JP2009057465A - Polyester and method for producing polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polyester having a low formaldehyde content. <P>SOLUTION: The polyester contains a titanium element of 3×10<SP>-5</SP>to 30×10<SP>-5</SP>mole with respect to 1 mole of a dicarboxylic acid component constituting the polyester, in which the amount of a dialkyleneglycol copolymer is not more than 1.3 wt.% with respect to the weight of the polyester. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyester having a low content of aldehydes.

  In recent years, polyester containers centered on polyethylene terephthalate have been noted for their excellent transparency, excellent mechanical properties, balanced gas barrier properties and excellent hygiene, soy sauce, sauce, cooking oil, juice, beer, It is used in food containers such as carbonated drinks and containers for detergents, cosmetics, pharmaceuticals, etc., and has made remarkable developments. However, a polyester having ethylene terephthalate as a main repeating unit contains aldehydes by-produced in the melt polymerization of the polyester in the pellet. And, in addition to the aldehydes remaining when this pellet is molded into a container such as a bottle or film, it is also regenerated at the time of molding, and as a result of being sealed in the container material, this bottle or film container has a carbonated beverage, When liquid foods such as edible oil and juice are filled, aldehydes are eluted in these liquid foods, which adversely affects the taste and smell, which is a major drawback of polyester containers.

  As a result of studying a method for polymerizing polyethylene terephthalate free from such drawbacks, the present inventors have invented solid-state polymerized polyethylene terephthalate containing very little formaldehyde contained in a molded product.

  It is described that the amount of regenerated acetaldehyde during molding of a polyester resin can be suppressed by polycondensation in the presence of a specific amount ratio of a compound of a metal element such as a titanium compound and magnesium and a phosphorus compound (for example, a patent) Reference 1). However, there is a problem in that the effect of suppressing the formation of formaldehyde during molding is insufficient.

  Further, it is described that the amount of acetaldehyde and formaldehyde generated can be suppressed by adding so-called vitamin E during molding (see, for example, Patent Document 2). However, vitamin E has a drawback that it has low heat resistance and decomposes during melt molding, and it is difficult to say that the effect is sufficient. Further, a technique for reducing the acetaldehyde content and the formaldehyde content is disclosed, but it cannot be said that a sufficiently low value is still achieved as the formaldehyde content (see, for example, Patent Documents 3 and 4). .

JP 2002-226563 A JP 2003-138111 A JP 09-003179 A JP-A-10-168168 Japanese Patent Application Laid-Open No. 08-073611

  An object of the present invention is to provide a polyester having a low formaldehyde content.

The present invention contains 3 × 10 ⁻⁵ to 30 × 10 ⁻⁵ mol of titanium metal element with respect to 1 mol of all dicarboxylic acid components constituting the polyester, and the amount of dialkylene glycol copolymer is 1 with respect to the weight of the polyester. .3% by weight or less of polyester.

  By polymerizing using titanium as the catalyst metal, it is possible to provide a polyester resin having a formaldehyde content of 1.2 ppm or less and a polyester molded product.

Hereinafter, the polyester of the present invention will be described in detail.
(1) Glycol component The glycol component constituting the polyester of the present invention is mainly composed of ethylene glycol and 1,4-butanediol, but 1,2-propylene glycol, 1,3-propylene glycol, neopentyl glycol. 1 type or 2 types or more of alkylene glycols, such as hexamethylene glycol, decamethylene glycol, cyclohexanediol, cyclohexanedimethanol, triethylene glycol, poly (oxy) ethylene glycol, polytetramethylene glycol, polytrimethylene glycol They may be mixed and can be arbitrarily selected depending on the purpose.
In addition, aromatic diols such as naphthalenediol, bisphenol A, and resorcin may be selected within the intended range.

(2) Dicarboxylic acid component The dicarboxylic acid component used in the present invention mainly includes terephthalic acid and naphthalenedicarboxylic acid. For example, isophthalic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfone Aromatic dicarboxylic acids such as dicarboxylic acids; alicyclic dicarboxylic acids such as 1,2- or 1,3-cyclohexanedicarboxylic acid, hexahydroterephthalic acid; adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, etc. A polyester obtained from a dicarboxylic acid component such as an aliphatic dicarboxylic acid and a glycol component. The above compounds may be used alone or in combination of two or more, and can be arbitrarily selected depending on the purpose.

  Further, a trifunctional or higher polyfunctional compound such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid or gallic acid may be copolymerized as a glycol component or dicarboxylic acid component. Well, a monofunctional compound such as о-benzoylbenzoic acid or naphthoic acid may be added as necessary. Also, a small amount of hydroxycarboxylic acid such as lactic acid, glycolic acid, p-oxybenzoic acid, m-oxybenzoic acid, salicylic acid, mandelic acid, hydroacrylic acid, glycolic acid, 3-oxypropionic acid, asiatic acid, quinobaic acid, or A small amount of the alkyl ester may be used.

(3) Third component In the present invention, the content of dialkylene glycol as a copolymer component is required to be 1.3% by weight or less based on the total weight of the polyester. When the dialkylene glycol content exceeds 1.3% by weight, the amount of formaldehyde in the polyester exceeds 1.2 ppm, and the object cannot be achieved. This is presumably because ether bonds in dialkylene glycol components such as diethylene glycol are easily oxidatively decomposed in the presence of oxygen to produce highly reactive peroxides and radicals. The dialkylene glycol may be added as a raw material from the beginning of the polyester production process, or may be obtained by etherification reaction of two main glycol molecules constituting the polyester in the polyester production process. Specific examples of dialkylene glycol as a copolymerization component from these points include dialkylene glycol which is commercially available and easily available, or glycol obtained by etherification of glycol which is commercially available as a polyester raw material. ), Di (trimethylene) glycol, dipropylene glycol, dibutylene glycol [di (tetramethylene) glycol], dihexylene glycol [di (hexamethylene) glycol].
However, as described above, oxidative decomposition generates highly reactive peroxides and radicals, so it is not desirable to increase the copolymerization amount of the ether component.

(4) Manufacturing method The said polyester should just be manufactured using the manufacturing method of conventionally well-known polyester. For example, an esterification reaction is performed using terephthalic acid and ethylene glycol, or a transesterification reaction is performed using a lower alkyl ester of terephthalenedicarboxylic acid (for example, dimethyl ester) and ethylene glycol. It can be produced by further polymerizing the product.

  Further, the polyester obtained in the melt polymerization step may be pelletized and then polymerized in the solid phase polymerization step for further increase in molecular weight or reduction of impurities such as aldehydes and oligomers, if necessary. . Any known method may be adopted as a method for carrying out solid phase polymerization.

  However, in order to make the copolymerization amount of dialkylene glycol 1.3% by weight or less based on the polyester weight, it is preferable not to add a large amount of dialkylene glycol to the reaction vessel until the initial stage of polymerization, preferably all In order to suppress the occurrence of a large amount of dialkylene glycol by side reaction by adding 1.3% by weight or less of dialkylene glycol based on the weight of polyester, the following polycondensation is performed immediately after the esterification reaction or after the transesterification reaction. It is important to start the reaction, shorten the esterification reaction time or transesterification reaction time, and lower the esterification reaction temperature or transesterification reaction temperature. For example, regarding the reaction time, the esterification reaction time or the transesterification reaction time can be completed within 4 hours, preferably within 3 hours 30 minutes.

(5) Catalyst The present invention is characterized in that a titanium compound is used as a polymerization catalyst, and as a result, a specific amount of titanium metal element is contained in the polyester. In the present invention, the titanium compound to be used needs to use a titanium compound that is soluble in the polyester from the viewpoint of reducing foreign matters resulting from the catalyst.

In addition, in the polyester of the present invention, the titanium compound preferably soluble in the polyester is required to be 3 × 10 ⁻⁵ to 30 × 10 ⁻⁵ mol as a titanium metal element with respect to 1 mol of all dicarboxylic acid components. There is. When the titanium metal element is less than 3 × 10 ⁻⁵ mol, the productivity of the polyester is lowered, and a polyester having a target molecular weight cannot be obtained. On the other hand, when the titanium metal element exceeds 30 × 10 ⁻⁵ mol, the thermal stability is lowered, the formaldehyde by-product is promoted, and the target polymer cannot be obtained. The deterioration and the deterioration of the hue become large, and a polyester resin with excellent quality cannot be obtained.

Moreover, when manufacturing polyester, it is also possible to use a transesterification catalyst and / or a stabilizer. As these catalysts and stabilizers, those known as polyester catalysts and stabilizers can be used.
As other polymerization catalyst, the titanium compound soluble in the polyester is not particularly limited, and tetraisopropoxy titanium, tetrapropoxy titanium, tetra-n-butoxy titanium, tetraethoxy titanium, tetraphenoxy titanium, octaalkyl trititanate. Or alkyl titanates such as hexaalkyl dititanate, aryl titanates, reaction products of alkyl titanates or aryl titanates and phosphites, alkyl titanates or aryl titanates To raise titanium compounds in which organic groups are covalently bonded, ionic bonds or coordinate bonds to titanium atoms, which are reaction products consisting of reaction products of esters and trimellitic acid and phosphite compounds Can . Further examples include titanium hydroxide and α-titanic acid. Titanium dioxide usually added as a matting agent in polyester does not fall under “titanium compounds soluble in polyester”.

  In addition, conventionally known polymerization catalysts such as germanium compounds and antimony compounds can be used in combination. Examples of the germanium compound include germanium monoxide and germanium dioxide. Examples of the antimony compound include antimony trioxide and antimony acetate.

(6) Stabilizer Although not essential in the present invention, a stabilizer may be added in order to increase the thermal stability during processing of the obtained polyester. Stabilizers include phosphoric acid esters such as hydroxyethyl dimethyl phosphate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, phosphites such as triphenyl phosphite, trisdodecyl phosphite, methyl acid phosphate, dibutyl phosphate, monobutyl Phosphorus compounds such as phosphate acidic phosphoric acid ester, phosphoric acid, phosphorous acid, hypophosphorous acid and polyphosphoric acid are preferred.
The added amount of these stabilizers is usually 5 to 1000 ppm, preferably 10 to 500 ppm as the weight of phosphorus element in the stabilizer with respect to the weight of all the polymerization raw materials.

(7) Additives Other additives, for example, colorants such as cobalt acetate, antioxidants, ultraviolet absorbers, antistatic agents or flame retardants may be used as necessary.

  Hereinafter, more specific contents of the present invention will be described by showing examples. However, the present invention is not limited to the contents of these examples. Analysis / evaluation performed in Examples and Comparative Examples was performed by the following methods.

(A) Intrinsic viscosity (IV)
After 0.6 g of polyethylene terephthalate was dissolved in 50 cc of o-chlorophenol by heating, the solution was once cooled, and the solution was calculated from the solution viscosity measured at 35 ° C. using an Ubbelohde viscometer.

(B) Measurement of formaldehyde content in polyester by 2,4-dinitrophenylhydrazine (DNPH) method After freezing and pulverizing a sample, the sample is placed in a vial, filled with pure water, capped and treated at 120 ° C. for 1 hr. This is cooled to room temperature, 0.1% DNPH solution is added and shaken to derivatize the aldehydes. Acetaldehyde was quantified by analyzing this solution by liquid chromatography and measuring the amount of acetaldehyde-2,4-dinitrophenylhydrazone. Formaldehyde can also be measured by the same method.
As the column, TSkgel ODS-80Ts made by TOSOH was used. The 0.1% DNPH solution is a solution in which 2,4-dinitrophenylhydrazine is dissolved in a phosphoric acid aqueous solution to a concentration of 0.1 wt%.

(C) Measurement of diethylene glycol (DEG) and dibutylene glycol content The polyester sample was decomposed with hydrazine hydrate and measured by gas chromatography (GC).

(D) Measurement of oligomer (cyclic trimer of ethylene terephthalate unit) content After a polyester sample is pulverized with a pulverizer, a certain amount is weighed and dissolved once in a small amount of hexafluoroisopropanol / chloroform, and then constant with chloroform. Dilute to concentration (50 g / L). This sample was subjected to gel permeation chromatography (GPC, Waters ALC / GPC244 type) to detect the separation of the low molecular weight region and its peak, and based on the calibration curve obtained from the standard sample of the cyclic trimer, the polymer The amount of the cyclic trimer was quantified.

(E) Determination of polyester-containing metal element The catalyst metal element (Ti, Ge, Sb) concentration in the polyester is obtained by heating and melting a granular sample on an aluminum plate, and then forming a molded body having a flat surface with a compression press. Quantitative analysis was performed using a fluorescent X-ray apparatus (Rigaku Corporation 3270E type).

[Example 1]
A mixture of 100 parts by weight of dimethyl terephthalate, 52.7 parts by weight of ethylene glycol, and 0.026 parts by weight of tetra-n-butoxytitanium was charged into a reactor equipped with a stirrer, a rectifying column and a methanol distillation condenser. . While the temperature of the reactor was gradually raised from 140 ° C., transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the system. The EI reaction rate obtained from the methanol effluent amount reached 95% 3 hours and 30 minutes after the start of the reaction. Next, the obtained reaction product is transferred to another reactor equipped with a stirrer and a glycol distillation condenser, and the temperature is gradually raised from 250 ° C. to 280 ° C., and the pressure is reduced from normal pressure to a high vacuum of 30 Pa. The polymerization reaction was carried out. While tracing the melt viscosity of the reaction system, the polymerization reaction was terminated when the polymerization time reached 50 minutes. The molten polymer was removed from the reactor, consolidated into a plate, cut and pelletized.

The obtained pellets were pre-crystallized at 160 ° C. for 5 hours, then charged into a stationary solid-state polymerization apparatus, and subjected to a solid-state polymerization reaction at 215 ° C. for about 15 hours under a nitrogen flow to have an intrinsic viscosity of 0.740 dL / g. Polyethylene terephthalate pellets were obtained.
Next, the polyethylene terephthalate chip obtained by the above method was dried at 160 ° C. for 5 hours, and then molded into a 3 cm × 3 cm × 3 mm, 3 g plate at a cylinder temperature of 285 ° C. using an injection molding machine HM7-C manufactured by Nissei. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Example 2]
The same procedure as in Example 1 was performed except that 1,4-butanediol was used as the glycol component. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Example 3]
The same procedure as in Example 1 was performed except that 2,6-dimethylnaphthalate was used as the dicarboxylic acid component. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Example 4]
The same procedure as in Example 1 was performed except that 1,4-butanediol was used as the glycol component and 2,6-dimethylnaphthalate was used as the dicarboxylic acid component. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Reference Example 1]
In a catalyst preparation tank equipped with a stirrer, nitrogen circulation pipe, and heating device, 21 parts by mass of ethylene glycol was mixed and stirred, and then 0.023 parts by weight of acetic acid and 0.162 parts by mass of titanium tetrabutoxide were slowly and gradually added. And kept at 50 ° C. for 2 hours to obtain a transparent ethylene glycol solution of a titanium compound. Hereinafter, this solution is abbreviated as “TBT / EG solution”. When the titanium concentration of this solution was measured using fluorescent X-rays, it was 1.0%.

Furthermore, in another catalyst preparation tank (stirrer, nitrogen circulation piping, heating device attached), 17.57 parts by mass of ethylene glycol was heated to 120 ° C. while stirring, and 0.147 parts by mass of monobutyl phosphate was added. Then, the mixture was dissolved by heating and stirring, and the whole amount of the TBT / EG solution prepared previously was slowly added gradually, and then stirred and held at a temperature of 120 ° C. for 1 hour to complete the reaction between the titanium compound and the phosphorus compound. . The reaction product was present as a fine precipitate in a cloudy state. Hereinafter, this solution is abbreviated as “TBMBP catalyst solution”. As a result of separating and purifying fine precipitates in the solution from various parts of the solution and performing various analyzes, the fine precipitates are compounds represented by the following general formula (I) and are functionally functional. It was confirmed that the group R ₁ was a titanium / phosphorus compound having a normal butyl group.

[Example 5]
The titanium compound obtained in Reference Example 1 was used as a catalyst in the same manner as in Example 1 except that 0.001 part by weight was used as the titanium element. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Comparative Example 1]
It implemented similarly to Example 1 except having used 0.016 weight part of germanium dioxide as a catalyst instead of the titanium compound. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Comparative Example 2]
It implemented like Example 1 except having replaced with a titanium compound and using 0.038 weight part of diantimony trioxide as a catalyst. Table 1 shows evaluation results such as formaldehyde content and acetaldehyde content.

[Examples 6 to 14, Comparative Examples 3 to 4]
Diethylene glycol (DEG) was charged in advance into the reactor used in Example 1 so as to have the diethylene glycol content shown in Table 2, and the temperature and time of solid phase polymerization were adjusted so that the intrinsic viscosity (IV) shown in Table 2 was obtained. Except for the adjustment, the same procedure as in Example 5 was carried out to obtain polyethylene terephthalate. The results are shown in Table 2. For reference, the data of Example 5 are also shown in Table 2 again.

  When a polyester is produced according to the present invention, a polyester resin having a very low content of aldehydes and a polyester molded product can be provided by polymerization using a titanium compound as a catalyst metal. The molded product obtained by the present invention is suitable for food packaging / filling containers, medical packaging containers and the like, and has great industrial significance.

Claims (2)

3 × 10 ⁻⁵ to 30 × 10 ⁻⁵ mol of titanium metal element is contained per 1 mol of all dicarboxylic acid components constituting the polyester, and the amount of copolymerized dialkylene glycol is 1.3 wt. % Polyester or less. A process for producing a polyester, which is an aromatic dicarboxylic acid or a derivative thereof, an alkylene glycol, and a titanium compound in an amount of 3 × 10 ⁻⁵ to 30 × 10 ⁻⁵ molar equivalents relative to 1 mol of all dicarboxylic acid components constituting the polyester. Is used as a catalyst and polycondensation is carried out so that the amount of dialkylene glycol copolymerization is 1.3% by weight or less based on the weight of the polyester.