TECHNICAL FIELD

The present invention relates to a modified elastomer composition, to a crosslinked elastomer composition, and to a molded article thereof.

The first invention relates to a modified elastomer composition and a crosslinked elastomer composition that are excellent in compression set, durability, and extrusion-molded appearance and to a molded article using the same.

The second invention relates to a novel low-gloss modified elastomer composition and a novel low-gloss crosslinked elastomer composition excellent in compression set, durability, blocking resistance, and moldability and to a molded article using the same.

BACKGROUND ART

A thermoplastic elastomer is an elastomer that softens and becomes flowable when heated and exhibits rubber elasticity when cooled. The thermoplastic elastomer has moldability equivalent to that of thermoplastic resins and also has rubber elasticity. The thermoplastic elastomer is recyclable and is therefore used in a wide variety of applications such as automobile components, building components, medical components, wire-coating materials, and sundry goods.

When a thermoplastic elastomer is used in applications that require sealing properties, it is important for the thermoplastic elastomer to have good rubber elasticity, good compression set characteristics, good moldability, and good extrusion-molded appearance.

Since a thermoplastic resin such as a polyolefin is mixed into a thermoplastic elastomer in order to provide thermoplasticity, its compression set characteristics are insufficient as compared with thermosetting rubber, so that the applications of the thermoplastic elastomer are limited. A thermosetting rubber such as EPDM has good compression set characteristics but requires a long crosslinking process, and its durability is low.

PTL 1 to PTL 3 propose silane-modified elastomer compositions with improved compression set. In PTL 1 to PTL 3, it is necessary to add a large amount of an unsaturated silane compound in order to improve the compression set, and this impairs economic efficiency and productivity. Moreover, these silane-modified elastomer compositions are highly glossy and are not suitable as sealing materials. Another problem is that, during or after the formation of pellets, blocking is likely to occur.

Also, PTL 4 proposes a silane-modified elastomer composition. In PTL 4, the compression set (70° C.×22 hours) was only a little over 50% and was insufficient.

PTL 5 proposes a dynamically vulcanized thermoplastic elastomer composition using a vulcanizing agent such as a phenolic resin. In PTL 5, since the components of the thermoplastic elastomer composition include a non-crosslinked thermoplastic resin, the compression set is insufficient, as described above.PTL 1: International Publication No. 2016/140251PTL 2: International Publication No. 2016/140252PTL 3: International Publication No. 2016/140253PTL 4: Japanese Patent No. 5346285PTL 5: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-516098

SUMMARY OF INVENTION

An object of the first invention is to provide a modified elastomer composition and a crosslinked elastomer composition that exhibit compression set characteristics comparable to those of thermosetting rubbers in the related art, have durability and moldability comparable to those of thermoplastic elastomer compositions in the related art, and have good extrusion-molded appearance and to provide a molded article of the modified elastomer composition or the crosslinked elastomer composition.

The inventors have found that a modified elastomer composition obtained by graft modification of a composition containing: an ethylene-α-olefin-non-conjugated diene copolymer rubber; an ethylene-α-olefin copolymer rubber containing no non-conjugated diene units; polyethylene, polypropylene, or a propylene-α-olefin copolymer; and an unsaturated silane compound or a crosslinked elastomer composition obtained by subjecting the above modified elastomer composition to a crosslinking reaction can have compression set characteristics comparable to those of thermosetting rubbers and easy extrusion moldability comparable to that of thermoplastic elastomers. These compression set characteristics and extrusion moldability have been thought to be impossible to achieve simultaneously, and a molded article excellent in compression set and having good extrusion-molded appearance can thereby be obtained. Thus, the first invention has been completed.

The first invention is summarized in the following [1] to [10].

[1] A modified elastomer composition comprising following components (A) to (D) and grafted with following component (E):

component (A): an ethylene-α-olefin-non-conjugated diene copolymer rubber;

component (B): an ethylene-α-olefin copolymer rubber in which a content of ethylene units is 60% to 99% by mass and which contains no non-conjugated diene units;

component (C): polyethylene and/or a propylene-based resin in which a content of propylene units is 40% to 100% by mass;

component (D): an unsaturated silane compound; and

component (E): a peroxide.

[2] The modified elastomer composition according to [1], wherein a content of component (A) is 5 to 70 parts by mass based on 100 parts by mass of a total of component (A) and component (B), wherein a content of component (B) is 95 to 30 parts by mass based on 100 parts by mass of the total of component (A) and component (B), wherein a content of component (C) is 1 to 200 parts by mass based on 100 parts by mass of the total of component (A) and component (B), and wherein a content of component (D) is 0.01 to 3 parts by mass based on 100 parts by mass of the total of component (A) and component (B).
[3] The modified elastomer composition according to [1] or [2], wherein a density of component (B) is 0.880 g/cm3or less.
[4] The modified elastomer composition according to any of [1] to [3],

wherein an amount of component (E) used is 0.01 to 3 parts by mass based on 100 parts by mass of a total of component (A) and component (B).

[5] The modified elastomer composition according to any of [1] to [4] further comprising component (F): a crosslinking aid in an amount of 0.001 to 2 parts by mass based on 100 parts by mass of a total of component (A) and component (B).

[6] The modified elastomer composition according to any of [1] to [5],

wherein component (D) is a compound represented by following formula (1):
RSi(R′)3(1)
where R is an ethylenically unsaturated hydrocarbon group; R's are each independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms; and at least one of R's is an alkoxy group having 1 to 10 carbon atoms.
[7] The modified elastomer composition according to any of [1] to [6], further comprising component (G): a softener in an amount of 0.5 to 200 parts by mass based on 100 parts by mass of a total of component (A) and component (B).
[8] The modified elastomer composition according to any of [1] to [7],

wherein component (C) is polyethylene and/or a propylene-based resin in which a content of ethylene units is 0% to 50% by mass.

[9] A crosslinked elastomer composition prepared by subjecting the modified elastomer composition according to any of [1] to [8] to a crosslinking reaction using component (H): a silanol condensation catalyst.

[10] A molded article prepared by molding the modified elastomer composition according to any of [1] to [8] or the crosslinked elastomer composition according to claim9.

An object of the second invention is to provide a low-gloss modified elastomer composition and a low-gloss crosslinked elastomer composition that exhibit compression set characteristics comparable to those of thermosetting rubbers in the related art and having durability, blocking resistance, and moldability comparable to those of thermoplastic elastomer compositions in the related art and to provide a molded article of the modified elastomer composition or the crosslinked elastomer composition.

The inventors have found that a modified elastomer composition obtained by graft modification of a composition containing an ethylene-α-olefin-non-conjugated diene copolymer rubber, an ethylene-α-olefin copolymer rubber containing no non-conjugated diene units, and an unsaturated silane compound or a crosslinked elastomer composition obtained by subjecting the above modified elastomer composition to a crosslinking reaction can have compression set characteristics comparable to those of thermosetting rubbers and blocking resistance and moldability comparable to those of thermoplastic elastomers. These compression set characteristics, blocking resistance, and moldability have been thought to be impossible to achieve simultaneously. Thus, the second invention has been completed.

The second invention is summarized in the following [11] to [19].

[11] A modified elastomer composition comprising following components (A), (B′), and (D) and grafted with following component (E):

component (A): an ethylene-α-olefin-non-conjugated diene copolymer rubber;

component (B′): an ethylene-α-olefin copolymer rubber whose melting end peak temperature measured using a differential scanning calorimeter (DSC) is 90° C. or higher and which contains no non-conjugated diene units;

component (D): an unsaturated silane compound; and

component (E): a peroxide.

[12] The modified elastomer composition according to [11], wherein a content of component (A) is 5 to 80 parts by mass based on 100 parts by mass of a total of component (A) and component (B′), wherein a content of component (B′) is 95 to 20 parts by mass based on 100 parts by mass of the total of component (A) and component (B′), and wherein a content of component (D) is 0.01 to 5 parts by mass based on 100 parts by mass of the total of component (A) and component (B′).
[13] The modified elastomer composition according to [11] or [12],

wherein an amount of component (E) used is 0.01 to 3 parts by mass based on 100 parts by mass of a total of component (A) and component (B′).

[14] The modified elastomer composition according to any of [11] to [13],

wherein a density of component (B′) is 0.880 g/cm3or less.

[15] The modified elastomer composition according to any of [11] to [14], further comprising component (F): a crosslinking aid in an amount of 0.001 to 2 parts by mass based on 100 parts by mass of a total of component (A) and component (B′).

[16] The modified elastomer composition according to any of [11] to [15],

wherein component (D) is a compound represented by following formula (1):
RSi(R′)3(1)
where R is an ethylenically unsaturated hydrocarbon group;
R's are each independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms; and at least one of R's is an alkoxy group having 1 to 10 carbon atoms.
[17] The modified elastomer composition according to any of claims [11] to [16], further comprising component (G): a softener in an amount of 0.5 to 200 parts by mass based on 100 parts by mass of a total of component (A) and component (B′).
[18] A crosslinked elastomer composition prepared by subjecting the modified elastomer composition according to any of [11] to [17] to a crosslinking reaction using component (H): a silanol condensation catalyst.
[19] A molded article prepared by molding the modified elastomer composition according to any of [11] to [17] or the crosslinked elastomer composition according to [18].

Advantageous Effects of Invention

The first invention can provide a modified elastomer composition and a crosslinked elastomer composition that are excellent in compression set characteristics and have good durability, good extrusion moldability, and good extrusion-molded appearance and can also provide a molded article using the modified elastomer composition or the crosslinked elastomer composition.

The second invention can provide a low-gloss modified elastomer composition and a low-gloss crosslinked elastomer composition that are excellent in compression set characteristics and have good durability, good blocking resistance, and good moldability and can also provide a molded article using the modified elastomer composition or the crosslinked elastomer composition.

When the modified elastomer composition and crosslinked elastomer composition of the present invention and the molded article using the same are used for applications that use thermosetting rubbers in the related art and require good rubber elasticity, particularly for automobile components such as glass run channels and weather strips, it is expected to obtain products with better quality than products in the related art.

