EP3740331A2

EP3740331A2 - Method for producing moulds and cores suitable for producing fibre composite bodies or cast parts in metal or plastic, mould base material and binder used in the method and moulds and cores produced according to the method

Info

Publication number: EP3740331A2
Application number: EP19700768.5A
Authority: EP
Inventors: Ivo Herzog
Original assignee: Reinsicht GmbH
Current assignee: Reinsicht GmbH
Priority date: 2018-01-15
Filing date: 2019-01-07
Publication date: 2020-11-25
Also published as: JP7486431B2; US12064807B2; KR102601424B1; RU2762467C1; WO2019137871A2; BR112020014235A2; JP2024020228A; MX2020007551A; DE102018200607A1; US20200338629A1; CN112166000B; WO2019137871A3; CN112166000A; KR20200106192A; JP2021510635A

Abstract

The invention relates to a method for producing moulds and cores suitable for producing fiber composite bodies or cast parts made from metal or plastic from a particulate mould base material and a multi-component binder by means of 3D printing. According to the invention, the particulate mould base material is pretreated with at least one silicon-organic compound which has a polar hydrophilic end and a non-polar hydrophobic end. After forming a layer from the pretreated particulate moulding material, the binder or at least one component of the binder is applied to the layer in liquid form. The organosilicon compound is contained in moulds and cores produced according to the method. The mould base material and the silicon-organic compound can be part of a set used for carrying out the method.

Description

Process for the production of molds and cores suitable for the production of fiber composite bodies or castings of metal or plastic, mold bases which can be used in the process and

Binder and molds and cores produced by the process

The invention described below relates to a method for producing molds and cores suitable for the production of fiber composite bodies or castings from metal or plastic from a particulate molding material and a multicomponent binder by means of 3D printing as well as mold bases and binders which can be used in the method and according to the method Asked forms and cores.

In a variety of technical products are components of metal, plastic or a fiber composite material (a composite material comprising a matrix of a plastic and a fiber material embedded in the matrix) are used, which have a cavity in its interior. The manufacture of such components is difficult, in particular if the cavity is to have a complex geometry, for example an elongated, curved shape or a shape with undercuts, while at the same time the cavity surface must be smooth and of high quality. One possible way to produce such components in one piece is casting using so-called "lost shapes". In this technique, a mold part (the so-called "core") is produced in an upstream step, which speaks in size and shape to the cavity to be formed ent. The core is arranged in a casting mold consisting of further molded parts, into which subsequently a liquid metal, a liquid polymer material or a liquid polymer is injected in a preliminary manner. In the manufacture of fiber composite bodies, the core is coated before being arranged in the casting tool with a fiber material. After casting you get a fiber composite body or a casting of metal or plastic with the desired cavity, in which, however, still the core is inserted. This is then removed, which due to the he imagined complex geometry of the cavity can not be done without destroying the core. The core is "lost" as a molded part.

From the metal casting, it is known to use cores made of Anorga African materials such as sand for the production of cavities in castings. Such cores can be used in plastic casting, provided that their surface is sealed. They are made from a form material mixture comprising a binder and a suitable particulate inorganic material, the so-called mold base. The binder holds the particles of the molding material together. and is thus responsible for the structural integrity of the nuclei. The cores must be able to withstand the thermal and mechanical stresses occurring during a casting process. After casting, the cores are usually crushed by vibration. When using a water-soluble binder, for example a binder based on magnesium sulfate, of water glass or based on polyphosphate and / or borate, the cores can be dissolved out of the interior of castings with water after the casting process.

In order to produce such cores from inorganic materials, a molding material mixture is usually prepared to form a refractory base molding material, usually sand, and a binder. This is processed in a mold to the desired shape or core. For the manufac turing of cores in the so-called core shooting method a molding material mixture under defined tem pressure and defined temperature in a core box (a mold, which usually consists of two moldings or mold halves, the space in use at least one hollow interior in the form of to be produced Kerns - a so-called Formnest - include) introduced. After curing of the binder, the finished core can be removed from the core box and used as intended.

More recently, molds and cores have been increasingly produced using 3D printing. A printer for producing 3D components usually has at least one movable print head, which functions similarly to a print head of a conventional inkjet printer. Instead of ink, however, a liquid binder is usually applied to a layer of a refractory molding material via this printhead. In this case, the individual 2D layers of a 3D model dissected into these individual layers by means of a computer can serve as the data basis.

For layered construction of a mold or a core for the plastic or metal casting by means of 3D printing, a first layer of the refractory base molding material is arranged in a frame. Then, in a first printing step, the binder is applied over the at least one print head. The binder bonds individual particles of the basic molding material together. In simple terms, the 3D printer draws a two-dimensional image of a first layer of the 3D component. Thereafter, a second layer of the refractory base molding material is formed on the first layer. In a second printing step, the binder is also applied to this layer, the amount of binder being dimensioned such that not only particles of the molding material within the second layer stick together with one another, but also particles from the first layer with particles from the second layer. Layer by layer, the 3D component is built up. Special attention should be paid to a uniform order of the individual layers. As a rule, the layers must be compacted before the binder application, for example by means of a roller or by means of vibration.

Suitable devices for the production of molds and cores by means of 3D printing are commercially available. The structure of a suitable for the production of molds and cores 3D printer is shown schematically for example in Fig. 1 of WO 2016/019937 Al derVoxeljet AG.

From DE 102014118577 Al a method for the production of molds and cores by means of 3D printing is known. In this case, the binder used is a mixture of water glass and at least one phosphate and / or at least one borate and as a molding material such as quartz sand materials. The molding base may be added with a binder for the binder.

From WO 2012/175072 Al another method for the production of molds and cores by means of 3D printing is known. In this case, layers of a feu solid base material are formed to the layered structure of a 3D component, which is added to a spray-dried alkali metal silicate solution. This can be activated by means of water, which is applied to the layers via a print head, and binds together with the water moistened particles of the molding base material after a subsequent rocking process.

WO 2011/087564 A1 also relates to a method for producing molds and cores by means of 3D printing. Here, a printable mixture of a refractory base molding material, cement and a water glass is formed, from which a 3D component is built up in layers.

When 3D printing of molds and cores, the problem may arise that when applying water-based binder, the binder does not remain directly at the position of the job, but gravitationally sinks into deeper layers. In addition, the binder extends laterally and also glued outside of the areas to be printed individual particles of the molding material together. This effect is also known by the term fluid migration. Since the time periods between printing successive layers are often too small for already printed layers to be able to dry or cure to a relevant extent, this problem is exacerbated by the printing of each wider layer. Depending on the sorption capacity of the molding material, this can lead to very significant deviations from the respectively applicable geometric specifications concerning the shape to be printed or the core to be printed. There are usually several factors that can influence the extent of fluid migration. This is in particular the amount and concentration of the binder and the energy input during curing of the added binder. Detailed explanations of this topic can be found, for example, in the dissertation by Ramakrishnan, Robert, entitled "3-D printing with an inorganic molding material system" from 2016 (submitted on 24 September 2015 to the Technical University of Munich and adopted by the Faculty of Mechanical Engineering on January 25, 2016. Chairman Univ.-Prof. Dr. Günther Reinhart, Examiner Univ.-Prof. Dr.-Ing. Wolfram Volk and Univ.-Prof. Dr. rer C. Lüth).

It is an object of the present invention to provide an improved method for providing molds and cores for the production of fiber composite bodies or cast parts from metal or plastic by means of 3D printing.

To achieve this object, the invention proposes the method with the features mentioned in claim 1, the molds and cores having the features mentioned in claim 13, the particulate molding base material with the features mentioned in claim 14 and the set with the features mentioned in claim 15 ,

The method according to the invention serves as the initially discussed methods known from the prior art for the production of molds and cores suitable for the production of fiber composite bodies or castings of metal or plastic. According to the invention, these are produced by means of 3D printing from a particulate mold base material and a multicomponent binder. The method always includes the following steps: a. The particulate molding base material is treated with at least one organosilicon compound having a polar hydrophilic end and a nonpolar hydrophobic end. b. A layer of the pretreated particulate molding material is formed.

c. The binder or at least one component of the binder (in short: binder component) is applied in liquid form to the layer, as a rule via one or more print heads of a 3D printer.

Analogous to the usual procedure for the production of molds and cores explained at the outset by means of 3D printing, steps b. and c. repeated several times. On a first layer of the pre-treated molding base material of the binder or the at least one component is introduced, followed by the formation of a second layer of the pre-treated molding base material the first layer and again followed by application of the binder or binder component. This is repeated until the layered construction of the desired shape or core is completed.

Mold base material

The mold base used preferably comprises a particulate material, on the surface of which the hydrophilic end of the organosilicon compound can bind. Preferably, the ver used molding base material consists of such a material. The pretreated molding base material preferably consists of the particulate material and the organosilicon compound.

In preferred embodiments, at least one particulate inorganic material which is insoluble in water (at room temperature) is chosen as the particulate material. This is preferably selected from the group consisting of sand, glass, oxide, ceramic, metallic and glass ceramic materials and mixtures of the aforementioned materials.

The sand can be natural or synthetic. In particular quartz sand, zircon sand, chrome ore sand, mullite sand and olivine sand are possible.

In particular, inorganic glasses which are chemically inert to water or aqueous solutions, at least in the temperature range between 0 ° C. and 200 ° C., are suitable as glasses.

Among the known oxidic materials are in particular metal oxides such as Alumini umoxid for use in question.

Particles of carbides, nitrides, oxides, silicides and known clay minerals such as, for example, kaolinite are to be understood as meaning ceramic particles.

By the term "glass ceramics" is meant glasses which have crystalline ceramic particles embedded in an amorphous glass phase.

Additionally or alternatively, as a particulate material hollow microspheres, in particular aluminum silicate microbubbles and / or hollow glass microspheres, granules, and / or spherical shaped body based on glass, ceramic or metals or metal alloys can be used. Glass recycling products such as glass granules and expanded glass granules as well as expanded clay and other inexpensive, particulate materials can also be used.

A use of low-melting particles, for example, from a low-melting glass, is usually only in the production of molds in question, which serve for the production of fiber composite bodies or castings made of plastic. For the processing of liquid metals, such as liquid aluminum, forms of these materials are not well suited. As molding material suitable in these cases, in particular high-temperature-resistant sand and the mentioned ceramic particles.

Preferably, the particulate material has a melting point> 600 ° C, preferably greater than 900 ° C, more preferably> 1200 ° C and particularly preferably> 1500 ° C.

In some further preferred embodiments, at least one particulate inorganic material soluble in water (at room temperature) is chosen as the molding material. This is preferably a water-soluble salt.

The usable water-soluble salts include, in particular, salts from the group with sodium chloride (NaCl), potassium chloride (KCl) and sodium carbonate (Na ₂ CO ₃ ). Also included are nitrates, especially sodium nitrate (NaN0 ₃ ) and potassium nitrate (KN0 ₃ ).

The salts mentioned are suitable in particular for molds for the production of fiber composite bodies or castings made of plastic.

In some other preferred embodiments, at least one particulate organic material soluble in water (at room temperature) is chosen as the molding material. It is preferably a water-soluble polymer or a salt of an organic acid such as e.g. Sodium acetate or mixtures of these materials or urea, citric acid or tartaric acid.

These materials are particularly suitable for molds for the production of fiber composite bodies or castings from low-melting plastic.

The particulate molding material particularly preferably has an average particle diameter (d50 value) of 10 μm to 800 μm, preferably between 30 μm and 300 μm. Furthermore, it may be preferred that the particulate mold base has a surface according to DIN ISO 9277 be in the range of 50 cm ² / g and 500 cm ² / g.

The particle size distribution of the molding base material is preferably chosen such that it leads to a densely packed constellation in the cores and forms to be produced, in accordance with the empirically determined grain distributions according to Litzow or Filler. This is preferably used to minimize infiltrating pore spaces.

Silicon organic compound

The polar hydrophilic end of the organosilicon compound preferably comprises at least one functional group selected from the group consisting of flydroxy (-OH), flydroxylate (-O-), amino (-NH ₂ ), ammonium (-NFI 4+), carboxyl ( -COOFI) or carboxylate groups. In particular, the hydrophilic end may also comprise several of these groups, that is, for example, several flydroxylate groups.

The nonpolar hydrophobic end of the organosilicon compound comprises at least one alkyl group, preferably from the group with methyl, ethyl and propyl. In preferred embodiments, the hydrophobic end may also comprise a plurality of alkyl groups.

In a particularly preferred embodiment, the polar, hydrophilic and the non-polar, hydrophobic end are bonded to the same Si atom. In this case, the organosilicon compound is preferably an alkyl silanolate, in particular an alkali metal silanolate, particularly preferably a potassium methyl silanolate.

In further preferred embodiments, the organosilicon compound is tripotassium methylsilane triolate (empirical formula CH ₃ K ₃ O ₃ Si, also known under the name potassium methyl silicate).

In another particularly preferred embodiment, the non-polar, hydrophobic end of the organosilicon compound is bound to a Si atom and the hydrophilic end is bonded to a C atom. In this case, it is further preferable that the Si atom and the C atom are connected via a chain with n atoms, where n is an integer between 1 and 150, and the atoms are selected from C atoms and O atoms and Si atoms. In further preferred embodiments, the organosilicon compound is a compound having the structural formula (I)

where n is an integer between 1 and 100 and m is an integer between 1 and 10 and R is preferably an H atom.

Particularly preferred as the organosilicon compound 3- (polyoxyethylene) propylhepta- methyltrisiloxane used.

Pre-treated molding base material

For pretreatment, the particulate molding base material is mixed with the at least one silicon-organic compound. There is an optimum amount in which the organosilicon compound is added to the molding base. If the content is too low, there is a risk that the addition of the organosilicon compound does not have a sufficient effect. If the proportion is too high, there is a risk that the particulate molding material will be so strongly hydrophobized that the individual particles of the molding material will no longer be able to enter into a sufficient interaction with the binder during the subsequent printing process.

The pretreated molding base material is usually in the form of a free-flowing product.

Particularly preferably, the organosilicon compound is added to the particulate molding base material in the pretreatment in an amount such that it is contained in the pretreated molding base material in a weight fraction of at least 0.001% by weight and not more than 0.1% by weight (referenced to the dry weight of the pretreated molding base material). Within this range, a proportion in the range of 0.01 wt .-% to 0.05 wt .-% is more preferred. This applies in particular to the cases in which a molding base material having the mentioned preferred mean particle diameter (d 50 value) of 10 μm to 800 μm is used as the particulate molding material and in which the organosilicon compound is an alkali metal silanolate, in particular potassium methyl siliconate or a compound of the formula ( 1), in particular 3- (polyoxyethylene) propylheptamethyltrisiloxane. The amount in which the organosilicon compound is added to the particulate molding base material also influences the extent to which the initially mentioned fluid migration takes place. An optimum value for the proportion by weight of the organosilicon compound, in particular within the genann th range of 0.01 wt .-% and 0.1 wt .-%, can be determined by means of experimental studies.

A suitable procedure for this is known from the initially mentioned dissertation by Ramakrishnan. This includes the production of standardized test specimens comprising a structure of several ren concentric rings according to specified pressure parameters. These specimens are blown off after their production with compressed air at a defined working pressure of 8 bar. The air stream removes unbound particulate matter in the interstices of the filigree rings. After blowing out the weight of the specimens is determined by means of a fine balance.

The more fluid migration occurs, the more material remains in the interim spaces in the form of adhesions. These adhesions lead to an increase in weight, which is measured by means of Feinwaa ge.

The fluid migration expresses what percentage of the mass of a test specimen is above its nominal mass. This can be calculated from the density of the disc specimens and the nominal volume of the specimen (from the CAD data). By using the organosilicon compound can produce test body whose weight deviates less than 0.1% of its target weight.

The organosilicon compound is preferably attached to the surface of the pretreated mold base, more preferably via its hydrophilic end.

binder

In preferred embodiments, the binder is characterized by the following features:

It comprises at least one water-soluble binder component.

• It comprises at least one water-insoluble binder component.

It comprises water or an aqueous solution, in particular an aqueous alkaline solution.

Optionally, the binder also comprises at least one additive which affects its processing properties, for example polyethylene glycol, a wetting agent such as sodium 2-ethylhexyl sulfate (Sulphetal), a surfactant (Byk) or a rheological additive. It is preferred that the water-soluble binder component comprises at least one member of the group consisting of water glass, magnesium sulfate, phosphate and borate.

Water glasses are both from a melt solidified, glassy, water-soluble Alka lisilikate, especially sodium, potassium, and lithium silicates, as well as their aqueous solutions. Sodium water glasses are particularly suitable for use in the context of the present invention. It is also possible to use a mixture of two or more different water glasses.

A characteristic feature of water glasses is their modulus, which is understood to mean the molar ratio Si0 ₂ : M ₂ O in the water glass, wherein M is preferably selected from Li ⁺ , K ⁺ or Na ⁺ . In the present case, preference is given to using water glasses whose modulus is in the range from 1.2 to 4.5, particularly preferably in the range from 1.5 to 3.3.

In GB 782 205 A an alkali water glass is described, which is also suitable in the context of the present invention as a binder and can be cured by the introduction of C0 ₂ . Other ge suitable water-based binders are known for example from DE 199 25 167 Al, DE 10 2007 045 649 Al or from US 5474606 A.

Borates are salts or esters of boric acids. Boric acid itself can be counted among the borates who, it is often referred to as trihydrogen borate. The salts are characterized in that they contain in their ionic lattice as anion the borate ion B0 ₃ ³ or a condensed form thereof (for example in game B ₄ 0 ₅ (OH) ₄ ² , tetraborate).

As phosphates in addition to classical phosphates such as ammonium phosphate in particular also polyphosphates and hydrogen phosphates such as sodium hydrogen phosphate can be used.

Polyphosphates are, as is known, condensation products of salts of ortho-phosphoric acid (H ₃ P 0) with the general empirical formula M _{h + 2} R _h 0 _{3h +} i and the structure MO- [P (0M) (0) -0] _n - M, where M is a monovalent metal and n can easily be up to three or even four digits. Very often, however, the short-chain (ie, in fact oligo) phosphates are also counted among the polyphosphates, where n can be, for example, a number from 8 to 32. Cyclic polymers are referred to as metaphosphates.

Suitable binders based on polyphosphate and / or borate for use in the context of the present invention are described, for example, in WO 92/06808 A1. Other suitable phosphate Binder based compounds are known from DE 103 59547 B3 or from DE 195 25307 A1 or from US Pat. No. 5,711,792 A.

In some particularly preferred embodiments, the binder used according to the invention comprises, as phosphate, sodium hexametaphosphate ((NaPO ₃ ) ₆ ).

The water-insoluble binder component preferably comprises at least one member selected from the group consisting of particulate silica, especially particulate amorphous silica, and particulate calcium carbonate.

That the addition of silicon dioxide to a molding material mixture can be advantageous with a water glass-based binder is already known from DE 2434431 Al the company E.l. du Pont de Nemours and Co. known. The addition significantly increases the strength of water-glass bonded shapes and cores.

The particulate silicon dioxide is preferably used as a suspension in water, in particular as a colloidal aqueous suspension. The suspension used in this case preferably has a solids content in the range of 10 wt .-% to 80 wt .-% (based on the total mass of Sus suspension used).

In the case of particularly preferred embodiments, the suspension is a suspension produced by condensation, preferably of low molecular weight silica, of particles. The particulate silica may also be produced otherwise, for example by means of flame pyrolysis of silicon tetrachloride. Natural amorphous silicic acids, for example those described in DE 10 2007 045 649 A1, can also be used.

The particulate silicon dioxide preferably has an average particle diameter (d 50 value) in the range from 5 nm to 1.5 μm, particularly preferably in the range from 10 nm to 1 μm.

The preparation of colloidal suspensions of particles by condensation of low molecular weight Kie selsäure is a known process. Low molecular weight silicic acids, such as monosilicic acid (orthosilicic acid), di-silicic acid or triacetic acid, tend to condense, especially under acidic or basic conditions. If these low molecular weight silicas condense, the formation of the Wanted colloidal suspensions. These are commercially available with a wide variety of average particle sizes.

Particles and colloidal suspensions used particularly preferably according to the invention are prepared from pure monosilicic acid.

The binder used according to the invention is particularly preferably formed by mixing the following components in the following proportions:

The at least one water-soluble binder component in a proportion in the range of 40 wt .-% to 99 wt .-%, in particular in the range of 50 wt .-% to 80 wt .-%.

The at least one water-insoluble binder component in a proportion in the range from 1% by weight to 40% by weight, in particular in the range from 5% by weight to 30% by weight.

The water or the aqueous solution, in particular the aqueous alkaline solution, in an amount ranging from 10% by weight to 60% by weight.

All percentages are based on the total added weight of all components of the binder including the water or aqueous solution. The proportions of the components add up to 100% by weight.

application variants

In principle, it is possible to provide the binder in the form of a mixture of all of its constituents and to apply it to the layer of the pretreated particulate molding base material. In a particularly preferred embodiment, however, at least one component of the binder is contained as a stationary binder component in the layer of the molding material. Only the übri components of the binder are applied in liquid form to the layer.

According to a first preferred variant of the method, the stationary binder component is the water-insoluble binder component or one of the water-insoluble binder components. Particularly preferably, the mold base material is pretreated component in this case with the stationary binder. Thus, it is possible, for example, to mix the molding material with the descriptive NEN colloidal aqueous silica suspension before a layer is formed from the molding material, then the remaining components of the binder, for example a Water glass, are applied in liquid form, in particular about the one or more mentioned printing heads.

The at least one binder component, which is applied in liquid form to the layer, preferably comprises at least one member selected from the group consisting of water, an aqueous hydroxide solution (in particular caustic soda or potassium hydroxide solution), a waterglass solution, an aqueous solution of magnesium sulphate, an aqueous solution Phosphate solution and an aqueous borate solution, depending on the particular binder used.

According to a second preferred variant of the method, the stationary binder component is the water-soluble binder component or one of the water-soluble binder components. More preferably, the molding base material is also pretreated with the stationary binder component in this case. It is thus possible, for example, to mix the molding base material with water glass as binder component before a layer is formed from the molding base material, to which the remaining components of the binder, for example the described colloidal aqueous silica suspension, are then applied in liquid form.

Heat-curing and self-curing process variants

Depending on the binder used, it may be preferable to cure the binder after application of the binder or the at least one component of the binder to the layer. In particular, the following procedures are available for this:

• Hardening is carried out by means of microwave radiation.

• Hardening is carried out chemically, in particular by means of C0 ₂ or by means of a self-curing additive.

• Hardening is thermal.

Such a thermosetting process variant may be advantageous, for example, under the following conditions:

The mold base is a sand treated with the alkyl silanolate, especially with potassium methyl silicate.

• A water glass solution is applied to the layer as a liquid binder component. In this case, hardening by means of microwave radiation preferably takes place. Particularly in the production of cores or molds for casting applications, it may be preferable that the above-mentioned particulate silica be contained in the layer of the molding base as the stationary binder component.

In most preferred embodiments of the method according to the invention, however, the binder is chosen such that self-curing is possible. Two particularly preferred self-hardening process variants are described below:

In a variant (1) with self-hardening binder

The molding base material is a sand treated with an organosilicon compound according to formula (I),

• is in the layer of the molding material as a stationary binder component an ester hardener such as diacetin or triacetin contain, and

• The water glass solution is applied to the layer as a liquid binder component.

Also in this process variant no curing by means of microwave is required (instead it follows the cure by a hardening sol-gel conversion without use of thermal energy gie) and also here it may be given in the production of cores or molds for casting applications before, in the layer from the mold base as a stationary binder component the above-mentioned he particulate silica is included.

In a variant (2) with self-hardening binder

Is the molding material is a sand, which is treated with an organosilicon compound according to formula (I) is in the layer of the molding material as a stationary binder component hold the water glass ent, and is on the layer as part of a liquid binder component an ester hardener, example Diacetin or triacetin, applied. Also in this process variant no curing by means of microwave is required (instead it follows the cure by a hardening sol-gel conversion without use of thermal energy gie) and also here it may be given in the production of cores or molds for casting applications before, in the layer from the mold base as a stationary binder component the above-mentioned he particulate silica is included.

Molds and cores made according to the method

Molds and cores produced by the process have a content of the organosilicon compound, in particular in the range of 0.01 to 0.09 wt .-%.

In preferred embodiments, they are further distinguished by one of the following or a combination of the following features:

The forms and cores comprise at least one member of the group consisting of magnesium sulfate, phosphate and borate, in particular in a proportion in the range of 0.3 to 2.5 wt .-%, particularly preferably in the range of 0.5 to 1.0 wt .-%.

The molds and cores comprise particulate silica with an average particle diameter (d50 value) in the range from 5 nm to 1.5 μm, in particular in a proportion in the range from 0.1 to 1.0% by weight.

Set for creating shapes and cores

The set according to the invention always comprises the following components:

At least one organosilicon compound having a polar hydrophilic end and a non-polar hydrophobic end, and

• at least one member of the group consisting of water glass, magnesium sulfate, phosphate and borate.

The two components are usually contained separately in the set.

In preferred embodiments, the kit further comprises at least one of the following components:

A particulate molding material. • At least one member of the group of silica and calcium carbonate.

• An aqueous hydroxide solution.

The solid among said additional components, in some preferred embodiments, are already mixed with the particulate molding base.

Further features of the invention and advantages resulting from the invention will become apparent from the following exemplary embodiments, on the basis of which the invention will be explained. The embodiment described below is merely illustrative and for a better understanding of the invention and is in no way limiting.

(1) Provision of a potassium formylate-pretreated particulate molding base

99.98 parts by weight of GS14 type sand from STROBEL QUARZSAND GmbH, located in Freihung, Germany (mean particle size = 0.13 mm, theoretical specific surface area = 176 cm ² / g) were mixed with 0.02 part by weight of an aqueous solution with 34 wt. - Mix% of potassium methylsiliconate and mix thoroughly.

(2) Provision of a 3- (polyoxyethylene) propylheptamethyltrisiloxane pretreated particulate molding base

99.98 parts by weight of GS14 type rubber from STROBEL QUARZSAND GmbH, based in Freihung, Germany (mean particle size = 0.13 mm, theoretical specific surface area = 176 cm ² / g), were admixed with 0.02 part by weight of 3- (polyoxyethylene) propylheptamethyltrisiloxane and thoroughly mixed.

(3) Provision of a printable water glass containing binder component

The waterglass-containing binder component was Betol 50T (aqueous solution of modified sodium silicate with a modulus of 2.6 and a solids content of 44% by weight (Woellner GmbH & Co. KG, Ludwigshafen, Germany) with water and optionally a small proportion of a surfactant mixed.

(4) providing a water-insoluble binder component As the first water-insoluble binder component, an amorphous Si0 ₂ powder synthetic origin was provided with an average particle size in the range of 0.1 to 0.3 pm.

(5) Preparation of core with self-curing binder

In order to produce a core for the aluminum casting, 99 parts by weight of the molding base material treated according to (2) were mixed with 1 part by weight of the SiO ₂ powder prepared according to (4). From the mixture, a layer was formed. This was then compacted. The formed layer had a uniform layer thickness in the range of 0.2 mm to 0.5 mm. In some areas, the water-glass-containing binder component prepared according to (3) was printed onto this layer. After printing, a new layer of the mixture was formed on the printed layer and compacted to a layer thickness in the range mentioned. This layer was also printed again with the water-glass-containing binder component prepared according to (3). This process was repeated until the desired core was completed. This was hardened by means of microwave radiation.

The hardened core fulfilled geometric shape specifications much better than a core made under comparable conditions with untreated mold base.

Claims

claims

A method of producing molds and cores of a particulate molding material and a multicomponent binder by means of 3D printing suitable for the production of fiber composite bodies or castings from metal or plastic, comprising the steps

a. the particulate molding base material is pretreated with at least one organosilicon compound having a polar hydrophilic end and a nonpolar hydrophobic end,

b. a layer of the pretreated particulate molding base is formed, and c. the binder or at least one component of the binder is applied in liquid form to the layer,

wherein steps b. and c. be repeated several times.

2. The method of claim 1 with at least one of the following additional features and / or additional steps:

a. The mold base comprises a particulate material, to the surface of which the hydrophilic end of the organosilicon compound can bind.

b. As the molding material, at least one water-insoluble inorganic material is selected.

c. The at least one water-insoluble inorganic material is selected from the group consisting of sand, glass, oxide, ceramic and glass-ceramic materials and mixtures of the aforementioned materials.

d. As the molding material, at least one water-soluble inorganic material is selected.

e. The at least one water-soluble inorganic material is a water-soluble salt. f. As the molding material, at least one water-soluble organic material is selected. G. The at least one water-soluble organic material is a water-soluble polymer or a salt of an organic acid or a mixture of these materials.

H. The particulate molding material has an average particle diameter (d50 value) of 10 pm to 800 pm, preferably between 30 pm and 300 pm.

i. The particulate molding base material has a surface determined according to DIN-ISO 9277 in the range of 50 cm ² / g and 500 cm ² / g.

3. The method according to any one of the preceding claims with at least one of the following additional features and / or additional steps: a. the polar hydrophilic end of the organosilicon compound comprises a hydroxy (-OH), a hydroxylate (-O), an amino (-NH ₂ ), an ammonium (-NH ₄ ⁺ ), a carboxyl (-COOH) or a carboxylate group.

b. The non-polar hydrophobic end of the organosilicon compound comprises at least one alkyl group, preferably from the group with methyl, ethyl and propyl.

c. The polar, hydrophilic and the non-polar, hydrophobic end are connected to the same Si atom.

d. The organosilicon compound used is an alkyl silanolate, in particular an alkali metal silanolate.

e. The nonpolar, hydrophobic end of the organosilicon compound is bound to a Si atom and the hydrophilic end is bonded to a C atom.

f. The Si atom and the C atom are connected via a chain with n atoms, where n is an integer between 1 and 150 and the atoms are selected from C atoms and 0 atoms and Si atoms.

G. As the organosilicon compound, a compound having the structural formula (I)

where n is an integer between 1 and 100 and m is an integer between 1 and 10 and R is an H atom.

H. As the organosilicon compound, 3- (polyoxyethylene) propylheptamethyltrisiloxane is used.

4. The method according to any one of the preceding claims with the following additional step: a. For pretreatment, the organosilicon compound is added to the particulate molding base in the pretreatment in an amount such that it is contained in the pretreated molding base material in a proportion by weight of at least 0.01% by weight and not more than 0.2% by weight on the dry weight of the pretreated molding base).

5. The method according to any one of the preceding claims with at least one of the following additional features and / or additional steps:

a. The binder comprises at least one water-soluble binder component. b. The water-soluble binder component comprises at least one member of the group consisting of water glass, magnesium sulfate, phosphate and borate.

c. The binder comprises at least one water-insoluble binder component.

d. The water-insoluble binder component comprises at least one member selected from the group consisting of particulate silica and calcium carbonate.

e. The binder comprises water or an aqueous solution, in particular an aqueous alkaline solution.

f. The binder includes an additive that affects its processing properties.

6. The method according to any one of the preceding claims with at least one of the following addi tional features and / or additional steps:

a. At least one binder component is present as a stationary binder component in the layer of the molding material.

b. The stationary binder component is the water-insoluble binder component or one of the water-insoluble components.

c. The stationary binder component is the water-soluble binder component or one of the water-soluble components.

d. The masterbatch was pretreated with the stationary binder component.

e. The at least one binder component applied in liquid form to the layer comprises at least one member selected from the group consisting of water, an aqueous hydroxide solution, a water glass solution, an aqueous solution of magnesium sulfate, an aqueous phosphate solution, and an aqueous borate solution.

7. The method according to any one of the preceding claims with at least one of the following addi tional features and / or additional steps:

a. After application of the binder or at least one component of the binder to the layer, the binder is cured.

b. The curing takes place by means of microwave radiation.

c. The hardening takes place chemically.

d. The curing takes place thermally.

8. The method according to any one of claims 6 or 7 with the following additional features and / or additional steps:

a. The molding base material is a sand which has been treated with the alkyl silanolate, in particular with potassium methyl siliconate. b. Optionally (for casting application) is contained in the layer of the molding material as statio nary binder component, the silicon dioxide.

c. Waterglass solution is applied to the layer as a liquid binder component.

d. There is a hardening by means of microwave radiation.

9. The method according to any one of claims 6 or 7 with the following additional features and / or additional steps:

a. The molding base is a sand treated with the organosilicon compound of formula (I).

b. Optionally, the silicon dioxide contained in the layer of the molding material as stationary Binderkomponen te.

c. In the layer of the molding base material is used as a stationary binder component as a hardener an ester hardener.

d. The waterglass solution is applied to the layer as a liquid binder component.

10. The method according to any one of claims 6 or 7 with the following additional features and / or additional steps:

c. The water glass is contained as stationary components of the binder in the layer.

d. An ester hardener is applied to the layer as a liquid binder component.

11. For the production of fiber composite bodies or castings made of metal or plastic appro designated forms and cores with the feature

a. The molds and cores have a content of the organosilicon compound ranging from 0.01 to 0.2% by weight;

and optionally at least one of the following additional features

b. The molds and cores are made by a method according to any one of the preceding claims. and or

c. The forms and cores comprise at least one member selected from the group consisting of magnesium sulfate, phosphate and borate, in particular in a proportion in the range of 0.3 to 2.5% by weight; and or

d. The molds and cores comprise particulate silica, in particular in a proportion in the range of 0.1 to 1.0 wt .-%.

A particulate molding base material for use in a method according to any one of the preceding claims, having on its surface at least one organosilicon compound having a polar hydrophilic end and a nonpolar hydrophobic end.

13. Set for producing suitable for the production of fiber composite bodies or castings from metal or plastic molds and cores from a particulate mold base material and egg nem multi-component binder by means of 3D printing, in particular for use in a Ver drive according to one of the preceding claims, comprising a , At least one organosilicon compound having a polar hydrophilic end and a nonpolar hydrophobic end, and

b. At least one member of the group with water glass, magnesium sulfate, phosphate and borate, and optionally c. a particulate molding material and / or

d. at least one member of the group comprising silica and calcium carbonate; and / or e. an aqueous hydroxide solution.