RU2528673C1 - Complex anti-aging agent for rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: complex anti-aging agent for rubber contains a powdered carrier - zinc oxide, and a liquid fusion of anti-aging agents, obtained at 70-90°C, containing N-isopropyl-N-phenyl-n-phenylenediamine, boric acid in the form of a melt obtained beforehand in ε-caprolactam at temperature of 110-115°C, salicylic acid and additionally zinc oxide.

EFFECT: invention provides a high level of thermal-oxidative and ozone resistance of rubber containing a complex anti-aging agent during prolonged use.

2 tbl, 2 ex

Description

The invention relates to the production of a comprehensive antioxidant for rubbers, which provides the latter with the best preservation of properties in the process of thermo-oxidative and ozone aging, and can be used in the tire and rubber industry to provide thermo-oxidative and ozone resistance to rubbers for a long time of their operation.

It is known [RF Patent for the invention 2279450, MKI C08K 13/02, C08K 5/18, C08K 5/20, C08K 9/04, C08L 21/00, publ. 07/10/2006] the use of a composite antioxidant for rubbers, consisting of a liquid alloy of antioxidants and a powdered carrier in a mass ratio of 50:50. The liquid alloy of antioxidants is a eutectic alloy of N-isopropyl-N-phenyl-n-phenylenediamine and ε-caprolactam at a ratio of 60: 40 wt. Composite antioxidant allows the rubber to provide a sufficiently high level of ozone resistance for a long time of their operation. However, the disadvantage of the composite antioxidant is the need to treat the powdered carrier with surface-active substances, which complicates the technological scheme of its preparation and entails additional economic costs.

Known vulcanizable rubber compound [RF patent for the invention No. 2236423, MKI C08L 7/00, 9/00, 9/02, C08K 13/02, publ. 09/20/04 BI No. 26], which includes a composite antioxidant in an amount of 0.5-5.0 wt.h. per 100.0 parts by weight rubber, consisting of a liquid alloy of antioxidants obtained at a temperature of 70-90 ° C in the following ratio of components, parts by weight:

N-isopropyl-N-phenyl-n-phenylenediamine 35.00-40.00 N, N'-diphenyl-p-phenylenediamine 10.00-24.00 2-mercaptobenzthialol 6.00-10.00 ε-caprolactam 35.00-40.00

and a powdered carrier, and the ratio of the alloy of antioxidants and powdered carrier is, wt.h .:

antioxidant alloy 15.00-50.00 powder carrier 50.00-85.00

However, in this case, the composite antioxidant does not provide vulcanizates with a high level of protection against ozone aging. Its action is mainly aimed at ensuring the durability of rubbers in the conditions of thermo-oxidative aging.

Closest to the claimed complex antioxidant may be a composite antioxidant, which is introduced into the rubber compound [RF Patent for the invention No. 2443730, MKI C08L 7/00, C08L 9/00, C08L 9/06, C08K 3/24, C08K 3/36 , C08K 5/18, C08K 13/02, publ. 05.27.12 BI No. 6] and consists of a powdered carrier - colloidal silicic acid and a liquid alloy of antioxidants obtained at a temperature of 70-90 °, containing N-isopropyl-N-phenyl-n-phenylenediamine, 6-caprolactam, polymer 2.2, 4-trimethyl-1,2-dihydroquinoline, stearic acid, boric acid in the form of a previously obtained melt in ε-caprolactam at a temperature of 110-115 ° C with the following ingredients, parts by weight:

N-isopropyl-N-phenyl-n-phenylenediamine 50.00 -55.00 ε-caprolactam 20.00 -22.00 stearic acid 5.00-6, 50 boric acid 20.00-22.00

moreover, the ratio of the alloy of antioxidants and powder carrier is, wt.h .:

antioxidant alloy 55.00-60.00 colloidal silicic acid 40.00-45.00

The preparation of this product, in contrast to the above antioxidant, when natural sodium bentonite is used as the carrier powder, does not complicate the technological scheme. The use of preventive-type chemical antioxidants in it, antioxidants breaking the oxidation chain, as well as boric acid, allows rubbers to maintain a sufficiently high level of thermo-oxidative and aging resistance in conditions of high humidity. However, in this case, the composite antioxidant does not provide a high level of protection against ozone aging for a long time.

The problem to which this invention is directed is to obtain a comprehensive antioxidant that provides a high level of thermo-oxidative and ozone resistance to rubbers for a long time of their operation.

The technical result is to obtain a comprehensive antioxidant for rubbers, providing a high level of thermo-oxidizing and ozone resistance to rubbers for a long time of their operation.

The technical result is achieved by obtaining a complex antioxidant for rubbers, consisting of a powder carrier and a liquid alloy of antioxidants obtained at 70-90 ° C, containing N-isopropyl-N-phenyl-n-phenylenediamine, ε-caprolactam, boric acid in the form of previously obtained melt in ε-caprolactam at a temperature of 110-115 ° C, characterized in that the alloy contains salicylic acid and additionally zinc oxide in the following ratio of ingredients, parts by weight:

N-isopropyl-N-phenyl-n-phenylenediamine 50.00-45.20 ε-caprolactam 14.50-13.4 boric acid 6.00-5, 70 salicylic acid 23.00-27.60 zinc oxide 6.50-8.10

moreover, as the powder carrier is used zinc oxide in the ratio, parts by weight:

antioxidant alloy 30.00-20.00 zinc oxide 70.00-80.00

A comprehensive antioxidant for rubbers provides effective protection in the process of oxidative and ozone aging due to the synergism of antioxidants - N-isopropyl-N-phenyl-n-phenylenediamine and ε-caprolactam. The prolonging effect of the complex antioxidant is enhanced by the adsorption interaction in the antioxidant alloy – carrier surface system. The effectiveness of the protection against ozone exposure is additionally provided by boron, which is part of boric acid, and then its derivatives in the complex, and directly in the surface layer of rubbers. In this case, the action of boron is similar to that which takes place, for example, in nuclear reactors, when boron absorbs fast neutrons. It is known that to protect against fast neutrons during the operation of nuclear reactors, control rods are used that contain cadmium or boron - elements that strongly absorb neutrons, which, by changing the degree of absorption of neutrons, regulate the progress of the chain reaction or stop it quickly as necessary [V. Levin . Nuclear physics and nuclear reactors. 4th ed. M .: Atomizdat, 1979. - 288 s]. There is information about the effect of neutrons on other processes. So, scientists from the Institute of Physics and Economics of the Russian Academy of Sciences discovered [A.V. Syroeshkin, N.V. Plotnikova, V.B. Lapshin. Neutron field at the Earth’s surface and the biosphere, 2011. - 204 s] that nonequilibrium electrochemical systems are abnormally sensitive to ultra-weak thermal neutron fluxes. If we shift the influence of neutrons on the studied object - the surface layers of rubber, then boron, absorbing neutrons, the concentration of which, although small, is sufficient to energetically excite double bonds of rubber, can reduce the destructive effect of ozone.

Salicylic acid at the initial stage of alloy preparation together with ε-caprolactam is used to create a dispersion medium in which crystalline ingredients dissolve. In addition, salicylic acid leads to the formation of zinc complex compounds, which ultimately contributes to the creation of a more regular spatial vulcanization structure that is resistant to thermal oxidative and ozone aging. Volcanizates with its participation are characterized by increased module values.

The conditions for neutron absorption by boron are created by a medium represented by an alloy of salicylic acid, ε-caprolactam and N-isopropyl-N-phenyl-n-phenylenediamine, in which boron in the form of its derivatives is represented, at least, in the form of colloidal particles, but not large dispersed particles. Evidence of this is the fact that alloys are transparent under normal conditions in thin layers. Alloys have a fairly low dropping point of 60 -90 ° C.

Zinc oxide in the process of preparing the alloy is necessary for the formation of a medium salt - zinc salicylate. Under the condition that zinc salicylate is formed, the formation of a complex salt cannot be ruled out, where in the ligand sphere zinc coordinates N-isopropyl-N-phenyl-n-phenylenediamine, ε-caprolactam, boric acid (or its derivatives). Thus, zinc oxide enhances the protective properties of the resulting antioxidant, which is expressed in the thermo-oxidizing and ozone resistance of rubbers over a long period of their operation.

The following substances are used in the complex antioxidant: N-isopropyl-N-phenyl-n-phenylenediamine TU 2492-002-05761637-99; ε-caprolactam GOST 7850-86; boric acid GOST 9656-75; salicylic acid GOST 624-70; zinc oxide GOST 10262-73.

The use of the proposed method N-isopropyl-N-phenyl-n-phenylenediamine less than 45.20 wt.h. not advisable, since the product is less effective in protecting against thermo-oxidative aging. When the content of N-Isopropyl-N-phenyl-n-phenylenediamine is more than 50.00 parts by weight the amount of this product in the rubber sample (2 parts by weight per 100 parts by weight of rubber) increases, which leads to a proportional decrease in the proportion of boron and a deterioration in the protective functions of the complex antioxidant as a whole from the action of ozone.

The content of ε-caprolactam in the dosage range of 14.50-13.40 parts by weight provides alloys in the form of viscous liquids suitable for unloading the product from the reactor and its further encapsulation.

The effectiveness of the protection against the effects of ozone is observed when the content of boric acid is in the range of 6.00-5.70 parts by weight, and a higher acid content is possible, but the viscosity of the alloy increases so much that difficulties arise in the technological process of its preparation .

The content of salicylic acid 23.00-27.60 wt.h. is determined by its stoichiometric amount necessary for the formation of zinc salicylate, which, in turn, is necessary to create conditions for obtaining a product providing thermo-oxidative and ozone resistance to rubbers for a long time of their operation.

As a powdery carrier, zinc oxide is used, which, in essence, is a hard shell of the capsules, and such a shell is sufficiently dense, which prevents the penetration of the liquid substance of the capsule through it and the conversion of the powdered product into a paste. The use of zinc oxide as an encapsulating substance also provides an additional activating effect, which, in turn, contributes to the formation of a regular spatial vulcanization structure. In this case, 70.00-80.00 parts by weight zinc oxide in the complex antioxidant is justified by the technological properties of the product as a whole. When the content of zinc oxide is more than 80 parts by weight a decrease in the protective properties of the complex antioxidant is observed. When the content is less than 70 parts by weight the resulting complex antioxidant is a pasty product.

The alloy is produced in a heated reactor equipped with an anchor type mixer:

- at a temperature of 110-115 ° C, the calculated amount of ε-caprolactam and boric acid is loaded, the homogenization of the alloy proceeds quite quickly and is accompanied by the release of gaseous substances. Homogenization continues until the latter is completely isolated, which is 50-60 minutes when loading components within 100-200 g;

- then the melt temperature is lowered to 70-90 ° C and N-isopropyl-N-phenyl-n-phenylenediamine is charged, the melt is completely melted and homogenized (another 10-15 minutes), after which salicylic acid is charged and also for 10- 15 min achieve complete homogenization of the melt;

- the next step, zinc oxide is introduced in portions in the melt, the number of such portions can be 5-6 in order to avoid intense gas generation, the consequence of this is the raising of the melt column. Homogenization is completed after loading the last portion of zinc oxide, continuing mixing for 40-60 minutes.

The calculated amount of the powdered carrier is loaded into the obtained alloy, roughly mixed in a “drunk barrel” type apparatus, after which the whole mass is transferred for encapsulation into a ball mill. In laboratory conditions, a 3 dm ball mill was used. Ball loading exceeded the mass of the product as a whole by 2 times. Unloading of the finished product is carried out after 60-90 minutes in a receiving tank.

Example 1. The alloy is carried out in a heated reactor equipped with an anchor type mixer:

- at a temperature of 110-115 ° C, 14.50 g of ε-caprolactam and 6.00 g of boric acid are loaded, the alloy is homogenized for 50-60 minutes;

- then reduce the temperature in the reactor to 70-90 ° C and load 50.00 g of N-isopropyl-N-phenyl-n-phenylenediamine, melt for 10-15 minutes, then load 23.00 g of salicylic acid and mix 10-15 minutes;

- at the next stage, 6.50 g of zinc oxide is introduced into the alloy in portions of 1.30 g each. Homogenization is completed after loading the last portion of zinc oxide, continuing mixing for 40-60 minutes.

233 g of zinc oxide (which is 70 parts by weight) are loaded into the obtained alloy, roughly mixed with a spatula, and then transferred for encapsulation into a ball mill. Unloading of the product is carried out after 60-90 minutes in a receiving tank.

In the proposed example 1 receive a comprehensive antioxidant. The protective actions of the inventive integrated antioxidant against the effects of heat, oxygen and ozone on the rubber were evaluated in an object represented by a vulcanized rubber compound for the manufacture of a tire tread. The composition and properties of the rubber mixture containing the complex antioxidant prepared according to example 1 are shown in table 1 (composition 3, 4), table 2 (composition 3, 4).

Example 2. The preparation of a complex antioxidant similar to example 1, with the difference that the quantitative content of the components in the alloy is, g: 45.20 - N-isopropyl-N-phenyl-n-phenylenediamine; 13.40 - ε-caprolactam; 5.70 boric acid; 27.60 - salicylic acid; 8.10 - zinc oxide. 400 g of zinc oxide (which is 80 parts by weight) are loaded into the obtained melt, roughly mixed, and then transferred to a ball mill for encapsulation. Unloading of the product is carried out after 60-90 minutes in a receiving tank.

The protective actions of the inventive integrated antioxidant against the effects of heat, oxygen and ozone on the rubber were evaluated in an object represented by a vulcanized rubber compound for the manufacture of a tire tread. The composition and properties of the rubber mixture containing the complex antioxidant prepared according to example 2 are shown in table 1 (composition 5, 6), table 2 (composition 5, 6).

For comparison, control rubber compounds were prepared for the manufacture of agricultural tire tread containing a composite antioxidant (prototype) according to example 1 described in RF patent No. 2443730. The composition and properties of rubber compounds are presented in table 1 and 2. The composition of the mixture 1 and 2 contain a composite antioxidant made according to the prototype. Known and proposed rubber compounds are prepared according to standard conditions, vulcanized in a press with electric heating at a temperature of 155 ° C in optimum. In rubber mixtures, the following can be used as rubbers: polyisoprene GOST 14925-79, butadiene GOST 14924-75, styrene butadiene GOST 11138-78, butadiene-methyl styrene GOST 23492-83, etc., as well as their combinations. Vulcanizing agents, accelerators are selected from the group: GOST 1271-93 sulfur, GOST 740-76 thiurams, GOST 739-74 thiazoles, TU 6-14-756-78 sulfenamides, GOST 40-80 guanidines, GOST 14888-62 organic peroxides; vulcanization activators: zinc oxide GOST 202-84, magnesium oxide GOST 844-79, etc. In addition, plasticizers can be introduced into the rubber mixture (rosin GOST 19113-84, pyroplast GOST 8728-88, oil PN-6 GOST 8728-88 , oleic acid GOST 7580-91, etc.), fillers (carbon black GOST 7885-86, chalk GOST 12085-88), pore-forming substances (carbon dioxide GOST 8050-64, etc.), dyes (titanium dioxide pigment GOST 9808- 65, etc.) and other additives, for example, modifiers (hepsol HKP TU 6-01-5-81-97, resorcinuroprotin complexes TU 41994745-95-2, etc.).

Table 1 Composition of rubber compounds based on a combination of rubbers SKI-3, SKD and SKMS-30 ARKM-15 Ingredients The composition of the rubber mixture per 100 parts by weight rubber one 2 3 four 5 6 Rubber SKI-3 40.00 40.00 40.00 40.00 40.00 40.00 SKD rubber 40.00 40.00 40.00 40.00 40.00 40.00 Rubber SKMS-30ARKM-15 20.00 20.00 20.00 20.00 20.00 20.00 Carbon black N550 60.00 60.00 60.00 60.00 60.00 60.00 Zinc oxide 4.00 4.00 4.00 4.00 4.00 4.00 Benzoic acid 0.50 0.50 0.50 0.50 0.50 0.50 Pine Rosin 2.00 2.00 2.00 2.00 2.00 2.00 Resin Pyroplast 2.00 2.00 2.00 2.00 2.00 2.00 Norman Oil 11.00 11.00 11.00 11.00 11.00 11.00 Oleic Acid 2.00 2.00 2.00 2.00 2.00 2.00 Ground sulfur 0.80 0.80 0.80 0.80 0.80 0.80 Santogard PVI 0.20 0.20 0.20 0.20 0.20 0.20 Sulfenamide 0.50 0.50 0.50 0.50 0.50 0.50 Captax 0.30 0.30 0.30 0.30 0.30 0.30 Acetonanil 2.00 2.00 2.00 2.00 2.00 2.00 Protective wax 2.00 2.00 2.00 2.00 2.00 2.00 Composite Antioxidant (prototype) 2.00 3.00 - - - Complex antioxidant (example 1) - - 2.00 3.00 - - Complex antioxidant (example 2) - - - - 2.00 3.00

table 2 Physico-mechanical properties of rubber compounds and vulcanizates based on a combination of rubbers SKI-3, SKD and SKMS-30 ARKM-15 Name of indicator Composition number one 2 3 four 5 6 Minimum torque, Nm (GOST 12484-65) 1.36 1.37 1.05 1,03 1.05 1,04 Maximum torque, Nm (GOST 12484-65) 5.41 5.39 4.78 4.80 4.78 4.90 The start time of vulcanization (ts), min (GOST 12484-65) 5,4 5.2 7.6 7.8 7.8 7.6 The time to reach the degree of vulcanization of 50%, min (GOST 12484-65) 19.3 19.1 13.0 12.8 13,2 12.9 Optimal vulcanization time, min 34.2 34.2 32.6 32,4 32,4 32,7 Mooney viscosity (130 ° C), arb. (GOST 10722-76) 31 thirty 29th 29th 29th 29th The time for exceeding the minimum torque by 5 units. Mooney min 44 44 43 43 43 43 Time to exceed the minimum torque by 35 units. Mooney min 54 54 53 53 53 53 Conditional tensile strength, MPa (GOST 270-75) 10,4 10.9 11.8 12.1 11.3 11.9 Conditional stress at 300% elongation, MPa (GOST 270-75) 3.6 3.6 4.2 4.0 4.0 4.2 Elongation at break,% (GOST 270-75) 700 700 700 710 700 700 Change in conditional tensile strength during thermo-oxidative aging (72 h × 100 ° C),% (GOST 9.024-74) -23 -twenty -17 -13 -17 -fourteen Change in conditional tensile strength during thermo-oxidative aging (96 h × 100 ° C),% (GOST 9.024-74) -28 -24 -eighteen -eighteen -twenty -fifteen Change in elongation at break during thermo-oxidative aging (72 h × 100 ° C),% (GOST 9.024-74) -40 -40 -39 -38 -39 -38 Change in elongation at break during thermo-oxidative aging (96 h × 100 ° C),% (GOST 9.024-74) -44 -38 -43 -39 -43 -38 Ozone resistance, hours (GOST 9.026-74) one one 1.25 1,5 1.25 1,5

As follows from the data of rheometric tests, the claimed product provides mixtures with an increase in the induction period. A characteristic feature is also a decrease in the rate of structuring in the main period, but nevertheless, for rubber compounds containing a complex antioxidant to the optimal control vulcanization time (containing a prototype) even a slight increase in modules is characteristic, as evidenced by the data in Table 2.

From the results of physical and mechanical tests of vulcanized rubber mixtures shown in Table 2, it follows that the proposed complex antioxidant protects against the action of heat and oxygen to a greater extent, and its long-term participation in the protection of rubbers from ozone, which is expressed by an increase in the time of ozone resistance of rubbers, is especially visible.

Thus, the use of the proposed composite antioxidant provides a high level of thermal oxidative and ozone resistance to rubbers for a long time of their operation.

Claims (1)

Comprehensive antioxidant for rubbers, consisting of a powdered carrier and a liquid alloy of antioxidants obtained at 70-90 ° C, containing N-isopropyl-N-phenyl-n-phenylenediamine, ε-caprolactam, boric acid in the form of a previously obtained melt in ε-caprolactam at a temperature of 110-115 ° C, characterized in that the alloy contains salicylic acid and additionally zinc oxide in the following ratio of ingredients, parts by weight:
N-isopropyl-N-phenyl-n-phenylenediamine 50.00-45.20 ε-caprolactam 14.50-13.40 boric acid 6.00-5.70 salicylic acid 23.00-27.60 zinc oxide 6.50-8.10
moreover, as the powder carrier is used zinc oxide in the ratio, parts by weight:
antioxidant alloy 30.00-20.00 zinc oxide 70.00-80.00