JPH0344098B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester film that maintains the rigidity unique to polyester films and has excellent adhesive properties. Traditionally, films made mainly of polyethylene terephthalate have been characterized by their rigidity, heat resistance,
It is used in a variety of applications due to its excellent properties such as water resistance, but although it has these properties, it has the disadvantage that it is difficult to bond and requires a special adhesive. Therefore, the inventors of the present invention have arrived at the present invention as a result of intensive studies aimed at providing a film with improved adhesiveness while maintaining high rigidity and high heat resistance. In order to achieve the above object, the present invention has the following composition: 0.2 to 7 mol% of a comonomer containing at least one metal sulfonate group, and a molecular weight of 100 to 7 mol%.
500 diethylene glycol comonomers from 2 to 15
It is characterized by a polyester film copolymerized with mol%. The comonomer containing a metal sulfonate group of the present invention (hereinafter abbreviated as comonomer A) has the general formula (However, in the above formula [], Z is the trivalent carbon number 6
~12 aromatic or aliphatic hydrocarbon group having 1 to 6 carbon atoms, R ₁ and R ₂ are

【formula】

【formula】

[Formula] −(CH ₂ ) _o OH,

[expression] and

selected from the group consisting of [Formula], and R ₁ and R ₂ may be the same or different. Note that X is lower alkyl having 1 to 6 carbon atoms, nm is an integer of 1 to 10, and M is a metal. A preferred example of comonomer A is 3,5-
Sodium di(carbomethoxy)benzenesulfonate, potassium 3,5-di(carbomethoxy)benzenesulfonate, sodium 1,8-di(carbomethoxy)naphthalene-3-sulfonate,
Examples include potassium 2,5-di(carbomethoxy)benzenesulfonate and potassium 2,5-bis(hydroxyethoxy)benzenesulfonate. The copolymerization ratio of comonomer A is 0.2 to 7 mol% with respect to the dicarboxylic acid component or diol component,
Preferably it is 2 to 6 mol%. If this is less than 0.2 mol%, preferably less than 2 mol%, an easily cuttable and easily adhesive PET film cannot be obtained.
On the other hand, if it exceeds 7 mol %, the properties of the resulting film such as water resistance, solvent resistance, and elastic modulus will be significantly reduced. The copolymerization ratio of the diethylene glycol comonomer (hereinafter abbreviated as comonomer B) of the present invention is 2 to 15 mol%, preferably 5 to 15% by mole, based on the diol component.
It is 13 mol%. Note that by-produced diethylene glycol may be included as long as it does not affect the properties. If comonomer B is less than 2 mol%, easy cutting property will not be exhibited even if the intrinsic viscosity of the polymer is lowered, whereas if it exceeds 15 mol%, water resistance, solvent resistance, heat resistance and elastic modulus etc. characteristics deteriorate significantly. The polyester copolymerized with comonomer A and comonomer B of the present invention refers to a polyester, preferably a polyester in which 78 mol% or more of ethylene terephthalate units are copolymerized with comonomers A and B (hereinafter referred to as polyester P).
(abbreviated as polyester Q), or a polyester in which polyester P is mixed with a polyester in which comonomers A and B are not copolymerized (hereinafter abbreviated as polyester Q). In addition, the ratio of polyester Q to polyester P [Q/(P+Q)×
100] is 0 to 94%, preferably 0 to 50%.
In addition, in the present invention, it is preferable that polyester Q is not mixed. To produce the copolymerized polyester of the present invention,
Comonomers A, B are combined in the presence or absence of a difunctional acid such as isophthalic acid, adipic acid, P-oxybenzoic acid or a derivative thereof, such as terephthalic acid or a functional derivative thereof and ethylene glycol or ethylene oxide. It is produced by copolymerizing with an ethylene terephthalate-forming monomer according to a conventional method. If the ethylene terephthalate unit content is less than 78 mol%, the resulting film will have a lower modulus of elasticity, poor water resistance, particularly when exposed to boiling water, and solvent resistance will also be lowered, which is not preferred. In the production of the copolymerized polyester referred to in the present invention, any known esterification, transesterification, or polycondensation catalyst may be used. Depending on the purpose, silica, kaolin, talc, TiO ₂ ,
A lubricant such as BaSO ₄ and additives such as pigments, dyes, antioxidants, and weathering agents may also be optionally used. After drying, the copolymerized polyester obtained above is melt-extruded to form a sheet-like unstretched film, and then biaxially stretched, preferably the biaxially stretched film is heat-treated to form the desired film. be able to. The biaxial stretching may be longitudinal or transverse sequential stretching or biaxial simultaneous stretching, and the stretching ratio is not particularly limited, but usually 2.0 to 5.0 times is appropriate. In order to provide anisotropy to the cutting, the stretching ratios in the vertical and horizontal directions can be changed arbitrarily. Alternatively, after longitudinal or transverse stretching, the film may be re-stretched in either the longitudinal or transverse directions. Furthermore, in the present invention, in addition to the single-layer biaxially stretched film, a composite film in which the copolymerized polyester of the present invention and other polyester are laminated, preferably the composite film has a shear py impact value of 15 kg cm/mm in at least one direction. It also includes composite films that are ² or less. The combination of composite layers is not particularly limited, but when the polyester of the present invention and other polyester are laminated in multiple layers, at least one layer consisting of the polyester of the present invention is preferably added as the outermost layer. Provided on both outer layers. Further, in the case of a composite film, one of the layers made of the polyester of the present invention or another polyester may be unstretched or uniaxially stretched, but the other must necessarily be biaxially stretched. Such composite films can be produced by coextrusion, melt coating a uniaxially oriented film of one polymer with the other, solution coating followed by stretching, melt coating a biaxially oriented film of one polymer with the other,
Solution coating methods etc. can be applied. After biaxial stretching, heat treatment is performed to obtain a shear py impact value of 15 kg cm/mm ² or less and to impart easy cutting properties, and the temperature is 200 to 245°C, preferably 210 to 245°C.
It is ℃. The ease of cutting of copolymerized polyester is considerably affected by the heat treatment temperature; when the amount of copolymerization is large, easy cutting ability can be achieved by heat treatment at a relatively low temperature, but when the amount of copolymerization is small, , 210-240°C high temperature heat treatment is preferred. Of course, even in low-temperature heat treatment, if the heat treatment time is increased, the ease of cutting is improved. In addition, as another method for imparting easy cutting properties, it is desirable to use a low intrinsic viscosity polymer and form it into a film. The intrinsic viscosity of the copolymerized polyester film is 0.45 to 0.70, but in order to provide easy cutting properties, the intrinsic viscosity is preferably in the range of 0.45 to 0.63 (measured at 25°C in orthochlorophenol solvent). . Polymers with lower intrinsic viscosity than conventional ordinary films are preferred in order to exhibit easy cutting properties.
Lowering the intrinsic viscosity also lowers the melt viscosity, but []
By copolymerizing comonomers of the formula,
High melt viscosity can be achieved with low intrinsic viscosity. In order to modify the surface properties of the polyester film, treatments such as corona discharge treatment, embossing treatment, flame treatment, anchor coating treatment, etc. may be performed during film formation or during the processing step. The ease of cutting that can be further imparted to the biaxially stretched film according to the present invention can be confirmed by actually cutting it by hand. As a guideline for cuttability, it is desirable that the tensile strength at break is 12 Kg/mm ² or less, and B. As a guideline for easy cutting ability in high-speed cutting, it is desirable that the Shalpy impact value be 15 Kg/cm/mm ² or less. Of course, the easier it is to cut, the easier it is to show the above values in both the longitudinal and lateral directions, but even if only one direction deviates from the above values, the ease of cutting by hand will still be satisfactory. Regarding adhesiveness, the standard is that the adhesive strength when using cellophane ink is equivalent to the adhesive strength to cellophane. As explained above, the polyester film of the present invention has the properties inherent to polyester film (heat resistance, water resistance, chemical resistance, high elastic modulus), and has excellent ink printability (adhesion) comparable to that of cellophane. It is used for drug packaging, food packaging,
It is preferably applied to general light packaging films such as cigarette packaging, and tapes such as adhesive tapes and band strings. Films with a Shalpy impact value of 15 Kg·cm/mm ² or less are suitable for use in movies and video photography, where problems may arise due to excessive film strength. In addition, the measured values of each characteristic are based on the following method. (1) Ease of cutting A 20 micron thick film was cut from the edge using both hands and classified into the following ranks. 〇…Can be cut as easily as or more easily than cellophane. △: It is more difficult to cut than cellophane, but it can be cut. x: Cutting is difficult and the shape of the cut portion is disordered. (2) Breaking strength Tensile speed for a sample of 10 mm width x 50 mm length
Measured at 300mm/min. (3) Shally Pee Impact Value The energy required to break was measured for a sample of 10 mm width x 100 mm length using a Shally Pey impact tester manufactured by Toyo Seiki. (4) Ink adhesion Gravure printing was performed using cellophane ink, and judgment was made using a scratch test using adhesive tape. 〇...Good △...Slightly peeling ×...Peeling (5) Rigidity The tensile elastic modulus was measured and classified into the following ranks. ○: 300Kg/mm ² or more △: 200-300Kg/mm ² ×: 200Kg/mm ² or less (6) Heat resistance The melting point of the polymer was measured and classified into the following ranks. 〇: 240℃ or higher △: 225~240℃ ×: 225℃ or lower (7) Thickness unevenness 〇: Thickness unevenness (%) shown by the following formula is 5% or less, △: 5% to 50% , Those with 50% or less are indicated by ×. Thickness unevenness (%) = Maximum thickness - Minimum thickness / Average thickness of film x 100 Next, embodiments of the present invention will be described based on Examples. Examples 1, 2, Comparative Examples 1 to 8 The amount of dimethyl-5-sodium sulfoisophthalate (hereinafter abbreviated as SI) added during the polymerization step
By changing the amount of DEG added, SI− with various copolymerization ratios
DEG copolymerized polyethylene terephthalate (intrinsic viscosity 0.58) is made, extrusion cast, and stretched under the most easily cuttable stretching conditions for the raw material (stretched by 3.0 times in the longitudinal direction at 90°C, stretched by 3.7 times in the width direction at 100°C). double stretching)
After biaxial stretching, the film was further heat-treated at 230°C.
Ten types of 25 micron copolymerized polyethylene terephthalate films were obtained. Table 1 shows the physical property values of the obtained film. As is clear from Table 1, if the SI and DEG copolymerization ratio is low, adhesiveness and easy cutting properties are not developed. When only a large amount of SI was copolymerized, the viscosity of the raw material increased significantly, making it impossible to form a film. If the DEG copolymerization ratio increases, the rigidity and heat resistance will decrease, which is not preferable.
SI copolymerization ratio is 0.2 to 7 mol%, DEG copolymerization ratio is 2
It can be seen that when the amount is in the range of ~15 mol %, a polyester film with good cuttability, adhesiveness, and thickness unevenness can be obtained while maintaining rigidity and heat resistance.
If the SI and DEG copolymerization ratio exceeds the range of the present invention, heat resistance and thickness unevenness will deteriorate,

[Table] (Note) *marks indicate examples.
Moreover, it is water resistant, especially susceptible to boiling water. Example 3 SI and DEG were added during polymerization, and copolymerized polyethylene terephthalate (intrinsic viscosity at 25°C in O-chlorophenol of 0.56 at 25°C) with a SI copolymerization amount of 4 mol% and a DEG copolymerization amount of 12 mol% was put into an extruder. supply
The sheet was melt extruded at 280°C, and the molten material that came out of the die was cooled and solidified in a cooling drum at 25°C while applying static electricity.The sheet was then heated to 88°C and stretched 2.8 times in the longitudinal direction, followed by 95°C. It was stretched 4.0 times in the width direction at ℃, heat-set at 225℃, and then rolled up. The copolymer film thus obtained had a thickness of 25 microns and exhibited the physical properties shown in Table 2. The resulting polyester film can be easily cut by hand and has a high Young's modulus. This film is not only easy to cut, but also has excellent adhesive properties.After printing a cellophane printing ink based on synthetic rubber on one side of the film of this example, extrusion of 15 microns of polyethylene was carried out and laminated. Then, a packaging bag was created using polyethylene as a sealing layer. It was easier to cut by hand and had better adhesion than conventional PET bags.

[Table] Comparative Examples 9, 10 5 as the metal sulfonate group in Example 1
- Polyethylene terephthalate (intrinsic viscosity 0.58) was prepared by copolymerizing sodium sulfoisophthalic acid with polyethylene glycol having a molecular weight of 1000 instead of DEG, and biaxially stretched and heat-treated under the same extrusion stretching conditions as in Example 1 to 25 μm. A film was formed. Table 3 shows the properties of the film thus obtained. It can thus be seen that when a comonomer other than diethylene glycol is used as a copolymerization component, particularly easy cleavability is not achieved.

【table】

Claims (1)

[Claims] 1 0.2 to 7 mol% of a comonomer containing at least one metal sulfonate group, 2 to 15 mol% of a diethylene glycol comonomer with a molecular weight of 100 to 500
Copolymerized polyester film.