Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1997-11-24
2000-07-25
Sells, James
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156327, 523511, 523513, B29C 6506
Patent
active
060932708
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for bonding substrates using a water-free or low-water, partly crystalline adhesive which is solid at room temperature, to the adhesive and to its production.
BACKGROUND OF THE INVENTION
Processes for bonding substrates with adhesives solid at room temperature are known, thus, the hotmelt adhesives solid at room temperature are first heated until they become tacky and are then applied in the form of a melt to the substrates to be bonded. After the substrates have been fitted together, the hotmelt adhesives set physically and solidify on cooling through crystallization or an increase in viscosity. Raw materials for such hotmelt adhesives are, for example, polyethylene vinyl acetate, polyamide, polyester and polyurethane. One such PU hotmelt adhesive is described in WO 94/13726. This document claims a water-soluble, high molecular weight nonionic partly crystalline polyurethane as the basis for a hotmelt adhesive. The polyurethane is characterized by the following structural units: residue of m-tetramethyl xylene diisocyanate (TMXDI), and H.sub.5)-- and --CH.sub.2 --CH.sub.2 --CH.sub.2 -- cycloalkylene group containing 2 to 44 carbon atoms and, more particularly, 6 to 36 carbon atoms, preferably 5 to 25% by weight, based on a)+c) in the polyurethane.
Hotmelt adhesives have the general disadvantage that a heat source is required for melting.
Adhesives solid at room temperature which are suitable for bonding without melting, for example adhesive sticks, are also known. In order to bond substrates with an adhesive stick, the adhesive stick is simply drawn over the substrate to be bonded and the substrate thus coated with adhesive is fitted together with the other substrate. The adhesive which is tacky at room temperature sets by evaporation of the solvent or the water or by diffusion of the solvent or the water into the substrate.
One such adhesive stick is described in EP 405 329. The dimensionally stable, soft-rubbing adhesive stick consists of an aqueous formulation of a polyurethane as binder, a soap gel as the shaping gel-forming component and, if desired, auxiliaries. The polyurethane is a reaction product of a polyol or polyol mixture, an isocyanate component with a functionality of 2 or more, a component capable of salt formation in alkaline aqueous solution and/or a nonionic hydrophilic modifier and, if desired, a chain-extending agent. In Example 1d, a polyurethane was prepared from 29.7 parts by weight of isophorone diisocyanate, 100 parts by weight of polyethylene propylene glycol with an EO content of 10% and a molecular weight of 2,000, 6.8 parts by weight of dimethylol propionic acid and 2.2 parts by weight of NaOH. In the acetone process, an aqueous dispersion with a solids content of 36% by weight was prepared. Finally, the adhesive was produced from 82 parts by weight of this PU dispersion and 2 parts by weight of water, 7 parts by weight of glycerol, 3 parts by weight of PPG 600, 3 parts by weight of sodium palmitate and 3 parts by weight of sodium stearate. The adhesive had a melt viscosity of 2.4 Pas at 60.degree. C. An adhesive stick of the type in question has the disadvantage that it requires a sealed pack, otherwise it would be in danger of drying out and its properties would be adversely affected. In addition, paper curls under the effect of the high water content of the adhesive.
These disadvantages are avoided in an adhesive stick which consists of a solid adhesive component and a microencapsulated solvent (cf. GB 995,524). Unfortunately, this adhesive stick has the disadvantage that, after use, a skin forms over its surface and has to be laboriously removed before the adhesive stick can be used again.
The disadvantages of a water-based adhesive stick are also avoided by the adhesive stick based on wax, polypropylene and rosin according to DE 20 22 464. The stick is activated by frictional heat, the uppermost adhesive layer melting. On cooling, the stick sets almost instantaneously so that correction is no longer possible. In addition, the handl
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Encyclopedia of Polymer Science and Technology, vol. 11, Interscience Publishers div. of John Wiley & Sons (editors: H. Marh & N. Gaylord) "Polyester" p 62-128.
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Donothek Horst
Ferencz Andreas
Fischer Herbert
Huebner Norbert
Kuhn Joerg
Harper Stephen D.
Henkel Kommanditgesellscahft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Sells James
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