Low-volatility and low-dissolution silica gel isolation pad and preparation process

Abstract

The invention belongs to the technical field of sample injection isolation pads, and discloses a low-volatility and low-dissolution silica gel isolation pad and a preparation process. The silica gel shock insulator is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber, 40 to 50 parts of fumed silica, 8 to 10 parts of mixture of hexamethyl cyclotrisilazane and octamethyl cyclotetrasilazane, 0.5 to 0.8 part of diethyl maleate, 2 to 3 parts of diphenyl silanediol, 3 to 5 parts of titanium dioxide and 0.5 to 1 part of vulcanizing agent. According to the invention, through reasonable formula design and optimization of the types and contents of the raw materials, the molded rubber material is ensured to have a relatively good crosslinking degree, vulcanized small-molecular products are effectively prevented from excessively migrating to the surface, and meanwhile, part of small-molecular substances are extracted in advance by adopting a specific production process, so that the service life of the rubber material is prolonged. The product is ensured to have better cleanliness in the subsequent use process, and the low-volatility and low-dissolution silica gel insulation pad is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of sample injection septa, and particularly relates to a low-volatile, low-dissolution silica gel septum and a preparation process thereof. Background Art

[0002] The injection septum, also called the injection pad or injection pad, is one of the important components for introducing samples into the chromatographic column in gas chromatograph analysis. Its main function is to separate the system flow path from the outside, maintain air tightness, and ensure that there is enough carrier gas column head pressure to allow the gas flow to flow through the chromatographic column. In gas phase analysis, the injection septum is a consumable that is replaced more frequently, because after long-term use, the septum may be contaminated, lost, leaked, etc., which will affect the accuracy of the analysis results.

[0003] With the replacement and technological upgrading of testing instruments, the detection limit and precision of the instruments have been significantly improved. Based on this background, people have more stringent requirements on the dissolution and volatility performance of conventional consumables used as testing instruments. Silicone septa are common materials for injection septa due to their good thermal stability, excellent chemical stability and anti-aging properties. Injection septa are often prepared by high-temperature vulcanization process. Conventional production processes are prone to produce various by-products during the molding process of silicone septa. The presence of these by-products will cause various interferences in subsequent terminal use. Summary of the invention

[0004] The purpose of the present invention is to provide a low-volatile, low-dissolution silica gel spacer and a preparation process, which has the effects of low volatility and low dissolution of byproducts and better cleanliness during use.

[0005] The above technical purpose of the present invention is achieved through the following technical scheme: a low-volatile, low-dissolution silica gel spacer, the raw materials of which include the following components by weight: 100 parts of methyl vinyl silicone rubber, 40-50 parts of fumed silica, 8-10 parts of a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, and 0.5-0.8 parts of diethyl maleate.

[0006] By adopting the above technical scheme, fumed silica, also known as fumed silica, is used as a reinforcing agent for silicone rubber to improve the mechanical properties of silicone rubber. The silicone rubber compound added with fumed silica will gradually harden and reduce plasticity. In order to effectively overcome the above defects, the present invention adds a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane. Diethyl maleate, also known as diethyl maleate, is a colorless transparent liquid used as a softener and plasticizer for rubber. It can increase the elasticity and toughness of rubber, reduce the hardness of rubber, and improve the processing performance of rubber.

[0007] The present invention is further configured as follows: the raw materials further include the following components: 2-3 parts of diphenylsilanediol, 3-5 parts of titanium dioxide, and 0.5-1 part of a vulcanizing agent.

[0008] By adopting the above technical solution, diphenylsilanediol is used as a silicone rubber structure controller to reduce the structuring phenomenon of silicone rubber and improve the processing performance of rubber. Titanium dioxide is a white pigment that is applied to silicone rubber to play a role in reinforcement, anti-aging and filling. Vulcanizing agent is a substance that can cause the rubber molecular chain to undergo a cross-linking reaction, so that the linear molecules form a three-dimensional network structure, thereby reducing plasticity and increasing elasticity and strength. Except for some thermoplastic rubbers that do not require vulcanization, natural rubber and various synthetic rubbers need to be vulcanized with vulcanizing agents. Rubber has valuable use value only after vulcanization, and its mechanical properties will be greatly improved.

[0009] The present invention is further configured as follows: the vulcanizing agent is a vulcanizing agent DBPMH.

[0010] By adopting the above technical solution, the vulcanizing machine of the present invention selects the vulcanizing agent DBPMH, which can meet the vulcanization requirements of the present invention.

[0011] The present invention is further configured as follows: the ratio of hexamethylcyclotrisilazane to octamethylcyclotetrasilazane is 1:1-3.

[0012] Another object of the present invention is to provide a process for preparing the above-mentioned low volatility, low dissolution silica gel spacer, comprising the following steps: S1, mixing, taking methyl vinyl silicone rubber, fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide, mixing them to make them uniform, and then placing them in an oven at 120° C. for heat treatment for 1.5 hours; S2, placing the mixed material for a period of time; S3, refining, adding the placed material into the vulcanizing machine for refining; S4, calendering, calendering the re-refined material; S5, film output; S6, vulcanization molding, the vulcanization condition is 180℃, 15min; S7, secondary vulcanization, the vulcanization conditions are 190℃, 10min, and vacuum vulcanization is carried out in a vacuum drying oven; S8, three-time vulcanization, vulcanization conditions are 200℃, 70min; S9, punching, punching the vulcanized material into required sizes; S10, pre-cleaning, placing the punched material in an environment of -0.1MPa and flushing with nitrogen for 5-10min; S11, cleaning, using a solvent to clean the material; S12, drying: drying the material at 20-35° C. to obtain a silica gel septum.

[0013] By adopting the above technical scheme, the secondary vulcanization of the present invention is selected in vacuum vulcanization, which is conducive to the diffusion of volatile small molecules. The present invention is innovatively designed with a pre-cleaning step, which can not only preliminarily clean the impurities on the surface of the material, but also take away the volatile substances by flushing with clean nitrogen in a vacuum negative pressure environment. Then, the solvent is used for cleaning to obtain a silica gel septum.

[0014] The present invention is further configured as follows: in step S1, methyl vinyl silicone rubber is put into a rubber mixer, and fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide are added while mixing, and the mixture is placed in an oven at 120° C. for heat treatment for 1.5 hours.

[0015] The present invention is further configured as follows: in step S2, the placement time is 24 hours.

[0016] The present invention is further configured as follows: in step S3, the refining time is 10-30 minutes.

[0017] By adopting the above technical solution, the plasticity of the material decreases after being parked, and it must be re-refined before further processing.

[0018] The present invention is further configured as follows: in step S11, the solvent used for cleaning is ethanol or acetone or isopropanol.

[0019] The beneficial effects of the present invention are as follows: the present invention ensures that the molding rubber has a good degree of cross-linking through reasonable formula design and by optimizing the types and contents of various raw materials, effectively preventing excessive migration of sulfurized small molecule products to the surface, and at the same time adopts a specific production process to extract some small molecule substances in advance, thereby ensuring that the product has good cleanliness during subsequent use, thereby obtaining a low-volatile, low-dissolution silicone gasket. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1: A low-volatile, low-dissolution silicone gasket, the raw materials of which include the following components, by weight: 100 parts of methyl vinyl silicone rubber, 40 parts of fumed silica, 8 parts of a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, 0.5 parts of diethyl maleate, 2 parts of diphenylsilanediol, 3 parts of titanium dioxide, and 0.5 parts of a vulcanizing agent, the ratio of hexamethylcyclotrisilazane to octamethylcyclotetrasilazane is 1:1, and the vulcanizing agent is a vulcanizing agent DBPMH.

[0022] The preparation process of the silicone septum is as follows: S1. Mixing: Take methyl vinyl silicone rubber, fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide. Put the methyl vinyl silicone rubber into a rubber mixer, add fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide while mixing. Mix to make it uniform, and then place it in an oven at 120°C for heat treatment for 1.5 hours.

[0023] S2, placing the mixed material for 24 hours; S3, refining, adding the placed material to the vulcanizing machine for refining, the refining time is 10min; S4, calendering, calendering the re-refined material; S5, film output; S6, vulcanization molding, the vulcanization condition is 180℃, 15min; S7, secondary vulcanization, vulcanization conditions are 190℃, 10min, vacuum vulcanization in a vacuum drying oven; S8, three-time vulcanization, vulcanization conditions are 200℃, 70min; S9, punching, punching the vulcanized material into required sizes; S10, pre-cleaning, placing the punched material in an environment of -0.1MPa and flushing with nitrogen for 5 minutes; S11, cleaning, using a solvent to clean the material, the solvent is ethanol or acetone or isopropanol; S12, drying: drying the material at 20-35° C. to obtain a silica gel septum.

[0024] Example 2: A low-volatility, low-solubility silicone gasket, the raw materials of which include the following components, by weight: 100 parts of methyl vinyl silicone rubber, 50 parts of fumed silica, 10 parts of a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, 0.8 parts of diethyl maleate, 3 parts of diphenylsilanediol, 5 parts of titanium dioxide, and 1 part of a vulcanizing agent, the ratio of hexamethylcyclotrisilazane to octamethylcyclotetrasilazane is 1:3, and the vulcanizing agent is vulcanizing agent DBPMH.

[0025] The preparation process of the silicone septum is as follows: S1. Mixing: Take methyl vinyl silicone rubber, fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide. Put the methyl vinyl silicone rubber into a rubber mixer, add fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide while mixing. Mix to make it uniform, and then place it in an oven at 120°C for heat treatment for 1.5 hours.

[0026] S2, placing the mixed material for 24 hours; S3, refining, adding the placed material to the vulcanizing machine for refining, the refining time is 20min; S4, calendering, calendering the re-refined material; S5, film output; S6, vulcanization molding, the vulcanization condition is 180℃, 15min; S7, secondary vulcanization, vulcanization conditions are 190℃, 10min, vacuum vulcanization in a vacuum drying oven; S8, three-time vulcanization, vulcanization conditions are 200℃, 70min; S9, punching, punching the vulcanized material into required sizes; S10, pre-cleaning, placing the punched material in an environment of -0.1MPa and flushing with nitrogen for 10 minutes; S11, cleaning, using a solvent to clean the material, the solvent is ethanol or acetone or isopropanol; S12, drying: drying the material at 20-35° C. to obtain a silica gel septum.

[0027] Example 3: A low-volatile, low-dissolution silicone gasket, the raw materials of which include the following components, by weight: 100 parts of methyl vinyl silicone rubber, 45 parts of fumed silica, 9 parts of a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, 0.6 parts of diethyl maleate, 3 parts of diphenylsilanediol, 4 parts of titanium dioxide, and 0.8 parts of a vulcanizing agent, the ratio of hexamethylcyclotrisilazane to octamethylcyclotetrasilazane is 1:3, and the vulcanizing agent is vulcanizing agent DBPMH.

[0028] The preparation process of the silicone septum is as follows: S1. Mixing: Take methyl vinyl silicone rubber, fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide. Put the methyl vinyl silicone rubber into a rubber mixer, add fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide while mixing. Mix to make it uniform, and then place it in an oven at 120°C for heat treatment for 1.5 hours.

[0029] S2, placing the mixed material for 24 hours; S3, refining, adding the placed material to the vulcanizing machine for refining, the refining time is 20min; S4, calendering, calendering the re-refined material; S5, film output; S6, vulcanization molding, the vulcanization condition is 180℃, 15min; S7, secondary vulcanization, vulcanization conditions are 190℃, 10min, vacuum vulcanization in a vacuum drying oven; S8, three-time vulcanization, vulcanization conditions are 200℃, 70min; S9, punching, punching the vulcanized material into required sizes; S10, pre-cleaning, placing the punched material in an environment of -0.1MPa and flushing with nitrogen for 10 minutes; S11, cleaning, using a solvent to clean the material, the solvent is ethanol or acetone or isopropanol; S12, drying: drying the material at 20-35° C. to obtain a silica gel septum.

[0030] Experimental part Volatile concentration test: Accurately weigh the sample and bake it in a constant temperature oven at (150±1)℃ until the mass is constant (the difference in mass between two tests does not exceed 0.002g). The volatile matter concentration is calculated according to the following formula: W=(m1-m2) / m1×100%, where W is the volatile matter concentration (%), m1 is the mass of the sample before baking (g), and m2 is the mass of the sample after the mass is constant at 150℃ (g).

[0031] Total migration test: the simulant is 95% ethanol, the test environment is 60℃, and the total migration of each example is measured. The total migration test method refers to "European Commission. Commission directive 2002 / 72 / EC relating to plastic materials and articles intended to come into contact with foodstuffs[J].Official Journal,2002,L220:18-90".

[0032] Table 1 Group Volatile matter concentration / % <![CDATA[Total migration amount / mg / dm 2 > Example 1 0.12 3 Example 2 0.13 3 Example 3 0.11 3

Claims

1. A low volatility, low dissolution silica gel septum, characterized by: The raw materials include the following components by weight: 100 parts of methyl vinyl silicone rubber, 40-50 parts of fumed silica, 8-10 parts of a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, and 0.5-0.8 parts of diethyl maleate.

2. The low volatility, low dissolution silica gel spacer according to claim 1, characterized in that: The raw materials also include the following components: 2-3 parts of diphenylsilanediol, 3-5 parts of titanium dioxide, and 0.5-1 part of a vulcanizing agent.

3. A low volatility, low dissolution silica gel spacer according to claim 2, characterized in that: The vulcanizing agent is vulcanizing agent DBPMH.

4. The low volatility, low dissolution silica gel spacer according to claim 1, characterized in that: The ratio of hexamethylcyclotrisilazane to octamethylcyclotetrasilazane is 1:1-3.

5. A process for preparing a low volatility, low dissolution silica gel spacer according to any one of claims 1 to 4, characterized in that: The following steps are included: S1, mixing, taking methyl vinyl silicone rubber, fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide, and mixing them to make them uniform; S2, placing the mixed material for a period of time; S3, refining, adding the placed material into the vulcanizing machine for refining; S4, calendering, calendering the re-refined material; S5, film output; S6, vulcanization molding, the vulcanization condition is 180℃, 15min; S7, secondary vulcanization, the vulcanization conditions are 190℃, 10min, and vacuum vulcanization is carried out in a vacuum drying oven; S8, three-time vulcanization, vulcanization conditions are 200℃, 70min; S9, punching, punching the vulcanized material into required sizes; S10, pre-cleaning, placing the punched material in an environment of -0.1MPa and flushing with nitrogen for 5-10min; S11, cleaning, using a solvent to clean the material; S12, drying: drying the material at 20-35° C. to obtain a silica gel septum.

6. The process for preparing a low-volatile, low-dissolution silica gel spacer according to claim 5, characterized in that: In step S1, methyl vinyl silicone rubber is put into a rubber mixer, and fumed silica, a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, diethyl maleate, diphenylsilanediol, and titanium dioxide are added while mixing. After mixing to make it uniform, it is placed in an oven at 120° C. for heat treatment for 1.5 hours.

7. The process for preparing a low-volatile and low-dissolution silica gel spacer according to claim 5, characterized in that: In step S2, the placement time is 24 hours.

8. The process for preparing a low-volatile and low-dissolution silica gel spacer according to claim 5, characterized in that: In step S3, the refining time is 10-30 minutes.

9. The process for preparing a low-volatile and low-dissolution silica gel spacer according to claim 5, characterized in that: In step S11, the solvent used for cleaning is ethanol, acetone or isopropanol.