HK1100168A - Coating of a polymer layer using low power pulsed plasma in a plasma chamber of a large volume - Google Patents

Description

Coating polymer layers using low power pulsed plasma in a large volume plasma chamber

The present invention relates to the coating of surfaces, in particular the production of oil-and water-repellent surfaces, and to the coated articles obtained therefrom.

Oil and water repellent treatments for a variety of surfaces have been widely used. For example, it is preferable to impart the properties to a solid surface such as metal, glass, ceramic, paper, polymer, or the like to improve preservation properties, or to prevent or inhibit staining.

One particular substrate that requires such coatings is fabrics, particularly for outdoor apparel applications, sportswear, casual wear, and military applications. Their treatment generally requires the incorporation of a fluoropolymer, or more specifically, the fixing of a fluoropolymer on the surface of the garment fabric. The degree of oil and water repellency is closely related to the number and length of fluorocarbon groups or portions thereof that can be matched to the available space. The greater the concentration of this portion, the more protective the coating is.

However, in addition to this, the macromolecular compounds must also be able to form a durable bond with the matrix. Oil and water repellent textile treatments are typically based on fluoropolymers applied to fabrics in the form of aqueous emulsions. The fabric can remain breathable as the treatment simply covers the fabric with a very thin liquidproof film. To impart durability to these coatings, they are sometimes used in combination with a crosslinking resin that binds the fluoropolymer treatment to the fibers. Although this allows to obtain good durability with respect to washing and dry cleaning, the crosslinking resin can seriously damage the cellulose fibres and reduce the mechanical strength of the material. Chemical methods for making oil and water repellent textiles are disclosed, for example, in WO 97/13024 and British patent No.1,102,903 or in the Handbook of Fibre Science and Technology, M.Lewin et al (Marcel and Dekker Inc., New York, (1984) Vol.2, part B, Chapter).

Plasma deposition techniques have been used quite widely to deposit polymeric coatings on various surfaces. This technique is considered to be a clean dry technique generating little waste, compared with the conventional wet chemical method. In the case of this method, plasma is generated from organic molecules to which an electric field is applied. When plasma is generated in the presence of a substrate, the radicals and molecules of the compounds in the plasma polymerize in the gas phase and react with the growing polymer film on the substrate. Conventional polymer synthesis tends to produce structures containing repeat units that are very similar to the monomer species, whereas polymer networks produced using plasma can be very complex.

WO 98/58117 describes the use of monomeric unsaturated organic compounds, in particular unsaturated halogenated hydrocarbons, which polymerize on the surface using plasma deposition techniques to form an oil-or water-repellent coating on the surface. The method forms good oil-proof and water-proof coating and uses 470cm³The small-sized device of (2) will be explained.

For most industrial applications, larger production plants are required. However, initial experiments have shown that repeating the conditions used in a small device in a large plasma chamber does not produce satisfactory results.

According to the present invention there is provided a method of depositing a polymeric material on a substrate, the method comprising introducing a gaseous monomeric material into a plasma deposition chamber, initiating a glow discharge in the plasma deposition chamber and operating at 0.001w/m³～500w/m³For a time sufficient to apply a voltage as a pulsed field to form a polymer layer on the surface of the substrate.

The expression "gaseous" as used herein means a gas or a vapour, either alone or in admixture, as well as an aerosol.

These conditions are particularly suitable for depositing good quality oil and water repellent surfaces of uniform thickness in large plasma chambers, for example, in which the volume of the plasma zone is greater than 500cm³Plasma chamber of, for example, greater than or equal to 0.5m³E.g. 0.5m³～10m³And suitably about 1m³. Thus, the device is provided withThe resulting layer has good mechanical strength and remains substantially intact through conventional washing processes.

The power levels, and in particular the power densities, which provide the best results are lower than the values conventionally used in this type of process. This is quite unexpected. In particular, the applied power is 0.001w/m³～100w/m³Suitably 0.01w/m³～10w/m³。

The size of the plasma chamber is selected to accommodate the particular substrate to be treated, but is typically of a reasonably large size to accommodate a plasma region having the above-mentioned volume. For example, a generally cuboidal plasma chamber may be suitable for various purposes, but if desired, an elongate or rectangular plasma chamber may also be constructed, for example in the case of substrates which typically have a profile such as wood, a roll of fabric or the like. The web can be processed using a "roll to roll" arrangement.

The plasma chamber may be a sealable container so as to be usable for a batch process, or may include an inlet and an outlet for the substrate so as to be usable for a continuous process. In particular in the latter case, the pressure conditions necessary to generate a plasma discharge in the plasma chamber are maintained with a high-volume pump, as is common in devices with a "whistling exhaust", for example.

In particular, the monomer material is a material as described in WO 98/58117. In particular, the material comprises an organic compound having a chain of carbon atoms, preferably at least a portion of the carbon atoms having halogen substituents.

In particular, the compounds are unsaturated and thus contain at least one double or triple bond that can react to form a polymeric compound. The compound preferably contains at least one double bond.

By "chain" is meant that the carbon atoms form a straight or branched chain. Suitably, the chain is not cyclic. The compounds used in the process of the invention comprise at least one such chain. Suitable chains have 3 to 20 carbon atoms, more suitably 6 to 12 carbon atoms.

The monomer compounds used in the process may contain double or triple bonds in the chain and thus may comprise alkenes or alkynes, respectively. Alternatively, the compound may comprise an alkyl chain, which may have a halogen substituent, as a substituent attached to the unsaturated moiety, either directly or through a functional group such as an ester group or a sulfonamide group.

The term "halo" or "halogen" as used herein refers to fluoro, chloro, bromo and iodo. Particularly preferred halo groups are fluoro groups. The term "aryl" refers to aromatic cyclic groups such as phenyl and naphthyl, particularly phenyl. The term "alkyl" refers to a straight or branched chain of carbon atoms, suitably up to 20 carbon atoms in length. The term "alkenyl" refers to a straight or branched unsaturated chain suitably having 2 to 20 carbon atoms.

Monomeric compounds whose chain contains unsaturated alkyl or alkenyl groups are suitable for the production of water-repellent coatings. The coating may also provide oil repellency by substituting at least some of the hydrogen atoms in these chains with at least some halogen atoms.

Thus in a preferred aspect, the monomer compound comprises a haloalkyl moiety or comprises a haloalkenyl group. Thus, the plasma used in the process of the present invention will preferably comprise monomeric organic compounds containing unsaturated haloalkyl groups.

Examples of monomeric organic compounds used in the process of the invention are compounds of the formula (I)

Wherein R is¹、R²And R³Independently selected from hydrogen, alkyl, haloalkyl or aryl which may have a halogen substituent; and R¹、R²Or R³At least one of (A) is hydrogen, R⁴Is a group X-R⁵Wherein R is⁵Is alkyl or haloalkyl, X is a bond; formula-C (O) O (CH)₂)_nA Y-group, wherein n is an integer of 1 to 10, Y is a bond or a sulfamoyl group; or a group- (O)_pR⁶(O)_q(CH₂)_t-, wherein R⁶Is an aryl group which may have a halogen substituent, p is 0 or 1, q is 0 or 1, t is 0 or an integer of 1 to 10, and if q is 1, t is a number other than 0.

For R¹、R²、R³And R⁵Suitable haloalkyl groups are fluoroalkyl groups. The alkyl chain is a straight or branched chain and may contain cyclic moieties.

For R⁵The alkyl chain suitably contains greater than or equal to 2 carbon atoms, suitably 2 to 20 carbon atoms and preferably 6 to 12 carbon atoms.

For R¹、R²And R³The alkyl chain preferably has 1 to 6 carbon atoms.

R⁵Preferably a haloalkyl group, more preferably a perhaloalkyl group, particularly preferably of formula C_mF_2m+1Wherein m is an integer greater than or equal to 1, suitably 1 to 20, preferably 6 to 12, such as 8 or 10.

For R¹、R²And R³Suitable alkyl groups have 1 to 6 carbon atoms.

However, it is preferred that R¹、R²And R³At least one of (A) is hydrogen and preferably R¹、R²、R³Are all hydrogen.

Wherein X is a group-C (O) O (CH)₂)_nY-, and n are integers providing suitable spacers. In particular, n is 1 to 5, preferably about 2.

For Y, suitable sulfamoyl groups include those of the formula-N (R)⁷)SO₂A group of (a) wherein R⁷Is hydrogen or is, for example, C_1-4Alkyl groups such as alkyl, particularly methyl or ethyl.

In one embodiment, the compound of formula (I) is a compound of formula (II)

CH₂＝CH-R⁵ (II)

Wherein R is⁵As described above in connection with formula (I).

In the compound of formula (II), X in formula (I) is a bond.

In a preferred embodiment, however, the compound of the formula (I) is an acrylate of the formula (III)

CH₂＝CR⁷C(O)O(CH₂)_nR⁵ (III)

Wherein n and R⁵R is as described above in connection with formula (I)⁷Is hydrogen, C_1-10Alkyl or C_1-10A haloalkyl group. In particular, R⁷Is hydrogen or C, such as methyl_1-6An alkyl group. Specific examples of compounds of formula (III) are compounds of formula (IV)

Wherein R is⁷As mentioned above, and is in particular hydrogen and x is an integer from 1 to 9, for example from 4 to 9, preferably 7. In this case, the compound of formula (IV) is 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate.

When these compounds are used in the process of the invention, coatings with good hydrophobic and oleophobic values can be obtained. These properties can be tested by using a "3M test method" such as 3M oil resistance test I (3M test method, 10/1/1988) and water resistance test (3M water resistance test II, water/ethanol drip test, 3M test 1, 3M test method, 10/1/1998). These tests were designed to detect fluorochemical coatings on all types of fabrics by determining the following properties:

(a) the water stain resistance was determined using a mixture of water and isopropanol.

(b) The resistance to wetting of the fabric was determined by selecting a series of hydrocarbon liquids having different surface tensions.

Since other factors such as fabric structure, fiber type, dyes, other modifiers also affect stain resistance, the intent of these tests is not to provide an absolute amount of fabric resistance to staining by aqueous or oily materials. However, these tests can be used to compare various coatings. The water repellency test involves dropping 3 standard test drops of water and isopropyl alcohol in a specific ratio (volume ratio) onto a plasma polymerized surface, which can be considered to repel 3 drops of liquid if 2 of the 3 drops do not wet the fabric after 10 seconds. In view of this, the grade of the water repellency is defined as the grade at which the test liquid having the highest proportion of isopropyl alcohol among the test liquids passing the test is located. In the case of the oil repellency test, 3 drops of hydrocarbon liquid were placed on the coated surface. The test is passed if no penetration or wetting of the fabric occurs at the liquid-fabric interface after 30 seconds and no significant wicking occurs around 2 of the 3 drops.

The oil repellency rating is defined as the highest rating of the test liquid that does not wet the fabric surface (where an increase in rating corresponds to a decrease in hydrocarbon chain length and a decrease in surface tension).

The results obtained using these tests vary depending on the nature of the substrate, in particular the roughness of the substrate, but, by mass production, certain products obtained with the process of the invention achieve hydrophobic values of up to 10 and oleophobic values of up to 8. In fact, some coated materials show repellency to heptane and pentane, which represents the degree to which the oleophobicity deviates from the conventional 3M rating.

Other compounds of formula (I) are styrene derivatives known in the polymerization art.

Plasmas suitable for use in the method of the invention include non-equilibrium plasmas such as those generated by Radio Frequency (RF), microwave or Direct Current (DC). They may be operated at atmospheric or subatmospheric pressure, as is known in the art. In particular, however, they are generated by Radio Frequency (RF).

The gas supplied to the plasma chamber may comprise only the vapour of the monomer compound, but is preferably combined with a carrier gas, in particular an inert gas such as helium or argon. In particular, helium is a preferred carrier gas because it minimizes monomer fragmentation.

The ratio of monomer gas to carrier gas is suitably from 100: 1 to 1: 100, for example from 10: 1 to 1: 100, especially from about 1: 1 to 1: 10, for example about 1: 5. This helps to achieve the high flow rates required by the process of the present invention. The gas or gas mixture is suitably supplied at a rate of at least 1 standard cubic centimeter per minute (sccm) and preferably from 1sccm to 100 sccm.

The gas is suitably pumped into the chamber by lowering the pressure in the chamber by means of a pump, or the gas may be pumped into the chamber.

The polymerization is suitably carried out using a vapour of the compound of formula (I) in a process chamber maintained at a pressure of from 0.01mbar to 300mbar, suitably from about 80mbar to 100 mbar.

A glow discharge is then ignited by applying a high-frequency voltage, for example a high-frequency voltage of 13.56 MHz. The voltage is suitably applied to the process chamber from the inside or outside using electrodes, but in the case of a large process chamber it is preferable to apply the voltage from the inside.

The applied electric field is suitably a pulsed field of power of up to 500W, suitably about 40W. The sequence used for the applied pulses results in a very low average power, e.g. the on-time in the sequence: the ratio of the off-time is 1: 500 to 1: 1000. A specific example of the sequence is one in which the power is turned on for 20. mu.s and the power is turned off for 1000. mu.s to 20000. mu.s. A typical average power thus obtained is 0.04W.

The electric field is suitably applied for 30 seconds to 90 minutes, preferably 5 minutes to 60 minutes, depending on the nature of the compound of formula (I) and the matrix, etc.

Even when manufactured on a large scale, it has been found that plasma polymerisation of the compounds of formula (I), particularly at much lower average powers than previously used, produces deposition of highly fluorinated coatings exhibiting high levels of hydrophobicity and oleophobicity. In addition, a high degree of structure retention of the compounds of the formula (I) occurs in the coating, which is attributable to the direct polymerization of olefin monomers, such as fluoroolefin monomers, via their highly reactive double bonds.

It should be noted that, particularly in the case of the polymerization of the compounds of formula (III) above, low power pulsed plasma polymerization produces well-adhered coatings that exhibit excellent water and oil repellency. In addition, the coating has a good uniform thickness.

The higher degree of structure retention can be attributed to free radical polymerization occurring at off and less cleavage at on in the duty cycle.

The gas is suitably supplied to the plasma chamber along a temperature gradient. For example, gas is pumped into the plasma chamber along a heated tube that leads from a gas source. Depending on the nature of the monomer used, it may be appropriate to heat the tube so that the temperature of the gas entering the chamber is between 30 ℃ and 60 ℃. In particular, the temperature of the gas entering the chamber is higher than the temperature of the gas leaving the gas source, preferably about 10 ℃. Furthermore, the gas source is suitably maintained at room temperature, or at a slightly elevated temperature, such as 30 ℃, depending on the nature of the monomers involved.

By thus heating the supply tube and plasma chamber, the inventors have found that monomer vapour can be efficiently delivered into the plasma chamber and once inside the plasma chamber, flow can be maintained. This results in efficient deposition and polymerization of the monomer and minimizes any gas condensation that may occur at the "cold spot" of the piping system. Although heating of the plasma chamber has been used in the past in plasma etching processes to maintain the flow of the etch products so that they can be exhausted from the chamber, this method is not necessary in the present invention and heating is not expected to be preferred.

The novel apparatus used in the above method constitutes a further aspect of the invention. In particular, the apparatus comprises a plasma deposition chamber, a pumping system arranged to supply gaseous monomer into the plasma deposition chamber, at least two electrodes arranged to ignite a plasma in the plasma deposition chamber and programmed to pulse the power supply to the electrodes to 0.001w/m within the plasma region in the plasma deposition chamber³～500w/m³A power control unit for generating plasma.

The pump system is suitably a system as described below: the system is capable of supplying large quantities of vapor into a plasma chamber and ensuring that it remains in the chamber for a minimum residence time sufficient to achieve the desired effect. It may include a series of pumps and large conduits. The pumping system may also be arranged to pump gas from the plasma chamber to evacuate air and/or reduce pressure, as required.

In one embodiment, the pump system comprises two pumps. A first pump or roots pump (suitably a high capacity pump) is arranged to draw any vapour, including water vapour or other contaminants, from the plasma chamber. To accomplish this efficiently in a reasonable time frame, it is convenient to arrange the pump in the vicinity of the plasma chamber, taking into account the size of the chamber, and to communicate with the chamber via a single straight pipe having as large a diameter as possible. A valve is provided in the tube to enable the chamber to be sealed once the plasma chamber is evacuated.

The second pump is suitably a small capacity pump such as a dry rotary pump. The pump is suitably in communication with the plasma chamber via the same opening as the first pump. The pump is arranged to draw the monomer, together with any carrier gas, into the plasma chamber at a suitable rate and to maintain the desired pressure and residence time of the gas in the chamber.

The pump unit suitably has an opening to the furnace, so that any residual monomer or debris is incinerated in the furnace and the gas is then safely vented to the atmosphere.

The apparatus preferably further comprises a heating unit for the plasma chamber. They may be integral with the chamber walls or present in a housing surrounding the chamber. They may comprise electrical components or components containing recirculated heating oil, suitably under the control of a temperature controller to ensure that the desired temperature is maintained in the chamber.

The apparatus also preferably includes a container for the monomer which communicates with the plasma chamber by means of a suitable tube and valve arrangement. The vessel preferably has a heater which can heat the monomer above room temperature and then introduce the monomer into the chamber, if desired. The vessel, the pipe leading out of the vessel to the plasma chamber and the plasma chamber itself are preferably heated, and the heating unit is arranged to produce a temperature gradient which increases progressively along the monomer path.

If desired, a supply of carrier gas may be in communication with the container and, if desired, gas from the supply may be admitted into the container to produce a gas flow into the plasma chamber sufficient to achieve the desired result.

In use, in a batch process, the article to be coated may be placed in a plasma chamber. In one embodiment, they are pre-made garments that require coating with a water and/or oil repellent coating. By depositing the polymer on the finished garment, rather than on the fabric used in production, an otherwise uncoated area of "all over" coating can be achieved, including at seams such as zippers, fasteners or stitching.

The chamber is then evacuated, for example using the entire pump set (but particularly a large roots pump disposed therein). Once the chamber is evacuated, suitably heated monomer vapour can be admitted into the chamber from the container. This may be achieved, for example, by using a second pump to draw it from a container containing a source of liquid monomer. The vessel is suitably heated to a temperature sufficient to cause vaporisation of the monomer.

It is also preferred that the pipes and conduits leading from the container to the chamber are also heatable. This means that it is ensured that monomer is not lost via condensation in the feed pipe.

If desired, a carrier gas (which may be an inert gas such as argon or helium, and preferably helium) is passed into the chamber to provide a gas flow sufficient to achieve the desired concentration and volume uniformity of the monomer in the chamber.

Alternatively, the monomer vapor may be withdrawn from the vessel and then mixed with the carrier gas. Preferably, the monomer vapor is passed through a liquid/vapor flow controller prior to mixing. This arrangement allows for better controllable mixing to achieve the desired ratio of carrier gas to monomer. In addition, the environment of the monomer, particularly the temperature, will be controlled regardless of the flow requirements. Further, the reactive monomer may be suitably stored in the container under an inert atmosphere such as a nitrogen atmosphere. The vessel may be suitably pressurized to bring the nitrogen gas above atmospheric pressure to assist in the flow of monomer vapour from the vessel into the lower pressure plasma chamber.

A glow discharge is then ignited in the chamber, for example by applying a high frequency voltage such as 13.56 MHz. The power supply is then pulsed as described above to produce a very low average power. As a result, the monomer is activated and adheres to the surface of the substrate, forming a polymer layer thereon. At the low powers used in the process of the present invention, the unsaturated monomers form a uniform layer with high structural integrity. The effect depends on the nature of the monomers used, but the specific examples provided above may give excellent hydrophobicity and/or oleophobicity.

The invention will now be described in more detail by way of example with reference to the accompanying schematic drawings in which:

FIG. 1 illustrates a monomer supply system that can be used in embodiments of the present invention;

FIG. 2 illustrates a pump system that can be used in embodiments of the present invention; and

FIG. 3 illustrates an alternative apparatus that can be used in embodiments of the present invention.

The apparatus depicted in fig. 1 shows a processing system comprising a plasma chamber 1. A heating element containing recirculated heating oil is integrated with the outer wall of the plasma chamber 1. The temperature in the chamber may be measured by a thermocouple (not shown) and this information is provided to the heater controller to maintain the desired temperature in the plasma chamber 1. Also in the plasma chamber, a pair of opposed electrodes are provided with about 1m formed therebetween³The plasma region of (a). The electrodes are connected to a suitable power source that is controllable and programmable.

A monomer delivery tube 3 incorporating a valve 5 is inserted into the plasma chamber 1. At one end of the tube 3 a sealable chamber 7 for the monomer is provided. In the chamber 7 is arranged a support 9 on which an open container 11 for the monomers 13 is placed. The chamber 7 is equipped with a controllable heater, for example a band heater 15, extending around the chamber 7.

In addition, an inert gas source 17 such as argon or helium is communicated with the chamber 7 through a pipe 19, and a valve 21 and a manual valve 23 are provided in the pipe 19 together with a mass flow controller 25. The gas source is controllable and can be observed with a display 27.

The plasma chamber 1 is equipped with a pumping system as illustrated in figure 2. The pump system comprises a combination of a roots pump and a rotary pump arranged to evacuate the plasma chamber. The roots pump 29 communicates with the plasma chamber through a tube 31 which is preferably straight and has as large a diameter as possible. The diameter of the tube in this case is 160 mm. By ensuring that there is no bend in tube 31, heat conduction losses can be minimized. An isolation valve 33 is provided in the pipe 31 to isolate the pump 29 from the plasma chamber.

A low capacity rotary pump 35 is also provided, the rotary pump 35 being communicable with the pipe 31 on the downstream side of the valve 33 through a smaller pipe 37 of, for example, 63mm diameter, the pipe 37 being provided with an Automatic Pressure Control (APC) valve 39 and an isolation valve 41. A flexible bypass tube 43, also fitted with a valve 45, communicates the roots pump 29 directly with the rotary pump 35.

Finally, a furnace 47 is provided downstream of the rotary pump 35 to enable incineration of any gases discharged from the system.

The illustrated combination of roots and rotary pumps provides a total of about 350m³The pump speed per hour enables rapid evacuation of the plasma chamber.

An alternative arrangement is illustrated in figure 3. In this figure, the electrode 2 is shown in the chamber 1. The electrode is electrically connected to the RF generator 4 through an RF matching unit 6. The RF generator 4 is controlled by a function generator 8 set to generate pulses in the RF field. The RF matching unit ensures that the pulse modulation in the chamber 1 coincides with the pulse modulation generated in the generator 4.

In this case the pump system is slightly different, with the difference that the roots pump 29 and the rotary pump 35 communicate with each other through a separate 3-way treatment/roughing selector valve 40, the 3-way treatment/roughing selector valve 40 replacing the valves 41 and 45 of the embodiment of fig. 2. A pipe 37 including a process pressure control valve 39 is also in communication with the valve. As a result, the roots pump in combination with the rotary pump may draw gases from the process chamber 1 and discharge them into the furnace 47 in a manner generally similar to that described above with respect to fig. 1 and 2. For rapid withdrawal of gas from the chamber this can be done by opening valves 33 and 40 and operating pump 29 and, if necessary, pump 35. However, the roots pump 29 may be isolated from the system by: the valve 33 and the regulating valve 40 are closed and the more controllable gas flow through the chamber is caused by the use of the pump 35, wherein the pump 35 is able to draw gas out through the pipe 37 when the valve 39 is opened.

Also in this apparatus, the monomer feed apparatus is also modified to make it more controllable. Specifically, a separate monomer treatment unit 10 is provided. It includes a monomer reservoir 12 in which monomer can be stored under controlled environmental conditions in the monomer reservoir 12. For example, the monomer may be kept in the dark under an atmosphere of an inert gas such as nitrogen supplied from a suitable gas source 14. These conditions minimize the chance of premature polymerization of the monomers.

The monomer can be supplied from the storage tank 12 outwards through a pipe 16 leading downwards from the monomer container 11 (not shown in this case). The flow is assisted by maintaining the pressure of the inert gas in the tank at a pressure slightly above atmospheric pressure to create a pressure differential. A nitrogen purge valve 32 is also provided in the system.

The tube 16 suitably carries the monomer into a liquid/vapor flow controller 18 included in a temperature controlled gas unit 20. The temperature within the controller 18 is monitored and controlled to ensure that any condensed monomer is volatilised and that vapour of the required concentration leaves the controller via valve 22 into gas injection unit 24.

In this unit, the monomer vapor is mixed with a desired amount of carrier gas, such as helium, from a suitable source 17 and passed through a helium mass flow controller 26 into an injector unit 24. Valves 28 and 30 may be used to isolate helium source 17 if desired. The temperature of the controller 26 may be independently controlled to supply gas to the injection unit 24 at a pressure suitable to achieve the desired mixture. The mixture produced in the injection unit 24 is fed into the chamber 1 via the pipe 3, wherein the pipe 3 can be closed by the valve 5 in a similar manner as described above in relation to the part of fig. 1.

Example 1

A pillow case is suspended between the electrodes in the plasma chamber (and hence within the plasma region) of the apparatus of figures 1 and 2. In addition, sample 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate (10g) was placed in container 11 in monomer chamber 7. Valves 5, 21, 23 and 33 are closed at this time.

The plasma chamber is then rapidly (within 5 minutes) evacuated to a pressure of 2 x 10 by opening valves 33 and 45 and operating pumps 29 and 35 to draw air from the plasma chamber^-3Bar. The rotary pump 35 is then isolated from the system by closing valves 33 and 45.

The plasma chamber is then heated by a heater in the chamber wall of the process chamber 1 and maintained at a temperature of 40 c to 50 c, particularly 50 c.

Similarly, the belt heater 15 was operated to heat the monomer chamber 7 to a temperature of 45 ℃ and maintain the temperature.

Valves 39 and 41 are then opened, as are valves 21 and 23, and helium gas from source 17 is drawn into chamber 7 by operating rotary pump 35 at a rate of 60 sccm. Helium gas acts as a carrier to carry the monomer vapor into the plasma chamber as it passes through the monomer.

After 2 minutes (during which time any residual air has been purged from the system), the desired pressure is reached in the plasma chamber and an RF plasma is ignited between the electrodes. The power supply is pulsed so that it is switched on for 20 mus and off for 20000 mus.

The gas withdrawn from the plasma chamber was discharged through the pipe 37 and the pump 35, and sent into the furnace 47 maintained at 300 ℃.

After 30 minutes, valves 39 and 41 were closed to isolate pump 35 and the system was vented with dry nitrogen. The pillow case was removed and tested for oil repellency and water repellency using the 3M oil repellency test I (3M test, 1/10 1988) and water repellency tests (3M Water repellency test II, Water/ethanol drip test, 1/3M test, 1/10 1998). The result of the water repellency value was 10 and the result of the oil repellency value was 8 even after washing with a conventional washing machine.

In contrast, pillow cases treated under similar conditions but with 200 watts of RF power applied continuously at 13.56MHz produced coatings that were prone to abrasion.

Claims (21)

1. A method of depositing a polymeric material on a substrate, the method comprising introducing a gaseous monomeric material into a plasma deposition chamber, initiating a glow discharge in the plasma deposition chamber and operating at a rate of 0.001w/m³～500w/m³For a time sufficient to apply a voltage as a pulsed field to form a polymer layer on the surface of the substrate.

2. The method of claim 1, wherein a volume of a plasma region in the plasma deposition chamberProduct of 0.5m or more³。

3. A method as claimed in claim 1 or 2, wherein the power applied is 0.001w/m³～100w/m³。

4. A method as claimed in claim 3, wherein the power applied is 0.04w/m³～100w/m³。

5. A method according to any preceding claim, wherein the monomeric material is an unsaturated organic compound comprising a chain of carbon atoms with or without halogen substituents.

6. The method of claim 5, wherein the monomeric material is a compound of formula (I):

wherein R is¹、R²And R³Independently selected from hydrogen, alkyl, haloalkyl or aryl with or without halogen substituents; and R¹、R²Or R³At least one of (A) is hydrogen, R⁴Is a group X-R⁵Wherein R is⁵Is alkyl or haloalkyl, X is a bond; formula-C (O) O (CH)₂)_nA Y-group, wherein n is an integer of 1 to 10, Y is a bond or a sulfamoyl group; or a group- (O)_pR⁶(O)_q(CH₂)_t-, wherein R⁶Is an aryl group having a halogen substituent or having no halogen substituent, p is 0 or 1, q is 0 or 1, t is 0 or an integer of 1 to 10, and if q is 1, t is a number other than 0.

7. The method of claim 6, wherein the compound of formula (I) is an acrylate of formula (III):

CH₂＝CR⁷C(O)O(CH₂)_nR⁵ (III)

wherein n and R⁵As defined in claim 6, R⁷Is hydrogen or C_1-6An alkyl group.

8. The method of claim 7, wherein the acrylate of formula (III) is 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate.

9. A method according to any preceding claim, wherein the gaseous monomer compound is supplied into the plasma deposition chamber with a carrier gas.

10. The method of claim 9, wherein the carrier gas is helium.

11. The method of any preceding claim, wherein gaseous material is supplied into the plasma deposition chamber at a rate of at least 1 standard cubic centimeter per minute (sccm).

12. A method according to any preceding claim, wherein the vapour of the compound of formula (I) in the plasma deposition chamber is maintained at a pressure of from 0.01mbar to 300 mbar.

13. A method according to any preceding claim, wherein the power supply is pulsed in the following sequence: in this sequence, the power is turned on for 20. mu.s and turned off for 1000. mu.s to 20000. mu.s.

14. The method of any preceding claim, wherein gas is supplied into the plasma deposition chamber along a temperature gradient.

15. A method according to any preceding claim, wherein the plasma deposition chamber is heated during the deposition process.

16. Apparatus for depositing a polymeric material on a substrate, the apparatus comprising: a plasma deposition chamber, at least two electrodes arranged to ignite a plasma in the plasma deposition chamber, a pump system arranged to supply a monomer gas into the plasma deposition chamber and programmed to pulse the power supplied to the electrodes to 0.001w/m within a plasma region in the plasma deposition chamber³～500w/m³A power control unit for generating plasma.

17. The apparatus of claim 167, further comprising a heating unit for the plasma deposition chamber.

18. The apparatus of claim 16 or 17, further comprising a container for monomer in communication with the plasma deposition chamber.

19. The apparatus of claim 18, wherein the heating unit is arranged to create a gradually increasing temperature gradient between the vessel and the plasma deposition chamber.

20. Apparatus according to claim 16, substantially as hereinbefore described with reference to the accompanying drawings.

21. A method of depositing a polymeric material on a substrate, the method being substantially as hereinbefore described with reference to the examples.