JPS603347B2 - Partial plating method for metal parts materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for partially plating metal component materials.

When performing surface treatments such as pickling, alkali degreasing, or plating on metal parts materials, it is now necessary to perform the surface treatment on only a portion of the material.

Such partial treatment is effective in saving precious metal resources during plating, for example. In addition, we also provide rust prevention for metals that can withstand corrosive environments such as seawater desalination equipment, heat exchangers that use seawater as cooling water, etc., where sea salt adheres due to the evaporation of salt water at high temperatures and high humidity. Craftsmanship is also required. An object of the present invention is to provide a simple method for partially plating metal parts with precious metals, etc., using a highly chemical-resistant paint that can withstand such metal surface treatment and corrosive environments. . Paints containing natural vegetable oils conventionally used for the above-mentioned purposes are not necessarily satisfactory in terms of chemical resistance. That is, when it comes into contact with, for example, a plating solution or an alkaline solution used for plating pretreatment, hydroxyl groups (monoOH) originating from natural vegetable oils are removed.
) and the carboxyl group (-COOH) to form a resin soap, which has the disadvantage that the adhesive coating is dissolved and separated. In addition, conventionally, when partially plating metal parts with precious metals, the method used was to first mask the unnecessary parts with polyethylene tape, Teflon tape, etc., and then apply plating to the required parts. Depending on the shape of the material, it may not be possible to sufficiently mask areas other than the plated parts, which limits the range of application.
Therefore, there is a drawback that plating is applied to parts that do not require actual potting, which is also a big problem from the point of view of saving precious metal resources. The present invention has been made in view of the above points.

That is, in the plating method of the present invention, when partially plating a metal part material, after masking the part to be plated with a masking material, the part not to be plated is coated with 50 to 8% by weight of hydroxy group-containing acrylic resin. / Applying a strong chemical-resistant paint characterized by a resin component consisting of 15 to 35% by weight of a resin and 5 to 2% by weight of an epoxy resin and a solvent, and then heating and drying the applied paint. The present invention is characterized in that a strong chemical-resistant coating film is formed on the portions that do not require lacquering, then the masking material is removed, and then the portions from which the masking material has been removed are plated. The paint used in the present invention forms a three-dimensional network structure by containing the three components of hydroxy group-containing acrylic resin, melamine resin, and epoxy resin, and reduces free carboxyl groups and hydroxyl groups as much as possible to carry out the saponification reaction as described above. It has the property of forming a coating film that does not induce.

That is, the highly chemical-resistant paint of the present invention contains 50 to 80% (by weight) of a hydroxy group-containing acrylic resin, 15 to 35% of an amino resin, and 5 to 5% of an epoxy resin.
It is characterized in that the resin content consists of ~20% and the solvent. The present invention will be explained in more detail below.

The paint used in the present invention contains a hydroxy group-containing acrylic resin as a main component.

Here, the hydroxy group-containing acrylic resin is a general term for polymers of acrylic acid and its derivatives that have a hydroxy group, and includes polymers such as acrylic acid or methacrylic acid and their esters and acrylamide that have a hydroxy group. Contains copolymers. Hydroxy groups are introduced, for example, by esterification with polyhydric alcohols such as ethylene glycol at the monomer stage.
The paint used in the present invention contains an epoxy resin and an amino resin in addition to the hydroxy type acrylic resin.

Here, epoxy resin refers to a polymer compound containing two or more epoxy groups in the molecule, and amino resin refers to a resin containing a methylol group obtained by a condensation reaction between a compound containing an amine/group and an aldehyde group. Used in a generic sense,
These include melamine resin, urea resin, guanamine resin, aniline aldehyde resin, etc. The paint used in the present invention contains the above three resins, hydroxy type acrylic resin, 5
0-80%, amino resin 15-35%, epoxy resin 5
It can be obtained by blending in a proportion of ~20% and dissolving or dispersing it in a solvent such as an aromatic, alcohol, ester, or ketone.

When the paint used in the present invention described above is applied to a treated material and dried by heating for 25 minutes at, for example, 180 qo, a three-dimensional polymeric resin film is produced by the reaction between the acrylic resin, epoxy resin, and amino resin. Three-dimensional polymerization due to the reaction between these resins is thought to be mainly due to the following mechanism. 01 Reaction between the epoxy group in the epoxy resin and the amino group in the amino resin or acrylic resin Each of the atoms of the amino group participates in the reaction that generates an -OH group through the ring connection of the epoxy group.

■ The reaction between the epoxy group and the methylol group in the amino/resin or the hydroxyl group in the etherified methylolmelamine reacts with the epoxy group and opens the epoxy group to form a hydroxyl group.

The generated hydroxyl groups form a three-dimensional network structure by endless condensation (dehydration) reactions with the methylol groups in the amino resin together with the hydroxyl groups resulting from ring opening of the epoxy group in reaction '1} above. [3} Reaction between the epoxy group and the carboxyl group in the acrylic resin The carboxyl group and hydroxyl group in the acrylic resin undergo an addition reaction with the epoxy group in the epoxy resin.

In addition, the following reactions also occur. (Butylated melamine resin) (Epoxy resin, acrylic resin hydroxyl group) (R, resin skeleton) and melamine (epoxy resin, acrylic resin hydroxyl group) (R: resin skeleton). The above-described reaction is repeated to form a three-dimensional network polymer coating.

The paint used in the present invention is the above-mentioned paint.

It contains an oxy-type acrylic resin, an epoxy resin, and an amide/resin in an optimal amount ratio to form the above-mentioned three-dimensional network structure and provide a coating film with excellent chemical resistance. In other words, if the resin content of the paint is 50% hydroxy acrylic resin, the chemical resistance, which is a characteristic of hydroxy acrylic resin, will decrease, and if it exceeds 80%, the reactive groups necessary for crosslinking reaction will be reduced. The balance becomes poor, the crosslinking becomes rough, and the chemical resistance decreases. If the amino resin content is 15%, the crosslinking will be insufficient and the chemical resistance will deteriorate, and if it exceeds 35%, the crosslinking will become too dense, resulting in decreased flexibility and brittleness. Furthermore, if the epoxy resin content is less than 5%, the coating film may lack flexibility (and become unable to follow the expansion and contraction of the base material, or if the epoxy resin content is less than 5%)
If it exceeds this, the crosslinking density will become coarse and the chemical resistance will decrease. In addition to the above resin, carbon black may be added to the coating material used in the present invention.

Carbon black has the effect of giving the paint used in the present invention the property of hiding the base material and improving heat dissipation. Generally, in order to metal plate a metal part material, the surface to be plated must be a clean surface of the base metal. Usually, a rust preventive oil applied for temporary rust prevention is removed using a degreasing agent such as trichlorethylene, and then the oxide film on the metal surface is removed by treatment with acid or alkali, or both. Further, prior to plating, it may be refined with sulfuric or nitric acid. When plating a metal part material with a precious metal, for example, in the case of silver plating, steps such as zinc plating or copper plating are performed in advance, and then silver plating is performed.

The main purpose of plating metal parts for industrial equipment is to improve abrasion resistance and conductivity, and aesthetics often only has a secondary meaning. Many of the metals used for plating in this way are expensive, so if only the necessary parts could be plated, a great deal of resources and costs could be saved.
As a specific example of the present invention, application to partial plating of heat exchanger fins will be explained with reference to the drawings.

When silver plating is applied to the treated surfaces 2 and 3 of the heat exchanger fin 1 as shown in FIG.
A masking material 4 such as a heat-resistant tape is applied to the surface, and then, as shown in FIG. 2, the coating material 5 of the present invention is applied to the entire surface and dried by heating at 180 oo for 25 minutes to form a three-dimensional network structure coating film. .

After the coating film is formed, the masking material on the surfaces 2 and 3 to be plated is peeled off, and the entire fin 1 is immersed in a plating bath to perform electrolytic plating. As a result, a fin in which only the required surfaces 2 and 3 are silver-plated is obtained. Of course, if it is possible to apply the paint partially, there is no need to use a masking agent. In the above example, it has been described that the paint used in the present invention is used to treat surfaces other than partially plated surfaces, but the paint used in the present invention is completely the same and is treated with acids, alkalis, trichloride, and other chemicals. In partial surface treatment, it can be used to act as a protective film on the untreated surface.

Furthermore, it is also possible to transfer a portion that has been partially copperized to a partial silver finish for the purpose of improving electrical conductivity. The paint used in the present invention can also be used in combination with an undercoat to provide a rust-preventive coating that can withstand strongly corrosive environments on steel components.

The undercoat used here is composed mainly of epoxy resin, to which is added an amount of the above-mentioned amino resin capable of forming a three-dimensional network, for example, one having the following composition. Eboxy resin varnish 60~
65 Amino resin varnish 6.5-7.51
00% pigment: C, K20・4C 3-2n○13
Day 20・BaS04
30-31 For example, as a rust preventive pigment, 4Cr03
The rust-preventing effect when using , Netsun○, and Pan-20 is explained as follows.

'B) The metal base is made passivated, and the y-* that adheres to the metal is 20ZmCh040C0210days201Fe2030Cr
By the reaction of 20, water-insoluble (ZnOH)2C03
This makes the film denser and enhances the anti-corrosion effect.

Cr04 oxidizes corrosion products to form insoluble ferric salts, and the ferric salts are deposited in the film to suppress the action of corrosion factor ions and serve as resistance to the progress of corrosion. As mentioned above, the plating method of the present invention uses a coating material with excellent chemical resistance to plate only the desired parts of the metal component material, and by using this,
Since partial precious metal plating can be performed, precious metals can be saved compared to the conventional case where the entire surface is unavoidably plated. In addition, by using it as a heavy anticorrosion paint, it has the effect of enabling use in environments that strongly corrode metals.
The present invention will be explained below with reference to Examples.

'1} Paint composition resin: hydroxy type acrylic resin 28.9%, butylated melamine resin 8.2%, bisphenolepoxy resin 4
．． 1% Pigment: Carbon black 1.6% Solvent, (Toluene 60: Butanol 10: Diacet alcohol 20: Methyl ethyl ketone 10) 57.2% Viscosity 70~8 eaves ec'2} Painting on heat exchanger cooling fins Apply the above paint to food cup No. 1 with thinner. 4 Using a viscometer, 2 pi 0, 80 to 9 sand' is applied to the diluted paint solution, degreased in advance with Triclean, etc., and plated.・Sun 2012
Suppresses LO reaction.

'o} Dip the heat exchanger cooling fin, whose surface is masked with a masking material due to the action of CQ in the air, and keep it still until the paint drips and the fluidity of the paint film disappears. After drying, the masking material was removed and the film was dried by heating at 180° C. for 25 minutes.

Glue Stability CC against silver plating process after painting process
12=CHC1 (triclene) 9p○ steam degreasing → NaO
H95°C treatment → Zn substitution plating treatment in KCN hybrid grade → Ag plating in AgCN and KCN hybrid grade →
After going through the process of washing with water and then washing with hot water, a partially Ag-plated surface was secured.

The stability of the coating film was maintained even after undergoing these harsh process conditions.
■ Fog resistance after going through the above [3' process] In order to secure the Ag-plated surface of the above glue, the area was treated with silver, and then salt water was applied continuously for 35 minutes under conditions of 15% NaC and 35°C and pseudo% humidity.
It was confirmed that the coating maintained its stability even after being sprayed for feeding time, and had strong chemical resistance and strong anti-bell strength.

[Brief explanation of drawings]

Figures 1 and 2 are partial perspective views of heat exchanger fins that are partially plated using a strong chemical-resistant paint. Show the rear. 1...Fin, 2, 3...Plated parts, 4...Masking material, 5...Coating film with strong chemical resistant paint. Figure 2 Hair Z diagram

Claims (1)

[Claims] 1 When partially plating a metal part material, first mask the part you want to plate with a masking material, then apply 50% hydroxyl group-containing acrylic resin to the part that does not need to be plated.
A strong chemical-resistant paint characterized by consisting of a solvent and a resin component consisting of ~80% by weight, 15-35% by weight of an amino resin, and 5-20% by weight of an epoxy resin is applied, and then the applied paint is A metal, characterized in that a strong chemical-resistant coating film is formed on the parts that do not require plating by heating and drying, and then the masking material is removed, and then plating is applied to the parts from which the masking material has been removed. Partial plating method for component materials.