ACRYLIC RUBBER COMPOSITION

Abstract

An acrylic rubber composition that includes a blend product of an acrylic rubber [I] containing a copolymer of an ethyl acrylate/n-butyl acrylate/2-methoxyethyl acrylate/carboxyl group-containing vinyl monomer, and an acrylic rubber [II] containing a copolymer of an alkoxyalkyl acrylate/2-ethylhexyl acrylate/alkyl methacrylate/ethyl acrylate/carboxyl group-containing vinyl monomer; the blend product being compounded with silica and a plasticizer.

Claims

1. An acrylic rubber composition comprising a blend product of an acrylic rubber [I] comprising copolymer of an ethyl acrylate/n-butyl acrylate/2-methoxyethyl acrylate/carboxyl group-containing vinyl monomer, and an acrylic rubber [II] comprising copolymer of an alkoxyalkyl acrylate/2-ethylhexyl acrylate/alkyl methacrylate/ethyl acrylate/carboxyl group-containing vinyl monomer; the blend product being compounded with silica and a plasticizer.

2. The acrylic rubber composition according to claim 1, wherein the acrylic rubber [I] and the acrylic rubber [II] are blended in a weight ratio of 10:90 to 40:60.

3. The acrylic rubber composition according to claim 1, wherein the weight ratio of each monomer after acrylic rubber blending comprises 16 to 30 wt. % of ethyl acrylate, 0.1 to 15.5 wt. % of n-butyl acrylate, 28 to 33.5 wt. % of the alkoxyalkyl acrylate or 2-methoxyethyl acrylate, 17.5 to 33.5 wt. % of 2-ethylhexyl acrylate, 8 to 14.5 wt. % of the alkyl methacrylate, and 1 to 3 wt. % of the carboxyl group-containing vinyl monomer.

4. The acrylic rubber composition according to claim 1, wherein the alkyl methacrylate is methyl methacrylate.

5. The acrylic rubber composition according to claim 1, wherein the carboxyl group-containing vinyl monomer is a monoalkyl fumarate.

6. An acrylic rubber blend product comprising an acrylic rubber [I] comprising copolymer of an ethyl acrylate/n-butyl acrylate/2-methoxyethyl acrylate/carboxyl group-containing vinyl monomer, and an acrylic rubber [II] comprising copolymer of an alkoxyalkyl acrylate/2-ethylhexyl acrylate/alkyl methacrylate/ethyl acrylate/carboxyl group-containing vinyl monomer, wherein the weight ratio of each monomer after acrylic rubber blending comprises 16 to 30 wt. % of ethyl acrylate, 0.1 to 15.5 wt. % of n-butyl acrylate, 28 to 33.5 wt. % of the alkoxyalkyl acrylate or 2-methoxyethyl acrylate, 17.5 to 33.5 wt. % of 2-ethylhexyl acrylate, 8 to 14.5 wt. % of the alkyl methacrylate, and 1 to 3 wt. % of the carboxyl group-containing vinyl monomer.

7. The acrylic rubber composition according to claim 1, wherein 30 to 120 parts by weight of silica, based on 100 parts by weight of the acrylic rubber blend product, is compounded.

8. The acrylic rubber composition according to claim 1, wherein the plasticizer is an ester-based plasticizer.

9. The acrylic rubber composition according to claim 1, wherein 2 to 8 parts by weight of a plasticizer, based on 100 parts by weight of the acrylic rubber blend product, is compounded.

10. The acrylic rubber composition according to claim 1, wherein a crosslinking agent for carboxyl group is further comprised.

11. The acrylic rubber composition according to claim 10, which is used as a crosslinking molding material for sealing materials.

12. A sealing material obtained by crosslinking molding of the acrylic rubber composition according to claim 11.

Description

EXAMPLES

[0048] The following describes the present invention with reference to Examples.

Example 1

[0049] Using a sealed kneader, the following components were compounded and kneaded based on 100 parts by weight of an acrylic rubber blend product comprising 30 parts by weight of ACM-1 and 70 parts by weight of ACM-2 (monomer weight ratio of EA:BA:MEA:EHA:MMA:MBF=24.5:9.6:30.1:23.8:10.5:1.5).

TABLE-US-00003 Silica (Nipsil E74P, produced by Tosoh 75 parts by weight Corporation) Silane coupling agent (Z-6011, produced by 1 part by weight Dow Toray Co., Ltd.) Stearic acid (produced by Miyoshi Oil & 1 part by weight Fat Co., Ltd.) Liquid paraffin (Liquid Paraffin 70S, 2 parts by weight produced by Sanko Chemical Industry Co., Ltd.) Antioxidant (Nocrac CD, produced by 2 parts by weight Ouchi Shinko Chemical Industrial Co., Ltd.) Plasticizer (ADK CIZER C-9N, 5 parts by weight produced by ADEKA Corporation)
Then, the following components were added using an open roll to prepare a crosslinkable acrylic rubber composition.

TABLE-US-00004 Vulcanizing agent (CHEMINOX AC-6, 0.6 parts by weight produced by UNIMATEC CO., LTD.) Vulcanization accelerator (Vulcofac 1 part by weight ACT-55, produced by Safic-Alcan)
The acrylic rubber blend product was subjected to press vulcanization at 180° C. for 6 minutes, followed by oven vulcanization (secondary vulcanization) at 175° C. for 10 hours, thereby obtaining an acrylic rubber crosslinked product.

Example 2

[0050] In Example 1, the amount of ACM-1 was changed to 10 parts by weight, and the amount of ACM-2 was changed to 90 parts by weight, respectively. The monomer weight ratio of the copolymer was EA:BA:MEA:EHA:MMA:MBF=18.5:3.2:32.7:30.6:13.5:1.5).

Example 3

[0051] In Example 1, the amount of ACM-1 was changed to 20 parts by weight, and the amount of ACM-2 was changed to 80 parts by weight, respectively. The monomer weight ratio of the copolymer was EA:BA:MEA:EHA:MMA:MBF=21.5:6.4:31.4:27.2:12.0:1.5).

Example 4

[0052] In Example 1, the amount of ACM-1 was changed to 40 parts by weight, and the amount of ACM-2 was changed to 60 parts by weight, respectively. The monomer weight ratio of the copolymer was EA:BA:MEA:EHA:MMA:MBF=27.5:12.8:28.8:20.4:9.0:1.5).

Example 5

[0053] In Example 1, the amount of the plasticizer was changed to 2 parts by weight.

Example 6

[0054] In Example 1, the amount of the plasticizer was changed to 8 parts by weight.

Comparative Example 1

[0055] In Example 1, 60 parts by weight of carbon black (Seast S, produced by Tokai Carbon Co., Ltd.) was used in place of silica.

Comparative Example 2

[0056] In Comparative Example 1, 100 parts by weight of ACM-2 (The monomer weight ratio of the copolymer was EA:BA:MEA:EHA:MMA:MBF=15.5:0:34.0:34.0:15.0:1.5) was used in place of the acrylic rubber blend product.

Comparative Example 3

[0057] In Example 1, 100 parts by weight of ACM-2 was used in place of the acrylic rubber blend product.

Comparative Example 4

[0058] In Example 1, the amount of silica was changed to 70 parts by weight, and no plasticizer was used.

Comparative Example 5

[0059] In Example 1, the amount of silica was changed to 80 parts by weight, and the amount of the plasticizer was changed to 10 parts by weight, respectively.

Comparative Example 6

[0060] In Example 1, the amount of ACM-1 was changed to 50 parts by weight, and the amount of ACM-2 was changed to 50 parts by weight, respectively. The monomer weight ratio of the copolymer was EA:BA:MEA:EHA:MMA:MBF=30.5:16.0:27.5:17.0:7.5:1.5).

Comparative Example 7

[0061] In Example 1, 0.5 parts by weight of 2,4,6-trimercapto-S-triazine (Nocceler TCA, produced by Ouchi Shinko Chemical Industrial Co., Ltd.) was used as the vulcanizing agent, and 1.5 parts by weight of zinc dibutyldithiocarbamate (Nocceler BZ-P, produced by Ouchi Shinko Chemical Industrial Co., Ltd.) was used as the vulcanization accelerator. However, crosslinking could not be performed.

[0062] Using the acrylic rubber blend product obtained in each of Examples 1 to 6 and Comparative Examples 1 to 6 above, the scorch stability of the composition was measured, and using the acrylic rubber crosslinked product, normal state physical properties, extraction resistance, oil resistance, cold resistance, water resistance after hydrolysis, and hydrolyzability were measured and evaluated. [0063] Scorch stability: according to JIS K6300 corresponding to ISO 289 [0064] Normal state physical properties: according to JIS K6253 and JIS K6251 corresponding to ISO 37

[0065] T5 value of >5.0 was evaluated as ⊚, 3.0 to 5.0 as ◯, and <3.0 as X. [0066] Extraction resistance test: according to JIS K6258 corresponding to ISO 1817

[0067] The volume change rate (ΔV) after dipping in a dipping test oil IRM 901 at 150° C. for 70 hours was measured. ΔV of −2 to +2% was evaluated as ⊚, −5 to −3% or +3 to +5% as ◯, and ≤−6% or ≥+6 as X. [0068] Oil resistance test: according to JIS K6258 corresponding to ISO 1817

[0069] The volume change rate (ΔV) after dipping in a dipping test oil IRM 903 at 150° C. for 70 hours was measured. ΔV of ±0 to +25% was evaluated as ⊚, +26 to +29% as ◯, and ≥+30 as X. [0070] Cold resistance test: according to JIS K6261-4 corresponding to ISO 2921

[0071] TR10 values were measured. TR10 value of ≤−28 was evaluated as ⊚, −27 to −25 as ◯, and ≥−24 as X.

[0072] Water resistance test after hydrolysis: according to JIS K6258 corresponding to ISO 1817

[0073] The volume change rate (ΔV) after dipping in a 1 wt. % zinc chloride aqueous solution at 120° C. for 500 hours was measured. ΔV of ±0 to +5 was evaluated as ⊚, +6 to +10% as ◯, and ≥+11 as X. [0074] Hydrolysis resistance test: according to JIS K6258 corresponding to ISO 1817

[0075] The volume change rate (ΔV) after dipping in a 1 wt. % zinc chloride aqueous solution at 120° C. for 500 hours, followed by drying in the air at 120° C. for 70 hours was measured. ΔV of −9 to ±0% was evaluated as ⊚, −15 to −10% as ◯, and ≤−16 as X.

[0076] The following table 1 (Examples) and table 2 (Comparative Examples) show the results of the above test of physical properties.

TABLE-US-00005 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 [Scorch stability ] T5    4.8    5.1    4.9    4.5    4.6    4.9 Evaluation ◯ ⊚ ◯ ◯ ◯ ◯ [Normal state physical properties] Hardness Hs (Points)  68  68  68  68  69  67 Breaking strength (MPa)    9.51    9.34    9.63    9.41    9.80    9.00 Elongation at break (%) 180 190 170 190 180 180 [Extraction resistance] Volume change rate (%)  −3  −2  −3  −3  −1  −5 Evaluation ◯ ⊚ ◯ ◯ ⊚ ◯ [Oil resistance] Volume change rate (%) +25 +28 +27 +23 +27 +23 Evaluation ⊚ ◯ ◯ ⊚ ◯ ⊚ [Cold resistance] TR10 −26 −26 −26 −26 −25 −27 Evaluation ◯ ◯ ◯ ◯ ◯ ◯ [Water resistance after hydrolysis] Volume change rate (%)  +4  +8  +5  +7  +5  +4 Evaluation ⊚ ◯ ⊚ ◯ ⊚ ⊚ [Hydrolysis resistance] Volume change rate (%) −13 −10 −12 −14 −13 −14 Evaluation ◯ ◯ ◯ ◯ ◯ ◯

TABLE-US-00006 TABLE 2 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 [Scorch stability] T5    2.5    2.9    5.3    4.3    5.1    4.3 Evaluation X X ⊚ ◯ ⊚ ◯ [Normal state physical properties] Hardness Hs (Points)  72  72  69  69  67  68 Breaking strength (MPa)    11.00    11.00    9.32    10.30    8.78    9.77 Elongation at break (%) 220 230 200 170 180 160 [Extraction resistance] Volume change rate (%)  −2  −1  −2  +1  −6  −3 Evaluation ⊚ ⊚ ⊚ ⊚ X ◯ [Oil resistance] Volume change rate (%) −31 +34 +30 +29 +21 +21 Evaluation X X X ◯ ⊚ ⊚ [Cold resistance] TR10 −26 −26 −26 −24 −28 −27 Evaluation ◯ ◯ ◯ X ⊚ ◯ [Water resistance after hydrolysis] Volume change rate (%) +11 +17 +14  +6  +4  +9 Evaluation X X X ◯ ⊚ ◯ [Hydrolysis resistance] Volume change rate (%) −12  −8  −9 −12 −14 −17 Evaluation ◯ ⊚ ⊚ ◯ ◯ X

[0077] The above results demonstrate the following.

[0078] (1) In each Example, the volume change after the hydrolysis resistance test is small, and oil resistance and cold resistance are well balanced.

[0079] (2) Comparative Example 1, in which carbon black is used in place of silica, is inferior in scorch stability, oil resistance, and water resistance after hydrolysis.

[0080] (3) Comparative Examples 2 and 3, in which ACM-1 is not blended, and only ACM-2 is used as an acrylic rubber, are inferior in oil resistance and water resistance after hydrolysis.

[0081] (4) Comparative Example 4, in which no plasticizer is used, is inferior in cold resistance.

[0082] (5) Comparative Example 5, in which a plasticizer is excessively used, is inferior in extraction resistance.

[0083] (6) Comparative Example 6, in which the blending ratio of the general-purpose acrylic rubber is high, is inferior in hydrolysis resistance.