CS206136B1 - Method of stabilization of polyamids - Google Patents

Description

The invention relates to a method of stabilizing polyamides against degradation during processing and in articles thereof during use.

Polymeric polyamides are not particularly resistant to degradation during processing and use, as they are subject to it both under the effects of sunlight and under the influence of moisture and oxygen, especially at elevated temperatures.

Various stabilizing additives are also added in combination to increase the service life of the products. Patent and other literature in this respect is very extensive. They are often protected by the addition of copper, manganese compounds, possibly in combination with other components. With regard to copper compounds, in particular their combinations with halides, in particular iodides, are protected. The production of linear polyamide fibers to which 0.005-0.5 wt. % copper phthalate and 0.05-0.5 wt.% alkali metal iodide.

In the following description, it is a combination of copper compounds with other iodides, where a combination of salt, copper with zinc iodide, cadmium, arsenic, stibium or bismuth is used.

Another addition to the combination of copper with iodides is the addition of copper chloride, potassium iodide and crystalline magnesium chloride. As further more complex combinations of these basic components, the addition of copper compounds, quaternary ammonium iodide, and organic copper compounds.

It is further known to use combinations of copper compounds with bromides to stabilize polyamide by immersion in a boiling solution of a mixture containing copper acetate, sodium dihydrophosphate and potassium bromide, or by adding a concentrate consisting of polyamide, copper bromide, or iodide and calcium bromide, zinc or magnesium. It is further known to stabilize combinations of copper and manganese compounds with inorganic halogen compounds of the alkali metal salt of an organic aromatic acid imide. ·

Also disclosed are manganese compounds as polyamide stabilizers. These include the addition of the manganese compound itself in the form of the Mn salt of ¹¹ phosphonic acid semi-esters. Also included are manganese compounds wherein a synergistic mixture consisting of a phenolic compound, an organic phosphorus compound, and an organic manganese salt is used.

Thus, in the described series of stabilizers and stabilization systems recommended by the known patent and conventional literature for stabilizing polyamides, Cu ¹¹ and Mn ¹¹ compounds, their mutual combinations and combinations with halides, especially alkali metal iodides, predominate, phosphorus compounds as acid derivatives being frequent. phosphorous or phosphorous.

Known reaction of a solution of Cu ¹¹ salt and an alkali iodide

Cu ² + (aq) + 2 J '(aq) = CuJ + 1/2 J ₂ A CuJ precipitate is formed which is light to white in color, but released iodine tends to dark brown-red. This coloring is also transferred to a polymer whose resulting color is dark gray to gray-violet.

It has now been found that the formation of said coloring of the polyamide can be completely suppressed by the addition of a suitable type of organic phosphite, which forms a light gray complex with both stabilizing agents. In this respect, the different types of phosphites differ considerably from each other, as confirmed by the overview of their amount needed to decolorize and the appearance of the precipitate formed in Table 1.

Table 1: Comparison of the appropriate phosphite and the appearance of precipitates (to 0.004 mole of an aqueous solution of CuCl ₂ .2H ₂ O was added 0.01 mole of an aqueous solution of KJ. The resulting tan precipitate was then added to an amount of an organic phosphite to achieve decolorization. It :

Fosfit Potř. moles Appearance clot tris- (nonylphenyl) phosphite 0.0120 white after heating diphenylisodecyl- phosphite 0.0112 2 layers, bottom white precipitate diisodecylphenyl- phosphite 0,0065 on standing 2 layers diisooktylpenta- aerythritol diphosphite 0.0059 white villous clot. «

Λ «α *

Due to the consumption of both species of phosphites can be assumed that there is a complex compound of the type Cu / (phosphite) ⁺ 4 / J ^_ the uptake and triphenyl phosphite diphenylalkyl is doubled. This compound is an effective stabilizer protecting polyamides against the effects of light, heat and oxygen. In order to provide protection against hydrolytic degradation, its protective effect is increased by the simultaneous addition of, for example, carbodimide.

The preparation of a suitable complex stabilizer and its protective effect in stabilizing polyamides is evident from the following examples:

Example 1

To the polymerization batch consisting of 200 kg of 6-caprolactam, 0.1 wt. % butylamine acetate and 5 wt. % water added combination of stabilizers:

0.015 wt. % CuC1 ₂ .2H ₂ O + 0.075 wt. % KJ.

! The polymerization was then carried out under normal conditions.

The obtained PA-6 was granulated, and produced from the granulate by pressing samples of film thickness

0.10—0.15 mm. Their stability against photooxidation, thermooxidation, weathering and humidity is given in Table 2.

Example 2

To the polymerization batch as in Example 1 was added 0.15 wt. % of diisoctylpentaerythritol diphosphite, and the polymerization was carried out as in Example 1, as well as the preparation of films to evaluate the stabilizing effect. The result is shown in Table 2.

Example 3

In addition to the polymerization batch according to Example 2, 0.006 wt. % manganese acetate. The evaluation of the foils obtained is shown in Table 2.

Example 4

An additional 1 wt. % polycarbodiimide. Foil samples from the obtained PA-6 were evaluated and the properties are shown in Table 2.

Example 5

To 0.11 moles of molten 6-caprolactam was added 0.03 moles of potassium iodide and 0.01 moles of crystalline copper chloride. Diisoctylpentaerythritol diphosphite (0.022 mol) was added to the resulting red-brown mixture. The resulting solid off-white complex was ground to a powder after cooling. This powdery complex stabilizer was added to the polymerization batch of Example 1. Polymerization yielded stabilized PA-6 and prepared film samples for evaluation. The results are shown in Table 2.

Example 6

0.35 moles of crystalline cupric chloride was mixed with 0.12 moles of manganese acetate and 0.90 moles of potassium iodide and introduced into the melt of distearylpentaerythritol diphosphite with stirring. Upon cooling, a light gray mass of the complex was obtained, which was crushed to a powder. 20 wt. % of this complex was mixed in a fluidic mixer with 80 wt. % polyethylene powder and melt blended on a twin screw extruder. The extruded string was cut into granular concentrate containing 20% stabilized system.

0.75% of this concentrate was melt homogenized with PA-6 to stabilized polyamide. The foil was pressed from it and its stability evaluated similarly to other samples. The result is shown in Table 2.

Example 7

To the polymerization batch as in Example 1 was ^:

20613 », in addition 0.15 wt% diethyl 3,5-di-t-butyl-4-hydroxybenzylphosphonate was added. Foil samples were made in the same way from the obtained polymer and subjected to stability evaluation. The results are shown in Table 2.

Example 8

An addition of 0.12 wt. % diisodecylphenyl phosphite. After polymerization, foil samples were prepared from the obtained PA-6 to evaluate stability. Their values are shown in Table 2.

Example 9

To 150 g of molten 6-caprolactan was added 15 g of crystalline cupric chloride and 75 g of potassium iodide, and to the resulting red-brown suspension were added 200 g of diisoctylpentaerythritol diphosphite and 5 g of glycerin. The resulting mixture was continuously metered into the melt of alkali polymerized 6-polycaprolactam in the demonomer zone of the extruder in an amount of 0.15 wt. %. Foil samples were prepared from the stabilized alkaline PA-6 obtained in the same manner as in the previous cases and subjected to stability evaluation. These results are also summarized in Table 2.

In the described examples, which do not, of course, limit the process according to the invention, the stabilization efficiency was compared with different ratios of the stabilizing components and the different types of phosphite antioxidants used. The additives were added both to the monomer feedstock and to the melt of the finished PA-6, either alone or in the form of a ready-made and isolated stabilizing complex or its concentrate.

Summary Table 2 confirms the very good protective effect of the new stabilization method on various kinds of degradation conditions. It shows a stabilizing effect on PA-6 thermo-oxidation, its photooxidation and natural weathering as well as conditions of increased hydrolytic stress.

The procedures by which photooxidation and thermooxidation stability of said samples have been evaluated are described in the literature.

Photooxidation was evaluated by oxygen absorption in l / m ² , thermooxidation by exposure at 180 ° C, during which the color development rate was measured and expressed as _{400 400} nm.h, as well as the time to ductility drop to 25% of the starting value in h. weathering is expressed by the time of exposure to ductility to 25% of the baseline value in kJ. cm ^-2 and finally hydrolysis resistance when exposed in a humidity cabinet at 55 ° C and 95% rel. humidity at ductility and tensile strength,% of baseline, after 400 days exposure.

A comparison of the resulting values of unstabilized PA-6 with the values of the proposed stabilization system shows that this system increases the polymer's resistance to thermooxidation by about 7% according to the color development and / or color development. 8—10 x according to drop of ductility, against photooxidation according to oxygen absorption 3–4 X, against weathering 3–6 x and against hydrolysis

1.5 - 2 x according to tensile strength resp. min. 3-4 times according to the ductility development.

The differences between the different types of phosphites are not very large. The addition of polycarbodiimide positively affects the resistance to hydrolysis, but slightly decreases the other effects observed.

An advantage of the described stabilization system is also that the resulting complex can be isolated in the solid state and converted into a concentrate, both in polyamide and, for example, in polyethylene. This granulate concentrate, in turn, can advantageously be uniformly mixed and dosed to the polyamide non-stabilized granules directly in the hoppers of injection or extrusion or other plastics processing machines.

Table 2 Comparison of efficiency of described stabilization methods:

Way stabilization Stability against fotooxidaci abs. oxygen 1. rrT ² thermooxidation color development Δ. 1Γ ¹ at 180 ° C ductility drop to 25% of initial value after exposure h decrease of ductility to 25% of initial value after kJ.cm ^-2 hydrolysis at 55 ° C and 95% relat. humidity after 400 days% default value fortress ductility 0 0.0213 0.179 1 90 61 0 * 1 0.0070 0.024 8.2 356 98 52 2 0.0056 0,022 10.5 410 104 67 3 0.0053 0.024 9.8 740 101 63 4 0.0082 0,028 295 120 78 5 0.0060 0,025 6 0.0046 0,023 560 7 0.0068 0,027 8 0,0058 0,026 9 0.0093 0,046

* zero value was reached after 160 days of exposure

Claims (5)

1. A method for stabilizing polyamides against degradation. or during processing and products thereof during use, characterized in that a stabilization system consisting of 0.001-1.0 wt. % Cu salt, or a combination thereof with 0.0001-0.5 wt. % of Mn salts, 0.001 - 1 wt. % alkali iodide and 0.001-2 wt. % of organic phosphite in the ratio to each other, in which they form an uncoloured complex and, where appropriate, 0.1-2.0 wt. % of an anti-hydrolyzing agent such as polycarbodiimide. 2. The stabilization process according to claim 1, wherein the stabilizing additives are added directly to the monomer prior to polymerization. VYNALEZU 3. Process according to claim 1, characterized in that the stabilizing additives are added to the melt of the finished polyamide. 4. The stabilization method according to claim 1, characterized in that the stabilizing additives are converted beforehand into a stabilizer. forms of the complex. 5. The stabilization method according to claim 1, wherein the stabilizer is a concentrate of a stabilizing system complex which is added to the polyamide melt after polymerization or to the polyamide granulate prior to processing.