RU2846121C1 - Epoxy composition for powder coatings - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to paint industry. disclosed epoxide composition for powder coatings is characterized by that it contains, wt. %: 60.000 of epoxy diane resin ED-10, 0.800-1.200 of spreading agent, 2.700 of curing agent – dicyandiamide, 0.03-0.10 of functionalised with amino groups of nanofibres of aluminium oxide with diameter from 3 to 50 nm, balance is filler – barium sulphate, wherein composition of filler additionally includes pigments.

EFFECT: high strength, hardness of the coating, resistance to abrasive wear and longer service life of protected structures when exposed to aggressive media.

1 cl, 2 tbl, 4 ex

Description

The invention relates to the paint and varnish industry and is intended to protect metal surfaces from destruction when exposed to aggressive environments (salt solutions, acids, alkalis, oil, oil products) and abrasive wear.

The current level of technology includes a wide range of powder paints based on epoxy resins with a mass fraction of epoxy groups up to 13%. These paints are applied in the form of powders to metal parts in order to protect them and impart decorative properties to the surface. To obtain such paints, the epoxy resins used are usually mixed in a twin-screw extruder with a filler that imparts decorative properties to the coating and a curing agent, which is usually dicyandiamide [Yakovlev A. D. Powder Paints - L.: Chemistry, 1987. - 216 p., ill.].

The disadvantage of these materials is that the resulting coating, when used in the composition of dicyandiamine and epoxy resin with the number of equivalents of reactive groups less than 13, has insufficiently high impact strength, elasticity and resistance to aggressive environments (solutions of acids and bases).

The closest composition in technical essence, taken by the authors as a prototype, is the epoxy resin composition [WO 2012174989 A1, IPC C09D4/00, published 27.12.2012], having a curing component and an epoxy component. The curing component is included in the composition in an amount of 8% to 70% by weight of the composition of the primary curing agent and from 0.001% to 5% by weight of the composition of the secondary curing agent. The epoxy composition also includes from 30% to 92% by weight of the composition of the epoxy component. The number of equivalents of reactive groups in the curing component is approximately 0.50-0.98 times greater than the number of equivalents of epoxy groups in the epoxy component.

The disadvantage of the known composition, taken as the closest analogue, is that the coating based on it has low hardness, resistance to mechanical impact (impact, bending) and exposure to aggressive environments.

The technical problem solved using the developed composition consists of creating improved means of protecting metal surfaces from destruction under mechanical impact and exposure to aggressive environments (solutions of salts, acids, alkalis, oil, petroleum products).

The technical result of the invention is an increase in the strength, hardness of the coating, resistance to abrasive wear and a longer service life of the protected structures when exposed to aggressive environments.

The technical result is achieved in that the known epoxy resin ED-10 (according to GOST 10587-84) is mixed with a filler, which is synthetic barium sulfate, rutile, alumina, silica, carbon black or a mixture thereof, a spreading agent, a hardener - dicyandiamide, and also, according to the invention, additionally contains a cohesive nanofibrous agent (aluminum oxide nanofibers functionalized with amine groups), uniformly distributed in the epoxy resin with the following ratio of components in the coating, wt.%:

epoxy diane resin ED-10 60,000 dicyandiamide 2,700 spreading agent 0.800-1.800 aluminum oxide nanofibers 0.001-5.000 filler the rest

And also the fact that a low-viscosity polyester resin with carboxyl groups is used as a hardener and part of the epoxy resin in a ratio in which the mole fraction of epoxy groups is equal to the mole fraction of carboxyl groups.

And also the fact that the filler used is a material from a group containing barium sulfate, rutile, alumina, silica, carbon black or a mixture of them.

And also the fact that pigments are additionally introduced into the filler composition.

Aluminum oxide nanofibers are also synthesized using a similar technology described in the work of Simunin, M.M.; Voronin, A.S.; Fadeev, Y.V.; Mikhlin, Y.L.; Lizunov, D.A.; Samoilo, A.S.; Chirkov, D.Y.; Voronina, S.Y.; Khartov, S.V. Features of Functionalization of the Surface of Alumina Nanofibers by Hydrolysis of Organosilanes on Surface Hydroxyl Groups. Polymers 2021, 13, 4374.

The function of the cohesive agent is to form a hybrid structure when added to the epoxy resin. The aluminum oxide nanofibers are chemically bonded to the epoxy resin through functional amino groups on the surface, which leads to reinforcement of the polymer and an increase in its strength due to the cohesive energy.

The introduction into the composition as an additive of functionalized amino groups of aluminum oxide nanofibers with a diameter of 3-50 nm and a length of 0.2-5 μm of the claimed composition and uniformly distributed in the epoxy resin, in the appropriate amount, ensures the production of a denser structure of the composition. This effect is achieved due to an arbitrary chemical reaction between the functional amino groups on the surface of the nanofibers and the epoxy groups of the resin and a hybrid nanofiber-resin system is formed, which ensures an increase in mechanical strength, relative hardness and resistance to abrasive wear.

The proposed epoxy composition can be used as a protective anti-corrosion coating for metal, while improving the physical and mechanical characteristics: mechanical strength - up to 200 kg * cm for direct and reverse impact according to GOST 4765, relative hardness up to 2N on a pencil while maintaining high adhesion as in conventional powder paints, while the corrosion current using the new coating with its thickness of 60-80 μm drops to 0.120 μA / cm ² while for a conventional paint coating this value is 0.550 μA / cm ² .

The following substances were used to obtain the proposed epoxy coating composition:

- Epoxy diane resin ED-10 according to GOST 10587-84,

- Dicyandiamide, produced by Tianjin Icason Technology Co., Ltd,

- Bottling agent LA-88 Telko,

- Barium sulfate according to GOST 11380-74,

- Aluminum oxide nanofibers functionalized with amino groups, produced by Nanosintez LLC, - Are synthesized by analogy with the work of Simunin, M.M.; Voronin, A.S.; Fadeev, Y.V.; Mikhlin, Y.L.; Lizunov, D.A.; Samoilo, A.S.; Chirkov, D.Y.; Voronina, S.Y.; Khartov, S.V. Features of Functionalization of the Surface of Alumina Nanofibers by Hydrolysis of Organosilanes on Surface Hydroxyl Groups. Polymers 2021, 13, 4374.

This invention is illustrated by the following examples of specific implementation.

Example 1

Initially, the components of the epoxy composition are mixed in a drum mixer, where 1 g of aluminum oxide nanofibers functionalized with amino groups are successively loaded, then 1800 g of ED-10 epoxy resin, 81 g of dicyandiamide, 24 g of LA88 filling agent, and 1094 g of barium sulfate. After mixing the mixture for 1 hour, it is immersed in the receiving hopper of a twin-screw extruder, which mixes the mixture at a temperature of 120 °C, which is then poured onto cold rollers, and the resulting tape is cooled and crushed with a crusher, followed by grinding into powder.

The coatings were applied using powder painting on a steel plate made of 08kp steel 125×75×0.5 mm.

The remaining compositions were prepared according to example 1; a standard coating based on ED-10 was used for comparison. Table 1 shows the ratio of raw materials in percent.

Table 1

Composition of the composition Content, wt.% Reference Examples of compositions 1 2 3 4 Epoxy diane resin ED-10 60 60 60 60 60 Dicyandiamide 2.7 2.7 2.7 2.7 2.7 Spreading agent 0.8 0.8 0.9 1.0 1,2 Barium sulfate 36.5 36.47 36.34 36.22 36 Aluminum oxide nanofibers 0 0.03 0.06 0.08 0.10

The prepared compositions have undergone laboratory tests.

Tests were carried out on:

• GOST 15140-78 “Paint and varnish materials. Methods for determining adhesion”,

• GOST 4765-73 "Paint and varnish materials. Method for determining impact strength",

• GOST R 54586-2011 (ISO 15184:1998) “Paints and varnishes. Method for determining the pencil hardness of a coating”.

The obtained properties of the manufactured compositions were compared with the closest analogue. Data on the properties of the composition are given in Table 2.

Table 2

Name of indicators The closest analogue Examples of compositions 1 2 3 4 Direct impact strength, kg/cm 50 80 80 100 120 Reverse impact strength, kg/cm 20 40 60 60 80 Pencil hardness NV N N N N

As can be seen from Table 2, the use of an epoxy composition with aluminum oxide nanofibers functionalized with amino groups makes it possible to increase the strength and hardness of the coating disclosed in the closest analogue of the invention.

Claims (2)

An epoxy composition for powder coatings, characterized by the fact that it includes epoxy diane resin ED-10, a spreading agent, a hardener - dicyandiamide, a filler - barium sulfate, pigments are additionally introduced into the filler, the composition also contains aluminum oxide nanofibers functionalized with amino groups with a diameter of 3 to 50 nm in the following ratio of components, wt.%: epoxy diane resin ED-10 60,000 dicyandiamide 2,700 spreading agent 0.800-1.200 aluminum oxide nanofibers 0.03-0.10 filler the rest