Baking process

Industrial production of copper phthalocyanine usually favors either the phthaUc anhydride—urea process (United States, United Kingdom) (1,52,53) or the (9-phthalodinitrile process (Germany, Japan) (54,55). Both can be carried out continuously or batchwise in a solvent or bake process of the soHd reactants (56). 

Developments in the carbonizing of fabric (77) have been aimed at reducing the volume of acid used (78,79), in order to reduce energy in drying and save neutralization costs, and at the use of generally available textile processing equipment, eg, the padmangle, for appHcation of the acid in a pad-dry-bake process (80). 

The cymidin is now sulphonated, 100 parts by weight of cymidin being slowly added to 69 parts by weight of sulphuric acid (sp. gr. 1 84), contained in a shallow dish, and the solid crystalline mass of cymidin sulphate thus obtai ed is then converted into cymidin sulphonic acid by an identical method to that tised in the so-called baking process for the preparation of stilphanilic acid from aniline sulphate. 

Sanding is carried out at this stage and, after clean-up, the final colour or top-coat is applied. There is some variation in the resin chemistry used. Alkyds crosslinked with melamine-formaldehyde are widely used for non-metallic pigmentation. Metallics are usually based on acrylics for better durability. The acrylic may be thermoset with melamine-formaldehyde or a thermoplastic lacquer (plasticised copolymer of methyl methacrylate). A thickness of about 50ftm is applied and stoved for 20 min at 130°C (lacquers receive a bake-sand-bake process for a smoother appearance). 

Bakers often use additives to change the dough in certain ways and give themselves more control over the baking process. 

The manufacture of sulfur dyes involves sulfurisation processes, the chemistry of which remains rather mysterious and may arguably be considered still to be in the realms of alchemy The processes involve heating elemental sulfur or sodium polysulfide, or both, with aromatic amines, phenols or aminophenols. These reactions may be carried out either as a dry bake process at temperatures between 180 and 350 °C or in solvents such as water or aliphatic alcohols at reflux or at even higher temperatures under pressure. C. I. Sulphur Black 1, for example, is prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

The physical properties of automotive enamels are in large part determined by the crosslink structure developed in the paint films during the baking process. Enamels which are not cured sufficiently (undercured) are generally sensitive to humidity and solvents. In addition, they may be prone to chipping and cold cracking. Faints which have been baked excessively (overcured) exhibit intercoat adhesion failure. That is, subsequent coats... 

The one stage of the baking process that can easily be worked continuously is baking. The bread is fed into a tunnel oven and emerges baked at the other end. 

Pacu, common and scientific names, 3 187t Pad-bake process, 8 25 Pad-batch dyeing, cold, 9 177-178 Padding, 9 165... 

Aromatic aminosulfonic acids, which play a major role in connection with pigment lakes, are produced by sulfonating the corresponding nitro compound and then reducing it to an aminosulfonic acid. An alternative technique, known as baking process, involves exposing an amine/dihydrosulfate to a temperature of 200 to 300°C in order to effect rearrangement to p-aminosulfonic acid. Ortho-sulfonation prevails if the para position is occupied. In contrast to sulfonation techniques with sulfuric acid, this method avoids wastewater contamination with sulfuric acid. 

The first technical process involved heating phthalonitrile with copper bronze or copper(I)chloride at 200 to 240°C in copper pans. Several variations of this technique were developed in Germany prior to the Second World War. The reaction was performed either without or in the presence of a solvent. A basic distinction is commonly made between the baking process and the solvent process both may be carried out either by continuous or by batch technique. 

The solvent method may also be performed either by continuous (in cascades) or by batch operation. Continuous techniques in particular have gained considerable technical importance. A phthalonitrile/copper chloride solution is typically treated at 120 to 140°C in a flow tube furnace and the temperature subsequently increased to 180 to 250°C. The entire process requires approximately 1.5 to 2 hours and affords the pigment in practically quantitative yield. The excellent purity of the product eliminates the need for additional purification with dilute acid or base prior to finishing, a procedure which plays a major role in the baking process. These... 

The first commercial copper phthalocyanine synthesis, a baking process, involved melting phthalic anhydride with urea at 150°C in the presence of boric acid. Cop-per(II)chloride was then added and the temperature increased to approximately 200°C until the copper phthalocyanine production was completed. The reaction mixture was cooled and the crude product milled. After being washed, first with dilute sodium hydroxide solution and then with dilute sulfuric acid, the material was filtered off and dried. The crude copper phthalocyanine obtained was then... 

The baking process has remained much the same until the present day at a stoichiometric ratio of 1 4, phthalic anhydride or phthalic acid reacts with an ammonia releasing compound. The reaction may also start from other suitable materials, such as phthalic acid derivatives, including phthalic acid esters, phthalic acid diamide, or phthalimide. Appropriate ammonia releasing agents include urea and its derivatives, such as biuret, guanidine, and dicyanodiamide. The fact that a certain amount of urea decomposes to form side products makes it necessary to use excess urea. Approximately 0.2 to 0.5, preferably 0.25 equivalents of copper salt should be added for each mole of phthalic anhydride. 0.1 to 0.4 moles of molybdenum salt per mole of phthalic anhydride is sufficient. The reaction temperature is between 200 and 300°C. 

The baking process, particularly the batch variety, presents a number of serious disadvantages. Not only does the reaction produce solid urea decomposition products, but it also releases large amounts of ammonia and ammonium salts which escape by sublimation. The foam which is thus formed makes for a porous reaction mixture, which in turn even prevents heat conduction. Moreover, the reaction mixture tends to adhere to the surface of the reaction vessel and the stirring unit a phenomenon which adds to the complexity of the problem. 

On the other hand, economically advantageous routes by continuous baking process have also been described in recent years. The processes are carried out in self-cleaning mixing apparatus such as double screw extruders. More recent patent literature claims yields as high as 80%. 

The solvent is removed from the solid product by filtration or centrifugation to afford a crude Copper Phthalocyanine Blue of a quality that makes intermediate purification unnecessary. In contrast to the product obtained by the baking process, this material is pure enough to be used directly for further pigment manufacture. Crude Copper Phthalocyanine Blue, on the other hand, which evolves as the solvent is removed by distillation, contains so many impurities that it must be boiled before being utilized further. 

Phthalic anhydride and urea, together with copper(I)chloride and ammonium molybdate, are heated to 200°C in trichlorobenzene. The ratios between the components are the same as in the baking process. Carbon dioxide and ammonia are released to yield Copper Phthalocyanine Blue. The reaction is complete after 2 to 3 hours, producing a yield between 85% and more than 95%. 

On a technical scale aniline is heated with one mole only of H2S04, i.e. as acid sulphate the temperature is about the same as that given above. (The baking process.) Compare this process, which can also be used in the laboratory, with that here described. 

Aniline is very easily sulphonated, for example, by heating its sulphate ( baking process). This change recalls that of aniline acetate into acetanilide. Actually, it is very probable that an analogous product acylated at the amino-group, a sulphaminic acid, is first formed, since examples of this type of change are known, e.g. the conversion of phenylhydroxylamine to p-aminophenol and of phenylnitramine to... 

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