JPS6328127B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester fibers, and more particularly to polyester fibers with improved heat resistance stability suitable for cords 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 reinforced cords 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 wholly aromatic polyamide fibers with rigid molecular chains. On the other hand, as a more general-purpose synthetic fiber, rubber reinforced cord made of polyethylene terephthalate, which has high strength and low equilibrium moisture content, is known to have excellent dimensional stability and high resistance to thermal deterioration. Tensile strength decreases significantly under heavy load and high speed conditions that generate heat. 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 portion of the fiber structure, which may cause the amine compounds contained in the rubber to This is thought to be due to chemical deterioration. 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 purpose of the present inventor is to eliminate the drawbacks of tire cords due to the above two factors, and to eliminate heavy loads that generate high temperatures.
The object of the present invention is to provide a polyester fiber that has sufficient strength even under high speed conditions and is particularly useful as a rubber reinforcing material. Yet another object of the present invention is to provide desired polyester fibers relatively easily and at low cost. According to the present invention, a monomer or polymerization of an ester consisting of a dicarboxylic acid component having a polycyclic condensation or at least two benzene rings and an ethylene glycol component based on the weight of the polyester containing ethylene terephthalate as a main repeating unit. 0.5 to 7% by weight of prepolymer with a degree of less than 10
Provided is a polyester fiber for a rubber reinforcing cord, which is a fiber made of a composition obtained by an additive reaction and has a breaking elongation of 20% or less. In the present invention, "polyester" refers to a substance whose main constituent is ethylene terephthalate repeating units, and which contains polyethylene terephthalate as its main component, 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 phenols (Irganox), 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 °C. However, as will be described later, if the intrinsic viscosity exceeds 0.90, the melt viscosity of the composition increases after the addition reaction of the ester or prepolymer, making it difficult to melt and mold it into a fiber shape. desirable. In the present invention, the monomer or degree of polymerization of the ester consisting of a dicarboxylic acid component having a condensed polycyclic ring or at least two benzene rings is added to the polyester.
A polyester composition is obtained by adding and reacting 0.5 to 7.0% by weight of a prepolymer of 10 or less. Examples of the dicarboxylic acid component having a condensed polycyclic ring or at least two benzene rings include those represented by the following structural formula. These dicarboxylic acid components form esters with the ethylene glycol component, and are added to the polyester as monomers or in the form of prepolymers containing oligomers with a degree of polymerization of 10 or less. In the present invention, an ester monomer obtained from the dicarboxylic acid component or a prepolymer having a degree of polymerization of 10 or less is added before or after the completion of polyester polymerization. Generally, when monomers or prepolymers are added before the completion of polymerization of polyester, the system is at least
It is preferable to react with polyethylene terephthalate by maintaining the temperature at 280°C or higher.
In addition, when the polyester is added and mixed after completion of polymerization, the polyester is made into pellets or powder, and the ester monomer or prepolymer obtained from the other dicarboxylic acid component is made into powder, and a drum tumbler, ribbon blender, etc. After sufficiently mixing the two, the mixture may be reacted by heating at a temperature of 280° C. or higher, or the solid mixture may be melt-spun as it is at a temperature of 280° C. or higher, and the reaction may be caused during the melt-spinning. In any case, it is necessary to add at least the above acid component to the end of the linear polyethylene terephthalate molecule in a range of 0.5 to 0.7% by weight based on the polyester and heat and mix at 280°C or higher so that at least the above acid component reacts effectively. . In this case, if the amount added is less than 0.5%, the desired heat-resistant stability effect will not be achieved, and if it exceeds 7%, the acid component will be randomly incorporated into the molecular chain of the linear polyethylene phthalate, so that the resulting polyester composition The melting point decreases significantly, making it impossible to obtain the desired heat-resistant stability effect. The polyester fiber with good heat resistance stability in the present invention is generally produced by adjusting the polyester composition obtained as described above to a melt viscosity that allows melt molding, and then extruding it from a spinneret and molding it into a fiber by a conventional method. It can be obtained by In this case, a method may be adopted as needed, such as a method of cooling after discharge, winding it into an undrawn filament and then heating and stretching heat treatment in a separate process, or a method of cooling after discharge and immediately heating and stretching heat treatment without winding it into an undrawn filament. can. In particular, in the latter direct drawing method, it is useful in terms of the performance of the resulting fibers that the unsolidified yarn is immediately subjected to a two-step drawing heat treatment after being melted and discharged.
By the above-mentioned stretching, the elongation at break of the resulting fiber is adjusted to 20% or less, which has conventionally been commonly used for polyester fibers for rubber reinforcing cords. In the polyester fiber of the present invention, the ester consisting of a dicarboxylic acid component having a condensed polycyclic ring or at least two benzene rings that undergoes an addition reaction is bonded to the molecular terminal, resulting in a polyester fiber with a relatively low free carboxyl concentration. For example, in the case of a two-layer structure model such as a crystalline phase and an amorphous phase, when the fiber structure is organized by forming it into a fibrous shape and performing oriented crystallization, the amorphous phase is a condensed polycyclic or amorphous phase. Both have excellent chemical resistance (especially to amines) because they are relatively dense due to the presence of two benzene rings. Also, depending on the combination of melt molding methods, the fiber structure is relatively homogeneous and the crystal phase-obligatory phase is not clear, so it is relatively stable against amine decomposition. Therefore, if the polyester fiber obtained by the present invention is made into a cord by a conventional method and used for reinforcing rubber, 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. Examples of the present invention will be described in detail below, but the present invention is not limited thereto. Example 1 Polyethylene terephthalate pellets with an intrinsic viscosity of 0.71 were mixed with 1.5% by weight of powder of ethylene glycol diester of 4,4'-diphenyldicarboxylic acid, dried at 160°C for 6 hours, and then melt-spun using an extruder. It is fed to a spinning machine, heated and melted to a maximum temperature of 300℃, discharged from a spinneret with a hole diameter of 0.4 mm and 192 holes, cooled, and oiled at a speed of 400 m/min.
I rolled it up. After that, it rotates at 80m/min.
Heated roll at 100℃, second heated at 140℃
Using a roll and a third roll heated to 195° C., the film was stretched to a total stretching ratio of 6.0 and heat-treated. The strength and elongation retention rate when the obtained yarn was subjected to constant length and relaxation heat deterioration for 60 minutes in a constant temperature bath at 250°C were
Shown in the table. Note that Experiment No. 2 is a comparative example in which ethylene glycol diester of 4,4'-diphenyl dicarboxylic acid was not added or mixed.

[Table] Example 2 Ethylene terephthalate was polymerized by a conventional method,
Ethylene was prepared separately 10 minutes before polymerization was completed.
Add 2,6-naphthalate pentamer and heat at 320℃
The mixture was reacted for 10 minutes to obtain a polyester composition with an intrinsic viscosity of 0.67. This composition was supplied to a spinning machine equipped with an extruder, melted at 330°C, and spun and drawn in the same manner as in Example 1 to obtain a drawn yarn. Next, this drawn yarn was heated in a dry heat constant temperature bath at 250℃ for 60 minutes.
Table 3 shows the strength and elongation retention rate when thermally degraded over a certain length.

【table】

Claims (1)

[Claims] 1 A polyester containing ethylene terephthalate as a main repeating unit is added with a monomer of an ester consisting of a dicarboxylic acid component having a condensed polycycle or at least two benzene rings and an ethylene glycol component, or a polymerization degree of 10 based on the weight of the polyester. A polyester fiber for rubber reinforcing cord, which is a fiber made of a composition obtained by adding and reacting 0.5 to 7% by weight of the following prepolymers, and having a breaking elongation of 20% or less.