Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1992-10-09
1993-12-14
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524236, 524284, 524591, 524714, 524773, 524839, 524840, C08L 7504
Patent
active
052704335
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the use of special, substantially clear, aqueous and at least largely solventless polyurethane dispersions as universal household adhesives and to a process for their production.
Universal household adhesives, also known as multipurpose adhesives, are used for bonding a number of substrates encountered in the home (paper, cardboard, photographs, fabrics, leather, felt, bast, cork, films, metals, such as aluminium and iron, china, ceramics, glass, wood, various plastics, including for example polystyrene foams). The adhesives in question are expected to produce an adequate adhesive effect on these various substrates which differ chemically and physically in their surface structure and which are normally subjected to a special surface treatment before bonding.
Compared with the large variety of classes and types of adhesive used in industry and workshops, there are only a few substances which are capable of meeting the stringent demands imposed on the universality of a multipurpose household adhesive. Among those substances, only polyvinyl acetate and its copolymers are widely used--normally in solution or, for glueing wood, in the form of a dispersion.
The demand for universality represents a particularly difficult selection criterion for an adhesive. Ultimately, it means that the adhesive molecules must show equally high affinity for polar and apolar interfaces. Accordingly, the statement that a certain substance is suitable as an adhesive does not indicate to the expert whether it can also be used as a universal household adhesive.
In addition to the universality requirement, there has also recently been a demand for solventless, physiologically safe, clear, aqueous formulations of neutral odor in the field of universal household adhesives. However, these formulations are intended at the same time to lead to adhesives of which the dried films in turn have a certain resistance to water. In addition, these water-based adhesives are also intended to be able to bond substrates that are difficult to bond, such as plastics. They are also intended to have a long storage life.
This requirement profile could not be fully satisfied either on the basis of the binders hitherto preferred for universal adhesives, namely polyvinyl acetate and vinyl acetate copolymers, or by such alternatives as nitrocellulose. Although polyvinyl acetate can be produced without solvents in the form of aqueous dispersions, the dispersions obtained are not transparent, but milky white. They show good performance properties when used, for example, as wood glue. The acrylates and styrene acrylates widely used as dispersion adhesives are also not known on the market in the form of transparent household adhesives with the properties mentioned.
It is known that specially selected embodiments of the aqueous polyurethane dispersions known for decades are suitable as multipurpose universal adhesives. Polyurethane dispersions consist of adducts of polyfunctional isocyanates (isocyanate component) with polyfunctional OH compounds (polyol component) which contain co-condensed units capable of salt formation in aqueous solution. It has surprisingly been found that polyurethane dispersions in which the polyol component is based on polypropylene glycol and the isocyanate component is based on tetramethyl xylene diisocyanate, are also suitable as universal household adhesives and provide good adhesion values. It has also surprisingly been found that dispersions of the type in question can be produced without using inert solvents.
2. Discussion of Related Art
DE-OS 36 30 045 broadly describes an adhesive based on an aqueous dispersion of polyurethanes containing incorporated carboxylate and/or sulfate groups of which the basic diisocyanate component consists of a mixture of at least two (cyclo)aliphatic diisocyanates. The DE-OS mentions numerous polyols, numerous isocyanate compounds and numerous salt-forming components as modifying agents. It also mentions the chain-extendin
REFERENCES:
Encyc. of Chem. Tech., Kirk-Othmer, vol. 18, 1982, pp. 633-645.
Angew. Makromol. Chem., D. Dieterich, 1981, pp. 133-165.
Journal of Water Borne Coatings, Zermani, 1984, pp. 2 et seq.
Meth. organischen Chem., Houben-Weyl, vol. E20, Part 131, pp. 1659-1663 and 1671-1681.
Journal of Cellular Plastics, Arendt, 1982, pp. 376-383.
Encyklop. der tech. Chemie, Weinheim/Bergstrasse, 1974, pp. 311-313.
Gierenz Gerhard
Gruetzmacher Roland
Hoefer Rainer
Klauck Wolfgang
Maier Wolfgang
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
Welsh Maurice J.
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