Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
  • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
  • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • B22C1/2273—Polyurethanes; Polyisocyanates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/54—Polycondensates of aldehydes
  • C08G18/542—Polycondensates of aldehydes with phenols

Definitions

• the present invention relates to urethane foundry binders. More particularly, it relates to binder systems, based on urethane polymers, for use in the production of foundry moulds and cores.
• Urethane foundry binder systems are conventionally employed in the form of two components, a resin component, such as a phenolic resin, and a polyisocyanate hardener component which, when mixed together, react to produce a polyurethane.
• the two components may be mixed together before being mixed with a foundry aggregate, such as sand, or may be mixed with the foundry aggregates sequentially.
• the resin component, and usually the polyisocyanate component are employed in the form of solutions in order to keep the viscosities of the components at a reasonably low level so that they can be uniformly distributed throughout the foundry aggregate during mixing.
• solvents makes it possible for other materials, which can influence or modify the properties of the binder system, those of the moulding mixture, (i.e., the mixture of the binder and the foundry aggregate prior to moulding) or those of the final moulds or cores, to be incorporated.
• the isocyanate component is traditionally employed as a solution in a non-polar solvent, typically a high boiling aromatic hydrocarbon
• the phenolic resin component is traditionally employed as a solution in a mixed solvent system comprising a polar solvent, for compatibility with the phenolic resin, and a non-polar solvent, typically a high boiling aromatic hydrocarbon, to provide compatibility with the polyisocyanate.
• a non-polar solvent typically a high boiling aromatic hydrocarbon
• the present invention is based on a discovery of the inventors that these and other disadvantages of the prior art binder systems may be overcome by using a novel solvent system in a two-part urethane binder.
• the present invention provides a two-component foundry binder system for use in the manufacture of foundry moulds and cores comprising, as first component, a solution in a solvent of a phenolic resin having free hydroxyl groups and, as second component, a liquid polyisocyanate or a solution in a solvent of a polyisocyanate, which polyisocyanate is capable of reacting with the phenolic resin of the first component, when the first and second components are mixed together, to produce a polyurethane characterised in that the solvent in the first component comprises butyl diglycol acetate.
• the phenolic resin of the first component of the two-component binder system is preferably a non-aqueous condensation product obtained by the reaction of a phenol, preferably the compound phenol itself, with an aldehyde which typically will be formaldehyde.
• the phenolic resin will have free hydroxyl groups available for reaction with the isocyanate groups in the polyisocyanate.
• the phenolic resin is a predominantly ortholinked benzylic ether phenol-formaldehyde resole resin which is either uncapped or capped with alkoxy groups, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy and isobutoxy groups.
• Such resins may be prepared by the condensation reaction of phenol and formaldehyde (50% aqueous solution) and/or paraformaldehyde at a temperature of 95 to 105°C in the presence of an ortho-directing catalyst, such as an acetate or naphthenate of zinc, tin, manganese, cobalt or lead. Once the polymer has been condensed to the desired level it is dehydrated under reduced pressure to a specified viscosity and free phenol content.
• an ortho-directing catalyst such as an acetate or naphthenate of zinc, tin, manganese, cobalt or lead.
• the second component of the two-component urethane foundry binder system of the present invention comprises an aliphatic, cycloaliphatic or aromatic polyisocyanate preferably having from 2 to 5 isocyanate groups and mixtures of these.
• Suitable polyisocyanates include aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate, and aromatic polyisocyanates such as 2,4- and 2,6-toluene diisocyanate, diphenylmethyl diisocyanate, and the dimethyl derivatives thereof.
• suitable polyisocyanates are 1 ,5-naphthalene diisocyanate, triphenyl methane triisocyanate, xylylene diisocyanate, and the methyl derivatives thereof, polymethylenepolyphenol isocyanates and chlorophenylene-2,4-diisocyanate.
• the preferred polyisocyanates are aromatic polyisocyanates and particularly diphenylmethane diisocyanate and triphenylmethane triisocyanate.
• the polyisocyanate will be employed in sufficient concentrations to cause the curing of the phenolic resin.
• the polyisocyanate will be employed in a range of 10 to 500 weight percent of polyisocyanate based on the weight of the phenolic resin.
• the polyisocyanate if liquid, may be used without a solvent although it may also be used in the form of a solution in a solvent in order to ensure thorough and uniform mixing with the other components and with a granular refractory material. Solid or viscous polyisocyanates will have to be employed as solutions in a solvent.
• the polyisocyanate will be employed as a solution in a solvent comprising at least one di-isobutyl ester of a dibasic acid, typically a 4-8C alkanedioic acid, since the use of such a solvent system improves the humidity resistance of moulds and cores obtained.
• Di-isobutyl esters of dibasic acids are polar and, despite the teaching in the art that the use of polar solvents may be detrimental to urethane systems, do not cause any problems of compatibility with the polyisocyanate.
• the di-isobutyl ester will be a di-isobutyl ester of a saturated dicarboxylic acid of general formula HOOC(CH 2 ) x COOH, wherein x is an integer of from 2 to 4, for example di-isobutyl succinate, di-isobutyl glutarate and di-isobutyl adipate and mixtures of two or more of these.
• these esters have low odour and their use does not create unpleasant conditions in the workplace unlike high-boiling aromatic hydrocarbons such as naphthalene and alkyl-substituted benzenes which are conventionally used as the solvent for the polyisocyanate component in the prior art binder systems.
• the di-isobutyl ester of a dibasic acid, or mixtures thereof, may be used as the sole solvent for the polyisocyanate or may be used together with one or more esters selected from 2 to 8C alkyl esters of a 12 to 18C fatty acid.
• the use of at least one such fatty acid ester, as cosolvent, is found to improve the strength performance of moulds and cores formed from moulding mixtures comprising a binder system containing such cosolvents.
• the esters will be ethyl, butyl or 2-ethylhexyl esters of 12-18C fatty acids and examples of such esters include ethyl oleate, ethyl rapeate, ethyl palmitate (also known as ethyl palmeate), butyl oleate, 2-ethylhexyl palmitate and 2- ethylhexyl cocoate.
• fatty acid esters as "ethyl rapeate” and "2-ethylhexyl cocoate” what is meant is the ethyl esters and 2- ethylhexyl esters of the fatty acids derived from rapeseed oil and coconut oil, respectively. These may be mixtures of two or more ester compounds such as ethyl oleate, ethyl palmitate, ethyl laurate and the like. We have found that the best strength improvements are obtained in this invention by using ethyl rapeate or ethyl palmitate as the cosolvent for the polyisocyanate component of the binder system.
• the fatty acid ester cosolvent and the di- isobutyl ester of a dibasic acid are used in approximately equal amounts, on a % by weight basis, as the solvent for the polyisocyanate component.
• the total solvent comprises from 20 to 30% by weight of the second component of the binder system.
• the first component of the two-component binder system comprises a solution of the phenolic resin in one or more of 1 to 4C alkanoic acid esters of glycols or glycol ethers, i.e., 1 to 4C alkanoic acid esters of lower alkylene diols, such as formates, acetates, propionates and butyrates of ethylene glycol, propylene glycols and butylene glycols and ethers of these.
• 1 to 4C alkanoic acid esters of glycols or glycol ethers i.e., 1 to 4C alkanoic acid esters of lower alkylene diols, such as formates, acetates, propionates and butyrates of ethylene glycol, propylene glycols and butylene glycols and ethers of these.
• esters used in the prior art have a disagreeable odour or have a detrimental effect on the final properties of moulds and cores obtained from moulding mixtures containing them.
• the esters used in the present invention are not only less odorous than the ester solvents proposed in the prior art but that their use as solvents for the phenolic resin gives final products having properties at least as good as those of products obtained using prior art ester solvent systems.
• 1 to 4C alkanoic acid esters of"glycols and glycol ethers that can be used include butylene glycol diacetate and butyl diglycol acetate. We particularly prefer butyl diglycol acetate as the solvent for the phenolic resin in view of the good results obtained using it.
• the use of one or more fatty acid esters as cosolvent for the phenolic resin component is preferred since these esters enhance the performance of the final products.
• these esters are 2 to 8C alkyl esters of 12 to 18C fatty acids, for example ethyl oleate, ethyl rapeate, ethyl palmitate, butyl oleate, 2-ethylhexyl palmitate and 2-ethylhexyl cocoate.
• the two- component binder system includes a first component which comprises a solution of a phenolic resin in a solvent system which is a mixture of butyl diglycol acetate (as major solvent component) and a fatty acid ethyl ester (as minor solvent component) and a second component which comprises a solution of a polyisocyanate in a solvent system which is a mixture of 50% by weight of at least one di-isobutyl ester of a dibasic acid with 50% by weight of a fatty acid ethyl ester.
• the fatty acid ethyl ester used as a cosolvent in each of the first and second components of the binder system is selected from ethyl rapeate and ethyl palmitate, with ethyl palmitate being most preferred. It is also preferred that the same fatty acid ethyl ester will be used as cosolvent in both the first and second components of the binder system.
• One or both components of the binder system of the present invention may contain one or more other additives to modify the properties of the binder system or products obtained using the binder system.
• a silane adhesion promoter such as 3-glycidylpropyl trimethoxysilane may be incorporated in either or both components to improve adhesion between the binder and the foundry aggregate used.
• Phenylphosphonic chloride which is known to improve bench life characteristics of moulding mixtures, may also be incorporated.
• the present invention also provides a method of making a foundry mould or core which comprises the steps of mixing the two-component binder system as described herein with a foundry aggregate, moulding the resultant mixture into the desired shape and allowing the binder system to harden and cure.
• the two components of the binder system may be premixed before being added to and being mixed with the foundry aggregate.
• one of the components of the binder system may be added to and mixed with a granular refractory material and then the other component may be added to and mixed with the existing mixture of the refractory material and binder component.
• Curing of the binder will typically be carried out according to techniques known in the art, such as by the use of a gaseous amine, such as triethylamine or dimethylisopropylamine or by the use of a liquid tertiary amine, such as phenyl propyl pyridine, which is incorporated into the mixture of components.
• a gaseous amine such as triethylamine or dimethylisopropylamine
• a liquid tertiary amine such as phenyl propyl pyridine
• the foundry aggregate typically sand, will form the major constituent of the mixture with the binder system.
• the amount of binder used will typically be less than 10% by weight of foundry aggregate and more typically will be in the range of from 0.2 to 5% by weight of the foundry aggregate.
• UCB 150 Base PF is a benzylic ether resole resin prepared as follows:
• the sand and hardener were mixed together for 1 minute to ensure an even sand/hardener mixture (setting 3 on the mixer speed control was used).
• the required amount of the part 1 resin (COMPONENT ONE) was weighed into a paper cup and then transferred to the sand. The sand/hardener mixture and the resin were then mixed together to ensure thorough and even mixing.
• a gassing lid specially made to fit, was placed onto the top of the flexural box and clamped to the top of the box. Gaseous triethylamine was passed into the box for a period of 5 minutes at a flow rate of 15 cm 3 /S to cure the samples in the moulds.
• the first three flexural pieces were tested immediately after the curing procedure was terminated and the fourth, fifth and six pieces were tested one hour after termination of the curing procedure.
• the seventh, eighth and ninth pieces were tested 24 hours after curing and the tenth, eleventh and twelfth pieces, immediately after termination of the curing procedure, were placed in a humidity cabinet where they remained for 24 hours. They were then removed from the humidity cabinet and tested immediately after removal.
• the conditions of the humidity cabinet (HL 4033 Heraeus Vosch) were set at 20°C and 100% relative humidity.
• All flexural strengths are expressed as kg/cm "2 .
• RPDE-9 (Rhone Poulenc) is a mixture of ⁇ 15% dimethyl adipate, ⁇
• Coasol is a trademark of Chemoxy International pic and comprises di-isobutyl glutarate 55-65% di-isobutyl adipate 12-23% di-isobutyl succinate 15-25%
• Glymo Silane is 3-glycidylpropyl trimethoxysilane
• a sand/hardener/part 1 mixture was prepared as described above and the mixture was stored in a 2.5 I metal tin. Flexural transverse pieces were prepared as described above.
• flexural pieces were prepared as described in Examples 1 to 6 with the exception that a liquid catalyst was incorporated into the binder mixture, as shown, instead of the samples being cured by gassing (as in the case of Examples 1 to 6).
• Some flexural pieces so prepared were tested as described in Examples 1 to 6, 1 hour after the introduction of the catalyst, others were tested 2 hours after the introduction of the catalyst and others were tested 24 hours after the introduction of the catalyst into the binder mixture. Further samples were kept in a humidity cabinet for 24 hours at 50% relative humidity before being tested.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)
• Mold Materials And Core Materials (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 1999
  • 1999-06-03 GB GBGB9912812.6A patent/GB9912812D0/en not_active Ceased
• 2000
  • 2000-06-01 WO PCT/GB2000/002106 patent/WO2000074873A2/en not_active Application Discontinuation
  • 2000-06-01 EP EP00935373A patent/EP1181120A2/de not_active Withdrawn
  • 2000-06-01 AU AU50919/00A patent/AU5091900A/en not_active Abandoned
• 2001
  • 2001-11-30 NO NO20015866A patent/NO20015866D0/no not_active Application Discontinuation

Non-Patent Citations (1)

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