EP1371771A1 - Method of removing sizing material from textiles - Google Patents

Abstract

Process for desizing fabrics made from sized yarn, comprises cooling the fabric to embrittle the size and mechanically removing the embrittled size from the fabric.

Description

The invention relates to a method for physical desizing of tissues.

Textile yarns must be sized before the weaving process, in order to be satisfactory in the subsequent process stage, the weaving mill To maintain running properties. In this finishing process different, known sizing agents are used in aqueous solution (also as a wash liquor or simply Referred to as size or liquor) at concentrations of 0.5 - 50 wt .-% and at temperatures of 20 - 95 ° C by means of a size application device or size machine (Trough, roller applicator, foam applicator, squeegee, Foulard, etc.) applied.

Finishing means covering the thread with a protective cover sheath so that it is woven by the mechanical Stress in the weaving machine is not damaged and breaks or tears.

For example, starch, Polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, Carboxymethyl starch, acrylates and various polysaccharides used.

For further processing (dyeing-finishing) of the fabric the sizing agent if possible by washing or desizing completely removed from the tissue. Out Environmental protection, but also for cost reasons, there is a need to recover the respective size and reuse.

For this purpose, for example, in the prior art Sizing agents using ultrafiltration systems (membrane technology) filtered from the wash liquor. This solution (about 4 to 10%) can then be concentrated and again for sizing be used. However, this procedure is very cost-intensive: an ultrafiltration system costs inclusive the creation of the appropriate operational Infrastructure about DEM 3 million. There are also large amounts of water necessary, taking into account the concerns of environmental protection is undesirable. About 70% of the wastewater from the textile industry come from raw weaving mills and go for desizing back.

If the fabric has to be sold desized, there is one Drying necessary, although the fabric for further processing (Dyeing-finishing) again subjected to a wet process becomes. The required drying creates additional Costs in the amount of about 0.3 - 0.6 DEM / meter of tissue.

A disadvantage of wet desizing processes (i.e. Desizing by washing out) is that at dyed yarn also leftovers of the dye in the recovered Finishing solution, i.e. the wash fleet, solved are so that they are for undyed yarns or otherwise dyed Yarns cannot be reused. A separation from dye-free and dye-containing wash liquors very difficult and requires continuous Process.

The object of the invention is therefore to provide a Method with the above, adhering to the prior art Problems can be eliminated.

a) einer Kältebehandlung zur Versprödung des Schlichtemittels unterzogen und anschließend

b) das versprödete Schlichtemittel mechanisch aus dem Gewebe entfernt wird.

According to the invention, therefore, a method for the physical desizing of fabrics made from sized yarn is provided, in which the fabric

a) subjected to a cold treatment for embrittlement of the sizing agent and then

b) the embrittled sizing agent is mechanically removed from the fabric.

The advantages of the method according to the invention are that it is not a wet process, i.e. there will be none large amounts of water for washing out the sizing agent needed, and therefore no drying is required. This saves energy and water, which the Benefits the environment. The "dry size" can be easy to collect and reuse. In the case of single color Fabrics can be »dry when contaminated with dye Sizes «can be reused for the same-colored yarns.

Further advantageous and / or preferred embodiments of the method according to the invention are the subject of the dependent claims.

All are suitable for the process according to the invention Cold treatment embrittling sizing agents. About that there are no special restrictions. As concrete Examples include polyvinyl alcohol (PVA) and polyvinyl acetate called. PVA is in thermoplastic, which is very common as Sizing agent is used and at temperatures in the Brittle and then range from -20 ° C to -40 ° C mechanically crushed or ground.

It is clear to the person skilled in the art that the temperature range in which the Embrittlement occurs so that mechanical removal of the Sizing agent is possible from the chemical-physical Properties of the sizing agent used depend is. Suitable sizing agents and temperature ranges for embrittlement, however, can be done by simple experiments easily determine. Of course it can also be on any low temperatures are cooled, for reasons of economy the temperature range is chosen so that the desired embrittlement effect is occurring.

According to the method of the invention, the yarns are, for example with PVA or polyvinyl acetate (or other Sizing agents that can later become brittle). After weaving, the fabric goes through a cooling system, in which there is embrittlement of the sizing agent a suitable temperature is cooled, in the case of PVA for example to a temperature in the range from -20 ° C to - 40 ° C.

The cooling process used is not subject to any particular one Restrictions and will be determined by the professional in accordance with the practical Circumstances selected, for example depending from the chemical-physical properties of the used sizing agent, dimensions and weaving density of the fabric, the rate of heat exchange etc.

For example, the fabric can simply be used with cooling gases such as vaporized with cold nitrogen or cooling liquids or be wetted to achieve the necessary cooling. Of course, the cold treatment must last long enough so that sufficient heat can be exchanged and dissipated can. Suitable cooling times are, however, by simple preliminary tests to investigate. Depending on the temperature of the cooling medium e.g. 1 to 5 min. For very low temperatures or if cooling should take place very quickly, too Liquid gases are used. It is also possible that Allow tissue to pass through a cooling drum or cooling roller. Taking into account temperature fluctuations that occur in practice and in terms of one for optimization of the process from a technical and economic point of view required range of variation of the process conditions is a wide temperature range from -2 to - 70 ° C is expected to be suitable and sufficient. Preferred temperatures are likely to be at Removal of PVA and / or PVAC sizing agents in the area from -20 to -40 ° C. The temperature information mentioned should not however rule out that at times or locally or at certain procedural stages Purposes, e.g. for removing residues of sizing agents or for special portions of tissue, much lower temperatures can be reached down to temperatures of liquid nitrogen (-195.8 ° C), as in its direct influence can be achieved.

Cold treatment makes the sizing agent used brittle or crystalline and can be dried Remove the form mechanically from the fabric. For mechanical Methods known per se can be considered such as e.g. Beating, brushing, tapping, application of vibrations, Sucking, kinking, upsetting, stretching, pressing, blowing, etc. There are no particular restrictions.

The product, the recovered size, falls into dry form, which means that no special operational infrastructure for return transport is necessary.

The recovered sizing agents from fabrics with undyed or plain colored yarns can be separated easily and reused if necessary.

In addition, the inventive method is not on Minimum throughputs, as is the case with ultrafiltration systems the case is, but can depend on the individual Be tailored to your needs. The procedure can therefore also be used in small or medium-sized companies that cannot carry out wet processes for desizing.

Claims (5)

Process for the physical desizing of fabrics from sized yarn, in which the fabric a) subjected to a cold treatment for embrittlement of the sizing agent and then b) the embrittled sizing agent is mechanically removed from the fabric. A method according to claim 1, wherein as a sizing agent Polyvinyl alcohol or polyvinyl acetate is used. The method of claim 1 or 2, wherein the cold treatment at a temperature in the range of -2 ° C to - 70 ° C, preferably from -20 ° C to -40 ° C, performed becomes. Method according to one of the preceding claims, wherein the cold treatment by steaming or wetting with a cooling gas or a cooling liquid or with the help a cooling drum or cooling roller. Method according to one of the preceding claims, wherein the mechanical removal of the embrittled sizing agent by beating, brushing, tapping, using Vibrations, suction, kinking, upsetting, stretching, pressing or bubbles occur.