Preparation method of anti-impact modifier for PVC (polyvinyl chloride) production

Abstract

The invention discloses a preparation method of an impact modifier for PVC (polyvinyl chloride) production, and relates to the technical field of chemical production, the preparation method comprises the following steps: feeding n-butyl acrylate, styrene, a cross-linking agent, an emulsifier and deionized water into a stirring kettle for stirring and mixing, and dropwise adding a first initiator and a buffer agent for reaction; then adding the modified nano kaolin, glycidyl methacrylate, a second initiator and a grafting agent into the reaction kettle for reaction; adding an antioxidant into the mixing kettle, dropwise adding tetrathiodiacrylate, and performing spray drying to obtain modifier powder; the preparation method comprises the following steps: mixing and crushing nano calcium carbonate, maleic anhydride grafted polyolefin elastomer and sodium stearate to prepare intermediate powder; and mixing the intermediate powder with the modifier powder to prepare the impact modifier. Therefore, after the modified nano kaolin is added into the anti-impact modifier, the anti-impact modifier has good compatibility, the dimensional stability of the PVC product can be enhanced, formation of a sea-island structure is assisted, and the stress transfer efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a method for preparing an impact modifier for PVC production. Background Art

[0002] PVC (polyvinyl chloride) is a popular and widely used synthetic material today. It has a wide range of uses and ranks second among all synthetic materials in terms of usage. However, the processing performance and product performance of PVC are poor and cannot meet the requirements of use. Various additives must be added during the processing to improve the processing performance.

[0003] Traditional additives are mainly modifiers, such as CPE, ACR and other modification additives. However, existing modification additives are difficult to improve the impact resistance of PVC, which leads to the imbalance of toughness and rigidity in PVC finished products. To this end, the Chinese patent with publication number "CN114702629B" discloses "a PVC modifier and its preparation method", and its technical scheme is: "The modifier is composed of a core layer, a first shell layer and a second shell layer from the inside to the outside, the core layer is obtained by adding an expander to a small-particle core layer to expand the diameter, the particle size of the core layer is 120-150nm, and the particle size of the modifier is 200-250nm. The PVC modifier with a three-layer core-shell structure prepared in this technical scheme can not only improve the transparency of PVC but also improve the impact resistance and mechanical properties of PVC. The particle size of the PVC modifier prepared in this technical scheme is relatively uniform, which improves the storage stability and performance stability of the PVC modifier. In addition, the residual monomers in the final product are less, and the reaction monomers have a higher conversion rate, so that the PVC modifier has stable and better performance".

[0004] The above solution improves the impact strength through the design of the core-shell structure, but it does not solve the problem of low interfacial stress transfer efficiency during the production process of PVC, which leads to limited improvement in its impact resistance. Summary of the invention

[0005] In view of the above defects, the purpose of the present invention is to provide a method for preparing an impact modifier for PVC production, aiming to solve the problem in the prior art that the interfacial stress transfer efficiency of PVC during the production process is low, resulting in limited improvement in its impact resistance.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: A method for preparing an impact modifier for PVC production comprises the following steps: Step 1, flexible core preparation; 80-90 parts of n-butyl acrylate, 5-8 parts of styrene, 0.5-1.5 parts of a crosslinking agent, 1.2-2.2 parts of an emulsifier and 2-5 parts of deionized water are sequentially sent to a stirring kettle for stirring and mixing, and then 2.5-3 parts of a first initiator are added dropwise to the stirring kettle. After the addition is completed, 3-5 parts of a buffer are added and continued to be stirred. The reaction temperature is 60-70° C. and the reaction time is 2-4 hours to obtain a flexible core emulsion; Step 2: preparing the intermediate layer; 70-80 parts of the flexible core emulsion in step 1 are taken into a reactor by weight, 3-8 parts of modified nano-kaolin and 5-15 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 0.5-1.2 parts of a second initiator and 2.5-3.5 parts of a grafting agent are added in sequence, the temperature is raised to 65-75° C., and the reaction is carried out for 2-3 hours to obtain a mixed emulsion; Step 3, preparation of modifier powder; 75-85 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 0.6-1.2 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.3-0.8 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 65-68° C. by gradient heating, and stirred for 3-4 hours to obtain a modified emulsion, which is then spray-dried to obtain a modifier powder; Step 4, finished product preparation; By weight, 80-90 parts of nano calcium carbonate, 4-7 parts of sodium stearate, and 6-10 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 145-155° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for pulverization to obtain an intermediate powder with an agglomerated particle size of ≤5 μm; 3-5 parts of the intermediate powder and 95-97 parts of the modifier powder obtained in step 3 are sent to a high-speed mixer for dispersion for 15-25 minutes at a speed of 800-1200 rpm to obtain an impact modifier.

[0007] Wherein, in step 1, the crosslinking agent is composed of 70-80 parts of divinylbenzene, 10-20 parts of triethylene glycol acrylate and 5-10 parts of diacetone acrylamide, by weight.

[0008] Wherein, in step 1, the first initiator is composed of 50-60 parts of ammonium persulfate and 40-50 parts of ascorbic acid by weight.

[0009] Wherein, in step 1, the buffer is sodium dihydrogen phosphate or disodium hydrogen phosphate.

[0010] Wherein, in step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 550-600℃, calcination time 1.5-3h; b. The calcined kaolin in step a is sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor is 300-400W, and the treatment time is 0.5-1h; c. Take the activated kaolin in step b, add it and potassium acetate in a mass ratio of 1:1.1-1.2 into deionized water to mix, then ultrasonically treat the mixed solution for 2-3h to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent in a mass ratio of 3:1, and then mix the compounded solution with ethanol in a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution in a mass ratio of 0.2-0.3:1 into a mixing tank for mixing, the temperature in the mixing tank is 70-80°C, and the reaction time is 3-4h to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0011] Wherein, in step d, while feeding the modified nano-kaolin into the ball mill, polyethylene oxide also needs to be added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.5-0.7:1.

[0012] Wherein, in step 1, the emulsifier is composed of 60-70 parts of sodium dodecylbenzene sulfonate, 10-20 parts of polyvinyl alcohol and 5-10 parts of potassium oleate by weight.

[0013] Wherein, in step 2, the second initiator is composed of 70-80 parts of cumene hydroperoxide and 20-30 parts of sodium formaldehyde sulfoxylate by weight.

[0014] Wherein, in step 2, the grafting agent is composed of 40-50 parts of styrene, 25-35 parts of vinyl chloride and 10-15 parts of acrylonitrile by weight.

[0015] Wherein, in step three, the antioxidant is pentaerythritol tetraester or β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl.

[0016] After adopting the above technical solution, the beneficial effects of the present invention are: First, after the impact modifier is added to the modified nano-kaolin, due to its good compatibility, it can effectively enhance the dimensional stability of PVC products, assist in the formation of the "sea-island" structure, and improve the stress transfer efficiency. At the same time, the rigid kaolin is combined with the PVC flexible chain segment to improve the tensile and impact resistance of the finished PVC product, and also ensure the toughness of the finished PVC product. Second, the maleic anhydride grafted polyolefin elastomer can form a certain degree of mesh structure during the PVC processing process, and cooperate with the "sea-island" structure to jointly improve the material's fatigue resistance and significantly improve the notched impact strength of the finished PVC product. DETAILED DESCRIPTION

[0017] 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.

[0018] Example: A method for preparing an impact modifier for PVC production comprises the following steps: Step 1, flexible core preparation; 80-90 parts of n-butyl acrylate, 5-8 parts of styrene, 0.5-1.5 parts of a crosslinking agent, 1.2-2.2 parts of an emulsifier and 2-5 parts of deionized water are sequentially sent to a stirring kettle for stirring and mixing, and then 2.5-3 parts of a first initiator are added dropwise to the stirring kettle. After the addition is completed, 3-5 parts of a buffer are added and continued to be stirred. The reaction temperature is 60-70° C. and the reaction time is 2-4 hours to obtain a flexible core emulsion; Step 2: preparing the intermediate layer; 70-80 parts of the flexible core emulsion in step 1 are taken into a reactor by weight, 3-8 parts of modified nano-kaolin and 5-15 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 0.5-1.2 parts of a second initiator and 2.5-3.5 parts of a grafting agent are added in sequence, the temperature is raised to 65-75° C., and the reaction is carried out for 2-3 hours to obtain a mixed emulsion; Step 3, preparation of modifier powder; 75-85 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 0.6-1.2 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.3-0.8 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 65-68° C. by gradient heating, and stirred for 3-4 hours to obtain a modified emulsion, which is then spray-dried to obtain a modifier powder; Step 4, finished product preparation; By weight, 80-90 parts of nano calcium carbonate, 4-7 parts of sodium stearate, and 6-10 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 145-155° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for pulverization to obtain an intermediate powder with an agglomerated particle size of ≤5 μm; 3-5 parts of the intermediate powder and 95-97 parts of the modifier powder obtained in step 3 are sent to a high-speed mixer for dispersion for 15-25 minutes at a speed of 800-1200 rpm to obtain an impact modifier.

[0019] In this solution, the commercially available brand of the maleic anhydride grafted polyolefin elastomer is Mitsui MD715.

[0020] In step 1, the crosslinking agent is composed of 70-80 parts of divinyl benzene, 10-20 parts of triethylene glycol acrylate and 5-10 parts of diacetone acrylamide by weight.

[0021] In step 1, the first initiator is composed of 50-60 parts of ammonium persulfate and 40-50 parts of ascorbic acid by weight.

[0022] In step 1, the buffer is sodium dihydrogen phosphate or disodium hydrogen phosphate.

[0023] In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 550-600℃, calcination time 1.5-3h; b. The calcined kaolin in step a is sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor is 300-400W, and the treatment time is 0.5-1h; c. Take the activated kaolin in step b, add it and potassium acetate in a mass ratio of 1:1.1-1.2 into deionized water to mix, then ultrasonically treat the mixed solution for 2-3h to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent in a mass ratio of 3:1, and then mix the compounded solution with ethanol in a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution in a mass ratio of 0.2-0.3:1 into a mixing tank for mixing, the temperature in the mixing tank is 70-80°C, and the reaction time is 3-4h to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0024] In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide is also added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.5-0.7:1.

[0025] In step 1, the emulsifier is composed of 60-70 parts of sodium dodecylbenzene sulfonate, 10-20 parts of polyvinyl alcohol and 5-10 parts of potassium oleate by weight.

[0026] In step 2, the second initiator is composed of 70-80 parts of cumene hydroperoxide and 20-30 parts of sodium formaldehyde sulfoxylate, by weight.

[0027] In step 2, the grafting agent is composed of 40-50 parts of styrene, 25-35 parts of vinyl chloride and 10-15 parts of acrylonitrile by weight.

[0028] In step 3, the antioxidant is pentaerythritol tetraester or β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl.

[0029] Embodiment 1: The above scheme is used to prepare a PVC impact modifier, wherein: In step 1, 80 parts of n-butyl acrylate, 5 parts of styrene, 0.5 parts of a crosslinking agent, 1.2 parts of an emulsifier and 2 parts of deionized water are sequentially sent to a stirring tank for stirring and mixing, and then 2.5 parts of a first initiator are added dropwise to the stirring tank. After the addition is completed, 3 parts of a buffer are added and continued to be stirred. The reaction temperature is 60° C. and the reaction time is 2 hours to obtain a flexible core emulsion; In step 2, 70 parts by weight of the flexible core emulsion in step 1 are taken into a reactor, 3 parts of modified nano-kaolin and 5 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 0.5 parts of a second initiator and 2.5 parts of a grafting agent are added in sequence, the temperature is raised to 65° C., and the reaction is carried out for 2 hours to obtain a mixed emulsion; In step 3, 75 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 0.6 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.3 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 65° C. by gradient heating, and the modified emulsion is obtained after stirring for 3 hours, and the modifier powder is obtained by spray drying; In step 4, 80 parts of nano calcium carbonate, 4 parts of sodium stearate, and 6 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 145° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for crushing to obtain an intermediate powder with an agglomerated particle size of ≤5 μm, 3 parts of the intermediate powder and 95 parts of the modifier powder are sent to a high-speed mixer for dispersion for 15 minutes, and the speed of the high-speed mixer is 800 rpm to obtain an impact modifier.

[0030] In step 1, the crosslinking agent is composed of 70 parts of divinyl benzene, 10 parts of triethylene glycol acrylate and 5 parts of diacetone acrylamide by weight. The first initiator is composed of 50 parts of ammonium persulfate and 40 parts of ascorbic acid. The buffer is sodium dihydrogen phosphate.

[0031] In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 550℃, calcination time 1.5h; b. The calcined kaolin in step a was sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor was 300W and the treatment time was 0.5h. c. Take the activated kaolin in step b, add it and potassium acetate into deionized water at a mass ratio of 1:1.1, and then ultrasonically treat the mixed solution for 2 hours to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent at a mass ratio of 3:1, and then mix the compounded solution with ethanol at a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution into a mixing tank at a mass ratio of 0.2:1 to mix, the temperature in the mixing tank is 70°C, and the reaction time is 3 hours to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0032] In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide also needs to be added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.5:1.

[0033] In step 1, the emulsifier is composed of 60 parts of sodium dodecylbenzene sulfonate, 10 parts of polyvinyl alcohol and 5 parts of potassium oleate by weight. The second initiator is composed of 70 parts of cumene hydroperoxide and 20 parts of sodium formaldehyde sulfoxylate. The grafting agent is composed of 40 parts of styrene, 25 parts of vinyl chloride and 10 parts of acrylonitrile.

[0034] In step 3, the antioxidant is pentaerythritol tetraester.

[0035] Embodiment 2: The difference between this embodiment and embodiment 1 is that: In step 1, 82 parts of n-butyl acrylate, 6 parts of styrene, 0.7 parts of a crosslinking agent, 1.5 parts of an emulsifier and 3 parts of deionized water are sequentially sent to a stirring tank for stirring and mixing, and then 2.7 parts of a first initiator are added dropwise to the stirring tank. After the addition is completed, 3.5 parts of a buffer are added and continued to be stirred. The reaction temperature is 62° C. and the reaction time is 2.5 hours to obtain a flexible core emulsion; In step 2, 74 parts of the flexible core emulsion in step 1 were taken into a reactor by weight, 5 parts of modified nano-kaolin and 8 parts of glycidyl methacrylate were added to the reactor, stirred and mixed, and then 0.8 parts of the second initiator and 2.8 parts of the grafting agent were added in sequence, the temperature was raised to 68° C., and the reaction was carried out for 2.4 hours to obtain a mixed emulsion; In step 3, 78 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 0.8 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.5 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 66° C. by gradient heating, and the modified emulsion is obtained after stirring for 3.4 hours, and the modifier powder is obtained by spray drying; In step 4, 84 parts of nano calcium carbonate, 5 parts of sodium stearate, and 7 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 148° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for crushing to obtain an intermediate powder with an agglomerated particle size of ≤5 μm, 3.8 parts of the intermediate powder and 95.5 parts of the modifier powder are sent to a high-speed mixer for dispersion for 18 minutes at a speed of 900 rpm to obtain an impact modifier.

[0036] In step 1, the crosslinking agent is composed of 74 parts of divinyl benzene, 14 parts of triethylene glycol acrylate and 7 parts of diacetone acrylamide by weight. The first initiator is composed of 54 parts of ammonium persulfate and 44 parts of ascorbic acid. The buffer is disodium hydrogen phosphate.

[0037] In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 560℃, calcination time 2h; b. The calcined kaolin in step a was sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor was 340W and the treatment time was 0.7h. c. Take the activated kaolin in step b, add it and potassium acetate into deionized water at a mass ratio of 1:1.15, and then ultrasonically treat the mixed solution for 2.4 hours to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent at a mass ratio of 3:1, and then mix the compounded solution with ethanol at a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution into a mixing tank at a mass ratio of 0.24:1 to mix, the temperature in the mixing tank is 74°C, and the reaction time is 3.4 hours to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0038] In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide also needs to be added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.55:1.

[0039] In step 1, the emulsifier is composed of 64 parts of sodium dodecylbenzene sulfonate, 14 parts of polyvinyl alcohol and 6 parts of potassium oleate by weight. The second initiator is composed of 74 parts of cumene hydroperoxide and 24 parts of sodium formaldehyde sulfoxylate. The grafting agent is composed of 44 parts of styrene, 28 parts of vinyl chloride and 11 parts of acrylonitrile.

[0040] In step 3, the antioxidant is octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0041] Embodiment 3: The difference between this embodiment and embodiment 1 is that: In step 1, 88 parts of n-butyl acrylate, 7 parts of styrene, 1.2 parts of a crosslinking agent, 2 parts of an emulsifier and 4 parts of deionized water are sequentially sent to a stirring tank for stirring and mixing, and then 2.8 parts of a first initiator are added dropwise to the stirring tank. After the addition is completed, 4 parts of a buffer are added and continued to be stirred. The reaction temperature is 68° C. and the reaction time is 3 hours to obtain a flexible core emulsion; In step 2, 78 parts of the flexible core emulsion in step 1 are taken into a reactor by weight, 7 parts of modified nano-kaolin and 12 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 1 part of the second initiator and 3 parts of the grafting agent are added in sequence, the temperature is raised to 70° C., and the reaction is carried out for 2.8 hours to obtain a mixed emulsion; In step 3, 80 parts by weight of the mixed emulsion in step 2 are fed into a mixing kettle, and then 1 part of an antioxidant is added to the mixing kettle, stirred and mixed, and 0.7 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 67° C. by gradient heating, and the modified emulsion is obtained after stirring for 3.8 hours, and the modifier powder is obtained by spray drying; In step 4, 88 parts of nano calcium carbonate, 6 parts of sodium stearate, and 8 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 152° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for crushing to obtain an intermediate powder with an agglomerated particle size of ≤5 μm, 4.4 parts of the intermediate powder and 96.5 parts of the modifier powder are sent to a high-speed mixer for dispersion for 20 minutes at a speed of 1000 rpm to obtain an impact modifier.

[0042] In step 1, the crosslinking agent is composed of 78 parts of divinylbenzene, 18 parts of triethylene glycol acrylate and 8 parts of diacetone acrylamide by weight. The first initiator is composed of 58 parts of ammonium persulfate and 48 parts of ascorbic acid. The buffer is disodium hydrogen phosphate.

[0043] In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 580℃, calcination time 2.5h; b. The calcined kaolin in step a was sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor was 380W and the treatment time was 0.8h. c. Take the activated kaolin in step b, add it and potassium acetate in a mass ratio of 1:1.18 into deionized water to mix, then ultrasonically treat the mixed solution for 2.8 hours to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent in a mass ratio of 3:1, and then mix the compounded solution with ethanol in a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution in a mass ratio of 0.28:1 into a mixing tank for mixing, the temperature in the mixing tank is 78°C, and the reaction time is 3.8 hours to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0044] In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide also needs to be added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.65:1.

[0045] In step 1, the emulsifier is composed of 68 parts of sodium dodecylbenzene sulfonate, 18 parts of polyvinyl alcohol and 8 parts of potassium oleate by weight. The second initiator is composed of 78 parts of cumene hydroperoxide and 28 parts of sodium formaldehyde sulfoxylate. The grafting agent is composed of 48 parts of styrene, 30 parts of vinyl chloride and 13 parts of acrylonitrile.

[0046] In step 3, the antioxidant is octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0047] Embodiment 4: The difference between this embodiment and embodiment 1 is that: In step 1, 90 parts of n-butyl acrylate, 8 parts of styrene, 1.5 parts of a crosslinking agent, 2.2 parts of an emulsifier and 5 parts of deionized water are sequentially sent to a stirring tank for stirring and mixing, and then 2.8 parts of a first initiator are added dropwise to the stirring tank. After the addition is completed, 4 parts of a buffer are added and continued to be stirred. The reaction temperature is 70° C. and the reaction time is 4 hours to obtain a flexible core emulsion; In step 2, 80 parts by weight of the flexible core emulsion in step 1 are taken into a reactor, 8 parts of modified nano-kaolin and 15 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 1.2 parts of a second initiator and 3.5 parts of a grafting agent are added in sequence, the temperature is raised to 75° C., and the reaction is carried out for 3 hours to obtain a mixed emulsion; In step 3, 85 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 1.2 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.8 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 68° C. by gradient heating, and the modified emulsion is obtained after stirring for 4 hours, and the modifier powder is obtained by spray drying; In step 4, 90 parts of nano calcium carbonate, 7 parts of sodium stearate, and 10 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 155° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for crushing to obtain an intermediate powder with an agglomerated particle size of ≤5 μm, 5 parts of the intermediate powder and 97 parts of modifier powder are sent to a high-speed mixer for dispersion for 25 minutes at a speed of 1200 rpm to obtain an impact modifier.

[0048] In step 1, the crosslinking agent is composed of 80 parts of divinylbenzene, 20 parts of triethylene glycol acrylate and 10 parts of diacetone acrylamide by weight. The first initiator is composed of 60 parts of ammonium persulfate and 50 parts of ascorbic acid. The buffer is disodium hydrogen phosphate.

[0049] In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcination temperature 600 ℃, calcination time 3h; b. The calcined kaolin in step a was sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor was 400W and the treatment time was 1h. c. Take the activated kaolin in step b, add it and potassium acetate into deionized water at a mass ratio of 1:1.2, and then ultrasonically treat the mixed solution for 3 hours to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent at a mass ratio of 3:1, and then mix the compounded solution with ethanol at a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution into a mixing tank at a mass ratio of 0.3:1 to mix, the temperature in the mixing tank is 80°C, and the reaction time is 4 hours to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

[0050] In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide also needs to be added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.7:1.

[0051] In step 1, the emulsifier is composed of 70 parts of sodium dodecylbenzene sulfonate, 20 parts of polyvinyl alcohol and 10 parts of potassium oleate by weight. The second initiator is composed of 80 parts of cumene hydroperoxide and 30 parts of sodium formaldehyde sulfoxylate. The grafting agent is composed of 50 parts of styrene, 35 parts of vinyl chloride and 15 parts of acrylonitrile.

[0052] In step 3, the antioxidant is pentaerythritol tetraester.

[0053] Comparative Example 1: The difference between this comparative example and Example 1 is that no modified nano-kaolin is added in step 2.

[0054] Comparative Example 2: The difference between this comparative example and Example 1 is that the amount of modified nano-kaolin in step 2 is 0.5 parts.

[0055] Comparative Example 3: The difference between this comparative example and Example 1 is that no maleic anhydride-grafted polyolefin elastomer is used in step 4.

[0056] Comparative Example 4: The difference between this comparative example and Example 1 is that the amount of maleic anhydride grafted polyolefin elastomer used in step 4 is 2 parts.

[0057] 5-15 parts of the products in Examples 1 to 4 and Comparative Examples 1 to 4 were respectively selected, mixed with 100 parts of PVC resin, and then melt-blended by a twin-screw extruder at an extrusion temperature of 180-190° C. and a screw speed of 300-500 rpm to obtain a PVC finished product.

[0058] The PVC finished products were tested and the results are as follows:

[0059] It can be seen from the above table that without the use of modified nano-kaolin, the impact resistance of the finished PVC product is greatly reduced at all temperatures; even if the amount of modified nano-kaolin is small, the final modifier will improve the impact resistance of the finished PVC product. After analysis, we found that the modified kaolin forms a chemical bond with the PVC molecular chain and has good interfacial compatibility; at the same time, the nano-scale modified nano-kaolin can reduce molecular agglomeration and assist in the formation of the "sea-island" structure, thereby improving stress transfer efficiency. The combination of rigid kaolin and PVC flexible chain segments improves the tensile and impact resistance of the finished PVC product, and also ensures the toughness of the finished PVC product.

[0060] It can be seen from the above table that maleic anhydride grafted polyolefin elastomer will also affect various indicators of PVC finished products. After analysis, we concluded that this is because maleic anhydride derivatives can form a certain degree of network structure during the PVC processing process, and cooperate with the "sea-island" structure to improve the material's fatigue resistance, improve the impact energy absorption efficiency, and significantly improve the notched impact strength of PVC finished products.

[0061] In summary, this solution has the following advantages: First, after the impact modifier is added to the modified nano-kaolin, due to its good compatibility, it can effectively enhance the dimensional stability of PVC products, assist in the formation of the "sea-island" structure, and improve the stress transfer efficiency. At the same time, the rigid kaolin is combined with the PVC flexible chain segment to improve the tensile and impact resistance of the finished PVC product. Second, the maleic anhydride grafted polyolefin elastomer can form a certain degree of mesh structure during the PVC processing process, and cooperate with the "sea-island" structure to jointly improve the material's fatigue resistance and significantly improve the notched impact strength of the finished PVC product.

[0062] The present invention is not limited to the above-mentioned specific implementation modes. Various changes made by ordinary technicians in this field based on the above-mentioned concepts without creative work are all within the protection scope of the present invention.

Claims

1. A method for preparing an impact modifier for PVC production, characterized in that: The following steps are involved: Step 1, flexible core preparation; 80-90 parts of n-butyl acrylate, 5-8 parts of styrene, 0.5-1.5 parts of a crosslinking agent, 1.2-2.2 parts of an emulsifier and 2-5 parts of deionized water are sequentially sent to a stirring kettle for stirring and mixing, and then 2.5-3 parts of a first initiator are added dropwise to the stirring kettle. After the addition is completed, 3-5 parts of a buffer are added and continued to be stirred. The reaction temperature is 60-70° C. and the reaction time is 2-4 hours to obtain a flexible core emulsion; Step 2: preparing the intermediate layer; 70-80 parts of the flexible core emulsion in step 1 are taken into a reactor by weight, 3-8 parts of modified nano-kaolin and 5-15 parts of glycidyl methacrylate are added to the reactor, stirred and mixed, and then 0.5-1.2 parts of a second initiator and 2.5-3.5 parts of a grafting agent are added in sequence, the temperature is raised to 65-75° C., and the reaction is carried out for 2-3 hours to obtain a mixed emulsion; Step 3, preparation of modifier powder; 75-85 parts of the mixed emulsion in step 2 are fed into a mixing kettle by weight, and then 0.6-1.2 parts of an antioxidant are added to the mixing kettle, stirred and mixed, and 0.3-0.8 parts of tetrathiodiacrylate are added dropwise to the mixing kettle, and the temperature in the mixing kettle is increased to 65-68° C. by gradient heating, and stirred for 3-4 hours to obtain a modified emulsion, which is then spray-dried to obtain a modifier powder; Step 4, finished product preparation; By weight, 80-90 parts of nano calcium carbonate, 4-7 parts of sodium stearate, and 6-10 parts of maleic anhydride grafted polyolefin elastomer are hot mixed at 145-155° C. and then cold mixed to below 45° C. to obtain a mixture; the mixture is sent to a jet mill for pulverization to obtain an intermediate powder with an agglomerated particle size of ≤5 μm; 3-5 parts of the intermediate powder and 95-97 parts of the modifier powder obtained in step 3 are sent to a high-speed mixer for dispersion for 15-25 minutes at a speed of 800-1200 rpm to obtain an impact modifier.

2. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 1, the crosslinking agent is composed of 70-80 parts of divinyl benzene, 10-20 parts of triethylene glycol acrylate and 5-10 parts of diacetone acrylamide by weight.

3. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 1, the first initiator is composed of 50-60 parts of ammonium persulfate and 40-50 parts of ascorbic acid by weight.

4. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 1, the buffer is sodium dihydrogen phosphate or disodium hydrogen phosphate.

5. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 2, the preparation method of modified nano kaolin is: a. Send kaolin to the calcining furnace, calcining temperature 550-600℃, calcining time 1.5-3h; b. The calcined kaolin in step a is sent to an argon plasma reactor for activation treatment. The operating power of the argon plasma reactor is 300-400W, and the treatment time is 0.5-1h; c. Take the activated kaolin in step b, add it and potassium acetate into deionized water at a mass ratio of 1:1.1-1.2, and then ultrasonically treat the mixed solution for 2-3 hours to obtain a mixed solution; compound the silane coupling agent and the titanate coupling agent at a mass ratio of 3:1, and then mix the compounded solution with ethanol at a mass ratio of 9:1 to obtain a surface treatment solution, and add the surface treatment solution and the mixed solution into a mixing tank at a mass ratio of 0.2-0.3:1 to mix, the temperature in the mixing tank is 70-80°C, and the reaction time is 3-4 hours to obtain a modified nano-kaolin solution; d. The modified nano-kaolin liquid is dried to obtain modified nano-kaolin, and the modified nano-kaolin is fed into a ball mill with a ball-to-material ratio of 12:1 and a ball mill speed of 400 rpm to obtain modified nano-kaolin, wherein the particle size of the modified nano-kaolin is ≤150 nm.

6. The method for preparing an impact modifier for PVC production according to claim 5, characterized in that: In step d, while the modified nano-kaolin is fed into the ball mill, polyethylene oxide is also added into the ball mill, and the mass ratio of polyethylene oxide to the modified nano-kaolin is 0.5-0.7:

1.

7. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 1, the emulsifier is composed of 60-70 parts of sodium dodecylbenzene sulfonate, 10-20 parts of polyvinyl alcohol and 5-10 parts of potassium oleate by weight.

8. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 2, the second initiator is composed of 70-80 parts of cumene hydroperoxide and 20-30 parts of sodium formaldehyde sulfoxylate, by weight.

9. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 2, the grafting agent is composed of 40-50 parts of styrene, 25-35 parts of vinyl chloride and 10-15 parts of acrylonitrile by weight.

10. The method for preparing an impact modifier for PVC production according to claim 1, characterized in that: In step 3, the antioxidant is pentaerythritol tetraester or β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl.

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