United States Patent [191 [11] 4,172,733 Moritsu et a1. [45] Oct. 30, 1979

[54] COMPOSITIONS _ [56] References Cited U.S. PATENT DOCUMENTS [75] Inventors: Ylkihzl Moritsu, Nishinomiya; Kooji Yamada, Kashihara; Masatoshi 3,479,216 11/1969 Counts et a1...... 252/514 Wada, lzumiotsu; Eiji Munemoto, 4,029,605 6/1977 Kosiorek ...... 252/514 Hirakata, all of Primary Examiner-Lorenzo B. Hayes Attorney, Agent, or Firm—Armstrong, Nikaido, [13] Assignee: Okuo Chemical mm 00., Ltd., Marmelstein & Kubovcik Osaka, Japan [57] ABSTRACT [21] Appl. No.: 851,638 A vitreous enamel composition comprising 1 part by weight of a vitreous enamel solid component composed [22'] Filed: Nov. 15, 1977 of (1) 90-999 wt. % of powder consisting predom inantly of 40 to 80 wt. % of Si02, l-25 wt. % of at least [51] Int. Cl.2 ; ...... (119D 5/38 one of B203 and CaO, and l-20 wt. % of R20 in which [52] US. Cl...... 106/115; 106/ 1.21; R is K, Na or Li, and (2) 0.1-10 wt. % of palladium 106/ 1.28; 106/54; 252/514 powder, and l-20 parts by weight of an organic vehicle. [58] m of Search ...... 106/ 1.21, 1.24, 1.28, 106/].15, 54; 252/514; 427/101, 102, 126 6 Claims, No Drawings 4,172,733 1 "2 dium powder, and l-20 parts by weight of an organic VITREOUS ENAMEL COMPOSITIONS Y‘ vehicle admixed with the solid component. According to this invention it is essential that the This invention relates to vitreous enamel composi vitreous enamel composition contain‘ a glass powder tions, and more‘particularly to vitreous enamel compo consisting predominantly of 40-80 wt.‘ % of SiOz, l-25 sitions for undercoating the glass and ceramic articles to wt. % of at least one of B203 and CaO, and l-20 wt. % be electrolessly plated. I ' of R20 in which R is as de?ned above. The glass pow Generally the surface‘ of glass and ceramic articles der of this invention, although free from any com can not be coated by’electroless plating when subjected ponent, has a relatively low melting point which is directly thereto. ‘It is therefore necessary to depositon usually about l000° to about 1250° C. and can be ?red at the surface of such‘an article palladium, silver, gold or a relatively low temperature. Moreover the powder can a derivative thereof to sensitize the. surface for electro be ?red at temperatures in a wider range than lead glass, less plating. The sensitizing substance must be deposited while retaining the form of glass powder, giving a po on the surface with high adhesion and as uniformly as rous layer of ?red glass powder on glass or ceramic possible free of local irregularities. Additionally the articles. Since the glass powder is ?red on the surface of layer of the sensitizing material should preferably be the ceramic article, the vitreous layer can be formed as rough-surfaced to the greatest possible extent. adhered thereto with high bond strength. The surface of’ glass and ceramic articles is usually In this invention, the glass powder of the above com sensitized by applying a sensitizing material directly to position is used conjointly with the organic vehicle in an amount of 1 to 20 times the amount by weight of the the surface (to be hereinafter referred to as “direct cata powder, the amount of the vehicle being exceedingly lyzing method”), by applying a silver paste composed greater than was conventionally used in vitreous enamel of a small amount of silver powder and an organic vehi compositions of this type. Consequently, a rough-sur cle in not more than one half the amount (by weight) of the silver and ?ring the resulting coating (to be herein faced layer of the glass powder can be formed uni 25 formly on the surface of glass and ceramic articles. after referred to as “silver past ?ring method”), and by The glass powder of this invention is composed pref applying a vitreous enamel composition composed of erably of 45-75 wt. % of SiOg, 3-15 wt. % of at least lead glass, an organic acid salt of sensitizing material one of B103 and CaO and 5-15 wt. % of R20. The and a small amount of organic vehicle, followed by composition of the glass powder is determined based ?ring (to be hereinafter referred to as “glass enamel 30 mainly on the melting temperature of the glass powder, ?ring method”). , the temperature range in which the powder can be With the direct catalyzing method, the adhesion be ?red, the adhering properties and strength of the ?red tween the sensitizing material and the surface of the layer obtained. With less than 40 wt. % of SiOz present, article is very low, rendering the'electroless coating the ?red vitreous layer is liable to by the adhered to the article only with very low strength. 35 plating bath, with the result that the subsequent plating According to the silver paste ?ring method, the electro process gives metal coatings of reduced bond strength. less plating is limited only to plating which With more ‘than 80 wt. % of SiO; present, too high a requires the use of large quantities of expensive silver, ?ring temperature (melting temperature) will be re hence commercially very disadvantageous. The vitre quired, adversely affecting the glass or ceramic article ous enamel ?ring method has the following drawbacks. per se and producing a tendency to reduce the catalytic Since the glass component used is lead glass which is properties of the palladium powder. Further if the low melting, there is an extreme limitation on the range amount of at least one of B203 and CaO is less than 1 wt. of adjustable temperatures for forming on the surface of %, difficulty, is likely to arise in melting the glass pow ceramic articles a ?red layer in which the lead glass der. Conversely if it is more than 25 wt. %, the resulting retains its particulate form. Frequently, therefore, the vitreous layer will have a reduced chemical stability glass particles per se are fused, giving a smooth-sur and become'susceptible to corrosion by the plating bath. faced vitreous layer instead of forming a porous rough Further if R20 is present in an amount of less than 1 wt. surface. Moreover the glass tends to cover the sensitiz %, difficulty is likely to take place in melting the glass ing material, rendering the ‘material less exposed, with powder. With use of more than 20 wt. % of R20, a the result that the electroless coating, if formed, will 50 reduced chemical stability and increased susceptibility have reduced adhesion thereto. to corrosion by the plating bath will result. An object of this invention is to provide a vitreous Insofar as the above components are used within the enamel composition capable of giving coatings on ranges de?ned above, at least one or two of BaO, MgO, which platings can be formed with outstanding adhe NaF, ZnO, Tioz, ZIOZ, S1102, A1203, Bi203 and F6203 son. I 55 can be used in an amount of up to 20 wt. % in this Another object of this invention is to provide a vitre invention. Among these components, BaO and MgO act ous enamel composition which permits electroless de to promote vitri?cation, while NaF serves to adjust the position of nickel, cobalt and other metals as well as melting temperature of the glass powder. ZnO, TiOz, copper. ZrOg, A1203, Fe2O3, etc., are effective in giving an These and other objects of this invention will become 60 improved chemical stability to the glass powder. apparent from the following description. ' The glass powder can be produced according to the The vitreous enamel composition of this invention is usual method. For example, a vitreous mixture of the characterized in that the composition comprises: 1 part above composition is melted in the usual manner at by weight of a vitreous enamel solid component com l300°-l600°~ C. for l-6 hours and the molten mass is posed of (1) 90-999 wt. % of glass powder consisting 65 quenched in water and thereafter mechanically treated predominantly of 40-80 wt. % of SiO;, l-25 wt. % of at in a ball mill or the like. The resulting slurry is dried to least one of B203 and CaO, and 1-20 wt. % of R20 in obtain a cake, which is then pulverized by suitable which R is K, Na or Li, and (2) 0.1-10 wt. % of palla means such as oscillating screen. The glass powder of

__ 4,172,733 3 4 this invention is usually 0.5 to 20's, more particularly 0.5 85 wt. % of isopropyl alcohol is well suited to the prep to 10p. in particle size. aration of the present composition adapted for coating. According to this invention, a palladium powder is Paste-like thermoplastic compositions amenable to admixed with the glass powder to obtain a vitreous screen printing can be prepared with use of wax-like enamel solid component. Useful palladium powders are 5 vehicles composed of 40-60 wt. % of stearyl or cetyl ?nely divided metal palladium and inorganic com alcohol and 60-40 wt. % of thermoplastic resin, such as pounds thereof, such as palladium oxide, palladium a wax-like mixture of 40 wt. % of stearyl alcohol, 5 wt. hydroxide, palladium black, etc. Palladium oxide is % of polyethylene glycol (trademark: “PEG-1540,” prepared by the usual manner, for example palladium product of Sanyo Chemical Industries Co., Japan), 2 wt. chloride is heated with sodium nitrate at a temperature % of cellulose resin (“EC-N-22”), 3 wt. % of acrylic of about 600° C. Palladium hydroxide is produced by resin (trademark: “Acrybase BM-2003,” product of adding an aqueous solution of palladium chloride to Fujikura Kasei Co., Japan), and 50 wt. % of corn sodium hydroxide to precipitate palladium hydroxide, starch. removing the resulting precipitate and drying the pre According to this invention, a substance which will cipitate removed. Further palladium black is prepared 15 not melt during the ?ring of the composition can be by dissolving palladium chloride in an aqueous solution incorporated into the composition in an amount of l-20 of hydrochloric acid, adding formalin to the solution, wt. % based on the composition. Examples of such adjusting the resulting solution to a pH of more than 7, substances are barium sulfate, sulfate kaolin, heating the resulting alkaline solution at a temperature feldspar, siliceous sand, alumina, etc. The time when to of 50° to 80° C. for several hours to precipitate palla 20 add the substance is not particularly limited; for exam dium black and separating the palladium black from the ple, it may be added to the glass powder, or to the solution, followed by washing with water and drying. organic vehicle and the vitreous enamel solid compo These palladium powders are used in an amount of nent when the latter two are mixed together. 0.1-l0 wt. %, preferably l-8 wt. %, based on the vitre The vitreous enamel compositions of this invention ous enamel solid component. If the proportion of the 25 are applicable to glass and ceramic articles by any of palladium powder is less than 0.1 wt. %, it is difficult to various usual methods. When the composition is in the permit the formation of platings, whereas even if it is in form of a paste, the desired design is printed through an excess of 10 wt. %, further improved results will not be appropriate screen on the surface of glass and ceramic achievable. The method of mixing the glass powder articles. Compositions adapted for coating are applied with the palladium powder is not particularly limited 30 to the desired surface portion of articles by the usual but a wide variety of methods are employable. Typi method as by spraying or immersion. With composi cally, the powders are mixed together in a mortar for at tions adapted for use with transfer paper, the design of least 3 hours. the decalcomania can be transferred as it is. The vitre The vitreous enamel composition of this invention is ous enamel composition applied to the glass or ceramic prepared by diluting the glass enamel solid component 35 article is then ?red in the usual manner. The ?ring con with an organic vehicle in an amount of l to 20 times, ditions are determined as desired in accordance with the preferably 1 to 10 times the solid component. Useful composition of the vitreous enamel composition and the organic vehicles are those which can be evaporated off kind of the glass or ceramic article. Usually the ?ring is on decomposition when the vitreous enamel composi conducted at 550° to 900° C. for about 2 to about 30 tion is ?red. Examples are organic solvents, the mixture 40. minutes. The ?ring step causes the organic vehicle com of water and organic solvents, and solutions or disper ponent to evaporate off upon decomposition, forming a sions of resins in water or such solvents. Examples of layer of the glass powder containing the palladium organic solvents are terpene, esters, ethers, aromatic powder on the surface of the article. Subsequently, the hydrocarbons, more particularly pine oil, turpentine oil, article is subjected to an electroless plating process in diethylene glycol monobutyl ether, ethylene glycol 45 the usual manner, whereby a metal plating is formed on monobutyl ether, amyl acetate, toluene, xylene, etc. the glass powder layer. Prior to the electroless plating, Examples of useful resins are natural and synthetic res the article can be pretreated in a simple usual manner as ins. Examples of useful natural resins are balsam, gum by being immersed in about l-20% aqueous solution of damar, copal, rosin, etc. Examples of useful synthetic hydrochloric acid at room temperature to about 60° C. resins are cellulose resin, acrylic resin, polyamide, poly for about 2 to about 30 minutes. For the electroless ester, polyvinyl acetate, polyethylene glycol, polyvinyl plating, a wide variety of baths are usable, typical of acetal, polyvinyl alcohol, etc. Examples of aqueous which are an acid or alkaline electroless nickel plating solutions or dispersions are aqueous solutions of polyvi bath containing sodium hypophos?te, an electroless nyl alcohol, polyvinyl acetate emulsion, acryl emulsion. nickel or copper plating .bath containing sodium boron Also usable are organic solvent solutions or dispersions 55 hydride or like boron-type reducing agent, other usual of various resins. Typical of organic vehicles are a mix electroless gold, silver, brass and cobalt plating baths, ture of 76 wt. % of pine oil, 6 wt. % of polyester resin etc. (trademark; “Barnok D-161,” product of Dainippon Ink The vitreous enamel compositions of this invention ' and Chemicals, INC., Japan), 12 wt. % of cellulose are applicable to a wide variety of glass and ceramic resin (trademark; “EC-N-22,” product of Hercules, 60 articles which remain stable at the ?ring temperature, U.S.A.) and 6 wt. % of polyvinyl resin (trademark: such as articles made of soda lime silica glass, borosili “Eslec BL-l,” terpolymer of vinyl butyral, vinyl ace cate glass or like glass, various ceramic articles, ferites tate and vinyl alcohol, manufactured by Sekisui Chemi semicondutors, alumina plates etc. cal Co., Japan), a mixture of 96 wt. % of pine oil and 4 The vitreous enamel compositions of this invention wt. % of the above-mentioned cellulose resin. These 65 are readily applicable to glass and ceramic articles over vehicles are useful for preparing the vitreous enamel the entire surface or desired portion thereof by any of compositions of this invention in the form of a paste. A the usual methods such as ordinary screen printing, vehicle composed of 15 wt. % of the cellulose resin and transfer printing, spraying or like coating method, de 4,172,733 5 6 pending on the kind and proportion of the organic vehi through a 200-mesh screen. The printed plate is placed cle used in the composition. The composition applied to into a box furnace the internal temperature of which is the article can be ?red with case without entailing de thereafter raised at a rate of 40° C./ min. The composi formation of the‘ article itself, forming a layer with a tion is ?red at 630°-_*:l0° C. for 10‘ minutes. very porous surface on which the palladium powders, The vitreous enamel test piece thus prepared is im i.e., the sensitizing material, are uniformly distributed as mersed in a 10% solution of hydrochloric acid at 50° C. exposed over the entire surface area. Since the vitreous for 10 minutes for pre-treatment and is subsequently enamel compositions of this invention, when applied to electrolessly plated in a ?ve-fold dilution of “Acid type glass or ceramic articles and ?red in the usual manner, Chemical Nickel Plating Solution,” product of Okuno give a highly sensitized porous vitreous layer on the Chemical Industry Co. at 90° C. for 10 minutes to form article integral therewith, a uniform plating of metal a uniform nickel plating on the test piece. The plating is such as copper, nickel, cobalt, gold, silver or the like held adhered to the ?red alumina plate with bond can be subsequently electrolessly formed on the article strength of as high as 0.7 kg/mm2. The bond strength is with high adhesion due to the resulting anchorage and measured by soldering a copper wire 0.5 mm in diame chemical bond between the sensitizing material and the terto the nickel plating and pulling the copper wire at plated metal. 7 _ ‘ right angles to the plate on a tension tester (product of Thus the present invention is very useful in forming Shimazu Seisakusho Co., Ltd., Japan). on glass and ceramic articles decorative or colored metal coatings with high durability. The vitreous EXAMPLE 2 enamel compositions of this invention are useful also for A vitreous mixture of the following composition is glazing glassware and ceramic warebecause of their prepared. . outstanding resistance to acids and alkalis. _ This invention will be described below with refer ence to examples, in which the percentages are all by % 25 weight. . SiOz 60 B203 7 EXAMPLE 1 A1103 5 N320 14 A vitreous mixture of the following composition is ZrO 5 prepared. TiO; 9 30

% The mixture is fused at 1500‘? C. in an electric furnace

SiOg _ 12.0 and then quenched in‘ water to‘ obtain a vitreous . CaO 9.6 The wet frit is ground in a pot mill for 4 days to prepare MgO 4.4 a slurry, which is dried and thereafter comminuted on a NaZO 13.0 ' ZOO-mesh oscillating screen to obtain a glass powder A1203 1.0 v according to this invention. The glass powder and the palladium powder obtained The mixture is fused at [400° C. in an electric furnace ' in Example 1 are mixed together in the speci?ed pro and then quenched in water to obtain a vitreous frit. 40 portions shown in Table l. The organic vehicle dis The wet frit is ground in a pot mill for 4 days to prepare closed below is added to the mixture in two times the a slurry, which is dried and thereafter comminuted on a amount by weight of the solid of the mixture, and the ZOO-mesh oscillating screen to obtain a glass powder resulting mixture is kneaded for 5 hours to obtain vitre according to this invention. The glass powder has a ous enamel compositions. coefficient of expansion of 96X 10-7 cm/cm'/°C. ‘and particle-size distribution of: 34.2% of smaller than 2p, 36.0% of 2-4p., 17.0% of 4-6u, 9.7% of 6-8;], and 3.1% Organic vehicle: ‘ % of larger than 8p. Pine oil . 80 On the other hand, palladium chloride is dissolved in Cellulose resin as shown in Example l 15 an aqueous solution of hydrochloric acid, formalin is 50 Polyvinyl acetal ("Eslec BL-l added to the solution, and the resulting solution is ad product of Sekisui Chemical Co.) 5 justed to a pH of about 8 with sodium hydroxide. The solution is heated at 80° C. for 1 hour, and the palladium black separated out is ?ltered off, washed with water The vitreous enamel composition is printed, in an and spontaneously dried to obtain a palladium powder. 55 amount of 0.005 g/cmz, on a tired pure alumina plate A 940 g portion of the glass powder and a 60 g por throughia 300-mesh screen. The printed plate is placed tion of the palladium powder obtained as above are into abox furnace the internal temperature of which is mixed together in a mortar for 5 hours. An oil serving as thereafter raised at a rate of 30° C./ min. The composi an organic vehicle and composed of 96% of pine oil and tion is ?red at 740°: 10° C. for 15 minutes. 4% of cellulose resin (trademark: “EON-22,” product 60 The vitreous enamel test piece thus prepared is im of Hercules INC.) is added to the mixture in three times mersed in a 10% solution of hydrochloric acid at 45° C. the amount by weight of the solids of the mixture. The for 15 minutes for pre-treatment and is subsequently resulting mixture is kneaded for 5 hours, and the paste electrolessly plated in an electroless plating bath com obtained is further treated with three rollers to prepare posed of 1000 ml of “Sylek #202” ‘(product of du Pont) a uniform vitreous enamel composition of this inven 65 and 28 ml of ,“Sylek #222” (product of du Pont). The tion. resulting piece thus plated is checked for the following The vitreous enamel composition is printed, in an plating properties. The results‘ are given in Table 1 amount of 0.005 g/cmz, on a fired pure alumina plate below. . 4,172,733 7 8 Table 1 No. ' 1 2 3 4 s Proportions of glass glass powder (%) 99.95 99.8 95.0 90.0 87.0 powder and Palladium Palladium Powder 0.05 0.2 5.0 10.0 13.0 powder . Plated area (%) 10 100 100 100 100 Bond stren lb 0.8 1.2 1.8 1.8 1.7 (Kg/mm )

. . Table 2 The above bond strength is measured 1n the same 1 manner as in Example 1. No‘ 2 3 4 5 Proportions of solid EXAMPLE 3 component and organic l/0.2 V2 V7 l/l5 l/25

. . . , _ . 15 vehicle ' A vitreous mixture of the following compos1t1on 1s Plated 3,13%) 20 100 100 100 70 prepared. Bond strength (kglmmz) 0.1 2.0 1.8 1.0 0.05

% What is claimed is: 1. A vitreous enamel composition for undercoating SiOz 72.0 20 CaO 9.6 glass and ceramic articles to be electrolessly plated MgO 4.4 comprising 1 part by weight of a vitreous enamel solid A120 3 l .0 component composed of N820 13.0 (l) 90-99.9 wt. % of glass powder consisting of 40 to 25 80 wt. % of 810;, 1-25 wt. % of at least one of The glass powder according to this invention is pre B203 and CaO, 1-20 wt. % of R20 in which R is K, pared in the same manner as in Example 2 from the Na, or Li and up to 20 wt. % of at least one of BaO, above vitreous mixture. MgO, NaF, Z110, TiOz, Z1'02, SnOz, A1203, Bi2O3 74 parts by weight of glass powder, 20 parts by and F8203, and weight of alumina and 6 parts by weight of palladium (2) 0.1-10 wt. % of palladium powder, and 1-20 parts oxide are mixed together in a mortar for 5 hours. The by weight of an organic vehicle. same organic vehicle as in Example 2 is added to the 2. The vitreous enamel composition according to mixture in the speci?ed proportions disclosed in Table 2 claim 1, in which said glass powder consists of 45-75 and'the resulting mixture is kneaded for 5 hours to wt. % of SiO;, 3-15 wt. % of at least one of B203 and ' obtain vitreous enamel compostions. 35 CaO, and 5-15 wt. % of R20 in which R is K, Na or Li. The vitreous enamel composition is printed, in an 3. The vitreous enamel composition according to amount of 0.005 g/cmz, on a ?red pure alumina plate claim 1, inpwhich said vitreous enamel solid component through a 300-mesh screen. The printed plate is placed is composed of (1) 92-99 wt. % of glass powder consist into a box furnace the internal temperature of which is ing of 40 to 80 wt. % of SiOg, 1-25 wt. % of at least one thereafter raised at a rate of 30° C./min. The composi 40 of B203 and CaO, and l-20 wt. % of R20 in which R is tion is ?red at 660°:t10" C. for 15 minutes. K, Na or Li, and (2) l to 8 wt. % of palladium powder. The vitreous enamel test piece thus prepared is im 4. The vitreous enamel composition according to mersed in a 10% solution of hydrochloric acid at 50°C. claim 1, in which said organic vehicle is contained in an for 15 minutes and subsequently in a 20% solution of amount of l-lO parts by weight based on 1 part by sodium hypophosphite at 85° C. for 5 minutes for pre 45 weight of the vitreous enamel solid component. ‘ treatment. The pre-treated piece is then electrolessly 5. The vitreous enamel composition according to plated in an electroless plating bath (“TMP,” Chemical claim 1 which further contains at least one of substances Copper Plating Solution, product of Okuno Chemical not melting'during ?ring of the composition. Industry Co., Japan) composed of 1 part by volume of 6. The vitreous enamel composition according to A-type, 1 part by volume of B-type and 4 parts by vol claim 5, in which said substance is at least one of barium ume of water at 25° C. for 15 minutes. The resulting sulfate, calcium sulfate, kaolin, feldspar, siliceous sand piece thus plated is checked for the following plating and alumina. properties. The results are given in Table 2 below. is * t i *

55

65