US-20260125587-A1 - PROCESS FOR PRODUCING A STORAGE-STABLE ACTIVATOR FOR GLASS AND CERAMIC SUBSTRATES

US20260125587A1US 20260125587 A1US20260125587 A1US 20260125587A1US-20260125587-A1

Abstract

The invention relates to a process for preparing an adhesion-promoting pre-treatment composition, comprising the steps: a) providing a reaction vessel containing 100 parts by weight of an alcohol having 1 to 4 carbon atoms; b) adding at least one organosilane OS in an amount that between 0.15 and 0.8 parts by weight of silicon are added and optionally adding at least one organoitianate OT in an amount that between 0.01 and 0.8 parts by weight of titanium are added and optionally adding at least one organozirconate OZ in an amount that between 0.01 and 0.8 parts by weight of zirconium are added; c) adding an acid A in an amount that the resulting pH is between 3.5 and 7; d) adding water, wherein the amount of water added is at least equimolar to or in a molar excess to the molar amount of hydrolyzable silicon-, titanium-, and or zirconium-bound groups present in all added organosilane OS, organoitianate OT, and organozirconate OZ, wherein the amount of water is at most 25 parts per weight; e) optionally, adding further additives selected from colorants, UV markers, condensation catalysts, or stabilizers; f) waiting, optionally under stirring, shaking, and/or heating, until all hydrolyzable groups present in all added organosilane OS, organoitianate OT, and organozirconate OZ are hydrolyzed. The process yields a highly storage-stable adhesion-promoting pre-treatment composition that is useful for automotive glass replacement operations regardless of the ambient climate and enables long-lasting adhesive bonds with improved water stability.

Inventors

Michael Schlumpf
Nicole KUBE

Assignees

SIKA TECHNOLOGY AG

Dates

Publication Date: 20260507
Application Date: 20230816
Priority Date: 20220906

Claims (15)

1 . A process for preparing an adhesion-promoting pre-treatment composition, comprising the steps: a) providing a reaction vessel containing 100 parts by weight of an alcohol having 1 to 4 carbon atoms; b) adding at least one organosilane in an amount that between 0.15 and 0.8 parts by weight of silicon are added and adding at least one organoitianate in an amount that between 0.01 and 0.8 parts by weight of titanium are added and adding at least one organozirconate in an amount that between 0.01 and 0.8 parts by weight of zirconium are added; c) adding an acid in an amount that the resulting pH is between 3.5 and 7; d) adding water, wherein the amount of water added is at least equimolar to or in a molar excess to the molar amount of hydrolyzable silicon-, titanium-, and or zirconium-bound groups present in all added organosilane, organoitianate, and organozirconate, wherein the amount of water is at most 25 parts per weight; e) adding further additives selected from colorants, UV markers, condensation catalysts, or stabilizers; f) waiting, under stirring, shaking, and/or heating, until all hydrolyzable groups present in all added organosilane, organoitianate, and organozirconate are hydrolyzed.
2 . The process as claimed in claim 1 , wherein the acid in step c) is a carboxylic acid or an alkylsulfonic acid.
3 . The process as claimed in claim 1 , wherein organosilane comprises at least one organosilane or condensate thereof that has at least one Si-bonded hydrolyzable group and has at least one primary and/or secondary amino group.
4 . The process as claimed in claim 1 , wherein organosilane comprises organosilanes or oligomers of these organosilanes that have at least one Si-bonded hydrolyzable group and have at least one further functional group bound to the Silicon atom via at least one carbon atom and optionally ether oxygen or nitrogen atoms, the functional group selected from alkyl groups, alkylene groups, phenyl groups, epoxy groups, mercapto groups, hydroxyl groups, (meth)acrylate groups, isocyanate groups, anhydride groups, silane groups, and isocyanurate groups.
5 . The process as claimed in claim 1 , wherein organotitanate is a tetraalkoxytitanate.
6 . The process as claimed in claim 1 , wherein organozirconate is a tetraalkoxyzirconate.
7 . The process as claimed in claim 1 , wherein the alcohol having 1 to 4 carbon atoms is ethanol.
8 . The process as claimed in claim 1 , wherein acid is added in step c) in an amount that the resulting pH is between 4 and 6.5.
9 . The process as claimed in claim 1 , wherein the amount of water added in step d) is between 0.3% and 15% by weight, based on the total composition after step d).
10 . The process as claimed in claim 1 , wherein in step e), a silane condensation catalyst is added.
11 . The process as claimed in claim 1 , wherein the composition after step e) comprises, based on the total composition: between 80% and 95% by weight of the alcohol; between 1% and 3.5% by weight of organosilane; between 1% and 3.5% by weight of organotitanate; between 0.3% and 2% by weight of acid; between 0.3% and 15% by weight of water; and between 0.01% and 0.2% of a silane condensation catalyst; wherein organosilane and organotitanate may be partially or fully hydrolyzed by the water in the composition.
12 . An adhesion-promoting pre-treatment composition obtained from a process as claimed in claim 1 , wherein all added organosilanes and added organotitanates and added organozirconates are fully hydrolyzed.
13 . A process for bonding substrates, the process comprising treating at least one of the substrates with the adhesion-promoting pre-treatment composition as claimed in claim 12 as adhesion promoter or activator.
14 . The process as claimed in claim 13 , wherein at least one of the substrates treated with the adhesion-promoting pre-treatment composition is a glass or glass ceramic substrate.
15 . The process as claimed in claim 13 , further comprising applying a polyurethane adhesive or an adhesive based on silane-functional polymers to at least one of the substrates.

Description

TECHNICAL FIELD The invention relates to a process for preparing an adhesion-promoting pre-treatment composition, which is suitable as adhesion promoting activator, in particular for glass and ceramic substrates, as well as the composition itself and to the use thereof. PRIOR ART Adhesive bonding of substrates using adhesives such as polyurethanes is a widely used technique in construction and manufacturing. However, some substrates (bonding substrates) can be problematic in this regard since they are unable to build up sufficient initial adhesion with certain adhesives, or there is loss of adhesion overtime, particularly under demanding environmental conditions such as heat or humidity. Adhesion promoter compositions, also called activators, that are applied to such problematic substrates before the adhesive in order to form an interlayer between the substrate and the adhesive or to generate covalently bound chemical bonding moieties for the adhesive to react onto have long been used for that reason, with the goal to improve adhesion or to maintain a proper adhesion over the lifetime of the adhesively bonded article. A particularly important field of use of adhesion promoter compositions is automotive glass repair (AGR), since these applications involve difficult to bond substrates such as glass and ceramics, which often do not easily bond with the commonly used adhesives for this application, in particular those based on polyurethanes, which are most commonly used in this field. Furthermore, especially in AGR applications, the bonding process is often done under unfavorable conditions, e.g., cold or humid climate, yet it is always desired that the adhesive bond is formed as quickly and as durable as possible. Typically, such adhesion-promoting compositions are organic or aqueous solutions containing dispersed or dissolved organosilanes, which enable an ideal interlayer or at least covalently attached reactive groups for bonds of glasses and ceramics and curable adhesives once the latter have been deposited and crosslinked on the substrates's surface. More particularly, such adhesion promoter compositions are used as primers and activators, i.e., as adhesion-promoting undercoat or adhesion-promoting cleaning compositions. Such compositions frequently contain inert, readily volatile solvents in order to assure rapid flash-off (evaporation of the solvent). However, the content of organic solvent is disadvantageous in terms of environmental compatibility and occupational safety. Furthermore, when using solvent-based silane-containing pre-treatment compositions, it is generally required to add significant amounts of silane hydrolysis- and condensation-catalysts to these compositions in order to ensure a sufficiently fast reaction of these silanes on the substrates. This, however, severely impairs the storage and handling stability of such compositions, as small amounts of humidity entering the composition's container readily leads to undesired precipitations and gelation reactions. Aqueous adhesion promoter compositions based on organosilanes and containing water as solvent are known as EHS-friendly alternatives to solvent-based such compositions. They furthermore are clearly not sensitive to hydrolysis caused by contact with additional water and can be easily handled. However, they also have some significant disadvantages. A problem with silane-based aqueous adhesion promoter compositions is that they have either relatively low storage stability (shelf-life) coupled with adequate reactivity or inadequate reactivity coupled with adequate storage stability. This is because the silanes used have hydrolyzable functional groups that are hydrolyzed on mixing with water to form silanol groups (Si—OH). Such silanol groups are frequently reactive and condense spontaneously with one another under formation of condensation products of relatively high molecular weight, which leads to insoluble precipitates in the adhesion promoter compositions and impairment of their function. In addition, the use of aminosilanes and/or mercaptosilanes in such aqueous adhesion promoter compositions is known. The emulsifying of mercaptosilanes or oligosilane-mercaptosilane mixtures in water is particularly difficult since the mercaptosilanes are not water-soluble before the silane groups are hydrolyzed. In order to bring these silanes into water, prior to the hydrolysis, complete homogeneous distribution has to be assured. In addition, the pH has to be adjusted with acids, for example acetic acid, such that the condensation that occurs as a further reaction is slowed as far as possible. Therefore, the silanes and the water have to be rapidly mixed homogeneously, which requires special mixing apparatuses. The effect of this is that aqueous adhesion promoter compositions are generally sold as 2-component systems (e.g., Sika HydroPrep®-100 from Sika Schweiz AG) and a mixing process for the mixing of the two components is required on site pri