USE OF A POROUS FILLER FOR REDUCING THE GAS PERMEABILITY OF AN ELASTOMER COMPOSITION

Abstract

A porous filler for reducing the gas permeability of an elastomer composition, a process for producing the elastomer composition comprising the porous filler, and the elastomer composition itself. The porous filler is selected from surface-reacted calcium carbonate, precipitated hydromagnesite and mixtures thereof. The addition of the porous filler to the elastomer composition allows for reducing the gas permeability of the elastomer composition while retaining or improving the mechanical properties of the elastomer composition.

Claims

1. A process for the preparation of an elastomer composition having a reduced gas permeability, the process comprising: crosslinking a precursor composition to form the elastomer composition, the precursor composition comprising: a crosslinkable polymer; and a porous filler comprising a filler material selected from the group consisting of surface-reacted calcium carbonate, precipitated hydromagnesite and mixtures thereof, wherein the surface-reacted calcium carbonate is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors in an aqueous medium, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source and mixtures thereof.

2. The process of claim 1, wherein the filler material has a BET specific surface area from 20 to 200 m.sup.2/g; and/or a volume median particle size d.sub.50 from 0.1 to 75 μm; and/or a volume top cut particle size d.sub.98 from 0.2 to 150 μm; and/or an intra-particle intruded specific pore volume in the range from 0.1 to 3.0 cm.sup.3/g, determined by mercury porosimetry measurement.

3. The process of claim 1, wherein the porous filler further comprises a surface-treatment layer on at least a part of the surface of the filler material, wherein the surface-treatment layer is formed by contacting the filler material with a surface-treatment composition in an amount from 0.07 to 9 mg/m.sup.2 of the filler material surface.

4. The process of claim 3, wherein the surface-treatment composition comprises at least one unsaturated surface-treatment agent selected from the group consisting of mono- or di-substituted succinic anhydride containing compounds comprising unsaturated carbon moieties, mono- or di-substituted succinic acid containing compounds comprising unsaturated carbon moieties, mono- or di-substituted succinic acid salts containing compounds comprising unsaturated carbon moieties, unsaturated fatty acids, salts of unsaturated fatty acids, unsaturated esters of phosphoric acid, salts of unsaturated phosphoric acid esters, abietic acid, salts of abietic acid, trialkoxysilanes comprising unsaturated carbon moieties and mixtures thereof.

5. The process of claim 3, wherein the surface-treatment composition comprises at least one saturated surface-treatment agent selected from the group consisting of I) a phosphoric acid ester blend of one or more phosphoric acid mono-ester and/or salts thereof and/or one or more phosphoric acid di-ester and salts thereof, II) at least one saturated aliphatic linear or branched carboxylic acid and salts thereof, III) at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C.sub.2 to C.sub.30 in the substituent and salts thereof, IV) at least one polydialkylsiloxane, V) at least one trialkoxysilane, and VI) mixtures of the materials according to I) to V).

6. The process of claim 1, wherein the crosslinkable polymer is selected from the group consisting of ethylene-propylene rubber, ethylene-propylene-diene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, styrene-butadiene rubber, polyisoprene, hydrogenated nitrile-butadiene rubber, polychloroprene, isobutene-isoprene rubber, chloro-isobutene-isoprene rubber, brominated isobutylene-isoprene rubber, acrylic rubbers, butadiene rubbers, epichlorhydrin rubbers, silicone rubbers, fluorocarbon rubbers, polyurethane rubbers, polysulfide rubbers, thermoplastic rubbers, and mixtures thereof.

7. The process of claim 1, wherein the porous filler is contained in the precursor composition in an amount in the range from 5 to 175 parts per hundred (phr) based on the total weight of the crosslinkable polymer in the precursor composition.

8. The process of claim 1, wherein the precursor composition further comprises an additive.

9. The process of claim 1, wherein a) the Shore A hardness of the elastomer composition is increased by at least 3% compared to the same elastomer composition, wherein the porous filler is replaced by carbon black in an isovolumic amount, and/or b) the air permeability is decreased by at least 5% compared to the same elastomer composition, wherein the porous filler is replaced by carbon black in an isovolumic amount, wherein the carbon black has a statistical thickness surface area (STSA) of 39±5 m.sup.2/g, measured according to ASTM D 6556-19, and wherein the Shore A hardness is measured according to NF ISO 7619-1:2010 and the air permeability is measured according to NF ISO 2782-1:2018.

10. A process for the preparation of an elastomer composition having a reduced gas permeability, the process comprising the steps of a) providing a crosslinkable polymer, b) providing a porous filler comprising a filler material selected from the group consisting of surface-reacted calcium carbonate, precipitated hydromagnesite and mixtures thereof, wherein the surface-reacted calcium carbonate is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors in an aqueous medium, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source and mixtures thereof, c) optionally providing a further filler, d) mixing, in any order, the crosslinkable polymer of step a), the porous filler of step b) and optionally the further filler of step c) to form a mixture, and e) crosslinking the mixture obtained in step d) to form an elastomer composition having a reduced gas permeability.

11. The process of claim 10, wherein the porous filler further comprises a surface-treatment layer on at least a part of the surface of the filler material, wherein the surface-treatment layer is formed by contacting the filler material with a surface-treatment composition in an amount from 0.07 to 9 mg/m.sup.2 of the filler material surface.

12. The process of claim 10, wherein crosslinking step e) is performed by i) the addition of a crosslinking agent and a crosslinking coagent, and subsequent thermal crosslinking at a temperature of at least 100° C., optionally in combination with compression molding at a pressure of at least 100 bar, and/or ii) curing by ultraviolet light radiation, electron-beam radiation, nuclear radiation, gamma radiation, microwave radiation and/or ultrasonic radiation.

13. An elastomer composition having a reduced gas permeability formed from a composition comprising a crosslinkable polymer, a porous filler selected from the group consisting of surface-reacted calcium carbonate, precipitated hydromagnesite and mixtures thereof, and a further filler, wherein the surface-reacted calcium carbonate is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors in an aqueous medium, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source and mixtures thereof.

14. The elastomer composition of claim 13, wherein the volume ratio of the porous filler to the further filler is in the range from 10:90 to 90:10.

15. An article comprising the elastomer composition of claim 13, wherein the article is selected from the group consisting of tubeless articles, membranes, sealings, O-rings, gloves, pipes, cables, electrical connectors, oil hoses, balls and shoe soles.

16. A porous filler for reducing the gas permeability of an elastomer composition comprising an elastomer, the porous filler comprising: a filler material selected from the group consisting of: surface-reacted calcium carbonate, which is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors in an aqueous medium, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source; precipitated hydromagnesite; and mixtures thereof, wherein the filler material has: a BET specific surface area from 20 to 200 m.sup.2/g, a volume median particle size d.sub.50 from 0.1 to 75 μm, a volume top cut particle size d.sub.98 from 0.2 to 150 μm, and an intra-particle intruded specific pore volume in the range from 0.1 to 3.0 cm.sup.3/g, determined by mercury porosimetry measurement.

17. The process of claim 2, wherein the filler material has a BET specific surface area from 20 to 200 m.sup.2/g.

18. The process of claim 2, wherein the filler material has a volume median particle size d.sub.50 from 0.1 to 75 μm.

19. The process of claim 2, wherein the filler material has a volume top cut particle size d.sub.98 from 0.2 to 150 μm.

20. The process of claim 2, wherein the filler material has an intra-particle intruded specific pore volume in the range from 0.1 to 3.0 cm.sup.3/g.

Description

EXAMPLES

Measuring Methods

[0428] The number-average molecular weight M.sub.n is measured by gel permeation chromatography, according to ISO 16014-1:2019 and ISO 16014-2/2019.

[0429] The Brookfield viscosity is measured by a Brookfield DV-III Ultra viscometer at 24° C.±3° C. at 100 rpm using an appropriate spindle of the Brookfield RV-spindle set and is specified in mPa.Math.s. Once the spindle has been inserted into the sample, the measurement is started with a constant rotating speed of 100 rpm. The reported Brookfield viscosity values are the values displayed 60 seconds after the start of the measurement. Based on his technical knowledge, the skilled person will select a spindle from the Brookfield RV-spindle set which is suitable for the viscosity range to be measured. For example, for a viscosity range between 200 and 800 mPa.Math.s the spindle number 3 may be used, for a viscosity range between 400 and 1 600 mPa.Math.s the spindle number 4 may be used, for a viscosity range between 800 and 3 200 mPa.Math.s the spindle number 5 may be used, for a viscosity range between 1 000 and 2 000 000 mPa.Math.s the spindle number 6 may be used, and for a viscosity range between 4 000 and 8 000 000 mPa.Math.s the spindle number 7 may be used.

[0430] The acid number is measured according to ASTM D974-14.

[0431] The specific surface area (in m.sup.2/g) is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:2010). The total surface area (in m.sup.2) of the filler material is then obtained by multiplication of the specific surface area and the mass (in g) of the corresponding sample.

[0432] The iodine number is measured according to DIN 53241/1.

[0433] Volume median particle size d.sub.50 is evaluated using a Malvern Mastersizer 2000 Laser Diffraction System. The d.sub.50 or d.sub.98 value, measured using a Malvern Mastersizer 2000 Laser Diffraction System, indicates a diameter value such that 50% or 98% by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement are analysed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005.

[0434] The weight median grain diameter is determined by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph™ 5100 or 5120, Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and sonicated.

[0435] The processes and instruments are known to the skilled person and are commonly used to determine the particle size of fillers and pigments.

[0436] The specific pore volume is measured using a mercury intrusion porosimetry measurement using a Micromeritics Autopore V 9620 mercury porosimeter having a maximum applied pressure of mercury 414 MPa (60 000 psi), equivalent to a Laplace throat diameter of 0.004 μm nm). The equilibration time used at each pressure step is 20 seconds. The sample material is sealed in a 3 cm.sup.3 penetrometer for analysis. The data are corrected for mercury compression, penetrometer expansion and sample material compression using the software Pore-Comp (Gane, P. A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., “Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations”, Industrial and Engineering Chemistry Research, 35(5), 1996, p. 1753-1764).

[0437] The total pore volume seen in the cumulative intrusion data can be separated into two regions with the intrusion data from 214 μm down to about 1-4 μm showing the coarse packing of the sample between any agglomerate structures contributing strongly. Below these diameters lies the fine interparticle packing of the particles themselves. If they also have intraparticle pores, then this region appears bi-modal, and by taking the specific pore volume intruded by mercury into pores finer than the modal turning point, i.e. finer than the bi-modal point of inflection, the specific intraparticle pore volume is defined. The sum of these three regions gives the total overall pore volume of the powder, but depends strongly on the original sample compaction/settling of the powder at the coarse pore end of the distribution.

[0438] By taking the first derivative of the cumulative intrusion curve the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, are revealed. The differential curves clearly show the coarse agglomerate pore structure region, the interparticle pore region and the intraparticle pore region, if present. Knowing the intraparticle pore diameter range it is possible to subtract the remainder interparticle and interagglomerate pore volume from the total pore volume to deliver the desired pore volume of the internal pores alone in terms of the pore volume per unit mass (specific pore volume). The same principle of subtraction, of course, applies for isolating any of the other pore size regions of interest.

Analysis on Elastomer Samples:

[0439] For all tests on the elastomer compositions, a minimum period of 16 h was kept between molding and testing of the rubber samples. The samples were kept in a controlled environment (temperature: 23±2° C., relative humidity: 50±5%).

Tear Resistance

[0440] Tear resistance (DELFT) was measured according to NF ISO 34-2:2015 on a Zwick Z005 or Z100 device using the parameters outlined in Table 1.

TABLE-US-00001 TABLE 1 Tear resistance (DELFT) measurement parameters. Standard: NF ISO 34-2 Type of test piece: Delft Preparation of test piece: Samples were cut from sheets of 2 ± 0.2 mm thickness Cutting direction perpendicular to calendering direction State: Initial Temperature: 23 ± 2° C. Relative Humidity: 50 ± 5% Number of test pieces used: 3 Test specimen conditioning Minimum 16 h at before test: 23° C. and 50% RH Rate of grip separation: 500 mm/min

Hardness Shore A

[0441] Hardness (Shore A) was measured according to NF ISO 7619-1 on a Bareiss Digitest II apparatus using the parameters outlined in Table 2.

TABLE-US-00002 TABLE 2 Hardness (Shore A) measurement parameters. Standard: NF ISO 7619-1 or NF ISO 48-4 (EPDM series 3) Type of device: A Type of test piece: 50 × 25 × (2.0 ± 0.2) mm Number of test pieces used: 3 Test carry out: 3 s Preparation of test piece: Samples were cut from sheets of 2 ± 0.2 mm thickness State: Initial Temperature: 23 ± 2°C Relative Humidity: 50 ± 5% Number of measurements: 5 Unit: points Test specimen conditioning Minimum 16 h at 23° C. before test: and 50% RH

Gas Permeability

[0442] As indicated by NF ISO 2782-1, the gas permeability of a rubber film may be defined as the rate at which it is penetrated by a certain gas. Permeability can be expressed in terms of liters of gas per square meter of rubber per 24 hours. The tests were conducted by introducing a round rubber sample in a hermetically closed chamber. The pressure was measured on both sides of the chamber and an absolute 4 bar pressure of air was introduced in one side of the chamber. The permeability was determined by the time needed for the air to pass through the rubber. The tests were conducted at 60° C. and 50% relative humidity, using Air (79% Nitrogen and 21% Oxygen gas). The samples were let to heat for 30 min before each test. All tests were held until there was at least a 0.3 bar increase in pressure in the lower chamber. The air permeability is given in (m.sup.2 Pa.sup.−1 s.sup.−1).

Tensile Test & Modulus M50

[0443] Tensile test including M50 measurement were measured according to NF ISO 37:2017-11 on a Zwick Roell Z005, device using the parameters outlined in Table 3.

TABLE-US-00003 TABLE 3 Tensile test and modulus M50 measurement parameters. Standard NF ISO 37:2017-11 Type of test piece Type H2 Preparation of test piece Samples were cut from sheets of 2 ± 0.2 mm thickness Cutting direction Parallel of calendering direction State Initial Temperature 23 ± 2° C. Relative humidity 50 ± 5% Number of test pieces used 3 Units MPa for strength, % for elongation Test specimen conditioning Minimum 16 h at 23° C. and before test 50% relative humidity Conditioning after ageing in air None Conditioning after immersion None Rate of grip separation 500 mm/min

Materials

Treatment A

[0444] Treatment A is a low molecular weight polybutadiene functionalized with maleic anhydride (M.sub.n=3100 Da, Brookfield viscosity: 6500 cps+/−3500 ©25° C., acid number: 40.1-51.5 meq KOH/g, total acid: 7-9 wt.-%; microstructure (molar % of butadiene): 20-35% 1,2-vinyl functional groups), available under the trade name RICON® 130MA8.

Powder 1

[0445] Powder 1 is a surface-reacted calcium carbonate composed of 80% hydroxyapatite and 20% calcite as measured by XRD analysis (BET=85 m.sup.2/g, d.sub.50 (vol)=6.1 μm, d.sub.98 (vol)=13.8 μm, total intra particle intruded specific pore volume 0.004-0.43 μm=1.28 cm.sup.3 g.sup.−1), prepared with the following method:

[0446] In a mixing vessel, 350 liters of an aqueous suspension of natural ground calcium carbonate was prepared by adjusting the solids content of a ground marble calcium carbonate from Hustadmarmor, Norway with a particle size distribution of 90 wt.-% less than 2 μm as determined by sedimentation, such that a solids content of 10 wt.-%, based on the total weight of the aqueous suspension, is obtained.

Whilst mixing the suspension, 62 kg of a 30% concentrated phosphoric acid was added to said suspension over a period of 10 minutes at a temperature of 70° C. Finally, after the addition of the phosphoric acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying.

Powder 2

[0447] Powder 2 is a surface-reacted calcium carbonate (BET=139 m.sup.2/g, d.sub.50 (vol)=6.1 μm, d.sub.98 (vol)=14.2 μm, total intra particle intruded specific pore volume 0.004-0.31 μm=1.00 cm.sup.3 g.sup.−1) prepared with the following method:

[0448] In a mixing vessel, 350 liters of an aqueous suspension of natural ground calcium carbonate was prepared by adjusting the solids content of a ground marble calcium carbonate from Hustadmarmor, Norway with a particle size distribution of 90 wt.-% less than 2 μm as determined by sedimentation, such that a solids content of 10 wt.-%, based on the total weight of the aqueous suspension, is obtained.

Whilst mixing the suspension, 62 kg of a 30% concentrated phosphoric acid was added to said suspension over a period of 10 minutes at a temperature of 70° C. Additionally, during the phosphoric acid addition, 1.9 kg of citric acid was added rapidly (about 30 s) to the slurry. Finally, after the addition of the phosphoric acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying.

Powder 3

[0449] Powder 3 has been prepared by surface-treating powder 1 with 5 wt.-% of treatment A. To carry out the treatment, the treatment agent (35 g) was first dispersed in 300 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0450] A suspension of powder 1 (700 g in 6 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then filtered on a Büchner funnel and dried overnight in an oven (110° C.). The dried filter cake was then deagglomerated using a Retsch SR300 rotor beater mill (total intra particle intruded specific pore volume 0.004-0.43 μm=1.06 cm.sup.3 g.sup.−1).

Powder 4

[0451] Powder 4 has been prepared by surface-treating powder 1 with 7.5 wt.-% of treatment A. To carry out the treatment, the treatment agent (37.5 g) was first dispersed in 200 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0452] A suspension of powder 1 (500 g in 6 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then filtered on a Büchner funnel and dried overnight in an oven (110° C.). The dried filter cake was then deagglomerated using a Retsch SR300 rotor beater mill (total intra particle intruded specific pore volume 0.004-0.43 μm=1.07 cm.sup.3 g.sup.−1).

Powder 5

[0453] Powder 5 has been prepared by surface-treating powder 2 with 5 wt.-% of treatment A. To carry out the treatment, the treatment agent (35 g) was first dispersed in 300 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0454] A suspension of powder 2 (700 g in 7 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then filtered on a Büchner funnel and dried overnight in an oven (110° C.). The dried filter cake was then deagglomerated using a Retsch SR300 rotor beater mill (total intra particle intruded specific pore volume 0.004-0.27 μm=0.85 cm.sup.3 g.sup.−1).

Powder 6

[0455] Powder 6 has been prepared by grinding powder 2 in a Dyno-mill grinder and then surface-treating it with 5 wt.-% of treatment A. To carry out the treatment, 800 g of this powder was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 5 minutes (700 rpm, 120° C.). After that time, 5 wt.-% of treatment A (40 g) was added to the mixture. Stirring and heating was then continued for another 15 minutes (120° C., 700 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 6, BET specific surface area=101.2 m.sup.2/g, d.sub.50 (vol)=5.9 μm; d.sub.98 (vol)=13 μm, total intra particle intruded specific pore volume 0.004-0.04 μm=0.323 cm.sup.3 g.sup.−1).

Powder 7

[0456] Powder 7 is a precipitated hydromagnesite (BET specific surface area=46.7 m.sup.2/g, d.sub.50 (vol)=8.75 μm; d.sub.98 (vol)=29 μm, total intra particle intruded specific pore volume 0.004-0.53 μm=1.188 cm.sup.3 g.sup.−1)

Powder 8

[0457] Powder 8 has been prepared by surface-treating powder 7 with 5 wt.-% of treatment A. To carry out the treatment, the treatment agent (35 g) was first dispersed in 400 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution. A suspension of powder 7 (700 g in 6 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then filtered on a filter press and dried overnight in an oven (110° C.). The dried filter cake was then deagglomerated using a Retsch SR300 rotor beater mill (total intra particle intruded specific pore volume 0.004-0.48 μm=1.082 cm.sup.3 g.sup.−1)

Powder 9

[0458] Powder 9 has been produced through wet grinding of powder 7 (BET specific surface area=46.5 m.sup.2/g, d.sub.50 (vol)=7.9 μm; d.sub.98 (vol)=27 μm).

Powder 10

[0459] Powder 10 is an untreated precipitated hydromagnesite (BET specific surface area=42.7 m.sup.2/g, d.sub.50 (vol)=11.6 μm; d.sub.98 (vol)=47 μm, total intra particle intruded specific pore volume 0.004-0.31 μm=0.507 cm.sup.3 g.sup.−1), obtainable by the method as described in WO2011054831 A1.

Powder 11

[0460] Powder 11 is an untreated precipitated hydromagnesite (BET specific surface area=70.1 m.sup.2/g, d.sub.50 (vol)=6.3 μm; d.sub.98 (vol)=70 μm, total intra particle intruded specific pore volume 0.004-0.43 μm=0.983 cm.sup.3 g.sup.−1)

Powder CE1 (Comparative)

[0461] Powder CE1 is a N550 carbon black filler obtained from Orion engineered Carbons GmbH (Purex® HS 45, iodine number: 43±5 mg/g; STSA surface area (according to ASTM D 6556): 39±5 m.sup.2/g).

Powder CE2 (Comparative)

[0462] Powder CE2 is a surface-treated ultrafine ground calcium carbonate (BET specific surface area: 44.1 m.sup.2/g).

Elastomer Compounding

Examples Series 1: EPDM Elastomer Composition

Step 1—Internal Mixing

[0463] As a first step, each batch were mixed in a HAAKE internal mixer with 300 cm.sup.3 capacity equipped with Banbury rotors. The temperature was set at 40° C. at the beginning of each mixing, during the process the temperature raised up to 90° C., depending on the filler being incorporated. The following process had been used for each batch (Table 4):

TABLE-US-00004 TABLE 4 Internal mixing procedure. Time Speed (min) Operation (rpm) t = 0 Introduction of elastomer precursor 40 and mineral filler (40° C.) t = 1 Insertion of carbon black and oil 40 t = 5 Dumping of the mixture 40

Step 2—External Mixing

[0464] For the second step, mixing with the peroxide crosslinking agent was performed on a cylinder mixer (150×350). All the elastomer precursors were mixed with the same times, cylinder speeds, and cylinder spacing. The cooling system was set to 25° C. and the metal guides were set as to allow the elastomer precursor to occupy 70% of the cylinder surface. In between two accelerations the cylinders are cleaned and are let cool. The detail proceedings for this process are described in Table 5 below.

TABLE-US-00005 TABLE 5 External mixing procedure. Time Cylinder (min) Operation Spacing (mm) t = 0 Introduction of the mix from Step 1 1 t = 2 Insertion of the crosslinking system 1 t = 6 5 thin passings 0.6 Calendering sheet, thickness 2 mm 2

Step 3—Compression Molding

[0465] Sheets of the elastomer composition were produced by compression molding at 160 or 180° C. and 100 kgf/cm pressure. This way, small 150×150×2 mm sheets were prepared. The crosslinking time, which determines the molding time, was determined through a rheological MDR test.

EPDM Elastomer Compositions

[0466] The following elastomer compositions of Table 6 were obtained following the method described above. All elastomer compositions had an isovolumic amount of fillers. All fillers were coupled 50/50% with carbon black in volume. Therefore the carbon black reference batch contains 100 phr of N550. The other batches contain 50 phr of N550 and a slightly variable amount of mineral filler in function of their density, in order to have an amount of mineral filler equivalent to the volume of 50 phr of carbon black (indicated in Table 6 with an asterisk).

TABLE-US-00006 TABLE 6 EPDM elastomer compositions Example EPDM-E3 EPDM-E4 EPDM-E5 EPDM-CE1 EPDM Vistalon 100 100 100 100 2504 from Exxon Mobil (phr) Powder 3 (phr)  72* Powder 4 (phr)  70* Powder 5 (phr)  68* Powder CE1 (phr)  50  50  50 100 Torilis 6200  10  10  10  10 plasticizer (phr) Peroxide DC40  7  7  7  7 crosslinking agent (phr) Rhenogran TAC  2  2  2  2 50% crosslinking coagent (phr)

[0467] The obtained elastomer compositions had the following properties.

TABLE-US-00007 TABLE 7 Shore A hardness of the elastomer compositions. Sample Hardness (Shore A) EPDM-E3 86 EPDM-E4 89 EPDM-E5 85 EPDM-CE1 81

TABLE-US-00008 TABLE 8 Effect on tear resistance in EPDM: Sample DELFT (MPa) EPDM-E3 35.4 EPDM-E4 34.8 EPDM-E5 30.9 EPDM-CE1 24.9

TABLE-US-00009 TABLE 9 Effect on air permeability in EPDM: Air permeability (m.sup.2 .Math. Pa.sup.−1 .Math. s.sup.−1)/ Sample 60° C. & 4 bars EPDM-E3 1.46E−16 EPDM-E4 1.47E−16 EPDM-E5 1.42E−16 EPDM-CE1 1.76E−16

Example Series 2: NBR Elastomer Compositions

[0468] The following elastomer compositions of Table 10 were obtained following the method described above. All elastomer compositions had an isovolumic amount of fillers. All fillers were coupled 50/50% with carbon black in volume. Therefore the carbon black reference batch contains 40 phr of N550. The other batches contain 20 phr of N550 and a slightly variable amount of mineral filler in function of its density, in order to have an amount of mineral filler equivalent to the volume of 20 phr of carbon black (indicated in Table 10 with an asterisk).

TABLE-US-00010 TABLE 10 NBR elastomer compositions. Example NBR-E3 NBR-E4 NBR-E5 NBR-CE1 NBR Perbunan P3445 100 100 100 100 from Arlanxeo (phr) Powder 3 (phr)  29* Powder 4 (phr)  28* Powder 5 (phr)  27* Powder CE1 (phr)  20  20  20  40 Diisononyl phthalate  5  5  5  5 plasticizer (phr) Peroxide DC40  7  7  7  7 crosslinking agent (phr) Rhenogran TAC 50%  2  2  2  2 crosslinking coagent (phr)

[0469] The obtained elastomer compositions had the following properties.

TABLE-US-00011 TABLE 11 Effect on Hardness in NBR elastomer compositions: Sample Hardness (Shore A) NBR-E3 72 NBR-E4 74 NBR-E5 74 NBR-CE1 69

TABLE-US-00012 TABLE 12 Effect on air permeability in NBR elastomer compositions: Air permeability (m.sup.2 .Math. Pa.sup.−1 .Math. s.sup.−1)/ Sample 60° C. & 4 bars NBR-E3 1.75E−17 NBR-E4 1.68E−17 NBR-E5 1.75E−17 NBR-CE1 1.97E−17

[0470] The examples show that the inventive fillers were able to reduce the air permeability of the inventive elastomer compositions. The effect is also observed, when the filler is not used in addition to another filler, but also when replacing part of the (carbon black) filler in the elastomer composition. At the same time, the inventive elastomer compositions exhibit an increased hardness, compared to an elastomer composition not containing the inventive filler. Thus, the use of the inventive fillers allows for improving the mechanical properties while at the same time reducing the gas permeability of an elastomer composition.

Examples Series 3: EPDM Elastomer Composition

Step 1—Internal Mixing

[0471] As a first step, each batch were mixed in a 2 L Banbury internal mixer. The temperature was set at 40° C. at the beginning of each mixing, during the process the temperature raised up to 150° C., depending on the filler being incorporated. The following process had been used for each batch (Table 13):

TABLE-US-00013 TABLE 13 Internal mixing procedure. Time Speed (min:s) Operation (rpm) t = 00:00 Introduction of EPDM 50 t = 00:50 Addition of the filler 50 t = 02:30 Addition of 2/3 of Powder CE1 50 t = 05:30 Addition of 1/3 of Powder CE1 + 50 paraffinic oil t = 06:30 Ram cleaning 50 t = 08:30 Dropping 50

Step 2—External Mixing

[0472] For the second step, mixing with the peroxide crosslinking agent was performed on a cylinder mixer (300×700). All the elastomer precursors were mixed with the same times, cylinder speeds, and cylinder spacing. The cooling system was set to 40° C. and the metal guides were set as to allow the elastomer precursor to occupy 70% of the cylinder surface. The detail proceedings for this process are described in Table 14 below.

TABLE-US-00014 TABLE 14 External mixing procedure. Time Cylinder (min:s) Operation Spacing (mm) t = 00:00 Introduction of the mix from Step 1 2.5 t = 01:30 Insertion of the crosslinking system 2.5 t = 06:00 3 thin passes 0.5 Calendering sheet, thickness 2 mm 2

Step 3—Compression Molding

[0473] Sheets of the elastomer composition were produced by compression molding at 180° C. and 200 bar pressure. This way, small 300×300×2 mm plates were made. The curing time, which determines the molding time, was determined through a rheological test in MDR. The T98 was taken as time of curing for the press plates. The fabrication of the compression set test specimens was done with the same procedure, meaning by compression molding. The curing time used was the addition of 10 min to the T98 as the thickness of these test specimens is higher than the press plates.

EPDM Elastomer Compositions

[0474] The following elastomer compositions of Table 15 were obtained following the method described above. All elastomer compositions had an isovolumic amount of fillers. All fillers were coupled 50/50% with carbon black in volume. Therefore the carbon black reference batch contains 100 phr of N550. The other batches contain 50 phr of N550 and a slightly variable amount of mineral filler in function of their density, in order to have an amount of mineral filler equivalent to the volume of 50 phr of carbon black (indicated in Table 15 with an asterisk).

TABLE-US-00015 TABLE 15 EPDM elastomer compositions Example EPDM-CE1 bis EPDM-CE2 EPDM-E6 EPDM-E8 EPDM-E9 EPDM-E10 EPDM-E11 EPDM Vistalon 2504N from 100 100 100 100 100 100 100 Exxon Mobil (phr) Carbon black - N550 100 50 50 50 50 50 50 (Powder CE1) Powder CE2 60.3* Powder 6 72.5* Powder 8 60.8* Powder 9 61.4* Powder 10 61.1* Powder 11 72.2* Torilis 6200 plasticizer (phr) 10 10 10 10 10 10 10 Peroxide DC40 crosslinking 7 7 7 7 7 7 7 agent (phr) Rhenogran TAC 50% 2 2 2 2 2 2 2 crosslinking coagent (phr)

[0475] The obtained elastomer compositions had the following properties.

TABLE-US-00016 TABLE 16 Shore A hardness of the elastomer compositions. Sample Hardness (Shore A) EPDM-CE1 bis 79.1 EPDM-CE2 70.8 EPDM-E6 82.9 EPDM-E8 83.1 EPDM-E9 81.4 EPDM-E10 80.4 EPDM-E11 82.2

[0476] It can be seen that the shore A hardness is improved with the inventive fillers.

TABLE-US-00017 TABLE 17 Effect on tensile modulus (M50—modulus at 50% elongation) Sample M50 (MPa) EPDM-CE1 bis 3.7 EPDM-CE2 1.9 EPDM-E6 4.5 EPDM-E8 4.4 EPDM-E9 3.5 EPDM-E10 4.2 EPDM-E11 3.7

[0477] Furthermore, the M50 modulus is maintained or improved with the inventive fillers.

TABLE-US-00018 TABLE 18 Effect on air permeability in EPDM: Air permeability (m.sup.2 .Math. Pa.sup.−1 .Math. s.sup.−1)/ Sample 60° C. & 4 bars EPDM-CE1 bis 1.88E−16 EPDM-CE2 2.07E−16 EPDM-E6 1.62E−16 EPDM-E8 1.52E−16 EPDM-E9 1.70E−16 EPDM-E10 1.62E−16 EPDM-E11 1.46E−16

[0478] All inventive fillers induce a lower air permeability into the elastomer compositions, compared to the comparative fillers.