Title of Invention

A TWO COMPONENT-BINDER SYSTEM BASED ON POLYURETHANE FOR FOUNDRY MOULDING MATERIALS AND A METHOD FOR PREPARING THE SAME

Abstract A two component-binder composition based on polyurethane for foundry moulding materials and a method for preparing the same" The invention relates to a two-component binder composition based on polyurethane for foundry moulding materials and to a method for preparing the same. This composition consists of a phenolic resin containing free OH groups and a phenolic isocyanate with fatty acid methyl esters as solvent, said fatty acid esters being methyl monoesters of one or more fatty acid having carbon chain of 12 or more C atoms.
Full Text

The present invention relates to a two component-binder
system based on polyurethane for foundry moulding materials and a method for preparing the same.
To produce casting molds and cores, frequently binder systems on the basis of polyurethane are used. These are two-component systems, one compo¬nent of which consists of polyols with a minimum of two OH groups in the molecule and the other of polyisocyanates with a minimum of two NCO groups in the molecule. These two components, in dissolved form, are added to a basic granular molding material (in most cases sand) and are subjected to a curing reaction by adding a catalyst.
In a typical example of such systems, the polyol 1s a precondensate of phenol or phenol compounds with aldehydes which contains free OH groups (hereinafter referred to as "phenolic resin"), and the polyisocyanate is an aromatic polyisocyanate, such as diphenylmethanediisocyanate. Tertiary amines are used as catalyst. Depending on whether the cold-box process or the nobake process is used, the catalyst, in combination with the remaining ingredients of the binder system, 1s added either immediately prior to pro¬cessing the molding material mixture or after the molding material mixture, which Is Initially produced without catalyst, has been added into a mold in which the mixture is sfassed with gaseous amine.
In this type of system, solvents are required to ensure that during mixing with the basic molding material, the components of the binding agent are maintained at a sufficiently low viscosity. This Is particularly true with respect to phenolic resins which, due to their higher viscosity

always require a solvent, but it also applies to polylsocyanates. One pro¬blem encountered in this context is that the two binder components require different types of solvents. Thus, as a rule, nonpolar solvents work well with polylsocyanates but are not readily compatible with phenolic resins, and the reverse applies to polar solvents. In practice, it is therefore common to use mixtures of polar and nonpolar solvents which are balanced specifically for the binder system used. In this context, It should be en¬sured that the boiling range of the Individual components of this mixture is not too low so that the solvent does not turn prematurely ineffective due to evaporation.
The nonpolar solvents preferably used so far were high-boiling aroma¬tic hydrocarbons (mainly in the form of mixtures) with a boiling range above approximately 150' c at normal pressure, and the polar solvents used were, among other things, certain sufficiently high-boiling esters, such as the "symmetrical" esters described in the German Patent Specification No. 2,759,262, the add residue and the alcohol residue of which contain a re¬latively large number of C atoms within the same range (approximately 6 -13 atoms).
In spite of all the advantages of polyurethane binders for foundry technology, these binders have one serious drawback In that they are re¬sponsible for evaporations and the gas evolution in the working place, which, in most cases, cannot be prevented by protective measures, such as fume hoods, or similar devices. As a result of the fact that, in the mean¬time, it was possible to reduce the residual content of free formaldehyde and free phenol, the development in the area of resins has led to products which cause very low workplace exposure; and even with respect to the esters which, by nature, have a disagreeable smell, it has been possible to improve the situation markedly by the use of the symmetrical esters mentio¬ned above, but what remains is the problem of exposure to the high-bqiling aromatic hydrocarbons in the working place, which so far could not be dis¬pensed with. These aromatic hydrocarbons are generally alkyl-substltuted benzenes, toluenes, and xylenes. To ensure the highest possible boiling point, however, they may, in addition, also contain compounds with conden¬sed benzene rings, i.e., naphthalene, etc., which are substances considered hazardous to human health and which are released not only after casting but already during the production of the molding material mixtures.

This problem is to be solved by this Invention. Briefly, this is achieved according to this Invention through the use of methyl esters of higher fatty acids as the solvent or solvent component for the individual or both components of the polyurethane binders. In this context, the term "methyl esters of higher fatty acids", hereinafter referred to as "fatty acid methyl esters", includes all monomethyl esters of fatty acids having a carbon chain of 12 C atoms or more. These methyl esters can be readily pre¬pared by transesterification of fats and oil of vegetable of animal origin which are normally available in the form of triglycerides or can be pre¬pared without problems by esterification of fatty acids obtained from such fats and oils.
Rapeseed oil methyl ester is a typical example of an ester on the ba¬sis of vegetable oils; 1t is a suitable solvent, particularly since it is available at low cost in the form of diesel fuel. But the methyl esters of other vegetable oils, such as soybean oil, linseed oil, sunflower oil, peanut oil, tung oil, palm kernel oil, coconut oil, castor oil and/or olive oil, can also be used. In addition, marine animal oil, tallows, and animal fats can also serve as starting materials for methyl esters that are to be used according to this invention.
The fats and oils which serve as starting materials can be used in random mixtures. They need not be either fresh and pure natural products, but may be used in the form of hydrogenated fats and oils or those which have been otherwise modified in the C chain. Even waste oils and waste fats, e.g., used table oils or oils used for frying, can be used as starting materials for the methyl esters that are to be used according to this invention. Thus, a further aspect of this invention is to make use of waste materials that are harmful to the environment.
The invention is based on the surprising discovery that the fatty acid methyl esters which are polar solvents can surprisingly perform, in a very outstanding manner, the function of the nonpolar solvents required to date and can thus entirely or substantially replace these. Thus, it is possible for the first time to offer a solvent which can be suitably used for both components of a polyurethane binder system and which, at the same time, may make the use of nonpolar solvents, especially of high-boiling aromatic hydrocarbons completely superfluous. In view of the fact that it

was so far not possible to use any of the polar solvents proposed for use in polyurethane binder systems without the addition of nonpolar solvents, this finding was not to be expected.
A 100 % replacement of the high-boil1ng aromatics by fatty acid methyl esters is to be preferred especially for environmental protection reasons since in this case, the ecological advantages of this invention can be fully utilized. It is^_however, also possible to use these methyl esters together with high-boiling hydrocarbons if this should be expedient in Individual cases. If the amount of the fatty acid methyl esters exceeds the amount of the hydrocarbons, the ecological advantages of the Invention are stm sufficiently evident, although to a degree which gradually decreases. Overall, the invention thus provides an environmentally compatible variant of the conventional binder/solvent systems, even when the methyl esters are used together with relatively small amounts of aromatics, said variant not being inferior to these conventional systems- It is of course also possible to use solvents containing fatty acid methyl esters and high-boiling aroma¬tics, in which, conversely, the amount of aromatics predominates over the amount of fatty acid methyl esters, but in this case the ecological advan¬tages of the invention are no longer sufficiently evident.
In addition, in certain cases it may be useful to also add an ad¬ditive, which increases the polarity of the solvent, to the solution of the phenolic resin in the methyl ester. Suitable for this purpose are many polar components, for example a mixture of dimethyl esters of dicarboxylic acids with 4 to 6 carbon atoms, also known as "dibasic esters", abbreviated as "DBE". The use of this type of polarizing additive in no way entails a change of the basic advantages obtained when fatty acid methyl esters are used as solvents for polyurethane binder systems.
The rapeseed oil methyl ester mentioned above as a typical example of the solvents to be used according to this invention is an environmentally harmless and natural COg-neutral product. It is high-boiling and suffici¬ently thin-bodied, i.e., it meets the physical requirements of a solvent for polyurethane binder systems. In addition, it is also nearly odor-free and considered to be harmless with respect to emissions measured in the workplace. Furthermore, it is not classified as a combustible hazardous substance, a fact that makes transportation and storage of the solutions

prepared (with this methyl aster) very easy. In addition, during casting, almost none of the undesirable gaseous breakdown products form since the numerous double bonds (rapesead oil contains predominantly mono- und poly¬unsaturated fatty acids) react to form solid compounds which do not evolve gas. When rapeseed oil methyl esters are used as the solvent, the maximum permissible exposure limits are not even approached. Furthermore, rapeseed oil methyl ester has an excellent release effect and thus facilitates the removal of cores and molds, which obviates the use of additional release agents.
The same applies to the other fatty acid methyl esters and fatty acid methyl ester mixtures. Due to Its easy processibility, the methyl ester of soybean oil deserves special mention. Particularly satisfactory results were obtained with the methyl ester of linseed oil - in some cases even better than with rapeseed methyl ester. Castor oil methyl ester is a parti¬cularly suitable solvent for phenol resin but, due to its content of OH groups, it Is less satisfactory for polyisocyanates and, on the other hand, has the advantage that, owing to these OH groups, it is incorporated in the polyurethane. Other methyl esters are listed in Table I.


In the examples, the invention is explained in the preferred embodiment in which the high-boiling aromatics have been completely replaced by fatty acid methyl esters and is compared with results which are obtained with the use of conventional solvents. When the fatty acid methyl esters were used together with high-boiling aromatics as solvents, the results fall in the range between the results indicated below as "according to this invention" and those indicated below as "conventional solution for comparison purposes".
Accordingly, the present invention provides a two-component binder system based on polyurethane for foundry moulding materials, containing: a phenolic resin containing free OH groups, a polyisocyanate and fatty acid methyl esters as solvent constituent for the phenolic resin and as sole solvent or solvent constituent for the polyisocyanate, wherein the fatty acid methyl esters are the methyl monoesters of one or more fatty acids having a carbon chain of 12 or more C atoms and are selected from the group consisting of methyl esters of rapeseed oil, soja oil, linseed oil, sunflower oil, peanut oil, wood oil, palm oil, coconut oil, castor oil and olive oil, the methyl esters of marine animal oils, tallows and animal fats, the methyl esters of waste oils and waste fats as well as methyl palmitate, methyl stearate, methyl laurate, methyl oleate, methyl sorbate, methyl linoleate, methyl linolenate, methyl arachidonate and methyl behenate, wherein the fatty acid methyl ester content is greater than the content of any high-boiling aromatic hydrocarbons that may be present.
Accordingly, the present invention also provides a method for the preparation of a foundry moulding material binder system as described above, wherein the phenolic resin and the polyisocyanate are dissolved in the fatty acid methyl esters as solvent constituent for the phenolic resin and as sole solvent or solvent constituent for the polyisocyanate,

Example 1: Preparation of a phenolic resin (precondensate) 385.0 pbw of phenol 176.0 pbw paraformaldehyde, and 1.1 pbw zinc acetate
were placed into a reaction vessel which was equipped wtih a cooler, a thermometer, ahd-a stirrer. The cooler was set to reflux. The temperature was allowed to rise continuously to 105' C within one hour and was subse¬quently maintained atfjhis temperature for two to three hours until a re¬fractive index of 1.590 was reached. Subsequently, the cooler was set to atmospheric distillation, and the temperature was increased to 125* C -126* C within one hour until a refractive index of approximately 1.593 was reached. This was followed by vacuum distillation until a refractive index of 1.612 was reached. The yield was 82 - 83 X of the raw materials used.
This phenolic resin was used to produce test specimens according to the cold box process (Example 2) and test specimens according to the no-bake process (Example 3).
Example 2: Cold box process
After reaching the desired value, the phenolic resin according to Example 1 was used to prepare solutions which had the following composi¬tion:
According to this invention ("resin solutibn 2E') 100.0 pbw of phenolic resin according to Example 1 54.5 pbw of rapeseed oil methyl ester, and
27.3 pbw of QBE (T) (mixture of dimethyl esters of dicarboxylic edde wtth 4 to
6 carbon atoms)
0.3 % aminosilane Oder amidosilane


0.8 pbw activator 2E Conventional mixture for comparison purposes ("Cores 2V") 100.0 pbw quartz sand H32
0.8 pbw resin solution 2V, and
nn nhw nctlvfttor 9V

Subsequently, the flexural strength of the test specimens obtained in this manner was determined using the GF method. In Table II, the flexural strength of cores 2E and of cores 2V are compared. The same tests were car¬ried out first using a mixture from which test specimens were produced im¬mediately after mixing was concluded and next (to assess the so-called "sand life") with a mixture that was first stored for 1 hour and then pro¬cessed into test specimens. The flexural strength was assessed immediately after gassing (initial strength) and 1 and 24 hours after gassing (final strength).

Table III illustrates several performance properties of cores 2E in comparison with cores 2V. Six different test series were carried out, such as:
Test series 1: The cores were stored for 1 day in the laboratory,
immersed in water sizing on the following day, air-dried, and tested after 1 and 2 days.
Test series 2: The cores were immersed in water sizing, air-dried, and tested after 1 and 2 days.
Test series 3: The cores were stored for 1 day in the laboratory,
immersed in water sizing on the following day, dried for 1 hour in the oven at 150* C, and tested after chilling (*).
Test series 4: The cores were immersed in water sizing, dried for
1 hour in the oven at 150' C, and tested after chilling (*).

Tast series 5: The cores were stored for 1 day 1n the laboratory, stored on the following day at a relative humidity of 100 X, and tasted after 1 and 2 days.
Tast series 6: The cores were stored at a relative humidity of 100 %; and tested after 1 and 2 days.

Tables II and III show that in all cases, the cores which were produced according to this invention have practically the same flexural strength as the cores that were produced using the conventional method. The important difference is that there Is no longer a noticeable contamination of the working place when cores 2E are produced and cast. The properties during casting were confirmed by specimens cast in the laboratory.
Example 3: No-bake-process
Following the instructions in Example 1, resin solutions with the following composition were prepared from the phenolic resin:
According to the invention ("resin solution 3E")
58 pbw phenolic resin
14 pbw rapeseed oil methyl ester, and
28 pbw of DBE (T)
Conventional mixture for comparison purposes Cresin solution 3V")
58 pbw of phenolic resin
28 pbw of DBE
14 pbw of HydroSOl AFD (Blxtur* of high-boUfng aroMtlc hydrocarbon*)
The polyisocyanate solutions used for the no-bake process had the following composition:

According to this Invention ("activator 3E")
85 pbw of dlphenylmethanedlisocyanate
15 pbw of rapeseed oil methyl ester
Conventional mixture for comparison ourposes ("activator 3V"'>
70 pbw of dlphenylmethanedlisocyanate
30 pbw of Hydrosol AFD
Subsequently, molding material mixtures of the following cofflposition were prepared In a vibratory mixer:
According to this invention ("mixture 3E") 100.0 pbw of quartz sand H32
0.9 pbw of resin solution 3E
0.9 pbw of activator 3E

Conventional mixture for comparison purposes ("mixture 3V") 100.0 pbw of quartz sand H32
0.9 pbw of resin solution 3V
0.9 pbw of activator 3V
2.0 X of phenylpropylpyridine
These mixtures are tamped Into molds and allowed to cure. Both mixtures were set after 2 min and cured after 3 min. After 1 hour, 2 hours, and 24 hours, the flexural strength of the cured mixtures were determined. The fle-xural strength of the mixture according to this invention is Invariably su¬perior to that of the conventional mixture. As to the contamination of the working place, the statements in Example 2 also apply here.



WE CLAIM:
1. A two-component binder system based on polyurethane for foundry moulding materials, containing: a phenolic resin containing free OH groups, a polyisocyanate and fatty acid methyl esters as solvent constituent for the phenolic resin and as sole solvent or solvent constituent for the polyisocyanate, wherein the fatty acid methyl esters are the methyl monoesters of one or more fatty acids having a carbon chain of 12 or more C atoms and are selected from the group consisting of methyl esters of rapeseed oil, soja oil, linseed oil, sunflower oil, peanut oil, wood oil, palm oil, coconut oil, castor oil and olive oil, the methyl esters of marine animal oils, tallows and animal fats, the methyl esters of waste oils and waste fats as well as methyl palmitate, methyl stearate, methyl laurate, methyl oleate, methyl sorbate, methyl linoleate, methyl linolenate, methyl arachidonate and methyl behenate, wherein the fatty acid methyl ester content is greater than the content of any high-boiling aromatic hydrocarbons that may be present.
2. The two-component binder system as claimed in claim 1, wherein said high-boiling aromatic hydrocarbons is not used as co-solvent.
3. The binder system as claimed in claim 1 or 2, wherein the fatty acid methyl esters is the sole solvent for the polyisocyanate.
4. The binder system as claimed in claim 1, wherein the fatty acid methyl esters together with high-boiling aromatic hydrocarbons are the solvent, at least for the polyioscyanate, the fatty acid methyl ester content being greater than the hydrocarbon content.

5. The binder system as claimed in claim 1 or 2, wherein the fatty acid methyl
esters together with solvents of higher polarity are the solvent, at least for the
phenolic resin.
6. A method for the preparation of a foundry moulding material binder system
according to one of claims 1 to 5, wherein the phenolic resin and the
polyisocyanate are dissolved in the fatty acid methyl esters as solvent
constituent for the phenolic resin and as sole solvent or solvent constituent for
the polyisocyanate.
7. The method for the preparation of foundry moulds and cores in a known
manner from a moulding material mixture that is bound by means of a binder
system based on polyurethane, wherein the binder system according to one of
claims 1 to 5 is employed.
8. A two-component binder system based on polyurethane for foundry moulding
materials substantially as herein described and exemplified.
9. A method for the preparation of a foundry moulding material binder system
substantially as herein described and exemplified.


Documents:

1916-mas-1996 others.pdf

1916-mas-1996 abstract.pdf

1916-mas-1996 claims.pdf

1916-mas-1996 correspondence others.pdf

1916-mas-1996 correspondence po.pdf

1916-mas-1996 description (complete).pdf

1916-mas-1996 form-2.pdf

1916-mas-1996 form-26.pdf

1916-mas-1996 form-4.pdf

1916-mas-1996 form-6.pdf

1916-mas-1996 petition.pdf


Patent Number 196392
Indian Patent Application Number 1916/MAS/1996
PG Journal Number 20/2006
Publication Date 19-May-2006
Grant Date 29-Dec-2005
Date of Filing 30-Oct-1996
Name of Patentee M/S. HUTTENES ALBERTUS CHEMISCHE WERKE GMBH
Applicant Address WIESENSTRASSE 23-64, 40549 DUSSELDORF-HEERDT
Inventors:
# Inventor's Name Inventor's Address
1 DR MAREK TORBUS, UERDINGER STRASSE 250, 46800 KREFELD;
2 GREAD PHILIPPE MARIO LADEGOURDIE, RETHELSTRASSE 161, 40237 DUSSELDORF;
PCT International Classification Number B22C1/22
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 196 12 017.9 1996-03-15 Germany
2 195 42 752.1 1995-11-01 Germany