UTILIZATION OF POLYETHYLENE-CONTAINING MIXTURES TO FORM LONG-CHAIN ALKYL DICARBOXYLIC ACIDS BY WAY OF OXIDATIVE DEGRADATION

Abstract

The present invention relates to a process for producing a mixture that is insoluble in water of a homologous series of a number of various long-chain (C.sub.8) alkyl dicarboxylic acids, more particularly ,-n-alkyl dicarboxylic acids, by oxidative degradation of polyethylene (PE)-containing mixtures with oxygen, and to the mixtures or compositions obtainable therefrom and to their uses.

Claims

1. A process for the preparation of a water-insoluble mixture of a homologous series of a plurality of different linear ,-alkyl dicarboxylic acids having a carbon chain length of at least C.sub.8, starting from polyethylene-containing mixtures by oxidative cleavage with an oxygen-containing reaction gas, comprising: providing a polyethylene-containing mixture which has a total polyethylene content of at least 50% by mass with an HDPE content of at least 5.0% by mass, whereby the polyethylenes contained each have a weight-average molecular weight (Mw) of at least 20,000 g/mol, and heating the mixture provided to a temperature in a range from above the melting point of the polyethylene-containing mixture to 300 C. in an oxygen-containing reaction gas consisting of at least 5% by volume of oxygen at a process pressure of at least 1 bar in the presence of at least one catalyst in order to oxidatively decompose the polyethylene-containing mixture, wherein the resulting product mixture comprises a plurality of different linear ,-alkyl dicarboxylic acids with a carbon chain length of at least C8 and an acid number of at least 100 mg KOH/g.

2. The process according to claim 1, wherein the polyethylene-containing mixture employed has a secondary raw material content of at least 50% by mass.

3. The process according to claim 2, wherein the polyethylene-containing secondary raw material stream employed has a total polyethylene content of at least 90% by mass and a relative HDPE content of at least 50% by mass.

4. The process according to claim 1, wherein at least one catalyst selected from the group consisting of N-hydroxyphthalimide (NHPI), metals and metal salts is employed, wherein the metals are selected from the group of Mo, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt and Au, and wherein the cation of the metal salts is selected from the group of Mn, Fe, Co, Ni, Cu, Zn, Cr, V, Ti, Ru, Rh, Pd, Ag, Mo, W, Re, Os, Ir, Pt and Au and the anion of the metal salts is at least one selected from the group consisting of laurate, myristate, palmitate, palmitoleate, stearate, oleate, erucate, naphthenate, acetate, acetylacetonate, chloride, bromide, iodide, nitrate, oxide, sulfate, carbonate and phosphate.

5. The process according to claim 1, wherein the catalyst comprises at least one catalyst which is not soluble in the product mixture.

6. The process according to claim 5, wherein the catalyst which is insoluble in the product mixture is selected from the group of transition metal oxides, noble metals, supported noble metals and supported metal salts.

7. The process according to claim 6, wherein the catalyst comprises a manganese oxide.

8. The process according to claim 5, wherein the catalyst comprises N-hydroxyphthalimide.

9. The process according to claim 1, wherein a catalyst mixture is used, consisting of at least two catalysts, wherein at least one of the catalysts comprises at least one catalyst which is not soluble in the product mixture and at least one catalyst which is soluble in the product mixture.

10. The process according to claim 9, wherein the catalyst soluble in the product mixture is selected from the group consisting of transition metal salts soluble in the product mixture and N-hydroxyphthalimide.

11. The process according to claim 5, wherein the catalyst which is not soluble in the product mixture is separated from the reaction mixture or the reaction product after the reaction with the oxygen-containing reaction gas.

12. The process according to claim 1, wherein the amount of the at least one catalyst is 0.0001 to 10.0% by mass, based on 100% by mass of the polyethylene-containing mixture employed.

13. The process according to claim 1, wherein the reaction is carried out in water or in an aqueous medium as reaction medium.

14. The process according to claim 1, wherein the product mixture is purified by at least one process selected from the group consisting of filtration, drying, precipitation, extraction, crystallization, fractional distillation, steam distillation and column chromatography.

15. The process according to claim 1, wherein at least 50 mol % of the detectable products obtained have a carbon chain length in the range of C.sub.8 to C.sub.34 as determined by gas chromatography using linear ,-alkyl dicarboxylic acids as reference substances.

16. A mixture of a homologous series of a plurality of different linear ,-alkyl dicarboxylic acids having a carbon chain length of at least C.sub.8, obtainable by a process according to claim 1, wherein at least 50 mol % of the detectable products obtained have a carbon chain length in the range C.sub.8 to C.sub.34 as determined by gas chromatography using linear ,-alkyl dicarboxylic acids as reference substances.

17. A composition consisting essentially of a water-insoluble mixture of a homologous series of at least 10 different linear ,-alkyl dicarboxylic acids having a carbon chain length in the range from C.sub.8 to C.sub.34, the proportion of water-soluble compounds and compounds having a carbon chain length of C.sub.35 or more being less than 10% by mass.

18. The mixture according to claim 16, wherein the average carbon chain length of the mixture, which is defined as the maximum of a distribution determined by gas chromatography using linear ,-alkyl dicarboxylic acids as reference substances, is C.sub.9.

19. The mixture according to claim 16, wherein the mixture contains at least 5% by mass of keto-functionalized and/or hydroxy-functionalized ,-alkyl dicarboxylic acids.

20. The mixture according to claim 16, wherein the mixture contains at least 5% by mass of ,-alkyl dicarboxylic acids with a chain length C.sub.19.

21. The mixture according to claim 16, wherein the mixture contains at least 10% by mass of ,-alkyl dicarboxylic acids with a chain length in the range C.sub.19 to C.sub.34.

22-25. (canceled)

26. A pure linear ,-alkyl dicarboxylic acid having a carbon chain length in the range from C.sub.8 to C.sub.34, an emulsifier, a water-based lubricant, or a biodegradable polyester prepared from the mixture of claim 16.

27. The process according to claim 7, wherein the catalyst comprises manganese dioxide.

28. The mixture according to claim 18, wherein the average carbon chain length of the mixture is in the range from C.sub.12 to C.sub.28.

29. The mixture according to claim 19, wherein the mixture contains 5 to 20% by mass of keto-functionalized and/or hydroxy-functionalized ,-alkyl dicarboxylic acids

30. The mixture according to claim 20, wherein the mixture contains 5 to 80% by mass of ,-alkyl dicarboxylic acids with a chain length C.sub.19.

31. The mixture according to claim 21, wherein the mixture contains 10 to 80% by mass of ,-alkyl dicarboxylic acids with a chain length in the range C.sub.19 to C.sub.34.

Description

[0113] The following examples and the accompanying figures serve to illustrate, but are not limited to, the present invention.

[0114] FIG. 1 shows a gas chromatogram of the chain length distribution of the product of a reaction carried out analogously to Example 1 (vide infra) at 150 C., 30 bar and 16 h and worked up according to Example 1. The sample preparation for GC analysis is described in the examples. The dashed lines show the respective retention times of ,-alkyl dicarboxylic acid standards. The peak of the solvent is marked with S.

[0115] FIG. 2 shows the development of the oxygen content in the gas phase after the reaction with manganese(II) palmitate (Mn(Palm).sub.2) and MnO.sub.2 for varying reaction times. Obviously, the activities of the homogeneous catalyst Mn(Palm).sub.2 and the heterogeneous catalyst MnO.sub.2 are comparable. The catalyst seems to have a slight induction phase, but after that the activities approach each other.

[0116] FIG. 3 shows a comparison of the infrared spectra (1650 to 1850 cm-1) of reactions A: without catalyst (example 21 below); B: with Mn(Palm).sub.2 (example 19 below) and C: with MnO.sub.2 (example 15). Dashed lines show the deconvolution (Lorentz curves) of the carbonyl band into ketone and ester band. It can be seen that the homogeneous catalyst Mn(Palm).sub.2 and the heterogeneous catalyst MnO.sub.2 behave essentially analogously. Without a catalyst, a higher proportion of ketone is present, which is also a disadvantage.

[0117] FIG. 4 shows a comparison of the infrared spectra (1650 to 1850 cm-1) of reactions A: with fresh MnO.sub.2 (example 15) and B: with recovered MnO.sub.2 (example 24). Dashed lines show the deconvolution of the carbonyl band into ketone and ester band. It can be seen that the reaction products with fresh and recycled catalyst are comparable. The same applies to the activities, as can be seen from the oxygen conversions in Table 4.

ACID NUMBER (AN)

[0118] To determine the acid number, stock solutions were prepared gravimetrically from the respective reaction mixtures (accuracy 0.0001 g) in i-PrOH with a concentration of approx. 10 mg/mL (0.2). Subsequently, aliquots of 0.5 mL each corresponding to approx. 5 mg sample were taken volumetrically and again determined gravimetrically (accuracy 0.0001 g). The total sample quantity was therefore determined completely gravimetrically. The sample was supplemented with the titration solvent to a total volume of 10 mL. The titration solvent consisted of 500 mL i-PrOH, 500 mL toluene, 1 mL deionized water and 500 mg phenolphthalein. The sample prepared in this way was titrated with freshly prepared KOH solution in i-PrOH (0.02 M) in an automated titration apparatus with optical endpoint detection. The optical endpoint was calibrated using a benzoic acid sample as a reference for each sample series and then used for the evaluation of the samples.

Carbon Chain Lengths of the Prepared ,-n-Alkyl Dicarboxylic Acids

[0119] The carbon chain lengths of the prepared ,-n-alkyl dicarboxylic acids in the product mixture to be analyzed were determined by gas chromatography (GC-FID) (Perkin Elmer Clarus 500; column length=30 m, diameter=0.320 mm, film thickness=0.25 m, 5% phenylmethylpolysiloxane). The samples were previously treated with basic hydrazine to remove interfering ketodicarboxylic acids for GC analysis and then derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as COOTMS ester. The retention times of the different chain length ranges were defined using measurements of long-chain ,-n-alkyl dicarboxylic acids as standards. The respective ,-n-alkyl dicarboxylic acids of chain lengths C.sub.4, C.sub.6, C.sub.7, C.sub.8, C.sub.9, C.sub.10, C.sub.12, C.sub.14, C.sub.15, C.sub.23, C.sub.26 and C.sub.32, as shown in Table 1 below, were used for this purpose.

TABLE-US-00001 TABLE 1 Chain length dicarboxylic acid reference (as -TMS ester) Retention time [min] 32 10.40 26 8.44 23 7.89 18 6.88 14 5.94 12 5.42 10 4.86 9 4.58 8 4.25 7 3.91 6 3.56 4 2.08

Gas Phase Analysis

[0120] To determine the oxygen content of the gas phase after the reaction, the residual pressure of the steel autoclave was released into a gas sample bag. This gas sample (200 ml) was analyzed using an oxygen meter (ZhongAn S316).

Optical Emission Spectrometry with Inductively Coupled Plasma (ICP-OES)

[0121] The residual manganese content was determined using ICP-OES (Spektro Arcos ICP-OES) after microwave digestion with a CEM MARS6.

Infrared Spectroscopy

[0122] 20 mg of the sample obtained was esterified in a mixture of 0.5 ml chloroform, 0.5 ml methanol and 0.1 ml concentrated hydrochloric acid at 65 C. for 3 hours. The hydrochloric acid contained was neutralized by adding 100 mg sodium hydrogen carbonate and the solvent was distilled off. The resulting mixture was dissolved in 1 ml chloroform, filtered through a Teflon filter (pore size: 0.2 m) and the solvent was distilled off. The residue was analyzed by ATR-IR spectroscopy (Perkin Elmer Spectrum 100).

[0123] The following abbreviations are used in the examples: [0124] HDPE: high-density polyethylene [0125] MnO.sub.2: Manganese(IV) oxide [0126] Mn(Palm).sub.2: Manganese(II) palmitate [0127] Mn(acac).sub.2: Manganese(II) acetylacetonate [0128] NHPI: N-hydroxyphthalimide [0129] T.sub.m: Melting point [0130] DSC: Differential scanning calorimetry [0131] M.sub.W: Melting point [0132] wt %: Percent by weight

Example 1

[0133] First, 200 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), MW=71.2 kg/mol) were weighed out in a glass insert and mixed with a magnetic stirring rod. This glass insert was placed in a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized at room temperature with synthetic air (20.0% oxygen by volume, 80.0% nitrogen by volume) to 20.0 bar, then placed in a heating block preheated to 200 C. and heated for 1 h. The reaction time represents the start of the reaction time. The start of the reaction time is represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block and the pressure was immediately released to end the reaction. The melt cake was cooled to room temperature hen dissolved in 7 ml of hot xylene (130 C.) and the resulting solution precipitated in 30 ml of cold methanol (20 C.). The insoluble components were centrifuged off and the solvents (xylene and methanol) of the separated centrifugate were again removed by distillation. The resulting residue of 73 mg was then analyzed by titration and was found to have an acid value of 158 mg KOH/g product.

Examples 2 to 5

[0134] Example 2 was carried out analogously to example 1, whereby the granulated HDPE was further mixed with 1.0% by mass manganese(II). Example 3 was prepared analogously to Example 1, with a further 1.0% by mass of iron(III) stearate being added to the granulated HDPE. Example 4 was prepared analogously to Example 1, with a further 1.0% by mass of copper(II) stearate being added to the granulated HDPE. Example 5 was prepared analogously to Example 1, with the further addition of 0.1% by mass N-hydroxyphthalimide (NHPI) and 2.5% by mass 12-tricosanone as initiator to the granulated HDPE. The results are summarized in Table 2.

Examples 6 to 10

[0135] Examples 6 to 9 were carried out analogously to Examples 2 to 5, with the further addition of water as reaction medium to the mixture of HDPE and catalyst (according to Examples 2 to 5) (2.5 mass equivalents of water with respect to HDPE). Example 10 was carried out analogously to Example 1, whereby 0.1% by mass N-hydroxyphthalimide (NHPI) and 2.5 mass equivalents of water were added to the granulated HDPE. The results are summarized in Table 2.

Example 11

[0136] Example 11 was performed analogously to Example 1, with the addition of 0.1% by mass manganese(II) stearate and 0.1% by mass cobalt(II) stearate to the granulated HDPE. The results are summarized in Table 2.

TABLE-US-00002 TABLE 2 Yield of centrifugate with regard Example to HDPE employed [% by mass] Acid number[mg KOH/g] 1 37 158 2 48 187 3 33 166 4 26 159 5 51 128 6 49 144 7 44 252 8 28 181 9 53 109 10 38 146 11 45 232

Example 12

[0137] 200 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), M.sub.W=71.2 kg/mol) mixed with 0.77 wt % manganese (IV) oxide (MnO.sub.2) were weighed in a glass insert. This was placed in a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized to 20.0 bar at room temperature using a compressor and subsequently placed in a heating block preheated to 180 C. and heated for 1 h. The start of the reaction time was represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block the pressure was released and the gas phase was analyzed. The results are summarized in Tables 3 and 5.

Examples 13 and 14

[0138] Examples 13 and 14 were performed analogously to Example 12, with reaction times of 2 h and 3 h respectively. The results are summarized in Table 3.

Example 15

[0139] 200 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), M.sub.w=71.2 kg/mol) mixed with 0.77 wt % manganese (IV) oxide was weighed in a glass insert. This was placed in a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized to 20.0 bar at room temperature using a compressor and then placed in a heating block preheated to 180 C. and heated for 4 hours. The start of the reaction time was represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block the pressure was released and the gas phase was analyzed. (The results of this analysis are summarized in Tables 3, 4 and 6). The melt cake was cooled to room temperature and then extracted with 5 ml chloroform (65 C.). The mixture was cooled to room temperature and filtered through a Teflon filter (pore diameter: 0.2 m). The insoluble residue was extracted again with 5 ml chloroform (65 C.) and filtered off. The solvent was removed by distillation. A product of 131 mg was obtained. The product obtained has a residual manganese content of 89 ppm (analysis by ICP-OES).

Examples 16 to 18

[0140] Examples 16, 17 and 18 were carried out analogously to Examples 12, 13 and 14 respectively, using 5 wt % manganese (II) palmitate (Mn(Palm).sub.2) instead of manganese (IV) oxide. The results are summarized in Table 3.

Example 19

[0141] Example 19 was carried ot analogously to Example 15, using 5 wt % manganese(II) palmitate (Mn(Palm).sub.2) instead of manganese(IV) oxide. 103 mg of product were obtained. The results are summarized in Tables 3 and 4.

Example 20

[0142] Example 20 was carried out analogously to Example 13 whereby additionally 10 mg of N-hydroxyphthalimide (NHPI) were added. The results are summarized in Table 5.

Example 21

[0143] 200 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), M.sub.W=71.2 kg/mol) were weighed in a glass insert.

[0144] This glass insert was placed in a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized to 20.0 bar at room temperature using a compressor and then placed in a heating block preheated to 180 C. and heated for 4 hours. The start of the reaction time was represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block the pressure was released and the gas phase was analyzed. (The results of this analysis are summarized in Table 4.) The molten cake was cooled to room temperature and then extracted with 5 ml chloroform (65 C.). The mixture was cooled to room temperature and filtered through a Teflon filter (pore diameter: 0.2 m). The insoluble residue was extracted again with 5 ml chloroform (65 C.) and filtered off. The solvent was removed by distillation. 152 mg of product were obtained.

Example 22

[0145] 3000 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), M.sub.W=71.2 kg/mol) mixed with 10 wt % manganese (IV) oxide were weighed into a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized to 20.0 bar at room temperature using a compressor and subsequently placed in a heating block preheated to 160 C. and heated for 2 h. The start of the reaction time was represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block and the pressure was released. The melt cake was then extracted with 400 ml 1,2-dichlorobenzene (150 C.). The mixture was cooled to room temperature and the supernatant solution was removed as completely as possible from the separated catalyst. The catalyst phase was centrifuged off (3500 rpm, 10 min). The insoluble catalyst residue was first extracted again hot (150 C.) with 45 ml 1,2-dichlorobenzene, then twice with 45 ml chloroform and centrifuged off. The residue was dried overnight at 5 mbar and 60 C.

[0146] Subsequently, 200 mg of granulated HDPE (Purell GB 7250, LyondellBasell Industries, density: 0.952 g/cm.sup.3, T.sub.m=134 C., crystallinity=62% (DSC), M.sub.W=71.2 kg/mol) mixed with 0.77% by weight of the previously separated catalyst were weighed in a glass insert. This glass insert was placed in a steel autoclave (with needle valve, manometer and bursting disk). This steel autoclave was then pressurized to 20.0 bar at room temperature using a compressor and then placed in a heating block preheated to 180 C. and heated for 4 hours. The start of the reaction time was represented by the insertion of the steel autoclave into the preheated heating block. After the reaction time had elapsed the steel autoclave was removed from the heating block the pressure released and the gas phase analyzed (the results of this analysis are summarized in Table 6.) The melt cake was cooled to room temperature and then extracted with 5 ml chloroform (65 C.). The mixture was cooled to room temperature and filtered through a Teflon filter (pore diameter: 0.2 m). The insoluble residue was extracted again with 5 ml chloroform (65 C.) and filtered off. The solvent was removed by distillation. 109 mg of product were obtained.

TABLE-US-00003 TABLE 3 Comparison of the reactions carried out in examples 12 to 19 with MnO.sub.2 and Mn(Palm).sub.2 Reaction time Proportion of O.sub.2 after the reaction [%] [h] MnO.sub.2 Mn(Palm).sub.2 1 17.0 11.8 2 8.0 6.1 3 5.6 3.2 4 3.4 2.5

TABLE-US-00004 TABLE 4 Comparison of reactions without catalyst, with MnO.sub.2 and with Mn(Palm).sub.2. Proportion of O.sub.2 Example Catalyst after the reaction [%] 15 MnO.sub.2 3.4 19 Mn(Palm).sub.2 2.5 21 without catalyst 9.1

[0147] The data in Table 4 shows that the catalyst significantly accelerates the reaction, with the homogeneous catalyst Mn(Palm).sub.2 and the heterogeneous catalyst MnO.sub.2 exhibiting comparable activities. Without catalyst a significantly slower reaction is observed.

TABLE-US-00005 TABLE 5 Comparison of reactions with MnO.sub.2 and with or without the addition of NHPI. Proportion of O.sub.2 Example Catalyst after the reaction [%] 12 MnO.sub.2 17.0 20 MnO.sub.2 + NHPI 13.1

[0148] The data in Table 5 shows that NHPI bridges the initially lower activity of the heterogeneous catalyst MnO.sub.2.

TABLE-US-00006 TABLE 6 Comparison of the reactions with fresh and recovered MnO.sub.2. Proportion of O.sub.2 Example Catalyst after the reaction [%] 15 Fresh MnO.sub.2 3.4 24 Recovered Catalyst 3.3