POLYAMIDE COMPOSITION FOR LIQUID-ASSISTED INJECTION MOULDING APPLICATIONS

Abstract

The disclosure relates to a polyamide composition including (i) at least one aliphatic polyamide comprising repeating units derived from the polycondensation of hexamethylenediamine and adipic acid; (ii) at least one semi-aromatic polyamide comprising repeating units derived from the polycondensation of hexamethylenediamine, adipic acid and at least one aromatic dicarboxylic acid; (iii) at least one fibrous filler; (iv) at least one particulate filler; (v) at least one heat stabilizer; and (vi) at least one further additive. The polyamide composition exhibits excellent processing properties in the preparation of articles using liquid-assisted injection moulding processes.

Claims

1. A polyamide composition comprising: (i) at least one aliphatic polyamide comprising repeating units derived from a polycondensation of hexamethylenediamine and adipic acid; (ii) at least one semi-aromatic polyamide comprising repeating units derived from a polycondensation of hexamethylenediamine, adipic acid and at least one aromatic dicarboxylic acid; (iii) at least one fibrous filler; (iv) at least one particulate filler; (v) at least one heat stabilizer; (vi) at least one further additive; (vii) optionally at least one polyamide selected from homopolymers of -caprolactam (PA6), copolymers of -caprolactam with hexamethylenediamine and terephthalic acid and copolymers of -caprolactam with hexamethylenediamine and isophthalic acid; and (viii) optionally at least one polyamide selected from homopolymers of hexamethylenediamine and sebacic acid (PA6.10).

2. The polyamide composition according to claim 1, wherein the at least one semi-aromatic polyamide comprises repeating units derived from at least one aromatic dicarboxylic acid in an amount of at least 5 mol.-%, based on a total weight of the at least one semi-aromatic polyamide.

3. The polyamide composition according to claim 1, wherein the at least one semi-aromatic polyamide is selected from homopolymers and/or copolymers of hexamethylenediamine and adipic acid with terephthalic acid and/or isophthalic acid.

4. The polyamide composition according to claim 1, wherein the at least one semi-aromatic polyamide is selected from copolymers of hexamethylenediamine, adipic acid and terephthalic acid (PA6.6/6.T), copolymers of hexamethylenediamine, adipic acid and isophthalic acid (PA6.6/6.I), copolymers of hexamethylenediamine, adipic acid, terephthalic acid and isophthalic acid (PA6.6/6.T/6.I) and mixtures of these semi-aromatic polyamides.

5. The polyamide composition according to claim 1, wherein the at least one aliphatic polyamide is selected from homopolymers of hexamethylenediamine and adipic acid (PA6.6), copolymers of hexamethylenediamine, adipic acid and -caprolactam (PA6.6/6) and mixtures of these aliphatic polyamides.

6. The polyamide composition according to claim 1, wherein the at least one fibrous filler is selected from glass fibres, ceramic fibres, carbon fibres, and thermostable polymer fibres.

7. The polyamide composition according to claim 1, wherein the at least one particulate filler is selected from mineral fillers, glass beads, glass flakes, and milled glass fibres.

8. The polyamide composition according to claim 1, wherein the at least one fibrous filler is selected from glass fibres and the at least particulate filler is selected from glass beads.

9. The polyamide composition according to claim 1, wherein the at least one additive is selected from colorants, mould release agents, flame retardants, toughening modifiers, and additives to facilitate the mixing of the components or the moulding of the composition.

10. The polyamide composition according to claim 1, further comprising: (i) 40 to 70 wt.-%, based on a total weight of the polyamide composition, of the at least one aliphatic polyamide comprising repeating units derived from the polycondensation of hexamethylenediamine and adipic acid; (ii) 4 to 30 wt.-%, based on the total weight of the polyamide composition, of the at least one semi-aromatic polyamide comprising repeating units derived from the polycondensation of hexamethylenediamine, adipic acid and at least one aromatic dicarboxylic acid; (iii) 10 to 40 wt.-%, based on the total weight of the polyamide composition, of the at least one fibrous filler; (iv) 1 to 20 wt.-%, based on the total weight of the polyamide composition, of the at least one particulate filler; (v) 0.1 to 2 wt.-%, based on the total weight of the polyamide composition, of the at least one heat stabilizer; (vi) 0.1 to 2 wt.-%, based on the total weight of the polyamide composition, of the at least one further additive; (vii) 0 to 20 wt.-%, based on the total weight of the polyamide composition, of the at least one polyamide selected from homopolymers of -caprolactam (PA6), copolymers of -caprolactam with hexamethylenediamine and terephthalic acid and copolymers of -caprolactam with hexamethylenediamine and isophthalic acid; and (viii) 0 to 20 wt.-%, based on the total weight of the polyamide composition, of the at least one polyamide selected from homopolymers of hexamethylenediamine and sebacic acid (PA6.10).

11. The polyamide composition according to claim 10, wherein the at least one aliphatic polyamide is selected from homopolymers of hexamethylenediamine and adipic acid (PA6.6) and copolymers of hexamethylenediamine, adipic acid and -caprolactam (PA6.6/6) and wherein only the repeating units derived from hexamethylenediamine and adipic acid account to an amount of 40 to 70 wt.-% of the at least one aliphatic polyamide based on the total weight of the polyamide composition.

12. (canceled)

13. A process for preparing an article, the process comprising at least the following process steps: (a) providing a polyamide composition according to claim 1; (b) preparing a substantially liquid melt of the polyamide composition; and (c) conducting a liquid-assisted injection moulding process in order to obtain the article.

14. An article comprising at least the polyamide composition according to claim 1.

15. An article obtained by the process according to claim 13.

Description

EXAMPLES

[0136] Preparation of the polyamide compositions:

[0137] As examples and comparative examples, several polyamide compositions were prepared.

[0138] The following components were used as starting materials:

[0139] Component (i): [0140] (i-a) PA6.6 homopolymer [0141] (i-b) PA6.6/6 copolymer having a molar composition of repeating units derived from hexamethylene diamine:adipic acid:-caprolactam of 45.0%:45.0%:10.0%(in mol-% each)

[0142] Component (ii):

[0143] (ii-a) PA6.6/6.T copolymer having a molar composition of repeating units derived from hexamethylene diamine:terephthalic acid:adipic acid of 50.0%:32.5%:17.5% (in mol-% each)

[0144] (ii-b) PA6.T/6.I copolymer having a molar composition of repeating units derived from hexamethylene diamine:terephthalic acid:isophthalic acid of 50.0%:35.0%:15.0% (in mol-% each)

[0145] Component (iii): [0146] (iii) glass fibre chopped strands having an average length of 4.5 mm and an average diameter of 10 m

[0147] Component (iv): [0148] (iv-a) glass beads having an average diameter of 20 m [0149] (iv-b) glass beads having an average diameter of 40 m [0150] (iv-c) glass beads having an average diameter of 5 m [0151] (iv-d) glass beads having an average diameter of 100 m

[0152] Component (v): [0153] (v) copper salts as heat stabilizer

[0154] Component (vi): [0155] (vi-a) ethylene bis-stearamide as mould release agent [0156] (vi-b) colorants (solvent black/nigrosine) [0157] (vi-c) modified ethylene bis-stearamide (TAF, surface improvement agent)

[0158] Component (vii) [0159] (vii) PA6 homopolymer

[0160] Component (viii): [0161] (viii) PA6.10 homopolymer

[0162] Component (ix): [0163] (ix) PA6/6T copolymer

[0164] Compositions for moulding according to the invention were prepared by mixing in a twin-screw type extruder ZSK 18 W at a rate of 12 kg/h and a rotation speed of equal screw 300 rev/min, at a temperature in the range of from 265 C. to 340 C., depending on the formulation of the various components and amounts as disclosed in Table 1 below.

TABLE-US-00001 TABLE 1 Composition of Comparative Examples C1 to C5 and Examples E1 to E9 according to the invention. Examples Components C1 C2 E1 C3 E2 E3 C4 E4 C5 E5 (i-a) 67 57 61 63 47 46.7 27 11 67 51 (i-b) 40 40 (ii-a) 6 16 16 16 16 (ii-b) (iii) 20 20 20 20 20 20 20 20 23 23 (iv-a) 10 10 10 10 10 10 10 10 7 7 (iv-b) (iv-c) (iv-d) (v) 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 (vi-a) 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 (vi-b) 2 2 2 2 2 2 2 2 2 2 (vi-c) 0.3 (vii) 10 4 4 4 (viii) (ix) Components E6 E7 E8 E9 C6 C7 E10 E11 E12 E13 (i-a) 47 47 47 47 0 47 16 47 47 (i-b) (ii-a) 16 16 16 16 47 16 16 16 (ii-b) 20 (iii) 23 23 23 23 23 23 23 7 23 23 (iv-a) 7 7 7 7 7 7 23 (iv-b) 7 (iv-c) 7 (iv-d) 7 (v) 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 (vi-a) 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 (vi-b) 2 2 2 2 2 2 2 2 2 2 (vi-c) (vii) 4 4 51 4 4 4 4 4 (viii) 4 (ix) 16 indicates data missing or illegible when filed

[0165] Samples were prepared from each of these compositions C1 to C5 and E1 to E9 in accordance with the demands described below.

[0166] The following properties were determined:

[0167] Tensile Strength:

[0168] Tensile strength was determined according to ISO 527-2/1A. Values are given in MPa

[0169] Flexural strength:

[0170] Determination of flexural strength at maximum load was carried out according to ISO 178 with test samples having a size of 506 mm and a thickness of 4 mm. Support separation: 40 mm. Test rate was 14 mm/min. Values are given in MPa.

[0171] Charpy unnotched impact strength:

[0172] Charpy unnotched impact strength was determined according to ISO 179/1eU with test samples having a size of 506 mm and a thickness of 4 mm. Support separation: 40 mm. Test equipment: 4 J pendulum impact tester. Values are given in kJ/m.sup.2.

[0173] Charpy notched impact strength:

[0174] Charpy notched impact strength was determined according to ISO 179/1eA with test samples having a size of 506 mm and a thickness of 4 mm. Support separation: 40 mm. Test equipment: 4 J pendulum impact tester. A 0.8 mm-wide U-shaped notch was made on the broad side of the specimens. The notch depth was of the specimen thickness. The edges outlining the notch root had a curvation radius of <0.1 mm. Values are given in kJ/m.sup.2.

[0175] Heat deformation temperature:

[0176] Heat deformation temperature was determined at 1.82 MPa according to ISO 75/Af. Values are given in C.

[0177] Flexural strength after aging

[0178] Flexural strength after aging was determined after aging the specimen (prepared by injection molding according to DIN EN ISO 527-2/1A) in a glycol/water mixture (1:1 by weight) at 130 C. for 1000 hours. Following the aging process, flexural strength was determined according to DIN EN ISO 178 at room temperature with the undried specimen after 1 hour. Values are given in MPa.

[0179] Gloss with flat chip:

[0180] Surface gloss was tested using a Benchtop Spectrophotometer (model Ci7800 manufactured by X-rite, Inc.). The testing was made in gloss test. The specimens were flat chips having dimensions of 962 mm.

[0181] Spiral flow:

[0182] The polyamide composition is melted and then injected into a spiral shaped moulding cavity mounted on an injection-moulding machine under real processing conditions. The spiral length with 2 mm thickness can be determined as a function of melt temperature, injection pressure and the mould temperature and is a direct measure for the flowability (i.e. viscosity) of the polyamide composition.

[0183] Results of the tests:

[0184] The results of the tests for all Examples and Comparative Examples are summarized in Table 2.

[0185] As shown in Table 1, Comparative Example C1 is a PA6.6 based composition filled with glass fibres and glass beads. C1 exhibits a gloss with flat chip of 76.8.

[0186] In Comparative Example C2, 10 wt.-% of the PA6.6 are substituted by PA6, a well-known additive to improve the surface of glass fibre filled PA66 compositions (cf. Table 1). The gloss is improved from 76.8 to 90.3 (cf. Table 2).

[0187] However, according to inventive Example E1, substituting 6 wt.-% of PA6.6 by PA6.6/6.T results in an improvement of surface gloss with flat chip to 91.6 (cf. Tables 1 and 2). Thus, although E1 comprises only 6 wt.-% of PA6.6/6.T compared to 10 wt.-% of PA6 used in Comparative Example C2, a higher surface gloss was achieved (91.6 for Example E1 compared to 90.3 for Comparative Example C2). PA6.6/6.T thus results in significantly higher surface improvement compared to PA6.

[0188] Moreover, flexural strength of the PA6 containing sample according to Comparative Example C2 was significantly deteriorated after aging in glycol/water. Comparative Example E1 exhibits a value for 70 MPa, which decreases to 46 MPa for Comparative Example 2 comprising PA6. By contrast, introducing PA6.6/6.T resulted in only far lower decrease of flexural strength after aging from 70 MPa (Comparative Example C1) to 63 MPa (Example E1).

[0189] In addition also the further determined mechanical properties such as tensile strength, flexural strength, Charpy unnotched impact strength, Charpy notched impact strength, heat deformation temperature, and spiral flow remain substantially unchanged in Example E1 compared to Comparative Example C1.

TABLE-US-00002 TABLE 2 Properties of the Comparative Examples C1 to C5 and inventive Examples E1 to E9. Examples Properties C1 C2 E1 C3 E2 E3 C4 E4 C5 E5 Tensile 141 138 140 141 144 144 140 138 148 158 Strength [MPa] Flexural 210 205 207 209 205 205 209 202 220 231 strength [MPa] Charpy 48 54 46 51 45 46 51 43 50 54.9 unnochted impact strength [kJ/m.sup.2] Charpy 6.3 6.6 6.3 6.5 6.2 6.4 6.8 6.2 7.5 8 notched impact strength [kJ/m.sup.2] Heat 236 229 234 230 227 226 217 215 238 233 deformation temperature at 1.82 mPa Flexural 70 46 63 58 43 43 28 16 73 73.9 strength after aging [MPa] Gloss with 76.8 90.3 91.6 70.4 96 91 94 96.6 77.7 93.6 flat chip Spiral flow 58.8 53.6 57.1 49.5 57.3 60.2 58.5 60.9 59 59.5 [mm] Properties E6 E7 E8 E9 C6 C7 E10 E11 E12 Tensile 158 150 158 152 160 162 156 96 173 Strength [MPa] Flexural 226 223 229 214 236 244 240 158 252 strength [MPa] Charpy 53.6 44.9 50 35.7 57 59 46 31 64 57 unnochted impact strength [kJ/m.sup.2] Charpy 7.6 7.5 7.9 7.1 8.51 8.43 8.53 3.71 9.32 9.21 notched impact strength [kJ/m.sup.2] Heat 232 230 232 232 197 221 238 189 235 235 deformation temperature at 1.82 mPa Flexural 59 54 67.7 65.2 29 41.7 55 26.3 56.4 56 strength after aging [MPa] Gloss with 98.4 96.45 96.9 91.2 99 98.3 99.1 98.7 97.2 flat chip Spiral flow 59.4 62.6 60.1 36.9 65.8 59.7 62 64.3 59.3 [mm] indicates data missing or illegible when filed

[0190] The comparison of Comparative Example C3 and Examples E2 and E3 reveals that also the properties of blends of PA6.6 and PA6 comprising glass fibres may further be improved by the addition of PA6.6/6.T (cf. Tables 1 and 2). Just like Comparative Example C1, all three Examples C3, E2 and E3 comprise a sum of about 67 wt.-% of polyamide. However, in each of the three examples C3, E2 and E3, 4 wt.-% of the PA6.6 is replaced by PA6. Additionally in

[0191] Examples E2 and E3, further 16 wt.-% of the PA6.6 is replaced by 16 wt.-% of PA6.6/6.T (Example E2, cf. Table 1) or by 15.7 wt.-% of PA6.6/6.T and 0.3 wt.-% of TAF, a modified ethylene bis-stearamide which is reported to improve the surface of glass fibre filled polymer compositions (Example E3, cf. Table 1).

[0192] As can be seen in Table 2, substituting 16 wt.-% of the PA6.6 of the polyamide composition according to Comparative Example C3 results in an improvement of the surface gloss from 70.4 to 96 in Example E2. The incorporation of TAF, however, failed to further improve surface gloss. In contrast, Example E3 resulted in a lower gloss than E2 (96 for Example E2 compared to 91 for Example E3, cf. Table 2). However, both Examples E2 and E3 have a substantially higher surface gloss than Comparative Example C3.

[0193] In addition also the further determined mechanical properties such as tensile strength, flexural strength, Charpy unnotched impact strength, Charpy notched impact strength, heat deformation temperature, and spiral flow remain substantially unchanged in Examples E2 and E3 compared to Comparative Example C2. Flexural strength of Examples E2 and E3 remains above 43.

[0194] Comparative Example C4 and Example E4 demonstrate the effect of the invention in polyamide compositions comprising PA6.6 and PA6.6/6. Again, both example compositions comprise 67 wt.-% of polyamides. In particular, both comprise 40 wt.-% of PA6.6/. Comparative Example C4 further comprises 27 wt.-% of PA6.6, whereas Example E4 comprises 11 wt.-% of PA6.6 and 16 wt.-% of PA6.6/6.T (cf. Table 1. The remainder is identical in both compositions.

[0195] As can be seen in Table 2, surface gloss is improved from 94 for Comparative Example C4 to 96.6 for Example E4. In addition, also the further determined mechanical properties such as tensile strength, flexural strength, Charpy unnotched impact strength, Charpy notched impact strength, and heat deformation temperature remain substantially unchanged in Example E4 compared to Comparative Example C4. Moreover, spiral flow is improved.

[0196] Compared to the previous discussed examples and comparative examples, Comparative Example C5 and Examples E5 to E9 comprise a higher amount of glass fibre filler (23 wt.-% instead of 20 wt.-%), whereas the overall amount of filler remains unchanged at 30 wt.-% (cf. Table 1).

[0197] Comparative Example C5 comprises PA6.6 as only polyamide and exhibits a surface gloss of 77.7. By replacing 16 wt.-% of the PA6.6 by PA6.6/6.T (cf. Example E5 in Table 1), in improvement of gloss from 77.7 to 93.6 is observed (cf. Comparative Example E5 and Example E5 Table 2).

[0198] In Example E6, further 4 wt.-% of PA6.6 were substituted by PA6 compared to Example E5 (cf. Table 1) while maintaining the total amount of polyamide unchanged. This results in a further improvement of the surface gloss from 93.6 for Example E5 (or 77.7 for Comparative Example C5, respectively) to 98.4 for Example E6 (cf. Table 2). Example 7 differs from Example 6 in comprising glass beads with an average particle diameter of 40 m instead of 20 m. Comparable results are obtained.

[0199] In Example E8, further 4 wt.-% of PA6.6 were substituted by PA6.10 compared to Example E5 (cf. Table 1) while maintaining the total amount of polyamide unchanged. This also results in an improvement of the surface gloss from 93.6 for Example E5 (or 77.7 for Comparative Example C5, respectively) to 96.9 for Example E8 (cf. Table 2).

[0200] In Example E9, further 20 wt.-% of PA6.6 were substituted by PA6.T/6.I compared to Comparative Example C5 (cf. Table 1) while maintaining the total amount of polyamide unchanged. This results in a further improvement of the surface gloss from 77.7 for Comparative Example C5 to 91.2 for Example E9 (cf. Table 2).

[0201] In addition, also further mechanical properties are improved. For example, tensile strength before aging is improved for all Examples E5 to E9 compared to Comparative Example C5. On the other hand, the tensile strength after aging in glycol/water mixture is only slightly deteriorated for Examples E5 to E9 and in particular Examples E5, E8 and E9 compared to Comparative Example C5. Likewise, good results or even improvements in properties such as flexural strength, Charpy unnotched impact strength, Charpy notched impact strength, heat deformation temperature, and spiral flow were observed and often remained substantially unchanged in Examples E5 and E9 compared to Comparative Example C5.

[0202] Comparative Example C6 demonstrates the advantageous effects of the presence of PA6.6 or a copolymer thereof in the composition. Since major application of the compositions of the invention are coolant tubes, excellent coolant resistance is needed. If PA6.6 is replaced with PA6, a significant decline in the glycol resistance is observed. Moreover, the heat deformation temperature decreases.

[0203] Comparative Example C7 demonstrates the advantageous effects of the presence of PA6.6/6.T as compared to PA6/6.T in the composition. If PA6.6/6T is replaced with PA6/6T, a significant decline in glycol resistance is observed. Moreover, the heat deformation temperature decreases.

[0204] Example E10 demonstrates the advantageous effects due to the amount (ratio) of PA6.6 and PA6.6/6.T in the composition. The ratio of PA6.6 to PA 6.6/6T affects the Charpy unnotched impact and glycol resistance.

[0205] Example E11 demonstrates the relevance of the amount (ratio) of fibrous and particulate filler for the observed technical effect. The ratio affects the mechanical properties, the heat deformation temperature and the glycol resistance.

[0206] Examples E12 and E13 demonstrate the influence of particle fillers having particle diameters of more than 60 m and less than 20 m, respectively.

[0207] Conclusion:

[0208] The above examples and comparative examples show that the surface properties, in particular surface gloss of an article prepared from a polyamide composition comprising at least one aliphatic polyamide, at least one semi-aromatic polyamide, at least one fibrous filler, at least one particulate filler, at least one heat stabilizer, and at least one further additive as defined above, is significantly improved compared to polyamide compositions which do not comprise the at least one semi-aromatic polyamide. At the same time, further mechanical properties typically remain substantially unchanged. In particular, the polyamide composition in accordance with the present invention exhibits a good resistance towards alcohols, in particular glycols, as indicated by the comparably good flexural strength after aging was determined after aging the sample in a glycol/water mixture (1:1 by weight) at 130 C. for 1000 hours. The polyamide compositions are therefore exceptionally well suited to be used in the production of articles which are intended to be in contact with glycol and glycol mixtures, such as hollow articles to be used in the automotive industry.