JPS6149408B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester fibers, and more particularly to polyester fibers with good heat resistance stability for reinforcing rubber products. In recent years, pneumatic tires have come to be increasingly subjected to harsh handling due to the increase in the traveling speed of automobiles and the faster takeoff and landing speeds of airplanes. For this reason,
Various attempts have been made to provide improved rubber reinforcements designed to withstand the severe impacts and high temperatures of handling at high speeds or under heavy loads. Examples include inorganic materials such as glass fibers and steel fibers, and rigid wholly aromatic polyamide fibers. On the other hand, rubber reinforcements made of polyethylene terephthalate, which has higher strength and lower equilibrium moisture content as a general-purpose synthetic fiber, are known to have excellent dimensional stability and a high degree of resistance to thermal degradation at high temperatures. Under conditions of heavy loads and high speeds, the tensile strength decreases significantly. These disadvantages of polyethylene terephthalate fibers may be due to the large number of free carboxyl groups in the molecular chain and depolymerization due to hydrolysis, or the loose structure of the amorphous part of the fiber structure and the amine compounds contained in the rubber. This is thought to be due to the chemical deterioration caused by heat. In particular, some improvements have been made to reduce the number of free carboxyl groups for the former, but the current situation is that these cannot simultaneously eliminate the latter factor. The object of the present invention is to eliminate the above-mentioned two factors and provide a polyester fiber that has sufficient strength even under heavy load and high speed conditions that generate high temperatures. Yet another object of the present invention is to provide desired polyester fibers relatively easily and at low cost. According to the present invention, an ester monomer having at least one benzene ring in both the dicarboxylic acid component and the dioxy component, based on the weight of the polyester, is added to the end of the polyester containing ethylene terephthalate as a main repeating unit. A polyester fiber having good heat resistance stability is provided which is made of a polymer or a composition obtained by adding and reacting a polymer in an amount of 0.5 to 7 wt%. The term "polyester" used in the present invention refers to a substance whose main constituent is ethylene terephthalate repeating units, and which mainly contains polyethylene terephthalate, but contains a third component within a range that does not essentially change its properties (for example, 15 mol% or less). A copolyester obtained by copolymerizing may also be used. Furthermore, additives well known in the field, particularly heat stabilizers, such as sterically hindered phenol (lrganox), aromatic amines (Sumilizer PB), phosphorus-containing compounds, and sulfur-containing compounds (Sumilizer TPL) are added to the above polyester. This is also useful in the present invention. Furthermore, the degree of polymerization of the above-mentioned polyester should be selected appropriately depending on the type of polyester and its use, but generally in the case of polyethylene terephthalate, the degree of polymerization is 35%.
A suitable material has an intrinsic viscosity of 0.5 or more as measured with an O-chlorophenol solution at .degree. However, if the intrinsic viscosity exceeds 0.90, the melt viscosity of the composition increases after the addition reaction of the ester or polymer, making it difficult to melt and mold it into a fiber shape, as will be described later.
It is desirable to set it to 0.5-0.9. In the present invention, a polyester composition is obtained by adding and reacting 0.5 to 7 wt % of an ester monomer, prepolymer or polymer having at least one benzene ring to both the dicarboxylic acid component and the dioxy component to the above polyester. Here, examples of the acid component having at least one benzene ring include terephthalic acid, isophthalic acid, methyl terephthalic acid, or 4,4'-diphenyl dicarboxylic acid, and the dioxy component having at least one benzene ring. Examples of this include compounds represented by the following structural formula. It goes without saying that the above dicarboxylic acid components may be used alone or in combination of two or more. The ester formed from the dicarboxylic acid component and the dioxy component is reacted with the polyester in the form of a monomer, a prepolymer containing an oligomer, or a polymer. In the present invention, the ester monomer, prepolymer or polymer obtained from the dicarboxylic acid component and dioxy component is added before or after the completion of polymerization of the polyester. In the former case, the monomer or prepolymer is added and the mixture is heated to at least 280°C before the polyester polymerization is completed.
It is preferable to maintain the temperature above and react with linear polyethylene terephthalate. In the latter case, after the polymerization of the polyester is completed, the polyester is made into pellets or powder, and a polymer obtained from the above-mentioned dicarboxylic acid component and dioxy component in the same shape is mixed using, for example, a drum tumbler, a ribbon blender, etc. It is also preferable to carry out the reaction by heating at a temperature of 280°C or higher, or by blending both polymers in a molten state at 280°C or higher.
In any case, at least the above-mentioned rigid dicarboxylic acid component and dioxy component are added to the molecular terminal of the linear polyethylene terephthalate in a range of 0.5 to 7 wt% based on the polyester so that they react effectively and the temperature is higher than 280℃. It is necessary to heat it to If the amount added is less than 0.5%, the desired heat resistance stability effect will not be achieved, and if it exceeds 7%, the dicarboxylic acid component and dioxy component will be randomly incorporated into the molecular chain of linear polyethylene terephthalate, resulting in a poor polyester composition. The melting point of the substance decreases significantly, and the effect of heat resistance stability is lost. Polyester fibers with good heat resistance stability in the present invention are generally obtained under various conditions as described below. That is, the polyester composition obtained as described above is adjusted to a melt viscosity that can be melted and molded, and then discharged from a spinneret and molded into a fiber by a conventional method. In this case, there is a method in which the product is cooled after being discharged, wound once into an undrawn yarn shape, and then heated and stretched at a high magnification in a separate step, or cooled after discharged, and immediately heated and stretched at a high magnification without being wound once into an undrawn yarn shape. etc. can be adopted at any time. In particular, in the latter direct drawing method, the yarn that has not yet solidified after being melted and discharged is immediately drawn at a high magnification.
The stage drawing heat treatment is useful in terms of the performance of the resulting fibers. In the polyester fiber of the present invention, an ester consisting of a dicarboxylic acid component and a dioxy component having at least one benzene ring in the molecule that reacts with the polyester is bonded to the molecular end, resulting in a relatively low free carboxyl concentration. Not only does it have a low polyester fiber, but when it is formed into a fiber and is oriented and crystallized to organize the fiber structure, for example, in the case of a two-layer structure model such as a crystalline phase and an amorphous phase, it becomes an amorphous phase. Due to the presence of a highly rigid benzene ring, it is relatively dense and has excellent chemical resistance (especially to amines). Also, depending on the combination of molding methods, the fiber structure is relatively homogeneous and the crystalline phase and amorphous phase are not clearly defined, so it is relatively stable against amine decomposition. Therefore, if the polyester fiber obtained according to the present invention is made into cords by a conventional method and used as a rubber reinforcing material, it will become an extremely useful reinforcing material with little loss of strength even under conditions of heavy loads and high speeds that generate high temperatures. For such rubber reinforcing materials, it is essential to impart sufficient molecular orientation and crystallinity to the polyester fibers by the above-mentioned molding method. Polyester fibers obtained by applying the method are also useful because they have good heat resistance stability suitable for other uses (for example, weft yarns for sudare). That is, the polyester composition is melted, discharged through a spinneret, and taken off at a high speed of 2,000 m/min, preferably 2,500 m/min or more, so as to become a partially oriented yarn, and the elongation of the wound yarn is adjusted to 70 to 200%.
Alternatively, the spinning speed is adjusted to less than 2000 m/min, especially 800 to 1500 m/min, and the undrawn yarn is wound and further stretched at a low magnification (1.3 to 3.0) to give the final elongation of the drawn yarn to 70 to 1500 m/min. This is about the yarn obtained by adjusting it to 200%. This yarn is treated with steam,
Heat-treated yarn with a dry heat shrinkage rate of +5 to -2% at 150°C for 30 minutes is extremely suitable as a weft for tire cord fabrics. That is, it has a cutting elongation of 60% or more even after being heat-treated for free shrinkage at 245°C for 2 minutes. Therefore, in a tire cord fabric (gray fabric) using the heat-treated yarn as the weft yarn, the weft yarn has excellent dimensional stability at room temperature, so there is no concern about uneven width of the gray fabric due to uneven shrinkage of the weft yarn, and the warp yarns are spaced evenly apart. is held in Moreover, the elongation of the weft threads of this gray fabric does not substantially decrease even after dip treatment (245℃ for several minutes), so the weft threads stretch uniformly during tire molding (especially during inflation), and as a result, the warp spacing remains uniform. This results in a homogeneous tire. As mentioned above, the polyester fiber of the present invention has excellent heat resistance stability during high-temperature processing, and therefore is useful not only as a rubber reinforcing material but also as a yarn for weft yarns of tire cord fabrics, and has great industrial significance. Examples of the present invention will be described in detail below, but the present invention is not limited thereto. Example 1 Polyarylate pellets (U-8000 Natural, manufactured by Unitika Co., Ltd.) were mixed with polyethylene terephthalate pellets having an intrinsic viscosity of 0.64 in the proportions shown in Table 1, dried at 160°C for 6 hours, and then equipped with an extruder. It is fed to a melt spinning machine and heated to a maximum temperature of 330℃ to melt it, and the pore size is 0.4 mm.
The material was discharged from a spinneret with 192 holes, cooled, oiled, and wound at 400 m/min. Thereafter, it was stretched to a total stretching ratio of 6.0 and heat treated using a heated roll at 100°C rotating at 80 m/min, a second roll heated to 140°C, and a third roll heated to 195°C. . Table 1 shows the strength and elongation retention when the obtained yarn was thermally degraded for 60 minutes in a constant temperature bath at 250°C.

[Table] Example 2 Polyethylene terephthalate pellets with an intrinsic viscosity of 0.64 were mixed with 2.5 wt% of polyacrylate pellets (U-8000 Natural, manufactured by Unitika Co., Ltd.), dried at 160°C for 6 hours, and then melted using an extruder. It was supplied to a spinning machine, heated and melted to a maximum temperature of 320°C, discharged from a spinneret with a hole diameter of 0.35 mm and 36 holes, cooled, oiled, and wound as a partially oriented yarn at 3300 m/min. Winding ivy yarn at 100t/m
While twisting the yarn, turn it back into the cylinder, and in this state
Steam treatment was performed at 135°C for 30 minutes. Furthermore, this set yarn was heated at (a) 150℃ for 30 minutes, (b) 230℃ for 2 minutes, (c) 240℃
The dry heat shrinkage (DHS) and elongation (DE) at 150°C were measured after free heat treatment at 245°C for 2 minutes and (d) at 245°C for 2 minutes. The results are shown in Table 2.

【table】

[Table] Ratio: Comparative Example Example 3 Ethylene terephthalate was polymerized by a conventional method,
It was prepared separately 15 minutes before polymerization was completed. Ester 3 of acid component (terephthalic acid/isophthalic acid = 50/50 mol%) and diol component (bisphenol A)
A polyester composition having an intrinsic viscosity of 0.66 was obtained by adding 2.5 wt% of polymer and reacting at 300°C for 15 minutes. This composition is fed into a spinning machine equipped with an extruder.
After melting at 300° C., a stretched and heat-treated yarn (Experiment No. 10) was obtained in the same manner as in [Example 1], and a partially oriented yarn (Experiment No. 11) was obtained in the same manner as in [Example 2]. experiment
For No. 10, the strength elongation retention rate after 60 minutes at 250℃, and for Experiment No. 11, (a) 150℃ x 30 minutes, (d)
DHS and DEA after treatment at 245°C for 2 minutes were determined. The results are shown in Tables 3 and 4, respectively.

【table】

【table】

Claims (1)

[Claims] 1 At the end of a polyester containing ethylene terephthalate as a main repeating unit, an ester monomer, prepolymer, or A polyester fiber with good heat resistance stability characterized by being made of a composition obtained by adding and reacting 0.5 to 7 wt% of a polymer.