Solid adhesive material which peels off smoothly

Details Solid adhesive material which peels off smoothly Solid adhesive material which peels off smoothly

1998-08-24

2001-11-13

Sergent, Rabon (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

C156S331400, C156S331700, C528S059000, C528S067000, C528S073000, C528S074500, C528S905000, C560S024000, C560S025000, C560S026000, C560S033000, C560S115000, C560S157000, C560S158000, C560S165000, C560S166000, C560S330000, C560S336000, C564S032000, C562S027000

Reexamination Certificate

active

06316573

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a firm, adhesive and smooth-rubbing paste based on reaction products of polyisocyanates, to its production and to its use.
2. Discussion of Related Art
Pastes of the type in question are known. Thus, DE 24 19 067 describes a stick of a gel-forming agent, water and an active component. The gel-forming agent is a reaction product of an aromatic diisocyanate with mono- and/or dialkanolamines containing 2 to 16 carbon atoms. The active component can be an adhesive, for example polyacrylamide, polyvinyl acetate, polyacrylate, polyvinyl alcohol, polyvinyl methyl ether and synthetic or natural rubbers. There is no mention of a polyurethane as the adhesive component. The stick has to be protected against drying out to remain usable.
EP 405 329 describes firm, smooth-rubbing adhesive sticks based on a soap gel as the gel-forming component and an aqueous polyurethane dispersion as the adhesive component. The polyurethane is a reaction product of a polyol or a polyol mixture, an isocyanate component with a functionality of two or more, a component capable of salt formation in the form of an alkaline aqueous solution and/or a nonionic hydrophilic modifying agent and, if desired, a chain-extending agent. The adhesive stick contains water and has to be protected against drying out to remain usable.
WO 94/113726 describes a hydrophilic high molecular weight nonionic polyurethane which may be used in water-free form as a hotmelt adhesive. The polyurethane is characterized by the following structural units:
a) —O—(CH
2
—CH
2
—O)
n
—,
 where n =8 to 500 and more particularly 20 to 300;
b) —CO—NH—X—NH—CO—, where X is an aliphatic or cycloaliphatic radical, more particularly a residue of m-tetramethyl xylene diisocyanate (TMXDI);
c) —O—Y—O,
 where Y is a hydrophobic group, more particularly either
 (—CH
2
—CH(CH
3
)—O)
m
—CH
2
—CH(CH
3
)—,
 (—CH
2
—CH(C
2
H
5
)—O)
m
—CH
2
—CH(C
2
H
5
)— and
 (—CH
2
—CH
2
—CH
2
—CH
2
—O)
m
—CH
2
—CH
2
—CH
2
—CH
2
—
 where m =8 to 500 and more particularly 20 to 300,
 or alkylene or cycloalkylene groups containing 2 to 44 and, more particularly, 6 to 36 carbon atoms,
c) making up 0 to 40% by weight, preferably 2 to 30% by weight and more preferably 5 to 25% by weight, based on a)+c) in the polyurethane.
There is no reference to bonding at room temperature in the water-free state.
Earlier German patent application 195 19 391 describes a polyurethane adhesive which may be used in water-free form as an adhesive stick. The polyurethane may be prepared from the following components:
a) at least one aliphatic or aromatic diisocyanate, preferably from the following group: MDI, TDI, HDI, IPDI and, above all, TMXDI,
b) at least one crystallizing polyester or polyether diol, more particularly from the following group:
polyethylene glycol with a molecular weight (number average) of 200 to 40,000,
polytetrahydrofuran with a molecular weight of 200 to 4,000,
copolymer of ethylene oxide and propylene oxide with a molecular weight of 200 to 40,000, preferably a block copolymer with the structure PEG/PPG/PEG and with a PEG content of 10 to 80% by weight, and
a polyester diol, more particularly polycaprolactone with a molecular weight of 200 to 50,000,
c) optionally at least one diol capable of forming ions, more particularly for forming carboxylates, and
d) optionally at least one trihydric or higher polyol, such as glycerol and TMP, and
e) optionally at least one hydrophobic diol, more particularly from the following group:
polypropylene glycol with a molecular weight of 200 to 4,000 and
alkanediol containing 1 to 100, preferably 2 to 50 and more preferably 5 to 30 carbon atoms, the ratio of isocyanate groups to hydroxyl groups being variable from 0.5 to 1.2:1 and, more particularly, from 0.7 to 1:1.
The adhesive stick does not contain any free NCO groups.
The strengths of all adhesive sticks are high enough for paper, but not for other substrates. In addition, the wet strengths of the adhesive pastes mentioned are very poor. Accordingly, the problem addressed by the present invention was to provide a firm smooth-rubbing adhesive paste which would not have any of these disadvantages and which would be distinguished not only by easy handling, but also by favorable performance properties. More particularly, the adhesive paste would be easy to apply, would allow for early correction of the bond and would still develop high ultimate strength and, optionally, water resistance.
The solution provided by the invention is defined in the claims and lies essentially in a firm, smooth-rubbing adhesive paste based on reaction products of a polyisocyanate, the paste being water-free and containing moisture-reactive NCO groups.
A paste is regarded as “firm” when it is capable of forming dimensionally stable geometric objects on its own. In particular, it should have a deformation load of 10 to 150 at 20° C. as measured by the compressive strength method described hereinafter.
A paste is regarded as “adhesive” when it is capable of attaching lightweight materials at least, such as paper or paperboard, to flat surfaces at room temperature, even without fixing.
A paste is regarded as “smooth-rubbing” when between 0.5 and 0.1 mm per m and, more particular, between 0.25 and 0.35 mm/m are rubbed off at the application temperature, more particularly at 20 to 25° C., as measured by the rub-off method described hereinafter. According to the invention, the application temperature may rise to 10° C. below the melting point. It may of course also be above the melting point, in which case the paste is applied in the same way as a normal hotmelt adhesive.
The isocyanate content of the paste according to the invention is in the range from 0.5 to 20 g NCO/100 g of paste and, more particularly, in the range from 1 to 15 g.
The polyisocyanates are reacted directly or indirectly with monofunctional fatty derivatives. The monofunctional fatty derivatives are preferably fatty alcohols, fatty amines and fatty acids. Fatty alcohols are linear saturated or unsaturated primary alcohols obtainable by reduction of triglycerides, fatty acids or fatty acid methyl esters. Specific examples are capryl alcohol, 1-nonyl alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, erucyl alcohol, ricinol alcohol, linoleyl alcohol, linolenyl alcohol, arachidyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol, brassidyl alcohol.
Fatty acids are aliphatic saturated carboxylic acids with, almost exclusively, an unbranched carbon chain. They are normally prepared from fats and oils. Specific examples of fatty acids are capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, palmitoleic acid, oleic acid and erucic acid.
The fatty amines are normally prepared from the fatty acids with ammonia via the fatty acid amide and fatty acid nitride stage. However, the nitrile may also be directly prepared from the fat with ammonia. By virtue of these reactions, the fatty amines have the same number and the same structure as the fatty alcohols and fatty acids mentioned above. The amino groups may also be substituted by an R
1
group, where R
1
is an alkyl group containing 1 to 30 carbon atoms and, more particularly, 1 to 18 carbon atoms. Corresponding fatty derivatives containing SH groups instead of OH group may also be used. The fatty derivatives may of course also be prepared by petrochemical methods and may even have an odd number of carbon atoms.
The paste according to the invention may consist a) of a product of the direct or indirect reaction of a polyisocyanate with a fatty derivative in combination with a “liquid polyisocyanate” and b) solely of a reaction product of a polyisocyanate. Mixtures of a) and b) are of course also possible.
Variant a) is a gel structure of at least two components, the solid gel-forming compon

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