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Silicone-modified polyacrylate aqueous emulsion varnish is a new topic in the study of paper varnish in recent years. While maintaining the advantages of polyacrylic ester aqueous varnish, the varnish is resistant to dirt, abrasion and flexibility. Sexuality has improved significantly. However, technical issues such as the selection of organic silicon monomers and the introduction of organosilicon monomers into copolymers have yet to be further studied. Based on this, we have carried out research on core/shell styrene-propylene-silicone copolymer emulsions. This article focuses on the preparation of styrene-acrylonitrile-silicone copolymer emulsion and its chemical structure and properties.
1 Preparation of styrene (St), methyl methacrylate (MMA), butyl acrylate (BA), carboxyl-containing monomers (G-1), etc. as hard core monomers, MMA, BA, with epoxy groups The monomer (G-2) is a soft shell-1 monomer, MMA, BA, G-2, a silicone monomer (G-Si), etc. is a soft shell-2 monomer, with a dodecyl benzene sulfonate Sodium (SDBS) and polyethylene glycol octyl phenyl ether (OP) are compound emulsifiers. Ammonium persulfate (APS) is the initiator. It uses pre-emulsification, step emulsion polymerization and phased pH control. A hard-shell, soft-shell styrene-acrylonitrile-silicone copolymer emulsion was developed. The amount of compound emulsifier and the ratio of compound emulsifier, the addition amount of PH adjuster and the method of addition, the ratio of soft/hard monomer in the core, the dosage of G-1, G-2 and G-Si monomers, and the shell pretreatment were systematically studied. The influences of emulsion dropping rate and feeding method, insulation polymerization temperature, stirring speed and Other processing conditions on emulsion polymerization stability, emulsion stability and emulsion film performance.
2 The chemical structure of benzene-propylene-silicone copolymers through low-temperature film formation experiments, fractional extraction experiments, copolymer hot melt flow experiments, film acetone dissolution tests, and infrared spectroscopy (IR) analysis show that benzene-propylene-silicone In the copolymer emulsion, the carboxyl group-carrying carboxyl group reacts with the epoxy group-bearing epoxy group to form a chemical bond between the core and the shell by the grafting mechanism; nearly half of the organosilicon monomers are involved. Copolymerization; the macromolecules in the emulsion are not substantially cross-linked, and a moderate cross-linked structure is formed by a self-crosslinking mechanism during the drying film formation.
3 Relationship between process conditions and properties of emulsions and latex films 3.1 Addition amount of pH adjuster and addition method Additive amount of pH adjuster 0.2g (add as a solution) is added before shell 2 pre-emulsion is added dropwise, and emulsion polymerization is stable. Excellent stability, storage stability and calcium ion stability, latex film stain rate is zero, hardness HB, adhesion and chemical resistance are excellent, the film appearance at room temperature is transparent and transparent, and the film is transparent, bright and blue at 50°C. obvious.
3.2 The amount of compound emulsifier and the ratio of compound emulsifier 3.0%, emulsifier ratio SDBS/OP=70/30, the emulsion polymerization stability, storage stability and calcium ion stability are higher, latex film The stain rate is zero, hardness HB, water absorption is relatively low, adhesion and chemical resistance are excellent, the film appearance at room temperature is transparent and bright, and the film is transparent, bright and blue at 50°C.
3.3 Core and shell-1 Insulation polymerization temperature Nuclear and shell-1 Insulation Polymerization temperature 80-85°C, emulsion reaction is complete and polymerization stability is high, calcium ion stability, storage stability is good, latex membrane fouling The rate is zero, hardness HB, water absorption is relatively minimum, water resistance is the best, adhesion and chemical resistance are excellent, low-temperature film formation performance is good.
3.4 Shell-2 Late Insulation Polymerization temperature The optimum temperature for polymerization polymerization is 85-90°C, especially at 85°C. The emulsion has higher polymerization stability, better calcium stability, better storage stability, and latex film. The stain rate is zero, the hardness is HB, the water absorption is small, the adhesion and the chemical resistance are excellent, and the low temperature film forming performance is good.
3.5 Shell monomer pre-emulsion drop rate Shell monomer pre-emulsion drop rate 2ml/min emulsion not only complete reaction, but also has the highest polymerization stability, calcium ion stability and storage stability is better, latex membrane water resistance Sex is also good, stain rate is zero, hardness HB, adhesion and chemical resistance are excellent, low-temperature film formation performance is good.
3.6 Shell monomer pre-emulsion feeding method Compared with the one-time feeding method, it is more appropriate to drop the shell pre-emulsion using the semi-boundary drop method. The prepared emulsion copolymer has good emulsion polymerization stability, storage stability and calcium ion stability. The emulsion has good film forming properties, and the latex film has excellent chemical resistance and stain resistance, and has a certain hardness. The water resistance of the latex film is slightly lower than that of the latex film produced by the one-shot feeding method.
3.7 Initiator dosage The emulsion with 0.20-0.25% of initiator has relatively high stability and moderate viscosity. The emulsion has good film forming property and the latex film has excellent chemical resistance. And dirt and water resistance, and have a certain degree of hardness and adhesion.
3.8 Effect of Stirring Speed ​​on Stability of Emulsion Polymerization In order to ensure that the polymerization reaction proceeds normally and the emulsion properties are good, a stirring speed of 230 rpm is suitable.
3.9 G-1 dosage The amount of G-1 is different, and the rheological behavior of the emulsion has roughly the same rule. The amount of G-1 is 3 to 4%, and the thermal oxidation starting temperature of the copolymer is above 220°C. The thermal oxidation resistance is better. The transparency of the dried film is high, and the blue light is more pronounced in the low-temperature drying film. The water resistance of the latex film is also better, the stain rate is zero, the hardness HB, adhesion and chemical resistance are excellent.
3.10 G-Si dosage G-Si content ≤10%, the emulsion polymerization is normal, and the stability is high. It has little effect on the calcium ion stability and storage stability of the emulsion. The introduction of the silicone monomer does not change the rheological behavior of the emulsion. At the same shear rate (γ), ηa increases with the increase of the concentration of silicone monomer; at a constant shear rate (60S-1), the concentration of silicone monomer increases, and the viscosity of the copolymer emulsion affects the temperature. With increased sensitivity, the Tg of silicone-containing copolymers is higher than that of silicone-free ones. Adding a higher content (for example, 10%) of the silicone monomer can reduce the hardness of the latex film and improve the transparency of the film, the degree of blue light, and the film properties have little effect.
When the dosage of G-2 with epoxy group is 6-8%, emulsion polymerization stability, storage stability and calcium ion stability are high. The rheological behavior of copolymer emulsion is close to the rheological behavior of Newtonian fluid. The initial temperature of copolymer thermal oxidation (To) is generally above 220°C, and the thermal oxidation resistance is relatively good. The latex film has a stain rate of zero, a hardness of HB, a relatively low water absorption, excellent adhesion and chemical resistance, and the film appearance at room temperature is transparent and bright, and the film is transparent, bright and blue at 50°C.
3.12 When the core/shell ratio is 50/50, the polymerization reaction is normal, the amount of gel is the least, the polymerization stability is the highest, the calcium ion stability and storage stability of the emulsion are relatively good, and the emulsion flow of the copolymer is relatively good. The behavior is close to that of Newtonian fluid; To above 225°C, the copolymer's resistance to thermal oxidation is better. The latex film has zero stain rate, excellent hardness HB, excellent adhesion and chemical resistance. The film at room temperature has a transparent appearance and is transparent and bright at 50° C., and has a clear blue light.
3.13 In the core, the ratio of soft/hard monomers in the core is 30/70. The thermal oxidation stability of the copolymer in the copolymer emulsion is better, and the blue light of the emulsion film formed at low temperature is more obvious. Fewer wrinkles, flat film surface; latex film has excellent stain resistance, chemical resistance. (From "China Packaging News")
1 Preparation of styrene (St), methyl methacrylate (MMA), butyl acrylate (BA), carboxyl-containing monomers (G-1), etc. as hard core monomers, MMA, BA, with epoxy groups The monomer (G-2) is a soft shell-1 monomer, MMA, BA, G-2, a silicone monomer (G-Si), etc. is a soft shell-2 monomer, with a dodecyl benzene sulfonate Sodium (SDBS) and polyethylene glycol octyl phenyl ether (OP) are compound emulsifiers. Ammonium persulfate (APS) is the initiator. It uses pre-emulsification, step emulsion polymerization and phased pH control. A hard-shell, soft-shell styrene-acrylonitrile-silicone copolymer emulsion was developed. The amount of compound emulsifier and the ratio of compound emulsifier, the addition amount of PH adjuster and the method of addition, the ratio of soft/hard monomer in the core, the dosage of G-1, G-2 and G-Si monomers, and the shell pretreatment were systematically studied. The influences of emulsion dropping rate and feeding method, insulation polymerization temperature, stirring speed and Other processing conditions on emulsion polymerization stability, emulsion stability and emulsion film performance.
2 The chemical structure of benzene-propylene-silicone copolymers through low-temperature film formation experiments, fractional extraction experiments, copolymer hot melt flow experiments, film acetone dissolution tests, and infrared spectroscopy (IR) analysis show that benzene-propylene-silicone In the copolymer emulsion, the carboxyl group-carrying carboxyl group reacts with the epoxy group-bearing epoxy group to form a chemical bond between the core and the shell by the grafting mechanism; nearly half of the organosilicon monomers are involved. Copolymerization; the macromolecules in the emulsion are not substantially cross-linked, and a moderate cross-linked structure is formed by a self-crosslinking mechanism during the drying film formation.
3 Relationship between process conditions and properties of emulsions and latex films 3.1 Addition amount of pH adjuster and addition method Additive amount of pH adjuster 0.2g (add as a solution) is added before shell 2 pre-emulsion is added dropwise, and emulsion polymerization is stable. Excellent stability, storage stability and calcium ion stability, latex film stain rate is zero, hardness HB, adhesion and chemical resistance are excellent, the film appearance at room temperature is transparent and transparent, and the film is transparent, bright and blue at 50°C. obvious.
3.2 The amount of compound emulsifier and the ratio of compound emulsifier 3.0%, emulsifier ratio SDBS/OP=70/30, the emulsion polymerization stability, storage stability and calcium ion stability are higher, latex film The stain rate is zero, hardness HB, water absorption is relatively low, adhesion and chemical resistance are excellent, the film appearance at room temperature is transparent and bright, and the film is transparent, bright and blue at 50°C.
3.3 Core and shell-1 Insulation polymerization temperature Nuclear and shell-1 Insulation Polymerization temperature 80-85°C, emulsion reaction is complete and polymerization stability is high, calcium ion stability, storage stability is good, latex membrane fouling The rate is zero, hardness HB, water absorption is relatively minimum, water resistance is the best, adhesion and chemical resistance are excellent, low-temperature film formation performance is good.
3.4 Shell-2 Late Insulation Polymerization temperature The optimum temperature for polymerization polymerization is 85-90°C, especially at 85°C. The emulsion has higher polymerization stability, better calcium stability, better storage stability, and latex film. The stain rate is zero, the hardness is HB, the water absorption is small, the adhesion and the chemical resistance are excellent, and the low temperature film forming performance is good.
3.5 Shell monomer pre-emulsion drop rate Shell monomer pre-emulsion drop rate 2ml/min emulsion not only complete reaction, but also has the highest polymerization stability, calcium ion stability and storage stability is better, latex membrane water resistance Sex is also good, stain rate is zero, hardness HB, adhesion and chemical resistance are excellent, low-temperature film formation performance is good.
3.6 Shell monomer pre-emulsion feeding method Compared with the one-time feeding method, it is more appropriate to drop the shell pre-emulsion using the semi-boundary drop method. The prepared emulsion copolymer has good emulsion polymerization stability, storage stability and calcium ion stability. The emulsion has good film forming properties, and the latex film has excellent chemical resistance and stain resistance, and has a certain hardness. The water resistance of the latex film is slightly lower than that of the latex film produced by the one-shot feeding method.
3.7 Initiator dosage The emulsion with 0.20-0.25% of initiator has relatively high stability and moderate viscosity. The emulsion has good film forming property and the latex film has excellent chemical resistance. And dirt and water resistance, and have a certain degree of hardness and adhesion.
3.8 Effect of Stirring Speed ​​on Stability of Emulsion Polymerization In order to ensure that the polymerization reaction proceeds normally and the emulsion properties are good, a stirring speed of 230 rpm is suitable.
3.9 G-1 dosage The amount of G-1 is different, and the rheological behavior of the emulsion has roughly the same rule. The amount of G-1 is 3 to 4%, and the thermal oxidation starting temperature of the copolymer is above 220°C. The thermal oxidation resistance is better. The transparency of the dried film is high, and the blue light is more pronounced in the low-temperature drying film. The water resistance of the latex film is also better, the stain rate is zero, the hardness HB, adhesion and chemical resistance are excellent.
3.10 G-Si dosage G-Si content ≤10%, the emulsion polymerization is normal, and the stability is high. It has little effect on the calcium ion stability and storage stability of the emulsion. The introduction of the silicone monomer does not change the rheological behavior of the emulsion. At the same shear rate (γ), ηa increases with the increase of the concentration of silicone monomer; at a constant shear rate (60S-1), the concentration of silicone monomer increases, and the viscosity of the copolymer emulsion affects the temperature. With increased sensitivity, the Tg of silicone-containing copolymers is higher than that of silicone-free ones. Adding a higher content (for example, 10%) of the silicone monomer can reduce the hardness of the latex film and improve the transparency of the film, the degree of blue light, and the film properties have little effect.
When the dosage of G-2 with epoxy group is 6-8%, emulsion polymerization stability, storage stability and calcium ion stability are high. The rheological behavior of copolymer emulsion is close to the rheological behavior of Newtonian fluid. The initial temperature of copolymer thermal oxidation (To) is generally above 220°C, and the thermal oxidation resistance is relatively good. The latex film has a stain rate of zero, a hardness of HB, a relatively low water absorption, excellent adhesion and chemical resistance, and the film appearance at room temperature is transparent and bright, and the film is transparent, bright and blue at 50°C.
3.12 When the core/shell ratio is 50/50, the polymerization reaction is normal, the amount of gel is the least, the polymerization stability is the highest, the calcium ion stability and storage stability of the emulsion are relatively good, and the emulsion flow of the copolymer is relatively good. The behavior is close to that of Newtonian fluid; To above 225°C, the copolymer's resistance to thermal oxidation is better. The latex film has zero stain rate, excellent hardness HB, excellent adhesion and chemical resistance. The film at room temperature has a transparent appearance and is transparent and bright at 50° C., and has a clear blue light.
3.13 In the core, the ratio of soft/hard monomers in the core is 30/70. The thermal oxidation stability of the copolymer in the copolymer emulsion is better, and the blue light of the emulsion film formed at low temperature is more obvious. Fewer wrinkles, flat film surface; latex film has excellent stain resistance, chemical resistance. (From "China Packaging News")
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