CN111501075A

CN111501075A - Plastic electroplating pretreatment process

Info

Publication number: CN111501075A
Application number: CN202010370935.4A
Authority: CN
Inventors: 李�杰
Original assignee: Qingyuan Minhui Auto Parts Co ltd
Current assignee: Qingyuan Minhui Auto Parts Co ltd
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2020-08-07

Abstract

The invention provides a plastic electroplating pretreatment process, which sequentially comprises the steps of oil removal, hydrophilicity, coarsening, neutralization, pre-immersion electrolysis, palladium activation, glue dissolution and chemical plating, wherein the pre-immersion electrolysis comprises the following steps: the plastic substrate carried on the hanger is soaked in hydrochloric acid, and then current is applied to carry out electrolysis. Wherein, the electrolysis process takes the hanger conducting point as the cathode and takes the iridium-titanium material as the anode. According to the invention, electrolysis operation is added on the basis of the traditional pre-dipping process, titanium with an iridium layer coated on the surface is used as an anode, and proper current is applied to effectively activate the hanging point, so that the good binding force between the hanging point and the following pre-plated nickel is ensured, the skin explosion of the hanging point is avoided, the generation of impurity points is reduced, and the product yield is improved.

Description

Plastic electroplating pretreatment process

Technical Field

The invention belongs to the technical field of plastic electroplating, and particularly relates to a plastic electroplating pretreatment process.

Background

The plastic electroplating is to plate metal on the surface of plastic to improve the appearance and endow the metal with the property, so that the product has the dual characteristics of plastic and metal. The traditional plastic electroplating process comprises the processes of oil removal, hydrophilicity, coarsening, neutralization, presoaking, palladium activation, dispergation, chemical plating, metal electroplating and the like, wherein the presoaking step is to soak a plastic product hung on a hanger in an acid solution, so that the palladium activation in the subsequent process is prevented from being diluted by water, the stability of palladium water is kept, the plastic product is contacted with a hanger conductive point of the hanger through the hanging point of the plastic product, and the current is conducted to a plating layer on the plastic product through the hanger conductive point in the electroplating process.

The pre-dipping step is only simple acid dipping, so that the hanging point cannot be effectively activated, the metal layer after the nickel pre-plating is not well contacted with the hanging point, and the crust breaking is caused to generate impurity points.

Disclosure of Invention

The invention aims to solve the problems and provides a plastic electroplating pretreatment process, which solves the problem that the hanging point cannot be activated in the plastic electroplating process, so that the metal layer is not well contacted with the hanging point after subsequent nickel plating, and the skin explosion is caused to generate impurity points.

The plastic electroplating pretreatment process provided by the invention sequentially comprises the steps of degreasing, hydrophilization, coarsening, neutralization, presoaking electrolysis, palladium activation, dispergation and chemical plating, wherein the presoaking electrolysis comprises the following steps: the plastic substrate carried on the hanger is immersed in acid, and then current is applied to perform electrolysis.

Further, the current density of the electrolysis is 0.4-1.0 ASD, and the corresponding voltage is 3-4V; in some embodiments, the current density is 0.5 ASD.

Further, the electrolysis time is 0.5-2 min; in some embodiments, the electrolysis time is 1 min.

Further, the anode used for electrolysis is titanium coated with an iridium layer on the surface, and the iridium layer completely wraps the titanium inside.

Further, the thickness of the iridium layer is more than or equal to 5 mu m.

Further, the electrolysis takes the hanger conducting point as a cathode.

Further, the hanger conductive points are made of stainless steel, and in some embodiments, the stainless steel may be S316 stainless steel.

Further, the acid is hydrochloric acid, and the concentration of the hydrochloric acid is 50-100 ml/L.

Further, the degreasing agent adopted in the degreasing step comprises 20-30 g/L of NaOH and Na₂CO₃30～40g/L，Na₃PO₄20-30 g/L emulsion1-3 g/L of the agent, 50-55 ℃ of oil removing temperature and 3-5 min of oil removing time, and through the steps, oil and dust attached to the surface of the plastic can be removed quickly and effectively.

Further, the hydrophilic agent adopted in the hydrophilic step is H₂SO₄The concentration is 50-70 g/L, the temperature of the hydrophilic step is 50-55 ℃, and the time is 1-2 min.

Further, the coarsening agent adopted in the coarsening step comprises: CrO₃390～410g/L，H₂SO₄390-410 g/L, the coarsening temperature is 65-70 ℃, the time is 10.5-13 min, the plastic surface becomes rough after coarsening, and the surface area is increased.

Further, a neutralization solution adopted in the neutralization step comprises 20-40 ml/L of hydrochloric acid and 10-20 ml/L of a neutralizing agent, the neutralization step is carried out at room temperature, the neutralization time is 1-2 min, and residual hexavalent chromium on the surface of the plastic can be effectively removed after neutralization.

Further, the activating agent adopted in the palladium activating step comprises 170-240 ml/L13-25 ppm of hydrochloric acid and SnC L₂3-5 g/L, the activation temperature is 20-25 ℃, the activation time is 2-3 min, and a catalytic layer with metal activity is formed on the surface of the plastic through palladium activation.

Further, in the step of degumming, the concentration of a degumming agent is 220-320 g/L, the degumming temperature is 50-60 ℃, and the time is 1.5-2 min.

Furthermore, the electroplating solution adopted in the chemical plating step comprises 25-32 g/L g of nickel sulfate, 10-16 g/L g of sodium hypophosphite, 35-50 g/L g of sodium citrate and 35-50 g/L g of ammonium chloride, the chemical plating temperature is 33-38 ℃, the chemical plating time is 7-10 min, and a chemical nickel conducting layer is deposited on the surface of the plastic.

Compared with the prior art, the method has the advantages that the electrolytic operation is added on the basis of the traditional pre-dipping process, the hanger conducting point is used as the cathode, the titanium with the iridium layer (the inert coating layer is coated on the surface to prevent the anode from being dissolved in the electrolytic process) is used as the anode, the proper current is applied, the hanging point of the plastic base material is effectively activated, the good bonding force between the hanging point and the metal nickel in the subsequent chemical plating process is ensured, the skin explosion of the hanging point is avoided, the generation of impurity points is reduced, the product yield is improved, the comprehensive yield is improved to 95% compared with the non-electrolytic condition, and the defective proportion caused by foreign matters and the impurity points is reduced to 0 from 3% -10%.

Drawings

FIG. 1 is a hydrochloric acid electrolytic bath used in the immersion electrolysis step of the present invention, wherein A represents a titanium-clad copper conductive rod, B represents a titanium-iridium material, C represents a hanger, and D represents a product hanging point;

FIG. 2 shows the electroless plating effect of the hanging point of example 1, wherein C represents a hanger and D represents a hanging point of a product;

FIG. 3 shows the effect of kiss-point electroless plating of comparative example 1, with position D indicating the product kiss-point;

FIG. 4 shows the effect of kiss-point electroless plating of comparative example 2, with position D indicating the product kiss-point;

FIG. 5 shows the effect of the kiss-point electroless plating of comparative example 3, and position D shows the kiss-point of the product.

Detailed Description

According to the invention, the electrolytic operation is added on the traditional pre-dipping process, so that the hanger point of the hanger is effectively activated, the good bonding force between the hanger point and the subsequent pre-plated nickel is ensured, the generation of impurity points is required to be reduced, and the product yield is improved. The technical solution of the present invention is further illustrated by the following specific examples. Other raw materials used in the following examples are those conventionally commercially available, unless otherwise specified. The test methods used are, unless otherwise specified, conventional or in accordance with relevant standard requirements.

Example 1

The plastic electroplating pretreatment process provided by the invention comprises the following steps:

(1) oil removal

Loading the plastic base material on an S316 stainless steel hanger, soaking the plastic base material to form a mixture containing 20-30 g/L of NaOH and Na₂CO₃30～40g/L、Na₃PO₄20-30 g/L and 1-3 g/L of OP emulsifier in degreasing agent for plasticsThe substrate is degreased to remove oil and dust attached to the surface of the plastic. The oil removing temperature is 50-55 ℃, and the oil removing time is 3-5 min. After oil removal, the plastic substrate is put into a cleaning tank and washed clean by water.

(2) Hydrophilic

Soaking the plastic base material in H of 50-70 g/L₂SO₄Hydrophilic treatment is carried out to change the plastic surface from hydrophobic to hydrophilic. The temperature is set to be 50-55 ℃ and the time is 1 min. After the end, the plastic substrate is put into a cleaning tank and washed clean by water.

(3) Coarsening

The composition comprises CrO₃390～410g/L、H₂SO₄And (3) carrying out coarsening treatment on the plastic base material by using a coarsening agent of 390-410 g/L, wherein the coarsening temperature is 65-70 ℃, the time is 10.5-13 min, and then, completely washing the plastic base material by using water, and after the completion, putting the plastic base material into a washing tank and completely washing the plastic base material by using water.

(4) Neutralization

And (3) neutralizing the plastic base material by using a neutralization solution at room temperature, wherein the neutralization solution comprises 20-40 ml/L of hydrochloric acid and 10-20 ml/L of a neutralizing agent, the neutralization time is 1-2 min, so as to remove residual hexavalent chromium on the surface of the plastic, and then, washing the plastic base material by using water.

(5) Pre-immersion electrolysis

Soaking the neutralized plastic base material in a hydrochloric acid electrolytic tank, wherein the hydrochloric acid electrolytic tank is filled with hydrochloric acid with the concentration of 50-100 ml/L, a hanger conducting point is used as a cathode, a titanium-coated copper conducting rod is used as an anode rod, a titanium-iridium material is used as an anode, a voltage of 3-4V and a current density of 0.5ASD are applied for electrolysis, the time is about 1min, current flows to a contact point (hanging point) between the plastic base material and the hanger through the anode, the hanging point is activated, and after the completion, the plastic base material directly enters a palladium activation tank for palladium activation.

The titanium-coated copper conducting rod is a material with a titanium layer coated on the surface of copper, and the thickness of the titanium layer is about 1 mm; the titanium-iridium material is prepared by coating an iridium layer on the surface of pure titanium, wherein the thickness of the iridium layer is more than or equal to 5 mu m, and the roughness is about 0.5.

The hydrochloric acid electrolytic tank is shown in figure 1, wherein A represents a titanium-coated copper conducting rod, B represents a titanium-iridium material, C represents a hanger, and D represents a hanging point of a product (plastic base material).

(6) Activation of Palladium

Putting the plastic base material after the pre-dipping electrolysis into a solution containing 170-240 ml/L of hydrochloric acid, 13-25 ppm of PD and SnC L₂Activating palladium in an activating agent of 3-5 g/L at 20-25 ℃ for 2-3 min, and then washing with water.

(7) Dispergation

And (3) carrying out degumming treatment on the activated plastic base material to strip off tin colloid adsorbed around palladium and provide catalytic points for the subsequent chemical nickel reaction, wherein the concentration of the adopted degumming agent is 220-320 g/L, the degumming temperature is 50-60 ℃, and the time is 1.5-2 min.

(8) Chemical plating

And (2) carrying out chemical plating by using an electroplating solution which comprises 25-32 g/L of nickel sulfate, 10-16 g/L of sodium hypophosphite, 35-50 g/L of sodium citrate and 35-50 g/L of ammonium chloride at the temperature of 33-38 ℃ for 7-10 min, and then plating a nickel layer on the surface of the plastic substrate.

And after the chemical plating is finished, finishing the plastic electroplating pretreatment process, and then performing metal electroplating, namely plating copper or other metals on the plastic base material to obtain a plastic electroplating finished product.

The hanging point chemical plating effect of the embodiment is shown in fig. 2, and it can be seen that the electroplated layer and the hanging point at the hanging point are tightly and firmly combined, and the phenomena of poor binding force such as looseness, skin explosion and the like do not exist, so that the defects of grain point burrs and impurity points caused by the fact that the electroplated layer at the hanging point is adsorbed on a product due to poor binding force of the hanging point can be avoided.

The product after chemical plating (namely the product after nickel plating) is detected, the comprehensive yield of the product is 95%, the hanging point and the plating layer are firmly combined, the conditions such as skin explosion and the like do not occur, the defective product proportion caused by foreign matter and foreign matter points caused by skin explosion of the hanging point is directly changed into zero from 3% before improvement, and the yield of the whole electroplating product is improved.

Comparative example 1

The only difference between this comparative example and example 1 was that the current density of the prepreg electrolysis was reduced to 0.4 ASD. The effect after electroless plating is shown in FIG. 3, but the bonding strength between the plating layer and the hanging point is not strong at the non-peeling position, although the peeling area of the hanging point is reduced when the current density is reduced, mainly because the current density is too low to achieve a good activation effect.

In addition, if the current density exceeds 1.0ASD, the excessive current not only wastes energy but also generates a serious hydrogen evolution phenomenon to influence the working environment because the hanging point area is constant.

Comparative example 2

The only difference between this comparative example and example 1 is that the anode used in the pre-dip electrolysis was replaced with graphite.

As shown in fig. 4, it can be seen from fig. 4 that the graphite is used as an anode in the pre-immersion electrolysis stage, and the metal layer of the plastic electroplating finished product finally obtained has granular crust at the hanging point after the plastic base material is subjected to the electroless plating. This is mainly because when graphite is used as the anode, black particles are generated in the plating solution, and foreign matters are generated on the surface of the product, which causes peeling.

Comparative example 3

The only difference between this comparative example and example 1 is that: the anode used for the pre-immersion electrolysis is made of pure titanium material and does not have an iridium coating.

The picture of the plastic electroplated product of this example is shown in fig. 5, and it can be seen from fig. 5 that the hanging point of the plastic electroplated product still has skin cracking by using pure titanium as the anode of the pre-immersion electrolysis. This phenomenon is mainly caused by the poor conductivity of pure titanium, which results in the failure of effective activation of the hanging point and is not favorable for plating a metal layer on the hanging point. Meanwhile, the pure titanium used as the anode can also decompose hydrochloric acid, generate a large amount of acid mist and influence the product quality.

Comparative example 4

This comparative example is similar to example 1 except that step (5) omits electrolysis and is soaked with hydrochloric acid of the same concentration for the same time.

As a result, the peeling phenomenon occurs at the hanging point after the chemical plating, and the defective proportion caused by foreign matters and impurity points generated by the peeling is about 3% to 10%.

In conclusion, in the plastic electroplating pretreatment process, the hanger conducting point is taken as the cathode while the plastic base material is presoaked, the iridium-titanium material is taken as the anode, and the current is applied for electrolysis, so that the hanger conducting point can be effectively activated, the comprehensive yield is improved to 95% compared with the situation of non-electrolysis, and the foreign matters and impurity points are reduced to 0 from 3% -10%.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A plastic electroplating pretreatment process is characterized in that: sequentially comprising the steps of degreasing, hydrophilizing, coarsening, neutralizing, presoaking electrolysis, palladium activation, dispergation and chemical plating;

wherein the pre-immersion electrolysis comprises the steps of: the plastic substrate carried on the hanger is immersed in acid, and then current is applied to perform electrolysis.

2. A plastic pre-plating treatment process according to claim 1, characterized in that: the current density of the electrolysis is 0.4-1.0 ASD.

3. A plastic pre-plating treatment process according to claim 2, characterized in that: the electrolysis time is 0.5-2 min.

4. A plastic pre-plating treatment process according to claim 1, characterized in that: the anode used for electrolysis is titanium coated with an iridium layer on the surface.

5. A plastic electroplating pretreatment process according to claim 4, wherein the plastic electroplating pretreatment process comprises the following steps: the thickness of the iridium layer is more than or equal to 5 mu m.

6. A plastic pre-plating treatment process according to claim 1, characterized in that: the electrolysis takes the conductive point of the hanger as the cathode.

7. A plastic electroplating pretreatment process according to claim 6, characterized in that: the hanger conducting point is made of stainless steel.

8. The plastic electroplating pretreatment process according to claim 1, wherein the acid is hydrochloric acid, and the concentration of the hydrochloric acid is 50-100 ml/L.

9. The pretreatment process for plastic electroplating according to claim 1, wherein the degreasing agent used in the degreasing step comprises NaOH 20-30 g/L and Na₂CO₃30～40g/L，Na₃PO₄20-30 g/L of emulsifier 1-3 g/L.

10. A plastic pre-plating treatment process according to claim 1, characterized in that: the hydrophilic agent adopted in the hydrophilic step is H₂SO₄The concentration of the hydrophilic coating is 50-70 g/L, the temperature of the hydrophilic step is 50-55 ℃, and the time is 1-2 min.