JP2001510852A - Purification of propylene oxide - Google Patents

Abstract

  (57) [Summary] Purification of propylene oxide by distillation just before use.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for purifying propylene oxide.

[0002] Such a method has hitherto been described extensively. U.S. Patent No. 3,578,568 discloses a method for separating water, methanol, acetone, and acetaldehyde from propylene oxide by extractive distillation using ethylene glycol, propylene glycol, ethylene glycol monomethyl ether or diethylene glycol monomethyl ether as an extraction solvent. ing. U.S. Pat. No. 4,692,535 discloses that propylene oxide (PO) is contacted with activated carbon or attapulgite sorbents.
A method for purifying propylene oxide is disclosed. The amount of poly (propylene oxide) decreases. In a comparative test, distilled propylene oxide containing poly (propylene oxide) caused foam collapse and 82 ° C. in a carbon steel vessel.
It has been shown that distilled propylene oxide heated for 2 days and 7 days also causes foam collapse. The specification does not disclose how propylene oxide was distilled or whether distilled propylene oxide could be used. In fact, the specification discloses that the method of preventing foam collapse is to use propylene oxide treated with the adsorbent described above.

[0003] US Pat. No. 3,580,819 discloses a crude propylene oxide containing propylene, water and high boiling oxygen-containing impurities, which is subjected to a two-stage distillation method, and then contacted with an aqueous selective solvent for propylene oxide (PO). And a method for recovering propylene oxide by distilling PO from a solvent. The starting material contains only 8.1% by weight of PO. French Patent No. 1469339 and US Pat. No. 3,398,062 describe a purification process by distilling crude propylene oxide, including propylene chloride, water, dissolved gases, acetaldehyde and propionaldehyde, and removing the overhead fluid via a separator. Is disclosed. The starting material contains a relatively low amount of propylene oxide (88%) and the distillation
It is performed under relatively harsh conditions using steam. DE 1040783 discloses a process for producing polyethers, in which PO is introduced into a reaction vessel via a reflux tower. Most of the PO in the reaction vessel evaporates and is returned to the reflux tower,
There it is condensed and the liquid mixture at the bottom of the reflux column is re-poured into the reaction vessel. No purification of the PO is performed except for the removal of the inert gas. US Patent No. 51605
No. 87 and US Pat. No. 5,133,839 are another example of a disclosure about extractive distillation of PO. No. 5,160,587 discloses a comparative distillation without using an extractive distillation solvent. That is, the distillation column has a considerably large number of stages and the amount of impurities in the PO used as the starting material is also quite high. Despite the complexity of the refined refinement process, it is known that the quality of propylene oxide degrades over time and reflects the quality of polyether polyols made from PO and the quality of polyurethanes made from the polyols. Have been. Storage or transport of PO at room temperature appears to have a negative effect. The storage or transportation as described above is preferably carried out with PO
The temperature should be as low as possible above the melting point of Furthermore, the storage or transport of PO in contact with mild steel or carbon steel is particularly important if the steel is air,
Where it can come into contact with moisture, water or oxygen, it appears to have a bad effect. Such storage or transport should preferably take place with the PO in contact with stainless steel or steel coated with an inert layer. Due to the different storage and transport methods used by PO manufacturers, users will face different grades of commercial grade PO, and such quality will eventually be Affects the quality of the manufactured product. To date, it is not completely understood what changes in propylene oxide cause degradation in the quality of polyols and polyurethanes. Given the above circumstances, there is a need for good and consistent quality PO used to make materials, especially polyether polyols,
And there is a need for an easy way to achieve this.

[0004] Surprisingly, despite the fact that the cause is not completely known, the propylene oxide is subjected to a simple distillation just before it is consumed to produce the polyol, and It has been found that the quality of polyurethane can be greatly improved. More surprisingly, it has also been found that the quality of PO already having a high degree of purity can be improved by a simple distillation method.

Accordingly, the present invention provides a method for purifying propylene oxide by distillation, characterized in that distillation is carried out immediately before using propylene oxide; and the use of PO subjected to distillation immediately before use; It relates to a process for producing a product from PO which has just been subjected to distillation. The invention further provides that the starting material for PO is preferably 0.2% by weight.
The following relates to a method of purifying PO by distillation, more preferably having up to 0.1% by weight and most preferably up to 0.05% by weight of impurities and using 1-10 plates of real trays.

The distillation is preferably carried out within one week before using the PO, more preferably 4
Within one day and most preferably within two days prior to use. PO may be used immediately after distillation.

The PO used for the distillation may be any PO having a low impurity content,
In particular, any commercially available PO may be used. Preferably PO is 0
. 2% by weight or less, more preferably 0.1% by weight or less and most preferably 0.0% by weight.
Contains up to 5% by weight of impurities.

The distillation may be carried out by simply evaporating the PO and collecting the evaporated PO, and preferably comprises a heater at the bottom or a heating jacket and a coil, and It is carried out in a conventional distillation column equipped with a vent near the top for discharging the inert gas supplied with the PO together with the condenser. To avoid entrainment of droplets in the vapor stream, the tower can include 1-10 actual trays and preferably 2-8 actual trays. PO is fed to the bottom of the distillation column from a main storage tank for PO storage, which has been kept out of contact with the atmosphere with an inert gas, heated and condensed in a condenser. The purified PO from the condenser is stored as a liquid in an intermediate storage tank or fed directly to the process using it until it is used to produce the product. Inert gas is preferably N _2. The distillation step may be carried out at normal pressure or slightly elevated pressure (1-3 bar absolute) and at 35-60 ° C. or at 0.99 to 0.5 bar absolute at normal temperature (where the heater is Not required). The former condition is preferred. The distillation step may be carried out batchwise, semi-continuously and preferably continuously. No chemicals other than inert gas are added to PO.

The equipment used for storage and distillation is preferably designed so that all metal surfaces in contact with PO are stainless steel surfaces. Room temperature water may be supplied to the condenser as cooling means.

[0010] Preferably, no further purification of the PO takes place between the distillation according to the invention and the use of the PO purified thereby. Impurities accumulate at the bottom of the distillation column. This bottom fraction may be removed continuously or discontinuously. This bottoms fraction can be incinerated, separately purified, returned to the main storage tank, or free of impurities such as glycols and glycol ethers and polyols used in rigid polyurethane foam production. It may be used for applications where its presence does not affect or has little effect.

The purified PO has an equivalent weight of any known PO, especially for the polymer, more particularly for the polyether polyol, in particular 500 or more, preferably 1000 or more, and at least 10% by weight, preferably Can be used for the production of polyether polyols containing at least 25% by weight and most preferably at least 50% by weight of oxypropylene units.

[0012] Polyether polyols as described above are known in the art, and methods for making them are likewise known. PO is fed into the reactor as a liquid from the intermediate storage tank or from the condenser of the distillation column to produce the polyether polyol. These may be homopolymers of PO and copolymers of PO with other alkylene oxides, such as ethylene oxide and butylene oxide. The copolymer can be a block copolymer, a random copolymer, or a combination thereof. The present invention also relates to such a polyether polyol prepared from a product as described above, in particular PO purified according to the present invention.

The polyether polyols as described above may be used for the preparation of polyurethanes, especially polyurethane foams, especially flexible foams and elastomers. The invention further relates to such polyurethanes.

The present invention is illustrated by the following examples. Example 1 a) Commercial propylene oxide was used, which was transported through a carbon steel pipeline of about 300 meters and contained impurities in an amount of 0.2% by weight or less. Half of this PO was distilled at 50 ° C. and normal pressure, condensed and collected (using N ₂ as inert gas, and jacket and coil, condenser near the top and venting at the top). Using a one-stage reactor equipped with a real tray).

B) Undistilled PO with an equal amount of polyol (Arcol 1374,
Alco, a polyol widely used in the preparation of flexible polyurethane foams (
Arco). Next, the PO was removed from the polyol by vacuum distillation until the PO remaining in the polyol was 50 parts per million (ppm) or less.

C) Distillation in fresh alcohol 1374 and step a), step b) was repeated with PO used within one day after distillation. Flexible foams were produced in the same manner using alcohol 1374 treated with undistilled PO (reference TAU) and alcohol 1374 treated with distilled PO (reference TAD).

110 parts by weight of the following polyol composition were reacted with 75 parts by weight of Suprasec 2420, an MDI-based polyisocyanate prepolymer available from Imperial Chemical Industries (ICI) (Suprasec) Is a trademark of ICI). Steps 1b), 1c) and the preparation of the flexible foam took place within 3 days after the distillation of PO in step 1a).

[0018] Polyol composition (parts by weight):

[0019]

[Table 1]

Each component was poured into an open container, mixed and reacted. The height / weight ratio (H / W) of the foam was measured. The results are as follows:

[0021]

[Table 2]

Example 2 Propylene oxide was used which was transported in a stainless steel cylindrical container and contained levels of impurities up to 0.2% by weight. PO was charged to a 12 liter stainless steel reactor purged with N ₂ three times to remove all oxygen. The distillate outlet of the reactor was open (the reactor did not include a fractionating column, so the actual number of tray stages was one) and the PO was heated from room temperature to 40-50 ° C, The temperature was then maintained for 5 hours (the reactor was equipped with a heating jacket with the coil; water was used as the heating fluid for the coil). At the end of the distillation, a small amount of nitrogen was injected. PO was collected in the glass flask from the bottom of the condenser. The amount of distilled PO collected was about 14.9 kg (distillation was performed in two batches).

Examples 1b and 1c were repeated using undistilled PO from the cylindrical vessel and PO distilled as above and stored in the glass flask for 2 days. A flexible foam was produced as described in Example 1. The H / W ratio of TAD was 18% higher than that of TAU.

Example 3 In this example, undistilled and distilled PO from Example 2 (after storage in a glass flask for 2 days) was used.

By a standard method, a polyoxypropylene polyol derived from glycerol having an OH value of 352 mg KOH / g is propoxylated and ethoxylated, has an OH value of 28 mg KOH / g and 15.4% by weight. A polyol having oxyethylene groups (all terminals) was obtained.

Some propoxylation of polyols having an OH value of 352 mg KOH / g
Propoxylation of the other portions was performed using distilled PO, while undistilled PO was used.

From the thus obtained polyol, a foam was produced according to Example 1. A flexible polyurethane foam using undistilled PO has a coarse cell structure,
Had a shrinkage (recession) of 1.4% and an H / W of 176,
On the other hand, when distilled PO was used, it had a good fine cell structure and 188 H
/ W and a shrinkage of 7% (all measurements were taken 24 hours after foam production).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) (C08G 18/48 (C08G 18/48 101: 00) 101: 00) (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ) , MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI GB, GE, GH, GM, GW, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK , MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZW F term (reference) 4C048 KK01 4H006 AA02 AD11 BB61 BC38 BC51 BC52 4J005 AA04 4J034 DA01 DB03 DB07 DG03 DG04 DG05 DG08 DG10 DG12 HA01 HA07 HC12 HC61 HC64 HC67 HC71 LB02 NA03 QB15 QC01

Claims (28)

[Claims] 1. A method for purifying propylene oxide by distillation, wherein the distillation is performed immediately before using propylene oxide. 2. The method according to claim 1, wherein the distillation is performed within one week before using propylene oxide. 3. The method according to claim 1, wherein the distillation is carried out within 4 days before the use of propylene oxide.
The method described in. 4. The process according to claim 1, wherein the distillation is carried out within two days before the use of propylene oxide. 5. The process according to claim 1, wherein the distillation is carried out at a pressure of 1 to 3 bar absolute and at a temperature of 35 to 60 ° C. 6. The process as claimed in claim 1, wherein the distillation is carried out at normal temperature and at an absolute pressure of 0.99 to 0.5 bar. 7. The process according to claim 1, wherein the propylene oxide before distillation contains up to 0.2% by weight of impurities. 8. The process according to claim 1, wherein the propylene oxide before distillation contains up to 0.1% by weight of impurities. 9. The method of claim 1, wherein the propylene oxide before distillation contains no more than 0.05% by weight of impurities.
9. The method according to any one of items 1 to 8. 10. The method according to claim 1, wherein 1 to 10 actual tray stages are used. 11. The method according to claim 1, wherein 2 to 8 actual tray stages are used. 12. The method according to claim 1, wherein no chemical other than an inert gas is added to the PO. 13. A process for purifying propylene oxide by distillation, wherein the propylene oxide before distillation contains less than 0.2% by weight of impurities and uses 1 to 10 actual tray stages. Purification method. 14. The process according to claim 13, wherein the distillation is carried out at a pressure of 1 to 3 bar absolute and at 35 to 60 ° C. 15. The distillation according to claim 13, wherein the distillation is carried out at normal temperature and at an absolute pressure of 0.99 to 0.5 bar.
The method described in. 16. The propylene oxide before distillation contains up to 0.1% by weight of impurities.
16. The method according to any one of items 15 to 15. 17. The propylene oxide prior to distillation containing up to 0.05% by weight of impurities.
17. The method according to 3 to 16. 18. The method according to claim 13, wherein 2 to 8 actual tray stages are used. 19. The method according to claim 13, wherein no chemical other than an inert gas is added to the PO. 20. Use of propylene oxide produced according to claims 1 to 19. 21. The use according to claim 20, wherein said use is a polymer production. 22. The use according to claims 20 and 21, wherein said use is the production of a polyether polyol. 23. The method according to claim 20, wherein said use is the preparation of a polyether polyol having an equivalent weight of 500 or more and containing at least 10% by weight of oxypropylene.
Use as described in. 24. A polymer produced using propylene oxide, purified according to claims 1 to 19. 25. The polymer according to claim 24, wherein said polymer is a polyether polyol. 26. The polymer according to claim 24, wherein the polymer is a polyether polyol having an equivalent weight of 500 or more and containing at least 10% by weight of oxypropylene. 27. Polyurethane produced from a polymer according to claim 24. 28. The polyurethane of claim 27, wherein said polyurethane is an elastomer or a flexible foam.