Resin composition for cores, and core

Abstract

The present invention provides a resin composition for cores, the resin composition enabling the production of a core that exhibits high heat resistance and does not deform even under molding conditions for super engineering plastic. Also provided is a core formed using the resin composition for cores. The present invention is a resin composition for cores which contains a polyvinyl alcohol resin, and an organic fiber having a melting point of 200°C or higher.

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 the materials used in 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: 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 organic fibers having a melting point of 200°C or higher. Disclosure (2) is a core resin composition of Disclosure (1), in which the fiber diameter of the organic fibers is 50 μm or less. Disclosure (3) is a core resin composition of Disclosure (1) or (2), in which the organic fibers are aramid fibers. Disclosure (4) is a core resin composition of Disclosure (1), (2), or (3), in which the content of the organic fibers is 3% by weight or more and 40% by weight or less. Disclosure (5) is a core resin composition further containing a heat-resistant filler, in which the total surface area of ​​the heat-resistant 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 heat-resistant filler per unit mass of the core resin composition ２ / g) B: Average particle diameter (m) of heat-resistant filler D: Content (mass%) of heat-resistant filler in resin composition for core E: Density (g / m ３The present disclosure (6) is the core resin composition of the present disclosure (5), in which the average particle size of the heat-resistant filler is 1 nm or more and 100 nm or less. The present disclosure (7) is the core resin composition of the present disclosure (5) or (6), in which the content of the heat-resistant filler is 5 mass% or more and 70 mass% or less. The present disclosure (8) is the core resin composition of the present disclosure (1), (2), (3), (4), (5), (6), or (7), in which the melt flow rate (MFR) under a 230°C, 10 kg load condition is 50 g / 10 min or less. The present disclosure (9) is the core resin composition of the present disclosure (1), (2), (3), (4), (5), (6), (7), or (8), in which the easy-release agent is contained in an amount of 0.1 mass% or more and 2 mass% or less. The present disclosure (10) is a core resin composition according to the present disclosure (1), (2), (3), (4), (5), (6), (7), (8), or (9), containing 0.1% by mass or more and 10% by mass or less of a plasticizer. The present disclosure (11) is a core resin composition according to the present disclosure (1), (2), (3), (4), (5), (6), (7), (8), (9), or (10), which is in pellet form. The present disclosure (12) is a core made using the core resin composition according to the present disclosure (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), or (11). 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 incorporating organic fibers having a melting point of 200° C. or higher. They have also discovered that the use of such a core resin composition makes it 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.

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

[0009] 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, 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 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.

[0010] 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.

[0011] The weight average molecular weight (Mw) of the polyvinyl alcohol resin is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 14,000 or more, particularly more preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 40,000 or less, particularly more preferably 32,000 or less, and most preferably 24,000 or less. 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 main polyvinyl alcohol resins are contained, the weight average molecular weight (Mw) is preferably 8,000 or more, more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 11,000 or more, particularly preferably 14,000 or more, especially more preferably 17,000 or more, preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, especially preferably 40,000 or less, especially more preferably 30,000 or less, and most preferably 20,000 or less.

[0012] The number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 4,000 or more, more preferably 4,500 or more, even more preferably 5,000 or more, even more preferably 10,000 or more, and particularly preferably 16,000 or more, and is preferably 90,000 or less, more preferably 60,000 or less, even more preferably 30,000 or less, even more preferably 25,000 or less, and particularly preferably 22,000 or less.

[0013] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyvinyl alcohol resin is preferably 1.0 or more, more preferably 1.2 or more, even more preferably 1.4 or more, even more preferably 1.6 or more, and 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, KF-807 (Shodex), etc. can be used.

[0014] 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 extrusion and 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, more preferably 20 mPa·s or less, and even 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.

[0015] 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.

[0016] 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.

[0017] The content of the polyvinyl alcohol resin in the core resin composition is preferably 40% by mass or more, more preferably 50% by mass or more, 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.

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

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

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

[0021] Examples of polymerization catalysts used in polymerizing the vinyl ester include 2-ethylhexyl peroxydicarbonate ("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.

[0022] 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.

[0023] Examples of olefins include ethylene, propylene, 1-butene, and isobutene. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of unsaturated acids other than (meth)acrylic acid, and 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.

[0024] <Organic Fibers> The core resin composition contains organic fibers having a melting point of 200°C or higher. By containing the organic fibers, heat resistance can be improved. In the case of fibers whose melting point cannot be measured, the thermal decomposition onset temperature or softening temperature can be used instead. In that case, heat resistance can be improved if any of the melting point, softening temperature, or thermal decomposition onset temperature is 200°C or higher. The organic fibers referred to above have an aspect ratio of 12 or higher. The aspect ratio is preferably 20 or higher, more preferably 35 or higher, and even more preferably 50 or higher.

[0025] Examples of the organic fibers include aramid fibers, nylon fibers, rayon fibers, polyester fibers, cellulose fibers, etc. Among these, aramid fibers are preferred because they can further enhance heat resistance.

[0026] The melting point of the organic fiber is 200°C or higher, preferably 250°C or higher, and more preferably 300°C or higher. There is no particular upper limit, and in the spirit of the present application, a higher melting point is preferable. The melting point can be confirmed by a differential scanning calorimeter (DSC). If the melting point cannot be measured by DSC because it is higher than the decomposition temperature, the thermal decomposition onset temperature can be measured using a thermogravimetric analyzer or the like, and the measured value can be used. TG-DTA or the like can also be used.

[0027] From the viewpoint of heat resistance, the fiber diameter of the organic fiber is preferably 50 μm or less, more preferably 35 μm or less, even more preferably 25 μm or less, and even more preferably 17 μm or less, and is preferably 3 nm or more, more preferably 1 μm or more.

[0028] The organic fibers may be discontinuous fibers in which the fibers are intermittently divided, or may be continuous fibers in which the fibers are not divided. When the organic fibers are discontinuous fibers, the average fiber length of the organic fibers is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more. The average fiber length is preferably 5 mm or less, and more preferably 3 mm or less. The average fiber length can be confirmed using a microscope or the like with a size measurement function.

[0029] The content of the organic fibers in the core resin composition is preferably 3% by weight or more and 40% by weight or less. By keeping it within this range, heat resistance can be further improved. The content of the organic fibers is more preferably 4.5% by weight or more, even more preferably 9% by weight or more, and more preferably 35% by weight or less. Furthermore, when other fillers are also mixed, the content can be further reduced, in which case 20% by weight or less is even more preferable, and 10% by weight or less is particularly preferable.

[0030] <Heat-Resistant Filler> The core resin composition preferably further contains a heat-resistant filler. By containing a heat-resistant filler, heat resistance can be further improved.

[0031] In the core resin composition, the total surface area of ​​the heat-resistant 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 heat-resistant filler per unit mass of the core resin composition ２ / g) B: Average particle diameter (m) of heat-resistant filler C: Amount (g) of resin composition for core D: Content (mass%) of heat-resistant filler in resin composition for core E: Density (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 heat-resistant filler (m ２ ) (4π × (B / 2) ２ The number of heat-resistant fillers per 1 g of the core resin composition is calculated by multiplying the content (g) of the heat-resistant filler per 1 g of the core resin composition (C (g) x D (mass%) / 100 ÷ C (g)) by the mass (g) per heat-resistant filler (density x average volume per heat-resistant filler = E x 4 / 3 x 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 making the total surface area per unit mass 15 m / g 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. There is no particular upper limit to the total surface area per unit mass, and the larger the better, but the upper limit is naturally limited by the particle size, amount, density, etc. of the heat-resistant filler. The heat-resistant filler may be one type, 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 heat-resistant filler using the above formula (1) for each heat-resistant filler and adding them up.

[0032] The total surface area of ​​the particulate filler per unit mass can be adjusted by the average particle size, density, and amount of filler. The surface area of ​​the particulate filler is calculated from the average particle size, density, and amount of filler of the primary particles, but the particle shape is not necessarily limited to spherical. Shapes other than spherical include, for example, plate-like, needle-like, rugby-like, hollow, and porous, and may also have a higher-order structure in which multiple particles are connected or overlapped. The surface area of ​​the filler in the present application is calculated from the average particle size, density, and amount of primary particles, but the particle shape is not necessarily limited to spherical. Shapes other than spherical include, for example, plate-like, needle-like, rugby-like, hollow, and porous, and may also have a higher-order structure in which multiple particles are connected or overlapped.

[0033] The average particle diameter of the heat-resistant 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 filler in the core resin composition can be kept 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-based 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 analyzer or the like.

[0034] The density of the heat-resistant filler is 0.5 g / cm ３ More than 0.7 g / cm ３ More preferably, 0.9 g / cm ３ More 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.

[0035] Examples of materials for the heat-resistant 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).

[0036] The content of the heat-resistant 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 heat-resistant 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.

[0037] <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.

[0038] 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.

[0039] 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 improving heat resistance through crosslinking and ensuring water solubility when removing the core resin, boron compounds are preferred, and boric acid is more preferred.

[0040] 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, which makes it possible to suppress a sudden increase in viscosity when the core resin composition is kneaded to produce it or when heated during the subsequent injection molding, while also ensuring water solubility when the core resin is removed.

[0041] <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.

[0042] 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.

[0043] 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.

[0044] <Plasticizer> The core resin composition may contain a plasticizer. By containing a plasticizer, moldability can be improved.

[0045] 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.

[0046] 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 the content within this range, good extrusion and injection moldability and good water solubility can be achieved. The content of the plasticizer is more preferably 0.5% by mass or more, even more preferably 1% by mass or more, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

[0047] <Others> The core resin composition may also contain other additives such as antioxidants, colorants, antifoaming agents, ultraviolet absorbers, and preservatives.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The core resin composition preferably has a melt flow rate (MFR) of 50 g / 10 min or less at 230°C under a load of 10 kg. By ensuring that the MFR falls within this range, heat resistance can be improved. There is no particular lower limit for the MFR, and there is no particular problem as long as it can be molded using an injection molding machine. The upper limit is more preferably 35 g / 10 min or less, even more preferably 25 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. The MFR can be measured, for example, by a method in accordance with ASTM D1238, using an initial weight of 7.5 g and a measurement time interval of 0.25 minutes.

[0054] The melt flow rate (MFR) under the above-mentioned conditions of 230°C and 10 kg load can be adjusted by the composition and amount of the polyvinyl alcohol resin, the type and amount of the organic fiber, the fiber diameter, the type and amount of the heat-resistant filler, the average particle diameter, the total surface area, the type and amount of the crosslinking agent, and the type and amount of the plasticizer.

[0055] The core resin composition can be obtained by mixing, for example, polyvinyl alcohol resin, organic fibers, and other additives such as heat-resistant fillers, easy-release agents, plasticizers, antioxidants, and other additives that 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.

[0056] The form of the core resin composition is not particularly limited, and may be, for example, pellets, powder, or the like.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0064] 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. Nitrogen gas was blown in for 30 minutes to replace the atmosphere, and 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, the reaction solution was cooled. After cooling, the polymerization rate was measured by 1H-NMR measurement, and it was found to be 99%. Next, the remaining vinyl acetate monomer was removed together with methanol under reduced pressure while additional methanol was added, 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%. Saponification was carried out at 40°C. The resulting solid was pulverized, washed with methanol, and then dried to obtain PVA1. The degree of saponification of the resulting PVA1 was measured by a method in accordance with 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 Corporation) 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 resulting 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 3.5 mPa s.

[0065] 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.

[0066] 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.

[0067] The following organic fibers other than polyvinyl alcohol resin, inorganic fibers, antioxidants, heat-resistant fillers, and peel-off agents were used: <Organic fibers> Aramid fiber: Teijin Co., Ltd., Conex B2.2x1, thermal decomposition starting temperature 340°C, fiber diameter 15 μm, fiber length 1.07 mm, aspect ratio 71 Cellulose nanofiber: Chuetsu Pulp Co., Ltd., nanoforest-PDP / N-PDP34, thermal decomposition starting temperature 300°C <Inorganic fibers> Carbon fiber: Nippon Polymer Sangyo Co., Ltd., CFMP-30 <Antioxidant> Sumilizer GP (phenol-phosphorus antioxidant): Sumitomo Chemical Co., Ltd. <Heat-resistant filler> Carbon black: Tokai Carbon Co., Ltd., TOKABLACK #5500, average particle size 25 nm, density 1.9 g / cm ３ <Easy-peel agent> Monoglyceride stearate: Electrostripper TS-5 manufactured by Kao Corporation. The melting point of the organic fiber was measured using an SDT Q 600 manufactured by TA Instruments, and the fiber diameter and fiber length were measured at 10 or more points using a KEYENCE DIGITAL MICROSCOPE VHX-500, and the average values ​​were used. Furthermore, the density of the heat-resistant filler was measured using an electronic hydrometer (AccuPyc II 1345 manufactured by Shimadzu Corporation), and the average particle size was quoted from the catalog value.

[0068] (Examples 1 to 10, Comparative Examples 1 to 3) Polyvinyl alcohol resin, organic fibers, inorganic fibers, antioxidants, heat-resistant fillers, and easy-release agents were mixed to obtain the formulations 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.

[0069] (Evaluation Method) The obtained resin compositions for cores were evaluated by the following methods. The results are shown in Table 1.

[0070] (1) Total surface area (m) of the heat-resistant 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 heat-resistant filler per unit mass of the core resin composition ２ / g) B: Average particle diameter (m) of heat-resistant filler D: Content (mass%) of heat-resistant filler in resin composition for core E: Density (g / m ３ )

[0071] (2) Heat Resistance A 10 mm diameter SUS304 steel ball was heated to 300°C and placed on a plate-shaped pellet of the 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 "×".

[0072] (3) 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.

[0073]

[0074] 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 a core, comprising a polyvinyl alcohol resin and organic fibers having a melting point of 200°C or higher.

2. A resin composition for a core according to claim 1, wherein the fiber diameter of the organic fibers is 50 μm or less.

3. A resin composition for a core according to claim 1 or 2, wherein the organic fiber is an aramid fiber.

4. A resin composition for cores according to claim 1, 2 or 3, wherein the content of said organic fibers is 3% by weight or more and 40% by weight or less.

5. The resin composition further contains a heat-resistant filler, and the total surface area of ​​the heat-resistant filler per unit mass of the resin composition for cores calculated by the following formula (1) is 10 m ２ The resin composition for a core according to claim 1, 2, 3 or 4, wherein the modulus of elasticity is 1 / g or more. A: Total surface area (m) of the heat-resistant filler per unit mass of the core resin composition ２ / g) B: Average particle diameter (m) of heat-resistant filler D: Content (mass%) of heat-resistant filler in resin composition for core E: Density (g / m ３ ) 6. A resin composition for a core according to claim 5, wherein the average particle size of the heat-resistant filler is 1 nm or more and 100 nm or less.

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

8. A resin composition for a core according to claim 1, 2, 3, 4, 5, 6 or 7, which has a melt flow rate (MFR) of 50 g / 10 min or less at 230°C under a load of 10 kg.

9. A resin composition for a core according to claim 1, 2, 3, 4, 5, 6, 7 or 8, containing 0.1% by mass or more and 2% by mass or less of an easy-release agent.

10. A resin composition for a core according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, containing 0.1% by mass or more and 10% by mass or less of a plasticizer.

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

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

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