Dimer acid-based polyesters

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Chem. Descrip. Dimer acid-based polyester polyol Uses Modifier (increases flexibility, impact resist., toughness, hydrolytic stability) for industrial coatings (automotive, coil, textile, leather, wood lacquers) building block for PU elastomers, primers, sealants, elastic coatings... 

Dimer acid-based polyesters are mainly the condensation products of di- or polyfunctional hydroxy compounds and dimer acid. The dimer acid-based polyester originated back in the 1940s [55-57] and gained enough commercial importance because of their fine properties. Polyesters with a wide spectrum of properties can be obtained. These polyesters derive their distinctive physical properties—like flexibility and resistance to heat, corrosion, and chemicals—from dimer acids used in their production. In addition to simple polyesters, many copolyesters based on... 

Due to adhesion and flexural properties, the dimer acid-based polyesters are used as lubricants, adhesives and formed the basis of flexographic inks and heat seal coatings. They are used as vibration dampers when sandwiched between metal sheets [58]. 

Several papers and patents on polyesterification of dimer acid with various glycols under different experimental conditions appeared in the literature. The dimer acid-based polyesters with a slight variation in composition enjoy a variety of applications. Observations show that a particular property of the product can be enhanced or suppressed by the choice of a proper additive. 

The method and apparatus employed for the synthesis of dimer-acid based polyesters with butanediol, as well as for metal polyesters of dimer acid and butanediol, was the direct condensation technique [91,97]. Provisions were made to control the reaction temperature and to remove the volatile byproducts (such as stirring and continuous flow of inert gas Nj). 

Dimer acid-based polyesters being used as thermoplasts, thermoset, and elastomers are used in large quantities as adhesives and coatings. The polyesters, as we have reported herein, may have various commercial applications. Owing to the flexural properties, these low molecular weight linear polyesters of dimer acid may be used as plasticizers providing internal lubrication for various polymers, such as polyimides and inorganic coordination polymers, which may have very poor processibility. 

Dimer acid-based hot melt adhesives with good adhesion to metal were used for adhering side seams in tin cans [72-75). Phenolic -OH group-containing polyester and a polyolefin were reacted to give graft copolymers useful as adhesives [76]. 

All these studies show that many dimer acid-based polymers are based on the flexural and adhesion properties of dimer acid. A considerable amount of work has been reported on polyesters as well as other polymers. Among the polyesters based on dimer acid s versatile composition are those used to achieve high performance speciality polyesters. Efforts are made only to increase molecular weight little effort has been made to prepare polyesters of low molecular weight useful as plasticizers. A couple of references [88,89] describe the preparation of plasticizers comprising glycidyl esters of dimer acid and epoxy resin compositions containing them. 

It is quite apparent from the state-of-art of the subject that a variety of dimer acid-based polymeric systems has been investigated from the viewpoint of commercial applications. However, their plasticizing polyester still are known on a limited scaie also, no research in the area of metal containing dimer acid polyesters has been done. The kinetics of the polyesterification of dimer acid with different polyhydroxy compounds was studied by Bajpai and Nivedita [90-94]. 

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

Dimer and trimer alcohols introduced into the structure of PU confer on them very high hydrophobicity, water repellency, flexibility and chemical stability. The polyester urethanes based on dimeric diols and dimeric acids are the most hydrolysis resistant polyester urethanes known so far [73]. 

Table 11.2 gives a survey about major use areas for adhesives based on renewable sources. The share of renewable raw materials in the sealants market is well below 5%. Numbers in Table 11.2 do not include polyurethanes containing oleochemical-based polyols, vegetable oil-based polyesters and polyamides based on dimer fatty acids in total estimated at 35 mto in 2006, 42 mto in 2010. Projection into 2010 shows that without disruptive innovations the share of natural-based adhesives will further decline to a mere 15% in total. 

A distinct set of hot-melt adhesives are designed through synthetic rather than formulation means. Thus, polyesters and polyamides are synthesized with appropriate monomers to provide the desired performance. The polyester chemistry used to make these hot-melt adhesives is the same as that used to make polyester film and fiber but the molecular weight is usually lower and the mixtures of diols and diesters are chosen to control crystallinity and flexibility. One class of monomers used to make polyamide amide hot melts is based on dimer acids that are made from natural products. 

Polyesters or polyamides fi om unsaturated fatty acids diamines or dimer diol-based glycols... 

The commercial polyester elastomers are mostly based on poly(tetrameth-ylene oxide) (PTMO) as flexible segment and poly(butylene terephthalate) (PBT) as rigid segment. Yet, many chemical modifications of some particular segments and also segments of totally different chemical structure have been examined and applied. Thus, in addition to PTMO [1,2,11-16], poly(ethylene oxide) (PEO) [17-22], poly(aliphatic oxide) (C2-C4) copolymers [23-30], poly (butylene succinate), and other aliphatic polyesters [31-35], polycaprolac-tone (PCL), polypivalolactone (PVL) [36,37], aliphatic polycarbonates (PC) [38-41], dimerized fatty acid (DFA)-based polyesters [42-50], polyamide 66 and derivatives [47-57], polyolefins [58-60], rubbers [61-63], and polydimethyl-siloxane [64,65] are used as flexible segments of polyester elastomers. 

Powder coatings are formulated from the reaction product of trimethylolpropane and IPDI, blocked with caprolactam, and polyester polyols. The saturated polyester polyols are based on aromatic acid diols, neopentyl glycol, and trimellitic anhydride for further branching. To avoid the release of caprolactam in the curing reaction, systems based on IPDI dimer diols are used. 

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