Laser-markable polyamide composition

Abstract

The invention relates to a laser-markable polyamide composition comprising: a first phase comprising Sb.sub.2O.sub.3 and an aliphatic polyamide with an amide density AD1, and a second phase comprising an aliphatic polyamide with an amide density AD2, wherein AD1-AD2 is at least 0.01, and wherein the amount of Sb.sub.2O.sub.3 is between 0.1 and 5 wt %, a halogen-free flame retardant in an amount of between 1 to 25 wt %, wherein the amount in weight percentage are based on the total amount of composition. The invention also relates to a process for preparing a laser-markable polyamide composition, as well as laser-marked products comprising the composition.

Claims

1. A laser-marked product formed from a laser-markable polyamide composition, wherein the laser-markable polyamide composition comprises: (a) a first polyamide phase comprising an aliphatic polyamide with an amide density AD1 and between 0.1 and 5 wt. %, based on total weight of the polyamide composition, of Sb.sub.2O.sub.3, (b) a second polyamide phase comprising an aliphatic polyamide with an amide density AD2, and (c) between 1 to 25 wt. %, based on total weight of the polyamide composition, of a halogen-free flame retardant, wherein each of the amide densities AD1 and AD2 is a ratio of the number of CONH groups per CH.sub.2 groups in the polymer repeat units of the aliphatic polyamides of the first and second polyamide phases, respectively, and wherein a difference between the amide densities AD1 and AD2 (AD1-AD2) is at least 0.01.

2. The laser-marked product according to claim 1 wherein AD1-AD2 is at least 0.02.

3. The laser-marked product according to claim 1, wherein the aliphatic polyamide in the first phase is polyamide-46 and the aliphatic polyamide in the second phase is chosen from the group of polyamide-6 or polyamide-66 or blends thereof.

4. The laser-marked product according to claim 1, wherein the laser-markable composition further comprises a laser-marking synergist.

5. The laser-marked product according to claim 4, wherein the laser-marking synergist is a Sn containing metal compound.

6. The laser-marked product according to claim 1, wherein the flame retardant is a triazine based flame retardant.

7. The laser-marked product according to claim 1, wherein the laser markable composition comprises a weight ratio of the aliphatic polyamide having the amide density AD1 to the aliphatic polyamide having the amide density AD2 of at least 1:2.5.

8. The laser-marked product according to claim 7, wherein the laser-markable composition further comprises a laser-marking synergist.

9. The laser-marked product according to claim 7, wherein the laser-markable composition is free of polyolefins.

10. The laser-marked product according to claim 8, wherein the laser-markable composition comprises between 0.025 and 0.5 wt % of the laser-marking synergist.

11. The laser-marked product according to claim 4, wherein the laser-markable composition comprises between 0.025 and 0.5 wt % of the laser-marking synergist.

12. The laser-marked product according to claim 8, wherein AD1-AD2 is at least 0.02 and at most 0.1.

Description

EXAMPLES

(1) All materials were compounded on a 25 mm co-rotating twin screw extruder (Berstorff ZE25UTX). The laser-marking additive and flame retardant were added downstream and the other ingredients were added to the throat of the extruder. Various custom made masterbatches were used as described in the ingredients section below and in table 2. The final compositions with laser-marking additives present were molded into various shapes for property testing: 80801 mm plaques for laser-marking evaluation and glow-wire testing. 80804 mm plaques for CTI testing 0.75 mm UL94V specimen for the vertical burning test
GWFI tests were conducted in accordance with IEC60695-2-12. CTI testing was done in accordance with IEC 60112 (with solution A) and vertical burning tests were conducted in accordance to UL 94V.

(2) Laser-marking result was judged manually by laser-marking injection molded plates with dimensions 80801 mm at various intensities and marking speeds. Laser-marking evaluations were performed with a diode-pumped Trumpf VMc5 laser system. So-called evaluation matrices were marked. In such matrices, the marking speed (v [mm/sec]) and frequency (f [kHz]) are varied at given power (p [%]), focal distance (z=0 [in focus] or 6 mm above the sample) and line spacing. The evaluation matrices indicate which contrast can be obtained at certain marking speed with varying laser parameters. An evaluation of the laser-marking performance with respect to contrast and marking speed in terms ranging from excellent (+++) to poor () is given in Table 3.

(3) Ingredients:

(4) PA6: Akulon K122 from DSM, aliphatic polyamide with an amide density of 0.20, melting temperature T.sub.m=220 C. PA46: Stanyl KS200 from DSM, aliphatic polyamide with an amide density of 0.25, melting temperature T.sub.m295 C. Glass fiber: 173X-11p from 3B fiberglass Flame retardant: melamine cyanurate MC50 from BASF Mold release: Calcium-stearate from Faci Stabilizer: Irganox 1098 from Ciba specialty chemicals Laser-marking-synergist: Laserflair (LF) LS820 from Merck Laser-marking-synergist: Stanostat (ST) CP5C from Keeling and Walker GR261715 Sb.sub.2O.sub.3 (80 wt %) in PA6 (20 wt %): Antiox from Campine NV GR5538 Sb.sub.2O.sub.3 (80 wt %) in PA46 (20 wt %): custom made from Campine NV GR5537 Sb.sub.2O.sub.3/stanostat CP5C (76/4 wt %) in PA46 (20 wt %): custom made from Campine NV GR5535 Sb.sub.2O.sub.3/stanostat CP5C (76/4 wt %) in PA6 (20 wt %): custom made from Campine NV

(5) TABLE-US-00002 TABLE 2 ingredients masterbatch in wt % with respect to the total amount of masterbatch Ingredients MB1 MB2 MB3 GR261715 Sb.sub.2O.sub.3/PA6 62.5 GR5537 Sb.sub.2O.sub.3/stanostat CP5C in PA46 62.5 GR5538 Sb.sub.2O.sub.3/PA46 62.5 K122 PA6 25 37.5 37.5 KS200 PA46 12.5 AD1 0.20 0.25 0.25 AD2 0.20 0.20 0.20 T [ C.]* 312 315 317 *Step a1) and a2) were carried out at the temperature given in Table 2, last row.

(6) TABLE-US-00003 TABLE 3 Laser-markable polyamide compositions and results Ingredients Comparative Comparative Comparative in wt % A B C Ex 1 Ex 2 Ex 3 Ex 4 K122 63.6 66.725 65.6 61.2 65.6 64.6 65.6 Melamine Cyanurate 11 11 11 11 11 11 11 glass fiber 20 20 20 20 20 20 20 Calcium-stearate 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Irganox 1098 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Antiox GR261715 4 laserflair LS820 1 1 1 GR5535 (PA6 based) 1.875 MB1 3 MB2 6.4 3 3 MB3 3 T [ C.]* 289 292 290 289 292 290 291 Amount of Sb.sub.2O.sub.3 3.2 1.425 1.5 3.2 1.425 1.5 1.5 [wt %] Amount of Synergist 1.0 LF 0.075 ST 0 1.0 LF 0.075 ST 1.0 LF 0 [wt %] CTI 400 (350) 600 600 (525) 400 (350) 600 425 (375) 600 marking result ++ + + +++ ++ ++ ++ GWFI @ 1 mm 960 960 960 960 960 960 960 UL 94V @ 0.75 mm V2 V2 V2 V2 V2 V2 V2 *this is the temperature at which the laser-markable composition was prepared by blending all components as listed in Table 3.

Comparative A

(7) Comparative A consists of a laser-marking additive of Sb.sub.2O.sub.3 and Laserflair LS820 as synergist. The only polyamide present in the composition is PA6, therefore only one phase exists. The composition was prepared in one step at a temperature as denoted in Table 3. It is clearly seen that laser-marking performance is sufficient but the composition suffers from low CTI value.

Comparative B

(8) In the composition of Comparative B a lower amount of laser-marking additive is used in combination with an alternative synergist. The only polyamide present in the composition is PA6, therefore only one phase exists and the composition was prepared in one step at a temperature denoted in Table 3. This results in better CTI value as compared to comparative example A, but the laser-marking contrast is poor.

Comparative C

(9) In comparative C a lower amount of Sb.sub.2O.sub.3 is used and no synergist is present. The custom made laser-marking masterbatch was prepared by a first step of mixing Sb.sub.2O.sub.3 and polyamide 6 at a temperature above 220 C. This masterbatch, GR261715, was subsequently added to a blend of polyamide 6 and polyamide 46, for which the majority is polyamide 6. AD1-AD2 is here thus less than 0.01, namely 0.0. The sample has good CTI but also low laser-marking contrast.

Example 1

(10) Example 1 uses as laser-marking additive Sb.sub.2O.sub.3 and Laserflair LS820 as synergist at identical concentrations as Comparative Example A. In Example 1 MB2 was used. Antimony trioxide was added to PA46 at a temperature above the melting temperature of PA46, subsequently, this masterbatch was blended with PA6 at the temperature denoted in Table 2 to give MB2. The components as denoted in Table 3 were blended at a temperature given in Table 3 to yield a laser-markable polyamide composition. This results in sufficient CTI value (comparable to comparative A) but in better laser-marking contrast, as compared to Comparative Example A.

Example 2

(11) Example 2 a lower amount of laser-marking additive is used in combination with an alternative synergist, as compared to Example 1. Moreover, the synergist is added in a first step. Antimony trioxide and stanostad were added to PA46 at a temperature above the melting temperature of PA46, subsequently, this masterbatch was blended with PA6 at the temperature denoted in Table 2 to give MB3. The components as denoted in Table 3 were blended at a temperature given in Table 3 to yield a laser-markable polyamide composition. This results in the similar CTI performance as comparative B but in better laser-marking contrast, as compared to comparative example B.

Example 3

(12) Example 3 uses a lower concentration Sb.sub.2O.sub.3 than comparative A. The same synergist is used as in comparative A. Antimony trioxide was added to PA46 at a temperature above the melting temperature of PA46, subsequently, this masterbatch was blended with PA6 at the temperature denoted in Table 2 to give MB2. The components as denoted in Table 3 were blended at a temperature given in Table 3 to yield a laser-markable polyamide composition. The result is an improved CTI performance as compared to comparative A, and also better laser-marking contrast.

Example 4

(13) Example 4 uses the same laser-marking additive package as in comparative C. In contrast to comparative C the masterbatch was based on a PA46 to which subsequently PA6 was added in order to obtain the masterbatch: Antimony trioxide was added to PA46 at a temperature above the melting temperature of PA46, subsequently, this masterbatch was blended with PA6 at the temperature denoted in Table 2 to give MB2. The components as denoted in Table 3 were blended at a temperature given in Table 3 to yield a laser-markable polyamide composition. Compared to comparative C this results in a better CTI value and improved laser-marking performance.

(14) The results in the table 3 clearly show that a polyamide composition according to the invention shows higher laser-marking result, or similar laser-marking result when the amount of antimony trioxide is reduced. This can be concluded when Comparative example A is compared to Example 1. Example 1 shows better laser-marking compared to a composition based on only PA6.

(15) Surprisingly, the CTI value is improved by employing the polyamide composition according to the invention, as well as the process according to the invention. This is seen when comparative example A is compared to examples 2, 3, and 4. In Examples 2, 3, and 4 a significant lower amount of antimony trioxide is employed, while the laser-marking result remains the same. All the CTI values have improved for examples 2, 3 and 4 compared to comparative example A.