EP2188437A1

EP2188437A1 - Starch-based printing thickening agent for reactive printing

Info

Publication number: EP2188437A1
Application number: EP08801247A
Authority: EP
Inventors: Sabine Ramaker-Stam; Holger Stegink
Original assignee: Emsland Staerke GmbH
Current assignee: Emsland Staerke GmbH
Priority date: 2007-09-10
Filing date: 2008-08-28
Publication date: 2010-05-26
Also published as: RU2010114156A; DE102007043109A1; WO2009033451A1

Abstract

The invention relates to a printing thickening agent for reactive printing, containing at least one starch in a quantity of at least 50 % by weight in relation to the total weight of the printing thickening agent. According to the invention, the starch has a DS value of between 0.2 and 0.6 and is cross-linked using between 0.05 and 0.50 % by volume of a cross-linking agent. The invention also relates to the use of said agent.

Description

Starch-based pressure thickener for the reactive pressure

The present invention relates to a printing thickener for reactive printing and its use.

The term "textile printing" refers to a localized, patterned dyeing of textiles, which can be carried out by various methods and in which both synthetic and natural textiles can be used.

The most diverse printing methods are known, for example direct printing, etching pressure, reserve pressure. Also a wide variety of printing techniques, such as Rouleauxdruck, planographic printing, rotary film printing, transfer printing, inkjet printing, etc., are available.

Each printing technique is carried out by a special procedure involving printing, drying, steaming and washing to finally obtain the finished printed product.

In terms of dye classes, printing generally distinguishes between pigment printing, reactive printing, dispersion pressure and cooling pressure. About 30% of all printed materials are produced worldwide using the reactive printing process, so that the reactive pressure is in second place in terms of quantity after pigment printing.

Reactive dyes can enter into chemical bonds with a cellulose fiber due to their reactive groups in the presence of alkali (soda), whereby particularly good frictional and wet fastness properties are achieved. In the alkaline medium, the reactive groups react with the hydroxyl groups of the cellulose. However, the dyes also react with the hydroxyl groups of the water and any pressure-thickening agent that is to provide a suitable viscosity for the reactive dyes used. For this reason, in addition to synthetic products which are free of OH groups, so far mainly alginate has been used in the prior art as a natural raw material for pressure thickeners, since it also contains no free hydroxyl groups. Other natural printing However, thickeners which are based, for example, on starch, react with the dyes. This eventually leads to a handle hardening on the goods and a deterioration of rubbing fastness.

As alginates are increasingly used in the food industry and the demand for alginates is steadily rising, it is easy to find bottlenecks in raw materials. Furthermore, the prices for alginates are quite high at about 3 to 4 Euro / kg. At present there is no alternative to alginates based on a natural raw material which would be suitable for the reactive pressure to form a pressure thickener.

It is therefore an object of the present invention to overcome the disadvantages of the prior art and to provide a pressure thickening agent based essentially on a natural raw material which can be used for reactive printing. In particular, a reaction of the printing thickener with the reactive dyes should be avoided, the printing thickener for all printing techniques, such as planographic printing and rotary film printing to be suitable. This is especially true for a use in stencil printing techniques that place great demands on the purity of the products used.

The object is achieved by a reactive pressure printing thickener which contains at least one starch in an amount of at least 50% by weight, based on the total weight of the printing thickener, wherein the starch has a DS value of 0.2 to 0.6 and is crosslinked with 0.05 to 0.50 vol% of a crosslinking agent. The DS value describes the degree of substitution DS of hydroxyl groups per glycose unit of starch, as known to those skilled in the art.

It is preferred that the starch is present in a proportion of 50 to 99% by weight, preferably 50 to 80% by weight, more preferably 65 to 75% by weight, based on the total weight of the printing thickener. It is also proposed that the starch preferably has a DS value between 0.3 and 0.4.

Also preferably, the starch is crosslinked with 0.2 to 0.4% by volume of the crosslinking agent.

Particularly preferred is the starch corn starch.

One embodiment is characterized in that the etherifying agent is sodium monochloroacetate and / or monochloroacetic acid and / or the crosslinking agent is epichlorohydrin.

It is also proposed that the pressure thickener is mechanically modified, preferably by roll drying.

It is particularly preferred that the pressure thickener contains at least one further natural and / or synthetic pressure thickener in addition to the at least one starch.

The further thickener may be selected from sodium polyacrylate, sodium alginate and mixtures thereof.

The use of the pressure thickener in combination with reactive dyes is also according to the invention.

The use on natural fibers, such as cotton and viscose, is preferred.

Surprisingly, it has been found that a starch-based pressure thickener can be provided for reactive printing wherein the starch is highly cross-linked and highly etherified which when used in a reactive printing process results in excellent printing results. These print results include a high color depth, sharp contours, a level color loss and a soft touch of the substrate.

The basic building block of all starches is the α-amylose, with each amylose molecule within the starch chain each having three free, reactive hydroxyl groups. These hydroxyl groups are prepared by suitable modification, i. by etherification and / or crosslinking, made incapable of reaction, so that the starches in reaction with the reactive dyes in particular can no longer cause grip hardening.

Drack thickeners should have the highest possible viscosity, but must be easy to filter, in particular for stencil printing, since otherwise the stencils would become clogged after a short time. By using the highly crosslinked and highly etherified starches, it is now possible according to the invention to provide optimum viscosity and filterability for the pressure thickener. A preferred embodiment of the invention, wherein the viscosity and filterability are further improved, is characterized in that in addition to the starch (in a proportion of at least 50 wt .-%) yet another other natural and / or synthetic thickener is used. Such a further thickener may, for example, be sodium polyacrylate, sodium alginate or mixtures, a particularly preferred pressure thickener consisting of 70% by weight of starch and 30% by weight of the further thickening agent.

It has also been found that corn starch is likely to be particularly well suited for use as a pressure thickener, due to its small grain size and short structure. It is also preferred that the starch used is cold water soluble.

Corresponding starch-based products have so far only been used for a very small percentage of the reactive pressure. Further features and advantages of the invention will become apparent from the following detailed description of exemplary embodiments, to which the invention should by no means be restricted.

Corn starch derivatives with different degrees of etherification and crosslinking were prepared and their viscosity was measured by means of a Brookfield viscometer in an 8% concentration and the filtration value.

To determine the viscosity, 460 g of tap water are weighed into a 1 1 scale and then added with stirring with a double-bladed stirrer and a Heidolph stirrer 40 g of product. The solution is dissolved for 15 minutes at 800 rpm. Is measured with a Brookfield viscometer type RVT at 20 rpm and 2O ⁰ C.

To determine the filterability or the filtration value, 100 g of product are dissolved in 1,900 g of tap water for 1 hour at 700 rpm (double-bar stirrer and Heidolph stirrer). Subsequently, the solution rests for 1 hour. Thereafter, the solution is filtered off under vacuum through a 45 μm sieve. Time and negative pressure are measured.

The results for the individual corn starch derivatives are given below in Table 1. Table 1 also shows the quantities of products 1-6 used in the printing paste.

Table 1

Reactive pressure tests on pure cotton were carried out for all corn starch derivatives, using a laboratory printing table from Zimmer and a fixer from Mathis. The quality of the print was 100% CO with a pattern of 002 / 1-60 mesh.

The printing paste was composed of 5 g / kg Revatol ^® NS (dyeing and printing products, Clariant), 25 g / kg sodium carbonate, 100 g / kg urea, printing thickener with a specified in Table 1 and 100 g / kg Cibacron ^® Turquoise Blue P-GR 50% as a dye, the remainder being water. The printing was carried out on a laboratory printing table from Zimmer with a squeegee of 10 mm, a magnetic stage of 2/3 and a speed of 1.5 m / minute. The steam was fixed at a temperature of 103 ° C (saturated steam) for a period of 7 minutes. A pressure wash was then performed in three consecutive baths. The first wash was done cold for 3 minutes without additives, the second wash in a bath of 95 ° C for 3 minutes with an addition of 1 g / l Kieralon ^® DB (washing and wetting agent, BASF). A third wash was finally done cold for a minute with no additives.

Good print results were obtained for all products. It showed that the product with the number 2 delivered the best print results on pure cotton. In particular, a high color depth, sharp contours, a level color loss and a soft handle of cotton. However, the viscosity and the filterability were still improved.

These disadvantages could be eliminated by adding other natural and / or synthetic thickeners.

example 1

A crosslinked corn starch ether was prepared by reacting corn starch with 10 moles of sodium monochloroacetate (DS: 0.4) and 0.375% by volume of epichlorohydrin. For this purpose, 2,000 g of corn starch were suspended in 2,400 ml of tap water and 500 ml of 1 N NaOH was added. The slurry was heated to 4O ⁰ C in a water bath. 7.5 ml of epichlorohydrin (0.375% by volume) were added and reacted with corn starch for 24 hours at 40-42 ° C. Then, 1,165 g (10 mol) of sodium monochloroacetate was added and the slurry gelatinized with 550 ml of NaOH (50%). The resulting mass was dried on a roll of 3 rolls at 2-3 rpm, and 7-8 bar steam pressure. The product was then screened through a 2 mm sieve.

70% by weight of the crosslinked and roller-dried corn starch ether thus obtained was mixed with 30% by weight of sodium polyacrylate and dried together on a roller. The Brookfield viscosity was measured as indicated above and was 20,000 mPa.s, while the filterability gave values of <60 seconds at 0.2 bar. The incorporation amount of the corn starch ether thus prepared in the printing paste was 50 g / kg.

For the printing thickener thus obtained, printing tests were carried out as described above, and the printing results were compared with a printing thickener based on 100% alginate. It was found that the depth of color, levelness and contours of the printing thickener according to the invention were better than with a pressure-reducing agent based on 100% alginate. The handle was identical for both pressure thickeners. Furthermore, wet and dry rub fastnesses were measured with a Crockmeter (Crockmeter Model 255 from James H. Heal, Halifax, England, method ISO 105-A03) were compared for the pressure thickener according to the invention and the alginate-based pressure diluent. For measurement, printed areas of a cotton fabric to be tested were rubbed under controlled conditions against a white cotton fabric. The color of the abrasion was compared with the gray scale and graded. The smaller the value, the worse the authenticity. The scale ranges from 1 to 5. The results of the wet and dry rub fastness tests are shown in Table 2.

Table 2

As shown in Table 2, the printing thickener of the present invention exhibits wet and dry rubbing fastnesses which can be compared very well with those for a 100% alginate based printing thickener.

Features of the invention disclosed in the foregoing description and in the claims may be essential to the practice of the invention in its various embodiments both individually and in any combination thereof.

Claims

Ansprfiche

1. pressure-sensitive reactive pressure printing agent which contains at least one starch in a proportion of at least 50 wt .-%, based on the total weight of the Druckverdickungs- means, wherein the starch has a DS value of 0.2 to 0.6 and with 0.05 to 0.50% by volume of a crosslinking agent is crosslinked.

2. Printing thickener according to claim 1, characterized in that the starch in an amount of 50 to 99 wt .-%, preferably 50 to 80 wt .-%, more preferably 65 to 75 wt .-%, based on the total weight of the pressure thickener, is present.

3. Pressure thickener according to claim 1 or 2, characterized in that the starch has a DS value between 0.3 and 0.4.

4. Pressure thickener according to one of the preceding claims, characterized in that the starch is crosslinked with 0.2 to 0.4% by volume of the crosslinking agent.

5. Pressure thickener according to one of the preceding claims, characterized in that the starch is corn starch.

6. Pressure thickener according to one of the preceding claims, characterized in that the etherifying agent is sodium monochloroacetate and / or monochloroacetic acid.

7. Pressure thickener according to one of the preceding claims, characterized in that the crosslinking agent is epichlorohydrin.

8. Pressure thickener according to one of the preceding claims, characterized in that it is mechanically modified, preferably by roller drying.

9. pressure thickener according to one of the preceding claims, characterized in that it contains at least one additional natural and / or synthetic thickening agent in addition to the at least one starch.

10. Pressure thickener according to claim 9, characterized in that the further thickener is selected from sodium polyacrylate, sodium alginate and mixtures thereof.

11. Use of the printing thickener according to one of claims 1 to 10 as a printing thickener in combination with reactive dyes.

12. Use according to claim 10 on natural fibers, such as cotton and viscose.