Acrylic rubber composition containing filler combination of lignin-based filler and carbon black

Abstract

The present invention relates to a curable rubber composition comprising at least one acrylic rubber and / or at least one acrylic-based rubber, which is curable by means of at least one curing agent, at least one curing agent, which is suitable for curing said rubber, at least one lignin-based filler F1, which is different from carbon black, and which has an STSA surface area of up to 200 m² / g, and at least one filler F2, which is a carbon black, to a kit-of-parts comprising the constituents of said curable rubber composition in spatially separated form, a cured rubber composition obtainable from the curable rubber composition or the kit-of-parts, several used related to filler F1 being present in the curable rubber composition, a use of said composition, the kit-of-parts or the cured rubber composition for manufacturing articles, parts and / or components, said articles, parts and / or components per se, and processes for preparing them.

Description

[0001] Acrylic rubber composition containing filler combination of lignin-based filler and carbon black

[0002] The present invention relates to a curable rubber composition, a kit-of-parts comprising the constituents of said curable rubber composition in spatially separated form, a cured rubber composition obtainable from the curable rubber composition or the kit-of-parts, several used related to one of the fillers being present in the curable rubber composition, a use of said composition, of the kit-of-parts or of the cured rubber composition for manufacturing articles, parts and / or components, to said articles, parts and / or components per se, and to processes for preparing them.

[0003] Background of the invention

[0004] Acrylic or acrylic based rubbers are inter alia characterized by a high ozone resistance, an excellent thermal stability, and a very good heat resistance. Due to these properties, these materials are e.g. in particular frequently used in the automotive industry, where each of these properties as well as a lightweight construction plays an important role. Acrylic or acrylic based rubbers can be cured with different curing agents and / or systems, of which the most important and widely used one is the diamine curing. Acrylic or acrylic based rubbers, however, often have a relatively low viscosity, which results in a stickiness of these rubbers to the processing equipment, which is undesired in terms of processability of these materials and productivity of the process making use of them, e.g., when preparing vulcanizates thereof for the automotive industry.

[0005] The employment of fillers such as reinforcing fillers in rubber compositions such as in compositions comprising acrylic or acrylic based rubbers is known in the prior art. For example, the employment of reinforcing fillers increases the viscosity of the rubbers and improves the fracture behavior of the vulcanizates. Here, industrial carbon blacks represent the most commonly used reinforcing fillers. Industrial carbon blacks are produced by incomplete combustion of organic compounds or by thermal decomposition of hydrocarbons. Most of the industrial carbon blacks are produced by the furnace process. Because of the high amount of CO2 during the production process, it is desirable to avoid, or at least to reduce to a minimum, the use of fossil energy sources and of fossil raw materials for the production of such fillers. In addition, industrial carbon blacks may often not be usable for certain applications for color reasons, and, furthermore have a comparably high density, which is disadvantageous from the viewpoint of aiming at the aforementioned lightweight construction, e.g., in the automotive industry. Finally, conventional rubber compositions comprising acrylic or acrylic based rubbers as well as conventional fillers such as industrial carbon black not always exhibit sufficient compression sets, e.g., after ageing such as after ageing and having been in contact with hot air, which is undesired in terms of the lifetime of the products used.

[0006] Thus, there is a need to provide filler containing rubber compositions comprising acrylic and / or acrylic based rubbers, in particular for preparing vulcanizates thereof by means of curing said rubber compositions, which are suitable for use in the automotive industry, in which the amount of carbon black used as filler can be reduced for sustainability reasons, preferably without any negative impact as far as the mechanical properties of the resulting vulcanizates are concerned such as elongation at break, which furthermore have a reduced density compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers such that the vulcanizates thereof hence can be effectively used for lightweight construction of suitable articles, in particular in the automotive industry, which additionally exhibit excellent compression sets, e.g., after ageing such as after ageing and having been in contact with hot air, again compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers, and which do not show any stickiness or at least show a significantly reduced stickiness to the processing equipment used compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers, such that the processability of these materials and the productivity of the process making use of them is improved.

[0007] Problem

[0008] It has been therefore an objective underlying the present invention to provide filler containing rubber compositions comprising acrylic and / or acrylic based rubbers, in particular for preparing vulcanizates thereof by means of curing said rubber compositions, in which the amount of carbon black used as filler can be reduced for sustainability reasons, preferably without any negative impact as far as the mechanical properties of the resulting vulcanizates are concerned such as elongation at break, which furthermore have a reduced density compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers such that the vulcanizates thereof hence can be effectively used for lightweight construction of suitable articles, in particular in the automotive industry, which additionally exhibit excellent compression sets, in particular after hot air ageing, again compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers, and which do not show any stickiness or at least show a significantly reduced stickiness to the processing equipment used compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers, such that the processability of these materials and the productivity of the process making use of them is improved.

[0009] Solution

[0010] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. by the subject matter described herein.

[0011] A first subject-matter of the present invention is a curable rubber composition comprising at least one acrylic rubber and / or at least one acrylic-based rubber, which is curable by means of at least one curing agent, at least one curing agent, which is suitable for curing the at least one acrylic rubber and / or at least one acrylic-based rubber, at least one lignin-based filler F1 , which is different from carbon black, and which has an STSA surface area of up to 200 m2 / g, and at least one filler F2, which is a carbon black. A further subject-matter of the present invention is a kit-of-parts comprising, in spatially separated form, as part A) at least a part of a rubber composition according to the present invention, wherein part A) does, however, not comprise the at least one curing agent, optionally as part B) the remaining part of the rubber composition according to the present invention not being present in part A), wherein part B) does, however, not comprise the at least one curing agent, and as part C) at least the at least one curing agent as defined as constituent in connection with the curable rubber composition according to the present invention.

[0012] A further subject-matter of the present invention is a cured rubber composition, which is obtainable by curing the curable rubber composition according to the present invention, or by curing a curable rubber composition obtainable by combining and mixing parts A), optionally B) and C) of the kit of parts according to the present invention.

[0013] A further subject-matter of the present invention is a use of at least one filler F1 as defined in the context of the curable rubber composition according to the present invention, in particular when used in combination with at least one filler F2 as also defined in the context of the curable rubber composition according to the present invention, for improving the compression set of cured rubber compositions, preferably of the cured rubber composition according to the present invention, in particular including improving said compression set after ageing, preferably for simultaneously improving the compression set and at least one further physical property selected from density, elongation at break, tensile strength and hardness of cured rubber compositions, preferably of the cured rubber composition according to the present invention, and / or for reducing the stickiness of curable rubber compositions, preferably of a curable rubber composition according to the present invention.

[0014] A further subject-matter of the present invention is a use of the curable rubber composition according to the present invention, of the kit of parts according to the present invention, or of the cured rubber composition according to the present invention, for manufacturing articles, parts, and / or components, which preferably are suitable for use in the automotive, transportation, and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably are selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

[0015] A further subject-matter of the present invention is an article, part and / or component, which is in each case obtainable from the curable rubber composition according to the present invention, the kit-of-parts according to the present invention or from the cured rubber composition according to the present invention, and which preferably is suitable for use in the automotive, transportation, and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably is selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

[0016] A further subject-matter of the present invention is a process for preparing the article, part and / or component according to the present invention, wherein said process comprises at least one step, according to which the curable rubber composition according to the invention is shaped into the article, part and / or component, preferably before curing has been performed, by at least one of injection molding, compression molding, transfer molding, extrusion, coextrusion, extrusion coating, vacuum forming, melt spinning, electrospinning, laminating, and calendering.

[0017] It has been in particular surprisingly found that the rubber compositions according to the present invention comprising at least one acrylic rubber and / or at least one acrylicbased rubber such ACM and / or AEM can be efficiently subjected to curing by means of a suitable curing agent and that vulcanizates thereof can be produced, which in turn are suitable for use e.g. in the automotive industry. Further, it has been in particular surprisingly found that the rubber compositions according to the present invention allow the amount of carbon black used as filler and being present therein to be significantly reduced compared to conventional carbon black containing rubber compositions comprising acrylic or acrylic-based rubbers, which is advantageous in terms of sustainability. It has been found in this context that said reduction particularly does not have any negative impact as far as elongation of break of the resulting vulcanizates is concerned, to the contrary.

[0018] Moreover, it has been in particular surprisingly found that the rubber compositions according to the present invention and the vulcanizates obtainable therefrom have a reduced density compared to conventional filler containing rubber compositions comprising acrylic and / or acrylic-based rubbers such that the vulcanizates thereof hence can be effectively used for lightweight construction, in particular in the automotive industry. It has been found that this can be achieved by partial replacement of carbon black by filler F1 .

[0019] In addition, it has been in particular surprisingly found that the rubber compositions according to the present invention and the vulcanizates obtainable therefrom exhibit excellent compression sets, e.g., after ageing such as after ageing and having been in contact with hot air, in particular when compared to conventional filler containing rubber compositions comprising acrylic or acrylic based rubbers. It has been found that this can be achieved by partial replacement of carbon black by filler F1 .

[0020] Finally, it has been in particular surprisingly found that the rubber compositions according to the present invention do not show any stickiness or at least show a significantly reduced stickiness to the processing equipment used compared to conventional filler containing rubber compositions comprising acrylic or acrylic-based rubbers, such that the processability of these materials and the productivity of the process making use of them is advantageously improved. It has been found that this can be achieved by partial replacement of carbon black by filler F1 . Detailed description of the invention

[0021] The term “comprising” as used in the present invention in connection with, for example, the curable rubber composition according to the invention preferably has the meaning “consisting of.” In this context, for example, with regard to the curable rubber composition according to the invention, one or more of the further constituents optionally contained that are mentioned hereinafter may also be contained therein in addition to the constituents mandatorily present therein. All constituents may be present in each of their preferred embodiments mentioned hereinafter.

[0022] The amount of all constituents described herein, such as the constituents contained in the curable rubber compositions according to the invention (comprising in each case all the mandatory constituents and, moreover, all the optional constituents), add up in total to 100% by weight in each case.

[0023] Curable rubber composition

[0024] Acrylic rubber and / or at least one acrylic-based rubber

[0025] The at least one acrylic rubber and / or at least one acrylic-based rubber is curable by means of at least one curing agent.

[0026] Acrylic rubbers and acrylic-based rubbers are known by a person skilled in the art. The term “acrylic” includes “acrylic” and / or “methacrylic”, preferably means, however, only acrylic. Similarly, “acrylate” means “acrylate” and / or “methacrylate”, but preferably only means “acrylate”. An acrylic rubber and an acrylic-based rubber both are formed at least partially from “acrylic monomers” and / or “methacrylic monomers”, preferably at least partially from “acrylic monomers”.

[0027] Acrylic rubbers in the sense of the present invention preferably are acrylic rubbers, which are obtainable solely from monomers, which are acrylic monomers. Examples thereof are some kinds of ACM rubbers. Acrylic-based rubbers in the sense of the present invention preferably are acrylic rubbers, which are obtainable from both at least one monomer, which is an acrylic monomer, and at least one co-monomer, which is an ethylenically unsaturated monomer such as a vinylic monomer, but which is not an acrylic monomer. Examples thereof are some ACM rubbers as well as AEM rubbers (ethylene acrylate rubbers).

[0028] Preferably, the at least one acrylic rubber and / or at least one acrylic-based rubber is selected from acrylic copolymers, more preferably from acrylic copolymers, wherein at least one acrylic monomer and at least one co-monomer being different therefrom and being either also an acrylic monomer or an ethylenically unsaturated monomer such as a vinylic monomer, which is not an acrylic monomer, have been used for the preparation of said acrylic copolymer, even more preferably from acrylic copolymers, wherein at least one acrylic ester of an aliphatic Ci-Cso-monoalcohol as at least one acrylic monomer and at least one co-monomer being different therefrom and being either also an acrylic ester of an aliphatic Ci-Cso-monoalcohol or an ethylenically unsaturated monomer such as a vinylic monomer, have been used for the preparation of said acrylic copolymer.

[0029] Suitable acrylic monomers for preparing the at least one acrylic rubber and / or at least one acrylic-based rubber are preferably non-functionalized acrylic esters of aliphatic Ci-C3o-monoalcohols. Examples of suitable monomers are methyl acrylate, methyl (meth)acrylate, ethyl acrylate, ethyl (meth)acrylate, n-propyl acrylate, n-propyl (meth)acrylate, i-propyl acrylate, i-propyl (meth)acrylate, n-butyl acrylate, n-butyl (meth)acrylate, i-butyl acrylate, i-butyl (meth)acrylate, t-butyl acrylate, t-butyl (meth)acrylate, methoxyethyl acrylate, methoxyethyl (meth)acrylate, ethoxyethyl acrylate and ethoxyethyl (meth)acrylate. Such monomers are, e.g., used for preparation of ACM rubbers and AEM rubbers.

[0030] Suitable co-monomers, which can be used for preparing the at least one acrylic-based rubber, preferably are non-functionalized ethylenically unsaturated monomers such as vinylic monomers, which are not acrylic monomers. Examples of such suitable comonomers are ethylene and propylene as well as styrene. Ethylene is, e.g., necessarily used for preparing ethylene acrylate rubbers (AEM). AEM rubbers are copolymers obtainable from ethylene and at least one acrylic monomer such as methyl acrylate. Optionally, additionally at least one suitable acid functional monomer such as at least one monomer bearing a carboxylic acid group such as acrylic acid is additionally used for the preparation of AEM rubbers. Optionally, at least one of the monomers used for preparing the at least one acrylic rubber and / or at least one acrylic-based rubber, such as at least one acrylic monomer and / or at least one ethylenically unsaturated monomer such as a vinylic monomer, which is not an acrylic monomer, comprises at least one functional group, preferably at least one functional group selected from carboxylic acid groups, hydroxy groups, epoxide groups and halogen atoms such as chlorine atoms. It is also possible to use suitable precursor monomers and to generate the at least one functional group in a polymer analogous reaction after preparation of the acrylic rubber and / or the acrylicbased rubber. For example, OH-groups can be generated from epoxide groups via a ring-opening reaction. Preferably, monomers having at least one aforementioned functional group are used in an amount in a range of from 0 or 1 .0 to 10.0 wt.-%, based on the total weight of all monomers used for preparing the acrylic and / or acrylic-based rubbers.

[0031] Suitable acrylic monomers for preparing the at least one acrylic rubber and / or at least one acrylic-based rubber, which bear at least one functional group, such as at least one functional group selected from carboxylic acid groups, hydroxy groups, epoxide groups and halogen atoms such as chlorine atoms, are 2-hydroxyethyl acrylate, 2- hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, acrylic acid, methacrylic acid, glycidyl methacrylate, and glycidyl acrylate.

[0032] Suitable ethylenically unsaturated monomers for preparing the at least one acrylicbased rubber, which bear at least one functional group, such as at least one functional group selected from carboxylic acid groups, hydroxy groups, epoxide groups and halogen atoms such as chlorine atoms, but which are not acrylic monomers, are 2- chlorovinyl ether, vinyl chloroacetate, allyl glycidyl ether, and allyl alcohol.

[0033] The polymerization of the monomers used for preparing acrylic rubbers and / or acrylicbased rubbers preferably is performed radically or anionically, more preferably radically, such as by free-radical emulsion polymerization. Suitable initiators such as persulphates, peroxides and / or azo compounds can be used. Preferably, at least one emulsifier is used as well such as at least one Cs to C24 alkyl sulphonate, e.g., to prevent hydrolysis of the ester bonds of the acrylic monomers used. The average molecular weight of the acrylic rubber and / or at the acrylic-based rubber preferably is controlled and / or adjusted by the amount of the at least one initiator used.

[0034] Curing agent

[0035] The at least one curing agent is suitable for curing the at least one acrylic rubber and / or at least one acrylic-based rubber.

[0036] Preferably, the at least one curing agent is present in the composition in an amount in a range of from 0.1 to 15 phr, more preferably of from 0.2 to 10 phr, even more preferably of from 0.5 to 7.5 phr, still more preferably of from 0.7 to 5 phr.

[0037] The phr (parts per hundred parts of rubber by weight) specification used herein is the quantity specification commonly used in the rubber industry for rubber compositions. The dosage of the parts by weight of the individual constituents is always based on 100 parts by weight of the total mass of all rubbers present in the composition.

[0038] A person skilled in the art is aware of suitable curing agents that can be used for curing acrylic rubbers and / or acrylic-based rubbers. The selection of the curing agent inter alia depends on the type of the desired application and / or the type of the acrylic rubber and / or acrylic-based rubber used, e.g., with respect to whether it bears functional groups or not and what kind of functional groups.

[0039] Preferably, the at least one curing agent is selected (i) from amines and / or amine derivatives, more preferably from diamines and / or diamine derivatives, still more preferably from organic diamines and / or organic diamine derivatives, yet more preferably from aliphatic and / or aromatic diamines and / or diamine derivatives, most preferably from aliphatic diamines and / or diamine derivatives, (ii) alkali metal and / or earth alkali metal soaps, more preferably alkali metal and / or earth alkali metal salt of at least one fatty acid, wherein said alkali metal and / or earth alkali metal soaps are optionally used in combination with sulfur and / or at least one sulfur donor, (iii) quaternary ammonium salts, more preferably quaternary ammonium salts of at least one fatty acid, wherein said quaternary ammonium salts are optionally used in combination with sulfur and / or at least one sulfur donor, (iv) carboxylic acids and / or carboxylic acid derivatives, preferably dicarboxylic acids and / or dicarboxylic acid derivatives, (v), peroxide curing agents, and (vi) mixtures of any of (i) to (v). Examples of peroxide curing agents are organic peroxides such as dialkyl peroxides, alkyl aryl peroxides, diaryl peroxides, alkyl peracid esters, aryl peracid esters, diacyl peroxides, polyvalent peroxides, and mixtures thereof. Specific examples of organic peroxides are di-tert. butyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane, dicumyl peroxide, tert-butylcumyl peroxide, tert-butyl peroxybenzoate, dibenzoyl peroxide, 1 ,1 -di(tert- butyl peroxy)-3,3,5-trimethylcyclohexane and bis-(tert-butyl peroxy)- diisopropylbenzene and mixtures thereof.

[0040] Curing agents (i) and / or (ii) are particularly suitable for curing acrylic rubbers and / or acrylic-based rubbers, which comprise halogen atoms such as chlorine atoms, e.g., when at least one of 2-chlorovinyl ether and / or vinyl chloroacetate has been used for their preparation.

[0041] If sulfur and / or at least one sulfur donor is present in curing agents (ii) and / or (iii), preferably the relative weight ratio of alkali metal and / or earth alkali metal soaps in case of (ii) and of quaternary ammonium salts in case of (iii) to sulfur / sulfur donor is at least 5:1 , more preferably at least 10:1. Typically, elemental sulfur in the form of Ss rings is used for curing by means of sulfur. The Ss ring is either opened thermically or by alkaline substances. The sulfur may be present in the curable rubber composition as soluble or insoluble sulfur. As an alternative or in addition to elemental sulfur, at least one sulfur donor may be employed. In this case, sulfur is released from such sulfur donors during curing only. Examples for sulfur donors are sulfur-containing chemical compounds such as 4.4‘-dithiomorpholine (DTDM) and tetramethyl thiuram disulfide (TMTD).

[0042] Curing agents (ii) and / or (iii) and / or (iv) are particularly suitable for curing acrylic rubbers and / or acrylic-based rubbers, which comprise epoxide groups, e.g., when at least one of allyl glycidyl ether and / or glycidyl acrylate has been used for their preparation.

[0043] Curing agents (i) and / or (iv) are particularly suitable for curing acrylic rubbers and / or acrylic-based rubbers, which comprise acid groups such as carboxylic acid groups, e.g., when acrylic acid has been used for their preparation. Amines in the sense of the present invention are preferably compounds, which comprise at least one amino group, more preferably at least one primary amino group. Amine derivatives in the sense of the present invention are preferably compounds, from which amines such as diamines can be released under curing conditions. Diamines in the sense of the present invention are preferably compounds, which comprise at least two amino groups, more preferably at least two primary amino groups and / or at least one primary and at least one secondary amino group.

[0044] Examples of suitable amines are diamines as well as amines selected from guanidines, biguanidines such as OTBG (o-tolylbiguanidine), DOTG (di-o-tolylguanidin) and DPG (diphenyl guanidine). Examples of suitable diamines are alkylene diamines such as Ci to Cs alkylene diamines. A more specific example is methylene diamine, which is particularly a suitable curing agent for AEM rubbers. Another specific example is hexamethylenediamine. An example of a diamine derivative is hexamethylenediamine carbamate (HMDA), in which one amino group has been transferred into a carbamate group. Under curing conditions, a diamine, namely hexamethylenediamine, can be generated therefrom.

[0045] Examples of alkali metal and / or earth alkali metal soaps are sodium and / or potassium stearate. An example of a quaternary ammonium salt is ammonium adipate benzoate.

[0046] Dicarboxylic acid derivatives in the sense of the present invention are preferably compounds, from which dicarboxylic acids can be released under curing conditions.

[0047] Optionally present curing accelerator

[0048] Optionally, at least one curing accelerator is present in the composition, which is different from the at least one curing agent. The proportion of the at least one accelerator in the curable rubber composition according to the invention preferably is 0 or 0.1 to 10 phr, more preferably 0 or 0.2 to 8 phr, even more preferably 0 or 0.2 to 6 phr, most preferably 0 or 0.2 to 3 phr. Example of curing accelerators are tertiary amines such as DBU (1 ,8- diazabicyclo[5.4.0]undecene-7) and DABCO. DBU is in particular preferred. Such tertiary amines may be optionally absorbed on a suitable carrier such as a silica carrier.

[0049] Optionally present additional additive

[0050] Optionally, at least one additional additive present in the composition, which is different from the at least one curing agent and the optionally present curing accelerator. The proportion of said at least one additive in the curable rubber composition according to the invention preferably is 0 or 0.1 to 10 phr, more preferably is 0 or 0.5 to 8 phr, and most preferably is 0 or 1 to 5 phr.

[0051] Such additives include, for example, saturated fatty acids with preferably 12 to 24, more preferably 14 to 20 and most preferably 16 to 18 carbon atoms, such as stearic acid and the zinc salts of the aforementioned fatty acids, as well as zinc oxide.

[0052] Lignin-based filler F1

[0053] The at least one lignin-based filler F1 is different from carbon black and has an STSA surface area of up to 200 m2 / g. The method for the determination of the STSA surface area (statistical thickness surface area) is disclosed in the ‘methods’ section hereinafter.

[0054] The terms filler and organic filler are known to a person skilled in the art. Preferably, the filler F1 employed according to the invention is a reinforcing filler, i.e. , an active filler. Reinforcing or active fillers are characterized by a higher specific surface area than inactive fillers and, in contrast to inactive (non-reinforcing) fillers, they can change the viscoelastic properties of a rubber by interacting with the rubber within a rubber composition.

[0055] Preferably, the least one filler F1 has an STSA surface area in a range of from 2.5 to 200 m2 / g, more preferably of from 5.0 to <200 m2 / g, even more preferably of from 7.5 to 175 m2 / g, still more preferably of from 10.0 to 150 m2 / g.

[0056] Preferably, the least one filler F1 has a BET surface area of up to 200 m2 / g. More preferably, the least one filler F1 has a BET surface area in a range of from 3.0 to 200 m2 / g, more preferably of from 6.0 to <200 m2 / g, even more preferably of from 8.0 to 175 m2 / g, still more preferably of from 12.0 to 150 m2 / g. The method for the determination of the BET surface area (specific total surface area according to Brunauer, Emmett and Teller) is disclosed in the ‘methods’ section hereinafter.

[0057] Preferably, the least one filler F1 has a d99 value of <25 pm, more preferably <20 pm, even more preferably <18 pm, still more preferably <15 pm, yet more preferably <10 pm. The method for the determination of the d99 value is described hereinbelow in the ‘methods’ section and is carried out by means of laser diffraction according to ISO 13320:2009.

[0058] Preferably, the least one filler F1 has a weight average molecular weight in a range of from 1000 to 4000 Da, more preferably of from 1300 to 3700 Da, even more preferably of from 1700 to 3200 Da, yet more preferably of from 2500 to 3000 Da, still more preferably of from 2600 to 2900 Da, most preferably of from 2650 to 2850 Da, in each case when determined based on the soluble fraction of the filler F1. The method for the determination of the weight average molecular weight is described hereinbelow in the ‘methods’ section.

[0059] Preferably, the least one filler F1 has a polydispersity index (PDI) in a range of from 1 .5 to 5.0, more preferably of from 1 .8 to 4.5, even more preferably of from 1 .9 to 4.3, still more preferably of from 2.1 to 4.0, yet more preferably of from 2.4 to 3.5, most preferably of from 2.6 to 3.2, when determined based on the soluble fraction of the lignin-based filler. The polydispersity index can be determined by the same method used for determining the weight average molecular weight. The PDI is calculated as the weight average molecular weight divided by the number average molecular weight.

[0060] Preferably, the at least one filler F1 has an ash content in a range of from 0.1 to 3.0 wt.-%, more preferably of from 0.1 to 2.5 wt.-%, even more preferably of from 0.2 to 2.0 wt.-%, still more preferably of from 0.3 to 1 .5 wt.-%, yet more preferably of from 0.4 to 1 .0 wt.-%.

[0061] Preferably, the at least one filler F1 has a solubility in 0.1 M NaOH in a range of from

[0062] 1 to 40 wt.-%, more preferably of from 3 to 35 wt.-%, even more preferably of from 5 to 30 wt.-%. The method for the determination of the solubility is disclosed in the ‘methods’ section hereinafter.

[0063] Preferably, the at least one filler F1 has a density of at most 1.50 g / cm3More preferably, the at least one filler F1 has a density of 1.00 to 1.50 g / cm3, even more preferably of 1 .15 to 1 .35 g / cm3, still more preferably of 1 .10 to 1 .40 g / cm3. The method for the determination of the density is disclosed in the ‘methods’ section hereinafter.

[0064] Preferably, the least one filler F1 has a carbon content in a range from >60% by weight to <90% by weight, more preferably from >60% by weight to <85% by weight, even more preferably from >60% by weight to <80% by weight. The method for the determination of the carbon content is disclosed in the ‘methods’ section hereinafter.

[0065] Preferably, the at least one filler F1 has an oxygen content in a range from >8% by weight to <30% by weight, more preferably from >10% by weight to <30% by weight, even more preferably from >15% by weight to <30% by weight, relative to the ash-free and water-free filler, respectively. The oxygen content can be determined by high- temperature pyrolysis, for example using the EuroEA3000 CHNS-0 Analyzer of the company EuroVector S.p.A.

[0066] Preferably, the at least one filler F1 has at least one kind of functional groups that is selected from phenolic OH groups, phenolate groups, aliphatic OH groups, carboxylic acid groups, carboxylate groups and mixtures thereof.

[0067] Preferably, the at least one filler F1 has a pH value in a range from 6 to 10, more preferably in a range of from 6 to 9, even more preferably in a range from 7 to 9, still more preferably in a range from 7 to <9.

[0068] The term “lignin-based” in the sense of the present invention preferably means that one or more lignin moieties and / or one or more lignin scaffolds are present in the filler F1. Lignins are solid biopolymers that are incorporated into plant cell walls and thus effect the lignification of plant cells. As such, they are present in biomass and in particular in biologically renewable raw materials, and they therefore represent - in particular in hydrothermally treated form - an environmentally friendly filler alternative compared to fillers such as carbon blacks that are obtainable from fossil materials.

[0069] The term “lignin-based filler” in the sense of the present invention preferably means that that the filler F1 is present in a form that is obtainable by means of hydrothermal treatment of at least one kind of lignin-containing biomass such as at least one kind of lignin-containing phytomass, wherein the hydrothermal treatment preferably has been carried out at a temperature in a range from >100 °C to <300 °C, more preferably from >150 °C to <250 °C.

[0070] Suitable processes for hydrothermal treatment, in particular of lignins, are, e.g., described in WO 2017 / 085278 A1 and WO 2017 / 194346 A1 as well as in EP 3 470 457 A1 . Hydrothermal treatment in the sense of the present invention preferably means a hydrothermal carbonization (HTC), which in turn may also be referred to as "aqueous carbonization at elevated temperature and pressure". Hydrothermal treatment preferably refers to a hydrothermal carbonization treatment of a lignin-containing material, which is a thermochemical conversion process of the lignin-containing material in an aqueous suspension. The lignin-containing material preferably is selected from a group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitated lignin, biomass originating lignin, lignin from alkaline pulping process, lignin from soda process, lignin from organosolv pulping, lignin from alkali process, lignin from enzymatic hydrolysis process, and any combination thereof. Preferably, the lignin is wood based lignin, which can originate from softwood and / or hardwood, and / or originates from annual plants or from any combination thereof.

[0071] "Kraft lignin" is to be understood to be originated from kraft black liquor, which is an alkaline aqueous solution of lignin residues, hemicellulose, and inorganic chemicals used in a kraft pulping process. The black liquor from the pulping process comprises components originating from different softwood and hardwood species in various proportions. Lignin can be separated from the black liquor by different techniques including precipitation and filtration. The precipitated lignin can be purified from inorganic impurities, hemicellulose and wood extractives using acidic washing steps. Further purification can be achieved by filtration. "Flash precipitated lignin" is to be understood as lignin that has been precipitated from black liquor in a continuous process by decreasing the pH of a black liquor flow, under the influence of an over pressure of 200 to 1000 kPa, down to the precipitation level of lignin using a carbon dioxide based acidifying agent, preferably carbon dioxide, and by suddenly releasing the pressure for precipitating lignin. The lignin may be derived from an alkali process. The “alkali process” can begin with liquidizing biomass with strong alkali followed by a neutralization process. After the alkali treatment, the lignin can be precipitated in a similar manner as presented above. The lignin may be derived from steam explosion. Steam explosion is a pulping and extraction technique that can be applied to wood and other fibrous organic material. "Biorefinery lignin" is to be understood to mean lignin that can be recovered from a refining facility or process where biomass is converted into fuel, chemicals, and other materials. "Supercritical separation lignin" is to be understood that lignin that can be recovered from biomass using supercritical fluid separation or extraction technique. The lignin may be derived from a “hydrolysis process”. The lignin derived from the hydrolysis process can be recovered from paperpulp or wood-chemical processes. The lignin may originate from an “organosolv process”. Organosolv is a pulping technique that uses an organic solvent to solubilize lignin and hemicellulose. “Enzymatic hydrolysis processes” are to be understood to comprise enzymatic hydrolysis of a plant-based feedstock, such as a wood-based feedstock such as enzymatic hydrolysis of cellulose. Enzymatic hydrolysis is a process, wherein enzyme (s) assist (s) in cleaving bonds in molecules with the addition of elements of water.

[0072] The lignin-containing material may be dissolved in alkaline solution first, prior to the hydrothermal treatment, such as NaOH. The dissolution may be accomplished by heating the mixture of lignin and alkaline solution to about 80 °C, adjusting the pH to a value above 7, such as 9 - 11 , and mixing the mixture of lignin and alkaline solution for a predetermined time. The mixing time may be continued for about 2 to 3 hours. The dissolved lignin material may then be subjected to a hydrothermal treatment such as a hydrothermal carbonization treatment. The hydrothermal carbonization treatment may take place in a reactor or if needed in several parallel reactors, working in a batchwise manner. The dissolved lignin material may be preheated before being entered in the reactor (s). The temperature in the reactor(s) may be 150 to 300 °C or to 250 °C and the pressure may be 20 to 30 bar. The residence time in the reactor(s) may be about three to six hours. In the reactor, the lignin is carbonized, whereby a stabilized lignin derivative with a high specific surface area may be precipitated. The formed slurry comprising the carbonized lignin may then be removed and cooled. Consequently, a slurry comprising lignin-based filler F1 is formed. The slurry comprising lignin-based filler F1 may be fed to a separation unit such as a filter press, wherein the precipitated lignin-based filler F1 may be separated from the slurry, e.g., in form of a filter cake. The separated lignin-based filler F1 , which may be present in form of a filter cake, may be crushed and dried. Before crushing drying, the lignin-based filler F1 may be, if needed, washed. The crushed lignin particles may be dried and used as such as the lignin-based filler. However, preferably after drying the lignin particles obtained are subsequently subjected to a milling step in order to obtain lignin particles with smaller particle sizes.

[0073] Optionally, the starting material used for the hydrothermal treatment, i.e. , the lignincontaining material, can be reacted with at least one crosslinker before the hydrothermal treatment is carried out. The crosslinker preferably has at least one functional group which can react with the crosslinkable groups of the lignin. Preferably, the crosslinker has at least one functional group selected from aldehyde, carboxylic acid anhydride, epoxide, hydroxyl and isocyanate groups or a combination thereof. Preferably, the crosslinker is selected from aldehydes, epoxides, acid anhydrides, polyisocyanates and / or polyols, in particular from aldehydes such as formaldehyde, furfural and / or sugar aldehydes. The crosslinker can react with free ortho and para positions of the phenolic rings, with aromatic and aliphatic OH groups, and / or with carboxyl groups of the lignin.

[0074] Biomass as defined herein is any biomass, wherein the term “biomass” herein includes phytomass, i.e., biomass originating from plants, zoomass, i.e., biomass originating from animals, and microbial biomass, i.e., biomass originating from microorganisms including fungi. The biomass particularly preferred herein for the production of the fillers is phytomass, preferably dead phytomass.

[0075] Preferably, the at least one filler F1 has a14C content in a range from 0.20 to 0.45 Bq / g of carbon, more preferably of from 0.23 to 0.42 Bg / g of carbon. The required14C content cited above is achieved by organic fillers obtainable from biomass. Thus, fillers obtained from fossil materials, such as fossil fuels in particular, do not have a corresponding14C content. For example, when filler F2 is a carbon black obtainable from fossil materials, it does not have a corresponding14C content.

[0076] Preferably, the least one filler F1 is present in the composition in an amount in a range of from 0.25 to 150 phr, more preferably of from 0.75 to 125 phr, even more preferably of from 1.00 to 100 phr, still more preferably of from 1.50 to 85 phr, yet more preferably of from 1 .75 to 70 phr, most preferably of from 2.0 to 60 phr.

[0077] Preferably, the least one filler F1 is present in the composition in an amount that exceeds the amount of the at least one filler F2.

[0078] Preferably, the relative weight ratio of the at least one filler F1 to the at least one filler F2 is in a range of from to 600:1 to 1 :600, more preferably of from 300:1 to 1 :300, even more preferably of from 150:1 to 1 :150, still more preferably of from 100:1 to 1 :100, yet more preferably of from 50:1 to 1 :50, still more preferably of from 40:1 to 1 :40, even more preferably of from 30: 1 to 1 :30, yet more preferably of from 25: 1 to 1 :25 or to 1 : 1 , still more preferably of from 20: 1 to 1 :20 or to 1 .1 :1 , yet more preferably of from 15:1 to 1 :15 or to >1.1 :1.

[0079] Filler F2

[0080] The at least one filler F2 is different from filler F1 and is a carbon black.

[0081] The carbon black can be a carbon black obtainable from biomass and / or renewable and / or recycled raw materials, but may also be an industrial carbon black obtainable from fossil materials such as particular a furnace carbon black, as classified as general- purpose carbon blacks under ASTM Code N660 or under ASTM Code N550.

[0082] A person skilled in the art is aware that carbon blacks have a high carbon content of at least 95 wt.-%, based on the total weight of the filler. The same applies to filler F2, which hence preferably has a higher carbon content than filler F1 .

[0083] Preferably, the least one filler F2 has an STSA surface area of up to 200 m2 / g, more preferably in a range of from 2.5 to 200 m2 / g, even more preferably of from 5.0 to <200 m2 / g, yet more preferably of from 7.5 to 175 m2 / g, still more preferably of from 10.0 to 150 m2 / g.

[0084] Preferably, the least one filler F2 is present in the composition in an amount in a range of from 0.25 to 150 phr, more preferably of from 0.75 to 125 phr, still more preferably of from 1.00 to 100 phr, even more preferably of from 1.50 to 85 phr, yet more preferably of from 1 .75 to 70 phr, most preferably of from 2.0 to 60 phr.

[0085] Optional filler F3

[0086] The composition may further contain at least one further filler F3, which is different from both fillers F1 and F2 and preferably is, if present, at least one inorganic filler and / or an organic filler. Examples of inorganic fillers are phyllosilicates such as clay minerals, for example talc, carbonates such as calcium carbonate, silicates such as for example calcium, magnesium, and aluminum silicates, and oxides such as for example magnesium oxide, silica including, e.g., rice husk silica, and or silicic acid.

[0087] Examples of organic fillers F3 different from filler F1 and filler F2 are organic fillers, which are different from lignin-based filler F1 , but which are also obtainable from biomass and / or renewable and / or recycled raw materials, for example by means of hydrothermal treatment.

[0088] Further optional constituents

[0089] The rubber composition may optionally contain at least one organosilane, which has at least one hydrolysable group and which preferably further has at least one sulfur atom. Examples are 4-mercaptobutyltrialkoxysilane and / or 6- mercaptohexyltrialkoxysilane and / or 3-mercaptopropyltrialkoxysilane, wherein alkoxy groups preferably mean, independently from one another, methoxy or ethoxy groups. Further examples are bis(dimethylethoxysilylpropyl)tetrasulfide (DMESPT), bis(dimethylethoxysilylpropyl)-disulfide (DMESPD), bis(triethoxysilylpropyl)tetrasulfide (TESPT), bis(triethoxysilylpropyl)disulfide (TESPD) and mixtures thereof. If such an organosilane is present, it is preferably contained in the rubber composition in a quantity that preferably lies in a range from 0.25 to 10 phr, more preferably from 0.25 to 7.5 phr, even more preferably from 0.5 to 5 phr. The rubber composition may contain further optional constituents, such as plasticizers / softening agents and / or antidegradants and / or retarding agents and / or light stabilizing additives and / or pigments and / or processing aid additives.

[0090] Kit-of-parts

[0091] A further subject-matter of the present invention is a kit-of-parts comprising, in spatially separated form, as part A) at least a part of a rubber composition according to the present invention, wherein part A) does, however, not comprise the at least one curing agent, optionally as part B) the remaining part of the rubber composition according to the present invention not being present in part A), wherein part B) does, however, not comprise the at least one curing agent, and as part C) at least the at least one curing agent as defined as constituent in connection with the curable rubber composition according to the present invention.

[0092] Thus, part A) is not yet curable as such, and thus at this point of time represents a rubber composition that is not yet curable by means at the at least one curing agent. The same applies to optionally present part B). The curing is only possible after mixing the parts A) and optionally B) with C).

[0093] Preferably, rubber(s) and filler(s) of the rubber composition on the one hand and the at least one curing agent on the other hand are spatially separated from each other in the kit of parts and can thus be stored. The kit of parts serves for the preparation of a curable rubber composition. Thus, for example, the rubber composition constituting the one part of the kit of parts comprising rubber(s) and filler(s) and optionally other constituents, including, e.g., at least one fatty acid such as stearic acid, can be employed as part A) in a first stage for preparing the curable rubber composition, and the second part of the kit of parts, namely part C), comprising the at least one curing agent, can be employed in a second stage of said process. For example, it is possible that part A) comprises the complete rubber composition according to the present invention except of the curing agent. In this case, part B) is not needed. It is also possible that part A) comprises only part of the rubber composition according to the present invention except of the curing agent, e.g., only part of fillers F1 and / or F2 and / or only part of the at least one acrylic or acrylic-based rubber. Another rubber different from said rubber and / or the remaining part of the at least one acrylic or acrylic-based rubber not present in part A) and / or another filler F3 being different from fillers F1 and F2 and / or the remaining part of filler(s) F1 and / or F2 and / or optionally further constituents can then be used as part B).

[0094] All preferred embodiments described hereinabove in connection with the curable rubber composition according to the invention are also preferred embodiments with regard to the kit of parts according to the invention.

[0095] Cured rubber composition

[0096] A further subject-matter of the present invention is a cured rubber composition, which is obtainable by curing the curable rubber composition according to the present invention, or by curing a curable rubber composition obtainable by combining and mixing both A), optionally B) and C) of the kit of parts according to the present invention.

[0097] All preferred embodiments described hereinabove in connection with the curable rubber composition and the kit-of-parts according to the invention are also preferred embodiments with regard to the cured rubber composition according to the invention.

[0098] The preparation of the cured rubber composition according to the invention is carried out preferably in two stages, i.e. , stages 1 and 2. In the first stage (stage 1 ), a rubber composition as a base mixture (masterbatch) is prepared first, by mixing all constituents employed for the preparation of the rubber composition according to the invention with each other, but at least without the at least one curing agent. In the second stage (stage 2), the at least one curing agent, and optionally additional constituents such as optionally present curing accelerator(s), are admixed to the rubber composition obtained after stage 1 . Alternatively, the preparation of the cured rubber composition according to the invention is carried out preferably in one mixing stage only, wherein all parts of the rubber composition including the curing agent are mixed with each other. For example, said stage can be performed for example in that at first the at least one acrylic and / or acrylic-based rubber is added into a suitable mixing chamber and mixed, followed by addition of only part of the remaining constituents of the composition such as only 50 wt.-% of all remaining constituents including the curing agent, and by then, after mixing, adding the remaining part of all constituents followed by further mixing.

[0099] Before curing, the curable rubber compositions thus prepared may go through processes that are preferably customized or tailored for the final articles. The rubber compositions may be formed into a suitable shape as required for the curing process, preferably by extrusion, compression molding, transfer molding, injection molding or calendering. Curing may be carried out in vulcanization molds by means of pressure and temperature, or the curing is carried out without pressure in temperature-controlled channels in which air or liquid materials provide heat transfer, or the curing is performed in an autoclave.

[0100] Uses of filler F1

[0101] A further subject-matter of the present invention is a use of at least one inventively used filler F1 as defined in the context of the curable rubber composition according to the present invention, in particular when used in combination with at least one filler F2 as also defined in the context of the curable rubber composition according to the present invention, for improving the compression set of cured rubber compositions, preferably of the cured rubber composition according to the present invention, in particular including improving said compression set after ageing, preferably for simultaneously improving the compression set and at least one further physical property selected from density, elongation at break, tensile strength and hardness of cured rubber compositions, preferably of the cured rubber composition according to the present invention, and / or for reducing the stickiness of curable rubber compositions, preferably of a curable rubber composition according to the present invention. All preferred embodiments described hereinabove in connection with the curable rubber composition and the kit-of-parts according to the invention and the cured rubber composition according to the invention are also preferred embodiments with regard to the aforementioned uses related to filler F1 according to the invention.

[0102] Uses of curable and cured composition and of kit-of-parts

[0103] A further subject-matter of the present invention is a use of the curable rubber composition according to the present invention, of the kit of parts according to the present invention, or of the cured rubber composition according to the present invention, for manufacturing articles, parts and / or components, which preferably are suitable for use in the automotive, transportation, and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably are selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

[0104] All preferred embodiments described hereinabove in connection with the curable rubber composition and the kit-of-parts according to the invention and the cured rubber composition according to the invention and the aforementioned uses related to filler F1 according to the invention are also preferred embodiments with regard to the aforementioned use according to the invention.

[0105] Article, part and / or component

[0106] A further subject-matter of the present invention is an article, part and / or component, which is in each case obtainable from the curable rubber composition according to the present invention, the kit-of-parts according to the present invention or from the cured rubber composition according to the present invention, and which preferably is suitable for use in the automotive, transportation, and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably is selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

[0107] All preferred embodiments described hereinabove in connection with the curable rubber composition and the kit-of-parts according to the invention and the cured rubber composition according to the invention and the aforementioned uses related to filler F1 according to the invention and the further aforementioned uses according to the invention are also preferred embodiments with regard to the article, part and / or component according to the invention.

[0108] Process

[0109] A further subject-matter of the present invention is a process for preparing the article, part and / or component according to the present invention, wherein said process comprises at least one step, according to which the curable rubber composition according to the invention is shaped into the article, part and / or component, preferably before curing has been performed, by at least one of injection molding, compression molding, transfer molding, extrusion, coextrusion, extrusion coating, vacuum forming, melt spinning, electrospinning, laminating, and calendering.

[0110] All preferred embodiments described hereinabove in connection with the curable rubber composition and the kit-of-parts according to the invention and the cured rubber composition according to the invention and the aforementioned uses related to filler F1 according to the invention and the further aforementioned uses according to the invention and the article, part and / or component according to the invention are also preferred embodiments with regard to the process for preparing article, part and / or component according to the invention. METHODS

[0111] 1. STSA and BET surface area

[0112] The STSA and BET surface area was each determined according to standard ASTM D6556-21.

[0113] 2. Carbon content

[0114] The carbon content was determined by elemental analysis according to DIN 51732: 2014-07.

[0115] 3. Particle size distribution

[0116] The particle size distribution was determined by laser diffraction of the material to be investigated dispersed in water (1 % by weight in water) according to ISO 13320:2020,. The volume fraction is specified, for example, as d99 in pm (the diameter of the grains of 99% of the volume of the sample is below this value). The values d90 and d25 (in pm) can be determined in the same way.

[0117] 4.14C content

[0118] The determination of the14C content (content of biologically based carbon) was carried out by means of the radiocarbon method according to DIN EN 16640:2017-08.

[0119] 5. Ash content

[0120] The ash content was determined according to the standard DIN 51719:1997-07.

[0121] 6. Density

[0122] The density was determined according to standard ISO 21687:2007-03.

[0123] 7. Solubility in NaOH (aq.)

[0124] The solubility was measured in the following manner: First, a sample was dried at a temperature of 60 °C for four hours. A sample mass of 0.5 g was weighed and suspended in 50 ml of 0.1 M NaOH at a concentration of 1 % having a temperature of 22 °C. Mixing was continued for 1 hour, then the sample was placed on a glass microfiber paper (1.6 pm) and the filter paper with the sample was dried at a temperature of 60 °C for 2 hours. The portion of the sample, which has dissolved, could then be determined gravimetrically.

[0125] 8. Average molecular weight

[0126] The weight average molecular weight was determined with size exclusion chromatography (SEC) by using 0.1 M NaOH as eluent and a sample amount of about 1 mg / ml, which was dissolved in 0.1 M NaOH. The weight average molecular weights were measured against polystyrene sulfonate standards. UV detector at a wavelength of 280 nm was used. Number average molecular weights as well as polydispersity index were determined also by this method.

[0127] 9. Shore A hardness

[0128] Shore A hardness was tested according to ASTM D2240-15 (2021 ).

[0129] 10. Compression set

[0130] Compression set was measured after 24 hours at 70°C following ISO815-1 :2019.

[0131] 11. Tensile properties

[0132] Tensile properties (tensile strength, elongation at breaks and M100) were determined following ASTM D412-16 (2021 ).

[0133] 12. Curing characteristics

[0134] Moving die rheometer (MDR) was used to assess the cure characteristics. Testing was conducted at 180 °C for 60 mins, following ASTM D5289-19a. Minimum and maximum torgue (ML, MH) were measured. Further, the time period was determined in which the torgue, starting from the time of the minimum torgue ML, reaches 90% of the maximum torgue MH, respectively. The time period was designated as too. Further, the time for the viscosity to increase 2 units above ML (designated as ts2) was measured. EXAMPLES

[0135] The following examples further illustrate the invention, but are not to be construed as limiting its scope.

[0136] 1.1 Examples 11a, 12a, and 13a (all inventive) as well as example C (comparative)

[0137] The exact compositions of 11 a, I2a, I3a, and C can be seen from the following Table 1.1.

[0138] Table 1.1

[0139] The commercially available product HyTemp® H57 has been used as acrylic rubber (ACM). The commercially available product CORAX® N550 having an STSA surface area of about 39 m2 / g has been used as carbon black. Lignin based fillers 1 , 2 and 3 are organic fillers, which are obtainable by hydrothermal treatment of a lignin material: lignin-based filler 1 (UPM BioMotion® X10) has an STSA surface area of about 11 m2 / g, lignin-based filler 2 (UPM BioMotion® X20) has an STSA surface area of about 23 m2 / g, and lignin-based filler 3 (UPM BioMotion® X40) has an STSA surface area of about 40 m2 / g. Commercially available products have been used in each case as plasticizer, stearic acid, antioxidant, and processing aid. The commercially available product Intercure® 1 , which is a diamine derivative, has been used as diamine curing agent. The commercially available product Rhenogran® XLA-60 has been used as curing accelerator. 1.2 Examples 11b, 12b, and 13b (all inventive) as well as example C (comparative)

[0140] The exact compositions of 11 b, I2b, I3b, and C can be seen from the following

[0141] Table 1.2. The composition of example C is identical to the one shown in Table 1.1 , but has been reproduced for better comparison.

[0142] Table 1.2

[0143] The same products (acrylic rubber, carbon black, lignin-based fillers, plasticizer, stearic acid, antioxidant, processing aid, diamine, and curing accelerator) as indicated in Table

[0144] 1.1 have been used for preparing the compositions of Table 1.2 as well.

[0145] 1.3 Each of the compositions shown in Tables 1.1 and 1.2 was prepared using a HAAKE Rheomix® OS / 3100 of 300 cm3chamber volume with Banbury style rotors set at 40 °C and 60 rpm using a fill factor of 75% in a two-steps mixing cycle, following the procedure and conditions outlined in Tables 1.3a (step 1 )) and 1.3b (step 2)).

[0146] Table 1.3a - step 1 ) Table 1 ,3b - step 2)

[0147] The compositions were cured in at 180 °C for a period of too + 5 minutes. Afterwards, post curing was performed at a temperature of 175 °C for a period of 4 h.

[0148] 1.4 It has been observed that the inventive compositions 11a, I2a and I3a as well as 11 b, I2b and I3b showed a significantly reduced tendency to stick to the processing equipment during and after their preparation than comparative composition C, as for example measurable by the respective amount stuck to said equipment. Hence, a significantly reduced tackiness was achieved by partial replacement of carbon black as filler with at least one lignin-based organic filler in the acrylic rubber compositions.

[0149] 2. Investigation of physical properties of the cured compositions as well as of the cure characteristics

[0150] 2.1 The curing characteristics for curing the compositions of examples 11a, I2a and I3a as well as C have been investigated. The results are summarized in Table 2.1 .

[0151] Table 2.1

[0152] 2.2 The curing characteristics for curing the compositions of examples 11 b, I2b and I3b as well as C have been investigated. The results are summarized in Table 2.2. Table 2.2

[0153] 2.3 Some physical properties of the cured compositions of examples 11 a, I2a and I3a (all inventive) as well as of example C (comparative) have been investigated according to the methods described in the ‘methods’ section. The results are summarized in Table 2.3.

[0154] Table 2.3

[0155] As it is evident from Table 2.3 cured examples 11 a to I3a inter alia show an improved (increased) elongation at break, at least in case of 11 a and I3a, in comparison to cured example C. Further, the hardness is in each case lower and in case of 11a the compression set results are improved at 70 °C.

[0156] 2.4 Some physical properties of the cured compositions of examples 11 b, I2b and I3b (all inventive) as well as of example C (comparative) have been investigated according to the methods described in the ‘methods’ section. The results are summarized in Table 2.4. Table 2.4

[0157] As it is evident from Table 2.4 cured examples 11 b to I3b inter alia show an improved (increased) elongation at break in comparison to cured example C. Further, the hardness is in each case lower.

[0158] 3. Investigation of physical properties of the cured compositions after ageing

[0159] 3.1 In order to investigate the effects of ageing with respect to compression set, ageing of post cured samples of the cured compositions has been performed with hot air for a period of 168 h at a temperature of 175 °C. Compression set of the cured compositions of examples 11 a, I2a and I3a (all inventive), 11 b, I2b and I3b (all inventive) as well as of example C (comparative), after aforementioned ageing, have been investigated again according to the method described in the ‘methods’ section. The results thereof as well as the tensile strength measured after ageing are summarized in Tables 3.1 and 3.2.

[0160] Table 3.1 Table 3.2

[0161] 3.2 In order to investigate the effects of ageing, ageing of post cured samples of the cured compositions has been performed with hot oil (IRM903) for a period of 168 h at a temperature of 175 °C. Some properties of the cured compositions of examples 11 a, I2a and I3a (all inventive), 11 b, I2b and I3b (all inventive) as well as of example C (comparative), after aforementioned ageing, have been investigated according to the methods described in the ‘methods’ section. The results are summarized in Tables 3.3 and 3.4.

[0162] Table 3.3

[0163] Table 3.4

Claims

CLAIMS1 . A curable rubber composition comprising at least one acrylic rubber and / or at least one acrylic-based rubber, which is curable by means of at least one curing agent, at least one curing agent, which is suitable for curing the at least one acrylic rubber and / or at least one acrylic-based rubber, at least one lignin-based filler F1 , which is different from carbon black, and which has an STSA surface area of up to 200 m2 / g, and at least one filler F2, which is a carbon black.

2. The composition according to claim 1 , characterized in that at least the least one filler F1 has an STSA surface area in a range of from 2.5 to 200 m2 / g, preferably of from 5.0 to <200 m2 / g, more preferably of from 7.5 to 175 m2 / g, even more preferably of from 10.0 to 150 m2 / g.

3. The composition according to claim 1 or 2, characterized in that the least one filler F1 is present in the composition in an amount in a range of from 0.25 to 150 phr, preferably of from 0.75 to 125 phr, more preferably of from 1 .00 to 100 phr, even more preferably of from 1.50 to 85 phr, yet more preferably of from 1 .75 to 70 phr, most preferably of from 2.0 to 60 phr.

4. The composition according to one or more of the preceding claims, characterized in that the relative weight ratio of the at least one filler F1 to the at least one filler F2 is in a range of from to 600:1 to 1 :600, preferably of from 300:1 to 1 :300, more preferably of from 150:1 to 1 :150, still more preferably of from 100:1 to 1 :100, even more preferably of from 50:1 to 1 :50.

5. The composition according to one or more of the preceding claims, characterized in that the least one filler F1 has a d99 value of <25 pm, preferably<20 pm, more preferably <18 pm, even more preferably <15 pm, still more preferably <10 pm.

6. The composition according to one or more of the preceding claims, characterized in that the least one filler F1 has a carbon content in a range from >60% by weight to <90% by weight, preferably from >60% by weight to <85% by weight, more preferably from >60% by weight to <80% by weight.

7. The composition according to one or more of the preceding claims, characterized in that the least one filler F1 has a weight average molecular weight in a range of from 1000 to 4000 Da, preferably of from 1300 to 3700 Da, more preferably of from 1700 to 3200 Da, yet more preferably of from 2500 to 3000 Da, still more preferably of from 2600 to 2900 Da, most preferably of from 2650 to 2850 Da, in each case when determined based on the soluble fraction of the filler F1 .

8. The composition according to one or more of the preceding claims, characterized in that the at least one curing agent is present in the composition in an amount in a range of from 0.1 to 15 phr, preferably of from 0.2 to 10 phr, more preferably of from 0.5 to 7.5 phr, even more preferably of from 0.7 to 5 phr.

9. The composition according to one or more of the preceding claims, characterized in that the at least one curing agent is selected (i) from amines and / or amine derivatives, preferably from diamines and / or diamine derivatives, more preferably from organic diamines and / or organic diamine derivatives, even more preferably from aliphatic and / or aromatic diamines and / or diamine derivatives, yet more preferably from aliphatic diamines and / or diamine derivatives, (ii) alkali metal and / or earth alkali metal soaps, preferably alkali metal and / or earth alkali metal salts of at least one fatty acid, wherein said alkali metal and / or earth alkali metal soaps are optionally used in combination with sulfur and / or at least one sulfur donor, (iii) quaternary ammonium salts, preferably quaternary ammonium salts of at least one fatty acid, wherein said quaternary ammonium salts are optionally used in combination with sulfur and / or at least one sulfur donor, (iv) carboxylic acids and / or carboxylic acidderivatives, preferably dicarboxylic acids and / or dicarboxylic acid derivatives, (v) peroxides, and (vi) mixtures of any of (i) to (v).

10. The composition according to one or more of the preceding claims, characterized in that the at least one acrylic rubber and / or at least one acrylicbased rubber is selected from acrylic copolymers, preferably from acrylic copolymers, wherein at least one acrylic monomer and at least one co-monomer being different therefrom and being either also an acrylic monomer or an ethylenically unsaturated monomer such as a vinylic monomer, which is not an acrylic monomer, have been used for the preparation of said acrylic copolymer, more preferably from acrylic copolymers, wherein at least one acrylic ester of an aliphatic Ci-Cso-monoalcohol as at least one acrylic monomer and at least one co-monomer being different therefrom and being either also an acrylic ester of an aliphatic Ci-Cso-monoalcohol or an ethylenically unsaturated monomer such as a vinylic monomer, have been used for the preparation of said acrylic copolymer.

11. A kit-of-parts comprising, in spatially separated form, as part A) at least a part of a rubber composition as defined in any one or more of the preceding claims, wherein part A) does, however, not comprise the at least one curing agent, optionally as part B) the remaining part of the rubber composition according to the present invention not being present in part A), wherein part B) does, however, not comprise the at least one curing agent, and as part C) at least the at least one curing agent as defined in one or more of claims 1 , 8 and 9.

12. A cured rubber composition, which is obtainable by curing the curable rubber composition according to one or more of claims 1 to 10, or by curing a curable rubber composition obtainable by combining and mixing both A), optionally B) and C) of the kit of parts according to claim 11 .

13. A use of at least one filler F1 as defined in one or more of claims 1 to 7, in particular when used in combination with at least one filler F2 as defined in one or more of claims 1 and 4, for improving the compression set of cured rubber compositions, preferably of the cured rubber composition according to claim 12, in particular including improving said compression set after ageing, preferably for simultaneously improving the compression set and at least one further physical property selected from density, elongation at break, tensile strength and hardness of cured rubber compositions, preferably of the cured rubber composition according to claim 12, and / or for reducing the stickiness of curable rubber compositions, preferably of a curable rubber composition according to one or more of claims 1 to 10.

14. A use of the curable rubber composition according to one or more of claims 1 to 10, of the kit of parts according to claim 11 , or of the cured rubber composition according to claim 12 for manufacturing articles, parts and / or components, which preferably are suitable for use in the automotive, transportation, and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably are selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

15. An article, part and / or component, which is in each case obtainable from the curable rubber composition according to one or more of claims 1 to 10, the kit- of-parts according to claim 11 or from the cured rubber composition according to claim 12, and which preferably is suitable for use in the automotive, transportation and / or aerospace and / or engineering and / or construction industry, and / or are suitable to be used as consumer goods, wherein said articles, parts and / or components are more preferably is selected from sealings such as precision sealings, hoses, membranes, filters, diaphragms, gaskets, dampers, cables, cable sheathings, medical devices, molded parts, and articles for fluid handling applications.

16. A process for preparing the article, part and / or component according to claim 15, wherein said process comprises at least one step, according to which the curable rubber composition according to one or more of claims 1 to 10 is shaped into the article, part and / or component, preferably before curing has been performed, by at least one of injection molding, compression molding, transfer molding, extrusion, coextrusion, extrusion coating, vacuum forming, melt spinning, electrospinning, laminating, and calendering.

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