SE189361C1

SE189361C1 -

Info

Publication number: SE189361C1
Authority: SE
Publication date: 1963-01-01

Description

Uppfinnare: F M Kelley Prioritet begard frdn den 18 februari 1957 (USA) Foreliggande uppfinning avser ett f5rfarande for belaggning av fluorerade polymerer med tunna kontinuerliga filmer av metall. Inventor: F M Kelley Priority Applied From February 18, 1957 (USA) The present invention relates to a process for coating fluorinated polymers with thin continuous films of metal.

Polymerer av fluorerad eten, sasom polytelrafluoreten, polyklortrifluoreten och sampolymerisat av tetrafluoreten och fluorerade olefiner, aro i h8g grad anvandbara dielektriska material, som finna stor anvandning inom elektrisk och elektronisk industri. Forutom sina elektriska egenskaper aro de 'fluorerade etenpolymererna ytterst varmestabila och korrosionsbestandiga och Oro salunda speciellt lampliga for elektrisk isolering under ogynnsamma forhallanden. En anima egenskap hos poly-fluoretener, speciellt polytetrafluoreten, är deras ytterst laga adhesion till andra material. Denna egenskap är en olagenhet vid framstallningen av artiklar, som erfordra en shdan metalliserad yta, som anvandes i tryckta kretsar. Vidhaftningsmedel, som anvandas vid bindning av metall vid polyfluoreten, Oro dyra, svara och tidsodande att anbringa och ha i alimanhet icke underlagets utomordentliga egenskaper, vilket shlunda gOr det svart att anvanda polyfluoretenerna med asseende ph de egenskaper, for vilka de arc lampliga. Direkt belaggning av metall pa polytetrafluoreten har hittills gjorts under anvartdning avosintrad, i forvag formad artikel, pa vilken metallen avsattes on sont darefter sintras. Olagenheterna med delta forfarande Ore den formade artikelns svaghet ()eh darav foljande svarighet att anbringa metallen samt sintringssteget, som kan orsaka oxidation av metallen och forvrangning av polymeren, som kontraherar och expanderar under sintringen: och shlunda astadkommer sonderbrytning av den kontinuerliga metallfilmen. Polymers of fluorinated ethylene, such as polytelrafluoroethylene, polychlorotrifluoroethylene and copolymers of tetrafluoroethylene and fluorinated olefins, are highly useful dielectric materials, which are widely used in the electrical and electronic industry. In addition to their electrical properties, the fluorinated ethylene polymers are extremely heat-stable and corrosion-resistant, and are particularly suitable for electrical insulation under adverse conditions. An animating property of polyfluoroethylenes, especially polytetrafluoroethylene, is their extremely low adhesion to other materials. This property is a disadvantage in the manufacture of articles which require such a metallized surface which is used in printed circuits. Adhesives used in bonding metal to polyfluoroethylene are expensive, responsive and time consuming to apply and generally do not have the excellent properties of the substrate, which is why it is difficult to use the polyfluoroethylenes with respect to the properties for which they are suitable. Direct coating of metal on polytetrafluoroethylene has hitherto been done using a sintered, pre-formed article on which the metal was deposited and subsequently sintered. The disadvantages of the delta process are the weakness of the molded article () and the consequent difficulty in applying the metal and the sintering step, which can cause oxidation of the metal and distortion of the polymer, which contracts and expands during sintering: and thus causes the continuous metal film to break.

Enligt foreliggande uppfinning framstalles vidhaftande, kontinuerliga belaggningar av metall pa polyfluoretenytor och anbringas helaggningar ph fardiga artiklar, som lake erfordra ytterligare bearbetning. Upplinningen avser dessutom framstallning av metallbelagda polyfluoretenytor, som leda elektricitet med minimalt motstand. According to the present invention, continuous, continuous coatings of metal are made on polyfluoroethylene surfaces and whole coatings or finished articles are applied which do not require further processing. The invention also relates to the production of metal-coated polyfluoroethylene surfaces, which conduct electricity with minimal resistance.

Enligt f8religgande uppfinning bringas den polyfluoretenyta, som skall belaggas, i liontakt med en losning av en alkalimetall i ett icke-metalliskt losningsmedel, som kan vata polyfluoretenen, varefter metall i finfiirdelad form avsattes ph den yta, som skall belaggas. Det har namligen visat sig, att vidhaftande, kontinuerliga helaggningar av metall kunna erhallas p0. polyfluoretenytor utan anvandming av hindemedel genom behandling av ytan tiled en losning av en alkalimetall, sasom en losning av natrium i flytande ammoniak. Den erhallna ytan Or ytterst vidhaltande for metaller, och metaller, som avsatts pa ytan i kolloidal form, bilda tunna, starkt vidhaftande filmer. I motsats till kolloidal metal], som avsatts pa obehandlade ytor av polyfluoreten, sasom polytetrafluoreten, kan metallfilmen icke avlagsnas frail ytan av hehandlade material med hjalp av vidhaftande tejp, sasom »Scotch cellofantejp. According to the present invention, the polyfluoroethylene surface to be coated is brought into contact with a solution of an alkali metal in a non-metallic solvent which can wipe the polyfluoroethylene, after which metal in finely divided form is deposited on the surface to be coated. Namely, it has been found that adherent, continuous metal alloys can be obtained p0. polyfluoroethylene surfaces without the use of barrier agents by treating the surface with a solution of an alkali metal, such as a solution of sodium in liquid ammonia. The resulting surface is extremely adherent to metals, and metals deposited on the surface in colloidal form form thin, strongly adherent films. Unlike colloidal metal, which is deposited on untreated surfaces of polyfluoroethylene, such as polytetrafluoroethylene, the metal film cannot be deposited from the surface of treated materials with the aid of adhesive tape, such as Scotch cellophane tape.

Den vidhaftande ytan pa polyfluoretener erhalles, sasom ovan namnts, genom behandling av polymerytan med en losning av en i ett icke-metalliskt losningsmedel, som kan vata polyfluoretenen. Den exakta kemiska uppbyggnaden av den erhatlna, morkfargade, vidhaftande ytan liar icke slutgiltigt identifierats, men det har visat sig, att ytan icke innehaller flagon metall och icke leder elektricitet och icke kan avlagsnas ph kemisk rag utan fOrstoring av polymeren. De anvanda losningsmedlen i detta forfarande aro losningsmedel, som vata polymeren och kunna halla alkalimetallen i losning och som icke reagera kemiskt med alkalimetallen for frigaring av vale. DeL lampligaste och mest 2— — lattillgangliga losningsmedlet ãr ammoniak. Det ãr lampligt, emedan det bildar mycket .stabila losningar ax alkalimetallen, vilka snabbt reagera med polymeren„ medan de ge upphov till vidhaftande ytor. Andra lampliga losningsmedel aro lagmolekylara aminer och pyridin. Ax alkalimetallerna foredrages natrium pa grund av dess laga lcostnad och latttillganglighet, men. andra alkalimetaller, sãsom litium, aro, lika anyandbara. Det är des's-LI-tom mOjligt att anvanda losningar av alkaliska jordartsmetaller, sasom kalcium eller magnesium. Reaktion:shenagenheten hos, dylika losningar Sr em-ellertid betydligt lagre. Alkalimetalikoncentrationen i lasningsmedlet ham mindre betydelse. I allmanhet anyandes en 1-procentig losning, e-hurti hogre och lagre koncentrationer reagera lika bra. Den manod lOsnino och den. tid, som erfordras for bildnin,g av den vidhaftande ytan, variera med storleken pa den. yta, som skall belaggas, pa den anvanda losningens koncentration och typen av anyan-d fluoretenpolymer. Optimala forhallanden kunna emellertid latt bestammas genom forsok i liten skala. Vid kontakt med losningen morkriar polyfluoretenytan och antar snabbt en morkbrun farg. Det har visat sig, att en likformig, morkbrun yta gem maximal yidhaftning for metall. Om materialet halles i kontakt med los-nin-gen for lange, erhalles on svart yta, som am mindre vidhaftande. En sadan overbehandlad yta kan emellertid forbattras genom tvattning med ett starkt oxiderande medel, saso:m salpetersyra. I allmanhet erhalles en. starkt vidhaftande yta, om den. yta, som skall beldggas, vates med en 1-procentig losning av natrium i ammoniak under cirka 10-30 sekunder och darefter tyattas fri frdn behandlingslosning. The adhesive surface of polyfluoroethylenes is obtained, as mentioned above, by treating the polymer surface with a solution of one in a non-metallic solvent which can wet the polyfluoroethylene. The exact chemical structure of the heated, dark-colored, adherent surface has not been definitively identified, but it has been found that the surface does not contain flake metal and does not conduct electricity and cannot be deposited chemically without enlarging the polymer. The solvents used in this process are solvents which wet the polymer and can keep the alkali metal in solution and which do not chemically react with the alkali metal to release the whale. The most suitable and most readily available solvent is ammonia. This is convenient because it forms very stable solutions of the alkali metal, which react rapidly with the polymer while giving rise to adhesive surfaces. Other suitable solvents are low molecular weight amines and pyridine. Ax alkali metals prefer sodium due to its low cost and readiness, but. other alkali metals, such as lithium, aro, are equally indestructible. It is possible to use solutions of alkaline earth metals, such as calcium or magnesium. Reaction: the shenagen unit of, such solutions Sr em- however, significantly lower. The alkali metal concentration in the lasing agent is less important to him. In general anyandes a 1% solution, e-hurti higher and lower concentrations respond equally well. It manod lOsnino and it. time required for the formation of the adhering surface varies with its size. surface to be coated, on the concentration of the solution used and the type of anyan-d fluoroethylene polymer. However, optimal conditions can be easily determined by small-scale experiments. Upon contact with the solution, the polyfluoroethylene surface turns brown and quickly assumes a dark brown color. It has been found that a uniform, dark brown surface gives maximum adhesion to metal. If the material is kept in contact with the solution for too long, a black surface is obtained which is less adherent. However, such an untreated surface can be improved by washing with a strong oxidizing agent, such as nitric acid. In general, one is obtained. strongly adhering surface, if. surface to be bleached is soaked with a 1% solution of sodium in ammonia for about 10-30 seconds and then cleared from the treatment solution.

Den. behandlade ytan haftar vid all-a me-taller, som i allmanhet anvandas for belaggningsandamal, oni metallen aysattes: i finfordelad, kolloidal form. Sadana metaller Oro aluminium, koppar, silver, krom, nickel, germanium, tenn och liknande, ledande metaller. Olika teknik kan anvandas fOr avsattning av metallen pa den behandlade ytan :ay polyfluoretenen och innefattar sadan teknik, som metallbelaggning i vakumn eller kemisk reduktion av en metallsaltlosning till metall. The. The treated surface adheres to all metals, which are generally used for coating purposes, on which the metal is applied: in finely divided, colloidal form. Sadana metals Oro aluminum, copper, silver, chromium, nickel, germanium, tin and the like, conductive metals. Various techniques can be used to deposit the metal on the treated surface: on the polyfluoroethylene and include such techniques as metal coating in a vacuum or chemical reduction of a metal salt solution to metal.

Det har -visat sig, att i hog grad vidhaftande kontinuerliga filmer med tjocklekar mellan 0,1 och 0,5 mikroner kunna erhallas lined denna teknik for belaggning av metall vid anyandning ax behandlade polyfluoretenytor. Sasom Yid belaggning av andra plaster med metall bora de ytor, som skola belaggas, nog-grant renoZras fore den vernica belacb - nngen. It has been found that highly adherent continuous films having thicknesses between 0.1 and 0.5 microns can be obtained with this technique for coating metal on any other treated polyfluoroethylene surfaces. As Yid coating of other plastics with metal drills the surfaces to be coated, nog-grant renoZras fore den vernica belacb - nngen.

Be enligt foreliggande uppfinnin,g anyanda polyfluoretenerna aro, polymerer, som erhallas fran fluorerade etener, och sampolymerisat av fluorerad eten och etyleniskt omattade monomerer. Exempel pd. sadana polymerer och sampolymerisat aro polytetrafluoreten, polyklortrifluoreten, polyvinylidenfluorid och :sampolymerisat av tetrafluoreten och klortrifluoreten, tetraeten och hexafluorpropylen och liknande monomerer. Vidhaftnin-gen hos: den behandlade ytan stiger i allmanhet med polymerens fluorhalt, yarvid salunda polytetrafluoreten ger den mest yidhaftande ytan. Goda resultat erhallas i allmanhet med polymerer, i yilka atminstone 50 % ax andra kolbindningar an kol-kolbindningarna utgoras ay kol-fluor-bindningar. According to the present invention, there are other polyfluoroethylenes, polymers obtained from fluorinated ethylenes, and copolymers of fluorinated ethylene and ethylenically unsaturated monomers. Example pd. such polymers and copolymers are polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride and: copolymers of tetrafluoroethylene and chlorotrifluoroethylene, tetraethylene and hexafluoropropylene and similar monomers. The adhesion of: the treated surface generally increases with the fluorine content of the polymer, while the polytetrafluoroethylene gives the most adhesive surface. Good results are generally obtained with polymers in which at least 50% of other carbon bonds than the carbon-carbon bonds are formed in carbon-fluorine bonds.

Uppfinningen askadligg8res narmare I foljande exempel. The invention is further illustrated in the following examples.

Exempel 1. En 0,075 mm tjock polytetrafluoretenskiva med storleken 25X 50 mm2 doppades i en 1-procentig losning ax natrium i ,amomniak under 30 sekunder. Den behandlade Men tvattades med vatten och aceton och torkades darefter. Den behandlade polytetrafluoretenen hangdes darefter i 30 nil vattenhaltig, ammo,niakalisk silyernitratlOsning (Tollens reagens), som inneh011 3 g silvernitrat. Till d-enna losning sattes darefter 5 ml 37-procentig formaldehydlosning. mom kort hade en silverspegel bildats pi den. behandlade ytan. Den silverbelagda polyteirafluoretenen sk8ljdes med yatten och torkades. Ytan var belaP.:d med ett kontinuerligt skikt av silver med en tjocklek ay 0,005 mm. Konduktiviteten hos den belagda metallen narmade sig den rena metallytans. Example 1. A 0.075 mm thick polytetrafluoroethylene sheet measuring 25X 50 mm 2 was dipped in a 1% solution of sodium in ammonia for 30 seconds. The treated Men was washed with water and acetone and then dried. The treated polytetrafluoroethylene was then suspended in 30 ml of aqueous, amino, niacalic silyl nitrate solution (Customs reagent), containing 3 g of silver nitrate. To this solution was then added 5 ml of 37% formaldehyde solution. Mom briefly, a silver mirror had formed on it. treated surface. The silver-plated polyteirafluoroethylene was rinsed with the yacht and dried. The surface was coated with a continuous layer of silver with a thickness of 0.005 mm. The conductivity of the coated metal approached the pure metal surface.

For provning ay den metalliserade ytans vidhaftning pressades en tryckkanslig Seot:ch: cellofantejp mat den metalliserade ytan och avlagsnades snabbt. Obetydliga mangder silver taste vid tejpen vid aylagsnandet. Resistiviteten hos metallbelaggnin-gen f8rbley densamma. Forfarandet for belaggning med silver uppre-pades pa ett obehandlat .stycke polytetrafluoreten; nagon kontinuerlig belaggning kunde icke erhallas och silyrets vidhaftning vid polymerytan var ytterst dalig. For testing the adhesion of the metallized surface, a pressure sensitive Seot: ch: cellophane tape was pressed onto the metallized surface and quickly removed. Insignificant amounts of silver taste on the tape during eyelash cutting. The resistivity of the metal coating remains the same. The procedure for plating with silver was repeated on an untreated piece of polytetrafluoroethylene; no continuous coating could be obtained and the adhesion of the silage to the polymer surface was extremely poor.

Exempel 2. Prom av polytetrafluoreten skivor be-handlades, med natriumlosning i flytande ammoniak, sasom beskrivits, i exempel 1. Filmen placerades darefter i en yakuumkammare, som inneh011 en volframtrad i form ay en korg med 3 g aluminium, pa ett as-stand ay 10 cm frau metallkorgen. Kammaren evakuerades till ett tryek ay 5X10- mm Hg. Elektrisk shorn tillfordes yolframtraden, tills aluminiet i korgen smalt och forangats. En aluminiumbelaggning av 0,0075 nun erh011s pa. 2 minuter. Belaggningen var kontin,uerlig och vidhaftande och kunde icke avlagsnas yid provet med »Scotch» tejp. Belaggningens laga resistivitet forblev oforandrad vid prov med »Scotch» tejp. Utan forbehandling var det icke mojligt :att erhalla vidhaftande belaggningar. Example 2. Prom of polytetrafluoroethylene sheets were treated, with sodium solution in liquid ammonia, as described in Example 1. The film was then placed in a vacuum chamber containing a tungsten wire in the form of a basket of 3 g of aluminum, on an as-stand ay 10 cm frau metal basket. The chamber was evacuated to a tryek ay 5X10- mm Hg. Electric shorn is fed to the yolf wire until the aluminum in the basket has narrowed and evaporated. An aluminum coating of 0.0075 nun erh011s pa. 2 minutes. The coating was continuous, dishonest and sticky and could not be removed yid the test with «Scotch» tape. The low resistivity of the coating remained unchanged when tested with «Scotch» tape. Without pre-treatment it was not possible: to obtain adherent coatings.

Fors:Wet upprepades med anvandning av silver, koppar och germanium. Vidhaftande, — —3 kontinnerliga belaggningar erhollos i samtliga fall. Rapids: Wet was repeated using silver, copper and germanium. Adhering, - —3 contaminated coatings were obtained in all cases.

Exempel 3. Ett prov av ett sampolymerisat av tetrafluoreten och hexafluorpropen med storleken 13 mm X50 mmX2,5 mm doppades i en 1-procentig lOsning av .natrium i flytande ammoniak under 30 sekunder. Den pa detta salt behandla.de biten tvattades med vatten och aceton och torkades darefter i Mt. Pro-vet placerades darefter i en vakuumkammare pa ett avstand av 10 cm frail en volframtract i form av en konisk korg, som inneholl 200 mg germanium. Kammaren evakuerades till ett tryck av 5X10- mm Hg. Volframtra, den uppvarmdes med en elektrisk strom, varvid germaniet I korgen smalte och forangades. En 0,0125 mm tjock germaniumbeliiggning .erholls pa. 10 sekunder. 13elaggningen var kontinuerlig och vidhaftande och kunde icke avlagsnas vid prov med »Scotch» tejp. Utan forbehandling var det icke mojligt att erhalla vidhaftande belaggningar. Example 3. A sample of a copolymer of tetrafluoroethylene and hexafluoropropylene having a size of 13 mm X50 mmX2.5 mm was dipped in a 1% solution of sodium in liquid ammonia for 30 seconds. The piece treated with this salt was washed with water and acetone and then dried in Mt. The sample was then placed in a vacuum chamber at a distance of 10 cm from a tungsten funnel in the form of a conical basket containing 200 mg of germanium. The chamber was evacuated to a pressure of 5X10 mm Hg. Tungsten, it was heated with an electric current, whereby the germaniet in the basket melted and evaporated. A 0.0125 mm thick germanium coating is recovered. 10 seconds. The application was continuous and adherent and could not be removed during tests with "Scotch" tape. Without pre-treatment, it was not possible to obtain continuous coatings.

Liknande resultat erh011os med krom och term Exempel 4. Ett prov av polyklortrinuoreten behandlades med en lOsning av natrium i flytande ammoniak, sasom beskrivits i exempel 3. Provet placerades i en vakuumkammare och belades med germanium genom avdunstning, sasom beskrivits i exempel 3. En kontinuerlig, vidhaftande, 0,0075 min tjock belaggning erh011s pa, 10 sekunder. Utan forbehandling var det icke mojligt att erhalla vidhaftande belaggningar. Similar results were obtained with chromium and term Example 4. A sample of the polychlorotrinuethylene was treated with a solution of sodium in liquid ammonia as described in Example 3. The sample was placed in a vacuum chamber and coated with germanium by evaporation as described in Example 3. A continuous , adhering, 0.0075 min thick coating erh011s pa, 10 seconds. Without pre-treatment, it was not possible to obtain continuous coatings.

Forsoket upprepades med anvandning av krom och term. Vidhaftande, kontinuerliga belaggningar .erhollos 1 hada fallen. The experiment was repeated using chromium and term. Adherent, continuous coatings .erhollos 1 hada fallen.

Forfarandet enligt uppfinningen 5r lika anvfindbart pa sintrade som osintrade polymerytor; det är anyandbart pa formsprutade, strangsprutade eller formpressade foremal. The process of the invention is equally applicable to sintered and unsintered polymer surfaces; it is breathable on injection molded, extruded or extruded objects.

FOrfarandet kan dessutom tillampas pa polyfluoretenfOremal av olika storlek och form, sasom solida foremal, tunna Miner eller till och med fibrer. Sasom ovan namnts aro belaggningarna kontirmerliga, starkt vidhaltande och bOjliga. The process can also be applied to polyfluoroethylene formulations of various sizes and shapes, such as solid forms, thin mines or even fibers. As mentioned above, the coatings are contourable, highly durable and flexible.

Den enligt uppfinningen metallbelagda polyfluoretenen har ett stort anvandningsomrade sasom slutlig produkt eller mellanprodukt. Belaggningsforfarandet kan salunda anvandas for belaggning av polyfluoretenisolerade tradar for att astadkomma ett satt for utlantning av de elektriska pakanningar, som upptrada, tvars over isolerande skikt. Belaggningsforfarandet fir speciellt lampligt fOr framstallning av tryekta och inlagda kretsar. Tryckta kretsar framstallas genom belaggning av polymerytan med ett material, sasom paraffin, utskfirning av kretsen i vaxet och darefter utsattande av polymeren for forfarandet enligt uppfinningen samt avlags,- nande av paraffinet; detta lamnar endast den onskade kretsen metalliserad. Andra anvandningsomra.den innefatta anyandningen av me- tallipolyfluoretenytor, sasom elektro- der i kondensorer. De metallbelagda ytorna kunna anvandas for ytterligare metallbelaggning. Lod kan direkt smaltas pa belaggningen, och ledningar ku,nna hadas vid belaggningen. Manga andra anvandningsomraden framga fOr fackmannen. The polyfluoroethylene coated metal according to the invention has a wide range of uses as a final product or intermediate. The coating process can thus be used for coating polyfluoroethylene-insulated wires to provide a means of aligning the electrical seals that have been applied across insulating layers. The coating process is particularly suitable for the production of printed and inlaid circuits. Printed circuits are prepared by coating the polymer surface with a material such as paraffin, cutting out the circuit in the wax and then exposing the polymer to the process of the invention and depositing the paraffin; this leaves only the desired circuit metallized. Other applications include the use of metallipolyfluoroethylene surfaces, such as electrodes in capacitors. The metal-coated surfaces can be used for additional metal coating. Solder can be melted directly on the coating, and wires can be worn during the coating. Many other applications will be apparent to those skilled in the art.

Claims

Patent claim: A process for applying layers of metal in colloidal form to polyfluoroethylene surfaces, the surface to be coated being brought into contact with an alkali metal solution capable of wetting the polyfluoroctene, in particular a charge of sodium in liquid ammonia, characterized in that finely divided metal 'was then deposited on the run. Request Publications: Patent Letters from the United Kingdom 765 284.