RU2373184C2 - Method of producing phenylenediamine antioxidant for emulsion-polymerised rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves reacting derivative of maleic anhydride with n-aminodiphenylamine while heating to temperature not above 90°C. The derivative of maleic anhydride used is alkenyl succinic anhydride or a mixture of alkenyl succinic anhydrides of general formula:

, where n=6,8,10,12,14,16,18 with molar ratio of maleic anhydride links to n-aminodiphenylamine equal to 1.0-1.05:1.0.

EFFECT: improved processing characteristics of antioxidant, characterised by low dropping point, high efficiency for emulsion-polymerised rubber and latex, protection of said rubber from thermal-oxidative ageing.

1 tbl, 7 ex

Description

The invention relates to the field of production of antioxidants of rubber emulsion polymerization and commodity latexes, specifically to the production of antioxidants of the phenylenediamine type.

A known method of producing amine antioxidant for various types of synthetic rubbers N, N′-diphenylphenylenediamine-1,4 (diaphen FF) (Chemical additives to polymers. / Handbook. - M: Chemistry, 1984, p. 39). The synthesis is carried out by condensation of aniline with hydroquinone or with n-aminophenol, at high temperatures, up to 200 ° C, using sophisticated equipment. The main disadvantage of this method of obtaining a stabilizer is the need to use expensive and scarce raw materials - hydroquinone or n-aminophenol.

The stabilizer obtained by this method has a number of other disadvantages, such as poor solubility in polymers, the difficulty of introducing it into emulsion polymerization rubbers, and therefore it is not used in industrial practice to stabilize emulsion polymerization rubbers and latexes.

There is also known a method of producing an antioxidant of the phenylenediamine type, N-isopropyl-N-phenyl-n-phenylenediamine (diaphen FP) (A.S. Czechoslovakia 219094, MKI C07C 85/08, 07/15/1985). Diafen FP or its analogues with a higher molecular weight alkyl radical is obtained by treating n-aminodiphenylamine with ketones in the presence of copper chromite catalysts at a temperature of 120-220 ° C under a hydrogen pressure of 2-15 MPa. This method is characterized by high fire and explosion hazard and complex technological design. In addition, the stabilizer obtained by this method has several disadvantages, which are its high volatility and high solubility in acidic aqueous solutions. As a result, its use to stabilize the rubbers of emulsion polymerization is limited, since during coagulation it is largely washed out of rubber and into sewage.

A known method of producing polymer antioxidants by reacting a copolymer of maleic anhydride with ethylene, or α-olefin, or styrene, or octadecene, or methyl vinyl ether with compounds containing simultaneously hydrazide or amine groups and groups of spatially hindered phenol or spatially hindered amine and other groups responsible for the stabilizing effect (US No. 4863999, MKI T08F 8/30, 055.09.1989). The disadvantage of this method is that as a result of the reaction, products with imide structures are formed:

These are highly polar compounds that combine well with synthetic polymers selected from the group: polyolefin, acrylic polymers, polystyrene, polyphenyl ether, polycarbonate, polyamide, or mixtures thereof. However, they are poorly compatible with the most common rubbers, such as styrene butadiene, polybutadiene, polyisoprene.

A known method for producing an amine antioxidant by treating epoxidized linseed oil with an aromatic amine, such as α-naphthylamine, aniline, toluidine, anisidine, with an equimolecular ratio of epoxy and amine groups (B. M. Badran, AF Younan ea High MW material Shows potential as antioxidant and antiradiations agent Elastomerics, v. 122, N 2, p. 26-33, 1990). The process is carried out at a temperature of 130-140 ° C in an inert atmosphere for three hours. The disadvantages of this method are as follows:

1) In the synthesis of an antioxidant, reactions of intermolecular crosslinking take place in parallel, leading to a difficultly regulated increase in molecular weight and deterioration of the technological properties of the resulting antioxidant;

2) It is necessary to use the antioxidant obtained by this method in fairly high dosages (2-3 wt.% Per 100 wt. Parts of rubber).

A known method of producing an antioxidant for emulsion polymerization rubbers (RF №2130013, IPC С07С 233/7, С08К 5/20, 1999) by interacting with heating maleic tall oil containing tar and fatty acids in a mass ratio of 1-2: 1, respectively, with mass the proportion of bound maleic anhydride 10-30% with n-aminodiphenylamine, with a mass ratio of maleated tall oil: n-aminodiphenylamine 100: 18-54, respectively. The disadvantages of this method are as follows: tall oils used for maleinization contain (depending on the wood from which they are obtained) 30-60% of resin acids; 30-60% fatty acids; up to 20% of neutral substances, up to 4% of them insoluble in petroleum ether. In this regard, in the resulting antioxidant there remains a significant amount of "ballast" products that do not protect latexes, rubbers, rubber based on them from thermo-oxidative aging. Therefore, when using such antioxidants, it is necessary to increase their dosage. In addition, the disadvantage is the unpleasant smell of tall oils and derivatives based on them.

Closest to the proposed one is a method for producing an amine antioxidant (RU No. 2130033, IPC C08F 8/32, C08L 9/02, 9/06, 1999) by treatment with heating of a polymer containing units of bound maleic anhydride, n-aminodiphenylamine in a medium organic solvent, where low molecular weight (co) polymers based on diene monomers with a molecular weight of 600-2000 containing grafted maleic anhydride units in an amount of 10-30% are used as polymers, with a weight ratio of grafted maleic anhydride and n-aminodiphenylamine a 1: 0.9-1.9. The disadvantages of this method are the following:

1) The effectiveness of the antioxidant obtained by this method is determined by the fragments contained in it with the phenylenediamine structure:

However, the content of these fragments is small - approximately 25% of the total mass of the product. As a result, in order to achieve a stable stabilization effect, it is necessary to use sufficiently large dosages of such antioxidants, as a rule, more than 1.5%.

2) The antioxidants obtained by the prototype are resinous products with a dropping point of the order of 98 ° C, which creates technological difficulties in their packaging and dosing.

The objective of the proposed invention is to obtain an amine antioxidant, in the case of which it would be possible to reduce its effective dosage while maintaining high effectiveness of its protective effect for latexes and rubbers of emulsion polymerization and rubbers based on them from thermo-oxidative aging, as well as characterized by improved technological properties.

The technical result consists in obtaining a phenylenediamine antioxidant with a high content of fragments with a phenylenediamine structure and characterized by a low dropping point.

The technical result is achieved by the fact that the method of producing a phenylenediamine antioxidant for emulsion polymerization rubbers involves the interaction of a maleic anhydride derivative with n-aminodiphenylamine, when heated no higher than 90 ° C, while alkenyl succinic anhydride or a mixture of alkenyl succinic anhydrides of the general formula are used as a maleic anhydride derivative:

where n = 6, 8, 10, 12, 14, 16, 18

with a molar ratio of alkenyl succinic anhydride and n-aminodiphenylamine, respectively, 1.0-1.05: 1.0.

Obtained according to the claimed method, the phenylenediamine antioxidant is characterized by a higher content of fragments with a phenylenediamine structure of -35.5-49%, which allows to reduce its content in rubber to 0.3-0.7%, and is characterized by a lower dropping point - <20-30 ° C.

Also, the inventive method for producing a phenylenediamine antioxidant is technologically simpler than the known one, does not require special equipment, can be implemented both in a solvent medium and without a solvent.

The structure of the antioxidant is proven by IR spectroscopy. In the IR spectra of antioxidants obtained by the claimed method, the following absorption bands are present: 1660 cm ^-1 - OO stretching vibration band (amide 1), 1518 cm ^-1 - intense deformation band C = O related to the carbonyl group and stretching vibration band C = C alkenyl radical. In this case, there is no absorption band at 1780 cm ^-1 , characteristic of the imide structure. These data prove the formation of monoamide structures as a result of the synthesis.

Figure 1 shows a table in which the characteristics of the synthesis methods and the protective properties of the antioxidant for rubbers of emulsion polymerization obtained according to examples of implementation of the claimed method 1-7 are presented.

For the synthesis of antioxidants by the claimed method, alkenyl succinic anhydrides are used - maleinization products of olefins of the general formula C _p H _2p , where n = 6, 8, 10, 12, 14, 16, 18.

Obtaining an antioxidant - a reaction with n-aminodiphenylamine is carried out at a temperature not exceeding 90 ° C. An increase in temperature above 90 ° C is undesirable due to the formation of imides:

Accordingly, the polarity of the product increases, its solubility and effectiveness as an antioxidant decrease.

The synthesis in the environment of an organic solvent is technologically more complicated, however, in this embodiment it is easier to maintain the necessary temperature conditions and to exclude the formation of imide. Ketones (acetone, methyl ethyl ketone) or alcohols (methyl, ethyl, isopropyl) can be used as a solvent. The solvent from the reaction mass is distilled off.

Due to the fact that the resulting product contains a carboxyl group, it easily interacts with aqueous alkalis to form a stable emulsion. The emulsion does not delaminate during storage, unlike the well-known industrial antioxidants, it is easily introduced into rubber latex. Isolation of rubber from latex is carried out using conventional technology, using acid and salt or a salt-free coagulation agent as coagulants. At the same time, the antioxidant remains in the rubber and is not washed out in wastewater.

The invention is illustrated by examples of specific performance.

Example 1

A mixture of alkenyl succinic anhydrides (n = 12 and 14 with a mass ratio of 7: 3) in an amount of 100 g and p-aminodiphenylamine in an amount of 650 g are loaded into a reactor equipped with a coolant jacket, a molar ratio of the reaction components is 1: 1. The process is carried out with stirring, a temperature of 65-70 ° C for 1.5 hours. The resulting product at the reaction temperature has the appearance of a dark viscous liquid, at room temperature it is dark oily. The molecular weight of the obtained antioxidant is 467.5, the mass ratio of units of maleic anhydride and n-aminodiphenylamine, respectively 1.00: 1.88, the mass fraction of nitrogen in the antioxidant 5.98%.

To introduce an antioxidant into rubber, a 20% aqueous alkaline solution is prepared from it, which is introduced into latex. Isolation of rubber from latex is a mixture of salt + acid coagulants.

Examples 2-6.

All operations were carried out as in example 1, while changing the composition of alkenyl succinic anhydrides, the mass ratio of the components and the use of solvent. The synthesis conditions and characteristics of the products are shown in the table. Data on the stabilizing properties of the products are also given here. The work was performed on styrene-butadiene rubber of the SKS-30ARKP brand. Based on the antioxidants obtained in Examples 1-6, their aqueous alkaline solutions are prepared with a concentration of 15-20% and a pH of 10-11. The solution is introduced into the rubber latex, and the rubber is isolated from the latex in the usual manner using sodium chloride and sulfuric acid as coagulants. In order to check the stabilizing properties of antioxidants, rubber is tested under accelerated aging conditions: heat treatment of rubber in an air thermostat (150 ° C, 1 hour), thermomechanical treatment on rollers (100 ° C, 20 min). The change in the properties of rubber is evaluated by the gel content, Defoe stiffness, elastic recovery and Carrer plasticity.

Example 7 (control).

200 g of low molecular weight polybutadiene (µ _p = 1000) containing 19.5% grafted maleic anhydride is dissolved in 200 g of acetone. To the resulting solution was poured 148.9 g of a 50% solution of n-aminodiphenylamine. The mixture was stirred at 50 ° C. for 4 hours. An antioxidant solution is obtained - low molecular weight polybutadiene containing N (4-anilinophenyl) succinamic acid.

To introduce an antioxidant into the rubber of emulsion polymerization, an emulsion is prepared from it: 1100 g of a 3% aqueous solution of sodium hydroxide are poured into an acetone solution of the antioxidant and acetone is distilled off. The introduction of the antioxidant in rubber is carried out analogously to example 1 and 2. The table shows the test results of the obtained antioxidant in accelerated aging.

A method of obtaining a phenylenediamine antioxidant ... No. p / p The name of indicators The values of the indicators in the examples one 2 3 four 5 6 7 (prototype) one The mass ratio of fractions of α-olefins used in the preparation of antioxidants: C _l2 H ₂₄ : C ₁₄ H ₂₈ 7: 3 C ₆ H ₁₄ : C ₁₄ H ₂₈ 1: 4 C ₁₄ H ₂₈ one C ₈ H ₁₆ : C ₁₆ H ₃₂ 2: 3 C ₁₂ H ₂₄ one C ₁₈ H ₃₆ one 2 The molar ratio of units of maleic anhydride and paraaminodiphenylamine: 1: 1 1.05: 1 1.05: 1 1.05: 1 1.05: 1 1.05: 1 1: 1 3 The solvent used to obtain the antioxidant methanol ethanol acetone acetone four Synthesis temperature, ° С 70 ÷ 5 50 ÷ 5 75 ÷ 5 65 ÷ 5 50 ÷ 5 75 ÷ 5 20 ÷ 5 5 Synthesis time, hour 1,5 3.0 2.5 2.0 3.0 2.0 6 6 Mass fraction of bound nitrogen in antioxidant,%: * 5.98 6.20 5.81 5.99 6.20 5.60 2.00 ** 6.03 6.14 5.85 6.01 6.21 5.53 2.04 7 Drop point of antioxidant, ° С <20 <20 <20 <20 <20 thirty 80 8 Mass fraction of antioxidant in rubber,% 0.4 0.3 0.5 0.6 0.5 0.7 1.3 9 Mass fraction of gel in rubber: Initial after heat aging (150 ° C, 60 min) 0.9 1,0 0.8 0.9 0.8 0.9 0.9 After machining (100 ° C, 20 min) 2,4 2.6 2.6 2.5 2.7 2.5 2.7 10 Defo stiffness, N Source 8.7 8.6 8.8 8.9 8.7 8.8 8.9 After machining (100 ° C, 20 min) 6.3 6.4 6.2 6.5 6.6 6.7 6.2 eleven Carrera ductility: Source 0.33 0.32 0.34 0.33 0.33 0.34 0.34 After machining (100 ° C, 20 min) 0.41 0.42 0.41 0.41 0.39 0.40 0.42 * - found fraction of nitrogen, the analysis was performed by the Kjeldahl method;
** - estimated nitrogen fraction

Claims (1)

A method of producing a phenylenediamine antioxidant for emulsion polymerization rubbers by reacting a maleic anhydride derivative with p-aminodiphenylamine when heated to not higher than 90 ° C, characterized in that alkenyl succinic anhydride or a mixture of alkenyl succinic anhydrides of the general formula are used as the maleic anhydride derivative

where n = 6, 8, 10, 12, 14, 16, 18 with a molar ratio of units of maleic anhydride and p-aminodiphenylamine 1.0-1.05: 1.0.