KR100306919B1 - Polyester dipped cord for the selvage of tire cord fabric - Google Patents

Abstract

The present invention relates to a polyester deep cord for cell busy forming a joint of overlapping ends of tire cord paper. The cell busy cord of the present invention has a low initial modulus and a low heat shrinkage ratio as compared to the ground cord constituting the cord paper. As a result, it has an excellent shape stability at the internal injection air pressure and molding temperature during tire manufacturing and molding, thereby improving partial shape instability of the tire generated during tire manufacturing or use.

Description

Polyester dipped cord for selvedge of tire cord paper {Polyester dipped cord for the selvage of tire cord fabric}

The present invention relates to a polyester deep cord for rubber reinforcement, and more particularly, to a polyester deep cord suitable for use in a region where tire cord paper overlaps twice when manufacturing a tire (hereinafter, referred to as 'selviji'). will be.

Here, the dip cord means a cord treated with a dipping liquid for imparting adhesion to rubber.

Typical examples of the fibers used as rubber reinforcements for tires include nylon, rayon and polyester.

Among them, nylon tire cords are mainly used for bias tires for trucks and large buses because of their superior strength and toughness depending on the inherent properties of nylon fibers. However, the nylon tire cord has a problem in that a flat spot phenomenon occurs due to poor modulus and poor heat shrinkage properties, poor shape stability, and low glass transition temperature.

Rayon tire cords have been mainly used in high-speed driving radial tires such as passenger cars because they have very low dry heat shrinkage, excellent thermal dimensional stability, and shape stability, depending on the properties of rayon fibers. However, Rayon tire cords have a problem of low modulus and severe deterioration in cord manufacturing.

Aromatic polyester fiber represented by polyethylene terephthalate has benzene ring in its molecular structure and its molecular chain is rigid, and the tire cord made of these has better elastic modulus, fatigue resistance and glass transition temperature than nylon or rayon tire cord. It has a high flatness, so there is little flat spot and creep property and durability are excellent. Accordingly, polyester tire cords are frequently used in radial tires for passenger cars.

Industrial high strength polyethylene terephthalate typically exhibits significant shrinkage upon heating. Incorporating such industrial polyester fibers into the rubber matrix of a tire also allows the fibers to stretch and relax continuously during each tire revolution as the tire rotates during use. More specifically, tire rotation causes cyclic stress deformation as the internal air pressure presses and axially loads the fiber reinforcement of the tire. Since more energy is consumed during the stretching of the fiber than it recovers during the relaxation of the fiber, this energy difference is dissipated as heat and is called hysteresis loss or work loss. Changes in physical properties due to heat generation during tire driving are caused by moisture and amines contained in the rubber solution during the processing of known rubber solutions for tire cord manufacturing. In particular, when the concentration of the carboxyl groups in the polyester molecular chain increases, it becomes more intense. Lowers fatigue resistance.

Recently, as tire performance and radialization have progressed, demand for polyester tire cords having superior physical properties compared to nylon and rayon is increasing. Accordingly, in addition to the excellent physical properties of the polyester, the disadvantages of the polyester, that is, minimizing the heat generated by the hysteresis loss, the research and development of the polyester to improve the fatigue resistance has been actively made.

As a method for improving such a decrease in fatigue resistance, for example, US Pat. No. 4,101,525 and US Pat. No. 4,195,052 describe methods for improving fatigue resistance by increasing molecular chain fluidity of non-government using high-speed spinning. . However, this method using high-speed spinning is effective in improving fatigue resistance, but the molecular chain length in the non-uniform region becomes uneven and long, and loose molecular chains coexist, resulting in high strength loss and physical property differences between the inner and outer layers of the fiber. There is a disadvantage in that the property change due to the deterioration of the properties and the defect of the microstructure is large.

In addition, the above-mentioned US patents draw highly oriented unstretched yarn by high-speed spinning using steam or the like, and highly oriented stretched yarn, that is, 85 mol% or more of single yarn island composed of polyethylene terephthalate is also 1-20 denier and at 150 ° C. It is exemplified to manufacture a cord by immersing a multi-stretched yarn having a work loss of 0.004 to 0.02 lb.in in a rubber solution and using the same in a tire.

However, these methods can suppress the form deformation and work loss of the entire tire cord paper, but the tire manufacturing deformation occurs in the selvedge portion where the cord paper overlaps during tire manufacturing, and these parts are subjected to intensive stress from the outside while driving the tire. Due to the heat generation due to the more work loss due to the repeated movement of the contraction and relaxation there is a problem that the physical property change due to heat is severe.

Therefore, an object of the present invention is to provide a new polyester deep cord which does not cause the above problems when constructing selvedge of tire cord paper.

In order to solve the above problems, in order to minimize the effect of the overlap of the cords involved in the manufacture of tires, the cords are doubled when the tires are manufactured by constructing the tire cords of less than 5 strands on both sides of the cords with specific physical properties. The characteristics of the cord (hereinafter referred to as 'SelVive Code') of the overlapped areas have almost the same physical properties as the main component code (hereinafter referred to as 'ground cord'). It is surprising to know that the deformation of the selvedge cord according to the air pressure is the same as that of the ground cord, so that the stress distribution received from the outside during the tire running becomes uniform throughout.

Therefore, according to the present invention, which solves the above-mentioned problems, the edge of the tire cord paper fabric is composed of polyester yarns and treated with a conventional dipping liquid in order to impart the adhesiveness to rubber. Provided is a polyester deep cord for selvedge, characterized in that:

(a) 40% or less crystallinity,

(b) a birefringence of 0.19 or less,

(c) a strength of at least 3.0 g / d,

(d) at least 35% elongation at break;

(e) a median elongation of 15 to 30%, measured at a load of 2.0 g / d,

(f) 1.0% or less of dry heat shrinkage measured under conditions of 177 ° C × 2 minutes × 0.008 g / d.

Hereinafter, the present invention will be described in more detail.

The deep cord provided by the present invention is a deep cord constituting a joint portion (selvedge) at the overlapping ends of tire cord paper.

According to the present invention it is measured at a load of (a) crystallinity of 40% or less, (b) birefringence of 0.19 or less, (c) strength 3.0 g / d or more, (d) cutting elongation 35% or more, (e) 2.0 g / d A polyester deep cord for cell-visgi that satisfies at least one intermediate elongation of 15 to 30% and (f) 1.0% or less of dry heat shrinkage measured under conditions of 177 ° C x 2 minutes x 0.008 g / d Has a middle elongation of 400% or more and 1000% or less of the ground cords that make up the cord paper, and the selvage cords are each composed of 5 strands or less. It satisfies mm or less.

Preferably, the selvedge cord of the present invention is composed of the left and right five strands of the tire cord paper edge, and has a low initial modulus and a low heat shrinkage rate compared to the ground cord which mainly constitutes the cord paper, Having good shape stability at molding temperatures improves partial shape instability of the tires produced during tire manufacture or use.

Preferably, the polyester yarn constituting the selvedge cord of the present invention may be produced by a direct drawing process comprising the following steps:

(A) 90 mol% or more of polyethylene terephthalate and a polyester melt having an intrinsic viscosity of 0.9 dl / g or more is extruded through a spinneret having a plurality of openings at a radial tension of 0.5 g / d or less to form a molten spun yarn step,

(B) passing the molten spun yarn through a delayed cooling zone and passing the solidified zone through a cooling zone of a blower zone adjacent to the zone, and

(C) stretching the solidified yarn to form a stretched yarn that satisfies a single yarn fineness of 2 to 5 denier, a crystallinity of 20% or less, a birefringence of 0.19 or less, a strength of 3.0 g / d or more and a melting temperature of 255 ° C or less; .

In particular, the polyester yarn of the present invention is composed of a polyester terephthalate of 90 mol% or more and composed of a polyester having an intrinsic viscosity of 0.9 dl / g or more, (iii) a crystallinity of 20% or less, (ii) a birefringence of 0.19 or less, A) It is preferable to satisfy all the conditions of 3.0 g / d or more of intensity | strength, (i) melting temperature of 255 degrees C or less, and (iii) 2-5 denier of single yarn fineness.

In the polyester yarn of the present invention, when the single yarn fineness is larger than the above range, birefringence difference occurs between the inner and outer layers due to poor cooling, and when the single yarn fineness is small, the initial modulus increase and the strong decrease rate due to the high-speed spinning effect due to excessive spinning drift. It is so severe that it is impossible to maintain a certain level of strength, and in the case of forming a high orientation with a crystallinity of more than 20% and a birefringence of more than 0.19, the formation of relatively low amorphous portions causes excessive initial modulus increase. The high radial tension is difficult to express the crystallinity of the yarn required in the present invention due to the crystallization progression by the orientation of the molecular chain during the formation of the unstretched yarn, which also leads to the rise of the above-mentioned modulus with high orientation Will be.

If the modulus is high (the ratio between the ground cord and the selvage cord is less than 400%), the difference in strain due to the injected air pressure increases the depth of the joint, and the strain difference between the ground cord and the ground cord is increased. When the ratio of the median elongation of the selvedge cord is more than 1000%, the junction portion is protruded, which also causes the same problem of stress concentration due to the deformation difference with the surroundings, and high dry heat shrinkage of the cord is imparted during molding. Thermal deformation due to high temperatures.

In addition, the low cutting elongation causes physical properties to be deteriorated due to the decrease in the stress absorption capacity against external repetitive stress, and at the same time, the final deep cord causes the deformation of the tire due to external force (while driving).

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples.

[Examples and Comparative Examples]

In the direct spinning apparatus, polyethylene terephthalate polymer having an intrinsic viscosity of 0.95 was melt-spun at 290 ° C. Extruded through a spinneret having a diameter of 0.60 mm and 240 detention holes and 160, and a thermos was installed underneath the detention. The detention temperature was prevented from cooling (delay cooling), and the temperature of the cooling air was cooled and solidified under the condition of 80 ° C or lower under the thermos. At this time, the radiation tension and the spinning speed were as shown in Table 1 or 2 below.

After the two-ply yarns, polyester drawn yarns were prepared by adjusting the discharge amount so that the fineness of the final yarn was 1000 deniers. Physical properties of the drawn yarn are shown in Tables 1 and 2 below.

In addition, this stretched yarn was subjected to the twisting and dipping process according to the conventional method to produce a deep cord. Physical properties of the prepared deep cord are shown in Tables 1 and 2 below.

In addition, the tire was manufactured from tire cord paper using the manufactured cord as a selvedge code, and the depth change of the cord joint was measured after tire production. The results are shown in Table 1 below.

Item Example One 2 3 4 Filament Manufacturing Conditions Radial tension (g / d) 0.43 0.30 0.27 0.48 Spinning speed (m / min) 2600 155 960 290 Drawing material Single thread fineness (de / filament) 2.09 03.12 3.12 2.09 Tensile strength (g / d) 4.1 3.5 3.2 4.4 Birefringence 0.1832 0.1810 0.1791 0.1871 Crystallinity (%) 15.8 below 10 below 10 18.7 Melting temperature (℃) 252 248 248 253 Deep Code Properties Crystallinity (%) 32.2 33.5 34.0 35.5 Birefringence 0.1833 0.1827 0.1804 0.1882 Strength (g / d) 3.8 3.5 3.3 4.4 Elongation at break (%) 42.1 44.4 45.8 38.6 Dry heat shrinkage (%) 0.7 0.4 0.4 0.9 Intermediate Elongation (%) 18.8 26.5 27.2 17.6 Tire manufacturing properties 100 × (Main component code middle body) / (Deep code middle body) 480 677 695 450 Tire deformation depth (mm) 0.75 0.40 0.38 0.83

Item Comparative Example One 2 3 4 5 Filament Manufacturing Conditions Radial tension (g / d) 0.52 0.60 0.64 0.68 0.25 Spinning speed (m / min) 3100 3300 3500 4000 850 Drawing material Single thread fineness (de / filament) 2.09 3.12 3.12 2.09 2.09 Tensile strength (g / d) 4.3 3.5 3.2 2.8 2.8 Birefringence 0.1902 0.1908 0.2005 0.2033 0.1684 Crystallinity (%) 21.7 23.8 25.7 29.0 below 10 Melting temperature (℃) 256 257 257 259 246 Deep Code Properties Crystallinity (%) 38.8 42.1 37.2 44.8 39.2 Birefringence 0.1872 0.1904 0.1988 0.2004 0.1876 Strength (g / d) 3.9 3.8 3.5 3.5 3.5 Elongation at break (%) 32.2 35.4 38.8 38.2 69.2 Dry heat shrinkage (%) 0.8 0.6 0.6 0.4 1.2 Intermediate Elongation (%) 14.7 13.9 13.2 9.8 40.9 Tire manufacturing properties 100 × (Main component code middle body) / (Deep code middle body) 376 355 336 250 1146 Tire deformation depth (mm) 0.75 0.40 0.38 0.83 Extrusion 0.3

As can be seen from Tables 1 and 2, the selvedge cord according to the present invention has a low initial modulus and a low heat shrinkage ratio compared to the ground cord, which has excellent shape stability at internal injection air pressure and molding temperature during tire production and molding. It is possible to solve the problem of partial shape instability of the tire that occurs when manufacturing or using the tire.

Claims (2)

A polyester yarn composed of the edge part of a tire cord paper fabric and treated with a conventional dipping liquid for imparting adhesiveness to rubber, and the tire cord paper selvage polyester characterized by satisfying the following characteristics simultaneously: Deep Code: (a) 40% or less crystallinity, (b) a birefringence of 0.19 or less, (c) a strength of at least 3.0 g / d, (d) at least 35% elongation at break; (e) a median elongation of 15 to 30%, measured at a load of 2.0 g / d, (f) 1.0% or less of dry heat shrinkage measured under the conditions of 77 ° C × 2 minutes × 10.008 g / d. 2. The polyester deep cord for selvedge of tire cord paper according to claim 1, wherein the tire cord paper edge portion is constituted within five left and right strands.