CHLOROPRENE-BASED RUBBER COMPOSITION, VULCANIZED OBJECT OBTAINED FROM SAID CHLOROPRENE-BASED RUBBER COMPOSITION, AND VULCANIZED MOLDED OBJECT OBTAINED FROM CHLOROPRENE-BASED RUBBER COMPOSITION

Abstract

A chloroprene-based rubber composition capable of obtaining a vulcanizate having excellent compression set resistance and excellent heat resistance, a vulcanizate of the chloroprene-based rubber composition, and a vulcanized molded body of the chloroprene-based rubber composition having excellent compression set resistance and heat resistance. A chloroprene-based rubber composition including 100 parts by mass of a chloroprene-based rubber, 0.1 to 10 parts by mass of an organic peroxide, and 0.1 to 40 parts by mass of a compound having one or more thioether structures is provided.

Claims

1. A chloroprene-based rubber composition comprising 100 parts by mass of a chloroprene-based rubber, 0.1 to 10 parts by mass of an organic peroxide, and 0.1 to 40 parts by mass of a compound having one or more thioether structures.

2. The chloroprene-based rubber composition of claim 1, wherein the chloroprene-based rubber comprises a chloroprene polymer containing an unsaturated nitrile monomer unit.

3. The chloroprene-based rubber composition of claim 1, wherein the compound having one or more thioether structures has two or more ether structures.

4. The chloroprene-based rubber composition of claim 1, wherein the compound having one or more thioether structures has a molecular weight of 300 or more.

5. The chloroprene-based rubber composition of claim 1, wherein the unsaturated nitrile monomer is acrylonitrile.

6. The chloroprene-based rubber composition of claim 1, wherein the chloroprene-based rubber composition comprises 0.5 to 4 parts by mass of a maleimide compound with respect to 100 parts by mass of the chloroprene-based rubber.

7. The chloroprene-based rubber composition of claim 1, wherein the chloroprene-based rubber composition comprises 2 to 75 parts by mass of acetylene black with respect to 100 parts by mass of the chloroprene-based rubber.

8. The chloroprene-based rubber composition of claim 1, wherein the chloroprene-based rubber composition comprises 1 to 25 parts by mass of zinc powder with respect to 100 parts by mass of the chloroprene-based rubber.

9. A vulcanizate of the chloroprene-based rubber composition of claim 1.

10. A vulcanized molded body of the chloroprene-based rubber composition of claim 1.

Description

EXAMPLES

<Manufacturing Chloroprene Polymer (AN 5%)>

[0078] To a polymerization vessel with an inner volume of 3 liters equipped with a heating and cooling jacket and a stirrer, 32 parts by mass of chloroprene monomer, 14 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, 5.00 parts by mass of potassium rosinate (manufactured by Harima Chemicals Group, Inc.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. The chloroprene monomer was added in portions from 20 seconds after the initiation of polymerization. Based on the change in the heat quantity of the refrigerant for 10 seconds from the start of polymerization, the flow rate to be added in portions was adjusted with a solenoid valve. Thereafter, the flow rate was readjusted every 10 seconds, and the addition was continuously performed in portions. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer reached 50%, phenothiazine as a polymerization terminator was added to terminate the polymerization. Thereafter, unreacted monomers were removed from the reaction solution under reduced pressure to obtain a latex containing a chloroprene-acrylonitrile copolymer.

[0079] The pH of the obtained latex containing the chloroprene-acrylonitrile copolymer is adjusted to 7.0 and freeze-coagulated on a metal plate cooled to −20° C. and demulsified to obtain a sheet. The sheet was washed with water and dried at 130° C. for 15 minutes to obtain a solid chloroprene-acrylonitrile chloroprene-based rubber containing 5% by mass of acrylonitrile monomer unit (AN 5%).

[0080] The amount of the unsaturated nitrile monomer unit contained in the chloroprene-based rubber was calculated from the content of nitrogen atoms in the chloroprene-based rubber. Specifically, the nitrogen atom content in 100 mg of the chloroprene-based rubber was measured using an elemental analyzer (SUMIGRAPH 220F: manufactured by Sumika Chemical Analysis Service, Ltd.) to calculate the content of the acrylonitrile monomer unit. The measurement conditions for elemental analysis were as follows. The temperature of the electric furnace was set to 900° C. for the reaction furnace, 600° C. for the reduction furnace, 70° C. for the column temperature, and 100° C. for the detector temperature. Oxygen gas was flowed at 0.2 mL/min as combustion gas, and helium gas was flowed at 80 mL/min as carrier gas. Calibration curves were prepared using aspartic acid (10.52%), which has a known nitrogen content, as a standard.

<Manufacturing Chloroprene-Based Rubber (AN10%), (AN15%), (AN20%)>

[0081] Each of a chloroprene-based rubber (AN 10%) having 10% by mass of the acrylonitrile monomer unit, a chloroprene-based rubber (AN 15%) having 15% by mass of the acrylonitrile monomer unit, and a chloroprene-based rubber (AN 20%) having 20% by mass of the acrylonitrile monomer unit contained in the chloroprene-based rubber was manufactured in the same manner as the method for manufacturing the chloroprene-based rubber (AN 5%), except that the acrylonitrile monomer added during polymerization was changed so that the amount of acrylonitrile monomer units in the resulting chloroprene-based rubber has 10, 15, or 20% by mass of the acrylonitrile monomer unit.

Examples 1 to 21, Comparative Examples 1 to 5

(Manufacturing Rubber Composition)

[0082] The above-mentioned chloroprene-based rubber and each compound shown in Tables 1 to 3 were kneaded with an 8-inch open roll in the amounts shown in Tables 1 to 3 to obtain rubber compositions. The compounds used in Tables 1 to 3 are as follows.

<Chloroprene-Based Rubber>

[0083] Chloroprene-based rubbers (AN 5, 10, 15, 20%): chloroprene-based rubbers produced by the above-described method and having 5, 10, 15, and 20% by mass of the acrylonitrile monomer unit respectively.

[0084] Mercaptan-modified chloroprene rubber: manufactured by Denka Company Limited (Mooney viscosity ML.sub.1+4 (100° C.)=60)

<Organic Peroxide>

[0085] PERBUTYL P-40: “PERBUTYL (registered trademark) P-40” (1,4-bis [(t-butylperoxy) isopropyl] benzene) manufactured by NOF CORPORATION

[0086] PERHEXA V-40: “PERHEXA (registered trademark) V-40” (n-butyl 4,4-di-(t-butylperoxy) valerate) manufactured by NOF CORPORATION

<Maleimide Compound>

[0087] VULNOC PM: “VULNOC (registered trademark) PM” (N,N′-m-phenylene bismaleimide) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD

<Compound Having Thioether Structure>

[0088] Vulkanol OT: “Vulkanol OT” (a mixture including compound A containing one or more thioether structures and two or more ether structures and compound B containing one or more thioether structures and three or more ether structures as main components) manufactured by Lanxess AG

[0089] Vulkanol 88: “Vulkanol 88” (molecular weight: 308.5, compound with the following structure) manufactured by Lanxess AG

##STR00002##

[0090] Vulkanol 85: “Vulkanol 85” (compound containing one thioether structure and two or more ether structures) manufactured by Lanxess AG

[0091] NOCRAK 400: “NOCRAK (registered trademark) 400” (dilauryl thiodipropionate, molecular weight: 514.84) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD

##STR00003##

[0092] ADEKA STAB AO-412S: “ADEKA STAB AO-412S” (molecular weight: 1161.94) manufactured by ADEKA Corporation

##STR00004##

<Carbon Black>

[0093] FEF: “Asahi #60UG” manufactured by Asahi Carbon Co., Ltd.

[0094] Acetylene black: “Denka black granules” manufactured by Denka Company Limited

<Others>

[0095] Zinc powder: “Zinc powder #F” manufactured by SAKAI CHEMICAL INDUSTRY CO., LTD.

[0096] Plasticizer: “ADEKA CIZER (registered trademark) R-735” (polyether ester-based) manufactured by ADEKA Corporation

[0097] Vulcanizing agent: Zinc oxide: “Zinc oxide type 2” manufactured by SAKAI CHEMICAL INDUSTRY CO., LTD.

[0098] Vulcanization accelerator: NOCCELER TMU: “NOCCELER TMU” (trimethylthiourea) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD

[0099] Antioxidant: NOCRAC CD: NOCRAC (registered trademark) CD” (4,4′-bis (α, α-dimethylbenzyl) diphenylamine) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD

[0100] Acid acceptor: Kyowamag 150: “Kyowamag (registered trademark) 150” (magnesium oxide) manufactured by Kyowa Chemical Industry Co., Ltd.

[0101] Lubricant/processing aid: Stearic acid: “Stearic acid 50S” manufactured by New Japan Chemical Co., Ltd.

(Manufacturing Vulcanized Molded Body)

[0102] The obtained rubber composition was press-vulcanized under conditions of 180° C. for 30 minutes to prepare a sheet-like vulcanized molded body having a thickness of 2 mm. The following evaluations were performed on the obtained vulcanized molded bodies. The evaluation results are shown in Tables 1 to 3.

(Evaluation of Vulcanized Molded Body)

(1) Oil Resistance

<Measurement of Oil Resistance of Vulcanized Rubber>

[0103] The oil resistance of the samples prepared by the method described above was measured according to JIS K6258. The oil type used was IRM903 oil. The oil resistance was evaluated based on the volume change rate (ΔV) after immersion at 130° C. for 72 hours according to the following evaluation criteria.

[0104] A: The volume change rate (ΔV) was 15 or less.

[0105] B: The volume change rate (ΔV) was more than 15 and 25 or less.

[0106] C: The volume change rate (ΔV) was more than 25 and 35 or less.

[0107] D: The volume change rate (ΔV) was more than 35 and 45 or less.

[0108] E: The volume change rate (ΔV) was more than 45 and 55 or less.

[0109] F: The volume change rate (ΔV) was over 55.

(2) Heat Resistance

[0110] For the sample prepared by the above method, the elongation at break (Eb) was measured after leaving the test piece under the conditions of 150° C. for 72 hours in accordance with JIS K 6257:2017, and its rate of change (%). was calculated and evaluated according to the following evaluation criteria.

[0111] A: The rate of change was −12 or more.

[0112] B: The rate of change was −24 or more and less than −12.

[0113] C: The rate of change was −36 or more and less than −24.

[0114] D: The rate of change was −48 or more and less than −36.

[0115] E: The rate of change was −60 or more and less than −48.

[0116] F: The rate of change was less than −60.

(3) Compression Set Resistance

[0117] Each sample prepared by the method described above was measured at a test temperature of 130° C. and a test time of 72 hours, in accordance with JIS K 6262:2013, and evaluated according to the following evaluation criteria.

[0118] A: The compression set resistance was 0% or more and 25% or less.

[0119] B: The compression set resistance was more than 25% and 30% or less.

[0120] C: The compression set resistance was more than 30% and 35% or less.

[0121] D: The compression set resistance was more than 35% and 40% or less.

[0122] E: The compression set resistance was more than 40% and 45% or less.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 11 Composition Chloroprene-based Chloroprene-based rubber (Parts by rubber composition composition mass) (AN5%) Chloroprene-based rubber 100 100 100 100 100 100 100 100 100 100 100 composition (AN10%) Chloroprene-based rubber composition (AN15%) Chloroprene-based rubber composition (AN20%) Mercaptan-modified Chloroprene rubber Organic peroxide PERBUTYL P-40 1 1 1 1 1 1 1 1 1 1 1 PERHEXA V-40 Compound having Vulkanol OT 2 5 10 20 30 10 10 thioether structure Vulkanol 88 10 Vulkanol 85 10 NOCRAK 400 2 ADEKA STAB AO-412S 2 Carbon black FEF 40 40 40 40 40 40 40 40 40 40 40 Acetylene black Zinc powder Zinc powder Plasticizer RS-735 10 10 Vulcanizing agent Zinc oxide type 2 5 5 5 5 5 5 5 5 5 5 5 Acid acceptor Kyowamag 150 4 4 4 4 4 4 4 4 4 4 4 Vulcanization accelerator NOCCELER TMU Co-crosslinking agent VULNOC PM 2 2 2 2 2 2 2 2 2 1 3 Antioxidant NOCRAK CD 3 3 3 3 3 3 3 3 3 3 3 Lubricant/Processing aid Stearic acid 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Evaluation Oil resistance B B B B B B B B B B B Heat resistance D D C C C C C D D C C Compression set resistance A A A A A A A A A B A

TABLE-US-00002 TABLE 2 Example 12 13 14 15 16 17 18 19 20 21 22 Composition Chloroprene-based Chloroprene-based rubber 100 (Parts by rubber composition composition mass) (AN5%) Chloroprene-based rubber 100 100 100 100 100 100 100 composition (AN10%) Chloroprene-based rubber 100 composition (AN15%) Chloroprene-based rubber 100 composition (AN20%) Mercaptan-modified 100 Chloroprene rubber Organic peroxide PERBUTYL P-40 1 1 1 1 2 5 1 1 1 1 PERHEXA V-40 1 Compound having Vulkanol OT 10 10 10 10 10 10 10 10 10 10 10 thioether structure Vulkanol 88 Vulkanol 85 NOCRAK 400 ADEKA STAB AO-412S 2 Carbon black FEF 40 40 40 40 40 40 40 40 40 Acetylene black 35 35 Zinc powder Zinc powder 5 Plasticizer RS-735 Vulcanizing agent Zinc oxide type 2 5 5 5 5 5 5 5 5 5 5 5 Acid acceptor Kyowamag 150 4 4 4 4 4 4 4 4 4 4 4 Vulcanization accelerator NOCCELER TMU Co-crosslinking agent VULNOC PM 2 2 2 2 2 2 2 2 Antioxidant NOCRAK CD 3 3 3 3 3 3 3 3 3 3 3 Lubricant/Processing aid Stearic acid 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Evaluation Oil resistance B B B B B B B C B A E Heat resistance B C B A C C D C C C C Compression set resistance A A A B C B B A A A B

TABLE-US-00003 TABLE 3 Comparative Example 1 2 3 4 Composition Chloroprene-based Chloroprene-based rubber (Parts by rubber composition composition mass) (AN5%) Chloroprene-based rubber 100 100 100 100 composition (AN10%) Chloroprene-based rubber composition (AN15%) Chloroprene-based rubber composition (AN20%) Mercaptan-modified Chloroprene rubber Organic peroxide PERBUTYL P-40 1 1 15 Compound having Vulkanol OT 10 50 10 thioether structure Carbon black FEF 50 40 40 40 Acetylene black Zinc powder Zinc powder Plasticizer RS-735 10 Vulcanizing agent Zinc oxide type 2 5 5 5 5 Acid acceptor Kyowamag 150 4 4 4 4 Vulcanization accelerator NOCCELER TMU 1 Co-crosslinking agent VULNOC PM 2 2 Antioxidant NOCRAK CD 3 3 3 3 Lubricant/Processing aid Stearic acid 0.5 0.5 0.5 0.5 Evaluation Oil resistance B B B Heat resistance D F F Compression set resistance E A B  could not be molded