MXPA97007530A - Recovery of dimethyl tereftalate from polime mixtures - Google Patents
Recovery of dimethyl tereftalate from polime mixturesInfo
- Publication number
- MXPA97007530A MXPA97007530A MXPA/A/1997/007530A MX9707530A MXPA97007530A MX PA97007530 A MXPA97007530 A MX PA97007530A MX 9707530 A MX9707530 A MX 9707530A MX PA97007530 A MXPA97007530 A MX PA97007530A
- Authority
- MX
- Mexico
- Prior art keywords
- chloride
- base
- process according
- polymer
- dimethyl terephthalate
- Prior art date
Links
- 239000000203 mixture Substances 0.000 title description 4
- 238000011084 recovery Methods 0.000 title description 3
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 title 1
- WOZVHXUHUFLZGK-UHFFFAOYSA-N Dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229920000642 polymer Polymers 0.000 claims abstract description 22
- VEXZGXHMUGYJMC-UHFFFAOYSA-M chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 20
- 229920002959 polymer blend Polymers 0.000 claims abstract description 8
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims abstract description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000002585 base Substances 0.000 claims description 24
- 239000005033 polyvinylidene chloride Substances 0.000 claims description 20
- 229920001328 Polyvinylidene chloride Polymers 0.000 claims description 16
- OKKJLVBELUTLKV-UHFFFAOYSA-N methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 16
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 238000006140 methanolysis reaction Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 12
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 5
- 239000004800 polyvinyl chloride Substances 0.000 claims description 5
- 238000002360 preparation method Methods 0.000 claims description 4
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 claims description 3
- -1 bisphosphonate salts Chemical class 0.000 claims description 3
- LSNNMFCWUKXFEE-UHFFFAOYSA-M bisulfite Chemical class OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 claims description 3
- 150000001734 carboxylic acid salts Chemical class 0.000 claims description 3
- 238000006460 hydrolysis reaction Methods 0.000 claims description 3
- 239000011780 sodium chloride Substances 0.000 claims description 3
- 229940112871 Bisphosphonate drugs affecting bone structure and mineralization Drugs 0.000 claims description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N HCl Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 abstract description 17
- 230000015556 catabolic process Effects 0.000 abstract 1
- 125000001309 chloro group Chemical group Cl* 0.000 abstract 1
- 230000004059 degradation Effects 0.000 abstract 1
- 238000006731 degradation reaction Methods 0.000 abstract 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 description 9
- 229920001223 polyethylene glycol Polymers 0.000 description 8
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 7
- 238000007792 addition Methods 0.000 description 5
- 150000001805 chlorine compounds Chemical group 0.000 description 5
- 238000000354 decomposition reaction Methods 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- SQGYOTSLMSWVJD-UHFFFAOYSA-N Silver nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000002479 acid--base titration Methods 0.000 description 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229940077747 antacids containing calcium compounds Drugs 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000005340 bisphosphate group Chemical group 0.000 description 1
- 150000004663 bisphosphonates Chemical class 0.000 description 1
- 235000012970 cakes Nutrition 0.000 description 1
- 150000001674 calcium compounds Chemical class 0.000 description 1
- 229940043430 calcium compounds Drugs 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 230000005591 charge neutralization Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 125000003827 glycol group Chemical group 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000001264 neutralization Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229920000406 phosphotungstic acid polymer Polymers 0.000 description 1
- 229920003217 poly(methylsilsesquioxane) Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 238000003918 potentiometric titration Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Abstract
The dimethyl terephthalate is recovered from polymer mixtures containing polymers of terephthalic acid and glycol and a chloride polymer, by adding a base to neutralize the hydrochloric acid formed by the degradation of the chloro polymer.
Description
Recovery of Dimethyl Terephthalate from Polymer Mixtures
Field of the Invention This invention relates to the recovery of dimethyl terephthalate from mixtures of polymers containing (1) a polymer of terephthalic acid and a glycol and (2) a chloride-containing polymer, by methanolysis.
Background of the Invention The European patent application, published, No. 0,484,963 A2 of R.E. Michel (Published May 13, 1992) describes the preparation of dimethyl terephthalate by the methanolysis of polymers containing units of terephthalic acid and glycol units. These polymers can be mixed with other materials such as polyvinylidene chloride see runs 8 and 9 of the Table. U.S. Patent No. 3,633,780 describes the calcination of chloride bottles of
REF: 25556 polyvinyl in the presence of CaCÜ3 that reacts with the hydrochloric acid released. European Patent No. 254,538 describes the calcination of waste containing polyvinyl chloride and the neutralization of the resulting gas by passing it through a dry alkaline material. Japanese Patent No. 54,052,873 describes the dispersion of basic calcium compounds over polyvinyl chloride to neutralize the hydrochloric acid formed during the incineration. Polyvinylidene chloride (PVDC) is often used to coat the poly (ethylene glycol) terephthalate (PET) film in order to improve the adhesion of other coatings and improve the insulation properties. In addition, another polymer containing chloride, polyvinyl chloride (PVC), is used to manufacture bottles and can not be separated from poly (ethylene glycol) (PET) terephthalate using existing submerging / floating technology. These chloride polymers decompose at temperatures well below the melting temperature of poly (ethylene glycol) terephthalate (PET) to liberate HCl. The hydrochloric acid generated in the methanolysis reactor that results from the decomposition of chloride-containing polymers disperses the chlorides throughout the purification system and results in general corrosion and / or cracking or stress cracking of the steel equipment. stainless.
Brief Description of the Invention The present invention is a process for the preparation of dimethyl terephthalate from a polymer mixture containing (1) a. polymer of terephthalic acid and a glycol and (2) a chloride-containing polymer, comprising (a) combining the polymer mixture with a base whose hydrolysis constant is greater than that of the chloride ion (b) by holding the product of step (a) to methanolysis and (c) recover dimethyl terephthalate. The amount of base added should not be more than about equal to a mole basis to the amount of chloride contained in the polymer mixture. Since only the necessary labile chloride is reacted to achieve the benefits of the invention, the amount of base added is usually and only one half of two thirds of the molar amount of chloride in the polymer. Usually, the chloride-containing polymer is selected from the group consisting of polyvinylidene chloride and polyvinyl chloride. Usually, the base is selected from the group consisting of carboxylic acid salts, bisphosphate salts, bisulfite salts, alkali metal hydroxides, alkaline earth metal hydroxides. Usually, the methanolysis is carried out by treating the product of step (a) in the reaction zone with methanol vapor at a temperature above 230 degrees C, and continuously removing the vapors of methanol, dimethyl terephthalate and glycol from the reaction zone. Usually, the vapors removed from the reaction zone contain about 3 moles of methanol for each mole of dimethyl terephthalate. A preferred base is sodium hydroxide. By using the invention, the chlorides can be restricted to the reactor-solution system by adding the base to the reactor feed tank.
Detailed Description A description of the complete methanolysis process can be found in published European patent application No. 0,484,963 A2. The addition of the base to the feed system for the methanolysis can be carried out by any number of media. A solid base could be added through the solid feed system with poly (ethylene glycol) terephthalate (PET) while a liquid base could be added directly to the feed tank. The mode of addition must be one in which the base is well dispersed in the melting-dissolving boiler. A base in this case is any material whose hydrolysis constant is greater than that of the chloride ion. This would include materials such as carboxylic acid salts, bisphosphonate and bisulfite salts, as well as alkali and alkaline earth metal hydroxides. In order to minimize yield losses of dimethyl terephthalate, the excess base, greater than one equivalent per "mol" of the chloride-containing polymer, should not be used.
Most pieces or residues of poly (ethylene glycol) terephthalate (PET), of low price, which is economically suitable for conversion back to its reagents, contain some chloride-containing polymer. If the chlorides are not contained in the feed preparation and the reactor system, as relatively harmless salts, the rest of the plant will be subject to severe corrosion. The good dispersion of the base is an important variable as the efficiency of the operation of this process is considered. It is also important to control the amount of base to limit the formation of terephthalate salts, which would reduce the yield of usable products form methanolysis. However, if salts of terephthalic acid are used as the base in this process, their conversion to terephthalic acid by the HCl formed from the decomposition of the chloride-containing polymer will increase the yield of intermediates usable for this process.
Example
Preliminary Test: Determine if the base would neutralize the hydrochloric acid formed by heating a mixture containing poly (ethylene glycol) terephthalate and PVDC. The apparatus consisted of a well-insulated and electrically heated flask and a steam discharge tube that drives two flushing bottles or series scrubbers that contained saturated NaOH. The flask was also equipped with an inlet of a nitrogen sweep and a mechanical stirrer. To start a run, the flask was charged with a 60-40 mixture of poly (ethylene glycol) terephthalate (PET) and dimethyl terephthalate (DMT) and heated to > 260C. A pellet of 10 g of dimethyl terephthalate (DMT) containing 1 g of PVDC was added to begin a run. A purge of soft nitrogen was started and heating was continued for one hour. In some examples an equivalent amount of base, based on the theoretical amount of Cl available from polyvinylidene chloride (PVDC), was well dispersed in the melt before the addition of pellet containing polyvinylidene chloride (PVDC). The efficiency of gas purification was verified by vaporizing 48% HCl in the apparatus and by decomposing polyvinylidene chloride (PVDC) in the absence of poly (ethylene glycol) (PET) / dimethyl terephthalate (DMT) terephthalate. The value for HCl was determined by the acid-base titration of the scrubber or scrubber flasks and the value for the chloride was determined by the potentiometric titration with silver nitrate. The dispersion effect was verified by the decrease in the stirring speed.
EFFECT OF SODIUM HYDROXIDE ON GASEOUS HCL
Power g.PET/DMT Temp. Base HCl (1) Cl- Addition 5 mL of HCl 0 24 0 No 100 0. 5N l.OOg of PVDC 0 270 No 54 50 l.OOg • of PVDC 200 265 No 30 28 l.OOg of PVDC 220 270 If (2) < 1 < 1 l.OOg of PVDC 220 270 If (3) < 1 < 1 l.OOg of PVDC 220 270 If (4) 14 13 (1)% of volatile Cl, for tests using PVDC this number is theoretical and based on 2 Cl / mol of PVDC. (2) An equivalent based on 2Cl / mol of PVDC, NaOH. (3) An equivalent based on 2Cl / mol of PVDC, Na2TPA. (4) Repetition of (2) with poor base dispersion.
The decomposition of the PVDC in the absence of DMT appears to be only one chloride per "mol" of polymer that can be thermally subjected. This is something shown by the decomposition in PET / DMT. In any case, the results show that the addition of base, which has been well dispersed in the melt, eliminates the emission of HCl vapor.
Example 1
In a 2 L glass resin pot kettle, equipped with a heating mantle, 400 g of PVDC (1% by weight) polyethylene terephthalate film, coated, was placed. The warm-up started. As the film begins to melt 25% by weight, aqueous sodium hydroxide was sprayed into the kettle until the film completely melted and a total of 6.6 g of caustic solution was used. The molten film was cooled, ground and placed in the methanolysis reactor. The methanolysis of the above sample was conducted at 290 C and 4,915 kg / cm 2 (70 psig) in the reactor described in European Patent No. 0,484,963 A2 (Published May 13, 1992). The flow of liquid methanol to the reactor was 200 ml / hr and the reaction was carried out for four hours. Analysis of the effluent from the condensed reactor showed a conversion of 83% to DMT, 88% conversion to ethylene glycol, and a 10% conversion to the mixed glycol methyl ester of TPA. Five percent of the initial feed remained in the reactor as a cake down the methanol vapor feed line.
It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.
Having described the invention as above, property is claimed as contained in the following:
Claims (7)
1. A process for the preparation of dimethyl terephthalate of a polymer mixture containing (1) a polymer of terephthalic acid and a glycol and (2) a chloride-containing polymer, characterized in that it comprises (a) combining the polymer mixture with a base whose Hydrolysis constant is greater than that of chloride ion (b) subjecting the product from step (a) to methanolysis and (c) recovering dimethyl terephthalate.
2. The process according to claim 1, characterized in that the amount of the base is not more than about equal in a mol basis to the amount of chloride contained in the polymer mixture.
3. The process according to claim 2, characterized in that the chloride-containing polymer is selected from the group consisting of polyvinylidene chloride and polyvinyl chloride.
4. The process according to claim 3, characterized in that the base is selected from the group consisting of carboxylic acid salts, bisphosphonate salts, bisulfite salts, alkali metal hydroxides, alkaline earth metal hydroxides.
5. The process according to claim 4, characterized in that the methanolysis is carried out by treating the product of step (a) in a reaction zone with methanol vapor at a temperature above 230 degrees C and continuously removing the vapors from methanol, dimethyl terephthalate and glycol from the reaction zone.
6. The process according to claim 5, characterized in that the vapors removed from the reaction zone contain about 3 moles of methanol for each mole of dimethyl terephthalate.
7. The process according to claim 6, characterized in that the base is sodium hydroxide.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/420,164 US5504122A (en) | 1995-04-11 | 1995-04-11 | Recovery of dimethyl terephthalate from polymer mixtures |
| US420164 | 1995-04-11 | ||
| PCT/US1996/004038 WO1996032367A1 (en) | 1995-04-11 | 1996-03-25 | Recovery of dimethyl terephthalate from polymer mixtures |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| MX9707530A MX9707530A (en) | 1997-11-29 |
| MXPA97007530A true MXPA97007530A (en) | 1998-07-03 |
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