ES2587576A1 - Application procedure for antifriction coatings (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Application procedure for antifriction coatings. The present invention describes a method of applying antifriction coatings on a substrate, comprising the steps of providing a substrate and projecting onto said substrate a cold plasma at atmospheric pressure comprising an ionization gas and an atomized liquid coating precursor. The coating precursor comprises siox groups and nitrogen groups; and the thickness of the coating applied on the substrate is greater than 1000 nm. (Machine-translation by Google Translate, not legally binding)

Description

Field of the Invention

The present invention relates generally to the field of application of anti-friction coatings, for example in the automotive sector in which anti-friction coatings are used on window seals and similar elements.

Background of the invention

The method of applying coatings using plasma is called plasma polymerization. Thin strata of the order of nano and micrometers can be deposited in the gas phase by means of plasma polymerization. The selection of precursors to be deposited and plasma operating parameters

(equipment power, precursor flow, gas flow, etc.), determines the specific characteristics of the coating obtained, and therefore, the characteristics of the modified surface, which can be hydrophilic, hydrophobic, adhesion promoter, anti-friction, anti-corrosive, anti-reflective, anti-bacterial, etc.

Solid coating application systems

based

in the technology of the plasma (by example, evo

(deposition

chemistry in phase from steam) Y PVD

(deposition

physical

in phase from steam), be they know widely in the

technique

Y its use is very extended. The coatings

solids that are applied by these procedures allow to improve the functional characteristics of a surface, for example increasing its hardness (in tools of cartel or its resistance to corrosion. Most of these known technologies employ thermal plasmas in which the surface temperature it varies

between

200-1000 "C. Without embargo, East interval from

temperatures

may to provoke a phase from transformation

thermal

from softening irreversible, or changes in the

shape,

in most of the plastic materials.

S

At case of sensitive plastic materials to such

temperatures

high, habitually be employ methods from

covering

through liquids set chemically Y

expensive

techniques such how the flocking. For example, in the

industry

of the car l ~ esulta habitual use bliss

10

technique from flocking, by example for the together from the

windows.

Without embargo, these systems from covering

they present several drawbacks since, for example, they are expensive, they present complications in their

application, generate rejections in the quality controls of

15 manufacturing lines and have a high cost. The use of plastic materials (for example ethylene propylene diene rubber -EPDM -or thermoplastic elastomer polymer -TPE-) in the automobile industry is widespread due to its particular

20 elastic properties and their high coefficient of friction; particularity: s that favor the tightness of the interior of the interior of the car against water, dust and noise. However, in some parts of the vehicle where there is a slip between these

25 materials (for example, j of the electric window or rubber of the windshield wiper) and, for example, the glass of the windows of the doors, this high coefficient of friction supposes a problem. As mentioned, several types of coatings 30 (chemically fixed liquid coatings and flocking areas) are currently used to reduce friction in these areas, with the aforementioned drawbacks. Research in improving the performance of

mechanical systems subject to severe conditions of use

(high pressures and temperatures, etc.) and with special lubrication needs, it constitutes an area of increasing interest in recent years. The progressive miniaturization of the equipment has brought traditional liquid lubricants close to their limits of applicability. To this fact must be added the increasingly restrictive legislation due to the environmental and health problems that their employment can generate. In many cases, the liquid lubrication of these materials presents many problems due to the operating conditions to which they will be subjected. This is what happens, for example, in the jWltas and profiles used in the automobile industry (door and window insulating tires, windshield wipers, etc.).

The method of flocking in these materials is a common process that consists of incorporating in certain areas of the profile geometry, polyamide (PA) or polyester (PE) fibers with a normal orientation to the profile surfaces, and which gives an effect notable in reducing the coefficient of friction in contact with the moving elements, for example, the windows of a vehicle's electric window "However, this flocking process is not valid for areas where said treated surfaces are subjected to a high contact pressure with moving elements, for example, the contacts in the locking systems ~ =: of vehicles with removable hood.These flocked areas do not resist this work and are destroyed providing visible aesthetic-functional defects in the form of bald spots, with the consequent fracture in the tightness of the joints.

The PA or PET fibers that are used to float certain areas of the sealing systems for the

automotive sector, are very specific products with very technical characteristics. This means that they have a high cost, in addition to needing technologically complex installations.

(EDM, application of adhesive, projection of the fibers under an electrostatic field, high voltage static and stabilization of the adhesive by heat).

As an alternative to e: 3rd methods, the application of coatings by means of a "cold" plasma source (APCP, "A tmospheric Presure Cold Plasma") is known in the art.

For example, document ES 2345986 T3 discloses a procedure for covering a surface of a substrate using a plasma jet, to which a

powder

from grain fine that shape he covering, by means, medium

from

a conveyor  from powder controlabl e in a quantity

dosed

By

other side, he document US 2002195950 To the gives to

know

a plasma that be produces in a space from

treatment by diffusion of a plasma gas at atmospheric pressure and subjecting it to an electric field created by two metal electrodes separated by a dielectric material, a vapor phase precursor is mixed with the plasma, and a substrate material is coated by deposition in vapor phase of the vaporized substance at atmospheric pressure in the plasma field.

however, no process is known in the art by means of .A.PCP optimized to apply anti-friction coatings on plastic materials, for example in the automotive industry, which provide satisfactory results in terms of coefficient of friction and durability thereof.

Therefore, it would be desirable to have an alternative method of applying antifriction coatings

that at least partially solves the inconveniences presented by the prior art.

Summary of the invention

To solve the problems of the prior art, this document describes a method of applying antifriction coatings comprising the steps of:

provide a substitute; and project a cold plasma at atmospheric pressure onto said substrate. comprising an ionization gas and an atomized liquid coating precursor;

In addition, the process of the invention is characterized in that the coating precursor comprises SiOx groups

Y

nitrogen groups I

Y

he

thickness of the covering applied on

he

substratum

is above 1000 nm.

features

additional preferred of the

Method according to the present invention are disclosed in the dependent claims.

Brief description of the figures

The present invention will be better understood with reference to the following figures illustrating preferred embodiments of the invention, provided by way of example, and which should not be construed as limiting the invention in any way.

Figure 1 is a schematic of the system employed in the preferred embodiment of the process of the present invention.

Figure 2 is a graph representing the

coefficient of friction as a function of the distance traveled during the test for several coated substrate samples according to the process of the present invention. An uncoated substrate sample and a coated sample are also shown as controls by a flocking method according to the prior art.

Figure 3 is a graph showing the average friction coefficient as a function of the number of passes and the plasma power used.

Figure 4 is a graph showing the thickness as a function of the number of passes and the plasma power used.

Figure 5 is a graph showing the average surface temperature of the substrate as a function of the number of passes and the plasma power used.

Detailed description of the preferred embodiments

The procedure disclosed in this document has an ideal application, although not exclusively, in the automobile industry. An example of this application is related to rubber profiles

(for example, EPDM or TPE) used in a vehicle. The elasticity and high coefficient of friction of these elements makes them ideal for ensuring the vehicle's tightness against water, dust and noise, but in some parts of the vehicle, this high coefficient of friction is a problem (for example, in the joint of the glass window).

As mentioned above, the process of projecting on said cold plasma substrate at atmospheric pressure comprising the ionization gas and an atomized liquid coating precursor.

from

application  from coatings antifriction according the

realization

favorite from the Present invention understands

the stages of:

provide

a substratum; Y

In addition, the process: o is characterized in that the coating precursor comprises SiOx groups and nitrogen groups1s; and the thickness of the coating applied on the substrate is greater than 1000 nm.

According to the preferred embodiment of the present invention, the step of projecting the cold plasma on the substrate is repeated for at least six passes.

Silicon oxides (SiOx) promote friction reduction and increase wear resistance of 15 l to coated surface. , while the nitrogen groups promote the adhesion of the applied coating, a fundamental characteristic to ensure its durability. According to your preferred embodiment of the present invention, the coating recursor is (3

Aminopropyltriethoxysilane (APTES), which has the formula shown below:

...... ....

CH, CK¡b ~ J.I, CH, CH, (NH ;:

¡'' Sil ': ........

. / \.

CH, CfhQ 9-éH, CH,

-

or. or'"

Furthermore, the substrate on which said anti-friction coating is applied is preferably, but not limited to, thermoplastic elastomer polymer tulle.

(TPE).

The cold plasma at atmospheric pressure used in the process of the present invention can be applied, according to your preferred embodiment, by technical tula

30 selected corona discharge, dielectric barrier and radiofrequency discharge.

Corona discharge (commonly called CORONA) is a type of plasma generated by low density current. It consists of the cathode-filament and an anode between which a low frequency pulsed current is generated. The gas used is ai: r-e. The plasma created forms a crown-shaped flash around the cathode. When large surfaces are treated, the treatment is not homogeneous

in

all its surface.

For

sort out East trouble, in the last years be

he has

developed the technique from discharge from barrier

Dielectric (DED) This technique represents a new advance in terms of the uniformity of plasma discharge compared to corona treatments. The DBD plasma device consists of: 2 metal electrodes in which at least one of these electrodes is coated with a dielectric material. To ensure stable plasma generation, the distance between the electrodes is limited to a few millimeters. Plasma gas flows between this space. The discharge occurs from a pulsed or sinusoidal voltage. Depending on the composition of the gas, the voltage and the excitation frequency, the discharge can be of filament or glow type. The use of dielectric materials plays an important role as it limits the discharge current allowing the transition arc to work with continuous or pulsed current and distributes the discharges in a safe way, ensuring a correct surface treatment.

The radiofrequency (RF) discharge consists of 2 concentric electrodes, through which the working gas circulates. The excitation current is low power, which allows a stable discharge. Plasma is produced in the purchased space, between both electrodes and,

depending on the power. of the current, these must

Cool by water or air. The dispesitive commonly

known as APPJ (atmospheric pressure plasma jet

"atmospheric pressure plasma jet") usually corresponds to a

5

RF type plasma. In some models, as in the

DBD type equipment, one of the electrodes is coated

of a dielectric material. In these cases, the only

difference between these RF type equipment and Wl equipment

type DED is the current dI:! gas excitation (voltage and

10

frequency)

According to the preferred embodiment of the present

invention, cold plasma ;; 1 atmospheric pressure is applied

by means of an APP device, J of type by radiofrequency.

According to another preferred embodiment of the present

fifteen

invention, the substrate temperature is maintained throughout

moment below 100 ° C, more preferably below

of 92 ° C, so that its degradation is avoided.

The ionization gas I = mixed for the application of

plasma on the substrate can be any gas of

twenty

ionization commonly known in the art.

Preferably, said ionization gas is selected from

nitrogen, helium, argon, air, etc. and more preferably

It is nitrogen.

Atmospheric pressure cold plasma can be applied to

2S

any suitable power that allows to obtain a

adequate antifriction coating on the substrate in

question. According to a preferred embodiment, said power

is equal to or less than 450 W, more preferably equal to or

less than about 350 W.

30

An application example is described below.

specific to the procedure, or disclosed herein

document.

Flat samples of elastomer polymer were coated

thermoplastic (TPE) of dimensions 100xSOx2 mm according to the process of the present invention. This material is the same as that used in the profiles and joints of cars, being the only difference to the geometry of the

5 samples

For the application of the coating, an APPJ type device shown in the attached figure 1 was used. Said device has a liquid precursor inlet (10) and an ionization gas inlet (12) in its part

Top 10 Inside, the equipment comprises, concentrically arranged, a dielectric material (14), a high power electrode (16), an earth electrode.

(18) and a ceramic spacer (20). The plasma jet produced (22) is illustrated in the figure with a shadow

15 gray The dashed line represents the route of each pass made with said device, in the direction of the indicated arrows. The person skilled in the art will know the operation of a device of this type and therefore it is not explained in more detail in this document.

20 The samples were coated using three different precursors (APTES, TEaS and HMDSO) that have the following formulas: formulas:

HMDSO

TEOS

All precursors have different forms of silicon oxides: SiOx. These silicon oxides, due to the transformations that occur in the plasma, will be deposited in different forms, SiC, SiOSi, SiH, etc. SiOsi molecules are responsible for the reduction

of the coefficient of friction.

The APTES compound, in addition to SiOx, has an amine group, -NHz. These amines will be deposited on the target substrates in different forms of nitrogen compounds. As will be seen below, these compounds are key to the adhesion of the silicon oxides present in the APTES, with the consequent reduction of the coefficient of friction and high durability of the applied coating.

In all cases the precursors used are liquid and are introduced into the plasma stream. It will be understood that it is also possible to use gases as said precursors.

The coatings were made using 3 different plasma powers: 350, 450 and 550 W. The plasma power is related to. the degree of decomposition of the liquid precursor in the plasma. For example, a high potency promotes the creation of more SiOSi molecules, without

embargo,

destroy the lUlions molecular from the amines,

increases

the temperature of the substrate Y creates tensions

residual

in the coating.

In addition, coatings were made with 1, 2, 3, 6, 12 and 18 passes.

All substrate samples were activated with the last Wla (without applying coating) before applying the different coatings, in order to clean and prepare the surface of the substrate.

The following table presents the summary of the combinations of power, number of passes and coating precursor used in the tests:

I TEOS atomized precursor 1

I

(W)

of the

45 0 550

350 I 450 I 550 1

3 50

350 I 450 I 550

one 2

2 2

2 I 2 I 2

2 I 2 I 2 3

3 3

6

liI

12 18

18 I 18 I 18

18 I 18 I 18

These tables indicate (with a gray background) those

5 combinations whose coefficient of average friction (CF) has been lower than that obtained by the flocking procedure.

The instrument to measure the coefficient of friction of the different samples covered by the

The method of the present invention was a rotary tribometer with a nominal load of 1 Newton, W1 at a total distance of 4000 meters, a radius of 2.5 mm and a linear velocity of 2 cm / s. Figure 2 shows: the results obtained in

15 these tests. As a control, an uncoated substrate sample (TPE) and a mediant coated substrate sample were also analyzed. :: W1 prior art flocking procedure (FLOC). For the sake of clarity, only the results of

20 test samples coated with APTES using 2, 6, 12 and 18 passes and with a power of 350 and 550 W.

To identify the graph of the coefficient of friction (CF) corresponding to each sample a coding is used that includes the number of passes and the power

25 of the plasma used in each case. For example, to the sample coated with 6 passes and a plasma power of 350 W

It is code 6p350.

None of the samples in which TEOS and HMDSO were used as a coating precursor had a lower coefficient of friction than the one obtained by the flocking procedure. Dl: among the samples coated with APTES, only the combinations in which a number of passes equal to or greater than 6 and a plasma power of 350 Iil and a number of passes of 6 and a plasma power of 4! 30 were used W obtained lower CF than the one obtained by the flocking procedure (gray background samples from the table before: r-ior). Therefore, it is observed that to obtain adequate results, the coating precursor must have: r, in addition to SiOx groups, nitrogen groups (which are not present in either the TEOS molecule or the HMDSO molecule).

In addition, Figures 3, 4 and 5 show the average friction coefficient, the thickness and the average temperature of the sample, respectively, as a function of the number of passes and the plasma power used.

In Figure 3 it can be seen that optimal friction coefficient results are obtained for a number of passes equal to or greater than 6 and a plasma power of 350 W and a number of passes of 6 and a plasma power of 450 w.

In Figure 4 it is appreciated that, for the optimal samples (6p350, 12p350, 1: 9p35D and 6p45D) the thickness of the coating obtained is always greater than 1000 nm.

In addition, in Figure S it can be seen that, for the optimum results obtained (6p350, 12p350, 18p350 and 6p450) the sample temperature is maintained at all times below 92 ° C.

Therefore, the present invention discloses an optimized method of applying an anti-friction coating on a substitute, in which the coating precursor has g: SiOx breaks as well as nitrogen groups, and the coating is applied to a temperature below 92 ° C and has at least one micron

5 thick

Although the present invention has been described with reference to preferred embodiments thereof, the person skilled in the art may devise changes and modifications without thereby departing from the scope of the

10 attached claims.

Claims (12)

one.

Coatings application procedure

antifriction comprising the stages of:

-provide a substrate; Y

project on said substrate a cold plasma to

atmospheric pressure comprising a gas of

ionization and a liquid coating precursor

atomized;

characterized by that

the coating precursor comprises SiOx groups

and nitrogen groups; Y

the thickness of the coating applied on the

substrate is greater than 1000 nm.

2.

Method according to claim 1, characterized

because it also includes maintaining the temperature of the

substrate below 92 ° C throughout the entire

process.

3 .

Method according to any of the claims

previous, characterized by the stage of projecting

the cold plasma on the substrate is repeated for at

minus six passes.

Four .

Procedure according to any of the claims

above, characterized in that the cold plasma a

atmospheric pressure is applied by a technique

selected crown discharge, discharge

dielectric and radiofrequency barrier.

5 .

Procedure according to claim 4, characterized

why cold plasma at atmospheric pressure is applied

by tulle APPJ type device by

radiofrequency

6.

Method according to any of the claims

above, characterized in that the substrate is

constituted by a thermoplastic elastomer polymer.

7.

Method according to any one of claims 1-5, characterized in that the substrate is constituted by ethylene rubber p: l: 'diene opylene.

8.

Procedure according to any of the claims

5 1-5, characterized in that the substrate is constituted by a rubber profile or joint used in a vehicle. 9. Method according to any of the claims above, characterized in that the coating precursor is (3-aminoopropyl) triethoxysilane.

10.

Process according to any of the preceding claims, characterized in that the ionization gas is nitrogen.

eleven.

Procedure according to any of the claims

15 above, characterized in that the cold plasma at atmospheric pressure SE! applies to a power equal to or less than 450 W. 12. Method according to any of claims 1-11, characterized in that the cold plasma under pressure Atmospheric 20 is applied at a power of approximately 350 W.