阅读说明：本技术 用于回收方法的粉末涂料废料的处理 (Treatment of powder coating waste for recycling processes ) 是由 康斯坦策·舍费尔 阿斯特丽德·约翰-穆勒 于 2019-03-04 设计创作，主要内容包括：本发明涉及一种用于回收利用粉末涂料废料的方法,其中借助于反应物处理粉末涂料废料,使得降低或者消除其对表面并且特别地对金属表面的粘附。通过根据本发明的粉末涂料废料的处理,有可能在热影响下对其进行进一步的加工并且将其用作不同回收方法中或者其它方法中的原材料。(The invention relates to a method for recycling powder coating material waste, wherein the powder coating material waste is treated by means of reactants such that the adhesion thereof to surfaces and in particular to metal surfaces is reduced or eliminated. By the treatment of the powder coating material waste according to the invention it is possible to further process it under the influence of heat and use it as a raw material in different recycling processes or in other processes.)

1. A method for recycling powder coating waste, the method comprising the steps of:

a) providing a powder coating waste;

b) providing a reactant;

c) mixing the powder coating waste with the reactant to obtain a mixture of reactant and powder coating waste that can be further processed,

it is characterized in that the preparation method is characterized in that,

the reactant is a surfactant.

2. The method according to the preceding claim, wherein,

it is characterized in that the preparation method is characterized in that,

the powder coating waste is in powder form.

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

it is characterized in that the preparation method is characterized in that,

the powder coating waste is solvent-free.

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

it is characterized in that the preparation method is characterized in that,

the reactant is a saturated carboxylic acid, preferably a saturated fatty acid, especially of empirical formula C_nH_2n+1Saturated fatty acids of COOH, wherein preferably n ═ 5 to 30.

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

it is characterized in that the preparation method is characterized in that,

the reactant is stearic acid.

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

it is characterized in that the preparation method is characterized in that,

the reactant is polyethylene glycol (PEG).

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

it is characterized in that the preparation method is characterized in that,

the reactants have a melting temperature of at least 50 ℃, preferably at least 60 ℃.

8. The method according to the preceding claim, wherein,

it is characterized in that the preparation method is characterized in that,

further processing of the mixture of reactants and powder coating waste is effected at a temperature of at least 60 ℃.

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

it is characterized in that the preparation method is characterized in that,

the powder coating waste comprises a thermoset old powder coating.

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

it is characterized in that the preparation method is characterized in that,

the powder coating waste comprises synthetic resins, particularly preferably epoxy resins, polyester resins and/or acrylate resins or mixtures thereof.

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

it is characterized in that the preparation method is characterized in that,

the powder coating waste has functional groups that can contribute to adhesion on metal surfaces, and the reactant causes deactivation of the functional groups.

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

it is characterized in that the preparation method is characterized in that,

the functional group is selected from the group comprising hydroxyl, epoxy, carboxyl, amino and/or ester groups.

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

it is characterized in that the preparation method is characterized in that,

said mixture of reactants from c) and powder coating waste comprises:

1)90-99.5 wt.% of said powder coating waste, and

2)0.5 to 10 wt.% of the reactants,

wherein wt.% is based on the total weight of the mixture of reactants and powder coating waste and is less than or equal to 100 wt.%.

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

it is characterized in that the preparation method is characterized in that,

in further processing the mixture of reactants from c) and powder coating waste, the mixture is at least partially in contact with a metal surface.

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

it is characterized in that the preparation method is characterized in that,

further processing of the mixture of reactants from c) and powder coating waste is effected in an extruder and/or injection molding machine.

16. The method according to the preceding claim, wherein,

it is characterized in that the preparation method is characterized in that,

further processing of the mixture of reactants from c) and powder coating waste is effected in an extruder to obtain plastic strands which are subsequently processed into granules.

17. A powder coating product produced by the method according to any one of the preceding claims under conditions to recycle powder coating waste.

Technical Field

The invention relates to a method for recycling powder coating material waste, wherein the powder coating material waste is treated by means of reactants, whereby the adhesion thereof to surfaces, preferably metal surfaces, is reduced or eliminated. By the treatment of the powder coating material waste according to the invention, it can be further processed under the influence of heat and used as a raw material in different recycling processes or in other processes.

Background

Worldwide, about 110 million tons of powder coatings are manufactured each year, and this trend is still rising. Powder coating is a solventless material which is used more and more frequently for the coating of surfaces, in particular for spraying metal surfaces.

Unlike other coating techniques that use wet coatings, powder coatings do not require the use of solvents and thus do not produce any emissions during their processing. When applying powder coatings, overspray of up to 55% is produced, which, owing to their insufficient purity, cannot be put into production any more. In the production of powder coatings, additional powder coating waste is additionally produced, for example as a result of excessively fine grinding or other incorrect filling, or as a result of storage, in particular over-storage in stock or storage under unfavorable storage conditions.

Every year, powder coating waste worldwide amounts to about 50 million tons. The resulting powder coating residues must often be disposed of with great expense. Here, a cost of about 120-180 EU/ton is incurred for the user of the powder coating. This is particularly serious because powder coating is a very good quality material and costs of about 4000 euro/ton are incurred at the time of purchase.

For wet coatings, a series of recycling processes are known, with a particular focus on the treatment of volatile solvents.

From WO 2016/044938 a1, it is known to clean latex paints in order to provide polymer films therefrom. This is achieved by reducing the moisture in the latex paint and removing volatile components (such as the solvent ethylene glycol) by means of organic acids.

DE 4301491C 1 discloses a process for the recycling or processing of solvent-containing synthetic resin coating wastes into solvent-free recyclates. For this purpose, the synthetic resin coating wastes are admixed with an acyl polyglycol ester emulsifier.

EP 0212214 a2 discloses a process for the reprocessing of coating wastes by conversion into aqueous emulsions. The coating material waste contains a solvent and the conversion of the coating material waste in crosslinked form is effected by addition of a surfactant and under the action of mechanical forces.

DE 4421669 a1 describes the production of a water-soluble one-component coating which can be recovered from the ultrafiltrate of the overspray without additives.

WO 97/43056 discloses a method for reprocessing solvent-in-water emulsions which are used to dissolve overspray from paint spray booths. The emulsion contains a solvent and paint particles dissolved therein. WO 97/43056 describes different process steps in order to separate volatile organic carbonyl compounds from emulsions.

The above-mentioned coating and paint residues are not comparable to powdered powder coating wastes, in particular due to their liquid form and the presence of solvents. Therefore, the above-mentioned method does not provide any suggestion for the recycling of powder coating wastes.

Instead, it has been common to incinerate powder coating wastes with sewage sludge or with household waste to date. Only a few methods are known which focus on the recovery of powder coating waste:

EP 0793741B 1 discloses a method in which a fibrous web is processed together with powder coating waste as a binder. The fabric and binder are mixed with each other and produced as a continuous prepreg, with the mixture being heated slightly.

WO 1996/15891 a1 describes mixing thermoplastic powder coating waste in the molten state in an extruder, followed by breaking the extrudate into granules, which are finally ground into new deposited powders. This process is only possible in the case of thermoplastic powder coatings, since, unlike thermosetting powder coatings, they can be melted again after complete reaction.

WO 2015/006987 a1 describes a mixture of powdered powder paint waste and cement powder, wherein the mixture is subsequently filled into a mould and hardened.

DE 4028567C 2 indicates a method for recycling an overspray powder coating back to the manufacturing process of the powder coating. The overspray is added to the mixture of raw materials and subsequently passed with it through the extrusion process. Here, melting of the overspray occurs. The disadvantage is that overspray adheres to the metal surfaces of the extruder, which can lead to production delays.

For this reason, DE 19748159 a1 suggests compressing the powder coating waste and carrying out the subsequent grinding without an extrusion process. During the compression process, depending on the composition of the powder coating waste, melting and sticking on the press tool can occur as a result of the heating. In addition, unlike processing powder coating wastes in extrusion processes, high quality standards, particularly in metal spraying, cannot be consistently maintained.

The reason why the possibility of further processing of the powder coating material waste has hitherto been low is that irreversible adhesion of the powder coating material components to the metal occurs on heating, whereby the device is damaged or even rendered unusable. This fact greatly limits the possibilities of recycling routes for value retention.

Accordingly, there is a need for alternative recycling methods that overcome the disadvantages of the prior art.

Disclosure of Invention

The object of the present invention is to provide a method for recycling that overcomes the disadvantages of the prior art. In particular, it is an object of the present invention to provide a method in which powder coating wastes are treated so that further processing is possible, but without irreversible adhesion to the metal surface.

This object is achieved by a method according to claim 1. The dependent claims present preferred embodiments for achieving this object.

The present invention preferably relates to a method for recycling powder coating material waste in the following steps:

a. providing a powder coating waste;

b. providing a reactant;

c. mixing the powder coating waste with the reactants to obtain a mixture of reactants that can be further processed and powder coating waste,

wherein the reactant is a surfactant.

The central recycling idea on which the invention is based is the use of powder coating waste as raw material for recycling, by means of e.g. extrusion and injection moulding. In such further processing processes, the methods up to now lead to irreversible adhesion of the powder coating waste mixture to the metal surfaces, in particular of containers or tools. The first method of preventing adhesion by coating the metal surface with a non-stick coating has not achieved satisfactory results.

In contrast, according to the invention, it has been recognized that surface adhesion during further processing can be avoided by chemical deactivation of reactive or functional groups in the powder coating material waste.

Surprisingly, excellent results are achieved here with the incorporation of surfactants as reactants into the powder coating waste. The mixing of the reactants, preferably in powder form, can advantageously be carried out at room temperature and does not require any costly steps. In contrast, a mixture of reactants and powder coating waste is reliably obtained, which can be further processed without disadvantageously adhering to the surface. The further processing includes in particular the usual further processing of the powder coating for the manufacture and/or application thereof. During the further processing process, the mixture of reactants and powder coating wastes can already be processed and extruded at a temperature of 50 ℃. Preferably, the mixture is heated to a temperature of at least 60 ℃ in order to obtain plastic strands, for example in an extruder, which are subsequently granulated.

In a preferred embodiment of the invention, the method comprises: the mixture of reactants and powder coating waste is further processed at a temperature of at least 60 ℃.

Preferably, the deactivation of the adhesion-promoting functional groups of the powder coating material waste is not already effected when the powder coating material waste is mixed with the reactants, which, as explained above, can also be carried out at room temperature. By heating the mixture of reactants and powder coating material waste, on the other hand, reactions are catalysed which reliably deactivate the functional groups of the powder coating material waste, i.e. at least convert the functional groups of the powder coating material waste, so that no sticking or sticking on the surface of the container or tool occurs during further processing.

The method according to the invention is also characterized by simple operability and high economy associated therewith. By incorporating the reactants, the powder coating waste can be reliably converted into a product that can be further processed. Conventionally, in order to manufacture fillers from powder coating wastes, it is required that the old powder coating can be hardened (to reduce reactivity) and then subjected to rough grinding and fine grinding. All of these steps require significant human or machine expense. In contrast, with the method according to the invention, the powder coating material waste can be mixed directly with the reactants for the production of the filler without further expensive work steps.

Surprisingly, it is possible by adding the reactants according to the invention to recover powder coating waste materials having a completely different composition, so that they can be reliably processed further. The terms "powder coating waste" and "old powder coating" are used synonymously.

According to EN ISO 8130-14:2004, powder coatings are thermoplastic or thermosetting fine resin particles which generally contain pigments, fillers and additives, which remain integral if stored under suitable conditions and produce a coating after application by melting and, if necessary, hardening. Powder coating in the sense of the present invention means a thermoplastic or thermosetting coating powder with a solids content of 100%. Unlike other coatings, powder coatings do not contain any solvents. Thus, the powder coating waste is also preferably solvent-free.

In the sense of the present invention, solvent-free preferably means that it does not contain any coating solvent. Coating solvents are solvents that are used to adjust the properties of a wet coating during the coating process and the film forming process. Unlike other coating material constituent components, the solvent does not become a constituent component of the resulting coating layer. The coating solvent particularly belongs to the group of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, alcohols, glycols, glycol ethers, ketones, esters and the like. Examples of coating solvents are: n-hexane, mineral spirits, cyclohexane as aliphatic hydrocarbon; xylene or solvent naphtha as aromatic hydrocarbons; or propanol, n-butanol and isobutanol as the alcohol. As glycol ethers, use is made of, for example, ethylene glycol butyl ether, diethylene glycol monobutyl ether, ethylene glycol and ethylene glycol diethyl ether. Common esters are butyl acetate, ethyl acetate and 2-ethylene glycol butyl ether acetate, while, for example, butanone and acetone are used as ketones.

Typically, the coating solvent is liquid at 25 ℃ and has a boiling point of 25 ℃ to 220 ℃ at 1013 mbar. For powder coatings, reactive diluents can be used instead of solvents, which reduce the viscosity for processing. Unlike solvents, however, reactive diluents crosslink with the binder of the coating and can become part of the coating through copolymerization during subsequent curing.

Powder coatings or powder coating waste in the sense of the present invention therefore preferably comprise paint materials which are solvent-free and preferably have a solids content of 100%. The powder coatings or powder coating wastes according to the invention are therefore also clearly distinguished from those paint residues described in WO 2016/044938 a1, DE 4301491C 1, EP 0212214 a2, DE 4421669 a1 and WO 97/43056. The paint residues present in the prior art have solvents and are therefore not powder coatings. One of ordinary skill in the art will recognize that there are significant chemical and physical differences between these materials. For example, latex paints and latex paint wastes are not comparable to powder coatings in the sense of the present invention. Synthetic resin coating wastes also differ in their composition from powder coating wastes, and therefore must also be handled in a completely different manner, for example in terms of disposal. Another preferred characteristic of powder coatings in the sense of the present invention is that they are not present as an aqueous suspension. Powder coating wastes in the sense of the present invention are also preferably not present in crosslinked form. Powder coatings are very hydrophobic and therefore cannot be processed in aqueous form. Therefore, the person skilled in the art would not have the motivation to derive technical teaching, for example from EP 0212214 a2 or DE 4421669 a1, for solving the problem according to the invention. The solvent-containing emulsions disclosed in WO 97/43056 are also not of any chemical relevance to powder coatings in the sense of the present invention. Solvent-containing liquid paint residues as described in the prior art must be treated in a manner completely different from powder coatings in the sense of the present invention.

The main component of powder coatings is a binder, which encapsulates the solid matter particles in the coating and determines the basic properties of the obtained coating film, such as surface state, hardness and stability. The binder is generally composed of long-chain compounds, mainly organic compounds, which contain reactive or functional groups. For powder coatings, use is made in particular of synthetic resins which can be crosslinked to one another or to branched macromolecules by means of curing agents. In addition, colorants (including pigments, dyes), additives (including leveling agents, degassing agents, waxes, structuring agents) or fillers (including calcium carbonate, talc, barium sulfate) may be added to the powder coating. The colorants, additives and fillers can be adapted to the respective requirements.

As types of base powder coatings, thermoplastic powder coatings and thermosetting powder coatings are known.

Thermosetting (cured) powder coatings are the type of powder coatings that, after melting and interleaving, achieve film formation by chemical crosslinking at elevated temperatures. Thermosetting powder coatings preferably consist of the following resin and curing agent systems:

epoxy resins based on bisphenol A (EP systems) belong to the important powder coating systems, of which accelerated or modified dicyandiamide (DCD) is the most important curing agent. The solubility of DCD in epoxy resins affects the film quality and can be improved by modification. Thus, for example, the chemical resistance and corrosion protection can be increased by phenols or the durability against solvents, acids and discoloration can be improved by hydrogenating carboxylic acids. In contrast, imidazole derivatives are used as curing agents only in matt coatings. These powder coatings are used in particular for coating pipelines and pipes and in the electronics industry for interior areas.

For the manufacture of powder coatings, solid types with a melting point range between 60 ℃ and about 90 ℃ according to Kofler are mainly used as epoxy resins. In order to be able to obtain three-dimensionally crosslinked polymers from epoxy resins, the resins should be reacted with comonomers (curing agents) or initiators. The addition reactions carried out in this process have the great advantage that they are carried out without the formation of volatile by-products. In addition, upon opening a strained epoxy group containing a short C-O bond, a longer acyclic C-O bond is created. As a result, the curing process is associated with a very low volume shrinkage, which is important in particular for technical processing. The ring tension of the epoxy groups makes the epoxy resin highly reactive with respect to a large number of chemical compound classes, whereby a large number of different curing agents can be used for the crosslinking reaction. The choice of the curing agent here also depends on the processing method, the reaction conditions and the desired product properties.

The following reaction equation illustrates the curing of an epoxide with a phenol curing agent:

phenol 1 here has two free electron pairs on the oxygen of the hydroxyl group and a high electronegativity, so that it is particularly nucleophilic. Thus, it is capable of nucleophilic attack on the normal ring C atom of epoxide 2. In epoxide 2 shown above, the ring C atom on the left is preferred for this attack because it has less steric resistance than the ring on the right. The attack results in an open loop that already benefits from the high loop tension of the three loops. The alcoholate produced is protonated to alcohol 3 by the following tautomeric rearrangement.

The following reaction equation illustrates the curing of epoxides with imidazoline derivatives:

imidazole 1 undergoes nucleophilic attack on the less sterically hindered ring carbon of epoxide 2 through a free electron pair on the nitrogen, followed by ring opening which benefits from high ring tensions. Alcoholate 3 is protonated to alcohol 4 by tautomeric rearrangement. In addition, curing of epoxy resins by means of anhydrides is known.

The polyester system is composed in particular of an acid polyester-based resin and a curing agent from hydroxyalkylamides. The layer thickness is mostly limited to 120 μm due to the moisture released in the curing reaction, since otherwise 'pinholes' may occur. For most powder coatings, layer thicknesses below 100 μm are sought, so that this limitation can be practically ignored. The polyester-based powder coating has excellent durability in the open air and high stability against fading by ultraviolet rays. Their chemical resistance is slightly lower than that of epoxy resins.

Polyester is preferably understood to be a high molecular weight compound in which the monomer units are bonded to one another via ester groups and which is synthesized by polycondensation of difunctional carboxylic acids or derivatives thereof with diols.

Saturated polyesters are preferably used in powder coating systems because of their specific, chemical and application-technical properties. It preferably consists only of hydroxyl and/or carboxyl functional groups and is therefore also preferably combined with a polarity-complementary resin. For example, low molecular melamine resins or isocyanate resins that are highly crosslinked with methanol have been demonstrated.

Hybrid systems refer to powder coatings based on mixtures of epoxy resins and polyesters. For the production of epoxy/polyester hybrid powder coatings (hybrid systems), it is preferred to use polyester resins which contain terminal free carboxyl groups in the molecule, which cause steric crosslinking by addition to the epoxy groups. The COOH-functional polyester resin preferably has a molar mass of a few kilograms per mole and is referred to as a matrix resin or curing agent due to its higher molar mass than the epoxy resin. The mixing ratio of epoxy resin (EP) to Polyester (PES) preferably varies between 60:40 and 10: 90. Powder coatings based on such hybrid systems have improved color fastness and uv resistance. Hybrid systems are mainly used for indoor applications because of their less weather resistance.

The following formula shows the reaction mechanism for crosslinking the acidic polyester resin and the epoxy resin at 200 deg.C/10 minutes.

The carboxylic acid 1 can cause nucleophilic ring opening on the epoxide 2 by the free electron pair of the OH group in the carboxyl group, thereby forming the alcoholate 3. Subsequently, by tautomerism, the hydroxy ester 4 is produced.

The polyurethane powder coating is preferably a powder coating comprising polyurethane as binder. Examples are polystyrene-polyurethane (SP-PUR) or acrylate resin-polyurethane (AC-PUR systems), which are characterized by their particular weathering resistance. Preferred polyurethane powder coatings are based on OH-functional polyester or acrylate resins, which can be crosslinked with isocyanate adducts such as the block derivative isophorone diisocyanate.

The acrylate powder coating is preferably based on an acrylate resin, preferably an epoxy-functional acrylate resin. For example, the acrylate resin dodecanedicarboxylic acid (AC-DAA powder coating) is an epoxy functional acrylate resin crosslinked with dodecanedicarboxylic acid.

Advantageously, the addition of the reactants according to the invention allows further processing to generate powder coating waste when manufacturing or applying the aforementioned powder coatings.

Preferably, the powder coating waste processed for use in the method according to the invention comes from powder coatings based on epoxy systems, polyester systems, hybrid systems, polyurethane systems or acrylate systems.

In a preferred embodiment of the invention, the method is characterized in that the powder coating material waste comprises synthetic resins, particularly preferably epoxy resins, polyester resins and/or acrylate resins or mixtures thereof. These powder coating wastes are characterized in that they have a high adhesion to the metal surface without special treatment and thus cause production disturbances and wear of the apparatus during further processing without the addition of the reactants according to the invention.

In a preferred embodiment of the invention the process is characterized in that the functional groups are selected from the group comprising hydroxyl, epoxy, carboxyl, amino and/or ester groups.

Functional groups in the sense of the present invention preferably refer to chemical groups in the powder coating waste that contribute to adhesion to the metal. Thus, the functional group may also be referred to as a reactive group. According to the invention, it is recognized that the recovery process can be optimized significantly by chemically deactivating functional or reactive groups in the powder coating material waste.

In a preferred embodiment of the invention, the powder coating waste has functional groups capable of contributing to adhesion on the metal surface, wherein the reactants cause deactivation of the functional groups.

In particular, molecules from the surfactant group are suitable as reactants. Surfactants belong to the molecular class of amphiphilic substances. Molecularly, surfactants are characterized by hydrophobic (non-polar) hydrocarbon residues and hydrophilic (polar) molecular moieties. A systematic classification of surfactants is achieved on the basis of hydrophilic molecular moieties or hydrophilic groups (see fig. 36).

The anionic surfactant preferably has-COO^-(carboxylates), -SO₃(sulfonate) or-O-SO^3-(sulfate) as hydrophilic group. The cationic surfactant preferably has-NR₄ ⁺(ammonium) as hydrophilic group. The nonionic surfactant is preferably characterized by-O-R (polyether) or-O-H (polyol) as the hydrophilic group. The amphoteric or zwitterionic surfactants preferably comprise the hydrophilic group-NR₂ ⁺- (ammonium) or carboxylates (-COO)^-)。

According to the invention, it is recognized that the deactivation of the functional groups of the powder coating is achieved by the hydrophilic groups of the surfactants, so that undesired adhesion, in particular on metal surfaces, can be avoided.

Anionic surfactants are particularly preferred. In the sense of the present invention, anionic surfactants in particular also include carboxylic acids.

Carboxylic acids in this sense are aliphatic, cyclic or aromatic monocarboxylic or polycarboxylic acids. Preferred molecules have one or more saturated or unsaturated, branched or unbranched carbon chains with or without other functional groups or monocyclic, polycyclic or aromatic carbon regions (hydrophobic regions), and one or more carboxyl groups (hydrophilic regions). Thus, carboxylic acids may also be referred to as hydrophobic carboxylic acids.

In a preferred embodiment, the reactant is a saturated carboxylic acid. Saturated carboxylic acids are distinguished by a particularly stable and effective mode of action by the saturated hydrocarbon residues as hydrophobic constituents. Saturated hydrocarbon chains also give rise to preferred thermal characteristics, such as higher melting temperatures. It can thereby be ensured that the desired success occurs even when the mixture of powder coating material and reactants is preferably heated.

In a preferred embodiment, the carboxylic acid is a fatty acid. Fatty acids are monocarboxylic acids, i.e. carboxylic acids having only one carboxyl group. The fatty acid may be a branched, unbranched, cyclic, saturated or unsaturated fatty acid. Non-limiting examples include:

undecylenic acid C₁₀H₁₉COOH，

Oleic acid C₁₇H₃₃COOH，

Nervonic acid C₂₃H₄₅COOH，

Linoleic acid C₁₇H₃₁COOH，

Marigold acidC₁₇H₂₉COOH，

Arachidonic acid C₁₉H₃₁COOH，

Oleic acid of fishC₂₁H₃₁COOH，

Tartar acidC₁₈H₃₂O₂，

Vernonic acid

C₁₈H₃₂O₃，

Ricinoleic acid C₁₈H₃₄O₃，

Sterculic acid

C₁₉H₃₄O₂，

Lactobacilli acidC₁₉H₃₆O₂，

Malvalic acid C₁₈H₃₂O₂

Chaulmoogra C₁₈H₃₂O₂Or also

Fungus alkyd

Wherein: r1 is a linear alkane, C₂₀–C₂₄(ii) a R2 is a complex structure of up to 60 carbon atoms.

In a particularly preferred embodimentIn embodiments, the reactant is a saturated fatty acid, particularly preferably of empirical formula C_nH_2n+1Saturated fatty acids of COOH, wherein preferably n ═ 5 to 30. Non-limiting examples include:

octanoic acid C₇H₁₅COOH，

Capric acid C₉H₁₉COOH，

Dodecanoic acid C₁₁H₂₃COOH，

Palmitic acid C₁₅H₃₁COOH，

Octadecanoic acid C₁₇H₃₅COOH，

Nonadecanoic acid C₁₈H₃₇COOH，

Phytanic acid C₁₉H₃₉COOH，

Hexacosanoic acid C₂₅H₅₁COOH, or

Tetradecanoic acid C₃₃H₆₇COOH。

In a particularly preferred embodiment of the invention, the reactant is stearic acid (octadecanoic acid).

In another preferred embodiment of the invention, the reactant is palmitic acid (hexadecanoic acid).

Carboxylic acids, especially the preferred carboxylic acids mentioned, are surprisingly reliable for the deactivation of functional groups in powder coating wastes. Carboxylic acids are distinguished by a hydrophobic residue (R) and one or more carboxyl groups COOH. Fig. 1 shows chemical reactions that, during their progress, may contribute to the deactivation of functional groups in powder coatings. These include acidic hydrolysis of nitriles, esterification of carboxyl groups, nucleophilic or electrophilic ring opening of epoxy groups, anhydride formation, amidation or ester hydrolysis.

The following reactions can be used to deactivate the corresponding functional groups with the aid of carboxylic acids.

Hereinafter, the chemical formula is shown by means of a saturated carboxylic acid having an unbranched aliphatic carbon chain. However, the residue (R) may also have a branched, saturated or unsaturated hydrophobic region.

Esterification:

alcohol 2 acts nucleophilically on the carbonyl carbon of the carboxyl group of carboxylic acid 1 via the free electron pair of the hydroxyl oxygen. In the process, the hydroxyl groups are formally dissociated, which combine with the hydroxyl protons of the alcohol 2 to form water 3, which immediately escapes as water vapor (gaseous) at a reaction temperature of 200 ℃. Ester 4 is produced.

Both nucleophilic and electrophilic ring opening of the epoxy group provide the same product. The two reactions differ in mechanism as follows:

nucleophilic ring opening:

the carboxylic acid 1 acts on the less sterically hindered carbon atom of the epoxide 2 via the free electron pair of the hydroxyl group of the carboxyl group, the bond of the epoxide folding back and opening the ring. Forming intermediate stage 3. The alcoholate oxygen combines with the excess protons of the ester groups, leaving the ester oxygen uncharged at the residue R₁By-production of alcohol groups and hence of the hydroxy ester (4).

Electrophilic ring opening:

since the carbonyl carbon in carboxylic acid 1 is positively polarized due to the higher electronegativity of oxygen and thus assumes an electrophilic site, it can be nucleophilically attacked by the epoxy of epoxide 2. The carbonyl oxygen is thereby negatively charged and intermediate product 3 is formed. Which theoretically can be further reacted in two different ways. In one aspect, one of the free electron pairs of the negatively charged oxygen can fold into a double bond, thereby reforming the carbonyl group. The hydroxyl groups of the original acid groups are thus dissociated in the form of hydroxides. It can be immediately attached to the positively charged carbon atom of the intermediate product and thus the hydroxy ester 4 is formed from the secondary carbonium ion. On the other hand, it is theoretically also possible to consider intramolecular ring interactions in which negatively charged oxygen attacks the positively charged carbon atom and thus forms the unstable hydroxy acetal 5. Since a sterically hindered polymer structure is observed here, this variant should be regarded more as a theoretical by-product. In addition, similar to the Erlenmeuer's law, it can be assumed that the alcohol group directly on the acetal carbon is not stable and therefore dissociates rapidly, or that the acetal itself cleaves and generates a gem-diol which is readily equilibrated immediately according to the Erlenmeuer's law, in which both the hydrated and dehydrated forms of the ester are present.

Anhydride formation:

the hydroxyl oxygen in the carboxyl group of carboxylic acid 1 nucleophilically attacks the carbonyl carbon of carboxylic acid 2. Intermediate 3 is produced here. To compensate for charge separation, protons tautomerically rearrange to negatively charged oxygen, thereby producing hydroxyl groups. Since the gem-diol (4) is formed in the process, the Heramee principle works according to which, after the tautomeric rearrangement of the protons, additional water (6) can be dissociated from the hydroxyl group as neutral molecule. The free electron pair of the negatively charged oxygen folds to form a carbonyl group and thus a carboxylic anhydride 7.

Amidation:

the nucleophilic nitrogen of the amino group of primary amine 2 nucleophilically attacks the carbonyl carbon of carboxylic acid 1. Intermediate 3 is produced. The protons tautomerize from the positively charged nitrogen to the negatively charged oxygen, forming the gem-diol (4). The proton rearranges from one of them to the other hydroxyl group according to the early rule and dissociates water 6. Producing the amide 7. Similarly, a reaction mechanism suitable for the reaction of the secondary amine shown in the formation of the acid anhydride proceeds.

Acid ester hydrolysis:

polyester 1 attacks the protons (from dilute acid) present in catalytic amounts by the free electron pair of the carbonyl oxygen. This gives rise to mesogenic intermediates 2 and 3. The nucleophilic water (4) can now attack the generated carbenium ion 3. Since water is less nucleophilic, this attack is only possible by the carbenium ion generated by the addition of a proton. An addition product 5 is produced which tautomerizes the protons of the additional water on the ether oxygen and thus forms an intermediate 6. Neutral alcohol molecules 7 can thereby be dissociated, resulting in mesogenic intermediates 8 and 9. To obtain carboxylic acid 10, protons are dissociated from the previous carbonyl oxygen.

In another preferred embodiment of the invention, the reactant is a saturated, monounsaturated or polyunsaturated fatty alcohol.

In the sense of the present invention, the fatty alcohols are preferably simple or polyvalent, aliphatic, cyclic or aromatic hydrophobic alcohols. The fatty alcohol preferably comprises a hydrophobic residue R and a hydroxyl group. Preferred fatty alcohols can be presented in the formula R-OH, wherein R is any linear or branched, saturated or unsaturated alkyl group having 6 to 30 carbon atoms. Saturated fatty alcohols are particularly preferred.

Examples of suitable fatty alcohols are: 1-hexanol, 1-heptanol, 1-octanol, 1-decanol, 1-dodecanol (lauryl alcohol), 1-tetradecanol (myristyl alcohol), 1-hexadecanol (cetyl alcohol), 1-heptadecanol (also known as "Margarylalkohol"), 1-octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol), 1-docosanol (behenyl alcohol), 1-tetracosanol (lignoceryl alcohol), 1-hexacosanol (ceryl alcohol), 1-octacosanol (montanyl alcohol), 1-triacontanol (melissyl alcohol), cis-9-hexadecen-1-ol (palmitoleyl alcohol), cis-9-octadecen-1-ol (oleyl alcohol), trans-9-octadecen-1-ol (trans-oleyl alcohol), Cis-11-octadecen-1-ol, cis-9, 12-octadecadien-1-ol (linalool), 6,9, 12-octadecatrien-1-ol (gamma-linalool).

Advantageously, the fatty alcohol also allows for the deactivation of functional groups in the powder coating waste. This relates in particular to powder coating wastes having hydroxyl, epoxy, carboxyl, amino and/or ester groups as functional groups.

The mechanism of action of the fatty alcohol is similar to that described above for the hydrophobic carboxylic acid. This relates in particular to the acidic hydrolysis of nitriles and the nucleophilic and electrophilic ring opening.

In another preferred embodiment of the invention, the reactant is polyethylene glycol (PEG). The terms polyethylene glycol and PEG are used synonymously. Thus, in the sense of the present invention, the surfactant as reactant also preferably comprises PEG, which, owing to the polar hydroxide groups, can be coordinated to a nonionic surfactant.

PEG in the sense of the present invention preferably means a linear or branched polymer comprising a structure of empirical formula- (-CH2-CH2-O-) n-, wherein n ═ 2 to 4000, preferably n ═ 5 to 400. Thus, PEG preferably comprises a chain of monomers (-CH2-CH 2-O-). The designation PEG preferably also indicates in particular that there is a majority (i.e. more than 50%) -CH₂CH₂Polymers of the base unit of the O-monomer. Chemically, PEG refers to the polyether of the diol (divalent alcohol) ethylene glycol. The empirical formula is R₁-(-CH2-CH2-O-)n-R₂The PEG of (A) may have different residues, particularly preferably R₁Is H and R₂＝OH。

Excellent results can be obtained with surfactants as reactants, in particular the preferred saturated carboxylic acids and polyethylene glycols mentioned. By using the reactants, the powder coating waste can be further processed at various temperatures without sticking or other processes that interfere with the process. In addition to the aforementioned reactions, the low adhesion of the mixture of reactants and powder coating on the surface is also due to van der waals forces, which via the presumed micelle formation, cause a decrease in adhesion between the surfactants.

In addition, it is preferred that the reactants are present in powder form at room temperature in order to make simple mixing with the powder coating waste possible.

Particularly preferably, surfactants having a melting temperature of more than 30 ℃, preferably more than 50 ℃, particularly preferably more than 60 ℃ are used, since they can be incorporated in powder form into powder coating wastes. It is also possible to use reactants which melt at temperatures below 30 ℃. In this case, it is introduced into the powder coating material waste by means of a spraying or sprinkling device.

The increased melting temperature of the preferred surfactants above 50 ℃, preferably above 60 ℃ also influences the further processability of the mixture of reactants and powder coating wastes particularly positively. For example, it is preferred that further processing of the mixture of reactants and powder coating waste is effected at a temperature of at least 60 ℃, sometimes at significantly higher temperatures. By selecting reactants with a melting temperature above 60 deg., it can be ensured that sufficient stability exists in the different process steps and that a permanent deactivation of the functional groups of the powder coating waste is achieved.

A further advantage of saturated carboxylic acids, in particular stearic acid, is their compatibility with the powder mixture. They are dust-free, have good free-flowing properties, are resistant and have high abrasion resistance. They are also suitable for storage in silos and can thus be used on an industrial scale.

Advantageously, a small amount of reactants is already sufficient to deactivate the functional groups of the powder coating waste, thus obtaining a product that can be further processed.

In a preferred embodiment of the invention, the method is characterized in that the mixture of reactants and powder coating waste comprises:

1)90-99.5 wt.% of powder coating wastes, and

2)0.5 to 10 wt.% of reactants,

wherein wt.% is for the total weight of the mixture of reactants and powder coating waste and is less than or equal to 100 wt.%.

This embodiment is distinguished by particularly high economics, since only small amounts of reactants have to be used. Nevertheless, these mixtures still provide excellent results in terms of processing and utilization of various powder coating wastes.

In a further preferred embodiment, the method is characterized in that, during the further processing of the mixture of reactants and powder coating material waste, the mixture is at least partially in contact with the metal surface. Further processing of the powder coating in an extruder or injection molding machine, contact of the powder coating with the metal surface usually occurs. Without the use of powder coating material scrap processed by the method according to the invention, severe caking or sticking occurs in particular on metal surfaces. Prevention of this contribution to adhesion by chemical deactivation of the functional groups of the powder coating waste is also a significant advantage of the present invention, which has a particular effect in this preferred embodiment.

In a further preferred embodiment, the process is characterized in that the further processing of the mixture of reactants from c) and powder coating waste is effected in an extruder and/or injection molding machine.

In another preferred embodiment, the method is characterized in that the further processing of the mixture of reactants and powder coating waste is effected in an extruder to obtain plastic strands which are subsequently processed into granules. Here, the mixture may preferably be heated to at least 60 ℃, 70 ℃, 80 ℃ or 90 ℃. The occurrence of sticking can also be excluded at these temperatures by adding reactants. Instead, it is possible to obtain, in a reliable manner, from the plastic strand, pellets which can be used, for example, directly in an injection molding machine.

In another embodiment, the invention also relates to powder coating products which are produced by recycling powder coating waste under the conditions of carrying out the method according to the invention or a preferred embodiment thereof. Particularly preferably, the further processed powder coating waste is used as a filler in various industrial applications.

Drawings

Hereinafter, the present invention will be described in detail with reference to examples, but is not limited thereto.

It is noted that various alternatives to the embodiments of the invention described may be employed in order to carry out the invention and to obtain a solution in accordance with the invention. The process according to the invention or the powder coating products obtainable therefrom are therefore not limited in their implementation to the preferred embodiments mentioned. Rather, a large number of design variants are conceivable which may deviate from the presented solution. The aim of the claims is to define the scope of the invention. The scope of protection of the claims is intended to cover the process according to the invention and the powder coating products obtainable therefrom and their equivalent embodiments.

FIG. 1: reaction between stearic acid and different polar groups of the powder coating

FIG. 2: comparison of unhardened old powder coating residues (bottom) with hardened powder coating residues (top). Sample batch 2 (black) is NH₄Cl/KOH, while sample batch 1 (red) was guanidine carbonate.

FIG. 3: deadhesion test of old powder coating residues (batch 1) mixed with 2% stearic acid

FIG. 4: deadhesion test of old powder coating residue (batch 2) mixed with 3% stearic acid

FIG. 5: DSC curve of hardened old powder coating residue containing 2% stearic acid (batch 1)

FIG. 6: DSC curve of hardened old powder coating residue containing 3% stearic acid (batch 1)

FIG. 7: FTRI spectra of old powder coating residue (batch 1) incorporating 2% stearic acid

FIG. 8: FTRI spectra of old powder coating residue (batch 1) spiked with 3% stearic acid

FIG. 9: FTIR spectra of pure stearic acid

FIG. 10: FTIR spectra of a single type of epoxy powder coating hardened at 200 ℃ for 10 minutes

FIG. 11: FTIR spectra of a single type of epoxy powder coating containing 2% stearic acid hardened at 200 ℃ for 10 minutes

FIG. 12: FTIR spectra of a single type of polyester powder coating hardened at 200 ℃ for 10 minutes

FIG. 13: FTIR spectra of a single type of polyester powder coating containing 2% stearic acid hardened at 200 ℃ for 10 minutes

FIG. 14: FTIR spectra of a single species of hybrid powder coating hardened at 200 ℃ for 10 minutes

FIG. 15: FTIR spectra of a single type of hybrid powder coating containing 2% stearic acid hardened at 200 ℃ for 10 minutes

FIG. 16: FTIR spectra of old powder coating residues (batch 1, red) hardened at 200 ℃ for 10 minutes.

FIG. 17: FTIR spectrum of old powder coating residue containing 2% stearic acid (batch 1, red) hardened at 200 ℃ for 10 minutes.

FIG. 18: rheometer measured curve traces of unhardened old powder coating residue (batch 2) (red curve) and unhardened old powder coating residue comprising 2% stearic acid (batch 2) (blue curve)

FIG. 19: adhesion and detackification of powder coatings in crucibles with and without addition of stearic acid, respectively

FIG. 20: MFR values of LLDPE (sample C) in comparison with samples A and B

FIG. 21: curve path of LLDPE in stress-strain diagram

FIG. 22: curve locus of sample A in stress-strain diagram

FIG. 23: curve locus of sample B in stress-strain diagram

FIG. 24: measurement data of notched-bar impact swinging test consisting of LLDPE (sample C), sample A and sample B

FIG. 25: the notch of sample a impacted the fracture surface of the sample (10 x magnification). And shooting by a Leica microscope.

FIG. 26: the notch of sample B impacts the fracture surface of the sample (10 x magnification). And shooting by a Leica microscope.

FIG. 27 is a schematic view showing: SEM image of pure LLDPE

FIG. 28: a) SEM image of sample a (50% LLDPE with 50% hardened old powder coating residue (batch 3)). Amplifying by 2000 times; b) SEM image of sample B (50% LLDPE with 50% unhardened old powder coating residue (batch 3), including 2% stearic acid). 2000 times magnification

FIG. 29: a) SEM image of sample B consisting of unhardened old powder coating residue (batch 3) including 2% stearic acid. Amplifying by 1000 times; b) SEM image of sample B consisting of unhardened old powder coating residue (batch 3) including 2% stearic acid. 2000 times magnification

FIG. 30: FTIR profile of pure LLDPE (sample C)

FIG. 31: FTIR plot of sample A (50% LLDPE with 50% hardened old powder coating residue (batch 3))

FIG. 32: FTIR plot of sample B (50% LLDPE with 50% unhardened old powder coating residue (batch 3), including 2% stearic acid)

FIG. 33: DSC measurement of pure LLDPE (sample C)

FIG. 34: DSC measurement of sample A (50% LLDPE with 50% hardened old powder coating residue (batch 3))

FIG. 35: DSC measurement of sample B (50% LLDPE with 50% unhardened old powder coating residue (batch 3), comprising 2% stearic acid)

FIG. 36: overview on the classification of surfactants

Detailed Description