Study On Preparation And Modification Of Self-Crosslinking Core-Shell Structure Styrene-Acrylic Emulsion

With the development of society,the environmental protection situation has gained more and more attention.The volatile substance from the solvent-based resin emulsion can really a series of environmental problems.Therefore,is imminent to develop the environmentally friendly emulsions.Particularly,the water-based acrylic emulsion provides a good choice for solving the above problems owing to the low VOC.However,the development of acrylic emulsion is limited due to the poor water resistance and stain resistance.Thus,it is necessary to modified the acrylic latex.Interestingly,acrylic emulsion modified by silicone can combine the advantages of both.For this case,the hot stickiness,cold brittleness,and hydrophobic properties of acrylic emulsion can be improved.Firstly,the preparation technology for synthesizing the styrene acrylic emulsion has been investigated systematically,and the influence of each polymer component on the performance of the styrene-acrylic emulsion was explored based on the synthesize single-structure styrene-acrylic emulsion with pre-emulsified seed process.St,MAA,BA,2-EHA are chosen as polymerization monomers,K12 and AEO7 are used as emulsifiers,NMA and AA are applied for cross-linking process,and KPS was adopted for initiators.It is found that the prepared styrene-acrylic emulsion exhibits excellent performance when 3.50 wt.%emulsifier of the total polymerized monomers,and K12:AEO7=3:1,the amount of KPS is 0.50 wt.%of the whole polymerized monomer,the amount of NMA and AA are 0.50wt.%and 1.00 wt.%of the main monomer respectively.The styrene-acrylic emulsion with single-structure not gelatin during polymerization.And the average size of the emulsion is 80nm,PDI=0.036,these conclusions show that the particle size of the styrene-acrylic emulsion is controllable and it`s dispersion is uniform.Then the cross-linking degree of the latex film is 47.8 wt.%,tested by xylene,which can achieve the requirements of industrial production.Based on the particle design perspective,the core-shell structure(hard core soft shell,soft core hard shell)self-crosslinking styrene-acrylic emulsion was prepared.And the performance of the emulsion and it`s latex film was tested.The characterization results show that:the average particle size of two kinds core-shell styrene-acrylic latex are about 100 nm,and the PDI are less than 0.10.And the average particle size of the core-shell structure latex is about 20 nm longer than the single structure.It can be found from the IR analysis spectrum that the characteristic absorption peak of C-O-C,C=O and-CH₃ appeared at 1156 cm^-1,1729 cm^-1 and 2959 cm^-1respectively,implying that the main chain structure of styrene-acrylic emulsion was.Moreover,the TGA analysis chart shows that the thermal weight loss of the two kinds of structure emulsion films is above 98.5 wt.%.Also,compared with the 26.16°contact angle of single structure latex film,the contact angle of core-shell structure(hard core soft shell,soft core hard shell)styrene-acrylic emulsion film increases to 35.20°and 55.89°respectively.At this time,the latex films of single and core-shell structures were soaked in water for 72h.The experimental results showed that the water absorption of the latex films were 29.70 wt.%(single structures),20.64 wt.%(hard core soft shell),15.27 wt.%(soft core hard shell)respectively.Which were improved compared with the single structure.Lastly,according to the contact angle and water immersion experiment results of the latex films,it can be concluded that the hydrophobic performance of emulsion film,styrene-acrylic of soft-core hard-shell structure is more advanced.In order to obtain latex with better performance,KH-560 and KH-570 were chose to modify the styrene-acrylic emulsion with soft-core and hard-shell structure.The characteristic absorption peak of Si-O bond appeared in the IR analysis spectrum at 1060cm^-1,it indicated that the silicone improver was successfully grafted to the main chain structure of the emulsion.The TGA analysis profiles showed that when the amount of KH-570 was 2.0 wt.%of the total polymerized monomer,the thermal weight loss rate of the modified latex film is 2.33 wt.%,higher than that of the latex film without modification.It showed that the thermal performance of the modified latex film has been improved.And when the amount of KH-560,KH-570 was0.50 wt.%of the main monomers,the contact angle of the latex films increased 1.55°(KH-560)and 20.16°(KH-570)compared with the before modification.In summary,when the modifier was same,the thermal and hydrophobic properties of emulsion and it`s film modified by KH-570 was more advanced than KH-560.Finally,it is found that the styrene-acrylic emulsion with soft-core hard-shell structures has controllable particle size(the average particle size is 114 nm),the dispersion is uniform(PDI=0.022),and the thermal and hydrophobic performance are significantly improved.