Reprocessable vulcanized chloroprene rubber and method for producing the same

Abstract

The application discloses vulcanized neoprene rubber capable of being repeatedly processed and a preparation method thereof, and the preparation method comprises the following steps: mixing a vulcanizing agent containing both a disulfide bond and a nitrogen atom with neoprene uniformly, and then performing vulcanization crosslinking by heating, so that the vulcanized neoprene rubber capable of being repeatedly processed is obtained. The disulfide bond in the crosslinking unit can be exchanged at high temperature, so that the vulcanized neoprene rubber is endowed with the characteristic of being capable of being repeatedly processed at high temperature. The prepared vulcanized neoprene rubber is excellent in original mechanical properties and reprocessing mechanical properties. In addition, no metal oxide is used for vulcanization in the application, so that the color interference of the metal oxide and the environmental pollution problem are avoided, and the green and sustainable development concept of rubber materials is met. The preparation method is convenient to process and safe to operate, and is suitable for the processing of existing general rubber processing equipment. The vulcanized neoprene rubber of the application can be used for improving the repeatedly processing performance of sulfur-regulated neoprene rubber and mercaptan-regulated neoprene rubber, and the application range is wider.

Description

Technical Field

[0001] This invention relates to vulcanized chloroprene rubber, and more specifically, to a reprocessable vulcanized chloroprene rubber and its preparation method. Background Technology

[0002] Chloroprene rubber (CR) is a synthetic rubber produced using 2-chlorobutadiene as a monomer. It appears as milky white, beige, or light brown sheets or blocks. Due to the polar interactions along the polymer chains of chloroprene rubber, it possesses not only the basic properties of ordinary rubber but also a series of superior properties, such as high strength, high resilience, and a wide operating temperature range. It also exhibits excellent comprehensive characteristics including solvent resistance, wear resistance, flame retardancy, and aging resistance. Chloroprene rubber comes in many varieties, which can be divided into general-purpose and special-purpose types according to their applications. General-purpose types (mainly including sulfur-modified and mercaptan-modified types) are generally used for various oil-resistant and weather-resistant industrial products, such as conveyor belts, sealing components, and wires and cables. Special-purpose types are mainly used as adhesives and in various latexes.

[0003] Due to the strong polarity of the high molecular weight chains in chloroprene rubber, traditional sulfur vulcanization is inefficient. Currently, chloroprene rubber is typically vulcanized using a compound of zinc oxide and magnesium oxide (metal oxides), along with vulcanization accelerators to further improve the vulcanization speed and effective crosslinking point density. In existing technologies, imidazole compounds, peroxides, and trithiocyanate are also used in chloroprene rubber vulcanization systems. However, the vulcanized rubber produced by these technologies is difficult to reprocess, and the metal oxides used in processing increase the risk of environmental pollution, hindering the green and circular application of rubber materials. Furthermore, with industrial development and the widespread use of chloroprene rubber, the operating environment of chloroprene rubber products is becoming more complex, placing higher demands on the applicability of reprocessable chloroprene rubber.

[0004] Therefore, it is essential to develop a reprocessable, environmentally friendly, and widely applicable vulcanized chloroprene rubber. Summary of the Invention

[0005] To address the problem of the difficulty in reprocessing vulcanized chloroprene rubber in existing technologies, this invention provides a reprocessable vulcanized chloroprene rubber and its preparation method. The vulcanizing agents provided in this invention all contain disulfide bond structural units, and the three-dimensional network nodes of the vulcanized chloroprene rubber all contain disulfide bonds. This method utilizes the exchangeable property of disulfide bonds in the crosslinking units at high temperatures, resulting in vulcanized chloroprene rubber that is reprocessable under high-temperature conditions.

[0006] To achieve the above objectives, the present invention provides a method for preparing reprocessable vulcanized chloroprene rubber, the method comprising the following steps: mixing a vulcanizing agent containing both disulfide bonds and nitrogen atoms with chloroprene rubber, followed by heating for vulcanization crosslinking, thereby obtaining the reprocessable vulcanized chloroprene rubber.

[0007] In chloroprene rubber, the carbon atoms in the allyl chloride groups carry a partial positive charge, and the lone pair electrons of the nitrogen atoms in aliphatic or aromatic vulcanizing agents undergo a nucleophilic reaction, resulting in cross-linking.

[0008] Specifically, the vulcanizing agent is one or more of 4,4'-bipyridine disulfide, 2,2'-bipyridine disulfide, 3,3'-dithiodimethylbis(pyridine-2-amine), pyrithiol, KAT5 (Tip60) inhibitor, 2,2'-dithiobisthiazole, 2,2'-dithiobis(4-methylthiazole), dibenzothiazole disulfide, 8,8'-quinolinyl disulfide, 4,4'-dithiodiphenylamine, 2,2'-dithiodiphenylamine, and 3,3'-dithiodiphenylamine. See the specific structural formula for details. Figure 1 .

[0009] Specifically, the mass ratio of the vulcanizing agent to the chloroprene rubber is (0.5-10):100.

[0010] Specifically, chloroprene rubber is mixed with a vulcanizing agent after thin-passing, the temperature of which is 40-60℃ and the number of passes is 3-6.

[0011] Furthermore, after the vulcanizing agent is added to the chloroprene rubber, it is subjected to a second thin pass at a temperature of 40–60°C, and the number of passes is 3–6.

[0012] Specifically, the conditions for the vulcanization crosslinking are: temperature 140–200°C, time 5–30 min.

[0013] Specifically, the method of repeated processing is as follows: repeated processing is carried out by hot pressing at 160-200°C for 10-20 minutes.

[0014] Furthermore, the pressure of the hot pressing is 3 to 10 MPa.

[0015] Furthermore, before hot pressing, the vulcanized chloroprene rubber is pulverized into particles with a particle size greater than 50 mesh.

[0016] In another aspect, the present invention provides a reprocessable vulcanized chloroprene rubber prepared by the above-described preparation method.

[0017] Through the above technical solution, the present invention achieves the following beneficial effects:

[0018] 1. Compared with existing chloroprene rubber vulcanization methods, this invention utilizes the exchangeable disulfide bonds in the crosslinking unit at high temperatures to endow vulcanized chloroprene rubber with reprocessable properties under high temperature conditions. The prepared vulcanized chloroprene rubber has excellent original mechanical properties and reprocessing mechanical properties.

[0019] 2. Compared with existing chloroprene rubber vulcanization methods, this invention does not use metal oxides for vulcanization, thus avoiding the color interference and environmental pollution problems caused by metal oxides, and conforming to the concept of green and sustainable development of rubber materials.

[0020] 3. The method for preparing reprocessable vulcanized chloroprene rubber proposed in this invention is convenient to process and safe to operate, and is applicable to the processing of existing general rubber processing equipment; this invention can be used to improve the reprocessability of both sulfur-modified and mercaptan-modified chloroprene rubber, making it more widely applicable. Attached Figure Description

[0021] Figure 1 This is a commonly used crosslinking agent structure containing disulfide bonds;

[0022] Figure 2 It is a crosslinking reaction formula containing a disulfide group vulcanizing agent and chloroprene rubber. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Unless otherwise specified, all reagents used in the following examples are commercially available products.

[0025] Example 1

[0026] Preparation method of reprocessable vulcanized chloroprene rubber:

[0027] (1) 100g of chloroprene rubber was passed through a two-roll mill three times at a temperature of 40°C. Then 0.5g of 4,4'-bipyridine disulfide was added and passed through the two-roll mill six times at a temperature of 60°C to obtain a mixed rubber compound.

[0028] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 140°C and the time is 30 minutes to obtain the reprocessable vulcanized chloroprene rubber.

[0029] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0030] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0031] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 50-mesh sieve. The material passing through the sieve was hot-pressed at 160℃ and 3MPa pressure for 10 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0032] Example 2

[0033] Preparation method of reprocessable vulcanized chloroprene rubber:

[0034] (1) 100g of chloroprene rubber was passed through a two-roll mill 6 times at a temperature of 60°C. Then 10g of 2,2'-bipyridine disulfide was added and passed through the two-roll mill 3 times at a temperature of 40°C to obtain a mixed rubber compound.

[0035] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment at a temperature of 200°C for 5 minutes to obtain the reprocessable vulcanized chloroprene rubber. The crosslinking reaction process is as follows: Figure 2 As shown, the carbon atoms in the allyl chloride group of the chloroprene rubber molecular chain carry a partial positive charge, and the lone pair electrons of the nitrogen atom in the pyridine group of the vulcanizing agent undergo a nucleophilic reaction to generate quaternary ammonium salt and thus crosslink.

[0036] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0037] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0038] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 100-mesh sieve. The material passing through the sieve was hot-pressed at 200°C and 10MPa for 20 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0039] Example 3

[0040] Preparation method of reprocessable vulcanized chloroprene rubber:

[0041] (1) 100g of chloroprene rubber was passed through a two-roll mill 4 times at a temperature of 50°C. Then 2g of 3,3'-dithionylbis(pyridine-2-amine) was added and passed through the two-roll mill 4 times again at a temperature of 42°C to obtain a mixed rubber compound.

[0042] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 150°C and the time is 10 min to obtain the reprocessable vulcanized chloroprene rubber.

[0043] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0044] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0045] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 60-mesh sieve. The material passing through the sieve was hot-pressed at 170°C and 3MPa for 12 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0046] Example 4

[0047] Preparation method of reprocessable vulcanized chloroprene rubber:

[0048] (1) Pass 100g of chloroprene rubber through a two-mill 5 times at a temperature of 42°C, then add 1g of pyrithione and pass it through the two-mill 5 times again at a temperature of 55°C to obtain a mixed rubber compound.

[0049] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 160°C and the time is 15 minutes to obtain the reprocessable vulcanized chloroprene rubber.

[0050] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0051] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0052] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 70-mesh sieve. The material passing through the sieve was hot-pressed at 180°C and 6MPa for 16 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0053] Example 5

[0054] Preparation method of reprocessable vulcanized chloroprene rubber:

[0055] (1) Pass 100g of chloroprene rubber through a two-mill three times at a temperature of 50°C. Then add 5g of KAT5 (Tip60) inhibitor and pass through it again six times at a temperature of 60°C to obtain a mixed rubber compound.

[0056] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 170°C and the time is 20 min to obtain the reprocessable vulcanized chloroprene rubber.

[0057] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0058] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0059] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through an 80-mesh sieve. The material passing through the sieve was hot-pressed at 180°C and 4MPa for 17 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0060] Example 6

[0061] Preparation method of reprocessable vulcanized chloroprene rubber:

[0062] (1) 100g of chloroprene rubber was passed through a two-mill 4 times at a temperature of 52°C. Then 8g of 2,2'-dithiobisthiazole was added and passed through the two-mill 5 times again at a temperature of 48°C to obtain a mixed rubber compound.

[0063] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 180°C and the time is 25 minutes to obtain the reprocessable vulcanized chloroprene rubber.

[0064] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0065] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0066] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 50-mesh sieve. The material passing through the sieve was hot-pressed at 185°C and 7MPa for 18 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0067] Example 7

[0068] Preparation method of reprocessable vulcanized chloroprene rubber:

[0069] (1) 100g of chloroprene rubber was passed through a two-roll mill 5 times at a temperature of 56°C. Then 7g of 2,2'-disulfidebis(4-methylthiazole) was added and passed through the two-roll mill 3 times again at a temperature of 45°C to obtain a mixed rubber compound.

[0070] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 190°C and the time is 30 minutes to obtain the reprocessable vulcanized chloroprene rubber.

[0071] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0072] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0073] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 90-mesh sieve. The material passing through the sieve was hot-pressed at 190℃ and 10MPa pressure for 19 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0074] Example 8

[0075] Preparation method of reprocessable vulcanized chloroprene rubber:

[0076] (1) 100g of chloroprene rubber was passed through a two mill 6 times at a temperature of 60°C. Then, 6g of dibenzothiazole disulfide was added and passed through the two mill 4 times again at a temperature of 55°C to obtain a mixed rubber compound.

[0077] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 145°C and the time is 20 min to obtain the reprocessable vulcanized chloroprene rubber.

[0078] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0079] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0080] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 70-mesh sieve. The material passing through the sieve was hot-pressed at 195°C and 8MPa for 12 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0081] Example 9

[0082] Preparation method of reprocessable vulcanized chloroprene rubber:

[0083] (1) 100g of chloroprene rubber was passed through a two-mill 5 times at a temperature of 45°C. Then 9g of 8,8'-quinolinyl disulfide was added and passed through the two-mill 3 times again at a temperature of 48°C to obtain a mixed rubber compound.

[0084] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 155°C and the time is 25 min, thus obtaining the reprocessable vulcanized chloroprene rubber.

[0085] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0086] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0087] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 60-mesh sieve. The material passing through the sieve was hot-pressed at 160℃ and 9MPa pressure for 13 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0088] Example 10

[0089] Preparation method of reprocessable vulcanized chloroprene rubber:

[0090] (1) 100g of chloroprene rubber was passed through a two-roll mill 4 times at a temperature of 48°C. Then 1.5g of 4,4'-dithiodiphenylamine and 1.5g of 2,2'-dithiodiphenylamine were added and passed through the two-roll mill 6 times again at a temperature of 56°C to obtain a mixed rubber compound.

[0091] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 160°C and the time is 10 min to obtain the reprocessable vulcanized chloroprene rubber.

[0092] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0093] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0094] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through an 80-mesh sieve. The material passing through the sieve was hot-pressed at 165°C and 6MPa for 11 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0095] Example 11

[0096] Preparation method of reprocessable vulcanized chloroprene rubber:

[0097] (1) 100g of chloroprene rubber was passed through a two-roll mill three times at a temperature of 52°C. Then, 1g of 3,3'-dithiodiphenylamine, 2g of 4,4'-bipyridine disulfide and 1g of pyrithiol were added and passed through the two-roll mill five times again at a temperature of 40°C to obtain a mixed rubber compound.

[0098] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 175°C and the time is 6 minutes to obtain the reprocessable vulcanized chloroprene rubber.

[0099] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0100] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0101] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through a 100-mesh sieve. The material passing through the sieve was hot-pressed at 175°C and 5MPa for 14 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0102] Example 12

[0103] Preparation method of reprocessable vulcanized chloroprene rubber:

[0104] (1) 100g of chloroprene rubber was passed through a two-roll mill 6 times at a temperature of 55°C. Then 2.5g of 2,2'-dithiodiphenylamine and 2.5g of 3,3'-dithiodiphenylamine were added and passed through the two-roll mill 4 times again at a temperature of 42°C to obtain a mixed rubber compound.

[0105] (2) The mixed rubber compound obtained in step (1) is heated for vulcanization and crosslinking treatment. The vulcanization temperature is 180°C and the time is 10 min to obtain the reprocessable vulcanized chloroprene rubber.

[0106] The reprocessable vulcanized chloroprene rubber obtained in step (2) above was placed at room temperature for 24 hours and its tensile strength was tested.

[0107] The repeated processing method for vulcanized chloroprene rubber is as follows:

[0108] The vulcanized chloroprene rubber prepared above was cut into small pieces, then mechanically crushed under liquid nitrogen freezing, and then passed through an 80-mesh sieve. The material passing through the sieve was hot-pressed at 185°C and 3MPa for 15 minutes. The above processing was repeated 3 times, and its tensile strength after repeated processing was tested.

[0109] Performance testing

[0110] Repeat processing efficiency (γ) is defined as the tensile strength (σ) of the sample after reprocessing. Recycled ) and the initial tensile strength (σ) prepared by the first vulcanization Virgin The ratio of ) to:

[0111]

[0112] In the formula, σRecycled represents the tensile strength of the recycled sample; σVirgin represents the initial tensile strength of the prepared sample, tested at room temperature with a tensile rate of 500 mm / min. The specific test results of the initial tensile strength and recycle efficiency of vulcanized chloroprene rubber are shown in Table 1.

[0113] Table 1 Test Results

[0114]

[0115]

[0116] As can be seen from Table 1, the initial tensile strength of the reprocessable vulcanized chloroprene rubber prepared in Examples 1 to 12 is 4.8 to 5.8 MPa, and the processing efficiency can still reach more than 68% after three reprocessing cycles. It can be seen that the vulcanized chloroprene rubber prepared by the present invention has excellent reprocessing performance.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing reprocessable vulcanized chloroprene rubber, characterized in that, The process includes the following steps: 4,4'-bipyridine disulfide, 2,2'-bipyridine disulfide, 3,3'-dithiodimethylbis(pyridine-2-amine), pyrithiol, KAT5 (Tip60) inhibitor, 8,8'-quinolinyl disulfide, 4,4'-dithiodiphenylamine, 2,2'-dithiodiphenylamine, and 3,3'-dithiodiphenylamine are mixed evenly with chloroprene rubber at a mass ratio of (0.5~10):

100. The mixture is then subjected to vulcanization and crosslinking at 140~200℃ for 5~30 min to obtain the reprocessable vulcanized chloroprene rubber. The reprocessing method involves hot pressing at 160~200℃ for 10~20 min.

2. The preparation method according to claim 1, characterized in that, After passing through a thin tube, the chloroprene rubber is mixed with a vulcanizing agent. The temperature of the thin tube is 40~60℃, and the number of passes is 3~6.

3. The preparation method according to claim 2, characterized in that, After the vulcanizing agent is added to the chloroprene rubber, it is subjected to a second thin pass at a temperature of 40~60℃, and the number of passes is 3~6.

4. The preparation method according to claim 1, characterized in that, The pressure of the hot pressing is 3 to 10 MPa.

5. The preparation method according to claim 1, characterized in that, Before hot pressing, the vulcanized chloroprene rubber is crushed into particles with a particle size greater than 50 mesh.

6. A reprocessable vulcanized chloroprene rubber, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 5.

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