Adhesion promoting system for rubber compositions

Abstract

An adhesion promoting system for a rubber composition, comprising a novolak resin prepared by the reaction of an aldehyde A1 with a phenolic compound and an organic manganese salt.

Description

[Technical field]

[0001] The present disclosure relates to the field of adhesion promotion systems for rubber compositions. The disclosure is further directed to rubber compositions including the adhesion promotion systems, methods of making rubber articles, and methods of using the adhesion promotion systems. [Background technology]

[0002] In the conventional manufacture of various rubber articles, such as automobile tires and conveyor belts, reinforcing materials such as metal or synthetic fibers are usually used to enhance the performance. To ensure the long-term properties of such reinforced rubber articles, it is of utmost importance to provide adequate adhesion between the reinforcing materials and the rubber-based composition used to manufacture the rubber goods. To ensure adequate adhesion, the most implemented solution relies on incorporating adhesion promoters into the base rubber composition.

[0003] In such circumstances, various adhesion promoters are used in the art, such as the so-called resorcinol novolak adhesion promoters described in EP 0 440 036 A1 (Hesse et al.) or resorcinol itself adhesion promoters described in US 4,148,769 A (Swarts et al.). As is well recognized in the art, the use of resorcinol leads to health and environmental problems, especially due to the evaporation of resorcinol during rubber processing conditions. Furthermore, resorcinol adhesion promoters tend to age prematurely, especially under high temperature and / or high humidity conditions. Resorcinol-free adhesion promoters are described in EP 0 473 948 A2 (Singh et al.) and EP 0 827 971 A1 (Burkhart et al.). The adhesion promoters described in these references lead either to slow vulcanization of the corresponding rubber blends or to undesirable smoke generation during rubber processing.

[0004] Other adhesion promoters known to improve adhesion between reinforcing materials and rubber compositions use cobalt salts. However, cobalt compounds are designated as possible carcinogens to humans and therefore have significant toxicity and environmental concerns. Furthermore, the use of cobalt compounds is usually associated with an unstable supply chain and limited availability, which inevitably leads to increased costs. Patent document EP 3 636 700 A1 (Ozkutukcu et al.) describes rubber compositions that provide enhanced curing and adhesion properties, using very specific zinc compositions, referred to as active zinc compositions, with very specific surface areas in very specific ranges. The very specific specification of the required active zinc compositions, together with the elaborate methods for obtaining the latter, inevitably increases the overall technical complexity and the associated production costs.

[0005] Without disputing the technical advantages associated with solutions known in the art, there remains a need for an adhesion promotion system for rubber compositions that at least partially overcomes the deficiencies discussed above. Summary of the Invention [Means for solving the problem]

[0006] In one aspect, the present disclosure relates to an adhesion promoting system for a rubber composition, the system comprising a novolak resin prepared by reaction of an aldehyde A1 with a phenolic compound and an organic manganese salt.

[0007] In another aspect, the present disclosure is directed to a rubber composition comprising the adhesion promotion system described above and a rubber component.

[0008] In yet another aspect of the present disclosure, there is provided a method for making a rubber article, comprising the steps of: a) Prepare an adhesion promoter system as described above. b) adding an adhesion promoting system to the rubber component to form the rubber composition described above. c) optionally vulcanizing or crosslinking or curing the rubber composition.

[0009] In yet another aspect, the present disclosure relates to a method of using the adhesion promotion system described above to promote adhesion between a rubber composition and a reinforcing agent in contact with the rubber composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In a first aspect, the present disclosure relates to an adhesion promoting system for a rubber composition, the system comprising a novolac resin prepared by reaction of an aldehyde A1 with a phenolic compound, the adhesion promoting system further comprising an organic manganese salt.

[0011] In the context of the present disclosure, it has surprisingly been found that the above adhesion promoting systems are particularly suitable for enhancing the adhesive properties of the rubber composition, especially to reinforcing agents that typically come into contact with the rubber composition in conventional engineered rubber articles.

[0012] Additionally, it has been discovered that the adhesion promoting system of the present disclosure provides excellent adhesion properties to rubber compositions even under extreme conditions such as high temperature and humidity. This is a particularly surprising discovery since manganese salts are known to be highly hygroscopic in nature. Thus, it would be intuitively expected that the use of manganese salts would lead to poor adhesion properties under exposure to high humidity, especially in combination with extreme temperature conditions.

[0013] Additionally, it has been found that adhesion promoting systems as described herein maintain superior mechanical properties and characteristics such as stiffness, hardness, flexibility or structural strength for the cured (or vulcanized) rubber composition. Even more surprisingly, it has been found that the adhesion promoting systems also maintain outstanding properties associated with the cure and processability (e.g., cure rate, mixing and compounding properties, flowability, extrudability, applicability, paintability or shaping properties, etc.) of the rubber composition in the uncured (or unvulcanized) state.

[0014] Without wishing to be bound by theory, it is believed that these superior property and performance attributes are due in particular to the use of a specific combination of (a) a novolac resin prepared by reaction of an aldehyde A1 with a phenolic compound, and (b) an organo-manganese salt. Without wishing to be further bound by theory, this specific combination of components together helps to impart advantageous rheological properties, particularly viscosity, to the rubber composition along with excellent cure (or vulcanization) characteristics.

[0015] The adhesion promoter system is further characterized by one or more of the following advantageous benefits: (i) a simple and cost-effective manufacturing process based on readily available starting materials and minimized manufacturing steps, (ii) simplicity and versatility of formulation, (iii) relative safety of handling due to the use of small amounts of materials or products that may have harmful effects on the human body or have environmental issues, and (iv) the ability to use metal-based salts with a stable and non-conflicting supply chain.

[0016] In the context of the present disclosure, a technically and economically viable alternative to the use of cobalt and cobalt salts as adhesion promoters for rubber compositions has been found. The use of organomanganese salts as described herein is not only not hindered by the ESH (environmental safety and health) issues normally associated with cobalt, but also provides substantial cost-effectiveness considering that cobalt ore is 14 times more expensive than manganese ore.

[0017] The adhesion promotion system of the present disclosure is therefore eminently suitable for the manufacture of conventional reinforced engineered rubber articles such as pneumatic tires or conveyor belts, for example in automated industrial production lines for rubber articles.

[0018] In the context of the present disclosure, the expression "organomanganese salt" is meant to denote a salt comprising a manganese cation and an organic anion, the organic anion being in particular the conjugate base of an organic acid that contains at least one covalent carbon-hydrogen bond.

[0019] The adhesion promoting system of the present disclosure includes as a first component a novolac resin prepared by reaction of an aldehyde A1 with a phenolic compound.

[0020] The novolak resin used herein is not particularly limited as long as it is prepared by reacting an aldehyde A1 with a phenolic compound. Suitable novolak resins for use herein will be easily identified by one of ordinary skill in the art in light of the present disclosure.

[0021] The aldehydes A1 advantageously used in the preparation of the novolak resins are aliphatic monoaldehydes, preferably saturated, having one aldehyde group --CHO and having from 1 to 10 carbon atoms.

[0022] In an advantageous embodiment, the aldehyde A1 used herein is selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde and any mixtures thereof. In a particularly advantageous embodiment, the aldehyde A1 used herein is formaldehyde.

[0023] Virtually any phenolic compound having at least one reactive hydrogen atom on an aromatic ring and at least one phenolic hydroxyl group, i.e. at least monofunctional in reactivity with aldehydes, is suitable for preparing the novolak resins used herein. These include monocyclic or polycyclic phenolic compounds that may be monofunctional, difunctional, trifunctional or higher in reactivity with, for example, formaldehyde. The hydrogen atom reactive with aldehydes is the hydrogen atom that is in the ortho or para position of the aromatic ring relative to a hydroxyl group or other substituent with +I and / or +M effect.

[0024] Phenolic compounds suitable for the preparation of novolac resins are monocyclic and polycyclic hydroxyaromatics with one hydroxyl group (monophenols) or with one or more hydroxyl groups (polyphenols), optionally substituted with linear, branched or cyclic alkyl groups, oxyalkyl groups or halogen atoms having 1 to 20 carbon atoms, at least one reactive hydrogen atom being attached to one of the aromatic rings. These phenolic compounds may be used individually or as mixtures. Advantageously used are phenol itself, the various cresol and xylenol isomers, isomers of ethylphenol, propylphenol or isopropylphenol, and p- or o-substituted alkylphenols having up to 18, especially up to 15, carbon atoms in the side chain. It is also possible to use phenols substituted with olefinically unsaturated groups, such as, for example, o- or p-vinylphenol or p-isopropenylphenol, and phenolic substances reacted with dicyclopentadiene (DCPD) and / or styrene and / or colophony.

[0025] Polycyclic monohydric phenolic compounds such as isomeric hydroxynaphthalenes, optionally substituted as described above, and monocyclic polyhydric phenols such as pyrocatechol, resorcinol, hydroquinone, pyrogallol, and phloroglucinol may also be suitably used.

[0026] Alternatively, polycyclic polyhydric phenolic compounds such as isomers of bishydroxyaryl compounds in which aromatic structures are linked by direct bonds or by ethenyl, ether, carbonyl, sulfonyl, carbonyloxy or carboxamide groups, such as diphenylmethane, diphenylethane, diphenylpropane (bisphenol A), dihydroxybiphenyl, dihydroxystilbene, dihydroxydiphenylether, dihydroxybenzophenone, dihydroxydiphenylsulfone, dihydroxyphenylbenzoate and dihydroxybenzanilide (which may be optionally substituted with alkyl or alkoxy groups or halogen atoms as described above), can be suitably used. Other polyhydric polycyclic phenolic compounds such as isomeric dihydroxynaphthalenes and trihydric and polyhydric hydroxyaromatics can also be suitably used in the preparation of the novolak resins used herein.

[0027] In an advantageous embodiment of the disclosure, the phenolic compound used herein is selected from the group consisting of phenol, cresol, resorcinol, monoalkylphenols and any mixtures thereof. In a particularly advantageous embodiment, the phenolic compound used herein is (includes) phenol.

[0028] In a typical embodiment, the novolak resin used herein is prepared by reacting an aldehyde A1 with a phenolic compound and further with an acid (catalyst). Suitable acids used herein are, but are not limited to, advantageously strong mineral acids and / or their acidic derivatives, in particular sulfuric acid, in particular alkali metal or ammonium hydrogen sulfates, half esters of sulfuric acid with aliphatic alcohols having 1 to 20 carbon atoms, phosphoric acid, hydrochloric acid or organic acids such as alkanesulfonic acids and arylsulfonic acids having 1 to 20 carbon atoms, in particular p-toluenesulfonic acid, and aliphatic monobasic and dibasic carboxylic acids having 1 to 20 carbon atoms, such as chloroacetic acid, trifluoroacetic acid, and in particular oxalic acid dihydrate. Lewis acids such as aluminum trichloride, zinc trichloride, and tin trichloride, as well as boron trifluoride and its ether compounds, are also suitable.

[0029] Advantageously, the acid used herein is selected from the group consisting of oxalic acid, maleic acid, dodecylbenzenesulfonic acid, para-toluenesulfonic acid and any mixture thereof. Preferably, the acid is selected from the group of oxalic acid and para-toluenesulfonic acid.

[0030] The novolac resins used herein may be prepared using conventional techniques and methods generally known to those skilled in the art. Exemplary methods of preparation are described, for example, in GB 1448374 A (Hesse et al.).

[0031] In another embodiment, the adhesion promoting system of the present disclosure further comprises a urethane-aldehyde resin, in particular prepared by condensation of an aldehyde A2 with an alkyl urethane. It has been found that such an adhesion promoting system provides a further enhanced adhesion promoting effect to rubber compositions, in particular to reinforcing agents.

[0032] The urethane-aldehyde resin used herein is not particularly limited, and can be easily identified by those skilled in the art in light of the present disclosure. In a typical embodiment, the urethane-aldehyde resin is prepared by acid-catalyzed condensation of aldehyde A2 with alkyl urethane, optionally in the presence of a catalyst.

[0033] Suitable aldehydes A2 for use in the synthesis of the urethane-aldehyde resins may be selected from the same compounds as those listed under item A1 in the context of the preparation of the novolac resins hereinafter.

[0034] In an advantageous embodiment, the aldehyde A2 used herein is selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde and any mixtures thereof. In a particularly advantageous embodiment, the aldehyde A2 used herein is formaldehyde.

[0035] The alkylurethanes used in the synthesis of the urethane-aldehyde resins include, but are not limited to, monoalkylurethanes or alkylene bisurethanes.

[0036] Advantageously, the alkylurethanes used in the preparation of the urethane-aldehyde resins are monoalkylurethanes, in particular selected from the group consisting of ethylurethane, butylurethane, 2-ethylhexylurethane, decylurethane, and any mixtures thereof.

[0037] The urethane-aldehyde resins used herein may be prepared using conventional techniques and methods generally known to those skilled in the art. Exemplary preparation methods are described, for example, in EP 2 432 810 A1 (Scafer et al.).

[0038] The adhesion promoting system of the present disclosure further comprises an organic manganese salt. The organic manganese salt used herein is not particularly limited as long as it contains an organic anion. Suitable organic manganese salts for use herein will be readily identified by one of skill in the art in light of the present disclosure.

[0039] In this context, inorganic manganese salts such as, for example, manganese oxide, manganese sulfate, manganese bromide, manganese carbonate, manganese chloride, or manganese nitrate do not qualify as organic manganese salts within the meaning of the present disclosure.

[0040] In an exemplary embodiment, an organomanganese salt as used herein comprises an organic anion that is a conjugate base of an organic acid that contains at least one covalent carbon-hydrogen bond.

[0041] Advantageously, the organic manganese salts used in the present disclosure are manganese salts of carboxylic acids, particularly manganese salts of aliphatic or alicyclic carboxylic acids having 2 to 30, 2 to 25, 2 to 20, 4 to 20, or 6 to 20 carbon atoms.

[0042] More advantageously, the organic manganese salt is a manganese salt of a mono- or dicarboxylic acid, in particular a manganese salt of a monocarboxylic acid.

[0043] In an advantageous embodiment, the organic manganese salts used herein are selected from the group of manganese salts of fatty acids and in particular of manganese salts of aliphatic or cycloaliphatic carboxylic acids (saturated and unsaturated) having from 6 to 30 carbon atoms.

[0044] Preferably, the organic manganese salt is selected from the group consisting of manganese (hexanoate), manganese (heptanoate), manganese (octanoate), manganese (2-ethylhexanoate), manganese (nonanoate), manganese (decanoate), manganese (neodecanoate), manganese (dodecanoate), manganese (hexadecanoate), manganese (octadecanoate), manganese (oleate), manganese (linoleate), manganese (cyclohexanebutyrate), manganese (naphthenate), and any mixture thereof.

[0045] In particular, manganese salts of saturated aliphatic or alicyclic monocarboxylic acids having 6 to 30 carbon atoms are particularly beneficial because they have no (at least only slight) adverse effect during crosslinking or vulcanization of the rubber composition. Moreover, these particular manganese salts are believed to not only impart advantageous miscibility properties to the rubber composition as a whole, but also to further enhance the adhesive capabilities between the rubber composition and the reinforcing agent by further promoting the dispersion of the organic salt in the vicinity of the reinforcing agent or the absorption of the organic manganese salt on the reinforcing agent surface.

[0046] More preferably, the organic manganese salt is selected from the group consisting of manganese hexanoate, manganese 2-ethylhexanoate, manganese neodecanoate, manganese hexadecanoate, manganese octadecanoate, manganese oleate, manganese linoleate, manganese cyclohexanebutyrate, and any mixture thereof.

[0047] In particularly preferred aspects of the disclosure, the organic manganese salt is selected from the group consisting of manganese (2-ethylhexanoate), manganese (neodecanoate), manganese (octadecanoate), and any mixtures thereof.

[0048] The organic manganese salts used herein may be prepared using conventional techniques and methods generally known to those skilled in the art. One exemplary common preparation method consists in reacting an organic acid, particularly a carboxylic acid, with manganese oxide, manganese hydroxide or manganese carbonate. Another exemplary common preparation method consists in a) reacting an organic acid, particularly a carboxylic acid, with sodium hydroxide to obtain the sodium salt of the organic acid, and then b) reacting the sodium salt of the organic acid with manganese chloride.

[0049] Alternatively, the organic manganese salts used herein may be purchased from conventional pharmaceutical suppliers.

[0050] The formulation of the adhesion promoter system, and particularly the respective amounts of novolak resin and organomanganese salt present in the system, may vary within wide ranges depending on the desired performance and application.

[0051] Advantageously, the adhesion promoting system comprises: a) 5 to 35%, 5 to 30%, 7 to 25%, 10 to 20% or 10 to 15% by weight of an organic manganese salt; and b) 65 to 95%, 70 to 95%, 75 to 93%, 80 to 90% or 85 to 90% by weight of a novolac resin; (wt % is based on the total weight of the adhesion promoting system).

[0052] The disclosed adhesion promotion systems may also take a variety of forms and may be used or incorporated into the rubber composition according to a variety of techniques or configurations.

[0053] In one exemplary embodiment, the adhesion promoting system as described may be in the form of a split system, with the novolac resin and the organomanganese salt being used as physically separate entities and therefore separately incorporated into a conventional rubber composition by appropriate procedures.

[0054] A split system is advantageous because it allows for more flexibility, tailoring and more formulation flexibility with respect to the incorporation of the novolac resin and organo-manganese salt into a conventional rubber composition.

[0055] In a further advantageous embodiment, the adhesion promoting system is in the form of a (pre)mixture of the novolac resin and the organo-manganese salt. The (pre)mixed system is advantageous because it provides a ready-to-use adhesion promoting composition that can be conveniently incorporated into conventional rubber compositions in a single addition step.

[0056] Without wishing to be bound by theory, it is believed that the (pre)mixed system improves the compatibility and miscibility of the organo-manganese salt in the rubber composition compared to the incorporation of the organo-manganese salt alone, which advantageous property is further believed to ultimately translate into enhanced adhesion properties between the rubber composition and the reinforcing agent.

[0057] In the particular embodiment in which the adhesion promoting system is in the form of a (pre)mixture of a novolac resin and an organo-manganese salt, the (pre)mixture may advantageously be in the form of a dispersion, the organo-manganese salt being dispersed in the novolac resin, whereas commercially available organo-manganese salts are generally dispersed in a hydrocarbon solvent.

[0058] In a more advantageous embodiment, the (pre)mixture is in the form of a blend, in which the organo-manganese salt is blended with the novolac resin, which is believed to further improve the compatibility and miscibility of the organo-manganese salt and the novolac resin in the rubber composition.

[0059] Additionally, the formulations can provide adhesion promoting systems in solid form, which are essentially taken from the hydrocarbon solvents in which commercially available organomanganese salts are dispersed. Adhesion promoting systems in the form of solid formulations are particularly useful in the context of general industrial manufacturing of rubber articles. Exemplary solid formulations used herein are generally in the form of pellets, beads or flakes.

[0060] The composition of the formulation, particularly the respective contents of the novolak resin and the organomanganese salt in the system, may vary within wide ranges depending on the desired performance and application.

[0061] In advantageous embodiments, the weight ratio of novolak resin to organomanganese salt in the formulation is from 5:95 to 35:65, from 7:93 to 25:75, or from 10:90 to 15:85.

[0062] The premix of novolac resin and organomanganese salt may be prepared using conventional techniques and methods generally known to those skilled in the art. One exemplary preparation method is to add the novolac resin to the organomanganese salt (typically in a form dispersed in a hydrocarbon solvent) and heat the reactive mixture until the novolac resin melts. The mixture is then stirred to ensure complete homogenization and the residual solvent is removed under reduced pressure.

[0063] In another aspect, the present disclosure is directed to a rubber composition comprising the adhesion promotion system described above and a rubber component.

[0064] The rubber component used herein is not particularly limited. Virtually any rubber component generally known in the art may be used in the context of the present disclosure. Suitable rubber components for use herein will be readily identified by one of ordinary skill in the art in light of the present disclosure. Exemplary rubber components for use herein are described in detail, for example, in EP 2 432 810 A1 (Schafer et al.). Particularly suitable rubber components for use herein are sulfur crosslinkable or sulfur vulcanized rubber components.

[0065] In an exemplary embodiment, the rubber component used in the rubber composition is selected from the group consisting of natural rubber, polyisoprene (IR), polybutadiene, styrene / butadiene rubber (SBR), acrylonitrile rubber, butyl rubber, ethylene / propylene / diene terpolymer rubber (EPDM), and any mixture thereof.

[0066] The amount of adhesion promoting system present in the rubber composition may vary within wide limits depending on the desired performance and application.

[0067] In an advantageous embodiment, the rubber composition comprises 0.5 to 15.0 phr, 0.5 to 12.0 phr, 0.5 to 10.0 phr, 1.0 to 8.0 phr, 1.0 to 6.0 phr, 1.0 to 5.0 phr, 1.5 to 5.0 phr, 1.5 to 4.5 phr, or 2.0 to 4.0 phr of the adhesion promoting system based on 100 parts by weight of the rubber component.

[0068] With regard to the content of the organic manganese salt, and particularly with regard to the content of metallic manganese, the content in the rubber composition as a whole may vary within a wide range, but for optimum performance, particularly with regard to adhesion performance, it has been found to be beneficial to control the respective contents in the rubber composition.

[0069] Advantageously, the rubber composition comprises, based on 100 parts by weight of the rubber component, 2.00 phr or less, 1.80 phr or less, 1.60 phr or less, 1.50 phr or less, 1.40 phr or less, 1.20 phr or less, 1.00 phr or less, 0.80 phr or less, 0.70 phr or less, 0.60 phr or less, 0.50 phr or less, 0.40 phr or less, 0.35 phr or less, or 0.30 phr or less of an organic manganese salt.

[0070] In another advantageous embodiment, the rubber composition comprises, based on 100 parts by weight of the rubber component, 0.10 to 2.00 phr, 0.10 to 1.60 phr or less, 0.15 to 1.40 phr, 0.15 to 1.20 phr, 0.20 to 1.00 phr, 0.20 to 0.90 phr, 0.20 to 0.85 phr, 0.20 to 0.80 phr, 0.20 to 0.70 phr, 0.20 to 0.60 phr, 0.25 to 0.50 phr, 0.25 to 0.40 phr, or 0.25 to 0.35 phr of an organic manganese salt.

[0071] In yet another advantageous embodiment, the rubber composition contains, based on 100 parts by mass of the rubber component, 0.25 phr or less, 0.22 phr or less, 0.20 phr or less, 0.18 phr or less, 0.16 phr or less, 0.14 phr or less, 0.12 phr or less, 0.10 phr or less, 0.09 phr or less, 0.08 phr or less, 0.07 phr or less, 0.06 phr or less, or 0.05 phr or less of metallic manganese.

[0072] In yet another advantageous embodiment, the rubber composition comprises, based on 100 parts by weight of the rubber component, 0.020 to 0.200 phr, 0.025 to 0.180 phr, 0.030 to 0.160 phr, 0.030 to 0.140 phr, 0.035 to 0.120 phr, 0.040 to 0.120 phr, 0.040 phr to 0.110 phr, 0.0450 to 0.105 phr, 0.050 to 0.100 phr, 0.050 to 0.090 phr, 0.050 to 0.080 phr, 0.050 to 0.070 phr, or 0.050 to 0.060 phr of metallic manganese.

[0073] In the context of the present disclosure, it has been found that rubber compositions having an organo-manganese salt content, in particular a manganese metal content, outside the ranges detailed above tend to lead to less than optimal performance, in particular with regard to adhesion performance between the rubber composition and the reinforcing agent(s).

[0074] In an exemplary embodiment, the rubber composition used herein further comprises a reinforcing agent. The reinforcing agent used herein is not particularly limited. Virtually any reinforcing agent generally known in the art may be used in the context of the present disclosure. Suitable reinforcing agents for use herein will be readily identified by those skilled in the art in light of the present disclosure. Exemplary reinforcing agents for use herein are described in detail in EP 2 432 810 A1 (Schafer et al.).

[0075] Advantageously, the reinforcing agents used herein are in particular selected from the group consisting of reinforcing fibers, reinforcing filaments, reinforcing wires, reinforcing cords and any combination thereof.

[0076] More advantageously, the reinforcing agent comprises a material selected from the group consisting of metals (particularly steel), polymers, ceramics, textiles, composites and any combination thereof.

[0077] As will be readily apparent to those skilled in the art, the rubber compositions used herein may further comprise additives that are conventional in the art. Suitable conventional additives include, but are not limited to, vulcanizing or crosslinking or curing agents, fillers, anti-aging agents, antioxidants, tackifiers, mineral oils, plasticizers, processing aids, and any mixtures thereof. Additional additives for use herein are, for example, exemplified in detail in EP 2 432 810 A1 (Schafer et al.).

[0078] In an advantageous embodiment, the rubber composition of the present disclosure further comprises a vulcanizing or crosslinking or curing agent, a filler, an additive, and any mixture thereof. Preferably, the vulcanizing or crosslinking or curing agent used herein comprises sulfur and / or a sulfur donor, optionally in combination with an accelerator and / or an activator.

[0079] The rubber compositions described herein may be prepared, processed and crosslinked (vulcanized) according to techniques and methods generally known to those skilled in the art, for example, using internal mixers, kneaders or mixing rolls.

[0080] The adhesion promotion system and rubber composition of the present disclosure are eminently suitable for the manufacture of conventional reinforced engineered rubber articles.

[0081] In another aspect, the present disclosure is therefore directed to an article comprising the rubber composition described above. Exemplary articles include, but are not limited to, pneumatic vehicle tires, conveyor belts, power transmission belts, high pressure hoses, and gaskets.

[0082] Advantageously, the article of the present disclosure is an engineered rubber article, in particular an engineered rubber article, more in particular a pneumatic vehicle tire or a conveyor belt.

[0083] In yet another aspect, the present disclosure is directed to a method for preparing an adhesion promoting system in the form of a formulation as described above, comprising the steps of a) preparing a novolac by adding a novolac resin to an organomanganese salt (optionally in the form of a dispersion in an organic solvent) to form a reactive mixture, b) heating the reactive mixture until the novolac resin is (completely) melted, c) homogenizing the mixture by stirring, and d) optionally removing any residual solvent.

[0084] The present disclosure further relates to a method for preparing the adhesion promoter system described above, comprising the step of preparing a novolac resin by reaction of an aldehyde A1 with a phenolic compound in the presence of a urethane-aldehyde resin.

[0085] The present disclosure further relates to a method for making the above-described rubber composition, the method comprising the step of adding the above-described adhesion promoting system to a rubber component.

[0086] In yet another aspect of the present disclosure, there is provided a method for making a rubber article, comprising the steps of: a) Prepare the adhesion promoter system described above. b) adding an adhesion promoting system to the rubber component to form the rubber composition described above. c) Optionally, vulcanizing or crosslinking or curing the rubber composition.

[0087] In yet another aspect, the present disclosure relates to a method of using the adhesion promotion system described above to promote adhesion between a rubber composition and a reinforcing agent in contact with the rubber composition, the reinforcing agent being specifically selected from the group consisting of reinforcing fibers, reinforcing filaments, reinforcing wires, and any combination thereof.

[0088] The present disclosure further relates to the use of the above adhesion promotion system in the manufacture of rubber articles, particularly selected from the group of pneumatic vehicle tires and belt conveyors.

[0089] The present disclosure further relates to a method of promoting adhesion between a rubber composition and a reinforcing agent in contact with the rubber composition, the method comprising the step of incorporating into the rubber composition an adhesion promoting system as described above. EXAMPLES

[0090] The present disclosure is further described in the following examples, which are for illustrative purposes only and are not intended to limit the scope of the appended claims. [Test Method] Evaluation of adhesion properties (tensile test according to ASTM D2229)

[0091] Preparation of sample pieces for adhesive ability test (Examples 1 to 4 and Comparative Examples 1 to 2) The rubber composition was heat-treated with a test double roller to prepare a rubber sheet with a width of 100 mm, a thickness of 6 mm and a length of 400 mm. Two rubber pieces with a width of 12.5 mm, a thickness of 6 mm and a length of 200 mm were cut out from the rubber sheet. * 0.24 / 9 * A 0.225HT steel cord (manufactured by Kisswire Corporation) was sandwiched between the two rubber pieces described above and vulcanized at about 150° C. to prepare a rubber composition test piece with the steel cord adhered thereto.

[0092] Preparation of Sample Specimens for Adhesion Ability Testing (Examples 5-6) The rubber composition was heat-treated with a test double roller to prepare a rubber sheet with a width of 100 mm, a thickness of 3 mm, and a length of 90 mm. Two rubber pieces with a width of 10 mm, a thickness of 3 mm, and a length of 90 mm were cut out from the rubber sheet. * 2 * A 0.25HT steel cord (manufactured by Bekaert) was sandwiched between the two rubber pieces described above and vulcanized at about 150° C. to prepare a rubber composition test piece with the steel cord adhered thereto.

[0093] Method for evaluating adhesive ability (Examples 1 to 4 and Comparative Examples 1 and 2) The above test pieces were subjected to tensile tests according to ASTM D2229 to measure the adhesion between the rubber and the steel cord. The following three types of measurements were performed to measure the adhesion. Initial adhesion: One test piece was prepared by vulcanization under the vulcanization conditions described above, and measurements were taken after 24 hours. Adhesive strength after hydrothermal aging test: The test pieces sulfurized under the above sulfurization conditions were subjected to humidity aging at 95°C and 100% relative humidity (RH) for 7 days, and the adhesive strength was measured. Adhesive strength after extended hydrothermal aging test: The test pieces sulfurized under the above sulfurization conditions were placed at 95°C and 100% RH for 14 days to subject them to humidity aging, and the adhesive strength was measured.

[0094] Method for evaluating adhesive ability (Examples 5 and 6) The above test pieces were subjected to tensile tests according to ASTM D2229 to measure the adhesion between the rubber and the steel cord. The following three types of measurements were performed to measure the adhesion. Initial adhesion: One test piece was prepared by vulcanization under the vulcanization conditions described above, and measurements were taken after 24 hours. Adhesive strength after hydrothermal aging test: The test pieces sulfurized under the above sulfurization conditions were immersed in 95°C water for 7 days to subject them to water immersion aging, and the adhesive strength was measured. Adhesive strength after extended hydrothermal aging test: The test pieces sulfurized under the above sulfurization conditions were immersed in 95°C water for 14 days to undergo water immersion aging, and the adhesive strength was measured.

[0095] raw materials The following raw materials were used in the examples: Manganese (2-ethylhexanoate) was obtained from Borchers and is available under the trade name Octa-Soligen Manganese 10HS, 60% by weight in hydrocarbon. Manganese (neodecanoate) was obtained from Borchers and is available under the trade name Deca Manganese 8, 60% by weight in hydrocarbon. Cobalt stearate (20.5%), available from Borchers under the trade name Manobond 740C. MnO 2 , manganese oxide salt, trade name MnO 2 Available from Nantong Runfeng Chemical Co. ALNOVOL PN320, a novolac type phenolic resin, is available from allnex GmbH, Germany. A natural rubber SVR grade is available commercially from HB Chemicals under the trade name SVR 3L. Carbon black grade N326, available from Cabot Corporation under the trade designation Regal 300. Stearic acid is available from PT. SUMI ASIH under the trade name SA 1801. Silica, available from Evonik under the trade name Ultrasil VN3. TMQ, antioxidant, polymeric 2,2,4-trimethyl-1,1-dihydroquinoline, available commercially from China Sunsine Chemical Holdings Ltd. under the trade name TMQ. Oil, processing oil, available commercially from Orgkhim Biochemical Holding under the trade name Norman-346. ZnO, zinc oxide, available from Zink US (Changshu) Metal Co. under the trade name Zinc Oxide 210P. HMMM, hexamethoxymethylmelamine, available commercially from Allnex under the trademark Cyrez 964. Sulfur, sulfur powder, available from Eastman Chemical Company under the trade name HDOT 20. DCBS, N,N-dicyclohexyl-2-benzothiazole sulfonamide, is available commercially from China Sunsine Chemical Holdings Ltd. under the trade name DCBS. TBBS, Nt-butyl-benzothiazole sulfonamide, available commercially from China Sunsine Chemical Holdings Ltd. under the trade name TBBS.

[0096] Example 1: Preparation of a blend of manganese (2-ethylhexanoate) and novolac resin (blend 1) Manganese 2-ethylhexanoate (74.2 g, 60% in hydrocarbon) was placed in a four-necked round-bottom flask (1 L). Then, novolac resin (PN320, 400.0 g) was added and the mixture was heated to 170°C under protective gas (N2). Once the novolac resin had melted, it was stirred to homogenize (2 h). The solvent was removed under reduced pressure (15 mbar, 1.5 h, 170°C) to form a material with a melt viscosity of about 11060 mPas, a capillary viscosity of about 1110 mPas, and a melting point of about 90°C.

[0097] Example 2: Preparation of a Blend of Manganese (Neodecanoate) and Novolac Resin (Blend 2) Manganese neodecanoate (474.0 g, 60% in hydrocarbon) was placed in a four-necked round-bottom flask (6 L). Then, novolac resin (PN320, 2930.2 g) was added and the mixture was heated to 145° C. under protective gas (N2). Once the novolac resin was melted, it was stirred to homogenize (2 h). The solvent was removed under reduced pressure (15 mbar, 1 h, 145-160° C.) to form a material with a melt viscosity of about 8585 mPas, a capillary viscosity of about 1391 mPas, and a melting point of about 87° C.

[0098] Example 3: Base Rubber Substrate To test the effectiveness of the adhesion promoting system of the invention in a vulcanizable rubber compound, a base rubber mix was prepared by thoroughly mixing the ingredients in Table 1 below in a kneader at about 140°C.

[0099] [Table 1]

[0100] Example 4: Exemplary Rubber Compositions During compounding, the following additional ingredients (added in parts per hundred parts of rubber) were added to separate portions of the base rubber mixture in the order of the rows shown in Table 2 below to prepare the following exemplary rubber compositions, each portion containing exactly 100 phr of natural rubber: Comparative Example C1 contains cobalt stearate as the organometallic salt, Comparative Example C2 contains inorganicIn the rubber composition of Example 5, the manganese salt and the novolac resin were incorporated into the base rubber mix as a compound obtained as detailed in the procedure described in Example 1. In the other exemplary rubber compositions, these two components were incorporated into the base rubber mix separately.

[0101] [Table 2]

[0102] Adhesive Ability [Table 3]

[0103] As can be seen from the results shown in Table 3, the adhesion promotion system of the present invention (see particularly Examples 1-4) when used in a rubber composition provided excellent adhesion to brass-plated steel cord, even under severe humid aging conditions. These adhesion results were very similar to the adhesion results obtained using a comparative cobalt salt (Comparative Example 1). Conversely, compared to the adhesion results obtained using the adhesion promotion system of the present invention (see Example 4), inorganic The adhesion performance results obtained with manganese salts were found to be poor (above 10%). Furthermore, it was found that the adhesion performance obtained when manganese salt and novolac resin were incorporated as a compound into a rubber mix (see Example 5) was improved (by almost 10%) compared to the adhesion performance results obtained when the same compound was used but the components were added separately to the rubber mix (see Example 6).

Claims

1. A system for promoting adhesion in rubber compositions, wherein the system comprises a novolac resin and an organic manganese salt prepared by the reaction of aldehyde A1 with a phenol compound.

2. The system according to claim 1, wherein the organic manganese salt is a manganese salt of a carboxylic acid, particularly a manganese salt of an aliphatic or alicyclic carboxylic acid having 2 to 30 carbon atoms, 2 to 25 carbon atoms, 2 to 20 carbon atoms, 4 to 20 carbon atoms, or 6 to 20 carbon atoms.

3. The system according to claim 1, wherein the organic manganese salt is selected from the group consisting of manganese (hexanoic acid), manganese (2-ethylhexanoic acid), manganese (neodecanoic acid), manganese (hexadecanoic acid), manganese (octadecanoic acid), manganese (oleic acid), manganese (linoleic acid), manganese (cyclohexanebutyrate), manganese (naphthenic acid), and any mixture thereof.

4. The aforementioned system, a) 5 to 35% by weight, 5 to 30% by weight, 7 to 25% by weight, 10 to 20% by weight, or 10 to 15% by weight of the organic manganese salt and b) 65 to 95% by weight, 70 to 95% by weight, 75 to 93% by weight, 80 to 90% by weight, or 85 to 90% by weight of the novolac resin, Includes, The system according to claim 1, wherein the weight percentage is based on the total weight of the system.

5. The system according to claim 1, wherein the aldehyde A1 is selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, oxalaldehyde, and any mixture thereof.

6. The system according to claim 1, wherein the phenol compound is selected from the group consisting of monohydric phenol compounds, polyhydric phenol compounds, and any mixture thereof.

7. The system according to claim 1, wherein the novolac resin is prepared by the reaction of an aldehyde with a phenol compound and an acid.

8. The system according to claim 1, wherein the system is in the form of a (preliminary) mixture of the novolac resin and the organic manganese salt.

9. The (preliminary) mixture is in the form of a compound, The system according to claim 8, wherein the novolac resin is blended with the organic manganese salt.

10. A rubber composition comprising the adhesion-enhancing system and rubber component described in claim 1.

11. The composition according to claim 10, comprising, based on 100 parts by mass of the rubber component, metallic manganese in an amount of 0.25 phr or less, 0.22 phr or less, 0.20 phr or less, 0.18 phr or less, 0.16 phr or less, 0.14 phr or less, 0.12 phr or less, 0.10 phr or less, 0.09 phr or less, 0.08 phr or less, 0.07 phr or less, 0.06 phr or less, or 0.05 phr or less.

12. The composition according to claim 10, comprising 0.020 to 0.200 phr, 0.025 to 0.180 phr, 0.030 to 0.160 phr, 0.030 to 0.140 phr, 0.035 to 0.120 phr, 0.040 to 0.120 phr, 0.040 phr to 0.110 phr, 0.045 to 0.105 phr, 0.050 to 0.100 phr, 0.050 to 0.090 phr, 0.050 to 0.080 phr, 0.050 to 0.070 phr, or 0.050 to 0.060 phr of metallic manganese based on 100 parts by mass of the rubber component.

13. The composition according to claim 10, further comprising a reinforcing agent selected from the group consisting of reinforcing fibers, reinforcing filaments, reinforcing wires, reinforcing cords, and any combination thereof.

14. A method for manufacturing rubber articles, a) Steps of preparing the adhesion-promoting system according to any one of claims 1 to 9, b) The step of adding the adhesion-enhancing system to the rubber component to form the rubber composition according to any one of claims 10 to 13, and c) A method for producing a rubber article, comprising an optional step of sulfurizing, crosslinking, or curing the rubber composition.

15. A method of using the adhesion-enhancing system according to any one of claims 1 to 9 to promote adhesion between a rubber composition and a reinforcing agent in contact with the rubber composition, wherein the reinforcing agent is selected from the group consisting particularly of reinforcing fibers, reinforcing filaments, reinforcing wires, and any combination thereof.