JPH10330501A - Heat-resistant thin-wall container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to provide good heat resistance, chemical resistance and strength and reduce the soaking of odor into contents, by substituting the terminals of a polyester resin made from an aromatic (or aliphatic) dicarboxylic acid and an aliphatic diol by a carboxylated or hydroxylated monofunctional compound so as to give a specified content of terminal hydroxyl groups. SOLUTION: The polyester resin used comprises, e.g. a polybutylene terephthalate resin made from terephthalic acid and 1,4-butane diol as the main constituent elements, optionally copolymerized with other constituent. It comprises one having a substantially linear structure. Examples of the monofunctional compound used for substituting the terminals of a polyester resin include benzoic acid and toluic acid. The content of terminal hydroxyl groups of the polyester resin after substitution should be at most 40 mcq/kg. The substitution of the, terminals by the monofunctional compound so as to provide the content of terminal hydroxyl groups as specified above can give a remarkable effect of reducing the odor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-resistant thin-walled container made of polyester resin. More specifically, the present invention relates to a heat-resistant thin-walled container which is excellent in heat resistance and moldability, and in which the contents of foods and the like are less likely to cause a resin odor to pass through.

[0002]

2. Description of the Related Art Conventionally, in plastic containers, resins used in accordance with their applications include polyolefin resins typified by polypropylene resins and polyethylene resins, polystyrene resins, and polychlorinated resins. There are a wide variety of products such as vinyl resin, polycarbonate resin, and polyethylene terephthalate resin. There are also various molding methods such as injection molding, vacuum molding, blow molding, compression molding, etc., which are used properly according to the use and purpose of the container. Of these, the injection molding method has a greater degree of freedom in the shape of the container than other molding methods and is widely used. Injection-molded containers are often required to be thin in terms of lightness and resin usage, and in this regard, amorphous polymers such as polycarbonate and polyarylate have high viscosity when melted. Often not suitable for. Also, a resin having a very low crystallization rate, such as polyethylene terephthalate, is not preferable because it adversely affects the molding cycle of injection molding. Further, when the use of the container is sensitive to odors such as foods and cosmetics, the polyolefin has a peculiar odor called olefin odor, which may not be suitable. In addition, in food applications, heat resistance in a microwave oven may be required, and those having a low melting point have a problem in that the applications are limited. In this respect, polybutylene terephthalate and polybutylene naphthalate are excellent in moldability, heat resistance and odor. However, in order to cope with thin-wall molding, when using resins having relatively low polymerization degree and excellent fluidity, if the foods as contents are put in a long-time or high-temperature environment, these resins may be used. In some cases, a peculiar smell may be transferred to foods and the like, causing a problem, and the use range is limited. Therefore, a container which is thin, has heat resistance, and has little resin smell has been desired.

[0003]

In view of the above situation, the present inventor has developed a thin-walled molding method such as injection molding while taking advantage of the excellent properties of polybutylene terephthalate and polybutylene naphthalate resin. As a result of intensive studies to obtain containers with less odor transfer to foods, cosmetics, and other fillers, polybutylene terephthalate, in which the terminal of the polymer is replaced with a specific compound and the hydroxyl terminal group is limited to a specific amount, It has been found that such an object can be achieved by using polybutylene naphthalate or the like,
This has led to the present invention. That is, the present invention is a heat-resistant thin-walled container made of a polyester resin, wherein the polyester resin has an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and an aliphatic diol as main components, and a part of the polymer terminal or A heat-resistant thin wall characterized by being a polyester resin having a substantially linear structure, the whole being substituted with a monofunctional compound having a carboxyl group or a hydroxyl group, and having a hydroxyl terminal group amount of 40 meq / kg or less. For containers.

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, the feature of the present invention is that a polyester resin mainly contains an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and an aliphatic diol, and a part or all of the polymer terminals have a carboxyl group or a hydroxyl group. Is substituted with a functional compound, and the amount of hydroxyl end groups is
The point is to use one having a substantially linear structure of 40 meq / kg or less. Here, the amount of hydroxyl terminal groups can be quantified by ¹ H-NMR, and if the amount of hydroxyl terminal groups exceeds 40 meq / kg, the odor peculiar to the resin becomes remarkable, which is not preferable. In the present invention, a polybutylene terephthalate-based resin having terephthalic acid and 1,4-butanediol as main constituents, and a naphthalene dicarboxylic acid and 1,4-butanediol have main constituents among the above polyester resins. With respect to the polybutylene naphthalate-based resin used as the element, the effect of reducing the odor by remarkably replacing the terminal with a specific monofunctional compound and limiting the amount of hydroxyl terminal groups is remarkable.

In the present invention, if the above-mentioned dicarboxylic acid and diol are the main constituents,
It may be a polyester resin obtained by copolymerizing other components. Specific examples of the copolymer component include isophthalic acid,
Phthalic acid, naphthalenedicarboxylic acid, biphenylenedicarboxylic acid, stilbenedicarboxylic acid, 2,2- (biphenylcarboxyphenyl) propane, succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid and the like, and ester-forming derivatives thereof, such as alkyl Esters and the like. Specific examples of the aliphatic diol include ethylene glycol, 1,3-propanediol,
1,6-hexanediol, diethylene glycol, triethylene glycol, cyclohexanedimethanol,
Neopentyl glycol, an ethylene oxide adduct of bisphenol A, an ethylene oxide adduct of bisphenol S, and the like can be given.

Next, the monofunctional compound having a carboxyl group or a hydroxyl group for substituting the terminal of the polyester resin is not particularly limited. However, in the case of a compound having a low molecular weight, the polymer terminal may be adjusted depending on conditions such as temperature and reduced pressure during the production of the polyester. The monofunctional compound is preferably an organic compound having 7 or more carbon atoms, because the compound is volatilized without being introduced into the solvent and is easily distilled out of the system. Examples of particularly preferred compounds include benzoic acid, toluic acid, tert-butylbenzoic acid, aromatic carboxylic acids such as naphthoic acid, and derivatives thereof such as alkyl esters, or high molecular weight alcohol compounds such as phenoxybenzyl alcohol. is there. Polyester resins not substituted with these substituents and having a hydroxyl terminal group amount of 40 meq / kg or less, have a high degree of polymerization and a small total terminal group amount, or have other terminal groups such as a carboxyl terminal group. The end amount of the type is large. A polyester resin having a small total terminal amount, that is, a high degree of polymerization, has poor fluidity and makes it impossible to injection mold a thin container. For this reason, polyester resin is 250 according to ASTM D-1238.
Melt index measured under conditions of ° C and a load of 2160 g
40 or more are preferred. But the melt index
If it exceeds 170, the strength of the container decreases, which is not preferable. Further, a container made of a polyester resin having many other terminals such as a carboxyl terminal group is not preferable because of poor hydrolysis resistance and heat stability. For these reasons, it is necessary that the terminal be substituted with a monofunctional group as a polyester having a hydroxyl terminal group of 40 meq / kg or less and excellent fluidity.

The heat-resistant thin-walled container obtained by the present invention may be used, if necessary, with a suitable heat stabilizer, an ultraviolet absorber, an antistatic agent, a flame retardant or a flame retardant auxiliary, a dye or a pigment, a coloring agent, a fluidity or a release property. Lubricants, lubricants, crystallization promoters, inorganic substances such as glass fibers and glass beads, other thermoplastic resins and the like for improving the moldability may be contained alone or in plurals as long as the purpose is not hindered.

[0008] The heat-resistant thin-walled container of the present invention can be easily produced by a conventionally known molding method, particularly by simple injection molding.

[0009]

The thin heat-resistant container obtained according to the present invention has excellent heat resistance, chemical resistance and strength inherent in polyester resins such as polybutylene terephthalate or polybutylene naphthalate, and is used for foods, cosmetics and the like. It has the feature that there is little odor transfer to the packing which is severe against odor.

[0010]

(Resin synthesis method)

Production Example 1 (A-1) Dimethyl terephthalate 2178 g, butanediol 1415
g, tetrabutyl titanate 1.25 g, and p-tert-
81.5 g of butyl benzoic acid was charged into a reaction vessel equipped with a stirrer and a rectification column. The transesterification esterification reaction was performed while the temperature was raised from 140 ° C to 200 ° C over 90 minutes. At this time, methanol and water reached 90% of the theoretical amount. Here, the distilling route was switched from the rectification tower to the direct cooling tower connected to the vacuum pump, and the pressure was gradually reduced while increasing the temperature from 200 ° C to 250 ° C, and reached 0.5 torr in about 40 minutes. A polycondensation reaction was performed at 250 ° C. and 0.5 torr for 2 hours, and the polymer was taken out and pelletized. The MI of this polymer was 290. This is 2
Solid phase polymerization was performed for 30 hours under a nitrogen stream at 00 ° C.
-1 was obtained. The MI of the obtained polymer was 105, and the amount of hydroxyl end groups was 14 meq / kg.

Production Example 2 (A-2) 2178 g of dimethyl terephthalate, 1415 butanediol
g, tetrabutyl titanate 1.25 g, and p-tert-
18.4 g of butyl benzoic acid was charged into a reaction vessel equipped with a stirrer and a rectification column. The transesterification esterification reaction was performed while the temperature was raised from 140 ° C to 200 ° C over 90 minutes. At this time, methanol and water reached 90% of the theoretical amount. Here, the distilling route was switched from the rectification tower to the direct cooling tower connected to the vacuum pump, and the pressure was gradually reduced while increasing the temperature from 200 ° C to 250 ° C, and reached 0.5 torr in about 40 minutes. A polycondensation reaction was performed at 250 ° C. and 0.5 torr for 2 hours, and the polymer was taken out and pelletized. The MI of this polymer was 140. This is 2
Solid phase polymerization was performed for 30 hours under a nitrogen stream at 00 ° C.
-2 was obtained. The MI of the obtained polymer was 43, and the amount of hydroxyl end groups was 15 meq / kg.

Production Example 3 (A-3) 2232 g of dimethylnaphthalate, 1153 g of butanediol,
1.25 g of tetrabutyl titanate and 65.6 g of p-tert-butylbenzoic acid were charged into a reaction vessel equipped with a stirrer and a rectification column. The transesterification esterification reaction was performed while raising the temperature from 140 ° C to 220 ° C over 90 minutes. At this time, methanol and water reached 90% of the theoretical amount. Here, the distilling route is switched from the rectification tower to the direct cooling tower connected to the vacuum pump,
Gradually reduce the pressure while raising the temperature from 220 ° C to 260 ° C to about 40
It reached 0.5 torr in a minute. A polycondensation reaction was performed at 260 ° C. and 0.5 torr for 2 hours, and the polymer was taken out and pelletized. The MI of this polymer was 120. 200 ℃
The solid-state polymerization was carried out for 30 hours under a nitrogen stream of Polymer A-3.
I got The MI of the obtained polymer was 68, and the amount of hydroxyl end groups was 15 meq / kg.

Production Examples 4 to 6 (A-4 to 6; comparative products) Dimethyl terephthalate or dimethyl naphthalate and butanediol are usually used in the same manner as in Production Examples 1 to 3 except that no monofunctional compound is used. Melt polymerization was carried out under the conditions for producing polyester to obtain a resin.

The various test methods and evaluation criteria are as follows. [Heat resistance] Heat for 1 hour with a hot air dryer set at 160 ° C, measure the dimensions, top diameter, bottom diameter, and depth of the container, calculate the retention by the following formula, and calculate the retention rate according to the following evaluation criteria. did. Retention rate (%) = Dimension after heating / Dimension before heating × 100 ○ Good: Retention rate of each part is 99% or more and less than 101% △ Slightly good: Retention rate of each part is 98% or more and less than 99%, or
101% or more and less than 102% x Bad: Retention rate of each part is less than 98% or 102% or more [Odor] Fill the obtained container with water, and then release after heating for 2 minutes in the following microwave oven. It was cooled and compared with a Pyrex glass container subjected to the same treatment. The evaluation was performed by 10 panelists, and judged according to the following criteria. Microwave Oven ER6205 manufactured by Toshiba Oscillation frequency 2450MHz Maximum output 500W ○ Good: little polymer odor △ Slightly poor: slightly polymer odor × Poor: polymer odor

[0015]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a view showing the shape of a thin-walled container prepared in an example, where (a) is a plan view and (b) is a schematic sectional view.

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Claims (6)

[Claims] 1. A heat-resistant thin-walled container made of a polyester resin, wherein the polyester resin has an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and an aliphatic diol as main components, and a part of a polymer terminal or A heat-resistant thin wall characterized by being a polyester resin having a substantially linear structure, the whole being substituted with a monofunctional compound having a carboxyl group or a hydroxyl group, and having a hydroxyl terminal group amount of 40 meq / kg or less. container. 2. The polyester resin is a polybutylene terephthalate resin mainly containing terephthalic acid and butanediol, or a polybutylene naphthalate resin mainly containing naphthalenedicarboxylic acid and butanediol. The heat-resistant thin-walled container according to claim 1. 3. The heat-resistant thin-walled container according to claim 1, wherein the aliphatic diol contains 1,4-butanediol as a main component. 4. The heat-resistant thin-walled container according to claim 1, wherein the monofunctional compound is an organic compound having a carboxyl group or a hydroxyl group and having 7 or more carbon atoms. 5. The heat-resistant thin-walled container according to claim 1, wherein the polyester resin has a melt index of from 40 to 170 as measured by ASTM D-1238 at 250 ° C. under a load of 2160 g. 6. The heat-resistant thin-walled container according to claim 1, wherein the heat-resistant thin-walled container is formed by injection molding.