DE19630193C2 - Surface treatment process for a seal and / or a plain bearing for sealing or storing two parts that move against one another - Google Patents

Description

The invention relates to a surface treatment method for a manufactured seal and / or a plain bearing for sealing or storage two mutually moving parts made of a material that at least in the surface area of the articles made of acrylonitrile butadiene rubber (NBR) exists, or similar materials in the surface area having.

Seals are made of an acrylonitrile butadiene rubber (NBR) material well known.

A technical teaching has become known from US Pat. No. 4,292,150. exposed surface areas of a manufactured elastomeric printing plate to be treated with iodine.

US Pat. No. 4,300,970 describes rubber materials and resin can be better connected with iodine treatment can.

The teaching of US Pat. No. 4,188,426 is to apply a fluorocarbon film to apply a substrate using a plasma coating apparatus.  

According to the technical teaching of JP 04-198240 A, a material for Formation of seals have an iodine content.

To change the surface properties of NBR seals or to improve, the surface of the seals is treated, for example by talcumizing, molycotizing, coating, graphitizing, X- Selecting, fluorinating or chlorinating (AF treatment).

In the known AF treatment with chlorine, the surface of the Seal hardened by post-crosslinking the surface with chlorine gas. Due to this artificial aging, these AF-treated seals can subject to higher wear. In addition, at Post-crosslinking of the materials tensions and cracks on the Sealing surface arise that in connection with gases not the Enable the desired sealing function and thereby an increased Cause leakage.

Even with the treatment with fluorine the seals are due to the post-crosslinked active fluorine in such a way that cracks appear in its surface can and therefore fluorinated seals not for sealing gases should be used. In addition, the fluorine is with the Reaction temperatures in the gaseous state before, so extreme extensive safety precautions have to be taken. Are also procedures use the fluorine, polluting.

In contrast, the present invention is based on the object Develop surface treatment processes through its application improves the lubricity of a seal and / or a plain bearing without the surface of the seal and / or the plain bearing significantly damage.  

This object is achieved in that Surface areas of the seal and / or the plain bearing produced subsequently treated with iodine in such a way that post-crosslinking of the Seal and / or the plain bearing with the inclusion of iodine on the surface entry.

Iodine is an easy to use, relative non-hazardous element that is a solid at room temperature. Iodine is fluorine and chlorine compared to the other two halogens inert. Dealing with these two halogens requires handling with iodine no excessive safety precautions and is iodine more environmentally friendly.

Treatment of the NBR material with iodine-containing compounds or with Iodine is a kind of post-vulcanization. This treatment of the NBR Post-crosslinking of the surface occurs with iodine. The However, surface crosslink density is less than in iodine treatment with fluorine and chlorine.

The advantages of the method according to the invention are described below using seals. The term "seals" is understood to mean any type of seal, in particular O-rings, which are used to seal fluids in static and / or dynamic applications or only as plain bearings:

• - No odor nuisance compared to NBR seals with Chlorine or fluorine treated;
• - no deterioration of material properties compared untreated NBR seals; the properties of with iodine treated NBR seals remain close to the starting material;  
• - Treating the surface of NBR seals leads inevitably also to treat deeper layers, so that there is a gives a certain depth effect;
• - dirt-free handling possible, so that expanded Areas of application e.g. B. result in medicine;
• - The use of those treated according to the invention should also be harmless Molded parts should be in the food sector because the iodine stored only is present in concentrations which, from today's perspective, are none cause health effects;
• - Better assembly is possible because the NBR treated with iodine Seals can be stretched up to 60% without their Surface cracks appear or they lose their elasticity;
• - Improved friction / sliding (minimizing friction) with iodine treated seals and over their entire service life in the substantially constant friction / sliding; and
• - Increased service life and thus better long-term effect, so that the iodine treated seals for dynamic applications can be used.

1 to 1000 µg iodine, preferably 20 to 400 µg iodine, can be stored per cm ^{2 of} material surface. On the one hand, enough iodine must be stored in the surface in order to achieve the above-mentioned effects at all. On the other hand, too much iodine must not be stored in the surface, as this would lead to embrittlement of the NBR material.

According to the invention, an NBR material containing an iodine can be used Expose fluid or solid. For example, an NBR seal exposed to a gas or solid containing iodine or into an iodine containing liquid can be immersed. The respective  Let the fluid or solid act on the NBR seal can be easily determined experimentally.

In a very particularly preferred embodiment of the Manufacturing method according to the invention can be the NBR material expose to low pressure iodine plasma. This plasma treatment enables short treatment times and has compared to other procedures the main advantage that the iodine plasma generated, i. H. ionized iodine Atoms, some of which react chemically with the material to be treated, d. H. can be chemically stored in acrylonitrile butadiene rubber.

A particularly advantageous development of this embodiment is characterized in that the plasma is generated in a rotary drum in which the NBR material to be treated and 1 to 1000 μg iodine powder, preferably 20 to 400 μg iodine powder, are located per cm ^{2 of} material surface. The parameters of the plasma (temperature, treatment time, acceleration voltage,...) Are set until the iodine has penetrated deep into the surface of the NBR material.

In a very preferred embodiment of this training one can Carry out the plasma treatment for as long as iodine powder is still in the rotary drum is located. The rotating drum becomes a predetermined amount added to iodine powder and then the plasma treatment for so long carried out until there is no more iodine powder in the rotating drum, but is completely embedded in the NBR material. The one for that the required plasma treatment time can be easily experimented Determine the variation in the plasma treatment time. Plasma treatment times in the range of approx. 5 minutes are in the experiments carried out so far sufficient to achieve the required goal.  

In another embodiment of the invention Manufacturing process can contain the NBR material in iodine Embed powder, preferably iodine powder. According to the desired one The penetration depth of the iodine into the NBR material becomes the Diffusion parameters, e.g. B. diffusion temperature and diffusion time.

In a further embodiment, this is used to treat the seals used iodine before adding it to the rotary drum in the gaseous Condition transferred and then in gaseous form to the treatment process fed. The treatment of the seals will go even further uniform.

Further advantages of the invention result from the description and the illustrated figures. Likewise, the above and the According to the invention, the features listed further are each individually for one or more can be used in any combination. The Embodiments shown and described are not as to understand the final list, but rather have exemplary character for the description of the invention. It shows:

FIG. 1 shows the surface of a reactive treated with iodine NBR seal in 2000 times magnification;

Fig. 2, the surface of an untreated NBR seal in magnified 2000 times;

Figure 3 shows the surface of an AF-treated NBR seal in magnified 2000 times.

FIG. 4 shows the surface of a reactive treated with iodine NBR seal that is stretched by 25%, times 2000 in magnification;

Fig. 5 the surface of an untreated NBR-seal that is stretched by 25%, times 2000 in magnification; and

Fig. 6, the surface of an AF treated NBR-seal that is stretched by 25%, times 2000 in magnification.

At the top edge of FIGS. 1 to 6, a distance is marked which corresponds to 20 µm.

Before the properties of NBR seals treated with iodine will be described, the manufacturing process of these seals portrayed.

O-ring seals made of acrylonitrile butadiene rubber (NBR) with pre-cleaned surfaces are exposed to a low pressure iodine plasma. The plasma is generated in a rotating drum in which the NBR seals and iodine powder to be treated are located. For 1000 O-ring seals with an inner diameter of 15 mm and a cord thickness of 3 mm, 0.1 to 5 g of iodine are required. This corresponds to an iodine requirement of 20 to 400 µg iodine per cm ² sealing surface.

The parameters of the plasma (temperature, treatment time, Acceleration voltage,. , .) and the amount of iodine powder adjusted in such a way that the iodine is applied deeply into the application Penetrates the surface of the NBR material. The plasma treatment is like this For a long time, there was still free iodine powder in the rotating drum  located. The iodine is then completely stored in the NBR seals. The plasma treatment time required for this can be experimentally determined constant other plasma parameters easily by varying the Determine the plasma treatment time.

Figs. 1 to 3 are scanning electron micrographs of a reactive treated with iodine NBR O-ring seal (Fig. 1), an untreated NBR O-ring seal (Fig. 2) and an AF-treated NBR-O -Ring- seal ( Fig. 3).

In comparison to the surface of an untreated seal ( FIG. 2), certain mountain and valley structures can be seen on the surface reacted with iodine in FIG. 1, the treated surface being smooth and having no cracks or the like. In contrast, the (treated with chlorine) AF treated seal is structured down to its depth. The individual depressions are partially connected to each other so that later leakage paths of gases past the seal can already be guessed at.

FIGS. 4 to 6 are scanning electron micrographs of a reactive treated with iodine NBR O-ring seal (Fig. 4), an untreated NBR O-ring seal (Fig. 5) and an AF-treated NBR-O -Ring- seal ( Fig. 6), the inner diameter of which is widened by 25%. The areas whose structure appeared conspicuous without enlargement were examined in particular. Such expansion by 25% and more occur, for. B. when installing seals in their corresponding groove spaces.

Soiling was found on the untreated surface of the seal ( FIG. 5), as later surface tests showed. Despite the stretch, the surface is smooth and shows no cracks. The seal reacted with iodine ( FIG. 4) also has a mountain and valley structure in the expanded state as in the non-expanded state ( FIG. 1). Despite the 25% expansion, the surface is closed and there are no cracks or similar in the surface. In contrast, the expansion exposes the cracks present in the surface of the AF-treated seal. The friction behavior of the three seal types (untreated; iodine treated; AF treated) was tested. The friction tests were carried out on a tensile testing machine. The seals were installed in a groove and pulled over a glass plate with a defined surface when not lubricated and the friction was determined. The following O-rings were examined:

• 1.OR 012 N70B200V AF-treated (chlorinated)
• 2. OR 012 N70B200V untreated
• 3. OR 012 N70B200V treated with iodine

The friction behavior of the O-rings was determined at two process speeds: a) v = 200 mm / min b) v = 500 mm / min. Three measurements were carried out on each O-ring type. The following friction values resulted:

In the case of the untreated O-ring (2nd), a peak could generally be seen at the beginning of the Friction curve are determined, d. that is, these O-rings had to be first a static friction can be overcome.

In contrast, such an initial static friction ("breakaway force") with the O-ring (3.) surface-treated with iodine cannot be found. The AF-treated O-ring (1.) showed slightly lower friction values than the O-ring treated with iodine (3rd).

Treatment of an NBR O-ring seal with iodine resulted in one Reduction of friction compared to an untreated seal, d. that is, treatment with iodine led to gliding intensification. Especially this meant that the adhesive strength of the seals treated with iodine be significantly reduced.

Claims (6)

1. Surface treatment method for a manufactured seal and / or slide bearing for sealing or storing two parts that move against one another from a material that consists at least in the surface area of acrylonitrile butadiene rubber (NBR) or has materials that are related in the surface area, characterized in that the surface areas of the seal and / or the slide bearing produced are subsequently treated with iodine in such a way that the surface of the seal and / or the slide bearing is subsequently crosslinked with iodine being embedded. 2. Surface treatment method according to claim 1, characterized characterized in that the seal and / or the plain bearing one Exposed to iodine-containing fluid or solid. 3. Surface treatment method according to claim 1 or 2, characterized characterized in that the NBR material is an iodine plasma exposes. 4. Surface treatment method according to claim 3, characterized in that the plasma is generated in a rotary drum in which the NBR material to be treated and per cm ² material surface are 1 to 1000 µg iodine powder, preferably 20 to 400 µg iodine powder. 5. Surface treatment method according to claim 4, characterized characterized that you can take the plasma treatment for so long performs how iodine powder is still in the rotating drum.   6. Surface treatment method according to claim 2, characterized characterized that one contains the NBR material in iodine Powder, preferably iodine powder, embedded.