JPH059524B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing twisted polyester yarn for rubber reinforcement. More specifically, the present invention relates to a method for producing twisted polyester yarn having highly improved fatigue resistance, dimensional stability, and high strength and used for tire cords, belts, etc. for rubber reinforcement. [Prior art] Polyester yarn has a higher initial modulus and better dimensional stability than polyamide yarn, and satisfies the performance requirements for belt materials and carcass materials for passenger car radial tires, so its usage has increased in recent years. is increasing. However, compared to polyamide yarn, polyester yarn has inferior fatigue resistance in tires when used as a tire cord, so it is not used as tire cord for vehicles other than passenger cars, such as light trucks, trucks, and buses. is the reality. If it is possible to impart fatigue resistance similar to that of polyamide fibers, it is expected that the amount of use as tire cords will increase dramatically, and it will also be possible to reduce the number of twists when processing tire cords. , it becomes possible to more effectively utilize the properties of high modulus and high dimensional stability of polyester yarn. The present inventors first determined that the spinning speed (take-up speed)
By drawing polyester yarn manufactured by high-speed spinning at 2000 m/min or higher at a drawing speed of 100 m/min or less, it has improved strength, initial modulus, dimensional stability, and fatigue resistance compared to conventional polyester yarn for rubber reinforcement. discovered that it was possible to significantly improve sexual
A patent application was filed (Japanese Unexamined Patent Publication No. 186607/1983). However, when the drawn yarn obtained by high-speed spinning and low-speed drawing according to the method of the invention is twisted at 200 to 600 times/m after winding according to the conventional method,
The ratio of the strength of the twisted yarn to the strength of the original drawn yarn,
That is, it has been found that there still exists a defect in that the strength utilization rate of the first twisted yarn is still not sufficiently high and the strength of the drawn yarn cannot be utilized effectively enough. (The method of performing stretching and twisting (pre-twisting) in separate steps will be explained later with reference to FIGS. 3 and 4.) [Problems to be Solved by the Invention] The present invention is We have developed a twisted yarn that can solve the problems that could not be improved even with the manufacturing method proposed in Publication No. 58-186607, and can make dip cords that have excellent fatigue resistance, dimensional stability, and high strength. An object of the present invention is to provide a method for manufacturing polyester twisted yarn for rubber reinforcement. [Means for Solving the Problems] As a result of intensive research to further improve the method described in Japanese Patent Application Laid-open No. 186607/1987, the present inventors have found that
By stretching undrawn polyester yarn produced by high-speed spinning at a spinning speed (take-up speed) of 2000 m/min or higher at a drawing speed of 40 m/min or lower, and immediately and continuously twisting it without winding it up, It was discovered that the completely unexpected effect of improving the twisted yarn strength utilization rate can be obtained, and the present invention was achieved. That is, the method for manufacturing the polyester twisted yarn for rubber reinforcement according to the present invention has an intrinsic viscosity of 0.65 to 1.2.
The polyester polymer is melted and discharged from a spinneret, cooled and solidified, and then wound once at a take-up speed of 2000 m/min or more to form a multifilament undrawn yarn with a birefringence of 20 × 10 ^-3 or more. It is characterized in that it is hot stretched at a stretching speed of 40 m/min or less, immediately and continuously twisted at a rate of 200 to 600 times/m, and then wound up as a twisted yarn. The polyester used in the present invention is one in which 85 mol% or more of its repeating units are composed of ethylene terephthalate, and in particular polyethylene terephthalate produced from terephthalic acid or a functional derivative thereof and ethylene glycol is the main target. However, less than 15 mol% of terephthalic acid or its functional derivative, which is the acid component constituting polyethylene terephthalate, is preferably
Less than 10 mol% of e.g. isophthalic acid, adipic acid, sebacic acid, azelaic acid, naphthalic acid,
At least one of difunctional acids such as P-oxybenzoic acid, 2,5-dimethylterephthalic acid, or functional derivatives thereof may be substituted, or a portion of the glycol component ethylene glycol may be replaced. It may be a copolymer in which less than 15 mol % of at least one dihydric alcohol such as diethylene glycol or 1,4-butadiol is substituted. Further, these polyesters may contain antioxidants, flame retardants, adhesion improvers, matting agents, coloring agents, and the like. In the method of the present invention, it is necessary that the polyester polymer used to produce the polyester twisted yarn for rubber reinforcement has an intrinsic viscosity of 0.65 to 1.2. If the intrinsic viscosity is less than 0.65, the strength of the obtained polyester yarn will be low and the object of the present invention will not be achieved. On the other hand, when polyester polymers with an intrinsic viscosity exceeding 1.2 are spun at high speeds as in the method of the present invention, yarn breakage occurs frequently just below the spinneret, making stable spinning difficult, and the strength is not as high as expected. However, the dimensional stability is also poor. Polyester polymers experience viscosity reduction during melt spinning (for example, a polymer with an intrinsic viscosity of 1.2 typically has a
Decreases to 1.10. ). From the balance of strength, dimensional stability, and fatigue resistance, the intrinsic viscosity of polyester yarn is
It should be between 0.65 and about 1.1. The intrinsic viscosity of the polyester polymer referred to here is expressed by the formula lim c→olnηr/C [where ηr is the solvent used (ortho-
chlorophenol) represents the relative viscosity divided by the viscosity, and C is the polymer concentration in grams per 100 ml of solution. ] Calculate. In the polyester melt spinning of the present invention, it is necessary that the take-up speed is 2000 m/min or more.
If the take-up speed is less than 2000 m/min, although a high-strength polyester yarn can be obtained, the dimensional stability and fatigue resistance when formed into a dip cord are insufficiently improved. Furthermore, as the spinning speed increases, dimensional stability and fatigue resistance improve, but it becomes difficult to obtain sufficient strength. A more preferred range of take-off speed is 2500 m/min to 5000 m/min. The method for measuring fatigue resistance here is to apply two 1000 denier polyester multifilament yarns with 500 turns/m of first twist in the S direction to a final twist of approximately 2200 denier in the Z direction. Make ply-twisted yarn. Furthermore, the ply-twisted yarn is processed into a Litzler Computer.
A dip code is created by performing dip processing using a conventional method. This dip code is JIS L
-1017 Perform tube fatigue test according to method 1, 3, 2, 1A. The testing machine was a Goodyear type, and a rubber tube with dip cord embedded concentrically was bent at a 95° angle to produce 3.5 kg/cm ^2.
Apply an internal pressure of G, rotate the tube at 850 rpm, and measure the time until the tube ruptures due to fatigue of the dip cord. The birefringence index of the highly oriented polyester undrawn yarn in the method of the present invention needs to be 20×10 ⁻³ or more. If it is less than 20×10 ^-3 , even if the degree of polymerization of the polyester is increased or decreased, the improvement in fatigue resistance will not be sufficient, and when the heating element and the yarn come into contact, the yarn will melt. . Birefringence is 20
As the fatigue resistance increases beyond ×10 ⁻³ , fatigue resistance improves, but it becomes increasingly difficult to obtain sufficient strength.
A more preferable range of birefringence is 20×10 ^-3 to
It is 110×10 ^-3 . Birefringence can be measured using a Berek compensator attached to a polarizing microscope.
In the present invention, the values were measured at 25°C using an Olympus POM model and using olive oil as the immersion liquid. The method of the present invention is based on the premise that the winding step and the stretching and twisting step are separated. The influence of drawing speed on the physical properties of drawn yarn is extremely large.
This is an important element of the structure of the present invention. The stretching speed is
It is essential that the speed is 40 m/min or less; if it exceeds this, the rotational speed of the spindle will become excessive and the strength of the twisted yarn will decrease. A more suitable range is 2
~30m/min. It is desirable that the drawing in the present invention be carried out in one stage, and there is no need to carry out multi-stage drawing, which was conventionally considered essential in the production of high-strength yarns. Also,
Conventionally, when producing high-strength yarn, the temperature of the drawing rolls is usually maintained at a temperature higher than room temperature. Even if both the stretching rolls are kept at room temperature, stretching can be carried out without any problem. This phenomenon, together with one-stage stretching, greatly exceeds conventional wisdom. In order to improve the dimensional stability of the drawn yarn, it is necessary to provide a heating element between the first drawing roll and the second drawing roll, and draw the yarn while heating it in contact with the heating element. . In order to obtain the desired dimensional stability, the temperature of the heating element is between 200 and 255° C., and the contact time is between 2 and 0.2 seconds. 2 below 200℃
Dimensional stability is insufficient even if the temperature exceeds 255 seconds.
If the temperature exceeds .degree. C., the yarn will melt when it breaks, and the finishing agent applied to the yarn will undergo severe thermal deterioration, resulting in problems such as fluffing. The higher the birefringence of the undrawn yarn, the better it is to draw at a higher temperature. In addition, one of the major features of the method of the present invention is that conventionally the stretching process and the twisting (pre-twisting) process corresponding to 200 to 600 times/m were separated (see Figures 3 and 4). ) as one continuous process (see Figure 2). That is, when drawing and twisting at 200 to 600 times/m are performed in one continuous step according to the method of the present invention, the tensile strength utilization rate of the first twisted yarn can be improved. This applies 200 to 600 times/m to the filament, which is still mobile after being stretched.
It is thought that this is because the local stress concentration caused by the twisting is alleviated because the twisting process is equivalent to . By continuously performing stretching and twisting in this way, the strength utilization rate of the first twisted yarn can be increased,
It is possible to obtain a ply-twisted yarn having a relatively high value of strength, and as a result, as detailed in the examples below, the strength of the ply-twisted yarn (raw cord) and dip cord is also lower than that obtained by conventional manufacturing methods (drawing and processing). It is possible to achieve a higher value compared to a manufacturing method in which twisting is performed in a separate process. Note that the number of twists is usually determined by the characteristic design of the tire; for example, in the case of a 1100 ^d yarn, it is approximately 500 twists/twist.
In the case of a yarn of 1,500 ^d , approximately 400 twists/m is selected, but since the method of the present invention can achieve high fatigue resistance, the number of twists can be reduced to 200 to 300 twists/m. Examples of apparatus suitable for carrying out the method of the present invention are shown in FIG. 1 for a spinning process and in FIG. 2 for a stretching and twisting process, but the present invention is not limited to these examples. In FIG. 1, molten polyester polymer is discharged from a spinneret 1 having a large number of pores, passes through an atmosphere in which the temperature near the yarn is adjusted by a heating tube 2 installed directly below the spinneret, and then is passed through a cold air chamber 3 to a constant temperature. It is cooled and solidified by the cold air blowing out at high speed,
After applying the finishing agent with the oiling roll 4,
While being taken up by a take-up roll 5 at room temperature, it is wound up as an undrawn yarn package 7 by a winder 6. The undrawn yarn package 7 wound up in this manner is supplied to a drawing heat treatment and twisting device as a raw yarn for the drawing and twisting process shown in FIG. Stretched. A yarn heating element 9 is installed between the godet rolls 8 and 10 to perform heat treatment. The drawn and heat-treated yarn 11 is wound and gripped around feed rolls 12, 14 and press rolls 13, sent out at a constant speed to a twisting section, and fitted onto a spindle via a ring 15 equipped with a sliding traveler. 200 to 600 on the inserted bobbin 16
It is wound up as a pre-twisted yarn 17 which is twisted once/m. 18 is a drawing pin, and 19 and 20 are yarn guides, which are used as appropriate. FIGS. 3 and 4 schematically show examples of apparatus for carrying out typical stretching and twisting steps, respectively, according to conventional methods. The spun and wound undrawn yarn package 7' is supplied to a drawing heat treatment device as a raw yarn for the drawing process shown in FIG.
After passing through 9', it is stretched between godet rolls 8' and 10', each having a separator roll. A yarn heating element 9' is installed between the godet rolls 8' and 10' to perform heat treatment.
The yarn thus drawn and heat-treated is drawn yarn pirn 2.
1'. As shown in FIG. 4, the drawn yarn 21' is wound and held around the feed rolls 12', 14' and the press roll 13', and is sent out at a constant speed to the twisting section, where a sliding traveler is arranged. The yarn is wound as a lower twisted yarn 17' onto a bobbin 16' which is fitted onto a spindle via a thread 15'. 19'', 19, and 20' are thread guides. As detailed above, the manufacturing method of the present invention skillfully combines the structural requirements to achieve high strength, dimensional stability, and fatigue resistance. It is possible to stably obtain twisted polyester yarn suitable for carcass materials of radial tires, rubber reinforcing materials for belts, etc., and stretching and twisting can be performed in one process. [Example] Below The present invention will be specifically explained with examples.In the examples, each measurement value was measured by the following method. (1) Cutting strength and cutting elongation Using a tensile tester, the yarn length was 25 cm, and the tensile strength was measured using a tensile tester. speed 30
Measurements are made at cm/min in an atmosphere of 25°C and 60% humidity. (2) Drying shrinkage rate The yarn is heat treated in an air bath at 160°C for 30 minutes without any load. The yarn lengths before and after heat treatment are measured as L ₁ and L ₂ , respectively, and the drying shrinkage rate is calculated using the following formula. Drying shrinkage rate (%) = L ₁ −L ₂ /L ₁ ×100 (3) Fatigue resistance A tube fatigue test using the Gutdeyer method was conducted in accordance with JIS L-1017, 1.3.2.1A method. Tube shape Inner diameter 12.7mm Outer diameter 26.0mm Length 230mm Bending strength 95° Internal pressure 3.5Kg/cm ² G Rotation speed 850rpm A fatigue test was conducted under the above conditions, and the time until the tube burst due to dip cord fatigue was measured. . Example 1 Polyethylene terephthalate with a fixed viscosity of 0.95 [measured with 35° orthochlorophenol] was melt-spun using the apparatus shown in Figure 1, wound once as an undrawn yarn, and then drawn using the apparatus shown in Figure 2. Twisted, approx.
A multifilament twisted yarn (pre-twisted yarn) of 1000 denier and 384 filaments was obtained. That is, in FIG. 1, a spinneret 1 having 384 orifices with a diameter of 0.30 mm is used, spinning is carried out at a spinning temperature of 310°C, and the inner surface temperature of a heating cylinder 2 with a length of 50 cm is set to 350°C. Heat the yarn by keeping it at ℃,
After cooling and solidifying with cold air at 20°C in the cooling chamber 3 and applying a spinning finishing agent with the oiling roll 4, the winder 6 and the take-up roll 5 rotating at room temperature are rotated at substantially constant speed as shown in Table 1. I set it to the speed shown below and took it up once. Next, in the drawing device shown in FIG.
Stretching was performed using a 15 mm ceramic stretching pin at the stretching ratio shown in Table 1. At this time, the temperature of the godet roll 8 was set at 100°C, and the temperature of the heating element 9 installed between the godet rolls 8 and 10 was set at 230°C. Godetstrol 10 was set at 160°C and its surface speed was set at 13 m/min. Feed rolls 12 and 1
The surface speed of No. 4 was increased by 1% compared to the surface speed of Godetrol No. 10, and tension was applied. then
500 times/in the S direction on a bobbin rotating at 6000 rpm
Heated yarn with m first twist added (first twist yarn)
It was rolled up as a winding. 500 for these two pre-twisted yarns
A ply-twisted yarn of 2250 denier, that is, a raw cord, was obtained by applying ply-twisting in the Z direction at a rate of twists/m. I created a dip code from this raw code using a Ritzler computer processor. Table 1 shows the physical properties of the first twisted yarn, raw cord, and dip cord. For comparison, stretching and twisting were performed under the same conditions as above, except that the stretching and twisting were performed in separate steps as described in JP-A-58-186607 ( Test No. 10). The drawn yarn strength listed in Table 1 (in the present invention, a pre-twisted yarn can be obtained but the drawn yarn itself cannot be obtained) is as follows: The yarn was collected from the yarn and its strength was measured.
The first twist yarn strength utilization rate and the second twist yarn strength utilization rate are both the strength utilization rate with respect to the drawn yarn strength, and the strength utilization rate is increased in the manufacturing method of the present invention compared to the conventional example (Test No. 10). It can be seen that This is also shown in the absolute values of the strengths shown in the columns of top-twist yarn (raw cord) strength and dip cord strength in Table 1 (therefore, the performance effects in Examples 2 to 5 described later are The strength of the twisted yarn (raw cord) and dip cord is shown here). Also, from Table 1, the strength utilization rate of the top-twisted yarn is approximately 3% lower than the strength utilization rate of the first-twisted yarn, but there is no change in the ranking between the test examples, and it is the strength of the first-twisted yarn that influences the value of the first-twisted yarn strength. It can be seen that this is the utilization rate. Also, as can be seen by comparing the dip cord physical properties column of Test No. 10 (comparative example) with a take-up speed of 3000 m/min and Test No. 9 with a take-up speed of 5000 m/min, if the manufacturing method of the present invention is used, Even though the pulling speed is as high as that of the conventional method, the strength is
A dip code equivalent to 3000m/min is obtained. As is clear from Table 1, the collection speed is
In the range of 2000 m/min or more, a twisted yarn (pre-twisted yarn) that becomes a dip cord with excellent strength, fatigue resistance, and dimensional stability was obtained. It is also found that the strength is superior to the method described in JP-A-58-186607.

【table】

[Table] ** Ratio of strength to drawn yarn strength Example 2 The undrawn yarn produced in Example 1 with a take-up speed of 3000 m/min and the other conditions being the same was subjected to the same drawing and twisting method of Example 1. , only the extension speed is
The conditions shown in Table 2 were set to obtain a twisted yarn (pre-twisted yarn). Using this twisted yarn, a raw coat cord and dip cord were obtained in the same manner as in Example 1. Physical properties are the second
Shown in the table.

[Table] This was carried out as a separate process.
It can be seen that the strength is improved compared to the method described in JP-A-58-186607. Example 3 A raw cord and a dip cord were obtained under the same conditions as in Example 2 except that the number of first twists was 200 times/m. The physical properties are shown in Table 3.

【table】

[Table] This was carried out as a separate process.
Example 4 An undrawn yarn of 2180 denier/384 filament was obtained under the same conditions as in Example 1 except that the take-up speed was 3000 m/min. This undrawn yarn was drawn and twisted using the apparatus shown in FIG. 2 at a drawing speed of 13 m/min. At this time, the temperature conditions of the rolls and heating elements, and the stretching conditions were set as shown in Table 4. Raw cords and dip cords were obtained under the same stretching conditions as in Example 1 from the obtained first twisted yarn, and their physical properties are shown in Table 4. Even if both the first roll and the second roll are kept at room temperature, stretching and twisting can be performed without any problem,
It is also seen that almost the same physical properties can be obtained with the dip cord as in the case where the first and second rolls are heated.

[Table] Example 5 Using the apparatus shown in FIGS. 1 and 2 in the same manner as in Example 1, the degree of polymerization of polyethylene terephthalate was changed and spinning was carried out at a constant take-up speed of 3000 m/min, and the drawing speed was 13 m/min. The yarn was drawn for 1 minute, and twisted continuously at 500 times/m to obtain a pre-twisted yarn. Table 5 shows the physical properties of raw cord and dip cord obtained using this pre-twisted yarn under the same conditions as in Example 1.

【table】

[Table]
[Effect of the invention] In the production method of the present invention, the take-up speed (spinning speed)
2000 m/min, it is possible to improve fatigue resistance, and by adopting a stretching heat treatment twisting method in which twisting is continuous with stretching, it is possible to improve the tensile strength utilization rate of the first twisted yarn. As a result, it is possible to obtain a twisted yarn (pre-twisted yarn) from which a dip cord having excellent fatigue resistance, dimensional stability, and high strength can be made.

[Brief explanation of drawings]

FIG. 1 is a typical melt-spinning equipment layout for producing the undrawn polyester yarn of the present invention, and FIG. 2 is an example of the layout of a drawing, heat treatment and twisting equipment. Further, FIGS. 3 and 4 are examples of layout diagrams of a stretching device and a twisting device, respectively, in the conventional method. 1... Spinneret, 2... Heating cylinder, 3... Cold air chamber, 4... Oiling roll, 5... Taking-off roll,
6... Winder, 7, 7'... Undrawn yarn package, 8, 8'... First drawing roll, 9, 9'... Yarn heating element, 10, 10'... Second drawing roll, 11, 1
1'...drawn yarn, 12, 12', 14, 14'...feed roll, 13, 13'...press roll, 15,
15'...ring, 16,16'...bobbin, 17,1
7'... Twisted thread (pre-twisted thread), 18, 18'... Stretching pin, 19, 19', 19'', 19, 20, 2
6... Yarn guide, 21'... Drawing yarn pirn.

Claims (1)

[Claims] 1. In the method for producing twisted polyester yarn for rubber reinforcement, a polyester polymer with an intrinsic viscosity of 0.65 to 1.2 is melted and discharged from a spinneret, cooled and solidified, and then wound once at a take-up speed of 2000 m/min or more to remove birefringence. It is made into a multifilament undrawn yarn with a drawing ratio of 20×10 ^-3 or more, then hot drawn at a drawing speed of 40 m/min or less, and immediately continuously drawn at 200 to 600 m/min.
A method for producing a polyester twisted yarn for rubber reinforcement, which comprises twisting the twisted yarn at a rate equivalent to twists/m and winding it up as a twisted yarn.