Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-17
2002-07-09
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S507000
Reexamination Certificate
active
06417261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an adhesive stick produced from a water-based preparation of a synthetic polymer of adhesive character and a soap gel as the shaping gel-forming component and, optionally, other auxiliaries. The invention also relates to a process for the production of such sticks and to their use.
2. Discussion of the Related Art
Adhesive sticks (=dimensionally stable stick-like adhesives which leave behind a tacky film when rubbed onto a receiving surface) are now part of everyday life. They contain water-soluble or water-dispersible synthetic polymers of adhesive character dissolved in an aqueous organic liquid phase together with a shaping gel-form component. The gel-forming component is selected in particular from alkali metal or ammonium salts of aliphatic carboxylic acids, more particularly containing from about 12 to 22 carbon atoms. If the basically high-tack water-based preparations of the synthetic polymers of adhesive character are heated together with small quantities of the gel-forming component based on fatty acid soaps to relatively high temperatures, more particularly above 50° C., and if this solution is subsequently left standing to cool, the mixture solidifies to a more or less stiff soap gel in which the shaping and comparatively rigid micelle structure of the soap gel is predominantly in evidence at first. This provides for the known production and handling of such adhesives in stick form in closable tubes. When the stick is rubbed onto a receiving surface, the micelle structure is destroyed so that the rigid mixture is converted into a paste-like state in which its adhesive character is predominant.
Originally, the polyvinyl pyrrolidone (PVP) mentioned in DE 18 11 466 proved to be the most important polymer of adhesive character. Although the adhesive sticks made with polyvinyl pyrrolidone offered sufficient strength for gluing paper, there was still a need to obtain sticks which could be used more universally and with which bonds of greater strength could be produced. In particular, there was a need to prevent paper/paper bonds established with the sticks from separating again under climatically unfavorable conditions. The use of polyurethane as the polymer of adhesive character contributed towards solving that problem.
EP 405 329 describes firm, soft-rubbing adhesive sticks based on a soap gel as the shaping gel-forming component and an aqueous poly-urethane dispersion as the adhesive component. The polyurethane is a reaction product of a polyol or a polyol mixture, a difunctional or poly-functional isocyanate component, a component capable of salt formation in alkaline aqueous solution and/or a nonionic hydrophilic modifying agent and, optionally, a chain-extending agent. Although improvements were in fact obtained in this way, the strengths and heat resistance values were still not good enough for special cases.
SUMMARY OF THE INVENTION
Accordingly the problem addressed by the present invention was to provide a dimensionally stable soft-rubbing composition which would not have any of these disadvantages and which would be distinguished not only by easy handling, but also by favorable performance properties. In particular, easy application would be combined with initial repositionability of the bond and high tack would be combined with high ultimate strength and also with high heat resistance.
The solution provided by the invention is defined in the claims and consists essentially in the use of a mixture of polyurethane and polyvinyl pyrrolidone as the synthetic polymer of adhesive character.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive stick is “dimensionally stable” because its constituent composition is capable of forming stable geometric shapes at room temperature (20° C.). More particularly, an adhesive stick with a diameter of 16 mm should have a deformation load of 25 to 50 N as measured by the compressive strength method described hereinafter at a temperature of 20° C.
The constituent paste of the adhesive stick is preferably “soft-rubbing” because a uniform film without any unevenness is obtained on copying paper (Sonnecken 5015 Speziell Copier) under low pressure (see “rubbing” test).
An “water-based preparation” in the context of the invention is understood to be an aqueous mixture of the polymers irrespective of the degree of dispersion (true solution, colloidal solution or dispersion).
The adhesive sticks according to the invention contain a polyurethane (PU) as the adhesive polymer component. The polyurethane is a reaction product of at least one polyol, at least one polyfunctional isocyanate, at least one component capable of salt formation in alkaline aqueous solution and/or a nonionic hydrophilic modifying agent and, optionally, at least one chain-extending agent.
According to the invention, polyurethane dispersions are preferred starting materials for adhesive sticks which are opaque, translucent or transparent in appearance and in which the polymer would appear to be present at least partly in solution. The specialist knowledge of the poly-urethane expert, who can influence the degree of distribution through the percentage content of ionic and/or nonionic constituents, is relevant in this regard. Accordingly, the water-based preparation preferably contains the polyurethane in the form of a dispersion.
The polyurethane dispersions used as synthetic polymer in adhesive sticks are prepared from a polyol or a polyol mixture as an essential starting product. Broadly speaking, these polyols should contain at least two reactive hydrogen atoms and should be substantially linear, although they may also be branched. Their molecular weight is in the range from 300 to 40,000 and preferably in the range from 500 to 20,000. Suitable polyols are polyester polyols, polyacetal polyols, polyether polyols, polythioether polyols, polyamide polyols or polyester amide polyols containing 2 to 4 hydroxyl groups which may also be partly replaced by amino groups. Polyurethanes of polyether and/or polyester polyols are preferred.
Suitable polyether polyols are, for example, the polymerization products of ethylene oxide, propylene oxide, butylene oxide and their copolymerization or graft polymerization products and the polyethers obtained by condensation of polyhydric alcohols or mixtures thereof and those obtained by alkoxylation of polyhydric alcohols, amines, polyamines and aminoalcohols. Isotactic polypropylene glycol may also be used. The preferred polyether polyol is polytetrahydrofuran. Polytetrahydrofuran in the context of the present invention is the collective name for polyethers which can be theoretically or actually prepared by ring-opening polymerization of tetrahydrofuran and which contain a hydroxyl group at either end of the chain. Suitable products have a degree of oligomerization of about 1.5 to 150 and preferably in the range from 5 to 100.
Another preferred class of polyols are polycarbonate polyols. Preferred polycarbonate polyols are aliphatic types, i.e. esters of carbonic acid with dihydric C
2-10
alcohols. Polycarbonate polyols based on carbonic acid and bisphenol A are less suitable.
Suitable polyacetal polyols are, for example, the compounds obtainable from glycols, such as diethylene glycol, triethylene glycol, 4,4-dioxethoxydiphenyl dimethyl methane, hexanediol and formaldehyde. Suitable polyacetals may also be produced by polymerization of cyclic acetals.
Among the polythioether polyols, the condensation products of thiodiglycol on its own and/or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or aminoalcohols are particularly suitable. Depending on the co-components, the products are polythioethers, polythio mixed ethers, polythioether esters, polythioether ester amides. Polyhydroxyl compounds such as these may also be used in alkylated form or in admixture with alkylating agents.
The polyester, polyester amide and polyamide polyols include the predominantly linear condensates obtained from polybasic saturated and unsaturated
Klauck Wolfgang
Maier Wolfgang
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Seifert Arthur G.
Yoon Tae H.
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