JPH0428806B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester fibers for reinforcing rubber, and more particularly to polyester fibers for reinforcing rubber which contain polyethylene terephthalate or polyethylene terephthalate as a main component and have improved dimensional stability and durability. It goes without saying that polyester fibers, represented by polyethylene terephthalate fibers, have established a firm position as general-purpose industrial fibers.
It is also well known that it is widely used especially in rubber reinforcement applications due to its excellent properties such as high strength, high modulus, low shrinkage, and high durability. However, when polyester fibers are reconsidered for use as rubber reinforcement, the performance of polyester fibers needs to be further improved due to the need to improve the performance of rubber products and the performance of polyester fibers themselves in order to compete with other materials. It is strongly hoped that this will happen. In other words, in terms of the performance of rubber products, it is desirable to improve durability and dimensional stability, and in terms of the performance of polyester fibers, it is desirable to simultaneously improve the contradictory properties of high modulus and low shrinkage. In terms of dimensional stability, it is desired to provide the same performance as existing rayon fibers and to improve the resistance to decomposition in rubber. Polyester fibers conventionally used for rubber reinforcement are made by melt-spinning polymers with a high degree of polymerization.
It is roughly divided into two types: the so-called high-strength type, which is obtained by stretching at a high magnification, and the so-called dimensional-stable type, which emphasizes dimensional stability while sacrificing strength by using methods such as low polymerization degree method or low fiber orientation method. However, the former lacks dimensional stability, while the latter lacks strength and durability, and neither can meet the recent demands for satisfying each characteristic value at a high level at the same time. In this way, it is technically possible to emphasize and improve one property of high strength, high modulus, low shrinkage, and high durability at the expense of other properties; While keeping the characteristics of
Alternatively, it has been impossible within the scope of the prior art to improve the desired characteristics while attempting to improve the properties, as this is a trade-off. Against this background, the present invention was made as a result of intensive research to develop an innovative polyester fiber that satisfies various properties that should be provided as a rubber reinforcing material and that should be improved at the same time. Specifically, the purpose of the present invention is to develop a polyester fiber that has sufficient strength as a rubber reinforcing material, has improved modulus and dimensional stability (shrinkability), and has improved durability. However, recently, for the same purpose, JP-A-53-58031, JP-A-53-58032, JP-A-57-154410, JP-A-57
New technologies such as No.-154411 and JP-A-57-161119 have been proposed. The content of JP-A No. 53-58031 is that a polymer with a relatively high degree of polymerization is subjected to high contraction stress spinning, contrary to the low stress spinning method that is the mainstream of conventional methods, and then stretched to achieve total fiber orientation. The aim was to improve durability by increasing the degree of shrinkage and reducing the orientation of the amorphous region in particular, thereby reducing shrinkage and reducing energy loss due to repeated stretching and compression. Although the shrinkage and energy loss of this yarn are certainly improved, on the other hand, it is accompanied by a significant decrease in strength, as in the case of the conventional general-purpose technique of lowering the degree of polymerization, which is expected from the characteristics of the yarn. Not only is it difficult to obtain a moderate level of durability in rubber, but it also has disadvantages such as being susceptible to hydrolysis and amine decomposition due to the low orientation of the fiber structure. It is not something to be satisfied with. Also, JP-A-53-58032 is JP-A-53-58031.
This relates to a method for manufacturing polyester fibers, which involves rapid cooling in the curing zone directly below the spinneret, which results in poor spinnability and poor drawability, and in particular, to increase the strength of the resulting fibers. When the stretching ratio is increased, there are problems with yarn-spinning properties such as frequent yarn breakage during stretching, and fibers with sufficiently satisfactory performance cannot be obtained. JP-A-57-154410 is superior to JP-A-53-58031 and JP-A-53-58032 in that it employs a high stress spinning method.
Although it is the same as No. 2, it has been further optimized by limiting the modulus, dry heat shrinkage rate, degree of polymerization, degree of fiber orientation, and crystal size. However, the raw yarn obtained by this method is
There is no major difference in performance from the yarn obtained by the method of No. 58032,
In particular, the problems of insufficient durability and strength in rubber, which are considered to be disadvantageous, have not been sufficiently solved. JP-A-57-154411 is similar to JP-A-57-154410, but adds a factor to limit the concentration of terminal carboxyl groups to a low concentration in order to cover decomposition in rubber. , compared to the average terminal carboxyl group concentration of commercially available polyester fibers, which is about 30 equivalents/10 ⁶ g, the limit value of 25 equivalents/10 ⁶ g or less is not much different;
Differences in methods for reducing the terminal carboxyl group concentration,
Considering the fact that the decomposition resistance effect after low carboxylization differs depending on the fiber structure, this does not certainly compensate for the lack of practical effectiveness of the technique of JP-A-57-154410. In addition, the above technology
In both cases, the aim was to improve the shrinkage of the raw yarn and link it directly to the low shrinkage of the cord in rubber. As is well known, when using fiber as a rubber reinforcement material, it is almost without exception necessary to undergo high-level processing steps such as twisting, adhesive processing, and heat treatment at high temperatures. The performance that is at issue as a commercial cord is, of course, the performance of the so-called dip cord after these processes, but in general, the performance of the raw yarn changes greatly depending on these high-order processing conditions. In particular, the heat shrinkability, which is a factor of thermal history, is due to the fact that the thermal conditions during processing are much harsher than the thermal conditions during yarn production. Generally speaking, the heat shrinkability of the treated cord does not match the size of the heat shrinkability. In this respect, it is dangerous to claim that improving the shrinkage of the treated cord is achieved by improving the shrinkage of the raw yarn. JP-A No. 57-161119 uses the same technology as above,
This is an attempt to improve the durability and heat shrinkability of the treated cord by adding characteristics to the load-elongation curve and heat shrinkage characteristics of the raw yarn, with a focus on the cord performance after treatment while using high stress spun fiber as a base. This method is particularly different from the above-mentioned technology in that the heat shrinkage of the yarn is set rather high, and is attracting attention. However, the performance of cords obtained using this method is still insufficient in terms of strength, etc., and the decomposition resistance in rubber has not been improved. It cannot produce a satisfactory effect. As described above, all of the above-mentioned technologies have their own characteristics, but it is difficult to obtain rubber reinforcing fibers that simultaneously improve the required performance to a high level using these technologies alone. The present invention has succeeded in providing a polyester fiber for rubber reinforcement that has high strength, high dimensional stability, and high durability all at once, which could not be obtained using conventional techniques. That is, the gist of the present invention is a polyester fiber for rubber reinforcement, which is a fiber made of polyethylene terephthalate or a polyester containing polyethylene terephthalate as a main component, and is characterized in that it simultaneously satisfies the following properties. (a) Intrinsic viscosity: 0.90 or more (b) Strength: 7.5 g/d or more (c) Total orientation: 0.70 to 0.77 (d) Amorphous region orientation: 0.70 or less (e) Initial modulus: 100 g/d or more (f) Intermediate modulus: Initial modulus value or more (g) Crystallinity: 0.40 to 0.55 (h) Ammonia decomposition strength retention rate: 70% or more The polyester fiber of the present invention is processed to make a cord for rubber reinforcement. It is designed to provide the best cord performance through the usual twisting, adhesive treatment, and heat treatment process. In other words, the various conditions during raw yarn production and the processing conditions during higher-order processing are connected to improve and optimize the performance of the dip cord after high-order processing. The polyester fiber dip cord according to the present invention has outstanding total performance in terms of strength, modulus, shrinkability, and durability, and has high strength comparable to conventional high-strength type yarns and high modulus similar to rayon fiber dip cord. It is an innovative rubber reinforcing material that has the following characteristics: low shrinkage, and high durability that far exceeds the common knowledge of conventional polyester fiber cords. The present invention will be explained in detail below. Polyethylene terephthalate as used in the present invention means conventionally known polyethylene terephthalate, and the raw materials and manufacturing method are not particularly limited. Polyethylene terephthalate whose main component is polyethylene terephthalate refers to polyester in which the polyethylene terephthalate component accounts for 90 mol% or more of the structural units of the polymer, and the polyethylene terephthalate component accounts for 90 mol% or more of the structural units of the polymer.
The following copolymerization components include various glycol components,
It may contain various dicarboxylic acid components. Next, the fiber characteristics of the polyester fiber of the present invention will be described in order. The intrinsic viscosity is determined by using a 1:1 (weight ratio) mixed solution of phenol and tetrachloroethane as a solvent.
The value measured at 20℃ must be 0.90 or higher. This means that it has a high molecular weight of 30,000 or more when expressed in number average molecular weight. Strength is a value measured according to the method of JIS-L-1017, that is, a value obtained by dividing the strength at cutting in a load-extension test by the actual fineness before measurement, and is 7.5 g / d or more. provided that. The total degree of orientation is the value obtained by dividing the birefringence of the fiber determined by the Beretsk compensator method using a normal polarizing microscope by 253 × 10 ^-3 , which is the theoretical limit birefringence value of polyethylene terephthalate fiber.
The condition is that it is within the range of 0.70 to 0.77. Note that if the total degree of orientation is outside this range, the strength or initial modulus will be low, and the dimensional stability will be poor. The degree of orientation of the amorphous region means a value determined by the following formula, and the degree of orientation of the amorphous region is 0.70 or less. fa=Δn−XfcΔnc/(1−X)Δna Where, fa: Orientation degree of amorphous region Δn: Birefringence X: Crystallinity Δnc: Intrinsic birefringence of crystal (=0.220) Δna: Intrinsic birefringence of amorphous ( = 0.275) fc: Crystal alignment function In the above equation, fc is the average orientation angle θ measured by wide-angle X-ray diffraction, that is, the average angle of the diffraction arc (010) (100) Using the average orientation angle θ obtained by analyzing the width, it is determined by fc=1/2 (3cos ² θ−1). In the present invention, this fc is not particularly limited, but the polyester fiber of the present invention has an fc of 0.93 or more.
Give the fc value. The crystallinity X means a value determined by the following formula using the fiber density (ρ: g/cm ³ ), and is within the range of 0.40 to 0.55. X=ρc(ρ-ρa)/ρ(ρc-ρa) Where, ρc: Crystal density (=1.455g/cm ³ ) ρa: Amorphous density (=1.335g/cm ³ ) The initial modulus and intermediate modulus are Among the factors constituting the invention, there is a particularly important consensus, but the modulus in the present invention is determined by conducting a tensile test and measuring stress (strength) on the vertical axis and strain (elongation) on the horizontal axis. It means the slope of the tangent to the stress-strain curve, that is, the differential coefficient. In the present invention, the unit is the elongation change (%), and the corresponding stress change (strength: g/
d), that is, g/d. The initial modulus in the present invention means the slope of the rise of the stress-strain curve described above, which is
Conventionally, as defined in JIS-L-1017,
It is exactly the same as the commonly used initial modulus. The intermediate modulus refers to the modulus at a point in the differential coefficient of the stress-strain curve that exhibits a maximum value different from the initial modulus in an area approximately midway between the rising point and the cutting point. The initial modulus and intermediate modulus will be explained in more detail using drawings. Figure 1 shows the differential coefficient obtained by analyzing the stress-strain curve, that is, the modulus on the vertical axis and the stress of the stress-strain curve on the horizontal axis, from the rising point of the stress-strain curve to the cutting point. This diagram illustrates the change in the modulus of . In FIG. 1, the solid line shows the polyester fiber of the present invention, and the dotted line shows the conventional polyester fiber. The maximum modulus of A is the initial modulus, and the maximum modulus of B is the intermediate modulus. C means a cutting point, and this modulus is called the end point modulus. Needless to say, the strength indicated by C means strength itself, which is one of the characteristics in the present invention. This modulus in the present invention is JSI-L-1017
It is determined geometrically from the load-extension curve obtained in a tensile test according to the law, but it is also possible to automatically determine it by processing the data with a computer. In the present invention, this initial modulus is 100 g/d.
The conditions are as follows, and the intermediate modulus is greater than or equal to the initial modulus value. This is a particularly important condition for optimizing the performance of the deep dip cord that is the object of the present invention, and by satisfying this condition in addition to other conditions, improved Dimensional stability, durability,
Strength can be obtained at the same time. The present invention belongs to the complete opposite of the conventionally proposed method, which prefers to make the end point modulus as small as possible. While conventional methods focus on improving the toughness of the raw yarn itself and improving the strength utilization rate during twisting, the key point of the present invention is to improve the toughness of the raw yarn itself and the strength utilization rate during twisting. The yarn design has been optimized by fully considering the processing steps involved and linking these post-processing conditions. The present invention is the first invention based on such a technical idea. As shown in FIG. 1, it is clear that while conventional fibers have an intermediate modulus that is smaller than the initial modulus, the opposite is true for the fibers of the present invention. Ammonia decomposition strong retention rate means 5g of fiber is 2
Ammonia gas was injected into the tube at a rate of 10 ml per minute, and the temperature was kept at 150°C for 3 hours and 30 minutes.The cutting strength of the fiber after treatment was compared to the cutting strength before treatment. It means the value obtained by dividing by and multiplying by 100, and in the present invention, the condition is that this strong ammonia retention rate is 70% or more. Regarding each characteristic of the fiber of the present invention, the intrinsic viscosity, strength, initial modulus, intermediate modulus, and crystallinity are related to the modulus-heat shrinkage of the dip cord, that is, the dimensional stability, and all the properties have a comprehensive causal relationship. This is related to the durability of the dip cord, but by satisfying all of the characteristics at the same time, a rubber reinforcing cord with improved various performances as defined in the present invention can be obtained. Next, a method for producing polyester fibers having each characteristic value as defined in the present invention will be explained. It is easy to obtain polyester fibers having an intrinsic viscosity of 0.90 or more as used in the present invention. That is, it is made into fibers by melting and extruding separately produced polyester chips using an extruder or the like, or by introducing a continuously produced molten polymer directly into a spinning machine and spinning it, and then drawing it. In this case, it can be obtained by spinning a polymer having an intrinsic viscosity higher than that of the target fiber, which compensates for the decrease in the degree of polymerization during melting and the decrease in the degree of polymerization during spinning. The manufacturing process of polyester fiber of the present invention is as follows:
The basic process of polymer → melt spinning → stretching is the same as before, but in this spinning → stretching process, there is a so-called two-step method in which both are literally done in separate steps, a so-called spin-draw method in which both are done in succession, and a half-spun method. The spin draw → re-stretching method (half spin draw method) in which drawing is performed and stretching is added later, and the so-called POY method in which only spinning is performed without subsequent substantial stretching can be adopted. The spinning conditions are such that the stress of the spun yarn is 0.05 to 1.5 g/
d or higher and conventional low stress conditions.
Compared to around 0.01g/d, clearly higher conditions are required. In order to satisfy this high stress spinning condition, it is necessary to take off the spun yarn at a high speed and increase the cooling rate so that the spinning tension becomes sufficiently high. The most effective method for rapidly cooling the spun yarn is to blow cooling air directly under the spinneret. However, when this method is adopted, yarn breakage may occur when the spun yarn is taken off at high speed. They occur frequently and cannot be spun smoothly. For this reason, it is necessary to provide a heated spinning hood directly below the spinneret, and to quickly cool the spun yarn after passing it through the heated spinning hood. As a heating spinning hood, the atmospheric temperature is 250℃ or higher and the length is 2.5~10cm.
cm, preferably 2.5 to 7.5 cm. Further, it is appropriate that the spinning take-off speed is 700 to 5000 m/min. Note that since the formation of the fibrous structure is promoted by increasing the cooling rate, there is a risk that variations in the cooling rate will cause variations in the fibrous structure, so it is particularly necessary to perform the cooling uniformly. For this reason, the total number of filaments, the single yarn denier of the yarn, the diameter and arrangement of the discharge holes of the spinneret,
Polymer temperature just before spinning, temperature and length of heated spinning hood, cooling air blowing method (circumferential blowing, horizontal blowing), cooling air temperature, speed, blowing length, etc. , it is necessary to create an optimal combination in relation to the spinning speed. The birefringence of the spun undrawn yarn is 10×10 ^{-3 to 70×10 -3 or higher, which is significantly higher than 1×10 -3 to 3} ×10 ^-3 in the case of conventional low stress spinning. It is preferable to set the value to the above value. The spun undrawn yarn is then stretched, and the stretching method includes heating rollers, heating plates,
A method of stretching in one or more stages under heating using a steam jet or the like is employed. As mentioned above, the spinning-drawing process may be continuous or discontinuous. The stretching ratio is linked to the spinning stress, and the higher the spinning stress, the more the orientation has already progressed during the spinning stage, so the total stretching ratio can be reduced. The spinning stress-stretching ratio, heat treatment conditions during or after stretching determine the strength, total orientation degree, amorphous region orientation degree, initial modulus, intermediate modulus, and crystallinity in the present invention. The larger the spinning stress, the smaller the total orientation degree and the amorphous region orientation degree, and the larger the stretching ratio, the larger the strength, total orientation degree, amorphous region orientation degree, initial modulus, and intermediate modulus. Alternatively, the greater the heat treatment after stretching, the greater the degree of crystallinity. Conditions for increasing the intermediate modulus, which are important requirements of the present invention, include performing the heat treatment during or after stretching at as low a temperature as possible, and minimizing the relaxation after stretching. In the above-mentioned relationship between the yarn spinning conditions and each characteristic, each yarn spinning condition may be set so as to satisfy the conditions of each characteristic as referred to in the present invention. The relationship between these spinning conditions and each characteristic value of the obtained fibers will be described later in Examples. Strong ammonia retention is a valuable parameter that indicates hydrolysis resistance and amine decomposition resistance in rubber. This improvement in hydrolysis resistance and amine decomposition resistance in rubber is important for the durability of actual rubber products, as well as the structural parameters of the fibers, that is, the stable fiber structure that can withstand repeated mechanical stretching and compression. From this perspective, methods have been proposed to directly reduce the concentration of terminal carboxyl groups in polymers, which is directly linked to improving properties. However, as a result of studies conducted by the present inventors, there is no doubt that reducing the terminal carboxyl group concentration is a method that meets the objective. It has been found that using degradability as a measure is extremely dangerous. That is, methods for reducing the concentration of terminal carboxyl groups include optimizing process conditions during polymer production and spinning to suppress their formation and increase as much as possible, using solid phase polymerization, using epoxy compounds, carbonate compounds, There is a method of blocking the terminal carboxyl group by adding and reacting an oxazoline compound, etc.
It has been found that there are differences in the effects of low-carboxyl group fibers due to differences in these methods and differences in fiber morphology and structure. In fact, I learned that it has a negative effect on the performance of the fiber, and that the apparent reduction in carboxyl groups may not have the meaning of improving performance. Against this background, the inventors selected ammonia decomposition as a meaningful parameter. This ammonia decomposition property is hydrolysis resistance in rubber, amine decomposition resistance,
More realistically, the reliability of the data is that there is a clear correlation with the deterioration resistance of the cord when rubber products are put into practical use, and that the value obtained for the ammonia decomposition property can be obtained steadily and reproducibly. This is also a parameter of great practical significance. The conditions of the present invention require that this ammonia decomposition strength retention rate be 70% or more, whereas conventional polyester fibers have a strength retention rate of 65% or less.
In order to satisfy this condition, at least low carboxylization is necessary, and usually 20 equivalents/10 ⁶ g
Below, preferably 15 equivalents/10 ⁶ g or less is desired.
However, as mentioned above, the carboxyl group concentration does not have an absolute meaning, and the effect of lowering the carboxyl group should be confirmed by the ammonia decomposition resistance. The method for lowering the carboxyl group is not particularly limited as long as it satisfies the requirements of the present invention, but preferably solid phase polymerization, N-glycidyl phthalimide, N-glycidyl tetrahydrophthalimide, phenyl glycidyl ether, etc. A method of adding and reacting an epoxy compound, ethylene carbonate, etc. as an end-blocking agent, and a method of combining these methods are recommended. Note that the terminal carboxyl group concentration here is
Dissolve 0.15 g of fiber in 5 ml of benzyl alcohol, dilute by adding 10 ml of chloroform, then 5 ml of benzyl alcohol, and dissolve the phenol red in a 70/30 benzyl alcohol/methanol mixed solution of 0.1 N potassium hydroxide. This value is obtained by neutralization titration as an indicator. The polyester fibers obtained in the present invention are twisted in a conventional manner to form a raw cord, then treated with an adhesive and heat-treated to form a dip cord, which is then applied to rubber structures as a rubber reinforcing agent. For the twisted yarn, either the usual method of first twisting → final twisting and piling up a plurality of yarns, or the method of performing only one twisting can be adopted. The number of twists is also selected depending on the application, but for tire ^cord , for example, T The number of twists such that the twist coefficient expressed in (display denier) is 600 to 2600 is shown as a specific example. Adhesive treatment is performed to improve the adhesion between the polyester cord and the rubber, but it is usually treated with an epoxy compound, ethylene urea compound, isocyanate compound, etc., and then treated with a resorcinol-formalin-latex (RFL) liquid. A method of treating with a mixture of a novolac resin obtained from resorcinol-formalin and RFL, a method of treating with a mixture of a parent polyester component such as bis(dihydroxyphenylmethyl)chlorophenol and RFL, etc. are adopted. Heat treatment after applying the adhesive is carried out in the sense of heat setting to fix the adhesive and impart dimensional stability to the fibers, and the conditions are usually 180 to 260°C under constant length or elongation of up to about 30%. The temperature is set for 20-300 seconds. Of course, the above-mentioned depth conditions can be changed depending on the application. When the polyester fiber of the present invention is made into the above-mentioned ordinary dip cord, it has extremely excellent performance and very preferably satisfies the performance improvement aimed at by the present invention.
This treated cord can be preferably applied as a reinforcing material for rubber structures such as tires, conveyor belts, hoses, and V-belts. Hereinafter, the present invention will be explained in more detail with reference to Examples. In the example, the raw cord was twisted 49 times/10cm in the Z direction (first twist) using a ring twisting machine, and then twisted 49 times/10cm in the S direction while combining two cords. (ply twist). Further, the dipping treatment was carried out using a single dipping machine manufactured by Ritzler under the following conditions. Dip liquid Resorcin-Formalin-Zenta Tsukura Tsuratex-based RFL dispersion 83 parts Solid content ratio 16.6-5.4-100 Adjusted to PH9.5 with NaOH, total solid content 20% Pexal 17 parts Total 100 parts (Note 1) Zentatsu Kulatex is Butadiene-styrene-vinylpyridine ternary copolymer latex, trade name of General Tire and Rubber Company. (Note 2) Pexal is an ammonia aqueous solution of 2,6-bis(2',4'-dihydroxyphenylmethyl)-4-chlorophenol with a solid content of 20%.
ICI product name. Dip conditions Drying zone 80℃ x 30 seconds Curing zone Sakae 40℃ x 80 seconds x 2 times Dip tension 0.5Kg/cord In addition, unless otherwise specified in the text, the physical properties of yarn and cord in the examples are JIS- Measured according to the method of L-1017. Note that the heat treatment when measuring the dry heat shrinkage rate of raw yarn and dip cord is particularly important for the former.
The conditions of stress-free treatment were adopted: 180°C x 15 minutes and the latter 177°C x 30 minutes. In addition, as a test to investigate the decomposition resistance in rubber, dip cord was embedded in rubber and 140
A test piece that had been pressure-vulcanized at 50Kg/ ^cm2 for 30 minutes at ℃ was heat treated at a high temperature of 170℃ for 30 minutes in a nitrogen atmosphere, and the strength ratio of the cord in the rubber before and after this high temperature heat treatment was calculated as the strength retention rate. (%) was used. The fatigue test was conducted by employing the Gutdeyer method and Mallory tube test method described in JIS-L-1017, and by measuring the time until tube rupture. In addition, in the table, dip cord performance, *
The marked items indicate that the desired performance level targeted by the present invention has not been reached. Example 1 0.3% by weight of N-glycidyl phthalimide was blended into polyethylene terephthalate chips with an intrinsic viscosity of 1.18 and a terminal carboxyl group concentration of 20 equivalents/10 ⁶ g, and an extruder-type spinning machine was used at a polymer temperature of 300°C and a discharge rate of 300 g/min. Under the conditions, the hole diameter is 0.3mm,
After melting and extruding the yarn from a spinneret with 400 holes and passing it through a heating hood with an ambient temperature of 300°C and a length of 5cm installed directly below the spinneret,
After cooling and solidifying by blowing cooling air at 20°C from a cylindrical blowing device, and applying a spinning oil agent using an oiling roller, the first pair of room temperature (non-heated) A pair of second rollers (Nelson type) rotating at 2300 m/min at 210°C are drawn while being stretched by 2.3 times. Nelson type), then guided to a pair of third rollers (Nelson type) rotating at 2280 m/min at room temperature to adjust the tension, and then wound up with a winder at a speed of 2250 m/min. The spinning tension under these conditions was 0.1 g/d. The obtained yarn was a so-called half-spin draw yarn and was subjected to the next drawing. Stretching is performed using a device arranged in the order of roller 1, roller 2, heater plate, roller 3, and roller 4, and the respective temperatures are 100°C, 140°C, and 200°C.
℃, room temperature, and the rotation speed of the rollers was 167 m/min,
The drawn yarn was wound at 190 m/min, 200 m/min, and 200 m/min. In this way, the characteristics of the raw yarn of 1000d/400f polyethylene terephthalate yarn obtained by stretching 2.25 times in the spin-drawing stage, 1.20 times in the re-drawing stage, and 2.7 times in total and the performance of the dip cord are shown below. Shown in 1. As a comparative example, a conventionally known polyethylene terephthalate yarn for tire yarns is also shown. As is clear from Table 1, the yarn of the present invention has almost the same strength as the conventional high-strength type yarn in terms of deep cord performance, that is, the performance that directly represents the performance as a rubber reinforcing material. It can be seen that while exhibiting dimensional stability equal to or higher than that of the dimensional stability type yarn, fatigue resistance and resistance to thermal decomposition in rubber are significantly superior to both conventional yarns. As described above, the yarn of the present invention is the first to have all the characteristics required as a dip cord for rubber reinforcement. When reviewing the performance of the yarn, the strength, dry heat shrinkage rate, initial modulus, etc. of the yarn of the present invention are by no means better than conventional yarns, but as detailed in the text, By setting the characteristic value within a specific range, the performance as a dip cord, which is necessary for practical use, will be extremely good, even though the performance level at the yarn stage is low.

[Table] As explained in the text, Fig. 1 shows the modulus-strength curve obtained by analyzing the load-elongation curve of the yarn, and the solid line in the figure indicates the yarn of the present invention,
The dotted line indicates the conventional thread. The characteristic that the intermediate modulus B of the yarn of the present invention is large is obvious at a glance. Example 2 A polyethylene terephthalate chip with an intrinsic viscosity of 1.13 and a terminal carboxyl group concentration of 6 equivalents/10 ⁶ g obtained by adding and reacting ethylene carbonate during melt polymerization and then performing solid phase polymerization after chipping was used. When spinning and drawing with the same equipment and process as in Example 1, the polymer temperature during spinning was
The temperature is 305℃, the pore diameter is 0.4 mm, and the number of holes is 300 as a spinneret.
The temperature of the cooling air is 20℃, the temperature of the first roller during half spin draw is room temperature, the temperature of the steam jet is 310℃, the temperature of the second roller is 210℃, and the temperature of the third roller is 20℃. The temperature was set to room temperature, and the temperature of roller 1 was set to 110°C during reheat stretching, and the temperature of roller 2 was set to 110°C.
The temperature of roller 4 was 150℃, the temperature of roller 4 was room temperature, and the stretching speed was constant at 200 m/min. , the temperature of the roller 3 and the stretching ratio were changed as appropriate, and the results are shown in Table 2.
Fifteen types of 1000d/300f polyethylene terephthalate yarns were produced. Table 2 shows the key points of the yarn manufacturing conditions and dip cord performance. As is clear from Table 2, Nos. 2, 3-1, 5-1 and 6 satisfy the yarn characteristics specified in the present invention.
It can be seen that -1 shows excellent dip code performance. On the other hand, No. 1 was obtained by the conventional low-stress spinning method, and is inferior to the material of the present invention in terms of dry heat shrinkage rate, dimensional stability, and fatigue resistance. In addition, comparative examples No. 3-2, 3-3, 3-4,
4, 5-3, 5-4, 6-1 and 6-2 are No.1
Although it is recognized that the dry heat shrinkage rate, dimensional stability, and fatigue resistance are improved as a result of the adoption of the high stress spinning method, compared to the one of the present invention, the dip cord strength and fatigue resistance are improved. It can be seen that the results are significantly lower than the previous one. The main difference between the inventive examples and the comparative examples is that the yarn of the present invention has a large intermediate modulus, as described above. explain. Nos. 3-1, 3-2, 3-3, and 3-4 are the characteristics of raw yarn obtained by changing the presence or absence of a heating hood and the heat treatment temperature during reheat stretching under conditions of a spinning speed of 1000 m/min. This is a comparison. Here, in the present invention example No. 3-1, which was spun using a heating hood, sufficient stretching was possible despite the low heat treatment temperature during reheat stretching, and it exhibited excellent yarn properties. . On the other hand, in No. 3-4, which did not use a heating hood, the reheat drawability at low temperatures was extremely poor, a sufficient draw ratio could not be obtained, and the yarn strength only showed a low value. Also, although this is an example in which a heating hood is not used, in Nos. 3-2 and 3-3, reheat stretching is possible under high temperature conditions, and although a high-strength yarn is obtained, the intermediate modulus is small, and the deep cord It did not show sufficient strength and fatigue resistance in terms of performance. No.5-1, 5-2, 5-3, 5-4 and 5-5
This is a comparison of the properties of raw yarn obtained under the conditions of a spinning speed of 1900 m/min and with or without a heating hood and with different heat treatment temperatures during reheat stretching, similar to the No. 3 series. Similar to the No. 3 series, No. 5-1 and 5-2, which are obtained by spinning using a heating hood and reheat-stretching at a relatively low temperature, have excellent yarn properties such as high strength and intermediate modulus. , and the dip cord performance was also excellent, but No. 5-3 and 5
-4 has a low intermediate modulus, and the strength and fatigue resistance of the dip cord are poor;
No. 5 had low strength due to insufficient reheat stretching. The No. 6 series is an example under conditions of a spinning speed of 2500 m/min, and shows the same results as the No. 3 and 5 series. Furthermore, as seen in No. 6-2, the installation of a heating hood is not a necessary and sufficient condition for obtaining the fiber of the present invention, and even if a heating hood is installed and yarn spinning is performed, the reheat drawing temperature cannot be increased. If the intermediate modulus of the yarn is set to be small, the strength of the dip cord will decrease, which is not preferable. In addition, No. 3-2, 3-3, 4, 5-3, 5-
The yarns of No. 4, 6-2 and 6-3 are published in Japanese Patent Application Laid-open No. 1983-
This corresponds to that obtained by the method disclosed in Publication No. 58032. As is clear from the above examples, the raw yarn of the invention example has almost the same strength as that of the comparative example, but
This results in a significant difference in strength retention and fatigue resistance when processed into dip cords. As is clear from the data in Table 2, there is a large difference in thermal decomposition resistance in rubber even though the terminal carboxyl group concentrations are approximately the same level. This indicates that the terminal carboxyl group concentration cannot directly be used as a measure of decomposition resistance in rubber. The data in Table 2 also shows that the ammonia decomposition property of the yarn is a sensitive measure of the decomposition resistance in rubber.

【table】

[Table] Example 3 Using the same spinning equipment as in Example 1 and using the same polyethylene terephthalate chips as in Example 2, the spun yarn was taken to the first roller and then directly led to the wanderer without being stretched. The yarn was wound up, and then the resulting undrawn yarn was drawn. At this time, the conditions were the same except that the polymer temperature during spinning was 300°C, the cooling air temperature was 20°C, the cooling air blowing speed was 0.8 m/sec, the spinneret hole diameter was 0.5 mm, and the number of holes was 250. With the spinning conditions shown in Table 3,
A raw yarn of 1000d/250f was produced. Table 3 summarizes the yarn characteristics and dip cord performance. As is clear from Table 3, inventive examples Nos. 8-1, 8-2, 8-3, 9 and 11 were compared with comparative examples Nos. 7, 8-4, 8-5 and 10. It shows good dip cord performance. In the No. 8 series, the presence or absence of a heating hood during spinning and the thermal history during stretching were compared. -3
The intermediate modulus of the yarn is large, the dip cord is high in strength, and the fatigue resistance is very good, whereas in Comparative Examples No. 8-4 and 8-5, the strength of the yarn is similar to that of the present invention example. Although they are equivalent, it can be seen that they are significantly inferior in strength and fatigue resistance to dip cords. No. 10 is a comparative example showing that undrawn yarn obtained under spinning conditions that do not use a heating hood is difficult to draw at low temperatures. In addition, No. 8-1, 8-2, 8-3 of the present invention example
In the relationship between spinning conditions and intermediate modulus,
It is shown that the lower the stretching temperature and the lower the relaxation rate, that is, the higher the third stage stretching ratio, the greater the intermediate modulus of the raw yarn.

【table】

[Table] Example 4 Polyethylene terephthalate chips with different intrinsic viscosities and concentrations of terminal carboxyl groups were prepared, and the yarn shown in Table 4 was produced under exactly the same spinning and drawing conditions as No. 8-2 of Example 3. did. As is clear from the yarn characteristics and dip cord performance shown in Table 4, Comparative Example No. 12 lacks strength,
In No. 15, the overall performance was unsatisfactory due to insufficient decomposition resistance in rubber, but in Nos. 13 and 14, examples of the present invention, exhibited excellent dip cord performance.

【table】

[Table] Example 5 Using the same spinning machine as in Example 1, using chips with the same polymer composition, and spinning under the same conditions, the yarn was spun using a first roller (Nelson type), a steam jet heating drawing device, It was introduced into a spin draw machine in which a second roller (Nelson type), a third roller (Nelson type), a fourth roller (Nelson type), and a winder were arranged in this order, and was stretched and wound. The conditions were that the first roller speed was 1000 m/min, the temperature of each roller was room temperature, 180°C, 180°C, and 150°C in order, and the stretching ratio was 2.6 times in the first stage, 1.1 times in the second stage, and 0.99 in the third stage.
It was doubled. The properties of the obtained yarn are: intrinsic viscosity 0.95, terminal carboxyl group concentration 13 equivalents/10 ⁶ g, strength 7.8 g/d,
Total orientation degree 0.76, amorphous region orientation degree 0.64, initial modulus 107 g/d, intermediate modulus 120 g/d,
Crystallinity is 0.50, ammonia decomposition strength retention rate is 82%, dip cord performance is strength 5.6g/d, dry heat shrinkage rate 4.1%, modulus 60g/d, dimensional stability
14.6, fatigue resistance of 780 minutes, and decomposition resistance in rubber of 89%, demonstrating excellent dip cord performance. Comparative Example The same yarn spinning test as in Example 5 was conducted using the same apparatus as in Example 5 except that it did not have a heating spinning hood. The single yarn wound around the third drawing roller frequently, and smooth yarn spinning was not possible. In addition, the obtained fiber had an intrinsic viscosity of 0.97, a terminal carboxyl group concentration of 12 equivalents/10 ⁶ g, a strength of 7.1 g/d,
Total orientation degree 0.75, amorphous region orientation degree 0.64, initial modulus 102 g/d, intermediate modulus 114 g/d,
The crystallinity was 0.48, the ammonia decomposition strength retention rate was 83%, and the strength was low.

[Brief explanation of drawings]

FIG. 1 shows the modulus obtained by analyzing the load-elongation curve on the vertical axis and the strength on the horizontal axis. In the figure, the solid line shows an example of the fiber according to the present invention, and the dotted line shows an example of the conventional yarn. Also, A,
B and C represent the initial modulus, intermediate modulus, and end point modulus, respectively.

Claims (1)

[Scope of Claims] 1. A polyester fiber for rubber reinforcement, which is a fiber made of polyethylene terephthalate or a polyester containing polyethylene terephthalate as a main component, and is characterized in that it simultaneously satisfies the following properties. (a) Intrinsic viscosity: 0.90 or more (b) Strength: 7.5 g/d or more (c) Total orientation: 0.70 to 0.77 (d) Amorphous region orientation: 0.70 or less (e) Initial modulus: 100 g/d or more (f) Intermediate modulus: Initial modulus value or higher (g) Crystallinity: 0.40 to 0.55 (h) Strong ammonia decomposition retention rate: 70% or higher