MXPA96004545A - Procedure for the preparation of polyace copolymer - Google Patents

Abstract

The present invention provides a process for the preparation of a thermally very stable polyacetal copolymer having very small unstable terminals with a high polymerization yield, with the copolymerization of trioxane as the main monomer, with a comonomer copolymerizable therewith, wherein a isopoly acid or a salt thereof is used as the polymerization catalyst, the catalyst can be simply deactivated in a small amount of a deactivating solution after the polymerization, and the washing step is not required, the copolymerization is carried out with an isopoly acid or a salt thereof used as a polymerization catalyst until the residual monomers reach a maximum of 10% by weight of all the monomers fed, and a solution containing a deactivator for the above catalysts is added in an amount of 0.01 to 10% by weight, based on the resulting crude polymer, to deactivate the catalyst, followed by subjection of the intact raw polymer to an unwashed heat melting treatment

Description

PROCEDURE FOR LPI PREPARATION OF POLYACETAL COPLCYMER FIELD OF THE INVENTION The present invention relates to a process for the preparation of a polyacetal copolymer, more preferably metal, to a process for the preparation of a copolymer of pol ace + to < What is excellent about quality is there is 1 heat, and a simple cloth using an isopoly-acid or an acid salt of the same in the copolymer is used as the main raw material. a copolomerable comonoinero together with him.

DESCRIPTION OF THE RELATED TECHNIQUE 15 Has + now, the coplanarization MV LO? H of the poxano as the main monomer with a "cyclic or formal cyclic ter that has two or more carbon atoms to already ent ent ent es horn as rosemary, has been known as a procedure for the preparation of a flake! Uñero de poliacot.al. Cationic catalysts proposed for use on a codend include ionic acids, particularly boron, stannous, titanium, fosioro, arsenic and intimate halides; for example, t-boron trifluoride, tet tin chloride, i titanium, pentacLoride of phosphorus, pentat 1 phosphorus urea, pe nt arsenic fluoride and pentaf 1 antimony uroide; and complex compounds or salts thereof; protic acids, for example, acid per < lonco; acid esters proton i < There are, in particular, alcoholic acid alcohols in the interior, for example, perchlorate of tertiary hydrogen; proton-acid anhydrides, particularly anhydrides of per-odoric acid and carboxylic acids, for example, acetyl perchlorate, or hexaf-1-phosphate of t-runet] loxonium, hexafluoride, or o of tpf ni lrneti lo, t et ra ti uoroborato de acetilo, hexaf luoi otos l ato acetyl and hexaf Acomethyl Jouoroarsenate. Among them, boron fluoride or a coordinated compound of boron tri fluoride with an organic compound, for example, ethers, is the most suitable as a copolymerization catalyst for t-poxane as the main monomer and is used extensively. Conventional polymerization catalysts, such as a boron trifluoride compound, are required in relatively large amounts (eg 40 ppm or more in l> g to monomers). total), and therefore difficult to [[]) sufficiently carry out a deactivation treatment after polymerization. When the deactivation treatment is achieved, the residual matter that originates in the catalyst accelerates decomposition? < * r * a restrict the yield of polymerization and the degree of polymerization.

In addition, there is a problem that the presence of identifiable quantities of the unstable terminals requires a step of compiled stability. That is, in the copolymerization of tpoxane i.on < The former is conventional as described above, and the deactivation of the catalyst after the r > polymerization, and insufficient deactivation thereof accelerates a decomposition of the resolving polymer and causes a major cause to damage-a subsequent stabilization of the resulting polymer. Therefore, until now, in the case where boron p-fluoride is used as a catalyst, a complicated and complicated procedure has been required, in order to sufficiently carry out a deactivation treatment of the catcher-a a large amount of a deactivating solution to the product obtained after the polymerization to effect the deactivation treatment, and the product is 1 '? wash sufficiently to remove the residual monomer and a residue originating in the catalyst, followed by separation and drying of the treatment solution or recovery of the monomers from the wash solution. Such a procedure is also not preferred from an economic point of view. In addition, all are proposed in which, for pampering The complexity accompanied by the deactivation treatment of the catalyst, the aggregate amount of deactivator solution is reduced, and the washing of the catalyst is excluded. 7 crude polymer (for example, 3P-0-52 -5728, 3P ~ n-57-8041, 1P-A-b2-28590g, and 3P-A-B3-2751'3). However, commonly known catalysts such as a boron tri fluoride type catalyst can not be deactivated sufficiently by such methods, and it is extremely difficult to obtain copolymers having good heat stability. In particular, although a 5 increase in the polymerization yield makes it less necessary to recover monomers by Washing, the resulting polymer is also optionally unsharpened, and a complicated stabilization treatment is required in a subsequent step. After all, the steps are not simplified. (1) Furthermore, the resulting polymer has limited stability and is therefore not preferred in quality standards.

BRIEF DESCRIPTION OF THE INVENTION In view of this existing situation, an object of the present invention is to prepare a fingernail copolymer which has a very small amount of thermoline, unstable even when the polymerization yield increases and which is thermally very stable, by a simple procedure in Which one (1 catalyst can easily be deactivated in a small amount of a deactivating solution and a washing step is unnecessary.) Intensive investigations made by the present inventors to achieve the object described above, have been made.

The result is the finding that the particular use of an acidic Li-acid or an acid salt thereof as a catalyst makes it possible to deactivate the catalytic converter and probably with an deactivator, at the same time that the catalyst has a characteristically The polymerization activity can achieve the object described above, and thus complete the present invention. A process for the preparation of a polycarboxylic copolymer by the copoiirnerization of the tpoxane or the master monoinner with a cyclic or a cyclic formal having at least one carbon-carbon-carbon bond as a component, characterized because the copolyzing is carried out using an isopoly acid or an acid salt of the same polymerization catalyst until the remaining monomers reach at least 10% by weight of all the monomers fed, followed by the addition of a solution containing a deactivator for the above catalyst in an amount of 0.01 to 10% by weight based on the resulting crude polymer, to deactivate the catalyst, and a subsequent heat fusion treatment of the intact raw polymer without washing it. The present invention is characterized in the preparation of a polyacetal iron copolymer which provides very small unstable parts, even when the polymer is heat set as it is, and which is very thermally stable, particularly using an isopoly acid or an acid salt of mine. or a polymerization catalyst, which provides a very high polymerization activity and increases the polymerization yield with a very small amount of catalyst and can then be deactivated very effectively, and in the small amount of deactivating solution, so that the residual matter that originates in the catalyst does not fully exert damaging effects and the washing pass is not required. This is specifically effective, whereas in the case of conventional boron fluoride-type catalysts, adverse effects such as decomposition caused by matter originating in the catalyst even after deactivation are difficult to avoid. of my mo.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be explained hereafter in "The isopoly acid is synonymous with isomultiple acid, homonuclear c-ondensate acid, or homogeneous muLtipie acid and is a higher molecular inorganic oxygen acid comprising a condensation product of an acid of inorganic oxygen with a single type of metal, which is derived from a salt of sopoly Ia represented by the following formula (1) or (2): m1l20. nM 2? 5- xH20 (1) m1i2? - nllVio3- H2O (2) where M1 represents primarily an alkali metal; MV represents vanadium, niobium or tantalum, which belong to the group V > > 1st lepodic table; MV1 i ^ pre ent to chromium, motibdene, tungsten or uiaruo, which belong to group VI of l < ? < < peri '/ dica; m and n each represents an en + ero of 1 or more; and x represents a number of (1 to 1. The isopolyzide can be prepared by different methods, such as a method in which an isopolycid salt solution represented by the formulas (1) or (2) described above is treated. , by e loLo isopo 1 unol i dato, isopoly tungstate and i sopol ivanadato, with remasters of ion exchange, and a method in which a mineral acid is added to a concentrated solution and extracted with ether. In addition, acidic salts having a form in which the protons of L5 these acids are partially replaced with different Les targets. Specific examples of these isopolysates include, for example, isopolytic acid such as para-atonic acid and metastatic acid; isopolirnolibdi acid co tal such as paranoloic acid and ammonium acid, and ivanadic acid and opol. Among them, the preferred isopolytic acid is preferred. The amount of the isopoly acid acid salt used as a polymerization catalyst for monomers that ? They comprise a trioxane first, depends on the type of them, and the polution can be controlled by changing it appropriately. In general, the amount of the ism is on a scale of 0.05 to 100 ppin, preferably 0.1 to 50, based on the amount to + of the monomers that are to be pollinated. An amount used of preferably 0.1 to 10 ppm is sufficient for the isopoly acid to have a very strong activity, such as parathiol acid. The copolymerization capable of being carried out even in such small amounts of catalyst is effective for the control of at least undesirable reactions such as the main chain decomposition of the polymer and depopulation, which are caused by the catalyst, and economically dangerous. In the present invention, it is preferred to carry out the reaction entirely, to add to the inventors the preceding catalyst which is diluted in an inert solvent which has no adverse effect on the polymerization. Preferred as diluents are ether compounds which contain organic solvents which can dissolve the isopoiiaeide or the acid salt thereof, for example, n-butylether. However, the diluent should not be restricted to this. Trioxane, which is a cyclic trimer of Ldehyde form is used as the main monomer in the present invention. The ommonomer used in the present invention is a cyclic ether or a cyclic formal having at least one adjacent carbon-carbon-bond bond, and all conventional comonomers used for copolymerization with tnoxane can be used. .. Typical examples of tricyclic or trivalent, for example, 1, 1-di-oxolane, form L -diet i lena L i co 1, fornal-1, 4- butaned? ol, 1, J-dioxane, ethylene oxide, oxidizing agent, > pr-opylene and epi clorh? dr-? na In addition, cyclic esters can also be used, for example fi-propiolactone, and vinyl compounds, for example stretch! In addition, Iquilen diglycidyl ether or difopnal can also be used as a comonomer to allow the copolymer to form a molecular or branched or entangled structure. They include, for example, butanedi? L-dirnetlidengl icer-yl ether and butanediol diglycidyl ether. In particular, preferred copolymers include cyclic ether or cyclic formals such as 1,3-d-oxolane, potassium-diethylene glycol, formal -1,4-butanediol, and ethylene oxide. of the cornonorian used in the present invention is 0.1 to mole%, preferably 0.2 to 10 mole% based on the trioxane. The amount of less than 1 mol% increases in unstable terminals and deteriorates stability. The excess amount softens the resulting polymer and lowers the melting point 0. Therefore, both are not preferred. In the polymerization process of the present invention, publicly known chain transfer agents, for example, linear low molecular weight acids, such as methylal, can be added as well as to control the degree of polymerization according to the objectives. The polymerization system is preferably maintained in the condition "so that the impurities which are not present in the hydrogens are substantially not present., for example, water, meL.nol,, u,? lo fo r-mi co o s irn11a r. The polymerization of the present invention can be carried out with the same facilities and all that are used for conventional copolymerization of tpoxane. That is, either an intermittent system or a continuous system can be employed and a method is generally applied in which liquid polymers are used to obtain a solid, powder or polymer? bulk, as the polymerization progresses. With respect to the polymerization apparatuses used in the present invention, conventional reactors equipped with a stirrer for an intermediate system can be used, and for a continuous system the continuous polymerization apparatuses for tnoxane that have been proposed can be used. to the roof, such as a co-kneader, a mixer of continuous extrusion type double arrow of propeller, a mixer-continuous type double arrow of vane, and others that have been proposed until now. In addition, two or more types of polymerization equipment can be used in combination. The polymerization temperatures are on a scale from 60 to 120 ° C, particularly pre-measured from 65 to 100 ° C. In the present invention, the unreacted elements remaining after the polymerization have to reach 10% by weight or less, preferably 5% by weight or less, and most preferably 1% by weight or less. This is because the present invention is directed primarily at not leading to the washing of the polymerization product, and therefore, there is no increased amount of residual monomers. By reducing the unreacted monomers, the polymerization rate can be raised to a more reliable level. Fn el >According to the present invention, this can easily be achieved by adequately controlling the amount of catalyst used and the polymerization time (the residence time in a continuous system). In particular, since the catalyst used in the present invention has a high activity, the polymerization can be completed for a relatively short period of time even with a small amount of the catalyst. In addition, a portion of the residual monomers may be removed by evaporation to control the residual quantities at a given amount. Then, after the end of the copying, Ii i < c i n, a given amount of a solution containing a deactivator is added to the catalyst - and mixed with the raw polymer in which the residual monomers are reduced to 1% by weight or less to deactivate the catalyst. The deactivator used in the present invention can agglomerate an amount sufficient to neutralize and deactivate the catalyst and is preferably added in the form of a deactivating solution prepared by dissolving or dispersing the deactivator in water or an organic solvent.

In this case, the given amount of the deactivating solution is 0.01 to 1 n% by weight, preferably 0.05 to 5% by weight and particularly preferred 0.1 to 3% in p < -so, based on the weight of crude polymer. The present invention is characterized by why? the amount of deactivated solution is very small, and it is absolutely insufficient to wet the raw polymer to make it suspension. However, in combination with the characteristics of the specific catalyst used in the present invention, the catcher can be deactivated sufficiently even in such a small amount by stirring and mixing well with the green polymer. The present invention is characterization ada because even if the material originating from the catalyst remaining after ivación desac, the crude polymer can be melted as such by heating without separating ysn washing the deactivating solution and exerting adverse effects such as Acceleration of the decomposition of the polymer to obtain the stable polyacetal cop-copol. All base materials publicly known to use horn type catalysts tp fluoride conventional boron are effective as ivador OFF used in the present invention and include, for example, ammonium, various amine compounds, compounds of trivalent and oxides phosphorus, hydroxides, salts Organic acids or inorganic acid salts of alkali metals or metals at cali noterreos. These deactivators are added in the form of an aqueous solution or a solution in organic solvent on a scale of one < fixed or minor intity. , amine compounds include primary, secondary and tertiary aliphatic amines and aromatic amines, for example methylamin, dirnet i J arnin, trinirnet iiarnin, etiiarnin, diethylamine, tietimamine, butyiamine, dibutinlarin, t-butylamine, and their corresponding Icoholanins (for example, triethanolamine and the like), aniline, di-phenylalanine, heterocyclic amines and hindered amines (various pipen di derivatives). Trivalent phosphorus compounds include, for example, rhephenylphosphine. Alkali metal or alkaline earth metal compounds include oxides, hydroxides, salts of weak inorganic acids, such as carbonates, bicarbonates, phosphates, borates and silicates, salts of organic acids such as acetates, oxalates, formates, benzoates, terephthalates, isophthalates, phthalates and fatty acid salts, alkoxides such as methoxide, ethoxide, n-butoxy, sec-buto gone and tei- liutoxi or, and phenoxides of alkali metals or alkaline earth metals. Among them, oxides, carbonates and salts of fatty acids are preferably used. The components of alkali metals or metals to quino terreos include lithium, sodium, potassium, cesium, magnesium, calcium, strontium and barium. Among cilia, lithium, sodium, potassium, magnesium and calcium are preferably used. Specifically, calcium hydroxide, magnesium hydroxide, calcium carbonate, calcium carbonate, calcium stearate and 2-h are particularly preferred. droxiest ear of 1 to 1 C l. To dissolve - > 1 deactivator - water or an organic solvent is used. The organic solvent includes alcohols such as methanol and ethanol, ketones such as acetylene and acetone, aromatic compounds such as benzene, toluene and xylene, and saturated hydrocarbons such as cyclohexane, n-hexane and n-heptane. Water is particularly preferred. This method is specifically ingested by a method for the addition of the deactivating solution described above to the crude lime. In order to effectively carry out the dispersion and the contact, the solution is preferably sprayed on the crude polymer or stirred and mixed sufficiently after the addition of the solution. In a catalyst deactivation treatment, the crude polymer is preferable? fine powder. For this purpose, a polymer reactor preferably has the function of pulverizing a bulk polymer., or the reaction product can be pulverized separately by a grinder - after the polymerization, and then the deactivator is added. In addition, spraying and stirring can be carried out at the same time in the presence of the deactivator. With respect to the grain size, the crude polymer in deactivation treatment, 90% or more of the crude polymer, has a grain size of 3 m or less, preferably 2 rnm or less and more preferably 1. in or less the deactivation ratios are from 20 to 120 ° C, preferably from 40 to ip ° C. In particular, a reliance on the unstable portions of the crude polymer can be eliminated at this stage by treating it at relatively high temperatures. In the case where a solution of an amine compound or an aqueous solution of arnonia is particularly used as a deactivator, the effects thereof are markedly improved. In addition, in the present invention, prescribed stabilizers are preferably added after or at the same time as the deactivation treatment, if necessary. The substances as such, given with the examples of deactivators described above, have a function as a stabilizing component in many cases. It is important to add as stabilizers other compounds than those mentioned above, substances known to the public as stabilizers for conventional polyacetal reams, for example, several hindered phenol-type antioxidants. Decorations, different nitrogen-containing compounds, metal oxides, and salts of fatty acids can be added and used as a component. Anti-oxidants are phenol-hindered type include, for example 2, 6-di-t-but j 1-4-met-11-phenol, b? L "3- (3-t-butyl-5-methyl-4-hydroxyl ester)? Onethol from t petglinol, bis - T - (, -d -t-but? l-4-hydroquinone) propionatol of L, 6-hexanod? ol, tet raquis Ib l "3 - (3, 5 -d -t-but? l-4-h? Jrox? feni 1) propylate! methane, N, N'-hexameth 11 en-b i í 3, 5 -di - 1 - but i 1 -4 -hydrox i hydr oci narin da), 2 t I? U t i 1 - fi - (3 '-t -but 11 -5' -inet 11-2 '- h i d rox i benc 11) - 4 - e ti 1 femlacplato, and 3, g- i T? -. { (3- -but? L-4-hydrox? -5-rnet i] phenyl) propioni lox i} - 1, 1 '-dirnet ile 111-2,4,0,10-t et raoxaspiro L5, 51 -undecano. Nitrogen-containing compounds include di-cyanodiarnide, elamine or derivatives thereof, urea or derivatives thereof, benzot-p-azole compounds, piper-dma compounds (hindered amines), and polyalkane or copolymer vanes. the same (for example, nylons h, 12, 6 / L2, 6/66/610, and 6/66/610/12.) The oxides of alkaline earth metals are premeasured as metallic oxides, and metal salts of Fatty acids include calcium salts or magnesium salts of higher fatty acids.Also, if necessary, various other additives, for example fillers such as glass fiber, crystal accelerators (nuclear agents), can be added and mixed at this stage, and releasing agents In the present invention, the brutin polymer mixed with the deactivator for the catalyst is then subjected to a heat melt treatment, the heat fusion treatment in the present invention is carried out preferably at temperatures within a range of a melting point of the resulting lime po or higher and up to 250 ° C, particularly in preferred form the point (ie fu) or above and up to 10 ° C. Temperatures greater than 250 ° C are not preferred since. > The folimer is broken down. A heat treatment apparatus should not be specifically restricted. Apparatus is required which has the ability to knead a molten polymer and the function of v < entilacion and includes, for example, extruder kneaders.

(Single arrow or multi-arrow ontmua having at least one ventilation hole and co-kneaders "In the present invention, the polymerization catalyst is then completely deactivated in this melt-kneading treatment, and the Mixed ivadora accelerates the decomposition and elimination of unstable parts of the raw polymer and is eliminated from the ventilarte fiarte together with the water added with the deactivator, other solvents, and residual monomers, so that pellets can be obtained from the copolymer of stable cicetal pol.To achieve this purpose, it is natural to preferably reduce the pressure in the ventilation hole by aspiration.

EXAMPLES The examples of the present invention should be stated immediately, but it is natural that the present invention should not be restricted to cilia.

The terms and measurement methods used in the examples and the comparative examples are shown below. > < % or ppm: shown by weight. «Residual monomer: shown in% of residual monomers based on all monomers fed. melt index (ni): shows a melt index (g / 10 m n) measured at 190 °; this is evaluated as a characteristic value corresponding to a molecular weight; that is, the lower the Mi, the higher the molecular weight- .. * Alkali decomposition regime (a quantity of> unstable parts present): pellets are sprayed from the dye copolymer, and lg of them is placed in 100 ml of an aqueous 50% methanol solution containing 0.5% ammonium hydroxide to heat them to 180 ° C for 45 minutes in a closed container, then a quantity of urine 1 is analyzed quantitatively. which is formed by decomposition and elutes towards the solution, showing in% on the basis of the polymer * Diet of weight loss by heating: shown by a regime of weight loss observed when 5 g of the copolymer pellets are heated to 230 ° C for 45 minutes in the case of Examples 1 to 13 and comparative examples 1 to 3. A continuous mixing reactor was used, which had a cross-section formed by the partial overlap of two circles in which a barrel equipped with a shirt on the outside to pass a heat transfer medium (cooling medium) and on the inside two arrows 13 swivels equipped with a pallet assembly for the < G? trition and propulsion in a longitudinal direction, where it is imitated or < ontically trioxane that < It contained 3.5% of a cornonornero shown in Table 1 and 700 ppm of inet t 1 to 1 as chain transfer agent while passing hot water of 70 ° C through the jacket and rotating the two rotating arrows; In the same place and at the same time, an iopolyacid catalyst (a solution prepared by forgetting it in -? ed in-but 11 ico), shown in Table 1, was added in an amount shown in Table L, based on The most important thing is to carry out the imep zac ion copol. Then, after the reaction product is discharged from a discharge port of this polymerization apparatus, it is subsequently continued polishing in a different apparatus (a part of the polymer was sampled to determine the residual amount of monomers), a solution is added deactivator shown in Table 1, and then the polymer is passed through a shredder to see it, and the pulverized polymer is stirred at 60 ° O for 30 minutes (the pulverized polymer of 90% or more had a grain size of 2 mm or less). Then, 0.5% of tetrakis-Fmet iinien- (3,5-d? -t-but? 1 -4-h? Drox? Phen? 1 Jpropuonat or] meta or as a stabilizer- and 0.2% is added. I licked it to shake them and mix them for 5 minutes in a Honschel mixer. Then the polymer melts and kneades at a temperature of 2J0 ° W at a vacuum of 5 mm Hg in the ventilation part. means of an arrow dredge extrusion machine equipped with a / hiler and it is used to prepare pellets, the pellets are dried and then their MI, decomposition rate by c-alor, and Weight loss regime due to heating The results of these are shown in Table 1. For comparison purposes, the copolymers were prepared in the same way, using but i etelato-t pf 1 urea uro bor-o as the catalyst (Table 2).

Table 1 Table 1 (continued) Table 2 Table 2 (continued) / ' As e < According to the explanations and the examples of rites above, the production process of the present invention is a procedure that is much simplified compared to the conventional procedures since a washing pass is used. , wherein the catalyst can be completely deactivated; There are problems such as decomposition and decay associated with the catalyst; can-? The polyacetal copolymer can be obtained with fewer unstable parts, and the polyacetal eopoluner having excellent quality can be prepared economically.

Claims (1)

1. NOVELTY OF THE INVENTION CLAIMS '> 1. A process for the preparation of a polyaoetal lime flake by the copolymerization of trioxane as the main monomer with a cyclic or cyclic formal ether having at least one carbon-carbon bond or a :: ommonomer, characterized in that the copolymerization is off-filled (lf) using an acid or an acid salt of the same, or a polymerization catalyst until the residual inorganizers reach at most 10% by weight of all the monomors fed, followed by the addition of a solution containing an off. ivador- for said catalyst in an amount of (1.01 15 to 10% by weight based on the resulting polymer, to deactivate the catalyst, and a subsequent heat fusion treatment of the intact crude polymer without washing it., 2. The process for the preparation of the copolymer of polyacetal as claimed in the 20 go-claim 1, further characterized in that said polymerization catalyst is an isopoly acid or an acid salt thereof derived from an isopolylation salt represented by the following formulas f) or (2): Mi 20- nMV20s • XH20 (1); rriMi 20- nrf i 03 - XH20 (?), where Mi represents primarily an alkali metal; liv 25 represents vanadium, niobium or tantalum which belong to group V of the periodic table; Mv * represents chromium, olibdene, tungsten or uranium belonging to the group VT 1e the periodic tabLa; rn and n represent each an integer of at least 1; x represents a number from 0 to 50. 3.- Procedures for the preparation < i tm polyacetal copolymer, in accordance with conditions 1 or 2, further characterized in that said acid or acid salt thereof is acid paratigative, metatuncstic acid, paramolytic acid, acid me + a ol ibdi or an acid salt of the same. 4. The process for the preparation of a polyacetal coater, according to any of claims 1 to 3, further characterized in that said cornonorne is at least one selected from the e 1,3-dioxolane, forrnal-diet ilengl i col, formal -1, 4-butanediol, and ethoxylated oxide. 5.- The process for the preparation of a polyacetal lime product in accordance with any of the above indications 4, further characterized in that said solution containing the deactivator for the catalyst is an aqueous solution or organic solvent containing The deactivator comprises at least one compound selected from ammonia, amine compounds, trivalent phosphorus compounds, and oxides, hydroxides, inorganic and organic salts of alkali metals or alkaline and non-iron metals. 6.- The procedure for the preparation d < -.- a flake! A polyacetal nail according to any one of claims 1 to 5, further characterized in that the catalyst is subjected to a deactivation treatment in the condition in which the crude lime flake is sprayed in such a way that grain sizes of 0.3 inpi or less-is reach at least 40%. The process for the preparation of a polyacetal Lunero flake, according to any of claims 1 to 6, further characterized in that the * Ratuinic nt of fusion by heat is effected after the later addition of a stabilizer.