SK153197A3 - A process of bleaching fabrics - Google Patents

Abstract

The present invention relates to the bleaching of fabrics with a hypochlorite-containing composition. The well known prejudice against using hypochlorite bleaches to bleach synthetic fabrics because of the resulting fabric yellowing is addressed by the presence of silicate salts in the bleaching medium.

Description

Technical field

The present invention relates to bleaching fabrics with a bleaching composition containing hypochlorite.

BACKGROUND OF THE INVENTION

Bleaching agents are well known in the art. It is also known that bleaching compositions based on hypochlorite as a bleaching agent are preferred over oxygen bleaches, especially for performance reasons, especially at lower temperatures.

However, there are some limitations to the benefits of hypochlorite reagents. It is well known from consumers that hypochlorite can cause yellowing of bleached fabrics. This is particularly the case with synthetic fabrics and there is indeed bias against

I use hypochlorite bleaches on synthetic fabrics, as seen from the warnings on commercially available hypochlorite bleaches. Also, many fabrics made of or containing synthetic fibers are labeled as unbleachable by the manufacturer.

It is therefore an object of the present invention to solve the problem of yellowing of synthetic fabrics when bleaching with hypochlorite bleaches.

We have found that this problem can be effectively solved if the hypochlorite solutions used to bleach synthetic fabrics further contain an effective amount of an alkali metal salt of silicate. It is believed that the presence of silicate in the solution plays a role in modifying or preventing hypochlorite from affecting brighteners that are placed on the surface of synthetic fabrics during their manufacture and / or when washing fabrics with laundry detergents containing brighteners, possibly due to the control of metallic impurities such as Cu , Fe, Ni and Co. In the absence of silicate, it is assumed that it is the hypochlorite action on the brighteners placed on the surface of synthetic fabrics that causes the yellowing phenomenon. We have actually observed that the yellowing prevention effect is related to the presence of a brightener placed on the surface of the synthetic fabric. This invention is very practical since most modern synthetic fabrics have brighteners placed on the surface.

US 3,056,645 and US 3,030,171 disclose a method for bleaching fabrics which includes hypochlorite-containing compositions. Silicates are mentioned as an optional component and neither of these documents discusses the presence of brighteners on the fabric surface, nor the beneficial effect of silicate, as the present invention.

US 4,120,650 discloses a method for bleaching fabrics with a solution comprising anionic and non-ionic surfactant, chlorine bleach and oxygen bleach under controlled conditions. Silicates are mentioned as an optional component and this method is said to be applicable to synthetic fabrics. The presence of brighteners on fabrics has not been discussed.

US 2,733,120 describes a process for bleaching fabrics with hypochlorite in the presence of soap. Silicate is mentioned as an optional component and the document does not discuss synthetic fabrics and yellowing.

US 1,931,245 discloses a composition comprising hypochlorite and silicate and its use for bleaching viscose fibers. Silicate is said to protect the aluminum support used in the process against corrosion.

EP 351,947 discloses a hypochlorite-containing composition and a brightener selected for its stability in the composition. Silicates are mentioned as an optional component.

The co-pending European applications 93203153, 93870070.7, 94202716 and 94870103 describe compositions containing hypochlorite and silicate, but do not discuss their possible application to synthetic fabrics having brighteners placed on their surface.

SUMMARY OF THE INVENTION

Summary of the Invention

The present invention relates to a method of bleaching a synthetic fabric having a brightener placed thereon, wherein the fabric is contacted with an aqueous solution of a bleaching amount of an alkali metal hypochlorite and an effective amount of an alkali metal salt of a silicate, wherein the yellowing of said fabric is reduced or removed.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for bleaching synthetic fabrics having a brightener placed on the surface, hereinafter referred to as fabrics.

Fabrics can be divided into natural fabrics, ie. fabrics made of cotton, viscose, flax, silk and wool and others which are synthetic fabrics. Many synthetic fabrics are available, all made from polymeric fibers of synthetic origin. Most commonly used are polyamide, polyester, Lycra and Elasthane. As used in the present invention, synthetic fabrics also include fabrics containing both natural and synthetic fibers.

However, these fabrics, because they are not ideally white, are treated during manufacture with an optical fluorescent brightener such that the brightener is placed, preferably adsorbed, on the surface of the fabrics. This brightener layer is partially restored to a certain extent in the subsequent wash, when fabrics are washed with a detergent containing optical brighteners, which is the vast majority of all detergents. Optical fluorescent brighteners are well known in the art and can be described as having conjugated double bonds and / or an aromatic structure that allows them to absorb UV light and fluoresce. Most of the prior art brighteners belong to the group of stilbenes, and such compounds have been extensively described in the art in the art.

of the invention, the fabrics are bleach solution, other than water, i. alkali metal

In the process of the present invention, they contact an aqueous containing two essential ingredients, an alkali metal hypochlorite and a silicate salt.

Such a bleaching solution is conveniently made by diluting a suitable amount of a bleaching composition in a suitable amount of water. The bleaching agent used to make the bleaching solution may be dry, i. powdered or granulated, composition or liquid composition. Liquid compositions are preferred over granulated, especially for ease of manufacture, purity and cost reasons.

Various forms of hypochlorite which are commercially available or mixtures thereof are used in the preparation of the liquid composition for use in the process of the present invention. The nature of the hypochlorite cations is not critical in the present invention, and sodium hypochlorite is generally used as it is commercially available in large quantities and is economically advantageous. The bleaching solutions of the present invention contain from 0.001% to 1% by weight, relative to active chlorine, of hypochlorite, preferably from 0.0015% to 0.6%, most preferably from 0.002% to 0.5%.

The second necessary component of the bleaching solutions used in the process of the present invention is an alkali metal salt of silicate or a mixture thereof. Again, the nature of the silicate cation is not critical, but sodium silicate is most commonly used because it is economically advantageous. The bleaching solutions used in the process of the present invention contain an effective amount of silicate. By effective amount is meant an amount sufficient to substantially reduce the yellowing of the fabric as compared to the same silicate-free composition. In determining the amount of silicate to be used, it should be appreciated that the more silicate, the greater the anti-yellowing effect. But from a certain amount, the silicate begins to precipitate. In addition, for a given amount of silicate, the anti-yellowing effect decreases with the hardness of the water and with the increasing content of heavy metal ions in the wash solution. However, under all conditions, there is an anti-yellowing effect when the silicate is used in bleaching compositions. The bleaching compositions of the present invention comprise 0.0015% to 0.5%, preferably 0.002% to 0.25%, most preferably 0.0025% to 0.15% by weight of the alkali metal salt of silicate or mixtures thereof.

The preferred bleach solution of the present invention has a pH of 8 to 14, preferably 8.5 to 13, and most preferably 9 to 12. In addition, preferred solutions of the present invention contain 0% by weight to 1.0% by weight, preferably 0.005% by weight to 0.5 % by weight, most preferably 0.01% by weight to 0.25% by weight, of a chelating and / or filler system or mixtures thereof. Indeed, we have found that each of these preferred features, alone or in combination, has an effect on the anti-yellowing effect. A lower pH favors the oxidizing effect on the brightener such that higher pH values within the limits that have been mentioned are preferred. Suitable pH adjusting agents include strongly alkaline sources such as sodium hydroxide in amounts of 0% to 5% by weight, preferably 0.0002% to 0.15% by weight, most preferably 0.0005% to 0.1% by weight .

With regard to chelating agents, heavy metal ions in water prefer radical action on the brightener, so that a chelating agent for said heavy metal ions is desirable. In this embodiment of the present invention, a limited filler or chelating agent may be used, and any fillers or chelating agents well known in the art may be used. This aspect, and particularly effective chelating agents, has been discussed in co-pending EP 93203153.

The compositions that can be used according to the present invention further comprise, as an optional but preferred component, a buffer system which helps to maintain the whitening pH is not a method according to any particular hypochlorite, a mass solution in the stated range, even after dilution. Maintaining a suitable pH is indeed important, inter alia, because it minimizes the formation of hypochlorous acid, which we have found to be responsible for damaging bleached fabrics.

In the process of the present invention, a bleaching solution is produced by diluting the bleaching composition in a suitable amount of water to achieve the hypochlorite and silicate concentrations mentioned above. In general, it is desirable to start with bleaching compositions which contain from 2% to 10% by weight of the total composition relative to the active up to 6% by weight, up to 5% by weight and 0.02% by weight to 5 chlorine, preferably the 3 most preferred 4 readings. , preferably most preferably 0.2% and such a bleaching composition, bleaching from the basis of the total composition 0.1% to 2% by weight, up to 1.6% by weight, diluted in water to a concentration of 0.5 g / l to 1% by weight. 100 g / l, preferably 1.0 g / l to 50 g / l, most preferably 5.0 g / l to 25.0 g / l.

The bleached fabrics are then contacted The time required for sufficient depends on the degree of soiling, but is generally 1 minute to 24 hours, preferably 3 minutes to 1 hour, most preferably 5 minutes to 30 minutes. Finally, the fabric is selected from the bleaching solution and the remainder of the bleaching solution is rinsed from the fabric with water. The bleaching method described in the present invention can be carried out before or after washing the fabrics with a detergent. Bleaching can also be accomplished at the same time as cleaning by adding the bleaching solution to a suitable amount of detergent.

The bleaching temperature affects bleaching and yellowing. More specifically, the elevated temperature accelerates bleaching, i.

necessary for whitening the dirt, but yellowing. However, the effect of the silicate against yellowing is achieved at any temperature.

The anti-yellowing effect of the present invention is evaluated by comparing the composition of the present invention with the same silicate-free composition. The degree shortens the time also deepens

Ί yellowing can be determined by both visual and instrumental evaluation. The visual difference in yellowness between samples treated with various means is determined by a panel of experts. Instrumentally, the evaluation is performed using colorimeters such as Ganz Griesser instruments (e.g., Datacolor Spectraflash SF 500, Machbet White-eye 500) or ZEISS ELREPHO or others available, for example, from Hunterlab or Gardner.

DETAILED DESCRIPTION OF THE INVENTION

- experimental part

The results of the tests below were obtained by the following test procedure. 8.5 ml of each composition was diluted into 1000 ml of water to form a homogeneous bleaching medium. The synthetic fabrics used in this test were women's Rosalinda panties from Vigues De Lengeria S.A., composed of 80% polyamide and 20% Lycra, brightened. The fabrics were immersed in the medium for 30 minutes. They were then removed and rinsed. Fabric yellowing was evaluated by three specialists on three repeating samples according to a scale in which:

there is no difference between samples I think there is a small difference I'm sure there is a difference is a big difference

A positive value indicates that the sample is less yellow than the reference. Samples were also evaluated instrumentally with a Ganz Griesser instrument (Datacolor Spectraflash SF 500).

The following compositions were tested as described.

Component Composition l (% by weight)

Means 2

AvC12 4.95 Sodium carbonate 1.25 Sodium hydroxide 1.40 Sodium silicate 0.5

5.10

0.30

0.45

Water and minor ingredients rest up to 100% rest up to 100%

The results of the fabric yellowing evaluation were as follows:

Difference between Device 1 and Device 2 Visual Rating Instrumental (Group Score Units) (Db) + 4, Os + 6.9s sec - statistically significant difference + = Device 1 is better than Device 2

- other examples:

The following compositions were also made by mixing the listed ingredients in the indicated proportions.

component means 3 (% by weight) AvC12 4.95 Sodium carbonate 1.25 Sodium hydroxide 1.0 Sodium silicate 0.5 Water and minor components the remainder to 100 component means 4 (% by weight) AvC12 4.95 Sodium carbonate 1.25 Sodium hydroxide 0.5 Sodium silicate 0.5 Water and minor components the remainder to 100

component Means 5 (% by weight) AvC12 4.95 Sodium carbonate 1.25 Sodium hydroxide 0.25 Sodium silicate 0.5 Water and minor components the remainder to 100 component Means 6 (% by weight) AvCl2 4.95 Sodium carbonate 1.25 Sodium hydroxide 1.4 Sodium silicate 1.0 Water and minor components the remainder to 100 component Means 7 (% by weight) AvC12 4.95 Sodium carbonate 1.25 Sodium hydroxide 2.0 Sodium silicate 0.25 Water and minor components the remainder to 100 component Means 8 (% by weight) AvC12 2.0 Sodium carbonate 1.25 Sodium hydroxide 1.4 Sodium silicate 1.0 Water and minor components the remainder to 100 component Means 9 (% by weight) AvCl2 2.0 Sodium carbonate 1.25 Sodium hydroxide 1.4

continuation: component Resource 9 0.5 the remainder to 100 Sodium silicate Water and minority ingredients component Means 10 (% by weight) AvC12 2.0 Sodium carbonate 1.25 Sodium hydroxide 1.4 Sodium silicate 0.25 Water and minority ingredients the remainder to 100 component Means 11 (% by weight) AvC12 2.0 Sodium carbonate 0.5 Sodium hydroxide 0.25 Sodium silicate 0.5 Water and minority ingredients the remainder to 100 component Means 12 (% by weight) AvC12 7.0 Sodium carbonate 0.25 Sodium hydroxide 0.00 Sodium silicate 0.5 Water and minority ingredients the remainder to 100 component Means 13 (% by weight) AvC12 7.0 Sodium carbonate 0.25 Sodium hydroxide 1.0 Sodium silicate 0.5 Water and minority ingredients the remainder to 100

component Means 14 (% by weight) AvC12 7.0 Sodium carbonate 0.25 Sodium hydroxide 1.0 Sodium silicate 1.0 Water and minor components the remainder to 100 component Means 15 (% by weight) AvC12 7.0 Sodium carbonate 1.25 Sodium hydroxide 5.0 Sodium silicate 1.0 Water and minor components the remainder to 100

Industrial usability

The compositions of the present invention are industrially useful for producing bleaching compositions for hypochlorite-based synthetic fabrics that do not cause yellowing of the fabrics.

Claims (8)

PATENT CLAIMS A method for bleaching a synthetic fabric having a brightener placed on its surface, characterized in that the fabric is contacted with an aqueous solution of a bleaching amount of an alkali metal hypochlorite or a mixture thereof and an effective amount of an alkali metal salt of a silicate or mixture thereof, said fabric limited or completely removed. Method according to claim 1, characterized in that the solution contains 0.0015% by weight to 0.5% by weight of salts of the alkaline mixture, preferably 0.002% by weight, most preferably 0.15% by weight. % of silicate metal or up to 0.25% by weight of 0.0025% by weight; Method according to any one of the preceding claims, characterized in that the solution contains 0.001% by weight to 1% by weight of alkali metal hypochlorite, preferably 0.0015% to 0.6% by weight, most preferably 0.002% to 0.5% by weight. Method according to any one of the preceding claims, characterized in that the solution has a pH of 8 to 14, preferably of 8.5 to 13, and most preferably of 9 to 12. Method according to any one of the preceding claims, characterized in that the solution further comprises 0% by weight to 1.0% by weight of alkali metal carbonate salts, preferably 0.005% by weight to 0.5% by weight, most preferably 0.01% by weight to 0% by weight. , 25% by weight. Process according to any one of the preceding claims, characterized in that the solution is produced with and by diluting with water a bleaching agent containing from 2 to 10% by weight, preferably from 3 to 10% by weight. 6% by weight, most preferably 4% by weight to 5% by weight of alkali metal hypochlorite or a mixture thereof and 0.02% by weight to 5% by weight, preferably 0.1% to 2% by weight, most preferably 0.2% to 1.6% by weight % by weight of alkali metal salts of silicate or mixtures thereof, to a final concentration of 0.5 g / l to 100 g / l. Method according to any one of the preceding claims, characterized in that the fabrics are contacted with the bleaching solution for a period of 1 minute to 24 hours, preferably 3 minutes to 1 hour, most preferably 5 minutes to 30 minutes. Method according to any one of the preceding claims, characterized in that the bleaching solution has a temperature of 4 ° C to 60 ° C, preferably 10 ° C to 50 ° C, most preferably 20 ° C to 40 ° C. Method according to any one of the preceding claims, characterized in that the synthetic fabrics comprise polyamide and / or polyester and / or Lycra and / or Elasthane.