Process for the preparation of 1,2-cyclohexanedicarboxylic acid dialkyl esters

Abstract

The subject of this invention is a method for preparing dialkyl 1,2-cyclohexanedicarboxylate, which is achieved by cyclohydrogenation of the corresponding dialkyl phthalate with a CO value of less than 0.1 mg KOH / g. The subject of this invention also concerns the use of the 1,2-cyclohexanedicarboxylate thus prepared as a plasticizer, particularly for PVC, or as a component of plasticizer compositions.

Description

[0001] This invention relates to a method for preparing dialkyl 1,2-cyclohexanedicarboxylate, which is achieved by cyclohydrogenation of the corresponding dialkyl phthalate with a CO value less than 0.1 mg KOH / g. The subject matter of this invention is also the use of the 1,2-cyclohexanedicarboxylate thus prepared as a plasticizer, or a component of a plasticizer composition, for plastics, particularly PVC.

[0002] Plasticizers are used in many industrial sectors to make plastics such as polyvinyl chloride (PVC) softer and more flexible. Phthalate esters, the diesters of (o)phthalic acid, have been the dominant class of plasticizers for many years. However, in recent years, the importance of alkyl esters of cyclohexanedicarboxylic acid has also increased, largely due to discussions about the potential health problems associated with phthalate-based plasticizers. Dialkyl esters of 1,2-cyclohexanedicarboxylic acid, in particular, have played a major role, while dialkyl esters of 1,4-cyclohexanedicarboxylic acid have also gained increasing attention in recent years.

[0003] Dialkyl esters of 1,2-, 1,3-, and 1,4-cyclohexanedicarboxylic acid can be prepared by hydrogenation (hereinafter referred to as cyclohydrogenation) of the aromatic rings of the corresponding phthalates, isophthalates, or terephthalates. Such cyclohydrogenation reactions have been industrialized on a large scale in some cases, such as for the production of DINCH, the diisononyl ester of 1,2-cyclohexanedicarboxylic acid.

[0004] The reaction rate of cyclohydrogenation is a key factor in the economics of this method, as it affects both investment and operating costs.

[0005] Therefore, the object of the present invention is to provide a method for preparing dialkyl 1,2-cyclohexanedicarboxylate that maintains a high hydrogenation rate, thereby improving the productivity of the hydrogenation process. Furthermore, catalyst deactivation should be reduced.

[0006] Surprisingly, it has now been found that dialkyl phthalates with alkyl groups having 8 or 9 carbon atoms can be hydrogenated more easily and rapidly when their carbonyl values ​​(CO values) do not exceed a certain threshold. Therefore, using the corresponding dialkyl phthalates in cyclohydrogenation increases productivity and thus the economics of the method. Furthermore, the amount of components that deactivate the hydrogenation catalyst is reduced, thereby allowing the catalyst activity to remain at a high level for a longer period.

[0007] Therefore, the method of the present invention is a method for preparing dialkyl 1,2-cyclohexanedicarboxylate, wherein the two alkyl groups in the dialkyl 1,2-cyclohexanedicarboxylate each have 8 or 9 carbon atoms, and wherein the method includes at least the following steps: a) Preparation of dialkyl phthalate, wherein phthalic anhydride or dimethyl phthalate is reacted with a C8 or C9 alcohol, and a portion of a low-boiling phase distilled under negative pressure of 500 to 900 mbar absolute pressure during the reaction is discharged, said low-boiling phase comprising at least unreacted alcohol and reaction byproducts. b) Cyclohydrogenating the dialkyl phthalate generated in step a) with a hydrogen-containing gas in the presence of a heterogeneous hydrogenation catalyst, wherein the two alkyl groups in the dialkyl phthalate each have 8 or 9 carbon atoms, to generate the corresponding dialkyl 1,2-cyclohexanedicarboxylate, characterized in that: The dialkyl phthalate used in the cyclohydrogenation of step b) has a CO value of less than 0.1 mg KOH / g, preferably less than 0.08 mg KOH / g, more preferably less than 0.07 mg KOH / g, and particularly preferably less than 0.01 mg KOH / g.

[0008] CO esters are defined as milligrams of KOH equivalent to the amount of hydroxylamine required to oxime 1 gram of a substance. The CO value is determined by reacting a substance dissolved in a carbonyl-free alcohol with excess hydroxylamine to form the corresponding oxime, and then back-titering the unconsumed hydroxylamine with hydrochloric acid.

[0009] To determine the CO value, the equivalence point must first be established using calibration solutions. For this purpose, calibration solutions containing varying amounts of cyclohexanone are prepared in a suitable solvent, such as carbonyl-free methanol. The theoretical CO value is given by the following formula: .

[0010] The prepared calibration solutions were titrated with 0.1 mol / L hydrochloric acid. The measured pH values ​​were then plotted against the respective hydrochloric acid consumption curves, and the equivalence points were determined. The system was then calibrated using these methods.

[0011] The determination of the CO value of an unknown sample can be performed as follows. First, a suitable amount of sample is pre-loaded into a reaction vessel and dissolved in 50 mL of a suitable solvent, such as carbonyl-free methanol. A blank value determination without the sample must be performed beforehand using the solvent, such as methanol, as described below. Bromophenol blue is added to the sample solution in the solvent, such as methanol, and the pH is adjusted, if necessary, by adding hydrochloric acid or sodium hydroxide solution to make the solution greenish-yellow (corresponding to a pH of approximately 3). Then, 20 mL of hydroxylamine solution (c = 0.24 mol / L) is added, and the resulting solution in the reaction vessel is refluxed and boiled for 1 hour.

[0012] After cooling to room temperature, rinse the reflux condenser with 10 mL of solvent, such as carbonyl-free methanol, and then titrate the reaction solution with 0.1 mol / L hydrochloric acid until the equivalence point.

[0013] The CO value can then be calculated using the following formula: Where V B V represents the amount of hydrochloric acid consumed (ml) in the blank value determination. H F represents the amount of hydrochloric acid consumed (ml) in the sample to be analyzed. HCl c is the titer of hydrochloric acid. HCl M is the concentration of hydrochloric acid (mol / L). KOH Given that the molar mass of KOH is 56.11 g / mol, E p The value is the sample weight (g).

[0014] The cyclohydrogenation can proceed more quickly if the CO value of the dialkyl phthalate used in step b) is less than 0.1. Among the dialkyl phthalates of 1,2-cyclohexanedicarboxylate thus prepared, in which the alkyl groups each have 8 or 9 carbon atoms, dialkyl phthalates of 1,2-cyclohexanedicarboxylate in which the alkyl group is 2-ethylhexyl or isononyl are preferred. Further preferred are dialkyl phthalates of 1,2-cyclohexanedicarboxylate in which the two alkyl groups have the same number of carbon atoms. Therefore, di-2-ethylhexyl phthalate or diisononyl phthalate is preferred, as they produce di-2-ethylhexyl phthalate or diisononyl phthalate (DINCH) during cyclohydrogenation. Particularly preferred is that the product generated during cyclohydrogenation according to the invention is diisononyl phthalate (DINCH).

[0015] To obtain the corresponding dialkyl phthalate for cyclohydrogenation in step b), the preparation method according to step a) of the present invention is used. Here, the preparation of the dialkyl phthalate is achieved by reacting phthalic anhydride or dimethyl phthalate with a C8 or C9 alcohol and removing a portion of the low-boiling phase distilled under negative pressure at an absolute pressure of 500 to 900 mbar during the reaction. This low-boiling phase contains at least unreacted alcohol and reaction byproducts. Removing the reaction byproducts ensures a reduction in CO value.

[0016] The preparation of the dialkyl phthalate of the present invention by esterification of phthalic anhydride with an alcohol or mixture of alcohols having 8 or 9 carbon atoms can be carried out by all known methods. However, esterification is preferably carried out by removing the reaction water by azeotropic distillation with the alcohol, and replenishing all or part of the liquid volume removed from the reaction by azeotropic distillation with the alcohol used. Hereinafter, liquid volume refers to the volume of liquid removed from the reaction by azeotropic distillation, which consists mainly of reaction water and alcohol. It is preferred that the removed liquid volume is fully compensated.

[0017] The esterification of phthalic anhydride to produce dialkyl phthalates can be carried out according to the present invention by autocatalysis, acid catalysis, or base catalysis. The esterification catalyst used can be a Lewis acid, a Brønsted acid, or an organometallic substance. Preferred esterification catalysts are alkoxides, sulfonic acids, carboxylates, or chelates of titanium or zirconium, wherein the catalyst molecule may contain one or more metal atoms. Tetra(isopropyl) orthotitanate and tetrabutyl orthotitanate are particularly used. The catalyst concentration depends on the nature of the catalyst. For the preferred titanium compound, it is 0.005% to 1.0% by weight, particularly 0.01% to 0.3% by weight, based on the reaction mixture.

[0018] The esterification of the present invention is preferably carried out in a reaction vessel, wherein the reaction mixture is thoroughly mixed by a stirrer or a circulating pump. The reactants and catalyst may be added to the reactor simultaneously or sequentially. The catalyst may be introduced at the beginning or after the reaction temperature is reached, either in pure form or as a solution (preferably dissolved in one of the raw materials). The alcohol to be reacted, used as an azeotropic agent, may be used in stoichiometric excess. Preferably, an excess of 5% to 50%, more preferably an excess of 10% to 30%, is used, based on the amount of phthalic anhydride used.

[0019] When using a titanium catalyst, the reaction temperature in esterification is between 120°C and 270°C, preferably between 130°C and 270°C. The optimal temperature depends on the feedstock, reaction progress, and catalyst concentration. The optimal temperature for each specific condition can be easily determined experimentally. Higher temperatures will increase the reaction rate and promote side reactions, such as the elimination of water from the alcohol or the formation of colored byproducts.

[0020] The transesterification of dimethyl phthalate with C8 or C9 alcohols is also a known method, described in the prior art, for example, in WO 2009 / 095126 A1. Transesterification is typically carried out in the liquid phase. Here, dimethyl phthalate is reacted with its respective alcohol or mixture of alcohols in the presence of a suitable catalyst. The methanol generated during transesterification is preferably separated during the reaction. Since the reaction temperature is typically above the boiling point of methanol, the methanol can be readily separated as vapor.

[0021] The alcohol used in the esterification or transesterification of dialkyl phthalates is an alcohol or mixture of alcohols having 8 or 9 carbon atoms. Preferably, the alcohol used in the esterification is 2-ethylhexanol or isononol. More preferably, the alcohol is isononol. In this invention, isononol refers to a mixture of primary C9 alcohols that can be either straight-chain or branched.

[0022] The esterification or transesterification according to the invention in step a) is preferably carried out in a discontinuous manner. The preferred discontinuous operation mode here is particularly batch production. This produces a quantity limited by the reactor volume, and then the reaction is terminated. After the reactor is emptied, a new batch production can then begin.

[0023] A suitable reactor is one known to those skilled in the art for the synthesis of dialkyl phthalates. A suitable reactor particularly includes a distillation column through which the generated water or methanol, as well as any unreacted alcohols, can be separated. Preferably, the distillation column is fixedly connected to one or more reactors of the method of the present invention. In this case, the reactor appears to constitute the bottom of the distillation column. Due to the existing reaction temperature, water or methanol may have entered the gas phase during esterification or transesterification and be separated by the distillation column. The resulting loss of liquid volume can be compensated by supplying the alcohol or a mixture of alcohols used.

[0024] The temperature for the preparation of dialkyl phthalates depends on various factors, such as the reaction scheme, but is preferably between 150°C and 260°C. This temperature range is suitable for both esterification and transesterification. The pressure during esterification and transesterification is preferably between 0.5 and 10 bar absolute. The temperature and pressure are preferably adjusted so that the water or methanol produced can be separated during the reaction.

[0025] At the end of the reaction, the resulting dialkyl phthalate is present in the reaction solution, which contains, in addition to the compound produced, at least unreacted alcohol or a mixture of unreacted alcohols. Since esterification or transesterification may generate byproducts with lower boiling points than the alcohol or mixture of alcohols used, these byproducts are also typically present in the reaction solution. Possible byproducts include alkenes formed by eliminating a water group or monocarboxylic acids (esters) formed by eliminating at least one acid or ester group, which leads to an increase in CO value.

[0026] As previously mentioned, a low-boiling phase, primarily water and alcohols, is distilled off during the reaction, such as unreacted alcohols from esterification or transesterification and / or methanol. At the end of the reaction, due to the increased conversion rate, less water or methanol is generated by esterification or transesterification. This separation is assisted by applying a negative pressure of 500 to 800 mbar absolute pressure, preferably 520 to 750 mbar absolute pressure. This also has the advantage that the generated reaction byproducts are converted along with the low-boiling phase. Therefore, at least a portion of the low-boiling phase is removed, thereby reducing the amount of reaction byproducts in the (final) reaction solution.

[0027] Preferably, negative pressure is applied only when the reaction conversion reaches a threshold. In a preferred embodiment, negative pressure is applied when the reaction conversion reaches at least 92%, more preferably at least 95%. For this purpose, the reaction conversion has been monitored during the reaction. However, one or more other parameters may also be monitored during the reaction, instead of the conversion, wherein said one or more parameters may optionally be used to infer the conversion or more generally the reaction progress after prior calibration.

[0028] The application of negative pressure can be achieved by known devices or machines. An example of such a suitable device is a (vacuum) pump, which can generate negative pressure within the reactor. The temperature at which negative pressure is applied can correspond to the reaction temperature. If negative pressure is applied with a certain delay after the conversion threshold has been reached, the temperature can also be lower than the reaction temperature.

[0029] The portion of the low-boiling phase that first transforms during the distillation process (i.e., the portion of the low-boiling phase that is first distilled out when negative pressure is applied) is at least partially discharged and discarded. Based on the total amount of all distilled low-boiling phases (separated to produce crude product), the amount of the discharged portion of low-boiling phase is preferably 0.05 to 8% by weight, more preferably 0.1 to 4% by weight.

[0030] The cyclohydrogenation of dialkyl phthalate according to step b) is known in principle to those skilled in the art. This cyclohydrogenation is carried out using a hydrogen-containing gas. In principle, the hydrogen-containing gas used can be any mixture of hydrogen-containing gases that does not contain harmful amounts of catalyst poisons (e.g., carbon monoxide or hydrogen sulfide). A gas mixture containing an inert gas can also be used. The hydrogen-containing gas used is preferably hydrogen with a purity ≥95%, particularly ≥98%. The inert gas component can be, for example, nitrogen or methane. Preferably, the amount of hydrogen-containing gas used is in excess, particularly at most 200%, preferably 5% to 100%, more preferably 10% to 50%, based on the stoichiometric amount required to achieve the desired conversion rate.

[0031] In step b) of the present invention, the cyclic hydrogenation further employs a heterogeneous hydrogenation catalyst, which preferably contains at least one transition metal, more preferably a metal from Group 8 of the periodic table. The preferred transition metals are platinum, rhodium, palladium, cobalt, nickel, or ruthenium, or a mixture of two or more of these, with ruthenium being particularly preferred as the active metal. In addition to the aforementioned metals, the catalyst may also contain at least one metal from Group 7 and Group 11 of the periodic table. Rhenium and / or copper are preferred.

[0032] The content of transition metal in the hydrogenation catalyst of the present invention is preferably 0.1 to 10% by weight, particularly preferably 0.3 to 5% by weight, and most particularly preferably 0.5 to 3% by weight.

[0033] The heterogeneous hydrogenation catalyst used is preferably a supported catalyst, i.e., it contains a support material. The support material can be activated carbon, silicon carbide, alumina, silica, aluminosilicate, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, or mixtures thereof. Titanium dioxide or alumina is particularly preferred as the support material. These support materials may also contain alkali metals, alkaline earth metals, and / or sulfur.

[0034] The cyclic hydrogenation of dialkyl phthalates according to the invention is preferably carried out in at least one hydrogenation unit. A hydrogenation unit in the invention refers to a unit comprising one or more reactors, which may be connected in parallel and / or in series, i.e., the reactor or reactor assembly in which cyclic hydrogenation occurs. In a particularly preferred embodiment, cyclic hydrogenation is carried out in at least two hydrogenation units connected in series, wherein at least one of these two hydrogenation units operates in a recirculation mode, i.e., a portion of the respective hydrogenation output is returned. It may be advantageous that both of the at least two hydrogenation units in the cyclic hydrogenation are operated in a recirculation mode. It may also be advantageous that the last hydrogenation unit operates in a straight-through mode. In a particularly preferred embodiment of the invention, cyclic hydrogenation is carried out in two hydrogenation units connected in series, wherein the first hydrogenation unit operates in a recirculation mode, while the last hydrogenation unit operates in a straight-through mode.

[0035] In another embodiment, cyclic hydrogenation is carried out in at least three hydrogenation units connected in series, wherein at least the first two hydrogenation units operate in a cyclic mode. The last hydrogenation unit may also operate in a cyclic mode, corresponding to an embodiment in which all at least three hydrogenation units operate in a cyclic mode. The last hydrogenation unit may also operate in a through-flow mode.

[0036] Another particularly preferred embodiment is the parallel arrangement of reactors, such as in a tubular reactor.

[0037] At this point, each reactor can operate adiabatic, variable-temperature, or near-isothermal, meaning the temperature rise (the difference between the reactor's inlet and outlet temperatures) is typically less than 15 K. Specifically, reactors operating in recirculation mode are preferably in near-isothermal mode, meaning the temperature rise is preferably less than 15 K. For reactors operating in non-recirculation mode, the preferred temperature rise within the reactor is below 35 K, more preferably below 25 K. Cooling devices can be installed between each hydrogenation unit to reduce the temperature before entering the next hydrogenation unit.

[0038] The cyclohydrogenation of dialkyl phthalates according to the invention is preferably carried out in a three-phase reactor in a liquid / gas mixed phase or liquid phase manner, wherein the hydrogen-containing gas is distributed in the liquid reactant / product stream in a manner known per se. To obtain uniform liquid distribution, improved heat dissipation, and / or high space-time yield, the reactor operating in recirculation mode preferably passes through a flow rate of 10 to 400 m² / h of empty reactor cross-section, preferably 20 to 200 m², more preferably 40 to 150 m² / h. 3 The reactor operates at high liquid loads. The liquid loads in reactors operating in circulation mode can be the same or different. Preferably, the liquid load is highest in the first reactor and decreases in subsequent reactors operating in circulation mode. One or more reactors can be partially submerged in liquid or can function entirely as trickle bed reactors.

[0039] The cyclohydrogenation of dialkyl phthalates can be carried out in the absence of a solvent or in the presence of a solvent. The solvent used can be any liquid that forms a homogeneous solution with the reactants and products, is inert under hydrogenation conditions, and is easily separable from the product. The solvent can also be a mixture of substances and optionally contains water. The following substances can be used as solvents in cyclohydrogenation: straight-chain or cyclic ethers, such as tetrahydrofuran or dioxane, and aliphatic alcohols with alkyl groups containing 1 to 13 carbon atoms. Preferred alcohols as solvents include isopropanol, n-butanol, isobutanol, n-pentanol, 2-ethylhexanol, nonanol, mixtures of industrial nonanol, decanol, mixtures of industrial decanol, and tridecanol. When using an alcohol as a solvent, it may be suitable to use the alcohol or mixture of alcohols that will be generated during the saponification of the product. This excludes byproducts generated due to transesterification. Another preferred solvent is the hydrogenation product itself.

[0040] By using solvents, the reactant concentration in the reactor feed can be limited, thereby enabling better temperature control within the reactor. This minimizes side reactions and thus increases product yield. The reactant content in the reactor feed is preferably between 1% and 70%. In reactors operating in recirculation mode, the desired concentration range can be adjusted by the recirculation ratio (the ratio of returned hydrogenation output to reactants). The reactant concentration in the reactor feed is preferably reduced from the first reactor to the last.

[0041] Another possible method for temperature control is to dilute the hydrogen-containing gas used for hydrogenation, particularly hydrogen, with an inert gas. The inert gas can be selected from nitrogen, helium, neon, argon, carbon dioxide, and mixtures thereof. Nitrogen or carbon dioxide is preferred because they are the most readily available and inexpensive. More preferably, nitrogen is used as the inert gas in the method of the present invention. By diluting the hydrogen-containing gas used for hydrogenation, the reaction can be slowed down, thereby controlling the temperature. This method is also suitable for starting the reactor after catalyst installation or regeneration when a suitable solvent is unavailable.

[0042] The cyclohydrogenation of dialkyl phthalates according to the present invention is preferably carried out in a pressure range of 3 to 300 bar, particularly preferably 15 to 200 bar, and most preferably 50 to 200 bar. The pressures in the individual reactors may be the same or different. Preferably, these pressures are the same or approximately the same, i.e., differing from each other by a maximum of 10%.

[0043] The hydrogenation temperature for cyclic hydrogenation is preferably 50 to 250°C, more preferably 80 to 200°C. The hydrogenation temperatures in each reactor may be the same or different.

[0044] The product obtained by the method of the present invention is a corresponding composition, which depends on the feedstock and the conversion rate during hydrogenation. The composition generated during the cyclohydrogenation of the present invention preferably has a content of more than 96% by weight, particularly more than 98% by weight, and more preferably more than 99% by weight of dialkyl 1,2-cyclohexanedicarboxylate. This mixture can be used directly or after purification. Byproducts can be separated, for example, by distillation or by stripping with steam or an inert gas (e.g., nitrogen). Small amounts of low-boiling substances are preferably separated by steam stripping in the temperature range of 120°C to 240°C, particularly preferably in the range of 150°C to 200°C, and preferably at a pressure of 0.05 to 0.1 bar.

[0045] Dialkyl 1,2-cyclohexanedicarboxylates having 8 or 9 carbon atoms in each of the two alkyl groups according to the present invention can be advantageously used as plasticizers or components of plastic compositions, as additives in inks or paints, as adhesives or as components of adhesives, as solvents in sealants.

[0046] The prepared dialkyl 1,2-cyclohexanedicarboxylate can also be used as a plasticizer in the form of a mixture with other plasticizers, especially so-called fast-setting agents. The proportion of the 1,2-cyclohexanedicarboxylate of the present invention in a mixture with other plasticizers is preferably 15 to 95% by weight, more preferably 20 to 90% by weight, and most preferably 25 to 85% by weight, wherein the sum of the proportions of all present plasticizers is 100% by weight. Compositions consisting of dialkyl 1,2-cyclohexanedicarboxylate and other plasticizers can be used as plasticizer compositions in plastics and plastic compositions, adhesives, sealants, paints, inks, plastisols, or inks.

[0047] Plastic compositions comprising 1,2-cyclohexanedicarboxylate may contain polymers selected from: polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyacrylates, particularly polymethyl methacrylate (PMMA), polyalkyl methacrylate (PAMA), fluoropolymers, particularly polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyvinyl acetal, particularly polyvinyl butyral (PVB), polystyrene polymers, particularly polystyrene (PS), expandable polystyrene (EP). S), acrylonitrile-styrene acrylate (ASA), styrene-acrylonitrile (SAN), acrylonitrile-butadiene-styrene (ABS), styrene-maleic anhydride copolymer (SMA), styrene-methacrylic acid copolymer, polyolefins, especially polyethylene (PE) or polypropylene (PP), thermoplastic polyolefins (TPO), polyethylene-vinyl acetate (EVA), polycarbonate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyoxymethylene (POM), polyamide (PA), polyethylene glycol (PEG), polyurethane (PU), thermoplastic polyurethane (TPU), polysulfide (PSu), biopolymers, especially polylactic acid (PLA), polyhydroxybutyric acid (PHB), polyhydroxyvalerate (PHV), polyesters, starch, cellulose and cellulose derivatives, especially nitrocellulose (NC), ethyl cellulose (EC), cellulose acetate (CA), cellulose acetate / butyrate (CAB), rubber or silicone, and mixtures or copolymers of the above polymers or their monomer units. The compositions of the present invention preferably comprise PVC or homopolymers or copolymers of ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, methacrylate, acrylates, branched or unbranched alcohols having one to ten carbon atoms, acrylates or methacrylates having an alkyl group bonded to the oxygen atom of the ester group, styrene, acrylonitrile, or cyclic olefins.

[0048] Polyvinyl chloride (PVC) is especially preferred.

[0049] The PVC type contained in the plastic composition of the present invention is preferably suspension PVC, bulk PVC, micro-suspension PVC, or emulsion PVC. The composition of the present invention preferably contains 5 to 200, more preferably 10 to 150 parts by weight of the plasticizer of the present invention, based on 100 parts by weight of polymer.

[0050] In addition to the above-mentioned components, the plastic composition may also contain other components, particularly such as further plasticizers, fillers, pigments, stabilizers, co-stabilizers (e.g., epoxidized soybean oil), lubricants, foaming agents, accelerators, antioxidants, rheology modifiers, or bactericides.

[0051] The plastic composition of the present invention, consisting of dialkyl 1,2-cyclohexanedicarboxylate and the above-mentioned polymer material, can be used as a plastic composition, adhesive, sealant, paint, ink, plastisol, artificial leather, floor covering, chassis protection, fabric coating, roofing film, wallpaper or ink, or for the production of the above products.

[0052] Plastic products made from plasticizer compositions can include, for example, profiles, seals, food packaging, films, toys, medical products, roofing panels, artificial leather, floor coverings, chassis protection, coated fabrics, roofing membranes, wallpaper, and cable and wire sheaths. Preferred applications in this class include food packaging, toys, medical products, wallpaper, roofing membranes, fabric coatings, and floor coverings.

[0053] The present invention is illustrated below by way of examples. These examples are merely selected embodiments and do not constitute any limitation.

[0054] Example 1: Cyclohydrogenation of diisononyl phthalate (DINP) The cyclohydrogenation of DINP was experimentally performed, in which the DINP conversion over time was measured. The following DINP samples were tested for this purpose.

[0055] DINP-1 is a Vestinol® 9 product from Evonik Oxeno GmbH & Co. KG. The CO value was determined according to the method given in the instructions and was 0.006 mg KOH / g.

[0056] DINP-2 is a product of a South Korean company. The CO value, determined according to the method given in the instructions, is 0.048 mgKOH / g.

[0057] DINP-3 is a Kanatol-900 product from the Indian KLJ Group. The CO value, determined according to the method given in the instructions, is 0.15 mg KOH / g.

[0058] Cyclohydrogenation of DINP samples Various DINP samples (diisononyl phthalate) were subjected to batch hydrogenation in a tubular reactor with an inner diameter of 40 mm and a length of 250 mm using a circulating operation. Here, the liquid and gas phases flowed concurrently through the tubular reactor in a trickle bed. The catalyst used in hydrogenation was a shell-type catalyst consisting of 1% Ru supported on titanium dioxide (Aerolyst 7711, Evonik Operations GmbH). A mixture consisting of 25 g of hydrogenation catalyst and 25 g of inert material (composed of γ-Al₂O₃, Axens Spheralite 538E) was used in the tubular reactor, each in the form of a 1.5 mm extrusion. The amount of DINP used in hydrogenation was consistently 1000 g. H₂ was regulated using an exhaust gas operation mode, where a constant exhaust gas flow rate of 1 L / h (47.8 m³) was set. 3 m -2 h -1 All experiments were conducted at a device pressure of 90 bar and a tubular reactor temperature of 110°C. After passing through a heat exchanger below the reactor, gas-liquid separation was performed via a separator. The gas phase was continuously released into the exhaust gas. Over an 8-hour period, the liquid phase was consistently returned to the tubular reactor via a heated preheater. The reaction progress within the reactor (DINP conversion over time) was recorded using online Raman spectroscopy.

[0059] The results are shown in Table 1 below.

[0060] Table 1: Conversion rate (%) of DINP to DINCH over time .

[0061] As can be seen from the table, cyclohydrogenation proceeds significantly faster when using DINP (DINP-1 and DINP-2) with CO values ​​within the required protection range.

Claims

1. A method for preparing a dialkyl 1,2-cyclohexanedicarboxylate, wherein each of the two alkyl groups has 8 or 9 carbon atoms, wherein the method comprises at least the following steps: a) Preparation of dialkyl phthalate, wherein phthalic anhydride or dimethyl phthalate is reacted with a C8 or C9 alcohol, and a portion of a low-boiling phase distilled under negative pressure of 500 to 900 mbar absolute pressure during the reaction is discharged, said low-boiling phase comprising at least unreacted alcohol and reaction byproducts. b) Cyclohydrogenating the dialkyl phthalate generated in step a) with a hydrogen-containing gas in the presence of a heterogeneous hydrogenation catalyst, wherein the two alkyl groups in the dialkyl phthalate each have 8 or 9 carbon atoms, to generate the corresponding dialkyl 1,2-cyclohexanedicarboxylate, characterized in that: The dialkyl phthalate used in the cyclohydrogenation of step b) has a CO value of less than 0.1 mg KOH / g, preferably less than 0.08 mg KOH / g, more preferably less than 0.07 mg KOH / g, and particularly preferably less than 0.01 mg KOH / g.

2. The method according to claim 1, wherein the two alkyl groups of the 1,2-cyclohexanedicarboxylic acid dialkyl ester are 2-ethylhexyl or isononyl, respectively.

3. The method according to claim 2, wherein the dialkyl 1,2-cyclohexanedicarboxylate is diisononyl 1,2-cyclohexanedicarboxylate or di-2-ethylhexyl 1,2-cyclohexanedicarboxylate.

4. The method according to any one of claims 1 to 5, wherein the heterogeneous hydrogenation catalyst used in the cyclohydrogenation comprises a transition metal on a support material.

5. The method according to claim 4, wherein the transition metal is a Group 8 (iron group) metal of the periodic table, preferably ruthenium.

6. The method according to claim 4, wherein the carrier material is selected from activated carbon, silicon carbide, alumina, silicon dioxide, aluminosilicate, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, or mixtures thereof.

7. The method according to claim 6, wherein the carrier material is titanium dioxide or aluminum oxide.

8. The method according to any one of claims 4 to 7, wherein the transition metal content in the heterogeneous hydrogenation catalyst is 0.1% to 10% by weight, preferably 0.3% to 5% by weight, and especially 0.5% to 3% by weight.

9. The method according to any one of the preceding claims, wherein cyclic hydrogenation is carried out in at least one hydrogenation unit, preferably in at least two hydrogenation units in series, wherein at least one of the at least two hydrogenation units operates in a cyclic mode.

10. The method according to any one of the preceding claims, wherein the hydrogenation temperature in the cyclohydrogenation is 50 to 250°C.

11. The method according to any one of the preceding claims, wherein the cyclohydrogenation is carried out in a pressure range of 3 to 300 bar.

12. Use of the 1,2-cyclohexanedicarboxylic acid dialkyl ester prepared according to any one of claims 1 to 11 as a plasticizer or a component of a plasticizer composition in plastics or plastic compositions.

13. The use of the 1,2-cyclohexanedicarboxylic acid dialkyl ester prepared according to any one of claims 1 to 11 as an additive in inks or paints, adhesives or adhesive components, sealants, or as a solvent.

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