JP3087770B2 - Wrap film for packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging wrap film using a flexible copolymerized polyester film, and more particularly to a packaging wrap film most suitable for use as a food wrap film.

[0002]

2. Description of the Related Art As a wrap film for packaging, particularly a wrap film mainly for food packaging, a stretched film of soft vinyl chloride or a stretched film of polyvinylidene chloride has been frequently used. The packaging wrap film is desired to have good flexibility that can conform to the shape of the object to be wrapped, as well as high hygiene, heat resistance, and low cost, particularly as a food wrap film.

[0003]

However, the conventional wrapping film for packaging made of a soft vinyl chloride film or polyvinylidene chloride has the following problems.

First, in the case of soft vinyl chloride, the plasticizer migrates to the surface with time (bleed out), and the bleed-out plasticizer may cause hygienic problems. Since the surface layer is formed, dust and the like may adhere to the surface layer, which may cause a problem of hygiene and a problem of deterioration of transparency.

[0005] Further, since there is a possibility that a monomer may be precipitated from the soft vinyl chloride, there is a possibility that a hygienic problem may occur from this aspect as well.

[0006] Further, since soft vinyl chloride has poor oil resistance, there is a possibility that a problem may occur when wrapping oily substances in foods.

[0007] Further, since heat resistance of soft vinyl chloride is not so high, when cooking with food wrapped,
Depending on the heating temperature and the heating time, there is a problem of softening and melting.

On the other hand, polyvinylidene chloride has no problem of plasticizer bleed-out and has higher oil resistance and heat resistance than soft vinyl chloride, but has a high cost and has a problem in suitability as a wrap film for food.

Further, since it contains a halogen element together with soft vinyl chloride and polyvinylidene chloride, it generates harmful gases when incinerated. For this reason, the treatment of used wrap film is limited, and as a result, the use of these films in large amounts as wrap film for packaging, particularly for food wrap film, is also limited due to environmental problems. Become.

The present invention focuses on the problems of the conventional wrapping film made of a soft vinyl chloride film and polyvinylidene chloride, and has the necessary flexibility and does not contain a plasticizer. It is an object of the present invention to provide a low-cost packaging wrap film that is extremely suitable for large-scale use and does not cause problems of hygiene and transparency deterioration due to bleed-out, and does not generate harmful gas even during incineration.

[0011]

According to the present invention, there is provided a wrapping film for packaging according to the present invention comprising a copolymerized polyester film having a ΔTcg of 60 ° C. or less, and having a tensile Young's modulus obtained by stretching at least in one axial direction. 0.1-50kg /
It consists of a mm ^2.

The copolymerized polyester constituting the flexible polyester film of the present invention has a cold crystallization temperature (Tcc).
And difference from glass transition temperature (Tg) (Tcc-Tg)
Is required to be 60 ° C. or lower, preferably 50 ° C. or lower. If ΔTcg is too large, the tensile Young's modulus may increase over time,
Problems such as deterioration in flexibility occur.

Specific examples of the composition of the copolymerized polyester include the following. That is, as a soft segment, polyoxyalkylene glycol such as polyethylene glycol and polytetramethylene glycol, or HOOC- such as polyε-caprolactone, azelaic acid, sebacic acid, dodecandionic acid, and dimer acid are used.
[CH ₂ ] _n- COOH is preferably an aliphatic polyester composed of an aliphatic dicarboxylic acid and an aliphatic and / or alicyclic diol. Particularly, the soft segment contains a long-chain aliphatic dicarboxylic acid. Is preferable in terms of improving flexibility and transparency.

In the present invention, the long-chain aliphatic dicarboxylic acid is a dicarboxylic acid having an alkylene group having 8 to 60 carbon atoms, such as sebacic acid, eicoic acid, dodecandioic acid, dimer acid, etc. The range of from 50 to 50 is preferable because the flexibility becomes good.

Particularly, in the present invention, among the long-chain aliphatic dicarboxylic acids, a long-chain branched aliphatic dicarboxylic acid having a branched structure is preferable, and among them, the use of dimer acid is preferred for flexibility and transparency. Is preferable for improving the Here, the dimer acid is a mixture of a linear branched structure and a cyclic branched structure obtained by dimerizing an unsaturated aliphatic carboxylic acid methyl ester such as methyl oleate, and usually has an unsaturated bond in the molecule. However, it is preferable that the bromine value is set to 0.05 to 10 g / 100 g, more preferably 0.1 to 5 g / 100 g, because of excellent flexibility and transparency.

The hard segment of the above-mentioned copolymerized polyester has a melting point of 20 when composed solely of a polymer.
0 ° C or higher, glass transition temperature of 90 ° C or lower, ΔTcg of 8
The temperature is preferably 0 ° C. or lower in order to improve oil resistance, durability, and the like. It is preferably composed of at least one selected from aromatic and / or alicyclic ester units such as a rate. In particular, those having a terephthalic acid residue are preferable because they have good oil resistance and durability.

Here, the intrinsic viscosity of the copolyester preferably used is 0.5 to 2.0 dl / g,
Preferably, it is 0.7 to 1.8 dl / g. By setting the intrinsic viscosity in such a range, both the film forming property and the mechanical properties of the polyester film are improved.

Further, the melting point (T
m) is practically preferably from 130 to 250 ° C., and more preferably from 140 to 230 ° C.
Further, the glass transition temperature (Tg) is preferably 10 ° C. or lower, more preferably 0 ° C. or lower.

In the present invention, the copolymerized polyester is HO- (CH ₂ ) _2n -OH (n: 1) as an alcohol component.
10 to 10), at least 40 to 99% by mole of aromatic dicarboxylic acid residues and 6 to 6% of long-chain aliphatic dicarboxylic acid residues based on the total acid components.
It is preferable to contain 0-1 mol%.

Here, the alcohol component HO (CH ₂ ) _2n
-OH (n: 1 to 10) means ethylene glycol,
1,4 butanediol, 1,6 hexanediol, 1,
It is an aliphatic diol component such as 8-octanediol. Preferably, n is in the range of 1 to 4 in order to improve the mechanical properties and oil resistance of the flexible film.

The copolymerized polyester in the present invention includes:
It is preferable to contain at least two of the above alcohol components. Here, in the present invention, it is defined that each alcohol component is present when the content is 5 mol% or more.

When the alcohol component is composed of a one-component system, there arise problems that the self-adhesiveness becomes too strong and the transparency is deteriorated. In particular, it is preferable that one of the diol components is 1,4-butanediol because the mechanical properties and transparency are improved.

Although it is permissible to contain a small amount of a branched glycol residue such as propylene glycol or neopentyl glycol, it is usually preferable to keep the amount to less than 10 mol%, preferably less than 5 mol%. Similarly, an alcohol component containing an ether group such as diethylene glycol is allowed to be contained as a by-product. Usually, it is in the range of about 0.01 to 4 mol%.

The copolymerized polyester of the present invention preferably contains 40 to 99 mol% of an aromatic dicarboxylic acid residue,
Long-chain aliphatic dicarboxylic acid residues are contained in an amount of 60 to 1 mol%. When the amount of the aromatic dicarboxylic acid residue is less than 40 mol%, the durability becomes poor. On the other hand, when the amount of the aromatic dicarboxylic acid exceeds 99 mol%, the flexibility is lost and the film becomes unsuitable as a wrap film for packaging.

Here, the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5 sodium sulfoisophthalic acid, diphenic acid, etc. Among them, terephthalic acid has both durability and flexibility. It is preferable because it becomes good. The long-chain aliphatic dicarboxylic acid is as described above.

The flexible film comprising the copolymerized polyester of the present invention has a tensile Young's modulus of 0.1 to 50 kg / mm ^2.
It is necessary to be in the range of, preferably, 1 to 30
kg / mm ² . If the tensile Young's modulus is too small or too large, problems arise in the winding property in forming a flexible film, the suitability in processing into a wrapping film for packaging, and the stretching.

The haze of the flexible polyester film of the present invention is preferably 5% or less. If the haze exceeds 5%, the transparency of the wrapping film for packaging, which is required depending on the application, deteriorates. In particular, food wrap films often require transparency after being left under high temperature and high humidity for a long period of time. Therefore, it is preferable to keep the haze low even in such an environment.

Further, in the packaging wrap film of the present invention, it is preferable to impart high durability, for example, high weather resistance, according to the application. By imparting the weather resistance, it is possible to prevent the flexibility, transparency, and elongation of the wrap film for packaging from being lowered when used outdoors. For that purpose, an ultraviolet absorber (for example, benzotriazole type: TINUVIN 23 manufactured by Ciba-Geigy Japan Ltd.)
4. Nippon Cyanamid Co., Ltd. CYASORB UV
5411, inorganic particles: zinc oxide, titanium oxide, iron oxide, etc.) is effective in a range that does not impair the transparency of the film. The addition may be kneading, laminating, or coating. As the ultraviolet absorber, the above-mentioned benzotriazole-based and inorganic particle-based are preferable,
A hydroquinone-based, salicylic acid-based, or benzophenone-based ultraviolet absorber may be used.

If necessary, an antioxidant, an antistatic agent and an inorganic filler may be added to the flexible polyester film constituting the packaging wrap film of the present invention. By adding an antioxidant, the chemical resistance of the packaging wrap film, especially oil resistance, can be improved. By adding an antistatic agent,
During processing of a wrapping film for packaging, the antistatic performance during use can be improved, and the addition of an inorganic filler can improve the blocking resistance and the absorption and / or reflection of infrared rays.

Examples of the antioxidant include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol and 4,4'-thiobis- (3-methyl-6-tert-butylphenol). 2,2-di (4-hydroxyphenyl)
Propane, 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, Pentaerythritol-tetra- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, 1,3,5-tris (4-t
-Butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate; thiodipropionate such as di-n-dodecyl -Thiodipropionate, di-n-octadecyl-thiodipropionate, aliphatic sulfides and disulfides such as di-n-dodecyl sulfide, di-n-
Octadecyl sulfide, di-n-octadecyl disulfide; aliphatic, aromatic or aliphatic-aromatic phosphites and thiophosphites such as tri-n-dodecyl-phosphite, tris (n-nonylphenyl) phosphite, tri-n-dodecyl -Trithiophosphite, phenyl-di-n-nacilphosphite, di-n-
Octadecyl-pentaerythritol diphosphite and the like can be mentioned.

Examples of the antistatic agent include quaternary ammonium salts, amines, imidazolines, amine oxide ethylene adducts, polyethylene glycols, and sorbitan esters.

Examples of the inorganic filler include silica, talc, calcium carbonate and the like, and these can be used alone or in combination of two or more. The compounding amount is 5.0 per 100 parts by weight of the polymer.
It is up to 3.0 parts by weight, preferably up to 3.0 parts by weight.

The flexible polyester film of the present invention comprises:
It is a film stretched in at least one axial direction. Since a thin film is obtained by stretching, a film having an optimum thickness as a food wrap film can be obtained. Stretching may be either uniaxial stretching or biaxial stretching. 1
In the case of axial stretching, it is preferable to perform transverse stretching (widthwise stretching) from the viewpoint of productivity.

When the wrapping film of the present invention is used especially as a food wrapping film, the wrapping film has good flexibility that can conform to the shape of the food to be wrapped, and the films adhere to each other in a slightly adhesive manner. It is often required to be able to seal the
Accordingly, it is preferable that the film itself has a certain level of tackiness. It is preferable that this tackiness can be maintained even after being left for a long time under high temperature and high humidity, for example.

Next, a method for producing the packaging wrap film of the present invention will be described, but it is needless to say that the present invention is not limited to this.

A. Production of Copolyester Aromatic and / or alicyclic dicarboxylic acid constituting a predetermined hard segment or a dimethyl ester composed of these and a soft segment and an alcohol component corresponding thereto are added, and the copolyester is prepared by a well-known polyester polymerization method. Get.

B. Production of flexible polyester film for packaging wrap film After drying the thus obtained copolymerized polyester, it is melt-extruded from an extruder, and discharged from a die in a sheet or cylindrical shape using a T-type die or a circular die, The sheet is rolled into a cooling roll or a cooling medium such as water and solidified (the sheet or cylinder thus obtained is hereinafter referred to as a cast film).
The temperature range is 80 ° C., and the cooling temperature is 5 to 90 ° C.
, Preferably in the range of 15 to 70 ° C.

Next, the cast film is stretched in at least one axial direction. In the case of uniaxial stretching, it is preferable to stretch in the width direction using an oven (tenter), and in the case of biaxial stretching, it is stretched in the longitudinal direction using stretching rolls and the like, and then in the width direction. Either sequential biaxial stretching for stretching or simultaneous biaxial stretching for stretching substantially simultaneously in both directions may be used. Subsequently, heat treatment is performed. The heat treatment temperature is in a temperature range from Tcc to the melting point (Tm) of the copolymerized polyester, and preferably in a temperature range from Tcc to Tm-10 ° C. Although the processing time is not particularly limited, it is usually 1
The time is preferably from seconds to 30 minutes, and a particularly preferable method is a heat roll controlled at a predetermined temperature, hot water, an oven or steam or heat treatment.

Next, after the heat treatment, the film is guided to a drying roll or a drying oven as needed, cooled to a room temperature by a cooling roll, and subjected to a surface treatment or the like, if necessary, and wound up.

(Method for Measuring Characteristics and Method for Evaluating Effects) Next, the method for evaluating the characteristics and the method for evaluating the effects of the wrapping film for packaging of the present invention and the flexible film constituting the film will be described.

(1) Mechanical properties Regarding tensile Young's modulus, ASTM-D-882-81
It is measured according to (Method A). However, the measurement was performed at 25 ° C.

(2) Bromine value According to ASTM-D-1159. The unit is g / 100g
Expressed by

(3) Intrinsic viscosity (IV) Measured at 25 ° C. using o-chlorophenol as a solvent. The unit is dl / g.

(4) Melting point (Tm), glass transition temperature (Tm)
g), cold crystallization temperature (Tcc), ΔTcg Determined using a differential scanning calorimeter DSC2 (manufactured by PerkinElmer). The mixture was melted and maintained at 280 ° C. for 5 minutes under a nitrogen stream, and then cooled using liquid nitrogen. When the sample thus obtained was heated at a rate of 10 ° C./min, the specific heat change based on the transition from the glassy state to the rubbery state was read, and this temperature was taken as the glass transition temperature (Tg). The exothermic peak temperature accompanying crystallization was defined as a cold crystallization temperature (Tcc), and the endothermic peak temperature based on crystal melting was defined as a melting point (Tm). ΔTcg is defined by the following equation. ΔTcg = Tcc−Tg

(5) Film haze (100 μm conversion haze, H ₁₀₀ ) Aging was performed at 40 ° C. and 90% RH for 2 weeks, and the film haze before and after aging was measured according to JIS-K-6714.
It is measured in accordance with H ₁₀₀ (%) = H × 100 / d Here, H is an actual measured value of haze (%), and d is a film thickness (μm) of the haze measuring portion.

(6) Film Adhesion The film was aged at 40 ° C. and 90% RH for 2 weeks, and the adhesiveness of the film before and after aging was evaluated. The adhesiveness of the films was evaluated by sticking the films to each other and peeling them by hand.

[0047]

Example 1 10 mol% of dimethyl dimerate (manufactured by Unichema, bromine number 1 g / 100 g) and 5 mol% of adipic acid as acid components
And 85 mol% of terephthalic acid, 55 mol% of ethylene glycol and 45 mol% of 1,4-butanediol as alcohol components, and an intrinsic viscosity (IV) of 0.8.
The copolymerized polyester of No. 5 was polymerized. The obtained polymer was vacuum-dried at 120 ° C. by a conventional method, melted at 220 ° C. with a 90 mmφ extruder, extruded into a sheet from a T-die,
In a state where water was condensed on a cooling roll at 20 ° C., electrostatic application casting was performed. The obtained film is 3.3 with a tenter.
It is stretched laterally twice and further heat-treated at 130 ° C for 10 seconds.
A transparent film having a thickness of 30 μm was obtained.

The properties shown in Table 1 were measured and evaluated for the flexible polyester film for producing the packaging wrap film and the produced packaging wrap film. As a result, the tensile Young's modulus, the film haze before and after aging, and the film adhesiveness before and after aging showed favorable values.

Example 2 20 mol% of dimethyl dimerate and 80 mol% of terephthalic acid were used as the acid component, 37 mol% of ethylene glycol and 63 mol% of 1,4-butanediol were used as the alcohol component. ) 0.80 copolymerized polyester was polymerized. A polyester film was obtained from the obtained polymer in the same manner as in Example 1, and a wrap film for packaging was produced.

As a result, as shown in Table 1, a packaging wrap film having substantially the same characteristics as in Example 1 was obtained.

Comparative Example 1 50 parts by weight of dioctyl phthalate (DOP: Kyowa Hakko Kogyo Co., Ltd.) and 100 parts by weight of calcium stearate powder as a stabilizer were added to 100 parts by weight of polyvinyl chloride having an average degree of polymerization of about 1300. Parts by weight, zinc stearate powder 0.2 parts by weight, and epoxidized soybean oil 10 parts by weight were added and kneaded with a roll having a surface temperature of 160 ° C., and then a 30 μm-thick press sheet was formed.

As shown in Table 1, the obtained sheet
Aging at 0 ° C. and 90% RH for 2 weeks resulted in deterioration of transparency (haze) probably caused by bleed out of the plasticizer, and also reduced film adhesion.

Comparative Example 2 10 mol% of dimethyl dimer and 90 mol% of terephthalic acid were used as an acid component, and 10 mol% of ethylene glycol and 90 mol% of 1,4-butanediol were used as an alcohol component. ) A copolyester of 0.75 was polymerized. The obtained polymer was vacuum-dried at 120 ° C. by a conventional method, and was dried with a 90 mmφ extruder.
C., melted and extruded from a T-die into a sheet, and cast on a cooling roll at 40.degree. C. to obtain a film having a thickness of 30 .mu.m.

The obtained film is as shown in Table 1.
Poor flexibility, high film haze before aging,
Film adhesiveness before and after aging was also poor.

[0055]

[Table 1]

[0056]

As described above in detail, when the packaging wrap film of the present invention is used, the packaging wrap film is composed of a flexible polyester film having excellent flexibility, tensile Young's modulus, transparency and adhesiveness. be able to. Further, the polyester film constituting the packaging wrap film of the present invention has no bleed-out problem because the polymer does not contain a plasticizer, unlike the conventional packaging wrap film made of soft vinyl chloride, and the bleed-out does not occur. There is no problem of hygiene and transparency deterioration. Also,
Environmental problems at the time of incineration etc. can be eliminated,
The usable range can be greatly expanded. further,
The cost can be reduced as compared with a conventional wrapping film made of polyvinylidene chloride.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI B29L 7:00 C08L 67:02 (58) Investigated field (Int.Cl. ⁷ , DB name) C08J 5/18 B29C 55/02 -55/16 B65D 65/02

Claims (3)

(57) [Claims] 1. Cold crystallization temperature (Tcc) and glass transition temperature
ΔTcg defined by the difference (Tcc−Tg) from the degree (Tg)
Consists of a copolymerized polyester film having a temperature of 60 ° C. or less,
A wrap film for packaging, characterized in that the film has a tensile Young's modulus of at least 0.1 to 50 kg / mm ² obtained by stretching in at least one axial direction. 2. The copolymerized polyester contains at least two diol component residues selected from HO— (CH ₂ ) _2n —OH (n: 1 to 10) as an alcohol component,
An aromatic dicarboxylic acid residue is added in an amount of 40 to 99 with respect to the total acid component.
Mol%, long chain aliphatic dicarboxylic acid residue of 60 to 1 mol%
The wrapping film for packaging according to claim 1, which contains the wrapping film. 3. The packaging wrap film according to claim 2, wherein the long-chain aliphatic dicarboxylic acid is dimer acid.