Thermoplastic elastomer composition and method for producing the same

Abstract

To provide a thermoplastic elastomer composition having a sea-island structure with a PA composing a continuous phase and an ACM crosslinked product and / or an XNBR crosslinked product composing a dispersion phase even with a smaller content of the polyamide (PA) than a content of a carboxy-modified acrylic rubber (ACM) or a carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), the thermoplastic elastomer composition excellent in moldability, flexibility and tensile break elongation as well as excellent in refrigeration oil resistance, without adding a large amount of plasticizer.SOLUTION: A thermoplastic elastomer composition includes: a component A, a cross-linked elastomer selected from a group composed of a carboxy-modified acrylic rubber crosslinked product and a carboxy-modified acrylonitrile-butadiene copolymer rubber crosslinked product; a component B, a polyamide; and a component C, an acrylonitrile-butadiene copolymer rubber un-crosslinked product. In the thermoplastic elastomer composition, a content of the component A is 60 to 85 vol.%, a content of the component B is 14 to 39 vol.%, and a content of the component C is 1 to 25 vol.%, in a total 100 vol.% of the components A to C. The thermoplastic elastomer composition has a sea-island structure having a continuous phase composed of the component B and a dispersion phase composed of the component A, with the component C finely dispersed in the continuous phase composed of the component B.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermoplastic elastomer composition and a method for producing the same, and more particularly, to a dynamically crosslinked thermoplastic elastomer composition and a method for producing the same.

Background Art

[0002] A thermoplastic elastomer composition containing a polyamide and a diene copolymer rubber is known as a polymer material having excellent tensile properties. For example, Japanese Patent Application Laid-Open No. 52-105952 (Patent Document 1) discloses an elastoplastic composition containing 50% by mass or less of a polyamide and 80% by mass or less of a nitrile rubber (for example, acrylonitrile-butadiene copolymer rubber (NBR)). However, in this elastoplastic composition, there is a problem that sufficient tensile properties are not necessarily obtained even when a crosslinking agent is added during the mixing of the polyamide and NBR to cause dynamic crosslinking.

[0003] Therefore, Japanese Patent Application Laid-Open No. 2001-49037 (Patent Document 2) proposes a method in which first, a crosslinking agent is blended with NBR, and then a polyamide is mixed with the obtained NBR composition. By this method, a thermoplastic elastomer composition in which a polyamide serves as a matrix and the NBR composition is dispersed therein can be obtained, and it is also described that a decrease in tensile properties can be suppressed. However, even in the thermoplastic elastomer composition described in Patent Document 2, there is a problem that sufficient moldability and flexibility cannot be obtained.

[0004] Also, a thermoplastic elastomer composition containing a polyamide and an acrylic rubber is known. For example, Japanese Patent Application Laid-Open No. 2016-121227 (Patent Document 3) discloses a thermoplastic elastomer composition containing 100 parts by mass of a carboxyl group-containing acrylic rubber, 15 to 100 parts by mass of a polyamide-based polymer, and 0.01 to 25 parts by mass of an epoxy group-containing polymer as a material having excellent flexibility. However, in the thermoplastic elastomer composition described in Patent Document 3, in order to actually reduce the hardness, it is necessary to use a large amount of an ester-based plasticizer in combination, and there is a problem that bleeding and elution of the plasticizer are likely to occur.

[0005] Furthermore, in International Publication No. 2005-042624 (Patent Document 4), a polyamide resin or a polyester resin having a melting point of 160 to 300°C and a flexural modulus at a temperature of 23°C of 10,000 kgf / cm 2 The following 20 to 95% by weight of a polyamide resin or a polyester resin and at least one rubber selected from the group consisting of an acrylic rubber, a nitrile rubber, a hydrogenated nitrile rubber, and an epihalohydrin rubber of 5 to 80% by weight are dynamically crosslinked while kneading to form a thermoplastic elastomer composition, which is disclosed as a material having excellent heat resistance, compression set, and fatigue resistance. However, in the thermoplastic elastomer composition described in Patent Document 4, in order to actually obtain a polyamide resin (especially PA6) having a flexural modulus of 10,000 kgf / cm 2 The following, it is necessary to use a large amount of a plasticizer such as a phthalic acid ester compound in combination, and there are problems such as a decrease in heat resistance and an increase in bleeding and elution of the plasticizer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present invention has been made in view of the problems of the above prior art, and even when the content of polyamide (PA) is less than the content of carboxy-modified acrylic rubber (ACM) or carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), PA forms a continuous phase, and an ACM crosslinked product and / or an XNBR crosslinked product form a dispersed phase, and a sea-island structure is formed. An object of the present invention is to provide a thermoplastic elastomer composition that is excellent in moldability, flexibility, tensile elongation at break, and oil resistance for refrigerators without adding a large amount of plasticizer, and a method for producing the same.

MEANS FOR SOLVING THE PROBLEMS

[0008] As a result of intensive studies to achieve the above object, the present inventors first melt-knead ACM or XNBR together with PA and dynamically crosslink them, and then add a soft thermoplastic elastomer and melt-knead them. By making the melt-kneading process into two steps (the primary melt-kneading process is the dynamic crosslinking process of ACM or XNBR, and the secondary melt-kneading process is the fine dispersion process of the soft thermoplastic elastomer), a sea-island structure in which PA is a continuous phase and ACM crosslinked products or XNBR crosslinked products are dispersed phases is obtained, and furthermore, a thermoplastic elastomer composition in which the soft thermoplastic elastomer is finely dispersed in the continuous phase composed of PA is obtained. It has been found that such a thermoplastic elastomer composition is excellent in moldability, flexibility, and tensile elongation at break.

[0009] However, the present inventors have found that a thermoplastic elastomer composition containing a polyolefin-polyamide graft copolymer as the soft thermoplastic elastomer has a problem that the refrigeration oil becomes turbid in the refrigeration oil resistance test.

[0010] Therefore, as a result of further intensive research by the present inventors, it has been found that the uncrosslinked acrylonitrile-butadiene copolymer rubber (NBR) is insoluble in refrigeration oil, has excellent refrigeration oil resistance, and is nano-dispersed in PA. Furthermore, by utilizing such properties of NBR, after melt-kneading ACM or XNBR with PA and dynamically crosslinking them, NBR is added and melt-kneaded. By performing the melt-kneading process in two steps (the primary melt-kneading process is the dynamic crosslinking process of ACM or XNBR, and the secondary melt-kneading process is the fine dispersion process of NBR), a sea-island structure in which PA is the continuous phase and the ACM crosslinked product or XNBR crosslinked product is the dispersed phase is obtained. Furthermore, a thermoplastic elastomer composition in which uncrosslinked NBR is finely dispersed in the continuous phase composed of PA is obtained. It has been found that such a thermoplastic elastomer composition is excellent in moldability, flexibility, and tensile elongation at break, and also excellent in refrigeration oil resistance.

[0011] That is, the thermoplastic elastomer composition of the present invention is A. A crosslinked elastomer selected from the group consisting of a carboxy-modified acrylic rubber crosslinked product and a carboxy-modified acrylonitrile-butadiene copolymer rubber crosslinked product, B. A polyamide, C. An uncrosslinked acrylonitrile-butadiene copolymer rubber, and is a thermoplastic elastomer composition containing the same. With respect to a total of 100% by volume of components A to C, the content of component A is 60 to 85% by volume, the content of component B is 14 to 39% by volume, and the content of component C is 1 to 25% by volume. A sea-island structure comprising a continuous phase composed of component B and a dispersed phase composed of component A is formed, and component C is forming a finely dispersed phase having an average diameter of 10 to 2000 nm finely dispersed in the continuous phase composed of component B.

[0012] Moreover, the manufacturing method of the thermoplastic elastomer composition of the present invention is A'. An uncrosslinked elastomer selected from the group consisting of an uncrosslinked carboxy-modified acrylic rubber and an uncrosslinked carboxy-modified acrylonitrile-butadiene copolymer rubber, and D. a crosslinking agent, and B. a polyamide are melt-kneaded to dynamically crosslink component A' to obtain a crosslinked kneaded product in a primary melt-kneading step, To the crosslinked kneaded product obtained in the primary kneading step, C. an uncrosslinked acrylonitrile-butadiene copolymer rubber is added and melt-kneaded to obtain a thermoplastic elastomer composition according to any one of claims 1 to 4 in a secondary melt-kneading step, which is characterized by including the above.

[0013] In the thermoplastic elastomer composition and its production method of the present invention, it is preferable that the uncrosslinked acrylonitrile-butadiene copolymer rubber is at least one selected from the group consisting of an uncrosslinked carboxy-modified acrylonitrile-butadiene copolymer rubber and an uncrosslinked hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber.

[0014] Also, in the thermoplastic elastomer composition and its production method of the present invention, it is preferable that the polyamide is polyamide 6.

[0016] Also, in the production method of the thermoplastic elastomer composition of the present invention, it is preferable that the crosslinking agent is a polyvalent amine-based crosslinking agent.

[0017] In addition, by the method for producing the thermoplastic elastomer composition of the present invention, a sea-island structure in which PA is the continuous phase and the ACM crosslinked product or XNBR crosslinked product is the dispersed phase is obtained. Further, uncrosslinked NBR is finely dispersed in the continuous phase composed of PA. Although the reason why a thermoplastic elastomer composition excellent in moldability, flexibility, elongation at break, and excellent in oil resistance for refrigerators is obtained is not necessarily clear, the present inventors speculate as follows. That is, first, when a soft thermoplastic elastomer is added after melt-kneading and dynamically crosslinking ACM or XNBR together with PA as described above, since the soft thermoplastic elastomer is preferentially melt-kneaded with PA, the soft thermoplastic elastomer is finely dispersed in the continuous phase composed of PA and PA is alloyed. Further, a sea-island structure in which PA is the continuous phase and the ACM crosslinked product or XNBR crosslinked product is the dispersed phase is maintained. Since the continuous phase PA serving as the constraint phase is preferentially softened compared to the ACM crosslinked product or XNBR crosslinked product forming the dispersed phase, the present inventors speculate that the resulting thermoplastic elastomer composition is excellent in moldability, flexibility, and elongation at break. However, when, for example, a polyolefin-polyamide graft copolymer is used as the soft thermoplastic elastomer, since an oligomer of polyolefin not grafted with polyamide is present in the polyolefin-polyamide graft copolymer, the present inventors speculate that this oligomer is dissolved and extracted in high-temperature refrigerator oil, and the extracted components precipitate at room temperature, resulting in turbidity in the refrigerator oil.

[0018] In contrast, in the present invention, ACM or XNBR is melt-kneaded with PA to dynamically crosslink, and then NBR is added, so that the reaction of ACM or XNBR with the crosslinking agent is suppressed, and NBR is preferentially melt-kneaded with PA, so that the soft NBR uncrosslinked material is finely dispersed in the continuous phase made of PA, and PA is made into an alloy resin. Furthermore, a sea-island structure in which PA is the continuous phase and the ACM crosslinked material or XNBR crosslinked material is the dispersed phase is maintained, and the PA in the continuous phase, which becomes the constrained phase, is preferentially softened over the ACM crosslinked material or XNBR crosslinked material that forms the dispersed phase, so that the obtained thermoplastic elastomer composition has excellent moldability, flexibility, and tensile elongation at break, and further, the inventors presume that since the NBR uncrosslinked material does not dissolve in refrigerating machine oil even at high temperatures, the refrigerating machine oil does not become cloudy, and the refrigerating machine oil has excellent resistance to refrigerating machine oil. Effect of the Invention

[0019] According to the present invention, even if the content of polyamide (PA) is smaller than the content of carboxy-modified acrylic rubber (ACM) or carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), a sea-island structure is formed in which PA forms a continuous phase and an ACM cross-linked product and / or an XNBR cross-linked product form a dispersed phase, and it is possible to provide a thermoplastic elastomer composition and a production method thereof that are excellent in moldability, flexibility, and tensile elongation at break as well as in resistance to refrigeration oil without adding a large amount of plasticizer. [Brief description of the drawings]

[0020]

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Embodiments for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described in detail according to its preferred embodiments.

[0022] First, the carboxy-modified acrylic rubber (ACM), carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), polyamide (PA), acrylonitrile-butadiene copolymer rubber (NBR), and crosslinking agent used in the present invention will be described.

[0023] (Carboxy-modified acrylic rubber) The carboxy-modified acrylic rubber (ACM) used in the present invention is not particularly limited, but those obtained by polymerization of (meth)acrylic acid esters and unsaturated carboxylic acid-based monomers are preferred.

[0024] (Meth)acrylic acid esters are methacrylic acid esters and / or acrylic acid esters, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and methoxyethyl (meth)acrylate. Such (meth)acrylic acid esters may be used alone or in combination of two or more. Furthermore, acrylic rubber also includes ethylene acrylate rubber (AEM). In addition, examples of unsaturated carboxylic acid-based monomers include unsaturated carboxylic acids and their salts, unsaturated carboxylic acid anhydrides, etc. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, oleic acid, linoleic acid, linolenic acid, crotonic acid, 2-pentenoic acid, maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, aconitic acid, crotonic acid, etc. Examples of unsaturated carboxylic acid anhydrides include maleic anhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride, succinic anhydride, etc.

[0025] The Mooney viscosity ML1+4(100°C) of ACM is not particularly limited, but 15 to 100 is preferred, and 25 to 65 is more preferred. When the Mooney viscosity ML1+4(100°C) of ACM is less than the lower limit, the mechanical properties (especially tensile properties) tend to decrease. On the other hand, when it exceeds the upper limit, the processability tends to decrease during mixing with polyamide.

[0026] Although there is no particular limitation on the carboxyl group content of ACM, the acid value is preferably 1 to 80 mg / g, more preferably 2 to 40 mg / g, and still more preferably 3 to 30 mg / g. When the acid value of ACM is less than the above lower limit, the reactivity with the crosslinking agent tends to decrease. On the other hand, when it exceeds the above upper limit, gelation tends to occur due to self-condensation or reaction with polyamide.

[0027] (Carboxy-modified acrylonitrile-butadiene copolymer rubber) Although there is no particular limitation on the carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR) used in the present invention, XNBR having an acrylonitrile unit content of 20 to 60% by mass (butadiene unit of 80 to 40% by mass) is preferred, and XNBR having an acrylonitrile unit content of 30 to 50% by mass (butadiene unit of 70 to 50% by mass) is more preferred. When the acrylonitrile unit content is less than the above lower limit, the oil resistance and chemical resistance of the thermoplastic elastomer composition tend to decrease. On the other hand, when it exceeds the above upper limit, the cold resistance tends to decrease.

[0028] Further, as the XNBR used in the present invention, hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber (H-XNBR) is preferred. By using H-XNBR, the heat resistance, oil resistance, ozone resistance, mechanical strength, and abrasion resistance of the thermoplastic elastomer composition can be improved, and the gas permeability can be reduced.

[0029] Although there is no particular limitation on the unsaturated group content of H-XNBR, the hydrogenation rate is preferably 80% or more, more preferably 85% or more, still more preferably 95% or more, particularly preferably 99% or more, and the iodine value is preferably 50 mg / 100 mg or less, more preferably 40 mg / 100 mg or less, still more preferably 20 mg / 100 mg or less. H-XNBR with a hydrogenation rate less than the above lower limit or an iodine value exceeding the above upper limit has low heat resistance and may be colored or the material may deteriorate due to heating during kneading or molding when using a polyamide with a high melting temperature. There is no particular limitation on the upper limit of the hydrogenation rate or the lower limit of the iodine value of H-XNBR.

[0030] The Mooney viscosity ML1+4(100 °C) of XNBR is not particularly limited, but is preferably 20 to 100, more preferably 35 to 80. When the Mooney viscosity ML1+4(100 °C) of XNBR is less than the above lower limit, the mechanical properties (especially tensile properties) tend to deteriorate. On the other hand, when it exceeds the above upper limit, the processability tends to deteriorate during mixing with polyamide.

[0031] The carboxyl group content of XNBR is not particularly limited, but the acid value is preferably 1 to 80 mg / g, more preferably 10 to 40 mg / g, still more preferably 15 to 35 mg / g, and particularly preferably 20 to 30 mg / g. When the acid value of XNBR is less than the above lower limit, the reactivity with the crosslinking agent tends to decrease. On the other hand, when it exceeds the above upper limit, gelation tends to occur due to self-condensation or reaction with polyamide.

[0032] (Polyamide) The polyamide (PA) used in the present invention is not particularly limited, and examples thereof include polyamide 11, polyamide 12, polyamide 610, polyamide 1010, polyamide 6, polyamide 1012, polyamide 66, polyamide 46, polyamide MXD6, polyamide 6T, polyamide 9T, polyamide 10T, and copolymers thereof. Such polyamides may be used alone or in combination of two or more. Among these polyamides, from the viewpoints of suppressing the deterioration of ACM, XNBR, and NBR at the processing temperature during production and suppressing the decomposition of the crosslinking agent, polyamide 11, polyamide 12, polyamide 610, polyamide 1010, and polyamide 6 are preferable, and polyamide 6 is more preferable from the viewpoint of ensuring the heat resistance of the thermoplastic elastomer composition during high-temperature use.

[0033] Also, the melting temperature of the polyamide is not particularly limited, but is preferably 150 to 300°C, more preferably 180 to 280°C, and still more preferably 200 to 260°C. When the melting temperature of the polyamide is less than the lower limit, the heat resistance of the resulting thermoplastic elastomer composition tends to decrease. On the other hand, when it exceeds the upper limit, the heat resistance of the crosslinking agent is insufficient, and the target phase structure (that is, a phase structure in which a continuous phase is formed by the polyamide and a dispersed phase is formed by ACM or XNBR) cannot be obtained, or the mechanical properties tend to decrease due to the deterioration of ACM, XNBR, or NBR.

[0034] The melt viscosity (MFR) of the polyamide is not particularly limited, and generally, polyamides classified as injection grades can be used, but it is preferable to use high-flow polyamides. When the MFR of PA is low, it tends to cause abnormal heat generation during dynamic crosslinking or impair the fluidity of the thermoplastic elastomer composition. For example, in the case of PA6, the MFR at 235°C and 2.16 kg is preferably 1 g / 10 min or more, and more preferably 5 g / 10 min or more.

[0035] (acrylonitrile-butadiene copolymer rubber) The acrylonitrile-butadiene copolymer rubber (NBR) used in the present invention is not particularly limited, but NBR having an acrylonitrile unit content of 20 to 60% by mass (butadiene unit 80 to 40% by mass) is preferable, and NBR having an acrylonitrile unit content of 30 to 50% by mass (butadiene unit 70 to 50% by mass) is more preferable. When the acrylonitrile unit content is less than the lower limit, the oil resistance and chemical resistance of the thermoplastic elastomer composition tend to decrease. On the other hand, when it exceeds the upper limit, the cold resistance tends to decrease.

[0036] In addition, examples of the NBR used in the present invention include unmodified acrylonitrile-butadiene copolymer rubber (NBR), carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), and hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber (H-XNBR). Such acrylonitrile-butadiene copolymer rubbers may be used alone or in combination of two or more. Among such acrylonitrile-butadiene copolymer rubbers, those having reactive and compatible functional groups are preferred from the viewpoint of improving compatibility with PA, and XNBR having a carboxyl group and / or maleic anhydride group and its hydride (H-XNBR) are more preferred. From the viewpoint of improving the heat resistance, oil resistance, ozone resistance, mechanical strength, and abrasion resistance of the thermoplastic elastomer composition and reducing gas permeability, H-XNBR is particularly preferred.

[0037] The Mooney viscosity ML1+4(100°C) of NBR is not particularly limited, but is preferably 20 to 100, more preferably 35 to 80. When the Mooney viscosity ML1+4(100°C) of NBR is less than the above lower limit, the mechanical properties (particularly, tensile properties) tend to decrease. On the other hand, when it exceeds the above upper limit, the processability tends to decrease during mixing with polyamide.

[0038] The carboxyl group content of XNBR is not particularly limited, but the acid value is preferably 1 to 80 mg / g, more preferably 10 to 40 mg / g, still more preferably 15 to 35 mg / g, and particularly preferably 20 to 30 mg / g. When the acid value of XNBR is less than the above lower limit, the compatibility with polyamide tends to decrease. On the other hand, when it exceeds the above upper limit, gelation tends to occur due to self-condensation or reaction with polyamide.

[0039] The unsaturated group content of H-XNBR is not particularly limited, but the hydrogenation rate is preferably 80% or more, more preferably 85% or more, still more preferably 95% or more, and particularly preferably 99% or more. The iodine value is preferably 50 mg / 100 mg or less, more preferably 40 mg / 100 mg or less, and still more preferably 20 mg / 100 mg or less. When the hydrogenation rate of H-XNBR is less than the above lower limit or the iodine value exceeds the above upper limit, the heat resistance of H-XNBR is low, and when a polyamide with a high melting temperature is used, it may be colored or material deterioration may occur due to heating during kneading or molding. In addition, there is no particular limitation on the upper limit of the hydrogenation rate or the lower limit of the iodine value of H-XNBR.

[0040] (Crosslinking agent) The crosslinking agent used in the present invention is not particularly limited as long as it has heat resistance at the temperature during dynamic crosslinking by melt kneading of ACM and / or XNBR and PA, and can crosslink ACM and / or XNBR. However, from the viewpoints of suppressing the reaction with PA and the reactivity with the carboxyl group of ACM or XNBR, a polyvalent amine-based crosslinking agent is preferred.

[0041] Examples of the polyvalent amine-based crosslinking agent include carbamate-based compounds such as hexamethylenediamine carbamate and 4,4'-methylenebiscyclohexylamine carbamate; amine-based compounds such as 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl sulfone, diethyltoluenediamine, diethylenetriamine, polymethylenediamine, polyetherdiamine, polyethyleneimine, and dicyandiamide; dihydrazide-based compounds such as adipic acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide; and the like. Such crosslinking agents may be used alone or in combination of two or more. Among these polyvalent amine-based crosslinking agents, from the viewpoints of the storage stability of the pre-kneaded product and the reactivity during dynamic crosslinking, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, hexamethylenediamine carbamate, and 4,4'-methylenebiscyclohexylamine carbamate are more preferred.

[0042] The addition amount of the crosslinking agent is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.3 to 3 parts by mass, based on 100 parts by mass of ACM or XNBR. If the addition amount of the crosslinking agent is less than the above lower limit, the crosslinking of ACM or XNBR does not proceed sufficiently, and it tends to be difficult to obtain the phase structure of the present invention in which PA becomes the continuous phase. On the other hand, if the addition amount of the crosslinking agent exceeds the above upper limit, the crosslinking of ACM or XNBR becomes fast, making it easy to form coarse particles, and the excess crosslinking agent tends to react with the uncrosslinked materials of PA and NBR, easily reducing the moldability.

[0043] [Manufacturing method of thermoplastic elastomer composition] Next, the manufacturing method of the thermoplastic elastomer composition of the present invention will be described. The manufacturing method of the thermoplastic elastomer composition of the present invention is A'. A premix containing an uncrosslinked elastomer selected from the group consisting of an uncrosslinked carboxy-modified acrylic rubber (ACM) and an uncrosslinked carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), and D. a crosslinking agent, and B. polyamide (PA) are melt-kneaded to obtain a crosslinked kneaded product by dynamically crosslinking component A', a primary melt-kneading step To the crosslinked kneaded product obtained in the primary kneading step, C. an uncrosslinked acrylonitrile-butadiene copolymer rubber (NBR) is added and melt-kneaded to obtain the thermoplastic elastomer composition according to any one of claims 1 to 4, a secondary melt-kneading step is a method including. In addition, within a range not impairing the effects of the present invention, a part of the uncrosslinked NBR can be blended in the primary melt-kneading step, and a part of PA or a part of the uncrosslinked ACM and / or XNBR can be blended in the secondary melt-kneading step.

[0044] Such a manufacturing method can be carried out using a melt-kneading machine. Such a melt-kneading machine is not particularly limited, and examples thereof include batch-type melt-kneading machines such as Brabender, Laboplastomill, pressure kneader, mixing roll, Banbury mixer, and open roll; continuous-type melt-kneading machines such as single-screw extruder and twin-screw extruder.

[0045] (Primary melting and kneading process: Dynamic cross-linking process) First, a pre-kneaded material (ACM uncrosslinked material and / or XNBR uncrosslinked material containing a cross-linking agent) containing component A' (ACM uncrosslinked material and / or XNBR uncrosslinked material) and component D (cross-linking agent) is obtained. At this time, an amount of cross-linking agent necessary for cross-linking the uncrosslinked elastomer is added to the ACM uncrosslinked material and / or XNBR uncrosslinked material (uncrosslinked elastomer), and the pre-kneaded material is obtained by kneading at a temperature equal to or lower than the reaction start temperature of the cross-linking agent used. By thus preparing the uncrosslinked elastomer containing the cross-linking agent in advance, when PA is added in the subsequent stage and dynamically cross-linked, although the content of PA is smaller than the content of the ACM uncrosslinked material or XNBR uncrosslinked material, PA forms a continuous phase and the ACM crosslinked material and / or XNBR crosslinked material form a dispersed phase.

[0046] Next, the pre-kneaded material and component B (PA) are melt-kneaded to dynamically cross-link the uncrosslinked elastomer, thereby obtaining a cross-linked kneaded material in which PA forms a continuous phase and the ACM crosslinked material and / or XNBR crosslinked material form a dispersed phase.

[0047] In the dynamic cross-linking process, the melt-kneading temperature when dynamically cross-linking the uncrosslinked elastomer is set as appropriate according to the PA and uncrosslinked elastomer used. For example, it is preferably set 0 to 80°C higher than the melting point of PA, and the kneading time during dynamic cross-linking is preferably 0.2 to 30 minutes.

[0048] (Secondary melting and kneading process: Microdispersion process) Next, by adding component C (unvulcanized NBR) to the crosslinked kneaded product obtained in the primary kneading step and melt-kneading, a thermoplastic elastomer composition in which unvulcanized NBR is finely dispersed in a continuous phase made of PA is obtained. In the production method of the present invention, after melt-kneading and dynamically crosslinking the unvulcanized ACM or unvulcanized XNBR together with PA in this way, the melt-kneading step is divided into two steps, that is, adding unvulcanized NBR and melt-kneading, so that a sea-island structure in which PA is the continuous phase and the crosslinked ACM or crosslinked XNBR is the dispersed phase can be surely obtained, and furthermore, a thermoplastic elastomer composition in which unvulcanized NBR is sufficiently finely dispersed in the continuous phase made of PA can be obtained.

[0049] In the fine dispersion step, the temperature at which the unvulcanized NBR is melt-kneaded with the crosslinked kneaded product is appropriately set according to the unvulcanized NBR and PA used, but it is preferably set 0 to 80°C higher than the melting temperature or softening temperature of the unvulcanized NBR, and the kneading time is preferably 0.2 to 30 minutes. However, when the melting temperature of PA exceeds the melting temperature or softening temperature of the unvulcanized NBR, it is preferably set 0 to 80°C higher than the melting temperature (melting point) of PA.

[0050] The compounding ratios of component A' (unvulcanized ACM and / or unvulcanized XNBR), component B (PA), and component C (unvulcanized NBR) in the primary melt-kneading step and the secondary melt-kneading step are appropriately set so that the contents of component A (crosslinked ACM and / or crosslinked XNBR), component B (PA), and component C (unvulcanized NBR) in the resulting thermoplastic elastomer composition are predetermined contents within the ranges described below, respectively. Therefore, the compounding ratio of component A' (unvulcanized ACM and / or unvulcanized XNBR) is 60 to 85% by volume (more preferably 65 to 75% by volume), the compounding ratio of component B (PA) is 14 to 39% by volume (more preferably 22 to 35% by volume), and the compounding ratio of component C (unvulcanized NBR) is 1 to 25% by volume (more preferably 3 to 15%) (assuming the total amount of components A' to C is 100% by volume).

[0051] As a method for producing such a thermoplastic elastomer composition of the present invention, specifically, a method using the following batch-type melt kneader and a method using a continuous-type melt kneader are preferably adopted.

[0052] (Method using a batch-type melt kneader) (1) Preparation of an uncrosslinked ACM and / or uncrosslinked XNBR (pre-kneaded product) containing a crosslinking agent The pre-kneaded product can be obtained by kneading the uncrosslinked ACM and / or uncrosslinked XNBR with the crosslinking agent at a temperature equal to or lower than the reaction initiation temperature of the crosslinking agent used. In a batch-type melt kneader, it is preferable to perform kneading at a set temperature of 100°C or lower within 30 minutes.

[0053] (2) Dynamic crosslinking In a batch-type melt kneader, while melt-kneading PA and the pre-kneaded product in a chamber set 0 to 80°C higher than the melting temperature of PA, the uncrosslinked ACM and / or uncrosslinked XNBR are dynamically crosslinked to obtain a crosslinked kneaded product in which the crosslinked ACM and / or crosslinked XNBR are the dispersed phase and PA is the continuous phase. Then, an uncrosslinked NBR is added to the obtained crosslinked kneaded product and melt-kneaded to obtain the thermoplastic elastomer composition of the present invention in which the uncrosslinked NBR is finely dispersed in the continuous phase of PA.

[0054] (Method using a continuous-type melt kneader) In a continuous-type melt kneader, the pre-kneaded product prepared by a batch-type melt kneader is supplied to the upstream part, dynamic crosslinking is performed by melt-kneading with PA in the middle part, and the thermoplastic elastomer composition of the present invention can be obtained by supplying and melt-kneading the uncrosslinked NBR in the downstream part.

[0055] Also, after obtaining a pre-kneaded product by kneading the uncrosslinked ACM and / or uncrosslinked XNBR with the crosslinking agent in the upstream part of the continuous-type melt kneader, dynamic crosslinking is performed by supplying PA in the middle part, and the thermoplastic elastomer composition of the present invention can also be prepared by supplying and melt-kneading the uncrosslinked NBR in the downstream part.

[0056] The temperature of the upstream part is set to be equal to or lower than the reaction start temperature of the crosslinking agent. The temperature of the middle part is preferably set 0 to 80°C higher than the melting temperature of PA, and the temperature of the downstream part is preferably set 0 to 80°C higher than the melting temperature or softening temperature of the uncrosslinked NBR. However, when the melting temperature of PA is higher than the melting temperature or softening temperature of the uncrosslinked NBR, the set temperature of PA described above is followed. Further, the PA supplied in the middle part is preferably supplied in a molten state by a single-screw extruder or the like. Thereby, the dispersion of the uncrosslinked ACM and / or uncrosslinked XNBR and PA is promoted, and the moldability and mechanical properties of the resulting thermoplastic elastomer composition tend to be further improved.

[0057] (Other methods) A method for producing a thermoplastic elastomer composition containing no uncrosslinked NBR using the above batch-type melt kneader or continuous melt kneader, and melt kneading the thermoplastic elastomer composition and the uncrosslinked NBR in another kneader to obtain the thermoplastic elastomer composition of the present invention, or a method for obtaining the thermoplastic elastomer composition of the present invention by melt blending a thermoplastic elastomer composition containing no uncrosslinked NBR and the uncrosslinked NBR during product molding using an injection molding machine, an extrusion molding machine, or the like may also be used.

[0058] [Thermoplastic elastomer composition] Next, the thermoplastic elastomer composition of the present invention will be described. The thermoplastic elastomer composition of the present invention comprises A. A crosslinked elastomer selected from the group consisting of a carboxy-modified acrylic rubber (ACM) crosslinked product and a carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR) crosslinked product, B. Polyamide (PA), C. An uncrosslinked acrylonitrile-butadiene copolymer rubber (NBR), A thermoplastic elastomer composition containing the following components A, B, and C, wherein, based on 100% by volume of the total of components A to C, the content of component A is 60 to 85% by volume, the content of component B is 14 to 39% by volume, and the content of component C is 1 to 25% by volume, a sea-island structure is formed comprising a continuous phase composed of component B and a dispersed phase composed of component A, and component C is finely dispersed in the continuous phase composed of component B. By forming such a sea-island structure and further finely dispersing the uncrosslinked NBR in the continuous phase composed of PA, even when the content of PA is less than that of ACM or XNBR, the thermoplastic elastomer composition of the present invention is excellent in moldability, flexibility, and elongation at break, and is also excellent in oil resistance for refrigerators. Such a thermoplastic elastomer composition of the present invention can be obtained by the method for producing the thermoplastic elastomer composition of the present invention described above.

[0059] In the thermoplastic elastomer composition of the present invention, the content of component B (PA) is 14 to 39% by volume (more preferably 22 to 35% by volume), the content of component A (crosslinked elastomer: crosslinked ACM and / or crosslinked XNBR) is 60 to 85% by volume (more preferably 65 to 75% by volume), and the content of component C (uncrosslinked NBR) is 1 to 25% by volume (more preferably 3 to 15%) (assuming the total amount of components A to C is 100% by volume). When the content of PA is less than the lower limit, it becomes difficult for PA to form a continuous phase. On the other hand, when it exceeds the upper limit, the properties as a resin become higher than those as an elastomer, resulting in a decrease in elongation at break and an increase in tensile modulus. Also, when the content of the crosslinked elastomer (crosslinked ACM and / or crosslinked XNBR) is less than the lower limit, the properties as a resin become higher than those as an elastomer, resulting in a decrease in elongation at break and an increase in tensile modulus. On the other hand, when it exceeds the upper limit, it becomes difficult for PA to form a continuous phase. Furthermore, when the content of the uncrosslinked NBR is less than the lower limit, the effect of improving moldability and flexibility cannot be obtained. On the other hand, when it exceeds the upper limit, it becomes difficult to be finely dispersed in PA, and the uncrosslinked NBR tends to become a continuous phase and the heat resistance decreases.

[0060] Further, in the thermoplastic elastomer composition of the present invention, the volume ratio of component B (PA) to component C (uncured NBR) (component B: component C) is preferably in the range of 50:50 to 97:3, and more preferably in the range of 70:30 to 90:10. When the ratio of component C (uncured NBR) to component B (PA) is less than the lower limit, the effects of improving moldability, flexibility, and tensile elongation at break by adding the uncured NBR tend not to be sufficiently obtained. On the other hand, when it exceeds the upper limit, it becomes difficult to be finely dispersed in PA, and the uncured NBR tends to form a continuous phase and the heat resistance decreases.

[0061] In the thermoplastic elastomer composition of the present invention, as described above, a sea-island structure including a continuous phase composed of component B (PA) and a dispersed phase composed of component A (crosslinked elastomer: crosslinked ACM and / or crosslinked XNBR) is formed, and component C (uncured NBR) is finely dispersed in the continuous phase composed of component B (PA). However, a part of component B (preferably 7% by volume or less) may be a dispersed phase, a part of component A (preferably 20% by volume or less) may be a continuous phase, or a part of component A (preferably 20% by volume or less) and a part of component B (preferably 10% by volume or less) may form a co-continuous phase. Further, a part of component B (preferably 10% by volume or less) or a part of component C (preferably 5% by volume or less) may be contained in component A.

[0062] In such a sea-island structure, the dispersed phase is usually formed by individual particles composed of component A (crosslinked elastomer: ACM crosslinked product and / or XNBR crosslinked product) dispersed in a continuous phase composed of component B (PA). Therefore, the diameter of this dispersed phase corresponds to the particle size of the particles composed of the ACM crosslinked product or the XNBR crosslinked product. The average diameter of the dispersed phase is preferably from 100 nm to 100 μm, more preferably from 200 nm to 50 μm, and still more preferably from 500 nm to 20 μm. When the average diameter of the dispersed phase is less than the lower limit, the moldability of the thermoplastic elastomer composition tends to decrease. On the other hand, when it exceeds the upper limit, the surface appearance and tensile properties of the molded article obtained from the thermoplastic elastomer composition tend to decrease. The average diameter of the dispersed phase can be determined as follows. That is, a scanning electron microscope (SEM) photograph (5,000 times or 10,000 times) of the thermoplastic elastomer composition (or its molded article) is taken. In the obtained SEM image, the outer shape of the dispersed phase is traced and the surrounded area is filled. The diameter of this filled area is measured using image analysis software, and the average value is taken as the average diameter of the dispersed phase.

[0063] Also, the average diameter of the finely dispersed phase of component C (unvulcanized NBR) finely dispersed in the continuous phase composed of component B (PA) is preferably from 10 to 2000 nm, more preferably from 30 to 1000 nm, still more preferably from 50 to 800 nm, and particularly preferably from 100 to 500 nm. When the average diameter of the finely dispersed phase is less than the lower limit, PA and the unvulcanized NBR become uniform, so the heat resistance of the thermoplastic elastomer composition tends to decrease. On the other hand, when it exceeds the upper limit, it may not be finely dispersed in the continuous phase composed of component B, or the tensile properties tend to decrease. The average diameter of the finely dispersed phase can be determined as follows. That is, a transmission electron microscope (TEM) photograph (50,000 times) of the thermoplastic elastomer composition (or its molded article) is taken. In the obtained TEM image, the outer shape of the finely dispersed phase is traced and the surrounded area is filled. The diameter of this filled area is measured using image analysis software, and the average value is taken as the average diameter of the finely dispersed phase.

[0064] In addition, in the thermoplastic elastomer composition of the present invention, various additives such as antioxidants, mold release agents, plasticizers, flame retardants, colorants, lubricants, crosslinking accelerators, crosslinking aids, crosslinking retardants, reinforcing materials, anti-aging agents, softening agents, antistatic agents, etc. may be blended as long as the effects of the present invention are not impaired. Furthermore, rubber components other than ACM, XNBR, and the NBR used, and resin components other than PA may be blended.

Examples

[0065] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. The carboxy-modified acrylic rubber, polyamide, carboxy-modified acrylonitrile-butadiene copolymer rubber, soft thermoplastic elastomer, crosslinking agent, crosslinking aid, and antioxidant used in the Examples and Comparative Examples are shown below. (i) Carboxy-modified acrylic rubber (ACM) ACM (AR12): Carboxy-modified acrylic rubber (“Nipol AR12” manufactured by Nippon Zeon Co., Ltd., specific gravity: 1.1, Mooney viscosity ML1+4 (100 ° C): 33.0, acid value: 7.3 mg / g). (ii) Polyamide (PA) PA6 (CM1001): Polyamide 6 (“Amilan CM1001” manufactured by Toray Industries, Inc., density: 1.13 g / cm 3 ). PA6 (1022B): Polyamide 6 (“UBE Nylon 1022B” manufactured by Ube Industries, Ltd., density 1.14 g / cm 3 ). (iii) Acrylonitrile-butadiene copolymer rubber (NBR) H-XNBR (Zetpol2510): Hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber (“Zetpol 2510” manufactured by Nippon Zeon Co., Ltd., specific gravity: 0.98, Mooney viscosity ML1+4 (100 ° C): 45, AN content: 35.2%, iodine value: 12 mg / 100 mg or less, acid value: 23 mg / g). NBR (Nipol DN631): Acrylonitrile-butadiene copolymer rubber (Nipol DN631 manufactured by Zeon Corporation, specific gravity: 0.99, Mooney viscosity ML1+4 (100 °C): 50, AN content: 33.5%, iodine value: 270 mg / 100 mg, methacrylic acid content: 0.8 mass%). H-XNBR (Zetpol 3710): Hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber (Zetpol 3710 manufactured by Zeon Corporation, specific gravity: 0.98, Mooney viscosity ML1+4 (100 °C): 48, AN content: 23.6%, iodine value: 12 mg / 100 mg or less, acid value: 23 mg / g). (iv) Soft thermoplastic elastomer LP21H: PA6 / polyolefin graft copolymer (Apolya LP21H manufactured by Arkema, specific gravity: 0.99, tensile modulus: 100 MPa, MFR: 7.4 g / 10 min (235 °C, 2.16 kg)). (v) Crosslinking agent AC-9: 4,4-Methylenebiscyclohexylamine (CHEMINOX AC-9 manufactured by Unimatech Co., Ltd.). ADH: Adipic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.). (vi) Crosslinking aid 2E4MZ-A: 2-Ethyl-4-methylimidazole triazine salt (Curezol 2E4MZ-A manufactured by Shikoku Chemicals Corporation). (vii) Antioxidant A-611: Blend-type antioxidant (Adekastab A-611 manufactured by ADEKA Corporation, a mixture of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Adekastab AO-60) and tris(2,4-di-tert-butylphenyl)phosphite (Adekastab 2112) in a mass ratio of 1:1).

[0066] Also, various evaluations of the thermoplastic elastomer compositions obtained in the examples and comparative examples, namely, observation of the appearance state of the press-molded sheet, refrigerating machine oil resistance test, measurement of various tensile tests, hardness measurement, and observation of the phase structure, were carried out by the following methods, respectively.

[0067] (1) Preparation of a press-molded sheet of a thermoplastic elastomer composition As a mold, a simple mold composed of an upper plate, a middle plate with a thickness of 2 mm having a region of 100 mm × 100 mm cut out in the central part, and a lower plate was used. Approximately 24 g of the thermoplastic elastomer compositions obtained in the examples and comparative examples was placed in the central part of the middle plate of this mold, sandwiched between the upper plate and the lower plate, and a press-molded sheet (100 mm × 100 mm × 2 mm) was prepared using a vacuum heating press ("IMC-1824 type" manufactured by Iwamoto Seisakusho Co., Ltd.) under a vacuum of 235 °C and a pressure of -0.098 MPa.

[0068] (2) Visual observation of the appearance of the press-molded sheet The appearance state of the press-molded sheet was visually observed and evaluated according to the following criteria. A: It had a smooth surface state. B: No defects were observed in the surface appearance. C: Slight deterioration (roughness) was observed in the surface appearance. D: Molding was impossible or the surface appearance was significantly deteriorated (with unevenness throughout).

[0069] (3) Refrigerator oil resistance test In a nitrogen atmosphere, at a temperature of 125 °C, 13 g of the press-molded sheet was immersed in 50 g of refrigerator oil ("Compressor oil ND-OIL11 for car air conditioner" manufactured by Idemitsu Kosan Co., Ltd.) for 219 hours. Then, the press-molded sheet was taken out from the refrigerator oil, and the turbidity state of the refrigerator oil at room temperature was visually observed and evaluated according to the following criteria. A: No turbidity (transparent). B: Slight turbidity. C: Significant turbidity.

[0070] (4) Tensile test From the press-formed sheet, a JIS dumbbell-shaped No. 3 test piece was produced using a punching die for rubber and used as a tensile test piece. For this tensile test piece, using an Instron universal testing machine (Instron Corporation's "Model 5566"), in accordance with JIS K6251, a tensile test was carried out under the conditions of a chuck distance of 40 mm and a tensile speed of 500 mm / min, and the tensile strength, tensile elongation at break, 10% modulus, and 100% modulus were determined. And regarding the tensile elongation at break, those of 150% or more were judged as excellent (A), those of less than 150% and 100% or more were judged as good (B), and those of less than 100% were judged as defective (C).

[0071] (5) Hardness measurement Three press-formed sheets were stacked to prepare a sample for hardness measurement. For this sample for hardness measurement, the A hardness and D hardness were measured using two types of hardness testers (Akashi Corporation's handy hardness tester "Hardmatic HH-315 (Type A)" and Akashi Corporation's handy hardness tester "Hardmatic HH-317 (Type D)").

[0072] (6) Phase structure observation <Scanning electron microscope (SEM) observation> An observation sample was cut out from the end of the press-formed sheet, and an observation surface was prepared by freeze fracture. The PA phase of this observation surface was subjected to etching treatment with oxygen plasma, and further, after applying a platinum coat to make it conductive, using a scanning electron microscope ("SU3500" manufactured by Hitachi High-Technologies Corporation), a secondary electron image was observed at an acceleration voltage of 5 kV.

[0073] <Transmission electron microscope (TEM) observation> A small piece was cut out from the press-formed sheet, embedded in resin to prepare an observation sample, and then an ultra-thin section with a thickness of about 100 nm was prepared using a cryo-ultramicrotome. The PA phase and the soft thermoplastic elastomer phase of this ultra-thin section were stained with phosphotungstic acid and ruthenium tetroxide, respectively, and the ultra-thin section after staining was subjected to carbon vapor deposition treatment. The ultra-thin section after carbon vapor deposition was observed using a transmission electron microscope ("H-8100" manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV.

[0074] (Example 1) In a co-rotating twin-screw reactive extruder (manufactured by Nippon Steel Corporation, "TEX30α 77BW-20V") with the temperature of the upstream section set at 50°C, the temperatures of the middle and downstream sections set at 230°C, the extrusion rate set at 10 kg / hour, and the screw rotation speed set at 200 rpm, ACM (AR12), a crosslinking agent (AC-9), a crosslinking aid (2E4MZ-A), and an antioxidant (A-611) were supplied from the raw material supply port of the upstream section in the compounding amounts shown in Table 1 respectively for pre-kneading in the upstream section. To the obtained pre-kneaded material, PA6 (CM1001) was supplied from the raw material supply port of the middle section in the compounding amount shown in Table 1, and melt-kneading was carried out in the middle section to dynamically crosslink ACM. To the obtained crosslinked kneaded material, H-XNBR (Zetpol2510) was supplied from the raw material supply port of the downstream section in the compounding amount shown in Table 1, and blending treatment (fine dispersion treatment by melt-kneading) was carried out by melt-kneading in the downstream section to obtain a thermoplastic elastomer composition having the composition shown in Table 1.

[0075] Regarding the obtained thermoplastic elastomer composition, observation of the appearance state of the press-molded product, a refrigerating machine oil resistance test, measurement of various tensile tests, hardness measurement, and observation of the phase structure (SEM observation and TEM observation) were carried out by the above-mentioned methods respectively. The obtained results are shown in Table 1, Figure 1A (SEM observation), and Figure 1B (TEM observation). From the results of the SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 forms a continuous phase and the ACM crosslinked product forms a dispersed phase. Also, from the results of the TEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, the uncrosslinked H-XNBR forms a fine dispersed phase with an average diameter of about 200 nm in the continuous phase composed of PA6.

[0076] (Comparative Example 1) The compounding amount of PA6 (CM1001) was changed to the compounding amount shown in Table 1, and a thermoplastic elastomer composition having the composition shown in Table 1 was prepared in the same manner as in Example 1 except that H-XNBR (Zetpol2510) was not used. For the obtained thermoplastic elastomer composition, various evaluations were carried out in the same manner as in Example 1. The obtained results are shown in Table 1 and FIG. 2 (SEM observation). From the results of SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 forms a continuous phase and the ACM crosslinked product forms a dispersed phase.

[0077] (Comparative Example 2) A thermoplastic elastomer composition having the composition shown in Table 1 was prepared in the same manner as in Example 1 except that a soft thermoplastic elastomer (LP21H) was supplied in the compounding amount shown in Table 1 instead of H-XNBR (Zetpol2510). For the obtained thermoplastic elastomer composition, various evaluations were carried out in the same manner as in Example 1. The obtained results are shown in Table 1, FIG. 3A (SEM observation), and FIG. 3B (TEM observation). From the results of SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 forms a continuous phase and the ACM crosslinked product forms a dispersed phase. Also, from the results of TEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, the soft thermoplastic elastomer (LP21H) forms a finely dispersed phase with an average diameter of about 500 nm in the continuous phase composed of PA6.

[0078]

Table 1

[0079] As shown in Table 1, it was found that all of the thermoplastic elastomer compositions obtained in Example 1 and Comparative Examples 1 to 2 were excellent in the appearance of the press-molded product and the elongation at break. Further, from the results of the 10% modulus measurement, 100% modulus measurement, and hardness measurement, it was found that the thermoplastic elastomer composition obtained in Example 1 had improved flexibility compared to the thermoplastic elastomer composition obtained in Comparative Example 1. Furthermore, it was found that the thermoplastic elastomer composition obtained in Example 1 had improved resistance to refrigerant oil compared to the thermoplastic elastomer composition obtained in Comparative Example 2.

[0080] From the above results, it was confirmed that the thermoplastic elastomer composition obtained in Example 1 was excellent in moldability, flexibility, elongation at break, and resistance to refrigerant oil without adding a large amount of plasticizer.

[0081] (Example 2) After supplying ACM (AR12) to the chamber of a Laboplastmill (manufactured by Toyo Seiki Seisakusho Co., Ltd., "10C100", chamber: R100H, blade shape: roller type) with the chamber temperature set at 50°C and the rotor rotation speed set at 10 rpm, a crosslinking agent (ADH) and an antioxidant (A-611) were supplied so as to have the compounding amounts shown in Table 2, respectively. After the total amount was supplied, the rotor rotation speed was increased to 30 rpm and kneading treatment was performed for 5 minutes. After the treatment was completed, the kneaded product (pre-kneaded product) obtained by opening the chamber with the rotor stopped was recovered.

[0082] Next, the chamber temperature of the lab plast mill was set to 245°C and the rotor rotation speed was set to 10 rpm. PA6 (CM1001) was supplied into the chamber. When the material temperature reached 240°C or higher, the rotor rotation speed was increased to 30 rpm and the pre-kneaded material was supplied to obtain the compounding amounts shown in Table 2. After supplying the entire amount of the pre-kneaded material, the rotor rotation speed was increased to 100 rpm and kneaded for 10 minutes to dynamically crosslink ACM (dynamic crosslinking treatment by melt kneading). After the treatment was completed, the rotor rotation speed was decreased to 30 rpm, and then H-XNBR (Zetpol2510) was supplied to obtain the compounding amounts shown in Table 2 (added after dynamic crosslinking). The rotor rotation speed was increased to 100 rpm and a blending treatment (fine dispersion treatment by melt kneading) was performed for 5 minutes to obtain a thermoplastic elastomer composition having the composition shown in Table 2.

[0083] For the obtained thermoplastic elastomer composition, various evaluations were carried out in the same manner as in Example 1. The obtained results are shown in Table 2, Figure 4A (SEM observation), and Figure 4B (TEM observation). From the results of the SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 formed a continuous phase and the ACM crosslinked product formed a dispersed phase. Further, from the results of the TEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, the uncrosslinked H-XNBR formed a fine dispersed phase with an average diameter of about 1000 nm in the continuous phase composed of PA6.

[0084] (Example 3) A thermoplastic elastomer composition having the composition shown in Table 2 was obtained in the same manner as in Example 2, except that PA6 (1022B) was supplied to obtain the compounding amounts shown in Table 2 instead of PA6 (CM1001). For the obtained thermoplastic elastomer composition, various evaluations were carried out in the same manner as in Example 1. The obtained results are shown in Table 2 and Figure 5 (SEM observation). From the results of the SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 formed a continuous phase and the ACM crosslinked product formed a dispersed phase.

[0085] (Example 4) An elastomeric composition was obtained in the same manner as in Example 2, except that NBR (Nipol DN631) was supplied in the amounts shown in Table 2 instead of H-XNBR (Zetpol 2510). Various evaluations were carried out on the obtained elastomeric composition in the same manner as in Example 1. The results obtained are shown in Table 2 and FIG. 6 (SEM observation). From the results of the SEM observation, it was confirmed that in the obtained elastomeric composition, PA6 forms the continuous phase and the ACM crosslinked product forms the dispersed phase.

[0086] (Example 5) An elastomeric composition was obtained in the same manner as in Example 2, except that H-XNBR (Zetpol 3710) was supplied in the amounts shown in Table 2 instead of H-XNBR (Zetpol 2510). Various evaluations were carried out on the obtained elastomeric composition in the same manner as in Example 1. The results obtained are shown in Table 2 and FIG. 7 (SEM observation). From the results of the SEM observation, it was confirmed that in the obtained elastomeric composition, PA6 forms the continuous phase and the ACM crosslinked product forms the dispersed phase.

[0087] (Comparative Example 3) An elastomeric composition having the composition shown in Table 2 was prepared in the same manner as in Example 2, except that a soft thermoplastic elastomer (LP21H) was supplied in the amounts shown in Table 2 instead of H-XNBR (Zetpol 2510). Various evaluations were carried out on the obtained elastomeric composition in the same manner as in Example 1. The results obtained are shown in Table 2 and FIG. 8 (SEM observation). From the results of the SEM observation, it was confirmed that in the obtained elastomeric composition, PA6 forms the continuous phase and the ACM crosslinked product forms the dispersed phase.

[0088]

Table 2

[0089] As shown in Table 2, it was found that all of the thermoplastic elastomer compositions obtained in Examples 2 to 5 and Comparative Example 3 were excellent in the appearance, tensile elongation at break, and flexibility of the press-molded products. Further, in the thermoplastic elastomer compositions obtained in Examples 2 to 5, it was found that the oil resistance to refrigerator oil was improved as compared with the thermoplastic elastomer composition obtained in Comparative Example 3.

[0090] From the above results, it was confirmed that the thermoplastic elastomer compositions obtained in Examples 2 to 5 were excellent in moldability, flexibility, and tensile elongation at break, and also excellent in oil resistance to refrigerator oil without adding a large amount of plasticizer.

[0091] (Example 6) A thermoplastic elastomer composition having the composition shown in Table 3 was prepared in the same manner as in Example 2, except that H-XNBR (Zetpol2510) was supplied in the blending amounts shown in Table 3 instead of ACM (AR12). Various evaluations were carried out on the obtained thermoplastic elastomer composition in the same manner as in Example 1. The obtained results are shown in Table 3, Figure 9A (SEM observation), and Figure 9B (TEM observation). From the results of SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 formed a continuous phase and the H-XNBR crosslinked product formed a dispersed phase. Further, from the results of TEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, the uncrosslinked H-XNBR formed a finely dispersed phase with an average diameter of about 300 nm in the continuous phase composed of PA6.

[0092] (Comparative Example 4) A thermoplastic elastomer composition having the composition shown in Table 3 was prepared in the same manner as in Example 6, except that the blending amount of PA6 (CM1001) was changed to the blending amount shown in Table 3 and H-XNBR (Zetpol2510) was not supplied after dynamic crosslinking. Various evaluations were carried out on the obtained thermoplastic elastomer composition in the same manner as in Example 1. The obtained results are shown in Table 3 and Figure 10 (SEM observation). From the results of SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 formed a continuous phase and the H-XNBR crosslinked product formed a dispersed phase.

[0093] (Comparative Example 5) A thermoplastic elastomer composition having the composition shown in Table 3 was prepared in the same manner as in Example 6, except that after dynamic crosslinking, a soft thermoplastic elastomer (LP21H) was supplied in the amounts shown in Table 3 instead of H-XNBR (Zetpol2510) (added after dynamic crosslinking). For the obtained thermoplastic elastomer composition, various evaluations were carried out in the same manner as in Example 1. The obtained results are shown in Table 3 and FIG. 11 (SEM observation). From the results of SEM observation, it was confirmed that in the obtained thermoplastic elastomer composition, PA6 forms a continuous phase and the H-XNBR crosslinked product forms a dispersed phase.

[0094]

Table 3

[0095] As shown in Table 3, it was found that all of the thermoplastic elastomer compositions obtained in Example 6 and Comparative Examples 4 to 5 have excellent appearance of press-molded products. Also, in the thermoplastic elastomer composition obtained in Example 6, it was found that the tensile elongation at break was improved compared to the thermoplastic elastomer composition obtained in Comparative Example 4. Furthermore, from the results of 10% modulus measurement, 100% modulus measurement, and hardness measurement, it was found that in the thermoplastic elastomer composition obtained in Example 6, the flexibility was improved compared to the thermoplastic elastomer composition obtained in Comparative Example 4. Also, in the thermoplastic elastomer composition obtained in Example 6, it was found that the oil resistance to a refrigerator was improved compared to the thermoplastic elastomer composition obtained in Comparative Example 5.

[0096] From the above results, it was confirmed that the thermoplastic elastomer composition obtained in Example 6 is excellent in moldability, flexibility, tensile elongation at break, and oil resistance to a refrigerator without adding a large amount of plasticizer.

Industrial Applicability

[0097] As described above, according to the present invention, even when the content of polyamide (PA) is less than the content of carboxy-modified acrylic rubber (ACM) or carboxy-modified acrylonitrile-butadiene copolymer rubber (XNBR), a sea-island structure is formed in which PA forms a continuous phase and the ACM crosslinked product and / or the XNBR crosslinked product form a dispersed phase. It is possible to provide a thermoplastic elastomer composition that is excellent in moldability, flexibility, and tensile elongation at break without adding a large amount of plasticizer and is also excellent in oil resistance for refrigerators, and a method for producing the same.

[0098] Therefore, the thermoplastic elastomer composition of the present invention has good appearance quality and is excellent in moldability and flexibility, so it is useful as tubes, hoses, packings, belts, boots, coating materials, sheets, covers, etc. Further, since the thermoplastic elastomer composition of the present invention is also excellent in oil resistance for refrigerators, it is particularly useful as tubes, hoses, packings, belts, coating materials, etc. for refrigerators.

Claims

1. A. A crosslinked elastomer selected from the group consisting of a carboxy-modified acrylic rubber crosslinked product and a carboxy-modified acrylonitrile-butadiene copolymer rubber crosslinked product, B. A polyamide, C. An uncrosslinked acrylonitrile-butadiene copolymer rubber, A thermoplastic elastomer composition containing the same, wherein, based on a total of 100% by volume of components A to C, the content of component A is 60 to 85% by volume, the content of component B is 14 to 39% by volume, and the content of component C is 1 to 25% by volume. A sea-island structure including a continuous phase composed of component B and a dispersed phase composed of component A is formed, and component C forms a finely dispersed phase having an average diameter of 10 to 2000 nm in the continuous phase composed of component B and is finely dispersed. A thermoplastic elastomer composition characterized by this.

2. The thermoplastic elastomer composition according to claim 1, wherein the uncrosslinked acrylonitrile-butadiene copolymer rubber is at least one selected from the group consisting of an uncrosslinked carboxy-modified acrylonitrile-butadiene copolymer rubber and an uncrosslinked hydrogenated carboxy-modified acrylonitrile-butadiene copolymer rubber.

3. The thermoplastic elastomer composition according to claim 1 or 2, wherein the polyamide is polyamide 6.

4. A'. An uncrosslinked elastomer selected from the group consisting of an uncrosslinked carboxy-modified acrylic rubber and an uncrosslinked carboxy-modified acrylonitrile-butadiene copolymer rubber, and D. A primary melt-kneading step of melt-kneading a pre-kneaded product containing a crosslinking agent and B. A polyamide, and dynamically crosslinking component A' to obtain a crosslinked kneaded product; Adding C. An uncrosslinked acrylonitrile-butadiene copolymer rubber to the crosslinked kneaded product obtained in the primary kneading step, melt-kneading, and a secondary melt-kneading step of obtaining the thermoplastic elastomer composition according to any one of claims 1 to 3. A method for producing a thermoplastic elastomer composition, characterized by including the same.

5. The method for producing a thermoplastic elastomer composition according to claim 4, wherein the crosslinking agent is a polyvalent amine-based crosslinking agent.

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