JP2000119386A - Polyester resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester resin and/or polyester resin melt-molded products that are economical, high in productivity, and suitable for a variety of uses. SOLUTION: After polycondensation reaction, a polymer is extruded out through a vented extruder, as it is molten, to give the objective polyester resin. The resultant polyester resin has an intrinsic viscosity of 0.55-0.9 dl/g, an acetaldehyde content of <=30 ppm and a Color-b value of <=4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an economical, high-productivity, high-quality polyester resin for a melt molded article suitable for various uses.

[0002]

2. Description of the Related Art Conventionally, polyester resins typified by polyethylene terephthalate have been used as materials for melt-molded articles due to their excellent transparency, mechanical strength, heat resistance, gas barrier properties, and the like, especially carbonated beverages, juices, and mineral water. And the like, or as a material for molded articles such as films and sheets. These melt molded articles are usually obtained by melting a polyester resin and injecting it into a mold by an injection molding method, or extruding the resin by an extrusion molding method and cooling it into a film, sheet or the like on a cooling roll. Obtainable. Furthermore, fibers and nonwoven fabrics can also be obtained by spinning from a nozzle. Depending on these uses, a volatile component contained in the polyester resin, particularly an acetaldehyde component, may become a problem.

Conventionally, a polyester resin having a low content of acetaldehyde has been subjected to a process of cooling a molten polyester resin having a high content of acetaldehyde after the polycondensation reaction, and solidifying the resin into a chip-like form. You can get through. However, this method requires not only complicated steps but also energy for re-melting the chips in the case of molding.

On the other hand, Japanese Unexamined Patent Publication No.
In Japanese Patent No. 238643, the intrinsic viscosity is 0.5 to 0.75 d.
There is disclosed a method of forming a 1 / g molten polyethylene terephthalate resin into a preform by increasing the intrinsic viscosity to 0.75 to 0.95 dl / g and reducing the acetaldehyde content in a post-condensation reactor. I have. This method is more economical than the conventional method in that a compact is obtained without passing through the steps of solidification and remelting, but the residence time in the post-polymerization reactor is increased in order to increase the intrinsic viscosity. Is 30
It takes about 60 minutes, which is a problem from the viewpoint of productivity. In addition, there is a problem that coloring occurs due to a long residence time.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned economic problems of the conventional polyester resin or polyester resin molded product for a melt molded product, and is suitable for various uses, has high productivity and high transparency. It is an object of the present invention to provide a high-quality, high-quality polyester resin for a melt molded article or a polyester resin molded article.

[0006]

The polyester resin for solving the above-mentioned problems is a polyester resin obtained through a vented extruder in a molten state after the polycondensation reaction, and the polyester resin has an intrinsic viscosity of 0. .55-
A polyester resin characterized by 0.9 dl / g, acetaldehyde content of 30 ppm or less, and color b value of 4 or less.

Further, a method for producing a polyester resin, characterized in that the polyester resin is produced so that the intrinsic viscosity after extruding with a vent and the intrinsic viscosity before extruding are in the range of -0.1 to 0.08 dl / g. It is.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a polyester resin or a polyester resin molded product for a melt molded product of the present invention will be described in detail.

The polyester resin of the present invention is a polyester resin substantially composed of one or more aromatic dicarboxylic acid components and one or more glycol components such as polyethylene terephthalate and polyethylene naphthalate, and polyethylene terephthalate is preferably used. Can be

[0010] The polyethylene terephthalate of the present invention comprises:
It is a linear polyester resin containing 85 mol% or more of ethylene terephthalate units as a main repeating unit, and preferably a linear polyester resin containing 95 mol% or more.

The dicarboxylic acids used by copolymerizing with polyethylene terephthalate include isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-
Aromatic dicarboxylic acids such as 4,4′-dicarboxylic acid and diphenoxyethane dicarboxylic acid and functional derivatives thereof, p
-Oxyacids such as oxybenzoic acid and oxycaproic acid and functional derivatives thereof, adipic acid, sebacic acid, succinic acid, aliphatic dicarboxylic acids such as glutaric acid and its functional derivatives, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid Acids and their functional derivatives.

Examples of the glycol used as a copolymer in the polyethylene terephthalate include aliphatic glycols such as diethylene glycol, trimethylene glycol, tetramethylene glycol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, and bisphenol A. And aromatic glycols such as alkylene oxide adducts of bisphenol A.

Further, other copolymerizable components comprising a polyfunctional compound which can be used in a polyester resin comprising polyethylene terephthalate include trimellitic acid and pyromellitic acid as acid components. Glycerin as a glycol component,
Pentaerythritol and the like can be mentioned. The amount of the copolymerization component composed of these polyfunctional compounds must be such that the polyester resin maintains a substantially linear shape.

The method for producing the polyester of the present invention will be described. After each raw material is esterified in the presence of an esterification catalyst, it is subjected to liquid phase polymerization in the presence of a polymerization catalyst to reach a predetermined molecular weight, and then sent to a vented extruder to reduce acetaldehyde loss. Done. Examples of the production method include a batch method and a continuous method (single-can method, multi-stage method). Hereinafter, an example of a preferable production method in a continuous / multi-stage method will be described using polyethylene terephthalate as an example.

First, 1.02 to 1.4 mol, preferably 1.03 to 1.0 mol per mol of terephthalic acid or its ester derivative.
A slurry containing 3 moles of ethylene glycol is prepared and continuously supplied to the esterification reaction step.

In the esterification reaction, water or alcohol produced by the reaction is removed from the system by a rectification column under the condition that ethylene glycol is refluxed using a multistage apparatus in which at least two esterification reactors are connected in series. Perform while removing. The temperature of the first stage esterification reaction is 240-27.
0 ° C, preferably 245-265 ° C, pressure 150-2000torr
r, preferably 300 to 1200 torr. The temperature of the final esterification reaction is usually from 250 to 280 ° C, preferably from 255 to 280 ° C.
~ 275 ° C and the pressure is usually 0.1-1200 torr, preferably 0.5-1000 torr. When the reaction is carried out in three or more stages, it is preferable to set the reaction conditions of the intermediate stage esterification reaction so as to change stepwise from the first stage conditions to the final stage conditions. It is desirable that the esterification reaction rate in the final stage reaches 90% or more, preferably 93% or more. By these esterification steps, a low-order condensate having a molecular weight of about 500 to 5,000 is obtained.

The above esterification reaction is carried out using Zn, Cd, M
n, Co, Ca, Ba and other fatty acid salts, carbonates and metals M
When a catalyst such as g, Pb, Zn, Sb, or Ge oxide is used, the reaction can be accelerated. In particular, when dimethyl terephthalate is used as a raw material, it is preferable to add a catalyst. When terephthalic acid is used as a raw material, the reaction can be performed without a catalyst. In addition, diethylene glycol is dimerized to generate diethylene glycol, and diethylene glycol is copolymerized in the main chain, which may reduce the strength of the resin. In order to prevent this, tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, and quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide It is also preferable to add a small amount of a basic compound such as lithium carbonate, sodium carbonate, potassium carbonate, and sodium acetate. The proportion of dioxyethylene terephthalate component units in the main chain of polyethylene terephthalate is preferably 5 mol% or less based on all diol components.

Next, the obtained low-order condensate is supplied to a multi-stage liquid phase condensation polymerization step. The polycondensation reaction conditions are such that the reaction temperature of the first stage polycondensation is 250 to 290 ° C., preferably 260 to 290 ° C.
~ 280 ° C and a pressure of 500-20 Torr, preferably 200
~ 30 Torr, the final stage polycondensation reaction temperature is 265 ~ 300
° C, preferably 275-295 ° C, pressure 10-0.1 Torr
r, preferably 5 to 0.5 Torr. When the reaction is carried out in three or more stages, it is preferable to set the reaction conditions of the intermediate stage esterification reaction so as to change stepwise from the first stage conditions to the final stage conditions. Preferably, the degree of increase in intrinsic viscosity (IV) achieved in each of these polycondensation reaction steps is distributed smoothly.

The polycondensation reaction uses a polycondensation catalyst. As the catalyst, germanium compounds such as germanium dioxide, germanium tetraethoxide, and germanium tetra n-butoxide, antimony catalysts such as antimony trioxide, and titanium catalysts such as titanium tetrabutoxide are preferable. Among these catalysts, a germanium dioxide compound is preferable in terms of hue and transparency, and antimony trioxide is preferable in consideration of fast crystallinity and cost. The amount of the catalyst is 0.0005 to 0.2% by weight, preferably 0.00
01-0.1% by weight.

The limiting viscosity of the molten resin used in the present invention after the polycondensation reaction to be supplied to the vented extruder can be set to a desired limiting viscosity depending on the application. In particular, when the limiting viscosity is 0.7 dl / g or more. It is effective for

Further, the polyester resin after the melt polymerization thus obtained is sent to an extruder equipped with a vent while keeping the molten state, and deacetaldehyde is carried out. As the extruder with vent used in the present invention, 1
Either a screw extruder or a twin screw extruder can be used, but a twin screw extruder is preferable from the viewpoint of acetaldehyde reduction efficiency. The screw of the twin-screw extruder may be any of a meshing type, a non-meshing type and an incompletely meshing type, and may be any one of the same direction and different direction rotation.

The resin temperature in the extruder with vent is 2
50 ° C to 300 ° C is preferred. The degree of decompression of the vented extruder is 50 torr or less, preferably 20 torr.
The object can be achieved below, more preferably below 10 torr.

The polyester resin of the present invention thus obtained has a color b value of preferably 4 or less.
More preferably 3.0 or less, further preferably 2.5 or less, particularly preferably 2.0 or less, most preferably 1.5 or less.
It is as follows. When the color b value exceeds 4, coloring of the obtained resin is strongly felt even with the naked eye, and a molded product is not obtained.

As in the present invention, when the resin is dealdehyded using a vented extruder, the coloring of the resin is considerably greater than in the case where conventional melt polymerization or solid state polymerization is performed after melt polymerization. Become stronger. This is a characteristic phenomenon when dealdehyde is performed from the resin using a vented extruder. The causes are: heat generated by the screw and barrel of the extruder, heat degradation of the resin due to local temperature rise due to heating of the heater of the barrel, and slight vacuum leakage between the barrels in the extruder with vent. This is probably because the resin is exposed to oxygen-containing air and the resin is decomposed.

The polyester resin of the present invention has an intrinsic viscosity after the vented extruder−an intrinsic viscosity before the extruder−0.1 to 0.08 dl in order to prevent coloring due to an increase in the residence time in the vented extruder. / G in the range of, preferably, -0.08 to
In the range of 0.05 dl / g, more preferably -0.0
In the range of 5 to 0.02 dl / g, most preferably -0.02 dl / g.
It can be obtained by producing in the range of 03 to 0 dl / g.

Intrinsic viscosity after extruder with vent-If the intrinsic viscosity before extruder is less than -0.1 dl / g, not only is it not economical, but also sometimes the resulting polyester resin has insufficient mechanical properties. In addition, the intrinsic viscosity after the extruder with a vent was −0.08 dl before the extruder.
If it exceeds / g, it is necessary to stay in the vented extruder for a long time, and not only the productivity is deteriorated, but also adverse effects such as deterioration of the color b value and increase of the AA value are caused.
The residence time in the decompression region in the vented extruder is preferably 5 minutes or less. It is more preferably 4 minutes or less, further preferably 3 minutes or less, particularly preferably 2 minutes or less.

The limiting viscosity of the polyester resin of the present invention is from 0.55 to 0.9 dl / g. Preferably 0.6 to
0.85 dl / g, more preferably 0.63 to 0.8
3 dl / g. When the intrinsic viscosity is lower than 0.55 dl / g, the mechanical properties of the obtained polyester resin are not sufficient. On the other hand, when the intrinsic viscosity is 0.9 dl / g or more, residence in a melt polymerization machine or an extruder equipped with a vent becomes longer, causing a problem of coloring, and furthermore, productivity is lowered, which is not preferable.

The above-mentioned coloring can be further prevented by adding a phosphorus-containing compound. When the phosphorus content is less than 1 ppm, the effect of preventing coloring is not sufficient.
If the phosphorus content exceeds 1000 ppm, not only the effect as a stabilizer is saturated, but also problems such as a reduction in the reaction rate occur. When a phosphorus compound is added as a stabilizer, the phosphorus content is preferably 1 to 1000 ppm (weight as phosphorus element). More preferably 1
0 to 500 ppm, more preferably 20 to 300 pp
m.

Examples of the phosphorus-containing compound include phosphoric esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate and tricresyl phosphate, triphenyl phosphite, trisdodecyl phosphite, tris Phosphites such as nonylphenyl phosphite, methyl acid phosphate,
Preferred examples include acidic phosphate esters such as isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate, and phosphoric acid and polyphosphoric acid.

The phosphorus-containing compound may be added during the esterification reaction step or during the polycondensation reaction step. Further, it may be added to the inside of the extruder with vent or to the step of supplying to the extruder which likes to vent. Of course, it may be added sequentially for each step.

The acid value of the polyester resin of the present invention is preferably 80 equivalents / ton or less. 80 equivalents / to
When n exceeds n, the reaction rate becomes slow, and the residence time in a melt polymerization reactor or a vented extruder needs to be increased, and coloring may occur.

The acetaldehyde content of the polyester resin of the present invention is 30 ppm or less. If it exceeds 30 ppm, the odor of the resin and the molded article becomes strong, and the usable applications are limited.

The polyester resin of the present invention contains a compound containing at least one metal element selected from the group consisting of alkali metals, alkaline earth metals, Zn, Mn, and Co, in particular, Mg, Ca, Zn, It is preferable that at least one compound containing at least one metal element selected from Mn and Co is included. By containing these, transparency and color tone can be further enhanced. The content of these compounds is 1 to 100 with respect to the polyester resin as a value obtained by adding the weight of each element.
0 ppm, even 3 to 500 ppm, especially 5 to 30 ppm
It is preferably 0 ppm.

When the resin after melt polymerization is directly molded without passing through the solid state, the temperature rise crystallization temperature is higher than that of the resin after passing through the solid state. When it is used for a molded article requiring crystallinity such as a preform for use, the temperature-rise crystallization temperature of the molded article may exceed 180 ° C. and the productivity of the molded article may be poor. By adding the phosphorus element-containing compound and the above-mentioned metal element-containing compound, the resin can be heated to a crystallization temperature of 140 ° C. necessary for crystallization.
~ 180 ° C.

This is because the resin supplied in the solid state (chip form) contains fine powder of resin which is easily crystallized in the resin drying step, the chip end face in the resin drying step is crystallized, The resin itself has already been slightly crystallized due to crystallization of the chip due to the impact of contact between the chips, and the resin that has been subjected to solid-phase polymerization is in a state that is easily crystallized by performing crystallization treatment etc. On the other hand, it is considered that there is no factor for accelerating the crystallization in the case of directly forming a molded product from melt polymerization. It is considered that by adding a phosphorus element-containing compound and a metal element-containing compound to the resin, these components, particularly metal ions, become crystal nuclei and bring about a crystallization promoting effect.

The cyclic trimer content in the molten resin after the polycondensation reaction supplied to the vented extruder used in the present invention or in the polyester resin obtained through the vented extruder is substantially 5000 ppm or more. Further, in order to achieve the polyester resin of the present invention, it is necessary that the amount of acetaldehyde after the extruder with a vent minus the amount of acetaldehyde before the extruder is substantially 10 ppm or more.

The polyester resin used in the present invention may be provided with a coloring agent, an ultraviolet absorber, an antioxidant, an antistatic agent, a lubricant, a nucleating agent, a release agent, etc., if necessary, without impairing the object of the present invention. It can be added in a range.

As the form of the polyester resin of the present invention, a biaxial extruder with a vent may be used to make chips by using an underwater cut granulator, or it may be directly introduced into a molding machine and molded. From the viewpoint of economy, it is particularly preferable to perform direct molding. In the case of molding, any molding method such as extrusion molding and injection molding can be performed, but injection molding is particularly preferable.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. The method for measuring the main characteristic values will be described below.

1) Intrinsic viscosity of polyester resin (hereinafter referred to as “IV”) It was determined from the solution viscosity at 30 ° C. in a 1,1,2,2-tetrachloroethane / phenol (2: 3 weight ratio) mixed solvent.

2) Acetaldehyde (hereinafter referred to as AA) content of the polyester resin 1 g of a sample was sealed in a glass ampoule together with 2 ml of water.
After acetaldehyde was extracted with water by immersion in a 160 ° C. oil bath for 2 hours, the amount of acetaldehyde in the water was quantified by gas chromatography to determine the amount of acetaldehyde in the resin.

3) Color b value of polyester resin (hereinafter referred to as Co-b) Measured as follows using a color difference meter TC1500MC88 manufactured by Tokyo Denshoku. Chips or samples cut into chips of about 2 mm square were arranged in a glass cell with the glossy surface facing down, and put into the cell for 8 minutes. Shake the cell more lightly,
After packing tightly, resin was added until the lid was formed, and the lid was closed. The cell filled with the resin was placed on a sample table and measured. The measurement is performed by turning about 120 degrees each time the cell is measured once.
The measurement was performed twice, that is, at 120 degrees in three directions, and the average was obtained.

4) Acid value of polyester resin (hereinafter referred to as AV) About 0.5 g of a sample is dissolved in 20 ml of benzyl alcohol, and chloroform is added for dilution. AV was determined by a titration method using a 1 / 50N aqueous potassium hydroxide solution. Phenol red was used as an indicator.

5) Content of cyclic trimer (hereinafter referred to as CT) of polyester resin A sample is dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and further diluted with chloroform.
After adding methanol to precipitate a polymer, the mixture is filtered. The filtrate was evaporated to dryness, made up to volume with dimethylformamide, and quantified by liquid chromatography.

6) Phosphorus content and Mg content Calculated from the amounts charged during the production of the polyester resin.

(Examples 1-3, Comparative Examples 1-2) The polyethylene terephthalate molten polymer obtained by continuous polycondensation was
It was extruded with a biaxial extruder equipped with a 37 mmφ vent, water-cooled, and formed into chips. The results are shown in Table 1.

[0046]

[Table 1]

(Example 4) IV obtained by continuous polycondensation = 0.71 d
l / g, AA = 51 ppm, Co-b = 0.7, AV = 16 eq / ton, phosphorus content 50 ppm, Mg content 25 ppm, a polyethylene terephthalate molten polymer was extruded at a temperature of 290 ° C. by a twin screw extruder equipped with a 37 mmφ vent. Vent vacuum degree 6tor
After extruding for 1.7 minutes with a residence time of 1.7 min, the mixture was directly supplied to an injection molding machine, and a 2 L bottle preform was molded at a molding temperature of 290 ° C. and a molding cycle of 55 seconds. as a result,
IV = 0.72 dl / g, AA = 15ppm, Co-b = 1.3, AV = 16 equivalent / to
A preform for a bottle having a low aldehyde content and a good color tone having an n phosphorus content of 50 ppm and a Mg content of 25 ppm was obtained.
The polymer immediately before the injection molding machine was sampled, and the heating crystallization temperature was measured by DSC. 168 ° C. DSC
For the measurement, about 10 g of the polymer in a molten state was placed in a stainless steel vat, allowed to cool naturally, and the resin 0.1 g from the inside of the polymer.
1 g was cut out and sealed in an aluminum pan under nitrogen, and the lid was sealed. The measurement was performed at a heating rate of 10 ° C./min from around 0 ° C.

[0048]

According to the polyester resin of the present invention, it is possible to economically produce a high-quality color resin or a molded product having a low aldehyde content and suitable for various uses such as bottles and films.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hidekazu Yoshida 10-24 Toyocho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. Inside Tsuruga Plant (72) Keisuke Suzuki 10-24 Toyocho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. Tsuruga factory F-term (reference) 4F201 AA24 AR17 BA01 BC01 BC02 BC12 BD05 BK36 BM06 BM14

Claims (2)

[Claims] Claims: 1. A polyester resin obtained through an extruder equipped with a vent in a molten state after a polycondensation reaction, wherein the polyester resin has an intrinsic viscosity of 0.55 to 0.9.
A polyester resin having a dl / g, an acetaldehyde content of 30 ppm or less, and a color b value of 4 or less. 2. The method for producing a polyester resin according to claim 1, wherein the intrinsic viscosity after the extruder with vent-the intrinsic viscosity before the extruder is -0.1 to 0.08 dl.
/ G in the range of 0.1 g / g.