RU2180617C2 - Method and device for preliminary activation of surface of molded products of crystalline polymers in glow discharge before painting - Google Patents

Abstract

FIELD: treatment of products made of polypropylene for improvement of adhesion properties of paintwork to the surface pf products without any change of the physicomechanical properties of material, applicable in automotive industry, the principal field of application- working of parts of the vehicle exterior, such as bumpers, moldings, radiator grills, etc. before painting operation. SUBSTANCE: the product is preliminarily degreased in a water-alkaline solution, rinsed with running water, wiped with isopropyl alcohol, and then placed in a vacuum chamber, and activation is accomplished in vacuum, in the medium of residual air in the plasma of glow discharge of direct or alternating current excited between the electrodes at a pressure in the chamber within 10 to 50 Pa and voltage across the electrodes within 350 to 500 V, the products are being worked during 1.5 to 2 min. The method is accomplished with the aid of a device having the body of the vacuum chamber, cover, machining attachments, products to be worked, glow-discharge electrodes. At such a process the whole surface of all products loaded in the vacuum chamber is being worked simultaneously. EFFECT: maximum simplified construction of the equipment and enhanced capacity, reduced power consumption and saving of expensive gases. 2 cl, 1 dwg _

Description

 The invention relates to methods for processing products from polypropylene, to improve the adhesive properties of the paint coating to the surface of the products without changing the physical and mechanical properties of the material and can be used in the automotive industry.

 The preferred area of application is the processing of vehicle exterior parts such as bumpers, moldings, radiator grilles, etc., before the painting operation.

 Currently, various methods are used to activate the surface of polymer products. Among them are the introduction of inert fillers at the stage of manufacture of parts, etching of the surface with chemical reagents, and open flame treatment. The most promising are processing methods using various types of electrical discharges, such as corona, smoldering, etc.

 A known method and device for plasma processing in vacuum (US Pat. US 5415819, published in the abstract collection "Invention of the World", issue 024, 5 for 1996, IPC B 29 C 71/04), in which for processing products used a device containing two or more electrically conductive elements isolated from each other. Products to be processed are placed between the elements so as to create a small limited gap between the surface to be treated and at least one of the elements. A vacuum is created in the said gap, and then an ionized gas is introduced. Between elements that act as electrodes, an electric field is created that converts gas into plasma. As a result of the interaction of plasma with the surface of the product, the surface acquires the ability to better accept the coating.

 Such an invention has a significant drawback. Creating a limited gap between the surface of the product and one of the elements requires the individual manufacture of the latter, taking into account the size and shape of a particular product.

There is also a known method and processing device in which the surface treatment of polypropylene molded products is carried out (Pat. Japan 62-28812, published in the abstract collection "Invention of the World", issue C08, 23 for 1987, IPC C 08 J 7/00 ), in which the surface of the product from copolymers of polypropylene is contacted at a pressure of 100 mm Hg. with a low-temperature plasma obtained by excitation of a glow discharge in a medium of gaseous oxygen, nitrogen, argon and / or helium, with a plasma treatment intensity of 100 ... 60,000 W / cm ² .

 The disadvantage of this invention is the need to create a preliminary vacuum and subsequent inlet of the reaction gases, which leads to an increase in the duration of the process, additional energy consumption and the cost of reaction gases.

 New in the invention is that in the proposed method for pre-activating the surface of molded polypropylene products before painting, the treatment is carried out by exposing the product surface to a low-temperature glow discharge plasma in a residual air environment, while the adhesive strength of the paint coating to the product is increased and leads to energy savings, reduction of process time, as no need to supply any gases or gas mixtures.

 The purpose of the invention is the activation (hydrophilization) of the surface of polypropylene in order to increase the adhesive strength of the paint coating to the product. It can be used to activate the surface of volumetric, complex-shaped products.

 The invention is illustrated by the fact that in the method of pre-activating the surface of the molded polypropylene products in a glow discharge before painting by exposing the surface of the product to electric energy according to the invention, the products are pre-degreased in an aqueous alkaline solution, washed with running water, dried from moisture, wiped with isopropyl alcohol, and then placed in a vacuum chamber and carry out activation in a vacuum in a residual air medium in a plasma of a glow discharge of constant or alternating current excited between two copper electrodes at a pressure of 10 ... 50 Pa, a voltage between electrodes of 350 ... 500 V, and processing of products is carried out for 1.5 ... 2 min.

 In a device for pre-activating the surface of molded polypropylene articles in a glow discharge before painting, consisting of a chamber having a housing including two electrodes isolated from each other, to create an electric field between them according to the invention, the housing of the vacuum chamber is made in the form of a horizontal cylinder, which contains the housing cover and tooling, and copper electrodes are installed at the ends of the vacuum chamber, isolated from its housing and are located opposite each other in the form of frames and or vertical rods.

 The invention is illustrated by the drawing, which shows a device for activating the surface of bulk polypropylene products in a glow discharge before painting.

 The device comprises a housing 1 of the vacuum chamber, which is a horizontally arranged cylinder, with pre-selected dimensions of the vacuum chamber, a cover 2, tooling 3, workpieces 4, electrodes 5 and 6 of a glow discharge. The electrodes 5 and 6 are made of copper and are either a frame or two vertical rods mounted opposite each other at the ends of the chamber and isolated from each other and from the housing 1 of the vacuum chamber.

 The invention is as follows. The processed products 4 are degreased in a water-alkaline solution, washed with running water, dried from moisture, wiped with isopropylene alcohol and hung on technological equipment 3, loaded into a vacuum chamber, from which air is pumped out to a pressure of 10 ... 50 Pa. After that, two electrodes 5 and 6, between which the workpiece 4 is located, are supplied with a voltage of 350 ... 500 V DC or an alternating frequency of 50 Hz. As a result of this, a glow discharge plasma is excited in the vacuum chamber and articles 4 are processed for 1.5 ... 2 min.

 Carrying out activation is preferable when feeding the electrodes with alternating current, while the glow discharge acquires a wave character and a uniform distribution of the plasma density is achieved over the entire volume of the chamber.

 Due to the volumetric combustion of a glow discharge plasma, uniform processing of all products loaded into the chamber is carried out simultaneously over the entire surface of each product.

 With this treatment, the duration of maintaining the active properties of the surface, i.e. the storage time of the products after being removed from the chamber before applying the soil is up to 12 hours, after which re-processing is necessary.

 After the activation process, a leveling primer and enamel are applied to obtain a decorative effect.

 Tests of the adhesive strength of the paintwork to the surface of the product showed compliance with the requirements for the details of the exterior of the car.

Such a technical solution allows simultaneously processing all products loaded into the vacuum chamber over the entire surface, which leads to the maximum simplification of equipment and increased productivity, as well as when processing in a glow discharge by alternating current between two electrodes isolated from the grounded chamber, they receive plasma of uniform intensity throughout the volume a vacuum chamber, and use as reaction gas residual air eliminates the need for a vacuum pump to 10 ^-1 Pa and further napu Single reaction gases or mixtures of gases and, consequently, besides saving expensive gas and electricity significantly reduces the duration of the evacuation chamber and greatly increases productivity.

Claims (2)

 1. The method of preliminary activation of the surface of molded polypropylene products in a glow discharge before painting by exposing the surface of the part to electrical energy, characterized in that the products are previously degreased in an aqueous alkaline solution, washed with running water, dried from moisture, wiped with isopropyl alcohol, and then placed in a vacuum chamber and carry out activation in a vacuum, in the environment of the residual air in the plasma of a glow discharge of direct or alternating current at a pressure of 10-50 PA, excited th between the two electrodes at a voltage between the electrodes of 350-500 V, the processing of products is carried out for 1.5-2 minutes  2. A device for pre-activating the surface of molded polypropylene articles in a glow discharge before painting, consisting of a chamber having a housing including two electrodes isolated from each other, to create an electric field between them, characterized in that the housing of the vacuum chamber is made in the form of a horizontal a cylinder, which contains a housing cover and technological equipment, and copper electrodes are installed at the ends of the vacuum chamber, isolated from its body and are located opposite each other in the form of frames ki or vertical rods.