Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1993-09-20
1998-10-27
Szekely, Peter A.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1563318, 156332, B32B 3120, C08J12308, C08J17504, C08J16702
Patent
active
058273930
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hotmelt adhesive, to its use, to a bonding process and to parts by joined coated with the hotmelt adhesive.
2. Discussion of Related Art
A hotmelt adhesive is a one-component, water-free, solventless adhesive which is solid at room temperature, which is applied as a melt for bonding and which establishes the bond by solidifying on cooling. The parts to be joined are normally fitted together immediately and, at the most, a few minutes after application of the adhesive melt. However, they can only be coated in the first instance and then stored for more or less long periods before, finally, the adhesive is activated by heating to the application temperature. Since the hotmelt adhesive has to be melted not only for application, but also for bonding the parts to be joined, its handling involves disadvantages. Bonds of large surface area involving small amounts of adhesive and long waiting times before the parts are fitted together are not possible without additional heating.
There are also pressure-sensitive adhesives which are applied from the melt. The adhesives in question are adhesives which are permanently tacky at room temperature and which adhere immediately to almost all substrates under light pressure. Although they can also be used for establishing bonds of large surface area after relatively long waiting times, the strengths of the resulting bonds are very poor. Accordingly, they are mainly used when subsequent separation is required as is the case, for example, with adhesive plasters, labels, adhesive tapes, etc. To avoid unwanted bonding, the tacky surfaces have to be covered with a silicone paper.
Hotmelt adhesives of this type are known, for example, from the "Technische Information" brochure of Tivoli-Werke AG, Hamburg. The product TIVOMELT 9617/11 is known from the "Technische Information" of March, 1986 relating to the reactive hotmelts TIVOMELT 9600 and TIVOMELT 9617. The reactive hotmelt in question is a polyurethane (PUR) prepolymer hotmelt adhesive which reacts with moisture. The product has a particularly long open time in which bonding can be carried out. Immediately after application, it has adhesive properties. This means that the materials to be joined have to be fixed during the setting phase. After an initial phase of about 10 minutes, a rapid increase in strength occurs through crystallization. The accompanying reaction with moisture is over after 2 to 7 days, depending on the ambient temperature and humidity level. The product TIVOMELT 9617/76 has a much higher initial strength and forms a distinctly harder film. The setting rate bears a certain similarity to that of conventional hotmelts.
DE-A1-32 36 313 describes a hotmelt adhesive of the following constituents: prepolymeric isocyanate, thermoplastic polyurethane and a low molecular weight synthetic resin. 10 Seconds after its application from the melt, the part to be joined is applied and pressed on (see Application Example 1).
Japanese patent JP 61 115 977 describes a hotmelt adhesive of the following constituents: aromatic oil, an NCO-functional urethane prepolymer, a tackifier, for example a coumarone resin, a coumarone/indene resin, a terpene/phenol resin, a styrene resin or a terpene resin.
The problem addressed by the present invention was to improve the handling properties of hotmelt adhesives with only a negligible effect, if any, on their strength properties.
DESCRIPTION OF THE INVENTION
The solution provided by the invention is defined in the claims. It is based essentially on the observation that certain hotmelt adhesives can set in the same way as contact adhesives. Consistent with the general definition, the hotmelt adhesive according to the invention is solid at room temperature and hardly anything adheres to it in the absence of pressure. It is free from water and volatile solvents.
The expression "open time" is understood to be the time in which bonding can be carried out under pressure. It is of the order of 10 minutes or lon
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Biele Regina
Kinzelmann Hans-Georg
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Szekely Peter A.
Szoke Ernest G.
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