Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-10-04
1997-09-23
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...
525437, C08L 6702
Patent
active
056705840
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to polyester compositions, containing polymeric liquid crystals (LCP) suitable for the preparation of stretched articles such as films and fibres, endowed with high mechanical properties, particularly a high elastic modulus.
It is known that liquid crystals (LCP) are used as a reinforcing material of thermoplastic polymers to improve their mechanical properties. The improvement is shown when the LCP quantity is at least 10% by weight of the polymeric matrix. Quantities lower than 5% determine under the conditions of experimental use only marginal increases.
The lowest concentrations used in literature do not have values lower than 1-2% by weight. This is due to the fact that with these low concentrations, and under the experimental use conditions there is no improvement of the resin mechanical properties. The improvements, moreover, depend on the degree of stretching carried out. Stretching ratios of at least 20:1 are necessary in the case of cooled filaments at the extruder exit to obtain the highest increases. In the case of films where the practicable stretching ratios are generally between 2:1 and 10:1, there are no significant improvements of consequence of the insufficient molecular orientation obtainable (A. M. Sukhadia et al.--Intern.
SUMMARY OF THE INVENTION AND DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENT
Polymer Processing VII (1992) 3, 218-228). It has been unexpectedly found that it is possible to obtain oriented articles, such as fibres, films and bioriented containers, endowed with high mechanical properties, particularly with a high elastic modulus, by starting from polyester resins mixed with a polyfunctional upgrading compound, capable of increasing the molecular weight of the resin by polycondensation and/or polyaddition reactions in the solid state with the end groups of the resin. And the containing in the polymer matrix, relatively small quantities, lower than 5% by weight of a liquid polymeric crystal.
The formed article has to be subjected to stretching to obtain the desired effect. The stretching ratio is at least 2:1 and is generally between 2:1 and 10:1.
The stretching temperature is a little higher than the Tg of the polymer in the case of stretching of films and bioriented articles. Suitable temperatures are between 80 and 120.degree. C. Regarding the fibres, the stretching can be carried out in two phases. In the first phase, the stretching is carried out at temperatures lower than Tg. In the second phase, the stretching is carried out at higher temperatures.
In the case of films, the stretching ratio is preferably between 4:1 and 9:1. In the case of fibres, the stretching ratio is preferably between 2:1 and 6:1.
The LCP crystals are incorporated into the polyester resin under such mixing conditions, as to assure a homogeneous distribution of the same in the polymer matrix. The preferred method comprises mixing of the liquid crystals in the melted polymer mass at a temperature between 250 and 320.degree. C. The temperature is chosen in accordance with the processability temperature of the liquid crystal. Therefore, it generally increases when the latter increases. Twin screw extruders are preferably used. Counter rotating and intermeshing twin screw extruders are particularly suitable. The residence time in the extruder is generally between 20 and 200 sec.
The polymer mixture coming out of the extruder can be pelletized, and the chips used for the preparation of the stretched articles. Alternatively, the blend is sent directly to the filming or spinning apparatus.
The polyester resins of the present invention are converted into fibres and stretched films or other bioriented articles according to the conventional techniques. Examples of bioriented articles are the sheets in which the biorientation is obtained by calendering, and the bioriented containers obtained by injection blow molding.
The liquid crystals are preferably used in a quantity lower than 2% by weight on the resin. Preferably, the crystals are used
REFERENCES:
patent: 3553157 (1971-01-01), Dijkstra et al.
patent: 3637595 (1972-01-01), Cottis et al.
patent: 3804805 (1974-04-01), Kuhfuss et al.
patent: 4093595 (1978-06-01), Elliott
patent: 4161470 (1979-07-01), Calundann
patent: 4360658 (1982-11-01), Jackson, Jr. et al.
patent: 4447577 (1984-05-01), Bayha
patent: 4668760 (1987-05-01), Boudreaux, Jr. et al.
patent: 5324795 (1994-06-01), Suenaga
A.M. Sukhadia et al., "Mixing History on the Morphology and Properties of Thermoplastic/LCP Blends," Intern. Polymer Processing VII 3, 218-228 (Munich 1992).
Chemical Abstracts, vol. 97, no. 24, Dec. 13, 1982, abstract no. 199462h, Asahi Chemical Ind. Co., Ltd., "Polyester blend fibers," p. 69, col. 2 (JP A 82 101 020).
Al Ghatta Hussain Ali Kashif
Cobror Sandro
Severini Tonino
Manzo Edward D.
Murphy Mark J.
Short Patricia A.
Sinco Engineering S.p.A.
LandOfFree
Polyester compositions suitable for the manufacture of fibres an does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyester compositions suitable for the manufacture of fibres an, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyester compositions suitable for the manufacture of fibres an will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1938951