Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1995-12-12
1997-02-18
Diamond, Alan D.
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9418, 252 857, 427384, 427389, 428473, C14C 900
Patent
active
056037333
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB95/00842 filed Apr. 10, 1995.
This invention relates to the treatment of leather so as to render it water-repellant while maintaining or improving its flexibility.
Processes are known for rendering leather water-repellant, often combined with retanning the leather, by the application of certain polymeric materials. Fat liquoring processes may also render the leather water-repellant. Various processes of this type are described in EP-A-372,746, EP-A-412,389 and AU-A-90/60227 and in our European Application No. 93306480.0.
Processes involving the use of a polymeric material have the tendency to reduce the flexibility of the leather.
It is known to treat leather with a conventional amphoteric surfactant, such as coco-amidopropyl betaine, but this is not very effective at rendering the leather either water-repellant or flexible.
Other amphoteric surfactants are known. An example of such surfactants is in GB 1398277. Another amphoteric compound is the sulphonate-containing material described in GB 1401984 as being suitable for finishing textiles, paper or leather. The sulphonate group or groups in such materials would interfere with the properties we are seeking.
It would be desirable to provide an improved treatment of leather by which leather can be given an improved combination of water-repellency and flexibility, including softness.
According to the invention, leather is rendered flexible and water-repellant by a process comprising treating the leather with an aqueous solution of an amphoteric surfactant which has molecular weight below 5,000 and which includes at least 1 surfactant hydrophobe group of at least 8 carbon atoms, at least 2 cationic groups, and at least 2 anionic groups wherein the anionic groups are carboxylic groups.
The invention includes leather impregnated with the defined surfactant.
In this specification we use the term cationic to embrace free base, acid addition and quaternary ammonium salts, and we use the term anionic to embrace free acid and acid salts, of carboxylic acid groups.
The molecular weight must be low in order to achieve the desired flexibility. Generally the molecular weight is below 2000. The surfactant can be a low molecular weight polymeric material or condensate having two or more of the hydrophobic groups; for instance it can be a polymer of 2 to 20usually 3 to 10recurring monomer units some or all of which include a hydrophobic group (for instance R defined below). When the material is a polymer, the molecular weight can be determined by any conventional manner suitable for that polymer, for instance gel permeation chromatography.
Preferably the surfactant is a monomeric material (ie it does not contain a recurring unit derived from a monomer) and usually contains only one of the surfactant hydrophobe groups.
Preferred materials comprise a polyamine on to which is substituted one or more hydrophobic groups and at least two carboxylic acid groups.
Preferred surfactants for use in the invention have the formula ##STR1## or a water soluble salt thereof wherein R is the surfactant hydrophobic group, generally alkyl, alkaryl or aralkyl of at least 8 carbon atoms two of the groups Q are carboxylic (i.e., not hydrogen) all carboxylic.
The preferred surfactant hydrophobic group R has up to 24 carbons, often 12 or 14 up to 20 or 24 carbons. Preferably it is C.sub.8-24 alkyl, most preferably C.sub.12-18 alkyl
The preferred group A is CH.sub.2).sub.y where y is 2 to 6 and the preferred groups B are each (CH.sub.2).sub.x where x is 1 to 4.
It is often preferred that n is 1, 2, 3 or 4 (preferably 3), x is 1 or 2 and y is 2 or 3 (preferably 3). When Z is a direct bond (or sometimes an ether linkage) and n is 2, 3 or 4, such compounds can be made by, for instance, reacting a fatty amine with a nitrile such as acrylonitrile, reducing the product to form an amine, repeating this sequence as often as desired, and then reacting the product with chloracetic acid (B=CH.sub.2) or with acrylic acid (B=CH.sub.2 CH.sub.2).
Another preferred group of comp
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Aiston Finlay D.
Allen Adrian S.
Allied Colloids Limited
Diamond Alan D.
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