Silicone-acrylate emulsion and method for its preparation

Abstract

The application discloses a kind of silicone-acrylate emulsion and preparation method thereof, the silicone-acrylate emulsion is made by including the following weight parts of raw materials by polymerization reaction: silicon monomer 15~60 parts, acrylate monomer 10~40 parts, emulsifier 5~20 parts, initiator 1~15 parts, water 40~60 parts, reaction temperature is 80~120 DEG C, reaction time is 5~9h.The silicone-acrylate emulsion of the application is with silicone monomer as core structure, and the silicone-acrylate emulsion prepared by copolymerization addition reaction with acrylate.The silicone-acrylate emulsion prepared by the application has high silicon content, good emulsion stability, good high and low temperature resistance, and the preparation method and process are non-toxic and non-polluting, the product prepared is low pollution, green and environmental protection, high performance, strong water resistance, and can be used for environmental protection type coating.

Description

Technical Field

[0001] This invention relates to the field of polymer chemical synthesis technology, and in particular to a silicone-acrylic emulsion and its preparation method. Background Technology

[0002] Polyacrylate coatings are among the most important polymer coatings available today, widely used due to their excellent weather resistance, adhesion, acid and alkali resistance, and corrosion resistance. However, poor water resistance, poor high and low temperature resistance, and poor weather resistance limit their application. In the main chain structure of organosilicon molecules, the Si-O bond energy is high, and there is a large molecular volume and low cohesive energy density, thus exhibiting good high and low temperature resistance, weather resistance, and water resistance. Using organosiloxane-acrylate copolymerization can effectively combine the respective advantages of organosiloxanes and acrylic resins to prepare silicone-acrylic emulsion products with superior performance. With increasing environmental awareness, the development of green, environmentally friendly, and high-performance coatings has become an important trend, making the design of high-silicon-content acrylate coatings particularly crucial.

[0003] There are two methods for synthesizing organosilicon-acrylate emulsions: physical modification and chemical modification. Physical modification involves preparing an organosilicon emulsion from organosiloxane monomers, which is then blended with an acrylic ester emulsion for modification. However, organosilicon-acrylate emulsions prepared by this method have low stability. Chemical modification involves forming chemical bonds between the organosilicon monomers and acrylate monomers, improving their compatibility. Commonly used chemical modification methods include: ① graft copolymerization, which introduces organosilicon segments into the acrylic copolymer through the condensation reaction of the active functional groups (-OH, -OR) at the ends or side groups of the organosilicon monomers with acrylate monomers; ② emulsion polymerization, which uses organosilicon monomers containing unsaturated double bonds to undergo free radical copolymerization with acrylate monomers, thereby obtaining a more structurally stable silicone-acrylic emulsion. Relatively speaking, emulsion polymerization has advantages such as easy reaction control, rapid heat dissipation, no by-products, and the ability to design latex particles, making it the most widely used method.

[0004] Traditional preparations of silicone-acrylate emulsions involve modifying acrylates with silicone monomers, resulting in products with low silicone content, making it difficult to fully utilize the superior properties of silicone. Existing technologies involve complex and energy-intensive processes, and the reactants experience a dramatic increase in viscosity after polymerization, which can clog reaction channels. Furthermore, the resulting products have low silicone content and poor water resistance in the coating.

[0005] Therefore, as acrylic coatings continue to develop towards high performance, it is particularly important to prepare silicone-acrylic emulsions with high silicon content. Summary of the Invention

[0006] The purpose of this invention is to provide a silicone-acrylic emulsion and its preparation method, specifically involving a method for preparing a silicone-acrylic emulsion by emulsion copolymerization, with the main raw materials being vinyl-containing silicone monomers and acrylates, under the initiation of organic peroxides.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a silicone-acrylic emulsion, the method comprising the following steps: mixing water and emulsifier and adding them to a reaction vessel, stirring until homogeneous; then mixing silicone monomer, acrylate monomer and initiator and adding them dropwise to the reaction vessel, controlling the reaction temperature of the reaction vessel within the range of 80 to 120°C, and the reaction time within 5 to 9 hours, and obtaining the silicone-acrylic emulsion after the reaction is completed;

[0009] The weight parts of each raw material are as follows: 15-60 parts of silicon monomer, 10-40 parts of acrylate monomer, 5-20 parts of emulsifier, 1-15 parts of initiator, and 40-60 parts of water.

[0010] In some embodiments, the weight parts of each raw material in the method of the present invention are: 30-60 parts of silicon monomer, 10-30 parts of acrylate monomer, 8-16 parts of emulsifier, 5-12 parts of initiator, and 40-60 parts of water.

[0011] Preferably, the weight parts of each raw material in the method of the present invention are: 40-60 parts of silicon monomer, 10-20 parts of acrylate monomer, 8-16 parts of emulsifier, 6-12 parts of initiator, and 40-60 parts of water.

[0012] The silicone-acrylic emulsion prepared by the method of the present invention has a high silicone content, approximately 12 wt% to 15 wt%, thereby giving the product superior performance. The silicone content of the emulsion is increased by increasing the weight part of the silicone monomer and decreasing the weight part of the acrylate monomer. Therefore, the weight part of the silicone monomer in the present invention is 15 to 60 parts, preferably 30 to 60 parts, more preferably 40 to 60 parts; and the weight part of the acrylate monomer is 10 to 40 parts, preferably 10 to 30 parts, more preferably 10 to 20 parts.

[0013] In some embodiments, the silicon monomer of the present invention is selected from one or more of tetramethyltetravinylcyclotetrasiloxane, 1,3-divinylhexamethylcyclotetrasiloxane, and silicone resin.

[0014] Preferably, the silicon monomer is one of tetramethyltetravinylcyclotetrasiloxane, 1,3-divinylhexamethylcyclotetrasiloxane, or silicone resin.

[0015] Preferably, the silicon monomer is a silicone resin.

[0016] More preferably, the silicone resin is prepared by the following steps:

[0017] The tetrafunctional organosilicon monomer and the end-capping agent are added to the reactor at a mass ratio of 100:(4~18), and the catalyst is added at a mass percentage of 1%~10%, and the deionized water is added at a mass percentage of 30%~60%. The mixture is stirred at 90℃~110℃ for 3~5h.

[0018] After the reaction is complete, an organic solvent is added for extraction and separation. The organic phase is washed with a weak alkaline solution until neutral, and then dried to obtain the silicone resin.

[0019] Preferably, the organic solvent is selected from benzene, toluene, and xylene.

[0020] Preferably, the weakly alkaline solution is selected from potassium bicarbonate and sodium bicarbonate, and the mass concentration of the weakly alkaline solution is 2wt% to 15wt%.

[0021] The tetrafunctional organosilicon monomer is methyl orthosilicate or ethyl orthosilicate.

[0022] The capping agent is one or a mixture of two of tetramethyldivinyldisiloxane and hexamethyldisiloxane.

[0023] Preferably, the capping agent is a mixture of tetramethyldivinyldisiloxane and hexamethyldisiloxane; more preferably, the mass ratio of tetramethyldivinyldisiloxane to hexamethyldisiloxane is (3-9):(1-7).

[0024] The catalyst is concentrated hydrochloric acid or sulfonic acid-based polystyrene exchange resin.

[0025] In some embodiments, the acrylate monomers of the present invention are selected from one or more of methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate.

[0026] In some embodiments, the emulsifier of the present invention is selected from one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate.

[0027] Preferably, the emulsifier is a mixture of any two of the above emulsifiers, and the weight ratio of the two emulsifiers is (1-4):(1-3), preferably (1-3):(1-2).

[0028] Preferably, the emulsifier is selected from any two of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyoxyethylene sorbitan monolaurate, and polyoxyethylene sorbitan monostearate.

[0029] The emulsifier used in this invention plays a decisive role in emulsion stability, with nonionic emulsifiers exhibiting better stability. Furthermore, the HLB value of the emulsifier also affects emulsion stability. Simultaneously, the amount of emulsifier used also influences the emulsion; too low an emulsifier content leads to emulsion instability, while too high an content negatively impacts product performance. Therefore, the weight range of the emulsifier in this invention is 5–20 parts, preferably 8–16 parts. The HLB value of the emulsifier described in this invention is 8–14, preferably 10–14.

[0030] In some embodiments, the initiator of the present invention is selected from one of benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, and diisopropyl peroxide.

[0031] This invention controls the degree of polymerization of an emulsion by controlling the amount of initiator. The amount of initiator affects the molecular weight of the polymer. If there is too little initiator, during the initial stage of polymerization, some monomers will undergo chain growth to form high molecular weight substances, causing a sharp increase in viscosity, which will encapsulate active groups and lead to uneven molecular weight distribution. If there is too little initiator, more active groups will be generated, resulting in lower molecular weights for the polymers. Therefore, the initiator of this invention is 1 to 15 parts by weight, preferably 5 to 12 parts, and more preferably 6 to 12 parts.

[0032] In some embodiments, the reaction temperature of the present invention is 95–120°C.

[0033] In some embodiments, the reaction time of the present invention is 7 to 9 hours.

[0034] Reaction temperature and reaction time also have a significant impact on the polymerization reaction. Too low a reaction temperature and too short a reaction time can lead to incomplete reaction, or even no polymerization at all; while a suitable reaction temperature and a longer reaction time are beneficial for improving the conversion rate, but excessively long reaction times can lead to energy and resource waste. Therefore, the optimal reaction temperature in the method of this invention is 80–120°C, preferably 95–120°C, and the optimal reaction time is 5–9 hours, preferably 7–9 hours.

[0035] Secondly, the present invention provides a silicone-acrylic emulsion prepared by the method described in the present invention.

[0036] In some embodiments, the silicone-acrylic emulsion of the present invention is obtained by polymerization reaction of raw materials comprising the following parts by weight: 15-60 parts of silicone monomer, 10-40 parts of acrylate monomer, 5-20 parts of emulsifier, 1-15 parts of initiator, and 40-60 parts of water; the reaction temperature is 80-120°C, the reaction time is 5-9 hours, and the silicone-acrylic emulsion is obtained after the reaction is completed.

[0037] The method for synthesizing silicone-acrylic emulsion provided by this invention is simple and the preparation process is non-toxic and pollution-free. The resulting coating product combines the excellent properties of both silicone monomers and acrylates, exhibiting low pollution, environmental friendliness, excellent high and low temperature resistance and corrosion resistance, and significantly enhanced water resistance. It can be used in high-performance environmentally friendly coatings and can be industrially produced. Detailed Implementation

[0038] The following examples further illustrate specific embodiments of the present invention. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] Example 1

[0040] The preparation method of the silicone-acrylic emulsion in this embodiment is as follows:

[0041] 40 parts water and 8 parts composite emulsifier (octylphenol polyoxyethylene ether to polyoxyethylene sorbitan monostearate in a 3:2 mass ratio) were mixed and added to a reaction vessel and stirred until homogeneous. Then, 40 parts tetramethyltetravinylcyclotetrasiloxane, 20 parts ethyl 2-methacrylate monomer, and 8 parts benzoyl peroxide were mixed and added dropwise to the reaction vessel. The vessel temperature was controlled at 95℃, and the reaction time was 7 hours. After the reaction, a highly stable emulsion product was obtained. The emulsion showed a silicone content of 13.4 wt%. The prepared coating film did not exhibit significant deformation at temperatures ranging from -50℃ to 250℃, demonstrating good temperature resistance. The water absorption rate of the coating film was only 2.0%, and no whitening occurred after immersion in water for 10 days.

[0042] Example 2

[0043] The preparation method of the silicone-acrylic emulsion in this embodiment is as follows:

[0044] 40 parts water and 8 parts composite emulsifier (composed of fatty alcohol polyoxyethylene ether and polyoxyethylene sorbitan monostearate in a 1:1 mass ratio) were mixed and added to a reactor and stirred until homogeneous. Then, 40 parts 1,3-divinylhexamethylcyclotetrasiloxane, 15 parts methyl acrylate monomer, and 6 parts benzoyl peroxide were mixed and added dropwise to the reactor. The reactor temperature was controlled at 95℃, and the reaction time was 7 hours. After the reaction, a highly stable emulsion product was obtained. The emulsion showed a silicone content of 13.1 wt%. The prepared coating film did not exhibit significant deformation at temperatures ranging from -50℃ to 250℃, demonstrating good temperature resistance. The water absorption rate of the coating film was only 2.1%, and no whitening occurred after immersion in water for 10 days.

[0045] Example 3

[0046] In this embodiment, the silicon monomer is silicone resin. The preparation method of silicone resin is as follows: Tetraethyl orthosilicate and a capping agent (tetramethyldivinyldisiloxane and hexamethyldisiloxane in a mass ratio of 9:1) are added to a reactor at a mass ratio of 100:6. Concentrated hydrochloric acid is added at a mass percentage of 10%, followed by deionized water at a mass percentage of 40%. The mixture is stirred at 100°C for 5 hours. After the reaction is complete, an appropriate amount of toluene is added for extraction and separation. The organic phase is then washed with a 15wt% sodium bicarbonate solution until neutral. The organic phase is then dried to obtain the silicone resin.

[0047] The preparation method of the silicone-acrylic emulsion in this embodiment is as follows:

[0048] 60 parts water and 16 parts composite emulsifier (composed of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a mass ratio of 4:3) were mixed and added to a reactor and stirred until homogeneous. Then, 60 parts silicone resin, 10 parts methyl acrylate monomer, and 12 parts benzoyl peroxide were mixed and added dropwise to the reactor. The reactor temperature was controlled at 110℃, and the reaction time was 7 hours. After the reaction, a highly stable emulsion product was obtained. The silicone content of the emulsion was tested to be 14.3 wt%. The prepared coating film showed no significant deformation at temperatures ranging from -50℃ to 250℃, exhibiting good temperature resistance. The water absorption rate of the coating film was only 1.6%, and no whitening occurred after immersion in water for 10 days.

[0049] Example 4

[0050] In this embodiment, the silicon monomer is silicone resin. The preparation method of silicone resin is as follows: Tetraethyl orthosilicate and a capping agent (tetramethyldivinyldisiloxane and hexamethyldisiloxane in a mass ratio of 4:6) are added to a reactor at a mass ratio of 100:12, and sulfonated polystyrene exchange resin is added at a mass percentage of 6%, followed by 40% deionized water. The mixture is stirred at 110°C for 4 hours. After the reaction is completed, an appropriate amount of toluene is added for extraction and separation. The organic phase is then washed with a 5 wt% sodium bicarbonate solution until neutral, and the organic phase is dried to obtain silicone resin.

[0051] The preparation method of the silicone-acrylic emulsion in this embodiment is as follows:

[0052] 60 parts water and 10 parts composite emulsifier (composed of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a 1:1 mass ratio) were mixed and added to a reaction vessel and stirred until homogeneous. Then, 60 parts silicone resin, 18 parts methyl acrylate monomer, and 12 parts benzoyl peroxide were mixed and added dropwise to the reaction vessel. The vessel temperature was controlled at 110℃, and the reaction time was 7 hours. After the reaction, a highly stable emulsion product was obtained. The silicone content of the emulsion was tested to be 13.9 wt%. The prepared coating film showed no significant deformation at temperatures ranging from -50℃ to 250℃, exhibiting good temperature resistance. The water absorption rate of the coating film was only 1.8%, and no whitening occurred after immersion in water for 10 days.

[0053] Comparative Example 1

[0054] Comparative Example 1 was prepared using the same method as Example 1, except that the silicon monomer used was tetramethyldivinyldisiloxane. The resulting silicone-acrylic emulsion product was tested and found to have a silicone content of 8.4 wt%. The prepared coating exhibited severe deformation at temperatures ranging from -50°C to 250°C, demonstrating poor temperature resistance. The coating had a water absorption rate of 10.0%, and after immersion in water for 10 days, the coating showed slight whitening.

[0055] Comparative Example 2

[0056] Comparative Example 2 was prepared using the same method as Example 1, except that the emulsifiers used were Span-80 and Tween-60. The resulting silicone-acrylic emulsion product had a silicone content of 13.4 wt%. The prepared coating film showed no significant deformation at temperatures ranging from -50°C to 250°C, exhibiting good temperature resistance. The water absorption rate of the coating film was 2.2%, and after immersion in water for 10 days, there was no obvious whitening. However, the emulsion broke down after 48 hours.

[0057] Comparative Example 3

[0058] Comparative Example 3 was prepared using the same method as Example 1, except that the weight of the emulsifier was 5 parts. The resulting silicone-acrylic emulsion product exhibited obvious stratification.

[0059] Comparative Example 4

[0060] Comparative Example 4 was prepared using the same method as Example 1, except that the initiator was 20 parts by weight. The resulting silicone-acrylic emulsion product showed a significant increase in viscosity. The silicone content of the emulsion was measured to be 13.3 wt%. The prepared coating film did not undergo significant deformation at temperatures ranging from -50°C to 250°C, exhibiting good temperature resistance. The water absorption rate of the coating film was measured to be 2.6%. After soaking in water for 10 days, the coating film did not show any whitening, but the emulsion broke down after standing for 12 hours.

[0061] Comparative Example 5

[0062] Comparative Example 5 was prepared using the same method as Example 1, except that the reaction time was 4 hours and the reaction temperature was 75°C. As a result, almost no reaction occurred, and no silicone-acrylic emulsion product was obtained.

[0063] Comparative Example 6

[0064] Comparative Example 6 was prepared using the same method as Example 1, except that the weight parts of the silicon monomer and acrylate were 25 parts and 40 parts, respectively. The resulting silicone-acrylic emulsion product was found to have a silicone content of 6.2 wt%. The prepared coating film exhibited severe deformation at temperatures ranging from -50°C to 250°C, demonstrating poor temperature resistance. The water absorption rate of the coating film was 15.0%, and the film turned white after being soaked in water for 10 days.

[0065] Comparative Example 7

[0066] Comparative Example 7 was prepared using the same method as Example 1, except that the proportion of the emulsifier was adjusted so that the HLB value of the emulsifier was 6. The resulting silicone-acrylic emulsion product exhibited obvious stratification.

[0067] Experimental Example 1

[0068] The properties of the silicone-acrylic emulsions obtained in Examples 1-4 of this application and Comparative Examples 1-7 were compared, including the silicone content of the silicone-acrylic emulsion, the HLB value of the emulsifier, the stability of the emulsion, the resistance to high and low temperatures, the water absorption rate of the coating film, and the degree of whitening after immersion. The results are shown in Table 1.

[0069] Table 1. Properties of silicone-acrylic emulsions from Examples 1-4 and Comparative Examples 1-7

[0070]

[0071]

[0072] Conclusion: As shown in Table 1, the silicone-acrylic emulsion prepared by this application through the optimal ratio of each component and the optimal preparation method has high silicone content, good emulsion stability, good high and low temperature resistance, strong water resistance, and is environmentally friendly and can be used in environmentally friendly coatings.

[0073] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a silicone-acrylic emulsion, characterized in that, The method includes the following steps: Water and emulsifier are mixed and added to a reaction vessel, and stirred evenly. Then, silicone monomer, acrylate monomer and initiator are mixed and added dropwise to the reaction vessel. The reaction temperature of the reaction vessel is controlled within the range of 80-120℃, and the reaction time is 5-9 hours. After the reaction is completed, the silicone-acrylic emulsion is obtained. The weight parts of each raw material are as follows: 30-60 parts of silicon monomer, 10-30 parts of acrylate monomer, 8-16 parts of emulsifier, 5-12 parts of initiator, and 40-60 parts of water. The silicon monomer is selected from one or more of tetramethyltetravinylcyclotetrasiloxane, 1,3-divinylhexamethylcyclotetrasiloxane, and silicone resin; The emulsifier is selected from one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate; the HLB value of the emulsifier is 8 to 14.

2. The method according to claim 1, characterized in that, The silicon monomer is a silicone resin.

3. The method according to claim 1 or 2, characterized in that, The silicone resin is prepared by the following steps: The tetrafunctional organosilicon monomer and the end-capping agent are added to the reactor at a mass ratio of 100:(2~18), and the catalyst is added at a mass percentage of 1%~15%, and the deionized water is added at a mass percentage of 20%~60%. The reaction is stirred at 60℃~110℃ for 3~7h. After the reaction is complete, an organic solvent is added for extraction and separation. The organic phase is washed with a weak alkaline solution until neutral, and then dried to obtain the silicone resin.

4. The method according to claim 3, characterized in that, The tetrafunctional organosilicon monomer is methyl orthosilicate or ethyl orthosilicate.

5. The method according to claim 3, characterized in that, The capping agent is one or a mixture of two of tetramethyldivinyldisiloxane and hexamethyldisiloxane.

6. The method according to claim 5, characterized in that, The capping agent is a mixture of tetramethyldivinyldisiloxane and hexamethyldisiloxane.

7. The method according to claim 6, characterized in that, The mass ratio of tetramethyldivinyldisiloxane to hexamethyldisiloxane is (3-9):(1-7).

8. The method according to claim 3, characterized in that, The catalyst is concentrated hydrochloric acid or sulfonic acid-based polystyrene exchange resin.

9. The method according to claim 1, characterized in that, The acrylate monomer is selected from one or more of methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate.

10. The method according to claim 1, characterized in that, The emulsifier is a mixture of any two emulsifiers, and the weight ratio of the two emulsifiers is (1-4):(1-3).

11. The method according to claim 1, characterized in that, The initiator is selected from one of benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, and diisopropyl peroxide.

12. A silicone-acrylic emulsion prepared by any one of claims 1-11.

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