JP2000044605A - Plasticizing of cross-linked hydrogenated nbr - Google Patents

Abstract

PROBLEM TO BE SOLVED: To plasticize a cross-linked hydrogenated NBR without damaging the quality of a simple virgin rubber substance even if the virgin rubber is mixed with the NBR, at a low cost to provide a recycled rubber useful as a sealing material or the like by adding hydrogen peroxide thereto and subjecting the added product to a pressurizing and heating treatment. SOLUTION: (B) Hydrogen peroxide is added to (A) a cross-linked butadiene- acrylonitrile rubber (NBR), and the added product is subjected to a pressurizing and heating treatment. Preferably, a mechanical shear force is added to the treated product to provide the objective recycled rubber. For example, the pressurizing and heating treatment is carried out under 2-50 kg/cm2 pressure at 100-200 deg.C for 5-48 hr by using 35% hydrogen peroxide as the component B in an amount of 20-100 pts.wt. based on the component A of 100 pts.wt. The recycled rubber can be cross-linked by the method the same as the one for a virgin rubber because the recycled rubber thus obtained does not include the components inhibiting a cross-linking reaction. When the recycled rubber is mixed with the virgin rubber the mixture provides a cross-linked product having vulcanized properties and thermal stability not inferior to these of the cross-linked product of the single virgin rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a crosslinked hydrogenated NBR.
A plasticizing method. More specifically, the present invention relates to a method for plasticizing crosslinked hydrogenated NBR that provides a reclaimed rubber that can withstand practical use.

[0002]

2. Description of the Related Art Open steam method (bread method), digester method (digestion method), mechanical method (mechanical method), UHF heat desulfurization method and the like are conventionally known for regenerating vulcanized scrap rubber. In these methods, desulfurization cans, digesters, reclaimers, supermixers, UHF heat treatment equipment and the like are used. Since the treatment is performed under high-temperature or high-pressure conditions, not only enormous energy consumption is required but also stimulation is required. There is also a great demand for improved working environments such as odors and high temperatures.

[0003] In other words, in the method of plasticizing and regenerating vulcanized rubber, a regenerative treatment agent such as a peptizer (a chemical softener acting to cut molecules; peptizer), oil or the like is used, and high temperature and high pressure treatment is performed. Irritating odor in the regenerating process, and when the obtained reclaimed rubber is mixed with virgin rubber, the incorporation of a regenerating agent cannot be avoided. As a result, the use of the rubber material mixed with the recycled rubber is limited.

[0004] In addition, objects to plasticize and regenerate vulcanized rubber are often used tires, and these include natural rubber and sulfur.
Sulfur vulcanized rubber such as BR is generally used as a plasticizing method for hydrogenated NBR which is peroxide-crosslinked.
Each of the above methods is not an appropriate method. In addition, hydrogenated N
BR is expensive in itself, and its effective use of crosslinked rubber waste is an important issue from the viewpoint of cost reduction and environmental problems.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for plasticizing crosslinked hydrogenated NBR which can effectively use a recycled rubber obtained by plasticizing. To provide.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Hydrogen peroxide is added to the crosslinked hydrogenated NBR, heat-treated under pressure, and preferably achieved by a method of plasticizing the crosslinked hydrogenated NBR by applying a mechanical shear force.

[0007]

DETAILED DESCRIPTION OF THE INVENTION Crosslinked hydrogenated NB to be plasticized
R is a hydrogenated NBR obtained by crosslinking an organic peroxide or sulfur. As the hydrogenated NBR, an NBR having an unsaturated bond amount in the molecular main chain of about 30% or less, preferably about 10% or less. Hydride whose Mooney viscosity ML _{1 + 4} (100
C.) of about 50 to 85 is generally used, but those of 100 or more can also be used.

The actual objects to be treated are burrs, debris, defective molded products, etc. when vulcanized and molded. If pulverized in advance before the plasticizing treatment, not only the handleability is improved but also the plasticization is improved. This is preferable because the time required for the above can be reduced.

As the hydrogen peroxide used for the plasticizing treatment, a hydrogen peroxide having a concentration of about 3 to 40% is used, and 35% aqueous hydrogen peroxide is generally used. In the case of 35% hydrogen peroxide, it is about 10 parts by weight or more per 100 parts by weight of cross-linked hydrogenated NBR,
It is preferably used in a proportion of about 20 to 100 parts by weight. If the amount of aqueous hydrogen peroxide is less than this, it is necessary to extend the plasticization time, while if used at a higher ratio,
Although the plasticization time can be shortened, the amount of water contained in the reclaimed rubber increases, and it takes time to dry it. A similar tendency is observed for the concentration of the hydrogen peroxide solution.

[0010] Hydrogen peroxide is decomposed into water and active oxygen by a heat treatment, and in the process, cross-linked hydrogenated NBR is decomposed.
Plasticize and soften. This plasticizing treatment with aqueous hydrogen peroxide is performed under pressure and heating conditions. Pressurization is carried out by using a closed container such as an autoclave and heating it to be used under pressure. The pressure in the sealed container increases as the amount of the used hydrogen peroxide solution increases, but the pressure is 5 kg / cm ²
Can be sufficiently plasticized, generally about 2-5
A pressure of 0 Kg / cm ² is applied. Heating conditions are about 100-200
C. for about 5-48 hours, preferably about 120-180 ° C. for about 10-24
The heating time can be shortened by increasing the heating temperature.

If the rubber contains a large amount of water after the plasticizing treatment, a mechanical dehydration treatment or a drying treatment in a constant temperature bath or an oven is performed. When not including much water, it can be used as it is without performing the water removal treatment.

It is preferable to apply mechanical shearing to the rubber after the plasticizing treatment by using a roll, an extruder or the like.
As a roll, a refiner roll having a high carbon chromium bearing steel drilled structure is preferably used, and as an extruder, a twin screw extruder is preferably used. When such a mechanical shear force is applied, a plasticized and softened reclaimed rubber having a smooth surface can be obtained.

In the thus obtained recycled rubber,
Because it does not contain components that inhibit the crosslinking reaction,
By newly adding a cross-linking agent or a cross-linking accelerator such as an organic peroxide thereto, re-cross-linking can be performed in the same manner as in virgin rubber.

The reclaimed rubber may be mixed with virgin rubber and used, for example, about 5 to 300 parts by weight, preferably about 5 to 150 parts by weight, per 100 parts by weight of virgin rubber. Compared with a crosslinked product obtained from virgin rubber alone, a crosslinked product having no inferiority in vulcanizate properties and heat resistance can be obtained.

[0015]

The cross-linked hydrogenated NBR, particularly peroxide cross-linked hydrogenated NBR, is difficult to plasticize with a regenerating agent such as a peptizing agent or oil. The compounding composition of rubber changes before and after, and the properties such as physical properties change when virgin rubber is mixed with recycled rubber, and depending on the required quality of rubber products, it may not be possible to increase the mixing ratio of recycled rubber. Even if the recycled rubber obtained by the method is mixed with virgin rubber and crosslinked, the same quality as that of virgin rubber alone can be maintained. This not only expands the range of applications of the recycled rubber, but also achieves effective waste utilization and cost reduction.

The application of the recycled rubber is not limited to a molding material for a sealing material such as an O-ring and a packing, but can be applied to various applications where hydrogenated NBR is generally used.

[0017]

Next, the present invention will be described with reference to examples.

Example 1 Hydrogenated NBR (Zepol 1020 manufactured by Nippon Zeon) 100 parts by weight SRF carbon black 30 亜 鉛 zinc oxide 5 〃 stearic acid 0.5 〃 1,2-polybutadiene (MW2000) 2 〃 adipic acid ether ester plasticizer (Viscosity 20cps) 5 〃 Diphenylamine anti-aging agent 1.5 〃 Imidazole anti-aging agent 1.5 〃 Dicumyl peroxide 8 を Knead each of the above components using 3L kneader and open roll, 180 ° C for 6 minutes Press vulcanization, vulcanizing burrs with a roll spacing of 0.1 mm and a roll temperature of 4
The mixture was passed through a 10-inch type refiner roll machine adjusted to 0 ° C. about 10 times, and coarsely pulverized.

After adding 40 parts by weight of 35% aqueous hydrogen peroxide to 100 parts by weight of the coarsely ground crosslinked hydrogenated NBR, the mixture was placed in an autoclave and subjected to a heat treatment at 150 ° C. for 15 hours. After the heat treatment, the autoclave is opened and air-cooled or water-cooled.

The rubber that has been plasticized in this manner is dried for 15 minutes in a thermostat at 120 ° C.
0.1mm, passed through a 10-inch refiner roll machine adjusted to a roll temperature of 40 ° C 20 times, then wound around the roll,
The mixture was turned over for 5 minutes and kneaded. As a result of performing dispensing with a roll interval of 1 mm, a reclaimed rubber sheet having the same surface condition as the virgin rubber sheet was obtained.
The irritating odor of this recycled rubber sheet was small.

When the lowest torque value of the rheometer ODR (180 ° C.) was measured to evaluate the degree of plasticization of the obtained recycled rubber, a value of 11 kgf · cm was obtained.

Also, 43.5 parts by weight of virgin rubber
0 parts by weight or 80 parts by weight of the reclaimed rubber was compounded, kneaded, and press vulcanized (180 ° C, 6 minutes), and measured for normal physical properties and air aging test (normal physical properties after 120 ° C, 70 hours) Change) and obtained the following results. Measurement and test items Virgin rubber recycled rubber 40 parts Recycled rubber 80 parts [Normal physical properties] Hardness (JIS A) 75 77 78 Tensile strength (MPa) 22.8 24.7 24.5 Elongation (%) 238 236 246 [Air aging test] Hardness Change (points) +7 +5 +6 Tensile strength change (%) +12 +10 +16 Elongation change (%) -10 -15 -15

Example 2 In Example 1, the heat treatment conditions in the autoclave were changed to 120 ° C. and 15 hours. The irritating odor of the reclaimed rubber sheet was small, and the minimum torque value of the ODR (180 ° C.) was 40 kgf · cm.

Example 3 In Example 1, the heat treatment conditions in the autoclave were changed to 150 ° C. and 5 hours. The stimulated odor of the recycled rubber sheet was small, and the minimum torque value of the ODR (180 ° C.) was 25 kgf · cm.

Example 4 Hydrogenated NBR (Zetpol 1020) 100 parts by weight FEF carbon black 40 亜 鉛 zinc oxide 5 〃 stearic acid 0.5 〃 diphenylamine-based antioxidant 1.5 〃 sulfur 0.5 0.5 thiuram-based vulcanization accelerator (Ouchi Shinko Chemical product Noxeller TRA) 0.7 チ Thiuram-based vulcanization accelerator (Noxeller TT) 0.7 〃 Thiazole-based vulcanization accelerator (Noxeller M) 0.5 しAfter press vulcanization at 14 ° C. for 14 minutes, pulverization, pressure heating and kneading with a refiner roll were carried out under the same conditions as in Example 1 below. Regenerated rubber sheet has low irritating odor,
The minimum torque value of R (180 ° C.) was 15 kgf · cm.

Comparative Example 1 To 100 parts by weight of the coarsely ground crosslinked hydrogenated NBR of Example 1 was added 40 parts by weight of a torque resin phosphate plasticizer, and the same plasticizing treatment as in Example 1 was performed. The surface of the obtained reclaimed rubber sheet had irregularities, and the reclaimed rubber had a large irritating odor. It was impossible to measure the ODR (180 ° C.) minimum torque value.

Comparative Example 2 In Comparative Example 1, a mixed diallyl disulfide peptizer (Seiko Chemical's MR-906) was further used.
Only similar results were obtained.

Comparative Example 3 In Comparative Example 1, the same amount of distilled water was used instead of tricresyl phosphate. The irregularities on the surface of the obtained recycled rubber sheet were large, but the irritating odor of the recycled rubber was small. It was impossible to measure the ODR (180 ° C.) minimum torque value.

Comparative Example 4 In Example 1, the heat treatment with the addition of aqueous hydrogen peroxide was not performed. The irregularities on the surface of the obtained recycled rubber sheet were large, but the irritating odor of the recycled rubber was small. Note that O
It was not possible to measure the DR (180 ° C.) minimum torque value.

Claims (3)

[Claims] 1. Crosslinked hydrogenated NB characterized by adding hydrogen peroxide to crosslinked hydrogenated NBR and subjecting it to pressure and heat treatment.
R plasticization method. 2. The method for plasticizing crosslinked hydrogenated NBR according to claim 1, wherein a mechanical shearing force is applied after the heat treatment under pressure. 3. A hydrogenated NBR mixture obtained by mixing regenerated hydrogenated NBR plasticized by the method according to claim 1 or 2 with virgin hydrogenated NBR.