Crosslinking of Polyamides in the Melt

Abstract

The present invention relates to a process for preparing a crosslinked polyamide (vP) by providing a melt (S), which comprises at least one polyamide (P) containing furan units and at least one dienophile at a first temperature T.sub.1, and cooling the melt (S) subsequently to a second temperature T.sub.2 which is below the melting temperature T.sub.M of the at least one polyamide (P), to give the crosslinked polyamide (vP). The present invention further relates to a crosslinked polyamide (vP) obtainable by the process of the invention.

Claims

1. A process for preparing a crosslinked polyamide (vP), comprising the steps of i) providing a melt (S) which comprises components A) at least one polyamide (P) having a melting temperature T.sub.M and comprising diene units of the general formula (I) ##STR00004## in which R.sup.1 and R.sup.2 independently of one another are selected from C.sub.1-C.sub.10 alkanediyl, B) at least one dienophile which comprises at least two dienophile units which are reactive toward the diene units present in component A), at a first temperature T.sub.1 which is above the melting temperature T.sub.M of component A), ii) cooling the melt (S) to a second temperature T.sub.2 which is below the melting temperature T.sub.M of component A), to give the crosslinked polyamide (vP).

2. The process according to claim 1, wherein component A) reacts with component B) in step ii) in a [4+2]-cycloaddition to give the crosslinked polyamide (vP).

3. The process according to claim 1, wherein component A) has a glass transition temperature T.sub.G and the second temperature T.sub.2 in step ii) is above the glass transition temperature T.sub.G of component A).

4. The process according to claim 1, wherein the first temperature T.sub.1 in step i) is in the range from 90 to 380 C.

5. The process according to claim 1, wherein the second temperature T.sub.2 in step ii) is in the range from 80 to 300 C., the second temperature T.sub.2 being lower than the first temperature T.sub.1.

6. The process according to claim 3, wherein the glass transition temperature T.sub.G of component A) is in the range from 0 to 150 C.

7. The process according to claim 1, wherein the melting temperature T.sub.M of component A) is in the range from 80 to 330 C.

8. The process according to claim 1, wherein the at least two diene units present in component B) are selected independently of one another from the group consisting of CC double bonds, CO double bonds, and CS double bonds.

9. The process according to claim 1, wherein component B) comprises at least two structural units each selected from the group consisting of bismaleimide, benzophenone, acrylates, methacrylates, acrylonitriles, maleic acid, maleic anhydride, and maleic esters.

10. The process according to claim 1, wherein the melt (S) additionally comprises as component C) in the range from 0 to 2 wt % of at least one endgroup regulator, based on the sum of the wt % of the components A), B), and C) present in the melt (S).

11. The process according to claim 10, wherein component C) is selected from the group consisting of propionic acid, benzoic acid, naphthoic acid, and succinic anhydride.

12. The process according to claim 1, wherein the melt (S) additionally comprises as component D) in the range from 0.5 to 5 wt % of at least one radical scavenger, based on the total weight of the components A), B), C), and D) present in the melt (S).

13. The process according to claim 12, wherein component D) is selected from the group consisting of copper salts, aromatic amines, sterically hindered amines (HALS), sterically hindered phenols, phosphites, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and derivatives of 2,2,6,6-tetramethylpiperidine-1-oxyl.

14. The process according to claim 1, wherein the melt (S) comprises the following components: A) from 83 to 99 wt % of component A), B) from 0.5 to 10 wt % of component B), C) from 0 to 2 wt % of at least one endgroup regulator, D) from 0.1 to 5 wt % of at least one radical scavenger, based in each case on the sum of the wt % of the components A) to D) present in the melt (S).

15. A crosslinked polyamide (vP) obtainable by a process of claim 1.

Description

EXAMPLES

[0210] In the examples the following components were used: [0211] A) PA 6/F6 (80/20) (/w), copolymer of caprolactam (80 wt %) with 2,5-bis(aminomethyl)furan and adipic acid (together 20 wt %). [0212] A) PA 6 with a relative viscosity in 1% H.sub.2SO.sub.4 of 2.2 (Ultramid B22, BASF SE) [0213] B1) Bis(maleimidophenyl)methane (CAS 13676-54-5) [0214] B2) Bis(3-ethyl-5-methyl-4-maleimidophenylmethane) (CAS 105391-33-1) [0215] B3) N,N-1,3-bis(maleimido)benzene (CAS 3006-93-7) [0216] C) Succinic anhydride (CAS 108-30-5) [0217] D) 4-Hydroxy-TEMPO (2226-96-2)

[0218] Preparation of the Crosslinked Polyamides (VP)

[0219] The crosslinked polyamides (vP) were produced in a DSM miniextruder with conical twin screw and attached injection molding unit. For this purpose the melt, composed of component A) and/or A) and also, optionally components B1), B2), B3), C), and D), was provided at 230 C. and mixed for 5 minutes. Thereafter tensile bars (type 1 according to ISO 37:2011 (E)) were produced by injection molding, the melt (S) having been cooled in accordance with step ii). The mold temperature (corresponding to the second temperature T.sub.2), the extruder temperature (corresponding to the first temperature T.sub.1), the pressure, and the duration are reported in table 1.

[0220] Characterization of the Crosslinked Polyamides (VP)

[0221] The properties reported in table 1 for the crosslinked polyamides (vP) were determined as follows: [0222] weight-average molecular weight M.sub.w; number-average molecular weight M.sub.n: measured after filtration through Millipore Millex FG (0.2 m) filters in hexafluoroisopropanol+0.05% potassium trifluoroacetate on a styrene-divinylbenzene column with PMMA standard from 0.8 kDa to 1820 kDa. Measurement at 35 C. with 1 mL/min flow rate and 1.5 mL/mg sample concentration [0223] VN (viscosity number): 0.5 g/ml polymer was dissolved in phenol/ortho-dichlorobenzene (1:1) and then the viscosity number was determined (in accordance with ISO 307) [0224] E-Modulus (modulus of elasticity): measured according to ISO 527-2 (2012) [0225] Yield stress: measured according to ISO 527-2 (2012) [0226] Yield strain: measured according to ISO 527-2 (2012) [0227] Breaking stress: measured according to ISO 527-2 (2012) [0228] Flow behavior (rheology): measured at 230 C. on a DHR-1 rotational rheometer from TA Instruments with plate/plate geometry (diameter 25 mm, height 1.0 mm-1.6 mm). Preheat time 1.5 min and 1.0% deformation in the frequency sweep and 10% deformation in the time sweep). The loss modulus and the storage modulus were determined. Prior to the measurement, the samples were dried under reduced pressure at 80 C. for 7 days. [0229] tan : for the determination of the Tan (loss factor), the ratio of loss modulus to storage modulus was ascertained, the loss modulus and the storage modulus having been determined by means of rheology.

TABLE-US-00001 TABLE 1 V1 2 3 4 5 V6 7 8 V11 A) 98.3% 97.3% 96.3% 94.3% 92.3% 94.3% 94.3% 100% A) 94.3% B1) 1.0% 2.0% 4.0% 6.0% 4.0% B2) 4.0% B3) 4.0% C) 1.0% 1.0% 1.0% 1.0% 1.0% 1.0% 1.0% 1.0% D) 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% VN 58.1 73.3 81.4 86.3 87.9 113.5 95.2 105.1 98.2 E-Modulus [MPa] 2274 3153 3316 3237 3238 3026 3330 3336 2108 Yield stress [MPa] 70.96 93.54 96.19 95.33 95.03 85 97.47 96.15 73.46 Yield strain [%] 3.39 3.68 3.64 3.73 3.75 3.97 3.75 3.67 3.78 Breaking stress [MPa] 62.01 61.02 78.06 76.62 75.22 67.25 77.83 77.96 63.24 M.sub.w [g/mol] (GPC) 88 000 47 800 M.sub.n [g/mol] (GPC) 12 300 16 700 tan [10 rad/s] after 8.98 2.11 1.27 0.7 10.7 30 minutes Solubility of sample in 96% yes no no no H.sub.2SO.sub.4 after rheology measurement. (30 min, 210 C.) (T(H.sub.2SO.sub.4) = 23 C.) Solubility of sample in 96% yes yes yes yes H.sub.2SO.sub.4 after rheology. (30 min, 210 C.) (T(H.sub.2SO.sub.4) = 100 C.) Injection molding: Mold temperature [ C.] 60 55 55 55 55 55 55 55 55 Extruder temperature [ C.] 230 230 230 230 230 230 230 230 230 Pressure [bar] 8 10 10 12 12 9 12 12 12 Duration [s] 9 9 9 9 9 9 9 9 9

[0230] The crosslinked polyamides (vP) produced in accordance with the invention are notable for particularly high modulus of elasticity, particularly high yield stress, high breaking stress, high yield strain, and reduced solubility in sulfuric acid.