KR100524162B1 - Polybutylene Terephthalate Resin Composition - Google Patents

Abstract

The present invention is polybutylene terephthalate; Polyethylene terephthalate; Glycidyl methacrylate-containing ethylene copolymers; Thermoplastic polyester elastomers which are reaction products of dimethyl terephthalate, 1,4-butanediol and polytetramethylene glycol; And it relates to a polybutylene terephthalate resin composition containing a glass fiber, the composition is excellent in toughness and surface properties is very useful as a exterior structural material.

Description

Polybutylene Terephthalate Resin Composition

The present invention relates to a polyester resin composition, and more particularly, to a polybutylene terephthalate (hereinafter, abbreviated as "PBT") resin composition suitable for exterior parts requiring high toughness.

In general, PBT resin has excellent heat resistance, excellent chemical resistance and mechanical strength, and excellent molding processability. It is also widely used as an industrial material because of its excellent electrical properties. However, due to the high degree of crystallinity, the material is vulnerable and has a disadvantage in that impact resistance against sudden impact or external stress is small. It is conventionally known to reinforce glass fibers in order to improve this. Reinforcing PBT resin with glass fiber increases both tensile and impact strength, but does not improve the fragile properties. Also, as the glass fiber increases, the surface property such as glass fiber protruding from the surface causes another problem. .

Therefore, methods to contain various kinds of impact modifiers and additives for surface modification have been proposed to compensate for the above disadvantages.

One of the most widely used methods for improving the impact resistance of PBT is a method of adding an alpha-olefin copolymer as described in Japanese Patent Laid-Open Nos. 45-26233 and 45-26224. The molded article prepared by the composition according to this method initially exhibits relatively excellent physical properties, but has a disadvantage in that the physical properties of the molded article gradually deteriorate with time due to poor compatibility between the PBT and the alpha-olefin copolymer.

As another prior art, US Pat. Nos. 4,485,212 and 4,558,096 describe a method for adding a graf copolymer of styrene and acrylonitrile to an PBT in an alpha-olefin copolymer. This method improves impact strength and slightly improves compatibility between polyester and alpha-olefins, but is not satisfactory.

In addition, US Pat. No. 4,445,719, Japanese Patent Application Laid-Open No. 50-23448 and Japanese Patent Application Laid-open No. 50-23448 improve the impact resistance and formability by adding a butadiene-based copolymer to an epoxy compound, but have the disadvantage of poor heat resistance and poor moldability. .

Japanese Patent Application Laid-Open No. 63-4566 discloses glycidyl-containing copolymers, ethylene-1-butene copolymers and ethylene-1-propylene copolymers derived from glycidyl ester groups of α-olefins and α, β-unsaturated acids. By adding to improve the impact temperature at room temperature and low temperature, but has a disadvantage of poor heat resistance.

In addition, as a prior art for improving the surface characteristics of PBT, Korean Patent Publication No. 94-14265 discloses adding 62-70% by weight of barium sulfate to 15-30% by weight of PBT and 8-25% by weight of polyethylene terephthalate (PET). There is a content of a composition suitable for exterior use in molded articles such as kitchen containers by adding%. In this case, the surface properties are quite excellent, but the toughness is insufficient and can be broken in a sudden impact.

Accordingly, the present invention provides a polyester resin composition suitable for exterior structural materials that require toughness by simultaneously improving toughness and surface properties in view of the disadvantages of the prior art.

According to the present invention, which solves the above problems, a polybutylene terephthalate resin composition containing the following components is provided:

(a) 30-65% by weight of polybutylene terephthalate having an intrinsic viscosity of 0.8-1.4 dl / gr,

(b) 5-20% by weight polyethylene terephthalate with an intrinsic viscosity of 0.6-0.9 dl / gr;

(c) 2-10% by weight glycidyl methacrylate-containing ethylene copolymer;

(d) 5-20% by weight of thermoplastic polyester elastomer which is a reaction product of dimethyl terephthalate, 1,4-butanediol and polytetramethylene glycol; And

(e) 5-40% glass fibers.

Hereinafter, the present invention will be described in more detail.

In the present composition, polybutylene terephthalate (PBT) as a main component is a polymerization product of terephthalic acid and 1,4-butanediol, and its intrinsic viscosity is suitably 0.8-1.4 dl / gr, and the composition components (a) Based on the total amount of (e) to (e), the content ratio is suitably 30 to 65% by weight. The PBT content is preferably determined in consideration of the minimum content of polyethylene terephthalate (b) expressing the gloss and the content of the thermoplastic polyester elastomer (d) involved in toughness.

Polyethylene terephthalate is blended to improve surface properties and is excellent in compatibility with polyester resins such as polybutylene terephthalate. In general, polyethylene terephthalate is not used alone as a structural material because of its slower crystallization rate than polybutylene terephthalate, because injection molding is poor, which causes problems in mass production and significantly lower strength of the material. Polyethylene terephthalate suitable for use in the present composition is suitable for intrinsic viscosity of 0.6-0.9 dl / gr, PET of such a high intrinsic viscosity can be prepared through a solid state polymerization process. Low-viscosity polyethylene terephthalate without solid phase polymerization is not suitable because pellets may be fused during drying. If the content of PET in the present composition is too high, the molding cycle time (injection molding time) becomes long, which does not mold release and makes mass production difficult, because the crystallization time of PET is significantly slower than PBT. On the contrary, if the content of PET is too low, it is difficult to obtain the desired glossiness.

The ethylene copolymer containing glycidyl methacrylate represented by the following structural formula has an epoxy group at the terminal, and when reacted with the polyester by heat when compounding the composition in an extruder, imparts excellent toughness to the composition.

CH ₃ O ／ ＼H ₂ C 〓CCO-CH ₂ -CH-CH ∥ O

Glycidyl methacrylate-containing ethylene copolymer used in the composition is characterized by low glass transition temperature (Tg) and excellent processability. A commercially available example of glycidyl methacrylate-containing ethylene copolymer is Igetabond E manufactured and sold by Sumitomo, Japan. Igetabond E contains about 12% by weight of glycidyl methacrylate in the ethylene copolymer and has a specific gravity of 0.94 and a glass transition temperature of -26 ° C.

The thermoplastic polyester elastomer in the composition is a reaction product of dimethyl terephthalate, 1,4-butanediol and polytetramethylene glycol, and has excellent compatibility with polyesters such as polybutylene terephthalate and no crosslinking during melting. Excellent workability and toughness reinforcement effect.

For example, the composition may be introduced into an extruder or compounder at the composition ratio described above, kneaded at a cylinder temperature of 230 to 270 ° C., cooled in a cooling bath, and commercialized in pellet form.

The properties and advantages of the composition of the present invention will become more apparent from the examples described below. Of course, the following examples are intended to illustrate the invention but not to limit it.

Example 1

47 wt% of polybutylene terephthalate (PBR) resin having an intrinsic viscosity of 0.82 dl / gr and 15 wt% of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.77 dl / gr were added to the compounder. In this case, polyethylene terephthalate was prepared by a solid phase polymerization process. 3% by weight of Igetabond E as glycidyl methacrylate-containing ethylene copolymer; 5 wt% of thermoplastic polyester elastomer (TPE) consisting of dimethyl terephthalate, 1,4-butanediol and polytetramethylene glycol and 30 wt% of glass fiber were added to express rigidity. In addition, 0.3 phr of the primary stabilizer of the hindered phenol (in parts by weight) and 0.35 phr of the phosphorus-based secondary stabilizer were added as an additive for expressing thermal stability. After the addition, the mixture was kneaded at a cylinder temperature of 250 ° C. and cooled in a cooling bath to prepare pellets. The prepared pellets were dried in a drier at 120 ° C. for 4 hours and dried to a moisture content of 0.01% or less, and the dried pellets were used in an injection molding machine at a cylinder temperature of 250 ° C., a mold temperature of 80 ° C., an injection holding time of 10 seconds and a cooling time of 12 seconds And a specimen was processed under the conditions of injection pressure 120-140 bar.

Melt Index (MI) was measured for the evaluation of tensile strength, elongation, impact strength, and flowability using the prepared test pieces. In addition, a specimen was fabricated using a mold having a polished surface, and surface gloss was measured using the specimen. The physical properties were measured by the following method, and the results are shown in Table 1 below.

-Tensile strength and elongation: According to ASTM D638, measure using a Type 1 specimen at a speed of 5mm / min under conditions of temperature 23 ± 2 ℃, relative humidity 50 ± 5%, atmospheric pressure. Elongation was recorded as a value at the yield point, measured at least five times and expressed as an average value.

-Impact Strength: According to ASTM D256, it represents the energy when a 1/4 "thick specimen is broken by Pendulum. It is measured at least 5 times and expressed as an average value.

-Flowability: The melt flow index was measured according to ASTM D1238. MI is an easily measurable index for evaluating the fluidity of a material. It is not easy to predict the behavior at high shear rates such as injection molding because it mainly measures the behavior at low shear rates. However, it can be appropriately used for the evaluation of fluidity due to the use or addition of the same kind of additives. In this experiment, measured under a load of 2160g at a temperature of 250 ℃, it is expressed as the weight discharged per 10 minutes, measured at least five times as an average value.

-Surface gloss: Reflectance of 60 ° was measured according to ASTM D523 by using Gardner micro gloss meter, but at least 5 times was expressed as average value.

[Examples 2 to 3 and Comparative Examples 1 to 5]

The same procedure as in Example 1 was repeated except that the composition components and contents were changed as shown in Table 1 below. Physical properties of the composition according to each example are shown in Table 1 below.

division Example Comparative Example One 2 3 One 2 3 4 5 Composition PBT (% by weight) 47 42 52 70 60 55 62 31 PET (% by weight) 15 15 10 - - 15 - 15 TPE (wt%) 5 8 5 - 10 - 3 12 Igetabond E (% by weight) 2 5 3 - - - 5 12 Fiberglass (wt%) 30 30 30 30 30 30 30 30 Primary Stabilizer (phr) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Secondary stabilizer (phr) 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 Properties Tensile Strength (㎏ / ㎠) 1250 1200 1230 1270 1170 1230 1150 780 Tensile Elongation Yield Point (%) 4.0 7.0 4.2 3.5 4.7 3.3 8.6 15.2 Impact strength (kgcm / cm) 15 20 14 9.0 5.0 8.3 16 34 MI (250 degrees Celsius * 2160 g) 8 9 10 15 23 5 4 One Surface gloss (60 °) 66 65 62 58 60 68 53 43

As can be seen from Table 1, in the case of Comparative Example 1 without using PET, TPE and Igetabond E, tensile elongation, impact strength, flowability and surface properties were poor, Comparative Example without using PET and Igetabond E In case of 2, the tensile strength and impact strength were low and the fluidity was poor. In Comparative Example 3 without TPE and Igetabond E, tensile elongation, impact strength and fluidity were inadequate. In the case of Example 4, toughness and fluidity surface properties were inadequate, and in Comparative Example 5 in which Igetabond E was used in excess, the toughness and fluidity surface properties were inadequate. However, the compositions of Examples 1 to 3 according to the present invention show an evenly improved overall physical properties required for the exterior structural material. As such, it can be seen that the present composition simultaneously satisfies toughness and surface properties suitable for exterior structural materials.

Claims (1)

Polybutylene terephthalate resin composition containing the following components: (a) 30-65% by weight of polybutylene terephthalate having an intrinsic viscosity of 0.8-1.4 dl / gr, (b) 5-20% by weight polyethylene terephthalate with an intrinsic viscosity of 0.6-0.9 dl / gr; (c) 2-10% by weight glycidyl methacrylate-containing ethylene copolymer; (d) 5-20% by weight of thermoplastic polyester elastomer, the reaction product of dimethyl terephthalate, 1,4-butanediol and polytetramethylene glycol; And (e) 5-40% glass fibers.