JP2000044701A - Lactic acid-based polymer biaxially oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a lactic acid-based polymer biaxially oriented film excellent in handling properties, traveling properties, transparency and adhesion and which does not generate print dropping-out in printing and is suitable for packaging applications. SOLUTION: In a film comprising a lactic acid-based polymer containing an aliphatic polyester having a main repeating unit of the general formula: O-CHR-CO (wherein R is H or a 1-3C alkyl group) as a main component, the number of protrusions a PCC value, per unit area at a center plane of roughness of at least one surface is between 600/mm2 and 2500/mm2 inclusive and the three-dimensional surface roughness SRa, is between 0.03 μm and 0.07 μm inclusive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched lactic acid-based polymer film, and more particularly to a biaxially stretched lactic acid-based polymer film having excellent handling properties, running properties, transparency and adhesiveness. Further, the present invention relates to a biaxially stretched lactic acid-based polymer film which is suitable for packaging and the like, which does not cause printing omission during printing.

[0002]

2. Description of the Related Art In recent years, with the increasing public awareness of environmental protection, plastics that do not degrade or disappear over time and are not detrimental to the natural environment for all plastic processed products when disposed in the natural environment. Products are required.

Conventionally, films for packaging various products including foods include aromatic polyesters represented by polyethylene, polypropylene and polyethylene terephthalate,
Various polyamide plastics are used. These films for packaging materials are collected after use, and disposed of either by incineration or burying in soil. However, it is well known that the collection requires a great deal of labor, and is actually left uncollected and causes various problems such as environmental pollution. In addition, in the case of incineration, the thermal power is too strong, the furnace is severely damaged, a large amount of fuel is required, and the cost is high. on the other hand,
When buried in the soil, there is a problem that the waste does not have biodegradability and remains semipermanently in the soil. Under such circumstances, demands for various packaging films having good biodegradability are increasing.

[0004] As a fundamental solution to the above problem, various biodegradable polymer materials in which the polymer itself has biodegradability have been studied. Among them, polylactic acid has been widely known as a hydrolysable polymer, and is used as a molded product for pharmaceutical use (JP-B-41-2734, JP-B-63-68155, etc.) Various applications have been studied as basic raw materials for versatile materials.

[0005] Among them, lactic acid-based polymer biaxially stretched films are expected to be used in a wide range of applications including general packaging materials because they have transparency, biodegradability, and excellent mechanical properties equivalent to general-purpose films. I have.

In general, a film is required to have a winding property at the time of molding and a slip property at the time of using the product. If the slipperiness is insufficient, poor handling properties will occur during the production and processing of the film, and the slipperiness will be poor due to poor slippage during contact with the guide rolls when the film is running. Occurs. In order to improve the slipperiness, the film is added with an organic lubricant such as a fatty acid ester, a fatty acid and a fatty acid amide, and an antiblocking agent for inorganic fine particles such as silica and calcium carbonate. An application example in which the handling is improved by improving the handling is disclosed in JP-A-8-3491.
No. 3 and JP-A-9-278997. Therefore, Japanese Patent Application Laid-Open No. 8-349 has been proposed to improve the handling property.
13 and the lubricant described in JP-A-9-278997, the running properties were improved, but it was necessary to laminate it with a sealant film made of polyolefin or the like in order to form a packaging bag. Insufficiency was caused by the addition of an organic lubricant. By adding the above-mentioned lubricant and anti-blocking agent, it was difficult to achieve both the running property and the adhesiveness required for film processing suitability and packaging use.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a biaxially stretched lactic acid-based polymer film having excellent handling properties, running properties, transparency and adhesiveness. The present invention provides a biaxially stretched polymer film.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present invention has been achieved. That is, in the lactic acid-based polymer biaxially oriented film, said projection density PCC value per unit area of at least one side of the roughness center plane of the film is 600 / mm ² or more and 2500 / mm ² or less, and tertiary Original surface roughness SRa is 0.03μm or more, 0.07μm
A biaxially stretched lactic acid polymer film characterized by the following.

[0009] In the biaxially stretched lactic acid polymer film of the present invention, the number of protrusions per unit area on the central surface of the roughness, PCC value, needs to be 600 / mm ² or more. If the PCC value is less than 600 pieces / mm ² , the handling properties will be poor. On the other hand, if the PCC value is greater than 2500 / mm ² , the transparency becomes poor. Preferably, the PPC value is 1000 to 2200 pieces / mm ² .

Further, in the biaxially stretched lactic acid polymer film of the present invention, the three-dimensional surface roughness SRa is 0.03 μm
It is necessary to be above. Three-dimensional surface roughness SRa is 0.03
If it is less than μm, the handling properties will be poor. On the other hand, if the three-dimensional surface roughness SRa is greater than 0.07 μm, the transparency will be poor, and furthermore, the printing will be missed due to the white particles generated by shaving the projections during printing.

When the lactic acid-based polymer biaxially stretched film of the present invention is used for applications requiring transparency, such as packaging, the number of protrusions per unit area on the center plane is defined as PCC.
The value and the three-dimensional surface roughness SRa can be improved by setting them within a predetermined range, but more preferably by setting the haze to 8% or less.

The general formula -O-CHR-C used in the present invention
A lactic acid-based polymer mainly composed of an aliphatic polyester having O- (R represents H or an alkyl group having 1 to 3 carbon atoms) as a main repeating unit is, for example, polylactic acid,
Examples thereof include polyglycolic acid and poly (2-oxybutyric acid), but are not limited thereto. In some cases, these may be used alone, or a mixture or a copolymer may be used. Compounds having an asymmetric carbon in the polymer include optical isomers such as L-form, DL-form, and D-form.
Also, a mixture of these isomers may be used. The above-mentioned polymers used as materials for these films are produced by a known method such as ring-opening polymerization of a corresponding dehydrated cyclic ester compound of α-oxyacid.

In the present invention, the biodegradable aliphatic polyester used has a viscosity average molecular weight of 5,000 to 500,000. If the viscosity average molecular weight is less than 5,000, the physical properties of the obtained film are remarkably poor, and the decomposition rate is too high, which is not preferable for achieving the object of the present invention. Also,
In order to ensure sufficient extrudability during film production and biaxial stretching with a biaxial stretching machine, the viscosity average molecular weight is preferably 10,000 or more. On the other hand, a high viscosity polymer having a viscosity average molecular weight of 500,000 or more has a problem that melt extrusion becomes difficult. For these reasons, the preferable range of the viscosity average molecular weight is 40,000 to 300,000.

The biaxially stretched lactic acid polymer film of the present invention may contain inorganic particles, organic salt particles or crosslinked polymer particles as a lubricant.

Examples of the inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, and fluorine oxide. Lithium oxide and the like.

In particular, in order to obtain a film having a low haze while obtaining good handling properties, silica particles of an aggregate formed by aggregating primary particles are preferable as the inorganic particles.

Examples of the organic salt particles include calcium oxalate, terephthalate such as calcium, barium, zinc, manganese and magnesium.

Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin may be used.

The method of adding the above-mentioned lubricant to the lactic acid-based polymer of the present invention is not particularly limited, but a method of dispersing or dissolving the lubricant in a predetermined solvent and dispersing the above-mentioned lubricant in the system,
Alternatively, there is a method of dispersing the lubricant during a synthetic polymerization reaction.

The number of protrusions PCC and the three-dimensional surface roughness SRa on the central surface of the roughness are adjusted by the film forming conditions and lubricant particles. The type and amount of the lubricant particles are not particularly limited as long as the number of protrusions PCC value on the central surface of the roughness and the three-dimensional surface roughness SRa fall within a predetermined range, but the average particle system of the lubricant is 0.5μm or more and 5μm
Or less, particularly preferably 1 μm or more and 4 μm or less, and the addition amount is 0.02% by weight or more and 0.5% by weight or less, particularly preferably
It is not less than 0.03% by weight and not more than 0.5% by weight.

When the average particle size of the lubricant is less than 0.5 μm, it is difficult to make the three-dimensional surface roughness SRa 0.03 μm or more, and
If it is larger than μm, the number of protrusions on the center plane is 600 PCC values
It is difficult to reduce the three-dimensional surface roughness SRa to 0.07 μm or less at / mm ² or more. If the addition amount is less than 0.02% by weight, it is difficult to make the three-dimensional surface roughness SRa 0.03 μm or more when the number of protrusions on the central surface is 600 or more PCC / mm ² , and if it is more than 0.5% by weight, the three-dimensional surface roughness It is difficult to reduce the SRa to 0.07 μm or less.

The biaxially stretched lactic acid-based polymer film of the present invention may contain a nucleating agent, an antioxidant, an anti-coloring agent, a pigment, a dye, an ultraviolet absorber, a release agent, a lubricant, a flame retardant, You may mix | blend an antistatic agent.

Examples of the organic lubricant include hydrocarbon resins, fatty acid esters, paraffins, higher fatty acids, aliphatic ketones,
And fatty acid amides are known. In the present invention, by setting the surface form of the film to the form described in the first aspect, it is possible to impart a lubricating property. Therefore, it is not always necessary to add an organic lubricant. In addition, when these organic lubricants are added, the organic lubricant bleeds out to the film surface, so that the adhesive strength after lamination with the sealant film with polyolefin or the like becomes insufficient. Is preferred.

The biaxially stretched lactic acid polymer film used in the present invention can be formed by a known film forming method. As a film forming method, a uniaxial stretching method or an inflation method of stretching in a longitudinal direction or a transverse direction, a simultaneous biaxial stretching method,
A biaxial stretching method such as a sequential biaxial stretching method may be used. For example,
As the sequential biaxial stretching method, in addition to the method of performing longitudinal stretching and transverse stretching or transverse stretching and longitudinal stretching in order, horizontal / longitudinal / longitudinal stretching method, vertical / horizontal / longitudinal stretching method, vertical / longitudinal / horizontal stretching method, etc. A stretching method can be adopted. In addition, you may perform a heat setting process, a vertical relaxation process, a horizontal relaxation process, etc. as needed.

The stretching conditions vary depending on the lubricant to be added, and the combination is particularly limited as long as the PCC value of the number of protrusions on the central surface of the roughness and the three-dimensional surface roughness SRa fall within predetermined ranges. But not vertically
In the case of a method of stretching in the horizontal direction after stretching in steps or more, it is preferable that the refractive index (Nx) in the longitudinal direction after the stretching in the longitudinal direction is 1.555 or less. When Nx is set to be larger than 1.555, the formation of surface projections becomes insufficient during the manufacturing process, and the handling property tends to be poor.

An antistatic agent, an inorganic lubricant, an ultraviolet absorber, and the like may be added to the adhesion modifying layer within a range that does not impair the effects of the present invention.
Additives such as an organic lubricant, an antibacterial agent, and a photooxidation catalyst can be contained, and these are contained in the coating agent and applied to the surface of the substrate.

As a method for applying a coating solution containing a graft copolymer to a lactic acid-based polymer biaxially stretched film substrate to form an adhesion-modified layer, a gravure method, a reverse method, a die method, a bar method, A known coating method such as a dipping method can be used.

The coating amount of the coating solution is 0.00
5 to 10 g / m ² , preferably 0.02 to 0.5 g / m ²
m ² . If the coating amount is less than 0.005 g / m ² , sufficient adhesive strength with the adhesion modifying layer cannot be obtained. 10
When it is more than g / m ² , blocking occurs, and there is a practical problem.

The adhesion modifying layer may be formed by applying the above-mentioned coating solution to a biaxially stretched lactic acid-based polymer biaxially stretched film base material,
After applying the above-mentioned coating solution to the unstretched or uniaxially stretched lactic acid-based polymer biaxially stretched film substrate, drying and, if necessary, further heat-setting after uniaxial stretching or biaxial stretching. good. When applied on a lactic acid-based polymer biaxially stretched film, the lactic acid-based polymer biaxially stretched film is subjected to corona treatment, flame treatment, Surface treatment such as line irradiation may be performed. Even when the film is stretched after the following application, the same effect can be obtained. After applying the above-mentioned coating solution to the unstretched or uniaxially stretched lactic acid-based polymer biaxially stretched film substrate, drying and stretching, the drying temperature after application is dried under conditions that do not affect the subsequent stretching. By performing heat fixing at 140 ° C. or more after stretching, the coating film becomes strong, and the adhesiveness between the adhesion-modified layer and the lactic acid-based polymer biaxially stretched film substrate is dramatically improved.

The easily-adhesive lactic acid-based polymer biaxially stretched film obtained in the present invention can obtain good adhesive strength in a wide range of applications. Specifically, photographic photosensitive layers, diazo photosensitive layers, mat layers, magnetic layers, inkjet ink receiving layers, hard coat layers, printing inks and UV inks, adhesives such as dry laminations and extrusion laminations, metals or inorganic substances, or their oxidation. Examples thereof include a thin film layer, an organic barrier layer, and the like obtained by vacuum evaporation, electron beam evaporation, sputtering, ion plating, CVD, plasma polymerization, and the like.

The adhesion-modified layer of the easily adhesive lactic acid-based polymer biaxially stretched film of the present invention has good adhesion to various materials, but in order to further improve the adhesion and printability, the adhesion-modified layer is added to the adhesion-modified layer. Further, surface treatment such as corona treatment, flame treatment, and electron beam irradiation can be performed.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to only these examples. In addition,
The evaluation method of the film is shown below. (1) Three-dimensional surface roughness SRa The film surface was measured with a stylus type three-dimensional surface roughness meter (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.) with a needle radius of 2 μm and a load.
A cut-off value of 0 in the longitudinal direction of the film with a condition of 30 mg.
Measured over a measurement length of 1 mm at 25 mm, at 2 μm pitch
It is divided into 500 points, and the height of each point is determined by a three-dimensional roughness analyzer (SP
A-11). The same operation was repeated 150 times at intervals of 2 μm in the width direction of the film, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer. Next, SRa was determined using an analyzer.

(2) PCC (peak count contribution) value 0.00a from the reference plane having the reference height when calculating the SRa
The number of protrusions having a 625 [mu] m or more in height that represents the per 1 mm ^2. (3) Haze 300A manufactured by Nippon Seimitsu Kogaku Co., Ltd. according to JIS-K6714
It measured using. (4) Refractive index The refractive index in the longitudinal direction of the film was determined using an Abbe refractometer 1T manufactured by Atago Optical Co., Ltd.

(5) Handling and printability of the film The film is formed into a tape having a narrow slit, rubbed on a metal guide roll and run at high speed for a long time, and the tape tension after the guide roll is rubbed. And the amount of white powder generated on the surface of the guide roll were evaluated and ranked in five stages as shown below. (B) Handling properties Class 1; large tension (many scratches) Class 2; medium tension (many scratches) Class 3; medium tension (some scratches) Class 4; medium tension (small scratches) Class 5: tension Small (no scratches) (b) Printability 1st grade: very high generation of white powder 2nd grade; many occurrences of white powder 3rd grade: slight occurrence of white powder 4th grade: almost no occurrence of white powder 5th grade; No white powder

(6) Evaluation of Adhesion Adhesive AD585 / CAT- was applied on the corona-treated surface of the biaxially stretched lactic acid polymer film obtained in each of the examples and comparative examples.
10 (manufactured by Toyo Morton Co., Ltd.) at 2 g / m ² and then unstretched polypropylene film, 60 μm
(P1120, manufactured by Toyobo Co., Ltd.) was laminated by a dry lamination method to form a sealant layer to obtain a lactic acid-based polymer biaxially stretched film laminate. The dry and wet peel strengths were measured. The measurement conditions are the results of a 90 ° peel test at a tensile speed of 100 mm / min.

Examples 1 and 2 and Comparative Examples 1 and 2 Tin octylate 0.03 as a catalyst was added to 100 parts by weight of L-lactide.
A part by weight was charged into a reaction vessel, and the reaction was carried out at 190 ° C. for 1 hour in the reaction vessel. After the reaction was completed, the obtained reaction system was depressurized to distill off residual L-lactide. The intrinsic viscosity of the obtained polymer was 1.85 and the viscosity average molecular weight was 68600. The lubricant is L-lactide slurry and average particle system
1.8 μm aggregated silica particles (SYLYSIA 350 manufactured by Fuji Silysia Chemical Ltd.) were added in different amounts before the start of the L-lactide polymerization reaction.

The lactic acid-based polymer was vacuum-dried at 110 ° C. for 4 hours by a conventional method, then extruded from a T-die at 200 ° C., brought into close contact with a 16 ° C. casting drum by electrostatic charge, and rapidly solidified to obtain a cast film. . 2. The cast film was heated by a roll heated to 75 ° C., and then heated in the longitudinal direction.
After stretching 5 times, preheat to 60 ° C in a tenter and 70 ° C to 75 ° C
The film was stretched 3.8 times in the width direction while raising the temperature, heat-fixed at 155 ° C, further relaxed 5% in the width direction at 150 ° C, and subjected to transverse relaxation treatment to obtain a biaxially stretched lactic acid-based polymer film having a thickness of 12 µm. . Table 1 shows the characteristic values of these stretched films. Here, the longitudinal refractive index Nx after longitudinal stretching is 1.469.
Met. The films obtained in Examples 1 and 2 and Comparative Example 1 had good transparency, but the films obtained in Comparative Example 2 had poor transparency.

Example 3 A film was prepared in the same manner as in Example 1 except that the added lubricant was 0.10 parts by weight of spherical silica particles (AMT-silica # 100B manufactured by Mizusawa Chemical Industry Co., Ltd.), and the obtained results were obtained. Are shown in Table 1. The longitudinal refractive index Nx after the completion of the longitudinal stretching was 1.469. Further, the transparency of the obtained film was good.

Comparative Example 3 A film was prepared in the same manner as in Example 1 except that spherical silica particles (AMT-Silica # 500B manufactured by Mizusawa Chemical Industry Co., Ltd.) were added in an amount of 0.12 parts by weight as a lubricant. The results are shown in Table 1. The longitudinal refractive index Nx after longitudinal stretching is 1.469
Met. Further, the transparency of the obtained film was poor.

Comparative Example 4 A film was prepared in the same manner as in Example 1 except that the longitudinal stretching was performed at a temperature of 65 ° C. and a magnification of 3.5. The longitudinal refractive index Nx after the completion of the longitudinal stretching was 1.558. Further, the transparency of the obtained film was good. Comparative Example 5 As an added lubricant, silica particles having an average particle diameter of 7 nm (manufactured by Nippon Aerosil Co., Ltd., trade name Aerosil 300) were used as an inorganic lubricant, and Neutron S was used as an organic lubricant.
Except for using Nippon Seika Co., Ltd., a film was prepared in the same manner as in Example 1, and the obtained results are shown in Table 1. Comparative Example 6 A film was prepared in the same manner as in Comparative Example 5 except that the amount of the organic lubricant added was set to zero as the added lubricant, and the obtained results are shown in Table 1.

[0041]

[Table 1]

[0042]

According to the present invention, a biaxially stretched lactic acid-based polymer film having excellent handling properties, running properties, transparency and adhesiveness, and a lactic acid-based polymer suitable for packaging and the like, which is free from printing omission during printing. A biaxially stretched film can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 (72) Inventor Tadashi Okudaira 2-1-1 Katata, Otsu-shi, Shiga Toyobo Co., Ltd. In-house F-term (reference) 4F071 AA43 AD02 AD06 AE11 AF30Y AF52 AF53 AF58 AH04 BA01 BB06 BB08 BC01 BC14 BC16 4F210 AA24 AB07 AG01 QA02 QC05 QG01 QG18 QW07 4J002 BC012 BC022 BD152 BG012 CC032 CC162 CC192 CD002 DH046 DJ016 DJ036 DJ046 EG056 EG106 FD170 FD172 FD176 GG02 GJ01 GP03 GS01

Claims (4)

[Claims] (1) a main repeating unit represented by the general formula -O-CH
In a film made of a lactic acid-based polymer containing an aliphatic polyester as R-CO- (R represents H or an alkyl group having 1 to 3 carbon atoms) as a main component, at least one unit having a roughness on the center plane is used. Number of protrusions per area PCC
A biaxially stretched lactic acid-based polymer film having a value of not less than 600 / mm ^{2 and not} more than 2500 / mm ² and a three-dimensional surface roughness SRa of not less than 0.03 μm and not more than 0.07 μm. 2. The biaxially stretched lactic acid-based polymer film according to claim 1, wherein the haze is 8% or less. 3. The biaxially stretched lactic acid-based polymer film according to claim 1, wherein a lubricant having an average particle size of 0.5 μm or more and 5 μm or less is added in an amount of 0.02% by weight or more and 0.5% by weight or less. . 4. The biaxially stretched lactic acid polymer film according to claim 1, wherein the aliphatic polyester is polylactic acid.