JP3107728B2 - Polyester resin composition for food packaging film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in self-adhesiveness in a wide temperature range from low to high temperatures required for food packaging films, and is excellent in heat resistance, cutting properties and transparency, and is suitable for incineration. The present invention relates to a polyester resin composition for a food packaging film having properties such as not generating toxic gas and a food packaging film obtained by molding the same.

[0002]

2. Description of the Related Art Conventionally, when food is stored in a container and stored in a refrigerator or the like,
As a food packaging film, a film mainly composed of polyvinylidene chloride resin, polyvinyl chloride or the like or a low-density polyethylene film is widely used. They are,
This is because the container is sealed using the self-adhesiveness, transparency, flexibility, and the like of the film, and it is possible to mainly prevent drying of the food during storage. The properties required for food packaging films include, in addition to the self-adhesiveness described above, cutting properties with a saw blade when cutting to the required dimensions for packaging food, etc., strength in the packaged state, and transparency. Basically, recently, with the spread of microwave ovens, a demand for a food packaging film having excellent heat resistance adapted to microwave ovens has been increasing. However, currently used polyvinylidene chloride film,
As can be easily understood from the chemical structure, polyvinyl chloride and other films have chlorine atoms in the polymer skeleton, and therefore contain hydrogen chloride gas generated during incineration of used waste. It is pointed out about toxicity, and it is not preferable to use the film as a food packaging film having a short use cycle from the viewpoint of environmental protection.

[0003] On the other hand, low-density polyethylene film is apt to be torn because it is too weak in packaging.
When used in a microwave oven, there is a disadvantage that the film is broken by heat. In addition, a film obtained by blending a copolymer of ethylene and an α-olefin or a polypropylene with the copolymer, which is generally called a polyolefin film, has insufficient heat resistance in a microwave oven,
There is a drawback that the odor barrier property of the contents is poor, which is not preferable. In recent years, a polyester film has been developed as a similar food packaging film, and generally, a polyethylene terephthalate resin (hereinafter abbreviated as a PET resin) representing a polyester resin, a polybutylene terephthalate resin (hereinafter abbreviated as a PBT resin). Abbreviated)
In the case of a PET resin film, by stretching it, and in the case of a PBT resin film, regardless of whether or not it is stretched, it is excellent in heat resistance, oil resistance, chemical resistance, and barrier properties against odor of the contents. Become. However, when the polyester resin is used as a film as it is, there is a drawback that self-adhesiveness, which is the most important property as a food packaging film, is inferior.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent generation of toxic gas at the time of incineration disposal, that is, to have excellent environmental suitability. It is an object of the present invention to provide a food packaging film which has a self-adhesive property required for a food packaging film, has sufficient heat resistance to microwave heating, and is excellent in cutting properties and odor barrier properties. . The present inventors have solved the above problems, and as a result of intensive studies to provide an ideal food packaging film, a composition in which a specific plasticizer and a tackifier are blended in a specific range amount with respect to a polyester resin. It has been found that a film made of a product satisfies all the above-mentioned required properties and is extremely excellent as a food packaging film, and has completed the present invention. That is, the present invention provides a polyester resin composition for a food packaging film comprising (A) a polyester resin, (B) 0.1 to 15% by weight of a plasticizer and (C) 0.1 to 50% by weight of a tackifier, and the composition. It is a food packaging film formed by molding a product.

[0005] As the polyester resin (A) used in the present invention, polyesters having a peak melting point of 170 ° C or higher are preferred. In a film using a polyester resin having a melting point peak value of less than 170 ° C., when a food packaged with the food packaging film is heated in a microwave oven, heat resistance may be insufficient, and in particular, the melting point peak value may be reduced. 18
It is preferable to use a polyester resin having a temperature of 0 ° C. or higher from the viewpoint of heat resistance. From these viewpoints, preferred as the polyester resin used in the present invention are those in which the acid component constituting the polyester is mainly terephthalic acid residues and the diol component is mainly 1,4-butanediol residues and / or ethylene glycol residues. Is a polyester resin. If the melting point peak value satisfies the above range, a copolymerized polyester can be used. As the acid component of the copolymerization component, succinic acid, glutaric acid, adipic acid, piperic acid, suberic acid, azelaic acid, sebacic acid, dodecane diacid, an aliphatic dicarboxylic acid represented by dimer acid, or isophthalic acid , Phthalic acid, 2,6
An aromatic dicarboxylic acid represented by naphthalenedicarboxylic acid and the like; and trimesic acid, trimellitic acid and the like can be used as a branching component. One or more of these copolymer components may be used. In addition, ethylene glycol, 1,3-
Propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,10-decanediol, cyclohexane Aliphatic / alicyclic diols exemplified by diols and the like, or polyglycols such as diethylene glycol, triethylene glycol, tetraethylene glycol and polyethylene glycol or aromatic diols exemplified by bisphenol A and ethoxylated bisphenol S, as a branching component Pentaerythritol or the like may be used. In addition, a component having a hydroxyl group and a carboxylic acid group in one molecule typified by 4-hydroxybenzoic acid may be used as the copolymerization component as long as the performance of the polyester resin is not largely changed. Further, the polyester resin used in the present invention is not limited by the method for producing the same, but also by a so-called direct polycondensation method in which an acid component and a diol component are esterified by a dehydration reaction and then condensed. The dicarboxylic acid moiety may be obtained by a transesterification method using a methyl ester, an ethyl ester, a butyl ester and a diol component as starting materials. On the other hand, the intrinsic viscosity of the polyester resin used in the present invention is preferably in the range of 0.4 to 1.5, particularly preferably in the range of 0.6 to 1.4 from the viewpoint of moldability, since the film is formed later.

Next, the plasticizer (B) used in the present invention will be described in detail. A plasticizer is generally defined as one that imparts plasticity to a substance, and generally well-known plasticizers include phthalic acid, adipic acid, trimellitic acid, glycerin, and citric acid. Among these, a plasticizer having good compatibility with the polyester resin and preferable in the present invention is a polyester plasticizer, a citrate ester plasticizer, a glycerin plasticizer, a phthalate ester plasticizer, a phosphate ester plasticizer, Examples include phthalic acid plasticizers, glycol plasticizers, trimellitic acid plasticizers, adipic acid plasticizers, and epoxy plasticizers.
The polyester plasticizer used in the present invention has an acid component in which an aliphatic dibasic acid such as adipic acid and sebacic acid and / or an aromatic dibasic acid residue such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and diphenyldicarboxylic acid are contained. Wherein the diol component comprises residues such as propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, ethylene glycol, and diethylene glycol. In particular, those in which the acid component is an adipic acid or terephthalic acid residue are preferred. Considering the plasticizing effect and cost, adipic acid residues are preferable, and considering the compatibility with the polyester resin, a plasticizer containing terephthalic acid, which is a component of the polyester resin, is preferable, and adipic acid and terephthalic acid residues are preferable. Is preferred. Poor compatibility with the polyester resin results in poor transparency when formed into a film. Further, it is preferably liquid, and when the molecular weight is high, the plasticizing effect is reduced. On the contrary, when the molecular weight is low, heat resistance is poor. In the citric acid ester plasticizer used in the present invention, the hydroxyl group of citric acid is acetylated,
In addition, at least one or more carboxylic acid groups form an aliphatic ester. When the hydroxyl group of citric acid is in a free state, the affinity for the polyester resin is significantly deteriorated, and in preliminary drying before film forming,
Bleed-out of numerous additives from the composition pellets. Also, one of the carboxylic acid groups of citric acid
The individual is necessarily esterified with an aliphatic alcohol having 1 to 30 carbon atoms. Examples of such a citric acid derivative include acetyl tributyl citrate, acetyl triethyl citrate, acetyl tri (2-ethylhexyl) citrate, acetyl tridecyl citrate, and acetyl propionyl dibutyl ethyl citrate. In the glycerin-based plasticizer used in the present invention, one of three hydroxyl groups of glycerin is esterified by an aliphatic monocarboxylic acid having 4 to 30 carbon atoms, and at least one hydroxyl group is acetylated. Things. When two or more hydroxyl groups of glycerin are in a free state, the affinity for the polyester resin is remarkably deteriorated, and a large amount of additives bleed out from the composition pellets in preliminary drying before film formation. One of the hydroxyl groups of glycerin is always esterified with an aliphatic monocarboxylic acid having 4 to 30 carbon atoms. The portion forming the ester is particularly preferably an aliphatic monocarboxylic acid having 10 to 30 carbon atoms, for example, lauric ester, stearic ester, oleic ester, montanic ester and the like. Specific examples of the glycerin ester compound that can be used in the present invention include glycerin monoacetomonolaurate, glycerin monoacetomonostearate, glycerin monoacetomonostearate, glycerin monoacetomonomonate, and the like. Is mentioned. Examples of the phthalate plasticizer used in the present invention include dialkyl phthalates such as dibutyl phthalate, dioctyl phthalate, and diheptyl phthalate, and dibenzyl phthalate. Examples of the phosphate plasticizer used in the present invention include trioctyl phosphate, triphenyl phosphate, diphenyl-2-ethylhexyl phosphate, and the like. Examples of the tetrahydrophthalic acid-based plasticizer used in the present invention include dioctyl tetrahydrophthalate, diisodecyl tetrahydrophthalate, and the like. Examples of the glycol plasticizer used in the present invention include polyethylene glycol, polyethylene glycol benzoate and the like. Examples of the trimellitic acid-based plasticizer used in the present invention include tributyl trimellitate, trioctyl trimellitate, and trihexyl trimellitate. The adipic acid plasticizer used in the present invention includes dioctyl adipate, diisooctyl adipate, didecyl adipate, diisodecyl adipate and the like. The epoxy plasticizer used in the present invention generally refers to an alkyl epoxystearate and an epoxy triglyceride from soybean oil. In addition, the epoxy plasticizer may be mainly made of bisphenol A and epichlorohydrin. Very good flexibility can also be obtained by using a so-called epoxy resin. However, the epoxy resin must be liquid at room temperature. In the case of a solid, the flexibility is undesirably reduced. Preferable plasticizers used in the present invention are as described above, but more preferable in terms of gas generation during film formation are polyester plasticizers and epoxy plasticizers having excellent heat resistance. The plasticizer used in the present invention may be used alone or in combination of two or more. Particularly, the combined use of a polyester plasticizer and an epoxy plasticizer is preferable because the effect of imparting flexibility to the film is large, and the desired effect can be satisfied with a small amount. The amount of the plasticizer (B) to be added to the polyester resin (A) is 0.1 to 15 with respect to the polyester resin (A).
%, Preferably 2 to 12% by weight. If the amount of the plasticizer is less than 0.1% by weight, it is not preferable because the flexibility of the film comprising the composition is not sufficiently obtained. If the amount exceeds 15% by weight, the bleeding of the additive from the film of the composition becomes excessive. As a result, blocking of the film becomes intense, making it difficult to take up the film during film formation.

Next, the details of the tackifier (C) used in the present invention will be described. Tackifiers (tackifiers) are substances added to improve the adhesion between rubber films during mastication and mixing of rubber, and are mainly composed of rosin-based resins, terpene-based resins, Aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin,
Phenolic resins, chroman-indene resins, styrene resins, xylene resins, and the like. The tackifier used in the present invention may be a commercially available tackifier, but if the compatibility with the polyester resin is poor, the transparency becomes poor when formed into a film, so consider the compatibility with the polyester resin. From this point, rosin-based resins, phenol-based resins, and chroman-indene resins are preferred. Among them, a rosin-based resin having better compatibility is preferable. The tackifier used in the present invention may be a single type or a combination of two or more types. The compounding amount of the (C) tackifier in the (A) polyester resin is 0.1 to 50% by weight, preferably 1 to 30% by weight, based on the (A) polyester resin. If the blending amount of the tackifier is less than 0.1% by weight, it is not preferable because the tackiness of the film comprising the composition is not sufficiently obtained, and if it exceeds 50% by weight, the tackiness of the composition film is too large. It is not preferable because it is difficult to handle.

As described above, the present invention is characterized in that a specific amount of each of (B) a plasticizer and (C) a tackifier is used in combination. When used as a food packaging film,
Self-adhesiveness and flexibility are two particularly important properties,
In order to combine these two properties, (B) plasticizer and
(C) Combined use of tackifier is mandatory. If one of them is not blended, a film having both self-adhesiveness and flexibility cannot be obtained.

The composition of the present invention may further contain, if necessary, a conventionally known substance, in addition to the plasticizer and the tackifier.
That is, a lubricant, a slip agent, an antiblocking agent, a stabilizer, an antistatic agent, an antifogging agent, a pigment and the like may be appropriately blended within a range that does not impair the performance of the intended film. Further, a small amount of another thermoplastic resin may be supplementarily added according to the purpose within a range not impairing the effects of the present invention.

The method for preparing the composition of the present invention is not particularly limited, and it can be prepared by a well-known method. The composition ratio indicated in the present invention refers to the component composition in a state of a resin raw material immediately before being supplied to an extruder or in a state of being formed into a film. The conditions may be selected as appropriate for the conditions, and are not particularly limited, and they may be blended in a molten state after completion of polycondensation, in a pellet state, or in a stage before film formation. Further, the composition of the present invention may be melt-kneaded by an extruder before film forming, processed into pellets, and then supplied to a film forming machine. The film of the present invention is formed by melting and kneading the above components by a usual T-die method, air cooling or water cooling inflation method.

[0011]

According to the present invention, a polyester resin material is used to provide a food packaging film which satisfies all the properties required for a food packaging film, such as self-adhesiveness, transparency, and microwave heat resistance. is there. Polyvinylidene chloride film and the like have a problem of hydrogen chloride gas generation during incineration disposal, but the polyester resin composition of the present invention does not generate toxic gas during incineration, and is practically used as a new food packaging film because of its environmental suitability. It is extremely effective.

[0012]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 Preparation Example of Polyester Resin as Component (A) 1938.1 g of dimethyl terephthalate and 1348.8 g of 1,4-butanediol were reacted with 1.7 g of tetrabutyl titanate, a transesterification catalyst, equipped with a stirrer and a distillation tube. After the vessel was charged and purged with nitrogen sufficiently, the temperature was raised to 140 ° C. under normal pressure, and stirring was started. Further, the temperature was gradually raised to distill off methanol as a by-product. When the temperature reached 210 ° C, the pressure in the reactor was gradually reduced, and the temperature was kept constant at 250 ° C while maintaining the pressure at 0.2 ° C.
Stirring was continued at a pressure of 1 torr for 2.5 hours to prepare a polyester resin (A1) having an intrinsic viscosity of 1.03 and a melting point of 223 ° C. still,
Polyester resin A1 used in the following Examples and Comparative Examples
A to A6 were prepared in the same manner using the components shown in Table 1 as the acid component and the diol component at the compounding ratios shown in Table 1. The melting point of the polyester resin was measured with a DSC manufactured by Perkin-Elmer Co., at a heating rate of 10 ° C / min. [Materials of raw materials] 10% by weight of a polyester plasticizer (B1) as a plasticizer of the component (B) and 10% by weight of a rosin resin (C1) as a tackifier of the component (C) are mixed with the above polyester resin. Then, the mixture was charged into a Henschel mixer and pre-blended. Next, this blend was supplied to a 40 mmφ twin screw extruder, extruded into a strand, and pelletized by a strand cutter. The plasticizers (B2 to B7) and tackifiers (C2 to C4) used in the following Examples and Comparative Examples are shown in Tables 2 and 3. About this pellet,
After preliminary drying, the film was formed and various physical properties were evaluated. Table 4 shows the results. [Film forming] The pre-dried pellets were supplied to a hopper of a film forming machine (T die, 20 mmφ single screw extruder), extruded from a die into a film, and cooled by a cooling roll to form a film. The following evaluation was performed on this film. In the following Examples and Comparative Examples, a film was stretched by stretching the film vertically and horizontally = 2 × 2 times in some cases. 1. Tensile elastic modulus Dumbbell-type test piece with a distance of 40 mm between the marked lines
mm) was set in a tensile tester (Orientec RTM-100), and a tensile test was performed at a tensile speed of 100 mm / min to measure an initial elastic modulus. 2. Appearance of film The presence or absence of bleed was confirmed during film formation. The evaluation criteria are as follows. ○ Good Bleed is almost not seen △ Slightly bad Not clear in appearance but sticky to touch × Poor Bleed can be confirmed only by appearance 3.Self-adhesiveness of film A test film with a width of 10cm x 10cm was tested on a glass plate. After pressure bonding, the force required for peeling was measured by a tensile test and evaluated according to the following evaluation criteria. 30 30 g or more 20 20 g or more and less than 30 g 10 10 g or more and less than 20 g × less than 10 g 4. Transparency of film HAZE measurement was performed according to ASTM D 1003 and evaluated. Examples 2 to 25, Comparative Examples 1 to 7 In the same manner as in Example 1, various polyester resins, plasticizers and tackifiers were blended in the ratios shown in Tables 4 to 6,
The film was formed, and the physical properties were measured. The results are shown in Tables 4 to 6.

[0013]

[Table 1]

Note 1: Components are expressed in mol% Note 2: TPA terephthalic acid IPA isophthalic acid DDA dodecanedicarboxylic acid BD 1,4-butanediol EG ethylene glycol CHDM cyclohexanedimethanol

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 67/00-67/04

Claims (7)

(57) [Claims] 1. A polyester resin composition for a food packaging film comprising (A) a polyester resin and (B) 0.1 to 15% by weight of a plasticizer and (C) 0.1 to 50% by weight of a tackifier. 2. The plasticizer (B) is a polyester plasticizer, a citrate ester plasticizer, a glycerin plasticizer, a phthalate ester plasticizer, a phosphate ester plasticizer, a tetrahydrophthalic acid plasticizer, The polyester resin composition for a food packaging film according to claim 1, which is a glycol plasticizer, a trimellitic plasticizer, an adipic plasticizer, or an epoxy plasticizer. 3. The polyester resin composition for a food packaging film according to claim 1, wherein (B) the plasticizer is a polyester plasticizer and / or an epoxy plasticizer. (C) a tackifier comprising: a rosin-based resin;
Terpene resin, aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin, phenolic resin, chroman
The polyester resin composition for a food packaging film according to any one of claims 1 to 3, which is an indene resin, a styrene resin, or a xylene resin. (5) The plasticizer (B) is a polyester plasticizer and / or
2. The polyester resin composition for a food packaging film according to claim 1, wherein the polyester resin is an epoxy plasticizer, and (C) the tackifier is a rosin resin. 6. The compounding amount of the plasticizer (B) is 2 to 12% by weight, and (C)
The polyester resin composition for a food packaging film according to any one of claims 1 to 5, wherein the amount of the tackifier is 1 to 30% by weight. 7. A food packaging film obtained by molding the polyester resin composition according to any one of claims 1 to 6.