Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1989-03-03
1991-11-12
Simmons, David A.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1562755, 1562757, 219 1055M, B32B 3100, H05B 664
Patent
active
050644947
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the at least partial curing of sealants and adhesives, particularly in connection with the direct glazing of motor vehicles, in which at least part of the sealant and adhesive is heated.
Sealant and adhesive compositions have already been proposed (German patent application P 37 05 427.9), which can be initiated both by heat and moisture, so that they can be set or hardened by brief heating and then subsequently cured by moisture. These are one component polyurethane sealants and adhesives based on telechelic isocyanate prepolymers of aromatic diisocyanates in stoichiometric excess and polyols, which contain a catalyst for moisture initiation and a blocked, heat-activatable cross-linking agent.
The polyurethane prepolymers to be used are prepared in per se known manner from excess aromatic diisocyanate and a polyol. Suitable aromatic diisocyanates are e.g. diphenyl methane diisocyanate (MDI), toluylene diisocyanate (TDI), naphthalene diisocyanate, p-phenylene diisocyanate and 1,3-bis(isocyanate-methyl)-benzene and m or p-tetramethyl xylene diisocyanate (m- or p-TMXDI).
The polyol component can be constituted by polyether polyols, such as polyethylene oxide, polypropylene oxide and copolymers thereof, polyester polyols and hydrofunctional acrylates and methacrylates.
The preferred catalysts for moisture initiation of the aromatic isocyanate prepolymers are tin compounds, such as tin (II) octoate, dibutyl tin laurate and dibutyl tin maleate. It is also possible to use organomercury, lead and bismuth compounds, such as e.g. phenyl mercury acetate or lead naphthenate. Tertiary diamines, e.g. Dabco and cyclic compounds, such as diacabicycloundecene (DBU) or combinations with heavy metals are also suitable.
Suitable blocked, heat-activatable crosslinking agents are complexed amines, particularly the complex compound of methylene dianiline (MDA) and NaCl. The formula of this complex compound is generally given as (MDA).sub.3.NaCl. The compound is available from Uniroyal under the trade name Caytur. By heating to temperatures between 120.degree. and 160.degree. C. thermal decomposition of the complex compound takes place and the liberated methylene dianiline leads to the crosslinking of the polyurethane prepolymer. Normally the MDA complex is used in substoichiometric quantity. Although the brief heating only leads to an incomplete crosslinking, it still gives the system an adequate mechanical initial strength. Complete curing and achieving the final strength is brought about by the reaction of the isocyanate prepolymer with moisture.
Suitable crosslinking agents are also polyamino or polyhydroxy-functional compounds, such as methylene dianiline or polyester polyols, which are microencapsulated and are consequently unavailable at ambient temperature for reacting with the isocyanate prepolymer. Encapsulation can take place in a particularly advantageous manner with the aid of methyl methacrylate or other (meth) acrylates, which only soften at temperatures above 100.degree. C. Even though the polyamino or hydroxy-functional compound is solid at ambient temperature, but softens as from approximately 60.degree. C., heating to temperatures above 100.degree. C. leads to the softening or swelling of the shell or envelope of the microcapsules and therefore to the release of the crosslinking agent. Such crosslinking agents have the advantage that they contain no NaCl or other metal salt.
Such a one-component polyurethane system is characterized by its excellent adhesion to metal and pretreated glass and is therefore particularly suitable for the direct glazing of cars. On adding suitable fillers and rheology aids, the system has an extremely good stability, so that it can be mechanically applied in the desired profile shape to the glass windshields and the like and can be inserted with the same into the vehicle body.
In order to be able to process such heat and moisture-initiating sealants and adhesives in an optimum simple manner during the direct glazing of motor vehicles or also du
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Duck Edward W.
Hirthammer Michael
Scheffler Ingolf
Barry Chester T.
Fabiano Vincent L.
Looper Valerie E.
Simmons David A.
Teroson G.m.b.H.
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