COPOLYAMIDE COMPOSITIONS COMPRISING REINFORCING FIBERS AND HAVING HIGH MODULUS STABILITY AND USES THEREOF

Abstract

A copolyamide including at least two distinct units A and X.sub.1Y of formula A/X.sub.1Y, wherein: A is a repeating unit obtained by polycondensation of: at least one C.sub.9 to C.sub.18 amino acid, or at least one C.sub.9 to C.sub.18 lactam, or at least one C.sub.4-C.sub.36 dicarboxylic acid Cb; X.sub.1Y is a repeating unit obtained from the polycondensation of at least one C.sub.9 to C.sub.18 linear aliphatic diamine (X.sub.1), and at least one aromatic dicarboxylic acid (Y), to prepare a composition comprising between 35 and 65% of reinforcing fibers, relative to the total weight of the composition, and for which the flexural modulus or tensile modulus, measured after an identical conditioning, does not vary by more than 20% in the temperature range from 20° C. to 40° C.

Claims

1. A use of a copolyamide comprising at least two distinct units A and X.sub.1Y of the formula A/X.sub.1Y, wherein: A is a repeating unit obtained by polycondensation: of at least one C.sub.9 to C.sub.18 amino acid, or of at least one C.sub.9 to C.sub.18 lactam, or of at least one C.sub.4-C.sub.36 diamine Ca with at least one C.sub.4-C.sub.36 dicarboxylic acid Cb; said at least one diamine Ca being a linear or branched aliphatic diamine, and said at least one Cb diacid being a linear or branched aliphatic diacid, X.sub.1Y is a repeating unit obtained from the polycondensation of at least one C.sub.9 to C.sub.18 linear aliphatic diamine (X.sub.1) and at least one aromatic dicarboxylic acid (Y), for preparing a composition comprising between 35 and 65% by weight of reinforcing fibers, relative to the total weight of the composition, and whose flexural modulus or tensile modulus, measured after identical conditioning, does not vary by more than 20% in the temperature range from 20° C. to 40° C.

2. The use according to claim 1, wherein X.sub.1Y is a repeating unit obtained by polycondensation of at least one C.sub.10 to C.sub.18 aliphatic diamine (X), and at least one aromatic dicarboxylic acid (Y).

3. The use according to claim 1, wherein Y is the terephthalic acid.

4. The use according to claim 1, wherein X.sub.1Y is a unit selected from units 10T, 12T and a mixture thereof.

5. Use according to claim 1, where in the copolyamide with the formula A/X.sub.1Y, A is an amino acid or a lactam.

6. The use according to claim 1, wherein in the copolyamide with the formula A/X.sub.1Y, A is a C.sub.11 or C.sub.12 amino acid or lactam.

7. The use according to claim 1, wherein said copolyamide is semi-crystalline.

8. The use according to claim 1, wherein said copolyamide consists solely of the units A and X.sub.1Y of formula A/X.sub.1Y.

9. The use according to claim 1, wherein said copolyamide comprises at least one third unit Z, distinct from the A and X.sub.1Y units, and corresponds to the general formulation A/X.sub.1Y/Z wherein: the units A and X.sub.1Y are as defined in claim 1, Z is chosen from a unit obtained from an amino acid, a unit obtained from a lactam and a unit having the formula (Cc diamine).Math.(Cd diacid), with c representing the number of carbon atoms in the diamine and d representing the number of carbon atoms in the diacid, c and d each being between 4 and 36, with the proviso that the caprolactam or aminohexanoic acid are excluded from the definition of the lactam and the amino acid of Z and that when the Cc diamine is a C6 diamine, then terephthalic acid is excluded from the definition of the Cd diacid.

10. The use according to claim 9, wherein said copolyamide consists only of three units of the formula A/X.sub.1Y/Z.

11. The use according to claim 10, wherein the reinforcing fibers are selected from glass fibers and carbon fibers, or a mixture thereof.

12. A composition, particularly useful for injection molding, comprising: from 35 to 70% by weight of at least one copolyamide as defined in claim 1, between 35 and 65% by weight of reinforcing fibers; from 0 to 10% by weight of at least one impact modifier; from 0 to 20% by weight of at least one filler; and from 0 to 5% by weight of at least one fluidifying agent; and from 0 to less than 2% by weight of additives, with the proviso that the ratio by weight of reinforcing fibers to copolyamide does not exceed 1.75 when the reinforcing fibers are non-circular in cross-section and have a cross-sectional area from 1.5 to 5.0×10.sup.−6 cm.sup.2; the sum of the proportions of each constituent of said composition being equal to 100%.

13. The composition according to claim 12, wherein the copolyamide is selected from PA11/10T, PA11/12T, PA12/10T, PA12/12T, PA1010/10T, PA1012/10T, PA1010/12T, PA1012/12T, PA1210/10T, PA1212/10T, PA1210/12T, PA1212/12T.

14. The composition according to claim 12, wherein the reinforcing fibers are selected from glass fibers, carbon fibers, or a mixture thereof.

15. The composition according to claim 14, wherein the glass fibers are selected from glass fibers of a non-circular cross-section and glass fibers of a circular cross-section, carbon fibers, and a mixture thereof.

16. A method of manufacturing the composition as defined in claim 12, wherein the constituents of the said composition are mixed by compounding.

17. A molded article obtainable from the composition according to claim 12, by injection molding.

18. The molded article according to claim 17, for electrical applications and electronic.

Description

EXAMPLES

[0289] The invention will be explained in more detail in the following examples.

Example 1: Synthesis of the Copolyamides of the Invention

[0290] The various polyamides (comparison) and copolyamides of the invention were prepared according to the usual techniques for polyamide and copolyamide synthesis.

[0291] Synthesis of CoPa 11/10T representative of the various copolyamides:

the aminoundecanoic, decanediamine and terephthalic acid monomers are loaded together in the reactor according to the desired mass ratio. The medium is first inerted to remove the oxygen that can generate yellowing or secondary reactions. Water can also be charged to improve heat exchange. Two temperature rise and pressure plateaus are conducted. The temperature (T°) and pressure conditions are chosen to allow the medium to melt. After having reached the maintenance conditions, degassing takes place to allow the polycondensation reaction. The medium becomes viscous little by little and the reaction water formed is caused the nitrogen purge or applying a vacuum. When the stoppage conditions are reached, related to the desired viscosity, stirring is stopped and the extrusion and granulation can start. The granules obtained will then be compounded with the fiberglass.

Compounding

[0292] The compositions were prepared by mixing the polymer granules with short fibers when melted. This mixture was made by compounding on a twin-screw co-rotating MC26 type extruder with a flat temperature profile (T°) at 290° C. The screw rate is 250 rpm and the flow rate is 20 kg/h.

[0293] The introduction of the glass fibers is achieved by side feeding.

[0294] Additives and fillers are added during the compounding process in the main hopper.

[0295] The following compositions were prepared (E=Example of the invention CE=Comparative example):

TABLE-US-00001 TABLE 1 Composition E1 E2 E3 E4 E5 E6 E7 E8 CE1 CE2 11/10T 48.40 38.46 48.40 38.46 38.46 (28/72 by weight) PA1010 39.46 PA1010/10T 38.46 (28/72 by weight) PA12/10T 38.46 (28/72 by weight) PA11/12T 38.46 (28/72 by weight) PA11 39.46 Prepolymer PA11 5.00 monoNH2 Irganox ® 245 0.1 0.08 0.1 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Irgafos ® 168 0.2 0.16 0.2 0.16 0.16 0.16 0.16 0.16 0.16 0.16 Calcium stearate 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Talc Steamic 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 OOS DG Fiber with circular 50.00 60.00 55.00 60.00 60.00 cross-section CSX 451J Fiber with 50 60.00 60.00 60.00 60.00 non-circular cross-section CSG 3PA-820

[0296] Irganox® 245 and Irgafos® 168 are anti-oxidants

CSX 451J circular cross-section fiber and CSG 3PA820 non-circular cross-section fiber (also known as flat fiber) are marketed by the company Nittobo Injection
100*100*1 mm.sup.3 plates were prepared by injecting the different compositions: [0297] Injection temperature: 300° C. [0298] Mold temperature: 80° C.

[0299] The cycle time is adjusted according to the compositions to allow injection of the compositions and is less than 50 seconds.

Example 2: Variation in Flexural Modulus after Water Sorption

[0300] In order to evaluate the impact of moisture on the flexural modulus, the flexural modulus of specimens of the compositions obtained was measured on an Instron 5966 machine manufactured by the Instron company. The compositions are dried compositions and compositions saturated in water at 65° C. beforehand.

[0301] The tests were carried out at different temperatures, from −10° C. to 60° C.

[0302] In the injection-molded plates, specimens with dimensions according to ISO 178 but with a thickness of 1 mm were cut out in the direction of injection.

The results are shown in Tables 2 to 8 below:

TABLE-US-00002 TABLE 2 PA11 + 60% glass fiber circular section = CE1 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 3 20 3 16 13 40 12 31 60 27 38

TABLE-US-00003 TABLE 3 PA1010 + 60% circular glass fiber = CE2 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 3 20 2 15 18 40 9 30 60 22 39

TABLE-US-00004 TABLE 4 PA11/10T (28/72 by weight) + 50% glass fiber circular section = E modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 0 0 20 0 1 1 40 1 10 60 3 25

TABLE-US-00005 TABLE 5 PA11/10T (28/72 by weight) + 60% glass fiber circular section = E2 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 0 1 20 1 4 1 40 1 12 60 3 29

TABLE-US-00006 TABLE 6 PA11/10T (28/72 by weight) + 50% glass fiber non-circular section (flat fiber) = E3 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 0 20 1 2 2 40 1 9 60 3 23

TABLE-US-00007 TABLE 7 PA11/10T (28/72 by weight) + 60% glass fiber non-circular section (flat fiber) = E4 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 1 20 2 4 1 40 3 13 60 5 28

TABLE-US-00008 TABLE 8 PA11/10T (28/72 by weight) + 5% prepoPA11 + 55% glass fiber circular section = E5 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 0 1 20 1 5 −1 40 2 16 60 7 31

TABLE-US-00009 TABLE 9 PA1010/10T (28/72 by weight) + 60% glass fiber non-circular section (flat fiber) = E6 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 0 20 1 3 1 40 3 12 60 4 26

TABLE-US-00010 TABLE 10 PA12/10T (28/72 by weight) + 60% glass fiber non-circular section (flat fiber) = E7 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 1 20 3 4 2 40 3 14 60 5 26

TABLE-US-00011 TABLE 11 PA11/12T (28/72 by weight) + 60% glass fiber non-circular section (flat fiber) = E8 modulus loss in modulus loss in modulus ratio at 20° C. dry state (%) saturated state (%) between saturated and (M.sub.−10 − M.sub.T/ (M.sub.−10 − M.sub.T/ dry state (%) M.sub.−10) × 100 M.sub.−10) × 100 M.sub.20 saturated/M.sub.20 dry −10 0 0 0 1 2 20 2 5 2 40 4 14 60 5 28

Example 3: Variation in Tensile Modulus after Water Sorption

[0303] In order to evaluate the impact of moisture on the tensile modulus, the tensile modulus of specimens of the compositions obtained on an Instron 5966 machine manufactured by the Instron company was measured, dry compositions and compositions saturated in water at 65° C. beforehand.

[0304] The tests were carried out at different temperatures, from −10° C. to 60° C.

[0305] In the injection-molded plates, specimens with dimensions according to ISO 527 but with a thickness of 1 mm were cut out in the direction of injection.

[0306] The same trends as those observed for flexural modulus are found for tensile modulus.

[0307] Tables 2 to 8 and Example 3 show that the compositions of the invention have a higher modulus stability than the comparison compositions CE1 and CE2 for both flexural and tensile.