DE2046689C3 - Process for the pretreatment of acrylonitrile-butadiene-styrene resins for electroless metal plating - Google Patents

Description

4. The method according to claim 3, characterized in that it is true according to the standard 90 ^c -Abziehprüfverfahren, that the glycol diacetate concentration is in iiegt.

the aqueous medium at the saturation concentration It has also already been proposed that the adhesive strength

tration ± 4 percent by volume is maintained. by pretreating the plastic surface

5. The method according to claim 3, characterized in that before etching with a strongly oxidizing acid draws that a buffer solution is used. 30 improve. A

6. The method according to claim 5, characterized by those ketone-based used, which is a very good draws that sodium acetate used as a buffer contains solvent for the ABS resin. One such will. Method is for example in the US patent

7. The method according to claim 1, characterized in 34 45 350 described. Pretreatment with a records that the glycol diacetate solution has such a system, however, for various reasons Temperature is kept between 32 and 54 ° C. found no entry into the practice. This pre-

8. The method according to claim 1 or 7, characterized in that the action system has an adverse effect characterized by having a contact time of about 0.5 on the aesthetic appearance of the finished coated until applied for about 3 minutes. Molded body, and it has been shown that the adhesive

40 strength of electrolessly deposited nickel is not sufficiently improved. Although there is a

certain improvement in adhesive strength except for such

Values on the order of 2.3 to 2.7 kg / cm, but this is accompanied by a

The invention relates to a method for pretreatment 45 undesired hollowing out of the resin body treatment of acrylonitrile-butadiene-styrene resins (post-pretreatment agents that cause damage hereinafter referred to as ABS resins) for the electroless leads within the resin molding and an Ab metal coating, in which the surface of the resin solution from parts of the molded plastic body Bringing improvement in the adhesion of the applied joint with the metal coating, tall layer first with a solvent for the 50. The object of the invention is therefore to provide an improved Resin and then using a highly oxidizing process to produce ABS resins for the Acid is brought into contact. indicate electroless metal plating with whose

Recently there has been a great demand for the help it is possible to improve the adhesive strength between the Process for metal coating of non-conductive metal coating and the ABS resin substrate into ver moldings, especially plastic objects. 55 improve without doing the above A plastic coated with a metal counter-disadvantages occur.

stood united in itself the favorable properties It has now been found that this task through

of the plastic and the advantageous properties a process for the pretreatment of acrylonitrile Metal, so that in such a coated butadiene-styrene resins (ABS resins) for the current-shaped body the technical and aesthetic advantages 60 loose metal coating can be solved in the case of both materials can be used. On the surface of the resins to improve adhesion in this way it is possible, for example, to first apply a lightly of the applied metal layer deformable object with a light weight solvent for the resin and then with a made of an acrylonitrile butadiene styrene resin (ABS strongly oxidizing acid), Resin) with high impact resistance, the 65 that is characterized in that the resin is anesthetic and mechanical properties through the use of the strong oxidizing acid with a Lö-application a metal coating can be improved solution of glycol diacetate in one over the resin be able. essentially inert medium for a

glazing and satin finishing of the resin surface using sufficient organic pretreatment solutions.

corresponding period of time is brought into contact. consider glycol diacetate as the main caustic, in one

According to the invention, preference is given to such a glycol resin which is essentially inert with respect to the ABS resin

diacetate solution is used, the concentration of which is contained around the medium, preferably water. It can-

a maximum of 4 percent by volume of the maximum saturation 5 different media are used,

concentration deviates. This will be ζ. B water, acetic acid, alcohols, glycols, glycolic

particularly advantageous results with respect to the adhesive ethers and mixtures thereof. For economic

strength of the metal coating on the plastic grounds, water is preferred, which is used for the metal

Luhstrat scored. layering is the most commonly used medium.

With the present invention it is possible, although the medium used according to the invention, Haftfeu.gkeit the electrolessly applied metal in the pretreatment solution should be inert to the ABS layer, for example with copper or nickel on a resin, it can be very inherent dynamically increase value of ub; r 5.4 kg / cm. The adhesive strength. The function of a dynamic system is from speed when the method according to the invention is used in FIG. 1 of the drawing can be seen. It has proceedings improved still further by using as strong i ₅ shown namely that, as shown in Fig. 1, oxidizing acid after the pretreatment j _{n CMEM} media exhibits a chromic acid, and trivalent chromium ions ent in the glycol diacetate - Has limited solubility, e.g. B. in water, optimal holding solution is used and the electroless Beschich- results are achieved when the Glykoltete substrate before normal storage in a diacetate concentration between the saturation value of a dilute aqueous solution of a nonionic or ao of the solution and a 4% below Value of anionic surfactant dips to fluctuates. Curve A of FIG. 1 explains the means of drying out the absorbed salts and an oxy- ler adhesive strength which, for a given ABS resin date, prevent the electrolessly applied layer from becoming substrate using a pure glycol diacetate. A further improvement in the pretreatment solution containing the adhesive strength at a given temperature can be achieved according to the invention by the fact that the temperature (in the present case 35 ° C.) can be aimed immediately after the pretreatment.

before treatment with the strongly oxidizing acid glycol diacetate is in the presence of water

by washing with an acid or base a hydrolyses with the formation of acetic acid and ethylene

carries out drolysis. glycol. This reaction is reversible and takes place

According to a preferred embodiment of the invention, strictly according to the law of mass action. Grounding the resin surface increases the rate of reaction, but the pre-etching agent (glycol diacetate) in front of it has only a slight influence on the equilibrium of the treatment with the strongly oxidizing acid. The acetic acid formed increases the hydrolyzed. Solubility of glycol diacetate, as shown by curve B

According to a further preferred embodiment 35 of FIG. 1 shows. To maintain an optimal

the invention is as an inert medium an aqueous paint adhesive strength is the addition of glycol

Medium used. diacetate to increase the effects of acetic acid

According to a further preferred embodiment required to increase the glycol diacetate concentration

the invention will keep the process in the presence of a value that is around 4% around the saturation

Buffer solution, preferably in the presence of the nourishing value fluctuates around 40,

trium acetate. The presence of hydrogen ions catalyzes

According to a further preferred embodiment also the hydrolysis and leads to a different invention, the glycol diacetate concentration becomes exercise of curve B to the right to the extent that more acetic acid is formed in the aqueous medium at the saturation concentration.

It was found that the influence of the acetic acid content, formation by adding alkalis, such as sodium hydroxide, potassium hydroxide or ammonium hydroxide, according to a further preferred embodiment, of the invention the glycol diacetate solution can be canceled on one. The alkalis should be under Maintained temperature between 32 and 54 ° C, and stir it vigorously and only in such an amount a treatment time of about 0.5 to about 50 will be added so that the system is nearly neutral Applied for 3 minutes. and ideally at a pH below 7.2

Other objects, features and advantages of the invention are contemplated.

result from the following description in terms of Acetate salts are formed, which in general

bond with the drawing. The solubility of the glycol diacetate shows my

F i g. 1 shows a graphic representation of the adhesive strength, and the system then acts on those in FIG

ability of copper on an ABS resin substrate as shown as curve C.

Function of Glycol Diacetate Concentration in a Although less glycol diacetate in an acetate

aqueous medium and system containing salts are brought into solution

F i g. 2 a schematic representation of what can be achieved without changing a

additional method according to the invention for pretreatment 60 other size, such as. B. the temperature or the

development of an ABS resin substrate for the electroless Me dwell time, optimal adhesive strength, provided

tall coating. that the glycol diacetate concentration on the saturation

In the ABS resins used according to the invention supply value ± 4 percent by volume is maintained. One

it is usually with a metal bc control can also be done by adding a buffer solution,

layerable resin-65 _z . B. a sodium acetate solution, be exercised,

Grades made by interpolymerization of acrylic, which keeps the solution at about the neutral point,

nitrile, butadiene and styrene. Preferably sodium acetate is used at the beginning

The aqueous medium containing glycol diacetate for the pretreatment according to the invention and

then added from time to time as required in order to have only a limited solubility in water,

the. Keep solution neutral. The surface layer consists predominantly of the effect of the

The essence of sodium acetate consists in the dissolving water, and the loss of glycol diacetate through

ability of glycol diacetate to decrease again, and vaporization is low.

depending on the sodium acetate concentration, the 5 After pretreatment of the surface of the ABS

curve close to curve C. Harzes with the glyculine used according to the invention

Although usually even the presence of a small amount of diacetate solution, the object can then simply be rinsed with glycol diacetate concentrations and exerted a positive influence on the adhesive strength directly in a strong oxidizing acid. 1 explains that optimum results are attacked with ₁₀ % of the ABS resin, whereupon the glycol diacelate concentrations are obtained which fluctuate by about 4% around the saturation value when subjected to a conventional electroless metal coating.

Koldiacetat in the medium only a limited Although the pre-etching according to the invention with

Has solubility. Surprisingly, this has been found in a glycol diacetate solution to each electroless metal

as independent of the saturation point applicable ER i ₅ can be adapted coating process, one turns

grasslands. So the maximum concentration of for best results is preferably that

Glycol diacetate in water at 35 ⁰ C for about 15.8%. As in Fig. 2 procedure. According to FIG. 2

already mentioned, the upper solubility limit will be that of the electroless metal plating.

by the presence of acetic acid alone, objects to be treated optionally in an alkali

set and by the presence of acetate salts ₂₀ ic detergent, which is usually at about

degraded. Irrespective of the shift of 54 ⁰ C is kept, washed to remove

However, the saturation point is the mean adhesive strength on the surface of the object

between the electrolessly deposited metal and grease or oil. The dwell time is short and is in

The ABS resin substrate works best when the glycol- usually only takes 1 to 2 minutes. This level can be

Diacetate concentration will drop by about 4 percent by volume by 25 if the ABS articles are free of grease. When

the saturation concentration of the solution around the object, however, with the alkaline cleaning agent

fluctuates. As shown in FIG. 1 shows that if the agent is changed, it must be cleaned before treatment

the bond strengths within this range only with the glycol diacetate solution in water, preferably

little. It allows fluctuations in operation and pre-deionized water to be rinsed

temporary inattentiveness on the part of the per- 30 As already mentioned, the glycol diacetate pre-

sonals too. etching solution preferably at a temperature between

When using a medium other than water, 32 ° C and the softening point of the ABS resin

in which glycol diacetate is more soluble, that is held, and the residence time in the pre-etch solution is

Glycol diacetate preferably only in one such usually briefly and is 0.5 to 3 minutes, before-

Amount present that a devitrification and satin finish 35 preferably about 1 minute. Longer residence times

the surface of the ABS resin substrate. can be used but do not result in any

It is believed that this has a particular advantage in the beginning.

the porosity of the surface increases and thereby Although it is sufficient if the pretreated in this way the butadiene content of the surface is subject to attack by an object with water, preferably deionized The strong oxidizing acid is more easily accessible. Water, rinsed, and etches with the strong one power will. As a rule, the amount of oxidizing acid that will be added to achieve dips This effect required amount of glycol diacetate, the object is preferably short, usually if this is good or unlimited in the carrier medium for 30 to 120 seconds, in an In to 5 η acid is soluble, less than 40 percent by volume. For further or basic solution, in order to convey on the surface Even etching can hydrolyze non-permanent glycol diacetate. Every ionic wetting agents with advantage of the acid or base according to the invention with the exception of acetic acid used pre-etching solution can be added. be used. This solution is usually aul

In it, other substances can also be kept at a lower room temperature and serves to reduce the glycol

Amounts, which as a solvent for ABS resins diacetatätning wash off and an impurity

can serve, be included. If such substances 50 of the strong oxidizing acid with hydrolysis pro

are present, however, they must not prevent the products from gelling.

Surface cause which is detrimental to that after which the object is again in water, before

Appearance of the finished item has been proven. preferably deionized water, rinsed and then ii

Since the effect of glycol diacetate solutions is only an etching bath of a strongly oxidizing acid

borrowed in a devitrification and satin finish of the surface 55 although all known oxidizing acid solutions

of the ABS resin substrate, the substrate can be used for the butadiene portion of the ABS resin

Long cells can be immersed in the etchant without damage, it is preferable to use a pure one

will. For practical reasons, however, chromic acid etching is used. The chrome sauna used

Usually dwell times between 0.5 and 3 minutes, the etching solution contains 1.02 to 1.26 kg of chromic acid per 1 Li

preferably from about 1 minute. 60 solution, which is about the normal solubility of Chron

The solution stamp is not overly critical. acid in water. A higher solubility

Elevated temperatures reduce the pretreatment "A-earth due to the presence of trivalent chromium ions"

treatment process and temperatures between 32 ° C and achieved in the reduction of hexavalent chromium

the softening point of the ABS resin, preferably during the oxidation of the ABS resin surface g

from 32 to 54 ° C., in particular from 38 to 43 ° C. 65. An initial solution with high chrome

can be used to advantage. In the case of an acid content, the addition of v < Operation at higher temperatures shows the value of oxalic acid to a chromic acid solution under Fig of water as a solution medium. Since glycol diacetate of trivalent chromium ions, followed by the addition

in

from chromium trioxide to the solution formed under the object, where these dry out, again on formation of an oxidizing acid with the desired is raised. These phenomena affect the hexavalent chromium content to be obtained. the appearance and the adhesive strength between metal The etching with the strong oxidizing acid takes place and metal. It has now been found that when the electrolessly coated ABS resin is immersed at about 43.degree. C. up to the deformation temperature, preferably between 43.degree. C. and about 43.degree , especially between 60 and 66 ^U C. The verionic surfactant in an amount of dwell times is between 5 and 10 minutes, depending on the type of ABS resin being treated, which is from about 0.5 to about 2 percent by volume. Solution a thin protective film during aging

After etching with the strongly oxidizing acid, _{la forms} on the surface of the object,
the ABS resin is then subjected to a spray rinse. Any water-soluble anionic is suitable, in which the remaining acid is strong or nonionic surfactants, e.g. B. from the surface of the object herunlerge ethylene oxide condensate with at least 8 ethylene washes. oxide groups, modified with phosphate, sulfate or sulfate

This is followed by one or more Wasscrspü- ₁₅ iizierte Äthylenoxide can. Alkyl aryl sulfate, dimethyl octane solutions and a final cleaning with a diol, oxyethylated sodium salts, amine polyglycol alkaline cleaning agent that does not contain any condensates, modified linear alcohol ethoxylates or silicates. This cleaning agent is preferably alkylphenol ethoxy sulfate, sodium heptadecryl sulfate, mild and free from alkalis. The detergent and mixtures thereof. As a rule, the contact is usually kept at a temperature between 43 _2O cycles with the aqueous solution of the surface-active agent and 54 ° C, and the dwell time of the counter-agent, about 4 to 5 minutes immersion in it, is 3 to 5 Minutes. Tap water and a deionized rinse

After the final alkaline cleaning, water. The formation of the thin film prevents one

the object can then be any process of corrosion and drying out of the adsorbed

for electroless metal plating using ₂₅ salts. After aging with the passage of warm air

of, for example, copper or nickel subjected during the desired period of time, usually

will. Usually, the pre-treated ABS can last 15 minutes or longer and up to 4 hours or more

Subject to this in a solution of tin (H) chloride longer at room temperature, the protective coating

Hydrochloric acid to sensitize the plastic surface through contact with an alkaline cleaning agent

immersed by adsorption of tin (II) ions 30 and removed by a brief rinse in sulfuric acid,

will. This is usually followed by immersion. After removing the coating, it is de-energized

in a solution of a noble metal salt, e.g. B. of palladium-coated object then electrolytically

dium chloride, on, to activate the ABS counter-coated.

stood by reducing the noble metal ions to the although many of the steps described above

Metal. The 35 formed on the ABS article can be omitted and the one with glycol diacetate

Precious metal film then acts as a catalyst in the pretreated item after a water rinse

chemical metal plating bath, in which the directly immersed in the oxidizing acid and then

so activated ABS object is immersed. directly under the electroless metal coating

A wide variety of copper and nickel throws can be produced, it has been found that when assembling for electroless metal plating, great care must be taken when cleaning the thinning. A copper-containing composition after each treatment stage, for example, consists essentially of a cumulative beneficial effect. This is done by having a soluble copper (II) salt, such as copper sulfate; Observation confirms that the adhesive strength against a complexing agent for the copper (II) ion, as in control samples which were not pretreated by contact with Rochelle salt, and an alkali hydroxide for a glycol diacetate, when the pH value was used: a Carbonate as a buffer of conventional adhesion test methods was improved. and a reducing agent for copper (II) ion, when using glycol diacetate as the main one, such as formaldehyde. The mechanism by which pretreatment agent, under such conditions, affects articles with a catalyzed surface, e.g. B. that only a satin finish of the ABS resin is achieved, ABS objects with catalytically active Palla- 50, the treated objects have a uniform diummetall on their surface, as above appearance. The deposited metal coating is equally autocatalytically metallic in such solutions and the adhesive strength z. B. by electrolessly stripped, is described in the literature with the surface being separated from copper or nickel (compare, for example, US Pat. No. 2,874,072). exceptionally high, regardless of the

Subsequent to the electroless metal plating method 55 applied electroless metal plating method. The ABS object can then be coated in the usual way. In addition, one achieves high adhesive strengths of over with copper, nickel, gold, silver or chromium, electro- 5.4 kg / cm without hollowing or unfavorable effects, forming the desired flow of the resin substrate . In standard peel tests, the surface of the object. In such destruction detection methods, it has been found that ultimate bond strength depends, in part, on the defectiveness primarily on the resin-to-metal bond strength between metal and metal. An interface appeared and that along with that it was found that when the electroless metal was removed little or no plastic from the ABS coated ABS article was removed for 24 hours or resin. This improvement in bond length ages, and this has a beneficial effect on strength without impairing the structural bond strength between metal and plastic. 65 ABS resin integrity achieved. It has also been found that this is partly due to the following examples are intended to illustrate the invention in greater detail, and by means of the tendency of the surface to oxidize. In all comparative tests, the migration of the absorbed salts to the surface was determined by ABS resin articles made from identical resins

identical conditions in order to exclude the differences caused by differences in resin and differences in the method of manufacture of the item. The Abzichfcstigkeitcn were determined so that a 2.54 cm wide strip of the deposited metal honed at an angle of 90 ³ C to the resin surface using a Dillon Abziehtcstvorrichtung.

Examples 1 to 6

According to the method explained above according to FIG. 2 were made from cylindrical shaped objects

10

ABS resins for the electroless metal coating pretreated using an aqueous solution containing glycol diacetate was contained in a concentration of 11.5 volume percent and maintained at about 40 ⁰ C. For comparison purposes, in each case an identical article was made for coating without pretreatment with glycol diacetate. The results obtained are summarized in the following Table I, in which the deduction

o strengths to an average panel thickness of 0.11 mm are turned off and the control samples are objects that have not been pretreated with the glycol diacctate solution were subjected.

Electroless Mctall-
coating solution Medium deduction
strength Middle area
the peel strength kg / cm kg / cm kg / cm example 1
Control A copper
copper 4.19
3.32 4.03 to 5.73
2.86 to 3.94 Example 2
Control B copper
copper 4.83
3.36 3.49 to 5.45
2.86 to 3.76 Example 3
Control C copper
copper 4.54
3.14 3.53 to 5.63
2.42 to 3.71 Example 4
Control D nickel
nickel 4.54
2.81 2.77 to 6.09
0.81 to 3.88 Example 5
Control E nickel
nickel 4.24
2.65 2.32 to 5.64
1.21 to 3.80 Example 6
Control F nickel
nickel 4.70
3.38 4.16 to 5.41
2.37 to 3.66

Example 7

Here a procedure was used in which the samples were simply immersed in a Solution of the following composition was rinsed with deionized water.

Volume percentage

Glycol diacetate 41

Acetic acid 40

Ethylene glycol 19

The solution was maintained at about 40 ⁰ C. Μεη achieved an average peel strength of 3.92 kg / cm for plates coated with electroless copper. Identical panels, which, however, were not subjected to the pretreatment according to the invention, showed a peel strength of 1.7 kg / cm.

Example 8

The procedure of Example 7 was repeated, this time using a pretreatment solution of the following Composition was used:

Volume percentage

Glycol diacetate 37

Acetic acid 36

Ethylene glycol 17

Water 10

Compared with the peel strength of 1.7 kg / cm for panels that had not been pretreated, it was mean

Peel strength of 3.6 kg / cm was obtained for electroless copper-plated plates.

Example 9

The procedure of Example 7 was repeated, this time using a pretreatment solution of the following Composition was used:

Volume percent '

Glycol diacetate 13.6

Acetic acid 13.3

Ethylene glycol 6.4

Sodium Acetate 20.0% Ge

weight / volume water rest

The mean peel strength was 3.4 kg / cm with electroless copper plating.

Example 10

Following the procedure of Example 7 Plattet were washed with a 12% ⁰ 40 C warm solution of glycol diacetate in water for 1 minute-treated. The plates were rinsed, electrolessly coated with copper and then electrolytically coated to a thickness of 0.1 mm with shiny ductile copper. Dl

table control plate, which had not been treated with the glycol diacetate solution, rejected a Ab tensile strength of 2.15 kg / ran.

1 sheet of drawings

Claims (3)

r) Although ABS resins, like most plastics, patent claims: are electrically non-conductive, they can be coated with a metal coating by means of an electroless metal coating. 1. Process for the pretreatment of acrylonitrile can be seen. This is usually carried out in the manner of butadiene-styrene resins for electroless metal ₅ , that the surface of the plastic is coated by etching the surface of the resin to improve the adhesion of the metal applied prior to the electroless metal coating with a strong oxidizing acid by tallschicht first with a solvent for the application of coating on the germination art resin, and then surface with a strongly oxydieren- fabric by this one with a Edelmetallden acid into contact gebrachtwird.dadu rc h _lo salt solution, for example, Palladium chloride solution, characterized in that the resin brings before contact and the application of the strongly oxidizing acid with a plastic surface provided with the coating nuclei in an autocatalysis solution of glycol diacetate in an opposite table solution for electroless metal coating of a resin essentially inert medium for a resin dives, with a first ex erzug is formed of a metal, for the devitrification and the satin finish Harzober- i ₅ such as copper or nickel, surface by chemical deposition sufficient period ia touch overall. The metal pool obtained in this way is. coating acts like a carrier that supports the subsequent 2. The method according to claim 1, characterized by applying a thicker metal coating shows that this enables electrolytic deposition to remain on the resin surface. bene glycol diacetate before treatment with the ao The disadvantage of the previously known electroless strongly oxidizing acid is hydrolyzed. Coating method is that the adhesive strength 3. The method according to claim 1, characterized in the electrolessly applied metal coating on the draws that as an inert medium, an aqueous ABS resin substrate is relatively small and only Medium is used. in the order of 0.9 to 2.1 kg / cm, loading