JPH07207002A - Thermoplastic polyester resin - Google Patents

Abstract

PURPOSE:To provide a thermoplastic polyester resin which hardly generates monomers during melt molding. CONSTITUTION:A polyester resin is provided which mainly comprises ethylene terephthalate units and of which part of the molecular ends are blocked with a monocarboxylic acid and/or a monohydric alcohol and the increase in amts. of monomers due to thermal melting is 40ppm or lower.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermoplastic polyester resin used for a film, a container or a sheet. More specifically, the present invention relates to a thermoplastic polyester resin that hardly generates monomers during melt molding.

[0002]

2. Description of the Related Art Polyester, particularly polyethylene terephthalate (hereinafter referred to as PET), is widely used for fibers, films and the like because of its excellent mechanical properties and chemical properties. In recent years, in particular, its use in beverage bottles and food containers has rapidly spread.

Generally, hollow containers such as bottles are manufactured by supplying a thermoplastic polyester resin to a molding machine such as an injection molding machine to mold a preform for a hollow molded body, and heating the preform to blow-mold it. To do. For containers such as trays, a thermoplastic polyester resin is supplied to an extruder and extruded from a T-die to prepare a sheet,
The sheet is manufactured by rolling.

In producing these, terephthalic acid (hereinafter referred to as TPA), monohydroxyethyl terephthalate (hereinafter referred to as MHET), bishydroxyethyl terephthalate (hereinafter referred to as BH) is prepared from a molten polyester resin.
Monomers such as ET) precipitate. It is known that they contaminate the injection part of the injection molding machine and the cooling roller of the sheet molding machine, and also have the effect of adhering a sublimable annular trimer generated from the resin during blow molding to the mold. For this reason, it is necessary to clean these parts at regular intervals, which causes a decrease in productivity.

So far, little has been known about a method of suppressing the generation of these monomers during melt molding.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to suppress the generation of the above-mentioned monomers during melt molding, and as a result, a part of the end of PET is a monovalent carboxylic acid and / or It has been found that a resin with less generation of monomers during melt molding can be provided by blocking with a monohydric alcohol, and the present invention has been completed.

[0007]

That is, the present invention is a PE
A polyester resin containing T as a main component,
A part of the terminal is blocked with a monovalent carboxylic acid and / or a monovalent alcohol, and the amount of increase of the monomers by heating and melting is 40 ppm or less, more preferably 20 p.
The present invention relates to a thermoplastic polyester resin characterized by being pm or less.

The PET forming the skeleton in the present invention has ethylene terephthalate as the main repeating unit, but it is also possible to replace a part of the glycol component and / or dicarboxylic acid component with another glycol or dicarboxylic acid. For example, trimethylene glycol, tetramethylene glycol, neopentyl glycol,
1,4-cyclohexanedimethanol, 2,2-bis (4-β-hydroxyethoxydiphenyl) propane,
Bis (4-β-hydroxyethoxyphenyl) sulfone, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-
Examples thereof include naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, azelaic acid and sebacic acid.

The end groups of PET obtained under ordinary polymerization conditions are a carboxyl group (-COOH) and a hydroxyl group (-OH), and these end groups are monovalent such as an alkyl group or an aryl group at the other end. By blocking with carboxylic acid or alcohol, it is heated under normal heating and melting conditions (280 to 300 ° C,
5-20 minutes), TPA, MHET, BH
It is possible to suppress the increase amount of monomers such as ET to 40 ppm or less.

It is preferable that 30% or more of all the terminal groups in the polymer be blocked with a monovalent carboxylic acid and / or a monovalent alcohol, and it is particularly preferable that all of the carboxyl groups and hydroxyl groups be blocked. If it is less than 30%, the generation of monomers generated during heating and melting may not be suppressed.

The monohydric alcohol for blocking the carboxyl group may be any type as long as it has a group such as an alkyl group or an aryl group at the other end. However, if the alkyl group is too long, the skeleton becomes P
Mechanical properties and thermal characteristics of ET, such as crystallinity, heat resistance,
Alcohols having 26 or less carbon atoms are preferred because they often lead to reduced mechanical strength. In particular, those having an aryl group have a structure similar to PET,
It is more preferable because it does not significantly change the characteristics of PET.

On the other hand, as the monovalent carboxylic acid or carboxylic acid ester for blocking the hydroxyl group, any kind having an alkyl group or an aryl group at the other end can be used, like the above-mentioned alcohols. Those having 22 or less carbon atoms are preferable. Needless to say, it is more advantageous to have an aryl group as in the case of alcohol.

The above monohydric alcohol, monovalent carboxylic acid and carboxylic acid ester are reacted with an active terminal group at any stage of the process for producing PET, which is the skeleton, from the step of producing a film, sheet, bottle, etc. Although a predetermined polymer can be obtained, it is preferably carried out in the polymerization step in order to complete the reaction. However, the polymerization (including transesterification) is carried out at a temperature of 240 ° C. or higher at atmospheric pressure to 1 torr.
Since it is carried out under the following reduced pressure, there is a high risk that the monovalent alcohol or carboxylic acid having a low boiling point will be evaporated during the reaction. Therefore, it preferably has a boiling point of 200 ° C. or higher, and more preferably 220 ° C. or higher.

Examples of preferable monohydric alcohols, carboxylic acids and carboxylic acid esters which satisfy the above conditions are nonyl alcohol, lauryl alcohol, myristyl alcohol, stearyl alcohol, benzyl alcohol, cinnamyl alcohol, capric acid and lauric acid, Examples include myristic acid, stearic acid, benzoic acid, naphthoic acid, butyl benzoate and propyl benzoate.

The increase in the content of the monomers in the molded article produced by heating and melting the thermoplastic polyester of the present invention is 40 ppm or less, preferably 20 ppm or less, before the molding. Contamination often occurs.

[0016]

The thermoplastic polyester resin of the present invention is
Generation of monomers such as TPA, MHET, and BHET during heating and melting is small. Therefore, when manufacturing a molded product,
Contamination due to the adhesion of these monomers and the contamination due to the sublimable cyclic trimer hardly occur, and it is not necessary to frequently remove the dirt such as the mold, so that the productivity can be remarkably improved.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples. Various measuring methods used in the present invention are shown below. -Resin intrinsic viscosity It is a value measured at 20 ° C at a concentration of 1.0 g / dl in a mixed solvent of phenol / tetrachloroethane = 1/1.

Content of monomers 2.0 g of resin is dissolved in a mixed solvent of hexafluoroisopropanol / chloroform = 1/1, further diluted with chloroform, and then concentrated under reduced pressure to remove hexafluoroisopropanol. Then, a mixed solvent of methanol / chloroform = 1/1 was added to precipitate the polymer, and the filtrate filtered through a membrane filter was subjected to high performance liquid chromatography (column: radial pack C18 (manufactured by Nippon Waters), eluent: 35% methanol solution). +
PIC-A Reagent (Nippon Waters) 0.005mo
1 / L).

Example 1 254 parts by weight of bis (β-hydroxyethyl) terephthalate, 110 parts by weight of terephthalic acid, 4 parts by weight of a 0.8% aqueous solution of germanium oxide, and 1.5 parts by weight of a 5% aqueous solution of trimethylphosphoric acid were added to a rectifying column. After being charged into a polymerization vessel having a temperature of 50 ° C., it was heated to 250 ° C. with stirring while flowing a slight amount of nitrogen.
During this period, by maintaining the temperature of the rectification column at 90 to 95 ° C,
Ethylene glycol was refluxed and only water was distilled out of the system. Calculated from the amount of distilled water, when the transesterification rate reached 90%, benzoic acid-
Add 2.2 parts by weight of n-butyl, 250 ° C for about 30 minutes
Was esterified. Then, the pressure was gradually reduced while continuing heating and stirring, and the inside of the can was set to a high vacuum of 5 torr or less over about 1 hour. During this time, the temperature was raised to 280 ° C. After continuing polymerization for about 4 hours in this state, return to normal pressure,
The content was extruded into a gut shape, cooled with water, and then a pelletized polymer was obtained using a cutter.

This polymer was treated under reduced pressure of 1 torr or less,
Solid phase polymerization was carried out at 225 ° C. for 15 hours to obtain a polymer having an intrinsic viscosity of 0.77. The amount of monomers contained in this polymer is shown in the upper part of Table 1.

The resulting polymer was dried under reduced pressure at 150 ° C. to a water content of 100 ppm or less, and then 2
A plate-shaped molded product was produced at 90 ° C. Table 1 shows the amount of monomers in the plate-shaped molded product (lower row) and the amount of increase with respect to the monomers before molding.

Example 2 As a blocking agent, 0.8 part by weight of stearyl alcohol and -n-butyl benzoate were used instead of -n-butyl benzoate.
Polymerization, molding, and content measurement of monomers were performed in the same manner as in Example 1 except that 2 parts by weight was added. The results are shown in Table 1.

Example 3 Polymerization, molding and content measurement of monomers were carried out in the same manner as in Example 1 except that 2.5 parts by weight of stearic acid was added as a blocking agent instead of -n-butyl benzoate. went. The results are shown in Table 1.

Comparative Example 1 Polymerization, molding, and content measurement of monomers were carried out in the same manner as in Example 1 except that the blocking agent was not added. The results are shown in Table 1.

[0025]

[Table 1]

Claims (2)

[Claims] 1. A polyester resin comprising polyethylene terephthalate as a main constituent, wherein a part of the terminal is blocked with a monovalent carboxylic acid and / or a monovalent alcohol, and the amount of monomers is increased by heating and melting. An amount of 40 ppm or less, a thermoplastic polyester resin. 2. The increase in the amount of monomers due to heating and melting is 2
The thermoplastic polyester resin according to claim 1, which is 0 ppm or less.