Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L5/00—Solid fuels
  • C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
  • C10L5/06—Methods of shaping, e.g. pelletizing or briquetting
  • C10L5/10—Methods of shaping, e.g. pelletizing or briquetting with the aid of binders, e.g. pretreated binders
  • C10L5/14—Methods of shaping, e.g. pelletizing or briquetting with the aid of binders, e.g. pretreated binders with organic binders

Definitions

• This invention relates to a fuel briquetting composition which includes fuel particles, an alkaline phenolic resin, an esterified phenolic resin, a water-activated green strength additive and water. Also, it relates to a method of making fuel briquettes using a phenolic resin composition produced from esterified phenolic resins under alkaline conditions having a reduced content of unreactive by-products.
• phenolic resins may be cured under alkaline conditions through reaction with organic esters, including lactones and organic carbonates.
• organic esters including lactones and organic carbonates.
• ester curing of alkaline phenolic resole resins is described in DE-C-1,065,605, DE-C-1,171,606, JP-A-49-16793 and JP-A-50-130627.
• a highly alkaline phenolic resole resin in aqueous solution may be cured at ambient temperature by reaction with an organic ester by contacting the resin with the ester in the form of a liquid or a gas.
• Such techniques find use in the bonding of sand in refractory applications, such as in the production of foundry moulds and cores (US-A-4,426,467, US-A-4,468,359, US-A-4,474,904).
• the hardening of alkaline phenolic resins using ester curing agents involves the saponification of the ester, but it is a disadvantage that the alcohol products of the saponification reaction are not incorporated into the final resin structure but remain in the cured mass as non-resinous compounds in the form of free alcohols.
• the presence of free alcohol in the cured composition is considered to be disadvantageous in the applications where there is need for high strength and water resistance.
• an esterified phenolic resin as curing agent for an alkaline phenolic resin binder in the preparation of a cured phenolic resin composition.
• an esterified phenolic resin as the curing agent the release of free alcohols during the saponification stage is avoided as a phenol-formaldehyde resin is the alcohol of the saponification reaction and forms part of the final phenol-formaldehyde polymer matrix.
• a fuel briquetting composition comprising a mixture of
• Coal briquettes produced using the process described in EP-A-0241156 have poor water repellency properties because the esters used as hardeners react to form hygroscopic free alcohol by-products, such as glycerol and glycols.
• the briquettes may absorb up to 15% water based on the dry product weight.
• the physical strength of the briquette reduces with increasing water content.
• a particular advantage of using an esterified resole is that the reactive resole product of the hardening reaction is incorporated into the polymer matrix of the binder and imparts a degree of humidity resistance to the briquette with the physical strength of the briquette maintained during storage in damp conditions.
• phenol-formaldehyde resole resin and "phenol-formaldehyde novolak resin” are, of course, terms well known in the phenolic resin art.
• Resoles are thermosetting, i.e., they form an infusible three-dimensional polymer upon the application of heat and are formed by condensing a phenol with a molar excess of formaldehyde in the presence of a basic catalyst.
• Phenol-formaldehyde novolak resins are phenol-ended chain polymers formed by the reaction of formaldehyde with a molar excess of a phenol, typically in the presence of an acidic catalyst.
• novolak resins are permanently fusible non-curing resins which are conventionally cured into an insoluble, infusible resin by reaction with a formaldehyde donor curing agent, such as hexamethylenetetramine, at elevated temperature.
• a formaldehyde donor curing agent such as hexamethylenetetramine
• the preferred phenol-formaldehyde resins used in the present invention are based on the condensation product of formaldehyde with phenol, itself.
• condensation products may be manufactured in known ways by reacting phenol and formaldehyde in the presence of basic or acidic catalysts, although the preparation of such materials does not form part of this invention.
• basic catalysts employed for this purpose the resin product will possess free methylol groups in a proportion which will depend primarily on the ratio of formaldehyde to phenol. These methylol groups are attached to phenolic ring carbon atoms at ring positions which are ortho and/or para to the phenolic hydroxyl groups.
• the molar ratio of phenol:formaldehyde used in the condensation reaction will be in the range of from 1:1.2 to 1:3.0, preferably from 1:1.5 to 1:3.0.
• the amount of alkali used as condensation catalyst will typically be about 0.1-2% by weight based on the weight of the phenol used, generally sufficient to maintain a pH of at least 8, but may be considerably higher.
• the degree of condensation of such a resole resin can conveniently be described by reference to two parameters; the residual solids on heating at 100°C to constant weight and the viscosity of the resole solution.
• the phenol-formaldehyde resole resin will have a solids content of from 30-95% preferably 50 to 75%, by weight and a viscosity of from 0.1 to 100 poise, preferably 1 to 25 poise, at 25°C.
• condensation catalysts useful in the preparation of resole resins include the oxides and hydroxides of sodium, potassium, lithium, barium, calcium and magnesium.
• the phenol-formaldehyde novolak resin may be made in any of the known ways. In order to obtain a resin having the properties of a novolak, that is to say, in order to obtain a product which does not thermoset upon heating, it is necessary to react the phenol and the formaldehyde in a molar ratio of less than 1 mole of formaldehyde to each mole of the phenol.
• the novolak resin may be prepared using any of the catalysts commonly employed for this purpose.
• Suitable acid catalysts include the strong mineral acids, such as sulphuric, phosphoric and hydrochloric acids, and organic acids, such as oxalic and salicylic acids or anhydrides, such as maleic anhydride.
• an acid-catalysed novolak resin it is only necessary to employ sufficient of the acidic material to obtain a satisfactory rate of resinification and the proportion required will vary with the type of acid used.
• the strong mineral acids such as sulphuric acid or hydrochloric acid
• this will generally be in the range of from 0.02 to 1.0%, and preferably from 0.1 to 0.6%, by weight based on the weight of the phenol employed.
• organic acids such as oxalic acid or maleic anhydride, it is typical to use amounts in the range of from 0.1 and 10%, and preferably from 1 to 5%, by weight based on the weight of the phenol employed.
• the novolak resins formed are preferably treated, when the reaction is substantially complete, to remove unreacted phenol. This is because we have found that free phenol in the novolak resin appears to inhibit the crosslinking mechanism that takes place when the esterified phenol-formaldehyde resole resin reacts with the novolak resin in the presence of alkali and, therefore, causes a loss of strength in the product. Removal of free phenol may most conveniently be accomplished by steam distillation, but other methods of removing unreacted phenol, such as precipitation of the resin from solution and washing of the precipitate prior to drying, may be employed. It will be clear that many benefits of the invention will not be achieved in full measure if substantial amounts of free phenol are left in the resin.
• the alkaline phenol-formaldehyde resin will be a novolak resin since phenolic novolak resins in aqueous alkaline solution are storage stable.
• a storage stable binder obviously has the advantage particularly that it can be used and stored in warm and hot climates.
• the emission of formaldehyde is reduced compared to the case where an alkaline resole resin is reacted with the esterified resole resin.
• the curing agent used for the phenol-formaldehyde resole resin or the phenol-formaldehyde novolak resin in accordance with the present invention is an esterified phenolic resole resin.
• the esterified phenolic resin will be an esterified phenol-formaldehyde resole resin or an esterified phenol-formaldehyde novolak resin except in the case when the alkaline phenolic resin binder is an alkaline phenol-formaldehyde novolak the esterified phenolic resin curing agent will be an esterified phenol-formaldehyde resole resin.
• Such an esterified resole resin will typically be prepared by esterifying one or more methylol groups present in a phenol-formaldehyde resole resin which has been produced as described earlier.
• the esterified phenol-formaldehyde resole resin will contain one or more esterified methylol groups positioned ortho and/or para to a phenolic hydroxyl group or esterified phenolic hydroxyl group.
• the esterified resole resins are typically organic carboxylate esters. These esters may be derivable from any aliphatic, alicyclic or aromatic mono-, di- or polybasic carboxylic acid capable of forming esters with methylol groups.
• esterified methylol-containing resole resin it is also possible for an esterified methylol-containing resole resin to contain ester groups derived from more than one of these acids.
• the esters will be those formed from lower carboxylic acids, especially formic acid and acetic acid.
• the acid component of the ester group this is intended only as descriptive of the type of group and it is not intended to indicate that the acid itself need be employed for the manufacture of the methylol ester.
• the ester may be formed in any known way and the procedure adopted may be varied, as will be known to those skilled in the art, to suit the particular compounds being produced. Examples of some methods of esterification that may be used include:-
• esterified resole resin by the action of an acid anhydride on mono-, di-, or tri-dialkylamino methyl substituted phenols or phenol derivatives.
• phenolic resole resins are acid sensitive and in most cases it will be necessary to esterify the methylol groups, and optionally the phenolic hydroxyl groups, on a phenolic resole resin by an indirect route, so as to avoid gelation of the resin.
• the tendency to gel may be reduced or eliminated by blocking the phenolic -OH groups by esterifying or etherifying them, as described, for example, in DE-C-474,561.
• any catalyst employed to promote the esterification reaction must not be capable of entering into further reaction with the esterified methylol groups of the product of the esterification reaction under the reaction conditions used.
• An example of a suitable esterification catalyst is pyridine.
• a preferred procedure is to form the acetate ester of methylol-containing phenolic resole resin by introducing ketene into a solution of the methylol-containing phenolic resole resin.
• the ketene is preferably generated immediately prior to use, typically in equipment such as that described in US 2,541,471 or 3,259,469.
• the acetoacetate ester of the phenolic compound is obtained.
• Other esters may be formed by ester exchange.
• Suitable ester groups include formate, acetate, acetoacetate, acrylate, propionate, lactate, crotonate, methacrylate, butyrate, isobutyrate, caproate, caprylate, benzoate, toluate, p-amino-benzoate, p-hydroxybenzoate, salicylate, cinnamate, laurate, myristate, palmitate, oleate, ricinoleate, stearate, oxalate, succinate, fumarate, maleate, adipate, phthalate, azelate and sebacate.
• Acetate esters form a particularly preferred class of compounds according to the present invention.
• esterification reaction evolves water, it may be accelerated by the use of non-aqueous conditions, as well as by the use of non-boiling solvent capable of forming an azeotrope with water.
• the esters of the present invention may typically be prepared by choosing conditions which preferentially esterify the methylol (-CH 2 OH) groups and not the phenolic -OH groups in the resole.
• the esterified resole resin may be one in which all of the phenolic hydroxyl groups themselves are esterified, i.e., it contains no free phenolic hydroxyl groups. This is because, in such a case, the esterified resole resin will be stable on storage due to the inactivation of the phenolic -OH group, even at relatively high ambient temperature.
• the preferred amount of acid used will be equal, on a molar basis, to the content of free methylol groups.
• the preferred amount of acid used will be equal, on a molar basis, to the content of free methylol groups.
• esterification at low temperature an excess of acid may be required to introduce esterification at low temperature.
• any residual free acid should be removed from esterified resole resin before the latter is reacted with the alkaline phenolic resin in the production of the fuel briquettes since any residual free acid present in the esterified resole resin will reach with and so neutralise the alkali present.
• the curing agent may, alternatively, be an esterified phenol-formaldehyde novolak resin in the case where the binder is an alkaline resole resin.
• Phenol-formaldehyde novolak resins do not normally contain methylol groups. For this reason, an esterified phenol-formaldehyde novolak resin contains only esterified phenolic -OH groups. Under alkaline conditions a cross-linking reaction involving an esterified novolak will only occur if free methylol groups are introduced such are found in the form of an alkaline resole resin.
• the fuel briquetting composition of the present invention also, preferably, contains, as diluent, at least one ester selected from monomethyl esters of an aliphatic carboxylic acid, dimethyl esters of an aliphatic dicarboxylic acid and diethyl esters of an aliphatic dicarboxylic acid.
• ester diluents include the methyl and ethyl esters of formic acid, acetic acid, propionic acid, lactic acid, stearic acid and oleic acid and the dimethyl and diethyl esters of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and maleic acid.
• Resin A 50g was added to a polypropylene jar with screw on lid and hardened by the addition of resole acetate 7.5g.
• the lid was placed on the polythene jar and the formaldehyde concentration was measured after 20 minutes, using a Draeger.
• Formaldehyde 0.2/a detection tube (part no. 6733081) which was inserted through a hole drilled in the polypropylene lid.
• the manufacturer's instructions for use procedure 234-33081e were followed.
• the procedure was repeated using Resin B. A reading was taken after 3 strokes of the Draeger pump.

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Citations (5)

• 1999
  • 1999-06-23 GB GBGB9914537.7A patent/GB9914537D0/en not_active Ceased
• 2000
  • 2000-06-22 EP EP00305291A patent/EP1063277A3/fr not_active Withdrawn

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