Process for producing monomer compositions and use of these for producing a polyamide molding

Abstract

A process for producing an activated monomer composition comprising at least one lactam and/or lactone, one catalyst, and one activator permits storage of the resultant monomer composition, since this is stable with respect to polymerization. Said monomer composition is used inter alia in producing a polyamide molding via ring-opening, anionic polymerization.

Claims

1. A process for producing a solid crystalline monomer composition (C), which can be stored without polymerization of the monomer, the composition comprising: i) at least one caprolactam monomer (M); ii) at least one catalyst (K); and iii) at least one activator (A); the process comprising: a) mixing of components (M), (K), and (A), and also optionally further components at a temperature of from 70 to 160 C.; b) cooling and crystallizing the mixture obtained in step a) to a temperature of from 0 C. to 25 C.; and c) optionally pelletizing the cooled mixture, to obtain a solid crystalline monomer composition, which can be stored without polymerization of the monomer, wherein the molar ratio of monomer (M) to catalyst (K) is from 1:1 to 10,000:1, wherein the at least one catalyst (K) is selected from the group consisting of sodium caprolactamate, potassium caprolactamate, magnesium bromide caprolactamate, magnesium chloride caprolactamate, magnesium biscaprolactamate, sodium hydride, sodium, sodium hydroxide, sodium ethanolate, sodium methanolate, sodium propanolate, sodium butanolate, potassium hydride, potassium, potassium hydroxide, potassium methanolate, potassium ethanolate, potassium propanolate, and potassium butanolate, wherein the at least one activator (A) comprises at least one of an aliphatic diisocyanate, an aromatic diisocyanate, and a polyisocyanate, and wherein in b) the mixture is cooled to a temperature of from 0 C. to 25 C. within a period of from 1 to 60 seconds with a cold stream of gas.

2. The process according to claim 1, wherein the composition (C) further comprises at least one component selected from the group consisting of a filler, a reinforcing material (F), a polymer (P), and a further addition (Z).

3. A process for producing a polyamide molding, comprising polymerizing a solid crystalline composition (C) via heating to a temperature of from 120 to 250 C., the composition (C) comprising i) at least one caprolactam monomer (M); ii) at least one catalyst (K); and iii) at least one activator (A); wherein the molar ratio of monomer (M) to catalyst (K) is from 1:1 to 10,000:1, wherein the at least one catalyst (K) is selected from the group consisting of sodium caprolactamate, potassium caprolactamate, magnesium bromide caprolactamate, magnesium chloride caprolactamate, magnesium biscaprolactamate, sodium hydride, sodium, sodium hydroxide, sodium ethanolate, sodium methanolate, sodium propanolate, sodium butanolate, potassium hydride, potassium, potassium hydroxide, potassium methanolate, potassium ethanolate, potassium propanolate, and potassium butanolate, wherein the at least one activator (A) is selected from the group consisting of an aliphatic diisocyanate, an aromatic diisocyanate, and a polyisocyanate, obtainable via a process comprising: a) mixing of components (M), (K), and (A), and also optionally further components at a temperature of from 70 to 160 C.; b) cooling and crystallizing the mixture obtained in a) to a temperature of from 0 C. to 25 C. within a period of from 1 to 60 seconds with a cold stream of gas; and c) optionally pelletizing the cooled mixture, wherein the composition is stored before polymerization.

4. The process for producing a polyamide molding according to claim 3, comprising: i) melting the composition (C) at a temperature of from 70 C. to 160 C.; j) charging the molten composition (C) to a mold cavity; k) polymerizing the composition (C) via heating to a temperature of from 120 C. to 250 C.

5. The process for producing a polyamide molding according to claim 3, wherein the polyamide molding comprises a filler and/or of reinforcing material in the range from 30 to 90% by weight.

Description

Example 1

(1) 834 g/h (7062 mmol/h) of (epsilon)-caprolactam, 115 g/h (144 mmol/h) of Bruggolen C 10 catalyst (17% w/w (epsilon)-caprolactamate in (epsilon)-caprolactam) and 51 g/h (14 mmol/h) of Bruggolen C 20 initiator (80% w/w capped diisocyanate in -caprolactam) were mixed in a PTW 16 extruder at 70 C. and 130 rpm, and 1.0 kg/h, using 2 mm die. The mixture was cooled by a cold stream of gas (coldfeed 0 C.). The mixture was pelletized at room temperature under nitrogen.

(2) One week later, the resultant caprolactam pellets were injection-molded at a product temperature of 80 C. in an Arburg 270 S injection molding machine with vertically arranged injection unit. The temperature profile of the cylinder was 60 C./65 C./70 C./75 C. Injection time was 0.8 s, and hold pressure time was 2 s. The melt was injected into a mold using a mold temperature of 150 C. The polymerization process was then allowed to proceed for 5 minutes. The resultant polyamide molding was removed from the mold.

(3) The content of residual monomer (caprolactam) in the polyamide product was determined chromatographically. The intrinsic viscosity of the polyamide product was determined to ISO 307 at 5 C. in 96% sulfuric acid. The polymer obtained comprised 0.9% by weight of residual caprolactam, and its intrinsic viscosity was 195.

Example 2

(4) 834 g/h (7062 mmol/h) of (epsilon)-caprolactam, 3000 g/h of glass beads, 115 g/h (144 mmol/h) of Bruggolen C 10 catalyst (17% w/w (epsilon)-caprolactamate in -caprolactam) and 51 g/h (14 mmol/h) of Bruggolen C 20 initiator (80% w/w capped diisocyanate in (epsilon)-caprolactam) were mixed in a PTW 16 extruder at 70 C. and 130 rpm, and 3.0 kg/h, using 2 mm die. The mixture was cooled by a cold stream of gas (coldfeed 0 C.).

(5) The mixture was pelletized at room temperature under nitrogen.

(6) One week later, the resultant caprolactam pellets were injection-molded at a product temperature of 80 C. The melt was injected at T=150 C. into a mold cavity. The polymerization process was then allowed to proceed for 5 minutes. The polyamide molding obtained was removed from the mold. The resultant polymer comprised 1.5% by weight of residual caprolactam, and its intrinsic viscosity was 230.

Example 3

(7) The monomer composition produced as in inventive example 1 was stored for one month. The polymerization process was then carried out as described in inventive example 1. The resultant polyamide comprised 0.95% by weight of residual caprolactam monomer content, and its intrinsic viscosity was 191.

(8) It was therefore possible to demonstrate that the monomer compositions produced by means of the process of the invention are stable over a long period, i.e. even after a long time they can still undergo full polymerization.

Example 4

(9) A composition was produced as stated in inventive example 1, but the mixing of the -caprolactam, of the catalyst, and of the initiator here was conducted in a round-bottomed flask, with use of a magnetic stirrer. The components were charged to the flask in a glovebox under dry nitrogen. After production of the composition, the aperture of the flask was sealed and the system was removed from the glovebox. The composition was cooled in an icebath.

(10) The composition was then stored at room temperature for one week. The polymerization process was then conducted for 10 min at a temperature of 150 C. The polyamide product comprised 0.85% by weight of residual caprolactam monomer, and its intrinsic viscosity was 200.

Examples 5.1 to 5.8

(11) Catalyst used for the following examples 5.1 to 5.8 comprised a solution of sodium lactamate in (epsilon)-caprolactam (Addonyl NL catalyst, Rhein Chemie), and the activator was an oligomer derived from hexamethylene diisocyanate, dissolved in N-methylpyrrolidone (Addonyl 8108, Rhein Chemie).

(12) The components were melted under dry nitrogen and then stirred for 30 seconds under dry nitrogen in a glass container thermostated to 100 C. The (epsilon)-caprolactam melt mixed with the additives was introduced gravimetrically into a steel mold heated to 150 C. The product was demolded after 5 minutes. The shape and the appearance of the molding were evaluated, as also was the content of residual monomers ((epsilon)-caprolactam). The caprolactam preparations used in the comparative examples were produced separately under dry inert gas and stored in watertight plastics containers.

Comparative Example 5.1

(13) The following compositions were produced:

(14) Catalyst melt: 1.5 g of catalyst were incorporated by stirring under inert gas into a mixture made of 100 g of (epsilon)-caprolactam from BASF SE, melted at 90 C.

(15) Activator melt: 1.0 g of activator were incorporated at 90 C. by stirring under inert gas into a mixture made of 100.0 g of (epsilon)-caprolactam.

(16) The two melts were intimately mixed under dry nitrogen by stirring (30 seconds) in a flask heated to 90 C., and were poured gravimetrically into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(17) Appearance: good, residual caprolactam 1.1%

Comparative Example 5.2: Addition of Short Glass Fibers

(18) A catalyst melt was produced as described in example 5.1.

(19) Activator melt: 1.0 g of activator and 40 g of commercially available short glass fibers with size for polyamides (OCV) were incorporated at 90 C. by stirring under inert gas into a mixture made of 100.0 g of (epsilon)-caprolactam.

(20) The two melts were intimately mixed under dry nitrogen by stirring (30 seconds) in a flask heated to 90 C., and were poured gravimetrically into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(21) Appearance: good, residual caprolactam 3.6%, odor of caprolactam

Comparative example 5.3: No Exclusion of Water

(22) A catalyst melt was produced as described in inventive example 5.1.

(23) Activator melt: 1.0 g of activator was incorporated at 90 C. by stirring into a mixture made of 100.0 g of (epsilon)-caprolactam.

(24) The two melts were intimately mixed by stirring (5 seconds) in a flask heated to 90 C., and were poured gravimetrically into the steel mold preheated to 150 C. Operations were not carried out under dry inert gas (nitrogen). The product was demolded after 5 minutes. This gave a homogeneous block.

(25) Appearance: poor (streaking, discoloration), residual caprolactam 5.1%, odor of caprolactam

Comparative Example 5.4: Addition of Short Glass Fibers and no Exclusion of Water

(26) A catalyst melt was produced as described in inventive example 5.1.

(27) Activator melt: 1.0 g of activator and 40 g of commercially available short glass fibers with size for polyamides (OCV) were incorporated at 90 C. by stirring into a mixture made of 100.0 g of (epsilon)-caprolactam.

(28) The two melts were intimately mixed by stirring (5 seconds) in a flask heated to 90 C., and were poured gravimetrically into the steel mold preheated to 150 C. Operations were not carried out under dry inert gas (nitrogen). The product was demolded after 5 minutes. This gave a homogeneous block.

(29) Appearance: very poor (streaking, yellowing), residual caprolactam 8.7%, strong odor of caprolactam

Example 5.5

(30) 101.5 g of solid (epsilon)-caprolactam in the form of flakes already comprising 1.5 g of catalyst were mixed under inert gas with 101.0 g of solid (epsilon)-caprolactam which already comprised 1.0 g of activator, and melted, and stirred for 5 seconds.

(31) The melt was poured at 90 C. into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(32) Appearance: good, residual caprolactam 1.1%

Example 5.6: Addition of Short Glass Fibers During Compounding

(33) 101.5 g of solid (epsilon)-caprolactam in the form of flakes already comprising 1.5 g of catalyst were mixed with 141.0 g of solid (epsilon)-caprolactam which already comprised 1.0 g of activator, and 40 g of commercially available short glass fibers with size for polyamides (OCV), and melted, and stirred for 5 seconds.

(34) The melt was poured at 90 C. into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(35) Appearance: good, residual caprolactam 1.2%

Example 5.7: Addition of Short Glass Fibers Prior to Processing

(36) 101.5 g of solid (epsilon)-caprolactam in the form of flakes already comprising 1.5 g of catalyst were mixed with 101.0 g of solid (epsilon)-caprolactam which already comprised 1.0 g of activator, and 40 g of commercially available short glass fibers with size for polyamides (OCV), and melted, and stirred for 5 seconds.

(37) The melt was poured at 90 C. into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(38) Appearance: good, residual caprolactam 1.6%

Example 5.8: (Only 1 Component)

(39) 202.5 g of solid (epsilon)-caprolactam in the form of flakes already comprising 1.5 g of catalyst and 1.0 g of activator were melted under inert gas, and not stirred.

(40) The melt was poured at 90 C. into the steel mold preheated to 150 C. The product was demolded after 5 minutes. This gave a homogeneous block.

(41) Appearance: good, residual caprolactam 1.0%

(42) The inventive examples and comparative examples 5.1 to 5.8 demonstrate that the process of the invention can produce better polyamide moldings at lower cost.

(43) The process of the invention also provides products with better appearance; in most cases it is also possible to reduce odor markedly. The latter feature can be explained via lower residual content of unreacted monomers.