Polyamides with improved optical properties

Abstract

The invention relates to the use of thermoplastic molding compositions comprising D) from 30 to 99% by weight of a thermoplastic polyamide E) from 0.01 to 10% by weight of an organic isocyanate or diisocyanate, or a mixture of these F) from 0 to 60% by weight of other additional substances,
where the sum of the percentages by weight of A) to C) is 100%,
for the production of moldings of any type with improved haze (measured in accordance with ASTM D1003) and/or improved clarity (measured in accordance with ASTM D1003) and/or increased laser transparency (measured at a wavelength of 1064 nm by means of a thermoelectric power measurement).

Claims

1. A method of producing a molding comprising a thermoplastic molding composition comprising admixing A) from 30 to 99% by weight of a thermoplastic polyamide selected from the group consisting of PA 6 and PA 66, B) from 0.01 to 10% by weight of cyclohexyl trans-1,4-diisocyanate and phenylene 1,4-diisocyanate, and C) from 0 to 60% by weight of other additional substances, where the sum of the percentages by weight of A) to C) is 100% and the thermoplastic molding composition is free of polyoxymethylene, wherein the molding has improved haze, measured in accordance with ASTM D1003, and/or improved clarity, measured in accordance with ASTM D1003, and/or increased laser transparency, measured at a wavelength of 1064 nm by means of a thermoelectric power measurement, wherein the haze value of the molding, measured in accordance with ASTM D1003, is at least 5% lower than that of a reference polymer composition without component B), measured from a test sample of thickness 1.3 mm, wherein the clarity value of the molding, measured in accordance with ASTM D1003, is at least 5% higher than that of a reference polymer composition without component B), measured from a test sample of thickness 1.3 mm, and wherein the laser transparency of the molding, measured at a wavelength of 1064 nm by means of a thermoelectric power measurement, is at least 1% higher than that of a reference polymer composition without component B), measured from a test sample of thickness 1.3 mm.

2. The method according to claim 1, where the thermoplastic molding composition comprises A) from 30 to 99% by weight, B) from 0.01 to 5% by weight, and C) from 0 to 50% by weight.

3. The method according to claim 1, further comprising an organic isocyanate compound of formula R1−N═C═O, where the moiety R1 represents linear C1-c14-alkyl moieties, branched C3 to C12-alkyl moieties, unsubstituted or substituted C3 to C14-cyclo-alkyl moieties, or unsubstituted or substituted aromatic moieties having from 6 to 20 carbon atoms.

4. The method according to claim 3 wherein the further organic isocyanate compound is selected from the group consisting of: cyclohexyl isocyanate and phenyl isocyanate.

5. The method according to claim 1 further comprising extruding the thermoplastic molding composition.

6. The method according to claim 1 further comprising pelletizing the thermoplastic molding composition.

7. The method according to claim 1 wherein the thermoplastic molding composition comprises 0.5 to 2% by weight of the organic diisocyanate B).

Description

EXAMPLES

(1) The following components were used:

(2) Component A/1

(3) Nylon-6 with intrinsic viscosity IV 150 ml/g, measured on a 0.5% by weight solution in 96% by weight sulfuric acid at 25° C. in accordance with ISO 307 (the material used being Ultramid® B27 from BASF SE).

(4) Component A/2

(5) PA 66 with IV 150 ml/g (Ultramid® A27 from BASF SE)

(6) Materials:

(7) B1 cyclohexyl trans-1,4-diisocyanate (CAS 7517-76-2)

(8) B2 hexamethylene diisocyanate (CAS 822-06-0)

(9) B3 dicyclohexylmethane 4,4′-diisocyanate (CAS 5124-30-1)

(10) B4 methylenebis(phenyl 4,4′-diisocyanate) (CAS 101-68-8)

(11) B5 toluene 2,4-diisocyanate (CAS 584-84-9)

(12) B6 cyclohexyl isocyanate (CAS 3173-53-3)

(13) B7 phenylene 1,4-diisocyanate (CAS 104-49-4)

(14) B8 phenyl isocyanate (CAS 103-71-9)

(15) B9 isophorone diisocyanate (CAS 4098-71-9)

(16) Structural Formulae:

(17) ##STR00009##
Processing:
Compounding—DSM:

(18) The polyamide pellets and the respective isocyanates (1% by weight) were weighed into a glass flask and then incorporated by compounding under nitrogen in a conical twin-screw extruder (DSM Xplore, 15 cc). The polyamide without additional materials was processed in the same manner to obtain the reference sample. The following parameters were used:

(19) Residence time: 3 min.

(20) Barrel temperature: 260° C.

(21) Melt temperature: from 240° C. to 245° C.

(22) Rotation rate: 200 rpm

(23) Injection Molding—DSM:

(24) The compounded polymers were injection-molded in a 10 cc DSM Micro-Injection molding apparatus. For this, the molten compounded material was charged under nitrogen directly to the cylinder of the injection-molding machine. The melt was then injected into a polished rectangular mold measuring 30 mm×30 mm×1.27 mm. The following parameters were used:

(25) Mold: Plaque, polished; 30 mm×30 mm×1.27 mm

(26) Mold temperature: 70° C.

(27) Cylinder temperature: 260° C.

(28) Injection pressure: from 10 to 12 bar

(29) Measurement Methods:

(30) Polymer Crystallization Temperature

(31) The crystallization behavior of the polymer mixtures is determined by means of differential scanning calorimetry (DSC) in a manner known per se (ISO 11357-2:2013). The determination is carried out under nitrogen in open aluminum crucibles at a heating rate and cooling rate of 20 K/min. After the first heating procedure the sample is retained in the melt for 5 min in order to delete the thermal history of the polymer. The DSC measurement is advantageously repeated once or twice on the same sample, in order to ensure that the respective polyamide has a defined thermal history. The crystallization temperature Tk was determined in accordance with DIN EN ISO 11357-3. The crystallization temperature Tk is the exothermic peak minimum of the DSC curve during the first cooling procedure at 20 K/min after a defined thermal history.

(32) Optical Characterization (Haze, Clarity):

(33) Haze, clarity, and transmission were measured with a haze gard plus tester (BYK-G, Gardner®, illumination CIE-E) at room temperature. The measurement was made in accordance with ASTM D1003. The time elapsed after the injection-molding process for measurement of the haze and clarity values was from 24 to 48 h.

(34) TABLE-US-00004 TABLE 1 Composition of the compounded materials A/1 Ex. (% by A/2 B1 B2 B3 B4 B5 B6 B7 B8 B9 No. wt.) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)  1 comp. 100 0 0 0 0 0 0 0 0 0 0  2 99 0 1 0 0 0 0 0 0 0 0  3 99 0 0 1 0 0 0 0 0 0 0  4 99 0 0 0 0 0 0 0 0 0 0  5 99 0 0 0 1 0 0 0 0 0 0  6 99 0 0 0 0 1 0 0 0 0 0  7 99 0 0 0 0 0 1 0 0 0 0  8 99 0 0 0 0 0 0 1 0 0 0  9 99 0 0 0 0 0 0 0 1 0 0 10 99 0 0 0 0 0 0 0 0 1 0 11 99 0 0 0 0 0 0 0 0 0 1 12 comp. 0 100 0 0 0 0 0 0 0 0 0 13 0 99 1 0 0 0 0 0 0 0 0

(35) TABLE-US-00005 TABLE 2 Haze Clarity Composition [%] [%] 1 comp. 99.8 63.6 2 25.5 97.4 3 72.7 59.5 4 95.4 55.9 5 97.5 30.3 6 96.1 82.2 7 80.1 41.8 8 92.5 9.1 9 86.7 88.2 10 91.6 24.1 11 97.2 28.7 12 comp. 99.6 5.5 13 63.6 96.1