DE1128654B - Process for the stabilization of polyoxymethylenes by polymeric compounds containing amide nitrogen - Google Patents

Description

Process for stabilizing polyoxymethylenes by polymer, Compounds containing amide nitrogen It is known to use formaldehyde under certain Conditions to polymerize to eupolyoxymethylene.

The heat resistance of these products is ensured by reaction with carboxylic acid anhydrides, z. B. acetic anhydride, d. H. by esterification of the end groups. The end group blocking can also be done in other ways, e.g. B, by implementing with Alkyl sulfates. Thermoplastics are produced in this way whose molecular weights are generally above 20,000.

The stability of the polymers mentioned can be reduced by the modification of the end groups can be increased by adding so-called »formaldehyde acceptors«. Substances suitable for this purpose have already been phenols, hydrazines, urea, Casein and polyamides are suggested. The effectiveness of these stabilizers is in in some cases not entirely satisfactory; they have an effect, especially in the case of a proportionate long heating of the plastic, e.g. B. during the shaping, a yellow to Brown-yellow color of the originally white plastic.

It has been found that the resistance of, if necessary, by End group blocking of modified polyoxymethylene against thermal degradation is essential improved and at the same time a discoloration of the plastic when heated to a large extent Can be prevented if the polymeric formaldehyde is either polyacrylic acid amide and / or polymethacrylic acid amide and / or copolymers of acrylic and methacrylic acid amide in amounts of 0.5 to 30 percent by weight, based on the polymeric formaldehyde, clogs.

These polyacrylic or polymethacrylic acid amides differ of the polyamides known as stabilizers in that they contain the amide groups sides wear constantly. If the stabilizing effect is already achieved with quantities of about 0.1% of the two polymeric acid amides or with corresponding amounts of If mixed polymers of these amides occur, the new stabilizers are also used in amounts from 0.5 to 30%, preferably from 1 to 10%, only of practical use Value.

Polyacrylic or polymethacrylic acid amide or the copolymers the corresponding monomers can in any way, for. B. by mixing grinding, Rolling or extruding, can be incorporated into polyoxymethylene. The use Thermal stabilizers of the known type can be recommended in special cases. The addition of known antioxidants and UV protection agents is advantageous.

The same applies to the introduction of pigments, fillers or dyes possible.

The effectiveness of the new stabilizers is shown in the table below, in which the thermal stability of unstabilized polyoxymethylenes is compared with that of polyoxymethylenes stabilized according to the invention and in a known manner. At the same time, the color of the test products, which were white in their initial state, is given after heating to 222 ° C. for 30 and 90 minutes Product suffers when heated to 222 "C. Product | Stabilizers | Ksss- | Color after heating to 222 "C value Type j QuantityOlo 0/0 / min. after 30 minutes t after 90 minutes 8.0 white Polyoxymethylene t polymethacrylic acid amide 2.0 2.5 white / pale yellow pale yellow dihydrate j polymethacrylic acid amide 5.0 1.5 white / pale yellow pale yellow Polymethacrylic acid amide 10.0 1.2 white / pale yellow pale yellow Product stabilizers KW22- paint after heating to 222 ° C Type Quantity%% Min. after 30 minutes after 90 minutes - - 0.8 white white Polyamide (comparative tests) 5.0 0.3 dark brown black Polyamide (comparative tests) 10.0 0.3 dark brown black Polymethacrylic acid amide 2.0 0.4 white yellow pale yellow Polymethacrylic acid amide 5.0 0.2 pale yellow light brown Polyacrylic acid amide 5.0 0.4 pale yellow light brown Polyoxymethylene copolymer of 5.0 0.5 white white diacetate 300 /, methacrylic acid amide and 700 /, methyl methacrylate Mixed polymer of 10.0 0.4 white white 30 '/, methacrylic acid amide and 70 '/, methyl methacrylate

Claims (2)

PATENT CLAIMS: 1. Method for stabilizing, if necessary polyoxymethylenes modified by end group blocking by polymeric amide nitrogen containing compounds, characterized in that the polymeric, amide nitrogen Compounds containing polyacrylamide and / or polymethacrylamide and / or Copolymers of acrylic and methacrylic acid ampha in amounts of 0.5 to 30 percent by weight, based on the polymeric formaldehyde. 2. The method according to claim 1, characterized in that one additionally Usual thermal stabilizers and / or antioxidants and / or UV protection agents are used.