Organic silicon modified polyurethane-acrylate composite emulsion and preparation method thereof

Abstract

The invention discloses an organic silicon modified polyurethane-acrylate composite emulsion and a preparation method of the organic silicon modified polyurethane-acrylate composite emulsion, and relates to the technical field of polymer composite emulsions. Comprising the following raw materials: 70 to 120 parts of oligomer polyol with an average molecular weight of 500 to 2000, 5 to 15 parts of a composite organosilicon component, 40 to 80 parts of diisocyanate, 0.05 to 0.2 part of a catalyst, 2 to 5 parts of a hydrophilic chain extender, 3 to 6 parts of a self-crosslinking hydrophilic chain extender, 4 to 12 parts of a neutralizer, 2 to 8 parts of a water-based chain extender and 50 to 150 parts of an acrylate monomer. 1-5 parts of an acrylate functional monomer, 1-3 parts of a cross-linking agent, 2-8 parts of an emulsifier and 0.5-3 parts of an initiator; the organic silicon modified polyurethane-acrylate composite emulsion prepared by the invention has a composite core-shell structure taking organic silicon modified polyurethane as a core and an acrylate polymer as a shell, so that the emulsion can form a more compact and more stable three-dimensional cross-linked network during film formation, and the weather resistance, water resistance, mechanical strength and surface glossiness of a coating film are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite emulsion technology, specifically relating to an organosilicon-modified polyurethane-acrylate composite emulsion and its preparation method. Background Technology

[0002] In the current printing industry, with the development towards green and low-carbon trends, water-based coatings, inks, and adhesives are gradually replacing traditional solvent-based products. Polyurethane and water-based acrylates are currently the main raw materials. Among them, polyurethane, due to the presence of strong polar bonds such as urethane bonds in its molecular chain, has excellent flexibility, abrasion resistance, adhesion, and low-temperature resistance. Water-based acrylates, on the other hand, have high hardness, excellent weather resistance, chemical resistance, and gloss retention, and have lower raw material costs, making them important raw material resins for environmental protection and green development.

[0003] However, polyurethane alone also has some inherent drawbacks, such as poor water resistance, low hardness, poor heat resistance, and relatively high production costs, which limits its application in certain high-performance fields. Waterborne acrylates, on the other hand, have poor flexibility at room temperature, poor film-forming properties, high brittleness, and lower wear resistance than polyurethane. To combine the advantages of both, the industry has developed a polyurethane-acrylate composite system to achieve complementary advantages between polyurethane and waterborne acrylates.

[0004] Currently, polyurethane-acrylate composite systems are typically prepared by physical blending or conventional emulsion polymerization. However, due to the significant differences in molecular structure between polyurethane and acrylate, their compatibility is poor, and micro-phase separation is prone to occur, leading to a substantial decrease in the mechanical properties and stability of the coating film, failing to achieve the expected performance. On the other hand, conventional emulsion polymerization methods can only achieve simple physical mixing or limited grafting reactions, making it difficult to form stable chemical bonds at the molecular level, resulting in limited improvement in the wear resistance and water resistance of the composite material.

[0005] To address these issues, we propose a silicone-modified polyurethane-acrylate composite emulsion and its preparation method, which effectively synergizes the advantages of polyurethane, acrylate, and silicone to improve the mechanical properties of the coating. Summary of the Invention

[0006] The purpose of this invention is to provide a silicone-modified polyurethane-acrylate composite emulsion and its preparation method, which can effectively synergize the advantages of polyurethane, acrylate and silicone to improve the mechanical properties of the coating film, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An organosilicon-modified polyurethane-acrylate composite emulsion, by weight, comprises the following raw materials: 70-120 parts of oligomeric polyol with an average molecular weight of 500-2000, 5-15 parts of composite organosilicon component, 40-80 parts of diisocyanate, 0.05-0.2 parts of catalyst, 2-5 parts of hydrophilic chain extender, 3-6 parts of self-crosslinking hydrophilic chain extender, 4-12 parts of neutralizer, 2-8 parts of water-based chain extender, 50-150 parts of acrylate monomer, 1-5 parts of acrylate functional monomer, 1-3 parts of crosslinking agent, 2-8 parts of emulsifier, and 0.5-3 parts of initiator;

[0009] The composite organosilicon component is prepared by reacting organosilicon monomers containing double bonds, hydroxyl-terminated organosilicon oligomers, and hydroxyl-containing acrylate functional monomers in a mass ratio of 1:2:0.5.

[0010] Preferably, the composite organosilicon component is prepared by adding a double-bonded organosilicon monomer, a hydroxyl-terminated organosilicon oligomer, and a hydroxyl-containing acrylate functional monomer in a dry, inert gas-protected flask at a mass ratio of 1:2:0.5, reacting under the action of a catalyst at a temperature of 60-65°C for 2-3 hours.

[0011] Preferably, the organosilicon monomer containing double bonds is vinyltriethoxysilane, the hydroxyl-terminated organosilicon oligomer is hydroxyl-terminated polydimethylsiloxane, the hydroxyl-containing acrylate functional monomer is hydroxyethyl acrylate, and the catalyst is dibutyltin dilaurate.

[0012] Preferably, the oligomeric polyol is one or more of polytetrahydrofuran ether diol, polypropylene glycol, polyethylene glycol, and polyisopropylene glycol reagent.

[0013] Preferably, the diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0014] Preferably, the hydrophilic chain extender is selected from one or more of dimethylolpropionic acid and dimethylolbutyric acid reagent.

[0015] Preferably, the self-crosslinking hydrophilic chain extender is an acetoacetic acid derivative of dimethylolbutyric acid.

[0016] Preferably, the neutralizing agent is one or more of triethylamine, N,N-dimethylethanolamine reagent.

[0017] Preferably, the acrylate monomer is selected from one or more of methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isobutyl acrylate, and isooctyl acrylate monomers.

[0018] Based on the above description of an organosilicon-modified polyurethane-acrylate composite emulsion, this invention also provides a method for preparing an organosilicon-modified polyurethane-acrylate composite emulsion, comprising the following steps:

[0019] S1. Add oligomeric polyol and composite organosilicon components to a dry flask protected by inert gas, and dehydrate under vacuum at 110-120℃ for 2 hours.

[0020] S2. Cool down to 80-85℃, add diisocyanate and catalyst, and keep the reaction at this temperature for 2-3 hours to obtain organosilicon-modified polyurethane prepolymer;

[0021] S3. Cool the silicone-modified polyurethane prepolymer to below 60°C, add a hydrophilic chain extender and acetone solvent, and keep it at the temperature for 1-2 hours to obtain the chain-extended reactant.

[0022] S4. Further cool the chain-extended reactants to 30-40℃, add a neutralizing agent and a self-crosslinking hydrophilic chain extender, stir and react for 0.5 hours to obtain the modified material;

[0023] S5. Under high-speed shear stirring, the modified material is slowly added to deionized water to emulsify it, and an emulsion is obtained.

[0024] S6. Add an aqueous chain extender to the emulsion, carry out the chain extension reaction in the aqueous phase, and continue stirring for 0.5-1 hour to obtain the aqueous chain extender.

[0025] S7. The aqueous chain extender was distilled under reduced pressure to remove acetone, resulting in a stable organosilicon-modified polyurethane emulsion.

[0026] S9. Mix the initiator with deionized water to prepare an initiator aqueous solution. Add one-fifth of the initiator aqueous solution to the reaction vessel. Under continuous stirring, mix the acrylate monomer, acrylate functional monomer, crosslinking agent and emulsifier with deionized water to prepare an emulsion.

[0027] S10. Place the silicone-modified polyurethane emulsion in a reactor equipped with a stirring, condensing and dripping device, heat it to 75-85℃, and add the emulsion and the remaining initiator aqueous solution dropwise at a uniform rate and simultaneously for 2-4 hours.

[0028] S11. After the addition is complete, continue to keep warm for 1-2 hours, then cool the system to below 40°C, filter with a 250-mesh filter cloth to obtain the final product.

[0029] The present invention provides an organosilicon-modified polyurethane-acrylate composite emulsion and its preparation method, which have the following advantages compared with the prior art:

[0030] 1. This invention integrates the composite organosilicon component into the molecular networks of polyurethane and acrylate simultaneously in the form of stable chemical bonds, rather than through simple physical blending. This achieves a synergistic effect of the flexibility and high adhesion of polyurethane, the weather resistance and high hardness of acrylate, and the excellent hydrophobicity and thermal stability of organosilicon, fundamentally overcoming the phase separation defects that are prone to occur in traditional composite systems.

[0031] 2. The composite organosilicon component of the present invention has dual reactive properties of hydroxyl groups and double bonds. The hydroxyl groups can undergo chain extension reaction with the polyurethane prepolymer, firmly attaching the siloxane segments to the main chain by chemical bonds; the double bonds can participate in the subsequent polymerization of acrylate, forming an interpenetrating-grafted network at the interface, ensuring that the organosilicon is stably and uniformly distributed in the composite emulsion, completely solving the problems of easy migration and phase separation of organosilicon caused by simple blending or single grafting, and significantly improving the water resistance, wear resistance, flexibility and thermal stability of the coating film.

[0032] 3. This invention uses a self-crosslinking hydrophilic chain extender. On the basis of the emulsification function of traditional hydrophilic chain extenders, crosslinking sites are introduced. After film formation, it can undergo a crosslinking reaction with the water-based chain extender and form a denser chemical crosslinking network in synergy with the physical entanglement network of polyurethane-acrylate, further enhancing the structural stability and durability of the coating film.

[0033] 4. The organosilicon-modified polyurethane-acrylate composite emulsion prepared by the present invention has a composite core-shell structure with organosilicon-modified polyurethane as the core and acrylate polymer as the shell, which enables the emulsion to form a denser and more stable three-dimensional cross-linked network during film formation, significantly improving the weather resistance, water resistance, mechanical strength and surface gloss of the coating film. Attached Figure Description

[0034] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides a silicone-modified polyurethane-acrylate composite emulsion, comprising the following raw materials by weight: 70-120 parts of oligomeric polyol with an average molecular weight of 500-2000, 5-15 parts of composite silicone component, 40-80 parts of diisocyanate, 0.05-0.2 parts of catalyst, 2-5 parts of hydrophilic chain extender, 3-6 parts of self-crosslinking hydrophilic chain extender, 4-12 parts of neutralizer, 2-8 parts of water-based chain extender, 50-150 parts of acrylate monomer, 1-5 parts of acrylate functional monomer, 1-3 parts of crosslinking agent, 2-8 parts of emulsifier, and 0.5-3 parts of initiator;

[0037] Specifically, the composite organosilicon component is prepared by reacting a double-bonded organosilicon monomer, a hydroxyl-terminated organosilicon oligomer, and a hydroxyl-containing acrylate functional monomer in a mass ratio of 1:2:0.5. During preparation, the composite organosilicon component is prepared in a dry, inert gas-protected flask (nitrogen gas is used as the inert gas), by adding the double-bonded organosilicon monomer, the hydroxyl-terminated organosilicon oligomer, and the hydroxyl-containing acrylate functional monomer in a mass ratio of 1:2:0.5, reacting under the action of a catalyst at a temperature of 60-65℃ for 2-3 hours. By simultaneously introducing the composite organosilicon component into the molecular network of polyurethane and acrylate in a stable chemical bond form, and using a self-crosslinking hydrophilic chain extender, a synergistic effect among the three is achieved.

[0038] The organosilicon monomer containing double bonds is vinyltriethoxysilane VTES, the hydroxyl-terminated organosilicon oligomer is hydroxyl-terminated polydimethylsiloxane PDMS-OH, the hydroxyl-containing acrylate functional monomer is hydroxyethyl acrylate HEA, and the catalyst is dibutyltin dilaurate DBTDL.

[0039] In the composite organosilicon component, hydroxyl groups can be used for chain extension of the polyurethane prepolymer, firmly attaching siloxane segments to the main chain via chemical bonds. Simultaneously, their double bonds can participate in the subsequent acrylate polymerization stage, forming an 'interpenetrating-grafting' network at the polyurethane-acrylate interface. This dual-reaction characteristic solves the problems of easy migration and phase separation of organosilicon caused by simple blending or single grafting, ensuring stable and uniform distribution of organosilicon in the composite emulsion, and synergistically improving the water resistance, abrasion resistance, flexibility, and thermal stability of the coating film.

[0040] The oligomeric polyol is one or more of polytetrahydrofuran ether diol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and polyisopropylene glycol reagent.

[0041] The diisocyanate is one or more of isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, and 4,4'-dicyclohexylmethane diisocyanate H12MDI;

[0042] The hydrophilic chain extender is selected from one or more of dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA);

[0043] The self-crosslinking hydrophilic chain extender is DMBA-AA, an acetoacetate derivative of dimethylolbutyrate (DMBA).

[0044] The neutralizing agent is one or more of triethylamine (TEA) and N,N-dimethylethanolamine (DMEA).

[0045] The aqueous chain extender is one or more of dimethylolpropionic acid (DMPA) and N-methyldiethanolamine (MDEA);

[0046] The acrylate monomer is selected from one or more of the following monomers: methyl methacrylate (MMA), ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isobutyl acrylate, and isooctyl acrylate.

[0047] The acrylate functional monomers are one or more of acrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate (HEA), and isooctyl acrylate (2-EHA);

[0048] The emulsifier is selected from one or more of sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and fatty alcohol polyoxyethylene ethers; the initiator is preferably ammonium persulfate (APS).

[0049] By employing a self-crosslinking hydrophilic chain extender, crosslinking sites are introduced in addition to the emulsifying function of traditional hydrophilic chain extenders. After film formation, it can undergo a crosslinking reaction with the water-based chain extender, and synergistically form a denser chemical crosslinking network with the physical entanglement network of polyurethane-acrylate, further enhancing the structural stability and durability of the coating film.

[0050] Based on the above description of an organosilicon-modified polyurethane-acrylate composite emulsion, this invention also provides a method for preparing the organosilicon-modified polyurethane-acrylate composite emulsion, such as... Figure 1 As shown, it includes the following steps:

[0051] S1. Add oligomeric polyol and composite organosilicon components to a dry flask protected by inert gas, and dehydrate under vacuum at 110-120℃ for 2 hours.

[0052] S2. Cool down to 80-85℃, add diisocyanate and catalyst, and keep the reaction at this temperature for 2-3 hours to obtain organosilicon-modified polyurethane prepolymer;

[0053] S3. Cool the silicone-modified polyurethane prepolymer to below 60°C, add a hydrophilic chain extender and acetone solvent, and keep it at the temperature for 1-2 hours to obtain the chain-extended reactant.

[0054] S4. Further cool the chain-extended reactants to 30-40℃, add a neutralizing agent and a self-crosslinking hydrophilic chain extender, stir and react for 0.5 hours to obtain the modified material;

[0055] S5. Under high-speed shear stirring, the modified material is slowly added to deionized water to emulsify it, and an emulsion is obtained.

[0056] S6. Add an aqueous chain extender to the emulsion, carry out the chain extension reaction in the aqueous phase, and continue stirring for 0.5-1 hour to obtain the aqueous chain extender.

[0057] S7. The aqueous chain extender was distilled under reduced pressure to remove acetone, resulting in a stable organosilicon-modified polyurethane emulsion.

[0058] S9. Mix the initiator with deionized water to prepare an initiator aqueous solution. Add one-fifth of the initiator aqueous solution to the reaction vessel. Under continuous stirring, mix the acrylate monomer, acrylate functional monomer, crosslinking agent and emulsifier with deionized water to prepare an emulsion.

[0059] S10. Place the silicone-modified polyurethane emulsion in a reactor equipped with a stirring, condensing and dripping device, heat it to 75-85℃, and add the emulsion and the remaining initiator aqueous solution dropwise at a uniform rate and simultaneously for 2-4 hours.

[0060] S11. After the addition is complete, continue to keep warm for 1-2 hours, then cool the system to below 40°C, filter with a 250-mesh filter cloth to obtain the final product.

[0061] To verify the performance of the organosilicon-modified polyurethane-acrylate composite emulsion prepared by the method provided in this invention, the following specific examples are provided:

[0062] Example 1

[0063] An organosilicon-modified polyurethane-acrylate composite emulsion, by weight, comprises the following raw materials: 100 parts polytetrahydrofuran ether diol (PTMG), 42 parts IPDI diisocyanate, 8 parts composite organosilicon component, 0.1 parts dibutyltin dilaurate (DBTDL), 4 parts dimethylolpropionic acid (DMPA), 4.5 parts triethylamine (TEA), 3 parts N-methyldiethanolamine (MDEA), 60 parts methyl methacrylate (MMA), 3 parts acrylate functional monomer, 1.7 parts crosslinking agent, 1.2 parts emulsifier, 2.4 parts sodium dodecyl sulfate (SDS), and 0.8 parts ammonium persulfate (APS); wherein the emulsifier is a mixture of dodecylphenol polyoxyethylene ether and sodium dodecyl sulfate in a 2:4 ratio; and the acrylate functional monomer is a mixture of 30 parts isooctyl acrylate 2-EHA and 3 parts hydroxyethyl acrylate (HEA).

[0064] The preparation process of this silicone-modified polyurethane-acrylate composite emulsion is as follows:

[0065] 1. Synthesis of silicone-modified polyurethane emulsion:

[0066] First, in a dry, nitrogen-protected four-necked flask, 100 parts of polytetrahydrofuran ether diol (PTMG) (Mn=1000) and 8 parts of the composite organosilicon component were added. The mixture was dehydrated under vacuum at 120°C and -0.095 MPa for 2 hours. Then, the system was cooled to 85°C, the vacuum was released, and under a nitrogen atmosphere, 42 parts of diisocyanate (IPDI) and 0.1 parts of dibutyltin dilaurate (DBTDL) were added. The reaction was maintained at this temperature for 3 hours. The -NCO content was monitored by di-n-butylamine titration to obtain the composite organosilicon-modified polyurethane prepolymer. The composite organosilicon-modified polyurethane prepolymer was then cooled to 60°C. Add 4 parts of dimethylolpropionic acid (DMPA) and 40 parts of acetone and continue the reaction for 1 hour. Then, further cool to 30°C, add 4.5 parts of triethylamine (TEA) and 4 parts of acetoacetate derivative (DMBA-AA), and stir the reaction for 0.5 hours. After the reaction is complete, slowly add 230 parts of deionized water under high-speed shear at 3000 rpm for 30 minutes to emulsify. After emulsification, add 3 parts of N-methyldiethanolamine (MDEA), and continue stirring the reaction for 1 hour to carry out aqueous chain extension. Finally, remove acetone by vacuum distillation at 40°C and -0.09 MPa to obtain a stable organosilicon-modified polyurethane emulsion.

[0067] 2. Preparation of initiator aqueous solution and emulsion:

[0068] An initiator aqueous solution was prepared by mixing 0.8 parts of ammonium persulfate (APS) and 20 parts of deionized water. One-fifth of the initiator aqueous solution was added to the reaction vessel. Under continuous stirring, 60 parts of methyl methacrylate (MMA), acrylate functional monomers, 1.7 parts of crosslinking agent, 1.2 parts of emulsifier, and 50 parts of deionized water were mixed to prepare an emulsion.

[0069] 3. Synthesis of silicone-modified polyurethane-acrylic acid composite emulsion:

[0070] The synthesized organosilicon-modified polyurethane emulsion was transferred to a reactor equipped with a stirring, condensing, and dripping device. The temperature was raised to 80°C. The prepared emulsion and the remaining initiator aqueous solution were added dropwise to the organosilicon-modified polyurethane emulsion at a uniform rate and simultaneously. The dripping time was controlled to be completed within 3 hours. After the dripping was completed, the reaction was continued at a constant temperature for 2 hours to ensure that the monomers were fully polymerized. Finally, the system was cooled to below 40°C and filtered through a 250-mesh filter cloth.

[0071] Example 2

[0072] The similarities will not be repeated here. The difference from Example 1 is that the amount of the composite organosilicon component is increased to 12 parts.

[0073] Example 3

[0074] The similarities will not be repeated here. The difference from Example 1 is that the amount of the composite organosilicon component is reduced to 4 parts.

[0075] Example 4

[0076] The similarities will not be repeated here. The difference from Example 1 is that the amount of crosslinking agent is increased to 2.55 parts.

[0077] Example 5

[0078] The similarities will not be repeated here. The difference from Example 1 is that the amount of crosslinking agent is reduced to 0.85 parts.

[0079] Example 6

[0080] The similarities will not be repeated here. The difference from Example 1 is that the emulsifier used is a mixture of dodecylphenol polyoxyethylene ether and sodium dodecyl sulfate in a 1:1 ratio.

[0081] Example 7

[0082] The similarities will not be repeated here. The difference from Example 1 is that the emulsifier used is a mixture of dodecylphenol polyoxyethylene ether and sodium dodecyl sulfate in a ratio of 4:2.

[0083] Comparative Example 1

[0084] The similarities will not be repeated here. The difference from Example 1 is that no composite organosilicon component is used in the synthesis of organosilicon-modified polyurethane emulsion. Instead, a polyurethane-acrylate composite emulsion is synthesized directly.

[0085] Comparative Example 2

[0086] The similarities will not be repeated here. The difference from Example 1 is that the synthesized organosilicon-modified polyurethane emulsion was used directly for testing.

[0087] Comparative Example 3

[0088] The similarities will not be repeated here. The difference from Example 1 is that in the synthesis of silicone-modified polyurethane emulsion, hydroxyl-terminated polydimethylsiloxane modifier is used to replace the composite silicone component to synthesize silicone polyurethane-acrylate composite emulsion.

[0089] Comparative Example 4

[0090] The similarities will not be repeated here. The difference from Example 1 is that the same amount of dimethylolpropionic acid (DMPA) was used to replace the self-crosslinking hydrophilic chain extender DMBA-AA in the synthesis of silicone-modified polyurethane emulsion to synthesize silicone polyurethane-acrylate composite emulsion.

[0091] The silicone polyurethane-acrylate composite emulsions prepared in Examples 1 to 7 and the silicone polyurethane-acrylate composite emulsions prepared in Comparative Examples 1 to 4 were subjected to performance tests, and the test methods are as follows:

[0092] I. Test Items:

[0093] 1. Sun protection rating

[0094] The sun resistance rating is based on the ISO 12040-1997 standard, and is divided into 1-8 levels, with level 1 being the worst and level 8 being the best.

[0095] 2. Water absorption rate

[0096] The water absorption rate is referenced to the standard GB / T16578-2008 "Test of water absorption rate of acrylic emulsion".

[0097] 3. Adhesion

[0098] Adhesive to coated paper, the adhesion strength is referenced to standard GB / T13217.7-2009 "Test Method for Adhesion Strength of Liquid Ink".

[0099] 4. Gloss

[0100] Gloss (coated paper) reference standard GB / T13217.2-2009 "Test Method for Gloss of Liquid Ink".

[0101] 5. Coloring power

[0102] Coloring strength (coated paper) is referenced to standard GB / T13217.6-2008 "Test Method for Coloring Strength of Liquid Ink".

[0103] II. Test Results

[0104] The test results of the silicone polyurethane-acrylate composite emulsions prepared in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1:

[0105] Table 1

[0106]

[0107] From the data in Table 1, we can conclude that:

[0108] Examples 1-7 using the composite silicone component had a sun resistance rating of 5-7, while Comparative Example 1 without silicone modification had a rating of only 5, and Comparative Example 2, which used silicone-modified polyurethane emulsion directly without acrylate grafting, had a rating of only 4. This indicates that the introduction of the composite silicone component can effectively enhance the coating's resistance to UV aging, and the composite system of silicone-modified polyurethane grafted with acrylate is superior to the single polyurethane system.

[0109] The water absorption rates of Examples 1-7 were only 3.1%-3.8%, far lower than the water absorption rates of Comparative Example 1 (10.9%), Comparative Example 2 (16.8%), Comparative Example 3 (6.8%), and Comparative Example 4 (8.2%). This is because the siloxane segments of the composite organosilicon have strong hydrophobicity, and the organosilicon migration problem is solved by chemical bonds connecting to the main chain, interfacial interpenetration, and grafting networks, thus ensuring stable hydrophobicity. In contrast, single polyurethane (Comparative Example 2), ordinary organosilicon blends (Comparative Example 3), or non-self-crosslinking systems (Comparative Example 4) cannot form a dense hydrophobic network.

[0110] The adhesion of Examples 1-7 was 88%-100% and the gloss at 60° was 85-94 GU, while the adhesion of Comparative Example 1 was 85% and the gloss was 76 GU, and the adhesion of Comparative Example 2 was 80% and the gloss was 70 GU, which were significantly lower. This indicates that the synergistic effect of silicone modification and acrylate grafting can improve the adhesion between the coating and the substrate and the surface smoothness.

[0111] Compared with Comparative Example 4, which uses ordinary DMPA instead of DMBA-AA, Comparative Example 4 has a much higher water absorption rate than Example 1, and its gloss and tinting strength are also lower than those of Example 1. This indicates that the self-crosslinking chain extender can form a denser chemical network through the crosslinking reaction after film formation, reducing water molecule penetration and improving the gloss and color uniformity of the coating film. In contrast, ordinary hydrophilic chain extenders can only provide emulsification and cannot form additional crosslinks, resulting in a decrease in water resistance and surface properties.

[0112] In summary, the silicone-modified polyurethane-acrylate composite emulsion prepared by this invention has a composite core-shell structure with silicone-modified polyurethane as the core and acrylate polymer as the shell. It is semi-transparent in appearance and can form a uniform and glossy coating film. Moreover, the emulsion can form a denser and more stable three-dimensional cross-linked network during film formation, which significantly improves the weather resistance, water resistance, mechanical strength and surface gloss of the coating film.

[0113] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A silicone-modified polyurethane-acrylate composite emulsion, characterized in that: By weight, the raw materials include the following: 70-120 parts of oligomeric polyols with an average molecular weight of 500-2000, 5-15 parts of composite organosilicon components, 40-80 parts of diisocyanates, 0.05-0.2 parts of catalyst, 2-5 parts of hydrophilic chain extender, 3-6 parts of self-crosslinking hydrophilic chain extender, 4-12 parts of neutralizer, 2-8 parts of water-based chain extender, 50-150 parts of acrylate monomers, 1-5 parts of acrylate functional monomers, 1-3 parts of crosslinking agent, 2-8 parts of emulsifier, and 0.5-3 parts of initiator; The composite organosilicon component is prepared by reacting organosilicon monomers containing double bonds, hydroxyl-terminated organosilicon oligomers, and hydroxyl-containing acrylate functional monomers in a mass ratio of 1:2:0.

5.

2. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The composite organosilicon component is prepared by adding a double-bonded organosilicon monomer, a hydroxyl-terminated organosilicon oligomer, and a hydroxyl-containing acrylate functional monomer in a dry, inert gas-protected flask at a mass ratio of 1:2:0.

5. The mixture is then reacted under the action of a catalyst at a temperature of 60-65°C for 2-3 hours.

3. The silicone-modified polyurethane-acrylate composite emulsion according to claim 2, characterized in that: The organosilicon monomer containing double bonds is vinyltriethoxysilane, the hydroxyl-terminated organosilicon oligomer is hydroxyl-terminated polydimethylsiloxane, the hydroxyl-containing acrylate functional monomer is hydroxyethyl acrylate, and the catalyst is dibutyltin dilaurate.

4. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The oligomeric polyol is one or more of the following: polytetrahydrofuran ether diol, polypropylene glycol, polyethylene glycol, and polyisopropylene glycol.

5. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

6. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The hydrophilic chain extender is selected from one or more of dimethylolpropionic acid and dimethylolbutyric acid reagents.

7. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The self-crosslinking hydrophilic chain extender is an acetoacetic acid derivative of dimethylolbutyric acid.

8. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The neutralizing agent is one or more of triethylamine and N,N-dimethylethanolamine reagent.

9. The silicone-modified polyurethane-acrylate composite emulsion according to claim 1, characterized in that: The acrylate monomer is selected from one or more of the following monomers: methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isobutyl acrylate, and isooctyl acrylate.

10. A method for preparing a silicone-modified polyurethane-acrylate composite emulsion, comprising preparing the silicone-modified polyurethane-acrylate composite emulsion according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Add oligomeric polyol and composite organosilicon components to a dry flask protected by inert gas, and dehydrate under vacuum at 110-120℃ for 2 hours. S2. Cool down to 80-85℃, add diisocyanate and catalyst, and keep the reaction at this temperature for 2-3 hours to obtain organosilicon-modified polyurethane prepolymer; S3. Cool the silicone-modified polyurethane prepolymer to below 60°C, add a hydrophilic chain extender and acetone solvent, and keep it at the temperature for 1-2 hours to obtain the chain-extended reactant. S4. Further cool the chain-extended reactants to 30-40℃, add a neutralizing agent and a self-crosslinking hydrophilic chain extender, stir and react for 0.5 hours to obtain the modified material; S5. Under high-speed shear stirring, the modified material is slowly added to deionized water to emulsify it, and an emulsion is obtained. S6. Add an aqueous chain extender to the emulsion, carry out the chain extension reaction in the aqueous phase, and continue stirring for 0.5-1 hour to obtain the aqueous chain extender. S7. The aqueous chain extender was distilled under reduced pressure to remove acetone, resulting in a stable organosilicon-modified polyurethane emulsion. S9. Mix the initiator with deionized water to prepare an initiator aqueous solution. Add one-fifth of the initiator aqueous solution to the reaction vessel. Under continuous stirring, mix the acrylate monomer, acrylate functional monomer, crosslinking agent and emulsifier with deionized water to prepare an emulsion. S10. Place the silicone-modified polyurethane emulsion in a reactor equipped with a stirring, condensing and dripping device, heat it to 75-85℃, and add the emulsion and the remaining initiator aqueous solution dropwise at a uniform rate and simultaneously for 2-4 hours. S11. After the addition is complete, continue to keep warm for 1-2 hours, then cool the system to below 40°C, filter with a 250-mesh filter cloth to obtain the final product.

Images