High strength polyester filamentary yarn

Abstract

A polyester multi-filamentary yarn having a novel internal microstructure, polyester tire cord produced from the yarn and a process for production thereof are provided. The polyester yarn has a novel three-phase microstructure consisting of crystalline, amorphous and mesomorphous portions which are changed to a structure having crystalline and amorphous portions during formation of a tire cord. The polyester resin contains at least 90 mol. % polyethylene terephthalate. The resin is melt-spun and solidified by quenching to produce an undrawn yarn having a birefringence of 0.03 to 0.08, which is then drawn at a total draw ratio of 1.4:1 to 2.2:1 and thermally treated and relaxed. The resulting filamentary yarn is dipped in a rubber solution to produce a tire cord which exhibits excellent dimensional stability and fatigue resistance when it is incorporated into the rubber matrix of a tire.

What is claimed is: 
     
       1. A polyester filamentary yarn comprising at least 90 mol. % polyethylene terephalate and having a fineness of 3-5 denier per filament wherein said polyester has a crystalline orientation function (fc) of at most 0.94, percent crystallinity (Xc) of 0.320-0.45, and has a three-phase microstructure consisting of crystalline, amorphous and mesomorphous portions, the proportion of the mesomorphous portion is 5-15 percent based upon the total amount of crystalline, amorphous and mesomorphous portions of said polyester, and wherein the amount of the mesomorphous portion and the total amount of crystalline, amorphous and mesomorphous portions are determined by the equation   percent of mesomorphous portion=I meso/I total×100,     wherein I meso is the amount of mesomorphous portion in the polyester calculated from the X-ray intensity of the peak for the (010) crystal plane in a quantitative equatorial diffraction pattern of the polyester and I total is the sum of the crystalline, mesomorphous and amorphous portions of the polyester calculated from said quantitative equatorial X-ray diffraction pattern.   
     
     
       2. The polyester yarn of claim 1, wherein said yarn has: i) a crystalline orientation function (fc) of at most 0.94,   ii) an amorphous orientation function (fa) of at least 0.60,   iii) a long period value of at most 155 Å, where fa(1-Xc)>0,330 where Xc is the percent crystallinity and is a value of 0.30-0.45.   
     
     
       3. The polyester yarn of claim 2, wherein said polyester has a three-phase microstructure consisting of crystalline, amorphous and mesomorphous portions, the proportion of the mesomorphous portion is 5-15 percent based upon the total amount of crystalline, amorphous and mesomorphous portions of said polyester, and wherein the amount of the mesomorphous portion and the total amount of crystalline, amorphous and mesomorphous portions are determined by the equation   percent of mesomorphous portion=I meso/I total×100,     wherein I meso is the amount of mesomorphous portion in the polyester calculated from the X-ray intensity of the peak for the (010) crystal plane in a quantitative equatorial diffraction pattern of the polyester and I total is the sum of the crystalline, mesomorphous and amorphous portions of the polyester calculated from said quantitative equatorial X-ray diffraction pattern.   
     
     
       4. The polyester yarn of claim 2, wherein said yarn has a terminal modulus of at most 20 g/d. 
     
     
       5. The polyester yarn of claim 1, wherein said yarn has a terminal modulus of at most 20 g/d. 
     
     
       6. The polyester yarn of claim 1, where said yarn has a crystal volume of 0.5-1.54×10 5  Å 3 . 
     
     
       7. A polyester filamentary yarn comprising at least 90 mol % polyethylene terephthalate and having a fineness of 3-5 denier per filament, wherein said yarn is: i) a crystallinity of 30-45 percent by weight,   ii) a crystallite size in the of at most 65 Å   iii) a crystal volume of 0.5×10 5  Å 3  -1.54×10 5  Å 3 .   
     
     
       8. The polyester yarn of claim 7, wherein said yarn has: i) a crystalline orientation function (fc) of at most 0.94,   ii) an amorphous orientation function (fa) of at least 0.60,   iii) a long period value of at most 155 Å, where fa(1-Xc) 0.330 where Xc is the percent crystallinity and is a value of 0.30-0.45.   
     
     
       9. The polyester yarn of claim 8, wherein said polyester has a three-phase microstructure consisting of crystalline, amorphous and mesomorphous portions, the proportion of the mesomorphous portion is 5-15 percent based upon the total amount of crystalline, amorphous and mesomorphous portions of said polyester, and wherein the amount of the mesomorphous portion and the total amount of crystalline, amorphous and mesomorphous portions are determined by the equation   percent of mesomorphous portion=I meso/I total×100,     wherein I meso is the amount of mesomorphous portion in the polyester calculated from the X-ray intensity of the peak for the (010) crystal plane in a quantitative equatorial diffraction pattern of the polyester and I total is the sum of the crystalline, mesomorphous and amorphous portions of the polyester calculated from said quantitative equatorial X-ray diffraction pattern.   
     
     
       10. The polyester yarn of claim 8, wherein said yarn has a terminal modulus of at most 20 g/d. 
     
     
       11. A polyester filamentary yarn comprising at least 90 mol % polyethylene terephthalate and having a fineness of 3-5 denier per filament, wherein said yarn has a maximum thermal stress of at most 0.5 g/d in the temperature range of from 60° C. to 250° C. and exhibits decreasing slope above 210° C. in a thermal stress versus temperature curve. 
     
     
       12. The polyester yarn of claim 11, wherein said yarn has: i) a crystalline orientation function (fc) of at most 0.94,   ii) an amorphous orientation function (fa) of at least 0.60,   iii) a long period value of at most 155 Å, where fa(1-Xc)>0.330 where Xc is the percent crystallinity and is a value of 0.30-0.45.   
     
     
       13. The polyester yarn of claim 12, wherein said polyester has a three-phase microstructure consisting of crystalline, amorphous and mesomorphous portions, the proportion of the mesomorphous portion is 5-15 percent based upon the total amount of crystalline, amorphous and mesomorphous portions of said polyester, and wherein the amount of the mesomorphous portion and the total amount of crystalline, amorphous and mesomorphous portions are determined by the equation   percent of mesomorphous portion=I meso/I total×100,     wherein I meso is the amount of mesomorphous portion in the polyester calculated from the X-ray intensity of the peak for the (010) crystal plane in a quantitative equatorial diffraction pattern of the polyester and I total is the sum of the crystalline, mesomorphous and amorphous portions of the polyester calculated from said quantitative equatorial X-ray diffraction pattern.   
     
     
       14. The polyester yarn of claim 12, wherein said yarn has a terminal modulus of at most 20 g/d. 
     
     
       15. A polyester filamentary yarn comprising at least 90 mol % polyethylene terephthalate and having a fineness of 3-5 denier per filament, wherein said yarn has: i) a crystalline orientation function (fc) of at most 0.94,   ii) an amorphous orientation function (fa) of at least 0.60,   ii) a long period value of at most 155 Å and where said yarn is characterized in that fa(1-xc)>0.330 where Xc is the percent crystallinity and is a value of 0.30-0.45.