Phenolic applications, coatings

NB Daia for the three important ihermosetting materials (phenolics, aminoplastics and epoxide resins) were not covered in the 1998 review on which the 1997 data was based. The 1987 figures for these materials do include a substantial percentage of use in adhesive, surface coating and laminate applications. 

The main application of poly (vinyl formal) is as a wire enamel in conjunction with a phenolic resin. For this purpose, polymers with low hydroxyl (5-6%) and acetate (9.5-13%) content are used. Similar grades are used in structural adhesive (e.g. Redux) which are also used in conjunction with phenolic resin. Poly(vinyl formal) finds some use as a can coating and with wash primers. Injection mouldings have no commercial significance since they have no features justifying their use at current commercial prices. 

The term aminoplastics has been coined to cover a range of resinous polymers produced by interaction of amines or amides with aldehydes. Of the various polymers of this type that have been produced there are two of current commercial importance in the field of plastics, the urea-formaldehyde and the melamine-formaldehyde resins. There has in the past also been some commercial interest in aniline-formaldehyde resins and in systems containing thiourea but today these are of little or no importance. Melamine-phenol-formaldehyde resins have also been introduced for use in moulding powders, and benzoguanamine-based resins are used for surface coating applications. 

At one time urea-formaldehyde was used extensively in the manufacture of plywood but the product is today less important than heretofore. For this purpose a resin (typically U-F molar ratio 1 1.8)-hardener mixture is coated on to wood veneers which are plied together and pressed at 95-110°C under pressure at 200-800 Ibf/in (1.38-5.52 MPa). U-F resin-bonded plywood is suitable for indoor application but is generally unsuitable for outdoor work where phenol-formaldehyde, resorcinol-fonnaldehyde or melamine modified resins are more suitable. 

Epoxy phenolic coatings These materials are also cured at relatively high temperatures and are made by the reaction of the epoxy resin with the phenolic resin. They are slightly less critical in application requirements, are less sensitive to curing conditions and can be applied in thicker coats. The best use for both these materials is as tank linings used for the storage or food products, drinks, etc. or for process plant, evaporators, etc. that contain boiling water. 

The production test showed that the epoxy phenolic enamel was the preferred enamel for coating tinplate containers used in packaging irradiation-sterilized ham and beef. The preferred end-sealing compound for the same application was the blend of cured and uncured isobutylene-isoprene copolymer. 

Cardanol, a main component obtained by thermal treatment of cashew nut shell liquid (CNSL), is a phenol derivative having mainly the meta substituent of a C15 unsaturated hydrocarbon chain with one to three double bonds as the major. Since CNSL is nearly one-third of the total nut weight, a great amount of CNSL is obtained as byproducts from mechanical processes for the edible use of the cashew kernel. Only a small part of cardanol obtained in the production of cashew kernel is used in industrial fields, though it has various potential industrial utilizations such as resins, friction-lining materials, and surface coatings. Therefore, development of new applications for cardanol is very attractive. 

The CB sheet is coated on the back with microcapsules 5 to 10 pm in diameter, in which leuco dye solution in a nonvolatile solvent is contained. The CF sheet is coated on the front with an acidic coreactant such as reactive clay, zinc salt of salicylic acid derivatives, zinc-modified phenolic resin, etc. On the application of pressure, the microcapsule is ruptured in the area delineated by the pressure pattern, and the leuco dye solution is thereby transferred to the CB sheet to bring about a color-forming reaction with acidic coreactant resulting in a distinct image on the surface of the CF sheet. By inserting a middle sheet (or sheets) called the CFB sheet, which is coated on the front and back with acidic coreactant and microcapsules, respectively, multiple copies can be obtained. 

Phenolic novolacs, 18 760-761 Phenolic resin adhesives, 18 783-784 Phenolic resin can coatings, 18 38 Phenolic resin composites, 18 792-794 Phenolic resin drying-oil varnishes, 18 783 Phenolic resin fibers, 18 797-798 mechanical properties of, 18 798 Phenolic resin foam, 18 795-796 Phenolic resin manufacturers, U.S., 18 774 Phenolic resin polymerization, 18 760-765 alkaline catalysts in, 18 762-765 neutral catalysts in, 18 761-762 strong-acid catalysts in, 18 760-761 Phenolic resin prepregs, 18 793 Phenolic resin production unit, 18 766 Phenolic resins, 10 409 18 754-755, 756-802 22 10 26 763 in abrasive materials, 18 786-787 in air and oil filters, 18 790 additional reactants in, 18 759 analytical methods for, 18 774-779 applications of, 18 781-798 batch processes for, 18 766 from biomass and biochemical processes, 18 769-770... 

Tertiary amines such as benzyldimethylamine, 2-(dimethyl aminoethyl) phenol, etc. form an anion with epoxide which leads to their polymerisation. These are used mainly for adhesives and surface coating applications. 

In the development of a reactive non-chrome post-treatment, a variety of phenolic resins were synthesized and commercial phenolic resins evaluated. It was found that phenol-formaldehyde resins, creso1-forma1dehyd e condensates, ortho-novo 1 ak resins, and phenol-formaldehyde emulsions gave positive results when employed as post-treatments over zinc and iron phosphate conversion coatings. The above materials all possessed drawbacks. The materials in general have poor water solubility at low concentrations used in post-treatment applications and had to be dried and baked in place in order to obtain good performance. The best results were obtained with poly-4-vinylphenol and derivatives thereof as shown in the following structure (8,9,10)... 

There are important modifications of alkyds that help in specific applications. Phenolics can be added to improve film hardness and water resistance, but these confer increased yellowing tendencies on the final coating. Silicones impart heat resistance and exterior durability. Styrene increases the drying speed. Methyl methacrylate when added gives faster drying properties and improves the color and durability of the coating. 

When two polymeric systems are mixed together in a solvent and are spin-coated onto a substrate, phase separation sometimes occurs, as described for the application of poly (2-methyl-1-pentene sulfone) as a dissolution inhibitor for a Novolak resin (4). There are two ways to improve the compatibility of polymer mixtures in addition to using a proper solvent modification of one or both components. The miscibility of poly(olefin sulfones) with Novolak resins is reported to be marginal. To improve miscibility, Fahrenholtz and Kwei prepared several alkyl-substituted phenol-formaldehyde Novolak resins (including 2-n-propylphenol, 2-r-butylphenol, 2-sec-butylphenol, and 2-phenylphenol). They discussed the compatibility in terms of increased specific interactions such as formation of hydrogen bonds between unlike polymers and decreased specific interactions by a bulky substituent, and also in terms of "polarity matches" (18). In these studies, 2-ethoxyethyl acetate was used as a solvent (4,18). Formation of charge transfer complexes between the Novolak resins and the poly (olefin sulfones) is also reported (6). 

The thermal stability of epoxy phenol-novolak resins is useful in adhesives, structural and electrical laminates, coalings, castings, and encupsulalions for elevated temperature service. Filament-wound pipe and storage lanks. liners liir pumps and other chemical process equipment, and conosion-resisiant coatings are typical applications using the chemically resistant properties of epoxy novolak resins. 

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