Preparation method of a polyacrylate foaming regulator

Abstract

The present invention relates to the field of foaming regulators, and particularly to a preparation method of a polyacrylate foaming regulator, which comprises the following steps: core layer preparation: mixing methyl methacrylate, butyl acrylate and divinylbenzene, pre-emulsifying them in portions with an emulsifier, and then carrying out thermal-initiated polymerization with ammonium persulfate to form a highly rigid crosslinked network; intermediate layer construction: introducing 2-hydroxyethyl acrylate as a functional monomer on the surface of the core layer, combining ultraviolet light pre-polymerization and thermal-initiated supplementary reaction to strengthen the interfacial bonding force; shell layer coating: using a compound of ethyl acrylate and dodecafluoroheptyl methacrylate, and forming a fluorine gradient shell layer by dynamic addition in portions to achieve the balance of superhydrophobicity and interfacial adhesion; photo-thermal synergistic curing: quickly shaping the surface layer with ultraviolet light, and the thermal initiator penetrates deep into the layer to improve the conversion rate. The foaming regulator prepared by the present invention through core-shell structure design, stepwise polymerization process and photo-thermal dual-initiating system can significantly improve the performance of foamed materials.

Description

Technical Field

[0001] The present invention relates to the field of foaming regulators, and particularly to a preparation method of a polyacrylate foaming regulator. Background Art

[0002] The polyacrylate foaming regulator is a regulator that can effectively increase the cohesion and homogeneity of the polyvinyl chloride (PVC) melt by increasing the pressure and torque of the PVC melt, making the obtained PVC products denser. It has all the basic characteristics of general PVC processing aids. The only difference from general PVC processing aids is that the molecular weight of the polyacrylate foaming regulator is much higher than that of general PVC processing aids.

[0003] The functions of the polyacrylate foaming regulator mainly include promoting the plasticization of PVC; improving the melt strength of the PVC foaming material to prevent the coalescence of bubbles to obtain uniformly foamed products; and ensuring good fluidity of the melt to obtain products with good appearance.

[0004] The key factor in increasing the weight of PVC foamed sheets is to improve the melt strength of PVC. At present, there are various methods to improve the melt strength of PVC, but the most effective way is to add a polyacrylate foaming regulator. Generally speaking, the higher the viscosity of the polyacrylate foaming regulator, the more obvious the improvement effect on the melt strength. However, a polyacrylate foaming regulator with high viscosity will cause the bubbles in the PVC melt to be unable to expand, thereby affecting the surface gloss, processing fluidity, and uniformity of the PVC products. In addition, it will indirectly affect the heat distortion temperature, strength, and low-temperature resistance of PVC. Summary of the Invention

[0005] In order to solve the foregoing technical problems, the present invention provides a preparation method of a polyacrylate foaming regulator. By adopting a three-layer core-shell structure, while improving the melt strength, a more uniform cell structure is formed, solving the contradiction between the melt strength of PVC and the inability of bubbles to expand; by adopting a dynamic emulsification method, the emulsion particle size is effectively controlled, and the uniformity of the regulator components is improved, solving the problems of uneven melt bubbles and low closed-cell rate; a photo-thermal dual-initiating system is adopted to shorten the reaction time and solve the problem of low synthesis efficiency, which is specifically realized through the following technical solutions.

[0006] A preparation method of a polyacrylate foaming regulator according to the present invention includes the following steps:

[0007] S1. Mix methyl methacrylate, butyl acrylate, and divinylbenzene to prepare a core layer monomer composition for standby;

[0008] S2. Mix isooctyl acrylate, styrene, and 2-hydroxyethyl acrylate to prepare an intermediate layer monomer composition for standby;

[0009] S3. Prepare and set aside a shell monomer composition by mixing ethyl acrylate and dodecafluoroheptyl methacrylate;

[0010] S4. Prepare and set aside an emulsifier by mixing sodium dodecyl sulfate and octylphenol polyoxyethylene ether;

[0011] S5. Mix the core monomer composition, the emulsifier, and deionized water, and stir for pre-emulsification for 10 min;

[0012] S6. Add the emulsifier in 3 portions at 20-min intervals each to obtain a core pre-emulsion;

[0013] S7. Add ammonium persulfate to the core pre-emulsion, heat to 75 °C, and react for 1 h to obtain a core prepolymer;

[0014] S8. Add the intermediate layer monomer composition, hexamethylphosphoric triamide, and a TPO initiator to the core prepolymer, pre-polymerize under ultraviolet light irradiation, then raise the temperature to 65 °C, add ammonium persulfate, and continue to react for 2 h to obtain a double-layer prepolymer;

[0015] S9. Prepare and set aside a shell pre-emulsion by mixing the shell monomer composition and the emulsifier, add the shell pre-emulsion to the double-layer prepolymer in 4 portions at 30-min intervals each, and react at 70 °C for 3 h to obtain a three-layer prepolymer;

[0016] S10. Cool to room temperature, filter, and adjust the solid content to 40% - 45% to obtain the target product.

[0017] Preferably, in step S1, the mass ratio of methyl methacrylate, butyl acrylate, and divinylbenzene is 60 - 80:20 - 30:0.5 - 2.

[0018] Preferably, in step S2, the mass ratio of isooctyl acrylate, styrene, and 2-hydroxyethyl acrylate is 10 - 14:4 - 6:1 - 2.

[0019] Preferably, in step S3, the mass ratio of ethyl acrylate and dodecafluoroheptyl methacrylate is 7 - 9:1 - 3.

[0020] Preferably, in step S4, the mass ratio of sodium dodecyl sulfate and octylphenol polyoxyethylene ether is 1:2 - 4.

[0021] Preferably, in step S5, the mass ratio of the core monomer composition, the emulsifier, and deionized water is 15 - 20:1 - 1.2:250 - 350.

[0022] Preferably, in step S5, the stirring speed is 8000 - 12000 r / min.

[0023] Preferably, in step S6, the mass ratio of the emulsifier added each time to the core layer monomer composition in step S1 is 1:40 to 50.

[0024] Preferably, in step S9, the mass ratio of the shell layer monomer to the emulsifier is 10 - 15:1.

[0025] After adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0026] 1. A three - layer core - shell structure is adopted. The core layer forms a highly rigid three - dimensional network through a cross - linker, improving the compressive strength and heat distortion temperature. Hydroxyethyl acrylate is introduced as a functional monomer in the intermediate layer to enhance the interfacial bonding force. The shell layer combines the flexibility of ethyl acrylate with the fluorinated chain segment of dodecafluoroheptyl methacrylate to achieve super - hydrophobicity on the surface and high adhesion on the bottom layer.

[0027] 2. Sodium dodecyl sulfate and octylphenol polyoxyethylene ether are compounded to reduce the critical micelle concentration and reduce the total amount of emulsifier used. By adding emulsifier in portions to refine the latex particles, while improving the emulsion stability, step - by - step polymerization and gradient distribution are achieved.

[0028] 3. A photo - thermal dual - initiation system is adopted. In the pre - polymerization stage of the intermediate layer, ultraviolet light irradiation is used to quickly cure the surface and shallow - layer monomers, forming a dense cross - linked network, shortening the reaction time. Through subsequent thermal initiation to penetrate the deep unreacted area, the conversion rate is increased and the residual monomers are reduced. Specific Embodiments

[0029] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. For the purpose of making the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only provided to provide a better understanding of the present invention by showing examples of the present invention.

[0030] An embodiment of the present invention provides a preparation method of a polyacrylate foaming regulator, including the following steps:

[0031] S1. Based on a total of 100 parts by weight, 60 - 80 parts by weight of methyl methacrylate, 20 - 30 parts by weight of butyl acrylate, and 0.5 - 2 parts by weight of divinylbenzene are mixed to prepare a core layer monomer composition;

[0032] Among them, divinylbenzene is used as a cross-linking agent here. In this process, the divinyl structure of divinylbenzene can copolymerize with the monomers of methyl methacrylate and butyl acrylate in free radical polymerization, connecting different polymer chains through chemical bonds to form a three-dimensional cross-linked network.

[0033] The above cross-linked structure restricts the free movement of molecular chains, can significantly increase the glass transition temperature and mechanical strength of the polymer, prevent the cell walls from collapsing due to softening during the foaming process, and the cross-linked network enhances the melt elasticity, making the material more likely to maintain stability during high-shear processing and reducing cell coalescence or rupture.

[0034] At the same time, by utilizing the microscopic inhomogeneity of the cross-linking points, it can serve as the sites for bubble nucleation, promoting uniform cell nucleation and avoiding local over-foaming or collapse.

[0035] S2. Based on the total weight parts being 100, 50 - 70 parts by weight of isooctyl acrylate, 20 - 30 parts by weight of styrene, and 5 - 10 parts by weight of 2-hydroxyethyl acrylate are mixed to prepare an intermediate layer monomer composition;

[0036] In the above steps, 2-hydroxyethyl acrylate is added as a functional monomer to isooctyl acrylate and styrene. Mainly by utilizing the hydroxyl group characteristics in 2-hydroxyethyl acrylate, it can form hydrogen bonds or covalent bonds with polar groups (such as carboxyl groups, epoxy groups) in the core layer or shell layer, strengthening the interfacial bonding force of the core-shell structure.

[0037] In addition, when 2-hydroxyethyl acrylate is used in the intermediate layer, its molecular chains can further improve the mechanical interlocking between the core and the shell through entanglement or adsorption, playing the role of physical anchoring, thereby enhancing the stability of the overall structure and reducing the risk of interlayer delamination.

[0038] S3. Based on the total weight parts being 100, 70 - 90 parts by weight of ethyl acrylate and 10 - 30 parts by weight of 1H,1H,2H,2H-perfluorooctyl methacrylate are mixed to prepare a shell layer monomer composition;

[0039] The fluorinated monomer 1H,1H,2H,2H-perfluorooctyl methacrylate is mixed with ethyl acrylate as the shell layer structure. Relying on the unique properties of fluorine atoms, it endows the core-shell structure polymer with significant functional advantages and performance improvements.

[0040] The long fluorocarbon chain of 1H,1H,2H,2H-perfluorooctyl methacrylate can significantly reduce the surface energy of the material, making the shell layer show strong hydrophobicity, even superhydrophobicity, effectively repelling water, oil and pollutants. A micro-nano structure similar to the "lotus leaf effect" is formed on its surface, making it difficult for stains to adhere.

[0041] The high bond energy and low polarizability of the carbon-fluorine bonds in dodecafluorooctyl methacrylate endow this shell layer with extremely strong tolerance to acids, bases, solvents, and oxidants, effectively extending the service life of materials in corrosive environments. Additionally, the shielding effect of fluorine atoms can absorb ultraviolet light, reducing the photodegradation of the polymer backbone and thus greatly enhancing the weather resistance of the melt.

[0042] Furthermore, the fluorinated shell layer simultaneously exhibits high-temperature stability and flame retardancy. The fluorinated shell layer maintains its structural integrity at high temperatures, delaying thermal decomposition. Fluorine elements can inhibit the free radical chain reaction during combustion, reducing the flammability of the material.

[0043] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 1:2 - 4.

[0044] Sodium dodecyl sulfate is an anionic surfactant, and octylphenol polyoxyethylene ether is a non-ionic surfactant. When the two are compounded as an emulsifier system, they can significantly improve the emulsification efficiency and product performance through synergistic effects in the emulsion polymerization of core-shell structured polymers.

[0045] The dual effects of the charge repulsion of sodium dodecyl sulfate and the steric hindrance of octylphenol polyoxyethylene ether can significantly enhance the emulsion stability.

[0046] S5. Mix the core layer monomer composition, emulsifier, and deionized water in a mass ratio of 15 - 20:1 - 1.2:250 - 350, and pre-emulsify for 10 min under high-speed shearing.

[0047] S6. Add the emulsifier in 3 portions during the polymerization process. The mass ratio of the emulsifier added each time to the core layer monomer composition is 1:40 - 50, with an interval of 20 min each time, and control to obtain the core layer pre-emulsion.

[0048] The compounding of sodium dodecyl sulfate and octylphenol polyoxyethylene ether can rapidly reduce the interfacial tension, forming small and uniformly distributed monomer droplets, providing uniform nucleation sites for the core layer polymerization. Moreover, the steric hindrance of octylphenol polyoxyethylene ether slows down the migration of monomers from small droplets to large droplets, maintaining the uniformity of the core layer particle size.

[0049] Sodium dodecyl sulfate can form a strong electric double layer on the core surface, resisting the collision and coalescence of latex particles in the initial stage of polymerization. Combining with the PEO chain of octylphenol polyoxyethylene ether further enhances the spatial barrier. Meanwhile, under high-speed conditions and by adding the emulsifier in portions, the emulsion particle size can be effectively controlled to be 80 - 150 nm.

[0050] Among them, the stirring speed is 8000 - 12000 r / min.

[0051] S7. Add ammonium persulfate accounting for 0.5% - 1.5% of the total weight of the core layer monomer composition to the core layer pre-emulsion, heat it to 75°C and react for 1 h to obtain the core layer prepolymer;

[0052] Ammonium persulfate is a water-soluble initiator. Free radicals are mainly generated in the aqueous phase and initiate polymerization by diffusing into the interior of monomer droplets or micelles. Ammonium persulfate decomposes when heated to 60 - 80°C to generate sulfate radicals, which then initiate the chain polymerization reaction of monomers through free radicals.

[0053] S8. Add the intermediate layer monomer composition accounting for 30% - 50% of the total weight of the core layer monomer composition, hexamethylphosphoric triamide accounting for 0.5% - 2% of the total weight of the core layer monomer composition, and TPO initiator accounting for 1% - 3% of the total weight of the core layer monomer composition to the core layer prepolymer, pre-polymerize under ultraviolet light irradiation, then raise the temperature to 65°C and add ammonium persulfate accounting for 0.5% - 1.5% of the total weight of the core layer monomer composition and continue to react for 2 h to obtain the double-layer prepolymer;

[0054] Among them, the TPO initiator is trimethylbenzoylphosphine oxide.

[0055] Among them, the ultraviolet light irradiation is realized by a 50W LED ultraviolet lamp, and the irradiation time is 30 min.

[0056] In the above steps, ultraviolet light-initiated polymerization is achieved first. Ultraviolet light promotes the TPO initiator to generate free radicals, which further initiate the copolymerization reaction of monomers acrylate, styrene, and 2-hydroxyethyl acrylate in the intermediate layer monomer.

[0057] In the above process, hexamethylphosphoric triamide can improve the monomer solubility and segment mobility, promote the polymerization uniformity, and realize the uniform dispersion of the intermediate layer monomer on the surface of the core layer.

[0058] And hexamethylphosphoric triamide can extend the free radical lifetime through coordination, improve the polymerization rate and molecular weight.

[0059] Ultraviolet light initiates the local polymerization or cross-linking of the intermediate layer monomer to form a preliminary interface structure. There may be residual unreacted monomers or insufficiently cross-linked regions, which need to be further cured through subsequent thermal reactions.

[0060] Raise the temperature of the reaction system to 65°C and add ammonium persulfate to react for 2 hours. Through the supplementary polymerization and cross-linking initiated by heat, continue to initiate the polymerization of unreacted monomers to make up for the limitations of the ultraviolet light stage.

[0061] Generally, the rapid decomposition temperature of ammonium persulfate is 70°C. Here, a decomposition temperature of 65°C is adopted to avoid violent reactions leading to explosive polymerization while ensuring the continuous generation of free radicals.

[0062] This step combines a photo-thermal dual-initiating system. Ultraviolet light can trigger the rapid polymerization of surface or shallow monomers within seconds to minutes, forming a preliminary cross-linked network and precisely controlling the reaction area. The thermal initiator continuously generates free radicals during the subsequent heating stage, penetrating into the deep areas or shadow areas that cannot be reached by light to ensure maximum overall conversion rate.

[0063] S9. Prepare a shell pre-emulsion by mixing 15% - 25% of the shell monomer composition based on the total weight of the core layer monomer composition and an emulsifier at a mass ratio of 10 - 15:1. Add the shell pre-emulsion to the double-layer prepolymer dynamically in 4 portions at 30-minute intervals, and react at 70 °C for 3 hours to obtain a three-layer prepolymer.

[0064] Sodium dodecyl sulfate in the emulsifier preferentially adsorbs at the interface between the middle layer and the shell layer, reducing the interfacial tension between the shell monomer and the middle layer and promoting uniform encapsulation of the shell layer.

[0065] The long-chain PEO of octylphenol polyoxyethylene ether in the emulsifier dynamically adjusts its adsorption during the polymerization of the shell layer to adapt to the change in the hydrophobicity of the shell monomer.

[0066] The synergistic effect of the emulsifier can enhance the shear resistance of the latex particles under high-speed stirring or high solid content, thus avoiding shell layer breakage.

[0067] Adding the pre-emulsion in multiple portions can achieve stepwise polymerization of the shell layer, avoiding shell layer embrittlement caused by premature cross-linking of dodecafluoroheptyl methacrylate.

[0068] In addition, adding dodecafluoroheptyl methacrylate in portions can achieve a concentration gradient of fluorine from the surface to the inside. The high fluorine content on the surface layer enhances hydrophobicity, and the low fluorine content on the bottom layer maintains adhesion to the middle layer.

[0069] S10. Cool to room temperature, filter, and adjust the solid content to 40% - 45% to obtain the target product.

[0070] Cooling to room temperature in a timely manner can slow down or stop the activity of residual free radicals, avoiding broadening of the molecular weight distribution caused by excessive polymerization or cross-linking.

[0071] Filtration and solid content adjustment respectively improve the purity of the product and optimize the product performance from the perspective of application adaptability, ensuring the best balance between the functionality and processability of the core-shell material.

[0072] To facilitate further understanding of the present invention, several embodiments and comparative examples of the present invention are given below:

[0073] Example 1:

[0074] S1. Prepare a core layer monomer composition by mixing 75 parts by weight of methyl methacrylate, 24 parts by weight of butyl acrylate, and 1 part by weight of divinylbenzene based on a total of 100 parts by weight;

[0075] S2. Prepare an intermediate layer monomer composition by mixing 65 parts by weight of isooctyl acrylate, 28 parts by weight of styrene, and 7 parts by weight of 2 - hydroxyethyl acrylate based on a total of 100 parts by weight;

[0076] S3. Prepare a shell layer monomer composition by mixing 80 parts by weight of ethyl acrylate and 20 parts by weight of dodecafluorooctyl methacrylate based on a total of 100 parts by weight;

[0077] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 1:3 for standby;

[0078] S5. Mix the core layer monomer composition, emulsifier, and deionized water in a mass ratio of 17:1:280, and pre - emulsify for 10 min under high - speed shearing;

[0079] S6. Add the emulsifier in 3 portions during the polymerization process. The mass ratio of the emulsifier added each time to the core layer monomer composition is 1:45, with an interval of 20 min each time, to obtain a core layer pre - emulsion;

[0080] S7. Add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to the core layer pre - emulsion, heat to 75 °C, and react for 1 h to obtain a core layer prepolymer;

[0081] S8. Add 40% of the intermediate layer monomer composition based on the total weight of the core layer monomer composition, 1% of hexamethylphosphoric triamide based on the total weight of the core layer monomer composition, and 2% of TPO initiator based on the total weight of the core layer monomer composition to the core layer prepolymer. Pre - polymerize for 30 min under the irradiation of 50 W ultraviolet light, then raise the temperature to 65 °C and add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition and continue to react for 2 h to obtain a double - layer prepolymer;

[0082] S9. Prepare a shell layer pre - emulsion by mixing 20% of the shell layer monomer composition based on the total weight of the core layer monomer composition and the emulsifier in a mass ratio of 12:1. Add the shell layer pre - emulsion to the double - layer prepolymer in 4 portions dynamically with an interval of 30 min each time, and react at 70 °C for 3 h to obtain a three - layer prepolymer;

[0083] S10. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0084] Example 2:

[0085] S1. Prepare a core layer monomer composition by mixing 70 parts by weight of methyl methacrylate, 28 parts by weight of butyl acrylate, and 2 parts by weight of divinylbenzene based on a total of 100 parts by weight;

[0086] S2. Prepare an intermediate layer monomer composition by mixing 60 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of styrene, and 10 parts by weight of 2-hydroxyethyl acrylate based on a total of 100 parts by weight;

[0087] S3. Prepare a shell layer monomer composition by mixing 70 parts by weight of ethyl acrylate and 30 parts by weight of dodecafluorooctyl methacrylate based on a total of 100 parts by weight;

[0088] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 1:3 for standby;

[0089] S5. Mix the core layer monomer composition, emulsifier, and deionized water in a mass ratio of 17:1:280, and pre-emulsify for 10 min under high-speed shearing;

[0090] S6. Add the emulsifier in 3 portions during the polymerization process. The mass ratio of the emulsifier added each time to the core layer monomer composition is 1:45, and the interval between each addition is 20 min to obtain a core layer pre-emulsion;

[0091] S7. Add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to the core layer pre-emulsion, heat to 75 °C, and react for 1 h to obtain a core layer prepolymer;

[0092] S8. Add 40% of the intermediate layer monomer composition based on the total weight of the core layer monomer composition, 1% of hexamethylphosphoric triamide based on the total weight of the core layer monomer composition, and 2% of TPO initiator based on the total weight of the core layer monomer composition to the core layer prepolymer. Pre-polymerize for 30 min under the irradiation of 50 W ultraviolet light, and then raise the temperature to 65 °C and add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to continue the reaction for 2 h to obtain a double-layer prepolymer;

[0093] S9. Prepare a shell layer pre-emulsion by mixing 20% of the shell layer monomer composition based on the total weight of the core layer monomer composition and the emulsifier in a mass ratio of 12:1. Add the shell layer pre-emulsion to the double-layer prepolymer in 4 portions dynamically at intervals of 30 min each, and react at 70 °C for 3 h to obtain a three-layer prepolymer;

[0094] S10. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0095] Example 3

[0096] S1. Prepare a core layer monomer composition by mixing 75 parts by weight of methyl methacrylate, 24 parts by weight of butyl acrylate, and 1 part by weight of divinylbenzene based on a total of 100 parts by weight;

[0097] S2. Prepare an intermediate layer monomer composition by mixing 65 parts by weight of 2-ethylhexyl acrylate, 28 parts by weight of styrene, and 7 parts by weight of 2-hydroxyethyl acrylate based on a total of 100 parts by weight;

[0098] S3. Prepare a shell layer monomer composition by mixing 80 parts by weight of ethyl acrylate and 20 parts by weight of dodecafluoroheptyl methacrylate based on a total of 100 parts by weight;

[0099] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether at a mass ratio of 1:4 for standby;

[0100] S5. Mix the core layer monomer composition, emulsifier, and deionized water at a mass ratio of 17:1:280, and pre-emulsify for 10 min under high-speed shearing;

[0101] S6. Add the emulsifier in 3 portions during the polymerization process. The mass ratio of the emulsifier added each time to the core layer monomer composition is 1:45, and the interval between each addition is 20 min to obtain a core layer pre-emulsion;

[0102] S7. Add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to the core layer pre-emulsion, heat to 75 °C and react for 1 h to obtain a core layer prepolymer;

[0103] S8. Add 40% of the total weight of the intermediate layer monomer composition based on the core layer monomer composition, 1% of hexamethylphosphoric triamide based on the core layer monomer composition, and 2% of TPO initiator based on the core layer monomer composition to the core layer prepolymer. Pre-polymerize for 30 min under the irradiation of 50 W ultraviolet light, then raise the temperature to 65 °C and add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to continue the reaction for 2 h to obtain a double-layer prepolymer;

[0104] S9. Prepare a shell layer pre-emulsion by mixing 20% of the total weight of the shell layer monomer composition based on the core layer monomer composition and the emulsifier at a mass ratio of 12:1. Add the shell layer pre-emulsion to the double-layer prepolymer in 4 portions dynamically at intervals of 30 min each, and react at 70 °C for 3 h to obtain a three-layer prepolymer;

[0105] S10. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0106] Comparative Example 1:

[0107] S1. Prepare a core layer monomer composition by mixing 75 parts by weight of methyl methacrylate, 24 parts by weight of butyl acrylate, and 1 part by weight of divinylbenzene based on a total of 100 parts by weight;

[0108] S2. Prepare an intermediate layer monomer composition by mixing 65 parts by weight of isooctyl acrylate, 28 parts by weight of styrene, and 7 parts by weight of 2-hydroxyethyl acrylate based on a total of 100 parts by weight;

[0109] S3. Prepare a shell layer monomer composition by mixing 80 parts by weight of ethyl acrylate and 20 parts by weight of dodecafluorooctyl methacrylate based on a total of 100 parts by weight;

[0110] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 1:3 for standby;

[0111] S5. Mix the core layer monomer composition, emulsifier, and deionized water in a mass ratio of 17:2:280, and pre-emulsify for 10 min under high-speed shearing to obtain a core layer pre-emulsion;

[0112] S6. Add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to the core layer pre-emulsion, heat to 75 °C and react for 1 h to obtain a core layer prepolymer;

[0113] S7. Add 40% of the intermediate layer monomer composition based on the total weight of the core layer monomer composition, 1% of hexamethylphosphoric triamide based on the total weight of the core layer monomer composition, and 2% of TPO initiator based on the total weight of the core layer monomer composition to the core layer prepolymer, pre-polymerize for 30 min under the condition of 50 W ultraviolet light irradiation, then raise the temperature to 65 °C and add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to continue the reaction for 2 h to obtain a double-layer prepolymer;

[0114] S8. Prepare a shell layer pre-emulsion by mixing 20% of the shell layer monomer composition based on the total weight of the core layer monomer composition and the emulsifier in a mass ratio of 12:1, add the shell layer pre-emulsion to the double-layer prepolymer, and react at 70 °C for 3 h to obtain a three-layer prepolymer;

[0115] S9. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0116] Comparative Example 2:

[0117] S1. Prepare a core layer monomer composition by mixing 75 parts by weight of methyl methacrylate, 24 parts by weight of butyl acrylate, and 1 part by weight of divinylbenzene based on a total of 100 parts by weight;

[0118] S2. Prepare an intermediate layer monomer composition by mixing 65 parts by weight of isooctyl acrylate, 28 parts by weight of styrene, and 7 parts by weight of 2-hydroxyethyl acrylate based on a total of 100 parts by weight;

[0119] S3. Prepare a shell layer monomer composition by mixing 80 parts by weight of ethyl acrylate and 20 parts by weight of dodecafluorooctyl methacrylate based on a total of 100 parts by weight;

[0120] S4. Prepare an emulsifier by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether at a mass ratio of 1:3 for standby;

[0121] S5. Mix the core layer monomer composition, emulsifier, and deionized water at a mass ratio of 17:1:280, and pre-emulsify for 10 min under high-speed shearing;

[0122] S6. Add the emulsifier in 3 portions during the polymerization process. The mass ratio of the emulsifier added each time to the core layer monomer composition is 1:45, and the interval between each addition is 20 min to obtain a core layer pre-emulsion;

[0123] S7. Add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition to the core layer pre-emulsion, heat to 75 °C, and react for 1 h to obtain a core layer prepolymer;

[0124] S8. Add 40% of the total weight of the intermediate layer monomer composition based on the core layer monomer composition and 1% of hexamethylphosphoric triamide based on the total weight of the core layer monomer composition to the core layer prepolymer. Raise the temperature to 65 °C, add ammonium persulfate accounting for 1% of the total weight of the core layer monomer composition, and continue to react for 2 h to obtain a double-layer prepolymer;

[0125] S9. Prepare a shell layer pre-emulsion by mixing 20% of the total weight of the shell layer monomer composition based on the core layer monomer composition and the emulsifier at a mass ratio of 12:1. Add the shell layer pre-emulsion to the double-layer prepolymer in 4 portions dynamically at intervals of 30 min each, and react at 70 °C for 3 h to obtain a three-layer prepolymer;

[0126] S10. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0127] Comparative Example 3:

[0128] S1. Prepare a monomer composition by mixing 75 parts by weight of methyl methacrylate, 24 parts by weight of butyl acrylate, 1 part by weight of divinylbenzene, 26 parts by weight of isooctyl acrylate, 11.2 parts by weight of styrene, 2.8 parts by weight of 2-hydroxyethyl acrylate, 16 parts by weight of ethyl acrylate, and 4 parts by weight of dodecafluorooctyl methacrylate based on a total of 160 parts by weight,

[0129] S2. Prepare a surfactant by compounding sodium dodecyl sulfate and octylphenol polyoxyethylene ether at a mass ratio of 1:3 for later use;

[0130] S3. Mix the monomer composition, surfactant, and deionized water at a mass ratio of 17:1:280, and pre-emulsify for 10 min under high-speed shearing;

[0131] S4. Add the surfactant in 3 portions during the polymerization process. The mass ratio of the surfactant added each time to the monomer composition is 1:45, with an interval of 20 min each time to obtain a pre-emulsion;

[0132] S5. Add ammonium persulfate accounting for 1% of the total weight of the monomer composition to the pre-emulsion, heat to 75 °C, and react for 4 h to obtain a prepolymer;

[0133] S6. Cool to room temperature, filter, and adjust the solid content to 40% to obtain the target product.

[0134] Test the intrinsic viscosity of the ultra-high viscosity polyacrylate foaming regulators prepared in Examples 1 to 3 and Comparative Examples 1 to 3. The test results are as follows:

[0135]

[0136] Prepare test specimens from the polyacrylate foaming regulators, polyvinyl chloride, and additives prepared in Examples 1 to 3 and Comparative Examples 1 to 3 according to the ratios shown in the following table. The ratios are shown in the following table:

[0137]

[0138] Prepare test specimens according to the above ratios and conduct performance tests on each specimen. The results are as follows:

[0139]

[0140] It can be seen from the above data that:

[0141] 1. The core-shell structure of Example 1 is complete, the interfacial bonding is strong, and the mechanical properties and thermal stability are optimal. Its performance is similar to that of Example 2. However, in Example 2, the content of dodecafluoroheptyl methacrylate in the shell structure is relatively high, and its hydrophobicity is slightly better than that of Example 1. In Example 3, the addition ratio of the surfactant is increased, effectively improving the dispersibility, resulting in the lowest melt index.

[0142] 2. Based on Example 1, in Comparative Example 1, the addition method of the surfactant is adjusted, and the dynamic addition in portions is no longer used, resulting in poor emulsification effect and poor performance in terms of gloss, compressive strength, and tensile strength.

[0143] 3. Comparative Example 2: Based on Example 1, photo-thermal dual initiation was no longer used, and only thermal initiation was adopted, resulting in insufficient cross-linking and shorter chain segments, thus affecting the comprehensive properties of the foaming material.

[0144] 4. Comparative Example 3: Based on Example 1, the core-shell structure was no longer used, and monomers were polymerized by mixing. The molecular weight was low and the distribution was wide, resulting in overall inferior performance.

[0145] In accordance with the embodiments of the present invention as described above, these embodiments do not elaborate on all details and do not limit the invention to only the specific embodiments described. Obviously, many modifications and variations can be made according to the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modified use based on the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyacrylate foaming regulator, characterized in that: The following steps are involved: S1, methyl methacrylate, butyl acrylate and divinylbenzene are mixed to form a core layer monomer composition for later use; S2, mixing isooctyl acrylate, styrene and hydroxyethyl acrylate to form an intermediate layer monomer composition for later use; S3, mixing ethyl acrylate and dodecafluoroheptyl methacrylate to form a shell monomer composition for later use; S4, mixing sodium lauryl sulfate and octylphenol polyoxyethylene ether to form an emulsifier for standby use; S5, mixing the core layer monomer composition, the emulsifier and the deionized water, and stirring for pre-emulsification for 10 minutes; S6, adding emulsifier three times, each time with an interval of 20 minutes, to obtain a nuclear layer pre-emulsion; S7, adding ammonium persulfate to the core layer pre-emulsion, heating to 75° C. and reacting for 1 h to obtain a core layer prepolymer; S8, adding the middle layer monomer composition, hexamethylphosphoric triamide and TPO initiator to the core layer prepolymer, prepolymerizing under ultraviolet light, then heating to 65° C., adding ammonium persulfate and continuing the reaction for 2 h to obtain a double-layer prepolymer; S9, mixing the shell monomer composition with an emulsifier to prepare a shell pre-emulsion, adding the shell pre-emulsion to the double-layer prepolymer 4 times, each time at an interval of 30 minutes, and reacting at 70° C. for 3 hours to obtain a three-layer prepolymer; S10, cooling to room temperature, filtering, and adjusting the solid content to 40% to 45% to obtain the target product.

2. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S1, the mass ratio of methyl methacrylate, butyl acrylate and divinylbenzene is 60-80:20-30:0.5-2.

3. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S2, the mass ratio of isooctyl acrylate, styrene and hydroxyethyl acrylate is 10-14:4-6:1-2.

4. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S3, the mass ratio of ethyl acrylate to dodecafluoroheptyl methacrylate is 7-9:1-3.

5. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S4, the mass ratio of sodium dodecyl sulfate to octylphenol polyoxyethylene ether is 1:2-4.

6. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S5, the mass ratio of the core layer monomer composition, the emulsifier, and the deionized water is 15-20:1-1.2:250-350.

7. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S5, the stirring speed is 8000-12000 r / min.

8. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S6, the mass ratio of the emulsifier added each time to the core layer monomer composition in step S1 is 1:40-50.

9. The method for preparing the polyacrylate foaming regulator according to claim 1, characterized in that: In step S9, the mass ratio of the shell monomer to the emulsifier is 10-15:1.

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