Patent ID: 11884846
Assignee: BASF SE
Field: Basic materials chemistry (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A pressure-sensitive adhesive composition in the form of an aqueous polymer dispersion, the pressure sensitive adhesive composition comprising:
(a) a tackifier;
(b) a compound A comprising at least two functional groups capable of undergoing a crosslinking reaction with keto groups or with aldehyde groups; and
(c) a pressure-sensitive adhesive polymer formed by emulsion polymerization from
(i) at least 60% by weight, based on a sum of the monomers, of at least one soft (meth)acrylic ester monomer having, when polymerized as a homopolymer, a glass transition temperature of less than 0° C.,
(ii) 0.1% to 10% by weight, based on the sum of the monomers, of at least one monomer having at least one acid group,
(iii) at least 5% and less than 20% by weight, based on the sum of the monomers, of styrene,
(iv) 0.3% to 5% by weight, based on the total amount of the monomers, of at least one ethylenically unsaturated compound K having at least one functional group selected from keto groups and aldehyde groups, and optionally
(v) one or more further monomers distinct from (i) to (iv),

with the exception of monomers having at least two non-conjugated polymerizable vinyl groups,
wherein the polymerization is carried out in the presence of 0 to 1 parts by weight of a chain transfer agent per 100 parts by weight of the monomers,
wherein after film formation on a substrate, the pressure-sensitive adhesive polymer has a gel content geltot of at least 80% by weight based on a polymer film produced from the pressure-sensitive adhesive polymer,
wherein the gel content geltot is at least partially based on a crosslinking of the keto or aldehyde groups of a polymer with compound A and a gel content gelK of the pressure-sensitive adhesive polymer based on crosslinking of the keto or aldehyde groups of the polymer with compound A is at least 30% by weight,
wherein the gel content in part is optionally based on covalent, irreversible crosslinking not effected by crosslinking of the keto or aldehyde groups of the polymer with compound A and a gel content gel0 of the pressure-sensitive adhesive polymer based on covalent, irreversible crosslinking not effected by crosslinking of the keto or aldehyde groups of the polymer with compound A is from 0% to not more than 50% by weight,
wherein a glass transition temperature of the polymer before crosslinking of the keto or aldehyde groups of the polymer with compound A is below 10° C., and
wherein after drying, the pressure-sensitive adhesive composition forms a film having a tack of not less than 10 N/25 mm measured as loop tack relative to a steel surface at 23° C., 50% relative humidity and at a tearoff speed of 300 mm/min.