FORMULATION OF NOVOLAK RESINS FOR ENHANCING THE ACID RESISTANCE OF POLYAMIDE COMPOSITIONS

Abstract

Novolak resins are incorporated for enhancing the acid resistance of polyamide compositions. Polyamide compositions containing such novolak resins are useful for producing various plastic shaped articles, such as calibrated particles or injection-molded parts, and are particularly useful for the recovery of sludge, liquids, and gases present in underground reservoirs, especially in the field of hydrocarbon extraction such as crude oil or natural gas.

Claims

1. The use of a novolac resin, condensation product of a phenolic compound with an aldehyde or a ketone, for increasing the acid resistance of a polyamide composition.

2. The use as claimed in claim 1, characterised in that the polyamide is selected from the group consisting of the polyamide -6, the polyamide PA-6,6, the polyamide PA-6,10, the polyamide PA-11, the polyamide PA-12, the polyamide PA-6,12, poly(meta-xylylene adipamide), the polyamide PA-6,6/6,T, the polyamide PA-6, 6/6,I, and blends and copolyamides.

3. The use as claimed in claim 1 or 2, characterized in that said composition comprises from 40 to 90% by weight of polyamide, relative to the total weight of the composition.

4. The use as claimed in any one of claims 1 to 3, characterized in that the composition comprises from 5 to 40% by weight of novolac resin, relative to the total weight of the composition.

5. The use as claimed in any one of claims 1 to 4, characterized in that the novolac resin has a degree of condensation between 2 and 15.

6. The use as claimed in any one of claims 1 to 5, characterized in that the novolac resin is a condensation product of phenol and formaldehyde. 7. The use as claimed in any one of claims 1 to 6, characterized in that the novolac resin has a molecular weight between 500 and 3000 g/mol, preferably between 800 and 2000 g/mol.

8. The use as claimed in any one of claims 1 to 7, characterized in that the polyamide composition comprises at least, one reinforcing and/or bulking filler, selected from the group consisting of glass fibers, carbon fibers, aramid fibers, clays, kaolin, mica, wollastonite, silica, talc, graphite, silicon carbide and nanoparticles.

9. The use of a composition as claimed in any one of the preceding claims, as a filter in the field of the recovery of muds, liquids and gases present in underground reservoirs, and in particular in the field of the extraction of hydrocarbons, such as crude oil or natural gas.

10. A calibrated particle having a mean particle size (D50) between 0.2 and 2 mm comprising polyamide and a novolac resin as claimed in claim 1.

Description

EXPERIMENTAL SECTION

[0045] The tests presented below are inspired by the API HP 58 (American Petroleum Institute) standard.

Procedure

Sample Preparation

[0046] 1) Polyamide PA-6,6 and variable proportions of novolac resin (Rhnosin RB) are melt blended in a twin-screw extruder.

[0047] 2) Granules are obtained by chopping rods exiting the extruder. Pellets are also obtained by an underwater cutting process.

[0048] 3) 15 g of pellets or of granules are placed in a crystallizing dish. Said pellets or granules are dried in an oven for 48 h under vacuum under a purge of nitrogen at 80 C. The pellets or granules are recovered, and placed in a desiccator in order to return them to ambient temperature. The water content of the polymer m.sub.water is then measured with a Karl Fischer device.

65 C. Test for 30 Minutes in 15% HCl

[0049] 5 g of sample to be tested are weighed with a D 329 METTLER AE 240 laboratory balance (accuracy: 3.10.sup.3 g). The initial mass is m.sub.polymer.sup.o thus obtained. The sample is placed in a 250 ml flat-bottomed reactor. 100 ml of a 15% hydrochloric acid solution (solution prepared by diluting a 30% hydrochloric acid solution) are added. The measuring cylinder used has an accuracy of +/1.0 ml at 20 C. The reactor is sealed. The test is carried out without stirring. A slight purge of nitrogen is used (verification owing to the bubbler at the inlet and outlet of the reactor). The reactor is immersed in an oil bath at 65 C. and the timer is started as soon as the reactor is immersed. The test lasts 30 min.

[0050] At the end of the test, the reactor is disassembled and the solution is filtered through a pleated filter paper. It is rinsed with deminerailzed water and the pH is measured.

[0051] The filtered substance is recovered and placed in a beaker. 200 ml of demineralised water are added with a magnetic stirrer and the beaker is placed on a stirrer plate for one hour. Then the pH is checked with pH paper in order to follow the change in the concentration of HCl. It is rewashed twice noting the pH at the end of each washing process.

[0052] At the end of the washing processes, the substance is recovered in an aluminum dish. The substance is left overnight under a ventilated fume hood. Finally the filter paper is weighed.

[0053] The substance is dried in an oven for 48 h under vacuum under a purge of nitrogen at 80 C. The substance is then placed in a desiccator in order for it to return to ambient temperature. The substance is weighed and the final mass m.sub.polymer.sup.f is thus obtained.

[0054] Observation: an assay of the chlorides after the test was carried out on several samples. Around 0.12% of Cl.sup. remains in the sample. The water as say indicates a water content of around 0.42% after the acid test.

Expression of the Results

[0055] The mass loss (ML) is measured by the following equation:

ML=[(m.sub.polymer.sup.om.sub.polymer.sup.f)/m.sub.polymer.sup.o]*1000.5%

[0056] A mass loss of 11% is observed with a composition comprising a polyamide PA-6,6, a mass loss of only 0.7% with a composition comprising a polyamide PA-6,6 and 25% by weight of novolac resin, and a mass loss of only 1.5% with a composition comprising a polyamide PA-6,6 and 10% by weight of novolac resin (novolac by weight, relative to the total weight of the composition).