MXPA96005232A - Aglomerante system on base of polyurethane for mixed mixed semiproduct for the manufacture of molding of foundry and mac - Google Patents

Abstract

The use of higher fatty acid methyl esters, ie of monomethyl esters of fatty acids with a carbon chain from 12 C atoms, for example, rapeseed methyl ester, as the sole solvent or solvent component for individual components or both, is described. components of binder systems of molded semiproduct of cast iron on a polyurethane base, the components of which comprise a phenol resin containing free OH groups and a polycyanate as a reactant. Fatty acid methyl esters can be at the same time the only solvent, they can be used, at least for the polyisocyanate, also together with high-boiling aromatic hydrocarbons (where then the fraction of methyl esters of fatty acid in the solvent must predominate over the fraction of hydrocarbons), and which can be used, at least for the phenol resin, under the addition of solvents of high polarity. Thanks to the use of methyl esters of fatty acid, remarkable advantages result. In particular, the addition, which until now had always been essential, of aromatic hydrocarbons of high boiling point can be dispensed with entirely or to a large extent.

Description

AGLOMERANTE SYSTEM ON BASE OF POLYÜRETANO FOR MIXED MIXED SEMIPRODUCT FOR THE MANUFACTURE OF MOLDING OF FOUNDRY AND MALE.

D E S C R I P C I O N During the manufacture of casting molds and hammers, a large volume of agglomeration systems based on polyurethane is used. These are two-component systems, one of which consists of polyalcohols with at least two OH groups in the molecule and the other component consists of polyisocyanates with at least two NCO groups in the molecule. These two components are mixed, in dissolved form with a basic material of granular mold (usually sand) and, by the addition of a catalyst, is brought to the hardening reaction. In a typical example of these systems, polyaJ. cohol is a phenol precondensate containing free OH groups or phenol compounds with aldehydes (hereinafter abbreviated "phenol resin") and the polyisocyanate an aromatic polyisocyanate such as diphenylmethane diisocyanate. As a catalyst, tertiary amines are used. Depending on whether you work according to the Coldbox procedure or the 'No-Bale * procedure, the ad- tion of the catalyst is checked either together with the other components of the binder system, immediately before the treatment of the semi-finished product mixture. . either after the introduction of the mixture of molded semi-product, first produced without a catalyst, in a molding tool in which the mixture is gassed with the amine in the gaseous state. In this type of system, solvents are needed to maintain the agglomerating components, during mixing with the basic mold material, in a sufficiently low viscous state. This is true for phenol resins which, due to their high viscosity, regularly require a solvent, but also for polyisocyanates. At the same time, it is a problem that the two agitator components require different types of solvents. Thus, as a rule, homopolar solvents are suitable for polyisocyanates and only to a lesser extent compatible - with fneol resins, whereas for polar solvents the opposite is true. In practice, mixtures of solvents - polar and homopolar, adjusted to the respective binder system - are therefore generally used. The individual components of this mixture must not have, at the same time, a boiling range that is too low, so that the solvent does not cease to be effective too quickly due to evaporation. Homopolar solvents thus far serve - preferably high-boiling aromatic hydrocarbons (generally in the form of mixtures) with a boiling range of greater than about 150 ° C - normal pressure, and as polar solvents have been used, inter alia, certain esters with a sufficiently high point, such as, for example, the "symmetrical" resins described in DE-PS 27 59-262, in which both the acid moiety and the alcohol moiety have a number of atoms of C (approximately 6-13 atoms of C) relatively large, located in the same area. Despite all the advantages of polyurethane binders for the casting technique, it represented -always a decisive disadvantage- the fact that the evaporations and the detachments of gases gave rise to considerable loads in the workplace, which as a rule can not be eliminated with protective measures - such as extractor hoods or similar. Although the development of the resins has meanwhile led, thanks to the reduction of the content of the remainder in free formaldehyde or in free phenol, to products with a very small load as well as to the use of esters that for they have an uncomfortable odor, the utilization of the aforementioned asymmetric ester has brought about a remarkable improvement in this respect., although the problem of loads in the workplace is maintained because of the aromatic compounds of high boiling point, to which - until now it has not been possible to renounce. These aromatic compounds are usually benzoles, toluols and alkyl-substituted xylenes. However, to ensure a boiling point as high as possible, they can also contain compounds with concentrated benzene nuclei, ie naphthalenes, etc., considered among the substances most harmful to health, and be released not only after finishing. the spillage but also be released already during the manufacture of mixtures of molded semi-finished products. The invention wants to help in this respect. According to the invention this is achieved, briefly stated, by the use of methyl esters of higher fatty acids as solvents or solvent components for individual components to the two components of the polyurethane binder. Under the designation - "methyl ester of higher fatty acids", abbreviated "methyl esters of fatty acid", all the monomethyl esters of fatty acids with a carbon chain from 12 carbon atoms are included here. These esters met Lies can be manufactured without problems by transesification of fats and oils of vegetable or animal origin, existing as a rule as triglycerides, or by esterification of fatty acids, obtained from such fats and oils. The methyl ester of rapeseed oil is a typical example of an ester based on vegetable oils and is an adequate solvent, because it is available at a good price, in sufficient quantity, in the form of diesel fuel. Likewise, the methyl esters of other vegetable oils can also be used, such as, for example, soybean oil, linseed oil, sunflower oil, peanut oil, wood oil, palm oil. , of coconut oil, castor oil and / or olive oil. Oils of marine animals, tallow and animal fats can also be used as starting materials for methyl esters which can be used according to the invention. The fats and oils that serve as starting material can exist in any mixture. They do not have to be fresh and pure natural products either; it may also be hardened and modified fats and oils in their chain of C. They can also be used as starting material for the methyl esters which can be used according to the invention, residual oils and fats, such as example of used table or fat for frying. Thus, a further aspect of the invention is that a suitable use possibility is provided for these old materials harmful to the environment. The invention is based on the surprising knowledge that fatty acid methyl esters representing polar solvents can surprisingly take over the function of the previously required homosolar solvents in an excellent manner and can therefore be completely replaced or big measure. As a result, for the first time, it is possible to provide a solvent which is uniformly suitable for the two components of a polyurethane binder system and which can render superfluous the use of homopolar solvents, in particular high-boiling aromatics. This result could not be expected in view of the fact that all the polar solvents proposed hitherto for polyurethane binder systems can not be used without additional homopolar solvents. Especially for reasons of environmental protection, a 100% substitution of the high-boiling aromatic compounds by fatty acid methyl ester is preferred, since they are then fully apparent the ecological advantages of the invention. However, it is also possible to use these methyl esters together with high-boiling aromatic hydrocarbons, if necessary in individual cases. To the extent that at the same time the fatty acid methyl ester fraction predominates over the hydrocarbon fraction, the ecological advantages of the invention also exist clearly, albeit to a degree that it gradually weakens with the reduction content in methyl esters. In total it is therefore provided by the invention, also when the methyl esters are used in minor amounts of aromatic compounds, a variant tolerable by the environment-environment to the conventional binder / solvent systems, which does not remain behind the conventional systems in their performance from the point of view of the -technical foundry. Naturally, solvents with a content of methyl esters of fatty acids and high-boiling aromatics can also be used, in which, in contrast to the fraction of aromatic compounds, the fatty fraction predominates over the fraction of esters of fatty acids. , although then the eco-logical advantages of the invention are no longer sufficiently evident. For the rest, in some cases it may be indicated to add an additive that increases the polarity of the solvent to the solution of the phenol resin in the methyl ester. Numerous polar compounds are suitable for this purpose-for example, a mixture, designated as "Dibasic Ester" or -daily "DBE" -of dimethyl esters of C 4. CB "-dicarboxylic acids. Because of such a polarizing additive, the basic advantages of the use of methyl esters of fatty acids as solvents for polyurethane binder systems are not modified in any way. The rapeseed oil methyl ester already known as a typical example of the solvents to be used according to the invention, is a natural product that respects the environment and is neutral with respect to CO2. It has a high boiling point and is sufficiently fluid, that is to say it satisfies the physical demands imposed on a solvent for polyurethane binder systems. In addition, it is practically odorless and is classified as not harmful in the workplace. It is also not classified as a flammable dangerous substance, which significantly simplifies the transport and storage of the solutions manufactured with it. In addition, during the spillage, there is little room for unwanted gaseous byproducts, because the innumerable double bonds (rapeseed oil contains mostly unsaturated fatty acids one or several times react giving fixed compounds, which do not emit gases. tolerable in the workplace is not achieved, or approximately, during the use of the methyl ester of rapeseed oil as a solvent, otherwise the rapeseed oil methyl ester also gives an excellent separation effect. When separating the males from the molds, it is not necessary to use additional separation means For the other methyl esters of fatty acid and mixtures of methyl esters of fatty acid the same affirmations are fulfilled. due to its problem-free processability, the soybean oil methyl ester, especially good results were achieved in particular cases in cluso better than with the methyl ester of rapeseed oil - with the methyl ester of the -linaza oil. The methyl ester of castor oil is particularly suitable as a solvent for the phenol resin, although there is less consideration for polyisocyanates due to its OH group content, and on the contrary it has the advantage that, because of these OH groups, it is incorporated into the polyurethane. Table 1 lists other methyl esters.

Table 1: Methyl ester of fatty acid Melting point Boiling point (° C) r Palmic acid methyl ester 29.5 129 - 133 Stearic acid methyl ester 38.5 443 (at 747 Torr) Methyl ester of lauric acid 261 - 262 Methyl ester of oleic acid 19 215-216 (at 15 Tor Methyl esters of sorbic acid 170 Methyl ester of linoleic acid -35 207-208 (at 11 To Methyl ester of linolenic acid 207 (at 14 Torr) Methyl ester of araquien acid 46-47 215-216 (at 10 Tor Methyl ester of hehnic acid 53-54 224 (at 20 hPa The following examples are intended to explain the invention without limiting it. The quantity indication "Gl" used in the examples means part by weight. Commercial names are indicated by "(H)". In the examples, the invention is explained in the preferred embodiment in which the high-boiling aromatics have been completely replaced by methyl esters of fatty acid and compared with the same.

The results obtained with the use of conventional solvents. When the methyl esters were used together with high-boiling aromatic compounds, the results were in the area between the results represented below as "according to the invention" and "comparison conventional". Example 1: Manufacture of a phenol resin (precondensate) In a reaction vessel, equipped with coolant, thermometer and agitator, 385.0 GT of paraformaldehyde and 176.0 GT of paraformaldehyde and 1.1 GT of acetate were introduced. zinc. The refrigerator was refluxed. The temperature was brought up continuously, in the range of-one hour, to 105 ° C and was maintained two to three hours at said temperature, until a refractive index of 1.590 was reached. Then the refrigerator was switched to atmospheric distillation and the temperature was increased, in the-one hour interval, to 125-126 ° C, until it was reached. A refractive index of approximately 1,593 was obtained. - A distillation in acry was then carried out up to a refractive index of 1.612. The product accounted for 82 83% of the raw materials introduced. This phenol resin was used for the manufacture of test pieces according to the 'Coldbox' procedure (example 1, solutions were made, when the real value was reached, which presented the composition indicated below: According to the invention ("Resin solution 2E") 100.0 GT phenol resin according to Example 1 54.5 GT rapeseed oil methyl ester and 27.3 GT DBE (H) (mixture of dimethyl esters of C 4 -C acid dicarboxylic acids) 0.3% aminosilane or amidosilan "Conventional comparison" ("2V resin solution) 100.0 GT of phenol resin according to Example 1 29m9 GT Isophoron (cyclic ketone) 23.0 GT Triacetin (glycerin triacetate) (H) 40.0 GT Solvesso 150 (C, QC, 3-mixture of aromatic compounds) 16.7 GT Plastomol DOA (dioctyladipate) In addition, the following polyisocyanate solutions were prepared: "According to the invention" ("Activator 2E") 80 - 85 GT Diphenylmethane diisocyanate (technical MDI) 15 - 20 GT rapeseed oil methyl ester and - 0.2 GT acid chloride "Conventional comparison; (" Activator 2V ") 77.5 GT Diphenylmethane diisocyanate (MDl technical) íH) 19.0 GT Shellsol R (Mixture of hydrocarbons - with 85% aromatics) 3.0 GT Essovarsol 60 (H) (aliphatic and cycloaliphatic hydrocarbons) 0.3 GT 0 0,3 GT Silan acid chloride.

Next, mixtures of molded semi-finished products were mixed by mixing quartz sand, resin solution and activator intimately in an oscillating mixer. With -, c these mixtures were fired, with a firing pressure of 4 bar, specimens (+ GF + bolt), which were then gassed for 10 sec. 3 4 bar pressure gassing with dimethylisopropylamine and then swept with air for 10 sec. The mixtures had the following composition: "According to the invention" ("Males 2E") 100 GT sand quartz H32 0.8 GT resin solution 2E and 0.8 GT activator 2E "Comparative Conventional (" 2V Males ") 100 GT quartz sand H32 0.8 GT resin solution 2V and 0.8 GT 2V activator Then, the resistances were determined -bending the test pieces obtained according to the CF method. Table II compares the values of the resistance of the 2E males and the 2V males. At the same time - the same studies were carried out, on the one hand, with - a mixture treated immediately after mixing to give mold bodies and, on the other, with a mixture with servada 1 hour after mixing (for evaluate the so-called "life time of the sand") and then treated to obtain mold bodies. The determination of the resistance values was verified immediately after gassing (initial resistance) as well as 1 hour or respectively 24 hours after gassing (final resistance). or TABLE II: Resistance to bending in N / cm Table III shows some technical properties of the use of 2E males compared to 2V males. For this, six different series of tests were carried out, that is to say. Series 1: Males stored 1 day in the laboratory, immersed the next day in water mold lubricant, air-dried, checked after 1 day or 2 days. Series 2: Males submerged in water mold lubricant, air dried, checked after 1 or 2 days. Series 3: Males stored 1 day in the laboratory, immersed the next day in water mold lubricant, dried for 1 hour in the oven at 150 ° C, tested after cooling (*). Series 4: Males submerged in water mold lubricant, dried for 1 hour in the oven at 150 ° C, tested after in cold (*). Series 5: Males stored 1 day in the laboratory, stored the next day with RLF (relative humidity of the air) of 100%, checked after 1 respectively 2 days. Series 6: Males stored with RLF (air humidity of 100%), tested after 1. respectively 2 days. 2 TABLE III: Resistance to bending in N / cm Tables II and III make it possible to recognize that the products manufactured according to the invention have in practically all cases the same strength values as conventionally manufactured cores. The essential difference is that the 2E cores do not already generate a perceptible load in the workplace during their manufacture or during their spillage. The behavior during the spill has been confirmed by test spills carried out in the laboratory.

Example 3: 'No-Low' Process From the phenol resin according to Example 1 resin solutions were made with the following composition: According to the invention ("3E resin solution") 58 GT phenol resin 14 GT ester oil rapeseed oil 28 GT DBE (H) Conventional comparison ("3V resin solution") 58 GT phenol resin 28 GT DBE (H) 14 GT Hydrosol AFD (H) (mixture of high-boiling aromatic compounds) The polyisocyanate solutions used for the * No-Bake 'process had the following composition: the invention ("Activator 3E") 85 GT diphenylmethane diisocyanate 15 GT rapeseed oil methyl ester Conventional comparison ("Activator 3V") 70 GT diphenylmethane diisocyanate 30 GT Hydrosol AFD (H) Next, mixtures were made in an oscillating mixer. molded semi-finished product with the following compositions: "According to the invention" ("3E mixture") 100.0 GT quartz sand 1132 0.9 GT resin solution 3E 0.9 GT activator.2E 2.0% phenylpropylpyridine (the percent refers to resin solution) "Conventional comparison (" 3v mixture ") 100.0 GT quartz sand H32 0 0,9 GT resin solution 3V 0,9 GT 3V activator 2.0% phenylpropylpyridine (the so much percent is referred to the resin solution) l- > These mixtures were compacted in molds and left to set. The two mixtures had then tightened - of 2 min. and they were forged after 3 min. After 1 hour respectively, 2 hours or 24 hours, the flexural strengths of the set mixtures were determined. The strength values obtained are compared to each other in Table IV, where it is recognized that the resistance values of the mixture according to the invention are markedly better than those of the conventional mixture. As regards the load in the workplace, the same as in Example 2 is fulfilled.

TABLE III: Resistance to bending in N / crn

Claims (11)

R E I V I N D I C A C I O N S

1. - Polyurethane based binder system for molded cast iron semi-finished products containing a phenol resin, containing free OH groups, and a polyisocyanate as a reactant as well as fatty acid methyl ester as a solvent or as a component of the dissolvent, at least for one of the two reactants, characterized in that the methyl esters of fatty acid are the methylmonoesters of one or more fatty acids with a carbon chain from 12 carbon atoms.

2. Binder system according to the claim 1, which contains methyl esters of fatty acid as sole solvent, at least for the polyisocyanate.

3. The binder system according to claim 1, which contains methyl esters of fatty acid together with high-boiling aromatic hydrocarbons as a solvent, at least for the polyisocyanate, where the fatty acid methyl ester fraction predominates on the fraction of aromatic hydrocarbons.

4. Binder system according to claim 1, which contains methyl esters of fatty acid together with solvents of high polarity as solvents, at least for the phenol resin.

5. Process for the manufacture of a molded semifinished cast iron binder system which as a reagent comprises a phenol resin containing free OH groups and a polyisocyanate, where the phenol resin and / or the polyisocyanate are dissolved in fatty acid esters as a solvent or as a component of the solvent and where the methyl esters of fatty acid with the methyl monoesters of one or more fatty acids with a carbon chain from 12 carbon atoms.

6. Process according to claim 5, characterized in that the methyl esters of fatty acid are used with only solvent, at least for the polyiso cyanate.

7. Process according to claim 5, characterized in that the fatty acid methyl esters are used, together with high-boiling aromatic hydrocarbons, as a solvent at least for the polyisocyanate, and because the fraction of the esters Methyls of fatty acid predominates over the fraction of hydrocarbons.

8. Process according to claim 5, characterized in that the methyl esters are used, together with solvents of high polarity, as solvents for at least the phenol resin. 9.- Use of methyl esters of higher fatty acids as solvents or solvent components for individual components or the two components of binder systems of molded semi-finished product based on polyurethane, whose components comprise a resin of phenol. containing free OH groups and a polycyanate as a reagent. 10. Processing for the manufacture of casting molds and cores from a molded semiproduct mixture, which is agglomerated by means of an agitator system based on polyurethane, which comprises a phenol resin containing free OH groups and a polyisocyanate as a reactant, characterized in that one or two of the binder components are (are) dissolved in a solvent containing fatty acid methyl ester. 11.- Use of a binder based on polyurethane containing a phenol resin containing free OH groups and a polyisocyanate as reagent as well as methyl ester of fatty acid as solvent, therefore for less than one of the two reagents, to agglomerate mixtures of semi-finished products molded during the manufacture of casting molds and cores. SUMMARY The use of higher fatty acid methyl esters, that is, of monomethyl esters of fatty acids with a carbon chain of more than 12 C atoms, for example, methyl ester of rapeseed oil, as the only one is described. solvent or solvent component - for individual components or the two components of binder systems of molded semiproduct of cast iron or on a polyurethane base, the components of which comprise a phenol resin containing free OH groups and a polyacyanate as reactant. Fatty acid methyl esters can be the only solvent at the same time, they can also be used, at least for the polyisocyanate, also jun-l- >; with high boiling point aromatic hydrocarbons (where then the fraction of the fatty acid methyl esters in the solvent must predominate over the - fraction of the hydrocarbons), and that they can be used, - at least for the phenol resin , under the addition of diso_l 2 ventes of high polarity. Thanks to the use of fatty acid methyl esters, there are notable advantages, in particular, the addition, which up to now had always been essential, of hy- 25 aromatic hydrocarbons with high boiling point.