JP2004277472A - Polyester resin and molding comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester resin which has excellent flowability, when injection-molded, and from which thin or complicated shape injection moldings can easily be molded. <P>SOLUTION: The polyester resin comprising a dicarboxylic acid component consisting mainly of terephthalic acid and a diol component consisting mainly of ethylene glycol is characterized by containing a multi-functional compound component in an amount of 0.05 to 0.2 mol.% based on the acid component in the resin and having a number-average mol. wt. of 20,000 to 25,000 and a dispersion degree of ≥2.1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyester resin having high fluidity, and more particularly to a polyester resin having excellent fluidity and suitable for obtaining a thin molded article by injection molding, and an injection molded article comprising the same.
[0002]
[Prior art]
Polyester resins have advantages such as excellent chemical resistance, heat resistance, mechanical strength, toughness, and excellent moldability, and are used in various applications such as mechanical parts, electronic parts, and vehicle parts. In particular, its excellent fluidity is advantageous for obtaining a thin molded article by injection molding. For example, polyethylene terephthalate resin (hereinafter referred to as PET resin) is used alone or as a composite material reinforced with glass fiber or the like. It is widely used for parts with thin or complex shapes.
[0003]
The flowability of the polyester can be adjusted by adjusting its molecular weight, and a lower molecular weight polyester has a higher flowability and can be subjected to injection molding of a thin complicated shape. However, the mechanical strength and toughness of polyester strongly depend on its molecular weight, and if a low-molecular-weight polyester is used in order to increase the fluidity, the mechanical properties of the obtained molded article are reduced. Therefore, the lower limit of the molecular weight of the polyester that can be used for the mechanical strength required for the product is determined, and its use is restricted.
[0004]
In addition, instead of reducing the molecular weight, there is a method of blending a fluidity improver represented by a stearic acid ester or a montanic acid ester.However, these low molecular weight esters are used to promote hydrolysis of the polyester. The mechanical properties of the resulting molded article are reduced. Therefore, it has been difficult to achieve both maintaining the mechanical properties at a high level and increasing the fluidity by reducing the melt viscosity.
[0005]
On the other hand, it is well known that by adding a low molecular weight compound having good solubility in a resin as a plasticizer, only the melt viscosity is reduced without changing the molecular weight of the resin. It is also used for However, a problem when a low molecular compound is added is also known at the same time. For example, problems such as contamination due to bleed-out of the plasticizer due to migration of the plasticizer, heat resistance lowering due to lowering of the glass transition temperature, and lowering of mechanical properties often occur. In addition, in order to plasticize a resin with good chemical resistance, such as polyethylene terephthalate, in addition to the fear of such deterioration in physical properties, it is necessary to select a special compound, which is disadvantageous in terms of cost and durability. Will increase.
[0006]
[Patent Document 1]
JP-A-4-275327 [Patent Document 2]
Japanese Patent Application Laid-Open No. 4-325546 [Patent Document 3]
Japanese Patent Application Laid-Open No. 4-32547 [Patent Document 4]
Japanese Patent Application Laid-Open No. H4-248867
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a polyester resin which is excellent in fluidity at the time of injection molding and can easily mold an injection molded article having a thin or complicated shape. .
[0008]
[Means for Solving the Problems]
The object is to provide a polyester resin containing terephthalic acid as a main dicarboxylic acid component and ethylene glycol as a main diol component, wherein a polyfunctional compound component is contained in an amount of 0.05 to 0.2 mol% based on an acid component in the resin. This is achieved by a polyester resin having an average molecular weight of 20,000 to 25,000 and a dispersity of 2.1 or more.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Although the polyester resin of the present invention mainly uses terephthalic acid as an acid component, a small amount of another dicarboxylic acid component can also be used. In this case, the proportion of terephthalic acid in the acid component is preferably at least 50 mol%, more preferably at least 60 mol%. The other copolymerizable acid component is, specifically, adipic acid, oxalic acid, malonic acid, succinic acid, azelaic acid, aliphatic dicarboxylic acids such as sebacic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid , An aromatic dicarboxylic acid such as diphenyldicarboxylic acid, an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, and dimer acid. These may be used alone or in combination of two or more.
[0010]
The polyester resin of the present invention mainly uses ethylene glycol as a diol component, but a small amount of another glycol component can also be used. In this case, the proportion of ethylene glycol in the diol component is preferably at least 50 mol%, more preferably at least 60 mol%. The other copolymerizable diol component specifically includes diethylene glycol, butanediol, neopentyl glycol, propylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, bisphenol A or bisphenol S. Diethoxy compounds and the like. These may be used alone or in combination of two or more.
[0011]
The polyester resin of the present invention comprises a raw material containing terephthalic acid or an ester-forming derivative thereof and ethylene glycol or a derivative thereof as a main component, at least one kind selected from the group consisting of antimony, titanium, germanium, tin, and zinc. It is produced by an esterification reaction step or a transesterification reaction step, a liquid phase polycondensation reaction step, and, if necessary, a solid phase polymerization reaction step using a metal element-containing compound as a catalyst.
[0012]
The esterification reaction step is performed at a temperature of 240 to 280C and a pressure of 20 to 300 kPa. At this time, only water generated by the esterification reaction between the acid component and the glycol component is released out of the system. When a small amount of a basic compound is added in this esterification reaction step, a polyester having a small amount of side reaction products can be obtained. Examples of such a basic compound include tertiary amines such as triethylamine, tributylamine and benzylmethylamine, and quaternary amines such as tetraethylammonium hydroxide, tetrabutylammonium hydroxide and trimethylbenzylammonium hydroxide.
[0013]
The transesterification step is carried out at a temperature of 210-250 ° C. in the presence of a transesterification catalyst. At this time, only the components generated by the transesterification reaction between the acid component and the glycol component are released out of the system. Examples of the transesterification catalyst used in this transesterification reaction step include metal salt compounds such as calcium acetate, cobalt acetate, manganese acetate, and magnesium acetate.
[0014]
The liquid phase polycondensation reaction step is performed in the presence of a polycondensation reaction catalyst at a temperature of 250 to 300 ° C. and a reduced pressure of 13.3 to 665 Pa. In the liquid phase polycondensation reaction step, the unreacted diol component is distilled out of the system from the low-order condensate of the acid component and the diol component obtained in the esterification reaction step or transesterification reaction step.
[0015]
As the polycondensation reaction catalyst used in the present invention, germanium dioxide, germanium compounds such as germanium tetraethoxide, germanium tetrabutoxide, antimony trioxide, antimony pentoxide, antimony tartrate, antimony compounds such as antimony acetate, tetrabutyl titanate and the like Titanium compounds, tin compounds such as tin acetate, and zinc compounds such as zinc acetate. Among them, a germanium compound is preferable in terms of the color tone and transparency of the obtained resin. The polycondensation reaction catalyst is added as an aqueous solution or ethylene glycol solution having a predetermined catalyst concentration.
[0016]
In the liquid phase polycondensation reaction step, a stabilizer may be added to prevent side reactions such as thermal decomposition of the polyester resin. Examples of the stabilizer include phosphoric esters such as trimethylphosphoric acid, triethylphosphoric acid and triphenylphosphoric acid, phosphorus compounds such as phosphorous acid and polyphosphoric acid, and hindered phenol compounds.
[0017]
The polyester resin of the present invention has a number average molecular weight of 20,000 to 25,000 and a dispersity of 2.1 or more. When the number average molecular weight and the degree of dispersion are in this range, it is possible to maintain both the mechanical properties at a high level and to reduce the melt viscosity to increase the fluidity. When the number average molecular weight is less than 20,000, the mechanical properties (particularly impact strength) of the obtained polyester resin are reduced. When the number average molecular weight exceeds 25,000 and when the degree of dispersion is less than 2.1, the effect of improving the fluidity of the obtained polyester resin does not appear even when the polyfunctional compound is added.
[0018]
The limiting viscosity of the polyester having such a number average molecular weight is usually preferably from 0.50 to 0.60 dl / g, more preferably from 0.55 to 0.60 dl / g.
[0019]
The polyester resin of the present invention preferably has a melt flow rate (hereinafter, referred to as MFR) at a temperature 30 to 40 ° C. higher than the melting point of the polyester resin, of 15.0 g / 10 minutes or more. When the MFR is 15.0 g / 10 min or more, a molded product having a thin wall or a complicated shape can be easily obtained, and thus it is preferable.
[0020]
The MFR of the present invention is measured according to JIS K7210. Specifically, a polyester resin is filled into a cylinder having a JIS inner diameter of 9.55 mm and a length of 162 mm, and a melted polymer is placed at a test temperature, and a plunger having a weight of 325 g and a diameter of 9.48 mm is placed on the cylinder to uniformly disperse the molten polymer. Is the flow rate of the molten polymer extruded from a 2.095 mm diameter orifice provided at the center of the cylinder while applying a load to the cylinder.
[0021]
The polyester resin of the present invention has a polyfunctional compound having three or four ester bond-forming functional groups in one molecule in its production process (hereinafter simply referred to as a polyfunctional compound) in order to improve fluidity. Is preferably contained. A polyfunctional compound is a compound that forms an ester bond by reacting with a carboxyl group or a hydroxyl group in a polyester molecular chain, and specifically, a carboxyl group, a hydroxyl group, or an alkyl ester such as a methyl ester group or an ethyl ester group. It is a compound having a group. By including such a polyfunctional compound, a crosslinked structure is formed in the polyester molecular chain, whereby the melting properties are improved and the fluidity is improved.
[0022]
Specific examples of the polyfunctional compound include pentaerythritol, trimethylolpropane, trimellitic acid and their acid anhydrides, pyromellitic acid and their acid anhydrides, and polyfunctional alcohols and acids such as trimesic acid. Can be mentioned. It is necessary that the content of the polyfunctional compound is 0.05 to 0.2 mol%, preferably 0.05 to 0.1 mol%, based on the acid component in the polymer. If the content of the polyfunctional compound is less than 0.05 mol%, the extrusion moldability is not sufficiently improved, and if it exceeds 0.2 mol%, the crosslinking proceeds excessively and the fluidity is reduced. Oxide generation may occur.
[0023]
The method for producing the injection molded article of the present invention is not particularly limited, and can be performed using a known injection molding apparatus.
[0024]
【The invention's effect】
The polyester resin of the present invention has excellent fluidity at the time of injection molding, and can easily produce an injection molded article having a thin wall and a complicated shape.
[0025]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
The measuring method and evaluation of each physical property followed the following method.
[0026]
(1) The number average molecular weight and the degree of dispersion Polyester resin is dissolved in a mixed solution of HFIP (hexafluoroisopropyl alcohol) / chloroform = 50/50 (weight ratio), and then, at 35 ° C., Waters High Performance Liquid Chromatography LC Module. It measured using plus.
[0027]
(2) Intrinsic viscosity (IV)
The polyester resin was dissolved in a mixed solution of phenol / tetrachloroethane = 60/40 (weight ratio) and measured at 20 ° C. using an automatic viscosity meter SS-270LC manufactured by Shibayama Scientific Instruments.
[0028]
(3) Melt flow rate (MFR)
The measurement was carried out using Melt Indexer TYPE C-5059 manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K7210. Specifically, a polyester resin was filled into a cylinder having an inner diameter of 9.55 mm and a length of 162 mm, and melted at a test temperature (the melting point of each resin + 30 to 40 ° C.). The plunger was placed on the molten polymer to uniformly apply a load, and the flow rate of the molten polymer extruded from an orifice having a diameter of 2.095 mm provided at the center of the cylinder was measured.
[0029]
(4) Mechanical strength Using a JIS No. 1 test piece molded at a molding temperature of 250 ° C., a mold temperature of 40 ° C., an injection pressure of 100 MPa, and a cooling time of 40 seconds with a Nestal SG75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a tensile strength. , Flexural strength and flexural modulus were measured in accordance with JIS K 7110.
[0030]
(5) Izod impact strength A JIS No. 1 test piece (3.18 mm (1 mm) molded by a Nestal SG75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. at a molding temperature of 250 ° C., a mold temperature of 40 ° C., an injection pressure of 100 MPa, and a cooling time of 40 seconds. / 8 inch) with a thickness notch) according to JIS K 7110.
[0031]
(6) Formability of thin-walled molded product Molding temperature 250 ° C, mold temperature 40 ° C, injection pressure 100MPa, cooling time 40 seconds, thickness 0.5mm, inner diameter 70mm, using Nestal SG75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. A 120 mm high cylindrical cup was molded.
：: A cup having a uniform thickness distribution was formed.
×: A cup having a normal shape could not be formed.
[0032]
(Manufacture of polyester resin)
Predetermined amounts of an acid component and a glycol component were charged into a stainless steel autoclave at the copolymerization ratios shown in Table 1, and an esterification reaction was carried out at 250 ° C. and 200 kPa. After completion of the esterification reaction, predetermined amounts of an antimony trioxide catalyst and trimethyl phosphate were added, and a polycondensation reaction was performed at 280 ° C. under a reduced pressure of 66 Pa. Table 1 shows the evaluation results of the average molecular weight, the degree of dispersion, the IV, and the MFR of the obtained polyester resin. The MFR was performed at 285 ° C. in Example 1 and Comparative Example 1, 265 ° C. in Examples 2 to 5 and Comparative Examples 2 to 5, and 200 ° C. in Example 4 and Comparative Example 4.
[0033]
(Manufacture of injection molded products)
Examples 1 to 6, Comparative Examples 1 to 6
The mechanical strength and Izod impact strength were measured using a JIS No. 1 test piece molded at a molding temperature of 250 ° C., a mold temperature of 40 ° C., an injection pressure of 100 MPa, and a cooling time of 40 seconds using a Nestal SG75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. It was measured according to K 7110. Table 2 shows the results. The molded article molded in Comparative Example 3 had a large content of the polyfunctional compound, and generation of a gel was observed. The molded article formed in Comparative Example 4 was very brittle and was broken when it was taken out of the molding machine, so that the mechanical properties could not be measured.
[0034]
[Table 1]

[0035]
[Table 2]

[0036]
[Table 3]

[0037]
[Table 4]

[0038]
[Table 5]

[0039]
[Table 6]

Claims (2)

A polyester resin containing terephthalic acid as a main dicarboxylic acid component and ethylene glycol as a main diol component, containing a polyfunctional compound component in an amount of 0.05 to 0.2 mol% based on an acid component in the resin, and having a number average molecular weight of 20,000. A polyester resin having a polydispersity of 2.1 to 25,000. A molded article obtained by injection molding the polyester resin according to claim 1.