Preparation And Properties Of Solvent-Free Fluorinated Spolyurethane-Polyacrylate Emulsions And The Application On The Paper

The demand quantity of specialty paper is large at present and the performance requirements of the specialty paper are also higher, which requires that the paper has good physical properties, water and oil proofing effect, etc. As a new environmentally friendly surface sizing agent, waterborne polyurethane (WPU) is attracting more and more attention of people. However, the water resistance of films of waterborne polyurethane are poor. Organic fluorine groups can be introduced to the waterborne polyurethane in order to improve the water resistance. The polarizability of C-F chemical bond is small, the bond length is short and the intermolecular cohesive force is small, therefore, the organic fluorine polymers generally have extremely low surface energy, water and oil can’t spread on its surface. In this paper, waterborne polyurethane/polyacrylate(WPUA) was modified by organic fluorine, and the fluorinated polyurethane/polyacrylate (FPUA) emulsion was prepared by the introduction of small molecule chain extender (AAS) to solve the shortcoming of poor stability of FPUA emulsion.In this paper, WPUA was synthesized by the methods of seed emulsion polymerization and chain extension with isophorone diisocyanate (IPDI) and polyester polyol(PCL1000) as the main raw materials, hydroxyl ethyl acrylate (HEA) as functional monomer, aliphatic diamine sulphonate (AAS) as chain extender, methyl methacrylate (MMA) and butyl acrylate (BA) as radical polymerization monomers. Stable FPUA composite emulsions without organic solvent were synthesized using 1H,1H,2H,2H-perfluoroalkyl ethyl acrylates acrylate (FA) and 1H,1 H,2H,2H-perfluorooctanol (FOH), respectively. The effects of FA, FOH, AAS and the connection way of fluorinated groups on the properties of FPU emulsion and latex films were discussed. The main research content of this paper is as follows:(1) The FA modified PUA emulsion and FOH modified PUA emulsion were synthesized respectively while the R value is 1.23. A series of WFPUA emulsion and films were prepared through changing the content of FOH and FA. The appearance and storage stability of the emulsion were observed. The particle size of emulsion, surface structure, waterproof and fouling resistance, thermal stability of films were characterized. The results showed that the latex particle size increased gradually, waterproof and fouling resistance was improved, its thermal stability also increased with the increase of F content. The test results of particle size of emulsion showed that the particle size of FOH modified PUA emulsion is smaller, the emulsion stability is better than FA modified PUA emulsion. The results of contact angle and water resistance test showed that the waterproof and oil resistance of FA modified PUA films is better than the FOH modified PUA in the case of FA and FOH equal dosage.(2) The FPUA emulsion and latex films with different AAS content were prepared by regulating the dosage of the chain extender (AAS) in the FPUA polymerization process. The appearance and storage stability of the emulsion were observed. And the particle size of the emulsion, water and fouling resistance and thermal stability of the films were discussed. The results showed that the water resistance of the films is best when the amount of AAS in FPUA is 8wt% and optimized content of organic fluorine is 4wt%.(3) The FPUA composite emulsion is used in papermarking as surface sizing agents. The surface sizing application result showed that the paper’s burst tearing and tensile strength are both improved by surface sizing. Surface morphology of the paper sized with the FPUA emulsion was observed by scanning electron microscope(SEM). The porosity on the paper surface decreased because of the filmforming of FPUA emulsion on the paper fiber. The static contract angle of water with the paper were 137.5° and the contract angle of diiodomethane with the paper reached 116.8°. Moreover, the burst strength, tearing strength and tensile strength of the paper were all improved, indicating the perfect application effect of FPUA emulsion as surface sizing agent.