Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Reexamination Certificate
2001-11-28
2003-11-18
Mayekar, Kishor (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
C204S165000, C008S128100
Reexamination Certificate
active
06649029
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to nonfelting wool and a process for antifelt finishing by treating the wool with a plasma and also to an aftertreatment with a specific finishing agent.
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, especially self-dispersing isocyanates, have long been used as auxiliaries for the antifelt finishing of textiles. However, self-dispersing isocyanates, the use of which has become preferred, do not always provide a completely satisfactory antifelt finish on the treated textiles when used alone.
DE-A 198 587 34 and DE-A 198 587 36 disclose the antifelt finishing of wool by combination of a plasma treatment with an after-treatment using such self-dispersing isocyanates. To apply these self-dispersing isocyanates to the wool, it is first necessary to prepare aqueous dispersions. Since such dispersions have only a very limited shelf life, due to the ensuing crosslinking reaction of the isocyanate end groups in water, they have to be prepared relatively shortly before use for wool treatment.
DE-A 2 035 172 describes a process for the antifelt finishing of wool in which the wool is treated with a polyurethane latex liquor and the fabric is dried and subsequently cured. To be able to prepare latices suitable for finishing, organic solvents and external emulsifiers have to be used at the prepolymerization stage. The prepolymers initially obtained are subsequently fully polymerized by addition of a chain extender.
DE-A 26 57 513 discloses a process for the antifelt finishing of wool using reaction products of polyisocyanates with hydroxyl-functional compounds.
DD 5381 describes a process for preparing hydrophilic basic polyurethanes from diisocyanates, diprimary aliphatic glycols containing one or more basic tertiary nitrogen atoms in open chain, and diprimary glycols without basic nitrogen. Possible applications mentioned for such products are very generally films, fibers, sizing and hand modifying agents, animalizing agents, and sizing agents for paper.
DD 5379 describes a process for preparing hydrophilic basic polyurethanes from diisocyanates and nitrogenous glycols containing, in the chain between the hydroxyl groups, one or more tertiary nitrogen atoms in which third valencies are saturated by monovalent alkyl groups that do not have more carbon atoms than the shortest carbon chain between a hydroxyl group and tertiary nitrogen. Possible applications mentioned for such products are very generally films, fibers, sizing and hand modifying agents, animalizing agents, and sizing agents for paper.
DD 5367 describes very specific polyurethanes prepared from diisocyanates and N,N′-di[oxyalkyl]piperazines.
It is an object of the present invention to provide an improved process for the antifelt finishing of wool.
SUMMARY OF THE INVENTION
The present invention accordingly provides a process for antifelt finishing of wool comprising
(a) exposing wool to a plasma in a pretreatment, and
(b) treating the plasma-treated wool with an aqueous dispersion of cationic polyurethanes.
DETAILED DESCRIPTION OF THE INVENTION
The plasma treatment of the wool in step (a) of the process of the invention is effected either as a low temperature plasma treatment at reduced pressure or as a corona treatment at normal pressure.
The low temperature plasma treatment is extensively described in DE 196 16 776 C1 (counterpart of U.S. Pat. No. 6,103,068, hereby expressly incorporated by reference). The wool is exposed to a radiofrequency discharge of a frequency of 1 kHz to 3 GHz and a power density of 0.003 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 process is preferably carried out under a pressure of 0.1 to 1 mbar and for a period of 2 to 5 minutes.
The actual low temperature plasma is generated by feeding in electromagnetic radiation in the frequency range of 1 kHz to 3 GHz. In a preferred variant, the low temperature plasma is generated via a microwave discharge of 1 to 3 GHz (the power density at the outcoupling is especially 0.1 to 15 W/cm
2
). The electromagnetic radiation can be supplied continuously or pulsed. A pulsed high frequency discharge having a pulsing frequency of up to 10 kHz is especially advantageous.
When non-polymerizing gases are additionally used as plasma process gases, they are introduced into the plasma treatment space at a flow rate of up to 200 l/h. Useful non-polymerizing gases are in particular oxygen, nitrogen, noble gases, especially argon, air, or mixtures thereof.
The design and construction of a low temperature plasma reactor are known. Preference is given to using an electrodeless reactor having an outcoupling for microwaves. The wool to be treated is preferably placed underneath the outcoupling unit. The distance of the wool from the outcoupling unit is preferably 1 to 30 cm, especially 2 to 10 cm. After the wool to be treated has been introduced into the reactor, the reactor is suitably evacuated with vacuum pumps in such a way that the pressure during the plasma treatment is in the range of 10
−2
to 10 mbar, preferably 0.1 to 1 mbar. A continuous flow-through operation is preferably carried out by applying specific vacuum locks that make it possible for the material to enter and exit without leakage.
Alternatively to this embodiment of the low temperature plasma treatment under low pressure, the wool can also be subjected to a corona treatment at a pressure in the range of 100 mbar to 1.5 bar, preferably at atmospheric pressure. The corona treatment is described in detail in DE-A 198 587 36 (counterpart of U.S. Pat. No. 6,242,059, hereby incorporated by reference).
The corona treatment subjects the wool to a high frequency discharge having a power density of customarily 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 DE-A 197 31 562. The corona treatment is preferably carried out via 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.
Performing the corona treatment at a pressure in the range from 100 mbar to 1.5 bar, preferably at atmospheric pressure, has the advantage over the low pressure plasma treatment at 10
−2
to 10 mbar that the equipment needed is very much less complicated than in the case of the low pressure treatment. Vacuum pumps are not required, nor is it necessary to fit special vacuum locks.
The special effect of the plasma treatment in step (a) of the process of the invention might 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
Heinen Ralf
Jansen Bernhard
Kümmeler Ferdi
Akorli Godfried R.
Bayer Aktiengesellschaft
Eyl Diderico van
Mayekar Kishor
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