The invention relates to a method for conferring durable water repellence to woven or non-woven fabric, to a composition for conferring durable water repellence to woven or non-woven fabric and to woven or non-woven fabric treated with the said composition.

Methods for conferring durable water repellence to woven or non-woven fabric are known in the art. Up to now, the provision of durable water repellence to fabric has relied on fluorocarbon-based treatments that are highly effective and extraordinarily durable. However, the by-products such as fluor surfactants and derivatives based on C8 and C6 fluor surfactants are toxic and persist in the environment, a combination that makes it unacceptable despite its excellent performance. Many coatings that are fluor-free today have a short life span. A water repellent rain shell functionally degrades into a wind shell long before the garment itself wears out.

JP2020153057 describes a vinyl-based polymerisation of a specific divinyl compound with a molecular weight of 600 or more involving chemical bonding of the vinyl polymer to polyester fabric. An additional film is applied, comprising a fluorinated copolymer or an acrylic monomer that is polymerized with a perfluoroalkyl group having 6 or less carbon atoms. The additional film is crosslinked by a melamine resin.

EP3919673 describes a special fabric surface that resembles the surface of lotus flower leaves to mimic the water repellence thereof. This artificial lotus-like surface can be treated by commonly known water repellents.

WO201 6/000831 describes a composition for application on textiles to confer water repellence, wherein three different acrylate monomers, one of which containing fluorine, are polymerized to a polyacrylate by the aid of an azo initiator. Apart from the thus obtained polyacrylate, the composition comprises a wax.

The present invention provides method for conferring durable water repellence to woven or non-woven fabric and a fibre treatment composition that can impart water repellence having excellent washing durability to a fibre product without the need to incorporate fluor components for water repellence, and without the need for use of silicone, isocyanates or melamine boosters. The present method for conferring durable water repellence to woven or non-woven fabric results in a highly durable and sustainable water repellent coating on the fabric, that remains unaffected even after 100 or more rounds of machine washing.

To this end, the method comprises the following steps: i) treating the fabric with an aqueous composition, the composition comprising: a. an aqueous solvent comprising at least 80 w/w% water, and 20 w/w% or less of a water miscible organic solvent comprising at least two functional OH groups, and b. 0.1 - 40 w/w% of an acrylic ester having the formula 1 :

, wherein A ¹ is H or CH3, and A ² is C1-C30 linear or branched, saturated or unsaturated hydrocarbon that may have an alicyclic or aromatic ring, the acrylic ester being dissolved, emulsified or dispersed in the aqueous solvent, ii) heating the treated fabric to 120 - 200°C.

According to the method of the present invention, the water miscible solvent participates in a chemical reaction with the acrylic ester through the functional OH groups thereof.

By the heat treatment step ii), a (trans)esterification reaction is initiated between a water miscible solvent molecule and the acrylic ester. A covalent C-O-C bond is formed between one of the at least two OH groups of the water miscible solvent molecule and with the oxygen of the C=0 group of the acrylic ester of formula 1. Since the water miscible solvent molecule has at least two functional OH groups, the acrylic ester acquires a functional OH group, enabling the said ester to bond with the fabric fibre by this OH group through hydrogen bridging. With ‘functional OH group’ is therefore meant that the said group is capable of forming the said C-O-C bond. The conditions are chosen such, that the above reaction or reactions can take place, e.g. at acid pH.

Without being bound to any scientific explanation, it is also possible that the transesterification reaction proceeds, wherein the aqueous solvent molecule becomes esterified with the CH2=C(A ¹ )COO moiety of the acrylate ester, and the A ² moiety to become covalently linked to a terminal OH group. In the latter case, the A ² moiety binds to the fibric fibre by hydrogen bridging of its newly acquired terminal OH group. It is also possible that the transesterification reaction results in both, i.e. an incomplete and a complete esterification process, both resulting in the fibre acquiring a hydrophobic A ² moiety bound thereto through hydrogen bridging. Since the result of the heat treatment is that the A2 moieties become bound to the fabric, this step is also to be regarded as a curing step.

It is however clear that the composition of the present invention does not comprise an acrylate polymer, i.e. a polymer comprising a plurality of acrylate monomers, in particular three or more, polymerized to one another, e.g. by the use of an azo initiator. Further, by the above definition, it is also clear that the said acrylic ester is free of fluorine groups.

Suitable acrylic esters as defined above for step i)b. are known in the art, such as Unidyne XF series (Daikin, Japan).

The heat treatment results in a fabric, the fibres of which comprising hydrophobic A ² moieties stably bound thereto through hydrogen bridging, therewith acquiring a very strong and sustainable water repellence.

The water miscible solvent can comprise more than 2 functional OH groups, but the presence of 2 functional OH groups is preferred. Accordingly, the water soluble aqueous solvent is preferably an organic water miscible solvent, more preferably chosen from the group, consisting of: ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol dimethyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, polypropylene glycol and hexylene glycol. Most preferred is tripropylene glycol.

The aqueous solvent preferably comprises at least 0.1 w/w% of the water miscible solvent, preferably at least 0.2 w/w%.

The aqueous solvent preferably comprises 90 - 99.9 w/w% water and 0.1 - 10 w/w% of the water miscible solvent, more preferably 95 - 99.8 w/w% water and 0.2 - 5 w/w% of the water miscible solvent, or 95 - 99 w/w% water and 1 - 5 w/w% miscible organic solvent.

The composition preferably comprises 0.2 - 20 w/w% acrylic ester, more preferably 0.5 - 10 w/w%, even more preferably 1 - 6 w/w%. For optimal water repellence, the surface tension of the coating should be about 25 mN/m ² . To this end, the A ² moiety is preferably alkyl. The A ² moiety of the acrylic ester preferably has 12 to 24 carbon atoms, more preferably 12 to 21 carbon atoms, even more preferably 18 carbon atoms. A -CH2- moiety confers about 31 mN/m ² , whereas a terminal -CH3 confers 22 mN/m ² . This means that a higher -CH3 content will result in a coating with a lower surface tension and therewith to a stronger water repellence. A higher -CH3 content can be obtained by increasing the number of branches in the hydrocarbon chain. Therefore, although the A ² moiety can be linear, the said moiety is preferably branched.

It has been found that a coating applied to a fabric according to the above method remain very stably attached to the fabric. It was observed that the fabric remained fully preserved during 100 washing cycles, followed by drying in a tumble dryer operated with a regular drying program, i.e. involving heating. It was however observed that the coating started to wear after about 10 washing cycles when drying was performed without added heating (so-called “line drying”).

The coating could be further improved by including a polyisocyanate having at least 3 crosslinking isocyanate groups in the aqueous composition. It was surprisingly found that the presence of polyisocyanate resulted in a significant increased stability of the coating, without any noticeable wear after 30 washing cycles followed by line drying. The functional OH groups of both the water miscible solvent molecules and of the acrylic ester comprising a functional OH group as a result of the above described transesterification reaction, as well as the A2 moiety with a functional OH group obtained this way are covalently bound to the polyisocyanate, resulting in a crosslinked web of hydrophobic carbohydrate moieties, the web being formed by interconnection of the polyisocyanate molecules linked to one another via covalent linkage with the functional OH groups of the water miscible solvent molecules. Since these molecules comprise 2 or more functional OH groups, these function to link polyisocyanate molecules to one another, to form a hydrogen bridge bond with the fabric fibre, and to provide a functional group to the acrylic ester of the A2 moiety, respectively.

The polyisocyanate can e.g. be aromatic or aliphatic, and suitable polyisocyanates are known in the art. Since the polyisocyanate is in an aqueous composition, e.g. water-based, the polyisocyanate is preferably blocked, e.g. by blocking groups known in the art, such as phenol, nonyl phenol, methylethylketoxime (MEKO), alcohols, e-caprolactam, amides, imidazoles, or pyrazoles. JP2020007657 describes a fibre treatment composition containing a water repellent and such a blocked polyisocyanate. In order for the blocked polyisocyanates to become active, i.e. to become unblocked, the water is to be removed first, e.g. by drying, followed by a subsequent heating step. A very attractive isocyanate is a trimer based on aliphatic hexamethylene-1 ,6-diisocyanate, in particular HDI trimer (Kowa, NY, US).

The weight ratio acrylic ester : isocyanate is 100 : 5 - 100, preferably 100 : 30 - 80, more preferably 100 : 50 - 70, most preferably 100 : 60. It was found that a relatively high ratio acrylic ester : isocyanate results in the most stable coating.

In step ii), the heating is preferably performed at 130 - 200°C, more preferably 140 - 200°C, more preferably 145 - 200°C 180°C, even more preferably at 145 - 180°C, still even more preferably at 150 - 170°C and most preferably around 160°C. It has been found that such a heating step result in an excellent reaction between the components (water miscible solvent, and acrylic ester, and if present, the polyisocyanate) and binding to the fabric. In case of the presence of a blocked polyisocyanate in the composition, the said polyisocyanate becomes unblocked at such a temperature as well.

The optimal heating temperature may also depend on the treated fabric. In case of e.g. an ultra high molecular weight polyethylene, the heating temperature is preferably kept below 140°C, in particular around 130°C, since above the said temperature, deformation of the material can take place. For other fabrics that are more temperature resistant, the drying temperature is preferably higher, as described above, most preferably around 160°C. The heating step can be performed by exposure of the treated fabric to a hot air stream, or by residing in a heat chamber, or e.g. by ironing. The skilled person will be aware of the proper temperature choice. The heating step is preferably performed for 30 seconds to 10 minutes, preferably for 1 - 3 minutes.

It is preferred that the fabric as treated in step i) is dried before being subjected to the heating step ii). Such a pre-drying step becomes particularly important in the presence of a polyisocyanate, since the crosslinking reaction is preferably to be performed in a water free environment. In case there is no isocyanate present in the composition, it becomes also possible to combine the heating with the drying. However, drying can usually take place at a lower temperature than heating. Heating is preferably as described above, e.g. between 120°C and 200°C, or at 145 - 200°C, whereas drying preferably takes place preferably between 100 and 140°C, preferably below 140°C. Such a pre-drying step may therefore be more energy saving. Drying is preferably carried out for about 1 - 10 minutes, preferably about 1 - 3 minutes.

In a very attractive embodiment, the composition is free of silicon and/or melamine compounds, and for the sole function of water repellence, the composition is preferably fluorine free as well. This means that there are no compounds present in the composition that have fluorine groups in their molecular backbone.

However, in order to provide a stable and wear resistant coating that is not only water repellent but also oil repellent, the composition of the invention comprises in an attractive embodiment a fluorinated C2-C20 alkyl compound comprising a terminal acryl group, as e.g. is described in JP2020153057, and as are known in the art, e.g. The Unidyne TG Series (Daikin, Japan). By including such a fluor acrylic ester in the composition, this fluor acrylic ester will be susceptible to the transesterification reaction with the water miscible solvent as the fluorine free acrylic ester of formula 1 as described above, and will therefore result in a fluorinated hydrocarbon moiety bound to the fabric fibre through hydrogen bridging, and be able to participate in the crosslinking with the polyisocyanate, if present.

By the provision of such a fluorinated acrylic ester, not only water repellence, but also oil repellence is obtained. Very attractively, the fluorinated alkyl compound is defined as the fluorine free acrylic ester of formula 1 , wherein for the fluorinated compound, the A2 moiety is a C6-C20 alkyl, 1 to 6 of the carbon atoms being fully substituted with fluorine. The term ‘fully substituted with fluorine’ means that all the H atoms of the respective carbon atom have been replaced by a fluorine atom. A saturated terminal carbon atom will, when fully substituted, have three fluorine atoms, and a saturated internal carbon, i.e. flanked by two adjacent carbon atoms by a single bond, will have two fluorine atoms. This means that the fluorine groups can be scattered throughout the alkyl backbone. Such compounds are e.g. known from WO201 6/096128. Very attractively, the A2 of the fluorinated compound is a C ₆ alkyl, all 6 of the carbon atoms being fully substituted with fluorine.

Since the surface tension of -CF ₂ - groups is 18 mN/m ² , and of terminal -CF ₂ and -CF ₃ groups is 15 mN/m ² and 6 mN/m ² , respectively, a branched fluorinated alkyl compound with terminal -CF ₂ and -CF ₃ groups, in particular -CF ₃ groups is preferred.

The composition preferably comprises in w/w% an equal amount of both non- fluorinated and fluorinated acrylic esters. The composition preferably comprises 0.2 - 20 w/w% acrylic ester, more preferably 0.5 - 10 w/w%, even more preferably 1 - 6 w/w% of the fluorinated C2-C20 alkyl compound. In case of the presence of a fluorinated acrylic ester, the weight ratio of isocyanate, if present, to acrylic acid is determined by the sum of both the fluorinated and fluor free acrylic esters present in the composition.

The method of the invention can also be applied to fabric fibres before being assembled to a fabric or textile, instead of treatment of the fabric or textile. A similar water repellence is obtained when a fabric or textile is produced from such treated fibres.

The fibres and/or the fabric is preferably chosen from polyester, polyamide, acrylate, ultra high molecular weight polyethylene (e.g. Dyneema, DSM, Netherlands), cotton or aramide or a mixture of two or more thereof. It was found that the repellent coating was stably and strongly bonded to these types of fabric. To this end, the fabric preferably comprises polyester and/or polyamide, more preferably polyester.

The treatment of step i) is preferably chosen from dipping the fabric in the composition, or spraying the composition onto the fabric. Dipping means that the fabric is immersed in the composition. Dipping is preferred, but spraying is a very attractive home appliance, where the fabric can be sprayed from an aerosol comprising the composition, whereafter the heat treatment can be performed by ironing. In an industrial setting, the treated fabric is preferably dipped and padded subsequently, in order to remove superfluous liquid composition.

In another aspect, the invention relates to a composition for conferring durable water repellence to woven or non-woven fabric as described above.

In still another aspect, the invention relates to fibres, woven or non-woven fabric as described herein, treated with the composition, in particular as described herein.

The invention will now be further illustrated by way of examples and figure, showing a possible industrial set up for the method of the invention.

The arrows reflect the transportation direction of the fabric 1 , guided by guidance rollers 2. The process is continuous, e.g. without interruption. Fabric 1 is immersed in a bath 3 comprising the composition 4 of the invention. After leaving the bath 3, the fabric 4 passes through two padding rolls 5, squeezing the superfluous liquid composition from the fabric. The fabric is dried with hot air in drying chamber 6, where the temperature is e.g. 130°C, and eventually enter a heating chamber, where the temperature is e.g. 160°C.

Examples Water repellence

Samples of PES 1 fabric 135 gr/m ² and PES 2 fabric 190 gr/m ² (MB Sportswear, Eindhoven Netherlands) were washed 100 times according to the method of Iso 6330 3G or 4H.

After washing, the water repellence is measured by the ISO 4920 (version 2012- 12) spray method

Commercial washing cycles:

The water repellence measured by the Iso 4920 spray method after washing 120 times according to the method of using a commercial washing machine of the type Miele Twindos (Germany) using the program Express 2.0 and the detergent Colour Reus extra strong against stains, extra clean (Henkel, Germany). The program specifications and the contents of the detergent are given in tables 1 and 2, respectively.

Table 1 : Washing program Table 2: Ingredients detergent Oil repellence

Oil repellence is measure after washing 100 times of samples as described above according to the AATCC118 method 118-1997.

Sample preparation

The fabric sample was cut 15 x 15 cm from the reel and by dipping the fabric for 1 minute in the coating emulsion. The uncoated fabric was weighed in duplo. After dipping, the coated sample was placed on a rubber sleeve of a manual coating unit (RK prints) for the padding process. With a smooth roller with a weight of 10 kg the excess of emulsion was squeezed out by 2 times rolling the roller over the fabric.

The samples were dried in an oven with forced air ventilation for 3 minutes at 130°C ; subsequently the sample was cured for 1 minute at 160°C. After curing, the sample was weighted in duplo again.

Possible compositions for use in examples 1 - 8 are given in table 3. The experiment have been performed with the compositions given in table 4.

In examples 1 , 3, 5 - 10, a polyester woven fabric PES 135 gr/m ² (‘pique’) (MB Sportswear, Eindhoven Netherlands) was used, whereas in examples 2 and 4 195 gr/m ² ‘smooth’ (MB Sportswear, Eindhoven Netherlands) was used.

It was observed that all examples, after the washing cycles and drying in a tumble dryer (AEG Lavatherm Protex plus, AEG, Germany, with the program setting ‘cotton extra dry’) retained their water repellence. Grade iso 5 was measured for all samples before the first washing and after 100 or 120 times washing. Grade 5 means that no sticking or wetting of the upper surface was observed.

The same was true for examples 1 and 3 when the dipping was replaced by spraying and the padding was replaced by tumbling in a tumble dryer as described above. Heating was performed by ironing at 150°C (level**) for example 1 and at 200°C (level***) for example 2, in conformity with the ironing prescriptions of the fabric manufacturer. Also for these samples, Grade iso 5 was measured for all samples before the first washing and after 100 or 120 times washing.

The oil repellence for examples 3, 4, 8 - 10 as measured according to AATCC118 was grade 5 - 6 after 100 - 120 times washing followed by the above tumble drying. It was however observed that in case of line drying, i.e. without heating the dried fabric, a coating that has been subjected to crosslinking with polyisocyanate remained stably bound as compared to the results for all coatings after tumble drying, whereas the coatings without comprising the isocyanate (NCO) crosslinkages tended to loosen from the fabric after 10 - 12 washing cycles, see table 5. It was observed that a weight ratio acrylic ester : polyisocyanate of above 30 gave the best bonding.

Table 5