NOVEL COMPOSITIONS FOR PRODUCING CAST POLYAMIDES

Abstract

The present invention relates to novel compositions for production of cast polyamides.

Claims

1. A composition comprising: at least two components selected from a) a solidified lactam melt comprising 0.1-5% by weight of at least one polymeric aromatic carbodiimide, or of at least one uretdione, or both, b) a solidified lactam melt comprising 0.2-5% by weight of at least one catalyst selected from the group of: lactam magnesium halide, alkali metal aluminodilactamate, alkali metal and alkaline earth metal lactamate, and c) a solidified lactam melt comprising 0.2-5% by weight of at least one catalyst selected from the group of: lactam magnesium halide, alkali metal aluminodilactamate, alkali metal and alkaline earth metal lactamate, and 0.1-5% by weight of at least one polymeric aromatic carbodiimide, or of at least one uretdione, or both, or the component c) only.

2. The composition as claimed in claim 1, wherein the composition comprises the solidified lactam melt c) in combination with solidified lactam melt b).

3. The composition as claimed in claim 1, wherein the lactam melt comprises compounds of the formula (I) ##STR00003## where R is an alkylene group having 3 to 13 carbon atoms.

4. The composition as claimed in claim 1, wherein the uretdione is prepared proceeding from monomeric compounds selected from the group of isophorone diisocyanate, cyclohexyl 1,4-diisocyanate, 1,1-methylenebis(4-isocyanatocyclohexane), 1,2-bis(4-isocyanatononyl)-3-heptyl-4-pentylcyclohexane, and hexamethylene 1,6-diisocyanate, and combinations thereof.

5. The composition as claimed in claim 1, wherein the uretdione comprises compounds which are obtained proceeding from an aromatic isocyanate selected from the group consisting of 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, naphthylene 1,5-diisocyanate, methylenediphenyl 4,4-diisocyanate, 1,3-bis(3-isocyanato-4-methylphenyl)-2,4-dioxodiazetidine, N,N-bis(4-methyl-3-isocyanatophenyl)urea, and tetramethylxylylene diisocyanate, and combinations thereof.

6. The composition as claimed in claim 1, wherein the polymeric aromatic carbodiimide is at least one compound of the formula (II)
R.sup.1(NCNR.sup.2).sub.mR.sup.3 (II) in which m is an integer from 2 to 500, R.sup.1R.sup.2NCO, R.sup.2NHCONHR.sup.4, R.sup.2NHCONR.sup.4R.sup.5 or R.sup.2NHCOOR.sup.6, R.sup.2=arylene or C.sub.7-C.sub.18-aralkylene, and R.sup.3NCO, NHCONHR.sup.4, NHCONR.sup.4R.sup.5 or NHCOOR.sup.6, where R.sup.4 and R.sup.5 in R.sup.1 and R.sup.3 are the same or different, and are each independently a C.sub.1-C.sub.6-alkyl, C.sub.6-C.sub.10-cycloalkyl or C.sub.7-C.sub.18-aralkyl radical and R.sup.6 has one of the definitions of R.sup.1 or is a polyester or polyamide radical or (CH.sub.2).sub.hO[(CH.sub.2).sub.kO].sub.gR.sup.4, where h=1-3, k=1-3, g=0-12 and R.sup.4H or C.sub.1-C.sub.4-alkyl.

7. The composition as claimed in claim 1, wherein the solidified lactam melts of a), b) and/or c) are in the form of at least one of: powder, pellets, granules and flakes.

8. A solidified lactam melt comprising: 0.2-5% by weight of at least one catalyst selected from the group consisting of: lactam magnesium halide, alkali metal aluminodilactamate, alkali metal and alkaline earth metal lactamate, and 0.1-5% by weight of carbodiimide or uretdione, or both, and obtained by mixing at least one melt of caprolactam and 0.1-5% by weight of at least one polymeric aromatic carbodiimide, or of at least one uretdione, or both, and at least one melt of caprolactam and 0.2-5% by weight of at least one catalyst selected from the group of: lactam magnesium halide, alkali metal aluminodilactamate, alkali metal and alkaline earth metal lactamate, at temperatures of 70-120 C. over a period of 1-60 seconds, and subsequent finishing with cooling.

9. A process for producing cast polyamides by polymerizing the composition of claim 1 in a casting mold at a temperature of 100 to 160 C.

10. A cast polyamide obtained by polymerizing a composition as claimed in claim 1.

Description

[0095] The examples which follow serve to illustrate the invention without having any limiting effect.

[0096] Working Examples:

[0097] Reagents:

[0098] (A) Dry caprolactam (softening point >69 C.) from Lanxess Deutschland GmbH;

[0099] (B) Addonyl Kat NL from Rhein Chemie Rheinau GmbH, approx. 18% sodium caprolactamate in caprolactam;

[0100] As activators:

[0101] (C) Addonyl 8108: aliphatic polyisocyanate solution, commercially available from Rhein Chemie Rheinau GmbH;

[0102] (D) Desmodur H: hexamethylene diisocyanate, commercially available from Bayer MaterialScience AG,

[0103] (E) Stabaxol P: aromatic polymeric carbodiimide, commercially available from Rhein Chemie Rheinau GmbH;

[0104] (F) Stabaxol I: aromatic monomeric carbodiimide, commercially available from Rhein Chemie Rheinau GmbH;

[0105] (G) Addolink TT: dimeric TDI uretdione, commercially available from Rhein Chemie Rheinau GmbH;

[0106] (H) Addonyl OTT: dimeric TDI uretdione, commercially available from Rhein Chemie Rheinau GmbH.

[0107] Procedure and Testing:

[0108] Production of the Two-Component Mixture from a) and b) (2 K Powder Mixture)

[0109] Caprolactam was melted at 75 C. and dried under reduced pressure for 20 min. Thereafter, the respective activator (apparent from table 1) was added while stirring, and the mixture was homogenized and poured into a nitrogen-blanketed aluminum mold. After the melt had solidified, it was comminuted and transferred into a nitrogen-blanketed sample bottle and stored.

[0110] In an analogous manner, caprolactam was melted at 75 C. and dried under reduced pressure for 20 min. Thereafter, Addonyl Kat NL was added while stirring, and the mixture was homogenized and poured into a nitrogen-blanketed aluminum mold. After the melt had solidified, it was pulverized and transferred into a nitrogen-blanketed sample bottle and stored.

[0111] After 30 days, the corresponding powders comprising activator and catalyst were mixed in a mass ratio of 1:1 and transferred into a sample bottle, which was then used directly for the polymerization experiments described below.

[0112] Production of the One-Component Mixture c) (1 K Mixtures)

[0113] Caprolactam was melted at 75 C. and dried under reduced pressure for 20 min. Thereafter, the respective activator (apparent from table 1) was added while stirring, and the mixture was homogenized. In analogous manner, caprolactam was melted at 75 C. and dried under reduced pressure for 20 min. Thereafter, Addonyl Kat NL was added while stirring and homogenized. The catalyst and activator melts thus obtaining were then combined and homogenized at 75 C. for a few minutes. The contents were then poured into a nitrogen-blanketed aluminum mold. After the melt had solidified, it was pulverized and transferred into a nitrogen-blanketed sample bottle and stored. After 30 days, the powder comprising activator and catalyst was transferred into a sample bottle and used for the polymerization experiments described below.

[0114] Polymerization Experiments

[0115] The sample bottles were placed into a drying cabinet at 160 C. After about 30 min, the sample was removed. The results are compiled in table 2.

TABLE-US-00001 TABLE 1 Formulations Experi- ment (A) (B) (C) (D) (E) (F) (G) number Type of mixture [g] [g] [g] [g] [g] [g] [g] 1 2 K powder mixture 388.8 8.0 3.2 2 2 K powder mixture 388.8 8.0 1.0 3 2 K powder mixture 388.8 8.0 3.2 4 2 K powder mixture 388.8 8.0 3.2 5 2 K powder mixture 388.8 8.0 3.2 6 2 K powder mixture 388.8 16.0 3.2 7 2 K powder mixture 377.6 16.0 6.4 8 1 K mixture 388.8 8.0 3.2 9 1 K mixture 388.8 8.0 3.2 10 1 K mixture 388.8 8.0 3.2

TABLE-US-00002 TABLE 2 Results of the cast polymerization Storage Experiment Polymerization Appearance stability 1 (comparative) No or incomplete inhomogeneous reaction 2 (comparative) No or incomplete inhomogeneous reaction 3 (inventive) Complete reaction homogeneous >30 days 4 (comparative) No reaction 5 (inventive) Complete reaction homogeneous >30 days 6 (inventive) Complete reaction homogeneous >30 days 7 (inventive) Complete reaction homogeneous >30 days 8 (comparative) No/incomplete inhomogeneous reaction 9 (inventive) Complete reaction homogeneous >30 days 10 (inventive) Complete reaction homogeneous >30 days The residual monomer content of the inventive cast polyamides was less than 1% by weight.

[0116] Through the controlled and precise setting and selection of the activator and catalyst components required, it is therefore possible to provide storage-stable compositions which enabled use for production of polyamide castings with very low apparatus complexity.

[0117] Examples for Production of Cast PA6 Polymer Moldings and of Cast PA6 Polymer Composite Moldings from the Inventive Composition:

EXAMPLE 11

[0118] Production of the Two-Component Mixture from a) and b) (2 K Powder Mixture)

[0119] 193.6 g of caprolactam were melted at 75 C. Thereafter, 6.4 g of Addonyl OTT from Rhein Chemie Rheinau were added while stirring, and the mixture was homogenized and post-dried under reduced pressure for 5 min, and the melt was poured into a nitrogen-blanketed cold aluminum mold at 21 C. After the melt had solidified, it was comminuted and transferred into a nitrogen-blanketed sample bottle and stored at 6 C. in a refrigerator for one week.

[0120] In an analogous manner, 184 g of caprolactam were melted at 75 C. Thereafter, 16 g of Addonyl Kat NL were added while stirring, and the mixture was homogenized and post-dried under reduced pressure for 5 min and poured into a nitrogen-blanketed cold aluminum mold at a temperature of 21 C. After the melt had solidified, it was pulverized and transferred into a nitrogen-blanketed sample bottle. The corresponding and at 6 C. in a refrigerator for one week stored.

[0121] These powders, comprising activator or catalyst, were removed from the refrigerator, mixed and introduced into a nitrogen-blanketed reservoir vessel/three-neck flask and then melted at a temperature of 90 C. and stored at this temperature for the experiments described hereinafter.

[0122] Every 10 minutes, a plastic pipette was used to take a 2 ml sample which was transferred into a test tube of internal diameter 5 mm heated to 170 C. with the aid of an oil bath.

[0123] Over a period of 30 minutes, it was possible to polymerize the melt to completion through the increase in temperature. The specimens were visually homogeneous.

EXAMPLE 12

[0124] As in example 11, about 400 g of the activated caprolactam melt were made up in a three-neck flask under nitrogen.

[0125] A steel mold having a cavity of dimensions 20300.2 cm consisted of two halves and was sealed with the aid of silicone seals. Before the experiment, two plies of predried glass fiber fabric (from PPG), basis weight about 600 m.sup.2, 2/2 twill construction) were placed into the cavity and mechanically fixed. Twill isalongside plain weave and satin weaveone of the three basic construction types for woven materials.

[0126] The steel mold had two bores through which the activated caprolactam melt from example 11 could flow into the cavity; through the second bore, after complete filling, the excess melt could emerge again.

[0127] The steel mold was heated to 170 C. and, with the aid of a vacuum pump which had been connected to one of the bores of the steel mold, the activated caprolactam melt from example 11 was sucked into the mold, where it soaked the fabric and then polymerized to completion.

[0128] After 30 minutes, the mold was opened and a fully polymerized composite plastic sheet was removed.

[0129] The composite plastic sheet was fully through-polymerized; the residual monomer content determined via a methanol extraction was below 1% by weight.

EXAMPLE 13

[0130] Production of a One-Component Mixture (1 K Powder Mixture)

[0131] 193.6 g of caprolactam were melted at 75 C. Thereafter, 6.4 g of Addonyl TT from Rhein Chemie Rheinau were added while stirring, and the mixture was homogenized and post-dried under reduced pressure (<0.1 mbar) for another 5 min.

[0132] At the same time, in a second batch, 184 g of caprolactam were melted at 75 C. and, thereafter, 16 g of Addonyl Kat NL were added while stirring, and the mixture was homogenized for 5 min and post-dried under reduced pressure (<0.1 mbar) for 5 min.

[0133] The two melts were combined by adding the activator-containing melt to the catalyst-containing melt and the combined melts were stirred for another 30 seconds.

[0134] Thereafter, the melt mixture was poured into a nitrogen-blanketed aluminum mold having a temperature of 21 C. After the melt had solidified, it was pulverized and transferred into a nitrogen-blanketed sample bottle and stored at 6 C. in a refrigerator for one week.

[0135] This powder, comprising both activator and catalyst, was removed from the refrigerator and introduced into a nitrogen-blanketed three-neck flask, where it was melted at a temperature of 90 C., and the melt mixture was stored at this temperature.

[0136] Every 10 minutes, a plastic pipette was used to take a 2 ml sample which was transferred into a test tube of internal diameter 5 mm which was heated to 170 C. with the aid of an oil bath.

[0137] Over a period of 30 minutes, it was possible to polymerize the melt to completion through the increase in temperature. The specimens were visually homogeneous.

EXAMPLE 14

[0138] Production of the Two-Component Mixture of a) and b) (2 K Powder Mixture), by Combining Powders a) and b) after the Production and then Storing this Powder Mixture at Temperatures Below 10 C.

[0139] 193.6 g of caprolactam were melted at 75 C. Thereafter, 6.4 g of Addonyl TT from Rhein Chemie Rheinau were added while stirring, the mixture was homogenized and post-dried under reduced pressure (<0.1 mbar) for 5 min, and the melt was poured into a nitrogen-blanketed aluminum mold having a temperature of 21 C. After the melt had solidified, it was comminuted.

[0140] In an analogous manner, 184 g of caprolactam were melted at 75 C. Thereafter, 16 g of Addonyl Kat NL were added while stirring, and the mixture was homogenized and post-dried under reduced pressure (<0.1 mbar) for 5 min and poured into a nitrogen-blanketed aluminum mold having a temperature of 21 C. After the melt had solidified, it was likewise comminuted into flakes.

[0141] The two powders were mixed in a mass ratio of 1:1 and transferred in the form of flakes into a nitrogen-blanketed sample bottle and stored at 6 C. in a refrigerator for one week.

[0142] These flakes were removed from the refrigerator and introduced into a nitrogen-blanketed three-neck flask, then melted at a temperature of 90 C., and the melt obtained was used for the production of a composite plastic as described in example 12.

[0143] In this case too, it was possible to produce a composite plastic sheet which had a residual monomer content of about 1% by weight.