Preparation method of organic silicon demolding emulsion

Abstract

The invention discloses a preparation method of an organic silicon demolding emulsion, which comprises the following steps: compounding an emulsifier to stably disperse a silicone oil emulsion into a water phase with a small particle size, and carrying out crosslinking chain extension through emulsion polymerization to prepare the emulsion. The particle size is smaller, layering and floating oil are avoided, and the number of times of repeated demolding is more. The emulsifier is prepared by compounding a cationic emulsifier and a nonionic emulsifier according to a proper ratio. The prepared emulsion can enable silicon-oxygen bonds and the cross-linking agent in a system to be subjected to better cross-linking polymerization, demolding can be performed for more times after the emulsion is sprayed on a mold, and meanwhile, the adhesion of a product to the mold is reduced, so that the service life of the mold is prolonged. The method is low in production cost, and the polymerized silicon emulsion is stable and safe in performance. And a stable emulsion system can be provided for modification of a subsequent polymerization reaction.

Description

Technical Field

[0001] The invention relates to the technical field of mold release emulsions, and in particular to a method for preparing an organosilicon mold release emulsion. Background Art

[0002] Due to the special properties of silicone emulsions such as high and low temperature resistance and low surface tension, they are also widely used in release agent products. Compared with other traditional release agent products, silicone release agents have significant advantages such as low concentration, multiple uses, good demoulding effect, no solvent, and no oil-water separation phenomenon when diluted. The formula of the composite emulsifier was designed and optimized by using the HLB method (hydrophilic-lipophilic balance method) and the restricted mixing uniform design method, and the non-ionic composite emulsifier required for silicone emulsion was prepared. Then the phase inversion emulsification method was used, and a high shear homogenizer was selected for shear stirring. The effects of process parameters such as emulsifier content, emulsification time, stirring rate, emulsification temperature, pH value, etc. on the performance of the emulsion were investigated. Under the optimized conditions, a silicone emulsion with small particle size (nanoscale), fine and uniform, and excellent performance was prepared.

[0003] The preparation process is simple and easy to operate, and there are two forms of the prepared product:

[0004] 1. In W / O (water-in-oil) type silicone emulsion, water is the dispersed phase and silicone is the continuous phase. 2. In O / W (oil-in-water) type silicone emulsion, water is the continuous phase and silicone is the dispersed phase. There are two common methods for preparing silicone emulsion release agents (i.e. water-based silicone release agents), which can be prepared by mechanical emulsification or emulsion polymerization: the mechanical emulsification method is to first polymerize silicone oil to form silicone siloxane polymers, and then use a shearing machine to shear and disperse them with the addition of raw materials such as water phase and emulsifier to form silicone emulsion release agent; the emulsion polymerization method is a polymerization method in which, in a system with water or other liquid solvents as the medium, separated micelle particles are produced according to the oligomer mechanism or micelle mechanism, and free radical or ion addition polymerization is carried out inside the micelle particles to produce polymers.

[0005] The disadvantage is that in order to prepare an excellent silicone emulsion, it is necessary to find a suitable emulsifier and mixing ratio, as well as an emulsification process. If the emulsifier selection, mixing ratio and emulsification process are inappropriate, it is very easy to cause emulsion instability and poor emulsion polymerization effect in the later stage, which directly affects the performance of the release agent. Summary of the invention

[0006] In order to solve the problems mentioned in the above background technology, the present invention provides a method for preparing an organic silicone demoulding emulsion, which is prepared by compounding an emulsifier so that the silicone oil emulsion is stably dispersed into the water phase with a very small particle size, and then cross-linking and chain extension are performed by emulsion polymerization to prepare the emulsion. Compared with the past, the performance of the emulsion has been greatly optimized, so that it has the characteristics of smaller particle size, no stratification, no oil floating, and more repeated demoulding times. The emulsifier is obtained by compounding a cationic emulsifier and a nonionic emulsifier in a suitable ratio.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The specific preparation method of silicone release emulsion is as follows:

[0009] 1. Mechanical forced emulsification and dispersion stage

[0010] S1. Add 1-2% of compound emulsifier into the container at 50±2℃ and stir evenly;

[0011] S2, slowly add the 20-24% dimethylhydroxy silicone oil to be emulsified into the stirred S1, and then stir the two thoroughly;

[0012] S3, slowly add 1-5% paraffin oil into S2 under stirring and emulsify it evenly;

[0013] S4. Slowly add the measured water to step S3 under stirring. Add water slowly and stir thoroughly for a period of time. After adding water, keep stirring for 30±10 minutes. When foam is generated and covers the surface of the dispersion liquid, add 0.3-0.5% of the measured defoamer, and finally add an appropriate amount of triethanolamine to adjust the pH to 7. The obtained emulsion is a milky white fine emulsion with a slightly blue light and a uniform particle size distribution.

[0014] Emulsion polymerization stage

[0015] S5, the emulsion prepared above is heated, nitrogen is introduced, the temperature is maintained at 57±2°C, and then 11-12% methyltriethoxysilane (MTMS) is added dropwise to the system, and the timing is maintained for 4H±10min from the start of the addition to ensure that the reaction does not overheat. After the reaction is completed, the temperature is lowered to room temperature, the pH is adjusted to 6-7 with triethanolamine, and then filtered;

[0016] S6. Then, 1-5% sodium bicarbonate is added to the S5 system, and after stirring for 10-15 minutes, the temperature is raised to 60±2° C., 1-3% trimethylchlorosilane is slowly added dropwise, and finally, the system is filtered through a 200-mesh filter cloth to obtain an organosilicon release emulsion.

[0017] Preferably, the compound emulsifier is prepared by compounding CTAB and OP-10 in a mass ratio of 1:2.

[0018] Preferably, the compound emulsifier is DBSA and SE-10 compounded in a mass ratio of 1:2.

[0019] Preferably, the defoamer is a polyether silicone oil defoamer.

[0020] The invention firstly performs mechanical emulsification to prepare a pre-emulsion, then performs a synthesis reaction, and finally performs an end-capping reaction to obtain the product.

[0021] Dimethylhydroxy silicone oil molecular formula: HO[(CH3)2SiO] n H

[0022] Emulsion polymerization process:

[0023]

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

[0025] This improved method aims to improve the defects of the current emulsion release agents on the market, such as easy oil bleaching, easy yellowing, corrosion of mold substrates, and few demolding times. By compounding the cationic emulsifier and the non-ionic emulsifier, the lipophilic and hydrophilic base ratios can form a uniform and stable O / W (oil-in-water) system with silicone oil to the greatest extent. The prepared emulsion can allow the silicon oxygen bonds and cross-linking agents in the system to be better cross-linked and polymerized. After such an emulsion is sprayed on the mold, more demolding can be performed. At the same time, it also reduces the stickiness of the product to the mold, thereby extending the service life of the mold. The prepared demolding emulsion has good stability and no stratification, is friendly to the demolding substrate, and is not easy to age and yellow. This method has low production costs and the performance of the silicone emulsion after polymerization is stable and safe, and can also provide a stable emulsion system for the modification of subsequent polymerization reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0027] Figure 1 Schematic diagram of the emulsification mechanism of the emulsifier of the present invention;

[0028] Figure 2 This is a schematic diagram of the preparation process of the emulsion of the present invention;

[0029] Figure 3 It is a schematic diagram of demoulding of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0031] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0032] Example 1

[0033] Emulsifier made of CTAB and OP-10

[0034] 1. Add 120g of dimethyl silicone oil to 6g of emulsifier (CTAB: OP-10 = 1:2) of hexadecyl trimethylammonium bromide (CTAB) and alkyl acid polyoxyethylene ether (OP-10), and add 5g of paraffin oil under stirring to mix evenly. Maintain the mixed system at 50°C, use a high-speed disperser to mix evenly at 600rpm, then adjust the disperser speed to 3000rpm and use a peristaltic pump to drop 300g of 50°C deionized water to form an O / W (oil in water) state. When a large amount of foam is generated during the dropwise addition, 1.5g of defoamer can be added. After the dropwise addition, add an appropriate amount of triethanolamine to adjust the pH to 6-7.

[0035] 2. Add the prepared emulsion into the reaction bottle and heat it up. Then introduce 0.2 m nitrogen. 3 / h, maintaining the reaction temperature at 57°C, and then slowly adding 56g of methyltriethoxysilane (MTMS) into the system with a peristaltic pump, the dropping rate is 0.2-0.3g / min, and the reaction is maintained for 4h from the start of the addition. After the reaction is completed, the temperature is lowered to room temperature, the pH is adjusted to 6-7 with triethanolamine, and then filtered with a 200-mesh filter cloth.

[0036] 3. Add the filtered emulsion into the reaction bottle, add 5g of sodium bicarbonate to the system, stir for 10-15min, heat the system to 60°C, then slowly add 8g of trimethylsilyl chloride for end-capping, keep the reaction for 3 hours, and finally filter through a 200-mesh filter cloth to obtain the silicone release emulsion.

[0037] Example 2

[0038] Emulsifier compounded with DBSA and SE-10

[0039] 1. Add 120g of dimethyl silicone oil to 6g of emulsifier (DBSA: SE-10 = 1:2) of dodecylbenzenesulfonic acid (DBSA) and fatty acid polyoxyethylene ester (SE-10), and add 10g of paraffin oil under stirring to mix evenly. Maintain the system at 50°C, use a high-speed disperser to mix evenly at 600rpm, then adjust the disperser speed to 3000rpm and use a peristaltic pump to drop 300g of 50°C deionized water to form an O / W (oil in water) state. When a large amount of foam is generated during the dropwise addition, 1.5g of defoamer can be added. After the dropwise addition, add an appropriate amount of triethanolamine to adjust the pH to 6-7.

[0040] 2. Add the prepared emulsion into the reaction bottle and heat it up. Then introduce 0.2 m nitrogen. 3 / h, maintaining the reaction temperature at 57°C, then slowly adding 56g of methyltriethoxysilane (MTMS) into the system with a peristaltic pump, the dropping rate is 0.2-0.3g / min, the reaction is maintained for 4h from the start of the addition, after the reaction is completed, the temperature is lowered to room temperature, the pH is adjusted to 6-7 with triethanolamine, and then filtered with a 200-mesh filter cloth.

[0041] 3. Add the filtered emulsion into the reaction bottle, add 5g of sodium bicarbonate to the system, stir for 10-15min, heat the system to 60°C, then slowly add 8g of trimethylsilyl chloride for end-capping, keep the reaction for 3 hours, and finally filter through a 200-mesh filter cloth to obtain the silicone release emulsion.

[0042] Comparative Example 1

[0043] Performance testing and comparative experiments

[0044] (1) Determine the centrifugal stability of the sample

[0045] Take about two-thirds of the emulsion in the centrifuge tube, and use a centrifuge to test the emulsion in the embodiment at a speed of 3000r / min for 30min, and record the state of the emulsion in the centrifuge tube to observe whether it is separated into layers and floating oil. The test results are shown in Table 1:

[0046] Table 1 Sample centrifugation test results

[0047]

[0048] (2) Determine the corrosiveness of the sample to the mold material

[0049] Immerse Fe, Al, Zn and steel bars in sealed stock solution tanks respectively, and place these tanks in a 60℃ oven for one day and night, then take them out. Check whether the metal bars are corroded or discolored, or whether the release agent is discolored or delaminated. The test results are shown in Table 2:

[0050] Table 2 Sample corrosion test results

[0051]

[0052] (3) Determination of average demolding times

[0053] Take a certain amount of demoulding emulsion and dilute it 30 times with deionized water, spray it on the cast iron mold, put it in a 100±2℃ oven for 30 minutes, and then mold the epoxy modified polyurethane polymer material. The average demoulding times of using the demoulding agent once are shown in Table 3;

[0054] Table 3 Average demoulding times of release agents

[0055]

[0056] (4) Determination of sample electrolyte stability

[0057] Weigh 3g of the emulsion into a 150ml beaker, add 97ml of a 2% MgCl2 aqueous solution, let stand at 25°C for 24h, and record the emulsion stratification and oil bleaching phenomenon as shown in Table 4;

[0058] Table 4 Stability of samples in electrolyte environment

[0059]

[0060] (5) Determination of yellowing properties of samples

[0061] Take 5 g of sample and dilute it to 100 g with deionized water, place it in an oven for 30 min and measure the yellowing temperature, as shown in Table 5;

[0062] Table 5 Yellowing temperature of samples

[0063]

[0064] Comparison of the above test results highlights the good performance of the present invention in terms of stability, demoulding times, corrosion resistance and yellowing resistance. Under the emulsification of the compound emulsifier, the system material can be dispersed more evenly, allowing the next step of the synthetic reaction to be cross-linked more thoroughly. At the same time, the organic silicon material used in the present invention has low surface energy, which reduces the peeling force and improves the demoulding effect. Since the polymer skeleton of the demoulding agent is composed of silicon-oxygen bonds, the bond energy of the silicon-oxygen bonds is high, the heat resistance is excellent, and the anti-yellowing effect is outstanding.

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a silicone release emulsion, characterized in that: The following steps are involved: (I) Mechanical forced emulsification and dispersion stage: S1. Add the compound emulsifier into the container and stir evenly at 50±2℃; S2, slowly add the prepared emulsified dimethyl hydroxy silicone oil to the mixed emulsifier in S1 under stirring, so that the two are fully stirred; S3, slowly add paraffin oil into S2 under stirring and emulsify it evenly; S4, slowly adding water to step S3 under stirring, slowly adding water and stirring for a period of time, and maintaining stirring after the addition of water is completed; when foam is generated and covers the surface of the dispersion liquid, add a defoamer, and finally add triethanolamine to adjust the pH to 7. The obtained emulsion is a milky white fine emulsion with a slightly blue light and a uniform particle size distribution; (II) Emulsion polymerization stage: S5, heating the emulsion prepared above, introducing nitrogen, maintaining the temperature at 57±2°C, then adding methyltriethoxysilane dropwise to the system to ensure that the reaction does not overheat, cooling to room temperature after the reaction, adjusting the pH to 6-7 with triethanolamine, and then filtering; S6. Then, sodium bicarbonate is added to the S5 system, and the mixture is stirred. The temperature is then raised to 60±2° C., trimethylchlorosilane is slowly added dropwise, and finally, the mixture is filtered through a 200-mesh filter cloth to obtain an organosilicon release emulsion.

2. The method for preparing a silicone release emulsion according to claim 1, characterized in that: The compound emulsifier is prepared by compounding CTAB and OP-10 in a mass ratio of 1:

2.

3. The method for preparing a silicone release emulsion according to claim 1, characterized in that: The compound emulsifier is prepared by compounding DBSA and SE-10 in a mass ratio of 1:

2.

4. The method for preparing a silicone release emulsion according to claim 1, characterized in that: The defoamer is a polyether silicone oil defoamer.

5. The method for preparing a silicone release emulsion according to claim 1, characterized in that: After adding water in S4, the stirring time is maintained for 30±10min 。 6. The method for preparing a silicone release emulsion according to claim 1, characterized in that: When methyltriethoxysilane is added dropwise to S5, the time is maintained for 4H±10min from the start of the addition.

7. The method for preparing a silicone release emulsion according to claim 1, characterized in that: Sodium bicarbonate was added to the S6 and stirred for 10-15 min, and the filter cloth used for filtering was 200 mesh.

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