JPH07179590A - Polyester resin chip - Google Patents

Abstract

PURPOSE:To obtain polyester resin chips prevented from defective molding even in case of being virtually free from any plasticizer or crystal nucleating agent and shortened in its molding cycle time, by specifying the crystallization characteristics of polyethylene terephthalate resin chips. CONSTITUTION:The crystallization characteristics of polyester resin chips with polyethylene terephthalate as the main polyester component are altered so as to satisfy the relationship, Ts/Tc<=0.9 [where, Ts is half-crystallization time (see) at 120 deg.C for the 40wt.% portion from the surface side of said chip and Tc 60wt.% portion from the central side of said chip.]. The alteration can be accomplished by changing the crystallization rate of the chip surface by impact treatment of the chips.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene terephthalate type polyester resin chip. The polyester resin chip of the present invention has crystallization characteristics suitable for molding, and is therefore useful as a molding material in various moldings.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Has excellent mechanical properties, heat resistance, chemical resistance, electrical properties, etc., and is widely used as an engineering plastic in electric, electronic parts, automobile parts, parts for heat appliances, etc. Generally, PET is once used as a chip. A desired final molded product is manufactured by molding and subjecting the chips to a molding device. However, since PET has a relatively low crystallization rate as an injection molding material, it has drawbacks such as molding defects such as burrs and long cycle times. Conventionally, in order to solve these problems, addition of a plasticizer such as polyethylene glycol, copolymerization, and addition of a crystal nucleating agent have been carried out. However, according to such a method, bleed-out of the plasticizer; melting point, glass transition temperature (Tg)
Heat resistance is reduced due to the decrease in the temperature; problems such as coloring occur.

On the other hand, the crystallization characteristics of PET are often used for transparent containers such as bottles and trays, but in these fields as well, control of the crystallization rate may be important. For example, in a heat-resistant bottle, sufficient transparency is obtained in the injection molding process and the blow molding process, and moreover, an appropriate crystal that can be rapidly crystallized in the mouth crystallization process and the bottle body heat setting process. The speed of conversion is needed. Also in this case, addition of a crystal nucleating agent, molecular weight, diethylene glycol (D
EG) It is possible to control the crystallization rate by controlling the amount of copolymerization, the content of oligomers, the type and amount of catalyst, the end group, etc., but other factors such as generation of acetaldehyde, deterioration of physical properties such as strength, deterioration of heat resistance, etc. It is not a very effective means because it often affects the characteristics.

[0004]

It is an object of the present invention to be excellent at the time of molding even when it is composed mainly of a polyester mainly composed of an ethylene terephthalate component and does not substantially contain a compounding agent such as a plasticizer or a crystal nucleating agent. It is intended to provide a polyester resin chip capable of exhibiting crystallization characteristics.

[0005]

The inventors of the present invention have conducted research to achieve the above object, and as a result, the crystallization rate of PET is increased by giving a constant impact to the polyethylene terephthalate resin chip. Found. That is, the present invention is a polyester resin chip made of polyester comprising a dicarboxylic acid unit mainly containing a terephthalic acid unit and a glycol unit mainly containing an ethylene glycol unit, which is 40% by weight from the surface side. The semi-crystallization time Ts (second) at 120 ° C. and the semi-crystallization time Tc (second) at 120 ° C. of 60% of the portion from the center side satisfy the following mathematical expression (1) Ts / Tc ≦ 0.9 (1). It is a polyester resin chip characterized by the above.

For the polyester resin chip of the present invention, 40% from the surface side of the chip and 60% from the center side of the chip were measured by the isothermal crystallization method on a weight basis.
When the half crystallization times at 20 ° C. are Ts (seconds) and Tc (seconds), the above formula (1) is satisfied. Polyethylene terephthalate-based polyester resin chips that do not satisfy this condition are slow to crystallize at the time of molding and in a molded product, which causes inconveniences such as a longer molding cycle and insufficient mechanical performance.

The molecular main chain of the polyester in the present invention contains about 50 mol% each of a glycol unit and a dicarboxylic acid unit as main structural units. The main portion of the dicarboxylic acid unit, preferably 40 to 50 mol% of all structural units, is occupied by terephthalic acid units, and the main portion of the glycol unit, preferably 4 of all structural units.
Ethylene glycol units account for 0 to 50 mol%.

The polyester in the present invention may contain other dicarboxylic acid units in a small amount of about 10 mol% or less of all structural units, preferably 5 mol% or less of all structural units. For example, units of aromatic dicarboxylic acid such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, paraphenylenedicarboxylic acid, sodium sulfoisophthalate; succinic acid, glutaric acid, adipic acid, suberin If necessary, one or more units of an aliphatic dicarboxylic acid unit such as an acid, dodecanedioic acid, or cyclohexanedicarboxylic acid can be contained.

The polyester in the present invention may contain other glycol units in a small amount of about 10 mol% or less of all structural units, preferably 5 mol% or less of all structural units. For example, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, bisphenol A
It may contain one or more glycol units such as ethylene oxide adducts of Furthermore, the polyester in the present invention has a trivalent or higher valent unit derived from a trifunctional or higher polyfunctional compound such as trimellitic acid or pentaerythritol, as long as the amount is not so large as to substantially impair the thermoplasticity. It may be included if necessary.

The polyester used in the present invention may be produced according to any of the methods generally employed for producing ordinary polyethylene terephthalate polyester. For example, a dicarboxylic acid raw material consisting of a dicarboxylic acid mainly composed of terephthalic acid or a lower alkyl ester thereof and a glycol raw material mainly composed of ethylene glycol are subjected to an esterification reaction or a transesterification reaction to produce a low polymer, This low polymer is melt-polycondensed to produce polyester, and then this polyester is made into chips of any shape such as dice, columnar shape, etc., and if desired, solid-phase polymerization of the chips is carried out to achieve high polymerization of chips. Polyethylene terephthalate type polyester can be manufactured.

In the above-mentioned method, the esterification reaction or transesterification reaction for obtaining a low polymer is carried out usually by mixing a mixture of the above-mentioned glycol raw material and dicarboxylic acid raw material under atmospheric pressure or at an absolute pressure of about 3 Kg / cm ² or less. The esterification reaction is carried out at a pressure of about 230 to 280 ° C., or at a pressure of about 160 to 2 under normal pressure or its vicinity.
It is carried out by transesterification at 30 ° C. In that case, the ratio of dicarboxylic acid raw material: glycol raw material used is
The molar ratio is about 1: 1 to about 1: 1.5 by the esterification reaction and about 1: 2 by the transesterification reaction.
˜about 1: 3 is recommended. The above-mentioned melt polycondensation for obtaining a polyester from a low polymer is usually carried out at a temperature of about 260 to 290 ° C in the presence of a polymerization catalyst such as germanium dioxide or antimony trioxide. And
By such melt polycondensation, it is usually about 0.40 to 0.
It is possible to obtain a polyester having an intrinsic viscosity of 75 dl / g (measured at 30 ° C. in an equal weight mixed solvent of phenol / tetrachloroethane).

Further, the above esterification reaction, transesterification reaction or melt polycondensation may be carried out by adding a diethylene glycol by-product inhibitor such as tetraalkylammonium hydroxide, triethanolamine or triethylamine, if necessary.

The above-mentioned solid phase polymerization is usually pre-crystallized at a temperature of 190 ° C. or lower, and is usually carried out under reduced pressure or flowing an inert gas such as nitrogen gas while flowing chips to about 190 to 2
It is preferably carried out by heating to a temperature of 40 ° C. In order to obtain a final molded product having good mechanical properties, the intrinsic viscosity (measured at 30 ° C. in an equal weight mixed solvent of phenol / tetrachloroethane) of the finally obtained polyester resin chip is about 0.60 to 1. It is desirable to carry out solid phase polymerization so that the range is 20 dl / g.

The polyester resin chips of the present invention can be obtained by subjecting the polyethylene terephthalate polyester resin chips obtained as described above to mechanical impact. As a method of giving an impact, there are various methods such as a blending method using a rotary tumbler, a method of hitting a polyester resin chip against a hard object such as a metal plate by entraining it in a fluid such as air, a method of dropping from a high place, etc. Although any method may be used, it is preferable from the viewpoint of the effect of improving the crystallization rate to repeatedly and sufficiently give a strong impact as long as the chip is not damaged. The temperature at the time of giving an impact is preferably in the range of 0 to 160 ° C. If the temperature is too high, the polyester resin may undergo deterioration such as thermal decomposition. Further, even if the temperature is cooled to the room temperature or lower, the effect corresponding to it is not increased. Therefore, it is industrially advantageous to treat at around room temperature.

The polyester resin chips obtained by melt polycondensation usually have a Ts / Tc value of more than 0.9 (often about 1.0). Further, in the case of a polyester resin chip obtained by solid phase polymerization, T
The value of s / Tc becomes larger than 1.0.

According to the studies conducted by the present inventors, it has been confirmed that the impact of the chip changes the conformation of the ethylene group portion of the polyester molecule near the chip surface from the gauche type to the trans type. . Therefore, the crystallization rate of the chip surface portion increases (that is, Ts decreases) due to a change in conformation due to the impact treatment on the chip, and as a result, the value of Ts / Tc becomes 0.9 or less. It is estimated that

The polyester resin chip of the present invention can be used as a molding material in the same manner as ordinary polyethylene terephthalate polyester resin.
For example, the sheet-like material can be formed by an extrusion molding method using a T die, a calendar roll method, or the like. or,
It is also possible to obtain a hollow container such as a bottle by a blow molding method from a preform obtained by an injection molding method or a pipe molding method, and, if desired, after compounding with a filler such as glass fiber, an injection molded product is obtained. It is also possible to obtain. Further, a fibrous material can be obtained by the melt spinning method.

[0018]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. In addition,
In the following examples and comparative examples, the evaluation method of the obtained polyester resin is as follows. (1) Intrinsic viscosity 3 in an equal weight mixed solvent of phenol / tetrachloroethane
It was measured at 0 ° C.

(2) Ts and Tc Polyester resin chips were dissolved in a mixed solvent of hexafluoroisopropanol / chloroform (1/1 weight ratio), and filtration was carried out at the stage where 40% of the weight from the chip surface side was dissolved. did. By reprecipitating the obtained filtrate with methanol, a polyester resin occupying 40% of the chip surface side was obtained. In addition, the rest of the chip obtained by the above filtration was dissolved in a mixed solvent of hexafluoroisopropanol / chloroform (1/1 weight ratio), and the obtained solution was reprecipitated with methanol to obtain a chip center side. A polyester resin occupying 60% of the area was obtained. Regarding the polyester resin occupying 40% of the chip surface side and the polyester resin occupying 60% of the chip center side, the half-crystallization time (Ts and Ts Tc) was measured. A pulverized product of the polyester resin was melted at 290 ° C. for 10 minutes by a differential scanning calorimetry (DSC) method (using a differential scanning calorimeter TC10A manufactured by METTLER CORPORATION), and then 110 ° C.
110 ℃ / min
The temperature was raised to 120 ° C. at the rate of, and then isothermal crystallization was performed at 120 ° C. The time from the start of the isothermal crystallization process until the area reaches half the area of the exothermic peak based on the crystallization observed in the relationship diagram between time and heat quantity,
The half-crystallization time was used.

(3) Semi-crystallization time of injection molded product Cylinder temperature 2 using polyester resin chips
Injection molding was performed under the conditions of 90 ° C., mold temperature of 12 ° C., and cycle time of 35 seconds to prepare an injection molded article in the form of a bottle preform. Using the obtained pulverized product of the injection-molded product, the temperature was increased from room temperature to 120 ° C. at a rate of 110 ° C./min by a differential scanning calorimetry (DSC) method (using a differential scanning calorimeter TC10A manufactured by METTLER CORPORATION). Warmed, then isothermal crystallization at 120 ° C. The time from the start of the isothermal crystallization process to the time when it reaches the area of 1/2 of the area of the exothermic peak due to crystallization observed in the relationship diagram between time and heat quantity was defined as the half-crystallization time of the injection-molded product.

Example 1 Ethylene glycol and terephthalic acid were adjusted to a molar ratio of 1.2: 1 to form a slurry, and the slurry was pressurized (at an absolute pressure of 2.5 K).
g / cm ² ), the esterification rate is 95% at a temperature of 250 ° C.
To produce a low-polymer by esterification reaction.
Next, 100 ppm of germanium dioxide was added as a catalyst, and the low polymer was polycondensed at a temperature of 280 ° C. under a reduced pressure of 1 torr absolute pressure to prepare a polymer having an intrinsic viscosity of 0.60 dl / g. This polymer was extruded from a nozzle in a strand shape and cut into a cylindrical chip having a length of 3.2 mm and a diameter of 2.8 mm. This polymer chip is 150 ℃
After drying for 5 hours at 20 ° C under flowing nitrogen,
Intrinsic viscosity is 0.7 after solid-state polymerization for 15 hours at 5 ℃.
A polyester resin chip having 5 dl / g and a bulk specific gravity of 0.91 was obtained. 10 kg of the obtained chip was charged in a rotary tumbler made of stainless steel having a content of 147 liters, and the chip was impacted by rotating the tumbler at 25 rpm for 18 hours at room temperature. T of the obtained chip
Table 1 shows the semi-crystallization time of s, Tc, and an injection-molded product using the same. <Comparative Example 1> Table 1 shows Ts and Tc of chips and the half-crystallization time of injection-molded products when the treatment by the tumbler was not performed. <Example 2, Comparative Examples 2 and 3> Table 1 shows Ts and Tc of the chips and the half-crystallization time of the injection-molded products obtained when the treatment conditions by the tumbler were changed.

[0022]

[Table 1]

From the above results, it can be seen that the molded product obtained by using the polyester resin chip of the present invention of the example has a remarkably improved crystallization rate.

[0024]

By using the polyester resin chip of the present invention, it is possible to obtain a molded product with an improved crystallization rate even when a compounding agent such as a plasticizer or a crystal nucleating agent is not substantially contained. it can.

Claims (1)

[Claims] 1. A polyester resin chip made of polyester comprising a dicarboxylic acid unit mainly containing a terephthalic acid unit and a glycol unit mainly consisting of an ethylene glycol unit, which is 40% by weight from the surface side. Semi-crystallization time Ts (seconds) at 60 ° C. and half-crystallization time T at 120 ° C. of 60% from the center side
A polyester resin chip characterized in that c (second) satisfies the following formula (1) Ts / Tc ≦ 0.9 (1).