WO2025225512A1 - Polyester and feeding bottle - Google Patents

Abstract

The present invention provides a polyester wherein: a dicarboxylic acid constituent unit is a constituent unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof; and a diol constituent unit includes a constituent unit derived from any isosorbide, and 27.5 mol% or more of a constituent unit derived from 1,4-cyclohexanedimethanol among a total 100 mol% of said diol constituent units. A feeding bottle according to the present invention is formed using said polyester.

Description

Polyester and baby bottles

The present invention relates to polyesters and baby bottles.

Due to its excellent heat resistance, transparency, and mechanical properties, polyester is widely used in areas such as packaging materials, molded products, and films. Among these, polyethylene terephthalate (PET) is a resin with a particularly well-balanced combination of mechanical properties, solvent resistance, aroma retention, weather resistance, and recyclability, and is widely used primarily for bottles and films. However, PET has drawbacks in terms of heat resistance. Specifically, its glass transition temperature is around 80°C, making it unsuitable for applications requiring high heat resistance, such as products used inside automobiles, packaging for imports and exports, food packaging that undergoes retort processing or microwave heating, and baby bottles and tableware that undergo heat sterilization.

JP 2017-105873 A

In response to the above-mentioned issues, for example, Patent Document 1 proposes a polyester resin having dicarboxylic acid structural units and diol structural units, in which 5 to 90 mol % of the diol structural units are diol units having a cyclic acetal skeleton and 5 to 90 mol % are alicyclic diol units. However, for applications such as baby bottles that require heat resistance and impact resistance, further improvements in these properties are required.

The present invention therefore aims to provide a polyester and a baby bottle that have high heat resistance and impact resistance.

[1]
A baby bottle formed using a polyester containing dicarboxylic acid structural units and diol structural units,
the dicarboxylic acid structural unit is a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof,
A baby bottle, wherein the diol structural units contain 27.5 mol % or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide, based on a total of 100 mol % of the diol structural units.
[2]
The baby bottle according to [1], wherein the diol structural units contain 5 mol % or more of structural units derived from isosorbide within a total of 100 mol % of the diol structural units.
[3]
The baby bottle according to [1] or [2], wherein the diol structural unit further contains a structural unit derived from ethylene glycol.
[4]
The baby bottle according to any one of [1] to [3], wherein the content of the structural units derived from the 2,6-naphthalenedicarboxylic acid and/or its ester derivative is 100 mol % in a total of 100 mol % of the dicarboxylic acid structural units.
[5]
A polyester comprising dicarboxylic acid structural units and diol structural units,
the dicarboxylic acid structural unit is a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof,
The polyester, wherein the diol structural units contain 27.5 mol % or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide, based on a total of 100 mol % of the diol structural units.

The present invention makes it possible to provide polyester and baby bottles that have high heat resistance and impact resistance.

The following describes in detail an embodiment of the present invention, but the present invention is not limited to this embodiment. Note that in this specification, "A to B" (A and B are numerical values) means "greater than or equal to A and less than or equal to B."

[First embodiment]
The baby bottle according to the first embodiment is a baby bottle formed using a polyester. In the first embodiment, the polyester contains dicarboxylic acid structural units and diol structural units, and the dicarboxylic acid structural units are structural units derived from 2,6-naphthalenedicarboxylic acid and/or its ester derivatives. In the first embodiment, the diol structural units in the polyester contain 27.5 mol% or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide, based on a total of 100 mol% of the diol structural units. In the first embodiment, by forming a baby bottle using a polyester containing such structural units, a baby bottle with high heat resistance and impact resistance can be provided.

Here, baby bottles are used for infants after being heat sterilized by boiling or steam, and may also be carried by users when they go out. Therefore, baby bottles are required to have heat resistance that can withstand high temperatures and high impact resistance that prevents them from breaking when accidentally dropped while containing contents, ensuring safety, even if they are lightweight (e.g., thin-walled). Polyesters containing the above-mentioned desired structural units have the high heat resistance and impact resistance required of baby bottles, making them particularly suitable for use in baby bottles.
Furthermore, in baby bottles, high transparency is required so that the state of the milk to be given to infants and the state of the container (for example, whether or not solid milk remains dissolved, whether or not there is dirt in the milk or on the container, etc.) Polyesters containing the above-described desired structural units have the high transparency required for baby bottles, and are therefore particularly suitable for use in baby bottles.

The polyester in the first embodiment will be described below.
In a first embodiment, the polyester comprises the following dicarboxylic acid and diol building blocks:

(Dicarboxylic acid structural unit)
In the first embodiment, the dicarboxylic acid structural unit is a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof, which can improve the heat resistance of the polyester.
Hereinafter, a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or its ester derivative will also be referred to as a "2,6-naphthalenedicarboxylic acid structural unit."

Here, "the dicarboxylic acid structural units are structural units derived from 2,6-naphthalenedicarboxylic acid and/or its ester derivatives" means that dicarboxylic acid structural units other than 2,6-naphthalenedicarboxylic acid structural units are not intentionally included. Furthermore, the content of 2,6-naphthalenedicarboxylic acid structural units in the dicarboxylic acid structural units may be 100 mol % out of a total of 100 mol % of dicarboxylic acid structural units.

In the first embodiment, ester derivatives from which dicarboxylic acid structural units can be derived include, but are not limited to, diesters of dicarboxylic acids and saturated hydrocarbon alcohols such as methanol.

(Diol structural unit)
In the first embodiment, the diol structural units contain 27.5 mol% or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide (1,4:3,6-dianhydro-D-sorbitol) relative to a total of 100 mol% of the diol structural units.
When the diol structural units contain 27.5 mol % or more of structural units derived from 1,4-cyclohexanedimethanol, the impact resistance of the polyester can be improved. Furthermore, when the diol structural units contain structural units derived from isosorbide, the heat resistance can be improved.
Hereinafter, structural units derived from 1,4-cyclohexanedimethanol or isosorbide will also be referred to as "1,4-cyclohexanedimethanol structural units" or "isosorbide structural units." These same terms will also be used to refer to structural units derived from specific diols.

The content of 1,4-cyclohexanedimethanol structural units in the diol structural units may be 30 mol% or more, or may be 35 mol% or more, 40 mol% or more, or 45 mol% or more. Furthermore, the upper limit of the content of 1,4-cyclohexanedimethanol structural units in the diol structural units is not particularly limited, but can be, for example, 100 mol% or less, or 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 55 mol% or less, 50 mol% or less, 45 mol% or less, 40 mol% or less, or 35 mol% or less.

The content of isosorbide structural units in the diol structural units may be 0 mol% (i.e., not contained), but is preferably more than 0 mol%. The content of isosorbide structural units is more preferably 5 mol% or more, even more preferably 7.5 mol% or more, and even more preferably 10 mol% or more. The upper limit of the content of isosorbide structural units in the diol structural units is preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 55 mol% or less, and particularly preferably 45 mol% or less. In addition, the content of isosorbide structural units in the diol structural units may be 5 to 70 mol%, 5 to 60 mol%, 5 to 55 mol%, 5 to 45 mol%, 5 to 35 mol%, 5 to 25 mol%, 5 to 15 mol%, 15 to 70 mol%, 15 to 60 mol%, 15 to 55 mol%, 15 to 45 mol%, 15 to 35 mol%, 15 to 25 mol%, 25 to 70 mol%, 25 to 60 mol%, 25 to 55 mol%, 25 to 45 mol%, 25 to 35 mol%, 35 to 70 mol%, 35 to 60 mol%, 35 to 55 mol%, 35 to 45 mol%, 45 to 70 mol%, 45 to 60 mol%, or 45 to 55 mol%.
When the diol structural units contain 5 mol % or more of isosorbide structural units, the heat resistance of the polyester can be further improved.

In the first embodiment, the diol structural units may contain any diol structural units in addition to 1,4-cyclohexanedimethanol structural units and isosorbide structural units. Alicyclic diol structural units among such diol structural units include, but are not limited to, structural units derived from 1,3-cyclohexanedimethanol, 1,2-decahydronaphthalenedimethanol, 1,3-decahydronaphthalenedimethanol, 1,4-decahydronaphthalenedimethanol, 1,5-decahydronaphthalenedimethanol, 1,6-decahydronaphthalenedimethanol, 2,7-decahydronaphthalenedimethanol, tetralindimethanol, norbornenedimethanol, tricyclodecanedimethanol, pentacyclododecanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, etc.

In the first embodiment, other optional diol structural units include structural units derived from aliphatic diols such as ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, propylene glycol, and neopentyl glycol; polyether compounds such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; bisphenols such as 4,4'-(1-methylethylidene)bisphenol, methylenebisphenol (bisphenol F), 4,4'-cyclohexylidenebisphenol (bisphenol Z), and 4,4'-sulfonylbisphenol (bisphenol S); alkylene oxide adducts of the above bisphenols; aromatic dihydroxy compounds such as hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, and 4,4'-dihydroxydiphenylbenzophenone; and alkylene oxide adducts of the above aromatic dihydroxy compounds.

In the first embodiment, when the diol structural unit contains any diol structural unit other than the 1,4-cyclohexanedimethanol structural unit and the isosorbide structural unit, it is preferable to contain an ethylene glycol structural unit. By containing the ethylene glycol structural unit, a more inexpensive polyester can be obtained.
In this case, the content of ethylene glycol structural units is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, based on a total of 100 mol% of diol structural units. The upper limit of this content is preferably 75 mol% or less, more preferably 65 mol% or less, even more preferably 55 mol% or less, and even more preferably 45 mol% or less.

Furthermore, the content of ethylene glycol structural units in the diol structural units is 5 to 75 mol%, 5 to 67.5 mol%, 5 to 65 mol%, 5 to 62.5 mol%, 5 to 55 mol%, 5 to 45 mol%, 5 to 35 mol%, 5 to 25 mol%, 15 to 75 mol%, 15 to 67.5 mol%, 15 to 65 mol%, 15 to 62.5 mol%, 15 to 55 mol%, 15 to 45 mol%, 15 to 35 mol%, 15 to 25 mol%, 25 to 75 mol%, 25 to 67.5 mol%, 25 to 65 mol %, 25 to 62.5 mol%, 25 to 55 mol%, 25 to 45 mol%, 25 to 35 mol%, 35 to 75 mol%, 35 to 67.5 mol%, 35 to 65 mol%, 35 to 62.5 mol%, 35 to 55 mol%, 35 to 45 mol%, 45 to 75 mol%, 45 to 67.5 mol%, 45 to 65 mol%, 45 to 62.5 mol%, 45 to 55 mol%, 55 to 75 mol%, 55 to 67.5 mol%, 55 to 65 mol%, 55 to 62.5 mol%, or 65 to 75 mol%.

In the first embodiment, the combination of dicarboxylic acid structural units and diol structural units is not particularly limited, but for example, a combination in which the dicarboxylic acid structural units are 2,6-naphthalenedicarboxylic acid structural units and the diol structural units are composed of 27.5 to 95 mol % 1,4-cyclohexanedimethanol structural units, 5 to 70 mol % isosorbide structural units, and 0 to 67.5 mol % ethylene glycol structural units, based on a total of 100 mol % of the diol structural units, is preferred.

(Other ingredients)
In the first embodiment, the polyester may contain, within the scope of the object of the present invention, monoalcohol units such as butyl alcohol, hexyl alcohol, and octyl alcohol; trihydric or higher polyhydric alcohol units such as trimethylolpropane, glycerin, 1,3,5-pentanetriol, and pentaerythritol; monocarboxylic acid units such as benzoic acid, propionic acid, and butyric acid; polycarboxylic acid units such as trimellitic acid and pyromellitic acid; and oxyacid units such as glycolic acid, lactic acid, hydroxybutyric acid, 2-hydroxyisobutyric acid, and hydroxybenzoic acid.

It may also contain a polymerization catalyst and various additives. Examples of additives include antioxidants, light stabilizers, UV absorbers, plasticizers, extenders, matting agents, drying regulators, antistatic agents, anti-settling agents, surfactants, flow improvers, drying oils, waxes, fillers, colorants, reinforcing agents, surface smoothing agents, leveling agents, curing reaction accelerators, and chain extenders. Resins and oligomers such as polyolefins, polyesters, polyamides, polycarbonates, acrylonitrile resins, vinyl chloride resins, vinyl acetate resins, polyacrylic acid, polymethacrylic acid, polystyrene, ABS resins, polyimide resins, and AS resins can also be added.

(Physical properties of polyester)
In the first embodiment, from the viewpoint of heat resistance, the glass transition temperature of the polyester is preferably 123°C or higher, and more preferably 125°C or higher. When the glass transition temperature is within the above range, the polyester can be suitably used in baby bottles, which require high heat resistance. The glass transition temperature can be measured based on the method described in the examples below. The glass transition temperature can be adjusted to the above-mentioned preferred range, for example, by appropriately selecting the dicarboxylic acid constituent units and diol constituent units of the polyester based on the above-mentioned preferred embodiments.

In the first embodiment, the calorific value of the crystallization peak during cooling of the polyester is preferably 5 J/g or less, and more preferably 3 J/g or less. When the crystallization peak during cooling is within the above range, the crystallinity of the polyester tends to be lower. Therefore, the polyester can have high transparency, and baby bottles using the polyester can also have high transparency. The calorific value of the crystallization exothermic peak during cooling can be measured using a differential scanning calorimeter by heating the material in a nitrogen gas (30 ml/min) stream at a rate of 20°C/min, holding it at 280°C for 1 minute, and then cooling it at a rate of 10°C/min, and then measuring the area of the exothermic peak. The calorific value of the crystallization peak during cooling can be adjusted to fall within the above-mentioned preferred range, for example, by appropriately selecting the dicarboxylic acid constituent units and diol constituent units of the polyester based on the above-mentioned preferred embodiment.

In the first embodiment, it is preferable that the number of breakages of test pieces obtained from the polyester in an Izod test under the following conditions is zero.
The Izod test is carried out in accordance with JIS K7110 using 10 test pieces, each having a length of 63.5 mm, a width of 12.7 mm and a thickness of 3.2 mm, and no notch, obtained by injection molding polyester, using a hammer with a capacity of 4 J.
When the number of broken pieces is zero, the polyester is suitable for use in baby bottles, which require high impact resistance. The number of broken pieces can be adjusted to fall within the preferred range described above, for example, by appropriately selecting the dicarboxylic acid constituent units and diol constituent units of the polyester based on the preferred embodiment described above.

(Manufacturing method of baby bottles)
In the first embodiment, the method for producing the polyester is not particularly limited, and a conventionally known method can be used. Examples include melt polymerization methods such as transesterification and direct esterification, and solution polymerization. Conventionally known transesterification catalysts, esterification catalysts, various stabilizers such as etherification inhibitors, heat stabilizers, and light stabilizers, and polymerization regulators can also be used.
In the first embodiment, the method for producing a baby bottle using polyester is not particularly limited, and any conventionally known method can be used, such as extrusion blow molding, extrusion stretch blow molding, thermoforming, injection blow molding, and injection stretch blow molding.

Second Embodiment
Next, the polyester according to the second embodiment will be described.
The polyester of the second embodiment is a polyester containing dicarboxylic acid constituent units and diol constituent units, in which the dicarboxylic acid constituent units are constituent units derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof, and the diol constituent units contain 27.5 mol % or more of constituent units derived from 1,4-cyclohexanedimethanol and any constituent units derived from isosorbide, relative to a total of 100 mol % of the diol constituent units.
In the second embodiment, a polyester having high heat resistance and impact resistance can be provided.

The polyester of the second embodiment can be the same as the polyester used in the baby bottle of the first embodiment, and the preferred aspects of the polyester in the first embodiment described above can also be applied to the polyester of the second embodiment.

The polyester of the second embodiment can be used for baby bottles, or for applications requiring heat resistance and impact resistance equivalent to those required for baby bottles, such as products used inside automobiles, packaging materials for import and export, food packaging materials for retort processing or microwave heating, and containers such as tableware that undergo heat sterilization.

The above describes an embodiment of the present invention, but the baby bottle and polyester of the present invention are not limited to the above examples and can be modified as appropriate.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples in any way.

[Evaluation method]
The polyesters in the examples were evaluated as follows.
(1) Composition and Content of Dicarboxylic Acid Structural Units and Diol Structural Units in Polyester The composition and content of dicarboxylic acid structural units and diol structural units contained in the polyester were analyzed by ¹ H-NMR measurement. The measurement was performed using an Ascend™ 500 manufactured by Bruker BioSpin K.K. Deuterated chloroform was used as the solvent.

(2) Heat Resistance Heat resistance was evaluated by measuring the glass transition temperature (Tgm) of the polyester. The glass transition temperature was measured using a differential scanning calorimeter (model: DSC/TA-50WS) manufactured by Shimadzu Corporation, by placing approximately 10 mg of a sample in an unsealed aluminum container and heating it in a nitrogen gas (30 ml/min) stream at a heating rate of 20°C/min. The glass transition temperature was determined as the temperature at which the temperature changed by half the difference in the baseline before and after the transition in the DSC curve.
The heat resistance was evaluated in three stages according to the following criteria: × (bad), ◯ (good), and ⊚ (excellent).
×: Glass transition temperature is less than 123°C. ○: Glass transition temperature is 123°C or more and less than 125°C. ⊚: Glass transition temperature is 125°C or more.

(3) Impact Resistance Impact resistance was evaluated by an Izod test in accordance with JIS K7110. Ten unnotched test pieces, each measuring 63.5 mm in length, 12.7 mm in width, and 3.2 mm in thickness, obtained by polyester injection molding were subjected to a test using a 4 J hammer at 23°C and 50% relative humidity, and the number of pieces that did not break was counted. The tester used was an Izod impact tester manufactured by Ueshima Seisakusho Co., Ltd. Table 1 shows the number of pieces that did not break out of the ten pieces.
The impact resistance was evaluated in two stages, x (poor) and ◯ (excellent), according to the following criteria.
×: When broken ○: When none of the pieces broke

(4) Overall Evaluation When there was a rating of x (poor) in the evaluations of (2) heat resistance and (3) impact resistance, the overall evaluation was rated as x (poor), and the rest was rated as o (excellent).

[Synthesis of Polyester]
The polyesters of the examples and comparative examples were synthesized as follows.
Example 1
A 30 L polyester production apparatus equipped with a packed column rectification column, a partial condenser, a total condenser, a cold trap, a stirrer, a heating device, and a nitrogen inlet tube was charged with 36.90 mol of dimethyl 2,6-naphthalenedicarboxylate, 3.69 mol of isosorbide, 11.07 mol of 1,4-cyclohexanedimethanol, and 22.14 mol of ethylene glycol as raw material monomers, and 0.005 mol% of tetra-n-butoxytitanium and 0.001 mol% of potassium acetate were added to dimethyl 2,6-naphthalenedicarboxylate (total dicarboxylic acid components). The mixture was heated to 225°C under a nitrogen atmosphere to carry out a transesterification reaction. After the reaction conversion of the dicarboxylic acid components was increased to 90% or more, 0.025 mol% of germanium dioxide and 0.05 mol% of triethyl phosphate were added to the dicarboxylic acid components, and the temperature and pressure were gradually increased, and polycondensation was finally carried out at 280°C and 0.1 kPa or less. When the melt viscosity reached a suitable level, the reaction was terminated to obtain a polyester.
When the composition and content of the obtained polyester were analyzed by the above-mentioned method, it was found to be 100 mol % of 2,6-naphthalenedicarboxylic acid constituent units, 10 mol % of isosorbide constituent units, 30 mol % of 1,4-cyclohexanedimethanol constituent units, and 60 mol % of ethylene glycol constituent units.

(Examples 2 to 7, Comparative Examples 1 to 5)
In Examples 2 to 7 and Comparative Examples 1 to 5, polyesters were produced in the same manner as in Example 1, except that raw material monomers were adjusted and charged to obtain the monomer ratios shown in Table 1. When the compositions and contents of the obtained polyesters were analyzed by the methods described above, the structural units and content ratios were found to be as shown in Table 1.

The meanings of the abbreviations in Table 1 are as follows:
ISB: Isosorbide CHDM: 1,4-cyclohexanedimethanol EG: Ethylene glycol DMT: Dimethyl terephthalate NDCM: Dimethyl 2,6-naphthalenedicarboxylate

The results in Table 1 show that the polyesters of each example have high heat resistance and impact resistance because the dicarboxylic acid structural units are 2,6-naphthalenedicarboxylic acid structural units and the diol structural units contain 27.5 mol% or more of 1,4-cyclohexanedimethanol structural units and optional isosorbide structural units. On the other hand, the contents of dicarboxylic acid structural units and diol structural units in each comparative example are outside the ranges of this embodiment, and therefore are inferior in either heat resistance or impact resistance.

The present invention makes it possible to provide polyester and baby bottles that have high heat resistance and impact resistance.

Claims (5)

A baby bottle formed using a polyester containing dicarboxylic acid structural units and diol structural units,
the dicarboxylic acid structural unit is a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof,
A baby bottle, wherein the diol structural units contain 27.5 mol % or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide, based on a total of 100 mol % of the diol structural units. The baby bottle of claim 1, wherein the diol structural units contain 5 mol % or more of structural units derived from isosorbide, based on a total of 100 mol % of the diol structural units. The baby bottle according to claim 1 or 2, wherein the diol structural units further contain structural units derived from ethylene glycol. The baby bottle according to claim 1 or 2, wherein the content of structural units derived from 2,6-naphthalenedicarboxylic acid and/or its ester derivatives is 100 mol % out of a total of 100 mol % of the dicarboxylic acid structural units. A polyester comprising dicarboxylic acid structural units and diol structural units,
the dicarboxylic acid structural unit is a structural unit derived from 2,6-naphthalenedicarboxylic acid and/or an ester derivative thereof,
The polyester, wherein the diol structural units contain 27.5 mol % or more of structural units derived from 1,4-cyclohexanedimethanol and any structural units derived from isosorbide, based on a total of 100 mol % of the diol structural units.