DE1105161B - Process for stabilizing macromolecular polyformaldehyde - Google Patents

Description

GERMAN

It is known to polymerize formaldehyde to macromolecular polyformaldehyde. Macromolecular Polyformaldehyde must be stabilized against the degradation in the heat that occurs from the chain ends. This can be done e.g. B. achieve by handling the macromolecular polyformaldehyde with acetic anhydride. The polyformaldehyde pre-stabilized in this way is, however, still sensitive to oxygen, especially in the heat must therefore be further stabilized. It occurs when heating macromolecular polyformaldehyde, in particular when the polymer is deformed in the melt, not only a slight elimination of monomeric formaldehyde but also split the linear chains in a short time under the influence of atmospheric oxygen Time in fragments. This reduces the average molecular weight and the mechanical properties of the polymers deteriorate considerably.

Macromolecular polyformaldehyde is therefore already present, the end groups of which are closed in the usual way were, so-called antioxidants were added before the deformation. As antioxidants, for. B. Hydrazines or hydrazides as well as aromatic amines, ureas or phenols are used. With these Compounds, especially those containing phenolic groups, can break down the macromolecular Already largely prevent polyformaldehyde. The results obtained, however, are never always unsatisfactory, especially because the polymers stabilized in a known manner during and in part tend to discolour even after processing.

It has now been found that macromolecular polyformaldehyde and its end groups can be used in the customary manner were sealed against degradation and discoloration by heat and oxygen by nitrogenous compounds Can advantageously stabilize if the nitrogen-containing compounds hydrazones of the general formula

—CH = N — n:

.R ¹

¹ R ²

40

used. In the formula given, R ¹ , R ² and R ^{8 can be} alkyl, cycloalkyl or aryl radicals.

Suitable hydrazones are, for example, ct-N-methyl-N-phenylbenzaldehyde hydrazone, aN-methyl-N-phenyl-0,0 - di - tert-butyl - ρ - hydroxy - benzaldehyde hydrazone, α - N - methyl - N -phenyl - piperonal hydrazone, α - N - methyl-N-phenyl-vanillin hydrazone, aN-methyl-N-tolyl-benzaldehyde hydrazone or ct-N-butyl-N-phenyl-benzaldehyde hydrazone. Hydrazones in which R ³ denotes aryl radical have proven to be particularly effective. The aryl radical can also be substituted here.

Method of stabilization
of macromolecular polyformaldehyde

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Wolfgang Hellmayr, Mannheim,

and Dr. Adolf Hrubesch, Ludwigshafen / Rhine,

have been named as inventors

The hydrazones are expediently in an inert organic solvent, for example in Acetone, petroleum ether, benzene, carbon tetrachloride, methanol or ethanol dissolved. With the solutions will then the macromolecular polyformaldehyde is kneaded. In general, only relatively small amounts are required Amounts of hydrazones to provide good stabilization. These amounts are about 0.05 to 10 percent by weight, preferably 0.5 to 1 percent by weight, based on the amount of polyformaldehyde to be stabilized.

The stabilizers used according to the invention are particularly effective when they are used together with about 0.1 to 10 percent by weight, based on the amount of polyformaldehyde to be stabilized, of a polyamide or mixed polyamides. As polyamides, for. B. the polycondensation products from adipic acid and hexamethylenediamine or polycaprolactam in question. Mixed polyamides are, for example, the polycondensation products from adipic acid and hexamethylenediamine and caprolactam or those from these two Components and bis (p-aminocyclohexyl) methane. Mixed polymers of caprolactam and caprylic lactam or Oenanthlactam can be used together with the stabilizers mentioned.

The macromolecular polyformaldehydes stabilized according to the invention are thermally very stable and hardly discolour even when heated for a long time in the presence of oxygen. The amounts of formaldehyde thermally split off in the unit of time are only very small. The polymers can therefore be sprayed and ^{treated on conventional processing machines at temperatures of up to about 230 °} C. without degradation or discoloration occurring.

109 577/428

The parts mentioned in the examples are parts by weight.

example 1

100 parts of a polyformaldehyde, the end groups of which have been closed with acetate groups, with a basic viscosity of 2.9 are mixed with 100 parts of acetone in which 1 part of a-N-methyl-N-phenyl-benzaldehyde hydrazone dissolved is mixed up. The product is then dried in vacuo at 80 ° C. for 30 minutes.

200 mg each of the product stabilized in this way are heated ^{to 222 ° C. in a decomposition glass apparatus in a thermostat.} The depolymerized formaldehyde and

other gaseous decomposition products - mainly formic acid - are released by air flowing through the Product is piped away from the hot room. The thermal stability of the product is determined by measuring the weight loss after weighing back after 20, 40 and 80 minutes of test duration.

The result can be seen from Table 1, where, in addition to the weight loss, the change in the basic viscosity of the samples is given in the course of the heating. The table shows the measurement data for comparison for polyformaldehyde stabilized with 2,2'-methylenebis (3-ethyl-6-tert-butylphenol) and for unstabilized polyformaldehyde specified.

Table 1
Acetylated polyformaldehyde ([77] = 2.9 in air at 222 ° C)

Added antioxidant
(l ° / o) Decomposed polyform
aldehyde in percent
after minutes
20 "j 40 I 80 54
28
11 72
44
17th 20th [η] after
Minutes
40 80 Discoloration
only after
Minutes None 46
7th
5 0.3
1.4
2.7 0.2
0.65
2.4 ~ 0, l
0.5
1.9 no
10
no 2,2'-methylene-bis- (3-ethyl-6-tert.butylphenol)
aN-methyl-N-phenyl-benzaldehyde hydrazone ...

Example 2

In the manner indicated in Example 1, a sample of an acetylated polyformaldehyde with an intrinsic viscosity of 1.34 with 1% each of aN-methyl-N-phenylbenzaldehyde hydrazone or 2,2'-methylenebis (3-ethyl-6-tert-butylphenol ) stabilized. The mixtures were now nor ever 3 ° / ₀ of a mixed polyamide (MP) from the same

Share adipic acid, hexamethylenediamine, caprolactam and bis- (p-aminocyclohexyl) methane, previously described in 70 parts of methanol, 20 parts of benzene and 10 parts. Water was dissolved, added, and the whole thing was added kneaded and, as described in Example 1, dried. The result of the stability test is given in the table 2 emerges.

Table 2
Acetylated polyformaldehyde with 3 ° / ₀ polyamide ([η] = 1.34 in air at 222 ° C)

Added antioxidant
(I ⁰ W 20th Zer
aid « rm-
: ent 80 20th [ή] after minutes
I ⁴⁰ I. 80 None 11
1
1 34
6th
4th 0.8
1.25
1.25 0.35
0.95
1.0 aN-methyl-N-phenyl-benzaldehyde hydrazone ...
2,2'-methylene-bis- (3-ethyl-6-tert.butylphenol) set polyfo
: hyd in Proi
after minutes
40 0.7
1.08
1.13 23
3
2

Example 3 viscosity 1.66 with 1 ° / ₀ aN-methyl-N-phenyl-salicyl-

As in Example 1, a sample of an acetylated 50 aldehyde hydrazone or 2,2'-methylenebis (3-ethyl-6-tertiary- and stabilized with 3% of the mixed polybutylphenol described in Example 2). The test result goes out amides stabilized polyformaldehyde with the basis of Table 3.

Table 3
Acetylated polyformaldehyde with 3% polyamide ([η] = 1.66 in air at 222 ° C)

Added antioxidant
(l ° / o) 20th Decomposed polyfo
aldehyde in Proi
after minutes
I 40 rm-
: ent 80 20th [ij] after minute
I 40 at 80 None 4th
2
1.5 26.5
8th
6th 1.2
1.3
1.6 0.5
0.5
1.1 aN-methyl-N-phenyl-benzaldehyde hydrazone ...
aN-methyl-N-phenyl-salicylaldehyde hydrazone .. 7.5
3
2.5 0.8
1.3
1.35

Example 4 diamide and 0.125 parts of powdered a-N-methyl-

100 parts of a powdery polyformaldehyde mixed with N-phenyl-benzaldehyde hydrazone. These

the basic viscosity 1.6 are dry in a ball mixture is then ^{extruded at 205 0} C by means of a mill with 0.35 parts of pulverulent dimethyloladipine screw press. The resulting strand of acid diamide, 0.35 part of powdered adipic acid 70 is granulated and extruded again at 205.degree.

The product, which is still white after the second pressing, is granulated. The basic viscosity is 1.54.

200 mg of the product are heated to 220 ° C. in a decomposition apparatus. As described in example 1, the thermal stability of the product is determined. The result is shown in Table 4.

Table 4

Polyformaldehyde acetylated with 0.35% Dimethyloladipinsäurediamid, 0.35 ° / ₀ adipamide and O, 125 ° / ₀ α - N - methyl - N - phenyl - benzaldehyde after two extrusion in air at 222 ° C

Decomposed polyformaldehyde
in percent after minutes

10 20th 40 80 0.4 0.8 2.1 5.4

Claims (2)

Patent claims: 1. A method for stabilizing macromolecular polyformaldehyde, its end groups in conventional Were sealed in a way that prevents degradation and discoloration by heat and oxygen nitrogen-containing compounds, characterized in that the nitrogen-containing compounds Hydrazones of the general formula R ³ -CH = N- in which R ¹ , R ² and R ^{3 can be} alkyl, cycloalkyl or aryl radicals are used. 2. The method according to claim 1, characterized in that the nitrogen-containing compounds Hydrazones as well as polyamides can be used. ι 109577 / 4.28 4.61