WO1999046434A1 - Method for producing cellulosic moulded bodies - Google Patents

Abstract

The invention relates to a method for producing cellulosic moulded bodies, especially fibres, from solutions of cellulose in an aqueous, tertiary amine oxide by preparing the solution from a cellulose suspension in aqueous, tertiary amine oxide, extruding the solution through a mould, transferring the moulded solution through an air gap into a precipitation bath and rinsing and drying the resulting moulded body. The invention is characterized in that a colorant and/or colorant precursor is added to the solution and/or cellulose suspension and in that more than 95 weight %, in relation to the original quantity of colorant or colorant precursor used, of said colorant and/or colorant precursor is insoluble in the cellulose solution.

Description

 1 Process for the production of cellulosic moldings

The present invention relates to a process for producing cellulosic moldings, in particular fibers, from solutions of cellulose in an aqueous tertiary amine oxide.

Synthetic fibers such as polyamide and polyester as well as viscose fibers are now routinely dyed with a dope. Only pigments are used for spin dyeing, which are usually sold in the form of granules or pasta. Generally, pigments are dispersed in the polymer melt or mass.

In the case of viscose spin dyeing, the pigment preparations are metered in either in portions (cellar process) or to the main viscose line (injection process).

The advantages of spin dyeing include:

• Large batches of the same color can be achieved

• The coloring has high wet fastness

• The conventional dyeing process is no longer necessary, which results in energy savings, raw material savings (chemicals, water) and lower wastewater pollution

• no loss of dye

• The problem of splicing when coloring (streakiness) is eliminated

• Homogeneous dye distribution in the fiber, uniform coloring

• Fast color changes are possible with spinning dosing

It is known to produce cellulosic fibers by the so-called amine oxide process. A solution of cellulose is formed from a cellulose suspension in an aqueous tertiary amine oxide (preferably N-methyl-morpholine-N-oxide - NMMO) by evaporation of excess water and is extruded through a spinneret. The filaments formed are passed through an air gap into a precipitation bath, washed and 2 dried. Fibers produced in this way are also called “solvent-spun” fibers or “Lyocell fibers”.

It has been shown that the realization of a spin dyeing in the amine oxide process leads to various problems:

The circulation in the Lyocell process can lead to the accumulation of pigments, dyes and additives (e.g. from pigment preparations). The thermal instability of the cellulose solution in NMMO also results in a very narrow selection of colorants. Spinning problems caused by undissolved pigment particles should also be taken into account.

WO 94/20653 describes the production of matted regenerated fibers by adding hollow bodies made of acrylate polymers or styrene-acrylate copolymers.

According to WO 96/27638, matting, pigmentation of cellulosic threads, films and membranes are made up of compositions which consist of solid particles which are embedded in a matrix of cellulose, NMMO, water and possibly other additives and are inert to this matrix . The use of inorganic or organic pigments for pigmenting cellulose threads is also described.

DE 195 19 024 describes a process for the spin dyeing of regenerated cellulose fibers by adding and spinning a formulation of canonized polysaccharide and an anionic dye to a viscose composition, alkali cellulose or a cellulose solution. In general, this document also describes the use of this process in solutions of cellulose in an amine oxide. According to the authors of this document, the use of a cationized polysaccharide is necessary to prevent washing out of the incorporated dye from a regenerated cellulose fiber.

The object of the present invention is to provide improved colored cellulosic moldings, in particular fibers, produced by the amine oxide process. This object is achieved by adding a colorant and / or a colorant precursor to the solution of the cellulose in the tertiary amine oxide and / or the cellulose suspension in the tertiary amine oxide, which colorant or which colorant precursor in the cellulose solution is based on more than 95% by weight on originally used colorant or colorant precursor is insoluble.

In the amine oxide process, it has surprisingly been found that, in contrast to viscose spin dyeing, in addition to the conventional pigments for spin dyeing, direct, reactive, vat or sulfur dyes and also development dyes can be used, provided that the colorants used in the solution of the cellulose in the tertiary amine oxide essentially are insoluble. Colorants or colorant precursors which are more than 97% by weight and more preferably more than 99% by weight insoluble in the cellulose solution are preferred.

Obtaining good results is apparently not from the simultaneous presence of a cationic polysaccharide in the solution, e.g. described in DE-A 195 19 024, depending.

The amount of colorants or colorant precursors used is chosen such that the content of colorant or colorant precursor in the resulting shaped body, based on cellulose, is 0.1 to 5% by weight, preferably 0.5 to 3% by weight.

The advantage of a spin dyeing of Lyocell fibers is that the problem of streaky dyeing due to the tendency of the fibers to fibrillate under mechanical stress is avoided. In spin dyeing, all shades can be adjusted by mixing fewer starting dyes. The dyeing process is independent of the usual dyeing parameters such as temperature, dyeing time, substantivity, reactivity, diffusion behavior, etc. In this way, large quantities of fibers can be produced with a constant depth of color and uniform dyeing across the fiber cross-section. 4

The dyes used have no negative influence on the quality of the solution (grade), the spinning safety and the fiber data.

It should be noted that metal-containing colorants should not be added to the suspension before solution preparation due to the thermal decomposability of the cellulose solution. However, if the colorant used is essentially insoluble in the cellulose solution, as required by the invention, it is possible to add the colorant to the solution.

The colorant or the precursor of a colorant can be added in powder or granule form or as a liquid brand (pasta) or in the form of a masterbatch (cellulose / colorant) for NMMO / cellulose suspension preparation or for solution preparation.

A preferred embodiment of the process according to the invention is characterized in that a vat or a sulfur dye in the oxidized form is added to the cellulose suspension or the cellulose solution.

It is thus possible in a simple manner to produce solvent-spun fibers which are spin-dyed with vat or sulfur dyes in a single step, since the

The dye can already be added in the oxidized and thus coloring form.

This is e.g. not possible in the production of viscose fibers because the viscose is a reducing medium and therefore the oxidized form of the dye is not stable in this medium.

A further preferred embodiment of the method according to the invention is characterized in that the dye precursor of a development dye is added.

It is known to treat fibers with a dye precursor and to pass the fibers thus treated through a bath which contains a component which e.g. by a

Coupling reaction with the dye precursor can form the finished dye. To this 5

If a few dye precursors (e.g. naphthol components) are selected, it is possible to produce a wide variety of colors on the fiber by varying the diazo component.

A general overview of the chemistry of developing dyes is given by ULLMANN's Encyclopedia of Industrial Chemistry, 5th edition, volume A3, pages 303 ff.

It has now been shown that it is possible to use dye precursors, e.g. Add Naphtol components, the cellulose suspension or the cellulose solution. The resulting shaped body contains the naphthol component and can now be finish-dyed in a known manner with a solution which contains the desired diazonium compound.

This dyeing step can be carried out immediately after the fiber has been washed out. A dye precursor, such as a naphthol component (e.g. 2-hydroxy-3-naphthoic acid anilide), is added to the suspension or solution preparation. The dye development (coupling) on the never dried fiber takes place in a post-treatment step immediately after the washout process. For dye development, the staple fibers or staple fibers primed with a Naphtol AS component are passed through a solution which contains a dye-fast salt or a diazonium salt solution of a dye base. This is due to the choice among different

Dye-proofing salts, with the same primer, enable a very quick change of shades.

However, it is also possible to deliver the fiber before dye development. The fiber then contains the dye precursor and can be used in any further processing stage, e.g. to a fabric that is ready-dyed according to the customer's requirements.

It is thus possible, by selecting a few dye precursors (eg naphthol components), to provide solvent-spun fibers which contain the dye precursor and by selecting a wide variety of diazonium components in a wide range of colors from the respective customer to the desired dyed product 6 can be treated further. The customer saves the first stage (applying the naphthol component) of the normally two-stage development dyeing process.

Organic pigments and pigment preparations such as e.g. Azo pigments, carbonyl pigments such as Anthraquinones, quinacridones, as well as polymethines, sulfur dyes and phthalocyanines in question. Anthraquinone dyes are particularly suitable.

Examples: General implementation:

The pigments or dyes were suspended or dissolved in an NMMO / water mixture, after which the cellulose was added. The suspension was made into a spinnable mass by evaporating excess water in a known manner. 1-3% dye based on cellulose was used.

To determine the amount of dye which can be washed out, lg fibers were spun in a known precipitation bath volume (450 ml), wound onto a godet (0.6 m / min) and washed out at the same time (150 ml). The spinning time was 33 minutes in each case. The threads were then washed for 15 minutes in a post-treatment bath (200 ml) at room temperature. The washed-out dye content can then be determined by VIS spectroscopic examination of the precipitation and washing baths and is a measure of the solubility of the dye in the cellulose solution.

The cellulose solutions are composed as follows (data in% by weight):

15% cellulose 76% NMMO 9% H ₂ O 0.1% propyl gallate (GPE) as a stabilizer

0.15-0.45% (1-3% based on cellulose) dye The solution was extruded at a temperature of 115 ° C. through a nozzle with a hole diameter of 100 μm through an air gap of 30 mm in length into an aqueous precipitation bath and drawn off by means of a godet.

This process was used to produce dyed solvent-spun cellulose fibers using a variety of dyes and pigments. Table 1 lists the colorants tested and their solubility in the cellulose solution (the percentages relate to the amount of added dye based on cellulose):

Table 1

Colorants Colorant class Solubility

Supramin Red GW 1% acid dye soluble

Supramin Red GW 3% acid dye soluble

Naphtol AS 1% development dye insoluble

Solophenyl Red 2B 3% direct dye soluble

Drimaren Brillantrot K-BL 3% reactive dye soluble

Cibacron Red C-2G 3% reactive dye soluble

Cassulfon Red 2G 3% sulfur dye insoluble

Indigo 3% vat dye insoluble

Indanthrene Blue DB 3% vat dye insoluble

Sandospers Red E-BN 1% azo pigment soluble

Sandorin Yellow 6GL isoindolinone pigment soluble

Sandorin Orange 6RL heterocycl. Ni complex pigment soluble

Sandorin Red BN Azo Cond. Pigment insoluble

Sandorin Magenta BLTE Quinacridone pigment insoluble

Bordeaux Sandorin 2RL thioindigo pigment insoluble

Sandorin Violet BLP dioxazine pigment insoluble

Sandorin Blue RL 21 Indanthrene-Pigment unlöslichSandorin Blue RL indanthrene pigment insoluble

Sandorin Blue RL 21 indanthrene pigment insoluble

Sandorin Blue BLNF mod. Rod. α-phthalocyanine insoluble pigment

Sandorin Blue 2GLS20 ß-phthalocyanine pigment insoluble

Sandorin Green 3GLS type FP Phthalocyanine Cl / Cu pigment partially soluble

Graphtol Real Yellow RP Monoazo Ca salt pigment soluble

Graphtol Real Orange 5 GL Monoazo Mn complex pigment soluble

Graphtol Orange 3RT monoazo pigment partially soluble

Graphtol Feuerrot 3 RL Monoazo Sr salt partially soluble

Graphtol True Red 2GLD Monoazo soluble

Graphtol Schwarz Carbon Black insoluble

Graphtol Black EB Aniline Black insoluble

The specified trade names of the colorants are partly protected trademarks.

NMMO solubility of different colorants:

To check the NMMO solubility of different pigment classes, a mixture of 3.8 g of NMMO monohydrate, 0.45 g of H ₂ O and 15 mg of pigment was heated in a test tube at 100 ° C. for two hours.

It was found that small pigment molecules such. B. yellow, orange or certain red pigments are soluble in NMMO under the given conditions. When the solution cools, the pigment particles largely precipitate out again. The solubility of small pigment molecules means that a significant proportion of the pigment can get into the precipitation bath during the spinning process. The pigments that are soluble in NMMO are primarily azo pigments and mostly color lacquers, i.e. metal complexes containing sulfo or carboxyl groups (Ni ⁺⁺ , Mn ⁺⁺ , Sr ⁺⁺ , Ca ⁺⁺ ). 9

In contrast, larger azo pigment molecules, mainly shades of blue but also red, can be spun in without any problems. They are insoluble in NMMO and are not washed out of the fiber in the precipitation bath.

5 Anthraquinone (indanthrene) and indigoide (indigo, thioindigo) vat dyes also proved to be insoluble. Oxidized vat dyes (e.g. indigo, indanthrene) do not dissolve in the cellulose solution. In a cellulose solution to which indigo has been added, fine pigment particles of approx. 10 μm in size can be seen under the microscope.

10. Dioxazines, quinacridones and blue phthalocyanines were also found to be insoluble.

In most cases, the addition of pigments did not result in any noteworthy influence on the spinning safety, fiber data and the wet abrasion values of the fibers.

15 spinning the dye precursor of a developing dye:

1% Naphtol AS® (based on cellulose) was suspended in the NMMO / water mixture. After kneading with pulp, the Naphtol AS® was distributed homogeneously. The spinning mass was spun in a precipitation bath and then passed through a 20 diazonium salt solution (dyeing fast salt solution). The water-insoluble development dye forms in the fiber. The short residence time in the developing bath is sufficient to dye the fiber. Small amounts of Naphtol AS® are washed out in the development bath and form insoluble dye particles there. This offers the possibility of using less water-soluble naphthols as primers and thus preventing the formation of a sediment from water-insoluble development dye. The advantage of the development dyes is that several colors can be achieved with one primer simply by the choice of dye fastness salts in the aftertreatment. This enables a quick color change by simply replacing the dye salt in the aftertreatment.

30

The results of the tests carried out can be summarized as follows: 10

• Small pigment molecules (mostly yellow, orange and partly red pigments) can dissolve in NMMO under the conditions of spinning mass production and thus get into the precipitation bath. • Azo metal complex pigments - Ni, Mn, Sr, Ca salts of sulfo or carboxyl group-containing azo pigments are also relatively soluble.

• Vat dyes in the oxidized form (e.g. indanthrene, indigo, thioindigo), dioxazines, quinacridones and blue phthalocyanines were NMMO-insoluble.

• The solution quality of the cellulose solution is not impaired by the pigment addition.

• The spinning safety is not impaired in most cases.

• The fiber data are usually retained.

• Dye yield and color properties can be influenced by adjusting the conditions in the air gap. • Copper-containing metal complex pigments such. B. Cu phthalocyanines (high fastness properties,

Color strengths and brilliance) reduce the thermal activity of the cellulose solution if they are added to the cellulose suspension before the production of the cellulose solution.

Claims

11 claims: 1) Process for the production of cellulosic moldings, in particular fibers, from solutions of cellulose in an aqueous tertiary amine oxide by preparing the solution from a cellulose suspension in the aqueous tertiary amine oxide, extruding the Solution through a shaping tool, passing the shaped solution over an air gap into a precipitation bath and washing and drying the formed body, characterized in that a colorant and / or a colorant precursor is added to the solution and / or the cellulose suspension, which colorant or which colorant precursor is more than 95% by weight insoluble in the cellulose solution, based on the colorant or colorant precursor originally used. 2) Method according to claim 1, characterized in that the colorant or the colorant precursor in the cellulose solution to more than 99% by weight, based on the colorant or colorant precursor originally used, is insoluble. 3) Method according to Anspmch 2, characterized in that a vat or sulfur dye is added in oxidized form. 4) Method according to one of claims 1 to 3, characterized in that an anthraquinone dye is added. 5) Method according to one of claims 1 or 2, characterized in that a dye precursor of a developing dye is added. 6) Method according to Anspmch 5, characterized in that the shaped body containing the dye precursor of the development dye is passed after washing through a bath in which the dye is developed. 12 7) Spun-dyed, solvent-spun cellulosic fiber, obtainable by a process according to one of claims 1 to 6. 8) Solvent-spun cellulosic fiber, characterized in that the fiber contains the dye precursor of a developing dye.