PROCESS FOR MODIFYING THE SURFACE POLARITY OF RUBBER SUBSTRATES

Abstract

The present invention relates to a process for modifying the surface polarity of elastomeric rubber substrates to facilitate their cold bonding to other rubber substrates or non-elastomeric substrates of a different material, preferably metal, by chlorinating the elastomeric rubber substrate surface by treatment with a chloride-containing composition and a peroxymonosulfate-containing composition. Further aspects relate to the thus-obtained surface-modified rubber substrates, processes of bonding them to other substrates by use of an adhesive, as well as the thus-obtained bonded substrates.

Claims

1. A process of modifying a surface of an elastomeric rubber substrate, comprising steps of: (a) applying a first composition and a second composition to an elastomeric rubber substrate surface, wherein the first composition is an aqueous composition comprising chloride (CO, and the second composition is an aqueous composition comprising peroxymonosulfate; (b) optionally applying a third composition comprising activated carbon; and (c) incubating the first and second compositions, and the third composition if present, on the elastomeric rubber substrate surface for a time period and under conditions producing chlorination of the elastomeric rubber substrate surface.

2. The process according to claim 1, wherein the first composition is an aqueous 1M to 6M sodium chloride solution.

3. The process according to claim 2, wherein the second composition is an aqueous 10M to 30M persulfate solution.

4. The process according to claim 3, wherein the first and second composition are applied in a weight ratio of about 3:1 to 1:3.

5. The process according to claim 4, wherein the first and/or second and/or third composition is applied to the elastomeric rubber substrate surface in an amount that ranges from 500 to 900 g/m.sup.2.

6. The process according to claim 1, wherein step (c) is carried out for 5 to 60 minutes.

7. The process according to claim 1, further comprising a step of cleaning the substrate surface after step (c).

8. The process according to claim 1, wherein the first composition further comprises a hydroxide.

9. The process according to claim 8, wherein the first composition contains the hydroxide in a concentration of 0.5 M to 3 M.

10. The process according to claim 9, wherein the hydroxide comprises sodium and/or potassium hydroxide.

11. The process according to claim 1, wherein the first composition is an aqueous solution of sodium chloride and the second composition is an aqueous solution of potassium monopersulfate.

12. The process according to claim 11, wherein the first composition is present in a concentration of 1M to 6M and the second composition is present in a concentration of 10M to 30M.

13. An elastomeric rubber substrate having a surface modified by the process of claim 1.

14. A process of forming a bond between a first substrate and a second substrate, wherein the first substrate comprises an elastomeric rubber substrate having a chlorinated surface made according to the process of claim 1 and the second substrate is a rubber or metal substrate, wherein the process comprises: (a) applying an adhesive composition to a to-be-bonded surface of the second substrate; (b) contacting the chlorinated surface of the first substrate and the to-be-bonded surface of the second substrate with the applied adhesive under pressure thereby forming the bond.

15. The process according to claim 14, further comprising a step of cleaning the rubber and/or metal substrate surfaces prior to steps (a) and/or (b).

16. The process according to claim 14, wherein step (b) is carried out at a temperature of 15 to 30° C. and a relative humidity of 85% or less.

17. The process according to claim 14, wherein step (b) is carried out by rolling.

18. The process according to claim 14, wherein the adhesive composition is a 2K epoxy, polyurea, silicone or polyurethane adhesive comprising a resin formulation and a hardener formulation.

19. A bonded product made according to the process of claim 14.

Description

EXAMPLES

Example 1

[0076] First Composition:

[0077] 27 wt.-% sodium chloride, 73 wt.-% deionized water.

[0078] Second Composition:

[0079] 70 wt.-% potassium peroxymonosulfate (KHSO.sub.5), 30 wt.-% deionized water.

[0080] Mix ratio of first composition and second composition was 1:1 by weight.

[0081] Third Composition:

[0082] 100 wt.-% active carbon (flakes)

2K Polyurea Adhesive

[0083] Hardener Formulation:

[0084] 100 wt.-% Ethacure 420 (hindered secondary amine curing agent; Albemarle (US))

[0085] Resin Formulation:

[0086] 100 wt.-% Desmodur N3900 (aliphatic polyisocyanate; Covestro, DE)

[0087] Hardener and resin were mixed in a ratio of 1:1.3 by weight.

Preparation

[0088] Sodium chloride and water were shaken until sodium chloride was completely dissolved. Potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was well wetted.

Process:

[0089] (1) The substrates (mild steel, SBR, NR) to be bonded were well cleaned to remove dirt, oil and grease by use of Loctite 7063 (Henkel, DE); [0090] (2) The metal substrates were sandblasted and again cleaned with Loctite 7063; [0091] (3) The second composition containing the peroxymonosulfate was applied to the rubber surface by a plastic spatula; [0092] (4) The rubber was covered with a cloth, the active carbon was applied thereon, followed by the first composition, the surface was covered by a plastic foil and let react for 15 minutes; [0093] (5) The cloth and the foil were removed, the surface washed with water and cleaned with a cloth; [0094] (6) The resin and hardener component of the adhesive were mixed by hand and applied as one single coat on the metal surface for roll peel specimens or the rubber surface for T peel specimens; and [0095] (7) The roll peel specimens (rubber to metal substrates) and T peel specimens (rubber to rubber substrates) were assembled by rolling (20° C., relative humidity <85%.

Testing:

[0096] Floating Roll Peel Resistance, relative peel resistance of adhesive bonds between one rigid adherend and one flexible adherend, was tested per ASTM D 3167-03.

[0097] Adhesive Peel Strength Testing, peel separation strength of two flexible materials that have been bonded together, T-peel strength was tested per ASTM D1876.

TABLE-US-00001 TABLE 1 Example 1 Test Results Test Result Roll Peel with SBR after 3 days at room 18N/mm temperature (ASTM D 3167-03) Roll Peel with NR after 3 days at room 14N/mm temperature (ASTM D 3167-03) T Peel with SBR after 3 days at room 10N/mm temperature (ASTM D1876) T Peel with NR after 3 days at room 13N/mm temperature (ASTM D1876)

Example 2

[0098] First Composition:

[0099] 27 wt.-% sodium chloride, 73 wt.-% deionized water.

[0100] Second Composition:

[0101] 70 wt.-% potassium peroxymonosulfate (KHSO.sub.5), 30 wt.-% deionized water.

[0102] Mix ratio first and second composition 1:1 by weight.

[0103] Third Composition:

[0104] 100 wt.-% active carbon (flakes)

2K Epoxy Adhesive

[0105] Resin Formulation:

[0106] 99 wt.-% DER 356 P (Bisphenol-A/F based epoxy resin, Dow), 0.01 wt.-% Defoamer 1244 (Antifoaming agent, Solutia); 0.99 wt.-% Silane A187 (Epoxy silane, Momentive)

[0107] Hardener Formulation:

[0108] 95.99 wt.-% Ancamine 1922A (Evonik), 3.00 wt.-% fumed silica, 1.00 wt.-% tris(dimethylaminomethyl)phenol, 0.01 wt.-% (Antifoaming agent, Solutia)

[0109] Hardener and resin were mixed in a ratio of 31:100 by weight.

Preparation:

[0110] Sodium chloride and water were shaken until sodium chloride was completely dissolved. Potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was well wetted. DER356, defoamer and epoxy silane were dispersed under dynamic vacuum until homogeneous mixture with a high speed dispenser. Ancamine 1922A, fumed silica, tris(dimethylaminomethyl)phenol and defoamer were dispersed under dynamic vacuum until homogeneous mixture with a high speed dispenser.

Process:

[0111] (1) The substrates (mild steel, SBR, NR) to be bonded were well cleaned to remove dirt, oil and grease by use of Loctite 7063 (Henkel, DE); [0112] (2) The metal substrates were sandblasted and again cleaned with Loctite 7063; [0113] (3) The second composition containing the peroxymonosulfate was applied to the rubber surface by a plastic spatula; [0114] (4) The rubber was covered with a cloth, the active carbon was applied thereon, followed by the first composition, the surface was then covered by a plastic foil and reacted for 15 minutes; [0115] (5) The cloth and the foil were removed, the surface washed with water and cleaned with a cloth; [0116] (6) The resin and hardener component of the adhesive were mixed by hand and applied as one single coat on the metal surface for roll peel specimens or on the rubber surface for T peel specimens; [0117] (7) The roll peel specimens (rubber to metal substrates) and T peel specimens (rubber to rubber substrates) were assembled by rolling (20° C., relative humidity <85%.

Testing:

[0118] Testing was performed as described for Example 1.

TABLE-US-00002 TABLE 2 Example 2 Test Results Test Result Roll Peel with SBR after 3 days at room 19N/mm temperature (ASTM D 3167-03) Roll Peel with NR after 3 days at room 10N/mm temperature (ASTM D 3167-03) T Peel with SBR after 3 days at room 13N/mm temperature (ASTM D1876) T Peel with NR after 3 days at room 14N/mm temperature (ASTM D1876)

Example 3

[0119] First Composition:

[0120] 21 wt.-% sodium chloride, 8 wt.-% sodium hydroxide, 71 wt.-% deionized water.

[0121] Second Composition:

[0122] 70 wt.-% potassium peroxymonosulfate (KHSO.sub.5), 30 wt.-% deionized water.

[0123] Mix ratio first and second composition 1:1 by weight.

2K Silicone Adhesive

[0124] Hardener Formulation:

[0125] LOCTITE SI 5610 B

[0126] Resin Formulation:

[0127] LOCTITE SI 5610 A

[0128] Hardener and resin were mixed in a volume ratio of 1:2.

Preparation

[0129] Sodium chloride, sodium hydroxide and water were shaken until sodium chloride was completely dissolved. Potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was well wetted.

[0130] Process: [0131] (1) The substrates (mild steel, SBR, NR) to be bonded were well cleaned to remove dirt, oil and grease by use of Loctite 7063 (Henkel, DE); [0132] (2) The metal substrates were sandblasted and again cleaned with Loctite 7063; [0133] (3) The second composition containing the peroxymonosulfate was applied to the rubber surface by a plastic spatula; [0134] (4) The rubber was covered with a cloth and the first composition was applied and let react for 15 minutes; [0135] (5) The cloth was removed, the surface washed with water and cleaned with a cloth; [0136] (6) The resin and hardener component of the adhesive were applied by pneumatic gun as one single coat on the metal surface for roll peel specimens or the rubber surface for T peel specimens; [0137] (7) The roll peel specimens (rubber to metal substrates) and T peel specimens (rubber to rubber substrates) were assembled by rolling (20° C., relative humidity <85%).

Testing:

[0138] Testing was performed as described for Example 1.

TABLE-US-00003 TABLE 3 Example 3 Test Results Test Result Roll Peel with SBR after 3 days at room 4N/mm temperature (ASTM D 3167-03) T Peel with SBR after 3 days at room 5N/mm temperature (ASTM D1876)