JPS6237664B2 - - Google Patents

Description

[Detailed description of the invention]

[] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition with excellent low-temperature heat-sealability and uses thereof. More specifically, the present invention provides crystalline polybutene-1 in an ethylene-propylene crystalline random copolymer having a specific composition.
The present invention relates to a resin composition having a specific composition blended with the above, and a biaxially oriented polypropylene film having this resin composition laminated on at least one side. The low temperature heat sealing properties of this resin composition make this composite biaxially oriented polypropylene film useful for overlapping 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. Overlap packaging is generally carried out on high-speed automatic packaging machines at a rate of 200 to 400 pieces per minute, and therefore requires suitability for high-speed automatic packaging. 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, films for overlapping packaging must have transparency to make the product look beautiful, and must also have moisture resistance to protect the product. 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 may be prepared by dissolving chlorinated polypropylene, polyvinylidene chloride, etc. in an organic solvent such as toluene, ethyl acetate, or methyl ethyl ketone, or by applying an undercoating 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, it is currently not possible to obtain a composite biaxially oriented polypropylene film laminated with an ethylene resin that is fully satisfactory as an overlap packaging film. On the other hand, examples of propylene-based resins include ethylene-propylene copolymer (JP-A-46-31478) and propylene-butene-1 copolymer (JP-A No. 46-31478).
50-128781) and ethylene-propylene-butene-1 copolymer (Japanese Patent Application Laid-Open No. 49-35487). However, although propylene-based resins should be satisfactory in terms of rigidity, transparency, hot-slip properties, and scratch resistance, they have the 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, compositions in which polybutene-1 is blended with propylene-based resins have been proposed as low-temperature heat-sealability imparting resin compositions. 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,
By blending a large amount of polybutene-1 at 35% by weight or more, it is possible to impart low-temperature heat-sealing properties, but when blending such a large amount of polybutene-1, the biaxially oriented polypropylene film originally has Transparency and gloss are lost. 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 solve the above-mentioned problems by using a blend composition of an ethylene-propylene random copolymer and polybutene-1 as a resin having low-temperature heat-sealing properties. The goal is to achieve this goal. Therefore, the resin composition according to the present invention has the following (a)
and (b) (the composition is based on the total weight of (a) and (b)). (a) Ethylene content of 1.5 to 10% by weight, and 180 to 100% by weight
Ethylene-propylene random copolymer with MFR lower than that of (b) at the same temperature in the range of 300°C (composition is based on copolymer weight) 97.5 to 65% by weight (b) MFR of 5 to 50 g/10 min crystalline polybutene-1 2.5 to 35% by weight Further, the composite biaxially oriented polypropylene film according to the present invention includes a layer made of biaxially oriented crystalline polypropylene and the following resin composition bonded to at least one side thereof. It is characterized by being made up of layers of material. Resin composition A resin composition containing the following (a) and (b) (composition is:
(based on the total weight of (a) and (b)). (a) Ethylene content of 1.5 to 10% by weight, and 180 to 100% by weight
Ethylene-propylene random copolymer with MFR lower than that of (b) at the same temperature in the range of 300°C (composition is based on copolymer weight) 97.5 to 65% by weight (b) MFR of 5 to 50 g/10 minutes of crystalline polybutene-1 2.5 to 35% by weight As described above, the resin composition according to the present invention comprises an ethylene-propylene random copolymer of a specific composition and a specific MFR and a crystalline polybutene of a specific MFR.
1, the content of polybutene-1 is as low as 35% by weight, and it does not require special substances such as bisamide, and is necessary as an overlapping material for biaxially oriented polypropylene films. It can provide low-temperature heat sealability. [] Detailed description of the invention 1 Ethylene-propylene random copolymer (a) One of the essential components of the resin composition according to the present invention is:
It is an ethylene-propylene random copolymer. The ethylene component content of this copolymer is 1.5-10
%, the propylene component content is preferably in the range of 98.5 to 90%, and particularly preferably the ethylene component content is in the range of 2 to 10%.
%, and the propylene component content is 98 to 90% (all based on copolymer weight). As long as the ethylene-propylene random copolymer has the above-mentioned ethylene content, the effects of the present invention will not be impaired in any way even if various ethylene-propylene random copolymers with different ethylene contents are used as a blend. do not have. Also within the scope of this invention are ethylene-propylene-comonomer random copolymers in which an amount of comonomer, such as pentene-1, is further copolymerized with less than the smallest component in a given copolymer within this composition range. be. It is appropriate for this ethylene-propylene random copolymer to have an MFR (melt flow rate) value of about 1 to 30, but the specific MFR value correlates with that of polybutene-1(b) to be combined with it. (Details below) Ethylene-propylene random copolymer (a) is
For example, it can be produced by the method described in Japanese Patent Publication No. 43-27419. 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 with an MFR value in the range of 5 to 50 g/10 minutes can be used, but the specific MFR
The value needs to be correlated with that of the ethylene-propylene random copolymer with which it is to be combined (details below). If the MFR of polybutene-1 is less than 5 g/10 minutes, the transparency and low-temperature heat sealability of the product film will be insufficient, and if it exceeds 50 g/10 minutes, the product film will cause blocking. Polybutene-1, for example,
Polybutene, which is particularly effective in the present invention, can be produced by the method described in the publication, and 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 essentially contains the above-mentioned ethylene-propylene random copolymer (a) and crystalline polybutene-1 (b). 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 needs to be greater than the MFR value of the ethylene-propylene random copolymer at the same temperature in the range of 180 to 300°C. polybutene-1
If the MFR value is equal to or 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. In addition, the MFR value in the text is ASTMD
This is a value measured under the conditions of 190℃/2.16Kg load/10 minutes according to the E conditions of 1238-1973. Another factor regulating the resin composition according to the present invention is the quantitative ratio. 97.5-65% by weight of ethylene-propylene random copolymer, polybutene-1
ranges from 2.5 to 35% by weight, preferably ethylene-
97.5-70% by weight of propylene random copolymer,
Polybutene-1 is 2.5 to 30% by weight (all based on the total amount of both). Polybutene-1 is 2.5
If it is less than 35% by weight, sufficient low-temperature heat-sealability cannot be achieved, while if it exceeds 35% by weight, not only the improvement effect is saturated, but also the transparency deteriorates and the low-temperature heat-sealability deteriorates in many cases. Getting worse. 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 according to the present invention 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. It is preferable that such a biaxially stretched film of crystalline polypropylene has a stretching ratio of 3 times or more in each axis (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 is no limit to the overall thickness of the composite biaxially stretched polypropylene film of the present invention, but it is generally desirable to have a thickness of 10μ to 100μ, preferably 15μ to 50μ.
μ is desirable. The thickness of the base biaxially stretched polypropylene film is preferably about 13 to 45 μm. The lamination thickness of the blend composition of ethylene-propylene random copolymer and polybutene-1, which is a resin composition imparting low-temperature heat-sealability, is set at
The thickness is desirably 0.2μ to 10μ, preferably 0.5 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 films, 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 on both sides may be laminated. 5. Manufacture of composite biaxially stretched polypropylene film An example of the method for manufacturing the composite biaxially stretched polypropylene film imparted with low-temperature heat-sealability according to the present invention is as follows. The lamination method is such that a blend composition of ethylene-propylene random copolymer and polybutene-1, which is a low-temperature heat-sealable resin composition, is laminated 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 a material/polypropylene or a 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 are 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. Alternatively, a mixture of ethylene-propylene copolymer and polybutene-1 may be laminated onto a polypropylene substrate, and then stretched biaxially. 6 Experimental Examples Heat seal strength, HAZE, strength at break, elongation, Young's modulus,
MFR, melting point and scratch resistance were measured under the following conditions. (1) Heat-sealing strength Using a 5mm x 200mm heat-sealing bar, cut a 20mm-wide test piece from the heat-sealed sample under heat-sealing conditions of heat-sealing pressure of 1Kg/cm ² and heat-sealing time of 0.5 seconds at each set temperature. ,
T-peel strength was measured using an Instron testing machine at a tensile speed of 500 mm/min. (2) HAZE Measured using a HAZE meter manufactured by Toyo Seiki Seisakusho in accordance with ASTM D 1003-61. (3) Strength at break and elongation Measured using an Instron testing machine according to ASTM D 882-67. (4) Young's modulus Measured using an Instron testing machine in accordance with ISO R 1184-70. (5) MFR Measured according to ASTM D 1238-1973 E conditions. (6) Melting point (Tm) Using PerkinElmer's DSC, the peak of the melting curve at a sample amount of 5.0 mg and a heating rate of 10°C/min was adopted. Temperature correction is In, Bi,
“Heat measurement” using Sn, Pb and Ga 3 83
(1976) and others. In addition, the melting point of Polybutene-1 is the melting point of Form, and Polybutene-1 changes to Form in about one week at room temperature.
(melting point approximately 130℃) (J. Polymer Sci.
, A-1 59 (1963)). (7) Scratch resistance 50g of sand with a particle size of 40 to 50 mesh is dropped onto the surface of a film sample held at 45° from a height of 1.5m, and scratch resistance is expressed as the difference in HAZE before and after dropping 50g of sand with a grain size of 40 to 50 mesh. Example 1 Polypropylene (MFR/1g/10
90% by weight of ethylene-propylene random copolymer (MFR 3g/10min, ethylene content 4% by weight, Tm 139°C) as a low-temperature heat-sealable resin.
1 (MFR 18g/10min, Tm 111℃) 10% by weight
A composite biaxially stretched polypropylene film was obtained by laminating the blended compositions in a supermixer for 2 minutes at the following ratio and sequentially biaxially stretching them in the following manner. polypropylene and the blend composition, respectively.
Melt coextrusion at 240°C into a three-layer composition of blend composition/polypropylene/blend composition using a two-resin three-layer T-die by a 65φ and 35φ extruder, onto a 250φ metal roll with a surface temperature of 30℃. The sheet was solidified into a sheet, which was then preheated, and then stretched 5 times in the longitudinal direction at 115° C. using the difference in circumferential speed of the rolls. Following the longitudinal stretching, the transverse direction was stretched 10 times in a tenter oven at 165°C.
Heat fixed at ℃. The thickness structure of the obtained composite biaxially stretched polypropylene film was determined by the blend composition/
Polypropylene/blend composition = 1/18/1μ
It was hot. The heat seal strength and HAZE measurement results of these films are shown in Table 1. Comparative Examples 1 to 3 In order to compare with Example 1, ethylene-propylene random copolymer (MFR = 3 g/10 minutes, Tm 139°C, ethylene content 4% by weight) was used as a heat-sealable resin (Comparative Example 1) , medium density polyethylene (MFR 3.2g/10 minutes, Tm119℃, density 0.922g/
cm ³ (Comparative Example 2), and low density polyethylene (MFR 8.0g/10 min, Tm 109℃, density 0.918g/
cm ³ ) (Comparative Example 3) was coextruded with polypropylene in the same manner as in Example 1 to obtain a composite biaxially stretched polypropylene film. Table 1 shows the measurement results of the heat seal strength, HAZE, and scratch resistance of the obtained film.

[Table] Example 2 and Comparative Example 4 Using the same resin and the same method as Example 1,
The blending ratio of the low-temperature heat-sealable resin composition was varied. The results are shown in Table 2.

[Table] Example 3 and Comparative Example 5 The blending ratio of the low-temperature heat-sealable resin composition was kept constant (10% by weight of polybutene-1), and ethylene-propylene random copolymer (EP) and polybutene-1 (PB) were mixed. Table 3 shows the results of various changes in the magnitude relationship of MFR. The method is the same as in Example 1.

[Table] Example 4 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 in the same manner as above. Table 4 shows the measurement results of heat seal strength, scratch resistance and HAZE of this film.

[Table] Example 5 A composite biaxially oriented polypropylene film was obtained by conducting substantially the same experiment as in Example 1 except as specified below. 1 Material Resin base layer: Polypropylene (MFR 1g/10min) ^*1 Heat seal layer: Ethylene-propylene random copolymer (MFR 3g/10min, ethylene content 4% by weight) ^*
1 90% by weight Polybutene-1(A) (MFR 18g/10min) ^*1 Polybutene-1(B) (MFR 2.8g/10min)
10% by weight 2 Layer structure of biaxially oriented polypropylene film ^*
2 base layer/heat sealing layer = 38μ/7μ 3 Heat sealing conditions ^*2 90 to 120°C, 2Kg/cm ² , 1 second *1: Same as Example 1 *2: Example of JP-A No. 114482/1982 The results are shown in Table 5 below.

【table】

Claims (1)

[Claims] 1. characterized by including the following (a) and (b):
Resin composition (composition is based on the total weight of (a) and (b)). (a) Ethylene content of 1.5 to 10% by weight, and 180 to 100% by weight
Ethylene-propylene random copolymer whose MFR is smaller than that of (b) at the same temperature in the range of 300°C (composition is based on copolymer weight) 97.5 to 65% by weight (b) MFR from 5 to 50g/10min crystalline polybutene-1 2.5-35% by weight 2 Characterized by consisting of a layer made of biaxially stretched crystalline polypropylene and a layer made of the following resin composition bonded to at least one side of the layer. ,
Composite biaxially oriented polypropylene film. Resin composition A resin composition containing the following (a) and (b) (composition is:
(based on the total weight of (a) and (b)). (a) Ethylene content of 1.5 to 10% by weight, and 180 to 100% by weight
Ethylene-propylene random copolymer whose MFR is smaller than that of (b) at the same temperature in the range of 300°C (composition is based on copolymer weight) 97.5 to 65% by weight (b) MFR from 5 to 50 g/10 minutes of crystalline polybutene-1 2.5 to 35% by weight 3 The composite biaxially stretched polypropylene film according to claim 2, wherein the layer made of the resin composition is stretched in at least one direction. 4. The composite biaxially stretched polypropylene film according to claim 3, wherein the layer made of the resin composition is biaxially stretched.