JPS5850615B2 - Method for producing granular oxymethylene polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The preparation of oxymethylene polymers (POM) by copolymerization of formaldehyde or cyclic oligomers of formaldehyde, in particular 1,3,5-trioxane, with suitable comonomers, in particular cyclic ethers or cyclic acetals, is known (
For example, US Patent Nos. 3,027,352 and 38,030
(See specification No. 94).

Furthermore, it is known that particulate oxymethylene polymers can be obtained by introducing a solution of the oxymethylene polymer into a precipitant at a temperature just below the melting temperature of the oxymethylene polymer (US Pat. No. 3,371,066). (see book).

In the present invention, a solution or a fine dispersion of an oxymethylene polymer is heated to a temperature of 1 to 10
0.1 to 2 oxyalkylene units having 2 to 8 adjacent carbon atoms in addition to the oxymethylene units can be added to a turbulent liquid coolant kept at a low temperature of 0.1 to 2 °C.
In preparing particulate oxymethylene polymers containing 0% by weight in the backbone, the oxymethylene polymer is dissolved or dispersed in a methanol/water mixture having a methanol content of at least 75% by weight. A 3-35% by weight solution or dispersion at a temperature of 5-65°C above the temperature of at least 7% by weight used as a coolant.
The oxymethylene polymer is precipitated by introducing it into a methanol/water mixture with a methanol content of 5% by weight, the amount of precipitated oxymethylene polymer in the resulting suspension being at most 25% by weight, and The method is characterized in that the particulate polyoxymethylene polymer is subsequently separated and dried.

The invention further relates to particulate oxymethylene polymers produced by the method described above.

In the present invention, the oxymethylene polymer is defined as having 2 to 8, especially 2.
0.1 to 20, especially 0.5 to 10% by weight of oxyalkylene units having 3 or 4 adjacent carbon atoms,
Means poly(oxymethylene).

Particularly suitable are oxymethylene polymers with a content of oxyalkylene units of 1 to 5% by weight.

Oxymethylene polymers are prepared in a known manner by bulk-1 suspension- or solution polymerization of monomers in the presence of cationic catalysts at temperatures of e.g. (See specification No. 3027352).

In this case, the cationic catalysts used are (1) protic acids, such as perchloric acid, (2) esters of protic acids, in particular esters of perchloric acid and lower aliphatic alcohols, such as tert-butyl perchlorate, (3) proton Anhydrides of acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids, such as acetyl perchlorate, (4) Lewis acids, especially boron, tin,
Halides of titanium, phosphorus, arsenic and antimony such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride and antimony pentafluoride and (
5) Complex compounds or salt-like compounds, especially ethetate or oniuni salts of Lewis acids, such as boron trifluoride-diethyl etherate, boron trifluoride-d-n-butyl etherate,
Triethyloxonium tetrafluoroporate, trioxonium-hexafluorophosphate, triphenylmethylhexafluoroarsenate, acetyl 7-
) lafluoroborate, acetyl hexafluorophosphate and acetyl hexafluoroarsenate are used.

The amount of catalyst used during the copolymerization depends, inter alia, on the degree of its capacity; generally the catalyst is in an amount of 0.1 to 2000 ppm, in particular 0.2 to 500 ppm, based on the total amount of the compound to be polymerized.
used with a weight of

Sufficiently effective catalysts, such as boron trifluoride, are preferably used in amounts of 10 to 150 ppm, in particular 20 to 100 ppm, based on the total amount of compounds to be polymerized.

The corresponding molar amounts are lower for the complex or salt-like compounds of the catalysts mentioned above.

Very strongly acting catalysts, such as perchloric acid, are used in amounts of 0.2 to 10, in particular 0.3 to 5 ppm.

It is generally recommended to use the catalyst in diluted form.

Gaseous catalysts are diluted with inert gases such as nitrogen and noble gases such as argon, while liquid or solid catalysts are dissolved in inert solvents.

Particularly suitable solvents are aliphatic or cycloaliphatic hydrocarbons and nitrable aliphatic or aromatic hydrocarbons.

Examples include dichlorohexane, methylene chloride, ethylene chloride, nitromethane and nitrobenzene.

The weight ratio of catalyst to diluent is usually 5 to 1:1000.
0, especially 1:10 to 1:100.

Catalysts that act very strongly have a ratio of 1:5000 to 1:
Preferably, it is diluted at a rate of 20,000.

The polymerization process is carried out in particular under an inert gas atmosphere and with exclusion of moisture.

Particularly suitable inert gases are noble gases such as argon and nitrogen.

Among the compounds copolymerizable with trioxane, (a) 3
．． Cyclic ethers with 4 or 5 ring members, (b
) Cyclic acetals, especially formals, having 5 to 11, especially 5, 6, 7 or 8 ring members and Ke) linear polyacetals, especially polyformals, are suitable.

As the comonomer for trioxane, in particular the formula (wherein (
A) R1 and R2 are the same or different and each represent an aliphatic alkyl residue having a hydrogen atom, 1 to 6, especially 1,2,3 or 4 carbon atoms; and (a) X is 1; .2 or 3 and y is the same as O or & b) x is the same as O, y is the same as 1.2 or 3 and Z is the same as 2 or ( c) X is the same as O, y is the same as 1 and 2 is 3.4.5 or 6
or CB)R” is 2 to 6, especially 2.3
or an alkoxymethyl or phenoxymethyl residue having 4 carbon atoms, in which X is the same as 1 and y is the same as O and R2 has the abovementioned meaning. be.

As cyclic ethers used are, for example, ethylene oxide, propylene oxide, styrene oxide, cyclohexene oxide, oxacyclobutane and phenylglycidyl ether, while as cyclic formals, for example 1
・3-dioxolane, 1,3-dioxane, 1,3-dioxepane and 1,3,6-drioquincan and 4-
Methyl 3-dioxolane, 4-phenyl 3-dioxolane, 1.3-dioxolane and 1.3-dioxacyclohebutene (5) are used.

Suitable linear polyformals are in particular poly(1,3-dioxolane) and poly(1,3-dioxepane).

For the production of oxymethylene polymers with a defined molecular weight range, it is preferred to carry out the polymerization in the presence of regulators.

For this purpose, formaldehyde dialkyl acetals having 3 to 9, especially 3.4 or 5 carbon atoms are used, such as formaldehyde dimethyl acetal, -diethyl acetal, -diethyl acetal and -dibutyl acetal, and lower aliphatic alcohols, especially 1 to 5 carbon atoms. Alkanols with 4 carbon atoms, such as methanol, ethanol, glopanol and butanol, are suitable.

The modifier is usually used in an amount of 0.0% based on the total amount of the compound to be polymerized.
It is used in amounts of up to 5% by weight, especially from 0.005 to 0.1% by weight.

Oxymethylene polymers are advantageously subjected to controlled partial thermal decomposition to generate primary alcohol end groups in order to remove unstable moieties (U.S. Pat. No. 3,174,948;
(See specification No. 219623 and No. 3666714)
.

The heat treatment is carried out at a temperature of 130 DEG to 200 DEG C., in particular 140 DEG to 190 DEG C., especially under non-acidic conditions, in an aqueous/methanolic solution, preferably with base-reactive compounds such as lower tertiary aliphatic amines such as triethyl- or triethanol. It is carried out in the presence of an amine or a secondary alkali phosphate such as disodium hydrogen phosphate.

Particular preference is given to temperatures between 150 and 180°C.

The heat treatment time is 10 seconds to 2 hours depending on the temperature, especially 1
The duration ranges from 60 minutes to 60 minutes.

The higher the temperature, the shorter the residence time can be measured.

About 1 to 2 minutes at 180°C, about 5 to 10 minutes at 160°C, about 10 to 30 minutes at 150°C and about 20 to 60 minutes at 140°C are sufficient. be.

The treatment is carried out in particular with significant exclusion of oxygen.

Solutions or fine dispersions of oxymethylene polymers with a polymer content of 3 to 35% by weight, in particular 5 to 30% by weight, are used as starting materials for the process according to the invention.

Very good results were obtained with oxymethylene polymers of 10 to 2
obtained using a polymer solution or monodispersion containing 5% by weight.

The solvent or dispersant used is a methanol/water mixture with a methanol content of at least 75% by weight, in particular a mixture of 99.9 to 80% by weight of methanol and 0.1 to 20% by weight of water. Ru.

Particular preference is given to mixtures of 99.5 to 85% by weight of methanol and 0.5 to 15% by weight of water, in which case it is best to use mixtures of 99 to 90% by weight of methanol and 1 to 10% by weight of water. results.

The temperature of the solution or dispersion is 5 to 65° C., in particular 10 to 60° C., above the half-melting temperature of the oxymethylene polymer; a temperature range of 25 to 55° C. above the half-melting temperature is particularly advantageous.

A mixture of methanol and water, the composition of which is similar to that of the solvent or dispersant, is likewise used as coolant and precipitant.

The coolant has a temperature from 1 to 10, especially from 1 to 5, especially from 2 to 4°C below the melting temperature of the oxymethylene polymer.

The amount of precipitated oxymethylene polymer in the suspension resulting from introduction of the polymer solution or dispersion is at most 25%, in particular 5 to 15% by weight.

The methanol used within the scope of the present invention may contain methanol-soluble organic impurities (which are usually produced as by-products during the synthesis of oxymethylene polymers), such as formaldehyde, cyclic oligomers of formaldehyde, methylal, glycols, glycols, etc. It may contain up to 30, especially 10% by weight of formal, glycol monomethyl ether, glycol dimethyl ether as well as lower aliphatic alcohols, lower aliphatic esters and acetone.

Half melting temperature means the temperature at which solid polymer particles suspended in a methanol/water mixture soften and become viscous without completely melting at the surface.

The melting temperature depends on the composition and molecular weight of the polymer and the type of solvent or dispersant.

The melting temperature of the oxymethylene polymers used according to the invention is from 100 to 140°C, in particular from 125 to 135°C.

The process according to the invention is carried out, for example, in an autoclave equipped with a stirrer.

In this autoclave, a coolant and a precipitant are charged and the solution or dispersion of the oxynoerene polymer is introduced into the precipitant through a dip tube or nozzle, which is preferably heated;
The latter is then kept in a turbulent state by stirring.

The method may be carried out batchwise or continuously.

In continuous operation, the resulting polymer suspension is removed at the bottom of the autoclave to the extent that the solution or dispersion and optionally additional precipitant are added.

The average residence time of oxymethylene polymer in the settling tank is 1
minutes to 12 hours, especially 2 to 120 minutes.

Depending on the temperature applied in each case, the pressure is from 5 to 40 bar, in particular from 8 to 30 bar.

Separation of the particulate oxymethylene polymer obtained by precipitation or flocculation is carried out by conventional separation methods such as filtration, decantation or centrifugation.

The oxymethylene polymer to be separated is finally 20 to 13
Drying is carried out at a temperature of 5°C, especially from 50 to 120°C.

Drying under an inert gas atmosphere, such as a noble gas or nitrogen atmosphere, is recommended.

The oxymethylene polymer obtained by the present invention is a macromolecule, and its reduced specific viscosity (R3V) is 0.3 to 2.
0 especially 0.5 to 1.5dll? (measured at a temperature of 140 DEG C. in a 0.5% by weight solution of the polymer in r-butyrolactone, which contains 2% by weight of diphenylamine as stabilizer).

Microcrystalline melting point of oxymethylene polymer is 140 to 18
0° C., and its melt index value is from 0.1 to 50, in particular from 1 to 30 g/10 min (measured according to DIN 53735 at a temperature of 190° C. and a load of 2.161 i).

The process according to the invention is characterized in that it allows the production of granular oxymethylene polymers with a high solids content (after precipitation) and a high bulk density (after drying).

The bulk density of the granular product is generally at least 300? /l
A laboratory fluidized mixer (revolutions per minute 3
000 rpm) for 2 minutes.

The oxymethylene polymers obtainable according to the invention can additionally be stabilized against the effects of heat, oxygen and/or sunlight by intimate mixing with stabilizers.

Homogenization is usually carried out in commercially available mixing equipment, such as extruders, at temperatures up to 250° C., especially above the melting point of the polymer, which is between 180 and 210° C.

The amount of stabilizers added is in total from 0.1 to 10% by weight, in particular from 0.5 to 5% by weight, based on the total mixture.

Suitable stabilizers are inter alia bisphenol compounds, alkaline earth salts of carboxylic acids and guanidine compounds.

As bisphenol compounds, in particular monobasic 4-hydroxyphenylalkanoic acids substituted once or twice with alkyl residues containing 1 to 4 carbon atoms (which are 7 to 13, especially 7.8 or 9 esters of aliphatic di-, tri- or tetrahydric alcohols containing 2 to 6, especially 2.3 or 4 carbon atoms, e.g. 3-butyl-4-hydroxyphenyl)
-pentanoic acid, β-(3-)-y-5-tert-phthyl-4-hydroxyphenyl)-propionic acid, (3,5-
C-tert-butyl-4-hydroxyphenyl)-acetic acid, β
-(3,5-di-tert-phthyl-4-hydroxyphenyl)-propionic acid or (3,5-di-isopro-4-
hydroxyphenyl)-toethylene glycol acetate, propanediol-(1・2), propanediol (1・
3) Esters of butanediol (1.4), hexanediol (1.6), 1.1.1-trimethylolethane or pentaerythritol are used.

Alkaline earth salts of carboxylic acids, especially alkaline earth salts of aliphatic, especially di- or tribasic carboxylic acids containing 2 to 20, especially 3 to 9 carbon atoms, containing hydroxyl groups. For example, the calcium or magnesium salts of stearic acid, castor oil acid, lactic acid, mandelic acid, malic acid or citric acid are used.

Examples of guanidine compounds include compounds of the formula (wherein R means a hydrogen atom, a cyano group, or an alkyl residue having 1 to 6 carbon atoms) such as cyanoguanidine, N-cyano-N'-methyl-guanidine, N-cyano-N'-methyl-guanidine, -Cyano-N'-ethylguanidine, N-cyano-N'-iso-propylguanidine, N-cyano-N
'-tert-butylguanidine or N-R-dicyanoguanidine is used.

The guanidine compound is optionally 0.0% of the total mixture.
It is used in an amount of 1 to 1, in particular 0.1 to 0.5% by weight.

Furthermore, the oxymethylene polymers prepared according to the invention can be added with known sun stabilizers, such as benzophenone, acetophenone or triazine derivatives.

Other customary additives such as dyes, pigments, reinforcing agents and fillers may be added as well.

The oxymethylene polymer can be processed by any of the methods customary for thermoplastic synthetic resins, such as injection molding, extrusion, blow molding,
It can be processed by melt spinning and deep drawing.

This polymer can be used in semi-finished products and finished products such as molded products such as bars, rods, plates, strips, bristles, threads, fibers, films, foils,
Suitable as material for manufacturing pipes and hoses and household items such as dishes and pots, and mechanical parts such as cases and gears.

The polymers can be used as engineering plastics, inter alia, for producing dimensionally stable and precise molded parts.

Example 1 Trioxane 98% by weight and ethylene oxide 2% by weight
R8V-value o, 65aJ/g, microcrystalline melting point 1
3 kg of a copolymer having 65 DEG C. and a melting index of 12=25 P/10 min are mixed in an autoclave with 30 kg of a mixture consisting of 85% by weight of methanol, 14.9% by weight of water and 0.1% by weight of trimethylamine.

The resulting suspension is heated to 160'C under nitrogen for 5 minutes, during which time the polymer dissolves.

2 kg of this solution per minute are passed continuously through a dip tube into a mixture consisting of 85% by weight methanol and 15% by weight water, which is kept under nitrogen in a turbulent flow in a separate autoclave and at a temperature of 125°C. 10- to be introduced (12
At a polymer half-melt temperature of 7°C, the temperature of the precipitant is thereby 2°C below the half-melt temperature.

). The pressure in the autoclave during the dissolution or precipitation step is 17 or 9 bar.

After the introduction is complete, let it settle for 7 minutes. The particulate polymer is discharged at the bottom of the autoclave and the solvent and precipitant are suctioned off.
Separate by filtration.

The solids content of the solid product is approximately 40%.

After drying and homogeneous mixing, the polymer has a bulk density of 350 P/J.

Example 2 Example 1 is repeated, but a mixture consisting of 90% by weight of methanol, 9.9% by weight of water and 0.1% by weight of triethylamine is used as solvent and as precipitant, respectively, and the solvent temperature is 170°C.

The granular polymer has a solids content of approximately 38% after suctioning off the solvent and precipitant and exhibits a bulk density of 3 sOS'/l after drying and homogeneous mixing.

Example 3 Trioxane 98% by weight and ethylene oxide 2% by weight
R8V-value 0.65 dl/f, microcrystalline melting point 1
7.5 kg of a copolymer with a melting index of 12 = 25 P/10 min at 65° C. are combined with 22.5 kg of a mixture consisting of 96.5% by weight of methanol, 3.4% by weight of water and 0.1% by weight of triethylamine in an autoclave. Mix.

The mixed suspension is heated to 180° C. for 5 minutes under nitrogen, during which time the polymer dissolves.

This solution was poured into a mixture consisting of 96.5% by weight of methanol and 3.5% by weight of water (which was placed in a separate autoclave in turbulent conditions under nitrogen and at a temperature of 131°C) by dipping continuously within 30 minutes. The temperature of the precipitant is thereby 2° C. below the half-melt temperature.

). The pressure in the autoclave during the dissolution or precipitation step is 30 or 10 bar.

15 minutes after the end of the introduction, the precipitated particulate polymer is discharged at the bottom of the autoclave and separated by suction filtration of the solvent and precipitant.

The solids content of the solid product is approximately 45%.

After drying and homogeneous mixing, the dry polymer has a bulk density of 450 V
/l.

Comparative Example Trioxane 98% by weight and ethylene oxide 2% by weight
A copolymer 3 having an R8V-value of 0.65 dJ/f, a crystallite melting point of 165° C. and a melting index of 12=251/10 min is made of 60% by weight of methanol, 39.9% by weight of water and 0.1% by weight of triethylamine. Mixture 3 consisting of
Mix with 0 kg.

The resulting suspension is heated to 160° C. for 5 minutes, when the polymer dissolves.

This solution is cooled to a temperature of 135°C.

2 per minute of the solution was continuously passed through the dip tube into a mixture consisting of 60% by weight methanol and 40% by weight water, which was in an autoclave under nitrogen under turbulence and 12
10 kg (kept at a temperature of 5°C) (127°C
At the half-melting temperature of the polymer, the temperature of the precipitant is thereby 2° C. below the half-melting temperature.

). Seven minutes after the introduction is complete, the precipitated particulate polymer is discharged at the bottom of the autoclave and separated by suction filtration of the solvent and precipitant.

The solids content of the solid product is approximately 33%.

After drying and homogeneous mixing, the bulk density of the dry product is 270?
/l.

Claims (1)

[Scope of Claims] 1. The production of oxymethylene units by introducing a solution or fine dispersion of an oxymethylene polymer into a turbulent liquid coolant maintained at a temperature of 1 to 10° C. below the half-melting temperature of the oxymethylene polymer. In addition, in preparing particulate oxymethylene polymers containing in the main chain 0.1 to 20% by weight of oxyalkylene units having 2 to 8 adjacent carbon atoms, a methanol content of at least 75% by weight is used. The oxymethylene polymer is dissolved or dispersed in a methanol/water mixture in a 3-35% strength solution or dispersion by weight at a temperature of 5-65° C. above the melting temperature, used as a coolant. at least 7
The oxymethylene polymer is precipitated by introducing it into a methanol/water mixture with a methanol content of 5% by weight, the amount of precipitated oxymethylene polymer in the resulting suspension being at most 25% by weight and obtained A process characterized in that the particulate oxymethylene polymer is subsequently separated and dried. 2. The method according to claim 1, characterized in that a mixture of 99.9 to 80% by weight of methanol and 0.1 to 20% by weight of water is used as a solvent or dispersant and as a coolant. 3. The manufacturing method according to claim 1, wherein the solvent or dispersant is a base-reactive compound.