IT202000027666A1 - PROCESS FOR THE PURGE AND BLEACHING OF TEXTILE FIBERS THROUGH THE USE OF NATURAL ESTERS OF POLYGLYCEROL - Google Patents

Description

?PROCESS FOR THE PURGE AND BLEACHING OF TEXTILE FIBERS THROUGH

THE USE OF NATURAL POLYGLYCEROL ESTERS?

TECHNICAL SECTOR

the present invention relates to the scouring and bleaching treatment of textile fibres. In particular, the present invention relates to the use of biodegradable surfactants, based on natural polyglycerol esters, for the scouring and bleaching of textile fibres.

STATE OF THE ART

How ? Known to experts in the sector, scouring and bleaching are fundamental preliminary operations in the ennobling cycle of textile fibers, allowing the removal of substances extraneous to the fiber which can interfere in the subsequent dyeing and finishing phases, compromising the quality? of the final product. Among the products involved in the scouring and bleaching phases, surfactants play an essential role. However, the presence of surfactants in the effluents of the dyeworks poses problems of an environmental nature, given the well-documented toxicity? of these molecules, for example for aquatic organisms.

The ecological aspect of industrial production processes is today a deeply felt socio-environmental problem. The interest in the protection of the environment, in addition to the ethical implications, also has economic implications: the sectors most? evolved consumers are increasingly orienting? their choices towards products that are more? respectful of the environment. In particular, biodegradability, especially biodegradability? in a short time, ? a property? much desired.

An important and widely used parameter as an indicator for assessing biodegradability? of a substance or mixture of substances ? the ?chemical oxygen demand?, generally indicated in the sector with the acronym COD (acronym of the English ?Chemical Oxygen Demand?). In short, this parameter indicates the milligrams of oxygen per liter (mgO2/L), necessary for the complete chemical oxidation of the organic and inorganic compounds present in a water sample. In Italy, the method for determining the COD? codified by the publication ?METHOD 5135 - CHEMICAL OXYGEN REQUEST (COD) IN WATER MATRIX BY CUVETTE TEST?, Manuals and Guidelines 117/2014 edited by ISPRA - Higher Institute for Environmental Protection and Research.

The problem of the presence of surfactants in the drains of the dry cleaners has made s? attention focused in recent years on the problems related to the environmental impact of such waste. Under the impetus of requests for products more and more? attentive to the quality? of the environment ? time to the development of formulations pi? quickly biodegradable ? the major manufacturers of textile auxiliaries have increased their research and development efforts in this sense, in order to improve the quality? of effluents, penalized above all by the high values of COD.

At the moment, the research on new formulations ? oriented above all on products containing non-ionic surfactants (known in the sector as ?BiAS?, from the English ?Bismute Active Substance?) which are currently used mainly with respect to the anionic surfactants (MBAS, from ?Methylen Blue Active Subtances?) used previously, such as alkylaryl sulphonates (LAS, from ?Linear-Alkyl Sulphonates?), alkyl sulphates (AS), generally biodegradable in relatively long times and coming from non-renewable sources, due to their excellent performance.

Currently, linear ethoxylated alkanols (AE) are widely used as BiAS for scouring and bleaching treatments, such as for example those disclosed in US patent application 2020/0139323 A1 and in the documents cited therein. To ensure good performance, these products are used in large quantities, between 1% and 10% of the weight of the fiber to be treated, and may not be completely degraded within the 24-48 time spent in the consortium purifier or corporate, thus constituting criminal damage against the receiving body of water according to the regulations in force. Furthermore, the presence of derivatives of ethylene oxide, also coming from from non-renewable sources, pu? negatively affect the toxicological characteristics of the formulation itself. Finally, formulations based on AE may be ineffective in completely removing the spinning oils and other substances extraneous to the fibre, interfering in the subsequent processing stages.

Due to these drawbacks, the known processes do not allow the optimization of the scouring and bleaching steps with a view to achieving an eco-compatible and sustainable textile economy.

? therefore, the need is still felt to have available a method for scouring and bleaching textile fibers which, in addition to overcoming the aforementioned drawbacks, is able to guarantee the same or superior performances to the traditional methods.

SUMMARY OF THE INVENTION

The main purpose of the present invention ? to overcome the technical disadvantages described above, through the use of biodegradable surfactants based on natural polyglycerol esters for the scouring and bleaching of textile fibres.

Furthermore, the discharged effluent has the advantage of being readily biodegradable and of complying with the discharge regulations in view of environmentally friendly and sustainable processes.

DETAILED DESCRIPTION OF THE INVENTION

With the terms ?biodegradable surfactant? it indicates a surfactant that ? decomposable into at least two fragments more? small by bacteria, fungi, enzymes or other biological agents that are naturally present in a biological environment. A biodegradable surfactant can? be derived from a biological source or synthesized by chemical synthesis or semi-synthesis. A semisynthesis? a type of chemical synthesis that uses at least in part compounds isolated from biological sources (such as plant material or bacterial or cell cultures) other than fossil sources. In particular, the biodegradable surfactants used in the present invention can be produced from vegetable and renewable sources.

With the term ?natural esters? in the present description compounds obtained by esterification of polyglycerols with carboxylic acids (or their derivatives) obtained from natural sources are meant.

The term ?about? includes the ranges of operating conditions and parameters which may normally be employed in the present invention.

All other terms used in the description of the present invention, unless otherwise specified, must be interpreted according to their ordinary meaning known to the person skilled in the art.

In a first aspect, the present invention refers to the use of biodegradable surfactants based on natural polyglycerol esters for the preparation of a scouring and bleaching bath for textile fibres.

The purge and bleaching treatment takes place preferably through the following stages: a) load, in which a quantity defined by weight of fiber to be treated;

b) closure, in which the equipment closes once the loading is completed;

c) introduction of water, preferably in a ratio of about 10:1 weight/weight with respect to the mass of fiber to be treated, of at least one biodegradable surfactant consisting of one or more? natural esters of polyglycerol, at least one alkali agent and optionally at least one oxidizing agent;

d) heat treatment, in which the mass, depending on the nature of the fibre, is treated at a temperature preferably between 50?C and 110?C, plus? preferably between 80 and 100°C, for a period between about 30 and about 60 minutes. In these conditions the sterilization of the treated material and its stabilization is also obtained, since it is no longer? apt to undergo putrefaction phenomena;

e) cooling, in which the temperature is lowered to a value such as to allow the subsequent safe opening of the treatment equipment;

f) opening, in which the treatment equipment is opened;

g) discharge of the treated mass and of the treatment effluent.

After the completion of the unloading of stage g), the cycle restarts from stage a). In a second aspect of the present invention, biodegradable surfactants used in the present invention include natural polyglycerol esters, such as for example those disclosed in US 8,227,399 B2 and US 2020/0129397 A1 and documents cited therein, prepared from raw materials of plant origin and from renewable sources. Preferably, the quantity? of biodegradable surfactants used? of about 2% weight/weight with respect to the mass of fiber to be treated.

The X-polyglycerols to be used in the invention are commercially available products; they can be prepared by methods established in the art including, for example, the homopolymerization of pure glycerol, the latter being obtained from natural sources such as for example vegetable oils.

Natural polyglycerol esters can be prepared by mixing in an inert medium (for example, under a nitrogen atmosphere) and under stirring pure polyglycerol-X (PG-X), wherein X, the average degree of polymerization of the units? of glycerol, ? any whole number in the range of 3-12, single or in combination of at least two (for example, a pure polyglycerol-4 or a mixture of pure polyglycerol-4 and pure polyglycerol-6) with monocarboxylic fatty acids, consisting of chains in the C8-C30 range, to produce an esterification. When used in combination of the two, the polyglycerols-X are found in a ratio preferably between 1:1 mol/mol and 1:3 mol/mol, more? preferably 1:1 mol/mol.

In another aspect, natural polyglycerol esters can be prepared by mixing under an inert medium (e.g., under a nitrogen atmosphere) and stirring pure polyglycerol-X (PG-X), wherein X, the average degree of polymerization of the units ? of glycerol, ? any whole number in the range of 3-12, single or in combination of at least two (for example, a pure polyglycerol-4 or a mixture of pure polyglycerol-4 and pure polyglycerol-6) with dicarboxylic acids from natural sources, made up of chains in the C4-C10 range, to produce an esterification. Examples of said dicarboxylic acids include succinic acid, adipic acid, sebacic acid. When used in combination of the two, the polyglycerols-X are found in a ratio preferably between 1:1 mol/mol and 1:3 mol/mol, more? preferably 1:1 mol/mol.

In another aspect, natural polyglycerol esters can be prepared by mixing under an inert medium (e.g., under a nitrogen atmosphere) and stirring pure polyglycerol-X (PG-X), wherein X, the average degree of polymerization of the units ? of glycerol, ? any whole number in the range of 3-12, single or in combination of at least two (for example, a pure polyglycerol-4 or a blend of pure polyglycerol-4 and pure polyglycerol-6) with hydroxy fatty acids from natural sources, such as 12-hydroxystearic acid and ricinoleic acid, to produce an esterification. When used in combination of the two, the polyglycerols-X are found in a ratio preferably between 1:1 mol/mol and 1:3 mol/mol, more? preferably 1:1 mol/mol.

The carboxylic acids can also be added as a second step of the synthesis after the polyglycerols-X have been mixed. The carboxylic acids can be of a single type or be a mixture of, for example, two types of fatty acids, such as caprylic and capric acid, but are preferably of a single type (such as lauric) to optimize the reproducibility? of the surfactant performance. The fatty acids are added at a concentration to obtain a substitution of about 0.9 to about 1.5 hydroxyl groups per polyglycerol-X molecule, preferably a substitution of about 1 hydroxyl group per polyglycerol-X molecule, i.e. approximately one molar equivalent 1:1 of polyglycerols-X with respect to the fatty acid chain. The fatty acid:polyglycerol ratio can vary between 1:1 and 2.5.

The polyglycerols-X and fatty acids are mixed at a temperature between about 70°C and 110°C, preferably between about 75°C and about 90°C. C, and more? preferably at about 90°C.

Optionally, the reaction ? carried out in the presence of suitable catalysts for the esterification process. Suitable catalysts include any catalyst usable in the preparation of esters including, but not limited to, lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methylate, sulfuric acid, methanesulfonic acid (MSA), paratoluenesulfonic acid (PTSA), and others solid-based supported acid catalysts.

The esterification reaction is carried out at a temperature ranging from about 140?C to about 180?C, depending on the starting raw materials. The reaction is carried out under conditions which prevent oxidation of the ingredients (for example, under a nitrogen atmosphere). The duration of the reaction? between about 30 minutes and about two hours, preferably about one hour. Possible secondary reactions, such as for example the cyclization of polyglycerols-X to give derivatives of sorbitan, can progressively increase their entity? with reaction times of more than one hour.

In a further aspect, natural polyglycerol esters can be prepared by mixing under an inert medium (e.g., under a nitrogen atmosphere) and stirring pure polyglycerol-X (PG-X), wherein X, the average degree of polymerization of the units ? of glycerol, ? any whole number in the range of 3-12, single or in combination of at least two (for example, a pure polyglycerol-4 or a blend of pure polyglycerol-4 and pure polyglycerol-6) with oils from plant sources, such as for example olive oil, rapeseed oil, sunflower oil, soya oil, linseed oil, to produce a transesterification under the same conditions as the esterification reactions described above. When used in combination of the two, the polyglycerols-X are found in a ratio preferably between 1:1 mol/mol and 1:3 mol/mol, more? preferably 1:1 mol/mol.

In all of the above cases, the esterification reaction can be pushed to completion using methods known in the art, such as for example by continuous distillation of water which is formed as a by-product of esterification, at atmospheric pressure or at reduced pressure.

The yields are higher than 98% and the natural polyglycerol esters obtained can be purified by the techniques known in the art, such as for example extraction in an aqueous or aqueous-alkaline medium to remove traces of unreacted raw materials and catalysts.

Examples of alkaline agents for use in step c) of the process of the present invention include hydroxides of alkali or alkaline earth metals, such as for example sodium, potassium, magnesium, calcium, barium hydroxide, alkali carbonates, such as for example sodium carbonate , potassium, used as such or in aqueous dispersion. A favorite alkaline agent? 50% sodium hydroxide in water, used in a ratio of about 3 mL/L to the scouring and bleaching bath. Another favorite alkaline agent? sodium carbonate, used as such at a concentration in the scouring and bleaching bath of 2 g/L.

Examples of oxidizing agents for use in stage c) of the process of the present invention include hydrogen peroxide, sodium perborate, peracetic acid, or chlorinated products, such as for example sodium hypochlorite, calcium hypochlorite, sodium chlorite, dichloroisocyanurate sodium (DCIC), chloramine-T, used as such or in aqueous dispersion. The preferred oxidizing agent of the present invention is 35% hydrogen peroxide in water, used in a ratio to the scouring and bleaching bath of about 5 mL/L.

The expert of the technique will agree? that, depending on the nature and problems of the fiber to be treated, other additives can be used such as reducing agents (for example sodium hydrosulphite), sequestering agents and stabilizing agents.

The method of the present invention can be advantageously used for the purging and bleaching prior to dyeing and subsequent processing of articles based on textile fibers of vegetable origin (including cellulose derivatives, such as for example cotton, linen, hemp, jute), of animal origin (such as wool, silk, alpaca, cashmere), of artificial origin (such as rayon, rayon acetate, viscose), of synthetic origin (such as polyamides, polyesters, polyacrylates, polyvinyls, polypropylenes, polyurethanes, elastomers), and their combinations. The expert of the technique will appreciate? that, given the wide range of natural and renewable sources available for the synthesis of biodegradable surfactants such as those used in the present invention, the properties? physico-chemical characteristics of the latter, especially the hydrophilic-lipophilic balance (HLB), can be tuned according to the required performances.

Finally, the expert of the technique will appreciate? that the method described in the present invention ? applicable to industrial processes and to continuous and discontinuous plants for the scouring and bleaching of textile fibers.

The present invention ? illustrated in more detail by the following examples.

In the examples, the measurement of the COD values after the different scouring and bleaching treatments according to the invention and according to the prior art? was carried out following the IRSA-CNR 5135 method.

EXAMPLE 1

This example refers to the preparation of esters obtained from PG-4 and a mixture of caprylic and caprinic acids (i.e., n-octanoic and decanoic acids, respectively).

In an inert nitrogen atmosphere and under mechanical stirring, 69 g of PG-4 and 35 g of a commercially available mixture of caprylic acid and caprinic acid (about 1:1 weight/ weight). The system ? been kept in these conditions up to acidity? residual < 10 mg KOH/g, by continuously distilling the water that forms from the esterification reaction. The final blend? was then cooled and dumped.

EXAMPLE 2

This example refers to the preparation of the ester of PG-6 and lauric acid. In an inert environment under a nitrogen atmosphere and under mechanical stirring, 65 g of PG-6 and 38 g of lauric acid were heated to a temperature of 160-180?C. The system ? been kept in these conditions up to acidity? residual < 10 mg KOH/g, by continuously distilling the water that forms from the esterification reaction. The final blend? was then cooled and dumped.

EXAMPLE 3

This example refers to the preparation of PG-6 ester and olive oil. In an inert environment under a nitrogen atmosphere and under mechanical stirring, 54 g of PG-6 and 45 g of olive oil were heated to a temperature of 180-210 ?C. The system ? been kept in these conditions for one hour until completely clear. The final blend? was then cooled and dumped. Acid value: < 10 mg KOH/g.

EXAMPLE 4

This example refers to the preparation of a mixture of esters of PG-4, PG6, succinic acid and stearin.

In an inert environment under a nitrogen atmosphere and under mechanical stirring, 35 g of PG-4, 25 g of PG-6 and 8 g of succinic acid were heated to a temperature of 160-180°C. The system ? been kept in these conditions up to acidity? residual < 10 mg KOH/g, by continuously distilling the water that forms from the esterification reaction. The mixture ? was then added with 25 of commercial stearin, and maintained at a temperature of 160-180 ?C up to acidity? residual < 10 mg KOH/g, by continuously distilling the water that forms from the esterification reaction. The final blend? was then cooled and dumped.

EXAMPLE 5

This example refers to a scouring and bleaching treatment process with a surfactant of the present invention, consisting of the natural polyglycerol esters of Example 1.

The treated fabric consisted of 92% cotton and 8% elastomer.

Recipe of the bath carried out with laboratory equipment:

Polyglycerol esters: 2% on the weight of the fiber to be treated.

50% NaOH: 3 mL/L of bath

35% H2O2: 5 mL/L of bath

Bath ratio: 10:1

Treatment conditions: 98 ?C for one hour.

COD bath after treatment: 284 mg/Kg.

EXAMPLE 6 (COMPARATIVE)

The test of Example 5 is repeated under the identical conditions, with the only difference that a C12-C13 ethoxylated surfactant of the prior art is used as surfactant.

COD bath after treatment: 338 mg/Kg.

EXAMPLE 7

This example refers to a scouring and bleaching treatment process with a surfactant of the present invention, consisting of a 1:1 mixture by weight of the natural polyglycerol esters obtained in Examples 1 and 3.

An 80% viscose and 8% elastomer knitted fabric is treated.

Recipe of the bath carried out with laboratory equipment:

Polyglycerol esters: 2% on the weight of the fiber to be treated.

Na2CO3: 2 g/L of bath

35% H2O2: 5 mL/L of bath

Bath ratio: 10:1

Treatment conditions: 80 ?C for one hour.

COD bath after treatment: 260 mg/Kg.

EXAMPLE 8 (COMPARATIVE)

The test of Example 7 is repeated under the identical conditions, with the only difference that a C12-C13 ethoxylated surfactant of the prior art is used as surfactant.

COD bath after treatment: 350 mg/Kg.

EXAMPLE 9

This example refers to a scouring and bleaching treatment process with a surfactant of the present invention, consisting of a 1:1 mixture by weight of the natural polyglycerol esters obtained in Examples 1 and 3.

The treated fabric consisted of 80% polyamide and 20% elastomer.

Recipe of the bath carried out with laboratory equipment:

Polyglycerol esters: 2% on the weight of the fiber to be treated.

Na2CO3: 2 g/L of bath

Bath ratio: 10:1

Treatment conditions: 80 ?C for 40 minutes.

COD bath after treatment: 410 mg/Kg.

EXAMPLE 10 (COMPARATIVE)

The test of Example 9 is repeated under the identical conditions, with the only difference that a C12-C13 ethoxylated surfactant of the prior art is used as surfactant.

COD bath after treatment: 450 mg/Kg.

EXAMPLE 11

? was performed a test with activated sludge in order to further verify the biodegradability? of the natural esters of the invention. ? a test was prepared in an activated sludge batch pilot reactor (ISO 14851 method), comparing the abatement times of the lactulose reference, of a C12-C13 ethoxylated surfactant of the prior art and of a surfactant based on natural polyglycerol esters ( 1:1 weight/weight mixture of the products obtained from Examples 1 and 3).

After 24 hours, there was a reduction of 84% of lactulose, 81% of the surfactant based on natural polyglycerol esters and only 32% of the C12-C13 ethoxylated surfactant. After 48 hours, the knockdowns of lactulose and natural polyglycerol ester surfactant were over 95%, while the removal of C12-C13 ethoxylated surfactant was only 46%.

Claims (10)

1. Process of scouring and bleaching of textile fibers, comprising the following stages: a) load, in which a quantity? defined by weight of fiber to be treated; b) closure, in which the equipment closes once the loading is completed; c) introduction of water, preferably in a ratio of about 10:1 weight/weight with respect to the mass of fiber to be treated, of at least one biodegradable surfactant consisting of one or more? natural esters of polyglycerol, at least one alkali agent and optionally at least one oxidizing agent; d) heat treatment, in which the mass, depending on the nature of the fibre, is treated at a temperature preferably between 50?C and 110?C, plus? preferably between 80 and 100°C, for a period between about 30 and about 60 minutes; e) cooling, in which the temperature is lowered to a value such as to allow the subsequent safe opening of the treatment equipment; f) opening, in which the treatment equipment is opened; g) discharge of the treated mass and of the treatment effluent. 2. Process according to claim 1 wherein said natural polyglycerol esters used in step c) are formed by the esterification of pure X-polyglycerols, wherein X represents the number of units? glycerol and ? an integer included in the range 3-12, with one or more? carboxylic fatty acids. 3. Process according to claim 2, wherein said natural polyglycerol esters contain between 0.9 and 1.5 radicals derived from carboxylic acids per unit? of polyglycerol-X. 4. Process according to any one of claims 2 to 4, wherein said one or more? polyglycerol-X esters are two of said esters in a ratio of 1:1 mol/mol to 1:3 mol/mol. 5. A process according to any one of claims 2 to 4, wherein said carboxylic fatty acids are C8-C30 monocarboxylic acids from natural sources. 6. Process according to any one of claims 2 to 4, wherein said carboxylic fatty acids are C4-C10 dicarboxylic acids from natural sources, preferably succinic acid, adipic acid and sebacic acid. 7. Process according to any one of claims 2 to 4, wherein said carboxylic fatty acids are fatty hydroxy acids from natural sources, preferably 12-hydroxystearic acid and ricinoleic acid. 8. Process according to any one of claims 2 to 4, wherein said natural polyglycerol esters are produced by transesterification of said X-polyglycerols with an oil selected from olive oil, rapeseed oil, sunflower oil, soya oil and linseed oil. 9. Process according to any one of the preceding claims, in which the alkaline agent used in step c) of the process is? selected from hydroxides or carbonates of alkali or alkaline earth metals and mixtures thereof. 10. Process according to any one of the preceding claims, wherein the oxidizing agent used in stage c) of the process is? selected from hydrogen peroxide, sodium perborate, peracetic acid, chlorinated products and mixtures thereof.