Process for the treatment of cellulosic moulded bodies

Details Process for the treatment of cellulosic moulded bodies Process for the treatment of cellulosic moulded bodies

1999-06-15

2001-06-05

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Treating shaped or solid article

C008S190000, C264S345000

Reexamination Certificate

active

06241933

ABSTRACT:

The invention relates to a process for the treatment of cellulosic moulded bodies whereby the moulded bodies are contacted with an aqueous solution of a textile agent having two reactive groups in alkaline medium.
BACKGROUND OF THE INVENTION
In the last few decades intensive efforts were undertaken to produce alternative environmentally-friendly processes as a result of the environmental problems associated with the well-known viscose process. One of the most interesting things to take shape in the recent past was the possibility to dissolve cellulose in an organic solvent without the formation of a derivative and to extrude moulded bodies from this solution. Fibres spun from solutions of this kind were given the generic name of Lyocell by BISFA (The International Bureau for the Standardization of Man-Made Fibres) whereby a mixture of an organic chemical and water is meant by an organic solvent. Moreover, fibres of this kind are known as “solvent spun fibres”.
It has turned out that a mixture of a tertiary amine oxide and water is particularly well suited as the organic solvent for the production of Lyocell fibres respectively other moulded bodies N-methyl-morpholine-N-oxide (NMMO) is thereby principally used as the amine oxide. Other suitable amine oxides are disclosed in EP-A 0 553 070. Processes for the production of cellulosic moulded bodies from a solution of cellulose in a mixture of NMMO and water are for example disclosed in U.S. Patent Ser. No. 4,246,221 or PCT-WO 93/19230. In this respect the cellulose is precipitated from the solution into an aqueous precipitation bath. Fibres manufactured in this way are characterised by a high fibre tenacity in a conditioned and wet state, a high wet modulus and a high loop strength.
One special property of these fibres is the high propensity to fibrillate, particularly when put under strain in a wet state, such as happens for example during the washing process. Whilst this property is perfectly desirable for certain fibre applications and produces interesting effects, the workability for other purposes, such as textiles for example, which should be wash-resistant, is reduced.
Thus, no effort was spared to reduce the fibrillation behaviour with various measures.
Numerous publications deal in particular with the possibility to reduce the tendency to fibrillate of the fibres by treating these with substances which have a cross-linking effect on cellulose.
According to EP-A-0 538 977 the fibres, which can be either freshly spun or already dried, are treated in an alkaline milieu with an aqueous system which contains a chemical reagent with 2 to 6 functional groups which can react with cellulose. In EP-A-0 538 977 derivatives of cyanuric chloride, and substituted dichlortriazines in particular, are named as suitable substances. Moreover, addition products of cyanuric chloride and poly(ethylene glycol) monomethylether are used.
From EP-A-0 616 071 it is known that fibre materials containing cellulose, such as textiles for example, should be treated amongst other things with metallic salts of partial hydrolyzates of cyanuric chloride to give the textiles crease resistant and easy care properties. The use of substances of this kind to treat solvent spun fibres is not, however, mentioned.
In relation to the reduction of the tendency to fibrillate of cellulosic moulded bodies, which are shaped from a solution of cellulose in tertiary amine oxides, no publication exists to date despite numerous efforts in this field which describes the use of multifunctional textile agents the effect of which justifies the, in the main, high price of these substances.
SUMMARY OF THE INVENTION
Thus it is the task of this invention to make a process available for the treatment of cellulosic moulded bodies, which are shaped from solutions of cellulose in aqueous tertiary amine oxides, using multifunctional textile auxiliary agents, which leads to the efficient improvement of the properties of the moulded bodies as a result of using favourably priced treating substances and, in the case of fibres, of the tendency to fibrillate in particular.
This task is resolved by a process in accordance with the first part of claim
1
which is characterised in that a compound of the formula
whereby X is halogen, R═H or an ionic residue and n=0 or 1, respectively a salt of this compound is used as the textile auxiliary agent. As a halogen residue X chlorine should be given preference.
Surprisingly it was shown that the textile agents used in accordance with the invention, which are relatively favourably priced, have just as great an effect or even produce a greater improvement in the properties of the moulded bodies treated as for example the substances known from EP-A 0 538 977 which are manufactured in a laborious manner. Thus it is possible to solve for example the problem of the tendency to fibrillate of solvent-spun fibres in an economic way.
In comparison to the addition products of cyanuric chloride and non-ionic residues as described in EP-A 0 538 977 the compounds according to the invention are present in ionic form in the aqueous solution in the alkaline milieu.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferably a salt, particularly a metallic salt of a compound in accordance with formula (I), in which n=0, i.e. a salt of 2,4-dichloro-6-hydroxy 1.3.5-triazine, is used. Sodium, potassium or lithium salt are preferably used as the metallic salt.
It is, however, also possible to use 2,4dichloro-6-hydroxy 1.3.5-triazine as such whereby the ionic form is formed in the alkaline medium of the treatment of the moulded body.
Preferably the residues R are anionic residues, e.g. —SO
3
or —C
1
-C
6
-alkyl—SO
3
or CO
2
or—C
1
-C
6
-alkyl—CO
2
. The residues R can, however, also be cationic. Residues R with e.g. —C
1-C
6
-alkyl—N
+
(C
1
-C
4
-alkyl)
3
are given preference.
In one preferred embodiment of the invention the treated cellulosic moulded bodies are never dried fibres. Solvent-spun fibres in their state before the first drying are designated as “never dried” fibres. It has been shown that the use of compounds of the formula (I) on never dried fibres in particular produces a considerable reduction in the tendency to fibrillate.
Moreover, the use of compounds of formula (I) on already dried solvent-spun fibres or textiles made of these, e.g. fabrics, warp-knitted fabrics or knitted fabrics, produces excellent results.
The pH value of the aqueous solution of the textile auxiliary agent preferably equals 12 to 14 when it is brought into contact with the moulded bodies.
In another preferred embodiment of the invention the pH value of the aqueous solution of the textile auxiliary agent is only held in a weak alkaline range from 7 to 9, e.g. from 7,5 to 8,5 and preferably from 8 to 9 when bringing into contact with the moulded bodies. Since the two reactive halogen substituents of the compounds according to formula (I) have difference reactivities, first of all a reaction of the first reactive group of the textile auxiliary agent takes place with the cellulose. The moulded bodies are then pressed and brought into contact with an alkaline aqueous solution with a pH value of 11 to 14, e.g. a pH value of 13. The reaction of the second reactive group of the textile auxiliary agent thereby takes place with the cellulose. This embodiment of the invention is described in the following as the “two-bath” process.
The advantage of this preferred embodiment of the invention is that hydrolysis of the substance in accordance with formula (I) can be put last with only weak alkaline pH values and fewer hydrolysis losses have to be taken into account. This contributes to the economic efficiency of the process.
In a preferred embodiment of the invention the moulded bodies are submitted to heat treatment during or after the bringing into contact with the aqueous solution of the textile auxiliary agent. In the case of the two bath process the heat treatment can take place during and/or after being brought into contact with the weak alkaline solution of the

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