Production method of PVC foaming regulator

Abstract

The invention belongs to the technical field of processing aids, and relates to a production method of a PVC (polyvinyl chloride) foaming regulator, which comprises the following steps: preparing deionized water and a compound emulsifier into emulsion; adding butyl acrylate, ethyl acrylate, methyl methacrylate and modified nano calcium carbonate to prepare a pre-emulsion; adding part of the pre-emulsion and an initiator into the emulsion, and supplementing the initiator after a period of time to obtain a seed polymerization solution; uniformly mixing the residual pre-emulsion with a chain transfer agent, dropwise adding the mixture into the seed polymerization liquid, and preserving heat; adding a demulsifier, and performing vacuum drying to obtain polymer particles; and uniformly mixing a calcium-zinc stabilizer, calcium stearate and the polymer particles, heating, adding oxidized polyethylene wax, dispersing at a high speed, and cooling to obtain the PVC foaming regulator. Through material modification, polymerization process optimization and the synergistic effect of compounded components, the defects of a traditional PVC foaming regulator in the aspects of stability, melt strength, lubrication balance and dispersity are systematically overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of processing aids, and specifically relates to a production method of a PVC foaming regulator. Background Art

[0002] PVC foaming regulator is a regulator that increases the pressure and torque of PVC melt, thereby effectively increasing the cohesion and homogeneity of PVC melt and making the resulting PVC products denser.

[0003] The Chinese invention patent with publication number CN118440236A discloses a modified foaming regulator and its preparation method and application. The raw materials for its preparation include at least methacrylate alkyl ester monomers, acrylate alkyl ester monomers, modified functional monomers, emulsifiers, co-emulsifiers, initiator solution, and water. The modified functional monomer is at least one of fluorinated acrylate monomers and ethylene monomers. The patent optimizes the copolymerization formula and process of methacrylate alkyl ester monomers, acrylate alkyl ester monomers, and modified functional monomers to ensure that the subsequent PVC foam material has a uniform and dense pore structure and a lower density.

[0004] Low-density foam materials have been widely used in the protective packaging of electronic products and fragile items due to their excellent lightweight properties. However, such materials often have deficiencies in mechanical strength, which limits their application in certain occasions with high strength requirements. In contrast, although higher-density materials show higher strength and load-bearing capacity, they are often accompanied by increased packaging costs. Despite this, low-density foam materials still need to be improved in terms of cushioning performance. Therefore, how to ensure that low-density foam materials have higher mechanical strength while maintaining their lightweight has become a problem that needs to be solved urgently. Summary of the invention

[0005] In view of the problems existing in the existing PVC foaming regulator, the present invention proposes a production method of a PVC foaming regulator, aiming to systematically solve the above problems, which is specifically achieved through the following technical solutions: A method for producing a PVC foaming regulator comprises the following steps: S1. In a reaction kettle, add 55-60 parts by mass of deionized water and 3-5 parts by mass of a composite emulsifier, stir mechanically and heat to 45° C. to prepare an emulsion; S2, add 10-15 parts by mass of ethyl acrylate, 25-30 parts by mass of butyl acrylate, and 40-50 parts by mass of methyl methacrylate to the emulsion, emulsify at 3000 rpm for 20 min, add 10-15 parts by mass of modified nano calcium carbonate, and continue stirring for 30 min to form a pre-emulsion; S3, prepare another reactor, add 20% to 30% of the total volume of the pre-emulsion, stir mechanically and heat to 75 to 80°C, add 0.4 to 0.6 parts by mass of initiator, react for 30 to 40 minutes, then add 0.3 to 0.5 parts by mass of initiator, continue to react for 1 to 1.5 hours, and obtain a seed polymerization solution; S4, the seed polymerization liquid is heated to 85-90°C, the remaining pre-emulsion is mixed with 1.5-3 parts by mass of chain transfer agent and then dripped into the seed polymerization liquid. After the dripping is completed, the temperature is kept for 1 hour; S5, adding 1.5 to 3 parts by weight of demulsifier to the system of step S4, mechanically stirring for 45 minutes, vacuum drying, air flow pulverization, to obtain polymer particles; S6. Evenly mix 1-1.5 parts by mass of calcium zinc stabilizer, 0.3-0.5 parts by mass of calcium stearate and polymer particles, heat to 120° C., add 0.8-1 parts by mass of oxidized polyethylene wax, disperse at a high speed of 1500 rpm for 30 minutes, and cool to room temperature to obtain a PVC foaming regulator.

[0006] Preferably, the modified nano calcium carbonate comprises the following preparation steps: S21, dispersing nano calcium carbonate in anhydrous ethanol to form a dispersion with a mass concentration of 15%, heating to 60° C., adding a titanate coupling agent in an amount of 1% of the total mass of the dispersion, and stirring for 30 min; S22, adding 2% stearic acid of the total mass of nano calcium carbonate, maintaining 60°C and continuing stirring for 20 minutes; S23, centrifugation, ethanol washing 3 times, vacuum drying to obtain modified nano calcium carbonate.

[0007] Preferably, the compound emulsifier is compounded by sodium lauryl sulfate and alkylphenol polyoxyethylene ether in a mass ratio of 2:3.

[0008] Preferably, the initiator is potassium persulfate.

[0009] Preferably, the chain transfer agent is n-dodecyl mercaptan.

[0010] Preferably, the demulsifier is prepared by mixing aluminum sulfate and citric acid in a mass ratio of 3:1.

[0011] Preferably, in step S4, the dropping time is controlled within 2 to 3 hours.

[0012] After adopting the above technical solution, the beneficial effects of the present invention are: The PVC foaming regulator of the present invention successfully solves the defects of traditional PVC foaming materials in terms of stability, melt strength, lubrication balance and dispersibility through comprehensive application of material modification, polymerization process optimization, synergistic effect of compound components, reasonable initiation system and monomer ratio and nanoparticle dispersion process. At the same time, these improvement measures also significantly improve the pore structure and mechanical properties of PVC foaming materials, providing a better choice for the application of PVC foaming materials. DETAILED DESCRIPTION

[0013] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with 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 the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention.

[0014] Example 1 This embodiment provides a method for producing a PVC foaming regulator, which is prepared by sequentially preparing an emulsion, preparing a pre-emulsion, staged emulsion polymerization, demulsification and drying, and compounding auxiliary agents.

[0015] S1. Emulsion preparation Add 55 parts by mass of deionized water to the reactor, and add 3 parts by mass of a compound emulsifier mixed with sodium dodecyl sulfate (anionic type) and alkylphenol polyoxyethylene ether (non-ionic type) at a mass ratio of 2:3. Mechanically stir and heat to 45°C to fully dissolve the compound emulsifier in the deionized water and form micelles, providing a stable environment for subsequent monomer emulsification. Finally, an emulsion is obtained.

[0016] Through the synergistic effect of the compound emulsifier, the key physical and chemical conditions are provided for the emulsification polymerization of the subsequent monomers, which directly affects the molecular weight, melt strength and cell uniformity of the PVC foaming regulator and the final foamed product.

[0017] S2. Preparation of pre-emulsion 10 parts by mass of ethyl acrylate, 25 parts by mass of butyl acrylate and 40 parts by mass of methyl methacrylate were added to the emulsion, and the mixture was emulsified using a high-speed stirrer at 3000 rpm for 20 minutes in order to evenly disperse the monomers in the emulsion. Then, 10 parts by mass of modified nano calcium carbonate were added and stirred for 30 minutes to ensure that it was evenly dispersed in the emulsion. Finally, a pre-emulsion was obtained.

[0018] As an inorganic filler, nano calcium carbonate can enhance the mechanical properties of foamed materials. At the same time, as a heterogeneous nucleation point, nano calcium carbonate can promote the uniform nucleation and growth of pores during the foaming process, thereby limiting the excessive expansion of pores and achieving a narrow distribution of pore size and high density. Nano calcium carbonate needs to be modified when used, and the modification process includes the following steps: First, nano-calcium carbonate was dispersed in anhydrous ethanol to form a dispersion with a mass concentration of 15%, and the dispersion was heated to 60°C, and a titanate coupling agent (NDZ-201) of 1% of the total mass of the dispersion was added, and stirred for 30 minutes; then, stearic acid of 2% of the total mass of the nano-calcium carbonate was added, and the temperature was maintained at 60°C and stirred for 20 minutes; finally, the solid matter was collected by centrifugation, washed with ethanol three times, and vacuum dried to obtain modified nano-calcium carbonate.

[0019] The long-chain alkyl of NDZ-201 is covalently bonded to the surface of nano-calcium carbonate to form a hydrophobic layer, which makes the surface energy of nano-calcium carbonate particles more compatible with the acrylate monomer, reduces the interfacial tension between nano-calcium carbonate and acrylate monomer, and thus improves the compatibility between the two. In the subsequent polymerization process, the long-chain structure of stearic acid can be physically entangled with the acrylate monomer, preventing the secondary agglomeration of nano-calcium carbonate particles caused by shear force under high-speed stirring.

[0020] The modification process constructs a "strong-weak" combined gradient interface layer through the synergistic effect of the chemical bonding of the titanate coupling agent and the physical adsorption of stearic acid, achieving efficient hydrophobicization and stable dispersion of nano calcium carbonate. This surface engineering strategy lays the foundation for the uniform distribution of nanoparticles and the optimization of the polymer-filler interface in the subsequent emulsion polymerization, ultimately making the PVC foam products have both high mechanical strength and fine pore structure.

[0021] S3, first stage aggregation First, take out 20% of the total volume of the pre-emulsion, which will be used for seed polymerization. Add the pre-emulsion to another reactor, purge with nitrogen to remove the air in the reactor. Stir mechanically and heat to 75°C. First add 0.4 parts by mass of potassium persulfate to start the polymerization reaction. After 30 minutes of reaction, add 0.3 parts by mass of potassium persulfate and continue the reaction for 1 hour to maintain the polymerization reaction to obtain a seed polymerization solution.

[0022] Potassium persulfate decomposes to generate free radicals after heating, and the free radicals attack the monomers and start chain growth. In the initial stage, the potassium persulfate concentration is low, which can control the nucleation rate, thereby forming seed latex particles with uniform particle size. As the reaction proceeds, the added potassium persulfate can maintain the free radical concentration in the system, promote the polymerization of the seed particle surface, avoid the reaction stagnation caused by the decrease in monomer concentration, and ensure the uniformity of molecular weight.

[0023] S4, second stage aggregation The seed polymerization solution was heated to 85°C, and the remaining pre-emulsion was mixed with 1.5 parts by mass of n-dodecyl mercaptan. The pre-emulsion and n-dodecyl mercaptan mixed evenly were added dropwise to the seed polymerization solution, and the addition time was controlled within 2 hours to ensure a smooth reaction. After the addition was completed, the temperature was kept for 1 hour to obtain a polymerization solution.

[0024] In the second stage of polymerization, the pre-emulsion is slowly added dropwise to make the monomer concentration lower than the critical micelle concentration, forcing the monomer to polymerize preferentially on the surface of the seed particles rather than forming new latex particles, thereby avoiding secondary nucleation and forming a core-shell structure with a narrow particle size distribution. The dropwise addition speed matches the polymerization rate, so that there is always a small amount of monomer in the system for the newly generated free radicals to initiate chain growth, and at the same time, n-dodecyl mercaptan limits excessive molecular weight growth through chain transfer.

[0025] S5, Demulsification and Drying 1.5 parts by weight of a demulsifier prepared by mixing aluminum sulfate and citric acid in a mass ratio of 3:1 was added to the polymer solution, and mechanical stirring was performed for 45 minutes. After the stirring was completed, the polymer solution was centrifuged, vacuum dried, and air flow crushed to obtain polymer particles.

[0026] After the emulsion polymerization is completed, the monomer is converted into a polymer through a free radical polymerization reaction and dispersed in the water phase in the form of solid latex particles. The surface of these latex particles will wrap the residual emulsifier to form a stable double-layer structure. The aluminum ions generated by the ionization of aluminum sulfate can neutralize the negative charge, destroy the stability of the double layer, and destabilize the latex particles.

[0027] At the same time, aluminum ions generate Al(OH)3 colloids under the acidic conditions of citric acid. Al(OH)3 colloids aggregate the latex particles in the polymer solution into flocs through adsorption and bridging. The density of the flocs is higher than that of the water phase. The latex particles settle with the flocs, while the dissolved monomers (such as residual butyl acrylate) remain in the water phase, achieving preliminary separation. The flocs are then collected by centrifugation and the water is removed by vacuum drying.

[0028] S6. Compounding additives 1 part by mass of calcium zinc stabilizer (solid calcium zinc stabilizer), 0.3 part by mass of calcium stearate and polymer particles were uniformly mixed. Then the temperature was raised to 120°C, 0.8 part by mass of oxidized polyethylene wax was added, high-speed dispersion was performed at 1500 rpm for 30 minutes, and the mixture was cooled to room temperature to obtain PVC foaming regulator P-001.

[0029] Calcium zinc stabilizer inhibits HCl produced by thermal decomposition during PVC processing, prevents yellowing or degradation of the melt, and improves the weather resistance of the product. Compounded with calcium stearate, it balances internal and external lubrication to avoid melt sticking to the wall or excessive plasticization. Oxidized polyethylene wax can coat bubbles, inhibit gas diffusion and cell merging, and maintain cell density.

[0030] At high temperature, the oxidized polyethylene wax melts to form a liquid phase. Under high-speed shearing, the liquid phase is torn into droplets, which collide with solid particles (a mixture of calcium zinc stabilizer, calcium stearate, and white polymer powder) to achieve infiltration and adsorption of solid particles, and then spread into a film. After cooling to room temperature, the wax film solidifies to form a rigid shell layer, with the core being calcium zinc stabilizer, calcium stearate, and polymer particles.

[0031] In the early stage of PVC product processing, the shell layer remains solid, forming a physical barrier to delay the premature reaction of calcium zinc stabilizer and HCl and avoid the "zinc burn" phenomenon. After the shell layer melts in the later stage, the oxidized polyethylene wax reduces local shear heat generation through lubrication, distributes heat evenly, and reduces the risk of degradation caused by hot spots. At the same time, the core calcium zinc stabilizer, calcium stearate and polymer particles are gradually released and evenly dispersed in the PVC matrix, weakening the entanglement between PVC chains and balancing the plasticization rate.

[0032] Example 2 A method for producing a PVC foaming regulator comprises the following steps: S1, add 58 parts by mass of deionized water and 3.5 parts by mass of a composite emulsifier (compounded with sodium lauryl sulfate and alkylphenol polyoxyethylene ether in a mass ratio of 2:3), stir mechanically and heat to 45°C to prepare an emulsion; S2, add 12 parts by mass of ethyl acrylate, 28 parts by mass of butyl acrylate, and 45 parts by mass of methyl methacrylate to the emulsion, emulsify at 3000 rpm for 20 min, add 12 parts by mass of modified nano calcium carbonate, and continue stirring for 30 min to form a pre-emulsion; S3, prepare another reactor, add 25% of the total volume of the pre-emulsion, stir mechanically and heat to 78°C, add 0.5 parts by mass of potassium persulfate, react for 35 minutes, then add 0.4 parts by mass of potassium persulfate, continue to react for 1.2 hours, and obtain a seed polymer solution; S4. The seed polymerization liquid is heated to 86°C, and the remaining pre-emulsion is mixed with 2 parts by mass of n-dodecyl mercaptan and then dripped into the seed polymerization liquid. The dripping time is controlled within 2.5 hours. After the dripping is completed, the temperature is kept for 1 hour; S5, adding 2 parts by weight of a demulsifier prepared by mixing aluminum sulfate and citric acid in a mass ratio of 3:1, mechanically stirring for 45 minutes, vacuum drying, and air flow pulverizing to obtain polymer particles; S6. Evenly mix 1.2 parts by mass of calcium zinc stabilizer, 0.35 parts by mass of calcium stearate and polymer particles, heat to 120° C., add 0.85 parts by mass of oxidized polyethylene wax, disperse at a high speed of 1500 rpm for 30 minutes, and cool to room temperature to obtain PVC foaming regulator P-002.

[0033] Example 3 A method for producing a PVC foaming regulator comprises the following steps: S1, add 60 parts by mass of deionized water and 5 parts by mass of a composite emulsifier (compounded with sodium lauryl sulfate and alkylphenol polyoxyethylene ether in a mass ratio of 2:3), stir mechanically and heat to 45°C to prepare an emulsion; S2, add 15 parts by mass of ethyl acrylate, 30 parts by mass of butyl acrylate, and 50 parts by mass of methyl methacrylate to the emulsion, emulsify at 3000 rpm for 20 min, add 15 parts by mass of modified nano calcium carbonate, and continue stirring for 30 min to form a pre-emulsion; S3, prepare another reactor, add 30% of the total volume of the pre-emulsion, stir mechanically and heat to 80°C, add 0.6 parts by mass of potassium persulfate, react for 40 minutes, then add 0.5 parts by mass of potassium persulfate, continue to react for 1.5 hours, and obtain a seed polymer solution; S4. The seed polymerization liquid is heated to 90°C, and the remaining pre-emulsion is mixed with 3 parts by mass of n-dodecyl mercaptan and then dripped into the seed polymerization liquid. The dripping time is controlled within 3 hours. After the dripping is completed, keep warm for 1 hour; S5, adding 3 parts by mass of a demulsifier prepared by mixing aluminum sulfate and citric acid in a mass ratio of 3:1, mechanically stirring for 45 minutes, vacuum drying, and air flow pulverizing to obtain polymer particles; S6. Evenly mix 1.5 parts by mass of calcium zinc stabilizer, 0.5 parts by mass of calcium stearate and polymer particles, heat to 120°C, heat to 90°C, add 1 part by mass of oxidized polyethylene wax, disperse at a high speed of 1500 rpm for 30 minutes, cool to room temperature, and obtain PVC foaming regulator P-003.

[0034] Three types of PVC foaming regulators, P-001, P-002, and P-003, and ZB-400 PVC foaming regulator produced by Zibo Huaxing Additive Co., Ltd. were prepared and applied to PVC foam decorative panels, respectively, and then the sample performance was tested. The results are shown in Table 1.

[0035] Embodiment 1-3 surpasses the traditional product (ZB-400) in terms of mechanical properties, pore uniformity and thermal stability through nano-calcium carbonate modification and core-shell structure controlled release synergistic stabilization system.

[0036] Table 1. Comparison of comprehensive performance of PVC foaming regulators

[0037] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order 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 the modified use based on the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing a PVC foaming regulator, characterized in that: The steps include: S1. In a reaction kettle, add 55-60 parts by mass of deionized water and 3-5 parts by mass of a composite emulsifier, stir mechanically and heat to 45° C. to prepare an emulsion; S2, add 10-15 parts by mass of ethyl acrylate, 25-30 parts by mass of butyl acrylate, and 40-50 parts by mass of methyl methacrylate to the emulsion, emulsify at 3000 rpm for 20 min, add 10-15 parts by mass of modified nano calcium carbonate, and continue stirring for 30 min to form a pre-emulsion; S3, prepare another reactor, add 20% to 30% of the total volume of the pre-emulsion, stir mechanically and heat to 75 to 80°C, add 0.4 to 0.6 parts by mass of initiator, react for 30 to 40 minutes, then add 0.3 to 0.5 parts by mass of initiator, continue to react for 1 to 1.5 hours, and obtain a seed polymerization solution; S4, the seed polymerization liquid is heated to 85-90°C, the remaining pre-emulsion is mixed with 1.5-3 parts by mass of chain transfer agent and then dripped into the seed polymerization liquid. After the dripping is completed, the temperature is kept for 1 hour; S5, adding 1.5 to 3 parts by weight of demulsifier to the system of step S4, mechanically stirring for 45 minutes, vacuum drying, air flow pulverization, to obtain polymer particles; S6. Evenly mix 1-1.5 parts by mass of calcium zinc stabilizer, 0.3-0.5 parts by mass of calcium stearate and polymer particles, heat to 120° C., add 0.8-1 parts by mass of oxidized polyethylene wax, disperse at a high speed of 1500 rpm for 30 minutes, and cool to room temperature to obtain a PVC foaming regulator.

2. The method for producing a PVC foaming regulator according to claim 1, characterized in that: The modified nano calcium carbonate comprises the following preparation steps: S21, dispersing nano calcium carbonate in anhydrous ethanol to form a dispersion with a mass concentration of 15%, heating to 60° C., adding a titanate coupling agent in an amount of 1% of the total mass of the dispersion, and stirring for 30 min; S22, adding 2% stearic acid of the total mass of nano calcium carbonate, maintaining 60°C and continuing stirring for 20 minutes; S23, centrifugation, ethanol washing 3 times, vacuum drying to obtain modified nano calcium carbonate.

3. The production method of the PVC foaming regulator according to claim 1, characterized in that: The compound emulsifier is prepared by compounding sodium lauryl sulfate and alkylphenol polyoxyethylene ether in a mass ratio of 2:

3.

4. The method for producing a PVC foaming regulator according to claim 1, characterized in that: The initiator is potassium persulfate.

5. The method for producing a PVC foaming regulator according to claim 1, characterized in that: The chain transfer agent is n-dodecyl mercaptan.

6. The method for producing a PVC foaming regulator according to claim 1, characterized in that: The demulsifier is prepared by mixing aluminum sulfate and citric acid demulsifier in a mass ratio of 3:

1.

7. The method for producing a PVC foaming regulator according to claim 1, characterized in that: In step S4, the dropping time is controlled within 2 to 3 hours.

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