Aqueous pretreatment for bonded joints with increased heat stability

Abstract

An aqueous composition including: a) at least one epoxy silane containing at least one epoxy group and at least one hydrolysable group bound to Si, b) at least one non-ionic wetting agent and either c1) between 0.2 and 2 wt. % of at least one mercapto silane containing at least one mercapto group and at least one hydrolysable group bound to Si, and as many water-soluble acids as required for the pH of resulting composition to be between 1 and 6, on the condition that epoxy silane content amounts to between 0.2 and 1 wt. %, or c2) between 0.1 and 1 wt. % of a water-soluble organotitanate, in relation to entire weight of aqueous composition, and as many water-soluble bases as required for the pH of resulting composition to be between 8 and 14, on the condition that the epoxy silane content amounts to between 0.2 and 0.5 wt. %.

Claims

1. An aqueous composition comprising a) at least one epoxysilane having at least one epoxy group and at least one Si-bonded hydrolyzable group, b) at least one nonionic wetting agent, and either c1) 0.2% to 2% by weight, based on the total weight of the aqueous composition, of at least one mercaptosilane having at least one mercapto group and at least one Si-bonded hydrolyzable group, and a sufficient amount of a water-soluble acid that the pH of the resulting composition is between 1 and 6, with the proviso that the epoxysilane is present in an amount of 0.2% to 1% by weight, based on the total weight of the aqueous composition; or c2) 0.1% to 1% by weight of a water-soluble organotitanate, based on the total weight of the aqueous composition, and a sufficient amount of the a water-soluble base that the pH of the resulting composition is between 8 and 14, with the proviso that the epoxysilane is present in an amount of 0.2% to 0.5% by weight, based on the total weight of the aqueous composition; wherein the composition is a one-component aqueous composition comprising 95-98% by weight, based on the overall composition, of water.

2. The composition as claimed in claim 1, wherein the at least one wetting agent is selected from emulsifiers and surfactants from the group of polyethers, polyethersiloxanes, pyrrolidones and modified natural oils.

3. The composition as claimed in claim 1, wherein the epoxysilane comprises glycidoxypropyltrimethoxysilane and/or glycidoxypropyltriethoxysilane.

4. The composition as claimed in claim 1, wherein the composition comprises further organosilanes or oligomers of these organosilanes that have at least one Si-bonded hydrolyzable group and have at least one further functional group selected from primary amino groups, secondary amino groups, hydroxyl groups and isocyanurate groups.

5. The composition as claimed in claim 1, wherein the composition comprises constituent c1) and the mercaptosilane comprises mercaptopropyltrimethoxysilane and/or mercaptopropyltriethoxysilane.

6. The composition as claimed in claim 1, wherein the composition comprises constituent c1) and the acid comprises a carboxylic acid.

7. The composition as claimed in claim 1, wherein the composition comprises constituent c2) and the organotitanate comprises a tetraalkoxytitanate.

8. The composition as claimed in claim 1, wherein the composition comprises constituent c2) and the base comprises a compound having at least one tertiary amine group.

9. The composition as claimed in claim 1, wherein the composition comprises 95.05-98% by weight of water and: 0.3% to 1% by weight of glycidoxypropyltrimethoxysilane, based on the total weight of the aqueous composition, 0.1% to 2% by weight of at least one wetting agent selected from polyethers, polyethersiloxanes, pyrrolidones and modified natural oils, 0.3% to 1% by weight of mercaptopropyltrimethoxysilane, based on the total weight of the aqueous composition, and 0% to 0.3% by weight of at least one amino- or isocyanuratosilane, based on the total weight of the aqueous composition, and a sufficient amount of a water-soluble acid that the pH of the resulting composition is between 2.5 and 5.

10. The composition as claimed in claim 1, wherein the composition comprises 95.05-98% by weight of water and: 0.2% to 0.4% by weight of glycidoxypropyltrimethoxysilane, based on the total weight of the aqueous composition, 0.1% to 2.5% by weight of at least one wetting agent selected from polyethers and pyrrolidones, 0.3% to 0.6% by weight of tetraalkoxytitanate, 0% to 1.5% by weight of at least one aminosilane, based on the total weight of the aqueous composition, and a sufficient amount of a water-soluble base that the pH of the resulting composition is between 9 and 11.5.

11. A method comprising applying the aqueous composition as claimed in claim 1 to a substrate as an adhesion promoter or primer.

12. The method as claimed in claim 11, wherein the substrate is a glass or glass ceramic substrate.

13. The method as claimed in claim 11, wherein the application of the aqueous composition is for direct glazing in automobile construction.

14. The method as claimed in claim 11, wherein the aqueous composition is applied together with a polyurethane adhesive.

Description

EXAMPLES

(1) The invention is elucidated further by examples which follow, but these are not intended to limit the invention in any way. Unless stated otherwise, all figures are based on weight. More particularly, the numbers in the tables for the respective compositions mean percent by weight, based on the total weight of the respective example composition.

(2) Raw Materials Used

(3) TABLE-US-00001 TABLE 1 Raw materials used. Sil A1110 3-Aminopropyltrimethoxysilane Silquest ® A1110, Momentive Performance Materials Sil A1120 N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane Silquest ® A1120, Momentive Performance Materials Sil A1170 Bis(trimethoxysilylpropyl)amine Silquest ® A1170, Momentive Performance Materials Sil A187 3-Glycidoxypropyltrimethoxysilane Silquest ® A187, Momentive Performance Materials Sil A189 3-Mercaptopropyltrimethoxysilane Silquest ® A189, Momentive Performance Materials A-Link 597 Tris(3-(trimethoxysilyl)propyl) isocyanurate Silquest ® A-Link ® 597, Momentive Performance Materials KR 44 Titanate; 2-propanolato, tris(3,6-diaza)hexanolato titanium(IV), Ken-React ® KR 44, Kenrich Petrochemicals Hydropalat Wetting agent; modified natural oil, free of silicone, Hydropalat ® 3037, Cognis, Germany Byk 349 Wetting agent; polyether-modified siloxane, BYK-349, BYK Chemie GmbH, Germany CHP Wetting agent; N-cyclohexyl-2-pyrrolidone TOU Wetting agent; 2,5,7,10-tetraoxaundecane Acetic acid Acetic acid, 99% TMG Tetramethylguanidine

(4) Production of the Compositions

(5) All compositions C1 to C10 according to tables 2 and 3 were produced in 100 mL laboratory glass bottles.

(6) Compositions C1 to C4 and C9 to C10 were produced as aqueous premix and silane premix.

(7) The aqueous premix was produced in each case by adding the wetting agent to an initial charge of water, adding acid and homogenizing by mixing. The respective silane premix was produced in a separate bottle by initially introducing the CHP wetting agent and adding the further constituents, if used, in the following sequence while stirring: Sil A189, Sil A187, Sil A1170, A-Link 597, Sil A1120, Byk 349. Subsequently, the mixture was homogenized in a laboratory shaker.

(8) The silane premix was then added to the aqueous premix while stirring within about 10 seconds. This was followed by stirring for a further two minutes and homogenizing in a laboratory shaker.

(9) The constituents of compositions C5 to C8 were added gradually to a single vessel while stirring in the sequence specified in the table. This was followed by stirring for a further two minutes and homogenizing in a laboratory shaker.

(10) TABLE-US-00002 TABLE 2 Compositions C1-C4 and C9-C10; “n/m” means that the value was not measured. Ingredients (% C1 C4 C9 C10 by wt.) (Ref.) C2 C3 (Ref.) (Ref.) (Ref.) Aque- Deionized 92.5 95.05 97.4 93.8 97.05 97.5 ous water premix Hydropalat 0.5 0.5 0.5 0.5 0.5 0.5 Acetic acid 4.4 2.0 0.2 4.4 0.2 0.4 Silane CHP 0.9 0.9 0.9 0.9 2 0.9 premix Byk 349 0.1 0.1 0.1 0.1 0.1 0.1 Sil A189 0.3 0.65 0.3 0.3 — — Sil A187 — 0.65 0.3 — — 0.3 Sil A1170 0.65 0.15 — — — — A-Link 597 — — 0.3 — — 0.3 Sil A1120 0.65 — — — 0.15 — Total 100 100 100 100 100 100 pH (of the combined 3.7 2.9 4.4 n/m n/m 4.0 premix)

(11) TABLE-US-00003 TABLE 3 Compositions C5 to C8. Ingredients (% by wt.) C5 C6 C7 C8 (Ref.) Deionized water 96.95 95.95 95.95 99.35 TOU 2 2 2 — TMG 0.4 0.4 0.4 — KR44 0.4 0.4 0.4 0.4 Sil A187 0.25 0.25 0.25 0.25 Sil A1110 — 1 — — Sil A1120 — — 1 — Total 100 100 100 100 pH 12.3 11.4 11.3 10.2

(12) Testing

(13) The aqueous compositions C1 to C8 formed were tested for the heat stability of the adhesive bonds on various substrates as adhesion promoter in combination with various adhesives. To this end, adhesive bonds that had been stored at room temperature (RT) for 7 days (d) or 90° C. for 7 to 34 days were tested by the method specified below.

(14) The adhesive used was a Sikaflex®-250, which is a commercially available one-component moisture-curing polyurethane adhesive which contains polyurethane prepolymers having isocyanate groups and is commercially available from Sika Schweiz AG.

(15) The substrates used were: “Float glass (Sn)”: float glass in which the tin side was used for adhesion testing, Rocholl, Germany; “Float glass (air)”: float glass in which the air side was used for adhesion testing, Rocholl, Germany; “VSG”: VSG ceramic, Ferro 14279, Rocholl, Germany; “ESG”: ESG ceramic, Ferro 14251, Rocholl, Germany; “Frit 3402”: ESG ceramic, Ferro AD 3402, Rocholl, Germany.

(16) All substrate faces were cleaned immediately prior to the application of the adhesion promoter compositions by wiping-off by means of a cellulose cloth (Tela®) that had been soaked with an isopropanol/water mixture (2:1) and flashed off for at least 2 minutes prior to the application of the adhesion promoter composition.

(17) The aqueous compositions were applied to the particular substrate by means of a cellulose cloth soaked therewith (Tela®, Tela-Kimberly Switzerland GmbH) and flashed off for 10 minutes (“wipe-on”). For comparative purposes, identical applications were undertaken, except with wiping-off 3 minutes after application with a dry cellulose cloth (Tela®, Tela-Kimberly Switzerland GmbH) (“wipe-on/off”). A triangular bead of the adhesive was applied by means of expression cartridge and nozzle at 23±2° C. and 50% rel. air humidity. The adhesive itself was equilibrated in a closed cartridge at 60° C. for 2 h prior to application.

(18) The cured bond with the adhesive was tested after a curing time of 7 days under controlled climatic conditions (23° C., 50% rel. air humidity) (RT), and after subsequent heat storage (90° C.) in an oven for 7 to 34 days.

(19) The adhesion of the adhesive was tested by means of the ‘bead adhesion test’. This involves cutting into the bead at its end just above the bond surface. The cut end of the bead is held with round-nose pliers and pulled away from the substrate. This is done by cautiously rolling up the bead onto the tip of the pliers, and making a cut at right angles to the bead pulling direction down to the bare substrate. The bead pulling speed should be chosen such that a cut has to be made about every 3 seconds. The test distance must correspond to at least 8 cm. What is assessed is the adhesive remaining on the substrate after the bead has been pulled away (cohesion fracture). The adhesion properties are assessed by visual determination of the cohesive fraction of the bonding area.

(20) The higher the proportion of cohesive fracture, the better the assessment of the adhesive bond. Test results with cohesion fractures of less than 70% are typically considered to be inadequate. The results are summarized in tables 4 to 9.

(21) It is clearly apparent from the results that the aqueous adhesion promoter compositions of the invention achieve good results even after prolonged heat storage, while the noninventive adhesion promoters used as a comparison show a distinct reduction in performance in the case of prolonged heat storage.

(22) TABLE-US-00004 TABLE 4 Bonding results on float glass (air). Float glass (air) RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 on 100 100 80 15 15 5 (Ref.) on/off 100 50 65 25 15 5 C2 on 100 100 100 100 100 100 on/off 100 100 100 100 100 98 C3 on 100 100 100 100 100 98 on/off 100 100 100 100 100 95 C4 (Ref.) on/off 95 80 40 5 0 0 C5 on 95 100 100 100 100 100 on/off 100 100 100 100 100 100 C6 on 100 100 100 100 100 100 on/off 100 90 100 100 100 95 C7 on 95 100 100 100 100 100 on/off 100 100 100 100 100 100 C9 (Ref.) on/off 100 100 40 60 20 0 C10 (Ref.) on/off 100 100 30 5 n/m n/m

(23) TABLE-US-00005 TABLE 5 Bonding results on float glass (Sn). Float glass (Sn) RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 (Ref.) on 100 100 85 30 35 5 on/off 100 60 20 5 5 0 C2 on 100 100 100 100 100 100 on/off 100 100 100 98 75 30 C3 on 100 100 100 100 100 100 on/off 100 98 100 98 98 95 C4 (Ref.) on/off 100 95 40 10 5 0 C5 on 75 100 100 100 100 100 on/off 80 100 100 100 100 98 C6 on 98 95 95 100 100 100 on/off 98 95 100 100 100 100 C7 on 95 100 100 95 100 98 on/off 100 100 100 100 100 100 C8 (Ref.) on 20 100 100 100 100 100 on/off 10 100 100 100 100 100

(24) TABLE-US-00006 TABLE 6 Bonding results on VSG. VSG RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 (Ref.) on 100 100 95 60 60 80 on/off 98 100 95 5 5 0 C2 on 100 100 100 100 100 100 on/off 85 100 100 90 90 50 C3 on 100 100 100 100 100 100 on/off 70 100 95 95 85 70 C4 (Ref.) on/off 10 n/m n/m n/m n/m n/m C5 on 50 100 100 95 98 95 on/off 95 100 100 95 98 40 C6 on 100 100 100 100 100 65 on/off 100 100 100 100 100 65 C7 on 90 100 100 95 85 50 on/off 100 100 100 100 75 40 C8 (Ref.) on 20 n/m n/m n/m n/m n/m on/off 30 n/m n/m n/m n/m n/m C9 (Ref.) on/off 5 n/m n/m n/m n/m n/m

(25) TABLE-US-00007 TABLE 7 Bonding results on ESG. ESG RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 (Ref.) on 100 100 100 45 85 5 on/off 100 100 90 30 10 5 C2 on 100 100 100 100 100 100 on/off 90 100 100 100 100 100 C3 on 100 100 100 100 100 100 on/off 80 100 100 100 100 100 C4 (Ref.) on/off 0 n/m n/m n/m n/m n/m C5 on 80 100 100 100 100 100 on/off 98 100 100 100 100 100 C6 on 100 100 100 100 90 95 on/off 100 100 100 100 95 98 C7 on 100 100 100 100 100 100 on/off 100 100 100 100 100 100

(26) TABLE-US-00008 TABLE 8 Bonding results on Frit 3402. Frit 3402 RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 (Ref.) on 100 100 100 100 100 100 on/off 100 100 100 100 95 80 C2 on 100 100 100 100 100 100 on/off 98 100 100 100 100 98 C3 on 100 100 100 100 100 100 on/off 85 100 100 100 98 90 C4 (Ref.) on/off 25 n/m n/m n/m n/m n/m C5 on 100 100 100 100 100 100 on/off 98 100 100 100 100 95 C6 on 100 100 100 100 100 100 on/off 100 100 100 100 90 80 C7 on 100 100 100 100 100 95 on/off 100 100 100 100 100 95

(27) TABLE-US-00009 TABLE 9 Bonding results on all substrates (average). Average RT (d) 90° C. (d) Pretreatment wipe 7 7 14 21 28 34 C1 (Ref.) on 100 100 92 50 59 39 on/off 99.6 82 74 33 26 18 C2 on 100 100 100 100 100 100 on/off 94.6 100 100 97.6 93 75.2 C3 on 100 100 100 100 100 99.6 on/off 87 99.6 99 98.6 96.2 89 C5 on 80 100 100 99 99.6 99 on/off 94.2 100 100 99 99.6 86.6 C6 on 99.6 99 99 100 98 92 on/off 99.6 97 100 100 97 87.6 C7 on 97 100 100 98 97 81.6 on/off 100 100 100 100 82 77