POLYMER COMPOSITION, MOLDED PART AND PROCESSES FOR PRODUCTION THEREOF

Abstract

The present invention relates to a polymer composition, consisting of (A) 30-90 wt. % of at least one thermoplastic polymer comprising at least a semi-crystalline semi-aromatic polyamide (SSPA-1) in an amount in the range of 30-90 wt. %; (B) 10-70 wt. % of at least one reinforcing agent, and (C) 0-25 wt. % of one or more other components; wherein the SSPA-1 consists of (A-1-a) 90-100 wt. % of repeat units derived from (i) an aromatic dicarboxylic acid and (ii) diamines, and (A-1-b) 0-10 wt. % of repeat units derived from other monomers; the diamines (ii) consist of 80-95 mole % of a linear aliphatic diamine, 5-20 mole % of 2-methyl-pentamethylene diamine, and 0-10 mole % of other diamines; and the SSPA-1 has a melting temperature (Tm) of at least 300 C. The invention further relates to a molded part made of the composition, a process for making the composition and a process for making the molded part.

Claims

1. Reinforced thermoplastic polymer composition, consisting of: (A) polymer comprising at least a first semi-crystalline semi-aromatic polyamide (SSPA-1); (B) 10-70 wt. % of at least one reinforcing agent, and (C) 0-25 wt. % of one or more other components, wherein the SSPA-1 is present in an amount in the range of 30-90 wt. %; has a melting temperature (Tm) of at least 300 C.; and consists of: (A-1-a) 90-100 mole % of repeat units derived from (i) aromatic dicarboxylic acid and (ii) diamines, and (A-1-b) 0-10 mole % of repeat units derived from other monomers; and the diamines (ii) consist of 80-95 mole % of linear aliphatic diamine, 5-20 mole % of 2-methyl-pentamethylene diamine, and 0-10 mole % of other diamines; and wherein the mole percentages (mole %) of the diamines are relative to the total molar amount of diamines; the mole % of (A-1-a) is based on the combined molar amount of the aromatic dicarboxylic acid (i) and the diamines (ii); the mole % of (A-1-a) and (A-1-b) are relative to the total molar amount of monomeric repeat units (A-1-a) and (A1-b) in the SSPA-1; the weight percentages (wt. %) of components (A), (B) and (C) and of the S SPA-1 are relative to the total weight of the composition, while the sum of (A), (B) and (C) is 100 wt. %.

2. Polymer composition according to claim 1, wherein the SSPA-1 has a melting temperature in the range of 310-350 C.

3. Polymer composition according to claim 1, wherein the aromatic dicarboxylic acid is selected from terephthalic acid, 2,6-naphthalene dicarboxylic acid and 4,4-biphenyl dicarboxylic acid, or a combination thereof, and preferably is terephthalic acid.

4. Polymer composition according to claim 1, wherein the diamines (ii) consist of 5-15 mole % of 2-methyl-pentamethylene diamine, 85-95 mole % of a linear aliphatic diamine, and 0-5 mole % of other diamines.

5. Polymer composition according to claim 1, wherein the linear diamines comprise 40-95 mole % of a C2-C8 diamine, more preferably 60-95 mole % of a C2-C6 diamine, relative to the total molar amounts of diamines.

6. Polymer composition according to claim 1, wherein component (B) comprises inorganic fibers or inorganic fillers, or a combination thereof.

7. Polymer composition according to claim 1, wherein component (B) comprises glass fibers or carbon fibers, or a mixture thereof.

8. Polymer composition according to claim 1, wherein component (B) is present in an amount in the range of 30-50 wt. %, relative to the total weight of the composition.

9. Process for preparing a polymer composition according to claim 1, comprising steps of: (1) providing polymer comprising at least a first semi-crystalline semi-aromatic polyamide (SSPA-1), and at least one reinforcing agent, and optionally one or more other components, and (2) melt-mixing the said components in the following amounts: (A) the polymer comprising 30-90 wt. % of the first semi-crystalline semi-aromatic polyamide (SSPA-1) (B) 10-70 wt. % of the least one reinforcing agent, and (C) 0-25 wt. % of the one or more other components, wherein the SSPA-1: has a melting temperature (Tm) of at least 300 C.; and consists of: (A-1-a) 90-100 mole % of repeat units derived from (i) aromatic dicarboxylic acid and (ii) diamines, and (A-1-b) 0-10 mole % of repeat units derived from other monomers; and the diamines (ii) consist of 80-95 mole % of linear aliphatic diamine, 5-20 mole % of 2-methyl-pentamethylene diamine, and 0-10 mole % of other diamines; and wherein the mole percentages of the diamines are relative to the total molar amount of diamines; the mole % of (A-1-a) is based on the combined molar amount of the aromatic dicarboxylic acid (i) and the diamines (ii); the mole % of (A-1-a) and (A-1-b) are relative to the total molar amount of monomeric repeat units (A-1-a) and (A1-b) in the SSPA-1; the weight percentages (wt. %) of components (A), (B) and (C) and of the SSPA-1 are relative to the total weight of the composition, while the sum of (A), (B) and (C) is 100 wt. %.

10. Process according claim 9, wherein the polymer composition is a composition.

11. Molded part made of, or comprising an element made of a polymer composition.

12. Molded part according to claim 11, wherein the molded part is an automotive part, or a part of an electronic device.

13. Molded part according to claim 12, wherein the molded part or the element comprised by the molded part, is made in a mold with a multi-gate cavity.

14. Process for making a molded part comprising a step comprising injection molding of a polymer composition into a mold, wherein the polymer composition is a polymer composition according to claim 1.

15. Process according to claim 15, wherein the mold is a mold with a multi-gate cavity.

Description

[0095] The invention is further illustrated with the following non-limiting examples and comparative experiments.

Materials

[0096] PA-1 PA-6T/DT (60/40 molar ratio): Zytel HTN51G45HSL, glass fiber reinforced grade (commercially available from DuPont) [0097] PA-2 PA-6T/4T copolymer (65/35 molar ratio) (made by DSM) [0098] PA-3 PA-6T/4T/DT copolymer (58/32/10 molar ratio) (made by DSM)

[0099] Herein the polyamides consist of repeat units derived from respectively: 1,6-hexanediamine and terephthalic acid (abbreviated as 6T), 1,4-butanediamine and terephthalic acid (abbreviated as 4T), and 2-methyl-pentamethylene diamine and terephthalic acid (abbreviated as DT).

Compounding

[0100] Polyamide compositions were prepared on a twin screw extruder, employing standard molding conditions. For the compositions of Examples I-Ill and Comparative Experiments A and B, the temperature of the extruded melt was typically about 350-360 C. For Comparative Experiment C the melt temperature was about 330 C. After the melt compounding the resulting melt was extruded into strands, cooled and cut into granules.

Injection MoldingPreparation of Test Bars for Mechanical Testing

[0101] Dried granulate material was injection molded into a mold to form test bars conforming ISO 527 type 1A; the thickness of the test bars was 4 mm. The polyamide compositions were injection molded into appropriate test molds using a standard injection molding machine. Test bars were prepared using either a single gated mold for standard test bars or a double gated mold for production of test bars with a weld line, each gate located at an opposite end of the sample and causing the formation of a weld line, while applying the same conditions as for the standard test bars. The setting temperature of the T-melt in the injection molding machine was about 330 C. for PA-1 and 350 C. for PA-2 and PA-3; the temperature of the mold was 140 C.

Testing

[0102] Melting temperature (Tm)

[0103] The measurements of the melting temperature (Tm) were carried out with a Mettler Toledo Star System (DSC) using a heating and cooling rate of 10 C./min. in an N2 atmosphere. For the measurements a sample of about 5 mg pre-dried powdered polymer was used. The pre-drying was carried out at high vacuum, i.e. less than 50 mbar and a 130 C. during 16 hrs. The sample was heated from 0 C. to a temperature about 30 C. above the melting temperature at 10 C./min, immediately cooled to 0 C. at 10 C./min and subsequently heated to about 30 C. above the melting temperature again at 10 C./min. For the melting temperature Tm the peak value of the melting peak in the second heating cycle was determined, according to the method of ISO-11357-1/3, 2011.

Tensile Strength

[0104] The tensile strength was measured in a tensile test according to ISO 527/1 at 150 C., at a drawing speed of 5 mm/min.

Weldline Strength

[0105] The weldline strength was measured in a tensile test according to ISO 527/1 at 23 C., at a drawing speed of 5 mm/min.

[0106] The compositions and test results have been summarized in Table 1.

TABLE-US-00001 TABLE 1 Compositions and properties of Examples I-III and Comparative Experiments (A-C) CE-A EX-I CE-B EX-II CE-C EX-III Composition (wt.%) PA-6T/4T (65/35) 59.2 54.6 PA-6T/4T/DT (58/32/10) 59.5 54.6 49.5 PA-6T/DT (60/40) 54.5 Glass fibers 40 40 45 45 45 50 Additive package 0.8 0.5 0.4 0.4 0.5 0.5 (ST + MRA) Properties Tm ( C.) 342 337 342 337 300 337 Tensile strength 135 134.4 140 136 83 138 at 150 C. [MPa] Weldline strength 59.4 73.4 70 78 69 81 at 23 C. [MPa]

[0107] The results show an increased weldline strength for the compositions according to the invention, compared to corresponding compositions not comprising 2-methyl-pentamethylene diamine terephthalamide units, while the tensile strength at high temperature remains at a high level. This result is highly surprising and in contrast with the known composition comprising a larger amount of 2-methyl-pentamethylene diamine terephthalamide units, which shows a lower weldline strength and a significant drop in tensile strength at high temperature.