Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-03-04
2003-11-18
Dawson, Robert (Department: 1712)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C428S428000, C528S017000, C528S018000, C528S023000, C528S035000
Reexamination Certificate
active
06649016
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to silane functional adhesive composition and to a method of bonding a window to a painted substrate using the adhesive without the need for a primer for the painted substrate.
Polyurethane sealant compositions are used for bonding non-porous substrates, such as glass, to nonporous substrates, these are described in U.S. Pat. No. 4,374,237 and U.S. Pat. No. 4,687,533, both incorporated herein by reference. U.S. Pat. No. 4,374,237 describes a polyurethane sealant containing urethane prepolymers which have been further reacted with secondary amine compounds containing two silane groups. U.S. Pat. No. 4,687,533 describes a polyurethane sealant containing urethane prepolymers which contain silane groups which have been prepared by reacting a polyisocyanate having at least three isocyanate groups with less than an equivalent amount of an alkoxysilane having a terminal group containing active hydrogen atoms reactive with isocyanate groups to form an isocyanatosilane having at least two unreacted isocyanate groups. In a second step, the isocyanatosilane is mixed with additional polyisocyanate and the mixture is reacted with a polyol to form a polyurethane prepolymer having terminal isocyanato groups and pendant alkoxysilane groups. EP 856,569 discloses the use of polyoxyalkylene polymer terminated with silanes having hydrolyzable groups bonded thereto blended with a polyoxyalkylene polymer having no cross-linking groups to bond glass to metal.
However, when such sealants are used to bond glass substrates to painted substrates, such as for window installation in vehicle manufacturing, the lap shear strength of the bonded substrate may be less than desirable for safety or structural purposes. Consequently, a separate paint primer comprising a solution of one or more silanes is typically applied to a painted substrate prior to the application of the sealant in most vehicle assembly operations for bonding the windshield and the rear window. The use of a primer in assembly operations is undesirable in that it introduces an extra step, additional cost, the risk of marring the paint surface if dripped on an undesired location and exposes the assembly line operators to additional chemicals.
U.S. Pat. No. 5,147,927 discloses an adhesive which can bond to the electrocoat primer layer without the need to prime the electrocoat surface. The adhesive is used in a process which requires masking the area where the glass window will be bonded into a vehicle before the painting process, removing the masking after painting and then bonding the glass to the previously masked area. The adhesive comprises a silane capped polyurethane polymer and an aminosilane electrocoat adhesion promoter. The composition described may further include standard silanol curing catalyst, including tin catalysts, and an accelerating agent of titanate esters, with amine substituted titinate esters preferred. The problem with this process is that the sealant does not bond to the painted surface without a primer and requires extra steps in masking the bond area.
Automotive OEMs have demanded that the paint suppliers provide more robust acid resistant paint systems which stand up to harsh environmental conditions. These paint systems are difficult to bond to due to the increased chemical resistance of the paints. One problem with developing an adhesive which bonds to these paint systems on an automobile is that there are several different paint chemistries. The automobile producers also demand an adhesive for bonding glass into a vehicle which cures rapidly so that the vehicle can be moved without the glass falling out or slipping from the desired location. Additionally, it is important that the adhesive demonstrate stability prior to application, that is does not cure before being applied to bond the glass into the vehicle. If the adhesive cures in the delivery system in the auto plant, the assembly time must be shut down while the adhesive delivery system is purged. Such a shut down is very costly for the automotive companies and must be avoided. In addition to the above needs, such adhesives need to demonstrate rapid cure upon exposure to ambient conditions and good stability before application. In addition the adhesive needs to bond, or link up, to the unprimed painted surface as soon as possible so the risk of the window moving from where it is placed is reduced. Automobiles last upwards of 10 years and the adhesive needs to maintain its' integrity and hold the window into the vehicle for the life of the vehicle under a variety of difficult conditions. Thus what is needed is an adhesive which can be applied to the automotive paints especially difficult to bond to paints, to bond glass into a vehicle without the need to use a primer, which adhesive also demonstrates strong adhesion, adhesive strength rapid cure, fast link-up, good stability and long term durability.
SUMMARY OF THE INVENTION
The invention is an adhesive composition comprising A) one or more polymers having a flexible backbone and silane moieties capable of silanol condensation; B) one or more titanates or zirconates having one or more ligands comprising hydrocarbyl phosphate esters and/or a hydrocarbyl sulfonate esters; and C) an anhydrous strong organic acid which is miscible with the polymer and enhances the bonding of the adhesive to a coated substrate in the absence of a primer.
In one embodiment, the invention is a method of bonding glass to a painted substrate, such as a window in a vehicle. The process comprises applying to the glass or the unprimed coated substrate an adhesive as described herein; contacting the glass with the unprimed coated substrate wherein the adhesive is located between the window and the substrate; and allowing the adhesive to cure.
The adhesive and method of the invention allows the bonding of glass to a coated substrate without the need for priming the surface of the substrate to which it is bonded. This is especially useful for bonding windows into automobiles. The adhesive further demonstrates excellent adhesive and cohesive strength, excellent stability before application, rapid cure rate, rapid link up and long term durability.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive composition of the invention contains a polymer having a flexible backbone and having silane moieties capable of silanol condensation. The polymer with a flexible backbone can be any polymer with a flexible backbone which can be functionalized with a silane capable of silanol condensation. Among preferred polymer backbones are polyethers, polyurethanes, polyolefins and the like. Among more preferred polymer backbones are the polyethers and polyurethanes, with the most preferred being the polyethers. Even more preferably the polymer is a polyether having silane moieties capable of silanol condensation. In one embodiment, the polymer useful in the invention is a polymer as disclosed in Yukimoto et al., U.S. Patent 4,906707; Iwakiri et al., U.S. Pat. No. 5,342,914; Yukimoto U.S. Pat. No. 5,063,270; Yukimoto et al., U.S. Pat. No. 5,011,900; Suzuki et al. U.S. Pat. No. 5,650,467, all incorporated herein by reference. More preferably such polymers are oxyalkylene polymers containing at least one reactive silicon group per molecule. The oxyalkylene polymer which can be used in the present invention includes polymers having a molecular chain represented by formula (1):
—(R—O)
n
— (1)
wherein R represents a divalent alkylene group having 2 to 4 carbon atoms, and preferably 2 to 3 carbon atoms; and n represents the number of repeating units. The oxyalkylene polymer may have a straight chain or a branched structure, or a mixed structure thereof. From the viewpoint of availability an oxyalkylene polymer having a repeating unit represented by formula (2) is preferred:
—CH(CH
3
)CH
2
O— (2)
The polymer may contain other monomer units but preferably comprises the monomer unit of formula (1) in a proportion of at least about 50 percent by weight, particularly about 80 percent by weight o
Heberer Daniel P.
Wu Ziyan
Dow Global Technologies Inc.
Zimmer Marc S.
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