JPS6114261B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a reinforcing material for rubber structures, particularly a polyester having excellent adhesion to rubber, sufficient fatigue resistance and workability, and suitable for reinforcing rubber structures, particularly for reinforcing tires. Concerning the method of manufacturing cords. Polyester cord has relatively high Young's modulus and strength, as well as excellent flat spot resistance and heat resistance, so it has recently been used as a reinforcing cord for rubber structures, especially passenger car tires, instead of nylon cord. It became. Polyester cords are generally made by first twisting a polyester yarn consisting of a large number of single yarns that have been drawn and heat set, then plying the yarns, then ply twisting them to form a cord, and then applying an adhesive to the resulting cord. Manufactured by post-heat treatment. However, polyester cords inherently have poor adhesion to rubber compared to nylon cords. Conventionally, various studies have been made to improve this adhesiveness, but in any case, in order to satisfy the required adhesiveness, it is necessary to apply a sufficient amount of adhesive. However, a cord with a sufficient amount of adhesive becomes significantly less flexible.
When this flexibility is impaired, not only workability deteriorates but also fatigue resistance deteriorates. If the amount of adhesive applied is reduced in consideration of workability and fatigue resistance, adhesion becomes insufficient, and adhesion and flexibility are antithetical, and it has been extremely difficult to satisfy both. The present invention has been studied to provide a polyester cord that satisfies both adhesion and flexibility at the same time, and it has been found that the deterioration in flexibility is caused by deformation of the single yarns during heat treatment after applying the adhesive. I learned that this is caused by an increase in the mutual contact area. As a result of further intensive research based on this knowledge, we established a specific relationship between the fineness of the yarn used to make the cord and the fineness of the single yarns that make up this yarn, and also determined the heat setting temperature before applying the adhesive and the fineness after applying the adhesive. The present invention was achieved based on the discovery that a polyester cord that maintains high adhesion to rubber and has sufficient flexibility can be obtained by setting a specific relationship between the heat treatment temperature and the heat treatment temperature. That is, the present invention involves first twisting, doubling, and ply twisting a drawn and heat-set polyester yarn whose main repeating unit is ethylene terephthalate to form a cord, and then applying an adhesive to the cord and then heat-treating the yarn. When manufacturing rubber structure reinforcement materials, the relationship between the fineness of the yarn and the fineness of the single yarns constituting the yarn is expressed by the following formula (1). (In the formula, De is the fineness (denier) of the yarn,
de indicates the fineness (denier) of the single yarn constituting the yarn. ), and the relationship between the yarn temperature during heat setting before applying adhesive and the cord temperature during heat treatment after applying adhesive is expressed by the following formulas () and () T ₂ -10<T ₁ <T ₂ +10... ...() 200<T ₂ <250 ...() (where, T ₁ is the yarn temperature (℃) during heat setting before applying adhesive, and T ₂ is the cord temperature during heat treatment after applying adhesive (℃) ) is a manufacturing method for a rubber structure reinforcing material characterized by satisfying the following.The polyester constituting the yarn used in the present invention is mainly polyethylene terephthalate consisting of a terephthalic acid component and an ethylene glycol component. However, a part of the terephthalic acid component (usually 10 mol% or less, preferably 5 mol% or less)
Even if it is a polyester in which the ethylene glycol component is replaced with another difunctional carboxylic acid component, and/or a part of the ethylene glycol component (usually 10 mol% or less, preferably 5 mol% or less) is replaced with another diol component. It may be. Further, such polyester may contain additives such as stabilizers, colorants, etc., as necessary. The degree of polymerization of such polyester can vary over a wide range, but if it is too high, the Young's modulus of the resulting cord tends to be low or the heat shrinkage rate tends to be high, while if it is too low, the strength decreases. The intrinsic viscosity of the yarn is usually
It ranges from 0.3 to 1.0, preferably from 0.5 to 0.9. Note that the intrinsic viscosity referred to in this specification was determined from a value measured at a temperature of 25° C. using orthochlorophenol as a solvent. The yarn made of the above-mentioned polyester can be obtained by spinning and drawing a polyester having a suitable intrinsic viscosity according to a conventional method. During spinning, the fineness (De) of the yarn after drawing and the fineness (de) of the single yarns that make up this yarn are calculated using the following formula () It is necessary to set the number of holes in the spinneret, the discharge amount, and the winding speed so as to satisfy the following. The fineness of the yarn after drawing varies depending on the use, the number of yarns to be folded during cord production, etc., and cannot be unconditionally specified. For example, when making a cord to be used for reinforcing passenger car tires, when the number of yarns is two, it is usually 1000 to 1,500 denier, and when the number of yarns is three, it is usually 800 to 1,500 denier. Once the fineness of this yarn is determined, the fineness of the single yarn constituting it, that is, the number of holes in the spinneret, may be selected within the range of the above formula (). If the relationship between the fineness of the yarn after drawing and the fineness of the single yarn is out of the range of the above formula (), that is, when the fineness of the single yarn is too large or too small compared to the fineness of the yarn, adhesion as described below will be applied. Even if the heat setting temperature of the yarn before application of the agent and the heat treatment temperature of the cord after application are optimized, the flexibility of the resulting cord will be compromised if the desired adhesion is to be maintained. The undrawn yarn obtained by spinning is drawn, heat-set to impart dimensional stability to the drawn yarn, and then pre-twisted, doubled, and ply-twisted to form a green cord, and an adhesive is applied to the obtained green cord. After applying this, it is further heat treated to create a product code. In the method of the present invention, among these steps, the heat treatment temperatures before and after applying the adhesive have a special relationship. That is, if the yarn temperature at the time of heat setting of the yarn before applying adhesive is T ₁ (°C), and the cord temperature at the time of heat treatment of the cord after applying adhesive is T ₂ (°C), then T ₁ and T ₂ are It is necessary to satisfy the following formulas () and () T ₂ −10<T ₁ <T ₂ +10 ……() 200<T ₂ <250 ……(). The heat treatment of the cord after applying the adhesive is done to obtain high strength, high Young's modulus, and low shrinkage of the cord.
It is necessary to carry out the process at a high temperature of 250℃. The cords subjected to this heat treatment are different from yarns subjected to heat setting before applying adhesive, as they are usually first twisted 20 to 50 times/10cm and then ply twisted an additional 20 to 50 times/10cm after doubling. , the single yarns are mutually tightened with strong force and are susceptible to cross-sectional deformation during heat treatment. Therefore,
If the heat setting temperature of the yarn before applying the adhesive is insufficient and the yarn temperature T ₁ at this time is lower than the range of the above formula (), the single yarn cross section will become polygonal during the heat treatment of the cord after applying the adhesive. As a result, the single yarns are arranged in a close-packed arrangement with few gaps, and as a result, the contact area between the single yarns becomes large, and the flexibility of the resulting cord is significantly impaired. Also,
When T ₁ is higher than the range of the above formula (), the flexibility of the obtained cord is not impaired, but its strength retention rate is greatly reduced, making it unsuitable as a reinforcing material. However, if T ₁ and T ₂ satisfy the above formulas () and (), and the fineness (De) of the yarn after drawing and the fineness (de) of the single yarn constituting this yarn are
When satisfies the above formula (), a rubber structure reinforcing material is obtained which has flexibility while maintaining excellent adhesion and has excellent adhesion, fatigue resistance, and workability. In the method of the present invention, any heating means can be employed for the heat setting of the yarn, the heat treatment of the cord, and the heating during stretching, but usually a liquid bath, a gas bath,
A heating roller or the like is preferably used. Note that any stretching method may be employed for stretching the unstretched yarn, but since high strength is required, multi-stage stretching of two or more stages is preferred. Further, as the adhesive applied to the raw cord, any adhesive can be used as long as it is applicable to the polyester cord of the rubber structure reinforcing material. The present invention will be explained in further detail by giving examples below.
In addition, the strong retention rate (%) in the examples is
Based on JISL1017 (1963), page 19, 1-3-2-2 Disk fatigue strength (Gutdrich method). however,
The operating conditions were an ambient temperature of 80°C, a compression ratio of 17.5%, an elongation ratio of 5.8%, a rotation speed of 2300 rpm, and a time of 23 hours.
Peel adhesion strength (Kg/cord) was determined by embedding 5 treated cords in rubber and measuring the peel strength of the 5 cords after vulcanization (150℃ x 30 minutes x vulcanized plate surface pressure 25Kg/cm ² ). The true average value is shown. The Gurley hardness (mg) was measured using a Gurley measuring device manufactured by Testee KK. Examples 1 and 2 and Comparative Examples 1 and 2 Polyethylene terephthalate with an intrinsic viscosity of 0.89 is listed in Table 1. Using spinnerets with various hole numbers, the discharge rate was 417 g/min, the discharge temperature was 300°C, and the winding speed was
After melt spinning at 458 m/min, the first stage of stretching was carried out at a temperature of 80°C at various ratios listed in Table 1, followed by the second stage of stretching at a temperature of 300°C at a ratio of 1.6 times, followed by shrinkage. Heat setting was performed for 2 seconds at a bath temperature of 5% and a bath temperature of 380°C. The temperature of the yarn at the exit of the heat set bath (T ₁ ) was measured with a Barnes surface thermometer.
It was 240℃. The total fineness (De) of the obtained yarn was 1500 denier, and the single yarn fineness (de) was as shown in Table 1. After first twisting this yarn 400 times/m, two yarns are combined and further twisted 400 times/m to form a raw cord, and an initial condensate of phenol formaldehyde resin and resorcin formaldehyde is applied to this raw cord as an adhesive. Adhesives consisting of water-dispersed mixtures with rubber latex added to them (e.g.,
-3794), the first stage heat treatment was carried out at a bath temperature of 240℃ for 60 seconds, followed by the second stage heat treatment at a bath temperature of 240℃ for 60 seconds.
It was heat treated in stages. The temperature (T ₂ ) of the treatment cord at the outlet of the second stage heat treatment bath was 235°C. Table 1 shows the characteristics of the obtained processed code.

[Table] Examples 3 and 4 and Comparative Examples 3 and 4 The same procedure as in Example 2 was carried out except that the temperature of the hot setting bath after stretching was changed to various temperatures listed in Table 2. The characteristics of the obtained processed code are shown in Table 2.

【table】

Claims (1)

[Scope of Claims] 1. A drawn and heat-set yarn made of polyester whose main repeating unit is ethylene terephthalate is first twisted, doubled and plied to form a cord, and then an adhesive is applied to the cord. When producing a rubber structure reinforcement material by heat treatment, the relationship between the fineness of the yarn and the fineness of the single yarns constituting the yarn is expressed by the following formula (1). (In the formula, De is the fineness (denier) of the yarn,
de indicates the fineness (denier) of the single yarn constituting the yarn. ), and the relationship between the yarn temperature during heat setting before applying adhesive and the cord temperature during heat treatment after applying adhesive is expressed by the following formulas () and () T ₂ -10<T ₁ <T ₂ +10... ...() 200<T ₂ <250 ...() (where, T ₁ is the yarn temperature (℃) during heat setting before applying adhesive, and T ₂ is the cord temperature during heat treatment after applying adhesive (℃) ).) A method for manufacturing a rubber structure reinforcing material, characterized by satisfying the following.