JPWO2011010615A1 - Halogen-containing acrylic rubber composition and vulcanized product thereof - Google Patents

Abstract

[PROBLEMS] To realize a substitute for a vulcanization accelerator that does not generate carcinogenic nitrosamine in a vulcanization system that uses trithiocyanuric acid as a vulcanizing agent, and has excellent scorch stability and vulcanization. To provide a halogen-containing acrylic rubber composition capable of obtaining a vulcanizate having a high speed and excellent compression set. In a halogen-containing acrylic rubber composition containing a halogen-containing acrylic rubber, a vulcanizing agent containing a sulfur donor compound, and a vulcanization accelerator, trithiocyanuric acid is used as the vulcanizing agent, and the vulcanization accelerator is used. Using calcium hydroxide, 0.1 to 3.0 parts by weight of trithiocyanuric acid and 0.1 to 9 parts by weight of calcium hydroxide per 100 parts by weight of the halogen-containing acrylic rubber. [Selection figure] None

Description

  The present invention relates to a halogen-containing acrylic rubber composition and a vulcanized product thereof, and more specifically, a vulcanization accelerator having excellent scorch stability, high vulcanization speed, excellent compression set characteristics, and no generation of carcinogenic nitrosamines. The present invention relates to a halogen-containing acrylic rubber composition and a vulcanized product thereof.

  In the conventional halogen-containing acrylic rubber composition, when the halogen-containing acrylic rubber is to be crosslinked with trithiocyanuric acid, it contains a dithiocarbamate metal salt and thiuram sulfide as in Patent Document 1 and Patent Document 2, and is within a preferable range. By blending, vulcanization speed, scorch stability, and mechanical properties such as tensile strength and compression set (CS) have been satisfied.

  At this time, in order to crosslink the halogen-containing acrylic rubber with trithiocyanuric acid, a compound composed of a secondary amine is generally used as a vulcanization accelerator from the viewpoint of physical properties and vulcanization speed.

  However, when a vulcanization accelerator composed of secondary amine is used, nitrogen oxide generated during vulcanization or nitrogen oxide remaining in rubber reacts with secondary amine, and nitrosodimethylamine, which is a carcinogenic substance, is produced. appear.

  As vulcanization accelerators that generate nitrosamines, there are thiazole, sulfenamide, thiuram, and dithiocarbamate, and among these, 2- (N, N- And diethylthiocarbamoylthio) benzothiazole, N-oxydiethylene-2-benzothiazolylsulfenamide, tetramethylthiuram disulfide, zinc diethyldithiocarbamate and the like.

  On the other hand, Patent Document 3 discloses a vulcanization system comprising sulfur or a sulfur donor compound and a higher fatty acid metal salt for vulcanization of a halogen-containing acrylic rubber. Examples of sulfur-donating compounds include 2,4,6-trimercaptotriazine and polymer sulfur.

  The higher fatty acid metal salt is a compound known as a vulcanization accelerator. Patent Document 3 discloses as a higher fatty acid metal salt, for example, sodium stearate, potassium stearate, potassium myristate, sodium palmitate, calcium stearate. , Magnesium stearate, sodium oleate, potassium oleate, barium oleate.

  When the higher fatty acid metal salt of Patent Document 3 is used as a vulcanization accelerator, nitrosamine is not generated.

JP-A-2-173149 JP-A-9-328596 Japanese Patent Laid-Open No. 11-181209

  As described above, when a sulfur donor compound such as 2,4,6-trimercaptotriazine is used as a vulcanizing agent, a vulcanization accelerator that does not generate nitrosamine can be selected for the vulcanization system of halogen-containing acrylic rubber. This is an important issue. In Patent Document 3, potassium stearate or sodium stearate is used as a vulcanization accelerator, but the scorch stability (T5) is poor (see Comparative Examples 8 and 9 of this application), and calcium stearate as a vulcanization accelerator. Is used, the vulcanization rate (T90) is slow and the compression set (CS) is inferior (see Comparative Example 10). Moreover, in Comparative Example 8 using potassium stearate as a vulcanization accelerator, a problem of foaming during vulcanization was also confirmed.

  Further, Example 1 of Patent Document 3 is a vulcanization system formulation in which the vulcanizing agent is sulfur and the vulcanization accelerator is sodium stearate. In this case, although there is no problem in the vulcanization speed, compression set ( CS) is considerably inferior (see Comparative Example 7).

  Further, according to experiments by the present inventors, nitrosamine is used in a vulcanization-based formulation using a sulfur donor compound such as 2,4,6-trimercaptotriazine as a vulcanizing agent and zinc diethyldithiocarbamate as a vulcanization accelerator. (Comparative Example 2), when zinc dibenzyldithiocarbamate, tetrabenzyldithiuram sulfide, and tetrakistiuram sulfide are used, the vulcanization rate (T90) is slow and the compression set (CS) Are inferior (Comparative Examples 3, 4, 5).

  Accordingly, the object of the present invention is to realize a substitution of a halogen-containing acrylic rubber with a vulcanization accelerator that does not generate carcinogenic nitrosamine in a vulcanization system using trithiocyanuric acid as a vulcanizing agent, and scorch stability. An object of the present invention is to provide a halogen-containing acrylic rubber composition and a vulcanized product thereof, which can provide a vulcanized product which is excellent in resistance, has a high vulcanization speed and excellent compression set.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

  The invention according to claim 1 is a halogen-containing acrylic rubber composition containing a halogen-containing acrylic rubber, a vulcanizing agent containing a sulfur donor compound, and a vulcanization accelerator, and using trithiocyanuric acid as a vulcanizing agent. Calcium hydroxide is used as a sulfur accelerator, and 0.1 to 3.0 parts by weight of trithiocyanuric acid and 0.1 to 9 parts by weight of calcium hydroxide are contained with respect to 100 parts by weight of the halogen-containing acrylic rubber. This is a halogen-containing acrylic rubber composition.

  The invention according to claim 2 is the halogen-containing acrylic rubber composition according to claim 1, wherein the calcium hydroxide is contained in an amount of 1 to 5 parts by weight with respect to 100 parts by weight of the halogen-containing acrylic rubber. is there.

  The invention described in claim 3 is characterized in that the vulcanized product obtained by vulcanizing the halogen-containing acrylic rubber composition described in claim 1 or 2 has a compression set (%) of less than 30%. Halogen-containing acrylic rubber vulcanizate.

  According to the present invention, the halogen-containing acrylic rubber is replaced with a vulcanization accelerator that does not generate carcinogenic nitrosamine in a vulcanization system using trithiocyanuric acid as a vulcanizing agent, and has excellent scorch stability. It is possible to provide a halogen-containing acrylic rubber composition and a vulcanized product thereof from which a vulcanized product having a high vulcanization rate and excellent compression set can be obtained.

  Embodiments of the present invention will be described below.

<Halogen-containing acrylic rubber>
The halogen-containing acrylic rubber used in the halogen-containing acrylic rubber composition of the present invention is mainly composed of at least one of alkyl acrylate, alkoxyalkyl acrylate, alkylthioalkyl acrylate, cyanoalkyl acrylate and the like (about 60 to 99.8% by weight). Further, an addition reaction product of glycidyl compound such as vinyl chloroacetate, allyl chloroacetate or glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ester and monochloroacetic acid is about 0.1 to 10% by weight, preferably about 1%. A copolymer obtained by copolymerization of ˜5% by weight is used, and other vinyl compounds can be copolymerized within the range of 30% by weight or less in this copolymer.

  Examples of the halogen-containing acrylic rubber include halogen and / or carboxyl group-containing acrylic rubber, for example, unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and maleic acid, and mono-lower alkyl maleates. A copolymer obtained by copolymerizing a saturated dicarboxylic acid monoester in an amount of about 0.1 to 10% by weight, preferably about 1 to 5% by weight is used.

<Vulcanizing agent>
In the present invention, trithiocyanuric acid is used as the vulcanizing agent, and specifically 2,4,6-trimercaptotriazine is used.

  The amount is 0.1 to 3.0 parts by weight, preferably 0.2 to 1.0 parts by weight, based on 100 parts by weight of the halogen-containing acrylic rubber. If it is less than 0.1 parts by weight, the effect as a vulcanizing agent cannot be obtained effectively, and if it exceeds 3.0 parts by weight, the compression set (CS) characteristics and the scorch stability (T5) are significantly impaired.

  In the present invention, the vulcanizing agent is preferably 2,4,6-trimercaptotriazine alone, and when 0.05 part by weight or more of sulfur is used in combination, the compression set (CS) characteristics and the scorch stability (T5) are impaired. No (see Comparative Example 12). When using together sulfur, it is preferable to set it as 0.03 weight part or less.

  In the present invention, sulfur is not employed alone as a vulcanizing agent. This is because the object of the present invention cannot be achieved (Comparative Example 11).

<Vulcanization accelerator>
Calcium hydroxide is effective as a vulcanization accelerator used in the present invention, and should normally be used alone.

  In the present invention, a vulcanization accelerator such as sodium stearate or potassium stearate may be used in combination with calcium hydroxide as long as the effects of the present invention are not impaired. That is, when a very small amount (for example, 0.01 parts by weight or less) of these is added, there is almost no adverse effect on vulcanization characteristics and compression set (CS) characteristics, so when calcium hydroxide is used alone. The same effect can be demonstrated. By adding a very small amount of a vulcanization accelerator other than calcium hydroxide, an effective effect does not occur. On the other hand, when the addition amount is increased, naturally vulcanization characteristics and compression set (CS) characteristics are inferior.

  In the present invention, calcium hydroxide may be solid or liquid, but usually a powder available as a commercial product is preferable.

  Examples of commercially available products include “Caldic # 1000” manufactured by Omi Chemical Co., Ltd.

  The amount of calcium hydroxide added is in the range of 0.1 to 9 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the halogen-containing acrylic rubber. Within such a range, the vulcanization rate (T90) is fast, the scorch stability (T5) is excellent, and the compression set (CS) is excellent.

  When magnesium hydroxide, which is the same alkaline earth metal hydroxide as calcium hydroxide, was used, insufficient vulcanization occurred and it was difficult to obtain a vulcanizate (Comparative Example 6). .

  Further, even when sulfur is used as the vulcanizing agent and calcium hydroxide is used as the vulcanization accelerator, as shown in Comparative Example 11, the vulcanization rate (T90) is slow and the compression set (CS) is inferior, The object of the present invention cannot be achieved.

<Other ingredients>
In the halogen-containing acrylic composition having the above components as essential components, other necessary compounding agents are appropriately blended. Speaking of fillers and reinforcing agents, for example, when used as vulcanized moldings of various sealing materials, carbon black is mainly blended for uses such as O-rings and packings, and white carbon and diatomaceous earth for uses such as oil seals. Etc. are suitably blended, and inorganic silica and the like are blended and used appropriately for the metal laminated parts. As for anti-aging agents, general anti-aging agents such as amines, phenols, and benzimidazoles, and antioxidants are used. Among them, 4 ′, 4′-bis (α, α-dimethylbenzyl) diphenylamine, 2-mercaptobenzimidazole and its zinc salt are used. Regarding processing aids, stearic acid, fatty acid WAXs, and plasticizers such as mineral oil and PAO are used to improve kneadability, improve handling of rubber compounds, and improve mold release during vulcanization molding. .

<Preparation of composition>
The composition is prepared using a sealed kneader such as a pressure kneader or a Banbury mixer or an open kneader such as an open roll, and the vulcanization is generally performed at about 150 ° C. to 250 ° C. at about 1 to 1. 30 minutes is preferable, and it is performed by heat compression such as press vulcanization, injection molding vulcanization, injection molding vulcanization or the like, and if necessary, oven vulcanization or steam at about 150 ° C. to 200 ° C. for about 1 to 24 hours. Vulcanization is performed as secondary vulcanization.

<Physical properties of composition and vulcanizate>
The halogen-containing acrylic rubber composition and the vulcanized product thereof according to the present invention are characterized by having the following characteristics.

  First, the halogen-containing acrylic rubber composition of the present invention is excellent in vulcanization speed. In the present invention, the vulcanization rate was measured at T90 and T5.

  T90 is measured in accordance with JIS K6300-2 by measuring the vulcanization speed at 180 ° C. using a rotorless rheometer, and obtaining the minimum torque ML and the maximum torque MH from the vulcanization curve. The time (minutes) required to reach the% torque value was determined.

  The halogen-containing acrylic rubber composition of the present invention has a T90 of less than 7 minutes, preferably less than 5 minutes.

  T5 was measured according to JIS K6300-1 at 125 ° C. using a Mooney viscometer (L rotor), and the time (minutes) required to increase 5 points (T5) from the lowest value of the Mooney viscometer was measured.

  The halogen-containing acrylic rubber composition of the present invention has a scorch stability (Mooney scorch) T5 of 4 minutes or longer.

  Secondly, the halogen-containing acrylic rubber vulcanizate of the present invention has excellent compression set (CS) characteristics. For the compression set (CS), the test piece was evaluated for compression set (%) after 150 ° C. × 70 hours in accordance with JIS K 6262.

  The halogen-containing acrylic rubber vulcanizate of the present invention has a compression set (CS) (%) of less than 30%.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

Example 1
Active halogen-containing acrylic rubber (Unimatec Co. product Knox tight PA404K) 100 parts by weight, FEF carbon black (Tokai Carbon Co. product SEAST SO, Nitrogen adsorption specific surface ^area: 42m 2 / g, DBP absorption amount (A ^method): 115cm 3 / 100g ) 60 parts by weight, 20 parts by weight of surface-treated natural silica (actifil VM56 manufactured by Hoffman Mineral Co., Ltd.), 2 parts by weight of an amine anti-aging agent (Onouchi Shinko Co., Ltd., product knock rack CD), wax-based processing aid (product of Seiko Chemical Co., Ltd.) Halogen containing 1 part by weight of Santite R, 0.5 part by weight of 2,4,6-trimercaptotriazine (Onouchi Shinsei Co., Ltd. product Noxeller TCA) and 1 part by weight of calcium hydroxide (Ohmi Chemical Co., Ltd. cardic # 1000) Each component of the containing acrylic rubber composition is kneaded with an open roll, 180 ° C., 5 minutes The test piece (22.5 mm × 12.5 mm × 2.0 mm) was produced by press vulcanization of the above and oven vulcanization at 175 ° C. for 15 hours.

<Evaluation>
Table 1 shows the results of evaluation based on the following evaluation methods.

1. Measurement of normal state properties (1) Rubber hardness Hs: Measured with a type A durometer according to JIS K6253.
(2) Tensile strength TB (MPa); compliant with JIS K6251.
(3) Elongation EB (%); compliant with JIS K6251.

2. Compression set (CS)
The test piece (22.5 mm × 12.5 mm × 2.0 mm) was evaluated for compression set (CS) (%) after 150 ° C. × 70 hours (25% compression) in accordance with JIS K 6262. . If the compression set (CS) (%) is less than 30%, it indicates that the compression set (CS) characteristics are excellent.

3. Vulcanization rate characteristics (T90)
For the halogen-containing acrylic rubber composition, in accordance with JIS K6300-2, the vulcanization speed at 180 ° C. is measured using a rotorless rheometer, and the minimum torque ML and the maximum torque MH are obtained from the vulcanization curve. T90 (time (minute) until reaching 90% torque value of maximum torque value) was obtained. If T90 is less than 7 minutes, it is the range of the present invention, and if it is less than 5 minutes, it is a more preferable range.
Evaluation criteria ◎: Less than 5 minutes ○: Less than 7 minutes Δ: Less than 10 minutes ×: More than 10 minutes

4). Scorch stability (T5)
About the above halogen-containing acrylic rubber composition, in accordance with JIS K6300, using a Mooney viscometer (L rotor) at 125 ° C., the time required to increase 5 points (T5) from the minimum value of the Mooney viscometer (minutes) Was measured.
Evaluation criteria ○: 4 minutes or more Δ: 3-4 minutes ×: less than 3 minutes

5. Detection of N-nitrosamine N-nitrosamine is detected by preparing a rubber sheet of 10 mm × 10 mm × 0.5 mm from the above test piece, adsorbing N-nitrosamine gas released from the sheet on an adsorbent, and performing gas chromatography. Detected with. The case where N-nitrosamine was not detected was designated as “-”, and the case where N-nitrosamine was detected was designated as “x”.

Example 2
In Example 1, it evaluated similarly except having changed the compounding quantity of calcium hydroxide into 3 weight part. The results are shown in Table 1.

Example 3
In Example 1, it evaluated similarly except having changed the compounding quantity of calcium hydroxide into 5 weight part. The results are shown in Table 1.

Example 4
In Example 2, instead of FEF carbon (Tokai Carbon Co. product seast SO), special carbon (Asahi Carbon Co., Ltd. product Asahi # 50H, Nitrogen adsorption specific surface area: 20 m ² / g, DBP absorption compared to FEF carbon) the amount (a ^method): 110cm 3 / ^100g) except for using was evaluated in the same manner. The results are shown in Table 1.

Comparative Example 1
In Example 1, it evaluated similarly except not using calcium hydroxide. The results are shown in Table 1.

Comparative Example 2
In Example 1, it evaluated similarly except having used zinc diethyl dithiocarbamate (Ouchi Shinsei Co., Ltd. product Noxeller EZ) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 3
In Example 1, it evaluated similarly except having used zinc dibenzyldithiocarbamate (Ouchi Shinsei Co., Ltd. product Noxeller ZTC) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 4
In Example 1, it evaluated similarly except having used tetrabenzyl thiuram disulfide (Ouchi Shinsei Co., Ltd. product Noxeller TBZTD) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 5
In Example 1, it evaluated similarly except having used tetrakis (2-ethylhexyl) thiuram disulfide (Ouchi Shinsei Co., Ltd. product Noxeller TOT-N) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 6
In Example 1, it evaluated similarly except having used magnesium hydroxide instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 7
In Example 1, the same procedure was performed except that sulfur (colloidal sulfur) was used instead of 2,4,6-trimercaptotriazine, and alkaline soap (sodium stearate) was used instead of calcium hydroxide. And evaluated. The results are shown in Table 1.

Comparative Example 8
In Example 1, it evaluated similarly except having used alkaline soap (potassium stearate) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 9
In Example 1, it evaluated similarly except having used alkali soap (sodium stearate) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 10
In Example 1, it evaluated similarly except having used alkali soap (calcium stearate) instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 11
In Example 1, it evaluated similarly except having used sulfur (colloidal sulfur) instead of 2,4,6-trimercaptotriazine which is a vulcanizing agent. The results are shown in Table 1.

Comparative Example 12
In Example 1, instead of 2,4,6-trimercaptotriazine alone as a vulcanizing agent, 0.45 part by weight of 2,4,6-trimercaptotriazine and 0.05 part by weight of sulfur (colloidal sulfur) were added. Evaluation was performed in the same manner except that it was added together. The results are shown in Table 1.

Comparative Example 13
In Example 1, it evaluated similarly except having changed the compounding quantity of calcium hydroxide into 10 weight part. The results are shown in Table 1.

  In Table 1, Comparative Examples 1 and 6 were partially unmeasurable due to insufficient vulcanization, and Comparative Example 8 was partially unmeasurable due to foaming during vulcanization.

(Evaluation)
When vulcanizing a halogen-containing acrylic rubber using 2,4,6-trimercaptotriazine as a vulcanizing agent, in order to prevent the generation of nitrosamine and obtain a sufficient vulcanization rate while maintaining scorch stability, It turns out that the mixing | blending of calcium oxide is excellent.

  From the result of Comparative Example 11, when sulfur is used instead of 2,4,6-trimercaptotriazine, the vulcanization rate and compression set (CS) (%) are inferior, and therefore cannot be used in the present invention. .

  From the results of Comparative Example 12, when sulfur and 2,4,6-trimercaptotriazine were used in combination, when the amount of sulfur was 0.05 parts by weight, the vulcanization rate and compression set ( CS) (%) is inferior and cannot be used in the present invention. According to the inventors' additional experiments, when the amount of sulfur is 0.05 parts by weight or more, the vulcanization rate and compression set (CS) (%) are the same as in the case of 0.05 parts by weight. However, it was confirmed that it cannot be used in the present invention, and it was confirmed that the effect of the present invention may be exhibited at 0.03 weight or less.

Claims (3)

In a halogen-containing acrylic rubber composition containing a halogen-containing acrylic rubber, a vulcanizing agent containing a sulfur donor compound, and a vulcanization accelerator,
Trithiocyanuric acid is used as a vulcanizing agent, calcium hydroxide is used as a vulcanization accelerator, 0.1 to 3.0 parts by weight of trithiocyanuric acid and 0% of calcium hydroxide with respect to 100 parts by weight of the halogen-containing acrylic rubber. A halogen-containing acrylic rubber composition comprising 1 to 9 parts by weight.   The halogen-containing acrylic rubber composition according to claim 1, wherein the calcium hydroxide is contained in an amount of 1 to 5 parts by weight with respect to 100 parts by weight of the halogen-containing acrylic rubber.   A halogen-containing acrylic rubber vulcanizate, wherein the vulcanized product obtained by vulcanizing the halogen-containing acrylic rubber composition according to claim 1 or 2 has a compression set (%) of less than 30%.