Resins, preparation

Obtained by K.OH fusion of many resins. Prepared by fusion of m-benzenedisulphonic acid with caustic soda, also obtained to some extent in the NaOH fusion of o-and p-ben-zenedisulphonic acids. 

Furfural has been used as a component in many resin appHcations, most of them thermosetting. A comprehensive review of the patent Hterature describing these uses is beyond the scope of this review. A few, selected recent patents and journal articles have been referenced. Resins prepared from the condensation products of furfural with urea (47), formaldehyde (48), phenols (49,50), etc, modified by appropriate binders and fillers are described in the technical Hterature for earlier appHcations, see reference 1, which contains many references in an appendix. 

Foaming polystyrene resin prepared by blending with gas deHvers an opaque, low density sheet useful for beverage-bottle and plastic can labels as a water-resistant paper substitute (see Styrene polymers). 

Unsaturated polyester resins prepared by condensation polymerization constitute the largest industrial use for maleic anhydride. Typically, maleic anhydride is esterified with ethylene glycol [107-21-1] and a vinyl monomer or styrene is added along with an initiator such as a peroxide to produce a three-dimensional macromolecule with rigidity, insolubiUty, and mechanical strength. 

Naphthalenediol. This diol is made by the fusion of sodium 2,7-naphthalenedisulfonate with molten sodium hydroxide at 280—300°C in ca 80% yield. A formaldehyde resin prepared from this diol has excellent erosion resistance, strength, and chemical inertness it is used as an ablative material in rocket-exhaust environments (76). 

Second, in the early 1950s, Hogan and Bank at Phillips Petroleum Company, discovered (3,4) that ethylene could be catalyticaHy polymerized into a sohd plastic under more moderate conditions at a pressure of 3—4 MPa (435—580 psi) and temperature of 70—100°C, with a catalyst containing chromium oxide supported on siUca (Phillips catalysts). PE resins prepared with these catalysts are linear, highly crystalline polymers of a much higher density of 0.960—0.970 g/cnr (as opposed to 0.920—0.930 g/cnf for LDPE). These resins, or HDPE, are currentiy produced on a large scale, (see Olefin polymers, HIGH DENSITY POLYETHYLENE). 

Resoles. The advancement and cure of resole resins foUow reaction steps similar to those used for resin preparation the pH is 9 or higher and reaction temperature should not exceed 180°C. Methylol groups condense with other methylols to give dibenzyl ethers and react at the ortho and para positions on the phenol to give diphenyknethylenes. In addition, dibenzyl ethers eliminate formaldehyde to give diphenyknethanes. 

Neoprene—phenohc contact adhesives, known for thein high green strength and peel values, contain a resole-type resin prepared from 4-/-butylphenol. The alkyl group increases compatibiHty and reduces cross-linking. This resin reacts or complexes with the metal oxide, eg, MgO, contained in the formulation, and increases the cohesive strength of the adhesive. In fact, the reactivity with MgO is frequently measured to determine the effectiveness of heat-reactive phenoHcs in the formulation. 

The neat resin preparation for PPS is quite compHcated, despite the fact that the overall polymerization reaction appears to be simple. Several commercial PPS polymerization processes that feature some steps in common have been described (1,2). At least three different mechanisms have been pubUshed in an attempt to describe the basic reaction of a sodium sulfide equivalent and -dichlorobenzene these are S Ar (13,16,19), radical cation (20,21), and Buimett s (22) Sj l radical anion (23—25) mechanisms. The benzyne mechanism was ruled out (16) based on the observation that the para-substitution pattern of the monomer, -dichlorobenzene, is retained in the repeating unit of the polymer. Demonstration that the step-growth polymerization of sodium sulfide and /)-dichlorohenzene proceeds via the S Ar mechanism is fairly recent (1991) (26). Eurther complexity in the polymerization is the incorporation of comonomers that alter the polymer stmcture, thereby modifying the properties of the polymer. Additionally, post-polymerization treatments can be utilized, which modify the properties of the polymer. Preparation of the neat resin is an area of significant latitude and extreme importance for the end user. 

Table 2. Polybasic Acids Used in Alkyd Resin Preparation...

Fig. 5. Electron photomicrographs of several HIPS resins prepared using different types of mbbers.

There was a tendency to use these resins mixed with urea—formaldehyde or melamine-type resins. Preparation of pure tria2ones or uron resins is difficult and expensive (61,62). Furthermore, the basic nature of the amine nitrogen in tria2one permits the use of mixtures of tria2ones with other agents to yield finishes that retain strength in hypochlorite bleaching. 

The thermal glass-transition temperatures of poly(vinyl acetal)s can be determined by dynamic mechanical analysis, differential scanning calorimetry, and nmr techniques (31). The thermal glass-transition temperature of poly(vinyl acetal) resins prepared from aliphatic aldehydes can be estimated from empirical relationships such as equation 1 where OH and OAc are the weight percent of vinyl alcohol and vinyl acetate units and C is the number of carbons in the chain derived from the aldehyde. The symbols with subscripts are the corresponding values for a standard (s) resin with known parameters (32). The formula accurately predicts that resin T increases as vinyl alcohol content increases, and decreases as vinyl acetate content and aldehyde carbon chain length increases. 

Requirements for heat- and cold-curing denture-base resins prepared from powder—liquids, gels, preopolymerized blanks, and fluid resins composed of acryflc, vinyl, and polystyrene polymers are given in ANSI/ADA specification no. 12 for denture-base polymers. 

Gel-permeation chromatography studies of epoxy resins prepared by the taffy process shown n values = 0, 1, 2, 3, etc, whereas only even-numbered repeat units are observed for resins prepared by the advancement process. This is a consequence of adding a difunctional phenol to a diglycidyl ether derivative of a difunctional phenol in the polymer-forming step. 

Truly porous, synthetic ion exchangers are also available. These materials retain their porosity even after removal of the solvent and have measurable surface areas and pore size. The term macroreticular is commonly used for resins prepared from a phase separation technique, where the polymer matrix is prepared with the addition of a hq-uid that is a good solvent for the monomers, but in which the polymer is insoluble. Matrices prepared in this way usually have the appearance of a conglomerate of gel-type microspheres held together to... 

Two classes of resol are generally distinguished, water-soluble resins prepared using caustic soda as catalyst, and spirit-soluble resins which are catalysed by addition of ammonia. The water-soluble resins are usually only partially dehydrated during manufacture to give an aqueous resin solution with a solids content of about 70%. The solution viscosity can critically affect the success in a given application. Water-soluble resols are used mainly for mechanical grade paper and cloth laminates and in decorative laminates. 

Urea is a white crystalline compound with a melting point of 132.6°C and is highly soluble in water. It is substantially cheaper than the other intermediate (formaldehyde) used in the resin preparations. 

In the literature, various other types of resin preparation procedures are described, e.g. yielding uron structures [20-22] or triazinone rings in the resins [23,24]. The last ones are formed by the reaction of urea and an excess of formaldehyde under basic conditions in the presence of ammonia or an amine, respectively. These resins are used to enhance the wet strength of paper. 

Coherent block of granular plastic molding compound or of fibrous mixture with or without resin. Prepared by sufficiently compressing material, forming a block that can be handled readily. 

A wide range of resins prepared by polymerisation of compounds containing vinyl groups is available. Those most commonly used in paint manufacture are of the following types ... 

Epoxy adhesives are cross-linked resins prepared in two steps. The first step involves SN2 reaction of the disodium salt of bisphenol A with epichloro-hydrin to form a low-molecular-weight prepolymer. This prepolymer is then "cured" into a cross-linked resin by treatment with a triamine such as H2NCH2CH2NHCH2CH2NH2-... 

Cure of alkyd resin A varnish is prepared by mixing 100 g of the alkyd resin prepared above, 0.05 g of Co(II) 2-ethylhexanoate, 0.05 g of calcium 2-etliyl-hexanoate, and 0.02 g of lead 2-ethylhexanoate. This mixture is held for 24 h in a closed flask before use. A thin layer of this varnish, applied on a metal plate, forms a hard, glossy coating after 24 h drying at room temperature. 

Linear novolac resins prepared by reacting para-alkylphenols with paraformaldehyde are of interest for adhesive tackifiers. As expected for step-growth polymerization, the molecular weights and viscosities of such oligomers prepared in one exemplary study increased as the ratio of formaldehyde to para-nonylphenol was increased from 0.32 to 1.00.21 As is usually the case, however, these reactions were not carried out to full conversion, and the measured Mn of an oligomer prepared with an equimolar phenol-to-formaldehyde ratio was 1400 g/mol. Plots of apparent shear viscosity versus shear rate of these p-nonylphenol novolac resins showed non-Newtonian rheological behavior. 

Mandal and Hay28 used MALDI-TOF mass spectrometry to determine the absolute molecular masses and endgroups of 4-phenylphenol novolac resins prepared in xylene or chlorobenzene. Peaks with a mass difference of 44 (the molecular weight of a xylene endgroup) suggested that reactions conducted in xylene included some incorporation of xylene onto the chain ends when a strong acid such as sulfuric acid was used to catalyze the reaction. By contrast, no xylene was reacted into the chain when a milder acid catalyst such as oxalic acid was used. No chlorobenzene was incorporated regardless of the catalyst used. 

The most common crosslinking agent for novolac resins is HMTA which provides a source of formaldehyde. Novolac resins prepared from a phenol-formaldehyde (F/P) ratio of 1/0.8 can be cured with 8-15 wt % HMTA, although it has been reported that 9-10 wt % results in networks with the best overall performance.3... 

Phenol-epoxy reaction. See also Epoxy-phenolic reaction entries tertiary amine-catalyzed, 412 triphenylphosphine-catalyzed, 412 Phenol-formaldehyde novolac resin, preparation of, 429... 

Phenol-formaldehyde resole resins, preparations of, 429 Phenolic-based networks, 376 Phenolic compounds, 62 Phenolic cyanate resins, 418... 

Unsaturated polyesters (UPs), 4, 18, 19 from PET waste, 560-561 Unsaturated polyester/styrene resin, preparation and cure of, 101 Unsaturated polyester thermosetting resins, syntheses of, 101-103 Unstirred interfacial process, 155 U-Polymer, 77... 

Measurement and Control Hardware for Laboratory-Scale Resin Preparations... 

---