HK1151279A - Mixtures of diisononyl esters of terephthalic acid, method for the production thereof and use thereof - Google Patents

Description

Mixtures of diisononyl terephthalates, method for the production thereof and use thereof

The invention relates to mixtures of diisononyl terephthalates, i.e. diisononyl terephthalates which are present in the form of an isomer mixture, wherein the isomeric nonyl residues (Nonylrest) bonded (gebunded) in the ester mixture have a specific degree of branching. The invention also relates to a method for producing said mixtures and to the use thereof.

Polyvinyl chloride (PVC) is the most economically important polymer. It is widely used in the form of hard PVC and soft PVC.

For the preparation of soft PVC, plasticizers are added to PVC and those used in most cases are phthalates, in particular di-2-ethylhexyl phthalate (DEHP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP).

The discussion regarding reproduction-toxicity effects has in some cases led to an increased degree of identification marking under the legislation of hazardous materials and also to limitations of the use of toys for young children and it must therefore be assumed that the use of these phthalates will be significantly reduced in the future, in particular in sensitive applications such as food packaging and medical applications. There is therefore a need for plasticizers that do not suffer from the requirement of identifying labels and that can be used as a substitute for DEHP or DINP and that can be made from a large number of raw materials available worldwide.

Another substance that is available in large quantities in addition to phthalic acid, with estimated annual yields of millions of tons, is terephthalic acid (PTA) or the derivative dimethyl terephthalate (DMT). An example of a product made on a large scale from terephthalic acid is polyethylene terephthalate (PET). However, only one monomeric terephthalate has so far achieved some industrial importance as plasticizer for PVC, namely di-2-ethylhexyl terephthalate (DEHT or DOTP).

Cooper (in the paper, "An Alternative to DEHP in Plastic PVC", in Vinyl formulas Division, 16)^thAnnual compounding Conference, Harrah's/Harvey's Resort, Lake Tahoe, Nevada, 7.2005, 17-19 days), phthalic acid diesters, in particular di-2-ethylhexyl phthalateThe polyester has a different metabolism from that of the terephthalic acid diester. During decomposition in the organism, the terephthalate is first completely hydrolyzed to produce alcohol and terephthalic acid, while the phthalate is only hydrolyzed to produce monoesters. These monoesters, or subsequent products produced therefrom by oxidative subsequent reactions, are identified in laboratory studies as toxicologically active substances. Since di-2-ethylhexyl phthalate and di-2-ethylhexyl terephthalate are metabolized differently, according to james l. cooper, di-2-ethylhexyl terephthalate has significantly lower toxicity than di-2-ethylhexyl phthalate.

It can therefore be assumed that other plasticizers, which are likewise based on terephthalates, likewise undergo a completely analogous (genau so) complete hydrolysis to terephthalic acid during decomposition, and that these terephthalates therefore likewise have a lower toxicity than the corresponding phthalates.

Since cyclohexanedicarboxylates, which are likewise proposed as phthalate substitutes and are obtainable by ring-hydrogenation (kernhydriving) of the corresponding phthalates, have the advantage that, like phthalates, terephthalates can be prepared by a single-stage esterification reaction starting from readily available starting materials, without any additional hydrogenation stage. The result is that the transfer of production to terephthalate requires only a low degree of adaptation of the production plant and no capital expenditure for the plant for the hydrogenation stage.

There is little literature describing esters derived from terephthalic acid and isononanol, i.e. a mixture of branched and optionally linear nonanols, and these have not been marketed as plasticizers to date either.

US 2,628,207 describes terephthalates as plasticizers and C is described in this document₈Alcohol esters are particularly preferred because they are said to exhibit the best effects against elevated molar masses, including plasticization and low volatility. No information is disclosed about diisononyl terephthalates.

Soc.plat.eng, tech.pap (1976), 22, 613-. In the case of a terephthalate with an average chain length of 9 carbon atoms, it is described that a minimum proportion of 30% of branched alcohol is required in order to obtain a liquid plasticizer compatible with PVC. With respect to properties, it is stated that the properties of a terephthalate are generally similar to the corresponding phthalate having a side chain one carbon atom long.

Several other publications such as DE 19927978 mention only diisononyl terephthalate or, in a few cases, also the possibility of use as plasticizer, an example being JP2001240844, which describes the use as plasticizer in polyurethane systems. However, there has never been a clear study of the performance of the application technique, and in particular there has been no study of these as a relationship to the composition or degree of branching of the isononyl side chains.

Starting from the known prior art, the object of the present invention was to provide diisononyl terephthalates which are very suitable as plasticizers, in particular for the plasticization of PVC.

The function of the plasticizer is to lower the glass transition temperature of the plastic to be plasticized to such an extent that it remains sufficiently flexible at the use temperature. The glass transition temperature of the material should also be below the use temperature. Thus, a suitable diisononyl terephthalate should exhibit as low a glass transition temperature as possible. The glass transition temperature of DEHP will be used herein as a guide value and is about-80 ℃ (measured by means of differential scanning calorimetry, DSC).

Thus, where certain tolerances are allowed, it should be found that a mixture of isomeric dinonyl terephthalates is produced which has a glass transition temperature below-70 ℃, ideally below-80 ℃.

Technical experience teaches that the lower the degree of branching of the alcohol content in the ester mixture, the lower the glass transition temperature is generally. Thus, di-n-nonyl terephthalate should actually be the most suitable material.

However, when n-nonanol is used to prepare the corresponding dinonyl terephthalate, the resulting esters are found to have only limited availability as plasticizers for PVC, since they are solid at room temperature (see comparative example 4) and are therefore unsuitable as plasticizers for the most quantitatively important plastisol applications. The glass transition temperature of the ester cannot be detected by means of DSC (no amorphous region).

Likewise, esterification of the triple branched (dreifachverzweigt)3, 5, 5-trimethylhexanol obtained by hydroformylation of diisobutylene also only produces terephthalates which are solid at room temperature. Therefore, it was not entirely correct to have to branch at least 30% of the C9 alcohols in order to avoid crystallization, as demonstrated in Soc. platt. Eng., Tech. pap (1976), 22, 613-.

Surprisingly, it has now been found that isononyl terephthalate mixtures which contain at least two structurally different nonyl residues and which have an average degree of branching of from 1.0 to 2.2 are liquid even at low temperatures of as low as about-70 ℃ and exhibit glass transition temperatures below-70 ℃. These isononyl terephthalates are therefore particularly suitable as plasticizers, in particular for PVC.

Accordingly, the present invention provides a mixture of diisononyl esters of terephthalic acid wherein the average degree of branching of the bonded isomeric nonyl residues in the ester mixture is from 1.0 to 2.2.

The invention further provides a process for preparing mixtures of diisononyl esters of terephthalic acid, characterized in that the preparation process uses a mixture of isomeric nonanols having an average degree of branching of from 1.0 to 2.2.

The invention also provides for the use of the inventive mixtures as a plasticizer or as part of a plasticizer composition in plastics or plastic components, or as an additive in paints (Farbe) or paints (Lacke), in adhesives or adhesive components, or in sealers (dichtungsass), or as a solvent.

Finally, the invention provides plastics and plastic compositions comprising the inventive mixtures of diisononyl terephthalates, in particular plastics and plastic compositions based on PVC, PVB or PAMA, and also plastic articles produced from these compositions.

The inventive mixtures of diisononyl terephthalates are characterized in that the branching degree of the isononyl radicals of the diisononyl esters contained in the mixtures is between 1.0 and 2.2, preferably between 1.1 and 2.1. Particularly preferred degrees of branching are from 1.1 to 2.0 and in particular from 1.2 to 1.5.

Here, the isononyl residues are based on primary nonanols.

¹H NMR method or¹³The C NMR method can be used to measure the average degree of branching of the isononyl residues in the terephthalic acid diester mixture. According to the invention, preferably by means of¹H NMR spectra on diisononyl esters in deuterochloroform (CDCl)₃) The degree of branching was measured on the solution in (1). For example, by dissolving 20mg of the material in 0.6ml CDCl₃(containing 1 mass% TMS) and charged into a NMR tube having a diameter of 5mm to record a spectrum. The substances to be investigated and the CDCl used can be first of all₃Dried over molecular sieves to exclude any errors due to the measured value of water that may be present. The method of measuring the degree of branching is advantageous compared with other methods of characterizing alcohol residues, as described for example in WO03/029339, because water impurities have substantially no influence on the results of the measurements and their evaluation. In principle, any commercially available NMR apparatus can be used for NMR spectroscopic studies. The NMR spectroscopic study used an Avance model 500 apparatus from Bruker. Spectra were recorded at 300K using a 5mm BBO (broadband observer) probe with a delay d1 of 5 seconds, 32 scans, a pulse length of 9.7 μ s and a scan width of 10000 Hz. Resonance signals were recorded compared to the chemical shift of tetramethylsilane as an internal standard (TMS ═ 0 ppm). Similar results were obtained with other commercially available NMR equipment using the same operating parameters.

Terephthalic acid diisocynatePreparation of nonyl ester mixtures¹The H NMR spectrum has a resonance signal of minima of 0.5ppm up to the lowest valley in the range of 0.9-1.1ppm, which signal is formed essentially by the signal of the methyl hydrogen atom of isononyl. Signals in the chemical migration range of 3.6-4.4ppm can be attributed substantially to the hydrogen atom of the methylene group adjacent to the oxygen of the alcohol or alcohol residue. Quantification is performed by measuring the area under each resonance signal, i.e. the area comprised between the signal and the baseline. Commercially available NMR apparatus have means for integrating the signal area. In this NMR spectroscopic study, the integration was performed using "xwinnnmr" software, version 3.5. Then, the signal integrated value of the minimum value of the lowest valley in the range of 0.5 up to 0.9 to 1.1ppm was divided by the signal integrated value of 3.6 to 4.4ppm to obtain an intensity ratio representing the ratio of the number of hydrogen atoms present in the methyl group to the number of hydrogen atoms present in the methylene group adjacent to the oxygen atom. Since each methyl group has three hydrogen atoms and there are two hydrogen atoms in each methylene group adjacent to an oxygen atom, each intensity must be divided by 3 and 2, respectively, to obtain the ratio of the number of methyl groups in the isononyl residue to the number of methylene groups adjacent to an oxygen atom. Since linear primary nonanols which have only one methyl group and one methylene group adjacent to an oxygen atom contain no branching and therefore necessarily have a degree of branching of 0, the quantity 1 must be subtracted from this ratio.

Thus, the branching degree V can be calculated from the measured intensity ratio according to the following formula:

V＝2/3*I(CH₃)/I(OCH₂)-1

v here denotes the degree of branching, I (CH)₃) Denotes the area integral attributed essentially to methyl hydrogen atoms, and I (OCH)₂) Represents the area integral of methylene hydrogen atoms adjacent to oxygen atoms.

The nature and number of alcohol residues contained in the diisononyl ester mixture can also be measured by saponifying the ester in an alkaline solution and then analyzing the alcohol by GC. Care must be taken here that the GC conditions (in particular the column material and column dimensions and temperature profile) allow the separation of the alcohol into the individual isomers.

The isomeric nonanols or isononanol mixtures to be used in the process according to the invention for preparing these diisononyl terephthalate mixtures can generally be prepared by hydroformylation of octenes, which in turn can be prepared in various ways. Typical feedstocks for octene production include commercial C₄Stream, initially except with saturated butane and optional impurities such as C₃And C₅In addition to olefins and acetylenic compounds, it may also contain all isomeric C' s₄An olefin. Oligomerizing the olefin mixture except for higher oligomers such as C₁₂And C₁₆Mixtures of isomeric octenes are obtained predominantly in addition to the olefin mixtures. These octene mixtures, from which higher oligomers are removed, preferably by distillation, are hydroformylated to the corresponding aldehydes and then hydrogenated to alcohols. The composition of these industrial nonanol mixtures, i.e. the isomer distribution, depends on the starting materials and on the oligomerization process and the hydroformylation process.

Further examples of octene mixtures which may be used are those obtained by the so-called polymerization gasoline process (Polygas Verhahren) in which C is reacted over a solid acidic catalyst, preferably over a solid phosphoric acid catalyst₃/C₄The mixture is oligomerized (SPA process). This process is described in particular in documents US 6,284,938, US 6,080,903, US 6,072,093, US 6,025,533, US5,990,367, US5,895,830, US5,856,604, US5,847,252 and US5,081,086. The nonanols obtained by these processes usually also comprise an octanol and decanol content and optionally also undecanol, so that here the average chain length may deviate from 9 carbon atoms. However, this has no effect on the measurement of the degree of branching V by the above-described method.

Due to the raw materials used and due to process considerations, this C-rich₉C of (A)₈-C₁₁The composition of the alcohol mixture is significantly more complex, so that the distribution of the individual peaks in the corresponding gas chromatograph cannot be achieved without significant additional costs. The mixture is characterized in that the proportion of n-nonanol is generally significantly below 2%.

Typical distributions in such products have 2-6% octanol, 70-78% nonanol, 15-25% decanol and up to 2% undecanol. The boiling range (boiling onset to drying point) is 202 ℃ to 219 ℃ at atmospheric pressure. The EU risk assessment of diisononyl phthalate (DINP 1, CAS No. 68515-48-0, Jayflex DINP) from the polygasoline process shows: the alcohol used for this purpose consists of 5 to 10 mass% of methyl ethyl hexanol, 45 to 55 mass% of dimethyl heptanol, 5 to 20 mass% of methyl octanol, 0 to 1 mass% of n-nonanol, and 15 to 25% of decanol.

Commercially available embodiments of this type of isononyl alcohol mixtures have the following composition (manufacturer: Exxon), which mixtures can be used for preparing the diisononyl terephthalates used according to the invention:

1.73-3.73 mol% 3-ethyl-6-methylhexanol;

0.38-1.38 mol% 2, 6-dimethylheptanol;

2.78-4.78 mol% 3, 5-dimethylheptanol;

6.30-16.30 mol% 3, 6-dimethylheptanol;

5.74-11.74 mol% 4, 6-dimethylheptanol;

1.64-3.64 mol% 3, 4, 5-trimethylhexanol;

1.47 to 5.47 mol% 3, 4, 5-trimethylhexanol, 3-methyl-4-ethylhexanol and 3-ethyl-4-methylhexanol;

4.00-10.00 mol% 3, 4-dimethylheptanol;

0.99-2.99 mol% of 4-ethyl-5-methylhexanol and 3-ethylheptanol;

2.45-8.45 mol% of 4, 5-dimethylheptanol and 3-methyloctanol;

1.21-5.21 mol% 4, 5-dimethylheptanol;

1.55-5.55 mol% 5, 6-dimethylheptanol;

1.63-3.63 mol% 4-methyloctanol;

0.98-2.98 mol% 5-methyloctanol;

0.70-2.70 mol% 3, 6, 6-trimethylhexanol;

1.96-3.96 mol% 7-methyloctanol;

1.24-3.24 mol% 6-methyloctanol;

0.01-3 mol% of n-nonanol;

25 to 35 mol% of other alcohols having 9 and 10 carbon atoms;

the sum of the components mentioned therein is 100 mol%.

The degree of branching measured according to the above-described process for nonanol mixtures of this composition is generally from 1.4 to 2.2, in particular from 1.5 to 2.0, and very typically from 1.6 to 1.9.

Particularly preferred mixtures of isomeric nonanols which can be used in the process according to the invention are those obtainable by hydroformylation of isomeric octene mixtures and subsequent or simultaneous hydrogenation. Here, the isomeric octene mixture is obtained by contacting a hydrocarbon mixture comprising butenes with an oligomerization catalyst, in particular with a catalyst formally comprising nickel oxide. The proportion of isobutene in the hydrocarbon mixture is preferably less than 20% by weight, preferably less than 10% by weight, particularly preferably less than 5% by weight, very particularly preferably less than 3% by weight, particularly preferably less than 1% by weight, preferably from 0.01 to 1% by weight and particularly preferably from 0.05 to 0.5% by weight, based on the butenes. For example, the preparation of isomeric octenes by oligomerization of substantially linear butenes over a supported nickel catalyst is known as the OCTOL process, which is described, for example, in EP 0395857 or EP 1029839.

The isomeric octene mixture is then fed to a hydroformylation process. The hydroformylation process may be carried out in the presence of a modified or unmodified cobalt catalyst or a modified or unmodified rhodium catalyst. The hydroformylation process is preferably carried out in the presence of an unmodified cobalt compound. The hydroformylation process is usually followed by a hydrogenation process. These hydroformylation/hydrogenation processes are known, for example, from EP 0850905 and EP 1172349. The hydroformylation process may also be carried out in the presence of a rhodium catalyst. These hydroformylation processes are well known. Particular hydroformylation processes which have particularly good suitability for preparing mixtures of isomeric nonanols which can be used in the process according to the invention are described, for example, in WO 2004/020380 or DE 10327435. The processes described in those documents are carried out in the presence of cyclic carbonates.

It may also be advantageous to first fractionate the isomeric octene mixture before it is fed to the hydroformylation process, as described in EP 1172349. In this way, octene fractions (octenfrak) can be produced which have particularly good suitability for the preparation of mixtures of isomeric nonanols which can be used in the process according to the invention. Said fractions can then be used in a relatively simple manner by mixing of suitable fractions to obtain an isomeric octene mixture and this mixture is suitable for preparing an isomeric nonanol mixture for use in the process of the present invention.

The following commercially available nonanol mixtures prepared in this manner and particularly suitable for preparing the diisononyl terephthalates according to the invention have approximately the following composition (manufacturer: Evonik OXENO)

2.0-12.0 mol% of n-nonanol;

12.0-30.0 mol% 6-methyloctanol;

12.0-30.0 mol% 4-methyloctanol;

1.0-7.0 mol% 2-methyloctanol;

5.7-11.7 mol% 3-ethylheptanol;

1.0-4.5 mol% 2-ethylheptanol;

0.5-4.0 mol% 2-propylhexanol;

8.0-22.0 mol% 4, 5-dimethylheptanol;

5.0-16.0 mol% 2, 5-dimethylheptanol;

1.5-4.5 mol% 2, 3-dimethylheptanol;

1.0-7.5 mol% 3-ethyl-4-methylhexanol;

0.5-6.0 mol% 2-ethyl-4-methylhexanol;

0.2 to 6.5 mol% of other primary alcohols having 9 carbon atoms;

the sum of the components mentioned therein is 100 mol%.

The nonanol mixture of this composition generally has a degree of branching of from 1.1 to 1.4, in particular from 1.2 to 1.3, measured according to the method described above.

In a variant of the OCTOL process using a catalyst comprising nickel, for example, a catalyst comprising Ti or comprising Zr is used for the preparation of the octene mixture. These alternative variants and in particular catalysts are described, for example, in EP 1171413.

The following commercially available nonanol mixtures prepared in this way and particularly suitable for preparing the diisononyl terephthalates according to the invention have, for example, the following composition (manufacturer: BASF)

6.0-16.0 mol% of n-nonanol;

12.8-28.8 mol% 6-methyloctanol;

12.5-28.8 mol% 4-methyloctanol;

2.0-7.3 mol% 2-methyloctanol;

5.7-11.7 mol% 3-ethylheptanol;

1.3-3.9 mol% 2-ethylheptanol;

1.0-3.7 mol% 2-propylhexanol;

3.2-16.0 mol% 4, 5-dimethylheptanol;

4.0-16.0 mol% 2, 5-dimethylheptanol;

1.0-4.0 mol% 2, 3-dimethylheptanol;

1.0-7.5 mol% 3-ethyl-4-methylhexanol;

1.0-5.0 mol% 2-ethyl-4-methylhexanol;

0.5 to 6.5 mol% of other alcohols having 9 carbon atoms;

the sum of the components mentioned therein is 100 mol%.

The degree of branching measured according to the above-described process for isononyl alcohol mixtures of this composition is generally from 1.0 to 1.4, in particular from 1.2 to 1.3.

However, it is also possible to use, as isomeric nonanol mixture in the process according to the invention, mixtures obtained by mixing isomerically pure nonanol and/or isomeric nonanol fractions. A large number of isomerically pure nonanols are commercially available. Nonanol mixtures or nonanol fractions are likewise commercially available, which do not have the properties preferred for the process according to the invention. Simple mixing of these isomerically pure nonanols with nonanol mixtures can produce nonanol mixtures which have the desired average degree of branching and provide a mixture of terephthalic diesters having the desired properties.

The isononanol mixture to be used desirably contains not more than 0.0001 to 10 mol% of 3, 5, 5-trimethylhexanol. The mixture preferably contains less than 5 mol%, in particular less than 1 mol% and particularly preferably less than 0.5 mol% of 3, 5, 5-trimethylhexanol.

The proportion of n-nonanol in the isononanol mixture to be used is from 0.001 to 20 mol%, preferably from 1 to 18 mol% and particularly preferably from 5 to 15 mol%.

The content of 3, 5, 5-trimethylhexanol and n-nonanol in the alcohol mixture can generally be measured by gas chromatographic analysis (GC).

The nonanol mixture obtained by saponification of the diisononyl esters of the invention preferably comprises from 0.001 to 20 mol%, preferably from 0.5 to 18 mol%, particularly preferably from 6 to 16 mol%, of unbranched nonanols (i.e. n-nonanols). These mixtures additionally comprise 5 to 90 mol%, preferably 10 to 80 mol%, particularly preferably 45 to 75 mol%, of nonanols having a single branching (mit einer Verzweigung), and 5 to 70 mol%, preferably 10 to 60 mol%, particularly preferably 15 to 35 mol%, of doubly branched nonanols, and finally 0.1 to 15 mol%, preferably 0.1 to 8 mol%, particularly preferably 0.1 to 5 mol%, of triply branched nonanols. In addition, these nonanol mixtures may comprise from 0 to 40 mol%, preferably from 0 to 30 mol%, particularly preferably from 0.1 to 6.5% by weight, of further components. The other components are usually decanols, octanols or more than triply branched nonanols, where the sum of all components mentioned is 100 mol%.

The diisononyl terephthalate mixture of the invention can be prepared by the following route:

a) transesterification of terephthalates with alkyl residues having less than 8 carbon atoms using mixtures of isomeric primary nonanols

b) Esterification of terephthalic acid with a mixture of primary nonanols

c) Transesterifying, wholly or partially, the dinonyl terephthalate or the isomeric dinonyl terephthalate mixture with primary nonanols or with a mixture of primary nonanols

d) The isomerically pure nonyl terephthalates are mixed with one another, with a mixture of nonyl terephthalates, or with a mixture of two or more dinonyl terephthalates.

The mixtures of isomeric dinonyl terephthalates according to the invention are preferably prepared by the routes a) and b).

If diisononyl terephthalate is prepared by transesterification, the preferred starting material is dimethyl terephthalate (DMT), which is produced industrially on a large scale.

For example, transesterification processes are catalyzed using Bronsted or Lewis acids or bases as catalysts. Regardless of which catalyst is used, the temperature-dependent equilibrium is generally adjusted between the starting materials (dialkyl terephthalate and isononyl alcohol) and the product (diisononyl terephthalate and the alcohol liberated from the dialkyl terephthalate used). In order to shift the equilibrium towards the terephthalate esters which are advantageous for the present invention, distillation may advantageously be used to remove the alcohol derived from the feed ester from the reaction mixture.

Furthermore, in this embodiment of the process of the invention, a total excess of alcohol can advantageously be used. The starting alcohol is preferably used in a molar excess of 5 to 50%, in particular 10 to 30%, of the molar amount required to form the dialkyl terephthalate of the invention.

As transesterification catalysts, it is possible to use acids, such as sulfuric acid, methanesulfonic acid or p-toluenesulfonic acid, or metals or compounds thereof. Examples of suitable metals or compounds thereof are tin, titanium, zirconium, which are used in the form of finely divided metals or, where appropriate, in the form of their salts, or as oxides or in the form of soluble organic compounds. Unlike catalysts based on protonic acids, metal catalysts are high temperature catalysts which usually achieve their full activity only above 180 ℃. These metal catalysts based on metals or compounds thereof can be advantageously used, since these catalysts are found to form by-products, such as olefins formed from the alcohols used, less than catalysts based on protic acids. Examples of metal catalysts which are particularly preferably used are tin powder, stannous (II) oxide, stannous (II) oxalate, titanium esters, such as tetraisopropyl orthotitanate or tetrabutyl orthotitanate, and zirconium esters, such as tetrabutyl zirconate. Basic catalysts such as alkali or alkaline earth metal oxides, hydroxides, bicarbonates, carbonates or alkoxides may also be used. Within this group, alkoxides such as sodium methoxide are preferably used. Alkoxides can also be prepared in situ from alkali metal and nonanol or isononanol mixtures. Particular preference is given to using alkoxides whose alcohol residue is identical to one of the alcohols involved in the reaction.

The catalyst concentration can vary within wide limits and depends inter alia on the nature of the catalyst. The catalyst concentration is preferably from 0.005 to 2.0% by mass, based on the reaction mixture. The optimum concentration of each catalyst can be readily determined by preliminary experiments and is obtained by a compromise between as small an amount of catalyst as possible (i.e. cost) and as high a reaction rate as possible. In the case of particularly preferred tetrabutyl orthotitanate, the preferred concentration is, for example, from 0.05 to 1% by mass, based on the dialkyl terephthalate used.

The transesterification process is preferably carried out at a temperature of 100 ℃ and 220 ℃. It is particularly preferred to select the temperature so high as to allow distillative removal of the alcohol from the feed ester from the reaction mixture at the specified pressure.

These crude ester mixtures can be worked up in the same manner as those prepared by esterification of terephthalic acid as described hereinafter.

All known processes can be used for the preparation of the dinonyl terephthalate mixtures of the present invention by terephthalic acid esterification with a mixture of primary nonanols. However, the esterification step is preferably carried out by a process comprising: wherein the water of reaction is removed by azeotropic distillation with the alcohol and the amount of liquid removed from the reaction by azeotropic distillation is additionally supplemented in whole or in part by the alcohol. The term liquid amount is used hereinafter for the liquid volume removed from the reaction by azeotropic distillation, which consists mainly of reaction water and alcohol. The amount of liquid removed is preferably replaced entirely. This can be achieved, for example, by feeding alcohol into the reactor in a level-controlled manner (standgeregelt). For technical reasons, a complete replacement of the removed liquid quantity may not be possible or only be possible with difficulty. In these cases, the amount of liquid removed is only partially replaced, for example only the amount of alcohol, while the amount of reaction water removed is not replaced, but the proportion of replacement is generally more than 90%, preferably 95-98%.

It may also be necessary to return more liquid than is removed by distillation, i.e. not only the amount of alcohol removed but also the replacement reaction water and also further alcohol to the reactor. In this embodiment of the esterification process, the proportion of the amount of liquid removed which is replaced by alcohol is 110-100%, preferably 105-100%.

An advantage of this embodiment of the esterification process is that the reaction rate is increased compared to known discontinuous processes. The result may be a shortened cycle time, thereby achieving a higher space-time yield.

The esterification process may be autocatalytic or catalytic. Esterification catalysts which may be used are lewis acids or bronsted acids or organometallic substances, which do not necessarily have to act as acids. Preferred esterification catalysts are alkoxides, carboxylates of titanium or zirconium or chelate compounds, wherein the catalyst molecule may contain one or more metal atoms. In particular, tetra (isopropyl) orthotitanate and tetra (butyl) orthotitanate are used.

The esterification process is preferably carried out in a reaction vessel, wherein the reaction mixture can be intimately mixed by means of a stirrer or circulation pump. The feed and catalyst may be charged to the reactor simultaneously or sequentially. If one of the starting materials is solid at the charging temperature, it is expedient to introduce it beforehand into the liquid starting components. The solid starting material may be fed in the form of powder, granules, crystals or melts. In order to shorten the batch time, it is advisable to start heating during charging. The catalyst can be introduced in pure form or as a solution preferably dissolved in one of the starting materials, initially or only after the reaction temperature has been reached.

The alcohol to be reacted which acts as entrainer can be used in stoichiometric excess. Preference is given to using an excess of from 5 to 50%, particularly preferably from 10 to 30%.

The catalyst concentration depends on the catalyst properties. In the case of the titanium compounds preferably used, they are from 0.005 to 1.0% by mass, in particular from 0.01 to 0.3% by mass, based on the reaction mixture.

When a titanium catalyst is used, the reaction temperature is 160 ℃ to 270 ℃. The optimum temperature depends on the starting materials, the progress of the reaction and the catalyst concentration. They can be readily determined experimentally for any particular situation. Higher temperatures increase the reaction rate and favor side reactions, such as dehydration from alcohols or the formation of colored by-products. In order to remove the reaction water, it is required that the alcohol can be removed from the reaction mixture by distillation. The desired temperature or desired temperature range can be adjusted by the pressure in the reaction vessel.

The amount of liquid to be returned to the reaction may partly or wholly consist of the alcohol obtained by the azeotropic distillate work-up. It is also possible to carry out a post-treatment at a later point in time and to replace the amount of liquid removed in whole or in part with fresh alcohol, i.e. the alcohol provided in the storage container. In other embodiments of the esterification process, the removed liquid is worked up to give the alcohol, preferably to give the alcohol in pure form.

Once the reaction has ended, the reaction mixture consisting essentially of the full ester (the desired product) and the excess alcohol contains small amounts of ester carboxylic acid in addition to the catalyst and/or the subsequent products obtained from the catalystAnd/or unreacted carboxylic acid. To work up these crude ester mixtures, the excess alcohol is removed, the acidic compounds are neutralized, the catalyst is destroyed and the solid by-products produced therein are removed. Here, the predominant part of the alcohol is removed by distillation at atmospheric pressure or under vacuum. The final traces of alcohol can be removed, for example, by steam distillation, in particular at temperatures in the range from 120 ℃ to 225 ℃. The removal of the alcohol can for example be the first or last step of the work-up.

Neutralization of acidic species, such as carboxylic acids or ester carboxylic acids or optionally acidic catalysts, may be carried out by adding basic compounds of alkali and alkaline earth metals. These may be used in the form of their carbonates, bicarbonates or hydroxides. The neutralizing agent can be used in solid form or preferably as a solution, in particular as an aqueous solution. Neutralization may be carried out immediately after the end of the esterification reaction, or after the removal of most of the excess alcohol by distillation. It is preferred to neutralize with aqueous sodium hydroxide at a temperature above 150 ℃ immediately after the end of the esterification reaction. The water introduced with the lye can then be removed by distillation together with the alcohol.

Further details of suitable esterification processes which can be used as esterification step in the process of the present invention can be found, for example, in EP 1186593 and EP 1300388.

The esterification process can be carried out particularly advantageously in the manner described in DE 102005021075.9.

Since terephthalic acid is only difficult to dissolve in the alcohol to be used in the esterification process, even at the boiling point, it is possible by using an overpressureTo increase solubility and thereby increase the reaction rate. Otherwise, the batch time may be significantly longer.

These problems do not arise if DMT is used in the transesterification process. Starting from DMT, the corresponding terephthalate can generally be obtained in a shorter batch time than when using phthalic acid as starting material. The preparation of the diisononyl terephthalates according to the invention by transesterification from DMT is therefore particularly preferred.

The diisononyl terephthalate mixtures of the invention can advantageously be used as a plasticizer or as part of a plasticizer composition in plastics or plastic components, or as an additive in paints or lacquers, in adhesives or adhesive components, or in sealants, or as a solvent.

The advantages of the diisononyl terephthalate mixtures according to the invention are the following:

the diisononyl terephthalates according to the invention are more versatile than isomerically pure dialkyl terephthalates having 9C atoms in the side chain, such as di-n-nonyl terephthalate and di-3, 5, 5-trimethylhexyl terephthalate, since they are liquid at room temperature and can therefore also be used in plastisol processes which are notable in number and in which application at room temperature is only possible by using a liquid plasticizer phase. Since they are liquid even at low temperatures as low as about-70 ℃ and exhibit a glass transition temperature below-70 ℃ or in some cases can reach temperatures as low as the glass transition temperature without any crystallization at all, they can moreover be pumped without difficulty even at very low temperatures and are therefore preferably suitable for corresponding industrial applications.

They have a lower viscosity when compared to the corresponding dialkyl terephthalates having a higher degree of branching, which is advantageous for processing in the plastisol process. They have better compatibility with the polymer when compared to the less branched isomers.

The inventive diisononyl terephthalate mixtures or mixtures of these with plastics, preferably PVC, PVB and PAMA, may also comprise further compounds which can be used as plasticizers. Among these compounds, particularly preferred esters are, for example, the following compounds:

dialkyl phthalates preferably having 4 to 13 carbon atoms in the alkyl chain; trialkyl trimellitates having preferably 6 to 10 carbon atoms in the side chain; dialkyl adipates preferably having 6 to 10 carbon atoms; dialkyl terephthalates having in each case preferably from 4 to 8 carbon atoms, in particular from 4 to 5 carbon atoms, in the side chain; alkyl 1, 2-cyclohexanedicarboxylates, alkyl 1, 3-cyclohexanedicarboxylates and alkyl 1, 4-cyclohexanedicarboxylates, preference being given here to alkyl 1, 2-cyclohexanedicarboxylates having preferably in each case 4 to 10 carbon atoms in the side chain; ethylene glycol dibenzoate; alkyl sulfonates of phenols preferably having an alkyl residue containing from 8 to 22 carbon atoms; a polymeric plasticizer; glycerides, trialkyl citrates having free or carboxylated OH groups and an alkyl residue having from 4 to 10 carbon atoms, and alkyl benzoates preferably having from 7 to 13 carbon atoms in the alkyl chain. In all cases, the alkyl residues may be linear or branched and may be the same or different.

In addition to diisononyl terephthalate, the compositions particularly preferably comprise alkyl benzoates, preferably isononyl, nonyl, isodecyl or decyl benzoate, or 2-propylheptyl benzoate, having in particular 7 to 13 carbon atoms in the alkyl radical. Likewise particularly preferred are mixtures of diisononyl terephthalates and diamyl terephthalates.

The proportion of diisononyl terephthalate according to the invention in the mixture with other plasticizers is preferably from 15 to 95%, particularly preferably from 20 to 90% and very particularly preferably from 25 to 85%, where the mass proportion of all plasticizers present amounts to 100%.

The compositions mentioned, consisting of diisononyl terephthalate and other plasticizers, can be used as plasticizer compositions in plastics and plastics compositions, in adhesives, in sealants, in paints, in plastisols or in inks.

The inventive plastic composition comprising the inventive diisononyl terephthalate mixture may contain a polymer selected from the group consisting of: polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyacrylates, in particular polymethyl methacrylate (PMMA), Polyalkylmethacrylates (PAMA), 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-butadiene-styrene (ABS), styrene-maleic anhydride copolymers (SMA), styrene-methacrylic acid copolymers, 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), polysulphide (PSu), biopolymers, in particular polylactic acid (PLA), polyhydroxybutyric acid (PHB), polyhydroxyvaleric acid (PHV), polyesters, starch, cellulose and cellulose derivatives, in particular Nitrocellulose (NC), Ethylcellulose (EC), Cellulose Acetate (CA), cellulose acetate/butyrate (CAB), rubber or silicone, and mixtures or copolymers of the mentioned polymers or their monomer units. The composition of the invention preferably comprises PVC or a homopolymer or copolymer based on: ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, methacrylic acid esters, acrylic acid esters or methacrylic acid esters having an alkyl residue of a branched or unbranched alcohol having 1 to 10 carbon atoms bonded to the oxygen atom of the ester group, styrene, acrylonitrile or cyclic olefins.

The PVC-based compositions of the invention preferably comprise suspension PVC, bulk PVC, microsuspension PVC or emulsion PVC. The composition of the present invention preferably contains 5 to 200, preferably 10 to 150 parts by mass of the plasticizer of the present invention based on 100 parts by mass of the polymer.

In addition to the components mentioned, the compositions of the invention may also comprise further components, such as in particular further plasticizers, fillers, pigments, stabilizers, co-stabilizers, such as epoxidized soybean oil, lubricants, blowing agents, propellants, antioxidants or biocides.

The compositions according to the invention consisting of diisononyl terephthalate and the abovementioned polymeric materials can be used as plastics compositions, adhesives, sealants, lacquers (Lacke), paints (Farbe), plastisols, artificial leather, floor coverings, underbody cladding, textile coatings, wallpaper or inks, or for the preparation of these.

Examples of plastic articles made using the plasticizer composition may be: profiles, gaskets, food packaging, foils, toys, medical items, roofing sheets, artificial leather, floor coverings, underbody shields, coated fabrics, wallpaper, wire and cable sheathing. Preferred fields of application from this group are food packaging, toys, medical articles, wallpaper and floor coverings.

The following examples are intended to illustrate the invention and are not intended to limit the invention thereto.

Example (b):

example 1 (inventive): preparation from terephthalic acid and isononyl alcohol from Evonik OXENO OlefinichemieDiisononyl terephthalate(DINTP)

In a 4 liter stirred flask with distillation bridge, with reflux distributor, 20cm multi-pack (multifil) column, stirrer, dip tube, dropping funnel and thermometer, 830g (5mol) of terephthalic acid (Sigma Aldrich), 2.08g (0.25 mass%, based on terephthalic acid) of tetrabutyl orthotitanate and 1800g (12.5mol) of isononyl alcohol (EvonikOXENO oleofinichemie) prepared by the OCTOL method were used as initial charge and esterified at 230 ℃. After 9 hours the reaction was complete and then the excess alcohol was removed by distillation at 180 ℃ and 3 mbar. The mixture was then cooled to 80 ℃ and neutralized with 6ml of a 10 mass% aqueous NaOH solution. The steam distillation is then carried out at a temperature of 180 ℃ and a pressure of 20 to 5 mbar. The batch was then dried at this temperature at 5 mbar and filtered after cooling to 120 ℃. GC showed 99.9% ester content.

The degree of branching of the alcohol side chain of the ester was measured as XX.

The glass transition point (the so-called "average value" according to DIN) was measured by Differential Scanning Calorimetry (DSC) to be-83 ℃. No melting signal was detected.

The product can thus be used without difficulty as a plasticizer in plastisols, as shown in example 6.

Example 2 (inventive): DINTP preparation from dimethyl terephthalate (DMT) and isononyl alcohol

In a 2 l stirred flask with distillation bridge, with reflux distributor, 20cm multiple packed column, stirrer, dip tube, dropping funnel and thermometer, 388g (2mol) DMT (Oxxynova), 1.16g (0.3 mass%, based on DMT) tetrabutyl orthotitanate and the first 288g of isononyl alcohol (Evonik OXENO) in a total of 720g (5mol) were used as initial charge. The system was slowly heated until all solids were no longer visible and then the stirrer was turned on. The mixture was further heated until methanol appeared on the reflux distributor. The reflux distributor was adjusted to maintain the overhead temperature constant at about 65 ℃. The remainder of the alcohol was slowly fed in starting at the bottom of the column at a temperature of about 230 c in such a way as to avoid the temperature in the flask dropping below 220 c and to maintain sufficient reflux. Samples were occasionally studied by GC and the content of diisononyl terephthalate was measured. When the diisononyl terephthalate content was 99.8%, the transesterification was stopped.

Example 3 (inventive): DINTP preparation from terephthalic acid and isononyl alcohol from ExxonMobil

In a 4 l stirred flask with distillation bridge, with reflux distributor, 20cm multiple-packed column, stirrer, dip tube, dropping funnel and thermometer, 830g (5mol) of terephthalic acid (Sigma Aldrich), 2.08g (0.25% by mass, based on terephthalic acid) of tetrabutyl orthotitanate and 1728g (12mol) of isononanol (Exxal 9, ExxonMobil) from the polygas process were used as initial charge and esterified at 245 ℃. After 10.5 hours the reaction was complete and then the excess alcohol was removed by distillation at 180 ℃ and 3 mbar. The system was then cooled to 80 ℃ and neutralized with 12ml of 10 mass% aqueous NaOH solution. The steam distillation is then carried out at a temperature of 180 ℃ and a pressure of 20 to 5 mbar. The batch was then dried at this temperature at 5 mbar and filtered after cooling to 120 ℃. GC showed 99.9% ester content.

The glass transition point (average according to DIN) was measured by DSC to be-76 ℃.

The degree of branching of the alcohol side chain of the ester was measured as XX.

Thus, the higher degree of branching of the alcohols used here is sufficient in itself to increase significantly the glass transition point of the corresponding esters and thus also to increase their ability to reduce the glass transition point of PVC to such an extent that it remains flexible even at relatively low outdoor temperatures.

Example 4 (comparative example): DINTP preparation from terephthalic acid and n-nonanol

Analogously to example 1, n-nonanol (FLUKA) is esterified with terephthalic acid and worked up as described above. When the product, which according to GC had an ester content of > 99.8%, was cooled to room temperature, it solidified.

The melting point was measured by DSC to be 46 ℃ and for this purpose the initial rise in the melting signal (known as "onset") was used. No glass point could be detected.

Example 5 (comparative example): DINTP preparation from terephthalic acid and 3, 5, 5-trimethylhexanol

Analogously to example 1, 3, 5, 5-trimethylhexanol (FLUKA) was esterified with terephthalic acid and worked up as described above. When the product, which according to GC had an ester content of > 99.5%, was cooled to room temperature, it solidified.

When the melting point was measured by DSC, two melting signals were detected. The initial rise (so-called "onset") of the lower of the two curves was 42 ℃. No glass point could be detected.

Example 6: preparation of plastisols

A plastisol was prepared using the diisononyl terephthalate of the invention prepared according to example 1 as follows:

100g of dinonyl terephthalate, 6g of epoxidized soybean oil (DRAPEX 39) and 3g of Ca/Zn stabilizer (MARK CZ 140) were first weighed into a PE beaker and then 200g of PVC (Vestolit B7021) was added. The temperature of all liquids was previously adjusted to 25 ℃. The mixture was stirred manually with a paste spatula in such a way that no more powder was present which was not wetted. The mixing beaker was then clamped in the clamping device of the dissolver mixer. The rotational speed was set at 1800 rpm before the stirrer was immersed in the mixture. Once the stirrer was turned on, stirring was continued for such a long time until the temperature on the digital display of the temperature sensor reached 30.0 ℃. This ensures that the plastisol is homogeneous using a certain energy input. The temperature of the plastisol was then immediately adjusted to 25.0 ℃.

Example 7: plastisol viscosity measurement

The viscosity of the plastisol prepared in example 6 was measured analogously to DIN 53019 using a physicasr 4000 rheometer (Paar-Physica) controlled by the relevant US 200 software, using the following manner:

the plastisol was again stirred in a storage vessel with a spatula and tested in a Z3 measuring system (DIN 25mm) according to the operating instructions. The test was performed automatically by the above software at 25 ℃. The following conditions were used:

·100s^-1pre-cut 60s period, not record any test value

Downward slope at 200s^-1Starting and going down to 0.1s^-1The distribution is logarithmic in 30 steps, with the measuring points lasting 5s in each case.

And after the test, automatically post-processing the test data through software. Viscosity is shown as a function of shear rate. The tests were carried out after a storage time of 2 hours under standard climatic conditions.

FIG. 1 plots the viscosity of a plastisol as a function of shear rate.

From which the person skilled in the art readily sees that the plastisols have good processing ability, since the shear rate is in the middle range (10 s)^-1) The viscosity of the inner plastisol is relatively low and the initial rise is relatively mild over the higher shear rate range.

Claims (15)

1. A mixture of diisononyl esters of terephthalic acid, characterised in that the average degree of branching of the isomeric nonyl residues bonded in the ester mixture is from 1.0 to 2.2.

2. Mixture according to claim 1, characterized in that the average degree of branching of the bonded isomeric nonyl residues in the ester mixture is from 1.1 to 2.1.

3. Mixture according to claim 1, characterized in that the average degree of branching of the bonded isomeric nonyl residues in the ester mixture is 1.1 to 2.0.

4. Mixture according to claim 1, characterized in that the average degree of branching of the bonded isomeric nonyl residues in the ester mixture is 1.2 to 1.5.

5. A mixture according to any one of claims 1 to 4, characterized in that the isomeric nonyl residues bonded in the ester mixture are based on primary nonanols.

6. Process for the preparation of a mixture of diisononyl terephthalates according to any of claims 1 to 5, characterized in that the preparation of the isononyl ester uses a mixture of isomeric nonanols having an average degree of branching of 1.0 to 2.2.

7. Process according to claim 6, characterized in that the preparation is carried out by transesterification of terephthalates with alkyl residues of less than 8 carbon atoms with a mixture of isomeric primary nonanols.

8. Process according to claim 6, characterized in that the preparation process is carried out by esterifying terephthalic acid with a mixture of primary nonanols.

9. Process according to claim 6, characterized in that the preparation is carried out by total or partial transesterification of dinonyl terephthalate or of a mixture of isomeric dinonyl terephthalates with primary nonanols or with a mixture of primary nonanols.

10. Process according to claim 6, characterized in that the preparation process is carried out by mixing isomerically pure nonyl terephthalates with one another, with a mixture of isomerically pure nonyl terephthalates with nonyl terephthalates, or with a mixture of two or more dinonyl terephthalates.

11. The process according to any of claims 6-10, characterized in that the isononanol mixture to be used comprises not more than 0.0001 to 10 mol% of 3, 5, 5-trimethylhexanol.

12. The process according to claim 11, characterized in that the mixture comprises less than 5 mol%, in particular less than 1 mol%, and particularly preferably less than 0.5 mol% of 3, 5, 5-trimethylhexanol.

13. Process according to any of claims 6 to 12, characterized in that the proportion of n-nonanol in the isononanol mixture to be used is from 0.001 to 20 mol%, preferably from 1 to 18 mol% and particularly preferably from 5 to 15 mol%.

14. Use of the diisononyl terephthalate mixture of claims 1-5 as part of a plasticizer or plasticizer composition in plastics or plastic components, or as an additive in paints or lacquers, adhesives or adhesive components, or sealers, or as a solvent.

15. Plastics or plastic compositions, in particular based on PVC, PVB or PAMA, and plastic articles produced therefrom, characterized in that they comprise a diisononyl terephthalate mixture according to claims 1 to 5.