Inks and varnishes

subscribe my you tube channel


"brhane amha multimedia "

1. By Brhane Amha Chemical engineering Part -1-printing inks raw materials manufactured stages Ink color, drying &curing The printing process Part-2- industrial polishes introduction application Polishing tools & machines

2. inks

3. Printing ink Inks classify into two: Printing inks and Writing inks Over 90 per cent of inks are printing inks, in which color is imparted by pigments rather than the dyes used in writing inks. Printing inks occupy an integral and versatile position in our daily lives. Used in printing money , newspapers , food packaging , clothes , magazine, greeting cards,

4. Raw material of printing ink Pigment The role of pigment is to color the ink . it can also provide gloss, abrasiveness, and resistance, to attack by light, heat, solvent etc Example of pigments used in inks ;

5. Resins Used to bind the other ingredients of the ink together so that it firm and they bind the ink to the paper.

6. Solvents Are used to keep the ink liquid in order to transfer the ink to the surface to be printed. At this point the solvent must separate from the body of the ink to allow the image to dry and blind to the surface.

7. Additives : Are used to alter the final properties of the paint. These include: Plasticisers which enhances the flexibility of printed film. Wax which promotes rub(friction) resistance. Drier ,which catalyzes the oxidation reaction of inks that dry by oxidation . Chelating agent , which increase the viscosity of ink (aluminum chelate) and promotes adhesion (titanium chelate) Surfactant , which improve wetting of either the pigment or substrate. Alkali , which controls the viscosity/solubility of acrylic resins in water based inks.

8. Inks manufactured Ink manufacture Varnish preparation and Disposal of pigments Step 1 – varnish preparation: Is a mixture of solvent , resins and additives . it wet the pigment particles and binds the pigment to the printed surface. There are two main types of vanishes : oleoresinous and non oleoresinous . Oleoresinous vanish manufacture: this process occurs in closed kettles where the oil and solvent are heated to allow for rapid solutioning or transesterification at the temperatures ranging from 120- 260 for a few minutes to several hours. Non oleoresinous varnisn manufacture: these are simple resin solutions that do not require high temperatures during manufacturing . The process involves breaking up the resins particles and dissolving them in a solvent in either a cavitation or a rotor/stator mixer.

9. Step 2 - Disposal of pigments After the manufacture of vanish, the next step involves mixing or disposal pigments into it. If pigment clumps are formed there have to be broken up with the help of some specially designed equipments for even dispersal of pigments throughout the resin. Three roll mills: consists of a series of roller rotating in opposite directions. the pigment particles that are fed between the roller compressed and crushed.

10. B bead mill : Ink has to be pumped into the chamber and the beads (charge) are set in motion by a series of spinning discs or pins . The beads in motion break up or grind the pigment clumps and provide even dispersal of ink. the dispersed ink is then sieved out off the chamber: the beads remain behind and may be reused. C cavitation mixers : are very efficient in dispersal of pigments such as titanium dioxide.

11. Ink color , drying and curing Color In printing inks, four different colors of ink are employed: cyan, magenta , yellow and black. All other colors can be formed by ‘ overprinting’ these inks. eg red is produced by overprinting yellow and magenta. Cyan, magenta and yellow add together to give brown color . Drying and curing: after its application over the substrate to be printed, the ink undergoes drying or curing by any one or by suitable combination of the following processes. evaporation – some inks dry or cure by evaporation of solvent. Penetration – for porous surfaces, the solvent penetrates into the bulk of the printing surface and dry ink is left on the surface. Oxidation – in case of inks where drying oil is used as solvent, curing occurs by the reaction of atmospheric oxygen with unsaturation of oil. Radiation curing – involves a series of polymerization reactions which are instigated under the influence of radiation.e.g., uv

12. The printing processes ( I)letterpress printing It is a commercial printing technique where many copies of an image are produced by repeated, direct impression of an inked, raised surface against sheets or a continuous roll of paper . Application: Letter press printing is used in commercial operation and specialty operations including business cards, company letterhead, proofs, billheads, forms, posters, embossing, hot leaf stamping and others.

13. ( ii) Screen Printing- Inks do not have to transfer from an image surface to the substrate but actually pass through the image , which is the stencil on the screen. Application: Used in different industries, from clothing to product labels, fabric labels to circuit board printing and others due to its compatibility with a variety of materials, including textiles, ceramics, metal, wood, paper, glass, and plastic.

14. ( iii) Flexography Printing Process: Widely used to print packaging materials , In this technique, from a roll a substrate is fed into the machine and is finally pulled off through a series of printing units and as a consequence of this action the image is printed on the substrate. Each colour is provided by a single printing unit. (Iv) gravure printing process Is used for long run printing with sharper, fine and clear images . Applications include printing magazines, greeting cards, gift-wraps, labels, flexible packaging, cartons and others

15. Part two INDUSTRIAL POLISHES

16. INTRODUCTION Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action, leaving a surface with a significant specular reflection Polishing is one of the oldest processing methods, first used on the making of stone implements.   Polishing  is one finishing loose abrasive process, used to generate surfaces with very high tolerances in geometry, surface integrity, and roughness characteristics . It is still one of the most important finishing methods.

17. Con’t … There are various types of polishes having industrial and domestic applications ; abrasive polish , aluminium polish, motor car polishes, cellulose friction polishes, furniture polishes, leather belt polishes, pine oil metal polish etc …

18. Con’t … Polishing particles remove small elements of a surface and make them smooth. This smoothness is obtained by rubbing the surface with the polishing particles with a rotating disk. Polishing is the best method today to obtain the finest surface. High accuracy and ultra-precision technology are indispensable ingredients for polishing today.

19. Con’t … Polishing uses a larger number of multi point or random cutting edges for effective material removal. Abrasive finishing processes are accepted in a wide range of material applications and industries. Typical examples are: finishing of various components used in aerospace , automotive , mechanical seals , fluid handling , and many others precision engineering industries.

20. Con’t … Polishing is a final process that usually follows lapping to give the final surface characteristics of size, surface roughness, and flatness required for the parts. Polishing is used in many materials from steels to composite ceramics. It does not create a good planarization of the parts which should be done in lapping prior to polishing, since it corrects flatness in low discrepancies not in a big scale.

21. Con’t Polishing is often used to enhance the appearance of an item , prevent contamination of instruments, remove oxidation, create a reflective surface, or prevent corrosion in pipes. In   metallography  and  metallurgy , polishing is used to create a flat, defect-free surface for examination of a metal's  microstructure  under a microscope. Silicon-based polishing pads or a diamond solution can be used in the polishing process. Polishing stainless steel can also increase the sanitary benefits of stainless steel.

22. Con’t … The removal of oxidization (tarnish) from metal objects is accomplished using a metal polish or tarnish remover; this is also called polishing . To prevent further unwanted oxidization, polished metal surfaces may be coated with wax, oil, or lacquer. This is of particular concern for copper alloy products such as brass and bronze .

23. APPLICATIONS Polishing may be used to enhance and restore the looks of certain metal parts or object on  cars  and other vehicles,  handrails ,  cookware , kitchenware , and architectural metal .

24. Con’t …

25. Con’t … In other applications such as pharmaceutical, dairy, and specialty plumbing, pipes are polished to help prevent corrosion and to eliminate locations where bacteria or mold may reside ..

26. POLISHING MATERIALS − calcined alumina − iron oxide   − chromium oxide − diamond   − silicon carbide   − boron nitride − boron carbide − polishing chalk

27. Polishing and tools machines   

28. Typical polishing sequences Start with a hard polishing tool and a coarse paste . Then change to a softer polishing tool with the same paste . Then use a medium-hard polishing tool and a medium coarse paste . Change to a soft polishing tool with the same paste . Finally , use a soft polishing tool and a fine paste.

29. Time-consuming and expensive polishing can be cut by observing certain rules Polishing should be carried out in dust free places. Hard dust particles can easily contaminate the abrasive and ruin an almost finished surface. Each polishing tool should be used for only one paste grade and kept in dust-proof containers. Hands and workpiece should be cleaned carefully between each change of paste grade, the workpiece with a grease solvent and the hands with soap. Paste should be applied to the polishing tool in manual polishing, while in machine polishing, the paste should be applied to the workpiece

30. Con’t … Polishing pressure should be adjusted to the hardness of the polishing tool and the grade of the paste. For the finest grain sizes, the pressure should only be the weight of the polishing tool. Heavy material removal requires hard polishing tools and coarse paste. Finish polishing of plastic moulds should be carried out in the release directional. Polishing should start in the corners, edges and fillets or other difficult parts of the mould . Be careful with sharp corners and edges, so they are not rounded off. Preferably use hard polishing tools

31. THE END THANK YOU FOR YOUR ATTENTION !!!