Semi-aromatic polyamide
The invention relates to a semi-aromatic polyamide, and a polyamide composition comprising the semi-aromatic polyamide, comprising a diamine component (a) comprising, based on the total number of moles of the diamine component (a): between 5 and 30 mole % of at least one C2-C5 diamine, between 5 and 30 mole % of at least one C7+ diamine, and between 45 and 90 mole % of a C6 diamine; and a dicaboxylic acid component (b) comprising, based on the total number of moles of the dicaboxylic acid component (b): at least 50 mole % of terephthalic acid and at most 50 mole % of another dicarboxylic acid.
1. A semi-aromatic polyamide comprising a diamine component (a) and a dicarboxylic acid component (b), wherein
the diamine component (a) comprises, based on the total molar amount of the diamine component (a):
(a1) 5-30 mole % of at least one C2-C5 diamine,
(a2) 5-30 mole % of 1,10-decanediamine, and
(a3) 50-90 mole % of a C6 diamine which consists of at least 75 mole %, relative to the total molar amount of C6 diamine, of 1,6-hexanediamine; and wherein
the dicarboxylic acid component (b) comprises, based on the total molar amount of the dicaboxylic acid component (b):
(b1) at least 60 mole % of terephthalic acid, and
(b2) at most 40 mole % of another dicarboxylic acid, and wherein
the semi-aromatic polyamide has a melting temperature (Tm) in a range of 310-340° C. as measured according to ASTM D3418-97 by differential scanning calorimetry (DSC) with a heating rate of 20° C./minute.
2. The semi-aromatic polyamide according to claim 1 , wherein a molar amount of the 1,10-decanediamine is larger than a molar amount of the C2-C5 diamine.
3. The semi-aromatic polyamide according to claim 1 , wherein the C2-C5 diamine is present in an amount of 5-15 mole %, and/or the 1,10-decanediamine is present in an amount of 10-25 mole %, relative to the total molar amount of the diamine component (a).
4. The semi-aromatic polyamide according to claim 1 , wherein the C2-C5 diamine is 1,4-butane diamine.
5. The semi-aromatic polyamide according to claim 1 , which comprises terephthalic acid in an amount of 60-90 mole %, relative to the molar amount of the dicaboxylic acid component (b).
6. The semi-aromatic polyamide according to claim 1 , having a melting temperature (Tm) in the range of 310-330° C.
7. The semi-aromatic polyamide according to claim 1 , having a glass transition temperature (Tg) in the range of 105-130° C.
8. A process for preparing the semi-aromatic polyamide according to claim 1 , which comprises:
a first step of preparing a prepolymer from a mixture of the dicarboxylic acid components (b1) and (b2), and the diamine components (a1) and (a3) while omitting from the mixture an amount of the 1,10-decanediamine component (a2) thereby resulting in a prepolymer comprising predominantly carboxylic acid end groups, and
a second step of adding the amount of the 1,10-decanediamine component (a2) withheld from the mixture in the first step to a melt of the prepolymer formed by the first step and further polymerizing the prepolymer to thereby obtain the semi-aromatic polyamide polymer.
9. A polyamide composition, consisting of:
(A) 30-100 wt. % of the semi-aromatic polyamide as in claim 1 ,
(B) 0-70 wt. % of reinforcing agents and/or fillers, and
(C) 0-50 wt % of other additives and/or other polymers.
10. A molded part consisting of a semi-aromatic polyamide according to claim 1 .