Hydroxyl-polyurethan

As far as component A is concerned, these adhesives consist of a hydroxyl-polyurethane dissolved in a solvent, with a polyisocyanate, also in the liquid state, admixed as component B. The crosslinkage thus possible enables higher cohesive strength of the adhesive layer compared to the abovementioned one-component systems, and therefore even higher resistance towards chemical and physical stress. 

In contrast to solvent-based systems, the PUR dispersions (Section 5.4) are characterized by their incombustibility and thus by considerably smoother processing. They are high molecular weight hydroxyl polyurethanes disperged in water. Apart from the physically setting one-component systems, two-component systems are also applied, with component B containing special polyisocyanates that react with the -O-H-groups of the hydroxyl polyurethane in aqueous solution. 

The hydroxyl groups can be esterified normally the interesting diacrylate monomer (80) and the biologicaky active haloacetates (81) have been prepared in this manner. Reactions with dibasic acids have given polymers capable of being cross-linked (82) or suitable for use as soft segments in polyurethanes (83). Polycarbamic esters are obtained by treatment with a diisocyanate (84) or via the bischloroformate (85). 

Uses. The largest uses of butanediol are internal consumption in manufacture of tetrahydrofuran and butyrolactone (145). The largest merchant uses are for poly(butylene terephthalate) resins (see Polyesters,thermoplastic) and in polyurethanes, both as a chain extender and as an ingredient in a hydroxyl-terminated polyester used as a macroglycol. Butanediol is also used as a solvent, as a monomer for vadous condensation polymers, and as an intermediate in the manufacture of other chemicals. 

Polyurethanes. About 3% of the U.S. polyurethanes market in 1988 was derived from the condensation product of polyisocyanates with low molecular weight polyadipates having hydroxyl end groups (195). In 1986 this amounted to 29,000 t, or 4% of total adipic acid consumption. The percentage was similar in Western Europe. About 90% of these adipic acid containing polyurethanes are used in flexible or semirigid foams and elastomers, with the remainder used in adhesives, coatings, and spandex fibers. 

Diester/Ether Diol of Tetrabromophthalic Anhydride. This material [77098-07-8] is prepared from TBPA in a two-step reaction. First TBPA reacts with diethylene glycol to produce an acid ester. The acid ester and propylene oxide then react to give a diester. The final product, a triol having two primary and one secondary hydroxyl group, is used exclusively as a flame retardant for rigid polyurethane foam (53,54). 

Eyrol 51 is a water-soluble Hquid containing about 21% phosphoms. It is made by a multistep process from dimethyl methylphosphonate, phosphoms pentoxide, and ethylene oxide. The end groups are principally primary hydroxyl and the compound can thus be incorporated chemically into aminoplasts, phenoHc resins, and polyurethanes. Eyrol 51, or 58 if diluted with a small amount of isopropanol, is used along with amino resins to produce a flame-retardant resin finish on paper used for automotive air filters, or for backcoating of upholstery fabric to pass the British or California flammabiHty standards. 

Propylene oxide and other epoxides undergo homopolymerization to form polyethers. In industry the polymerization is started with multihinctional compounds to give a polyether stmcture having hydroxyl end groups. The hydroxyl end groups are utilized in a polyurethane forming reaction. This article is mainly concerned with propylene oxide (PO) and its various homopolymers that are used in the urethane industry. 

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

Cationic, anionic, and amphoteric surfactants derive thek water solubiUty from thek ionic charge, whereas the nonionic hydrophile derives its water solubihty from highly polar terminal hydroxyl groups. Cationic surfactants perform well in polar substrates like styrenics and polyurethane. Examples of cationic surfactants ate quaternary ammonium chlorides, quaternary ammonium methosulfates, and quaternary ammonium nitrates (see QuARTERNARY AMMONIUM compounds). Anionic surfactants work well in PVC and styrenics. Examples of anionic surfactants ate fatty phosphate esters and alkyl sulfonates. 

This process is based on the very high reactivity of the isocyanate group toward hydrogen present ia hydroxyl groups, amines, water, etc, so that the chain extension reaction can proceed to 90% yield or better. Thus when a linear polymer is formed by chain extension of a polyester or polyether of molecular weight 1000—3000, the final polyurethane may have a molecular weight of 100,000 or higher (see Urethane polymers). 

Polyurethane foams may be rigid, semi-rigid or flexible. They may be made from polyesters, polyethers or natural polyols such as castor oil (which contains approximately three hydroxyl groups in each molecule). Three general processes are available known as one-shot, prepolymer or quasi-prepolymer processes. These variations lead to 27 basic types of product or process, all of which have been used commercially. This section deals only with flexible foams (which are made only from polyesters and polyethers). Since prepolymers and... 

Polyurethanes are essentially the reaction products of polyisocyanates and polyesters containing free hydroxyl groups. They are comparable with the... 

A urethane is typically prepared by nucleophilic addition reaction between an alcohol and an isocyanate (R—N = C=0), so a polyurethane is prepared by reaction between a cliol and a diisocyanate. The diol is usually a low-molecular-weight polymer (MW 1000 amu) with hydroxyl end-groups the diisocyanate is often toluene-2,4-diisocyanate. 

Example 5. Glycolysis of Polyurethanes with Propylene Oxide after Pretreatment with Ethanolamine.55 A rigid polyurethane foam (ca. 100 g) was dissolved in 30 g ethanolamine by heating. Excess ethanolamine was stripped, leaving a clear solution. Infrared and GPC analysis indicated that the clear solution obtained contained some residual polyurethane, aromatic polyurea, aliphatic polyols, aromatic amines, and N,N -bis(f -hydroxyethyljurea. Next the mixture was dissolved in 45 g propylene oxide and heated at 120°C in an autoclave for 2 h. The pressure increased to 40 psi and then fell to 30 psi at the end of the 2-h heating period. The product was a brown oil with a hydroxyl number of485. 

Polyurethanes are thermoset polymers formed from di-isocyanates and poly functional compounds containing numerous hydroxy-groups. Typically the starting materials are themselves polymeric, but comprise relatively few monomer units in the molecule. Low relative molar mass species of this kind are known generally as oligomers. Typical oligomers for the preparation of polyurethanes are polyesters and poly ethers. These are usually prepared to include a small proportion of monomeric trifunctional hydroxy compounds, such as trimethylolpropane, in the backbone, so that they contain pendant hydroxyls which act as the sites of crosslinking. A number of different diisocyanates are used commercially typical examples are shown in Table 1.2. 

Singer S.M. and Allot M.T., Thermoplastic polyurethane elastomer based on a saturated hydroxyl terminated polyol, difunctional aromatic chain extender and 1,5-naphthalene diisocyanate, US Patent 5 599 874, 1997. 

Both pigmented and unpigmented polyurethane paints have been prepared using a polyester resin containing hydroxyl functional groups and the biuret trlmer of hexamethylenedllsocyanate as a crosslinker. The molar ratio of hydroxyl/isocyanate has been chosen 1.0 and the pig-ment/binder ratio 0.6. 

We can make polyurethanes via one- or two-step operations. In the single-stage process, diols and isocyanates react directly to form polymers. If we wish to make thermoplastic linear polymers, we use only diisocyanates. When thermosets are required, we use a mixture of diisocyanates and tri- or polyisocyanates residues of the latter becoming crosslinks between chains. In the first step of the two-stage process, we make oligomers known as prepolymers, which are terminated either by isocyanate or hydroxyl groups. Polymers are formed in the second step, when the isocyanate terminated prepolymers react with diol chain extenders, or the hydroxyl terminated prepolymers react with di- or polyisocyanates. 

We create polyurethanes from prepolymers by chain extension. In the case of hydroxyl-terminated prepolymers the chain extender is an isocyanate. If we use a diisocyanate, the resulting polymer is linear. If we substitute some or all of the diisocyanate with a tri- or... 

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