Pressure sensitive adhesive and its preparation
View Patent ↗A pressure sensitive adhesive composed of a mixture comprising a) a styrene block copolymer having a star-shaped structure and a molecular weight M w of more than 300,000 g/mol, or having elastomer blocks which contain more than 30% by weight of 1,2-linked diene in their block structure, or both, and which is crosslinkable by exposure to UV-light or electron beams, and b) one or more block copolymers composed of vinylaromatic blocks and elastomer blocks, the block polyvinylaromatic content being greater than 20%, and c) one or more tackifier resins.
1. A double-sided stretchable pressure sensitive adhesive sheet strip, which, when bonded to a substrate is detachable from said substrate by stretching, said pressure sensitive adhesive sheet strip being formed from a composition comprising a mixture of:
a) a styrene block copolymer having a star-shaped structure and a molecular weight Mw of more than 300,000 g/mol, or having elastomer blocks which contain more than 30% by weight of 1,2-linked diene in their block structure, and which is crosslinkable by exposure to UV-light or electron beams, and
b) one or more block copolymers having polyvinylaromatic blocks and elastomer blocks, the polyvinylaromatic block content being greater than 20% by weight, and
c) one or more tackifier resins.
2. A single-sided stretchable pressure sensitive adhesive sheet strip, the side opposite the adhesive side being neutralized, which, when bonded to a substrate is detachable from said substrate by stretching, said pressure sensitive adhesive sheet strip being formed from a composition comprising a mixture of:
a) a styrene block copolymer having a star-shaped structure and a molecular weight Mw of more than 300,000 g/mol, or having elastomer blocks which contain more than 30% by weight of 1,2-linked diene in their block structure, and which is crosslinkable by exposure to UV-light or electron beams, and
b) one or more block copolymers having polyvinylaromatic blocks and elastomer blocks, the polyvinylaromatic block content being greater than 20% by weight, and
c) one or more tackifier resins.
3. The adhesive as claimed in claim 1 or 2 , wherein the block copolymers according to 1 b) have polystyrene end blocks.
4. The adhesive as claimed in claim 1 or 2 , wherein the block copolymers have a polyvinylaromatics fraction of from 20 to 40% by weight, and/or a triblock content of more than 60% by weight, or both.
5. The adhesive as claimed in claim 4 , wherein said polyvinylaromatic fraction is from 25% to 35% by weight.
6. The adhesive as claimed in claim 4 , wherein said triblock content is more than 75% by weight.
7. The adhesive as claimed in claim 1 or 2 , wherein the styrene block copolymer according to 1 a) comprises 1,2-linked polybutadiene or polyisoprene.
8. The adhesive as claimed in claim 1 or 2 , wherein the styrene block copolymer is formed of styrene-butadiene block copolymer or styrene-isoprene block copolymer.
9. The adhesive as claimed in claim 1 or 2 , wherein the styrene block copolymer has polydiene-containing elastomer blocks.
10. The adhesive as claimed in claim 9 , wherein said polydiene-containing elastomer blocks are copolymers of two or more different 1,3-dienes.
11. The adhesive as claimed in claim 1 or 2 , wherein the styrene block copolymer is functionalized.
12. The adhesive as claimed in claim 11 , wherein said styrene block copolymer is functionalized by being maleic anhydride-modifid or silane-modified.
13. The adhesive as claimed in claim 1 or 2 , comprising 20 to 70% by weight of styrene block copolymer, based on the weight of the adhesive.
14. The adhesive as claimed in claim 13 , wherein said amount of styrene block copolymer is 30 to 60% by weight.
15. The adhesive as claimed in claim 14 , wherein said amount of styrene block copolymer is 35 to 55% by weight.
16. The adhesive as claimed in claim 1 or 2 , further comprising blend components selected from the group consisting of plasticizers, aging inhibitors, processing assistants, fillers, dyes, optical brighteners, and stabilizers.
17. The adhesive as claimed in claim 1 or 2 , further comprising crosslinking promoters.
18. A method for producing a pressure sensitive adhesive sheet strip for providing a bond which can be parted again by stretching in the direction of the bond plane, which comprises applying the pressure sensitive adhesive of claim 1 or 3 to an elastically-stretchable backing.
19. A process for preparing the pressure sensitive adhesive for the pressure sensitive adhesive sheet strips according to claims 1 and 2 , which comprises mixing
(i) a styrene block copolymer having a star-shaped structure and a molecular weight M w of more than 300,000 g/mol, or having elastomer blocks containing more than 30% of 1,2-linked diene in the elastomer block structure, or both, and which is crosslinkable by exposure to UV-light or electron beams, and
(ii) one or more block copolymers composed of polyvinylaromatic blocks and elastomer blocks, the polyvinylaromatic block content being greater than 20%, and
(iii) one or more tackifier resins with elastomer blocks, and exposing the mixture to UV-light or electron beams.