RU2846339C2 - Primer - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polymer pin-type linear insulators, namely to primers providing reliable connection of silicone rubber with polyamide body. Primer used can be maleic anhydride solutions in an organic solvent with concentration of 0.625-10 %.

EFFECT: significant simplification and cheapening of primer production technology and possibility of its application irrespective of atmospheric air humidity.

1 cl, 3 dwg, 1 tbl, 10 ex

Description

Every year, the production volumes of polymer pin insulators used on power transmission lines with voltage up to 35 kV are increasing.

The typical design of the insulators is shown in Fig. 1: 1 - insulator body made of glass-filled polyamide, 2 - ribbed thermosetting silicone rubber (HTV), 3 - hole for the support pin. The presence of the pin is the reason for the name of the insulators - "pin".

It is fundamentally important that the silicone rubber adheres well to the polyamide surface. Otherwise, a short circuit may occur along the line "wire → polyamide surface → silicone sheath-housing surface interface → metal pin" (the pin is not shown in Fig. 1).

Good adhesion of electrical insulating silicone rubber to the surface of polyamide is ensured by preliminary application of a “binder” to the insulator body, which acts as a primer (RU 2431898 C1, IPC H01B 17/00, 2011; RU 193324, IPC H01B 17/20, SPC H01B 17/20, 2019).

The nature of the “binder” (primer) is not specified in the documents, but, as a rule, these are complex solutions of hydrolyzable silicates, titanates, reactive silanes/oligomeric siloxanes and target additives in organic solvents.

An example is the primer from Wacker Chemie AG (US 7575655 B2. IPC C08L 83/14, G09B 1/38, C08L 83/02, C08L 83/04, C09D 183/02, C09D 183/14, 2009). The proposed primer contains five components:

A - tetraalkoxysilane (or a mixture of tetraalkoxysilanes) and/or the product(s) of its (their) partial hydrolytic polycondensation;

B - a catalyst for the hydrolytic polycondensation of tetraalkoxysilanes, selected from the group consisting of salts, alkoxides and chelates of metals, as well as products of their partial hydrolysis). Particularly preferred are tetramethyl titanate, tetraethyl titanate and tetra-n-butyl titanate;

C - silicone resin. In the preferred embodiment, this is an oligoorganosiloxane with methyl (ethyl) and vinyl groups;

D - organic individual or mixed solvent. In the case of alcohols, ethanol, isopropanol and especially sec-butanol or their mixtures are preferred;

E - reactive alkoxysilane: vinyltriethoxysilane, 3-(methacryloxy)propyltrimethoxysilane, 3-(glycidyloxy)propyltrimethoxysilane, 1,2-bis(triethoxysilyl)ethane, 3-(acryloxy)methyltrimethoxysilane, etc.

The primer may also contain peroxides such as di-tert-butyl peroxide, tert-butyl hydroperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, cumyl hydroperoxide, bis(2,4-dichlorobenzoyl)peroxide, etc., bis(4-methylbenzoyl)peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and vinyl tri(tert-butylperoxy)silane.

The introduction of dressed dispersed fillers is permitted.

The primer is prepared by mixing components A, B, C, E and possibly other optional components in solvent D in a suitable mixing device. Mixing of the initial components is recommended to be carried out at 60-80°C for 1-2 hours.

The primer is applied to the substrates using various methods known in the technology of forming coatings from solution paints and varnishes. The formed coatings require drying, for example, for 1 minute to two hours at temperatures from 20 to 50°C or for 1-30 minutes at temperatures from 90 to 150°C.

Each specific case of obtaining and using a primer is determined by the chemical nature of the original components.

The primer's undoubted advantage is its versatility, providing high adhesion to ferrous and non-ferrous metals, polyamide, epoxy and other plastics, as well as glass and building materials.

The disadvantages of the primer are:

1) multi-component nature and associated transportation costs;

2) the high price of all components used and, consequently, the primer;

3) moisture is required for hydrolysis of active components. Drying of the primer applied to the substrate is preferably carried out at a relative air humidity of 40-60%. In real weather conditions, this may require frequent adjustment of the drying conditions, and the creation of the required conditions is associated with financial costs for an air humidifier;

4) in the case of organizing the production of primer in Russia under license, questions will arise regarding the acquisition of a number of imported components.

Unexpectedly, the possibility of using maleic anhydride as a primer in the production of linear pin insulators, or more precisely, its 0.625-20% solutions in organic solvents, was discovered.

Maleic anhydride is currently produced by PJSC SIBUR-Holding (Website of PJSC SIBUR-Holding. - https://skportal.mserv.me/publication/trends/maleinovyy-angidrid-ot-stroitelstva-i-neftedobychi-do-farmatsevtiki/). The areas of application of maleic anhydride are diverse, including as a hardener for epoxy materials.

Benzene, xylene, toluene, chloroform, dioxane, ethyl acetate can be used as solvents. The preferred solvent is isopropyl alcohol. The resulting solutions are viable for at least three months.

Example 1 (according to the invention). The primer is prepared by dissolving 2.5 g of maleic anhydride in 22.5 g of isopropanol at a temperature of 20-25°C for 2.5-2 hours in a closed container with stirring in a laminar mode. The resulting solution is applied with a soft brush in a thin layer onto 2 bars of type 1 according to GOST 19109-2017 made of polyamide 6 (until a wet surface is obtained) and dried at a temperature of 60°C for 30 minutes.

Next, assemble the structure shown in Fig. 2, where: 1 - bars made of polyamide 6; 2 - a piece of silicone rubber SilFor 306/E 7040 from Euro Chemicals rolled at room temperature, measuring 2×1.3 mm; and 3 - a thin layer of dry primer.

The structures are placed in a ventilated drying cabinet, a load is applied based on the calculation of creating a primary pressure of 7.65 kPa. Vulcanization of rubber is carried out according to the mode: heating from 90-100 ° C to 180 ° C for 13-14 minutes and then holding at 180 ° C for 20 minutes. In the resulting test samples, the thickness of the vulcanized rubber fluctuates from 3.8 to 4.1 mm.

The adhesive joints obtained are actually subjected to deformation under tensile conditions at a rate of 20 mm/min. The loading diagram of the adhesive joint is shown in Fig. 3, where 1 is an auxiliary block (a thin primer layer is not shown). Since the thickness of the auxiliary block is 3 mm, both tangential and normal stresses (bending and tearing stresses) arise in the adhesive joints. The tests are stopped after reaching the recorded maximum tensile forces.

The conditional shear stress is calculated, the adhesive joint is finally separated, the nature of the destruction (adhesive or cohesive) is monitored, an attempt is made to manually tear the rubber off the surface of the bars and the adhesion area is recorded as the area clearly covered by a layer of rubber, or more precisely, its remains on the surface of the bars, using a well-known method (CN 110256956, IPC).

Examples 2-5 (according to the invention). The experiment is carried out as indicated in Example 1, but solutions of maleic anhydride of different concentrations are used.

Examples 6-7 (control). The experiment is carried out as indicated in example 1, but solutions of maleic anhydride of different concentrations are used.

Examples 8 and 9 (comparative). The experiment is carried out as indicated in example 1, but using the primer AUX G 3242 PRIMER from Wacker Chemie AG (Germany, sold by Euro Chemicals LLC) and RQJL-029 Ruigi New Material Technology Co. Ltd. (China).

The results obtained are presented in the table.

Example Primer Concentration in isopropanol, % Conventional shear stress, MPa Adhesion area, % 1 Maleic anhydride 10 40 95 2 The same 5 40 95 3 The same 2.5 40 90 4 The same 1.25 40 85 5 The same 0.625 40 85 6 The same 0.3125 37.5 35 7 Isopropanol 100 0 0 8 Maleic anhydride 20 40 65 9 G 3242 30 42.5 100 10 RQJL-029 30 42.5 50

From the analysis of the data presented in the table, it follows that the proposed primer provides a significantly greater adhesive capacity of silicone rubber to the surface of polyamide 6. Slightly inferior to the German analogue in the formation of the final result, the proposed primer is more technologically advanced in application and significantly more effective in terms of cost.

Claims (2)

A primer for the production of polymer pin insulators, comprising maleic anhydride and an organic solvent in the following mass ratio of components: Maleic anhydride 0.625-10 Organic solvent Rest