JPS6150974B2 - - Google Patents

Description

[Detailed description of the invention]

[] BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to a resin composition with excellent low-temperature heat sealability. More specifically, the present invention provides:
This invention relates to a resin composition having a specific composition in which crystalline polybutene-1 is blended with an olefin-butene-1 copolymer having a specific composition. Due to the low-temperature heat-sealing properties of this resin composition, a composite biaxially oriented polypropylene film formed by laminating this resin composition on at least one side is particularly useful for overlap packaging. Biaxially oriented polypropylene films imparted with heat-sealing properties are widely used in the packaging field due to the various properties that biaxially oriented polypropylene films have, such as transparency, rigidity, strength, and moisture resistance. Among biaxially oriented polypropylene films that have been heat-sealable by various methods, films that have low-temperature heat-sealability on both sides are particularly used in the field of overlap packaging (outer packaging). Overlap packaging films are mainly used for overlapping products packed in paper boxes, such as cigarettes, pharmaceuticals, soaps, caramels, etc. Overwrap packaging is generally performed on high-speed automatic packaging machines at a rate of 200 to 400 pieces per minute, so a high degree of automatic packaging suitability is required. That is, the first performance required for automatic overlap packaging is low temperature heat sealability. As mentioned above, since the weight of the packaged item is generally less than 100g, heat sealing strength is not so required.
It is necessary to have a heat seal strength of 100g/2cm width or more from around ℃. The second required performance is that the film must have rigidity, strength, slipperiness, and antistatic properties to prevent it from bending or breaking during feeding, since the film is sent to a packaging machine at high speed for packaging. It is. In addition to the above-mentioned suitability for automatic packaging, overwrap packaging films need to have transparency to make products look beautiful, and moisture-proof properties to protect products. Prior Art One method for imparting low-temperature heat-sealability to a biaxially oriented polypropylene film for use in such overlap fields is to apply a heat-sealability imparting agent to a biaxially oriented polypropylene film that has just been processed and formed. A so-called coating method is known. In this case, the heat sealability imparting agent is mainly composed of chlorinated polypropylene, polyvinylidene chloride, etc., dissolved in an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, etc., or an undercoat with an isocyanate adhesive solution. vinylidene chloride/acrylonitrile copolymer emulsion to be applied;
etc. However, although the coating method can impart low-temperature heat-sealability, it requires a process separate from the biaxially oriented polypropylene film manufacturing process, such as applying a heat-sealing agent or drying with hot air after applying an organic solvent. Not only is the manufacturing process complicated, but the manufacturing cost is also high. Furthermore, since the heat-sealability imparting agent is applied, not only the inherent transparency of the biaxially oriented polypropylene film is impaired, but also, when an organic solvent is used, the organic solvent may remain in the coating layer. Since it is difficult to avoid, it is undesirable from a sanitary point of view. In order to avoid the problems of high cost and residual solvent of such coating methods, a resin composition having a lower melting point than that of the base polypropylene is laminated to the base polypropylene in the production process of the biaxially oriented polypropylene film for low-temperature heat sealing. A method of biaxial stretching has been proposed. This lamination method is
This is an extremely superior method as it has higher productivity and simplifies the manufacturing method compared to the coating method. Ethylene-based resins and propylene-based resins have been proposed as the low-temperature heat-sealable resin composition used in this method. Examples of ethylene-based resins include low-density polyethylene, medium-density polyethylene (Japanese Patent Publication No. 101420/1984), and ethylene-vinyl acetate copolymer (Japanese Patent Publication No. 1973-101420).
- Publication No. 11353), etc. have been proposed. However, in the case of ethylene-based resin, although it can provide low-temperature heat-sealing properties due to its low melting point, it has low rigidity and
It has disadvantages such as poor transparency, hot slip properties, and scratch resistance. As a result, the present situation is that a composite biaxially oriented polypropylene film laminated with an ethylene resin cannot be used as a film for overlapping packaging. On the other hand, examples of propylene-based resins include ethylene-propylene copolymer (Japanese Patent Publication No. 46-31478) and propylene-butene-1 copolymer (Japanese Patent Publication No. 31478/1989).
50-128781), ethylene-propylene-butene-1 copolymer (JP-A-49-35487), etc. have been proposed. However, in the case of propylene-based resins, although they should be satisfactory in terms of rigidity, transparency, hot-slip properties, and scratch resistance, they have a disadvantage of inferior low-temperature heat-sealability due to their higher melting points compared to ethylene-based resins. There is. As a result, even with a composite biaxially oriented polypropylene film laminated with a propylene resin, it is currently not possible to obtain a film that is satisfactory as an overlap packaging film. In order to improve the low-temperature heat-sealability, which is a drawback of propylene-based resins as heat-sealability imparting agents, a composition in which polyptene-1 is blended with propylene-based resin has been proposed as a low-temperature heat-sealability imparting resin composition. There is. For example, JP-A-51-114482 discloses that by blending polybutene-1 in an amount of 5% by weight or more with an olefin polymer and further adding a specific bisamide, transparency can be improved by changing the crystal system of polybutene-1. Methods have been proposed to suppress the decrease in heat sealability and heat sealability. JP-A-51-150560 discloses a propylene-butene-1 random copolymer whose butene-1 content is 10-15% by weight, blended with 35-65% by weight of polybutene-1. Low-temperature heat-sealing agents have been proposed. Japanese Patent Application Publication 1973-
Publication No. 150561 discloses an ethylene-propylene random copolymer with an ethylene content of 0.5 to 4.5.
A low-temperature heat-sealability imparting agent has been proposed in which 45 to 65% by weight of polybutene-1 is blended with 45% to 65% by weight of polybutene-1. However, to the best of the knowledge of the present inventors, these proposals cannot be said to be fully satisfactory.
That is, in the case of JP-A-51-114482, a specific bisamide must be added. Japanese Patent Application Publication 1973-
In the case of No. 150560 and JP-A-51-150561,
It is possible to impart low-temperature heat-sealing properties only by blending a large amount of polybutene-1 at 35% by weight or more.
If these are blended, the inherent transparency and gloss of the biaxially oriented polypropylene film will be impaired. As shown above, we have developed a resin composition that imparts low-temperature heat-sealability that is fully satisfactory for use in overlap packaging without impairing the inherent properties of biaxially oriented polypropylene film, and a biaxially oriented polypropylene film laminated with this composition. At present, a stretched polypropylene film has not yet been obtained. [] Summary of the invention The present invention aims to provide a solution to the above-mentioned problems, and utilizes a blend composition of olefin-butene-1 copolymer and polybutene-1 as a resin having low-temperature heat-sealing properties. Therefore, it is an attempt to achieve this purpose. Therefore, the resin composition according to the present invention comprises the following olefin-butene-1 copolymer (a) and polybutene-1 copolymer (a).
1(b), the MFR of polybutene-1(b) at the same temperature in the range of 180 to 350°C is olefin-
It is characterized by having a value not smaller than that of the butene-1 copolymer. (a) Olefin-butene-1 copolymer consisting of 0.5 to 5% by weight of ethylene component, 98.5 to 70% by weight of propylene component, and 1 to 25% by weight of butene-1 component (composition is based on copolymer weight)
97.5 to 70% by weight (b) Crystalline polybutene-1 2.5 to 30% by weight As described above, the resin composition according to the present invention has a composition containing a specific composition of olefin-butene-1 copolymer and crystalline polybutene-1. It has a low content of polybutene-1 of up to 30% by weight, and does not require special substances such as bisamide, and has the low-temperature heat sealing properties necessary as an overlapping material for biaxially oriented polypropylene films. can give. [] Detailed description of the invention 1 Olefin-butene-1 copolymer (a) One of the essential components of the resin composition according to the present invention is
It is an olefin-butene-1 copolymer. This copolymer generally has the following composition. Monomer component weight% ^* Ethylene 0.5-5 Propylene 98.5-70 Butene-1 1-25 *Based on copolymer weight Particularly preferred composition ratio is ethylene component 0.5-5
2.0% by weight, propylene component 91.5-83% by weight,
The butene-1 component is 8 to 15% by weight. As long as the olefin-butene-1 copolymer has an ethylene, propylene, and butene-1 content within the above-mentioned ranges, the effects of the present invention will still be obtained even if a blend of various olefin-butene-1 copolymers is used. It won't cause any damage. Also within the scope of this invention are olefin-butene-1-comonomer copolymers in which an amount of comonomer, such as pentene-1, is further copolymerized with less than the minimum component in a given copolymer within this composition range. It is. This olefin-butene-1 copolymer is
An MFR (melt flow rate) value of about 1 to 30 is appropriate, but the specific MFR value needs to be correlated with that of polybutene-1 to be combined with it (details will be described later). The olefin-butene-1 copolymer can be produced, for example, by the method described in JP-A-49-35487. 2 Polybutene-1(b) Another essential component of the resin composition according to the present invention is crystalline polybutene-1. Crystalline homopolybutene-1 is one representative example, but it may also be a copolymer with a small amount of comonomer (eg, ethylene, propylene, pentene-1) as long as it can be called crystalline polybutene-1. Polybutene-1 preferably has an MFR value of 1 g/10 minutes or more, particularly preferably about 5 to 50 g/10 minutes. The specific MFR value is
It is necessary to correlate this with that of the olefin-butene-1 copolymer with which it is to be combined (see details later). Polybutene-1, for example,
The polybutene which can be produced by the method described in the publication and which is particularly effective in the present invention can be produced by adjusting the amount of hydrogen added during polymerization, the polymerization temperature, the amount of catalyst, etc.
1 can be obtained. In addition, the polybutene-1 obtained or given in this way can be
If it does not have an MFR value, the MFR value can be adjusted by molecular cleavage, fractionation, etc. 3. Resin composition The resin composition according to the present invention contains the above-mentioned olefin-
Butene-1 copolymer (a) and crystalline polybutene-
(b) is essential. Specific selection of both essential components is made from the viewpoint of the MFR value and quantitative ratio of both resins. That is, first, the MFR value of polybutene-1 must be equal to or greater than the MFR value of the olefin-butene-1 copolymer at the same temperature in the range of 180-300°C. Polybutene
If the MFR value of 1 is smaller than that of the olefin-copolymer, the surface of the product film will be rough, resulting in poor transparency and low-temperature heat sealability.
The MFR value in the text is based on ASTM D 1238-1973.
This is a value measured under the conditions of 190°C/2.16Kg load/10 minutes according to the E condition. Another factor regulating the resin composition according to the present invention is the quantitative ratio. 97.5 to 70% by weight of olefin-butene-1 copolymer, 2.5% of polybutene-1
~30% by weight, preferably 97-70% by weight of olefin-butene-1 copolymer, polybutene-1
is 3 to 30% by weight (all based on the total amount of both)
It is. If polybutene-1 is less than 2.5% by weight, sufficient low-temperature heat sealing properties cannot be achieved;
If it exceeds 30% by weight, transparency will deteriorate and low-temperature heat sealability will also deteriorate. Both resins can be made into the resin composition of the present invention by any method that allows uniform mutual dispersion of both resins. For example, there is a method in which both powders are dry-blended in a predetermined ratio using a super mixer or the like, or further melt-kneaded, or directly melt-kneaded without dry-blending. It is also possible to mix and knead one of the two resins, for example polybutene-1, in a predetermined proportion or more to form a master pellet, and then dilute this with the other resin to adjust the composition to a predetermined composition. In addition to the above-mentioned two essential components, the resin composition according to the present invention includes various auxiliary components that are usually added to resin compositions, such as antioxidants, antiblocking agents,
It may contain a slip agent, an antistatic agent, a coloring agent, etc. It may also contain a small amount of kneadable or compatible resin. 4 Composite Biaxially Stretched Polypropylene Film The composite biaxially oriented polypropylene film to which the resin composition of the present invention is applied is a laminated structure formed by bonding the above resin composition to one or both sides of a biaxially oriented polypropylene film. . A typical example of polypropylene used as a base material is crystalline homopolypropylene, but as long as the biaxial stretching effect can be achieved or it can be said to be crystalline, copolymers of propylene and a small amount of other comonomers, such as other olefins, can be used. It may be. In such a biaxially stretched film of crystalline polypropylene, the stretching ratio in each axis is preferably 3 times or more (the upper limit is about 12 times). The layer of the resin composition of the present invention bonded to at least one side of such a biaxially stretched polypropylene film may be unstretched or uniaxially or biaxially stretched. This layer of low-temperature heat-sealable resin is coextruded with the polypropylene layer, or is provided by stretching a laminate that has been melt-extruded onto an unstretched or uniaxially stretched polypropylene film to bring the polypropylene film into a biaxially stretched state. (Details will be described later), so it is usually uniaxially or biaxially stretched. However, considering the melting point of the laminated resin composition, it will be molten or semi-molten during the final stage of stretching, and will not be substantially oriented. There are no restrictions on the overall thickness of this composite biaxially stretched polypropylene film, but it is generally desirable to have a thickness of 10μ to 100μ, preferably 15μ to 50μ.
is desirable. The thickness of the base biaxially stretched polypropylene film is preferably about 13 to 45 μm. The laminated thickness of the blend composition of olefin-butene-1 copolymer and polybutene-1, which is a low-temperature heat-sealable resin composition, is 0.2μ on each side of the composite biaxially stretched polypropylene film.
~10μ is desirable, preferably 0.5μ to 5μ. When the thickness of the laminated layer is less than 0.2μ, not only sufficient heat sealing strength cannot be obtained, but also low temperature heat sealing properties cannot be imparted. If the thickness of the laminated layer exceeds 10% of the total film thickness, heat-sealing strength and low-temperature heat-sealing properties can be imparted, but the rigidity and strength, which are characteristics of biaxially oriented polypropylene, will be impaired. In the case of double-sided layering, the thickness of the laminated layer of the low-temperature heat-sealable resin composition may be different on both sides, and resin compositions having different compositions may be laminated on both sides. 5. Manufacture of composite biaxially stretched polypropylene film An example of a method for manufacturing a composite biaxially stretched polypropylene film imparted with low-temperature heat-sealing properties for use with the resin composition of the present invention is as follows. The lamination method is such that a blend composition of olefin-butene-1 copolymer and polybutene-1, which is a low-temperature heat-sealing resin composition, is layered on at least one side of the polypropylene base. The method of forming a melt coextrusion sheet with a two-layer structure or a three-layer structure of the composition/polypropylene or blend composition/polypropylene/blend composition allows the low-temperature heat-sealable resin composition to be easily and uniformly laminated thinly. This is desirable because there is no risk of air being trapped between the layers of the base polypropylene and the low-temperature heat-sealable resin composition. However, after first forming a base polypropylene into a sheet, a low-temperature heat sealing resin composition is applied at least on this unstretched sheet or on a longitudinally uniaxially stretched sheet obtained by uniaxially stretching this unstretched sheet in the longitudinal direction. It is also possible to adopt a method of melt extrusion lamination on one side. Longitudinal stretching is performed on the 2
Layered or three-layered sheets can be produced, for example, using differential roll circumferential speeds, which are known to those skilled in the art.
That is, stretching 3 to 8 times, preferably 4 to 6 times, in the machine direction at 90-140° C., preferably 105-135° C., followed by stretching in the transverse direction, for example, in a tenter oven known to those skilled in the art, 3-8 times, preferably 4-6 times. Stretch 12 times, preferably 6 to 11 times. In order to prevent heat shrinkage during heat sealing, it is desirable to heat set at a temperature of 120 to 170° C. following lateral stretching. Furthermore, following heat fixation, corona treatment may be performed for the purpose of improving printability, promoting bleeding of the antistatic agent, and the like. 6 Examples The heat seal strength, HAZE, strength at break, elongation, MFR, melting point, and Young's modulus in the following Examples and Comparative Examples were measured under the following conditions. (1) Heat-sealing strength Using a 5mm x 200mm heat-sealing bar, heat-sealing pressure 1Kg/cm ² and heat-sealing time 0.5 at each set temperature.
A 20 mm wide test piece was cut from the sample heat-sealed under the heat-sealing conditions of 2 seconds, and the T-peel strength was measured using an Instron tester at a tensile speed of 500 mm/minute. (2) HAZE Measured using a HAZE meter manufactured by Toyo Seiki Seisakusho in accordance with ASTMD1003-61. (3) Strength at break and elongation Measured using an Instron testing machine in accordance with ASTMD882-67. (4) Young's modulus Measured using an Instron testing machine in accordance with ISOR1184-70. (5) Measured according to E conditions of MFR ASTMD1238-1973. (6) Melting point (Tm) PerkinElmer DSC, sample amount 5.0 mg, heating speed 10
The peak of the melting curve at °C/min was taken. Temperature correction uses In, Bi, Sn, Pb, and Ga, and "thermal measurement" 3 . 83 (1976)). The melting point of polybutene-1 is the melting point of Form, and polybutene-1 changes to Form (melting point: about 130°C) in about a week at room temperature (J.
Polymer Sci., A-1 59 (1963). The present invention relates to a resin composition, and since this resin composition was developed as a heat-sealability imparting agent for biaxially oriented polypropylene film, the following examples will show how the resin composition of the present invention was used in this application. It is given as a concrete indication. Comparative examples are also given to demonstrate the critical importance of the requirements of the resin compositions of the present invention in this application. Example 1 Polypropylene (MFR=1g/
10 minutes, II = 98%, Im = 165°C), and ethylene-propylene-butene-1 copolymer (MFR = 4.8g/10
min, Tm=132℃, ethylene 1.2%, propylene 85.8%, butene-113%) to 95% polybutene-1 (MFR=18g/10min, Tm=111
C) 5% by weight for 2 minutes using a spar mixer, the blend composition was laminated under the following conditions and sequentially biaxially stretched to obtain a composite biaxially stretched polypropylene film. polypropylene and blend composition respectively
From a 115φ, 35φ extruder, melt coextrusion with a two-resin three-layer die at 240℃ to form a three-layer structure with blend composition/polypropylene/blend composition, and cooling of a 300φ with a surface temperature of 40℃. It was solidified on rolls to form a sheet, and then stretched 5 times in the machine direction at 115°C using the difference in circumferential speed of the rolls. Following the longitudinal stretching, the film was stretched 10 times in the transverse direction in a tenter oven at 160°C, and then heat-set at 150°C. The thickness structure of the obtained composite biaxially stretched polypropylene film was blend composition/polypropylene/blend composition=1μ/18μ/1μ. The heat seal strength of this film and
Table 1 shows the HAZE measurement results. Comparative Examples 1 to 5 For comparison with Example 1, the following resins were used as low-temperature heat-sealable resin compositions. Comparative Example 1 Ethylene-propylene-butene 1 copolymer (MFR = 4.8 g/10 min, Tm = 132°C, ethylene 1.2
weight%, propylene 85.8% by weight, butene-113% by weight), Comparative Example 2 Propylene-butene-1 copolymer (MFR=
11.8 g/10 min, Im = 137°C, propylene 83% by weight, butene - 117% by weight), Comparative Example 3 Ethylene-propylene copolymer (MFR = 7
g/10 minutes, Tm=139°C, ethylene 3% by weight, propylene 97% by weight), Comparative Example 4 Medium density polyethylene (MFR=3.2g/10 minutes,
Tm=119℃, density=0.922g/ ^cm3 ), Comparative Example 5 Low density polyethylene (MFR=8.0g/10min,
Tm = 109°C, density = 0.918 g/cm ³ ) A composite biaxially stretched polypropylene film was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the heat seal strength and HAZE of the obtained film.

[Table] From the results in Table 1, it is clear that the film laminated with the composition blended with polybutene-1 has excellent low-temperature heat sealability and transparency (HAZE). Ethylene-propylene-butene-
1 copolymer (Comparative Example 1), propylene-butene-
1 copolymer (Comparative Example 2) and ethylene-propylene copolymer (Comparative Example 3) have excellent transparency but poor low-temperature heat sealability; It is clear that polyethylene (Comparative Example 4) has excellent low-temperature heat sealability but poor transparency. Example 2 This example shows the results of polybutene-1 effective in the present invention.
It shows the range of MFR and the relationship between MFR of polybutene-1 and olefin-butene-1 copolymer. Ethylene-propylene-butene-1 copolymer (MFR=4.8g/10min, Tm=132℃, ethylene 1.2
5% by weight of polybutene-1 having various MFR values was added to 95% by weight (85.8% by weight of propylene, 113% by weight of butene) and dry blended for 2 minutes in a spar mixer to obtain each blend composition. It was laminated and stretched on polypropylene (MFR = 1 g/10 min, = 98%, Tm = 165°C) under the same conditions as in Example 1 to obtain a composite biaxially stretched polypropylene film having a total thickness of 20 μ and laminated with 1 μ on both sides. Ta. The heat seal strength of these films and
Table 2 shows the HAZE measurement results. Comparative Examples 6, 7 Polybutene-1 (MFR=3
g/10 min, Tm=111°C) (Comparative Example 6), and polybutene-1
(MFR=0.29g/10min) was blended with polypropylene (MFR=1g/10min, II=98%) under the same conditions as Example 1.
%, Tm = 165° C.) and stretched to obtain a composite biaxially stretched polypropylene film having a total thickness of 20 μm and having 1 μm laminated on both sides. The heat seal strength and
Table 2 shows the HAZE measurement results.

[Table] From the results in Table 2, the following facts are recognized. When the MFR of polybutene-1 is smaller than the MFR of olefin-polybutene-1 copolymer,
It is clear that both the low-temperature heat sealability and the transparency are inferior. Example 3 This example shows the effective ranges of ethylene content and butene-1 content of an olefin-butene-1 copolymer, which is one constituent resin of a blend composition that is a low-temperature heat-sealable resin composition, and This shows the effective blending ratio range of polybutene-1, which is the other constituent resin of the blend composition. Polybutene-1 (MFR=18 g/10 min, Tm=
111℃) with a content of 0, 1, 2.5, 5, 10, 20, 30,
The compositions were dry blended in a spar mixer for 2 minutes to give a weight percent of 50% and 100% by weight, and each composition was mixed with polypropylene (MFR) under the same conditions as in Example 1.
= 1g/10min, II = 98%, Tm = 165℃),
By stretching, a composite biaxially stretched polypropylene film having a total thickness of 20 μm was obtained by laminating each side to a thickness of 1 μm. Table 3 shows the heat-sealing temperature at which a heat-sealing strength of 100g/2cm can be obtained for these films.
Shown below.

[Table] From the results in Table 3, the following facts are recognized. The effective blending ratio of polybutene-1 to achieve a heat-sealing strength of 100 g/2 cm at a heat-sealing temperature of 100°C or less by blending polybutene-1 with various olefin-butene-1 copolymers is 2.5% by weight. It is clear that the content is in the range of 30% by weight or less. Example 4 The procedure was the same as in Example 1 except that a butene-1 copolymer with an ethylene content of 5% by weight (MFR = 20 g/10 minutes, Tm = 111°C) was used instead of polybutene-1. A composite biaxially stretched polypropylene film was obtained. Table 4 shows the measurement results of heat seal strength and HAZE of this film.

【table】

Claims (1)

[Claims] 1. Crystalline polybutene-1(b) containing the following olefin-butene-1 copolymer (a) and crystalline polybutene-1(b) at the same temperature in the range of 180 to 300°C. of
A resin composition characterized in that the MFR has a value not smaller than that of an olefin-butene 1 copolymer. (a) Olefin-butene-1 copolymer consisting of 0.5 to 5% by weight of ethylene component, 98.5 to 70% by weight of propylene component, and 1 to 25% by weight of butene-1 component (composition is based on copolymer weight)
97.5-70% by weight (b) Crystalline polybutene-1 2.5-30% by weight