JPH0442103B2 - - Google Patents

Description

[Detailed description of the invention]

Binders and binder systems for foundry cores and master molds are well known. In the foundry art, cores or master molds for producing metal castings are generally manufactured from a mixture of an aggregate material, such as sand, and a binding amount of a binder or binder system. Typically, after mixing the aggregate material and binder, the resulting mixture is tamped, sprayed or otherwise formed into the desired shape or model, and then subjected to a catalyst and/or heat. It is used to harden it into a hard hardened state. Although many different methods for forming main molds or cores have been developed in the foundry industry, a recent development called the "cold box" method has generated much interest. ing.
The "cold box" process is carried out by passing a gaseous catalyst through shaped resin-coated sand at room temperature to achieve crosslinking. In such systems, the resin material is generally dissolved in a solvent prior to coating the aggregate material. The “cold box” binder and method is described in U.S. Patent No.
No. 3905934, No. 3409579 and No. 4246157. The types of binders commonly used in "cold box" systems are disclosed in the above-mentioned US patents. These are generally polyurethanes made from polyhydroxy compounds and polyisocyanates. Polyhydroxy compounds are generally prepared from phenols and formaldehyde. Although such systems have gained market acceptance, there is still a need for "cold box" systems that exhibit improved bench life. Bench life, ie, the amount of time a sand mixture can be used satisfactorily after it has been produced, is much shorter in "cold box" systems than in mixtures used in other casting processes. "Cold box" sand mixtures begin to essentially lose their properties a few hours after mixing and often the effective pot life is even shorter than this, especially in hot, humid environments. In a typical "cold box" application, the sand is mixed with the polyhydroxy compound and polyisocyanate in a mixer such as a mill.
The sand is conveyed to a core blower, typically a hopper, where it is stored and fed to the blow head when needed. The sand mixture is cured by blowing into the core box using air pressure and passing a gaseous tertiary-amine catalyst through the mixture to form a cured polyurethane polymer that binds the sand into the desired shape. However, polyhydroxy compounds and polyisocyanates can react even in the absence of a catalyst. Slow reaction in the absence of catalyst while the sand is in the hopper and blowhead reduces flowability and reduces tensile strength when the core is cured in the core box. This results in weak and insufficiently tight cores that are prone to breakage during handling or storage. A core of insufficient tightness can produce a casting with unacceptable finish or defects such as permeability or erodibility. Sand that is no longer usable in the core machine must be swept out of the hopper and blowhead, as this causes waste of sand and downtime of the machine. Additionally, cleaning at the end of the workday is much easier if the sand remains in the blowhead and the hopper residue is soft and does not stick to the equipment. In accordance with the present invention, the inventors have discovered that the addition of certain phosphorus compounds to the binder prevents the non-catalytic reaction between the polyhydroxy compound and the polyisocyanate, resulting in an improved product with a long bench life. It has been found that a "cold box" binder system can be obtained. In accordance with the present invention, a cold box comprising a polyhydroxy component, an isocyanate group having two or more functional groups, and a catalyst sufficient to substantially completely catalyze the reaction between the polyhydroxy component and the isocyanate component. A foundry binder composition, wherein the composition comprises an additive selected from the group consisting of dichloroaryl-phosphine, chlorodiarylphosphorine, arylphosphone-dichloride, diarylphosphinyl-chloride, and mixtures thereof. characterized in that the additive is present in an amount equal to 0.02 to 3% by weight of the isocyanate component. The above binder composition is provided. Also provided in accordance with the present invention are polyisocyanate components useful in polyurethane binder compositions. The polyisocyanate component includes an additive selected from the group consisting of dichloroarylphosphine, chlorodiarylphosphine, arylphosphone-dichloride, diarylphosphinyl-chloride, and mixtures thereof; present in an amount equal to 0.02-3% by weight of The polyurethane binder compositions of the present invention are suitable for mixing with aggregate materials such as foundry sand or the like to produce foundry cores or master molds. During the manufacture of the core or master mold, sufficient catalyst is used to substantially complete the reaction between the components and the core or master mold is cured. The polyhydroxy component used in the practice of this invention can vary within a wide range. This can be any organic hydroxy compound that has two or more functional groups and is soluble in the solvent used.
Such polyhydroxy compounds may include simple aliphatic polyols, polyether polyols, phenolic resins, and mixtures thereof. Suitable polyhydroxy components are substantially free of water - i.e., contain less than about 5% water, especially less than about 1% water, based on the weight of the resin - and are compatible with the solvent used. Dissolved phenolic resins, such as phenolic resins formed by the reaction of phenolic compounds with aldehydes.
It is a resol resin or a phenolic novolac resin. Resoles (i.e., A-stage resins) as well as resitors (i.e., B-stage resins) are prepared by reacting a molar excess of an aldehyde, such as formaldehyde, with a phenolic compound in the presence of an alkali or metal ion catalyst. It can be manufactured by Novolac resins can be produced by reacting an excess number of moles of a phenolic component with an aldehyde in the presence of an acidic catalyst. The phenols used in producing such phenolic resins are generally any phenols that can be utilized in producing phenolic resins. The only limitation is that the resin made from the phenolic compound must form a homogeneous solution in the solvent at room temperature. Particularly suitable phenols that can be used include: phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,4-xylenol, 3,5-xylenol, 3,4, 5-
trimethylphenol, 2-ethylphenol,
3-ethylphenol, 3,5-diethylphenol, o-2-butylphenol, p-butylphenol, 3,5-dibutylphenol, p-
amylphenol, p-cyclohexylphenol, o-octylphenol, o-2-decylphenol, nonylphenol, 3,5-dicyclohexylphenol, p-phenylphenol, p-crotylphenol, 2-methoxyphenol, 3, 5-dimethoxyphenol, 3,
4,5-trimethoxyphenol, p-ethoxyphenol, 3-methyl-4-methoxyphenol and p-phenoxyphenol. One suitable phenolic component is a commercially available mixture containing about 80% o-cresol and about 18% phenol. However, it should be understood that other suitable phenolic resin components may also be used in the practice of the present invention. The aldehyde used in preparing the phenolic resin component used in the present invention can also vary within a wide range. In general, suitable aldehydes include all aldehydes used as described above in the production of phenolic resins, such as formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and benzaldehyde. Generally, the aldehydes used have the formula R'CHO, where R' is a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms. The most preferred aldehyde is formaldehyde. The isocyanate components that can be used in the binders according to the invention can likewise vary within a wide range and have more than one functional group. Examples of useful isocyanates are organic polyisocyanates such as toluylene-2,4-diisocyanate, toluylene-2,6-diisocyanate and mixtures thereof, especially the crude mixtures thereof available on the market. Other representative polyisocyanates include methylene-bis-(4-phenyl isocyanate), n-hexyl-diisocyanate, naphthalene-1,5-diisocyanate, cyclopentylene-1,3-diisocyanate, p
-Phenylene diisocyanate, toluylene-
There are 2,4,6-triisocyanate and triphenylmethane-4,4',4''-triisocyanate. Higher isocyanates include liquid reaction products of (1) diisocyanate and (2) polyol or polyamide. Additionally, isothiocyanates and mixtures of isocyanates can be used.Also, many commercially available impure or crude polyisocyanates are contemplated.Particularly preferred for use in the present invention are those having the general formula These are polyaryl-polyisocyanates represented by: In the above formula, R is selected from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms; selected from the group consisting of 10 alkyl groups and phenyl groups, and n has an average value of at least about 1, generally an average value of about 1 to 3. Typical commercially available isocyanates are:
Upjohn Co.'s PAPI−135−
is a polymethylene-polyphenyl isocyanate, having a Bruckfield viscosity at 25°C of about 200 cp and an isocyanate equivalent weight of 134. In general, the amounts of polyhydroxy and isocyanate components used in the binder compositions of the present invention are not critical and can be varied within wide limits. However, there should be at least enough isocyanate component present to substantially completely react with the polyhydroxy component. It is not critical that there is an excess of either unreacted component when the reaction is complete. The isocyanate component is generally used in the range from 15 to 400% by weight, based on the polyhydroxy component, and is advantageously used in the range from 20 to 200% by weight. However, while liquid isocyanates can be used undiluted, solid or viscous isocyanates can also be used, as long as sufficient solvent is used together with the polyhydroxy component.
Generally used together with organic solvents. In this regard, the isocyanate component may contain up to 80% by weight of solvent. Furthermore, according to the invention, both the polyhydroxy component and the isocyanate component are in practice advantageously dissolved in a solvent in order to provide a component/solvent mixture of the desired viscosity, thus e.g. This facilitates its use in coating materials with the respective components. In this regard, about 1000 cp or less,
In particular, sufficient solvent is used to provide a solution of each component with a Bruckfield viscosity of less than 250 cp. Furthermore, although the total amount of solvent can vary within a wide range, generally in the compositions of the present invention, the amount of solvent is between 5 and 70% based on the total weight of the polyhydroxy component.
Preferably, it is present in a range of 20 to 60% by weight. Solvents used in the practice of this invention are generally hydrocarbon solvents, including particularly polar organic solvents such as organic esters. Examples of suitable hydrocarbon solvents include benzene, toluene, xylene, ethylbenzene, high boiling aromatic hydrocarbon mixtures, heavy aromatic naphtha, and the like. It is advantageous to use hydrocarbon solvents with a flash point of 100ⓓ or more. As previously mentioned, the compositions of the present invention are particularly suitable for curing by the "cold box" process. When using the "cold box" process, the catalyst used is generally a volatile catalyst. Examples of advantageous catalysts include volatile tertiary amine gases. This is passed through a core or master mold, generally with an inert carrier such as air or _CO2 . In this regard, gas treatment conditions can vary over a wide range, but the amine catalyst should be in contact with as much binder as possible to ensure substantially complete reaction between the polyhydroxy and isocyanate components. should. Examples of volatile tertiary amine catalysts that can be used in the practice of this invention and provide rapid curing at ambient temperatures include trimethylamine,
Includes triethylamine and dimethylethylamine and their analogs. The binder compositions of the present invention may employ a wide variety of aggregate materials, such as silica sand, lake sand, zircon, chromite, and the like. They are particularly useful in foundry technology as bonding compositions for foundry sands. When used in this manner, the amount of binder composition can vary within wide limits and is not critical. However, at least a binding amount of the binder composition should be present to substantially completely cover all sand particles. Advantageously, the binder is present in the mixture in the range from 0.7 to 4.0% by weight, based on the total weight of the composition. The binder composition of the present invention is “cold boxed”.
When used in casting processes, the polyhydroxy component and isocyanate are first mixed with the aggregate material. Since the catalyst is added to the mixture as the last component of the composition, premature reactions between the components do not occur. The polyhydroxy component and the isocyanate component should not be brought into contact with each other until ready for use to avoid any premature reaction.
These components may be mixed with the aggregate material simultaneously or one after the other in suitable mixing equipment. It has been discovered that the addition of certain organophosphorus compounds slows the premature reaction of the binder components. This is particularly beneficial if the mixture of aggregate material and binder components is to be held for several hours before being placed in the core box. Useful organophosphorus compounds are selected from the following groups: dichloroarylphosphines, chlorodiarylphosphines, arylphosphone-dichlorides and diarylphosphinyl-chlorides. These have the following general structural formulas: ArPCl ₂ , Ar ₂ PCl, ArPOCl ₂ and
_Ar2POCl . In each formula, Ar is phenyl, naphthyl,
Aromatic groups such as substituted phenyl, substituted naphthyl and the like. The type of substituents can vary within wide limits. Examples of particularly suitable aryl groups include: o
-Toluyl, m-toluyl, p-toluyl, o-
Methoxyphenyl, m-methoxyphenyl and p-methoxyphenyl. The organophosphorus compound is conventionally mixed with the isocyanate component-containing solution at any time prior to its use in the binder system. The phosphorus compound can be mixed with the aggregate material neat or in solution. This addition may be made either before, simultaneously with, or immediately after the addition of other binder components to the aggregate material. Very low concentrations of organophosphorus compounds act to retard premature reaction of the binder components. The effective concentration of phosphorus compounds in the binder will vary somewhat with the type and purity of the binder and aggregate components. A particularly advantageous concentration of organophosphorus compounds used according to the invention is from 0.02 to 3% by weight of the isocyanate compounds. Other commonly used additives can optionally be used in the binder compositions of the present invention. Such additives include, for example, coupling agents.
This includes organic silanes known as agents. Use of such materials can enhance the adhesion of the binder to the aggregate material. Examples of useful coupling agents of this type include amino-silanes, epoxy-silanes, mercapto-silanes, hydroxy-silanes, and ureido-silanes, such as γ-aminopropyltrimethoxysilane, γ-
Hydroxypropyltrimethoxysilane, 3-ureidopropyl-triethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,
4-epoxycyclohexyl)trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and their analogs. In the practice of the invention, additives commonly utilized in casting manufacturing processes may also be added to the composition during the sand coating operation. Such additives include iron oxide, clay, potassium fluoroborate, wood flour, and the like. Using the binders of the present invention provides "cold box" systems with improved bench life when compared to previously used polyurethane binders. Although the polyurethane binders of the present invention are discussed in the context of a "cold box" casting system, they may also be used in other applications where it is necessary to mix each urethane component for some period of time before adding catalyst to the mixture. Can be used. The present invention will be explained in further detail by the following examples. In the examples all parts and percentages are by weight. Example 1 This example illustrates the use of various organophosphorus compounds in a urethane binder system.
The polyhydroxy component of the binder used in this test was Acme Flow 2030 Part 1 resin, a phenolic compound available from Acme Resin Corporation, Forest Park, Illinois.・It is a resol resin solution. Isocyanate solution has a flash point above 100〓25%
75% polymethylene in an aromatic hydrocarbon solvent
Manufactured by dissolving polyphenyl isocyanate. 100 parts of isocyanate solution,
Add 0.25 part of each additive listed in the table. The resole resin and isocyanate components are mixed with 20KK lake sand using a Hobart A-120-mixer. The casting mixture was allowed various time intervals before being used to create 1 inch dog bone tensile test samples. These are Redford CBT-1-
Produced by blowing the mixture into a core blower. The core was blown with air pressure of 50psi and
Gass at 30 psi for 3 seconds with 12% dimethylethylamine in CO ₂ and then 30 psi for 5 seconds with purified air. The tensile strength was determined after 1 minute of curing using the Detroit Testing Machine Company.
Company) Measure using a CST type tensile strength testing machine. The test results are shown in Table 1. 4 before gas treatment
These mixtures have good bench life resulting in cores exhibiting high tensile strength after holding for ~6 hours. Inhibitor, i.e. phenylphosphone
The sand mixture containing dichloride, dichlorophenylphosphine and chlorodiphenylphosphine exhibits a bench life that is superior to that of the control core without any additives. Also, this product is carboxylic acid chloride, benzoyl-
Superior to comparative test cores containing chloride. In further evaluating the sand/binder-mixture:
A compression test specimen 2 inches in diameter and 2 inches in height was packed with 170 g of sand mixture in a Dietert No.
Manufactured by tamping using a 315 sand tamper. Raw compressive strength is Deitelt No.454C
Measurements are taken after 24 hours using either a compression tester (up to 3 psi) or a No. 400 sand tester (up to 18 psi). Test specimens for measuring green compressive strength made using the binder of the present invention using three types of organophosphorus compounds exhibit 24-hour green compressive strength values of 7.9 to 10.3 psi.
In contrast, the green compressive strength after 24 hours of the control and the binder using benzoyl chloride is greater than 18 psi. These results show that the additives of the invention greatly reduce the tendency of casting mixtures containing polyhydroxy compounds and polyisocyanates to harden before adding the catalyst.

【table】

EXAMPLE 2 The procedure of Example 1 is followed, except that in each case the additive is 1% by weight of the isocyanate component solution. The results are shown again in Table 1. The table shows that the organophosphorus compounds of the present invention effectively inhibit premature reaction of the polyhydroxy and isocyanate components used in molding compositions. When a 24 hour green compressive strength test is conducted on the sand mixture of this example, the organic phosphorus compound containing mixture exhibits a green compressive strength value of 2.3 to 3.3 psi.
In contrast, specimens prepared without inhibitor or with benzoyl chloride as an additive exhibit green compressive strength values greater than 18 psi. This demonstrates the ability of the organophosphorus compound to prevent premature curing of the mixture.

【table】

【table】

【table】

Claims (1)

[Claims] 1. A combination for cold box casting comprising a polyhydroxy component, an isocyanate component having two or more functional groups, and a catalyst sufficient to catalyze the reaction between the polyhydroxy component and the isocyanate component. an additive selected from the group consisting of dichloroaryl-phosphine, chlorodiarylphosphine, arylphosphophone-dichloride, diarylphosphinyl-chloride, and mixtures thereof;
The additive is 0.02 to 3% by weight of the isocyanate component.
A binder composition characterized in that it is present in an amount equal to. 2. The binder of claim 1, wherein the additive is selected from the group consisting of dichlorophenylphosphine, chlorodiphenylphosphine, phenylphosphone dichloride, diphenylphosphineyl chloride, and mixtures thereof. Composition. 3 The aryl group of the additive is o-tolyl, m-tolyl, p-tolyl, o-methoxyphenyl,
A binder composition according to claim 1, wherein the binder composition is selected from m-methoxyphenyl and p-methoxyphenyl. 4. The binder composition according to any one of claims 1 to 3, wherein the polyhydroxy component is a phenolic resin. 5. The binder composition according to any one of claims 1 to 4, wherein the additive is dissolved in the isocyanate component.