Adhesion activating agent of rubbers to brass-coated metal

FIELD: metallurgy.

SUBSTANCE: there is described adhesion activating agent of rubbers to brass-coated metal, corresponding alloy of blocked by ε-caprolactam and higher fatty acids dy- and (or) polyisocyanate with cobalt stearate, boric acid and secondary phenylenediamine. Mentioned alloy is encapsulated by powder-like inorganic matter, selected from group, including colloidal silicic, kaolin, bentonite, zinc oxide, at ratio (wt %): 60-20 and 40-80 correspondingly.

EFFECT: hardening of rubber strength to brass-coated metal cord and its stability in conditions of thermal-oxidative and saline aging.

3 tbl, 13 ex, 2 dwg

The invention relates to the production of the adhesion promoter in the form of a chelate coordination complex consisting of a blocked di - and / or MDI, compounds of cobalt and boron, which can be used to improve the adhesion of rubber to lutunasobasoba the steel cord. The invention can be used in tire and rubber industry.

Known blocked with ε-caprolactam polyisocyanate obtained in the melt. As blocking agents use ε-caprolactam and higher fatty acid [RF Patent №2186059, C07C 263/18, 265/12, 265/14, publ. 07.07.1999].

The disadvantage of this modifier is relatively low stability of the adhesion of rubber latunirovannaya steel cord with salt aging (see table 3). In addition, the relatively low temperature dropping this product (50±4°C) may cause sticking his pellets in the summer, because already about 30°C it begins to soften.

The closest in technical essence is the modifier additive that consists of a mechanical mixture of phenol and/or epoxy resin, inorganic compounds of cobalt, boric acid and silicate filler [U.S. Pat. EN 2041893, C08L 61/10, C08L 63/00, publ. 20.08.1995].

The disadvantage of this of the modifying additive is dusting when the dosage that is hadset the environment in the manufacture of tyres and rubber products, poor dispersion of refractory inorganic components of the modifier in the elastomeric matrix. In addition, this modifier does not provide a sufficient level of adhesion of the rubber to lutunasobasoba metal, the resistance of rubbers to thermal-oxidative aging, and helps to improve the elastic modulus and hardness of rubber, which leads to increased heat buildup in the inner layers of thick-walled products, operating under dynamic loads, in particular tires.

The closest in technical essence is the promoter of adhesion of rubber to lutunasobasoba the steel - cobalt stearate (TU 2494-001-53904859-02)containing the composition of 9-10% cobalt and 0.7 to 1.0% boron [1].

However, this modifier does not provide a sufficiently high resistance rubber in General and adhesive compounds, in particular, to thermal-oxidative aging.

An object of the invention is to increase the strength of rubber latunirovannaya steel cord and its stability under conditions of oxidative and salt aging without deteriorating its performance.

The problem is solved through the use of the rubber adhesion promoter in the form of a chelate coordination complex consisting of a blocked di - and / or MDI, compounds of cobalt and boron, is able to provide the increased strength of rubber latunirovannaya steel cord and its stability under conditions of oxidative and salt aging, characterized by the optimum processing properties.

The promoter of adhesion of rubber to lutunasobasoba the steel cord obtained by alloying blocked with ε-caprolactam and higher fatty acids, di - and / or MDI with cobalt stearate, boric acid and secondary phenylenediamine with the following ratio of components, wt.%:

The alloy encapsulated powdered inorganic substance selected from the group comprising colloidal kremnekislyh, kaolin, bentonite, zinc oxide, in the following ratio, wt.%:

Increasing the strength of rubber latunirovannaya steel cord in the presence of developed promoter is achieved by increasing the activity of the cobalt and blocked MDI, forming a relatively stable chelate coordination complex.

The structure of the chelate coordination complex, provided that the cobalt has a coordination number equal to six, can be represented as follows:

The results of the study by NMR indicate the possibility of formation of such a chelate complex. Thus, the shift of the chemical shift of the proton of the NH groups present in the molecules blocked MDI, occurs as a result of participation in the complexation unshared pair of electrons of the nitrogen atom of the NH group (see scheme) or carbonyl group in the structure of the amide group (-NH-CO-) (diagram not shown). In any case, really is offset from the chemical shift of the NH-group in the direction of large quantities (see drawing a - a, b).

In the vulcanization process of the disintegration of the chelate complex leads to the fact that the blocked polyisocyanate, interacting with the zinc hydroxide formed is the result of surface oxidation lutunasobasoba steel cord, contributes to the formation of chemical bonds at the boundary of rubber-lacunary metal cord. This has the advantage that the stated promoter, because in contrast to the known modifiers (in particular, the prototype of cobalt stearate), claimed to be more effective for Korda, the surface of which, inevitably, to a greater or lesser extent, in the process of storage, obrezinivanie and vulcanization processes of oxidation.

The increase in thermal oxidative resistance of rubber is achieved by a reduction in the part of the promoters of the cobalt, which, as is well known [2], activates processes thermal oxidation of polymer compositions, as well as the introduction of the promoter secondary phenylendiamine.

In turn, released from the chelate complex is activated cobalt present in the promoter Bor provide the necessary strength and stability of connection by known mechanism, at substantially lower content in the rubber composition. So, instead of 1.0 parts by weight per 100 parts by weight of rubber in the application of cobalt stearate, is present in the rubber of 0.02 to 0.2 parts by weight of cobalt stearate in the case of declared adhesion promoter.

The presence of boron in the composition may be soluble in the composition of the boron oxide B₂O₃that is the result of money is tiravanija boric acid in the process of obtaining adhesion promoter.

Use as part of promoter adhesion of rubbers to lutunasobasoba the steel cord of antioxidant - secondary phenylenediamine, allows to mitigate the negative impact of the metal of variable valence, in this case cobalt, on the process of oxidative aging of the polymer. The introduction of the antioxidant in the composition allows more than very local, specific microvolume, to prevent the beginning of oxidation, catalyzed by cobalt. The desired effect of stabilization is not achieved by the additional introduction of the oxidant directly into rubber in quantities that correspond to its content in the composition of the proposed promoter. The usual dosage of antioxidant reach 0.5 to 2.0 parts by weight, and declared the promoter is not more than parts by weight 0,06

The process of obtaining adhesion promoter is as follows: the molten ε-caprolactam, secondary phenylenediamine and fatty acids at a temperature of 70-80°C is poured di - and / or polyisocyanate, the reaction block are 30-40 minutes under stirring, then add in the melt powdered alloy ε-caprolactam and boric acid and stirred for 15-20 min at a temperature of 70-80°C. After increasing the temperature to 100°C melt add the cobalt stearate is added and stirred for 15-30 min Obtained cobalt - and boron-containing blocked polyisocyanate is mixed with the powder the crustacean leaves the filling: in a closed apparatus (ball mill, disintegrator) at a temperature of 20-80°C to obtain microcapsules, the average size of which is not more than 100 microns.

As di and MDI are used: 2,4-toluylenediisocyanate; 2,6-diisocyanate and their mixtures; 4,4-diphenylmethanediisocyanate; mixtures of 4,4'-diphenylmethanediisocyanate and its dimers: a Polyisocyanate D (TU 11-3-03-38-106-90), the Polyisocyanate (TU 6-06-24-48-88), polyur.

As fatty acids are stearic and/or oleic acid.

As a secondary phenylendiamine use: N-isopropyl-N'-phenyl-n-phenylenediamine (deafen FP), N,N'-diphenyl-n-phenylenediamine (deafen FF).

To obtain adhesion promoter used cobalt stearate, corresponding to THE 2494-001-53904859-02.

As a powdery filler: colloidal silicic acid (BS-120, BS-100), kaolin, bentonite, zinc oxide.

Alloys ε-caprolactam and boric acid are prepared beforehand at a temperature of 90-100°C at a ratio of components (wt.%) 70-80 ÷ 30-20, respectively. Alloys ε-caprolactam - boric acid in the presented range correlations are characterized by the lowest melting temperature as close to the eutectic or represent eutectic ratio. The relatively low melting point alloys provides melting high-melting boric acid and its uniform distribution in the structure of blokiran the th MDI synthesis step.

Deviation from this ratio, or the use of boric acid without prior fusing with ε-caprolactam leads to the fact that boric acid is not melted at the stage of synthesis is blocked MDI, so unevenly distributed both in product and in rubber. In General, such a product to a lesser extent contributes to the stabilization of adhesive joints under conditions of salt aging (table 3).

The specified number of di - and / or MDI in the composition of the adhesion promoter on the one hand, provides him with the most high adhesive properties, on the other - optimal technological characteristics (a relatively long time to gelation during synthesis and the low viscosity of the reaction mass, relatively low melting temperature of the promoter). When the content of di - and / or MDI less than 15 wt.% deteriorate the adhesion properties of the product, when the content is more than 35 wt.% significantly reduces the time to gelation, which makes it almost impossible process to obtain the promoter of a particular composition and the desired properties due to the occurrence of adverse reactions.

The dosage interval ε-caprolactam, specified in the application, includes the number of ε-caprolactam, which is used to obtain alloys with boric acid. The minimum stated number is the number of ε-caprolactam is determined by the following conditions:

- first, in the reaction mass must be not less than equimolecular towards isocyanate groups, di - and / or MDI number of "free" ε-caprolactam. By "free" is understood as ε-caprolactam, which does not form a eutectic mixture with stearic acid at a ratio of substances of 1:1 (the number of ε-caprolactam in the eutectic melt can be from 4 to 10 wt.%), as well as ε-caprolactam, which is not included in the composition of the alloys with boric acid (the number of ε-caprolactam used in alloys with boric acid may range from 9 to 20 wt.%). For example, if the major part of the total number taken ε-caprolactam forms a eutectic relationship with stearic acid, its reactivity towards isocyanate groups decreases and increases flow velocity, undesirable side reactions;

- secondly, this quantity should be sufficient for compliance with the first condition, and for the formation of alloys with boric acid in the previously mentioned range of ratios.

The maximum stated amount of ε-caprolactam interdependent on the content of other components in the composition and in the case of the minimum of their content cannot be more than 69 wt.%.

When the content of fatty acids in the promoter less than 2 wt.% worse is its capability is to dispersion in rubber compounds, which adversely affects its adhesion efficiency, increases the cost of the promoter. The maximum content of fatty acids should not exceed 10 wt.%, because otherwise this leads to the need to reduce functionally active components of the composition.

Secondary phenylendiamine entered into the composition of the adhesion promoter to further protect the most exposed to various aggressive factors interfacial region from thermo-oxidative aging. In addition, secondary phenylendiamine, being present in the composition of the promoter in conjunction with the metal of variable valence (cobalt), prevent accelerated oxidative aging activated, as is well known, metals of variable valence. When the content of the secondary phenylendiamine less than 0.7 wt.% no observed effect stabilization, when the content is more than 10 wt.% does not increase the stabilizing action achieved in the specified range, this increases the cost of the promoter.

The presence of boron contributes to the stability of adhesive compound rubber with latunirovannaya steel cord in terms of vapor and salt aging. When the content of boric acid is less than 3.5 wt.% stability of rubber-cord tracks does not occur, due to maligakanda Bora less than 0.6 wt.%. If the content of boric acid exceeds 6 wt.% there is a saturation of its molten ε-caprolactam, with excess boric acid does not melt at a temperature synthesis conditions and settles upon termination of the mixing. The resulting heterogeneous promoter.

When the content of cobalt stearate less than 10 wt.% deteriorating the adhesion of the rubber to lutunasobasoba the steel cord. The increase of cobalt stearate in the product more than 30 wt.% does not improve the strength and stability of the adhesive connection.

We offer a range of doses of powder filling: 40-80 wt.% allows, on the one hand, to obtain the encapsulated product that has minimal dusting, to achieve the product is not sticky capsules, representing a cobalt-boron-containing blocked polyisocyanate, enclosed in a shell of powdered inorganic media. The optimum content of the powdered inorganic substance is determined by its type.

The adhesion promoter is introduced into the rubber compound for lining lutunasobasoba steel cord in the amount of 0.6 to 4.5 parts by weight per 100 parts by weight of rubber.

Rubber compound for lining lutunasobasoba steel cord, parts: rubber SKI-3 - 100,0; THE N-330 - 63,0; oil MO-S - 10,0; rosin - 1.0; stearin - 1,0; zinc white - 8,0; Eapen OP - 1,0; benzoic acid - 0.5; acetonyl - 0,5; sulfenamid M - 1,0; santogard PVI - 0,4; sulfur polymer (or copolymer) to 2.8 (or 3.5).

The vulcanization of rubber was carried out at 155°C for 20 minutes was Evaluated physico-mechanical characteristics according to GOST 270-75: conditional stress at 300% elongation, conditional tensile strength, elongation at tensile. Evaluated the bond strength of the rubber to lutunasobasoba the steel cord brand 9L 15/27 and its stability under conditions of salt, vapor (according to GOST 237859-79) and thermal-oxidative aging (according to GOST 9.024-74).

Examples

Table 1 shows the compositions of the products, illustrating the presented invention.

Promoters (compositions given in table 1) were introduced in the rubber mixture, instead of cobalt stearate. The compositions and properties of the rubber mixtures is given in table 2. The comparison was carried out with rubbers containing cobalt stearate and the blocked polyisocyanate obtained by the RF patent №2186059.

Rubber mixture obtained promoterami, in addition to a fairly good performance, have lower cost compared to rubbers containing cobalt stearate. When used for encapsulation of zinc oxide from a rubber compound was eliminated or reduced dosage of zinc oxide.

Techniques 1, 2, 5, 8, 9, 13 (see table 1) fall outside the scope Pref is effected in the claims ratios patentable adhesion promoters. Adhesion promoters, which are shown in examples 1, 2, 13, the rubber was not introduced as a result of their poor technological properties, unacceptable both for the manufacturer's products, and for consumers.

As follows from the data in table 3, the inventive adhesion promoters practically do not change the physico-mechanical properties of vulcanizates. In General, the properties of the vulcanizates meet the standards for this rubber composition: σ₃₀₀=13,7±2.0 MPa, σ_p≥18.0 MPa, ε_Rel≥320%.

A distinctive feature of the proposed promoters (see table 3), corresponding to the claimed compounds is the provision of a sufficiently high level of adhesion of rubber to steel cord, the stability of the adhesive compound with salt and thermal-oxidative aging. The vulcanizates also have a higher stability properties in terms of thermal-oxidative aging.

The change in the adhesion and properties of the vulcanizates after thermal-oxidative aging is to a greater extent in those cases where the adhesion promoters contain a high amount of metals of variable valence in the composition, in particular when using cobalt stearate, or when the deviation of the composition of the promoter.

Sources of information

1. Beavers Y.A. Mount rubber to steel cord with the use of the cation compounds of metals of variable valence / Waarom, Clendenin, Ellmore, Agapitova // Rubber & rubber, 2005. No. 2. - P.37-44.

2. Encyclopedia of polymers. Ed. Board: Vaganov (chapters. amended) and other V.3): Soviet encyclopedia, 1977. - S.

The ADH promoter is Ziya rubbers to lutunasobasoba the steel cord, characterized in that it consists of an alloy blocked with ε-caprolactam and higher fatty acids, di - and / or MDI with cobalt stearate, boric acid and secondary phenylenediamine with the following ratio of components, wt.%: