JPS62233248A - Biaxial-oriented double layer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for multilayer films for high-speed automatic packaging, has good slip properties in a wide temperature range, has significantly improved suitability for packaging machines, and has excellent transparency. and a biaxially stretched multilayer film with good low-temperature heat sealability.

[Conventional technology]

Multilayer films, such as biaxially oriented polypropylene films with heat-sealing properties, are widely used for overlapping packaging of foods, cigarettes, cassette tapes, etc. due to their properties such as transparency and rigidity. With the recent development of high-speed automatic packaging machines, the quality required for films suitable for automatic packaging has become more sophisticated than ever before. The most important performance requirement is low-temperature heat sealability.

As a method for imparting low-temperature heat-sealing properties, a method is known in which a low-melting point substance is dissolved in an organic solvent and coated on a stretched film substrate.

However, although films made by coating methods can have low-temperature heat-sealing properties, their sealing strength is weak, it is difficult to completely eliminate the solvent used during coating, and the process is separate from the stretched film manufacturing process. However, since the coating is carried out using the same method, the manufacturing cost is relatively high. In order to avoid the high cost of such coating methods, resins that provide low-temperature heat-sealability when producing biaxially oriented polypropylene films, such as propylene-ethylene random copolymer resins and propylene-ethylene-butene- A method of laminating random copolymer resins such as 1 random copolymer resin has been developed, and furthermore, by adding a second component such as polybutene=1 to this laminated layer, low-temperature heat sealability has been significantly improved.

However, as the speed of automatic packaging machines has increased in recent years, the suitability of films for packaging machines has not been improved at the present time, and the performance of low-temperature heat-sealable resins is not fully utilized.

In other words, clogging occurs at the film delivery section due to poor antistatic performance or slipperiness, poor slippage between the film and the metal guide of a high-speed automatic packaging machine, and furthermore, slipperiness between the sealed portion and the metal immediately after heat sealing. It has drawbacks such as defects.

Therefore, at present, a biaxially oriented polypropylene film that has low-temperature heat-sealability suitable for high-speed automatic packaging and satisfies packaging suitability has not yet been developed.

[Problem that the invention seeks to solve]

The present invention has been made to overcome the drawbacks of the prior art, namely, to develop a film that has low-temperature heat-sealability and is suitable for high-speed automatic packaging.

[Means for solving problems]

That is, the present invention provides a biaxially oriented film characterized in that a layer of a composition consisting of the following components A and B is laminated on at least one side of a crystalline propylene polymer or a base material layer containing the same as a main component. Multilayer film A component: ethylene content 3-8
At least one resin selected from a propylene-ethylene random copolymer resin having a weight percent of propylene-ethylene random copolymer resin and a propylene-ethylene-butene-1 random copolymer resin having an ethylene-containing MO of 15 to 5 weight percent and a butene-1 content of 3 to 25 weight percent. 100 parts by weight Component B: 0.01 to 0.3 parts by weight of non-melting silicone resin powder with an average particle size of 0.5 to 7 microns.

[For production]

The crystalline propylene polymer used in the present invention is a homopolymer of propylene, a majority by weight of propylene and other α-
Random or block combinations with olefins (ethylene, butene, hexene, 4-methylpentene, octene, etc.), unsaturated carboxylic acids or their derivatives (acrylic acid, maleic anhydride, etc.), aromatic vinyl monomers (styrene, etc.) ,
It is a graft copolymer. Isotactic index (II) is 40 or more, especially 60 or more, especially 80
The above is good. Propylene homopolymer is the best, but in that case, those with an II of 90 or higher, especially 95 or higher, and especially 98 or higher, are recommended in terms of film stiffness, film disintegration properties, and suitability for high-speed automatic packaging. It is suitable for Melt flow rate I- (MFR) is 0.5-10g/
10 minutes, particularly preferably 1 to 5 g/10 minutes.

The base material layer of the film of the present invention may consist only of such a polymer, but it may also contain other heat-resistant polymers such as ethylene polymer, butene polymer, etc., in an amount that does not deteriorate its properties, for example, within a range of 30% by weight or less. It may also contain a plastic polymer. In addition, it is of course possible to contain additives such as stabilizers such as antioxidants and weathering agents, processing aids, colorants, antistatic agents, lubricants, and antiblocking agents. In particular, those containing an antistatic agent are preferred. Preferred antistatic agents include fatty acid esters of glycerin, alkylamines, ethylene oxide adducts of alkylamines, and fatty acid esters thereof. In a film that is not provided with good antistatic performance, static electricity may accumulate during film running, resulting in poor fall-off properties.

In the present invention, a layer consisting of the components A and B described above is laminated as a surface layer on one or both surfaces of the base layer.

One such propylene-ethylene-random copolymer resin as component A has an ethylene content of 3 to 8% by weight, preferably 4 to 6% by weight. Ethylene content is 3% by weight
If it is less than that, the heat sealability will be poor and the material will not be suitable for high-speed automatic packaging. On the other hand, the ethylene content is 8% by weight.
Although good heat-sealing properties can be imparted to polymers exceeding the above range, the stickiness and scratch resistance of the film are significantly reduced, and no improvement is expected even by the addition of component B, which will be described later. In addition, the MFR of this item is 0.5-50g
/10 minutes is preferred, especially 1 to 20 g/10 minutes, particularly 2 to 10 g/10 minutes.

Further, the propylene-ethylene-butene-1 random copolymer resin, which is the other component A that can be used in the present invention, has an ethylene content of 0.5 to 5% by weight, preferably 1 to 4% by weight, and a butene content of 0.5 to 5% by weight, preferably 1 to 4% by weight. -1 content of 3 to 25% by weight, preferably 5 to 20% by weight. If the ethylene content is less than 0.5% by weight or the butene-1 content is less than 3% by weight, the heat sealability will be poor and the material will not be suitable for high-speed automatic packaging. On the other hand, polymers with an ethylene content of more than 5% by weight or a butene-1 content of more than 25% by weight can provide good heat-sealing properties, but the film becomes sticky and has poor scratch resistance, which is also caused by the addition of component B, which will be described later. No improvement is expected. The MFR of this material is preferably 0.5 to 50 g/10 minutes, particularly preferably 1 to 20 g/10 minutes, particularly 2 to 10 g/10 minutes.

Furthermore, the non-melting silicone resin powder of component B used in the present invention is a silicone resin powder having a three-dimensional network structure due to siloxane bonds, and the organic groups bonded to silicon include methyl group and ethyl group. Examples include aliphatic hydrocarbon groups such as , aromatic hydrocarbon groups such as phenyl, and unsaturated hydrocarbon groups having vinyl groups. Among them, methyl group is preferred. In addition, various modified silicone resin powders can also be used as long as they do not impair the effects of the present invention.

Silicone resin is generally available as a silicone varnish made by dissolving initial fasteners in a suitable solvent, but the silicone resin used in the present invention has an average particle size of 0.5 to 7 microns without solvent. (μ) in powder form,
It is a substantially insoluble and infusible substance that has been cured by heat.

In addition, the shape of the silicone resin powder used in the present invention is such that the sphericity f expressed by the following formula (11) is 0.8 or more, particularly, the sphericity is 0.85 or more, and the average particle size is 1 to 5μ.
Preferably, it falls within this range.

"=A/(π/4)/Dmax
(11 (where A is the cross-sectional area of the polymer powder 111
12. Dmax is the longest diameter l of the same cross section. ) The sphericity of silicone resin powder is determined by the following method. That is, the powder is placed on an electron microscope grid covered with a collodion support film, and observed and photographed at an appropriate magnification. The obtained photograph is processed with an image analyzer, and the sphericity f is determined using the above formula (1).

The value of sphericity given by this formula ranges from O to 1, with 1 being a perfect sphere. Sphericity particularly affects slipperiness.

If the average particle size of the silicone resin powder exceeds 7 μm, the transparency of the film will deteriorate, and if it is less than 0.5 μm, the effect of improving slipperiness will be reduced.

This special silicone resin powder can be appropriately selected from commercially available products.

The amount of component B added to 100 parts by weight of component A is 0.01 to 0.3 parts by weight, especially 0.02 to 0.25 parts by weight.
Parts by weight are preferred. If the amount of component B added is less than 0.01 part by weight, the effect of improving suitability for high-speed automatic packaging will be low, and if the amount added exceeds 0.3 part by weight, the original property of the biaxially stretched film, transparency, will be impaired. In addition, low-temperature heat sealability also deteriorates.

In addition to these essential components, additional components may be added to the surface layer of the film of the present invention. For example, 5 to 45 parts by weight of crystalline butene-1 polymer may be added to 100 parts by weight of component A. When added, low-temperature heat sealability can be further improved. Crystalline butene-1 polymers include butene-1 homopolymers as well as copolymers of butene-1 and other α-olefins, such as ethylene and propylene, whose melt flow rate is , 180
From the viewpoint of transparency, it is preferable that the melt flow rate be equal to or greater than the melt flow rate of component A at the same temperature in the range of 300°C to 300°C.

The surface NMi composition of the film of the present invention is generally prepared by mixing the above A and B components in a mixer such as a Henschel mixer, a blender, or a ribbon blender, and then kneading them in a kneader such as an extruder. It is true. At this time, a masterbatch may be prepared by blending component B in a larger amount than a predetermined amount, and this masterbatch may be used while being diluted with component A during molding. Note that it is also possible to adopt a method in which a mixture of components A and B is melted for the first time in the molding stage to form a composition.

Moreover, in this composition, it is preferable to mix 0.05 to 0.6 parts by weight of a nucleating agent with respect to 100 parts by weight of the component A. Preferred nucleating agents include sorbitol derivatives;
Specifically, 1.3,2.4-dibenzylidene-〇-sorbitol, 1.3,2.4-di-p-methyl-dibenzylidene-D-sorbitol, 1.3.2.4-dibenzylidene-D-sorbitol, -p
-Ethyl-dibenzylidene-D-sorbitol and the like. When these nucleating agents are added, the surface layer composition melted during heat sealing can be crystallized within a short time, so that the mechanical suitability after packaging is further improved. Furthermore, the transparency of the film is also improved.

If the amount of the sorbitol derivative added is less than 0.05 parts by weight, there is no effect of improving mechanical suitability, while if it exceeds 0.6 parts by weight, heat sealability is inhibited, which is not preferable.

The surface layer composition of the present invention may also contain various additives such as antioxidants, stabilizers, processing aids, colorants, antistatic agents, lubricants, and anti-fluffing agents in amounts that do not reduce its properties. It does not matter if it is contained.

A method for laminating this surface layer composition on the propylene polymer base layer described above is, for example, by melting and coextruding the composition on one or both sides of the propylene polymer resin of the base layer to form a sheet. The method of biaxially stretching this is
This composition is preferred because it can be easily and uniformly and thinly laminated, but a method of melt-extruding and coating the composition on an unstretched or uniaxially stretched base layer sheet can also be adopted.

Of the biaxial stretching, longitudinal stretching is first performed using the difference in peripheral speed of the rolls. That is, 90-140°C, preferably 105-1
Stretched 3 to 8 times, preferably 4 to 6 times, at 35°C, and then
It is then stretched transversely in a tenter oven by a factor of 3 to 12 times, preferably 6 to 11 times. In order to prevent heat shrinkage during heat sealing, it is desirable to heat set at 120 to 170° C. following lateral stretching.

Furthermore, corona treatment may be performed for the purpose of promoting printability and bleeding of the antistatic agent.

The thickness of the multilayer biaxially stretched film obtained in this manner is determined depending on its use, but is usually in the range of 5 to 100μ, preferably 10 to 40μ.

The thickness of the surface layer composition is preferably 0.3 to 2 microns, preferably 0.5 to 1.5 microns. When the thickness exceeds 2μ, the effect of improving mechanical aptitude is small. [Example] The evaluation method is as follows.

(1) Haze Measured using four films stacked in accordance with ASTM-D-1003.

(2) Slip property Measured according to the static friction coefficient measurement method of ASTM-D-1894. The slip property between films at high temperatures was measured using a slip tester equipped with a heater so that the film could be set at a predetermined temperature. The slip property with metal was measured by measuring the slip property of a Teflon-coated iron plate and a film.

(3) Heat sealing properties Using a heat sealing bar of 5w x 200ml and 1m, a 20mm wide sample was cut from the sample sealed under the heat sealing conditions of 1kg/am” heat sealing pressure and 0.5 seconds heat sealing time at each set temperature. , using a Schopper type testing machine, the specimen was pulled apart at a tensile speed of 500 m/min, and the maximum load was read.

(4) Melt flow rate 230°C, 2, 16 in accordance with ASTM-D-1238
It was measured using a kg load.

(5) After setting the film in a packaging machine, the film was cut with a cutter. At this time, the extent to which the film fell vertically without contacting the packaging machine was visually observed and evaluated.

(6) Resistance to metal slippage in a packaging machine After packaging was completed, the film at the heat-sealed portion was observed and the degree of shrinkage was evaluated.

(7) Appearance of packaging After packaging was completed, the cigarettes were evaluated in comparison with commercially available cigarettes wrapped in cellophane.

Examples 1 to 3 As a base material layer, VFR2.3g/10min and ll98.
100 parts by weight of 5% polypropylene, 0.6 parts by weight of glycerin monostearate, 0.1 parts by weight of N,N'bis(2-μ droxyethyl)alkylamine, and 0.3 parts by weight of fatty acid ester of polyoxyethylene alkylamine. A mixture of polypropylene was used. In addition, the surface layer has an ethylene content of 1.7% by weight and a butene-1 content of 12% by weight.
To 100 parts by weight of ethylene-propylene-butene-1 random copolymer with 5% by weight and MFR 6, Og/10 minutes,
Non-melting silicone resin powder having an average particle size of 2 μm and a sphericity of 0.989 was added in the proportions shown in Table 1.

In addition, as an antioxidant, 2,6-di-t-butyl-p
- 0.10 parts by weight of cresol and 0.05 parts by weight of calcium stearate as a hydrochloric acid catching agent were added, and after mixing, the mixture was pelletized. These compositions were laminated under the following conditions and sequentially biaxially stretched to obtain a biaxially stretched polypropylene multilayer film.

The base layer polypropylene and the surface layer composition were extruded using a three-layer die from an extruder with a diameter of 115mm and a diameter of 35mm, respectively, to form a three-layer structure of surface layer composition/polypropylene/surface layer composition. Sheets were formed by melt coextrusion at °C. Subsequently, the film was stretched 5 times in the longitudinal direction at 115° C. using the difference in peripheral speed of the rolls. Next, after stretching 10 times in the transverse direction in a tenter oven at 168°C, heat setting at 155°C,
Subsequently, one side of the film was subjected to corona discharge treatment to obtain a biaxially stretched multilayer film. Thickness configuration is 0.5μ/2
It was 2μ10.5μ.

The transparency, slip properties and heat seal properties of these films were measured.

Comparative Examples 1 to 2 Silica (manufactured by Fuji Davison Co., Ltd. Thyroid 244) was added in the proportions shown in Table 1 to obtain biaxially stretched composite films similar to Examples 1 to 3. This was similarly evaluated.

These results are shown in Table 1.

(Leaving space below) Example 4 g As a base layer, 100 parts by weight of MFRl, 9I/10min and 119% polypropylene, 0.5 parts by weight of glycerin monostearate, N,N'bis(2-hydroxyethyl)alkyl 0.1 ffi part of amine, 0.4 part by weight of fatty acid ester of polyoxyethylene alkylamine,
Polypropylene mixed with 0.04 parts by weight of erucic acid amide and 0.03 parts by weight of stearic acid amide was used.

In addition, as a surface layer, an ethylene-propylene-butene-1 random copolymer 8 with an ethylene content of 1.7% by weight, a butene-1 content of 12.5% by weight, and an MFR of 4.0 g/10 min.
0 parts by weight, ethylene content 1.0% by weight and MFRl 2
, 20 parts by weight of ethylene-butene-1 random copolymer of 0 g/10 min, average particle size 2 μ and sphericity 0.89.
0.10 parts by weight of the non-melting silicone resin powder of No. 8, 0.10 parts by weight of 2.6-di-t-butyl-p-cresol as an antioxidant, 0.05 parts by weight of calcium stearate as a hydrochloric acid catching agent, and a nucleating agent. As 1, 3, 2.
0.30 parts by weight of 4-di-p-ethyl-dibenzylidene-D-sorbitol was added, mixed, and pelletized. These compositions were molded in the same manner as in Example 1 to obtain biaxially stretched multilayer films.

The thickness configuration was 0.5μ/24μ10.5μ.

Using this film, cigarette packaging (Mild Seven) was carried out using a W-322 high-speed automatic packaging machine manufactured by Tokyo Automatic Machinery.

Example 5 The concentration of the non-melting silicone resin powder used in the surface layer of Example 4 was 0.15 parts by weight, and 1 was used as a nucleating agent.
, 3,2.4-di-p-ethyl-dibenzylidene-D-
Packaging was carried out in the same manner as in Example 4 except that sorbitol was not added.

Comparative Example 3 Packaging was carried out in the same manner as in Example 4, except that the non-melting silicone resin powder used in the surface layer of Example 4 was changed to 0.20 parts by weight of silica.

Comparative Example 4 The base material layer used in Example 5 was changed to a propylene-ethylene random copolymer with an MFR of 2.3 g/10 min and an ethylene content of 1.0 ft% by weight, and the non-melting silicone resin powder was replaced with a silica 0.5 g/10 min propylene-ethylene random copolymer. Packaging was carried out in the same manner as in Example 5 except that the amount was changed to 3 parts by weight.

These evaluation results are shown in Table 2.

(The following is a blank space) [Effects of the invention] As is clear from Tables 1 and 2, the film of the present invention has the following properties:
It can be seen that it has excellent transparency and low-temperature heat sealability, and has good suitability for high-speed automatic packaging.

Claims (1)

[Scope of Claims] 1. A biaxial polymer comprising a crystalline propylene polymer or a base material layer containing the same as a main component, and a layer of a composition consisting of the following components A and B laminated on at least one side of the base material layer. Stretched multilayer film. Component A: propylene-ethylene random copolymer resin with an ethylene content of 3 to 8% by weight and an ethylene content of 0.5 to 8% by weight
100 parts by weight of at least one resin selected from propylene-ethylene-butene-1 random copolymer resins having a butene-1 content of 5% by weight and a butene-1 content of 3 to 25% by weight Component B: average particle size of 0.5 to 7 microns 0.01 to 0.3 parts by weight of non-melting silicone resin powder2, the thickness of the composition layer consisting of components A and B is 0.3 to 0.3 parts by weight
2. The film of claim 1, which has a diameter of 2 microns. 3. Claim 1, wherein the non-melting silicone resin powder has a sphericity f expressed by the following formula (1) of 0.8 or more.
Or the film described in item 2. f=√[A/(π/4)]/Dmax(1) (where,
A is the cross-sectional area of the polymer powder mm^2, and Dmax is the longest diameter mm of the same cross-section. 4. The film according to any one of claims 1 to 3, wherein the non-melting silicone resin powder has an average particle size of 1 to 5 microns.