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 K 6726. The degree of polymerization of the polyvinyl alcohol resin was determined by measuring the viscosity of the aqueous solution according to JIS K 6726. As a result, the degree of saponification and the degree of polymerization were 98.0 mol% and 300, 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 6726, and was 4 mPa·s.

[0077] (Synthesis Example 2) [PVA2 (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 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%, 450, and 6.5 mPa·s, respectively.

[0078] (Synthesis Example 3) [PVA3 (Degree of Saponification 88.0 mol%, Degree of Polymerization 550)] By performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 30.0 parts by mass and the amount of methanol solution of sodium hydroxide added was changed to 0.01 mol% of the amount of 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 88.0 mol%, 550, and 5.5 mPa·s, respectively.

[0079] (Synthesis Example 4) [PVA4 (Degree of Saponification 88.0 mol%, Degree of Polymerization 1800)] By performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 80.0 parts by mass and the amount of methanol solution of sodium hydroxide added was changed to 0.01 mol% of the amount of sodium hydroxide relative to vinyl acetate, PVA4 was obtained with a degree of saponification, degree of polymerization, and viscosity of a 4% aqueous solution of 88.0 mol%, 1800, and 25.0 mPa·s, respectively.

[0080] (Synthesis Example 5) [PVA5 (Degree of Saponification 98.0 mol%, Degree of Polymerization 1800)] By performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 80.0 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, PVA5 was obtained with a degree of saponification, degree of polymerization, and viscosity of a 4% aqueous solution of 98.0 mol%, 1800, and 30.0 mPa·s, respectively.

[0081] The following were used as water-soluble fillers, non-water-soluble fillers, antioxidants, and release agents other than polyvinyl alcohol resin: <Water-soluble fillers> Water-soluble filler 1: Anhydrous potassium aluminum sulfate [Anhydrous AlK sulfate] Taiace K20 manufactured by Daimei Chemical Industry Co., Ltd., solubility 36.4 g, average particle size 5 μm, melting point 92.5 °C, density 1.7 g / cm³ ３ Water-soluble filler 2: Sodium acetate [Na acetate]. Sodium acetate manufactured by Nacalai Tesque Co., Ltd., solubility 46.4 g, melting point 324°C, density 1.5 g / cm³. ３Water-soluble filler 3: Anhydrous sodium sulfate [anhydrous sodium sulfate] Manufactured by Tomita Pharmaceutical Co., Ltd. Anhydrous sodium sulfate 300M, solubility 19.5g, melting point 884℃, density 2.7g / cm³ ３ <Non-water-soluble fillers> Non-water-soluble filler 1: Carbon black [CB] Manufactured by Tokai Carbon Co., Ltd. TOKA BLACK #5500, solubility 0.1 g or less, average particle size 25 nm [0.025 μm], density 1.9 g / cm³ ３ Non-water-soluble filler 2: Carbon black [CB], manufactured by Tokai Carbon Co., Ltd., SEAST TA, solubility 0.1 g or less, average particle size 122 nm [0.122 μm], density 1.9 g / cm³ ３ Non-water-soluble filler 3: Titanium oxide [TiO] ２ ] PF-690, manufactured by Ishihara Sangyo Co., Ltd., solubility 0.1 g or less, average particle size 210 nm [0.21 μm], density 4.0 g / cm³ ３ Non-water-soluble filler 4: Aluminum oxide, manufactured by Sigma-Aldrich, nanopowder, <50 nm particle size (TEM), solubility less than 0.1 g, average particle size 35 nm [0.035 μm], density 2.65 g / cm³ ３ Non-water-soluble filler 5: Silicon dioxide [SiO ２ ], Sigma-Aldrich nanopowder, 10-20nm particle size (BET), 99.5% trace metals basis, solubility 0.1g or less, average particle size 15nm [0.015μm], density 4.00g / cm ３<Antioxidant> Sumitomo Chemical Co., Ltd., SumiLizer GP (Antioxidant possessing both phenolic and phosphorus functional groups in a single molecule) <Easy Stripping Agent> Kao Corporation, Electro Stripper TS-5 (Glycerin fatty acid ester type (glycerin monostearate)) <Plasticizer> Fujifilm Wako Pure Chemical Industries, Ltd., Diglycerin (Polyhydric alcohol) The average particle size of the water-soluble and non-water-soluble fillers was taken from catalog values. The density was measured using Shimadzu Corporation's AccuPic II 1345. Furthermore, the solubility of the water-soluble and non-water-soluble fillers was measured using the following method: [Solubility Measurement] A slightly excessive amount of water-soluble or non-water-soluble filler was added to 100 mL of 80°C water until it no longer dissolved, and after stirring for 2 hours using a magnetic stirring bar, approximately 10 g of the supernatant of the dissolved aqueous solution was placed in an aluminum dish. Then it was dried in a 95°C oven for 3 hours. The weights of the empty aluminum tray, the aqueous solution placed inside, and the aluminum tray containing the dried residue were weighed, all of which had been measured beforehand. The weight of the solute was calculated by subtracting the weight of the empty aluminum tray from the weight of the aluminum tray containing the dried residue. The weight of the solvent was obtained by subtracting the weight of the solute from the weight of the measured solution (supernatant). From the obtained weight of the supernatant, weight of the solute, and weight of the solvent, the solubility in 100 mL of water at 80°C was calculated by referring to the density of water at 80°C.

[0082] (Example 1) Polyvinyl alcohol resin, water-soluble filler, and non-water-soluble filler were mixed according to the types and formulations 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 resin composition.

[0083] (Examples 2-5, 8) Polyvinyl alcohol resin, water-soluble filler, and non-water-soluble filler were mixed in the types and proportions shown in Table 1 to obtain resin composition pellets in the same manner as in Example 1.

[0084] (Example 6) Polyvinyl alcohol resin, water-soluble filler, non-water-soluble filler, and antioxidant were mixed in the types and proportions shown in Table 1 to obtain resin composition pellets in the same manner as in Example 1.

[0085] (Example 7) Polyvinyl alcohol resin, water-soluble filler, water-insoluble filler, antioxidant, and release agent were mixed in the types and proportions shown in Table 1 to obtain resin composition pellets in the same manner as in Example 1.

[0086] (Comparative Examples 2 and 3) Polyvinyl alcohol resin, water-soluble filler, and non-water-soluble filler were mixed in the types and formulations shown in Table 1, and resin composition pellets were obtained in the same manner as in Example 1.

[0087] (Comparative Example 1) A resin composition pellet was obtained in the same manner as in Example 1, except that a water-soluble filler was not added and the polyvinyl alcohol resin and a water-insoluble filler were mixed to the formulation shown in Table 1.

[0088] (Examples 9-15) Polyvinyl alcohol resin, water-soluble filler, non-water-soluble filler, antioxidant, release agent, and plasticizer were mixed in the types and proportions shown in Table 2 to obtain resin composition pellets in the same manner as in Example 1.

[0089] (Comparative Examples 4-5) Polyvinyl alcohol resin, water-soluble filler, and non-water-soluble filler were mixed in the types and formulations shown in Table 2, and resin composition pellets were obtained in the same manner as in Example 1.

[0090] (Evaluation Method) The obtained resin compositions were evaluated using the following method. The results are shown in Tables 1 and 2. Note that when preparing the test specimens used in "(3) Deflection Temperature" below by injection molding, molding may not be possible if the melt fluidity of the resin is low. In this case, it was classified as "unmold," and evaluation of "(2) Solubility (Water-soluble)" and "(4) Melt Viscosity" was not performed in addition to "(3) Deflection Temperature."

[0091] (1) Total surface area of ​​non-water-soluble filler Based on the following formula (1), the total surface area of ​​non-water-soluble filler per unit mass of resin composition was calculated. A: Total surface area of ​​non-water-soluble filler (m²) ２ ( / g) B: Average particle size of non-water-soluble filler (m) D: Content of non-water-soluble filler in resin composition (mass%) E: Density of non-water-soluble filler (g / m) ３ )

[0092] (2) Solubility (water solubility) Two g of the obtained resin composition was added to 1 L of 80°C hot water and stirred with a magnetic stirrer for 60 minutes. After removing the mixture and drying it in an 80°C hot air circulating dryer for 24 hours, the weight of the resin composition was measured and the solubility (weight %) was calculated.

[0093] (3) Deflection temperature was measured in accordance with ASTM D 648. Specifically, it was measured using the edgewise method with an HDT test apparatus 3M-2V (manufactured by Toyo Seiki Seisakusho Co., Ltd.), with a support distance of 100 mm, bending stress of 1.82 MPa, specified deflection of 1.0 mm, temperature rise rate of 2 °C / min, and medium: silicone oil. The test specimens were strips with a width of 12.7 mm, a length of 127 mm, and a thickness of 3 mm, manufactured using an injection molding machine.

[0094] (4) Melt viscosity (melt flow rate, MFR) The melt flow rate (MFR) of the resin composition was measured using a melt index tester No. 120-FWP (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) in accordance with ASTM D 1238, under the conditions of 230°C, a load of 10 kg, and 10 minutes.

[0095]

[0096]

[0097] According to the present invention, it is possible to provide a resin composition that can prevent thermal deformation at high temperatures, suppress excessive flow deformation and deformation rate at ultra-high temperatures, and produce cores with excellent water solubility.

Claims

1. A resin composition comprising a polyvinyl alcohol resin and a filler, wherein the filler contains a water-soluble filler having a solubility of 10 g or more in 100 mL of water at 80°C, and the content of the water-soluble filler in the resin composition is 5% by mass or more and 40% by mass or less.

2. The resin composition according to claim 1, wherein the filler contains only fillers having a melting point of 350°C or more and 5000°C or less.

3. The filler contains a water-insoluble filler whose solubility in 100 mL of water at 80°C is less than 10 g, and the total surface area A per unit mass of the resin composition of the water-insoluble filler represented by the following formula (1) is 10 m². ２ The resin composition according to claim 1 or 2. A: Total surface area of ​​non-water-soluble filler (m²) ２ ( / g) B: Average particle size of non-water-soluble filler (m) D: Content of non-water-soluble filler in resin composition (mass%) E: Density of non-water-soluble filler (g / m) ３ ) 4. The resin composition according to any one of claims 1 to 3, wherein the water-soluble filler contains at least one selected from the group consisting of alkali metals and alkaline earth metals.

5. The resin composition according to any one of claims 1 to 4, wherein the water-soluble filler has an average particle size of 0.1 μm or more and 500 μm or less.

6. The resin composition according to any one of claims 1 to 5, wherein the polyvinyl alcohol resin has a degree of polymerization of 4000 or less, a degree of saponification of 72 mol% or more and 99.8 mol% or less, and a viscosity of a 4% by mass aqueous solution of 150 mPa·s or less.

7. The resin composition according to any one of claims 1 to 6, which contains 0.1% by mass or more and 2% by mass or less of an antioxidant.

8. A resin composition according to any one of claims 1 to 7, comprising 0.1% by mass or more and 2% by mass or less of an easy-release agent, and 0.1% by mass or more and 10% by mass or less of a plasticizer.

9. A resin composition used for making a core in injection molding, according to any one of claims 1 to 8.

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