JP5236145B2 - Antistatic polypropylene film - Google Patents

Description

  The present invention relates to an antistatic polypropylene film having stable antistatic performance.

  Polyolefin films are widely used as packaging materials because they are inexpensive, such as good processability, excellent mechanical strength, transparency, secondary processability such as bag-making property, moisture resistance, and the like. However, since it has characteristics that are very easily charged with static electricity, there are problems such as adhesion of dust and the like, electric shock to workers, and scattering of ink during printing.

  As one of the methods for solving the above problems, an appropriate low molecular weight surfactant is added to the polyolefin film, and these surfactants are bleed on the surface of the polyolefin film. The method of imparting has been used.

  However, such a migration type antistatic agent mainly has the problems shown in (1) to (5). (1) Appearance defects (whitening phenomenon) occur due to excessive bleeding on the film surface. (2) The antistatic property tends to be poor under low humidity (it is easily influenced by humidity). (3) The bleed amount on the film surface is likely to fluctuate depending on the film forming state (conditions) (antistatic performance is difficult to stabilize). (4) The antistatic effect is reduced by wiping with water or an organic solvent. (5) Due to the low molecular weight existing on the film surface, the transferability / adhesiveness of ink, coat, etc. is hindered.

  As a means for solving the above-described problems, a high molecular weight antistatic agent is being studied in place of the low molecular weight surfactant. For example, a polyolefin film in which an antistatic resin layer made of a mixture of a polypropylene resin, a specific aromatic ring-containing polyetheresteramide and a polyamide resin, and a specific modified low molecular weight polypropylene is laminated on the surface of the polyolefin film has been proposed. (See Patent Document 1).

In addition, a block polymer having a structure in which a block of polyolefin (a) and a block of hydrophilic polymer (b) having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm are bonded alternately and repeatedly ( It is characterized by comprising a layer (X) having a thickness of 0.1 to 50 μm comprising an antistatic resin composition comprising A) and a polyolefin resin (B) as essential components, and a base layer (Y) comprising a thermoplastic resin. A multilayer film is also proposed (see Patent Document 2).

  However, in the polyolefin film using the antistatic resin layer of Patent Document 1, the compatibility between the polyolefin resin and the antistatic resin composition is insufficient. As a result, a film in which a polyolefin resin and a melt-kneaded antistatic agent resin composition are laminated conflicts with the original purpose of roll contamination during processing, poor appearance, and unstable antistatic performance due to molding conditions. It contained a defect.

Similarly, even in the polyolefin film using the antistatic resin layer of the above-mentioned Patent Document 2, it is pointed out that the antistatic agent has poor appearance and poor antistatic properties due to poor compatibility and rollability of the antistatic agent with polyolefin. Is done. In particular, defects such as the appearance of cloudy spots (see FIG. 1) and clouding of the entire surface (see FIG. 2) are observed. In both figures, the shaded area corresponds to the cloudy area.
JP-A-11-170456 JP 2002-321314 A

  The present invention has been made in view of the above points, exhibits stable antistatic properties even under low humidity, and no deterioration in antistatic properties is observed even after wiping with water or an organic solvent, Further, the present invention provides an antistatic polypropylene film as a polyolefin film having an antistatic property which is excellent in transparency and free from defects in appearance, while eliminating processing problems such as smoke generation and roll dirt during processing.

That is, according to the invention of claim 1, the hydrophilic polymer (a) and the modified polyolefin (b), a copolymer consisting of body volume resistivity of ^{1 × 10 5 ~1 × 10 11} Ω · cm der Risan modified The difference in melting point between the permanent antistatic agent (A), which is a polyolefin polyether block polymer, and the permanent antistatic agent (A) is within ± 20 ° C., and the MFR at 230 ° C. and 21.18 N is 2 to 20 g. An antistatic resin composition (X) composed of a polypropylene resin (B) for 10 minutes is laminated on the outermost layer of a base layer composed of a polypropylene resin (Y) and stretched in at least one direction. The weight ratio of the permanent antistatic agent (A) to the polypropylene resin (B) in the inhibitor resin composition (X) satisfies A: B = 5: 95 to 50:50, and the antistatic resin composition (X) Thickness according to the antistatic polypropylene film, characterized in that at 0.5μm or more.

The invention according to claim 2 relates to the antistatic polypropylene film according to claim 1 , wherein the haze is 5% or less as measured by JIS-K-7105.

  The antistatic polypropylene film of the present invention exhibits stable antistatic properties even under low humidity, and no deterioration of antistatic properties is observed even after wiping with water or an organic solvent. Further, processing problems such as smoke generation and roll contamination during processing are solved. Furthermore, it was excellent in transparency and the appearance defect (white turbidity) seen in the conventional film was improved. In addition, suitable properties are shown for printing with water-based inks.

  In the antistatic polypropylene film of the present invention, as defined in claim 1, the antistatic agent resin composition (X) is laminated on the outermost layer of the base layer made of the polypropylene resin (Y) and stretched in at least one direction ( A film obtained by uniaxial stretching) or biaxial stretching. This antistatic resin composition (X) is a melt kneading of a permanent antistatic agent (A) comprising a copolymer of a hydrophilic polymer (a) and a modified polyolefin (b) with a polypropylene resin (B), etc. Obtained by.

  That is, {antistatic polypropylene film of the present invention = antistatic resin composition (X) + polypropylene resin (Y)}, {antistatic resin composition (X) = permanent antistatic agent (A) + polypropylene resin (B)}, {permanent antistatic agent (A) = hydrophilic polymer (a) + modified polyolefin (b)}.

  The hydrophilic polymer (a) composing the permanent antistatic agent (A) is preferably generally called a polyether, such as polyether diol, polyether diamine, polyether ester amide, polyether amide imide, polyether urethane. , Polyether esters, polyether amides and modified products thereof.

  The modified polyolefin (b) composing the permanent antistatic agent (A) is a suitable polyolefin, in which a carbonyl group, a carboxyl group, an amino group, a hydroxyl group, etc. are introduced as a modifying group, and these are contained at least at one end. Polyolefin. Preferably, a carboxyl group-modified polyolefin is used.

The aforementioned hydrophilic polymer (a) and modified polyolefin (b) are suitably copolymerized to form the permanent antistatic agent (A). The permanent antistatic agent (A) has a volume specific resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm, whereby an antistatic agent resin composition (X) having a suitable surface specific resistivity is obtained. It is desirable because it is obtained.

Accordingly , in the permanent antistatic agent (A), an acid-modified polyolefin polyether block polymer is used in view of compatibility, rollability, antistatic performance and the like.

As this acid-modified polyolefin polyether block polymer, for example, Sanyo Kasei Kogyo Co., Ltd .: Pelestat OP300 (volume resistivity: 2 × 10 ⁷ Ω · cm), Toho Chemical Co., Ltd .: Anstex FT-P348 ( An acid-modified polypropylene polyether block polymer such as a volume resistivity: 8 × 10 ⁸ Ω · cm) is selected. Examples of the acid-modified polyolefin polyether block polymer include acid-modified polyethylene polyether block polymers.

  Examples of the polypropylene resin (B) include polypropylene homopolymers, copolymers of polypropylene and α-olefins such as ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and the like. And the like. Examples of the monomer other than the α-olefin copolymerizable with the α-olefin include vinyl acetate, maleic acid, vinyl alcohol, methacrylic acid, methyl methacrylate, and ethyl methacrylate.

  The polypropylene resin (Y) used as the base layer of the antistatic polypropylene film of the present invention is selected from the same resin composition as the polypropylene resin (B). The polypropylene resin (Y) can be a single layer film or a resin film in which the same or different resins are combined and laminated.

  In the above resin, the polypropylene resin (B) used in the present invention has a melting point difference within ± 20 ° C. from the permanent antistatic agent (A) and 230 ° C. · 21.18 N (230 ° C. · 2. 16kgf) (based on JIS-K-7210, ASTM-D-1238) MRF (melt flow rate) is 2 to 20 g / 10 min, more preferably MRF at 230 ° C. and 21.18 N is 5 to 10 g / 10 The resin that is the minute is selected.

  That is, the compatibility of the polypropylene resin (B) with the permanent antistatic agent (A) is improved by being regulated within the range of the melting point difference and MFR. For this reason, an excellent anti-static polypropylene film having good anti-static performance that ensures good rollability and has no defects in appearance can be obtained. Examples of the polypropylene resin (B) include Exelen SP89E3 manufactured by Sumitomo Chemical Co., Ltd., Novatec PP FX4E manufactured by Nippon Polypro Co., Ltd., Novatec PP FG3DE manufactured by The Company, Novatec PP CF1199 manufactured by The Company.

  The weight ratio of the composition of the permanent antistatic agent (A) composing the antistatic agent resin composition (X) to the polypropylene resin (B) is as follows: A: B = The weight ratio is 5:95 to 50:50, more preferably 10:90 to 30:70. When the weight ratio of the permanent antistatic agent (A) is 5 parts by weight or less in the antistatic agent resin composition (X), the antistatic performance is not exhibited. Further, when the weight ratio of the permanent antistatic agent (A) is 50 parts by weight or more in the antistatic agent resin composition (X), poor appearance occurs due to a decrease in compatibility with the polypropylene resin (B). Therefore, it is desirable to use the above weight ratio.

  Here, the kneading of the permanent antistatic agent (A) and the polypropylene resin (B) will be described. The permanent antistatic agent (A) and the polypropylene resin (B) are dry blended by a known mixer (such as a tumbler or a Henschel mixer) in units of parts by weight of the above-mentioned predetermined blending ratio. The mixture is melt kneaded by a kneader such as a pressure kneader. In this kneader, a twin screw extruder is preferably used in order to make the permanent antistatic agent (A) more finely dispersed.

  Furthermore, production of the antistatic polypropylene film of the present invention will be described. In stretching the film, a tenter method, a tubular method, a roll stretching method or the like is used. As a biaxial stretching method, for example, a layer made of an antistatic resin composition (X) and a base layer made of a polypropylene resin (Y) are coextruded from a T die to produce a sheet-like material. This is a method in which this sheet-like material is stretched in the longitudinal direction due to the difference in peripheral speed of the rolls, and then stretched in the transverse direction by a tenter (sequential stretching). Or it is the method of extending | stretching longitudinally and laterally simultaneously (simultaneous stretching) with a tenter. Of course, it is not limited to these stretching methods, and a stretching method and a stretching apparatus are suitably selected according to workability and resin characteristics.

  As described above, the antistatic polypropylene film of the present invention is a film in which the antistatic agent resin composition (X) is laminated on the outermost layer of the polypropylene resin (Y) as the base layer. The layer thickness of the antistatic agent resin composition (X) is preferably 0.5 μm or more, particularly 1 μm or more. As will be apparent from the examples described later, the above-mentioned layer thickness is suitable in consideration of the development of sufficient antistatic performance.

  Moreover, the antistatic agent resin composition (X) may be laminated on both surfaces of the outermost layer of the polypropylene resin (Y) as a base layer, and is laminated on only one surface side of the outermost layer of the polypropylene resin (Y). It is also good. Thus, by controlling the lamination surface of the antistatic agent resin composition (X), it is possible to provide an antistatic polypropylene film having antistatic performance corresponding to the production efficiency and the purpose of use. When the antistatic agent resin composition (X) is laminated on both surfaces of the base layer of the polypropylene resin (Y), the antistatic agent resin composition (X) on each surface can be the same or different from each other. It is.

As defined in claim 2 , the antistatic polypropylene film obtained on the basis of each composition and blending ratio has a haze of 5% or less, preferably 3% or less, as measured by JIS-K-7105. It is desirable to be. This is because when the haze is 5% or more, the transparency of the film is inferior and the commercial value is lowered.

  The antistatic polypropylene film of the present invention includes various additives and fillers used for ordinary polyolefin films, including antioxidants, lubricants, colorants, and UV absorbers, as long as the object of the invention is not impaired. Can be appropriately added as an additional component. Further, for the purpose of further improving the antistatic performance, a metal salt composed of a halide of an alkali metal or an alkaline earth metal may be added.

  Furthermore, according to the antistatic polypropylene film of the present invention, there is no change in the antistatic performance due to the presence or absence of surface treatment. Therefore, when printing on the antistatic polypropylene film, prior to printing, the film surface is activated by corona discharge treatment, flame treatment, plasma treatment, etc. Can be improved. For this reason, it is desirable to perform the surface activation treatment by any of the methods described above.

  The antistatic polypropylene film of the present invention in which the surface on which the antistatic agent resin composition (X) is laminated is subjected to activation treatment is printed with water-based ink on the laminated surface of the antistatic agent resin composition. If it is water-based ink printing, the kind of ink and the printing method are not particularly limited. In addition to water being used as the solvent for the water-based ink, alcohols, preferably lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, etc. may be used in combination, and there is no particular limitation on these.

  Also, general inorganic and organic pigments can be used as the colorant. For example, soluble and insoluble organic pigments such as azo, phthalocyanine, and naphthol, and inorganic pigments such as titanium oxide, calcium carbonate, petal, and carbon black. Is mentioned. In addition, as a resin binder for water-based inks, water-soluble or water-dispersible resins such as styrene-acrylic acid-based, styrene-maleic acid-based acrylic resins, polyurethane-based resins, rosin-modified resins, and the like can be used. It can be used as long as it can be produced, and can be used alone or in combination. As other additives, waxes, antifoaming agents, dispersing agents and the like may be used. A diluent using water / alcohols in combination may be used to adjust the viscosity of the ink during printing. Examples of the printing method include gravure printing, flexographic printing, offset printing, and ink jet printing.

  The antistatic polypropylene film of the present invention thus obtained can be used alone by being laminated with packaging materials, packaging materials for electronic parts, tape materials, paper, non-woven fabric, cellophane and the like. It is. In addition, it can be used as a label on another plastic resin molded article.

[Preparation of Antistatic Agent Resin Composition]
In preparing the antistatic agent resin composition, permanent antistatic agents and polyolefin resins shown in the following table were used. In the table, A-1, A-2 are acid-modified polypropylene polyether copolymer-based permanent antistatic agents, A-3 is a polyetheresteramide-based permanent antistatic agent, A-4 is a low molecular weight type antistatic agent, B -1 to B-5, B-7, and B-8 are polypropylene resins, and B-6 is a polyethylene resin. The special order products in the table are consigned manufactured products.

  In Example 1, the tumbler is such that the permanent antistatic agent (A-1) and the polypropylene resin (B-1) satisfy the blending ratio of (A-1) :( B-1) = 10: 90 by weight. Dry blended with (tumble mixer). Subsequently, after melt-kneading with a twin-screw extruder, extruded into a strand shape, cooled, cut into an arbitrary size and pelletized to obtain an antistatic resin composition (X-1) of Example 1.

[Prototype of polyolefin film]
The antistatic resin composition (X-1) and a homopolypropylene having a MFR of 3.0 g / 10 min and a crystallinity of 97% ((B-7) in Table 2) as a base layer (Y) were coextruded from a T-die. The thickness of the base layer (Y) is set to 20 μm by a tenter method biaxial stretching machine (manufactured by Mitsubishi Heavy Industries, Ltd.), and an antistatic agent resin composition layer (X-1) having a thickness of 1 μm is formed on one side thereof. An antistatic polypropylene film (Example 1) was obtained. Further, the antistatic agent resin composition (X-1) surface of the antistatic polypropylene film is subjected to corona discharge treatment (8.0 W) so that the wetting test (JIS-K-6768) has an index of 40 mN / m. Min / m ² )

  Subsequently, Examples 2 to 8 and Comparative Examples 1 to 8 were also prepared and prototyped by the same method as in Example 1 based on the blending ratios in Table 3 (Example) and Table 4 (Comparative Example) below. . Comparative Example 7 was produced in the same manner as in the other examples except that the layer thickness of the antistatic agent resin composition layer was 0.2 μm. In Comparative Example 9, 1.0% by weight of a low molecular weight type antistatic agent (A-4) was dry blended with polypropylene resin (B-3) and pelletized in the same manner as in Example 1 to obtain an antistatic agent resin composition. It was. Subsequently, this antistatic agent resin composition was extruded by a T-die to obtain an antistatic polypropylene film having a thickness of 20 μm. In addition, since the comparative example 2 used the polyethylene resin of B-6 for the base layer, it becomes an antistatic polyethylene film. In both Examples and Comparative Examples, corona discharge treatment was performed in the same manner as in Example 1 described above.

  For each of the obtained samples (Examples 1 to 8 and Comparative Examples 1 to 9), the film forming state, the appearance of the film, the surface specific resistivity, and the water-based ink printing characteristics were evaluated and measured. Comprehensive evaluation. Details of the evaluation and measurement methods are shown below.

[Film formation status]
Regarding smoke generation, the smoke generation state from the extruder part, the tenter outlet part, and the exhaust port of the film forming machine was visually observed. In the evaluation, “o” indicates that no smoke is generated, “Δ” indicates that smoke is slightly generated, and “x” indicates a cloudy white cloudy part around the film forming machine.

  About roll dirt, the roll (especially extending | stretching roll) which an antistatic agent resin composition touches was confirmed visually, and the presence or absence of the deposit | attachment to a roll was evaluated. In the evaluation, “o” indicates that there is no contamination, “Δ” indicates that the deposit was generated in 12 hours from the start of film formation, and “x” indicates that the deposit was generated in 10 minutes after the start of film formation.

[Appearance of film]
The haze was measured according to JIS-K-7105, and the haze per film was measured using a digital turbidimeter (Nippon Denshoku Industries Co., Ltd .: NDH-20D). The unit is (%).

  For the measurement of LSI, the transparency per film was measured using a visual transparency tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The unit is (%). Incidentally, LSI is an improved index for discrepancy between visual perception and haze. The LS value indicates diffuse transmitted light at a narrow angle, and indicates a value closer to the degree of cloudiness felt by human eyes than haze.

  Appearance defects were observed visually on the surface of the film on which the antistatic agent resin composition was laminated. Samples that were transparent over the entire surface were marked with “◯”. A sample in which white spots are scattered as shown in FIG. Furthermore, as shown in FIG.

[Surface resistivity]
The surface resistivity is in accordance with JIS-K-6911, using a high resistivity-resistivity meter (MCP-HT260, manufactured by Mitsubishi Yuka Co., Ltd.), and the surface resistivity (Ω) under the following conditions: It was measured.

  The measurement immediately after film formation refers to an atmosphere of 23 ° C. and 50% RH (hereinafter, the indicated humidity is relative humidity) for each sample film formed from the above-mentioned tenter method biaxial stretching machine. The surface resistivity of the surface on which the antistatic agent resin composition was laminated was measured.

  In the measurement after standing for 1 day, the film of each sample formed was aged in an atmosphere of 35 ° C. and 60% RH for 24 hours, and then measured in an atmosphere of 23 ° C. and 50% RH.

  In measurement after washing with water, commercially available nylon in which neutral detergent for tableware (Lion Corporation: Mama Lemon) was impregnated on the surface of the film formed of each sample on which the antistatic resin composition was laminated. Rinse 20 times with a sponge and rinse thoroughly with distilled water. After drying at 80 ° C. for 3 hours, the mixture was allowed to stand for 24 hours in an atmosphere of 23 ° C. and 50% RH, and then measured in an atmosphere of 23 ° C. and 50% RH.

  In the measurement after solvent wiping, the surface of the film formed of each sample was wiped off by rubbing 20 times using a nonwoven fabric soaked with toluene on the surface on which the antistatic agent resin composition was laminated, and 23 ° C. , After natural drying in a 50% RH atmosphere, measurement was performed in the same atmosphere.

  In addition, the film of each sample formed was aged in an atmosphere of 35 ° C. and 60% RH for 24 hours, and then measured in an atmosphere of 23 ° C. and 15% RH.

[Water-based ink printability]
Toyo Ink Mfg. Co., Ltd. “JW224 Aque Ecole Black” was used as the water-based ink, and this was diluted with a dedicated diluent solvent to prepare a solid content concentration of 30% by weight and an alcohol content concentration of 10%. The obtained water-based ink was printed by a gravure printing machine on the surface of each sample (Examples 1 to 8, Comparative Examples 1 to 9) on which the antistatic agent resin composition was laminated.

  The surface of the sample on which water-based ink printing was performed in this way was observed with an optical microscope (magnification 75 times), and the ink transfer state and the ink repellency of each sample were evaluated. In the evaluation, “o” was given when ink repelling was not observed at all and halftone dot reproducibility was good. A case where a large number of fine repellencies were observed and halftone dots were observed was designated as “Δ”. A large repellency was observed throughout and almost no halftone dots were given as “x”.

  From the results of evaluation and measurement on the samples of Examples 1 to 8 and Comparative Examples 1 to 9, the difference in melting point between the permanent antistatic agent (A) and the polypropylene resin (B) is ± 20 ° C., and the polypropylene resin (B ) Satisfying MRF of 2 to 20 g / 10 minutes, more preferably 5 to 10 g / 10 minutes, and furthermore, a compositional weight ratio between the permanent antistatic agent (A) and the polypropylene resin (B), A: B = 5: 95 to 50:50 weight ratio, more preferably 10:90 to 30:70 weight ratio of the antistatic polypropylene films of the examples are all better than the comparative examples in terms of index. Results were obtained. In addition, good antistatic performance was confirmed even under low humidity (20 ° C., 15% RH).

It is a schematic diagram showing the defect of the surface of the conventional antistatic film. It is another schematic diagram showing the defect on the surface of the conventional antistatic film.

Claims (2)

Permanent charging hydrophilic polymer (a) and the modified polyolefin (b) comprising a copolymer of the specific volume resistivity of ^{1 × 10 5 ~1 × 10 11} Ω · cm der Risan modified polyolefin polyether block polymers Polypropylene resin (B) having a melting point difference between the inhibitor (A) and the permanent antistatic agent (A) within ± 20 ° C. and an MFR at 230 ° C. and 21.18 N of 2 to 20 g / 10 min. An antistatic agent resin composition (X) consisting of the above and a laminate of the outermost layer of the base layer made of polypropylene resin (Y) and extending in at least one direction,
A weight ratio of the permanent antistatic agent (A) to the polypropylene resin (B) in the antistatic agent resin composition (X) satisfies A: B = 5: 95 to 50:50, and the antistatic agent resin An antistatic polypropylene film, wherein the layer thickness of the composition (X) is 0.5 μm or more. The antistatic polypropylene film according to claim 1 , wherein the haze is 5% or less as measured by JIS-K-7105.

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