Лако-красочные материалы — производство

Corrosion-resistant glass fiber reinforced composites were also produced on the basis of furfuryl alcohol thermosetting resins [3,16,60]. Thus, many furan-based glass fiber reinforced materials have been available for many years, particularly for the storage of chlorinated aromatic and aliphatic hydrocarbon solvents. Amongst the commercial units available one finds: (i) very large scrubbing towers packed with Raschig rings. These containers are resistant to hot (up to about 120°C) HCl and organic chlorides;

(11) large brink mist eliminators typically working close to 85° C; (iii) acid wash surge tanks used to store waste liquids with a pH of about 2 at temperatures of 55-60°C; and (iv) dryer exhaust water driven coolers for incoming hot (230°C) acidic HCl and aromatic vapors. These few examples do not cover all the equipment constructed on the basis of furan resin reinforced by fiberglass but they show clearly the usefulness of these materials in different industrial areas. Other applications include the use of 2 as a matrix for fiberglass in the production of wrappings of pipes carrying corrosive liquids and vapors

[12] . Thus, steel pipes previously coated with bitumen or coal tar pitch can be wrapped with a bonded glass fiber mat based on this type of resin. In this context, 2 is mixed with water in the presence of an emulsifying agent and an acid catalyst and the ensuing emulsion impregnates the mat. Then, the resulting composite is heated in order to remove the water and induce the acid-catalyzed polycondensation of the matrix.

Amongst the composites used one can cite furfuryl alcohol resins reinforced with carbon filled woven glass fiber (commercialized under the name of Permanite, manufactured by the IKO Group, Canada). The main mechanical properties of such composites are: tensile, shear, flexural, and compressive strengths of 15, 20, 39, and 41 MPa, respectively. Their average density, thermal conductivity, and coefficient of ther­mal expansion are 1.57kg/dm3, 3.44W/(m2K) and 1.8x10_5/°C. Permanite-based pipes are hard, tough, and rigid with exceptional resistance to thermal shocks. They can be used up to 140°C and should be protected against high tensional, torsional, and shear loads.

The combination of furanic derivatives with formaldehyde is also used in order to produce pipes. Haveg 61, manufactured by High Performance Alloys, Inc., Tipton, IN, can be cited as an example of these resins which are usually filled with acid-digested asbestos [16]. These composites are resistant to thermal shocks and have been used continuously at high temperatures (150°C). They have very low electrical and thermal conductivities. The main mechanical properties of these composites are: ultimate tensile, shear, and compressive strengths, at 26°C, of 28, 109, and 72 MPa, respectively. Their coefficient of thermal expansion is 3.2x10_5/°C. The working and hardening times of these resinous cements depend strongly on the working temperature [12]. Thus, for example, for carbon filled 2-based resin cement, the following critical values are found: at 16, 21, and 27°C the working and hardening times are 90, 60, and 30 min and 48, 20, and 12 h, respectively [12].

Azimov et al. [65] compared the performances of furan resins with those of conven­tional phenol-formaldehyde adhesives. They used these binders to assemble aluminum- to-aluminum and glass-to-glass structures and showed that furanic resins gave much higher rupture moduli in both systems studied. Rassokha and Avramenko [66] studied similar systems, but gave more information about the furan resin used. They used 5- and 6-based adhesives both in the presence and absence of zeolite-based fillers, and assembled aluminum-to-aluminum and glass-to-glass structures. They showed that the use of polyethylene-co-vinylacetate as a filler dispersant gave well dispersed sus­pensions and consequently the best mechanical properties of the assembly. Nikolaev et al. [67] studied the thermal stability of furan resins produced by the reaction between a furfuryl ether of glycerol and 2,4-toluene diisocyanate. They showed clearly that the incorporation of this resin into conventional adhesives improved their thermal stability. The mechanical properties of steel-to-steel assemblies based on these com­positions were found to follow the same tendency as that observed for the thermal properties.

Poly(hydroxymethyl furfurylidene-acetone) adhesive resins were synthesized and characterized [68-70] through the 5-formaldehyde adduct (19) and its acid-catalyzed poly­merization. The catalysts used were sulfuric, phosphoric, or p-toluenesulfonic acid. The authors postulated that the first condensation products resulted from the condensation of two methylol groups of two 19 molecules (adduct 20). They also proposed a hypothetical structure of the network formed after curing (21). It seems, however, difficult to envisage the acid-catalyzed resinification of 19 without the participation of hydrogen atoms at the C5 position of the furanic ring [2].

Macro-diisocyanates based on the reaction of an excess of 2,4-toluene diisocya­nate with different poly(dimethylsiloxane)diols of different lengths have been prepared by Nikolaev et al. [71]. These macro-diisocyanates were reacted with 2 in stoichio­metric proportions and the resulting adduct (22) was cured with a commercial epoxy resin in the presence of what was termed “poly(ethylene)-poly(amine)’’ at room temp — cerature, 80, and 100°C. The mechanical and thermal properties of steel-to-steel assemblies joined by these adhesives were better than those obtained using more common binders.

Bowles et al. [72] studied the copolymerization of different methacrylates with NCO- ethyl methacrylate to obtain dental adhesives. Furfuryl methacrylate (23) was among the monomers tested. The main objective of this investigation was to establish a correlation between the solubility parameter of the copolymers and their shear strength. It was moreover shown that the setting time of the furan-based copolymer was very short com­pared to that of aliphatic homologues, but its shear strength was relatively low.

Dopico et al. [73] prepared 5- and 6-based furan resins which, after acid-catalyzed polymerization, were subjected to epoxidation with thiokol in different proportions. In a second series of experiments, 6-7% of 2 was added to the epoxidized resins. They showed that all these resins presented a lower flexure resistance compared to unmodified totally furanic binder. Moreover, the addition of 2 was found to induce negative effects on the mechanical properties of metal-to-metal assemblies.

Furan resins have also been used as binders in grinding wheels [4]. In this field, 5-20% of phenolic resin in combination with 1 as a special wetting agent is added to the abrasive grains and the resulting wheels thereafter coated onto the surfaces of different substrates. Paper, cloth as well as composites based on glass fiber reinforced films, have been used as grinding wheel supports. Acid-catalyzed poly2 has also been used in the aircraft industry as a low-temperature setting adhesive to bond wood and plastic parts. This adhesive was found to be suitable for assemblies subjected to warping and other deformations at high temperatures [12].