Study On Synthesis Of Solvent-free Two-component Polyurethane Adhesive For Flexible Packaging

Solvent-free two-component polyurethane adhesive is a kind of Solvent-free andenvironmental friendly polyurethane adhesive, which has widly applications in theflexible packaging field. In this paper, By synthesizing MDI polyether polyurethanePrepolymers,polyester polyols and Mixing of the two components, Synthesis a kind ofsolvent-free two-component polyurethane adhesive which is suitable for flexiblepackaging.The research is mainly divided into three parts as follows:(1) the synthesis of MDI/PPG2000prepolymersUse4,4’-diphenylmethane diisocyanate (MDI),polypropylene glycol2000(PPG2000) as raw materials, under the condition of MDI and PPG2000mole ratio is3,T12as the catalyst, the reaction temperature is75degree, the reaction time is2h,MDI/PPG2000type polyurethane adhesive was synthesized, The prepolymer’sviscosity is1500mpa·s,NCO content was6.10%, the storage time is more than120days.(2) the synthesis of compounded polyester polyolIn order to improve the performance of polyester polyol, the experiment select theadipic acid (AA),phthalic anhydride (PA), diethylene glycol (DEG), neopentyl glycol(NPG) as raw materials, under the condition of P-toluene sulfonic acid as catalyst, theesterification reaction time is5h, the esterification reaction temperature is200degree,The acid value of esterification production is less than15mgKOH/g. under thecondition of reaction temperature is230degree, the reaction time is5h, use0.1%TPT as catalyst, the highest vacuum degree is0.09MPa, The raw material mole ratiois1.2, Synthetic polyester polyols, the acid value of polyester polyol is less than1mgKOH/g, the hydroxyl value is55, relative molecular weight is2000.such polyesterpolyol has good liquidity, high transparency, Appropriate viscosity.(3) the synthesis of solvent-free two-component polyurethane adhesiveUse MDI/PPG2000prepolymers, polyester polyols as raw material, under the condition of the mole ratio is1.15, the curing temperature is50degree, the curingtime is2days. synthesis the solvent-free two-component polyurethane adhesive. Thisadhesive peel strength of BOPET/PE materials is2.6N/mm, The highest waterabsorption is only1.5%, With a strong ability of anti-boiled, high transparency, longservice life, this kind of adhesive was very suitable for flexible packaging.Use infrared (IR) and thermogravimetric (TG) method to characterize the structure ofproduct. The test results shows that the MDI/PPG2000carbamate in the pre polymers,prove the reaction real happened between MDI and PPG2000; there are lots of-NHCOO-in the product, prove Polyester polyol synthesis method isfeasible,synthesis of polyurethane adhesive not only has high peel strength, strongability of anti-boiled, but also has high temperature resistant ability.