Resin composition and molded article

Abstract

To provide a resin composition that has high toughness and has suppressed decrease in elastic modulus, and to provide a molded article.SOLUTION: Provided is a resin composition that contains polyacetal resin (A) by 50 to 95 pts.mass, elastomer (B) by 5 to 50 pts.mass, and calcium carbonate (C), and in which calcium carbonate (C) is contained so that the total surface area of calcium carbonate (C) in the polyacetal resin (A) is 0.02 to 2.00 m2 per 1 g of polyacetal resin (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to resin compositions and molded articles, and more particularly to resin compositions having polyacetal resin as a main component. [Background technology]

[0002] Polyacetal resin is a plastic with excellent mechanical, electrical, and chemical properties, including chemical resistance, and is used in a wide range of applications. Here, the incorporation of elastomers into polyacetal resin has been considered (Patent Document 1, etc.). Furthermore, Patent Document 1 also describes the incorporation of particulate inorganic fillers. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-255569 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] To improve the toughness of a polyacetal resin composition, one might consider compounding an elastomer into the polyacetal resin. However, compounding an elastomer reduces the elastic modulus. The present invention aims to solve this problem and provides a resin composition and molded article that have high toughness and suppress the reduction in elastic modulus. [Means for solving the problem]

[0005] The above problems were solved by compounding calcium carbonate with an elastomer into the polyacetal resin. Specifically, the above problem was solved by the following means. <1> Polyacetal resin (A) is 50 to 95 parts by mass, Elastomer (B) in 5 to 50 parts by mass, Contains calcium carbonate (C), The calcium carbonate (C) in the polyacetal resin (A) has a total surface area of ​​0.02 to 2.00 m² per 1 g of polyacetal resin (A). 2 A resin composition containing the following components. <2> The average particle size of the calcium carbonate (C) is 0.001 to 0.30 μm. <1> The resin composition described above. <3> The elastomer (B) includes a core-shell elastomer. <1> or <2> The resin composition described above. <4> The elastomer (B) comprises a core-shell elastomer containing an acrylic resin in the shell. <1> or <2> The resin composition described above. <5> According to ISO 1133 for the aforementioned polyacetal resin (A), the melt volume rate (MVR) measured under conditions of 190°C and 2.16 kg load was 0.5 to 20 cm³. 3 / 10min <1> ~ <4> A resin composition as described in any one of the following. <6> The average particle size of the calcium carbonate (C) is 0.001 to 0.30 μm. The elastomer (B) comprises a core-shell elastomer containing an acrylic resin in the shell, According to ISO 1133 for the aforementioned polyacetal resin (A), the melt volume rate (MVR) measured under conditions of 190°C and 2.16 kg load was 0.5 to 20 cm³. 3 / 10min <1> The resin composition described above. <7> The resin composition is molded into a 4 mm thick multipurpose test specimen, and the tensile elongation measured under ISO 527 conditions is 80-200%. The resin composition is molded into a 4 mm thick multipurpose test specimen, and when a bending test is performed at a bending test speed of 2 mm / min according to the method described in ISO 178, the flexural modulus is 1010-1200 MPa. <1> ~ <6> A resin composition as described in any one of the following. <8> <1> ~ <7> A molded article formed from any one of the resin compositions described in that one. [Effects of the Invention]

[0006] According to the present invention, it has become possible to provide a resin composition having high toughness and suppressed decrease in elastic modulus, and a molded product.

Mode for Carrying Out the Invention

[0007] Hereinafter, a mode 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 only to the present embodiment. In this specification, "~" is used to mean including the numerical values described before and after it as a lower limit value and an upper limit value. In this specification, various physical property values and characteristic values are assumed to be those at 23°C unless otherwise specified. When the measurement methods and the like described in the standards shown in this specification differ depending on the year, they are assumed to be based on the standards as of January 1, 2022 unless otherwise specified.

[0008] The resin composition of the present embodiment contains 50 to 95 parts by mass of a polyacetal resin (A), 5 to 50 parts by mass of an elastomer (B), and calcium carbonate (C). The calcium carbonate (C) has a total surface area of calcium carbonate (C) in the polyacetal resin (A) of 0.02 to 2.00 m 2 such that it is contained per 1 g of the polyacetal resin (A). By adopting such a configuration, a resin composition having high toughness and suppressed decrease in elastic modulus can be obtained. In order to increase the toughness of a molded product formed from a polyacetal resin composition, it is conceivable to blend an elastomer. However, when an elastomer is blended, the elastic modulus of a molded product formed from the polyacetal resin composition tends to decrease. In the present embodiment, calcium carbonate has a total surface area of calcium carbonate (C) in the polyacetal resin (A) of 0.02 to 2.00 m 2By compounding the material in this way, the decrease in elastic modulus is effectively suppressed. This is presumed to be because calcium carbonate acts as a stress relaxant in the deformable region of the resin composition. In other words, if there is simply a large amount of calcium carbonate in a molded polyacetal resin product, it will act as a foreign substance. However, in this embodiment, since the molded product is made by compounding an elastomer with polyacetal resin, it deforms when subjected to impact. It is presumed that the small calcium carbonate particles contributed as stress relaxants during this deformation. The details of the present invention will be described below.

[0009] <Polyacetal resin (A)> The resin composition of this embodiment includes a polyacetal resin (A). The polyacetal resin (A) is not particularly limited and may be a homopolymer containing only divalent oxymethylene groups as constituent units, or a copolymer containing divalent oxymethylene groups and divalent oxyalkylene groups having 2 to 6 carbon atoms as constituent units.

[0010] Examples of oxyalkylene groups having 2 to 6 carbon atoms include oxyethylene, oxypropylene, and oxybutylene groups.

[0011] In polyacetal resins, the proportion of oxyalkylene groups having 2 to 6 carbon atoms to the total number of moles of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms is not particularly limited and can be 0.5 to 10 mol%.

[0012] In order to produce the above polyacetal resin (A), trioxane is usually used as the main raw material. In addition, in order to introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin, cyclic formal or 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, 1,3,6-trioxocane, etc., and specific examples of the cyclic ether include ethylene oxide, propylene oxide, and butylene oxide, etc. In order to introduce an oxyethylene group into the polyacetal resin (A), 1,3-dioxolane may be used as the main raw material, in order to introduce an oxypropylene group, 1,3-dioxane may be used as the main raw material, and in order to introduce an oxybutylene group, 1,3-dioxepane may be used as the main raw material. In the polyacetal resin, it is preferable that the amount of hemi-formal end groups, the amount of formyl end groups, and the amount of end groups unstable to heat, acid, and base are small. Here, the hemi-formal end group is represented by -OCH2OH, and the formyl end group is represented by -CHO.

[0013] The polyacetal resin (A) used in this embodiment has a melt volume rate (MVR) measured according to ISO1133 under the conditions of a temperature of 190 °C and a load of 2.16 kg of 0.5 cm 3 / 10 min or more, preferably 0.6 cm 3 / 10 min or more, more preferably 0.8 cm 3 / 10 min or more, still more preferably 1 cm 3 / 10 min or more, even more preferably 5 cm 3 / 10 min or more. By setting the value to be not less than the above lower limit, the productivity of the resin composition tends to be further improved. Further, the MVR of the polyacetal resin (A) is preferably 20 cm 3 / 10 min or less, more preferably 18 cm 3 / 10 min or less, still more preferably 14 cm 3 / 10 min or less, even more preferably 10 cm 3 / More preferably it is 10 minutes or less, 8cm 3 It is even more preferable that the interval be 10 minutes or less. By keeping it below the above upper limit, the dispersibility of elastomer (B) tends to improve. In particular, when a core-shell elastomer is used as elastomer (B), it tends to be possible to reduce its average secondary particle size.

[0014] In addition to the above, polyacetal resins described in paragraphs 0018 to 0043 of Japanese Patent Publication No. 2015-074724 can be used as polyacetal resins, and these contents are incorporated herein by reference.

[0015] <Elastomer (B)> The resin composition of this embodiment contains elastomer (B). By including elastomer (B), a resin composition with high toughness can be obtained. The elastomer is not specified in any particular way, and any known elastomer can be used. The elastomer may be a core-shell elastomer or an elastomer other than a core-shell elastomer (non-core-shell elastomer). In this embodiment, a core-shell elastomer is preferred.

[0016] Core-shell elastomers are multilayer polymers having a core and a shell layer that covers part or all of it. Examples include Kaneka's Kaneace series and Mitsubishi Chemical's Metabren series.

[0017] The type of core-shell elastomer used in this embodiment is not particularly limited, but the core is preferably a rubber-based polymer. The rubber-based polymer preferably contains at least one selected from butadiene-containing rubber, butyl acrylate-containing rubber, 2-ethylhexyl acrylate-containing rubber, and silicone-based rubber, and more preferably contains butadiene-containing rubber. The shell is preferably a polymer of one or more monomers such as (meth)acrylic acid ester and aromatic vinyl compounds, and more preferably a polymer (acrylic resin) in which units derived from (meth)acrylic acid ester account for 50% or more of the total mass. In this embodiment, it is preferable that the core-shell elastomer used contains a rubber-based polymer in the core and an acrylic-based resin in the shell. Using such a core-shell elastomer tends to more effectively exhibit the effects of the present invention.

[0018] Examples of non-core-shell elastomers used in this embodiment include polyolefin elastomers, polystyrene elastomers, polyurethane elastomers, polyester elastomers, copolyester ether elastomers, acrylic elastomers, and vinyl chloride nitrile elastomers.

[0019] <Blending ratio of components (A) and (B)> The resin composition of this embodiment contains 50 to 95 parts by mass of polyacetal resin (A) and 5 to 50 parts by mass of elastomer (B). In the resin composition of this embodiment, when the total amount of polyacetal resin (A) and elastomer (B) is 100 parts by mass, the content of polyacetal resin (A) is usually 50 parts by mass or more, preferably 55 parts by mass or more, more preferably 61 parts by mass or more, and even more preferably 64 parts by mass or more. Setting it above the lower limit tends to effectively suppress an excessive decrease in elastic modulus. Furthermore, in the resin composition of this embodiment, when the total amount of polyacetal resin (A) and elastomer (B) is 100 parts by mass, the content of polyacetal resin (A) is usually 95 parts by mass or less, and depending on the application, it may be 89 parts by mass or less, 85 parts by mass or less, 79 parts by mass or less, 75 parts by mass or less, or 70 parts by mass or less. Setting it below the upper limit allows for more effective expression of good toughness. Furthermore, in the resin composition of this embodiment, the total amount of polyacetal resin (A) and elastomer (B) is preferably 90% by mass or more, more preferably 92% by mass or more, and even more preferably 96% by mass or more. The upper limit of the total amount of polyacetal resin (A) and elastomer is the value at which the components other than calcium carbonate (C) are composed of polyacetal resin (A) and elastomer (B). The resin composition of this embodiment may contain only one type of polyacetal resin (A), or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range. The resin composition of this embodiment may contain only one type of elastomer (B), or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0020] <Calcium carbonate (C)> The resin composition of this embodiment contains calcium carbonate (C), and the total surface area of ​​calcium carbonate (C) in the polyacetal resin (A) is 0.02 to 2.00 m² per 1 g of polyacetal resin (A). 2It is included in such a way that the following occurs: The inclusion of calcium carbonate (C) contributes as a stress relaxant, more effectively suppressing the decrease in elastic modulus. Furthermore, by setting the total surface area of ​​calcium carbonate (C) above the lower limit, toughness tends to improve. Conversely, by setting it below the upper limit, it tends to more effectively prevent calcium carbonate (C) from becoming the fracture initiation point.

[0021] The total surface area of ​​calcium carbonate (C) in polyacetal resin (A) is 0.05 m² per gram of polyacetal resin (A). 2 Preferably, it is 0.08 m 2 It is more preferable that the value be greater than or equal to 0.10m 2 It is even more preferable that the value be greater than or equal to 0.12m 2 It is even more preferable that the above is true, and 0.20m 2 It is even more preferable that the above is true, and 0.25m 2 It is even more preferable that the above conditions are met. Furthermore, the total surface area of ​​calcium carbonate (C) in polyacetal resin (A) is 1.80 m² per 1 g of polyacetal resin (A). 2 Preferably, it is 1.50m 2 It is more preferable that the following conditions apply: 0.80m 2 It is even more preferable that the following conditions apply: 0.60m 2 It is even more preferable that the following conditions be met: 0.45m 2 The following is even more preferable. The total surface area of ​​calcium carbonate (C) in the polyacetal resin (A) is measured according to the example described below.

[0022] In this embodiment, the average primary particle diameter of calcium carbonate (C) is preferably 0.30 μm or less, more preferably 0.20 μm or less, even more preferably 0.10 μm or less, even more preferably 0.08 μm or less, even more preferably 0.06 μm or less, and even more preferably 0.04 μm or less. By keeping it below the above upper limit, it tends to be possible to more effectively suppress the initiation of fracture. Furthermore, the average particle size of the calcium carbonate (C) is preferably 0.001 μm or more, more preferably 0.005 μm or more, and even more preferably 0.01 μm or more.

[0023] In this embodiment, the specific surface area of ​​calcium carbonate (C) is 100 m². 2 It is preferable that the amount be less than or equal to 80m 2 It is more preferable that it be less than or equal to / g, 70m 2 It is even more preferable that it be less than or equal to / g, 60m 2 It is even more preferable that it be less than or equal to / g, 55m 2 It is even more preferable that it be less than or equal to / g, and 15m 2 It may be less than / g. By keeping it below the above upper limit, the handling properties of the calcium carbonate itself tend to be improved. Also, the specific surface area of ​​the calcium carbonate (C) is 1 m². 2 It is preferable that it is 5m or more per gram. 2 It is more preferable that it be 10m or more per gram. 2 It may be more than / g, 20m 2 It may be greater than or equal to the lower limit. By setting it above the lower limit, the effects of the present invention tend to be more effectively exhibited with a smaller amount of additive.

[0024] The calcium carbonate (C) content in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, based on 100 parts by mass of the total of the polyacetal resin (A) and elastomer (B). Setting it above the lower limit tends to improve the feedability of the resin composition during production. Furthermore, the calcium carbonate (C) content in the resin composition of this embodiment is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, even more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, based on 100 parts by mass of the total of the polyacetal resin (A) and elastomer (B). Setting it below the upper limit tends to effectively prevent it from becoming the starting point of fracture.

[0025] <Other ingredients> The resin composition of this embodiment may contain any conventionally known additives and fillers, as long as they do not impair the objectives of the present invention. Examples of additives and fillers used in this embodiment include thermoplastic resins other than polyacetal resins, ultraviolet absorbers, antioxidants, heat stabilizers, light stabilizers, formaldehyde scavengers, antistatic agents, carbon fibers, dyes, organic pigments such as carbon black, inorganic pigments such as titanium dioxide, glass fibers, glass flakes, potassium titanate whiskers, and the like. Details of these can be found in paragraphs 0113 to 0124 of Japanese Patent Application Publication No. 2017-025257, and these contents are incorporated herein by reference.

[0026] <Physical properties of resin compositions> The resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece, and the tensile elongation measured according to ISO 527 is preferably 80% or more, more preferably 90% or more, even more preferably 100% or more, even more preferably 105% or more, and even more preferably 110% or more. Furthermore, although the tensile elongation is not specifically defined, in practice it is 200% or less. Furthermore, when the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece and subjected to a bending test at a bending test speed of 2 mm / min according to the method described in ISO 178, the flexural modulus of elasticity is preferably 1010 MPa or higher, more preferably 1015 MPa or higher, and even more preferably 1020 MPa or higher. The upper limit of the flexural modulus of elasticity is practically 1200 MPa or less. Furthermore, when the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece and the tensile elongation measured according to ISO 527 is X%, and the resin composition obtained by removing calcium carbonate from the resin composition of this embodiment is similarly measured under the same conditions and the tensile elongation is Y%, then it is preferable that X / Y is 1.00 or more, more preferably 1.05 or more, even more preferably 1.10 or more, even more preferably 1.15 or more, and even more preferably 1.20 or more. A practical upper limit for X / Y is, for example, 1.90 or less. In this embodiment, it is preferable to satisfy both the tensile elongation and the flexural modulus, and more preferably to satisfy the X / Y ratio. These are measured according to the examples described later.

[0027] <Method for producing resin compositions> The resin composition of this embodiment contains the essential components described above and, if necessary, any other components described above. These raw materials can be mixed and kneaded using any conventionally known method for producing resin compositions.

[0028] Examples of mixing machines include kneaders, Banbury mixers, and extruders. There are no particular restrictions on the various conditions and equipment for mixing and kneading; they can be appropriately selected from any conventionally known conditions. Mixing is preferably carried out at a temperature above the melting temperature of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally 180°C or higher).

[0029] <Molded products> The molded article of this embodiment is formed from the resin composition of this embodiment. Furthermore, pellets obtained by pelletizing the resin composition of this embodiment can be molded by known molding methods such as injection molding, extrusion molding, compression molding, blow molding, and vacuum molding. There are no particular restrictions on the shape of the molded product, and it can be appropriately selected according to the application and purpose of the molded product. Examples include plate-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, annular, circular, elliptical, gear-shaped, polygonal, irregularly shaped, hollow, frame-shaped, box-shaped, panel-shaped, and cap-shaped products. The molded product of the present invention may be a part or a finished product.

[0030] <Application> Examples of the resin composition and molded articles formed from the resin composition of this embodiment include automotive parts such as trim clips, seat belt members, and headrest guides; building material parts; electrical and electronic components; office equipment parts; daily necessities parts; containers for frozen foods and beverages; home appliances such as refrigerator gaskets; hose clamps and gaskets; and cable ties. [Examples]

[0031] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0032] 1.Raw materials The following ingredients were used. [Table 1]

[0033] The melt volume rate (MVR) of the above polyacetal resin (A) was measured in accordance with ISO 1133 under conditions of a temperature of 190°C and a load of 2.16 kg.

[0034] <Method for Measuring Average Primary Particle Size of Calcium Carbonate> The average primary particle size of calcium carbonate was confirmed by SEM (scanning electron microscope). The unit was shown in μm.

[0035] <Method for Measuring Specific Surface Area of Calcium Carbonate> The specific surface area of calcium carbonate was calculated by the BET method. The unit was shown in m 2 / g.

[0036] 2. Examples 1 to 18, Comparative Examples 1 to 6 <Production of Resin Composition (Pellets)> Each component shown in Tables 2 to 5 was uniformly mixed at the ratios (parts by mass) shown in Tables 2 to 5 using a Super Mixer manufactured by Kawada Manufacturing Co., Ltd. The obtained mixture was melt-shear mixed at a cylinder temperature of 200°C, a screw rotation speed of 120 rpm, and a discharge rate of 10 kg / hour using a vented twin-screw extruder (PCM-30 manufactured by Ikegai Corporation) with a screw diameter of 30 mm, a screw length of 760, and a die nozzle diameter of 3.5 mm to produce pellets of the resin composition.

[0037] <Total Surface Area of Calcium Carbonate in POM> The total surface area of calcium carbonate in POM was calculated according to the following formula. Total surface area of calcium carbonate in POM = (amount of calcium carbonate added (parts by mass)) × (specific surface area of calcium carbonate (m 2 / g)) The unit was shown in area per 1 g of polyacetal resin (m 2 / g-POM).

[0038] <Tensile Elongation (X) at the Time of Adding Calcium Carbonate> [[ID=4​​​The units are shown in percentages (%).

[0039] <Tensile elongation (Y) without calcium carbonate added> As references for Examples 1-18 and Comparative Examples 1-6, resin compositions without calcium carbonate were prepared separately. These resin compositions were molded into 4 mm thick multipurpose test specimens and measured under ISO 527 conditions. The injection molding machine used was a Shibaura Machine Co., Ltd. EC-100S. The fully automatic bending tester used was a Shimadzu Corporation model. The units are shown in percentages (%).

[0040] <Tensile elongation ratio (X / Y) with and without calcium carbonate addition> From the tensile elongation with calcium carbonate added (X) and the tensile elongation without calcium carbonate added (Y), the tensile elongation ratio (X / Y) with and without calcium carbonate added was calculated.

[0041] <Flexural modulus> The pellets obtained above were heat-treated for 4 hours in a hot air circulating dryer at a temperature of 80°C. Next, the dried pellets were injection molded using an injection molding machine, with the cylinder temperature set to 195°C and the mold temperature set to 90°C, in accordance with the ISO 9988-2 standard. In this way, a 4 mm thick multipurpose test specimen (ISO test specimen) was obtained. Next, a bending test was performed on this 4 mm thick multipurpose test specimen (ISO test specimen) using a fully automatic bending tester, in accordance with the method described in ISO 178, at a bending speed of 2 mm / min, and the bending modulus was measured. The pellets obtained above were heat-treated for 4 hours in a hot air circulating dryer at a temperature of 80°C. The injection molding machine used was a Shibaura Machine Co., Ltd. EC-100S. The fully automatic bending tester used was a Shimadzu Corporation model. The results are shown in Tables 2 to 5. The unit is MPa.

[0042] [Table 2]

[0043] [Table 3]

[0044] [Table 4]

[0045] [Table 5]

[0046] As is clear from the above results, the molded articles formed from the resin composition of the present invention exhibited high toughness and suppressed reduction in elastic modulus.

Claims

1. Polyacetal resin (A) is used in a mixture of 50 to 95 parts by mass, Elastomer (B) is included in a mixture of 5 to 50 parts by mass, Contains calcium carbonate (C), The elastomer (B) is a core-shell elastomer containing butadiene-containing rubber in the core and an acrylic resin in the shell. The calcium carbonate (C) in the polyacetal resin (A) has a total surface area of ​​0.02 to 2.00 m² per 1 g of polyacetal resin (A). ２ A resin composition containing the following components.

2. The resin composition according to claim 1, wherein the average particle size of the calcium carbonate (C) is 0.001 to 0.30 μm.

3. According to ISO 1133, the melt volume rate (MVR) of the aforementioned polyacetal resin (A) measured under conditions of a temperature of 190°C and a load of 2.16 kg was 0.5 to 20 cm³. ３ The resin composition according to claim 1, wherein the density is / 10 min.

4. A molded article formed from the resin composition according to any one of claims 1 to 3.

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