Extractive reactions with cationic exchange resins as catalysts (acetalization of aldehydes with alcohols)

The acid catalysed acetalization of aldehydes such as formaldehyde, acetaldehyde, glyoxal and glyoxylic acid, with alcohols are reversible reactions. In order to enhance the conversion of aldehydes, extractive reactions were carried out with the alcohols (e.g. 2-ethyl hexanol and n-butanol) having very low to low solubility in water. In such cases alcohols, in addition to being reactants act as extractive solvents for the acetals formed in the reaction. An experimental investigation was carried out using cation-exchange resins (Indion-130, Amberlist-15 and Amberlite IR-120) as catalysts and significant conversion levels were realised for the reactions of formaldehyde and acetaldehyde; results were not encouraging for the extractive reactions of glyoxal and glyoxylic acid. The effect of different parameters, such as catalyst loading, temperature, mole ratio and aqueous phase concentration of aldehyde on the rate of reaction was studied.     

How does the Achiral Base Decide the Stereochemical Outcome in the Dynamic Kinetic Resolution of Sulfinyl Chlorides? A Computational Study

The dynamic kinetic resolution of sulfinyl chlorides by addition of the optically active alcohol DAGOH (diacetone D ‐glucose) in the presence of non‐chiral bases was theoretically studied at the ONIOM (Becke3LYP:UFF) level. The dependence of the stereochemical outcome on the nature of the base observed in this reaction was explored considering two electronically similar bases, pyridine and collidine, that are experimentally known to promote opposite diastereoselectivities. Our calculations reproduced the experimental result that the absolute configuration of sulfur in the major reaction product is R with pyridine but S with collidine. The analysis of the optimized geometries revealed that the most sterically active substituent around sulfur is the methyl of the substrate with pyridine but the base itself with collidine. This leads to an inversion of the chiral distribution of steric hindrance around sulfur that induces the reversal of the stereochemical outcome.     

Phenolic resins with phenyl maleimide functions: Thermal characteristics and laminate composite properties

Phenolic resins bearing varying concentrations of phenyl maleimide functions were synthesized by copolymerizing phenol with N‐(4‐hydroxyphenyl)maleimide (HPM) and formaldehyde in the presence of an acid catalyst. The resins underwent a two‐stage curing, through condensation of methylol groups and addition polymerization of maleimide groups. The cure characterization of the resin by dynamic mechanical analysis confirmed the two‐stage cure and the dominance of maleimide polymerization over methylol condensation in the network buildup process. The kinetics of both cure reactions, studied by the Rogers method, substantiated the earlier proposed cure mechanism for each stage. Although the initial decomposition temperature of the cured resin was not significantly improved, enhancing the crosslink density through HPM improved thermal stability of the material in a higher temperature regime. The anaerobic char yield also increased proportional to the maleimide content. Isothermal pyrolysis and analysis of the char confirmed that pyrolysis occurs by loss of hydrocarbon and nitrogenous products. The resins serve as effective matrices in silica‐ and glass fabric–reinforced composites whose mechanical properties are optimum for moderately crosslinked resins, in which failure occurs through a combination of fiber debonding and resin fracture. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1664–1674, 2001     

Development and start-up of a fixed bed reaction column for manufacturing antiknock enhancer MTBE

A laboratory fixed-bed reaction column is presented, in which a heterogeneouslyl catalyzed reversible fluid-phase reaction and the separation of the reaction product from unreacted or inert components by distillation are performed simultaneously. The rection studied, the formation of methyl tertiary butyl ether (MTBE) from methanol and isobutylene, is catalyzed by strongly acidic macroreticular ion exchange resins. Packing elements are Raschig rings, manufactured for the first time from the above-mentioned ion exchange resins. This in-house made catalyst shows practically the same ion exchange capacity as the commercial products. The control system installed in the equipment is capable of correcting strong disturbances os the steady state. As shown by expwrimental results, the superimposed distillation process occurs in such a way that the chemical equilibrium of the MTBE synthesis does not limit isobutylene conversion.     

Network structure/mechanical property relationship in multimethacrylates—Derivatives of nadic anhydride

In this article the syntheses of dimethacrylate and trimethacrylate esters as well as the mechanical and thermal properties of their copolymers with methyl methacrylate and styrene are investigated. The esters were obtained from acidic derivatives of nadic anhydride and glycidyl methacrylate. The addition reaction of glycidyl methacrylate and the acidic compound was carried out in the presence of basic catalyst—tetraethylammonium bromide. The monomers and resins were UV cured in the presence of a suitable photoinitiator which was 2,2‐dimethoxy‐2‐phenyloacetophenone. The prepared polymers were subjected to different studies concerning evaluation of their mechanical properties, thermal stability, dynamic mechanical behavior (DMA) as well as the estimation of the content of unreacted double bonds in the final product. The results proved their good thermal and mechanical properties. The degree of unsaturated bonds conversion was found to be growing with the amount of monovinyl monomer in the copolymer. Trimethacrylate‐based copolymers are characterized by a greater content of double bonds present in the obtained material compared to that of dimethacrylate‐based copolymers. As indicated by DMA the network structures of the copolymers seem to be more heterogeneous with the increasing weight fraction of trimethacrylate as well as dimethacrylate monomer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Two-step synthesis and characterization of urea–isobutyraldehyde–formaldehyde resins

Urea–isobutyraldehyde–formaldehyde (UIF) resins were synthesized from urea, isobutyraldehyde and formaldehyde using sulfuric acid as catalyst by two-step method. The effect of molar ratio of isobutyraldehyde to formaldehyde (n(I)/n(F)), molar ratio of aldehyde to urea (n(A)/n(U)), catalyst concentration and reaction time on the yield, hydroxyl value and softening point of UIF resins were investigated. The UIF resins were characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H-nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC) and thermogravimetric (TG). The results showed that the yield, hydroxyl value and softening point of the UIF resin were 76.5%, 90 °C and 32 mgKOH/g, respectively, when the molar ratio of urea to isobutyraldehyde to formaldehyde (n(U)/n(I)/n(F)) was 1.0/3.6/2.4, catalyst concentration was 6.0%, and reaction time in the second step reaction was 3.0 h. FT-IR and ¹H NMR results showed that α-H in isobutyraldehyde participated in the synthesis reaction of UIF resins, and the reaction was Mannich reaction. The amount of aldehyde groups in UIF resins increased with the increase of the amount of isobutyraldehyde. GPC results showed that the UIF resins had narrow molecular weight distribution and TG results indicated that the UIF resin had excellent heat resistance.     

New bisphenol novolac epoxy resins for marine primer steel coating applications

Bisphenol derived from reaction of phenol with benzaldehyde was prepared in the presence of sulfuric acid as catalyst. Bisphenol novolacs were synthesized in both melting and solution processes using p-formaldehyde and formalin solution in the presence of oxalic acid catalyst. ¹H NMR analysis shows a high methylene bridge contents using the novolacs synthesized in a melting process. The bisphenol novolac epoxy resin was prepared by reaction with epichlorohydrine in the presence of sodium hydroxide as a catalyst. The prepared novolac epoxy resins were cured with 1,2-amino ethyl piperazine (AEP) as a curing agent. The cured resins were evaluated as organic coating for steel. The mechanical properties of the cured epoxy resins were evaluated by measuring both impact resistance and hardness. The chemical resistances of the cured resins were evaluated through salt spray resistance, hot water immersion, solvent resistance, acid and alkali resistance measurements. The data indicate that the cured epoxy resins have excellent chemical resistances as organic coatings among other cured resins.     

Synthesis and properties of unsaturated epoxyfumarate resins

Synthesis and properties of epoxyfumarate and epoxymaleate resins obtained by the addition of acidic ester of maleic acid to the commercially available resin, Epidian 5, is presented. In acidic ester preparation, n‐hexanol was used. The resins were synthesized in one‐ and two‐step procedures. In the two‐step procedure, acidic hexyl maleate was synthesized separately and then used for the addition reaction with epoxy resin. In the one‐step synthesis, acidic ester was formed during the synthesis process. Properties of the obtained resins were compared. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3077–3084, 2000     

Synthesis and characterization of resins from urea and acrolein

The reactions of urea with acrolein in neutral and acidic media were studied by means of ¹H- and ¹³C-NMR spectroscopy. The addition of aldehyde groups to urea seems to be the first step of the reaction. In the second step in neutral medium the groups and the double bonds react with the amide groups. In the acidic medium the condensation of as second step was dominant. In the further course of the reaction highly crosslinked resins are formed which are insoluble and unmeltable. Chemical shifts of individual compounds are given. On the basis of these data, it was possible to set up tentative reaction schemes. The determination of the concentrations of reaction products as functions of reaction time allowed to establish the kinetics of individual reactions.     

Effect of acid strength distribution on de-t-butylation rate and catalyst fouling rate

De-t-butylation of t-butylbenzenes was carried out over a pyridine poisoned solid acidic catalyst to determine the effect of acid strength distribution on the reaction rate and catalyst fouling rate. The acid sites on the solid acidic catalyst were divided into three groups by their acid strength. Moderate acid sites, which were effective for the de-t-butylation but ineffective for the coke formation, were exclusively left on the catalyst surface by the partial poisoning. It is found that the present modification of the catalyst is useful in preparing an acid catalyst without catalyst fouling by coke deposition.     

Network structure/mechanical property relationship in crosslinked dimethacrylates of different chain lengths

In this article, the syntheses of three novel dimethacrylates of different chain lengths as well as the mechanical and thermal properties of their copolymers with methyl methacrylate and styrene were studied. The monomers were prepared by the reaction of glycidyl methacrylate with dicarboxylic acid esters obtained from maleic anhydride and ethylene, 1,4‐butylene and 1,6‐hexylene glycols. The addition reaction of glycidyl methacrylate and the acidic compound was carried out in the presence of basic catalyst, tetraethylammonium bromide. The monomers were UV‐copolymerized with methyl methacrylate and styrene in the presence of a photoinitiator which was 2,2‐dimethoxy‐2‐phenyloacetophenone. The prepared polymers were subjected to different studies concerning evaluation of their flexural properties, thermal stability, dynamic mechanical behavior as well as qualitative estimation of the content of unreacted double bonds. The dependence of glass transition temperatures (T_g) as well as degree of inhomogeneity on the crosslinking density has been examined in different copolymer systems. Evidence that the dependence of the T_g on the crosslinking density is not straightforward is presented. Dynamic mechanical measurements have demonstrated that the heterogeneity of the crosslinked polymers depends strongly on the crosslinking density of the system and the nature of methacrylate monomers used. Depending on the monomer size as well as its functionality, the resultant polymer may have features such as crosslinks or residual unsaturations that influence and define the properties of the materials. It is proved that the new dimethacrylates change their functionality in copolymerization with different monovinyl monomers. Also, the degree of unsaturated bonds conversion was found to be growing with the amount of monovinyl in the copolymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cross-linking of bisepoxide with divalent metal salts of p-aminobenzoic acid and anhydride

Cross-linking of bisepoxide with divalent metal salts of p-aminobenzoic acid and dicarboxylic acid anhydride was investigated. As the bisepoxide, bisphenol A diglycidyl ether was used and hexahydrophthalic anhydride was the anhydride used. As the divalent metal, Mg and Ca were selected. In the cross-linking reactions, the metal salts showed catalytic activities. In this case, the salt containing Mg exhibited higher catalytic activities than that containing Ca. The cross-linking reaction was supposed to proceed via a complex mechanism. The cured resins obtained contained amide and ester groups and ionic linkages. As for the physical properties of the novel metal-containing cured resins, tensile and flexural strengths decreased with an increase in the metal content. However, Rockwell hardness was not affected by the metal content. There was a good correlation between heat distortion temperature and T_g determined by dynamic mechanical properties. Against boiling water, the resins exhibited low weight gain, low change in dimension, and no change in external appearance. In addition, thermal decomposition was accelerated by the incorporated metal. © 1994 John Wiley & Sons, Inc.     

A novel reaction of epoxy resins with polyfunctional active esters

Addition reactions of commercial epoxy resins such as bisphenol-A diglycidylether (BADGE), ethylene glycol diglycidylether (EGGE), and N,N-diglycidylaniline (GAN) with various active esters such as di[S-(benzothizolyl)] thioadipate (BTAD), di(4-nitrophenyl) adipate (NPAD), di(S-phenyl) thioadipate (PTAD), and 4-nitrobenzoyl esters of polyfunctional phenols were carried out in neat using quaternary salts or crown ether-salts complexes as a catalyst at 50–130°C. The rate of addition reaction of BTAD was faster than that with other esters under the same reaction conditions. Furthermore, it was found that the rate of addition reaction of the epoxy resins with some active esters was strongly affected by the kind of epoxy resin, the structural formula of carboxylic acid, and the kind of catalyst. The reaction of epoxy resins with polyfunctional active esters proceeded quantitatively at the elevated temperatures. However, some of the mixtures of epoxy resin, polyfunctional active ester and the catalyst showed excellent storage stability at 30°C.     

Isomerisation of 1,2-Epoxyalkanes: Effect of Different Solid Acids on Product Distribution,Mechanism and Kinetics

The rearrangement of epoxides over acidic and superacidic catalysts leads to several products with selectivity to the desired aldehyde depending upon the nature of the catalyst surface and the reaction conditions. This paper reports the studies with 1,2-epoxyoctane as a model compound, over several catalysts such as sulphated zirconia and zeolites, and dodecatungstophosphoric acid, phosphoric acid and ZnCl₂ supported on silica, clay and carbon. The typical products of rearrangement are aldehyde, allylic alcohols, furan and aldol. A mechanism for the formation of these species is given. H₃PO₄/SiO₂, dodecatungstophosphoric acid supported on K-10 clay and ZSM-5 were found to be efficient under different conditions. A kinetic model is presented. © 1997 SCI.     

Synthesis and thermal properties of poly(urethane‐imide)

The synthesis and thermal properties of thermoplastic poly(urethane‐imide) (PUI) resins were studied. Model reaction studies on the reactions of 4,4′‐diphenylcarbamatodiphenylmethane and 4,4′‐diisocyanatodiphenylmethane with phthalic anhydride were performed. We found that the reaction of anhydrides with urethane groups could take place under certain reaction conditions. According to the model reaction studies, N‐2‐methyl‐pyrrolidone was employed as a solvent, and no catalyst was used in the polymerization. To restrain the side reaction of anhydrides with urethane groups, we adopted a two‐step chain‐extending procedure in a chain‐extending reaction. The inherent viscosity of PUI was 0.83–0.99 dL/g. The prepared polymers not only exhibited improved solubility in organic solvents but also formed flexible films. Thermogravimetric analysis showed that PUI exhibited a two‐step thermal weight‐loss pattern. The first step of the thermal degradation of PUI was attributed to the thermooxidizing cleavage of weak and labile linkage, such as urethane groups, isopropylidene, and methylene, except for imide rings. The polymer inherent viscosity decreased sharply during the first step of thermal degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 773–781, 2001     

Synthesis and structural characterization of urea–isobutyraldehyde–formaldehyde resins

Urea–isobutyraldehyde–formaldehyde (UIF) resins were synthesized using urea, isobutyraldehyde, and formaldehyde; sulfuric acid was used as a catalyst. The effects of molar ratio of urea/isobutyraldehyde/formaldehyde (U/I/F) on the properties of resins were investigated, and the structures of the resins were characterized by FTIR, ¹H-NMR, and ¹³C-NMR. When U/I/F was 1.0/3.6/2.4, the yield of the resin was 76.5%. The softening point and hydroxyl value were 90°C and 32 mg KOH/g, respectively. The FTIR, ¹H-NMR, and ¹³C-NMR results showed that an α-ureidoalkylation reaction occurred between urea and isobutyraldehyde to form a lactam. The UIF resins also contained hydroxyl groups and aldehyde groups; the content of aldehyde groups in the resin increased as the amount of isobutyraldehyde increased.     

Reactions of carbon monoxide with unsaturated fatty acids and derivatives: A review

The important reactions of carbon monoxide with unsaturated fatty derivatives that are reviewed in this paper include hydroformylation (the oxo reaction), Koch carboxylation and Reppe carbonylation. With oleic acid as a substrate, the products are C₁₉ bifunctional compounds e.g., formyl- or carboxy-stearic acid. Double bond isomerization before carbon monoxide addition is characteristic of these catalytic reactions; additionally, rearrangement to introduce methyl branching occurs in the Koch carboxylation. Isomerization does not occur when a rhodium-triphenylphosphine catalyst replaces cobalt in the oxo reaction. Properties of the C₁₉ dicarboxylic acids differ and depend upon method of preparation: Many areas of application have been reported for C₁₉ compounds-lubricants, plasticizers, polyurethanes, epoxy resins, leather and other coatings, unsaturated polyester resins and transparent polyamide plastics. Presented at the AOCS Meeting, Los Angeles, April 1972. N. Market. Nutr. Res. Div., ARS, USDA.     

Polymerization of resole resins with several formaldehyde/phenol molar ratios: Amine catalysts against sodium hydroxide catalysts

Triethylamine and sodium hydroxide catalyzed phenol/formaldehyde resole resins were investigated in terms of their behavior during both addition and polymerization reactions. Amine‐catalyzed prepolymers were mainly ortho‐substituted structures, whereas the sodium hydroxide catalyst directed the addition reaction to para reactive sites. During polymerization, triethylamine led to dimethylene ether bridges as the principal linkages between aromatic structures, increasing their final concentration as the starting hydroxymethyl group concentration increased. In contrast, the use of sodium hydroxide reduced dramatically the dimethylene ether bridge concentration, favoring methylene bridge formation. The influence of hydroxyl ions on the stability of quinone methide intermediates could be the reason for those differences. Despite the formation of dimethylene ether bridges, at higher curing temperatures, more oxidized groups started to appear in cured resoles when the formaldehyde/phenol molar ratio was higher. The presence of infrared bands associated with quinones, aldehydes, and/or carbonyl groups, mainly in high‐formaldehyde‐content resins, could indicate a direct oxidation process from dimethylene ether bridges and/or residual hydroxymethyl groups, without the formation of methylene bridges. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2623–2631, 2006     

Effects of molecular weight on the dynamic mechanical and rheological properties of anionically polymerized polyamide 6 containing nanofiber

Anionic ring‐opening polymerization of ε‐caprolactam leads to the formation of polyamide 6 (PA6). This reaction takes place at a significantly faster rate and gives a narrower molecular‐weight distribution than those obtained with other techniques. Because of this advantage, anionic polymerization of PA6 during melting was investigated in this work. In an internal mixer, PA6 was prepared via the melt polymerization of ε‐caprolactam as monomer with sodium caprolactam as a catalyst and hexamethylene diisocyanate as an activator. The effects of various concentrations of catalyst and activator on the rate of reaction and the amount of residual monomer were determined. Also, the physical and mechanical properties of PA6 prepared in this way and commercial PA6 prepared via hydrolytic processing were determined by differential scanning calorimetry and dynamic mechanical thermal analysis, as well as tensile, impact, and rheological tests. The experimental results showed that the composition which included 3% of catalyst and 3% of activator gave better properties than the other formulations. These conditions led to the lowest residual monomer content and better mechanical properties, as well. Another novel aspect of this investigation was nanofiber formation during the melt polymerization. The nanofibers had lower molecular weights than the matrix and thus created a special crystal structure different from that of the matrix. Mechanical property measurements showed that PA6 prepared by using this technique and the aforementioned formulation was similar to the commercial PA6. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Highly efficient antifouling property based on self‐generating hydrogel layer of polyacrylamide coatings

Pursuit of robust antifouling coatings is a persistent objective for marine materials. We present here the experimental realization of a series of polyacrylamide‐based resins with a self‐generating hydrogel layer, arising from the polymerization of acrylamide (AM), butyl acrylate, methacrylic acid, and AM derivatives. The mechanical strength and thermal stability are markedly enhanced due to the change of the structure of modified resins. The preliminary results indicate that resultant resins with crosslinking structure show satisfactory abrasion resistance and swelling properties. The results of antifouling panel testing in shallow submergence for three months reveal that the addition of AM derivatives leads to generation of a thin soft and dynamic layer of hydrogel, which enhances antifouling properties. The formation of hydrogel and self‐generating property make it promising in various antifouling applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44111.