| The technology of blue light curable inkjet printing for textile employs oligomers and monomers instead of polymeric binder used in conventional pigment inks to ensure a sufficient fluidity during inkjet process,and to solve a nozzle clogging problem suffered frequently in conventional pigment ink system.Conventional Photo-curable inkjet systems include photoinitiator systems(photoinitiator,co-initiator or photosensitizer,etc.),polymerization systems(oligomer and monomer),organic pigments and additives(dispersant,antioxidant,etc.).Oligomer and its polymerization system are an essential component in a photo-curable ink formulation,mainly determining the rheological properties of inkjet printing fluid,the physical and chemical properties of the resultant cured film.At present,epoxy,acrylate monomers and their oligomers with various functional groups are mainly applied in photopolymerization of hard and brittle patterned film on rigid substrates.The cured film has limitations in flexibility,elasticity and hand feel,which can not match the requirements of flexible textiles for the "soft,strong and flexible" properties of the film at the same time with low viscosity.And it also can not solve the inherent problems such as poor rubbing fastness and rough hand feel of pigment printing.By the way,in order to obtain high initiation rate and conversion,small molecular tertiary amines are generally added to the photo curing products as promoters or activators.These small tertiary amines are easy to migrate and have potential toxicity and risk,which limit their application in the field of textiles in direct contact with human body.In order to solve these problems,a series of polyurethane acrylate oligomers(PUA)modified by tertiary amine group have been synthesized by molecular design to improve the photoinitiation efficiency and reduce the possibility of potential safety risks caused by migration of small-molecular amines after curing.In addition,organic-inorganic hybrid is synthesized in situ by introducing siloxane copolymerization and silicon oxide.In addition,the PUA oligomers are integration functional modified by organic siloxane copolymer,in-situ synthesis of silicon oxide hybrid and hyperbranched.Finally,the polymer system with IPN structure is constructed by compounding with high-performance monomers,which not only ensures low viscosity,but also gives the cured film a soft,strong and flexible feeling.The structure-activity relationship between polymer hyperbranched structure and polymerization properties,mechanical properties and flow properties is elucidated.It provides a scientific basis for the construction and regulation of photo-curable polymerization system for textile.In order to promote the practical application of bule light curable digital inkjet printing technology,we also have studied the flow performance and jet theory of new blue light curable inkjet printing system,and developed high-performance integrated textile bule light curable digital printing ink and supporting equipment.The main results are as follows:1.Using HMDI,PTMG,BDO,MDEA and HEA as the main raw materials,a series of tertiary amine modified photosensitive polyurethane acrylate(PUA)oligomers with high photoactivity and conversion rate were designed and synthesized.At the same time,the toxicity and yellowing problems of the added small tertiary amine promoter were avoided.When the mass ratio of PUA to HEA was 1:9,IPN structure would be formed.The tensile stress was 1.5 MPa,the maximum elongation at break was 530%,the 100%elongation stress was less than 0.4MPa,and the transmittance of light area was more than 95%.2.The surface energy of PDMS was relatively low.After copolymerization with PUA,polysiloxane chain segment would move towards the surface of the blue light cured films with tertiary amine group in the process of photo-curing,which improved the photoinitiation efficiency.When the content of PDMS was less than 5 wt%,the mechanical tensile properties of the cured film remained more than 90%,and it could give the cured film better flexibility and water resistance.At this time,a connected micro phase structure of 50-70 μm thick with high content of polysiloxane was formed on the surface of the cured film,while the internal macromolecular polymerization network skeleton structure was complete and continuous3.Amino modified SiO2 with 98.3%modification rate and PUA-HEA were synthesized in situ to construct the organic-inorganic doped polymerization system.The breaking stress of the bule light cured film was 5.73mpa,the maximum elongation at break was 588%,the SiO2 particles were evenly dispersed and the organic-inorganic interface transition was stable with good flexibility.When 0.5%of CQ initiator and 1%of pigment blue 60 were added to the blue light curable digital ink,the hand feel of the printed fabric was soft,the dry rubbing fastness was 4-5,and the wet rubbing fastness was 4-54.The viscosity of the composite polymerization system of SiO2@PUA hyperbranched oligomer with HEA was low.SiO2 particles were grafted with the PUA chain segment,and a homogeneous macromolecular network was formed during photocuring.However,due to the short chain segment,the fracture stress of the cured film was 2.13,and the maximum elongation at break was 400%.5.TiO2@PUA-HEA integrated ink was prepared,and micro industrial flat printer TT-6042R was used to build a photo curable digital inkjet printing platform for textiles.Optimized the inkjet printing parameters,when the printing temperature was 45℃,the viscosity of the integrated photo curable ink was 4.2 mPa·s,the printing speed was about 30 cm/min(18 m/h),the patterned photo curable digital inkjet printed fabric was successfully prepared.This fabric had soft hand feel,clear and smooth pattern lines,precise positioning,full color,dry rubbing fastness of 4-5 and wet rubbing fastness of 4-5. |
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