Patent GB-784254-A (GB)
Title: Carbon-filled polyamides
IPC: C08K3/04
Filed: 1955-06-16
Abstract: A colloidal dispersion of carbon in water, suitable for adding to a polyamide-forming reaction mass to produce a carbon-filled polyamide, contains 5-10 per cent by weight of carbon having a maximum particle size of less than 500 preferably less than 200 millimicrons, and 5-10 per cent by weight of the carbon of a dispersing agent, preferably the sodium salt of a naphthalene sulphonic acid-formaldehyde condensation product.  The water should be freed from electrolytes by distillation or deionization.  The dispersions may be prepared by mixing the carbon in a solution in water of the dispersing agent to obtain a paste containing about 30 per cent carbon, recycling the paste through a mechanical homogenizer and diluting it between cycles to obtain a product containing 5-20 per cent, preferably 5-10 per cent carbon.  The product may be reprocessed through a sonic or ultrasonic homogenizer.  In an example a commercial channel black having an ultimate particle size of about 35 millimicrons was stirred into distilled water containing the preferred dispersing agent to form a paste containing about 25 per cent carbon and 6 per cent, by weight of the carbon, of dispersing agent.  The paste was then mixed on rolls, passed through a colloid mill at 20 mil clearance, diluted to 22 per cent carbon, processed at 2 mil clearance, diluted to 20 per cent carbon, processed at 1 mil clearance, diluted to 8 per cent carbon and reprocessed at 1 mil clearance.  The product was then processed in a sonic homogenizer operating on the cavitation principle and having a diaphragm oscillating at high intensity at 360 c.p.s.  In another example the final processing was through a valve type homogenizer and the number of steps in the first stage was reduced.ALSO:Carbon filled polyamides (including polyesteramides) are obtained by adding an aqueous colloidal dispersion of carbon containing a quantity of dispersing agent which is at least 5 per cent by weight of the carbon, to a fluid polyamide-forming mass while it is polymerizing and evaporating water from the resulting mass at a rate averaging at least 0.0038 pounds per minute per pound of polymer being produced until all the water present has been removed, the addition being completed in substantially less time than required to evaporate the added water under the circumstances.  The carbon remains dispersed without the aid of protective colloids or stirring. Preferably the carbon particles are less than 500 millimicrons in size, the dispersing agent is naphthalene sulphonic acid-formaldehyde condensation product, the water is deionized and is evaporated at at least 0.0046 pounds per minute.  The final product is preferably filtered before shaping into articles.  The quantity of dispersion added is usually such as to give a carbon content in the product of from 0.5 to 5 per cent, but more may be incorporated and the product blended with an unfilled polyamide.  In a typical example (Example (1)), a channel black of 35 millimicrons particle size was dispersed in water with the preferred dispersing agent to give a 25 per cent paste.  The paste was repeatedly worked mechanically with intermittent dilution to 8 per cent carbon.  Aqueous 50 per cent polyhexamethylenediammonium adipate to give 25 pounds of polymer, with a stabilizer consisting of KBr, NaH2PO4.H2O and copper acetate, was charged to an autoclave, boiled to displace air and heated under pressure to 250 p.s.i.g. at which venting took place.  At 224 DEG  C. addition of 6.25 pounds of dispersion commenced, being completed in 5 minutes. Water was evaporated at the rate of 0.006 pounds per minute per pound of polymer and heating continued with venting to 250 DEG C. After the final stages of polymerization the product was extruded and quenched in water, cut and dried to give a moulding powder. The inherent viscosity was 1.2.  The product was tested for degree of dispersion and opacity and a sample melted, filtered, extruded as 30 mil. filaments and tested for weather resistance.  In Example (5) a carbon-filled copolymer from hexamethylene diamine, sebacic acid, adipic acid and 6-caprolactam was produced in the presence of copper acetate and catechol.  The products of the invention have good weather resistance.  A long list of applications is given. Specifications 461,236, 504,714, 506,125, 535,421, 554,718 and 571,018, [all in Group IV], and U.S.A. Specification 2,345,533 are referred to.