Compsite paper material with a pressure-sensitive adhesive coating finished to be resistant to repulping

Abstract

The invention relates to a paper composite material with repulp-resistant adhesive coating, consisting of a paper carrier and an adhesive layer, characterized in that an intermediate coat of a dispersion polymer film containing a protective colloid and/or an emulsifying agent and with a glass transition temperature Tg of −20° to 40° is applied between the paper carrier and the adhesive coating. The invention also relates to a method for the production of paper composite material with repulp-resistant adhesive coating.

1 . Composite paper material with a pressure-sensitive adhesive coating finished to be resistant to repulping, comprising a paper carrier and a layer of pressure-sensitive adhesive, characterized in that an interlayer comprising a dispersion polymer film containing a protective colloid and/or an emulsifier and having a glass transition temperature Tg from −20 20  C. to +40° C., based on homo- or copolymers from the group consisting of homo- or copolymers of vinyl esters of alkylcarboxylic acids having 1 to 15 C atoms, homo- or copolymers of esters of (meth)acrylic acid of alcohols having 1 to 12 C atoms, and styrene/butadiene copolymers, has been applied between the paper carrier and the layer of pressure-sensitive adhesive.  
     
     
         2 . Process for producing a composite paper material with a pressure-sensitive adhesive coating, finished to be resistant to repulsing, characterized in that 
 a) in a first process step for producing the interlayer, an aqueous dispersion of a homo- or copolymer, stabilized by a protective colloid and/or emulsifier and having a glass transition temperature Tg from −20° C. to +40° C., from the group consisting of homo- or copolymers of vinyl esters of alkylcarboxylic acids having 1 to 15 C atoms, homo- or copolymers of esters of (meth)acrylic acid of alcohols having 1 to 12 C atoms, and styrene/butadiene copolymers, is applied and dried, and    b) in a second process step, a pressure-sensitive adhesive composition is applied to the polymer layer from the first process step and, if appropriate, is dried.    
     
     
         3 . Material or process according to  claim 1  or  2 , characterized in that the interlayer contains vinyl acetate homopolymer, vinyl acetate/ethylene copolymers, vinyl acetate/ethylene/vinyl chloride copolymers, vinyl acetate copolymers with the vinyl ester of an alpha-branched carboxylic acid having 5 to 10 C atoms, vinyl acetate/n-butyl acrylate copolymers, copolymers of methyl methacrylate with n-butyl acrylate and/or 2-ethylhexyl acrylate, and also copolymers of n-butyl acrylate or 2-ethylhexyl acrylate with styrene, which copolymers may, if appropriate, also contain water-soluble or crosslinkable, ethylenically unsaturated monomers, and/or these polymers are employed for producing the interlayer.  
     
     
         4 . Material or process according to  claim 3 , characterized in that the homo- and copolymers contain water-soluble, ethylenically unsaturated monomers up to a proportion of 5% by weight, relative to the total weight of the polymer.  
     
     
         5 . Material or process according to  claims 1  to  4 , characterized in that 0.1 to 5% by weight, relative to polymer, of emulsifier and/or 0.1 to 15% by weight, relative to polymer, of protective colloid, preferably partially saponified polyvinyl alcohol having a degree of hydrolysis of 60 to 95 mol %, are present.  
     
     
         6 . Material or process according to  claims 1  to  5 , characterized in that the polymers for producing the interlayer also contain 0.1 to 5% by weight of one or more auxiliary monomers for crosslinking or ethylenically polyunsaturated comonomers having a crosslinking action, each relative to the total weight of the polymer, or contain 0.1 to 3.0% by weight, relative to the polymer, of comonomers containing carbonyl groups, such as diacetoneacrylamide or crotonaldehyde, in combination with crosslinking agents containing hydrazide groups or crosslinking agents containing amino-oxy groups.  
     
     
         7 . Material or process according to  claims 1  to  6 , characterized in that the pressure-sensitive adhesives employed are those based on acrylic acid ester copolymers, copolymers of acrylic acid esters with vinyl esters and, if appropriate, ethylene, copolymers of acrylic acid esters or vinyl esters with esters of maleic and fumaric acids, or styrene/butadiene block copolymers, styrene/isoprene block copolymers, with a Tg of the copolymers below −20° C., in the form of polymer dispersions, hot-melt adhesives and radiation-crosslinkable systems.  
     
     
         8 . Material or process according to  claims 1  to  7 , characterized in that the pressure-sensitive adhesive layers and/or pressure-sensitive adhesive composition employed are those containing di- or polyfunctional crosslinking agents which react with hydroxyl-, amide- or carboxyl-functional polymers.  
     
     
         9 . Process according to  claim 2 , characterized in that, in process step a), the aqueous dispersion is applied to the paper carrier by means of a blade and is dried, or is applied to a paper provided with a silicone release layer, dried and transferred to the paper carrier by lamination and, in process step b), the application of the layer of pressure-sensitive adhesive is carried out either by direct application to the interlayer, for example by means of a blade or roller application, and, if appropriate, drying or radiative crosslinking, or by coating a release material, preferably siliconized release paper, with the pressure-sensitive adhesive, if appropriate drying it or radiatively crosslinking it, and subsequently laminating it to the paper carrier provided with the interlayer.