A process for light-assisted vulcanization of liquid polysulfide rubber

Abstract

The invention discloses a process for light-assisted liquid polysulfide rubber vulcanization, comprising the following steps: uniformly mixing liquid polysulfide rubber with a vulcanizing agent, reacting under light conditions, and standing after the reaction is completed to obtain cured polysulfide rubber, wherein the vulcanizing agent consists of delta-type MnO2, an accelerator TMTD, stearic acid and dibutyl phthalate. The invention does not need to change the formula of the vulcanizing agent, does not need to introduce a photosensitizer, takes delta-type MnO2 as a photocatalyst, and generates free radicals excited by photogenerated carriers under light conditions to initiate a polysulfide reaction, and the light excitation and traditional oxidative polysulfide act synergistically to achieve the purpose of rapid polysulfide. The invention can adjust the polysulfide reaction rate by changing the light conditions, and does not affect the final hardness value of the product. Compared with the traditional method of changing the formula of the vulcanizing agent and introducing the photosensitizer, the invention greatly saves construction costs and reduces unnecessary safety issues.

Description

Technical Field

[0001] The invention relates to the technical field of liquid polysulfide rubber vulcanization, and in particular to a process for light-assisted liquid polysulfide rubber vulcanization. Background Art

[0002] Liquid polysulfide rubber is an important special synthetic rubber variety. It can be cured at room temperature with a vulcanizing agent, is easy to use, and has the characteristics of oil resistance, solvent resistance, aging resistance, and excellent air tightness, water tightness and low-temperature flexibility. It has been widely used in aerospace, automotive machinery, construction, shipbuilding, petrochemical industry, electrical instrumentation and other fields, especially in aviation polysulfide rubber seals, which can be used for wing integral fuel tank seals, aircraft electrical component seals, aircraft cabin seals, wing surfaces and edges, fuselage rivet seals, etc.

[0003] Polysulfide sealant is based on liquid polysulfide rubber and can be cured at room temperature with a vulcanizing agent to become an elastic sealing material with good adhesion. The selection of the vulcanizing agent is very important for the sealing performance of polysulfide. The vulcanizing agents used in liquid polysulfide rubber are mostly oxides or peroxides such as ZnO, MnO 2 and Na 2 Cr 2 O 7 As the main components, especially MnO 2 The most widely used. MnO 2 It is an inorganic functional material with excellent performance, environmental friendliness and high technical content. Its molecular formula is MnO 2 , which is oxidizing, can be used as a vulcanizing agent to react with the reducing -SH in the liquid polysulfide rubber to form a disulfide bond (-SS-), so that the liquid polysulfide rubber is vulcanized to form an elastomer. The basic reaction mechanism of the thiol-terminated liquid polysulfide rubber and manganese dioxide is shown in the following chemical reaction formula:

[0004] 4R-SH+MnO 2 →RS-Mn-S-R+RSS-R+2H 2 O

[0005] RS-Mn-S-R+MnO 2 →RSS-R+2MnO

[0006] The performance of manganese dioxide has an important influence on the construction technology, aging resistance, mechanical properties and other properties of liquid polysulfide rubber.

[0007] Traditional liquid polysulfide rubber needs to add vulcanizing agent, and after mixing, it needs to wait for vulcanization in the air. The active period, non-stick period and vulcanization time are relatively long, the engineering efficiency is low, and it cannot meet the special needs of rapid polysulfide sealing. Changing the vulcanizing agent formula can increase the polysulfide speed, but it will bring problems such as cost and difficulty in reaction control. Light energy is a clean energy. If light is introduced into the polysulfide sealing system, the polysulfide sealing speed will be accelerated. Under ultraviolet light, free radical photoinitiators can quickly cure polysulfide. However, the cost of photosensitizers is relatively high, the degree of curing may not be enough, and the residual photoinitiator and photolysis products will transfer to the surface of the cured product, causing yellowing and aging, and will also produce certain toxicity and odor, limiting its further development. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a process for light-assisted liquid polysulfide rubber vulcanization to solve the technical problems existing in the prior art that the vulcanization rate is difficult to control, the cost is high, and the safety is difficult to ensure.

[0009] In order to achieve the above object, the present invention adopts the following technical scheme:

[0010] A process for light-assisted liquid polysulfide rubber vulcanization comprises the following steps: uniformly mixing the liquid polysulfide rubber with a vulcanizing agent, reacting under light conditions, and standing the mixture after the reaction is completed to obtain a cured polysulfide rubber, wherein the vulcanizing agent is a δ-type MnO 2 , accelerator TMTD, stearic acid and dibutyl phthalate.

[0011] Preferably, the mass ratio of the liquid polysulfide rubber to the vulcanizing agent is 10-15:1.

[0012] Preferably, the δ-type MnO 2 The mass ratio of the accelerator TMTD, stearic acid and dibutyl phthalate is 4-6:0.1-0.2:0.06-0.08:3-5. Further preferably, the delta-type MnO 2 The mass ratio of accelerator TMTD, stearic acid and dibutyl phthalate is 5:0.1:0.075:4.

[0013] Preferably, the optical power density is 500-5000 mW / cm 2 .

[0014] Preferably, the light reaction time is 20-70 min.

[0015] Preferably, the standing time is 4-8 hours.

[0016] The present invention also provides cured polysulfide rubber prepared by the above process.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention provides a process for light-assisted liquid polysulfide rubber vulcanization, which does not require changing the vulcanizing agent formula or introducing a photosensitizer, and uses δ-type MnO 2 As a photocatalyst, the free radicals generated by the excitation of photogenerated carriers under light conditions trigger the polysulfurization reaction. The light excitation works synergistically with the traditional oxidative polysulfurization to achieve the purpose of rapid polysulfurization.

[0019] (2) The present invention can control the polysulfide reaction rate by changing the light conditions without affecting the final hardness value of the product. Compared with the traditional method of changing the vulcanizing agent formula and introducing photosensitizer, it greatly saves construction costs and reduces unnecessary safety issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The optical power density in Example 1 of the present invention is 900 mW / cm 2 Hardness variation curve of

[0021] Figure 2 The optical power density in Example 2 of the present invention is 1140 mW / cm 2 Hardness variation curve of

[0022] Figure 3 The optical power density in Example 3 of the present invention is 1332 mW / cm 2 Hardness variation curve of

[0023] Figure 4 The optical power density in Example 4 of the present invention is 1332 mW / cm 2 , hardness change curve when the illumination time is 70min;

[0024] Figure 5 This is a hardness variation curve diagram under natural light conditions in Comparative Example 1;

[0025] Figure 6 This is a hardness variation curve diagram of Comparative Example 2 under dark conditions. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0027] It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention were purchased through commercial channels.

[0028] Example 1

[0029] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0030] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0031] Mix 2.51 g of vulcanizing agent and 25.1 g of liquid polysulfide rubber to obtain a mixture. Take 10 g of the mixture and put it into a mold. Control the distance between the light source and the mixture to 5 cm. Turn on the light source and adjust the light power density to 900 mW / cm 2 , irradiate with light for 30 minutes, and then let it stand for 4 hours to obtain the cured polysulfide rubber.

[0032] The Shore hardness of the samples was tested during the illumination process and the static process. The experimental results are as follows Figure 1 As shown in the figure, it can be seen that the Shore hardness of the sample is 24HA after 30 minutes of illumination. The hardness of the sample increases rapidly during the illumination process. After the illumination is stopped for 30 minutes, the hardness change of the sample gradually slows down during the static process.

[0033] Example 2

[0034] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0035] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0036] Mix 2.51 g of vulcanizing agent and 25.1 g of liquid polysulfide rubber to obtain a mixture. Take 10 g of the mixture and put it into a mold. Control the distance between the light source and the mixture to 5 cm. Turn on the light source and adjust the light power density to 1140 mW / cm 2 , irradiate with light for 30 minutes, and then let it stand for 7.5 hours to obtain the cured polysulfide rubber.

[0037] The Shore hardness of the samples was tested during the illumination process and the static process. The experimental results are as follows Figure 2 As shown in the figure, it can be seen that the Shore hardness of the sample is 37HA after 30 minutes of illumination. The hardness of the sample increases rapidly during the illumination process. After the illumination is stopped for 30 minutes, the hardness change of the sample gradually slows down during the static process, compared with 900mW / cm in Example 1. 2 The light intensity is greater than that of the embodiment, and the hardness changes more greatly during the light exposure process, and the vulcanization speed is faster.

[0038] Example 3

[0039] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0040] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0041] Mix 2.51 g of vulcanizing agent and 25.1 g of liquid polysulfide rubber to obtain a mixture. Take 10 g of the mixture and put it into a mold. Control the distance between the light source and the mixture to 5 cm. Turn on the light source and adjust the light power density to 1332 mW / cm 2 , irradiate with light for 30 minutes, and then let it stand for 7 hours to obtain the cured polysulfide rubber.

[0042] The Shore hardness of the samples was tested during the illumination process and the static process. The experimental results are as follows Figure 3 As shown in the figure, it can be seen that the Shore hardness of the sample is 40.5HA after 30 minutes of illumination. The hardness of the sample increases rapidly during the illumination process. After 30 minutes of illumination, the hardness change of the sample gradually slows down during the static process, compared with 900mW / cm in Example 1. 2 The light intensity is 1132 mW / cm2 in Example 2. 2 In this embodiment, the hardness changes more greatly during the illumination process and the vulcanization speed is faster. It can be seen that the stronger the illumination intensity, the faster the vulcanization speed.

[0043] Example 4

[0044] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0045] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0046] Mix 2.51 g of vulcanizing agent and 25.1 g of liquid polysulfide rubber to obtain a mixture. Take 10 g of the mixture and put it into a mold. Control the distance between the light source and the mixture to 5 cm. Turn on the light source and adjust the light power density to 1332 mW / cm 2 , and irradiate with light for 70 minutes to obtain cured polysulfide rubber.

[0047] The Shore hardness of the sample was tested during the illumination process. The experimental results are as follows Figure 4 As shown in the figure, the optical power density is 1332mW / cm 2 When the sample is exposed to light for 70 minutes, the hardness of the sample is 50HA, that is, the sample can reach the required hardness after 70 minutes of exposure to light, and the vulcanization time is greatly reduced.

[0048] Comparative Example 1

[0049] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0050] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0051] 2.51 g of a vulcanizing agent and 25.1 g of liquid polysulfide rubber were mixed evenly to obtain a mixture. 10 g of the mixture was put into a mold and allowed to stand naturally for 55 hours to obtain a cured polysulfide rubber.

[0052] The Shore hardness of the sample was tested during the natural placement process. The experimental results are as follows Figure 5 As shown in the figure, it can be seen that the hardness is 32HA after natural placement for 20 hours. As a comparison with different light intensities, the vulcanization speed is slow when placed under natural conditions.

[0053] Comparative Example 2

[0054] A process for light-assisted vulcanization of liquid polysulfide rubber, the specific steps are as follows:

[0055] 5.02 g of δ-MnO 2 , 3.98 g of dibutyl phthalate, 0.10 g of accelerator TMTD and 0.075 g of stearic acid were mixed uniformly to obtain a vulcanizing agent;

[0056] 2.51 g of a vulcanizing agent and 25.1 g of liquid polysulfide rubber were mixed evenly to obtain a mixture. 10 g of the mixture was put into a mold and placed in a dark condition for 52 hours to obtain a cured polysulfide rubber.

[0057] The Shore hardness of the sample was tested under dark conditions. The test results are as follows Figure 6 As shown in the figure, it can be seen that the hardness is 31HA after being placed in dark conditions for 20 hours. It can be seen that the vulcanization speed is slow under dark conditions.

[0058] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, some modifications and improvements can be made to the present invention. Therefore, any modification or improvement made without departing from the spirit of the present invention belongs to the scope of protection claimed in the present invention.

Claims

1. A process for light-assisted vulcanization of liquid polysulfide rubber, characterized in that: The method comprises the following steps: uniformly mixing liquid polysulfide rubber and a vulcanizing agent, reacting under light conditions, and standing after the reaction is completed to obtain a cured polysulfide rubber, wherein the vulcanizing agent is composed of delta-type MnO2, an accelerator TMTD, stearic acid and dibutyl phthalate; Optical power density is 500-5000mW / cm 2 ; The light reaction time is 20-70 minutes.

2. The process for light-assisted liquid polysulfide rubber vulcanization according to claim 1, characterized in that: The mass ratio of the liquid polysulfide rubber to the vulcanizing agent is 10-15:

1.

3. The process for light-assisted liquid polysulfide rubber vulcanization according to claim 1, characterized in that: The mass ratio of the delta-type MnO2, the accelerator TMTD, stearic acid and dibutyl phthalate is 4-6:0.1-0.2:0.06-0.08:3-5.

4. The process for light-assisted liquid polysulfide rubber vulcanization according to claim 1, characterized in that: The standing time is 4-8h.

5. The cured polysulfide rubber prepared by the process according to any one of claims 1 to 4.

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