Acrylate copolymer and preparation method thereof

Abstract

This application relates to the technical field of polymer processing aids, specifically disclosing an acrylate copolymer and its preparation method. The method comprises the following steps: S1: mixing hard and soft acrylate monomers, chloroethyl acrylate, amino-silica, divinylbenzene, an emulsifier, and water to obtain emulsion A; S2: mixing hard and soft acrylate monomers, chloroethyl acrylate, epoxy acrylate monomer, amino-silica, an emulsifier, and water to obtain emulsion B; S3: mixing hard acrylate monomers, long-chain alkyl acrylate monomers, chloroethyl acrylate, diacetone acrylamide, amino-silica, an emulsifier, and water to obtain emulsion C; S4: heating emulsion A to react, then sequentially adding emulsions B and C to react, adjusting the pH, adding dihydrazide, and drying to obtain the product. The acrylate copolymer prepared in this application can optimize plasticization efficiency, control pore structure, and enhance mechanical properties.

Description

Technical Field

[0001] The present application relates to the technical field of polymer processing aids, and more specifically, to an acrylate copolymer and a preparation method thereof. Background Art

[0002] Acrylate copolymers are the most commonly used foaming regulators in the processing of PVC products, particularly in rigid foam applications (such as building boards, billboards, and pipes). They achieve a high molecular weight primarily through emulsion polymerization. High-molecular-weight acrylate copolymers significantly accelerate the melting rate of PVC resin particles and promote uniform plasticization, resulting in a homogeneous melt. Furthermore, the polymer chains entangle in the melt, forming a network structure that significantly enhances the melt's viscosity and strength, thereby increasing melt cohesion. This effectively supports cell growth and prevents premature bubble rupture or collapse caused by excessive expansion. The result is foamed products with uniform and fine cells, a stable structure, low density, and excellent mechanical properties.

[0003] To meet the demand for higher-performance products (such as lower density, greater thickness, more complex cross-sections, and higher surface quality), molecular design and structural control of acrylic copolymers are key. One approach is to increase molecular weight, which is the most direct and effective way to improve melt strength. Higher molecular weight increases molecular chain entanglement, resulting in greater melt strength and greater ability to support large cells and prevent collapse. However, excessively high molecular weight can lead to difficulties in plasticization, increased torque, higher energy consumption, or reduced surface finish. A second approach is to synthesize core-shell structures, which is currently the mainstream and advanced technology for high-performance ACR foaming regulators. Compared to single homopolymers or copolymers, core-shell acrylic copolymers typically achieve superior overall performance (high melt strength, good processability, excellent cell structure, and high surface quality) at lower addition levels, making them the preferred choice for producing high-quality PVC foam products (particularly ultra-low density, free-foaming sheets, and thick-walled products).

[0004] The patent application document with publication number CN105254817A discloses a method for preparing a core-shell structured acrylic ester foaming regulator, comprising the following steps: (1) reacting deionized water, an emulsifier, an acrylic ester monomer, and an initiator to obtain a core-layer acrylic ester seed latex; (2) reacting the core-layer acrylic ester seed latex, deionized water, an emulsifier, an acrylic ester monomer, and an initiator to obtain an acrylic ester copolymer emulsion, and spray drying the resultant to obtain a core-shell structured acrylic ester foaming regulator.

[0005] In this technical solution, the acrylate copolymer is prepared solely by acrylate monomers (the acrylate monomer is methyl methacrylate, ethyl acrylate, or butyl acrylate) and initiators. Although it can form a basic core-shell structure, in the PVC processing environment, its molecular chains maintain melt strength only through physical entanglement. This physical entanglement is very prone to slip and disentanglement, resulting in a significant decrease in melt cohesion, which in turn makes it difficult for the melt to resist the bubble expansion pressure, causing bubble merging or collapse. Summary of the Invention

[0006] In order to improve the temperature resistance and shear resistance of an acrylate copolymer, the present application provides an acrylate copolymer and a preparation method thereof.

[0007] In a first aspect, the present application provides a method for preparing an acrylic acid ester copolymer, which adopts the following technical solution:

[0008] The preparation method of the acrylic acid ester copolymer of the present application comprises the following steps:

[0009] S1: 70-80 parts of hard acrylate monomer, 5-10 parts of soft acrylate monomer, 12-15 parts of chloroethyl acrylate, 1-2 parts of amino-modified nano-silica, 0.2-0.4 parts of divinylbenzene, 1-3 parts of emulsifier and 180-220 parts of water are mixed uniformly to obtain emulsion A;

[0010] S2: 20-30 parts of hard acrylate monomer, 50-60 parts of soft acrylate monomer, 8-10 parts of chloroethyl acrylate, 8-10 parts of epoxy acrylate monomer, 2.5-3.5 parts of amino-modified nano-silica, 1-3 parts of emulsifier and 180-200 parts of water were mixed uniformly to obtain emulsion B;

[0011] S3: 10-15 parts of hard acrylate monomer, 30-40 parts of long-chain alkyl acrylate monomer, 2-4 parts of chloroethyl acrylate, 1.5-2 parts of diacetone acrylamide, 3.5-4.5 parts of amino-modified nano-silica, 1.5-2 parts of emulsifier and 100-130 parts of water are mixed uniformly to obtain emulsion C;

[0012] S4: Under an inert atmosphere, emulsion A is heated to 70-90°C, an initial initiator is added, and the reaction is carried out for 2.5-3.5 hours. Emulsion B is added in stages, and an initiator is further added, and the reaction is carried out for 2-3.5 hours. Emulsion C is added, and an initiator is further added, and the reaction is carried out for 2.5-3.5 hours. The product is cooled, and the pH is adjusted to 7.5-8.5. 1.8-2.2 parts of dihydrazide are added, the temperature is raised to 75-85°C, and the temperature is kept for 30-50 minutes. The product is concentrated, spray-dried, and sieved to obtain the product; the parts are parts by mass.

[0013] This scheme constructs a gradient structure of acrylic copolymers with a hard core-soft transition layer-flexible shell layer. The core layer uses a high proportion of hard acrylic monomers and chlorine-containing monomers to form a rigid skeleton, induces molecular chain segment orientation through strong polarity, drives the epoxy groups in the transition layer to migrate to the shell interface, and forms a dipole interaction with the PVC matrix to achieve indirect anchoring; the middle layer uses soft and hard acrylic monomers in conjunction with epoxy acrylate and chloroethyl acrylate to construct a rigid-flexible transition structure and adjust the polarity; the shell layer uses long-chain alkyl acrylate monomers to reduce the surface polarity, and is combined with high-concentration amino-grouped nano-silica to form a dense functional layer through strong interfacial interactions. Through the gradient decreasing design of chloroethyl acrylate from core to shell, combined with the gradient increasing distribution of amino-grouped nano-silica, the long-chain alkyl monomer is synergistically improved to enhance the hydrophobicity and provide uniform nucleation sites for melt foaming; the dihydrazide and ketone carbonyl form partial cross-links during the heat preservation stage, enhancing thermal stability and melt strength, and together with the gradient structure, broadening the molecular chain motion temperature window and regulating the molecular chain rigidity in sections, ultimately achieving a significant expansion of the processing temperature range of the PVC / acrylate copolymer composite system and optimization of the bubble uniformity.

[0014] Preferably, the soft acrylic ester monomer is selected from any one of butyl acrylate, ethyl acrylate and isooctyl acrylate.

[0015] Preferably, the hard acrylate monomer is selected from any one of methyl methacrylate and ethyl methacrylate.

[0016] Preferably, the long-chain alkyl acrylate monomer is selected from any one of lauryl methacrylate, octadecyl methacrylate, and hexadecyl methacrylate.

[0017] Preferably, the epoxy acrylate monomer is selected from any one of glycidyl methacrylate and glycidyl acrylate.

[0018] Preferably, the emulsifier is sodium lauryl sulfate.

[0019] Preferably, the dihydrazide is selected from any one of adipic acid dihydrazide and sebacic acid dihydrazide.

[0020] Preferably, step S4: under an inert atmosphere, emulsion A is heated to 70-90° C., 1.2-1.7 parts of initiator are added, and the reaction is carried out for 2.5-3.5 hours. 25%-35% of the volume fraction of emulsion B is first added at a rate of 1-3 mL / min, and 0.4-0.6 parts of initiator are added, and the reaction is carried out for 0.5-1 hour. The remaining emulsion B is then added at a rate of 5-7 mL / min, and 0.8-1.2 parts of initiator are added, and the reaction is carried out for 1.5-2.5 hours. Emulsion C is added, and 0.6-1 parts of initiator are added, and the reaction is carried out for 2.5-3.5 hours. The mixture is cooled to 35-45° C., the pH is adjusted to 7.5-8.5, 1.8-2.2 parts of dihydrazide are added, the temperature is raised to 75-85° C., and the mixture is kept warm for 30-50 minutes. The mixture is concentrated, spray-dried, and sieved to obtain the product.

[0021] Preferably, the initiator is selected from any one of potassium persulfate and ammonium persulfate.

[0022] In this scheme, during the low-speed addition stage, the low initiator concentration promotes the intermediate layer monomer to preferentially graft and grow on the core layer surface, forming a gradient transition interface; during the high-speed stage, the high initiator concentration is combined to achieve rapid homopolymerization and enhance the chemical bonding between layers.

[0023] Preferably, the preparation method of the amino-modified nano-silica comprises the following steps:

[0024] Mix 50-60 parts of nano-silica and 200-240 parts of ethanol aqueous solution, adjust the pH to 4-5, add 2-4 parts of aminosilane coupling agent, mix evenly, heat to 65-75°C, react for 3-5 hours, cool, separate the solid and liquid, wash, and dry to obtain the product.

[0025] Preferably, in the ethanol-water solution, the volume ratio of ethanol to water is (1-2):1.

[0026] In this solution, the dispersion performance of nano-silica can be improved by amination treatment of nano-silica. At the same time, its long organic chain can also enhance the compatibility with the polymer, physically block the migration of some acidic substances, and help maintain the stability of the processing environment.

[0027] Preferably, the amino-modified nano-silica undergoes the following pretreatment steps before use:

[0028] Mix 20-30 parts of amino-modified nano-silica and 100-120 parts of toluene-ethanol composite solvent evenly, adjust the pH to 8.5-9.0, add 4-6 parts of glycidyl methacrylate and 0.15-0.25 parts of tetrabutylammonium bromide, raise the temperature to 90-100° C., react for 4.5-5.5 hours, cool, wash, and dry to obtain the product.

[0029] Preferably, the particle size distribution of the nano-silicon dioxide is 20-50 nm.

[0030] Preferably, in the toluene-ethanol composite solvent, the volume ratio of toluene to ethanol is (2.5-3):1.

[0031] In this scheme, under the catalysis of tetrabutylammonium bromide and weak alkaline conditions, the silanol groups on the surface of the amino-modified nano-silica undergo a ring-opening reaction with the epoxy groups in glycidyl methacrylate, thereby further introducing a polymerizable double bond on the surface of the amino-modified nano-silica. In the subsequent copolymerization reaction, the double bond undergoes free radical polymerization with the acrylate monomer to form a covalent bond connection, so that the nano-silica is stably anchored in each layer of the copolymer, avoiding shedding or agglomeration during processing.

[0032] Preferably, the emulsion B further comprises the step of adding 2 to 4 parts by mass of polyethylene glycol (600) diacrylate.

[0033] In a second aspect, the present application also provides an acrylate copolymer prepared by the above preparation method.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. This application constructs a three-layer structure of hard core-soft transition-flexible shell by gradient decreasing of chloroethyl acrylate and gradient increasing of amino-treated nano-silica. The core layer constructs a rigid skeleton with a high proportion of hard monomers and chlorine-containing monomers. Its strong polarity can induce molecular segment orientation and drive the epoxy groups in the transition layer to migrate to the shell interface, and finally realize indirect interface anchoring through dipole interaction with PVC through polar groups enriched in the shell; the hard skeleton provides high-temperature support for the foaming melt, and the middle layer adopts a segmented feeding process to enhance interface bonding and increase the heat deformation temperature. The high-concentration nano-silica in the shell inhibits the merging of bubbles through physical barriers, cooperates with long-chain alkyl monomers to reduce surface energy, optimizes bubble uniformity, and subsequently adds dihydrazide to form partial cross-linking to improve thermal stability.

[0036] 2. This application achieves enhanced interfacial bonding and uniform coating between the soft transition layer and the hard core by adding emulsion B in stages and coordinating with variable temperature control: in the low-speed addition stage, the low initiator concentration promotes the intermediate layer monomer to preferentially graft and grow on the surface of the core layer, forming a gradient transition interface; in the high-speed stage, with the high initiator concentration, rapid homopolymerization and coating are achieved, thereby enhancing the chemical bonding between the layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a torque-plasticization time-temperature relationship curve when the acrylic ester copolymer of Example 1 is used as a PVC foaming regulator. DETAILED DESCRIPTION

[0038] The present application is further described in detail below with reference to the embodiments.

[0039] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0040] The particle size distribution of nano-silica is 20~50nm.

[0041] Preparation Examples 1-3 Aminated Nano-Silica

[0042] Preparation Example 1

[0043] The preparation method of the amino-modified nano-silica in this preparation example comprises the following steps:

[0044] 55 g of nano-silica and 220 g of ethanol aqueous solution were added to a reactor, and then transferred to an ultrasonic device, ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 20 min, and then adjusted to pH 4.5 with 10% acetic acid by mass, and added with 2.75 g of silane coupling agent KH550. The mixture was stirred and mixed at a speed of 300 rpm, heated to 70°C, stirred and reacted for 4 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol three times, and dried in a vacuum drying oven at 60°C to constant weight to obtain the product.

[0045] Wherein, in the ethanol aqueous solution, the volume ratio of ethanol to water is 1:1.

[0046] Preparation Example 2

[0047] The preparation method of the amino-modified nano-silica in this preparation example comprises the following steps:

[0048] 50 g of nano-silica and 200 g of ethanol aqueous solution were added to a reactor, and then transferred to an ultrasonic device, ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 20 min, and then adjusted to pH 5 with 10% acetic acid by mass, and 2 g of silane coupling agent KH550 was added, and stirred and mixed at a speed of 300 rpm. The temperature was raised to 65°C, stirred and reacted for 5 h, cooled to room temperature, centrifuged, washed with anhydrous ethanol three times, and dried in a vacuum drying oven at 60°C to constant weight to obtain the product.

[0049] Wherein, in the ethanol aqueous solution, the volume ratio of ethanol to water is 2:1.

[0050] Preparation Example 3

[0051] The preparation method of the amino-modified nano-silica in this preparation example comprises the following steps:

[0052] 60 g of nano-silica and 240 g of ethanol aqueous solution were added to a reactor, and then transferred to an ultrasonic device and ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 20 min. Then, 10% acetic acid was used to adjust the pH to 4, and 4 g of silane coupling agent KH550 was added. The mixture was stirred and mixed at a speed of 300 rpm. The temperature was raised to 75°C, stirred and reacted for 3 hours, cooled to room temperature, centrifuged, washed with anhydrous ethanol three times, and dried in a vacuum drying oven at 60°C to constant weight to obtain the product.

[0053] Wherein, the volume ratio of ethanol to water in the ethanol aqueous solution is 1.5:1.

[0054] Preparation Example 4-5 Pretreatment of Aminated Nano-Silica

[0055] Preparation Example 4

[0056] The amino-modified nano-silica in this preparation example was subjected to the following pretreatment steps before use:

[0057] Under a nitrogen atmosphere, 20 g of amino-modified nano-silica and 100 g of a toluene-ethanol mixed solvent were added to a flask, and then transferred to an ultrasonic device. The mixture was ultrasonically treated for 20 min at a power of 300 W and a frequency of 40 kHz. 0.1 mol / L triethylamine toluene solution was slowly added dropwise while stirring at a stirring rate of 200 rpm. The pH was adjusted to 8.5, and 4 g of glycidyl methacrylate and 0.15 g of tetrabutylammonium bromide were added. The temperature was raised to 90°C, and the mixture was refluxed for 5.5 h. The mixture was cooled to room temperature, centrifuged, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 60°C to constant weight.

[0058] Wherein, in the toluene-ethanol mixed solvent, the volume ratio of toluene to ethanol is 3:1;

[0059] The amino-modified nano-silica was obtained from Preparation Example 1.

[0060] Preparation Example 5

[0061] The amino-modified nano-silica in this preparation example was subjected to the following pretreatment steps before use:

[0062] Under a nitrogen atmosphere, 30 g of amino-modified nano-silica and 120 g of a toluene-ethanol mixed solvent were added to a flask, and then transferred to an ultrasonic device. The mixture was ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 20 min. 0.1 mol / L triethylamine toluene solution was slowly added dropwise while stirring at a stirring rate of 200 rpm. The pH was adjusted to 9.0, and 6 g of glycidyl methacrylate and 0.25 g of tetrabutylammonium bromide were added. The temperature was raised to 100° C., refluxed for 4.5 h, cooled to room temperature, centrifuged, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 60° C. to constant weight to obtain the product.

[0063] Wherein, in the toluene-ethanol mixed solvent, the volume ratio of toluene to ethanol is 2.5:1.

[0064] The amino-modified nano-silica comes from Preparation Example 3.

[0065] Example 1

[0066] The preparation method of the acrylic acid ester copolymer of this embodiment comprises the following steps:

[0067] S1: 2 g of sodium lauryl sulfate and 200 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 1.5 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 10 min. Then, 75 g of methyl methacrylate, 8 g of butyl acrylate, 13 g of chloroethyl acrylate, and 0.3 g of divinylbenzene were slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion A.

[0068] S2: 2 g of sodium lauryl sulfate and 190 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. 3 g of amino-modified nano-silica was then added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 12 min. 25 g of methyl methacrylate, 55 g of butyl acrylate, 9 g of chloroethyl acrylate, and 9 g of glycidyl methacrylate were then slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion B.

[0069] S3: 1.8 g of sodium lauryl sulfate and 120 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 4 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 15 min. Then, 12 g of methyl methacrylate, 35 g of lauryl methacrylate, 3 g of chloroethyl acrylate, and 1.8 g of diacetone acrylamide were slowly added and stirred at 200 rpm to mix uniformly to obtain an emulsion C.

[0070] S4: Under nitrogen atmosphere, emulsion A was added to the reactor, the temperature was raised to 80 ° C, and potassium persulfate aqueous solution (mixed with 1.5 g of potassium persulfate and 10 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept for 3 hours, and then emulsion B was added at a rate of 1.5 mL / min until 30% of the total volume was added. At the same time, potassium persulfate aqueous solution (mixed with 0.5 g of potassium persulfate and 5 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept for 0.75 h, and then the remaining emulsion B was added at a rate of 6 mL / min. At the same time, potassium persulfate aqueous solution (mixed with 1 g of potassium persulfate and 5 g of deionized water) was added dropwise. After the addition is completed, keep warm for 2 hours, then add emulsion C at a rate of 3 mL / min, and simultaneously add potassium persulfate aqueous solution (mixed with 0.8 g of potassium persulfate and 5 g of deionized water). After the addition is completed, keep warm for 3 hours, cool to 40°C, adjust the pH to 8.0 with 0.1 mol / L triethylamine aqueous solution, add 2 g of adipic acid dihydrazide, stir and mix evenly, heat to 80°C, keep warm for 40 minutes, concentrate under reduced pressure at -0.09 MPa and 45°C to a solid content of 50%, spray dry (inlet air 145°C, outlet air 65°C), and pass through a 40-mesh standard sieve to obtain the product.

[0071] Wherein, the amino-modified nano-silica comes from Preparation Example 1.

[0072] Example 2

[0073] The preparation method of the acrylic acid ester copolymer of this embodiment comprises the following steps:

[0074] S1: 1 g of sodium lauryl sulfate and 180 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 1 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 10 min. Then, 70 g of ethyl methacrylate, 5 g of ethyl acrylate, 12 g of chloroethyl acrylate, and 0.2 g of divinylbenzene were slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion A.

[0075] S2: 1 g of sodium lauryl sulfate and 180 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. 2.5 g of amino-modified nano-silica was then added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 12 min. 20 g of ethyl methacrylate, 50 g of ethyl acrylate, 8 g of chloroethyl acrylate, and 8 g of glycidyl methacrylate were then slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion B.

[0076] S3: 1.5 g of sodium lauryl sulfate and 100 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 3.5 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 15 min. Then, 10 g of ethyl methacrylate, 30 g of octadecyl methacrylate, 2 g of chloroethyl acrylate, and 1.5 g of diacetone acrylamide were slowly added and stirred at 200 rpm to mix uniformly to obtain an emulsion C.

[0077] S4: Under nitrogen atmosphere, emulsion A was added to the reactor, the temperature was raised to 70 ° C, and an aqueous solution of ammonium persulfate (mixed with 1.2 g of ammonium persulfate and 10 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept at 3.5 h, and then emulsion B was added at a rate of 1 mL / min until 25% of the total volume was added. At the same time, an aqueous solution of ammonium persulfate (mixed with 0.4 g of ammonium persulfate and 5 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept at 1 h, and then the remaining emulsion B was added at a rate of 5 mL / min. At the same time, an aqueous solution of ammonium persulfate (mixed with 0.8 g of ammonium persulfate and 5 g of deionized water) was added dropwise. After the addition is completed, keep warm for 2.5 hours, then add emulsion C at a rate of 3 mL / min, and simultaneously add ammonium persulfate aqueous solution (mixed with 0.6 g of ammonium persulfate and 5 g of deionized water). After the addition is completed, keep warm for 3.5 hours, cool to 35°C, adjust the pH to 7.5 with 0.1 mol / L triethylamine aqueous solution, add 1.8 g of adipic acid dihydrazide, stir and mix evenly, heat to 75°C, keep warm for 50 minutes, concentrate under reduced pressure at -0.09 MPa and 45°C to a solid content of 50%, spray dry (inlet air 145°C, outlet air 65°C), and pass through a 40-mesh standard sieve to obtain the product.

[0078] Among them, the amino-treated nano-silica comes from Preparation Example 2.

[0079] Example 3

[0080] The preparation method of the acrylic acid ester copolymer of this embodiment comprises the following steps:

[0081] S1: 3 g of sodium lauryl sulfate and 220 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 2 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 10 min. Then, 80 g of methyl methacrylate, 10 g of isooctyl acrylate, 15 g of chloroethyl acrylate, and 0.4 g of divinylbenzene were slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion A.

[0082] S2: 3 g of sodium lauryl sulfate and 200 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 3.5 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 12 min. Then, 30 g of methyl methacrylate, 60 g of isooctyl acrylate, 10 g of chloroethyl acrylate, and 10 g of glycidyl acrylate were slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion B.

[0083] S3: 2 g of sodium lauryl sulfate and 130 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 4.5 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 15 min. Then, 15 g of methyl methacrylate, 40 g of hexadecyl methacrylate, 4 g of chloroethyl acrylate, and 2 g of diacetone acrylamide were slowly added and stirred at 200 rpm to mix uniformly to obtain an emulsion C.

[0084] S4: Under nitrogen atmosphere, emulsion A was added to the reactor, the temperature was raised to 90 ° C, and potassium persulfate aqueous solution (mixed with 1.7 g of potassium persulfate and 10 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept at 2.5 h, and then emulsion B was added at a rate of 3 mL / min until 35% of the total volume was added. At the same time, potassium persulfate aqueous solution (mixed with 0.6 g of potassium persulfate and 5 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept at 0.5 h, and then the remaining emulsion B was added at a rate of 7 mL / min. At the same time, potassium persulfate aqueous solution (mixed with 1.2 g of potassium persulfate and 5 g of deionized water) was added dropwise. After the addition is completed, keep warm for 1.5 hours, then add emulsion C at a rate of 3 mL / min, and simultaneously add potassium persulfate aqueous solution (mixed with 1 g of potassium persulfate and 5 g of deionized water). After the addition is completed, keep warm for 2.5 hours, cool to 45°C, adjust the pH to 7.5 with 0.1 mol / L triethylamine aqueous solution, add 2.2 g of sebacic acid dihydrazide, stir and mix evenly, heat to 85°C, keep warm for 30 minutes, concentrate under reduced pressure at -0.09 MPa and 45°C to a solid content of 50%, spray dry (inlet air 145°C, outlet air 65°C), and pass through a 40-mesh standard sieve to obtain the product.

[0085] Among them, the amino-modified nano-silica comes from Preparation Example 3.

[0086] Example 4

[0087] The difference between this embodiment and embodiment 1 is that:

[0088] The amino-treated nano-silica is pretreated amino-treated nano-silica, which comes from Preparation Example 4.

[0089] Other details are the same as in Example 1.

[0090] Example 5

[0091] The difference between this embodiment and embodiment 4 is that:

[0092] The pretreated amino-treated nano-silica comes from Preparation Example 5.

[0093] Other details are the same as in Example 4.

[0094] Example 6

[0095] The difference between this embodiment and embodiment 5 is that:

[0096] Step S2 is as follows: 2 g of sodium lauryl sulfate and 190 g of deionized water are added to a container, stirred and mixed at a speed of 200 rpm, then 3 g of amino-modified nano-silica is added, stirred and mixed at a speed of 800 rpm for 10 minutes, then transferred to an ultrasonic device, ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 12 minutes, and then 25 g of methyl methacrylate, 55 g of butyl acrylate, 9 g of chloroethyl acrylate, 9 g of glycidyl methacrylate and 2 g of polyethylene glycol (600) diacrylate are slowly added, and stirred and mixed at a speed of 200 rpm to obtain emulsion B;

[0097] Other details are the same as in Example 5.

[0098] Example 7

[0099] The difference between this embodiment and embodiment 6 is that:

[0100] Step S2 is as follows: 2 g of sodium lauryl sulfate and 190 g of deionized water are added to a container, stirred and mixed at a speed of 200 rpm, then 3 g of amino-modified nano-silica is added, stirred and mixed at a speed of 800 rpm for 10 minutes, then transferred to an ultrasonic device, ultrasonically treated at a power of 300 W and a frequency of 40 kHz for 12 minutes, and then 25 g of methyl methacrylate, 55 g of butyl acrylate, 9 g of chloroethyl acrylate, 9 g of glycidyl methacrylate and 4 g of polyethylene glycol (600) diacrylate are slowly added, and stirred and mixed at a speed of 200 rpm to obtain emulsion B;

[0101] Other details are the same as in Example 6.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is:

[0104] In step S1, step S2, and step S3, the amount of amino-modified nano-silica used is 1.5 g.

[0105] Other details are the same as in Example 1.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 1 is:

[0108] In step S1, step S2, and step S3, the amount of chloroethyl acrylate used is 9 g.

[0109] Other details are the same as in Example 1.

[0110] Comparative Example 3

[0111] The difference between this comparative example and Example 1 is:

[0112] S4: Under nitrogen atmosphere, emulsion A was added to the reactor, the temperature was raised to 80 ° C, and potassium persulfate aqueous solution (mixed with 1.5 g of potassium persulfate and 10 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept warm for 3 hours, and emulsion B was added at a rate of 6 mL / min. At the same time, potassium persulfate aqueous solution (mixed with 1.5 g of potassium persulfate and 10 g of deionized water) was added dropwise. After the addition was completed, the temperature was kept warm for 2.75 hours, and emulsion C was added at a rate of 3 mL / min. After the addition of potassium persulfate aqueous solution (mixed with 0.8 g of potassium persulfate and 5 g of deionized water), the mixture was kept warm for 3 h, cooled to 40°C, and the pH was adjusted to 8.0 with 0.1 mol / L triethylamine aqueous solution. 2 g of adipic acid dihydrazide was added and stirred to mix evenly. The mixture was heated to 80°C and kept warm for 40 min. The mixture was concentrated under reduced pressure at -0.09 MPa and 45°C to a solid content of 50%, and spray-dried (inlet air 145°C, outlet air 65°C). The mixture was passed through a 40-mesh standard sieve to obtain the product.

[0113] Other details are the same as in Example 1.

[0114] Comparative Example 4

[0115] The difference between this comparative example and Example 1 is:

[0116] S2: 3 g of sodium lauryl sulfate and 200 g of deionized water were added to a container and stirred at 200 rpm to mix uniformly. Then, 3.5 g of amino-modified nano-silica was added and stirred at 800 rpm for 10 min. The mixture was then transferred to an ultrasonic device and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 12 min. Then, 30 g of methyl methacrylate, 60 g of butyl acrylate, and 10 g of chloroethyl acrylate were slowly added and stirred at 200 rpm to mix uniformly to obtain emulsion B.

[0117] Other details are the same as in Example 1.

[0118] Performance testing

[0119] 1. Take 0.15 g of each of the acrylate copolymers prepared in Examples 1 to 7 and Comparative Examples 1 to 4, respectively, dissolve them in 50 mL of chloroform, keep the temperature at 25 ° C for 1 hour, take out and adjust the volume to obtain the test solution, and then use an Ubbelohde viscometer to measure the viscosity of the test solution and the viscosity of chloroform, and calculate the intrinsic viscosity. The specific results are shown in Table 1.

[0120] 2. The acrylate copolymers prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to performance tests according to the following steps. The test results are shown in Table 1:

[0121] 300 g of PVC resin (SG-5 type), 9.0 g of calcium-zinc composite stabilizer, 3.6 g of polyethylene wax, and 30 g of calcium carbonate were placed in a high-speed mixer and mixed at 300 rpm for 5 min. 28.5 g of acrylate copolymer was then added and mixed at 600 rpm for 10 min. The mixture was heated to 110° C., 21.6 g of dioctyl phthalate was added and mixed for 3 min. The mixture was cooled to 95° C., 5.4 g of azodicarbonamide was added, and the mixture was mixed at 1200 rpm for 8 min to obtain a mixture.

[0122] (1) Take part of the mixture and put it into the mixing chamber, set the temperature to 170℃ and the rotor speed to 35rpm. The time for the torque to rise to the maximum value is the plasticizing time (s); the average torque in the stable stage is the equilibrium torque (N·m);

[0123] (2) The remaining mixture was spread into the mold (specifications: 300mm×300mm×10mm, preheated to 175℃ in advance) with a thickness of 8mm. The pressure was maintained at 5MPa. After saturation for 15 minutes, the pressure was released and foaming was carried out. Water (flow rate 10L / min) was immediately passed to cool the mold surface to 40℃. The mold was opened and the sample was taken out for testing.

[0124] (a) Sample density and pore structure test: Cut 30 mm × 30 mm × 10 mm specimens (three parallel specimens), weigh the sample mass m0 and sample dimensions, and calculate the apparent density. Then, vacuum immerse the specimen in anhydrous ethanol for 3 h (vacuum degree 1 kPa), wipe the surface dry, weigh the saturated mass m1, weigh the mass of the hanging basket in anhydrous ethanol m2, place the sample in the hanging basket, weigh the total mass of the sample and hanging basket in anhydrous ethanol m3, and calculate the porosity; porosity = (m1-m0) × 100% / (m3-m2).

[0125] (b) Impact and compressive strength tests: Five parallel specimens (80 mm × 10 mm × 4 mm) were cut with an A-notch depth of 2.0 ± 0.1 mm and subjected to a simply supported beam impact test with a pendulum energy of 4 J. Five parallel specimens (30 mm × 30 mm × 10 mm) were cut and the stress (MPa) at 30% deformation was recorded.

[0126] Table 1 Performance test data of acrylic acid ester copolymers prepared in Examples 1 to 7 and Comparative Examples 1 to 4

[0127]

[0128] From the performance test data in Table 1, we can see that:

[0129] In Examples 1-3, a three-stage emulsion gradient design was employed. Emulsion A (primarily composed of hard acrylate monomers) constructed a rigid cross-linked core, providing initial shear response sites. Emulsion B (primarily composed of soft acrylate monomers) formed a flexible intermediate layer, reducing melt viscosity and optimizing plasticization efficiency. Emulsion C (primarily composed of long-chain alkyl acrylate monomers, supplemented with highly amino-filled nanosilica) constructed a hydrophobic reinforcing shell, modulating bubble surface tension and forming a physical barrier network to inhibit cell merging. In the key component gradient design, the amount of chloroethyl acrylate was gradually reduced. The high concentration of chloroethyl in Emulsion A, through dipole-dipole interaction with PVC, strengthened initial interfacial adhesion. The low concentration of chloroethyl in Emulsion C also prevented excessive interference of polar groups on molecular chain motion, achieving a balance between interfacial adhesion and segmental freedom. This synergistic effect, combined with the amino-filled nanosilica, inhibited nanoparticle aggregation and strengthened interfacial bonding.

[0130] In Comparative Examples 1 to 4, Comparative Example 1 did not adopt a gradient dosage of amino-treated nano-silica, resulting in insufficient interface reinforcement effect and a decline in melt strength and mechanical properties; in Comparative Example 2, the polar groups of chloroethyl acrylate were evenly distributed, interfering with PVC plasticization, causing melt surface tension imbalance, and deterioration of cell stability and interface compatibility; in Comparative Example 3, the staged feeding process of emulsion B was omitted, resulting in a broadening of molecular weight distribution and a sudden drop in melt strength, cell merging, and uncontrolled growth; in Comparative Example 4, the lack of cross-linking points reduced the interlayer bonding force, causing stress concentration and crack propagation along weak interfaces, resulting in a decline in mechanical properties.

[0131] In Examples 4 and 5, by grafting glycidyl methacrylate onto the surface of amino-modified nanosilica, the nanoparticles' tendency to agglomerate significantly decreased, resulting in a uniform distribution along the cell walls and significantly improving stress transfer efficiency. Furthermore, the double bonds of glycidyl methacrylate participate in copolymerization, increasing molecular chain rigidity through segment extension and crosslinking, while also boosting melt strength. Because the crosslinked structure restricts molecular chain motion and increases melt viscosity, the plasticizing time during material processing is prolonged. During the foaming process, the increased melt strength enhances cell wall stability, while the enhanced interfacial bonding significantly improves mechanical properties.

[0132] In Examples 6 and 7, polyethylene glycol (600) diacrylate is further introduced into emulsion B to form flexible crosslinks through double bond crosslinking. The long-chain flexible segments and acrylate segments regulate the melt elasticity and promote uniform nucleation through the dual effects of physical entanglement and chemical crosslinking. As the amount of polyethylene glycol (600) diacrylate increases, the crosslinking density gradually increases, the toughness of the pore wall is enhanced, the compressive strength increases due to the network support effect, and the impact strength is improved due to the energy dissipation effect of the flexible network.

[0133] from Figure 1 It can be seen that when using the acrylic copolymer in Example 1, the plasticization time was approximately 103 s and the equilibrium torque was approximately 27.2 N·m. During the mixing process, the temperature gradually increased over time, and the torque first decreased, then increased, and then stabilized. The initial decrease in torque is due to softening and melting of the material, increasing fluidity. The subsequent increase is due to uniform material dispersion and increased melt viscosity or cohesion. The subsequent stabilization indicates sufficient and stable plasticization. This trend reflects the coordination between melt fluidity and strength, demonstrating a good match between processing performance, mechanical properties, and cell characteristics.

[0134] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing an acrylic acid ester copolymer, characterized in that: The steps include: S1: 70-80 parts of hard acrylate monomer, 5-10 parts of soft acrylate monomer, 12-15 parts of chloroethyl acrylate, 1-2 parts of amino-modified nano-silica, 0.2-0.4 parts of divinylbenzene, 1-3 parts of emulsifier and 180-220 parts of water are mixed uniformly to obtain emulsion A; S2: 20-30 parts of hard acrylate monomer, 50-60 parts of soft acrylate monomer, 8-10 parts of chloroethyl acrylate, 8-10 parts of epoxy acrylate monomer, 2.5-3.5 parts of amino-modified nano-silica, 1-3 parts of emulsifier and 180-200 parts of water were mixed uniformly to obtain emulsion B; S3: 10-15 parts of hard acrylate monomer, 30-40 parts of long-chain alkyl acrylate monomer, 2-4 parts of chloroethyl acrylate, 1.5-2 parts of diacetone acrylamide, 3.5-4.5 parts of amino-modified nano-silica, 1.5-2 parts of emulsifier and 100-130 parts of water are mixed uniformly to obtain emulsion C; S4: Under an inert atmosphere, emulsion A is heated to 70-90°C, an initial initiator is added, and the reaction is carried out for 2.5-3.5 hours. Emulsion B is added in stages, and an initiator is further added, and the reaction is carried out for 2-3.5 hours. Emulsion C is added, and an initiator is further added, and the reaction is carried out for 2.5-3.5 hours. The product is cooled, and the pH is adjusted to 7.5-8.

5. 1.8-2.2 parts of dihydrazide are added, the temperature is raised to 75-85°C, and the temperature is kept for 30-50 minutes. The product is concentrated, spray-dried, and sieved to obtain the product; the parts are parts by mass.

2. The method for preparing an acrylate copolymer according to claim 1, wherein The soft acrylic acid ester monomer is selected from any one of butyl acrylate, ethyl acrylate and isooctyl acrylate.

3. The method for preparing an acrylate copolymer according to claim 1, wherein The hard acrylate monomer is selected from any one of methyl methacrylate and ethyl methacrylate.

4. The method for preparing an acrylate copolymer according to claim 1, wherein The long-chain alkyl acrylate monomer is selected from any one of lauryl methacrylate, octadecyl methacrylate, and hexadecyl methacrylate.

5. The method for preparing an acrylate copolymer according to claim 1, wherein The epoxy acrylate monomer is selected from any one of glycidyl methacrylate and glycidyl acrylate.

6. The method for preparing an acrylate copolymer according to claim 1, wherein The dihydrazide is selected from any one of adipic acid dihydrazide and sebacic acid dihydrazide.

7. The method for preparing an acrylate copolymer according to claim 1, wherein: The preparation method of the amino-modified nano-silica comprises the following steps: Mix 50-60 parts of nano-silica and 200-240 parts of ethanol aqueous solution, adjust the pH to 4-5, add 2-4 parts of aminosilane coupling agent, mix evenly, heat to 65-75°C, react for 3-5 hours, cool, separate the solid and liquid, wash, and dry to obtain the product.

8. The method for preparing an acrylate copolymer according to claim 7, wherein: The amino-modified nano-silica undergoes the following pretreatment steps before use: Mix 20-30 parts of amino-modified nano-silica and 100-120 parts of toluene-ethanol composite solvent evenly, adjust the pH to 8.5-9.0, add 4-6 parts of glycidyl methacrylate and 0.15-0.25 parts of tetrabutylammonium bromide, raise the temperature to 90-100° C., react for 4.5-5.5 hours, cool, wash, and dry to obtain the product.

9. The method for preparing an acrylate copolymer according to claim 1, wherein: The emulsion B further includes a step of adding 2 to 4 parts by mass of polyethylene glycol (600) diacrylate.

10. An acrylate copolymer obtained by the method for preparing an acrylate copolymer according to claim 1.

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