PT1557489E - Surface coatings - Google Patents

Abstract

A method of coating a surface with an oil and water repellent polymer layer, which method comprises exposing said surface to a continuous wave plasma comprising the compound of formula (I) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ CH 2 = CR 7 C(O)O(CH 2 ) n R 5 €ƒ€ƒ€ƒ€ƒ€ƒ(I) where n is an integer of from 1 to 10, R 7 hydrogen or C 1-6 alkyl and R 5 is a C 6-20 perhaloalkyl group.

Description

ΕΡ 1 557 489 / ΡΤ

DESCRIPTION " Surface Coatings " The present invention relates to the coating of surfaces, in particular to the manufacture of oil and water impermeable surfaces, as well as to the coated articles obtained therewith.

Oil and water impermeable treatments for a wide variety of surfaces are in common use. For example, it may be desirable to communicate such properties to solid surfaces, such as metal, glass, ceramics, paper, polymers etc., in order to improve their preservation properties, or to prevent or prevent dirt.

A particular substrate, which requires such coatings, consists of fabrics, in particular for applications in outdoor clothing, sportswear and leisure clothing and in military applications. Their treatments generally require the incorporation of a fluoropolymer into or more particularly attached above the surface of the garment fabric. The degree of oil or water tightness is a function of the number and length of fluorocarbon groups or parts that may be placed within the space available. The higher the concentration of these parts, the greater the waterproofing of the finish.

In addition, however, the polymeric compounds must be capable of forming durable bonds with the substrate. The treatments of oil and water impermeable textiles are generally based on fluoropolymers which are applied to the fabric in the form of an aqueous emulsion. The fabric remains breathable and air permeable since the treatment simply coats the fibers with a very thin, liquid impermeable film. In order to render these finishes durable, they are sometimes applied in conjunction with crosslink resins which attach the fluoropolymer treatment to the fibers. While good durability for washing and dry cleaning can be achieved in this manner, the crosslink resins can severely degrade the cellulosic fibers and reduce the mechanical strength of the material. Chemical methods for the manufacture of oil and water impermeable textiles are shown for example in WO 97/13024 and in British Patent No. 1 102 893 or in the book by M. Lewin et al., &Quot; Handbook of Fiber Science and Technology " Mareei and Decker Inc., New York (1984) Vol 2, Part B Chapter 2.

Plasma deposition techniques have been widely used for the deposition of polymer coatings on a range of surfaces. This technique is recognized as being a clean, dry technique which creates little waste compared to conventional wet chemical methods. Using this method, the plasmas are generated from small organic molecules, which are subjected to an ionizing electric field in a low pressure environment. When this is done in the presence of a substrate, excited ions, radicals and molecules of the compound in the plasma polymerize in the gas phase and react with an increasing polymer film on the substrate. Conventional synthesis of the polymer tends to produce structures containing repeating units which show a strong resemblance to the monomer species, given that the polymer network generated using a plasma can be extremely complex. The success or otherwise of plasma polymerization depends on a number of factors, including the nature of the organic compound. Reactive oxygen containing compounds such as maleic anhydride, has previously been subjected to plasma polymerization (Chem. Mater. Vol. 8, 1, 1996). U.S. Patent No. 5,328,576 describes the treatment of paper fabrics or surfaces to impart liquid sealing properties by subjecting the surfaces to pretreatment with an oxygen plasma followed by plasma methane polymerization.

However, plasma polymerization of the desirable oil and water impermeable fluorocarbons has proved more difficult to achieve. Cyclic fluorocarbons have been reported to undergo plasma polymerization more readily than their acyclic counterparts (H. Yasuda et al., J. Polym. Sci, Polym. Chem. Ed., 1977, 15, 2411). 3 Ε 1 557 489 / ΡΤ

Plasma polymerization of trifluoromethyl substituted perfluorocyclohexane monomers has been reported (A. M. Hynes et al., Macromolecules, 1996, 29, 18-21).

A process in which the textiles are subjected to a plasma discharge in the presence of an inert gas and subsequently exposed to a fluorine-containing acrylic monomer is described in SU-1158-634. A similar process for the deposition of a fluoroalkyl acrylate coating on a solid substrate is described in European Patent Application 0 049 884. Japanese Patent Application No. 816773 discloses the plasma polymerization of compounds including fluoro acrylates -substituted. In that process, a mixture of acrylate compounds with fluoro-substituted and an inert gas is subjected to an incandescent discharge. US 5 041 304 describes plasma polymerization of partially fluorinated alkenes and alkanes and cycloalkanes perfluorinated at atmospheric pressure by incandescent discharge of a gas mixture containing an inert gas. The mentioned compounds include, for example, fluoropropylene, difluoropropylene, etc., difluorobutene, trifluorobutene, etc., but preferred are perfluorinated compounds such as hexafluoropropylene and octafluorocycobutane.

Applicants have discovered an improved method of producing halo-polymer coatings which are impermeable to water and / or oil on the surfaces.

According to the present invention there is provided a surface coating method with an oil-impermeable polymer layer and water, the method comprising exposing said surface to a pulsed plasma comprising a compound of the formula (I) CH-R 5 (I) wherein R 5 is a perhaloC 6-20 alkyl group.

As used herein the term " halo " or " halogen " refers to fluoro, chloro, bromo and iodo. In particular, 4

Preferred halo groups are fluoro. Preferably, R5 is a perfluoroalkyl group of the formula CmF2m + i, where m is an integer from 6 to 12, such as 8 or 10. The term the hydrocarbon includes the alkyl, alkenyl or aryl groups. The term " aryl " refers to aromatic cyclic groups, such as phenyl or naphthyl, in particular phenyl. &Quot; alkyl " refers to the straight or branched chains of carbon atoms, suitably up to 20 carbon atoms in length. The term " alkenyl " refers to unsaturated straight or branched chains having suitably 2 to 20 carbon atoms.

Monomeric compounds in which the chains comprise unsubstituted alkyl or alkenyl groups are suitable for the production of coatings which are impermeable to water. Substituting at least some of the halogen atoms for oil sealing may be provided by the coating.

Plasmas suitable for use in the method of the invention include unbalanced plasmas such as those created by radio frequency (Rf), microwave or DC (direct current) frequencies. They may operate at atmospheric or sub-atmospheric pressures as is well known in the art. The plasma may comprise only the monomeric compound, in the absence of other gases or mixed for example with an inert gas. Plasmas consisting solely of the monomeric compound can be achieved as shown below by first discharging the reactor vessel to the extent possible, and then purging the reactor vessel with the organic compound for a period sufficient to ensure that the vessel is substantially free of other gases.

All compounds of formula (I) are known compounds or they may be prepared from known compounds using conventional methods. The coated surface according to the invention may be any solid substrate, such as fabrics, metal, glass, ceramics, paper or polymers. In particular, surface 5

And comprises a woven substrate such as a cellulosic fabric to which oil and / or waterproofing is to be applied. Alternatively, the fabric may be a synthetic fabric such as a nylon / acrylic fabric. The tissue may not be treated or may have undergone previous treatments. For example, it has been found that the treatment according to the invention can increase water impermeability and impart a good oil-impermeable finish to a fabric which already has a silicone finish which is only impermeable to water.

The exact conditions in which the plasma polymerization takes place in an efficient manner will vary depending upon such factors as the nature of the polymer, the substrate, etc., and will be determined using routine methods and / or techniques illustrated below. In general, the polymerization is conveniently carried out using vapors of compounds of formula (I) at pressures of from 0.01 to 10 mbar, suitably about 0.2 mbar.

An incandescent discharge is then triggered by the application of a high frequency voltage, for example 13.56 MHz.

The applied fields conveniently have an average power of up to 50 W. Suitable conditions include continuous fields, although the pulsed fields are better. Pulses are applied in a sequence which produces very low average powers, for example less than 10 W and preferably less than 1 W. Examples such frequencies are those in which the current is switched on for 20 ps and switched off for 1 000 ps to 20 000 ps.

The fields are conveniently applied for a period sufficient to give the desired coating. In general, this will be from 30 seconds to 20 minutes, preferably from 2 to 15 minutes, depending on the nature of the compound of formula (I) and the substrate, etc. Plasma polymerization of the compounds of formula (I), particularly at low average potencies, has been found to result in the deposition of highly fluorinated coatings exhibiting super water impermeability. In addition, a high level of structural retention of the compound of formula (I) occurs in the coating layer, which can be attributed to the direct polymerization of the alkene monomer, by means of its highly sensitive double bond.

Because the compound of formula (I) includes a perfluoroalkylated tip or portion, the process of the invention may have oil and water impermeability surface properties.

Thus, the invention further provides a substrate with water and / or oil impermeability which comprises a substrate comprising a coating of a haloalkyl polymer which has been applied by the method described above. In particular, the substrates are woven but may be solid materials such as biomedical devices. The invention will now be particularly described by way of example, with reference to the accompanying schematic drawings, in which: Fig. 1 shows a diagram of the apparatus used to effect plasma deposition; Fig. 2 is a graph showing the characteristics of a 1H, 1H, 2H-perfluoro-1-decene continuous wave plasma polymerization; Fig. 3 is a graph showing the pulsed plasma polymerization characteristics of 1H, 1H, 2H-perfluoro-1-dodecene at 50 W Pp, Ton = 20 ps and Toff = 10000 ps for 5 minutes; and Fig. 4 is a graph showing the characteristics of a continuous (a) and (b) pulsed plasma polymerization of 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate. 7 Ε 1 557 489 / ΡΤ

Example 1

Alkene 1H, 1H, 2H-perfluoro-1-dodecene (CioF2 CH2 = CH2) (Fluorochem F06003, 97% purity) plasma polymerization was placed into the further purified monomer tube (I) (Fig. 1) using freezing and thawing cycles. A series of plasma polymerization experiments were performed in an induction-connected (5) cylindrical plasma reactor vessel 4 cm 3 by volume, base pressure of 7 × 1 3 mbar, and with a flow rate of greater than 2 × 1 3 cm 3 min -1. The reactor vessel (2) was connected by means of a " viton " (3) to a gas inlet (4) and a needle valve (5) to the monomer tube (1).

A pressure gauge thermocouple (6) was connected by a Young tap (7) to the reactor vessel (2). Another Young's tap 8 has been connected to the air supply and a third 9 leads to a two-stage Edwards rotary pump E2M2 (not shown) by means of a cold liquid nitrogen siphon (10). All connections were fat free.

An LC junction 11 and a power meter 12 were used to connect the output of a 13.56 MHz radio frequency generator 13 which was connected to a power supply 14 to the coils of copper (15) surrounding the reactor vessel (2). This arrangement ensured that the steady-wave ratio (SWR) of the energy transmitted to the partially ionised gas in the reactor vessel (2) could be minimized. For pulsed plasma deposition, a pulsed signal generator (16) was used to trigger the radio frequency energy supply, and a cathode ray oscilloscope (17) was used to control the pulse width and amplitude. The mean energy < P > supplied to the system during pulsation is given by the following formula: - Pcw {Ton / (T0n + T0ff)} 8 ΕΡ 1 557 489 / ΡΤ where Ton / (Ton + Toff) is defined as the service cycle and Pcw is the energy continuous wave mean. In order to carry out the polymerization / deposition reactions the reactor vessel (2) was cleaned by immersing it overnight in a chlorinated bleach bath, then wiping with detergent and finally rinsing with isopropyl alcohol followed by oven drying. The reactor vessel (2) was then incorporated into the assembly as shown in Fig. 1 and further cleaned with a 50 W air plasma for 30 minutes. The reactor vessel 2 was then air-vented and the substrate to be coated 19, in this case a glass slide, was placed in the center of the chamber defined by the reactor vessel 2 in a glass plate 18. The chamber was then evacuated to the base pressure (7.2 x 10 3 mbar).

Perfluoroalkene vapor was then introduced into the reaction chamber at a constant pressure of -0.2 mbar and allowed to drain the plasma reactor, followed by ignition of the incandescent discharge. Typically a settling time of 2-15 minutes has been found to be sufficient to give complete coverage to the substrate. Thereafter, the radio frequency generator was shut down and the perfluoroalkene vapor was allowed to continue to pass over the substrate for a further 5 minutes before evacuating the reactor back to the base pressure, and finally ventilating it at atmospheric pressure.

Polymer deposited plasma coatings were characterized immediately after deposition by X-ray Photoelectron Spectroscopy (XPS). Full coverage by the plasma polymer was confirmed by the absence of any Si signals in the XPS (2p) as it passes through the underlying glass substrate.

A control experiment where the fluoroalkene vapor was allowed to pass over the substrate for 15 minutes and then pumped to the base pressure allowed to show the presence of a large Si signal in XPS (2p) originating from the substrate. Therefore coatings obtained during plasma polymerization are not only due to the absorption of the fluoroalkene monomer on the substrate. 9 Ε 1 557 489 / ΡΤ

The experiments were performed with average powers of the order of 0.3 to 50 W. The XPS spectrum results of a plasma polymer deposition with a 0.3 W continuous wave on a glass slide for 13 minutes are shown in Fig . 2.

It can be seen that in this case CF2 and CF3 are the main environments in the C (ls) envelope in XPS: CF2 (291.2 eV) 61% CF3 (293.3 eV) 12% 39 The remaining carbon environments comprised partially fluorinated carbon centers and a small amount of hydrocarbon (CxHy). The experimental and theoretically predicted values (taken from the monomer) are given in Table 1.

Table 1

Theoretical Experimental Theoretical F-C ratio: 1.70 ± 0.3 1, 75% CF2 group 61% ± 2% 75%% CF3 group 12% ± 2% 8% The difference between theoretical and experimental percentages of group CF2 and group CF3 can be attributed to the small amount of perfluoroalkene monomer fragmentation. Fig. 3 shows the XPS spectrum of C (1s) for a 5 minute pulsed plasma polymerization experiment where: Pcw = 50 W Ton = 20 ps

Toff = 10,000 ps < P > = 0.1 W The chemical composition of the deposited coating for a pulsed plasma deposition is given in Table 2 below. 10 Ε 1 557 489 / ΡΤ

Table 2

Theoretical Experimental Theory F: C 1.75 ± 0.7 1, 75% CF2 group 63% ± 2% 75%% CF3 group 10% ± 2% 8%

It can be seen that the CF2 region is better resolved and has a higher intensity which means less perfluoroalkyl tip fragmentation compared to continuous wave plasma polymerization.

Surface energy measurements were performed on slides produced in this manner using dynamic contact angle analysis. The results showed that the surface energy was of the order of 5-6 mJm-1.

Example 2 (comparative example)

Water and oil impermeability test

The pulsed plasma deposition conditions described in Example 1 above were used for coating a piece of cotton (3x8 cm) which was then assayed for its behavior to moisture using " Test Methods 3M " (3M Test 1 for oil impermeability, 3M Test Methods Oct. 1, 1988). As water impermeability test, 3M Test II for water impermeability, water droplet / alcohol assay, 3M Assay 1, 3M Test Methods, Oct. 1, 1988 was used. These assays are intended to detect a finish fluoroquímico in all types of fabrics measuring: (a) resistance to aqueous stains using mixtures of water and isopropyl alcohol. (b) the resistance of the fabric to moisture by a selected series of liquid hydrocarbons having different surface tensions.

These tests are not intended to give the absolute measurement of the resistance of the stain to aqueous or oily materials, since other factors such as fabric construction, fiber type, paints, other finishing agents , etc., also influence stain resistance. These tests can, however, be used to compare various finishes. The water impermeability tests comprise placing 3 drops of a standard test liquid consisting of volume specific percentages of water and isopropyl alcohol on the plasma polymerized surface. The surface is considered impermeable to this liquid if after 10 seconds, 2 of the 3 drops do not wet the tissue. From this, the degree of water impermeability is taken to be the test liquid with the highest percentage of isopropyl alcohol passing the test. In the case of the oil impermeability test, 3 drops of the liquid hydrocarbon are placed on the coated surface. If after 30 seconds there is no evidence of penetration or wetting of the tissue at the liquid-tissue interface around 2 of the 3 drops, then the assay is approved. The degree of oil impermeability is considered to be the highest test liquid which does not wet the fabric surface (where the increasing number corresponds to the hydrocarbon chain and decreasing surface tension).

The obtained classifications for pulsed plasma deposition of 1H, 1H, 2H-perfluoro-1-dodecane on cellulose were: Water 9 (10% water, 90% isopropyl alcohol) Oil 5 (dodecane)

These values compare well with commercial treatments.

Example 3 (comparative example)

Plasma Polymerization of Acrylates The method of Example 1 described above was repeated using 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate (Fluorochem F04389E, 98% purity) instead of perfluoroalkene. As in Example 1, low average potencies were used for the 12

Continuous wave and pulsed plasma polymerization experiments. For example, the XPS spectrum of a 1 W continuous plasma deposited polymer on a glass slide for 10 minutes is shown in Fig. 4 (a). 4 (b) shows the XPS C spectrum (ls) of a pulsed plasma polymerization experiment for 10 minutes where

Pcw = 40 W (average continuous wave energy)

Ton = 20 ps (pulse time on) T0ff = 20 000 ps (pulse time off) < P > = 0.04 W (average pulse energy) Table 3 compares the theoretical environments (taken from the monomer, CH 2 = CHCO 2 CH 2 CH 2 C 8 F 17) with what is actually found for the polymer coatings.

It can be seen that the CF2 group is the environment of prominent prominence in the XPS C (ls) envelope with 291.2 cV. The remaining carbon environments being CF3, partially fluorinated and oxygenated carbon centers and a small amount of hydrocarbons (CxHy). The chemical composition of the deposited coatings by pulsed plasma and continuous wave conditions are presented below in Table 4 (excluding satellite percentages), in conjunction with the theoretically expected compositions).

Table 3

Environment eV Theoretical percentages Experimental percentages ff3 293.2 7.7 7.8 ff3 291.2 53.8 47.0 0 II 01 1 0 289.0 7.7 13.0 CF 287.8-8.7 C- CFN / C-0 286.6 15.4 13.4 CC (0) = 0 285.7 7.7 3.9 x x H and 285.0 7.7 7.2

It can be seen in Fig. 4 (b) that the CF2 region is better resolved and has a higher intensity, which means that less perfluoroalkyl tip fragmentation occurs during pulsed plasma conditions compared to continuous wave plasma polymerization. In the case of continuous wave plasma experiments, low percentages of CF2 and CF3 groups occur.

Table 4

Theorists Continuous-wave plasma Pulsed plasma Relationship F: C 1.31 0.94 1.49% CF2 group 53.8% 27.2% 47.0% CF3 group 7.7% 3,8% 7,8%

Surface energy measurements as described in Example 1 show a surface energy of 6 mJnT1.

Example 4 (comparative example)

Water and oil impermeability test

Using the pulsed plasma deposition conditions of Example 3 except that they were applied for 15 minutes, pieces of cotton (3x8 cm) were coated with 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate. Similar cotton pieces were coated with the same compound using a 1 W continuous wave for 15 minutes. These were then subjected to oil and water impermeability tests as described in Example 2 above.

The samples were then subjected to Soxhlet extraction with benzotrifluoride for either 1 or 7 hours and the oil and water impermeability tests were repeated. The results, expressed as described in Example 2,

Time (hours Continuous wave Pulsed wave Oil impermeability Water impermeability Oil impermeability Water impermeability 0 7 4 8 10 1 - 2 6 7 7 - 2 5 7

Therefore these coatings are highly impervious to water and oil and have good durability. 14 Ε 1 557 489 / ΡΤ

Example 5 (Comparative example)

Treatment of silicone-coated synthetic fabric

A sample of a modified nylon / acrylic fabric which already contained a silicone coating to impart water impermeability was subjected to a pulsed acrylate plasma consisting of the compound CH 2 = CHCOO (CH 2) 2 C 8 F 7 and using the conditions described in Example 3 .

A sample of the same material was subjected to a two stage deposition process in which the tissue was first exposed to a 30 W continuous air plasma for 5 seconds followed by a vapor exposure of the same acrylate.

The products were then tested for oil and water impermeability as described in Example 2. In addition, the durability of the coating was then tested by subjecting the products to a 1 hour Soxhlet extraction with trichlorethylene.

The results were as shown in Table 5

Table 5

Treatment Waterproofing grades Before plasma After plasma After solvent extraction Pulsed plasma phase of W2 07.06, acrylate W10 W8 Air plasma followed by W2 01.01 (frontier) exposure to W3 W2 acrylate monomer

It will therefore be appreciated that the process of the invention may not only increase the water impermeability of such fabric but also impart oil impermeability to it, the durability of the coating being greater than that obtained using the known graft polymerization process of two steps.

Lisbon, 2011-03-30

Claims (9)

A method for coating a surface with a polymer layer, wherein the method comprises exposing said surface to a pulsed plasma comprising a compound of the formula (I) CH 2 = CH- R5 (I) where R5 is a perhaloalkyl group C20 -20 A method according to claim 1, wherein R5 is a perfluoroalkyl group of the formula CmF2m + i, where m is an integer of 6 to 1. A method as claimed in claim 1 or claim 2, wherein the surface is a surface of a fabric, metal, glass, ceramic, paper, or polymer substrate. A method according to claim 3, wherein the substrate is a tissue. A method according to any preceding claim, wherein the incandescent discharge is ignited in an atmosphere containing the compound at a gas pressure of from 0.01 to 10 mbar by a high frequency voltage. A method according to any preceding claim, wherein the plasma polymerization is carried out for 2 to 15 minutes. Substrate with water or oil impermeability, which comprises a substrate comprising a coating of a polymer which has been applied by the method according to any preceding claim. The substrate according to claim 7, which is a fabric. A garment article comprising a fabric according to claim 8. I COUNTS A compound of the formula: COUNTS ΕΡ 1 557 489 / ΡΤ 4/4 Fig.4.