DE1160180B - Stabilizing acylated and / or alkylated high molecular weight polyoxymethylenes - Google Patents

Description

Stabilizing acylated and / or alkylated high molecular weight Polyoxymethylenes High molecular weight a>, w'-dihydroxy-polyoxymethylenes show in their thermoplastic range between 170 and 200 "C only a low thermal stability on.

It is already known to use these w, w'-dihydroxypolyoxymethylenes Improvement of the thermal stability hydrazines, hydrazides, phenols, aromatic Add amines, urea and thiourea derivatives.

A further increase in the thermal stability of the w, w'-dihydroxy-polyoxymethylene can be achieved by acylating the hydroxyl end groups of the polyoxymethylene or be alkylated.

This means that formaldehyde is split off at temperatures> 180.degree substantially reduced from the chain ends. The elimination of formaldehyde by thermal cracking of the molecule caused by traces of acids and impurities is increased, and the degradation that can be observed is still sufficient, however, about the shape and physical properties of high molecular weight polyoxymethylene to deteriorate significantly. Moldings that of C; Blow out are interspersed, deteriorated mechanical properties, such as impact resistance and toughness, are the consequence.

From French patent 1131939 it is known to use polyoxymethylene diacetates add nitrogenous antioxidants. The use of these compounds however, it has the disadvantage that it causes severe discoloration of the with them stabilized products. It is also from the French patent specification 1179 857 known to polyoxymethylene diacetates by adding polymeric amides stabilize. In many cases, however, these connections are only relatively weak Effectiveness in terms of increasing the thermal stability of the polyoxymethylene derivatives mentioned, especially when such polyoxymethylenes are exposed to humid air and warmth stand. Ideal stabilizers should not only counteract the effects of heat, but also to be effective against the effects of air and moisture. It has also been found that the stabilizers according to the invention do not discolour the polyoxymethylene cause, but also the polyoxymethylene color the deformation of the stabilized products is preserved at high temperatures.

The subject matter of the invention is the use of organic nitrogen compounds of the general formula wherein X is an oxygen atom, a sulfur atom, an imino group or a phenylimino group, R hydrogen, an alkoxy group, phenyl, an alkylamino group, a phenylamino group, a dithiocarbamic acid group or a radical of the formula where X and R also tert. Are nitrogen atoms which form a symmetrically trisubstituted s-triazine ring with the carbon atom, and R1 denotes hydrogen, an alkyl group, an aryl group, an alkoxyalkyl group, an alkylamino group, an arylamino group, an aminocarbamide group or a carbalkoxyamino group, for stabilizing at the chain ends acylated and / or alkylated high molecular weight polyoxymethylenes.

It was by no means obvious to use such compounds for stabilization of blocked polyoxymethylenes at the chain ends.

In stabilizing the polyoxymethylenes blocked at the chain ends namely, it must be expected that when deformed this stabilized Products an elimination of the end groups and thus a deterioration of the thermal Stability of these products occurs.

For example, the following compounds can be used as stabilizers for these polyoxymethylenes are used become: 1,6-tetra-n-propyl-hydrazodicarbonamide, N, N, N "", N "" - Tetra-n-propyl-hydrazodicarbonamide, N, N, N "", N "" - Tetra-n-butyl-hydrazodicarbonamide, Hydrazodicarboxylic acid dipropyl ester, hydrazodicarboxylic acid dibutyl ester, N, N-dimethylhydrazine carboxylic acid lauryl ester, l-phenyl-4-dibutylsemicarbazide, 1,4-diphenylthiosemicarbazide, bis-thiourethane, N-methyl-phenyl-N'-methyl-phenyl-thiuram disulfide, tetramethyl-thiuram monosulfide, Tetrapropyl thiuram monosulfide, tetrapropyl thiuram disulfide, trimethylolmelamine tri-n-butyl ether, N-phenyl-N ', N', N ", N" -tetramethylguanidine, N ', N', N "-triphenylguanidine, N-phenyl-N ', N'-dimethylformamidine, N, N'-diphenylbenzamidine.

These compounds are used to stabilize high molecular weight polyoxymethylenes suitable, the z. B. with the help of acetic acid, propionic acid, benzoic acid or other carboxylic anhydrides acylated and / or with the help of ortho-esters, such as z. B. orthoformic acid esters, are alkylated in the usual way.

The stabilizers according to the invention are those already end-group stabilized Polyoxymethylenes in amounts of about 0.1 to 4 percent by weight, preferably of 0.5 to 4 percent by weight, added before processing and shaping, whereby the stabilizers can be used both individually and in any desired mixture can. It is also possible to use them in combination with known anti-aging agents for high molecular weight substances such as B. phenols, aromatic amines, sulfur-containing Compounds such as mercaptobenzothiazole, also with fillers such as carbon black, plasticizers, Process lubricants, inorganic and organic pigments and other additives.

The stabilizers or mixtures of these stabilizers can End-group-stabilized polyoxymethylenes are added in substance, advantageously however, dissolved in a solvent, they are sprayed or sprayed onto the products with excess solvents together with the end group-stabilized polyoxymethylenes intimately mixed and then the solvent evaporates The stabilizers according to the invention allow in particular processing of the high molecular weight end group stabilized Polyoxymethylenes by injection molding without affecting the molecular weights of the high molecular weight end-group stabilized polyoxymethylenes fall into areas, which are characterized by brittleness and low strength values.

The stabilizing effect of the stabilizers according to the invention is said to be shown in the following comparison: While a polyoxymethylene diacetate with an intrinsic viscosity of 0.85 - measured in dimethylformamide at 150 ° C. in 0.5% strength Solution - when melting under the action of air at 2000 C during a heating period of 2 minutes in a thin liquid melt, which after cooling a brittle and easily fragile film results, which consists of polyoxymethylenes, the only have an intrinsic viscosity of 0.2 results in the same sample with the same intrinsic viscosity with an addition of z. B. 0.5010 1,6-tetrapropyl-hydrazodicarbonamide, of a bis-thiourethane from 1 mole of hexamethylene diisocyanate and 2 moles of dodecyl mercaptan and tetramethyl thiuram monosulfide an internal one after the same treatment Viscosity from 0.59 to 0.65, the resulting films are tough, flexible and elastic.

By using the stabilizers according to the invention, therefore at the high processing temperatures, the molecular weight ranges with the valuable physical properties largely retained.

Examples and comparative experiments A high molecular weight polyoxymethylene diacetate, according to German patent specification 1109890 with aluminum oxide as a catalyst produced and according to the Belgian patent 586592 with diisopropyl-carbodiimide and Acetic anhydride is acetylated and has an inherent viscosity of 0.75 at 1500C in dimethylformamide, is given in the tables below Quantities and stabilizers mixed. The thermal stability is at 222 ° C under nitrogen certainly.

Table l No..-U ww dem = = 1 '~~~~~~~~~~~~~ zSiin ~ 1 no stabilizer o pis 18% ödkciiccdit 2 di- * naphthyl-pphenylenedianiine (Yergleichs- O, 5Wo QB: 0.73 80h, m ': ht elastic, attempt according to French patent- jc'-hschmutzg- script 1131939) blame Verfrbwg del9dobe already after hw Entitnmeiten ai Min-) 0 0 U il 3 (CEICEE NC-NF1-NH-CO, 5th train 0.71 100 !. clastia: h, tough, none Vcdrt- lii, N (CH2-CC rbebdkm Erhite (2 miium) 1) Weight loss of samples on heating to 222 ° C in N2 atmosphere after 2 hours. continuation No. sample Mcn amount nadtdcm 'dem n melting bmel stability1) properties 0 0 II II 4 (C4H9) 2 - N - C - NH - NH - m 0.5% 0.98 0.69 7010 elastic, tough, none Poly discoloration "N (GH9h I oxymethylene color in short Heating times (2 minutes) O 0 II II 5 C3H70CNHNHCOCaH7 oo / O 0.98 û, 63 golo elastic, tough, none Poly discoloration oxymethylene color in short Heating times (2 minutes) O 0 II 6 c4HsO - C - NH - NH - C - 0C4H9 0.50 / 0 0.98 0.59 10 ° lo elastic, tough, none Poly discoloration oxymethylene color in short Heating times a minutes) CH O 7 N - NH - C - OCH 0s5% 0.98 0.88 9010 elastic, tough, none / Discoloration, poly- oxymethylene color in short Heating times O c4H0 1 (2 minutes) II / C6fl5-NH-bnI-CN 8 discoloration, 10Io elastic, tough, none Poly discoloration c4Hg oxymethylene color in short Heating times S (2 minutes) 2) II I 9 cßHs - NH -NH C -Nil -Cs 5% 0.98 0.62 12% elastic, tough, none Discoloration, poly oxymethyleneiren color in short Heating times O 0 (2 minutes) 2) II elastic II 10 C4H9 5 - C - NH - (CH2) s - NH -C7 Ohio 0.98 0.61 8 Where elastic, tough, none L SC4H9 owl methylene own color in short EEfLitzwigszciten C7 \ S 5 Xw17 a 2 minutes) 2) II 11 / 11 NCSCN: 0.50 / 0 Q98 0.84 8% elastic, tough, none VeilärhunL Poly- C: 3H7 GH7 I oxymethylene native color in short Heating times (2 minutes) 2) 1) Weight loss of the samples on heating to 222 ° C. in an N2 atmosphere after 2 hours.

2) Mixtures 8, 9, 11 and 12 turn yellow during granulation and injection molding. continuation nIenn NL Probe Men in front of the property a Dark stability ') C3H7 S s CaH7 II II 7 12 NCSSCN 0.50 / 0 098 0.81 11% elastic, tough, none Poly discoloration C3H7 C3H7 oxymethylene color in short Heating times (2 minutes 1) Weight loss of the samples on heating to 222 ° C. in an N2 atmosphere after 2 hours.

2) The mixtures change color during granulation and injection molding 8, 9, 10, 11 and 12 yellowish.

Table II rlr 1 No. sample amount of the chdan thenno properties 2 Di-B-naphthyl-p-phenylenediamine (comparative o50 / o 0.98 0.73 80 / o not brittle, elastic, attempt according to French patent - but dirty - writing 1131 939) brown discoloration the melt sample after a short time Heating times (2 minutes) 3 CHsO.-CH2-NH7 O, 501o 0.98 0.55 11% elastic, flexible, no discoloration, N polyoxymethylene - -C C-NH CH2OC4H9 own color with - III short heating NN times (2 minutes) - \ lC / NH CH2OC4Hs CsH5 4 CH3 N CH3 0.50 / 0 0.98 0.63 90/0 elastic, flexible, II 7 no discoloration, NCN polyoxymethylene 7 own color at CH3 CH3 short heating times (2 minutes) CHs N 5 C6H5 - NH -. C - N - Cs 5 ° / 0 0.98 0.59 90/0 elastic, flexible, no discoloration, Polyoxymethylene own color at short heating 1 t. times (2 minutes) 2) 1) Weight loss of the samples on heating to 222 ° C in an N2 atmosphere after 2 hours 2) During granulation and injection molding, the mixtures 5, 6 and 7 change color. continuation No. sample amount before "& m after Yitdem Thenno- Melting Melting stability ') properties N-C6H5 7th 6 HC CH3 0.5 "lo 0.98 0.51 12010 elastic, low Brittleness, none N discoloration, poly oxymethylene CH3 color for short Heating times (2 minutes) 2) N C6H5 7th 7 CsHs-C 0.5 (> / o 0.98 0.57 1101o elastic, flexible, no discoloration, NH-C6H5 polyoxymethylene own color at short heating times (2 minutes) 2) ') Weight loss of the samples on heating to 222 C in an N2 atmosphere after 2 hours. 2) During granulation and injection molding, mixtures 5, 6 and 7 turn yellowish.

Claims (1)

PATENT CLAIM: Use of organic nitrogen compounds of the general formula where X is an oxygen atom, a sulfur atom, an imino group or a phenylimino group, R is hydrogen, an alkoxy group, phenyl, an alkylamino group, a phenylamino group, a dithiocarbamic acid group or a radical of the formula where X and R also tert. Are nitrogen atoms which form a symmetrically trisubstituted s-triazine ring with the carbon atom, and R1 is hydrogen, an alkyl group, an aryl group, an alkoxyalkyl group, an alkylamino group, an aryiamino group, an aminocarbamide group or a carbalkoxyamino group, for stabilizing those at the chain ends acylated and / or alkylated high molecular weight polyoxymethylene.