Synthesis Of Highly Hydrophobic Dyes For Polypropylene

It is difficult to dye unmodified polypropylene fabrics with commercial dyes,problems of showing light colors and poor color fastness are often associated.Fifteen dyes were selected to explore the influence of dye molecular structure on the dyeing properties of polypropylene fabrics.The log P values were predicted by Chem3D Ultra 8.0,the solubility parameters?were estimated using the Hoy group contribution method and Fedors group contribution method.Six highly hydrophobic dyes were synthesized from Sudan I:1-?phenyl azo?-2-naphthol,Sudan?:1-[4-?phenyl azo?phenyl azo]-2-naphthol,iodoethane,1-iodohexane and 1-iododecane through Williamson etherification reactions.The molecular structures of the six dyes were analyzed by ¹HNMR and FT-MIR.The dyeing properties of modified dyes were also evaluated.In addition,the dyeing properties of polypropylene fabrics after N₂plasma pretreatment were studied.The results indicate that highly hydrophobic azo dyes for dyeing polypropylene require log P values larger than 5,and solubility parameters close to polypropylene.When the length of substituted alkyl chain in the dye molecular structure increases within a certain range,and the K/S values and color fastness of the dyed samples increase.When the number of methyl substituents on aromatic hydrocarbons in the dye molecular structure increases,the K/S value of the dyed samples increase,but the rating of color fastness to rubbing,washing and dye transfer decrease.These highly hydrophobic dyes were named as dye a:1-?phenyl azo?-2-naphthyl ethyl ether,dye b:1-?phenyl azo?-2-naphthyl hexyl ether,dye c:1-?phenyl azo?-2-naphthyl decyl ether,dye d:1-[4-?phenyl azo?phenyl azo]-2-naphthyl ethyl ether,dye e:1-[4-?phenyl azo?phenyl azo]-2-naphthyl hexyl ether and dye f:1-[4-?phenyl azo?phenyl azo]-2-naphthyl decyl ether,respectively.The log P values of the six dyes are 5.68,7.42,9.09,8.12,9.85 and 11.52,respectively.The dyes all have high hydrophobicity,polypropylene fabrics can be dyed by them.The K/S values of the dyed samples are 4.3,8.3,13.3,11.3,20.0 and 19.0,respectively.The affinity values of the dyes to polypropylene nonwoven fabrics are 8.400,11.941,10.292,7.651,10.903 and 11.092 k J/mol.The adsorption fitting isotherms of polypropylene for the six dyes are consistent with that of the Nernst?dissolution?adsorption.For the modified dyes of Sudan I,when the carbon number of the alkyl substituent reaches 10,the color fastness to rubbing,washing,dye transfer and perspiration can reach rating 4 and above.For the modified dyes of Sudan?,when the carbon number of the alkyl substituent is 6 or 10,the color fastness to rubbing,washing,dye transfer and perspiration can reach rating 4 and above.The optimized process for polypropylene pretreatment with N₂plasma is:discharge power200W,discharge time 5min,and gas flow rate 80sccm.Compared to the unpretreated polypropylene,the K/S values of dyed samples after N₂plasma pretreatment are higher.The color fastness to rubbing,washing and dye transfer of the dyed samples don't decrease significantly.Polypropylene non-woven fabrics with N₂plasma pretreatment before dyeing is an effective method to improve color strength.