JPH0762083A - Method for removing residual ethylene oxide from polyethylene oxide - Google Patents

Abstract

PURPOSE:To efficiently remove toxic ethylene oxide from a high-molecular weight polyethylene oxide to an ultralow level by heating and decompressing a granular high-molecular weight polyethylene oxide under specific conditions. CONSTITUTION:This method for removing residual ethylene oxide from polyethylene oxide is to heat a granular polyethylene oxide having >=100000 average molecular weight (granular PEO) at 40-65 deg.C, preferably 50-60 deg.C and treat the granular PEO in an atmosphere under <=200mmHg pressure, preferably in a vacuum atmosphere under <=20mmHg pressure and remove the residual ethylene oxide from the granular PEO. The treatment is preferably carried out by using a Nauta mixer having an internal ribbon type stirrer, a jacket and a warm nitrogen blowing port, etc., while stirring the reactional mixture in a hermetically closed state. Furthermore, the treating time may be 20hr at 40 deg.C heating temperature under 20mmHg vacuum degree when, e.g. the amount of the residual ethylene oxide at 20-70ppm is reduced to <=10ppm.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a method for removing low molecular weight organic compounds from polymeric materials, and more particularly for removing traces of residual ethylene oxide from high molecular weight polyethylene oxide granules. It is about the method.

[0002]

2. Description of the Related Art Ethylene oxide (hereinafter abbreviated as EO)
Is known to have adverse effects on biological systems such as its toxicity and its teratogenicity and carcinogenicity. Therefore, when polyethylene oxide obtained by polymerizing EO (hereinafter abbreviated as PEO) is used for medical applications or food applications, PEO contains little or no EO. It is necessary not to.

Generally, there are the following two types known as PEO. That is, the first is what is called polyethylene glycol (PEG), which is a low molecular weight material having an average molecular weight of less than about 20,000, such low molecular weight PEO in liquid or wax form. Due to this, it is relatively easy to remove stagnant EO from the manufacturing process.

On the other hand, the second one is generally called PEO and is a high molecular weight material having an average molecular weight of about 100,000 or more. Such a high molecular weight PEO is a solid having a high degree of crystallinity. is there. Therefore, when the EO remaining in such a high molecular weight PEO is heated and removed, the surface of the PEO particles partially melts when heated,
It has the drawback of sticking to each other. Further, since PEO particles have weak resistance to shearing force, there is a drawback that the molecular weight is remarkably reduced. Therefore, it was practically very difficult to remove the residual EO in the high molecular weight PEO to a low level.

Further, in a typical EO polymerization process for producing high molecular weight PEO, about 20-70 p is added to the product.
Since it is common to include pm of pm, for example, 10p
Direct production of products with low residual EO levels, such as PEO with pm or less EO, was also particularly difficult.

Therefore, various methods for removing the EO remaining in the high molecular weight PEO have been studied so far, and a conventional EO removing method is disclosed in, for example, JP-A-5-156001. However, in this method, solid particulate material is added to high molecular weight PEO to prevent sticking (aggregation) of PEO and heating at normal pressure. Was needed. Moreover, in this method, PE
Since EO is removed at a temperature in the vicinity of the melting point of O, adhesion of high molecular weight PEO, which is a granular material, is likely to occur. It must be added, which in turn means that the foreign material is being positively added into the PEO. Therefore, P containing such additives
EO is often unusable or inconvenient depending on the application.

Under such circumstances, it is extremely important to develop a method capable of efficiently removing EO remaining in high molecular weight PEO without adding any additives.

[0008]

The present invention solves the problems in the prior art methods and is very useful in practice for removing residual EO in high molecular weight PEO from low levels to very low levels. It is an issue to provide such a method.

[0009]

The method for removing residual ethylene oxide from polyethylene oxide of the present invention removes residual ethylene oxide in high molecular weight polyethylene oxide granules having an average molecular weight of 100,000 or more. Wherein the high molecular weight polyethylene oxide granules are heated to a temperature of 40-65 ° C,
It is characterized in that the treatment is performed in a reduced pressure atmosphere of 200 mmHg or less. The present invention is also characterized in that, in the above-mentioned method, stirring is carried out when the high-molecular-weight polyethylene oxide particles are heated and subjected to a reduced pressure treatment.

That is, according to the method of the present invention, a high molecular weight PEO granule having an average molecular weight of 100,000 or more (generally, the trace level of EO is about 20 to 70 ppm) is used in an amount of 40 to 65.
It is heated to a temperature of ℃, preferably 50 to 60 ℃, the surrounding atmosphere is a reduced pressure atmosphere, preferably 200mmH
The method of the present invention is carried out under reduced pressure so as to obtain a reduced pressure atmosphere of g or less.
This is a method that can reduce the amount to 0 ppm or less.

The present invention will be described in detail below. First, in the present invention, the high molecular weight PEO granules to be treated are
Heat to a temperature in the range of about 40-65 ° C, considering that this PEO granulate is a crystalline material with a crystalline melting point (softening point and sticking point) in the range of about 65-67 ° C. The heating temperature may be equal to or lower than the melting point of the PEO granular material, and the range of 50 to 60 ° C. is particularly preferable. At this time, when the heating temperature is lower than about 40 ° C., the residual EO in the PEO granules is increased even if the degree of vacuum is increased.
It is difficult to reduce the amount efficiently, and conversely 70
If the heating is carried out at a temperature higher than 0 ° C, the PEO granules stick strongly to each other and cannot be used industrially.

The high molecular weight P suitable for the treatment according to the present invention
Although the particle size of the EO granules can be appropriately selected,
A particularly preferable range is about 0.18 to 1.00 mm. The following is an example of the particle size distribution of the high molecular weight PEO particles suitable for the present invention.

In the present invention, the method for heating the PEO particles is not particularly limited, and heating can be carried out by various methods. In the present invention, a preferable heating method is a method in which PEO particles are placed in a heated closed container and heated in a closed state. When this method is used, residual EO can be efficiently reduced. You can In addition, a gas inlet and a gas outlet are provided in the above-mentioned closed container, and a non-reactive gas such as heated nitrogen (warm nitrogen) is flowed into the closed container to supplementally heat the PEO particulate matter. Is also good.

In the present invention, the PEO granules are heated to the above temperature and the PEO atmosphere is set to 200 mmH.
The pressure is reduced to g or less, preferably 50 mmHg or less, and more preferably 20 mmHg or less. When reducing the atmosphere around the PEO granules to a reduced pressure atmosphere, it is preferable to industrially use a tray dryer, a rotary vacuum dryer, a depressurizable type Nauta mixer, or the like. A Nauter mixer having a mold stirrer, jacket, hot nitrogen blowing port, etc. is effective.

The residual EO amount is less than a certain amount, for example, 10
The depressurization time required to reduce to ppm or less is determined by a function of the heating temperature and the degree of depressurization. Therefore, as a matter of course, when the degree of reduced pressure (vacuum degree) is high, the time required for the treatment is short. For example, about 2
When reducing the amount of residual EO from 0 to 70 ppm to 10 ppm or less, heating temperature: about 40 ° C., decompression degree: 200 m
With mHg, a treatment time of about 40 hours is required, but with a heating temperature of about 40 ° C. and a degree of reduced pressure of 20 mmHg, the treatment time may be about 20 hours. Further, when the heating temperature is about 60 ° C., even if the degree of pressure reduction is 200 mmHg, the treatment for only 5 hours is sufficient.

Further, in the present invention, it is preferable to perform stirring while heating and depressurizing the PEO particles to be treated,
When stirring is performed, there is an advantage that sticking between PEO granules can be prevented, and there is an advantage that residual EO can be removed efficiently. However, in the present invention,
The stirring operation is optional and not essential.

In the present invention, the EO residual level in the high molecular weight PEO granules can be easily adjusted to 10 ppm by appropriately selecting the heating temperature, the degree of pressure reduction and the time during the treatment.
When compared with the treatment method performed under normal pressure under the same temperature condition, the method of the present invention is superior in that the residual EO can be reduced to a lower level in a short time.

As in the present invention, the method of removing residual EO by performing the pressure reduction treatment at a specific temperature requires a shorter treatment time than the conventional method, and since the treatment is performed at a relatively low temperature, the adhesion is reduced. Pure EO can be produced without the need to add impurities such as inhibitors. The present invention will be further described below with reference to examples.

The method of measuring the amount of residual EO used in the examples (semi-quantitative gas chromatography) is as follows. [Analysis Method of Residual EO] Residual EO in the high molecular weight PEO granules was measured by gas chromatography using headspace sampling and the standard addition method. The sample to be analyzed was placed in a closed vial, dissolved in 1,2-dichloroethane and a known amount of EO was added (Spike method).
This sample was warmed and held at 75 ° C. for 60 minutes to release residual EO, an aliquot of headspace gas was removed and injected into a gas chromatograph, and the data obtained was routinely added to the sample by the standard addition method. EO
Used to calculate the level. EO for routine analysis
A standard spiked analysis was performed using single spiked samples rather than multiple spikes. Then, by calculating the measured EO peak area per gram of the sample with the slope of the calibration curve created by plotting the amount of added EO (microgram) against the EO peak area per gram of the sample, Semi-quantitative analysis was performed.

The measurement conditions at this time are as follows. Instrument parameters Column: 10 mx 0.5 packed with polaplot U
3 mm capillary gas flow rate: Helium carrier 15 mL / min. Nitrogen replenishment gas: 15 mL / min. Detector: Flame ionization detector tube Temperature: Injector 200 ℃, Detector 250 ℃,
Column 70 ℃ for 5 minutes Heating program up to 190 ℃ + 15 ℃ / min. After that, hold the temperature for 7 minutes to finish

The sample used in the following examples is a high molecular weight PEO "ALCOX E-160 (trade name)" manufactured by Meisei Chemical Industry Co., Ltd.
The high molecular weight PEO having an average molecular weight of about 5,000,000 was produced by heterogeneous metal-catalyzed polymerization of EO monomer, and the residual EO in the product was about 40 ppm. The particle size of this high molecular weight PEO was in the range of 0.18 to 1.0 mm.

[0022]

EXAMPLES The above-mentioned high molecular weight PEO (ALCOX E-1)
60) was weighed in the predetermined amounts shown in Table 1 below, and then
The amount of residual EO in "ALCOX E-160" after the treatment was measured by the semi-quantitative gas chromatographic method described above by allowing the mixture to stay at the temperature, the degree of reduced pressure, and the treatment time shown in FIG. . The results are summarized in Table 1 below.
Shown in.

[0023]

[Table 1]

As can be seen from the results shown in Table 1, when the method of the present invention was used, high molecular weight PEO was obtained in a short time.
The EO remaining inside can be efficiently reduced to a low level, and adhesion between particles does not occur. From the above, it is understood that the method of the present invention is superior to the conventional processing method performed under normal pressure.

[0025]

When the method of the present invention is used, EO, which is a toxic gas, can be removed from high molecular weight PEO relatively easily, and the high molecular weight PEO obtained by the treatment has a low residual EO level. Therefore, it can be safely used in the production of plastic medical devices, food packaging materials, flocculants for clay and wood pulp mills, and drug delivery systems in terms of safety and hygiene.

[Procedure amendment]

[Submission date] October 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The method of measuring the residual EO amount using Oite in Example (semiquantitative gas chromatographic method) is as follows. [Analysis Method of Residual EO] Residual EO in the high molecular weight PEO granules was measured by gas chromatography using headspace sampling and the standard addition method. The sample to be analyzed was placed in a closed vial, dissolved in 1,2-dichloroethane and a known amount of EO was added (Spike).
Law). This sample was warmed and held at 75 ° C. for 60 minutes to release residual EO, an aliquot of headspace gas was removed and injected into a gas chromatograph, and the data obtained was routinely added to the sample by the standard addition method. Used to calculate EO levels. EO multiple spikes for routine analysis
Standard add-on analysis was performed using single dose samples rather than s). Then, the amount of added EO (microgram) with respect to the EO peak area per gram of the sample
Semi-quantitative analysis was performed by calculating the measured EO peak area per gram of the sample with the slope of the calibration curve created by plotting.

Claims (2)

[Claims] 1. A method for removing ethylene oxide remaining in a high molecular weight polyethylene oxide granule having an average molecular weight of 100,000 or more, wherein the high molecular weight polyethylene oxide granule is 40-65.
A method for removing residual ethylene oxide from polyethylene oxide, which comprises heating to a temperature of ° C and treating under a reduced pressure atmosphere of 200 mmHg or less. 2. The method according to claim 1, wherein stirring is performed when the high-molecular-weight polyethylene oxide particles are heated and subjected to a reduced pressure treatment.