DE2531001A1 - BINDING AGENTS AND THEIR USE FOR THE PRODUCTION OF HOLLOW SHAPES - Google Patents

Description

LAWYERS

DR. JUR. DlPL-CHEM. WALTER BEIL

ALFRED HOiPt ³ EMiX

DR. J ¹ JS. "-! ¹ L-CrM. Li.-J. WOLFP

DR. JIJR. h. \ r, 3:.:.! <. BtIL

623 FRANKFURTAM MAIN-HOCHSf

Our no. 19 943

Stauffer Chemical Company
Westport, Conn., V.St.A.

Binder and its use for the production of hollow molds

The present invention relates to binders for hollow molds, especially for the production of hollow molds for metal casting.

Precision casting of metals and other materials in molten material Condition is used in a variety of industries, and generally casting is in disposable molds. There is three general types of processes for making disposables iPormen that are classified as the procedure "with lost wax ", the single investment casting and double investment casting

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Procedure «These procedures have one feature in common, namely they use molds for one-time use, the shape generally being destroyed when the casting is removed will. For an economical process, a Die form made with which the heat-resistant Shapes are produced by one of the methods mentioned above.

In the manufacture of precision casting using investment casting technology with hollow molds, the models are made of wax, plastics, frozen mercury or other materials that can be easily removed from the mold. The investment casting process consists in making the model by injecting the model material into the mold and controlling it a sprue with the formation of a large number of models (pattern cluster).

In general, this multitude of models is transformed into a moving scene.

θ in θ i *
slurry coating mass immersed, drained, still moist with particulate! Mold material stuccoed and dried. Dipping, draining, stucking and drying are repeated as desired, depending on the thickness and strength of the desired hollow shape.

Then the removable model is made by melting or solvent treatment removed and the shape becomes more adequate by firing at one to remove the volatiles and achieve Bond hardened at a sufficient temperature. The molds are then heated and filled with molten metal and After cooling, the casting is freed from the sprue and finished in the usual way.

The manufacture of hollow molds is described in US Pat. No. 3,270,332, according to which 2 different coverings alternate

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applied to a disposable model. A cover consists of the solution of a gel-forming, acid-hydrolyzed Alkyl silicate, the other from a gel-forming basic Silicate ester. The acid hydrolyzed solution and the basic one Silicate esters of the applied coatings act on one another so that they cause one another to gel.

In US-PS 3,0? 9,656 the production of aminosilicates described by the exchange reaction between an alkyl silicate and an amino alcohol, the result of the reaction formed alcohol is removed. The aminosilicates can be combined with a refractory material and made into a disposable one Model can be applied. The coating is gelled by adding water. Aminoalkyl silicates were also used as Binders are described in US Pat. No. 3,112,538. The binder is combined with fine powders made of heat-resistant material to form a slurry which is based on a wax model is applied. Each coating is allowed to partially cure before the next coating is applied. The one with the coatings The fitted model is then cured for 24 hours before the wax model is removed.

A mixture of an alkyl silicate and an aminoalkyl silicate Containing binders are described in US Pat. No. 3,329,520. These binders are made with a heat resistant material and water combined and then in the desired j? orm poured.

A mixture of organic silicates and an amine with one pEa value above 7.8 is described in AU-PS 163 467. If this mixture contains an amine such as monoethanol = amine, it must be aged for at least 48 hours and up to 14 days before it can be used as a protective coating for sand cores can.

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The inventive method represents an improvement of the previous precision casting technology. For example, required the binder according to the invention has no aging time, that is to say that the agent is directly after mixing the ingredients usable. Furthermore, the resulting hollow shape is ready for use after air drying for just 1 to 3 hours. The binder according to the invention gels also in the presence of atmospheric moisture and does not require any additional water. Furthermore, this requires according to the invention Process only uses a single binder for the production of hollow molds, while many of the hollow molds produced up to now Form at least two different binders required.

The aim of the present invention is therefore a method for production of hollow molds, with a single binder, the molds being usable after 1 to 3 hours of drying meant to be. Another object of the invention is to provide a binder that does not gel Requires additional addition of water, just as little as the removal of alcohol, which is involved in the esterification of an organosilicate with an amino alcohol results.

These goals are achieved by covering previously cleaned and etched, removable models with a binding agent, which contains a heat-resistant material, stuccoed with a coarse heat-resistant material and then dries for the purpose of hardening the coating material. The sequence of steps is repeated until the desired coating thickness is achieved. That so produced, coated models can, if desired, be sealed with a backing coating, which has a hydrolyze silicate ester, a solvent and a heat-resistant Contains material.

The binder according to the invention consists of silicate esters,

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Amino alcohols and an organic solvent, preferably a low boiling alcohol or polyether.

The silicate esters which can be used according to the invention are tetraethyl orthosilicate, "condensed" ethyl silicate and ethyl silicate "40". "Condensed" ethyl silicate is Eetraäthylorthcsilikat with about 10 ^ £ polysilicates; It consists of the undistilled reaction product of silicon tetrachloride and 200-proof ethanol and has a nominal composition corresponding to 2 to 5 ^ΰ / ο ethanol, 90 to 95 $ orthosilicate and 5 to 10 $ poly = ethoxypolysilicates. Ethyl silicate "40" is a mixture of polysilicates with an average of 5 silicon atoms per molecule and a silica content of about $ 40. It is formed by reacting silicon tetrachloride with a little water-containing ethanol under such conditions that the silica content of approx. Φ ^ ο is reached. Other useful silicate esters are those obtained by the hydrolysis and condensation of ethyl silicate "40".

The amino alcohols suitable for the binders according to the invention can be given by the following formula

HOHN (R ¹ ) ₂

in which R is a divalent hydrocarbon radical having 1 to 6 carbon atoms, R ^{1 is} hydrogen or an alkyl radical having 1 to 6 carbon atoms or a radical of the formula -ROH, in which R is as defined above. Examples of suitable amino alcohols are mono-, di- and sriethanolamine, monoisopropanolamine, 2-amino-butane-1-ot, 3-aminopropane-i-oT., 2-dimethylamino-2-methylpropane-1- oX and the like.

Any organic solvent can be used Is a solvent for the silicate ester such as the amino alcohol,

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use. Preferably, the solvent should have a boiling point below about 25O ° O, and more preferably below about 15O ⁰ C. Examples of suitable organic solvents are aliphatic alcohols such as methanol, ethanol, isopropanol, butanol, ketones such as acetone, methyl ethyl ketone and aromatic hydrocarbons such as benzene, toluene and the like. Polyethers suitable as solvents in the binders according to the invention are glycol ethers such as monoalkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, dialkylene glycol dialkyl ethers and monoalkylene glycol dialkyl ethers. Examples of preferred glycol ethers are ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, ethylene glycol monohexyl ether, ethylene glycol monohexyl ether, ethylene glycol monobutylene glycol ether, like ethylene glycol monobutyl glycol ether, like ethylene glycol monobutyl glycol ether, like ethylene glycol monobutyl glycol ether, like ethylacetate like ethylacetate monobutyl glycol ether, like ethylacetate like ethylacetate like ethylacetate monobutyl glycol ethylacetate like ethylene glycol monobutyl ethers, ethylene glycol monobutyl ethers.

The amount of amino alcohol used in the binder is not critical. The amino alcohol can be in a molar ratio Amino alcohol to ethyl silicate from 1: 1 to 10: 1 and particularly preferably from about 3: 1 to 8: 1.

In general, the amount used in the binder ranges from at Silikatester to achieve a SiOP content of the order of 10 to 35 $ and more preferably about 15 to 30 wt _o $, based on the weight of the binder.

Numerous and varied refractory materials can be used in the binder of the present invention. in the in general, the well-known heat-resistant substances such as oxides and silicates of silicon, aluminum, zirconium, zinc, magnesium, Chrome and iDitan used. These include the acidic, neutral and amphoteric minerals, especially those whose main elements come from group II of the periodic table.

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men, the gel-forming acidic minerals such as AlIo = phane and basic minerals such as Zirkelite. Numerous synthetic materials should also be mentioned, including of zeolites, molecular sieves, ion exchange resins and similar substances. Furthermore, zircon, fired chamotte, Fired clay, silica powder, sand and hard-fire porcelain be used. Examples of acidic, weakly acidic or neutral amphoteric minerals are hard-fire porcelain, natural ones Silicic acid, zircon, Stillimanit, zirconite (mixture of silicates and oxides of zirconium) Mullite (highly heat-resistant Aluminum silicate), clays, magnesia and other metal oxides and silicates.

These refractory materials can be used alone or in mixing depending on the intended metal casting » The particle size of the refractory material is also made depending on the particular purpose for which the mold is being created is selected. In some cases it is advisable to use a mixture of relatively coarse and fine particles. In general one uses a coarser one in the stucco level heat resistant material than in the initial coating composition, creating a bond between a coating layer and the next is achieved.

A hollow mold according to the invention becomes a binder without any further use than that described above. However, if you want a sealing layer or support layer, you can use one Use binders that contain a heat-resistant material and silicate esters, for example pre-hydrolyzed silicate esters commercial type or those produced by acid hydrolysis of commercial ethyl silicates including monomeric Ürthosilikat, "condensed" ethylsilicate or Äthylsi = likat "40" can be obtained.

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To prevent premature gelation of the mass for the Sealant coating is a small amount of acid with stronger acidity than the hydrolyzed ethyl silicate or an acidic buffer added to the binder solution. The pH of the sealing coating composition should be in the range of about 1 to 3.2 are held. Suitable acids and buffers are, for example, hydrochloric acid, phosphoric acid, sulfuric acid and Ammonium nitrate. The amount of acid or buffer depends on the particular acid or buffer and that in the agent present heat-resistant material from «

In the sealing layer, the same heat-resistant materials can be used as in the previous coating composition will. In general, these are the oxides and silicates of silicon, aluminum, zirconium, zinc, tin, magnesium, Chromium, titanium and the like. Other heat-resistant materials such as fired chamotte, fired clay, silica flour, Sand or hard-fire porcelain can also be used.

These heat-resistant materials can be used individually or in any Combination are used, which appears suitable for the particular cast.

The same solvents can be used in the sealing layer as in the initial coating composition. Examples suitable solvents are alcohols, ketones and polyethers such as the monoalkylene glycol monoalkyl ethers, Dialkylene glycol monoalkyl ethers, monoalkylene glycol dialkyl ethers and dialkylene glycol dialkyl ethers.

The amount of binder in the coating composition becomes substantial by the particle size of the refractory material

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determined, because the greater the fineness, the easier it is for the binding agent to be absorbed the sooner more binding agent is required » In some cases where the refractory particles are coarse, the amount of binder required may be such that for every 1OÜ parts of heat-resistant material only one such The amount of binder required to provide part of the binder-SiOp is not required. If the particles are reversed of the heat-resistant material is extremely fine, the amount of binder that 1 part of Binder-SiOp provides is for every 4 Parts of heat-resistant material required. The ratio of refractory material to binder can be from about 4 to 100 parts of heat-resistant material per part of Binder-SiOp.

In general, the sealing layer is applied to the previously dried coating and then in the presence of atmos dried in spherical moisture. If you want to accelerate the gelation of the sealing layer, you can use a basic one Material like ammonia or organic amines like aliphatic, aromatic and cyclic amines up to 10 carbon atoms use. Examples of suitable amines are methylamine, mono-, di- and triethylamine, propylamine, n-butylamine, Cyelo = hexylamine, hydrazine, piperidine and the like.

After the model has been covered with the desired number of coatings, it is ^{dried at a temperature of 25 °} C. up to the liquefaction temperature of the model. The temperature can then be increased in a non-oxidizing atmosphere until it liquefies, with the model being removed. The resulting hollow shape is then fired at a temperature of about 500 to about 3000 ^° C. in an oxidizing atmosphere for about 1 to 12 hours.

In the following examples, parts relate to the

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if nothing else is said.

example 1

A Vachsbaum model is provided with a sprue and an inlet channel according to the requirements of the desired metal casting. The tree is briefly etched with a mixture of 75 % trichlorethylene and 25% isopropyl alcohol. and the excess is removed with isopropyl alcohol. The model is allowed to dry and then immersed in a binder prepared in the following way:

Binder composition Component parts

Ethyl silicate (condensed) 416 Ethanol 540

Ethanolamine 244

The binder is prepared by adding with stirring Etna = ethanolamine at 40 to 45 ⁰ G to a solution containing "fused" ethylsilicate and ethanol. The solution is stirred at this temperature for 1 hour, cooled to about 30 ° C. and filtered.

About 300 parts of the binder are mixed with about 200 parts of zirconia (0.044 mm) and 400 parts of hard-fire porcelain (product of the Ransom and Randolph Company as Rancosil # Λ) to form a slurry. The wax model is coated with the slurry with hard-fire porcelain amd; (Product of the Ransom & Randolph Company as "RancosilA") stuccoed and air dried for 15 minutes. The sequence of dipping and stuccoing is repeated twice. The precoated model is then dipped into a mixture containing 300 parts of the above binder, 100 parts of zirconium (0.074 mm) and

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Contains parts of hard-fire porcelain (Rancosil φ 2) , stuccoed with hard-fire porcelain sand (liancosil B) and air-dried for 15 minutes. The dipping and stuccoing sequence is repeated four times. The last layer is dried for 1 to 3 hours, then ^{the wax is removed at 2UO 0} O and then it is fired ^{at about 1000 0 G.} A hollow shape free of defects is obtained.

Example 2

The procedure of Example 1 is repeated but using of 122 parts of ethanolamine in the preparation of the binder. A hollow shape of considerable strength is obtained, which is free from defects.

Example 3

The procedure of Example 1 is repeated but using of 416 parts - "- thylsilicate" 40 "instead of the" condensed " Ethyl silicate. In this case, too, you get a hollow shape free of defects.

Example 4

The procedure of Example 1 is repeated, but replacing the ethanol with ethylene glycol monoethyl ether. You get a hollow shape with the desired strength.

example 5

A hollow mold is produced according to the method of Example 1, but the precoated model is provided with a backing layer coated from the following ingredients;

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Ingredient parts by weight

Water 0.5

"Silbond H-4" (partially hydrolys. 24.0 Silicate binder, manuf. Stauffer

Chemical Company)
Isopropyl alcohol 24.0

Hard-fire porcelain flour 148.0

("Nalcast PlW" manuf.
Nalco Chemical Company)

Water is added to the silicate binder Silbond H-4 and that The mixture is left to stand overnight before alcohol and hard-fire porcelain flour are added. On 3 »8 l of the slurry about 1 to 3 milliliters of sulfuric acid are added to the neutralize basic components.

The precoated model according to Example 1 is immersed in the slurry, excess slurry is removed and then it is stuccoed with coarse hard-fire porcelain flour (Nalcast S-2). The dipping and stuccoing sequence is repeated four times. The model coated in this way is then dried overnight and the wax is removed in a high pressure steam autoclave. The resulting hollow form is fired at a temperature of about 1000 ^° C., and while it is still hot, molten stainless steel is poured into the form. The casting is cooled and the mold is broken by vibration. The cast shows no cast skin or any defects.

Other additives added to the binder according to the invention are boron compounds and organic acids. Examples of suitable boron compounds are boric acid and Alkyl borates, the alkyl groups of which have 1 to 8 carbon atoms

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point. The term "borates" includes all alkanol esters of all boric acids. Suitable alkyl borates include l'ri = methyl borate, Sriäthylborat, riisobutylborat! Tripropyl l', Irimethpxyboroxin, ^r XRI-n ~ butoxyboroxin, Irihexoxyboroxin and the like. The borate or borate mixtures can be added in pure form or dissolved in a solvent, depending on the requirements.

Examples of organic acids that can be added to the binder are organic monocarboxylic acids with 1 to 10 Carbon atoms such as formic acid, acetic acid, propionic acid, butyric acid, hexanoic acid, octanoic acid, decanoic acid, 2-ethylbutyric acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid and the like.

The amount of the boron compound in the binder can be about 0.5 to 10 and preferably about 1 to 5 Gev /. ^ Based on weight of the binder. The amount of acid can be about 1 to 10 Gew.fi and preferably about 1.5 to 5 Gew. ^, Based on the binder.

By adding boron compound and organic acid, the stability of the binder is improved, i.e. these additives increase the storage life and pot life of the resulting additives Coating compound.

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Claims (6)

Claims 1. Binder, characterized by a silicate ester, an amino alcohol of the formula HORN (R ¹ ) ₂ in which R is a divalent hydrocarbon radical having 1 to 6 carbon atoms and R ^{1 is} hydrogen, an alkyl radical or a radical of the formula -ROH, in which R is as defined above, and. an organic solvent. 2. Binder according to claim 1, characterized in that it contains condensed ethyl silicate as the silicate ester. 3. Binder according to claim 1, characterized in that it contains silicate "40" as the silicate ester. 4 · Binder according to claim 1, characterized in that it contains monoethanolamine as amino alcohol. 5 · Binder according to claim 1, characterized in that it contains' -i-'riäthanolamin as amino alcohol. 6. A method for producing a hollow mold, characterized in that that a disposable model is coated with a compound which is a binder and a heat-resistant one Contains material, the binder made of a Si = licatester, an amino alcohol of the formula HORN (R ¹ ) in which R is a divalent hydrocarbon ^{radical and R 1 is} hydrogen, an alkyl radical or a radical of the formula -ROH, in which R is as defined above, 509886/0836 and sufficient organic solvent so that a SiOp content of 1U to 35 wt. $, based on the Weight of the binding agent, results, the coated model stuccoed, air-dried and the sequence of steps like ~ repeated until a coating of the desired thickness has been achieved. 7 »The method according to claim 6, characterized in that one a sealing layer applied, which consists of an agent which is a hydrolyzed silicate ester contains heat-resistant material and an organic solvent. · ■ '. Pure: Stauffer Chemical Company Westport, Coiln. , V.St.A. Dr.H.J.Wolff Attorney at Law 509886/0836