KR20180039358A - Polyester resin composition and molded artice manufactured therefrom - Google Patents

Abstract

The present invention relates to a polyester resin composition which includes polybutylene terephthalate (PBT), and 3 to 10 parts by weight of an ethylene-butyl acrylate copolymer based on 100 parts by weight of the polybutylene terephthalate; and to a plastic molded article produced from the composition. Accordingly, the present invention provides a polyester resin which is excellent in tensile elongation and flow index so as to be easily molded and improved in restoring force of a molded article while maintaining excellent tensile strength and impact strength.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyester resin composition and a molded article produced from the same. BACKGROUND OF THE INVENTION [0002]

The present invention relates to a plastic resin composition and a molded article thereof, and more particularly to a polyester resin composition with improved tensile elongation and molded articles produced therefrom.

Polybutylene terephthalate (PBT) among polyester resins is an engineering plastic with high crystallinity, excellent mechanical properties and heat resistance, and excellent dimensional stability against temperature changes. In particular, polybutylene terephthalate has a relatively low volume resistivity in engineering plastics, has excellent electrical properties such as electrical insulation, arc resistance, and dielectric breakdown strength due to its low moisture absorption rate. In addition, Can be shortened and exhibits a high yield in a short time. Due to these characteristics, polybutylene terephthalate is widely applied to electric and electronic products and automobile interior / exterior parts.

However, the polybutylene terephthalate has a disadvantage in that the shrinkage ratio in the perpendicular direction is relatively large at 1.7 to 2.1% due to its high crystallization property. In addition, when the low molecular weight polybutylene terephthalate is used for high fluidity, the tensile strength and the flexural strength are high, but the impact strength is low. Also, when a component such as a connector is used, The restoration force of the product can be hindered. In order to solve such a problem, a method of applying a high viscosity resin having a high molecular weight or adding an impact modifier to increase the impact strength thereof is generally used.

As a concrete example of the prior art, a method of applying a high viscosity resin is proposed in Korean Patent Laid-open Publication No. 10-2013-0068812. However, when the melt flow index of the high viscosity resin composition is less than 30 g / 10 min at a load of 2160 g and a temperature of 250 캜 Complex molding structure and thin film molding can not be done. When 60g / 10min or more, complicated structure and thin film structure can be injected. However, there is a problem that the hinge characteristic is deteriorated in the joint part of the product. Japanese Patent Publication No. 51-91958 and Japanese Patent Application Laid-Open No. 62-285947 disclose a method of adding an impact modifier. However, there is a limit to the problem of injection failure during molding due to increase in the flowability of the resin at the time of introducing an epoxy compound .

Accordingly, in the field of polyester materials, mechanical properties are maintained even in small and complex shaped parts, and development of techniques capable of improving the resilience against stress when applied to automobile parts is still a challenge.

Accordingly, it is an object of the present invention to provide a polyester resin which is excellent in tensile elongation and flow index while being excellent in tensile strength and impact strength as compared with conventional ones, and is easy to mold and improved in restoring force of a molded article. Further, .

A first preferred embodiment of the present invention for solving the above problems is a polybutylene terephthalate (PBT); And 3 to 10 parts by weight of an ethylene-butyl acrylate copolymer with respect to 100 parts by weight of the polybutylene terephthalate.

The polybutylene terephthalate according to the first embodiment may have an intrinsic viscosity of 0.6 to 1.8 dl / g and a weight average molecular weight (Mw) of 40,000 to 85,000. The ethylene-butyl acrylate copolymer has a weight average molecular weight Mw) of from 40,000 to 85,000.

The polyester resin composition according to the first embodiment may have a melt index (Melt Index) of 20 g / 10 min to 30 g / 10 min under the conditions of ASTM D1238 measurement standard, 235 캜 and 2.16 kg.

Further, the present invention is a molded article produced from the resin composition of the first embodiment as a second preferred embodiment of the present invention.

The molded article according to the second embodiment may have a tensile strength of 450 kgf / cm ² or more and a tensile elongation of 50% or more measured by ASTM D638 and an IZOD impact strength of 4.0 kg · cm / cm or more according to ASTM D256 measurement standard.

According to the present invention, it is possible to provide a polyester resin composition having excellent mechanical properties and high tensile elongation, and can be easily used as a material for various injection molded articles such as automobile connectors, electric / electronic sockets, have.

TECHNICAL FIELD The present invention relates to a polyester resin composition comprising polybutylene terephthalate, which is excellent in mechanical properties such as tensile strength, bending strength and impact strength, and particularly has an excellent tensile elongation, To a polyester resin composition capable of exhibiting physical properties.

More specifically, the present invention relates to polybutylene terephthalate (PBT); And 3 to 10 parts by weight of an ethylene-butyl acrylate copolymer with respect to 100 parts by weight of the polybutylene terephthalate. Hereinafter, the present invention will be described in detail.

Polybutylene Terephthalate (PBT)

In the present invention, the polybutylene terephthalate (PBT) may be one produced by condensation polymerization through direct esterification reaction or ester exchange reaction using 1,4-butanediol, terephthalic acid or dimethyl terephthalate as a monomer, The intrinsic viscosity (IV) measured at 20 캜 of the filtrate obtained after dissolving in methylene is preferably 0.6 to 1.8 dl / g using a Ubero type viscometer. If the intrinsic viscosity of the PBT is less than 0.6 dl / g, it may be difficult to secure the mechanical properties. If the intrinsic viscosity is more than 1.8 dl / g, the flow index may be lowered and molding and workability may be deteriorated.

The polybutylene terephthalate of the present invention preferably has a weight average molecular weight (Mv) in terms of polystyrene measured by gel permeation chromatography (GPC) of 40,000 to 85,000. If the weight average molecular weight is less than 40,000, And if it exceeds 85,000, the flowability may be deteriorated. Here, a more detailed method of measuring the weight average molecular weight is as follows.

- Analytical instruments: Agilent Technologies 1200Series

- Stationary phase: u Stragel 10 ³ 10 ⁴ 10 ⁵ (Analysis by connecting 3 columns in series)

- mobile phase: Chlorofrom / OCP standard solvent = 4/1, 1.0 ml / min

- Temperature: 40 캜 (stationary phase column and RI detector)

- Reference substance: Polystyrene

- Injection amount: 20 μl

Detector: Agilent G1316A RI, 40 [deg.] C

- Analysis time: 30 minutes

Ethylene-butyl Acrylate (Ethylene- butyul acrylate ) Copolymer

In the present invention, the ethylene-butylacrylate copolymer acts as an impact resistant agent, that is, an impact modifier, and improves the impact resistance and elongation of the polyester resin. (Ethylene-methyl acrylate copolymer (EMA), poly (methyl methacrylate) -g-poly (butadiene / styrene) graft copolymer) for the purpose of improving the impact resistance of conventional polyester resins, However, when an ethylene-butyl acrylate copolymer is added, the ethylene-butyl acrylate copolymer having a long chain in the molecular structure contributes to the improvement of the elongation, so that the restoring force of the component can be further improved .

Further, in comparison with the resin composition comprising maleic anhydride, which is another additive for improving impact resistance, the ethylene-butyl acrylate copolymer has no reactivity with polybutylene terephthalate and does not cause deterioration in flowability, It is possible to improve the property.

The ethylene-butyl acrylate copolymer may be a compound represented by the following formula (1), and it is preferable that the gel permeation as described above in consideration of the reactivity with the polyester terminal group, the compatibility with the polyester resin, It may be preferable that the polystyrene-reduced weight average molecular weight (Mw) measured by chromatography (GPC) is 40,000 to 85,000.

≪ Formula 1 >

The content of the ethylene-butylacrylate copolymer is 3 to 10 parts by weight per 100 parts by weight of polybutylene terephthalate in order to impart appropriate fluidity to the composition of the present invention without deteriorating the physical properties and particularly to ensure the tensile elongation characteristics And more preferably 3 to 5 parts by weight. If the content of the ethylene-butyl acrylate copolymer is less than 3 parts by weight, improvement in mechanical strength can not be expected. If the content is more than 10 parts by weight, the flowability may be deteriorated.

In addition, the polyester resin composition of the present invention may further contain an additive depending on required characteristics, and the additive may be selected from the group consisting of heat stabilizers, antioxidants, light stabilizers, release agents, compatibilizers, dyes, pigments, colorants, , Lubricants, and mixtures thereof. As the antioxidant, phenol type, phosphite type, thioether type or amine type antioxidant may be preferably used. Examples of the releasing agent include fluorine containing polymers, silicone oil, metal stearate, montanic acid metal salt, montanic ester wax Or a polyethylene wax may be preferable, but not always limited thereto.

In addition, the resin composition of the present invention can be provided in the form of melt-kneading using an extruder and producing it as a molding chip. At this time, a twin-screw extruder may be used for kneading the composition, and the temperature suitable for kneading may be 240 to 270 ° C. In order to prevent thermal decomposition of the composition during melt-kneading, it may be desirable to minimize the residence time, and the optimum screw rotation speed and output can be adjusted to about 80% of the maximum load in consideration of dispersibility.

As a result, the polyester resin composition of the present invention exhibits a melt index of 20 g / 10 min to 30 g / 10 min at 235 ° C and 2.16 kg according to ASTM D1238 measurement standard, The present invention can provide a plastic molded article produced from the resin composition. At this time, the molding method for producing the molded article may be injection molding, extrusion molding, compression molding, insert injection molding, low pressure injection molding, foam injection molding, and foam extrusion molding, but is not limited thereto.

Further, the molded article of the present invention has a tensile strength of 450 kgf / cm ² or more and a tensile elongation of 50% or more measured by ASTM D638 and an IZOD impact strength of 4.0 kg · cm / cm or more measured by ASTM D256, As shown in FIG.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for the purpose of illustrating the present invention more specifically, and the present invention is not limited thereto.

Example  1 to Example  3

Ethylene-butyl acrylate (Elvaloy 3427AC manufactured by Dupont) was mixed with 100 parts by weight of a polybutylene terephthalate resin (PBT, Kolon SPESIN) at the ratios shown in Table 1 below and kneaded in a twin-screw extruder , And the mixture was melt-kneaded and reacted in the extruder for 1 minute to prepare a polyester resin composition. Thereafter, the resin having undergone the reaction was extruded in the form of a chip, and dried using a dehumidifying dryer at 120 ° C for 4 hours.

Next, a molded body specimen was prepared by using a screw-type extruder to produce a polyester resin in the form of chips in accordance with the ASTM test standard under the manufacturing conditions of 250 to 260 ° C.

Comparative Example  1 to Comparative Example  6

The polyester resin compositions of Comparative Examples 1 to 6 were prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1 below.

division
(Parts by weight) PBT content EBA EMA MBS E-BA-GMA Example 1 100 3 Example 2 100 5 Example 3 100 10 Comparative Example 1 100 Comparative Example 2 100 One Comparative Example 3 100 15 Comparative Example 4 100 5 Comparative Example 5 100 5 Comparative Example 6 100 5 Comparative Example 7 100 10 * PBT: Kolon, product name: SPESIN
* Ethylene-Butyl Acrylate Copolymer (EBA): Elvaloy 3427AC
* Ethylene-Metyl Acrylate Copolymer (EMA): Dupont, Elvaloy 1330AC
* MBS (poly (methyl methacrylate) -g-poly (butadiene / styrene) graft copolymer): DOW, trade name: PARALOID EXL 2620
* E-BA-GMA (ethylene-butyl acrylate-glycidyl methacrylate terpolymer): Elvaloy PTW

Property evaluation

Tensile strength, impact strength, heat distortion temperature and flexural strain were measured by the following methods using the polyester resin compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 6, Respectively.

(1) Tensile strength and tensile elongation: A 1/8 inch specimen was prepared according to ASTM D638, and tensile strength and tensile elongation at room temperature (23 ° C) were measured.

(2) Impact strength: Izod notched impact strength was measured at room temperature (23 ° C) after a 1/4-inch specimen was produced according to ASTM D256.

(3) Melt index: The melt index was measured at 235 DEG C under a load of 2.16 kg in accordance with ASTM D1238.

The tensile strength
(kgf / cm ² ) Tensile elongation
(%) Impact strength
(kgcm / cm) Flow index
(g / 10 min) Example 1 531 217 4.13 28 Example 2 508 213 4.56 24 Example 3 462 82 5.37 20 Comparative Example 1 617 121 2.93 35 Comparative Example 2 581 113 2.53 34 Comparative Example 3 442 138 5.54 17 Comparative Example 4 510 20 4.45 30 Comparative Example 5 553 43 5.12 24 Comparative Example 6 520 67 4.21 18 Comparative Example 7 515 78 4.44 17

As a result of measurement of physical properties, it was found that the impact strength was improved in comparison with Comparative Example 1 which is a single material of polybutylene terephthalate (PBT) in the compositions of Examples 1 to 3, as shown in Table 2 above. However, in the case of Comparative Example 2, it was confirmed that the content of the ethylene-butyl acrylate copolymer was too small to exert its function as an impact modifier, and an excessively large amount of an ethylene-butyl acrylate copolymer was added , The flow index was drastically lowered as compared with Examples 1 to 3 due to the influence thereof, and it was found that difficulty in injection molding occurred.

Further, in the case of Example 2, the tensile strength and the impact strength are comparable to each other in comparison with Comparative Examples 4 to 6 in which the same amount or type of impact modifier is different, but the elongation is remarkably improved and, after the component injection molding, The tensile elongation was comparable to that of Example 3. However, the tensile elongation was comparatively low in Comparative Example 7, but the flow index was relatively low. As a result, It was judged to be unsuitable for injection molding.

Claims (6)

Polybutylene terephthalate (PBT); And
(1), wherein the polybutylene terephthalate is at least one selected from the group consisting of ethylene-butyl acrylate copolymer 3 to 10 parts by weight of a polyester resin composition.
≪ Formula 1 >

The polyester resin composition according to claim 1, wherein the polybutylene terephthalate has an intrinsic viscosity of 0.6 to 1.8 dl / g and a weight average molecular weight (Mw) of 40,000 to 85,000.
The polyester resin composition according to claim 1, wherein the ethylene-butyl acrylate copolymer has a weight average molecular weight (Mw) of 40,000 to 85,000.
The polyester resin composition according to claim 1, wherein the polyester resin composition has a melt index of 20 g / 10 min to 30 g / 10 min under the conditions of 235 ° C and 2.16 kg as measured according to ASTM D1238.
A molded article produced from the polyester resin composition according to any one of claims 1 to 4.
The molded article according to claim 5, wherein the molded product has a tensile strength of 450 kgf / cm ² or more measured by ASTM D638 and a tensile elongation of 50% or more, and an IZOD impact strength of 4.0 kg · cm / cm or more measured by ASTM D256 Shaped article.