JPH04145137A - Stretched film - Google Patents

Abstract

PURPOSE:To obtain the title film consisting of a polyester resin composition composed of a polyethylene terephthalate resin and copolymer polyester resin having a specific draw ratio in vertical and horizontal directions and a specific area draw ratio and having excellent gas barrier property and impact strength, etc. CONSTITUTION:The objective film consisting of a polyester resin composition composed of (A) 80-95wt.% polyethylene terephthalate resin containing >=80mol% ethylene terephthalate unit and (B) 5-20wt.% copolymer polyester consisting of (i) a dicarboxylic acid unit composed of 20-100wt.% isophthalic acid component unit and 0-80wt.% terephthalic acid component unit and (ii) dihydroxy compound unit composed of 5-90wt.% dihydroxyethoxyresolcinol component unit and 10-95wt.% ethylene glycol component unit and having >=2.8 draw ratio in vertical and horizontal directions and >=7.84 area draw ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a stretched film, and more particularly to a stretched film with excellent properties such as gas barrier properties, water vapor permeability, and impact strength.

TECHNICAL BACKGROUND OF THE INVENTION Packaging materials, particularly food packaging materials, require materials with good gas barrier properties because it is necessary to extend the shelf life of foods and maintain the freshness of foods for a long period of time. For example, when packaging foods containing oil components, it is necessary to prevent fats and oils from oxidizing due to oxygen permeation, so packaging materials with excellent barrier properties against oxygen are required. In addition, since containers for carbonated drinks and the like need to maintain coolness, container materials are required that have excellent barrier properties against carbon dioxide gas.

Various materials have been developed to meet these requirements, and examples of such materials include polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polyamide, and polyethylene terephthalate.

Films made of such polymers can be used as gas barriers.
In order to satisfy not only the properties but also other requirements (e.g. strength, moisture permeability, weather resistance), we are laminating films made of other types of polymers or coating the film surface with other types of materials. Multi-layering often provides additional practical value.

Among the above materials, PVC resins such as polyvinyl chloride and vinylidene chloride have excellent properties such as water resistance, non-toxicity, and flame retardancy, so they can be used alone or with other materials such as biaxially oriented. Laminated with polypropylene (OPP) film, it is widely used as agricultural sheets, food packaging films, etc.

However, since the film made with bare hands contains chlorine, it generates toxic hydrogen chloride gas when incinerated, polluting the atmosphere. It is desired to develop a film that does not generate

Examples of such resins include polyester resin compositions, and specifically, for example, PET (polyethylene terephthalate) resin is known.

PET resin generally has excellent mechanical strength and transparency, and also has good moldability such as melt moldability and stretchability, and is also lightweight. Therefore, various molded bodies made of PET resin are widely used, for example, as containers for carbonated drinks or sparkling drinks such as beer, or containers for seasonings, detergents, and cosmetics.

Furthermore, polyethylene terephthalate resin compositions in which various improvements have been made to polyethylene terephthalate resin have also been proposed.

JP-A No. 61-72051 discloses P, which has excellent transparency.
As an ET resin composition, a resin composition in which a copolymerized polyester resin is mixed with a PET resin has been proposed by the applicant of the present invention.

JP-A-58-167817 also discloses (A) a reactant selected from isophthalic acid, terephthalic acid and their Ct~4 alkyl esters, and mixtures thereof in all proportions; (B) 1. reactants consisting of 3-bis(2-hydroxyethoxy)benzene and ethylene glycol and optionally one or more other ester-forming dihydroxy organic hydrocarbon reactants; and optionally (C)bis(4- Copolyesters are disclosed that are comprised of reactants that are .beta.-hydroxyethoxyphenyl) sulfones and that these reactants are blended in specific proportions. It is also described that this copolyester is suitable for producing films and the like. However, regarding the film, this publication only describes the gas barrier properties of the (non-oriented) press-formed film.

In this way, in addition to the above proposals, conventional research on improving the transparency and gas barrier properties of PET resin compositions has focused on the composition of PET resin compositions, and has focused on improving the transparency and gas barrier properties of PET resin compositions. No attention was paid to the stretching ratio.

OBJECTS OF THE INVENTION The object of the present invention is to provide a stretched film with improved gas barrier properties possessed by a polyester resin. More specifically, an object of the present invention is to provide a stretched film with improved gas barrier properties without impairing the transparency and mechanical properties of polyethylene terephthalate.

Summary of the Invention The stretched film according to the present invention is made of a polyester resin composition containing 80 to 95% by weight of a polyethylene terephthalate resin and 5 to 20% by weight of a copolyester resin as described below. , 20~
100 mol% isophthalic acid component units and 0 to 80 mol? consisting of a cicarphonic acid structural unit consisting of a medium terephthalic acid component of h, a dihydroxy compound structural unit consisting of a dihydroxyethoxyresorcinol component unit of 5 to 9 () mol 96 and an ethylene glycol component unit of 10 to 95 mol %, vertically The stretching ratio in the direction is 2.8 times or more, preferably 3.0 times or more, particularly preferably 3.3 to 3.8 times, and the stretching ratio in the transverse direction is 2.8 times or more, preferably 3.0 times. Above, it is particularly preferably 3.2 to 3.5 times, and the area stretching ratio, which is the product of the longitudinal stretching ratio and the horizontal stretching ratio, is 7.84 times or more, preferably 9.0 times. As mentioned above, it is characterized in that it is particularly preferably stretched by 10.6 to 13.3 times.

The stretched film according to the present invention is made of the above-mentioned specific resin composition and is stretched in the above-mentioned amount, so it has particularly excellent gas barrier properties, water vapor permeability, and impact strength. .

In the present invention, the term film is used to include sheet.

DETAILED DESCRIPTION OF THE INVENTION The stretched film according to the present invention will be specifically described below.

The stretched film according to the present invention is made of a polyester resin composition containing polyethylene terephthalate and a copolymerized polyester resin.

Polyethylene terephthalate resin The polyethylene terephthalate resin used in the present invention is a polyester having ethylene terephthalate units as its main constituent unit.

The content of ethylene terephthalate structural units in the polyethylene terephthalate resin is usually 80 mol% or more, preferably 90 mol% or more. A polyethylene terephthalate resin containing such an ethylene terephthalate structural unit is composed of a diol component unit and a dicarboxylic acid component unit. The dicarboxylic acid component units constituting this polyethylene terephthalate resin may contain a small amount of other aromatic dicarboxylic acid component units in addition to the terephthalic acid component units. Examples of such aromatic dicarboxylic acid component units include isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid,
(2) Component units derived from 4-naphthalene dicarboxylic acid, succinic acid, adipic acid, oxalic acid, sebacic acid, etc. can be mentioned.

In the polyethylene terephthalate resin, the terephthalic acid component units constituting the resin are usually 80 to 100 mol%, preferably 90 to 100 mol%, and aromatic dicarboxylic acid component units other than the terephthalic acid component units are contained. is usually in an amount of 0 to 20 mol%, preferably 0 to 10 mol%, and the ethylene glycol component unit, which is a diol component unit, is usually 80 to 100 mol%, preferably 90 to 100 mol%. %, the diol component units other than the ethylene glycol component units are usually 0 to 20 moles96
, preferably in an amount of 0 to 10 mol%, and the polyfunctional compound component units are usually present in an amount of no more than 1 to 2 mol%, preferably 0 to 1 mol%. Other glycol components include I, 4-butacinol, nclohexane/methanol, neopentyl glycol, propylene glycol, and the like.

In addition, the intrinsic viscosity [η (measured in orthochlorophenol at 25°C) of the polyethylene terephthalate resin is usually 0.5 to 1.5 dl/g, preferably 0.6 to 1.2 dl/g. The melting point is usually in the range of 210 to 265°C, preferably 220 to 260°C, and the glass transition temperature is usually in the range of 50 to 100°C,
Preferably, the temperature is in the range of 60 to 90°C.

Copolymerized Polyester Resin The copolymerized polyester resin used in the present invention is composed of dicarboxylic acid structural units and dihydroxy compound structural units.

In a preferred embodiment of the present invention, in addition to the dihydroxy compound constituent unit, the hydroxy compound constituent unit includes a polyfunctional hydroxy compound constituent unit having at least three hydroxy groups as described below.

In the copolymerized polyester resin used in the present invention, among the dicarboxylic acid constituent units, 20 isophthalic acid constituent units are
It is desirable that the terephthalic acid component units are present in an amount of 0 to 100 mol%, preferably 50 to 98 mol%, and the terephthalic acid component units are present in an amount of 0 to 80 mol%, preferably 0.5 to 50 mol%.

When the amount of isophthalic acid component units in the dicarboxylic acid constituent units is within the above range, the resulting stretched film has particularly excellent gas barrier properties.

In addition, in the copolymerized polyester resin used in the present invention, among the dihydroxy compound constituent units, dihydroxyethoxyresorcinol component units are present in an amount of 5 to 90 mol%, preferably 10 to 85 mol%, and ethylene glycol component units are 10-95 mol%, preferably 15-90
Preferably, it is present in an amount of mol %.

If the amount of dihydroxyethoxyresorcinol component units in the dihydroxy compound constituent units is less than 5 mol%, there will be a tendency to be unable to suppress the generation of oligomers, while if it exceeds 90 mol%, the rate of polycondensation will decrease. Is it a trend?

The second copolymerized polyester resin preferably contains a polyfunctional hydroxy compound structural unit having at least three hydroxyl groups.

When the polyfunctional hydroxy compound structural unit is included in this way, the polyfunctional hydroxy compound structural unit #i is 0.05 to 1.0 with respect to 100 mole parts of the dicarboxylic acid component unit.
Desirably, it is present in an amount of molar parts, preferably 0.1 to 0.5 molar parts.

If the amount of the polyfunctional hydroxy compound structural unit is less than 0.05 mol part, there will be a tendency that the thickness unevenness of a molded article such as a stretched film made of the polyester resin composition will not be sufficiently improved; If it exceeds this amount, the resulting polyester resin composition tends to gel and become insolubilized. Therefore, when producing a biaxially stretched film using this resin composition, even if you try to mold an unstretched film from this polyester resin composition in advance, molding becomes difficult or the resulting stretched film shrinks. This is not preferable because the rate increases significantly.

Such polyfunctional hydroxy compound units are derived from compounds such as trimethylolethane, trimethylolpropane and trimethylolmethane.

Among these, trimethylolpropane is preferred.

The molecular weight of the copolymerized polyester resin used in the present invention is not particularly limited as long as it is within a range that allows the production of stretched films from the obtained polyester resin composition. Relative viscosity (IV) of resin is 0.6 dN
/g or more, preferably within the range of 0.8 to 0.90 di)/g.

In the polyester resin composition used in the present invention, the polyethylene terephthalate resin is present in an amount of 80 to 95% by weight, preferably 85 to 95% by weight, based on 100% of the total weight of the composition, and the copolymerized polyester resin 5
It is present in an amount of -20% by weight, preferably 5-15% by weight.

By adjusting the amount of polyethylene terephthalate resin and copolymerized polyester resin within the above range, a stretched film with improved gas barrier properties can be obtained without impairing the transparency and mechanical properties of polyethylene terephthalate. .

In order to produce the polyester resin composition used in the present invention, a method of mixing a polyethylene terephthalate resin and a copolymerized polyester resin using, for example, a Henschel mixer, a blender, a ribbon blender, a tumbler blender, etc. Melt and mix using an extruder, twin screw extruder, knee Y-, Banbury mixer, etc.
Alternatively, a method of pulverization can be adopted.

The polyester resin composition used in the present invention contains various compounds that are usually added to polyester, such as heat stabilizers, weather stabilizers, antistatic agents, lubricants, mold release agents, pigment dispersants, pigments, or dyes. Agents can be added within a range that does not impair the purpose of the present invention.

Stretched Film The stretched film according to the present invention is made of the polyester resin composition as described above, and the stretching ratio in the longitudinal direction is 2.8 times or more, preferably 3.0 times or more, and more preferably 3.3 to 3.
The stretching ratio in the transverse direction is 2.8 times or more, preferably 3.0 times or more, and more preferably 3.2 to 3.5 times.
It's double. Moreover, this stretched film has an areal stretching ratio of 7, which is the product of the stretching ratio in the longitudinal direction and the stretching ratio in the transverse direction.
．． It is stretched 84 times or more, preferably 9 times or more, and more preferably 10.6 to 13.3 times.

When an unstretched film made of a polyester resin composition is stretched at such a magnification, the resulting stretched film tends to have excellent gas barrier properties, water vapor permeability, impact strength, and the like. It should be noted that if the area stretching ratio is less than 7.84 times, there is a tendency that sufficient thickness precision cannot be obtained;
When it exceeds 3 times, the biaxially stretched film tends to be easily cut.

In such a stretched film according to the present invention, the wall thickness is the same as that of conventionally known stretched films, and is usually 5 μm to 20 μm.
0 μm, preferably about 10 μm to 120 μm.

Manufacture of Stretched Film To manufacture such a stretched film, the tenter method (
Various conventionally known methods can be used, such as longitudinal and transverse stretching, transverse and longitudinal stretching), simultaneous biaxial stretching, blow molding (tubular method), etc.

For example, in the tenter method, first, a polyester resin composition obtained by the method described above is melted at 280 to 290°C using an extruder, and then extruded through a T-die.
An unstretched sheet is obtained by cooling and solidifying on a casting drum.

Note that in order to obtain such an unstretched sheet, a casting method (solution casting method), a calender method, etc. may be employed.

The unstretched sheet obtained as described above is heated to about 80 to 110°C, preferably between a slow (front) drive roll and a fast (rear) drive roll, which are longitudinal stretching means. Stretching in the machine direction (machine direction, fine feed direction of the film) by 2.8 times or more, preferably 3.0 times or more, particularly preferably 3.3 to 3.8 times, while heating at a temperature of 80 to 100 ° C. , a uniaxially oriented film is obtained. Next, the uniaxially oriented film is introduced into a tenter, which is a means for stretching in the lateral direction, and while holding both ends of the film, it is heated at a temperature of about 80 to 110°C, preferably 80 to 100°C, while the film is stretched in the lateral direction. When stretched by 2.8 times or more, preferably 3.0 times or more, particularly preferably 3.2 to 3.5 times (in the plane direction perpendicular to the film conveyance direction), the surface orientation is highly stretched in both the longitudinal and lateral directions. A film (two-wheel stretched film) is obtained. In the present invention, the area stretching ratio of the two-wheel stretched film thus obtained is 7.84 times or more, preferably 9.
It is preferably 10.6 to 13.3 times or more.

In the present invention, the order of stretching in both the longitudinal and lateral directions is not limited to the above, and the stretching may be carried out in the lateral direction and then in the longitudinal direction, or in the longitudinal and lateral directions at the same time. Further, the longitudinal and lateral stretching operations may be performed in one stage or in multiple stages.

Furthermore, the stretched film obtained by biaxially stretching as described above is heated to 200 to 24°C (1°C, preferably 230 to 24°C).
Heat-setting (heat-setting) may be performed at a temperature of about 240° C., and heat-setting in this manner tends to improve the heat resistance, gas barrier properties, mechanical properties, etc. of the stretched film obtained.

Further, in the present invention, a stretched film can also be produced from an unstretched film as described above by blow molding.

In the blow molding method, the molten polyester resin composition is usually first extruded into a tube shape from a ring die attached to the tip of an extruder, and the resulting unstretched tube is rapidly cooled in a cooling tank, and then heated by infrared rays, etc. Heating using a heating means. Then, by introducing a gas such as air into the heated unstretched tube to apply internal pressure to the tube, or by reducing the pressure outside the unstretched tube, the unstretched tube is stretched in the transverse direction at the same magnification as described above. do. Moreover, when performing this stretching operation in the transverse direction, if tension is applied in the longitudinal direction and the film is stretched in the longitudinal direction so as to obtain the same stretching ratio as described above, a biaxially stretched film can be obtained. Note that the stretching operations in both the longitudinal and lateral directions are usually performed simultaneously in this manner, but the invention is not limited thereto.

After biaxial stretching as described above, the obtained tubular stretched film (stretched tube) is usually folded and wound up with nip rolls, or the tube is cut open and wound up. In addition, after biaxial stretching as described above, the obtained stretched tube is stretched by a method such as heating compressed gas in the tube to re-expand the stretched tube, and then heat-treated with infrared rays or the like. The molecular orientation of the stretched film may be stabilized by crystallization.

Further, the temperature when forming a stretched film from an unstretched film by blow molding is preferably 80 to 110°C, preferably 80 to 100°C. Stretching temperature is 80
If the temperature is lower than 110℃, the stretching processability tends to decrease.
If the value exceeds 100%, the tube tends to become unstable.

The 1v thickness of the stretched film thus obtained is usually 10 μm to 200 μm, although it depends on the intended use.
That's about it.

The stretched film obtained as described above can be used as it is for packaging foods, etc., or it can be laminated with films made of the same or different resins, metals, etc., and used as a multilayer film. Examples of the same or different resins (films) include aromatic polyamide,
Examples of the material include aliphatic polyamide, polyethylene, polypropylene, polystyrene, and polycarbonate, and examples of the metal include aluminum.

When producing such a laminated film, adhesives,
Lamination may be performed by a conventionally known method using an organic solvent or the like.

The thus obtained stretched film according to the present invention or a laminated film containing the film layer can be used for food packaging, industrial purposes, etc.

Effects of the Invention The stretched film according to the present invention is obtained by stretching an unstretched film made of a polyester resin composition containing a polyethylene terephthalate resin and a specific copolymerized polyester resin in a specific ratio at a specific (area) stretching ratio. Because of this structure, it has excellent gas resistance, water vapor permeability, and impact strength.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

[Examples] Example 1 The following resins were used in producing the polyester resin composition used in the present invention.

[Polyethylene terephthalate resin]: J 125 manufactured by Mitsui Pet Resin ■ (Relative viscosity measured at 25°C in 0-chlorophenol (
IV) is 0.79 dll/g. ) [Copolymerized polyester resin] - The median isophthalic acid component in the dicarboxylic acid constituent units is 90 mol 96, the terephthalic acid component unit is 10 mol %, the dihydroxyethoxyresorcinol component unit in the dihydroxy compound constituent units is 15 mol %, and ethylene It is a copolymerized polyester resin containing 85 mol % of glycol component units, and further contains 0.3 mol parts of trimethylolpropane structural units per 100 mol parts of dicarboxylic acid structural units. The relative viscosity (IV) measured in 0-chlorophenol at 25°C is 0.85 dfl/g.

After mixing the above copolymerized polyester resin IO weight % and polyethylene terephthalate resin 90 weight %, the obtained polyester resin composition (1) was molded using an extrusion molding machine manufactured by Mitsubishi Heavy Industries ■ to obtain an unstretched sheet. The molding temperature at this time was 290 to 300°C.

Next, the unstretched sheet obtained as described above was stretched at an area stretching ratio of 10 using a sequential biaxial stretching molding machine manufactured by Mitsubishi Heavy Industries, Ltd.
．． A biaxially stretched film was obtained by stretching 4 times [3.6 times in the vertical direction x 2.9 times in the horizontal direction].

The stretching temperature at this time was 90°C.

The thickness of the unstretched sheet was 840 μm, and the resulting gas barrier property was evaluated by the carbon dioxide permeability coefficient and oxygen gas permeability coefficient using a carbon dioxide permeation tester PERMATRARN-I manufactured by MODERN CONTROL (USA).
Using a V type, the temperature is 23℃ by the PERMATRAN method.
The carbon dioxide gas permeability coefficient of a sample consisting of a section of a (stretched) film with a thickness of 70 μm was measured under the condition of relative humidity 0%, and the carbon dioxide gas permeability coefficient was measured using a sample made by MODERN C0NTR0L (USA).
0XTI? Using AN 100 type, 0XTRAN method, temperature 23℃, relative humidity 0%, thickness 70μ
The oxygen gas and moisture permeability coefficients of the sample consisting of a section of the stretched film were measured by measuring the weight of water permeating through the stretched film in accordance with JI80280.

Using a film impact tester (manufactured by Toyo Seiki ■), the impact fracture energy of a test piece of 1 ('l fl m + m is 172 inches in diameter (
12.7 mm diameter) was used.

The results are shown in Table 1.

Example 2 In Example 1, the following resin was used as the copolyester resin, and the copolyester resin was 10% by weight.
An unstretched film was produced in the same manner as in Example 1, except that 90% by weight of the polyethylene terephthalate resin was used, and a biaxially stretched film was further produced using this unstretched film. The area stretching ratio of the film is 10.4 times [36 times in the vertical direction x 2.9 times in the clear direction,
The stretching temperature at this time was 90°C.

The thickness of the unstretched film was 850 ft m, and the thickness of the obtained stretched film was 70 μm.

[Copolymerized polyester resin] Isophthalic acid component in dicarboxylic acid constituent unit 141st or 9th position
0 mol 06 and the terephthalic acid component is about 10 mol %, and the dihydroxy compound composition is about the middle, and the dihydroxyethquin resorcinol component is about 7.5 mol? 6 and an ethylene glycol component (92.5 mol 96 at the 11-position, and further has a trimethylolpropane component 083 mol parts at the t↓j position relative to 1100 mol parts dicarboxylic acid component H). The relative viscosity (IV) measured in O-chlorophenol at 25°C is 0.
．． It is 85dg/g.

The obtained biaxially stretched film was evaluated in the same manner as in Example 1 for gas barrier properties, moisture permeability coefficient, and impact strength.

The results are shown in Table 1.

Comparative Example 1 In Example 1, the area stretching ratio was 9.9 times [vertical 3.4
A biaxially stretched film was produced in the same manner as in Example 1, except that the film was changed to [2.9 times x #fi], and its gas barrier properties, moisture permeability coefficient, and impact strength were determined and evaluated.

The results are shown in Table 1.

Comparative Example 2 In Example 1, the area stretching ratio was set to 8.7 times [vertical 3. (
A biaxially stretched film was produced in the same manner as in Example 1, except that the film was adjusted to [1 times x 2.9 times in width], and was evaluated for gas barrier properties, moisture permeability coefficient, and impact strength.

The results are shown in Table 1.

Comparative Example 3 In Comparative Example 1, only polyethylene phthalate resin was used without using copolymerized polyester resin, and the area stretching ratio was 9.9 times [3.4 times vertical x 2.9 times horizontal.
A biaxially stretched film was produced in the same manner as in Example 1, and the transparency, gas barrier properties, moisture permeability coefficient, and impact strength of the film were determined and evaluated.

The results are shown in Table 1.

Comparative Example 4 A biaxially stretched film was produced in the same manner as in Example 1, except that only polyethylene phthalate resin was used without using copolymerized polyester resin, and the gas resistance and moisture permeability coefficient were and impact strength were determined and evaluated.

The results are shown in Table 1.

Claims (1)

[Claims] 1) 80 to 95% by weight of polyethylene terephthalate resin
and 5 to 20% by weight of a copolymerized polyester resin, the copolyester resin comprising 20 to 100 mol% of isophthalic acid component units and 0 to 80 mol% of terephthalic acid component units. consisting of a dicarboxylic acid constituent unit consisting of a dicarboxylic acid constituent unit, and a dihydroxy compound constituent unit consisting of a dihydroxyethoxyresorcinol constituent unit of 5 to 90 mol% and an ethylene glycol constituent unit of 10 to 95 mol%, and the stretching ratio in the longitudinal direction is 2.8 times or more. , the stretching ratio in the horizontal direction is 2.8 times or more, and the area stretching ratio, which is the product of the stretching ratio in the longitudinal direction and the stretching ratio in the horizontal direction, is 7.84.
A stretched film characterized in that it has been stretched to more than double its original size. 2) A polyester resin composition comprising 0.05 to 1.0 mole parts of a polyfunctional hydroxy compound structural unit having at least three hydroxy groups per 100 mole parts of a dicarboxylic acid constituent monoposition. Stretched film according to item 1.