JP2019502768A - Polyurethane binder containing alcohol solvent - Google Patents

Abstract

Binder systems for molding material mixtures are useful when low release of aromatic solvents is required. This binder system has two components that are packaged separately for combination in use. The first component has a polyol-based resin having at least two —OH groups per molecule and an alkyl alcohol having 2 to 5 carbon atoms as a solvent. The second component has a polyisocyanate having at least two —NCO groups per molecule. The alkyl alcohol may be absolute ethanol and the first component is substantially free of aromatic hydrocarbon solvent. The second component will usually consist essentially of diphenylmethane diisocyanate (MDI) with a bench life extender of less than 0.1%. The first component may contain at least one fatty acid methyl ester and at least one dibasic ester. This binder system may be used to carry out either a “cold box” or “non-fired” method.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a copy of US Provisional Application No. 62 / 248,543, filed Oct. 30, 2015, which is incorporated by reference as if fully set forth herein. It is a non-provisional application and claims priority.

TECHNICAL FIELD This invention relates to polyurethane-based binder systems for use in cold box or non-fired processes. In this system, alcohol is used to at least partially replace the aromatic solvent. In particular, the alcohol selected is an alkyl alcohol having 2 to 5 carbon atoms. Most specifically, the alcohol selected is ethanol. In addition, more specifically, alcohol is used in the polyol-containing component of the two-component polyurethane-based binder system.

  When producing molds and cores, large amounts of polyurethane-based binder systems are used, particularly for mold and core production using a cold box or polyurethane unfired process. These systems require solvents and there continues to be a need to reduce emissions from these systems when used.

  In a typical polyurethane-based binder system, a two-component system is provided to the user. The first component contains a polyol component that includes a compound having at least two —OH groups per molecule. The second component is a polyisocyanate component that includes a compound having at least two isocyanate groups per molecule. The inclusion of a solvent in at least one of these components is considered almost axiom, and in many cases both components contain a solvent. When a solvent is included with each component, the components are usually sold in separate containers and are combined only at the time of use.

  Certain details of the polyol and polyisocyanate components are well documented in the art and need not be described in more detail here. However, when a solvent is used for each component, it is useful to note that it is particularly useful that the solvent is compatible when the components are mixed. Both polyol and polyisocyanate components will be used in liquid form. Liquid polyisocyanates may be used in undiluted form, but solid or viscous polyisocyanates may be used in the form of organic solvent solutions. In some cases known in the art, the solvent may comprise up to 80% by weight of the polyisocyanate solution. When the polyol used for the first component is a solid or highly viscous liquid, a suitable solvent is used to adjust the viscosity to allow proper application properties.

  As readily taught from the prior art, the solvent (s) selected are not intended to participate in any relevant manner in the catalytic reaction between the polyisocyanate and the polyol compound, but they are It can affect the reaction very well. For example, the two binder components have substantially different polarities. This limits the number of solvents that can be used. If these solvents are not compatible with both binder components, complete reaction and curing of the binder system is very difficult. Protic and aprotic types of polar solvents are usually good solvents for polyol compounds, but they are less suitable for polyisocyanate compounds. On the other hand, aromatic solvents are compatible with polyisocyanates, but are not entirely suitable for polyol resins.

  In the art, common aromatic solvents include so-called “BTX” solvents. Benzene, toluene, and xylene. In order to be industrially acceptable, a given solvent must meet several criteria, including the cost of the solvent, its environmental implications, and its health and safety implications. In some situations, these combinations may require a polyurethane-based binder system that reduces or eliminates the amount of aromatic solvent, particularly BTX solvent, to meet these criteria.

  Accordingly, it is still a challenge of the prior art to provide a polyurethane-based binder system that meets the lower limits on BTX solvent or volatile organic carbon (VOC) emissions for use in cold box or non-fired processes. It is not a goal.

  These disadvantages of the prior art are overcome at least in part by the present invention described in more detail below. A binder system for the molding material mixture is used when low release of aromatic solvents is required. This binder system has two components that are packaged separately for combination in use. The first component has a polyol-based resin having at least two —OH groups per molecule and an alkyl alcohol having 2 to 5 carbon atoms as a solvent. The second component has a polyisocyanate having at least two —NCO groups per molecule. The alkyl alcohol may be absolute ethanol and the first component is substantially free of aromatic hydrocarbon solvent. The second component typically consists essentially of diphenylmethane diisocyanate (MDI) with less than 0.1% bench life extender. The first component may contain at least one fatty acid methyl ester and at least one dibasic ester. This binder system may be used to perform “cold box” or “non-fired” methods.

  In some embodiments, the first and second components, respectively, are present in a weight ratio such that the first component weighs less than the second component. More specifically, a preferred embodiment uses about 48 parts by weight of the first component and about 52 parts by weight of the second component.

  In one preferred embodiment, the first component contains about 56.8% by weight polyol resin, 23.9% by weight of at least one dibasic ester, and 16.9% by weight alkyl alcohol. The balance is at least one fatty acid methyl ester.

  For use as a molding material mixture, an amount of refractory mold base material is mixed with the binder system components.

  Preferred refractory mold base materials include: Quartz ore sand, zirconium ore sand, chrome ore sand, olivine, chamotte, bauxite, aluminum silicate hollow spheres, glass beads, glass granules, spherical ceramic molding materials, and combinations thereof.

  In the molding material mixture, the binder system is present in an amount of 0.2-5% by weight, preferably in the range of 0.3-4% by weight, most preferably 0.4, based on the weight of the refractory mold base material. It is present in the range of ˜3% by weight.

  Through the use of this alcohol solvent, the method of producing molds or cores for molten metal casting is dependent on how the curing agent is applied to the binder system, the polyurethane “cold box” method or the polyurethane “non-fired” Can be law.

  A known method for producing cores, called the “cold box process”, has become very important in the casting industry. In this method, a two-component polyurethane system is used to bond the basic refractory molding material. The polyol component consists of a polyol having at least two OH groups per molecule, and the isocyanate component consists of a polyisocyanate having at least two NCO groups per molecule. The binder system is cured by passing gaseous tertiary amine therethrough as the molding material / binder system mixture is injected into the molding cavity (US Pat. No. 3,409,579). In the non-fired process, liquid amine is added to the binder system prior to molding to react the two components (US Pat. No. 3,676,392).

  According to U.S. Pat. No. 3,676,392 and U.S. Pat. No. 3,409,579, phenolic resins are used as polyols, which are liquids at temperatures up to about 130 ° C. in the presence of catalytic amounts of metal ions. It is obtained by condensing an aldehyde in the phase, preferably formaldehyde, with phenol. U.S. Pat. No. 3,485,797 describes the production of such phenolic resins in detail. In addition to unsubstituted phenol, substituted phenols, preferably o-cresol and p-nonylphenol may be used (see, eg, US Pat. No. 4,590,229). As an additional reaction component, according to EP-A-0177871 A2, phenolic resins modified with aliphatic monoalcohol groups having 1 to 8 carbon atoms can be used. As a result of alkoxylation, the thermal stability of the binder system should have increased. As a solvent for the polyol component, a mixture of a high boiling polar solvent (eg, ester and ketone) and a high boiling aromatic hydrocarbon is mainly used. In contrast, polyisocyanates are preferably dissolved in high boiling aromatic hydrocarbons.

  In the formulations described in EP 0 771599 A1 and WO 00/25957 A1, all or at least most of the aromatic solvent can be replaced by using fatty acid esters.

  In the polyurethane systems known from US Pat. No. 4,051,092, for example, dibutoxymethane, dipropoxymethane, diisobutoxymethane, dipentyloxymethane, dihexyloxymethane, dicyclohexyloxymethane, n-butoxyisopropoxymethane, Of solvents such as isobutoxybutoxymethane and isopropoxypentyloxymethane, acetaldehyde-n-propyl acetal, benzaldehyde-n-butyl acetal, acetaldehyde-n-butyl acetal, acetone-di-n-butyl ketal and acetophenone-dipropyl ketal In the presence, an epoxy resin, a polyester resin, or an aqueous phenol formaldehyde resin reacts with the diisocyanate. In the examples, ketal butyral (1- (butoxymethoxy) butane) is used. U.S. Pat. No. 4,116,916 and U.S. Pat. No. 4,172,068 have similar disclosures.

The use of diacetals in polyurethane systems, in particular the conversion products of C ₂ to C ₆ dialdehydes and C ₂ to C ₁₂ alcohols, is disclosed in WO 2006/092716 A1. Listed as diacetals are 1,1,2,2-tetramethoxyethane, 1,1,2,2-tetraethoxyethane, 1,1,2,2-tetrapropoxyethane, 1,1,3, 3-tetramethoxypropane and 1,1,3,3-tetraethoxypropane. Diacetal has been determined to allow for an extended processing time of the molding material mixture. However, this has a substantially detrimental effect on the stability of the fresh mixture (“immediate firing”). The loss of stability for the unmodified binder is from about 15% to about 20%.

  For most applications, the strength of the core and mold produced by known polyurethane binders is sufficiently high.

  However, if possible, to further increase the strength level to reduce the binder content without losing strength, i.e. without dropping below that required for good casting and safe handling. Interest is growing. There are several reasons for reducing the amount of binder, such as to reduce the amount of gases and condensates produced during casting, which can lead to casting defects and can contaminate the environment, etc. It is. In addition, the low binder content reduces the cost of reclaiming previously used used sand, and in particular, foundries are interested in using as little binder as possible for commercial reasons. There is.

  Of particular importance with regard to the strength level is appropriate when the core is assembled immediately after production or placed in a permanent metal mold, particularly in (partly) automated equipment to form complex core packages. It is to ensure the initial strength level.

  Accordingly, the problem addressed by the present invention is to produce molded articles for the casting industry using economically and ecologically advantageous solvents that result in lower and lower BTX and volatile organic carbon (VOC) emissions. It was to provide a polyurethane-based molding compound mixture that makes it possible to do so.

  The object of the present invention comprises at least one polyol component having a polyol having at least two —OH groups per molecule and at least one isocyanate component having a polyisocyanate having at least two —NCO groups per molecule. It is to provide a binder for a molding material mixture. The polyol component further comprises at least one alkyl alcohol, in particular an alkyl alcohol having 2 to 5 carbon atoms. Most specifically, the alkyl alcohol is absolute ethanol.

  The invention further comprises a basic refractory molding material and a binder system according to the invention with a maximum of 5 wt%, preferably a maximum of 4 wt%, particularly preferably a maximum of 3 wt%, based on the weight of the basic refractory molding material. It relates to a molding material mixture comprising. Suitable refractory materials include, for example, quartz ore sand, zirconium ore sand, or chromium ore sand, olivine, chamotte, bauxite, and the like. Molded materials produced synthetically can also be used, such as aluminum silicate hollow spheres (so-called microspheres), glass beads, glass granules, or spherical ceramic molding materials known as “cerabeads” or “carbaccucast”. . Mixtures of the above-mentioned refractory materials are also possible.

  In addition, the present invention relates to a method for producing a cast mold piece or core. This is because the refractory material has a binding amount of the invention of 0.2-5 wt%, preferably 0.3-4 wt%, particularly preferably 0.4-3 wt%, relative to the amount of refractory material. This is accomplished by mixing with the system to obtain a molding mixture. This molding mixture is placed in a mold and cured in a pattern to obtain a self-supporting cast mold piece. The cured molding mixture is separated from the pattern and further cured if necessary to obtain a hard solid cured cast mold piece. At this point, molten metal may be poured into the casting mold.

  Surprisingly, it has been found that the use of alkyl alcohols, particularly ethanol, as part of the binder formulation, easily meets the economic, ecological and practical performance criteria of the binder. As a further advantage, it has been found that alkyl alcohols improve the low temperature resistance of the binder component.

  In binder compositions that use a two-component approach to provide a polyurethane cold-box (PUCB) or polyurethane-no-bake (PUNB) binder system, there is a solution to the release problem. Looks like it ’s been served. In such systems, the Part I component comprises a polyol-based resin, a set of suitable complements, and an alkyl alcohol, and the Part II component includes a polyisocyanate with a set of suitable complements.

  The phenolic resin and polyisocyanate may be selected from the group consisting of compounds conventionally known to be used in cold box processes or non-calcined processes. This is because the concepts of the present invention are not believed to be inherent to these parts of the composition.

  Specifically referring to phenolic resin, the phenolic resin is generally selected from the condensation product of phenol and an aldehyde, in particular an aldehyde of the formula RCHO, where R is hydrogen or an alkyl moiety having 1 to 8 carbon atoms. is there. The condensation reaction is carried out in the liquid phase, typically at temperatures below 130 ° C. Some such phenolic resins are commercially available and will be readily known.

  Preferred phenolic resin components will include benzyl ether type phenolic resins. In individual cases, it may be advantageous to use alkylphenols, such as, for example, o-cresol, p-nonylphenol, or p-tert-butylphenol, in particular in a mixture with phenol, for the preparation of phenolic resins. If desired, these resins may be characterized by alkoxylated end groups obtained by capping hydroxymethylene groups with alkyl groups such as methyl, ethyl, propyl, and butyl groups.

  With respect to polymeric isocyanates, several commercially available polymeric isocyanates are directed to this particular market, but it may be preferable to use a polyisocyanate component including diphenylmethane diisocyanate (MDI). The isocyanate component (second component) of a two-component binder system for a polyurethane cold box or non-baking process usually comprises an aliphatic, cycloaliphatic or aromatic polyisocyanate preferably having 2 to 5 isocyanate groups. And mixtures of such polyisocyanates may also be used. Particularly suitable polyisocyanates among aliphatic polyisocyanates are, for example, hexamethylene diisocyanate, and particularly preferred among alicyclic polyisocyanates are, for example, 4,4′-dicyclohexylmethane diisocyanate. Particularly suitable among the isocyanates are, for example, 2,4′- and 2,6′-toluene diisocyanate, diphenylmethane diisocyanate, and dimethyl derivatives thereof. Further examples of suitable polyisocyanates are 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylene diisocyanate, and their methyl derivatives, polymethylene polyphenyl isocyanate (polymer MDI), and the like. All polyisocyanates react with the phenolic resin with the formation of a crosslinked polymer structure, but in practice aromatic polyisocyanates are preferred. Particularly preferred are diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate (polymer MDI), and mixtures thereof.

  The polyisocyanate is used at a concentration sufficient to effect curing of the phenolic resin. Generally, 10 to 500% by weight, preferably 20 to 300% by weight of polyisocyanate is used, based on the mass of the (undiluted) phenolic resin used. The polyisocyanate is used in liquid form. Liquid polyisocyanates may be used in undiluted form, solid or viscous polyisocyanates are used in the form of organic solvent solutions, and the solvent can account for up to 80% by weight of the polyisocyanate solution.

Traditionally, several solvents have been used for Part I and Part II components. One is a dibasic ester, generally a methyl ester of a dicarboxylic acid. Sigma-Aldrich sells this type of dibasic ester under the name DBE, which is believed to have the structural formula CH ₃ O ₂ C (CH ₂ ) _n CO ₂ CH ₃ , Here, n is an integer from 2 to 4. Another solvent is kerosene, which is understood to be the generic name for petroleum distillate cuts having boiling points in the range of 150-275 ° C.

  Other useful solvents are aromatic solvents commercially available as AROMATIC SOLVENT 100, AROMATIC SOLVENT 150, and AROMATIC SOLVENT 200, which are also known as SOLVESSO 100, SOLVESSO 150, and SOLVESSO 200, respectively. These have CAS registry numbers 64742-95-6, 64742-95-5, and 64742-94-5, respectively. SOLVESSO is a registered trademark whose Exxon has expired, but these solvents are called by their names even if they come from other sources.

Each part of the formulation also includes performance additives. A particularly preferred performance additive in the Part I component is hydrofluoric acid (which is usually used as a 49% aqueous solution, but may be used with different dilutions or different diluents). Coupling agents and additives based on fatty acids can also be used. Preferred performance additives in the Part II component include modified fatty oils and bench life extenders, which will include phospholeoxytrichloride (POCl ₃ ), phenyl dichlorophosphate, and benzyl phospholeoxydichloride.

  Recently developed binder systems use alkyl alcohols, especially ethanol, as the solvent instead of the conventionally used aromatic solvents. As with conventional systems, the binder is provided in two parts, which are preferably packaged separately and combined only in use. The Part I component contains a base polyol resin, a dibasic ester (“DBE”), a fatty acid alkyl ester such as rapeseed methyl ester or soy methyl ester, and ethanol. The Part II component is substantially diphenylmethane diisocyanate (MDI), but generally contains a small but effective amount (about 0.05% by weight) of a conventional bench life extender. It will be immediately noted that this formulation does not contain the aromatic solvents benzene, toluene, and xylene (commonly referred to collectively as “BTX”). Thus, binder systems having this composition may be useful in markets where BTX emissions are severely limited, but the flash point of this system may be disadvantageous in markets where flash point limitation is implemented. However, the economics and “green” nature of ethanol will provide benefits for selected markets.

  Ethanol is different from the BTX family of solvents because it is a reactive diluent in the binder system. For exemplary purposes only, other reactive diluents are used in furan, epoxy, and urethane resin formulations. Again by way of example only, some of these reactive diluents include triethylene glycol, resorcinol, and various mono- or bifunctional glycidyl ethers. However, the use of reactive diluents in conventional phenolic polyurethanes is not common mainly for the purpose of reducing costs. The reactive solvent or diluent can be polymerized during the curing process and dispersed within the polymer matrix. Because reactive diluents are involved in the reaction, lower amounts of volatile organic compounds (“VOC”) are expected. Since ethanol is a monofunctional alcohol, it can react with the isocyanate of the Part II composition to terminate the polyurethane. Alcohols with higher functionality can extend or crosslink the polymer.

  When using a solvent with reactive hydroxyl groups, it is important to consider the amount of isocyanate groups required to react completely with the total amount of polyol and solvent. Low “equivalent” solvents greatly increase the amount of isocyanate required. The formula for equivalence is well known in the industry and can be readily used by one skilled in the art. The inverse of “equivalent weight” is “equivalent”, which can also be calculated for each component according to known equations. Most usefully, the ratio of -NCO to -OH, most commonly multiplied by 100, is expressed as an "index".

  As a general rule, this index should be within about 15% of 100. However, when these calculations are made based on a binder composition containing ethanol and a polyol resin having an equivalent of 115 g / eq and containing parts I and II in a ratio of 60/40, an index of 58 is obtained. It is done. Even if Part II is 99.95% MDI, this system lacks sufficient isocyanate for complete reaction. When adjusting the ratio to 48/52, the index improves to 94 within the ideal range. This calculation does not assume ethanol loss due to evaporation during mixing. Thus, improved performance may be obtained by further refinement of the ratio.

  In addition, this calculation reveals that 1 wt% ethanol consumes 2.94 wt% MDI. Therefore, it is necessary to consider that the use of ethanol requires an increase in the amount of MDI, which can result in costs.

  Ethanol as the primary alcohol is more reactive than diacetone alcohol (CAS Reg. Nr. 1234-24-2) which has been used as a solvent in the binder system. This increase in reactivity is apparent in the results of actual working time. The addition of a bench life extender can solve some reactivity problems, but causes other problems. When ethanol is used, the binder may require additional catalyst to achieve reactivity comparable to standard systems. In addition, unfired binder systems have the problem of accelerating faster than 2.5 minutes of working time even with very strong catalysts. It is observed that the sand to be mixed is less fluid due to the lower total amount of solvent or the immature ethanol reaction. Finally, the bench life extender reduces the overall strength performance of the cured core and mold.

  To demonstrate this concept, several experimental formulations were devised and then used for tensile strength testing. In these examples, the polyol resin is a benzylic ether phenolic resin having a hydroxyl equivalent weight of 115 g / eq, CAS Reg. Nr. 9003-35-4. The dibasic ester used is a mixture of dimethyl glutarate, dimethyl succinate and dimethyl adipate. INNOVATI 170 is a commercially available methyl ester of fatty acids of soybean oil, CAS Reg. Nr. 67784-80-9.

  In the examples provided, isocyanate type 1 is a polymer diphenylmethane diisocyanate having an NCO content of 31-33%. 4-PPP is 4- (3-phenylpropyl) pyridine (4- (3-phenylpropyl) pyridine), CAS Reg. Nr. 2057-49-0. NMI is N-methyl imidazole, CAS Reg. Nr. 616-47-7. References to ethanol are to absolute ethanol.

Composition A
The first formulation, called Composition A, had the following Part I ingredients.

  The Part II ingredients for Composition A were as follows:

  Monophenyl dichlorophosphate has CAS Reg No 770-12-7. Composition A may be generally characterized as a binder system in which the BTX solvent is completely replaced by the ethanol of Part I component. Such systems may have commercial applications in markets where ethanol is readily available and BTX release is severely limited. As an example, such a market can be found in Brazil.

Composition B
A second formulation, called Composition B, had the following Part I ingredients.

  The Part II ingredients for Composition B were as follows:

  The Part I component of Composition B was modified by replacing the Part I DBE and INNOVATI 170 solvent of Composition A with an aromatic hydrocarbon solvent ("BTX solvent"). In addition, Composition B has the same Part II ingredients as Part II of Composition A.

Composition C
A third formulation, called Composition C, had the following Part I ingredients.

  The Part II ingredients for Composition C were as follows:

  Composition C is characterized as a conventional phenolic binder system used in the United States and is provided as a phenolurethane non-calcined binder baseline comparison for that market. Part II has a lower percentage of isocyanate type I than Compositions A and B because there is no ethanol in the Part I component used together.

Tensile Strength Test Tensile strength tests were performed on Wedron 410, 51 GFN quartz sand having a binder level of 1.2% by weight in each case.

  In the first test shown in Table 1 below, a conventional phenolurethane unfired binder formulation (Composition C) was compared to binders with ethanol-containing Part I (Compositions A and B). Unexpectedly, ethanol-containing systems require more catalyst to achieve comparable working and strip times, with an index of -NCO vs. -OH of 58 for the high index of 88 for composition C. However, because of insufficient isocyanate, the tensile strength could not be developed over time. Note that compositions A and B included a bench life extender in Part II to inhibit premature reaction between ethanol and isocyanate, resulting in high catalyst requirements.

  As is well known, the “working time” used above refers to the time between mixing the binder component and sand until the cast shape formed reaches a hardness that effectively prevents further work in the pattern. It can be understood roughly as an expression of the time that elapses. More technically, “working time” refers to the shape of the cast formed when the Detroit, MI Harry W. It is the time elapsed to reach a level of 60 on the Green Hardness “B” scale using a gauge sold by Dietert. Details of this test are found in many places, including shared US Pat. No. 6,602,931. “Strip time” is a rough definition of the elapsed time from mixing the binder component and sand to when the cast shape formed can be removed from the pattern. In the technical sense used herein, “strip time” is the time required for the cast shape formed to achieve a level of 90 on the same green hardness “B” scale. Therefore, the difference between the strip time and the work time is the amount of wasted time that cannot be worked on the formed mold but cannot yet be removed from the pattern.

  Compositions C and A were tested again using a “hotter” NMI catalyst to provide faster working times. Composition A required a higher NMI content in the mixed catalyst system in order to achieve the desired working time / strip time characteristics. As shown in Table 2 below, the results are consistent with the results in Table 1 and are not against expectations.

  As stated with respect to Table 1, Composition A was first tested at an index well below the desired index of about 90 to 110. The desired index can be obtained by adjusting the Part I to Part II ratio from 60/40 to 48/52. When this is done and the conditions in Table 1 are repeated, the tensile strength again does not match the conventional phenol urethane unfired binder baseline (Composition C in Table 1), but this binder develops strength over time. to continue.

  As stated, in Table 1, the binder was applied at 1.2% by weight. By increasing the binder to 1.48% by weight and using a ratio of 48/52, composition A was determined to have a 1 hr tensile strength of 157 and a tensile strength of 302 and 309 at 3 hr and 24 hr, respectively. It was done. Thus Composition A (1.48% binder) can approach the performance of the Composition C baseline (1.2% binder) by adjusting the proportion and amount of binder used. I understand.

VOC Tests Volatile organic carbon (“VOC”) can be measured by several different tests. The first of these tests is the EPA method (Method) 24. In that test, a sample weighing 0.3-0.5 g is dissolved in 3 ml of acetone and placed in an oven at 110 ° C. for 1 hour. The percentage of VOC is based on the weight lost. This test was performed on Compositions C, A, and B, a Part I component of a phenolurethane non-fired binder baseline and two ethanol-containing systems. The respective% VOCs were 53.9%, 51.8%, and 49.8%. These results are essentially equal and cannot be distinguished. The Part II component was not actually tested according to EPA Method 24, but for Compositions A and B, it is believed to be less than 5% VOC due to the high isocyanate and absence of AROMATIC 100 components. Since conventional Part II components have a VOC content according to EPA Method 24 in the range of 20% to 40%, an ethanol containing system would be expected to reduce the VOC content for the entire system.

  The second type of VOC test is the EPA Method 24 “Reaction” test. In this test, a sample of multi-component binder (ie, containing Part I, Part II, and catalyst) weighing about 0.3 g is mixed in the desired ratio and then dissolved in 3 ml of acetone. This is acclimated for 1-24 hours and placed in an oven at 110 ° C. for 1 hour. The percentage of VOC is based on the weight lost. Baseline composition (C) had 30.2% VOC in the EPA Method 24 “Reaction” test. When the ethanol-containing composition A was measured at a Part I / Part II ratio of 60/40, the EPA Method 24 “Reaction” was 14.4% VOC. When the same composition was measured at a more preferred 48/52 ratio, the EPA Method 24 “Reaction” VOC content dropped to 7.2%, a 50% reduction, about 20% of the baseline composition. Is the amount.

  A third type of VOC test that is considered relevant by one or more regulatory authorities is the OCMA test (Ohio Cast Metals Association). In this test, weight loss is measured for the sand and binder mixing bowl over a 24 hour period. Since the amount of binder can vary, the results can be reported as pounds of VOC per ton of mixed sand or pounds of VOC per pound of binder. When Baseline Composition C was tested with 4-PPP at a 55/45 ratio and 1.25 wt% BOB, the pounds of VOC per tonne of sand was 1.03 after 12 hours and after 24 hours. It is measured as 1.41, which translates to 0.050 and 0.069 pounds of VOC per pound of binder, respectively. It is noted that most of the weight loss of the ethanol-containing composition A occurred during mixing, which is not unexpected.

  Among alcohols with low molecular weight, ethanol will be in a unique position for this application. Methanol has a lower flash point and higher toxicity. In addition, methanol is unlikely to be available from renewable “green” sources. None of the isomers of propanol, higher molecular weight alcohols, all have a higher flash point than ethanol, but are typically not available by fermentation of renewable resources.

Claims (14)

A binder system for a molding material mixture comprising:
A first component having a polyol-based resin having at least two —OH groups per molecule and an alkyl alcohol having 2 to 5 carbon atoms as a solvent;
A second component having a polyisocyanate having at least two -NCO groups per molecule;
A binder system in which the respective components are packaged separately and combined in use.   The polyurethane binder precursor of claim 1, wherein the alkyl alcohol is absolute ethanol.   3. A binder system according to claim 1 or claim 2 wherein at least the first component is substantially free of aromatic hydrocarbon solvent.   The binder system of claim 1 or claim 2, wherein the first and second components, respectively, are present in a weight ratio such that the first component is less weight than the second component. .   3. A binder system according to claim 1 or claim 2, wherein the second component consists essentially of diphenylmethane diisocyanate (MDI) with a bench life extender of less than 0.1%.   3. The binder system according to claim 1 or claim 2, wherein the first component comprises at least one fatty acid methyl ester and at least one dibasic ester in addition to the polyol base resin and the alkyl alcohol.   The first component contains about 56.8% by weight of the polyol resin, 23.9% by weight of the at least one dibasic ester, and 16.9% by weight of the alkyl alcohol, with the balance being 7. The binder system according to claim 6, wherein the at least one fatty acid methyl ester.   3. The first and second components of claim 1 or claim 2, wherein the first and second components are packaged such that about 48 parts by weight of the first component is used with about 52 parts by weight of the second component. Binder system. Fireproof mold base material,
A molding material mixture comprising a binder system according to any one of the preceding claims.   The refractory mold base material comprises quartz ore sand, zirconium ore sand, chromium ore sand, olivine, chamotte, bauxite, aluminum silicate hollow sphere, glass beads, glass granules, spherical ceramic molding material, and combinations thereof 10. Molding material mixture according to claim 9, selected from the group.   The binder system is present in an amount of 0.2-5% by weight based on the weight of the refractory mold base material, preferably in the range of 0.3-4% by weight, most preferably 0.4-3. 11. Molding material mixture according to claim 9 or claim 10, present in the range of% by weight. A method for producing a mold or core for casting molten metal, comprising:
Providing an organic binder system and a refractory molding material, wherein the organic binder system is provided as two components that are not combined until in use;
Mixing the two components of the organic binder system with the refractory molding material to provide a moldable casting mixture;
Forming a mold or core with the moldable casting mixture;
Curing the formed mold or core.   13. The method of claim 12, wherein the method is a polyurethane “cold box” method and the curing step is accomplished by passing a gaseous tertiary amine through the formed mold or core.   The method of claim 12, wherein the method is a polyurethane “non-fired” method and the curing step is accomplished by adding a liquid phase tertiary amine to the two components and the refractory molding material. .