Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-12-18
1997-12-09
Short, Patricia A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525420, C08L 7700
Patent
active
056962088
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is directed to polyamide resins with improved rheological characteristics.
The polyamides of poly--.epsilon.--caprolactam and polyhexamethylene adipamide are resins which have found wide application in many sectors. In general they combine high strength and rigidity with good resistance to heat and abrasion. They are also characterized by resistance to chemical agents and flame. These resins do not, however, have satisfying rheological properties, for application in fields which require high dynamic viscosity of melt in the absence of shear forces, and lower viscosity when subjected to these forces. Due to this low sensitivity to shear forces (shear sensitivity) these polyamide resins are not processable, for example, by extrusion blow moulding processes.
In a previous patent application not yet published, Applicants have described alloys of polyester resins with polyamide resins, obtained by mixing the resins in melt state in the presence of a dianhydride of tetracarboxylic acid, preferably pyromellitic dianhydride, and subjecting the mixture to a polyaddition reaction in the solid state. The alloys obtained possess excellent mechanical characteristics. The content of polyamide resin is not more than 60% by weight. Essentially the alloys are formed of polyester resin modified with minor proportions of polyamide resin.
U.S. Pat No. 5,254,620 describes polyamide resins, modified with a minor percentage (0.5-5% by weight) of an elastomeric polyester resin obtained from high molecular weight polyoxyalkylene glycols, from low molecular weight glycols and from aromatic bicarboxylic acids. The addition of the elastomeric polyester resin improves the flow characteristics of polyamide, and also the flame resistance.
European patent application A 143 875 describes polyester resins with improved impact resistance characteristics, obtained by mixing the polyester resin with a polyamide-ester resin in quantity of 3 to 40% in weight and subjecting the mixture to heating at temperature from 15.degree. to 60.degree. C. lower than melting point of the polyester.
Japanese patent application 1272660 describes compositions of polyamide resins and polyester resins in quantities respectively from 5 to 95% by weight, containing a dianhydride of tetracarboxylic acid, preferably pyromellitic anhydride or the anhydride of 3,3', 4,4'-biphenyl-tetracarboxylic acid. The compositions are characterised by low absorption of water, and good mechanical properties.
Japanese patent application 46/035 377 describes blends of polyamide resin and polyester obtained by reaction of a polyamide resin, having both carboxylic terminal groups. The mixtures are suitable for the preparation of fibres.
SUMMARY OF THE INVENTION AND DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
Unexpectedly it has now been found that it is possible to obtain modified polyamide resins having improved rheological properties in the melt state (higher dynamic viscosity and viscoelasticity) by subjecting to a solid state polycondensation or polyaddition treatment, at temperatures lower than resin melting point and higher than approx. 150.degree. C., a mixture of the resin with a substance selected among: addition reaction with the NH.sub.2 terminal groups of the polyamide resin; and polyamide resin mixture.
The treatment in the solid state is prolonged until the shear sensitivity index of resin is increased by at least 3 times with respect to the value of the starting resin.
Shear sensitivity (Is) is the difference, divided by 100 rad/sec, between the dynamic viscosities in the melt (.eta.' expressed in poises) measured with a flat-cone rheometer RHEOMETRICS RMS 800 respectively with a deformation frequence of 1-100 rad/sec and with deformation of 0.04 rad for each oscillation, operating at 270.degree. C. under nitrogen and employing distance between plate and cone of 50 micron. The index value is approx. 100 poises per rad/sec in the case of nylon 6, while it is higher than at least 300 poises per rad/sec, and can rea
REFERENCES:
patent: 4876127 (1989-10-01), Khanna
patent: 5254620 (1993-10-01), Goetz et al.
patent: 5403896 (1995-04-01), Khanna
patent: 5468530 (1995-11-01), Gotz
Patent Abstracts of Japan: (JP,A,60 248 730) vol. 010, No. 123 (C-344), May 8, 1986.
Patent Abstracts of Japan: (JP,A,60 248 731) vol. 010, No. 123 (C-344), May 8, 1986.
Patent Abstracts of Japan: (JP,A,01 272 660) vol. 014, No. 037 (C-680), Jan. 24, 1990.
Abstract: Database WPI, Section Ch, Derwent Publications Ltd, London, GB; class A24, An 71-66091S (JP,B,46 035 337).
Al Ghatta Hussain Ali Kashif
Cobror Sandro
Manzo Edward D.
Murphy Mark J.
Short Patricia A.
Sinco Engineering S.p.A.
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