Tetraisopentyl esters of butanetetracarboxylic acid, production thereof and use thereof as plasticizers

Abstract

To provide an alternative to phthalic esters, which are important as plasticizers or plasticizer compositions for improving the processability of plastics or polymers.SOLUTION: There is provided a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, wherein 6 to 12 mol% of the isopentyl groups in the mixture are 2-methylbutyl groups, 88 to 94 mol% of the isopentyl groups in the mixture are n-pentyl groups and 0 to 4 mol% of the isopentyl groups in the mixture are 3-methylbutyl groups.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a tetraisopentyl ester of butanetetracarboxylic acid, its preparation, and its use as a plasticizer or part of a plasticizer composition for polymers. Also disclosed are a plasticizer composition comprising the tetraisopentyl ester of butanetetracarboxylic acid and a plastic composition comprising the tetraisopentyl ester of butanetetracarboxylic acid. [Background technology]

[0002] In many fields, plasticizers or plasticizer compositions are added to plastics or polymers to improve their processability and / or to adapt their properties relevant to their application. Due to their advantageous properties, the phthalate class of compounds, in particular diethylhexyl phthalate (DEHP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), remains one of the most important plasticizers for plastics and polymers, especially PVC and copolymers containing vinyl chloride. The possible toxicological effects of this class of substances have been debated, and replacements for phthalate plasticizers have been sought for many years.

[0003] As alternative plasticizers, various compounds have been discussed, such as alkyl esters of butanetetracarboxylic acid, which are known to the skilled artisan, for example from US Pat. No. 5,399,363. The alkyl esters of butanetetracarboxylic acid disclosed therein have a maximum proportion of 40% alkyl groups branched at the beta position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2011 / 0257317 Summary of the Invention [Problem to be solved by the invention]

[0005] For the tetraisopentyl ester of butanetetracarboxylic acid, it was surprisingly found that a specific molar ratio of 2-methylbutyl groups based on the total isomeric pentyl groups results in improved properties.The problem solved by the present invention was therefore to provide a tetraisopentyl ester of butanetetracarboxylic acid having improved properties. [Means for solving the problem]

[0006] The problem of the present application is solved by a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to claim 1. Preferred embodiments are specified in the dependent claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In the context of the present invention, the terms "iso-pentyl", "iso-pentyl group", etc. are used. This emphasizes that the esters according to the invention include various pentyl isomers, in particular 2-methylbutyl and / or 3-methylbutyl and / or n-pentyl. The terms "iso-pentyl", "iso-pentyl group", etc. should therefore be understood to be synonymous with the term "pentyl" and do not indicate a single specific C5-alkyl group.

[0008] The present invention therefore relates to a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, in which 6-12 mol% of the iso-pentyl groups are 2-methylbutyl groups, 88-94 mol% of the iso-pentyl groups are n-pentyl groups, and 0-4 mol% of the iso-pentyl groups are 3-methylbutyl groups. The percentages in each case refer to the sum of the iso-pentyl groups in the mixture. A preferred embodiment of the present invention provides a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, in which 6-10 mol% of the iso-pentyl groups are 2-methylbutyl groups, 90-94 mol% of the iso-pentyl groups are n-pentyl groups, and 0-2 mol% of the iso-pentyl groups are 3-methylbutyl groups. A particularly preferred embodiment of the present invention provides a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, wherein 7-9 mol % of the iso-pentyl groups are 2-methylbutyl groups, 91-93 mol % of the iso-pentyl groups are n-pentyl groups, and 0-2 mol % of the iso-pentyl groups are 3-methylbutyl groups.

[0009] It is clear that the mixtures according to the invention, in which 6-12 mole % of the iso-pentyl groups are 2-methylbutyl groups, are practically as good as the mixtures containing only n-pentyl groups. However, the advantage of the present application is that the effluent of the hydroformylation of butenes and the subsequent hydrogenation can be used for the preparation of ester mixtures. In order to obtain pure n-pentyl esters, this product must be subjected to a complex and expensive distillation to obtain n-pentanol, after which the esters are prepared using pure n-pentanol. According to the invention, it is preferred that there are as few 3-methylbutyl residues as possible in the mixture, so preferably less than 1 mol % of the iso-pentyl groups in the mixture are 3-methylbutyl groups, particularly preferably less than 0.5 mol % of the iso-pentyl groups in the mixture are 3-methylbutyl groups.

[0010] The mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to the invention can be prepared by esterifying 1,2,3,4-butanetetracarboxylic acid with a suitable isopentanol mixture. In this context, an isopentanol mixture should be understood to mean one that contains at least 2-methylbutanol and n-pentanol and / or 3-methylbutanol. Of course, during the esterification, it should be ensured that the mixture contains sufficient 2-methylbutanol to obtain the required amount of 2-methylbutyl groups in the ester formed. It is well known that the selection of a suitable isopentanol mixture is carried out by reaction and analysis of the ester formed.

[0011] The esterification is preferably carried out in the presence of a catalyst.In principle, any known catalyst system suitable for esterification can be used for this purpose.The catalyst suitable for esterification to produce the tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid according to the present invention is a titanate catalyst, such as tetra-n-butyl titanate, tetra-n-butyl zirconate or tetra-n-butyl sulfonate. The esterification for producing the esters according to the invention is preferably carried out at temperatures between 120°C and 250°C, more preferably between 140°C and 230°C, particularly preferably between 160°C and 215°C. The pressure during the esterification should preferably not be too high, as this increases the boiling point and therefore the esterification temperature, which increases the formation of by-products. The pressure during the esterification is therefore not more than 3 bar absolute, particularly preferably not less than 0.5 bar. During esterification, water is produced by the reaction of the acid groups with the alcohol, also called water of reaction. In a preferred embodiment of the invention, at least a portion of the reaction water formed is separated during the course of the reaction, which makes it possible, inter alia, to shift the equilibrium of the reaction in the right direction. The progress of the esterification reaction can be monitored by monitoring a parameter, for example the acid number or the amount of water. It can also be monitored by gas chromatography, which measures the reactant and / or product ratios. Here, online analytical techniques, such as for example NIR spectroscopy, can also be used.

[0012] Once the reaction has progressed to a sufficient extent, it can be stopped. This can be done, for example, by adding a base such as aqueous sodium hydroxide. The catalyst is usually destroyed in the process, as is well known to those skilled in the art. The reaction solution can then be purified by known methods, for example by means of thermal separation.

[0013] The mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to the invention exhibits advantageous properties when used as plasticizers for polymers. It is therefore a further object of the invention to use the mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, in particular the tetra-3-methylbutyl ester of 1,2,3,4-butanetetracarboxylic acid, as plasticizers for polymers. Suitable polymers are described below, preferably PVC or vinyl chloride-containing copolymers. The present invention also provides a plasticizer composition that contains, in addition to the mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, further plasticizers. Depending on the intended use, the plasticizer composition may contain one or more further plasticizers, which are in particular different from the inventive mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, in order to specifically adjust the properties of the resulting plasticizer composition. However, in a particularly preferred embodiment, the plasticizer composition contains less than 5% by weight, more preferably less than 0.5% by weight, particularly preferably less than 0.1% by weight, of phthalic acid esters, i.e. esters of orthophthalic acid.

[0014] Further plasticizers in the plasticizer composition of the present invention may be selected from the group consisting of adipates, benzoates, such as monobenzoates or glycol dibenzoates, chlorinated hydrocarbons (so-called chlorinated paraffins), citrates, cyclohexanedicarboxylates, epoxidized fatty acid esters, epoxidized vegetable oils, epoxidized acylated glycerides, furandicarboxylates, phosphates, succinates, sulfonamides, sulfonates, terephthalates, trimellitates, and oligomeric or polymeric esters based on adipic acid, succinic acid or sebacic acid. In a preferred embodiment of the invention, the plasticizer composition comprises a further plasticizer selected from the group consisting of alkyl benzoate esters, alkyl sulfonate esters of phenols, dialkyl adipates, glycerol esters, C4-C6 acids of polyols, trialkyl citric acid esters, acetylated trialkyl citric acid esters, glycol dibenzoates, trialkyl esters of trimellitic acid, dialkyl terephthalates, dialkyl phthalates, dialkyl isophthalates, esters of furandicarboxylic acid, dialkanoyl esters of dianhydrohexitols (e.g. isosorbide), epoxidized fatty acid alkyl esters, polymeric plasticizers such as polyadipates, and dialkyl esters of 1,2-, 1,3- or 1,4-cyclohexanedicarboxylic acid. In a further preferred embodiment, the further plasticizer comprised in the plasticizer composition is selected from the group consisting of C8-C13 alkyl benzoates, C4-C10 dialkyl adipates, pentaerythritol tetravalerate, acetylated trialkyl citric acid esters with C4-C9 alkyl groups, C4-C10 trialkyl trimellitates, C4-C9 dialkyl terephthalates, C4-C13 dialkyl phthalates, in particular C9-C13 dialkyl phthalates and C4-C10 dialkyl esters of 1,2-, 1,3- or 1,4-cyclohexanedicarboxylic acid.

[0015] It is therefore a further object of the present invention to provide a plastic composition comprising the mixture or plasticizing composition of the tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid of the present invention and one or more polymers. Suitable polymers are preferably PVC; homo- or copolymers based on ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, ethyl acrylate, butyl acrylate or methacrylate with alkoxy groups of branched or unbranched alcohols, acrylonitrile or cyclic olefins having 1 to 10 carbon atoms; polyvinylidene chloride (PVDC), polyacrylates, in particular polymethyl methacrylate (PMMA), polyalkyl methacrylates (PAMA), polyureas, silylated polymers, fluoropolymers, in particular polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyvinyl acetals, in particular polyvinyl butyral (PVB), polystyrene polymers, in particular polystyrene (PS), expandable polystyrene (EPS), acrylonitrile-styrene-acrylate (ASA), styrene-acrylonitrile (SAN), acrylonitrile-styrene-acrylate (SAN), acrylonitrile-styrene-acrylate (ASA), acrylonitrile-styrene-acrylate (SAN), acrylonitrile-styrene-acrylate (ACRYLONITRILE ... The polymer may be selected from the group consisting of acrylonitrile-butadiene-styrene (ABS), styrene-maleic anhydride copolymer (SMA), styrene-methacrylic acid copolymer, polyolefins, in particular 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, in particular polylactic acid (PLA), polyhydroxybutyral (PHB), polyhydroxyvaleric acid (PHV), polyesters, starch, cellulose and cellulose derivatives, in particular nitrocellulose (NC), ethylcellulose (EC), cellulose acetate (CA), cellulose acetate / butyrate (CAB), rubber and silicones. In a preferred embodiment, at least one polymer, or preferably at least 90% by weight of the two or more polymers in the plasticizer composition, is selected from the group consisting of polyvinyl chloride (PVC), polyalkyl methacrylate (PAMA), polyvinyl butyral (PVB), polyurethane, polysulfide, polylactic acid (PLA), polyhydroxybutyral (PHB), nitrocellulose, and copolymers of vinyl chloride with vinyl acetate or butyl acrylate. PVC is particularly preferred.

[0016] The amount of the mixture or plasticizer composition of the inventive tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid in the plastic composition is preferably from 5 to 150 parts by weight, preferably from 10 to 120 parts by weight, particularly preferably from 15 to 110 parts by weight, very particularly preferably from 20 to 100 parts by weight per 100 parts by weight of polymer. However, it may also be a composition containing one or more polymers comprising the inventive tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid in an amount of less than 20 parts by weight per 100 parts by weight of polymer.

[0017] Specific compositions / mixtures of plasticizers comprising the mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to the invention which are preferred in the context of the present invention are as follows: The object of the present invention is to provide a plastic composition, preferably comprising a mixture of tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid and diethylhexyl terephthalate (DEHT or DOTP) and at least one polymer, preferably PVC. A further preferred object of the present invention is to provide a plastic composition comprising a mixture of the tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid and a 1,2- or 1,4-cyclohexanedicarboxylic acid ester, in particular the corresponding diisononyl or di-2-ethylhexyl ester, and at least one polymer, preferably PVC. Further, there is provided a plastic composition, preferably comprising a mixture of a tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid, a trialkyl ester of trimellitic acid, the alkyl group of which has 4 or more carbon atoms, preferably 5, 8, 9 or 10 carbon atoms, and at least one polymer, preferably PVC. There is provided a plastic composition, preferably comprising a mixture of a tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid, a trialkyl ester of 1,2,4-cyclohexanetricarboxylic acid, the alkyl group of which has 4 or more carbon atoms, preferably 5, 8, 9 or 10 carbon atoms, and at least one polymer, preferably PVC. A further preferred object of the present invention is to provide a plastic composition containing a mixture of tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid and a fast gelling plasticizer selected from the group consisting of dibutyl terephthalate, di(iso)pentyl terephthalate, isodecyl benzoate, isononyl benzoate, acetyl tributyl citrate, tributyl citrate, dipropylene glycol dibenzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and mixtures of two or more thereof, and at least one polymer, preferably PVC.

[0018] The plastic composition of the present invention is preferably a component in adhesives, sealing compositions, coating compositions, varnishes, paints, plastisols, dry blends, foams, synthetic leather, flooring, especially the topcoat or foam layer thereof, roofing membranes, substrate protection, fabric coverings, cables, wire insulation, hoses, extrusions, films, automotive interiors, wallpaper, inks, toys, contact films, food packaging or medical products, tubing or blood bags. It is therefore a further object of the present invention to use the plastic composition of the present invention in an adhesive, a sealing composition, a coating composition, a varnish, a paint, a plastisol, a foam, synthetic leather, a flooring, in particular the topcoat or foam layer thereof, a roofing membrane, an undercoat protectant, a fabric covering, a cable, wire insulation, a hose, an extrusion, a film, an automotive interior, wallpaper, an ink, a toy, a contact film, a food packaging or a medical product, a tube or a blood bag.

[0019] As mentioned above, the terms "iso-pentyl", "iso-pentyl group" and the like are to be understood as synonymous with the term "pentyl" and do not refer to a single specific C5-alkyl group. Thus, the individual subject matter of the present invention can also be described as follows:

[0020] 1. A mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid in which 6 to 12 mol % of pentyl groups are 2-methylbutyl groups, 88 to 94 mol % are n-pentyl groups, and 0 to 4 mol % are 3-methylbutyl groups. 2. The mixture according to claim 1, wherein 6 to 10 mol % of the pentyl groups are 2-methylbutyl groups, 90 to 94 mol % are n-pentyl groups, and 0 to 2 mol % are 3-methylbutyl groups. 3. The mixture according to claim 1, wherein 7 to 9 mol % of the pentyl groups are 2-methylbutyl groups, 91 to 93 mol % are n-pentyl groups, and 0 to 2 mol % are 3-methylbutyl groups. 4. The mixture according to any one of claims 1 to 3, wherein not more than 1 mole percent of the pentyl groups are 3-methylbutyl groups. 5. The mixture according to claim 4, wherein not more than 0.5 mole percent of the pentyl groups are 3-methylbutyl groups.

[0021] 6. A process for preparing the mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to any one of claims 1 to 5, wherein the preparation is carried out by either esterifying 1,2,3,4-butanetetracarboxylic acid with a pentanol mixture or by transesterifying tetramethyl esters of 1,2,3,4-butanetetracarboxylic acid with a pentanol mixture. 7. The process of claim 6, wherein the water of reaction formed during the esterification is separated during the reaction. 8. The process according to claim 6 or 7, wherein the esterification is carried out at a temperature in the range of 120° C. to 250° C. 9. Use of the mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to any one of claims 1 to 5 as a plasticizer for polymers, particularly PVC or vinyl chloride-containing copolymers. 10. A plasticizer composition comprising a mixture of the tetraisopentyl ester of 1,2,3,4-butanetetracarboxylic acid in the mixture according to any one of claims 1 to 5 and at least one further plasticizing compound. 11. The plasticizer composition according to claim 10, wherein the further plasticizing compound is selected from the group consisting of adipates, benzoates, such as monobenzoates or glycol dibenzoates, chlorinated hydrocarbons (so-called chlorinated paraffins), citrates, cyclohexane dicarboxylates, epoxidized fatty acid esters, epoxidized vegetable oils, epoxidized acylated glycerides, furan dicarboxylates, phosphates, succinates, sulfonamides, sulfonates, terephthalates, trimellitates, and oligomeric or polymeric esters based on adipic acid, succinic acid or sebacic acid. 12. The plasticizer composition according to claim 10 or 11, containing less than 12.5% ​​by weight, more preferably less than 0.5% by weight, and particularly preferably less than 0.1% by weight of phthalate esters. 13. A plastic composition comprising a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid according to any one of claims 1 to 5 or a plasticizing composition according to any one of claims 10 to 12, and one or more polymers. 14. One or more polymers are selected from the group consisting of PVC; homo- or copolymers based on ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, ethyl acrylate, butyl acrylate or methacrylate with alkoxy groups of branched or unbranched alcohols with 1 to 10 carbon atoms, acrylonitrile or cyclic olefins; polyvinylidene chloride (PVDC), polyacrylates, polymethyl methacrylate (PMMA), polyalkyl methacrylates (PAMA), polyureas, silylated polymers, fluoropolymers, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyvinyl acetal, polyvinyl butyral (PVB), polystyrene polymers, polystyrene (PS), expandable polystyrene (EPS), acrylonitrile-styrene-acrylate (ASA), styrene-acrylonitrile (SAN), acrylonitrile-butadiene. 14. The plastic composition of claim 13, wherein the plastic composition is selected from the group consisting of diene-styrene (ABS), styrene-maleic anhydride copolymer (SMA), styrene-methacrylic acid copolymer, polyolefin, polyethylene (PE), polypropylene (PP), thermoplastic polyolefin (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), biopolymer, polylactic acid (PLA), polyhydroxybutyral (PHB), polyhydroxyvaleric acid (PHV), polyester, starch, cellulose, cellulose derivatives, nitrocellulose (NC), ethyl cellulose (EC), cellulose acetate (CA), cellulose acetate / butyrate (CAB), rubber, and silicone. 15. Use of the plastic composition according to topic 13 or 14 in an adhesive, a sealing composition, a coating composition, a varnish, a paint, a plastisol, a foam, synthetic leather, a flooring material, a topcoat, a roofing membrane, a substrate protection material, a fabric covering, a cable, an electric wire insulation, a hose, an extrusion molding, a film, an automotive interior material, a wallpaper, an ink, a toy, a contact film, a food packaging or a medical product, a tube or a blood bag.

[0022] The present invention will now be described with reference to examples which are illustrative and should not be construed as limiting. EXAMPLES

[0023] Synthesis of a mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid. The apparatus was charged with 5 moles of 1,2,3,4-butanetetracarboxylic acid (Alfa Aesar, purity: >98%) and the corresponding amounts of alcohols 2-methylbutanol, n-pentanol and 3-methylbutanol (2-methylbutanol: Sigma-Aldrich, purity ≥99%; 3-methylbutanol: Honeywell, purity ≥98.5%; n-pentanol: Honeywell, purity ≥99%). 3.4 g of tetra-n-butyl titanate (0.01 mol, Sigma-Aldrich, purity: >97%) was added thereto as catalyst to start the reaction. The reaction was carried out under nitrogen sparging. The reaction was slowly heated to the reaction temperature of 200° C. After the reaction temperature was reached, more alcohol was metered in. During the addition, care was taken to ensure that the reaction temperature did not fall below 200° C. During the esterification process, 360 ml of water was produced (20 moles of reaction water). The water formed during the reaction was continuously removed via a water trap. After the reaction water reached 360 ml, the reaction sample was used to measure the acid number (AN). The progress of the reaction was monitored at regular intervals via the AN until an AN of <0.5 mg KOH / g sample was reached. The mixture was then cooled and aqueous sodium hydroxide was added to destroy the catalyst. The reaction product from the esterification was transferred to a stirred flask. The apparatus was flushed with nitrogen (6 l / h). The reaction product was slowly heated under vacuum (approximately 1-5 mbar) until the temperature increased to 160°C. After complete distillation of the excess alcohol, the product was cooled to 80°C and filtered. The filtrate was subjected to NMR analysis to determine the composition of the ester groups in the product.

[0024] NMR analysis The composition of tetraiso-pentyl 1,2,3,4-butanetetracarboxylate, i.e., the ratio of different isomeric butyl groups to the total of all butyl groups, is, for example, 1 H NMR and 13 The composition can be determined by C NMR spectroscopy. For greater accuracy, the composition can be determined by NMR spectroscopy on a solution of a mixture of tetraiso-pentyl 1,2,3,4-butanetetracarboxylate in deuterated chloroform (CDCl3). 1 H-NMR spectroscopy was used. 1 To record H-NMR spectra, approximately 20 mg of material was dissolved in approximately 0.6 ml of CDCl3 (each containing approximately 1% by weight of TMS) and loaded into NMR tubes with a diameter of 5 mm. The CDCl3 used was first dried over molecular sieves to prevent degradation of the measurements due to the presence of water. NMR spectroscopy can in principle be carried out on any commercially available instrument. In the present NMR analysis, a Bruker Avance 500 instrument was used. 1H-NMR spectra were recorded using a 5 mm Prodigy Cryo Sample Head (CPPBO) equipped with a Bruker Cooling Unit (BCU 05) at a temperature of 300 K, a delay of d1 = 5 s, 32 scans, a pulse length of approximately 12 μs (30° excitation pulse) and a sweep width of 10000 Hz. The resonance signals were recorded relative to the chemical shifts of tetramethylsilane (TMS = 0 ppm) as an internal standard. Comparable results were obtained on other commercially available NMR instruments using the same operating parameters.

[0025] Figure 1 below is provided to facilitate understanding of the described measurement method. The relevant element here is the n-pentyl group (C14 H3 and C 10 H2), 2-methylbutyl group (C 23 H3, C 24 H3 and C 20 H2) and 3-methylbutyl group (C 33 H3 and C 30 H2) are the assigned numbers of the carbon atoms of the methylene group adjacent to the methyl group and the oxygen atom in each case.

[0026] Numbering of carbon atoms in different pentyl groups

[0027] [ka] where R is independently n-pentanol, 2-methylbutanol, or 3-methylbutanol.

[0028] A mixture of tetraiso-pentyl 1,2,3,4-butanetetracarboxylates was obtained. 1 The H-NMR spectrum shows isomeric pentyl substituents (C 14 H3, C 23 H3, C 24 H3, C 33 There are resonance signals in the range of 0.8-1.0 ppm formed by the signals of the hydrogen atoms of the methyl groups of the methyl groups (H3). The signals in the range of chemical shifts of 3.60-4.40 ppm are essentially those of the alcohol groups (C 10 H2, C 20 H2, C 30 H2) can be assigned to the hydrogen atom of the methylene group adjacent to the oxygen in H2. Here, the proton on C20 undergoes an upfield shift due to the adjacent tertiary carbon atom and appears between 4.03 ppm and 3.84 ppm, while the protons at C10 and C30 give signals at lower shifts of 4.20 ppm to 4.03 ppm and overlap each other. Quantification was performed by comparative determination of the area under each resonance signal, i.e., the area enclosed by the signal from the baseline. Commercially available NMR software has the programmable function to integrate the signal area. In this NMR spectroscopy study, integration was performed using the software TopSpin®, version 3.6. To determine the average degree of branching of the isomeric pentyl groups in the mixture according to the invention, first the integral of the signal in the range of 0.68-1.11 ppm (I(CH3)) is divided by the integral of the signal in the range of 3.60-4.40 ppm (I(OCH2)). In this way, the intensity ratio is obtained, which is the ratio of the number of hydrogen atoms present in the methylene groups to the number of hydrogen atoms present in the methylene groups adjacent to the oxygen. Since there are three hydrogen atoms per methyl group and two hydrogen atoms in each methylene group adjacent to the oxygen, in order to obtain the ratio of the number of methyl groups to the number of methylene groups adjacent to the oxygen in the pentyl group, the intensities must be divided by 3 and 2, respectively. Since a linear n-pentyl group with only one methyl group and one methylene group adjacent to the oxygen has no branching and therefore the degree of branching must be 0, 1 must be subtracted from the ratio. Therefore, the average branching degree DB can be calculated by the following formula:

[0029] DB=2 / 3*I(CH3) / I(OCH2)-1 where DB is the average degree of branching, I(CH3) is the area integral assigned to the methyl hydrogen atoms, and I(OCH2) is the area integral of the methylene hydrogen atoms adjacent to the oxygen. The product may contain 2-methylbutyl and 3-methylbutyl groups, each with a branching degree of 1, and n-pentyl groups with a branching degree of 0, and the maximum average branching degree of any tetraisopentyl ester is always 1. Thus, the deviation of the average branching degree from the value 1 gives the n-pentyl groups (x pentyl ) can be determined.

[0030] x Pentyl =1-DB The amount of 2-methylbutyl radical cannot be calculated by integrating the baseline separated signal in the range of 3.60 to 4.40 ppm. The signal of the proton on C20 (C 20 H2; multiplet between 3.95 and 4.28 ppm) are the signals of protons on C10 and C30 (C 10 H2 and C 30 H2; multiplet between 4.29 and 4.55 ppm) is separated.

[0031] Molar ratio of 2-methylbutyl groups (x 2-メチルブチル ) can be calculated according to formula (I).

[0032] x 2-メチルブチル =I(OC 19 H2) / I(OCH2) -OC 20 Intensity of the H2 proton signal (I(OC 20 The intensities of the OCH2 protons are calculated by relating the intensities of all the OCH2 protons (I(OCH2)). Therefore, the 3-methylbutyl radical (x 3-メチルブチル ) is calculated from the difference between the two previous molar mass fractions and 1.

[0033] x 3-メチルブチル =1-x 2-メチルブチル -x pentyl Using the methods described above, it was possible to determine the ratio of each residue in the sample (see Table 1). Table 1: Composition of the ester mixture by NMR analysis

[0034] [Table 1] *The present invention The ester mixtures in Table 1 were investigated for application-relevant properties.

[0035] 1) Plastisol manufacturing PVC plastisols such as those used in making topcoat films were prepared. The amounts of each in the plastisol formulation are reported in parts by weight (phr). The formulations are listed in Table 2. Table 2: Plastisol Formulations

[0036] [Table 2] The liquid ingredients were weighed first, then the powdered ingredients, into a PE beaker. The mixture was stirred manually with a spatula so that no unwetted powder remained. The mixing beaker was then fixed in the clamping device of the dissolving stirrer. After switching on the stirrer, the speed was slowly increased to about 2000 rpm (revolutions per minute). Meanwhile, the plastisol was carefully degassed. For this, the pressure was set to below 20 mbar. As soon as the plastisol had reached a temperature of about 30° C., the speed was reduced to about 350 rpm. The plastisol was then degassed for 9 minutes at that speed and at a pressure below 20 mbar. This ensured that no premature partial gelation occurred during the homogenization of the plastisol.

[0037] 1.1) Measurement of plastisol viscosity The viscosity of the plastisols prepared in Example 1) was measured using a Physica MCR 101 rheometer (from Anton Paar Germany GmbH) with accompanying software, using rotational mode and a CC27 measuring system. The measurements were carried out after the plastisols had been equilibrated at 25° C. for 24 hours after preparation. During the measurements the following were controlled: 100s -1 A preshear of 60 seconds was performed at 400° C., during which no measurements were taken. 200s -1 From 0.1s -1 A downward shear rate gradient to 30 was recorded, each of 10 seconds in duration. The measurements were performed at room temperature. Each measurement was performed for 10 s. -1 The viscosities obtained were at a shear rate of 100 .mu.m. The results of the viscosity measurements of the plastisols made with each of the listed plasticizers are listed in Table 3. Table 3: Viscosity measurement results

[0038] [Table 3] It is clear that the viscosity of the mixture according to the invention (sample 1) is comparable to that of sample 8 (the pure tetra-n-pentyl ester of 1,2,3,4-butanetetracarboxylic acid).

[0039] 1.2) Gelling properties The gelling properties of the plastisols of example 1) were tested using a Physica MCR 101 instrument (from Anton Paar) in vibration mode equipped with a parallel plate analysis system (PP25) operating under shear stress control. In order to achieve the best possible heat distribution, an additional temperature-controlled hood was connected to the system. The following measurement parameters were established: Mode: Temperature gradient (linear temperature ramp) Starting temperature: 25℃ Final temperature: 180℃ Heating / cooling rate: 5K / min Vibration frequency: 4 to 0.1 Hz ramp (logarithmic) Cycle frequency ω: 10s -1 Number of measurement points: 63 points Measurement point duration: 0.5 min Automatic Gap Adjustment Constant measurement point duration Gap width 0.5mm Analytical Procedure: A few drops of the plastisol to be measured were placed on the lower measuring system plate with a spatula, taking care to avoid introducing air bubbles. During the assembly of the analysis system, care was taken to ensure that a portion of the plastisol bulged out evenly from the measuring system after being moved together (no more than about 6 mm in any direction). A temperature-controlled hood was then placed over the samples and the measurements started. The so-called complex viscosity of the plastisols was measured as a function of temperature. The onset of the gelling process could be recognized by a sharp increase in the complex viscosity. The earlier this viscosity increase begins, the higher is the gelling ability of the system. From the measurement curves obtained, the temperature at which a complex viscosity of 1000 Pa*s was measured for each plastisol was determined by interpolation. The results are shown in Table 4. Table 4: Gelation rate measurement results

[0040] [Table 4] The gelation rate of the mixture according to the invention (sample 1) is as low as that of sample 8 (pure tetra-n-pentyl ester of 1,2,3,4-butanetetracarboxylic acid) and is therefore clearly significantly lower than the other comparative examples.

[0041] 2) Film manufacturing The plastisols produced in Example 1) were each processed into a film with a thickness of 1 mm. For this purpose, firstly, a high gloss release paper (from Sappi, Italy) was cut to a size of 30 x 44 cm and inserted into the clamping frame of an LTSV coating installation for a Matisse oven. The clamping frame was then placed on the guide frame, the Matisse oven (model LTF) was adjusted to 200 ° C and the frame was preheated after said temperature was reached. The coating bar was then inserted into the clamping means and the coating bar gap was adjusted in a preliminary experiment so that the film thickness after gelation was 1 mm (+ / - 0.05 mm). The plastisol was spread on the clamped release paper with the help of the coating bar (speed 3 m / min). The coating bar was then removed and the clamping frame was moved into the oven. After gelation (200 ° C for 2 min), the frame was removed from the oven and, after cooling, the film was removed from the paper.

[0042] 2.1) Volatility of plasticizer in film Three circles per sample were punched out from the PVC film prepared in Example 2) (circle; diameter: 5 cm). The samples were equilibrated in a desiccator for 16 hours. The sample circle was weighed on an analytical balance and placed in a wire basket, which was closed with a bulldog clip. 130 ml of activated carbon was introduced into a tin can (1 l tall). Then the first wire basket with the sample was placed in the middle of the activated carbon and another 130 ml of activated carbon was added to the sample circle. In total, the tin can was filled with 520 ml of activated carbon layer by layer and the three wire baskets were filled with sample. As a final step, another 130 ml of activated carbon was filled in the top layer. The tin can lid with holes was placed on the tin can without applying pressure. The filled tin cans were placed in a heating cabinet heated to 120 ° C in such a way that the ventilator in the cabinet was not closed and the cans did not touch each other. The air exchange and ventilation flaps were set at 10% each. After 72 hours at 120 ° C, the samples were again removed from the cabinet and cooled, then the individual samples were removed from the basket and reweighed on an analytical balance after conditioning in a desiccator for another 16 hours. The resulting mass difference is due to the loss of plasticizer. The average value was calculated from the three mass differences and the loss of plasticizer was calculated as a percentage. The results are shown in Table 5. Table 5: Results of volatility measurements

[0043] [Table 5] The viscosity of the mixture according to the invention (sample 1) is clearly the lowest of all the samples. Only sample 8 (pure tetra-n-pentyl ester of 1,2,3,4-butanetetracarboxylic acid) shows a relatively low volatility.

[0044] 2.2) Glass transition temperature by DSC For the measurements, small circles (φ4.5 mm) were punched out of the PVC film produced according to Example 2. The samples were analyzed in aluminium crucibles (perforated crucible lid) under nitrogen using a Mettler Toledo DSC 1 with the following settings: Dry nitrogen gas: approx. 45 ml (STP) / min (= standard ml / min) Nitrogen gas (purge gas): approx. 180 ml (STP) / min Cooling: Liquid nitrogen (auxiliary reservoir 1.5 bar) method: [1] 25.0 to 120.0 °C, 25.0 K / min [2] 120.0℃, 5.00 minutes isothermal [3] 120.0~-50.0℃, 25.0K / min [4] -50.0 to -120.0℃, 10.0K / min [5]-120.0℃, 3.00 minutes isothermal [6]-120~50.0℃, 10.0 K / min Sync switch on The different temperature gradients eliminate the thermal history of the sample, making the results more reproducible. For the glass transition, the peak maximum of the first derivative from the ramp [6] was evaluated. The resulting heat flow was plotted as a function of the measured temperature. The results are shown in Table 6. Table 6: Glass transition measurement results

[0045] [Table 6] The peak maximum of the mixture according to the invention (sample 1) is clearly as low as that of sample 8 (pure tetra-n-pentyl ester of 1,2,3,4-butanetetracarboxylic acid).

Claims

1. A mixture of tetraisopentyl esters of 1,2,3,4-butanetetracarboxylic acid, wherein 6 to 12 mol% of the isopentyl groups are 2-methylbutyl groups, 88 to 94 mol% of the isopentyl groups are n-pentyl groups, and 0 to 4 mol% of the isopentyl groups are 3-methylbutyl groups.

2. The mixture according to claim 1, wherein 6 to 10 mol% of the isopentyl groups are 2-methylbutyl groups, 90 to 94 mol% of the isopentyl groups are n-pentyl groups, and 0 to 2 mol% of the isopentyl groups are 3-methylbutyl groups.

3. The mixture according to claim 1, wherein 7 to 9 mol% of the isopentyl groups are 2-methylbutyl groups, 91 to 93 mol% of the isopentyl groups are n-pentyl groups, and 0 to 2 mol% of the isopentyl groups are 3-methylbutyl groups.

4. The mixture according to claim 1, wherein less than 1 mol% of the isopentyl groups are 3-methylbutyl groups.

5. The mixture according to claim 4, wherein less than 0.5 mol% of the isopentyl groups are 3-methylbutyl groups.

6. A process for producing the mixture described in claim 1, wherein the production is carried out by either esterifying 1,2,3,4-butanetetracarboxylic acid with an isopentanol mixture, or transesterifying a tetramethyl ester of 1,2,3,4-butanetetracarboxylic acid with an isopentanol mixture.

7. The process according to claim 6, wherein the reaction water formed during esterification is separated during the reaction.

8. The process according to claim 6, wherein the esterification is carried out at a temperature in the range of 120°C to 250°C.

9. Use of the mixture according to claim 1 as a plasticizer for polymers.

10. A plasticizer composition comprising the mixture described in claim 1 and at least one further plasticizing compound.

11. The plasticizer composition according to claim 10, wherein the further plasticizing compound is selected from the group consisting of adipic acid salts, benzoic acid salts, chlorinated hydrocarbons, citrate salts, cyclohexanedicarboxylate salts, epoxidized fatty acid esters, epoxidized vegetable oils, epoxidized acylated glycerides, frangic acid salts, phosphates, succinates, sulfonamides, sulfonates, terephthalates, trimellites, and oligomers or polymer esters based on adipic acid, succinic acid, or sebacic acid.

12. The plasticizer composition according to claim 10, which contains less than 5% by mass of phthalate ester.

13. A plastic composition comprising a mixture according to any one of claims 1 to 5 or a plasticizer composition according to any one of claims 10 to 12, and one or more polymers.

14. One or more polymers, PVC; Homo or copolymers based on ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, ethyl acrylate, butyl acrylate, or methacrylates having alkoxy groups of branched or unbranched alcohols having 1 to 10 carbon atoms, acrylonitrile, or cyclic olefins; Polyvinylidene chloride (PVDC); Polyacrylate; Polyurea; Silylated polymers; Fluoropolymer; Polyvinyl acetate (PVAc); Polyvinyl alcohol (PVA); Polyvinyl acetal; Polystyrene polymer; Polyolefin; Thermoplastic polyolefin (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; rubber; and silicone A plastic composition according to claim 13, selected from the group consisting of the following.

15. Use of the plastic composition according to claim 13 in adhesives, sealing compositions, coating compositions, varnishes, paints, plastisols, foams, synthetic leather, flooring materials, roofing films, substrate protection materials, fabric coverings, cables, wire insulation, hoses, extruded articles, films, automotive interior materials, wallpaper, inks, toys, contact films, food packaging, or medical products.