JPS62175478A - Method for stabilizing trioxan - Google Patents

Abstract

PURPOSE:To suppress formation of a very small amount of a polymer occurring in storing or transportation of a trioxan monomer and to stabilize trioxan so as not to have a bad influence on polymerization reaction, by using a noncyclic ether as a stabilizer. CONSTITUTION:Trioxan useful as a raw material monomer for producing a polyoxymethylene polymer or copolymer or a monomer mixture comprising trioxan as a main component is blended with a noncyclic ether so that trioxan is stabilized. An aliphatic ether such as diethyl ether, di-n-butyl ether, etc., or an aromatic ether such as diphenyl ether, etc., is used as the noncyclic ether. The amount of the non cyclic ether added is preferably 10-10,000ppm based on trioxan. A molecular weight modifier to control molecular weight of oxymethylene polymer, etc., may be present. EFFECT:Having no bad influence on physical properties of prepared polymer, capable of carrying out continuous polymerization, stably for a long time.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides stability during storage or transportation of trioxane, which is a raw material monomer for producing polyoxymethylene polymers or copolymers, or a monomer mixture containing trioxane as a main component. Please refer to the method of conversion.

[Conventional technology]

Trioxane or a mixture of trioxane and a monomer such as cyclic ether or cyclic formal (hereinafter sometimes referred to as trioxane monomer), which is a raw material for producing polyoxymethylene polymers or copolymers, is stored and transported using metal pipes and pumps. Contact with metals, etc. is unavoidable, and traces of traces of acid on the metal surface, or traces of acidic substances present in trace amounts, produce a small amount of polymer as suspended matter. In addition, the melting point of trioxane is 64°C, but if it is not heated during storage, it will solidify, and when used, it will be heated and melted, but this heating, melting, cooling,
By repeating the solidification cycle, the production of trace amounts of polymer is promoted. The polymer produced in this way is insoluble in the raw material monomer, so when it is transported, it may clog the pulp or filter in the pipeline, making transport impossible, or if the polymer comes into contact with the pump valve. The flow rate of transfer becomes unstable, and in severe cases, transfer becomes impossible.

In order to solve these inconveniences, conventional methods have been to avoid the cycles of heating, melting, cooling, and solidifying the raw materials as much as possible, and to filter out suspended matter using a filter.
A method is used to frequently remove polymers that accumulate in the filter.

However, the above-mentioned method does not essentially solve the inconvenience caused by the production of polymers, and is accompanied by operational complexity.
A new solution was desired.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for stabilizing trioxane monomer that suppresses the formation of trace amounts of polymer during storage and transportation of trioxane monomer and does not adversely affect the polymerization reaction.

[Means for solving problems]

According to the present invention, there is provided a method for stabilizing trioxane, which comprises adding acyclic ethers to trioxane.

According to the present invention, the addition of an acyclic ether suppresses the formation of polymer floats that conventionally occur during storage and transportation of trioxane, and promotes polymer formation even after repeated heating and melting and cooling and solidification. It has been found that there is no oxidation, does not affect the subsequent polymerization reaction, and does not adversely affect the physical properties of the resulting polymer.

The acyclic ethers used in the present invention are preferably, for example, aliphatic ethers or aromatic ethers.

For example, dialkyl ether is used as the aliphatic ether. The alkyl preferably has 1 to 12 carbon atoms,
Furthermore, 2 to 8 are preferable. Specific examples of these include diethyl ether, di-n-propyl ether, di-n-butyl ether, dihexyl ether, dioctyl ether, and the like.

Examples of aromatic ethers include diphenyl ether and dialkyl ether. Among these ethers, diethyl ether and di-n-butyl ether are particularly preferred.

The amount of acyclic ethers added is 10 to 10% relative to trioxane.
10.000 ppm is preferred, more preferably 10 to 1,000 ppm
ppm is preferred. If it is less than 10 ppm, there is no stabilizing effect of trioxane, and 10. If OOOppm is exceeded, the polymerization conversion rate will decrease.

In the present invention, other monomers used in combination with trioxane include, for example, cyclic ethers or cyclic formals other than trioxane, and the proportion of these comonomers used is 0.4 to 40 mol% relative to trioxane.
Preferably it is 0.4 to 1 mmol%. The cyclic ether or cyclic formal is represented by the general formula (1), for example.

R.

Here, in the formula, R, Rz, R3 and R4 are the same or different and represent a hydrogen atom, an alkyl group or an alkyl group substituted with a halogen.

R is a methylene group or an oxymethylene group (n is an integer of O to 3), or (CHz)-0CHz-2(OCH
It means a divalent group represented by z(1:Hi)-0CHz (n is equal to 1, m is an integer of 1 to 4). The alkyl groups mentioned above have 1 to 5 carbon atoms, the hydrogen atoms of which may be replaced by 0 to 3 halogen atoms, especially chlorine atoms.

Examples of the cyclic formal or cyclic ether that can be used in the present invention include ethylene oxide, 1.3-
Dioxolane, diglycol formal, shrimp chlorohydrin, styrene oxide, etc. are preferred, and cyclic formals such as 1,4-butanediol formal and 1,6-hexanediol formal are more preferred.

In addition, in the present invention, the molecular weight regulator added to control the molecular weight of the oxymethylene polymer or copolymer is mixed with trioxane or a monomer mixture of trioxane and other monomers such as cyclic formal or cyclic ether, and non-containing monomers. It can be made to coexist in a mixture with a cyclic ether.

Known molecular weight regulators can be used, and specific examples thereof include methylal, orthoformate, and the like.

Moreover, any known method may be used for the polymerization method of the oxymethylene polymer or copolymer carried out in the present invention. As a polymerization catalyst, for example, a Lewis acid can be used, and the Lewis acid includes boron trifluoride, and boron trifluoride organic coordination compounds such as boron trifluoride diethyl ether complex, boron trifluoride dibutyl ether complex, etc. , antimony trichloride, boron trichloride, aluminum trichloride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride.

Perchloric acid, trifluoromethanesulfonic acid and its anhydride, triphenylmethylhexafluoroantimonate allyldiazonium, hexafluorophosphate,
Examples include triethyloxonium tetrafluoroborate, molybdenum oxide acetylacetoate, etc., but among these, boron trifluoride coordination compounds are preferred, and boron trifluoride diethyl ether complex and boron trifluoride dibutyl ether complex are preferred. Particularly preferred.

These catalysts contain 1.0XI per mole of trioxane.
It is used in a proportion of 0-'' to 1.0×10-' mole.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The measured values used in the Examples and Comparative Examples were based on the following measuring method.

Reduced viscosity: Polymer concentration 0.5 g/d1 in p-chlorophenol/Ll, 2.2-tetrachloroethane (1:1 weight ratio) solution containing 2 wt% α-pinene. Measured at 60°C.

Rv(50): Percentage of polymer remaining when the polymer housing composition is heated at 222°C under vacuum for 50 minutes.

Example 1 Trioxane 59.7k in 801 stainless steel tank
g, 1751 g of ethylene oxide, and 62 g of di-n-butyl ether were added. After stopping the heat retention of the tank, the mixture was cooled to room temperature, solidified, and left for 12 hours, and then the temperature was raised to 80° C. again to perform melting. Stainless steel pipe from the tank,
The raw material was continuously supplied to the oxymethylene continuous polymerization reactor by a pump via a valve at a rate of 9.0 kg per hour, and 0.2 M dichloride of boron trifluoride di-n-butyl ether complex was added as a catalyst. Polymerization was carried out by adding 6×10-' mol of ethylene solution to 1 mol of trioxane. Polymerization was carried out continuously for 6 hours, but there was no clogging of valves or pipes, and the flow rate of the pump was extremely stable. The polymer thus obtained has a conversion rate of 92 to 94% and a reduced viscosity of 2.6 to 2.9 d! /g,
Rv(50) was stable at 95.4 to 96.6%. Furthermore, after the continuous polymerization was completed, the inside of the tank, pipes, and pump were inspected, but no polymer was found to be attached.

Comparative Example 1 8 (60.2 kg of trioxane in a stainless steel tank)
, 1766 g of ethylene oxide were added. After stopping the heat retention of the tank, the mixture was cooled to room temperature, solidified, and left for 12 hours, and then the temperature was raised to 80° C. again to perform melting. Polymer was already floating in the tank.

A pump passes from the tank through stainless steel pipes and valves to the polyoxymethylene continuous polymerization reactor at 9 pm per hour.
．． Polymerization was carried out in the same manner as in Example 1 by adding a catalyst. Thirty minutes after the start of the supply, the supply rate of the polymer raw material began to be disturbed. By constantly monitoring the flow rate and adjusting the pump supply speed,
Polymerization was continued for 0 minutes, but 1 hour after the start of supply, the filter installed between the pump and the tank was clogged with polymer, making it impossible to supply the raw material, and continuous polymerization was discontinued.

The polyoxymethylene polymer obtained within 1 hour after the start of supply had a conversion rate of 92-95% and a reduced viscosity of 2.6-2. !
11 dl/g, Rv(50) 95.2-96.
It was 2%.

The inside of the pipe and pump was inspected, but no polymer was found.

Example 2 Trioxane 42.5k in 801 stainless steel tank
g, ethylene oxide 1247 g, methisil 12 g.

4.3 g of di-n-butyl ether was added. The temperature of the tank was kept at 80°C and after storage for 12 hours, the tank was pumped through stainless steel pipes and valves to a continuous polyoxymethylene polymerization reactor at 9.50 mph per hour. The raw material was continuously supplied at a rate of 1.0 kg, and a catalyst was added to carry out polymerization.

Polymerization was carried out continuously for 4 hours and 30 minutes, but the valve was closed.

No blockages were found in the pipes, and the pump flow rate was stable.゛The polymer obtained in this way has a conversion rate of 92 to 94
%, reduced viscosity 2.3-2.6411g, Rv (50)
It was stable at 95.6-96.4%. After the continuous polymerization was completed, the inside of the tank, pipes, and pump was inspected, but no polymer adhesion was observed.

Comparative Example 2 In the same manner as in Example 2, trioxane, ethylene oxide, and methylal were added to the tank, but without adding di-n-butyl ether, the tank was kept warm at 80°C for 12 hours. The polymer was supplied from the tank to a continuous polymerization reactor at a rate of 9.0 kg/hour, and polymerization was carried out by adding a catalyst. After supply start 2
Polymerization was stable for some time, but after that the feed rate of raw materials began to become unstable and could no longer be controlled, and polymerization was stopped. After inspecting each device, it was discovered that the valves of the pumps were clogged with polymer, making normal operation impossible.

The polyoxymethylene polymer obtained within 2 hours after the start of supply had a conversion rate of 92-94% and a reduced viscosity of 2.1-2.
6dl/g, Rv(50) 94.8-96.1
%Met.

Examples 3-4 Table 1 was prepared as acyclic ether in the same manner as in Example 2.
As shown in Figure 2, the results of polymerization using diphenyl ether and diethyl ether are shown together with Example 1.2 and Comparative Example 1.2.

〔Effect of the invention〕

By adding acyclic ethers to the trioxane monomer, the present invention suppresses the formation of a trace amount of polymer suspended matter during storage and transportation of the trioxane monomer, and does not adversely affect the polymerization reaction. Polymerization can be carried out stably for a longer period of time than continuous polymerization by conventional methods without adversely affecting the physical properties of the resulting polymer.

Claims (3)

[Claims] (1) A method for stabilizing trioxane, which comprises adding an acyclic ether to trioxane or a monomer mixture containing trioxane as a main component. (2) The method for stabilizing trioxane according to claim 1, wherein the acyclic ether is selected from aliphatic ethers and aromatic ethers. (3) The method for stabilizing trioxane according to claim 1, wherein the amount of the acyclic ether added is in the range of 10 to 10,000 ppm of the trioxane.