JPH09100399A - Polyester resin composition for sealant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester resin composition having superior properties in flavoring, heat sealing at a low temperature, impact resistance, slitting property, etc. SOLUTION: This is a polyester resin composition for sealant containing (A) a copolymerized polyester 80 mole % or more of whose dicarboxylic acid component is terephthalic acid, 50-85 mole % and 15-50 mole % of whose glycol component is ethylene glycol and neopentyl glycol, respectively, and (B) an ethylene copolymer at a blending ratio of 80-99.7 pts.wt. copolymerized polyester (A) to 0.3-20 pts.wt. ethylene copolymer (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester resin for a sealant, which is used as a sealant for a paper container for foods, a plastic container, a bag, a lid of a tray container and the like and which is excellent in heat sealing property, flavor property and impact resistance. It relates to a composition.

[0002]

2. Description of the Related Art Usually, as food containers, paper containers and plastic containers are often used in order to reduce the weight, reduce production and distribution costs. Conventionally, the innermost layer of paper containers, plastic containers, etc. has been made of polyethylene or polyethylene in order to impart heat sealability. Polyolefin resins such as polypropylene have been used. Since these polyolefin resins have excellent heat sealing properties, they are widely used in this application.

[0003]

However, when this polyolefin resin is used as a sealant, the so-called flavor properties, such as adsorbing flavors of food to directly contact food and transferring the resin odor peculiar to polyolefin to food, are not good. It has been pointed out that. On the other hand, polyester resins are expected to be used as innermost sealant materials for food containers because of their better flavor properties compared to these. In general, a sealant for a paper container is required to have a flavor property, a heat seal property, an impact resistance, etc., and a sealant for a soft wrapping material such as snacks and chemicals is required to have a flavor property, a heat seal property, a gas barrier property, etc. However, there is no known polyester resin that satisfies all of these performance requirements. On the other hand, some attempts have been made to give impact resistance by blending a polyester resin having a good flavor property with a polyolefin resin. For example, in JP-A-2-277635, terephthalic acid, isophthalic acid and ethylene glycol are used. It has been proposed to blend polyethylene with polyester, but it is hard to say that it has low-temperature heat sealability comparable to that of polyethylene. In addition, Japanese Unexamined Patent Publication
JP-A-263860 and JP-A-5-209116 propose blending a polyolefin resin such as an ionomer with a polyester resin using terephthalic acid, isophthalic acid, ethylene glycol, and cyclohexanedimethanol. Since a crystalline polyester is used, crystallization occurs when the contents are hot-filled, making it difficult to obtain stable heat-sealing properties. The heat-sealing properties deteriorate over time. Had a defect that the seal portion became brittle and the impact resistance was lowered. The present invention solves the above problems in the prior art and provides a polyester-based sealant excellent in flavor, low-temperature heat-sealing property, impact resistance, slit property and the like.

[0004]

According to the present invention, as a sealant for food containers such as paper containers, terephthalic acid accounts for 80 mol% or more of the dicarboxylic acid component, and the glycol component accounts for 50 to 85 mol% of ethylene glycol. A resin composition comprising a copolymerized polyester (A) containing 15 to 50 mol% of neopentyl glycol and an ethylene-based copolymer (B), wherein the copolymerized polyester is added to 100 parts by weight of the resin composition. By using a polyester resin composition in which (A) is 80 to 99.7 parts by weight and the ethylene-based copolymer is 0.3 to 20 parts by weight, excellent function, particularly excellent impact resistance is exhibited. I found what to do.

As the dicarboxylic acid component of the polyester resin used in the present invention, terephthalic acid is 80 mol%, preferably 85 to 100 mol%, and other dicarboxylic acid components are 20 to 0 mol%, preferably 15 to 0. Mol%
It is. Examples of the aromatic dicarboxylic acid used in this polyester resin include orthophthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, in addition to terephthalic acid. 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, cyclohexanedicarboxylic acid and the like. In the polyester resin of the present invention, when the proportion of the aromatic dicarboxylic acid is less than 85 mol% of all the acid components, the glass transition temperature of the resin is lowered, and accordingly the flavor property is lowered and the film moldability is also poor. Therefore, it is not preferable. Furthermore, if the proportion of terephthalic acid in the aromatic dicarboxylic acid is less than 80 mol%, the mechanical properties of the film,
In particular, the impact resistance decreases, which is not preferable.

As the glycol component of the copolyester resin (A) used in the present invention, ethylene glycol is 50 to 85 mol%, preferably 60 to 80 mol% and neopentyl glycol 15 to 50 mol%, preferably 2
It is 0 to 40 mol%. When the ethylene glycol content is 85 mol% or more or the neopentyl glycol content is 15 mol% or less, the crystallinity of the resin develops, and as described above, the embrittlement in the seal portion and the deterioration of the sealability with time are not preferable. On the other hand, when the ethylene glycol content is 50 mol% or less or the neopentyl glycol content is 50 mol% or more, the flavor property is deteriorated or the impact resistance is deteriorated due to embrittlement of the resin itself, which is not preferable. Other glycol components used in this polyester resin (A) can be copolymerized at a ratio of 20 mol% or less. For example, diethylene glycol, 1,4-butanediol, propylene glycol, 2-methyl-1,3-propanediol, hexanediol, and 1,4-cyclohexanedimethanol are included. If these components exceed 20 mol%, flavor and It is not preferable because the impact resistance is lowered.

Further, the copolyester resin (A) used in the present invention may be copolymerized with a polycarboxylic acid or a polyol having a functionality of 3 or more with respect to the total acid component or glycol component. Polycarboxylic acids such as meritic acid or polyols such as glycerin, trimethylolpropane and pentaerythritol can be used. It is essential that the copolymerized polyester resin (A) used in the present invention is copolymerized with neopentyl glycol as a glycol component. This is because polyethylene terephthalate as a resin for polyester sealant can be heat-sealed by lowering its crystallinity without lowering its glass transition temperature. Further, since this component does not reduce the orientation of the polyethylene terephthalate molecule, it is important in imparting film elongation, that is, impact resistance.

Examples of the ethylene copolymer (B) used in the present invention include, in addition to polyethylene and polypropylene, α-olefins using 1-butene, 1-pentene, 1-hexene, acrylic acid, methacrylic acid. ,
It is an olefin-unsaturated carboxylic acid copolymer using itaconic acid, maleic anhydride or the like, and a so-called ionomer obtained by neutralizing a part or all of this with a monovalent or divalent metal ion. Examples of the metal ion for neutralizing the unsaturated carboxylic acid include ions of lithium, sodium, magnesium, zinc and the like. Particularly, use of an ionomer neutralized with zinc ion is preferable because the heat-sealing property is dramatically improved.

The blending ratio of the copolymer polyester resin (A) and the ethylene copolymer (B) used in the present invention is 80 to 80 when the total amount of these is 100 parts by weight. 99.7 parts by weight, preferably 8
5 to 99.5 parts by weight, and the ethylene-based copolymer (B) is 0.
It is 3 to 20 parts by weight, preferably 0.5 to 15 parts by weight. When the amount of the ethylene-based copolymer (B) used is 0.3 parts by weight or less, impact resistance, flexibility, slitting property, etc. are insufficient, which is not preferable. On the other hand, if the amount is 15 parts by weight or more, the flavor property is deteriorated and the resin odor is transferred to food, which is not preferable.

The copolymerized polyester resin (A) and the ethylene copolymer (B) used in the present invention may be compounded and granulated in advance with a kneader or may be dry blended. It is also possible to prepare a masterbatch and dilute it to a required concentration for use during film formation. Additives such as an antioxidant, a slip agent, an anti-blocking agent, and a coloring agent can be appropriately added to the composition of the present invention.

The composition of the present invention is used in packaging materials that require heat sealing. At this time, it is possible to directly form a laminate by melt extrusion on a plastic film such as a polyethylene terephthalate film, a metal foil such as an aluminum foil, or a material such as paper, and the composition film of the present invention is formed into a film in advance. After that, it can be laminated using another appropriate known adhesive.

[0012]

EXAMPLES The following examples are given to explain the present invention in more detail, but the present invention is not limited to these examples. The measured values described in the examples are measured by the following method. Sealing strength: A polyethylene terephthalate film having a thickness of 25 μm was used as a protective layer, and the surfaces of the sealing materials of the polyester resin or the composition thereof were matched with each other, and then 1
Thermal bonding under the conditions of 20 ° C. for 2 seconds and 2.1 kgf / cm ² ,
A peel tester was used to measure the peel adhesion strength at a pulling speed of 300 mm / min. Seal strength after boiling water treatment: The sealing material of the composition was immersed in boiling water at 95 ° C. for 1 minute, dried and then heat-bonded in the same manner, and the strength was measured.

Adsorption of d-limonene: Film-formed thickness 50 μm
The sealing material of 1 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 left at 20 ° C. for 2 weeks. By determining the weight difference of the sealing material before and after immersion d
-The adsorbed amount of limonene was obtained, and the relative value was obtained when the adsorbed amount of low density polyethylene was 100. Dropping bag test: Using a polyethylene terephthalate film having a thickness of 25 μm as a protective layer, a film-formed sealing material having a thickness of 50 μm was heat-bonded to a size of 10 cm × 10 cm to form a bag, and 100 ml of water was put therein. It was used as a sample. This was dropped from a predetermined height, the height at which the bag was broken was measured, and an average value of 10 samples was obtained. Slitting property: Slitting was performed during film formation of the composition film of the present invention, and the superiority or inferiority of the slit was visually evaluated. (○: good, ×: bad)

Example 1 A polyester resin (terephthalic acid / terephthalic acid /
/ Ethylene glycol / neopentyl glycol = 10
0 // 70/30) 97% by weight and zinc ionomer (ethylene / methacrylic acid = 85/15, neutralization degree 55)
%) 3 wt% is 250 with a twin screw kneader in the same direction of 30 mmφ
Mixed granulation at ℃. 40% of this polyester resin composition
A film having a thickness of 50 μm was obtained by forming a film with a 200 mm width die using a mmφ single-screw extruder. The resin composition and the obtained properties are shown in Tables 1 and 2. As is clear from Table 2, the seal strength is large and d
-Limonene adsorption was small, and it showed excellent impact resistance in a drop bag test and good slitting property.

Examples 2 to 6, Comparative Examples 1 to 6 Polyester resins and ethylene-based copolymers are shown in Tables 2 and 3.
Was used as a raw material in the ratio of, and mixed and evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

The polyester resin composition of the present invention satisfies the flavor property and the heat seal property by selecting the ratio of ethylene glycol and neopentyl glycol as the polyester resin, and further the ethylene copolymer is added. As a result, the impact resistance and the slit property, which tend to be insufficient only with the polyester resin, can be improved, and it is suitable as a resin composition for a sealant.

Claims (1)

[Claims] 1. 80% by mole or more of the dicarboxylic acid component is terephthalic acid, 50% to 85% by mol of ethylene glycol and 1% of neopentyl glycol as the glycol component.
A resin composition containing 5 to 50 mol% of a copolyester (A) and an ethylene copolymer (B),
Polyester resin for sealant, wherein the copolymerized polyester (A) is 80 to 99.7 parts by weight and the ethylene copolymer (B) is 0.3 to 20 parts by weight with respect to 100 parts by weight of the resin composition. Composition.