CS221575B1 - Method of increasing the resistance of polyamides in respect of the thermooxidation - Google Patents

Description

The invention relates to a method of increasing resistance ^p ol ^y and benzamides towards termooxidaci.

Polyamides, i.e. lactam polymethates or polycondensates of diamine and diacid salts, readily oxidize at temperatures above 100 ° C and lose strength and flexibility. In order to suppress thermo-oxidative degradation, stabilizers of a very diverse composition and mechanism of action are incorporated into the polyamides. Most often, they are substances which .přerušují autoxidisable chain, such as phenols (e.g., according to ^U S Pat. ^3,787,355 to add a polymer polynuclear phenols) or- amines (for example according to German Pat. 1,229,291 to diphenylamine derivatives of the ^{structure, CH} 3 S ^{C -} O ^NW 3 ' ^{C, CH} 3 ^J 3

CH & CH-C ₆ H _S ^s are giving ⁱⁿ the finished ^poly mer of ^p k ^p rolaktam'u). Furthermore polyamides hydroperoxides decomposers are added to products which have not act as initiators of further ^oxidation, such foisíity (e.g. lacI & trisnon ^{yl f} enylíosfit of ^{U.S. P} at. ^{3644 28} 0).

The stabilizers are incorporated either into the finished polymer or added to the reaction mixture prior to polymerization. The best dispersion of the stabilizer in the polyamide can be achieved by incorporating the stabilizer into the initial (polymerization mixture), thereby preventing both the monomer and the polymer formed from undesirable oxidation. - hundreds of hours at 300 cc), however, the added antioxidants are not always sufficiently stable.WcHe also plays a very important role in the volatility of the stabilizer at higher temperatures.^ři of vacuum^Edemonomer exposed to polymer melt under vacuum at rt^plotách nad^{- 250} ° C; za toch that podmrnek then v^ětšMost of the low molecular weight stabilizers flow out with^pwith monomer. In addition, some may adversely affect the polymerization process. For example, phenolic antioxidants strongly^br.zd^and and^- they even stop in larger amounts by anionic polymerization of lactams.

Numerous stabilizers (antioxidants) are in contact with water olyamidu ^p and ^Z e ^{It runs} HE ^m použwárn polyamide articles a fabric, -stalbiizátoru concentration decreases and thus resistance against the action of acidic potyamtáu u ^ ^p n ^Yss their temperatures.

Recently, the use of mixtures of polyamides prepared from various lactams, diamines and diacids as well as random and block copolymers containing different monomer units has been increasingly used. Thus, the stabilizer should protect the pirotins of thermooxidation by polyamides and copolyamides regardless of the structural units being different. While polyamides are produced predominantly by conventional hydrolytic polymerization, some types are more preferably prepared by cationic or anionic polymerization. Therefore, it is desirable to have available an antioxidant which can be incorporated into the starting polymerization mixture, both for the hydrolytic as well as for the anionic and cationic polymerization of lactams, or for the polycondensation of diamines and diacids.

All of these requirements are met by the proposed method of increasing the resistance of polyamides to thermooxidation, in which the polyamides are formed. the starting polymerization mixtures of the lactams or lactams or diamines and the diacidsolines, together with the catalytic and regulating components, introduce an antioxidant characterized in that it is a mixture of diphenylamine-based substances of the structure represented by the formula

(I) wherein R is α-methylbenzyl, x is independently from y equals 0-3, y-e independently from x equals 1-3.

This stabilizer is thermally stable and persists in the polyamide in an active form both during the entire polymerization process, whether hydrolytic, anionic or cationic, as well as during the processing of the polymer by injection or extrusion or during boiling water extraction.

The stabilizer is added in an amount of 0.02 to 2% by weight per polymer, preferably 0.1 - 0.4% by weight.

The stabilizer is added as a solution in, for example, toluene or molten caprolactam. The stabilizer may also be added in that it is applied to / or absorbed into the filler and then incorporated into the polymerization mixture. The stabilizer is added simultaneously with any component of the polymerization mixture, optionally in any order. In anionic polymerization, the stabilizer is preferably added before the addition of the initiator, i.e. the strong base.

The presence of the stabilizer in the mixture from the beginning of the polymerization protects both the reactants and the polyamide formed from undesired oxidation, thus improving its quality and reproducibility. This effect is particularly important in the anionic polymerization of lactams. The overall stabilizing effect achieved by said diphenylamine-based stabilizer is enhanced by its low volatility and post-compatibility with polyamides.

The advantages of the proposed method of stabilizing polyamides against thermooxidation are illustrated by the following examples.

Example i

0.85 g of cyclic phenyl isocyanate cyclic trimer, 0.167 g of a compound of structure I and 0.18 g of ε-caprolactam sodium are gradually dissolved in 100 g of ε-k-aprolactam at 90-100 ° C. The resulting reaction mixture was polymerized in a 0.5 cm layer at 190 ° C for 4 hours; · after cooling SE- planing hioblinky obtain a thickness from 30 to 50 u ^m, - which were extracted with boiling water (3 x 15 min in 100 ML water / g sample) and dried for 20 hrs. at 50 ° C / 133 mbar. The thermo-oxidative stability of the polymer was evaluated by (a) the length of the induction period of oxidation, i.e., the time the polymer consumes less than 2 mmol Qz / kg of polymer in an oxygen atmosphere and when it practically does not alter the chemical or physical properties of the polymer; oxygen consumption after the induction period. The induction period of oxidation at 180 ° C was 125 min, whereas for a sample prepared under the same conditions but without stabilizer, the induction period was only 6 min. The oxygen uptake rate for the stabilized sample was 12 mmol / kg. h, unstabilized · 80 -mmol / kg. h.

Example 2

The reaction mixture prepared and processed according to Example 1 except 0.05 g of the stabilizer of the formula I was used. The induction period of thermooxidation of the extracted sample was 110 minutes; without stabilizer, the induction period was 6 minutes.

Example - 3

The reaction mixture prepared and worked up according to Example 1 except that 0.50 g of a stabilizer of the formula I was used.

I. The induction period - oxidation of the extracted sample at 180 ° C was 240 minutes, while for the unstabilized sample only 6 minutes.

Example 4

In 10 g of ε-caprolactam, 0.085 g of the cyclic phenyl isocyanate trimmer, 0.0167 g of the stabilizer of the formula I and 0.1 µm of Synhydride R [i.e. 70% of a toluene solution of bis (2-methoxyethoxy) -dihydroxybutyrate was heated in a glass ampoule of 15 mm diameter in a thermostated bath at 190 ° C for 4 hours. The unextracted product (in the form of shavings 30 - 50 μπι) showed an induction period of oxidation (at 180 ° C) of 170 minutes. After extraction with boiling water and drying (method

В

With the bem shown in Example 1), the induction period did not change.

The polymer prepared under the same conditions using 4-isopropylamino-diphenylamine (at the same molar concentration as the stabilizer of formula I) had an induction period of 70 minutes in the non-extracted state, but only 15 minutes after extraction of the O '.

The polymer prepared without stabilizer had an induction period of 22 minutes in the unextracted state and 4 minutes after extraction and drying.

Example 5

0.10 g of ε-caprolactam hydrochloride and 0.334 g of the stabilizer of the formula I were dissolved in 20 g of ε-caproilactam and the resulting solution was heated to 230 ° C for 140 hours. The product was processed as in Example 1. At oxidation at 180 ° C, 1 g of the sample consumed 0.1 mmol of oxygen in 135 minutes, while the unstabilized polymer was consumed in 53 minutes.

Example 6

0.016 g of stabilizer of general formula I and 0.05 g of water were dissolved in 10 g of ε-caprolactam at 80 ° C and the resulting solution was polymerized in a sealed vial at 250 ° C for 20 hours. The product was processed as in Example 1. The induction period of oxidation at 180 ° C was 30 minutes, while for the non-stabilized polymer it was less than 2 minutes. The oxygen uptake rate after the induction period for the stabilized polymer was 16 mmol / kg. h, while unstabilized 160 mmol / kg. h.

Example 7

0.02 g of the stabilizer of the formula I, 0.065 g of water were dissolved in 10 g of capryllactam (8-octanlactam) at 80 ° C and polymerized in a sealed vial at 240 ° C for 20 hours. The product was treated as described in Example 1. The oxidation at 180 ° C was induction period 42 minutes, while the non-stabilized polymer was less than 2 minutes.

Example 8

The reaction mixture containing 20 g of laurolactam (12-dodecanlactam), 0.07 g of stabilizer of formula I and 0.019 g of water was polymerized in a sealed vial at 280 ^° C for 240 hours. The product was extracted with boiling benzene (3 x 10 minutes in 100 ml). benzein / g sample) and dried at 133 Pa and 60 ° C for 50 hours. At oxidation at 170 ° C, the product showed an induction period of 52 minutes, whereas for an unstabilized sample the induction period was less than 2 minutes.

Example 1 a d 9

In a ground-glass flask equipped with a distillation head and an inert inlet, 20 g of hexamethylenediammonium adipate (N-salts) and 0.034 g of the stabilizer of the formula I dissolved in 0.05 were heated in an argon stream (10 ml / min) for 1 hour at 280 ° C. g of toluene. After the treatment of the product as described in Example 1, the induction period of oxidation at 180 ° C was 40 minutes, while for an unstabilized sample it was less than 2 minutes.

Example 10

A solution of 0.06 g water in 10 g molten ε-capirOlactam is mixed with a solution of 0.019 g stabilizer of formula I in 1 g ω-laurolactam and finally a solution of 0.01 g stearic acid in 1 g molten ω-capiryllactam is added. The resulting mixture was polymerized in a sealed vial for 20 hours at 275 ° C. The product in the form of shavings was extracted and dried as described in Example 1. The induction period of oxidation at 170 ° C was 42 minutes, while without stabilizer it was less than 2 minutes.

Example 11

7.9 g of cyclic phenylisocyanate cyclic trimer are dissolved in 1000 g of molten ε-caprolactam at 130 [deg.] C. and 120 g of graphite, to which 2.2 g of the stabilizer of the formula I has been applied, are added under stirring. 10 ml of Synhydride * in 50 g of molten ε-caprolactam are added and the resulting reaction mixture is poured into a metal cylindrical mold formy 8 cm in diameter with a wall thickness of 4 mm, heated in an air thermostat at 180 ° C. After one hour, the thermostat is allowed to cool at a rate of 2 ^c / min. and after reaching a temperature of 120 ° C, the polyamide casting is swung out of the mold. The product in the form of shavings showed an induction period of oxidation of more than 150 minutes at 180 ° C, whereas the product without stabilizer had an induction period of 20 minutes.

Example 12

To the reaction mixture of Example 1, 15 g of glass fibers (length 5 mm) previously dried at 300 ° C / 1 mmHg were mixed. The reaction mixture was polymerized for 0.5 h at 230 ° C in a 20 mm layer. The polymer showed an induction period of oxidation at 180 ° C of 120 min, whereas the polymer without stabilizer was 5 minutes.

Claims (6)

OBJECT OF THE INVENTION Method for increasing the resistance of polyamides to thermooxidation, comprising polymerizing a mixture of lactam (s), lactam (s), neibo diamine and diacidelle, together with catalytic and regulatory components and a stabilizer, characterized in that the stabilizer is a mixture of substituted diphenylamine I (I) wherein R is alpha-methylbenzyl, x is 0-3 independently of у and у is 1-3 independently of x. 2. Process according to claim 1, characterized in that the stabilizer is added in an amount of 0.02 to 2% by weight per polymer, preferably 0.1 - 0.4% by weight. 3. A process according to claim 1, wherein the stabilizer is added in the form of a solution, for example in toluene or molten caprolactam. 4. The process according to claim 1, wherein the stabilizer is applied and / or absorbed into the filler and then incorporated into the polymerization mixture. 5. A process according to any one of claims 1 to 4, wherein the stabilizer is added simultaneously with any component of the polymerization mixture. 6. The process according to claim 1, wherein the stabilizer and the other components of the reaction mixture are added in any order, preferably during anionic polymerization the stabilizer is added before the addition of the initiator, i.e. the strong base.