Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/0001—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor characterised by the choice of material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/02—Making granules by dividing preformed material
  • B29B9/06—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/12—Making granules characterised by structure or composition
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
  • B29C45/14311—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles using means for bonding the coating to the articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/001—Combinations of extrusion moulding with other shaping operations
  • B29C48/0022—Combinations of extrusion moulding with other shaping operations combined with cutting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/04—Particle-shaped
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/05—Filamentary, e.g. strands
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/505—Screws
  • B29C48/57—Screws provided with kneading disc-like elements, e.g. with oval-shaped elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/505—Screws
  • B29C48/625—Screws characterised by the ratio of the threaded length of the screw to its outside diameter [L/D ratio]
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/04—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L59/00—Compositions of polyacetals; Compositions of derivatives of polyacetals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2021/00—Use of unspecified rubbers as moulding material
  • B29K2021/003—Thermoplastic elastomers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material

Definitions

• the present invention relates to an insert molded body, an anchor for attaching a seat belt, and a manufacturing method for an insert molded body.
• the present invention relates to an insert molded body whose main component is polyacetal resin.
• Polyacetal resin has high mechanical strength and rigidity, excellent resistance to oil and organic solvents, is well-balanced over a wide temperature range, and is easy to process. Therefore, polyacetal resin is a representative engineering plastic and is widely used in office equipment, digital home appliances, automobile parts, and other industrial parts.
• Patent Document 1 discloses a metal insert molding comprising a polyacetal resin composition containing 0.01 to 5 parts by mass of a hydrazide compound, 0.01 to 1 part by mass of polyethylene glycol, and a coloring pigment, relative to 100 parts by mass of a polyacetal resin having a melt flow rate of 1.0 to 5.0 g/10 min.
• the present invention aims to solve these problems, and to provide an insert molded body having a resin part and a metal part, in which the resin part has high weld elongation and is less likely to crack, as well as an anchor for attaching a seat belt, and a method for manufacturing the insert molded body.
• the present inventors conducted research and focused on the stress generated by the difference in linear expansion coefficient and shrinkage rate between the resin part and the metal part, among the causes of cracking in the resin part.
• they deliberately tried to use a soft polyacetal resin. That is, instead of reducing the generated stress, they considered alleviating the generated stress by using a soft polyacetal resin.
• the present inventors conducted further research and found that the above problem can be solved by selecting a core-shell elastomer as the elastomer, adjusting the maximum secondary particle diameter of the core-shell elastomer in the resin part to 1000 nm or less, and substantially not blending polyurethane. Specifically, the above problems were solved by the following means.
• An insert molded body having a resin part formed from a resin composition containing a polyacetal resin and an elastomer, and a metal part, wherein the elastomer contains a core-shell elastomer, a polyurethane content in 100% by mass of the resin composition is less than 1% by mass, a maximum secondary particle diameter of the core-shell elastomer in the resin part is 1000 nm or less, and a thickness ratio (resin part/metal part) of the resin part of the insert molded body to a thickness of the metal part is 1.5 or less.
• ⁇ 2> The insert molding according to ⁇ 1>, wherein the polyacetal resin has a melt volume rate (MVR) of 0.5 to 20 cm 3 /10 min, measured at 190° C. and 2.16 kg in accordance with ISO 1133 standard.
• MVR melt volume rate
• ⁇ 3> The insert molded body described in ⁇ 1> or ⁇ 2>, wherein the insert molded body has a three-layer structure in which the resin part, the metal part, and the resin part are in contact with each other in the above order.
• ⁇ 4> The insert molded body according to any one of ⁇ 1> to ⁇ 3>, wherein the insert molded body has a weld portion.
• ⁇ 5> The insert molding according to any one of ⁇ 1> to ⁇ 4>, wherein the maximum secondary particle diameter of the core-shell elastomer in the resin portion is 10 to 900 nm.
• ⁇ 6> The insert molding according to any one of ⁇ 1> to ⁇ 5>, wherein the content of the core-shell elastomer in the resin composition is 5 to 40 mass%.
• ⁇ 7> The insert molding according to any one of ⁇ 1> to ⁇ 6>, wherein in the core-shell elastomer, the core contains a butadiene-containing rubber and/or an acrylate-based rubber, and the shell contains an acrylic resin.
• the polyacetal resin has a melt volume rate (MVR) of 0.5 to 20 cm3 /10 min, measured according to ISO 1133 standard at 190°C and 2.16 kg, the insert molded body has a three-layer structure in which the resin part, the metal part, and the resin part are in contact with each other in the stated order, the insert molded body has a weld part, the maximum secondary particle diameter of the core-shell elastomer in the resin part is 10 to 900 nm, the content of the core-shell elastomer in the resin composition is 5 to 40 mass%, and in the core-shell elastomer, the core contains a butadiene-containing rubber and the shell contains an acrylic resin.
• MVR melt volume rate
• a seat belt mounting anchor comprising the insert molding according to any one of ⁇ 1> to ⁇ 8>.
• the present invention makes it possible to provide an insert molded body having a resin part and a metal part, in which the resin part has high weld elongation and is less likely to crack, as well as an anchor for attaching a seat belt and a method for manufacturing the insert molded body.
• FIG. 1 is a schematic diagram for explaining an insert molding according to the present embodiment.
• the insert molded body of this embodiment is an insert molded body having a resin part formed from a resin composition containing a polyacetal resin and an elastomer, and a metal part, the elastomer contains a core-shell elastomer, the content of polyurethane in 100% by mass of the resin composition is less than 1% by mass, the maximum secondary particle diameter of the core-shell elastomer in the resin part is 1000 nm or less, and the minimum value of the thickness ratio of the resin part of the insert molded body to the thickness of the metal part (resin part/metal part) is 1.5 or less.
• the resin part of this embodiment is formed from a resin composition containing a polyacetal resin and an elastomer.
• the resin part of this embodiment is usually formed by placing a metal part in a mold and insert injection molding the resin composition.
• a weld part is usually formed at the filling end or the insert part (around the metal fixing pin) in the mold, and such a weld part causes cracks.
• multiple weld parts may be formed in other places than the above. In this embodiment, by increasing the elongation of the weld part, it has been successfully suppressed effectively from cracking the weld part.
• the maximum secondary particle diameter of the core-shell elastomer in the resin portion is 1000 nm or less.
• the maximum secondary particle diameter of the core-shell elastomer 1000 nm or less it is considered to improve the dispersibility of the core-shell elastomer in the polyacetal resin.
• this can be achieved by selecting a twin-screw extruder when melt-kneading the polyacetal resin and the core-shell elastomer, increasing the rotation speed during melt-kneading, using a polyacetal resin with a low viscosity, selecting the material of the core-shell elastomer, etc. It is not necessary to satisfy all of these means for achieving this, and it can be achieved by appropriately selecting the desired means.
• the maximum secondary particle size of the core-shell elastomer is a value measured according to the examples described later.
• the maximum secondary particle diameter of the core-shell elastomer in the polyacetal resin is preferably 900 nm or less, more preferably 600 nm or less, even more preferably 400 nm or less, even more preferably 350 nm or less, and even more preferably 279 nm or less. By making it equal to or less than the upper limit, the weld elongation tends to be higher.
• the maximum secondary particle diameter of the core-shell elastomer is preferably 10 nm or more, more preferably 30 nm or more, even more preferably 50 nm or more, even more preferably 70 nm or more, even more preferably 100 nm or more, and even more preferably 110 nm or more. By making it equal to or more than the lower limit, the handleability and availability until melt kneading tend to be excellent.
• the resin portion of the present embodiment is formed from a resin composition, which will be described in detail below.
• the thickness of the resin part is preferably 0.5 mm or more at its thinnest part, and is preferably 20 mm or less. Also, the thickness of the resin part is preferably 0.5 mm or more at its thickest part, and is preferably 20 mm or less.
• the resin composition used in this embodiment contains a polyacetal resin.
• the polyacetal resin used in the present embodiment is not particularly limited, and may be a homopolymer containing only divalent oxymethylene groups as constituent units, or a copolymer containing a divalent oxymethylene group and a divalent oxyalkylene group having 2 to 6 carbon atoms as constituent units.
• Examples of oxyalkylene groups having 2 to 6 carbon atoms include oxyethylene groups, oxypropylene groups, and oxybutylene groups.
• the proportion of oxyalkylene groups having 2 to 6 carbon atoms in the total number of moles of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms is not particularly limited, but may be 0.5 to 10 mol %.
• trioxane is usually used as the main raw material.
• a cyclic formal or a cyclic ether can be used.
• Specific examples of the cyclic formal include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, and 1,3,6-trioxocane
• specific examples of the cyclic ether include ethylene oxide, propylene oxide, and butylene oxide.
• 1,3-dioxolane can be used as the main raw material.
• 1,3-dioxane can be used as the main raw material.
• 1,3-dioxepane can be used as the main raw material.
• the amount of hemiformal end groups, formyl end groups, and end groups that are unstable to heat, acid, or base is small.
• the hemiformal end group is represented by -OCH 2 OH
• the formyl end group is represented by -CHO.
• polyacetal resins described in paragraphs 0018 to 0043 of JP 2015-074724 A can be used as the polyacetal resin, the contents of which are incorporated herein by reference.
• the polyacetal resin preferably has a melt volume rate (MVR) of 0.5 cm3 /10 min or more, more preferably 1 cm3/10 min or more, even more preferably 3 cm3 /10 min or more, still more preferably 5 cm3 /10 min or more, and even more preferably 6 cm3 /10 min or more, as measured at 190°C and 2.16 kg in accordance with ISO 1133.
• MVR melt volume rate
• the melt volume rate (MVR) of the polyacetal resin measured in accordance with ISO 1133 at 190°C and 2.16 kg is preferably 20 cm3 /10 min or less, more preferably 18 cm3 /10 min or less, even more preferably 13 cm3 /10 min or less, still more preferably 10 cm3 /10 min or less, and even more preferably 8 cm3 /10 min or less.
• the resin composition used in the present embodiment may contain only one type of polyacetal resin, or may contain two or more types. When two or more types are contained, it is preferable that the MVR of the mixture is in the above range.
• the content of the polyacetal resin in the resin composition used in this embodiment is, based on 100 mass% of the resin composition, preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 75 mass% or more, even more preferably 80 mass% or more, even more preferably 85 mass% or more, and preferably 97 mass% or less, more preferably 96 mass% or less, even more preferably 95 mass% or less, even more preferably 94 mass% or less, and even more preferably 92 mass% or less.
• the resin composition used in the present embodiment may contain only one type of polyacetal resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.
• the resin composition used in the present embodiment contains an elastomer. By containing an elastomer, cracking of the metal insert molding is suppressed, and the impact resistance of the obtained resin part tends to be further improved.
• the elastomer used in the present embodiment includes a core-shell elastomer.
• a core-shell elastomer By including the core-shell elastomer, it is possible to impart flexibility to the resin composition.
• a core-shell elastomer is a polymer with a multi-layer structure having a core and a shell layer that covers all or part of the core.
• Known examples of such elastomers include Kane Ace series from Kaneka Corporation and Metablen series from Mitsubishi Chemical Corporation.
• the shell is preferably a polymer of one or more monomers such as (meth)acrylic acid ester and aromatic vinyl compound, and more preferably a polymer (acrylic resin) in which units derived from (meth)acrylic acid ester account for 50% by mass or more of the total.
• an acrylic resin By using an acrylic resin, it is possible to further improve dispersibility in the polyacetal resin.
• the core-shell elastomer used in the present embodiment preferably contains a butadiene-containing rubber and/or an acrylate-based rubber, and the shell preferably contains an acrylic resin. When such a core-shell elastomer is used, the effects of the present invention tend to be more effectively exhibited.
• the resin composition of the present embodiment preferably contains 5% by mass or more of the core-shell elastomer, more preferably 7% by mass or more, and even more preferably 8% by mass or more. By making it equal to or more than the lower limit, impact resistance tends to be further improved.
• the upper limit of the content of the core-shell elastomer is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and may be 15% by mass or less, 14% by mass or less, 12% by mass or less, or 11% by mass or less. By making it equal to or less than the upper limit, formaldehyde released from the resin composition tends to be effectively suppressed.
• the resin composition used in the present embodiment may contain only one type of core-shell elastomer, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.
• the resin composition used in this embodiment has a polyurethane content of less than 1% by mass in 100% by mass of the resin composition.
• the content of polyurethane in 100% by mass of the resin composition is preferably less than 0.5% by mass, more preferably less than 0.1% by mass, and even more preferably less than 0.01% by mass.
• the lower limit of the content of polyurethane in 100% by mass of the resin composition is preferably 0% by mass.
• the content of elastomers other than the core-shell elastomer (non-core-shell elastomer) in 100% by mass of the resin composition is preferably less than 1% by mass. In this way, by not including elastomers other than the core-shell elastomer (non-core-shell elastomer) or by using only a small amount of such elastomers, the weld elongation of the resin part of the obtained insert molding can be improved.
• the total amount of the polyacetal resin and the core-shell elastomer preferably accounts for 90% by mass or more of the resin composition, more preferably 95% by mass or more, and even more preferably 98% by mass or more. However, the total amount of the polyacetal resin and the core-shell elastomer does not exceed 100% by mass.
• the resin composition used in this embodiment may contain any conventionally known additives or fillers within the scope of the present invention.
• additives and fillers used in this embodiment include thermoplastic resins other than polyacetal resins, ultraviolet absorbers, antioxidants (hindered phenols, etc.), stabilizers (melamine, etc.), formaldehyde scavengers, stress relaxation agents, sliding agents, pigments, release agents, antistatic agents, carbon fibers, glass fibers, glass flakes, potassium titanate whiskers, and the like.
• the resin composition used in the present embodiment preferably contains a hindered phenol-based antioxidant, melamine (stabilizer), and a mold release agent as other components. Furthermore, when the resin composition used in the present embodiment is used for automobile applications, it preferably contains a hindered amine-based light stabilizer, an ultraviolet absorber, and a formaldehyde scavenger in addition to the hindered phenol-based antioxidant, melamine (stabilizer), and mold release agent.
• the resin composition used in the present embodiment may be configured to be substantially free of a colorant.
• substantially free of a colorant means that the content of the colorant is less than 0.01% by mass, and preferably less than 0.001% by mass, relative to 100 parts by mass of the polyacetal resin.
• the resin composition used in the present embodiment may be configured to be substantially free of color pigments.
• substantially free of color pigments means that the content of color pigments is less than 0.01% by mass, and preferably less than 0.001% by mass, relative to 100 parts by mass of the polyacetal resin.
• the resin composition used in this embodiment is preferably excellent in weld elongation.
• the resin composition is molded into an ASTM tensile test piece (thickness 1.6 mm, gates on both ends of the test piece) with a weld portion provided in the center of the test piece, and a tensile test is performed in accordance with ASTM D638.
• ASTM tensile test piece thickness 1.6 mm, gates on both ends of the test piece
• a tensile test is performed in accordance with ASTM D638.
• the weld elongation is preferably 10% or more, more preferably 12% or more, and even more preferably 15% or more.
• the upper limit of the weld elongation is not particularly limited, but is, for example, 150% or less. Weld elongation is measured as described in the Examples section below.
• the resin composition used in the present embodiment contains the above-mentioned essential components and the above-mentioned optional components as required.
• the production method thereof is preferably any method that results in a maximum secondary particle size in the above-mentioned range.
• One method for making the maximum secondary particle size fall within the above range is to use pellets obtained by melt-kneading raw materials containing polyacetal resin and elastomer using a twin-screw extruder at a rotation speed of 90 rpm or more.
• the dispersibility of the core-shell elastomer in the polyacetal resin is improved, and the maximum secondary particle size of the core-shell elastomer in the resin part of the obtained insert molding can be reduced.
• the polyacetal resin and the core-shell elastomer are mixed in a tumbler, extruded in a melt kneader, discharged from a die, formed into a strand shape, and then cut into pellets.
• L/D which is the ratio of the length L (mm) of the screw to the diameter D (mm) of the same screw, is preferably 20 or more, more preferably 30 or more, and preferably 100 or less, more preferably 70 or less.
• the screw diameter D (mm) is preferably 5 mm or more, and is preferably 40 mm or less, and more preferably 35 mm or less.
• the screw rotation speed during melt kneading is preferably 90 rpm or more, more preferably 95 rpm or more, more preferably 100 rpm or more, even more preferably 105 rpm or more, even more preferably 110 rpm or more, and even more preferably 115 rpm or more. Also, it is preferably 500 rpm or less, more preferably 400 rpm or less, and may be 350 rpm or less, 3000 rpm or less, 250 rpm or less, or 1200 rpm or less.
• the optimal screw rotation speed varies depending on the diameter, L/D, screw configuration, and discharge rate of the extruder, it is preferable to select the optimal rotation speed each time while checking the secondary particle diameter of the core-shell elastomer and the resin temperature during melt kneading.
• the discharge rate is preferably 5 kg/hr or more, more preferably 7 kg/hr or more, and is preferably 1,000 kg/hr or less, more preferably 800 kg/hr or less.
• the diameter of the extruder is preferably 10 mm or more, more preferably 20 mm or more, and more preferably 25 mm or more. Also, it is preferably 100 mm or less, preferably 90 mm or less, and more preferably 80 mm or less.
• the cylinder temperature during melt kneading can be set arbitrarily, but it is preferable to set it according to the torque during extrusion and the temperature of the resin composition during melt kneading (when discharged from the die).
• the preferred cylinder temperature is 170°C or higher from the viewpoint of the melting temperature of the polyacetal resin, and 240°C or lower from the viewpoint of thermal degradation and thermal decomposition of the polyacetal resin. Note that it is also possible to set a portion of the extruder cylinder to 170°C or lower or 240°C or higher within a range that does not affect melt kneading.
• the temperature of the resin composition during melt kneading should be equal to or higher than the temperature at which the polyacetal resin melts, specifically equal to or higher than the melting temperature of the polyacetal resin, but is preferably 170°C or higher, more preferably 190°C or higher, and is preferably 250°C or lower, more preferably 230°C or lower.
• the screw configuration of the twin-screw extruder is not particularly limited, but one preferred embodiment is one that has at least two kneading sections.
• the kneading section has a kneading disk and mainly contributes to melting the resin and dispersing the elastomer.
• the insert molded body of this embodiment has a metal portion.
• the material of the metal constituting the metal part is not particularly limited, and a molded body made of a known metal can be appropriately selected depending on the application.
• the metal part can be selected from iron, various stainless steels, aluminum and its alloys, copper, magnesium, titanium, and alloys containing them.
• the surface of the metal part may be previously subjected to a surface treatment such as anodizing or painting.
• the metal part used in this embodiment can be a metal part molded into a desired shape depending on the application, etc., and before insert molding, a molten metal or the like is poured into a mold of a desired shape to mold it into the desired shape, or it may be processed into the desired shape by cutting or the like using a machine tool or the like.
• the thickness of the metal part is preferably 0.5 mm or more and 20 mm or less at its thinnest part. Also, the thickness of the metal part is preferably 0.5 mm or more and 20 mm or less at its thickest part. It is not necessary for the metal portion to be entirely made of metal, and the interior of the metal portion may be hollow or filled with other materials.
• the insert molded product of the present embodiment usually has a weld portion.
• the weld portion refers to a welded portion formed at the interface between multiple resin flows that join together in a mold cavity when the insert molded product is molded.
• Fig. 1 is a schematic diagram for explaining the insert molded body of this embodiment, showing a cross section of the insert molded body.
• 1 indicates the flow direction of the resin composition of the insert molded body
• 2 (dotted line part) indicates a weld part
• 3 indicates a metal part
• 4 indicates a resin part.
• the insert molded product of the present embodiment may have one weld portion or two or more weld portions, but usually has two or more weld portions.
• the upper limit of the number of weld portions is practically 100 or less, and may be 50 or less, or 10 or less.
• the insert molded body of this embodiment preferably has a three-layer structure in which the resin part, the metal part, and the resin part are in contact with each other in the above-mentioned order.
• the two resin parts may be continuous or not, but are usually continuous.
• An example of a structure in which two resin parts are continuous is the structure shown in FIG. 1 described above. That is, in FIG. 1, there are resin parts 4 on both sides of the metal part 3, and when viewed from the flow direction 1 of the resin composition, the metal part and the resin part have a three-layer structure in which they are in contact with each other in the above-mentioned order, and the resin parts are continuous.
• the flow direction of the resin composition becomes two directions in the part having the metal part, and a weld part is formed. More preferably, in the insert molded article of the present embodiment, the entire surface of the inserted metal part is covered with the resin part, excluding the part that cannot be covered with the resin composition during molding, such as a hole for fixing the metal part to be inserted during molding, among the entire surface of the metal part.
• the insert molded body of this embodiment can be preferably used even in a structure in which the ratio of the thickness of the resin part to the thickness of the metal part (resin part/metal part) is small, the load on the resin part is large, and the structure is prone to cracking.
• the minimum value of the thickness ratio of the resin part to the metal part (resin part/metal part) of the insert molded body of this embodiment is 1.5 or less, and can be 1.2 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.65 or less, 0.60 or less, 0.55 or less, or 0.50 or less.
• the resin part of the insert molded body of this embodiment is less likely to crack and can be used suitably.
• the minimum value of the thickness ratio of the resin part to the metal part (resin part/metal part) of the insert molded body of this embodiment is preferably 0.1 or more, more preferably 0.15 or more, even more preferably 0.2 or more, even more preferably 0.22 or more, and even more preferably 0.25 or more.
• the insert molded body is preferably manufactured using pellets obtained by melt-kneading a resin composition containing polyacetal resin and an elastomer using a twin-screw extruder at a rotation speed of 90 rpm or more.
• the resin composition here is the resin composition described above.
• the insert molded article of this embodiment has excellent weld elongation, and therefore can be suitably used for seat belt attachment anchors (especially seat belt attachment anchors for automobile seat belts) and safety parts such as seat belt tongues.
• seat belt attachment anchors especially seat belt attachment anchors for automobile seat belts
• safety parts such as seat belt tongues.
• An example of an anchor for attaching a seat belt is shown in FIG. 1 and paragraph 0095 of JP-A-2022-98154, the contents of which are incorporated herein by reference.
• the insert molded article of this embodiment can be widely used for other automobile parts, building material parts, electric and electronic parts, office equipment parts, daily necessities parts, etc.
• the twin-screw extruder used was model PCM-30 manufactured by Ikegai Corporation, and the single-screw extruder used was model VS-40 manufactured by Tanabe Plastic Machinery Co., Ltd.
• the temperature of the resin composition when it was discharged from the die was measured by a K thermocouple.
• ⁇ Maximum secondary particle size of core-shell elastomer (nm)> A test piece for observation under a scanning electron microscope (SEM) was cut out from the center of the ISO test piece obtained above with a diamond knife so as to be parallel to the flow direction of the resin composition during molding. Osmium tetroxide was vapor-deposited onto the observation surface of the obtained test piece for SEM observation, and then an SEM image was obtained using a scanning electron microscope (SEM). From the obtained SEM image, the maximum length of the island portions derived from the elastomer was taken as the maximum secondary particle size of the elastomer.
• SEM scanning electron microscope
• the deposition of osmium tetroxide was performed using an "Osmium Coater” manufactured by Meiwafosis Co., Ltd. under conditions of 8 mA and 60 seconds.
• the scanning electron microscope used was a "Scanning Electron Microscope (SEM) S-4800” manufactured by Hitachi High-Technologies Corporation, and SEM images were obtained under conditions of acceleration voltage: 1 kV, signal: LA100 (U), emission current: 6 ⁇ A, and probe current: Normal.
• ⁇ Failure time of insert molding (hr)> The pellets obtained above were subjected to a heat treatment in a hot air circulation type dryer at a temperature of 80° C. for 4 hours. Next, the dried pellets were subjected to an injection molding machine with a cylinder temperature of 195° C. and a mold temperature of 80° C. to produce a metal insert molded piece with a thickness ratio of the resin part to the metal part (minimum value, thickness of the resin part/thickness of the metal part) of 0.5.
• the insert metal was made of S55C with a thickness of 2 mmt, which was heated to 80° C. on a hot plate before molding and then set in the mold immediately before molding.
• the injection molding machine used was an EC-100S manufactured by Shibaura Machine Co., Ltd.
• the insert molded body obtained above was placed in a hot air oven at 90°C and checked every 120 hours up to 1500 hours. Five experts visually checked the insert molded body, and the time (unit: hour) at which three or more experts judged it to be broken was evaluated. The results are shown in Tables 2 and 3 below.
• the insert moldings of the present invention had excellent weld elongation (Examples 1 to 5).
• the core-shell elastomer was not included (Comparative Example 1 and Comparative Example 5)
• the weld elongation was low and the time to failure of the insert molding was short.
• the maximum secondary particle diameter of the core-shell elastomer exceeded 1000 nm (Comparative Examples 2 to 4 and 7)
• the weld elongation was low and the time to failure of the insert molding was short.

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