GB1592886A - Coating articles with polyarylenesulphide resin compositions - Google Patents

Description

(54) COATING ARTICLES WITH POLYARYLENESULPHIDE RESIN COMPOSITIONS (71) We, DAIKIN KOGYO COMPANY LIMITED, a Japanese body corporate of Sin-hankyu Building, No. 8, Umeda, Kita-ku, Osaka-shi, Osaka-fu, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a novel finishing system for articles, and especially for articles formed of metals or ceramics.

It is well known that fluorocarbon polymers have desirable physical properties such as low coefficient of friction, nontackiness and high resistance to chemicals and heat and may be used in a wide variety of fields such as for domestic uses (as in coating irons, frying pans, etc), in the food industry, in the electric industry, in the machine industry and elswhere. However, due to the inherent nature of nontackiness, fluorocarbon polymers are generally poor in adhesion to other materials.

Thus, it is much more difficult to coat substrates with such polymers than with other known polymers. Several procedures have been proposed in an effort to overcome the above difficulty, including a method in which a primer coat is applied to a substrate prior to the coating of a fluorocarbon polymer topcoat in an effort to obtain strong adhesion of the topcoat to the substrate through the primer coat, a method in which a substrate surface is chemically or physically roughened to facilitate adhesion of the fluorocarbon polymer to the roughened substrate by a socalled anchoring effect, and a method in which a fluorocarbon polymer per se is "improved" so as to enhance its adhesion to substrates.

These prior proposals have not been wholly satisfactory. For example, conventional primer compositions generally contain strong acids or strong alkalis so that pollution of the working environment may result during preparation or use of the primer composition and wastage on a significant scale generally occurs in practice.

In recent years, polyarylene sulphide resins (hereinafter referred to simply as PAS), typical of which is polyphenylene sulphide,

(hereinafter referred to simply as PPS), have attracted some attention due to their characteristic properties of high resistance to heat and high affinity for fluorocarbon polymers. For example, in Japanese patent publication No. 51-31813/1976, there is proposed a method in which polyphenylene sulphide resin is sprayed over a blasted metal surface and baked to form a primer coat on which a fluorocarbon polymer topcoat is formed.It has also been proposed, in Japanese patent publication No. 12053/1976 and German Offenlegungsschrift No. 2152770, to employ primer compositions containing polyphenylene sulphide and a fluorocarbon polymer as principal components for applying a flurorocarbon resin on a primer coat derived from the composition.

Neither of these proposals is wholly satisfactory in our view. In the former method in which the primer consists essentially of the particulate polyphenylene sulphide resin, we have found that baking should be effected at a relatively low temperature of 233200C in order to obtain satisfactory adhesion between the fluorocarbon polymer topcoat and the primer coat. However, such low temperature baking has not been found to provide an adhesion satisfactory to us between the substrate and the primer coat. When the PPS is baked at a high temperature to permit the primer to strongly adhere to the substrate, the resulting primer coat becomes, we find, very poor in adhesion to the fluorocarbon polymer topcoat. Thus, we have now concluded that a primer coat consisting essentially PPS is not practical.Furthermore, though the PPS primer coat has a satisfactory hardness at a normal temperature, we find that its hardness is low at a high temperature of, for example, about 200"C. Under such high temperature conditions the primer coat is easily damaged and cannot be regarded as scratch resistant.

In the latter case where PPS admixed with a fluorocarbon polymer is used as a primer, we have found that adhesion between the primer and the fluorocarbon polymer topcoat is improved. However, adhesion between the primer coat and its metal substrate has also been found to be lowered. So far as we are aware, it has not yet been possible to select compositions for the system which provide adhesion both between the metal substrate and the primer coat and also between the primer coat and the topcoat. The final coated article may well exhibit lowered resistance to corrosion because of micropores produced in the primer coat layer.

The present invention has arisen out of our attempts to overcome or to avoid the problems of these previously proposed coating systems.

fn accordance with the present invention, we provide an article having a substrate provided in the following order with: an undercoat comprising a polyarylene sulphide resin; A primer coat derived from a fluorocarbon polymer-containing primer composition; and a fluorocarbon polymer topcoat.

We describe below, by reference to specific examples, embodiments of articles in accordance with this invention in which strong adhesion between the respective contacting layers is achieved so that the coated articles exhibit excellent resistance to corrosion, excellent properties inherent to fluorocarbon polymers and improved hardness even at high temperatures.

The undercoat, which may constitute the first layer on the substrate, may include a polyamideimide resin and/or polyimide resin.

The invention is hereinafter more particularly described by way of example only.

The undercoat (usually the first layer) is derived from an undercoat composition including a polyarylene sulphide resin. The polyarylene sulphide resins we have found to be useful in the practice of the present invention are polymers having the recurring unit of an aryl group and sulphur or the recurring unit composed of an aryl group and a group containing sulphur and oxygen. These polyarylene sulphide resins are particularly described in United States Patent No.

3,354,129, the disclosure of which is hereby incorporated by reference. PAS is preferably used in combination with a polyamideimide resin (hereinafter referred to simply as PAI) and/or a polyimide resin (hereinafter referred to simply as Pal), which are known to have relatively high resistance to heat.

PAI is characterized by having both amido radicals and imido radicals in the molecular structure thereof, and can be prepared, for example, by interaction of an aromatic diamine having an amido radical in the molecule thereof and an aromatic tetravalent carboxylic acid such as pyromellitic acid, by interaction of an aromatic trivalent carboxylic acid such as trimellitic anhydride and a diamine such as 4,4'diaminodiphenyl ether, and by interaction of a dibasic acid having an aromatic imido ring in the molecule thereof and adiamine.

PI is a high molecular weight polymer having imido linkages in the molecule thereof and obtained by interaction, for example, of an aromatic tetravalent carboxylic anhydride such as pyromellitic anhydride and an aromatic diamine such as diaminodiphenyl ether.

PAS has recently attracted special interest for use as a heat-resistant and a corrosion-resistant coating material. This resin has a very high hardness of 4H-5H when determined by a pencil test at normal temperature but is lowered in hardness below 2B at high temperatures of 18-200"C. Even if this resin is coated onto cookware, the coating film becomes poor in resistance to scratch at high temperatures. Thus, the cookware coated with PAS alone is practically, hard to use.

However, it has been found that when PAS is admixed with PAI and/or Pl, the resulting film not only has the favorable characteristics inherent to PAS such as resistance to heat and corrosion and non-tackiness, but also can prevent the film hardness from being lowered even when employed under high temperature conditions. Moreover, the film exhibits a high resistance to abrasion.

The first, undercoat layer is overlaid with the second, primer layer. This primer layer may be derived from any primer compositions which exhibit good affinity both for the first layer and for the third, fluorocarbon topcoat layer.

Various kinds of primer compositions which are commercially available as primers for fluorocarbon polymers may be used for the purpose of the present invention.

Primer compositions we have found to be useful in the practice of the present invention include dispersions containing a fluorocarbon and a binder having the above-mentioned affinity. Illustrative of the binders we have found usable in the practice of the invention are: (a) chromic acid, (b) organic chelate compounds of transition metals of group IV of the Periodic table such as titanium, sirconium, etc., (c) synthetic resins other than fluorocarbon polymers which have miscibility with the fluorocarbon polymers and are stable at a temperature of 1500C or more, such as PAS, PAI and Pl, (d) mixtures of inorganic oxides and phosphoric acid, (e) lithium, potassium, sodium or other alkali silicates, (f) amine silicates, and (g) colloidal silica. All of these materials are known to be used as a component of primers for fluorocarbon polymers.

The primer layer is then formed thereon with the third, fluorocarbon polymer topcoat layer. The fluorocarbon polymers useful for the above purpose are known ones including, for example, polyterafluoroethylene (PTFE), copolymers of tetrafluoroethylene and hexafluoropropylene, chlorotrifluoroethylene, perfluoroalkyltrifluorovinyl ether (R,OCFCF2) and the like, polychlorotrifluoroethylene, and mixtures thereof. The fluorocarbon polymer may be used in any forms such as powder, an aqueous dispersion obtained by an emulsion polymerization of a fluorocarbon monomer, a dispersion obtained by dispersing fluorocarbon polymer powder in an aqueous medium, an organosol, or an organosol-in-water emulsion.

These fluorocarbon polymers of various forms are commercially available as fluorocarbon polymer topcoat compositions and any of them may be suitably used for the purpose of the invention.

A variety of solid materials such as iron, aluminium, stainless steel, various kinds of alloys, ceramics, etc., are usable as a substrate to be coated. The surface of the substrate is generally treated to make it rough so as to facilitate adhesion of the first layer.

Suitably, the undercoat film containing PAS with or without being admixed with PAI and/or Pl is first formed on the surface of the substrate. With the undercoat containing PAS alone, a fine powder of PAS having a size of about 0.950 y may be applied, as it is, onto the substrate by any suitable powder coating method.

Alternatively, the PAS powder may be dispersed in an aqueous or organic medium using auxiliaries such as a surface active agent, which is then applied onto the substrate in any known ways and dried.

The PAS applied to the substrate is then baked at a relatively high temperature of about 330w00 C to cause the applied PAS to strongly adhere to the substrate.

Since a fluorocarbon polymer topcoat composition is not directly applied onto the PAS layer in our practice, the PAS can be baked at such relatively high temperature.

As described above, PAS is preferred to be mixed with PAI and/or Pl, since such layer is not only strongly adhered to the substrate, but also far improved in film hardness and resistance to abrasion under high temperature conditions. The mixing ratio of PAS to PAI and/or Pl is not critical. However, if the PAI and/or PI content is too small, the hardness and abrasion resistance of the obtained film is not improved to the extent desired. Too great content is unfavourable in view ot poverty in corrosion resistance of the film. We have found that the weight ratio of PAS to PAI and/or Pl is most suitably within a range of 20/1 to 1/2.The undercoat composition including PAS and PAI and/or Pl may be used in the form of a uniformly mixed powder or a solution or dispersion in liquid medium. Any of known coating methods may be used for the application of the composition.

To ensure formation of a uniform film of the undercoat composition in the form of dispersion or solution, it is preferred that the solution or dispersion contain a solvent capable of dissolving PAI and/or Pl under film-forming conditions.

Examples of such solvents are N-methylpyrrolidone, cresol, phenol, naphtha, dimethylformamide, dimethylacetamide, benzonitrile, methylglycol acetate, methyl ethyl ketone 2-nitropropane, ethylglycol acetate, ethyl acetate, xylene, toluene, methyl isobutyl ketone, and mixtures thereof including, for example, mixtures of N-methylpyrrolidone and toluene, ethyl acetate, butyl glycol, dioxane, etc.

The undercoat composition may further include a surface active agent such as an anionic active agent or a non-ionic active agent; a pigment such as an oxide of titanium or iron; a viscosity-controlling agent or a thickner such as methyl cellulose or ethyl cellulose; a levelling agent such as a fluorinated alkylcarboxylic acid or sulphonic acid; a film hardener such as metal powder or metal compounds; a wetting agent such as an organic solvent, and the like. As described hereinbefore, the undercoat composition is applied to the substrate surface by any of the known methods such as spraying, dipping, flow coating and the like. Where the composition contains volatile matter, such component is evaporated by heating.

Then, the applied composition is baked at a relatively high temperature of about 33OA000C to cause it to strongly adhere to the substrate.

Then, the primer coat for fluorocarbon resin is formed on the undercoat layer as the second layer. The primer composition is applied also by conventional methods such as spraying, dipping, flow coating and the liked, followed by drying and baking. The drying is conducted at a temperature of from a normal temperature to about 100"C. This is true of any drying treatments for the first to third layers. If the applied primer composition is directly baked, rapid gasification of the liquid medium by evaporation will undesirably cause occurrence of cracks or pinholes on the film surface. This will be completely avoided by the drying treatment as well known in the art. The baking temperature for the primer layer varies depending on the primer composition but is generally up to 4000C.

The present invention is based on an important finding that an undercoat layer composed of PAS with or without being admixed with PAI and/or Pl has strong adhesion to the primer layer for fluorocarbon resin. As will be seen from the description appearing hereinafter, the adhesion of the primer layer to the first layer and also to the third layer in examples of the invention is very high.

The fluorocarbon polymer topcoat composition to be applied to form the third layer is also applied in any conventional way such as spraying, electrostatic coating, flow coating, and the like. The optimum baking temperature is dependent on the type of the fluorocarbon polymer employed as well known to those skilled in the art. For example, with olytetrafluoroethylene, a copolymer of tetrafluoroethylene and chlorotri uoroethylene, a copolymer of tetrafluoroethylene and perfluoroalkyltrifluorovinyl ether, etc., the baking temperature is generally in the range of 340420"C, and preferably in the more limited range of 360--400"C.

With polychlorotrifl uoroethylene and copolymers containing chlorotrifluoroethylene as principal component, the baking is performed between 230 and 300"C, and preferably in the more limited range of 240 to 2700 C.

It is generally preferred that baking be conducted after each coating composition application to obtain good adhesion between the coats. We have found, however, that one of the three baking steps may be omitted in the practice of the present invention. That is: a dried undercoat layer may be directly coated with a primer composition coat without being first baked; or, alternatively, a topcoat composition coating may be applied on to a primer composition coat immediately after drying of the primer coat.

Examples of the resulting articles have been found to possess strong adhesion between the substrate and the fluorocarbon polymer topcoat. The adhesion is generally shown in terms of adhesion strength. Our three-layer coatings have been shown to have far improved adhesion strength over such previously proposed counterparts as we have been able to test, as will be apparent from the adhesion test set out in Example I below. For instance, in the case of an article having a chromic acid primer, we have found the adhesion strength to be about 2.0 kg/cm.

With a primer of a fluorocarbon polymer with PPS added (such as disclosed in Japanese patent publication No. 12053/1976) or a primer using PPS alone (such as disclosed in Japanese patent publication No. 31813/1976), we have found an adhesion strength in the range of 1.1.5 kg/cm. The adhesion strength in the range of 1.01.5 kg/cm. The adhesion strength of examples of our three-layer coating has been found to be as high as 2.5-3.2 kg/cm.

We have found that practical embodiments of our coated articles can almost completely withstand a corrosive atmosphere of either a liquid or a gas in view of excellent shut-off proporties of the coat. If the film surface is brought into contact with a corrosive material, the material can not reach the substrate surface, so that a metal or other material constituting the substrate can be completely protected. The complete protection of a metal substrate from a corrosive material can not be expected from coating films obtained by conventional methods wherein a primer is directly applied to a metal surface on which a topcoat is then applied. As a result, the prior art film is often blistered and the blisters are gradually increased. Finally, the film is completely separated from the metal substrate.The protecting effect of the coat in our examples is believed to be attributable in large measure to the undercoat layer. This will be understood in view of the fact that the undercoat layer made of PAS or a mixture of PAS and PAI and/or Pl contributes largely to the production of the favourable effects of the article as described hereinabove.

The following non-limiting examples will further illustrate the present invention, in which percentages are by weight unless otherwise defined.

Example I.

Preparation ofPPS Dispersion PPS powder obtained by pulverizing commercially available PPS in a high speed impact mill to have an average size of 10y 800 g Sodium lauryl sulphate 50 g Polyvinyl alcohol 30 g Ion exchanged water 1000g These components were mixed in a ball mill for 24 hours to obtain a PPS dispersion.

Preparation of Pf Dispersion Pl powder obtained by pulverizing Pl ("Kerimid 604--1000", product of Rhone Poulenc, France) "Kerimid" is a Registered Trade Mark, in the same manner as in the case of PPS, with an average particle size of 10 ,u 300 g Sodium lauryl sulphate 50g N-methylpyrrolidone 1000g Polyvinyl alcohol 30g Ion-Exchanged water 1000g These components were mixed and pulverized in a ball mill for 24 hours to obtain a Pl dispersion.

The thus obtained PPS dispersion and Pl dispersion were mixed in a container equipped with an agitator to give undercoat compositions for the first layer having the various mixing ratios indicated in Table 1.

An aqueous dispersion of polytetrafluoroethylene powder with an average size of 0.2 ,u was blended with the Pl dispersion prepared above in a PTFE/PI weight ratio of 3/1 and gently agitated to give a primer composition for the second layer.

200 mm x 200 mm x 1 mm iron plates were each sand blasted to make its surface rough and then cleaned with a blast of compressed air to give substrates to be coated. Each of the undercoat compositions was applied onto the substrate by a spraying method so as to have a thickness, after baking, of about 20 u, dried for 10 minutes in an infrared ray dryer, and then baked at 3900C for 20 minutes in a baking furnace. After cooling, the primer compositions was applied onto the first layer in the same manner and conditions as in the case of the first layer to form a second layer.

Thereafter, a commercially available polytetrafluoroethylene topcoat composition (produced by Daikin Kogyo Co., Ltd under the trademark Polyflon Enamel EK4108--GY, solid content of 41%, gray) was further applied in a baked thickness of about 25 M and dried and baked in the same manner as in the case of the first layer, thereby terming a topcoat strongly adhered to the second layer.

After cooling, the thus produced coated articles were subjected to the following tests to measure physical properties of their coated film. The test results are shown in Table I.

Pencil Hardness Test: In accordance with Japanese Industrial Standard KV894.

Brine Spray Test: In accordance with Japanese Industrial Standard Z-2371.

Heat-resistant Test: Test pieces were heated for predetermined periods of time in electric furnaces maintained at 3000C and 390"C, respectively, and then withdrawn from the furnaces to cool, followed by the pencil hardness test according to JIS Kid894.

Peeling Test: An iron plate treated to make its surface rough was coated on the half area of the surface with the undercoat composition to form a fused first layer and then with the primer composition to form a second fused layer. Then the topcoat composition was applied to the other half of the plate as well as to the second layer, followed by drying and baking. A part of the topcoat was manually peeled off which had no primer layer. Then, the topcoat layer was peeled out at a rate of 20 mm/min in a direction of 180 degree by means of an automatic recording tensile tester to determine the adhesion strength expressed in terms of kg/cm.

Example 2.

PAI solution (product of Hitachi Chem. Co., Ltd., "HI-400", xylene solution with a resin content of about 25%) 1500 g Sodium lauryl sulphate 30 g Surface active agent ("Triton X-100", product of Rohm & Haas Ltd. "Triton" is a Registered Trade Mark) 30 g Ion exchanged water 1200 g These components were mixed and pulverized in a ball mill for 100 hours to give a PAI dispersion. The PAI dispersion and the PPS dispersion obtained in Example I were mixed together in the different ratios indicated in Table 2, in a container equipped with an agitator to give undercoat compositions.

PAI dispersion mentioned above 100 g Aqueous PTFE dispersion used in Example 1 100g Aqueous 2%, methyl cellulose solution lOg These components were mixed and agitated to give a primer composition.

Then, iron plates which had been surface-treated in the same manner as in Example I were provided with the undercoat compositions to have a tilm thickness, after baking, of about 20 u dried, baked and cooled. Then, the primer composition was applied onto the undercoat layer in the same manner as in the undercoat (thickness after baking of 10 ,u). A PTFE topcoat composition, "Polyflon Enamel EKW183GB" (product of Daikin Kogyo Co., Ltd., with a solid content of 41%, grayish brown colour-"Polyflon" is a Registered Trade Mark) was then applied onto the primer layer in the same manner as in the primer to have a film thickness after baking of 20 y. Drying, baking and cooling of the undercoat, primer and topcoat were effected in the same conditions as in Example I. For comparative purposes, an iron plate was directly primed with. the primer composition and then overcoated with the topcoat composition, under the same conditions as above. The resulting coated articles were subjected to a series of tests. The results were as shown in Table 2.

Example 3.

PAI dispersion prepared in Example 2 1000 g Aqueous dispersion of a tetrafiuoroethylene hexafluoropropylene copolymer, polymer content of 55% ("Neofion ND-I", product of Daikin Kogyo Co., Ltd.) 1000 g Aqueous 2% polyvinyl alcohol solution 1000 g These components were mixed with agitation to obtain a primer composition.

Then, Example 2 was repeated using this composition for the formation of the second layer, and the aqueous copolymer dispersion "Neoflon ND-I" as the topcoat composition. Mixing ratios of PPS to PAI in the undercoat were as indicated in Table 3. The resulting coated articles were found to have the properties as shown in Table 3. The comparative sample in Table 3 had a first layer of the primer composition directly provided on an iron substrate, overlaid with the topcoat composition.

Example 4.

Similarly to Example 2, an iron plate which had been sand blasted and cleaned was undercoated with the PPS and PAI dispersion in the same manner as in Example 2 to form a first layer with a thickness of 15y after baking. Then, the following primer compositions (a) and (b) were separately applied in the same manner as in Example 2 to form a second layer with a thickness after baking of 108.

Composition (a): As described in Japanese laid-open publication No. 150735/1975, the following components were uniformly mixed to prepare a primer composition containing a titanium chelated compound.

Acetylacetone chelated compound of tetrabutyl titanate 1000g Aqueous PTFE dispersion (resin content 60%) 500 g Aqueous 20% titanium oxide dispersion (obtained by mixing titanium oxide with sodium lauryl sulphate in an amount of 30% of the titanium oxide in deionized water in a ball mill) 150 g Composition (b): The following components were uniformly mixed.

Aqueous 30% lithium polysilicate, product of Nissan Chem. Co., Ltd. 150 g Aqueous PTFE dispersion (resin content of 60%) 500 g Aqueous powdered mica dispersion (obtained by ball-milling 200 g of mica and 20 g of "Trito X-100" in 800 g of ion exchanged water for 50 hours) 300g A PTFE topcoat composition, "Polyflon Enamel EX--4108GY" product of Daikin Kogyo Co., Ltd., was appled onto the second, primer layer in the same manner as in Example 2 to have a film thickness of 20 after baking. Thus, threelayer coating was obtained. For comparative purposes, the compositions (a) and (b) were each directly applied onto an iron plate as primer layer, on which the aboveindicated topcoat composition was applied in the same manner as described above to give a two layer coating.

The test results are shown in Table 4.

Example 5.

PPS ("Ryton V-1" of Phillips Petroleum Co., U.S.A.) which had been finely powdered to have an average particle size of about 10 , and PAI ("HI-400" produced by Hitachi Chem. Co., Ltd., in the form of an xylene solution having a resin content of about 25%) were mixed with each other in such mixing ratios as indicated in Table 5. The mixtures were agitated in a high speed agitator for about 1 hour to give film-forming compositions. The composition were each sprayed over an aluminium plate having said blasted surface so as to have a film thickness, after baking, ranging from 15 to 20 it. Then, the applied composition was dried in an infrared ray dryer to sufficiently remove the volatile matters, and baked for 20 minutes in an electric heater maintained at 3700C.After cooling, the resulting coated plates were subjected to brine spray and pencil hardness tests with the results shown in Table 5.

TABLE 1

Physical properties Weight tatio of PPS/PI in Pencil hardness Heat resistance Brine spray Adhesion undercoat test strength composition 23 C 200 C 300 C x 30 hrs 390 C x 10 hrs (200 hrs) (kg/cm) 100/0 2H 2B 2H H no blister 2.5 100/5 2H HB 2H H " 2.7 100/10 2H F 2H H " 3.0 100/30 2H H 2H H " 3.4 100/50 2H H 2H HB " 3.6 0/100 3H 2H 2H B slighly 3.9 blistered TABLE 2

Physical properties Weight tatio of PPS/PI in Pencil hardness Heat resistance Brine spray Adhesion undercoat test strength composition 23 C 200 C 300 C / 30 hrs 390 C / 10 hrs (200 hrs) (kg/cm) 100/0 H 2B H H no blister 2.5 100/5 H HB H F " 2.8 100/10 2H H 2H F " 3.2 100/30 2H H 2H HB " 3.3 100/50 2H H 2H HB " 3.7 Comparative largely Example H F B < 2B blistered 2.2 TABLE 3

Weight ratio Physical properties of PPS/PAI in undercoat Pencil hardness Heat resistance Brine spray test Adhesion strength composition 23 C 390 C x 10 hrs (200 hrs) (kg/cm) 100/0 H H no blister 2.9 100/10 H F " 3.4 100/50 H HB " 3.8 0/100 2H HB slightly 4.2 blistered Comparative H H largely 2.5 Example blistered TABLE 4

s m o co 's o ,C 0 sa > Adhesion ,x hardness Heat D D W um 3a, First layer Second layer room temperature 39O0C x c w ~ ~ ~ ~ -e' .o PPS/PAI titanium ~~ ~ (100/10) chelate ..

a o H H no blister 2.3 (d Pm 06 t = v v chelate H < 2B largely 2.0 W composition oU blistered EK-4 )8GY e"' lithium 3:C CY s Ê = S :2 v c E CL W c Pc e . c c E c r O c < < c ~ E O W X òO w U 6 o rx ~v = w: O '~ t^ v aldwexg aldwexg aA!leledw D TABLE 5

Physical properties Pencil hardness (230C) Weight ratio room Brine spray test Test No. of PPS/PAI temp. 2000C (24hrs) 1 1/6 3H 2H blistered 2 1/3 3H 2H slightly blistered 3 1/1 4H 2H no blister 4 5/1 5H H 5 20/1 5H H 6 50/1 5H F 7 100/1 5H 2B WHAT WE CLAIM IS: 1. An article having a substrate provided in the following order with: an undercoat comprising a polyarylene sulphide resin; A primer coat derived from a fluorocarbon polymer-containing primer composition; and a fluorocarbon polymer topcoat.

2. An article according to Claim 1, wherein said fluorocarbon polymer topcoat consists essentially of a fluorocarbon polymer selected from homopolymers of tetrafluoroethylene and copolymers of tetrafluoroethylene.

3. An article according to Claim 1 or Claim 2, wherein the undercoat is formed by applying an undercoat composition comprising a polyarylene sulphide resin on to the substrate, drying the applied composition and baking the dried composition at a temperature of 330 to 4000 C.

4. An article according to any preceding claim, wherein said fluorocarbon polymer-containing primer composition includes a binder selected from chromic acid, organic chelate compounds of transition metals of group IV, synthetic resins other than fluorocarbon polymers which resins have miscibility with the fluorocarbon polymers and are stable at a temperature of at least 1500C, mixtures of.

inorganic oxides and phosphoric acid, alkali metal silicates, amine silicates, and colloidal silica.

5. An article according to any preceding claim, wherein the undercoat further comprises at least one imido-containing resin selected from polyamideimide resins and polyimide resins.

6. An article according to Claim 5, wherein the ration by weight of the polyarylene sulphide resin to the imido-containing resin ranges from 20: 1 to 1:2.

7. An article according to any preceding claim, wherein said polyarylene sulphide resin is a polyphenylene sulphide resin.

8. An article according to Claim 1 and substantially as hereinbefore described with reference to the Examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   TABLE 5

   Physical properties Pencil hardness (230C) Weight ratio room Brine spray test Test No. of PPS/PAI temp. 2000C (24hrs) 1 1/6 3H 2H blistered 2 1/3 3H 2H slightly blistered 3 1/1 4H 2H no blister 4 5/1 5H H 5 20/1 5H H 6 50/1 5H F 7 100/1 5H 2B WHAT WE CLAIM IS: 1.An article having a substrate provided in the following order with: an undercoat comprising a polyarylene sulphide resin; A primer coat derived from a fluorocarbon polymer-containing primer composition; and a fluorocarbon polymer topcoat.
2. 2. An article according to Claim 1, wherein said fluorocarbon polymer topcoat consists essentially of a fluorocarbon polymer selected from homopolymers of tetrafluoroethylene and copolymers of tetrafluoroethylene.
3. 3. An article according to Claim 1 or Claim 2, wherein the undercoat is formed by applying an undercoat composition comprising a polyarylene sulphide resin on to the substrate, drying the applied composition and baking the dried composition at a temperature of 330 to 4000 C.
4. 4. An article according to any preceding claim, wherein said fluorocarbon polymer-containing primer composition includes a binder selected from chromic acid, organic chelate compounds of transition metals of group IV, synthetic resins other than fluorocarbon polymers which resins have miscibility with the fluorocarbon polymers and are stable at a temperature of at least 1500C, mixtures of.

   inorganic oxides and phosphoric acid, alkali metal silicates, amine silicates, and colloidal silica.
5. 5. An article according to any preceding claim, wherein the undercoat further comprises at least one imido-containing resin selected from polyamideimide resins and polyimide resins.
6. 6. An article according to Claim 5, wherein the ration by weight of the polyarylene sulphide resin to the imido-containing resin ranges from 20: 1 to 1:2.
7. 7. An article according to any preceding claim, wherein said polyarylene sulphide resin is a polyphenylene sulphide resin.
8. 8. An article according to Claim 1 and substantially as hereinbefore described with reference to the Examples.