Process for bonding hydrophobic surfaces having cationic guar-containing primer coating thereon

Abstract

The instant invention relates to primary coating compositions that comprises a cationic polysaccharide, to be applied on a hydrophobic surface before a subsequent application of a polar or water based coating composition, such a as a paint or an adhesive.

Claims

1. A process for bonding two hydrophobic surfaces, the process comprising: (E1) contacting the two surfaces at least on certain zones with a primary coating composition consisting essentially of a cationic polysaccharide, wherein the cationic polysaccharide is a cationic guar, and wherein the composition is free of ionic surfactant, whereby a coating based on said cationic polysaccharide is obtained on said zones of the surfaces, (E2) injecting an aqueous composition, wherein the aqueous composition is an adhesive, between all or part of the zones of the surfaces covered by the cationic polysaccharide, as obtained in step (E1).

2. The process according to claim 1, wherein the cationic guar has a molecular weight between 20,000 and 5,000,000 g/mol.

3. The process according to claim 1, wherein the cationic guar is guar modified by quaternary ammonium cationic groups.

4. The process according to claim 3, wherein the quaternary ammonium cationic groups are ammonium groups carrying three radicals which are identical or different and selected from the group consisting of hydrogen and alkyl radical having from 1 to 22 carbon atoms.

5. The process according to claim 4, wherein the quaternary ammonium cationic groups are trialkylammonium.

6. The process of claim 1, wherein the adhesive is a waterborne adhesive.

Description

EXAMPLE

(1) The example illustrates the effect of the deposition of the Jaguar® C162 as a primer before the coating of a paint. The paint which was used in this example is the epoxy white paint of Akzo Nobel commercialized in France under the name “Epoxy monocouche—Julien—peinture directe sur surface lisse—séchage rapide”.

(2) The primer was deposited on polyethylene surfaces (square of 2 cm×2 cm—thickness: 2 mm) and then the paint was applied on the treated polyethylene.

(3) For seek of comparison, several tests were carried out with distinct conditions for the deposition of solution S, that are summarized in the table below.

(4) In each test, the polyethylene surface was first cleaned with isopropanol by immersion during 30 minutes at 20° C., overnight dried under hood, and then rinsed with water and dried.

(5) The rinsed and dried surface of polyethylene was then immersed in the aqueous solution S at 20° C., with an immersion time indicated below, and then the surface was dried, and optionally rinsed with water as indicated in the table (when rinsed with water, the surface was then dried)

(6) As a comparison, a blank (test no. 1) was performed in the same conditions, but without any pretreatment of the polyethylene surface; and another test (no. 6) as been performed with a commercial primer (namely the DUPLI-COLOR primer commercialized by Motip Dupli, applied by a spray coating according to the recommendation of the supplier).

(7) After coating of the paint and drying overnight, the cohesion of the paint was tested by using a LUMIFRAC apparatus: a metallic plate was adhesive bonded on the backside of the sample (on the “non painted” face of the sample) and cured at 22° C., the painted surface was cleaned with ethanol (fibre free cloth) and then dried by evaporation for more 15 minutes. Then a stamp was adhesive bonded to the paint surface (with a two-component epoxy adhesive 3M Scotch Weld DP 490) and the surface with this stamp was placed in the LUMIFRAC apparatus, wherein it was submitted to an increasing centrifugation leading to an increasing traction force (linea load increase of 10 N/s), that can also be expressed as a traction strength σ on the surface of the stamp adhesive bonded to the paint, expressed in MPa. When the traction became to high, a delamination of the paint occurred, reflecting the cohesion of the paint. The table below gives the traction strength σ.sub.limit where the delamination occurred for each test (the higher σ.sub.limit, the higher the cohesion).

(8) TABLE-US-00001 TABLE conditions of each test and measured σ.sub.limit Test no.: 1 6. (Blank) 2 3 4 5 (comparative) Immersion No 15 min 60 min Spray coating of time immersion Dupli Color in solution S the treated — no yes no yes no surface is rinsed with water ? σ.sub.limit (MPa) 0.594 1.955 1.736 2.922 2.395 3.224