CN112703070A

CN112703070A - Method for producing metal castings or hardened molded parts using aliphatic binder systems

Info

Publication number: CN112703070A
Application number: CN201980058558.6A
Authority: CN
Inventors: 克劳斯·里曼; 赫尔曼·利伯; 格拉尔德·拉德古尔迪耶; 尼尔斯·齐默尔; 于尔根·许贝特
Original assignee: Huettenes Albertus Chemische Werke GmbH
Current assignee: Huettenes Albertus Chemische Werke GmbH
Priority date: 2018-09-06
Filing date: 2019-09-05
Publication date: 2021-04-23
Also published as: MX2021002592A; WO2020049075A1; DE102018121769A1; EP3846952A1; TW202026071A

Abstract

A method for producing (i) a metal casting and/or (ii) a hardened molded part used in the casting of a metal casting, selected from a casting mold, a core and a riser, and a molding material mixture for use in the method are described. The use of aliphatic polymers crosslinked by one or more aliphatic polyisocyanates, which contain hydroxyl groups, as binders for moldings used in the casting of metal castings is also described. Also described are hardened molded parts for use in casting metal castings, including molded parts having green strength and molded parts that can preferably be produced according to the method according to the invention. The use of biopolymers from poly-D-glucosamine as binders or binder components for the production of moulded parts with green strength in the foundry industry is also described.

Description

Method for producing metal castings or hardened molded parts using aliphatic binder systems

Technical Field

The invention relates to a method for producing (i) metal castings and/or (ii) hardened molded parts selected from casting molds, cores and risers for use in casting metal castings, and to a molding material mixture, in particular for use in the method.

The invention also relates to the use of aliphatic polymers containing hydroxyl groups, which are crosslinked by one or more aliphatic polyisocyanates, as binders for mouldings used in the casting of metal castings.

The invention also relates to a hardened molded part for use in casting metal castings, as well as a molded part that is solid in the green state and preferably produced according to the method according to the invention.

The invention also relates to the use of a biopolymer from poly-D-glucosamine as a binder or binder component for the production of green state robust molded parts in the foundry industry.

Background

Cast mouldings for metal casting (hereinafter also simply referred to as "mouldings"), in particular cores, moulds and risers (including riser caps and riser jackets or riser sleeves), are generally composed of refractory moulding raw materials which, depending on the intended use, comprise one or more refractory solids, for example quartz sand; and/or one or more particulate light fillers, such as spheres comprised of fly ash; and a suitable binder that imparts sufficient mechanical strength to the molded article after removal from a molding tool (e.g., a case of molded articles, such as a core box or a mold box, see below). In the uncured state, the mixture of molding material and binder, which optionally can also contain further additives, is referred to as "molding material mixture".

The refractory solid is preferably present in particulate and free-flowing form, so that it can be introduced into a suitable hollow mould (moulding tool, see above) after being incorporated into the moulding material mixture and densified there. For this purpose, the risers and the core are introduced (i.e. shot) into the mould of the core shooter, usually under pressure. Relatively small molded parts are usually injected as such, while larger molded parts, in particular relatively large molds, are usually formed by stamping in a die box. In general, all molded parts can also be produced by stamping in suitable dies, for example in a hand molding process. In order to obtain an injectable or stampable moulding material mixture, its moisture content, in particular its water content, must be set appropriately, in the case of water-based binders, so that the moulding material mixture has sufficient form stability for the respective moulding step, or the ratio of the liquid component to its solid component of the moulding material mixture must be set accordingly.

Molded parts, such as molds, cores and risers, must meet the various requirements of a typical casting. The manner and extent to which these requirements are met is essentially determined by the binder used in its manufacture.

After the production of the molded part, i.e. immediately after the molded part has been removed from the production tool, the molded part should have a very high strength. The strength at this point in time ("initial strength", also referred to as "green strength"; see also below) is particularly important for the safe handling of the core, mold or riser when it is removed from the manufacturing tool.

In order that the molded part does not deform under the weight of the cast metal (i.e. maintains a good resistance to deformation during the casting process, also referred to as "casting strength") and that the metal castings produced therewith can be produced as far as possible without casting defects, a high final strength of the molded part (i.e. strength after complete hardening of the molded part) and a high heat resistance during the actual metal casting are also important, in particular for the cores and the casting molds. It is also important in this connection that the moulded parts used have a very clean or smooth surface without deformations etc., since otherwise surface defects of the moulded part may be transferred to the surface of the metal casting produced by it.

Furthermore, the high resistance of the molded parts to moisture containing water is a great advantage. In general, such high moisture resistance allows relatively long storage times of the molded parts even in harsh climatic conditions (hot, humid climates) and, ideally, for days or weeks, which simplifies or makes possible for the first time the molded parts for stocking and the storage thereof. In this way, industrial manufacture of metal castings using these mouldings benefits significantly in terms of flexibility. It has also been found that in all molded parts used for metal casting, in particular in the risers, water absorption (for example by absorption of moisture from the air during storage thereof) can lead to the formation of steam bubbles from corresponding water inclusions at high temperatures of the metal casting, which can lead to the formation of shrinkage cavities in the metal casting, whereby the metal casting subsequently becomes unusable. In extreme cases, an explosion may even occur due to sudden water vapor formation. The high moisture resistance of the molded parts is also advantageous, since it allows, for example, the use of the molded parts with different types of fire-resistant coatings, in particular also with water-based fire-resistant coatings. The refractory coating is a ceramic-based mold release agent, which in some cases is intended to prevent direct contact between the molded part (e.g., core) and the metal melt, so that the molded part is better able to withstand the high thermal stresses during metal casting.

With regard to high metal casting quality, it is also desirable for the molded part to absorb very little thermal energy from the metal melt, for example, endotherms due to the reaction of the binder, as can occur in the known melting reactions of water glass binders. Such absorption of heat energy may result in premature solidification of the metal melt, resulting in an incomplete casting. This characterization of the binder by its properties, i.e. its self-absorption of thermal energy, is also referred to as its "quenching properties". In particular in the case of risers, good thermal insulation is particularly desirable or necessary in order to keep the metal melt as liquid as long as possible during the metal casting and to achieve the formation of the smallest possible shrinkage cavities in the metal casting, while at most allowing the shrinkage cavities that occur to occur very far outside the finished metal casting (for example only in the riser).

After the casting process is complete, the molded part should then be decomposed as far as possible under the effect of the heat released from the cast metal, so that it loses its mechanical strength, i.e. loses the cohesion between the individual particles of molding material. Ideally, the molded part then disintegrates again into fine particles of the molding material, which can be removed from the metal cast without any difficulty and as far as possible without residues. If the molded part is a core, such advantageous disintegration properties lead to particularly good core removability of the metal casting.

In this connection, it is also particularly desirable that the decomposition of the molded parts, which is usually accompanied by thermal decomposition of the binder, takes place as far as possible in a non-emitting manner, i.e. without emitting unpleasant odours and/or even materials harmful to health, in order to keep the disturbance or health risks to the working staff in the foundry as low as possible or to reduce or ideally prevent such disturbances or health risks. Such damage caused by unpleasant odours and/or materials harmful to health may occur in particular during casting with hot metal melts, in which case in particular the risers which usually protrude from the casting mould become the main cause, but also after hardening of the metal casting when the latter is taken out of the casting mould ("disassembly" or "demoulding").

Different organic and inorganic binders, each having typical limitations or disadvantages, are known for the manufacture of molded parts for the foundry industry.

In the field of organic binders and binder systems, organic binder/binder systems are known whose hardening can be achieved by cold or hot methods, respectively.

In the thermosetting method, the molding material mixture, after being shaped, for example, by a heated molding tool, is heated to a temperature high enough to drive off the solvent contained in the binder and/or to initiate a chemical reaction that hardens the binder. One example of such a thermal hardening process is the "hot box process". Today, it is mainly used for the mass production of cores.

The method is referred to as a cold-hardening method, which is carried out essentially without heating the molding tool for core production, usually at room temperature or at a temperature caused by possible, for example, chemical reactions. Hardening is effected, for example, by introducing a gas into the molding material mixture to be hardened and triggering a suitable chemical reaction. One example of such a cold-hardening process is the "cold-box process", which is widely used today in the foundry industry.

However, according to the prior art, both the hot-box process and the cold-box process use organic binders based on phenolic resins. A disadvantage of the organic binder is that, regardless of its exact composition, when it decomposes, as it progresses through the temperatures prevailing during metal casting, considerable amounts of harmful substances, such as benzene, toluene and xylene (also referred to as "BTX" for short), are sometimes released. Furthermore, metal casting of such organic binders often results in undesirable emissions of odors and fumes or fumes. In the case of some such binder systems, undesirable emissions can occur even during the manufacture and/or storage of the molded parts.

As an alternative to the above-mentioned organic binders, corresponding inorganic binders are known which do not exhibit the above-mentioned phenomenon of releasing undesirable odors or harmful substances during metal casting, or exhibit this phenomenon only to a much lesser extent. An example of such an inorganic binder is water glass. Correspond toThe moulding material mixture of (a) consists essentially of moulding raw material (e.g. quartz sand) and water glass (as an aqueous solution of alkali metal silicate). The molded molding material mixture is produced, for example, by using CO₂It is cured by fumigation.

However, the use of such inorganic binders also involves other typical disadvantages: therefore, molded articles made from inorganic binders generally have only low strength. This is revealed in particular at the moment when the moulded part is removed from the tool. Furthermore, the generally low moisture resistance of these adhesives leads to a limitation in the storage capacity of the moldings produced therewith. Furthermore, inorganic binders do not generally exhibit satisfactory disintegration properties, so that it is then necessary to extensively rework metal castings produced with the aid of such molded parts. It is also known that water glass-bonded risers generally have less good insulating properties than risers bonded by means of organic binders. Finally, inorganic binder systems such as water glass are also known to absorb (i.e. dissipate) by themselves a large amount of thermal energy during metal casting, whereby the metal melt hardens relatively early, so that casting defects may result. This is particularly true for iron and steel castings where the casting temperatures required are high.

In the prior art, a series of organic binders have been discussed, as well as methods for manufacturing molded parts using such binders:

document DE 102007031376 a1 describes an alternative cold box process with the aid of crude oil.

Document DE 19615400 a1 describes polymers, their use as binders for the production of green ceramic bodies and a method for producing ceramic bodies.

Document JPH 06157860 a describes water-resistant compositions.

Document JPS 61276813 a discloses hardenable compositions.

Document EP 677346 a2 relates to a casting method using a casting core composed of a synthetic resin, a synthetic resin core, and a cast workpiece.

Document WO 96/26231 a1 describes chemical binders comprising ester-based polyols, isocyanates and catalysts.

Document WO 2011/044003 a2 relates to lignite-urethane based resins for foundry sands with improved properties.

Document WO 2017/071695 a1 describes binders for foundry sand that are free of phenolic resins.

Document WO 2017/093371a1 describes a method for manufacturing refractory composite granules and a riser element for the foundry industry, a corresponding riser element and use.

However, in accordance with the prior art, there is still a need for a method for producing metal castings or for producing hardened molded parts for use in casting metal castings, which method achieves one, more, and ideally all of the following advantageous properties:

a high initial strength of the molded part produced according to the method, which is sufficient at least for practical use purposes;

high final strength of the moulded article produced according to said method;

high casting resistance or heat resistance of the molded parts produced according to the method;

-a clean and smooth surface of a moulded article manufactured according to said method;

the very high moisture resistance or the very high water resistance of the molded parts produced according to the method results in very good or long-term storage capability of the molded parts, especially even under different climatic conditions, and/or the molded parts can be used with water-based coatings;

during metal casting, the lowest possible heat energy absorption and ideally good thermal insulation of the molded part produced according to the method;

the emission of odorous and/or harmful substances and also fumes or fumes of the molded parts produced according to the method is as low as possible, in particular under the conditions of metal casting, during the casting of light metals and their alloys and in iron and steel casting;

-at least partially using renewable starting materials;

very low outlay in terms of equipment when carrying out the method, in particular (even) performability without heatable tools (i.e. at least similar to known cold box manufacturing methods and performable with equipment in terms of the respective equipment).

Furthermore, there is a need for binders for molded articles in the casting of metal castings, and also for molding material mixtures for use in such methods, which binders have or achieve one, more, and ideally all of the advantageous relevant properties described above. Furthermore, there is a need for a molded article having one, more, and ideally all of the relevant properties mentioned in connection with the above-mentioned method. There is also a need for a binder which permits the production of green-strength molded parts for the foundry industry, in particular with regard to a flexible design of the respective production method.

Disclosure of Invention

It is therefore a primary object of the present invention to provide a method for producing metal castings or for producing hardened molded parts for use in casting metal castings, which method achieves or has one, more and ideally all of the above-mentioned advantageous properties, and a molding material mixture, in particular for the above-mentioned method.

It is another object of the present invention to provide a binder for use in molding when casting metal castings that has or achieves one, more, and ideally all of the advantageous related characteristics described above.

A particular object of the invention is also to provide a hardened molding for use in casting metal castings, which hardened molding has one, more and ideally all of the relevant properties mentioned in connection with the above-mentioned method.

Furthermore, it is an object of the present invention to provide a binder which allows green-strength molded parts for the foundry industry to be produced as far as possible also at room temperature.

It has now surprisingly been found that the main object and further objects and/or sub-objects of the present invention are achieved by a method according to the present invention for i) manufacturing a metal casting and/or ii) manufacturing a hardened molded part selected from a casting mould, a core and a riser for use in casting a metal casting, the method comprising the steps of:

v1) preparing a molding material mixture comprising (or consisting of):

a) at least one of the molding materials is selected from the group consisting of,

b) one or more aliphatic polymers each comprising a structural unit of the formula I containing a hydroxyl group

–CH₂-CH(OH)- (Ⅰ)，

c) As hardener component, one or two components selected from:

c1) one or more biopolymers selected from poly-D-glucosamine

And

c2) one or more preferably water-dispersible and/or aliphatic polyisocyanates as crosslinkers for the hydroxyl groups of the one or more aliphatic polymers;

and

d) water;

v2) molding the molding material mixture,

and then

V3) allowing the molded molding-material mixture or an unhardened downstream product resulting therefrom to harden in one or more steps,

so that a hardened molded part is obtained.

The invention and preferred combinations according to the invention of parameters, characteristics and/or components according to the invention are defined in the appended claims. Preferred aspects of the invention are also given or defined in the following description and in the examples.

By means of the method according to the invention, together with its variants and preferred variants, hardened molded parts for the foundry industry can be produced, in particular molds, cores and risers (insulated risers and exothermic risers, including riser caps and riser sleeves), which have a number of advantageous properties. One, more or ideally all of the advantageous properties mentioned above can be achieved according to the design of the method (or variants or preferred variants thereof). Common to all variants and embodiments of the method according to the invention is that only low emissions of odorous and/or harmful substances and also of fumes or smoke occur therein. In a preferred embodiment of the method according to the invention, even only very low emissions of odorous and/or harmful substances and also of fumes or smoke are generated. Furthermore, common to all variants and embodiments of the method according to the invention is that the molded parts produced therefrom have only a low tendency to absorb thermal energy and exhibit advantageous quenching properties.

In the above-described process according to the invention, the molding material mixture is preferably produced in step V1) by thoroughly mixing the components a) to d) with one another in order to obtain as homogeneous a distribution as possible in the molding material mixture. The mixing of the components with one another is carried out in a manner known per se, for example with the aid of stirrers suitable for these purposes, for example blade stirrers. For a preferred embodiment of components a) to c), see below.

In step V2), the molding material mixture is molded into a three-dimensional structure selected from the group consisting of a casting mold, a core, and a riser (including a riser cap and a riser sleeve). Step V2) is preferably performed in the moulding tool.

In the context of the present invention, the term "moulding tool" means any tool which can be used in the foundry industry for shaping moulded articles and for injection machines, in particular core shooters, into moulded articles, preferably selected from moulds, cores and risers (including riser caps and riser sleeves), in particular moulded article boxes (including mould boxes and core boxes).

If the molding in step V2) is carried out in an injection machine, the ratio of the total moisture content to the total solids content in the molding material mixture is preferably set for this purpose before or during the molding of the molding material mixture, so that the molding material mixture can be injected in the injection machine or can be punched out in a molding box. The setting can be easily performed by those skilled in the art.

Step V3) of the above-described method according to the invention comprises hardening the molded molding material mixture or an unhardened downstream product resulting therefrom, so that a hardened molded part results. Preferably, at least deformation-resistant, hardened moldings are produced by hardening in step V3). In this connection, "deformation-resistant" means that the molded part with this property retains its shape, so that it can be handled, for example transported at the manufacturing site to a subsequent further processing site, at least without losing or impairing its shape, for example even after removal of the molding tool.

In the context of the present invention, the hardening of the molded molding-material mixture or the unhardened downstream product resulting therefrom in step V3) comprises one, two or all three steps selected from the following (each of which may be used for a particular variant or embodiment of the method according to the invention):

v31) precipitating at least a portion of the biopolymer (in the molded molding material mixture and/or an unhardened downstream product formed therefrom) such that a molded article having green strength is produced (see below for details),

v32) treating the molded molding material mixture and/or the uncured downstream product formed therefrom and/or, if step V31 has been carried out beforehand, the molded part having green strength by heating and/or removing water (see below),

and

v33) crosslinking the hydroxyl groups of the aliphatic polymer(s) (component b)) of the formula i with the isocyanate groups of the polyisocyanate (component c1), if present, preferably of the water-dispersible and/or aliphatic polyisocyanate, in the molded molding material mixture and/or in the uncured downstream product formed therefrom and/or in the molded part having green strength (if step V31) has been carried out beforehand, so that a crosslinked molded part is produced as a cured molded part (see below for details).

In the context of the present invention and consistent with the general understanding in the art, the term "green strength" means "resistant to deformation or shape stable hardening or pre-hardening to have a stable shape, but not yet sufficiently hardened or fully hardened for the purpose originally set. Molded articles having green strength have a hardness sufficient to be removed from the molding tool or transferred to a next processing step, for example, but generally have not been sufficiently hard to achieve the end-set purpose for which the metal casting is being made. For example, when the method is preferably carried out without heatable molding tools, molded parts having green strength are produced in the method according to the invention: the molded part with green strength can then be further processed, in particular according to step V32) and/or step V33) of the method according to the invention, for example in a conventional drying oven, with or without the aid of molding tools for its production. In order to produce moldings with green strength in steps V3) or V31), the process according to the invention requires the presence of component c1), i.e.one or more biopolymers selected from the group of poly-D-glucamines, in the molding material mixture. The green-strength molded part obtained after step V31) is a hardened molded part for the purposes of the present invention.

In a preferred embodiment of the method according to the invention, wherein the hardening in step V3) comprises step V31), at least a portion, preferably the total amount, of the biopolymer(s) (preferably chitosan, see below) used in the method precipitates from the aqueous fraction of the molded molding material mixture or of the unhardened downstream product resulting therefrom. This is preferably achieved in a manner known per se by increasing the pH of these aqueous portions. Raising the pH can be performed in any known manner, for example by adding an aqueous base. The pH of the aqueous fraction of the molded molding-material mixture or of the unhardened downstream product resulting therefrom is preferably increased by gas-curing with the aid of one or more basic compounds which are gaseous under the reaction conditions, preferably one or more amines which are gaseous under the reaction conditions. Preferably, the gaseous amine or one of the gaseous amines is N, -dimethylpropylamine. By increasing the pH in the moulded moulding material mixture or an unhardened downstream product resulting therefrom, wherein the moulding material mixture or downstream product respectively comprises one or more biopolymers selected from the group consisting of poly D-glucosamine, preferably chitosan, at least a portion of which are precipitated out of the aqueous constituents of the moulded moulding material mixture or of the unhardened downstream product resulting therefrom, a moulded part with green strength is produced. The production of green-strength moldings according to the process according to the invention can be carried out in a manner known per se, in particular corresponding to the step of hardening or completely hardening the molded molding material mixture (or the unhardened downstream product resulting therefrom) in the cold-box process: since the production of molded parts having green strength according to the method according to the invention does not require a temperature increase (heating), this step can be carried out, for example, in a cold box tool known per se. For example, cold box core shooters without heating devices are suitable for this purpose without having to make significant changes thereto, since, for example, the step of completely curing the molded molding material mixture (or the uncured downstream product resulting therefrom) in the cold box process is likewise preferably effected by gas fumigation with gaseous amines. A green-strength casting mold, core and riser can be produced in the manner described above in accordance with the method according to the invention.

Preferably, the molded mold mixture (as obtained after step V2) and/or the unhardened downstream product resulting therefrom and/or the molded part with green strength (as obtained after step V31)) is further processed (see below), again according to step V32). After carrying out step V32), the moulded part produced according to the method according to the invention generally already has a hardness sufficient for producing a metal casting. As will be described in detail below, the treatment in step V3) or V32) is effected by heating the molded molding material mixture and/or the unhardened downstream product and/or the molded part with green strength resulting therefrom and/or by draining water from the molding material mixture, the downstream product or the molded part with green strength (as described above).

As long as it is feasible (i.e. if in the molding material mixture in step V1) component c2), i.e. the presence of one or more polyisocyanates (as defined above or below or as defined as preferred) as crosslinking agents for the hydroxyl groups of the aliphatic polymer(s), and is desired, the (hardened) molded part obtained after step V31) and/or after step V32) is further reacted in step V33) to a crosslinked (hardened) molded part by crosslinking the hydroxyl groups of the aliphatic polymer(s) of the formula I with the isocyanate groups of the aforementioned polyisocyanates. For the production of crosslinked moldings in steps V3) or V33), the presence of component c2), i.e. one or more polyisocyanates (as defined above or below or as preferred), as crosslinking agents for the hydroxyl groups of the aliphatic polymer or polymers, in the molding material mixture is required according to the process according to the invention.

Crosslinking of hydroxyl groups with isocyanate groups in step V33) is preferably carried out by: heating the molded molding material mixture and/or the unhardened downstream product and/or the molded part having green strength resulting therefrom, and preferably simultaneously discharging water therefrom, such that, when step V32) is carried out accordingly and component c2) is present in the molding material mixture, at least partial crosslinking of the hydroxyl groups with the isocyanate groups takes place (step V33)). In a variant of the process according to the invention in which step V3) comprises both step V32) and step V33), a crosslinked (hardened) molded part is thus produced as product or end product of the process according to the invention, which molded part is a hardened molded part for the purposes of the invention. See below for details.

The crosslinked (hardened) molded part (as obtained after performing both step V32) and step V33)) generally has a hardness sufficient for the manufacture of metal castings, and additionally preferably has an advantageously high moisture resistance or high water resistance. The initial strength, the final strength and the casting strength of such crosslinked (hardened) moldings are also generally correspondingly particularly high.

Preference is given to the process according to the invention described above, preferably the process (ii) according to the invention (preferably the process according to the invention described above or below) in which

A molding material mixture comprising (at least) component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, as hardener component c),

and preferably (additionally) comprises component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred), preferably aliphatic polyisocyanate(s), as a crosslinker for the hydroxyl groups of the aliphatic polymer(s),

and/or (preferably "and")

-the hardening in step V3) comprises

V31) (in the presence of component c1)) causes at least a portion of the one or more biopolymers to precipitate,

preferably by raising the pH of the aqueous portion of the molded molding material mixture, particularly preferably by contacting with an alkaline-reacting gaseous compound, preferably by gas-curing therewith, more particularly preferably by gas-curing with a gaseous amine,

so that a molded part with green strength is produced;

and/or (preferably "and")

V32) treating the molded molding material mixture and/or the uncured downstream product resulting therefrom and/or, if step V31) has been carried out beforehand, the molded part having a green strength

Heating the molded molding material mixture and/or the unhardened downstream product and/or the molded part with green strength resulting therefrom, preferably to a temperature in the range from 100 ℃ to 300 ℃, particularly preferably in the range from 150 ℃ to 250 ℃ and very particularly preferably in the range from 180 ℃ to 230 ℃,

and/or (preferably "and")

Removing water from the moulded moulding material mixture and/or from the unhardened downstream product resulting therefrom and/or from the moulded part having green strength.

In many cases, preference is also given to an embodiment of the above-described process according to the invention in which the molding material mixture comprises only component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, as hardener component c) (that is to say in which hardener component c) does not comprise component c2), i.e. one or more polyisocyanates). In this, in many cases preferred embodiment of the process according to the invention, step V31) is preferably carried out, i.e. at least a portion of the biopolymer(s) is/are precipitated, to produce a moulded part having green strength. In this embodiment of the method according to the invention, step V32) is preferably carried out with the aid of a molded molding material mixture (as obtained after step V2) and then without prior execution of step V31)), or-preferably-with the aid of a molded part having green strength (as obtained after step V31) and then in addition thereto and after prior execution of step V31)).

Removal of water in step V32) (in all variants of the method according to the invention comprising step V32) and removal of water) is carried out by one, two or all three measures selected from:

freeze-drying the molded molding material mixture and/or the unhardened downstream product resulting therefrom and/or the molded part having green strength,

vacuum drying of the molded molding material mixture and/or of the unhardened downstream product produced therefrom and/or of the molded part having green strength,

and

heating the molded molding material mixture and/or the green-strength molded part and/or the uncured downstream product produced therefrom (and removing water from the molded molding material mixture and/or the uncured downstream product produced therefrom and/or from the green-strength molded part). Preferably, the removal of water in step V32) (in all variants of the method according to the invention comprising step V32) and removal of water) is preferably performed by: heating the molded molding material mixture and/or the uncured downstream product produced therefrom and/or the molded article having green strength, and (preferably simultaneously) removing water from the molded molding material mixture and/or the uncured downstream product produced therefrom and/or from the molded article having green strength.

It is also preferred that the above-described process according to the invention, preferably the process (ii) according to the invention (preferably the above-described or below-described process according to the invention) is of the following design, wherein the moulding material mixture comprises only component c1), i.e. one or more biopolymers selected from the group of poly-D-glucosamine, as hardener component c), and that the process comprises in addition to and after the above-described step V31) the following steps:

v32) by treating a molded article having green strength as follows

Heating the molded part with green strength, preferably to a temperature in the range from 100 ℃ to 300 ℃, particularly preferably in the range from 150 ℃ to 250 ℃ and very particularly preferably in the range from 180 ℃ to 230 ℃,

and/or (preferably "and")

-removing water from the green-strength moulded article.

In a further particularly preferred embodiment of the process according to the invention, the molding material mixture comprises not only component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, but additionally component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred), as hardener component c). In this embodiment, molded parts having particularly advantageous properties can be produced, in particular molded parts having particularly high moisture resistance or particularly high water resistance and also having particularly high initial strength, particularly high final strength and particularly high casting resistance.

In the above-mentioned particularly preferred embodiment of the process according to the invention, the polyisocyanate in which the molding material mixture comprises component c1) and additionally also component c2) as hardener component c), component c2) is preferably selected from:

an aromatic polyisocyanate, preferably a water-compatible aromatic polyisocyanate, particularly preferably a water-dispersible aromatic polyisocyanate,

aliphatic polyisocyanates, preferably water-dispersible aliphatic polyisocyanates, particularly preferably the aliphatic polyisocyanates referred to hereinafter as preferred,

and

-mixtures thereof.

It is particularly preferred to use, as hardener component c2), a water-dispersible polyisocyanate in the process according to the invention described above or below (or in the process according to the invention described above or below which is referred to as preferred), if hardener component c2 is used or is present), which is preferably selected from the group consisting of water-dispersible aromatic polyisocyanates, water-dispersible aliphatic polyisocyanates and mixtures thereof. More particularly preferably, in the process according to the invention described above or below (or in the process according to the invention described above or below, which is referred to as preferred), a water-dispersible aliphatic polyisocyanate is used as hardener component c2) (if hardener component c2 is used or present).

Water-dispersible polyisocyanates are known per se in The art, in particular from WO 2011/144644A 1 or from The product manual "The Chemistry of Polyurethane Coatings" (08/05) of Bayer MaterialScience LLC. The method is characterized by the following characteristics: can be used as a crosslinking agent even in an aqueous or water-containing medium, particularly as a crosslinking agent for a non-aqueous hydroxyl group such as an alcoholic hydroxyl group. In contrast, aromatic polyisocyanates used in the foundry industry according to the prior art, for example as cold box binders, cannot be used in the desired manner in aqueous or water-containing media as is advantageous or even necessary in combination with aliphatic polymers which respectively comprise hydroxyl-containing structural units (in particular polyvinyl alcohol).

Particularly preferably, the water-dispersible polyisocyanate in the process according to the invention described above or below (or in the process according to the invention described above or below, which is referred to as preferred), as hardener component c2), (only hardener component c2) is to be used or present) is a water-dispersible polyisocyanate which meets the following selection criteria:

the water-dispersible polyisocyanates form a fluid in 24 hours of contact with water, the solid particles of which are not discernible to the naked eye without optical aids. To check whether the polyisocyanate is water dispersible, 100mg of polyisocyanate (preferably in the form of a 100 μm thick film) is provided into 100ml of water (at 20 ℃) and shaken on a commercially available shaking table for 24 hours. The polymer is water dispersible when solid particles are no longer recognizable after shaking, but the fluid has a turbidity (recognizable with the naked eye in the absence of the optical aid).

Aromatic polyisocyanates (as described above) have the advantage that: which can be crosslinked with one or more aliphatic polymers each comprising a structural unit of the formula I containing a hydroxyl group, are very suitable for producing moldings having high moisture resistance. However, the use of aromatic polyisocyanates is particularly disadvantageous when it is important in the foundry industry to work with as low a discharge as possible and to generate as little odorous and/or harmful substances as possible, since such undesirable emissions increasingly occur when aromatic polyisocyanates are used. In the context of the present invention, the term "aromatic polyisocyanates" is understood to mean polyisocyanates containing organic aromatic rings (i.e. aromatic hydrocarbons as structural elements).

Thus, in all variants of the process according to the invention in which component c2) is used in step V1), the polyisocyanates of component c2) preferably comprise aliphatic polyisocyanates, particularly preferably water-dispersible aliphatic polyisocyanates, and more particularly preferably the aliphatic polyisocyanates referred to hereinafter as preferred. Aliphatic polyisocyanates are used in aqueous or water-containing media considerably better than aromatic polyisocyanates on account of their reduced reactivity compared with aromatic polyisocyanates. In these preferred variants of the process according to the invention, in which component c2 is used in step (V1), the abovementioned aliphatic polyisocyanates, water-dispersible aliphatic polyisocyanates or (defined below) preferred aliphatic polyisocyanates preferably make up a proportion of the polyisocyanate or polyisocyanates used (or present) in the moulding material mixture of > 75% by weight, particularly preferably > 90% by weight and very particularly preferably > 95% by weight, based on the total mass of the polyisocyanate or polyisocyanates used (or present) in the moulding material mixture. In a particularly preferred variant of this embodiment of the process according to the invention, the polyisocyanates of component c2) comprise exclusively (i.e.100% by weight, based on the total mass of the polyisocyanate(s) used or present in the molding material mixture) aliphatic polyisocyanates, preferably exclusively water-dispersible aliphatic polyisocyanates, and particularly preferably exclusively the aliphatic polyisocyanates referred to below as preferred.

Aliphatic polyisocyanates have the advantage that: aliphatic polyisocyanates contribute less to the occurrence of odor substances and/or harmful substances and also to the undesired emission of smoke or fumes when carrying out the process according to the invention than, for example, aromatic polyisocyanates (i.e. organic polyisocyanates containing aromatic rings).

Accordingly, it is also preferred that the process according to the invention as described above, preferably the process (ii) according to the invention (preferably the process according to the invention as described above or hereinafter) is carried out in a continuous process, wherein

Component c2) of the molding material mixture, if used or present, comprises or consists of one or more water-dispersible polyisocyanates,

or

The polyisocyanate(s) (of component c2), if used or present) comprises one or more water-dispersible polyisocyanates, or the polyisocyanate (of component c2), if used or present), is one or more water-dispersible polyisocyanates.

In a particularly preferred embodiment of the method according to the invention, in which the molding material mixture comprises component c1) and additionally also component c2) as hardener component c), step V31) is preferably carried out in order to produce a molded part with green strength, even if at least a portion of the biopolymer(s) precipitates.

If step V32) is carried out in this embodiment of the method according to the invention, this step is carried out with the aid of the molded molding material mixture and/or with the aid of the unhardened downstream product produced from the molding material mixture (as obtained after step V2), or it is preferably additionally carried out with the aid of the molded part having green strength after step V31) is carried out. The removal of water in step V32) can be carried out by one, two or all three of the measures described above (freeze drying, vacuum drying, heating).

In a particularly preferred embodiment of the method according to the invention, in which the molding material mixture comprises component c1) and additionally also component c2) as hardener component c), step V33) is preferably carried out in addition to (and preferably simultaneously with) step V32). Crosslinking the hydroxyl groups with isocyanate groups in step V33) to produce crosslinked moldings preferably comprises:

heating the molded molding material mixture and/or the unhardened downstream product and/or the molded part having green strength resulting therefrom, preferably to a temperature in the range from 100 ℃ to 300 ℃, particularly preferably in the range from 150 ℃ to 250 ℃ and very particularly preferably in the range from 180 ℃ to 230 ℃,

and

removing water from the moulded molding material mixture and/or from the unhardened downstream product resulting therefrom and/or from the green-strength moulded part, preferably from the green-strength moulded part.

Hereby, in this case the hardening in step V3) of the method according to the invention comprises step V33) in addition to step V32) (as defined above).

As already mentioned, the moulding material mixture produced according to the method according to the invention and/or the unhardened downstream products resulting therefrom can be converted into hardened moulded parts or cross-linked (hardened) moulded parts, such as moulded parts with green strength produced according to the method according to the invention. That is to say, according to the method according to the invention, step V32) can be carried out after step V2) or after step V31). However, in contrast, it is not preferred to carry out step V31) after step V32), since precipitation (in step V31) of at least a part of the biopolymer(s) in the molded molding-material mixture and/or in the unhardened downstream product produced therefrom is generally technically meaningless or not feasible after heating the molded molding-material mixture and/or the unhardened downstream product produced therefrom or after removing water therefrom.

In one variant of the method according to the invention, in order to carry out step V32) (and preferably additionally or simultaneously to carry out step V33)), the molded molding-material mixture (produced in step V2) and/or the unhardened downstream product resulting therefrom is generally heated together with the molding tool (for example a molding-element cartridge or a shot) in a drying apparatus (for example a drying oven, a belt dryer, a pass-through dryer, a tunnel dryer or a drying belt) to the temperature described above, or also heated by leading heated gas, preferably heated air, through the molded molding-material mixture to the temperature described above, and preferably, particularly preferably simultaneously, water is removed from the molded molding-material mixture and/or the unhardened downstream product resulting therefrom. In this process variant, a drying oven, particularly preferably a convection drying oven, is preferably used as the drying device. The hardened molded part (if present or still present) can then generally be removed from the molding tool.

In a further variant of the method according to the invention, in order to carry out step V32) (and preferably additionally or simultaneously to carry out step V33)), in a drying apparatus (for example a drying oven, a belt dryer, a through-dryer, a tunnel dryer or a drying belt), the molded part with green strength which has been produced according to the method according to the invention is heated to the above-mentioned temperature either together with a molding tool (for example a molded part cartridge or a shot) or preferably without a molding tool, and water is preferably removed from the molded part with green strength, particularly preferably simultaneously. In this process variant, a drying oven, particularly preferably a convection drying oven, is also preferably used as the drying device.

The advantage of this last-mentioned method variant is in particular that the molded part with green strength does not have to be converted into a hardened molded part (in particular a crosslinked, hardened molded part) in the molding tool and in particular in the heatable molding tool, but can be removed from the molding tool (for example at room temperature) and can be converted separately into a hardened molded part (in particular a crosslinked molded part) in a suitable drying device (in particular by heating and removal of water as described above). In this way, unheated moulding tools, for example, cold box core shooters known per se, can be used for moulding material mixtures or the unhardened downstream products produced therefrom and/or for producing mouldings having green strength, so that, for example, for carrying out this process variant according to the invention, there is no need for costly and cost-intensive retrofitting of the preparation sites equipped for the cold box process. However, since the execution of the method variant is not limited to the execution in a non-heatable moulding tool, it can be executed at a preparation site equipped with different equipment, so that the other advantages of the method of the invention can be utilized very flexibly in industry.

In general, the precise process parameters of the process according to the invention, such as the duration of heating, the temperature of the drying oven or of the heated gas, the flow-through time of the heated gas (i.e. the duration over which the heated gas is conducted) and the pressure of the heated gas (if used), are set in step V32) and/or step V33) and are largely dependent on the properties of the molded part to be produced by hardening, such as its size, its weight, its volume or its wall thickness. The person skilled in the art is able to find suitable parameters in the preliminary tests in a manner known per se in the specific case, if necessary.

Furthermore, preference is given to a process according to the invention as described above, preferably a process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention), in which

The moulding material mixture comprises (at least) component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred), preferably aliphatic polyisocyanate(s),

and preferably additionally contains component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, as hardener component c),

and/or

-the hardening in step V3) comprises at least:

v32) treating the molded molding material mixture and/or the unhardened downstream product resulting therefrom and/or (in the presence of component c1) prior to carrying out step V31) the molded part having green strength,

and/or (preferably "and")

Removing water from the moulded moulding material mixture and/or from unhardened downstream products resulting therefrom and/or from moulded pieces having green strength,

and (apart from step V31) and/or V32), preferably apart from step V32), preferably V33) crosslinking the hydroxyl groups of the one or more aliphatic polymers of the formula i with the isocyanate groups of a polyisocyanate (as defined above or below or as preferred) in the molded molding material mixture and/or in the unhardened downstream product resulting therefrom and/or in the molded part having green strength, so that a crosslinked molded part is produced as hardened molded part.

In many cases, also preferred is the above-described preferred embodiment of the process according to the invention in which the molding material mixture comprises only hardener component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred), as hardener component c) (i.e. hardener component c) in this embodiment does not comprise component c1), i.e. one or more biopolymers selected from poly-D-glucosamine).

In this embodiment of the process according to the invention, in which the molding material mixture comprises only component c2) (but not component c1)) as hardener component c), the polyisocyanate of component c2) preferably comprises an aliphatic polyisocyanate, preferably a water-dispersible aliphatic polyisocyanate, in a proportion of > 75% by weight, particularly preferably > 90% by weight and very particularly preferably > 95% by weight, based on the total mass of the polyisocyanate or polyisocyanates of component c2) used (or present) in the molding material mixture, and particularly preferably (as described above and defined in more detail below) the aliphatic polyisocyanate to be used preferably according to the invention. In a particularly preferred variant of this embodiment of the process according to the invention, the polyisocyanates of component c2) comprise exclusively aliphatic polyisocyanates, preferably exclusively water-dispersible aliphatic polyisocyanates, particularly preferably exclusively aliphatic polyisocyanates which are described in detail below as being preferred, as component c 2). In this preferred embodiment of the process according to the invention, in which the molding material mixture contains only component c2 as hardener component c), no green-strength moldings are produced.

In a preferred embodiment of the method according to the invention, in which the molding material mixture contains only component c2) (but not component c1)) as hardener component c), step V32), and preferably additionally (and preferably simultaneously with step V32) step V33), is carried out analogously or correspondingly to what has been described above for the method embodiment in which the molding material mixture contains component c1) and additionally also component c2) as hardener component c). Here, step V32) is carried out with the aid of the molded molding material mixture (as obtained after step V2)) or the unhardened downstream product resulting therefrom (but without the use of a molded part having green strength), respectively.

With regard to a particularly preferred embodiment of the process according to the invention, wherein the molding material mixture comprises component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred), and additionally comprises component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, as hardener component c, see above.

Accordingly, it is preferred that the above-described method according to the invention (preferably the above-described or below-described method according to the invention) for producing a metal casting and/or ii) for producing a hardened molded part selected from a casting mould, a core and a riser for casting a metal casting comprises the following steps:

v1) producing a molding material mixture comprising the following components:

b) one or more aliphatic polymers, each comprising a structural unit of the formula I which contains a hydroxyl group,

–CH₂-CH(OH)- (Ⅰ)，

c) two components selected from the following as hardener components:

c1) one or more biopolymers selected from poly-D-glucosamine,

and

c2) one or more polyisocyanates (as hereinbefore or hereinafter defined or defined as preferred), preferably aliphatic polyisocyanates, particularly preferably water-dispersible aliphatic polyisocyanates, as crosslinking agents for the hydroxyl groups of the one or more aliphatic polymers;

and

d) water;

v2) molding the molding material mixture,

and then

V3) hardening the molded molding-material mixture or an unhardened downstream product resulting therefrom, wherein the hardening in step V3) comprises:

v31) precipitating at least a portion of the one or more biopolymers,

preferably by increasing the pH of the aqueous portion of the molded molding material mixture, particularly preferably by contact with an alkaline-reacting gaseous compound, preferably by gas fumigation of the gaseous compound, more particularly preferably by gas fumigation of a gaseous amine,

so that a molded part with green strength is produced;

and/or (preferably "and")

V32) by treating the moulded molding material mixture and/or the unhardened downstream product resulting therefrom and/or the moulded part having green strength, preferably after step V31 has been carried out beforehand)

Heating the molded molding material mixture and/or the unhardened downstream product resulting therefrom and/or heating the molded part having green strength (preferably heating the molded part having green strength), preferably to a temperature in the range from 100 ℃ to 300 ℃, particularly preferably in the range from 150 ℃ to 250 ℃ and very particularly preferably in the range from 180 ℃ to 230 ℃,

and/or (preferably "and")

Removing water from the molded molding material mixture and/or from the unhardened downstream products resulting therefrom and/or from the green-strength molded part (preferably from the green-strength molded part),

and (apart from step V31) and/or V32), preferably apart from step V32), preferably V33) crosslinking the hydroxyl groups of the aliphatic polymer(s) of the formula I with the isocyanate groups of the polyisocyanate(s) (used) in the molded molding material mixture and/or in the unhardened downstream products derived therefrom and/or in the molded part having green strength, preferably in the molded part having green strength,

so that a crosslinked molded part is produced as a hardened molded part.

In experiments per se, it has been found that (crosslinked) hardened moldings produced in accordance with the abovementioned particularly preferred variant of the process according to the invention (i.e. in accordance with the variant of the process according to the invention in which the molding material mixture comprises components c1) and c2) and in which step V32) comprises heating and removal of water and in which these two steps V32) and V33) are carried out) have a high initial strength, a particularly high final strength (after hardening or crosslinking), and also a particularly high casting resistance and a particularly high heat resistance even when iron or steel is cast. The advantageous smooth and clean surface structure of the (crosslinked) hardened molded part produced according to the above-described particularly preferred variant of the method according to the invention is also excellent. Furthermore, it has been found that (crosslinked) hardened molded parts produced according to the above-described particularly preferred variant of the method according to the invention have particularly good moisture and water resistance, so that they are very suitable for long-term storage for days or weeks even under severe climatic conditions (hot, humid climates). In the case of metal casting, such hardened (cross-linked) molded parts produced according to the above-described particularly preferred variant of the method according to the invention furthermore exhibit only a low absorption of thermal energy, which is reflected in a small degree of shrinkage cavity formation which occurs only in regions of the metal casting which are relatively far from the actual metal casting (for example in the riser shoulder). This characteristic makes this variant of the method according to the invention also particularly suitable for producing risers, in particular insulated risers. After the metal casting has been completed, the (crosslinked) hardened molded part produced according to this variant of the method according to the invention furthermore exhibits very advantageous removal properties, since it disintegrates to a very large extent by the heat released during the metal casting, thereby considerably simplifying the further processing of the correspondingly produced metal casting, since only a small or ideally no cleaning step has to be carried out at the produced metal casting.

A particular advantage of the molded parts produced according to the method according to the invention is their emission properties, in particular during metal casting and during the removal of metal castings produced with the aid of these molded parts produced according to the invention: thus, in the metal casting of light metals or alloys thereof (for example in the casting of aluminum), and also in the casting of iron or steel, or in the removal of correspondingly produced metal castings, the formation of fumes or fumes, the generation of unpleasant odours and/or the emission of substances which may be harmful to health, as is usually observed when using conventional organic casting binders, in particular containing aromatic compounds (such as in particular containing aromatic polyols and aromatic polyisocyanates), is substantially eliminated. This applies in particular to risers produced according to the method according to the invention. The insulated feeder produced according to the method according to the invention, in particular according to its preferred variant, has virtually no undesirable emissions even at the relatively low temperatures of light metal casting. The exothermic riser produced according to the method of the present invention has little undesirable emissions (e.g., smoke generation) even during or after burn-out. When primarily or exclusively aliphatic polyisocyanates are used as component c2) in the process according to the invention, preferably referred to herein as preferred aliphatic polyisocyanates, and/or when at most small amounts and preferably no further aromatic-containing components are used in the process according to the invention, particularly low smoke or fume formation is observed, particularly low occurrence of unpleasant odors and/or particularly low emission of potentially health-hazardous substances.

It is also preferred that the process according to the invention as described above, preferably the process (ii) according to the invention (preferably referred to above or below as the preferred process according to the invention),

aliphatic polymers used therein, each comprising structural units of the formula I which contain hydroxyl groups

Can be manufactured by at least partially saponifying polyvinyl acetate;

and/or

-selected from polyvinyl alcohol, polyvinyl acetate and mixtures thereof;

and/or

-75% by weight or more, preferably 90% by weight or more, particularly preferably 98% by weight or more, based on the total mass of the hydroxyl-containing organic polymer used in the molding material mixture as a whole, with the exception of the biopolymer or biopolymers selected from the group of poly-D-glucamines used as component c 1);

and/or

-comprises one or more polyvinyl alcohols,

the polyvinyl alcohol used is preferably used as a whole

Having a degree of hydrolysis of > 50 mol% (i.e. in the range of 50.1 mol% to 100 mol%), preferably determined according to the method as described in the documents DE 102007026166A 1 paragraphs [0029] to [0034],

and particularly preferably has a degree of hydrolysis in the range from 70 mol% to 100 mol%, more particularly preferably in the range from 80 mol% to 100 mol%, preferably determined according to the method in accordance with DIN EN ISO 15023-022017-02, draft appendix D

And/or

Having a dynamic viscosity in the range from 0.1 to 30 mPas, preferably in the range from 1.0 to 15 mPas, particularly preferably in the range from 2.0 to 10 mPas, determined at 20 ℃ in accordance with DIN53015:2001-02 at a 4% strength (weight/weight) aqueous solution of the polyvinyl alcohol used overall;

and/or

-75% by weight or more, preferably 90% by weight or more, particularly preferably 98% by weight or more, based on the total mass of the aliphatic polymers used in the molding material mixture as a whole, each comprising structural units of the formula I containing hydroxyl groups.

In a preferred embodiment of the process according to the invention, the aliphatic polymers to be used, which each comprise structural units of the formula I which contain hydroxyl groups, are present completely (i.e. up to 100% by weight) as polyvinyl alcohol(s).

The molding material mixture produced in step V1) of the process according to the invention comprises as hydroxyl-containing organic polymer component b), i.e.one or more aliphatic polymers each comprising a structural unit of the formula I which contains a hydroxyl group, and, if present or used, c1), i.e.one or more biopolymers selected from the group of poly-D-glucamines. In the process according to the invention, in the moulding material mixture produced in step (a), the components b) and, if present or used, c1) make up 95% by weight or more, particularly preferably 98% by weight or more, of the total mass of the hydroxyl-containing organic compounds used in the moulding material mixture as a whole. In a particularly preferred variant according to the invention, in the moulding material mixture produced in step V1), the components b) and, if present or used, c1) make up 100% by weight of the total mass of the hydroxyl-containing organic compound to be used in the moulding material mixture as a whole.

It is preferred according to the invention that for the production or in the production of the molding material mixture the one or more aliphatic polymers (component b)) each comprising a structural unit of the formula I which contains a hydroxyl group are used at least partially and preferably completely in step V1) as an aqueous mixture comprising one or more aliphatic polymers each comprising a structural unit of the formula I which contains a hydroxyl group. Preferably, the aqueous mixture comprises one or more aliphatic polymers in a total amount (concentration) in the range of from 10 to 40 wt. -%, particularly preferably in the range of from 15 to 35 wt. -%, more particularly preferably in the range of from 20 to 30 wt. -%, based on the total mass of the aqueous mixture comprising the one or more aliphatic polymers.

Preferably, the aliphatic polymer or polymers used, respectively comprising structural units of the formula I which contain hydroxyl groups, preferably polyvinyl alcohol or polyvinyl alcohols, are dissolved in the aqueous mixture at > 90% by weight, preferably > 95% by weight, based on the total mass of the aliphatic polymer or polymers used.

It has been found that the abovementioned aliphatic polymer or polymers, in particular the abovementioned preferred polyvinyl alcohol or polyvinyl alcohols, make a substantial contribution to the advantageous properties of the hardened moldings produced according to the invention. In particular, the above-mentioned one or more aliphatic polymers contribute to the good moisture or water resistance, the final strength and the casting resistance of the hardened molded parts produced according to the invention.

The aforementioned aliphatic polymer(s), in particular the aforementioned preferred polyvinyl alcohol(s), obviously also contributes substantially to this, or even is responsible for the advantageous low-emission properties of the hardened molded parts produced according to the method according to the invention or preferred variants thereof, in particular for the low or very low emission of fumes or fumes and/or odorous substances and/or harmful substances during or after metal casting, and for the low or very low emission of odorous substances and/or harmful substances during the production or storage of the hardened molded parts. This may be because: the aliphatic polymers to be used according to the invention contain virtually no or no aromatic constituents mentioned which are often responsible for harmful emissions.

The aliphatic polymer or polymers to be used according to the invention are therefore preferably free of aromatic-containing constituents and/or other constituents which, under the conditions of the process according to the invention, cause significant emissions of fumes, odours and/or harmful substances.

For the reasons mentioned above, it is preferred that the process according to the invention is not carried out in the presence of an organic compound containing an aromatic compound, or that the moulding material mixture produced in the process according to the invention is free of aromatics (i.e. the moulding material mixture produced in the process according to the invention preferably does not contain any organic compound containing an aromatic compound, and the ingredients used for its production also preferably do not contain any organic compound containing an aromatic compound).

Preferably, the molding material mixture produced in step V1) also does not comprise any compound selected from the group consisting of: an organotin compound, an organoaluminum compound, dimethylcyclohexylamine, an N-substituted pyrrolidone, an N-substituted imidazole, a triazine derivative, diazabicyclooctane or a quaternary ammonium salt (as described in WO 2017/071695A 1) as a catalyst for crosslinking the one or more aliphatic polymers (component b)) each comprising a structural unit of formula I containing a hydroxyl group with one or more polyisocyanates as a crosslinking agent for the hydroxyl groups of the one or more aliphatic polymers.

Furthermore, preference is also given to a process according to the invention as described above, preferably a process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention), in which

-the biopolymer or one or more of the biopolymers selected from poly-D-glucosamine comprises chitosan,

wherein the chitosan is preferably

With the aid of¹A degree of deacetylation of > 70 mol%, preferably > 75 mol%, and particularly preferably > 80 mol%, determined by H NMR spectroscopy,

and/or

Having a dynamic viscosity of > 500 mPas, preferably > 600 mPas, particularly preferably > 700 mPas, determined at 20 ℃ in accordance with DIN53015:2001-02 at 1% strength by weight of a 1% strength by weight solution of acetic acid,

and/or

The total mass of the aliphatic polymers used, each comprising structural units of the formula I containing hydroxyl groups

Total mass of biopolymer selected from poly-D-glucosamine used

Sum of

And

total mass of molding material used

Ratio of (A to B)

In the range from 0.2:100 to 13:100, preferably in the range from 0.3:100 to 10:100, particularly preferably in the range from 0.5:100 to 9: 100.

In the above-described embodiment of the process according to the invention, the degree of deacetylation of the chitosan to be used is preferably in the range from 65 to 95 mol%, particularly preferably in the range from 70 to 95 mol%, very particularly preferably in the range from 75 to 95 mol% and very particularly preferably in the range from 80 to 95 mol%.

In the above-described embodiment of the process according to the invention, the dynamic viscosity of the chitosan to be used is preferably in the range from 500 to 1100 mPas, particularly preferably in the range from 600 to 800 mPas, very particularly preferably in the range from 700 to 800 mPas, and very particularly preferably in the range from 720 to 770 mPas, determined at 20 ℃ according to DIN53015:2001-02 at a 1% strength by weight solution of acetic acid in 1% strength by weight chitosan (weight/weight) (with the aid of the reference numerals from DIN53015:2001-02

Falling ball viscometer determination).

It has been found that the above-mentioned preferred biopolymers selected from poly-D-glucamines, in particular the above-mentioned preferred chitosans, are particularly suitable for the production of moulding material mixtures according to the process of the invention in combination with further components to be used according to the invention, which moulding material mixtures can be converted firstly in step V31) into mouldings having green strength and subsequently, by further treatment in step V32) and preferably additionally in step V33), into hardened mouldings (or crosslinked hardened mouldings) having the advantageous properties described above. Furthermore, the use of biopolymers selected from poly-D-glucosamine opens up the possibility of producing hardened moldings for the foundry industry at least partially from renewable raw materials.

It is also preferred according to the invention that the biopolymer(s) (component c1)) selected from poly-D-glucosamine, if present or used, is/are used at least partially and preferably completely as an aqueous preparation comprising the biopolymer(s) selected from poly-D-glucosamine in step V1) for the production of a molding material mixture. Preferably, the aqueous preparation to be used in the method according to the invention comprises the one or more biopolymers selected from poly-D-glucosamine in a total amount (concentration) in the range of from 0.5 to 10 wt. -%, particularly preferably in the range of from 1 to 7.5 wt. -% and more particularly preferably in the range of from 1.5 to 5 wt. -%, based on the total mass of the aqueous preparation comprising the one or more biopolymers. The aqueous formulation can additionally comprise one or more suitable acids in an amount suitable to partially or completely dissolve the one or more biopolymers. Preferably, the aqueous formulation preferably comprises at most 5 wt.%, particularly preferably at most 2.5 wt.%, based on the total mass of the aqueous formulation, of one or more acids selected from acids having a pKa value in the range of from 3 to 7, preferably in the range of from 3.5 to 6.5, and preferably not comprising any aromatic organic compounds or residues. Particularly preferably, the one or more acids are one or more organic acids, preferably one or more mono-molecular organic acids. More particularly preferably, one or at least one of the acids is acetic acid.

Preferably, the biopolymer selected from the group consisting of poly-D-glucosamine, preferably chitosan, used is dissolved in the aqueous preparation at > 90 wt.%, preferably > 95 wt.%, based on the total mass of the biopolymer selected from the group consisting of poly-D-glucosamine used.

It is furthermore preferred that the process according to the invention, preferably the process (ii) according to the invention, as described above (preferably the process according to the invention referred to above or below as preferred), wherein component c2) of the moulding material mixture, if used or present, comprises one or more aliphatic polyisocyanates, preferably one or more water-dispersible aliphatic polyisocyanates.

Also preferred is a process according to the invention as described above, preferably a process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention), wherein the polyisocyanate(s) (if used or present) used as component c2) in step V1) comprises (one or more) aliphatic polyisocyanates (preferably in respect of the aliphatic polyisocyanates to be preferably used in the process according to the invention above and below), preferably (one or more) water-dispersible aliphatic polyisocyanates,

wherein preferably

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates are non-ionically or ionically hydrophilicized,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises a polyether group or a sulphonate group,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises polyether groups and furthermore urethane and/or allophanate groups,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises one or more 2,4, 6-trioxotriazinyl groups and preferably polyether groups or sulfonate groups, preferably polyether groups,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises one or more 2,4, 6-trioxotriazinyl groups and polyether groups and furthermore comprises urethane and/or allophanate groups, preferably urethane groups,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprise a self-emulsifiable and/or self-water-emulsifiable aliphatic polyisocyanate,

and/or

The aliphatic polyisocyanate(s) used make up ≥ 50% by weight, preferably ≥ 75% by weight, particularly preferably ≥ 90% by weight and very particularly preferably ≥ 98% by weight of the polyisocyanate(s) used overall in the moulding material mixture.

For the purposes of the present invention, the aliphatic polyisocyanates to be used in the process according to the invention which are described or defined in detail hereinabove as being preferred are also water-dispersible aliphatic polyisocyanates.

In a preferred embodiment of the above-described preferred variant of the process according to the invention, the aliphatic polyisocyanate(s) used (preferably the aliphatic polyisocyanates to be used preferably in the process according to the invention as described above or below) make up 100% by weight of the total mass of the polyisocyanate(s) used in the molding material mixture as a whole.

The abovementioned polyisocyanate or polyisocyanates to be used according to the invention, preferably as aliphatic polyisocyanate or polyisocyanates to be preferably used according to the invention, are preferably the following polyisocyanates: it has at least two free isocyanate groups, so that it is suitable for crosslinking with free hydroxyl groups of aliphatic polymers which in each case comprise structural units of the formula I which contain hydroxyl groups.

The above-mentioned aliphatic polyisocyanate or polyisocyanates to be used according to the invention or to be preferably used according to the invention preferably comprise aliphatic and/or cycloaliphatic polyisocyanates. For the reasons stated above (avoidance of emissions of fumes, odorous substances and/or harmful substances, better water compatibility or water dispersibility by the moldings produced according to the process of the invention), the aliphatic polyisocyanates to be used according to the invention or preferably to be used according to the invention preferably do not contain any aromatic groups (i.e. do not contain aromatics).

Preferably, the aliphatic polyisocyanate or polyisocyanates which have been described or defined in detail above and which are preferably to be used according to the invention are self-emulsifying or self-water-emulsifiable aliphatic polyisocyanates, for example as described in the following book written by Ulrich Meier-Westhues: "Polyurethane-Lacke, Kleb-und Dichtstoffe", Hanover: Vincentz Network 2007(ISBN: 3-86630-.

The one or more aliphatic polyisocyanates described or defined in detail above and preferably to be used according to the present invention preferably comprise aliphatic polyisocyanates selected from the group consisting of:

non-ionically hydrophilicized aliphatic polyisocyanates of the polyether urethane type, for example

3100、

VP LS 2306、

DA-L and

DN，

nonionically hydrophilicized aliphatic polyisocyanates of the polyether allophanate type, for example

304 and

305，

and

ionically hydrophilicized aliphatic polyisocyanates of the sulfonate type, for example

XP 2487/1、

XP 2547、

XP 2570 and

XP 2655。

particularly preferred aliphatic polyisocyanate(s) to be used in the process according to the invention are selected from the group of non-ionically hydrophilicized aliphatic polyisocyanates of the polyether urethane type, for example

3100、

VP LS 2306、

DA-L and

DN. More particularly preferred aliphatic polyisocyanates to be used in the process according to the invention are

DA-L(CAS RN 125252-47-3)。

It has been found that the preferred self-emulsifiable or self-water-emulsifiable aliphatic polyisocyanates described above are very suitable as crosslinkers for the one or more aliphatic polymers which each comprise structural units of the formula I which contain hydroxyl groups, i.e.also in aqueous mixtures or aqueous binder systems, under the conditions of the process according to the invention.

In the context of the following variant of the process according to the invention in which the molding material mixture produced in step V1) comprises (at least) component c2), i.e.one or more polyisocyanates (comprising only, or comprising, preferably also, in addition to component c1) as crosslinkers for the hydroxyl groups of one or more aliphatic polymers, as hardener component c), it is preferred that the abovementioned process according to the invention, preferably the process (ii) according to the invention (preferably the abovementioned or the following is referred to as preferred process according to the invention), in which one or more aliphatic polymers (component b)) comprising structural units of the formula I which contain hydroxyl groups and one or more polyisocyanates (component c2)) as crosslinkers for the hydroxyl groups of the one or more aliphatic polymers are provided as or used as aqueous mixture as first binder system, which comprises the following steps:

–CH₂-CH(OH)- (Ⅰ)，

And

c2) one or more polyisocyanates (as hereinbefore or hereinafter defined or as preferred) as a cross-linking agent for the hydroxyl groups of the aliphatic polymer(s).

The aqueous mixture as the first binder system (hereinafter also referred to as "first binder system") to be used in step V31) for producing the molding material mixture in the process according to the invention comprises, as a total mass, in the above-described range from 5 to 40% by weight, particularly preferably in the range from 7.5 to 35% by weight and very particularly preferably in the range from 10 to 30% by weight, of one or more aliphatic polymers comprising hydroxyl-containing structural units of the formula i.

The first binder system comprises one or more polyisocyanates (defined above or below or defined as preferred), preferably one or more aliphatic polyisocyanates, in a total amount in the range from 1 to 20% by weight, particularly preferably in the range from 2.5 to 15% by weight and more particularly preferably in the range from 3 to 10% by weight, based on the total mass of the first binder system to be used in the process according to the invention as described above.

In a preferred variant of the above-described method according to the invention, the weight fractions of components b), c2) (in each case as defined above) and d) in the aqueous mixture as the first binder system add up to 100% by weight, i.e. the total mass of the aqueous mixture as the first binder system.

Preferably, the aliphatic polymers which in each case comprise structural units of the formula I which contain hydroxyl groups are dissolved in an aqueous mixture as first binder system in an amount of > 90% by weight, particularly preferably > 95% by weight, based on the total mass of the aliphatic polymers used.

In the above-described or below-described variant of the process according to the invention in which the moulding material mixture produced in step V1) comprises (at least) component c2), i.e. one or more polyisocyanates (as defined above or below or as defined as preferred) (comprising only, or comprising, preferably also, in addition to component c1) as crosslinkers for the hydroxyl groups of the aliphatic polymer or polymers, as hardener component c), it is preferred that components b) and c2) of the moulding material mixture are brought into contact with one another immediately before, preferably not earlier than one hour before, the production of the moulding material mixture. In this way, an undesirable premature onset of the crosslinking reaction of the polyisocyanate(s) with the hydroxyl groups of the aliphatic polymer(s) is prevented (for example, when no molding raw material is yet present).

Experiments per se have also shown that moulding material mixtures which are particularly suitable for processing and moulding are obtained, for example, in a shooting machine or moulding box (e.g.a core box), if the components b), i.e.the aliphatic polymer(s), and c2), i.e.the polyisocyanate(s) (as defined above or below or as defined as preferred), of the moulding material mixture are used in the above-mentioned amounts or amount ratios in step V1.

Furthermore, experiments themselves have shown that, according to a preferred variant of the process of the invention, in which one or more aliphatic polymers (component b)) and one or more polyisocyanates (component c)) are used as the first binder system in the form of an aqueous mixture, components b) and c2) are caused to be mixed with one another particularly homogeneously, so that, for example, in the presence of molding raw materials (step V33), the hydroxyl groups of the one or more aliphatic polymers and the isocyanate groups of the polyisocyanate crosslinker are crosslinked particularly completely and so that the molded molding material mixture (or the unhardened downstream products resulting therefrom) is converted particularly completely and homogeneously into a hardened molded part or into a crosslinked, hardened molded part.

In the context of a preferred variant of the process according to the invention, in which the molding material mixture produced in step V1) comprises as hardener component c) component c1), i.e. one or more biopolymers selected from poly-D-glucamines, and also comprises component c2), i.e. one or more polyisocyanates as crosslinkers for the hydroxyl groups of one or more aliphatic polymers, it is preferred that the process according to the invention as described above, preferably the process (ii) according to the invention (preferably the above or below is referred to as the preferred process according to the invention), wherein components b), c1) and c2) are provided as or used as aqueous mixtures as second binder systems, comprising:

–CH₂-CH(OH)- (Ⅰ)，

c1) One or more biopolymers selected from poly-D-glucosamine

And

c2) one or more polyisocyanates (as hereinbefore or hereinafter defined or as defined as preferred), preferably one or more aliphatic polyisocyanates, as a crosslinker for the hydroxyl groups of the one or more aliphatic polymers.

The aqueous mixture to be used in the process according to the invention as the second binder system (hereinafter also referred to as "second binder system") preferably comprises one or more polyisocyanates (as defined above or hereinafter or as defined as preferred) in a total amount in the range from 5% to 30% by weight, particularly preferably in the range from 7.5% to 25% by weight and very particularly preferably in the range from 10% to 20% by weight, preferably the one or more aliphatic polymers each comprising a structural unit of the formula i containing hydroxyl groups, based on the total mass of the aqueous mixture.

Preferably, the aqueous mixture comprises one or more biopolymers selected from poly-D-glucosamine in a total amount in the range of from 0.25 to 5 wt. -%, particularly preferably in the range of from 0.4 to 3.5 wt. -% and more particularly preferably in the range of from 0.5 to 2.5 wt. -%, based on the total mass of the aqueous mixture to be used as the second binder system described above in the method according to the present invention.

Preferably, the second binder system comprises one or more polyisocyanates (as defined above or below or as preferred), preferably one or more aliphatic polyisocyanates, in a total amount in the range of from 1 to 15% by weight, particularly preferably in the range of from 2 to 10% by weight and more particularly preferably in the range of from 2.5 to 7.5% by weight, based on the total mass of the second binder system to be used in the process according to the invention described above.

In a preferred variant of the above-described method according to the invention, the weight fractions of components b), c1), c2) (in each case as defined above) and d) in the aqueous mixture as the second binder system add up to 100% by weight, i.e. the total mass of the aqueous mixture as the second binder system.

Preferably, the aliphatic polymers which in each case comprise structural units of the formula I which contain hydroxyl groups are dissolved in an aqueous mixture as second binder system in an amount of > 90% by weight, particularly preferably > 95% by weight, based on the total weight of the aliphatic polymer used.

It has been found that according to a preferred variant of the process according to the invention, wherein one or more aliphatic polymers (component b)), one or more biopolymers selected from poly-D-glucosamine (component c1)) and one or more polyisocyanates (component c2)) are used in the form of a second binder system, the components thereof are brought into particularly homogeneous mixing with one another, so that, in particular in the presence of a molding raw material, the hydroxyl groups of the one or more aliphatic polymers and the isocyanate groups of the crosslinking agent are crosslinked, in particular completely, so that the molded molding material mixture is converted, in particular completely and homogeneously, into a hardened molded part or into a crosslinked, hardened molded part.

Preference is given to a process according to the invention as described above, preferably a process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention), in which

(iii) (in step V1) the total mass of the aqueous mixture or mixtures used for the manufacture of the moulding material mixture, said aqueous mixture preferably being selected from: an aqueous mixture comprising one or more aliphatic polymers each having a structural unit of formula I containing a hydroxyl group; an aqueous formulation comprising one or more biopolymers selected from poly-D-glucosamine; an aqueous mixture as a first binder system and an aqueous mixture as a second binder system;

and

total mass of molding material used (step V1)

Ratio of (A to B)

In the range from 1:100 to 50:100, preferably in the range from 1.5:100 to 40:100, particularly preferably in the range from 2:100 to 35: 100.

In this case, the (numerical) ratio of the sum of the total mass of the aqueous mixture or mixtures used to the total mass of the molding raw materials used is preferably set such that a molding material mixture is produced which can be injected into or can be pressed into a molded part selected from the group consisting of casting molds, cores and risers. In this connection, it has been found that the appropriate ratio in the particular case (with correspondingly constant concentration of the aqueous mixture used) is in particular dependent on the type of moulding raw material used: thus, in the case of using a molding raw material (preferably quartz sand) having a lower bulk density, the above-mentioned suitable numerical ratio is generally in a higher range (i.e., close to the upper limit of 50:100 or 40: 100), whereas in the case of using a molding raw material (preferably quartz sand) having a higher bulk density, the above-mentioned suitable numerical ratio is inversely in a higher range (i.e., close to the lower limit of 1:100 or 1.5: 100).

Preference is given to a process according to the invention as described above, preferably a process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention) (preferably a process according to the invention in which the moulding material mixture comprises the component c1), i.e.the biopolymer or biopolymers selected from poly-D-glucosamine, and additionally the component c2), i.e.the polyisocyanate or polyisocyanates, as hardener component c)), wherein

And

the total mass of biopolymer chosen from poly-D-glucosamine (if present or used) used

Sum of

And

the total mass of the preferred aliphatic polyisocyanates (if present or used) used as crosslinking agents

Ratio of (A to B)

In the range from 1:1 to 10:1, preferably in the range from 1.5:1 to 7.5:1, particularly preferably in the range from 2:1 to 5: 1.

It has been found that when the process according to the invention is carried out in the amounts and ratios described above with the aid of the above-mentioned biopolymers selected from poly-D-glucosamine (component c1)), aliphatic polymers (component b)) each comprising structural units of the formula I containing hydroxyl groups, and preferably aliphatic polyisocyanates (component c2)) used as crosslinking agents, a molded part having green strength is produced which is very suitable for further processing according to the process according to the invention in a step of crosslinking the hydroxyl groups of one or more aliphatic polymers with the isocyanate groups of the crosslinking agents (step V33)), so that the molded part having green strength can be converted particularly well (in step V32) into a hardened molded part or (by step V32) and additionally by step V33)) into a crosslinked, hardened molded part.

Preferably, the process according to the invention as described above, preferably the process (ii) according to the invention (preferably referred to above or below as preferred process according to the invention),

wherein the (at least one) moulding raw material comprises

-a refractory solid in particulate form, preferably selected from one or more of the following:

oxides, silicates and carbides, respectively containing one or more elements selected from the group consisting of Si, Al, Zr, Ti, Mg, Fe and Ca,

mixed oxides, mixed carbides and mixed nitrides, each containing one or more elements selected from the group consisting of Si, Al, Zr, Ti, Mg, Fe and Ca,

and

-graphite

And/or

-a light filler in particulate form, preferably selected from one or more of the following:

core-shell particles, preferably having a glass core and a refractory shell, particularly preferably having a bulk density in the range of 470g/l to 500g/l, preferably as described in document WO 2008/113765a 1;

-refractory composite particles, preferably as described in document WO 2017/093371a1 or manufactured according thereto;

spheres, preferably spheres composed of fly ash, such as the sphere "Fillite 106" from Omya GmbH;

-perlite, preferably expanded perlite, such as, in particular, expanded perlite from RS Rohstoff-Sourcing GmbH, named "Eurocell 140", "Eurocell 145", "Eurocell 150" or "Eurocell 300";

-closed cell microspheres consisting of expanded perlite, preferably closed cell microspheres consisting of expanded perlite as described in document WO 2017/174826a 1;

-rice hull ash, preferably as described in document WO 2013/014118a 2;

-an expanded glass;

-hollow glass spheres

And

hollow ceramic balls, preferably hollow corundum balls.

The aforementioned one or more granular refractory solids can be used alone or in combination with one another to form the moulding raw material to be used in the process according to the invention. Likewise, one or more of the above-mentioned particulate light fillers can be used alone or in combination with one another to form a molding material to be used. It is of course also possible to use one or more granulated refractory solids in combination with one or more granulated light fillers as moulding material, thus forming the moulding material to be used. Depending on the intended use of the method according to the invention, i.e. depending on the hardened molded part to be produced, the person skilled in the art will select suitable molding raw materials, respectively. For example, in order to manufacture a simple casting mold, only quartz sand can be selected as a molding raw material. Furthermore, for example, for the production of the riser, it is possible to select a mixture of quartz sand and one or more particulate lightweight fillers, or for this purpose, it is also possible to select only one or more particulate lightweight fillers, preferably from the abovementioned preferred lightweight fillers.

In addition to the preferred inclusions described above, the moulding raw material to be used in the process according to the invention can also comprise constituents, preferably granules, which are preferably selected from elemental metals (e.g. aluminium), oxidizers and ignition agents. Thus, for example, in order to produce an exothermic riser, the moulding raw material to be used can contain, in addition to the above-mentioned constituents (selected from refractory solids and light fillers), aluminium, iron oxide, an oxidizing agent known per se for this purpose and an igniting agent known per se for this purpose.

It is also preferred that the method according to the invention as described above, preferably the method (ii) according to the invention (preferably the above or below referred to as preferred method according to the invention), is used for the production of metal castings by means of the following additional steps (preferably after the execution of step V32) and/or step V33), particularly preferably after the execution of the two steps V32) and V33): v4) contacting the hardened molded part, preferably as obtained after step V32) and preferably additionally after step V33), with a cast metal to produce a metal casting, wherein the cast metal is preferably hardened in contact with the hardened molded part,

wherein preferably

The casting metal is selected from the group consisting of aluminium, magnesium, tin, zinc and alloys thereof

And/or

The temperature of the cast metal during casting is not higher than 900 ℃;

so that a metal casting is produced.

In the above-described preferred method according to the invention for producing metal castings, the cast metal is at least partially and preferably completely liquid when it contacts the hardened molded part or the crosslinked hardened molded part. Any castable metal or any castable metal alloy, particularly light metals and alloys thereof, such as aluminium, magnesium, tin and zinc; and also iron and steel, are suitable as casting metals.

In experiments carried out in themselves, it has been found that, irrespective of the nature of the cast metal, at most small amounts and virtually no soot or smoke are formed or, ideally, no potentially harmful gaseous emissions to human health, for example as a result of decomposition of the crosslinking binder of the crosslinked hardened molded part under the action of the heated liquid cast metal, are produced when the hardened molded part produced according to the invention, in particular the crosslinked hardened molded part produced according to the invention, comes into contact with the cast metal. This applies even at relatively low temperatures in the range from 600 ℃ to 900 ℃, so that the above-described preferred method variant (i) is more particularly suitable for producing metal castings, wherein the cast metal is a light metal or a light metal alloy: that is, it is known that, at the relatively low temperatures prevailing in the casting of light metals (compared to the temperatures in the casting of iron or steel), the conventional cold box binders currently generally used are often only incompletely thermally decomposed, so that particularly intense smoke, fumes and soot formation occurs precisely in these cases-both at the time of casting the metal and also at the time of removal of the mold-and also a large release of gaseous aromatic-containing emissions which are often accompanied by unpleasant odors and potentially harmful to human health.

However, when using hardened molded parts produced by the method according to the invention or when carrying out the above-described preferred method variant (i) according to the invention, in particular the preferred method variant (i) described here, such disadvantages occur to a much lesser extent or, ideally, do not occur at all. The above-described preferred variant (i) of the method according to the invention is particularly effective when the method according to the invention is used to produce (variant (ii)) or to use (variant (i)) a riser or riser cap as a hardened molded part, in particular when it is crosslinked (in step V33)) according to the method according to the invention, since the position of the riser or riser cap at the contact surface of the casting mold with the ambient air during the metal casting poses particularly severe emission hazards from the riser or riser cap.

The invention also relates to a hardened molded part selected from the group consisting of a casting mold, a core and a riser for casting metal castings. Preferably by the above-described process (ii) according to the invention (preferably by the above-described or below-described process according to the invention, which is referred to as preferred), the hardened moldings comprise the following components:

–CH₂-CH(OH)- (Ⅰ)，

And

c) as hardener component, one or two components selected from:

c1) one or more, preferably precipitated, biopolymers selected from poly-D-glucosamine, preferably comprising chitosan,

and

c2) one or more preferably aliphatic, particularly preferably water-dispersible, aliphatic polyisocyanates, wherein preferably the hydroxyl groups of the aliphatic polymers (component b)) used, which in each case comprise structural units of the formula I containing hydroxyl groups, are present as hardened, preferably crosslinked, binders at least in part as a result of crosslinking with the isocyanate groups of the polyisocyanate or polyisocyanates used.

The explanations given above for the method according to the invention apply analogously with regard to the preferred embodiments of the molded parts hardened according to the invention and possible combinations of one or more aspects in relation to one another, and vice versa.

It is preferred that a green-strength moulded part comprising component c1), i.e. one or more precipitated biopolymers selected from poly-D-glucosamine, preferably comprising chitosan, as hardener component c), is used as the above-described moulded part hardened according to the invention.

If the green-strength moulded part according to the invention additionally comprises component c2), i.e. one or more preferably aliphatic, particularly preferably water-dispersible, aliphatic polyisocyanates, the polyisocyanate(s) and the aliphatic polymer(s) each comprising a hydroxyl-containing structural unit of the formula I preferably do not crosslink (with one another) in the green-strength moulded part.

It is also preferred that (crosslinked) hardened moldings which comprise the component c2), i.e. one or more preferably aliphatic, particularly preferably water-dispersible, aliphatic polyisocyanates, as hardener component c), the (crosslinked) hardened moldings which contain the hydroxyl groups of the aliphatic polymers (component b)) used, each comprising structural units of the formula i containing hydroxyl groups, are present as crosslinked, hardened binders at least in part as a result of crosslinking with the isocyanate groups of the polyisocyanate(s) (component c2)) used, as the aforementioned hardened moldings according to the invention.

If the moldings cured (or crosslinked, cured) according to the invention comprise binders which are crosslinked as a result of the crosslinking of the hydroxyl groups of the aliphatic polymers used (component b)) which in each case comprise structural units of the formula I containing hydroxyl groups with the isocyanate groups of the polyisocyanate(s) (component c2)) used, it is assumed for the purposes of the invention that, in the moldings according to the invention, the hydroxyl groups of the aliphatic polymers which have been crosslinked or are being crosslinked, after crosslinking by the isocyanate groups of the polyisocyanate(s) used, are no longer present (at least predominantly) in free form, but rather participate (at least predominantly) in the formation of urethane groups by means of the isocyanate groups.

The invention also relates to a hardened molded part selected from a casting mold, a core and a riser, produced or producible by the method according to the invention described above, preferably according to method (ii) according to the invention (or the preferred method according to the invention described herein).

The explanations given above for the method according to the invention and for the hardened molded part according to the invention apply analogously to the preferred embodiments of the hardened molded part produced or producible according to the invention and possible combinations of one or more aspects in relation to one another, and vice versa.

The aforementioned (cross-linked) hardened molded parts according to the invention (or corresponding, preferably cross-linked, hardened molded parts according to the invention described herein, or cross-linked, hardened molded parts which can be produced according to the above-described method according to the invention) are preferred, wherein

The total mass of hardened binder present in the moulded part

And

the ratio of the total mass of molding raw materials present in the molded part is in the range from 0.1:100 to 10:100, preferably in the range from 0.5:100 to 7:100, and particularly preferably in the range from 0.6:100 to 6: 100.

The invention also relates to a molding material mixture, preferably for producing hardened moldings (if component c1 is present) selected from the group consisting of casting molds, cores and risers for the casting of metal castings, including moldings with green strength, and/or crosslinked, hardened moldings, if component c2 is present), comprising the following components:

–CH₂-CH(OH)- (Ⅰ)，

c) As hardener component, one or two components selected from:

c1) one or more biopolymers selected from poly-D-glucosamine, preferably chitosan,

and

d) and (3) water.

In a particularly preferred variant of the above-described moulding material mixture according to the invention, the moulding material mixture comprises as hardener component c) the component c1), i.e. one or more biopolymers selected from the group of poly-D-glucamines, preferably chitosan, and additionally the component c2), i.e. one or more, preferably aliphatic, polyisocyanates as cross-linkers for the hydroxyl groups of the aliphatic polymer or polymers.

In a preferred variant of the above-described moulding material mixture according to the invention, the moulding material mixture comprises only component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, preferably chitosan, and no component c2), i.e. one or more, preferably water-dispersible and/or aliphatic polyisocyanates as cross-linkers for the hydroxyl groups of one or more aliphatic polymers, as hardener component c).

In a further preferred variant of the abovementioned moulding material mixture according to the invention, the moulding material mixture comprises only component c2), i.e. one or more aliphatic polyisocyanates (preferably one or more aliphatic polyisocyanates to be used herein preferably according to the invention) as crosslinkers for the hydroxyl groups of the aliphatic polymer(s); without the inclusion of component c1), i.e. one or more biopolymers selected from poly-D-glucosamine, preferably chitosan, as hardener component c).

The explanations given above for the method according to the invention, the hardened molded part according to the invention and the molded part produced or producible or hardened according to the invention apply analogously to the preferred embodiments of the molding material mixture according to the invention and possible combinations of one or more aspects in relation to one another, and vice versa.

The abovementioned moulding material mixtures according to the invention (or the abovementioned moulding material mixtures referred to herein as preferred according to the invention) are suitable for the abovementioned process according to the invention and are proposed for this purpose.

The invention also relates to the use of an aliphatic polymer cross-linked by one or more aliphatic polyisocyanates, preferably polyvinyl alcohol cross-linked in this way, comprising structural units of formula I containing hydroxyl groups, as a binder for hardened mouldings selected from the group consisting of casting moulds, cores and risers for the casting of metal castings

–CH₂-CH(OH)- (Ⅰ)。

The explanations given above for the method according to the invention, the hardened molded part produced or producible according to the invention, and for the molding material mixture according to the invention apply analogously with regard to preferred embodiments of the use according to the invention and possible combinations of one or more aspects in relation to one another, and vice versa.

The invention also relates to the use of a biopolymer selected from the group consisting of poly-D-glucosamine, preferably chitosan, as a binder or binder component for the production of hardened moulded parts, preferably moulded parts with green strength, selected from the group consisting of casting moulds, cores and risers in the foundry industry.

With regard to preferred embodiments of the use of the biopolymers according to the invention and possible combinations of one or more aspects in relation to one another, the explanations given above for the method according to the invention, the hardened moldings produced or producible according to the invention, the molding material mixtures according to the invention and the use of the aliphatic polymers crosslinked by one or more aliphatic polyisocyanates according to the invention apply analogously and vice versa.

Detailed Description

Example (c):

the examples given below are intended to illustrate and explain the invention in detail without limiting its scope.

Unless otherwise stated, experiments were performed under laboratory conditions (atmospheric pressure, temperature 20 ℃, atmospheric humidity 50%), respectively.

Example 1: preparation of moulding material mixtures

The ingredients indicated in table 1 below and described in more detail below in table 1 were used to make the molding material mixture.

The molding material mixtures "F-cold box" and "F-water glass" are control molding material mixtures not according to the invention or to be used according to the invention. The molding-material mixtures "F-V6" and "F-E6 +" are molding-material mixtures according to the invention or to be used according to the invention.

Table 1:composition of moulding material mixture

As a molding material, quartz sand BO 42(CAS No.014808-60-7) from Bodensteiner Sandwerk GmbH & Co. KG was used.

As aqueous PVAL mixture, a 25% strength by weight polyvinyl alcohol solution (> 93% polyvinyl alcohol) with a degree of hydrolysis of about 88 mol% and a dynamic viscosity in the range from 3.5mPa · s to 4.5mPa · s (measured at 20 ℃ according to DIN53015 as a 4% strength by weight aqueous solution), a methanol content: 3% by weight; CAS RN 25213-24-5(Kuraray Europe GmbH)).

As aliphatic polyisocyanates, use is made of nonionically hydrophilicized polyisocyanates of the polyether urethane type (CAS RN125252-47-3) "

DA-L”(Covestro AG)。

As an aqueous preparation of Chitosan, a 2.5% strength by weight solution (based on the total mass of the solution) of Chitosan 85/1000 (manufacturer's instructions: Heppe Medical Chitosan GmbH, degree of deacetylation 85 mol% and dynamic viscosity 1000 mPas) in an aqueous acetic acid solution at a concentration of 1% by weight was used (based on the total mass of the solution).

As the cold box activator 6324, polyisocyanate (activator 6324 by the company houttenes-Albertus Chemische Werke GmbH) which is generally used for manufacturing a cold box binder (benzyl ether-based polyurethane resin) is used.

As cold box gas resin 7241, a phenolic resin (gas resin 7241 from Huttenes-Albertus Chemische Werke GmbH) which is generally used for the production of cold box binders (polyurethane resins based on benzyl ethers) is used.

As the sodium water glass binder 48/50, an aqueous solution of a standard water glass binder (CAS RN 1344-09-8) having a water glass content (sodium silicate content) in the range of 35 to 50 wt.% and a pH in the range of 11 to 12 at 20 ℃ was used.

The molding material mixture was produced as follows:

molding material mixture F-cold box: the ingredients mentioned in Table 1 were mixed with one another by stirring in an electric mixer (Bosch Profi 67) until a homogeneous molding material mixture was formed. The molding material mixture cold box is for comparison purposes not manufactured according to the process according to the invention or not a molding material mixture to be used in such a process.

Molding material mixture F-water glass: the ingredients indicated in Table 1 were mixed with one another by stirring in an electric mixer (Bosch Profi 67) until a homogeneous molding material mixture was formed. The molding material mixture F — water glass is for comparison purposes not produced according to the method according to the invention or not a molding material mixture to be used in such a method.

Molding material mixture F-V6: the ingredients "aqueous PVAL mixture" and "aqueous formulation of chitosan" mentioned in table 1 were mixed with each other in the amounts given in table 1 as a binder premix in a glass beaker. The silica sand was then placed in an electric mixer (Bosch Profi 67) and then the binder premix was added and mixed with the silica sand while stirring. Stirring is continued until a homogeneous molding material mixture results. The moulding material mixture F-V6 is a moulding material mixture which is manufactured according to the method according to the invention or is to be used in such a method.

Molding-material mixture F-E6 +: the ingredients "aqueous PVAL mixture" and "aqueous formulation of chitosan" mentioned in table 1 were mixed with each other in the amounts given in table 1 as a binder premix in a glass beaker. Shortly before the preparation of the molding material mixture F-E6+, the aliphatic polyisocyanates in the amounts given in table 1 were added to the resulting binder premix and combined with the binder premix by mixing with one another (stirring motor with blade stirrer) to form a "second binder system" (for the purposes of the present invention). The silica sand was then placed in an electric mixer (Bosch Profi 67) and the resulting second binder system was then added while stirring and combined with the silica sand by mixing. Stirring is continued until a homogeneous molding material mixture results. The moulding material mixture F-E6+ is a moulding material mixture which is produced according to the method according to the invention or is to be used in such a method.

Example 2: production of standard bending bars as model mouldings

For testing purposes, standard bending bars (representing hardened mouldings for the casting of metal castings) (dimensions: 172mm × 23mm × 23mm) were produced by ramming from the mould mix F-cold box given in example 1, F-water glass, F-V6 and F-E6+, in a manner known to the person skilled in the art, corresponding to or similar to the method in specification P73(1996 month 2 edition) (hereinafter referred to as "VDG specification P73") of Verein Deutscher Gie β ereifachleute, No. 4.1.

(the process for hardening the moulding material mixture "F-cold box" and "F-water glass" corresponds to the process known from the prior art as described below) the upper bending bar is hardened as explained hereinafter:

bending bar B-cold box: the molding material mixture F-cold box (see example 1) was molded by ramming in a bent rod ramming mold as described above. Subsequently, corresponding to VDG specification P73, No.4.3, method A, the molded molding material mixture was hardened by conducting gaseous N, N-dimethylpropylamine (about 1ml of liquid, 15 seconds) through (under the process conditions) according to the cold box method.

Bending bar B-water glass: the molding material mixture F-water glass was molded by tamping in a bent rod tamping mold as described above. Subsequent CO in gaseous state₂Is directed through the molded molding material mixture (in a bent rod tamping mold).In CO₂After gas-curing the bending bar with green strength was removed from the mould (demoulding) and hardened by drying at 210 ℃ for 20 minutes in a drying oven and removing water by convection degassing of the drying oven (standard bending bar, here: bending bar B-water glass).

Bending bars B-V6 and B-E6 +: molding material mixtures F-V6 and F-E6+ (see example 1 for manufacture) were shaped by ramming in a bent-rod ramming mold, respectively, as described above. Gaseous N, N-dimethylpropylamine (corresponding to about 1ml of liquid, 15 seconds) (under process conditions) is then directed through the molded molding material mixture (gas-smoked in a bent rod ramming mold), thereby producing standard bent bars (i.e., illustrative hardened molded pieces-here green-strong), respectively, having green strength. These standard bending bars with green strength are then removed from the ramming moulds and treated in a drying oven at 210 ℃ for 20 minutes and degassed by convection in the drying oven to remove water, respectively, to give hardened mouldings (standard bending bars, in this case: bending bars B-V6) or hardened mouldings by means of a crosslinking step (bending bars B-E6 +).

Example 3: determination of the Final Strength of Standard bent bars

The standard bending bars produced in example 2 above were tested for final strength, respectively: for this purpose, the final strength of the standard bending bar B-cold box was tested 24 hours after manufacture. For this purpose, the final strength was tested 24 hours after the manufacture (drying) of standard bent bars B-water glass, B-V6 and B-E6 +. All standard bent rods were stored under laboratory conditions. The final intensity was determined three times each, as described in VDG specification P73, No.5.2, by means of a Georg Fischer intensity tester PFG type with a low pressure manometer (with motor drive).

In this way, the bending strength (final strength) of a standard bending bar as illustrated in table 2 below was found:

TABLE 2: ultimate strength of standard bent bar

From the values specified in table 2, it can be seen that, despite the lower final strength of the hardened moldings produced according to the process of the invention (standard bending bars) B-V6 and B-E6+ compared with conventional cold box-bonded moldings or water glass-bonded moldings, the final strength of the hardened moldings produced according to the process of the invention is virtually completely satisfactory. The standard bending bar B-E6+ (made with the aid of the cross-linking step) has a higher final strength value (close to the corresponding value for the cold box-bonded bending bar) than the standard bending bar B-V6 (made without the aid of the cross-linking step).

Example 4: determination of the Strength of Standard bent bars after being taken out of warehouse

As with the standard bent rods made in example 2 above, B-water glass and B-E6+ began to undergo storage testing 24 hours after their manufacture (corresponding to a time to ex-warehouse of "0"). For this purpose, the corresponding bending bars were stored in an air-conditioning cabinet at 40 ℃ and 90% relative atmospheric humidity for 60 hours and tested for their (residual) bending strength at the time intervals given in table 3 as described in example 3. The corresponding measured values of these flexural strengths are given in table 3 below:

TABLE 3: flexural Strength in an air-Conditioning Cabinet after 60 hours of storage

From the values given in table 3, it can be seen that the hardened moldings (standard bending bars) B to E6+ produced according to the process according to the invention exhibit a reduction in strength after 8 hours under storage conditions. However, its intensity then remains approximately constant for the remaining storage time and is sufficient for practical purposes. In contrast thereto, in the water glass-bonded control bent bar B-water glass, a significant decrease in strength was observed after a storage time of 24 hours, and this situation continued further to the end of the storage time until the bent bar was practically unusable.

Accordingly, even under severe weather conditions (high temperature and air humidity), the hardened molded parts (standard bent bars, produced by means of a crosslinking step) B-E6+ produced according to the method according to the invention are significantly better suited for storage than conventional water glass-bonded molded parts.

Example 5: determination of Water resistance of Standard bending bars

A standard curved bar made as in example 2 above was placed on a stand so that only its ends were supported (the support area was about 1/10 of the total area of the underside of the standard curved bar). The rack on which the standard bent rod is placed is introduced into a water-filled container such that the underside of the standard bent rod is in full contact with the water surface and is able to absorb water by capillary force. The water resistance of the standard bent bars was then visually evaluated over the time periods given in table 4 below.

The results of this test are given in table 4.

TABLE 4: water resistance of Standard bend bars

From the observations given in table 4, it can be seen that the standard bent bar bonded by the cold box binder is completely water resistant even after the longest exposure time of water given in table 4. The hardened curved bars B-V6 (produced without the aid of a crosslinking step) produced according to the method according to the invention absorb water after a short time and break after a while. The curved bars B-E6+ made according to the invention have a higher water resistance compared to the hardened (uncrosslinked) curved bars B-V6.

Example 6: performance of standard bending bars in iron casting

Standard bent bars, B-cold box (control), B-V6 (manufactured according to the process of the invention) and B-E6+ (manufactured according to the process of the invention), manufactured as in example 2 above, were coated in a manner known per se with a conventional alcohol coating (Koalid 4087 from Huttenes-Albertus GmbH) (conditions: completion time 17.3 seconds; immersion time 7 seconds; drying at 110 ℃ for 40 minutes; wall thickness in the wet state 325 μm).

The alcohol-coated standard bending bars were then inserted into furan resin moulds (dimensions 280mm x 200mm x 130mm) coated with undiluted conventional zirconium-containing coating (Zirkofluid 1219 from huttenes-Albertus GmbH) and cast with iron in such a way that they were placed in the mould (casting temperature approximately 1440 ℃; carbon content approximately 3.09% by weight, silicon content approximately 1.89% by weight, respectively, based on the total mass of iron cast), so that the standard bending bars were completely surrounded by the iron castings, respectively, and were subjected to the greatest stresses with regard to the supporting load (due to the iron as cast metal) during casting.

After the casting process, the remnants of the standard bent rods were removed from the iron casting by rotating the iron casting (so that the remnants of the standard bent rods could fall out of the downwardly oriented openings of the cavities of the iron casting created by the standard bent rods), and the removal performance (decoring performance) of the standard bent rods was visually evaluated here. Here, the following observations were made:

the remaining residue of the standard bent bar B-cold box (comparative) could hardly be removed from the iron casting in the above-described manner; they remain almost completely in the iron casting.

The residues of the standard bent rods B-V6 (manufactured according to the method according to the invention without the aid of a cross-linking step) and B-E6+ (manufactured according to the method according to the invention with the aid of a cross-linking step) can be removed very well and practically from the iron casting in the manner described above. Little visible residue remains in the iron casting.

From the observations mentioned above, it can be seen that the hardened moldings produced according to the process of the invention (in this case: standard bending bars B-V6 and B-E6+, representing cores, risers or molds) exhibit very good decoring or demolding properties and are therefore far superior in this respect to the control moldings (B-cold box).

Example 7: production of standard test bodies (standard bending) from insulating riser material as a molding material mixtureStick and standard Test cartridge)

The ingredients given in table 5 below were used to prepare molding material mixtures for insulated risers. The molding material mixture was prepared analogously to that illustrated in example 1 above.

The curved bars were subsequently molded from the molding material mixture obtained and hardened into standard curved bars similarly as in example 2 above. Furthermore, according to VDG Standard P38, a standard test cylinder (height: 50mm, diameter: 50mm) was produced from the resulting molding material mixture by ramming and hardened similarly as in example 2 above as a hardened moulding (for a standard bending bar and a standard test cylinder with molding material mixture F-E6+ (2), 30 minutes in a convection drying oven at 210 ℃). In the case of molding material mixture F-E6+ (2), standard bent rods or standard test cartridges produced as described above correspond respectively (by means of a crosslinking step) to the hardened moldings for the purposes of the present invention.

The final strengths of the obtained standard bending bar "B-cold box" (control) and the obtained standard bending bar B-E6+ (2) (manufactured according to the invention) were then determined similarly as in example 3 above. The results of all corresponding measurements are given in table 5 (average of 3 measurements each).

The values respectively determined for the gas permeability of the standard bending bar and the standard test cartridge and their weights are likewise given in table 5. Gas permeability is a test value that gives information about the compactness of a structure. In particular in the case of risers, this is a characteristic value which can give fully derived information about the casting gas during casting.

Table 5:composition of moulding material mixture for insulating risers

The ingredients given in table 5 "aqueous PVAL mixture", "aliphatic polyisocyanate", "aqueous formulation of chitosan", "cold box activator 6324" and "cold box gas resin 7241" correspond to the ingredients given in example 1.

From the results given above in table 5, it can be seen that the insulating riser compound manufactured according to the method according to the invention has similar characteristics to the riser compound manufactured according to the cold box method known from the prior art.

Example 8: casting moulded parts from aluminium

The insulated feeder (bottom closed) with the molding material mixture "F-cold box (2)" made above in example 7 was made by shooting in a core shooter in a manner known to the person skilled in the art (gas fumigation with catalyst N, N-dimethylpropylamine).

The insulated riser was shot on a core shooting machine with the aid of an insulated riser charge with molding material mixture "F-E6 + (2)" made according to the invention as in example 7 above, in the same mold (compared with the aid of the riser charge "F-cold box (2)"). Hardening was carried out at 210 ℃ for 30 minutes with removal of water in a drying cabinet (convection).

The insulated risers made from the two molding material mixtures used in the manner described above were placed in a cold-box-bonded sand mold and cast separately with aluminum to test their performance under metal casting conditions. Additional insulated risers, also made in this way, were placed in loose moulding sand and cast separately with iron instead of aluminium.

The following observations were made:

when the insulated risers produced with the aid of the comparative molding material mixture F-cold box (2) (not according to the method according to the invention) were cast with aluminium, severe fume formation was observed and this continued even after the casting risers had been removed from the sand molds.

When the insulated feeder produced with the aid of molding material mixture F-E6+ (2) (according to the method according to the invention) was cast from aluminum, no haze formation was observed. After casting, the insulated feeder produced according to the invention exhibits a significantly better removal performance than the insulated feeder produced by means of the control molding material mixture F-cold box (2), that is to say the insulated feeder produced according to the invention can be separated from the aluminum significantly more easily. The resulting aluminum castings exhibited significantly cleaner surfaces (i.e., no condensate deposition) than aluminum castings made with the aid of insulated risers made from the control molding material mixture F-cold box (2).

Example 9: trial casting of iron blocks

The molding material mixtures indicated in table 6 below were each molded as (insulated) risers in a core shooter in a manner known to the person skilled in the art.

In the case of the feeder mix "F-cold box (3)", hardening is carried out by gas-fumigation with the catalyst N, N-dimethylpropylamine in a manner known to the person skilled in the art. In the case of the riser charge "F-water glass (2)", hardening was carried out in a drying cabinet (convection) at 210 ℃ for 25 minutes. In the case of the feeder composition "F-E6 + (3)", hardening was carried out by heating in a drying cabinet (convection) at 210 ℃ and removing water for 30 minutes to give a crosslinked hardened molded part. This resulted in riser "riser-cold box" and "riser-water glass" not made according to the invention, and riser "riser-B-E6 +" made according to the invention.

TABLE 6: composition of molding material mixture for riser

The ingredients indicated in table 6 correspond to the ingredients indicated in example 1 and their meanings, respectively.

The usefulness, in particular the quality of the riser effect, was examined by using the above-mentioned risers in the test casting of iron blocks (models of metal castings), respectively. For this purpose, risers of the same size (i.e. respectively the same modulus) were used when blocks with a modulus (i.e. volume to surface area ratio) of 1.68cm were cast from iron (GGG40) at a casting temperature of 1400 ℃. To assess quality, a person skilled in the art of casting technology will generally use blocks with a significantly higher modulus than the risers, in order to be able to obtain the best information about hardening from experiments. The quality of the feeding action was evaluated on the depth of the shrinkage cavity extending into the block, wherein the deeper the shrinkage cavity extends into the block (metal casting), indicating a poorer feeding action.

After casting and cooling to room temperature, the test blocks produced as described above were sawn in the middle (in half) in order to expose their section and evaluate the quality of the casting and also of the feeder effect of the feeder used accordingly. The cross section of the test block obtained by sawing and the residual riser made of iron, visible as a result of the attachment thereto, were evaluated visually, the results being given here below:

significant crater formation extending into the metal casting was produced under test conditions when using cold box-bonded risers not made according to the present invention.

When using a water glass-bonded riser not produced according to the invention, a significant shrinkage cavity formation occurred under the test conditions, which largely extended into the metal casting. The low quality of the feeder effect of the water glass-bonded riser under the test conditions can be attributed here to the relatively high thermal energy absorption of the water glass binder (known as its disadvantageous "quenching behavior") and the resulting relatively early hardening of the cast metal.

In contrast, when using the riser "riser B-E6 +" produced according to the invention, no shrinkage cavities occur in the metal casting, but only substantially at the upper end of the residual riser of metal.

Thus, from the above observations it can be concluded that risers made according to the present invention have a significantly better feeding capacity than traditional cold-box or water glass-bonded risers used for controls.

Example 10: preparation of aqueous Binder systems

The ingredients indicated in table 7 below were used to prepare aqueous binder systems.

TABLE 7: components of aqueous Binder systems

The ingredients "aqueous PVAL mixture", "aliphatic polyisocyanate" and "aqueous formulation of chitosan" indicated in table 7 correspond to the ingredients indicated in example 1.

The aqueous binder systems WB-V6 and WB-E6+ are the aqueous binder systems to be used according to the invention. The aqueous binder system WB-E6+ corresponds to the above aqueous mixture as the second binder system.

Claims

1. A method i) for producing a metal casting and/or ii) for producing a hardened molded part for use in casting a metal casting, the molded part being selected from a casting mold, a core and a riser, the method comprising the steps of:

v1) preparing a molding material mixture comprising the following constituents:

–CH₂-CH(OH)- (Ⅰ)，

c) As hardener component, one or two components selected from:

c1) one or more biopolymers selected from poly-D-glucosamine

And

c2) one or more polyisocyanates as crosslinkers for the hydroxyl groups of the one or more aliphatic polymers;

and

d) water;

v2) molding the molding material mixture,

and then

V3) hardening the molded molding-material mixture or an unhardened downstream product produced therefrom in one or more steps,

so that a hardened molded part results.

2. The method according to claim 1, wherein the molding material mixture is prepared in step V1) by thoroughly mixing the components a) to d) with one another.

3. The method according to any one of the preceding claims,

wherein

-the moulding material mixture comprises the component c1) as hardener component c), the component c1) being one or more biopolymers selected from poly-D-glucosamine,

and/or

-said hardening in step V3) comprises

V31) precipitating at least a part of the one or more biopolymers,

preferably by increasing the pH of the aqueous portion of the molded molding material mixture, particularly preferably by contact with an alkaline-reacting gaseous compound, preferably by gas-gassing with said gaseous compound, more particularly preferably by gas-gassing with a gaseous amine,

so that a molded part with green strength is produced;

and/or

V32)

By heating the molded molding material mixture and/or the unhardened downstream product produced therefrom and/or the molded part having green strength, preferably to a temperature in the range from 100 ℃ to 300 ℃, particularly preferably in the range from 150 ℃ to 250 ℃, and more particularly preferably in the range from 180 ℃ to 230 ℃,

and/or

By removing water from the moulded moulding material mixture and/or from the unhardened downstream product resulting from the moulded moulding material mixture and/or from the green-strength moulded piece,

processing the molded molding material mixture and/or the unhardened downstream product produced from the molded molding material mixture and/or the molded part having green strength.

4. The method according to any of the preceding claims, preferably according to claim 3, wherein

-the moulding material mixture comprises the component c2) as hardener component c), the powder c2) being one or more polyisocyanates, preferably aliphatic polyisocyanates,

and/or

-said hardening in step V3) comprises

V32)

Preferably

By heating the molded molding material mixture and/or the downstream product produced from the molded molding material mixture and/or the molded part with green strength, preferably to a temperature in the range of 100 ℃ to 300 ℃, particularly preferably in the range of 150 ℃ to 250 ℃ and more particularly preferably in the range of 180 ℃ to 230 ℃,

and/or

to process the molded molding material mixture and/or the downstream product produced from the molded molding material mixture and/or the molded part having green strength,

and preferably

V33) crosslinking the hydroxyl groups of the one or more aliphatic polymers of the formula I with the isocyanate groups of the polyisocyanate in the moulded moulding material mixture and/or in the unhardened downstream product resulting from the moulded moulding material mixture and/or in the moulded part having green strength,

so that a crosslinked molded part is produced as a hardened molded part.

5. The process as claimed in any of the preceding claims, wherein the aliphatic polymers used each comprise a structural unit of the formula I which contains a hydroxyl group

Can be prepared by at least partial hydrolysis of polyvinyl acetate;

and/or

-is selected from polyvinyl alcohol, polyvinyl acetate and mixtures thereof

And/or

-75% by weight or more, preferably 90% by weight or more, particularly preferably 98% by weight or more, based on the total mass of the hydroxyl group-containing organic polymer used in the molding material mixture as a whole, with the exception of the biopolymer or biopolymers selected from the group of poly-D-glucamines used as component c1),

and/or

-comprises one or more polyvinyl alcohols,

wherein the polyvinyl alcohol used is preferably used as a whole

Having a degree of hydrolysis of > 50 mol%, which degree of hydrolysis is preferably determined according to the method as given in paragraphs [0029] to [0034] of the document DE 102007026166A 1,

and particularly preferably has a degree of hydrolysis in the range from 70 mol% to 100 mol%, more particularly preferably in the range from 80 mol% to 100 mol%, said degree of hydrolysis preferably being determined according to the method of DIN EN ISO 15023-022017-02 draft appendix D,

and/or

-having a dynamic viscosity in the range from 0.1 to 30mPa · s, preferably in the range from 1.0 to 15mPa · s, particularly preferably in the range from 2.0 to 10mPa · s, which is determined in each case according to DIN53015:2001-02 at 20 ℃ at a concentration of 4% of the overall (weight/weight) aqueous solution of the polyvinyl alcohol used;

and/or

-75% by weight or more, preferably 90% by weight or more, particularly preferably 98% by weight or more, based on the total mass of the aliphatic polymers respectively comprising hydroxyl-containing structural units of the formula I used in the molding material mixture as a whole.

6. The method according to any one of the preceding claims,

wherein

wherein the chitosan is preferably

and/or

Having a dynamic viscosity of > 500 mPas, preferably > 600 mPas, particularly preferably > 700 mPas, determined in each case according to DIN53015:2001-02 at 20 ℃ in a 1% strength by weight solution of the chitosan in 1% strength by weight acetic acid,

and/or

The total mass of the aliphatic polymers used, each comprising a structural unit of the formula I containing a hydroxyl group

And

total mass of biopolymer selected from poly-D-glucosamine used

Sum of

And

total mass of molding material used

Ratio of (A to B)

7. The method of any of the above claims, wherein the one or more polyisocyanates comprise one or more water-dispersible polyisocyanates.

8. The method of any of the above claims, wherein the one or more polyisocyanates comprise an aliphatic polyisocyanate,

wherein preferably

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises polyether groups and further comprises urethane and/or allophanate groups,

and/or

-the aliphatic polyisocyanate or one or more or all of the aliphatic polyisocyanates comprises one or more 2,4, 6-trioxotriazinyl groups and furthermore preferably comprises polyether groups or sulfonate groups, preferably polyether groups,

and/or

The aliphatic polyisocyanate(s) used represent ≥ 50% by weight, preferably ≥ 75% by weight, particularly preferably ≥ 90% by weight and very particularly preferably ≥ 98% by weight of the polyisocyanate(s) used overall in the moulding material mixture.

9. The method according to any one of the preceding claims,

wherein,

And

total mass of biopolymer selected from poly-D-glucosamine used

Sum of

And

the total mass of the preferred aliphatic polyisocyanates used as crosslinking agents

Ratio of (A to B)

10. The method according to any one of the preceding claims,

wherein the molding stock comprises:

-a refractory solid in particulate form selected from one or more of:

and

-graphite

And/or

-core-shell particles, preferably comprising a glass core and a refractory shell, particularly preferably having a bulk density in the range of 470g/l to 500 g/l;

-refractory composite particles;

-a sphere;

-perlite, preferably expanded perlite;

-closed cell microspheres consisting of expanded perlite;

-rice hull ash;

-an expanded glass;

-hollow glass spheres

And

hollow ceramic balls, preferably hollow corundum balls.

11. Method for producing metal castings according to any of the previous claims, preferably according to any of the claims 3 to 10, comprising the additional steps of:

v4) contacting the hardened molding, preferably as obtained after step V32) and preferably additionally after step V33), with a cast metal to produce a metal casting, wherein the cast metal preferably hardens upon contact with the hardened molding,

wherein preferably

-said casting metal is selected from the group consisting of aluminium, magnesium, tin, zinc and alloys thereof

And/or

-the temperature of the cast metal at the time of casting is not higher than 900 ℃;

so that a metal casting is produced.

12. Hardened moulded part for use in the casting of metal castings, preferably producible by the method according to any one of claims 1 to 11, selected from the group consisting of casting molds, cores and risers, comprising

–CH₂-CH(OH)- (Ⅰ)，

And

c) as hardener component, one or two components selected from:

c1) one or more preferably precipitated biopolymers selected from poly-D-glucosamine,

and

c2) one or more preferably aliphatic polyisocyanates,

wherein preferably the hydroxyl groups of the aliphatic polymer used, which respectively comprise structural units of the formula i containing hydroxyl groups, are present at least partly as binders which harden by crosslinking with the isocyanate groups of the polyisocyanate or polyisocyanates used, preferably as crosslinked, hardened binders.

13. A green-strength moulded article according to claim 12 comprising the component c1) as hardener component c), the component c1) being one or more precipitated biopolymers selected from poly-D-glucosamine, preferably comprising chitosan.

14. Hardened moulded part according to claim 12 or 13, comprising the component c2) as hardener component c), the component c2) being one or more, preferably aliphatic, polyisocyanates, wherein the hydroxyl groups of the aliphatic polymers used, each comprising structural units of formula i containing hydroxyl groups, are present at least partly as hardened binders which crosslink by crosslinking with the isocyanate groups of the polyisocyanate or polyisocyanates used.

15. A molding material mixture comprising the following ingredients:

–CH₂-CH(OH)- (Ⅰ)，

c) As hardener component, one or two components selected from:

-one or more biopolymers selected from poly-D-glucosamine

And

-one or more preferably water-dispersible and/or aliphatic polyisocyanates as cross-linking agents for the hydroxyl groups of the one or more aliphatic polymers;

and

d) and (3) water.

16. Use of an aliphatic polymer, preferably polyvinyl alcohol crosslinked in this way, comprising structural units of the formula I containing hydroxyl groups, crosslinked by one or more aliphatic polyisocyanates, as a binder for mouldings used in the casting of metal castings, selected from the group consisting of casting moulds, cores and risers

–CH₂-CH(OH)- (Ⅰ)。

17. Use of a biopolymer selected from the group consisting of biopolymers of poly-D-glucosamine, preferably chitosan, as a binder or binder component for the production of hardened moulded parts selected from the group consisting of casting moulds, cores and risers, preferably moulded parts with green strength, in the foundry industry.