This invention relates to the treatment of wool, and is particularly
concerned with a process for improving its resistance to shrinkage.
A process very widely used for this purpose entails subjecting the
wool to an oxidation treatment, usually a chlorination, as with free chlorine or
a hypochlorite or dichloroisocyanurate salt; removing unreacted (and potentially
very damaging) oxidising agent from the wool fibres, as by passage through a reducing
medium such as sodium sulphite solution, followed by a water rinse; and then treating
the wool with a synthetic resin to impart a resistance to shrinkage which supplements
that given by the oxidation treatment. Usually thereafter, but sometimes simultaneously
with the resin treatment, the wool is treated with a softening agent to soften
the harsh handle which it would otherwise have as a result of the resin treatment;
and in due course the treated wool is dried evenly at a moderately raised temperature
to ensure that adequate curing of the resin has taken place.
The process just outlined can be applied to the treatment of wool
tops (ie wool fibre before it is spun) as well as to the treatment of yarn and
of woollen piece goods and garments.
Probably the resins most used in the process are those obtained by
reaction of epichlorhydrin (a compound having a reactive epoxy group attached to
the radical -CH&sub2;Cl) with a polyamide whose repeating unit contains basic -NH-or
-NH&sub2; groups, as distinct from the non-basic -NH- groups of the amide linkage
-CO.NH-. Such a resin is for example that obtained by the reaction of epichlorhydrin
with the condensation product of a polyalkylene amine eg triethylene diamine (H&sub2;NCH&sub2;CH&sub2;NHCH&sub2;CH&sub2;NH&sub2;)
and adipic acid (HO&sub2;C.CH&sub2;CH&sub2;CH&sub2;CH&sub2;CO&sub2;H). Not all
such resin is exhausted onto the wool from whatever medium the epichlorhydrin
resin is applied, and there is now strong evidence that the resin-containing aqueous
effluent from the process is harmful because of the presence in it of chlorine
covalently bound to carbon, as in the -CH&sub2;Cl group.
We have now found that effluent problems can be greatly reduced,
and a treated wool product obtained with properties just as good as those that
result when an epichlorhydrin resin is employed, by using a colloidal melamine
resin as the resin to impart shrinkage. Colloidal melamine resins are used in the
treatment of paper to improve its wet strength, and are obtained by dissolving
a partially condensed melamine formaldehyde resin in an acid such as hydrochloric,
formic, acetic or lactic acid under controlled conditions, and further diluting
with water. The solution becomes infinitely miscible with water, and on aging
develops a bluish haze. The solution contains positively charged colloidal particles
of the melamine resin.
According to the invention, there is provided a process for the treatment
of wool to improve its resistance to shrinkage, by subjecting it first to an oxidation
treatment and then to a resin treatment to supplement the shrink resistance imparted
by the oxidation treatment, the resin treatment being accompanied or followed by
treatment with a softening agent to soften the harsh handle associated with use
of the resin, in which process the resin employed is a colloidal melamine resin
and the softening agent employed is a silicone polymer.
Preferably, the silicone polymer is dispersed in the colloidal melamine
resin,ie in the aqueous phase which constitutes the dispersion medium of that system.
There is described in EP-A-80272 a process for the shrink-resist
treatment of wool, by
a chlorinating the wool with an acidified hypochlorite
b removing excess chlorinating agent from the wool
c applying to the acidified wool an acid colloid solution of a methylol melamine
resin, which solution may contain a suitable softening agent, such as for example
those of the polyethylene type.
EP-A-80272 is not, however, concerned to avoid effluent problems
arising from the presence of -CH&sub2;Cl or like groups in the resin conventionally
used for wool treatment; nor does it mention the use of a silicone polymer as
softening agent, a use which we have found has the advantage over polyethylene
softeners of producing in the wool better stabilisation against shrinkage and better
non-felting properties during washing.
The silicone polymer employed as softening agent may be cationic,
but is preferably non-ionic. In general the silicone polymer used shows no chemical
reactivity towards the colloidal melamine resin.
The melamine resin employed is preferably one which has at least
two -CH&sub2;OR groups per melamine nucleus, where R = H or is an alkyl group containing
from one to four carbon atoms.
The invention is further illustrated by the following Examples.
An acidic melamine resin solution was produced by mixing the following
ingredients in the following proportions by weight.
The mixture was allowed to stand for 2 hours to develop colloidal
properties, and was then diluted with an equal volume of water to give a colloidal
melamine resin having a shelf life of more than 6 months.
The diluted composition (1 part by weight) was further diluted with
water (4 parts) and to this mixture was added an aqueous emulsion of a non-ionic
polydimethylsiloxane (0.5 parts by weight; silicone content 35% by weight). (The
silicone release agent sold by Basildon Chemicals under the designation BC330
is very suitable.)
The mixed melamine resin/silicone polymer composition was then applied,
from a bath adjusted with acetic acid to pH 5-6, to knitted wool garments which
had been conventionally chlorinated with a dichloroisocyanurate salt, treated
with antichlor, and rinsed.The bath temperature was slowly raised from ambient
to 40° C during 10 minutes, and held at that temperature for a further 10 minutes
to exhaust the melamine resin and silicone polymer onto the wool. Weight gain was
about 1.5% by dry weight of the wool.The material was then removed from the bath,
hydroextracted and tumble-dried at 60-80° C.
For the treatment of wool tops the procedure of Example 1 was modified
The mixed melamine resin/silicone polymer was applied in the 4th
bowl of a conventional 5-bowl unit to deposit about 1.5% of solid mixture onto
the tops. The treated tops were then passed to the 5th bowl, in which a cationic
substituted stearamide had been included as additional softener. The tops were
finally dried at 70-80° C.
A process for the treatment of wool to improve its resistance to shrinkage,
by subjecting it first to an oxidation treatment and then to a resin treatment
to supplement the shrink resistance imparted by the oxidation treatment, the resin
treatment being accompanied or followed by treatment with a softening agent to
soften the harsh handle associated with use of the resin, characterised in that
the resin used is a colloidal melamine resin and the softening agent is a silicone
A process according to claim 1, in which the silicone polymer is dispersed
in the colloidal melamine resin.
A process according to claim 1 or 2, in which the silicone polymer is non-ionic.
A process according to claim 3, in which the silicone polymer is a polydimethylsiloxane.
A process according to any of claims 1 to 4, in which the melamine resin has
at least two -CH&sub2;OR groups per melamine nucleus, where R = H or C&sub1;-&sub4;
A process according to any of claims 1 to 5, in which the oxidation treatment
is a chlorination.
A process according to claim 6, in which the chlorination utilises a dichloroisocyanurate
A process according to any of claims 1 to 7, applied to the treatment of wool
A process according to any of claims 1 to 7, applied to the treatment of knitted