Protective composition for users of cyanoacrylate adhesives

A protective composition is provided for application to the skin (especially the hands) of persons working with cyanoacrylate adhesive compositions ("superglues" ), to prevent accidental adhesion of skin to skin or to other substrates. The composition comprises a skin-compatible adhesion-inhibiting substance for cyanoacrylate monomers, the substance being incorporated in a conventional topical pharmaceutical base to produce, e.g., a skin cream. Any cyanoacrylate monomer-stabilizer which is kind to the skin can be used, but in addition a group of named zwitterionic aminosulfonic acids ("ZASA's") is proposed and preferred for the purpose. They have a preferred pK.sub.a at in the range of 6.0-8.3 at 20.degree. C.

BACKGROUND AND FIELD OF THE INVENTION 
This invention relates to precaution against a hazard in the use of 
adhesive compositions based on cyanoacrylate monomers. It relates in 
particular to a protective composition for the skin (especially the hands) 
of a person working with a cyanoacrylate adhesive or "superglue", and to a 
method using the composition, for protecting such a person's skin. 
Cyanoacrylate monomers, as is well known, polymerise rapidly on contact 
with certain activating substances in trace quantities. These substances 
include inorganic salts, carbonyl compounds such as urea, and Lewis bases 
such as water 
Human perspiration comprises mainly moisture, a small proportion of urea, 
inorganic salts, and some lactic acid. Human skin normally has a slightly 
acid reaction, with a pH of 5 to 6. Normal human skin serves as a very 
effective activating substrate for cyanoacrylate adhesives. There thus 
arises the notorious hazard involved in the use of these compositions, 
that traces of the composition on the skin are immediately activated, and 
skin so contaminated will on contact stick fast to other skin portions or 
substrate surfaces, with initial cure taking place within a few seconds. 
Persons thus affected may have great difficulty in freeing themselves, and 
in severe cases may even require surgical assistance. The problem is well 
known in factories where parts are assembled by means of "superglues" and 
the like, but the hazard is perhaps greater when inexperienced persons are 
handling cyanoacrylates. 
It is an object of this invention to provide an easily used protective 
means to render cyanoacrylate adhesives innocuous to persons using them. 
Accordingly, the invention provides a protective composition for the skin 
of a person working with a cyanoacrylate-type adhesive, which composition 
comprises a skin-compatible adhesion-inhibiting substance for 
cyanoacrylate monomers, said substance being incorporated in a 
dermatologically compatible base for topical application. 
DETAILED DESCRIPTION OF THE INVENTION 
The adhesion-inhibiting substance may be a skin-compatible conventional 
stabiliser for cyanoacrylate monomers, but in a preferred embodiment of 
the invention, said substance comprises at least one zwitterionic 
aminosulfonic acid (hereinafter ZASA) having a pK.sub.a at 20.degree. C. 
in the range of 6.0-8.3 (i.e. the molecules of the substance exist mainly 
in their dipolar form in the pH range 6.0-8.3). These ZASA's permit 
polymerisation of the adhesive but, surprisingly, they render the 
resulting solid non-adherent to the skin, so that it can be easily peeled, 
rubbed or washed off. 
The ZASA's so far investigated and found to have the properties necessary 
for use in compositions of the invention are set out, with their pK.sub.a 
values and trivial names, in the following list (all pK.sub.a values 
quoted in this specification are at 20.degree. C.): 
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2-(N--Morpholinyl)-ethane sulfonic 
6.15 MES 
acid 
N,N--bis-(2-Hydroxyethyl)-2- 
7.15 BES 
aminoethane sulfonic acid 
2-[N--(N'--2-Hydroxyethyl)-piperazinyl]- 
7.55 HEPES 
ethane sulfonic acid 
3-[N--(N'--2-Hydroxyethyl)-piperazinyl]- 
8.0 HEPPS 
propane sulfonic acid (or EPPS) 
Piperazine-1,4-bis-(2-ethane sulfonic 
6.8 PIPES 
acid) 
2-[N--tris-(Hydroxymethyl)-methylamino]- 
7.5 TES 
ethane sulfonic acid 
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All of them but HEPPS were described among others, by Good N. et al. in 
Biochemistry 1966, Vol 5, 467. "It is not difficult to synthesise 
aliphatic amines with appropriate acid dissociation constants"--to quote 
from the above-cited report. It may be added that the preparation of their 
aromatic analogues presents no particular difficulty either. To quote 
further from the report: "It is easy to design and prepare a wide variety 
of inexpensive compounds" (i.e., hydrogen ion buffers for biological 
research) "with desired dissociation constants, solubilities and 
reactivities . . . Many more could be prepared". All such easily 
accessible ZASA's, having pK.sub.a values within the above specified 
limits, are accordingly to be understood as suitable for use in 
compositions of the present invention, unless disqualified by 
dermatological incapatibility which, however, is thought to be unlikely. 
The proportion of the active ingredient by weight of the composition is in 
the range 0.05% to 30%, preferably 0.05% to 5.0%, most preferably 0.1% to 
1.0%. The topical base is selected from a wide variety of compositions 
formulated according to known principles for protective, cosmetic and 
pharmaceutical purposes. Such compositions include creams, solids, lotions 
and film-forming solutions among others. They may be presented in boxes, 
jars or squeezable tubes, both collapsible and non-collapsible. The solids 
may be presented as sticks for rubbing on to the skin. Some of the topical 
bases may be presented as papers, woven or non-woven fabric pieces, or 
pads, all impregnated with the composition.

The invention will be appreciated in greater detail from the following 
examples of specific embodiments thereof. 
EXAMPLE 1 
A skin cream is made up from the following recipe: 
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Parts by Weight 
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A. Oil Phase 
Stearic acid 13.0 
Microcrystalline wax 
6.5 
Olive oil 3.5 
Glyceryl monostearate 
3.5 
(acid-stable grade) 
Polyoxyethylene sorbitan 
12.0 
monolaurate.sup.1 
Silicone fluid (200-350 
3.0 
centistokes) 
B. Aqueous Phase 
HEPES 0.2 
Water (q.s. ad 100.0) 
58.3 
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.sup.1 The product sold under the trade name TWEEN 20 
This cream is rubbed into the hands before working with a cyanoacrylate 
adhesive composition. It will normally give protection against sticking of 
the fingers together or to an object being glued, for a working session of 
4-5 hours. It is non-greasy and comfortable to use. 
EXAMPLE 2 
An application stick is made from the following ingredients: 
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Parts by Weight 
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Eutanol G.sup.1 (2-octadodecanol) 
39.0 
Comperlan HS.sup.1 11.0 
(stearic acid monoethanolamide) 
Stearic acid 10.0 
HEPPS 5.0 
Ethanol 96% v/v 20.0 
Glycerol 15.0 
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.sup.1 Henkel International, Federal Republic of Germany. 
The ingredients other than ethanol are mixed and melted together. The 
temperature of the melt is brought below 70.degree., whereupon the ethanol 
is added and well mixed in. The melt is poured into suitable moulds and 
allowed to set. The resulting moulded sticks are removed from the moulds, 
wrapped individually in aluminium foil and packed. 
A stick is rubbed on the hands before working with a cyanoacrylate adhesive 
composition. The protection period is similar to that given by the 
compositions of the previous Example. 
EXAMPLE 3 
This example illustrates a typical formulation which can be used for 
preparing a protective composition in accordance with the invention, using 
any zwitterionic substances ("ZASA's") which have suitable properties, 
including those mentioned in the present specification. 
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Ingredient Parts by Weight 
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Stearic acid 10.05 
Vegetable oil (e.g. Sunflower) 
8.0 
Glyceryl monostearate (self- 
2.50 
emulsifying) 
Silicone oil (DC Silicone 200/350, 
0.50 
Dow Corning) 
TWEEN 20 (Polyoxyethylene 
10.40 
sorbitan monolaurate) 
The selected "ZASA" 0.10 to 1.00* 
Water (q.s. ad 100) 68.45 to 67.55 
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*A preferred proportion here is 0.55. 
The ingredients are put together by known pharmaceutical procedures, such 
as those set out in the previous examples. 
In addition to preservatives, other conventional pharmaceutically 
acceptable additives may be incorporated in the compositions of the 
invention. These include, for example, humectants, film formers and water 
repellents. Sorbitol is a useful humectant. A 4% mucilage of Methyl 
cellulose is a useful film former. The dimethyl silicones sold by Imperial 
Chemical Industries Ltd. of the UK under the trade designations F 110 and 
F 111, are useful water repellents. 
Compositions of the invention, when applied to a person's skin, prevent 
skin-to-skin adhesion, and adhesion of skin to other substrates, when a 
cyanoacrylate adhesive composition is present as a skin contaminant, or is 
present on a said substrate. They do not prevent polymerisation of the 
cyanoacrylate, however. They can be removed from the hands together with 
the polymerised cyanoacrylate contaminant by a simple soap and water wash. 
In the particular case of a composition of the invention which is a skin 
cream containing both HEPES and HEPPS, it has been found that the 
proportion of these active ingredients is desirably about 1 part of HEPES 
to 10 parts of HEPPS by weight. This yields a cream with desirable 
physical properties. 
When one is working with a cyanoacrylate adhesive and using a composition 
of the invention, one should take care to avoid contamination of the 
substrate with the composition, before the adhesive is applied thereto. 
Intended adhesive bonds can be accidentally rendered weak or ineffective 
by traces of the compositions of the invention. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the present invention, and all such 
modifications as would be obvious to one skilled in the art are intended 
to be included within the scope of the following claims.