Water-Soluble Pressure-Sensitive Adhesives Containing Carboxymethyl Starch with Improved Adhesion to Paper

摘要

Papermaking and printing operations require splicing the end of one paper roll to the beginning of another one,as well as splicing together a roll after defective material is cut out.It is important that such splices could be made quickly and easily with the aid of adhesive that rapidly attains maximum strength and retains it throughout subsequent operations.In the era where ecology and conservation are both vital concerns,it is important that the spliced portions should be returnable to the paper mill for reprocessing,thus it is essential that the splices(and in particularly the adhesive applied) should be water-dispersible and repulpable.This combination of requirements hinders using conventional adhesives such as rubber-resin pressure-sensitive ones.Water-soluble adhesives are known in the art of natural products,i.e.: dextrin,gelatine,casein or starch [1] or in the art of synthetic products,i.e.: poly(vinyl alcohol) or poly(vinyl pirroli-done) [2].However,under dry conditions this type of products lacks elasticity and viscosity,showing no pressure-sensitive adhesive properties.Additionally,the conventional water-soluble adhesives exhibit disadvantages such as little thermal strength and little resistance to ageing.The range of potentially suitable synthetic polymers is also very limited.On the one hand a large number of natural or synthesised polymers,by their nature,exhibit no adhesive properties,whilst on the other hand,the adhesive tapes industry aims to raw materials which are produced in large quantities and at low cost.It is not necessary to develop new base polymers,but rather specifically modify the polymers selected according to commercial criteria.An unusual and interesting challenge is giving to pressure-sensitive adhesive some water-solubility,which depends greatly on the hydrophilicity of the groups incorporated into the polymer chain.The most often used hydrophilic monomers for synthesis of water-soluble acrylic PSA are: acrylic acid,methacrylic acid,P-acryloy-loxypropionic acid and 2-hydroxypropyl acrylate [3-6].