JPH0284429A - Packaging material made of polyester - Google Patents

Abstract

PURPOSE:To obtain the subject material generating little acetaldehyde in molding and having excellent transparency, heat-resistance and strength by copolymerizing a specific amount of dimethylpropanediol to a polyester composed of terephthalic acid and ethylene glycol. CONSTITUTION:The objective material can be produced by copolymerizing 0.5-20mol% (based on the total glycol component) of 2,2-dimethyl-1,3-propanediol to a polyester containing terephthalic acid as a main acid component and ethylene glycol as a main glycol component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copolyester for packaging materials, and more specifically, it has a low amount of acetaldehyde regenerated during molding, and has excellent transparency, heat resistance, and mechanical strength. The present invention relates to a copolymerized polyester for packaging materials that has excellent properties and is useful as packaging materials for films, containers, etc.

[Prior Art J Polyethylene terephthalate has excellent mechanical and chemical properties! [It is widely used in films, industrial resins, etc., but recently it has also been used in bottles, cups,
It is also used for trays, etc. In particular, polyester bottles have come to be widely used as containers for foods, cosmetics, etc. due to their light weight and ease of handling.

However, when polyethylene terephthalate is used as a bottle, it is necessary to reduce the content of acetaldehyde (hereinafter abbreviated as AA), which has a negative effect on taste and odor, as much as possible compared to the bottle as a molded product. Conventionally, as a method for reducing acetaldehyde in polyethylene terephthalate, a so-called in-phase polymerization method has been known, in which chips or pulverized products of polyethylene terephthalate prepolymer are heat-treated at high temperature under reduced pressure or in an inert gas stream.

However, although AA in polyethylene terephthalate can certainly be reduced by this solid phase polymerization method, it has the disadvantage that AA is regenerated in the molded product due to melting and heating of the polyester resin during the injection molding step. have

For this reason, it has been desired to develop a new method that can further reduce AA in polyethylene terephthalate bottles.

[Objective of the Invention] The object of the present invention is to solve such problems, to reduce the amount of AA regenerated when melt-molding polyester resin, to have excellent transparency, heat resistance, and mechanical strength as a molded product, and to produce a film. Another object of the present invention is to provide a copolyester useful as a packaging material for containers and the like.

[Structure of the Invention] The present invention provides a polyester in which the main acid component is terephthalic acid and the main glycol component is ethylene glycol, in which 2,2-dimethyl-1,3-propanediol is added in an amount of 0.2-dimethyl-1,3-propanediol to the total glycol component. 5-20 mol%
This is a polyester packaging material characterized by being copolymerized.

Here, "main" refers to an amount exceeding 85 mol%.

Therefore, it is possible to contain ester units other than terephthalic acid and ethylene glycol in a range of less than 15 mol%, and such copolymerization components include terephthalic acid, ethylene glycol, and 2,2-dimethyl-1,3-
There are dicarboxylic acids and diols or oxyacids other than propanediol.

Specifically, aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid,
Diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid, etc.: Alicyclic dicarboxylic acids, such as decalin dicarboxylic acid, hexahydroterephthalic acid, etc.: Aliphatic dicarboxylic acids, such as malonic acid. Examples include succinic acid and adipic acid; glycol components include aliphatic diols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, and diethylene glycol; aromatic diols such as vitronone, catechol, naphthalenediol, and resorcinol; 4. 4'-dihydroxy-diphenyl-sulfone, bisphenol A [2.
2-bis(4-hydroxyphenyl)propane]. Tetrabromobisphenol A, bishydroxyethoxybisphenol A, etc.; Alicyclic diols, such as cyclohexanediol; Aliphatic oxycarboxylic acids, such as glycolic acid, hydroacrylic acid. 3-oxybrobionic acid, etc.; alicyclic oxycarboxylic acids, such as asiatic acid, quinobic acid, etc.; aromatic oxycarboxylic acids, such as salicylic acid, II-oxybenzoic acid. p-oxybenzoic acid, mandelic acid.

Examples include atrolactin acid.

Furthermore, a polyfunctional compound having a valence of 3 or more within the range where the polyester is substantially linear, such as glycerin.

Trimethylolpropane, pentaerythritol.

Trimellitic acid, trimesic acid, pyromellitic acid.

Tricarballylic acid. Gallic acid etc. may be copolymerized,
If necessary, monofunctional compounds such as 0-benzoylbenzoic acid, naphthoic acid, etc. may be added.

The copolymerized polyester of the present invention is 2,2-dimethyl-
It is essential to copolymerize 1.3-propanediol in an amount of 0.5 to 20 mol % based on the total glycol components.

If it is less than 0.5 mol%, the effect of suppressing regenerated AA is insufficient, and if it exceeds 20 mol%, the mechanical strength of the molded product will be insufficient. Preferably it is 1 to 15 mol%.

Also, regarding substituted compounds of 1,3-propanediol, 2-methyl-1,3-propanediol has a smaller AA reduction effect than 2,2-dimethyl-1,3-propanediol; 3- and 1,1-dimethyl-
1,3-propanediol also has a small effect on reducing AA by-products. Therefore, in order to achieve a low content of AA above a certain level, in the case of these substituted compounds, large amounts must be added in the polymer raw material charge;
As a result, a problem arises in that the physical properties of the molded article deteriorate.

Therefore, the 2,2-dimethyl-1,3-propanediol of the present invention is the most efficient way to reduce the A of polyester molded products.
A can be achieved, and the physical properties of the molded article can also be improved.

The copolymerized polyester of the present invention has an intrinsic viscosity [phenol/
It is preferably 0.3 to 1.5 (measured at 35°C using a mixed solvent of tetrachloroethane (weight ratio 60/40)). In particular, it is preferably 0.4 or more. Such a copolymerized polyester can be produced by a method conventionally used in the production of polyethylene terephthalate. For example, an ester reaction is carried out using terephthalic acid and ethylene glycol, a compound, or a transesterification reaction is carried out using a lower alkyl ester of terephthalic acid (e.g. dimethyl ester) and ethylene glycol, a compound, and the resulting reaction product is It can be produced by further polycondensation. In addition, when producing these polyesters, transesterification catalyst 1 polymerization catalyst,
It is preferable to use stabilizers and the like. As these catalysts, stabilizers, etc., those known as catalysts, stabilizers, etc. for polyester, particularly polyethylene terephthalate, can be used. In addition, other additives may be added as necessary, such as colorants, antioxidants, ultraviolet absorbers, and antistatic agents.

Flame retardants etc. may also be used.

[Effects of the Invention] The copolymerized polyester of the present invention regenerates a small amount of AA during molding, and the molded product exhibits excellent transparency, heat resistance, and mechanical strength. Therefore, it is extremely effective as a packaging material for films, containers, etc.

[Example] The present invention will be explained below with reference to Examples. In addition, "parts" in the examples mean parts by weight. Furthermore, the methods for measuring characteristics used in the examples are shown below.

- Intrinsic viscosity; [η] Calculated from the solution viscosity measured at 35°C using a mixed solvent of phenol/tetrachloroethane (60/40 weight ratio).

- Acetaldehyde (AA) A sample was ground in liquid N2, sealed in a glass insert, and quantified using a high-sensitivity gas chromatograph, and expressed in ppm (weight).

Example 1 and Comparative Example 1 3,000 parts of dimethyl terephthalate, 1,870 parts of ethylene glycol, 80 parts of 2,2-dimethyl-1,3-propanediol, and an ethylene glycol solution of titanium acetate (1.0 parts as titanium) 3.7 parts (% by weight) were placed in a transesterification reactor, the temperature was gradually raised from 150°C, the methanol distilled out was separated, and the transesterification reaction was carried out.

The liquid temperature at the completion of the reaction was 230°C. Then, 0.6 part was added, the reaction product was transferred to the polycondensation section, 42.2 parts of germanium dioxide ethylene glycol slurry (1615% by weight as germanium dioxide) was added, and the reaction was carried out for about 10 minutes under normal pressure. Gradually reduce the pressure in the reaction system,
50 s after 30 minutes N9. 2011118 after 90 minutes
9. After 120 minutes, the temperature was set to 0.5 and 1, while the liquid temperature was 230℃.
After 120 minutes, the temperature was gradually raised to 280° C., and after a polycondensation reaction was carried out at this temperature for 3 hours, the polycondensation section was pumped out into running water by a conventional method to form chips. The intrinsic viscosity of this chip was 0.63, and the AA content in the chip was 92 ppH1. It was 92 ppm. After pre-drying this chip at 160°C for 2 hours, the temperature was raised to 220°C for 30 minutes, and solid phase polymerization was carried out under a reduced pressure of 0.5 Torr in a nitrogen atmosphere for 6 hours to obtain an intrinsic viscosity of 0.74 in the chip. A polymer with an AA content of 1.5 ppm was obtained.

Further, the amount of 2,2-dimethyl-1,3-propanediol copolymerized in this polymer was examined and found to be 5 mol%.

Using the polymer obtained in this way, a cylindrical bottomed Barylin with a weight of 503 cm was molded using an injection molding wire with a cylinder temperature of 285°C, and then the Parylin was molded at an internal temperature of 90 to 105°C. After reheating, biaxial stretching was performed to obtain a bottle with an internal volume of 11. The AA content in the body of this bottle is 5.21)l)! It was I. As a comparative example, the same procedure was carried out except that 2,2-dimethyl-1,3-propanediol was removed, and the AA content in the body of the bottle was 7.5 ppm. Therefore, it was found that this polymer is highly effective in suppressing the regeneration of AA during melt molding.

Examples 2-4. Comparative Example 2.3 The polymerization reaction etc. were carried out in the same manner as in Example 1 except that the amount of 2.2-dimethyl-1,3-propanediol added was changed.

The results are shown in Table 1.

Comparative Examples 4 to 7 2.2-dimethyl-1,3-propanediol to 2-methyl-1,3-propanediol, 1.3-dimethyl-
Preparation and molding were carried out in the same manner as in Example 1 except that 1,3-propanediol was used and the amount added was changed. Table 2 shows the results.
It was shown to.

Table 2

Claims (1)

[Claims] In a polyester whose main acid component is terephthalic acid and whose main glycol component is ethylene glycol, 2,2-dimethyl-1,3-propanediol is copolymerized with 0.5 to 20 mol% of the total glycol component. A polyester packaging material characterized by: