JP2000281815A - Aliphatic polyester-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject oriented film excellent in processability causing neither planarity aggravation nor shear, etc., during printing and laminating processes, related to the important characteristics in wrapping films and adhesive tapes for perishables, processed foods, medicaments, medical equipment, electronic parts, etc., and excellent in hand tearability and twistability as well. SOLUTION: This film consists of a polymer predominant in an aliphatic polyester which is composed mainly of recurring unit of the general formula O-CHR-CO (R is H or a 1-3C alkyl) and has a reduced viscosity (ηsp/C) of 0.50-2.50 dL/g (e.g. polylactic acid), being <=30 deg. in the maximum strain of the orientation main axis and <=5% in the thermal shrinkage at 120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film made of an aliphatic polyester resin, and more particularly, to a fresh food, a processed food, a pharmaceutical, a medical device,
Useful for packaging and pressure-sensitive adhesive tapes that are excellent in processing suitability that does not cause deterioration in flatness or printing misalignment in printing or laminating processes, which are important properties in packaging films for electronic components, etc., and are also excellent in hand cutting and twisting properties. The present invention relates to a novel aliphatic polyester film.

[0002]

2. Description of the Related Art Conventionally, aliphatic polyester films such as polylactic acid are decomposed when disposed in the natural environment. For example, polylactic acid films are naturally hydrolyzed in soil and then harmless by microorganisms. It has been developed to be a specially degraded product.

[0003] Accordingly, such aliphatic polyester-based films have been developed with a priority on decomposing in the natural world, and as a result, the excellent properties inherent to aliphatic polyesters can be fully obtained. Did not.
In other words, as the orientation and crystallization of the film progress,
Since hydrolysis and decomposition by microorganisms were suppressed, it was necessary to suppress the orientation and crystallization of the film, and the strength and thermal dimensional stability were insufficient.

[0004] On the other hand, attempts have been made to improve the orientation and crystallinity of the film to improve the strength and the thermal dimensional stability. For example, Japanese Unexamined Patent Publication No. 7-207041 discloses a method comprising a polylactic acid polymer having a plane orientation degree ΔP of 3.0 × 10 ^−3.
And the heat of crystal fusion ΔHm when the film is heated and the heat of crystallization ΔC generated by crystallization during the temperature rise.
A polylactic acid film in which (ΔHm−ΔHc) with Hc is 20 J / g or more is disclosed.

[0005]

However, this polylactic acid film is not intended to improve post-processing stability such as hand-cutting property, twisting property, and printing property required for a packaging film. In the physical properties of the polylactic acid polymer film, the post-processing stability, for example, the dimensional stability at 120 ° C. required for printing, lamination, etc., is insufficient, and the above object is achieved at the same time. It is difficult. Furthermore, even in the prior art relating to other aliphatic polyester-based films, the reduced viscosity and physical properties of the polylactic acid polymer have been improved for the purpose of improving post-processing properties such as hand-cutting properties and twisting properties as a packaging film, and printability. The one we focused on did not exist before.

On the other hand, stretched polyethylene terephthalate films have excellent properties such as toughness, heat resistance, water resistance and transparency in packaging bags and adhesive tapes based on polyethylene terephthalate, an aromatic polyester, as a base film. It has been utilized. However, while the film has these excellent features, it is difficult to cut, it is difficult to tear the opening of the packaging bag, the adhesive tape is difficult to peel, and the fixability at the time of twisting is inferior, so that it is used for twist packaging. There were drawbacks such as inability to use.
As a method of solving such hand-cutting and twisting properties,
Polyester film oriented uniaxially
5-8551) and a polyethylene terephthalate film copolymerized with diethylene glycol (Japanese Patent Publication No.
50692) and the like.

However, among the above-mentioned methods of uniaxial orientation, the film is easily cut linearly in the direction of orientation, but is hard to be cut in directions other than the direction of orientation, and the method of copolymerizing other components impairs the inherent characteristics of polyethylene terephthalate. Had the disadvantage of being

On the other hand, cellophane has been conventionally known as a film having excellent hand-cutting properties. Cellophane is used for various packaging materials, adhesive tapes, etc. due to its excellent transparency, easy cutting property, twisting property and the like. However, on the other hand, cellophane has a hygroscopic property, and its characteristics fluctuate depending on the season, and it is difficult to supply a constant quality.

In order to solve the above-mentioned problems, the present invention generates print misalignment and wrinkles in a process such as printing and lamination which is usually performed on a film when used for a packaging film or an adhesive tape. The present invention provides an aliphatic polyester film having good twist fixability and good hand-cutting properties that can be easily cut by hand in any direction without restricting the directionality. It is an object.

[0010]

The aliphatic polyester film of the present invention has a main repeating unit represented by the general formula -O-
CHR-CO- (wherein R is hydrogen or a group having 1 to 3 carbon atoms)
And the reduced viscosity (ηsp / C) is 0.1.
It is made of a polymer containing an aliphatic polyester of 50 to 2.50 as a main component, and has a maximum distortion of the main orientation axis of 30 ° or less and a heat shrinkage at 120 ° C. of 5% or less. As a result, it is possible to obtain a film useful for general packaging and the like having excellent processability without causing dimensional change in the printing or laminating process or wrinkling.

In the present invention, the compound represented by the general formula -O-CHR-CO
The aliphatic polyester having-(R represents hydrogen or an alkyl group having 1 to 3 carbon atoms) as a main repeating unit is not particularly limited as long as it has a reduced viscosity (ηsp / C) described below. For example, polylactic acid, polyglycolic acid, poly (2-oxybutyric acid) and the like can be mentioned. The aliphatic polyester may be used alone, or a mixture or a copolymer may be used. Further, in the aliphatic polyester having an asymmetric carbon in the polymer, optical isomers such as L-form, DL-form and D-form exist, and any of them may be used.
A mixture of these isomers may be used. As the above-mentioned polymer used as a material of the film, a polymer produced by a known method such as ring-opening polymerization of a corresponding dehydrated cyclic ester compound of α-oxyacid can be used.

In the present invention, the aliphatic polyester used has a reduced viscosity (ηsp / C) of 0.50 or more.
Must be 50 or less. When the reduced viscosity is less than 0.50, breakage during film formation is large, and the physical properties of the obtained film are remarkably poor. On the other hand, if the reduced viscosity is larger than 2.5, not only the hand-cutting property and twisting property of the obtained film are reduced, but also the melt extrusion becomes high, so that melt extrusion becomes difficult. A preferred reduced viscosity range is 0.50 or more and 2.0 or less, more preferably 0.5
It is 0 or more and 1.80 or less.

The aliphatic polyester-based film of the present invention is formed from the above-mentioned polymer containing aliphatic polyester as a main component. And other components such as an arbitrary polymer can be contained according to the desired physical properties.

The method for forming the aliphatic polyester film of the present invention is not particularly limited, and a film formed by a generally known method can be used. It is particularly preferable that the film is heat-set after biaxial stretching. In this case, the stretching method is not particularly limited, and a film formed and stretched by a known method can be used.

In forming the aliphatic polyester film of the present invention, known extrusion methods such as a T-die method and an inflation method can be applied, and an unstretched film can be obtained by these methods. The extrusion temperature is preferably in the range of the melting temperature (Tm) of the polymer to be used to Tm + 70 ° C, more preferably in the range of Tm + 20 to Tm + 50 ° C. If the extrusion temperature is too low, it is difficult to obtain extrusion stability, and the film tends to be overloaded during film formation. Conversely, if it is too high, the decomposition of the polymer becomes severe, which is not preferable. The die of the extruder used at the time of the extrusion molding may have an annular or linear slit. The temperature of the die is preferably on the order of the extrusion temperature range.

When biaxially stretching the above unstretched film,
The first axis stretching and the second axis stretching may be performed sequentially or simultaneously.

The stretching temperature is preferably in the range of the glass transition temperature (Tg) of the polymer used to Tg + 50 ° C. More preferably, it is in the range of Tg + 10 to Tg + 40 ° C. If the stretching temperature is lower than Tg, stretching is difficult, and Tg + 50 ° C.
Exceeding the thickness is not preferred because the thickness uniformity and the mechanical strength of the obtained film decrease.

When the unstretched film is biaxially stretched,
The stretching in the vertical and horizontal directions may be performed in one stage or in multiple stages, but ultimately in each stretching direction is at least 3 times, more preferably at least 3.5 times, and the vertical and horizontal area ratio is 9 times. Stretching at least 20 times, more preferably at least 12 times is preferable from the viewpoint of uniformity of thickness and mechanical properties. When the longitudinal and transverse stretching ratios are each less than 3 times and the area ratio is less than 9 times, it is difficult to obtain a film having good thickness uniformity, and the improvement in physical properties such as mechanical strength is also poor.

In order to keep the refractive index (Nz) and the heat shrinkage in the thickness direction of the aliphatic polyester-based film of the present invention in predetermined ranges as described later, longitudinal stretching is performed in two or more steps, and at least once. Is Tg + 20 ° C to Tg + 40 ° C
In the range of 10000% / min, preferably 1%
It is desirable to include a step of stretching at 5000% / min, more preferably 20,000% / min or more.

The aliphatic polyester film of the present invention may have a single layer or a multilayer structure. In order to obtain a multilayer structure, a co-extrusion method, a coating method, or the like may be used in a manufacturing process. The aliphatic polyester film of the present invention may be subjected to a corona treatment, a plasma treatment, a flame treatment or the like for the purpose of improving the surface energy or the like.

The polymer constituting the aliphatic polyester-based film of the present invention may contain known additives as needed, as long as the function of the present invention is not impaired. Examples of the additives include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a lightfast agent, and an impact resistance improver. However, when the aliphatic polyester film of the present invention needs to be transparent and the contents visible after the heat seal layer is formed, high transparency is required even before the heat seal layer is formed. In addition, it is necessary to prevent the transparency from being lowered by the additives.

As the above lubricant, silica, titanium dioxide,
Aliphatic polyesters such as metal oxides such as talc and kaolinite; salts of metals such as calcium carbonate, calcium phosphate and barium sulfide; or particles composed of organic polymers such as cross-linked polystyrene resin, cross-linked acrylic resin, silicone resin, cross-linked polyester resin Examples of particles that are inert to the base polymer are exemplified.

When these lubricants are used, any one may be used alone or two or more may be used in combination, but the average particle system of the lubricant used is preferably 0.01 μm.
m to 3.0 μm, particularly 0.05 μm to 2.5 μm
m or less is preferable. Further, the addition amount is preferably 0.005% by weight or more and 2% by weight or less, particularly preferably 0.01% by weight or more and 1.0% by weight or less in order to achieve both transparency and slipperiness of the film. preferable.

In order to achieve both transparency and slipperiness, it is preferable to use two or more lubricants in combination. In particular,
Lubricant particles that are deformed during film formation (for example, organic lubricants with a low degree of crosslinking such as cross-linked polyethylene and cross-linked acrylic, and inorganic lubricants such as silica that are aggregates of primary particles) and ordinary lubricant particles that do not deform during film formation It is preferable to combine

In the present invention, the maximum value of the distortion of the principal axis of the aliphatic polyester system must be 30 ° or less, preferably 25 ° or less, more preferably 20 ° or less. If the maximum value of the distortion of the orientation main axis is more than 30 degrees, the film is distorted when the film is heated in the printing process, and color misregistration occurs when performing multicolor printing, which is not preferable.

The heat shrinkage of the aliphatic polyester film of the present invention at 120 ° C. must be 5% or less, and preferably 3% or less. If the heat shrinkage is more than 5%, not only the hand-cutting property is reduced, but also printing deviation occurs in the printing process and wrinkles occur during heat sealing, which is not preferable.

Further, the refractive index (Nz) in the thickness direction of the aliphatic polyester film in the present invention is preferably from 1.440 to 1.455, more preferably from 1.445 to 1.455. Nz is 1.4
If it is less than 40, breakage tends to occur in the step of forming the film. On the other hand, when the ratio exceeds 1.455, flatness is disordered when the film is heated in a printing or laminating step.

The value (Nx-Ny) obtained by subtracting the refractive index (Ny) in the width direction from the refractive index (Nx) in the longitudinal direction of the aliphatic polyester film in the present invention is preferably-
0.020 or more and 0 or less, more preferably -0.0.
It is 015 or more and 0 or less. When Nx-Ny is less than -0.020, when the film is heated in a printing or laminating step, the film is stretched due to the transport tension of the film, causing printing misalignment and ripples to deteriorate flatness. Also, N
When x-Ny exceeds 0, the thickness unevenness tends to be large, and the hand-cutting property also decreases. The thickness of the aliphatic polyester film of the present invention is not particularly limited.

[0029]

EXAMPLES Hereinafter, the contents and effects of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples unless departing from the gist thereof.

Example 1 To 100 parts by weight of poly-L-lactic acid having a reduced viscosity of 1.50, 0.06 parts by weight of aggregated silica particles having an average particle size of 1.8 μm was added as a lubricant for forming surface projections. The obtained polymer was extruded at a resin temperature of 210 ° C. using a 30 mm diameter extruder with a T-die, and then cooled with a chill roll at 20 ° C. to obtain an unstretched film having a thickness of 300 μm.
96 ° C film temperature with multiple ceramic rolls
And stretched 1.5 times in the machine direction at a stretching speed of 25000% / min between rolls, and further stretched 2.7 times in the longitudinal direction at 98 ° C. Next, the film was stretched 3.8 times in the transverse direction at 80 ° C. with a tenter-type stretching machine, and then heat-set at 155 ° C.
A 3% transverse relaxation treatment was performed at 35 ° C. to obtain a biaxially stretched film having a thickness of 20 μm.

Comparative Examples 1 and 2 A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 using poly-L-lactic acid having reduced viscosities of 2.82 and 0.43.

Comparative Example 3 The procedure of Example 1 was repeated except that the longitudinal stretching was performed at 68 ° C. by 3.2 times in one step, and the thickness was 20 μm in the same manner as in Example 1.
Was obtained.

Comparative Example 4 A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that the heat setting was performed at 140 ° C.

Example 2 A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that the heat setting was performed at 150 ° C.

With respect to Examples 1 and 2 and Comparative Examples 1 to 4,
Physical properties were evaluated by the following test methods. The results are summarized in Table 1.

(1) Reduced viscosity (ηsp / C): Example 1
* 2. 0.125 g of the polymer used in Comparative Examples 1 to 4 was dissolved in 25 ml of chloroform and measured at 25 ° C. using an Ubbelohde viscosity tube.

(2) Maximum value of the distortion of the main orientation axis When the film shape is a roll shape, it is 1000 m in the longitudinal direction.
m, cut out the entire width in the width direction, in the case of a sheet-shaped sample, draw a rectangle with the largest area inscribed in the sample shape, cut out a 100 mm square square that shares two sides with the vertices of the rectangle from four vertices, and align The principal axis was determined by microwave, and when the molecular orientation angle of the point measured first was 0 degree, the maximum value was determined from the one with the largest difference in the orientation angles of the other three points. In order to measure the orientation angle of the main axis by microwaves, a molecular orientation meter (MOA-200 manufactured by Kanzaki Paper Co., Ltd.) was used.
1A) was used.

(3) Thermal Shrinkage Ratio A film having a diameter of 50 mm was drawn around the intersection of the diagonal lines of the film cut into a square having a side of 100 mm, and the film was allowed to stand in a hot-air dryer heated to 120 ° C. for 30 minutes without load. Thereafter, the dimensional change was read by a digitizer, and the dimensional change was determined from the length (B) of the maximum position of contraction passing through the intersection of the diagonal lines using the following equation. Heat shrinkage at 120 ° C. = (50−B) / 50 × 100
(%)

(4) Refractive Indices (Nz, Nx, Ny) in Thickness, Longitudinal, and Width Directions For the films of Examples 1 and 2 and Comparative Examples 1 to 4, Abago refractometer 1T manufactured by Atago Co., Ltd. was used. And the respective refractive indices were measured.

(5) Hand-cutting property The film of Examples 1 and 2 and Comparative Examples 1-4 can be easily cut by hand when a tape-like sample having a width of 15 mm is cut by hand according to a sensory test. Is indicated by ○, the one that cannot be easily cut by hand is indicated by X, and the middle between O and X is indicated by Δ.

(6) Twistability The film obtained in Examples 1 and 2 and Comparative Examples 1 to 4 was subjected to a sensory test to determine that a 30-mm-wide tape-shaped sample did not return to its original state when twisted. 、, those that could not maintain the twisted state were marked as ×.

(7) Processing Suitability Gravure ink (Lamiace 61 white two-part type, manufactured by Toyo Ink Co., Ltd.) was gravure-printed on the surface of each of the films of Examples 1 and 2 and Comparative Examples 1 to 4 to form a printing ink layer. And then applying an adhesive AD585 / CAT-10 (manufactured by Toyo Morton Co., Ltd.) at a rate of 2 g / m ² , followed by dry laminating an unstretched polypropylene film, 60 μm (manufactured by P1120 Toyobo Co., Ltd.) according to a conventional method. To form a sealant layer to obtain an aliphatic polyester-based film laminate. In this process, the state of the film was observed and a three-step evaluation was performed. ；: Good film condition △: slight wrinkles and print misregistration ×; poor flatness, wrinkles and print misregistration

[0043]

[Table 1]

[0044]

The aliphatic polyester film of the present invention can be used for packaging of fresh foods, processed foods, pharmaceuticals, medical equipment, electronic parts, etc., which is an important property in the printing and laminating processes. It has excellent processability without occurrence of misalignment, and has excellent hand-cutting properties and twisting properties, and is extremely useful as a film for general packaging, an adhesive tape, or the like.

Continued on the front page (72) Inventor Keiji Mori 2-1-1 Katata, Otsu City, Shiga Prefecture Inside Toyobo Co., Ltd. Research Institute (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. F-term in the Company Research Laboratory (reference) 3E086 AD15 BA02 BA04 BA15 BA33 BB62 BB85 BB90 CA01 CA17 CA18 CA22 CA25 CA31 4F071 AA43 AA88 AF31Y AF52 AF61Y AH04 BA01 BB08 BC01 4F100 AK07B AK41A BA02 BA10A BA10B BA15A GBA GBA GBA JC00A JL01 JN18A YY00A

Claims (5)

[Claims] (1) a main repeating unit represented by the general formula -O-CH
R-CO- (where R represents hydrogen or an alkyl group having 1 to 3 carbon atoms) and a reduced viscosity (ηsp / C) of 0.50
An aliphatic polyester comprising an aliphatic polyester having a major component of not less than 2.50 and not more than 30.degree. And having a maximum strain of 30.degree. Or less and a heat shrinkage at 120.degree. Polyester film. 2. The refractive index (Nz) in the thickness direction is 1.440.
2. The aliphatic polyester film according to claim 1, wherein the film has a heat shrinkage of not more than 1.455 and a heat shrinkage at 120 ° C. of not more than 3%. 3. A value (Nx−Ny) obtained by subtracting a refractive index (Ny) in a width direction from a refractive index (Nx) in a longitudinal direction is −0.0.
The aliphatic polyester-based film according to claim 1, wherein the number is 020 or more and 0 or less. 4. The method according to claim 1, comprising a polymer mainly composed of an aliphatic polyester having a reduced viscosity (ηsp / C) of 0.50 or more and 1.80 or less. The aliphatic polyester film as described in the above. 5. The aliphatic polyester film according to claim 1, wherein the aliphatic polyester is polylactic acid.