KR930008191B1 - Polyester resin composition - Google Patents

Abstract

This new polyester is composed of complete aromatic polyester repeated structure as main chain and has improved crystalization speed and good heat resistance. The polyester composition is made by adding 0.05-10 wt.% polyester oligomer in polyethylene terephthalate of 0.4-1.5 dl/g of specific viscosity. The above complete aromatic polyester oligomer of formula (I) comprises 50 mol% 4-hydroxy- and 3-hydroxy-benzoic acid; 25 mol% terephthalic acid and isophthalic acid. In formula, (x+X):(z+1):(m+n) = 2:1:1; and p is integer of 2-30. After adding oligomer, inorganic fillers selected from talc, titanium dioxide, calcium carbonate and kaolin; and lubricant from sodium stearate, magnesium stearate, and n-pentyl glycol dibenzoate are added for improving crystalizing speed.

Description

Polyester resin composition

The present invention relates to a polyester resin composition, and more particularly, to a polyester resin composition having excellent heat resistance and improved crystallization rate by forming a wholly aromatic polyester having a new structure as a main component repeating unit.

Among conventional polyester resins, polyethylene terephthalate (hereinafter abbreviated as PET) has been widely used as a material for fibers, films, resin bottles, and various moldings. This is because PET has the advantages of excellent wear resistance, dimensional stability, mechanical properties, electrical properties, chemical resistance and weather resistance, low water absorption, and low price compared with other resins.

However, although PET may be present in a structurally crystalline state, it has a disadvantage in that the crystallization rate is slow as compared to nylon, polyacetal, polyethylene, and polypropylene, which are other crystals.

Further, another disadvantage of PET is that the glass transition temperature is about 70 ° C., so that the heat resistance of the amorphous resin is insufficient, when the use temperature is 100 ° C. or more, crystallization proceeds, thereby reducing volume and poor dimensional stability.

Accordingly, in order to improve physical properties such as heat resistance and dimensional stability of PET, the following methods have been generally used.

First, by using a method of reinforcing with glass fibers, in this case, the glass transition temperature does not increase, but because the glass fibers themselves are entangled with each other, the heat deformation temperature is increased, so that the volumetric deformation rate is lowered.

Secondly, PET is made into a complete crystalline state. According to this method, the resin in the crystalline state can have only the melting temperature, thereby improving the heat resistance to the melting temperature. However, since PET has a crystallinity of 50% or less, it is partially crystallized. Annealing the amorphous portion of the PET is converted to a crystalline state. For example, PET, which has a 20% crystalline component, generally has a crystalline component of about 30% by heat treatment. In addition, PET having a crystallinity of more than 50% is difficult to form in melt crystallization, because crystals that have started to form in many places need to grow. The existing part must be converted to a crystalline state, and the polymer chain must move. In this process, if a part of the polymer chain is already embedded in the crystal, the chain is hindered because it cannot move. In addition, impurities such as chain ends interfere with crystal formation.

On the other hand, in order to use PET as an engineering plastic, the degree of crystallinity must be improved, and in consideration of workability, injection molding should be possible under normal molding conditions.In view of pyrolysis and flowability required for injection, the injection temperature is around 270 ° C. The crystallization rate of suitable, unmodified general commercialized PET is known to be fastest around 150-190 ° C. Therefore, in order to mold such PET, a mold having a certain crystal can be obtained only when the temperature of the mold is maintained at 140 ° C. or higher, so that a general injection machine can be used, and PET which can satisfy both low energy consumption and high workability is required. It should have a crystallinity of at least 25% in a short time of about 30 seconds at temperatures below 100 ° C.

As such a method for improving the PET crystallization rate is known.

First, there is a method of shortening the growth time of the nucleus by adding a nucleating agent, and second, a method of adding a lubricant or reforming PET. These methods enhance the flow of the molecular chain at low temperatures to speed up the growth of crystals at low mold temperatures so that sufficient crystals are formed. In addition, the degree of crystallinity of the molded article is highly related to the release property of the molded article in addition to the heat resistance and dimensional stability, and the crystallinity of the resin affects the release property as well as the effect of adding the release agent. In other words, if the crystallinity is very low or high, the releasability is good.

On the other hand, as a technique for improving the crystallization rate in the low-temperature molding process, a method using inorganic materials such as talc, titanium dioxide, magnesium oxide and the like, and a method of adding an epoxy compound as an organic solidification accelerator are disclosed.

In addition, a method of adding a composition containing a hydrocarbon-based metal salt or an unsaturated hydrocarbon-based polymer metal salt having a carboxyl group, and a technique of improving the crystallization temperature from 205 ° C to 228 ° C by using an alkali metal salt in the form of a PET oligomer as a nucleating agent are known.

In addition, the crystallinity is 110.7 ° C by using an alkali salt of an aliphatic polycarboxylic acid and an acid sodium salt of a hydrogenated dimer structure as nucleating agents and a neopentyldibenzoate and a bisphenol A-epichlorohydrin copolymer as lubricants. Japanese Patent Laid-Open Publication No. 82-185, 346 discloses a technique of using talc and metal salts of benzoic acid as nucleating agents, polyalkylene glycols, aromatic carboxylic acids, esterified fatty acids and polybutylene terephthalates. A technique for controlling the crystallization temperature to 104 ° C using a polycaprolactam block copolymer and Denacol 841 as a lubricant has been proposed.

However, the conventional method using the inorganic material as described above shows a different effect as a nucleation agent depending on the particle size distribution or dispersibility of the inorganic material and does not show a satisfactory effect even if the amount added is increased. In addition, it is difficult to lower the crystallization start temperature, the crystallization of the surface layer of the molding formed in a low-temperature mold is very poor, and the physical properties of the epoxy-based compound as the crystallization accelerator of the organic material are not maintained, and the metal salt of the hydrocarbon-based polymer is used. There is a disadvantage that the moldability is lowered.

Accordingly, an object of the present invention is to provide a new PET composition having a high crystallization rate and excellent releasability and heat resistance by varying the constituent repeating units of the polyester.

Hereinafter, the present invention will be described in detail.

In the polyester resin composition, 50 mol% of 4-hydroxy benzoic acid and 3-hydroxy benzoate, 25 mol% of hydroquinone and 4,4'-dihydroxy biphenyl, 25 mol% of terephthalic acid and isophthalic acid A polyester resin composition in which the wholly aromatic polyester oligomer represented by the following structural formula (I) composed of the ratio of is added to polyethylene terephthalate having an intrinsic viscosity of 0.4 to 1.5 d1 / g at a ratio of 0.05 to 10% by weight. It is characterized by.

Here, (x + Y): (z + 1): (m + n) = 2: 1: 1, and p is an integer of 2-30.

Such a present invention will be described in more detail as follows.

The present invention relates to a polyethylene terephthalate (PET) resin having an intrinsic viscosity of 0.4 to 1.5 d1 / g measured at 25 ° C. in a solution in which 0.5 wt% of a polymer is added in a mixed solvent of phenol: tetrachloroethane = 1: 1 wt%. The wholly aromatic polyester oligomer represented by Structural Formula (I) is added in an amount of 0.05% to 10% by weight based on PET, wherein the amount of the wholly aromatic oligomer does not show the effect of heat resistance and crystallization rate when the amount of the wholly aromatic oligomer is small. The heat resistance of the is better but the crystallization rate is inversely slow problem occurs. In addition, the production cost of the wholly aromatic oligomer is increased, the compatibility of the resulting polymer is problematic and the surface of the specimen to be produced is roughened.

After the addition of the wholly aromatic oligomer, at least one selected from talc, titanium dioxide, calcium carbonate and kaolin is added as an inorganic filler, and at least one selected from sodium stearate, magnesium stearate and neopentyl glycol dibenzoate as lubricant. It is characteristic to improve the crystallization rate of polyester by addition.

That is, since the structure of the wholly aromatic oligomer of the formula (I) is composed of an aromatic compound based on the benzene ring, the heat resistance of the obtained polymer is further improved, and since the oligomer is a liquid crystal polymer, the polyethylene in which crystals and amorphous regions are mixed When mixed with a polymer such as terephthalate, it has an effect on the non-crystalline part to promote crystallization.

According to the present invention, each of the compounds of the inorganic filler and the lubricant as additives may be added in a molten state after the polymerization of the polyester is finished, and reinforced with glass fiber or imparted flame retardance to improve the physical properties of the polyester. In order to do so, it may be added in a compounding step.

In order to improve the physical properties of the resin composition of the present invention, fiber reinforcing agents such as glass fiber, carbon fiber, and cabla fiber may be reinforced and used, and bromine or chlorine flame retardant may be added to impart flame retardancy. In addition, a fiber reinforcement treated with silane or borane may be used to improve the adhesion with the polymer. In addition to this, a detergent, an antioxidant, a releasing agent or the like may be added.

On the other hand, the wholly aromatic polyester oligomer represented by the above general formula used in the present invention can be produced by the following method.

That is, the hydroquinone (melting point 172) of 4-hydroxy benzoic acid (melting point 213-214 degreeC, molecular weight 138.12) and 3-hydroxy benzoic acid (melting point 200.8 degreeC, molecular weight 138.12) are 50 mol% in the reactor equipped with a stirring device. Terephthalic acid (melting point of 300 ° C or higher, molecular weight of 166.13) and isophthalic acid (melting point of 341 to 175 ° C., molecular weight 110.11) and 4,4′-dihydroxy biphenyl (melting point 278 ° C., molecular weight 186.12) at 25 mol% ratio. The mixture which mixed 343 degreeC and molecular weight 166.13) in 25 mol% ratio is added, excess acetic anhydride is added to a reaction solvent, and a predetermined additive and a catalyst may be added as needed.

When the mixing process is completed, it is gradually heated. At this time, as a heating medium of the heating device, a mixed salt of sodium nitrate and potassium nitrate in a 1: 1 molar ratio is used, and the oxidation of the reactant is prevented by passing the purified nitrogen stream during the reaction. When the reaction is performed for 5 hours while maintaining the temperature at 220-240 ° C., the excess acetic anhydride and acetic acid, which participates in the reaction and is converted into by-products, flows out of the reactor as the mixture is converted into a melt. The product thus obtained is slowly quenched in water immediately after completion of the reaction, pulverized to a size of 50 to 100 mesh, completely dried at a temperature of 100 ° C. for 24 hours in a vacuum dryer, and the dried particles are again fined to 20 mesh or less. Grinded to size and used in the present invention.

The polyester resin of the present invention prepared by using the wholly aromatic polyester oligomer obtained by the above-described method has improved heat resistance and crystallization rate, and the molded product produced by the method is sufficiently crystallized even under normal molding conditions and under heating conditions. It has excellent dimensional stability and mechanical properties.

Therefore, the molded article using the resin composition of the present invention can be widely applied to the molding of various molded parts, sheets, laminates, containers, etc., and considering the excellent electrical properties, it is also very suitable for molding of electric, electronic and automotive parts. .

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

First, the method for evaluating the components of the polyester composition in the Examples is as follows.

[Mixing of polymer and additive]

The polymer and the additives were mixed and adjusted to be automatically added in the compounder according to the composition ratio. At this time, the temperature of the cylinder was set to 260 ~ 280 ℃ and the mixture was used to cut the chip state through a cooling bath.

[Formation of Test Piece]

The specimen was dried in a dehumidifying dryer at 160 ° C. for 4 hours, dried to have a moisture content of 0.01% by weight or less, and then molded in the injection molding machine as follows.

[Surface Characteristics of Molded Products]

After the injection molding, the appearance state of the test piece obtained from the mold was visually observed and evaluated.

[Releasability of moldings]

In the course of performing 50 times of injection tests, it measured by the number of times a test piece escaped without adhere | attaching to a metal mold | die.

[Shrinkage rate of moldings]

The shrinkage ratio with respect to the longitudinal length L of the test piece (127 x 12.7 x 3.2 mm) obtained in the mold after molding was measured and evaluated.

×100Shrinkage (%) =

× 100

L ₀ is the length of the mold.

[Evaluation of Crystallization Rate]

The difference between Tch and Tcc is determined by Tch as the crystallization temperature when the temperature is raised to 280 ° C using a differential scanning thermal analyzer at 20 ° C / min and Tcc as the crystallization temperature when cooling at 30 ° C / min. Called ㅿ Tc, this value was compared relative to evaluate the crystallization rate. The larger the range of 범위 Tc, the faster the crystallization rate.

Example 1

9.85 g of PET resin having an intrinsic viscosity of 0.65 d1 / g and 50 g of totally aromatic polyester oligomer, an additive of the present invention, 30 g of sodium stearate, 50 g of talc, and 20 g of neopentyl glycoldibenzoate were continuously mixed and cooled in a compounder. The pellet was prepared into pellets, and then the degree of crystallinity was evaluated using a differential scanning thermal analyzer. The results are shown in Table 1 below.

EXAMPLES 2-5

The addition amount and PET amount of the wholly aromatic polyester oligomer which is the additive of the present invention were carried out in the same manner as in Example 1 except for changing as shown in Table 1 below. The results are shown in Table 1 below.

[Examples 6-9]

30 wt% of glass short fibers (length 3mm) surface-treated with a silane compound was added to reinforce the physical properties, and the bromine-based flame retardant was mixed with the composition of Example 1 to form flame retardant to impart flame retardancy. The test piece was then molded with an injection molding machine to evaluate the crystallization rate and formability. The results are shown in Table 2 below.

[Comparative Examples 1-6]

The totally aromatic polyester oligomer, which is the additive of the present invention, was not used, and other conditions were performed as shown in Table 1 below, and the results are shown in Table 1 below.

[Comparative Examples 7-10]

Without using the wholly aromatic polyester oligomer of the present invention carried out in the same manner as in Examples 6-9, other conditions were carried out as in Table 2, the results are shown in Table 2 below.

TABLE 1

NPG: Neopentyl glycol dibenzoate

Na: Sodium Stearate

Oligomer: The wholly aromatic polyester oligomer of formula (I)

PET: Polyethylene Terephthalate

TABLE 2

30% by weight of glass fiber (G / F), 7.4% by weight of flame retardant (FR),

1.5 wt% of Sb ₂ O ₃ was added. ㅿ: Sync mark, ○: Good.

Claims (1)

A polyester resin composition comprising 50 mol% of 4-hydroxy benzoic acid and 3-hydroxy benzoic acid, 25 mol% of hydroquinone and 4,4'-dihydroxy biphenyl, and 25 mol% of terephthalic acid and isophthalic acid. A polyester resin composition, wherein the wholly aromatic polyester oligomer represented by the following structural formula (I) is added to polyethylene terephthalate having an intrinsic viscosity of 0.4 to 1.5 d1 / g at a ratio of 0.05 to 10% by weight.

Here, (x + Y): (z + 1): (m + n) = 2: 1: 1, and p is an integer of 2-30.