| Resource recycling is an important way to ensure resource safety in China.Recycling and regeneration of waste textiles is an important part of building resource recycling industry system.The recycling of waste polyester textiles,which accounts for the largest proportion of waste textiles,is a top priority.Alcoholysis and repolymerization of polyester textiles is a recycling method to obtain high value recycled materials.Waterborne polyurethane is a new type of polyurethane system which uses water as dispersive medium instead of organic solvent.It has been used in industry,textile,coating and medical treatment with the characteristics of non-toxic,pollution-free,energy saving and safety.As a coating agent,it can make the fabric obtain a series of excellent properties such as high strength,comfortable skin feeling,good air permeability and moisture permeability.However,polyester fabric and waterborne polyurethane are flammable materials themselves,which have shortcomings such as fast burning speed,large heat release,and high temperature melting drops resulting in secondary damage in the combustion process.In practical application,there are hidden dangers of fire,and it is easy to bring personal harm and economic loss to people.Therefore,it is particularly important to explore a scheme that can not only retain the excellent properties of waterborne polyurethane,but also improve its flame retardancy.In view of this,this topic mainly studies the following contents:（1）Using waste polyester fabric as raw material,glycol as alcoholysis reagent and zinc acetate as catalyst,alcoholysis products were obtained by ethylene glycol alcoholysis at room temperature and pressure.The structure and properties of the alcoholysis products were compared with that of analytical pure dihydroxyethyl terephthalate（BHET）.The optimum alcoholysis process parameters were obtained by optimizing the reaction conditions.Regenerated waterborne polyurethane（WPU）was synthesized by alcoholysis with isophorone diisocyanate（IPDI）as the main raw material.The following conclusions are drawn:The alcoholysis product of waste polyester fabric obtained by glycol alcoholysis method was confirmed to be consistent with the structure of commercial BHET after testing,analysis and comparison.According to the orthogonal test table with the yield of alcoholysis as the index,the optimal conditions of alcoholysis are as follows:the mass ratio of polyester to ethylene glycol is 1:4,the reaction temperature is 196°C,and the reaction time is 5h.Under these conditions,the yield of alcoholysis can reach 100%,the purity and yield of alcoholysis products are high,and the yield can reach more than 60%,and the process cost is low.Regenerated waterborne polyurethane was synthesized from alcoholysis products and IPDI.When the experimental conditions were n（-NCO）/n（-OH）=4,isocyanate radical index is 1.4,DMPA%=5%,TMP%=3%,neutralization degree is 100%,the waterborne polyurethane emulsion with milky white appearance,blue light and uniform particle size can be prepared.（2）Additive blending flame retardant modification of waterborne polyurethane.Select four type of added phosphorous flame retardants:four hydroxymethyl sulfate phosphorus,three hydroxyl phosphonic-A,ammonium polyphosphate and four hydroxyl phosphonic-B,which physical blending with homemade regeneration waterborne polyurethane,will the modified emulsion by impregnation method of load on the polyester fabric,made flame retardant modified polyester fabric.Single factor tests were designed with the types of flame retardants and load rate as indexes,and the microstructure,chemical structure,thermal stability,flame retardancy,mechanical properties and wearability of the modified polyester fabric were tested and characterized.The following conclusions are drawn:Under the same loading rate of 75%,the thermal stability and flame retardancy of the modified fabric are improved greatly compared with the original fabric,and the mechanical properties of the fabric such as strength and wear resistance,as well as the wear comfort properties such as air permeability,moisture permeability and hydrophilicity are improved to varying degrees.Among them,the comprehensive performance and practical application of four hydroxymethyl sulfate phosphorus group is the best,which limit oxygen index reaches 26.5%,the vertical combustion grade is V-0.The carbon residue rate of the fabric is 27.7%,the peak combustion heat release rate（PHRR）is 203.46 kW/m2,the total combustion heat release rate（THR）is 4.2 MJ/m2,and the total combustion smoke generation（TSP）is 0.9 m2.In terms of mechanical properties,the breaking strength,elongation at break and tear strength are 414 N,13.4%and 13 N,respectively.In terms of comfort,air permeability,moisture permeability and water contact angle reached 87.62 mm/s,6281.39g/m2d and 90.75°respectively.（3）Reactive flame retardant modification of waterborne polyurethane.The polymerization route of reclaimed waterborne polyurethane was optimized by synthesizing reactive flame retardant Tris-（hydroxymethyl）phosphine oxide（THPO）and coordinating with the nano-silicon dioxide modified by KH570 to obtain the phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.After coating polyester fabric,a phosphorus-silicon synergistic flame retardant modified fabric with stable flame retardant property and mechanical comfort was obtained.The effects of different THPO content,nano-silicon dioxide content and initial n（-NCO）/n（-OH）values on the properties of the modified fabric were tested and analyzed.The following conclusions are drawn:The thermal decomposition rate and thermal decomposition temperature of the phosphorus-silicon synergistic flame retardant modified polyester fabric are lower than those of the original polyester fabric,and the carbon residue rate is increased by 127%.When the mass fraction of THPO is 24%,the mass fraction of SiO2 is4%,and the initial n（-NCO）/n（-OH）=6,the LOI value of the phospho-silicon modified fabric reaches 29.7%,and the UL-94 rating reaches V-0.Its PHRR=86.35 kW/m2,THR=3.6 MJ/m2,TSP=0.8m2,the fire risk parameters are more than 35%lower than the original fabric.In terms of mechanical properties,the breaking strength,elongation at break,tear strength and wear times were 586 N,18.8%,27 N and 234 times,respectively.In terms of comfortable wear performance,the air permeability,moisture permeability and water contact angle of fabric are235.7 mm/s,7384.88 g/m2d and 103.5°respectively. |
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