Pressure-Sensitive Adhesives with High Molar Masses and Narrow Molar Mass Distribution and Process for Preparing them

• US 20130165606A1
• Filed: 12/19/2012
• Published: 06/27/2013
• Est. Priority Date: 12/21/2011
• Status: Active Grant

• Current Assignee: Tesa SE (maxingvest GmbH & Co. KGaA)
• Original Assignee: Tesa SE (maxingvest GmbH & Co. KGaA)
• Inventors: Prenzel, Alexander
• Granted Patent: US 8,846,833 B2
• Time in Patent Office: Days
• US Class Current: 526/89
• CPC Class Codes: C08F 2438/03 Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]
• CPC Class Codes: C08F 293/00 Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule on to polymers modified by introduction of unsaturated end groups C08F290/02
• CPC Class Codes: C09J 133/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof
• CPC Class Codes: C09J 133/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C09J 133/10 Homopolymers or copolymers of methacrylic acid esters
• CPC Class Codes: C09J 141/00 Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a bond to sulfur or by a heterocyclic ring containing sulfur; Adhesives based on derivatives of such polymers

Abstract

The invention relates to a process for preparing pressure-sensitive adhesives (PSAs) which have high molar masses in combination with a narrow molar mass distribution, and also to PSAs, especially polyacrylate-based PSAs, prepared accordingly.

It has been found that, surprisingly, polymers with high molar masses and a narrow molar mass distribution, more particularly polyacrylates with high molar masses and a narrow molar mass distribution, can be prepared outstandingly in particular by means of RAFT processes in the presence of a diradical initiator which undergoes thermal cyclization to form a diradical, these polymers being suitable for use as high-shear-strength PSAs.

Claims

1. A process for preparing pressure-sensitive adhesives, by carrying out a controlled radical polymerization reaction of an initial reaction charge, comprising one or more monomers in the presence of at least one radical initiator for preparing at least one polymer, characterized in that use is made as radical initiator of at least one cyclic 1,4-diradical which is generated by means of a cyclization reaction from a compound which has at least two unsaturated C—

C bonds (“

diradical-forming compound”

), the polymerization reaction being carried out in the presence of at least one chain transfer agent (“

polymerization regulator”

).

2. Process according to claim 1 wherein the compounds from which the cyclic 1,4-diradicals are generated are selected from the group consisting of endiynes, eneyneallenes, enediallenes, eneynecumulenes, eneallenecumulenes and cyclic diynes.

3. Process according to claim 2, wherein the compounds for generating the diradicals are selected from the following compounds

4. Process according to claim 1 further comprising a chain transfer agent of at least one compound having at least one functional group S—

C═

X, where X═

S, O or N.

5. Process according to claim 4, wherein the chain transfer agent is selected from the group consisting of dithioesters, dithiocarbonates, dithiocarbamates, trithiocarbonates, imidodithiocarbonates and xanthates (“

RAFT chain transfer agents”

).

6. Process according to claim 1 wherein the initial reaction charge comprises at least one acrylate-based monomer.

7. Process according to claim 1 wherein the ratio V of the amount-of-substance n_I of the diradical-forming compound to the amount-of-substance n_R of the chain transfer agent (“

polymerization regulator”

) is in the range of 2≦

V≦

64.

8. Process according to claim 1 wherein the acrylate-based polymers obtained are used as adhesives or are further-processed to adhesives.

9. Process according to claim 8 wherein the adhesives are pressure-sensitive adhesives.

13. Pressure-sensitive adhesive made according to the process of claim 1.

10. Pressure-sensitive adhesive comprising a base polymer component which base polymer component comprises at least one polymer having a weight-average molar mass of M_w≧

450 000 g/mol, a polydispersity of PD≦

5, characterized in that the polymer in question includes a cyclic structural element in the polymer backbone.

11. Pressure-sensitive adhesive according to claim 10, wherein

the cyclic structural element is an element from the group encompassing

five-membered rings,

aromatic six-membered rings,

fused aromatic systems,

heterosubstituted bicyclo[4.4.0]decadienes with a conjugated π

-system which extends over the bridging bond, more particularly 4,9-heterosubstituted bicyclo[4.4.0]deca-1,6-diene.

12. Pressure-sensitive adhesives according to claim 10 wherein the at least one polymer comprising cyclic structural elements in the polymer chains also has at least one group S—

C═

X, where X═

S, O and/or N.