Kinetics resins

Keywords and phrases Parameter estimation, reaction kinetics, resin production, chemical modelling, model verification, reparameterisation. 

Polymeric cation-exchange resins are also used in the separation of fmctose from glucose. The UOP Sarex process has employed both 2eohtic and polymeric resin adsorbents for the production of high fmctose com symp (HFCS). The operating characteristics of these two adsorbents are substantially different and have been compared in terms of fundamental characteristics such as capacity, selectivity, and adsorption kinetics (51). 

Cure kinetics of thermosets are usually deterrnined by dsc (63,64). However, for phenohc resins, the information is limited to the early stages of the cure because of the volatiles associated with the process. For pressurized dsc ceUs, the upper limit on temperature is ca 170°C. Differential scanning calorimetry is also used to measure the kinetics and reaction enthalpies of hquid resins in coatings, adhesives, laminations, and foam. Software packages that interpret dsc scans in terms of the cure kinetics are supphed by instmment manufacturers. 

Dynamic mechanical analysis provides a useful technique to study the cure kinetics and high temperature mechanical properties of phenoHc resins. The volatile components of the resin do not affect the scan or limit the temperature range of the experiment. However, uncured samples must be... 

A more economical route to MQ resin uses low cost sodium sihcate and trimethylchlorosilane as inputs (eq. 35) (395). The sodium sihcate process is initiated by acidifying an aqueous sodium sihcate solution to a pH of 2. The resulting hydrosol quickly builds molecular weight. The rate of this increase is moderated by the addition of an alcohol such as 2-propanol. The hydrosol is subsequentiy silylated by the addition of trimethylchlorosilane. This process, which is kinetically sensitive and limited to synthesizing M/Q ratios of 1 or less, is preferred when MQ resins having high (>1%) OH content are required (395). 

Divinylbenzene copolymers with styrene are produced extensively as supports for the active sites of ion-exchange resins and in biochemical synthesis. About 1—10 wt % divinylbenzene is used, depending on the required rigidity of the cross-linked gel, and the polymerization is carried out as a suspension of the monomer-phase droplets in water, usually as a batch process. Several studies have been reported on the reaction kinetics (200,201). 

The poly(vinyl alcohol) made for commercial acetalization processes is atactic and a mixture of cis- and /n j -l,3-dioxane stereoisomers is formed during acetalization. The precise cis/trans ratio depends strongly on process kinetics (16,17) and small quantities of other system components (23). During formylation of poly(vinyl alcohol), for example, i j -acetalization is more rapid than /ra/ j -acetalization (24). In addition, the rate of hydrolysis of the trans-2iQ. -A is faster than for the <7 -acetal (25). Because hydrolysis competes with acetalization during acetal synthesis, a high cis/trans ratio is favored. The stereochemistry of PVF and PVB resins has been studied by proton and carbon nmr spectroscopy (26—29). 

Kinetics of suspension PVC are identical to the kinetics of mass PVC, both increasing in rate with conversion (90). After polymerization to about 80—90% conversion, excess monomer is recovered, the slurry is steam-stripped in a column to a residual monomer level of about 0.0001% (10 ppm), excess water is centrifuged off, and the resin is dried with hot air. 

In general, the reaction between a phenol and an aldehyde is classified as an electrophilic aromatic substitution, though some researchers have classed it as a nucleophilic substitution (Sn2) on aldehyde [84]. These mechanisms are probably indistinguishable on the basis of kinetics, though the charge-dispersed sp carbon structure of phenate does not fit our normal concept of a good nucleophile. In phenol-formaldehyde resins, the observed hydroxymethylation kinetics are second-order, first-order in phenol and first-order in formaldehyde. 

Alkaline co-condensation to yield commercial resins and the products of reaction obtained thereof [93,94] as well as the kinetics of the co-condensation of mono methylol phenols and urea [104,105] have also been reported [17]. Model reactions in order to prove an urea-phenol-formaldehyde co-condensation (reaction of urea with methylolphenols) are described by Tomita and Hse [98,102, 106] and by Pizzi et al. [93,104] (Fig. 1). 

Because hydrolytic reactions are reversible, they are seldom carried out in batch wise processes [26,28,36,70]. The reactor is usually a double jacket cylindrical flask fitted with a reflux condenser, magnetic stirrer, and thermometer connected with an ultrathermostat. The catalyst is added to the reaction mixture when the desired temperature has been reached [71,72]. A nitrogen atmosphere is used when the reactants are sensitive to atmospheric oxygen [36]. Dynamic methods require more complicated, but they have been widely used in preparative work as well as in kinetic studies of hydrolysis [72-74]. The reaction usually consists of a column packed with a layer of the resin and carrying a continuous flow of the reaction mixture. The equilibrium can... 

In contrast to the above resins, the chelating resin Amberlite IRC-718 is based upon a macroreticular matrix. It is claimed to exhibit superior physical durability and adsorption kinetics when compared to chelating resins derived from gel polymers and should also be superior for use in non-aqueous solvent systems. 

NOTE A practical problem resulting from the rapid reaction kinetics of HQ is that when water containing HQ passes through an MBDl, it turns the resin black, obscuring visual observation of resin separation during regeneration. 

Fig. 11. Water vapour sorption kinetics in the same external conditions for as cast and hygrothermally damaged DGEBA-TETA neat resin...

Since anhydrides are much more reactive than carboxylic acids, reaction kinetics is controlled by the second step. The scope and apphcations of this reaction are the same as direct polyesterification but are practically limited to the synthesis of unsaturated polyesters and alkyd resins from phtliahc and maleic anhydrides (see Sections 2.4.2.1 and 2.4.23). 

This chapter emphasizes the recent mechanistic and kinetic findings on phenolic oligomer syntheses and network formation. The synthesis and characterization of both novolac- and resole-type phenolic resins and dieir resulting networks are described. Three types of networks, novolac-hexamethylenetetramine (HMTA),... 

Dynamic DSC scans of resole resins show two distinguishable reaction peaks, which correspond to formaldehyde addition and die formation of edier and metiiy-lene bridges characterized by different activation energies. Kinetic parameters calculated using a regression analysis show good agreement widi experimental values.75... 

Fig. 7 Kinetics of microwave-assisted loading of 2-chlorotrityl chloride resin with Fmoc-isoleucine at 110 °C. For comparison, the dashed line indicates the level of loading after 1 h at room temperature...

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