LASER-WELDABLE POLYESTER COMPOSITION, PREPARATION AND PROCESSING THEREOF AND APPLICATIONS THEREOF

Abstract

The present invention relates to a laser-weldable polyester composition, more particular to a laser-weldable fibre-rein-forced polybutylene terephthalate composition comprising: (A) a poly butylene terephthalate resin (PBT); (B) glass fibres; and (C) an alkali metal salt of a fatty acid with 24-40 carbon atoms; wherein component (B) is present in an amount in a range of 15-100 parts by weight, relative to 100 parts by weight of component (A) and component (C) is present in an amount in a range of 1.75-4.5 parts by weight, relative to 100 parts by weight of component (A). The invention also relates to a process for preparing the laser-weldable fibre-reinforced polyester composition, a process for making a moulded part from the laser-weldable fibre-reinforced polyester composition, a laser transparent moulded part made of the laser-weldable fibre-reinforced polyester composition, to a process for laser welding the laser transparent moulded part made of the laser-weldable fibre-reinforced polyester composition on laser-light-absorbent polymeric substrate, and a composite article comprising the moulded article made of the laser-weldable fibre-reinforced polyester composition bonded by laser welding on a laser-light-absorbent polymeric substrate.

Claims

1. A laser-weldable fibre reinforced polyester composition comprising: (A) a polybutylene terephthalate resin (PBT); (B) glass fibres; and (C) an alkali metal salt of a fatty acid with 24-40 carbon atoms; wherein component (B) is present in an amount in the range of 15-100 parts by weight, relative to 100 parts by weight of component (A), and component (C) is present in an amount in the range of 1.75-4.50 parts by weight, relative to 100 parts by weight of component (A).

2. A laser-weldable fibre reinforced polyester composition according to claim 1, wherein the polybutylene terephthalate resin (A) is a PBT homopolymer, or a PBT copolymer containing at least about 85 mol of copolymerized units of butylene (butylene units) and terephthalate (terephthalate units) and at most about 15 mol of copolymerized units of further comonomers (comonomer units), wherein the mol percentages (mol) of butylene units, terephthalate units and comonomer units are all relative to the total molar amount of moles of butylene units, moles of terephthalate units and moles of comonomers units in the copolymer.

3. A composition according to claim 1, wherein the polybutylene terephthalate resin (A) has a relative solution viscosity (RSV) Herein, the relative solution viscosity (RSV) is measured in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25 C. by the method according to ISO 307, in the range of 1.5-2.8 dl/g.

4. A composition according to claim 1, wherein component (B) is present in an amount in the range of 25-80 parts by weight (pbw), preferably 30-70 pbw, more preferably 35-60 pbw, relative to 100 pbw of component (A).

5. A composition according to claim 1, wherein the alkali metal in component (C) is sodium or potassium, or a combination thereof.

6. A composition according to claim 1, wherein the fatty acid in component (C) is a fatty acid with 26-36 carbon atoms, preferably a fatty acid with 28-32 carbon atoms.

7. A composition according to claim 1, wherein component (C) is present in an amount in the range of 2.0-3.75 parts by weight (pbw), more preferably 2.1-3.5 pbw, even more preferably 2.2-3.2 pbw, and most preferred 2.3-3.0 pbw, relative to 100 pbw of component (A).

8. A composition according to claim 1, consisting of 40-85 wt. % of component (A); 15-49.5 wt. % of component (B); 1-3.3 wt. % of component (C); and 0-20 wt. % of one or more additives (component (D)); wherein the weight percentages (wt. %) relative to the total weight of the composition.

9. A composition according to claim 1, wherein the composition comprises a laser light transparent colorant, preferably a black laser light transparent colorant, or a black-colouring combination of two or more different non-black laser light transparent colorants.

10. A composition according to claim 1, wherein the composition has a laser-light-transparency of at least 25.0%, preferably at least 30.0%, and more preferably at least 40%, at 1.2 mm thickness, or at least 15.0%, preferably at least 17.5%, and more preferably at least 20%, at 2.0 mm thickness, measured and 980 nm by the method according to TMG3 as described herein above.

11. A process for preparing a laser weldable fibre-reinforced polyester composition by melt-mixing, the process comprising melting of a polybutylene terephthalate resin and mixing (A) 100 parts by weight of the polybutylene terephthalate resin; (B) 15-100 parts by weight of glass fibres and (C) 1.75-4.5 parts by weight an alkali metal salt of a fatty acid with 24-40 carbon atoms.

12. A process according to claim 11, where the laser weldable fibre-reinforced polyester composition is a composition.

13. A process for making a moulded part from a laser weldable fibre-reinforced polyester composition, comprising moulding a laser weldable fibre-reinforced polyester composition into a preformed shape, the laser-weldable fibre reinforced polyester composition comprising (A) a polybutylene terephthalate resin; (B) glass fibres; and (C) an alkali metal salt of a fatty acid with 24-40 carbon atoms; wherein component (B) is present in an amount in the range of 15-100 parts by weight and component (C) is present in an amount in the range of 1.75-4.5 parts by weight, relative to 100 parts by weight of component (A).

14. A process according to claim 13, wherein the laser weldable fibre-reinforced polyester composition is a composition.

15. A laser-light-transparent moulded part made of a laser weldable fibre-reinforced polyester composition comprising (A) a polybutylene terephthalate resin; (B) glass fibres; and (C) an alkali metal salt of a fatty acid with 24-40 carbon atoms; wherein component (B) is present in an amount in the range of 15-100 parts by weight and component (C) is present in an amount in the range of 1.75-4.5 parts by weight, relative to 100 parts by weight of component (A).

16. A laser-light-transparent moulded part according to claim 15, wherein the laser weldable fibre-reinforced polyester composition is a composition.

17. A process for producing a composite article by laser welding, which comprises irradiating a laser beam on a contact surface of a laser-light-transparent moulded part and a laser-light-absorbent polymeric substrate, thereby forming a welded bond between the laser-light-transparent moulded part and the laser-light-absorbent polymeric substrate, wherein the laser-light-transparent moulded part is made of a laser weldable fibre-reinforced polyester composition as mentioned in claim 1.

18. A composite article comprising a laser-light-transparent moulded part bonded by laser welding on a laser-light-absorbent polymeric substrate, wherein the laser-light-transparent moulded part is made of a laser weldable fibre-reinforced polyester composition as mentioned in claim 1.

Description

[0139] As can be seen from all three FIGS. 2, 3 and 4, Na-stearate (C2) and Na-myristate (C3) show a steep drop in elongation-at-break and unnotched impact resistance at a content of 0.5 or 1 pbw, relative to 100 pbw of PBT and for the tensile strength at 1.5 pbw, relative to 100 pbw of PBT. In all three graphs Na-myristate (C3) shows a slight better performance than Na-stearate (C2) for the compositions with a Cx content in the range of 0.5-2.5 pbw, relative to 100 pbw of PBT. Meanwhile the properties are much better retained for the compositions comprising Na-montanate (C1). Even at a content of 4.5 pbw of Na-montanate (C1), relative to 100 pbw of PBT, all three properties of tensile strength, elongation-at-break and unnotched impact resistance are still at a higher retention level than those for the composition with Na-stearate (C2) at a content of 1.5 pbw, relative to 100 pbw of PBT.

TABLE-US-00005 TABLE 5 Laser Light Transmission and welding results for Examples III-IV and Comparative Experiments CE-A and CE-T. Product/Composition CE-A CE-T EX-V EX-III A1 (wt. %) 68 65.20 65.90 B1 (wt. %) 30 30 30 C1 (wt. %) 0 2.80 2.10 CX (wt. %) 0 0 0 D (wt. %) 2 2 2 C1/CX (phr) 0 4.29 3.19 LLT (1 mm) (%) 16-17 42-56 48-52 52-58 Welding time (s) vs laser power Low energy 3.9 3.4 2.7 2.4 Medium energy 3.0 2.4 1.8 1.7 High energy 2.5 1.8 1.4 1.3 Welding time (s) vs welding speed Low welding speed 2.0 1.6 1.4 Medium welding speed 1.9 1.4 1.3 High welding speed 2.1 1.7 1.5 Welding time (s) vs clamping pressure Low clamping pressure 2.2 1.6 1.5 Medium clamping pressure 1.8 1.4 1.3 High clamping pressure 1.6 1.4 1.2

[0140] Table 5 shows the laser light transmission and welding test results for two Examples (EX-III and EX-IV) and for two Comparative Experiments (CE-A and CE-T). CE-A is a fibre-reinforced polyester composition without additive to enhance the laser-light transparency, and CE-T is a commercially available product with high transparency but with unknown composition.

[0141] The data in the table show surprisingly good results in terms of welding behaviour for Examples II and III, both representing compositions according to the present invention. Herein the performance is much better than for the two Comparative Experiments, which is not surprising in view CE-A lacking an additive to enhance the laser-light transparency, but is highly surprising in respect of CE-T, which itself has a relatively high laser-light transparency.