Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of coating supply or source outside of primary...
Reexamination Certificate
1999-12-08
2001-06-05
Einsmann, Margaret (Department: 1751)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of coating supply or source outside of primary...
C427S569000, C008S128100, C008S115520
Reexamination Certificate
active
06242059
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to nonfelting wool and to a process for producing it by (a) a plasma treatment of the wool and (b) an after-treatment with aqueous dispersions of self-dispersing isocyanates.
The textile processing industry has a particular interest in reducing the felting tendency of wool, especially of raw wool or unprocessed wool. The felting of wool is customarily reduced by finishing with specific auxiliaries.
Isocyanates for the antifelt finishing of textiles are well known and can be used, for example, as described in DE-A 1,904,802, in organic solvents or, as described in DE-A 1,769,121, in aqueous dispersion with the aid of emulsifiers. Both organic solvents and possibly water-polluting emulsifiers are today no longer appropriate for ecological and occupational hygiene reasons. Prior artisans therefore developed self-dispersing isocyanates and also formulations containing very low levels of solvents or emulsifiers as auxiliaries and additives.
DE-A 1,794,221 describes the treatment of fiber materials with isocyanate prepolymers which still contain free isocyanate groups. This finishing process can take place in solvents such as perchloroethylene or in aqueous emulsion by using auxiliary emulsifiers.
U.S. Pat. No. 3,847,543 discloses a process for the antifelt finishing of wool using an aqueous dispersion simultaneously containing aliphatic isocyanates, OH-functional crosslinkers, and organometallic catalysts. Although this process takes place in an aqueous phase, auxiliary solvents and emulsifiers continue to be required.
DE-A 2,657,513 describes a process for the antifelt finishing of wool by treating the wool yarn with an aqueous liquor that contains the felt-proofing agent. The feltproofing agents used are reactive polyolefins, reaction products of polyisocyanates and hydroxyl compounds, silicone polymers, aziridine compounds, reaction products of epoxides with fatty amines and dicarboxylic acids or polyamides, reaction products with thiosulfate end groups, or, preferably, reaction products with mercapto end groups.
WO 95/30045 describes a process utilizing specific isocyanates for the antifelt finishing of wool. No solvents or emulsifiers are needed because the isocyanates used are water-dispersible. The wool is first subjected to a pretreatment with oxidizing agents, followed by a reductive treatment, before the water-dispersible isocyanates are used. The disadvantage with this process is that the oxidative and reductive pretreatment gives rise to wastewaters that must be properly neutralized and treated.
The prior art further includes another method for the antifelt finishing of wool where the wool is treated with a plasma. DE-A 4,344,428 discloses, for example, a process in which the wool is subjected to an antifelt finish comprising a combination of plasma or corona pretreatment and enzymatic aftertreatment. The wool is sensitized with a solution that contains sulfide ions prior to the enzyme treatment.
DE 196 16 776 Cl further describes a process for the antifelt finishing of wool where moist wool material having a water content of 4 to 40% by weight is exposed to a low pressure plasma treatment before being further processed into textile fabrics or sheets. The wool is subjected to a radio frequency discharge at a frequency of 1 kHz to 3 GHz and a power density of 0.001 to 3 W/cm
3
at a pressure of 10
−2
to 10 mbar for a period of 1 to 600 sec in the presence or absence of non-polymerizing gases. The disadvantage with this process is the complicated equipment. Specific vacuum pumps are needed, and vacuum locks must be fitted so that the material may enter and exit without streaming.
The German Patent Application bearing the file reference 197 36 542.6 (unpublished at the priority date of the present invention) discloses a process for the antifelt finishing of wool in which the wool is initially likewise pretreated with a low pressure plasma and subsequently aftertreated with aqueous dispersions of self-dispersing isocyanates. Again, the equipment needed for the low pressure plasma treatment is a disadvantage.
The invention has for its object to provide by a technically improved process nonfelting wool which after further processing into made-up merchandise does not felt and shrink in machine washing.
SUMMARY OF THE INVENTION
The present invention provides nonfelting wool prepared by a process comprising
(a) exposing wool to a plasma in a corona treatment, and
(b) subsequently treating the treated wool with an aqueous dispersion of self-dispersing isocyanates.
The present invention further provides a process for the antifelt finishing of wool comprising
(a) exposing the wool to a plasma in a corona treatment, and
(b) subsequently treating the treated wool with an aqueous dispersion of self-dispersing isocyanates.
DETAILED DESCRIPTION OF THE INVENTION
The wool used may be selected from a very wide range of wool materials, for example, raw wool after the raw wool scour, dyed or undyed wool slubbing, or dyed or undyed wool yarn, knits, or cloths. The water content of the wool is customarily 4 to 40% by weight (preferably 5 to 30% by weight, particularly preferably 6 to 25% by weight, especially 8 to 15% by weight).
Step (a) of the process of the invention requires that the wool be exposed to a plasma in a corona treatment. The corona treatment is carried out at a pressure within the range from 100 mbar to 1.5 bar, preferably at atmospheric pressure.
The corona treatment subjects the wool to a radiofrequency discharge customarily having a power density of 0.01 to 5 Ws/cm
2
for a period of 1 to 60 seconds (preferably 2 to 40 seconds, particularly 3 to 30 seconds) in the presence or absence of non-polymerizing gases. Suitable non-polymerizing gases are air, oxygen, nitrogen, noble gases, or mixtures thereof.
The actual plasma is generated by applying an alternating voltage of 1 to 20 kV in the frequency range between 1 kHz to 1 GHz (preferably 1 to 100 kHz) to electrodes, one or both poles being provided with an insulator material. The alternating voltage can be supplied either continuously or with individual pulses or with pulse trains and pauses in between.
The design and apparatus configurations of a corona reactor are known and described for example in the German Application bearing the file reference 197 31 562 (unpublished at the priority date of the present invention). The corona treatment is preferably carried out by electric discharges in the atmospheric pressure region, for which the wool to be treated is initially introduced into a sealed, tight treatment housing, charged there with the working gas (i.e., the above-mentioned non-polymerizing gas) and subsequently exposed to an electric barrier discharge in a gap between the two treatment electrodes. The distance of the wool material from the treatment electrodes is 0 to 15 mm (preferably 0.1 to 5 mm, particularly 0.3 to 2 mm). The treatment electrodes are preferably constructed as rotatable rolls, either or both of which are coated with electrically refractory dielectric material.
The special effect of the plasma treatment in step (a) of the process of the invention can be explained as follows. The liquid present in the fiber desorbs from the fiber surface as water vapor/gas during the process. High energy electrons, ions, and also highly excited neutral molecules or radicals are formed and act on the surface of the fiber, the water vapor desorbed from the fiber ensuring that particularly reactive particles are formed in the immediate vicinity of the respective fiber surface and these particularly reactive particles act on the surface.
The self-dispersing isocyanates useful in step (b) form part of the subject-matter of the German Patent Application bearing the reference number 197 36 542.6 (unpublished at the priority date of the present invention). Such isocyanates have an isocyanate content of 1 to 25% by weight, calculated as NCO (having a molecular weight of 42 g/mol), and are obtainable by reaction in any order of
(I) organic polyisocyanates having an avera
Jansen Bernhard
Kummeler Ferdinand
Müller-Reich Claus
Thomas Helga
Bayer Aktiengesellschaft
Einsmann Margaret
Gil Joseph C.
Henderson Richard E. L.
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