RU2154363C2 - Sheet material, process of improvement of characteristics of surface of sheet material, process of generation of plasma of glow discharge and device to initiate plasma of glow discharge - Google Patents

Abstract

FIELD: machining of surface of sheet materials. SUBSTANCE: invention refers to organic and inorganic polymer sheet material, specifically, to film, woven or unwoven fiber and deals with method of improvement of characteristics of surface of such material, with process of generation of plasma of glow discharge for modification of surface properties of organic and inorganic polymer material and with device for initiation of plasma of glow discharge. In correspondence with invention sheet material produced by blast from melt is treated in the course of preset time interval under atmospheric pressure with plasma of glow discharge generated by high- frequency amplifier generating voltage of root-mean-square values from 1.0 to 5.0 kV on frequency from 1.0 to 100.0 kHz. Device to initiate plasma of glow discharge has pair of laminated electrically insulated electrodes supplied from high-frequency amplifier. Space between electrodes is filled with air, nitrogen oxide or inert gas. Electrodes are charged from network of impedance matching whose adjustment makes it possible to generate most stable, homogeneous glow discharge. EFFECT: improved wettability of polymer sheet materials produced by blast from melt without formation of by-products. 25 cl, 13 dwg, 6 tbl

Description

 The invention relates to an organic and inorganic polymer sheet material, in particular to a film, woven or non-woven fiber, a method for improving the surface characteristics of such a material, a method for generating glow discharge plasma for modifying the surface properties of organic and inorganic polymeric materials, and a device for initiating a glow discharge plasma .

 One of the many options for using melt blown polymer sheet materials is their use as separator plates of batteries from liquid cells. The polymer compound itself is impervious to electrolyte. However, the nonwoven fibrous structure made by the melt blasting method, if its surface is sufficiently wetted by the electrolyte, is ion permeable. Unfortunately, most existing polymers such as polyamide, polypropylene, polyethylene and poly (ethylene terephthalate) do not have the necessary ability to wet.

 When using melt blown polymer sheet materials as separator plates of batteries, their wettability is currently achieved chemically using surfactants. At the same time, industrial waste representing a certain hazard is generated, and the product itself has a limited service life.

 Wettability is also a desirable property for fabrics and woven materials used to wipe or clean the body, for surgical sponges, dressings, feminine hygiene products, and reusable knitted fabrics. In addition, wettability is one of the important surface properties of materials used for printing and laminating.

 SU 1039438 A describes a sheet material of this kind obtained by melt blasting and having a surface having improved wettability and improved rewet ability.

 Recently, certain successes have been achieved in this area related to the processing of polymer sheet materials by glow discharge plasma. Usually the word "plasma" refers to a partially ionized gas consisting of ions, electrons and neutral particles. This state of matter can be obtained under the influence of either very high temperatures, or a strong direct current, or electric fields of high frequency. High-temperature or “hot” plasmas are represented by light-emitting celestial bodies, atomic explosions, and electric discharges. Glow discharge plasmas are formed by free electrons, which are excited by a direct current or high frequency electric field and then collide with neutral molecules. When electrons collide with neutral molecules, energy is transferred to the molecules and the formation of various active particles, which include protons, metastable particles, individual atoms, free radicals, molecular fragments, monomers, electrons and ions. These particles are chemically active and / or are able to physically modify the surface, and with their help it is possible to obtain chemical compounds with new surface properties or modify the properties of existing compounds accordingly.

 Low-power plasmas, known as non-luminous corona discharges, are widely used for surface treatment of thermosensitive materials such as paper, cotton wool and synthetic polymers such as polyethylene, polypropylene, polyolefin, polyamide and poly (ethylene terephthalate). Due to the relatively low energy content of the corona discharge plasma, they can change the surface properties of the material without damaging it.

 Glow discharge plasmas are another type of plasma with a relatively low specific power used for non-destructive modification of the surface of a material. Using such glow discharge plasmas, useful amounts of visible ultraviolet radiation can be obtained. An additional advantage of glow discharge plasmas is, therefore, the possibility of obtaining visible and ultraviolet radiation simultaneously in the presence of active particles. However, until now, glow discharge plasmas were usually generated under conditions of low rarefaction or partial vacuum at pressures below 10 torr, which determined the periodic nature of the process and required the use of an expensive vacuum system. In some polymer samples processed at low pressure by glow discharge plasmas, an improvement was found in the characteristics associated with their surface wettability. However, the chemical and physical mechanisms of this phenomenon are still unsolved and, after drying, the wettability of the surface of these samples decreases to the initial level. The possibility of re-wetting is unrealistic.

 One such process for treating the surface of a sheet of polymer material is disclosed in GB 1128595 A, when an improvement in the surface characteristics of a polymer sheet material is obtained by treating it with a glow discharge plasma generated in a gas volume located between two spaced electrodes by generating a uniform glow discharge plasma with active particles between said electrodes.

 The generation of low power density plasmas at atmospheric pressure is not new. Filamentous discharges between parallel plates in air at atmospheric pressure have been used in Europe since the end of the 19th century for the production of ozone in large quantities for the treatment of water used for public purposes. Such filamentary discharges, successfully used to produce ozone, cannot, however, be successfully used for surface treatment of materials, since plasma cords pierce or unevenly change the properties of the surface being treated.

 The objective of the present invention, taking into account all of the above, is to offer a process that does not create by-products to increase the wettability of melt blown polymer sheet materials and other types of polymer substrates.

 Another objective of the invention is to develop a process for generating glow discharge plasma for processing a polymer sheet material or film, which allows to obtain a product having stable properties and the ability to rewet.

 Another objective of the invention is to develop a method and apparatus for the continuous processing of polymer sheet material or film of unlimited length by a glow discharge plasma at atmospheric pressure and normal temperature.

 The objective of the invention is also the selection of the type and operating parameters of the glow discharge plasma for processing materials at pressures of about one atmosphere or slightly higher.

 All these tasks can be achieved using the technical equipment proposed below.

 The sheet material made by melt blasting and having a surface having improved wettability and improved ability to rewet, is obtained according to the invention by treating it for a predetermined period of time at atmospheric pressure with a glow discharge plasma generated by a high frequency amplifier emitting a voltage with a rms value of rms from 1 up to 5 kV at a frequency of 1 to 100 kHz.

 In one case, the plasma is initiated in an inert gas. In another case, the gas is helium, argon, air, or a mixture of these two gases.

 In a preferred embodiment, the sheet material is a polymeric material that is polypropylene.

 In this case, the processing of sheet material is carried out at a frequency in the range from 1 to 30 kHz.

 The proposed method for improving the surface characteristics of a polymer sheet material consists in treating the sheet material with a glow discharge plasma generated in a gas volume located between two spaced electrodes by generating a uniform glow discharge plasma with active particles located between said electrodes. According to the invention, a voltage with a rms value of 1 to 5 kV at a frequency of 1 to 100 kHz is applied to these electrodes from a high-frequency amplifier, and the sheet material is placed in the gap between the electrodes inside the plasma for a certain time under pressure differential conditions, through which the sheet material pass active particles.

 When implementing the method, an inert gas (helium, argon) or air, or a mixture of the two listed gases, is used.

 Obtained by the proposed method, the sheet material is a melt blown polymer sheet material.

 The method according to the invention is carried out at a frequency in the range from 1 to 30 kHz.

 In the process of the invention, a sheet material of unlimited length is used and stretched between the electrodes at a constant speed, subjecting it to plasma treatment for a predetermined time.

 A method for generating a glow discharge plasma in a volume between two electrodes supplied from a high-frequency amplifier with an impedance matching circuit is also proposed. According to the invention, voltage with a rms value from 1 to 5 kV at a frequency of from 1 to 100 kHz is applied to the electrodes from the amplifier and the volume between the electrodes is filled with gas at a pressure of 1 atmosphere, in which a glow discharge plasma can be initiated, while in the volume between the electrodes a homogeneous glow discharge plasma is initiated and maintained at a pressure of 1 atmosphere by creating a high-frequency electric field of such a frequency that, on the one hand, is large enough to hold the field of viable plasma ions between the electrodes, and, on the other hand, is insufficient to ensure that plasma electrons are also kept between the electrodes during the half-cycle of high-frequency voltage.

 In a preferred embodiment of the method, the electrodes are placed inside a gas-tight casing, into which a certain amount of gas of the above composition is continuously supplied, the distance between the electrodes being 5 cm or less, and at least the position of one of the electrodes is adjusted relative to the position of the other.

 It is also preferable that the frequency amplifier operates in the range from 1 to 100 kHz with a rms voltage value from 1 to 5 kV.

 The method is implemented using a device for initiating a glow discharge plasma containing a pair of electrically isolated electrodes powered by a high-frequency amplifier with an impedance matching circuit.

 According to the invention, this device generates a voltage with a rms value from 1 to 5 kV at a frequency of from 1 to 100 kHz, the electrodes to which the plates are shaped are arranged in parallel and fastened equidistantly opposite each other so that a volume is formed between them, which at pressure into 1 atmosphere is filled with gas, in which a glow discharge plasma can be initiated, while a device is provided for initiating and maintaining a uniform glow discharge plasma at a pressure of 1 atmosphere by The creation of a high-frequency electric field of such a frequency, which is, on the one hand, large enough to hold positive plasma ions between the electrodes, and on the other hand, insufficient to ensure that plasma electrons are also held between the electrodes during the half-cycle of the high-frequency voltage.

 The provided device for charging gas with the volume between the said plates contains a protective casing, inside of which are located the plates separated from each other by the volume.

 The device proposed for implementing the method also includes a gas supply device, due to the continuous supply of which the pressure inside the casing is maintained at the level of one atmosphere.

 The device also uses gas of the above composition.

 To increase the efficiency of the device, the electrode plates are liquid-cooled, while the tubes of the cooling system are attached to the plates to remove heat from them.

 As a result of the proposed technical means, it was possible to create an improved sheet material, which is preferably a polymer sheet material obtained by blowing from a melt, the surface of which was processed at constant atmospheric pressure by a glow discharge plasma. The above and other objectives of the invention, as already noted, are realized mainly with the help of a device based on a pair of electrically isolated metal plate electrodes, between which, if desired, an intermediate plate or grid can be placed.

 To expand the range of operating frequencies and other parameters providing a homogeneous (as opposed to filamentary) glow discharge, a matching impedance circuit is added to the device for charging electrodes. The parameters of this matching circuit are adjusted to obtain the most stable homogeneous glow discharge. Such conditions are achieved with a minimum reactive power of the plasma reactor.

 A high-frequency power amplifier connected to both electrodes produces at least 180 watts of reactive power and plasma power at rms (rms) operating voltage from 1 to 5 kV (rms) and a frequency of 1 to 100 kHz.

 To initiate the plasma, a standard Tesla electromagnetic coil is used, with which an electric discharge is generated in the gap between the high-frequency current excited by the plate electrodes. The electric field created between the metal plate electrodes must be powerful enough to ensure the breakdown of the gas located in the gap between the electrodes, and if instead of ordinary air this gap is filled with helium or argon, then the electric field power can be significantly reduced. The frequency of the current must be selected accordingly, as described in more detail below, since a discharge is not initiated at a too low frequency, and plasma filamentary discharges form between the plates at a too high frequency. Only at frequencies lying in a relatively narrow range, a uniform plasma mode without filament discharges will be ensured in the gap between the electrodes at atmospheric pressure.

 The initiation and subsequent maintenance of the plasma in the volume filled with atmospheric air, helium or argon between the plate electrodes allows the processing of a material such as a polymer film or sheet to give its surface the required characteristics, such as wettability and the ability to rewet.

The invention is further illustrated by the description of examples with reference to the drawings, in which the same elements have the same designations and which depict:
in FIG. 1 is a diagram of a device according to the invention;
in FIG. 2 is a circuit diagram of a charger with matching impedance circuit for powering the device of FIG. 1;
in FIG. 3, 4 and 5 are various variants of electrical circuits of the output circuit of the charger for the device shown in FIG. 1;
in FIG. 6 is a diagram of another embodiment of the device of the invention;
in FIG. 7 is a schematic representation of the upper chamber of an atmospheric glow plasma reactor with an intermediate mesh plate;
in FIG. 8A-B are graphs of alternating voltage, current, and power for a uniform glow discharge plasma;
in FIG. 9A-B are plots of alternating voltage and power for a filamentous plasma;
in FIG. 10 is a graph in a logarithmic scale of the dependence of the specific total power and plasma power in milliwatts per cubic centimeter (mW / cm ³ ) on the rms value of the voltage across the electrodes;
in FIG. 11 is a graph with a logarithmic scale on both axes of the dependence of the specific total power and plasma power (mW / cm ³ ) on frequency;
in FIG. 12 is a graph of the phase angle between the breakdown current and voltage versus amplifier frequency, corresponding to a specific embodiment of the invention;
in FIG. 13 is a graph of power consumption versus amplifier frequency illustrating a specific embodiment of the invention.

 In the schematic shown in FIG. 1 device, the electrodes 10 are made in the form of copper square plates with dimensions of 21.6 x 21.6 cm. Closed loops 11 are made of silver to the plates of the electrodes 10, made of a copper tube with a diameter of 0.95 cm, on the opposite edges of which are threaded nipples 12 and 13. The edges of the electrode plates are rounded with a radius of curvature equal to the distance from the electrode to the intermediate plate, which eliminates the possibility of electrical breakdown of the interelectrode space at the edges of the electrodes. Not shown in FIG. 1, a cooling system pumps coolant through a tubular loop 11 through inlet and outlet nipples 12 and 13.

 The plate of the electrodes 10 and the tubular loops 11, soldered to each other, are coated on all sides with a high dielectric strength insulating material 14, eliminating the possibility of an electric arc at the edges and on the back sides of the plate electrodes.

 It is preferable in the structure under consideration to provide a mechanism for regulating the distance between the plates of the electrodes 10, which should be up to approximately 5 cm with a parallel arrangement of the plates. Such a mechanism is shown schematically in FIG. 1 and is made in the form of control rods 15 connected to the plates of the electrodes 10. This design makes it possible to place a fixed intermediate plate 30 between the plates of the electrodes 10.

 Usually, parallelism is understood as the relative position of parallel planes, but the same term can be used to characterize the relative position of not plane, but equidistant surfaces. The same term can be used to describe the relative position of cylinders with parallel axes, as well as the relative position of the cylinder and the plane.

 To supply voltage to the plate electrodes 10, a low-impedance high-voltage high-frequency power amplifier 20 is used with independent regulation of voltage and frequency in the range from 1 to 5 kV and from 1 to 100 kHz. Between the high-frequency amplifier 20 and the electrode plates 10, a matching impedance circuit 31 shown in FIG. 2 and described in detail below.

 Lamellar electrodes are located inside the insulating casing 21, which makes it possible to create and control a certain gas atmosphere in a flat volume between the plates of the electrodes 10. Inside the insulating casing, a corresponding gas is supplied through the inlet pipe 22, which can be used as air, helium or argon, a mixture of helium or argon with oxygen or air; or a mixture of helium with argon. In any case, the pressure inside the insulating casing 21 is essentially atmospheric pressure, which eliminates or reduces the need for special seals to seal the casing. Typically, through a pipe 22, an amount of the corresponding gas is supplied into the casing under atmospheric pressure to compensate for its possible leakage from the casing. Since the pressure inside the casing 21 is equal to the external pressure, gas leaks from the casing due to the pressure drop are very small. The ventilation pipe 28 with a control shut-off valve 29 is used to purge the casing when starting the device. During normal operation, the valve 29 may be in the closed position.

 In the insulating casing 21 there are narrow windows 23 for passing sheet material W between the plate electrodes 10, which is wound from the drum 24 and wound onto the drum 25. The drums 24 and 25 have an adjustable drive, with which it is regulated depending on the properties of the processed sheet material the speed of its movement and the duration of the plasma treatment process in the gap between the electrodes.

 In order to expand the operating frequency range and other parameters providing a homogeneous (not filamentary) glow discharge, a matching impedance circuit is connected to the power supply for charging the electrodes 10, one of the variants of which is shown schematically in FIG. 2. The parameters of this circuit are regulated so that the glow discharge between the electrodes is of the most stable homogeneous character. This mode is ensured with a minimum value of the reactive power of the plasma reactor.

In FIG. 3-5 illustrate other advantageous designs of a power amplifier 20. In FIG. 3 shows a circuit in which the lower terminal T _{1 of the} electrode is grounded and the full operating voltage is applied to the upper terminal T ₂ . In FIG. 4 and 5 show electrically equivalent circuits in which half voltage with a phase offset of 180 ^° is applied to terminals T ₁ and T ₂ . In the circuit shown in FIG. 4, the center point of the transformer winding is grounded, and in FIG. 5 shows a semiconductor power circuit.

 In FIG. 6 shows a diagram of a device with two different versions of a device for continuously pumping plasma gas containing active particles through a sheet material. To do this, you can use either a bellows-type device 35 driven by a reciprocating rod 33 or a reciprocating piston mechanism consisting of a piston 36 and a rod 32. A change in the volume of the upper chamber is accompanied by periodic changes in the pressure drop across the sheet material W and the corresponding the flow of plasma gas through it. Alternatively, the cavity behind the piston 36 is connected to the lower chamber of the casing by a line 34, which is shown by dashed lines in FIG. 6.

 As shown in FIG. In the 6th embodiment of the proposed device, there is a grounded mesh 30 on which the sheet material W is moved moving inside the casing from one narrow window 23 to another. Such a grid helps to weaken the electric charge accumulating on the processed material and forms a supporting support structure such as a membrane for moving sheet material, under the action of a pressure differential between the upper chamber into which the gas enters and the lower chamber from which the gas is discharged. Under the influence of such a pressure differential, the sheet material W is internally saturated with gas, which contains active particles formed in the plasma.

 Electric fields in a homogeneous glow-discharge plasma reactor at atmospheric pressure have a low intensity (of the order of several kilovolts per centimeter), and if we talk about direct current, then a relatively small electric field is required for electric breakdown of the gas in the reactor. Gases such as helium and air penetrate under the influence of such weak electric fields, however, if all positive ions remain in the gap between two parallel or equally spaced electrodes, which significantly increases the duration of their existence in the plasma, then the electrons can freely pass to the isolated plate electrodes by recombining or creating a surface charge on them. The most preferable homogeneous atmospheric glow discharge plasma is formed, therefore, at a certain frequency of a high-frequency electric field, on the one hand high enough for trapping ions between the intermediate grid and the plate electrode, and on the other hand, not large enough for trapping electrons in this zone for half a period high frequency voltage. Electrons can be captured by bipolar electrostatic forces.

 If the current frequency is so low that both ions and electrons can reach the boundaries of the air gap and recombine a surface charge on them, then the duration of their existence in the gas will be so short that the plasma either does not initiate at all or is initiated as separate filamentary discharges between electrode plates. The frequency of the electric field should lie in a fairly narrow frequency range, ensuring the oscillatory nature of the movement of ions between the intermediate grid and the plate electrode, so that during the half-period of the oscillations the ions do not have time to reach any of the boundaries of the air gap and can exist for a sufficiently long period of time. For the formation of a homogeneous plasma, it is necessary that more mobile electrons can leave the space occupied by the plasma and reach its boundaries with impact. If the frequency is so high that both electrons and ions are held in the gap between the electrodes, then a filamentary plasma will be generated as a result of the discharge.

Not limited to the framework of any particular theory, the authors established a definite relationship between the distance between the electrodes and the rms value of the voltage across the electrodes and its frequency, which ensures that ions, but not electrons, are kept in the gap between the two electrodes and a homogeneous glow discharge plasma is obtained at atmospheric pressure . In FIG. 7 schematically shows the upper chamber of an atmospheric glow plasma reactor. The lower boundary of this zone is an intermediate carrier grid, the floating potential of which must correspond to the conditions of its grounding when high frequency voltage is applied to the electrodes in a push-pull circuit with grounding of the central branch. In this embodiment, the intermediate grid is connected to ground through an inductive choke. In the embodiment shown in FIG. 7, a rectangular coordinate system with the direction of the electric field along the x axis is adopted. The maximum amplitude of the electric field in the gap between the intermediate grid and the upper electrode is E ₀ , and the distance between the grid and electrodes is d. Shown in FIG. 7, the intermediate grid does not pass ions through the middle plane from the upper chamber of the reactor to the lower one and vice versa.

полученным из уравнения (2) заменой E на выражение формулы (1). Общее решение уравнения (3) имеет вид
x = C₁sinωt = C₂cosωt (4)
где постоянные C₁ и C₂ равны

и

Тлеющий разряд гелия при атмосферном давлении происходит с частотой ω/2π от 1 до 30 кГц и при этом для гелия при атмосферном давлении
v_ci≈6,8•10⁹ [столкновений ионов в секунду](7a)
и
v_ce≈1,8•10¹⁰[столкновений электронов в секунду](7б)
Частота столкновений ионов и электронов, определяемая выражениями (7а) и (7б), намного больше частоты поля, т.е. v_c ≫ ω. Соотношение v_c ≫ ω для ионов и электронов означает, что постоянная C₂ намного больше постоянной C₁ или

Зависящее от времени положение иона и электрона в электрическом поле между пластинами электродов можно определить путем подстановки выражения (8) в уравнение (4)

Среднеквадратичное значение (скз) перемещения иона или электрона в течение полупериода равно

Если V₀ является частотой возбуждения в Гц, то угловая частота определяется выражением
ω = 2πV₀, (11)
а максимальное электрическое поле между пластинами электродов может быть аппроксимировано максимальным напряжением V₀ между ними

Если рассматриваемый заряд проходит, пересекая зону разряда, от средней плоскости к одному из пластинчатых электродов в течение полного периода, то можно записать

Из выражения (13) следует, что для нарастания заряда между пластинами электродов среднеквадратичное значение перемещения частицы должно быть меньше половины свободного зазора. В варианте, показанном на фиг. 7, расстояние d равно расстоянию между промежуточной заземленной сеткой и находящимся под напряжением электродом. Подставляя выражения (11)-(13) в уравнение (10), получают следующую зависимость

Решая это уравнение относительно критической частоты V₀, выше которой в объеме плазмы должно происходить накапливание заряда, получают

В уравнении (15) частота столкновений v_c при одной атмосфере приблизительно определяется выражениями (7а) и (7б) для ионов и электронов соответственно, а среднеквадратичное значение напряжения равно напряжению, которое ограничивает верхний и нижний пределы режима однородного разряда.An electric field created between the electrodes shown in FIG. 7 is described by the equation
E = (E ₀ • sinωt, 0,0) (1)
It is believed that atmospheric glow discharge occurs in the magnetic field of a free plasma. The equation of motion of ions or electrons between two plates is determined by the Lorentz model, according to which electrons and ions collide only with a neutral background gas, and during each collision they give off all the energy received from the high-frequency electric field since the last collision with a neutral gas. In the Lorentz model, the equation of motion of ions or electrons has the following form:
F = ma = -mv _c v-eE, (2)
where the first term of the right-hand side characterizes the Lorentz collision, according to which, for each collision occurring with a frequency v _c , the angular momentum mv is lost. The x coordinate in FIG. 7 is defined by the equation

obtained from equation (2) by replacing E with an expression of formula (1). The general solution of equation (3) has the form
x = C ₁ sinωt = C ₂ cosωt (4)
where the constants C ₁ and C ₂ are equal

and

A glow discharge of helium at atmospheric pressure occurs with a frequency of ω / 2π from 1 to 30 kHz, and for helium at atmospheric pressure
v _ci ≈6.8 • 10 ⁹ [ion collisions per second] (7a)
and
v _ce ≈1.8 • 10 ¹⁰ [electron collisions per second] (7b)
The collision frequency of ions and electrons, determined by expressions (7a) and (7b), is much higher than the field frequency, i.e. v _c ≫ ω. The relation v _c ≫ ω for ions and electrons means that the constant C _{2 is} much greater than the constant C ₁ or

The time-dependent position of the ion and electron in the electric field between the electrode plates can be determined by substituting expression (8) in equation (4)

The root mean square value (RMS) of the movement of an ion or electron during a half-period is

If V ₀ is the excitation frequency in Hz, then the angular frequency is determined by the expression
ω = 2πV ₀ , (11)
and the maximum electric field between the plates of the electrodes can be approximated by the maximum voltage V ₀ between them

If the charge in question passes, crossing the discharge zone, from the middle plane to one of the plate electrodes for a full period, then we can write

It follows from expression (13) that, in order to increase the charge between the electrode plates, the rms value of the particle displacement should be less than half of the free gap. In the embodiment shown in FIG. 7, the distance d is equal to the distance between the intermediate grounded grid and the energized electrode. Substituting expressions (11) - (13) into equation (10), we obtain the following dependence

Solving this equation with respect to the critical frequency V ₀ , above which charge accumulation should occur in the plasma volume, one obtains

In equation (15), the collision frequency v _c in one atmosphere is approximately determined by expressions (7a) and (7b) for ions and electrons, respectively, and the rms voltage value is equal to the voltage that limits the upper and lower limits of the uniform discharge mode.

The modes that ensure operation at atmospheric pressure of the reactor of a homogeneous glow discharge plasma are given in table. 1. The nominal pressure during operation was equal to one atmosphere. Indicated in the table. 1, pressure deviations of several torr are not explained by fluctuations in daily atmospheric pressure, but are caused by a certain pressure drop on the intermediate grid necessary for the passage of active particles from the upper plasma through the processed sheet material. Indicated in the table. 1, the rms power values represent the value of the net power consumed by the plasma without reactive power, which is not involved in the discharge process. The total plasma volume between the plate electrodes is
S = 0.93d (cm) [liters], (16)
where d denotes the distance from the electrode to the intermediate grid in cm.

 Indicated in the table. 1, the values of specific power are much lower than in electric arc or plasma torches, and several orders of magnitude higher than with other types of plasma treatment, for example corona discharges. The specific power of the atmospheric glow discharge plasma, on the one hand, is not so large as to damage the material being processed, and on the other hand, they are higher than in corona discharge plasmas usually used for surface treatment, the number of active particles formed in which is much less than in the proposed embodiment. Plasma parameters such as electron kinetic temperature and density index are, to some extent, speculatively selected at the initial stage of development of the invention. The results of studies of the middle plane of the plasma using the Langmuir flotation sensor show that without grounding the intermediate grid, the plasma begins to shift toward positive potentials of the order of several hundred volts. Ionic kinetic temperatures are close to the room temperature of atoms, which they usually encounter at such high pressures; in this case, the number of high-energy electrons remains obviously large, and their effect on neutral background atoms is accompanied by the appearance of a glow discharge. The presence of excited states that emit visible photons means that the set of electrons has a kinetic temperature of the order of one electron volt. The diagnostic difficulties in measuring plasma parameters at such a high pressure are very significant, since the usual method using the Langmuir sensor in this case cannot be used due to the short mean free path of electrons commensurate with the Debye distance. The electron density indices can, however, be measured using microwave interferometers.

 In FIG. Figures 8 and 9 show for different frequencies graphs of changes in current and voltage in a helium medium at the same distance between the electrodes and the same gas flow rate. FIG. 8 corresponds to a uniform glow discharge at a frequency of 2.0 kHz, and FIG. 9 corresponds to a filament discharge mode at a frequency of 8.0 kHz, exceeding the operating frequency range of a uniform plasma. The high impedance of the proposed high-frequency power source allows you to get very close to the sinusoidal nature of the voltage change (curve B). The graph of the reactive current (curve C) has two discontinuities in the period associated with the breakdown of the plasma, one with a positive voltage and the other with a negative voltage. Curve A characterizes the change in the reactive current during a discharge in air, and not in helium under the same voltage and the same conditions. Under these conditions, plasma does not form in the air, and the power is completely reactive. Subtracting the reactive current (curve A) from the total plasma current (curve C), we obtain the active plasma current (curve D). The instantaneous power remaining in the plasma (curve E) is obtained by multiplying the value of the plasma current exceeding the reactive current (curve D) by the voltage at a given time (curve B). The average power is found by integrating the pulses shown in the corresponding time interval, followed by dividing the result by the duration of the integration interval. In this way, for the essentially non-sinusoidal nature of the current change, the values of the total power and specific power of the plasma were calculated. Shown in FIG. 8 and 9, the power change curves E relate to homogeneous (Fig. 8) and filamentary (Fig. 9) discharges, and by their shape it is possible to judge the nature of the discharge, homogeneous or filamentary.

 The plasma power is of particular interest because it is proportional to the rate of formation of active particles in the plasma; reactive power, on the other hand, determines the required power and the choice of power source and other necessary equipment. The total power of the power source is the sum of the plasma power and reactive power. In FIG. 10 on a logarithmic scale on both axes shows the dependence of the specific power of the plasma and the total specific power in milliwatts per cubic centimeter on the rms voltage applied to the parallel plates of the electrodes. The active volume of helium plasma in the example was 1.63 L, the distance d between the intermediate grid and each of the plate electrodes was 1.75 cm. In FIG. 11, the dependences of the specific plasma power and the total specific power on the frequency are shown on the same scale. The approximate boundary of the regime of a uniform plasma discharge is shown in the graphs by an arrow. The results shown in FIG. 11 relate to a helium plasma of the same volume and at the same electrode spacing as in FIG. ten.

 Example 1

 In a first example of the invention, the apparatus shown in FIG. 1, was used to obtain a glow discharge plasma at atmospheric pressure and normal temperature in helium at a distance between the electrode plates 10 of 3 cm. A voltage of 4.4 kV (rms) was applied to the electrode plates. During the experiments, with other constant parameters, the frequency of the current was increased as an independent variable. The angle of the phase shift of the breakdown current (graph in Fig. 12) with respect to the nodal points of the voltage wave was determined as a dependent variable. In addition, the dependence on the frequency of the total power required for plasma production, including the reactive power and the active plasma power, was determined, as shown in FIG. thirteen.

 Example 2

 In a second example of the invention shown in FIG. 1 device was used to obtain a helium plasma of a glow discharge in one atmosphere at a normal temperature and distance between electrodes 10 equal to 1.0 cm. In this example, the current frequency was kept constant at 30 kHz, and the voltage on the electrode plates was changed as an independent variable with the definition as dependent variables of the phase angle of the breakdown current (table 2) and the total power P (table 3).

 Example 3

 In the third example, the distance between the electrodes 10 was 1 cm, the voltage at the electrodes was 1.5 kB (SCR), the discharge was initiated at atmospheric pressure in a helium medium. The frequency of the current changed as an independent variable. In the table. Figure 4 shows the results of measurements of the dependent variable — the angle of the shift along the phase of the breakdown current, and in table. 5 - the corresponding values of the total power consumption.

 Example 4

 Using the device described above, helium plasma with the largest volume of 3.1 L was obtained with a distance between the plates of 3.2 cm, a voltage of 5 kV (SCR) and a frequency of 4 kHz.

 The melt blown sheet materials of polyamide, poly (ethylene terephthalate), polypropylene and polyethylene were subjected to the treatment described by a glow discharge plasma to obtain the required characteristics: increased wettability and rewet ability.

 The wettability of the material was objectively evaluated by one or two experiments: (a) measuring the contact angle of a water drop located on the surface of the material and (b) measuring the time necessary to achieve a wick effect over a certain length of the test material.

 As a result of these experiments, it was found that after plasma treatment for 2.5 min, the wettability and rewetability of polypropylene, polyamide, polyester and polyethylene films improved (the contact angle of the droplet with the surface decreased significantly).

For a film of poly (ethylene terephthalate) after treatment for 2.5 min with a glow discharge plasma at a voltage of 5 kV, a frequency of 4 kHz, and a distance of 4.5 cm between the electrode plates, the following results were obtained: the surface contact angle of the drop is 0 ^o , the duration of the wick effect 37.37 s according to the standard INDA absorption measurement method. Prior to plasma treatment, this material had a significant surface contact angle of the droplet and did not have any wick effect.

Similarly, after plasma treatment for 60 s with a polyamide film having a large surface contact angle of the droplet and without any wick effect, after wetting and secondary wetting, the following results were obtained: the surface contact angle of the droplet is 0 ^o , the duration of the wick effect is 16.61 c (tests according to the INDA method).

 In another series of experiments, two different melt blown sheet materials of poly (ethylene terephthalate) and polypropylene were tested. These materials were treated with glow discharge plasma at atmospheric pressure in helium or helium and active gas for a period of 0.5 to 2 minutes. A voltage of 1000 to 4000 V (rms) was applied to the electrodes with a frequency of 1 to 100 kHz. Sheet materials had fibers ranging in size from 2 to 2.5 microns with pore sizes of 20-25 microns and porosity of 90%. Some results of the experiments are given in table. 6.

 Wettability was evaluated by the contact angle, wick effect and the passage of fluid through the thickness of the material and the impregnation of its surface. The susceptibility of the material to the wick effect was evaluated according to the INDA standard (1st 10.1-92) by measuring the rise time of the liquid (double distillation water) to a height of 2.4 cm. The change in the physical state of the surface of the fibers was evaluated by microphotographs obtained with an ETEC Auto Scan electron microscope with an increase of 2000-4000 times.

 Despite the lack of experimental data in full, it can be argued that a homogeneous glow discharge plasma can be obtained from the one shown in FIG. 1 device at atmospheric pressure of ambient air at an electric field strength of 8 kV / cm.

Claims (25)

 1. The melt blown sheet material with a surface having improved wettability and improved rewet ability, characterized in that it is treated for a predetermined period of time at atmospheric pressure by a glow discharge plasma generated by a high frequency amplifier that produces a voltage with an rms value of 1 - 5 kV at a frequency of 1 - 100 kHz.  2. The sheet material according to claim 1, characterized in that the plasma is initiated in an inert gas.  3. The sheet material according to claim 2, characterized in that the gas is helium, argon, air or a mixture of the two gases listed.  4. The sheet material according to any one of claims 1 to 3, characterized in that it is a polymeric material.  5. The sheet material according to claim 4, characterized in that the polymeric material is polypropylene.  6. The sheet material according to any one of claims 1 to 5, characterized in that the processing is carried out at a frequency of 1 to 30 kHz.  7. A method for improving the surface characteristics of a polymer sheet material by treating the sheet material with a glow discharge plasma generated in a gas volume located between two spaced electrodes, by generating a uniform glow discharge plasma with active particles located between said electrodes, characterized in that these electrodes voltage is supplied from a high-frequency amplifier with a rms value of 1 - 5 kV at a frequency of 1 - 100 kHz, and the placement of sheet material in the gap between The electrodes inside the plasma are produced for a certain time under pressure differential conditions, under the action of which active particles pass through the sheet material.  8. The method according to claim 7, characterized in that the gas is an inert gas.  9. The method according to claim 7, characterized in that the gas is helium, argon, air or a mixture of the two gases listed.  10. The method according to any one of claims 7 to 9, characterized in that the sheet material is a melt blown polymer sheet material.  11. The method according to any one of claims 7 to 10, characterized in that the frequency is 1-30 kHz.  12. The method according to any one of claims 7 to 11, characterized in that the sheet material has an unlimited length and stretches between the electrodes at a constant speed, being subjected to plasma treatment for a given time.  13. A method for generating a glow discharge plasma in a volume between two electrodes supplied from a high-frequency amplifier with an impedance matching circuit, characterized in that the electrodes are supplied with voltage from the amplifier with an rms value of 1-5 kV at a frequency of 1-100 kHz and are filled at a pressure of 1 atmosphere of the volume between the electrodes with a gas in which a glow discharge plasma can be initiated, while a homogeneous glow discharge plasma is initiated and maintained in the volume between the electrodes at a pressure of 1 atmosphere due to the creation of a high-frequency electric field of a frequency that is, on the one hand, large enough to hold positive plasma ions between the electrodes, and on the other hand, insufficient to ensure that plasma electrons are also held between the electrodes during the half-cycle of the high-frequency voltage.  14. The method according to item 13, wherein the electrodes are placed inside a gas-tight casing, into which a certain amount of gas is continuously supplied.  15. The method according to p. 13 or 14, characterized in that the gas is helium, argon, air or a mixture of the two gases.  16. The method according to any one of paragraphs.13 to 15, characterized in that the distance between the electrodes is 5 cm or less.  17. The method according to p. 16, characterized in that at least the position of one of the electrodes is adjusted relative to the position of the other.  18. The method according to any one of paragraphs.13 to 17, characterized in that the frequency amplifier operates in the range from 1 to 100 kHz.  19. The method according to any one of paragraphs.13 to 18, characterized in that the rms voltage of the amplifier is 1 to 5 kV.  20. A device for initiating a glow discharge plasma containing a pair of electrically isolated electrodes powered by a high-frequency amplifier with an impedance matching circuit, characterized in that a voltage is generated with a rms value of 1 to 5 kV at a frequency of 1 to 100 kHz, the electrodes to which the shape of the plates is arranged in parallel and fastened equidistantly opposite each other so that a volume forms between them, which at a pressure of 1 atmosphere is filled with gas, in which the plate can be initiated the glow discharge azma, while a device is provided for initiating and maintaining a uniform glow discharge plasma at a pressure of 1 atmosphere by creating a high-frequency electric field of a frequency that is, on the one hand, large enough to hold positive plasma ions between the electrodes, and on the other hand insufficient to ensure that plasma electrons are also held between the electrodes during the half-cycle of high-frequency voltage.  21. The device according to p. 20, characterized in that the device for charging the volume between the said plates contains a protective casing, inside which are located separated from each other by the volume of the plate.  22. The device according to claim 20 or 21, characterized in that it includes a device for supplying gas, due to the continuous supply of which the pressure inside the casing is maintained at the level of one atmosphere.  23. The device according to any one of paragraphs.20 to 22, characterized in that the gas is helium, argon, air or a mixture of the two gases listed.  24. The device according to any one of paragraphs.20 to 23, characterized in that the plates are liquid-cooled.  25. The device according to paragraph 24, wherein the pipes of the cooling system are attached to the plates to remove heat from them. Priority on points:
10/29/1993 according to claims 1-19;
05/28/1993 according to claims 20-25.

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