US3394023A - Process for converting water-repellent surfaces of plastic into water-attractive surfaces - Google Patents

Description

United States Patent ABSTRACT OF THE DISCLOSURE This application relates to an electroless deposition, particularly one having magnetic properties, on a medium, and particularly a medium such as polyethylene terephthalate. The invention also relates to a method of preparing the medium such as polyethylene terephthalate for the deposition of the magnetic material and for thereafter depositing the magnetic material on such medium.

This is a continuation-in-part of application Ser. No. 414,399 (now abandoned), filled Nov. 27, 1964, which in turn was a contiuuation-in-part of application Ser. No. 212,442 (now abandoned), filed July 25, 1962, by George Wilhelm for a Process for Converting Water Repellent Surfaces of Plastic into Water Attractive Surfaces.

This invention primarily relates to converting waterrepellent surfaces of plastic material to water-attractive surfaces. In particular, this invention concerns converting water-repellent surfaces of plastic materials into waterattractive surfaces upon which magnetic memory materials may be deposited with superior results by elec troless or other methods of deposition;

Hitherto, previous methods of treating plastic materials for use as a base for magnetic memory materials have had disadvantages of high costs and poor results. In particular, such methods result in damage to the plastic materials and also result-in a relatively low signalto-noise ratio of the magnetic materials deposited on such abase.

It is, therefore, an object of my invention to provide an improved process for converting Water-repellent surfaces into water-attractive surfaces without damage to the plastic materials. 3

"Another object of my invention is to provide such a process which is relatively inexpensive and uses readily avialable material. t

A further object of my invention is to provide such a process which is substantially more effective than hitherto known methods for converting plastic materials to receive deposits of magnetic memory. materials.

A still further object of my invention is to provide a favorable increase of the signal-to-noise ratio of magnetic memory materials deposited on plastic film treated by my new process, particularly if the magnetic domains are oriented during deposition in a strong magnetic field and better wear characteristics.

Other objects and advantages of this invention will become more readily apparent with reference to the following discussion.

The following is an embodiment of my invention as performed on plastic film consisting of a polymer which is the reaction product of terephthalic acid and polyhydric alcohols. This plastic film is marketed under the trademark Mylar, and constitutes polyethylene terephthalate and is provided in the form of a roll of film in different thicknesses upon which magnetic memory materials may be deposited by electroless or other methods.

ICE

This plastic film is water repellent and is converted to a water-attractive film by my new process which uses the action of a phenol in an alkaline medium, preferably strongly alkaline. Any phenolic compound which is water soluble may be used..The desired alkalinity may be produced with any of the water-soluble hydroxides or carbonates of alkali or alkaline earth metals, or mixtures of them. i

I have found that such action of a phenol is an alkaline medium is enhanced by the addition of a water-soluble sulfonic or a water-soluble sulfinic acid. Also, any watersoluble salt of a sulfonic or sulfinic acid may be used such as, for example, formaldehyde-sulfoxylate sodium. A suitable range of concentration of each of these rea gents consists of from 0.1 to 1.0 mole per liter of each of the phenolic compound, sulfonic or sulfinic acid, or water-soluble saltof either, and the water-soluble hydroxide or carbonate, or both, as the case may be.

Example 1 To carry out a preferred embodiment of my process, 24 grams of phenol is dissolved in milliliters of a 40% by weight sodium hydroxide solution. This mixture is heated to a temperature ranging from 70 to 95 C., and then 20 grams of formaldehyde-sulfoxylate sodium is added. The resulting mixture is kept at a temperature from to 100 C. for from 5 to 30 minutes with stirring, after which time a white slurry is formed in a viscous solution. Upon cooling to 20 C., the slurry solidifies into a hard mass with long crystals.

In the preparation of the plastic film, the slurry formed as described above is heated to a temperature from 60 to 100 C. and a section of the plastic film is immersed for a period of time from 5 seconds to 5 minutes depending upon and varying inversely with the temperature in the slurry, and is then removed. I have found that 30 seconds time is preferable at C. The plastic film is then washed at least one minute with continuously runing water at the rate of one gallon per minute to remove any traces of the slurry remaining thereon. At this point, the plastic film which was water repellent is now water attractive and holds water on its surfaces. Further, the plastic film has not been damaged and after magnetic memory materials are subsequently deposited on it, a higher signal-to-noise ratio will be produced as a result of treatment of the film by my process.

I have found that a further step of treating the now water-attractive plastic film with a water solution of nitric acid will improve the adhesion of magnetic memory materials to the plastic film when deposited thereon by electroless or other methods of deposition. I have found that a Water solution of 70% nitric acid at room temperature such as 20 C. for 10 seconds to one minute of contact time with the film is adequate, as well as a water solution of 50% nitric acid in contact with the water-attractive film for 5 minutes at room temperature.

Further preparation of the now water-attractive plastic film before depositing magnetic memory materials is conventional and involves immersing the plastic film for 60 seconds in a reduction bath consisting of grams of stannous chloride, a liter of distilled water and 200 milliliters of 38% hydrochloric acid. Next, the plastic film is carefully washed with water to remove all traces of the reduction bath. The resulting plastic film is then immersed for one minute in an activating solution maintained at 60 C. The activating solution is made up of Water and palladium chloride with a concentration of 0.05 gram of palladium chloride per liter of distilled water adjusted to a pH of 3 with hydrochloric acid.

The plastic film is now ready to be plated by electroless or other methods with various materials suitable for use as magnetic memory materials.

When magnetic memory materials are deposited on plastic-film which has been treated by my new process, such materials will have a significantly higher signal-tonoise ratio than when they are plated on plastic film not so treated, and this higher signal-to-noise ratio is due solely to the treatment of the plastic film by my new process when orientation is used. The superior characteristics of the final product are also, to some extent, attributable to the absence of damage to the plastic film when treated with my new process.

The following are examples illustrating the electroless plating of various magnetic memory materials on plastic film treated by my new process.

Example 2a An electroless plating solution is prepared by dissolving 80 grams of sodium citrate, 40 grams of potassium sodium tartrate, 10 grams of sodium hypophosphite, 60 grams of nickelous sulfate and 30 grams of ferrous sulfate in 700 milliliters of distilled water by stirring and heating. The pH of the solution is adjusted to pH 9 with concentrated ammonia solution. The solution is heated at 90 C. while the treated plastic film is immersed in the solution for one to three minutes and is then removed and washed with water. As a result, the plastic film has become plated with a nickel-iron alloy having an increased signal-to-noise ratio over that obtained with other methods of preparing the plastic film.

Example 2b The same procedure is used as in Example 2a except that the electroless plating solution is made up of 80 grams of sodium citrate, 40 grams of potassium sodium tartrate, 10 grams of sodium hypophosphite, 10 grams of ethylene-diamine-tetra-acetic acid-sodium salt, 60 grams of cobalt sulfate, and 10 grams of ferrous sulfate. After treatment with this electroless plating solution, as described in Example 2a, the plastic film has become plated with a deposit of a cobalt-iron alloy having an increased signal to noise ratio over that obtained with other methods used to prepare plastic films such as Mylar for electroless or other types of plating with magnetic memory materials.

Example 2c The same procedure of Example 2a is used except that the electroless plating solution is made up of 80 grams of sodium citrate, 40 grams of potassium sodium tartrate, 10 grams of urea, 10 grams of sodium hypophosphite, 100 grams of cobalt sulfate and 4 grams of manganous sulfate.

After treatment with this solution as described in Example 2a the plastic film becomes plated with a deposit of a cobalt-manganese alloy having an increased signalto-noise ratio over that obtained with other methods used to prepare plastic films such as Mylar for electroless or other types of plating with magnetic memory materials.

The plastic material such as the poly-terephthalates may also be prepared by a modified method such as discussed below. This modified process actually constitutes the preferred embodiment. As a first step of this modified method, phenol and water are mixed in the ratio of 60 to 70 parts by weight of phenol to 30 to 40 parts by weight of water, which may be tap water. The plastic material such as the polyethylene terephthalate in the form of a thin tape is then disposed in a bath of the phenol solution in water for a suitable period of time such as a period between 5 seconds and one minute and at a suitable temperature such as a temperature between forty degrees centigrade and sixty five degrees centigrade. The amount of time for subjecting the plastic material such as the polyethylene terephthalate tape to the phenol solution is preferably between to 30 seconds.

A wetting agent may also be included in the solution in a suitable amount such as 0.05 to 2 milliliters of the Wetting agent to one gallon of water before the water is mixed with the phenol. A suitable wetting agent may be designated as MonawetMo7OE marketed by Mona Industries of Paterson, N]. This wetting agent may comprise approximately 70% of sodium di-octyl succinate in a solution of approximately 11% ethyl alcohol and approximately 19% water.

The phenol in the water solution tends to etch the surface of the plastic material such as the polyethylene terephthalate tape. The wetting agent in the solution increases the mixing of the phenol with the Water so as to enhance the etching action of the phenol on the surface of the plastic material. If the amount of phenol should be made excessively high in the water solution, the phenol will tend to crystallize. on the surface of the plastic material and produce inordinately great etching action on the tape and provide problems in obtaining a removal of the phenol from the tape in successive steps of the process. Certain solvents such as xylene may also be included in the solution to prevent crystallization of the phenol but these solvents sometimes present a problem of removal in subsequent steps.

The surface of the film is not delustered even after the film has been subjected to the phenol solution described in the previous paragraph. The surface of the film is not delustered since it has a smooth and shiny appearance even after it has been treated with the phenol solution. 'A smooth finish of the film is important since the layer of magnetic material subsequently deposited on the film will not have a uniform separation from a magnetic head at successive positions along the film if the finish of the film is not smooth. This will prevent information from being accurately recorded on the film and subsequently reproduced from the film.

As a next step in the modified process, the excess of phenol on the surface of the plastic material such as the polyethylene terephthalate is removed by a suitable solution. For example, a diluted solution of sodium hydroxide having a concentration in the order of ten percent to thirty percent in water can be used at room temperature to wash the phenol into the solution. Preferably, a twenty percent solution of diluted sodium hydroxide in water is used at room temperature. Actually, any alkali capable of dissolving phenol to produce phenolate can be used since phenolate is water soluble and becomes dissolved into the water solution. Other solvents such as ether and acetone can also be used to wash the phenol from the surface of the plastic material such as the polyethylene terephthalate. When a diluted solution of sodium hydroxide in water is used, the solution can be applied to the surface of the tape for a considerable period of time such as a period between one minute and ten minutes.

The surface of the plastic material such as polyethylene terephthalate is treated with concentrated sodium hydroxide as a next step in the modified process. The concentrated sodium hydroxide may be in a water solution with a. concentration of thirty percent to forty percent of sodium hydroxide in the solution. The surface of the plastic material such as the polyethylene terephthalate is disposed in a solution of the concentrated sodium hydroxide at an elevated temperature such as between sixty degrees and eighty degrees centigrade for a suitable period of time such as between thirty and ninety seconds. Preferably, the surface of the plastic material is subjected to the bath for approximately one minute at a temperature of eighty degrees centigrade. The sodium hydroxide tends to attack the surface of the plastic material such as the polyethylene terephthalate and hydrolyze the terephthalate chain so as to make the surface amenable to receiving the electroless deposition. By subjecting the surface of the plastic material to the previous steps, any tendency of the electroless deposition of magnetic material to flake from the surface of the plastic material is substantially eliminated, especially when the material is subsequently treated with the concentrated solution of sodium hydroxide. It should be appreciated that other materials than the concentrated solution of .sodium hydroxidecan be used to etch the surface of the plastic material such asthe polyethylene terephthalate. For example, other alkalis can also be used. Afterthe surface of the plastic material such as polyethylene terephthalate has been subjected to the concentrated solution of sodium'hydroxide, it is washed in tap water for a suitable period of time such as one minute. In this way, most of the sodium hydroxide remaining on the surface of the plastic material such as the polyethylene terephthalate is removed. The surface of the plastic material such as the polyethylene terephthalate is then ready to be subjected to the various baths for electrolessly depositing the magnetic material on the surface of the plastic material-As described above, the first bath may include stannousrchloride to obtain a reduced condition on the surface of the plastic material. Preferably, the surface of the plastic material such as the polyethylene terephthalate is subjected to two baths of stannous ions. The first bath tends toreact with any sodium hydroxide remaining on the surface ofthe plastic material so as to remove this sodium hydroxide from the surface of the plastic material. Because of this, the first bath tends to become somewhat inefrective relatively quickly. The second bath of the stannous ions then actually operates effectively to provide atreduction of the stannous salt on the surface of the plastic material. After the first bath has become somewhat ineifective'relatively because of the reaction of the chemicals in the bath with the sodium hydroxide remaining on the surface of the tape, the second bath may be used as the first bath and a new second bath may be formed. By using two baths of stannous ions, any tendency to create magnetic dropouts (dead spots from a magnetic standpoint) on the surface of the plastic material becomes minimized, especially in a continuous deposition process. After the-surface of the plastic material such as the polyethylene terephthalate has been subjected to a solution of stannous ions, the surface of the plastic material is immersed in a solution of palladium ions as discussed above. This causes'a layer of palladium to be deposited on the surface of the plastic material. The surface of the plastic material such as the polyethylene terephthalate tape is then disposedin a bath for obtaining an electroless deposition of magnetic-materials on the surface of the plastic material. This bath may have the following compositions by way of illustration:

(1) H =500;:B =6000 gauss thickness=20-30ainch 700 milliliters of water 80-:grams of sodium citrate 40 grams of potassium sodium tartrate grams of Versene complexing agent 10 grams of -sodium hypophosphite .100 grams of 'CoSO (cobalt sulfate) 4grams of MnSO (manganese sulfate) 100 milliliters of a 19% solution of ammonia in Water --for 5-5. /zmin. at 80" C. pH maintained at' approx. 10.

(.2) -H 250; B =6000 gauss.

700 milliliters of water 80 grams of sodium critrate 40 grams of potassium sodium tartrate 10 grams of Versene ,10.grams-of sodium hypophosphite 1 00,.grams of CoSO .7H O (cobalt sulfate) 3,4-grams of FeSO (iron sulfate) for 55 /2 min. at 80 C. pH maintained approximately 10.

j .The. hypophosphite salts in the solutions listed above constitute reducing agents to reduce the metallic. salts to metal. The citrate and tartrate salts serve as complexing agents in maintaining in solution the salts of the magnetic materials in the plating bath for reduction by the hypophosphite ion. The citrate. and tartrate salts also serve as buffers. Versene also serves as a complexing agent. The

ammonia serves to maintain the pH of the solution within particular limits such as between eight and ten.

The surface ofv the plastic material is exposed to the electroless baths for suitable-periods of time such as 5 to 5 /2 minutes at an elevatedtemperaturesuch aseighty degrees centigrade. tUnder such conditions, a magnetic layer of material is electrolessly deposited on the surface of the plastic material such as the polyethylene terephthalate tape with a suitable thickness such as. 20 to 30 microinches.

The materials produced by the methods constituting this invention have certain advantages over the prior art. One advantage is that the magnetic depositions electrolessly deposited on the surface of the plastic material such as the polyethylene terephthalate tape are firmly adhered to such surfaces and do not tend to flake from the tape. Furthermore, the resistance of the electroless deposition to Wear tends to be enhanced. For example, more than 100,000 error-free readings-have been obtained from materials which have been produced by the methods constituting this invention; furthermore, signal resolutions and magnetic retentivities considerably greater than materials today on the market have been obtained from materials produced by the methods constituting this invention. Packing densities of the magnetic information recorded on the materials constituting this invention have also considerably exceeded those of any materials now or previously on the market. It can be noted that this modified process renders itself very well for a continuous tape-making process.

It will be appreciated that the methods described above may be used With other plastic materials than polyethylene terephthalate. For example, the modified method described above has been used with some success to deposit magnetic materials by electroless techniques on a polyimide polymer film designated as H Film by DuPont. The modified method has also been used with some success to deposit magnetic materials by electroless techniques on the surface of a polycarbonate polymer film designated as Lexan by General Electric. However, when the polycarbonate film is used as: the plastic material instead of the polyethylene terephthalate, isopropyl alcohol is preferably used instead of sodium hydroxide to remove the phenol residues of the film before the electroless baths are applied.

After the electroless deposition of magnetic material has been formed on the surface of the plastic material such as the polyethylene terephthalate, a suitable materialmay be applied to the electroless deposition to provide a lubricating surface for the electroless deposition and to facilitate resistance to the Wear of the magnetic heads by the magnetic alloy on the plastic material. For example, a polytetrafluoroethylene material having a fluorocarbon telomer dispersion and designated by the trademark Vydax b'y DuPont may be mixed with a partially polymerized butyl titanate designated as Tyzor by DuPont to provide such a lubricating action. The material may be formed by a ratio of approximately one percent of Tyzor to ten to fifteen percent of Vydax diluted with Xylol solvent (a benzene ring compound). The resultant material may be applied to the electroless deposition at room temperature to provide the electroless deposition with a slippery surface. The Tyzor material constitutes an adhesive for the Vydax so as to enhance the adhesion of the Vydax to the magnetic material electrolessly deposited on the tape. The lubricating material is applied in a very thin layer so as to minimize the magnetic gap between the head and the electroless deposition on the surface of the plastic material such as the polyterephthalate.

While I have described preferred embodiments of my invention, it is understood that various improvements may be made in the materials, in other matters, and in their reaction conditions disclosed Without departing from the spirit and scope of my invention as claimed hereinafter.

7 What is claimed is:

1. A process for converting a water-repellent surface of a plastic material from a group consiting of a polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface and then electrolessly depositing a magnetic material on the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the Water-repellent surface of the plastic material with a phenol solution,

washing the phenol from the treated surface of the plastic material, thereafter subjecting the treated surface of the plastic material to a solution of a material for etching the surfaces of the plastic material and making the surfaces of the plastic material Water attractive,

disposing the plastic material in a bath of a stannous salt, thereafter disposing the plastic material in a bath of a palladium salt, and

thereafter disposing the plastic material in a bath including salts of at least one magnetic material from the group consisting of nickel, cobalt, iron and manganese, a complexing agent selected from a group consisting of citrates and tartrates and a hypophosphite to obtain a deposition of the magnetic material on the water-attractive surface of the plastic material. 2. A process according to claim 1 wherein the phenol solution is formed from 60% to 70% by weight of phenol to 30% to 40% by weight of water and is applied for a period between 5 seconds and 1 minute at a temperature between 40 C. and 65 C. and a concentrated solution of sodium hydroxide in the range of 30% to 40% is used as the etchant and is applied for a period of time between 30 and 90 seconds at a temperature between 60 C. and 80 C.

3. In a process for converting a water-repellent surface of a plastic material from a group consisting of polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface, the steps of:

treating the plastic material with water-soluble phenol in a water solution of a substance selected from the group consisting of Water-soluble hydroxides and water-soluble carbonates of alkali and alkaline earth metals and mixtures thereof, and subjecting the resulting plastic material to the action of a Water solution of nitric acid. 4. A process for converting a water-repellent surface of a plastic material from a group consisting of polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the water-repellent surface of the plastic material with a phenol solution to etch the surface,

subjecting the treated surface of the plastic material to a solution having properties of dissolving into the solution any excess of phenol on the surface of the plastic material,

thereafter subjecting the treated surface of the plastic material to a concentrated solution of sodium hydroxide to etch the surface of the plastic material and make the surface water-attractive,

thereafter subjecting the water-attractive surface of the plastic material to at least one bath of a stannous salt,

thereafter subjecting the surface of the plastic material to a bath of a palladium salt, and

thereafter subjecting the surface of the plastic material to a bath which has a hypophosphite salt as a reducing agent, a buffering agent from a group con sisting of citrate and tartrate salts, ammonium hydroxide as alkaline media and salts of magnetic materials from a group consisting of iron, nickel, cobalt and manganese to obtain an electroless deposition of the magnetic materials on the surface of the plastic film. 5. A process for electrolessly depositing magnetic materials on a surface of plastic materials from a group consisting of polyethylene terephthalate, a polyimide and a polycarbonate, the process consisting essentially of the following steps:

applying a phenol solution to the water-repellent surface of the plastic material where the phenol has properties of constituting a solvent for the plastic material,

removing any excess of the phenol from the waterrepellent surface of the plastic material, applying a solution of an alkali to the surface of the plastic material to etch the surface of the plastic material and make the surface water-attractive,

removing any excess of the alkali from the waterattractive surface of the plastic material,

thereafter applying a solution of stannous chloride to the etched surface of the plastic material, thereafter applying a palladium chloride solution to the surface of the plastic material, and

thereafter applying an electroless plating solution including a buffering agent from a group consisting of a tartrate and a citrate, a hypophosphite as a reducing agent, ammonium hydroxide as an alkaline media and salts of a magnetic material from a group consisting of iron, nickel, cobalt and manganese.

6. A process according to claim 5 wherein the phenol solution is formed from 60% to 70% of phenol by weight in 30% to 40% by weight of water and wherein the alkali material constitutes sodium hydroxide having a concentration of 30% to 40% by weight in 60% to 70% by Weight of water.

7. A process for converting a water-repellent surface on a plastic material from a group consisting of polyethylene terephthalate, a polyimide and polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the Water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the water-repellent surface of the plastic material with a phenol solution to convert the waterrepellent surface into a water-attractive surface; thereafter treating the water-attractive surface of the plastic material with a solution having properties of washing into the solution any of the phenol remaining on the water-attractive surface of the plastic material; applying a reducing agent to the water-attractive surface of the plastic material to chemically reduce this surface; and

applying to the water-attractive surface of the plastic material, for a sufiicient period of time to obtain the deposition of the magnetic materials on the waterattractive surface, an electroless bath which has the magnetic material, a reducing agent to reduce the'ions of the magnetic material and a complexing agent to prevent the precipitation of the magnetic material from the bath.

8. A process for converting a water-repellent surface of a plastic material from a group consisting of a polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the water-repellent surface of the plastic material with a phenol solution to make the surface water-attractive;

thereafter treating the plastic material with a substance selected from a group consisting of water-soluble hydroxides of alkali and alkaline earth metals and water-soluble carbonates of alkali and alkaline earth metals to remove from the water-attractive surface 9, of the plastic materialanyphe'nol deposited on this surface; t a

thereafter applying to the surface of the plastic material a solution having properties of making the sur- 7 face of the plastic material water-attractive;

applying to the water-attractive surface of the plastic material a stannous batht'o chemically reducethis surface; i applying to the chemically reduced surface of the plastic material a palladium bath to sensitize this surface; and i applying, for a controlled period of time to obtain the deposition of the magnetic material on the sensitized surface, to the sensitized surface of the plastic material an electroless bath which has the magnetic material, a reducing agent to reduce themagnetic material and a complexing agentjto prevent the precipitation of the magnetic material in the electroless bath. 7 9. The process set forth in claim 8 wherein the magnetic material in the electroless bath is selected from a group consisting of cobalt, nickel, iron and manganese and wherein the reducing, agent in the electroless bath consistitutes a hypophosphite and wherein the complexing agent in the electroless bath is selected from a group consisting of citrates and tartrates and wherein the phenol solution has a concentration of approximately 60% to 70% by weight of phenol and 30% to 40% by Weight of water and the concentrated solution of sodium hydroxide and wherein the solution having the properties of making the surface of the plastic material has a concentration of approximately 30% to 40% by weight of sodium hydroxide and approximately 60% to 70% by weight of water.

10. A process for converting a water-repellent surface of a plastic material from a group consisting of polyethylene terephthalate, a polyirnide and a polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the Water-repellent surface of the plastic material with a phenol solution to etch this surface;

applying to the water-repellent surface of the plastic material a solution having properties of dissolving into the solution any phenol deposited on the surface;

applying to the water-repellent surface of the plastic material a solution having properties of making waterattractive the water-repellent surface of the :plastic material;

applying to the water-attractive surface of the plastic material a bath having properties of sensitizing this surface; and

applying to the sensitized surface of a plastic material an electroless bath which has the magnetic material, a reducing agent to reduce ions of the magnetic materials and a complexing agent to prevent the precipitation of the magnetic material in the electroless bath.

11. The process set forth in claim 10 wherein the bath for making water-attractive the water-repellent surface of the plastic material constitutes a concentrated solution of sodium hydroxide.

12. The process set forth in claim 11 wherein a bath is applied to the water-attractive surface of the plastic material to chemically reduce this surface before the surface is sensitized.

13. A process for converting a water-repellent surface of a plastic material from a group consisting of a polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the water-repellent surface of the plasticmaterial with a phenol solution to etch thissurface; applying to the water-repellent surface of the plastic material a solution having properties of dissolving into the solution any phenol deposited on the solution; applying to the Water-repellentsurface of the-plastic material a concentratedsolution of sodium hydroxide with properties of making water-attractive the waterrepellent surface of the plastic material; applying to the water-attractive surface of the plastic material a palladiumbath for sensitizing this surface; and A applying to the sensitized surface of the plastic mate rial an electroless bath which has the magnetic material, a reducing agent to reduce the magneticmaterial and a complexing agenttoprevent the precipitation of the magnetic material in the electroless bath. t 14. Theprocess set forth in claim'13 wherein the phenol solution constitutes phenol and water in the ratio of 60 to 70 parts by weight of phenol to 30 to 40 parts by weight of water and'wherein a stannous bath-is applied to the water-attractive surface of the plastic material to chemically-reduce this surface before the surface is sensitized by the palladium bath. r

15. The process set forth in claim 14 wherein the magnetic material in the electroless bath is selected from elements in a group consisting of iron, cobalt, nickel and manganese, the reducing agent in the electroless bath constitutes a hypophosphite and the complexing agent in the electroless bath is selected from a group consisting of citrates and tartrates and wherein the phenol solution constitutes phenol and water in the ratio of 60 to 70 parts by Weight of phenol to 30 to 40 parts by weight of Water.

16. The process set forth in claim 15 wherein a stannous bath is applied to the Water-attractive surface of the plastic material to chemically reduce this surface before the surface is sensitized by the palladium bath and wherein the phenol solution is applied to the surface of the plastic material at a temperature between approximately 40 C. and 65 C. for a period of time between approximately 5 seconds and 1 minute and wherein the concentrated solution of sodium hydroxide contains approximately 30% to 40% by weight of sodium hydroxide and the remainder by weight of water.

17. A process for converting a Water-repellent surface of a plastic material from a group consisting of a polyethylene terephthalate, a polyimide and a polycarbonate to a water-attractive surface and applying an electroless deposition of a magnetic material to the water-attractive surface of the plastic material, the process consisting essentially of the following steps:

treating the water-repellent surface of the plastic material with a phenol solution; washing from the water-repellent surface of the plastic material any excess of phenol with a solution having properties of dissolving the phenol into the solution;

thereafter subjecting the treated surface of the plastic material to a concentrated solution of sodium hydroxide to etch the surface of the plastic material and make the surface water-attractive; washing from the water-attractive surface of the plastic material any excess of sodium hydroxide;

subjecting the Water-attractive surface of the plastic material to a solution having properties of chemically reducing the surface;

subjecting the reduced surface of the plastic material to a solution having properties of sensitizing the surface; and

subjecting the sensitized surface of the plastic material,

for a sufficient period of time to obtain a deposition on the sensitized surface of the plastic material, to an electroless bath which has the magnetic material, a reducing agent for obtaining a deposition of the magnetic material on the sensitized surface and a 11 complexing agent for preventing the precipitation of the magnetic material in the electroless bath. 18. The process set forth in claim 17 wherein the phenol solution contains 60% to 70% by weight of phenol and to by weight of water and wherein the solution of sodium hydroxide contains 30% to 40% by weight of sodium hydroxide and the remainder by weight of water.

19. The process set forth in claim 18 wherein the solution having properties of chemically reducing the surface is stannous, the solution having properties of sensitizing the surface primarily contains palladium and the magneticmaterial in the electroless bath is selected from a group consisting of iron, cobalt, nickel and manganese, the reducing agent in the electroless bath is a hypophosphite and the complexingagent in the electroless bath is selected from a group consisting of citrates and tartrates.

20. The processset forth in claim 19 wherein the phenol solution is applied to the surface at a temperature between approximately 40 C. and C. for a period of time between approximately 5 seconds and one minute and the solution of sodium hydroxide is thereafter applied at a temperaturebetween approximately 60 C. and C. for a period of time between approximately 30 seconds and seconds.

References Cited UNITED STATES PATENTS Crehan 117 47 Emerson 1l747 Nelson et al. 117-76 Kelley 117-47 Hookway et al. 117 -47 Chapman 41- 41 Foley 117 47 Koretzky etal. 11,7-47 Wenner v 29- Edwards 26078 Frantzen 156-7 Nadeau et al. 9687 Tsu et al. -Q 11 7 54 Chilton et al. f1 1,747

Bruner 15 6 2 FOREIGN PATENTS I Great Britain. Canada.

WILLIAM MARTIN, Primary Examiner. 25 W. D. HERRICK, Assistant Examiner.