CA1212660A - Powder for use in dry activation for electroless metallizing - Google Patents

Abstract

ABSTRACT

A catalytically active powder, its preparation, and a method for using the said powder for making insulating substrates activated to receive electrolessly deposited metal in a coherent metal layer are described. It is a plastic powder containing chemical compounds allowing that the acceleration of the catalyst is not carried out until the powder is melted down onto the substrate. The substrate need not be etched prior to the metallizing since the plastic melted down ensures a good adhesion between metal and plastics and between plastics and substrate. Furthermore, the colloidal nature of the catalyzing compounds has in a particular and especially durable manner been stabilized by the plastic powder. The use of the powder causes less risk to the environment since the catalyst may be transported as a dry powder, and since the etching of the substrate is avoided.

Description

The invention relates to a catalytically active powder, its prepara~ion, and a ~ekhod using khe said powder ~o ma~e insula~ing substrates ac~ivating ~or receiving electrolessly depas~ed metal in a coherent ~etal layer.

Catalytically active powders directly suitable for activating electroless ~etallizing have not been ~nown previously.

In deposition of metal on insulating substrates such as for instance plastics, the following steps may be employed: evaporation of metal under Yacuum~ application of conductive paints followed by electrGlytic metal deposition, and elec~roless metalli~ing, the latt,er in addition possibly being followed by electrolytic me~al 1 izi ng .

Electroless metallizing has gained widespread use within electrotech~ics as well as for metallizing finished plastics.
A disadvantage of the kno~ ~ethods for elec~roless metalli~ing is th_ series of wet process steps used within the commercial utilization in order to achieve a sufficient adhesion of the metal layer to the surface of the substrate. The process steps are ~requently carried out in the following sequence:
etching, r,eutralizing, sensitization9 activation~ acceleration, and electroless metal deposition. In a great number of processes, sensitization and activat,on consti~ute one process step, since the purpose thereof is to situate the ca~alyzing see~s on the surface of the substrate~ the said seeds catalyzing , , ~ .
, ,~",~

2 -the metal deposition from the bath in a metallizing bath.
Such a catalyst sensitizes and activates an insulating surface for electroless metallizing in one step and consists for instance of a mixture of SnC12 and PdC12, the so-called palladium-tin system. This system usually includes an aqueous solutionof a colloidal nature, since it is important to s~abil ke the system, as precipitation reactions otherwise occur involving aging and destruction of the catalyzing effect.

The patent literature refers to both organic and aqueous solutions9 which by influencing an insulating substrate may make the substrate receptive to electroless metal deposition.
Danish printed accepted specification No. 1329801 describes how a compound of an element from group 8 or lB of the periodic system or mixtures thereof in an organic solvent, which in addition may contain an adhesive, may wet a substrate and make it catalytically active. 6erman Offenlegungsschrift ~lo. 26 36 457 also s~ates an aqueous ca~aly~ic laquer for the production of printed circuits and comprislng a binder, a metal compound, a complex builder, ~nd 3 reducing agent.
Upon application and drying, the said ~etal compound is present as metal seeds which may be additionally reinforced through electroless m~tallizing. Aqueous solutions have previously been encumbered with the draw-back that hydrophobic plastics substrates can only be wetted with difficulty. This feature was especially recognized by the so-called ~wo-step process with separate sensi~i2ation and acti~a~ion steps, cf~ e.g.

., ~ , US patent No. 4,042,730, or more de-tailed Metallic Coating of Plas~tics by William Golde, Vol. I, especially Chapter V.
Danish paten-t applicatlons Nos. 1507/79, 4277/80, and 3300/81, published respec-tively October 11, 19~0, April 10, 1982 and January 24, 19~3; s-tate a method and powders for a dry sensitization of the surface of an insu:l.atiny substrate possessing several advantages compared with khe state of the art, inter alia concerning the distribution of the adhesion of the me-tal and concerning reduced expenses for the metal deposition. It should in this connection be stated that sensitization means one process step applying a chemical compound to the surface of a substrate. This chemical compound adheres an activator/catalyst to the substrate through a galvanic process by contact with an aqueous solu-. tion containing the said activator/catalyst.

Another manner of making substrates catalytic for electroless metal deposition includes adhering solid par-ticles to the surface of the substrate, the solid particles being catalytical towards electroless metal deposition.
Most suitable are the systems including particles of a colloidal nature, and systems are known including precious metals, as well as other systems having an effect with non-precious metals. The aqueous SnC12/PdC12 catalyst is the most frequently used, since reasonable stability of the aqueous solu-tion is obtainable. ~S patent No. 3,011,920 describes a process for preparing such a colloidal catalyst, which before use is accelerated by the addition of acid or base. Solid catalyst mixtures - used for the preparation of an optically transparent liquid - have been .2 ~ 3 described in US patent No. 3~67~,923~ Such systems are genera11y encumber.d with the problem of a lacking lony-term stability7 and the literature within the field describas aging effects and the importance of the use of an acce1erator solu~ion.
Within electroless metallizing, an accelerator sol~tion means a solution of chemica1s with an acid or alkaline reaction, the influence of which on the activated substrate pro~otes the initiation of an electroless metal deposition . In the present connection, the catalyst solution may in addition have an activating effect on the ca~alytic powder ~elted down, which corresponds to the fact that the catalyst solution in the hither~o known commercial utilization is activated before use through addition of a chemical. There is still doubt about!the actual functioning of ~hese systems, and a discussion ~hereof appears inter alia from "An Electron Diffraction Study on Mixed PdC12/SnCl2 Catalysts for Electroless Plating" by T. Osaka e~ al. in Jour. Electrochem. Soc., Nov.
1980, pp. 2443ff, and "A Study on Activation and Acceleration by Mixed PdC12/SnC12 Catalysts for Electroless Metal Deposition"
2~ by R. Zeblenski in the same journalj December 198~, pp. 2652ff.

It has long been desired to obtain an improved stability of the PdC12/SnCl2 catalysts which have gained a widespread use for processes within electrotechnics, cf. inter alia US patents PJos~ 4,18J,198 and 4,21~,7h8. Regarding the effect of these catalysts it is considered probable that the precious metal (e. g. Pd) in the elemental form is s~abilized by tin ; compounds in the solution.

As described in US patent No. 3,993,799 it has turned ou~
that systems including colloidal par~icles of non-precious metals are also cakalytic for electroless metal deposit;on when appropriate baths are employed. It has in connec~ion with such systems been diflicult to obtain high ca~alytic activity simultaneously with good stabillty. US patent No.

3,958,048 describes how the colloidal nature eould disappear in less than 24 hours. US patent No. 4,167,596 describes the use oP hydro-oxides understoo~ as a mixture of oxides and hydroxides of cobalt, nic~el, iron, copper, and mixtures thereof while adding stabili~ers, surfac~ants~ and reactivity-modifying compounds. After immersion of the substrate into s~ch a colloidal system, following rinsing a furkher im~ersion is carried out in a solution with a reducing compound~ Apart from the wetting of the substrate, such a process has ~he drawback that it cannot be carried out-selectively. It has been described in the patent literature how improved adhesion can be obtained, cf~ inter alia US patent NoO 4,233,344, wherein hydrazine hydrate is used as an adhesion-improviny agent. A change of the pH in the colloidal systemg cf. US
patent No. 4,220,678, changes the charge of the colloidal particles, which has an lnfluence on the adhesion of the said particles to the substrate.

It has thus been highly desired to improve the adhesion between ~5 colloidal, catalyzing systems and an insulating substrate and, i~ desired, to position the compounds catalytic for 2~i$~

electroless me-tallizing in a prescribed pattern. In addi~
tion it is of great commercial and practical importance to produce durable chemicals for use in electroless metallizing.

The present invention provides a powder con-taining fine-grained par-ticles of a meltable plastics material, one or more chemical compounds catalytic for electroless metal-liziny, in an arnount of 0.2-20% by weiyht and a surfactant in an amoun-t of 0.1 to 100 mille by weight, both being cal-cula-ted on the plastics material. Upon melting down onto a substrate and acceleration followed by electroless metalliz-ing the powder resul-ts in a metal layer adhering to the plastics powder melted down and having a limit defined by the distri-bution of the plastics powder melted down.

Catalytically active compounds which have proved particularly suitable as ingredients of a powder active for electroless metallizing are compounds of the metals from group 8 of the periodic system, such as iron, cobalt, nickel, ruthenium, rhodium, palladium and iridium. In conjuction with the cataly-tically active compound may be present a tin compound in which the tin is in the 2-~ oxidation state.

Hydroxides of iron, cobalt, nickel, copper and silver are capable of activatiny for electroless metallizing when unstable metallizing baths may be used.

~, ~-~2~ q~

A commercial catalyst of the PdC12/SnC12 type may be used as an ingredient in a powder according to khe invPn~ion.

The active chemical compounds for electroless metallizing may be dispersed as colloidal particles in the plastics 5 material, being a styrene/acryl-copolymer resin.

A mixture of glycerolmonostearate and glyceroldisteara-te (3% by weight of the plastics) constitutes a surfactant which as an ingredient in the powder melted down ensures a good contact wi~h the metallizing bath, whereby a coherent me~al layer is obtained.

A Fine-grained magnetic material may be incorporated into the powder in such a manner that the powder may be transferred magnetcstatically or charged electrostatically in a controlled manner by means of a magnetic brush arrangement.

1~ Preparation of the powder is preferably carried out by mixing the plastics material in finely divided form or prepared through emulsion polymerisation in aqueous medium with an aqueous solution or dispersi~n of 0.1 - lOO~o by weight of sur~actant9 calculated on the amount of plastic material, whereafter the ca~alyzing compound or compounds are added in an amount of 0.2 - lQ% by w~ight, calculated on the amount of plastics material, and drying the completed mixture upon adjustment of the des~red acidity. This method ensures d homogeneous distribution of the catalytically active compoundls) on each ~owder particle.

The plastics suspension may be spray driedp whereby a powder having a uniform particle size is obtained.

Prior to the drying of the plastics suspension, a reducing compound or compounds may be added9 the reaction o~ the reducing compound(s) with the catalytica11y active compound(s) improving the deposition of metal.
.

Preferably, the powder melted down onto a substra~e is treated in a salt-acid or alkaline medium with the purpose o~ improving the deposition of metal and obtaining an improved adhesion of the metal to the plastics po~der melted down.

The powder is applied to entire surface of the insulating substrate or that part of the surfacP which is desired to be metalli~ed, electroless metalli~ing is carried out ~fter melting down and acceleration.

The powder may be electrostatically transfered to a substrate.

Alternatively, magne~ic compounds incorporated may ensure magnetostatic transfer under the influence o~ magnetic poles provided on the substrate in a~vance.

2~
g The powder staked according to the invention, where a plastics powder contains the well-known PdCl2/SnCl2 catalysts or other precious metal catalysts of colloidal nature or hydro-oxides of non-previous metals, as well as surfactants, is characteri~.ed in that after melting down the powder onto a substrate and suitable acceleration, metallizing with a good adhesion and a sharp metallizing limit (boundary or edge) ar~ achieYable.
Such a powder provides an essential improvement compared to the prior art. Thus the durability of the catalyzing compounds has been considerably increased, not the least due to the acceleration not being carried out until the powder has been melted down onto the substrate, and not as by the conventional wet process where acceleration of ~he catalyst is carried out prior to immersion of the substrate. It has not previously been recognized that by using catalysts in the form of catalyzins plastics powder~ whether the powder oontains precious metal systems or non-precious meeal compounds, considerable advantages can be obtained. For instan~e, there is no need ~or etching of ~he substrate in order to form ?O cavities in which the catalyzing compound may be sucked up so as to ensure a good adhesion. Furthermore, the colloidal nature of the cataly~ing compounds of a powder ascording to the invention has been stabilized in a particular ~anner by the fine-gra~ned plastics powder usedO

L2~

The cataly~ic compounds in a powder according to the invention may include any des,red compound of the metals ~om group 8 of the periodic syste~, particularly iron, cobalt7 nickel, ruthenium, rhodium, palladium, iridium in addition to a tin 5 compound, the tin to as large an extent as possible being present in the oxidation step 2+, or another reducing compound of inorganic or organic nature. In addition, the catalytically ac~ive compound may be from group lB of t'ne periodic system, iOe. copper, silver, gold.

When the catalyzing compounds are complex compounds, i~ may be necessary to use an accelerator) which may be acid or alkaline, for the metallizing process. When commercial catalysts of ttle PdC12/SnC12 type are used, an aquevus salt acid solution (conc. HCl to H20 e.g. 1:2) is a suitable accelerator. In this manner the stabilizing alkaline halides are remo~ed from the cataly~ing powder melted down, wh~reby a more water permeable surface is achieved in addition. In the following metallizirg process, this increased surface porosity causes an extremely good adhesion of metal to melted down plastics powder.

For the preparation of a powder according to the invention including an Sn-Pd catalyst it may under certain circumstances be undesired that alkaline halides are used to for~ a complex compound with PdCl2, since this can result in a very fatty powder. However, US patent No. 4,2129768 states ~hat other halides are applica~le, e.g. CaC12~6H20 and LaC13. 7H20.
It has been found particularly advantageous for a powder according to the invention to utllize a double salt of CaC12.
6H20 and PdC12, since a very electros~atic powder is ~hereby ob~ained. Another manner of avoiding unfortunate properties by a powder including a conventional Sn-Pd catalyst, such as e.g. 9F from Shipley Corp.~ is to use a plastics emulsion instead of a jet-ground powder. In this manner khe concentration of the dDuble salt is reduced~ ~he dou~le salt con~aining the catalytically active meta7.

In the fleld of conventional elec'croless metallizin~, surfactants have usually been added to the baths used. It was not previously reco~nized that an improved effect was obtainable by means of a powder capable of activating the surface of a substrate lS for electroless metallizin~ and including a sur~actank.
The hydro~ho~ic part of this surFactant adheres to the hydrophobic plastics material, being the most essential ingredient of the powder, while the hydrophilic properties ensure a good contact bet~en the powder melted down and an aqueous medium.

Especially regarding commercial catalysts of the PdC12/SnC12 type the great advantage is obtained in conneckion with the invention in that the said catalyst is not actiYated for electroless metal deposition until the powder according to the invention has been melted down, the substrate with the powder melted down being immersed into an acid or alkaline medium. As a result, both the powder and a plastics film formed of said powder demonstrate a durability not preYiously known.

A method for the preparation of a powder according to the invention includes the steps of the plastics material in the fine-grained form or prepared by emulsion polymerisation in aqueous mediuln being mixed with an aqueous dispersion of a surfactant, whereafter the ca~alyzing compounds are added and dried upon adjustment of the desired acidity, e-97 10 spray dried. The method is thus carried out in an a~ueous medium, and colloidal particles present ther2in or precursors for such particles, inter alia as a consequence of the influence of the surfactant, adhere strongly to each plastics particle, acting as stabilizer as well as a cement during the melting down of the dry powder, the said cement binding the compounds activating/catalyzing for the electroless metallizing to the surface of the substrate. The aqueous medium furthermore has the advantage that par~ly hydrol~ysed and oxide-containing compounds are present, which can be ~elted down through for instance the spray drying process in the sur~ace of ~he powder particles and thereby improve the wetting of the melted down powder.

The preparation of a powder according to the invention including non-precious catalyst compounds may be carried out on the basis of commercially available solutions with stabilizers present therein and which ~ay be acceleraked in a suitable manner, or the colloidal particles may be precipitated prior to the drying process through the adrJition of reducing surf~c~-ac~ive and precipitating reagents. In the subsequ~nt drying 5 process, the colloidal nature is in a particular manner stabilized on the surface of each powder gain as islands of catalytically active compounds.

A powder according to the invention m~y be applied to an insulating substrate through sprînkling, electrostatic or 10 magnetostatic transfer directly to the substrate or via a light-sensitive master, cf~ the prior art. The powder is then melted d~wn in order to ob~ain a suitable adhesion to the substrate. If the catalyzing co~pounds are so stable that they cannot directly initia~e electroless metallizing, accel~ration can be carried out. Such acceleration may include the steps of the powder melted down on the substrate being subjec~ed ~o ~he influence of an acid or alkaline mediuln.
As a result the catalyzing compounds are made active for electroless metallizing. In addition, a more porous structure is obtained, which improves additionally the adhesion of the electrolessly deposited metal. In a la~er galvanic prooess it is possible to increase the thickness of the metal layer.

6~

With;n the neighbouring field, photocopying, magnetic one-component toners have gained inoreasing use. For use ln equipment using this principle, it is possible to prepare a powder which includes a magnetic material in each powder S particle, e.g. oxides of iron, the partlcle size of which is usually less ~han 2.5 ~m. In addi~ion it is possible to precipitate a thin layer of pallad1um on these grains of magnetic material, e.g. by reducing a palladium salt dissolved in a slurry of the said grains on~o their surface, e.g. by addition of formaldehyde. Whether these grains of magnetic material have a thin layer of palladium on the surface or no~. or are commercial powders such as for instance Bayferrox Gl fr~em~rk~ ~ f (Bayer Che~ie3, a powder according to the inventinn can be prepared which in each powder grain includes grains of magnetic ~aterial. I~ is most advantageous ~ha~ these are slurried in a plastics emulsion, to which one or more of the catalytically active compounds as well as a sur~actant are added, the surfactant i~proving the hydrophilic properties of the powder prepared when the powder is melted down onto an insulating subs~rate.

The invention thus provides a catalytically ac~ive powder which can be used directly to initiate electroless metallizing~
and which possesses a novel capacity of achie~ing good adhesion ~o the substrate as well as pore~free merging. The stability of the powder prepared has proved to be surprisingly good, and i~ is of great environmental importance ~hat transport of a catalyst for electroless metallizing by using the powder according -to the invention may be carried ou-t as transpor-t of a stable powder instead of being transpor-t of liquids detrimen-tal to environmen-t.

For further explanation of -the powder according -to the invention, its prepara-tion and use, the following Examples are given.

Example 1 __ _ A powder including the following ingredients:
Styrene plastics (Piccolastic D 125, a trademark of Hercules Corp.) 100 g PdC12 0.1 y SnC12.2H2O (all Sn-compounds have been converted into equivalent SnC12.2H2O) 5 g Surfac-tan-t (Span 60, a trademark of ICI-Atlas) 0.4 g Example 2 A powder as stated in Example 1 was prepared by 100 g of plastics material (Piccolastic D 125, a trademark) upon crushing being ground on a Trost jet mill. The finely ground powder was slurried in an aqueous dispersion contain-ing the surfactant in an amount corresponding to 4% by weigh-t of the plastics material. 5 g of SnC12.2H2~ were weighed ou-t and heated to 95C, whereafter 0.1 g of PdC12 was added. Upon cooling, this mixture was crushed and dissolved in water, whereafter this solution was added to the plastics suspension. Upon adjustment of the pH to 8 by means of ammonia water, the plastics suspension was dried on a spray drier (supplied under the trademark NIRO Atomizer model Minor) with a rate of rotation of the atomizer wheel of 35,000 rev/min. and with a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output temperature were 180C and 80C, respectively.

~L2~ 2~

_ample _ A powder including the Eollowing ingredients:
Piccotoner 1200 (a trademark of He:~cules Inc.) 100 y Ca-talyst 9F (Shipley Inc.) 5 g Atmer 122 (a trademark oE ICI-Atlas) 0.3 g Example a, A powder as s-tated in Example 3 was prepared by 100 g of Yiccotoner 1220 (a trademark) upon crushing being added to an aqueous dispersion containing 0.3 g oE Atmer 122 (a trademark) which is a surfactant, in 1 litre of liquid.
An amount corresponding to 5 g of solid matter of Catalyst 9F, which is a commercial catalyst of the PdC12SnC12 type produced by Shipley Inc., was diluted to a volume of 1 litre and pH was adjusted by means of a 6 NaOH solution to about pH ~. Under heavy stirring the diluted catalyst solution was added to the plastics suspension. By 6N NaOH pH was adjusted to 7, and the mixture was dried on a spray drier (NIRO (a trademark) Atomizer model Minor) with a rate of rotation of -the atomizer wheel of 35,000 rev/min and a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output tempera-ture were 180C and 80C, respectively.

6~i 13 Example 5 The use of powder as sta-ted in Example 3 i5 per-formed by applying it to an insula-ting substrate comple-tely or partly, -the powder being sprinkled through a serioyra-phic mask, transferred electropho:rographically or in ano-ther manner, whereafter it i9 melted down at a temperature of 140C. The subs-trate with the powder melted down is immer-sed :into a solution of concentrated hydrochloric acid and water in the ratio 1:3 for a period of 8 minutes. Subse-quen-tly, i-t is treated in an accelerator solution (supplied uncler the trademark Shipley l9H) for 3 minu-tes in order upon rinsing to be metallized in a Shipley 328 (a trademark) electroless copper bath at room temperature.

Example 6 A powder including the ingredients:
Org-D-21 (a trademark of Hercules Inc.)100 g AgNO3 7.5 g Atmer 114 (Surfactant, a trademark of ICI-Atlas) 0.3 g Example 7 A powder including the ingredients:
Org-D-21 (a trademark of Hercules Inc.)100 g C C 2 2 8.0 g Atmer 114 (surfactantr a trademark of ICI-Atlas) 0.3 g Example 8 A powder as stated in Example 6 was prepared by 100 g of plastic material upon crushing being ground on a Trost je-t mill. The finely ground powder was slurried in an a~ueous dispersion containing the surfactant (supplied under the trademark Atmer 114) in an amount corresponding to 3% by weight of the plastics material. An aqueous solution of the metal salt was added in the desired amount, whereaf-ter pH
was adjusted to 8 by 6N NaOH. Subsequently, the plastics suspension was dried on a spray drier (supplied under the ~,,,C

trademark NI~O Atomizer model Minor) with a rate of rotation oE the atomizer wheel of 35,000 ~ev/min and a feediny velo-city and supply of ho-t air adapted in such a manner tha-t~the input temperature and the output temperature werc 170~C an~
70C, respectively.

_ample 9 Analogous wi-th Example 8, a powder as sta-ted in Example 7 was prepared.

Example 10 A powder of a plastics material containing hydr-oxides of a metal present in one or more oxidation steps was prepared by 100 g of plastic material (supplied under the trademark Piccotoner 1200) being slurried in a dispersion of a surfactant (Atmer 122, a trademark of ICI-Atlas), the amount of which corresponded to 3~ by weight of the plastics powder. An aqueous solution was admixed which contained 8 g of CuC12, and during heavy stirring an aqueous solution af 2 g of ICBH4 was addi-tionally added, whereafter a 6N NaOH
solution was added until a pH of about 9 was reached. The resulting plastics suspension was dried on a spray drier (supplied under the trademark NIRO Atomizer model Minor) with a rate of rotation of the atomizer wheel of 35,000 rev/min and a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output temperature were 200C and 80C~ respectively.

.,, ,. . ~
,' :\

Example 11 An aqueous plastics emulsion (Dresinol, a trade-mark of Hercules Inc.~ corresponding to 100 g oE solid ma-t--ter was added to an aqueous dispersion of 0~3 y of sur~ac-tan-t (Span 60, a trademark of ICI~Atlas). ~uring heavy stirriny 30 g of Fe3O~ of a particle size of less than 0.5 ~rn were added -to the above. Fur-thermore, an aqueous solu-tion of Ca-talyst 9F (Shipley Inc.) was added in an amount corresponding to ~ of solid matterl and -the pH was adjusted to 8 by 6N NaOH, whereaf-ter spray drying was carried out on a ~IRO (a -trademark) Atomizer model Minor with a rate of rotation of the atomizer wheel of 35,000 rev/min and a feeding velocity and supply of hot air adapted in such a manner that the input tempeature and the output temperature were 160C and 65C9 respectively.

Example 12 A powder including the following ingredients:
Piccotoner 1200 (a trademark of Hercules Inc.) 100 g PdC12 0.4 g 2.6H2O 2.8 g 2. H2O 2.8 g Atmer 121 (a trademark of ICI-Atlas)0.3 g . . , ~ .
~ .:

Example 13 A method for -the preparation of a powder as stated in Example 12 included the following s-teps: 0.~ g oE PdClz were dissolved in 2.~ g of CaC12.6H~O which were kep-t melted at 95 C. After 15 minutes 2.8 g of SnC12~2H2O were added.
This solu-tion was now added -to a plastics suspension, where 100 g o~ Piccotoner 1200 ~a trademark) which in advance had been jet-ground, were slurried into 500 ml of distilled water, wherein 300 mg of surfactant Atmer 121 (a trademark of ICI-Atlas) were dispersed. The alkalinity was adjusted to pH 8 by 6N NaOH, and a NIRO (a trademark) Atomizer model Minor was used for the spray drying. The atomizer wheel was adjusted -to 35,000 rev/min, and the feeding velocity and supply of hot air were adjus-ted in such a manner that the input temperature and the output temperature were 180C and 80C, respectively.

2 ~ %~

Example 14 A powder as prepared by the mekhod described in Examp1e 11 was transferred in a device for photocopying, whereby po~ders containing magnetic matter are electrDstatically transferred to a light~sensitlve master, the masker optionally being a polyester film coated with a light-sensitive material.
A picture obtained electrostatically by illuminat10n on the light-sensitive surface charged to a positiYe high voltage of 2.8 ~V was produced by the said powder by means of a conventiona7 magn2t brush arrangement kep~ at ground potential. Transfer of ~he result~ng electrostatic picture to an insulating substrat2 was sarried out by charging the substrate.

A powder as prepared by the method described in Example 11 15 was used for developing a magnetically structured CrO2-coated polyester film, on which a magnetostatic picture was produced by illumination with a Xenon ~ ash la~p. During ~his procedure, the ~rO~-coated ~agneti~ed film was illuminated throush a photographic ~ilm where the light penetrated the bright areas 20 of the ~ilm and heated khe magnetize~tilm to ~ore than its ,' Curie point. The developing was carried out by a "powder `, cloud" technique (powder cloud in flow of air). The powder grains adhering to the magnetized film were subsequently transferred to an insulating ~ubstrate by the said subs~rate being brought to a positive potential of about 20 kY.

~2~2 Exam~le 16 Powders as s~ated in Examples 1, 3, 6, 7, and 11 were in turn transFerred electrostatically as fnllows. The powder was charged electrostatically to a voltage o~ 2u2 kV in a conventional device for electrostatic powder transfer. By means of a ~low of air the powder was transferred to a substrate whereaft~r it was melted down by heating to the melting temperature.

~e~
A powder with a composition as stated in Example 12 and prepared as stated in Example 13 was mixed in the weight ratio 2 to 100 with iron powder of a particle size of 50 to 100 ym (a conventional carrier for use in magne~ brushes). ~y such a developing mixture in a conventional magnet brush arrangement, latent electrostatic pictures were developed on a photo-sensitiYe master, which through conventional corona discharge had been charged to a negative high voltage of 3.2 kY and subsequently illumina~ed selectively by means of a patternD Transfer from the said photo-sensitiYe master was carried out by charging an insulating substrate so that the partioles werQ transferred 20 by attraction. In a conventional manner the particles were fixed to the insulating substrate and electroless ~etallizing was carried out~

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A powder for use in dry activation for elec-troless metallizing, containing fine-grained particles of a meltable plastics material, one or more chemical compounds catalytic for electroless metallizing, in an amount of 0.2 to 20 per cent by weight of the plastics material, and a surfactant in an amount of 0.1 to 100 per mille by weight of the plastics material.

2. A powder as claimed in claim 1, the one or more catalytically active compounds being selected from com-pounds of the metals from group 8 of the periodic system.

3. A powder as claimed in claim 1, the one or more catalytically active compounds being selected from com-pounds of iron, cobalt, nickel, copper, and silver, the said compounds being present as hydro-oxides, understood as mix-tures of hydroxides and oxides.

4. A powder as claimed in claim 1, in which a commercial one-component catalyst of the PdCl2/SnCl2 type is used as a catalyzing compound.

5. A powder as claimed in claim 1, the plastics material being a styrene/acryl-copolymer resin, and the catalyzing compound or compounds being colloidal particles dispersed in the plastics material.

6. A powder as claimed in claim 1, the surfactant consisting of a mixture of glycerolmonostearate and glyceroldistearate, the said mixture constituting 3% by weight of the plastics material.

7. A powder as claimed in claim 1, additionally containing fine-grained magnetic material.

8. A method of preparing a powder according to claim 1, in which a meltable plastics material in finely divided form or prepared by emulsion polymerisation in an aqueous medium is mixed with an aqueous solution or dispersion of a surfactant in an amount of 0.1 to 100 per mille by weight of the plastics material, one or more chemical compounds catalytic fior electroless metallizing are then added in an amount of 0.2 to 20 per cent by weight of the plastics material, and the resulting mixture is dried when it has a predetermined acidity.

9. A method as claimed in claim 8, in which the mixture is dried by spray drying.

10. A method as claimed in claim 8, in which a reducing agent is added to the catalyzing compound or compounds before the drying.

11. A method of using a powder as claimed in claim 1, in which the powder is melted down onto a substrate and the melted down powder is accelerated by immersion in an acid or alkaline medium.

12. A method as claimed in claim 11, in which the entire surface of the substrate or the part which is desired to be metallized is provided with the powder, which upon melting down and acceleration is metallized by subsequent electroless metallizing.

13. A method as claimed in claim 12, in which the powder is electrostatically transferred to a substrate.

14. A method as claimed in claim 12, in which the powder contains fine-grained magnetic material and the powder is applied magnetostatically under the influence of magnetic poles provided on the substrate in advance.