| Solvent-free two-component polyurethane adhesives have been widely used in flexible packaging materials,especially in the field of instant foods,due to the advantages of 100%solid content,no solvent volatilization,and environmental protection.It has the problems of low heat seal strength,large friction coefficient and high free monomer of composite film,which are the major challenges currently faced by the flexible packaging industry.In this paper,from the measurement of thermal conductivity and the use of infrared spectroscopy to quantitatively analyze the reasons for the low heat seal strength of the composite film,the main reason for the excessively high free monomer caused by the migration of the heat seal strength is obtained,so a design and synthesis A low free monomer polyurethane prepolymer and its corresponding curing agent.In this dissertation,polyester polyols are prepared by melt polycondensation.The optimal process for synthesizing polyester polyols and low chroma are explored through the controlled variable method.The corresponding main agents are designed and synthesized using polyester polyols as soft segments.Using polyester polyol and bio-based castor oil as curing agents,the properties of laminated polyurethane adhesives were studied.The feasibility of bio-based polyol castor oil as a curing agent was explored,and compared with the currently used products.First,the reason for the decrease in the heat seal strength of polyethylene was detected by infrared quantitative analysis of the adhesive layer-the free monomer in the adhesive precipitated to the inner layer of the PE to form a polyurea structure,which was caused by the free monomer in the main agent Too much,and proposed to develop low-free monomer solvent-free two-component polyurethane adhesive.Then use diethylene glycol,adipic acid,isononanol and terephthalic acid as raw materials to prepare a low-viscosity polyester polyol,which is used as the main component of the solvent-free two-component polyurethane adhesive in the next chapter.And the use of curing agents.The best process for synthesizing polyester,the hydroxyl value of the final product reaches 136.64mgKOH/g,the corresponding viscosity is 327.6Pa,and the acid value is 2.09mgKOH/g.Secondly,a self-made polyester polyol was used in combination with PPG as the OH component,and TDI and MDI were used as the NCO component to synthesize a low-free monomer polyurethane prepolymer.The best reaction temperature is 75?,and the best reaction time is 2.5h,with an NCO%of 10.81%and a free monomer TDI%It was 0.02%,and the free monomer MDI%was 12.07%.Simultaneous scale-up experiments were conducted.Finally,the polyurethane prepolymer was compounded with polyester polyol and castor oil respectively.The introduction of CO segments greatly improved the thermal stability of polyurethane.T5%increased by 15? and T50%increased from 358 ? by 385?..On the PET/AL/PE composite structure,the peel strength reached 5N/15mm.In BOPA/PE,the peel strength reached 4N/15mm.After the PET/AL/PE structure is subjected to the high-temperature retort test,the peel strength still reaches more than 4N/15mm.On the PA/PE structure,the friction coefficient reached 0.224.The friction coefficient on the PET/AL/PE structure reached 0.222. |
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