Processes for producing viscous epoxy syrups and epoxy syrups obtainable thereby

Abstract

A process for producing a viscous epoxy syrup from at least one liquid multifunctional epoxy, comprising the steps of: adding an initiator selected from the group consisting of electron-poor monoisocyanate, photoinitiator and thermal initiator to at least one liquid multifunctional epoxy; mixing the components; polymerizing the multifunctional epoxy such that the viscosity of the resulting epoxy syrup is at least twice as high, preferably at least four times as high and in particular at least ten times as high as the viscosity of the employed epoxy in the unreacted state makes it possible to produce epoxy adhesives having pressure-sensitive properties.

1 - 21 . (canceled) 
     
     
         22 . Epoxy adhesive obtained by a process comprising:
 providing an at least one liquid multifunctional epoxy;   adding to the at least one liquid multifunctional epoxy an initiator selected from the group consisting of an electron-poor monoisocyanate, a photoinitiator, and a thermal initiator;   mixing the at least one liquid multifunctional epoxy and the initiator;   cationically polymerizing the at least one liquid multifunctional epoxy, thereby forming an epoxy syrup comprising an at least one uncrosslinked polyepoxy; and   mixing the epoxy syrup with further components to form an epoxy adhesive,   
       wherein:
 a viscosity of the epoxy syrup is at least twice as high as a viscosity of the at least one liquid multifunctional epoxy before the addition of the initiator; and 
 the cationic polymerization is stopped upon reaching a desired viscosity by the addition of an initiator scavenger. 
 
     
     
         23 . Epoxy adhesive according to  claim 22 , wherein the at least one liquid multifunctional epoxy is a bisepoxy. 
     
     
         24 . Epoxy adhesive according to  claim 22 , wherein the at least one liquid multifunctional epoxy is a bisepoxycyclohexyl derivative or a bisepoxy based on bisphenol A, bisphenol S, or bisphenol F. 
     
     
         25 . Epoxy adhesive according to  claim 22 , wherein:
 the initiator is selected from the group consisting of a photoinitiator and a thermal initiator; and   the initiator is present in an amount of not more than 0.1 wt %.   
     
     
         26 . Epoxy adhesive according to  claim 22 , wherein:
 the initiator is an electron-poor monoisocyanate; and   the initiator is present in an amount of not more than 10 wt %.   
     
     
         27 . Epoxy adhesive according to  claim 26 , wherein the initiator is selected from the group consisting of a p-tolyl isocyanate, an o-tolyl isocyanate, and a sulphonyl isocyanate. 
     
     
         28 . Epoxy adhesive according to  claim 26 , wherein the process is carried out at a temperature between 20° C. and 120° C. 
     
     
         29 . Epoxy adhesive according to  claim 22 , wherein the initiator scavenger comprises a mixture of water and acetone, a solution comprising an alkali metal hydroxide, a solution comprising an alkaline earth metal hydroxide, a solution comprising an alkali metal hydroxide, or a solution comprising an alkaline earth metal alkoxide. 
     
     
         30 . Epoxy adhesive according to  claim 22 , wherein the epoxy syrup has a polydispersity D of at least 3. 
     
     
         31 . Epoxy adhesive according to  claim 22 , wherein:
 the at least one liquid multifunctional epoxy is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate; and   the viscosity of the epoxy syrup is at least 1 Pa s (1000 mPs).   
     
     
         32 . Adhesive tape comprising an epoxy adhesive according to  claim 22 . 
     
     
         33 . Epoxy adhesive according to  claim 22 , wherein:
 the at least one liquid multifunctional epoxy comprises a plurality of original epoxy groups; and   at least 65% of the plurality of original epoxy groups are present in the epoxy syrup.   
     
     
         34 . Epoxy adhesive according to  claim 22 , wherein the viscosity of the epoxy syrup is at least 10 Pa s. 
     
     
         35 . Epoxy adhesive according to  claim 22 , wherein the epoxy syrup has a weight-average molecular weight Mw in the range of 5,100 to 78,400 g/mol. 
     
     
         36 . Epoxy adhesive according to  claim 22 , wherein the at least one uncrosslinked polyepoxy has a molecular weight of from 2,000 to 300,000 g/mol. 
     
     
         37 . Viscous epoxy syrup comprising an at least one multifunctional epoxy monomer and an at least one uncrosslinked multifunctional polyepoxy prepared from the at least one multifunctional polyepoxy monomer by cationic polymerization, wherein:
 a viscosity of the viscous epoxy syrup is at least twice as high as a viscosity of a syrup of the at least one multifunctional epoxy monomer; and   the cationic polymerization was stopped upon reaching a desired viscosity.   
     
     
         38 . The viscous epoxy syrup according to  claim 37 , wherein the viscosity of the viscous epoxy syrup is at least 10 Pa s. 
     
     
         39 . The viscous epoxy syrup according to  claim 37 , wherein the viscous epoxy syrup has a weight-average molecular weight Mw in the range of 5,100 to 78,400 g/mol. 
     
     
         40 . The viscous epoxy syrup according to  claim 37 , wherein the at least one uncrosslinked multifunctional polyepoxy has a molecular weight of from 2,000 to 300,000 g/mol. 
     
     
         41 . Process for producing an epoxy adhesive comprising:
 providing an at least one liquid multifunctional epoxy;   adding to the at least one liquid multifunctional epoxy an initiator selected from the group consisting of an electron-poor monoisocyanate, a photoinitiator, and a thermal initiator;   mixing the at least one liquid multifunctional epoxy and the initiator;   cationically polymerizing the at least one liquid multifunctional epoxy, thereby forming an epoxy syrup comprising an at least one uncrosslinked polyepoxy; and   mixing the epoxy syrup with further components to form an epoxy adhesive,   
       wherein:
 a viscosity of the epoxy syrup is at least twice as high as a viscosity of the at least one liquid multifunctional epoxy before the addition of the initiator; and 
 
       the cationic polymerization is stopped upon reaching a desired viscosity by the reduction of the temperature at which the epoxy syrup is formed.