Surface coatings

Abstract

The invention provides a method of coating a fabric, e.g. a textile material, with a polymer coating, which method comprises contacting a fabric with a monomer and subjecting the monomer to low power plasma polymerization, wherein the monomer comprises the general formula (I): C.sub.nF.sub.2n+1C.sub.mX.sub.2mCR.sub.1Y—OCO—C(R.sub.2)═CH.sub.2, wherein n is 2 to 6, m is 0 to 9, X and Y are H, F, Cl, Br or I, R.sub.1 is H or alkyl, e.g. —CH.sub.3, or a substituted alkyl, e.g. an at least partially halo-substituted alkyl, and R.sub.2 is H or alkyl, e.g. —CH.sub.3 or a substituted alkyl, e.g. an at least partially halo-substituted alkyl.

Claims

1. A method of coating a fabric with a polymer coating, which method includes contacting a fabric with a monomer and subjecting the monomer to plasma polymerisation, wherein the monomer comprises the general formula (I):
C.sub.nF.sub.2n+1C.sub.mX.sub.2mCR.sub.1Y—OCO—C(R.sub.2)═CH.sub.2 wherein n is 2 to 6, m is 0 to 9, X and Y are H, F, Cl, Br or I, R.sub.1 is H or alkyl or a substituted alkyl and R.sub.2 is H or alkyl or a substituted alkyl, wherein the method comprises a step of outgassing the fabric in a plasma chamber before deposition of the coating in which the outgassing is performed by pumping away moisture and trapped gases from the fabric and away from the plasma chamber, whilst winding the fabric from a first roller to a second roller, and wherein the fabric is guided between said rollers during the step of subjecting the monomer to plasma polymerization in the plasma chamber.

2. A method according to claim 1, wherein after the outgassing step, the pressure inside the chamber is below a set base pressure for a next step which is a pre-treatment step or the plasma polymerisation step.

3. A method according to claim 1, wherein during the step in which the outgassing is performed by pumping away moisture and trapped gases whilst winding the fabric from a first roller to a second roller, the fabric passes through a zone for a plasma without a plasma being present.

4. A method according to claim 3, wherein the fabric is wound forwards and backwards between the first and second rollers at least two times for outgassing of the fabric, the fabric passing through a zone for a plasma without the plasma being present.

5. A method according to claim 3, wherein the outgassing is performed with the fabric passing the plasma zone at a speed from 1 to 20 m/min.

6. A method according to claim 1, wherein the polymer coating has a thickness of from 30 to 100 nm.

7. A method according to claim 1, the method further comprising the step of coating one or both surfaces of the fabric.

8. A method according to claim 1, further comprising pre-treating a roll of fabric prior to coating deposition, including the steps of winding the fabric between rollers, passing the fabric through a plasma zone, introducing an inert gas or a reactive and/or etching gas into the plasma zone, causing a plasma to form in the plasma zone.

9. A method according to claim 8, wherein the pre-treatment is performed with the fabric passing the plasma zone at a speed from 1 to 20 m/min.

10. A method according to claim 8, wherein the outgassing and the pre-treatment are combined in one single process step.

11. A method according to claim 8, wherein power for pre-treatment is applied either in continuous wave mode or pulsed mode, wherein when the power is applied in pulsed mode, the pulse frequency is from 100 Hz to 10 kHz and the duty cycle is from 0.05% to 50%.

12. A method according to claim 1, wherein power for plasma polymerisation is applied either in continuous wave mode or pulsed mode, wherein when the power is applied in pulsed mode, the pulse frequency is from 100 Hz to 10 kHz and the duty cycle is from 0.05% to 50%.

13. A method according to claim 1, further comprising the step of utilising the monomer to strike plasma without using an additional gas to strike the plasma.

14. A method according to claim 1, wherein the fabric comprises a synthetic material.

15. A method according to claim 1, wherein R.sub.1 is an at least partially halo-substituted alkyl.

16. A method according to claim 1, wherein R.sub.2 is an at least partially halo-substituted alkyl.

17. A method according to claim 1, wherein the fabric comprises natural fibres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order that the invention may be more readily understood, it will now be described by way of example only and with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic representation of a roll-to-roll plasma deposition apparatus;

(3) FIG. 2 shows a first electrode arrangement according to the prior art;

(4) FIG. 3 shows a second electrode arrangement according to the prior art;

(5) FIG. 4 shows a first electrode arrangement according to the present invention;

(6) FIG. 5 shows a second electrode arrangement according to the present invention;

(7) FIG. 6 shows a third electrode arrangement according to the present invention;

(8) FIG. 7 shows a fourth electrode arrangement according to the present invention; and

(9) FIG. 8 shows plan (a), side (b) and end (c) views of a radiofrequency electrode.

(10) FIG. 9 is a graph showing results of water absorption in an uncoated material after one minute, one hour and twenty-four hours drip-out.

(11) FIG. 10 shows oil repellency as a number of washing cycles.

(12) FIG. 11 shows spray test results related to numbers of washing cycle.

(13) FIG. 12 shows oil repellency with and without pretreatment compared to numbers of wash cycles.

(14) FIG. 13 shows spray test results from a number of washing cycles.

(15) FIG. 14 shows oil repellency in a function of numbers of Martindale abrasion cycles.

(16) FIG. 15 shows spray test results in a function of numbers of Martindale abrasion cycles.

DETAILED DESCRIPTION

(17) Referring first to FIG. 1 a roll-to-roll plasma deposition apparatus, indicated generally at 1, will now be described. The apparatus 1 comprises a plasma chamber 10, a first compartment 12 and a second compartment 14. The first 12 and second 14 compartments are the unwinding and winding up compartments, arranged at both sides of the plasma chamber. These compartments are known to those skilled in the art and will not be described in any further detail.

(18) The plasma chamber 10 comprises an array of electrode layers RF, M, the arrangement of which will be described in detail further below with reference to FIG. 4. The plasma chamber 10 further comprises a series of upper and lower rollers 101, 102 and load cells for guiding a sheet of textile material 16 between the electrode layers RF, M from a first roll 120 mounted in the first compartment 12 to a second roll 140 mounted in the second compartment 14.

(19) Schematic diagrams of electrode layer arrangements according to the prior art are shown in FIGS. 2 and 3. The most basic arrangement is shown in FIG. 2 in which a radiofrequency electrode layer and a ground electrode layer are arranged in a side-by-side relationship. This arrangement may be symbolized as M/RF, where ‘M’ denotes a ground electrode, ‘RF’ denotes a radiofrequency electrode, and ‘/’ denotes the space in which the textile material 16 passes. Upper 101 and lower 102 rollers are arranged to guide a sheet of the textile material 16 from one roll 120 to another roll 140. In use, and when an electromagnetic field is applied to the radiofrequency electrode layer RF, plasma is struck between the radiofrequency electrode layer RF and the ground electrode layer M. Such plasma is known as primary plasma. When monomer is present in the plasma chamber 10 this results in a polymer coating being applied to a surface of the sheet of textile material 16 that is facing the radiofrequency electrode layer RF, resulting in a sheet of textile material 16 having a uniform polymer coating applied to a single surface thereof.

(20) FIG. 3 shows a further arrangement in which additional radiofrequency electrode layers RF and ground electrode layers M are arranged alternately in a side-by-side relationship. This arrangement may be symbolized as M/RF/M/RF/M. Again, primary plasma is struck between a radiofrequency electrode layer RF and a ground electrode layer M such that a polymer coating is applied to a surface of the sheet of textile material 16 that is facing the radiofrequency electrode layer RF. The sheet of textile material 16 makes four passes and on each pass the same side of the textile material 16 facing the radiofrequency electrode layer RF is coated, resulting in a sheet of textile material 16 having a uniform polymer coating applied to a single surface thereof.

(21) In a first embodiment of the invention the electrode arrangement comprises ten electrode layers arranged in sequence as shown in FIG. 4. This arrangement may be symbolized as M/RF/M/RF/M/M/RF/M/RF/M (this represents the arrangement as shown in FIG. 1). In use, and when an electromagnetic field is applied to the radiofrequency electrode layers, plasma is struck between the electrode layers. A primary plasma is struck between a radiofrequency electrode layer RF and a ground electrode layer M. Therefore, whilst it is clear that the sheet of textile material 16 makes nine passes between the electrode layers, only the first and last four passes are through primary plasma zones.

(22) Accordingly, during the first four passes monomer is polymerised onto a first side of the sheet of textile material 16 whilst during the last four passes monomer is polymerised onto the obverse side of sheet of textile material 16, resulting in a sheet of textile material 16 having a uniform polymer coating applied to each surface thereof. During the fifth pass an insignificant quantity to no monomer is deposited onto the sheet of textile material 16.

(23) FIG. 5 shows a second simplified embodiment of the invention in which the electrode arrangement comprises four electrode layers arranged in sequence. This arrangement may be symbolized as M/RF/RF/M. In use, and when an electromagnetic field is applied to the radiofrequency electrode layer, plasma is struck between the electrode layers. A primary plasma is struck between a radiofrequency electrode layer RF and a ground electrode layer M. Therefore, whilst it is clear that the sheet of textile material 16 makes three passes between the electrode layers, only the first and third passes are through primary plasma zones. Accordingly, during the first pass monomer is polymerised onto a first side of the sheet of textile material 16 whilst during the third pass monomer is polymerised onto the obverse side of the sheet of textile material 16, resulting in a sheet of textile material 16 having a uniform polymer coating applied to each surface thereof. During the second pass an insignificant quantity to no monomer is deposited onto the sheet of textile material 16.

(24) In a third embodiment the electrode layers may be arranged as follows: RF/M/M/RF. Similarly, when an electromagnetic field is applied to the radiofrequency electrode layers, plasma is struck between the electrode layers. A primary plasma is struck between a radiofrequency electrode layer and a ground electrode layer. Therefore, whilst it is clear that the sheet of textile material 16 makes three passes between the electrode layers, only the first and third passes are through primary plasma zones. Accordingly, during the first pass monomer is polymerised onto a first side of the sheet of textile material 16 whilst during the third pass monomer is polymerised onto the obverse side of the sheet of textile material 16, resulting in a sheet of textile material 16 having a uniform polymer coating applied to each surface thereof. During the second pass an insignificant quantity to no monomer is deposited onto the sheet of textile material 16.

(25) The applicant has surprisingly discovered that the polymer coating has greater uniformity, as found when measurements were made in testing e.g. in contact angles for water and/or greater uniformity in oil repellency, when the ground electrode layers are placed at the outer positions as described in the first and second embodiments.

(26) In order to coat each side of the fabric the applicant has discovered that it is important to have a pair of identical electrode layers side-by-side in the series. For instance a pair of ground electrode layers, as described in the first or third embodiments, or a pair of radiofrequency electrode layers, as described in the second embodiment. This inventive arrangement results in the switching of polymer deposition from one side of the sheet of textile material 16 to another.

(27) In further embodiments additional arrangements may be envisaged. For instance, RF/M/RF/RF/M/RF or M/RF/M/M/RF/M. In these embodiments it is clear that the sheet of textile material 16 makes five passes between the electrode layers: the first, second, fourth and fifth passes being through primary plasma zones. Accordingly, during the first and second passes monomer is polymerised onto a first side of the sheet of textile material 16 whilst during the fourth and fifth passes monomer is polymerised onto the obverse side of the sheet of textile material 16, resulting in a sheet of textile material 16 having a uniform polymer coating applied to each surface thereof. During the third pass insignificant to no monomer is deposited onto the sheet of textile material 16.

(28) Similarly, even further embodiments are envisaged having additional electrode layers incorporated into the sequence, e.g. M/RF/M/RF/RF/M/RF/M or RF/M/RF/M/M/RF/M/RF or RF/M/RF/M/RF/RF/M/RF/M/RF or M/RF/M/RF/M/M/RF/M/RF/M or M/RF/M/RF/M/RF/RF/M/RF/M/RF/M or RF/M/RF/M/RF/M/M/RF/M/RF/M/RF and so on. As the number of electrode layers increases in the series so does the number of passes through a primary plasma zone. Accordingly, it is possible to control the thickness of the resultant polymer layer by increasing or decreasing the number of electrode layers in the sequence. Also, by increasing the number of electrode layers in the sequence it is possible to increase the speed within which the sheet of textile material 16 passes through the plasma chamber 10 without compromising on the quality of the polymer layer.

(29) In a further embodiment shown in FIG. 6 the electrode layers are arranged as follows: M*RF*M/M*RF*M, where ‘RF’ denotes a radiofrequency electrode layer, ‘M’ denotes a ground electrode layer, ‘*’ denotes a primary plasma zone and ‘/’ denotes the space in which the fabric passes. In this embodiment the plasma chamber 10 comprises a first electrode set (M*RF*M) and a second electrode set (M*RF*M), wherein the first and second electrode sets comprise electrode layers and wherein each electrode set comprises two ground electrode layers M and a single radiofrequency electrode layer RF. In this embodiment it is clear that the sheet of textile material 16 makes a single pass between the electrode sets (M*RF*M).

(30) Although we neither wish nor intend to be bound by any particular theory, we understand that the plasma created in between electrode sets (M*RF*M) of this embodiment of the invention cannot be described as either a pure primary or as a pure secondary plasma. Rather, the inventors consider that the electrode sets (M*RF*M) create a new hybrid form of plasma which is strong enough to start and maintain a polymerisation reaction at very low power, but which at the same time is benign enough not to break down the reactive monomers. Accordingly, during the first pass monomer is polymerised onto first and second sides of the sheet of textile material 16, resulting in a sheet of textile material 16 having a uniform polymer coating applied to each surface thereof.

(31) The processing speeds may be increased by adding further electrode sets (M*RF*M) to the plasma chamber 10, for example third, fourth, fifth and sixth electrode sets (M*RF*M) and so on. For example when adding a third electrode set (M*RF*M), the sheet of textile material 16 is coated on both sides in two passes, e.g. M*RF*M/M*RF*M/M*RF*M or RF*M*RF/RF*M*RF/RF*M*RF. FIG. 7 shows an example of an electrode arrangement having six electrode sets (M*RF*M) arranged in sequence. In this design, contrary to FIG. 1, the unwinding and the winding up take place in the same area at the same side of the plasma chamber.

(32) FIG. 8 shows a radiofrequency electrode layer RF in plan (a), side (b) and end (c) views. The radiofrequency electrode layer RF comprises a generally planar body formed from folded tubing 21. The tubing 21 may comprise a plurality of sections which are joined together by connectors 27. The tubing 21 is typically formed of a conductive metallic material such as aluminium, stainless steel or copper. The tubing 21 is hollow to allow for a temperature regulation fluid to be passed through the electrode layer RF to regulate the plasma at a predetermined temperature. The tubing 21 comprises a series of bends 22 formed at regular intervals along the tubing length. The tubing 21 curves back on itself at each bend 22 by approximately 180°. The tubing 21 has a diameter of approximately 10 mm and a wall thickness of approximately 2 mm. The distance between the tubing 21 before and after each bend 22 is approximately 5 times the diameter of the tubing 21.

(33) The tubing 21 is curved at each end so as to provide distal portions 25, 26 which are substantially orthogonal to the planar body. The distal portions 25, 26 may be connected to a fluid supply or egress line (not shown). Alternatively, the distal portions 25, 26 may be connected to the distal portions of adjacent or nearby electrode layers.

(34) The radiofrequency electrode layer RF further comprises a pair of connecting plates 23, 24 attached to the front and to the rear of the electrode layer 20 adjacent to the bends 22. The connecting plates 23, 24 provide both a means for attaching the radiofrequency electrode layer RF to the inside of the vacuum chamber 11 and electrical contacts for applying a load thereto.

(35) A ground electrode layer M (not shown in detail) typically comprises a planar sheet of aluminium.

(36) An example sequence of depositing a polymer coating to a roll of fabric is as follows: 1. A roll of fabric 120 to be treated is mounted in a first compartment 12 of the apparatus 1; 2. The free end of the fabric 16 is fed (manually or automatically) through the rollers 101, 102 within the plasma chamber 10 and then secured to an empty roll 140 in a second compartment 14; 3. The plasma chamber 10 is closed and the electrodes, which are mounted on the moving part of the machine, are slid in between the guiding rolls (and thus in between the textile); 4. The plasma chamber 10 is sealed and pumped down to the required predetermined base pressure; 5. The load cells are calibrated for optimal processing; 6. Gas inlet valve is opened and the evaporated liquid monomer is fed into the plasma chamber 10 in a controlled manner at a controlled rate; 7. An electromagnetic field is applied to the radiofrequency electrode layers RF and a low power continuous wave plasma is generated; 8. Power is applied to the rollers 101, 102 of the apparatus 1 in order to unwind fabric 16 from first roll 120, and wind it onto a second roll 140, during which time it passes between the electrode layers RF, M or sets of electrode layers M*RF*M, RF*M*RF where a polymer coating is deposited to each side of the fabric 16 before being wound onto second roll 140; 9. Once all of the fabric 16 has had a polymer coating applied thereto, the electromagnetic field is turned off and the plasma chamber 10 is ventilated to atmospheric pressure.
A second example sequence of depositing a polymer coating to a roll of fabric, e.g. in a 9000 l chamber, is as follows: 1. A roll of fabric 120 to be treated is mounted in a first compartment 12 of the apparatus 1; 2. The free end of the fabric 16 is fed (manually or automatically) through the rollers 101, 102 within the plasma chamber 10 and then secured to an empty roll 140 in a second compartment 14; 3. The plasma chamber 10 is closed and the guiding rolls and all the textile (on roll in the unwinding area, the free end of the fabric mounted on a core in the winding up area, and the textile guided through the guiding rolls), which are mounted on the moving part of the machine, are slid in between the electrodes; 4. The plasma chamber 10 is sealed and pumped down to a predetermined base pressure required for outgassing and pre-treatment; 5. The load cells are calibrated for optimal processing; 6. The gas inlet valve is opened and the inert gas for the pre-treatment, e.g. cleaning and/or activation and/or etching, which is combined with further gassing out of the textile prior to coating, is fed into the plasma chamber 10; 7. An electromagnetic field is applied to the radiofrequency electrode layers RF and a plasma is generated; this plasma may be either a continuous wave plasma or a pulsed wave plasma, the choice of plasma mode being dependent upon the required power level and determined to be optimum for the pre-treatment gas or gases used and/or for the size and design of the plasma equipment and/or for a particular textile being used; 8. Power is applied to the rollers 101, 102 of the apparatus 1 in order to unwind fabric 16 from first roll 120, and wind it onto a second roll 140, during which time it passes between the electrode layers RF, M or sets of electrode layers M*RF*M, RF*M*RF where moisture is removed from fabric 16 and where each side of the fabric 16 is pre-treated before being wound onto second roll 140; 9. Once all of the fabric 16 has been gassed out and pre-treated, the electromagnetic field is turned off and the plasma chamber 10 is pumped to the required lower base pressure for polymer layer deposition; 10. Gas inlet valve is opened and the evaporated liquid monomer is fed into the plasma chamber 10 in a controlled manner at a controlled rate; 11. An electromagnetic field is applied to the radiofrequency electrode layers RF and a low power plasma is generated; this plasma may be either a continuous wave plasma or a pulsed wave plasma, the choice of plasma mode being dependent upon the power level needed and determined to be optimum for a particular monomer being used to treat the material being treated and/or for the size and/or the design of the plasma equipment and/or for a particular textile being used; 12. Power is applied to the rollers 101, 102 of the apparatus 1 and fabric 16 is unwound from roll 140, passes between the electrode layers RF, M or sets of electrode layers M*RF*M, RF*M*RF where a polymer coating is deposited to each side of the fabric 16 before being wound onto roll 120; 13. Once all of the fabric 16 has had a polymer coating applied thereto, the electromagnetic field is turned off and the plasma chamber 10 is ventilated to atmospheric pressure.

Example 1

(37) An experiment was carried out on small rolls of a textile for use as a filtration media before scaling up to production level. The textile comprised a nonwoven synthetic material comprising polymer fibres. The roll was 1000 m long and 1.1 m wide.

(38) The process parameters are presented in Tables 1 and 2.

(39) TABLE-US-00001 TABLE 1 Parameter Value Liquid Monomer Supply (LMS) Temperature canister 130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 6 m Treatment speed 2 m/min Tension 1.5 kg (15N) Temperature walls 40-50° C. Electrodes & Generator Electrode configuration M/RF/M/RF/RF/M/RF/M Plasma type Primary Power 100-500 W Frequency 13.56 MHz Frequency mode cw Temperature RF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl acrylate Flow 40-100 sccm Pressure Base pressure 10-50 mTorr Work pressure 20-80 mTorr Residence time in plasma 3 minutes zone Oleophobicity Level 5 (ISO 14419-2010)

(40) TABLE-US-00002 TABLE 2 Parameter Value Liquid Monomer Supply (LMS) Temperature canister 130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 6 m Treatment speed 2 m/min Tension 1.5 kg (15N) Temperature walls 40-50° C. Electrodes & Generator Electrode configuration M/RF/M/RF/RF/M/RF/M Plasma type Primary Power 500-1000 W Frequency 13.56 MHz Frequency mode pulsed (10.sup.2-10.sup.4 Hz; duty cycle 0.1-20%) Temperature RF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl methacrylate Flow 40-100 sccm Pressure Base pressure 10-50 mTorr Work pressure 20-80 mTorr Residence time in plasma 3 minutes zone Oleophobicity Level 3 (ISO 14419-2010)

(41) The resultant coated textile according to Table 1 demonstrated good hydro- and oleophobic properties as well as efficient filtration so it was decided to scale up the process.

(42) The resulting hydro- and oleophobic properties of the textiles coated with the process according to Table 2 are lower than from the coated textiles according to Table 1. However, it is decided to scale up this process as well.

Example 2

(43) The processes of example 1 were increased in scale. The textile material was the same as that of example 1. The roll was 10000 m long and 1.1 m wide.

(44) The process parameters are presented in Tables 3 and 4.

(45) TABLE-US-00003 TABLE 3 Parameter Value Liquid Monomer Supply (LMS) Temperature canister 130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 12 m Treatment speed 4 m/min Tension 1.5 kg (15N) Temperature walls 40-50° C. Electrodes & Generator Electrode configuration M/RF/M/RF/M/RF/RF/M/RF/M/RF/M Plasma type Primary Power 200-800 W Frequency 13.56 MHz Frequency mode cw Temperature RF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl acrylate Flow 50-120 sccm Pressure Base pressure 30-50 mTorr Work pressure 70-90 mTorr Residence time in plasma 3 minutes zone Oleophobicity Level 5 (ISO 14419-2010)

(46) TABLE-US-00004 TABLE 4 Parameter Value Liquid Monomer Supply (LMS) Temperature canister 130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 12 m Treatment speed 4 m/min Tension 1.5 kg (15N) Temperature walls 40-50° C. Electrodes & Generator Electrode configuration M/RF/M/RF/M/RF/RF/M/RF/M/RF/M Plasma type Primary Power 700-1200 W Frequency 13.56 MHz Frequency mode pulsed (10.sup.2-10.sup.4 Hz; duty cycle 0.1-20%) Temperature RF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl methacrylate Flow 50-120 sccm Pressure Base pressure 30-50 mTorr Work pressure 70-90 mTorr Residence time in plasma 3 minutes zone Oleophobicity Level 3 (ISO 14419-2010)

(47) The resultant coated textile according to Table 3 demonstrated good hydro- and oleophobic properties as well as efficient filtration. The resulting hydro- and oleophobic properties of the textiles coated with the process according to Table 4 are lower than from the coated textiles according to Table 3.

(48) Results

(49) Oil Repellency

(50) Examples 1 and 2 show that low power continuous wave plasma polymerisation processes provide a better performance than pulsed wave plasma polymerisation processes. This is demonstrated by the oil repellency which is tested according to ISO 14419.

(51) The results are presented in Table 5, and show that the oil repellency for continuous wave coatings of A4 sheets is higher than for pulsed wave coatings, the effect being more pronounced for short treatment times, e.g. 2 minutes.

(52) TABLE-US-00005 TABLE 5 Oil repellency for continuous wave and pulsed wave Deposition mode Treatment time (min) Oil repellency Continuous wave (cw) 2 minutes L 6 Pulsed 2 minutes L 3 Continuous wave (cw) 5 minutes L 6 Pulsed 5 minutes L 4
Filtration Efficiency

(53) The filtration efficiency for standard filtration media and filtration media coated in accordance with the present invention were tested for three different grades of High Efficiency Particulate Arresting (HEPA) filter elements (grades F7, F8 and F9). Grades F7, F8 and F9 are indications given to secondary filter elements depending on their efficiency they should reach according to the BS EN 779 test standard. The required efficiency in use (middle efficiency) depends on the particle size to be filtered.

(54) For 0.4 μm particles, F7 grades should obtain a middle efficiency of 80-90%.

(55) For 0.4 μm particles, F8 grades should obtain a middle efficiency of 90-95%.

(56) For 0.4 μm particles, F9 grades should obtain a middle efficiency of more than 95%.

(57) The filtration of this test media is charged, i.e. to form an electret, and may be used in heating, ventilation or air conditioning (HVAC) systems.

(58) The initial and the middle filtration efficiency for 0.4 μm pores is measured according to standard European air filter test BS EN 779 for the standard filtration media and plasma coated filtration media in charged form and in discharged form. The filtration media is discharged by bringing into contact with isopropanol.

(59) The initial filtration efficiency is the efficiency of a clean, brand new filter element. It is obvious that once the filter is in use, its pores become blocked by filtered particles, and by consequence its efficiency increases during lifetime. The initial efficiency is thus the minimal efficiency.

(60) The results for the first fabric grade F7 are presented in Table 6. In order to pass the test the required average efficiency is 80 to 90% and the initial efficiency is 35% or more.

(61) TABLE-US-00006 TABLE 6 Standard Standard Plasma Plasma Type of F7— F7— treated F7— treated F7— filter charged discharged charged discharged Initial 55% 39% 70% 64% efficiency 0.4 μm Average 85% — 87% 87% efficiency 0.4 μm

(62) From Table 6 it is clear that the initial filtration efficiency for charged filter elements coated with an inventive coating is enhanced. Once the filters are discharged, the initial and average efficiency for standard filters drops highly, while the plasma treated filter elements do not show an efficiency drop for the average efficiency and a slight drop for the initial efficiency.

(63) The results for the second fabric grade F8 are presented in Table 7. In order to pass the test the required average efficiency is 90 to 95% and the initial efficiency is 55%.

(64) TABLE-US-00007 TABLE 7 Standard Standard Plasma Plasma Type of F8— F8— treated F8— treated F8— filter charged discharged charged discharged Initial 50% 33% 80% 87% efficiency 0.4 μm Average 83% 76% 92% 94% efficiency 0.4 μm

(65) From Table 7 it is clear that the initial and average filtration efficiency for charged filter elements coated with an inventive coating is enhanced. Once the filters are discharged, the initial and average efficiency for standard filters drops, while the plasma treated filter elements do show an efficiency increase for the average efficiency and for the initial efficiency.

(66) The standard filter elements do not have the required average efficiency of 90-95%, while the plasma coated filters reach the spec for both charged and discharged.

(67) The standard filter elements do not have the required initial efficiency of 55%, while the plasma coated filters reach the spec for both charged and discharged.

(68) Filtration efficiency is enhanced for discharged filter elements coated with an inventive coating. After discharge with isopropanol, the coating is still on the filter element preventing the latter from showing a decrease in efficiency.

(69) Penetration of Dispersed Oil Particles (DOP)

(70) Respirator masks having five layers of nonwoven meltblown polypropylene (15-30 g/m.sup.2) are electrostatically charged after coating with a coating according to Example 1. Evaluation of the penetration is done using a Certitest 8130 apparatus loading the textile with 200 mg of DOP-particles. The results are presented in Table 8.

(71) TABLE-US-00008 TABLE 8 Initial Penetration penetration after (x) Filter medium Conditioning (%) minutes (%) Supplier I—28 g/m.sup.2 Uncoated 1.20 6.40 (30) Supplier I—28 g/m.sup.2 Plasma coated 0.48 1.08 (30) Supplier I—22 g/m.sup.2 Uncoated 1.25 3.90 (10) Supplier I—22 g/m.sup.2 Plasma coated 0.40 0.75 (10) Supplier II—25 g/m.sup.2 Uncoated N.A. N.A. Supplier II—25 g/m.sup.2 Plasma coated 0.02 0.03 (10)

(72) It is clear from Table 8 that the plasma coated materials perform much better than the uncoated reference materials. The initial penetration is about 3 times less; the penetration after 10 to 30 minutes is 5 to 6 times less. The filtration efficiency for oily particles is enhanced by using an inventive coating.

(73) Filter Efficiency

(74) Diesel filters made of approximately 1 to 2 mm thick nonwoven polyethylene terephthalate (PET) of 500 g/m.sup.2 are coating with an inventive coating according to Example 2.

(75) The efficiency is tested by soaking the filter elements in water for 22 hours, followed by a drip out of a certain time (minute range) in vertical position. The weight increase is calculated and compared to non-coated reference samples of the same material.

(76) The results are presented in the following graph.

(77) From the graph shown in FIG. 9, it is clear that uncoated material absorbs a high volume of water, almost 1800% weight increase after 1 minute drip out.

(78) Samples coated with an inventive coating show extremely low water absorption values, less than 10% weight increase after 1 minute drip out.

(79) Washability

(80) Three different polyester woven fabrics coated with a low power plasma coating according to Table 3 from Example 2 have been washed according to ISO 15797 (2002).

(81) One complete washing cycle comprised the following steps: 1. Washing at 60° C. and using 20 g IPSO HF 234 without optical whitener per kilogram dry textile material; 2. Tumble drying; 3. Hot pressing at 180° C. (e.g. ironing).

(82) Five washing cycles have been performed one after the other, then the oil repellency was measured according to ISO 14419 and a spray test was performed according to ISO 9073—part 17 and ISO 4920.

(83) Next, five more washing cycles have been done and the oil repellency test and spray test have been repeated.

(84) The oil repellency in function of the number of washing cycles is presented in FIG. 10. FIG. 11 shows the spray test results in function of the number of washing cycles.

(85) In a further example another polyester woven fabric has been coated with and without a pre-treatment prior to the coating step. The process without pre-treatment is carried out according to Example 1.

(86) The process parameters for the process with pre-treatment are presented in Table 9.

(87) TABLE-US-00009 TABLE 12 Parameter Value Pre-treatment Gas Argon Flow 500-1000 sccm Treatment speed 6 m/min Power 500-750 W Frequency 13.56 MHz Frequency mode cw Liquid Monomer Supply (LMS) Temperature canister 130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 6 m Coating step speed 2 m/min Tension 1.5 kg (15N) Temperature walls 40-50° C. Electrodes & Generator Electrode configuration M/RF/M/RF/RF/M/RF/M Plasma type Primary Power during coating 100-500 W Frequency 13.56 MHz Frequency mode cw Temperature RF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl acrylate Flow 40-100 sccm Pressure Base pressure 10-50 mTorr Work pressure 20-80 mTorr Residence time in plasma 3 minutes zone during coating Oleophobicity Level 5 (ISO 14419-2010)

(88) The coated textiles have been washed according to ISO 15797 (2002).

(89) One complete washing cycle comprised the following steps: 1. Washing at 75° C. and using 20 g IPSO HF 234 without optical whitener per kilogram dry textile material; 2. Drying in a drying cabinet;

(90) After one washing cycle the oil repellency was measured according to ISO 14419 and a spray test was performed according to ISO 9073—part 17 and ISO 4920.

(91) Next, four more washing cycles have been completed and the oil repellency test and spray test have been repeated (values measured after 5 washings).

(92) Next, five more washing cycles have been done and the oil repellency test and spray test have been repeated (values measured after 10 washings).

(93) The oil repellency as a function of the number of washing cycles is presented in FIG. 12. FIG. 13 shows the spray test results in function of the number of washing cycles.

(94) From tables 13 and 14 it is clear that the textile samples that were pre-treated prior to coating have a better performance in washing. The improvement is more pronounced in spray testing, where the water repellency is tested. The difference in the level of oil repellency becomes visible after 10 washing cycles, as can be seen in FIG. 12. After 20 washing cycles the pre-treated fabric still has oil repellency level 3.

(95) Abrasion Durability

(96) Three different polyester woven fabrics coated with a low power plasma coating according to Example 2 have undergone an Martindale abrasion test. Because afterwards a spray test was performed, larger samples than normal were needed, and the set-up was slightly changed.

(97) A standard wool fabric was pressed with a force of 9 kPa onto a larger coated PES woven fabric. 5000 abrasion cycles have been done and the oil repellency was measured according to ISO 14419 and a spray test was performed according to ISO 9073—part 17 and ISO 4920. Then 5000 more abrasion cycles have been done and the oil repellency test and spray test have been repeated.

(98) FIG. 14 shows the oil repellency in function of the number of Martindale abrasion cycles and FIG. 15 shows the spray test results in function of the number of Martindale abrasion cycles.