Furfural-phenol resin

Furfural (furan-2-carbaldehyde Scheme 1) arises from the decomposition of sugars and is a commercially important raw material used in furfural-phenol resins and as a synthetic intermediate (see CHEC 1.15). 

Furan-2-carbaldehyde 8 is commonly referred to as furfural. It is produced on a large scale by the action of acids on sugars and is a commercially important raw material used in furfural-phenol resins and as a synthetic intermediate . The 2-furylmethyl radical is called furfuryl and, for example, the alcohol 9 is commonly known as furfuryl alcohol. The furan derivative 10 (ranitidine) was one of the first H2-antagonists for the treatment of gastric ulcers and a major contribution to modern medicine. 

Copolymers of furfural with phenol or phenol-formaldehyde polymers have been available commercially for many years. Since the acid-catalyzed reaction of furfural and phenol has been difficult to control, most industrial applications involve the use of alkaline catalysts. Furfural-phenol resins are used for their alkali resistance, enhanced thermal stability, and good electrical properties compared to phenol-formaldehyde resins. 

Resistance to chemical attack is generally improved by resin impregnation, which protects the underlying wood and reduces movement of Hquid into the wood. Resistance to acids can be obtained by impregnating with phenoHc resin and to alkaHes by impregnating with furfural resin (see Phenolic RESINs). 

Although most phenolic resins are made using formaldehyde, but other aldehydes have also been used. The only one of commercial importance is furfural which produces a resin having a high tensile and impact strength. 

PHENOL-FURFURAL RESIN, A phenolic resin that has a somewhat sharper transition than phenol-formaldehyde from the soft, thermoplastic stage to the cured, infusible state and can be fabricated by injection molding since it has little tendency to harden before curing conditions are reached. 

Furfuryl alcohol alone, or in combination with other cross-linkable binders such as phenolic reins, chemical by-products and pitch, catalyzed with acid, gives carbon yields of 35—56%. Furfural together with cyclohexanone, pitch, or phenolic resins gives, under acid catalysis, yields of 35—55% carbon under basic catalysis yields of 5—50% are achieved. Furfurylideneacetone resins (13 and 14), catalyzed by acid or base, give carbon yields of 48—56 and 30—35%, respectively (78). 

Total sugars Acetic acid Formic acid HMF Furfural Phenolics Raw hydrolyzate EJpH5.5 Activated charcoal B Anion-exchange resins... 

Petroleum polymer resins Phenol-furfural resins Phenolic resins Phenoxy resins Phthalic alkyd resins Phthalic anhydride resins Polyacrylonitrile resins Polyamide resins Polycarbonate resins Polyesters Polyethylene resins Polyhexamothylemediamine adipamide resins Polyisobutylenes Polymerization plastics, except fibers... 

Though many aldehydes can be made to react with phenol, only formaldehyde, the lowest molecular weight and most reactive aldehyde, is of major commercial importance. Acetaldehyde and butyraldehyde are used only to a limited extent and often in combination with formaldehyde. Furfural is also used, forming phenolic resins that readily oxidize resulting in dark brown to black products. 

Regardless of the fact that numerous investigations exist about the possibility of incorporating the furan heterocycle into wood adhesive formulations, their industrial exploitation is still modest. The first suggestion concerning the use of 1 in partial substitution of formaldehyde in phenolic resins was put forward in 1958 by Baxter and Redfern [18] who proposed that the furfural units were incorporated into the polymer skeleton following condensation reactions such as ... 

Phenol-formaldehyde resin Phenol-furfural resin. See Phenolic resin... 

Phenol-furfural resin. See Phenolic resin Phenol glycidyl ether. See Phenyl glycidyl ether Phenol, 5-[(2-hydroxyethyl) amino]-2-methyl-. See 2-Methyl-5-hydroxyethylaminophenol Phenol, 4-[(2-hydroxyethyl) amino]-3-nitro-. See 3-Nitro-p-hydroxyethylaminophenol Phenolic-epoxy resin... 

Interestingly, Kotosonov and co-workers [45] found that a phenol-furfural formaldehyde resin can be graphitized by the application of a pressure ( 50 MPa) in the temperature range 400-600°C, but outside these limits, virtually no graphitization can be achieved. 

Furan resins are also a low-volume consumption resin like amino resins, and are used as supplements to phenolic resins [33,34]. They are prepared by the reaction between a phenol and furan compounds such as furfural, furfuryl alcohol, and furan. Furan compounds can be used in place of formaldehyde in the conventional production of phenolic resins. The most popular and viable furan resins are prepared from furfuryl... 

Oil soluble linear phenolic resins were produced in 1928 by the reaction of foitnaldehyde with ortho or para-substatuted phenols. E.E. Novotny patented phenolic resins, produced by the condensation of phenol with furfural. 

Furfural has been used to extract color bodies from crude wood rosins. One of the earliest uses of furfural was as a solvent and processing aid for coal and coal products. Furfural has been used as a reactive solvent with pulverized phenolic resin in the manufacture of resin-bonded abrasive grinding wheels. The furfural serves as a plasticizer and wetting agent in the resin mix which is cold molded and cured during a baking cycle. Furfural becomes a reacted component in the final resin structure. 

As indicated previously, commercial phenolic resins are almost exclusively based on formaldehyde. Furfural is occasionally used to produce resins with good flow properties (See Section 19.3.)... 

TABLE VI Series of Furfural-Phenol Novolac Resins"... 

The furfural-phenol novolacs are stable under neutral or alkaline conditions but readily undergo a thermoset reaction on the acid side to give a black resin [74]. It is possible that the furfuryl ring system also takes part in the curing reaction to give in addition furan-type polymers [75]. 

Mikes recently reported on the preparation of mixed furfural-formaldehyde phenolic resins [76]. 

To a resin kettle equipped with a mechanical stirrer, thermometer, and reflux condenser are added 8.0 gm of potassium carbonate and 400 gm (4.06 moles) of phenol. The mixture is heated to 135°C to form a solution, and then 300 gm (3.1 moles) of furfural is added dropwise over a 30 min period while the temperature is maintained at 135°C. The mixture is refluxed for 3-3yhr, and the temperature drops to 116 C. The separated resin has a melting point of 82°C and is obtained in 106% yield based on phenol (resin contains water). The stroke cure (see Note below) is taken after adding 2% calcium oxide and 10% hexamethylenetetramine and in approximately 5 min. 

Bagasse, acid and water are refluxed for 16 hours to produce furfural. Phenol, melamine or urea are added and then allowed to condense under basic conditions (CaO) at reflux temperature for 4 hours. The water is then removed by forced evaporation. The residue, consisting of bagasse fibers and the generated resin is... 

Concluding from these experimental data, it is possible to use the lignan components of the Parana pine knot as a substitute chemical for phenol in the preparation of resins of the phenol--formaldehyde and phenol-furfural types. These renewable-source lignan resins may be used in the same field of the petrochemical phenolic resins. 

Historically, phenol-formaldehyde resins (phenolic resins, phenoplasts) are the oldest synthetic thermoset materials as early as in 1910 the first ones ( bakelite to their inventor Baekeland) were introduced. Who does not remember the black telephones and light switches that were popular in the 1930s and 1940s Phenolic resins are based on hydroxy-aromatic compounds (phenol and phenol derivatives) and aldehydes [2]. Furfural is occasionally used as aldehyde but by far the most widely used aldehyde is formaldehyde. Formaldehyde can be administered as an aqueous solution (formalin), polymeric solid (paraformaldehyde) or solid adduct with ammonia (hexamethylenetetramine, HMTA). The resins are formed by a step-growth mechanism in aqueous solution. 

Formaldehyde is the most common aldehyde used for making phenolic resins. Formaldehyde, being a gas, is normally used as a 37 to 41 % aqueous solution (formalin) or as a solid in polymeric form (paraformaldehyde) that thermally decomposes to formaldehyde during reaction. For some special purposes, furfural or another complex aldehyde is also used. 

The manufacture typically begins by first wetting each abrasive grain with a liquid resole resin. This will allow the powdered phenolic resin to coat and adhere to each grain. In some cases the abrasive can be coated with furfural, and the amount of HMTA added to the phenolic will depend on the amount of furfural used. ... 

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