EP0607717B1 - Process for the protection of a tool used for electroplating and tool protected according to this process - Google Patents

Description

The invention relates to a method for protecting an electroplating tool and a product obtained by this method.

The method of the invention consists more particularly in the application of a coating comprising at least two layers of different plastics on an electroplating tool. The plastics used belong to the family of plastisols.

Plastisols are mixtures of a suspension of powdered vinyl resin prepared according to the emulsion polymerization (or microsuspension) process in a liquid plasticizer, and adjuvants, such as stabilizers, fillers, pigments, swelling agents and others adjuvants. Under the action of heat, the plastisols are transformed into homogeneous solids.

The vinyl resins used to obtain plastisols are mainly polyvinyl acetate, polyvinyl ether, polyvinyl alcohol and poly (vinyl chloride) (PVC). For electroplating, we mainly use poly (vinyl chloride) (PVC).

The electroplating tool includes all kinds of electrolysis fixtures, intended to hold the parts which one wishes to chrome, nickel or coat with any metal, or which one wishes, on the contrary to demetallize. The pieces are immersed in chemically corrosive baths such as sulfochromatic, hydrochloric, nickel plating, chemical copper plating, chromium plating, gilding, silver plating, demetallization or the like.

French patent FR-2,456,131 describes a plastisol used for the coating of electrolysis fixtures. Previously, this plastisol made it possible to obtain sufficiently satisfactory coatings insofar as these had both sufficient mechanical or physical resistance to impact and sufficient protection against corrosion, for the usual conditions of galvanization.

US patent US-3,514,312 describes a method of coating a metal surface for the manufacture of a roll. The technique described in this document is not intended for the protection of an electroplating tool and it is envisaged that several layers of plastisol are applied. This document does not propose any particular provision such as the relative hardness of the plastisol in order to improve the resistance of electroplating tools.

However, modifications which have taken place both in terms of the galvanizing currents applied and in terms of the composition of the baths used, have resulted in insufficient protection of the tools, which is manifested in particular by premature cracking of the coating of the tools in general and springs in particular, due to excessive hardening of the plastisol.

Furthermore, it has been observed that during the drying of galvanized parts, in products containing chlorinated and fluorinated derivatives of hydrocarbons, these products partially absorb the plasticizers of the plastisols by taking up DOP (octyl phthalate) and DBP (benzyl phthalate) which, in solution, stains the parts to be dried.

Following the ban on the use of products containing certain chlorinated and fluorinated derivatives of hydrocarbons, these products will be replaced by products containing dichlorofluoroethane. These products have an even greater solvent power than those containing trichlorotrifluoroethane, because they have three more hydrogen atoms, two less fluorine atoms and one less chlorine atom.

Consequently, the aging of the plastisol will be increased considerably.

Indeed, the plastisols used until now contain as plasticizers dibutyl phthalates, benzylbutyl mixed phthalates, diethyl phthalates, dihexyl phthalates and diisononyl phthalates, which represents 60 to 70% by weight of plasticizer mixture relative to poly (vinyl chloride).

The plastisol described in patent FR-2,456,131 cited above has 35% by weight of plasticizer mixture (70 to 80% of octyl phthalate and 30 to 20% of octyl adipate) which makes it more resistant absorption of the solvent, but will not be sufficient for new drying products.

The object of the invention is to improve the plastisol coating of an electroplating tool in order to overcome the drawbacks noted.

• a) nettoyage et dégraissage de l'outillage,
• b) application d'une sous-couche d'adhérence sur l'outillage,
• c) étuvage de l'outillage,
• d) trempage de l'outillage dans un bain d'un premier plastisol,
• e) égouttement et séchage de l'outillage,
• f) étuvage de l'outillage d'une durée telle qu'il n'y ait pas gélification complète du premier plastisol,
• g) trempage de l'outillage dans un bain d'un deuxième plastisol d'une dureté, après polymérisation, supérieure à celle du premier plastisol,
• h) égouttement et séchage de l'outillage,
• i) étuvage de l'outillage jusqu'à gélification complète du deuxième plastisol.

The object of the invention is achieved by a method of protecting an electroplating tool with at least two layers of plastics from the plastisol family. This process includes the following steps:

• a) cleaning and degreasing of the tools,
• b) application of an adhesion undercoat on the tool,
• c) steaming of the tools,
• d) soaking the tool in a bath of a first plastisol,
• e) dripping and drying of the tools,
• f) steaming of the tool for a period such that there is no complete gelation of the first plastisol,
• g) soaking the tool in a bath of a second plastisol having a hardness, after polymerization, greater than that of the first plastisol,
• h) dripping and drying of the tools,
• i) steaming of the tooling until complete gelation of the second plastisol.

The particular conditions of the steaming of the tool after the application of the first layer of plastisol, namely the fact of avoiding a complete gelation of this layer, are intended to ensure an optimal bond between the first layer, or layer inner layer of plastisol and the second or outer layer of plastisol. This intimate bond or fusion is important, because it allows the plasticizers contained in the interior layer of plastisol, to migrate, during the drying of a piece of tool after galvanic treatment and during the use of the tool, towards the outer layer of plastisol.

Refueling the outer layer of plasticizers from the inner layer of plastisol makes it possible to avoid porosity and a loss of elasticity of the coating, due to the loss of plasticizers occurring when using known plastisol coatings.

The process of the invention is not limited to an application of two layers of plastisol. On the contrary, it is also possible to apply more than one inner layer of plastisol. The main thing is that the inner layers, whether made of one or more different plastisols, each have a hardness, after polymerization, lower than that of the outer layer of plastisol.

Regardless of the total number of layers of plastisol applied, the process of the invention makes it possible, by the suppleness or flexibility of the interior layers, to provide very good protection of the tools - and in particular of the springs or current leads - against mechanical constraints of use in electroplating, and, at the same time, by the hardness of the outer layer, a very good resistance of the tool against the increased chemical aggressiveness of the galvanizing baths currently used. The improvement in chemical resistance is more particularly important for tool springs, since the porosity of their coatings observed in the prior art favored a deposition of metal on the coatings.

The plastisols chosen for a particular embodiment of a coating according to the invention may contain different kinds of vinyl resin. But alternatively, the plastisols of the different layers can be prepared from the same vinyl resin. Preferably, poly (vinyl chloride) (PVC) will be used.

• les étapes de trempage de l'outillage dans un bain d'un premier plastisol, d'égouttement et de séchage de l'outillage, et de l'etuvage de l'outillage d'une durée telle qu'il n'y ait pas gélification complète du plastisol, sont répétées au moins une fois avec au moins un troisième plastisol, avant de procéder aux étapes de trempage de l'outillage dans le bain du deuxième plastisol, d'égouttement et de séchage de l'outillage, et d'étuvage de l'outillage jusqu'à gélification complète du deuxième plastisol;
• l'étuvage de l'outillage qui est effectué après l'application d'une sous-couche d'adhérence, est effectué à une température comprise entre 170°C et 190°C;
• l'étuvage de l'outillage qui est effectué après égouttement et séchage de l'outillage ayant été revêtu d'une couche de plastisol autre que la deuxième couche (couche extérieure), est effectué à une température comprise entre 150°C et 170°C pendant 15 à 20 minutes;
• l'étuvage de l'outillage après application d'une couche du deuxième plastisol, c'est-à-dire après application de la couche extérieure du revêtement, est effectué à une température comprise entre 180°C et 200°C pendant 30 à 35 minutes;
• l'étuvage de l'outillage après application de la couche extérieure est souvent effectué en deux phases, la première étant constituée par la montée en température de l'étuve jusqu'à une température comprise entre 160°C et 200°C, ce qui dure 15 à 20 minutes, et la deuxième étant une température comprise entre 180°C et 200°C appliquée pendant 30 à 35 minutes.
• les différentes étapes du procédé de l'invention, et notamment l'application d'une première couche d'un premier plastisol, l'égouttement et séchage de l'outillage, et l'étuvage de l'outillage sans gélification complète de la couche de plastisol, une répétition éventuelle au moins une fois de ces étapes avec au moins un troisième plastisol, ainsi que les étapes d'application d'une couche d'un deuxième plastisol constituant la couche extérieure du revêtement de l'outillage, l'égouttement et le séchage de l'outillage, et l'étuvage de l'outillage jusqu'à gélification complète du deuxième plastisol constituant la couche extérieure du revêtement, sont effectuées les unes après les autres sans pause notable entre les différentes étapes.

The invention also relates to a method for protecting an electroplating tool, having the following characteristics, considered in isolation or in all their technically possible combinations:

• the steps of soaking the tool in a bath of a first plastisol, of draining and drying the tool, and of baking the tool for a duration such that there is no complete gelation of the plastisol, are repeated at least once with at least a third plastisol, before proceeding to the steps of soaking the tool in the bath of the second plastisol, of draining and drying the tool, and steaming of the tooling until complete gelation of the second plastisol;
• the steaming of the tools which is carried out after the application of an adhesion undercoat, is carried out at a temperature of between 170 ° C and 190 ° C;
• the steaming of the tooling which is carried out after draining and drying of the tooling having been coated with a layer of plastisol other than the second layer (outer layer), is carried out at a temperature between 150 ° C and 170 ° C for 15 to 20 minutes;
• steaming of the tools after application of a layer of the second plastisol, that is to say after application of the outer layer of the coating, is carried out at a temperature between 180 ° C and 200 ° C for 30 to 35 minutes;
• steaming of the tools after application of the outer layer is often carried out in two phases, the first consisting of the temperature rise of the oven to a temperature between 160 ° C and 200 ° C, which lasts 15 to 20 minutes, and the second being a temperature between 180 ° C and 200 ° C applied for 30 to 35 minutes.
• the various stages of the process of the invention, and in particular the application of a first layer of a first plastisol, the dripping and drying of the tool, and the steaming of the tool without complete gelation of the layer of plastisol, a possible repetition at least once of these steps with at least a third plastisol, as well as the steps of applying a layer of a second plastisol constituting the outer layer of the coating of the tool, the drip and the drying of the tooling, and the steaming of the tooling until complete gelation of the second plastisol constituting the outer layer of the coating, are carried out one after the other without significant break between the different stages.

It is however conceivable, without departing from the scope of the invention, to carry out the various steps of the method of the invention at significant time intervals. This can happen, for example, when the process has to be carried out by means of an installation comprising only one tank for plastisols. In such a situation, it is inevitable to introduce breaks after application and cooking of a layer to all of the tools provided if the production of the next layer requires a change of bath.

However, it should be noted that the gelation started does not stop at the moment when the tools have left the oven. This entails the risk of a lower quality adhesion or fusion of this layer with the next layer and, by this, a reduction in the migration capacity of plasticizers from the lower layer (s) to the outer layer of plastisol.

The invention also relates to an electroplating tool protected by a first layer of a first plastisol and which is coated with at least a second layer of a second plastisol, the second plastisol being of a hardness, after polymerization, greater than that of the first plastisol.

• le premier plastisol a une dureté, après polymérisation, de 55 à 70 Shore A;
• le deuxième plastisol a une dureté, après polymérisation, de 70 à 90 Shore A.

The electroplating tool according to the invention can also have the following characteristics, considered in isolation or in all their technically possible combinations:

• the first plastisol has a hardness, after polymerization, of 55 to 70 Shore A;
• the second plastisol has a hardness, after polymerization, of 70 to 90 Shore A.

• La Figure 1 montre, en une coupe très schématisée, un outillage de galvanoplastie, et
• la Figure 2 montre une représentation très schématisée d'une disposition de stations de travail d'un dispositif pour la mise en oeuvre du procédé selon l'invention.

In what follows, the invention will be described with the aid of two exemplary embodiments of the method according to the invention, an exemplary embodiment of a tool according to the invention and an exemplary embodiment of a device for implementing the method according to the invention. The description is made with reference to the drawings, in which:

• Figure 1 shows, in a very schematic section, an electroplating tool, and
• Figure 2 shows a very schematic representation of a workstation layout of a device for implementing the method according to the invention.

EXAMPLE I : Double layer plastisol coating

• a) Préparation de l'outillage: sablage, dégraissage à l'aide de vapeurs de trichlore, rinçage avec de l'eau et séchage;
• b) application au pistolet d'une sous-couche d'adhérence sur l'outillage suivie d'un séchage du revêtement pendant 15 minutes à température ambiante;
• c) préchauffage de l'outillage dans une étuve à une température comprise entre 180 à 200°C pendant 30 minutes;
• d) trempage de l'outillage chaud dans le bain d'un premier plastisol; ce premier plastisol comprend, outre le poly(chlorure de vinyle) (PVC), un système plastifiant constitué de phtalate d'octyle et d'adipate d'octyle et représentant 60% en poids par rapport au PVC, un mélange thixotropiant constitué par des esters de l'hexylène glycol, de l'alcool benzylique, de l'essence de térébenthine et du pétrole, ainsi que des sels organiques d'étain;
• e) l'outillage est égoutté très lentement en le sortant dudit bain à une vitesse comprise entre 1 et 5 cm/minute; l'égouttement lent est important pour obtenir un revêtement fin et homogène sans coulure;
• f) l'outillage séché est chauffé dans une étuve à 160°C pendant 15 minutes;
• g) l'outillage est ensuite trempé dans un bain d'un deuxième plastisol; ce deuxième plastisol comprend, outre le poly(chlorure de vinyle) (PVC), un système plastifiant constitué de phtalate d'octyle et d'adipate d'octyle et représentant 45% en poids par rapport au PVC; un mélange thixotropiant constitué par des esters, de l'hexylène glycol, de l'alcool benzylique, de l'essence de térébenthine et de pétrole; et des sels organiques d'étain;
• h) l'outillage est égoutté très lentement en le sortant dudit bain à une vitesse comprise entre 1 et 5 cm/minute;
• i) étuvage de l'outillage à une température de 160°C pendant 15 minutes et ensuite à une température de 180°C pendant 30 minutes.

The process includes the following steps:

• a) Preparation of the tools: sandblasting, degreasing with trichlor vapor, rinsing with water and drying;
• b) spraying an adhesion undercoat on the tools followed by drying the coating for 15 minutes at room temperature;
• c) preheating the tools in an oven at a temperature between 180 to 200 ° C for 30 minutes;
• d) soaking the hot tools in the bath of a first plastisol; this first plastisol comprises, in addition to poly (vinyl chloride) (PVC), a plasticizer system consisting of octyl phthalate and octyl adipate and representing 60% by weight relative to PVC, a thixotropic mixture consisting of esters of hexylene glycol, benzyl alcohol, turpentine and petroleum, as well as organic tin salts;
• e) the tool is drained very slowly, leaving it from said bath at a speed of between 1 and 5 cm / minute; slow dripping is important to obtain a fine and homogeneous coating without sagging;
• f) the dried tool is heated in an oven at 160 ° C for 15 minutes;
• g) the tool is then soaked in a bath of a second plastisol; this second plastisol comprises, in addition to poly (vinyl chloride) (PVC), a plasticizer system consisting of octyl phthalate and octyl adipate and representing 45% by weight relative to PVC; a thixotropic mixture consisting of esters, hexylene glycol, benzyl alcohol, turpentine and petroleum; and organic tin salts;
• h) the tooling is drained very slowly, leaving it from said bath at a speed of between 1 and 5 cm / minute;
• i) steaming the tool at a temperature of 160 ° C for 15 minutes and then at a temperature of 180 ° C for 30 minutes.

EXAMPLE II Triple layer plastisol coating

• a) Préparation de l'outillage: sablage, dégraissage à l'aide d'un bain à base de lessive de soude, rinçage avec de l'eau et séchage;
• b) application d'une sous-couche d'adhérence sur l'outillage par trempage dans un bain d'un primaire correspondant, suivie d'un séchage du revêtement pendant 15 minutes à température ambiante;
• c) préchauffage de l'outillage dans une étuve à une température comprise entre 180 à 200°C pendant 30 minutes;
• d) l'outillage chaud est plongé dans le bain d'un premier plastisol; ce premier plastisol comprend, outre le poly(chlorure de vinyle) (PVC), un système plastifiant constitué de phtalate d'octyle et d'adipate d'octyle et représentant 60% en poids par rapport au PVC, un mélange thixotropiant constitué par des esters de l'hexylène glycol, de l'alcool benzylique, de l'essence de térébenthine et du pétrole, ainsi que des sels organiques d'étain;
• e) l'outillage est égoutté très lentement en le sortant dudit bain à une vitesse comprise entre 1 et 5 cm/minute;
• f) l'outillage séché est chauffé dans une étuve à 160°C pendant 15 minutes.
• g) les étapes d), e) et f) sont répétées une fois pour obtenir une couche supplémentaire du premier plastisol;
• h) l'outillage est ensuite trempé dans un bain d'un deuxième plastisol; ce deuxième plastisol comprend, outre le poly(chlorure de vinyle) (PVC), un système plastifiant constitué de phtalate d'octyle et d'adipate d'octyle et représentant 45% en poids par rapport au PVC; un mélange thixotropiant constitué par des esters, de l'hexylène glycol, de l'alcool benzylique, de l'essence de térébenthine et de pétrole; et des sels organiques d'étain;
• i) l'outillage est égoutté très lentement en le sortant dudit bain à une vitesse comprise entre 1 et 5 cm/minute;
• j) étuvage de l'outillage à une température de 160°C pendant 15 minutes et ensuite à une température de 180°C pendant 30 minutes.

The process includes the following steps:

• a) Preparation of the tools: sandblasting, degreasing using a soda lye bath, rinsing with water and drying;
• b) application of an adhesion undercoat on the tool by soaking in a bath of a corresponding primer, followed by drying of the coating for 15 minutes at room temperature;
• c) preheating the tools in an oven at a temperature between 180 to 200 ° C for 30 minutes;
• d) the hot tool is immersed in the bath of a first plastisol; this first plastisol comprises, in addition to poly (vinyl chloride) (PVC), a plasticizer system consisting of octyl phthalate and octyl adipate and representing 60% by weight relative to PVC, a thixotropic mixture consisting of esters of hexylene glycol, benzyl alcohol, turpentine and petroleum, as well as organic tin salts;
• e) the tool is drained very slowly, leaving it from said bath at a speed of between 1 and 5 cm / minute;
• f) the dried tool is heated in an oven at 160 ° C for 15 minutes.
• g) steps d), e) and f) are repeated once to obtain an additional layer of the first plastisol;
• h) the tool is then soaked in a bath of a second plastisol; this second plastisol comprises, in addition to poly (vinyl chloride) (PVC), a plasticizer system consisting of octyl phthalate and octyl adipate and representing 45% by weight relative to PVC; a thixotropic mixture consisting of esters, hexylene glycol, benzyl alcohol, turpentine and petroleum; and organic tin salts;
• i) the tool is drained very slowly, leaving it from said bath at a speed of between 1 and 5 cm / minute;
• j) steaming the tool at a temperature of 160 ° C for 15 minutes and then at a temperature of 180 ° C for 30 minutes.

Figure 1 shows, in a very schematic section, a tool obtained by means of the method according to Example I. Tool 1 is a basket in which are placed objects which must be coated with a metal. The tool can also be an electrolysis assembly to which are attached, during their galvanization, various parts, or any other suitable support.

The basket 1 is covered on its entire surface, that is to say both on the internal surface and on the external surface, with an adhesion underlayer 2 which, itself, is covered with a first layer 3 of a first plastisol. On layer 3 of the first plastisol is deposited a second layer 4 of a second plastisol.

The first layer of plastisol and the second layer of plastisol differ from each other, on the one hand, by their hardness after polymerization and, advantageously on the other hand, by their color. The particular color of each plastisol is obtained by an additive which does not cause a chemical reaction with the other components of the mixture.

Figure 2 shows, in a representation also very schematically, an installation constituting a device for the implementation of the method of the invention according to Example II. For the purposes of a simplified representation, the aspect of an optimal arrangement of the various elements of the device has been deliberately omitted.

The device for implementing the method of the invention comprises a first work station 5 intended for the preparation of the tool 1 according to the rules of the trade known per se. The work station 5 comprises means 6 necessary to be able to carry out a sanding of the tool 1, and a rinsing tank 7 in which the tool 1 is immersed after sanding.

It is understood that the first work station 5 can comprise either instead of, or in addition to the sanding means 6, a tank (not shown) intended for chemical degreasing by means of trichlor vapor or of a solvent.

The device for implementing the method according to the invention also comprises a second work station 8 intended for the application of the adhesion undercoat. The second work station 8 is represented diagrammatically by a tank containing an appropriate primer. The application of the primer to tool 1 can, however, also be done with a brush, or with a spray gun.

The device for implementing the method according to the invention also comprises a third work station 9, a fourth work station 10 and a fifth work station 11. The third, fourth and fifth work stations are intended for application of the first layer 3 of plastisol, of the second layer 4 of plastisol and of the third layer of plastisol (not shown in FIG. 1). Each of the work stations 9, 10 and 11 is represented by a tank containing the corresponding plastisol.

As a variant of the configuration set out above, the tank of the third work station 9 can be replaced by electrostatic spraying means in order to be able to apply the first layer of plastisol to the spray gun.

The device for implementing the method according to the invention furthermore comprises a sixth work station constituted by an oven 12 in which the tool 1 is heated according to the different stages of the method.

To facilitate the transport of the tool 1 from one work station to another, a means of transport and holding, represented by a rail 13 on which a carriage 14 can be moved, is provided.

The reference signs inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter, and in no way limit their scope.

Claims (9)

1. A process for the protection of a part by application of at least two plastic coats of the plastisol family, whereby the process comprises the following steps:

   a) cleaning and degreasing the part,

   b) application of an adhering undercoat on the part,

   c) stoving the part,

   d) dipping the part into a bath of a first plastisol,

   e) dripping and drying the part,

   f) stoving the part for a duration such as there is no complete gelation of the first plastisol,

   g) dipping the part into a bath of a second plastisol,

   h) dripping and drying the part,

   i) stoving the part until complete gelation of the second plastisol,

      whereas the process is characterised in that the part to be protected is a tool used for electroplating, and in that the second plastisol exhibits a hardness, after polymerisation, above that of the first plastisol.
2. A process according to claim 1, characterised in that the steps d) to f) are repeated at least once with at least a third plastisol, before resuming with steps g) to i).
3. A process according to any of the claims 1 and 2, characterised in that the stoving step c) is performed at a temperature ranging between 170°C and 190°C.
4. A process according to any of the claims 1 to 3, characterised in that the stoving step f) is performed at a temperature ranging between 150°C and 170°C for 15 to 20 minutes.
5. A process according to any of the claims 1 to 4, characterised in that the stoving step i) is performed at at least one temperature level, whereby the highest level does not exceed a temperature ranging between 180°C and 200°C, applied for 30 to 35 minutes.
6. A process according to any of the claims 1 to 5, characterised in that the steps d) to f) are repeated at least once, and the steps g) to i) are performed one after another without any noticeable pause between those various steps.
7. A tool used for electroplating (1) protected by a first coat (3) of a first plastisol, characterised in that the tool (1) is coated with at least a second coat (4) of a second plastisol, whereby the second plastisol exhibits a hardness, after polymerisation, above that of the first plastisol.
8. A tool according to claim 7, characterised in that the first plastisol exhibits a hardness, after polymerisation, ranging between 55 and 70 Shore A.
9. A tool according to claim 7 or 8, characterised in that the second plastisol exhibits a hardness, after polymerisation, ranging between 70 and 90 Shore A.

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