EP3060613A1

EP3060613A1 - Elastomeric body for vibration damping

Info

Publication number: EP3060613A1
Application number: EP14786605.7A
Authority: EP
Inventors: Michael Gutsch; Martin HEBER; Björn HELLBACH; Daniela BEYER; Detlef Cordts
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 2013-10-24
Filing date: 2014-10-02
Publication date: 2016-08-31
Also published as: DE102013017570A1; WO2015058835A1

Abstract

The invention relates to an elastomeric body (1) for vibration damping and/or suspension, comprising at least one layer of a flame-retardant coating (3) which overs at least one portion of the body (1). The elastomeric body comprises expandable graphite as the flame-retardant substance and the proportion of expandable graphite in the coating (3) is less than 15% by weight.

Description

Elastomeric body for vibration damping state of the art

Organic materials such as wood or paper are generally combustible. This applies, with a few exceptions, also for the class of plastics, ie materials based on synthetic or modified natural polymers.

Plastics find a variety of uses in our everyday lives. A particular use in the areas of construction and construction places special demands on the plastic materials used, which often also include sufficient fire protection. Legal regulations, standards and a number of other regulations usually describe the fire protection criteria that a plastic must fulfill in the respective application. Evidence that a plastic material meets the fire safety requirements applicable to its field of application is provided by fire protection tests that are specific to the application. Since plastics are generally flammable organic polymers, it is usually necessary to add flame retardants in order to pass the corresponding fire protection tests.

CONFIRMATION COPY Usually, the flame retardants are distributed homogeneously in the actual plastic material. However, this approach is disadvantageous from an economic point of view, since the flame retardants are needed mainly on the surface facing the fire - not, however, or in far less small dimensions, inside the plastic material. Another disadvantage resulting from the homogeneous incorporation of flame retardants in plastic materials is the fact that to achieve a flame retardant finish, especially when using non-halogenated flame retardants, usually requires greater amounts of usually more than 10 wt.% Of flame retardants which significantly degrades the mechanical properties of the plastic system.

Significantly more efficient than a homogeneously blended flame retardant therefore is the application of a flame-retardant coating, which locates the flame retardants where they are needed in case of fire. As a result, the two disadvantages described above can be eliminated.

Flame-retardant coatings for plastics are also state of the art. From EP 2 196 492, for example, an elastomeric body for vibration damping and suspension is known, wherein the body comprises at least one layer of an elastic and flexible flame-retardant coating. The flame retardant coating described there is based primarily on expandable graphites as flame retardants.

Expandable graphites are characterized by the fact that insulating barrier layers can be produced in the event of fire. This allows a plastic material coated with these materials to be preserved over a longer period of fire from thermal decomposition by the fire. Expandable graphites or intumescent graphites are graphites which have been treated with strong acids and / or oxidants. In this case, the acids and / or oxidants intercalate between the layer planes of the graphite (intercalation) and thereby break up the layer lattice structure. Under the influence of heat, the intercalated chemicals form gaseous products that move apart the individual carbon layers and cause the individual graphite particles to swell. The expansion volume is dependent on the type and amount of intercalated acid and the oxidizing agent and can be up to 400 times the original material in case of fire.

The flame retardant effect of the expandable graphites is based essentially on three effects. On the one hand, the expansion of the graphite consumes heat energy and thus cools the environment. In addition, non-combustible gases that dilute the combustion gases are produced during expansion. Finally, the formed Dämmschichten have low thermal conductivities over a large temperature interval, so that the underlying material is isolated from the external heat. The expandable graphites are among the most effective known flame retardants and have been used in the art for over 25 years.

The fields of application of expandable graphites are now diverse and range from coatings for steel beams, intumescent systems for fire and smoke resistant foreclosure of pipe and cable glands (EP 2 088 183 A1), intumescent fire protection tapes for safety cabinets to flame-retardant foams for aircraft or rail vehicle seats ( EP 2 260 066 A1). However, the use of expandable graphites also has some disadvantages. Particularly disadvantageous in the use of expandable graphites is their gray to black color, which results in materials containing effective amounts of fine powder expandable graphites also being dark gray to black in color. When using coarse expandable graphites with particle sizes above 100 pm, these are recognizable as separate dots in the later material. It is therefore common practice in practice to blacken materials blackened with effective amounts of coarse expandable graphite with black so as to render the individual particles of expandable graphite unrecognizable, thus providing a consistent appearance of the material for marketing purposes. The preparation of a uniform flameproof or dark gray deviating flame retardant coating or a uniform and color black or dark gray deviating flame retardant material is not possible when using finely powdered and / or coarse expandable graphites.

Another disadvantage with the use of expandable graphites and the coloring by means of soot particles is the increase of the electrical conductivity of the surface of the coating material. This effect is undesirable in applications where high electrical resistances are required, e.g. to avoid electrochemical corrosion or reactive currents.

Furthermore, when introducing expandable graphites into a liquid coating material, their viscosity is greatly increased. This has the disadvantage that the processability of the coating material deteriorates or even becomes impossible in some cases, such as in the spray process. The present invention was based on the object to provide an elastomeric body for vibration damping and / or suspension, on the one hand should have a very effective flame retardant and on the other hand has a different color from the black elastomer body and delimiting flame retardant coating. The elastomeric body should also be used for vibration damping and / or suspension, inter alia, for rail applications. Therefore, the flame retardant should be designed so that it reaches a hazard level of at least 1, but preferably 2 and more preferably 3 according to the new European standard for rail transport DIN EN 45545: 2013, requirement set R9. In addition to the requirements of DIN EN 45545: 2013, an insulating and particularly stable insulating layer is to be formed according to the invention, which protects the elastomeric body against damage from the fire during direct flame treatment over a period of at least 20 minutes.

As mentioned above, expandable graphite shows excellent flame protection. Against this background, the object of the invention is to provide effective flame protection for the elastomeric component, but at the same time avoid the disadvantages of expandable graphites for flameproof coatings described above.

DESCRIPTION OF THE INVENTION This object is achieved according to the invention by an elastomeric vibration damping and / or suspension body comprising at least one layer of a flame retardant coating covering at least a portion of the body, the elastomeric body comprising expandable graphite as the flame retardant and the proportion of expandable graphite in the coating less than 15% by weight, preferably less than 5% by weight, more preferably less than 2% by weight, even more preferably less than 1% by weight, and especially 0% by weight.

The elastomeric body according to the invention is characterized in that the body itself has expandable graphite as a flame retardant substance while the flame retardant coating has conventional flame retardant additives, which are preferably white and / or colorless.

Thus, the elastomeric body thus comprises at least one elastomeric (base) body having expandable graphite as a flame retardant substance. At least a portion of this body is further covered by at least one layer of flame retardant coating, wherein the proportion of expandable graphite in the coating comprises less than 15 wt%. Surprisingly, it has been found that despite the separation of the expandable graphite from the remaining flame retardants and the associated loss of synergetic effects between the expandable graphite and the remaining flame retardants, a highly effective flame protection can be achieved. Thus, in the event of fire, the elastomeric body according to the invention is able to build up an insulating barrier layer which can protect the body from damage by the flames over a period of 20 minutes. This makes it possible to reach hazard level 1, hazard level 2 and even hazard level 3 according to DIN EN 45545: 2013 requirement set R9.

The interference of the expandable graphite in an elastomer compound is technically easy to implement. The gray or black color of the graphite is not disadvantageous, since rubber compounds for industrial applications, especially for vibration applications, are often black anyway, since the added carbon black is a very favorable filler and provides the most balanced property profile for most applications.

Even unfilled or purely mineral-filled rubber compounds, which are not black per se, are often blackened with small amounts of carbon black. There are many reasons for this: In the production and processing of blends, color changes cause a great deal of cleaning work, which one would like to avoid. Unsightly discolorations due to discoloring anti-aging agents or penetrated oils, which suggest that a component is no longer in order, are covered. Last but not least, due to the high optical absorption of the carbon black, it is expected to be more stable against sunlight.

Due to the displacement of the expandable graphite from the coating into the black-colored, elastomeric body, according to the invention it is possible to dispense with the use of expandable graphite in the coating, which is advantageous for the described invention for various reasons. First, the flame retardant coating is therefore not necessarily black. This is advantageous on the one hand for aesthetic reasons, as it allows the coating color to be freely selected within the limits set by the materials used. Thus, for marketing, it is possible to label and promote certain flame retardant elastomeric bodies, and the user has an easy way of knowing whether or not an elastomeric product is equipped with a flame retardant coating. Furthermore, the fact that the coating can be provided with a desired color, an optical difference to be arranged under the coating elastomeric body can be made - the like set out above is usually black. This is advantageous, as this can cause holes, cracks or similar damage to the coating caused, for example, by abrasion, stone chips, vandalism, chemical attack, etc., to be easily discovered during maintenance work. Also, a colored coating could serve, for example, to differentiate original parts from spare parts or to differentiate the same designs in different materials.

Second, the provision of little or no amount of expandable graphite in the coating has the advantage that the electrical conductivity of the surface of the coating material is not undesirably increased, which reduces the possibility of electrochemical corrosion. The expandable graphite can be introduced in a simple manner with the units commonly used for the production of elastomers (internal mixer, rolling mill, calender, extruder) in an elastomeric mixture used to prepare the body. For hygienic, technological and economic reasons, the internal mixer is preferably used for mixing in the expandable graphite. As already explained above, it is possible according to the invention to dispense expandable graphite in the coating. This is advantageous because it reduces the processability of the coating material, e.g. can be avoided in the spray process.

It is also possible to stain the flame retardant coating, for example by adding organic dyes, such as phthalocyanines, or inorganic color pigments, such as TiO ₂ , C ^ Oz or Fe ₂ O ₃ . This makes it easy to distinguish between fire-protected and (less expensive) non-fire-resistant components. This can be a simple poka-yoke, which prevents a non-fire protected component from being installed in an application where fire protection is actually needed. For this purpose, amounts of pigment from 0.1% to 5%, in each case based on the total weight of the flame retardant coating, have proven to be particularly suitable.

It is also conceivable to provide the flameproof coating with a thermochromic material, which indicates by a color change that the elastomer was exposed to high operating temperatures. The thermochromic material can be used, for example, in amounts of from 0.1% to 5%, in each case based on the total weight of the flameproof coating.

According to a further embodiment of the invention, the coating has several layers of different composition. Thus, for example, a second, preferably differently pigmented, protective layer can be applied to a first layer which already provides a minimum protection. This embodiment has the advantage that when the first layer becomes visible, curative measures, for example renewal of the coating, change of the component, can be initiated immediately, without the fire protection being lost.

If two further differently pigmented protective layers are applied to a first protective layer, curative measures can be planned when the middle layer becomes visible and can be carried out at a later time.

According to a preferred embodiment of the invention expandable graphite is used with an onset temperature> 160 ° C, preferably from 180 ° C to 250 ° C. The onset temperature is defined here as the temperature at which the thermal expansion process of the expandable Graphite inserts. The use of expandable graphite having a high onset temperature is advantageous because such expandable graphite does not expand during a vulcanization process. In practice, elastomers are more often produced at higher vulcanization temperatures because the cure rate increases sharply with increasing temperature. As a rule of thumb, which is true in many but not all cases of course, is that increasing the vulcanization temperature by 10 ° C causes about a doubling of the vulcanization rate. Higher vulcanization temperatures therefore allow a cheaper production or an increase in capacity. A suitable graphite for the preferred embodiment of the invention is therefore, for example, a sulfuric acid-treated graphite having an onset temperature of about 250 ° C. It is also conceivable to use expandable graphites which contain volatile, organic acids such as acetic acid or inorganic acids such as nitric acid and have lower onset temperatures than sulfuric acid-based expandable graphites.

Practical experiments have shown that with expandable graphite having an average particle size of 100 pm to 800 pm, preferably from 180 pm to 500 pm, particularly good results can be achieved since these expandable graphites have with increasing particle size higher expansion volumes, which in case of fire for the formation of a sufficiently insulating insulation layer are necessary. Expandable graphites with an average particle size above 500 pm have the highest expansion volumes, but are commercially more difficult to acquire and are priced significantly higher than standard types with particle sizes of 80%> 300 pm.

According to a particularly preferred embodiment of the invention, the graphite has at least two fractions of different particle sizes. there It is advantageous if the average particle size of at least a first fraction, measured according to DIN 66165, at more than 180 μιη, preferably in the range of 180 [im to 800 m. The use of particles of this particle size is advantageous since, as described above, they have high expansion volumes when exposed to heat.

The mean particle size of the second fraction, measured according to DIN 66165, is advantageously less than 180 μm, preferably in the range of 50 μm to 120 μm. The use of particles of this particle size is advantageous because with them a particularly dense insulating layer can be formed. In the case of an expansion, the finer graphite expands, closing gaps in the more voluminous but at the same time less dense insulating layer formed by the coarse expandable graphite. This results in a very dense and well-insulating insulating layer, which shields the underlying elastomeric body well in front of the flames. Thus, bodies according to the invention which contain graphites of different particle sizes are distinguished both by a high flameproofing effect and by a high stability and density of the insulating layer formed.

Furthermore, it was surprisingly found that the elastomeric body additivated with the differently sized expandable graphites with respect to their further mechanical properties such as Shore hardness according to DIN ISO 7619-1, tensile strength according to DIN 53504 (S2), elongation at break according to DIN 53504 and compression set after DIN ISO 815 (specimen B, 25% deformation, method A) does not differ de facto in view of the measurement inaccuracies and possible batch fluctuations of exclusively soot-containing elastomers. Table 1 shows this with the example of a natural rubber mixture in which the soot fractions by expandable graphite were replaced (for better comparability of the formulations, the total amount of filler was kept constant).

Tab. Also, rheological parameters used to assess the processability and storage stability of an elastomer blend did not show any changes resulting in unstable or inadequate processes.

Practical experiments have shown that elastomeric bodies having a particularly good flame retardancy and stability can be obtained when the ratio of the first fraction to the second fraction is from 10: 1 to 1: 1, preferably from 5: 1 to 2: 1.

The proportion of expandable graphite in the elastomeric body may vary depending on the desired mechanical properties and, in particular, the desired flame retardancy. For example, proportions in an amount of from 10% by weight to 60% by weight, preferably from 15% by weight to 35% by weight, in each case based on the total weight of the elastomeric body, have proven to be suitable.

The elastomeric body may contain the following polymers (abbreviations according to ISO 1629: 1995): BR, ENR, HNBR, HR, IR, NBR, NR, SBR, XNBR, ACM, AEM, EPDM, EVM (name of the polymers according to ISO 1629: 1995) and / or mixtures thereof. The total polymer content based on the total weight of the elastomeric body is at least at least 33 % By weight, preferably from 40% by weight to 85% by weight, and especially from 50% by weight to 80% by weight. Further, for the preparation of the elastomeric body, binary, ternary or quaternary mixtures of the above-mentioned polymers can be used.

The elastomeric body may include one or more main bodies that are at least partially covered by the flame retardant coating.

According to one embodiment of the invention, the base body consists exclusively of elastomeric materials. In this embodiment, the outer surface of the body is preferably completely covered by the flame-retardant coating. According to an alternative embodiment of the invention, the elastomeric body consists of several partial bodies. The partial bodies may consist of elastomeric and / or non-elastomeric materials, for example metals, in particular steel and / or aluminum. In this embodiment, preferably, the outer surface of the elastomeric body part is covered by the flame-retardant coating. According to the invention, the elastomeric body has a flame-retardant coating. The coating may consist of a polymeric material, for example polyacrylate, polyethylene, polypropylene, polyamide, polyester, polyurethane, ethylene-vinyl acetate, polyvinyl acetate, polyvinyl chloride, polyvinyl alcohol and / or copolymers thereof and silicone. The application of the polymeric material to the elastomeric component can be carried out from aqueous dispersions, solutions, high-solids systems or directly.

Practical tests have shown that a very good flame retardancy can be achieved when the coating in the cured state Layer thickness of 0.5 mm to 5 mm, preferably from 1 mm to 3 mm and particularly preferably from 1, 5 mm to 2.5 mm.

According to a particularly preferred embodiment of the invention, the flame-retardant coating consists of polyurethane and has flame retardant additives, preferably in an amount of 5% to 60%.

As mentioned above conventional additives can be used for the flame-retardant coating, for example a) phosphorus-containing flame retardants such as red phosphorus, ammonium phosphate, ammonium polyphosphate (APP), Phosphatester of the general formula P (O) OR ₁ OR ₂ 0R ₃ (where Ri, R2 and R3 represents organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 C atoms and / or hydrogen atoms, which vary or may be the same), phosphonates of the general formula P (O) RiOR ₂ OR ₃ (where R ₁ , R ₂ and R _{3 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals 1 to 20 carbon atoms and / or hydrogen atoms, which may be different or the same), phosphinates of the general formula P (O) RiR ₂ 0R ₃

(Where Ri, R ₂ and R _{3 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 C-atoms and / or represent hydrogen atoms which are different or may be the same), phosphoramidates of the general formula (R 1 O) (R ₂ O) PONR ₃ R (where R 1, R ₂ , R ₃ and R _{4 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted

Represent radicals with 1 to 20 carbon atoms and / or hydrogen atoms, which may be different or the same) and phosphorodiamidates of the general formula (RO) PO (NR ₂ R ₃ ) (NR ₄ R 5) (wherein Ri, R ₂ , R ₃ , 4 and R _{5 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 C atoms and / or hydrogen atoms represent that may be different or the same).

Suitable representatives of the above-mentioned phosphorus compounds according to the invention are, for example, trioctyl phosphate, tricresyl phosphate, triphenyl phosphate, ethylenediamine diphosphate (EDAP), cresyldiphenyl phosphate, 2-ethylhexyldiphenyl phosphate, tris (2-ethylhexyl) phosphate, triethyl phosphate, dimethylpropane phosphonate; b) nitrogen-containing flame retardants such as melamine, melamine derivatives (salts with organic or inorganic acids such as boric acid, cyanuric acid, phosphoric acid or pyro / polyphosphoric acid) and melamine homologues such as melam, Meiern and melon; c) mineral flame retardants such as aluminum hydroxide (ATH) or magnesium hydroxide (MDH); d) Boron-containing compounds such as borates; e) nanocomposites (phyllosilicates based on aluminum silicate clay minerals, such as bentonite, vermiculite or montmorillonite); or mixtures thereof.

According to the invention, preference is given in the coating to using combinations of flame retardants which, due to synergistic effects, have markedly improved fire behavior. Particularly useful is the exploitation of synergies between phosphorus-containing and nitrogen-containing flame retardants, such as ammonium polyphosphate (APP) and melamine cyanurate. Thus, according to the invention, intumescent (lat .: intumescere = swelling) flame retardant systems, so-called intumescent agents, are particularly preferably used in the coating. By this, the expert understands flame retardant systems that form a voluminous, insulating protective layer in the event of fire. The intumescent effect is based on the synergistic interaction between an acid generator, a carbon source and a propellant. The chemical processes that lead to the formation of an insulating layer in case of fire can be described as follows: the acid generator is thermally split by the heat energy of the fire and releases an inorganic acid. Usually, phosphorus-containing flame retardants, such as, for example, ammonium polyphosphate (APP), function as acid formers, which release polyphosphoric acid in the event of fire.

> 250 ° C

(NH ₄ PO ₃ ) _n (HPO ₃ ) _n

- NH, The free polyphosphoric acid reacts with the carbon source, usually a polyhydric alcohol such as pentaerythritol or starch, by depriving it of water and thereby causing the formation of carbon.

(HP0 ₃ ) _n + C _x (H ₂ O) ["C"] _x + (HPO ₃ ) _n m H ₂ O

Simultaneously with the charring process, the propellant, usually a nitrogen-containing flame retardant, is thermally decomposed, resulting in gaseous decomposition products which cause the carbon forming to form and thus form an insulating carbon foam.

According to a preferred embodiment of the invention, the elastomeric body and / or the coating contains no or only small amounts of halogen-containing flame retardants. Thus, the proportion of halogen-containing flame retardants in the elastomeric body and / or the coating is preferably less than 5 wt.% And particularly preferably 0 wt.% By formulation. This is advantageous since halogen-containing flame retardants release hydrogen halide compounds in the event of a fire, which massively increase the smoke gas toxicity. For the same reason, it is advantageous if the elastomeric body and / or the coating contains antimony trioxide or only in a small amount. As mentioned above, the displacement of the conventional flame retardants from the elastomeric material into the coating is of great advantage since complications may otherwise be encountered in the processing of elastomers: conventional flame retardant chemicals can adversely affect the vulcanization or reduce the storage stability in terms of processing and / or finished product properties , Such problems are not expected and are not observed when introducing expandable graphites with sufficiently high onset temperatures into the elastomer matrix because of the high inertness of the graphite.

An example of this is shown in FIG. 1 for a natural rubber mixture with a conventional sulfur vulcanization system. FIG. 1 shows the influence of a) melamine borate and b) expandable graphite on the compression set of a natural rubber mixture as a function of the amount added in phr. While the replacement of a carbon black by melamine borate leads to a significant deterioration of the compression set, the replacement of a proportion of carbon black by expandable graphite shows no negative change in the compression set.

While the base mixture without flame retardant can be stored without problems for four weeks, the blends with flame retardants showed processing problems by scorching after only two weeks. Thus, it must often be determined by extensive experimental tests which flame retardant chemicals and in what quantity are suitable for a specific elastomer compound. This is different for each system and depends on both the base polymer and the vulcanization system. By shifting the flame retardants into the coating these problems can be circumvented as the interference is easily technically feasible from expandable graphite in an elastomer compound.

The elastomeric body according to the invention can be used in the sealing area, for example in the form of O-rings. It is also suitable for the production of bellows, tubes with or without tissue reinforcement and membranes with or without tissue reinforcement. Practical experiments have shown that the body according to the invention is also outstandingly suitable for the production of components for vibration damping and / or suspension, in particular in rail vehicle construction

In the following the invention will be explained in more detail with reference to several examples and figures.

Example 1: Flame-retardant elastomer formulation for vibration applications based on natural rubber

Elastomer formulation:

Natural rubber 100 phr

Carbon black N-774 5-80 phr

Naphthenic oil 20-0 phr

Paraffin wax 1-3 phr

Anti-aging agent TMQ 1-3 phr

Anti-aging agent IPPD 1-3 phr

Zinc oxide 2-10 phr

Stearic acid 1-2 phr

Sulfur 1-4 phr

Accelerator CBS 1-3 phr

Accelerator TMTD 0-1 phr

Expanding Bears Graphite Nord-Min 351 15-35 phr Expandable graphite North-Min 95 0-20 phr

Coating recipe: Impranil DLU 100 phr

Aflammit PPN 977 8-15 phr

Heliogen blue 1-4 phr

Preparation of the coating:

The preparation of the water-based, flame-retardant coating was carried out by means of a Speedmixer from Hauschild. Impranil DLU polyurethane dispersion was placed in a polypropylene mixing can and the powdery additives were added sequentially. The mixture was thoroughly homogenized for two minutes at 2300 rpm and applied to the elastomeric body by dipping. The drying of the layer was carried out at 80 ° C in a heating cabinet. The coating forms a protective insulating layer in case of fire, effectively protecting the rubber from the flames over a period of 5 minutes.

Example 2: Flame retardant elastomer formulation for vibration applications based on natural rubber

Elastomer formulation:

Natural rubber 100 phr

Carbon black N-774 5-80 phr Naphthenic oil 20-0 phr

Paraffin wax 1-3 phr

Anti-aging agent TMQ 1-3 phr

Anti-aging agent IPPD 1-3 phr

Zinc oxide 2-10 phr

Stearic acid 1-2 phr

Sulfur 1-4 phr

Accelerator CBS 1-3 phr

Accelerator TMTD 0-1 phr

Expandable graphite North-Min 251 15-35 phr

Expandable graphite North-Min 95 0-20 phr

Coating formulation:

Tetrahydrofuran 100 phr

TPU powder 30-40 phr

Aflammit PPN 977 10-20 phr

Heliogen blue 1-4 phr Preparation of the coating:

The TPU powder was dissolved in tetrahydrofuran overnight. The resulting medium to high viscosity solution was placed in a mixed can of polypropylene and the powdered additives were then added sequentially. The mixture was thoroughly homogenized for two minutes at 2300 rpm and applied to the elastomeric body by dipping. The layer was dried under suction at room temperature and then at 80 ° C in a vacuumed heating cabinet. The coating forms a protective insulating layer in case of fire, effectively protecting the rubber from the flames over a period of 5 minutes. Example 3: Flame-retardant elastomer formulation for oil-resistant vibration dampers based on NBR

Elastomer recipe: NBR rubber 100 phr (preferably 28 mol%

acrylonitrile)

Carbon black N-330 0-30 phr

Carbon black N-550 5-70 phr

Zinc oxide 5 phr

Plasticizer dioctyl adipate 5-25 phr

Anti-aging agent ODPA 1- 3 phr

Anti-aging agent IPPD 1-2 phr

Anti-aging agent TMQ 0-2 phr

Paraffin wax 1- 3 phr

Sulfur 1-2 phr

MBTS 0-1 phr

CBS 0-1 phr

Expandable graphite North-Min 351 15-35 phr

Expandable graphite North-Min 95 0-20 phr

Coating formulation:

Tetrahydrofuran 100 phr

TPU powder 30-40 phr

Aflammit PPN 977 10-20 phr Melamine 3-8 phr

Heliogen blue 1-4 phr

Preparation of the coating:

The TPU powder was dissolved in tetrahydrofuran overnight. The resulting medium to high viscosity solution was placed in a mixed can of polypropylene and the powdered additives were then added sequentially. The mixture was thoroughly homogenized for two minutes at 2300 rpm and applied to the elastomeric body by dipping. The layer was dried under suction at room temperature and then at 80 ° C in a vacuumed heating cabinet. The coating forms a protective insulating layer in case of fire, effectively protecting the rubber from the flames over a period of 5 minutes.

FIG. 2 shows by way of example the cross section of an elastomeric body (1) in the form of an oring or a roll spring. The elastomeric body comprises a circular base body (2). This is completely covered by the flame-retardant coating (3).

FIG. 3 shows by way of example the cross section of an elastomeric body (1) in the form of a bellows. The base body (2) is covered on the outer surface (4) of the flame-retardant coating (3), while the top (5) and the bottom (6) are not coated.

FIG. 4: FIG. 4 shows, by way of example, the cross section of an elastomeric body (1) in the form of a laminated spring. In this embodiment, the Basic body (2) 5 partial body (7,8). The partial bodies (7) are formed by metallic sheets. The partial bodies (8) are made of elastomeric materials. The partial bodies (8) are covered on the outer surfaces (4) of flame-retardant coatings (3).

FIG. 5: In FIG. 5, the cross-section of an elastomeric body (1) in the form of a round bearing is shown by way of example. In this embodiment, the base body (2) comprises 3 partial bodies (7, 8). The partial bodies (7) are formed by metallic sheets. The part body (8) consists of elastomeric materials. The partial body (8) is covered on the side surface (4) by a flame-retardant coating (3).

FIG. 6 shows by way of example in FIG. 6 the section from a cross section of an elastomeric body (1) in the form of a conical bearing. In this section, the basic body (2) comprises 3 partial bodies (7, 8). The partial bodies (7) are made of metallic materials. The partial bodies (8) are made of elastomeric materials. The partial bodies (8) are covered on the outer surfaces (4) of flame-retardant coatings (3).

Claims

claims

Elastomeric body (1) for vibration damping and / or suspension comprising at least one layer of a flame retardant

A coating (3) covering at least a portion of the body (1), characterized in that the elastomeric body comprises expandable graphite as a flame retardant and the amount of expandable graphite in the coating (3) is less than 15% by weight.

Elastomeric body (1) according to claim 1, characterized in that the onset temperature of the expandable graphite is more than 160 ° C.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the elastomeric body comprises mixtures of two or more expandable graphites

contains different average particle sizes.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the expandable graphite has a mean particle size of 180 μητι to 800 pm, preferably from 180 pm to 500 pm.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the proportion of the

expandable graphite from 10 wt .-% to 60 wt .-%, preferably from 15 wt .-% to 35 wt .-% based on the total weight of the elastomeric body.

6. Elastomeric body (1) according to one or more of the preceding claims, characterized in that the elastomeric body is a polymer selected from the group consisting of: BR, ENR, HNBR, HR, IR, NBR, NR, SBR, XNBR, ACM, AEM, EPDM, EVM, wherein the name of the polymers is abbreviated to ISO 1629: 1995, and / or mixtures thereof, and wherein the total polymer content based on the total weight of the elastomeric

Body is at least 33% by weight, preferably from 40% by weight to 85% by weight and in particular from 50% by weight to 80% by weight.

7. elastomeric body (1) according to claim 6, characterized in that the elastomeric body of binary, ternary or quaternary mixtures of the mentioned in claim 6 polymers is made.

8. An elastomeric body (1) according to one or more of the preceding claims, characterized in that the flame-retardant coating (3) is a polymer selected from the group consisting of polyacrylate, polyethylene, polypropylene, polyamide, polyester, polyurethane, polyvinyl acetate, ethylene vinyl acetate, Polyvinyl chloride, polyvinyl alcohol and / or their copolymers and silicone and / or mixtures of the aforementioned polymers as a polymeric matrix.

9. elastomeric body (1) according to one or more of the preceding claims, characterized in that the flame-retardant coating (3) contains polyurethane as a polymeric matrix. 0. Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) in the cured state, a layer thickness of 0.5 mm to 5 mm, preferably from 1 mm to 3 mm and more preferably from 1 , 5 mm to 2.5 mm.

11. elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) contains flame-retardant substances selected from the group consisting of:

- Phosphorus-containing flame retardants such as red

Phosphorus, ammonium phosphate, ammonium polyphosphate (APP), phosphate ester of the general formula P (0) ORiOR ₂ 0R ₃ (where Ri, R ₂ and R3 are organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated

represent cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 carbon atoms and / or hydrogen atoms, the

may be different or the same); Phosphonates of

general formula P (0) RiOR ₂ OR ₃ (where Ri, R2 and R _{3 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 carbon atoms and / or hydrogen atoms, which may be different or the same); Phosphinates of the general formula P (0) RiR ₂ OR ₃ (where Ri, R _{2 and} R _{3 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated

may be different or the same); Phosphoramidates of general formula (R ₁ 0) (R ₂ O) PONR ₃ R ₄ (wherein R ^ R _2, R ₃ and R _{4 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted radicals having 1 to 20 carbon atoms and / or hydrogen atoms, which may be different or the same) and phosphorodiamidates of the general formula (RiO) PO (NR ₂ R ₃ ) (NR ₄ R5) (where Ri, R ₂ , R ₃ , R ₄ and R _{5 are} organic, branched or unbranched, aromatic and / or saturated aliphatic and / or unsaturated aliphatic and / or saturated cycloaliphatic and / or unsaturated cycloaliphatic, substituted and / or unsubstituted Radicals having 1 to 20 carbon atoms and / or hydrogen atoms which may be different or the same); nitrogenous flame retardants, in particular melamine, melamine derivatives (salts with organic or inorganic acids such as boric acid, cyanuric acid, phosphoric acid or pyro / polyphosphoric acid) and melamine homologues such as melam, Meiern and melon; mineral flame retardants, such as

Aluminum hydroxide (ATH) or magnesium hydroxide (MDH);

Boron-containing compounds such as borates;

Nanocomposites, in particular phyllosilicates based on aluminum silicate clay minerals, such as bentonite, vermiculite or montmorillonite or mixtures thereof. Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) comprises a mixture of phosphorus-containing and nitrogen-containing

Flame retardants, in particular a mixture of

Ammonium polyphosphate (APP) and melamine cyanurate.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) contains phosphorus-containing and nitrogen-containing flame retardants and a carbon supplier, preferably a polyhydric alcohol, such as pentaerythritol and / or starch.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) organic and / or inorganic pigments and / or a

contains thermochromic material.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) has a different color than the elastomeric body (1).

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the coating (3) has at least two layers which are colored differently.

Elastomeric body (1) according to one or more of the preceding claims, characterized in that the elastomeric body is reinforced by a woven, knitted fabric, non-woven fabric and / or other textiles. Use of an elastomeric body (1) according to one or more of the preceding claims for producing a component for vibration damping and / or suspension.