Method for detecting polymerization degree of dimethyl siloxane mixed ring body

Abstract

The invention discloses a method for detecting the polymerization degree of a dimethyl siloxane mixed ring body. The method comprises the following steps: (1) pretreatment; (2) low-temperature polymerization removal; and (3) detecting the polymerization degree. The method has the advantages that the method is simple and easy to operate, alkali glue is added into DMC for polymerization reaction to obtain a polymerization sample, then the polymerization degree of the polymerization sample is detected, qualified DMC is used for production of downstream products 110 silicone rubber, the quality of the 110 silicone rubber products is guaranteed, and the method is suitable for popularization and application. And the production efficiency of the 110 silicone rubber is improved.

Description

Technical field:

[0001] The patent of this invention belongs to the field of chemical analysis technology, and specifically relates to a method for detecting the degree of polymerization of a dimethylsiloxane mixed ring. Background technology:

[0002] Dimethylsiloxane mixed ring (DMC for short) is the main raw material for the production of silicone rubber and silicone oil. It is also widely used in rubber filler processing and cosmetics. DMC is used to prepare silicone rubber, silicone oil and other polysiloxane products, which can be further processed into a variety of improved silicone rubbers and silicone oils with better high and low temperature resistance, good insulation performance, weather aging resistance, ozone resistance and radiation resistance. Due to the related manufacturing industry, it is closely related to people's lives.

[0003] The current method for preparing DMC is as follows: first, silicon powder and methyl chloride gas are reacted in the presence of a copper catalyst system to produce a methylchlorosilane mixed monomer; the synthesized mixed methyl monomer is separated by distillation to obtain dimethyldichlorosilane and other various refined monomers; dimethyldichlorosilane reacts with water in concentrated hydrochloric acid at a certain temperature and pressure to produce an organosilicon hydrolyzate and HCl gas; and the above-mentioned organosilicon hydrolyzate is cracked to obtain DMC.

[0004] The DMC currently produced needs to be tested using the national standard testing method, and qualified DMC products need to meet the following indicators: Appearance: colorless, transparent oily liquid, chromaticity / Hazen unit (platinum-cobalt color number) ≤10, refractive index: 1.3960-1.3970, total ring body mass fraction ≥99.50%, hexamethyldisiloxane mass fraction ≤0.01%, acid (in terms of HCI) mass fraction ≤0.001%; ​​Only when the DMC product is qualified can it be shipped out of the factory and sent to downstream manufacturers to produce 110 silicone rubber; However, when the above-mentioned qualified DMC products are used in the production of the downstream product 110 silicone rubber, non-polymerization or low viscosity will occur, which greatly affects the product quality and production efficiency of the 110 silicone rubber. Summary of the invention:

[0005] In view of this, the object of the present invention is to provide a method for detecting the degree of polymerization of a dimethylsiloxane mixed ring body. The method for detecting the degree of polymerization of a dimethylsiloxane mixed ring body provided by the present invention is simple and easy to operate, thereby ensuring the quality of 110 silicone rubber products and improving the production efficiency of 110 silicone rubber.

[0006] The technical solution of the present invention discloses a method for detecting the degree of polymerization of a dimethylsiloxane mixed ring body, which comprises the following steps:

[0007] (1) Pretreatment: Take a dimethylsiloxane mixed ring body sample and add it to a reactor, then introduce nitrogen into the sample at a flow rate of 5-10 L / min, heat the dimethylsiloxane mixed ring body sample to 75-85° C., and start a vacuum pump to evacuate the reactor at a rate of 15-60 L / min. After 30 minutes, stop the vacuum pump;

[0008] (2) Polymerization and degassing: adding alkali glue to the reaction kettle in step (1), the addition of alkali glue promotes the ring opening of the dimethylsiloxane mixed ring body, and polymerizes to form a linear body; then heating to 105-115°C and keeping the temperature for 85-95 minutes to carry out a polymerization reaction, then continuing to heat to 155-165°C, and turning on a vacuum pump to evacuate the reaction kettle at a rate of 15-60L / min. After 85-95 minutes, stop the vacuum pump, stop introducing nitrogen, and cool naturally to obtain a polymerized sample;

[0009] (3) Detecting the degree of polymerization: Take the polymer sample in step (2) and determine its degree of polymerization using the national standard detection method GB / T28610-2020.

[0010] Furthermore, the concentration of the reduced glue in the reactor in step (2) is 5-10 ppm.

[0011] Furthermore, the preparation method of the alkali glue comprises the following steps:

[0012] a. Adding materials for dehydration: first add the dimethylsiloxane mixed ring body sample to the mixing kettle, then add tetramethylammonium hydroxide, and then introduce nitrogen at a flow rate of 0.2-0.8L / min (while bubbling and stirring, avoid splashing of materials and pumping them away), the heating temperature in the mixing kettle is 50-70°C, the pressure is -0.09 to -0.06MPa, and maintained for 0.5-2h to obtain a dehydrated mixture;

[0013] b. Mixing reaction: continue to heat the dehydrated mixture in the mixing kettle in step (a) until the temperature reaches 80-90° C., the pressure in the mixing kettle is -0.1 to -0.15 MPa, and maintain for 1-3 hours to obtain the alkali glue;

[0014] Specifically, the polymerization reaction equation of the dimethylsiloxane mixed ring sample and tetramethylammonium hydroxide is as follows:

[0015]

[0016] Furthermore, in step (a), the mass ratio of the tetramethylammonium hydroxide to the dimethylsiloxane mixed ring sample is 1:4-5.5.

[0017] Furthermore, it also includes the following steps: the gas extracted by the vacuum pump in step (1) and step (2) is condensed through a condenser to obtain a light component liquid.

[0018] Advantages of the present invention:

[0019] The invention discloses a method for detecting the polymerization degree of a dimethylsiloxane mixed ring body. The method is simple and easy to operate. Alkaline glue is added into DMC to generate a polymerization reaction to obtain a polymerization sample, and then the polymerization degree of the polymerization sample is detected. Qualified DMC is used for the production of downstream products 110 series silicone rubber, thereby ensuring the quality of the 110 series silicone rubber products and improving the production efficiency of the 110 series silicone rubber. Specific implementation method:

[0020] The present invention is further described in detail below by way of examples.

[0021] Embodiment 1: A method for detecting the degree of polymerization of a dimethylsiloxane mixed ring, comprising the following steps:

[0022] (1) Pretreatment: Take 500 ml of the dimethylsiloxane mixed ring body sample and add it to the reactor. Then, nitrogen is introduced into the sample at a flow rate of 5-10 L / min. The dimethylsiloxane mixed ring body sample is heated to 75-85°C, and the vacuum pump is turned on to evacuate the reactor at a rate of 15-60 L / min. After 30 minutes, the vacuum pump is stopped.

[0023] (2) Polymerization and degassing: 5 ppm of alkali glue is added to the reactor in step (1), and then heated to 105-115°C for 95 min to carry out polymerization reaction, and then continued to heat to 155-165°C, and start the vacuum pump to evacuate the reactor at a rate of 15-60 L / min. After 95 min, stop the vacuum pump and stop introducing nitrogen, and cool naturally to obtain a polymerized sample.

[0024] Wherein, the preparation method of alkali glue comprises the following steps:

[0025] a. Adding materials for dehydration: first add 500g of dimethylsiloxane mixed ring sample to the mixing kettle, and then add 15g of tetramethylammonium hydroxide, and then introduce nitrogen at a flow rate of 0.2-0.8L / min, while bubbling and stirring to prevent the material from splashing and being pumped away. The heating temperature in the mixing kettle is 50-70°C, and the pressure is -0.09 to -0.06MPa, which is maintained for 0.5-2h to obtain a dehydrated mixture.

[0026] b. Mixing reaction: Continue heating the dehydrated mixture in the mixing kettle in step (a) until the temperature reaches 80-90° C. The pressure in the mixing kettle is -0.1 to -0.15 MPa and maintained for 1-3 hours to obtain the alkali glue.

[0027] The gas extracted by the vacuum pump in step (1) and step (2) is condensed by a condenser to obtain a light component liquid.

[0028] (3) Detection of degree of polymerization: Take the polymer sample in step (2) and determine its degree of polymerization using the national standard detection method GB / T28610-2020 to obtain a degree of polymerization of 150 to 153 × 10 4 , judge that the dimethylsiloxane mixed ring product is qualified.

[0029] Embodiment 2: A method for detecting the degree of polymerization of a dimethylsiloxane mixed ring, comprising the following steps:

[0030] (1) Pretreatment: Take 500 ml of the dimethylsiloxane mixed ring body sample and add it to the reactor. Then, nitrogen is introduced into the sample at a flow rate of 5-10 L / min. The dimethylsiloxane mixed ring body sample is heated to 75-85°C, and the vacuum pump is turned on to evacuate the reactor at a rate of 15-60 L / min. After 30 minutes, the vacuum pump is stopped.

[0031] (2) Polymerization degassing: add 8 ppm alkali glue to the reactor in step (1), then heat to 105-115°C and keep warm for 90 min to carry out polymerization reaction, then continue to heat to 155-165°C, and start the vacuum pump to evacuate the reactor at a rate of 15-60 L / min. After 90 min, stop the vacuum pump and stop introducing nitrogen, and cool naturally to obtain a polymerized sample.

[0032] Wherein, the preparation method of alkali glue comprises the following steps:

[0033] a. Adding materials for dehydration: first add 500g of dimethylsiloxane mixed ring sample to the mixing kettle, and then add 20g of tetramethylammonium hydroxide, and then introduce nitrogen at a flow rate of 0.2-0.8L / min, while bubbling and stirring to prevent the material from splashing and being pumped away. The heating temperature in the mixing kettle is 50-70°C, and the pressure is -0.09 to -0.06MPa, which is maintained for 0.5-2h to obtain a dehydrated mixture.

[0034] b. Mixing reaction: Continue heating the dehydrated mixture in the mixing kettle in step (a) until the temperature reaches 80-90° C. The pressure in the mixing kettle is -0.1 to -0.15 MPa and maintained for 1-3 hours to obtain the alkali glue.

[0035] The gas extracted by the vacuum pump in step (1) and step (2) is condensed by a condenser to obtain a light component liquid.

[0036] (3) Detection of degree of polymerization: Take the polymer sample in step (2) and determine its degree of polymerization using the national standard detection method GB / T28610-2020 to obtain a degree of polymerization of 150 to 153 × 10 4 , judge that the dimethylsiloxane mixed ring product is qualified.

[0037] Embodiment 3: A method for detecting the degree of polymerization of a dimethylsiloxane mixed ring, comprising the following steps:

[0038] (1) Pretreatment: Take 500 ml of the dimethylsiloxane mixed ring body sample and add it to the reactor. Then, nitrogen is introduced into the sample at a flow rate of 5-10 L / min. The dimethylsiloxane mixed ring body sample is heated to 75-85°C, and the vacuum pump is turned on to evacuate the reactor at a rate of 15-60 L / min. After 30 minutes, the vacuum pump is stopped.

[0039] (2) Polymerization degassing: add 10 ppm of alkali glue to the reactor in step (1), then heat to 105-115°C and keep warm for 85 min to carry out polymerization reaction, then continue to heat to 155-165°C, and start the vacuum pump to evacuate the reactor at a rate of 15-60 L / min. After 85 min, stop the vacuum pump and stop introducing nitrogen, and cool naturally to obtain a polymerized sample.

[0040] Wherein, the preparation method of alkali glue comprises the following steps:

[0041] a. Adding materials for dehydration: first add 500g of dimethylsiloxane mixed ring sample to the mixing kettle, and then add 25g of tetramethylammonium hydroxide, and then introduce nitrogen at a flow rate of 0.2-0.8L / min, while bubbling and stirring to prevent the material from splashing and being pumped away. The heating temperature in the mixing kettle is 50-70°C, and the pressure is -0.09 to -0.06MPa, which is maintained for 0.5-2h to obtain a dehydrated mixture.

[0042] b. Mixing reaction: Continue heating the dehydrated mixture in the mixing kettle in step (a) until the temperature reaches 80-90° C. The pressure in the mixing kettle is -0.1 to -0.15 MPa and maintained for 1-3 hours to obtain the alkali glue.

[0043] The gas extracted by the vacuum pump in step (1) and step (2) is condensed by a condenser to obtain a light component liquid.

[0044] (3) Detection of degree of polymerization: Take the polymer sample in step (2) and determine its degree of polymerization using the national standard detection method GB / T28610-2020 to obtain a degree of polymerization of 150 to 153 × 10 4 , judge that the dimethylsiloxane mixed ring product is qualified.

[0045] From Examples 1-3, it can be seen that the polymerization degree of the polymerized samples obtained after the reaction of different concentrations of reduced glue and samples is 150-153X10 4 This indicates that the concentration of alkali glue affects the speed of polymerization. The higher the concentration of reduced glue, the shorter the reaction time, but the effect on the degree of polymerization of the polymerized sample is limited. Therefore, the concentration of reduced glue does not affect the judgment of the quality of the polymerized sample.

[0046] Experiment: 110 glues with different relative viscosity average molecular weights were prepared using mixed dimethylsiloxane rings with different polymerization degrees. The specific preparation methods are shown in Table 1.

[0047] Table 1 Preparation of 110 glue

[0048]

[0049]

[0050] As can be seen from Table 1, the degree of polymerization is 150-200x10 4 The polymer sample can be used to produce a relative viscosity average molecular weight of 45-50x10 4 , 50-60x10 4 , 60-75x10 4 and 75x10 4 Therefore, the method for detecting the polymerization degree of dimethylsiloxane mixed ring body of the present invention can not only ensure the quality of subsequent 110 glue products, but also can guide which series of 110 glue the batch of dimethylsiloxane mixed ring body can be used to produce, which has extremely important guiding significance for the production of 110 glue with dimethylsiloxane mixed ring body.

[0051] The above are preferred embodiments of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for detecting the degree of polymerization of a dimethylsiloxane mixed ring, characterized in that: It includes the following steps: (1) Pretreatment: Take a dimethylsiloxane mixed ring body sample and add it to a reactor, then introduce nitrogen into the sample at a flow rate of 5-10 L / min, heat the dimethylsiloxane mixed ring body sample to 75-85° C., and start a vacuum pump to evacuate the reactor at a rate of 15-60 L / min. After 30 minutes, stop the vacuum pump; (2) Polymerization and degassing: add alkali glue to the reaction kettle in step (1), then heat to 105-115°C and keep warm for 85-95 min to carry out polymerization reaction, then continue to heat to 155-165°C, and start a vacuum pump to evacuate the reaction kettle at a rate of 15-60 L / min. After 85-95 min, stop the vacuum pump and stop introducing nitrogen, and cool naturally to obtain a polymerized sample; (3) Detecting the degree of polymerization: Take the polymer sample in step (2) and determine its degree of polymerization using the national standard detection method GB / T28610-2020.

2. The method for detecting the degree of polymerization of a dimethylsiloxane mixed ring according to claim 1, characterized in that: The concentration of the reduced glue in the reactor in step (2) is 5-10 ppm.

3. The method for detecting the degree of polymerization of a dimethylsiloxane mixed ring body according to claim 2, characterized in that: The preparation method of the alkali glue comprises the following steps: a. Adding materials for dehydration: first add the dimethylsiloxane mixed ring body sample to the mixing kettle, then add tetramethylammonium hydroxide, and then introduce nitrogen at a flow rate of 0.2-0.8L / min (while bubbling and stirring, avoid splashing of materials and pumping them away), the heating temperature in the mixing kettle is 50-70°C, the pressure is -0.09 to -0.06MPa, and maintained for 0.5-2h to obtain a dehydrated mixture; b. Mixing reaction: Continue heating the dehydrated mixture in the mixing kettle in step (a) until the temperature reaches 80-90° C. The pressure in the mixing kettle is -0.1 to -0.15 MPa and maintained for 1-3 hours to obtain the alkali glue.

4. The method for detecting the degree of polymerization of a dimethylsiloxane mixed ring body according to claim 3, characterized in that: The mass ratio of the tetramethylammonium hydroxide to the dimethylsiloxane mixed ring sample in step (a) is 1:4-5.

5.

5. The method for detecting the degree of polymerization of a dimethylsiloxane mixed ring according to claim 1, characterized in that: The method further comprises the following steps: the gas extracted by the vacuum pump in step (1) and step (2) is condensed through a condenser to obtain a light component liquid.

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