JPH06107924A - Polyester resin composition - Google Patents

Abstract

PURPOSE:To provide a polyester resin composition extremely excellent in heat sealability, flavoring property, film formability (extrusion processability) and mechanical strength. CONSTITUTION:The polyester resin composition comprises 100 pts.wt. of a branched polyester resin mixture and 5-50 pts.wt. of an ethylenic polymer, the branched polyester resin mixture consisting of (A) a polyester resin comprising an aromatic dicarboxylic acid component containing terephthalic acid as a main dicarboxylic acid and a glycol component containing ethylene glycol as a main glycol, containing a tri- or higher-functional polycarboxylic acid or polyol in an amount of 0.1-1.5mol/% based on the whole acid components or the whole glycol components, and having a reducing viscosity (etasp/c) of >=0.7 and a polystyrene-converted average mol.wt. (Mz) of 250X10<3> to 600X10<3> and (B) a non-branched polyester resin having a reducing viscosity (etasp/c) of >=0.7 in an (A)/(B) weight ratio of 95/5 to 40/60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin composition having excellent heat-sealing properties, flavor properties, film moldability (extrusion processability) and mechanical strength, and more specifically, food paper containers and plastics. The present invention relates to a polyester resin composition most suitable for a polyester resin sealing material used for containers and the like.

[0002]

2. Description of the Related Art In recent years, food paper containers and plastic containers have been frequently used in order to reduce the weight of food containers, reduce production and distribution costs, and to impart heat sealability to the innermost layer of paper containers, plastic containers, etc. Polyethylene has been used for. Polyethylene is widely used in this application because it has an excellent heat-sealing property and has a good film-forming property when laminated on paper or plastic, so that it can be easily processed and is excellent in production.
However, in recent years, as the tastes of consumers have been diversified and the contents of paper containers and plastic containers have spread to natural fruit juices and alcoholic beverages, heat seal materials superior to polyethylene have been demanded. In the background, while polyethylene has the characteristics described above, the flavor and aroma of the beverage are changed and the odor characteristic of polyethylene is generated, so that the original flavor of the beverage is lost. It has been pointed out that the so-called flavor is worse than that of containers such as glass bottles and PET bottles, and there is a strong demand for improvement.

On the other hand, a polyester resin has a better flavor property than polyethylene, and has already been disclosed in, for example, JP-A-60.
No. 206859 and Japanese Patent Laid-Open No. 63-81042 propose heat sealing materials for tableware containers. However, although these polyester resins have excellent heat sealability and flavor properties, when melt extruded onto paper or plastic film, a large necking phenomenon occurs at the bottom of the T-die, resulting in polyethylene-like properties. It is extremely difficult to form a film at high speed,
Extremely low productivity. Polyester resin generally has no mechanical properties, especially elongation, and is fragile to the stress applied to the packaging material after sealing the contents by heat sealing,
In reality, it has a drawback that the bag breaking strength is generally weak. Also, in the proposal disclosed in Japanese Patent Application No. 2-186723,
Although the heat-sealing property, flavor property, and extrusion processability are improved in a well-balanced manner, it contains 0.1 to 0.5 mol% of a trifunctional or higher polycarboxylic acid or polyol with respect to all acid components or all glycol components. Since the molecular weight is increased by solid-state polymerization, the heat sealing property is not sufficiently satisfactory.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a polyester resin composition having excellent heat-sealing property, flavor property, film moldability (extrusion processability) and mechanical strength.

[0005]

In view of the above problems, the present inventors have found a polyester resin composition having excellent heat-sealing properties, flavor properties, and mechanical properties, and having excellent film moldability (extrusion processability). As a result of intensive studies, the present invention has finally been completed. That is, the present invention comprises an aromatic dicarboxylic acid containing terephthalic acid as a main component, a glycol component containing ethylene glycol as a main component, and 0.1 or more of a polycarboxylic acid or a polyol having a functionality of 3 or more with respect to all acid components or all glycol components. ~ 1.
5 mol% is contained, reduced viscosity (ηsp / c) is 0.7 or more, and polystyrene-converted Z average molecular weight (Mz) is 250.
It comprises a polyester resin (A) having a branched chain of 10 ³ to 600 × 10 ³ , an aromatic dicarboxylic acid mainly composed of terephthalic acid, and a glycol component mainly composed of ethylene glycol, and has a reduced viscosity (ηsp / c). ) Is 0.
Polyester resin (B) having a branched chain of 7 or more
(A) / (B) = 95/5 to 40/60 (weight ratio) 100 parts by weight of a polyester resin mixture obtained by mixing the ethylene polymer further in an amount of 5 to 50 parts by weight. Is a polyester resin composition.

The branched polyester resin (A) used in the present invention comprises an aromatic dicarboxylic acid containing terephthalic acid as a main component as an acid component and a glycol component containing ethylene glycol as a main component, and the total acid component or all components. A polyester containing 0.1 to 1.5 mol% of a trifunctional or higher polycarboxylic acid or polyol with respect to a glycol component. In the polyester resin (A), the proportion of the aromatic dicarboxylic acid containing terephthalic acid as the main component as an acid component is 95 to 100 mol%, and 5
Aliphatic and / or alicyclic dicarboxylic acids can be used together in a proportion of less than mol%. The proportion of terephthalic acid in the aromatic dicarboxylic acid is 70-70% of the total acid components.
It is 100 mol%, and more preferably 75 to 95 mol%. Examples of the aromatic carboxylic acid used for the polyester resin (A) include, in addition to terephthalic acid, orthophthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, and the like. In particular, the combined use of terephthalic acid and isophthalic acid is desirable. Examples of the aliphatic or / alicyclic dicarboxylic acid that can be used in combination with the aromatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, azelaic acid,
Examples thereof include dodecanedioic acid and cyclohesane dicarboxylic acid. In the polyester resin (A) of the present invention, when the proportion of the aromatic dicarboxylic acid is less than 95 mol% with respect to all the acid components, the glass transition temperature of the resin is lowered and the flavor property is also lowered accordingly. In addition, the film formability also deteriorates. Further, if the proportion of terephthalic acid in the aromatic dicarboxylic acid is less than 70 mol%, the film moldability is deteriorated and the mechanical properties of the film are also deteriorated.

The glycol component of the polyester resin (A) is mainly composed of ethylene glycol, and the proportion of ethylene glycol in the glycol component is 90 to 100 mol%, more preferably 92 to 100 mol%. As the glycol component, other glycols such as diethylene glycol, 1,4-butanediol, propylene glycol and 1,4-cyclohexanedimethanol can be copolymerized in a proportion of less than 10 mol%. If the proportion of these components exceeds 10 mol%, the flavor property deteriorates, which is not preferable.

In the polyester used for the polyester resin (A), trifunctional or higher polycarboxylic acid or polyol is added to the total acid component or the total glycol component in an amount of 0.1.
It is necessary to contain 1 to 1.5 mol%, preferably 0.15 to 1.0 mol%. A trifunctional or higher polycarboxylic acid is an important point for improving the film moldability (extrusion processability) of the polyester resin sealing material. If the content is less than 0.1 mol%, the effect will not be obtained. Although the moldability is improved, the heat-sealing property is extremely lowered and a gel-like substance is generated. The above-mentioned trifunctional or more polycarboxylic acid used in the polyester resin (A) of the present invention is a known polyvalent carboxylic acid such as trimellitic acid or pyromellitic acid, and the polyol component is glycerin, trimethylolpropane, pentaerythritol, etc. Known polyhydric alcohols can be used.

The reduced viscosity (ηsp / c) of the polyester resin (A) is 0.70 or more, preferably 0.75 or more, and the polystyrene reduced Z-average molecular weight (M
It is essential that z) is 250 × 10 ³ or more and 600 × 10 ³ or less, and particularly 300 × 10 ³ or more and 550 ×
It is preferably 10 ³ or less. When the reduced viscosity of the polyester resin (A) is less than 0.7, the extrusion processability is lowered and the physical properties of the polymer are also lowered. The Z average molecular weight (Mz) is a very important factor in the present invention. If the Z-average molecular weight is less than 250 × 10 ³ , the extrusion processability of the film will be poor, and the necking phenomenon will strongly occur during film formation, making it difficult to obtain a normal film. Further, when the Z-average molecular weight exceeds 600 × 10 ³ , heat sealability and spreadability are deteriorated, which is not preferable. In the polyester resin (B) of the present invention, the proportion of the aromatic dicarboxylic acid containing terephthalic acid as the main component as an acid component is 95 to 100 mol%, and the proportion of the aliphatic or / and alicyclic dicarboxylic acid is less than 5 mol%. An acid can be used together. The proportion of terephthalic acid in the aromatic dicarboxylic acid is 50 to 90 mol%, more preferably 60 to 85 mol%, based on all the acid components. When the proportion of terephthalic acid is less than 50%, the strength and elongation decrease and the material becomes brittle.
On the other hand, when it is 90% or more, the heat sealability is remarkably deteriorated due to the crystallinity.

As the aromatic carboxylic acid used in the polyester resin (B) having no branched chain used in the present invention, other than terephthalic acid, for example, orthophthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid can be used. Acid etc. are mentioned. In particular, the combined use of terephthalic acid and isophthalic acid is desirable. Examples of the aliphatic or / alicyclic dicarboxylic acid that can be used in combination with the aromatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, cyclohesane dicarboxylic acid and the like. In the polyester resin (B) of the present invention, the proportion of the aromatic dicarboxylic acid in the total acid component is 95.
If it is less than mol%, the glass transition temperature of the resin is lowered, and accordingly the flavor property is also lowered. The glycol component of the polyester resin (B) of the present invention is mainly composed of ethylene glycol, and the proportion of ethylene glycol in the glycol component is 90 to 100 mol%, more preferably 92.
~ 100 mol%. The glycol component is 10
Other glycols such as diethylene glycol, 1,4-butanediol, propylene glycol, 1,4-cyclohexanedimethanol and the like can be copolymerized in a proportion of less than mol%. If the proportion of these components exceeds 10 mol%, the flavor property deteriorates. The reduced viscosity (ηsp / c) of the polyester resin (B) of the present invention is 0.
It should be 70 or more, preferably 0.75 or more. When the reduced viscosity of the polyester is less than 0.7, the extrusion processability is deteriorated and the physical properties of the polymer are also deteriorated.

The ethylene polymer blended in the composition of the present invention includes polyethylene, polypropylene, linear low density polyethylene, ethylene and α having 3 to 12 carbon atoms.
-A copolymer with an olefin, a copolymer of ethylene with a polar vinyl monomer and / or carbon monoxide, a copolymer obtained by grafting a polar vinyl monomer using these as base polymers, and two types of these copolymer component monomers. In combination with the above, a ternary or higher multi-component copolymer and the like can be mentioned. Examples of the polar vinyl monomer include vinyl acetate, carboxylic acid unsaturated ester such as vinyl propionate, methyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, diethyl maleate, acrylic acid. Glycidyl, unsaturated carboxylic acid ester such as glycidyl methacrylate, unsaturated carboxylic acid such as acrylic acid, methacrylic acid and itaconic acid, and unsaturated carboxylic acid salts such as lithium salt, sodium salt, magnesium salt and zinc salt thereof. And unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, and tetrahydrophthalic anhydride. In the case of a copolymerization pair with an unsaturated carboxylic acid salt, some or all of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer or ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer So-called ionomer resins neutralized with metal ions such as sodium and zinc can be used.

The polyester resin (A) and the polyester resin (B) obtained as described above are (A) / (B) =
The mixture is used in a ratio of 95/5 to 40/60 (weight ratio). The ratio of 90/10 to 50/50 is preferable. If the ratio of the two exceeds 95/5, the heat-sealing property becomes poor, and if it becomes less than 40/60, the extrusion processability deteriorates, and a necking phenomenon during film formation occurs, which is not preferable. In the present invention, the ethylene polymer is used in an amount of 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the mixture of the polyester resins (A) and (B). To be done. When the blending amount is less than 5 parts by weight, the effect of improving the mechanical properties of the polyester is not observed, and when the blending amount exceeds 50 parts by weight, the excellent flavor property of the polyester resin is deteriorated, which is not preferable.

In the present invention, the polyester resin (A), the polyester resin (B) and the ethylene polymer may be mixed in a solid state and used for film formation, or 3
After melting and kneading the seed resin, the resin may be taken out as pellets and used for film formation. For the purpose of improving the operability, siloids and other inorganic substances and organic substances may be added within a range that does not impair the characteristics of the polyester resin.

The polyester resin composition of the present invention obtained as described above is not only excellent in heat sealability, but also extremely excellent in flavor property as compared with polyethylene which is a representative of conventionally used seal materials. ing.
For example, when comparing the amount of limonene adsorbed as one evaluation of flavor property, it is 1 to several tens of minutes of polyethylene.
The amount of adsorbed perfume component of fruit juice beverage is small,
It shows that it is difficult to cause changes in aroma and taste.

Further, the polyester resin composition obtained by the present invention is excellent in film moldability and has less necking phenomenon. The conventional polyester resin has a large necking phenomenon, and the yield of the film is difficult and the yield is low, or a special molding machine is required, but the polyester resin of the present invention is comparable to polyethylene in terms of film moldability. It is excellent and features no special film forming machine. Taking advantage of these characteristics, the polyester resin composition of the present invention can be widely used as a sealant for paper containers for beverages such as natural fruit juice, milk and alcohol, plastic containers and the like.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measured values described in the examples are measured according to the following method. Z average molecular weight: An outflow curve was obtained by gel permeation chromatography and the average molecular weight in terms of polystyrene was evaluated. Here, the Z-average molecular weight (Mz) defined by the following equation was evaluated as the average molecular weight. Mz = ΣWi Mi ² / ΣWi Mi (Wi: weight of molecule of molecular weight Mi) Neck-in width: polyester resin (A), polyester resin (B) and ethylene-based polymer are mixed in a predetermined ratio, and a 40 mmφ extractor, The film was formed with a 200 mm width die and a die gap of 100 mm, and the difference between the die width and the obtained film width was defined as the neck-in width. Peel strength: Polyethylene terephthalate film with a thickness of 20 μm was used as a protective layer, and the polyester resin sealing materials were joined together and then heat-bonded at 150 ° C. for 2 seconds under the condition of ² Kgf / cm ² and Tensilon RT manufactured by Toyo Baldwin
Peel adhesion was measured with a M-100 tensile tester. Tensile strength and elongation: A polyester resin film having a thickness of 50 μm, a width of 5 mm, and a sample length of 30 mm was evaluated for an SS curve at a tensile speed of 300 mm / min by a Tensilon RTM-100 tensile tester manufactured by Toyo Baldwin, and The elongation property was evaluated. Adsorption of D-limonene: A film of a film-formed polyester resin composition having a thickness of 50 μm was placed in a sample bottle, D-limonene, which is one of the flavor components of fruit juice drinks, was added, and the mixture was allowed to stand at 20 ° C. for 2 weeks. The amount of D-limonene adsorbed was determined by determining the weight difference of the sealing material before and after the immersion, and the relative value was obtained when the amount of polyethylene adsorbed was 100.

Polyester resins (A-1) to (A-7)
Production example of dimethyl terephthalate 33.56 kg, dimethyl isophthalate 5.82 kg, ethylene glycol 27.28 kg, in a reactor equipped with a stirrer, thermometer, effluent cooler,
Charge 87.8 g of zinc acetate and 174.9 g of antimony trioxide,
The transesterification reaction was carried out for 3 hours while heating and stirring at 140 to 210 ° C. After the completion of the transesterification reaction, 192 g of trimetic anhydride was added and the esterification reaction was carried out for 1 hour while the temperature was raised from 200 ° C to 260 ° C. Next, the pressure in the system was gradually reduced, and after 40 minutes, 5 mmHg, then 26
A polycondensation reaction was carried out at 0 ° C. and 0.3 mmHg for 64 minutes to obtain a polyester resin having a reduced viscosity of 0.85. As a result of composition analysis by gas chromatography after ethanol decomposition, the composition of the polyester resin (A-1) was as shown in Table 1. Then, the polyester resins (A-2) to (A-7) were also treated in the same manner as above, and the polymerization time was changed to obtain polyester resins having the composition, reduced viscosity and Z-average molecular weight shown in Table 1.

Polyester resins (B-1) and (B-
2) Production example In a reaction vessel equipped with a stirrer, thermometer, and effluent cooler, 27.16 kg of dimethyl terephthalate, 11.64 kg of dimethyl isophthalate, and 27.28 kg of ethylene glycol.
Then, 87.8 g of zinc acetate and 17.49 g of antimony trioxide were charged, and the transesterification reaction was carried out for 3 hours while heating and stirring at 140 to 210 ° C. 200 after transesterification
The esterification reaction is carried out for 1 hour while the temperature is raised from ℃ to 260 ℃. Next, the pressure in the system was gradually reduced, and after 40 minutes, a polycondensation reaction was carried out at 5 mmHg for 5 minutes at 260 ° C. and 0.3 mmHg for 200 minutes to obtain a polyester resin having a reduced viscosity of 0.95. As a result of composition analysis by gas chromatography after ethanol decomposition, the composition of the polyester resin (B-1) was 70 mol% terephthalic acid, 30 mol% isophthalic acid, and 100 mol% ethylene glycol. Then, a polyester resin (B-2) was obtained by the same method.

Examples 1 to 4 Polyester resins (A-1) to (A-4) and polyester resins (B-1) and (B-2) were mixed in the proportions shown in Table 1, respectively. Then, as an ethylene resin, the density was 0.916 g / cm ³ , and the melt index was 2.3.
20% by weight each of low-density polyethylene resin of g / min was further mixed, and the mixture was mixed with a NSK 40 mmφ extruder for 2
The film was formed using a die with a width of 00 mm to obtain a film having a thickness of 50 μm. Table 1 shows the resin composition and the obtained properties.

Comparative Examples 1 to 4 Compositions were obtained in the same manner as in Example 1 except that the resins shown in Table 1 were used as the polyester resins, and the respective properties were evaluated. The results are also shown in Table 1.

[0021]

[Table 1]

[0022]

As is clear from Table 1, the composition of the present invention has a small neck-in width, a large peeling strength, a small amount of D-limonene adsorbed, and a considerable tensile elongation and a good balance. It can be seen that it shows excellent characteristics. Further, the polyester resin composition of the present invention is 1) extremely excellent in flavor property as compared with conventional polyethylene. 2) It has excellent film formability (extractability) and is extremely superior in productivity to conventional polyesters. 3) The adhesive strength of the obtained film is high. 4) The obtained film has sufficient mechanical strength, especially elongation, and is excellent in protecting contents. It has a well-balanced and excellent property, and is a great contribution to the industrial world.

Claims (1)

[Claims] 1. A polycarboxylic acid or polyol which comprises an aromatic dicarboxylic acid containing terephthalic acid as a main component and a glycol component containing ethylene glycol as a main component, and which has a trifunctional or higher functional polycarboxylic acid or polyol with respect to all acid components or all glycol components.
1 to 1.5 mol%, reduced viscosity (ηsp / c) is 0.7 or more, and polystyrene-converted Z average molecular weight (M
z) comprises a polyester resin (A) having a branched chain of 250 × 10 ³ to 600 × 10 ³ , an aromatic dicarboxylic acid mainly containing terephthalic acid, and a glycol component mainly containing ethylene glycol, and has a reduced viscosity. (Ηsp
/ C) is 0.7 or more, and the polyester resin (B) having no branched chain is (A) / (B) = 95/5 to 40/60
A polyester resin composition characterized in that 5 to 50 parts by weight of an ethylene polymer is further contained in 100 parts by weight of a polyester resin mixture obtained by mixing in a ratio of (weight ratio).