Method for producing adhesive strips for assembly, especially formed with three layers and based on thermally cross-linked, viscoelastic acrylate hot-melt adhesives
View Patent ↗A method of producing an adhesive tape having at least one carrier layer and two outer adhesive layers, wherein the carrier layer is from 300 μm to 5000 μm thick and is composed of a photoinitiator-free homogeneously thermally crosslinked polymer based on acrylate and/or methacrylate, in which at least one trimerized isocyanate crosslinker is added in the melt to a polyacrylate copolymer having primary hydroxyl groups and based on acrylic esters and/or methacrylic ester, a layer of the polyacrylate together with the crosslinker is conveyed to a coating unit, where pressure-sensitive adhesive layers are laminated onto both sides of the not-yet fully-crosslinked polyacrylate layer, and the crosslinking of the polyacrylate leads to a homogeneously crosslinked carrier layer.
1. A method of producing an adhesive tape having at least one carrier layer and two outer adhesive layers, wherein the carrier layer is from 300 μm to 5000 μm thick and is composed of a photoinitiator-free homogeneously thermally crosslinked polymer based on acrylate and/or methacrylate, in which at least one trimerized isocyanate crosslinker is added in the melt to a polyacrylate copolymer having primary hydroxyl groups and based on acrylic esters and/or methacrylic esters, a layer of the polyacrylate together with the crosslinker is conveyed to a coating unit, where pressure-sensitive adhesive layers are laminated onto both sides of the not-yet fully-crosslinked polyacrylate layer and the crosslinking of the polyacrylate leads to a homogeneously crosslinked carrier layer.
2. The method of claim 1 , wherein at least one of the layers is an adhesive layer having hydroxyl functionalities which react with isocyanate groups in the carrier layer.
3. The method of claim 1 , wherein at least one of the layers is a barrier layer on whose reverse face, in turn, adhesives have been coated.
4. The method of claim 1 , wherein the at least one layer has been physically pretreated.
5. The method of claim 1 , wherein the at least one trimerized isocyanate crosslinker is added in an extruder.
6. The method of claim 1 , wherein the temperature of the polyacrylate when the trimerized isocyanate crosslinker is added is between 60° C. and 120° C.
7. The method of claim 1 , wherein the residual monomer content of the polyacrylate when the crosslinker is added is not more than 1% by weight.
8. The method of claim 1 , wherein the primary hydroxyl groups of the polyacrylate are introduced by way of the (meth)acrylic esters, and the fraction of the acrylic esters and/or methacrylic esters containing hydroxyl groups is up to 25% by weight, based on the polyacrylate.
9. The method of claim 1 , wherein the polyacrylate is the product of following reactant mixture:
a1) 65% to 99% by weight of acrylic esters and/or methacrylic esters of the formula
CH 2 ═C(R I )(COOR II )
where R I ═H or CH 3 and R II is an alkyl chain having 1 to 20 carbon atoms,
a2) 1% to 20% by weight acrylates and/or methacrylates whose alcohol component contains at least one primary hydroxyl group, and/or vinyl compounds which are copolymerizable with acrylates and contain at least one primary hydroxyl group, and
a3) if the fractions of a1) and a2) do not add up to 100% by weight, 0% to 15% by weight olefinically unsaturated copolymerizable monomers containing functional groups.
10. The method of claim 4 , wherein said physical pretreatment is corona treatment.
11. The method of claim 1 , wherein said at least one trimerized isocyanate is at least one aliphatic and/or amine-deactivated isocyanate.
12. The method of claim 6 , wherein said temperature is between 70° C. and 100° C.