EP0119920A2 - Process for the simultaneous desizing and bleaching of textiles - Google Patents

Abstract

Desizing process - simultaneous bleaching of tissues in a bath comprising hydrogen peroxide, a sequestering agent, an amylase and a surfactant, characterized in that a buffer consisting of sodium tetraborate decahydrate is added to said bath . The adoption of the desizing process - simultaneous bleaching of fabrics according to the present invention leads to both good bleaching and good desizing, while allowing significant savings in water, steam, labor and investments.

Description

The present invention relates to an improved process for desizing and bleaching fabrics in a single operation in a bath based on hydrogen peroxide.

The applicant has developed such a process which is the subject of French patent application No. 80 27866.

The process of French patent application n ° 80 27866 uses a bath comprising hydrogen peroxide, sodium hydroxide, a sequestering agent, an amylase, a surfactant and optionally a stabilizing agent such as silicate of sodium.

• - d'une part les résultats obtenus dépendent du pH fixé au départ. En effet à un pH très alcalin le blanchiment est excellent mais le désencollage est en général insuffisant, inversement à un pH peu alcalin le désencollage est bon mais le blanchiment est insuffisant.
• - d'autre part le niveau des résultats est étroitement lié à la nature du tissu soumis au traitement de désencollage - blanchiment, la dégradation enzymatique des amidons générant des produits acides qui font évoluer le pH au cours de la réaction.

The industrial implementation of this process faces certain difficulties:

• - on the one hand, the results obtained depend on the pH set at the start. In fact, at a very alkaline pH, the bleaching is excellent but the desizing is generally insufficient, conversely at a slightly alkaline pH, the desizing is good but the bleaching is insufficient.
• - on the other hand the level of the results is closely linked to the nature of the tissue subjected to the desizing treatment - bleaching, the enzymatic degradation of the starches generating acid products which cause the pH to change during the reaction.

Depending on the quantity and nature of the starches used for sizing the fabric, the pH of the desizing-bleaching bath is more or less modified during the treatment, which leads to significant differences in the bleaching and desizing results.

These observations have led the applicant to seek a buffer capable of fixing the pH of the desizing - bleaching bath in order to have a desizing - simultaneous bleaching process making it possible to obtain both optimum desizing and whitening while respecting the degree of polymerization of the fiber.

The present invention responds to such an object and provides an improved process for desizing - simultaneous bleaching of tissues in a bath comprising hydrogen peroxide, a sequestering agent, an amylase and a surfactant, characterized in that add a buffer consisting of sodium tetraborate decahydrate to said bath.

During its research, the plaintiff tested numerous buffers and found with surprise that for no buffer except for sodium tetraborate decahydrate, both good desizing and good bleaching were obtained.

et un tampon constitué car du té-traborate de sodium décahydraté en quantité déterminée pour fixer le pH du bain à 9,8 (soit environ 10 g de tétraborate de sodium décahydraté pour 1 1 de bain).A desizing-bleaching bath which can be used according to the invention can for example comprise:

and a buffer consisting of sodium t-traborate decahydrate in a determined quantity to fix the pH of the bath at 9.8 (ie approximately 10 g of sodium tetraborate decahydrate per 1 1 of bath).

The adoption of the desizing - simultaneous bleaching process of the present invention allows significant savings in water, steam, labor and investment and leads to desizing - bleaching results greater than those obtained without buffer or in using another buffer allowing the pH of the bath to be fixed at an equivalent value.

In addition, the use of sodium tetraborate decahydrate as a buffer avoids working in a alkaline and thus protects the treated fabric against the formation of "breaks" during deposition.

The invention will now be described in more detail in the following nonlimiting examples.

EXAMPLES

• 1) imprégnation du tissu écru dans le bain de désencollage - blanchiment ; exprimage pour ne laisser dans le tissu que la quantité de bain nécessaire à la réaction. Cette quantité a été fixée à 100 % du poids de tissu sec.
• 2) Vaporisage pour porter le tissu à la température de réaction souhaitée 90 - 95°C.
• 3) Dépôt par enroulage ou en plis pendant une heure à température.

The desizing - bleaching tests described were carried out according to the following technique

• 1) impregnation of the unbleached fabric in the desizing bath - bleaching; expressing so as to leave in the tissue only the quantity of bath necessary for the reaction. This amount was set at 100% of the weight of dry fabric.
• 2) Spraying to bring the fabric to the desired reaction temperature 90 - 95 ° C.
• 3) Deposit by winding or in folds for one hour at temperature.

The treatment is followed by washing at 90 - 95 ° C, washing at 60 ° C and cold washing.

The basic desizing-bleaching bath used in the examples below is as follows:

EXAMPLES 1 to 5

Examples 1 to 5 below were carried out with a 100% cotton canvas of 160 g / m ² :

The following buffers have been tested (the quantities indicated are expressed in g per 1 1 of bath):

Examples 1 to 4 are comparative examples.

Example 5 illustrates a method according to the present invention.

The results are shown in Table I below.

Only the use of sodium metaborate (Ex. 3) gives a higher degree of white than that obtained with sodium tetraborate decahydrate (Ex. 5 according to the invention), but the level of residual starch obtained in l 'Example 3 is too high (the residual starch level of Example 3 is 0.61 while it is only 0.22 in Example 5 according to the invention).

In addition, the hydrophilicity of Example 5 is 10 times lower than that of Example 3. It will also be noted that the degree of polymerization (DP = 1,620) obtained in Example 5 according to the invention shows that the fiber is not degraded during the desizing - bleaching operation.

EXAMPLES 6 to 10

Examples 6 to ¹⁰ below were carried out with a 100% cotton cretonne of 190 g / m:

The buffers tested are as follows:

Examples 6 to 9 are comparative examples.

Example 10 illustrates a method according to the present invention.

The results are given in Table II below.

EXAMPLES 11 to 15

Examples 11 to 15 below were carried out with a 100% cotton poplin of 140 g / m ² :

The buffers tested are as follows:

Examples 11 to 14 are comparative examples

Example 15 illustrates a desizing-bleaching process according to the present invention.

The results are given in Table III below.

The above examples show that only the use of sodium tetraborate decahydrate according to the invention makes it possible to obtain both good whitening and satisfactory desizing.

EXAMPLES 16 to 18

The bath described above, to which 10 g / l of sodium tetraborate decahydrate was added, was used to carry out desizing - simultaneous bleaching of three different polyester fabrics - 67/33 cotton, the starch levels of which are respectively:

The results are given in Table IV below.

Desizing is total and the white obtained is remarkable.

Claims (1)

Desizing process - simultaneous bleaching of tissues in a bath comprising hydrogen peroxide, a sequestering agent, an amylase and a surfactant, characterized in that a buffer consisting of sodium tetraborate decahydrate is added to said bath .