Compositions comprising fluorine-containing polymer and siloxane

The invention relates to compositions which comprise water, at least one polymer with one or more perfluoroalkyl groups (RF groups) and at least one siloxane. It further relates to a process for treating fiber materials, where a composition of the specified type is applied to a fiber material.

It is known to treat fiber materials, such as, for example, wovens or knitted materials or nonwovens with compositions which comprise polymers which have one or more perfluoroalkyl groups (RF groups). This treatment can impart oil-repellency properties to the fiber materials. Such processes are described, inter alia, in FR-A 2 213 333, DE-A 2 702 632 and EP-A 234 724.

WO 2006/071 442 A1 describes "release compositions" for "release layers" and articles with "adhesive" properties. These compositions comprise relatively small amounts of a fluorine polymer, namely at most 5% by weight, and considerably larger amounts of fluorine-free polymers. The RF groups in the fluorine polymers are exclusively short- chain. WO 2004/069 919 A2 discloses mixtures which comprise fluorine polymers and siloxanes. The fluorine polymers are based on PTFE or PTFE copolymers. The siloxanes are copolymers which contain polyoxyalkylene units in the main chain but not in side chains. The purpose of these siloxanes consists in the stabilization of the fluorine polymer compositions. Finally, WO 03/089 712 A1 discloses compositions which comprise polyurethanes having RF groups and siloxanes. The RF-polyurethanes are formed (see claim 1 ) by reacting isocyanates having at least 3 NCO groups with monofunctional compounds which contain an RF group. The compositions have to further comprise copolymers of the type RF-(meth)acrylate/polyoxyalkylene (meth)acrylate; the latter have the function

of fluorine-containing surfactants. The compositions of this WO serve primarily for the finishing of carpets in order to impart oil-/water-repellency properties thereto. In example 3 of this WO, a composition is specified which, apart from fluorine polymer, also comprises a relatively large amount of siloxane. The weight ratio of fluorine polymer to siloxane is about 100 : 57. The purpose of adding siloxane lies, according to the details of this specification, in an "extender effect", namely in a partial replacement of the expensive RF polymer by the more cost-effective siloxane.

There is a series of strict requirements for articles made of nonwovens, of polyolefins, in particular of polypropylene-SMS nonwovens (spunbond-meltblown-spunbond), which are intended for use in the medical sector. Thus, the finished nonwovens have to have oil- and water-repellency properties, and in the so-called "EDANA test", which is described below, they must also attain at least grade 9, better still grade 10, specifically in relation to the repellency of isopropanol. These nonwovens must thus repel isopropanol virtually quantitatively, i.e. they must not be wetted by isopropanol or must only be wetted to an insignificant degree, i.e. they have to have a barrier to solvent- containing substances.

A further requirement which is placed on said polypropylene nonwovens is that, in the so-called "water column test", which is likewise described below, the height of the water column in the case of the nonwovens treated with polymer compositions, must have a value of at least 60% of the original height, i.e. the height before treatment.

It has been found that with compositions which are known from the prior art and which comprise fluorine polymers, the specified requirements are not met or not adequately met since either the repellent effect toward isopropanol or that toward water is insufficient. However, if compositions comprise polymers with RF groups but no relatively short- chain siloxanes, the isopropanol repellency of treated polypropylene nonwovens is inadequate. If an excessively large amount of siloxane is present in the compositions, then the requirements of the "water column test" are not met. The latter applies, for example, to the formulation according to example 3 of WO 03/089 712 A1.

It was the object of the present invention to provide compositions with which nonwovens made of polyolefins, in particular of polypropylene, can be treated and where these nonwovens, following the treatment, have excellent results with regard to repellency of isopropanol (according to "EDANA test") and with regard to penetration of water

(according to "water column test"). It was also an object of the invention to provide a process for treating fiber materials, in particular nonwovens made of polypropylene, with which articles can be obtained which produce excellent results in the "EDANA test" (repellency of isopropanol) and in the "water column test" (penetration of water into the fiber material).

The object was achieved by a composition which comprises water and at least one component A and at least one component B, where component A is either a polyurethane which can be obtained by reacting a divalent isocyanate with a dihydric alcohol, which contains at least one perfluoroalkyl group RF of the formula (I)

in which x is a number from 5 to 23, preferably from 7 to 19, where neither the divalent isocyanate nor the dihydric alcohol contains polyoxyalkylene groups, or where component A is a polymeric (meth)acrylic acid ester which contains polymerized units of the formula (II),

in which RF has the meaning given above, R ¹ is H or CH ₃ , and y is a number from 2 to 4, or where component A is a mixture which comprises one or more of said polyurethanes and/or one or more of said (meth)acrylic acid esters, where component B is a siloxane of the formula (III) or a mixture of such siloxanes

where all of the radicals R, independently of one another, are CH ₃ -, CH ₃ CH ₂ - or C ₆ H ₅ — , n is a number from 1 to 5, all of the radicals X, independently of one another, are R or a radical of the formula (IV)

- A - where R ³ is H or an alkyl radical having 1-4 carbon atoms, in particular H or methyl, but where at least one of all of the radicals X is a radical of the formula (IV), where in each of the units one of the radicals R ² is hydrogen and the other is hydrogen or a methyl group, where z is a number from 2 to 4 and preferably has the value 3, where t is a number from 2 to 12, preferably a number from 6 to 12, where the composition comprises 10 to 70% by weight of component A, where the weight ratio of component A to component B in the composition is in the range from 100 : 5 to 100 : 35, preferably in the range from 100 : 13 to 100 : 25, and also by a process for treating fiber materials, where a composition of the specified type is applied to the fiber materials.

A particular advantage of compositions according to the invention is that they can be applied to nonwovens made of polypropylene without the surface of the polypropylene having to be chemically modified beforehand, as is the case with many known processes.

The compositions according to the invention are very well suited to being applied to fiber materials and in this connection producing fiber materials which have good alcohol-, oil- and water-repellency properties. Fiber materials which can be used are fabrics in the form of wovens, knits or nonwovens. They can consist of natural or synthetic fibers and mixtures of such fibers. Of particular suitability are compositions according to the invention for treating nonwovens, with a particularly preferred embodiment consisting in applying compositions according to the invention which consist completely or predominantly, i.e. of 80 to 100% by weight, of polyolefin, in particular of polypropylene, to nonwovens. In this way, it is possible to produce nonwovens of polypropylene fibers which are exceptionally suitable for use in the medical sector and which meet the strict requirements imposed therein. These requirements consist firstly in the fact that in the test according to the so-called "EDANA

test", which is explained below, the nonwovens normally have to attain grade 9, but preferably grade 10, which relates to the repellency of isopropanol. Recently, a grade of 8 has also been accepted by the market. Secondly, in the so-called "water column test", the water column which arises in the case of the nonwovens treated with compositions according to the invention after they have been dried must be at least 60% of the height which the water column had on the untreated samples. The two test methods mentioned will now be explained.

1. EDANA test

This test gives information about which alcohol-repellency properties fabrics made of fiber materials have toward low molecular weight alcohols. The test is carried out with regard to the repellency of isopropanol, as is described in the paper "Standard

Test: WSP 80.8 (05), Standard Test Method for Alcohol Repellencv of Nonwoven

Fabrics", edition 2005, of the "European Disposables and Nonwovens Association".

The description of this test method is given in "World Wide Strategic Partner: Standard Test Methods for Nonwovens Industry. Author: INDA and EDANA". The test solutions used were mixtures of isopropanol/water with different mixing ratios.

The result of the test is expressed in grades from 0 to 10, with higher grades denoting more effective repellency of isopropanol.

2. Water column test The test gives information about hydrophilic properties of substrates. It was carried out in accordance with DIN ISO 811 (EN 20811 ), edition August 1992. The resistance of textiles to the penetration of water is measured by ascertaining the hydrostatic pressure height (height of the water column) which a fabric withstands. The higher the water column at which penetration through the textile takes place for the first time, the less hydrophilic the substrate.

It has been found that the treatment of nonwovens made of polypropylene with RF polymers alone, i.e. without co-use of siloxanes of the formula (III) results in inadequate repellency of isopropanol. This finding is particularly surprising since it was not to be expected that the relatively nonpolar RF polymer exhibits a lower repellency toward isopropanol then its combination with the hydrophilic siloxane.

It has been found that with regard to the use as component B, a careful selection of siloxanes has to take place and that in addition the mixing ratio of component A to

component B in compositions according to the invention must be within a narrow range. Otherwise, the strict requirements with regard to "EDANA test" and "water column test" cannot be met.

Often, it is desired or even required if the fiber materials treated with compositions according to the invention additionally have antielectrostatic properties. This can be achieved by also additionally applying an antistatic agent or a mixture of antistatic agents to the fiber materials besides compositions according to the invention. Suitable antielectrostatic products are known to the person skilled in the art and available on the market. Of suitability are, inter alia, products based on customary, known organic phosphorus compounds (e.g. phosphoric acid esters).

In the case of the preferred embodiment of the process according to the invention described below, in which a composition according to the invention is applied to a fiber material in the form of a foam, an antielectrostatic agent can be mixed with the composition before foaming takes place. The required amount of antistatic agent depends on the specific conditions and can be readily ascertained through a few experiments.

Compositions according to the invention have to comprise water and at least one component A and one component B. In addition, further constituents may also be present. As component A it is possible to use an individual polymer or a mixture of polymers, each of which corresponds to the description below.

Component A is a polymer which contains at least one perfluoroalkyl group, the latter also being referred to below as RF group. The polymer can also contain a plurality of groups RF. RF here is a radical of the formula (I).

CF ₃ -4-CF ₂ -|— (I)

In this formula, x is a number from 5 to 23, preferably x has a value in the range from 7 to 19. These values are average values since, on account of the molecular weight distribution during polymer syntheses, individual values of x can differ from one another if the average value of x is less than 5, the oil repellency of the finished materials is inadequate, as is the repellency toward isopropanol.

The polymers with RF groups which are suitable as component A are polyurethanes or poly(meth)acrylate esters. In the case of these (meth)acrylates, the alcohol component on the chain end has a radical RF, these are thus compounds which contain polymerized units of the formula (II)

in which y is a number from 2 to 4 and R ¹ is hydrogen or the methyl group. RF has the meaning given above.

Apart from (meth)acrylates, polyurethanes with groups RF are also highly suited as component A; these can be obtained by reacting divalent isocyanates with dihydric alcohols.

If component A is a polymeric (meth)acrylic acid ester, besides units of the aforementioned formula (II), this polymeric ester can also contain further polymerized units which originate from different monomers. Examples of such monomers which can be additionally incorporated are fluorine-free alkyl (meth)acrylic acid esters, vinylidene chloride, 3-chloro-2-hydroxypropyl (meth)acrylate, styrene, (meth)acrylamide, which is optionally substituted, e.g. N-methylolacrylamide. The product PHOBOL ^® NW from Huntsman Textile Effects (Germany) GmbH comprises a polymeric (meth)acrylic acid ester suitable as component A. Polymers suitable as component A are known to the person skilled in the art and commercially available, e.g. from Du Pont. Suitable products and their preparation can be found in the literature, e.g. in the specifications EP-A 1 088 929. US-A 3 491 169, US-A 3 818 074, US-A 5 214 121 , EP-A 348 350, US-A 3 968 066 and US-A 4 054 592 and in the European patent application No. 07012551.3.

From the group of polyurethanes, only those polyurethanes which can be obtained by reacting divalent isocyanates with dihydric alcohols, where each dihydric alcohol used contains at least one RF group are suitable as component A. If the isocyanates used as starting compounds contain more or fewer than two NCO groups and/or the alcohols used contain more or fewer than 2 OH groups, then no polymers suitable as

component A are formed.

In addition, neither the divalent isocyanates used as starting compounds, nor the dihydric alcohols used as starting compounds must contain polyoxyalkylene groups. They are thus in particular free from polyoxyethylene units. The (meth)acrylate esters which can be used as component A must also be free from polyoxyalkylene units. This is because it has been found that the fiber materials treated with compositions according to the invention would have inadequate water-repellency properties according to "water column test" if component A comprises polyoxyalkylene groups. All of the other products present in compositions according to the invention are also preferably free from polyoxyalkylene groups, with the exception of a certain content of polyoxyalkylene units in component B and optionally in a dispersant. Besides components A and B, yet further components may additionally be present in compositions according to the invention, e.g. fluorine-free polymers, flame retardants, dispersants or dispersant mixtures. All of these additionally used products with the exception of dispersants are preferably free from polyoxyethylene groups and also the fraction of polyoxyethylene units originating from dispersants in compositions according to the invention should only be as high as is absolutely necessary.

If polymeric (meth)acrylate esters are to be used as component A, then these can be prepared by known methods by reaction of (meth)acrylic acid or derivatives thereof with monoalcohols which have an RF group of said type at one chain end, and then free- radical polymerization using a customary free-radical initiator. Highly suitable monoalcohols for said reaction are compounds of the formula

in which RF has the meaning given above and y is a number from 2 to 4. In the reaction of the (meth)acrylic acid or derivative thereof with monoalcohol and subsequent polymerization, optionally with co-use of further unsaturated monomers, polymers are thus formed which contain polymerized units of the formula (II).

These are suitable as component A.

Component A must not be a uniform polymer. Instead, mixtures can also be used which comprise one or more polyurethanes and/or one or more polyacrylates of the specified types.

Compositions according to the invention which comprise a polymeric (meth)acrylic acid ester, in particular a copolymer, or a mixture of such polymeric esters as component A are particularly well suited.

Component B of compositions according to the invention is a siloxane of the formula (III) or a mixture of such siloxanes.

In this formula (III), all of the radicals R, independently of one another, are a methyl or ethyl or phenyl group. Preferably, 80 to 100% of all of the radicals R present are methyl groups. In formula (III), n has a value from 1 to 5. Siloxanes in which n = 1 are particularly well suited. If n assumes greater values than 5, no siloxanes suitable as component B are present.

All of the radicals X in formula (III) are, independently of one another, a radical R of the specified type or are a radical of the formula (IV).

where R > ^ύ 3 is H or an alkyl radical with 1-4 carbon atoms, in particular H or methyl.

At least one of all of the radicals X present, however, must be a radical of the formula (IV). In formula (IV), z is a number from 2 to 4, t is a number from 2 to 12,

preferably from 6 to 12. In each unit

of formula (IV), one of the radicals R ² is H and the other is H or CH ₃ .

In a preferred embodiment of compositions according to the invention, component B is a compound of the formula (Vl)

(CH ₃ ) ₃ Siθ4si(CH ₃ )(X)-O_^Si(CH ₃ ) _{3 (V} |)

or a mixture of such compounds, where m is a number from 1 to 4, a radical X is a radical of the formula (IV) as stated above and all of the other optionally present radicals X are CH ₃ -.

In a particularly preferred embodiment of compositions according to the invention, component B is a compound of the formula (V)

or a mixture of such compounds, where z and t have the meanings given above.

Siloxanes of the formula (III), (V) and (Vl) are commercially available and can be prepared by methods as are known to the person skilled in the art in the field of silicone chemistry. Such siloxanes can be obtained from Wacker Chemie AG or Evonik Goldschmidt GmbH.

In order to achieve the advantages of compositions according to the invention during the treatment of nonwovens made of polyolefins, it is necessary to observe certain quantitative ranges for water and the components A and B. The compositions must comprise 10 to 70% by weight of component A. In addition, the weight ratio of component A to component B must be in the range from 100 : 5 to 100 : 35. Particular

preference in this connection is given to a range from 100 : 13 to 100 : 25.

With regard to the relative fractions of the individual ingredients of compositions according to the invention, these can fluctuate within certain ranges. For example, compositions which have a content of fluorine (calculated as element F) in the range from 3.5 to 6.5% by weight and in which the weight ratio of water to component A is in the range from 1.3 : 1 to 2 : 1 are well suited. Compositions of this type are easy to prepare and can be readily stored. For the use in the treatment of nonwovens made of polypropylene, it is advantageous to further dilute these specified compositions with water. A particularly preferred embodiment of compositions according to the invention is therefore one in which it comprises water and component A in the weight ratio from 4 : 1 to 6 : 1. Compositions of this type can be readily foamed mechanically and applied as foam to fiber materials, which is a preferred method for the application of compositions according to the invention.

Compositions according to the invention can be prepared in a simple manner by mixing water, component A and component B at room temperature or, if appropriate, somewhat elevated temperature. If appropriate, further products are added to the compositions, such as, for example, antistatic agents, flame retardants etc. The individual constituents are normally mixed using a mechanical stirring operation. It is often possible, when selecting suitable quantitative ratios of the individual components, to foam compositions according to the invention and to apply them in the form of thus resulting foams to the fiber materials. This application method is preferred. In this way, it is possible to apply relatively small amounts of water to the fiber materials. The advantage compared with conventional bath applications is, inter alia, that then less time and energy is required in order to remove the water again from the fiber materials. High processing rates can therefore be achieved. The mentioned foaming can be carried out without additional use of a foam-forming agent through mechanical agitation with admittance of air, and devices known for this purpose are suitable. Thus, foams with a weight, for example, of from 20 to 100 g/l can be obtained. The foam can be applied to the fiber material, e.g. to the nonwoven, using conventional foam applicators at room temperature.

Following the treatment with compositions according to the invention, the fiber materials are dried in a known manner, e.g. at a temperature in the range from 80 to 12O ⁰ C. Subsequently, a condensation can be carried out at a further elevated temperature, e.g.

a temperature in the range from 120 to 140 ⁰ C. Preferably, the drying and condensation can be completed in one operation in order to thereby increase the productivity and save energy. At high commodity rates and under optimum drying/condensation conditions, the time can be just a few seconds.

Besides the mentioned use of nonwovens in the medical sector, fiber materials treated with compositions according to the invention can also be used in other sectors, e.g. in geotextiles, awnings or tarpaulins.

The invention will now be illustrated by working examples.

One of the following formulations was applied in each case to a sample of a polypropylene-SMS nonwoven with a weight per unit area of 60 g/m ² .

Formulation 1 (not according to the invention):

350 g/l of a standard commercial polyacrylate dispersion (OLEOPHOBOL SL-A01 , Huntsman Textile Effects (Germany) GmbH, corresponding to component A) 1 g/l of a standard commercial foamer.

Formulation 1 thus comprised no component B. The polyacrylate dispersion

(component A) was an aqueous dispersion which comprised about 12% by weight of a polyacrylate with RF groups.

Formulation 2 (according to the invention):

350 g/l of the same polyacrylate dispersion as in formulation 1 10 g/l of a siloxane of the aforementioned formula (III) (Wacker Silicone Oil L 066, corresponding to component B).

Formulation 3 (not according to the invention):

350 g/l of the same polyacrylate dispersion as in formulation 1 10 g/l of a long-chain polysiloxane with essentially more than 10 polyoxyethylene units in one side chain. This polysiloxane does not fall under the definition of component B.

Formulation 4 (according to the invention):

350 g/l of PHOBOL ^® NW from Huntsman Textile Effects (Germany) GmbH, an aqueous

dispersion which comprised about 14% by weight of a polyacrylate with RF groups, corresponding to component A

10 g/l of a siloxane of the aforementioned formula (III) (Wacker Silicone Oil L 066, corresponding to component B).

Formulation 5 (not according to the invention):

350 g/l of the same polyacrylate dispersion as in formulation 1

41 g/l of Silwet L-77 ^® surfactant (GE Silicones, corresponding to component B).

All of the formulations were converted to a foam with a weight of 60 g/l using a foaming apparatus. Only in the case of formulation 1 was the addition of a foamer necessary. The foams were then each applied to a sample of the polypropylene nonwoven in an amount such that the nonwoven had a 20% higher weight after application than the untreated nonwoven.

Following application of the foam formulations, the treated nonwovens were dried at 12O ⁰ C for one minute. Then, in each case, the alcohol repellency (isopropanol) was ascertained according to the EDANA test, and the water column test was carried out. The results are given in the table below:

It is obvious that the nonwovens treated with the formulations 2 or 4 according to the invention are superior to the nonwovens which have been treated with the formulations 1 , 3 or 5. Not only is the repellency effect toward isopropanol significantly better in the case of the nonwovens treated with the formulations 2 and 4 (grade 10 as opposed to 5) but the nonwovens treated with the formulations 2 and 4 are the only ones to meet the requirement that the height of the water column should have at least 60% of the value

which the untreated nonwoven sample exhibits in the water column test. It can be seen from example 5 not according to the invention that in the case of a higher fraction of component B in the formulation, the requirements with regard to "water column test" are no longer met.