STABILIZER FOR POLYAMIDES

Abstract

The present invention relates to a thermoplastic composition that provides improved thermal aging stability. The thermoplastic composition includes a polyamide resin, glass fibers, tin(II) oxalate, and a functional additive. It has been found that a combination of a polyamide resin with tin(II) oxalate and a functional additive produces a superior product demonstrating greater thermal stability than the polyamide resin alone.

Claims

1. A thermoplastic composition, comprising: a) a polyamide resin; b) reinforcing fibers; c) tin(II) oxalate; and d) a functional additive.

2. A thermoplastic composition, comprising: a) 30 to 99.9% of a polyamide resin; b) 0 to 70% of reinforcing fibers; c) 0.01 to 10% of tin(II) oxalate; and d) 0.1 to 20% of a functional additive.

3. The thermoplastic composition of claim 1, wherein the polyamide resin is at least one selected from the group consisting of Nylon 6, Nylon 6,6, Nylon 6,12, Nylon 4,6, Nylon 6,10, Nylon 7, Nylon 10, Nylon 10, 10, Nylon 12, Nylon 12, 12, Nylon 9T, Nylon 10 T, Nylon 6T, Nylon 6T/61, Nylon 6T/DT, and Nylon MXD-6.

4. The thermoplastic composition of claim 1, wherein the polyamide resin is semicrystalline polyphthalamide.

5. The thermoplastic composition of claim 1, wherein the reinforcing fibers is glass fibers.

6. The thermoplastic composition of claim 1, wherein the functional additive is polyalkenylene.

7. The thermoplastic composition of claim 1, further comprising at least one additive selected from the group consisting of lubricants, glass fillers, mineral fillers, impact modifiers, plasticizers, pigments, dyes, antioxidants, heat stabilizers, hydrolysis stabilizers, nucleating agents, flame retardants, synergists, drip suppressants, and blowing agents.

8. The thermoplastic composition of claim 1, wherein, after 1000 hours of hot air testing at 230 C., the thermoplastic composition is capable of retaining greater than 60% of its tensile strength.

Description

EXAMPLES

[0031] The following Examples demonstrate the present invention and its capability for use, The invention is capable of other and different embodiments, and its several details are capable of modifications in various apparent respects, without departing from the scope and spirit of the present invention. Accordingly, the Examples are to be regarded as illustrative in nature and non-limiting.

[0032] The following examples were performed using semicrystalline polyphthalamide (PPA) resin commercially available from EVONIK INDUSTRIES AG under the trade name VESTAMID Htplus M1000 Commercially available glass fibers were used, such as CHOPVANTAGE HP 3610 chopped glass fiber available from PPG Fiber Glass. A masterbatch of 80% polyalkenylene (VESTENAMER 8012) and 20% tin(II) oxalate was used. Tin(II) oxalate was commercially available from SIGMA-ALDRICH. Polyalkenylene under the trade name VESTENAMER 8012 was commercially available from EVONIKINDUSTRES AG.

[0033] Formulations were prepared by melt blending semicrystalline polyphthalamide (VESTAMID Htplus M1000) and the masterbatch of polyalkenylene (VESTENAMER 8012) and tin(II) oxalate in a 27 mm twin screw extruder. The extruder was maintained at about 320 C. with a screw speed of about 300 rpm, and a throughput of 20 kg/hour. The glass fibers were added to the melt through a screw side feeder and the compounded mixture was extruded in the form of strands, cooled in a water bath, chopped into pellets, dried at 120 C. for 16 hours. The pellets were tested for moisture content level of 0.1% and then injection molded as standard ISO tensile bars.

[0034] The tensile strength and elongation at break were measured according to ISO 527. The tests were performed using injection molded ISO tensile bars. The hot air aging tests were performed by according to the ISO 2578 testing method. Samples were heat aged in re-circulating air ovens to simulate aging conditions. At specific intervals of heat aging, the samples were removed from the oven and allowed to cool in a temperature and humidity controlled room. Finally, the aged samples and corresponding controls were conditioned for 16 hours before tested for mechanical and thermal properties.

TABLE-US-00001 TABLE 1 C1 Ex1 C2 Ex2 Ex3 Ex4 C3 Ex5 Ex6 VESTAMID HT plus M1000 100 94 70 65 60 55 50 45 40 Glass Fibers HP 3610 30 30 30 30 50 50 50 VESTENAMER 8012 * 4.8 4 8 12 4 8 Tin(II) Oxalate * 1.2 1 2 3 1 2 Aging at 230 C. Stress at break (MPa) 0 hr 103 81 216 189 170 155 288 234 195 500 hr 4 22 39 134 145 140 32 172 155 1000 hr 0 12 29 88 97 99 4 120 97 Aging at 230 C. Stress at break (normalized, %) 0 hr 100 100 100 100 100 100 100 100 100 500 hr 4 27 18 71 85 91 11 74 79 1000 hr 0 15 13 46 57 64 1 51 50 * a masterbatch of 80% VESTENAMER 8012 and 20% Tin(II) Oxalate has been used *C = Comparison Example Ex = Example Invention

[0035] Table 1 shows the results of resins with varying amounts of the master batch of polyalkenylene (VESTENAMER 8012) and tin(II) oxalate. The samples where tested for heat aging at 230 C. for 0 hr, 500 hrs, and 1000 hrs. Comparison of C1 with Ext (without glass fibers) shows the positive influence of VESTENAMER 8012/tin(II) oxalate with respect to heat aging. Comparison of C2 with Ex2 to Ex4 (with 30% of glass fibers) shows the positive influence of VESTENAMER 8012/tin(II) oxalate with respect to heat aging. Comparison of C3 with Ex5 and Ex6 with (50% of glass fibers) shows the positive influence of VESTENAMER 8012/tin(II) oxalate with respect to heat aging. For better comparison the normalized values for stress at break are also given. VESTENAMER 8012, also acts like an impact modifier. As the content of VESTENAMER 8012 increases the stress at break decreases.