EP0637322A1 - Procede de production de copolymeres de polyoxymethylene a stabilite thermique et leur utilisation - Google Patents

Procede de production de copolymeres de polyoxymethylene a stabilite thermique et leur utilisation

Info

Publication number
EP0637322A1
EP0637322A1 EP93909832A EP93909832A EP0637322A1 EP 0637322 A1 EP0637322 A1 EP 0637322A1 EP 93909832 A EP93909832 A EP 93909832A EP 93909832 A EP93909832 A EP 93909832A EP 0637322 A1 EP0637322 A1 EP 0637322A1
Authority
EP
European Patent Office
Prior art keywords
alkali metal
copolymer
fluoride
metal fluoride
added
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93909832A
Other languages
German (de)
English (en)
Inventor
Gerhard Reuschel
Hans Dieter Sabel
Dietrich Fleischer
Kaoru 3794-1 Imaizumi Yamamoto
Nagayoshi 3913-32 Ohbuchi Maeda
Makoto 8-6 Yodogawa-Cho Kamiya
Toshiro 324 Miyashita Murao
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hoechst AG
Original Assignee
Hoechst AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19924242900 external-priority patent/DE4242900A1/de
Application filed by Hoechst AG filed Critical Hoechst AG
Publication of EP0637322A1 publication Critical patent/EP0637322A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
    • C08G2/28—Post-polymerisation treatments

Definitions

  • This invention relates to a process for producing a polyoxymethylene copolymer having an improved heat stability and their use for the production of moldings. More particularly, it relates to a process for producing a polyoxymethylene copolymer containing a reduced number of unstable terminals and having an improved heat stability by using a specific compound for deactivating a catalyst in the cationic copolymerization of trioxane with a cyclic ether or a cyclic acetal.
  • POM Polyoxymethylene
  • a common polymerization process for producing the POM polymers comprises using a cyclic acetal such as trioxane as a main monomer and a cyclic acetal or a cyclic ether having adjacent carbon atoms as a comonomer, further adding a chain transfer agent for controlling the degree of polymerization depending on the purpose copol ⁇ merizing these monomers with the use of a cationically active catalyst, and then contacting the polymerization product with an agent for neutralizing or deactivating the catalyst or a solution thereof to thereby deactivate the catalyst.
  • a cyclic acetal such as trioxane
  • a cyclic acetal or a cyclic ether having adjacent carbon atoms as a comonomer
  • the obtained crude POM polymer After the completion of the copolymerization, the obtained crude POM polymer generally contains a considerably large amount of unstable terminals and, therefore, it is necessary to stabilize the POM polymer by eliminating the unstable parts therefrom. Thus, a complicated post-treatment process spending much energy is required therefor, which causes an economic disadvantage.
  • a crude POM copolymer containing a reduced amount of unstable parts is obtained after the polymerization, advantages such that the final product has an improved stability and that the post-treatment including stabilization can be simplified can be achieved. Accordingly, it has been desired to establish a process for producing a polymer containing a reduced amount of unstable parts in polymerization.
  • catalyst deactivators found in the proposals include in general organic and inorganic alkaline substances, for example, organic substances such as alkylamines, alkoxyamines and hindered amines and inorganic ones such as alkali and alkaline earth metal hydroxides, more particularly, calcium hydroxide (refer to Japanese patent Laid-Open No. 38713/1983).
  • the unstable hemiacetal end groups in trioxane copolymers can be selectively broken down, for example by treating the copolymer with aqueous solutions at temperatures of 120 to 220°C, if necessary with the addition of organic solvents, especially lower alcohols, trioxane or dioxolane; basic compounds, especially trialkylamines, also being able to be added to the solutions (G.W. Becker/D. Braun, unststoff Handbuch, Vol. 3/1 , p. 316, Kunststoff- Vienna, 1992).
  • a disadvantage of this process is the incomplete deactivation of the initiator. Initiator residues may remain in the polymer material and lead to chain scissions on heating the material, This results in a release of formaldehyde during processing, which can cause an odor nuisance and a health risk.
  • a basic disadvantage of this process is the accuracy required in setting the necessary pH value, which is generally set with strong acids.
  • the use of strong acids is always accompanied by the danger of a chain scission, since all polyoxymethylenes are sensitive to acids.
  • a further disadvantage of the aforedescribed process is the high proportion of 0.6 to 2 % by weight of sodium fluoride in the hydrolysis liquor, as is disclosed in the examples.
  • the stability of the polymers can be substantially improved, been in the neutral or alkaline pH range, by adding soluble alkali metal fluorides to the hydrolysis liquor. It has also been found that the stabilizing effect can be achieved with a fluoride ion concentration as low as approximately 0.02 % by weight.
  • the present invention relates to a process for producing a polyoxymethylene copolymer by copolymerizing trioxane as a main monomer with a cyclic ether or a cyclic formal as a comonomer by using a cationically active catalyst, characterized by contacting an alkali metal fluoride with the copolymer after the completion of the copolymerization to thereby deactivate the polymerization catalyst.
  • the present invention further relates to a process for preparing polyoxymethylene copolymers having improved thermal resistance by heating the crude polymer, obtained after the completion of the copolymerization to thereby deactivate the polymerization catalyst in an aqueous hydrolysis liquor having a pH value of ⁇ . 7.0, to which has been added from 20 to 400 ppm, preferably from 100 to 300 ppm, and in particular from 150 to 250 ppm, of fluoride ions in the form of an alkali metal fluoride.
  • the present invention is characterized in that the polymerization catalyst is very effectively deactivated by using the above-mentioned alkali metal fluoride, together with a commonly known basic substance, to thereby suppress the occurrence of side reactions during the deactivation and give a crude POM copolymer containing an extremely reduced number of unstable terminals. It has been furthermore found out that the catalyst deactivated with the above- mentioned deactivator becomes highly stable and, therefore, its function for promoting the depol ⁇ merization in the subsequent steps including high- temperature drying, melt treatment and molding can be remarkably suppressed,
  • the POM copolymer according to the present invention is produced by first copolymerizing trioxane as a main monomer with a cyclic ether or a cyclic formal as a comonomer in the presence of a cationically active catalyst.
  • the cyclic ether or the cyclic formal to be used as a comonomer herein is a cyclic compound having at least a pair of linked carbon atoms and an oxygen atom represented by the following general formula: *1
  • R R 2 , R 3 and R 4 may be either the same or different from each other and each represents a hydrogen atom or an alkyl group, in general, a hydrogen atom.
  • R 5 represents a methylene or oxmethylene group, an alkyl-substituted methylene or oxymethylene group (in this case, p is an integer of from 0 to 3), or a divalent group represented by the following formulae: -(CH 2 ) q -OCH 2 - or -(O-CH 2 -CH 2 ) q -OCH 2 -
  • Examples of such a comonomer include ethylene oxide, 1 ,3-dioxolane, 1,3- trioxepane, diethylene glycol formal, 1 ,4-butanediol formal, 1 ,3-dioxane and prop ⁇ lene oxide.
  • particularly preferable examples of the comonomer include ethylene oxide, 1 ,3-dioxolane, 1 ,4-butandiol formal and diethylene glycol formal (G. W. Becker/D. Braun, Kunststoff-Handbuch, Vol. 3/1 , p. 303, Kunststoff- Vienna, 1992).
  • the content of the comonomer may range from 0.2 to 10 % by weight, preferably from 0.4 to 5 % by weight, based on the trioxane.
  • an appropriate chain transfer agent may be added, if necessary, so as to control the molecular weight of the POM copolymer.
  • catalysts include Lewis acids, in particular, halides of boron, tin, titanium, phosphorus, arsenic, antimony and so forth, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachioride, phosphorus pentafluoride, arsenic pentafluoride and antimony pentafluoride, and compounds derived therefrom, such as complexes and salts thereof, protonic acids such as trifluoromethanesulfonic acid and perchloric acid, protonic acid esters such as perchlorates of lower aliphatic alcohols (for example, tert-butyl perchlorate), protonic acid anhydrides, in particular, mixed anhydrides of perchloric acid with lower aliphatic carboxylic acids (for example, acetyl perchlorate),
  • Lewis acids in particular, halides of boron, tin, titanium, phosphorus, arsen
  • boron trifluoride and coordination compounds of boron trifluoride with organic compounds (for example, ethers).
  • the polymerization of the present invention can be conducted by using the same apparatus and the same method as those employed in the known processes for polymerizing trioxane. More specifically, both of the batch process and the continuous one may be employed and any of the solution polymerization, melt bulk polymerization and other polymerization processes may be selected. From the industrial viewpoint, it is usual and preferable to use the continuous bulk polymerization process wherein liquid monomers are employed and a solid polymer in the form of a powdery mass is obtained as the polymerization proceeds. In this case, an inert liquid medium may be present together, if necessary.
  • the polymerization apparatus to be used in the present invention may be selected from among a Ko-kneader r a twin-screw continuous extruder, a two- shaft paddle-type continuous mixer as well as those which have been proposed as the apparatus for the continuous polymerization of trioxane.
  • a polymerization apparatus of a closed system may consist of two or more stages. It is particularly preferable to use an apparatus provided with a pulverizer whereby a solid polymer formed by the polymerization reaction can be obtained in the form of fine particles.
  • the crude polymer discharged from the polymerizer should be immediately contacted with a deactivator to thereby deactivate the polymerization catalyst.
  • the present invention is characterized in that the copolymer obtained is mixed with an aqueous solution comprising alkali metal fluoride and, if desired, C*,-C 4 - alcohols, trioxane or dioxolane, so that a fluoride ion concentration as mentioned above is achieved.
  • a fluoride of an alkali metal such as Li, Na, K, Rb or Cs is used as the deactivator and the crude copolymer is contacted therewith to thereby deactivate the catalyst. Preference being given to potassium fluoride.
  • the deactivator may be contacted with the polymerization, product in an arbitrary manner without restriction.
  • the contact may be achieved by adding the above-mentioned alkali metal fluoride to the crude polymer and thoroughly mixing.
  • the alkali metal fluoride is formulated into a solution in water and/or an organic solvent and the polymerization product is mixed with this solution, followed by the stirring of the resulting mixture in the form of a slurry.
  • Basic substances are generally added to set the pH value, for example sodium hydroxide, potassium hydroxide or calcium hydroxide.
  • Organic basic substances such as trialkylamines having 1 to 6 carbon atoms in the alkyl group, for example triethylamine, triethanolamine, triisopropanolamine, N,N- diethylmethylamine, are preferred.
  • the mixture is then heated in a closed system, a homogeneous solution being formed. Temperatures of from 170°C to 220°C, preferably from 180°C to 200°C, are necessary for this purpose.
  • the residence time is from 2 to 20 minutes, preferably from 5 to 15 minutes.
  • the polymer discharged from the polymerizer is in the form of fine particles.
  • the polymer is In the form of relatively large particles, it is preferable to rapidly pulverize the polymer in the above-mentioned solution of the deactivator following the discharge from the polymerizer.
  • the copolymer is subjected, if necessary, to washing, the separation and recovery of the unreacted monomers and drying and, furthermore, stabilization if necessary.
  • additives such as various stabilizers are added thereto and the copolymer is melt-kneaded and formulated into pellets, thus giving a product.
  • the POM copolymer of the present invention contains an extremely reduced number of unstable terminals and, therefore, the load in the stabilization step is relieved.
  • the residual unstable parts can be eliminated by volatilization in the melt-kneading extrusion step for adding, for example, stabilizers.
  • the copolymer obtained by the process according to the present invention contains a reduced amount of unstable parts as compared with those obtained by using the conventional deactivators and does not undergo depolymerization since the catalyst has been completely deactivated.
  • the post-treatment procedure can be simplified and the final product has a high heat stability.
  • the oxymethylene polymers treated according to the invention can be processed by all methods normally used for thermoplastics materials, for example injection molding, extrusion, extrusion blow molding, melt spinning and thermoforming.
  • the polymers are suitable as a material for producing molding of all types, in particular semi-finished and finished articles. They can be used in particular as qualitatively high-grade material of construction for manufacturing moldings with high dimensional stability having as smooth surface.
  • a melt index (g/10 min) measured at 190°C under a load of 2160 g is given. This is evaluated as a characteristic corresponding to the molecular weight. Namely, a lower Ml means a larger molecular weight (provided that a small amount of a given stabilizer is added before the measurement so as to prevent decomposition during the measurement).
  • a copolymer 1 g is added to 100 ml of a 50 % aqueous solution of methanol containing 0.5 % of ammonium hydroxide and heated in a closed container at 170°C for 45 minutes. Then, the amount of the formaldehyde decomposed and dissolved in the solution is determined and expressed in % based on the polymer.
  • Examples 1 to 10 and Comparative Examples 1 to 3 Use was made of a continuous mixing reactor which had a cross section composed of two circles partly overlapping each other and was provided with a barrel having a jacket for passing a heating (cooling) medium therethrough placed outside and two rotating shafts having stirring/screwing paddles located in the direction of the major axis placed therein.
  • TPP triphenylphosphine
  • Example 1 1 was repeated with the difference that triethanolamine was substituted by 125 mg triethylamine (pH value 10.1 ). The loss of weight was 0.05 %.
  • Comparative Example 4 50 g of ground crude polymer were mixed as in Example 11 with the hydrolysis liquor, but without the addition of fluoride (pH value 8.5) and then treated. The weight loss was 0.36 %.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)

Abstract

Procédé de production d'un copolymère de polyoxyméthylène, consistant à copolymériser du trioxane, utilisé comme monomère principal, avec un éther cyclique ou un formal cyclique utilisé comme comonomère, à l'aide d'un catalyseur à activité cationique, un fluorure de métal alcalin étant mis en contact avec le copolymère après l'achèvement de la copolymérisation afin de désactiver le catalyseur de polymérisation. Le traitement s'effectue à une valeur de pH » 7,0, ce qui permet d'obtenir un copolymère de polyoxyméthylène présentant une stabilité thermique améliorée.
EP93909832A 1992-04-24 1993-04-22 Procede de production de copolymeres de polyoxymethylene a stabilite thermique et leur utilisation Withdrawn EP0637322A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP10670592 1992-04-24
JP106705/92 1992-04-24
DE4242900 1992-12-18
DE19924242900 DE4242900A1 (de) 1992-12-18 1992-12-18 Verfahren zur Herstellung von thermisch stabilen Copolymeren des Trioxans und ihre Verwendung
PCT/EP1993/000979 WO1993022359A1 (fr) 1992-04-24 1993-04-22 Procede de production de copolymeres de polyoxymethylene a stabilite thermique et leur utilisation

Publications (1)

Publication Number Publication Date
EP0637322A1 true EP0637322A1 (fr) 1995-02-08

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EP93909832A Withdrawn EP0637322A1 (fr) 1992-04-24 1993-04-22 Procede de production de copolymeres de polyoxymethylene a stabilite thermique et leur utilisation

Country Status (3)

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EP (1) EP0637322A1 (fr)
KR (1) KR950701355A (fr)
WO (1) WO1993022359A1 (fr)

Families Citing this family (3)

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Publication number Priority date Publication date Assignee Title
US5965379A (en) * 1991-07-19 1999-10-12 Cytimmune Sciences Inc. Method for measuring endogenous cytokines
JP5829569B2 (ja) * 2012-04-23 2015-12-09 旭化成ケミカルズ株式会社 ポリアセタール共重合体の製造方法
JP7425795B2 (ja) * 2018-07-13 2024-01-31 ビーエーエスエフ ソシエタス・ヨーロピア 安定なポリオキシメチレンコポリマー（ｃＰＯＭ）の製造方法

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Publication number Priority date Publication date Assignee Title
DE1248939B (de) * 1967-08-31 Badische Anilin- &. Soda-Fabrik Aktiengesellschaft, Ludwigshafen/Rhem Verfahren zum Aufarbeiten von Copolvmerisaten des Trioxans
NL125851C (fr) * 1963-09-28
US3640945A (en) * 1967-10-10 1972-02-08 Basf Ag Thermal stability of copolymers of trioxane
IT1076228B (it) * 1977-01-17 1985-04-27 Sir Soc Italiana Resine Spa Procedimento atto a migliorare la stabilita' degli omopolimeri acetalici eterificati

Non-Patent Citations (1)

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Title
See references of WO9322359A1 *

Also Published As

Publication number Publication date
WO1993022359A1 (fr) 1993-11-11
KR950701355A (ko) 1995-03-23

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