Water dispersible alkyds

By depolymerizing PET waste with a polyol and subsequently condensing the oligomeric product with a polycarboxylic acid or anhydride, polyester resins are produced which have wide industrial applications. Depending on the polyol and polycarboxylic acid or anhydride used, saturated resins, alkyd resins, or unsaturated resins are obtained. PET wastes have been used for the production of alkyd resins in water thinnable paints. The materials obtained from the reaction of PET with a mixture of fatty acids high in linoleic acid content and trimethylolethane have been used in the preparation of water-dispersible coatings. Products of the depolymerization of PET with trimethylolpropane and pentaerythritol are used in the manufacture of high-solids paints. In the first step, PET is depolymerized with trimethylopropane and pentaerythritol at temperatures of 230-240°C. The final paint compositions contain 30-50% of PET depolymerization products.12... 

In addition to natural materials, synthetic polymers might also be present in works of art. Since the end of the nineteenth century, synthetic polymers have been produced and used in the field of cultural heritage, to restore works of art [3], but also as paint binders, such as alkyd resins and acrylic water dispersions. Most synthetic polymers can be detected by GC/MS only through thermal degradation followed by GC/MS [4,5] (Chapter 12 deals with the characterisation of synthetic resins in detail). 

Together, antifreeze, PET, and polyester polymers account for about 98% of the ethylene glycol produced in the United States. It is also used sometimes as a deicer for aircraft surfaces. The two hydroxyl groups in the EG molecule also make EG suitable for the manufacture of surfactants and in latex paints. Other applications include hydraulic brake fluid, the manufacture of alkyd resins for surface coatings, and stabilizers for water dispersions of urea-formaldehyde and melamine-formaldehyde The hygroscopic properties (absorbs moisture from the air) make EG useful as a humectant for textile fibers, paper, leather, and adhesives treatment. 

In mixed pigmentations, lecithin additives help to maintain a uniform mixmre in both alkyd and latex paints, ensuring uniform settling in storage. Latex paint redispersion is also made more effective with a water-dispersible lecithin additive than with a synthetic surfactant. Paint specimens with lecithin additives, remixed after 28 months of storage, maintained a very high level of uniform color stability (434). 

An acrylic-alkyd graft copolymer which is water-dispersible was prepared by Walus (30) by copolymerizing methyl methacrylate, butyl methacrylate and methacrylic acid in the presence of an epoxy-modified dehydrated castor oil alkyd which was pre-reacted with lEM. When formulated with NH this gives an air-dry water-dispersible alkyd... 

Modifications are possible to give more unusual properties to the resin. Inclusion of polyethylene glycol as polyol produces an alkyd which is water dispersible. One such alkyd has been used in white spirit-based gloss house paint. This paint can be washed from brushes using a weak detergent solution in water without requiring the use of organic solvent. 

Polyethylene glycols are used to modify alkyds and polyesters to obtain water-dispersible coatings. High-molecular-weight poly(ethylene oxide) is used to thicken chlorinated solvents that are used for paint and varnish removal (64). 

Wiersma et al. at DSM Research, Geleen, The Netherlands [284] described an interesting way of coating textile fibers with CP/polyurethane and CP/alkyd blends from aqueous colloidal dispersions made in a commercially available aqueous resin dispersions. The dispersions included a polyurethane-in-water dispersion (DSM Resins URAFLEX XP 401 UZ, 40% solids content). A variant of the template-type in-situ polymerization was used. After polymerization, the dispersed CP sol could be applied as a coating onto the textile fibers. CPs used included P(Py) and P(ANi). 

Whilst there are some thermoset acrylic emulsions cormnerdally available, the bulk of the thermoset resins, used as the main binder system, are produced in solution. Some may then be made waterborne by neutralisation and inversion (dispersion) into a water phase. Lower molecular weights favour this qrproach. The rate of conversion from solvent based to waterborne industrial thermoset coating systems has been, and is, much slower than the conversion from architectural alkyd paints to emulsion altonatives. There are two principle reasons for this. Firstly there are problems of application and substrate wetting of many waterborne systems. Secondly, the modifications frequently required to induce water dispersibility reduce one or more of the essential performance properties required from the cured film, compared to a solvent based system. Water resistance, with many films having an increased tendency for blushing is one example. However, for some applications, such as electrodeposition, only waterborne systems will work. 

As solvents, the amyl alcohols are intermediate between hydrocarbon and the more water-miscible lower alcohol and ketone solvents. Eor example, they are good solvents and diluents for lacquers, hydrolytic fluids, dispersing agents in textile printing inks, industrial cleaning compounds, natural oils such as linseed and castor, synthetic resins such as alkyds, phenoHcs, urea —formaldehyde maleics, and adipates, and naturally occurring gums, such as shellac, paraffin waxes, rosin, and manila. In solvent mixtures they dissolve cellulose acetate, nitrocellulose, and ceUulosic ethers. 

Both aqueous polymer-based systems (latex), made by emulsion or dispersion polymerization, and oil-modified alkyd resin-based systems are still in wide use [781], Table 12.2 shows the composition of a typical water-based emulsion paint. There is a wide variety of coatings, ranging from broad applicability to highly specialized, including latexes, amino resins, isocyanates, epoxy resins, acrylic resins, polyester... 

Several industrial systems involve emulsions, of which the following are worthy of mention. Food emulsions include mayonnaise, salad creams, deserts, and beverages, while personal care and cosmetics emulsions include hand creams, lotions, hair sprays, and sunscreens. Agrochemical emulsions include self-emulsifiable oils that produce emulsions on dilution with water, emulsion concentrates with water as the continuous phase, and crop oil sprays. Pharmaceutical emulsions include anaesthetics (O/W emulsions), hpid emulsions, and double and multiple emulsions, while paints may involve emulsions of alkyd resins and latex. Some dry-cleaning formulations may contain water droplets emulsified in the dry cleaning oil that is necessary to remove soils and clays, while bitumen emulsions are prepared stable in their containers but coalesce to form a uniform fihn of bitumen when apphed with road chippings. In the oil industry, many crude oils (e.g.. North sea oil) contain water droplets that must be removed by coalescence followed by separation. In oil slick dispersion, the oil spilled from tankers must be emulsified and then separated, while the emulsification of waste oils is an important process for pollution control. 

Disperse colorants Resin dispersions with synthetic resin binders (e. g. alkyd resins, polyurethane resins or polyacrylates), water content 35-45 %, organic solvent mixtures 5-10 %, additional other hydrocarbons 1,2-PG, EG, DPGMM, DEGMM, EGMB, DEGMB... 

Clear lacquers, wood glazings, water thinnable Resin dispersions from water-thinnable alkyd resins, polyurethane resins and polyacrylates, containing 35-85 % water, 5-10 % organic solvents, additional other solvents DEGMB, PGMM... 

Blue stain-preventing paints, water thinnable Fungicide-containing alkyd resin or acryl resin dispersions, est. 3 % organic solvents, additional other solvents Not declared... 

Other water-borne coatings include water-soluble emulsions, dispersions, and latex resins. Water-soluble resins are rare because most resins derived from vegetable oils are insoluble in water. The true emulsions are based on the emulsification of the oil or alkyd through either the action of a surfactant or a resin that has a surfactantlike character. The alkyd emulsions are readily prepared and can be used for OEM coatings and architectural applications. The submicron size droplets are stabilized by the thickeners (El-Aasser Sudol, 2004 Landfester, 2005 Landfester et al., 2004 Tsavalas et al., 2004 Weissenborn Motiejauskaite, 2000a,b). In dispersions, the resin is a solid and is dispersed in water. The latex resin is usually vinyl acetate, styrene, acrylates, or methacrylates radically copolymerized in a micelle to form particles 0.1 pm in diameter (Bloom et al., 2005 Brister et al., 2000 Jiratumnukul Van De Mark, 2000 Thames et al., 2005). 

A further progress perspective in the field of water-based paints could be their use for painting ships [205]. However, these studies are only in the beginning. The main difficulty is corrosion prevention. Maximum protection from stress corrosion cracking is ensured by alkyd paints combined with phenolic epoxy paints during a 6.5-year exposure [206]. These data were obtained on pre-contaminated steel plates. In Russia now water-based dispersion primers with anticorrosive properties have been developed and manufactured [207]. This was possible after incorporation of corrosion inhibitors combined with surfactants into the formulations. 

The stability improvement of Ti02 suspensions is important not only for water-based paints, but also for paints based on non-polar or low-polar solvents. It is shown in [208] that Ti02 powders modified with an anionic surfactant, e.g. sodium dodecyl sulphate, are dispersed to smaller sizes, and their sedimentation stability increases. The production of water-alkyd emulsions is inhibited due to low mechanical stability. These emulsions can easily break when exposed to shear forces such as those produced by pumps, and when intensively agitated during dispersion. [209] demonstrates that most stable emulsions can be obtained with alkyds showing high acid numbers, as well as with highly polymerised alkyds of low viscosities. 

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