|Title of Invention
|The invention relates to a binding agent which contains resol, a base and water and that is characterised in that the binding agent system additionally contains at least one aluminium-containing oxyanion and at least one boron-containing oxyanion.
THE PATENTS ACT 1970
[39 OF 1970]
THE PATENTS RULES, 2003
[See Section 10; rule 13]
ASHLAND-SUDCHEMIE-KERNFEST GMBH, of Reisholzstrasse 16-18, D-40721 Hilden, Germany,
The following specification particularly describes the invention and the manner in which it is to be performed:
The present invention relates to a Binder System.
CLAIM TO BENEFIT OF FILING DATE OF FOREIGN APPLICATIONS
Applicants claim the benefit of the filing dates of PCT/EP00/0775 filed on August 10, 2000 and German application 199 3$ 043.0 filed on August 12,1999:
FIELD OF THE INVENTION
The subject of the present invention is a phenolic resole binder system comprising a phenolic resole resin, water, a .base, a boron-containing oxyanion, and an aluminum-containing oxyanion. Cores and molds made with the binder exhibit, among other things, improved ending strength.
BACKGROUND OF THE INVENTION
In European patent document EP-A-0 323 096 an alkaline resole resin is described which can be used in the manufacture of cores and molds in the foundry industry, -whereby the hardening of the resin occurs through the introduction of CO2.
The strength of the cores which are manufactured in this way, however, despite increased binder additives, are lower than the strength of cores which are manufactured with other gas hardening processes (for example the polyurethane cold box process or the epoxy SO2 process). Thus, the applicability of these so-called resole CO2 processes is essentially limited to massive, single cores.
On the other hand, despite the lower strengths, castings are obtained which are of a very good quality. To widen the applicability of the resole CO2 process it would thus be desireable to have binders which could be used to manufacture molds and cores with higher strengths,
A basic component of the binder described in EP-A-0 323 096 is an oxyanion, especially a . borate ion. This oxyainan, when the pH value of the resole is reduced through introduction
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; of C02l should build a stable complex with the phenolic resin, which leads to hardening of the binder.
As alternatives to the borates, the stannate- and the aluminate ions are named ir/EP-A-0 323 096. By carefully examining the experimental data, it can be determined "that the strengths of the formulations, which contain stannates or alurninates, are doubtless lower than those containing borates. This is especially true in the case of the aluminates. Separate research with aluminates confirms these findings.
There is a growing interest in broadening the range of uses for the resole CO2 process. For this reason, it was the task of the present invention to make available a binder system for the resole CO2 process, with which cores with higher strengths could be manufactured.
SUMMARY OF THE INVENTION
The subject of the present invention is a phenolic resole binder system comprising a phenolic resole resin, water, a base, a boron-containing oxyanion, and an aluminum-containing, preferably an aluminous-containing oxyanion. Cores and molds made with the binder exhibit, among other things, improved ending strength.
Additionally, the invention relates to a process for the manufacture of a binder system, and to the preparation of a molding compound, which contains an aggregate and an effectively binding quantity, up to 10% by weight of the binder system, based on the weight of the aggregate.
Furthermore, the invention relates to a process for the manufacture of foundry cores and molds which comprises:
1. mixing of aggregates with the binder system in a binding quantity of up to 10% by weight based upon the weight of the aggregate;
2. introducing the molding mixture obtained in step 1 into a pattern;
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3. hardening the molding mixture in the form in order to obtain a self-supporting form; and
4. afterward, removal of the formed molding mixture from step (3) from the form and further hardening, resulting in a hard, firm, fully hardened founded piece.
Additionally, the invention relates to a process for the preparation of metal castings which comprises:
1. manufacture of a foundry core or mold based on the invention;
2. pouring metal in the molten state in or around this foundry core or mold;
3. cooling and hardening up of the metal; and
4. separating the casting from the foundry core or mold.
The use of both the boron-containing and aluminum-containing oxyanions is critical to obtaining improved properties of cores and molds made with the binder. Not only will the ending strength of the cores and molds be positively influenced, but also their strength rises within the first two hours after they are made. For this reason, cores and molds manufactured with the binder systems are more resistant to high moisture levels and to disintegration caused by water-based coatings.
DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Phenolic resole resins are manufactured by condensation of a phenolic component and an aldehyde component. The method of manufacturing them has been known for a long time and is described for example in A. Knop, W. Scheibe, Chemistry and Application of Phenolic Resins, Springer Verlag 91979) as well as in EP-A-0 323 096. Preferred resole resins are those which are described in EP-A-0 323 096. The preferred aldehyde resole resins consist mainly of molecules, in which the neighboring phenolic groups are linked through memylene bridges between the ortho- and para-positions, since these molecules possess a greater number of complex sites for oxyanions. Molecules in which the phenolic groups are combined over ortho-ortho-methylene bridges, have very few complex sites for oxyanions, and it is therefore preferred that there be few of such molecules or that none of such molecules be contained in the resole resins. In order to achieve this objective, all
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available positions in the phenolic groups, which are in ortho-standing to the phenolic hydroxy groups, should be shielded as methyoJate.
Phenols used to prepare the binders include any phenols, in particularly substituted phenols like cresols or nonyl phenols, or phenolic binders like bisphenol A, possibly in combination with phenol. Most preferred is phenol itself.
All aldehydes, which are conventionally used for the manufacture of phenolic resole resins, can be used within the scope of the invention. Examples of this are formaldehydes, butyraldehydes or glyoxal. Formaldehyde is especially preferred.
The phenolic resole resins are preferably manufactured through condensation of the phenolic components and the aldehydes in the presence of basic catalysts, such as ammonium hydroxide or some alkali metal hydroxides. It is preferable to use alkali metal hydroxide catalysts.
The molar ratio of aldehyde (given as formaldehyde) to phenol in the resole resin can vary between 1:1 to 3:1. However the preferred range is from 1.6:1 to 2.5:1.
Within the scope of this invention, oxygen-containing anions are indicated as oxyanions. The essence of this invention is that the binder system contains and aluminum-contairiing oxyanion, preferably an aluminous-containing oxyanion, and a boron-containing oxyanion.
Examples of aluminum-containing oxyanions are aiurainates. Examples of boron-containing oxyanions are borates.
The boron-containing and aluminum-containing oxyanions can be used direcdy or in the form of their salts. The salts contain primarily alkali- or alkaline earth metals as cations, whereby sodium and potassium salts are especially preferred because of their ready availability. It is, however, still possible to manufacture the oxyanions "in situ". Thus alrnninate is formed by the dissolving of aluminum compounds like aluminum hydroxide
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or aluminum alcoholates in alkaline solution. The aluminum alcoholates have the formula Al(OR)3, where R can be a saturated or unsaturated, branched or unbranched hydrocarbon chains with 1-10 carbon atoms. A solution of a boron compound such as boric acid or boric ester in alkaline solution serves as solution for the boron-containing oxyanions. As alkaline solution, the solution of a base in water is preferred, which is likewise used for mixing with the resole resin.
The atomic ratio A1:B of the boric- and aluminum-containing oxyanions is preferred for purposes of this invention to be in the range of 0.05:1 to 1:1. In this range cores are obtained with the invention based binder system, which exhibit especially good strength. The especially preferred range lies between 0.1:1 and 0.8:1. The ratio of the sum of the boric and aluminum atoms in the boron-containing oxyanions and aluminum-containing oxyanions to the number of the phenolic groups of the resole resins amounts to between 0.1; 1 -0 and 1.0:1.0, with between 0,3:1.0 and 0.6:1.0 being especially preferred
As bases, alkali hydroxides like sodium hydroxide and potassium hydroxide are preferred. The molar ratio of hydroxide ions to the phenolic groups in the binder system amounts to preferably 0.5:1 to 3.0:1. Next to the already mentioned components, the invention based binder system contains water, preferably in a quantity of 25 - 50 % by weight compared to the weight of the compound. The water serves to dissolve the base and, if necessary, the oxyanions. In addition it should give the binder a viscosity of 100 - 700 mPa"s, which is suitable for the application, and which ensures a uniform coating when mixed with the aggregate. The viscosity is determined, as is described in EP-A-0 323 096, with the help of a capillary.
The binder system can also contain up to 25% by weight of conventional additives, such as alcohols, glycols, and silanes.
A mixture of phenolic resin, water, and base can be formed in situ by reacting the phenol and formaldehyde in the presence of water and a base according to methods well known in
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^ the art. See for example EP-A-0 323 096, U.S. Patent 4,977,209, and U.S. Patent 4,468,359, all of which are hereby incorporated by reference.
The boron-containing oxyanion and aluminum-containing oxyanion is then mixed with the aqueous alkaline solution of phenolic resole resin. On the other hand, a phenolic resole resin with the base, the water, and the oxyanions. For instance, it is possible to first mix the phenolic resole resin with an aqueous solution of the base and afterward to mix in the oxyanions as solids, or even in the form of an aqueous solution. It is also possible to first mix the oxyanions with at least a part of the base and at least a part of the water, and to combine this mixture with the phenolic resole resin. Afterward, if appropriate, the rest of die base and water are added.
The binder system is used to form molding compositions by mixing the binder with a foundry aggregate. The molding compositions are used to make foundry cores and molds. The foundry cores and molds are used to cast metal parts. The aggregates used for this purpose and the processing steps are conventional and known under EP-A-0 183 782. The binder system is mixed with sand or a similar aggregate, in order to manufacture the molding compound. The molding compound contains an effectively binding quantity of up to 10% by weight of the invention based binder system compared to the weight of the aggregate. Processes for achieving a uniform mixture of binder system and aggregate are known to the expert. If necessary, the mixture can also contain other conventional ingredients, like iron oxide, powdered flax or wood fibers, pitch and mineral additives. In order to manufacture foundry cores and molds from sand, the aggregate must have a sufficiently large particle size. In this way the core or mold will have sufficient porosity, and volatile compounds can escape during the founding process. The average particle size of the aggregates in general should be between 200 and 400 um.
For standard foundry cores and molds, sand is preferred as the aggregate material, where at least 70% by weight and preferably more than 80% by weight of the sand is silicon dioxide. Zircon, olivine and chromite sands are likewise suitable as aggregate materials.
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The aggregate material is the main component of foundry cores and molds. In cores and molds of sand for standard applications, the binder portion in general consists of up to 10% by weight, and often between 0.5 and 7% by weight compared to the weight of the aggregate. Especially preferred are 0.6 to 5% by weight binder compared to the weight of the aggregate used.
The castings are allowed to cool and harden, so that they retain the external form they will have after being removed from the mold.
Conventional liquid or gaseous hardening systems can be used for hardening of the binder system. Examples of gaseous hardening systems include gaseous COz or volatile C1-C4 alkyl formate, e.g. methyl formate. However, cold hardening with a liquid catalyst is equally possible. Examples of liquid catalysts include low molecular weight lactones, organic carbonates, carboxylic acid esters, water glass esters, resole esters, and mixtures thereof.
AH quantities are given in parts by weight when not otherwise stated.
1. Aluminumous resoles through subsequent addition of Al-eompounds to a standard borate-containing resole CO; binder
1.1 Manufacture of the binder
While stirring constantly, the quantities of aluminum hydroxide or aluminum triisopropylate cited in Table I, are added as solids to a standard borate-containing resole CO2 binder (NOVANOL® binder 140, an aqueous alkaline phenolic resole binder containing potassium hydroxide and borate, manufactured by Ashland Sudchemie Kernfest GmbH, having a molar ratio of boron:phenol of 0.28:1) at a temperature of 40 - 50* C. Stirring is continued until a homogeneous solution is created.
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Table I (Aluminum compound added to aqueous alkaline phenolic resole binder containing borate)
Not based on the invention Based on the invention
Binder 1.1 1.2 1.3 1.4 1.5
Novanol 140 100 100 100 100 100
Aluminum hydroxide" - 2 - - -
Aluminum triisopropylatec - - 2 3 4
-1 . » — i 0.4:1 015:1 023:1 0.3:1
Ashland Siidchemic Kcmfest GmbH Martinal ON, Martinswerk GmbH Merck KgaA
1.2 Manufacture and testing of the molding material/binder mixture
2.5 parts by weight of the binder referenced in Table I are added to 100 parts by weight of Quarzsand H32 (Quarzwerke GmbH, Frechen) and intensively mixed in a laboratory mixer. With this mixture, test pieces are manufactured according to DIN 52 401, which are then hardened by gassing with CO2 (30 seconds, 2 liters CO2 per minute).
The strength of the test pieces is measured according to the GF method. In this way the flexural strength of the test pieces is measured 30 seconds after their manufacture (immediate strength) as well as after half an hour, one hour, two hours and 24 hours. The cores are placed into a moisture chamber (98% relative humidity) and kept there for 24 hours in order to measure their resistance to high moisture levels. Afterward the moisture test is made. The determination of strength of the test pieces to water based coating is given below:
Ten minutes after being manufactured, the cores are emerged for 3 seconds into Miratec W3 water based coating (Ashland Stldchemie Kernfest GmbH). Afterward 30 minutes at
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Table n (Test core properties)
Not based on the invention Based on the invention
Binder No. 1.1 1.2 1.3 1.4 1.5
Tensile strength (N/cm2)
Immediate 100 100 100 100 90
0.5 h 120 160 150 160 140
lh 140 170 160 180 160
2h 150 180 180 190 170
24h 170 200 210 210 210
24 h (98% Rel Humidity) 100 140 140 140 150
Water based coating 110 ISO 150 150 140
From Table II the following can be seen mat, after standing for only two hours, the invention based binders containing both a borate and aluminate (Nrs. 1.2 to 1.5) achieve at least the same level of strength as the binder containing only the borate (No. l."I) achieves after 24 hours. The strength of the modified binders climbs even higher after that. Their resistance to water based coatings and to high moisture levels is improved considerably by modification with aluminum binders.
2. Binders obtained by dissolving aluminum compounds in aqueous potassium hydroxide and adding this solution to the phenolic resole resin
2.1, Manufacture of the binder
With the manufacture of the commercial product, NOVANOL binder 140, after condensation of the resole resin, around 11.5 parts by weight of 50% potassium hydroxide are added to the product.
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The quantities of aluminum hydroxide, which are shown in Table III, are dissolved in 11.5 parts by weight of 50% potassium hydroxide. This solution is then used instead of the pure potassium hydroxide for the manufacture of NOV AN OL binder 140, in order to examine the influence of the manufacturing process on the properties of the binder system. The remaining ingredients, such as borate, and their quantities are not changed.
For the dissolving of the aluminum hydroxide, the potassium hydroxide is heated to around 95° C while stirring constantly and held at this temperature until a homogeneous solution is obtained. The addition of the aluminate solution to the phenolic resin follows at around 60° C, in order to avoid a phase separation, or crystalizing out.
(Binder formulations where aluminum compound is added to the binder in solid form is
dissolved in aqueous potassium hydroxide KOH)
Not based on the invention Based on the invention
Binder No. IV 2.1 2.2 2.3
Phenolic resin solution 88.5 88.5 88.5 88.5
50% KOH solution 11.5 11.5 11,5 11,5
Aluminum hydroxide6"* - 1.0 2.0 3.0
A1:B - 0.2:1 0.4:1 0.6:1
"Novanol 140, Ashland Stidchemie Kernfest GmbH bDissolved in the potassium hydroxide c Martinal ON, Martinswerke GmbH
2.2 Manufacture and testing of the molding material/binder mixture
Both correspond to the process described under 1.2
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The results are given in Table IV. The comparison of Table II and IV shows that the aluminumous binder exhibits the same advantages, regardless of whether the aluminum compound is added to the binder in solid form or dissolved in aqueous potassium hydroxide.
Table IV (Test core properties)
Not based on the invention Based on the invention
Binder No. 1.1 2.1 2.2 2.3
Flexural Strength (N/cm2) ,
Immediate 100 110 110 90
0.5 h 120 140 160 140
lh 140 160 160 150
2h 150 170 170 160
24 h 170 200 210 200
24 h (98% rel humidity) 100 120 150 140
water based coating 110 130 150 150
3. Comparative test: Complete replacement of borate with aluminate 3.1 Manufacture of the binder
For purposes of comparison two binders are manufactured which have an identical composition to Novanol 140, except that the borate is completely replaced by aluminum. The manufacture of the two similar resins was done by dissolving aluminum hydroxide in 50% potassium hydroxide as described in 2.1. The aluminate: phenol molar ratios are given in Table V.
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Table V (Aluminate: phenol and borate: phenol molar ratios)
Binder No. l.l1 3.1 3.2
B;P 0.28 - -
Al:P - 0.14 0.25
Novanol 140, Ashland Siidchemie Kernfest GmbH
3.2 Manufacture and testing of the molding material/binder mixture
The manufacture and testing of the molding material/binder mixture is done based on the process described in 1.2. The results are given in Table VI.
(Properties of test cores)
Binder No. LI 13.1 3.2
Flexural strength (N/cm2)
Immediate 90 a 10
0.5 h 120 - 20
lh 130 - 20
2h 150 - 20
24 h 170 - 20
24 h (98% rel hum) 110 - 20
Water based coating 110 - -
No cores could be manufactured
WE CLAIM :
1. A process for the manufacture of a binder system comprising:
(a) preparing a phenolic resole resin; and
(b) mixing the phenolic resole resin with a base, water, at least one aluminum containing, and at least one boron-containing oxyanion.
2. A process for the manufacture of a binder system as claimed in claim 1 whereby the phenolic resole resin is first mixed with an aqueous solution of the base and then the oxyanions are added to the mixture.
3. A process for the manufacture of a binder system as claimed in claim 2 whereby a mixture, which contains the oxyanions, at least a part of the base, and at least a part of the water is first mixed with the resole resin, and afterward the remaining base and water are added and mixed.
4. A process for the manufacture of foundry cores and molds comprising;
(a) mixing an aggregate with the binder system as claimed in one of claims lto 3 in a binding quantity of up to 10% by weight compared with the quantity of aggregate;
(b) introducing the foundry mixture obtained in step (a) into a mold;
(c) hardening the foundry mixture in the mold in order to obtain a self-supporting form; and
(d) removing the molded foundry mixture from step (c) from the mold and hardening it further, whereby a hard, solid, fully hardened founded piece is obtained.
5. A process as claimed in claim 4 whereby the foundry mold or core is hardened through treatment of the foundry mixture with gaseous carbon dioxide.
6. A process as claimed in claim 4 whereby the foundry core or mold is hardened with a Ci to C4 alkyl formate.
7. A process as claimed in claim 5 wherein the alkyl formate is methyl formate.
8. A process as claimed in claim 4 wherein the hardener is selected from the group consisting of lactones organic carbonate, carboxylic acid esters, and mixture thereof.
9. A process for casting a metal comprising:
(a) preparing a mold or core as claimed in claim 4.
(b) pouring metal in a liquid state in or around the mold or core;
(c) cooling and hardening the metal; and
(d) separating the casting from the mold and core.
Dated this 4th day of February, 2002.
OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|REISHOLZSTRASSE 16-18, D-40721 HILDEN.
|PCT International Classification Number
|C08K 3/24, C08K 3/38, B22C 1/22
|PCT International Application Number
|PCT International Filing date