Resin composition and molded article

Abstract

To provide a resin composition in which a weld line extends and impact strength is less likely to lower even at low temperatures, and a molded article formed from the resin composition.SOLUTION: A resin composition contains, with respect to 100 pts.mass of a polyacetal resin, 15-50 pts.mass of a partially crosslinked type thermoplastic polyurethane resin, wherein when the resin composition is molten and is molded into a dumbbell test piece having an ASTM D 638 Type I shape such that a weld line is formed by symmetrically filled with the molten resin composition from both ends, and tensile test is performed on the dumbbell test piece at speed of 10 mm / min, a breaking point is larger than a yield point, and notched Charpy impact strength under a temperature of -40°C when the resin composition is molded by a method according to JIS K 7111 and is subjected to notch processing is 9 kJ / m2 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin composition and a molded article. In particular, it relates to a resin composition mainly composed of a polyacetal resin.

Background Art

[0002] The polyacetal resin has high mechanical strength and rigidity, excellent oil resistance and organic solvent resistance, is a resin well-balanced in a wide temperature range, and has easy processability. Therefore, the polyacetal resin is widely used as a typical engineering plastic in OA equipment, digital household appliances, automotive parts and other industrial parts.

[0003] For example, in Patent Document 1, 1 to 120 parts by mass of a thermoplastic polyurethane (B) is blended with respect to 100 parts by mass of a polyacetal resin (A), and 0.01 to 5 parts by mass of a formaldehyde scavenger (C) is blended. The formaldehyde scavenger (C) is composed of at least one selected from the group consisting of a predetermined dihydrazone compound (C1) and a hydrazide compound (C2). The thermoplastic polyurethane (B) has a residual isocyanate amount of 0.10% by mass or less, a water content of 3000 ppm by mass or less, and a melt viscosity of 200,000 poise or more at 180°C. A polyacetal resin composition is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the above polyacetal resin composition is described as having excellent impact resistance, no consideration has been given to its impact resistance at low temperatures. In particular, the impact strength in a low temperature range of about -40°C is likely to decrease, and it is very difficult to maintain it high even at 1 kJ / m 2 . In addition, when the resin composition is injection molded, welds are formed. If the elongation of such welds is not excellent, cracking may occur depending on the application. An object of the present invention is to solve such problems, and to provide a resin composition in which weld lines extend and the impact strength hardly decreases even at low temperatures, and a molded article formed from the resin composition.

Means for Solving the Problems

[0006] Based on the above problems, the present invention has been solved by the following means. <1>A resin composition containing 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of a polyacetal resin, melting the resin composition, filling it symmetrically from both ends to form a weld line, and forming it into an ASTM D638 Type I dumbbell test piece. When a tensile test is performed on the dumbbell test piece at a speed of 10 mm / min, the breaking point is larger than the yield point, and when the resin composition is molded by a method compliant with JIS K 7111 and notch processed, the notched Charpy impact strength at a temperature of -40°C is 9 kJ / m 2 or more. Resin composition. <2>The resin composition according to <1>, further containing 0.01 to 5 parts by mass of a formaldehyde scavenger with respect to 100 parts by mass of the polyacetal resin. <3>The resin composition according to <2>, wherein the formaldehyde scavenger contains a dihydrazone compound represented by the formula (1).

Chemical formula

Advantages of the Invention

[0007] According to the present invention, it has become possible to provide a resin composition in which the weld line extends and the impact strength is less likely to decrease even at low temperatures, and a molded article formed from the resin composition.

Brief Description of the Drawings

[0008]

Figure 1

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an exemplification for explaining the present invention, and the present invention is not limited to only the present embodiment. In this specification, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value. In this specification, various physical property values and characteristic values are those at 23°C unless otherwise specified. When the standards shown in this specification vary depending on the year, and the measurement methods and the like are different, unless otherwise stated, they shall be based on the standards as of January 1, 2021.

[0010] The resin composition of this embodiment is a resin composition containing 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of a polyacetal resin. The resin composition is melted and molded into an ASTM D638 Type I dumbbell test piece filled symmetrically from both ends to form a weld line. When a tensile test is performed on the dumbbell test piece at a speed of 10 mm / min, the breaking point is larger than the yield point, and when the resin composition is molded by a method conforming to JIS K 7111 and notch processing is performed, the notched Charpy impact strength at a temperature of -40 °C is 9 kJ / m 2 It is characterized by the above. By adopting such a configuration, a resin composition can be obtained in which the weld line extends and the impact strength is less likely to decrease even at low temperatures.

[0011] The elongation of the above weld line and the impact resistance at low temperatures are achieved by adjusting the selection of the type of polyacetal resin, the use of a partially crosslinked thermoplastic polyurethane resin, the glass transition temperature of the partially crosslinked thermoplastic polyurethane resin, the kneading conditions, and the like. Specifically, as the kneading conditions, increasing the degree of kneading can be mentioned. By increasing the degree of kneading in this way, the particles of the partially crosslinked thermoplastic polyurethane resin become smaller and can be well dispersed in the polyacetal resin, and the effect of using the partially crosslinked thermoplastic polyurethane resin is more effectively exerted.

[0012] <Polyacetal resin> The resin composition of this embodiment contains a polyacetal resin. The polyacetal resin is not particularly limited in terms of its type or the like, and may be a homopolymer containing only a divalent oxymethylene group as a structural unit, or a copolymer containing a divalent oxymethylene group and a divalent oxyalkylene group having 2 or more carbon atoms as structural units. The carbon number of the oxyalkylene group having 2 or more carbon atoms is preferably 6 or less, more preferably 4 or less, and even more preferably 2. Specific examples of the oxyalkylene group having 2 or more carbon atoms include an oxyethylene group, an oxypropylene group, and an oxybutylene group, etc., and an oxyethylene group is preferred.

[0013] The polyacetal resin contains an oxymethylene group and an oxyalkylene group having 2 or more carbon atoms, and it is preferable that the oxyalkylene group is contained at a ratio greater than 0 mol and 2.0 mol or less per 100 mol of the oxymethylene group. More preferably, the ratio is 0.3 mol or more per 100 mol of the oxymethylene group, and even more preferably 0.5 mol or more. Also, as the upper limit of the ratio, it is preferably 1.5 mol or less, more preferably 1.3 mol or less, and even more preferably 1.1 mol% or less. By setting it below the upper limit value, the impact resistance at low temperatures (for example, -40°C) can be further improved.

[0014] In order to produce the above polyacetal resin, trioxane is usually used as the main raw material. Also, in order to introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin, for example, cyclic formal or cyclic ether can be used. Specific examples of cyclic formal include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, and 1,3,6-trioxocane, etc. Specific examples of cyclic ether include ethylene oxide, propylene oxide, and butylene oxide, etc. In order to introduce an oxyethylene group into the polyacetal resin, for example, 1,3-dioxolane can be used, for introducing an oxypropylene group, 1,3-dioxane can be used, and for introducing an oxybutylene group, 1,3-dioxepane can be introduced.

[0015] In the case of polyacetal resin, it is preferable that the amount of hemiacetal terminal groups, formyl terminal groups, and terminal groups unstable to heat, acids, and bases is small. Here, the hemiacetal terminal group is represented by -OCH2OH, and the formyl terminal group is represented by -CHO.

[0016] The melt index (MI) value of the above polyacetal resin is preferably 0.5 g / 10 min or more, and more preferably 50 g / 10 min or more. By setting such a value, the load on the motor of the extruder can be reduced, and the productivity of the resin composition (for example, pellets) can be improved. Further, the MI is preferably 150 g / 10 min or less, and more preferably 100 g / 10 min or less. By setting it below the above upper limit value, it is possible to make it less likely to generate vacuum voids. The MI value of the polyacetal resin is a measured value under the conditions of 190 °C and a load of 2.16 kg in accordance with ASTM-D1238.

[0017] The content of the polyacetal resin in the resin composition of this embodiment is preferably 60% by mass or more, more preferably 65% by mass or more, further preferably 70% by mass or more, still more preferably 75% by mass or more, and even more preferably 78% by mass or more. The upper limit is the amount at which the total amount of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin in the resin composition is 100% by mass. The resin composition of this 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 within the above range.

[0018] <Partially crosslinked thermoplastic polyurethane resin> The resin composition of this embodiment contains 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of the polyacetal resin. By including the partially crosslinked thermoplastic polyurethane resin, a resin composition excellent in impact resistance at low temperatures can be obtained. The partially crosslinked thermoplastic polyurethane resin used in this embodiment is preferably formed from a bifunctional polyol, a polyfunctional polyol, a chain extender, and a diisocyanate. By using such a partially crosslinked thermoplastic polyurethane resin, an outer skin excellent in weld elongation and strength can be obtained.

[0019] <<Bifunctional polyol>> The bifunctional polyol is a polyol having two hydroxy groups, and a wide range of bifunctional polyols generally used in the synthesis of polyurethane resins can be used. It is more preferably a linear polyether glycol having primary hydroxy groups at both ends, and even more preferably polytetramethylene glycol ether. The number average molecular weight of the bifunctional polyol is preferably 500 to 3000, and more preferably 800 to 2500. The number average molecular weight is a value calculated in terms of polystyrene according to GPC. Only one type of bifunctional polyol may be used, or two or more types may be used.

[0020] <<Polyfunctional polyol>> The polyfunctional polyol is a compound having more than two hydroxy groups at the terminals, and a wide range of polyols generally used in the synthesis of polyurethane resins can be used. The upper limit of the number of hydroxy groups possessed by the polyfunctional polyol is preferably three or less. The average functionality (the number of hydroxy groups per molecule) of the polyol used in this embodiment is preferably 2.01 to 3.0, and more preferably 2.1 to 2.5. By setting such a range, flexibility according to the purpose and use can be imparted, and improvement of various physical properties can be more effectively exhibited. Specifically, examples of the polyol used in the synthesis of the polyurethane resin include polyether polyol, polymer polyol, polyester polyol, etc., and polyester polyol is preferred. The polyester polyol is more preferably a polyester obtained by polycondensing an aliphatic difunctional polyol and / or an aliphatic polyol (preferably an aliphatic triol) with a carboxylic acid. As the difunctional polyol as a raw material of the polyester polyol, an aliphatic difunctional polyol having 3 to 10 carbon atoms is preferable, and 1,4-butanediol is more preferable. As the polyol as a raw material of the polyester polyol, a triol and / or a tetraol is preferable, an aliphatic triol having 3 to 12 carbon atoms is preferable, and trimethylolpropane is more preferable. As the dicarboxylic acid as a raw material of the polyester polyol, a dicarboxylic acid having 4 to 10 carbon atoms is preferable, an aliphatic dicarboxylic acid having 4 to 10 carbon atoms is more preferable, adipic acid and sebacic acid are further preferable, and adipic acid is even more preferable.

[0021] The number average molecular weight of the polyfunctional polyol used for the synthesis of the polyurethane resin is preferably 300 to 3000, and more preferably 500 to 2500. The number average molecular weight is a value calculated in terms of polystyrene according to GPC. Only one kind of polyfunctional polyol may be used, or two or more kinds may be used.

[0022] <<Chain extender>> In the synthesis of the partially crosslinked thermoplastic polyurethane resin, the type of the chain extender is not particularly limited. For example, a low molecular weight compound having two or more terminal hydroxy groups can be used, and a low molecular weight compound having two to three terminal hydroxy groups is preferable. Examples of the chain extender include difunctional polyols having 2 to 10 carbon atoms such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol. The molecular weight of the chain extender is preferably 62 to 380. Only one kind of chain extender may be used, or two or more kinds may be used. The blending amount of the chain extender is preferably 20 to 30 moles per 100 moles in total of the difunctional polyol, the polyfunctional polyol, and the diisocyanate.

[0023] <<Diisocyanate>> The diisocyanate can widely adopt diisocyanates generally used in the synthesis of polyurethane resins. The diisocyanate is not particularly limited, and examples thereof include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate (4,4'-methylenediphenyl diisocyanate) and 2,4-tolylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, and aliphatic diisocyanates such as hexamethylene diisocyanate. Aromatic diisocyanates are preferred, and 4,4'-diphenylmethane diisocyanate is more preferred. Only one type of diisocyanate may be used, or two or more types may be used.

[0024] <<Method for Producing Partially Crosslinked Thermoplastic Polyurethane Resin>> The method for producing a partially crosslinked thermoplastic polyurethane resin used in this embodiment includes a step of reacting a bifunctional polyol, a polyfunctional polyol, a chain extender, and a diisocyanate. After obtaining a prepolymer by reacting the bifunctional polyol, the polyfunctional polyol, and the diisocyanate, a chain extender may be added. The molar ratio (bifunctional polyol / polyfunctional polyol) of the bifunctional polyol and the polyfunctional polyol as raw materials for the partially crosslinked thermoplastic polyurethane resin is preferably 0.99 / 0.01 to 0.5 / 0.5. In addition, the reaction molar ratio of the diisocyanate to the total of the bifunctional polyol, the polyfunctional polyol, and the chain extender as raw materials for the partially crosslinked thermoplastic polyurethane resin, [diisocyanate / (bifunctional polyol + polyfunctional polyol + chain extender)] is preferably 1.10 to 0.95, and more preferably 1.08 to 0.99. By setting such a range, flexibility and physical properties according to the purpose and use can be more effectively exhibited.

[0025] <<Physical Properties of Partially Crosslinked Thermoplastic Polyurethane Resin>> The partially crosslinked thermoplastic polyurethane resin used in this embodiment preferably has a glass transition temperature of -40°C or lower, more preferably -45°C or lower, and even more preferably -48°C or lower, as measured by differential scanning calorimetry. By using a resin within the above upper limit, a resin composition and a molded article excellent in impact resistance at low temperatures can be obtained. The lower limit is preferably -100°C or higher, and more preferably -70°C or higher. When two or more partially crosslinked thermoplastic polyurethane resins are included, the higher value of Tg shall be adopted. The glass transition temperature is measured according to the peak temperature of tanδ obtained when the temperature is raised at a rate of 3°C / min and a vibration frequency of 10 Hz using a dynamic viscoelasticity measuring device.

[0026] In the resin composition of this embodiment, the content of the partially crosslinked thermoplastic polyurethane resin is 15 parts by mass or more, preferably 17 parts by mass or more, and more preferably 19 parts by mass or more, based on 100 parts by mass of the polyacetal resin. By setting the lower limit as above, the impact resistance tends to be further improved. Also, the content of the partially crosslinked thermoplastic polyurethane resin is 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and still more preferably 22 parts by mass or less, based on 100 parts by mass of the polyacetal resin. By setting the upper limit as above, the hardness of the obtained molded article can be further improved.

[0027] In the resin composition of this embodiment, the total of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, and still more preferably 98% by mass or more. The upper limit is 100% by mass. The resin composition of this embodiment may contain only one type of partially crosslinked thermoplastic polyurethane resin, or may contain two or more types. When two or more types are included, the total amount is preferably within the above range.

[0028] <Formaldehyde scavenger> It is preferable that the resin composition of the present embodiment further contains 0.01 to 5 parts by mass of a formaldehyde scavenger with respect to 100 parts by mass of the polyacetal resin. By including a formaldehyde scavenger, the amount of formaldehyde generated in the obtained molded product can be effectively reduced.

[0029] The formaldehyde scavenger preferably contains a hydrazone compound, and more preferably contains a dihydrazone compound represented by the formula (1). By using a hydrazone compound, it is presumed that the amide exchange reaction can be suppressed, the decrease in the molecular weight of the partially crosslinked thermoplastic polyurethane resin can be suppressed, and the generation of formaldehyde can be suppressed while suppressing the decrease in impact resistance.

Chemical formula

[0030] In formula (1), R 1 represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms, preferably an aliphatic hydrocarbon group having 4 to 20 carbon atoms, and more preferably an aliphatic hydrocarbon group having 6 to 12 carbon atoms.

[0031] The above aliphatic hydrocarbon group may be saturated or unsaturated, linear or branched, and more preferably a linear alkylene group. Specific examples of the aliphatic hydrocarbon group include, for example, alkylene groups such as butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group, nonadecylene group, and icosylene group. The above aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 6 to 12 carbon atoms (preferably a linear alkyl group having 6 to 12 carbon atoms). In this case, the reactivity between the dihydrazone compound and formaldehyde becomes higher, and the generation of formaldehyde is more effectively suppressed. Further, the contamination of the mold during the molding process can be more sufficiently suppressed.

[0032] The above alicyclic hydrocarbon group may be saturated or unsaturated. Examples of the alicyclic hydrocarbon group include cycloalkylene groups having 6 to 10 carbon atoms. Examples of the cycloalkylene group include cyclohexylene group.

[0033] Examples of the aromatic hydrocarbon group include arylene groups such as phenylene group and naphthylene group. A substituent may be bonded to at least a part of the carbon atoms of the aromatic hydrocarbon group. Examples of this substituent include a halogen group, a nitro group, an alkyl group having 1 to 20 carbon atoms, and the like.

[0034] In formula (1), R 2 ~R 5 each independently represents a hydrogen atom, a methyl group or an ethyl group, and at least one of R 2 and R 3 represents a methyl group or an ethyl group, and at least one of R 4 and R 5 represents a methyl group or an ethyl group. In formula (1), when R 2 and R 4 are ethyl groups, R 3 and R 5 are hydrogen atoms, and R2 and R 4 When is a methyl group, R 3 and R 5 is preferably a hydrogen atom or a methyl group, R 2 ~R 5 It is more preferable that any of them is a methyl group. In this case, the reactivity between the dihydrazone compound and formaldehyde becomes higher, and the generation of formaldehyde is more effectively suppressed. Further, the contamination of the mold during molding can be more sufficiently suppressed.

[0035] Specific examples of the dihydrazone compound represented by the formula (1) include, for example, 1,12-bis[2-(1-methylethylidene)hydrazino]]-1,12-dodecanedione, 1,12-bis(2-ethylidenehydrazino)-1,12-dodecanedione, 1,12-bis(2-propylidenehydrazino)-1,12-dodecanedione, 1,12-bis[2-(1-methylpropylidene)hydrazino]-1,12-dodecanedione, 1,12-bis[2-(1-ethylpropylidene)hydrazino]-1,12-dodecanedione, 1,10-bis[2-(1-methylethylidene)hydrazino]]-1,10-decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10-bis[2-(1-methylpropylidene)hydrazino]-1,10-decanedione, 1,10-bis[2-(1-ethylpropylidene)hydrazino]-1,10-decanedione, 1,6-bis[2-(1-methylethylidene)hydrazino]-1,6-hexanedione, 1,6-bis(2-ethylidenehydrazino)-1,6-hexanedione, 1,6-bis(2-propylidenehydrazino)-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-ethylpropylidene)hydrazino]-1,6-hexanedione, 1,3-bis[2-(1-methylethylidene)hydrazinocarbonyl]benzene and the like.

[0036] In the resin composition of the present embodiment, the content of the formaldehyde scavenger (preferably a hydrazone compound) is preferably 0.01 part by mass or more, more preferably 0.02 part by mass or more, and still more preferably 0.05 part by mass or more with respect to 100 parts by mass of the polyacetal resin. By setting the content to be not less than the lower limit value, the generation of formaldehyde when the residence time is long can be more effectively suppressed. Further, the content of the formaldehyde scavenger (preferably a hydrazone compound) is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and may be 1 part by mass or less with respect to 100 parts by mass of the polyacetal resin. By setting the content to be not more than the upper limit value, mold contamination can be more effectively suppressed. The resin composition of the present embodiment may contain only one kind or two or more kinds of formaldehyde scavengers. When two or more kinds are contained, it is preferable that the total amount is within the above range.

[0037] <Polyamide> The resin composition of the present embodiment preferably further contains 0.01 to 10.0 parts by mass of polyamide with respect to 100 parts by mass of the polyacetal resin. By containing polyamide, the low-temperature impact resistance can be increased. In the present embodiment, the polyamide is preferably at least one polyamide selected from the group consisting of polymerized fatty acid polyamide and polyamide elastomer, more preferably a polymerized fatty acid, and still more preferably a dimer acid. Here, the polymerized fatty acid polyamide refers to a polyamide composed of a polycondensate of a polymerized fatty acid and a diamine.

[0038] A polymerized fatty acid is a polymer of an unsaturated fatty acid or a product obtained by hydrogenating this polymer. Examples of polymerized fatty acids include dimers (dimer acids) of monobasic fatty acids having 10 to 24 carbon atoms and one or more double bonds or triple bonds, or hydrogenated products thereof. Examples of dimer acids include dimers of oleic acid, linoleic acid, and erucic acid. The amine value of the dimer acid polyamide is preferably 1.0 to 5.0 mgKOH / g.

[0039] Examples of diamines include hexamethylenediamine, heptamethylenediamine, octamethylenediamine, decamethylenediamine, and metaxylylenediamine.

[0040] A polyamide elastomer is a polyamide having a hard segment and a soft segment, where the hard segment is composed of polyamide and the soft segment is composed of a polymer other than polyamide. Examples of polyamides constituting the hard segment include nylon-6, nylon-6,6, nylon-6,10, their terpolymers, and polymerized fatty acid polyamides. Examples of polymers other than polyamide include aliphatic polyesters and aliphatic polyethers. Examples of aliphatic polyesters include poly(ε-caprolactone), polyethylene adipate, polybutylene adipate, and polybutylene succinate. Examples of aliphatic polyethers include polyoxyalkylene glycols such as polyethylene oxide and polypropylene oxide.

[0041] The content of the above polyamide (preferably dimer acid) is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, still more preferably 0.1 part by mass or more, and even more preferably 0.3 part by mass or more, based on 100 parts by mass of the polyacetal resin. The content of the polyamide is preferably 10.0 parts by mass or less, more preferably 9.0 parts by mass or less, still more preferably 7.0 parts by mass or less, even more preferably 5.0 parts by mass or less, and even more preferably 1.0 part by mass or less, based on 100 parts by mass of the polyacetal resin. The resin composition of the present embodiment may contain only one type of polyamide or may contain two or more types. When two or more types are contained, it is preferable that the total amount is within the above range.

[0042] <Other components> The resin composition of the present embodiment may contain any conventionally known additives or fillers within a range that does not impair the object of the present invention. Examples of the additives and fillers used in the present embodiment include thermoplastic resins other than polyacetal resins and partially crosslinked thermoplastic polyurethane resins, ultraviolet absorbers, antioxidants, stabilizers, antistatic agents, carbon fibers, glass fibers, glass flakes, potassium titanate whiskers, and the like. Details of these can be referred to the descriptions in paragraphs 0113 to 0124 of JP-A-2017-025257, and the contents thereof are incorporated herein.

[0043] A first form of the resin composition of the present embodiment is an embodiment in which the total of the polyacetal resin, the partially crosslinked thermoplastic polyurethane resin, the formaldehyde scavenger, and the polyamide optionally blended accounts for 95% by mass or more of the resin composition, and more preferably 99% by mass or more.

[0044] The second form of the resin composition of the present embodiment contains 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of a polyacetal resin. The glass transition temperature of the partially crosslinked thermoplastic polyurethane resin is -40°C or lower. The polyacetal resin contains an oxymethylene group and an oxyalkylene group having 2 or more carbon atoms, and the oxyalkylene group is contained at a ratio of more than 0 mol and 1.3 mol or less per 100 mol of the oxymethylene group. It is a resin composition. The above polyacetal resin, partially crosslinked thermoplastic polyurethane resin and their preferred ranges of details are the same as those of the resin composition of the above-described embodiment.

[0045] The resin composition of the present embodiment can be configured to substantially contain no core-shell type elastomer, and further no elastomer (excluding the partially crosslinked thermoplastic polyurethane resin). Substantially containing none means that the content of the core-shell type elastomer and further the elastomer is 5% by mass or less of the content of the partially crosslinked thermoplastic polyurethane resin contained in the resin composition, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0046] <Physical properties of the resin composition> The resin composition of the present embodiment is molded by a method conforming to JIS K 7111, and when notched, the notched Charpy impact strength at a temperature of -40°C is 9 kJ / m 2The above is the case. The impact resistance at such a low temperature can be achieved, for example, by selecting the type of polyacetal resin, using a partially crosslinked thermoplastic polyurethane resin, using a partially crosslinked thermoplastic polyurethane resin with a low Tg, or adjusting the kneading conditions. More specifically, it is achieved by performing at least one of using a polyacetal resin with a low proportion of oxyethylene units, using a polyurethane resin with a glass transition temperature of -40°C or lower, and increasing the intensity of kneading during melt kneading. By increasing the intensity of kneading during melt kneading, the particles of the partially crosslinked thermoplastic polyurethane resin become smaller and are better dispersed in the polyacetal resin, and it is presumed that the effect is more effectively exerted.

[0047] The resin composition of this embodiment is formed into a flat test piece of 100 mm × 40 mm × 2 mm, and the formaldehyde generation amount measured based on the German Automobile Industry Association Standard VDA275 method is usually 45 mass ppm or less, preferably 5 mass ppm or less, and more preferably 4 mass ppm or less per 1 g of the polyacetal resin. The lower limit value is ideally 0, but 0.1 mass ppm or more is practical.

[0048] The resin composition of this embodiment is melted, formed into an ASTM D638 Type I dumbbell test piece filled symmetrically from both ends to form a weld line, and when a tensile test is performed on the dumbbell test piece at a speed of 10 mm / min, the breaking point is larger than the yield point. When the polyacetal resin and the thermoplastic polyurethane resin are kneaded, in the dumbbell test piece with a weld line, due to the low adhesion of the weld part, it reaches breakage before facing the yield point. In this embodiment, by using a partially crosslinked thermoplastic polyurethane resin, the breaking point of the dumbbell test piece having a weld part being larger than the yield point can be used as a measure of the adhesion degree of the weld line.

[0049] <Method for manufacturing resin composition and molded article> The resin composition of this embodiment contains the above-described essential components and, if necessary, any of the above-described optional components. As its manufacturing method, any conventionally known method for manufacturing a polyacetal resin composition may be used, and these raw materials may be mixed and melt-kneaded.

[0050] Examples of the kneader include a kneader, a Banbury mixer, an extruder, etc. There are no particular restrictions on the various conditions and equipment for mixing and melt-kneading, and they may be appropriately selected and determined from any conventionally known conditions. The melt-kneading is carried out at a temperature equal to or higher than the temperature at which the polyacetal resin melts, for example, at the melting point + 5°C or higher, preferably at the melting point + 5°C to the melting point + 70°C. Also, in order to enhance the low-temperature impact resistance, the type and rotation speed of the screw may be adjusted so that the kneading becomes stronger.

[0051] The molded article of this embodiment is formed from the resin composition of this embodiment. The resin composition of this embodiment is melt-kneaded and manufactured into a molded article. Specifically, pellets obtained by pelletizing the resin composition of this embodiment may be molded by various molding methods to obtain a molded article, or the resin composition melt-kneaded by an extruder may be directly molded into a molded article without passing through the pellets. There are no particular restrictions on the shape of the molded article, and it can be appropriately selected according to the use and purpose of the molded article. For example, plate-shaped, plate-like, rod-shaped, sheet-shaped, film-shaped, cylindrical, annular, circular, elliptical, gear-shaped, polygonal-shaped, shaped articles, hollow articles, frame-shaped, box-shaped, panel-shaped, cap-shaped ones, etc. may be mentioned. The molded article of this embodiment may be a finished product or a component.

[0052] The method for molding the molded article is not particularly limited, and a conventionally known molding method can be adopted. For example, injection molding method, injection compression molding method, extrusion molding method, profile extrusion method, transfer molding method, blow molding method, gas-assisted blow molding method, blow molding method, extrusion blow molding, IMC (in-mold coating molding) molding method, rotational molding method, multi-layer molding method, two-color molding method, insert molding method, sandwich molding method, foam molding method, pressure molding method, etc. may be mentioned.

[0053] <Use> The resin composition and molded article of this embodiment can be suitably used in applications where a strong reduction in the amount of formaldehyde generation is required, such as automotive parts, electrical and electronic parts, precision mechanical parts, building materials and piping parts, daily necessities, cosmetic parts, medical device parts, indoor use parts, and the like. More specifically, as automotive parts, there are interior parts such as inner handles, fuel tank openers, seat belt buckles, assist straps, various switches, knobs, levers, clips, etc., electrical system parts such as meters and connectors, in-vehicle electrical and electronic parts such as audio equipment and car navigation equipment, parts that come into contact with metals typified by the carrier plate of a window regulator, door lock actuator parts, mirror parts, wiper motor system parts, parts of the fuel system, and other mechanism parts.

[0054] As electrical and electronic parts, there are constituent parts or members of devices with a large number of metal contacts, such as constituent parts or members of audio equipment such as cassette tape recorders, CD / DVD players, video equipment such as VTRs, 8mm video cameras, digital video cameras, and OA equipment such as copiers, facsimiles, word processors, and computers. Specific examples of these constituent parts or members include chassis, gears, levers, cams, pulleys, bearings, etc. Furthermore, it is also applicable to optical and magnetic media parts at least partially composed of molded articles, such as parts for music metal tape cassettes, digital audio tape cassettes, 8mm video tape cassettes, digital video cassettes, floppy disk cartridges, mini disk cartridges, DVD disk cartridges, etc.

[0055] Furthermore, the molded article of this embodiment is suitably used in a wide range of life-related parts, cosmetic-related parts, and medical-related parts, such as lighting fixtures, architectural hardware, piping, faucets, taps, toilet peripheral equipment parts, fasteners, stationery, lip cream and lipstick containers, cleaners, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, holders for injection needles, etc.

[0056] Especially in the field of automobiles, the interior of the vehicle is often placed in a closed environment, and the interior of the vehicle may also reach a relatively high temperature. The resin composition of this embodiment with a low formaldehyde generation amount is particularly preferably used for molded products in such fields.

Examples

[0057] The present invention will be further specifically described with reference to the following examples. The materials, usage amounts, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. When the measuring instruments used in the examples are difficult to obtain due to obsolete numbers, etc., measurements can be made using other devices having equivalent performance.

[0058] Raw materials <Polyoxymethylene resin (A)> (A-1) Yupital A10-03: An oxymethylene copolymer of trioxane and 1,3-dioxolane, a polyoxymethylene resin containing 1.0 mol% of oxyethylene units (MI: 50 g / 10 min) (The melt index (MI) is a measured value under the conditions of 190 °C and a load of 2.16 kg in accordance with ASTM-D1238.), melting point: 168 °C (A-2) Yupital F30-03: An oxymethylene copolymer of trioxane and 1,3-dioxolane, a polyoxymethylene resin containing 1.5 mol% of oxyethylene units (MI: 50 g / 10 min), melting point: 166 °C <Thermoplastic polyurethane resin (B)> (B-1) Gum Sen ARX-650: A partially cross-linked thermoplastic polyurethane resin, manufactured by Okada Engineering Co., Ltd., -50 °C (B-2) Estane S80A: A non-cross-linked thermoplastic polyurethane resin, manufactured by BASF, glass transition temperature -30 °C (B-3) Estane ET870: A non-cross-linked thermoplastic polyurethane resin, manufactured by BASF, glass transition temperature -55 °C (B-4) Milactran E385: Uncrosslinked thermoplastic polyurethane resin, manufactured by Nippon Milactran Co., Ltd., glass transition temperature -50 °C The above glass transition temperature was measured according to the peak temperature of tanδ obtained when the temperature was raised at a heating rate of 3 °C / min and a vibration frequency of 10 Hz using a dynamic viscoelasticity measuring device. <Formaldehyde scavenger (C)> (C-1): 1,6-bis[2-(1-methylethylidene)hydrazino]-1,6-hexanedione (C-2): Adipic acid dihydrazide <Polyamide (D)> (D-1) TXM-272: Dimer acid polyamide, manufactured by T&K TOKA Co., Ltd., amine value 3.0 mgKOH / g

[0059] Examples 1 to 3 and Comparative Examples 1 to 6 <Compound> As shown in Tables 1 and 2 below, each component was blended (the unit of the blending amount of each component in Tables 1 and 2 is parts by mass), and after pre-blending, it was put into the main feed port of a 26 mm diameter twin-screw extruder having one vent port and melt-mixed (extrusion conditions: L / D = 48, extrusion temperature = 215 °C, screw rotation speed = 240 rpm) to prepare pellets (resin composition).

[0060] <Molding of test pieces> Using the above pellets, the following test pieces were prepared by injection molding. (1) ISO dumbbell test piece An ISO dumbbell test piece with a thickness of 4 mm was molded from a single-point gate with the mold temperature set at 40 °C and the cylinder temperature set at 200 °C. (2) ASTM D638 Type I shape dumbbell test piece A dumbbell test piece with a shape in which the resin composition melted symmetrically from both ends to form a weld line was molded with the mold temperature set at 40 °C and the cylinder temperature set at 200 °C. (3) Flat plate for formaldehyde generation amount A flat plate test piece of 100 mm × 40 mm × 2 mm was molded with the mold temperature set at 80 °C and the cylinder temperature set at 215 °C.

[0061] <Weld elongation> A dumbbell test piece of ASTM Type I shape was subjected to a tensile test at a speed of 10 mm / min, and the breaking point was confirmed. When the breaking point was larger than the yield point, it was designated as A, and when it was smaller, it was designated as B, and the weld elongation was evaluated. Materials in which the weld does not elongate break before reaching the yield point. As shown in Fig. 1, materials that do not break even after exceeding the yield point serve as an index of strong weld elongation.

[0062] <Notched Charpy impact strength> For the ISO dumbbell test piece obtained above, notching was performed using a notching machine according to JIS K7111 to form a notch with an R of 0.25 mm and a depth of 2 mm. Subsequently, using a Charpy impact tester with a thermostat, in accordance with ISO 179-1, the Charpy impact strength at temperatures of 23°C and -40°C was measured using a 1 J hammer. The unit is kJ / m 2 as shown.

[0063] <Formaldehyde generation amount> On the day after producing the flat test piece, in accordance with the method described in the German Automobile Industry Association Standard VDA 275 (Automobile Interior Parts - Quantification of Formaldehyde Emission by the Revised Flask Method), the formaldehyde generation amount of the above flat test piece was measured by the following methods (1) to (3). (1) 50 mL of distilled water was placed in a polyethylene container, the lid was closed with the above flat test piece suspended in the air, and it was heated at 60°C for 3 hours in a sealed state. (2) Subsequently, after leaving it at room temperature for 60 minutes, the flat test piece was taken out. (3) The amount of formaldehyde absorbed in the distilled water in the polyethylene container was measured by the acetylacetone colorimetric method using a UV spectrometer. The value obtained by dividing this amount of formaldehyde by the mass of the polyacetal resin in the flat test piece was defined as the formaldehyde generation amount. The unit was shown as mass ppm / POM 1 g (the amount of formaldehyde generated per 1 g of polyacetal resin (mass ppm)).

[0064]

Table 1

Table 2

[0065] As is clear from the above results, the resin compositions (Examples 1 to 3) of the present embodiment were excellent in weld elongation and could maintain a high Charpy impact strength at low temperatures. In particular, considering that it is very difficult to improve the Charpy impact strength to a level of 2 kJ / m at room temperature and 1 kJ / m at low temperature, it can be seen that the resin compositions of Comparative Examples 1 to 6 are extremely remarkable. 2 level and 1 kJ / m at low temperature 2 level, it can be seen that it is extremely remarkable compared to the resin compositions of Comparative Examples 1 to 6. Furthermore, for Example 1, Example 2 in which a formaldehyde scavenger was blended could significantly reduce the amount of formaldehyde generated. Also, between Example 1 and Example 2, in addition to room temperature, the Charpy impact strength at low temperatures decreased. However, by further blending polyamide with respect to Example 2, it was possible to maintain the amount of formaldehyde generated at a low level and make the low-temperature Charpy impact strength equivalent to that of Example 1 (without blending a formaldehyde scavenger) (Example 3). This is extremely surprising technically and also has high value in terms of actual use.

Claims

1. A resin composition comprising 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of a polyacetal resin, wherein the partially crosslinked thermoplastic polyurethane resin is formed from a bifunctional polyol, a polyfunctional polyol, a chain extender, and a diisocyanate, the number average molecular weight of the bifunctional polyol is 500 to 3000, the polyfunctional polyol is a polyester having a number average molecular weight of 300 to 3000 and 2.01 to 3.0 hydroxy groups per molecule, the chain extender is a bifunctional polyol having a molecular weight of 62 to 380, the diisocyanate is an aromatic diisocyanate, the molar ratio of the bifunctional polyol to the polyfunctional polyol (bifunctional polyol / polyfunctional polyol) is 0.99 / 0.01 to 0.5 / 0.5, the glass transition temperature of the partially crosslinked thermoplastic polyurethane resin is -40°C or lower, the resin composition is melted and molded into an ASTM D638 Type I dumbbell test piece filled symmetrically from both ends to form a weld line, and when the dumbbell test piece is subjected to a tensile test at a speed of 10 mm / min, the breaking point is larger than the yield point, and The resin composition is molded by a method compliant with JIS K 7111, and when notched, the notched Charpy impact strength at a temperature of -40°C is 9 kJ / m ２ or more. a resin composition.

2. The resin composition according to claim 1, further comprising 0.01 to 5 parts by mass of a formaldehyde scavenger with respect to 100 parts by mass of the polyacetal resin.

3. The resin composition according to claim 2, wherein the formaldehyde scavenger contains a dihydrazone compound represented by the formula (1). 【Chemical 1】 (In formula (1), R １ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. R ２ to R ５ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and at least one of R ２ and R ３ represents a methyl group or an ethyl group, and at least one of R ４ and R ５ represents a methyl group or an ethyl group.)

4. In the formula (1), R １ The resin composition according to claim 3, wherein is an aliphatic hydrocarbon group having 6 to 12 carbon atoms.

5. In the formula (1), R ２ and R ４ are ethyl groups, R ３ and R ５ are hydrogen atoms, and when R ２ and R ４ are methyl groups, R ３ and R ５ are hydrogen atoms or methyl groups. The resin composition according to claim 3 or 4.

6. The resin composition according to any one of claims 2 to 5, wherein the resin composition is molded into a flat plate test piece of 100 mm × 40 mm × 2 mm, and the formaldehyde generation amount measured based on the German Automobile Industry Association standard VDA275 method is 5 ppm by mass or less per 1 g of the polyacetal resin.

7. The resin composition according to any one of claims 1 to 6, further comprising 0.01 to 10.0 parts by mass of a polyamide with respect to 100 parts by mass of the polyacetal resin.

8. The resin composition according to claim 7, wherein the polyamide is at least one polyamide selected from the group consisting of a polymerized fatty acid polyamide and a polyamide elastomer.

9. The resin composition according to any one of claims 1 to 8, wherein the glass transition temperature according to the differential scanning calorimetry of the partially crosslinked thermoplastic polyurethane resin is -40°C or lower.

10. The resin composition according to any one of claims 1 to 9, wherein the polyacetal resin contains an oxymethylene group and an oxyalkylene group having 2 or more carbon atoms, and the oxyalkylene group is contained at a ratio of more than 0 mol and 1.3 mol or less per 100 mol of the oxymethylene group.

11. Containing 15 to 50 parts by mass of a partially crosslinked thermoplastic polyurethane resin with respect to 100 parts by mass of the polyacetal resin, The partially crosslinked thermoplastic polyurethane resin is formed from a bifunctional polyol, a polyfunctional polyol, a chain extender, and a diisocyanate, The number average molecular weight of the bifunctional polyol is 500 to 3000, The polyfunctional polyol is a polyester having a number average molecular weight of 300 to 3000 and 2.01 to 3.0 hydroxy groups per molecule, The chain extender is a bifunctional polyol having a molecular weight of 62 to 380, The diisocyanate is an aromatic diisocyanate, The bifunctional polyol and the polyfunctional polyol have a molar ratio (bifunctional polyol / polyfunctional polyol) of 0.99 / 0.01 to 0.5 / 0.5, A resin composition in which the glass transition temperature of the partially crosslinked thermoplastic polyurethane resin is -40°C or lower, The glass transition temperature of the partially crosslinked thermoplastic polyurethane resin is -40°C or lower, The resin composition, wherein the polyacetal resin contains an oxymethylene group and an oxyalkylene group having 2 or more carbon atoms, and the oxyalkylene group is contained at a ratio of more than 0 mol and 1.3 mol or less per 100 mol of the oxymethylene group.

12. A molded article formed from the resin composition according to any one of claims 1 to 11.

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