JP7546391B2 - Graft copolymer and method for producing same - Google Patents

Description

The present invention relates to a graft copolymer and a method for producing the same.

α-Olefin/non-conjugated polyene copolymers are currently widely used in a variety of fields, including the automotive and industrial sectors. In recent years, there has been a demand for even higher added value for these materials.

One of the methods for adding new added value to polymers is graft polymerization onto polymers. Graft polymerization of acrylic monomers onto general polyolefins has been carried out in various ways in the past.

For example, Patent Document 1 discloses a graft copolymer obtained by graft copolymerizing a polyolefin material with an acrylic monomer such as acrylic acid by ultraviolet irradiation in the presence of a photosensitizer such as benzophenone. Patent Document 1 specifically discloses a graft copolymer using a polyethylene film, a polypropylene film, a woven fabric of polytetrafluoroethylene, or a polypropylene fiber as the polyolefin material, and also discloses that this graft copolymer can be used as a water absorbent material. Patent Document 1 also discloses that an ethylene propylene copolymer can be used as the polyolefin material.

Patent Document 2 also discloses a graft copolymer similar to that described in Patent Document 1, except that a polyolefin material having micropores of a specific size is used.

Generally, graft reactions using organic peroxides as initiators must be carried out at high temperatures, which can lead to problems with polymer decomposition. To avoid this problem, attempts have been made to carry out graft reactions at low temperatures.

As one attempt to avoid such problems, graft polymerization onto a polymer using an alkylboron as an initiator has been investigated (Patent Document 3, Non-Patent Document 1).
Here, Patent Document 3 discloses a graft copolymer obtained by first contacting a mixture containing an α-olefin polymer such as polyethylene or polypropylene, an alkylboron such as trihexylboron, and a solvent such as benzene with air at room temperature, and then adding a polar monomer such as 4-vinylpyridine or acrylonitrile and reacting at 20 to 150° C. Here, the examples in Patent Document 3 show that the reaction with the polar monomer is preferably carried out at 60 to 80° C. rather than at 125° C.

Patent Document 4 discloses a graft copolymer obtained by first mixing a polyolefin such as polyethylene, polypropylene, or ethylene-propylene copolymer with a trialkylborane such as tributylborane, maleic anhydride, and a solvent such as benzene at 0 to 150°C to form a reaction mixture containing a trialkylborane-maleic anhydride complex, and then contacting this reaction mixture with an oxygen-containing oxidizing agent such as air at 0 to 150°C. Here, Patent Document 4 specifies that the reactive species involved in the graft polymerization reaction is a peroxide generated by the addition of one molecule of oxygen to trialkylborane. Patent Document 4 further suggests that an alkoxy radical generated from this peroxide abstracts hydrogen from the polyolefin chain, and the resulting polymer radical reacts with maleic anhydride.

Patent Document 5 also discloses a graft copolymer obtained by contacting a mixture containing a polyolefin such as polyethylene, polypropylene, an ethylene-propylene copolymer, or a propylene-butene copolymer, tributyl boron, and water with air, and then reacting the mixture with a monomer such as methacrylic acid or a methacrylic acid ester. Patent Document 5 also discloses that the obtained graft copolymer has a core-shell structure consisting of a core portion including a main chain portion derived from the polyolefin, and a shell portion including a graft portion formed by graft polymerization of the monomer.

In addition, none of Patent Documents 3 to 5 mentions the use of EPDM rubber instead of polyolefin as the polymer to be graft polymerized.

Japanese Patent Application Publication No. 62-263213 Japanese Unexamined Patent Publication No. 63-83111 U.S. Pat. No. 3,141,862 US Patent Application Publication No. 2002/0198327 International Publication No. 2018/105682

MACROMOLECULES: vol38, 8966-8970 (2005)

Graft polymerization of ethylene-α-olefin-non-conjugated polyene copolymers has been performed by reacting maleic anhydride and other radical reactants. However, such graft polymerization is a high-temperature reaction, and there are concerns that the structure derived from the ethylene-α-olefin-non-conjugated polyene copolymer may collapse, or that gelation or disappearance may occur due to preferential reaction between non-conjugated polyenes during graft polymerization.

The present invention aims to obtain an ethylene-α-olefin-non-conjugated polyene copolymer that is modified while maintaining unsaturated bonds available for crosslinking reactions.

Through intensive research, the inventors discovered that a rubber composition in which some ethylidene groups remain can be obtained by modifying an ethylene-α-olefin-non-conjugated polyene copolymer, which contains a non-conjugated polyene having an ethylidene group as the non-conjugated polyene, under low-temperature conditions using organic boron as a radical reactant, and thus completed the present invention.

That is, the present invention relates to the following [1] to [6].
[1]
a main chain portion derived from an ethylene/α-olefin/non-conjugated polyene copolymer (A) comprising ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group;
and a graft portion derived from a (meth)acrylic acid alkyl ester polymer (B),
The (meth)acrylic acid alkyl ester polymer (B) comprises a structural unit derived from an acrylic acid alkyl ester compound and/or a methacrylic acid alkyl ester compound.

[2]
The graft copolymer (X) according to the above [1], wherein the α-olefin constituting the ethylene/α-olefin/non-conjugated polyene copolymer (A) is propylene.

[3]
The graft copolymer (X) according to any one of [1] to [2] above, characterized in that the alkyl group of the ester moiety of the alkyl acrylate compound or the alkyl methacrylate compound is a methyl group.

[4]
The graft copolymer (X) according to any one of the above [1] to [3], characterized in that it comprises a structural unit derived from ethylene, a structural unit derived from the above-mentioned α-olefin, a structural unit derived from the above-mentioned non-conjugated polyene having an ethylidene group, and a structural unit derived from the above-mentioned alkyl acrylate compound and/or alkyl methacrylate compound.

[5]
The graft copolymer (X) according to any one of the above [1] to [4], characterized in that the grafting rate defined by the following formula (I) is 0.01% by mass or more and 300% by mass or less.
Grafting rate (%)={(mass of graft copolymer (X))−(mass of ethylene/α-olefin/non-conjugated polyene copolymer (A))}/mass of ethylene/α-olefin/non-conjugated polyene copolymer (A)×100 (I)

[6]
A method for producing the graft copolymer (X) according to any one of the above [1] to [5], comprising the steps of:
A method for producing a graft copolymer, comprising a graft copolymerization step of graft copolymerizing the ethylene-α-olefin-non-conjugated polyene copolymer (A) with the alkyl acrylate compound and/or the alkyl methacrylate compound using alkylboron.

The present invention provides an ethylene-α-olefin-non-conjugated polyene copolymer that is modified while maintaining unsaturated bonds available for crosslinking reactions.

The present invention will be specifically described below.
<Graft Copolymer (X)>
The graft copolymer (X) of the present invention is
a main chain portion derived from an ethylene/α-olefin/non-conjugated polyene copolymer (A) (hereinafter, in this specification, may be simply referred to as "copolymer (A)") comprising ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group;
and a graft portion derived from a (meth)acrylic acid alkyl ester polymer (B) (hereinafter, in this specification, may be simply referred to as "polymer (B)").

Here, the (meth)acrylic acid alkyl ester polymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester compound.
That is, the graft copolymer (X) of the present invention is a graft copolymer of an ethylene-α-olefin-non-conjugated polyene copolymer (A) consisting of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group, and a poly(meth)acrylic acid alkyl ester polymer (B) which is a polymer or copolymer of an (meth)acrylic acid alkyl ester compound.

In the present invention, "(meth)acrylic acid" means acrylic acid or methacrylic acid, and "alkyl (meth)acrylate" means alkyl acrylate or alkyl methacrylate.

Also, the term "polymer" means a homopolymer or a copolymer.
In addition, in this specification, when a certain monomer constituting a polymer is M, the expression "structural unit derived from M" may be used. In this case, "structural unit derived from M" refers to a structural unit corresponding to monomer M, and when monomer M has a structure represented by R ¹ R ² C=CR ³ R ⁴ (R ¹ , R ² , R ³ , and R ⁴ are hydrogen atoms or suitable substituents that monomer M may have, and depending on the type of monomer M, two or more of R ¹ , R ² , R ³ , and R ⁴ may be bonded to each other to form a ring), the structural unit derived from M has a structure represented by -CR ¹ R ² -CR ³ R ⁴ -. For example, a structural unit derived from ethylene refers to a structural unit having a structure represented by -CH ₂ -CH ₂ -. Note that when monomer M has two or more double bonds capable of polymerization reaction, there may be two or more structures that "structural unit derived from M" can have.

Ethylene/α-olefin/non-conjugated polyene copolymer (A)
The ethylene/α-olefin/non-conjugated polyene copolymer (A) used in the present invention is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group. That is, the copolymer (A) has a structural unit derived from ethylene, a structural unit derived from an α-olefin having 3 to 20 carbon atoms (hereinafter, may be simply referred to as an "α-olefin-derived structural unit"), and a structural unit derived from a non-conjugated polyene having an ethylidene group (hereinafter, may be simply referred to as an "non-conjugated polyene-derived structural unit").

In the graft copolymer (X) of the present invention, the copolymer (A) constitutes the main chain portion.
Examples of the α-olefin having 3 to 20 carbon atoms constituting the copolymer (A) include propylene, butene-1, pentene-1, 2-methylbutene-1, 3-methylbutene-1, hexene-1, 3-methylpentene-1, 4-methylpentene-1, 3,3-dimethylbutene-1, heptene-1, methylhexene-1, dimethylpentene-1, trimethylbutene-1, ethylpentene-1, octene-1, methylpentene-1, dimethylhexene-1, trimethylpentene-1, ethylhexene-1, methylethylpentene-1, diethylbutene-1, and propylpentene-1. These α-olefins may be used alone or in combination of two or more. In other words, the copolymer (A) may contain only one type of structural unit derived from an α-olefin having 3 to 20 carbon atoms, or may contain two or more types.

As the α-olefin having 3 to 20 carbon atoms, among these, propylene, butene, hexene, and octene are preferred, propylene, butene, and octene are more preferred, propylene or butene are even more preferred, and propylene is particularly preferred.

An example of a non-conjugated polyene having an ethylidene group is 5-ethylidene-2-norbornene. The non-conjugated polyene having an ethylidene group may be used alone or in combination of two or more types. In other words, the copolymer (A) may contain only one type of structural unit derived from a non-conjugated polyene having an ethylidene group, or it may contain two or more types.

The copolymer (A) may be a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group, but is preferably a random copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group. Particularly preferred copolymers as the ethylene-α-olefin-non-conjugated polyene copolymer (A) according to the present invention include, for example, an ethylene-propylene-5-ethylidene-2-norbornene random copolymer and an ethylene-1-butene-5-ethylidene-2-norbornene random copolymer.

The copolymer (A) is not particularly limited in the copolymerization ratio of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group. However, in the copolymer (A), the molar ratio of the structural units derived from ethylene to the structural units derived from an α-olefin having 3 to 20 carbon atoms is 40/60 to 99.9/0.1, preferably 50/50 to 90/10, more preferably 55/45 to 85/15, and even more preferably 55/45 to 78/22. Here, when the copolymer (A) contains two or more structural units derived from an α-olefin having 3 to 20 carbon atoms, the molar ratio of the structural units derived from ethylene to the total structural units derived from an α-olefin having 3 to 20 carbon atoms is the above ratio. Such a copolymer (A) is preferable because it has excellent mechanical strength and low-temperature flexibility.

In addition, the content of the structural units derived from non-conjugated polyenes having ethylidene groups in 100% by mass of copolymer (A) (i.e., 100% by mass of the total content of all structural units), is 0.07 to 10% by mass, preferably 0.1 to 8.0% by mass, and more preferably 0.5 to 5.0% by mass. Here, when copolymer (A) contains two or more structural units derived from non-conjugated polyenes having ethylidene groups, the total content of the structural units derived from non-conjugated polyenes having ethylidene groups is the above-mentioned percentage. Such a copolymer (A) is preferable because the vulcanized rubber obtained from the composition of the present invention exhibits excellent rubber elasticity and has excellent mechanical properties.

The content of ethylene-derived structural units, the content of α-olefin-derived structural units, and the content of ethylidene-containing non-conjugated polyene-derived structural units in the copolymer (A) can be measured, for example, by ^13C -NMR spectroscopy, and peak identification and quantification can be performed according to the method described in "Polymer Analysis Handbook" (published by Asakura Publishing, pp. 163-170).

The copolymer (A) preferably has an intrinsic viscosity [η] measured in decalin solvent at 135°C in the range of 0.05 to 15 dL/g, more preferably 0.1 to 10 dL/g, and even more preferably 0.5 to 3 dL/g. In addition, the melt flow rate (MFR) measured at 190°C under a load of 2.16 kgf is usually 0.01 to 200 g/10 min, preferably 0.1 to 180 g/10 min, and more preferably 1 to 150 g/10 min.

The copolymer (A) is not particularly limited and can be prepared by a conventionally known method. In addition, a commercially available ethylene-α-olefin-non-conjugated polyene copolymer, which is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group, can also be used as the copolymer (A).

(Meth)acrylic acid alkyl ester polymer (B)
The graft copolymer (X) of the present invention has a graft portion derived from the (meth)acrylic acid alkyl ester polymer (B). In other words, in the graft copolymer (X) of the present invention, the (meth)acrylic acid alkyl ester polymer (B) constitutes the graft portion.

In the present invention, the graft copolymer (X) of the present invention may be obtained by introducing an (meth)acrylic acid alkyl ester polymer (B) into the ethylene-α-olefin-non-conjugated polyene copolymer (A), or may be obtained by polymerizing an acrylic acid alkyl ester compound or a methacrylic acid alkyl ester compound, which is a monomer of the (meth)acrylic acid alkyl ester polymer (B), in the presence of the ethylene-α-olefin-non-conjugated polyene copolymer (A).

The (meth)acrylic acid alkyl ester polymer (B) contains structural units derived from only one of the monomers, an acrylic acid alkyl ester compound or a methacrylic acid alkyl ester compound. In other words, the (meth)acrylic acid alkyl ester polymer (B) is a homopolymer of an acrylic acid alkyl ester compound or a copolymer of acrylic acid alkyl ester compounds, or a homopolymer of a methacrylic acid alkyl ester compound or a copolymer of methacrylic acid alkyl ester compounds.

The number of carbon atoms in the alkyl group of the ester moiety of the alkyl acrylate compound or alkyl methacrylate compound is usually 1 to 20, and preferably 1 to 10. In a particularly preferred embodiment of the present invention, the alkyl group of the ester moiety is a methyl group.

Specific examples of acrylic acid alkyl ester compounds include methyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, pentadecyl acrylate, stearyl acrylate, tridecyl acrylate, etc. Specific examples of methacrylic acid alkyl ester compounds include methyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, pentadecyl methacrylate, stearyl methacrylate, and tridecyl methacrylate.

By using such an alkyl acrylate compound or an alkyl methacrylate compound as a monomer, it is possible to introduce many graft moieties into the graft copolymer (X).

Graft copolymer (X)
The graft copolymer (X) of the present invention has a main chain portion derived from the above-mentioned ethylene-α-olefin-non-conjugated polyene copolymer (A) and a graft portion derived from the (meth)acrylic acid alkyl ester polymer (B). In the present invention, even when the chain length of the graft portion is longer than that of the main chain portion, the portion derived from the ethylene-α-olefin-non-conjugated polyene copolymer (A) is regarded as the main chain portion, and the portion derived from the (meth)acrylic acid alkyl ester polymer (B) is regarded as the graft portion.

In a typical embodiment of the present invention, the graft copolymer (X) comprises structural units derived from ethylene, structural units derived from the above-mentioned α-olefin, structural units derived from the above-mentioned non-conjugated polyene having an ethylidene group, and structural units derived from the above-mentioned alkyl acrylate compound and/or alkyl methacrylate compound.

Such a graft copolymer (X) of the present invention has a high introduction ratio of the graft moiety, and preferably has a grafting ratio defined by the following formula (I) of 0.01% by mass or more and 300% by mass or less.
Grafting ratio (%)=(mass of graft copolymer (X)−(mass of ethylene/α-olefin/non-conjugated polyene copolymer (A))/mass of ethylene/α-olefin/non-conjugated polyene copolymer (A)×100 (I)

Here, the grafting ratio can be calculated by applying the mass of the graft copolymer (X) = M1 + M2 + M3 + Mg and the mass of the ethylene-α-olefin-non-conjugated polyene copolymer (A) = M1 + M2 + M3 to the above formula (I), where M1 is the mass of the ethylene-derived structural units, M2 is the mass of the α-olefin-derived structural units, M3 is the mass of the ethylidene group-containing non-conjugated polyene-derived structural units, and Mg is the mass of the graft monomer-derived structural units, out of all the structural units constituting the graft copolymer (X). In other words, the grafting ratio can be calculated as Mg/(M1 + M2 + M3) × 100.

The graft copolymer (X) of the present invention has a certain ratio or more of ethylidene groups derived from the non-conjugated polyene in the main chain. This allows the graft copolymer (X) to have the characteristics of the ethylene-α-olefin-non-conjugated polyene copolymer (A) as the parent to a certain extent. Specifically, 70% or more of the ethylidene groups remain after modification, and preferably 80% of the ethylidene groups remain after modification. Here, the amount of ethylidene groups in the graft copolymer (X) can be determined using ¹³ C-NMR based on the location and integrated value of the peaks corresponding to the carbon atoms constituting the ethylidene groups.

The graft copolymer (X) of the present invention is not particularly limited, but the intrinsic viscosity [η] measured in decalin solvent at 135°C is preferably in the range of 0.05 to 15 dL/g, more preferably 0.1 to 10 dL/g, and even more preferably 0.5 to 3 dL/g.

The graft copolymer (X) of the present invention is not particularly limited, but the weight average molecular weight (Mw) is usually in the range of 60,000 to 400,000, preferably 70,000 to 150,000, and more preferably 80,000 to 150,000.

In addition, the graft copolymer (X) of the present invention preferably has a molecular weight distribution (Mw/Mn) calculated from the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the range of 1.5 to 6.0, more preferably 2.0 to 5.0, and even more preferably 2.5 to 4.0.

In the present invention, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values determined by gel permeation chromatography (GPC) under the conditions described in the Examples below.

The graft copolymer (X) of the present invention has a highly modified main chain derived from the ethylene-α-olefin-non-conjugated polyene copolymer (A) and a high proportion of graft moieties having polar groups are introduced, and therefore has high affinity with both hydrophilic and hydrophobic substances. Even when preparing a composition containing both a hydrophilic and a hydrophobic substance, a homogeneous composition can be easily prepared by coexisting the graft copolymer (X) of the present invention.

The graft copolymer (X) of the present invention is
The ethylene-α-olefin-non-conjugated polyene copolymer (A) can be obtained by a production method having a graft copolymerization step of graft copolymerizing the ethylene-α-olefin-non-conjugated polyene copolymer (A) with the alkyl acrylate compound and/or alkyl methacrylate compound using alkylboron. Here, the graft copolymer (X) may be obtained by introducing an alkyl (meth)acrylate polymer (B) into the ethylene-α-olefin-non-conjugated polyene copolymer (A) as described above, or may be obtained by graft copolymerizing an alkyl acrylate compound or an alkyl methacrylate compound, which is a monomer of the alkyl (meth)acrylate polymer (B), into the ethylene-α-olefin-non-conjugated polyene copolymer (A).

Among these, a method of graft copolymerizing an acrylic acid alkyl ester compound or a methacrylic acid alkyl ester compound, which is a monomer of the (meth)acrylic acid alkyl ester polymer (B), onto the ethylene-α-olefin-non-conjugated polyene copolymer (A) that serves as the main chain, can be preferably used.

Here, the mode of the graft copolymerization reaction between the ethylene-α-olefin-non-conjugated polyene copolymer (A) and an alkyl acrylate compound or an alkyl methacrylate compound tends to change depending on the type of initiator. Here, when such a graft copolymerization reaction is carried out in the presence of an organic peroxide such as a dialkyl peroxide, a diacyl peroxide, or an alkyl percarboxylate, the graft copolymerization reaction at the ethylidene group derived from the ethylene-α-olefin-non-conjugated polyene copolymer (A) and the reaction in which multiple ethylene-α-olefin-non-conjugated polyene copolymer (A) molecules bond to each other via the ethylidene group tend to proceed easily. In this case, the obtained graft copolymer tends to contain almost or completely no ethylidene groups, and the properties possessed by the ethylene-α-olefin-non-conjugated polyene copolymer (A), such as rubber properties, may be lost. On the other hand, when the graft copolymerization reaction between the ethylene-α-olefin-non-conjugated polyene copolymer (A) and an alkyl acrylate compound or an alkyl methacrylate compound is carried out in the presence of alkylboron, the graft copolymerization reaction tends to be carried out in a manner that maintains the ethylidene group derived from the ethylene-α-olefin-non-conjugated polyene copolymer (A) to some extent. In this case, the obtained graft copolymer tends to have the properties that the ethylene-α-olefin-non-conjugated polyene copolymer (A) had, for example, rubber properties, to some extent. For this reason, in the production of the graft copolymer (X) of the present invention, it is preferable to have a graft copolymerization step in which the ethylene-α-olefin-non-conjugated polyene copolymer (A) and an alkyl acrylate compound or an alkyl methacrylate compound are graft copolymerized using alkylboron. When ethylene-α-olefin-non-conjugated polyene copolymer (A) is graft-copolymerized with an alkyl acrylate compound or an alkyl methacrylate compound, which is a monomer constituting the (meth)acrylic acid alkyl ester polymer (B), using alkylboron, it is possible to suitably produce a graft copolymer (X) having a graft portion derived from the (meth)acrylic acid alkyl ester polymer (B) at a high grafting rate relative to the main chain portion derived from the ethylene-α-olefin-non-conjugated polyene copolymer (A).

In the graft copolymerization step using alkylboron, an initiator in which alkylboron is reacted with oxygen to form a peroxide can be used. Such a graft copolymerization reaction using alkylboron can be carried out by referring to the methods described in, for example, US3141862, Macromolecules 2005, 38, 8966-8970, J. APPL. POLYM. SCI. 2015,42186, and Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 47, 6163-6167 (2009), etc.

The alkyl boron is not particularly limited, but for example, trialkyl boron such as tributyl boron can be suitably used.
Examples of the solvent used in the graft polymerization reaction include, in addition to water, aromatic hydrocarbon solvents such as benzene, toluene, and xylene; aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane, and decane; alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, and decahydronaphthalene; chlorinated hydrocarbon solvents such as chlorobenzene, dichlorobenzene, trichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, and tetrachloroethylene; γ-butyrolactone; N-methyl-2-pyrrolidone; 2,4-pentadiene; dimethyl sulfoxide; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, and cyclohexanone; benzyl alcohol, 1-butanol, 2- Examples of the solvent include alcohols such as butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-ethyl-1-hexanol, normal propyl alcohol, isopropyl alcohol, ethanol, and methanol; ethers such as diethyl ether, ethylene glycol monomethyl ether, anisole, diphenyl ether, dioxane, and tetrahydrofuran; and esters such as ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, propylene glycol monomethyl ether acetate, acetyl tributyl citrate, n-alkyl adipate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and 3-methoxy-3-methyl-1-butyl acetate. These solvents may be used alone or in combination of two or more. Among these solvents, aliphatic hydrocarbon solvents such as normal hexane and heptane are particularly preferred from the standpoint of safety.

In carrying out the graft copolymerization reaction, the method and order of contacting the ethylene-α-olefin-non-conjugated polyene copolymer (A) with the graft monomers, acrylic acid alkyl ester compound or methacrylic acid alkyl ester compound, and alkyl boron, are not particularly limited, and various methods can be used. Also, the ethylene-α-olefin-non-conjugated polyene copolymer (A) may be impregnated in advance with an acrylic acid alkyl ester compound or methacrylic acid alkyl ester compound, or alkyl boron. In the graft copolymerization reaction, a known chain transfer agent can be used in combination to adjust the molecular weight of the graft polymer.

Regarding the order of contact between the alkylboron and oxygen, it is preferable to first charge the alkylboron into the reaction system, since it is the reaction initiation point, and then introduce oxygen for contact. In addition, it is preferable to thoroughly purge the remaining oxygen from the acrylic acid alkyl ester compound or methacrylic acid alkyl ester compound, which is the graft monomer, by subjecting it to nitrogen aeration treatment in advance.

In addition, various additives such as antioxidants such as hindered phenol compounds, process stabilizers, heat stabilizers, heat aging agents, weathering stabilizers, antistatic agents, slip prevention agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, nucleating agents, plasticizers, hydrochloric acid absorbers, flame retardants, blooming inhibitors, radical scavengers such as nitroxy radicals such as piperidines, known softeners, tackifiers, processing aids, adhesion promoters, carbon fibers, glass fibers, whiskers, and other fillers can be used in combination, as long as the purpose of the present invention is not hindered. In addition, it is also possible to blend small amounts of other polymer compounds as long as it does not deviate from the spirit of the present invention.

The above-mentioned graft copolymerization reaction can be carried out in any device capable of mixing and heating, without any particular restrictions. For example, either a vertical or horizontal reactor can be used. Specific examples include a fluidized bed, a moving bed, a loop reactor, a horizontal reactor with an agitator, a vertical reactor with an agitator, a rotating drum, etc. In addition, a multi-axis/rotation-revolution type mixer such as a planetary mixer, a kneader, a paddle dryer, a Henschel mixer, a static mixer, a V blender, a tumbler, or a Nauta mixer can also be used.

After the graft copolymerization reaction is completed, it is also preferable to have a washing step in which the resulting graft copolymer is washed with a solvent capable of dissolving unreacted acrylic acid alkyl ester compounds or methacrylic acid alkyl ester compounds, etc.

The solvent used in the washing step is not particularly limited, but is preferably a ketone or alcohol, and more preferably acetone or methanol. The washing temperature is not limited as long as the graft copolymer (X) produced is not damaged, but is preferably 0 to 110°C, more preferably room temperature to about 100°C.

Here, when the cleaning temperature is set higher than the boiling point of the cleaning solvent at atmospheric pressure, it is preferable to carry out the cleaning process in a sealed state in order to prevent the cleaning solvent from volatilizing.

The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.
In the following examples, the measurement and evaluation methods are as follows.

<Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw/Mn)>
The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured using a high temperature gel permeation chromatograph (GPC) PL-GPC220 manufactured by POLYMER LABORATORIES as follows. The separation columns used were TSKgel GMHHR-H(S)HT (2 columns) and TSKgel GMHHR-M(S) (1 column), the column temperature was set to 140°C, and the mobile phase was 1,2,4-trichlorobenzene. (TCB) was used, the development speed was 1.0 mL/min, the sample concentration was 1.0 mg/mL, the sample injection amount was 0.5 mL, and a differential refractometer/built-in device (POLYMER LABORATORIES) was used as a detector. A PD2040 type two-angle light scattering photometer (manufactured by Precision Detectors), and a PL-BV400 type bridge-type viscometer (manufactured by Polymer Laboratories) were used. The calibration of the instrument was performed using monodisperse polystyrene (manufactured by Tosoh Corporation, molecular weight 190,000) and linear polyethylene (NIST1475a dn/dc = 0.100 IV = 1.01). ) was calculated by dividing Mw measured by the above-mentioned measurement method by Mn also measured by the above-mentioned measurement method.

<Intrinsic viscosity [η]>
Using an automatic dynamic viscosity measuring device VMR-053PC manufactured by Rigo Co., Ltd. and an improved Ubbelohde type capillary viscometer, the specific viscosity η _sp in decalin at 135° C. was determined, and the intrinsic viscosity ([η]) was calculated using the following formula.
[η]=η _sp /{c(1+K・η _sp )}
(c: solution concentration [g/dl], K: constant)

<Polymer composition>
The mass fraction (mass%) of each of the constituent units constituting the ethylene-α-olefin-non-conjugated polyene copolymer (A) was determined by measurements by ¹³ C-NMR. The measurements were obtained by measuring the ¹³ C-NMR spectrum of the copolymer using an ECX400P nuclear magnetic resonance apparatus (manufactured by JEOL Ltd.) at a measurement temperature of 120° C., a measurement solvent of orthodichlorobenzene/deuterated benzene=4/1, and an accumulation number of 8000 times. Here, the content of the constituent units derived from the non-conjugated polyene constituting the ethylene-α-olefin-non-conjugated polyene copolymer (A) was determined based on the location of the peak corresponding to the carbon atom constituting the ethylidene group and the accumulated value.
Similarly, the mass fraction (mass %) of each of the structural units constituting the graft copolymer was also determined.

<Grafting rate (%)>
The graft ratio of the copolymer was calculated by the following formula (I).
Grafting ratio (%)=(mass of graft copolymer (X)−(mass of ethylene/α-olefin/non-conjugated polyene copolymer (A))/mass of ethylene/α-olefin/non-conjugated polyene copolymer (A)×100 (I)
Specifically, the grafting ratio was calculated by determining the mass M1 of the ethylene-derived structural units, the mass M2 of the α-olefin-derived structural units, the mass M3 of the non-conjugated polyene-derived structural units, and the mass Mg of the graft monomer-derived structural units for the graft copolymer (X) according to the method described in the above "Polymer composition", and then calculating the mass of the graft copolymer (X)=M1+M2+M3+Mg and the mass of the ethylene-α-olefin-non-conjugated polyene copolymer (A)=M1+M2+M3.

[Example 1] (Production of Graft Copolymer-1)
As the ethylene-α-olefin-non-conjugated polyene copolymer (A), ethylene-propylene-5-ethylidene-2-norbornene copolymer pellets (EPE-1) having an ethylene content of 65.9% by mass, a non-conjugated polyene content of 4.6% by mass, and an intrinsic viscosity [η] of 2.4 dL/g were used, and as the graft monomer, methyl methacrylate (MMA), which is a methacrylic acid alkyl ester compound in which the alkyl group in the ester moiety has one carbon atom, was used.

Under a nitrogen atmosphere, 500 mL of water and 100 g of ethylene-propylene-5-ethylidene-2-norbornene copolymer pellets (EPE-1) were placed in a 2 L separable flask, the liquid temperature was adjusted to 40°C, and nitrogen was bubbled into the liquid at a rate of 2 L per minute for 30 minutes while stirring (nitrogen bubbling). Then, 0.05 g of tributyl boron (TBB) was added, 30 mL of air was bubbled in, and the mixture was stirred at a temperature of 40°C for 30 minutes, after which 100 g of methyl methacrylate was added and reacted for 2 hours. After the reaction was completed, air was bubbled into the liquid at a rate of 2 L per minute for 5 minutes. The pellets were then filtered, thoroughly washed with acetone, and vacuum dried at 60°C for 120 minutes to obtain graft copolymer-1.

The yield of graft copolymer-1 was 111 g, and the grafting rate was 0.1% by mass.
The results are shown in the following Table 1. In addition, in the following Table 1, "ENB" refers to 5-ethylidene-2-norbornene.

[Comparative Example 1]
The ethylene-propylene-5-ethylidene-2-norbornene copolymer pellets (EPE-1) used in Example 1 were used as they were without being subjected to graft copolymerization.

The results are shown in Table 1 below.

Claims (4)

a main chain portion derived from an ethylene/α-olefin/non-conjugated polyene copolymer (A) comprising ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene having an ethylidene group;
and a graft portion derived from a (meth)acrylic acid alkyl ester polymer (B),
The (meth)acrylic acid alkyl ester polymer (B) contains a structural unit derived from an acrylic acid alkyl ester compound and/or a methacrylic acid alkyl ester compound ,
a graft copolymerization step in which the ethylene-α-olefin-non-conjugated polyene copolymer (A) is graft-copolymerized with the alkyl acrylate compound and/or the alkyl methacrylate compound using alkylboron;
and
A method for producing a graft copolymer, characterized in that the grafting rate defined by the following formula (I) is 0.01 mass % or more and 0.1 mass % or less:
Grafting rate (%)={(mass of graft copolymer (X))−(mass of ethylene/α-olefin/non-conjugated polyene copolymer (A))}/mass of ethylene/α-olefin/non-conjugated polyene copolymer (A)×100 (I) 2. The process according to claim 1, wherein the α-olefin constituting the ethylene/α-olefin/non-conjugated polyene copolymer (A) is propylene. The method according to any one of claims 1 to 2, characterized in that the alkyl group in the ester moiety of the alkyl acrylate compound or the alkyl methacrylate compound is a methyl group. The method according to any one of claims 1 to 3, characterized in that the graft copolymer (X) comprises a structural unit derived from ethylene, a structural unit derived from the α-olefin, a structural unit derived from the non-conjugated polyene having an ethylidene group, and a structural unit derived from the alkyl acrylate compound and/or the alkyl methacrylate compound .