A method for detecting the basicity of 107 gum alkali ester catalyst

Abstract

The present invention is a method for detecting the alkalinity of a 107 rubber alkali-ester catalyst. A method for detecting the alkalinity of a 107 rubber alkali-ester catalyst comprises: (1) fully mixing the alkali-ester catalyst with water and standing to separate into layers; (2) taking out the upper layer solution after separation, adding nitric acid, hydrofluoric acid and perchloric acid, and mixing evenly to obtain a solution 1; (3) heating at 170-190°C, and after the acid in the solution 1 evaporates to 1-2 drops, cooling to obtain a solution 2; (4) adding water to the solution 2 to obtain a solution 3; (5) detecting the potassium ion concentration in the solution 3. The method for detecting the alkalinity of a 107 rubber alkali-ester catalyst of the present invention uses 40-60°C water to wash out some of the free K adsorbed on the initiator. + , so that the content of initiator ‑R‑Si‑O‑Si‑OK in the alkali-ester catalyst used to prepare 107 glue can be accurately determined.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical detection, and specifically relates to a method for detecting the alkalinity of a 107 gum alkali ester catalyst. Background Art

[0002] 107 glue, also known as 107 room temperature vulcanized silicone rubber, uses methyl polysiloxane as raw material and undergoes polycondensation reaction under the catalytic action of potassium hydroxide to synthesize 107 glue. There are two common methods for preparing catalysts. One method is to dissolve potassium hydroxide in water to prepare a water-soluble alkaline catalyst, and the other method is to dissolve potassium hydroxide in methyl polysiloxane to prepare an alkaline lipid catalyst. The solubility of potassium hydroxide in water is 1100g / L, and the solubility in methyl polysiloxane is 2-5%.

[0003] Based on the reaction mechanism of 107 glue catalytic polymerization, the potassium ions in potassium hydroxide will connect to the Si-O - On the surface, -R-Si-O-Si-OK is formed. Due to the effective catalytic component -OK, commonly known as the initiator, the polysiloxane begins to accelerate the condensation. By adding phosphoric acid, the polymerization time is controlled, and finally 107 glue with different viscosities is formed. Water-soluble potassium hydroxide is generally prepared in a ratio of potassium hydroxide to water of 1:1. Potassium hydroxide can be completely dissolved. No need to measure K + The triggering dose cannot be determined.

[0004] When water-soluble potassium hydroxide is used as a catalyst, violent boiling will occur in the reactor. The polymerization temperature in the reactor is 150°C. When the water-soluble hydrogen hydroxide catalyst is added, the water vaporizes instantly, showing boiling in the reactor. When potassium hydroxide is dissolved in water, a large amount of heat will be released, which poses a safety hazard of splashing. Therefore, it is not easy to prepare in large quantities. Only 20ppm of K is needed for the polymerization of 107 glue. + , a 50% potassium hydroxide aqueous solution prepared in a 1:1 ratio, the added amount is very small 40g / T, and it is not easy to achieve automatic feeding control.

[0005] The use of potassium hydroxide alkali ester catalyst can just overcome the above-mentioned shortcomings of water-soluble potassium hydroxide. However, when using methyl polysiloxane as a potassium hydroxide solvent, the composition of methyl polysiloxane is different each time it is used, and it must be added in proportion. It is particularly important to accurately determine the content of the initiator R-Si-OK group in the alkali ester.

[0006] When using methyl polysiloxane to prepare potassium hydroxide alkali grease, the initiator content can be measured, and then used to calculate the alkali grease content. When using methyl polysiloxane to prepare potassium hydroxide alkali grease, there is a method for detecting the alkali grease: using tetrahydrofuran as a solvent, dissolving the alkali grease, and then + To titrate OH - , and then through OH- The method of measuring the concentration of potassium hydroxide based on the content of ions. However, this method cannot detect the concentration of the effective initiator R-Si-OK well.

[0007] In view of this, the present invention proposes a new method for detecting the alkalinity of 107 rubber alkali ester catalyst, and uses AAS and ICP-OES to further determine the concentration of effective initiator R-Si-OK in the alkali ester. Summary of the invention

[0008] The object of the present invention is to provide a method for detecting the alkalinity of a 107 rubber alkali ester catalyst, which has high accuracy and can detect the KOH content in the 107 rubber alkali ester catalyst converted by initiator-R-Si-O-Si-OK, and is suitable for alkaline ester solutions of various methyl polysiloxane solvents.

[0009] In order to achieve the above purpose, the technical solution adopted is:

[0010] A method for detecting the basicity of a 107 gum alkali catalyst comprises the following steps:

[0011] (1) After fully mixing the alkali-lipid catalyst and water, the mixture was allowed to stand and separate into layers;

[0012] (2) taking out the upper layer solution after stratification, adding nitric acid, hydrofluoric acid and perchloric acid, and mixing evenly to obtain solution 1;

[0013] (3) heating at 170-190° C., after 0.09-0.11 g of the acid in solution 1 evaporates to 1-2 drops, cooling to obtain solution 2;

[0014] (4) adding water to the solution 2 to obtain solution 3;

[0015] (5) The potassium ion concentration in the solution 3 is detected by ICP method, which is the alkalinity of the alkali-lipid catalyst.

[0016] Furthermore, in the step (1), the mass ratio of the alkali-fat catalyst to water is 15-25:45-55.

[0017] Furthermore, in the step (1), the mass ratio of the alkali-fat catalyst to water is 20:50.

[0018] Furthermore, in the step (1), the temperature of water is 40-60°C.

[0019] Furthermore, in the step (1), the temperature of water is 50°C.

[0020] Furthermore, in the step (2), the mass volume ratio of the upper solution to nitric acid, hydrofluoric acid and perchloric acid is 0.09-0.11 g: 10 ml: 2 ml: 2 ml.

[0021] Furthermore, in the step (2), the mass volume ratio of the upper solution to nitric acid, hydrofluoric acid and perchloric acid is 0.10g:10ml:2ml:2ml.

[0022] Furthermore, the mass volume ratio of the upper layer solution to solution 3 is 0.09-0.11 g:100 ml.

[0023] Furthermore, the mass volume ratio of the upper layer solution to solution 3 is 0.10g:100ml.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The technical solution of the present invention is to wash out part of the free K adsorbed on the initiator with water at 40-60°C. + , so that the content of initiator -R-Si-O-Si-OK in the alkali-ester catalyst for preparing 107 glue can be accurately determined, and then converted into KOH content, which is convenient for realizing automatic feeding control and production standardization.

[0026] 2. The technical solution of the present invention is applicable to alkaline grease solutions of various methyl polysiloxane solvents. DETAILED DESCRIPTION

[0027] In order to further explain the detection method of the basicity of a 107 rubber alkali ester catalyst of the present invention and achieve the expected purpose of the invention, the following is a detailed description of the detection method of the basicity of a 107 rubber alkali ester catalyst proposed according to the present invention, its specific implementation method, structure, characteristics and efficacy as follows in combination with the preferred embodiment. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0028] The following will further introduce in detail the detection method of the basicity of the 107 rubber alkali grease catalyst of the present invention in conjunction with specific embodiments:

[0029] The principle of the technical solution of the present invention is as follows: In the OH groups at both ends of methyl polysiloxane, K + At a certain temperature, part of K + Will and H + exchange, reaching an equilibrium to form -R-Si-O-Si-OK initiator, but some of them do not react with H + Combined K +, and the OH groups at both ends of methyl polysiloxane form a non-initiator of -R-Si-O-Si-OK-H by electrostatic adsorption. At this time, ultrapure water at 40-60°C is used to wash out the free non-initiator into ultrapure water. The potassium ion content in the upper oil phase is measured and converted into KOH content, which is the catalyst base fat alkalinity.

[0030] The technical solution of the present invention is:

[0031] A method for detecting the basicity of a 107 gum alkali catalyst comprises the following steps:

[0032] (1) After fully mixing the alkali-lipid catalyst and water, the mixture was allowed to stand and separate into layers;

[0033] (2) taking out the upper layer solution after stratification, adding nitric acid, hydrofluoric acid and perchloric acid, and mixing evenly to obtain solution 1;

[0034] (3) heating at 170-190° C., after 0.09-0.11 g of the acid in solution 1 evaporates to 1-2 drops, cooling to obtain solution 2;

[0035] (4) adding water to the solution 2 to obtain solution 3;

[0036] (5) The potassium ion concentration in the solution 3 is detected by ICP method, which is the alkalinity of the alkali-lipid catalyst.

[0037] Preferably, in step (1), the mass ratio of the alkali-fat catalyst to water is 15-25:45-55.

[0038] Further preferably, in the step (1), the mass ratio of the alkali-fat catalyst to water is 20:50.

[0039] Preferably, in step (1), the temperature of water is 40-60°C.

[0040] Further preferably, in the step (1), the temperature of water is 50°C.

[0041] Preferably, in step (2), the mass volume ratio of the upper solution to nitric acid, hydrofluoric acid and perchloric acid is 0.09-0.11 g: 10 ml: 2 ml: 2 ml.

[0042] Further preferably, in the step (2), the mass volume ratio of the upper solution to nitric acid, hydrofluoric acid and perchloric acid is 0.10 g:10 ml:2 ml:2 ml.

[0043] Preferably, the mass volume ratio of the upper layer solution to solution 3 is 0.09-0.11 g:100 ml.

[0044] Further preferably, the mass volume ratio of the upper solution to solution 3 is 0.10 g:100 ml.

[0045] Example 1.

[0046] The specific detection steps are as follows:

[0047] (1) Take 20 g ± 5 g of the prepared alkaline lipid solution and transfer it into a 100 ml beaker.

[0048] (2) Take ultrapure water at 50°C and add 50 g ± 5 g into a 100 ml beaker.

[0049] (3) Stir and mix the alkaline fat and ultrapure water thoroughly, wash with water, and let stand to separate the layers.

[0050] (4) Accurately weigh 0.1 g ± 0.01 g of the upper alkaline lipid phase into a ceramic crucible or a PTFE crucible, accurate to 0.0001 g.

[0051] (5) Add 10 ml of nitric acid, 2 ml of hydrofluoric acid, and 2 ml of perchloric acid into a crucible to obtain Solution 1.

[0052] Alternatively, microwave digestion can be used here, and 10 ml of nitric acid and 2 ml of hydrogen peroxide are added to a microwave digestion tube to obtain solution 1.

[0053] (6) Set the temperature of the electric heating plate to 180±10°C and heat the crucible until the acid evaporates. When 1-2 drops of acid remain at the bottom of the crucible, remove the crucible from the electric heating plate and cool it to obtain Solution 2.

[0054] During the heating process here, the acid can be observed to evaporate in the form of smoke.

[0055] If microwave digestion is used, set the microwave time to 120 min, cool naturally, and obtain Solution 2.

[0056] (7) Transfer the remaining acid, i.e., solution 2, to a 100 ml volumetric flask, rinse the crucible with ultrapure water several times, transfer the solution to the volumetric flask, and dilute to the mark with ultrapure water to obtain solution 3 for testing.

[0057] If microwave digestion is used, rinse the microwave tube with ultrapure water several times, transfer it to a volumetric flask, and dilute it to the mark with ultrapure water to obtain solution 3 for testing.

[0058] (8) Take 10 g ± 1 g of the lower aqueous phase, accurate to 0.0001 g, and transfer it to a 100 ml volumetric flask. Add ultrapure water to the mark to obtain Solution 4, which is to be tested.

[0059] (9) Use ICP or AAS to measure the potassium ion concentration in the upper alkaline lipid layer and the lower water layer, i.e., solution 3 and solution 4, respectively.

[0060] The content of R-Si-OK alkali fat in the effective ingredient solution 3 in the alkali fat (%) = instrument measurement value * V ÷ m * 10.

[0061] The instrumental value is K of ICP or AAS + Detection value, unit is mg / kg.

[0062] V is the constant volume in ml.

[0063] m is the weighing mass in g.

[0064] Experimental verification:

[0065] (1) Water-washable alkali grease verification design:

[0066] The operating steps of Example 1 were adopted. The difference was that different proportions of potassium hydroxide and different water temperatures (the water temperatures of steps (2)-(3) in Example 1) were used to measure and compare the solubility in the same batch of methylpolysiloxane solvent to verify the correctness of the method principle.

[0067] When the mass ratio of potassium hydroxide to methyl polysiloxane is 0.2%, potassium hydroxide can be completely dissolved in the methyl polysiloxane solvent, and there is no free K + , so the water-washing detection solution K + The blank value measured with pure water is: when the mass ratio of potassium hydroxide to methyl polysiloxane is 7%, potassium hydroxide cannot be completely dissolved in the methyl polysiloxane solvent at room temperature, and free K + , so the water-washing test solution can detect K + content.

[0068] ① Experimental data of ultrapure water washing layer are shown in Table 1:

[0069] Table 1

[0070]

[0071]

[0072] ② The experimental data of the oil phase layer are shown in Table 2.

[0073] Table 2

[0074] Mass ratio of potassium hydroxide to methyl polysiloxane 20℃ 40℃ 60℃ 80℃ 100℃ 0.2％ 0.135 0.131 0.133 0.11 0.098 1％ 0.702 0.706 0.705 0.673 0.658 2％ 1.39 1.385 1.388 1.30 1.295 3％ 2.088 1.925 1.92 1.88 1.86 5％ 3.1 3.048 3.04 2.992 2.87 7％ 3.168 3.159 3.14 2.825 2.55

[0075] ③ In alkaline lipid solution, K in water phase + and K in the oil phase + The total is shown in Table 3:

[0076] Table 3

[0077]

[0078] Combining the experimental data analysis in Table 1-3, we can see that:

[0079] 1. When the water temperature exceeds 60℃, the K in the initiator-R-Si-O-Si-OK group in the alkali grease can be + Wash down, and the higher the temperature, the K in the -R-Si-O-Si-OK group + The easier it is to wash off.

[0080] 2. When using water below 40℃, the K in the initiator-R-Si-O-Si-OK group in the alkaline grease cannot be washed out or only a small amount can be washed out. + .

[0081] 3. When using water at 40-60℃, there is basically no significant change.

[0082] 4. Ignoring instrument deviation and sample processing deviation, K in oil phase and water phase + The total value is basically consistent with the theoretical calculated value, with a theoretical deviation of -65ppm to +101ppm.

[0083] (2) Test experiment using different methyl polysiloxane solvents

[0084] Methyl polysiloxane is mainly divided into linear polysiloxane and cyclic polysiloxane. This time, three solvents, linear polysiloxane, cyclic polysiloxane and linear polysiloxane plus cyclic polysiloxane, were used respectively. Potassium hydroxide was added to the three solvents at a mass fraction of 2%. The test data after the experimental steps of Example 1 were as follows:

[0085] ① The experimental data of the oil phase layer are shown in Table 4:

[0086] Table 4

[0087]

[0088] ② The experimental data of the water phase layer are shown in Table 5:

[0089] Table 5

[0090]

[0091] ③Base esters in different solvents, K in the aqueous phase + and K in the oil phase + The total is shown in Table 6:

[0092] Table 6

[0093]

[0094]

[0095] Combining the experimental data in Table 4-6, we find that:

[0096] 1. Potassium hydroxide has better solubility in linear polysiloxane than in cyclic polysiloxane.

[0097] 2. The dissolution results obtained using different solvents are consistent.

[0098] 3. The detection method of this patent is applicable to alkaline lipid solutions of various methyl polysiloxane solvents.

[0099] The above is only a preferred embodiment of the embodiment of the present invention, and does not impose any form of limitation on the embodiment of the present invention. Any simple modification, equivalent changes and modifications made to the above embodiment based on the technical essence of the embodiment of the present invention are still within the scope of the technical solution of the embodiment of the present invention.

Claims

1. A method for detecting the basicity of 107 gum alkali catalyst, characterized in that: The following steps are involved: (1) After fully mixing the alkali-fat catalyst and water, the mixture is allowed to stand and separate into layers; the mass ratio of the alkali-fat catalyst to water is 15-25:45-55; (2) taking out the upper layer solution after stratification, adding nitric acid, hydrofluoric acid and perchloric acid, and mixing evenly to obtain solution 1; the mass volume ratio of the upper layer solution to nitric acid, hydrofluoric acid and perchloric acid is 0.09-0.11 g:10 ml:2 ml:2 ml; (3) heating at 170-190° C., after 0.09-0.11 g of the acid in solution 1 evaporates to 1-2 drops, cooling to obtain solution 2; (4) adding water to the solution 2 to obtain a solution 3; the mass volume ratio of the upper layer solution to the solution 3 is 0.09-0.11 g:100 ml; (5) Detecting the potassium ion concentration in the solution 3, i.e., the alkalinity of the alkali-lipid catalyst.

2. The detection method according to claim 1, characterized in that: In the step (1), the mass ratio of the alkali-fat catalyst to water is 20:

50.

3. The detection method according to claim 1, characterized in that: In the step (1), the temperature of water is 40-60°C.

4. The detection method according to claim 3, characterized in that: In the step (1), the temperature of water is 50°C.

5. The detection method according to claim 1, characterized in that: In the step (2), the mass volume ratio of the upper solution to nitric acid, hydrofluoric acid and perchloric acid is 0.10g:10ml:2ml:2ml.

6. The detection method according to claim 1, characterized in that: The mass volume ratio of the upper layer solution to solution 3 is 0.10g:100ml.

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