Resin composition

Abstract

One embodiment of the present invention relates to a resin composition. The resin composition contains an acid-modified polyolefin (B) and a free acid (C) derived from an acid anhydride or a carboxylic acid, which is a raw material for the acid-modified polyolefin (B). The content α [ppm] of the free acid (C) is 100 ppm or less.

Description

resin composition

[0001] One embodiment of the present invention relates to a resin composition.

[0002] It is known that the insulating performance of an insulating layer formed of polyolefin can be improved by adding a resin grafted with an acid anhydride such as maleic anhydride or a carboxylic acid to the insulating layer. For example, Patent Document 1 proposes a power cable having an insulating layer on the outside of the conductor made of a maleic anhydride-grafted polyethylene composition in which the amount of maleic anhydride grafted is 0.05 to 5% by weight. Patent Document 2 also proposes a resin composition of an olefin polymer containing (a) monomer units containing aromatic rings and (b) monomer units containing carboxyl groups and / or carboxyl group derivatives, wherein the content of component (a) is 2 × 10 per gram of the resin composition. －６ ~10 －４ mol, (b) content is 2 × 10 per 1 g of resin composition －７ ~10 －４ A resin composition for electrical insulation in mol has been proposed. Furthermore, Patent Document 3 describes a crosslinked resin composition made of polyethylene and polyethylene modified with a monomer containing a carboxyl group, wherein the monomer containing a carboxyl group per gram of the resin composition is 8.0 × 10 －７ ~5.0 x 10 －５ An insulating resin composition for DC cables in mol (mol) form has been proposed.

[0003] JP-A-63-150810 JP-A-07-149959 Patent No. 3424050

[0004] However, in recent years, there has been a demand for compositions that possess high-performance insulating properties and excellent insulating properties even under high-temperature conditions. As described in Patent Document 1, simply adding polyolefins grafted with maleic anhydride resulted in insufficient dielectric breakdown strength depending on the application, and also insufficient dielectric breakdown strength at high temperatures. While Patent Document 2 shows improvement in terms of dielectric breakdown strength, it requires the use of numerous monomers, making the manufacturing process complicated, and in some applications, the insulating performance under high-temperature conditions was insufficient. The composition described in Patent Document 3 also only showed confirmed insulating performance at around room temperature, and in some cases, the insulating performance under high-temperature conditions was insufficient.

[0005] One embodiment of the present invention provides a resin composition that exhibits high insulating performance under high-temperature conditions (e.g., 70°C).

[0006] As a result of further investigation by the inventors, it was found that the resin composition contains free acid generated during the preparation of acid-modified polyolefin, and that reducing the amount of free acid contained in the resin composition suppresses the excessive localization of space charge to the free acid, which is a polar substance, when a voltage is applied. As a result, it was found that it is possible to manufacture a resin composition with high insulating performance, and thus the present invention was completed.

[0007] In other words, the present invention has, for example, the following [1] to

[11] .

[0008] [1] A resin composition (X) comprising an acid-modified polyolefin (B) and a free acid (C) derived from a carboxylic acid or acid anhydride that is a raw material for the acid-modified polyolefin (B), wherein the content α [ppm] of the free acid (C) is 100 ppm or less.

[0009] [2] The resin composition (X) according to [1], wherein the ratio (α / β) of the content α [ppm] to the content β [mass%] of structural units derived from the carboxylic acid or acid anhydride is 800 or less.

[0010] [3] The resin composition (X) according to [1] or [2], wherein the MFR (230°C, 2.16 kg load) measured in accordance with ASTM D1238 is 0.01 to 1000 g / 10 min.

[0011] [4] Density measured in accordance with JIS K7112 is 850 to 1000 kg / m³ ３ The resin composition (X) described in any one of [1] to [3].

[0012] [5] A resin composition (X) according to any one of [1] to [4], further comprising polyolefin (A).

[0013] [6] A wire comprising a conductor, a wire insulation layer, and a protective layer in that order, wherein the wire insulation layer comprises the resin composition (X) described in any one of [1] to [5].

[0014] [7] An adhesive resin for battery casing materials comprising the resin composition (X) described in any one of [1] to [5].

[0015] [8] An adhesive resin for tab leads comprising the resin composition (X) described in any one of [1] to [5].

[0016] [9] Automotive part comprising the resin composition (X) described in any one of [1] to [5].

[0017]

[10] A method for producing a resin composition (X) according to any one of [1] to [4], comprising the steps of: preparing a first mixture containing the acid-modified polyolefin (B) and the free acid (C), obtained by reacting a polyolefin, which is a raw material for the acid-modified polyolefin (B), with a carboxylic acid or acid anhydride, which is a raw material for the acid-modified polyolefin (B); and washing the first mixture with acetone having a water content of 0.5% by mass or more to obtain a second mixture having a lower content of the free acid (C) than the first mixture.

[0018]

[11] A method for producing a resin composition (X) according to [5], comprising the steps of: preparing the polyolefin (A); preparing a first mixture containing the acid-modified polyolefin (B) and the free acid (C), obtained by reacting a polyolefin that is a raw material for the acid-modified polyolefin (B) with a carboxylic acid or acid anhydride that is a raw material for the acid-modified polyolefin (B); washing the first mixture with acetone having a water content of 0.5% by mass or more to obtain a second mixture having a lower content of the free acid (C) than the first mixture; and mixing the polyolefin (A) and the second mixture.

[0019] One embodiment of the present invention provides a resin composition that exhibits high insulating performance under high-temperature conditions (e.g., 70°C).

[0020] This is an example of a cross-sectional view of an electric wire according to one embodiment.

[0021] The present invention will be described below, but the various monomers in the present invention may be derived from fossil raw materials, from biological sources such as biomass, or from mixtures thereof.

[0022] ≪Resin Composition (X)≫ The resin composition (X) comprises an acid-modified polyolefin (B) and a free acid (C) derived from a carboxylic acid or acid anhydride that is a raw material for the acid-modified polyolefin (B).

[0023] <Acid-modified polyolefin (B)> Acid-modified polyolefin (B) is obtained by modifying a polyolefin with a carboxylic acid or acid anhydride. The type of unmodified polyolefin used as a raw material for acid-modified polyolefin (B) is not particularly limited. For example, polyolefin (A), described later, may be used as a raw material for acid-modified polyolefin (B). The acid-modified polyolefin (B) contained in the resin composition (X) may be one type or two or more types.

[0024] The weight-average molecular weight (Mw) of the unmodified polyolefin, which is the raw material for acid-modified polyolefin (B), as measured by gel permeation chromatography (GPC), is preferably 100,000 to 1,000,000, more preferably 200,000 to 800,000, in terms of polypropylene. Here, the conversion to polypropylene is performed using a pre-prepared polypropylene standard solution. The standard sample used for conversion may be changed depending on the raw material for acid-modified polyolefin (B). For example, if the raw material for acid-modified polyolefin (B) is polyethylene, the weight-average molecular weight (Mw) can be the value in terms of polyethylene. Even when the standard sample used for conversion is changed in this way, the preferred range for the weight-average molecular weight can remain within the range described above. When the weight-average molecular weight (Mw) of the unmodified polyolefin is within the range described above, the MFR of the acid-modified polyolefin (B) obtained by the modification treatment is likely to fall within the preferred range.

[0025] Unsaturated carboxylic acids can be used as raw materials for acid-modified polyolefins (B). Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, nadic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornenedicarboxylic acid, and various other unsaturated carboxylic acids such as bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic acid. Unsaturated carboxylic acid anhydrides can be used as raw materials for acid-modified polyolefins (B). Specific examples of unsaturated carboxylic acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, and bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic acid anhydride.

[0026] The content [mass%] of the structural unit derived from carboxylic acid or acid anhydride in the acid-modified polyolefin (B) is preferably 0.01 to 20 mass%, more preferably 0.05 to 10 mass%, and particularly preferably 0.1 to 5 mass%. The measuring method of the content [mass%] of the structural unit derived from carboxylic acid or acid anhydride in the acid-modified polyolefin (B) is as described in the examples below. When the value of the content [mass%] of the structural unit derived from carboxylic acid or acid anhydride in the acid-modified polyolefin (B) is within the above range, the melt flow rate (MFR) of the acid-modified polyolefin (B) obtained by the modification treatment is likely to fall within the preferred range described below.

[0027] The melt flow rate (MFR) of the acid-modified polyolefin (B) measured according to ASTM D1238 at 230 °C under a load of 2.16 kg is preferably 0.01 to 2000 g / 10 min, more preferably 0.1 to 1500 g / 10 min, still more preferably 0.2 to 1200 g / 10 min, and particularly preferably 0.2 to 1000 g / 10 min. When the melt flow rate of the acid-modified polyolefin (B) is within the above range, the mechanical strength of the molded body containing the acid-modified polyolefin (B) is likely to be good, and as a result, the mechanical strength of the molded body obtained from the resin composition (X) containing the acid-modified polyolefin (B) is also likely to be good. The melt flow rate of the acid-modified polyolefin (B) can be appropriately changed, for example, by mixing two or more kinds of acid-modified polyolefins (B) having different MFRs using an extruder, a mixer, etc.

[0028] The density of the acid-modified polyolefin (B) measured in accordance with JIS K 7112:1999 (density gradient tube method) is preferably 850 to 1000 kg / m ３ and more preferably 855 to 1000 kg / m ３ and still more preferably 860 to 980 kg / m ３ and particularly preferably 865 to 970 kg / m ３By using the acid-modified polyolefin (B) having a density within the above range, the mechanical strength of the molded article containing the acid-modified polyolefin (B) is likely to be good, and as a result, the mechanical strength of the molded article obtained from the resin composition (X) containing the acid-modified polyolefin (B) is also likely to be good. The density can be appropriately changed by mixing two or more types of acid-modified polyolefins (B) having different MFRs using an extruder, a mixer, etc.

[0029] <Production method of acid-modified polyolefin (B)> Hereinafter, an example of the production method of the acid-modified polyolefin (B) will be described. The production method of the acid-modified polyolefin (B) is not particularly limited as long as the obtained acid-modified polyolefin (B) satisfies the above-described requirements. However, as a preferable production method, a graft reaction between a polyolefin and a carboxylic acid or an acid anhydride can be mentioned. This graft reaction can be carried out using an organic peroxide as an initiator.

[0030] This graft reaction can be carried out without a solvent, but it is preferably carried out in the presence of an organic solvent. More specifically, the acid-modified polyolefin (B) can be obtained by bringing a polyolefin, a carboxylic acid or an acid anhydride, an organic peroxide, and an organic solvent into contact with each other and carrying out a graft reaction. By this graft reaction, when the acid-modified polyolefin (B) is produced, a mixture containing the acid-modified polyolefin (B) and a free acid (C) described later is obtained. After the graft reaction, a washing treatment is carried out as necessary.

[0031] <Free Acid (C)> Free acid (C) is an acid derived from a carboxylic acid or acid anhydride used as a raw material for the acid-modified polyolefin (B), and is a free acid that has not been incorporated into the acid-modified polyolefin (B). Free acid (C) may be the same substance as the carboxylic acid or acid anhydride used as a raw material for the acid-modified polyolefin (B), or it may be a substance obtained during the reaction between the carboxylic acid or acid anhydride used as a raw material for the acid-modified polyolefin (B) and the polyolefin. Furthermore, free acid (C) may contain both the carboxylic acid or acid anhydride used as a raw material for the acid-modified polyolefin (B), and a substance obtained during the reaction between the carboxylic acid or acid anhydride used as a raw material for the acid-modified polyolefin (B) and the polyolefin. Here, the substance obtained by the reaction of the carboxylic acid or acid anhydride used as a raw material is a substance obtained by the reaction of the carboxylic acid or acid anhydride used as a raw material under the conditions for producing the acid-modified polyolefin (B). The free acid (C) contained in the resin composition (X) may be one type or two or more types.

[0032] Specific examples of free acid (C) include the various unsaturated carboxylic acids mentioned as raw materials for acid-modified polyolefins (B), the various acid anhydrides mentioned as anhydrides of unsaturated carboxylic acids that serve as raw materials for acid-modified polyolefins (B), and substances obtained during the reaction of these with polyolefins.

[0033] For example, when maleic anhydride is used as a raw material for acid-modified polyolefin (B), maleic acid or fumaric acid may be produced by ring-opening of maleic anhydride. Furthermore, succinic acid may be produced by hydrogenation of the vinyl group of the maleic acid or fumaric acid produced by ring-opening. Therefore, when maleic anhydride is used as a raw material for acid-modified polyolefin (B), the free acids (C) will be maleic anhydride, maleic acid, fumaric acid, and succinic acid. Also, when maleic anhydride is used as a raw material, the content of free acids (C) in acid-modified polyolefin (B) is the total amount of maleic anhydride, maleic acid, fumaric acid, and succinic acid contained as free acids in acid-modified polyolefin (B).

[0034] <Polyolefin (A)> The resin composition (X) may further contain a polyolefin (A). The polyolefin (A) is not particularly limited, and any polyolefin can be used. Preferably, the polyolefin (A) is a polymer composed of one or more α-olefins selected from ethylene or α-olefins having 3 to 20 carbon atoms. In this specification, the term "polymer" may be simply used as a concept including homopolymers and copolymers. Also, the polyolefin (A) contained in the resin composition (X) may be one type or two or more types.

[0035] The α-olefin having 3 to 20 carbon atoms that leads to the constitutional unit of the polyolefin (A) may be a linear α-olefin or a branched α-olefin. Examples of the linear α-olefin that leads to the constitutional unit of the polyolefin (A) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. Examples of the branched α-olefin that leads to the constitutional unit of the polyolefin (A) include 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, etc. Among these, 4-methyl-1-pentene, ethylene, propylene, and butene are preferred, ethylene, propylene, and butene are more preferred, and ethylene and propylene are particularly preferred.

[0036] According to ASTM D1238, the melt flow rate (MFR) of polyolefin (A), measured at 230°C and a load of 2.16 kg, is preferably 0.01 to 1000 g / 10 min, more preferably 0.05 to 100 g / 10 min, and even more preferably 0.1 to 50 g / 10 min. When the melt flow rate of polyolefin (A) is within the above range, the dielectric breakdown performance of the resin composition (X) containing polyolefin (A) can be maintained while preserving the mechanical strength of the molded article obtained from the resin composition (X). The melt flow rate of polyolefin (A) can be appropriately changed, for example, by mixing two or more types of polyolefins having different MFRs using an extruder, mixer, or the like.

[0037] The density of polyolefin (A), measured in accordance with JIS K 7112:1999 (density gradient pipe method), is preferably 850 to 1000 kg / m³. ３ More preferably, 855 to 970 kg / m ３ And more preferably 860 to 940 kg / m ３ The ratio is preferably 865 to 930 kg / m³. ３ Therefore, by using a polyolefin (A) with a density within the aforementioned range, the mechanical strength of the molded article obtained from the resin composition (X) containing the polyolefin (A) can be ensured. The density can be appropriately changed, for example, by mixing two or more types of polyolefins (A) having different MFRs using an extruder, mixer, or the like.

[0038] [Method for producing polyolefin (A)] The method for producing polyolefin (A) is not particularly limited and can be produced using known methods. For example, one method involves polymerizing monomers that lead to the constituent units of polyolefin (A) in the presence of a catalyst consisting of a compound containing a transition metal such as vanadium, zirconium, titanium, or hafnium, and an organoaluminum compound (including organoaluminum oxy compounds) and / or an ionized ionic compound. Examples of such methods include those described in International Publication No. 2000 / 34420, Japanese Patent Publication No. 62-121710, International Publication No. 2004 / 29062, Japanese Patent Publication No. 2004-175707, and International Publication No. 2001 / 27124.

[0039] <Resin Composition (X)> The resin composition (X) of the present invention comprises an acid-modified polyolefin (B) and a free acid (C), and satisfies the following requirement (x-1). Preferably, the resin composition (X) satisfies the following requirement (x-2) in addition to the following requirement (x-1). The resin composition (X) may also contain a polyolefin (A).

[0040] [Requirement (x-1)] The content α [ppm] of free acid (C) in the resin composition (X) is 100 ppm or less, preferably 80 ppm or less, more preferably 50 ppm or less, and even more preferably 40 ppm or less. The lower limit of the content α [ppm] of free acid (C) is not particularly limited, but is usually 0.01 ppm or more. When the value of the content α [ppm] of free acid (C) in the resin composition (X) is within the above range, the insulation performance of the resin composition (X) is good, and the insulation performance of the resin composition (X) tends to be good even at high temperatures such as 70°C or higher.

[0041] The content of free acid (C) in the resin composition (X) may be determined by the method of the examples described later, or it may be calculated using the amount of polyolefin (A) used as a raw material for the resin composition (X), the amount of the mixture of acid-modified polyolefin (B) and free acid (C) used in the resin composition (X), and the content of free acid (C) in the mixture. The content of free acid (C) in the resin composition (X) may be below the limit of quantification of the method of the examples described later. If the content of free acid (C) in the resin composition (X) is below the limit of quantification, the content of free acid (C) in the resin composition (X) can be determined using the concentration of free acid (C) in the mixture containing acid-modified polyolefin (B) and free acid (C) used in the preparation of the resin composition (X), the amount of the mixture, and the amount of polyolefin (A) used as a raw material for the resin composition (X). Furthermore, if the resin composition (X) contains two or more types of free acids (C), the content α [ppm] is the total content of all free acids (C) contained in the resin composition (X).

[0042] [Requirement (x-2)] The ratio (α / β) of the content α [ppm] of free acid (C) in the resin composition (X) to the content β [mass%] of structural units derived from carboxylic acid or acid anhydride contained in the resin composition (X) is preferably 800 or less, more preferably 600 or less, even more preferably 400 or less, particularly preferably 300 or less, and most preferably 100 or less. The lower limit of the ratio (α / β) of the content α [ppm] of free acid (C) to the content β [mass%] of structural units derived from carboxylic acid or acid anhydride is not particularly limited, but is usually 0.01 or more, more preferably 9 or more. When the ratio (α / β) is within the above range, the insulation performance of the resin composition (X) is good. Furthermore, when the ratio (α / β) is within the above range, the insulation performance of the resin composition (X) tends to be good even at high temperatures such as 70°C or higher.

[0043] The free acid (C) content α [ppm] in the resin composition (X) is 100 ppm or less, preferably 80 ppm or less, more preferably 50 ppm or less, and even more preferably 40 ppm or less, as stated in requirement (x-1). The lower limit of the free acid (C) content α [ppm] is not particularly limited, but is usually 0.01 ppm or more. The method for determining the free acid (C) content α [ppm] is as described in requirement (x-1). When the value of the free acid (C) content α [ppm] in the resin composition (X) is within the above range, the ratio (α / β) of the resin composition (X) tends to fall within the preferred range.

[0044] The content β [mass%] of structural units derived from carboxylic acids or acid anhydrides in the resin composition (X) is preferably 0.001 to 5 mass%, more preferably 0.002 to 4 mass%, and even more preferably 0.004 to 3 mass%. The content of structural units derived from carboxylic acids or acid anhydrides in the resin composition (X) may be determined by the method of the examples described later, or it may be calculated using the amount of polyolefin (A) used as a raw material for the resin composition (X), the amount of acid-modified polyolefin (B), and the content of structural units derived from carboxylic acids or acid anhydrides contained in the acid-modified polyolefin (B). If there are two or more types of acid-modified polyolefins (B) contained in the resin composition (X), the content β [mass%] of structural units derived from carboxylic acids or acid anhydrides is the total content of structural units derived from carboxylic acids or acid anhydrides in all acid-modified polyolefins (B) contained in the resin composition (X). For example, there are n types of acid-modified polyolefins (B) (where n is any integer), and the content of structural units derived from carboxylic acids or acid anhydrides in the i-th acid-modified polyolefin (B) is β ｉ [Mass %] (where i is any integer less than or equal to n), the proportion of the i-th acid-modified polyolefin (B) contained in the resin composition (X) is r ｉ If we use [mass %], it can be calculated using the following formula.

[0045] If the content β [mass%] of structural units derived from carboxylic acids or acid anhydrides in the resin composition (X) is within the above range, it is easier to set the ratio (α / β) of the resin composition (X) within a preferred range.

[0046] When the resin composition (X) contains polyolefin (A), the content of polyolefin (A) in the resin composition (X) is preferably 10 to 99% by mass, more preferably 10 to 98% by mass, even more preferably 20 to 97% by mass, and particularly preferably 50 to 95% by mass (where the mass of the resin composition (X) is 100% by mass).

[0047] The content of acid-modified polyolefin (B) in the resin composition (X) is preferably 1 to 100% by mass, more preferably 2 to 90% by mass, even more preferably 3 to 80% by mass, and particularly preferably 5 to 50% by mass (assuming the mass of resin composition (X) is 100% by mass). Note that when the content of acid-modified polyolefin (B) in the resin composition (X) is 100% by mass, although free acid (C) derived from the raw materials of acid-modified polyolefin (B) is also contained in the resin composition (X), the concentration of free acid (C) is low, so the content of acid-modified polyolefin (B) can be considered as 100% by mass. When the content of acid-modified polyolefin (B) in the resin composition (X) is within the above range, it is easier to obtain the effect of improving insulation performance when the resin composition (X) is used as a modifier for an insulating layer.

[0048] According to ASTM D1238, the melt flow rate (MFR) of the resin composition (X), measured at 230°C and a load of 2.16 kg, is preferably 0.01 to 1000 g / 10 min, more preferably 0.1 to 500 g / 10 min, even more preferably 1 to 200 g / 10 min, and particularly preferably 1 to 7 g / 10 min. When the melt flow rate of the resin composition (X) is within the above range, it is easier to ensure mechanical strength when the molded body obtained from the resin composition (X) is used as an insulating layer. The melt flow rate of the resin composition (X) can be appropriately changed, for example, by mixing two or more resin compositions (X) having different MFRs using an extruder, mixer, or the like.

[0049] The density of the resin composition (X), measured in accordance with JIS K 7112:1999 (density gradient pipe method), is preferably 850 to 1000 kg / m³. ３ More preferably, 855 to 970 kg / m ３ More preferably 860 to 940 kg / m ３ Therefore, by using a resin composition (X) with a density within the aforementioned range, it is easier to ensure the mechanical strength of the insulating layer when a molded body obtained from the resin composition (X) is used as an insulating layer. The density can be appropriately changed, for example, by mixing two or more resin compositions (X) having different MFRs using an extruder, mixer, or the like.

[0050] The dielectric breakdown voltage at 90°C in DC of a molded article with a thickness of 100 μm obtained by molding the resin composition (X) is preferably 370 kV / mm or higher, more preferably 380 kV / mm or higher, and particularly preferably 390 kV / mm or higher. The upper limit of the dielectric breakdown voltage is not particularly limited, but is usually 700 kV / mm or lower.

[0051] The dielectric breakdown voltage at 70°C in DC of a molded article with a thickness of 100 μm obtained by molding the resin composition (X) is preferably 370 kV / mm or higher, more preferably 380 kV / mm or higher, and particularly preferably 390 kV / mm or higher. The upper limit of the dielectric breakdown voltage is not particularly limited, but is usually 700 kV / mm or lower.

[0052] <Other components contained in the resin composition (X)> The resin composition (X) may contain various conventionally known additives, such as antioxidants, weather stabilizers, ultraviolet absorbers, antistatic agents, anti-slip agents, anti-blocking agents, anti-fogging agents, nucleating agents, lubricants, pigments, dyes, anti-aging agents, hydrochloric acid absorbers, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, flame retardants, etc., to the extent that they do not impair the effects of the present invention. Regarding the content of the above-mentioned additives, the content of components other than polyolefin (A) and acid-modified polyolefin (B) in the resin composition (X) is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the total of polyolefin (A) and acid-modified polyolefin (B).

[0053] Furthermore, the resin composition (X) may also contain polymers other than polyolefin (A) and acid-modified polyolefin (B). In that case, the content of polymers other than polyolefin (A) and acid-modified polyolefin (B) in the resin composition (X) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the total of polyolefin (A) and acid-modified polyolefin (B).

[0054] ≪Method for Producing Resin Composition (X)≫ The resin composition (X) can be suitably produced by, for example, the following method. That is, the resin composition (X) can be produced by a method that includes the steps of: preparing a first mixture containing the acid-modified polyolefin (B) and the free acid (C), obtained by reacting a polyolefin, which is a raw material for the acid-modified polyolefin (B), with a carboxylic acid or acid anhydride, which is also a raw material for the acid-modified polyolefin (B); and washing the first mixture with acetone having a water content of 0.5% by mass or more to obtain a second mixture having a lower content of the free acid (C) than the first mixture.

[0055] If the resin composition (X) contains polyolefin (A), the method for producing the resin composition (X) includes, in addition to the steps of preparing the first mixture and the second mixture, the steps of preparing the polyolefin (A) and mixing the polyolefin (A) with the second mixture.

[0056] <Step to prepare the first mixture> The step to prepare the first mixture may correspond to a method for producing acid-modified polyolefin (B). When the step to prepare the first mixture corresponds to a method for producing acid-modified polyolefin (B), in this step, a polyolefin, which is a raw material for acid-modified polyolefin (B), is reacted with a carboxylic acid or acid anhydride, which is a raw material for acid-modified polyolefin (B). The reaction is preferably a graft reaction between the polyolefin and the carboxylic acid or acid anhydride. More preferably, the graft reaction is carried out in the presence of a solvent with an organic peroxide as an initiator.

[0057] Examples of organic peroxides used as initiators include alkyl peroxides, aryl peroxides, acyl peroxides, alloyl peroxides, ketone peroxides, peroxycarbonates, peroxycarboxylates, and hydroperoxides. Examples of alkyl peroxides include diisopropyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexine-3, and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; examples of aryl peroxides include dicumyl peroxide; examples of acyl peroxides include dilauroyl peroxide; examples of alloyl peroxides include dibenzoyl peroxide; examples of ketone peroxides include methyl ethyl ketone hydroperoxide and cyclohexanone peroxide; and examples of hydroperoxides include tert-butyl hydroperoxide and cumene hydroperoxide. Among these, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexyn-3, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, dicumyl peroxide, and dibenzoyl peroxide are preferred. One of these organic peroxides may be used, or two or more may be used.

[0058] The amount of organic peroxide used in the step of preparing the first mixture is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of polyolefin. When the amount of organic peroxide used is within the above range, the MFR of the resulting acid-modified polyolefin (B) tends to fall within a suitable range, and the amount of free acid (C) generated from the raw materials used in the preparation of the acid-modified polyolefin (B) also tends to fall within a suitable range.

[0059] Examples of solvents used in the graft reaction (denaturation reaction) include aliphatic hydrocarbons such as hexane, heptane, octane, decane, dodecane, tetradecane, and kerosene; alicyclic hydrocarbons such as methylcyclopentane, cyclohexane, methylcyclohexane, cyclooctane, and cyclododecane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, cumene, ethyltoluene, trimethylbenzene, cymene, and diisopropylbenzene; and halogenated hydrocarbons such as chlorobenzene, bromobenzene, o-dichlorobenzene, carbon tetrachloride, trichloroethane, trichloroethylene, tetrachloroethane, and tetrachloroethylene. Among these, alkyl aromatic hydrocarbons are particularly preferred. One type of solvent may be used, or two or more types may be used.

[0060] The amount of carboxylic acid or acid anhydride used in the step of preparing the first mixture is preferably 0.01 to 100 parts by mass, and more preferably 0.1 to 50 parts by mass, per 100 parts by mass of polyolefin. When the amount of unsaturated carboxylic acid or acid anhydride used is within the above range, the amount of free acid (C) generated from the raw materials used in the preparation of acid-modified polyolefin (B) tends to fall within a suitable range.

[0061] Furthermore, the first mixture containing the acid-modified polyolefin (B) and the free acid (C) may be a commercially available product. Note that commercially available acid-modified polyolefin (B) products contain the free acid (C).

[0062] <Step to obtain the second mixture> In the step to obtain the second mixture, the first mixture is washed to obtain a second mixture having a lower content of the free acid (C) than the first mixture. The step to obtain the second mixture corresponds to the washing treatment of the acid-modified polyolefin (B). In the step to obtain the second mixture, preferably the first mixture is washed with acetone containing water. Specifically, acetone containing water is added to the first mixture, stirred, and then filtered. The solid separated by filtration is the second mixture, which has a lower concentration of free acid (C) than the first mixture. The washing treatment may be performed once, or it may be performed two or more times. The number of washings is preferably 1 to 10 times, more preferably 2 to 5 times. The amount of acetone used during washing is preferably 200 to 1000 parts by mass, more preferably 250 to 500 parts by mass, per 100 parts by mass of the first mixture.

[0063] The water content of the acetone used in the step of obtaining the second mixture is preferably 0.5% by mass or more, more preferably 1.0 to 10% by mass, even more preferably 1.0 to 5.0% by mass, and particularly preferably 1.5 to 4.0% by mass, with the total mass of acetone and water being 100% by mass. When the water content of the acetone used in the step of obtaining the second mixture is within the above range, the free acid (C) in the first mixture can be dissolved in the acetone containing water, while the solubility of the acid-modified polyolefin (B) in the acetone containing water can be kept low. Preferably, the acid-modified polyolefin (B) is substantially insoluble in the acetone containing water.

[0064] The step of obtaining the second mixture yields a second mixture containing acid-modified polyolefin (B) and the free acid (C). Here, the content of the free acid in the second mixture is preferably 500 ppm or less, more preferably 200 ppm or less, and particularly preferably 100 ppm or less. The lower limit of the content of the free acid in the second mixture is not particularly limited, but is usually 0.1 ppm or more. The method for measuring the content of the free acid in the acid-modified polyolefin (B) is as described in the examples below. When the value of the content of the free acid (C) in the acid-modified polyolefin (B) is within the above range, it becomes easier to prepare a composition with excellent insulating performance. Furthermore, the resulting composition tends to have excellent insulating performance even at high temperatures such as 70°C or 90°C. Note that if the second mixture satisfies the above requirement (x-1), the second mixture itself becomes the resin composition (X).

[0065] <Step to prepare polyolefin (A)> The step to prepare polyolefin (A) may correspond to the method for producing polyolefin (A). Polyolefin (A) may be the same as the polyolefin used as a raw material for acid-modified polyolefin (B), or it may be different from the polyolefin used as a raw material for acid-modified polyolefin (B). The shape of polyolefin (A) is also arbitrary; for example, it may be in powder form or pellet form. Commercially available polyolefin may be used as polyolefin (A). Furthermore, the timing of the step to prepare polyolefin (A) can be any timing prior to the step of mixing polyolefin (A) with the second mixture.

[0066] <Step of mixing polyolefin (A) and the second mixture> In the step of mixing polyolefin (A) and the second mixture, a resin composition (X) is prepared by mixing polyolefin (A) and the second mixture. The second mixture itself may be a resin composition (X) that satisfies requirement (x-1). The mixing ratio of polyolefin and the second mixture is not particularly limited as long as it satisfies requirement (x-1). In the step of mixing polyolefin (A) and the second mixture, the polyolefin (A) and the second mixture may be mixed using a known method such as a Henschel mixer, V-blender, ribbon blender, or tumbler blender. In addition, in the step of mixing polyolefin (A) and the second mixture, after mixing polyolefin (A) and the second mixture, the mixture may be further melt-kneaded using a single-screw extruder, twin-screw extruder, kneader, etc., followed by granulation or pulverization.

[0067] ≪Molded article of resin composition (X)≫ A molded article is obtained by molding the resin composition (X).

[0068] (1) Molding Method Various known molding methods can be applied to the resin composition (X), such as injection molding, extrusion molding, injection stretch blow molding, blow molding, cast molding, calendar molding, press molding, stamping molding, inflation molding, and roll molding. These molding methods can be used to process the material into desired molded articles, such as films, sheets, hollow molded articles, injection molded articles, fibers, etc. The molding conditions are the same as those for conventionally known polyolefins.

[0069] (2) Shape There are no particular restrictions on the shape of the molded article obtained from the resin composition (X). For example, it may be tubular, film-like, sheet-like, membrane-like, tape-like, plate-like, rod-like, fibrous, nonwoven fabric-like, etc.

[0070] <<Applications of Resin Composition (X)>> Due to its high insulating properties, resin composition (X) can be used to form insulating layers such as wire insulation layers. Resin composition (X) can also be used as an adhesive resin for battery casings, an adhesive resin for tab leads, etc. Furthermore, resin composition (X) can be used as an automotive part. In addition, by adding resin composition (X) to other resins before molding, molded articles with good insulating properties can be produced. That is, resin composition (X) may also be used as a modifier for other resins.

[0071] One embodiment of the present invention is a wire comprising at least one conductor, at least one wire insulation layer surrounding the conductor, and at least one protective layer surrounding the conductor and the wire insulation layer, wherein the wire insulation layer comprises the above-described resin composition (X). One embodiment of this wire will be described with reference to Figure 1.

[0072] The electric wire 20 shown in Figure 1 comprises a conductor 10, an internal semiconducting layer 21, an electric wire insulation layer 22, an external semiconducting layer 23, a shielding layer 24, an adhesive layer 25, and a protective layer 26. Note that the electric wire 20 shown in Figure 1 is just an example, and for example, one or more of the internal semiconducting layer 21, external semiconducting layer 23, shielding layer 24, and adhesive layer 25 may be omitted. Also, one or more of the electric wire insulation layer 22, external semiconducting layer 23, shielding layer 24, adhesive layer 25, and protective layer 26 may be provided.

[0073] The conductor 10 is the central part that transmits electric current and is made of a conductive material such as copper or aluminum. The internal semiconducting layer 21 is a layer that eliminates the air gap between the conductor 10 and the wire insulation layer 22 and suppresses electric field concentration, and can be provided as desired.

[0074] The wire insulation layer 22 contains the above-mentioned resin composition (X) and is a layer that electrically insulates the conductor 10 and enables it to withstand high voltage.

[0075] The external semiconducting layer 23 is located outside the wire insulation layer 22 and is a layer for homogenizing the electric field; it can be provided as desired.

[0076] The shielding layer 24 prevents moisture from entering the layers inside the shielding layer 24 and protects the conductor 10 and the wire insulation layer 22, as well as any layers inside the shielding layer 24, from the external environment. It can be provided as an optional layer. The adhesive layer 25 is an optional layer provided to improve adhesion with the outer semiconducting layer 23, the shielding layer 24, or the protective layer 26. In the example shown in Figure 1, it is provided between the shielding layer 24 and the protective layer 26 to improve adhesion between the shielding layer 24 and the protective layer 26. Multiple adhesive layers 25 may also be provided. The protective layer 26 is an outer layer that provides mechanical protection and weather resistance. Such a wire 20 can be suitably used, for example, as a high-voltage wire.

[0077] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0078] <Method for measuring physical properties> <Melt flow rate (MFR)> The MFR of polyolefin (A) was measured according to ASTM D1238 under conditions of a temperature of 230°C and a load of 2.16 kg. The MFR of acid-modified polyolefin (B) and resin composition (X) were measured in the same manner.

[0079] <Density> The densities of polyolefin (A), acid-modified polyolefin (B), and resin composition (X) were measured in accordance with JIS K7112 (density gradient pipe method).

[0080] <Content of structural units derived from carboxylic acids or acid anhydrides in the resin composition (β)> The graft modification amount of acid-modified polyolefin (B) (i.e., the content of structural units derived from carboxylic acids or acid anhydrides used for modification, when the mass of acid-modified polyolefin (B) is taken as 100% by mass) was determined by infrared absorption spectrometry to be 1790 cm⁻¹ derived from the said structural units. －１The peak intensity was measured and quantified using a pre-prepared calibration curve. When the mixture of acid-modified polyolefin (B) and free acid (C) itself constitutes the resin composition (X) (i.e., when the resin composition does not contain polyolefin (A)), the content (β) of structural units derived from carboxylic acid or acid anhydride in the resin composition (X) was taken as the graft modification amount of acid-modified polyolefin (B). On the other hand, for resin compositions (X) containing polyolefin (A), the content (β) of structural units derived from carboxylic acid or acid anhydride in the resin composition (X) was determined using the graft modification amount of acid-modified polyolefin (B), the amount of acid-modified polyolefin (B), and the amount of polyolefin (A). The content (β) of structural units derived from carboxylic acid or acid anhydride was also determined for the resin compositions used in the comparative examples in the same manner as for resin composition (X).

[0081] <Concentration (α) of Free Acid (C) in Resin Composition> The mixture of acid-modified polyolefin (B) obtained by the preparation of acid-modified polyolefin (B) and free acid (C) was freeze-dried, p-xylene and pure water were added, refluxed, and then acetone was added. The precipitated resin was filtered, the filtrate was concentrated and dried, and then redissolved in pure water. The obtained solution was analyzed by capillary electrophoresis using inorganic anion analysis buffer and quantified using a one-check method with a calibration curve prepared in advance using standard samples. When the mixture of acid-modified polyolefin (B) and free acid (C) itself is the resin composition (X) (i.e., the resin composition does not contain polyolefin (A)), the obtained value was taken as the concentration of free acid (C) in the resin composition (X). For each resin composition containing polyolefin (A), the concentration (α) of the free acid (C) in the resin composition was measured by performing the same treatment on each resin composition as a sample. For resin compositions in which the concentration (α) of free acid (C) was below the limit of quantification, the concentration (α) of free acid (C) was calculated from the concentration of free acid (C) in the mixture of acid-modified polyolefin (B) and free acid (C), the amount of the mixture, and the amount of polyolefin (A).

[0082] <Determination of washing conditions in the process of obtaining the second mixture> [Preparation Example 1: Preparation of a mixture containing acid-modified polyolefin (B-0) and free acid (C)] 100 parts by mass of propylene homopolymer, which has an MFR (230°C, load 2.16 kg) of 15 g / 10 min and a melting point of 160°C, measured in accordance with ASTM D1238, was placed in a 1-liter glass autoclave and heated in an oil bath at 140°C while stirring under a nitrogen atmosphere. Next, a solution of 15 parts by mass of maleic anhydride dissolved in 60 parts by mass of toluene and a solution of 3.3 parts by mass of dicumyl peroxide as an organic peroxide dissolved in 45 parts by mass of toluene were added dropwise to the glass autoclave, and the entire amount was added dropwise over 3 hours. After the addition of the maleic anhydride toluene solution was completed, heating and stirring were continued for another 2 hours to complete the reaction. During the reaction, the planetary mixer was kept under a nitrogen atmosphere at all times. After the reaction was complete, the contents were cooled, removed, and placed in an autoclave.

[0083] For the washing process, water was added to acetone (water content = 0.2 mass%) to prepare washing acetone with a water content of 3.3 mass% (however, the water content is the value when the sum of the mass of water and the mass of acetone is taken as 100 mass%). 500 parts by mass of the washing acetone (water content = 3.3 mass%) containing water was added to an autoclave and the autoclave was sealed. After stirring at a rotation speed of 500 rpm for 30 minutes, filtration was performed. Subsequently, the same operation as the first washing was repeated a total of three times, except that the stirring time was changed to 20 minutes, and the mixture was vacuum dried at 60°C for 5 hours to obtain a mixture containing maleic anhydride-modified polypropylene (B-0) and free acid. The amount of free acid contained in the obtained mixture is shown in Table 1. Furthermore, since the added maleic anhydride reacts with water in the system to open its ring and is converted to either maleic acid or fumaric acid, and both maleic acid and fumaric acid can be partially reduced to succinic acid, the amount of free acid obtained is the total amount of free maleic acid, fumaric acid, and succinic acid.

[0084] [Preparation Examples 2-4 and Comparative Preparation Example 1] The same procedure as in Preparation Example 1 was followed, except that the amount of water in the acetone used in the washing process was changed as shown in Table 1. The amount of free acid contained in the resulting mixture is shown in Table 1.

[0085]

[0086] In Preparation Examples 1 to 4, the concentration of free acid in the second mixture after washing was suitable for the resin composition (X).

[0087] <Raw Materials> The following raw materials were used in the following examples and comparative examples.

[0088] [Polyolefin (A)] ・"Polyolefin (A-1)": Homopolypropylene, MFR (230°C, 2.16 kg load) = 3 g / 10 min, Density = 910 kg / m³ ３ Free acid (C) concentration = 0.0 ppm • "Polyolefin (A-2)": Ethylene butene copolymer (EBR), MFR (230°C, 2.16 kg load) = 6.7 g / 10 min, density = 893 kg / m³ ３ Free acid (C) concentration = 0.0 ppm • "Polyolefin (A-3)": Low-density polyethylene, MFR (190°C, 2.16 kg load) = 1.1 g / 10 min, MFR (230°C, 2.16 kg load) = 2.3 g / 10 min, Density = 919 kg / m³ ３ Free acid (C) concentration = 0.0 ppm • "Polyolefin (A-4)": Low-density polyethylene, MFR (190°C, 2.16 kg load) = 1.9 g / 10 min, MFR (230°C, 2.16 kg load) = 4.0 g / 10 min, Density = 919 kg / m³ ３ Free acid (C) concentration = 0.0 ppm

[0089] [Acid-modified polyolefin (B)] Acid-modified polyolefins (B-1), (B-2), and (B-4) prepared by the same method as in Preparation Example 1, and acid-modified polyolefin (B-3) prepared by Preparation Example 5 below were used. • "Acid-modified polyolefin (B-1)": Maleic anhydride-modified homopolypropylene (MFR (230°C, 2.16 kg load) = 500 g / 10 min, density = 906 kg / m³) ３Graft modification amount = 1.1% by mass. The mixture containing acid-modified polyolefin (B-1) contains 25 ppm of free acid (C). • "Acid-modified polyolefin (B-2)": Maleic anhydride-modified homopolypropylene (MFR (230°C, 2.16 kg load) = 1000 g / 10 min, density = 906 kg / m³). ３ Graft modification amount = 3.0% by mass). The mixture containing acid-modified polyolefin (B-2) contains 22 ppm of free acid (C). • "Acid-modified polyolefin (B-3)": Maleic anhydride-modified homopolypropylene (MFR (230°C, 2.16 kg load) = 500 g / 10 min, density = 906 kg / m³). ３ Graft modification amount = 0.60% by mass). The mixture containing acid-modified polyolefin (B-3) contains 2580 ppm of free acid (C). • Acid-modified polyolefin (B-4): Maleic anhydride-modified high-density polyethylene (MFR (190°C, 2.16 kg load) = 4.0 g / 10 min, density = 965 kg / m³). ３ Graft modification amount = 2.2% by mass. The mixture containing acid-modified polyolefin (B-4) contains 21 ppm of free acid (C).

[0090] [Preparation Example 5: Preparation of a mixture containing acid-modified polyolefin (B-3) and free acid (C)] 100 parts by mass of propylene homopolymer, which has an MFR (230°C, 2.16 kg load) of 3 g / 10 min and a melting point of 160°C, measured in accordance with ASTM D1238, 0.4 parts by mass of 2,5-dimethyl-2,5-ditert-butylperoxyhexane as an organic peroxide, and 1.2 parts by mass of maleic anhydride were mixed and fed into a twin-screw extruder set to a barrel temperature of 200°C. The mixture was melted and kneaded to obtain a mixture containing maleic anhydride-modified polypropylene (B-3) and free acid.

[0091] Since the main component of any mixture containing acid-modified polyolefin (B) is acid-modified polyolefin (B), in the following table, to make the components of the resin composition easier to see, the amount of the mixture of acid-modified polyolefin (B) and free acid (C) is listed as the amount of acid-modified polyolefin (B).

[0092] <Example 1> 94.6 parts by mass of polyolefin (A-1) was mixed with 5.4 parts by mass of a mixture of acid-modified polyolefin (B-1) and free acid (C) (concentration of free acid (C) was 25 ppm), and the mixture was melt-kneaded at 220°C using a single-screw extruder to prepare resin composition (X-1). The content α of free acid (C) in resin composition (X-1) was calculated to be 1.35 ppm (≒1.4 ppm) from the concentration of free acid (C) in the mixture of acid-modified polyolefin (B-1) and free acid (C) and the amount of the mixture. The free acid (C) in resin composition (X-1) is the total amount of maleic anhydride, maleic acid, fumaric acid, and succinic acid. The content β of structural units derived from carboxylic acids or acid anhydrides in resin composition (X-1) was 0.06% by mass.

[0093] [Evaluation of Dielectric Breakdown Strength] The obtained resin composition (X-1) was extruded at 240°C using a screw with a diameter of 50 mm and an effective length L / D = 28 to produce a single-layer film with a thickness of 100 μm at a take-up speed of 5 m / min. The die temperature was 240°C. The single-layer film of the resin composition (X-1) prepared above was cut into 100 mm squares, and the center was sandwiched from above and below with cylindrical electrodes with a diameter of 25 mm. The voltage during a short circuit was recorded using a DC dielectric breakdown tester. The ambient medium during measurement was silicone oil, and the measurement temperature was 90°C. The recorded voltage was divided by the sample thickness (mm) to obtain the dielectric breakdown strength. The obtained data is shown in Table 2.

[0094] <Examples 2-7, Comparative Examples 1-3> Resin compositions were prepared in the same manner as in Example 1, except that the type and amount of polyolefin (A) and the type and amount of modified polyolefin (B) used were changed as shown in Table 2, and the dielectric breakdown strength was determined. The obtained data are shown in Table 2.

[0095]

[0096] <Examples 8 and 9> The resin compositions were prepared in the same manner as in Example 1, except that the type and amount of polyolefin (A) and the type and amount of modified polyolefin (B) used were changed as shown in Table 3, and the measurement temperature for dielectric breakdown strength was changed to 70°C. The dielectric breakdown strength was then determined. The obtained data are shown in Table 2.

[0097]

[0098] 10 Conductor 20 Wire 21 Inner semiconducting layer 22 Wire insulation layer 23 Outer semiconducting layer 24 Shielding layer 25 Adhesive layer 26 Protective layer

Claims

1. A resin composition (X) comprising an acid-modified polyolefin (B) and a free acid (C) derived from a carboxylic acid or acid anhydride that is a raw material for the acid-modified polyolefin (B), wherein the content α [ppm] of the free acid (C) is 100 ppm or less.

2. The resin composition (X) according to claim 1, wherein the ratio α / β of the content α [ppm] to the content β [mass%] of structural units derived from the carboxylic acid or acid anhydride is 800 or less.

3. The resin composition (X) according to claim 1, wherein the MFR measured at 230°C and a load of 2.16 kg in accordance with ASTM D1238 is 0.01 to 1000 g / 10 min.

4. Density measured in accordance with JIS K7112 is 850-1000 kg / m³ ３ The resin composition (X) according to claim 1.

5. The resin composition (X) according to claim 1, further comprising polyolefin (A).

6. A wire comprising a conductor, a wire insulation layer, and a protective layer in that order, wherein the wire insulation layer comprises the resin composition (X) described in any one of claims 1 to 5.

7. An adhesive resin for battery casing materials comprising the resin composition (X) according to any one of claims 1 to 5.

8. An adhesive resin for tab leads comprising the resin composition (X) according to any one of claims 1 to 5.

9. An automotive part comprising the resin composition (X) according to any one of claims 1 to 5.

10. A method for producing a resin composition (X) according to any one of claims 1 to 4, comprising the steps of: preparing a first mixture containing the acid-modified polyolefin (B) and the free acid (C), obtained by reacting a polyolefin, which is a raw material for the acid-modified polyolefin (B), with a carboxylic acid or acid anhydride, which is a raw material for the acid-modified polyolefin (B); and washing the first mixture with acetone having a water content of 0.5% by mass or more to obtain a second mixture having a lower content of the free acid (C) than the first mixture.

11. A method for producing a resin composition (X) according to claim 5, comprising the steps of: preparing the polyolefin (A); preparing a first mixture containing the acid-modified polyolefin (B) and the free acid (C), obtained by reacting a polyolefin that is a raw material for the acid-modified polyolefin (B) with a carboxylic acid or acid anhydride that is a raw material for the acid-modified polyolefin (B); washing the first mixture with acetone having a water content of 0.5% by mass or more to obtain a second mixture having a lower content of the free acid (C) than the first mixture; and mixing the polyolefin (A) and the second mixture.

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