Other Polymer Polyols

In the practice, the most important polymer polyols are graft polyether polyols, PHD and PIPA polyols, but other good quality polymer dispersions in liquid polyethers have been created, which at this moment are not industrially important, such as  

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Uses. Neopentyl glycol is used extensively as a chemical intermediate in the manufacture of polyester resins (see Alkyd resins), polyurethane polyols (see Urethane polymers), synthetic lubricants, polymeric plasticizers (qv), and other polymers. It imparts a combination of desirable properties to properly formulated esterification products, including low color, good weathering and chemical resistance, and improved thermal and hydrolytic stabiUty. 

Another family of polyols is the filled polyols.llb There are several types, but die polymer polyols are die most common. These are standard polyether polyols in which have been polymerized styrene, acrylonitrile, or a copolymer thereof. The resultant colloidal dispersions of micrometer-size particles are phase stable and usually contain 20-50% solids by weight. The primary application for these polyols is in dexible foams where the polymer filler serves to increase foam hardness and load-bearing capacity. Other filled polyol types diat have been developed and used commercially (mainly to compete with die preeminent polymer polyols) include the polyurea-based PEID (polyhamstoff dispersion) polyols and the urethane-based PIPA (poly isocyanate polyaddition) polyols. 

The most important radical initiators used for polymer polyol synthesis are azoderivatives, such as azoisobutyrodinitrile (AIBN) [1, 3,13, 22]. Other initiators used successfully are peroxides (tert-amyl peroxides are very efficient), hydroperoxides and percarbonates, but the half life has to be lower than two minutes, at the polymerisation temperature (115-125 °C) [23-28]. 

Thus, the transfer agents commonly used are mercaptans (for example tert-dodecylmercaptane [62]), enol-ethers [63], carbon tetrachloride [64], isopropyl alcohol [56, 65], triethyl amine [38], and diethylamine, ethyl benzene toluene [66]. Tert-dodecylmercaptane is a very efficient transfer agent but, even used at very low concentrations (0.1-0.3%), generates an unpleasant odour (characteristic of mercaptans) in the final polymer polyol. This is the reason why other transfer agents, without unpleasant odour but with a modest transfer efficiency, are preferred, such as isopropyl alcohol, which needs to be used in higher concentrations (4-8% against final polymer polyol) ... 

Different PET chemolysis methods have been developed aimed at the production of TPA, DMT or BHET, all of them being possible monomers for the reconstruction of fresh polyesters. The exact monomer formed by PET depolymerization depends on the type of chemical agent used to break down the polymeric chains. In certain processes, the final product of PET chemolysis is a mixture of polyols, useful in the formulation of other polymers such as unsaturated polyesters, polyurethanes and polyisocyanurates. This is an interesting case of chemical recycling because the breakdown of one polymer leads to the raw materials for the preparation of a quite different class of plastics. 

These "polymer-polyols" are made by the in situ polymerization of vinyl monomers such as acrylonitrile (although grafting with other monomers has also been reported in a liquid polyol solution, e.g., polyether triol of molecular weight 3000) to give stable dispersions of the polymeric portion in the liquid polyol. Grafting is carried out with azobis(isobutyronitrile) or dibenzoyl peroxide as initiators at 80-90 °C. A polymer-polyol containing about 20% acrylonitrile appeared to be the best compromise between polyol viscosity and urethane foam properties (108). 

Both polymer-polyols as well as PUD polyols can be considered "reinforced" polyols since a number of physical properties as well as processing characteristics are enhanced. Both of the above types of polyols have been widely used in RIM and HR-foams but are finding applications also in other urethane fields. 

Rapid and intensive mixing, and a combination of turbulent and laminar flows, enables the acceleration of monomer polymerisation, an increase in its depth, and exclusion of large particle formation in the polyester. This defines the dispersing stability not only for polymer-polyol but for other compositions of polyol dispersions, and results in highly flexible polyurethane foam processability and a high quality of moulded articles. Some properties of polymer-polyol and flexible polyurethane foam are given in Tables 5.6 and 5.7 [27]. 

Chemistry Polyurethane is produced by the reaction of a polyol with an diisocyanate (or in some instances a polyisocyanate) in the presence of catalysts. The polyols of choice are poly(propylene glycol), block copolymers of ethylene oxide (10-15%) with propylene oxide, or the newer polymer polyols (based on polymers such as polystyrene or styrene-acrylonitrile copolymer). Polyester diols such as polycaprolactone diol can be used in place of the polyether polyol in this reaction. The isocyanate of choice is a mixture of the 2,4 and 2,6 isomers of tolylene di-isocyanate in the ratio of 80 20, generally referred to as 80 20TDI. Other isocyanates such as diphenylmethane di-isocyanate (MDI), hexamethylene di-isocyanate (HMDI), and isophorone di-isocyanate (IPDI) are also used. A tin-based or amine catalyst is used to promote the reaction. Given the wide choice of reactants available, the reaction can yield foams with a range of different mechanical and thermal characteristics. 

A practical route to reduce the effects of photo-degradation in PUs (as in the case of other polymers) is the addition of suitable light stabilizers by different ways. The most used procedure is the additive stabilization method. A more effective method to increase the maintenance of the stabilizer in the polymer is the chemical bonding of these compounds to the macromolecular chain even in the course of polyurethane synthesis. Some attempts to introduce in such way the stabilizers in polymers are known. Thus, a benzotriazole UV absorber was mixed with a prepolymer containing isocyanate groups and the chain extender directly into moulding machine (cone. 0.5%) [64, 323]. The stabilizer can be also mixed into polyol component before its reaction with the isocyanate component. The stabilizer that usually contains OH groups could form chemical bonds with the macromolecular chain in some extent [324]. 

A general class of lubricants is alkyl acids and their derivatives (esters, amides, alcohols, and metallic salts). Esters, including fatty esters, polyol esters, and wax esters, are reasonably compatible with PVC. They are also used in polystyrene and acrylic polymers. High-molecular-weight esters are used as external lubricants, and low-molecular-weight esters are used as internal lubricants. Simple primary fatty amides possess unique mold-release properties and are used as slip and mold-release agents for polyolefins and other polymers. The more complex bisamides, such as ethylene bis-stearamide, offer mold release as well as internal and external lubricity in materials such as PVC and ABS. Fatty alcohols are used primarily in rigid PVC. They are used as both internal and external lubricants, and they are useful when clarity is important. 

C. Acrylonitrile can be found as a liquid or vapor, and can also be found in polymer resins, rubbers, plastics, polyols, and other polymers having acrylonitrile as a raw or intermediate material. 

The urethane methacrylate polymer which contains no soft-block and the ethoxylated bisphenol A/MMA copolymer both have relatively low values of K q and their composites have fracture toughnesses approximately double that of the respective polymer. The urethane methacrylate polymer which contains a polyol soft-block, on the other hand, has a fracture toughness which is approximately twice that of the other polymers, but for the composite Kiq is increased only modestly. Thus, the higher the fracture toughness of the polymer then the less is the fracture toughness of the particulate composite enhanced relative to it. 

This reaction is a tool to introduce multifunctionality into an oleochemical. The methyl ester of oleic acid can be epoxidized and reacted in the above-mentioned manner. A large variety of polyols (e. g., by reacting epoxidized soybean oil with aleohols) are available for making polyurethanes and other polymers ( polymers from fats and oils) with interesting properties. E. can be rearranged to form keto-compounds (- keto fatty acids). 

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