Phenolic Varnishes, Insulating Compositions and Paints/Enamels based on Cardphenol (Technical Note: C - 16B)Card-Phenol popularly known as Cardanol is the active constituent of Cashew Nut Shell Liquid and is a monohydroxy phenol with a long Hydrocarbon side chain substituted in the meta position. It is manufactured from CNSL by a special process and serves as an excellent raw material for the preparation of high grade varnishes, Paints, Enamels and Insulating Compositions from its resins by the conventional methods or directly by the institutional processes. Its side chain contains on an average two unsaturated double bonds which contribute to easy linking and hence give better drying and baking properties to its compositions than those based on short chain substituted phenols such as Para-tertiary butyl and amyl phenols. The films of the Varnishes have high electric insulation and are highly resistant to water and chemicals. The long substituted chain leads to good flexibility of the film and also better compatibility with the drying oils. Cardphenol is available in two grades namely Standard and Special. The Standard grade has pale colour and is more suitable for baking or overnight drying compositions. Cardphenol Special, which has straw colour, is recommended for fast air drying compositions.
When Special grade is used in making Varnishes a reduction of more than 5% in drying time is obtained compared with Standard grade.
The coating can be prepared as usual from the phenolic resins based on Cardphenol or directly in one step by the institutional process where the need for preparing resins separately is avoided. The following formulations are given only as an illustration of the compositions based on Cardphenol. Similar compositions are more easily made with a ready made pure phenolic Resins namely Silex-55 which is based on a Co-polymer of Cardphenol & Styrene. The compositions based on Silex-55 have still better drying time film properties and Electric insulation. For details regarding Silex-55, kindly ask for our Technical note No. ST11. Modifications can be made in these formulations to suit specific requirements. We will be pleased to offer our assistance in such development work.
Cardphenol is heated to 130°C and Hexamine is added slowly for ½ an hour and the temperature is raised to 150°C and maintained at that temperature till the smell of ammonia ceases out and a string of 12” is obtained. Cobalt Octoate (3.5 parts) and manganese napthanate (3 parts) are added and the product is thinned with white spirit to 50% non-volatile and kept for atleast 48 hours for ageing. The film attains a hardness of about 950 gms. Within 4 to 5 hours with Special grade of Cardphenol and within 7 to 8 hours with the Standard Grade. It has comparatively poor flexibility but has better resistance to humidity and chemicals. Its application is recommended on sub-plastered or wood surfaces where the requirement regarding flexibility is not of much consequence.
Hexamine is reacted with Cardphenol at 130 to 140°C as described above. Drying oil and ester gum are added and are cooked at 200 to 240°C till a string of 20” is drawn. It is thinned with white spirit to 70% nonvolatile and driers are added. With Cardphenol Special: The film becomes tack free within about 3 hours and has a baking time at 120°C of about half hour and dries hard under ambient conditions within 5 to 6 hours reaching a scratch hardness of 1100 grams with satisfactory flexibility. With Cardphenol Standard: Airdrying time is longer and baking time at 120°C is about 45 minutes. The varnish (120 parts) is thinned with white spirit to 50% non-volatile and Titanium dioxide (72 parts), Zinc Oxide (8 parts) and Barytes (10 parts) are added and the mixture ground to ¼ Hegmann gauge 8. The film of the light cream colour paint applied on mild steel dries hard within 3 to 4 hours to a glossy finish having scratch hardness of about 1200 grams. It is resistant to water and 5% sodium carbonate solution for 48 hours.
Cardphenol formaldehyde condensate is prepared as in item 3.1 and to it 66 percent long linseed oil alkyd is added and the mixture is cooked at 240-260°C till a string of about 18” is obtained. It is thinned with white spirit to 50 percent non-volatile and driers are added as usual. The film of the varnish with Special grade dries hard to a golden yellow colour in about 4 hours under ambient conditions. The air dried film has scratch hardness of 1100 grams and baked film of 1200 grams. Both the films have satisfactory flexibility and better resistant to water (7 days), 5 percent sodium carbonate solution (7 days), 2 percent sulphuric acid solution (9 days), white spirit and turpentine (7 days). With Standard Grade Cardphenol the use of Medium oil Alkyd is recommended.
Silex-55 is heated up to 140°C and D.C.O. is added and the temperature is raised to 240°C and maintain the temperature till a string of 18-20 inches is obtained. Manganese napthanate (2 parts) and cobalt octoate (3 parts) are used as driers and the material is thinned with white spirit to 50% non-volatile. The film dries to a golden yellow colour in four hours with high gloss and is unaffected by water, 5% sodium carbonate solution and 2% sulphuric acid solution. Thinned steel plate is coated with the varnish in a roller-coating machine by a two-coat system, each time at 190° for 15 minutes. The golden coloured coating is resistant to 5% sodium chloride and 10% sugar solution. One kg cans fabricated from these coated tinned steel plates when filled with chopped garlic in brine, onion in 5% acetic acid solution on peas in water, their mouths sealed and heated in an autoclave at 20 psig for two hours, the film of the lacquer in all the cans are found unaffected by this treatment. Also no smell of lacquer can be detected in water, brine or acetic acid solution. The hardness of the films can be increased from 1100 grams to about 1250 grams if 10% of phenolic resin is added on the total weight of components during its processing. The break-down voltage of the corresponding varnish prepared from linseed stand oil (15 poises) is about 1900 volts per ml. and is excellent as Insulating or Impregnating varnish, (Silex-55 and DCO varnish).
Cardphenol and Hexamine are first reacted at 130°C as usual and butyl titanate is added after the condensate is formed. The temperature is raised to 200°C slowly and the mixture is heated to 250°C to get 12 to 14” string from its cold melts. It is thinned with White spirit to get 50 percent non-volatile. Driers are added as above. Good and hard film with a scratch hardness of about 1200 grams or more is obtained when it is baked for 45 minutes at 120°C. Its resistance to water and chemicals is very satisfactory and is not affected by sodium carbonate (5 percent), sulphuric acid (5 percent), caustic soda (1 percent) and white sprit for about 48 hours. Varnish is highly suitable for use as an electric insulating or Impregnating composition and where high resistance to water and alkali solutions is desired.
Silicone oils are added in small quantity to give the hammer effect. The size of the pattern is varying inversely with the amount of silicone oil. Application of hammer finishes is obtained by spray at higher viscosities then used with conventional paints to minimize sagging on vertical surface. The viscosity range is 50-70 secs in Ford cup No. 4. The articles are then stoved at 140°C for about 30 minutes. Coloured hammer finishes are produced by addition of conventional strainers to the above base paint.
Cobalt and manganese napthanates are added to give 3% cobalt metal and 0.1% manganese metal on the resin solid. Wrinkle finishes of this type are stoved for about 1 hour at 120°C. They are used mainly on instruments of various types and typewriters.
Cardphenol and its derivatives are manufactured by us under rigid and closely controlled process conditions. We have our own well-equipped research and development laboratories and are therefore in a position to provide detailed technical advice and suggestions for the application of this material. Caution: Because we cannot anticipate the conditions under which our product may be used, we do not guarantee the applicability or the accuracy of the above information. Users should make their own tests to determine the suitability of our products for their particular purpose. The products are sold without any such warranty either express or implied. Moreover the above information is not intended as recommendation to use our product in the infringement of any patent. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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