JPH0791349B2 - Process for producing new cyclic acetal polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel polymer composed of a cyclic polyacetal having a relatively low molecular weight and a narrow molecular weight distribution and a method for producing the same, and an additive for improving the physical properties of a resin, For example, it is useful as an additive for improving self-lubricating property and abrasion resistance of plastics, an additive for improving surface appearance, and as a raw material of segment constituents for producing a novel copolymer or various The present invention provides a substance useful as an intermediate for compound synthesis.

[Conventional technology and its problems]

Oxyalkylene polymers, especially linear oxymethylene polymers or copolymers predominantly containing repeating --CH ₂ O-- units, have been well known for many years. There are two known methods for producing these polymers: a method of polymerizing roughly using anhydrous formaldehyde as a main monomer, and a method of polymerizing a cyclic acetal such as trioxane, which is a cyclic trimer of formaldehyde, as a main monomer. There is.

In the former method, it is proposed to polymerize or copolymerize substantially anhydrous formaldehyde using an anionic or cationic active catalyst, and in the latter method, a low cyclic acetal such as trioxane is generally used as a main monomer to polymerize or copolymerize with a cationic active catalyst. This is a method of copolymerization.

Generally, the main component of the polymer or copolymer obtained by such a polymerization method has a linear chemical structure and has a wide molecular weight distribution, and these are useful as engineering plastics and are already on the market in large numbers. .

However, a cyclic acetal polymer having a relatively low molecular weight (molecular weight of 5000 or less) and a narrow molecular weight distribution and a method for isolating and producing the same have not been known at all.

[Means for Solving the Problems]

The present inventors have found that a polymer obtained by using a cationic active catalyst having a cyclic 3- to 4-mer monomer such as formaldehyde or trioxane as a monomer has a bimodal molecular weight distribution, and most of them have a linear end group as described above. Although it is a normal polymer to have, it was found that it contains a cyclic polymer having a narrow molecular weight distribution in addition to it, and as a result of further research, a method for isolating and producing it was completed, and if it is convenient for effective use of this substance, I succeeded in tightening.

That is, in the present invention, oxymethylene is used as a main chain constituent unit, and ▲ ▼ is 500 to 5000, and ▲ ▼ / ▲ ▼
(However, ▲ ▼; number average molecular weight, ▲ ▼; weight average molecular weight) is 1.0 to 1.5, and relates to an acetal polymer having a substantially endless cyclic molecular structure, and formaldehyde or formaldehyde cyclic 3- A homoacetal polymer obtained by polymerizing a tetramer as a monomer using a cationic active catalyst is hydrolyzed in an alkaline medium having a pH of 7 or more to remove an alkali decomposable substance, thereby removing the cyclic acetal polymer. The present invention relates to a manufacturing method.

The substance of the present invention and the method for producing and separating the substance are described in detail below.

As a first step in the production of the substance of the present invention, a homoacetal polymer is obtained by polymerizing formaldehyde or its cyclic trimer trioxane, tetramer tetraoxane and the like as monomers. In particular, trioxane is the most suitable monomer. In this case, in consideration of isolation of the substance of the present invention as described below, in the polymer, in the molecular chain-
The presence of copolymers having C—C bonds is not preferred. That is, as a monomer for polymer preparation, -C
It is desirable that conventional comonomers having a -C- bond, such as ethylene oxide, 1,3-dioxolane, and other formal having a -C-C- bond are substantially absent.

In the polymerization step of the present invention, a cation active catalyst is generally used as the catalyst. Specific examples of such a catalyst include Lewis acids, particularly halogens such as boron, tin, titanium, phosphorus, arsenic and antimony, for example, boron trifluoride,
Tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride,
Compounds such as arsenic pentafluoride and antimony pentafluoride, and complex compounds or salts thereof, protic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protic acids, especially esters of perchloric acid with lower aliphatic alcohols ( For example, perchloric acid tertiary butyl ester), anhydride of protic acid, especially mixed anhydride of perchloric acid and lower aliphatic carboxylic acid (eg acetyl perchlorate), or isopoly acid, heteropoly acid (eg phosphomolybdic acid). Alternatively, triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarzenate, acetylhexafluoroborate and the like can be mentioned. Among them, boron fluoride or a coordination compound of boron fluoride and an organic compound (for example, ethers) is the most general and suitable.

The polymerization method of the present invention can be carried out with the same equipment and method as those of the conventionally known polymerization methods of formaldehyde, trioxane and the like. That is, any of batch type and continuous type is possible, and any of solution polymerization, melt bulk polymerization, etc. may be used.
A general method is to use a liquid monomer to obtain a solid powdery polymer as the polymerization proceeds. In this case, an inert liquid medium may coexist if necessary.

As the polymerization apparatus used in the present invention, a reaction vessel with a stirrer generally used in a batch system can be used, and as a continuous system, a co-kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle type continuous mixer can be used. A continuous polymerization apparatus for trioxane or the like, which has been proposed so far, can be used.

When trioxane is the main monomer, the polymerization temperature is 64 to 120 ° C if the generally used bulk polymerization method is adopted.
It is performed in the temperature range of. A relatively low temperature within this range is more desirable. The polymerization time is related to the amount of catalyst and is not particularly limited, but generally 0.5 to 100 minutes of polymerization time is selected.
The polymer taken out from the outlet of the polymerization machine after a predetermined time has passed is usually a lump or a powder, and a part or all of the unreacted monomer is separated and supplied to the next step. The reaction system after completion of the polymerization may be directly subjected to the next hydrolysis reaction step, but ammonia, amines such as triethylamine and tri-n-butylamine, or hydroxides of alkali metals and alkaline earth metals Alternatively, other known catalyst deactivators may be added and mixed, or the polymerization catalyst may be neutralized and deactivated by adding and treating a solution containing these deactivators. At this time, if the polymer produced is in the form of a large lump, it is, of course, preferable to grind and process once after the polymerization.

The polymer thus obtained has a bimodal molecular weight distribution according to the analysis of the present inventors, and an alkali-decomposable linear acetal polymer having a wide molecular weight distribution and the object compound of the present invention. It was confirmed to be a mixture of cyclic acetal polymers having a narrow molecular weight distribution. Thus, this mixed polymer is subjected to a chemical treatment step for separating and removing the linear polymer as the second stage treatment.

This chemical treatment is a hydrolysis treatment in an alkaline medium. That is, the acetal mixed polymer is contact-treated with water containing an alkaline substance as an alkaline medium and / or another organic solvent. This alkaline substance is preferably soluble in the medium.

The alkaline substance may be a strong basic hydroxide such as an alkali metal or alkaline earth metal hydroxide, or a salt of a strong base and a weak acid, or ammonia or an organic base such as amines or amidines. Good. Specific examples of such alkaline substances include caustic soda, caustic potassium, sodium carbonate, sodium acetate, ammonium hydroxide, triethanolamine, triethylamine, tripropylamine, tetramethylguanidine and the like.

Water is the most common medium, but other, for example, primary, secondary, and tertiary alcohols may be used as a part or the whole of the medium. Suitable media are aqueous solutions containing aliphatic alcohols, preferably alcohols containing 1 to 20 carbon atoms, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, isobutyl alcohol, amyl alcohol, lauryl alcohol and the like. Is. Other suitable alcohols are aromatic alcohols, preferably alcohols having 1 to 20 carbon atoms, such as benzyl alcohol, β-phenylethyl alcohol, diphenylcarbitol, etc .; cycloaliphatic alcohols, preferably 1 To alcohols having 20 carbon atoms, such as 1,2-dimethylcyclopentane-1,2-diol, 1-methylcyclohexyl alcohol, etc .; polyhydric alcohols, preferably alcohols having 1 to 20 carbon atoms, Examples thereof include ethylene glycol and glycerol.

The alkaline medium prepared with such a constitution has a pH of 7.0 or higher, preferably 8.0 or higher during treatment.

The hydrolysis treatment temperature is preferably 90 to 220 ° C, most preferably 130 to 200 ° C. The pressure is determined by the temperature and the type of medium used, and it is possible to carry out not only normal pressure but also considerably high pressure.

The treatment with the alkaline medium can be carried out in either a heterogeneous system or a homogeneous system. This can be selected depending on the processing temperature and the type of medium. That is, in the case of water or a medium mainly composed of water, or when the treatment temperature is low, a heterogeneous system is formed. Polyoxymethylene is completely decomposed to formaldehyde, which is eluted into the medium and removed.

In general, when the temperature is high or when an organic medium that dissolves the entire polymer is used, the treatment is performed with a homogeneous solution. In this case, the mixed polymer is treated in a solution state as an almost homogeneous system, and the linear polymer having an end group is decomposed from its end to formaldehyde and dissolved in the medium in an extremely short time. Since the cyclic polyoxymethylene polymer, which is the object of the invention, is dissolved without being decomposed at all, it can be separated by a conventional method by precipitating the solution by cooling or adding a non-solvent. Generally, in the case of the former heterogeneous treatment, it takes a long time to complete the treatment, and in the case of a homogeneous treatment, a short time is sufficient.

Next, the amount of alkaline medium used can be varied over a wide range depending on the type of polymer, the type of alkaline substance, its strength (pH) and hydrolysis conditions, but at least an amount sufficient for the entire polymer to be immersed. is necessary.

In addition, the alkaline substance also neutralizes and deactivates the polymerization catalyst that decomposes any polymer during the hydrolysis process, suppresses the decomposition of the cyclic polymer, and selectively decomposes only the linear polymer. It is effective, and it is difficult to decompose the entire polymer and residually obtain the target substance of the present invention in an acidic medium.

The reaction time of hydrolysis varies depending on the properties of the alkaline medium, the hydrolysis conditions, its mode, the properties of the polymer, etc. as described above, but is generally about 10 seconds to about 10 hours, preferably 0.
2 to 120 minutes.

After completion of the hydrolysis reaction, the cyclic polymer is separated from the medium and, if necessary, cooled or added with a large amount of a non-solvent, washed, and dried.

The polymer thus obtained has a ▲ ▼ of about 500 to 5000 and a ▲ ▼ / ▲ ▼ of 1.0 to 1.5, and has a very narrow monomodal molecular weight distribution. Of the existing bimodal molecular weight distribution, the one with the higher molecular weight was decomposed and removed.

From the NMR spectrum and infrared spectrum analysis of this low molecular weight polymer, the polymer end is not detected, and it is considered that this polymer has a cyclic structure because it is stable to alkaline hydrolysis treatment. .

〔Example〕

Examples of the present invention will be shown below, but the present invention is not limited thereto.

The terms and measuring methods used in the examples are as follows.

Parts,% and ppm: All are by weight.

Molecular weight and molecular weight distribution: number average molecular weight (▲ ▼) using GPC (gel permeation chromatography) (solvent: hexafluoroisopropynol, temperature; 40 ° C)
And the weight average molecular weight (▲ ▼) were determined using the GPC-LALLS (low angle laser light scattering detector) method and a calibration curve obtained from a polymethylmethacrylate standard sample.

Example 1 200 parts of trioxane was placed in a closed autoclave having a jacket through which a heat medium can pass and a stirring blade,
After stirring and passing hot water of 70 ° C. through the jacket to maintain the temperature at about 70 ° C., a cyclohexane solution of trichloromethanesulfonic acid was added so as to have a catalyst concentration of 3 ppm (relative to monomer) to start polymerization. After 3 minutes, 300 parts of water containing 0.1% of autoclave hetributylamine was added to stop the reaction, the contents were taken out and crushed to 200 mesh or less, washed with acetone and dried, and then the polymerization yield, molecular weight and molecular weight distribution were measured. did.

The polymerization yield is 78%, the molecular weight distribution is bimodal, and the ▲ ▼ of the high molecular weight peak is 39,000.
▼ indicates 2.0, which is 84.8% of the whole. On the other hand, ▲ ▼ for the mountain on the low molecular weight side is 2,000,
▲ ▼ / ▲ ▼ indicates 1.1, which is 15.2% of the total
Was the ratio.

Next, 100 parts of this bimodal polymer was placed in 5000 parts of a 50% aqueous methanol solution containing 0.5% ammonium hydroxide,
After heating in a closed container at 180 ° C. for 45 minutes in a homogeneous system, the mixture was cooled to room temperature, the residue was filtered with a filter, washed with acetone and dried. The yield of this fixed product was 15.0% based on the polymer before treatment, and the molecular weight distribution of this product was unimodal and narrow.
▼ = 2,000 and ▲ ▼ / ▲ ▼ = 1.1. or,
As a result of ¹ H-NMR measurement, only a proton signal based on —CH ₂ O— was observed at 4.97 ppm, and the infrared absorption spectrum did not show absorption indicating the presence of a terminal group. Therefore, this substance is judged to have a cyclic structure.

Example 2 An effective length having a cross section in which two circles having an inner diameter of 80 mm partially overlap each other.
A continuous mixing reactor consisting of a barrel with a jacket for passing a heat medium to the outside of 1.3 m and two rotating shafts with a number of intertwined paddles inside the barrel was used.
Passing hot water at ℃, rotate the two rotating shafts in different directions at a speed of 100 rpm, and continuously supply trioxane to one end at a speed of 10 kg / hr. At the same time, dibutyl ether of boron trifluoride is supplied. The cyclohexane solution of the salt was continuously added to trioxane so that the catalyst concentration became 30 ppm to carry out polymerization, and the reaction mixture discharged from the other end was immediately ground to 100 mesh or less and triethylamine.
The polymerization catalyst was deactivated by throwing it in water containing 0.1%.
Next, a part of the polymer was washed with acetone and dried, and then the yield, molecular weight and molecular weight distribution were measured.

The polymerization yield is 60%, the molecular weight distribution is bimodal, and the peak on the high molecular weight side has ▲ ▼ of 41,000.
▼ indicates 2.1, which is a ratio of 86.0% to the whole. On the other hand, ▲ ▼ of the mountain on the low molecular weight side is 2,300,
▲ ▼ / ▲ ▼ indicates 1.1, 14.0% of the total
Was the ratio.

Next, isopropyl alcohol and caustic soda were further added to and mixed with this polymer slurry to give a polymer concentration of about 7
%, Isopropyl alcohol in the medium 40%, caustic soda
After adjusting to 0.5% and heating up to 200 ° C. to dissolve the whole uniformly, it is kept for about 15 minutes and then cooled to room temperature to collect solids, and the average molecular weight is measured in the same manner as in Example 1. did.

The yield of this solid based on the total polymer was 13.9%, ▲
▼ = 2,300, ▲ ▼ / ▲ ▼ = 1.1. Also, ¹ H
-NMR result of the measurement, -CH ₂ O-to 4.97ppm in the same manner as in Example 1
Only a proton signal based on
Also in the infrared absorption spectrum, there was no absorption indicating the presence of a terminal group. Therefore, it is determined to have a ring structure.

〔The invention's effect〕

As is clear from the above description and Examples, it becomes possible to obtain a novel cyclic acetal polymer having a relatively low molecular weight and a narrow molecular weight distribution, which has not been obtained by the present invention, and the cyclic acetal polymer is obtained. Is expected to be widely useful as an additive for improving the physical properties of resins, an intermediate for synthesizing various compounds, or a raw material for a segment constituent component for producing a novel copolymer.

Claims (4)

[Claims] 1. A method for hydrolyzing a homoacetal polymer obtained by polymerizing a formaldehyde or a cyclic trimer or tetramer of formaldehyde as a monomer using a cationic active catalyst in an alkaline medium having a pH of 7 or more to remove an alkali decomposable substance. Oxymethylene is a main chain constitutional unit, and ▲ ▼ is 500 to 5000, and ▲ ▼ /
▲ ▼ (however, ▲ ▼; number average molecular weight, ▲ ▼;
A method for producing an acetal polymer having a cyclic molecular structure having substantially no terminal group, having a weight average molecular weight of 1.0 to 1.5. 2. The method for producing a cyclic acetal polymer according to claim 1, wherein the monomer is trioxane. 3. The alkaline medium is mainly composed of water, alcohols or a mixture thereof, and contains an alkaline substance.
The method for producing a cyclic acetal polymer according to claim 1 or 2, which is a liquid having a pH of 8 or more. 4. The alkaline medium treatment is carried out at a temperature of 130 to 200 ° C.,
The method for producing a cyclic acetal polymer according to claim 1, 2 or 3, which is carried out for a time of 0.2 to 120 minutes.