Core resin composition and core

Abstract

The present invention provides a core resin composition that exhibits high heat resistance and can be used to produce a core that does not deform even under molding conditions of super engineering plastics. Also provided is a core obtained by using the core resin composition. The present invention is a core resin composition that contains a polyvinyl alcohol resin and has a melt flow rate (MFR) of 35 g / 10 min or less under a load condition of 10 kg at 230°C.

Description

Core resin composition and core

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

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

[0003] International Publication No. 2021 / 157375

[0004] Furthermore, in recent years, from the viewpoint of weight reduction, studies have been conducted to replace materials for automobile and other parts with super engineering plastics (super engineering plastics) that have excellent heat resistance. As a result of extensive research, the present inventors have discovered a problem in 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 disclosed in Patent Document 1 is used, the core resin deforms during molding. If the core resin deforms during molding, a molded product having the desired shape cannot be obtained.

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

[0006] Disclosure (1) is a core resin composition containing a polyvinyl alcohol resin and having a melt flow rate (MFR) of 35 g / 10 min or less at 230°C under a 10 kg load. Disclosure (2) is a core resin composition of Disclosure (1) in which the polyvinyl alcohol resin has a weight average molecular weight (Mw) of 200,000 or less and a degree of saponification of 72% or more and 99.8% or less. Disclosure (3) is a core resin composition of Disclosure (1) or (2) in which the polyvinyl alcohol resin has a viscosity of 30 mPa s or less in a 4% by mass aqueous solution. Disclosure (4) is a core resin composition further containing a particulate filler, wherein the total surface area of ​​the particulate filler per unit mass of the core resin composition calculated by the following formula (1) is 10 m ２ / g or more. A: total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) B: average particle diameter (m) of the particle filler D: content (mass%) of the particle filler in the resin composition for cores E: density (g / m ３Disclosure (5) is the core resin composition of Disclosure (4), in which the average particle diameter of the particulate filler is 1 nm or more and 100 nm or less. Disclosure (6) is the core resin composition of Disclosure (4) or (5), in which the content of the particulate filler is 5 mass% or more and 70 mass% or less. Disclosure (7) is the core resin composition of Disclosure (1), (2), (3), (4), (5), or (6), in which the easy-release agent is 0.1 mass% or more and 2 mass% or less. Disclosure (8) is the core resin composition of Disclosure (7), in which the easy-release agent is a glycerin fatty acid ester-based compound. Disclosure (9) is the core resin composition of Disclosure (8), in which the glycerin fatty acid ester-based compound is at least one selected from the group consisting of monoglyceride stearic acid ester, monoglyceride oleic acid ester, and diglyceride lauric acid ester. The present disclosure (10) is a core resin composition according to the present disclosure (1), (2), (3), (4), (5), (6), (7), (8), or (9), which is in the form of pellets. The present disclosure (11) is a core made using the core resin composition according to the present disclosure (1), (2), (3), (4), (5), (6), (7), (8), (9), or (10). The present invention will be described in detail below.

[0007] As a result of extensive research, the present inventors have discovered that a core resin composition containing a polyvinyl alcohol resin can exhibit high heat resistance by adjusting the melt flow rate (MFR) at 230°C under a load of 10 kg. Furthermore, they have discovered that by using such a core resin composition, it is possible to manufacture cores that do not deform even under high-temperature conditions, such as those used to mold super engineering plastics, and have thus completed the present invention. The MFR can be measured in accordance with ASTM D 1238, except for the above-mentioned conditions.

[0008] The core resin composition has a melt flow rate (MFR) of 35 g / 10 min or less under conditions of 230°C and a 10 kg load. This configuration exhibits high heat resistance, enabling the production of cores that do not deform even under high-temperature conditions such as those used for molding super engineering plastics. The MFR is preferably 25 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. The lower limit of the MFR is not particularly limited, but it should be sufficient as long as it can be molded using a molding machine for molding cores, and depends on the capabilities of the molding machine. The MFR can be measured, for example, using an initial weight of 7.5 g and a measurement time interval of 0.25 minutes, according to a method in accordance with ASTM D 1238.

[0009] The melt flow rate (MFR) under the above-mentioned conditions of 230°C and 10 kg load can be adjusted by the composition, such as the weight average molecular weight and degree of saponification, of the polyvinyl alcohol resin, the blending amount, the type, blending amount, average particle diameter, total surface area, and other shapes of particulate fillers, crosslinkers, plasticizers, mold-releasing agents, etc., of the particulate filler described below. The total surface area of ​​the particulate filler has a particularly large contribution, and adjusting the total surface area can reduce the MFR through the interaction between the polyvinyl alcohol resin and the particulate filler. Secondarily, the MFR can also be adjusted by the type of filler, the molecular weight of the polyvinyl alcohol resin, and the degree of saponification of the polyvinyl alcohol resin. Examples of other shapes of particulate fillers include plate-shaped, needle-shaped, rugby-shaped, fibrous, and higher-order structures in which primary particles are linked (e.g., chain-shaped, agyuroramate-shaped, layer-shaped), etc.

[0010] <Polyvinyl alcohol resin> The core resin composition contains a polyvinyl alcohol resin. By using a polyvinyl alcohol resin, it can be easily removed from the molded body by immersing it in water, for example.

[0011] The degree of polymerization of the polyvinyl alcohol resin is preferably 4000 or less. When the degree of polymerization is 4000 or less, the resin can exhibit sufficient 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, and is preferably 3400 or less, more preferably 2300 or less, even more preferably 1200 or less, and even more preferably 900 or less. The degree of polymerization can be determined, for example, by measuring the viscosity of polyvinyl acetate before saponification by gel permeation chromatography (GPC) or by measuring the viscosity of an aqueous solution in accordance with JIS K6726.

[0012] The saponification degree of the polyvinyl alcohol resin is preferably 72 mol% or more and preferably 99.8 mol% or less. By adjusting the saponification degree within the above range, the resin can exhibit sufficient solubility in water. The saponification degree is more preferably 80 mol% or more, even more preferably 87 mol% or more, even more preferably 92 mol% or more, particularly preferably 95 mol% or more, more preferably 99.5 mol% or less, and even more preferably 99 mol% or less. The saponification degree can be measured, for example, by a method conforming to JIS K6726. The saponification degree indicates the proportion of vinyl ester units that can be converted to vinyl alcohol units by saponification that are actually converted to vinyl alcohol units. The saponification degree can be controlled, for example, by adjusting the saponification conditions, i.e., the hydrolysis conditions.

[0013] The polyvinyl alcohol resin may be either an unmodified polyvinyl alcohol resin or a modified polyvinyl alcohol resin. Here, the term "unmodified polyvinyl alcohol resin" refers to a polyvinyl alcohol resin containing only vinyl ester units and vinyl alcohol units, while the term "modified polyvinyl alcohol resin" refers to a modified polyvinyl alcohol resin containing structural 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 include, in addition to the functional groups, their salts, such as sodium salts and potassium salts.

[0014] The content of the structural unit having a modifying group in the polyvinyl alcohol resin is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, and is preferably 20 mol% or less, more preferably 15 mol% or less, and even more preferably 12 mol% or less.

[0015] The weight average molecular weight (Mw) of the polyvinyl alcohol resin is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 15,500 or more, particularly preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 40,000 or less. When two or more polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) of the entire polyvinyl alcohol resin is calculated based on the weight average molecular weight of each resin and its weight fraction, and is obtained by summing the values ​​obtained by multiplying the weight average molecular weight of each polyvinyl alcohol resin by its weight fraction. When two or more polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 15,500 or more, particularly more preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, and particularly preferably 40,000 or less. When a plasticizer is further contained, the weight average molecular weight of the plasticizer and the entire PVA should be included in the calculation of the weight average molecular weight as the average molecular weight of the entire matrix, and the weight average molecular weight (Mw) is calculated based on the weight average molecular weight of each resin and its weight fraction as described above, and is obtained by summing the values ​​obtained by multiplying the weight average molecular weight of each plasticizer and polyvinyl alcohol resin by their weight fractions. When a plasticizer and one or more polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 14,000 or more, particularly preferably 15,500 or more, even more particularly preferably 20,000 or more, especially more preferably 22,000 or more, and is 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.

[0016] The number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 4,000 or more, more preferably 4,500 or more, and even more preferably 5,000 or more, and is preferably 90,000 or less, more preferably 60,000 or less, and even more preferably 30,000 or less.

[0017] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 1.0 or more, more preferably 1.2 or more, even more preferably 1.4 or more, even more preferably 1.6 or more, and preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.5 or less, and even more preferably 2.0 or less. The weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined, for example, by gel permeation chromatography (GPC), by measuring the polyvinyl ester before saponification by GPC, by measuring the polyvinyl ester obtained by re-esterifying the polyvinyl alcohol resin by GPC, or by measuring the viscosity of an aqueous solution in accordance with JIS K6726. For example, using polystyrene as the standard, columns such as TSKgel (Tosoh Corporation), PLgel (AMR Corporation), KF-806, and KF-807 (Shodex) can be used.

[0018] The polyvinyl alcohol resin preferably has a 4% by mass aqueous solution viscosity of 30 mPa·s or less. A 4% by mass aqueous solution viscosity of 30 mPa·s or less can provide fluidity suitable for injection molding and appropriate water solubility when used as a core. The 4% by mass aqueous solution viscosity is preferably 3 mPa·s or more, more preferably 5 mPa·s or more, and is preferably 20 mPa·s or less, more preferably 10 mPa·s or less. The 4% by mass aqueous solution viscosity can be measured, for example, by a method in accordance with JIS K6276 3.11.1 Rotational Viscosity Meter Method.

[0019] The content of the polyvinyl alcohol resin in the core resin composition is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 65% ​​by mass or more, and preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. The polyvinyl alcohol resin may contain multiple types of polyvinyl alcohol resins with different degrees of polymerization, saponification, etc. When the polyvinyl alcohol resin contains multiple types of polyvinyl alcohol resins, the content of the polyvinyl alcohol resin represents the total content of the multiple types of polyvinyl alcohol resins.

[0020] The polyvinyl alcohol resin can be obtained by polymerizing a vinyl ester to obtain a polymer, and then saponifying the polymer, i.e., by hydrolysis, in accordance with a conventionally known method. An alkali or an acid is generally used as a saponification catalyst.

[0021] Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, and vinyl benzoate.

[0022] The method for polymerizing the vinyl ester is not particularly limited, but examples thereof include solution polymerization, bulk polymerization, and suspension polymerization.

[0023] Examples of polymerization catalysts used in polymerizing the vinyl ester include 2-ethylhexyl peroxydicarbonate ("Trigonox EHP" manufactured by Tianjin McEIT Co., Ltd.), 2,2'-azobisisobutyronitrile (AIBN), t-butyl peroxyneodecanoate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di-cetyl peroxydicarbonate, and di-s-butyl peroxydicarbonate. One type of the polymerization catalyst may be used alone, or two or more types may be used in combination.

[0024] The polyvinyl alcohol resin may be a saponified polymer of a vinyl ester and another unsaturated monomer. Examples of the other unsaturated monomer include monomers other than the vinyl esters, which have an unsaturated double bond, such as a vinyl group. Specific examples include olefins, (meth)acrylic acid and salts thereof, (meth)acrylic acid esters, unsaturated acids other than (meth)acrylic acid, salts and esters thereof, (meth)acrylamides, N-vinylamides, vinyl ethers, nitriles, vinyl halides, allyl compounds, vinylsilyl compounds, isopropenyl acetate, sulfonic acid group-containing compounds, and amino group-containing compounds.

[0025] Examples of olefins include ethylene, propylene, 1-butene, and isobutene. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of unsaturated acids other than (meth)acrylic acid, and 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 vinyl silyl compounds include vinyltrimethoxysilane. Examples of sulfonic acid group-containing compounds include (meth)acrylamidoalkanesulfonic acids such as (meth)acrylamidopropanesulfonic acid and their salts, and olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid and their salts. Examples of amino group-containing compounds include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0026] <Particle Filler> The core resin composition preferably further contains a particle filler. By containing a particle filler, heat resistance can be further improved.

[0027] In the core resin composition, the total surface area of ​​the particle filler per unit mass of the core resin composition calculated by the following formula (1) is 10 m ２ / g or more is preferred. A: total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) B: Average particle diameter of particle filler (m) C: Amount of resin composition for core (g) D: Content of particle filler in resin composition for core (% by mass) E: Density of particle filler (g / m ３ The above formula (1) can be explained by the following formula (2). That is, the total surface area is the surface area per particle filler (m ２ ) (4π × (B / 2) ２ The number of particle fillers per 1 g of the core resin composition is calculated by multiplying the content (g) of particle fillers per 1 g of the core resin composition (C (g) × D (mass %) / 100 ÷ C (g)) by the mass (g) per particle filler (density × average volume per particle filler = E × 4 / 3 × π(B / 2) ３ ) is calculated. Regarding the density of the particulate filler, even if the particulate filler is a hollow particle or a porous particle, a particle density is adopted that takes into account the volume including the cavities and pores inside the particle. Since it is important not to take into account the area of ​​the depressions or pores in the total surface area of ​​the particulate filler, in the above formula (2), the particulate filler is approximated as a sphere and the total surface area of ​​the particulate filler per unit mass of the core resin composition is calculated. The total surface area per unit mass is calculated by dividing the total surface area per unit mass by 10 m ２ By adjusting the total surface area per unit mass to 15 m or more, it is possible to further increase the heat resistance and obtain a resin composition for a core that does not deform even under the molding conditions of super engineering plastics. ２ / g or more is more preferable, and 20m ２ / g or more is more preferable, and 23m ２ / g or more is even more preferable, and 28m ２ / g or more is particularly preferred, and 35m ２ / g or more is particularly preferred. The upper limit of the total surface area per unit mass is not particularly limited, but is naturally determined by the average particle size and the amount of addition of the particulate filler. There is no particular upper limit for the total surface area, but to increase the surface area, the particle size must be small, and if the particle size is too small, the effect of the particulate filler will be reduced. One type of particulate 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 per unit mass can be determined by calculating the total surface area of ​​each particulate filler using the above formula (1) for each particulate filler and adding them up.

[0028] The total surface area of ​​the particulate filler per unit mass can be adjusted by the average particle size, density, and amount of the particulate filler. The surface area of ​​the particulate filler is calculated from the average particle size, density, and amount of the primary particles, but the particle shape is not necessarily limited to a spherical shape. Other than spherical shapes, for example, plate-like, needle-like, rugby-like, hollow, porous, etc. are possible, and the particulate filler may have a higher-order structure in which multiple such shapes are connected or overlapped.

[0029] The average particle diameter of the particulate filler is preferably 1 nm or more and preferably 100 nm or less. By setting the average particle diameter within the above range, the surface area of ​​the particulate filler in the core resin composition can be set within a certain range, thereby imparting the necessary heat resistance to the resin composition. 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, 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 the average particle diameter within the above range, the particulate filler and the polyvinyl alcohol resin can be easily kneaded and mixed. The average particle diameter of the particulate filler can be measured, for example, using a particle size distribution measuring device.

[0030] The density of the particle filler is 0.5 g / cm ３ More than 0.7 g / cm ３ More preferably, 0.9 g / cm ３More preferably, 1.1 g / cm ３ More than 22 g / cm is particularly preferred. ３ Preferably, 13 g / cm or less ３ More preferably, 6 g / cm or less ３ More preferably, 4.5 g / cm ３ The following is particularly preferred. The density can be measured, for example, by an electronic densitometer. Even when the particle filler is a hollow particle or a porous particle, the particle density is determined by taking into account the volume including the cavities and pores inside the particle.

[0031] Examples of materials for the particle filler include metals, metal oxides, ceramics, carbon materials, and glass. Furthermore, resin particles having a melting point of 200°C or higher can also be used as the particle filler. 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 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 standpoints of cost performance, availability, and the like. Examples of resins having a melting point of 200°C or higher include polyethylene terephthalate, polyamide, aromatic polyamide (aramid), polyimide, and polyether ether ketone (PEEK).

[0032] The content of the particulate filler in the core resin composition is preferably 5% by mass or more and preferably 70% by mass or less. By setting the content within this range, heat resistance can be improved. The content of the particulate filler is more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 19% by mass or more, more preferably 50% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0033] <Crosslinking Agent> The core resin composition may contain a crosslinking agent. Examples of the crosslinking agent include oxoacids, boron compounds, divalent or higher metal hydroxides, diamines, polyamines, etc. Metal salts of the above acids may also be used.

[0034] Examples of the oxoacid include boric acid, silicic acid, phosphorous acid, polycarboxylic acid, and hydroxycarboxylic acid. The polycarboxylic acid is preferably an acid having two or more carboxyl groups, and the hydroxycarboxylic acid is preferably an acid having two or more carboxyl groups. Metal salts of the above acids may also be used. Among the above oxoacids, boric acid is particularly preferred. By using boric acid, a temporary protective material can be obtained that has sufficient water resistance during processing and can be easily removed with warm water when removal becomes necessary. Examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid. Examples of the boron compound include, in addition to the boric acids listed as the oxoacids, salts of boric acid. The boron compound may also be a hydrate. Examples of the salts of boric acid include borax, alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as calcium salts and magnesium salts, aluminum salts, and organic amine salts such as triethylamine, triethanolamine, morpholine, piperazine, and pyrrolidine. Among these, boric acid and borax are preferred.

[0035] Examples of the polycarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, poly(meth)acrylic acid, etc. Of these, succinic acid is preferred. Examples of the hydroxycarboxylic acid include glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, cytosine acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineraidic acid, cerebronic acid, quinic acid, shikimic acid, hydroxybenzoic acid, salicylic acid, creosote acid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orsellinic acid, gallic acid, mandelic acid, benzilic acid, atrolactic acid, mellotic acid, phloretic acid, coumaric acid, umbellic acid, caffeic acid, ferulic acid, sinapic acid, and hydroxystearic acid. Of these, malic acid and citric acid are preferred. Examples of the divalent or higher metal hydroxides include calcium hydroxide, magnesium hydroxide, barium hydroxide, aluminum hydroxide, iron hydroxide, zinc hydroxide, manganese hydroxide, and copper hydroxide. The crosslinking agents may be used alone or in combination of two or more. Among these, from the viewpoints of both imparting heat resistance and maintaining water solubility, boron compounds are preferred, and boric acid is more preferred.

[0036] The content of the crosslinking agent in the core resin composition is preferably 0.01% by mass or more and 2% by mass or less. By setting the content within this range, an appropriate crosslinked structure can be imparted and heat resistance can be improved.

[0037] <Easy-Removal Agent> The core resin composition may contain an easy-removal agent. By containing an easy-removal agent, the core resin can be more easily removed from the molded body.

[0038] The easy-release agent may be, for example, a glycerin fatty acid ester compound, such as monoglyceride stearic acid ester, monoglyceride oleic acid ester, or diglyceride lauric acid ester.

[0039] The content of the easy-release agent in the core resin composition is preferably 0.1% by mass or more and preferably 2% by mass or less. By setting the content within this range, the surface smoothness of the interior of the obtained molded product can be sufficiently improved. The content of the easy-release agent is more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, more preferably 1.6% by mass or less, and even more preferably 1.1% by mass or less.

[0040] <Plasticizer> The core resin composition may contain a plasticizer as long as it achieves the present invention. By containing a plasticizer, moldability can be improved.

[0041] Examples of the plasticizer include polyhydric alcohols, such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, polyethylene glycol, and polypropylene glycol.

[0042] From the viewpoint of easily controlling the MFR of the core resin composition within the above-mentioned range, it is preferable that the core resin composition does not contain the above-mentioned plasticizer. The content of the plasticizer in the core resin composition is preferably 0.1% by mass or more and preferably 10% by mass or less. By setting it within the above range, good extrusion and injection moldability and good water solubility can be achieved. The content of the plasticizer is more preferably 0.5% by mass or more, even more preferably 1% by mass or more, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

[0043] <Others> The core resin composition may also contain other additives such as antioxidants, colorants, antifoaming agents, ultraviolet absorbers, and preservatives.

[0044] As the antioxidant, known antioxidants can be used, such as phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, sulfur-containing antioxidants, etc. Also, antioxidants having both a phenolic functional group and a phosphorus-based functional group in one molecule can be used.

[0045] Examples of the phenol-based antioxidant include acrylate compounds such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate and 2,4-di-t-amyl-6-(1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)phenyl acrylate, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2 '-Methylene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(6-t-butyl-m-cresol), 4,4'-thiobis(3-methyl-6-t-butylphenol), bis(3-cyclohexyl-2-hydroxy-5-methylphenyl)methane, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxo alkyl-substituted phenolic compounds such as 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 triethylene glycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate); 6-(4-hydroxyphenyl)-2-methyl-2-propanol; and triazine group-containing phenolic compounds such as 6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3,5-dimethylanilino)-2,4-bis-octylthio-1,3,5-triazine, 6-(4-hydroxy-3-methyl-5-t-butylanilino)-2,4-bis-octylthio-1,3,5-triazine, and 2-octylthio-4,6-bis-(3,5-di-t-butyl-4-oxyanilino)-1,3,5-triazine.

[0046] Examples of the phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl)phosphite, tris(dinonylphenyl)phosphite, tris(2-t-butyl-4-methylphenyl)phosphite, tris(cyclohexylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, or monophosphite compounds such as 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene; and diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12 to C15) phosphite) 4,4'-isopropylidene-bis(diphenyl monoalkyl(C12 to C15) phosphite), 1,1,3-tris(2-methyl-4-di-tridecyl phosphite-5-t-butylphenyl)butane, or tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphite.

[0047] The antioxidant having both a phenolic functional group and a phosphorus functional group in one molecule is not particularly limited, and examples thereof include phosphite compounds having a phenol skeleton. Specific examples include 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]dioxaphosphepine, 2,10-dimethyl-4,8-di-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphene, and 2,4,8,10-tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphene. )propoxy]dibenzo[d,f][1,3,2]dioxaphosphepine, 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]dioxaphosphine, 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]dioxaphosphine, 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]dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-dibenzo[d,f][1,3,2]dioxaphosphepine, 2,10-dimethyl-4,8-di-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyloxy) 2,4,8,10-tetra-t-butyl-6-(3,5-di-t-butyl-4-hydroxybenzoyloxy)-12-methyl-12H-dibenzo[d,g][1,3,2]dioxaphosphine, 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]dioxaphosphine, 2,10-di-t-pentyl-4,Examples include 8-di-t-butyl-6-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6-[2,2-dimethyl-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-dibenzo[d,f][1,3,2]dioxaphosphepine, and the like.

[0048] The content of the antioxidant in the core resin composition is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and even more preferably 0.7% by mass or more, and is preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.2% by mass or less.

[0049] The core resin composition can be obtained by mixing, for example, polyvinyl alcohol resin, particle filler, and other additives such as easy-release agents, plasticizers, antioxidants, and the like, which are added as needed. The method for mixing the above components is not particularly limited, but examples include a method using a known kneading device or a method using an extrusion molding machine. Alternatively, mixing may be performed in the cylinder of an injection molding machine.

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

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

[0052] The core can be used to produce a molded body. The material that is molded together with the core to form the composite is not particularly limited, but because the core resin composition has particularly excellent heat resistance, it is possible to prevent deformation even when a super engineering plastic that is molded at high temperatures is used as the material.

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

[0054] A molded article having a hollow portion can be obtained by removing the core from the composite body. Examples of a method for removing the core include immersing the composite body in water or warm water.

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

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

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

[0058] Synthesis Example 1 [PVA1 (saponification degree 98.4 mol%, weight average molecular weight 15,000)] 2,000 parts by weight of vinyl acetate monomer and 200 parts by weight of methanol were added to a reactor equipped with a thermometer, a stirrer, and a cooling tube, and nitrogen gas was blown in for 30 minutes to replace the atmosphere with nitrogen. The reactor was then heated at 60°C for 30 minutes. Next, 456.5 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction time was over, the reaction solution was cooled. After cooling, １ The polymerization rate was measured by H-NMR measurement, and was found to be 99%. Subsequently, the remaining vinyl acetate monomer was removed together with methanol under reduced pressure while adding additional methanol, yielding a methanol solution containing 50% by weight of polyvinyl acetate. A methanol solution of sodium hydroxide was added to this methanol solution so that the amount of sodium hydroxide relative to the vinyl acetate was 0.07 mol %, and saponification was carried out at 40°C. The resulting solid was pulverized, washed with methanol, and then dried to obtain PVA1. The saponification degree of the resulting PVA1 was measured according to JIS K6726. The weight-average molecular weight of the polyvinyl alcohol resin was determined by measuring the weight-average molecular weight in terms of polystyrene by gel permeation chromatography using an LF-804 (manufactured by SHOKO) column. The resulting saponification degree and weight-average molecular weight were 98.4 mol % and 15,000, respectively. The viscosity of a 4% by mass aqueous solution of the obtained polyvinyl alcohol resin was measured using a rotational viscometer ("TVB-10" manufactured by Toki Sangyo Co., Ltd.) in accordance with JIS K6276 3.11.1 Rotational Viscometer Method, and was found to be 3.5 mPa·s.

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

[0060] Synthesis Example 3 [PVA3 (saponification degree 98.4 mol %, weight average molecular weight 22000)] PVA3 having a saponification degree, weight average molecular weight, and 4% by mass aqueous solution viscosity of 98.4 mol %, 22000, and 6.9 mPa s, respectively, was obtained by performing the same operations as in Synthesis Example 1, except that the amount of 2,2′-azobisisobutyronitrile added was changed to 22.9 parts by weight, and the amount of sodium hydroxide in methanol added was changed so that the amount of sodium hydroxide was 0.07 mol % based on vinyl acetate.

[0061] The following were used as particle fillers other than the polyvinyl alcohol resin, antioxidants, plasticizers, and peel-off agents: Titanium oxide 1: TTO-51(A) manufactured by Ishihara Sangyo Kaisha, Ltd., average particle diameter 20 nm, density 3.7 g / cm ３ Titanium oxide 2: PF-690 manufactured by Ishihara Sangyo Kaisha, Ltd., average particle size 210 nm, density 4.0 g / cm ３ Carbon black 1: TOKABLACK #5500 manufactured by Tokai Carbon Co., Ltd., average particle size 25 nm, density 1.9 g / cm ３ Carbon black 2: Seast TA manufactured by Tokai Carbon Co., Ltd., average particle size 122 nm, density 1.9 g / cm ３ Antioxidant: Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd. Plasticizer: Diglycerin S (chemical product name: diglycerin, molecular weight 166.17), manufactured by Sakamoto Pharmaceutical Co., Ltd. Peel-off agent: Monoglyceride stearate, Electrostripper TS-5, manufactured by Kao Corporation. The average particle size of the particle filler was cited from the catalog value. The density was measured using an Accupyc II1345, manufactured by Shimadzu Corporation.

[0062] Example 1 Polyvinyl alcohol resin, particle filler, and antioxidant were mixed to obtain the formulation shown in Table 1, and the mixture was pelletized at an extrusion temperature of 190°C to 210°C using a processing device "TEM26SX" manufactured by Toshiba Machine Co., Ltd., to obtain pellets of a resin composition for a core.

[0063] Examples 2 to 6 Polyvinyl alcohol resin, particle filler, antioxidant and easy-release agent were mixed to obtain the formulation shown in Table 1, and pellets of a resin composition for a core were obtained in the same manner as in Example 1.

[0064] Comparative Examples 1 and 2 Pellets of a resin composition for a core were obtained in the same manner as in Example 1, except that no particulate filler was added and the polyvinyl alcohol resin and antioxidant were mixed to obtain the formulation shown in Table 1.

[0065] Comparative Examples 3 to 6 Polyvinyl alcohol resin, particle filler, antioxidant and plasticizer were mixed to obtain the formulation shown in Table 1, and pellets of a resin composition for a core were obtained in the same manner as in Example 1.

[0066] (Evaluation Method) The obtained resin compositions for cores were evaluated by the following methods. The results are shown in Table 1.

[0067] (1) Total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) The total surface area of ​​the particulate filler per unit mass of the resin composition for a core was calculated based on the following formula (1). A: total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) B: average particle diameter (m) of the particle filler D: content (mass%) of the particle filler in the resin composition for cores E: density (g / m ３ )

[0068] (2) Melt Flow Rate (MFR) Using a melt index tester No. 120-FWP (manufactured by Yasuda Seiki Seisakusho, Ltd.), the melt flow rate (MFR) of the core resin composition was measured according to a method in accordance with ASTM D 1238 under the conditions of an initial weight of the core resin composition of 7.5 g, 230°C, a load of 10 kg, and a measurement time interval of 0.25 minutes.

[0069] (3) Heat Resistance A SUS304 steel ball having a diameter of 10 mm was heated to 300°C and placed on a plate-shaped resin composition at room temperature (20°C) for 1 minute. The diameter (mm) of the depression that formed when the ball sank was measured, and the heat resistance was evaluated as follows: less than 2 mm is marked "◎", 2 mm or more but less than 3 mm is marked "◯", and 3 mm or more is marked "×".

[0070]

[0071] According to the present invention, it is possible to provide a core resin composition that exhibits high heat resistance and enables the production of cores that do not deform even under the molding conditions of super engineering plastics, and also to provide a core made using the core resin composition.

Claims

1. A resin composition for cores, comprising a polyvinyl alcohol resin, and having a melt flow rate (MFR) of 35 g / 10 min or less under conditions of 230°C and a 10 kg load.

2. A resin composition for a core as described in claim 1, wherein the polyvinyl alcohol resin has a weight average molecular weight (Mw) of 200,000 or less and a degree of saponification of 72% or more and 99.8% or less.

3. A resin composition for cores as described in claim 1 or 2, wherein the polyvinyl alcohol resin has a viscosity of 30 mPa·s or less in a 4 mass% aqueous solution.

4. The resin composition further contains a particulate filler, and the total surface area of ​​the particulate filler per unit mass of the resin composition for a core, calculated by the following formula (1), is 10 m ２ The resin composition for a core according to claim 1, 2 or 3, wherein the modulus of elasticity is 1 / g or more. A: total surface area (m) of the particle filler per unit mass of the core resin composition ２ / g) B: average particle diameter (m) of the particle filler D: content (mass%) of the particle filler in the resin composition for cores E: density (g / m ３ ) 5. A resin composition for a core according to claim 4, wherein the average particle diameter of the particulate filler is 1 nm or more and 100 nm or less.

6. A resin composition for a core as described in claim 4 or 5, wherein the content of the particulate filler is 5% by mass or more and 70% by mass or less.

7. A resin composition for a core according to claim 1, 2, 3, 4, 5 or 6, containing 0.1% by mass or more and 2% by mass or less of an easy-release agent.

8. A resin composition for a core according to claim 7, wherein the easy-release agent is a glycerin fatty acid ester compound.

9. A resin composition for cores as described in claim 8, wherein the glycerin fatty acid ester compound is at least one selected from the group consisting of monoglyceride stearic acid ester, monoglyceride oleic acid ester, and diglyceride lauric acid ester.

10. The resin composition for cores according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, which is in the form of pellets.

11. A core made using the resin composition for cores according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

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