JPH0221420B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester elastomer compositions. The purpose is to provide an elastomer composition with improved crystallinity of the hard segment and excellent elastic properties. Polyester elastomers, which have aromatic polyester as a hard segment and polyether as a soft segment, have traditionally attracted attention as melt-moldable elastomers, but due to their compositional limitations, they are between rubber and plastics in terms of physical properties. Its uses have been developed, and recently it has been used in some molded products, coating agents, etc. This elastomer suppresses the fluidity of molecules in the soft segment by the crystal cohesive force of the hard segment, giving it elasticity, which lowers the secondary dislocation point of the soft segment and improves the crystallinity of the hard segment. improvement has become an important factor in improving elastic properties. The present inventors recognized that since the polyester elastomer has entropic elasticity, addition of a filler with a large specific heat is more effective than just a nucleating agent. The inventors have discovered that the same effect can be achieved if the affinity is high, and the present invention has been achieved. That is, the present invention uses a polyester elastomer with aromatic polyester as a hard segment and polyether as a soft segment, with a melting point of 231°C.
High melting point polybutylene terephthalate of more than 0.01
This is a polyester elastomer composition characterized by containing ~10% by weight. In the present invention, the "aromatic polyester" constituting the hard segment is a polyester containing an aromatic dicarboxylic acid as the main acid component and an aliphatic dihydroxy compound as the main glycol component. Here, "main" usually means 80 mol% or more of repeating units, and 20 mol% or less of other components may be copolymerized. Aromatic dicarboxylic acids referred to in the present invention include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl ketone dicarboxylic acid, diphenyl sulfone dicarboxylic acid, etc. is exemplified, and it is preferable that 50 mol% or more of the total acid components consist of the same acid. Examples of the aliphatic dihydroxy compound include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, etc., and it is preferable that 50 mol% or more of the total glycol component is composed of the same dihydroxy compound. Among these, the combination of terephthalic acid and tetramethylene glycol is particularly preferred. The polyether constituting the soft segment of the elastomer of the present invention means a polymer of the aliphatic glycol listed above, specifically polyethylene glycol, polypropylene glycol, polytetramethylene glycol, or a copolymer thereof. Illustrated. The molecular weight of such polyether is 500~
6000 is preferred, and 800-3000 is particularly preferred. Among these, polytetramethylene glycol is particularly preferred. The composition of the present invention needs to contain 0.01 to 10% by weight of high melting point polybutylene terephthalate. Here is "high melting point polybutylene terephthalate"
(hereinafter abbreviated as "high melting point PBT") is the endothermic peak temperature when the temperature is raised at 20℃/min using a differential calorimeter.
That is, it refers to polybutylene terephthalate with a melting point (Tm°C) of 231°C or higher. Traditionally, generally manufactured,
Commercially available polybutylene terephthalate is
It has a melting point of 220-230°C, usually around 225-228°C, and is known to have two types of crystal structures: α-type and β-type. However, the high melting point used in the present invention
PBT is a polymer with a melting point of 231°C or higher, preferably 235°C or higher, and even 240°C or higher, and it is not clear whether its crystal structure is the same as conventional ones. The high melting point PBT can be obtained by heat treating a normal PBT polymer at a temperature close to its melting point, for example around 200° C., for a long period of several tens of hours. High melting point PBT has a similar molecular structure to the polyester elastomer, which is the base polymer used as the matrix to be blended, and has a strong crystallization promoting effect, perhaps because it has affinity. Here, the "crystallization promotion effect" is determined by heating up to 250°C at a rate of 20°C/min in a nitrogen atmosphere using a differential calorimeter.
Therefore, after holding for 3 minutes, the exothermic peak temperature (Tcd℃) and endothermic peak (Tm
℃) and the difference △T (= Tm - Tcd),
A small ΔT means a large "crystallization promoting effect". In the present invention, the blending amount of the high melting point PBT is
It is necessary that the content is 0.01 to 10% by weight. If it is less than 0.01% by weight, the effect of promoting crystallization is small;
If it exceeds 10% by weight, although there is a promoting effect, the appearance deteriorates, such as becoming brittle or giving a foreign body feel. Furthermore, when molding into fibers, films, etc., pack pressure, filter overpressure, etc. tend to increase. preferably 0.05
~8% by weight, more preferably 0.1~5% by weight. Although the high melting point PBT can be blended into the polyester elastomer by any method, for example, the following method can be used. First, use high melting point PBT with an average particle size of 50μ or less.
It is preferably ground to 20μ or less, more preferably 5μ or less. Next, it is blended into a polyester elastomer in the following manner. 1. Add the high melting point PBT powder to the polyester elastomer at the final stage of polymerization, stir and mix, and then discharge. 2 Polyester elastomer pellets with high melting point
PBT is mechanically mixed using a mixer such as a tumbler or blender, and the mixture is directly subjected to melt molding. 3. The polyester elastomer blended with the high melting point PBT obtained in step 2 is once melt-extruded, pelletized using a pelletizer, and then subjected to melt molding. 4. When molding polyester elastomer, high melting point PBT is supplied in a fixed amount to the supply section or vent section, mixed into the polyester elastomer, and molded as it is. 5. High melting point PBT is mixed into the polyester elastomer while being fed in a constant quantity from the feed section or vent section of the extruder, and then the polyester elastomer is extruded and pelletized using a pelletizer, followed by melt molding. The polyester elastomer composition of the present invention is
Provides molded products with excellent crystallinity and good elastic properties. Molded products include ordinary injection molded products and extrusion molded products, as well as films, fibers, etc. The present invention will be specifically explained below with reference to Examples. In the examples, all parts represent parts by weight, and the intrinsic viscosity is calculated from the solution viscosity of an orthochlorophenol solution of the polymer at 35°C.
In addition, Tm means the endothermic peak temperature (°C), that is, the melting point, measured by heating at 20 °C/min with a differential calorimeter, and Tcd means the endothermic peak temperature (°C) measured with a differential calorimeter at 20 °C/min in a nitrogen atmosphere.
This is the endothermic peak temperature (°C) when the temperature is raised to 250°C at a rate of °C/min, held there for 3 minutes, and then lowered at a rate of 7°C/min. Furthermore, the 50% elongation modulus is JISL1073
(1977) The elongation elastic modulus at 50% elongation was measured using the elongation elastic modulus B method of the synthetic fiber yarn test method. Examples 1 to 5, Comparative Examples 1 to 2 147 parts of dimethyl terephthalate, 100 parts of tetramethylene glycol, 244 parts of polytetramethylene glycol with a number average molecular weight of 2000, and 0.31 part of tetrabutyl titanate were charged into a reactor and esterified at an internal temperature of 170°C. An exchange reaction was carried out. When 80% of the theoretical amount of methanol had been distilled, the temperature of the system was raised, and the pressure began to be reduced to 30 mmHg over about 30 minutes, and then to 3 mmHg over another 30 minutes, after which the internal temperature was reduced to 245°C under a vacuum of 1 mmHg.
The reaction was carried out for 240 minutes. The intrinsic viscosity of the resulting polyar was 1.40. This polyester elastomer was blended with predetermined amounts of various high melting point PBT listed in the following table, mixed in a tumbler, and then melted and extruded in an extruder to form pellets. The crystallization behavior of this blended elastomer pellet was as shown in the center column of the same table. This pellet was melt-spun at 260°C to obtain an elastic yarn of 135 denier. The elastic modulus of this elastic yarn at 50% elongation was as shown in the right column of the same table.

[Table] As is clear from this result, melting point (Tm)
In the elastomer compositions (Examples 1 to 5) to which PBT with a high melting point of 231° C. or higher is added, the effect of promoting crystallization is remarkable, and the elastic properties are also greatly improved. On the other hand, those without the addition of high melting point PBT (Comparative Example 1) and those with the addition of PBT with a melting point of less than 231°C (Comparative Example 2) had no crystallization promotion effect and had poor elastic properties. Ta.

Claims (1)

[Claims] 1 0.01 to 10% by weight of high melting point polybutylene terephthalate with a melting point of 231°C or higher is added to a polyester elastomer with aromatic polyester as a hard segment and polyether as a soft segment.
A polyester elastomer composition comprising: