Resin composition and molded article

Abstract

To provide a resin composition exhibiting excellent impact resistance and excellent flexural elasticity, and a molded article including the resin composition.SOLUTION: A resin composition comprising a polyacetal resin (A) and an acrylic block copolymer (B) having at least one polymer block (b1) containing methacrylate units and at least one polymer block (b2) containing acrylate units.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a molded article. [Background technology]

[0002] Polyacetal resin is a plastic having excellent mechanical properties, electrical properties, and chemical properties such as chemical resistance, and is used in a wide range of applications (see, for example, Patent Document 1). In order to impart various functions to polyacetal resin, the incorporation of various additives has been investigated.

[0003] Furthermore, Patent Documents 2 to 4 disclose resin compositions containing acrylic block copolymers and having excellent mechanical strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-11563 [Patent Document 2] International Publication No. 2023 / 171546 [Patent Document 3] Japanese Patent Publication No. 2020-164774 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-36019 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when an acrylic block copolymer is added as a rubber component to a polyacetal resin, the impact resistance is improved but the flexural modulus tends to decrease. Therefore, it is difficult to obtain a resin composition that is excellent in both impact resistance and flexural modulus, and no resin composition that is excellent in both impact resistance and flexural modulus has yet been obtained.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin composition that is excellent in both impact resistance and flexural modulus, and a molded article containing the resin composition. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by containing a polyacetal resin (A) and a specific acrylic block copolymer (B). Based on this finding, further research has led to the completion of the present invention.

[0008] The present inventors speculate that the mechanism of action of the present invention is as follows. In the resin composition of the present invention, the polyacetal resin (A) and the acrylic block copolymer (B) are not completely compatible with each other and exist in an incompatible state. Specifically, in the resin composition of the present invention, the acrylic block copolymer (B) is dispersed in a matrix of the polyacetal resin (A). This is also observed in actual transmission electron microscope (TEM) observations (see Figures 1 and 2). Here, if the number-average particle size of the acrylic block copolymer (B) dispersed in the matrix of the polyacetal resin (A) is large, the impact resistance will be high. 1 and 2, the black areas are the acrylic block copolymer (B). The black areas appear oval due to the effect of injection molding. Stress concentration occurs in the rubber component of the acrylic block copolymer (B) dispersed in the matrix of the polyacetal resin (A), promoting plastic deformation of the matrix of the polyacetal resin (A) near the acrylic block copolymer (B), thereby achieving an impact-modifying effect.

[0009] That is, the present invention provides the following [1] to

[11] . [1] A resin composition comprising a polyacetal resin (A) and an acrylic block copolymer (B) having at least one polymer block (b1) containing a methacrylic acid ester unit and at least one polymer block (b2) containing an acrylic acid ester unit. [2] The resin composition according to the above [1], which contains 1 to 30 parts by mass of the acrylic block copolymer (B) per 100 parts by mass of the polyacetal resin (A). [3] The resin composition according to the above [1] or [2], wherein the acrylic block copolymer (B) has a weight average molecular weight of 40,000 to 300,000. [4] The resin composition according to any one of the above [1] to [3], wherein the acrylic block copolymer (B) is a triblock copolymer in which the polymer block (b1) is bonded to both ends of the polymer block (b2). [5] The resin composition according to any one of the above [1] to [4], wherein the content of the polymer block (b1) in the acrylic block copolymer (B) is 1 to 52 mass %. [6] The resin composition according to any one of the above [1] to [5], wherein the polymer block (b2) contains a unit derived from an acrylate ester (b2-1) having an organic group having 1 to 12 carbon atoms. [7] The resin composition according to [6] above, wherein the acrylic acid ester (b2-1) is n-butyl acrylate. [8] The resin composition according to any one of the above [1] to [7], wherein the acrylic block copolymer (B) is dispersed in a matrix of the polyacetal resin (A). [9] A molded article comprising the resin composition according to any one of [1] to [8] above.

[10] The molded article according to the above [9], wherein the acrylic block copolymer (B) is dispersed in a matrix of the polyacetal resin (A).

[11] The molded article according to the above

[10] , wherein the number average particle size of the acrylic block copolymer (B) is 1 to 5 μm. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a resin composition having excellent impact resistance and flexural modulus, and a molded article containing the resin composition. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a transmission electron microscope (TEM) image of a MD parallel cross section of the injected product of the resin composition of Example 1 (magnification: 5000 times). [Figure 2] FIG. 2 is a transmission electron microscope (TEM) image of a MD parallel cross section of the injected product of the resin composition of Example 1 (magnification: 50,000 times). DETAILED DESCRIPTION OF THE INVENTION

[0012] An example of an embodiment to which the present invention is applied will be described below. The numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the embodiments or examples. Note that other embodiments are also included in the scope of the present invention as long as they are consistent with the spirit of the present invention.

[0013] The present invention will be described in detail below. In this specification, the preferred definitions can be adopted arbitrarily, and it can be said that a combination of preferred definitions is more preferred. In this specification, the expression "XX to YY" means "XX or more and YY or less." In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60." In addition, in this specification, the term "unit" (where "" indicates a monomer) means "a structural unit derived from", for example, "propylene unit" means "a structural unit derived from propylene".

[0014] [Resin composition] The resin composition of the present invention contains a polyacetal resin (A) and an acrylic block copolymer (B) having at least one polymer block (b1) containing a methacrylic acid ester unit and at least one polymer block (b2) containing an acrylic acid ester unit. According to the present invention, by containing a polyacetal resin (A) and a predetermined acrylic block copolymer (B), it is possible to provide a resin composition that is excellent in both impact resistance and flexural modulus.

[0015] The content of the acrylic block copolymer (B) relative to 100 parts by mass of the polyacetal resin (A) is not particularly limited, but from the viewpoint of impact resistance, it is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more. The content of the acrylic block copolymer (B) relative to 100 parts by mass of the polyacetal resin (A) is not particularly limited, but from the viewpoint of obtaining a molded article containing a resin composition with a suitable flexural modulus, it is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 27 parts by mass or less, even more preferably 25 parts by mass or less, even more preferably 23 parts by mass or less, even more preferably 22 parts by mass or less, and particularly preferably 20 parts by mass or less. The content of the acrylic block copolymer (B) relative to 100 parts by mass of the polyacetal resin (A) is not particularly limited, but is preferably 1 to 40 parts by mass, more preferably 1 to 30 parts by mass, even more preferably 2 to 30 parts by mass, even more preferably 3 to 27 parts by mass, even more preferably 4 to 25 parts by mass, even more preferably 5 to 23 parts by mass, even more preferably 7 to 22 parts by mass, and particularly preferably 10 to 20 parts by mass.

[0016] <Polyacetal resin (A)> The resin composition of the present invention contains a polyacetal resin (A). The polyacetal resin (A) is not particularly limited, but is preferably at least one selected from the group consisting of (ii) homopolymers containing only oxymethylene groups as structural units, and (iii) copolymers containing oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms as structural units. Among these, copolymers containing an oxymethylene group and an oxyalkylene group having two carbon atoms (for example, an oxyethylene group represented by -CH2-CH2-O-, -CH(CH3)-O-) as structural units are preferred, and -[CH2-O] n -[CH2-CH2-O] m - (n is an integer of 1 or more, m is an integer of 1 or more) is more preferable. The content of oxyalkylene groups having 1 to 6 carbon atoms in the total amount of constituent units of the polyacetal resin (A) is preferably 60 to 100 mass %, more preferably 80 to 100 mass %, and even more preferably 90 to 100 mass %. The total content of oxymethylene groups and oxyalkylene groups having two carbon atoms in the total amount of constituent units of the polyacetal resin (A) is preferably 60 to 100 mass%, more preferably 80 to 100 mass%, and particularly preferably 90 to 100 mass%.

[0017] The oxyalkylene group having 2 to 6 carbon atoms is not particularly limited, but is preferably at least one selected from the group consisting of an oxyethylene group, an oxypropylene group, and an oxybutylene group. These may be used alone or in combination of two or more. Of these, an oxyethylene group is preferred.

[0018] 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 in the polyacetal resin (A) is not particularly limited, but is preferably 0.5 to 10 mol %.

[0019] To produce the polyacetal resin (A), trioxane is usually used as the main raw material. To introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin (A), a cyclic formal, a cyclic ether, or the like can be used. Specific examples of cyclic formals are not particularly limited and include, for example, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, 1,3,6-trioxocane, etc. These may be used alone or in combination of two or more. Among these, 1,3-dioxolane is preferred from the viewpoint of introducing an oxyethylene group. Specific examples of cyclic ethers are not particularly limited and include, for example, ethylene oxide, propylene oxide, butylene oxide, etc. These may be used alone or in combination of two or more. Among these, ethylene oxide is preferred from the viewpoint of introducing an oxyethylene group. To introduce oxyethylene groups into the polyacetal resin (A), 1,3-dioxolane may be used as the main raw material; to introduce oxypropylene groups, 1,3-dioxane may be used as the main raw material; and to introduce oxybutylene groups, 1,3-dioxepane may be used as the main raw material. In the polyacetal resin (A), it is preferable that the amount of hemiformal terminal groups, formyl terminal groups, and terminal groups unstable to heat, acid, and base are small. Here, the hemiformal terminal groups are represented by -OCHOH, and the formyl terminal groups are represented by -CHO.

[0020] In addition to the above, the polyacetal resin (A) that can be used includes the polyacetal resins described in paragraphs 0018 to 0043 of JP-A No. 2015-074724, the contents of which are incorporated herein by reference.

[0021] Examples of commercially available polyacetal resins (A) include KEPITAL manufactured by Korea Polyacetal Co., Ltd.; DURACON and TEPCON manufactured by Polyplastics Co., Ltd.; DELLIN manufactured by DuPont; TENAC manufactured by Asahi Kasei Corporation; IUPITAL manufactured by Global Polyacetal Co., Ltd.; Celcon and Hostaform manufactured by Celanese; KOCETAL manufactured by Kolon Plastics; Ultraform manufactured by BASF; FORMOCON manufactured by Formosa Plastics; SABIC POM and SABITAL manufactured by SABIC; and the like.

[0022] The content of the polyacetal resin (A) in the resin composition of the present invention is not particularly limited, but from the viewpoint of abrasion resistance, it is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 73% by mass or more, even more preferably 75% by mass or more, even more preferably 77% by mass or more, even more preferably 78% by mass or more, and particularly preferably 80% by mass or more. The content of the polyacetal resin (A) in the resin composition of the present invention is preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 97% by mass or less, even more preferably 96% by mass or less, even more preferably 95% by mass or less, even more preferably 93% by mass or less, and particularly preferably 90% by mass or less. The content of the polyacetal resin (A) in the resin composition of the present invention is not particularly limited, but is preferably 60 to 99 mass%, more preferably 65 to 98 mass%, even more preferably 70 to 97 mass%, even more preferably 73 to 96 mass%, even more preferably 75 to 95 mass%, even more preferably 77 to 93 mass%, even more preferably 78 to 90 mass%, and particularly preferably 80 to 90 mass%. By setting the content within this range, the effects of the present invention tend to be more effectively exhibited. The resin composition of the present invention may contain only one type of polyacetal resin (A), or may contain two or more types. When the resin composition of the present invention contains two or more types of polyacetal resin (A), the total content of the polyacetal resin (A) in the resin composition of the present invention is preferably within the above range.

[0023] <Acrylic block copolymer (B)> The acrylic block copolymer (B) has one or more methacrylic acid ester polymer blocks (b1) and one or more acrylic acid ester polymer blocks (b2), and may further have any other polymer blocks as required.

[0024] (Methacrylate ester polymer block (b1)) The methacrylate polymer block (b1) is a polymer block having structural units derived from a methacrylate ester (ie, "methacrylate units"). The methacrylic acid ester is not particularly limited, and examples thereof include methacrylic acid esters having no functional group, such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and benzyl methacrylate; and methacrylic acid esters having a functional group, such as methoxyethyl methacrylate, ethoxyethyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate, glycidyl methacrylate, and tetrahydrofurfuryl methacrylate. These may be used alone or in combination of two or more kinds. That is, the methacrylic acid ester polymer block (b1) may be composed of one kind of methacrylic acid ester or two or more kinds of methacrylic acid esters. Among these, methacrylic acid esters having no functional group are preferred because the resulting resin composition has an excellent appearance when molded at high temperatures, and methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and benzyl methacrylate are more preferred, and methyl methacrylate is particularly preferred because it results in clearer phase separation between the methacrylic acid ester polymer block (b1) and the acrylic acid ester polymer block (b2), resulting in good mechanical strength (impact resistance and flexural modulus) of a molded article containing the resin composition. In order to achieve excellent mechanical strength (impact resistance and flexural modulus) and moldability, the acrylic block copolymer (B) preferably contains two or more methacrylic acid ester polymer blocks (b1). When the acrylic block copolymer (B) contains two or more methacrylic acid ester polymer blocks (b1), the methacrylic acid ester polymer blocks (b1) may be the same or different.

[0025] The peak top molecular weight (Mp) of the methacrylic acid ester polymer block (b1) is not particularly limited, but is preferably from 1,000 to 50,000, more preferably from 2,000 to 30,000. When the peak top molecular weight (Mp) of the methacrylic acid ester polymer block (b1) is equal to or greater than the lower limit, the cohesive strength of the resulting acrylic block copolymer (B) can be improved. When the peak top molecular weight (Mp) is equal to or less than the upper limit, the melt viscosity of the resulting acrylic block copolymer (B) can be prevented from increasing, thereby preventing a decrease in productivity when producing the resin composition.

[0026] The content of structural units derived from methacrylate ester in the methacrylate ester polymer block (b1) is not particularly limited, but from the viewpoint of the flexural modulus of a molded article containing the resin composition and compatibility with polyacetal resin, it is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass or less.

[0027] The glass transition temperature of the methacrylate ester polymer block (b1) is not particularly limited, but is preferably 80°C or higher, more preferably 90°C or higher, and particularly preferably 100°C or higher, because the methacrylate ester polymer block (b1) acts as a physical pseudo-crosslinking point at the normal use temperature of the resin composition, thereby improving the durability and heat resistance of the resin composition. The glass transition temperature of the methacrylic acid ester polymer block (b1) is not particularly limited, but is preferably 140°C or lower, more preferably 130°C or lower, and particularly preferably 120°C or lower. The glass transition temperature of the methacrylic acid ester polymer block (b1) is not particularly limited, but is preferably 80 to 140°C, more preferably 90 to 130°C, and particularly preferably 100 to 120°C. The glass transition temperature of the methacrylic acid ester polymer block (b1) can be measured by a differential scanning calorimeter (DSC).

[0028] The content of the methacrylic acid ester polymer block (b1) in the acrylic block copolymer (B) is not particularly limited, but in terms of excellent toughness of the resin composition, it is preferably 1 mass % or more, more preferably 3 mass % or more, even more preferably 5 mass % or more, and particularly preferably 7 mass % or more. The content of the methacrylic acid ester polymer block (b1) in the acrylic block copolymer (B) is not particularly limited, but is preferably 52% by mass or less, more preferably 51% by mass or less, even more preferably 50% by mass or less, still more preferably 40% by mass or less, and particularly preferably 28% by mass or less. The content of the methacrylic acid ester polymer block (b1) in the acrylic block copolymer (B) is not particularly limited, but is preferably 1 to 52 mass%, more preferably 3 to 51 mass%, even more preferably 5 to 50 mass%, still more preferably 7 to 40 mass%, and particularly preferably 7 to 28 mass%.

[0029] (Acrylate ester polymer block (b2)) The acrylic acid ester polymer block (b2) is a polymer block containing structural units derived from an acrylic acid ester (ie, "acrylic acid ester units").

[0030] Acrylic acid esters are classified into two types: (i) acrylic acid esters (b2-1) having an organic group having 1 to 12 carbon atoms, and (ii) acrylic acid esters other than the acrylic acid esters (b2-1). (i) The acrylic acid ester (b2-1) having an organic group having 1 to 12 carbon atoms is represented by the general formula (i-1) CH2=CH-COOR 1 (1) (In formula (1), R 1 represents an organic group having 1 to 3 carbon atoms), and (i-2) an acrylic acid ester (b2-1-1) represented by the general formula CH2=CH-COOR 2 (2) (In formula (2), R 2 represents an organic group having 4 to 12 carbon atoms) and acrylic acid esters (b2-1-2).

[0031] From the viewpoints of the impact resistance of a molded article containing the resin composition and compatibility with polyacetal resins, the acrylic acid ester polymer block (b2) preferably contains a unit derived from an acrylic acid ester (b2-1) having an organic group having 1 to 12 carbon atoms.

[0032] -Acrylic acid ester (b2-1-1)- R in acrylic ester (b2-1-1) 1The organic group having 1 to 3 carbon atoms represented by is not particularly limited, and examples thereof include alkyl groups having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, and an isopropyl group; and organic groups containing an element other than carbon (such as oxygen) and having a total of 1 to 3 carbon atoms, such as a methoxyethyl group, a hydroxyethyl group, an aminoethyl group, and a glycidyl group. These may be used alone or in combination of two or more.

[0033] The acrylic acid ester (b2-1-1) is not particularly limited, and examples thereof include acrylic acid esters without functional groups, such as methyl acrylate, ethyl acrylate, isopropyl acrylate, and n-propyl acrylate; and acrylic acid esters with functional groups, such as 2-methoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-aminoethyl acrylate, and glycidyl acrylate; etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a resin composition with a better appearance when molded at high temperatures, acrylic esters having no functional group are preferred, methyl acrylate and ethyl acrylate are more preferred, and methyl acrylate is particularly preferred.

[0034] -Acrylic acid ester (b2-1-2)- R in acrylic ester (b2-1-2) 2 The organic group having 4 to 12 carbon atoms represented by is not particularly limited, and examples thereof include alkyl groups having 4 to 12 carbon atoms such as butyl, amyl (pentyl), hexyl, cyclohexyl, ethylhexyl, octyl, decyl, isobornyl, and lauryl; aromatic ring groups having 6 to 12 carbon atoms such as phenyl and benzyl; and organic groups containing elements other than carbon (such as oxygen) and having a total of 4 to 12 carbon atoms such as ethoxyethyl, tetrahydrofurfuryl, diethylaminoethyl, and phenoxyethyl. These may be used alone or in combination of two or more.

[0035] The acrylic acid ester (b2-1-2) is not particularly limited, and examples thereof include acrylic acid esters without functional groups, such as n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, decyl acrylate, isobornyl acrylate, lauryl acrylate, cyclohexyl acrylate, phenyl acrylate, and benzyl acrylate; and acrylic acid esters with functional groups, such as 2-ethoxyethyl acrylate, 2-(diethylamino)ethyl acrylate, tetrahydrofurfuryl acrylate, and 2-phenoxyethyl acrylate. These may be used alone or in combination of two or more. Among these, acrylic esters having no functional groups are preferred in that the phase separation between the methacrylic ester polymer block (b1) and the acrylic ester polymer block (b2) is more distinct, alkyl acrylates having an alkyl group having 4 to 12 carbon atoms are more preferred, n-butyl acrylate and 2-ethylhexyl acrylate are even more preferred, and n-butyl acrylate is particularly preferred in that a resin composition having excellent flexibility, adhesiveness, and durability as measured by tensile strain at break is obtained.

[0036] -Acrylic acid esters other than acrylic acid esters (b2-1)- The acrylic acid ester having no organic group having 1 to 12 carbon atoms other than the acrylic acid ester (b2-1) (i.e., the acrylic acid ester having no organic group having 1 to 12 carbon atoms other than the acrylic acid ester (b2-1-1) and the acrylic acid ester (b2-1-2)) is not particularly limited, and examples thereof include acrylic acid esters having no functional group (acrylic acid esters having no organic group having 1 to 12 carbon atoms), such as octadecyl acrylate. These may be used alone or in combination of two or more.

[0037] The content of structural units derived from an acrylic acid ester in the acrylic acid ester polymer block (b2) is not particularly limited, but from the viewpoint of the impact resistance of a molded article containing the resin composition, it is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass or less.

[0038] Among the acrylic acid esters, from the viewpoint of obtaining a resin composition exhibiting appropriate tensile strain at break and flexibility, the acrylic acid ester (b2-1) having an organic group having 1 to 12 carbon atoms (i.e., at least one selected from the acrylic acid esters (b2-1-1) and (b2-1-2)) is preferred. Among the acrylic acid esters, acrylic acid esters having no functional groups are preferred in order to obtain a resin composition having improved toughness and appearance during high-temperature molding.

[0039] In order to obtain a resin composition having high melt tension and excellent moldability, the acrylic acid ester polymer block (b2) preferably contains a structural unit derived from an acrylic acid ester (b2-1-1).

[0040] When the structural units derived from an acrylic ester in the acrylic ester polymer block (b2) contain structural units derived from an acrylic ester (b2-1-1), the content of the structural units derived from the acrylic ester (b2-1-1) in the acrylic ester polymer block (b2) is, from the viewpoint of the impact resistance of a molded article containing the resin composition, preferably 1 to 100% by mass, more preferably 10 to 90% by mass, even more preferably 15 to 85% by mass, and particularly preferably 20 to 80% by mass, and may be 30 to 70% by mass, 50% by mass or less, or 50% by mass or more.

[0041] In one preferred embodiment, the acrylic acid ester polymer block (b2) contains a structural unit derived from an acrylic acid ester (b2-1-2), in order to easily impart flexibility to the resulting resin composition. The content of structural units derived from the acrylate ester (b2-1-2) in the acrylate ester polymer block (b2) is preferably 60% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, and may be 100% by mass, in order to more easily impart flexibility to the resin composition.

[0042] In one preferred embodiment, the acrylic acid esters that form the acrylic acid ester-derived structural units contained in the acrylic acid ester polymer block (b2) include two acrylic acid esters (b2-1-2) selected from acrylic acid esters having an organic group containing 4 to 12 carbon atoms, typically one acrylic acid ester (b2-1-2-1) having an organic group containing 4 to 6 carbon atoms (e.g., n-butyl acrylate) and one acrylic acid ester (b2-1-2-2) having an organic group containing 7 to 12 carbon atoms (e.g., 2-ethylhexyl acrylate). In this case, the mass ratio (b2-1-2-1) / (b2-1-2-2) of the structural units derived from the acrylic acid ester (b2-1-2-1) to the structural units derived from the acrylic acid ester (b2-1-2-2) is not particularly limited, but is preferably 90 / 10 to 10 / 90, more preferably 60 / 40 to 40 / 60, in order to exhibit good cold resistance. The mass ratio of the structural unit derived from the acrylic acid ester (b2-1-2-1) to the structural unit derived from the acrylic acid ester (b2-1-2-2) is 1 It can be determined by H-NMR measurement.

[0043] Examples of the combination of the acrylic acid ester (b2-1-2-1) and the acrylic acid ester (b2-1-2-2) used in the acrylic acid ester polymer block (b2) include n-butyl acrylate / 2-ethylhexyl acrylate. In this case, the acrylic acid ester (b2-1-2-1) and the acrylic acid ester (b2-1-2-2) used should have a solubility parameter difference of 0.3 to 2.5 (MPa). 1 / 2The solubility parameter can be calculated by the method described in "POLYMER HANDBOOK Fourth Edition," VII, pp. 675-714 (published by Wiley Interscience, 1999) and "Polymer Engineering and Science," 1974, Vol. 14, pp. 147-154.

[0044] The structural unit derived from an acrylic acid ester contained in the acrylic acid ester polymer block (b2) is preferably a structural unit represented by the general formula CH2=CH-COOR from the viewpoint of obtaining a resin composition having excellent cold resistance and tensile strength. 1 (1) (wherein, R 1 represents an organic group having 1 to 3 carbon atoms), and a structural unit derived from an acrylate ester (b2-1-1) represented by the general formula CH2=CH-COOR 2 (2)(wherein, R 2 In one preferred embodiment, the copolymer contains a structural unit derived from an acrylate ester (b2-1-2) represented by the formula: In this case, the mass ratio (b2-1-1) / (b2-1-2) of the structural units derived from the acrylic ester (b2-1-1) and the structural units derived from the acrylic ester (b2-1-2) in the acrylic ester polymer block (b2) is not particularly limited, but is preferably 90 / 10 to 5 / 95, more preferably 85 / 15 to 10 / 90, even more preferably 80 / 20 to 10 / 90, and particularly preferably 75 / 25 to 15 / 85, in order to achieve an excellent balance between the tensile strength resulting from the structural units derived from the acrylic ester (b2-1-1) and the cold resistance resulting from the structural units derived from the acrylic ester (b2-1-2). The mass ratio of the structural unit derived from the acrylate ester (b2-1-1) to the structural unit derived from the acrylate ester (b2-1-2) is 1 It can be determined by H-NMR measurement.

[0045] In one preferred embodiment, the structural units derived from acrylic esters contained in the acrylic ester polymer block (b2) include only structural units derived from acrylic esters (b2-1-1) and structural units derived from acrylic esters (b2-1-2).

[0046] When the acrylic acid ester polymer block (b2) is a copolymer containing structural units derived from two or more types of acrylic acid esters, it may contain a random copolymer, a block copolymer, or a gradient copolymer, but is usually preferably a random copolymer. When the acrylic block copolymer (B) contains two or more acrylic ester polymer blocks (b2), the structures of these acrylic ester polymer blocks (b2) may be the same or different. The total content of structural units derived from the acrylate esters (b2-1-1) and (b2-1-2) in the acrylate ester polymer block (b2) is not particularly limited, but from the viewpoint of the impact resistance of a molded article containing the resin composition, it is preferably 60% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0047] The acrylic block copolymer (B) may contain two or more acrylic acid ester polymer blocks (b2), and in that case, the two or more acrylic acid ester polymer blocks (b2) may be the same or different.

[0048] The glass transition temperature of the acrylic acid ester polymer block (b2) is not particularly limited, but is preferably −100 to 30° C., more preferably −80 to 10° C., even more preferably −70 to 0° C., and particularly preferably −60 to −10° C., in order to obtain a resin composition having excellent mechanical strength (impact resistance and flexural modulus) at room temperature. The glass transition temperature can be measured by a differential scanning calorimeter (DSC).

[0049] The acrylic acid ester polymer block (b2) may contain structural units derived from a methacrylic acid ester, provided that the effects of the present invention are not impaired. The methacrylic acid ester polymer block (b1) may contain structural units derived from an acrylic acid ester, provided that the effects of the present invention are not impaired. The methacrylate polymer block (b1) and the acrylate polymer block (b2) may contain structural units derived from monomers other than the methacrylate polymer block (b1) and the acrylate polymer block (b2), as necessary. The other monomers are not particularly limited, and examples thereof include vinyl monomers having a carboxyl group, such as (meth)acrylic acid, crotonic acid, maleic acid, and fumaric acid; aromatic vinyl monomers, such as styrene, α-methylstyrene, p-methylstyrene, and m-methylstyrene; conjugated diene monomers, such as butadiene and isoprene; olefin monomers, such as ethylene, propylene, isobutene, and octene; lactone monomers, such as ε-caprolactone and valerolactone; (meth)acrylamide; (meth)acrylonitrile; maleic anhydride; vinyl acetate; vinyl chloride; and vinylidene chloride. These may be used alone or in combination of two or more. When other monomers are used, they are used in an amount of preferably 40% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less, based on the total mass of the monomers used in each of the polymer blocks of the methacrylic acid ester polymer block (b1) and the acrylic acid ester polymer block (b2).

[0050] The content of the acrylic acid ester polymer block (b2) in the acrylic block copolymer (B) is not particularly limited, but in terms of excellent toughness of the resin composition, it is preferably 48% by mass or more, more preferably 49% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably 72% by mass or more. The content of the acrylic ester polymer block (b2) in the acrylic block copolymer (B) is preferably 99% by mass or less, more preferably 97% by mass or less, even more preferably 95% by mass or less, and particularly preferably 93% by mass or less. The content of the acrylic ester polymer block (b2) in the acrylic block copolymer (B) is not particularly limited, but is preferably 48 to 99 mass%, more preferably 49 to 97 mass%, even more preferably 50 to 95 mass%, still more preferably 60 to 93 mass%, and particularly preferably 72 to 93 mass%.

[0051] The total content of the methacrylic acid ester polymer block (b1) and the acrylic acid ester polymer block (b2) in the acrylic block copolymer (B) is not particularly limited, but from the viewpoints of the moldability of the resin composition and the impact resistance of a molded article containing the resin composition, it is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass or less.

[0052] (Other polymer blocks) The acrylic block copolymer (B) may contain other polymer blocks in addition to the methacrylic acid ester polymer block (b1) and the acrylic acid ester polymer block (b2), if necessary. The other polymer block is not particularly limited and examples thereof include polymer blocks or copolymer blocks containing structural units derived from monomers such as styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, butadiene, isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride, vinylidene chloride, etc.; polymer blocks containing polyethylene terephthalate, polylactic acid, polyurethane, polydimethylsiloxane; etc. The other polymer block also includes hydrogenated products of polymer blocks containing structural units derived from conjugated dienes such as butadiene and isoprene.

[0053] The acrylic block copolymer (B) can be represented by the general formula: when the methacrylate ester polymer block (b1) is represented by b1, the acrylate ester polymer block (b2) is represented by b2, and a polymer block having a structure different from the acrylate ester polymer block (b2) (excluding the methacrylate ester polymer block (b1)) is represented by b2'. (b1-b2) n (b1-b2) n -b1 b2-(b1-b2) n (b1-b2) n -b2' (b1-b2) n -Z (b2-b1) n -Z (wherein n is an integer of 1 to 30, Z represents a coupling site (the coupling site after a coupling agent reacts with a polymer terminal to form a chemical bond, and - represents a bond on each polymer block). When a plurality of b1 and b2 are contained in the formula, they may be polymer blocks of the same structure or polymer blocks of different structures.) Here, "different structures" means structures that are different in at least one of the monomer units constituting the polymer block, molecular weight, molecular weight distribution, stereoregularity, and, when a plurality of monomer units are present, the ratio of the respective monomer units and the form of copolymerization (random, gradient, block). The value of n is not particularly limited, but is preferably an integer of 1 to 15, more preferably an integer of 1 to 8, and particularly preferably an integer of 1 to 4. Among the above structures, from the viewpoint of excellent durability of the resin composition, (b1-b2) n , (b1-b2) n -b1, b2-(b1-b2) n , (b1-b2) nA linear block copolymer represented by -b2' is preferred, and a diblock copolymer represented by b1-b2; or a triblock copolymer represented by the formula b1-b2-b1 having blocks in the order of methacrylate polymer block (b1), acrylate polymer block (b2), and methacrylate polymer block (b1) (methacrylate polymer block (b1) is bonded to both ends of acrylate polymer block (b2)) is more preferred.

[0054] The acrylic block copolymer (B) may be used alone or in combination of two or more.

[0055] The peak top molecular weight (Mp) of the acrylic block copolymer (B) is not particularly limited, but from the viewpoints of impact resistance, flowability, and moldability, it is preferably 40,000 to 300,000, more preferably 50,000 to 290,000, and particularly preferably 60,000 to 280,000.

[0056] The weight average molecular weight (Mw) of the acrylic block copolymer (B) is not particularly limited, but is preferably 40,000 or more, more preferably 50,000 or more, and particularly preferably 59,000 or more, from the viewpoint of superior moldability. The weight average molecular weight (Mw) of the acrylic block copolymer (B) is not particularly limited, but is preferably 300,000 or less, more preferably 250,000 or less, even more preferably 200,000 or less, and particularly preferably 150,000 or less. The weight average molecular weight (Mw) of the acrylic block copolymer (B) is not particularly limited, but is preferably 40,000 to 300,000, more preferably 50,000 to 250,000, still more preferably 59,000 to 200,000, and particularly preferably 59,000 to 150,000.

[0057] The molecular weight distribution (Mw / Mn) of the acrylic block copolymer (B) is not particularly limited, but is preferably 1.00 or more, more preferably 1.05 or more, and particularly preferably 1.10 or more, from the viewpoint of excellent moldability when formed into a resin composition. The molecular weight distribution (Mw / Mn) of the acrylic block copolymer (B) is not particularly limited, but is preferably 1.40 or less, more preferably 1.35 or less, even more preferably 1.30 or less, and particularly preferably 1.25 or less. The molecular weight distribution (Mw / Mn) of the acrylic block copolymer (B) is not particularly limited, but is preferably 1.00 to 1.40, more preferably 1.05 to 1.35, even more preferably 1.10 to 1.30, and particularly preferably 1.10 to 1.25.

[0058] The peak top molecular weight (Mp), number average molecular weight (Mn), and weight average molecular weight (Mw) of the acrylic block copolymer (B) are values ​​determined by gel permeation chromatography (GPC) in terms of standard polystyrene, and the molecular weight distribution (Mw / Mn) is a value calculated from the above Mw and Mn values.

[0059] In the resin composition of the present invention, from the viewpoint of exerting an impact-modifying effect, it is preferable that the acrylic block copolymer (B) is dispersed in the matrix of the polyacetal resin (A). Here, "dispersed" refers to a sea-island structure in which the acrylic block copolymer (B) constitutes the island component and the polyacetal resin (A) component constitutes the sea component. When the acrylic block copolymer (B) is dispersed in the matrix of the polyacetal resin (A), stress concentration occurs in the rubber component of the acrylic block copolymer (B) dispersed in the matrix of the polyacetal resin (A) upon impact, promoting plastic deformation of the matrix of the polyacetal resin (A) near the acrylic block copolymer (B), thereby exerting an impact-modifying effect.

[0060] <<Method for producing acrylic block copolymer (B)>> The method for producing the acrylic block copolymer (B) is not particularly limited as long as the above-mentioned acrylic block copolymer (B) can be obtained, and any method based on a known technique can be used. Generally, the method for obtaining a block copolymer with a narrow molecular weight distribution is to adopt the living polymerization method of the monomer that becomes the structural unit.The living polymerization method is not particularly limited, and for example, can be mentioned the living polymerization method using an organic rare earth metal complex as a polymerization initiator (see Japanese Patent Laid-Open No. 06-93060), the living anionic polymerization method using an organic alkali metal compound as a polymerization initiator in the presence of a mineral acid salt such as an alkali metal or alkaline earth metal salt (see Japanese Patent Laid-Open No. 05-507737), the living anionic polymerization method using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound (see Japanese Patent Laid-Open No. 11-335432), atom transfer radical polymerization (ATRP) (see Macromolecular Chemistry and Physics, 2000, vol. 201, pp. 1108-1114) etc.

[0061] Among the above production methods, a method of living anionic polymerization in the presence of an organoaluminum compound in a solvent such as a hydrocarbon, using an organic alkali metal compound as a polymerization initiator, is preferred because the resulting block copolymer has high transparency, contains less residual monomer, has a reduced odor, and suppresses the generation of bubbles when molding the resin composition. This method is also preferred because the molecular structure of the methacrylic acid ester polymer block is highly syndiotactic, which has the effect of improving the heat resistance of the resin composition. Examples of organoaluminum compounds that can be used include those described in JP 2019-157067 A, such as isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum. The polymerization conditions described in JP 2019-157067 A can also be used.

[0062] The acrylic block copolymer (B) can be produced, for example, by repeating a process of forming a desired polymer block (e.g., a methacrylate polymer block (b1), an acrylate polymer block (b2)) at the end of a desired living polymer obtained by polymerizing monomers a desired number of times, and then terminating the polymerization reaction. According to the above-described method, it is possible to produce a diblock copolymer containing a methacrylate polymer block (b1) and an acrylate polymer block (b2); a triblock copolymer containing a methacrylate polymer block (b1), an acrylate polymer block (b2), and a methacrylate polymer block (b1), a methacrylate polymer block (b1), an acrylate polymer block (b2), and an acrylate polymer block (b2'); a tetrablock copolymer containing a methacrylate polymer block (b1), an acrylate polymer block (b2), a methacrylate polymer block (b1), and an acrylate polymer block (b2); and the like.

[0063] <Other optional ingredients> The resin composition of the present invention may contain other optional components as needed, as long as the effects of the present invention are not impaired. The other optional components are not particularly limited and include, for example, inorganic fillers, antioxidants, other polymers, softeners, tackifying resins, lubricants, light stabilizers, processing aids, colorants such as pigments and dyes, flame retardants, antistatic agents, matting agents, silicone oils, antiblocking agents, ultraviolet absorbers, release agents, foaming agents, antibacterial agents, antiviral agents, antifungal agents, fragrances, etc. These may be used alone or in combination of two or more.

[0064] The content of the optional components is not particularly limited as long as it is within a range that does not impair the properties of the resin composition, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 50 parts by mass or less, relative to 100 parts by mass of the total of the polyacetal resin (A) and the acrylic block copolymer (B), and may be 30 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, 1 part by mass or less, or even 0 parts by mass.

[0065] (Inorganic filler) The inorganic filler may be contained in the resin composition of the present invention for the purposes of improving the physical properties such as weather resistance, adjusting hardness, improving economy as an extender, and the like. The inorganic filler is not particularly limited, and examples thereof include calcium carbonate, talc, magnesium hydroxide, aluminum hydroxide, mica, clay, natural silicic acid, synthetic silicic acid, titanium oxide, carbon black, barium sulfate, glass balloons, glass fiber, etc. These may be used alone or in combination of two or more.

[0066] The content of the inorganic filler is not particularly limited as long as it is within a range that does not impair the properties of the resin composition, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 50 parts by mass or less, per 100 parts by mass of the polyacetal resin (A) and the acrylic block copolymer (B) in total.

[0067] (antioxidant) The antioxidant is not particularly limited, and examples thereof include hindered phenol-based antioxidants, phosphorus-based antioxidants, lactone-based antioxidants, hydroxyl-based antioxidants, etc. These may be used alone or in combination of two or more. Among these, hindered phenol-based antioxidants are preferred. The content of the antioxidant is not particularly limited as long as it is within a range that does not cause coloration when the resin composition is melt-kneaded, but is preferably 0.1 to 5 parts by mass per 100 parts by mass of the total of the polyacetal resin (A) and the acrylic block copolymer (B).

[0068] (Other polymers) The other polymer is not particularly limited and examples thereof include an olefin polymer having no polar group, a styrene polymer, a polyphenylene ether resin, polyethylene glycol, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of further improving the molding processability of the resin composition, an olefin polymer having no polar group is preferred. The olefin polymer having no polar group is not particularly limited, and examples thereof include polyethylene, polypropylene, polybutene, ethylene / α-olefin copolymers obtained by copolymerizing ethylene with an α-olefin such as propylene, 1-butene, 1-hexene, or 1-octene, propylene / ethylene copolymers, and propylene / α-olefin copolymers obtained by copolymerizing propylene with an α-olefin having 4 or more carbon atoms. These may be used alone or in combination of two or more. When the olefin polymer having no polar group is a copolymer of two or more types of monomers, such as an ethylene / α-olefin copolymer, a propylene / ethylene copolymer, or a propylene / α-olefin copolymer, the bonding form of these copolymers is not particularly limited, and may be, for example, a random copolymer or a block copolymer.

[0069] (tackifying resin) The tackifying resin is not particularly limited, and examples thereof include rosin-based resins, terpene-phenolic resins, terpene resins, aromatic hydrocarbon-modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, coumarone-indene resins, phenol-based resins, xylene resins, etc. These may be used alone or in combination of two or more. The softening point of the tackifier resin is not particularly limited, but from the viewpoint of moldability, it is preferably 85 to 160°C, more preferably 100 to 150°C, and particularly preferably 105 to 145°C.

[0070] The content of the tackifier resin is not particularly limited as long as it is within a range that does not impair the mechanical strength (impact resistance and flexural elasticity) of the resin composition, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the polyacetal resin (A) and the acrylic block copolymer (B) combined.

[0071] <Physical properties of resin composition> The resin composition preferably has a large MFR value, and although there are no particular restrictions, it is preferably 7.0 to 30.0 (g / 10 min), more preferably 8.0 to 20.0 (g / 10 min), and particularly preferably 9.0 to 15.0 (g / 10 min). The MFR of the resin composition can be measured by the method used in the examples described later.

[0072] <Method of manufacturing resin composition> The method for producing the resin composition of the present invention is not particularly limited as long as it is a method that can uniformly mix the polyacetal resin (A), the acrylic block copolymer (B), and other optional components that are added as needed. Examples of the method include a method in which the components are dissolved in a solvent, and then the resulting solution is cast and dried, and a melt-kneading method. Among these, the melt-kneading method is preferred from the viewpoint of enhancing the dispersibility of each of the constituent components. The melt-kneading can be carried out using a melt-kneading device such as a single-screw extruder, a twin-screw extruder, a kneader, a batch mixer, a roller, or a Banbury mixer, and the resin composition of the present invention can be obtained by melt-kneading preferably under conditions of 150 to 250°C and a screw rotation speed of 50 to 1000 rpm.

[0073] The resin composition of the present invention can be molded into a sheet or film, or molded into a multilayer with other sheets or films, and used for packaging of daily necessities, packaging of industrial materials, and packaging sheets and films for food. The resin composition of the present invention has improved toughness without impairing the excellent properties of the polyacetal resin (A) and can have excellent adhesive strength even to highly polar materials, and therefore can be used as a laminate structure having a layer formed from the resin composition of the present invention and a layer formed from a material other than the resin composition.

[0074] [Molded products] The molded article of the present invention contains the resin composition of the present invention. According to the present invention, by containing the resin composition of the present invention, it is possible to provide a molded article that is excellent in both impact resistance and flexural modulus.

[0075] The resin composition of the present invention can be processed into a molded article by a molding method such as extrusion molding, injection molding, blow molding, compression molding, calendar molding, or vacuum molding.

[0076] In the molded article of the present invention, it is preferred that the acrylic block copolymer (B) is dispersed in the matrix of the polyacetal resin (A) from the viewpoint of exhibiting an impact resistance improving effect.

[0077] The number average particle size of the acrylic block copolymer (B) in the molded article of the present invention is not particularly limited, but is preferably 1 to 5 μm from the viewpoint of impact resistance. The number average particle size of the acrylic block copolymer (B) in the molded article can be measured using a transmission electron microscope (TEM).

[0078] <Physical properties of molded products> The flexural modulus of the molded article is preferably large, and although there are no particular limitations, it is preferably 1.65 to 4.00 GPa, more preferably 1.70 to 3.00 GPa, and particularly preferably 1.80 to 2.50 GPa. The flexural modulus of the molded article can be measured by the method used in the examples described later.

[0079] The Charpy impact value of the molded product is preferably large, and although there are no particular restrictions, it is preferably 6.5 to 30.0 KJ / m 2 , more preferably 6.7 to 20.0 KJ / m 2 , particularly preferably 7.0 to 15.0 KJ / m 2 is. The Charpy impact value of the molded article can be measured by the method used in the examples described later.

[0080] <Physical properties of molded products> The spiral flow length of the molded article is preferably large, and although there are no particular limitations, it is preferably 30.0 to 70.0 mm, more preferably 35.0 to 60.0 mm, and particularly preferably 40.0 to 50.0 mm. The spiral flow length of the molded article can be measured by the method used in the examples described later.

[0081] the molded article of the present invention can be widely used as a variety of molded articles, such as hoses, tubes, belts, etc.; footwear applications such as sports shoes, fashion sandals, etc.; home appliance applications such as televisions, audio equipment, vacuum cleaners, refrigerator door seals, remote control switches, and mobile phones; office equipment applications; automotive applications such as bumper parts, rack and pinion boots, suspension boots, constant velocity joint boots, and body panels for automobile interior and exterior parts; civil engineering and construction applications such as civil engineering sheets, waterproof sheets, window frame sealants, building sealants, various hoses, and knobs; medical supplies such as gaskets for medical syringes, catheter tubes, infusion bags, and adhesive bandages; various grips for scissors, screwdrivers, toothbrushes, ski poles, etc.; stationery such as pen grips; sporting goods such as diving goggles and snorkels; various packing applications for the purposes of airtightness, waterproofing, soundproofing, and vibration prevention; leisure goods; toys; and industrial goods. The molded article of the present invention is not particularly limited in shape, structure, use, etc. [Example]

[0082] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0083] The evaluations in the Production Examples, Examples, and Comparative Examples were carried out according to the methods described below.

[0084] (MFR measurement) The melt flow rate (MFR) of each polyacetal resin (A) was determined in accordance with ISO 1133-1:2022 under conditions of 190°C and a load of 2.16 kg.

[0085] (density measurement) The density of each polyacetal resin (A) was determined in accordance with ISO 1183-1:2004.

[0086] (GPC measurement) The weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic block copolymer (B) were determined by gel permeation chromatography (GPC) using standard polystyrene equivalent molecular weights. The molecular weight distribution (Mw / Mn) was calculated from the Mn and Mw values. The measurement equipment and conditions were as follows: Equipment: GPC equipment "GPC8020" manufactured by Tosoh Corporation Separation columns: Tosoh Corporation's "TSKgel GMHXL", "G4000HXL" and "G5000HXL" connected in series Detector: Tosoh Corporation "RI-8020" Eluent: Tetrahydrofuran ·Eluent flow rate: 1.0ml / min Sample concentration: 1mg / 1mL Column temperature: 40℃

[0087] ( 1 H-NMR measurement) The content of each polymer block in the acrylic block copolymer (B) is 1 It was determined by H-NMR measurement. 1 The measurement equipment and conditions used for H-NMR measurement are as follows: Equipment: Nuclear magnetic resonance spectrometer "JNM-ECX400" manufactured by JEOL Ltd. Heavy solvent: deuterated chloroform 1 In the H-NMR spectrum, the signal at around 3.6 ppm is the hydrogen atom (-OC) bonded to the carbon atom adjacent to the oxygen atom contained in the ester group of the structural unit derived from methyl methacrylate (MMA). H The signal at around 3.7 ppm is attributed to the hydrogen atom (-OC) bonded to the carbon atom adjacent to the oxygen atom contained in the ester group of the structural unit derived from methyl acrylate (MA). H The signal at around 4.0 ppm is attributed to the hydrogen atom (-OC) bonded to the carbon atom adjacent to the oxygen atom contained in the ester group of the structural unit derived from n-butyl acrylate (nBA). H The molar ratio of the structural units derived from each monomer was calculated from the ratio of the integral values ​​of these signals, and the content of each polymer block was determined by converting this to a mass ratio based on the molecular weight of the structural units derived from the monomer.

[0088] (Production Example 1: Preparation of acrylic block copolymer (B-1)) (1) Into a nitrogen-purged, dried pressure vessel, 50.0 kg of toluene and 0.0444 kg of 1,2-dimethoxyethane were added with stirring at room temperature, followed by 0.383 kg of a toluene solution containing 296 mmol of isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, and then 0.0538 kg of a cyclohexane solution of sec-butyllithium containing 98.6 mmol of sec-butyllithium. (2) Next, 0.61 kg of methyl methacrylate (MMA) was added to the mixture at room temperature with stirring, and stirring was continued for another 60 minutes. The reaction mixture was initially yellow, but after stirring for 60 minutes it became colorless. (3) Thereafter, the internal temperature of the polymer solution was cooled to -30°C, and 7.50 kg of n-butyl acrylate (nBA) was added dropwise with stirring over 4 hours. After the dropwise addition was completed, stirring was continued at -30°C for an additional 5 minutes. (4) Then, 0.848 kg of methyl methacrylate (MMA) was added thereto, and the mixture was stirred overnight at room temperature. (5) After 0.240 kg of methanol was added to terminate the polymerization reaction, the resulting reaction solution was poured into stirred methanol to precipitate a white precipitate, which was then collected and dried to obtain an acrylic block copolymer (B-1). The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the resulting acrylic block copolymer (B-1) were determined by the above-mentioned GPC measurement. 1 The content of polymer block (b1) in the acrylic block copolymer (B-1) and the content of polymer block (b2) in the acrylic block copolymer (B-1) were determined by H-NMR measurement. The results are shown in Table 1.

[0089] (Production Examples 2 to 4: Preparation of Acrylic Block Copolymers (B-2) to (B-4)) Acrylic block copolymers (B-2) to (B-4) were produced in the same manner as in Production Example 1, except that the amounts of toluene, 1,2-dimethoxyethane, isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, and sec-butyllithium added in step (1), the amounts of monomers added in steps (2) and (4), the type and amount of monomer added in step (3), and the amount of methanol added in step (5) were changed as shown in Table 1. The Mw, Mw / Mn, and content of each polymer block of the resulting acrylic block copolymers (B-2) to (B-4) were determined in the same manner as above. The results are shown in Table 1.

[0090] (Examples 1 to 6, Comparative Examples 1 and 2) <Preparation of Resin Composition> The components listed in Table 2 were premixed according to the ratios shown in Table 2. The premixed mixture was melt-kneaded in a twin-screw extruder ("ZSK25" manufactured by Coperion) at 190°C and a screw rotation speed of 250 rpm to obtain a resin composition. The following physical properties of the obtained resin composition were measured.

[0091] <Measurement of MFR> The MFR of the resin compositions obtained in each example and each comparative example was measured under the conditions of 190 °C and a load of 2.16 kg in accordance with JIS K7210-1:2011. The measurement results are shown in Table 2. The fluidity was evaluated by the MFR.

[0092] <Measurement of flexural modulus> After drying the resin compositions obtained in each example and each comparative example in a hot air dryer set at 80 °C for 6 hours, injection molding was carried out under the conditions of a cylinder temperature of 190 °C and a mold temperature of 80 °C. After obtaining a multi-purpose test piece type A1 (total length l3: 170 mm, parallel part length l1: 80 mm, parallel part width b1: 10 mm, thickness h: 4 mm, grip part width b2: 20 mm, grip feeling distance L: 115 mm) defined in JIS K7139:2009, in accordance with JIS K 7171:2016, using the multi-purpose test piece type A1, the flexural modulus was measured under the conditions of a temperature of 23 °C and a flexural speed of 2 mm / min. The measurement results are shown in Table 2.

[0093] <Measurement of Charpy impact value> After drying the resin compositions obtained in each example and each comparative example in a hot air dryer set at 80 °C for 6 hours, injection molding of a multi-purpose test piece type A1 defined in JIS K7139:2009 was carried out under the conditions of a cylinder temperature of 190 °C and a mold temperature of 80 °C. A notch with a depth of 2 mm was made in the cut strip-shaped test piece type B2 (length l1: 80 mm, width b1: 10 mm, thickness h: 4 mm), and a Charpy impact test (impact resistance evaluation) was carried out in accordance with JIS K 7111-1 / 1eA:2012. The Charpy impact test was carried out at 23 °C. The measurement results are shown in Table 2. <<Injection molding conditions>> Resin drying conditions: 80 °C × 6 h Cylinder temperature: 190 °C Mold temperature: 80 °C Injection speed: 200 mm / s Test piece: Multi-purpose test piece type A1 defined in JIS K7139:2009 Molding machine: J100ADS-110U (manufactured by Nippon Steel Works, Ltd.)

[0094] <Spiral flow measurement> The spiral flow of the resin compositions obtained in Example 3 and Comparative Examples 1 and 2 was measured using a small electric injection molding machine SE18-DUZ manufactured by Sumitomo Heavy Industries, Ltd., at a thickness of 3 mm, an injection pressure of 120 MPa, an injection speed of 40 mm / sec, a cylinder temperature of 190°C, and a mold temperature of 80°C, and the fluidity (spiral flow) was evaluated based on the spiral flow length. The measurement results are shown in Table 2.

[0095] <Transmission electron microscope (TEM) measurements> The resin composition of Example 1 was injection molded under the following conditions to prepare a multipurpose test specimen Type A1 (total length l3: 170 mm, parallel section length l1: 80 mm, parallel section width b1: 10 mm, thickness h: 4 mm, gripping section width b2: 20 mm, gripper sensing distance L: 115 mm) as specified in JIS K7139:2009. MD-parallel cross-sectional sections of the multipurpose test specimen Type A1 were prepared. Here, MD-parallel cross-sections refer to cross-sections in the direction of resin flow during injection molding. The obtained test specimens were cut into 90 nm-thick sections using a diamond knife on an ultramicrotome (manufactured by Leica Microsystems). The obtained cross-sectional sections were exposed to a 10% aqueous solution of phosphotungstic acid, dried, and then observed using a transmission electron microscope (TEM) "HT770" (manufactured by Hitachi High-Tech Corporation) (accelerating voltage 100 kV, emission current 10 μA). The results at an observation magnification of 5,000 times are shown in Figure 1, and the results at an observation magnification of 50,000 times are shown in Figure 2. <<Injection molding conditions>> Resin drying conditions: 80°C x 6 hours Cylinder temperature: 190℃ Mold temperature: 80℃ Injection speed: 200mm / s Test piece: Multipurpose test piece type A1 specified in JIS K7139:2009 Forming machine: J100ADS-110U (manufactured by The Japan Steel Works, Ltd.)

[0096] [Table 1]

[0097] In Table 1, (*1) to (*3) have the following meanings. (*1): A toluene solution containing 296 mmol of isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum (*2): The ratio of the content (mass%) of structural units derived from acrylate ester (b2-1-1) having an organic group with 1 to 3 carbon atoms to the content (mass%) of structural units derived from acrylate ester (b2-1-2) having an organic group with 4 to 12 carbon atoms in the polymer block (b2). (*3): "MMA-nBA-MMA" means "a triblock copolymer of methyl methacrylate polymer block - n-butyl acrylate polymer block - methyl methacrylate polymer block," and "MMA-(nBA / MA)-MMA" means "a triblock copolymer of methyl methacrylate polymer block - (n-butyl acrylate / methyl acrylate) copolymer block - methyl methacrylate polymer block."

[0098] [Table 2]

[0099] In Table 2, each polyacetal resin (A) has the following meaning. POM (F2003): POM manufactured by Korea Polyacetal Co., Ltd. KEPITAL F20-03 (product name): Polyacetal resin only, melt flow rate (MFR) 9.0 g / 10 min, density 1.41 g / cm 3 POM (FU2020): POM KEPITAL TE-24 (FU2020) (product name) manufactured by Korea Polyacetal Co., Ltd.: A mixture of polyacetal resin and urethane resin.

[0100] Tables 1 and 2 show that a resin composition excellent in both impact resistance and flexural modulus can be obtained by containing a polyacetal resin (A) and an acrylic block copolymer (B) having at least one polymer block (b1) containing a methacrylic acid ester unit and at least one polymer block (b2) containing an acrylic acid ester unit.

[0101] From the viewpoint of flowability based on MFR, it can be seen from Table 2 that Examples 4 to 6 in which the acrylic block copolymer (B) is the acrylic block copolymer (B-2) or (B-4) are more preferable than Examples 1 to 3 in which the acrylic block copolymer (B) is the acrylic block copolymer (B-1). [Industrial Applicability]

[0102] The resin composition of the present invention is used, for example, in automobile parts, and specific examples thereof include seat belt buckle press buttons, fuel pump modules, fuel pumps, one-way valves, motor gears, meters, switches, wipers, sunroofs, bumper modules, steering wheels, shift levers, and accelerator pedals. Furthermore, in the electrical and electronic fields, the resin composition of the present invention is used as a rotating gear for office automation equipment, a part for a washing machine, a part for a refrigerator, and a part for an air conditioner. Furthermore, the resin composition of the present invention can be widely used in toys (miniature cars, dolls), clothing (fasteners, buckles, zippers), building materials (curtain hooks, shower faucet sprinkler panels and on-off buttons, toilet and washbasin faucet parts), sporting goods, medical device parts, medical instruments (insulin syringes), DIY supplies (power tools), etc. The molded article of the present invention can be widely used as various molded articles, and there are no particular limitations on the shape, structure, use, etc.

Claims

1. Polyacetal resin (A), and A resin composition comprising an acrylic block copolymer (B) having at least one polymer block (b1) containing a methacrylic acid ester unit and at least one polymer block (b2) containing an acrylic acid ester unit.

2. 2. The resin composition according to claim 1, comprising 1 to 30 parts by mass of the acrylic block copolymer (B) relative to 100 parts by mass of the polyacetal resin (A).

3. 3. The resin composition according to claim 1, wherein the acrylic block copolymer (B) has a weight average molecular weight of 40,000 to 300,000.

4. The resin composition according to claim 1 or 2, wherein the acrylic block copolymer (B) is a triblock copolymer in which the polymer block (b1) is bonded to both ends of the polymer block (b2).

5. 3. The resin composition according to claim 1, wherein the content of the polymer block (b1) in the acrylic block copolymer (B) is 1 to 52 mass%.

6. 3. The resin composition according to claim 1, wherein the polymer block (b2) contains a unit derived from an acrylate ester (b2-1) having an organic group having 1 to 12 carbon atoms.

7. The resin composition according to claim 6, wherein the acrylic acid ester (b2-1) is n-butyl acrylate.

8. The resin composition according to claim 1 or 2, wherein the acrylic block copolymer (B) is dispersed in a matrix of the polyacetal resin (A).

9. A molded article comprising the resin composition according to claim 1 or 2.

10. The molded article according to claim 9, wherein the acrylic block copolymer (B) is dispersed in a matrix of the polyacetal resin (A).

11. The molded article according to claim 10, wherein the number average particle size of the acrylic block copolymer (B) is 1 to 5 μm.

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