Preparation method of high-weather-resistance PVC (polyvinyl chloride) impact modifier

Abstract

The invention belongs to the technical field of high polymer material synthesis, and particularly provides a preparation method of a high-weather-resistance PVC (polyvinyl chloride) impact modifier, which comprises the following steps: preparing an AIM impact modifier: firstly synthesizing a double-layer nuclear emulsion step by step; preparing a first core layer emulsion and a second core layer emulsion from different monomers, an emulsifier and an initiator, and mixing to form a core mixed solution; preparing a shell emulsion in a reaction kettle, and then coating the shell emulsion with the inner core mixed solution to form an impact modifier solution. Shell fragments and oligomer are separated out through high-speed centrifugation, powder is obtained through washing and drying, and the shell fragments and the oligomer are separated; an ACR impact modifier is prepared, wherein hexafluoropropylene gas participates in a reaction in a closed reactor, and ACR seed emulsion is prepared; continuously introducing hexafluoropropylene, and adding nuclear layer raw materials in batches to form a nuclear layer structure; and mixing the ACR core layer product with a shell layer monomer, an emulsifier and the separated oligomer, demulsifying, washing with water, and drying to obtain the ACR impact modifier capable of improving the weather resistance of the PVC.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a method for preparing a highly weather-resistant PVC impact modifier. Background Art

[0002] PVC impact modifier is a type of chemical additive used to improve the impact resistance of polyvinyl chloride (PVC) materials. By adjusting its molecular structure or physical properties, it can significantly improve the toughness, weather resistance and processing performance of PVC products.

[0003] Common PVC impact modifiers include CPE impact modifier, ACM impact modifier, and AIM impact modifier. Chlorinated polyethylene (CPE) is a saturated polymer material, an impact modifier made by chlorinating HDPE, which can significantly improve the toughness and impact performance of PVC products, and can effectively promote the plasticization of PCV materials and improve their processing performance.

[0004] ACM impact modifier is a core-shell toughening modifier formed by ultra-high elongation chlorinated polyethylene and acrylate polymer. The product has ultra-high elongation at break and excellent processing properties, which significantly improves the toughness of PVC products and gives PVC products good processing properties.

[0005] AIM impact modifier, this product gives PVC products higher impact strength and excellent weather resistance, and can also promote the plasticization of PVC materials and improve processability. It is suitable for PVC profiles, PVC pipes and other fields. It can significantly increase the impact strength and has excellent weather resistance, and can also promote the plasticization of PVC materials and improve processability.

[0006] In the production process of each PVC impact modifier, a small amount of by-products will inevitably appear. In the cross-linking process of the core layer of the AIM impact modifier synthesis, if the monomer concentration is too high or the initiator is unevenly distributed, resulting in insufficient reaction in some areas, it is easy to cause local self-polymerization to generate oligomers. At the same time, during the compatibility process between the core layer and the shell layer, the difference in compatibility between the two will lead to increased interfacial tension and the formation of fragments, or during the processing, due to uneven stirring or temperature gradient, the shell structure will break, which will also form fragments.

[0007] Due to low molecular weight and insufficient cross-linking, oligomers cannot effectively absorb impact energy, resulting in weak points in the AIM dispersed phase. Shell fragments destroy the integrity of the core-shell structure, weaken the stress dispersion ability, and make the material more susceptible to crack propagation when subjected to stress. Summary of the invention

[0008] In view of the above-mentioned defects, the present invention provides a method for preparing a highly weather-resistant PVC impact modifier, which can remove oligomers and shell fragments as by-products in the AIM impact modifier and is used to improve the weather resistance of the ACR impact modifier.

[0009] To achieve the above object, the present invention provides the following technical solution: a method for preparing a highly weather-resistant PVC impact modifier, comprising the preparation of an AIM impact modifier and the preparation of an ACR impact modifier, wherein the preparation of the AIM impact modifier is as follows: Step 100: preparing an AIM first core layer emulsion; Step 101: preparing an AIM second core layer emulsion; Step 102: Mixing the AIM first core layer emulsion and the AIM second core layer emulsion to form an AIM inner core mixed solution; Step 103: preparing an AIM shell emulsion; Step 104: Mixing the AIM core mixture and the AIM shell emulsion to prepare an AIM impact modifier solution; Step 105: separating the shell fragments mainly composed of propyl methacrylate polymer and acrylate oligomers in the AIM impact modifier liquid by a high-speed centrifuge, and washing them with deionized water and drying them to obtain the final AIM impact modifier powder; Step 106: Separating the shell fragments mainly composed of acrylate oligomers and propyl methacrylate polymers through an ultrafiltration membrane of 5-20 nm, and the separation endpoint is determined by the permeate flow rate dropping to 15% of the initial value; The preparation of ACR impact modifier is specifically as follows: Step 200: adding deionized water, ACR core layer monomer, ACR emulsifier, ACR crosslinker and ACR initiator into a closed reactor and mixing them, while introducing hexafluoropropylene gas, and obtaining ACR seed emulsion after reaction; Step 201: Adding ACR seed emulsion and deionized water into a closed reactor, while introducing hexafluoropropylene gas, and intermittently adding ACR core layer monomer, ACR emulsifier, ACR crosslinking agent, and ACR initiator, mixing and reacting, and then heat preservation to obtain the core layer of the ACR particles; Step 202: Add ACR shell monomer, ACR emulsifier and AIM shell fragments sieved out in step 106 for preparing AIM impact modifier to the product obtained in step 201, in a weight percentage of 60-80 parts of the obtained product, 18-36 parts of ACR shell monomer and 2-4 parts of acrylate oligomer. After fully mixing, take out to break the emulsion, wash with water and dry to obtain ACR impact modifier.

[0010] As a further improvement of the present invention, step 100 specifically involves adding deionized water, AIM first core layer monomers, first core layer emulsifiers, first core layer initiators, and first core layer crosslinking agents into a reaction kettle to react and form an AIM first core layer emulsion; by mass percentage, 60-65 parts of deionized water, 30-35 parts of AIM first core layer monomers, 1.5-2 parts of first core layer emulsifiers, 1-1.5 parts of first core layer initiators, and 1-1.5 parts of first core layer crosslinking agents.

[0011] As a further improvement of the present invention, the AIM first core layer monomers are a mixture of n-butyl acrylate and methyl methacrylate, and the first core layer emulsifier is one of sodium dodecyl sulfate or polyoxyethylene ether non-ionic emulsifiers; the first core layer initiator is one of ammonium persulfate or APS water-soluble initiators; the first core layer crosslinking agent is acrylamide.

[0012] As a further improvement of the present invention, step 101 specifically involves adding deionized water, N-methylpyrrolidone, AIM second core layer monomers, second core layer emulsifiers, second core layer initiators, and second core layer crosslinking agents into a high-shear emulsifier to react and form an AIM second core layer emulsion; by mass percentage, 60-65 parts of deionized water, 6-8 parts of N-methylpyrrolidone, 25-30 parts of AIM second core layer monomers, 1.5-2 parts of second core layer emulsifiers, 1-1.5 parts of second core layer initiators, and 1-1.5 parts of second core layer crosslinking agents.

[0013] As a further improvement of the present invention, the AIM second core layer monomers are a mixture of ethyl methacrylate and styrene; the second core layer emulsifier is one of sodium dodecylbenzenesulfonate or a composite emulsification system; the second core layer initiator is one of an oil-soluble initiator or an oxidation-reduction initiator system, and the second core layer crosslinking agent is acrylamide.

[0014] As a further improvement of the present invention, step 103 specifically involves adding deionized water, AIM shell layer monomers, AIM shell layer emulsifiers, and AIM shell layer auxiliary agents into a reaction kettle to react and form an AIM shell emulsion; by mass percentage, 65-70 parts of deionized water, 25-30 parts of AIM shell layer monomers, 2-2.25 parts of AIM shell layer emulsifiers, and 0.5-0.75 parts of AIM shell layer auxiliary agents.

[0015] As a further improvement of the present invention, the AIM shell layer monomers are propyl methacrylate; the AIM shell layer emulsifiers are one of sodium dodecyl sulfate or polysorbate; the AIM shell layer auxiliary agents are a mixture of sodium stearate and styrenated phenol.

[0016] As a further improvement of the present invention, the ACR core layer monomer is one or a mixture of two of butyl acrylate or ethyl acrylate; the ACR emulsifier is used in a mixture of anionic and non-ionic types; the ACR crosslinking agent is one of divinylbenzene or diallyl phthalate, the ACR initiator is one of ammonium persulfate or potassium persulfate, and the ACR shell layer monomer is one of methyl methacrylate (MMA) or styrene (St).

[0017] As a further improvement of the present invention, in step 200, by mass percentage, it includes 45-55 parts of deionized water, 30-40 parts of ACR core layer monomer, 0.5-1.5 parts of ACR emulsifier, 1-2 parts of ACR crosslinking agent, 0.1-0.5 parts of ACR initiator, and 5-20 parts of hexafluoropropylene gas; In step 201, by mass percentage, it includes 5-15 parts of ACR seed emulsion, 45-55 parts of ionic water, 20-35 parts of ACR core layer monomer, 0.5-1.5 parts of ACR emulsifier, 1-2 parts of ACR crosslinking agent, and 5-20 parts of hexafluoropropylene gas.

[0018] As a further improvement of the present invention, in step 202, by mass percentage, it includes 60-80 parts of the product obtained in step 201, 18-36 parts of ACR shell layer monomer, and 2-4 parts of AIM shell layer fragments.

[0019] Advantages of the present invention: By using a high-speed centrifuge for centrifugal separation during the preparation of the AIM impact modifier, the AIM shell layer fragments and oligomers can be removed, which can further improve the purity of the obtained AIM impact modifier. At the same time, the AIM shell layer fragments and oligomers are separated by an ultrafiltration membrane. Since both ACR and AIM are core-shell structured acrylate copolymers, the acrylate oligomers without double bonds in the AIM by-products can be used to improve the weather resistance of PVC products prepared with the ACR impact modifier and avoid degradation caused by ultraviolet rays. Specific embodiments

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] The present invention provides a preparation method of a high-weather-resistant PVC impact modifier, including the preparation of an AIM impact modifier and the preparation of an ACR impact modifier.

[0022] The preparation of the AIM impact modifier is specifically as follows: Step 100: Prepare the AIM first core layer emulsion. Control the temperature of the reaction kettle at 50 - 55 °C and the rotation speed at 120 - 130 rpm. Add deionized water, the AIM first core layer monomers, the first core layer emulsifier, the first core layer initiator, and the first core layer crosslinking agent into the reaction kettle for reaction. After 1.2 - 1.5 h, an AIM first core layer emulsion with an average particle size of 180 - 190 nm is formed.

[0023] Step 101: Prepare the AIM second core layer emulsion. Control the temperature of the high - shear emulsifier at 60 - 65 °C and the rotation speed at 3000 - 3200 rpm. Add deionized water, N - methylpyrrolidone, the AIM second core layer monomers, the second core layer emulsifier, the second core layer initiator, and the second core layer crosslinking agent into the high - shear emulsifier for reaction. After 0.75 - 1 h, an AIM second core layer emulsion with an average particle size of 125 - 135 nm is formed.

[0024] Step 102: Prepare the AIM inner core mixture. Mix the AIM first core layer emulsion and the AIM second core layer emulsion at a mass ratio of 10 - 15:20 - 25, and stir at 50 - 55 °C for 0.5 - 0.8 h to form the AIM inner core mixture.

[0025] Step 103: Prepare the AIM shell emulsion. Control the temperature in the reaction kettle at 45 - 50 °C and the rotation speed at 80 - 90 rpm. Add deionized water, the AIM shell layer monomers, the AIM shell layer emulsifier, and the AIM shell layer auxiliary agent into the reaction kettle for reaction to form the AIM shell emulsion.

[0026] Step 104: Coating the AIM inner core with the AIM shell layer to form the AIM impact modifier liquid. Mix the AIM inner core mixture and the AIM shell emulsion in the reaction kettle at a mass ratio of 40 - 45:30 - 35, stir at 45 - 50 °C for 2 h, and then cool down to room temperature.

[0027] Step 105: Separate the AIM shell layer fragments mainly composed of poly (propyl methacrylate) and acrylate oligomers from the AIM impact modifier liquid to obtain the AIM impact modifier. The rotation speed of the high - speed centrifuge is between 7000 - 7200 rpm. After centrifugation and sedimentation for 25 - 30 min, through layer - by - layer collection, separate the mixture of AIM shell layer fragments and oligomers in the upper liquid phase from the AIM impact modifier liquid. The AIM impact modifier liquid after removing the mixture of AIM shell layer fragments and oligomers is cooled, rinsed with deionized water, and dried to obtain the final AIM impact modifier powder.

[0028] Step 106: Then, separate the acrylate oligomer and the AIM shell layer fragments mainly composed of poly(propyl methacrylate) through a 5 - 20 nm ultrafiltration membrane (such as a Lichang or Koch membrane). The separation end point is determined by the criterion that the permeate flux drops to 15% of the initial value.

[0029] As a further explanation of this embodiment, the molecular size of the acrylate oligomer is smaller than the membrane pore size and will pass through the membrane with the solution. The molecular size of the AIM shell layer fragments mainly composed of poly(propyl methacrylate) is larger than the membrane pore size and cannot pass through the membrane pores and is retained. When the membrane pore size of the ultrafiltration membrane is relatively large, a small part of the AIM shell layer fragments with relatively small molecular sizes will pass through the ultrafiltration membrane.

[0030] In the preparation of the AIM impact modifier, the AIM first core layer monomers are a mixture of n-butyl acrylate (BA) and methyl methacrylate (MMA), and the mass ratio of the two is 60 - 70%: 20 - 30%.

[0031] The first core layer emulsifier is one of sodium dodecyl sulfate (SDS) or polyoxyethylene ether non-ionic emulsifiers, which is used to stabilize the initial emulsion and control the particle size.

[0032] The first core layer initiator is one of ammonium persulfate or APS water-soluble initiators, which ensures a slow initiation of free radical polymerization.

[0033] The first core layer crosslinking agent is acrylamide (AM), which is used to enhance the crosslinking degree of the core layer.

[0034] In the preparation of the AIM impact modifier, the AIM second core layer monomers are a mixture of ethyl methacrylate (EMA) and styrene (St), and the mass ratio of the two is 50 - 60%: 30 - 40%.

[0035] The second core layer emulsifier is one of sodium dodecylbenzenesulfonate or a composite emulsification system (such as the compound of SDS and OP-10), which is used to improve the emulsion stability and reduce the particle size to 125 - 135 nm.

[0036] The second core layer initiator is one of an oil-soluble initiator (such as benzoyl peroxide, BPO) or an oxidation-reduction initiation system (such as sodium bisulfite), which is used to increase the reaction rate and control the crosslinking density.

[0037] The second core layer crosslinking agent is acrylamide (AM), which is used to enhance the crosslinking degree of the core layer.

[0038] In the preparation of the AIM impact modifier, the AIM shell layer monomer is propyl methacrylate, a hard shell material with good compatibility with PVC.

[0039] The AIM shell emulsifier is one of sodium dodecyl sulfate (SDS) or polysorbate, and is used for emulsion stabilization.

[0040] The AIM shell assistant is a mixture of sodium stearate and styrenated phenol, and the mass ratio of the two is 1:2.

[0041] In step 100, by mass percentage, it includes 60 - 65 parts of deionized water, 30 - 35 parts of AIM first core layer monomer, 1.5 - 2 parts of first core layer emulsifier, 1 - 1.5 parts of first core layer initiator, and 1 - 1.5 parts of first core layer crosslinking agent.

[0042] In step 101, by mass percentage, it includes 60 - 65 parts of deionized water, 6 - 8 parts of N - methylpyrrolidone, 25 - 30 parts of AIM second core layer monomer, 1.5 - 2 parts of second core layer emulsifier, 1 - 1.5 parts of second core layer initiator, and 1 - 1.5 parts of second core layer crosslinking agent.

[0043] In step 103, by mass percentage, it includes 65 - 70 parts of deionized water, 25 - 30 parts of AIM shell monomer, 2 - 2.25 parts of AIM shell emulsifier, and 0.5 - 0.75 parts of AIM shell assistant.

[0044] The preparation of ACR impact modifier is specifically as follows: Step 200: Prepare ACR seed emulsion. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.2 - 0.6 MPa and the temperature to be maintained at 65 - 80 °C. Add deionized water, ACR core layer monomer, ACR emulsifier, ACR crosslinking agent, and ACR initiator into the reactor and mix them. At the same time, introduce hexafluoropropylene gas. After the reaction, cool it to room temperature to obtain ACR seed emulsion.

[0045] Step 201: Prepare the core layer of ACR particles. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.2 - 0.6 MPa and the temperature to be maintained at 65 - 80 °C. Add ACR seed emulsion, deionized water into the reactor, introduce hexafluoropropylene gas at the same time, and intermittently add ACR core layer monomer, ACR emulsifier, ACR crosslinking agent, ACR initiator. After mixing and reacting, keep it warm. The holding temperature is 50 - 55 °C and the holding time is 2.5 - 3.5 h.

[0046] Step 202: Coat a shell layer outside the core layer of the ACR particles. Add the ACR shell monomers, ACR emulsifiers, and the oligomers screened out by the ultrafiltration membrane in Step 106 of the preparation of the AIM impact modifier to the product obtained in Step 201, and fully mix and react at 85 - 90 °C. Then take it out, demulsify, wash with water, and dry to obtain the ACR impact modifier.

[0047] In the preparation of the ACR impact modifier, the ACR core monomers are one or a mixture of two of butyl acrylate (BA) and ethyl acrylate (EA). When used in combination, the mass ratio of butyl acrylate (BA) to ethyl acrylate (EA) is 6:4.

[0048] In the preparation of the ACR impact modifier, the ACR emulsifiers are used in combination of an anionic type (such as sodium dodecyl sulfate SDS) and a non-ionic type (such as OP-10). When used in combination, the mass ratio of the anionic type (such as sodium dodecyl sulfate SDS) to the non-ionic type (such as OP-10) is 1:1.

[0049] In the preparation of the ACR impact modifier, the ACR crosslinking agent is one of divinylbenzene (DVB) and diallyl phthalate (DAP).

[0050] In the preparation of the ACR impact modifier, the ACR initiator is one of ammonium persulfate (APS) and potassium persulfate (KPS).

[0051] In the preparation of the ACR impact modifier, the ACR shell monomers are one of methyl methacrylate (MMA) and styrene (St).

[0052] In Step 200, by mass percentage, it includes 45 - 55 parts of deionized water, 30 - 40 parts of ACR core monomers, 0.5 - 1.5 parts of ACR emulsifiers, 1 - 2 parts of ACR crosslinking agents, 0.1 - 0.5 parts of ACR initiators, and 5 - 20 parts of hexafluoropropylene gas.

[0053] In Step 201, by mass percentage, it includes 5 - 15 parts of ACR seed emulsion, 45 - 55 parts of ionic water, 20 - 35 parts of ACR core monomers, 0.5 - 1.5 parts of ACR emulsifiers, 1 - 2 parts of ACR crosslinking agents, 0.1 - 0.5 parts of ACR initiators, and 5 - 20 parts of hexafluoropropylene gas.

[0054] In Step 202, by mass percentage, it includes 60 - 80 parts of the product obtained in Step 201, 18 - 36 parts of ACR shell monomers, 1.5 - 2 parts of ACR emulsifiers, and 2 - 4 parts of oligomers.

[0055] The following further describes the present invention in conjunction with embodiments.

[0056] Example 1: A preparation method of a high weather-resistant PVC impact modifier, specifically as follows: Step 100: Prepare the AIM first core layer emulsion. Control the temperature of the reaction kettle at 50 °C and the rotation speed at 120 rpm. Add 60 parts of deionized water, 30 parts of a mixture of n-butyl acrylate and methyl methacrylate with a mass ratio of 60:20, 1.5 parts of sodium dodecyl sulfate, 1 part of ammonium persulfate, and 1 part of acrylamide into the reaction kettle for reaction. After 1.2 - 1.5 h, an AIM first core layer emulsion with an average particle size of 185 nm is formed.

[0057] Step 101: Prepare the AIM second core layer emulsion. Control the temperature of the high-shear emulsifier at 60 °C and the rotation speed at 3000 rpm. Add 60 parts of deionized water, 6 parts of N-methylpyrrolidone, 25 parts of a mixture of ethyl methacrylate and styrene with a mass ratio of 50:30, 1.5 parts of sodium dodecylbenzenesulfonate, 1 part of benzoyl peroxide, and 1 part of acrylamide into the high-shear emulsifier for reaction. After 0.75 h, an AIM second core layer emulsion with an average particle size of 125 - 135 nm is formed.

[0058] Step 102: Prepare the AIM inner core mixture. Mix the AIM first core layer emulsion and the AIM second core layer emulsion according to a mass ratio of 10:20, and stir at 50 °C for 0.5 hour to form the AIM inner core mixture.

[0059] Step 103: Prepare the AIM shell emulsion. Control the temperature in the reaction kettle at 45 °C and the rotation speed at 80 rpm. Add 65 parts of deionized water, 25 parts of propyl methacrylate, 2 parts of polysorbate, and 0.5 part of a mixture of sodium stearate and styrenated phenol into the reaction kettle for reaction to form the AIM shell emulsion.

[0060] Step 104: Coating the AIM shell layer on the outer layer of the AIM inner core to form the AIM impact modifier liquid. Mix the AIM inner core mixture and the AIM shell emulsion in the reaction kettle according to a mass ratio of 40:30, stir at 45 °C for 2 h, and then cool down to room temperature.

[0061] Step 105: Isolate the AIM shell fragments mainly composed of acrylate oligomers and poly(propyl methacrylate) in the AIM impact modifier liquid to obtain the AIM impact modifier. Remove the AIM shell fragments and oligomers in the AIM impact modifier liquid by a high-speed centrifuge. The rotation speed of the high-speed centrifuge is between 7000 rpm, and after centrifugation, sediment for 25 min. Through layering collection, separate the mixture of AIM shell fragments and oligomers in the upper liquid phase from the AIM impact modifier liquid. The AIM impact modifier liquid after removing the mixture of AIM shell fragments and oligomers is cooled, rinsed with deionized water, and dried to obtain the final AIM impact modifier powder.

[0062] Step 106: Separate the AIM shell fragments mainly composed of acrylate oligomers and poly(propyl methacrylate) through a 20-nm ultrafiltration membrane (such as a Liheng or Koch membrane). The separation end point is determined by the permeate flux dropping to 15% of the initial value.

[0063] Step 200: Prepare the ACR seed emulsion. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.2 MPa and the temperature to be maintained at 65 °C. Add 45 parts of deionized water, 30 parts of a mixture of butyl acrylate and ethyl acrylate, 0.5 part of a mixture of sodium dodecyl sulfate SDS and OP-10, 1 part of divinylbenzene, and 0.1 part of potassium persulfate into the reactor and mix them. At the same time, introduce 5 parts of hexafluoropropylene gas. After the reaction, cool to room temperature to obtain the ACR seed emulsion.

[0064] Step 201: Prepare the core layer of the ACR particles. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.2 MPa and the temperature to be maintained at 65 °C. Add 5 parts of the ACR seed emulsion, 45 parts of deionized water into the reactor, and introduce 5 parts of hexafluoropropylene gas at the same time. Intermittently add 20 parts of a mixture of butyl acrylate and ethyl acrylate, 0.5 part of a mixture of sodium dodecyl sulfate SDS and OP-10, 1 part of divinylbenzene, and 0.1 part of potassium persulfate. After mixing and reacting, keep warm. The holding temperature is 50 °C and the holding time is 2.5 h.

[0065] Step 202: Coat the shell layer outside the core layer of the ACR particles. Add 18 parts of methyl methacrylate, 1.5 parts of ACR emulsifier, and 2 parts of the oligomers screened by the ultrafiltration membrane in Step 106 of the preparation of the AIM impact modifier to 60 parts of the product obtained in Step 201. Mix and react fully at 85 °C, take out, demulsify, wash with water, and dry to obtain the ACR impact modifier.

[0066] Example 2: The AIM impact modifier powder was prepared in the same manner as in Example 1, except that when separating the acrylate oligomer and the shell fragments mainly composed of poly(propyl methacrylate), a 10 nm ultrafiltration membrane (such as a Lichang or Koch membrane) was used.

[0067] Step 200: Prepare the ACR seed emulsion. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.4 MPa and the temperature to be maintained at 73 °C. Add 50 parts of deionized water, 35 parts of a mixture of butyl acrylate and ethyl acrylate, 1 part of a mixture of sodium dodecyl sulfate (SDS) and OP-10, 1.5 parts of divinylbenzene, and 0.25 parts of potassium persulfate into the reactor and mix them. At the same time, introduce 12.5 parts of hexafluoropropylene gas. After the reaction, cool to room temperature to obtain the ACR seed emulsion.

[0068] Step 201: Prepare the core layer of the ACR particles. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.4 MPa and the temperature to be maintained at 73 °C. Add 10 parts of the ACR seed emulsion, 50 parts of deionized water into the reactor, and introduce 12.5 parts of hexafluoropropylene gas at the same time. Intermittently add 27.5 parts of a mixture of butyl acrylate and ethyl acrylate, 1 part of a mixture of sodium dodecyl sulfate (SDS) and OP-10, 1.5 parts of divinylbenzene, and 0.3 parts of potassium persulfate. After mixing and reacting, keep warm. The heat preservation temperature is 53 °C and the heat preservation time is 3 h.

[0069] Step 202: Coat the shell outside the core layer of the ACR particles. Add 27 parts of methyl methacrylate, 1.75 parts of the ACR emulsifier, and 3 parts of the oligomer screened out by the ultrafiltration membrane in Step 106 of the preparation of the AIM impact modifier to 70 parts of the product obtained in Step 201, and mix and react fully at 88 °C. Take out, demulsify, wash with water, and dry to obtain the ACR impact modifier.

[0070] Example 3: The AIM impact modifier powder was prepared in the same manner as in Example 1, except that when separating the acrylate oligomer and the shell fragments mainly composed of poly(propyl methacrylate), a 5 nm ultrafiltration membrane (such as a Lichang or Koch membrane) was used.

[0071] Step 200: Prepare the ACR seed emulsion. Introduce N 2Replace the air with nitrogen gas, and then control the reactor pressure to be maintained at 0.6 MPa and the temperature to be maintained at 80 °C. Add 55 parts of deionized water, 40 parts of a mixture of butyl acrylate and ethyl acrylate, 1.5 parts of a mixture of sodium dodecyl sulfate (SDS) and OP-10, 2 parts of divinylbenzene, and 0.5 parts of potassium persulfate into the reactor and mix them. At the same time, introduce 20 parts of hexafluoropropylene gas. After the reaction, cool it to room temperature to obtain an ACR seed emulsion.

[0072] Step 201: Prepare the core layer of ACR particles. Introduce N 2 gas into the closed reactor to displace the air, and then control the reactor pressure to be maintained at 0.6 MPa and the temperature to be maintained at 80 °C. Add 15 parts of the ACR seed emulsion, 55 parts of deionized water into the reactor. At the same time, introduce 20 parts of hexafluoropropylene gas, and intermittently add 35 parts of a mixture of butyl acrylate and ethyl acrylate, 1.5 parts of a mixture of sodium dodecyl sulfate (SDS) and OP-10, 2 parts of divinylbenzene, and 0.5 parts of potassium persulfate. After mixing and reacting, keep it warm. The heat preservation temperature is 55 °C and the heat preservation time is 3.5 h.

[0073] Step 202: Coat a shell layer outside the core layer of the ACR particles. Add 36 parts of methyl methacrylate, 2 parts of ACR emulsifier, and 4 parts of the oligomer screened out by the ultrafiltration membrane in step 106 of the preparation of the AIM impact modifier into 80 parts of the product obtained in step 201, and mix and react fully at 90 °C. Take it out, demulsify, wash with water, and dry to obtain the ACR impact modifier.

[0074] Comparative Example 1: The preparation method of the highly weather-resistant PVC impact modifier described in Example 1 is adopted, and the difference is that: the addition of the oligomer is omitted in step 202.

[0075] Comparative Example 2: The preparation method of the highly weather-resistant PVC impact modifier described in Example 2 is adopted, and the difference is that: the addition of the oligomer is omitted in step 202.

[0076] Comparative Example 3: The preparation method of the highly weather-resistant PVC impact modifier described in Example 3 is adopted, and the difference is that: the addition of the oligomer is omitted in step 202.

[0077] Place the ACR impact modifiers prepared in Examples 1 - 3 and Comparative Examples 1 - 3, polyvinyl chloride (manufacturer: Weifang Shandao Chemical Co., Ltd., model: WELLPREN series PVC), and the additive ratio in a mixer to make a masterbatch; then place the masterbatch in a tablet press, set the temperature of the tablet press to 180 °C, and then add the masterbatch into the tablet press and press for 10 min to obtain a thin sheet with a thickness of 3 mm. After cooling to room temperature, obtain the test specimens.

[0078] Weather resistance test: According to Method A of Exposure Condition 2 in GB / T 16422.3, the test conditions are as follows: UVA-340 lamp tube, irradiation for 8 h (blackboard temperature 60 °C), irradiance 0.76 W / m 2 , spraying for 15 min, condensation for 3.75 h (blackboard temperature 50 °C). Compare the colors of the materials before and after aging, and test once every 100 hours. The total color difference △E obtained is the test result. The larger the △E value, the greater the color change and the worse the weather resistance of the product. For the comparison table of the weather resistance test results of each example and comparative example, see the details below:

[0079] It can be analyzed from the above table that after modifying PVC products with the high weather-resistant PVC impact modifier added with oligomer, the total color difference △E is lower than that of the PVC products modified with the ACR impact modifier prepared conventionally, and the weather resistance is significantly improved.

[0080] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above-mentioned implementation measures. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a highly weather-resistant PVC impact modifier, characterized in that: The invention comprises the preparation of an AIM impact modifier and the preparation of an ACR impact modifier, wherein the preparation of the AIM impact modifier is as follows: Step 100: preparing an AIM first core layer emulsion; Step 101: preparing an AIM second core layer emulsion; Step 102: Mixing the AIM first core layer emulsion and the AIM second core layer emulsion to form an AIM inner core mixed solution; Step 103: preparing an AIM shell emulsion; Step 104: Mixing the AIM core mixture and the AIM shell emulsion to prepare an AIM impact modifier solution; Step 105: separating the shell fragments mainly composed of propyl methacrylate polymer and acrylate oligomers in the AIM impact modifier liquid by a high-speed centrifuge, and washing them with deionized water and drying them to obtain the final AIM impact modifier powder; Step 106: Separating the shell fragments mainly composed of acrylate oligomers and propyl methacrylate polymers through an ultrafiltration membrane of 5-20 nm, and the separation endpoint is determined by the permeate flow rate dropping to 15% of the initial value; The preparation of ACR impact modifier is specifically as follows: Step 200: adding deionized water, ACR core layer monomer, ACR emulsifier, ACR crosslinker and ACR initiator into a closed reactor and mixing them, while introducing hexafluoropropylene gas, and obtaining ACR seed emulsion after reaction; Step 201: Adding ACR seed emulsion and deionized water into a closed reactor, while introducing hexafluoropropylene gas, and intermittently adding ACR core layer monomer, ACR emulsifier, ACR crosslinking agent, and ACR initiator, mixing and reacting, and then heat preservation to obtain the core layer of the ACR particles; Step 202: Add ACR shell monomer, ACR emulsifier and AIM shell fragments sieved out in step 106 for preparing AIM impact modifier to the product obtained in step 201, in a weight percentage of 60-80 parts of the obtained product, 18-36 parts of ACR shell monomer and 2-4 parts of acrylate oligomer. After fully mixing, take out to break the emulsion, wash with water and dry to obtain ACR impact modifier.

2. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: The step 100 specifically comprises adding deionized water, AIM first core layer monomer, first core layer emulsifier, first core layer initiator and first core layer crosslinker into a reaction kettle to react and form an AIM first core layer emulsion; in terms of mass percentage, the emulsion comprises 60-65 parts of deionized water, 30-35 parts of AIM first core layer monomer, 1.5-2 parts of first core layer emulsifier, 1-1.5 parts of first core layer initiator and 1-1.5 parts of first core layer crosslinker.

3. The method for preparing a highly weather-resistant PVC impact modifier according to claim 2, characterized in that: The AIM first core layer monomer is a mixture of n-butyl acrylate and methyl methacrylate, the first core layer emulsifier is one of sodium dodecyl sulfate or polyoxyethylene ether non-ionic emulsifier; the first core layer initiator is one of ammonium persulfate or APS water-soluble initiator; the first core layer crosslinker is acrylamide.

4. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: The step 101 specifically comprises adding deionized water, N-methylpyrrolidone, AIM second core layer monomer, second core layer emulsifier, second core layer initiator and second core layer crosslinker into the high shear emulsifier to react and form an AIM second core layer emulsion; in terms of mass percentage, the deionized water is 60-65 parts, the N-methylpyrrolidone is 6-8 parts, the AIM second core layer monomer is 25-30 parts, the second core layer emulsifier is 1.5-2 parts, the second core layer initiator is 1-1.5 parts and the second core layer crosslinker is 1-1.5 parts.

5. The method for preparing the highly weather-resistant PVC impact modifier according to claim 4, characterized in that: The AIM second core layer monomer is a mixture of ethyl methacrylate and styrene; the second core layer emulsifier is sodium dodecylbenzene sulfonate or a composite emulsification system; the second core layer initiator is an oil-soluble initiator or an oxidation-reduction initiation system, and the second core layer crosslinker is acrylamide.

6. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: The step 103 is specifically to add deionized water, AIM shell monomer, AIM shell emulsifier and AIM shell auxiliary agent into the reaction kettle to react and form an AIM shell emulsion, which comprises 65-70 parts of deionized water, 25-30 parts of AIM shell monomer, 2-2.25 parts of AIM shell emulsifier and 0.5-0.75 parts of AIM shell auxiliary agent in mass percentage.

7. The method for preparing the highly weather-resistant PVC impact modifier according to claim 6, characterized in that: The AIM shell monomer is propyl methacrylate; the AIM shell emulsifier is one of sodium dodecyl sulfate and polysorbate; and the AIM shell adjuvant is a mixture of sodium stearate and styrenated phenol.

8. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: The ACR core layer monomer is one of butyl acrylate and ethyl acrylate or a mixture of the two; the ACR emulsifier is a mixture of anionic and nonionic; the ACR crosslinker is one of divinylbenzene and diallyl phthalate, the ACR initiator is one of ammonium persulfate and potassium persulfate, and the ACR shell layer monomer is one of methyl methacrylate and styrene.

9. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: In step 200, the following are included, by mass percentage, 45-55 parts of deionized water, 30-40 parts of ACR core layer monomer, 0.5-1.5 parts of ACR emulsifier, 1-2 parts of ACR crosslinking agent, 0.1-0.5 parts of ACR initiator and 5-20 parts of hexafluoropropylene gas; In step 201, by mass percentage, 5-15 parts of ACR seed emulsion, 45-55 parts of ionized water, 20-35 parts of ACR core layer monomer, 0.5-1.5 parts of ACR emulsifier, 1-2 parts of ACR crosslinking agent and 5-20 parts of hexafluoropropylene gas are included.

10. The method for preparing a highly weather-resistant PVC impact modifier according to claim 1, characterized in that: In step 202, by weight percentage, 60-80 parts of the product obtained in step 201, 18-36 parts of ACR shell monomers, and 2-4 parts of AIM shell fragments are included.

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