阅读说明：本技术 用于回收利用玻璃纤维增强塑料的方法 (Method for recycling glass fiber reinforced plastics ) 是由 米夏埃尔·维特 德特勒夫·约阿希米 于 2020-04-06 设计创作，主要内容包括：本发明涉及一种用于回收利用玻璃纤维增强的塑料,特别是基于聚酰胺、聚对苯二甲酸丁二酯或聚对苯二甲酸乙二酯的塑料以从聚合物获得单体和回收用于玻璃纤维的玻璃的方法。(The invention relates to a method for recycling glass fiber reinforced plastics, in particular plastics based on polyamide, polybutylene terephthalate or polyethylene terephthalate, to obtain monomers from the polymer and to recover glass for glass fibers.)

1. A method for recycling GRP, characterized in that,

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of process step a) as an energy source, the glass-based components are heated and melted by using their combustion heat and at the same time the organic constituents are removed by conversion to gaseous combustion products.

2. The method of claim 1, wherein at least 50% by weight of the polymer matrix, preferably at least 50% by weight and at most 80% by weight of the polymer matrix, is depolymerized.

3. The method as claimed in claim 1 or 2, characterized in that the GRP components to be used in process step a) are collected beforehand in a similar type, preferably the same type, and are used in process step a) in a similar type, preferably the same type.

4. The process according to one or more of claims 1 to 3, characterized in that the GRP component to be used in process step a) is comminuted into small pieces before being used for the depolymerization.

5. The method according to one or more of claims 1 to 4, characterized in that prior to the depolymerization the GRPs to be used in process step a) are subjected to cleaning.

6. The process as claimed in one or more of claims 1 to 5, characterized in that the GRP to be used in process step a) is heated and subjected to pyrolytic cracking in the absence of air after the addition of additives.

7. The process as claimed in one or more of claims 1 to 5, characterized in that the GRPs to be used in process step a) are depolymerized in the presence of water or alcohol.

8. The process as claimed in one or more of claims 1 to 7, characterized in that, during or after process step a), the cleavage product and/or the added hydrolysis/solvolysis liquid is distilled off under reduced pressure.

9. The process according to one or more of claims 1 to 8, characterized in that in process step a) at least 20% by weight of the original polymer matrix remains in the organic residue.

10. The method as claimed in one or more of claims 1 to 9, characterized in that the cleavage product of the GRP (matrix) polymer produced in process step a) by cleavage of the polymer chain is supplied to a subsequent repolymerization to produce a recyclate plastic with the characteristics of a new material.

11. The process as claimed in one or more of claims 1 to 10, characterized in that the cleavage product is epsilon-caprolactam and the recyclate plastic is polyamide 6.

12. The process as claimed in one or more of claims 1 to 10, characterized in that the cleavage products are terephthalic acid and 1, 4-butanediol/its dehydration product tetrahydrofuran and the recyclate plastic is polybutylene terephthalate.

13. The method according to one or more of claims 1 to 12, characterized in that the cleavage product of the GRP (matrix) polymer produced in process step a) by cleavage of the polymer chain is at least partially also used as fuel for the combustion operation in process step b).

14. Method according to one or more of claims 1 to 13, characterized in that the impurities, additives and decomposition products remaining on the glass constituents are removed from the glass reinforcement/glass melt during the combustion process of process step b), preferably converted into CO by oxidation, using the remaining at least 20% by weight of organic material₂。

15. The method as claimed in one or more of claims 1 to 14, characterized in that additional energy is provided in process step b), preferably by means of a gas burner.

Technical Field

The present invention relates to a process for recycling glass fiber reinforced plastics, in particular plastics based on polyamide, polybutylene terephthalate or polyethylene terephthalate, to recover both the monomers of the polymer and the glass for the glass fibers.

Background

Modern, high resilience composite plastics are nowadays usually based on glass fibre reinforced thermoplastics, in particular on polyamides or polyesters based on terephthalic acid. Under the trade name of Cologne, LangsesDeutschland GmbHAndplastic pellet materials with chopped glass fiber reinforcement are sold and sold under the trade nameContinuous fiber reinforced semi-finished products/composites are sold. In the marketed pellet material, the mass fraction of glass fiber reinforcement is typically in the range from 5 to 80% by weight.

Glass-based fillers and reinforcing agents (particularly in the form of fibers) achieve considerable improvements in strength, toughness and stiffness compared to plastic parts without fillers or reinforcing agents. In recent years, this has led to many metal-based structures being replaced by glass fibre reinforced plastics (GRPs), particularly in automotive manufacturing.

The additional heat-stabilizing additives now make it impossible to use GRPs even in regions subjected to high thermal stresses, in particular in the field of motor vehicle engine compartments, for pure polymers which are not stabilized with these additives.

Today, GRP based components enable cost effective lightweight construction throughout the transportation field. The weight reduction achieved in motor vehicles leads to a significant reduction in energy consumption (fuel or electrical energy).

However, at the end of the use cycle (which in the case of motor vehicles ends up being sent to the car recovery plant), GRP-based components place very high demands on the recovery operations, especially when the intention is to replace new materials consisting of the same substance. This is more applicable to GRP components, which must be highly added for the target application to avoid or reduce degradation during use. In the context of the present invention, degradation is understood to mean a deterioration of the level of mechanical properties, in particular due to cleavage of the molecular chains of the (matrix) polymer.

Impurities also play an important role in the quality grade of GRP-based plastic recyclates. Mechanical recycling places particularly high demands on the plastic waste to be recycled when the recyclate is used for producing the same products or for other demanding applications. Mechanical recycling uses only physical methods. Physical methods include, for example, washing, drying, pulverizing, melting, compounding, melt filtering, and re-granulating. Of course, there are examples in which plastic waste can be recovered as good quality recyclates via physical methods. The following prerequisites are generally required:

parts made from GRPs must be collected in the same type of manner, the degree of contamination should be low, no significant polymer degradation occurs during the life cycle, and furthermore only very little foreign matter should be absorbed by the polymer matrix during the entire life cycle, such as specialty oils and their additives, for example in the case of engine and transmission oil pans for e.g. automobiles or trucks, or coolant in the case of cooling circuit parts such as coolant reservoirs. Such plastic-based recyclate materials can be reused for the production of new parts using conventional injection molding machines.

However, it has been found that only in very rare cases, mechanical recycling using purely physical methods produces quality grades equal to the original new product.

The following are deteriorating aspects of GRP that promote degradation and thus hinder mechanical recovery, particularly via purely physical methods:

the high content of chopped glass fibers prevents the use of melt filters during compounding, especially in the case where continuous cleaning and discharge of the separated impurities plays a decisive role in the quality improvement of the recyclates obtained in the mechanical recycling of unfilled thermoplastics.

During compounding, preferably in the case where a conventional co-rotating twin-screw extruder is typically used, the glass fibers are mechanically shortened, this effect having a direct adverse effect on the strength and toughness of the GRP/compound/composite.

-additives, in particular flame retardants or heat stabilizers, subject to change during the service life of the GRP, in particular at high continuous service temperatures. However, the degradation products of such additives remain in the mechanical recovery loop and thus in the GRP recovery.

There are, of course, a number of proposals to use physical methods in the mechanical recovery of GRPs to counteract degradation. For example, the effect of the reduction in fiber length in the recycle can be compensated for by the subsequent addition of longer fibers. However, this approach is naturally not applicable to continuous fiber reinforced composites and is therefore limited to chopped glass fiber reinforced GRPs.

However, polymer degradation can also be counteracted in various ways via targeted additions, in particular via chemically active chain extension.

However, it must be noted that degradation is a fundamental problem in the mechanical recovery of GRPs and it is not possible to run GRPs repeatedly through the use of a recovery circuit without significant impact on quality and product properties, particularly in terms of toughness, strength, stiffness, creep, heat resistance, etc.

As mentioned, remixing reduces fiber length. It is also generally not possible to directly remove the chopped glass fibers from the (matrix) polymer which is highly viscous in the molten state and thereby separate the fibers from the polymer matrix.

The high cost and complexity of separating the fibers from the matrix, optionally subjecting them to further cleaning and preparing them for use as recycled fibers must also ultimately be compared to the low cost of new glass fibers.

All three reasons explain why glass fibers from used GRP materials have so far been rarely recycled and reused as fillers or reinforcing agents.

WO 2017007965 a1 describes a process for depolymerizing unreinforced polyethylene terephthalate to obtain terephthalic acid and ethylene glycol therefrom. For this purpose, the polymer is added to a mixture of a nonpolar solvent swelling the polymer and an agent cleaving the ester functions and depolymerized. The recovery of fillers or reinforcing agents, in particular glass fibers, is not specified in WO 2017007965A 1.

EP 3023478 a2 discloses a method which makes it possible to recover fibres, in particular in the case of carbon fibre composite plastics. The process comprises first pyrolyzing a polymeric matrix of a composite plastic in a primary reactor at a temperature of 400 ℃ to 600 ℃. The remaining fibre residue and soot residue are washed, whereby the fibres adsorb water. The wet residue is then returned to the main reactor where the fibers are cleaned under oxidizing conditions of 350 ℃ to 400 ℃. The pyrolysis products formed in the first step during pyrolysis are not subjected to material recovery but are transferred to a second reactor, in which the toxic pyrolysis products are neutralized using thermal plasma up to 15000 ℃.

JP 2000034363 a describes a method for depolymerizing chopped glass fibre-reinforced polyamide 6 composite plastics, in which the polymer matrix is first depolymerized at a temperature of around 280 ℃ and then the entire reaction mixture is added to water and the caprolactam obtained by depolymerization, i.e. the monomeric building blocks of polyamide 6, is dissolved in water. Due to the significantly lower viscosity of the aqueous caprolactam solution, often only 1-100 mPa-s, the glass fibers can be removed from the continuous aqueous phase and washed.

The process of JP 2000034363 a has the disadvantage of energy-intensive distillation to obtain caprolactam of high purity from dilute aqueous caprolactam solutions. Further, the reuse of the glass fibers separated and washed in JP 2000034363A is not without problems. The removed and washed glass fibers from JP 2000034363 a no longer achieve the same reinforcing effect as the use of new glass fibers, as fiber length shortening occurs during processing. Furthermore, composite plastics today contain a large amount of additives which remain on the fibres and cannot be washed off completely with water. In these cases, the method according to JP 2000034363 a then also does not provide high-quality recycled fibers.

Finally, for optimal function, glass-based reinforcing fibers require good compatibility of the glass fiber surface with the polymer matrix, which is typically achieved via a custom surface coating (also known as sizing). It has proven impossible to apply a suitable size to the dried, recycled glass fiber agglomerates as obtained according to JP 2000034363 a. The aqueous size-treated fiber agglomerates cannot be re-isolated after drying and are in a feedable form. In any case, the quality of the new glass fibers cannot be obtained using the method described in JP 2000034363 a.

JP 2000037726 a also describes a method for removing glass fibers, here chopped glass fibers, when recycling composite plastics based on polyamide 6(PA 6). JP 2000037726 a involves first depolymerizing the PA6 polymer matrix and thereby separating it from the glass fibers. JP 2000037726 a furthermore describes that it is in principle also possible to recover the glass fibers by converting the residual constituents of PA6 used as matrix polymer remaining on the fibers by pyrolysis decomposition into gaseous constituents by heating to 400 ℃ to 700 ℃ at the end of depolymerization. The temperature required for pyrolysis must be supplied to the process from an external source. JP 2000037726 a finally describes the option of subsequently heating the "cleaned" fibres in this way to a temperature above their melting temperature. This energy for melting the glass fibers must also be provided from an external source.

Neither JP 2000034363 a nor JP 2000037726 a deal with the fundamental problem of additives additionally used in plastics, their degradation products or their removal from the wash water or pyrolysis products. The latter, however, is necessary to prevent these substances, which tend to interfere with the environment, from entering the environment.

Problems to be solved by the invention

Starting from the prior art described above, the problem addressed by the present invention is to provide a method for recycling GRPs, preferably GRPs based on polyamide 6, on polybutylene terephthalate (PBT) and on polyethylene terephthalate (PET), without the use of (washing) water for cleaning the glass fibers, by means of which not only the (matrix) polymer in its monomeric form but also the glass fibers in the form of glass suitable for glass fiber production can be recycled and processed in a polymerization process/glass fiber production process to polymer/glass fibers of new quality. At the same time, the additive should be discharged efficiently from the recovery circuit without adverse effects on the environment, and the process is economical enough for large industrial scale applications and also economically viable.

It has been surprisingly found that, in contrast to the teaching of the prior art described above, it is possible to produce glass fibres of new quality from the GRP material after use, in particular from glass fibre reinforced thermoplastics based on PA6, PET or PBT, while also removing the majority of the polymer matrix by depolymerization, which can be reconstituted to give the same original polymer.

Disclosure of Invention

The solution to this problem and therefore the subject of the present invention is a method for recycling GRPs by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) the organic fraction remaining in the residue at the end of method step a) is used as an energy source to heat and melt the glass-based component by using its combustion heat and at the same time to remove the organic constituents by conversion to gaseous combustion products.

Thus, in process step a), the polymer matrix/its cleavage products are not quantitatively removed from the glass fibers.

According to the invention, "problematic components" are in particular impurities and additives for the originally intended use of the GRP.

According to the invention, the components which are problematic with regard to the recovery of GRPs are preferably functional additives, in particular UV stabilizers, heat stabilizers, gamma stabilizers, antistatics, elastomer modifiers, flow promoters, mold release agents, flame retardants, emulsifiers, nucleating agents, plasticizers, lubricants, dyes, pigments or additives for increasing the electrical conductivity. These and further additives are described, for example, inMuller, Kunststoff-Additive [ Plastic additives ]]3 rd edition, sweat Zeller Press (Hanser-Verlag), Munich, Vienna, 1989 and Plastics Additives Handbook]5 th edition, suozel press, munich, 2001. In the context of the present invention, impurities are preferably additives and degradation products of impurities, in particular dust, soil, iron oxides in the form of rust or foreign substances which have penetrated into the polymer matrix or adhered thereto.

The method according to the invention therefore consists of two separate processes, wherein the components initially used for producing GRPs are separated into monomers and cleavage products on the one hand and into a glass melt on the other hand.

The method according to the invention also makes it possible to remove the components that are problematic for the recovery, in particular impurities, and thus to produce a recyclate with the characteristics of a new material.

The process according to the invention is characterized in that, when the (matrix) polymer on which the GRP is based is resynthesized from monomers produced as cleavage products, no substantial impairment of the product quality of the polymer is caused even by repeated use-recovery cycles. In the process according to the invention, the polymer matrix/(matrix) polymer to be recovered is recovered to an extent of more than 50% by weight to about 80% by weight.

For the sake of clarity, it is noted that the scope of the present invention covers all reported definitions and parameters in any desired combination, either in a general sense or within a preferred range. This applies not only to the material parameters but also to any form of use and method as described in the context of the present invention. Unless otherwise indicated, the listed standards are understood to mean the versions valid at the filing date. Unless otherwise indicated, the percentages reported are weight percentages. In the context of the present invention, the terms (matrix) polymer and polymer matrix have the same definition, wherein the focus/emphasis of the term polymer matrix is on the matrix and in the term (matrix) polymer the emphasis is on the polymer.

According to Kunststoffe.de, "Begriffdefinitionef us das werkstoffche Recycling", taken from W.Hellerich, G.Harsch, E.Baur, Werkstoff-F ü hrer Kunststoffe10/2010, page 55:

https://www.kunststoffe.de/themen/basics/recycling/werkstoffliches-recycling/artikel/begriffsdefinitionen-fuer-das-werkstoffliche-recycling-1001597.html

recyclate is an inclusive term referring to a molded material/processed plastic having defined characteristics. In many cases, the recyclate is mixed with the new material. Recyclates have historically undergone a manufacturing process. Masterbatches or blends produced from two or more plastics by processing (i.e. by a manufacturing process) are not considered recyclates.

The present invention preferably relates to a process wherein the GRP to be used in process step a) is heated and the polymer matrix of the GRP is subjected to cracking in the absence of air, optionally after addition of a catalyst or depolymerization promoting aid.

The invention therefore relates to a process in which, during or after process step a), the cleavage product and/or the added auxiliary, in particular the hydrolysis or solvolysis liquid, is distilled off under reduced pressure.

The present invention preferably relates to a process for recycling GRPs, wherein in process step a) at least 50% by weight of the polymer matrix is depolymerized.

The invention particularly preferably relates to a process for recycling GRPs, wherein in process step a) at least 50% by weight and at most 80% by weight of the polymer matrix is depolymerized.

In the case where method step b) is not carried out in a furnace for glass production, method step b) is followed by a further method step c) which is the removal of the glass melt for further processing.

Method step a)

The depolymerization in process step a) is preferably carried out with the addition of auxiliaries or catalysts to promote depolymerization. Preferred catalysts which promote the depolymerization of the (matrix) polymer are bases or acids or salts thereof. Inorganic bases or inorganic acids or salts thereof are particularly preferred. Very particular preference is given to using calcium hydroxide, calcium carbonate, sodium carbonate, potassium carbonate or phosphoric acid. These catalysts, which promote the depolymerization of the (matrix) polymer, are used in concentrations ranging from 0.1 to 20% by weight, preferably in concentrations ranging from 0.5 to 10% by weight, particularly preferably in concentrations ranging from 1 to 7% by weight, based in each case on the total polymer matrix introduced in process step a).

The polymer matrix of the GRP to be used in the method according to the invention preferably essentially contains at least one polymer from the group: polyamide 6(PA6), polyamide 66(PA66), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or a copolymer of PET and PBT. Substantially preferably is understood to mean a degree of at least 70% by weight, based on the polymer matrix introduced in process step a).

The polymer matrix of the GRP to be used in the process according to the invention preferably essentially contains polyamide 6(PA6), polyamide 66(PA66), polybutylene terephthalate (PBT) or a copolymer of PBT and PET.

The polymer matrix of the GRP to be used in the process according to the invention preferably essentially contains polyamide 6(PA6) or polyamide 66(PA 66).

The polymer matrix of the GRP to be used in the process according to the invention preferably essentially contains polybutylene terephthalate (PBT) or a copolymer of PBT and PET.

In the case of PA6, epsilon-caprolactam is obtained as depolymerization product in process step a). The depolymerization in process step a) preferably enables 50 to 80% by weight of the epsilon caprolactam originally used for its production to be recovered from PA 6.

In the context of the study conducted according to the present invention, it was found that at the start of the depolymerization of GRPs based on glass fiber reinforced PA6 carried out in method step a), a high decomposition rate was achieved and little foreign matter was observed in the cleavage product. According to the invention, the preferred cleavage product in the depolymerization of PA6 carried out in process step a) is epsilon-caprolactam. Potassium or sodium carbonate in particular leads to a high yield of epsilon-caprolactam.

Prior to use in the depolymerization, the GRP component to be used in process step a) is preferably collected in a similar type of manner and is also used in process step a) in a similar type of manner. Similar types are understood to mean that the plastics to be processed are identical in their base polymers, but differ from one another in specific properties, for example flame-retardant additives. See: kunststoffe.de, "Begriffsets definition en fur das Werkstoff Recycling", taken from W.Hellerrich, G.Harsch, E.Baur, Werkstoff-fur hr Kunststoffe10/2010, page 55:

https://www.kunststoffe.de/themen/basics/recycling/werkstoffliches-recycling/artikel/begriffsdefinitionen-fuer-das-werkstoffliche-recycling-1001597.html

the GRP component to be used in process step a) is particularly preferably collected in the same type of manner and used also in process step a) in the same type of manner before being used for the depolymerization, so that the cleavage product removed in process step a) does not need to be subjected to any costly and inconvenient treatment.

In the context of the present invention, the same type is understood to mean that plastics of the same grade according to DIN EN ISO 11469/VDA 260, optionally from different raw material producers, are processed. See: kunststoffe.de, "Begriffsets definition en fur das Werkstoff Recycling", taken from W.Hellerrich, G.Harsch, E.Baur, Werkstoff-fur hr Kunststoffe10/2010, page 55:

https://www.kunststoffe.de/themen/basics/recycling/werkstoffliches-recycling/artikel/begriffsdefinitionen-fuer-das-werkstoffliche-recycling-1001597.html

prior to use in the depolymerization, the GRP component to be used in process step a) is preferably first subjected to cleaning to prevent adhering impurities from being introduced into the pyrolysis of process step a).

Prior to use in depolymerization, the GRP component to be used in process step a) is preferably comminuted into small pieces to simplify/accelerate handling, transportability and depolymerization of the (matrix) polymer. In the context of the present invention, comminution is representative of any crushing process, in particular a mechanical crushing process. The disruption process arranged upstream of step a) of the method according to the invention was studied scientifically, for example, the UNISENSOR Sensorsysteme GmbH of the project partner Calls luer (Karlsruhe) in the project Recycling von Polymer aus Schredderfraken. DE 102014111871B 1 from this project relates to a device and a corresponding method for separating one or more material fractions from at least one material flow of a free-flowing base material, preferably from pieces of recyclable plastic. The content of DE 102014111871B 1 is incorporated in its entirety into the present application.

In a further preferred variant, the comminuted fraction is ground to provide particles having a particle size of less than <10mm, particularly preferably <5mm, prior to the depolymerization in process step a). The term ground material (which is obtained by grinding plastic) as used in this context particularly preferably has a different and irregular particle size (in the range from 2 to 5 mm) and may contain dust fractions. In this respect, see: kunststoffe.de, "Begriffsets definition en fur das Werkstoff Recycling", taken from W.Hellerrich, G.Harsch, E.Baur, Werkstoff-fur hr Kunststoffe10/2010, page 55:

https://www.kunststoffe.de/themen/basics/recycling/werkstoffliches-recycling/artikel/begriffsdefinitionen-fuer-das-werkstoffliche-recycling-1001597.html

in a further preferred variant, prior to the depolymerization in method step a), the comminuted fraction is ground to provide a powder having a particle size of less than <1mm and this powder is mixed with at least one depolymerization-promoting assistant and/or catalyst.

In one embodiment, the fraction obtained from the comminution (comminuted fraction) may be subjected to further processing, if desired, before being used for the depolymerization in process step a). The metal component adhering to the (matrix) polymer can preferably be removed using an additional process step and recovered separately. In this case, a magnetic separator or an induction separator is preferably used.

The selection of the at least one depolymerization-promoting catalyst and/or auxiliary agent is preferably carried out such that these undergo residue-free combustion in process step b) to provide energy or can remain as inorganic constituents in the glass component and ultimately in the recovered glass without having a significant effect on the quality of the glass.

It is preferred when in process step a) at least 20% by weight of the original polymer matrix remains as organic residue. This remaining at least 20% by weight of the polymer matrix is used in method step b) for melting the glass-based component, preferably glass fibers, via the combustion process and the generated heat of combustion.

This is preferred when this simultaneously releases the glass-based component of the organic impurities. It is preferred when a GRP component based on an easily and rapidly depolymerizable polymer is used in process step a). In the context of the present invention, preferred easily and rapidly depolymerizable polymers are polybutylene terephthalate (PBT), polyethylene terephthalate (PET) or polyamide 6(PA 6).

In the case of GRP fractions based on PA6, the depolymerization is preferably carried out by heating at a temperature <350 ℃ in the absence of oxygen, particularly preferably in the presence of at least one basic catalyst; in this case, depolymerization may be referred to as pyrolysis.

In the case of PBT-based GRPs to be recovered, the depolymerization in process step a) is preferably carried out in the presence of water as depolymerization-promoting aid. The depolymerization of PBT-based GRPs is preferably carried out at a temperature in the range from 240 ℃ to 350 ℃. This forms terephthalic acid and 1, 4-butanediol/its dehydration product tetrahydrofuran. The depolymerization can likewise be carried out in solvolytic form in the presence of an alcohol as auxiliary, which leads to the formation of the corresponding ester.

In the case of PET-based GRPs to be recovered, the depolymerization is preferably carried out in the presence of water and/or alcohol at a temperature exceeding 280 ℃.

Preferably and in one embodiment, the cleavage product of the GRP (matrix) polymer produced in method step a) by cleavage of the polymer chain (preferably after any necessary purification, especially by distillation) is provided to a subsequent repolymerization to produce a recyclate plastic with new material characteristics. The repolymerization of the cleavage products makes it possible, in particular after an additional purification of these cleavage products, known as monomers, to reproduce the same polymers/the same plastics, in particular to produce new GRPs based on the recyclates. This process variant is preferably used in the following cases: wherein the GRP (matrix) polymer contains only few monomers and ideally only one monomer and the monomer or monomers obtained are separable and purifiable by processes established on a large industrial scale, preferably by distillation or rectification.

GRPs which are particularly preferred for the treatment by the process according to the invention are those based on PA6 as (matrix) polymer, which in turn is based on epsilon-caprolactam as monomer.

Optionally or in a preferred embodiment, the monomer/lysate produced in process step a) is sent to large industrial scale processing equipment and purified together with monomers traditionally produced by petrochemical processes, before repolymerization to produce recycled plastics. Here too, the preferred large industrial-scale processing apparatus is a distillation apparatus or a rectification apparatus.

Preferably and in a further embodiment, part of the monomer/cleavage product of the GRP (matrix) polymer produced in process step a) by cleavage of the polymer chain is also used as additional fuel for the combustion operation in process step b). This process variant is preferably used in the following cases: wherein the GRP (matrix) polymer is composed of at least two different monomers or the polymer matrix is composed of a blend of at least two different plastics or there is no post-use plastic of the same type as the feed stream. Feed streams are a given term in process engineering. This means that the reactants flow (feed) into the process, in this case, the process for recycling GRP according to the invention.

The depolymerization, depending on the type of (matrix) polymer below, is preferably understood to mean hydrolysis, solvolysis or pyrolysis/thermolysis, which can be carried out in different process engineering units.

After the addition of suitable auxiliaries/catalysts, in particular basic catalysts, the GRPs to be used according to the invention, in particular polyamide-based GRPs, are preferably heated directly (thermolysis/thermolysis) in the absence of oxygen, preferably under a nitrogen atmosphere. This is preferably done using batch reactors which, by means of temporally staggered start-ups, can supply the material for the second process step b) in a quasi-continuous manner.

In the case where the (matrix) polymer, in particular PBT or PET, is depolymerized in process step a) via superheated steam or using an alcohol, preference is given to using an autoclave. After the exposure time, the volatile constituents are distilled off, preferably under reduced pressure, and the remaining residue is transferred to process step b).

Method step b)

Process step b) is preferably carried out in a rotary kiln-see U.S. Richers, Thermitche Behandlung voninForschungszentrum Karlsruhe GmbH, Kaersi Ruhr, 1995.

It is preferred when in process step a) not more than 20% by weight of the original (matrix) polymer remains as an organic residue, which is supplied to process step b) together with the glass-based component. This organic residue is burned in method step b), wherein the heat of combustion initially heats and finally melts the glass-based component. Process step b) is preferably carried out at a temperature in the range from 1300 ℃ +/-300 ℃.

By burning the remaining organic material, impurities, additives and decomposition products remaining on the glass-based component are simultaneously removed. The oxidation of organic impurities, additives and decomposition products to CO is preferably carried out₂And water.

It is preferred when the total energy used in process step b) is generated by combustion of the organic material/residue and glass-based components introduced into process step b).

However, in one embodiment, it is preferred to use a conventional gas burner to provide the additional energy in method step b). In a preferred embodiment, these are provided asCombustion of fuel based on C₁-C₄-hydrocarbon gaseous fuels. Natural gas or biogas is preferably used for this purpose.

The additional energy supply in process step b) should preferably be used when the combustion heat of the organic material/residue or of the polymer still present in the organic residue is not sufficient to reach the melting temperature of the glass-based component and/or exceeds the usual residence time of the glass-based component in the molten state until further processing.

The combustion of the organic material/residue in process step b) is preferably carried out by supplying air, an air-oxygen mixture or pure oxygen.

Process step b) is preferably carried out directly in the melting zone of the glass fiber production plant, wherein the organic material/organic residue is burnt with additionally introduced air/oxygen. The residue obtained in step a) of the process is fed as a side stream of the main feed stream of the inorganic glass raw material mixture into the melting zone of the furnace of the glass fiber production plant or is supplied as a solid to the furnace of the glass fiber production plant, optionally after being crushed, in particular comminuted. The solid feed may be carried out alone or in admixture with the main feed stream of the glass raw material mixture.

It is likewise preferred when process step b) is carried out in a space in the vicinity of the glass fiber production plant and the glass melt resulting from process step b) is directly combined with the glass melt of the glass fiber production plant.

In the case where the glass-based component of the GRP is glass fibers, the combustion operation in process step b) also produces on the surface of the glass fibers or size to be oxidized and discharged (preferably as CO) via the combustion gases₂Forms of (d) impurities.

Impurities or decomposition products from the polymer matrix of the GRP used, which cannot be oxidized to CO in process step b)₂) Preferably via combustion gas exhaust.

Impurities, additives or decomposition products thereof can form harmful substances in process step b). These are preferably supplied together with the generated combustion gas to exhaust gas purification in which harmful substances are intercepted to comply with legislative emission regulations.

Especially in the case where the combustion of the (matrix) polymer comprising bromine-or phosphorus-containing additive residues is carried out in process step b), toxic by-products which are undesirable for humans and the environment may in principle be formed and are therefore present in the combustion gases. However, as a result of modern exhaust gas purification, it is now easy to separate these from the exhaust gas so that these substances do not enter the environment and comply with legislative emission regulations. The german federal emission control act (laws concerning protection from harmful environmental influences from air pollution, noise, vibration and similar events) stipulates an important branch of the environmental act, especially in its latest version of 12.4.2019 (BGBl I p.432) and is a regulation related to practice to protect human, animal, plant, soil, water, atmospheric and cultural assets from infestations and emissions of immutable substances.

In one process variant of process step b), the organic (matrix) polymer adhering to the glass-based component, preferably the glass fibers, is initially pyrolyzed at elevated temperature and then the heat of combustion of the carbonization residue adhering to the glass components/glass fibers is used together with the heat of combustion of the pyrolysis gases and/or pyrolysis oil produced to melt the glass components/glass fibers.

It is particularly preferred to introduce the pyrolysis gases produced in process step b) at another point in the melting operation in the process according to the invention. It is also preferred that the pyrolysis gas is mixed directly with natural gas which is preferably used for the melting operation in process step b). This process variant makes it possible, even after complete depolymerization of the (matrix) polymer in process step a), to provide sufficient combustion heat in process step b) to melt the glass-based component, preferably glass fibers, and to maintain them at the melting temperature until further processing.

In the case where process step b) is carried out directly and immediately in the melting zone of a glass fiber production plant, it is preferred to use conventional glass fiber additives, in particular SiO₂、Al₂O₃、MgO、B₂O₃CaO is introduced into the glass/substrate resulting from step a) of the processIn the composition of matter residue.

Method step c)

If method step b) is not carried out in the glass production furnace or in the vicinity of its space, removal of the glass melt for subsequent further processing takes place in method step c).

It is preferred when the glass melt produced in method step c) is provided for the production of glass fibers or for the production of glass frits or glass spheres. It is particularly preferred when the glass components produced in process step c) are supplied to a conventionally operated furnace for producing glass fibers in order then to be available for re-spinning into glass fibers.

Since virtually all impurities are concentrated in the organic residue at the end of method step a) and are discharged in the form of combustion gases via a subsequent combustion process in method step b) and are thus removed from the glass constituents, the method according to the invention makes it possible to produce a high-quality glass melt, from which, in turn, a high-quality glass recyclate, in particular in the form of glass fibers, ground glass or glass frits, can be produced in a further processing step.

In the preferred case where the depolymerization/pyrolysis of the polymer matrix in process step a) reaches a level of no more than 80% by weight of the original GRP matrix, sufficient organic material remains on the glass component, the combustion of which provides sufficient heat of combustion to melt the glass-based components of the GRP, preferably the glass fibers, and provide it to mechanical recycling. Oxidation of impurities, additives and decomposition products remaining on the glass-based component to CO during combustion using no more than 20% by weight of the organic material remaining from the original (matrix) polymer₂And thus removed.

Detailed Description

The invention relates in particular to a method for recycling GRP by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of process step a) as an energy source, the glass-based component is heated and melted by using its heat of combustion and at the same time the organic constituents are removed by conversion to gaseous combustion products, provided that the polymer matrix is a copolymer based on polyamide 6(PA6), on polyamide 66(PA66), on polybutylene terephthalate (PBT) or on PBT and PET.

The invention relates in particular additionally to a method for recycling GRPs by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) the organic fraction remaining in the residue at the end of process step a) is used as an energy source to heat and melt the glass-based component by using its heat of combustion and at the same time to remove the organic constituents by conversion to gaseous combustion products, provided that the polymer matrix is based on polyamide 6(PA6) or on polyamide 66(PA66), in particular PA 6.

The invention also relates in particular to a method for recycling GRP by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of process step a) as an energy source, the glass-based component is heated and melted by using its heat of combustion and at the same time the organic constituents are removed by conversion to gaseous combustion products, provided that the polymer matrix is polybutylene terephthalate (PBT) based or a copolymer based on PBT and PET.

The invention also relates in particular to a method for recycling GRP by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of method step a) as an energy source, heating and melting the glass-based component by using its combustion heat and simultaneously removing the organic constituents by conversion to gaseous combustion products, and

c) separating the glass melt for further processing

With the proviso that the polymer matrix is a copolymer based on polyamide 6(PA6), on polyamide 66(PA66), on polybutylene terephthalate (PBT) or on PBT and PET.

The invention further relates in particular to a method for recycling GRPs by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of method step a) as an energy source, heating and melting the glass-based component by using its combustion heat and simultaneously removing the organic constituents by conversion to gaseous combustion products, and

c) separating the glass melt for further processing

Provided that the polymer matrix is based on polyamide 6(PA6) or on polyamide 66(PA66), in particular PA 6.

The invention relates finally, in particular, to a method for recycling GRPs by:

a) depolymerizing a polymer matrix of up to 80% by weight of GRP, removing a cleavage product resulting from the polymer matrix and enriching a remaining residue in a mixture of glass-based components, residual matrix, monomers, cleavage product and components for recovery of the problem, and

b) using the organic fraction remaining in the residue at the end of method step a) as an energy source, heating and melting the glass-based component by using its combustion heat and simultaneously removing the organic constituents by conversion to gaseous combustion products, and

c) separating the glass melt for further processing

With the proviso that the polymer matrix is based on polybutylene terephthalate (PBT) or on a copolymer of PBT and PET.

Examples of the invention

150g was obtained from the company Limited liability of Langshan GermanyBKV30H2.0 the resulting comminuted GRP was melted in a metal bath (T320 ℃) in a 500mL round-bottomed flask in a glass apparatus with KPG stirrer (blade stirrer and torque measurement). Based on the used plastic, 5% potassium carbonate was added as a finely powdered depolymerization catalyst.

The melting process is carried out statically and is only stirred periodically (approximately every 5 minutes), about 2 to 3 revolutions. Melting of 150g of the comminuted GRP was completed after about 40 minutes.

Under slow stirring at 12 revolutions per minute (rpm), the internal pressure was reduced in 50 mbar steps to 20 to 30 mbar and considerable foam development was observed.

The polyamide 6 starting material caprolactam was converted into a gaseous state and the whole apparatus was continuously heated using a hot air blower so that this monomer having a melting point of 68 ℃ did not become a solid state and caused clogging in the apparatus.

The following fractions of caprolactam shown in table 1 were obtained:

TABLE 1

Flask	Duration (min)	Quantity (g)
			1	32	43.14
2	25	40.34
			3	44	39.42
Sum of	101	82.90
			Yield of		79％

Caprolactam fractions 1 to 3 were analyzed by gas chromatography. The purity decreases from fraction 1 to fraction 3 but in each case proves to be suitable for repolymerization by hydrolytic polymerization. The proportion of caprolactam in these fractions is more than 99.5% by weight.

The residue remaining after depolymerization was divided into portions and transferred to a glass boat, which was surrounded by pure oxygen in a muffle furnace, ignited using a bunsen burner and burned without further heating.

At the end of the combustion process, the glass residue is separated off, dried and homogenized at 115 ℃ according to DIN 52331. These samples were then subjected to ICP-OES analysis.

Except for the measured CuO concentration (due to the use ofGraded thermal stability) withBKV30H2.0, there is no significant deviation in the glass composition of the glass residue as compared to the glass fibers used in the process.