JPS60109584A - Depolymerization of polyoxymethylene glycol - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material of polyurethane, in high activity, without causing the corrosion of the apparatus, by carrying out the depolymerization of polyoxytetramethylene glycol using a catalyst comprising a heteropolyacid containing a specific amount of water coordinated or mixed to the acid. CONSTITUTION:Tetrahydrofuran is produced by the depolymerization of polyoxytetramethylene glycol (PTMG), using a catalyst comprising a heteropolyacid (e.g. phosphomolybdic acid, phosphotungstic acid, etc.) containing <=15mol of water coordinated or mixed to 1mol of the acid. The amount of the heteropolyacid is preferably >=0.1wt%, especially >=1wt% of the PTMG, and the reaction is carried out at 50-200 deg.C, preferably 80-150 deg.C. The process is also useful to obtain a PTMG having sharp molecular weight distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for depolymerizing polyoxytetramethylene glycol (hereinafter abbreviated as P'I'MO) to tetrahydrofuran (hereinafter abbreviated as THF).

1) i' M (1 is an industrially important polymer that is the main raw material for spandex and polyurethane. As a raw material for spandex, the number average molecular spear is ♂0θ~3θ
PTMG of the order of θθ is preferably used, but industrially available PTMG generally has a wide molecular weight distribution, and includes everything from oligomer-like low molecules + and 1 substance to the enemy polymer clear substance. There is.

In some cases, such polyoxytetramethylene glycol may need to be depolymerized, in whole or in part, to tetrahydrofuran, a II; μ-based polymer. In such a case, for example, raw materials from non-standard or unnecessary products of q'II I;
Examples include fractional extraction of low molecular weight portions and polymer @ portions in order to sharpen the molecular weight distribution of PTM G, and reuse of polymers separated by vacuum distillation treatment as raw material monomers.

There has been a great deal of research into 'rHF' stop catalysts. In comparison, there are fewer studies on depolymerization, but the depolymerization of 'I' HF polymers containing antimony pentachloride (8bC4) and chlorine (11,Me
erwein.

D, Delfs, HoMorschel, An
gew, CI+em,, 7.2. ,9 ,),7(/
(6θ)), both ends are 0 using strongly acidic ion exchange resin.
14 groups, i.e., IJTM
Depolymerization of G (Japanese Unexamined Patent Publication No. 0-73-697), H2
There is a depolymerization of PTMG using an aqueous solution of 804 (U.S. Pat.

Although the polymerization of 1'HF is generally said to be an equilibrium reaction, it cannot be said that the catalyst required for the polymerization is necessarily suitable for the depolymerization of I'TMO. That is, P i' M
This is because depolymerization of O requires reactivity toward the terminal OH group. For example, fluorosulfonic acid, which is known as a bundling catalyst, is not effective because its activity is inhibited by terminal OH groups, and even if the reaction partially proceeds, it is decomposed by water produced by depolymerization. On the other hand, an aqueous H2804 solution and a strongly acidic ion exchange resin do not have i'HF polymerization activity, but are used as a depolymerization (IlII) medium.

However, each of these known depolymerization catalysts has drawbacks. That is, the H,804 water bath liquid is highly corrosive, and the strongly acidic ion exchange resin has a high temperature (/2θ~/j
(0°C), and the depolymerization rate is also insufficient.

As a result of intensive research into catalysts that are highly active and less corrosive for depolymerization, the inventors have discovered heteropolyacids as catalysts that satisfy these conditions, and have developed the present invention. I arrived at the eggplant.

That is, the present invention provides a depolymerization method for depolymerizing PTMG to give T )l F, which is characterized by using a heteropolyacid as a catalyst in which less than /j molecules of water are coordinated or present per molecule. It is.

Heteropolyacid is usually synthesized as an aqueous phase product of 20 to 0, but no depolymerization activity is observed when it is brought into contact with P'1'MO in this state. However, when examining the polymerization activity after drying the telopolyacid and changing the number of aqueous phases, it was found that when the number of aqueous phases was reduced to 7j or less for the heteropolyacid/molecule, decomposition activity appeared. do. It is also effective to react an anhydride of a heteropolyacid in the presence of water in an amount of 1 times or more per mole of the heteropolyacid. In this case, it is considered that the water coexisting in an amount of /j times the mole or less relative to the heteropolyacid mostly exists in a coordinated state to the heteropolyacid. Even if a heteropolyacid with a hydration number of 75 or more is used, or
Even if more than 5 times the mole of water is allowed to coexist, the depolymerization activity will appear if the amount of water in the system is later reduced to 73 times the mole or less of the heteropolyacid by some method. The smaller the number of aqueous phases, the higher the activity, preferably less than I, more preferably less than G.

In order to completely depolymerize P'I'MO to i'HF, it is common practice to remove THF from the reaction mixture by distillation, etc.
E is preferred. Moreover, when a depolymerization reaction occurs, PTM
Since 7 moles of water are generated per 1 mole of G, if the amount of water in the system exceeds 7j moles of heteropolyacid, remove water from the reaction system to keep the hydration number of heteropolyacid below /J-. It is necessary. A general method such as distillation is used to remove water from the reaction system. When the reaction is carried out while removing 'l' HF to the outside of the reaction thread, the water is 'I' HF.
If THF is not removed from the reaction system, for example, the distilled i''IIF can be dehydrated by a generally known method and then returned to the system.
A method such as dehydration using a desiccant that does not affect the catalyst activity is used.

Among MO, W, and V, the heteropolyacid in the present invention is
At least one persimmon oxide and other elements such as P,
8i, As, ()e, B, Ti, Ce,
It is a general term for oxyacids produced by condensation of oxyacids such as Co, and the atomic ratio of Oi1 to the representative is λ, j ~ 7.2
It is.

Specific examples of these heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdothanum dust vanadate, phosphorus dust vanadate, phosphomolybdoniobic acid, and tungsten silicoic acid. Acid, silicomolybdic acid, silicomolybdotungstic acid, silicomolybdotungstopanadic acid, kermanium tungstic acid, borotungstic acid, boromolybdic acid, boromolybdotungstic acid, boromolybdovanadate, phofmolybdothanum dust These include vanadic acid, cobalt molybdic acid, cobalt vanadic acid, cobalt tungsdic acid, arsenic molybdic acid, arsenic tungstic acid, titanium molybdic acid, and cerium molybdic acid.

The amount of heteropolyacid used is not particularly limited, but if the amount of heteropolyacid in the reactor is small, the depolymerization rate will be low. Furthermore, when the amount of heteropolyacid 11 is large, the range of acceptable water that may be present in the system is widened, and the smaller the amount of coordinated water, the higher the activity. It is best to use ``/east@person'' or above.

The temperature of the reactor IW is preferably 50 to 200°C, particularly 0 to 750°C. The depolymerization reaction is extremely slow below 50°C, and
At temperatures above 0°C, there is a risk of oxidative decomposition of PTMO.

However, when THF or water is removed from the system and the reaction is carried out at a temperature that cannot be removed at normal pressure, the reaction is carried out with the system under reduced pressure. The depolymerized yarn is particularly under high temperature conditions.
An inert atmosphere is preferred to prevent oxidation of MG and '1' HF.

Furthermore, in carrying out the present invention, it is also a preferred method to depolymerize a portion of THF, rather than completely depolymerizing it to THF. In this case, there is no need to remove water from the reaction system if the amount of water produced depending on the depolymerization rate is 7j times the mole of heteropolyacid or less, and furthermore, if it is not decomposed to an amount greater than the equilibrium amount with THF, i' HF also does not need to be removed from the reaction system.

Using the catalyst of the present invention, such P 'II' M (
When we attempted a partial decomposition of J, we surprisingly found that P i' M
It has been found that the number average molecular acid of (J) increases and, moreover, the molecule (1) distribution becomes sharper. Therefore, the method of the present invention is also useful as a method for sharpening the molecular distribution of PTMG.

The polyoxytetramethylene glycol mentioned in the method of the present invention includes -jI as well as T I4 F homopolymer.

A copolymer containing block polyoxytetramethylene chains, a copolymer of T )l F and an alkylene oxide such as ethylene oxide, propylene oxide, or epichlorohydrin, a copolymer of i' 11 F and a cyclic ether such as oxacyclobutane, etc. Polymerized polymers, THF polymers containing foreign molecules connected by ether bonds, etc., and also include those without terminal groups or substituents that inhibit catalyst activity.

The reaction is a reaction between P 1' M G and a predetermined hydration water heteropoly M
Since the reaction can be carried out with stirring, no particular 6 medium is required, but an inert material may be added to the reaction.

The reaction type can be either a patch type or a continuous type using a commonly used reactor with a mixing and stirring function. In the partial depolymerization reaction, the catalyst is P1f! J. PTMO is recovered by separation by washing with water or extraction.

Example / P 'I'' MG (Number average molecular weight θO) / θθV
Add to a three-piece flask equipped with a stirrer, thermometer, and condenser. Then, silicotungstic acid (H48iW12 (
)4o) Add 3f and heat to 730°C while stirring.
Heat to. The depolymerization reaction immediately proceeded, and in 7 hours, 9 of the charged P i' MG were depolymerized to i' HF.
Distilled out of the system.

Into three flasks similar to those recorded in Example/Example/, P
Various heteropolyacids 3 shown in the table -/ which were heated at high temperature and made into an anhydrous state with TMG (number average molecular weight / θ0) / θθ2
Add f. While stirring, heat to 730°C,
After 7 hours, i' HF distillation was measured. Table 7 of the results
nihosu.

Table - / Example 3 In a three tube flask equipped with a stirrer, reflux condenser and thermometer,
P T M G (number average molecular weight ♂θθ, Mw7'M
λθθV (n=λ, male) was prepared, heated at 25θ°C for 3 hours to make it anhydrous, and 1 tungstic acid was added. After raising the temperature to 700°C and continuing stirring for 7 hours, water λθθ1 and chloroformus θθt are added to the system and stirred, followed by separation into two phases. The catalyst is recovered from the aqueous phase, and from the chloroform mixture. / Otsu 62 P 'I' M U was obtained. The number average molecular weight of P T M G is /2θθ,
MWAn was 7.7.

In addition, the number average molecule I@, MwAn of P TMO
(Q weight average molecular weight/number average molecular weight) was measured using gel permeation chromatography (GPC).

Example PTMG (number average molecular weight/jθθ) λθθV is added to a Nitro flask equipped with a stirrer, a reflux condenser, and a thermometer. In addition, silicotungstic acid (H481W46・nH2O) with the number of coordinated waters shown in Table 2 adjusted to a constant value 61
Add 1. After stirring at 730°C for θ minutes, cool to room temperature,
Thereafter, PTMG was recovered using a recovery weighing scale I according to the method described in Example 3, and the initial depolymerization activity according to the number of coordinated waters was compared. Display the results -
Show it to Yu.

Table-no Samples A and RI show comparative examples.

Example j A copolymer of THF and ethylene oxide (containing ethylene oxide/θ flux ratio, number average molecular weight/θθθ
)/θθ1 is added. Next, after heating for 3 hours at θ°C for 2 nights, phosphotungstic acid (H
3PW1204o) Add V and add 1 while stirring.
Heat to 30°C. The depolymerization reaction proceeded immediately, and 9.2% of the charged polymer was decomposed in 7 hours and distilled out of the system.
' HF was collected.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] When polyoxytetramethylene glycol is depolymerized to obtain tetrahydrofuran, a depolymerization method characterized by using telopolyacid as a catalyst in which less than 1 molecule of water is coordinated or present.